Display device and method for manufacturing display device

Abstract

A display device (10) is configured such that when the optical path length of a first region (R1) that emits light of a peak wavelength λ is L1, the optical path length of a second region (R2) that emits light of the same color as the first region is L2, the phase shift in a reflective layer (XL) is φ, and N is a prescribed integer, 0<L2-L1<λ / 3, wherein λ×(N-φ / 2π)<2×L1<λ×(N+2 / 3-φ / 2π) or λ×(N-φ / 2π)<2×L2<λ×(N+2 / 3-φ / 2π) is satisfied.

Description

Display device and method for manufacturing the same

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

[0002] Patent Document 1 discloses a method for improving the viewing angle characteristics of a display device including a light-emitting element by forming regions in the light-emitting element where the thickness of the light-reflecting electrode varies.

[0003] Japanese Patent Publication No. 2007-234581

[0004] The conventional techniques have the problem that they are difficult to apply to display devices that include nanoparticle layers.

[0005] The display device according to the present disclosure includes a first region including a first light-reflecting layer, a conductive first light-transmitting layer, and a first nanoparticle layer located between the first light-reflecting layer and the first light-transmitting layer, wherein the optical path length from the first light-reflecting layer to the first light-transmitting layer is L1 and the first region emits light of a peak wavelength λ; a second light-reflecting layer, a conductive second light-transmitting layer, and a second nanoparticle layer located between the second light-reflecting layer and the second light-transmitting layer, wherein the optical path length from the second light-reflecting layer to the second light-transmitting layer is L2 and the second region emits light of the same color as the first region; and wherein φ is a phase shift of the light of the peak wavelength λ in the first light-reflecting layer and N is a predetermined integer, and 0<L2-L1<λ / 3, λ×(N-φ / 2π)<2×L1<λ×(N+2 / 3-φ / 2π), or λ×(N-φ / 2π)<2×L2<λ×(N+2 / 3-φ / 2π).

[0006] The display quality of the display device can be improved.

[0007] FIG. 1 is a plan view showing a configuration example of a display device according to this embodiment; FIG. 2 is a cross-sectional view showing a configuration example of a display device according to this embodiment; FIG. 3 is a graph showing the relationship between the deviation of the optical path length from the optimum cavity length and the maximum luminance angle; FIG. 4 is a cross-sectional view showing a configuration example of a display device according to this embodiment; FIG. 5 is a cross-sectional view showing a configuration example of a display device according to this embodiment; FIG. 6 is a cross-sectional view showing a configuration example of a display device according to this embodiment; FIG. 7 is a cross-sectional view showing a configuration example of a display device according to this embodiment; FIG. 8 is a cross-sectional view showing a configuration example of a display device according to this embodiment; FIG. 9 is a cross-sectional view showing a configuration example of a display device according to this embodiment; FIG. 10 is a cross-sectional view showing a configuration example of a display device according to this embodiment; FIG. 11 is a cross-sectional view showing a configuration example of a display device according to this embodiment;

[0008] FIG. 1 is a plan view showing an example of the configuration of a display device according to this embodiment. The display device 10 includes a display unit DA, a first driver circuit 11 (e.g., a data signal line drive circuit) and a second driver circuit 12 (e.g., a scanning signal line drive circuit and a light-emitting control line drive circuit) that drive the display unit DA, and a control circuit 13 that controls the first driver circuit 11 and the second driver circuit 12. The display unit DA may include a pixel circuit layer and a light-emitting element layer. The light-emitting element layer may include a light-emitting element SR(S) that emits red light, a light-emitting element SG(S) that emits green light, and a light-emitting element SB(S) that emits blue light, and the light-emitting elements S (SR, SB, SB) may be connected to pixel circuits PC formed in the pixel circuit layer. Each sub-pixel SP of the display device 10 may include the light-emitting element S and the pixel circuit PC.

