Display device
By employing a white insulating film or refractive index-matched film to redirect light from the side surfaces of LED elements, the LED display device effectively utilizes this light, enhancing efficiency and contrast.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- JAPAN DISPLAY INC
- Filing Date
- 2025-11-07
- Publication Date
- 2026-07-23
Smart Images
Figure JP2025039161_23072026_PF_FP_ABST
Abstract
Description
Display device
[0008] ,
[0007] , ,
[0001] The present invention relates to a display device, and more particularly to a technique effective when applied to a display device having, for example, a light emitting diode element.
[0002] Japanese Patent Application Laid-Open No. 2023-119574 (Patent Document 1) describes a substrate with partitions formed by a resin composition containing a resin, a photosensitive agent, a white pigment, and a yellow precursor compound, and a display device having a light emitting source selected from a liquid crystal cell, an organic EL cell, a mini LED cell, and a micro LED cell.
[0003] Japanese Patent Application Laid-Open No. 2023-23024 (Patent Document 2) describes a micro LED display device having a plurality of LED elements arranged in a grid pattern on a substrate and partitions separating the individual LED elements, with a diffusion reflection layer formed on the surface of the side wall of the partitions.
[0004] Japanese Patent Application Laid-Open No. 2023-119574, Japanese Patent Application Laid-Open No. 2023-23024
[0005] There is an LED (Light Emitting Diode) display device that uses a plurality of light emitting diode elements arranged on a substrate called a backplane as a light source. Basically, an LED display device uses the light emitted from the upper surface of the light emitting diode element. In this regard, from the perspective of efficiently utilizing the light emitted from the light emitting diode element, it is desirable to effectively utilize the light emitted from the side surface of the light emitting diode element.
[0006] Other problems and novel features will become apparent from the description of this specification and the accompanying drawings.
[0007] A display device according to an embodiment includes a backplane having a first electrode and a second electrode, a light emitting diode element disposed on the second electrode, and a white insulating film in contact with the side surface of the light emitting diode element.
[0008] One embodiment of the display device includes a backplane having a first electrode and a second electrode, a light-emitting diode element disposed on the second electrode, a first insulating film in contact with the side surface of the light-emitting diode element, and a second insulating film away from the light-emitting diode element and in contact with the first insulating film, wherein the refractive index of the first insulating film is smaller than that of the light-emitting diode element.
[0009] This is a plan view showing an example configuration of a display device. This is a circuit diagram showing an example configuration of the circuit around the pixels shown in Figure 1. This is a diagram showing the main configuration of the display device in Embodiment 1. This is a diagram showing the manufacturing process of the display device in Embodiment 1. This is a diagram showing the manufacturing process of the display device following Figure 4. This is a diagram showing the manufacturing process of the display device following Figure 5. This is a diagram showing the manufacturing process of the display device following Figure 6. This is a diagram showing the manufacturing process of the display device following Figure 7. This is a diagram showing the display device in Modification 1. This is a diagram showing the display device in Modification 2. This is a cross-sectional view showing the main configuration of the display device in Embodiment 2. This is a diagram showing the manufacturing process of the display device in Embodiment 2. This is a diagram showing the manufacturing process of the display device following Figure 12.
[0010] The embodiments will be described below with reference to the drawings.
[0011] This disclosure is merely an example, and any modifications that maintain the spirit of this disclosure while being appropriately conceivable by a person skilled in the art are naturally included within the scope of this disclosure.
[0012] Furthermore, in order to clarify the explanation, the drawings may schematically represent the width, thickness, shape, etc., of each part compared to the actual embodiment, but these are merely examples and do not limit the interpretation of this disclosure. In this specification and each drawing, elements similar to those shown in previously published drawings are denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.
[0013] In this embodiment, as an example of a display device using multiple light-emitting diode elements, a micro-LED display device equipped with multiple micro-LED elements is provided. Micro-LED elements have a smaller size (outer diameter) compared to general LED elements. Therefore, micro-LED display devices can display high-resolution images.
[0014] <Configuration of the display device> Figure 1 is a plan view showing an example of the configuration of a display device.
[0015] In Figure 1, the boundary between the display area DA and the peripheral area PFA, the control circuit 5, the drive circuit 6, and the multiple pixels PIX are each shown by dashed lines.
[0016] Figure 2 is a circuit diagram showing an example of the configuration of the circuit around a pixel shown in Figure 1. Note that the pixel circuit shown in Figure 2 is an example of an equivalent circuit corresponding to one pixel PIX shown in Figure 1.
