Display device and manufacturing method for same

Abstract

The purpose of the present invention is to provide a display device which can effectively reduce excitation light leakage and which improves color purity without causing deterioration of a color conversion layer, and also to provide a manufacturing method for the display device. This display device comprises a plurality of display pixels each equipped with a plurality of light emitting elements disposed on a substrate, a color conversion layer disposed on the light emitting elements, and a color filter disposed on the color conversion layer, and is characterized in that the spectral transmittance of the color filter at an emission peak wavelength of the light emitting elements is 30% or less, and the spectral transmittance of the color filter at a fluorescence peak wavelength transmitted through the color conversion layer is 80% or more.

Description

Display device and manufacturing method thereof

[0001] The present invention relates to a display device and a manufacturing method thereof.

[0002] Patent Document 1 discloses an invention related to a micro LED display device, which specifies the refractive index difference between an encapsulation portion that encapsulates each micro LED and a low refractive index layer that is laminated thereon.

[0003] Patent Document 2 discloses a display element and a display device in which a wavelength conversion section and a reflective layer that reflects the excitation light that has passed through the wavelength conversion section are stacked on a light source section that emits excitation light, and the reflective layer is formed from a dielectric multilayer film.

[0004] Although Patent Document 1 states that a color filter may be provided on the low refractive index layer, it does not provide a detailed explanation of the color filter.

[0005] In Patent Document 2, a dielectric multilayer film is formed on the wavelength conversion section. However, since the dielectric multilayer film is composed of a multilayer film in which a low refractive index material and a high refractive index material are stacked, the number of manufacturing steps is extremely large. Furthermore, the high heat generated during the process of forming the dielectric multilayer film affects the wavelength conversion section below, degrading the quantum dots contained in the wavelength conversion section. Furthermore, Patent Document 2 does not disclose the spectral characteristics of the dielectric multilayer film that can sufficiently reduce excitation light leakage.

[0006] International Publication No. 2022 / 209031 Japanese Patent Application Laid-Open No. 2022-096625

[0007] The present invention has been made in consideration of the above points, and aims to provide a display device and a manufacturing method thereof that can effectively reduce excitation light leakage and improve color purity without deteriorating the color conversion layer.

[0008] Alternatively, the present invention has an object to provide a light-emitting element with excellent light utilization efficiency, a display device that achieves both improved luminance and reduced crosstalk, or a display device that can improve color conversion efficiency.

[0009] One embodiment of the display device of the present invention comprises a plurality of display pixels each including a plurality of light-emitting elements arranged on a substrate, a color conversion layer arranged on the light-emitting elements, and a color filter arranged on the color conversion layer, wherein the spectral transmittance of the color filter at the emission peak wavelength of the light-emitting elements is 30% or less, and the spectral transmittance of the color filter at the fluorescence peak wavelength transmitted through the color conversion layer is 80% or more.

[0010] One embodiment of the method for manufacturing a display device of the present invention is the method for manufacturing a display device described above, characterized in that the color filter is formed at a heat treatment temperature of 150° C. or less.

[0011] According to the display device of the present invention, it is possible to effectively reduce the leakage of excitation light and improve color purity.

[0012] Furthermore, according to the method for manufacturing a display device, the heat treatment temperature during the formation of the color filter can be lowered, and the influence on the color conversion layer, particularly the deterioration of the quantum dots contained in the color conversion layer, can be suppressed.

[0013] FIG. 1 is a cross-sectional schematic diagram of a micro LED display as a display device in the first embodiment. FIG. 2 shows the emission spectrum of a blue light-emitting element. FIG. 3 shows the fluorescence spectrum of green quantum dots. FIG. 4 shows the fluorescence spectrum of red quantum dots. FIG. 5 shows the transmittance spectrum of a color filter. FIG. 6 shows the emission spectrum (green) when color filters are stacked. FIG. 7 shows the emission spectrum (red) when color filters are stacked. FIG. 8 is a graph showing the relationship between the emission wavelength of a light-emitting element and the chromaticity reproduction range (NTSC ratio). FIG. 9 is a cross-sectional schematic diagram showing a manufacturing process of a micro LED display in this embodiment. FIG. 10 is a cross-sectional view showing the structure of a display device in the second embodiment. FIG. 11 is an enlarged cross-sectional view emphasizing the structure of the partition wall in the second embodiment. FIG. 12 is a diagram showing the advantages of the inclined surface portions of the partition wall in the second embodiment in terms of front luminance and light utilization efficiency. FIG. 13 is an enlarged cross-sectional view emphasizing the structure of the partition wall in a first modification of the second embodiment. FIG. 14 is a diagram showing the advantages of the inclined surface portions of the partition walls in Modification 1 in terms of front luminance and light utilization efficiency. FIG. 15 is a diagram showing the advantages of the inclined surface portions of the partition walls in the second embodiment and Modification 1 in terms of front luminance and light utilization efficiency. FIG. 16 is an enlarged cross-sectional view emphasizing the structure of the partition walls in Modification 2 of the second embodiment. FIG. 17 is a diagram showing the difference in front luminance and light utilization efficiency between a case where the partition walls are provided with only inclined surface portions and a case where the partition walls are provided with both inclined and curved surface portions, when the light-emitting elements are micro LEDs. FIG. 18 is a diagram showing the difference in front luminance and light utilization efficiency between a case where the partition walls are provided with only inclined surface portions and a case where the partition walls are provided with both inclined and curved surface portions, when the light-emitting elements are OLEDs. FIG. 19 is a diagram showing variations of the curved surface portions provided on the partition walls. FIG. 20 is a schematic cross-sectional view of a micro LED display as a display device in the third embodiment. FIG. 21 is a schematic cross-sectional view of a micro LED display as a display device in a modification of the third embodiment. Fig. 22 is an enlarged schematic cross-sectional view showing an example of a partition wall layer, Fig. 23 is an enlarged schematic cross-sectional view showing an example of a partition wall layer, and Fig. 24 is an enlarged schematic cross-sectional view showing an example of a partition wall layer.FIG. 25 is a cross-sectional schematic diagram of a micro LED display as a display device according to the fourth embodiment. FIG. 26 is a schematic diagram illustrating the mechanism by which the optical path length of blue light (excitation light) is extended. FIG. 27 is a process diagram illustrating a method for forming partition walls constituting the display device according to the fourth embodiment. FIG. 28 is a process diagram illustrating a method for forming partition walls constituting the display device according to the fourth embodiment. FIG. 29 is a process diagram illustrating a method for forming partition walls constituting the display device according to the fourth embodiment. FIG. 30 is a schematic diagram of an optical simulation model used in a simulation experiment. FIG. 31 shows the results of a simulation experiment showing the relationship between the number of refractions of blue light and the amount of light when the partition wall layer has different surface roughnesses.

[0014] The following describes in detail an embodiment of the present invention, but the following description is merely an example (typical example) of the embodiment of the present description, and the present invention is not limited to these details as long as it does not deviate from the gist of the present invention. In addition, the notation "to" used below includes both the lower limit and the upper limit within the range.

[0015] <Background to the Invention of the Display Device of the First Embodiment> Liquid crystal on silicon (LCOS), laser beam scanning (LBS), or organic light emitting diode (OLED) microdisplays are currently mainstream for use in head-mounted displays for AR (Augmented Reality) / MR (Mixed Reality). However, these methods do not provide sufficient brightness in external light, and are therefore primarily used indoors.

[0016] In contrast, the micro LED method is considered to be more advantageous than the above methods in terms of brightness, and is expected to see expanded application in the future.

[0017] As a method for displaying full color using a micro LED display, a technology has been proposed in which blue light-emitting elements are used as light-emitting elements (LEDs), and color conversion (wavelength conversion) is performed using a color conversion layer using quantum dots, for example, to enable RGB display.

[0018] Patent Document 1 describes that a low refractive index layer may be provided on the color conversion layer, and a color filter may further be provided on top of the layer, but does not disclose detailed characteristics of the color filter.

[0019] Furthermore, Patent Document 2 requires the formation of a dielectric multilayer film, which increases the number of steps, and there are concerns that the heat acting on the color conversion layer during the formation of the dielectric multilayer film may deteriorate the quantum dots contained in the color conversion layer. Furthermore, the spectrum of the dielectric multilayer film required to remove blue light noise is not clarified. Therefore, the inventors conducted extensive research and developed a display device that can effectively reduce excitation light leakage and improve color purity.

[0020] <Description of Display Device of First Embodiment> The display device of the first embodiment is configured as a micro LED (Light Emitting Diode) display 1 shown in Fig. 1. Fig. 1 is a schematic cross-sectional view of the micro LED display 1.

[0021] As shown in Fig. 1, the micro LED display 1 includes a plurality of display pixels 2a, 2b, and 2c. For example, the display pixel 2a shown in Fig. 1 is a red display pixel, the display pixel 2b is a green display pixel, and the display pixel 2c is a blue display pixel.

[0022] As shown in Fig. 1, a plurality of light-emitting elements (LEDs) 4 are arranged on a substrate 3. For example, the light-emitting elements 4 are arranged in a matrix on the substrate 3. Each light-emitting element 4 is a blue light-emitting element. The substrate 3 is made of, for example, a silicon substrate (Si substrate). The type and material of the substrate 3 are not limited to silicon (Si), and may be a glass substrate or a sapphire substrate.