[0009] FIG. 2 is a cross-sectional view showing an example of the configuration of a display device according to this embodiment. As shown in FIG. 2, the display device 10 includes a first region R1 and a second region R2. The first region R1 includes a first light-reflecting layer X1, a conductive first light-transmitting layer Y1, and a first nanoparticle layer P1 located between the first light-reflecting layer X1 and the first light-transmitting layer Y1. The optical path length from the first light-reflecting layer X1 to the first light-transmitting layer Y1 is L1, and the display device 10 emits light LS with a peak wavelength λ. The second region R2 includes a second light-reflecting layer X2, a conductive second light-transmitting layer Y2, and a second nanoparticle layer P2 located between the second light-reflecting layer X2 and the second light-transmitting layer Y2. The optical path length from the second light-reflecting layer X2 to the second light-transmitting layer Y2 is L2, and the display device 10 emits light of the same color as the first region R1. In the display device 10, when the phase shift of light LS having a peak wavelength λ at the first light reflecting layer X1 is φ and N is a predetermined integer, 0<L2-L1<λ / 3, and λ×(N-φ / 2π)<2×L1<λ×(N+2 / 3-φ / 2π), or λ×(N-φ / 2π)<2×L2<λ×(N+2 / 3-φ / 2π), is satisfied.

[0010] Nanoparticles are particles with a maximum width of 1000 nm or less. The shape of the nanoparticles 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, they may have a polygonal cross-sectional shape, a rod-like three-dimensional shape, a branch-like three-dimensional shape, or a three-dimensional shape with an uneven surface, or a combination thereof. Typically, they are semiconductor particles, and may have a particle size of 1.0 nm to 50 nm. Nanoparticles are not limited to single crystals, and may be polycrystalline or amorphous.

[0011] Examples of nanoparticles include NiO nanoparticles, ZnO nanoparticles, lithium-doped ZnO (LZO) nanoparticles, manganese-doped ZnO (MZO) nanoparticles, aluminum-doped ZnO (AZO) nanoparticles, CuO nanoparticles, WO ３ Examples of nanoparticles include tungsten oxide (Tungsten Oxide) nanoparticles, MoOx (Molybdenum Oxide) nanoparticles, and TiO nanoparticles.

[0012] The first nanoparticle layer P1 and the second nanoparticle layer P2 containing nanoparticles may be mixed layers containing nanoparticles of different materials (e.g., a mixed layer of NiO nanoparticles and MZO nanoparticles), or may be mixed layers containing nanoparticles of different sizes (e.g., a mixed layer of ZnO nanoparticles with a particle size of 10 nm and MZO nanoparticles with a particle size of 25 nm).

[0013] FIG. 3 is a graph showing the relationship between the optical path length deviation from the optimal cavity length and the maximum luminance angle. In the display device 10, as shown in FIG. 3, L1 (first region R1) or L2 (second region R2) deviates from the optimal cavity length for light LS with wavelength λ within a range that can improve viewing angle characteristics, thereby improving display quality. The values ​​on the horizontal axis of FIG. 3 indicate ratios to wavelength λ (e.g., 0.1 on the horizontal axis indicates an optical path length deviation of 0.1 times the wavelength). The predetermined integer N may be any one of 1 to 3. The first region R1 and the second region R2 may contain the same light-emitting material, and the light LS with peak wavelength λ may be any one of red, green, and blue light.

[0014] As shown in FIG. 2 , the first and second light-reflecting layers X1 and X2 may be included in the same light-emitting element S, the first and second light-transmitting layers Y1 and Y2 may be included in the same light-emitting element S, and the first and second nanoparticle layers P1 and P2 may be included in the same light-emitting element S. The difference between the optical path length in the thickness direction of the first nanoparticle layer P1 and the optical path length in the thickness direction of the second nanoparticle layer P2 may be equal to or greater than the half-width at half maximum of the spectrum of the light LS emitted by the light-emitting element S. The difference in thickness between the first region R1 and the second region R2 may be less than 50 nm. This enhances the viewing angle improvement effect.

