Display device

Abstract

A first light-emitting element (D1) provided in a display device (1) according to the present disclosure has a first light-emitting layer (L1) that includes a first electrode (E1) and a first light-emitting material (Q1), a first lower side metal layer (12) that is semi-light-transmitting, a first intermediate layer (14), a first upper side metal layer (16) that is semi-light-transmitting, and a first light extraction surface (S1) in this order. Formed between the first lower side metal layer (12) and the first upper side metal layer (16) is a resonance structure which has the emission peak wavelength of the first light-emitting material (Q1) and which enhances light propagating in the front direction that is orthogonal to the first light extraction surface.

Description

display device

[0001] The present disclosure relates to a display device.

[0002] Patent Document 1 discloses a light-emitting device in which the organic EL section has a microcavity structure and a lens is provided on the light extraction surface.

[0003] Patent Publication No. 2011-29172

[0004] There is a demand for improvement in front brightness in light emitting elements and display devices including the light emitting elements.

[0005] The display device according to the present disclosure comprises a first light-emitting element having a first electrode, a first light-emitting layer located above the first electrode and containing a first light-emitting material, and a first light extraction surface located above the first light-emitting layer, wherein the first light-emitting element includes a semi-transparent first lower metal layer and a semi-transparent first upper metal layer between the first light-emitting layer and the first light extraction surface, and a first intermediate layer located between the first lower metal layer and the first upper metal layer, and a resonant structure is formed between the first lower metal layer and the first upper metal layer, the resonant structure having the emission peak wavelength of the first light-emitting material and strengthening light traveling in a forward direction perpendicular to the first light extraction surface.

[0006] According to the configuration of the present disclosure, a clear image display can be achieved in a display device including light-emitting elements.

[0007] FIG. 1 is a plan view showing an example of a schematic configuration of a display device according to an embodiment of the present disclosure; FIG. 2 is a cross-sectional view showing an example of a schematic configuration of a display region of a display device according to an embodiment of the present disclosure; FIG. 3 is a cross-sectional view showing an enlarged view of a first intermediate layer and a buffer layer shown in FIG. 2; FIG. 4 is a cross-sectional view showing an example of a schematic configuration of a display region of a display device according to an embodiment of the present disclosure; FIG. 5 is a cross-sectional view showing an example of a schematic configuration of a display region of a display device according to an embodiment of the present disclosure;

[0008] 1 is a plan view showing an example of a schematic configuration of a display device according to an embodiment of the present disclosure. As shown in Fig. 1, the display device 1 according to the present disclosure includes at least one light-emitting element DX. The display device 1 includes, for example, a display area DA in which a plurality of sub-pixels PX are provided, and a frame area NA in which a drive circuit DC for driving the display area DA is provided, and at least one of the plurality of sub-pixels PX includes a light-emitting element DX and a pixel circuit PC.

[0009] 2 is a cross-sectional view showing an example of a schematic configuration of a display region of a display device according to an embodiment of the present disclosure. As shown in FIG. 2, the display device 1 according to the present disclosure includes a first light-emitting element D1 having a first electrode E1, a first light-emitting layer L1 located above the first electrode E1 and including a first light-emitting material Q1, and a first light-extraction surface S1 located above the first light-emitting layer L1. The first light-emitting element D1 further includes a semi-transparent first lower metal layer 12 and a semi-transparent first upper metal layer 16 located between the first light-emitting layer L1 and the first light-extraction surface S1, and a first intermediate layer 14 located between the first lower metal layer 12 and the first upper metal layer 16. A resonant structure having the emission peak wavelength of the first light-emitting material Q1 is formed between the first lower metal layer 12 and the first upper metal layer 16, which enhances light traveling in a forward direction perpendicular to the first light-extraction surface. In the present disclosure, the term "between a certain layer and another layer located above the certain layer" refers to the space between the upper surface of the certain layer and the lower surface of the other layer. The "front direction" mentioned above refers to the front direction of the display device 1 and also to the front direction of the first light-emitting element D1.

[0010] According to the above configuration, the resonant structure between the first lower metal layer 12 and the first upper metal layer 16 can improve the light extraction efficiency of the first light-emitting element D1, as well as the front luminance and color purity of the first light-emitting element D1, thereby improving the clarity of the image displayed by the display device 1.

