Light-emitting element, method for manufacturing same, and display device equipped with same

Abstract

A light-emitting element (30a) is equipped with: a bank (22) in which a first opening (22o) having an inclined end face is formed; a first electrode (23) provided on the bank (22) so as to cover the first opening (22o); a light-emitting functional layer (25) provided on the first electrode (23); and a second electrode (26) provided on the light-emitting functional layer (25). The inclined end face from at least a lower end portion of the first opening (22o) to an end portion at which a thickness of the bank (22) is at half or more is formed as a first curved face (22i) that is convex downward such that an inclination of a tangent increases.

Description

Light-emitting element, method of manufacturing the same, and display device including the same

[0001] The present invention relates to a light-emitting element, a method for manufacturing the same, and a display device including the same.

[0002] In recent years, self-luminous display devices have been attracting attention as display devices that can replace liquid crystal display devices. Known light-emitting elements constituting subpixels of such display devices include, for example, organic electroluminescence (EL) elements and quantum dot light-emitting elements. Patent Document 1, for example, proposes a light-emitting device including a bank having a through-hole with a sloping opening sidewall, a lower electrode formed on the bank so as to close the through-hole, an upper electrode formed above the lower electrode, and an EL layer formed between the lower electrode and the upper electrode and adjacent to the lower electrode and the upper electrode, respectively. The lower electrode has a sloping surface along at least a portion of the sloping opening sidewall, the EL layer includes at least a light-emitting layer and has a sloping surface along at least a portion of the sloping surface of the lower electrode, and the upper electrode has a sloping surface along at least a portion of the sloping surface of the EL layer.

[0003] International Publication No. 2022 / 219732

[0004] However, a substrate (backplane substrate) having a TFT layer in which a plurality of thin film transistors (hereinafter also referred to as "TFTs") for driving the light-emitting elements is provided below the light-emitting elements. When the light-emitting elements are driven on this backplane substrate, the brightness of the end portions of the sub-pixels (portions of the inclined surfaces of the EL layer) may decrease, which leaves room for improvement.

[0005] The present invention has been made in consideration of these points, and its purpose is to suppress a decrease in brightness at the ends of a subpixel in a light-emitting element that constitutes a subpixel and in a display device that includes the same.

[0006] In order to achieve the above object, the light-emitting element of the present invention is a light-emitting element comprising: a bank in which a first opening having an inclined end surface is formed; a first electrode provided on the bank so as to cover the first opening; a light-emitting functional layer provided on the first electrode; and a second electrode provided on the light-emitting functional layer, wherein the inclined end surface from at least the lower end of the first opening to the end where the thickness of the bank is more than half is formed as a downwardly convex first curved surface with an increasing slope of the tangent.

[0007] The method for manufacturing a light-emitting element according to the present invention is a method for manufacturing a light-emitting element comprising: a bank in which a first opening having an inclined end surface is formed; a first electrode provided on the bank so as to cover the first opening; a light-emitting functional layer provided on the first electrode; and a second electrode provided on the light-emitting functional layer, and is characterized in that after the bank is formed, when the bank is exposed to light to form the first opening, a mask is used which has a gray-tone region around the first opening whose light transmittance is higher than that of a light-shielding region and lower than that of a light-transmitting region, thereby forming the inclined end surface at least from the lower end of the first opening to the end where the thickness of the bank is more than half into a downwardly convex first curved surface with an increasing slope of the tangent.

[0008] According to the present invention, in a light-emitting element constituting a sub-pixel and a display device including the same, it is possible to suppress a decrease in luminance at the end portion of the sub-pixel.

[0009] FIG. 1 is a cross-sectional view showing a schematic configuration of a quantum dot light-emitting device according to a first embodiment of the present invention, and an enlarged cross-sectional view of the periphery of a bank. FIG. 2 is a cross-sectional view showing a light-emitting functional layer constituting the quantum dot light-emitting device according to the first embodiment of the present invention. FIG. 3 is an enlarged cross-sectional view of the periphery of a bank and a plan view showing the corresponding planar shape of a gray-tone mask in a bank formation step for forming the bank constituting the quantum dot light-emitting device according to the first embodiment of the present invention. FIG. 4 is a cross-sectional view showing a schematic configuration of a quantum dot light-emitting device according to a second embodiment of the present invention, and an enlarged cross-sectional view of the periphery of the bank, and is a view corresponding to FIG. 1. FIG. 5 is a plan view showing a schematic configuration of a quantum dot display device including a quantum dot light-emitting device according to an embodiment of the present invention. FIG. 6 is a plan view of a display region of a quantum dot display device including a quantum dot light-emitting device according to an embodiment of the present invention. FIG. 7 is a cross-sectional view of a display region of a quantum dot display device including a quantum dot light-emitting device according to an embodiment of the present invention. FIG. 8 is an equivalent circuit diagram showing a pixel circuit of a quantum dot display device including a quantum dot light-emitting device according to an embodiment of the present invention.

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments.

[0011] Light-Emitting Element (Quantum Dot Light-Emitting Element) First Embodiment FIGS. 1 to 3 illustrate a first embodiment of a light-emitting element according to the present invention. In the following embodiments, quantum dot light-emitting elements, also known as nanoLEDs or QLEDs (Quantum-dot light-emitting diodes), are used as light-emitting elements. FIG. 1 is a cross-sectional view showing a schematic configuration of a quantum dot light-emitting element 30a according to this embodiment, and an enlarged cross-sectional view of the periphery of a bank 22. FIG. 2 is a cross-sectional view showing a light-emitting functional layer 25 constituting the quantum dot light-emitting element 30a. FIG. 3 is an enlarged cross-sectional view of the periphery of a bank 22 and a plan view showing the corresponding planar shape of a gray-tone mask M in a bank formation step for forming the bank 22 constituting the quantum dot light-emitting element 30a. The upper layer of the first electrode 23 is omitted from the enlarged views in FIGS. 1 and 3.

[0012] As shown in Fig. 1, the quantum dot light-emitting element 30a includes a bank 22 (wall), a first electrode 23, an edge cover 24, a light-emitting functional layer 25, and a second electrode 26, which are stacked in this order. The quantum dot light-emitting element 30a may include a connection electrode 21 as the bottom layer. The quantum dot light-emitting element 30a is configured as a top-emission type. Light emitted by the quantum dot light-emitting element 30a is extracted to the upper layer side (the sealing film 35 side in Fig. 7).