[0015] As shown in FIG. 2 , in a plan view, the maximum distance Lm (maximum distance) between a point in the first region R1 and a point in the second region R2 may be equal to or less than the peak wavelength λ. This can improve color unevenness. The minimum distance Ln (minimum distance) between a point in the first region R1 and a point in the second region R2 may be equal to or greater than the difference in thickness between the first region R1 and the second region R2. This can suppress a decrease in internal quantum efficiency and increase the luminance of the light-emitting element S including the first and second regions R1 and R2.

[0016] Multiple functional layers may be formed between the reflective layer XL, which includes the first light-reflecting layer X1 and the second light-reflecting layer X2, and the transmissive layer YL, which includes the first light-transmitting layer Y1 and the second light-transmitting layer Y2. At least one of the multiple functional layers may be a charge transport layer having a charge transport function. Furthermore, in the display device 10, the charge transport layer may be formed as a layer common to multiple light-emitting elements. The multiple functional layers may be multiple functional layers JL, TL, EL, and NL, as shown in FIG. 2 . The functional layer JL may be a hole injection layer, the functional layer TL may be a hole transport layer, the functional layer EL may be a light-emitting layer, and the functional layer NL may be an electron transport layer. The particle layer PL, which includes the first nanoparticle layer P1 and the second nanoparticle layer P2, may be the functional layer JL (e.g., a hole injection layer).

[0017] 2, L2-L1<λ / 6, and λ×(N-1 / 10-φ / 2π)<2×L2<λ×(N+1 / 10-φ / 2π). This allows for increased front luminance.

[0018] An aluminum layer may be used for the reflective layer XL. A nickel oxide nanoparticle layer functioning as a hole injection layer may be used for the functional layer JL. A poly-4-butyl-N,N-diphenylaniline (Poly-TPD) layer functioning as a hole transport layer may be used for the functional layer TL. A zinc oxide nanoparticle layer functioning as an electron transport layer may be used for the functional layer NL. In this case, the particle layer PL may be either a hole injection layer or an electron transport layer. An ITO (indium tin oxide) layer, a silver nanowire layer, or an ultrathin MgAg alloy layer may be used for the transmissive layer YL.

[0019] In calculating the optical path length, the distance between the top surface of the reflective layer XL and the top surface of the ITO layer that is the transmissive layer YL (the surface farther from the reflective layer XL) may be used, or the distance between the top surface of the reflective layer XL and the bottom surface of the silver nanowire layer or MgAg alloy layer that is the transmissive layer YL (the surface closer to the reflective layer XL) may be used.

[0020] The functional layer EL may be a quantum dot layer that functions as a light-emitting layer, and the quantum dot layer contains light-emitting quantum dots. The quantum dots may be fine particles having a particle size (outer diameter) of 1.0 nm to 100 nm, and may be spherical or non-spherical in shape. In this case, the particle layer PL may be the light-emitting layer.

[0021] The shape of the quantum dots is not limited to a spherical three-dimensional shape (circular cross-sectional shape) as long as it satisfies the above particle size range. For example, they 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. The quantum dots may be made of a semiconductor material. The semiconductor material may have a certain band gap and may be a material that generates electroluminescence. The wavelength range of the electroluminescence may be any of the red, green, and blue ranges.

[0022] The quantum dots may include at least one of a crystal of a II-VI group semiconductor such as MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, or HgTe, a crystal of a III-V group semiconductor such as GaAs, GaP, InN, InAs, InP, or InSb, or a crystal of a group IV semiconductor such as Si or Ge.

[0023] The quantum dots may have a core-shell structure in which a core made of a crystal of the above-mentioned semiconductor is overcoated with a shell material having a high band gap.

[0024] The quantum dot layer may contain a ligand that adsorbs (coordinates) to the quantum dot surface. The ligand may be an organic ligand or an inorganic ligand that contains, for example, a halogen.

[0025] The quantum dot layer may include an inorganic matrix material (e.g., an inorganic compound having a band gap larger than that of the quantum dots) that fills the gaps between the quantum dots. The inorganic matrix material may include at least one of zinc sulfide (ZnS) and magnesium sulfide (MgS) (described below).

