JP7741521B2 - Display panel - Google Patents

Description

This disclosure relates to a display panel equipped with multiple micro LEDs (Light Emitting Diodes) as light-emitting elements.

In recent years, display panels equipped with multiple micro-LEDs have been attracting a great deal of attention as they can be used in a wide range of fields, including AR (Augmented Reality), VR (Virtual Reality), and small to large display devices.

Japanese Patent Publication No. 2023-1062

Patent Document 1 describes an organic EL display device that includes a structure for absorbing or reflecting visible light, which includes a dome-shaped resin layer provided between adjacent light-emitting elements, and a portion of an organic layer (e.g., an electron injection layer) and a portion of a common reflective electrode layer that are continuous layers common to each light-emitting element and are provided along the shape of the dome-shaped resin layer.

However, in the case of the organic EL display device described in Patent Document 1, because it is provided with an organic layer (e.g., an electron injection layer) that is a continuous layer common to each light-emitting element, light emitted from a sub-pixel that includes a lit light-emitting element propagates through the organic layer (e.g., an electron injection layer) that is a continuous layer common to each light-emitting element, and becomes stray light, causing the adjacent sub-pixel that includes an unlit light-emitting element to appear to be emitting light (false lighting).

Furthermore, in the field of display panels equipped with multiple micro-LEDs, a common reflective electrode layer, which is a continuous layer common to each light-emitting element, cannot be provided, which poses the problem that the structure described in Patent Document 1 cannot be formed.

One aspect of the present disclosure aims to provide a display panel that reduces the possibility that light emitted from a lit light-emitting element becomes stray light.

In order to solve the above problems, the display panel of the present disclosure has:
The light-emitting device includes a plurality of light-emitting elements each including an island-shaped laminate composed of a plurality of laminated semiconductor layers including a light-emitting layer, an anode, and a cathode;
A light absorber that absorbs light in the visible light range and contains a material different from the material that constitutes the stack is provided between the island-shaped stacks that each of the plurality of light-emitting elements has.

One aspect of the present disclosure provides a display panel that reduces the possibility that light emitted from a lit light-emitting element becomes stray light.

1 is a cross-sectional view showing a schematic configuration of a display panel according to a first embodiment. 2 is a plan view of a display surface of the display panel shown in FIG. 1. 2A to 2C are diagrams for explaining a method of manufacturing the display panel shown in FIG. 1 . 4 is a diagram for explaining steps S20, S22, and S24 shown in FIG. 3. FIG. FIG. 4 is a diagram for explaining step S26 shown in FIG. 3. FIG. 4 is a diagram for explaining step S28 shown in FIG. 3. FIG. 4 is a diagram for explaining step S30 shown in FIG. 3. 4 is a plan view of the wafer after step S30 shown in FIG. 3 and before step S32 shown in FIG. 3 is performed, as viewed from the side on which the anode and cathode are formed. FIG. FIG. 10 is a cross-sectional view showing a schematic configuration of a display panel of Comparative Example 1. 10A and 10B are diagrams for explaining one of the factors that cause stray light in the display panel of the first embodiment and the display panel of the first comparative example. 11 is a diagram showing a case in which an adjacent sub-pixel including an extinguished light-emitting element is visually perceived as emitting pseudo-light due to stray light generated by the factors shown in FIG. 10 in a display panel of Comparative Example 1. FIG. 10A and 10B are diagrams for explaining another factor that causes stray light in the display panel of the first embodiment and the display panel of the first comparative example. 13 is a diagram showing a case in which an adjacent sub-pixel including an extinguished light-emitting element is visually perceived as emitting pseudo-light due to stray light generated by the factors shown in FIG. 12 in a display panel of Comparative Example 1. FIG. FIG. 10 is a diagram showing the distribution of stray light in a display panel of Comparative Example 1. 1 is a diagram for explaining the distribution of stray light in the display panel of embodiment 1 and the reason why the display panel of embodiment 1 can prevent light emitted from a lit light-emitting element from becoming stray light. FIG. 28 is a diagram showing the distribution of stray light obtained by optical calculation using the display panel of Comparative Example 2 shown in FIG. 27 as a model. FIG. 27 is a diagram showing the distribution of stray light obtained by optical calculation using the display panel of the second embodiment shown in FIG. 26 as a model, which includes a light absorber having a refractive index of 2.47 and a transmittance of 0.9. FIG. 27 is a diagram showing the distribution of stray light obtained by optical calculation using the display panel of the second embodiment shown in FIG. 26 as a model, which includes a light absorber having a refractive index of 2.47 and a transmittance of 0.7. FIG. 27 is a diagram showing the distribution of stray light obtained by optical calculation using the display panel of the second embodiment shown in FIG. 26 as a model, which includes a light absorber having a refractive index of 2.47 and a transmittance of 0.3. FIG. 27 is a diagram showing the distribution of stray light obtained by optical calculation using the display panel of the second embodiment shown in FIG. 26 as a model, which includes a light absorber having a refractive index of 2.47 and a transmittance of 0.1. FIG. 27 is a diagram showing the distribution of stray light obtained by optical calculation using the display panel of the second embodiment shown in FIG. 26 as a model, which includes a light absorber having a refractive index of 1.5 and a transmittance of 1. FIG. 27 is a diagram showing the distribution of stray light obtained by optical calculation using the display panel of the second embodiment shown in FIG. 26 as a model, which includes a light absorber having a refractive index of 3.47 and a transmittance of 1. FIG. 27 is a diagram showing the distribution of stray light obtained by optical calculation using the display panel of the second embodiment shown in FIG. 26 as a model, which includes a light absorber having a refractive index of 3.47 and a transmittance of 0.3. FIG. 2 is a cross-sectional view showing a schematic configuration of another display panel according to the first embodiment. FIG. 10 is a cross-sectional view showing a schematic configuration of still another display panel according to the first embodiment. FIG. 10 is a cross-sectional view showing a schematic configuration of a display panel according to a second embodiment. FIG. 10 is a cross-sectional view showing a schematic configuration of a display panel of Comparative Example 2. 28 is a diagram showing the distribution of stray light in the H1 direction shown in FIG. 2 in the display panel of the second embodiment shown in FIG. 26 and the display panel of the second comparative example shown in FIG. 27. FIG. 28 is a diagram showing the distribution of stray light in the H2 direction shown in FIG. 2 in the display panel of the second embodiment shown in FIG. 26 and the display panel of the second comparative example shown in FIG. 27. FIG. FIG. 10 is a cross-sectional view showing a schematic configuration of a display panel according to a third embodiment. FIG. 10 is a cross-sectional view showing a schematic configuration of a display panel of Comparative Example 3.