[0023] As shown in Fig. 1, a partition layer 5 is formed on a substrate 3 to separate the light-emitting elements 4. The side surfaces 5a of the partition layer 5 shown in Fig. 1 extend perpendicularly in the height direction from the surface of the substrate 3, but the side surfaces 5a may be inclined so that the width of each partition layer 5 increases as it approaches the substrate 3. The bottom of the partition layer 5 may also be a concave curved surface.

[0024] The barrier layer 5 has a light-reflecting function and is made of, for example, a white wall material. In order to obtain high light conversion efficiency in the micro LED display 1, the barrier layer 5 preferably has a large height. Although not limited to this, the height is preferably about 3 μm to 6 μm, and more preferably about 4 μm to 6 μm.

[0025] 1, the internal spaces of the partition wall layers 5 of the red display pixels 2a and the green display pixels 2b are filled with color conversion layers 6a and 6b. As shown in FIG. 1, the color conversion layers of the red display pixels 2a and the green display pixels 2b have red quantum dots 7 and green quantum dots 8 dispersed therein, respectively.

[0026] The quantum dots 7 and 8 are dispersed in a resin 9. The resin 9 is preferably a transparent resin. There are no limitations on the material of the resin 9, but examples thereof include acrylic resins, polyurethane resins, polyester resins, polyolefin resins, polycarbonate resins, polyethyleneimine resins, epoxy resins, and thioether resins.

[0027] The red quantum dots 7 preferably have a fluorescence peak wavelength of 600 nm to 680 nm, and the green quantum dots 8 preferably have a fluorescence peak wavelength of 520 nm to 560 nm. These quantum dots 7 and 8 absorb blue light as excitation light irradiated from the light-emitting element 4, and emit red or green light after color conversion.

[0028] Although the materials are not limited, because cadmium (Cd) is toxic and its use is restricted in various countries, it is preferable that the quantum dots 7 and 8 be cadmium-free. Furthermore, the quantum dots 7 and 8 preferably have a core-shell structure consisting of a core and a shell covering the core, such as ZnSe / ZnS, ZnSe / ZnSeS, ZnTe / ZnS, ZnSeTe / ZnS, or InP / ZnS. However, the quantum dots 7 and 8 may be composed of only a core. Furthermore, to improve dispersibility, it is preferable that the quantum dots 7 and 8 have a ligand (organic ligand) on their surfaces.

[0029] The particle size of the quantum dots 7 and 8 is several nanometers to several tens of nanometers. The fluorescence peak wavelength can be controlled by adjusting the particle size and composition. Note that the color conversion layers 6 a and 6 b may contain phosphors other than the quantum dots 7 and 8.

[0030] On the other hand, as shown in Figure 1, the internal space of the partition layer 5 of the blue display pixel 2c is filled with resin 9, but does not contain quantum dots. The resin 9 is preferably a transparent resin. "Transparent" means that the visible light transmittance is 50% or more, preferably 70% or more, and most preferably 90% or more. The visible light transmittance can be measured in accordance with JIS K 7375:2008.

[0031] As another example, white light may be used for the light emitting element 4 used in the blue display pixel 2 c , and blue quantum dots may be mixed into the resin 9 .

[0032] 1, the surfaces of the color conversion layers 6a, 6b and resin 9 may be formed at substantially the same height as the partition wall layer 5, or may be slightly lower than the partition wall layer 5. The thickness of the color conversion layers 6a, 6b is approximately 3 to 6 μm.

[0033] 1, a color filter 11 is provided on the surfaces of the color conversion layers 6a, 6b and the resin 9 via a barrier layer 10. The color filter 11 includes a red filter 11a, a green filter 11b, and a blue filter 11c.

[0034] Although the barrier layer 10 is not an essential layer, providing the barrier layer 10 can reduce the thermal influence on the quantum dots 7 and 8 in the color conversion layers 6a and 6b when the color filter 11 is formed. The barrier layer 10 may also be configured to reduce oxygen and moisture, which are causes of deterioration of the quantum dots 7 and 8. Furthermore, if there are irregularities between the surfaces of the partition layer 5 and the color conversion layers 6a and 6b and the resin 9, the barrier layer 10 can smooth out the irregularities. This allows the color filter 11 to be formed on a flat surface. The material of the barrier layer 10 is not limited, but is preferably an oxide film or a nitride film, for example, SiO ２ The thickness of the barrier layer 10 is not limited, but is about 50 nm to 1 μm.

[0035] The color filters 11 are arranged such that a red filter 11a is located at the position of the red display pixel 2a, a green filter 11b is located at the position of the green display pixel 2b, and a blue filter 11c is located at the position of the blue display pixel 2c.

[0036] The red filter 11a absorbs short wavelength blue light and transmits red light, the green filter 11b absorbs short wavelength blue light and transmits red light, and the blue filter 11c transmits blue light.

[0037] 1, microlenses 12a to 12c can be provided on the surface of the color filter 11. The microlenses 12a to 12c are optically transparent. Although not limited thereto, the microlenses 12a to 12c can be made of organic materials such as acrylic resin, epoxy resin, and silicon resin, or SiN, SiO ２ 1, the microlenses 12a to 12c are convex lenses, but they can also be concave lenses. The surface shapes of the microlenses 12a to 12c can be changed in various ways depending on the relationship between the refractive index and the layer located on the surface of the microlenses 12a to 12c.

[0038] <Characteristic Configuration of the Micro LED Display 1 of the First Embodiment> The micro LED display 1 of the first embodiment has the following characteristics: (1) The spectral transmittance of the color filter 11 at the emission peak wavelength of the light emitting element 4 is 30% or less. (2) The spectral transmittance of the color filter 11 at the fluorescence peak wavelength transmitted through the color conversion layers 6 a, 6 b is 80% or more.

[0039] The features of the micro LED display 1 of the first embodiment will be described below using the spectral characteristics of the light emitting element 4, the quantum dots 7 and 8, and the color filter 11 applied to this embodiment.

[0040] Figure 2 shows the emission spectrum of the blue light-emitting element. The horizontal axis of Figure 2 represents wavelength (nm), and the vertical axis represents spectral irradiance. As shown in Figure 2, the emission peak wavelength was approximately 450 nm. Note that the arrow L1 irradiated from the light-emitting element 4 shown in Figure 1 indicates blue light (excitation light).

[0041] Figure 3 shows the fluorescence spectrum of the green quantum dots 8. The green quantum dots 8 used in this experiment were InSe (particle size = 2 to 10 nm). The thickness of the color conversion layer 6b was 6 μm. The horizontal axis of Figure 3 represents wavelength (nm), and the vertical axis represents spectral irradiance.

[0042] Blue light emitted from the light-emitting element 4 is color-converted to green light by the green quantum dots 8. As shown in FIG. 3, a fluorescence peak wavelength was observed at approximately 550 nm. This indicates that blue light has been color-converted to green light. On the other hand, a peak of low emission intensity was also observed at approximately 450 nm, which indicates blue light, indicating that excitation light from the light-emitting element 4 remains. FIG. 1 shows that blue light L1 is color-converted to green light L2 by the green quantum dots 8, but also shows that some of the blue light L1 passes through the color conversion layer 6b.

[0043] Figure 4 shows the fluorescence spectrum of the red quantum dots 7. The red quantum dots 7 used in this experiment were InSe (particle size = 2 to 10 nm). The thickness of the color conversion layer 6b was 6 μm. The horizontal axis of Figure 3 represents wavelength (nm), and the vertical axis represents spectral irradiance.

[0044] Blue light emitted from the light-emitting element 4 is color-converted to red light by the red quantum dots 7. As shown in FIG. 4, a fluorescence peak wavelength was observed at approximately 620 nm. This indicates that blue light has been color-converted to red light. On the other hand, a peak of low emission intensity was also observed at approximately 450 nm, which indicates blue light, indicating that excitation light from the light-emitting element 4 remains. FIG. 1 shows that blue light L1 is color-converted to red light L3 by the red quantum dots 7, but also shows that some of the blue light L1 passes through the color conversion layer 6a.

[0045] Fig. 5 shows the transmittance spectrum of the color filter 11. Fig. 5 shows the spectrum of the red filter 11a and the green filter 11b of the color filter 11 shown in Fig. 1. In this experiment, the thickness of the color filter was changed to change the transmittance of the color filter.

[0046] As shown in Figure 5, five types of red filters 11a and five types of green filters 11b with different thicknesses were prepared. First, considering the green filter 11b, the spectral transmittance at a wavelength of 450 nm, which is the emission peak wavelength of the blue light-emitting element, was able to be reduced to 30% or less. For example, the numerical value "G 1.2%" on the graph line indicates that the spectral transmittance at a wavelength of 450 nm for the green (G) filter 11b is 1.2%. R indicates the red filter 11a. The same applies to the other graph lines.

[0047] On the other hand, the spectral transmittance at the fluorescence peak wavelength of 550 nm shown in the spectrum of Fig. 3 was able to be 80% or more. In this way, the green filter 11b satisfies both of the above-mentioned characteristics (1) and (2).