[0011] Specifically, the first intermediate layer 14 is optically transparent, and the upper surface of the first lower metal layer 12 and the lower surface of the first upper metal layer 16 each function as a light-reflecting surface. This forms a resonant structure between the first lower metal layer 12 and the first upper metal layer 16. For example, if the distance between the first lower metal layer 12 and the first upper metal layer 16 is D [nm] and the emission peak wavelength of the first light-emitting material Q1 is λ [nm], then D may be approximately λ × 0.2 [nm]. An error of, for example, 10 [nm] is allowed, and in this case, D ≦ λ × 0.2 + 10 [nm] and D ≧ λ × 0.2 - 10 [nm] may be satisfied.

[0012] The full width at half maximum of the emission spectrum of the first light-emitting material Q1 is preferably one-tenth or less of the emission peak wavelength of the first light-emitting material Q1. This can further improve the front brightness and color purity of the first light-emitting element D1. The first light-emitting material Q1 contains, for example, luminescent quantum dots that can emit light by recombination of holes and electrons.

[0013] In the present disclosure, "quantum dots" refers to dots having a maximum width of 100 nm or less. The shape of the quantum dots is not particularly limited as long as it satisfies the above-mentioned maximum width, and is not limited to a spherical three-dimensional shape (circular cross-sectional shape). For example, the quantum dots may have a polygonal cross-sectional shape, a rod-like three-dimensional shape, a branch-like three-dimensional shape, a three-dimensional shape with an uneven surface, or a combination thereof. In this embodiment, the quantum dots are semiconductor microparticles having a particle size of, for example, 100 nm or less, and may include II-VI group semiconductor compounds such as MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, and HgTe, and / or crystals of III-V group semiconductor compounds such as GaAs, GaP, InN, InAs, InP, and InSb, and / or crystals of Group IV semiconductor compounds such as Si and Ge. Furthermore, the quantum dots may have a core / shell structure in which the above-mentioned semiconductor crystal serves as a core and the core is overcoated with a shell material having a large band gap. The shell does not necessarily need to completely cover the core; it may be formed on at least a portion of the core.

[0014] The first electrode E1 may be light reflective, and a resonant structure having the emission peak wavelength of the first light-emitting material Q1 and intensifying light traveling in the front direction may be formed between the first electrode E1 and the first lower metal layer 12. This can further improve the light extraction efficiency of the first light-emitting element D1, as well as the front luminance and color purity of the first light-emitting element D1.

[0015] When the first electrode E1 functions as an anode, at least one of the first lower metal layer 12 and the first upper metal layer 16 may function as a cathode. Furthermore, when the first electrode E1 functions as a cathode, at least one of the first lower metal layer 12 and the first upper metal layer 16 may function as an anode. This eliminates the need to provide a separate electrode facing the first electrode E1 in the first light-emitting element D1, thereby reducing the number of manufacturing steps for the first light-emitting element D1.

[0016] The brightness of the first light-emitting element D1 in a direction at an angle of 40° or more to the front direction may be 50% or less of the brightness in the front direction, thereby further improving the front brightness and color purity of the first light-emitting element D1.

[0017] The first intermediate layer 14 may be conductive. In this case, the first lower metal layer 12 and the first upper metal layer 16 are electrically connected via the first intermediate layer 14. When the first electrode E1 functions as an anode, the first lower metal layer 12, the first intermediate layer 14, and the first upper metal layer 16 can cooperate to function as a cathode, thereby reducing the electrical resistance of the cathode. Also, when the first electrode E1 functions as a cathode, the first lower metal layer 12, the first intermediate layer 14, and the first upper metal layer 16 can cooperate to function as an anode, thereby reducing the electrical resistance of the anode. This reduction in electrical resistance is particularly beneficial when the first lower metal layer 12 and / or the first upper metal layer 16 are included in a common electrode across multiple light-emitting elements.

[0018] Alternatively, the first intermediate layer 14 may be insulating.

[0019] The first lower metal layer 12 and the first upper metal layer 16 may have the same composition and thickness or different thicknesses. For example, a thin film containing 50% or more by volume of silver (Ag), aluminum (Al), and gold (Au) and having a thickness of 1 nm to 40 nm exhibits semi-optical transparency. Furthermore, a thin film containing 50% or more by volume of an alkali metal such as lithium (Li) and an alkaline earth metal such as magnesium (Mg) and having a thickness of 1 nm to 40 nm exhibits semi-optical transparency. Any combination of these semi-optical transparent metal films may be used for the first lower metal layer 12 and the first upper metal layer 16.