[0013] 1 , the connection electrode 21 is provided below the bank 22 and the first electrode 23. The connection electrode 21 is in contact with and electrically connected to the first electrode 23. The connection electrode 21 is also electrically connected to the TFT layer 20 described below. That is, the connection electrode 21 electrically connects the first electrode 23 and the TFT layer 20.

[0014] 1, the bank 22 is provided on the connection electrode 21. A first opening 22o is formed in the bank 22. The first opening 22o is a through-hole that partially exposes the connection electrode 21. The peripheral end surface (inner peripheral surface) of the first opening 22o is formed as an inclined surface (hereinafter also referred to as an "inclined end surface") that is tapered (forward tapered) so that the first opening 22o narrows toward the lower layer side of the bank 22 (the connection electrode 21 side in FIG. 1).

[0015] Examples of materials that can be used to form the bank 22 include positive photosensitive resin materials such as polyimide resin, acrylic resin, polysiloxane resin, and novolac resin, and polysiloxane-based SOG (Spin On Glass) materials.

[0016] In the quantum dot light-emitting device 30a of this embodiment, as shown in the enlarged view in FIG. 1 , the inclined end face of the first opening 22o of the bank 22 is formed as a downwardly convex first curved face 22i, in which the slope of the tangent increases from the bottom end upward. Furthermore, the inclined end face is formed as a second curved face 22d, in which the slope of the tangent decreases, continuing from the first curved face 22i. That is, the inclined end face has an inflection point 22ip between the first curved face 22i and the second curved face 22d, where the slope of the tangent changes from an increasing trend to a decreasing trend (the direction of the curved face changes). In this way, the inclined end face is formed as two continuous curved faces.

[0017] 1, in the quantum dot light-emitting device 30a, the first curved surface 22i is formed on an inclined end surface extending from the bottom end of the first opening 22o to the end where the thickness of the bank 22 is more than half. In other words, the ratio of the thickness T22i of the first curved surface 22i to the thickness T22 of the bank 22 (the sum of the thickness T22i of the first curved surface 22i and the thickness T22d of the second curved surface 22d, 100%) is 50% or more. In other words, the thickness T22i of the first curved surface 22i is equal to or greater than the thickness T22d of the second curved surface 22d (T22i≧T22d). That is, the thickness T22i of the first curved surface 22i may be equal to or greater than the thickness T22d of the second curved surface 22d.

[0018] Furthermore, in the quantum dot light-emitting element 30a, as shown in the enlarged view in FIG. 1 , the width W22 of the inclined end face of the first opening 22o of the bank 22 in the direction perpendicular to the thickness direction of the bank 22 (the vertical direction in FIG. 1 ) (the horizontal direction in FIG. 1 ; hereinafter, also referred to as the “width direction of the bank 22”) is preferably at least twice the thickness T22 of the bank 22 [width W22 ≧ thickness T22 × 2, width W22 ≧ (thickness T22i + thickness T22d) × 2]. That is, the width W22 of the inclined end face may be equal to or greater than the thickness T22 of the bank 22. In this case, the opening diameter of the first opening 22o is the appropriate dimension. Note that the width W22 of the inclined end face refers to the horizontal distance between the lower end of the inclined end face of the first opening 22o and the upper end where the curved surface (inclined surface) changes to a horizontal surface.

[0019] In conventional quantum dot light-emitting devices, the inclined end face of the bank opening is formed as an upwardly convex curved surface (corresponding to the second curved surface 22d) in which the slope of the tangent line constantly decreases from the bottom end to the top end. In this structure, the intersection of the tangent lines of the curved surface is located outside the bank. When a conventional quantum dot light-emitting device having a bank with the above structure is driven on a backplane substrate, there is a problem in that the brightness at the bank opening end face (the upwardly convex curved surface) (the edge (periphery) of the subpixel described below) is reduced. This is thought to be due to the fact that although a portion of the light emitted upward from the light-emitting functional layer is reflected by the surface of the second electrode and its upper layer (not shown) and exits upward, insufficient light emission or reflection occurs due to factors such as the unevenness of the bank opening end face and variations in the film thickness of the light-emitting functional layer and the second electrode.

[0020] In contrast, in the quantum dot light-emitting element 30a of this embodiment, the inclined end surface of the first opening 22o of the bank 22 is formed into two curved surfaces, a downwardly convex first curved surface 22i and an upwardly convex second curved surface 22d, which are connected with each other at the inflection point 22ip. The thickness relationship between the curved surfaces 22i and 22d is specified as "T22i ≧ T22d." In this structure, the inclined end surface of the first opening 22o is a flat surface, reducing the film thickness variation of the first electrode 23, the light-emitting functional layer 25, and the second electrode 26 provided on the flat inclined end surface. As a result, when the quantum dot light-emitting element 30a including the bank 22 having the above structure is driven on a backplane substrate, the above-mentioned problems are suppressed. In the bank 22 having the above structure, as shown in the enlarged view in FIG. 3, the intersection 22it of the tangent t22i of the first curved surface 22i and the tangent t22d of the second curved surface 22d is located within the bank 22.

[0021] 1 , the first electrode 23 is provided so as to cover (block) the first opening 22o of the bank 22. The first electrode 23 is provided on the bank 22 and, within the first opening 22o, on the connection electrode 21. Because the first electrode 23 is provided along the inclined end face of the first opening 22o of the bank 22, the first electrode 23 directly above (along) the inclined end face has a similar surface (a curved surface having an inflection point 22ip).

[0022] The first electrode 23 has a function of injecting holes (positive holes) into the light-emitting functional layer 25. It is more preferable that the first electrode 23 be formed of a material with a large work function in order to improve the efficiency of hole injection into the light-emitting functional layer 25. Examples of materials that can be used for the first electrode 23 include metal materials such as silver (Ag), aluminum (Al), vanadium (V), cobalt (Co), nickel (Ni), tungsten (W), gold (Au), titanium (Ti), ruthenium (Ru), manganese (Mn), indium (In), ytterbium (Yb), lithium fluoride (LiF), platinum (Pt), palladium (Pd), molybdenum (Mo), iridium (Ir), and tin (Sn). Examples of materials that can be used for the first electrode 23 include astatine (At) / astatine oxide (AtO ２ ) or an alloy thereof. Furthermore, the material constituting the first electrode 23 may be, for example, a conductive oxide such as tin oxide (SnO), zinc oxide (ZnO), indium tin oxide (ITO), or indium zinc oxide (IZO). The first electrode 23 may also be formed by stacking multiple layers made of the above materials. Examples of compound materials with a large work function include indium tin oxide (ITO) and indium zinc oxide (IZO).