[0048] Next, considering the red filter 11a, the spectral transmittance at a wavelength of 450 nm, which is the emission peak wavelength of the blue light-emitting element, was able to be 30% or less. On the other hand, the spectral transmittance at a fluorescence peak wavelength of 620 nm, shown in the spectrum of Fig. 4, was able to be 80% or more. In this way, the red filter 11a satisfies both of the above-mentioned characteristics (1) and (2).

[0049] The color filter 11 of the first embodiment will be described in further detail. The color filter 11 used in the first embodiment is formed of a color filter material that cures at a low temperature. Here, "low temperature" refers to a temperature at which the quantum dots 7 and 8 dispersed in the color conversion layers 6 a and 6 b are less susceptible to thermal degradation (oxidation) during the film formation process of the color filter 11, specifically, 150°C or lower. As described above, the quantum dots 7 and 8 used in the first embodiment are preferably cadmium-free, and have, for example, ZnSe or InP as cores. Furthermore, the shell covering the surface of the core is formed of ZnS or the like. Cadmium-free quantum dots 7 and 8 can be effectively prevented from oxidation by heating the color filter material to a temperature of 150°C or lower.

[0050] The low-temperature curable color filter material is not limited to a material containing a colorant, a photopolymerizable monomer, a photopolymerization initiator, and a resin, and the photopolymerizable monomer is a compound represented by the formula [CH ２=CHC(=O)-(OC ｍ H ２ｍ ) ｎ -OCH ２ ] ３ -CCH ２ CH ３ (In general formula (1), m represents an integer of 1 to 3, n represents an integer of 0 to 2, and multiple m's and multiple n's may be the same or different.) The photopolymerization initiator preferably includes an oxime ester-based photopolymerization initiator.

[0051] Furthermore, the resin preferably contains a photosensitive acrylic resin. For example, the photosensitive acrylic resin is preferably a resin obtained by reacting the hydroxyl groups of a hydroxyl-containing polymer obtained by polymerizing an ethylenically unsaturated monomer (c) containing a hydroxyl-containing ethylenically unsaturated monomer (b) in the presence of a reaction product of the hydroxyl groups of a compound (a) having two hydroxyl groups and one thiol group in the molecule with the acid anhydride groups of pyromellitic anhydride and / or trimellitic anhydride, with the isocyanate groups of a compound (d) having one isocyanate group and one or more (meth)acryloyl groups. Furthermore, the content of the structural units derived from the hydroxyl-containing ethylenically unsaturated monomer (b) is preferably 35% by mass or more and 80% by mass or less relative to the total amount of structural units derived from the ethylenically unsaturated monomer (c).

[0052] The resin may include a thermoplastic resin or a thermosetting resin in addition to a photosensitive acrylic resin.

[0053] Known pigments can be used as the colorant as long as they do not impair the low-temperature properties (thermosetting at 150°C or less) of the color filter of this embodiment. For example, inorganic pigments can be used, such as metal oxide powders and metal sulfide powders, including barium sulfate, zinc oxide, lead sulfate, yellow lead, cadmium red, ultramarine, chromium oxide green, titanium black, and synthetic iron black. It is preferable to use them in combination with organic pigments.

[0054] The experiment shown in Fig. 5 was carried out using a color filter 11 formed from the above-mentioned color filter material, and the thickness of the color filter 11 was adjusted to control the transmittance of the color filter as shown in Fig. 5. The thickness was adjusted so that the transmittance was 1.2 to 30% at a wavelength of 450 nm. Specifically, in this experiment, the thickness of the color filter 11 was adjusted within the range of 1.16 to 1.18 µm.

[0055] In the present embodiment, in the above-mentioned characteristic point (1), the spectral transmittance is preferably 25% or less, more preferably 20% or less, even more preferably 10% or less, and even more preferably 5% or less.

[0056] FIG. 6 shows the emission spectrum (green) when the color filter 11 is laminated. FIG. 7 shows the emission spectrum (red) when the color filter is laminated. "No G-cut" and "No R-cut" shown in FIGS. 6 and 7 indicate a configuration in which a green filter and a red filter are not laminated. On the other hand, the other graph lines indicate a configuration in which the color filters described in FIG. 5 are laminated. As shown in FIGS. 6 and 7, by laminating the color filters of this embodiment having features (1) and (2), it was found that blue light (excitation light from the light-emitting element) can be effectively removed, and as a result, the color purity of green and red is improved.

[0057] As shown in Figures 6 and 7, the rejection rate of excitation light varies depending on the transmittance of the color filter. The experimental results revealed that by setting the spectral transmittance of the color filter 11 at the emission peak wavelength of the light-emitting element 4 to 30% or less, the spectral irradiance of the excitation light can be reduced to approximately 0.1 or less; by setting it to 20% or less, the spectral irradiance of the excitation light can be reduced to approximately 0.08 or less; and by setting it to 10% or less, the spectral irradiance of the excitation light can be reduced to approximately 0.05 or less. Figure 8 is a graph showing the relationship between the transmittance of a color filter and the chromaticity gamut at an emission wavelength of 450 nm. The chromaticity gamut can be expressed in terms of the NTSC ratio.

[0058] As shown in Figure 8, it was found that the NTSC ratio can be increased to 65% or more by setting the transmittance of the color filter at an emission wavelength of 450 nm to 30% or less. Also, it was found that the NTSC ratio can be increased to 72% or more by setting the transmittance of the color filter at an emission wavelength of 450 nm to 20% or less. Thus, it was found that a good color reproduction range can be obtained at the NTSC ratio.

[0059] By setting the transmittance of the color filter at an emission wavelength of 450 nm to 20% or less, the NTSC ratio can be increased to 72% or more, thereby satisfying the color reproduction standard for display devices.

[0060] <Manufacturing Method of Display Device of First Embodiment> FIGS. 9A to 9C are schematic cross-sectional views showing the manufacturing process of the micro LED display of this embodiment.

[0061] 9(a), a wafer with micro LEDs is prepared in which a plurality of light-emitting elements (LEDs) 4 are arranged on a substrate 3, and a partition layer 5 is formed to separate the light-emitting elements 4. Here, the light-emitting elements 4 are preferably blue light-emitting elements.

[0062] The method for forming the barrier layer 5 is not limited to a specific method, and may be an etching method, a photolithography method, a lift-off method, or the like.

[0063] 9(b), color conversion layers 6a, 6b are formed by filling the internal spaces 5b of the red display pixel 2a and the green display pixel 2b with a quantum dot-containing composition, among the internal spaces 5b partitioned by the partition layer 5. Here, it is preferable to use cadmium-free quantum dots, such as ZnSe or InP.

[0064] The internal space 5b of the blue display pixel 2c is filled with a resin 9. The resin 9 is preferably a transparent resin.

[0065] Next, SiO ２After forming a barrier layer (not shown) made of, for example, a red filter 11a, a green filter 11b, and a blue filter 11c, a color filter 11 is formed. It is preferable to use a low-temperature curing color filter material for the color filter 11. A thermosetting material containing the above-mentioned colorant, a photopolymerizable monomer, a photopolymerization initiator, and a resin can be used as the color filter material.

[0066] In the first embodiment, the heat treatment temperature of the color filter material can be set to 150° C. or less. Preferably, the heat treatment temperature can be set to 130° C. or less.

[0067] Quantum dots are subject to oxidation and other degradation when exposed to high temperatures. In the first embodiment, it is essential to form the color filter 11 on the color conversion layers 6 a, 6 b containing quantum dots. In a typical color filter formation process, the high heat treatment temperature leads to degradation of the quantum dots. However, in this embodiment, by using a low-temperature curing color filter material, the color filter 11 can be formed without degrading the quantum dots.

[0068] As shown in FIG. 5 , the transmittance of the spectrum of the color filter 11 can be controlled, for example, by the thickness of the color filter 11, so that the transmittance at the emission peak wavelength (450 nm) of the blue light-emitting element can be reduced and the transmittance at the fluorescence peak wavelength (green: 550 nm, red: 620 nm) of the light wavelength-converted by the quantum dots can be increased, thereby achieving excellent display characteristics.

[0069] <Background to Invention of Display Device of Second Embodiment> When inventing the display device 10 of the second embodiment shown in Fig. 10, the following problems were encountered. First, the technical background will be described.

[0070] WO 2022 / 117995 describes a light emitting diode array having a first layer and a dielectric layer. The first layer has a plurality of light emitting diodes arranged to emit light from a light emitting surface of the first layer. The dielectric layer extends over the light emitting surface of the first layer. The dielectric layer has a plurality of openings extending therethrough, each opening having an at least partially reflective inner surface. At least one of the openings is positioned at the center of one of the light emitting diodes so as to collimate the light emitted from the light emitting diodes when passing through it.

[0071] However, according to intensive research by the present inventors, when multiple partitions located at the boundaries of multiple openings in the dielectric layer are defined (defined) in the light-emitting diode array of WO 2022 / 117995, the multiple partitions may diffuse the light emitted from the first layer (multiple light-emitting diodes) laterally or prevent it from emitting due to internal reflection, which may result in a loss of front brightness of the light.