[0020] The first lower metal layer 12 may contain aluminum (Al). This configuration is beneficial when the first electrode E1 is an anode. Aluminum has a low electron affinity and is known to be a material that is favorable for electron injection. The thickness of the first lower metal layer 12 may be less than 10 nm. This configuration is more beneficial when the first lower metal layer 12 is electrically connected to the first upper metal layer 16. Even aluminum, which has high optical reflectivity, exhibits semi-optical transparency when its thickness is less than 10 nm.

[0021] The first light-emitting element D1 may optionally include one or more of a hole injection layer HIL, a hole transport layer HTL, and an electron blocking layer between the anode and the first light-emitting layer L1. The first light-emitting element D1 may optionally include one or more of an electron injection layer, an electron transport layer ETL, and a hole blocking layer between the cathode and the first light-emitting layer L1.

[0022] The display device 1 according to the present disclosure may further include a second light-emitting element D2 having a second electrode E2, a second light-emitting layer L2 located above the second electrode E2 and including a second light-emitting material Q2, and a second light-extraction surface S2 located above the second light-emitting layer L2. The second light-emitting element D2 further includes a semi-transparent second lower metal layer 22 and a semi-transparent second upper metal layer 26 located between the second light-emitting layer L2 and the second light-extraction surface S2, and a second intermediate layer 24 located between the second lower metal layer 22 and the second upper metal layer 26. A resonant structure having the emission peak wavelength of the second light-emitting material Q2 and enhancing light traveling in the forward direction is formed between the second lower metal layer 22 and the second upper metal layer 26. The first light-emitting element D1 and the second light-emitting element D2 may be adjacent to each other via a bank BK. The first light-emitting layer L1 and the second light-emitting layer L2 may emit light of different colors.

[0023] The display device 1 according to the present disclosure may further include a third light-emitting element D3 having a third light-emitting layer L3 emitting light of a different color from the first light-emitting layer L1 and the second light-emitting layer L2. The third light-emitting element D3 may have a configuration similar to that of the first light-emitting element D1, for example, including a third electrode E3, a third light-emitting layer L3 located above the third electrode and including a third light-emitting material Q3, and a third light-extraction surface S3 located above the third light-emitting layer. The third light-emitting element D3 may further include a semi-transparent third lower metal layer 32 and a semi-transparent third upper metal layer 36 located between the third light-emitting layer L3 and the third light-extraction surface S3, and a third intermediate layer 34 located between the third lower metal layer 32 and the third upper metal layer 36. Here, a resonant structure having the emission peak wavelength of the third light-emitting material Q3 is formed between the third lower metal layer 32 and the third upper metal layer 36, which enhances light traveling in a forward direction. The third light-emitting element D3 may be adjacent to the second light-emitting element D2 via the bank BK.

[0024] The bank BK may act as an edge cover that covers the edges of the first electrode E1 and the second electrode E2. The second electrode E2, the second lower metal layer 22, the second intermediate layer 24, and the second upper metal layer 26 may be made of the same material as the first electrode E1, the first lower metal layer 12, the first intermediate layer 14, and the first upper metal layer 16, respectively.

[0025] The display device 1 according to the present disclosure may further include a first relay metal layer 42 and a second relay metal layer 46 that overlap the bank BK in a planar view. The first lower metal layer 12 and the second lower metal layer 22 may be connected via the first relay metal layer 42, and the first upper metal layer 16 and the second upper metal layer 26 may be connected via the second relay metal layer 46. The first relay metal layer 42 may be made of the same material as the first lower metal layer 12 and the second lower metal layer 22 and may be continuous with the first lower metal layer 12 and the second lower metal layer 22. The second relay metal layer 46 may be made of the same material as the first upper metal layer 16 and the second upper metal layer 26 and may be continuous with the first upper metal layer 16 and the second upper metal layer 26.

[0026] The peak emission wavelength of the first light-emitting material Q1 may be longer than the peak emission wavelength of the second light-emitting material Q2. In this case, the distance between the first lower metal layer 12 and the first upper metal layer 16 is longer than the distance between the second lower metal layer 22 and the second upper metal layer 26. This optimizes the cavity effect in the first light-emitting element D1 and the second light-emitting element D2 according to the peak emission wavelength, i.e., the color. This improves the white brightness of the display device 1. Furthermore, the peak emission wavelength of the second light-emitting material Q2 may be longer than the peak emission wavelength of the third light-emitting material Q3. In this case, the distance between the second lower metal layer 22 and the second upper metal layer 26 is longer than the distance between the third lower metal layer 32 and the third upper metal layer 36.