[0023] As shown in FIG. 1 , the edge cover 24 is provided on the bank 22 and the first electrode 23 so as to cover the peripheral edge of the first electrode 23. The edge cover 24 has a second opening 24o formed therein that overlaps with the first opening 22o of the bank 22 in a plan view. The second opening 24o of the edge cover 24 is a through-hole that partially exposes the first electrode 23. The opening diameter of the second opening 24o of the edge cover 24 is larger than the opening diameter of the first opening 22o of the bank 22. Note that the peripheral end surface (inner peripheral surface) of the second opening 24o of the edge cover 24 may be formed as an upright surface that is upright in the thickness direction of the edge cover 24, or may be formed as an inclined surface.

[0024] Examples of materials that can be used to form the edge cover 24 include positive photosensitive resin materials such as polyimide resin, acrylic resin, polysiloxane resin, and novolac resin, and polysiloxane-based SOG (Spin On Glass) materials. The edge cover 24 may also be made of an inorganic insulating material such as silicon nitride (SiNx).

[0025] 1 , the light-emitting functional layer 25 is provided within the second opening 24o of the edge cover 24 so as to cover the second opening 24o of the edge cover 24. The light-emitting functional layer 25 is provided on the first electrode 23 and the edge cover 24 so as to cover the peripheral edge of the second opening 24o of the edge cover 24. Since the light-emitting functional layer 25 is provided along the surface of the first electrode 23 (i.e., the inclined end face of the first opening 22o of the bank 22), the light-emitting functional layer 25 directly above (along) the inclined end face has a similar surface (a curved surface having an inflection point 22ip).

[0026] As shown in FIG. 2, the light-emitting functional layer 25 includes a hole injection layer 1, a hole transport layer 2, a light-emitting layer 3, an electron transport layer 4, and an electron injection layer 5, which are provided in this order on the first electrode 23.

[0027] The hole injection layer 1 is also called an anode buffer layer, and has the function of bringing the energy levels of the first electrode 23 and the light-emitting functional layer 25 closer to each other, thereby improving the efficiency of hole injection from the first electrode 23 to the light-emitting functional layer 25. Examples of materials constituting the hole injection layer 1 include triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, phenylenediamine derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, and stilbene derivatives.

[0028] The hole transport layer 2 has a function of improving the efficiency of transporting holes from the first electrode 23 to the light-emitting functional layer 25. Here, examples of materials constituting the hole transport layer 2 include porphyrin derivatives, aromatic tertiary amine compounds, styrylamine derivatives, polyvinylcarbazole, poly-p-phenylenevinylene, polysilane, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amine-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, hydrogenated amorphous silicon, hydrogenated amorphous silicon carbide, zinc sulfide, and zinc selenide.

[0029] The light-emitting layer 3 is a region into which holes and electrons are injected from the first electrode 23 and the second electrode 26, respectively, and where the holes and electrons recombine when a voltage is applied between the first electrode 23 and the second electrode 26. The light-emitting layer 3 is formed of a material with high luminous efficiency. Examples of materials constituting the light-emitting layer 3 include metal oxinoid compounds (8-hydroxyquinoline metal complexes), naphthalene derivatives, anthracene derivatives, diphenylethylene derivatives, vinylacetone derivatives, triphenylamine derivatives, butadiene derivatives, coumarin derivatives, benzoxazole derivatives, oxadiazole derivatives, oxazole derivatives, benzimidazole derivatives, thiadiazole derivatives, benzthiazole derivatives, styryl derivatives, styrylamine derivatives, bisstyrylbenzene derivatives, trisstyrylbenzene derivatives, perylene derivatives, perinone derivatives, aminopyrene derivatives, pyridine derivatives, rhodamine derivatives, aquidin derivatives, phenoxazone, quinacridone derivatives, rubrene, poly-p-phenylenevinylene, and polysilane.

[0030] The electron transport layer 4 has a function of efficiently transferring electrons to the light-emitting layer 3. Examples of materials constituting the electron transport layer 4 include organic compounds such as oxadiazole derivatives, triazole derivatives, benzoquinone derivatives, naphthoquinone derivatives, anthraquinone derivatives, tetracyanoanthraquinodimethane derivatives, diphenoquinone derivatives, fluorenone derivatives, silole derivatives, and metal oxinoid compounds.

[0031] The electron injection layer 5 has a function of bringing the energy levels of the second electrode 26 and the light-emitting functional layer 25 closer to each other, thereby improving the efficiency of electron injection from the second electrode 26 to the light-emitting functional layer 25. This function makes it possible to reduce the driving voltage of the quantum dot light-emitting element 30a. The electron injection layer 5 is also called a cathode buffer layer. Here, examples of materials constituting the electron injection layer 5 include lithium fluoride (LiF), magnesium fluoride (MgF ２ ), calcium fluoride (CaF ２ ), strontium fluoride (SrF ２ ), barium fluoride (BaF ２ inorganic alkali compounds such as aluminum oxide (Al ２ O ３ ), strontium oxide (SrO), etc.

[0032] As shown in FIG. 1 , the second electrode 26 is provided so as to cover the edge cover 24 and the light-emitting functional layer 25. Since the second electrode 26 is provided along the surface of the light-emitting functional layer 25 (i.e., the inclined end face of the first opening 22o of the bank 22), the second electrode 26 directly above (along) the inclined end face has a similar surface (a curved surface having an inflection point 22ip). The second electrode 26 has the function of injecting electrons into the light-emitting functional layer 25. In order to improve the efficiency of electron injection into the light-emitting functional layer 25, the second electrode 26 is preferably made of a material with a small work function. Examples of materials constituting the second electrode 26 include silver (Ag), aluminum (Al), vanadium (V), cobalt (Co), nickel (Ni), tungsten (W), gold (Au), calcium (Ca), titanium (Ti), yttrium (Y), sodium (Na), ruthenium (Ru), manganese (Mn), indium (In), magnesium (Mg), lithium (Li), ytterbium (Yb), and lithium fluoride (LiF). The second electrode 26 may also be made of, for example, magnesium (Mg) / copper (Cu), magnesium (Mg) / silver (Ag), sodium (Na) / potassium (K), or astatine (At) / astatine oxide (AtO). ２ The second electrode 26 may be formed of an alloy such as lithium (Li) / aluminum (Al), lithium (Li) / calcium (Ca) / aluminum (Al), or lithium fluoride (LiF) / calcium (Ca) / aluminum (Al). The second electrode 26 may be formed of a conductive oxide such as tin oxide (SnO), zinc oxide (ZnO), indium tin oxide (ITO), or indium zinc oxide (IZO). The second electrode 26 may be formed by stacking multiple layers made of the above materials. Examples of materials with a low work function include magnesium (Mg), lithium (Li), lithium fluoride (LiF), magnesium (Mg) / copper (Cu), magnesium (Mg) / silver (Ag), sodium (Na) / potassium (K), lithium (Li) / aluminum (Al), lithium (Li) / calcium (Ca) / aluminum (Al), and lithium fluoride (LiF) / calcium (Ca) / aluminum (Al).