[0026] FIG. 4 is a cross-sectional view showing an example of the configuration of a display device according to this embodiment. The first nanoparticle layer P1 and the second nanoparticle layer P2 may contain inorganic nanoparticles (e.g., nickel oxide nanoparticles). A plurality of functional layers may be located between the reflective layer XL, which includes the first light-reflecting layer X1 and the second light-reflecting layer X2, and the transmissive layer YL, which includes the first light-transmitting layer Y1 and the second light-transmitting layer Y2. Among these functional layers, the functional layer JL (e.g., the hole injection layer), which has the greatest film thickness variation, may contain the first nanoparticle layer P1 and the second nanoparticle layer P2. In other words, the functional layer JL may be the particle layer PL. Because inorganic nanoparticles have a high refractive index, the viewing angle can be improved with a small film thickness difference compared to creating an optical path difference using other layers.

[0027] As shown in FIG. 4, the top surface XF of the reflective layer XL including the first light-reflecting layer X1 and the second light-reflecting layer X2 may be flatter than the top surface PF of the particle layer PL including the first nanoparticle layer P1 and the second nanoparticle layer P2.

[0028] 5 is a cross-sectional view showing an example of the configuration of a display device according to this embodiment. As shown in FIG. 5, a functional layer EL (e.g., a light-emitting layer) may include a first nanoparticle layer P1 and a second nanoparticle layer P2. That is, the functional layer EL may be a particle layer PL having a light-emitting function.

[0029] Fig. 6 is a cross-sectional view showing an example of the configuration of the display device according to this embodiment. In Fig. 1, the reflective layer XL is flat, but this is not limited to this. As shown in Fig. 5, a step layer ZL may be provided under a portion of the reflective layer XL to create a step in the reflective layer XL, thereby forming first and second regions R1 and R2 with different thicknesses.

[0030] 7 is a cross-sectional view showing an example of the configuration of the display device according to the present embodiment. As shown in Fig. 7, the first region R1 and the second region R2 may be included in the same light-emitting element S, or the first region R1 and the second region R2 may be included in the same sub-pixel SP formed by the light-emitting element S and the pixel circuit PC.

[0031] For example, a light-emitting element SR(S) having an emitting layer ER(EL) and emitting red light may include a first region R1 and a second region R2, a light-emitting element SG(S) having an emitting layer EG(EL) and emitting green light may include a first region G1 and a second region G2, and a light-emitting element SB(S) having an emitting layer EB(EL) and emitting blue light may include a first region B1 and a second region B2. The emitting layers ER, EG, and EB may be separately painted emitting layers EL.

[0032] In the light-emitting elements SR, SG, and SB of Figure 7, the difference in optical path lengths L1 and L2 between the first region R1 and the second region R2 may be greater than the difference in optical path lengths L1 and L2 between the first region G1 and the second region R2 > the difference in optical path lengths L1 and L2 between the first region B1 and the second region B2.

[0033] In Figures 1 to 7, the first light transmitting layer Y1 and the second light transmitting layer Y2 are made of an oxide semiconductor material, L1 may be the optical path length corresponding to the inner surface of the first light reflecting layer X1 and the outer surface of the first light transmitting layer Y1, and L2 may be the optical path length corresponding to the inner surface of the second light reflecting layer X2 and the outer surface of the second light transmitting layer Y2.

[0034] In Figures 1 to 7, the first light transmitting layer Y1 and the second light transmitting layer Y2 are made of a metal material, L1 may be the optical path length corresponding to the inner surface of the first light reflecting layer X1 and the inner surface of the first light transmitting layer Y1, and L2 may be the optical path length corresponding to the inner surface of the second light reflecting layer X2 and the inner surface of the second light transmitting layer Y2.