The following describes an embodiment of the present disclosure with reference to Figures 1 to 31. For the sake of convenience, components having the same functions as those described in specific embodiments will be denoted by the same reference numerals, and their description may be omitted.

[Embodiment 1]
Fig. 1 is a cross-sectional view showing a schematic configuration of a display panel 1 of embodiment 1. Note that anodes A1 to A3, cathodes K1 to K3, and insulating film PF are not shown in Fig. 1.

The display panel 1 shown in FIG. 1 includes an island-shaped laminate 11 composed of multiple stacked semiconductor layers including a light-emitting layer E1, a light-emitting element D1 including an anode A1 and a cathode K1, an island-shaped laminate 12 composed of multiple stacked semiconductor layers including light-emitting layers E1-E2, a light-emitting element D2 including an anode A2 and a cathode K2, an island-shaped laminate 13 composed of multiple stacked semiconductor layers including light-emitting layers E1-E3, and a light-emitting element D3 including an anode A3 and a cathode K3. Between the island-shaped laminates 11-13 included in each of the multiple light-emitting elements D1-D3, a light absorber LA that absorbs light in the visible light range is provided. The light absorber LA contains a material different from the material constituting the laminates 11-13.

In this embodiment, the light-emitting element (first light-emitting element) D1 is a blue light-emitting element that includes an island-shaped laminate 11 made up of multiple stacked semiconductor layers including a blue light-emitting layer E1, and emits blue light L1 from the light-emitting layer E1; the light-emitting element (second light-emitting element) D2 is a green light-emitting element that includes an island-shaped laminate 12 made up of multiple stacked semiconductor layers including a green light-emitting layer E2 and a light-emitting layer E1 that does not emit light; and the light-emitting element (third light-emitting element) D3 is a red light-emitting element that includes an island-shaped laminate 13 made up of multiple stacked semiconductor layers including a red light-emitting layer E3 and light-emitting layers E1 and E2 that do not emit light; and emits red light L3 from the light-emitting layer E3; however, the present invention is not limited to this example.

Figure 2 is a plan view of the display surface SM of the display panel 1 shown in Figure 1.

In this embodiment, as shown in FIG. 2, for example, one pixel PI includes a red subpixel RSUB, a green subpixel GSUB, and a blue subpixel BSUB, and the blue subpixel BSUB includes a light-emitting element (first light-emitting element) D1 that is a blue light-emitting element, the green subpixel GSUB includes a light-emitting element (second light-emitting element) D2 that is a green light-emitting element, and the red subpixel RSUB includes a light-emitting element (third light-emitting element) D3 that is a red light-emitting element. However, this is not limited to this, and for example, one pixel PI may further include subpixels of colors other than the red subpixel RSUB, green subpixel GSUB, and blue subpixel BSUB.

The light-emitting elements D1 to D3 shown in FIG. 1 are isolated from one another, allowing light emission to be controlled in subpixel units as shown in FIG. 2. In this embodiment, a display panel 1 is described as an example in which multiple monolithic wafers each having multiple light-emitting elements D1 to D3 emitting different colors are manufactured on a single growth substrate SK (e.g., a C-plane sapphire substrate), and the multiple wafers are aligned on a single drive substrate DK by wafer-by-wafer bonding via a conductive adhesive layer JC. However, this is not limiting. For example, as in the display panel 2 of embodiment 2 described below, multiple monolithic wafers each having multiple light-emitting elements D1' emitting the same color are manufactured on a single growth substrate SK, and the multiple wafers are aligned on a single drive substrate DK by wafer-by-wafer bonding via a conductive adhesive layer JC. Furthermore, as in the display panel 3 of the third embodiment described later, multiple chips each including a blue light-emitting element D1′, a green light-emitting element D2′, and a red light-emitting element D3′ may be manufactured, and the chips may be aligned on a single drive substrate DK and bonded to the drive substrate DK via a conductive adhesive layer JC. The display panels 1, 1a, and 1b described in this embodiment and the display panel 3 described in the third embodiment are display panels including multiple light-emitting elements that emit light of different colors. Therefore, by using a single display panel, it is possible to realize, for example, augmented reality (AR), virtual reality (VR), and small to large color display devices. On the other hand, the display panel 2 described in the second embodiment is a monochromatic display panel including multiple light-emitting elements that emit light of a single color. Therefore, by using three display panels, including a red monochromatic display panel, a green monochromatic display panel, and a blue monochromatic display panel, and optical components such as mirrors, it is possible to realize, for example, augmented reality (AR), virtual reality (VR), and small to large color display devices.

The manufacturing process for the display panel 1 of this embodiment will be described below with reference to Figures 3 to 7.

Figure 3 is a diagram for explaining the manufacturing method of the display panel 1 shown in Figure 1. Figure 4 is a diagram for explaining steps S20, S22, and S24 shown in Figure 3. Figure 5 is a diagram for explaining step S26 shown in Figure 3. Figure 6 is a diagram for explaining step S28 shown in Figure 3. Figure 7 is a diagram for explaining step S30 shown in Figure 3.

In step S20 shown in Figure 3, "growing a semiconductor crystal on a growth substrate," as shown in Figure 4, a semiconductor crystal SL is epitaxially grown on a growth substrate SK (e.g., a C-plane sapphire substrate) using an MOCVD apparatus or the like. The semiconductor crystal SL may be, for example, a nitride semiconductor crystal. Examples of nitride semiconductors include GaN-based semiconductors, as well as AlN (aluminum nitride) and InN (indium nitride).