[0033] Next, a method for manufacturing the quantum dot light-emitting element 30a of this embodiment will be described. The quantum dot light-emitting element 30a is formed by sequentially forming the connection electrodes 21, banks 22, first electrodes 23, edge covers 24, light-emitting functional layers 25 (hole injection layer 1, hole transport layer 2, light-emitting layer 3, electron transport layer 4, and electron injection layer 5) and second electrodes 26 on a pre-formed backplane substrate using a well-known method.

[0034] In the manufacturing method of the quantum dot light-emitting element 30a, in the bank formation step of forming the bank 22, a photosensitive resin film constituting the bank 22 is formed on the surface of the substrate on which the connection electrode 21 is formed, and then the resin film is exposed to light to form the first opening 22o. At this time, as shown in FIG. 3 , a gray-tone mask M is used to expose the resin film, intentionally creating an inflection point 22ip at the etched end surface of the resin film (i.e., the inclined end surface of the first opening 22o of the bank 22). For example, a gray-tone mask M is used that has a gray-tone region Agt around the first opening 22o of the pre-designed bank 22, the gray-tone region Agt having a light transmittance higher than that of the light-shielding region As that blocks light and lower than that of the light-transmitting (exclusion) region Ae that transmits light. Specifically, a gray-tone region Agt is provided in the portion where the first curved surface 22i is formed near the bottom end of the first opening 22o. Meanwhile, a light-shielding region As is provided in the portion where the second curved surface 22d is formed near the top end of the first opening 22o. A light-transmitting region Ae may be provided between the graytone region Agt and the light-shielding region As, if necessary. In this case, the light-transmitting region Ae is preferably provided around the intersection 22it of the tangent t22i of the first curved surface 22i and the tangent t22d of the second curved surface 22d. By performing an exposure process on the photosensitive resin film (bank 22) using a graytone mask M provided with these regions Agt, Ae, and As, as shown in FIG. 3, the inclined end face of the first opening 22o of the bank 22 is formed into two curved surfaces, a downwardly convex first curved surface 22i and an upwardly convex second curved surface 22d, which are continuous with each other at the inflection point 22ip. The graytone region Agt may have a structure, for example, provided with multiple slits, as shown in FIG. 3.

[0035] <Effects> As described above, the quantum dot light emitting device 30a of this embodiment and the method for manufacturing the same can provide the following effects.

[0036] In the quantum dot light-emitting element 30a, the first electrode 23, the light-emitting functional layer 25, and the second electrode 26 are sequentially disposed along the inclined end face of the first opening 22o of the bank 22 so as to cover the first opening 22o. The end face of the first opening 22o is formed into two curved surfaces, a downwardly convex first curved surface 22i and an upwardly convex second curved surface 22d, which are connected with each other at an inflection point 22ip. The thickness relationship between the curved surfaces 22i and 22d is specified as "T22i ≧ T22d." This flattens the inclined end face of the first opening 22o, stabilizes the film thicknesses of the first electrode 23, the light-emitting functional layer 25, and the second electrode 26, and reduces variation. As a result, when the quantum dot light-emitting element 30a is driven on a backplane substrate, brightness reduction at the inclined end face of the first opening 22o of the bank 22 (the end of the subpixel P, described below) can be suppressed.

[0037] Furthermore, in the quantum dot light-emitting element 30a, the relationship between the width W22 of the inclined end face of the first opening 22o of the bank 22 and the thickness T22 of the bank 22 itself is specified as "width W22 ≧ thickness T22 × 2" (width W22 ≧ (thickness T22i + thickness T22d) × 2), so that the opening diameter of the first opening 22o can be adjusted to an appropriate dimension.

[0038] In the manufacturing method of the quantum dot light-emitting element 30a, the inclined end face of the first opening 22o can be formed into a curved surface having an inflection point 22ip simply by providing a gray-tone region Agt around the pre-designed first opening 22o of the bank 22 (the portion corresponding to the inclined end of the first opening 22o). In other words, the quantum dot light-emitting element 30a can be easily manufactured using the conventional process (bank formation process) without adding any process steps or changing the process order.

[0039] Second Embodiment Next, a second embodiment of the present invention will be described with reference to Fig. 4. Fig. 4 is a cross-sectional view showing a schematic configuration of a quantum dot light-emitting element 30b of this embodiment and an enlarged cross-sectional view of the periphery of the bank 22, and corresponds to Fig. 1. The overall configuration of the quantum dot light-emitting element 30b is the same as that of the first embodiment described above, except for the configuration described below, and therefore a detailed description thereof will be omitted here. Furthermore, components similar to those of the first embodiment described above will be assigned the same reference numerals and their description will be omitted.

[0040] The quantum dot light-emitting element 30b of this embodiment differs from the quantum dot light-emitting element 30a of the first embodiment in the shape of the portions of the first electrode 23 and the light-emitting functional layer 25 that overlap with the first opening 22o of the bank 22 in a planar view. These portions are the bottoms of the first electrode 23 and the light-emitting functional layer 25 formed in the first opening 22o. As shown in FIG. 1 , in the quantum dot light-emitting element 30a, the bottoms of the first electrode 23 and the light-emitting functional layer 25 (and the corresponding bottoms of the connection electrode 21 and second electrode 26) are formed on a horizontal surface. On the other hand, in the quantum dot light-emitting element 30b, as shown in FIG. 4 , the bottom 23b of the first electrode 23 and the bottom 25b of the light-emitting functional layer 25 are formed on a concave curved surface recessed toward the lower layer side (the connection electrode 21 side in FIG. 4 ). In addition, in the quantum dot light-emitting element 30b, the bottom 21b of the connection electrode 21 and the bottom 26b of the second electrode 26 are also formed into concave curved surfaces in accordance with the shapes of the bottom 23b of the first electrode 23 and the bottom 25b of the light-emitting functional layer 25.

