Display element and display device

Abstract

The display element includes an array of light emitting layers and an array of conversion layers. The light emitting layer array includes a plurality of light emitting layers arranged in a two-dimensional manner and emitting light of a first wavelength. The conversion layer array includes a plurality of first conversion layers including a first coupling portion, a first extraction portion, and a first reflection portion. The first coupling portion is optically coupled to a portion of the plurality of light emitting layers. The first extraction portion and the first reflection portion face each other to alternately reflect the light of the first wavelength received via the first coupling portion and guide the light of the first wavelength in a direction away from the first coupling portion. The plurality of first conversion layers emit light of a second wavelength, which is obtained as a result of wavelength conversion of the light of the first wavelength, via the first extraction unit.

Description

Technical Field

[0001] The present invention relates to a display element and a display device. Background Art

[0002] In a display element and a display device for displaying an image, a known technology for achieving high color purity and high luminous efficiency uses a light-emitting layer including quantum dots. When the light-emitting layer uses primary light as excitation light, the light-emitting layer performs wavelength conversion. Therefore, the light-emitting layer can also be called a color conversion layer.

[0003] Patent document 1 describes a high-resolution display device with reduced manufacturing costs and improved macroscopic light utilization efficiency achieved by forming a monolithic structure including an inorganic micro LED array emitting blue light and a color conversion layer array corresponding to sub-pixels for RGB colors. According to Patent document 1, the device has a back optical configuration in which blue light used as excitation light is incident on the color conversion layer array corresponding to the sub-pixels for RGB colors from the back, and the color-converted light is emitted forward from the color conversion layer array. According to the display device described in Patent document 1, the back optical system ensures sufficient optical coupling area between the light-emitting element and the color conversion layer and sufficient macroscopic light utilization efficiency, which is the light propagation efficiency from the light-emitting element to the wavelength conversion layer. Patent document 1 describes a structure in which the color conversion layer includes quantum dots and light scattering materials. The color conversion layer may also be referred to as a wavelength conversion layer.

[0004] Citation List

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-86461 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] In the pixel structure of the back optical system described in Patent Document 1, the optical density of quantum dots present in the wavelength conversion layer in the layer thickness direction is set to a predetermined value or more to ensure that a sufficient amount of wavelength-converted light is emitted. In the pixel structure of the back optical system, primary light (excitation light) and secondary light (light after wavelength conversion) travel along the light path in the same direction. In addition, the pixel structure of the back optical system has an overlapping configuration in which a first window serving as a coupling region for guiding primary light to the wavelength conversion layer and a second window corresponding to a light-emitting surface through which the wavelength conversion layer emits light to a viewer include overlapping portions when viewed in the layer thickness direction of the conversion layer. In other words, in the pixel structure of the back optical system described in Patent Document 1, primary light (excitation light) and secondary light (light after wavelength conversion) are coaxially arranged.

[0009] In the pixel structure of the back optical system described in Patent Document 1, for example, the concentration of quantum dots, the absorption coefficient, or the thickness of the wavelength conversion layer can be adjusted to increase the optical density of the quantum dots, thereby increasing the luminous intensity per unit depth along the penetration depth of the primary light. According to the Beer-Lambert law, the absorption per unit depth of at least one of the primary light and the secondary light also increases, and due to the antagonism between the effect of luminescence and the effect of light absorption, the increase in the macroscopic light utilization efficiency relative to the increase in the optical density of the quantum dots reaches a stagnation period. Therefore, the pixel structure of the back optical system used in Patent Document 1 has limitations in improving the macroscopic light utilization efficiency by adjusting the optical density.

[0010] When the optical density of quantum dots in the wavelength conversion layer is reduced, although the absorption per unit depth of primary light and secondary light is reduced, the color purity of the emitted light is reduced because the primary light reaches the light-emitting surface of the color conversion layer. Although the reduction in color purity can be alleviated by placing a filter on the light-emitting side of the wavelength conversion layer, the macroscopic light utilization efficiency of the light emitted after color conversion is limited by the filter.

[0011] Therefore, the method of adjusting the optical density of the wavelength conversion layer in the layer thickness direction results in at least one of the conflicting problems of limited brightness and reduced color purity, and does not cause a fundamental improvement in the macroscopic light utilization efficiency of the wavelength conversion layer, and improvements to this problem are desired.

[0012] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a display element and a display device in which both macroscopic light utilization efficiency and color purity of a wavelength conversion layer are improved.

[0013] Solutions for solving problems

[0014] A display element according to an embodiment of the present invention includes a light-emitting layer array and a conversion layer array. The light-emitting layer array includes a plurality of light-emitting layers, which are arranged in a two-dimensional manner and emit light of a first wavelength. The conversion layer array includes a plurality of first conversion layers, which include a first coupling portion, a first extraction portion, and a first reflection portion. The first coupling portion is optically coupled to a portion of the plurality of light-emitting layers. The first extraction portion and the first reflection portion face each other to alternately reflect the light of the first wavelength received via the first coupling portion and guide the light of the first wavelength in a direction away from the first coupling portion. The plurality of first conversion layers emit light of a second wavelength obtained as a result of wavelength conversion of the light of the first wavelength via the first extraction portion.

[0015] Effects of the Invention

[0016] According to the display element of the present invention, it is possible to provide a display element and a display device in which both the macroscopic light utilization efficiency and the color purity of the wavelength conversion layer are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1A is a cross-sectional view of a pixel of a green display element according to the first embodiment.

[0018] Figure 1B is a partially removed plan view of a pixel of the green display element according to the first embodiment.

[0019] Figure 1C is a plan view of an array-shaped display element according to the first embodiment.

[0020] Figure 1D is a cross-sectional view of a pixel of a red display element according to the first embodiment.

[0021] Figure 1E is a cross-sectional view of a pixel of a blue display element according to the first embodiment.

[0022] Figure 2A A cross-sectional structure of a display element according to the first embodiment is shown.

[0023] Figure 2B A cross-sectional structure of a display element according to the prior art is shown.

[0024] Figure 2C The internal structure of the wavelength conversion layer according to the first embodiment is shown.

[0025] Figure 2D The internal structure of a wavelength conversion layer according to the prior art is shown.

[0026] Figure 3A is a cross-sectional view showing a pixel structure according to the prior art.

[0027] Figure 3B is a cross-sectional view showing a pixel structure according to the prior art.

[0028] Figure 4 Waveguide properties of conversion layers suitable for various embodiments are shown.

[0029] Figure 5A is a cross-sectional view of a pixel of a display element according to the second embodiment.

[0030] Figure 5B is a cross-sectional view of a pixel of a display element according to the third embodiment.

[0031] Figure 5Cis a cross-sectional view of a pixel of a display element according to a fourth embodiment.

[0032] Figure 5D is a cross-sectional view of a pixel of a display element according to the fifth embodiment.

[0033] Figure 5E is a cross-sectional view of a pixel of a display element according to the sixth embodiment.

[0034] Fig. 5F is a cross-sectional view of a pixel of a display element according to the seventh embodiment.

[0035] Fig. 6A is a cross-sectional view of a pixel of a display element according to the eighth embodiment.

[0036] Figure 6B A luminance distribution profile of a display element according to the eighth embodiment is shown.

[0037] Figure 6C is a cross-sectional view of a pixel of a display element according to a ninth embodiment.

[0038] Fig.6D A luminance distribution profile of a display element according to the ninth embodiment is shown.

[0039] Fig. 6E is a cross-sectional view of a pixel of a display element according to a tenth embodiment.

[0040] Fig. 6F A luminance distribution profile of a display element according to a tenth embodiment is shown.

[0041] Figure 6G is a cross-sectional view of a pixel of a display element according to an eleventh embodiment.

[0042] Figure 6H is a plan view of a pixel of a display element according to the eleventh embodiment.

[0043] Fig.6I is a cross-sectional view of a pixel of a display element according to the twelfth embodiment.

[0044] Figure 6J is a plan view of a pixel of a display element according to the twelfth embodiment.