As shown in FIG. 4, step S20 of forming the semiconductor crystal SL includes a first step of forming, in this order, a buffer layer BA, an underlayer U1, a cathode contact layer C1, an emission layer E1, an intermediate layer G1, a p-type layer H1, a tunnel junction layer T1, and an anode contact layer F1; a second step of forming, in this order, an underlayer U2, a cathode contact layer C2, an emission layer E2, an intermediate layer G2, a p-type layer H2, a tunnel junction layer T2, and an anode contact layer F2; and a third step of forming, in this order, an underlayer U3, a cathode contact layer C3, an emission layer E3, an intermediate layer G3, a p-type layer H3, a tunnel junction layer T3, and an anode contact layer F3. Each of the first to third steps described above can be performed sequentially, for example, in an MOCVD apparatus.

The buffer layer BA may be gallium nitride crystal (e.g., 40 nm thick) formed at a low temperature (e.g., below 600°C). The underlayers U1, U2, and U3 may be undoped gallium nitride crystal (e.g., 2 μm thick). The cathode contact layers C1, C2, and C3 may be n-type gallium nitride crystal (e.g., 2 μm thick). The light-emitting layers E1, E2, and E3 may be active layers with an MQW (multiple quantum well) structure. For example, the light-emitting layer E1, which emits blue light with a wavelength of approximately 450 nm, may be made of indium gallium nitride (mixed crystal with an In:Ga atomic ratio of 1:4) with a thickness of 50 nm and a 20% In (indium) composition. For example, the light-emitting layer E2, which emits green light with a wavelength of approximately 550 nm, may be made of indium gallium nitride (mixed crystal) with a 25% In composition. For example, an indium gallium nitride (mixed crystal) with an In composition ratio of 30% can be used as the light-emitting layer E3, which emits red light with a wavelength of approximately 630 nm. The intermediate layers G1, G2, and G3 may be p-type aluminum gallium nitride crystals (e.g., 20 nm thick). The p-type layers H1, H2, and H3 may be p-type gallium nitride crystals (e.g., 120 nm thick). The tunnel junction layers T1, T2, and T3 may be undoped gallium nitride crystals (e.g., 25 nm thick). The anode contact layers F1, F2, and F3 may be n-type gallium nitride crystals (e.g., 400 nm thick).

In step S22 shown in Figure 3, "The semiconductor crystal is patterned by etching to expose the anode contact layer and cathode contact layer," the semiconductor crystal SL is patterned by dry etching, as shown in Figure 4, to expose the cathode contact layers C1, C2, and C3 and the anode contact layers F1, F2, and F3. In this step, resist or an inorganic film patterned by lift-off (such as a silicon oxide film or nickel film) can be used as the etching mask. Reactive ion etching (RIE) using a halogen such as chlorine or fluorine can be used for dry etching. The etching mask is then removed using a remover, acidic solution, or the like.

In step S24 shown in Figure 3, "anodes are formed on the anode contact layer and cathodes are formed on the cathode contact layer simultaneously," as shown in Figure 4. Anodes A1, A2, and A3 are formed on the anode contact layers F1, F2, and F3, respectively, while cathodes K1, K2, and K3 are formed on the cathode contact layers C1, C2, and C3, respectively. Specifically, a vapor-deposited electrode material (e.g., a laminated film of aluminum and titanium) is patterned by lift-off using a resist as a mask.

In step S26 shown in FIG. 3, "Patterning the semiconductor crystal by etching to form stacks," the semiconductor crystal SL was patterned by dry etching to form island-shaped stacks 11, 12, and 13, as shown in FIG. 5. Here, areas other than those for element isolation were protected with resist, and the portions of the semiconductor crystal SL between elements were completely removed using, for example, a halogen-based RIE method, so that the growth substrate SK was exposed between the elements. The growth substrate SK itself may also be etched to form irregularities on the growth substrate SK. In this embodiment, for good electrical and optical element isolation, etching was performed to expose the surface of the growth substrate SK, and island-shaped stacks 11, 12, and 13 were formed on the growth substrate SK. Each of the island-shaped stacks 11, 12, and 13 has a sidewall W.

In step S28 of FIG. 3, "forming an insulating film covering the sidewalls of each stack," as shown in FIG. 6, an insulating film PF is formed covering the sidewalls W of each of the island-shaped stacks 11, 12, and 13, resulting in light-emitting elements D1, D2, and D3. Here, a mask covering the anodes A1, A2, and A3 and the cathodes K1, K2, and K3 is formed by photolithography or other methods, and then silicon oxide is formed by electron beam evaporation to cover the sidewalls W, forming the insulating film PF. The insulating film PF functions to prevent short circuits between elements and oxidation. While this embodiment describes a case where the insulating film PF is a silicon oxide film, this is not limited thereto. The insulating film PF may be a film containing any of a silicon oxide film, a silicon nitride film, a silicon oxynitride film, and an aluminum oxide film. Furthermore, the insulating film PF is preferably formed to a thickness of 3 nm or more and 100 nm or less in the direction perpendicular to the sidewalls W of the island-shaped stacks 11, 12, and 13. When an insulating film PF is formed to cover the sidewalls W of each of the island-shaped stacks 11, 12, and 13, as in this embodiment, the range of materials that can be used for the light absorber LA (described later) is broader. That is, when the insulating film PF is formed, a conductive material may be selected as the material for the light absorber LA. Note that, if a highly insulating material is selected as the material for the light absorber LA, step S28 shown in FIG. 3 may be omitted.

In step S30 shown in Figure 3, where a light absorber is formed between the laminates, as shown in Figures 1 and 7, the light absorber LA may be formed, for example, to a height corresponding to the thickness from the display surface DM-side surface of the buffer layer BA, which is the semiconductor layer closest to the display surface DM, which is the surface from which light from the light-emitting layers E1, E2, and E3 is emitted, to the display surface DM-side surface of the light-emitting layer E1, which is closest to the display surface DM. In this embodiment, an example is given in which the light absorber LA is formed to a height corresponding to the thickness from the display surface DM-side surface of the buffer layer BA to the display surface DM-side surface of the light-emitting layer E1, but this is not limited to this.