[0041] The bottom 23b of the first electrode 23 and the bottom 25b of the light-emitting functional layer 25 are portions where the first electrode 23 and the light-emitting functional layer 25 overlap in a plan view and electrically connect the two. By making these portions curved, the coverage of the first electrode 23 on the bank 22 is improved, and further, the contact area between the first electrode 23 and the light-emitting functional layer 25 is increased.

[0042] All of the matters described in the first embodiment above are applicable except for the structure of the bottom 23b of the first electrode 23 and the bottom 25b of the light-emitting functional layer 25 (the bottom 21b of the connection electrode 21 and the bottom 26b of the second electrode 26).

[0043] In the manufacturing method of the quantum dot light emitting element 30b, in the manufacturing method of the quantum dot light emitting element 30a described above, recesses may be formed in the surface of a backplane substrate (a planarization film 19 constituting the TFT layer 20 described later) provided below the quantum dot light emitting element 30b, in a portion that overlaps in plan view with the first opening 22o of the bank 22 that has been designed in advance. Specifically, a portion of the surface of the backplane substrate is intentionally formed into a concave curved surface that is recessed downward using a gray-tone mask. On the backplane substrate with this concave curved surface formed, the connection electrode 21, the bank 22, the first electrode 23, the edge cover 24, the light-emitting functional layer 25, and the second electrode 26 are sequentially formed in the same manner as in the manufacturing method of the quantum dot light emitting element 30a. In this manner, the bottom 21b of the connection electrode 21, the bottom 23b of the first electrode 23, the bottom 25b of the light-emitting functional layer 25, and the bottom 26b of the second electrode 26 are concavely curved along the concave curved surface of the backplane substrate.

[0044] <Effects> According to the quantum dot light emitting device 30b and the manufacturing method thereof described above, the following effects can be obtained in addition to the effects of the quantum dot light emitting device 30a and the manufacturing method thereof described above.

[0045] In the quantum dot light-emitting element 30b, the first electrode 23 and the light-emitting functional layer 25 overlap in a planar view, and the bottom 23b of the first electrode 23 and the bottom 25b of the light-emitting functional layer 25 (the corresponding bottom 21b of the connection electrode 21 and the bottom 26b of the second electrode 26), which are the portions that electrically connect the two, are formed into concave curved surfaces that are recessed toward the lower layer side. This can improve the coverage of the first electrode 23 on the bank 22. Furthermore, since the contact area between the first electrode 23 and the light-emitting functional layer 25 is increased, the effect of improving luminance of emitted light can be expected.

[0046] In the manufacturing method of the quantum dot light-emitting element 30b, the portion of the surface of the backplane substrate provided below the quantum dot light-emitting element 30b that overlaps with the first opening 22o of the pre-designed bank 22 in a planar view can be simply formed into a concave curved surface, and the bottom 23b of the first electrode 23 located above it can also be formed into a similar concave curved surface, making it easy to manufacture the quantum dot light-emitting element 30b.

[0047] <Display Device (Quantum Dot Display Device)> FIGS. 5 to 8 illustrate embodiments of the display device according to the present invention. In the following embodiments, a quantum dot display device including quantum dot light-emitting elements is exemplified as a display device including light-emitting elements. The quantum dot display device 50 of this embodiment includes at least one of the quantum dot light-emitting elements 30a and 30b described above as quantum dot light-emitting elements. That is, the quantum dot display device 50 may include only the quantum dot light-emitting element 30a, only the quantum dot light-emitting element 30b, or both the quantum dot light-emitting element 30a and the quantum dot light-emitting element 30b. In the following description, the quantum dot light-emitting element 30a and the quantum dot light-emitting element 30b will be referred to as the "quantum dot light-emitting element 30" without distinction. FIG. 5 is a plan view showing a schematic configuration of a quantum dot display device 50 including a quantum dot light-emitting element 30 according to an embodiment of the present invention. FIG. 6 is a plan view of a display region D of the quantum dot display device 50. FIG. 7 is a cross-sectional view of the display region D of the quantum dot display device 50. FIG. 8 is an equivalent circuit diagram showing a pixel circuit C of the quantum dot display device 50.

[0048] 5, the quantum dot display device 50 includes a display area D and a frame area F. In this embodiment, a rectangular display area D is exemplified, but this rectangular shape also includes substantially rectangular shapes such as shapes with arc-shaped sides, shapes with arc-shaped corners, and shapes with notches in part of the sides.

[0049] The display region D is an area where images are displayed and constitutes a screen. As shown in FIG. 5 , the display region D is, for example, rectangular. In this embodiment, a rectangular display region D is illustrated, but this rectangular shape also includes, for example, a substantially rectangular shape with arc-shaped sides, arc-shaped corners, or a shape with a notch on one side. As shown in FIG. 6 , a plurality of sub-pixels P are arranged in a matrix in the display region D. In addition, in the display region D, for example, a sub-pixel P having a red light-emitting region Lr for displaying red, a sub-pixel P having a green light-emitting region Lg for displaying green, and a sub-pixel P having a blue light-emitting region Lb for displaying blue are arranged adjacent to each other. Note that in the display region D, for example, three adjacent sub-pixels P each having a red light-emitting region Lr, a green light-emitting region Lg, and a blue light-emitting region Lb form one pixel. Note that the arrangement of the sub-pixels P is not particularly limited, and examples thereof include a pentatile arrangement and a stripe arrangement.

[0050] The frame region F is a region that constitutes the non-display portion other than the screen. As shown in Fig. 5 , the frame region F is provided around the display region D in, for example, a rectangular frame shape. A terminal portion T is provided at one end (the right end in Fig. 5 ) of the frame region F so as to extend in one direction (the vertical direction in Fig. 5 ). In addition, a folding portion B that can be folded, for example, 180° (in a U-shape) with the vertical direction in Fig. 5 as the folding axis is provided in the frame region F between the terminal portion T and the display region D so as to extend in one direction (the vertical direction in Fig. 5 ).