[0035] 8 and 9 are cross-sectional views showing an example of the configuration of a display device according to this embodiment. The display device 10 in Fig. 8 and Fig. 9 includes a first light-reflecting layer X1, a conductive first light-transmitting layer Y1, and a first nanoparticle layer P1 located between the first light-reflecting layer X1 and the first light-transmitting layer Y1, the distance between the inner surface of the first light-reflecting layer X1 and the outer surface of the first light-transmitting layer Y1 is D1, and includes a first region R1 emitting light LS of a peak wavelength λ, a second light-reflecting layer X2, a conductive second light-transmitting layer Y2, and a second nanoparticle layer P1 located between the second light-reflecting layer X2 and the second light-transmitting layer Y2. a second region R2 that emits light of the same color as the first region R1; and a second light-reflecting layer P2; a distance D2 between the inner surface of the second light-reflecting layer X2 and the outer surface of the second light-transmitting layer Y2; the first light-transmitting layer Y1 and the second light-transmitting layer Y2 are made of an oxide semiconductor material; and, where N is a predetermined integer, 0<D2-D1<0.175×λ, λ×(N+0.2)<4×D1<λ×(N+0.9), or λ×(N+0.2)<4×D2<λ×(N+0.9).

[0036] In the display device 10 shown in Figures 8 and 9, the first region R1 or the second region R2 deviates from the optimal cavity length for light LS having a wavelength λ within a range that can improve viewing angle characteristics, thereby improving display quality. The particle layer PL including the first and second nanoparticle layers P1 and P2 may be a hole injection layer or a light-emitting layer. In Figures 8 and 9, 0 < D2 - D1 < λ / 12, and λ × (N + 0.175) < 4 × D1 < λ × (N + 0.225), may be satisfied.

[0037] 10 and 11 are cross-sectional views showing an example of the configuration of a display device according to this embodiment. The display device 10 in Fig. 10 and Fig. 11 includes a first light-reflecting layer X1, a conductive first light-transmitting layer Y1, and a first nanoparticle layer P1 located between the first light-reflecting layer X1 and the first light-transmitting layer Y1, the distance between the inner surface of the first light-reflecting layer X1 and the inner surface of the first light-transmitting layer Y1 is d1, and includes a first region R1 emitting light LS of a peak wavelength λ, a second light-reflecting layer X2, a conductive second light-transmitting layer Y2, and a nanoparticle layer P1 located between the second light-reflecting layer X2 and the second light-transmitting layer Y2. a second nanoparticle layer P2, wherein the distance between the inner surface of the second light-reflecting layer X2 and the inner surface of the second light-transmitting layer Y2 is d2, and a second region R2 that emits light of the same color as the first region R1, wherein the first light-transmitting layer Y1 and the second light-transmitting layer Y2 are made of a metal material, and 0<d2-d1<0.175×λ, λ×(N+0.7)<4×d1<λ×(N+1.4), or λ×(N+0.7)<4×d2<λ×(N+1.4), where N is a predetermined integer.

[0038] In the display device 10 shown in Figures 10 and 11, the first region R1 or the second region R2 deviates from the optimal cavity length for the light LS having a wavelength λ within a range that can improve the viewing angle characteristics, thereby improving display quality. The particle layer PL including the first and second nanoparticle layers P1 and P2 may be a hole injection layer or a light-emitting layer. In Figures 10 and 11, 0 < d2 - d1 < λ / 12, and λ × (N + 0.675) < 4 × d1 < λ × (N + 0.725), may be satisfied.

[0039] 12 is a cross-sectional view showing an example of the configuration of a display device according to this embodiment. In FIG. 12, a light-emitting element SR(S) having an emitting layer ER(EL) and emitting red light may include a first region R1 and a second region R2, a light-emitting element SG(S) having an emitting layer EG(EL) and emitting green light may include a first region G1 and a second region G2, and a light-emitting element SB(S) having an emitting layer EB(EL) and emitting blue light may include a first region B1 and a second region B2. The emitting layers ER, EG, and EB may be individually painted emitting layers EL. Furthermore, the emitting region A1 of the first region R1 may include a plurality of luminescent quantum dots QD and an inorganic matrix material MX in contact with the plurality of quantum dots QD, and the emitting region A2 of the second region R2 may include a plurality of luminescent quantum dots QD and an inorganic matrix material MX in contact with the plurality of quantum dots QD.