[0027] For example, the first light-emitting material Q1 may emit red light, the second light-emitting material Q2 may emit green light, and the third light-emitting material Q3 may emit blue light, and the thickness of the first intermediate layer 14 may be greater than the thickness of the second intermediate layer 24, which may be greater than the thickness of the third intermediate layer 34. For example, the first intermediate layer 14 may be 126 [nm] thick, the second intermediate layer 24 may be 106 [nm] thick, and the third intermediate layer may be 92 [nm] thick, and each may be formed from a photocurable resin.

[0028] The distance between the first lower metal layer 12 and the first upper metal layer 16, and the distance between the second lower metal layer 22 and the second upper metal layer 26 are preferably 200 nm or less, respectively. This shortens the optical path difference between the interfering lights, thereby achieving a sufficient resonance effect. Similarly, for light-emitting elements other than the first light-emitting element D1 and the second light-emitting element D2, the distance between the lower metal layer and the upper metal layer is preferably 200 nm or less, regardless of the color.

[0029] The display device 1 according to the present disclosure may further include a buffer layer 44 disposed between the first relay metal layer 42 and the second relay metal layer 46. The thickness of the buffer layer 44 above the upper surface of the bank BK may be large enough not to enhance, but preferably to attenuate, light having the emission peak wavelength of the first light-emitting material Q1 traveling in the forward direction and light having the emission peak wavelength of the second light-emitting material Q2 traveling in the forward direction. This reduces light leakage (crosstalk) between the first light-emitting element D1 and the second light-emitting element D2. Reducing crosstalk reduces blurring of the image display. The buffer layer 44 may be made of the same material as the first intermediate layer 14 and the second intermediate layer 24 and may be continuous with the first intermediate layer 14 and the second intermediate layer 24.

[0030] Fig. 3 is an enlarged cross-sectional view showing the first intermediate layer and the buffer layer shown in Fig. 2. As shown in Fig. 3, a thickness Z1 of the buffer layer 44 in a cross section parallel to the normal to the first electrode E1 and passing through the slope of the bank BK may be larger than a thickness Z2 of the first intermediate layer 14 in a cross section parallel to the normal to the first electrode E1 and passing through the center of the first electrode E1.

[0031] The thickness Z2 is preferably a thickness that forms a resonant structure on the slope of the bank BK between the first relay metal layer 42 and the second relay metal layer 46, which has the emission peak wavelength of the first light-emitting material Q1 and intensifies light traveling in the forward direction. For example, for the emission peak wavelength of the first light-emitting material Q1, the thickness Z1 above the slope may be the m-th order resonator length or a value close to it, and the thickness Z2 above the first electrode E1 may be the n-th order resonator length or a value close to it. Here, m and n are natural numbers, and m>n.

[0032] (Cavity Length) When the resonant structure between the lower metal layer and the upper metal layer completely strengthens light, the following formula (1) holds; when it completely weakens light, the following formula (2) holds.

[0033] where m is the order of resonance, θ Ｄ is the phase shift due to reflection at the lower metal layer, θ Ｕ is the phase shift due to reflection in the upper metal layer, λ is the peak wavelength of light, n is the refractive index of the intermediate layer located between the lower and upper metal layers, and d is the distance from the top surface of the lower metal layer to the bottom surface of the upper metal layer, which is the thickness of the intermediate layer. Ｄ , θ Ｕ is set so that the degree m in the above formula (1) is a natural number when the distance d is positive, that is, so that the following formula (3) holds.

[0034] The value of the distance d when the above-mentioned constructive condition (1) is satisfied at the order m is defined as D ｍ The value of the distance d when the above weakening condition (2) is satisfied at the order m is d ｍ In a resonant structure that strengthens light of a peak wavelength λ, the following formula (4-1) holds, preferably the following formula (4-2) holds, and more preferably the following formula (4-3) holds. When generalized using a natural number k, the following formula (4-4) holds, and the larger k is, the more preferable. On the other hand, in a resonant structure that weakens light of a peak wavelength λ, the following formula (5-1) holds, preferably the following formula (5-2) holds, and more preferably the following formula (5-3) holds. When generalized using a natural number k, the following formula (5-4) holds, and the larger k is, the more preferable.