[0051] 7, the quantum dot display device 50 includes a resin substrate 10 provided as a base substrate, a TFT layer 20 provided on the resin substrate 10, a quantum dot light-emitting element layer 31 provided as a light-emitting element layer on the TFT layer 20, and a sealing film 35 provided on the quantum dot light-emitting element layer 31. The resin substrate 10 and the TFT layer 20 constitute the above-mentioned backplane substrate (circuit board).

[0052] The resin substrate 10 is made of an organic resin material such as polyimide (PI) resin.

[0053] As shown in Figure 7, the TFT layer 20 includes a base coat film 11 provided on a resin substrate 10, a plurality of first TFTs 9a, a plurality of second TFTs 9b, and a plurality of capacitors 9c provided on the base coat film 11 for each sub-pixel P, and a planarization film 19 provided on each of the first TFTs 9a, each of the second TFTs 9b, and each of the capacitors 9c. 7, the TFT layer 20 includes a base coat film 11, semiconductor layers 12a and 12b, a gate insulating film 13, a first wiring layer including gate lines 14 (see FIG. 6), gate electrodes 14a and 14b, and a lower conductive layer 14c, a first interlayer insulating film 15, a second wiring layer including upper conductive layer 16, a second interlayer insulating film 17, a third wiring layer including source lines 18f (see FIG. 6), source electrodes 18a and 18c, drain electrodes 18b and 18d, and a power line 18g, and a planarization film 19, which are stacked in this order on a resin substrate 10. Also, as shown in FIGS. 6 and 8, the TFT layer 20 includes a plurality of gate lines 14 extending parallel to one another in the horizontal direction in the drawings. Also, as shown in FIGS. 6 and 8, the TFT layer 20 includes a plurality of source lines 18f extending parallel to one another in a direction intersecting (orthogonal to) the plurality of gate lines 14, i.e., in the vertical direction in the drawings. 6 and 8, the TFT layer 20 is provided with a plurality of power supply lines 18g extending parallel to one another in the vertical direction in the drawings. Each power supply line 18g is provided adjacent to a corresponding source line 18f, as shown in Fig. 6. In the TFT layer 20, a first TFT 9a, a second TFT 9b, and a capacitor 9c are provided as a pixel circuit C in each sub-pixel P, as shown in Fig. 8. The pixel circuits C are arranged in a matrix corresponding to each sub-pixel P.

[0054] The base coat film 11, the gate insulating film 13, the first interlayer insulating film 15, and the second interlayer insulating film 17 may be made of, for example, silicon nitride (SiNx (x is a positive number)), silicon oxide (SiO ２The semiconductor layers 12a and 12b are each composed of a single layer or a stacked layer of an inorganic insulating film such as silicon oxynitride (SiON). The semiconductor layers 12a and 12b are composed of, for example, a low-temperature polysilicon film or an In—Ga—Zn—O-based oxide semiconductor film. The first wiring layer, the second wiring layer, and the third wiring layer are each composed of, for example, a metal single layer film of molybdenum (Mo), titanium (Ti), aluminum (Al), copper (Cu), tungsten (W), or the like, or a metal stacked layer film of Mo (upper layer) / Al (middle layer) / Mo (lower layer), Ti / Al / Ti, Al (upper layer) / Ti (lower layer), Cu / Mo, Cu / Ti, or the like.

[0055] The first TFT 9a and the second TFT 9b are p-type TFTs in which the semiconductor layers 12a and 12b are doped with impurities such as boron.

[0056] As shown in FIG. 8 , the first TFT 9a is electrically connected to the corresponding gate line 14 and source line 18f in each subpixel P. As shown in FIG. 7 , the first TFT 9a includes a semiconductor layer 12a, a gate insulating film 13, a gate electrode 14a, a first interlayer insulating film 15, a second interlayer insulating film 17, a source electrode 18a, and a drain electrode 18b, which are sequentially disposed on a base coat film 11. As shown in FIG. 7 , the semiconductor layer 12a is disposed on the base coat film 11 in an island shape and has, for example, a channel region, a source region, and a drain region. As shown in FIG. 7 , the gate insulating film 13 is disposed so as to cover the semiconductor layer 12a. As shown in FIG. 7 , the gate electrode 14a is disposed on the gate insulating film 13 so as to overlap the channel region of the semiconductor layer 12a. As shown in FIG. 7 , the first interlayer insulating film 15 and the second interlayer insulating film 17 are disposed so as to cover the gate electrode 14a. 7, the source electrode 18a and the drain electrode 18b are provided spaced apart from each other on the second interlayer insulating film 17. The source electrode 18a and the drain electrode 18b are electrically connected to the source region and the drain region of the semiconductor layer 12a, respectively, through contact holes formed in the stacked film of the gate insulating film 13, the first interlayer insulating film 15, and the second interlayer insulating film 17.

[0057] As shown in FIG. 8 , the second TFT 9b is electrically connected to the corresponding first TFT 9a and power line 18g in each subpixel P. As shown in FIG. 7 , the second TFT 9b includes a semiconductor layer 12b, a gate insulating film 13, a gate electrode 14b, a first interlayer insulating film 15, a second interlayer insulating film 17, a source electrode 18c, and a drain electrode 18d, which are sequentially disposed on a base coat film 11. As shown in FIG. 7 , the semiconductor layer 12b is disposed on the base coat film 11 in an island shape and has, for example, a channel region, a source region, and a drain region. As shown in FIG. 7 , the gate insulating film 13 is disposed so as to cover the semiconductor layer 12b. As shown in FIG. 7 , the gate electrode 14b is disposed on the gate insulating film 13 so as to overlap the channel region of the semiconductor layer 12b. As shown in FIG. 7 , the first interlayer insulating film 15 and the second interlayer insulating film 17 are disposed so as to cover the gate electrode 14b. 7, the source electrode 18c and the drain electrode 18d are provided spaced apart from each other on the second interlayer insulating film 17. The source electrode 18c and the drain electrode 18d are electrically connected to the source region and the drain region of the semiconductor layer 12b, respectively, through contact holes formed in the stacked film of the gate insulating film 13, the first interlayer insulating film 15, and the second interlayer insulating film 17.

[0058] In this embodiment, the first TFT 9a and the second TFT 9b are top-gate type TFTs, but the first TFT 9a and the second TFT 9b may be bottom-gate type TFTs.