[0017] Figure 1 shows the X and Y directions. The X and Y directions intersect each other. In the example described below, the X direction is perpendicular to the Y direction. Furthermore, the X-Y plane, which includes the X and Y directions, will be described as a plane parallel to the display surface of the display device.
[0018] Unless otherwise explicitly stated, "planar view" refers to a view of a plane parallel to the X-Y plane. Furthermore, the direction normal to the X-Y plane is described as the "Z direction" or thickness direction. The X, Y, and Z directions are intersecting directions. For example, the X, Y, and Z directions are orthogonal directions.
[0019] As shown in Figure 1, the display device DSP1 has a display area DA, a peripheral area PFA, and a plurality of pixels PIX. The peripheral area PFA surrounds the display area DA in a frame-like manner. The plurality of pixels PIX are arranged in a matrix within the display area DA.
[0020] The display device DSP1 also includes a substrate 10, a control circuit 5, and a drive circuit 6. The control circuit 5 and the drive circuit 6 are each formed on the substrate 10.
[0021] The control circuit 5 is a circuit for controlling the display in the display device DSP 1. For example, the control circuit 5 is a driver IC (Integrated Circuit) mounted on the substrate 10. In Figure 1, the control circuit 5 is arranged, for example, along one of the four short sides that make up the outer shape of the substrate 10. The control circuit 5 includes a signal line drive circuit. The signal line drive circuit is a video driver. The signal line drive circuit is a circuit that supplies video signals to video signal lines. The location and configuration examples of the control circuit 5 are not limited to the example shown in Figure 1. For example, in Figure 1, a circuit board such as a flexible substrate may be connected to the location shown as the control circuit 5. In this case, the control circuit 5 is mounted on the circuit board. Also, for example, the signal line drive circuit may be formed separately from the control circuit 5.
[0022] The drive circuit 6 is a scanning driver. The drive circuit 6 is a circuit that supplies scanning signals to the scanning signal line. The drive circuit 6 supplies scanning signals to the scanning signal line based on a control signal from the control circuit 5. The drive circuit 6 is arranged, for example, along each of the two long sides of the four sides that make up the outer shape of the substrate 10. In the example shown in Figure 1, in a plan view, the display area DA is located between the two drive circuits 6. The position and configuration examples of the drive circuit 6 are not limited to the example shown in Figure 1. For example, in Figure 1, a circuit board such as a flexible substrate may be connected to the position shown as the drive circuit 6. In this case, the drive circuit 6 is mounted on the circuit board.
[0023] Next, using Figure 2, we will explain an example of the configuration of a pixel circuit that drives a pixel PIX.
[0024] In Figure 2, a representative pixel circuit is shown to drive one pixel. Each of the multiple pixels PIX shown in Figure 1 is equipped with a circuit similar to the pixel circuit shown in Figure 2. The pixel circuit is a voltage signal type circuit that controls the light emission state of the LED element 20 based on the video signal Vsg supplied from the control circuit 5 (see Figure 1).
[0025] As shown in Figure 2, each pixel PIX is equipped with an LED element 20. The LED element 20 is a light-emitting diode element. The LED element 20 has an anode electrode 20EA and a cathode electrode 20EC.
[0026] The display device DSP1 is equipped with multiple types of wiring in the display area DA. These wirings include multiple scan signal lines GLS, GLR, GLB, multiple video signal lines VL, multiple power lines PL1, multiple power lines PL2, and multiple reset wiring RSL.
[0027] The scan signal lines GLS, GLR, and GLB extend in the X direction. The scan signal lines GLS, GLR, and GLB are connected to the drive circuit 6. For example, as shown in Figure 1, the scan signal lines GLS, GLR, and GLB for driving even-numbered pixels PIX among the pixels PIX arranged in the Y direction are connected to one drive circuit 6. In contrast, the scan signal lines GLS, GLR, and GLB for driving odd-numbered pixels PIX are connected to the other drive circuit 6. As another example, a configuration in which all of the scan signal lines GLS and GLR are connected to one drive circuit 6, and all of the scan signal lines GLB are connected to the other drive circuit 6 is also conceivable. Thus, there are cases in which one of the scan signal lines GLS, GLR, and GLB is connected to one drive circuit 6, and the rest are connected to the other drive circuit 6.