[0040] The inorganic matrix material means a component made of an inorganic substance (e.g., an inorganic semiconductor or an inorganic insulator) that contains and holds other substances, and can be referred to as a substrate, a base material, or a filler. The inorganic matrix material may be solid at room temperature. The inorganic matrix material has a thickness of 1000 nm along the plane direction perpendicular to the film thickness direction. ２ The continuous film may include a continuous film having an area of ​​1000 nm or more. A continuous film means a film that is not separated by materials other than the material that constitutes the continuous film in one plane. The inorganic material may be, for example, a metal sulfide semiconductor such as zinc sulfide (ZnS), or a silicon oxide (e.g., SiO ２ ) or other insulating material.

[0041] The inorganic matrix material MX may be formed to fill the spaces between adjacent quantum dots QD, and the concentration of the inorganic matrix material in the light-emitting region A1 may be different from the concentration of the inorganic matrix material in the light-emitting region A2. A high concentration of the inorganic matrix material means a high filling rate of the inorganic matrix material, while a low concentration of the inorganic matrix material means a low filling rate due to the formation of voids K, etc. For example, by making the concentration (filling rate) of the inorganic matrix material in the light-emitting region A2 greater than the concentration (filling rate) of the inorganic matrix material in the light-emitting region A1, the optical path length (L2) of the second region R2 can be made greater than the optical path length (L1) of the first region R1. In other words, because the difference in refractive index accentuates the optical path length difference, a viewing angle improvement effect can be achieved with a smaller film thickness difference.

[0042] In the light-emitting element SR (red light emission), light-emitting element SG (green light emission), and light-emitting element SB (blue light emission) shown in Figure 12, the difference in optical path length (L1·L2) between the first region R1 and the second region R2 may be greater than the difference in optical path length (L1·L2) between the first region G1 and the second region R2 > the difference in optical path length (L1·L2) between the first region B1 and the second region B2.

[0043] Fig. 13 is a cross-sectional view showing an example of the configuration of a display device according to this embodiment. In Fig. 2 and other figures, the first and second regions A1 and A2 are formed in the same light-emitting element S, but this is not limiting. As shown in Fig. 13, the display device 10 may include a light-emitting element SR1 including a first region R1 and another light-emitting element SR2 including a second region R2. The light-emitting elements SR1 and SR2 may emit light of the same color, or the first region R1 and the second region R2 may be included in different sub-pixels SP.

[0044] 14 is a flowchart showing a method for manufacturing a display device according to this embodiment. As shown in FIG. 14 , the method for manufacturing a display device according to this embodiment includes a step S10 for forming a reflective layer XL, a step S20 for applying a nanoparticle solution containing a plurality of particles to a base layer (e.g., the reflective layer XL), a step S30 for drying the applied nanoparticle solution, and a step S40 for forming a transmissive layer YL.

[0045] The nanoparticle solution may contain a plurality of particle groups (particle aggregates) having a dynamic diameter that is 5 times or more larger than each particle and less than 1 μm, and the volume ratio of the particle groups to the total volume of the solute (nanoparticles and particle groups) may be 40 to 60% or more.

[0046] The nanoparticle solution may contain multiple solvents, and at least two of the multiple solvents may have a weight percent concentration of 20% or more. For example, the nanoparticle solution may be a solution in which quantum dots containing InP are dispersed in a solvent containing octane and decane in a weight ratio of 7:3.

[0047] [Notes] The above-described embodiments are for the purpose of illustration and description, and are not intended to be limiting. Based on these examples and descriptions, it will be apparent to those skilled in the art that many variations are possible.