[0059] As shown in Fig. 8, the capacitor 9c is electrically connected to the corresponding first TFT 9a and power supply line 18g in each subpixel P. Here, as shown in Fig. 7, the capacitor 9c includes a lower conductive layer 14c formed in the same layer and made of the same material as the gate electrodes 14a and 14b, a first interlayer insulating film 15 provided so as to cover the lower conductive layer 14c, and an upper conductive layer 16 provided on the first interlayer insulating film 15 so as to overlap the lower conductive layer 14c. Note that the upper conductive layer 16 is electrically connected to the power supply line 18g via a contact hole formed in a second interlayer insulating film 17, as shown in Fig. 7.

[0060] As shown in FIG. 7, the planarization film 19 has a flat surface in the display region D, and is made of, for example, an organic resin material such as polyimide resin or acrylic resin, or a polysiloxane-based SOG (spin on glass) material.

[0061] 7, the quantum dot light-emitting element layer 31 is provided on the planarization film 19 that constitutes the TFT layer 20. The quantum dot light-emitting element layer 31 includes a plurality of quantum dot light-emitting elements 30 as a plurality of light-emitting elements arranged in a matrix corresponding to a plurality of sub-pixels P.

[0062] 7 , the quantum dot light-emitting element 30 is provided in this order on the planarization film 19, and includes a plurality of connection electrodes 21, a plurality of banks 22, a plurality of first electrodes 23, an edge cover 24, a plurality of light-emitting functional layers 25 provided on the first electrodes 23 for each sub-pixel P, and a second electrode 26 provided on the light-emitting functional layer 25 in common to the plurality of sub-pixels P. The quantum dot light-emitting element 30 is also covered with a sealing film 35.

[0063] As shown in FIG. 7 , the bank 22 has a plurality of openings 22o formed therein, exposing the connection electrodes 21, corresponding to the plurality of subpixels P. Portions of the surface of the bank 22 protrude upward in FIG. 7 to form island-shaped pixel photospacers (columnar spacers). The first electrodes 23 are arranged in a matrix within the openings 22o to correspond to the plurality of subpixels P. The first electrodes 23 are electrically connected to the drain electrodes 18d (or source electrodes 18c) of the second TFTs 9b via the connection electrodes 21 and contact holes formed in the planarization film 19. The peripheral edges of the first electrodes 23 are covered by edge covers 24 arranged in a grid pattern common to the plurality of subpixels P. The edge covers 24 have a plurality of second openings 24o formed therein, exposing the first electrodes 23. The light-emitting functional layers 25 are disposed on the first electrodes 23 and arranged in a matrix to correspond to the plurality of subpixels P. The second electrodes 26 are arranged to cover the light-emitting functional layers 25 and the edge covers 24.

[0064] 7, the sealing film 35 includes a first sealing inorganic insulating film 32 provided to cover the second electrode 26, a sealing organic film 33 provided on the first sealing inorganic insulating film 32, and a second sealing inorganic insulating film 34 provided to cover the sealing organic film 33, and has a function of protecting the light-emitting function layer 25 from moisture, oxygen, etc. The first sealing inorganic insulating film 32 and the second sealing inorganic insulating film 34 are made of, for example, silicon oxide (SiO ２ ) and aluminum oxide (Al ２ O ３ ), trisilicon tetranitride (Si ３ N ４ The sealing organic film 33 is made of an inorganic material such as silicon nitride (SiNx (x is a positive number)) or silicon carbonitride (SiCN). The sealing organic film 33 is made of an organic material such as acrylic resin, polyurea resin, parylene resin, polyimide resin, or polyamide resin.

[0065] The quantum dot display device 50 described above is configured such that, in each subpixel P, a gate signal is input to the first TFT 9a via the gate line 14 to turn the first TFT 9a on, a data signal is written to the gate electrode 14b and capacitor 9c of the second TFT 9b via the source line 18f, and a current from the power supply line 18g corresponding to the gate voltage of the second TFT 9b is supplied to the light-emitting functional layer 25, causing the light-emitting layer 3 of the light-emitting functional layer 25 to emit light and display an image. Note that in the quantum dot display device 50, even if the first TFT 9a is turned off, the gate voltage of the second TFT 9b is held by the capacitor 9c, so that light emission by the light-emitting layer 3 is maintained until the gate signal for the next frame is input.

[0066] Next, a description will be given of a method for manufacturing the quantum dot display device 50 of this embodiment. The method for manufacturing the quantum dot display device 50 includes a TFT layer forming step, a quantum dot light emitting element layer forming step, and a sealing film forming step.

[0067] <TFT layer formation process> For example, a base coat film 11, a first TFT 9 a, a second TFT 9 b, a capacitor 9 c, a planarization film 19, etc. are formed on the surface of a resin substrate 10 formed on a glass substrate using, for example, a well-known method, to form a TFT layer 20.

[0068] <Quantum dot light-emitting element layer forming process> A plurality of quantum dot light-emitting elements 30 are formed on the planarization film 19 of the TFT layer 20 formed in the TFT layer forming process to form a quantum dot light-emitting element layer 31. The method for forming the quantum dot light-emitting elements 30 is the same as the method for manufacturing the quantum dot light-emitting elements 30a and 30b.

[0069] <Sealing Film Forming Process> First, on the substrate surface on which the quantum dot light-emitting element layer 31 formed in the quantum dot light-emitting element layer forming process is formed, an inorganic insulating film such as a silicon nitride film, a silicon oxide film, or a silicon oxynitride film is deposited by plasma CVD using a CMM as a deposition mask so as to cover each quantum dot light-emitting element 30, thereby forming a first sealing inorganic insulating film 32. Next, an organic resin material such as an acrylic resin is deposited on the first sealing inorganic insulating film 32 by, for example, an inkjet method, thereby forming a sealing organic film 33. Thereafter, an inorganic insulating film such as a silicon nitride film, a silicon oxide film, or a silicon oxynitride film is deposited by plasma CVD using the CMM as a deposition mask so as to cover the sealing organic film 33, thereby forming a second sealing inorganic insulating film 34, thereby forming a sealing film 35. Through the above processes, a sealing film 35 can be formed in the display region D, in which the first sealing inorganic insulating film 32, the sealing organic film 33, and the second sealing inorganic insulating film 34 are stacked in order.

[0070] Finally, a protective sheet (not shown) is attached to the surface of the substrate, and then laser light is irradiated from the glass substrate side of the resin substrate 10 to peel the glass substrate from the underside of the resin substrate 10, and a protective sheet (not shown) is attached to the underside of the resin substrate 10 from which the glass substrate has been peeled. In this manner, the quantum dot display device 50 can be manufactured.