[0028] The video signal line VL, power lines PL1 and PL2, and reset wiring RSL extend in the Y direction. The video signal line VL is connected to the control circuit 5 (see Figure 1). The video signal Vsg and initialization signal are supplied to the video signal line VL from the control circuit 5. High potential Pdvdd is supplied to power line PL1 from the control circuit 5. Low potential Pvss, which is lower than high potential Pdvdd, is supplied to power line PL2 from the control circuit 5. The reset signal Vrs is supplied to the reset wiring RSL from the control circuit 5.
[0029] The control circuit 5 outputs a start pulse signal and a clock signal (not shown) to the drive circuit 6. The drive circuit 6 includes multiple shift register circuits. Based on the clock signal, the drive circuit 6 sequentially transfers the start pulse signal to the next stage shift register circuit. In this way, the drive circuit 6 sequentially supplies scan signals to each scan signal line GLS, GLR, and GLB.
[0030] The pixel circuit controls the LED element 20 based on the video signal Vsg supplied to the video signal line VL. To achieve this control, the pixel circuit includes a reset transistor RST, a pixel selection transistor SST, an output transistor BCT, a drive transistor DRT, a holding capacitor Cs, and an auxiliary capacitor Cad. The auxiliary capacitor Cad is an element provided to adjust the amount of light emitted.
[0031] The reset transistor RST, pixel selection transistor SST, output transistor BCT, and drive transistor DRT are switching elements made of thin-film transistors (TFTs). The conductivity type of the thin-film transistors is not particularly limited. For example, all transistors may be made of N-channel TFTs. However, at least one of the transistors may be made of P-channel TFTs.
[0032] The reset transistor RST, pixel selection transistor SST, output transistor BCT, and drive transistor DRT are formed, for example, using the same process and the same layer structure. These transistors have a bottom gate structure with polycrystalline silicon used for the semiconductor layer. As another example, the reset transistor RST, pixel selection transistor SST, output transistor BCT, and drive transistor DRT may have a top gate structure. For example, oxide semiconductors or polycrystalline GaN semiconductors can be used as the semiconductor layer.
[0033] The reset transistor RST, the pixel selection transistor SST, the output transistor BCT, and the drive transistor DRT each have a source electrode, a drain electrode, and a gate electrode. The gate electrode of each transistor is a control electrode. The source electrode and drain electrode of each transistor can also be simply referred to as electrodes.
[0034] The drive transistor DRT and the output transistor BCT are connected in series with the LED element 20 between power lines PL1 and PL2. The high potential Pvdd supplied to power line PL1 is set to, for example, 10V. The low potential Pvss supplied to power line PL2 is set to, for example, 1.5V.
[0035] The drain electrode of the output transistor BCT is connected to the power line PL1. The source electrode of the output transistor BCT is connected to the drain electrode of the drive transistor DRT. The gate electrode of the output transistor BCT is connected to the scan signal line GLB. The output transistor BCT is turned on / off by the control signal Gsb supplied to the scan signal line GLB. Here, "on" represents a conduction state, and "off" represents a non-conduction state. The output transistor BCT controls the light emission time of the LED element 20 based on the control signal Gsb.
[0036] The source electrode of the drive transistor DRT is connected to one electrode of the LED element 20 (here, the anode electrode 20EA). The other electrode of the LED element 20 (here, the cathode electrode 20EC) is connected to the power line PL2. The drive transistor DRT outputs a drive current to the LED element 20 based on the video signal Vsg.
[0037] The source electrode of the pixel selection transistor SST is connected to the video signal line VL. The drain electrode of the pixel selection transistor SST is connected to the gate electrode of the drive transistor DRT. The gate electrode of the pixel selection transistor SST is connected to the scan signal line GLS. The scan signal line GLS functions as a gate trace for signal writing control. The pixel selection transistor SST is turned on / off by the control signal Gss supplied from the scan signal line GLS. Turning the pixel selection transistor SST on / off switches the connection and disconnection between the pixel circuit and the video signal line VL. That is, by turning on the pixel selection transistor SST, the video signal Vsg or initialization signal from the video signal line VL is supplied to the gate electrode of the drive transistor DRT.