[0048] 10 Display device S Light-emitting element R1 First region R2 Second region X1 First light-reflecting layer Y1 First light-transmitting layer X2 Second light-reflecting layer Y2 Second light-transmitting layer P1 First nanoparticle layer P2 Second nanoparticle layer XL Reflecting layer PL Particle layer YL Transmitting layer

Claims

1. A display device comprising: a first light reflective layer, a conductive first light transmitting layer, and a first nanoparticle layer located between the first light reflective layer and the first light transmitting layer, wherein the optical path length from the first light reflective layer to the first light transmitting layer is L1, and a first region emitting light of a peak wavelength λ; a second light reflective layer, a conductive second light transmitting layer, and a second nanoparticle layer located between the second light reflective layer and the second light transmitting layer, wherein the optical path length from the second light reflective layer to the second light transmitting layer is L2, and a second region emitting light of the same color as the first region, wherein φ is a phase shift of the light of the peak wavelength λ in the first light reflective layer and N is a predetermined integer, and 0<L2-L1<λ / 3, λ×(N-φ / 2π)<2×L1<λ×(N+2 / 3-φ / 2π) or λ×(N-φ / 2π)<2×L2<λ×(N+2 / 3-φ / 2π).

2. A display device comprising: a first light reflective layer, a conductive first light transmitting layer, and a first nanoparticle layer located between the first light reflective layer and the first light transmitting layer, wherein the distance between an inner surface of the first light reflective layer and an inner surface of the first light transmitting layer is d1, and a first region emitting light of a peak wavelength λ; a second light reflective layer, a conductive second light transmitting layer, and a second nanoparticle layer located between the second light reflective layer and the second light transmitting layer, wherein the distance between the inner surface of the second light reflective layer and an inner surface of the second light transmitting layer is d2, and a second region emitting light of the same color as the first region, wherein the first light transmitting layer and the second light transmitting layer are made of a metal material, and wherein, N is a predetermined integer, 0<d2-d1<0.175×λ, λ×(N+0.7)<4×d1<λ×(N+1.4), or λ×(N+0.7)<4×d2<λ×(N+1.4).

3. A display device comprising: a first light reflective layer, a conductive first light transmitting layer, and a first nanoparticle layer located between the first light reflective layer and the first light transmitting layer, wherein the distance between an inner surface of the first light reflective layer and an outer surface of the first light transmitting layer is D1, and a first region emitting light of a peak wavelength λ; a second light reflective layer, a conductive second light transmitting layer, and a second nanoparticle layer located between the second light reflective layer and the second light transmitting layer, wherein the distance between the inner surface of the second light reflective layer and the outer surface of the second light transmitting layer is D2, and a second region emitting light of the same color as the first region, wherein the first light transmitting layer and the second light transmitting layer are made of an oxide semiconductor material, and wherein, N is a predetermined integer, 0<D2-D1<0.175×λ, λ×(N+0.2)<4×D1<λ×(N+0.9), or λ×(N+0.2)<4×D2<λ×(N+0.9).

4. The display device according to claim 1, wherein 0<L2-L1<λ / 6, and λ×(N-1 / 10-φ / 2π)<2×L1<λ×(N+1 / 10-φ / 2π).

5. The display device according to claim 2, wherein 0<d2-d1<λ / 12, and λ×(N+0.675)<4×d1<λ×(N+0.725).

6. The display device according to claim 3, wherein 0<D2-D1<λ / 12, and λ×(N+0.175)<4×D1<λ×(N+0.225).

7. The display device of claim 1, wherein the first light-transmitting layer and the second light-transmitting layer are made of an oxide semiconductor material; L1 is an optical path length corresponding to between an inner surface of the first light-reflecting layer and an outer surface of the first light-transmitting layer; and L2 is an optical path length corresponding to between an inner surface of the second light-reflecting layer and an outer surface of the second light-transmitting layer.

8. The display device of claim 1, wherein the first light-transmitting layer and the second light-transmitting layer are made of a metal material; L1 is an optical path length corresponding to between the inner surface of the first light-reflecting layer and the inner surface of the first light-transmitting layer; and L2 is an optical path length corresponding to between the inner surface of the second light-reflecting layer and the inner surface of the second light-transmitting layer.