[0045] Fig. 7A is a plan view of a pixel of a display element according to the thirteenth embodiment.

[0046] Figure 7B is a cross-sectional view of a pixel of a display element according to the thirteenth embodiment.

[0047] Figure 7C is a plan view of an array of display elements according to the thirteenth embodiment.

[0048] Fig. 8A is a plan view of a pixel of a display element according to the fourteenth embodiment.

[0049] Figure 8B is a cross-sectional view of a pixel of a display element according to a fourteenth embodiment.

[0050] Figure 8C is a plan view of an array of display elements according to the fourteenth embodiment. DETAILED DESCRIPTION

[0051] Now, a display element according to embodiments of the present invention will be described in detail. The present invention is not limited to these embodiments.

[0052] <First Embodiment>

[0053] Will refer to Figures 1A to 1E , Figure 2A and Figure 2C The display element 100 according to the first embodiment will be described.

[0054] Figure 1A is a cross-sectional view showing a pixel structure of a green display element 100G according to the present embodiment, and Figure 1B FIG. 1 is a partially removed plan view showing a pixel structure of the green display element 100G. Figure 1C is a plan view of an array-shaped display element 100 having a matrix pattern according to the present embodiment. Figure 1D is a cross-sectional view showing a pixel structure of a blue display element 100B according to the present embodiment. Figure 1E : is a cross-sectional view showing a pixel structure of a blue display element 100B according to the present embodiment. The two-dimensional arrangement of the display element may be a Delta arrangement (Δ arrangement) depending on the target display performance, and may be changed appropriately.

[0055] In the present specification, green, red, and blue are considered to have local maxima at least in wavelength bands of at least 515 nm and less than 545 nm, at least 615 nm and less than 645 nm, and at least 445 nm and less than 475 nm, respectively. More preferably, green, red, and blue have local maxima at wavelengths in regions of at least 528 nm and less than 532 nm, at least 628 nm and less than 632 nm, and at least 458 nm and less than 462 nm, respectively. In the embodiments described below, green light, red light, and blue light, which are secondary light having second to fourth wavelengths, each preferably have a bandwidth (full width at half maximum (FWHM)) with an upper limit of 10 nm.

[0056] (First Display Element Array)

[0057] Will refer to Figures 1A to 1C , Figure 2A and Figure 2C The green display element 100G that displays green is described below. Figure 1C As shown, the green display element 100G is a two-dimensional array of the unit 100-1 configured in a matrix pattern along the first direction D1 and the third direction D3. Alternatively, the green display element 100G may be a two-dimensional array of the unit 100-2 or the unit 100-3, or may be arranged in part or all of the display element arrays of the units 100-1, 100-2, and 100-3. Figure 1A is Figure 1B The plan view of the display element 100 shown in FIG. 1 is a cross-sectional view of the structure of the display element 100 taken along the plane AA'. Figure 1B In order to facilitate understanding of elements stacked in layers, the light shielding portion 10s, the first extraction portion 24, and the first conversion portion 26 are partially removed.

[0058] (Light-emitting layer array)

[0059] like Figure 1A and Figure 1B As shown, the green display element 100G according to the present embodiment includes a light-emitting layer array 10A, which includes a plurality of light-emitting layers 10 arranged in two dimensions and each emitting light L1 having a first wavelength. The light-emitting layer array 10A may be, for example, a self-luminous element such as an inorganic semiconductor light-emitting diode (LED), an organic light-emitting diode (OLED), or a semiconductor laser element. The light-emitting element constituting the first light-emitting layer 10 may be a micro light-emitting diode (LED) or a micro organic light-emitting diode (OLED) having a microcavity structure.

[0060] Since the light emitting element is a light source having directivity, the light L1 of the first wavelength can be guided into the first conversion section 20 in a waveguide mode.

[0061] In order to guide the first wavelength of light L1 to the first coupling portion 22 included in the first conversion layer 20 described below and prevent light from leaking to the area around each light-emitting layer 10, the light-emitting layer array 10A includes a shading portion 10s, which shields each light-emitting layer 10 in an area excluding the area where the light-emitting layer 10 is coupled to the first coupling portion 22.

[0062] (Transformation Layer Array)

[0063] The green display element 100G further includes a conversion layer array 20A including a plurality of first conversion layers 20 that convert the light L1 of the first wavelength guided from the light emitting layer array 10A into the light L2 of the second wavelength and change the propagation directions of the light L1 of the first wavelength and the light L2 of the second wavelength. Figure 1A and Figure 1BAs shown, the light propagation direction to be changed is the direction in which light propagates through each first conversion layer 20, and may also be referred to as a light transmission direction or a light utilization direction.

[0064] like Figure 1A and Figure 1B As shown, each first conversion layer 20 includes a first coupling portion 22 optically coupled to a portion of the light emitting layer 10. The first conversion layer 20 has a waveguide-shaped optical structure in which light L1 of a first wavelength (λ1) received via the first coupling portion 22 is reflected in alternating directions and guided in a direction D1 away from the first coupling portion 22 while being reflected multiple times. The waveguide-shaped optical structure includes a first extraction portion 24 and a first reflection portion 28 facing each other.

[0065] (Conversion Department)

[0066] like Figure 1A and Figure 2C As shown, each first conversion layer 20 includes a first conversion portion 26 including a plurality of light-responsive nanoparticles 30 serving as quantum dots. The first conversion layer 20 emits light L2 of a first wavelength (λ2) obtained by shifting light L1 of a first wavelength (λ1) toward a long wavelength side. In other words, the second wavelength λ2 is longer than the first wavelength λ1.

[0067] Each first conversion layer 20 can be regarded as a light-emitting layer that narrows the bandwidth Δλ1 around the central wavelength of the first wavelength light L1 to a bandwidth Δλ2 to generate secondary light L2 having a higher color purity than the primary light L1. The first conversion layer 20 may include a bandpass filter (color filter) instead of quantum dots to perform wavelength conversion.

[0068] The first conversion layer 20-1 and the second conversion layer 20-2 convert the light L1 of the first wavelength into light of a wavelength different from the wavelength of the light L1 of the first wavelength. The conversion layer array 20A includes the first conversion layer 20-1 that converts the light L1 of the first wavelength into the light L2 of the second wavelength and the second conversion layer 20-2 that converts the light L1 of the first wavelength into the light L3 of the third wavelength. The light L2 of the second wavelength is green, and the light L3 of the third wavelength is red. In the present embodiment, the thickness of the first conversion layer and the second conversion layer 20-2 is preferably 4 μm or more and 20 μm or less, and more preferably 6 μm or more and 10 μm or less.

[0069] The conversion layer may contain fluorescent particles dispersed in a resin. The fluorescent particles may be made of inorganic or organic materials, but quantum dots are preferably used because the light emitted by quantum dots has an emission spectrum with a narrow full width at half maximum and high color purity.

[0070] The inorganic particles used as quantum dots can be referred to as nanoparticles because of their size. The material of quantum dots can be, for example, semiconductor crystals, and can be nanoparticles of IV semiconductors, nanoparticles of III-V or II-VI compound semiconductors, or nanoparticles of compound semiconductors of combinations of three or more elements of II elements, III elements, IV elements, V elements, and VI elements. The examples of materials emitting light in the wavelength band used by display elements include CsS, CdSe, CdZnSe, CdSeTe, ZnSe, ZnTeSe, ZnTeS, InP, CuInS2, AgInS2, and Pb-based perovskites. These materials can be used to form the core of quantum dots, and the quantum dot material can be covered with a coating compound to form a core-shell structure. In this case, the shell is provided with a ligand.

[0071] The average particle size of quantum dots is preferably 2 nm or more and 15 nm or less. When the particle size of quantum dots is reduced to or below the Bohr radius of the excitons in the quantum dots, the band gap of the quantum dots changes due to the quantum size effect. For example, the Bohr radius of InP, which is a III-V semiconductor, is considered to be about 10 nm to 14 nm. Therefore, when the average particle size of quantum dots is 15 nm or less, the band gap can be controlled by the quantum size effect. When the average particle size of quantum dots is 2 nm or more, the crystal growth of quantum dots can be easily controlled during the synthesis of quantum dots.