[0038] The source electrode of the reset transistor RST is connected to the reset wiring RSL. The drain electrode of the reset transistor RST is connected to the source electrode of the drive transistor DRT and the anode electrode 20EA of the LED element 20. The gate electrode of the reset transistor RST is connected to the scan signal line GLR. The scan signal line GLR functions as a gate wiring for reset control. The reset transistor RST is turned on / off by the control signal Grs supplied from the scan signal line GLR. By switching the reset transistor RST on, the potentials of the source electrode of the drive transistor DRT and the anode electrode 20EA of the LED element 20 can be reset. That is, the potentials of the source electrode of the drive transistor DRT and the anode electrode 20EA of the LED element 20 can be reset to the reset signal Vrs supplied to the reset wiring RSL. In other words, the reset wiring RSL is wiring for resetting the voltage of the LED element 20.
[0039] The retaining capacitance Cs is connected between the gate electrode and source electrode of the drive transistor DRT. The auxiliary capacitance Cad is connected between the source electrode of the drive transistor DRT and the power line PL2.
[0040] The drive circuit 6 sequentially supplies scanning signals (control signals Gss, Grs, Gsb) to each of the scanning signal lines GL S, GL R, GL B. That is, the control signals Gss, Grs, Gsb are sequentially supplied to the scanning signal lines GL S, GL R, GL B of each line (a series of pixels PIX arranged in the X direction) based on the start pulse signal and the clock signal. Further, the control circuit 5 sequentially supplies the video signal Vsg and the initialization signal to each video signal line VL. The charge held in the holding capacitor Cs is initialized with the supply of the initialization signal as the video signal Vsg is supplied.
[0041] In the configuration as described above, the pixel circuit is driven by the control signals Gss, Grs, Gsb supplied to the scanning signal lines GL S, GL R, GL B. On the other hand, the LED element 20 emits light with a luminance corresponding to the video signal Vsg supplied to the video signal line VL.
[0042] <Basic idea> The LED display device uses the light emitted from the upper surface of the light-emitting diode element, but light is also emitted from the side surface of the light-emitting diode element. Therefore, an LED display device that can effectively utilize the light emitted from the side surface of the light-emitting diode element is desired.
[0043] Therefore, the basic idea is an idea of devising to change the direction of the light that is about to be emitted from the side surface of the light-emitting diode element so that this light is emitted from the upper surface in order to effectively utilize the light that is about to be emitted from the side surface of the light-emitting diode element. According to this basic idea, the light that is about to be emitted from the side surface can be effectively utilized. Hereinafter, an embodiment embodying the basic idea will be described.
[0044] <Embodiment 1> <<Configuration of the display device>> FIG. 3 is a cross-sectional view showing the main configuration of the display device 100 in Embodiment 1.
[0045] In FIG. 3, the display device 100 includes a backplane BP, an LED element 114, an insulating film 117, a contact hole 118, and a wiring 120.
[0046] As shown in FIG. 3, an LED element 114 is mounted on a backplane BP. The LED element 114 has an anode electrode 115 formed on the lower surface BS and a cathode electrode 116 formed on the upper surface US1 located on the side opposite to the lower surface BS.
[0047] Also, an insulating film 117 is formed on the backplane BP. The insulating film 117 is in contact with the side surfaces SS1 and SS2 of the LED element 114. The upper surface US2 of the insulating film 117 is flush with the upper surface US1 of the LED element 14. A contact hole 118 is formed in the insulating film 117. A wiring 120 is formed in the contact hole 118 and on the insulating film 117. The wiring 120 is composed of a transparent conductive film. For example, the transparent conductive film is an ITO (Indium Tin Oxide) film.
[0048] The backplane BP has a glass substrate 101, a silicon oxide film 102, a wiring 103, an organic insulating film 104, a contact hole 105, a wiring 106, a wiring 107, a silicon nitride film 108, a contact hole 109, a contact hole 110, an electrode 111, an electrode 112, and a bump electrode 113.
[0049] In FIG. 3, a silicon oxide film 102 is formed on the glass substrate 101. A wiring 103 is formed on the silicon oxide film 102. The wiring 103 is composed of, for example, a "TAT film" which is a laminated film of a titanium film, an aluminum film, and a titanium film in order from the lower layer.
[0050] Also, an organic insulating film 104 is formed on the silicon oxide film 102. The organic insulating film 104 is composed of, for example, an acrylic resin or an epoxy resin. The organic insulating film 104 covers the wiring 103.
[0051] A contact hole 105 is formed in the organic insulating film 104. A portion of the wiring 103 is exposed from the bottom of the contact hole 105. Wiring 106 is formed from inside the contact hole 105 and extending onto the organic insulating film 104. Wiring 107 is also formed on the organic insulating film 104. At the bottom of the contact hole 105, wiring 106 is connected to wiring 103.