[0071] <Effects> As described above, the quantum dot display device 50 of this embodiment can provide the following effects.

[0072] The quantum dot display device 50 includes a plurality of quantum dot light-emitting elements 30 as a plurality of light-emitting elements arranged in a matrix corresponding to a plurality of sub-pixels P in the quantum dot light-emitting element layer 31. This makes it possible to obtain the same effect as the quantum dot light-emitting elements 30a and 30b described above. That is, in the quantum dot display device 50, it is possible to suppress a decrease in brightness at the end of the sub-pixels P.

[0073] Other Embodiments In the above embodiments, quantum dot light-emitting elements have been described as examples of light-emitting elements, but the present invention is not limited to quantum dot light-emitting elements and can be applied to, for example, organic EL elements and the like.

[0074] In each of the above embodiments, the light-emitting functional layer has a five-layer laminated structure of a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, and an electron injection layer. However, the light-emitting functional layer may have a three-layer laminated structure of, for example, a hole injection layer / hole transport layer, a light-emitting layer, and an electron transport layer / electron injection layer.

[0075] In addition, in each of the above embodiments, a quantum dot light-emitting element in which the first electrode is an anode and the second electrode is a cathode is exemplified. However, the present invention can also be applied to a quantum dot light-emitting element in which the stacked structure of the light-emitting functional layer is reversed, and the first electrode is a cathode and the second electrode is an anode.

[0076] In each of the above embodiments, a quantum dot display device has been exemplified in which the electrode of the TFT connected to the first electrode is used as the drain electrode, but the present invention can also be applied to a quantum dot display device in which the electrode of the TFT connected to the first electrode is called the source electrode.

[0077] In the above embodiments, a quantum dot display device is used as the display device, but the present invention can also be applied to display devices such as an active matrix driving liquid crystal display device.

[0078] In the above embodiments, a quantum dot display device has been described as an example of a display device, but the present invention is not limited to quantum dot display devices and can be applied to any flexible display device, such as an organic EL display device equipped with organic EL elements.

[0079] As described above, the present invention is useful for a light-emitting element and a flexible display device including the same.

[0080] M Mask Agt Gray-tone region Ae Light-transmitting region As Light-shielding region 19 Planarization film 20 TFT layer (thin film transistor layer) 21 Connection electrode 21b Bottom of connection electrode 22 Bank 22o Bank opening T22 Thickness of bank W22 Width of inclined end face of first opening of bank 22i First curved surface 22d Second curved surface 22ip Inflection point T22i Thickness of first curved surface T22d Thickness of second curved surface t22i Tangent to first curved surface t22d Tangent to second curved surface 22it Intersection of tangent to first curved surface and tangent to second curved surface 23 First electrode 23b Bottom of first electrode 24 Edge cover 24o Opening in edge cover 25 Light-emitting functional layer 25b Bottom of light-emitting functional layer 26 Second electrode 26b Bottom of second electrode 30a, 30b, 30 Quantum dot light emitting element (light emitting element) 31 Quantum dot light emitting element layer (light emitting element layer) 32 First sealing inorganic insulating film 33 Sealing organic film 34 Second sealing inorganic insulating film 35 Sealing film 50 Quantum dot display device

Claims

1. A light-emitting device comprising: a bank in which a first opening having an inclined end surface is formed; a first electrode provided on the bank so as to cover the first opening; a light-emitting functional layer provided on the first electrode; and a second electrode provided on the light-emitting functional layer, wherein at least the inclined end surface from the lower end of the first opening to an end where the thickness of the bank is more than half is formed into a first curved surface that is convex downward with an increasing inclination of the tangent.

2. A light-emitting device according to claim 1, wherein the inclined end face of the first opening is formed into an upwardly convex second curved face, which is continuous with the first curved face and has a decreasing tangent gradient.

3. A light-emitting element according to claim 1 or 2, characterized in that the width of the inclined end face of the first opening is at least twice the thickness of the bank.

4. A light-emitting element according to any one of claims 1 to 3, characterized in that the first electrode and the light-emitting functional layer are formed into a concave curved surface that is recessed downward in a portion that overlaps with the first opening in a plan view.

5. A light-emitting element according to claim 4, wherein the second electrode is formed along the light-emitting functional layer such that the portion overlapping with the first opening in a plan view is curved in a concave shape recessed toward the lower layer.

6. A light-emitting element according to any one of claims 1 to 5, further comprising an edge cover for covering a peripheral edge of the first electrode, and wherein the edge cover is formed with a second opening that overlaps with the first opening in a plan view.

7. A light-emitting element according to claim 6, wherein the second opening has a larger diameter than the first opening.

8. The light-emitting element according to any one of claims 1 to 7, further comprising a connection electrode provided below the bank and the first electrode and electrically connected to the first electrode.

9. A method for manufacturing a light-emitting element comprising: a bank in which a first opening having an inclined end surface is formed; a first electrode provided on the bank so as to cover the first opening; a light-emitting functional layer provided on the first electrode; and a second electrode provided on the light-emitting functional layer, wherein after the bank is formed, when the bank is exposed to light to form the first opening, a mask is used in which a gray-tone region having a light transmittance higher than that of a light-shielding region and lower than that of a light-transmitting region is provided around the first opening, thereby forming the inclined end surface at least from the lower end of the first opening to the end where the thickness of the bank is more than half, into a first curved surface that is convex downward with an increasing inclination of the tangent.

10. A method for manufacturing a light-emitting element as described in claim 9, characterized in that a concave curved surface recessed downward is formed by exposing a portion of the surface of a backplane substrate provided below the light-emitting element that overlaps with the first opening in a planar view using a mask having a gray-tone region whose light transmittance is higher than that of a light-shielding region and lower than that of a light-transmitting region.

11. A display device comprising: a base substrate; a thin film transistor layer provided on the base substrate; and a light-emitting element layer provided on the thin film transistor layer and in which a plurality of light-emitting elements are arranged, wherein the plurality of light-emitting elements are light-emitting elements according to any one of claims 1 to 8.

12. The display device according to claim 11, wherein the plurality of light-emitting elements are quantum dot light-emitting elements.

13. The display device according to claim 11, wherein the plurality of light-emitting elements are organic electroluminescence elements.

14. The display device according to any one of claims 11 to 13, further comprising a sealing film provided so as to cover the light emitting element layer.

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