[0072] The quantum dot has a ligand on the surface. When the first quantum dot and the second quantum dot are provided, the ligand may have a cross-linked structure that cross-links the first quantum dot and the second quantum dot. Cross-linking refers to the coupling of a molecule to the first quantum dot and the second quantum dot. When the quantum dots are cross-linked by organic ligands, the distance between the quantum dots can be controlled based on the molecular length of the organic ligand. Specifically, the cross-linked structure may be a hydroxyl group, a thiol group or a carboxyl group. It is preferred to provide at least one or more organic molecules between the quantum dots. When a large number of organic ligands are provided, since both ends of each organic molecule are strongly coupled to the surface of the quantum dot, heat resistance and environmental resistance are improved, and the stability of the luminescent characteristics is improved.

[0073] The fluorescent particles used in the first conversion layer and the second conversion layer of this embodiment are preferably quantum dots with a half-maximum full width less than 50nm. For example, the quantum dots can be commonly available quantum dots, such as InP / ZnS quantum dots such as product numbers 776769, 776750, 776793, 776777 and 776785 that can be obtained from Sigma-Aldrich. Product number 776750 is preferred for the first conversion layer, and product number 776777 is preferred for the second conversion layer 20-2. As perovskite quantum dots, product numbers 905062, 900746, 900747 and 900748 can be used. Product numbers 905062 or 900746 are preferred for the first conversion layer, and product number 900748 is preferred for the second conversion layer 20-2.

[0074] In the first to third conversion parts 26 according to the present embodiment, the material used as the polymer matrix can be a monofunctional monomer or a bifunctional monomer, and examples of the material include acrylic resins, polyester resins, polyurethane resins, and polyamide resins. These materials can be mixed with light-responsive nanoparticles to achieve a viscosity and surface tension suitable for photolithography or inkjet film formation (inkjet printing). When the concentration of the monomer is 85 to 98 wt%, the concentration of the photopolymerization initiator is 2 to 5 wt%. Titanium oxide is not included. The resin part 17 contains a light scattering material such as titanium oxide that scatters blue light (L3), but the concentration of the material is preferably 5 wt% or less so that multiple scattering does not occur.

[0075] (Extraction Department)

[0076] The first extraction portion 24 is configured to have a higher spectral reflectance for the light L1 of the first wavelength propagating in the first direction D1 away from the first coupling portion 22 than for the light L2 of the second wavelength generated by the wavelength conversion in the first conversion layer 20 and propagating radially. When the first extraction portion 24 having such a structure is used together with the first reflection portion 28 described below, the propagation performance of the light L1 of the first wavelength serving as the source of the light L2 of the second wavelength in the layer and the generation region of the light L2 of the second wavelength are ensured.

[0077] The first extraction portion 24 is configured to have a higher spectral transmittance for the light L2 of the second wavelength than for the light L1 of the first wavelength. Therefore, among the light L1 of the first wavelength and the light L2 of the second wavelength mixed in the first conversion layer 20, the first extraction portion 24 limits the emission of the light L1 of the first wavelength from the display surface, and allows the emission of the light L2 of the second wavelength from the display surface. Therefore, high color purity is achieved.

[0078] The spectral reflection characteristic or spectral transmission characteristic of the first extraction portion 24 is obtained based on the difference in refractive index n between optical members (not shown) in contact with the two surfaces in the layer thickness direction (z direction) of the first conversion portion 26. Figure 1A As shown, in the display element 100 according to the present embodiment, the refractive index n1 of the first conversion portion 26 is higher than the refractive index n2 of the optical structure on the interface side of the first extraction portion 24 .

[0079] The first extraction portion 24 may be a dielectric multilayer film. Alternatively, the first extraction portion 24 may have a core-clad structure utilizing the refractive index difference as described above.

[0080] Next, reference will be made to a diagram showing a display element 200 according to a thirteenth embodiment. FIG. 5A to FIG. 5F , the waveguide-shaped optical structures of the first extraction section 24 and the first conversion section 26 are described in detail.

[0081] (Reflection part)

[0082] The first reflecting portion 28 is configured to have a higher spectral reflectance for the light L2 of the second wavelength than the first extracting portion 24. When the first reflecting portion 28 having such a structure is used together with the first extracting portion 24 described above, the propagation performance of the light L1 of the first wavelength serving as the source of the light L2 of the second wavelength in the layer and the generation region of the light L2 of the second wavelength are ensured.

[0083] The spectral reflection characteristic of the first reflection portion 28 is obtained based on the difference in refractive index n between optical members (not shown) in contact with the two faces in the layer thickness direction (z direction) of the first conversion portion 26. Figure 1A As shown, in the display element 100 according to the present embodiment, the refractive index n1 of the first conversion portion 26 is higher than the refractive index n2 of the optical structure (not shown) on the interface side of the first reflection portion 28 .

[0084] The first reflection portion 28 is a metal reflection member with low wavelength dependence utilizing plasma reflection. Alternatively, the first reflection portion 28 may be a dielectric multilayer film, or have a core-clad structure utilizing a refractive index difference similarly to the first extraction portion 24 .

[0085] The first conversion layer 20 includes a terminal light shielding portion 20 s at a terminal opposite to an end portion where the first coupling portion 22 is provided in the first direction D1 .

[0086] [Optical components]

[0087] Each optical component forms an interface between the optical component and the conversion portion 26 to constitute the extraction portion 24 or the reflection portion 28. The optical component constituting the extraction portion 24 is made of a light-transmitting material that allows the secondary light passing through the extraction portion 24 to pass through. The material may be, for example, an organic resin or an inorganic glass material. The optical component may be made of, for example, a transparent resin having a transmittance of 85% or more, more preferably 90% or more, for blue light, green light, and red light. The refractive index of the resin used as the optical component may be 1.45 or more and 1.5.

[0088] The refractive index of the optical member is set so that the conversion layer 20 is used as a waveguide. The refractive index (n1) of the conversion layer varies according to the type and concentration of the quantum dots. When the concentration is 0.01 to 5wt%, n1 is roughly in the range of 1.45 to 1.50. It is preferred that the refractive index (n2) of the optical member is set so that the refractive index difference Δ calculated as Δ=(n1-n2) / 2n1 is 0.3% to 2.0%. For example, in the case where the refractive index n1 of the conversion layer is 1.50, n2=1.490 when Δ=0.35%, and n2=1.455 when Δ=1.5%.

[0089] (Second Display Element Array)

[0090] Will refer to Figure 1C and 1D The red display element 100R which displays red is described. Figure 1C As shown, the red display element 100R is a two-dimensional array of cells 100-2 arranged in a matrix pattern along the first direction D1 and the third direction D3. Alternatively, the red display element 100R may be a two-dimensional array of cells 100-1 or cells 100-3, or may be arranged in part or all of the display element arrays of cells 100-1, 100-2, and 100-3.

[0091] Figure 1D A cross-sectional structure of a red display element 100R according to the present embodiment as the second display element array 100A is shown.

[0092] Similar to the green display element 100G, the red display element 100R according to the present embodiment includes a light emitting layer array 10A including a plurality of light emitting layers 10 and a conversion layer array 20A, the light emitting layer array 10A including a plurality of light emitting layers 10, and the conversion layer array 20A including a plurality of second conversion layers 40. Similar to each first conversion layer 20, each second conversion layer 40 can perform wavelength conversion on light L1 (primary light) of a first wavelength including blue or ultraviolet color toward the long wavelength side, and emit red secondary light as light L3 of a third wavelength from the second extraction portion 44. Similar to each first conversion layer 20, each second conversion layer 40 can reduce the bandwidth of light L1 (primary light) of a first wavelength including blue or ultraviolet color to a bandwidth smaller than the bandwidth of light L1 of the first wavelength to generate light L3 of a second wavelength as red secondary light, and emit light L3 of a third wavelength from the second extraction portion 44.