[0052] A silicon nitride film 108 is formed on the organic insulating film 104. The silicon nitride film 108 covers the wiring 106 and wiring 107. Contact holes 109 and 110 are formed in the silicon nitride film 108. Part of the wiring 106 is exposed from the bottom of contact hole 109. On the other hand, part of the wiring 107 is exposed from the bottom of contact hole 110.
[0053] Electrodes 111 are formed inside the contact hole 109 and on the silicon nitride film 108. At the bottom of the contact hole 109, the electrodes 111 are connected to the wiring 106. The electrodes 111 are made of, for example, a translucent material such as ITO.
[0054] In contrast, electrodes 112 are formed inside the contact hole 110 and on the silicon nitride film 108. At the bottom of the contact hole 110, the electrodes 112 are connected to the wiring 107. The electrodes 112 are made of, for example, ITO. Bump electrodes 113 are formed on the electrodes 112.
[0055] An LED element 114 is positioned on the bump electrode 113.
[0056] The LED element 114 has, for example, a "reverse tapered shape". In other words, the LED element 114 has an upper surface US1, a lower surface BS located on the opposite side of the upper surface US1, and side surfaces SS1 and SS2 that are in contact with the upper surface US1 and the lower surface BS, and in cross-sectional view, the length of the upper surface US1 is greater than the length of the lower surface BS. Here, the anode electrode 115 of the LED element 114 is connected to the bump electrode 113. Therefore, the anode electrode 115 is electrically connected to the electrode 112 via the bump electrode 113.
[0057] An insulating film 117 is formed on the backplane BP. The insulating film 117 is made of, for example, acrylic resin or epoxy resin. The insulating film 117 is in contact with the side surfaces SS1 and SS2 of the LED element 114. Contact holes 118 are formed in the insulating film 117. A part of the electrode 111 is exposed from the bottom of the contact holes 118. In this embodiment 1, a white pigment is added to the insulating film 117. Therefore, the insulating film 117 is a white insulating film.
[0058] Wiring 120 is formed inside the contact hole 118 and on the insulating film 117. At the bottom of the contact hole 118, the wiring 120 is connected to the electrode 111. The wiring 120 is also connected to the cathode electrode 116 of the LED element 114. Therefore, the cathode electrode 116 is electrically connected to the electrode 111 via the wiring 120.
[0059] The display device 100 in Embodiment 1 is configured as described above.
[0060] <<Features of Embodiment 1>> A feature of Embodiment 1 is that the insulating film 117 is made from a white insulating film. That is, the insulating film 117 that is in contact with the sides SS1 and SS2 of the LED element 114 has, for example, a white pigment added to it, and the insulating film 117 is made from a white insulating film. White insulating films have a high reflectivity of light (visible light). As a result, the light that is about to be emitted from each of the sides SS1 and SS2 of the LED element 114 is efficiently reflected by the white insulating film 117 that is in contact with the sides SS1 and SS2 of the LED element 114. As a result, the reflected light changes its direction of travel upward and is emitted towards the display surface.
[0061] In this way, Embodiment 1 embodies the basic idea of changing the direction of the light that is about to be emitted from each of the sides SS1 and SS2 of the LED element 114, so that this light is emitted from the top surface (display side). Therefore, according to Embodiment 1, by constructing the insulating film 117 from a white insulating film, the light that is about to be emitted from each of the sides SS1 and SS2 of the LED element 114 can be effectively utilized. In other words, according to Embodiment 1, the light emitted from the LED element 114 can be utilized efficiently.
[0062] <<Method of Manufacturing the Display Device>> Next, the method of manufacturing the display device 100 in Embodiment 1 will be described.
[0063] As shown in Figure 4, a backplane BP is prepared. The backplane BP has a glass substrate 101, a silicon oxide film 102, wiring 103, an organic insulating film 104, contact holes 105, wiring 106, wiring 107, a silicon nitride film 108, contact holes 109, contact holes 110, electrodes 111, electrodes 112, and bump electrodes 113.
[0064] Next, as shown in Figure 5, an LED element 114 is placed on the bump electrode 113 of the backplane BP. The LED element 114 has an anode electrode 115 formed on its lower surface BS and a cathode electrode 116 formed on its upper surface US1. By placing the LED element 114 on the bump electrode 113, the anode electrode 115 is electrically connected to electrode 112 via the bump electrode 113.