[0072] The display device of the second embodiment is, for example, a micro LED (Light Emitting Diode) display or an OLED (Organic Light Emitting Diode) display. OLED may be read as (or may be synonymous with) organic electroluminescence (EL). OLED may be read as (or may be synonymous with) micro OLED. Note that the light-emitting element 4 applied to the display device of this embodiment is not limited to a micro LED or an OLED, and the form of the display element or display device can be changed.

[0073] For example, micro LED displays are used in AR (Augmented Reality) glasses and VR (Virtual Reality) glasses. In particular, in AR glasses, the front brightness of the display device is important. Conventional technologies have room for improvement in terms of meeting the desired front brightness requirements. For example, in the above-mentioned International Publication No. 2022 / 117995, when multiple partition walls are defined at the boundaries of multiple openings in the dielectric layer, the multiple partition walls may diffuse light emitted from the first layer (multiple light-emitting diodes) laterally or prevent the light from emitting due to internal reflection, resulting in a loss of front brightness of the light.

[0074] The display device of the second embodiment is configured to address the above technical issues by increasing the front brightness of the display device and improving light utilization efficiency.

[0075] Fig. 10 is a cross-sectional view showing the structure of a display device according to the second embodiment. As shown in Fig. 10, the display device includes a substrate 3, light-emitting elements 4, a partition layer 30, a filler 40, an adhesive layer 50, and a cover glass 60. Note that a description of the same parts as those in the first embodiment shown in Fig. 1 will be omitted.

[0076] A plurality of light-emitting elements 4 shown in FIG. 10 are provided (embedded) on the upper surface of the substrate 3. Five light-emitting elements 4 are depicted here, arranged at equal intervals in the left-right direction of FIG. 10 . Each of the light-emitting elements 4 emits light from the bottom to the top of FIG. 10 . In other words, the up-down direction in FIG. 10 corresponds to the optical axis direction of the light-emitting element 4. The light emitted by the light-emitting element 4 is light having a certain range (spread) centered on the optical axis. In the second embodiment, the light-emitting element 4 is composed of an OLED (organic light-emitting diode). The light-emitting element 4 as an OLED has a flat shape when viewed in cross section (rectangular or circular when viewed from above).

[0077] A plurality of partition walls 30 are provided on the upper surface of the substrate 3. Here, six partition walls 30 are illustrated aligned at equal intervals in the left-right direction of FIG. 10 . The six partition walls 30 are arranged around five light-emitting elements 4 and at the boundaries between the five light-emitting elements 4. Each of the partition walls 30 has a reflective surface formed on its inner surface (side surface) and has the function of reflecting light emitted by the light-emitting elements 4 and guiding it from the bottom to the top in FIG. 10 . The reflectance of the reflective surface on the inner surface (side surface) of the partition wall layer 30 is preferably 100% (total reflection), but does not necessarily have to be total reflection. Details of the inner surface (side surface) of the partition wall layer 30 on which the reflective surface is formed will be described later.

[0078] 1 , the filler 40 corresponds to the color conversion layers 6 a, 6 b and the resin 9. The filler 40 is filled so as to fill the space (opening) between the upper surface of the substrate 3 on which the light-emitting elements 4 are provided and the inner surface (side surface) of the partition layer 30. The upper end surface of the space filled with the filler 40 coincides with a plane including the upper end surfaces of the plurality of (six) partition layers 30.

[0079] The adhesive layer 50 is provided on the upper end surfaces of the plurality of (six) partition wall layers 30 and on the upper end surfaces of the filling spaces of the filler 40. The cover glass 60 is a protective member for the display device 9 that is provided on top of the adhesive layer 50.

[0080] 10 , the refractive index of the filler 40 is set to be greater than the refractive index of the adhesive layer 50. The refractive index of the cover glass 60 may be approximately the same as the refractive index of the adhesive layer 50. As an example, the refractive index of the filler 40 may be 1.600, the refractive index of the adhesive layer 50 may be 1.523, and the refractive index of the cover glass 60 may be 1.520.

[0081] 11 is an enlarged cross-sectional view emphasizing the structure of the partition wall layer 30 according to the second embodiment. The structure of the inner surface (side surface) of the partition wall layer 30 on which the reflective surface is formed will be described in further detail with reference to FIG.

[0082] 11 , the partition layer 30 has, in a cross-sectional view, a bottom surface portion 31 that extends along the upper surface of the substrate 3, an upper surface portion 32 that is defined as a surface parallel to the bottom surface portion 31, and an inclined surface portion 33 that connects the bottom surface portion 31 and the upper surface portion 32. In FIG. 11 , the bottom surface portion 31, the upper surface portion 32, and the two inclined surface portions 33 that connect the left and right ends of the bottom surface portion 31 and the upper surface portion 32 form an isosceles trapezoid. Although the top view shape of the partition layer 30 is not shown, for example, the bottom surface portion 31 may be a large-diameter circular shape, the upper surface portion 32 may be a small-diameter circular shape, and the inclined surface portion 33 may be a partial conical side surface that connects the large-diameter circular bottom surface portion 31 and the small-diameter circular top surface portion 32 and gradually decreases in diameter toward the top. In other words, the partition layer 30 may have a truncated cone shape.

[0083] The inclined surface portions 33 of the partition layer 30 are inclined in an opening direction with respect to the optical axis (vertical direction in FIG. 1 ) of the light-emitting element 4, and the inclination angle is 10° or more with respect to the optical axis (vertical direction in FIG. 1 ) of the light-emitting element 4. Furthermore, the inclination angle of the inclined surface portions 33 of the partition layer 30 with respect to the optical axis (vertical direction in FIG. 1 ) of the light-emitting element 4 is preferably 14° or more, and more preferably 18° or more.

[0084] The inclination or degree of inclination of the inclined surface portions 33 of the partition layer 30 may be expressed in other words (interpreted) as, for example, the inclination in a direction opening with respect to the direction of light emission from the light emitting element 4. Alternatively, the inclined surface portions 33 of the partition layer 30 may be inclined with respect to the normal direction of the substrate 3. Alternatively, the inclined surface portions 33 of the partition layer 30 may be inclined in a direction in which the distance from the light emitting element 4 in the left-right direction in FIG. 1 increases as the distance from the light emitting element 4 in the up-down direction in FIG. 1 increases. In either case, the inclination angle of the inclined surface portions 33 of the partition layer 30 is 10° or more from the reference direction (reference angle), preferably 14° or more, and more preferably 18° or more (a gentler inclination angle is preferable from the viewpoint of improving front brightness).

[0085] The height of the partition layer 30 from the substrate 3 is preferably 3 μm or more, and more preferably 3 μm or more and 6 μm or less from the substrate 3 .

[0086] 11 , the inclination angle of the inclined surface portion 33 of the partition layer 30 is denoted by the symbol θ, and the height of the partition layer 30 from the substrate 3 is denoted by the symbol H. Note that, for example, when the height H of the partition layer 30 from the substrate 3 is set to be 3 μm or more and 6 μm or less, the pitch between adjacent light emitting elements 4 can be set to be 3 μm or more and 5 μm or less.

[0087] As a result of extensive research, the inventors of the present invention came up with the idea that in order to increase the front brightness of the display device 9 and improve the light utilization efficiency, it is effective to optimize the shapes of the plurality of partition layers 30 located around the plurality of light-emitting elements 4 and at the boundaries between the plurality of light-emitting elements 4. More specifically, it was found that it is effective to set the inclination angle θ of the inclined surface portions 33 of the partition layers 30 to 10° or more with respect to the optical axis of the light-emitting elements 4 and to set the height H of the partition layers 30 from the substrate 3 to 3 μm or more.

[0088] As a result, not only light emitted from the light-emitting element 4 that is not reflected by the inclined surface portion 33 of the partition layer 30 (light emitted directly above or at a small angle in Figures 10 and 11 ) but also light that has been reflected once at any part of the inclined surface portion 33 of the partition layer 30 is guided evenly to the boundary between the filler 40 and the adhesive layer 50 directly above or at a small angle in Figures 10 and 11 . In other words, by optimizing the direction of light reflection by the inclined surface portion 33 of the partition layer 30, it is possible to increase the front brightness of the display device and improve light utilization efficiency. In other words, as in the above-mentioned International Publication No. 2022 / 117995, it is possible to effectively prevent a situation in which light emitted from the light-emitting element is reflected by the partition wall an inappropriate number of times or in an inappropriate direction, resulting in lateral diffusion or failure to be emitted due to internal reflection.

[0089] The above-described effects can be more significantly achieved by setting the inclination angle θ of the inclined surface portions 33 of the partition layer 30 to 14° or more, or even 18° or more, with respect to the optical axis of the light emitting element 4, and / or by setting the height H of the partition layer 30 from the substrate 3 to 3 μm or more and 6 μm or less. If the height H of the partition layer 30 from the substrate 3 is too large or too small, it is inappropriate. For example, if the height H is less than 3 μm or more than 6 μm, the light emitted from the light emitting element 4 may be reflected by the partition layer 30 an inappropriate number of times or in an inappropriate direction, which may result in lateral diffusion or failure to be emitted due to internal reflection.