[0093] Similar to each first conversion layer 20, each second conversion layer 40 includes a second coupling portion 42, a second extraction portion 44, a second reflection portion 48, and a second conversion portion 46. The second conversion layer 40 having such a structure performs wavelength conversion on the light L1 of the first wavelength received via the second coupling portion 42 to generate the light L3 of the third wavelength, and emits the light L3 of the third wavelength via the second extraction portion 44 serving as a display surface.

[0094] Specifically, the conversion layer array 20A includes a second conversion layer 40, and the second conversion layer 40 includes a second coupling portion 42, which is optically coupled with the light emitting layer 10 in an area other than an area where the light emitting layer array 10A is optically coupled with the first conversion layer 20. In addition, each second conversion layer 40 includes a second extraction portion and a second reflection portion, which face each other to alternately reflect the first wavelength light L1 received via the second coupling portion 42 and guide the first wavelength light L1 in a direction D1 away from the second coupling portion 42. Each second conversion layer 40 performs wavelength conversion on the first wavelength light L1 to obtain a third wavelength light L3 and emits the third wavelength light L3 via the second extraction portion 44.

[0095] Similar to each first conversion layer 20 , each second conversion layer 40 includes second photoresponsive nanoparticles that convert the first wavelength light L1 into the third wavelength light L3 .

[0096] Similar to the first extraction portion 24, the second extraction portion 44 is configured so that the spectral reflectance of the light L1 of the first wavelength is higher than the spectral reflectance of the light L3 of the third wavelength. Similar to the first extraction portion 24, the second extraction portion 44 is configured so that the spectral transmittance of the light L3 of the third wavelength is higher than the spectral transmittance of the light L1 of the first wavelength.

[0097] Similar to the first reflecting portion 28 , the second reflecting portion 48 is configured to have a higher spectral reflectance with respect to the light L3 of the third wavelength than the second extracting portion 44 .

[0098] (Third Display Element Array)

[0099] Will refer to Figure 1C and 1E The blue display element 100B that displays blue is described below. Figure 1C As shown, the blue display element 100B is a two-dimensional array of cells 100-3 arranged in a matrix pattern along the first direction D1 and the third direction D3. Alternatively, the blue display element 100B may be a two-dimensional array of cells 100-1 or 100-2, or may be arranged in part or all of the display element arrays of cells 100-1, 100-2, and 100-3.

[0100] Figure 1D A cross-sectional structure of a blue display element 100B according to the present embodiment is shown as the second display element array 100A.

[0101] Similar to the green display element 100G and the red display element 100R, the blue display element 100B according to the present embodiment includes a light emitting layer array 10A including a plurality of light emitting layers 10 and a conversion layer array 20A, the light emitting layer array 10A including a plurality of light emitting layers 10, and the conversion layer array 20A including a plurality of third conversion layers 50. Similar to the green display element 100G, each third conversion layer 50 can receive light L1 (primary light) of a first wavelength including blue or ultraviolet color, generate light L4 of a fourth wavelength serving as blue secondary light having a bandwidth smaller than that of the light L1 of the first wavelength, and emit the light L4 of the fourth wavelength from the third extraction portion 54. Therefore, the third conversion layer 50 can change the propagation direction in the optical propagation path from the third coupling portion 52 to the third extraction portion 54 without performing wavelength conversion on the light L1 of the first wavelength.

[0102] Similar to each first conversion layer 20, each third conversion layer 50 includes a third coupling portion 52, a third extraction portion 54, a third reflection portion 58, and a third conversion portion 56. The third conversion layer 50 having such a structure performs wavelength conversion on the light L1 of the first wavelength received via the third coupling portion 52 to generate the light L4 of the fourth wavelength, and emits the light L4 of the fourth wavelength via the third extraction portion 54 serving as a display surface.

[0103] Specifically, the conversion layer array 20A includes a third conversion layer 50, and the third conversion layer 50 includes a third coupling portion 52, which is optically coupled with the light emitting layer 10 in an area other than an area where the light emitting layer array 10A is optically coupled with the first conversion layer 20. In addition, each third conversion layer 50 includes a second extraction portion and a second reflection portion, which face each other to alternately reflect the first wavelength light L1 received via the third coupling portion 52 and guide the first wavelength light L1 in a direction D1 away from the third coupling portion 52. Each third conversion layer 50 performs wavelength conversion on the first wavelength light L1 to obtain a fourth wavelength light L4 and emits the fourth wavelength light L4 via the third extraction portion 54.

[0104] Similar to each first conversion layer 20, each third conversion layer 50 may include third photoresponsive nanoparticles that convert the first wavelength light L1 into a fourth wavelength light L4 that is closer to the first wavelength than the second and third wavelengths. The fourth wavelength may be longer than the first wavelength and shorter than the second and third wavelengths.

[0105] The third extraction portion 54 is configured so that the spectral reflectance of the light L1 of the first wavelength is higher than the spectral reflectance of the light L4 of the fourth wavelength. Similar to the first extraction portion 24, the third extraction portion 54 is configured so that the spectral transmittance of the light L4 of the fourth wavelength is higher than the spectral transmittance of the light L1 of the first wavelength.

[0106] Similar to the first reflecting portion 28 , the third reflecting portion 58 is configured to have a higher spectral reflectance with respect to the light L4 of the fourth wavelength than the third extracting portion 54 .

[0107] The first conversion portion 26, the second conversion portion 46, and the third conversion portion 56 may contain a light scattering material such as titanium oxide for scattering the light L1 of the first wavelength. The concentration of the light scattering material in the first conversion portion 26, the second conversion portion 46, and the third conversion portion 56 is preferably less than or equal to a certain concentration so that multiple scattering between elements of the light scattering material does not occur, and the concentration may be 5 wt % or less.

[0108] <Technical Features>

[0109] Reference FIG. 2A to FIG. 2D , Figure 3A and Figure 3B , the display element 100 according to the present embodiment is compared with the display element 900 according to the prior art to describe the structural characteristics of the display element 100 and the unique effects of the present embodiment provided by the structural characteristics.

[0110] Figure 2A shows a cross-sectional structure of a display element 100 according to the first embodiment, and Figure 2CThe internal structure of the first conversion layer 20 according to the first embodiment is shown. Figure 2B shows a cross-sectional structure of a display element 900 according to the prior art, and Figure 2D The internal structure of a conversion layer 920 included in a display element 900 according to the prior art is shown. Figure 2C and Figure 2D The manner in which the photoresponsive nanoparticles 30 are dispersed in the first conversion region 26 of the display element 100 and in the conversion region 926 of the display element 900 are shown respectively.

[0111] The display element 100 and the display element 900 have differences A, B, and C described below.

[0112] Difference A is: in the optical propagation path from the coupling portion to the extraction portion, whether the propagation path of the primary light and the propagation path of the secondary light are non-coaxial or coaxial. In the display element 100, the optical propagation path from the first coupling portion 22 to the first extraction portion 24 has a non-coaxial configuration, in which the directions of the propagation paths of the primary light and the secondary light are different. On the contrary, in the display element 900, the optical propagation path from the coupling portion 922 to the extraction portion 924 has a coaxial configuration, in which the directions of the propagation paths of the primary light and the secondary light are the same. In other words, the display element 100 is configured so that when viewed along an axis parallel to the layer thickness direction D2 of the conversion layer 20, the first coupling portion 22 and the first extraction portion 24 do not overlap. The layer thickness direction D2 of the conversion layer 20 can also be referred to as the light extraction direction. The display element 100 can also be referred to as being configured so that when viewed in the first light propagation direction D1 of the conversion layer 20, the first coupling portion 22 and the first extraction portion 24 do not overlap.