[0065] Subsequently, as shown in Figure 6, an insulating film 117 is applied to the backplane BP. In particular, the insulating film 117 is formed so that its upper surface US2 is flush with the upper surface US1 of the LED element 114. As a result, the cathode electrode 116 is exposed from the insulating film 117. The insulating film 117 can be made of, for example, an acrylic resin with a white pigment added or an epoxy resin with a white pigment added. Therefore, the insulating film 117 is a white insulating film.
[0066] Then, as shown in Figure 7, contact holes 118 are formed in the insulating film 117 using photolithography and etching techniques. The contact holes 118 are formed to reach the electrode 111.
[0067] Next, as shown in Figure 8, wiring 120 is formed inside the contact hole 118 and on the insulating film 117, for example, by using a sputtering method. The wiring 120 is made of a translucent conductive film. For example, the translucent conductive film is an ITO film. Here, at the bottom of the contact hole 118, the wiring 120 is connected to the electrode 111. The wiring 120 is also connected to the cathode electrode 116 of the LED element 114. Therefore, the cathode electrode 116 is electrically connected to the electrode 111 via the wiring 120.
[0068] As described above, the display device 100 in Embodiment 1 can be manufactured.
[0069] <<Modification 1>> As described above, composing the insulating film 117 from a white insulating film is useful in that it changes the direction of the light that is about to be emitted from the sides SS1 and SS2 of the LED element 114, and makes it possible to emit this light from the top surface US1.
[0070] However, using a white insulating film as the insulating film 117 may reduce the contrast on the display surface. This is because a white insulating film has a high reflectivity, making it difficult to create dark areas of contrast.
[0071] Therefore, it is desirable to provide a light-shielding film 130 on the wiring 120, for example, as shown in Figure 9. Figure 9 is a diagram of the display device 100A in modified example 1. In Figure 9, a light-shielding film 130 is provided on the wiring 120.
[0072] The light-shielding film 130 has an opening OP that opens above the LED element 114. As a result, the light emitted from the LED element 114 towards the display surface is not blocked by the light-shielding film 130, but passes through the opening OP and is emitted towards the display surface. On the other hand, the light-shielding film 130 is formed above the insulating film 117, which is made of a white insulating film, except for the opening OP.
[0073] As a result, according to Modification 1, even when a white insulating film is used, the light-shielding film 130 makes it easier to create dark areas, thus improving contrast.
[0074] Thus, from the viewpoint of improving contrast, a light-shielding film 130 having an opening OP that opens above the LED element 114 may be provided on the wiring 120. The light-shielding film 130 can be made of a metal film such as chromium (Cr), and can be formed by a sputtering method or the like.
[0075] <<Modification 2>> Figure 10 shows the display device 100B in Modification 2.
[0076] In Figure 10, the insulating film 117 is, for example, a white anisotropic conductive film or a white nonconductive film. This eliminates the need to form a bump electrode between the anode electrode 115 and electrode 112 of the LED element 114. For example, in the display device 100 (see Figure 3) in which a bump electrode 113 is formed, the thickness of the insulating film 117 is about 2 μm to 3 μm. In contrast, in the display device 100B (see Figure 10) in which a bump electrode is not formed, the thickness of the insulating film 117 is about 1 μm to 1.5 μm. In other words, by constructing the insulating film 117 from a white anisotropic conductive film or a nonconductive film, the thickness of the insulating film 117 can be reduced.
[0077] For example, as shown in Figure 10, when the insulating film 117 is made of a white anisotropic conductive film or a nonconductive film, the upper surface of the insulating film 117 may be lower than the upper surface of the LED element 114.
[0078] An "anisotropic conductive film" is a film in which conductive particles are dispersed in a resin. When an anisotropic conductive film is heat-pressed, it exhibits conductivity in the direction of pressure (vertical direction) at the pressure-pressed area. Conversely, it exhibits insulating properties in the direction perpendicular to the pressure direction (plane direction). In other words, anisotropic conductive films exhibit "electrical anisotropy." In an anisotropic conductive film, conductive paths are formed between electrodes in the pressure direction as the conductive particles are crushed and come into contact. On the other hand, conductive particles that are not crushed remain dispersed in the resin, so insulating properties are maintained between them and adjacent electrodes in the planar direction.