Figure 24 is a cross-sectional view showing the schematic configuration of another display panel 1a according to embodiment 1. Figure 25 is a cross-sectional view showing the schematic configuration of yet another display panel 1b according to embodiment 1. The display panel 1a shown in Figure 24 includes light-emitting elements D1, D2, and D3. Light-emitting element D1 includes, as an island-shaped laminate 11, a first laminate including a light-emitting layer E1 (buffer layer BA, base layer U1, cathode contact layer C1, light-emitting layer E1, intermediate layer G1, p-type layer H1, tunnel junction layer T1, and anode contact layer F1). Light-emitting element D2 includes, as an island-shaped laminate 12, the first laminate and a second laminate including a light-emitting layer E2 disposed farther from the display surface DM than the first laminate (base layer U2, cathode contact layer C2, light-emitting layer E2, intermediate layer G2, p-type layer H2, tunnel junction layer T2, and anode contact layer F2). The light-emitting element D3 includes, as an island-shaped laminate 13, the first laminate, the second laminate, and a third laminate (base layer U3, cathode contact layer C3, light-emitting layer E3, intermediate layer G3, p-type layer H3, tunnel junction layer T3, and anode contact layer F3) including a light-emitting layer E3 provided farther from the display surface DM than the second laminate. The light absorber LA may be formed to a height equal to or less than the thickness from the display surface DM-side surface of the buffer layer BA, which is the semiconductor layer closest to the display surface DM, to the display surface DM-side surface of the light-emitting layer E3. In the display panel 1a, the light absorber LA is formed to a height corresponding to the thickness from the display surface DM-side surface of the buffer layer BA, which is the semiconductor layer closest to the display surface DM, to the display surface DM-side surface of the light-emitting layer E3. This is not limiting, and as in the display panel 1b shown in Figure 25, the light absorber LA may be filled so as to completely fill the spaces between the island-shaped laminates 11, 12, and 13 provided in each of the multiple light-emitting elements D1, D2, and D3.

As the light absorber LA, an organic compound or an inorganic compound can be used, and for example, a compound having a molecular structure including a pyridine skeleton may be used. In this embodiment, an insulating compound, for example, a black dye called black dye shown in the following (Chemical Formula 1) (trade name: N749, substance name: Ruthenium 620, Tris(N,N,N-tributyl-1-butanaminium)[[2,2'6',2''-terpyridine]-4,4',4''-tricarboxylato(3-)-N1,N1',N1']tris(thiocyanato-N)hydrogen ruthenate(4-)) was used as the light absorber LA. The molar absorbance in the visible light region of the black dye shown in the following (Chemical Formula 1) is 3 x 10 ^-3 to 7 x 10 ^-3 (1/M cm), and the molecular structure of the black dye shown in the following (Chemical Formula 1) includes three pyridine skeletons to which nitrogen and multiple functional groups are bonded. In addition, when an organic compound is used as the light absorber LA as in this embodiment, even if the anodes A1, A2, and A3 and the cathodes K1, K2, and K3 are covered with the light absorber LA during the process, the light absorber LA on the anodes A1, A2, and A3 and the cathodes K1, K2, and K3 can be oxidized and removed by ashing while protecting the element surface with a metal mask having openings in the anodes A1, A2, and A3 and cathodes K1, K2, and K3 portions.

The light absorber LA may contain one or more materials selected from modified acrylic resins, epoxy resins, urethane resins, cyanoacrylate resins, fluoroethylene resins, silicone resins, polyvinyl alcohol (PVA), and polyvinyl chloride (PVC). The light absorber LA may also contain one or more materials selected from azo dyes, quinone dyes, indigo dyes, polymethine dyes, styryl dyes, azo pigments, quinone pigments, indigo pigments, polymethine pigments, and styryl pigments. Furthermore, the light absorber LA may also contain one or more materials selected from carbon materials, metal sulfides, and semiconductor materials that absorb light in the visible light region.

In step S32 shown in Figure 3, "Mounting Light-Emitting Elements (First to Third Light-Emitting Elements) on a Drive Substrate," as shown in Figure 1, light-emitting elements D1, D2, and D3 are mounted on a drive substrate DK, which includes a drive circuit, via a conductive adhesive layer JC to obtain a display panel 1. The conductive adhesive layer JC can be made of solder or an anisotropic conductive adhesive. The display panel 1 shown in Figures 1 and 7 is configured so that holes from the anodes A1, A2, and A3 tunnel into the p-type layers H1, H2, and H3 via the n-type semiconductor anode contact layers F1, F2, and F3 and the tunnel junction layers T1, T2, and T3. This configuration allows the anodes A1, A2, and A3 and the cathodes K1, K2, and K3 to be simultaneously formed using the same material, simplifying the process compared to the typical method of forming the anodes and cathodes using different processes and materials. Another advantage is that the p-type (semiconductor) layer, which is prone to becoming highly resistive due to dry etching and mechanical polishing, does not need to be exposed, thereby stabilizing the electrical characteristics of the light-emitting device. After step S32 shown in FIG. 3, a step of peeling the growth substrate SK from the island-shaped stacks 11, 12, 13, the insulating film PF, and the light absorber LA by a laser lift-off method or the like may be performed to remove the growth substrate SK.

Figure 8 is a plan view of the wafer after step S30 shown in Figure 3 and before step S32 shown in Figure 3 is performed, viewed from the side on which the anode and cathode are formed.

In this embodiment, as shown in Figure 8, the island-shaped laminate 11 provided in light-emitting element D1, the island-shaped laminate 12 provided in light-emitting element D2, and the island-shaped laminate 13 provided in light-emitting element D3 each have a size of 20 μm x 120 μm in a planar view, and the laminates 11, 12, and 13 are each spaced 10 μm apart. However, this is not limited to this example.

9 is a cross-sectional view showing a schematic configuration of a display panel 51 of Comparative Example 1. FIG. 10 is a diagram illustrating one of the factors that cause stray light in the display panel 1 of Embodiment 1 and the display panel 51 of Comparative Example 1. FIG. 11 is a diagram illustrating a case in which stray light caused by the factor shown in FIG. 10 causes adjacent sub-pixels including turned-off light-emitting elements to appear to emit pseudo-light in the display panel 51 of Comparative Example 1. FIG. 12 is a diagram illustrating another factor that causes stray light in the display panel 1 of Embodiment 1 and the display panel 51 of Comparative Example 1. FIG. 13 is a diagram illustrating a case in which stray light caused by the factor shown in FIG. 12 causes adjacent sub-pixels including turned-off light-emitting elements to appear to emit pseudo-light in the display panel 51 of Comparative Example 1. FIG. 14 is a diagram illustrating the distribution of stray light in the display panel 51 of Comparative Example 1. FIG. 15 is a diagram illustrating the distribution of stray light in the display panel 1 of Embodiment 1 and the reason why light emitted from turned-on light-emitting elements can be prevented from becoming stray light in the display panel 1 of Embodiment 1.