[0090] 12 is a diagram showing the advantages of the inclined surface portions 33 of the partition layer 30 in the second embodiment in terms of front luminance and thus light utilization efficiency. Fig. 12 shows the luminance when the display device is viewed from the front when the partition layer 30 is not provided (light source only), when the inclined surface portions 33 are not provided in the partition layer 30 (0°), and when the inclination angle θ of the inclined surface portions 33 of the partition layer 30 is set to 10°, 14°, and 18°. The height H of the partition layer 30 from the substrate 3 is set to 6.0 μm.

[0091] As shown in FIG. 12 , compared to when the partition layer 30 is not provided (only the light source) or when the partition layer 30 is not provided with the inclined surface portion 33 (0°), when the inclination angle θ of the inclined surface portion 33 of the partition layer 30 is set to 10°, 14°, or 18°, the front luminance of the display device 9 can be increased and the light utilization efficiency can be improved (the magnitude of the effect is θ=18°>θ=14°>θ=10°).

[0092] <Modification 1> Fig. 13 is an enlarged cross-sectional view emphasizing the structure of the partition layer 30 of Modification 1 of the second embodiment. In Fig. 13, the structure of the partition layer 30 itself remains unchanged, but the light-emitting elements 4 arranged between adjacent partition layers 30 are configured as micro-LEDs (light-emitting diodes), whereas in the second embodiment, they are configured as organic light-emitting diodes (OLEDs). The micro-LEDs have a trapezoidal (pyramidal) cross-section, in contrast to the flat cross-section of OLEDs. The micro-LEDs can use light source elements that emit red (R), green (G), and blue (B) light that constitute pixels.

[0093] Fig. 14 is a diagram showing the advantages of the inclined surface portions 33 of the partition layer 30 in Modification 1 in terms of front luminance and thus light utilization efficiency. Fig. 14 shows the luminance when the display is viewed from the front when the partition layer 30 is not provided (light source only), when the inclined surface portions 33 are not provided in the partition layer 30 (0°), and when the inclination angle θ of the inclined surface portions 33 of the partition layer 30 is set to 10°, 14°, and 18°. The height H of the partition layer 30 from the substrate 3 is set to 6.0 µm.

[0094] As shown in FIG. 14 , compared to when the partition layer 30 is not provided (only the light source) and when the partition layer 30 is not provided with the inclined surface portion 33 (0°), when the inclination angle θ of the inclined surface portion 33 of the partition layer 30 is set to 10°, 14°, or 18°, the front luminance of the display can be increased and the light utilization efficiency can be improved (the magnitude of the effect is θ=18°>θ=14°>θ=10°).

[0095] 15 is a diagram showing the advantages of the inclined surface portions 33 of the partition layer 30 in terms of front luminance and light utilization efficiency in the second embodiment and Modification 1. It can be seen that whether the light-emitting element 4 is a micro LED or an OLED, the larger (more gentle) the inclination angle θ of the inclined surface portions 33 of the partition layer 30, the more it contributes to improving the front luminance and light utilization efficiency (the magnitude of the effect is θ=18°>θ=14°>θ=10°). Furthermore, in the example of FIG. 15 , the micro LED has superior front luminance and light utilization efficiency to the OLED.

[0096] <Modification 2> In Modification 2, by providing the partition layer 30 with curved surface portions (concave surface portions, curved portions) 34 that are continuous with the inclined surface portions 33 in portions where the inclined surface portions 33 are absent, it is possible to eliminate (make the conditions of the inclination angle θ of the inclined surface portions 33 of the partition layer 30 and the height H of the partition layer 30 from the substrate 3 in the second embodiment and Modification 1 described above. That is, even if the conditions of the inclination angle θ of the inclined surface portions 33 of the partition layer 30 and the height H of the partition layer 30 from the substrate 3 in the second embodiment and Modification 1 described above are not satisfied, by providing the partition layer 30 with the inclined surface portions 33 that are inclined in a direction opening with respect to the optical axis of the light emitting element 4 and the curved surface portions 34 that are continuous with the inclined surface portions 33 in portions where the inclined surface portions 33 are absent, it is possible to increase the front brightness of the display and improve the light utilization efficiency.

[0097] Fig. 16 is an enlarged cross-sectional view emphasizing the structure of the partition wall layer 30 of Modification 2. Fig. 16 illustrates the case where the light-emitting element 4 is an OLED, but the light-emitting element 4 may be composed of a micro-LED.

[0098] 16 , the curved surface portions 34 of the partition layer 30 are provided at the base portion (proximal end portion) of the partition layer 30 that is continuous with the substrate 3. That is, of the inner surface (side surface) of the partition layer 30, the upper portion in the height direction is the inclined surface portion 33, and the lower portion in the height direction is the curved surface portion 34. Furthermore, the curved surface portions 34 of the partition layer 30 are arranged so as to extend forward from the imaginary line of the inclined surface portion 33 in the portion where the inclined surface portion 33 does not exist as a reference, and to leave a small clearance between them and the side surface of the light-emitting element 4 (the curved surface portions 34 extend so as to protrude gently toward the light-emitting element 4).

[0099] As a result, not only the light emitted from the light-emitting element 4 that is not reflected by the inclined surface portions 33 and the curved surface portions 34 of the partition layer 30 (light emitted directly upward or at a small angle in FIG. 6 ) but also the light that has been reflected once at any portion of the inclined surface portions 33 and the curved surface portions 34 of the partition layer 30 is guided evenly to the boundary between the filler 40 and the adhesive layer 50 directly upward or at a small angle in FIG. 16 . In particular, the curved surface portions 34 can reflect even light that is emitted almost directly to the side from the light-emitting element 4 at directly upward or at a small angle in FIG. 16 . As a result of optimizing the light reflection direction by the inclined surface portions 33 and the curved surface portions 34 of the partition layer 30 in this way, the front brightness of the display can be increased, thereby improving light utilization efficiency.

[0100] Fig. 17 is a diagram showing the difference in front luminance and thus light utilization efficiency between when only the inclined surface portion 33 is provided on the partition layer 30 and when both the inclined surface portion 33 and the curved surface portion 34 are provided on the partition layer 30 when the light-emitting element 4 is a micro LED. Fig. 18 is a diagram showing the difference in front luminance and thus light utilization efficiency between when only the inclined surface portion 33 is provided on the partition layer 30 and when both the inclined surface portion 33 and the curved surface portion 34 are provided on the partition layer 30 when the light-emitting element 4 is an OLED. In both Figs. 17 and 18 , it can be seen that providing the inclined surface portion 33 and the curved surface portion 34 on the partition layer 30 contributes to improving the front luminance and light utilization efficiency.

[0101] 19A to 19C are diagrams showing variations of the curved surface portion 34 provided in the partition layer 30. In all of Fig. 19A to 19C, the curved surface portion 34 is provided based on an imaginary line (drawn by a two-dot chain line) of the inclined surface portion 33 in the portion where the inclined surface portion 33 does not exist.

[0102] In the example of Fig. 19A, the curved surface portion 34 is provided on the farther side of the partition wall layer 30 than the imaginary line (two-dot chain line) of the inclined surface portion 33 in the portion where the inclined surface portion 33 is absent. In the example of Fig. 19B, the curved surface portion 34 is provided on the nearer side of the partition wall layer 30 than the imaginary line (two-dot chain line) of the inclined surface portion 33 in the portion where the inclined surface portion 33 is absent. In the example of Fig. 19C, the curved surface portion 34 is provided on both the farther and nearer sides of the partition wall layer 30 than the imaginary line (two-dot chain line) of the inclined surface portion 33 in the portion where the inclined surface portion 33 is absent.

[0103] When the partition layer 30 is provided with the inclined surface portions 33 and the curved surface portions 34, when a tangent to the curved surface portion 34 at a predetermined point (for example, the deepest part) is defined, the inclination angle of the tangent to the curved surface portion 34 and the inclination angle of the inclined surface portion 33 of the partition layer 30 can be set to fall within a predetermined range (for example, ±5° or ±10°). In this case, it is possible to further improve the front brightness and the light utilization efficiency.

[0104] As another variation, the inclined surface portion 33 provided on the partition layer 30 may be divided into a plurality of inclined surface portions (inclined regions) having different inclination angles, and / or the curved surface portion 34 provided on the partition layer 30 may be divided into a plurality of curved surface portions (curved surface regions) having different curvatures (radii of curvature).

[0105] The manufacturing methods for the display devices described in the second embodiment, Modification 1, and Modification 2, particularly the method for forming the partition wall layer 30, are flexible and allow for various design modifications, but a simple example will be described below. Light source elements are arranged on the upper surface of the substrate, and a partition wall material is applied. A sacrificial layer / film (resist) is then patterned on the upper surface of the partition wall material, and isotropic etching such as dry etching or wet etching is performed to form the partition walls. A filler material is then filled, and an adhesive layer and a cover glass are then provided in that order.

[0106] As described above, the display device of the present embodiment includes a substrate, a plurality of light source elements provided on the substrate, and a plurality of partition walls provided on the substrate and surrounding the plurality of light source elements and positioned at the boundaries of the plurality of light source elements, the plurality of partition walls having inclined surface portions inclined in a direction opening with respect to the optical axes of the plurality of light source elements, the inclination angle of the inclined surface portions being 10° or more with respect to the optical axes of the plurality of light source elements, and the height of the plurality of partition walls being 3 μm or more from the substrate. Alternatively, the display device of the present embodiment includes a substrate, a plurality of light source elements provided on the substrate, and a plurality of partition walls provided on the substrate and surrounding the plurality of light source elements and positioned at the boundaries of the plurality of light source elements, the plurality of partition walls having inclined surface portions inclined in a direction opening with respect to the optical axes of the plurality of light source elements and curved surface portions continuous with the inclined surface portions at portions where the inclined surface portions are absent. This increases the front brightness of the display and improves light utilization efficiency.