[0113] Difference B is whether the reflective portion can be arranged over the entire area at a position facing the extraction portion. In the display element 100, the optical propagation path from the first coupling portion 22 to the first extraction portion 24 has a non-coaxial configuration. In contrast, in the display element 900, the optical propagation path from the coupling portion 922 to the extraction portion 924 has a coaxial configuration.

[0114] Difference C is: whether it is possible to reduce the optical density of the photoresponsive nanoparticles so that the absorption of the propagated primary and secondary light does not exceed the effect of luminescence.

[0115] The above-mentioned differences A to C will be further described.

[0116] According to differences A and B, the display element 100 of the present embodiment can be configured so that the first coupling portion 22 and the first reflecting portion 28 as optical elements having different functions can be configured at appropriate positions. Therefore, according to the display element 100, the light receiving characteristics of the first conversion layer 20 that receives the light from the light emitting layer 10 and the reflection characteristics of the first reflecting portion 28 can be set to appropriate optical characteristics without restricting each other. In other words, the first coupling portion 22 can be set to have a high transmittance for the light L1 of the first wavelength as the primary light, and the first reflecting portion 28 can be set to have a high reflectivity for both the light L1 of the first wavelength (primary light) and the light L2 of the second wavelength (secondary light). In addition, according to the display element 100, the reflecting portion 28 can be formed by a metal layer having a robust wavelength dependence, and the reflecting portion 28 can be set on the entire area behind the extraction portion 24. Therefore, the macroscopic light utilization efficiency of the light from the first conversion layer 20 can be improved.

[0117] On the contrary, the display element 900 according to the related art does not have the features of the differences A and B, and therefore, at the position indicated by reference numeral 922, both an optical coupling element for receiving the primary light from the light emitting layer 910 and a reflective element for reflecting the secondary light generated in the conversion layer 920 are required. Therefore, in the display element 900, at the interface indicated by reference numeral 922, at least one of the transmittance and the reflectance is limited, or the area indicated by reference numeral 922 needs to be divided into sections assigned to the corresponding characteristics. Therefore, the macroscopic light utilization efficiency of the light from the conversion layer 920 is limited.

[0118] In the display element 100 according to the present embodiment, the propagation path of the light L1 of the first wavelength does not extend in the layer thickness direction (z direction) of the display element 900, but extends in the layer surface direction (direction along the xy plane) substantially parallel to the layer surface, and the propagation distance increases by about one order of magnitude. Therefore, the display element 100 can be configured so that the optical density of the photoresponsive nanoparticles is reduced by about one order of magnitude from the optical density in the display element 900, and has a difference C.

[0119] Therefore, in the display element 100 of the present embodiment, the generation of secondary light is not easily restricted by the absorption of primary light and secondary light, and the macroscopic light utilization efficiency of the first conversion layer 20 is higher than that in the display element 900 .

[0120] The display element 100 according to the present embodiment and the display element 900 according to the related art will be further compared.

[0121] The display element 900 includes a light emitting layer 910 that emits light L1 of a first wavelength (blue, primary light) and a conversion layer 920 containing photoresponsive nanoparticles that receive the primary light from the light emitting layer 910 and emit light L2 of a second wavelength (green, secondary light). The light emitting layer 910 and the conversion layer 920 are stacked with a coupling portion 922 interposed therebetween. The layer thickness of the conversion layer 920 is several micrometers to ten micrometers. In order to achieve total absorption of the light L1 of the first wavelength in a propagation path having the above layer thickness, as shown in FIG. Figure 2D As shown, the conversion layer 920 contains the light-responsive nanoparticles 30 at a concentration of 10 to 30 wt%. In order to improve the utilization efficiency of the light L1 of the first wavelength and reduce the light leakage to the extraction surface 924, the conversion layer 920 contains, for example, 10 to 30 wt% of titanium oxide as the light scattering material 38. In the conversion layer 920, the light scattering material 38 scatters the light L1 of the first wavelength multiple times to increase the chance that the light L1 of the first wavelength is absorbed by the light-responsive nanoparticles 30 per unit thickness in the layer thickness direction (depth direction, z direction), thereby improving the wavelength conversion efficiency.

[0122] The photoresponsive nanoparticles 30 (quantum dots) have a small Stokes shift, and the emission band and the excitation band partially overlap. Therefore, self-absorption is likely to occur. Therefore, when the optical density of the photoresponsive nanoparticles 30 is high, the luminous efficiency is likely to be reduced due to self-absorption. In addition, since the photoresponsive nanoparticles 30 are close to each other, the luminous efficiency is likely to be reduced due to fluorescence resonance energy transfer (FRET). In addition, since the light scattering material 38 also scatters the wavelength-converted light as secondary light, the effective optical distance increases, resulting in a reduction in light extraction efficiency.

[0123] In particular, among the secondary light propagating in the direction opposite to the light extraction direction D1 and emitted to the outside of the conversion layer 920, the light re-incident on the conversion layer 920 may have a lower light extraction efficiency due to attenuation caused by the self-absorption of the photoresponsive nanoparticles 30 and the shielding effect of the light scattering material 38.

[0124] Will refer to Figure 3A and Figure 3B To describe the RGB pixel configuration according to the prior art.

[0125] Figure 3AThe display element 909 shown includes an optical member 918, which is disposed on the back side (the side adjacent to the light emitting layer 910) of the conversion layers 920-1 to 920-3 to form a coupling portion 922. The coupling portion 922 has a function for scattering the primary light L1 forward (toward the optical member 914) by using the difference in refractive index between the optical member 918 and the conversion layers 920-1 to 920-3. In order to balance the efficiency and forward reflection characteristics when receiving the primary light L1 from the light emitting layers 910-1 to 910-3, as described above, at least the reflection characteristics or the transmission characteristics of the coupling portion 922 are limited.

[0126] Figure 3B The display element 990 shown includes a dielectric multilayer film 917, which is provided on the back side (the side adjacent to the light emitting layer 910) of the conversion layers 920-1 to 920-3 to form a coupling portion 922. Therefore, among the wavelength converted light, the secondary light L2 and the secondary light L3 that propagate toward the light emitting layers 910-1 to 910-3 and return from the light emitting layers 910-1 to 910-3 are used.

[0127] As described above, in each of the display elements 909 and 990, the macroscopic light utilization efficiency is likely to be reduced due to the loss caused by the conversion layers 920-1 to 920-3 and the reduction in the utilization efficiency of the secondary light (light after wavelength conversion) emitted backward. The loss caused by the conversion layers 920-1 to 920-3 includes the self-absorption of quantum dots and the shielding effect of the light scattering material.

[0128] In order to balance the efficiency and the forward reflection characteristics when receiving the primary light L1 from the light emitting layers 910 - 1 to 910 - 3 , at least the reflection characteristic or the transmission characteristic of the coupling portion 922 is restricted as described above.

[0129] In contrast, in the display element 100 according to the present embodiment, the conversion layer 20 is used as a waveguide for the light L1 (primary light) of the first wavelength propagating in the first direction D1. The conversion layer 20 having a waveguide function converts the wavelength of the light L1 (blue light) of the first wavelength to obtain secondary light while guiding the light L1 of the first wavelength along the layer surface direction of the conversion layer 20 by total reflection. According to the structure of the present embodiment, the light L1 of the first wavelength (especially the blue light used as the primary light) propagates over a longer optical path length than in the structure of the prior art while undergoing wavelength conversion. For example, in a sub-pixel of 100μm×300μm, the optical path length can be 100μm in the short direction or 300μm in the long direction. According to the Beer-Lambert law, when the absorption optical path length increases, the concentration of quantum dots in the conversion layer 20 (the concentration of photoresponsive nanoparticles) can be reduced.