[0079] Therefore, when the insulating film 117 is made of a white anisotropic conductive film, when the LED element 114 is placed on the electrode 112, pressure is applied to the portion of the anisotropic conductive film interposed between the electrode 112 and the anode electrode 115, resulting in this portion of the anisotropic conductive film being conductive. As a result, the electrode 112 is electrically connected to the anode electrode 115 via the anisotropic conductive film. In other words, by using an anisotropic conductive film, the electrode 112 and the anode electrode 115 can be electrically connected without providing bump electrodes. On the other hand, no pressure is applied to the other parts of the insulating film 117. As a result, the other parts of the anisotropic conductive film maintain their insulating properties.
[0080] From the above, according to Modification 2, by composing the insulating film 117 from a white anisotropic conductive film or a white nonconductive film, the light that is about to be emitted from the side SS1 and side SS2 of the LED element 114 can be effectively utilized, and the need to form bump electrodes is eliminated, thus simplifying the manufacturing process of the display device 100B.
[0081] <Embodiment 2> <<Configuration of the display device>> Figure 11 is a cross-sectional view showing the main configuration of the display device 200 in Embodiment 2.
[0082] The configuration of the display device 200 in Embodiment 2 shown in Figure 11 is substantially the same as, for example, the configuration of the display device 100 in Embodiment 1 shown in Figure 3.
[0083] In the display device 200, as shown in Figure 11, an insulating film 117a is formed that is in contact with the side surfaces SS1 and SS2 of the LED element 114, and an insulating film 117b is formed that is away from the LED element 114 and in contact with the insulating film 117a. The refractive index of the insulating film 117a is smaller than that of the LED element 114. For example, the refractive index of the insulating film 117a is less than 1.4. Also, the refractive index of the insulating film 117a is smaller than that of the insulating film 117b.
[0084] <<Features of Embodiment 2>> The feature of Embodiment 2 is that the refractive index of the insulating film 117a in contact with the sides SS1 and SS2 of the LED element 114 is made smaller than the refractive index of the LED element 114 so as to reflect the light that is about to be emitted from the sides SS1 and SS2 of the LED element 114. As a result, as shown in Figure 11, the light that is about to be emitted from the sides SS1 and SS2 of the LED element 114 is reflected at the boundary between the insulating film 117a and the sides (SS1, SS2) of the LED element 114, and the reflected light changes its direction of travel upward and is emitted towards the display surface.
[0085] In this way, according to Embodiment 2, by utilizing reflection, the basic idea of changing the direction of the light that is about to be emitted from the sides SS1 and SS2 of the LED element 114 and causing this light to be emitted from the top surface (display side) can be realized.
[0086] Therefore, according to Embodiment 2, by making the refractive index of the insulating film 117a in contact with the sides (SS1, SS2) of the LED element 114 smaller than the refractive index of the LED element 114, so as to reflect the light that is about to be emitted from each of the sides SS1 and SS2 of the LED element 114, the light that is about to be emitted from each of the sides SS1 and SS2 of the LED element 114 can be effectively utilized. In other words, according to Embodiment 2, the light emitted from the LED element 114 can be efficiently utilized.
[0087] In particular, from the viewpoint of improving the reflection efficiency at the boundary between the insulating film 117a and the side surfaces (SS1, SS2) of the LED element 114, it is desirable to make the refractive index of the insulating film 117a smaller than that of the LED element 114 so that the conditions for total internal reflection are satisfied.
[0088] Furthermore, in order to efficiently generate total internal reflection, it is desirable that the LED element 114 has a "reverse tapered shape," as shown in Figure 11, for example. In other words, the LED element 114 has an upper surface US1, a lower surface BS located on the opposite side of the upper surface US1, and side surfaces SS1 and SS2 that are in contact with the upper surface US1 and the lower surface BS, and in cross-sectional view, it is desirable that the length of the upper surface US1 is greater than the length of the lower surface BS.
[0089] Furthermore, in Embodiment 2, considering that some light may not be totally reflected, it is desirable that the insulating film 117a be made of a film with high reflectivity in order to change the direction of propagation of the light that was not totally reflected upwards and emit it towards the display surface. Specifically, it is desirable that the insulating film 117a be made of a white insulating film.