9. The display device according to any one of claims 1 to 8, wherein the difference in thickness between the first region and the second region is less than 50 nm.

10. A display device as described in any one of claims 1 to 9, wherein a plurality of functional layers are located between a reflective layer including the first light-reflecting layer and the second light-reflecting layer, and a transmissive layer including the first light-transmitting layer and the second light-transmitting layer, and the first and second nanoparticle layers are included in the functional layer having the greatest film thickness variation among the plurality of functional layers.

11. The display device according to claim 10, wherein the reflective layer is located below the transmissive layer, and an upper surface of the reflective layer is flatter than an upper surface of the functional layer having the maximum film thickness variation.

12. A display device described in any one of claims 1 to 11, wherein the difference between the optical path length in the thickness direction of the first nanoparticle layer and the optical path length in the thickness direction of the second nanoparticle layer is equal to or greater than the half-width at half maximum of the emission spectrum of light having a peak wavelength λ.

13. The display device according to any one of claims 1 to 12, wherein, in a plan view, the maximum distance between a point in the first region and a point in the second region is λ or less.

14. A display device according to any one of claims 1 to 13, wherein, in a planar view, the smallest distance between a point in the first region and a point in the second region is equal to or greater than the difference in thickness between the first region and the second region.

15. The display device according to any one of claims 1 to 14, wherein the first nanoparticle layer and the second nanoparticle layer have a charge transport function.

16. The display device according to any one of claims 1 to 14, wherein the first nanoparticle layer and the second nanoparticle layer have a light-emitting function.

17. The display device according to any one of claims 1 to 16, comprising a light-emitting element including the first region and the second region.

18. The display device according to claim 17, wherein the first region and the second region are included in the same subpixel.

19. The display device according to any one of claims 1 to 16, comprising a light-emitting element including the first region and another light-emitting element including the second region.

20. The display device of claim 19, wherein the first region and the second region are included in different subpixels.

21. The display device according to any one of claims 1 to 20, wherein the light of the peak wavelength λ is any one of red, green and blue light.

22. The display device according to any one of claims 1 to 21, wherein the predetermined integer N is any one of 1 to 3.

23. The display device of claim 16, comprising a plurality of light-emitting elements emitting light of different colors, the plurality of light-emitting elements including a common charge transport layer, and the first nanoparticle layer and the second nanoparticle layer being included in the charge transport layer.

24. The display device of claim 23, wherein the charge transport layer is a hole injection layer.

25. A display device as described in any one of claims 1 to 23, wherein the first region and the second region each contain a plurality of luminescent quantum dots and an inorganic matrix material in contact with the plurality of quantum dots, and the second region has a higher concentration of inorganic matrix material than the first region.

26. A display device as described in any one of claims 1 to 25, comprising a red light-emitting element that emits red light, a green light-emitting element that emits green light, and a blue light-emitting element that emits blue light, wherein the first region and the second region are included for each of the red light-emitting element, the green light-emitting element, and the difference between L1 and L2 in the red light-emitting element > the difference between L1 and L2 in the green light-emitting element > the difference between L1 and L2 in the blue light-emitting element.

27. A method for manufacturing a display device according to any one of claims 1 to 3, comprising the steps of: applying a nanoparticle solution containing a plurality of particles to an underlayer; and drying the applied nanoparticle solution, wherein the nanoparticle solution contains a plurality of particle groups having a kinetic diameter that is at least 5 times larger than each particle and less than 1 μm, and the volume ratio of the particle groups to the total volume of the solute is 40 to 60% or more.

28. A method for manufacturing a display device according to any one of claims 1 to 3, comprising the steps of: applying a nanoparticle solution containing a plurality of particles and a plurality of types of solvents to an underlayer; and drying the applied nanoparticle solution, wherein the nanoparticle solution contains at least two of the plurality of types of solvents with a weight percentage concentration of 20% or more.

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