[0130] Compared with the display elements 900, 909 and 990 according to the prior art, in the display element 100 according to the embodiment, the optical path length for the light L1 of the first wavelength can be increased by about one order of magnitude. Therefore, the concentration of quantum dots can be reduced by one order of magnitude. When the concentration of quantum dots is low, the reduction of luminous efficiency caused by self-absorption and FRET can be suppressed, so that the luminous efficiency can be improved. Therefore, in the structure of the present embodiment, the concentration of quantum dots can be set to 0.01 to 5wt%. The concentration of quantum dots is determined based on the pixel size corresponding to the optical propagation path length of the primary light and the required display performance, the driving conditions of the primary light and other factors. In the structure according to the present embodiment, the reflective portion 28 does not need to be a wavelength selective mirror, and a metal mirror made of, for example, Al or Ag can be used. Alternatively, a wavelength selective mirror composed of a dielectric multilayer film can be used.

[0131] (Waveguide mode and launch mode)

[0132] Will refer to Figures 1A to 1E and Figure 4 The operation mode of the waveguide-shaped first to third conversion layers 20 - 1 to 20 - 3 will be described.

[0133] In the structure of the present invention, Figure 1A As shown, the refractive index (n2) of the first extraction portion 24 as an optical member for defining an interface is lower than the refractive index (n1) of the first conversion layer 20, and the first conversion layer 20 functions as a waveguide. As a result, the light L1 of the first wavelength (primary light, blue light) propagates and is guided while repeating total reflection in the first conversion layer 20. Figure 1B Only a portion of the light L2 of the second wavelength, which is the wavelength-converted light generated in the first conversion layer 20, is shown, and the path of the light L2 of the second wavelength reflected by the first reflection portion 28 is omitted. In fact, the light L2 of the second wavelength is generated in the propagation path of the light L1 of the first wavelength composed of a plurality of light paths, and is also generated around the propagation path due to the light scattering material. The secondary light generated in the first conversion layer 20 is emitted forward from the first conversion layer 20 after being scattered by the light scattering material and reflected by the reflection portion 28, or after reaching the extraction portion 24 directly from the light emitting point (wavelength conversion point).

[0134] In the case where a high refractive index layer (core) is arranged between low refractive index layers (cladding) to form a sandwich structure, total reflection occurs when the incident angle of light propagating through the core layer on the cladding exceeds the critical angle. Reflection at the core-cladding interface is repeated, so that the structure acts as a waveguide. Generally, among all radiation modes radiated isotropically from the core layer, the mode of light that repeats total reflection within the core layer is called a waveguide mode, and the mode of light extracted from the core layer is called an emission mode.

[0135] The waveguide mode is used for the light L1 of the first wavelength (primary light, blue, purple). For the light L2 of the second wavelength (green) and the light L3 of the third wavelength (red), in order to be able to extract light, it is set so that the component of the waveguide mode is smaller than the component of the emission mode. More preferably, for the light L2 of the second wavelength and the light L3 of the third wavelength, the emission mode is dominant relative to the waveguide mode.

[0136] In this specification, the waveguide parameter V for the optical waveguide is used to discuss the waveguide mode and the emission mode.

[0137] V<2.405 (Expression 1)

[0138] [Mathematical formula 1]

[0139]

[0140] Expressions 1 and 2 will now be discussed.

[0141] Here, d is the film thickness, λ0 is the wavelength of light, and n1 and n2 are the refractive indices of the core and cladding, respectively. When the waveguide parameter V satisfies V<2.405, the waveguide is used as a single-mode waveguide, in which only the fundamental waveguide mode can be guided for any wavelength, and other radiation modes are used as emission modes. When the relative refractive index difference Δ=(n1-n2) / 2n1 between the core and the cladding is set to an arbitrary value, the number of waveguide modes can be reduced by reducing the film thickness, so that the number of emission modes can be increased to improve the light extraction efficiency. When the film thickness is greater than 10μm, the waveguide is used as a multimode waveguide, and the number of waveguide modes increases, resulting in a decrease in light extraction efficiency. In the structure of the present invention, the thickness that enables the wavelength conversion portion to be reliably used as a waveguide is preferably less than 10μm. However, the film thickness may be greater than or equal to the above thickness.

[0142] Assume that the blue light, green light and red light used to define the display color correspond to 460nm, 530nm and 630nm respectively. As the wavelength increases, the waveguide parameters decrease, and the number of waveguide modes decreases accordingly. In other words, the film thickness and the specific refractive index difference can be set so that for green and red light, the mode is single mode, and for blue light, the mode is multimode. Therefore, the wavelength conversion section can be configured to act as a multimode waveguide for blue light, and so that for the wavelength converted light, the radiation mode is dominant to achieve efficient light extraction.

[0143] Figure 4The following boundary line is shown: For each of blue light, green light, and red light, based on the relationship between the specific refractive index difference Δ and the film thickness, the waveguide parameter V is V=2.405. Where any combination of the specific refractive index difference Δ and the film thickness is plotted, the mode for each color is single mode when the boundary line for that color is to the right of the plotted point, and is multi-mode when the boundary line for that color is to the left of the plotted point.

[0144] For example, when the film thickness is 3 μm and the specific refractive index difference Δ is Δ=0.35, for blue light, the mode is multimode, and for wavelength-converted light (green and red light), the mode is single-mode. In other words, the structure acts as a waveguide for blue light, and for wavelength-converted light, the emission mode is dominant. When the film thickness is 10 μm, the specific refractive index difference Δ needs to be Δ=0.03 to form a similar structure, and it is difficult to form a structure that sets a single mode for wavelength-converted light.

[0145] When the film thickness is further increased, it becomes impossible to produce the structure in practice. However, even without providing a completely single-mode, the effect of reducing the waveguide mode can be obtained by bringing the conditions closer to the single-mode conditions. Therefore, when the specific refractive index difference Δ is constant, the light extraction efficiency increases as the film thickness decreases. In a single-mode waveguide, part of the guided light (blue light in this example) leaks into the cladding as an evanescent wave. Therefore, the cladding can contain quantum dots with wavelength conversion function.

[0146] (Variation Example 1 of Conversion Layer)

[0147] Will refer to FIG. 5A to FIG. 5F Display elements 110 to 160 according to second to seventh embodiments are described. The second to seventh embodiments correspond to modifications of the first embodiment, which differ from the first embodiment in the optical configuration of the conversion layer including the coupling portion.

[0148] <Second Embodiment>

[0149] according to Figure 5A The display element 110 of the second embodiment shown is different from that of the first embodiment in that the display element 110 includes a coupling portion 23 that is separated from the light emitting layer 10 and has a gap provided between the light emitting layer 10 and the first conversion portion 26 .

[0150] <Third Embodiment>

[0151] according to Figure 5BThe display element 120 of the third embodiment shown is different from the first and second embodiments in that the display element 120 includes a coupling portion 23 that is separated from the light emitting layer 10 in a state where a coupling member 15 is provided between the light emitting layer 10 and the coupling portion 23. The light shielding portion 10s according to the present embodiment extends to the outer edge of the coupling member 15.

[0152] <Fourth Embodiment>

[0153] according to Figure 5C The display element 130 of the fourth embodiment shown is different from the first to third embodiments in that the display element 130 includes a coupling portion 23, which is separated from the light-emitting layer 10 in a state where a redirecting member 15 for changing the propagation direction is provided between the light-emitting layer 10 and the coupling portion 23. The light-shielding portion 10s of this embodiment extends to the outer edge of the redirecting member 15. The direction in which the primary light is emitted from the light-emitting layer 10 of this embodiment is the same as the second direction D2 parallel to the layer thickness direction of the first conversion layer 20. However, the extraction area for extracting the secondary light L from the first extraction portion 24 and the emission area for emitting the primary light L1 from the light-emitting layer 10 are offset from each other so as not to overlap in the x-direction, thereby forming a non-coaxial structure.

[0154] <Fifth Embodiment>

[0155] according to Figure 5D The display element 140 of the fifth embodiment shown is different from the first to fourth embodiments in that a window 24d with low wavelength selectivity is provided near the terminal of the first extraction portion 24 opposite to the end where the coupling portion 20 is provided. The light L1 of the first wavelength does not need to propagate beyond the terminal of the first light emitting layer 20 in a waveguide mode in a direction away from the coupling portion 20, and the component of the light L1 of the first wavelength is substantially absorbed before reaching the position where the window 24d is provided. Therefore, the window 24d is provided.