[0107] <Background to Invention of Display Device of Third Embodiment> When inventing the micro LED display 1 of the third embodiment shown in Fig. 20, the following problems were encountered. First, the technical background will be described.

[0108] WO 2022 / 117995 discloses an invention related to micro LED beam collimation, in which a reflective metal layer made of aluminum is formed on the surface of a barrier layer made of a dielectric.

[0109] British Patent Application Publication No. 2595250 discloses an invention relating to a light-emitting element array, which states that crosstalk can be improved by forming a partition layer by dispersing an organic semiconductor and absorbing light of a specific wavelength.

[0110] In WO 2022 / 117995, after forming the barrier rib layer, a reflective material made of aluminum must be formed by vapor deposition or the like, which complicates the process. Furthermore, the metallic luster causes glare in the displayed image, degrading display quality. In GB 2595250, light is absorbed by the barrier rib layer, reducing the amount of light extracted and lowering brightness.

[0111] Therefore, as a result of intensive research, the inventors have developed a display device in which the luminance is improved and crosstalk is reduced by surrounding the periphery of the light-emitting element with a reflective partition layer.

[0112] The display device in the third embodiment is configured as a micro LED (Light Emitting Diode) display 1 shown in Fig. 20. Fig. 20 is a schematic cross-sectional view of the micro LED display 1.

[0113] In Figure 20, for the same parts as those of the micro LED display 1 shown in Figure 1, please refer to the description of Figure 1.

[0114] 20 has a light-reflecting function and contains a white pigment 14. In order to obtain high light conversion efficiency in the micro LED display 1, it is preferable that the height of the partition layer 5 is large, and although not limited thereto, the height is preferably about 2 μm to 6 μm, and more preferably about 3 μm to 5 μm.

[0115] 20, the surfaces of the color conversion layers 6a, 6b and resin 9 may be formed at substantially the same height as the partition wall layer 5, or may be slightly lower than the partition wall layer 5. The thickness of the color conversion layers 6a, 6b is about 2 to 6 μm.

[0116] 20, a color filter 11 is provided on the surfaces of the color conversion layers 6a, 6b and the resin 9 via a barrier layer 10. The color filter 11 includes a red filter 11a, a green filter 11b, and a blue filter 11c. The thickness of the color filter 11 is not limited, but is, for example, about 0.5 μm to 2.0 μm.

[0117] Although the barrier layer 10 is not an essential layer, providing the barrier layer 10 can reduce the thermal influence on the quantum dots 7 and 8 in the color conversion layers 6a and 6b when the color filter 11 is formed. Furthermore, if there are irregularities between the surfaces of the partition layer 5 and the color conversion layers 6a and 6b and the resin 9, the barrier layer 10 can smooth out the irregularities. This allows the color filter 11 to be formed on a flat surface. There are no restrictions on the material of the barrier layer 10, but it is preferably an oxide film or a nitride film, for example, SiO ２ The thickness of the barrier layer 10 is not limited, but is about 50 nm to 1 μm.

[0118] The color filters 11 are arranged such that a red filter 11a is located at the position of the red display pixel 2a, a green filter 11b is located at the position of the green display pixel 2b, and a blue filter 11c is located at the position of the blue display pixel 2c.

[0119] The red filter 11a absorbs short wavelength blue light and transmits red light, the green filter 11b absorbs short wavelength blue light and transmits red light, and the blue filter 11c transmits blue light.

[0120] <Characteristic Configuration of the Micro LED Display 1 of the Third Embodiment> The micro LED display 1 of the third embodiment has the following characteristics: It has a light emitting element 4 and a partition layer 5 arranged around the light emitting element 4, and the partition layer 5 contains a white pigment 14.

[0121] 20 , the partition wall layer 5 contains a large number of white pigment particles 14, which are dispersed uniformly in the height direction. The shape of the white pigment particles 14 is not particularly limited and may be irregular, but is preferably spherical. In addition to the white pigment particles 14, the partition wall layer 5 also contains a binder resin 15, such as a composite resin of polysiloxane and an acrylic monomer.

[0122] The white pigment 14 preferably contains one or more selected from titanium dioxide, zirconium oxide, zinc oxide, barium sulfate, and composite compounds thereof. Of these, the white pigment 14 is more preferably titanium dioxide alone or contains titanium dioxide.

[0123] The content of the white pigment 14 in the partition wall layer 5 is preferably 15% by mass or more and 35% by mass or less, and more preferably 20% by mass or more and 30% by mass or less. If the content of the white pigment 14 is too low, the reflectance decreases, and the effect of achieving both reduced crosstalk and improved brightness is reduced. If the content of the white pigment 14 is too high, the durability and environmental resistance of the partition wall layer 5 are likely to decrease. Therefore, by setting the content of the white pigment 14 within the range of 15% by mass to 35% by mass, it is possible to achieve both reduced crosstalk and improved brightness, and also to obtain good durability and environmental resistance of the partition wall layer 5.

[0124] In the third embodiment, the reflectance of the partition layer 5 at a wavelength of 450 nm is preferably 65% ​​or more. That is, this reflectance indicates the reflectance of blue light. The reflectance is more preferably 70% or more, and even more preferably 75% or more.

[0125] In the third embodiment, the partition wall layer 5 containing the white pigment 14 can reflect the light beams L1 to L3, as shown in FIG. 20, thereby reducing crosstalk and light absorption, thereby improving brightness. In other words, brightness can be increased compared to a configuration in which the partition wall layer absorbs light of a specific wavelength. Furthermore, since the partition wall layer does not have a metallic luster, high-quality image display can be achieved.

[0126] 21 differs from FIG. 20 in the configuration of the color filter 11. In FIG. 21, yellow filters (Ye filters) 13 are provided at the positions of the red display pixels 2a and the green display pixels 2b, and the yellow filters 13 transmit red and green light. Other than that, the configuration is the same as that in FIG. 20.

[0127] 21 , the partition layer 5 also contains a white pigment 14, which preferably contains one or more selected from titanium dioxide, zirconium oxide, zinc oxide, barium sulfate, and composite compounds thereof, and the content of the white pigment 14 is preferably 15% by mass or more and 35% by mass or less, and more preferably 20% by mass or more and 30% by mass or less. In this embodiment, the reflectance of the partition layer at a wavelength of 450 nm can be made 65% or more, thereby achieving both reduced crosstalk and improved brightness.

[0128] In the third embodiment, the partition wall layer 5 in which the white pigment 14 is titanium dioxide and has a content of 20 to 30 mass % and the binder resin 15 contains polysiloxane and acrylic monomer can have a reflectance of about 75% at a wavelength of 450 nm.

[0129] <Regarding the Shape of the Partition Wall Layer 5> FIGS. 22 to 24 illustrate preferred shapes of the partition wall layer 5. To converge light within each of the display pixels 2a to 2c, the sidewalls of the partition wall layer 5 preferably have vertical surfaces 5c, as shown in FIG. 22. As shown in FIG. 22, the cross-sectional shape of the partition wall layer 5 is generally rectangular. Alternatively, as shown in FIG. 23, the sidewalls of the partition wall layer 5 may have inclined surfaces 5d that gradually narrow in the height direction. The cross-sectional shape of the partition wall layer 5 shown in FIG. 23 is trapezoidal. In this case, the inclination angle θ of the inclined surfaces 5d (the angle between the substrate 3) is preferably 80° or less, and more preferably 70° or less.

[0130] 24, the sidewalls of the partition layer 5 may include curved surfaces 5e. The curved surfaces 5e are preferably concave surfaces that are recessed so that the width of the partition layer 5 narrows in the height direction. As shown in FIG. 24, the curved surfaces 5e are formed at the base of the partition layer 5, and the vertical surfaces 5c shown in FIG. 3 or the inclined surfaces 5d shown in FIG. 4 are formed in the height direction, continuing from the curved surfaces 5e, thereby more effectively converging light into each of the display pixels 2a to 2c. This more effectively achieves both reduced crosstalk and improved brightness.

[0131] <Method of Forming the Barrier Layer 5> The method of forming the barrier layer 5 is not limited, but for example, a dry etching method can be used. In the dry etching method, a barrier material is applied by spin coating or the like, and a sacrificial film is formed on the surface of the applied layer. The sacrificial film is patterned by photolithography using a commercially available positive resist. Then, an fluorine-based gas (CF ４ Or C ４ F ８ The coating layer is dry-etched by etching, and the sacrificial layer is ２ It is removed by ashing and cleaning with an organic solvent.

[0132] The sidewall shape can be varied in various ways depending on the patterning shape of the sacrificial layer, the dry etching time, the output, and the like.

[0133] As described above, the display device of the third embodiment includes a light-emitting element and a partition wall layer disposed around the light-emitting element, and the partition wall layer contains a white pigment, thereby achieving both improved brightness and reduced crosstalk.