The display panel 51 of Comparative Example 1 shown in Figure 9 differs from the display panel 1 of Embodiment 1 only in that it does not include a light absorber LA. As shown in Figures 10 and 11, in the display panel 1 of Embodiment 1 and the display panel 51 of Comparative Example 1, light components emitted from the end faces of the light-emitting layers E1, E2, and E3 that propagate laterally toward adjacent subpixels can be one of the causes of stray light. As shown in Figure 10, the light emitted from the end faces of the light-emitting layers E1, E2, and E3 can be divided into light components with an emission angle θ of 0° or near 0° (less than ±5°) and light components with an emission angle θ of greater than ±5°. As shown in Figure 11, the light components with an emission angle θ of 0° or near 0° (less than ±5°) are components that are perpendicularly incident on the sidewalls of adjacent subpixels. These components are hardly reflected at the element/air and air/element interfaces, propagate while attenuating for relatively long distances, and become broad stray light without a clear peak. The attenuation is due to the semiconductors that make up the element, particularly the light-emitting layer and p-type layer. On the other hand, part of the light component with an emission angle θ greater than ±5° is reflected at the element/air and air/element interfaces, while the remainder propagates while being transmitted. The reflected light heads toward the growth substrate SK or the drive substrate DK, but the component heading toward the drive substrate DK is absorbed by the drive substrate DK and therefore hardly becomes stray light. On the other hand, the component heading toward the growth substrate SK becomes stray light that periodically forms peaks at the sidewalls of the element. As shown in Figures 12 and 13, in the display panel 1 of Embodiment 1 and the display panel 51 of Comparative Example 1, among the light emitted toward the front side (drive substrate DK side) and back side (growth substrate SK side) of the light-emitting layers E1, E2, and E3, light components with an absolute value of the emission angle θ greater than 0°, or generally greater than 5°, are reflected by the electrode on the front side (drive substrate DK side) and directed out of the element at the same emission angle as the incident angle, resulting in stray light with periodic peaks near the sidewalls of the element. On the other hand, light components with an emission angle θ of 0° or generally less than 5° do not constitute stray light. As shown in Figure 14, in the display panel 51 of Comparative Example 1 when only light-emitting element D1 is lit, a periodic stray light distribution corresponding to the arrangement and spacing of light-emitting elements D1, D2, and D3 is observed. In a display panel, stray light can cause image quality degradation, such as reduced contrast, virtual images, and false illumination.

Therefore, in the display panel 1 of this embodiment, the above-described light absorber LA is provided to prevent light emitted from lit light-emitting elements from becoming stray light. Based on Figure 12, light components with an absolute value of the output angle θ greater than 0°, generally greater than 5°, i.e., light components reflected by the front-side electrode (drive substrate DK side) and traveling out of the element at the same output angle as the incident angle, are reflected by the front-side electrode (drive substrate DK side) and incident on the light absorber LA, as shown in Figure 15. Such light components enter at a constant angle in the stacking direction of the light-emitting elements, refract, and change direction. As they propagate vertically through the light absorber LA, they are significantly absorbed and attenuated. Furthermore, stray light that reaches the interface between the light absorber LA and an adjacent light-emitting element is reflected and refracted, then changes direction and propagates, entering the light absorber LA and being attenuated before reaching a nearby light-emitting element. Similarly, light components with an output angle θ of 0° or near 0° (less than ±5°), as described above with reference to Figure 10, are also attenuated in the same way because they enter the light absorber LA at a certain angle. As described above, the display panel 1 of this embodiment, which is equipped with the light absorber LA described above, has the remarkable effect of reducing the intensity of stray light with periodic peaks due to the attenuation and refraction of light components by the light absorber LA.

16 is a diagram showing the distribution of stray light obtained by optical calculation using the display panel 52 of Comparative Example 2 shown in FIG. 27 as a model. FIG. 17 is a diagram showing the distribution of stray light obtained by optical calculation using the display panel 2 of Embodiment 2 shown in FIG. 26 as a model, which includes a light absorber LA having a refractive index of 2.47 and a transmittance of 0.9. FIG. 18 is a diagram showing the distribution of stray light obtained by optical calculation using the display panel 2 of Embodiment 2 shown in FIG. 26 as a model, which includes a light absorber LA having a refractive index of 2.47 and a transmittance of 0.7. FIG. 19 is a diagram showing the distribution of stray light obtained by optical calculation using the display panel 2 of Embodiment 2 shown in FIG. 26 as a model, which includes a light absorber LA having a refractive index of 2.47 and a transmittance of 0.3. FIG. 20 is a diagram showing the distribution of stray light obtained by optical calculation using the display panel 2 of Embodiment 2 shown in FIG. 26 as a model, which includes a light absorber LA having a refractive index of 2.47 and a transmittance of 0.1.

Here, optical models are created for the display panel 52 of Comparative Example 2 shown in Figure 27 and the display panel 2 of Embodiment 2 shown in Figure 26, and examples of the refractive index and transmittance of the light absorber LA that exhibits the desired effect are shown through optical calculations.

As shown in Figure 16, the stray light distribution obtained by optical calculation using the display panel 52 of Comparative Example 2 shown in Figure 27, which does not have a light absorber LA, as a model, shows a stray light distribution with a spike-shaped peak at the sidewall position of the light-emitting element D1', which is consistent with the experimental results shown in Figure 28. Furthermore, the intensity ratio between the light-emitting subpixel shown in Figure 16 and the spike-shaped stray light also closely matches the experimental results shown in Figure 28, confirming that stray light can be calculated by ray tracing if an optical model is constructed accurately.