[0156] <Sixth Embodiment>

[0157] according to Figure 5E The display element 150 of the sixth embodiment shown is different from the first to fifth embodiments in that a front reflection portion 28p is provided in a local region near the coupling portion 2 on the first extraction portion 4. This configuration is used to alleviate the following situation: in the upstream region along the propagation path of the first light emitting layer 20, the component ratio of the light L1 of the first wavelength to the light L2 of the second wavelength is high, and the forward leakage of the primary light L1 cannot be sufficiently reduced by the wavelength selectivity of the extraction portion 24.

[0158] <Seventh Embodiment>

[0159] according to Fig. 5FThe display element 160 of the seventh embodiment shown is different from the first to sixth embodiments in that a light shielding portion 24s is provided at a position near the coupling portion 2 on the first extraction portion 4. The light shielding portion 24s corresponds to an extension of the light shielding portion 10s. The light shielding portion 24s has an effect similar to that of the front reflection portion 28p according to the sixth embodiment.

[0160] (Variation Example 2 of Conversion Layer)

[0161] Will refer to FIG. 6A to FIG. 6J The display elements 170 to 210 according to the eighth to twelfth embodiments are described. The eighth to twelfth embodiments correspond to modifications of the first embodiment, which differ from the first embodiment in that the optical density of the photoresponsive nanoparticles has a specific distribution in the first conversion layer 20.

[0162] <Eighth Embodiment>

[0163] according to Fig. 6A The display element 170 of the eighth embodiment shown in the figure is different from that of the first embodiment in that the first conversion layer 20u includes a first conversion portion 26u, such as Figure 6B As shown, the first conversion portion 26u includes photoresponsive nanoparticles having a constant optical density in the first direction D1 (dashed lines).

[0164] In the first conversion layer 20u, based on the Beer-Lambert law, the amount of the second wavelength light L2 emitted from the first conversion portion 26u has a logarithmic distribution in the region from the coupling portion 22 to the end light shielding portion 20s. In order to place the center of gravity of light emission in each pixel at the center of the pixel, the spectral characteristics of other optical elements including the first extraction portion 24 and the first reflection portion 28 can be used to modify Figure 6B Brightness profile shown.

[0165] exist Figure 6B , Fig.6D and Fig. 6F In FIG. 1 , brightness indicates the amount of light emitted from the first extraction portion 24 per unit area.

[0166] <Ninth Embodiment>

[0167] according to Figure 6C The display element 180 of the ninth embodiment shown in the figure is different from the first embodiment and the eighth embodiment in that: Fig.6D As shown, the display element 180 has an optical density distribution (dashed line) in which the optical density of the photoresponsive nanoparticles increases in a step-by-step manner as the distance from the coupling portion 22 in the first direction D1 increases.

[0168] Therefore, if Fig.6DAs shown, in the display element 180, based on the Beer-Lambert law, the distribution of the amount of the light L2 of the second wavelength in the region from the coupling portion 22 to the end light shielding portion 20s is smoother than that of the eighth embodiment.

[0169] <Tenth Embodiment>

[0170] according to Fig. 6E The display element 190 of the tenth embodiment shown in the figure is different from the first embodiment, the eighth embodiment and the ninth embodiment in that: Fig. 6F As shown, the display element 190 has an optical density distribution (dashed line) in which the optical density of the photoresponsive nanoparticles increases continuously with increasing distance in the first direction D1 from the coupling portion 22. In other words, the first conversion layer 20 of the present embodiment has a first optical gradient, so that the optical density of the photoresponsive nanoparticles 38 increases with increasing distance in the layer surface direction of the first conversion layer 20 from the first coupling portion 22.

[0171] Fig. 6E The structure of the pixel whose display color is green is shown. Although the structure of the pixel whose display color is red is not shown, the brightness can be smoothed by using a structure similar to the structure of the display element 190 whose display color is green. In other words, the second conversion layer 20-2 has a second optical gradient so that the optical density of the photoresponsive nanoparticles 38 increases with the increase of the distance from the second coupling portion 22 in the layer surface direction of the second conversion layer 20-2.

[0172] like Fig.6D As shown, in the display element 180, based on the Beer-Lambert law, the distribution of the amount of the second wavelength light L2 in the region from the coupling portion 22 to the end light shielding portion 20s is still smoother than that of the ninth embodiment.

[0173] <Eleventh Embodiment>

[0174] according to Figure 6G and Figure 6H The display element 200 of the eleventh embodiment shown in the figure is different from the other embodiments in that: Figure 6H As shown, the wedge-shaped inactive region 25 is arranged so that the optical density of the photoresponsive nanoparticles increases continuously in space as the distance from the coupling portion 22 increases.

[0175] The wedge-shaped inactive region 25 may be composed of a region excluding only the photoresponsive nanoparticles among the components included in the first conversion region 26 .

[0176] <Twelfth Embodiment>

[0177] according to Fig.6I and Figure 6JThe display element 210 of the twelfth embodiment shown in the figure is different from the other embodiments in that: Fig.6I and Figure 6J As shown, the light emitting layer 10 is disposed at the center of the first coupling portion 20. Similar to the eighth embodiment, the first conversion layer 20 according to this embodiment includes photoresponsive nanoparticles having a constant optical density in a direction away from the coupling portion 22 along the xy plane.

[0178] Therefore, in the display element 210, the second wavelength light L2 (light after wavelength conversion) has a microscopic brightness distribution along the xy plane. However, since the emission beam distribution in each pixel is a roughly concentric rectangular ring emission distribution, the emission center of each RGB color coincides with the pixel center.

[0179] <Thirteenth Embodiment>

[0180] Will refer to 7A to 7C A display element 220 according to a thirteenth embodiment which is a modification of the display element 100 according to the first embodiment will be described. Figure 7B It is taken along the plane D-D' Fig. 7A 2 is a cross-sectional view of a display element 220 shown in FIG.

[0181] like Fig. 7A and 7C As shown in , the display element 220 according to the present embodiment includes a plurality of display elements 130-G, 130-R, and 130-B configured in a matrix pattern as green, red, and blue sub-pixels. For simplicity, in the present embodiment, in the drawings, suffixes "-G", "-R", and "-B" indicating the color of light emitted from each pixel may be used instead of sub-numbers "-1", "-2", and "-3".

[0182] like Figure 7BAs shown, the display element 220 includes a black matrix 20s for defining the periphery of the pixel and a first light emitting layer 10-1, a second light emitting layer 10-2, and a third light emitting layer 10-3 arranged in three types of regions surrounded by the black matrix 20s. The display element 220 also includes first to third conversion layers 20-1 to 20-3, and the first to third conversion layers 20-1 to 20-3 are optically coupled to the first to third light emitting layers 10-1 to 10-3 in corresponding regions of the three types of regions surrounded by the black matrix 20s. The display element 220 also includes an optical member 124 having a refractive index lower than that of the conversion layers 20-1 to 20-3 in front of the first to third conversion layers 20-1 to 20-3 to form extraction portions 24-1 to 24-3, respectively. The display element 220 further includes an optical member 128 having a refractive index lower than that of the first to third conversion layers 20-1 to 20-3 behind the first to third conversion layers 20-1 to 20-3 to form reflection portions 28-1 to 28-3, respectively. The black matrix 20s and the optical member 28 are bonded to a multilayer dielectric film 29.

[0183] When viewed along an axis parallel to the layer thickness direction of the display element 220, the first extraction portion 24-G and the second extraction portion 24-R are arranged adjacent to each other along the xy plane, so that the first extraction portion 24-G and the second extraction portion 24-R at least include non-overlapping portions. Similarly, when viewed along an axis parallel to the layer thickness direction of the display element 220, the second extraction portion 24-R and the third extraction portion 24-B are arranged adjacent to each other along the xy plane, so that the second extraction portion 24-R and the third extraction portion 24-B at least include non-overlapping portions. Figure 7B In the figure, for simplicity, the first extraction unit 24-G and the second extraction unit 24-R are omitted.