[0035] The present disclosure can be quantitatively understood by applying the above mathematical formulas.

[0036] (Manufacturing Method) Referring again to FIG. 2 , in an example of a manufacturing method of a display device according to an embodiment of the present disclosure, a substrate Sb is prepared, a plurality of pixel electrodes including a first electrode E1 and a second electrode E2 are formed on the substrate Sb, and a bank BK is formed between the pixel electrodes. Next, one or more of a hole injection layer HIL, a hole transport layer HTL, and an electron blocking layer are optionally formed on the plurality of pixel electrodes. Then, a first light-emitting layer L1 is formed above the first electrode E1, a second light-emitting layer L2 is formed above the second electrode E2, and light-emitting layers are appropriately formed above the other pixel electrodes. Then, one or more of an electron injection layer, an electron transport layer ETL, and a hole blocking layer are optionally formed on the plurality of light-emitting layers including the first light-emitting layer L1 and the second light-emitting layer L2 (step S70).

[0037] Subsequently, the first lower metal layer 12, the second lower metal layer 22, and the first relay metal layer 42 are formed. The first lower metal layer 12, the second lower metal layer 22, and the first relay metal layer 42 may be formed separately or simultaneously.

[0038] Next, the first intermediate layer 14, the second intermediate layer 24, and the buffer layer 44 are formed (step S90). The first intermediate layer 14, the second intermediate layer 24, and the buffer layer 44 may be formed separately or simultaneously by any method. For example, multiple layers with different thicknesses may be simultaneously formed from a photoresist material using a half-tone mask or a gray-tone mask. For example, multiple layers with different thicknesses may be formed sequentially using multiple different deposition masks.

[0039] The first intermediate layer 14, the second intermediate layer 24, the buffer layer 44, and one or more of the layers formed between the first lower metal layer 12 and the first upper metal layer 16 may be a stack of multiple layers. For example, the buffer layer 44 may include a layer formed simultaneously with the first intermediate layer 14 and a layer formed simultaneously with the second intermediate layer 24.

[0040] Subsequently, the first upper metal layer 16, the second upper metal layer 26, and the second relay metal layer 46 are formed. The first upper metal layer 16, the second upper metal layer 26, and the second relay metal layer 46 may be formed separately or simultaneously.

[0041] 4 is a cross-sectional view showing an example of a schematic configuration of a display region of a display device according to an embodiment of the present disclosure. As shown in FIG. 4, above the bank BK, the first relay metal layer 42 may be in contact with the second relay metal layer 46. In this case, the first lower metal layer 12 and the first upper metal layer 16 are electrically connected via the first relay metal layer 42 and the second relay metal layer 46.

[0042] According to the above configuration, the first lower metal layer 12 and the first upper metal layer 16 are electrically connected to each other regardless of whether the first intermediate layer 14 is conductive or insulating. Therefore, the first lower metal layer 12 and the first upper metal layer 16 can cooperate to function as a cathode (or anode), thereby reducing the electrical resistance of the cathode (or anode).

[0043] Furthermore, since the first intermediate layer 14 and the second intermediate layer 24 are discontinuous at least above the bank BK, light leakage (crosstalk) between the first light-emitting element D1 and the second light-emitting element D2 can be reduced. The reduction in crosstalk reduces blurring of image display. Crosstalk can also be reduced between the second light-emitting element D2 and the third light-emitting element D3.

[0044] [Embodiment 3] Fig. 5 is a cross-sectional view showing an example of a schematic configuration of a display region of a display device according to an embodiment of the present disclosure. As shown in Fig. 5, the first light-emitting element D1 may further include a semi-light-transmitting first inner metal layer 10 between the first light-emitting layer L1 and the first lower metal layer 12. A light-transmitting layer 11 made of the same material as the first intermediate layer 14 may be disposed between the first inner metal layer 10 and the first lower metal layer 12. Here, a resonant structure that enhances light having the emission peak wavelength of the first light-emitting material Q1 may be formed between the first inner metal layer 10 and the first lower metal layer 12.

[0045] Additionally / alternatively, the first light-emitting element D1 may further include a semi-light-transmitting first outer metal layer 18 between the first upper metal layer 16 and the first light extraction surface S1. A light-transmitting layer 17 made of the same material as the first intermediate layer 14 may be disposed between the first upper metal layer 16 and the first outer metal layer 18. Here, a resonant structure that intensifies light of the emission peak wavelength of the first light-emitting material Q1 may be formed between the first upper metal layer 16 and the first outer metal layer 18.