[0134] <Background to Invention of Display of Fourth Embodiment> When inventing the micro LED display 1 of the fourth embodiment shown in Fig. 25, the following problems were encountered. First, the technical background will be described.

[0135] Japanese Patent Laid-Open No. 2021-081724 discloses a photosensitive resin composition for forming partition walls and a display device using the same. Japanese Patent Laid-Open No. 2021-081724 states that by including a white pigment in the partition walls, it is possible to impart reflective properties to light directed toward the partition walls and improve light efficiency.

[0136] Japanese Patent Application Laid-Open No. 2020-205417 discloses an invention relating to a micro LED display device having a light-shielding portion in which the cross-sectional shape of the partition is an inverted tapered shape or a T-shape, and a reflecting portion provided on the side of the light-shielding portion. Japanese Patent Application Laid-Open No. 2020-205417 discloses that the display device has high brightness and contrast and can suppress color mixing of light between adjacent pixels.

[0137] Both JP 2021-081724 A and JP 2020-205417 A aim to improve the reflectivity of the partition walls. However, even if the reflectivity is increased, the color conversion layer filled inside the partition walls cannot completely convert the excitation light, and some of the excitation light reaches the light receiving surface. Therefore, the color conversion efficiency cannot be effectively improved. This also leads to a decrease in color purity.

[0138] The micro-LED method is considered to have an advantage over liquid crystal on silicon (LCOS), laser beam scanning (LBS), or organic light-emitting diode (OLED) microdisplays in terms of brightness, and is expected to see increased application in the future.

[0139] As a method for displaying full color using a micro LED display, a technology has been proposed in which blue light-emitting elements are used as light-emitting elements (LEDs), and color conversion (wavelength conversion) is performed using a color conversion layer using quantum dots to enable RGB display.

[0140] However, there is a problem that the color purity decreases when the blue light that cannot be completely converted mixes with the red light or the green light. In JP 2021-081724 A and JP 2020-205417 A, although the reflection characteristics of the partition wall are improved, the color conversion efficiency cannot be sufficiently increased.

[0141] As a result of intensive research, the inventors have invented a display device that can extend the optical path length of excitation light by controlling the surface roughness of the partition walls, thereby improving color conversion efficiency.

[0142] <Characteristic Configuration of Micro LED Display 1 of Fourth Embodiment> A display device in the fourth embodiment is configured as a micro LED (Light Emitting Diode) display 1 shown in Fig. 25. Fig. 25 is a schematic cross-sectional view of the micro LED display 1.

[0143] In Figure 25, for the same parts as the micro LED display 1 shown in Figure 1, please refer to the description of Figure 1.

[0144] The micro LED display 1 of the fourth embodiment has the following features: The surface roughness of the barrier layer 5 provided around the light emitting element 4 is 10 Å or more and less than 500 Å.

[0145] The "surface roughness" refers to the surface roughness of the side surface 5 a of the partition wall layer 5, and it is preferable that the surface roughness be within the above range for preferably 50% or more, more preferably 60% or more, even more preferably 70% or more, still more preferably 80% or more, still more preferably 90% or more, and most preferably 95% or more of the area of ​​the side surface 5 a.

[0146] The surface roughness can be measured by obtaining an SEM image of the cross section and calculating the calculated average roughness Ra of the side surface 5 a of the partition wall layer 5 from the SEM image, or by using an atomic force microscope. For example, an SU3500 manufactured by Hitachi High-Technologies Corporation can be used as the scanning microscope, and an NX20 manufactured by Park Systems Co., Ltd. can be used as the atomic force microscope. Furthermore, the surface roughness may be calculated by measuring approximately 50% of the center of the height of the partition wall layer 5 rather than the entire side surface 5 a of the partition wall layer 5.

[0147] In this way, by appropriately roughening the side surfaces 5a of the partition layer 5, the optical path length of blue light as excitation light can be extended, and color conversion efficiency can be improved.

[0148] Fig. 26 is a schematic diagram for explaining the mechanism by which the optical path length of blue light (excitation light) is extended. Fig. 26 shows a red display pixel 2a, but the same applies to a green display pixel 2b. As shown in Fig. 26, blue light L1 emitted from the light-emitting element 4 is converted into red light L4 by the red quantum dot 7. The red light L4 passes through the red color filter 11a.

[0149] On the other hand, blue light L5 and L6 traveling toward the barrier layer 5 is refracted by the moderately roughened side surface 5a of the barrier layer 5, returned to the inside of the color conversion layer 6a, and eventually converted into red light L4 by the red quantum dots 7. At this time, like the blue light L6, it is refracted by the barrier layer 5 multiple times, thereby extending the optical path length and, in other words, the residence time within the color conversion layer 6a. As a result, the probability of conversion into red light L4 by the red quantum dots 7 increases, improving the color change efficiency and, ultimately, the color purity.

[0150] Increasing the surface roughness of the partition wall layer 5 makes light more likely to be diffused, increasing the number of times that light is refracted at the partition walls. On the other hand, if the surface roughness is too high, the amount of light that enters the color filter from the color conversion layer decreases, leading to a decrease in brightness.

[0151] Therefore, in the fourth embodiment, the surface roughness of the partition wall layer 5 is set to a range of 10 Å or more and less than 500 Å. The surface roughness of the partition wall layer 5 is preferably 30 Å or more, and more preferably 50 Å or more. The surface roughness of the partition wall layer 5 is preferably 400 Å or less, more preferably 300 Å or less, and even more preferably 200 Å or less. The surface roughness of the partition wall layer 5 is more preferably in the range of 50 Å or more and 200 Å or less, and even more preferably 100 Å or more and 200 Å or less, or 50 Å or more and 100 Å or less.

[0152] This increases the number of refractions in the partition layer 5, thereby extending the optical path length and suppressing a decrease in the amount of light on the light-receiving side. The amount of light is evaluated, for example, based on the total amount of light when the side surface 5 a of the partition layer 5 is a mirror surface (surface roughness=0 Å).

[0153] The height t of the partition layer 5 is preferably 1 μm or more and 10 μm or less, more preferably 2 μm or more and 8 μm or less, and even more preferably 4 μm or more and 6 μm or less, which allows the optical path length to be appropriately extended and effectively suppresses a reduction in the amount of light.

[0154] Furthermore, the side surfaces 5a of the partition layer 5 are preferably formed perpendicular to the substrate 3, or are inclined so that the width of the partition layer 5 gradually narrows in a direction away from the substrate 3 (upward in the drawing). In this case, the inclination angle θ between the side surfaces 5a and the substrate 3 is preferably 80° or more and 90° or less. This makes it possible to effectively extend the optical path length while suppressing a reduction in the amount of light, thereby achieving high brightness and color purity. In addition, this is adaptable to higher resolution image sizes.

[0155] 27, a plurality of light-emitting elements 4 are formed on a substrate 3. The plurality of light-emitting elements 4 constitute an RGB pixel region.

[0156] Next, a partition wall material layer 22 is formed over the entire surface of the substrate 3. The partition wall material is not limited, and for example, a partition wall material containing a white pigment can be used. After the partition wall material layer 22 is applied, a heat treatment is performed. The heat treatment temperature is not limited, but is about 70°C to 150°C. The heat treatment time is about several minutes to several tens of minutes.

[0157] Next, as shown in FIG. 27 , a resist layer 23 is applied to the upper surface 22 a of the partition wall material layer 22. An existing material can be selected for the resist layer 23. As shown in FIG. 27 , a mask 24 is placed above the resist layer 23. The mask 24 has light-transmitting portions 24 a and non-transmitting portions 24 b. If the resist layer 23 is a positive type, the unexposed portions remain, whereas if the resist layer 23 is a negative type, the exposed portions remain. The patterns of the light-transmitting portions 24 a and non-transmitting portions 24 b of the mask 24 are changed depending on the type of resist layer 23. The mask 24 has a planar pattern of the partition wall layer 5. The resist layer 23 is exposed through the mask 24 and developed to form a resist pattern 23 a shown in FIG. 28 on the upper surface 22 a of the partition wall material layer 22.

[0158] Then, the partition material layer 22 not covered with the resist pattern 23a is removed by dry etching, and then the resist pattern 23a is removed (see FIG. 29).

[0159] By anisotropic dry etching, the side surfaces 5a of the partition layer 5 can be formed as substantially vertical or inclined surfaces.

[0160] For dry etching, existing methods such as reactive ion etching and reactive gas etching can be used. Although the dry etching conditions are not limited, the etching gas is preferably CHF ３ , C.F. ４ , F ２ , HBr, Ar, O ２ A mixed gas of two or more of these gases was used. As dry etching conditions, the flow rate of each gas was adjusted within a range of several sccm to 300 sccm. In addition, for reactive ion etching, the RF power was adjusted to approximately 500 W to 3000 W, the magnetic field output was adjusted to approximately 500 W to 2000 W, and the etching time was set to several minutes to several tens of minutes.

[0161] By adjusting the etching conditions described above, the surface roughness of the partition wall can be set within a range of 10 Å or more and less than 500 Å, and the range of the surface roughness can be further narrowed stepwise, and particularly preferably, it is possible to appropriately adjust the surface roughness within a range of 50 Å or more and 200 Å or less.