Figures 17 to 20 each show the distribution of stray light obtained by optical calculation using the display panel 2 of embodiment 2 shown in Figure 26, which includes the light absorber LA, as a model. To confirm the effect of the transmittance of the light absorber LA, the calculation results were shown, where the refractive index of the light absorber LA was fixed at 2.47, the same as that of GaN, and the transmittance was changed to 0.9, 0.7, 0.3, and 0.1. In this case, there is no difference in the refractive index between the semiconductor layer and the light absorber, so stray light is not refracted at the interface. Therefore, when the transmittance of the light absorber LA shown in Figure 17 is 0.9, it can be seen that broad stray light propagating in a direction parallel to the substrate surface is not significantly attenuated. On the other hand, the effect of the transmittance of the light absorber LA is significant. When the transmittance of the light absorber LA shown in Figure 18 is 0.7, it can be seen that the spike-like stray light intensity decreases as the transmittance decreases from 0.9 to 0.7. Furthermore, when the transmittance of the light absorber LA shown in Figure 19 is 0.3, and when the transmittance of the light absorber LA shown in Figure 20 is 0.1, it can be seen that reducing the transmittance to 0.3 or less significantly attenuates not only spike-like stray light but also broad stray light, and that stray light can be suppressed to the point where it is almost localized between the emitting light-emitting element and the adjacent light-emitting element.

Therefore, the transmittance of the light absorber LA in the visible light region is preferably 0.7 or less, and more preferably 0.3 or less.

Figure 21 is a diagram showing the distribution of stray light obtained by optical calculation using a model of the display panel 2 of embodiment 2 shown in Figure 26, which includes a light absorber with a refractive index of 1.5 and a transmittance of 1. Figure 22 is a diagram showing the distribution of stray light obtained by optical calculation using a model of the display panel 2 of embodiment 2 shown in Figure 26, which includes a light absorber with a refractive index of 3.47 and a transmittance of 1. Figure 23 is a diagram showing the distribution of stray light obtained by optical calculation using a model of the display panel 2 of embodiment 2 shown in Figure 26, which includes a light absorber with a refractive index of 3.47 and a transmittance of 0.3.

Figures 21 and 22 each show the distribution of stray light obtained by optical calculation using the display panel 2 of embodiment 2 shown in Figure 26, which includes a light absorber LA, as a model. To confirm the effect of the refractive index of the light absorber LA, the transmittance of the light absorber LA was fixed at 1, and the refractive index was varied between 1.5 and 3.47. As shown in Figure 21, when the refractive index of the light absorber LA is smaller than the refractive index of the semiconductor layer (e.g., 2.47), spike-like stray light is significantly suppressed in adjacent subpixels where it occurs. However, broad stray light propagates long distances and is barely suppressed. Conversely, as shown in Figure 22, broad stray light can be suppressed by using a light absorber LA with a refractive index larger than the refractive index of the semiconductor (e.g., 2.47). When the refractive index of the light absorber LA is smaller than that of the semiconductor layer, light that is nearly parallel to the substrate surface and incident at a shallow angle on the sidewall of the stacked body of the light-emitting element is refracted from the light absorber LA toward the atmosphere, whereas when the refractive index of the light absorber LA is larger than that of the semiconductor layer, the light is refracted toward the substrate surface and is attenuated by multiple reflections at shallow angles between adjacent subpixels. Broad stray light that propagates over a wide area reduces the contrast of a display panel, but this can be suppressed by making the refractive index of the light absorber LA larger than that of the semiconductor layer and increasing the difference between the two.

From the above, in order to suppress broad stray light that propagates over a wide range, it is preferable that the refractive index of the light absorber LA be 0.1 or more higher than the refractive index of the material that makes up the laminate 11' shown in Figure 26, and it is even more preferable that it be 1.5 or more higher.

Furthermore, from the viewpoint of suppressing spike-like stray light, it is preferable that the refractive index of the light absorber LA is smaller by 0.1 or more than the refractive index of the material constituting the laminate 11' shown in Figure 26, and it is even more preferable that it is smaller by 1.5 or more.

As shown in Figure 23, the stray light distribution obtained by optical calculation using the display panel 2 of embodiment 2 shown in Figure 26 as a model, which includes a light absorber LA with a refractive index of 3.47 and a transmittance of 0.3, demonstrates that the effects of refraction and absorption are obtained, and that both spike-like stray light and broad stray light are effectively suppressed.

From the above, the transmittance of the light absorber LA in the visible light region is 0.3 or less, and the refractive index of the light absorber LA is preferably 0.1 or more higher than the refractive index of the material constituting the laminate 11' shown in Figure 26, and more preferably 1.5 or more higher.

[Embodiment 2]
Fig. 26 is a cross-sectional view showing a schematic configuration of the display panel 2 of Embodiment 2. Fig. 27 is a cross-sectional view showing a schematic configuration of the display panel 52 of Comparative Example 2. Fig. 28 is a diagram showing the distribution of stray light in the H1 direction shown in Fig. 2 in the display panel 2 of Embodiment 2 shown in Fig. 26 and the display panel 52 of Comparative Example 2 shown in Fig. 27. Fig. 29 is a diagram showing the distribution of stray light in the H2 direction shown in Fig. 2 in the display panel 2 of Embodiment 2 shown in Fig. 26 and the display panel 52 of Comparative Example 2 shown in Fig. 27.

The display panel 2 of Embodiment 2 shown in FIG. 26 and the display panel 52 of Comparative Example 2 shown in FIG. 27 differ from the display panel 1 of Embodiment 1 and the display panel 51 of Comparative Example 1 described above in that they are monochrome display panels equipped with a plurality of light-emitting elements that emit light of one color. The display panel 2 of Embodiment 2 shown in FIG. 26 and the display panel 52 of Comparative Example 2 shown in FIG. 27 are blue monochrome display panels. Note that the display panel 2 of Embodiment 2 shown in FIG. 26 differs from the display panel 52 of Comparative Example 2 shown in FIG. 27 only in that it is equipped with a light absorber LA.

As shown in Figures 28 and 29, in both the distribution of stray light in the H1 direction shown in Figure 2 and the distribution of stray light in the H2 direction shown in Figure 2, it can be seen that in the case of the display panel 2 of embodiment 2 shown in Figure 26, the provision of the light absorber LA reduces both periodic spike-like stray light and broad stray light. Furthermore, compared to the display panel 52 of comparative example 2 shown in Figure 27, which does not have the light absorber LA, it can be seen that the intensity of stray light in the case of the display panel 2 of embodiment 2 shown in Figure 26 is reduced to at least one-quarter.