[0046] The second light-emitting element D2 may similarly include a second inner metal layer 20 and a light-transmitting layer 21, and a resonant structure that intensifies light of the emission peak wavelength of the second light-emitting material Q2 may be formed between the second inner metal layer 20 and the second lower metal layer 22. Additionally / alternatively, the second light-emitting element D2 may similarly include a second outer metal layer 28 and a light-transmitting layer 27, and a resonant structure that intensifies light of the emission peak wavelength of the second light-emitting material Q2 may be formed between the second upper metal layer 26 and the second outer metal layer 28.

[0047] The third light-emitting element D3 may similarly include a third inner metal layer 30 and a light-transmitting layer 31, and may additionally / alternatively include a third outer metal layer 38 and a light-transmitting layer 37.

[0048] The display device 1 according to the present disclosure may further include an inner relay metal layer 40 and / or an outer relay metal layer 48 that overlap the bank BK in a plan view. A buffer layer 41 may or may not be present between the inner relay metal layer 40 and the first relay metal layer 42, and a buffer layer may or may not be present between the second relay metal layer 46 and the outer relay metal layer 48.

[0049] The third embodiment can be combined with the first and second embodiments described above.

[0050] [Embodiment 4] Fig. 6 is a cross-sectional view showing an example of a schematic configuration of a display region of a display device according to an embodiment of the present disclosure. As shown in Fig. 6, the first intermediate layer 14 may contain a photoluminescent material P1. The photoluminescent material P1 can be excited by light having an emission peak wavelength of the first light-emitting material Q1 to emit light. The photoluminescent material P1 may contain, for example, luminescent quantum dots that can emit light upon photoexcitation.

[0051] According to the above configuration, the photoluminescent material P1 can absorb and re-emit light that propagates in a direction that cannot be extracted from the first light-emitting element D1, thereby improving the light extraction efficiency of the first light-emitting element D1 and further improving the front brightness of the first light-emitting element D1 through the photon recycling effect.

[0052] The photoluminescent material P1 may emit light of the same color as the first light-emitting material Q1. For example, the difference between the emission peak wavelength of the first light-emitting material Q1 and the emission peak wavelength of the photoluminescent material P1 may be 15 nm or less. Similarly, the photoluminescent material P2 may emit light of the same color as the second light-emitting material Q2. This can further improve the color purity of the first light-emitting element D1.

[0053] Similarly, the second intermediate layer 24 may contain a photoluminescent material P2. The photoluminescent material P2 can be excited by light having the emission peak wavelength of the second light-emitting material Q2 and emit light. The photoluminescent material P2 may emit light of the same color as the second light-emitting material Q2. Similarly, the third intermediate layer 34 may contain a photoluminescent material P3.

[0054] This fourth embodiment can be combined with the first to third embodiments described above.

[0055] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0056] 1 Display device 10 First inner metal layer 11 Light-transmitting layer 12 First lower metal layer 14 First intermediate layer 16 First upper metal layer 15 Light-transmitting layer 18 First outer metal layer 22 Second lower metal layer 24 Second intermediate layer 26 Second upper metal layer 42 First relay metal layer 44 Buffer layer 46 Second relay metal layer D1 First light-emitting element D2 Second light-emitting element BK Bank E1 First electrode E2 Second electrode L1 First light-emitting layer L2 Second light-emitting layer P1, P2 Photoluminescent material Q1 First light-emitting material Q2 Second light-emitting material S1 First light-extraction surface S2 Second light-extraction surface Z1, Z2 Thickness

Claims

1. A display device comprising a first light-emitting element having a first electrode, a first light-emitting layer located above the first electrode and containing a first light-emitting material, and a first light extraction surface located above the first light-emitting layer, wherein the first light-emitting element includes a semi-transparent first lower metal layer and a semi-transparent first upper metal layer located between the first light-emitting layer and the first light extraction surface, and a first intermediate layer located between the first lower metal layer and the first upper metal layer, and a resonant structure is formed between the first lower metal layer and the first upper metal layer, which has the emission peak wavelength of the first light-emitting material and strengthens light traveling in a forward direction perpendicular to the first light extraction surface.

2. The display device according to claim 1, wherein the first intermediate layer is optically transparent, and the upper surface of the first lower metal layer and the lower surface of the first upper metal layer each function as a light reflecting surface.