[0162] <Effects of the Fourth Embodiment> In the fourth embodiment, the surface roughness of the partition layer 5 is adjusted to a range of 10 Å or more and less than 500 Å. As a result, in the red-displaying pixel 2 a and the green-displaying pixel 2 b, even if the blue light (excitation light) emitted from the light-emitting element 4 cannot be completely color-converted, the optical path length can be extended so that the blue light remains in the color conversion layers 6 a, 6 b without being mixed with the red light or green light, and as a result, the color conversion efficiency can be improved and the color purity can be increased.

[0163] By adjusting the surface roughness to a range of 10 Å or more and less than 500 Å, more preferably 50 Å or more and 200 Å or less, it is possible to effectively suppress a decrease in the amount of light on the light receiving side, increase the number of refractions, and effectively extend the optical path length.

[0164] As described above, a display device according to a fourth embodiment includes light-emitting elements provided on a substrate, partition walls formed around the light-emitting elements, and color conversion layers on the light-emitting elements that fill the internal spaces of the partition walls, and the surface roughness of the partition walls is equal to or greater than 10 Å and smaller than 500 Å. By adjusting the surface roughness of the partition walls in this way, the optical path length of excitation light can be extended, color conversion efficiency can be increased, and a display device with excellent color purity can be provided.

[0165] The display devices of the second to fourth embodiments described above preferably include the following characteristic configurations of the first embodiment: (1) The spectral transmittance of the color filter at the emission peak wavelength of the light-emitting element is 30% or less. (2) The spectral transmittance of the color filter at the fluorescence peak wavelength transmitted through the color conversion layer is 80% or more. In the second embodiment, a color filter having the characteristic configurations of (1) and (2) above can be disposed in place of the cover glass 60.

[0166] Furthermore, in the above embodiment, the barrier rib layer has been described as a white barrier rib, but it can also be a black barrier rib. The material of the black barrier rib is not limited, but it can be formed, for example, from a material having a light-blocking property or a material containing a black pigment. Alternatively, it can be formed from a mixed color material containing a pigment of purple, blue, yellow, or the like. Examples of materials having a light-blocking property include carbon black and titanium black. Furthermore, a material that blocks visible light and transmits infrared light can also be used.

[0167] The display device of this embodiment can be used not only indoors but also outdoors under high brightness. The display device of this embodiment can also be applied to a micro LED display device, enabling miniaturization.

[0168] The present invention will be described in detail below with reference to examples carried out to clarify the effects of the present invention (fourth embodiment). Note that the present invention is not limited to the following examples. Using the optical simulation model shown in FIG. 30, evaluation was carried out using partition walls with different surface roughnesses.

[0169] 30 are partition walls A, color conversion layers B, color filters C, adhesive layers D, and cover glass F. The refractive index n of the cover glass F was 1.52, the refractive index n of the adhesive layer was 1.523, the refractive index n of the color filter was between 1.6 and 2.0, the refractive index n of the color conversion layer B was 1.6, and the reflectance of the partition walls A was 100%.

[0170] In the experiment, Experimental Examples 1 to 16 were used, which had different surface roughnesses of the partition walls. No surface roughness was used in Experimental Examples 1 and 9. In Experimental Examples 2 to 8 and 10 to 16, the surface roughnesses were 10 Å, 50 Å, 100 Å, 200 Å, 500 Å, 1000 Å, and 5000 Å.

[0171] The number of times that blue light emitted from the light-emitting element is refracted at the side surface of the partition wall was determined in terms of light dose. The light dose was measured using the surface of cover glass F shown in Figure 30 as the light-receiving surface. Table 1 shows an example in which the partition wall height was 4 μm, and Table 2 shows an example in which the partition wall height was 6 μm.

[0172]

[0173]

[0174] 31 shows the results of a simulation experiment showing the relationship between the number of refractions of blue light and the amount of light when the surface roughness of the partition walls is different.

[0175] As shown in Figure 31, Tables 1 and 2, it was found that the number of refractions or the average number of refractions increases as the surface roughness increases. However, when the surface roughness is 500 Å or more, the total light dose is significantly reduced when the total light dose for no surface roughness (surface roughness = 0 Å) is used as the standard. For this reason, a surface roughness of 500 Å or more was evaluated as x. Furthermore, when the surface roughness is 0 Å, the number of refractions does not exceed 6, and the evaluation was also x. For this reason, the surface roughness is set to a range less than 500 Å, preferably 200 Å or less.

[0176] It was found that if the surface roughness is 10 Å or more, six or more refractions are possible, and the optical path length can be extended. Also, if the surface roughness is 50 Å or more, the proportion of refractions of 10 or more increases, and the average optical path length can be extended further. Therefore, the surface roughness range of 50 Å to 200 Å was judged as ○.

[0177] From the above, the surface roughness of the partition walls is set to a range of 10 Å or more and less than 500 Å, and more preferably, 50 Å or more and 200 Å or less.

[0178] This application is based on Japanese Patent Application No. 2023-181514 filed on October 23, 2023, Japanese Patent Application No. 2023-183617 filed on October 26, 2023, Japanese Patent Application No. 2023-204584 filed on December 4, 2023, and Japanese Patent Application No. 2024-056259 filed on March 29, 2024. The contents of these applications are incorporated herein in their entirety.

Claims

1. A display device comprising a plurality of display pixels each comprising a plurality of light-emitting elements arranged on a substrate, a color conversion layer arranged on the light-emitting elements, and a color filter arranged on the color conversion layer, wherein the spectral transmittance of the color filter at the emission peak wavelength of the light-emitting elements is 30% or less, and the spectral transmittance of the color filter at the fluorescence peak wavelength transmitted through the color conversion layer is 80% or more.

2. The display device according to claim 1, further comprising a partition layer formed between adjacent ones of said color conversion layers.

3. The display device according to claim 1, wherein the color conversion layer includes quantum dots.

4. The display device according to claim 3, wherein the quantum dots are cadmium-free.

5. The display device according to claim 1, characterized in that it comprises blue, red and green display pixels, the red and green display pixels being formed by a laminated structure of the light-emitting element, the color conversion layer and the color filter.

6. The display device according to claim 1, wherein the light-emitting element is a blue light-emitting element.

7. The display device according to claim 1, wherein a microlens is formed on said color filter.

8. The display device according to claim 1, characterized in that the NTSC ratio is 65% or more.

9. The display device according to claim 2, characterized in that the partition layer has an inclined surface portion inclined in a direction opening with respect to the optical axis of the light-emitting element, the inclination angle of the inclined surface portion is 10° or more with respect to the optical axis of the light-emitting element, and the height of the partition layer is 3 μm or more from the substrate.

10. The display device according to claim 9, wherein the height of the partition layer from the substrate is 3 μm or more and 6 μm or less.

11. The display device according to claim 9, wherein the partition layer has a curved surface portion that is continuous with the inclined surface portion in a portion where the inclined surface portion is not present.

12. The display device according to claim 2, characterized in that the partition layer has an inclined surface portion inclined in a direction opening with respect to the optical axis of the light-emitting element, and a curved surface portion continuous with the inclined surface portion in a portion where the inclined surface portion is not present.

13. A display device as described in claim 11 or 12, characterized in that the curved surface portion is provided on the back side of the partition layer from the imaginary line of the inclined surface portion in the non-existent portion of the inclined surface portion, or on the front side of the partition layer from the imaginary line, or is provided across both the back and front sides of the partition layer from the imaginary line.

14. The display device according to claim 11 or 12, characterized in that the curved surface portion is provided at a base portion of the partition layer that is continuous with the substrate.

15. The display device according to claim 2, wherein the partition layer contains a white pigment.

16. The display device according to claim 15, wherein the white pigment contains at least one selected from the group consisting of titanium dioxide, zirconium oxide, zinc oxide, barium sulfate, and composite compounds thereof.

17. The display device according to claim 15, wherein the content of the white pigment in the partition layer is 15% by mass or more and 35% by mass or less.

18. The display device according to claim 15, wherein the reflectance of the partition layer at a wavelength of 450 nm is 65% or more.

19. The display device according to claim 15, characterized in that the side walls of the partition layer are formed to have at least one of a vertical surface extending perpendicular to the height direction, an inclined surface inclined so that the width of the partition layer narrows in the height direction, or a curved surface concave so that the width of the partition layer narrows in the height direction.

20. The display device according to claim 2, wherein the surface roughness of the barrier layer is 10 Å or more and less than 500 Å.

21. The display device according to claim 20, wherein the surface roughness of the partition layer is 50 Å or more and 200 Å or less.

22. The display device according to claim 20, wherein the side surfaces of the partition walls are formed in a direction perpendicular to the substrate, or are inclined so that the width of the partition walls gradually narrows in a direction away from the substrate.

23. The light-emitting element according to claim 1, characterized in that the light-emitting element is composed of a micro LED (Light Emitting Diode).

24. The light-emitting element according to claim 1, characterized in that the light-emitting element is composed of an OLED (Organic Light Emitting Diode).

25. A method for manufacturing a display device according to claim 1, characterized in that the color filter is formed at a heat treatment temperature of 150° C. or less.

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