[0090] <<Manufacturing Method for Display Device>> The manufacturing method for the display device 200 in Embodiment 2 is substantially the same as the manufacturing method for the display device 100 in Embodiment 1. Specifically, the steps shown in Figures 4 and 5 are the same as in Embodiment 1. After that, an insulating film 117a is applied to the backplane BP. Then, as shown in Figure 12, the insulating film 117a is patterned using photolithography and etching techniques. As a result, the insulating film 117a is formed to be in contact with the LED element 114. Next, an insulating film 117b is applied to the backplane BP. Then, as shown in Figure 13, the insulating film 117b is patterned using photolithography and etching techniques. As a result, the insulating film 117b is formed to be in contact with the insulating film 117a, away from the LED element 114.
[0091] The subsequent steps are the same as in Embodiment 1.
[0092] In this way, the display device 200 in Embodiment 2 can be manufactured.
[0093] The present invention has been described in detail above based on its embodiments, but it goes without saying that the present invention is not limited to the above embodiments and can be modified in various ways without departing from its essence.
[0094] Within the scope of the concept of the present invention, a person skilled in the art can conceive of various modifications and alterations, and it is understood that such modifications and alterations also fall within the scope of the present invention. For example, any addition, deletion, or design change of components, or addition, omission, or modification of processes, made by a person skilled in the art to the above-described embodiments, is also included within the scope of the present invention, as long as it retains the gist of the present invention.
[0095] Furthermore, any other effects and advantages brought about by the embodiments described herein that are clear from the description herein or that can be appropriately conceived by a person skilled in the art are naturally considered to be brought about by the present invention.
[0096] 5 Control circuit 6 Drive circuit 10 Substrate 20 LED element 20EA Anode electrode 20EC Cathode electrode BCT Output transistor BP Backplane Cad Auxiliary capacitance Cs Holding capacitance DA Display area DRT Drive transistor DSP1 Display device GLB Scan signal line GLR Scan signal line GLS Scan signal line Grs Control signal line Gsb Control signal line Gss Control signal line OP Aperture PFA Peripheral area PIX Pixel PIXA Pixel PIXB Pixel PIXC Pixel PL1 Power line PL2 Power line Pvdd High potential Pvss Low potential RSL Reset wiring RST Reset transistor SST Pixel selection transistor 100 Display device 100A Display device 100B Display device 101 Glass substrate 102 Silicon oxide film 103 Wiring 104 Organic insulating film 105 Contact hole 106 Wiring 107 Wiring 108 Silicon nitride film 109 Contact hole 110 Contact hole 111 Electrode 112 Electrode 113 Bump electrode 114 LED element 115 Anode electrode 116 Cathode electrode 117 Insulating film 117a Insulating film 117b Insulating film 118 Contact hole 120 Wiring 130 Light-shielding film 200 Display device
Claims
1. A display device comprising: a backplane having a first electrode and a second electrode; a light-emitting diode element disposed on the second electrode; and a white insulating film in contact with the side surface of the light-emitting diode element.
2. In the display device according to claim 1, the insulating film is an anisotropic conductive film or a nonconductive film.
3. In the display device according to claim 1, the light-emitting diode element has an upper surface, a lower surface located opposite to the upper surface, and a side surface in contact with the upper surface and the lower surface, wherein in a cross-sectional view, the length of the upper surface is greater than the length of the lower surface.
4. In the display device according to claim 1, the upper surface of the insulating film is at the same height as or lower than the upper surface of the light-emitting diode element.
5. In the display device according to claim 1, the light-emitting diode element has an upper electrode electrically connected to the first electrode and a lower electrode electrically connected to the second electrode.
6. In the display device according to claim 5, the insulating film has a contact hole reaching the first electrode, a translucent conductive film is formed inside the contact hole and on the upper surface of the insulating film, the translucent conductive film is connected to the upper electrode, and the upper electrode is electrically connected to the first electrode via the translucent conductive film.
7. The display device according to claim 6, wherein the display device includes a light-shielding film formed on the light-transmitting conductive film, the light-shielding film having an opening that opens above the light-emitting diode element.
8. A display device comprising: a backplane having a first electrode and a second electrode; a light-emitting diode element disposed on the second electrode; a first insulating film in contact with the side surface of the light-emitting diode element; and a second insulating film away from the light-emitting diode element and in contact with the first insulating film, wherein the refractive index of the first insulating film is smaller than that of the light-emitting diode element.
9. In the display device according to claim 8, the refractive index of the first insulating film is less than 1.
4.
10. In the display device according to claim 8, the light-emitting diode element has an upper surface, a lower surface located opposite to the upper surface, and a side surface in contact with the upper surface and the lower surface, wherein in a cross-sectional view, the length of the upper surface is greater than the length of the lower surface.