In the display panel 2 of embodiment 2 shown in Figure 26, the case where the light absorber LA is filled so as to completely fill the spaces between the island-shaped laminates 11' provided in each of the multiple light-emitting elements D1' has been described as an example, but this is not limited to this. The light absorber LA may be formed, for example, at a height equal to or less than the thickness from the display surface DM-side surface of the base layer U1, which is the semiconductor layer closest to the display surface DM, which is the surface from which light from the light-emitting layer E1 is emitted, to the display surface DM-side surface of the light-emitting layer E1 closest to the display surface DM, or the light absorber LA may be formed at a height corresponding to the thickness from the display surface DM-side surface of the base layer U1 to the display surface DM-side surface of the light-emitting layer E1.

[Embodiment 3]
Fig. 30 is a cross-sectional view showing a schematic configuration of a display panel 3 of embodiment 3. Fig. 31 is a cross-sectional view showing a schematic configuration of a display panel 53 of comparative example 3.

The display panel 3 of Embodiment 3 shown in FIG. 30 and the display panel 53 of Comparative Example 3 shown in FIG. 31 differ from the display panel 1 described above in Embodiment 1 and the display panel 51 of Comparative Example 1 in that they are manufactured by manufacturing a plurality of chips, each chip including a blue light-emitting element D1', a green light-emitting element D2', and a red light-emitting element D3', and bonding the chips to a single drive substrate DK via a conductive adhesive layer JC so that the chips are aligned on the drive substrate DK. The display panel 3 of Embodiment 3 shown in FIG. 30 differs from the display panel 53 of Comparative Example 3 shown in FIG. 31 only in that it includes a light absorber LA.

Although not shown, in both the distribution of stray light in the H1 direction shown in FIG. 2 and the distribution of stray light in the H2 direction shown in FIG. 2, the display panel 3 of embodiment 3 shown in FIG. 30 is able to reduce both periodic spike-like stray light and broad stray light by providing the light absorber LA. Furthermore, compared to the display panel 53 of comparative example 3 shown in FIG. 31, which does not have the light absorber LA, the intensity of stray light can be reduced to at least one-quarter in the case of the display panel 3 of embodiment 3 shown in FIG. 30.

In the manufacturing process of the display panel 3 of embodiment 3 shown in Figure 30, since each of the multiple light-emitting elements D1', D2', and D3' is individually chipped in step S26 shown in Figure 3, it is necessary to perform step S32 shown in Figure 3, in which each of the multiple chipped light-emitting elements D1', D2', and D3' is mounted on a drive substrate DK, before performing step S30 shown in Figure 3. Note that step S28 shown in Figure 3 has been omitted. Then, in step S30 shown in Figure 3, the gaps GP between the growth substrates SK created in step S32 described above can be used to fill the light absorber LA between the island-shaped laminates.

〔summary〕
The display panel according to aspect 1 of the present disclosure includes a plurality of light-emitting elements each having an island-shaped laminate composed of a plurality of stacked semiconductor layers including a light-emitting layer, an anode, and a cathode, and a light absorber that absorbs light in the visible light range and contains a material different from the material constituting the laminate is provided between the island-shaped laminates included in each of the plurality of light-emitting elements.

A display panel according to aspect 2 of the present disclosure is the display panel according to aspect 1, and may further include an insulating film between the island-shaped laminate and the light absorber.

A display panel according to aspect 3 of the present disclosure is the display panel according to aspect 1 or 2, and the transmittance of the light absorber in the visible light region may be 0.7 or less.

A display panel according to aspect 4 of the present disclosure is the display panel according to aspect 1 or 2, and the transmittance of the light absorber in the visible light region may be 0.3 or less.

A display panel according to aspect 5 of the present disclosure is a display panel according to any one of aspects 1 to 4, and the refractive index of the light absorber may be 0.1 or more higher than the refractive index of the material constituting the laminate.

A display panel according to aspect 6 of the present disclosure is a display panel according to any one of aspects 1 to 4, and the refractive index of the light absorber may be 1.5 or more higher than the refractive index of the material constituting the laminate.

A display panel according to aspect 7 of the present disclosure is a display panel according to any one of aspects 1 to 4, and the refractive index of the light absorber may be 0.1 or more lower than the refractive index of the material constituting the laminate.

A display panel according to aspect 8 of the present disclosure is a display panel according to any one of aspects 1 to 4, and the refractive index of the light absorber may be 1.5 or more lower than the refractive index of the material constituting the laminate.

A display panel according to aspect 9 of the present disclosure is a display panel according to any one of aspects 1 to 8, and the light absorber may be an organic compound or an inorganic compound.

A display panel according to aspect 10 of the present disclosure is a display panel according to any one of aspects 1 to 8, and the light absorber may include a pyridine skeleton.

A display panel according to aspect 11 of the present disclosure is a display panel according to any one of aspects 1 to 8, wherein the light absorber may include one or more selected from modified acrylic resin, epoxy resin, urethane resin, cyanoacrylate resin, fluoroethylene resin, silicone resin, polyvinyl alcohol (PVA), and polyvinyl chloride (PVC).

A display panel according to aspect 12 of the present disclosure is a display panel according to any one of aspects 1 to 8, wherein the light absorber may include one or more selected from azo dyes, quinone dyes, indigo dyes, polymethine dyes, styryl dyes, azo pigments, quinone pigments, indigo pigments, polymethine pigments, and styryl pigments.

A display panel according to aspect 13 of the present disclosure is a display panel according to any one of aspects 1 to 8, and the light absorber may include one or more selected from a carbon material, a metal sulfide, and a semiconductor material that absorbs light in the visible light region.

A display panel according to aspect 14 of the present disclosure is the display panel according to aspect 2, and the insulating film may include any one of a silicon oxide film, a silicon nitride film, a silicon oxynitride film, and an aluminum oxide film.

A display panel according to aspect 15 of the present disclosure is a display panel according to aspect 2 or 14, and the insulating film may be formed with a thickness of 3 nm or more and 100 nm or less in a direction perpendicular to the sidewall of the island-shaped laminate.

A display panel according to aspect 16 of the present disclosure is a display panel according to any one of aspects 1 to 15, and the light absorber may be formed to a height equal to or less than the thickness from the display surface side surface of the semiconductor layer closest to the display surface, which is the surface through which light from the light-emitting layer is emitted, to the display surface side surface of the light-emitting layer closest to the display surface.