3. The display device according to claim 1 or 2, wherein the distance between the first lower metal layer and the first upper metal layer is D [nm], the emission peak wavelength is λ [nm], and D≦λ×0.2+10 [nm] and D≧λ×0.2-10 [nm].

4. The display device according to any one of claims 1 to 3, wherein the full width at half maximum of the emission spectrum of the first light-emitting material is not more than one tenth of the emission peak wavelength.

5. A display device according to any one of claims 1 to 4, wherein the first electrode is light reflective, and a resonant structure is formed between the first electrode and the first lower metal layer, the resonant structure having the emission peak wavelength and enhancing light traveling in the forward direction.

6. A display device according to any one of claims 1 to 5, wherein the first electrode functions as an anode, and at least one of the first lower metal layer and the first upper metal layer functions as a cathode.

7. The display device according to any one of claims 1 to 6, wherein the luminance in a direction at an angle of 40° or more to the front direction is 50% or less of the luminance in the front direction.

8. The display device according to any one of claims 1 to 7, wherein the first light-emitting material includes quantum dots.

9. The display device according to any one of claims 1 to 8, wherein the first intermediate layer is conductive.

10. The display device according to claim 9, wherein the first lower metal layer and the first upper metal layer are electrically connected via the first intermediate layer.

11. The display device according to any one of claims 1 to 8, wherein the first intermediate layer is insulating.

12. The display device of any one of claims 1 to 11, further comprising a semi-light-transmitting first inner metallic layer between the first light-emitting layer and the first lower metallic layer.

13. The display device according to claim 12, wherein a light-transmitting layer made of the same material as said first intermediate layer is disposed between said first inner metal layer and said first lower metal layer.

14. The display device according to any one of claims 1 to 13, wherein the first lower metal layer comprises aluminum.

15. The display device according to any one of claims 1 to 14, wherein the first lower metal layer has a thickness of less than 10 nm.

16. The display device according to any one of claims 1 to 15, wherein the first intermediate layer contains a photoluminescent material.

17. The display device according to claim 16, wherein the photoluminescent material is excited by light having the emission peak wavelength.

18. The display device of claim 16 or 17, wherein the photoluminescent material includes quantum dots.

19. The display device according to any one of claims 16 to 18, wherein the difference between the emission peak wavelength of the first light-emitting material and the emission peak wavelength of the photoluminescent material is 15 nm or less.

20. A display device as described in any one of claims 1 to 19, comprising a second light-emitting element having a second electrode, a second light-emitting layer located above the second electrode and containing a second light-emitting material, and a second light extraction surface located above the second light-emitting layer, wherein the second light-emitting element includes a semi-transparent second lower metal layer and a semi-transparent second upper metal layer located between the second light-emitting layer and the second light extraction surface, and a second intermediate layer located between the second lower metal layer and the second upper metal layer, and a resonant structure having an emission peak wavelength of the second light-emitting material and strengthening light traveling in the forward direction is formed between the second lower metal layer and the second upper metal layer.

21. The display device according to claim 20, wherein the first and second light-emitting elements are adjacent to each other via a bank, and the first and second light-emitting layers emit light of different colors.

22. The display device described in claim 21, comprising a first relay metal layer and a second relay metal layer overlapping the bank in a planar view, the first lower metal layer and the second lower metal layer being connected via the first relay metal layer, and the second upper metal layer and the second upper metal layer being connected via the second relay metal layer.

23. The display device of claim 22, wherein the emission peak wavelength of the first luminescent material is greater than the emission peak wavelength of the second luminescent material, and the distance between the first lower metal layer and the first upper metal layer is greater than the distance between the second lower metal layer and the second upper metal layer.

24. A display device as described in claim 22 or 23, wherein a buffer layer is disposed between the first relay metal layer and the second relay metal layer, and the thickness of the buffer layer above the upper surface of the bank is sized to attenuate light having the peak emission wavelength of the first light-emitting material and traveling in the forward direction, and light having the peak emission wavelength of the second light-emitting material and traveling in the forward direction.

25. The display device according to claim 24, wherein the buffer layer is made of the same material as the first and second intermediate layers.

26. A display device as described in claim 24 or 25, wherein the thickness of the buffer layer in a cross section parallel to the normal to the first electrode and passing through the slope of the bank is greater than the thickness of the first intermediate layer in a cross section parallel to the normal to the first electrode and passing through the center of the first electrode.

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