A display panel according to aspect 17 of the present disclosure is a display panel according to any one of aspects 1 to 15, wherein the plurality of light-emitting elements include a first light-emitting element that emits a first color, a second light-emitting element that emits a second color different from the first color, and a third light-emitting element that emits a third color different from the first color and the second color, and the first light-emitting element has, as the island-shaped laminate, a first stacked body including a first light-emitting layer that emits the first color, and the second light-emitting element has, as the island-shaped laminate, a first stacked body including a first light-emitting layer that emits the first color, and a second light-emitting element that has, as the island-shaped laminate, a first stacked body and a second light-emitting layer that has, as the island-shaped laminate, a first light-emitting layer that emits the first color. and a second stack including a second light-emitting layer emitting the second color and disposed farther from a display surface than the first stack, and the third light-emitting element includes, as the island-shaped stack, the first stack, the second stack, and a third stack including a third light-emitting layer emitting the third color and disposed farther from the display surface than the second stack, and the light absorber may be formed to a height equal to or less than the thickness from the display surface side surface of the semiconductor layer closest to the display surface to the display surface side surface of the third light-emitting layer.

[Additional Notes]
The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

1, 1a, 1b, 2, 3 Display panel 11, 12, 13, 11', 12' Island-shaped laminated body W Side wall of island-shaped laminated body SK Growth substrate DM Display surface D1 to D3, D1' to D3' Light-emitting element E1 to E3 Light-emitting layer LA Light absorber PF Insulating film JC Conductive adhesive layer DK Drive substrate A1 to A3 Anode K1 to K3 Cathode L1 to L3 Light from light-emitting layer PI Pixel RSUB, GSUB, BSUB Sub-pixel H1 First direction H2 Second direction

Claims (17)

The light-emitting device includes a plurality of light-emitting elements each including an island-shaped laminate composed of a plurality of laminated semiconductor layers including a light-emitting layer, an anode, and a cathode;
a light absorber that absorbs light in the visible light region and that contains a material different from the material constituting the stack is provided between the island-shaped stacks that each of the plurality of light-emitting elements includes,
a display panel, wherein the light absorber is formed to a height corresponding to a thickness from a surface of the semiconductor layer closest to a display surface, which is a surface through which light from the light emitting layer is emitted, to a surface of the light emitting layer closest to the display surface. The light-emitting device includes a plurality of light-emitting elements each including an island-shaped laminate composed of a plurality of laminated semiconductor layers including a light-emitting layer, an anode, and a cathode;
a light absorber that absorbs light in the visible light region and that contains a material different from the material constituting the stack is provided between the island-shaped stacks that each of the plurality of light-emitting elements includes,
the plurality of light-emitting elements include a first light-emitting element that emits a first color, a second light-emitting element that emits a second color different from the first color, and a third light-emitting element that emits a third color different from the first color and the second color;
the first light-emitting element includes, as the island-shaped laminate, a first laminate including a first light-emitting layer that emits light of the first color;
the second light-emitting element includes, as the island-shaped laminate, the first laminate and a second laminate including a second light-emitting layer that emits light of the second color and is provided farther from a display surface, which is a surface through which light from the light-emitting layer is emitted, than the first laminate;
the third light-emitting element includes, as the island-shaped laminate, the first laminate, the second laminate, and a third laminate including a third light-emitting layer that emits light of the third color and is provided farther from the display surface than the second laminate,
the light absorber is formed at a height corresponding to a thickness from a surface of the semiconductor layer closest to the display surface that faces the display surface to a surface that is equal to or greater than the surface of the first light-emitting layer that faces the display surface and that is equal to or smaller than the surface of the third light-emitting layer that faces the display surface. The light-emitting device includes a plurality of light-emitting elements each including an island-shaped laminate composed of a plurality of laminated semiconductor layers including a light-emitting layer, an anode, and a cathode;
a light absorber that absorbs light in the visible light region and that contains a material different from the material constituting the stack is provided between the island-shaped stacks that each of the plurality of light-emitting elements includes,
the transmittance of the light absorber in the visible light region is 0.7 or less,
A display panel, wherein the refractive index of the light absorber is 0.1 or more higher than the refractive index of the material constituting the laminate. A display panel according to any one of claims 1 to 3, wherein an insulating film is provided between the island-shaped laminate and the light absorber. The display panel of claim 1 or 2, wherein the transmittance of the light absorber in the visible light region is 0.7 or less. The display panel of claim 1 or 2, wherein the transmittance of the light absorber in the visible light region is 0.3 or less. The display panel of claim 5, wherein the refractive index of the light absorber is at least 0.1 greater than the refractive index of the material constituting the laminate. The display panel of claim 3, wherein the refractive index of the light absorber is at least 1.5 higher than the refractive index of the material constituting the laminate. The display panel of claim 5, wherein the refractive index of the light absorber is at least 0.1 lower than the refractive index of the material constituting the laminate. The display panel of claim 9, wherein the refractive index of the light absorber is at least 1.5 lower than the refractive index of the material constituting the laminate. A display panel according to any one of claims 1 to 3, wherein the light absorber is an organic compound or an inorganic compound. A display panel according to any one of claims 1 to 3, wherein the light absorber includes a pyridine skeleton. The display panel of any one of claims 1 to 3, wherein the light absorber includes one or more selected from the group consisting of modified acrylic resin, epoxy resin, urethane resin, cyanoacrylate resin, fluoroethylene resin, silicone resin, polyvinyl alcohol (PVA), and polyvinyl chloride (PVC). The display panel of any one of claims 1 to 3, wherein the light absorber includes one or more selected from the group consisting of azo dyes, quinone dyes, indigo dyes, polymethine dyes, styryl dyes, azo pigments, quinone pigments, indigo pigments, polymethine pigments, and styryl pigments. A display panel according to any one of claims 1 to 3, wherein the light absorber includes one or more selected from the group consisting of carbon materials, metal sulfides, and semiconductor materials that absorb light in the visible light region. The display panel of claim 4, wherein the insulating film includes any one of a silicon oxide film, a silicon nitride film, a silicon oxynitride film, and an aluminum oxide film. The display panel of claim 4, wherein the insulating film is formed to a thickness of 3 nm or more and 100 nm or less in a direction perpendicular to the sidewalls of the island-shaped laminate.