[0184] <Fourteenth Embodiment>

[0185] Will refer to FIG. 8A to FIG. 8C The display element 230 according to the fourteenth embodiment will be described as a modification of the display element 230 according to the thirteenth embodiment. Figure 8B It is taken along the plane E-E' Fig. 8A A cross-sectional view of display element 230 is shown.

[0186] like Fig. 8A and Figure 8C As shown, the display element 230 according to the present embodiment is different from the display element 220 in that display elements 230-R, 230-G and 230-B forming red, green and blue pixels are stacked in the layer thickness direction of the conversion layer 20-R.

[0187] When viewed along an axis parallel to the layer thickness direction of the display element 230, the first extraction portion 24-G and the second extraction portion 24-R are stacked in the z direction, so that the first extraction portion 24-G and the second extraction portion 24-R include at least an overlapping portion. Similarly, when viewed along an axis parallel to the layer thickness direction of the display element 230, the second extraction portion 24-R and the third extraction portion 24-B are stacked in the z direction, so that the second extraction portion 24-R and the third extraction portion 24-B include at least an overlapping portion. Figure 8B In the figure, for simplicity, the first extraction unit 24-G and the second extraction unit 24-R are omitted.

[0188] like Figure 8B As shown, the display element 230 includes a black matrix 20s for defining the periphery of a pixel and a first light emitting layer 10-1, a second light emitting layer 10-2, and a third light emitting layer 10-3 arranged in one pixel area surrounded by the black matrix 20s. The display element 230 also includes first to third conversion layers 20-1 to 20-3, and the first to third conversion layers 20-1 to 20-3 are optically coupled to the first to third light emitting layers 10-1 to 10-3 in corresponding areas of the three types of areas surrounded by the black matrix 20s. The display element 230 also includes an optical member 35 having a refractive index lower than that of the conversion layers 20-1 to 20-3 in front of the first to third conversion layers 20-1 to 20-3 to form extraction portions 24-1 to 24-3, respectively. The display element 230 further includes an optical member 35 having a refractive index lower than that of the first to third conversion layers 20-1 to 20-3 behind the first to third conversion layers 20-1 to 20-3 to form reflection portions 28-1 to 28-3, respectively. The black matrix 20s and the lowermost optical member 128 are bonded to the multilayer dielectric film 29.

[0189] like Figure 8B As shown, the display element 230 includes display elements 230 -B, 230 -R, and 230 -G, which constitute sub-pixels and are stacked in this order in the light extraction direction from the display surface.

[0190] Wavelength selective optical layers 34 and 36 are arranged between the conversion layers 20-B, 20-G and 20-R. The optical layer 34 arranged between the conversion layers 20-B and 20-G is set as a wavelength selective layer, which is used to reflect blue light and transmit red light and green light, or absorb blue light, or have these two wavelength selective characteristics. The optical layer 36 arranged between the conversion layers 20-G and 20-R is set as a wavelength selective layer, which is used to reflect green light and transmit red light, or absorb green light, or have these two wavelength selective characteristics. The wavelength selective characteristics can also be called spectral characteristics.

[0191] The optical layer 34 and the optical layer 36 may be low refractive index layers having a refractive index lower than that of the optical member 35. When silicon dioxide SiO2 (refractive index = 1.45) is used as the core material, the refractive index of the optical member 35 is preferably 1.10 or more and 1.30 or less, and more preferably 1.10 or more and 1.15 or less.

[0192] It is assumed that the optical layers 34 and 36 are wavelength selective reflection layers. Among the light emitted from the conversion layer 230-B, the light emitted forward is directly extracted, and the light emitted backward is reflected by the optical layer 34 and extracted. Among the light emitted from the conversion layer 230-G, the light emitted forward is extracted via the optical layer 34 and the conversion layer 230-B, and the light emitted backward is reflected by the optical layer 36 and similarly extracted. Among the light emitted from the conversion layer 230-R, the light emitted forward is extracted via the optical layer 36, the conversion layer 230-G, the optical layer 34, and the conversion layer 230-B, and the light emitted backward is reflected by the reflection layer 20 and similarly extracted.

[0193] In such Figure 8B In the display element 230 shown as including multiple layers of sub-pixels, the resolution of the display pixels is Figure 7B The area of ​​the conversion layer is three times larger than that of the conversion layer in the display element 220, with the same resolution in FIG. Therefore, even when the absorption of light by the multilayer structure is taken into account, an improvement in brightness can be expected. Alternatively, when the stack has a thickness that is the same as that of the display element 220 when viewed in the z direction, Figure 8B When the projection area of ​​the conversion layer is the same as the projection area in the display element 220, the pixel size is 1 / 3 of the pixel size in the display element 220, and the resolution is increased by 3 times.

[0194] Example

[0195] A display element according to an example of the present invention will now be described in detail. However, the present invention is not limited to the example described below.

[0196] [Example 1]

[0197] (Clad Layer Production)

[0198] A 1 μm thick film containing 4.5 at% TiO2 in SiO2 was formed on a quartz substrate by co-sputtering of SiO2 and TiO2 (substrate A1). The refractive index was measured to be 1.477, and the relative refractive index difference Δ was measured to be 1.5. Similarly, a 100 nm thick Al film was formed on a quartz substrate as a reflective film by sputtering, and then a 1 μm thick optical film containing 4.5 at% TiO2 in SiO2 was formed by co-sputtering of SiO2 and TiO2 (substrate A2).

[0199] A 1 μm thick film containing 8.0 at% TiO2 in SiO2 was formed on a quartz substrate by co-sputtering of SiO2 and TiO2 (substrate B1). The refractive index was measured to be 1.495, and the relative refractive index difference Δ was measured to be 0.35. Similarly, a 100 nm thick Al film was formed on a quartz substrate as a reflective film by sputtering, and then a 1 μm thick film containing 8.0 at% TiO2 in SiO2 was formed by co-sputtering of SiO2 and TiO2 (substrate B2).

[0200] (Creation of conversion layer)

[0201] Cesium carbonate (10 parts), oleic acid (27 parts) and 1-octadecene (385 parts) were placed in a flask, heated to a liquid temperature of 120°C, and degassed using a vacuum pump for 30 minutes. The liquid was further heated and maintained at 150°C for 30 minutes in a dry nitrogen stream to obtain a cationic raw material solution.

[0202] In a separate treatment, lead (II) bromide (10 parts) and 1-octadecene (494 parts) were placed in a flask, heated to a liquid temperature of 120°C, and degassed using a vacuum pump for 1 hour. Oleic acid (89 parts) and oleylamine (31 parts) were then added, and the mixture was further degassed using a vacuum pump for 30 minutes. Thereafter, the liquid temperature was set to 185°C instead of using a nitrogen stream.

[0203] Cation raw material solution (40 parts) is added, and after 5 seconds, ice-cooled mixture is used. Ethyl acetate (2000 parts) is added, and mixture is subjected to centrifugation to remove supernatant. Obtained residue is dispersed in toluene, so that solid concentration is adjusted to 1 weight %.Therefore, acquisition is dispersed with the liquid of the luminescent nanocrystal with CsPbBr perovskite crystal structure.

[0204] The above CsPbBr3 dispersion was subjected to a dry nitrogen flow to remove the solvent, and was modulated to prepare an ink composition A containing 1 wt% of CsPbBr3 nanocrystals, 94 wt% of 3,3,5-trimethylcyclohexyl acrylate (TMCHA) and 5 wt% of 1-hydroxycyclohexyl phenyl ketone (Omnirad 184).

[0205] The above ink composition was applied to a glass substrate to form a film. The refractive index of the film was calculated from the reflection spectrum to be 1.500.

[0206] The above-mentioned ink composition A was printed on the optical film on the substrate A2 by using a material printer (DMP-2850 produced by Fujifilm Dimatix Co., Ltd.) to form a conversion layer with a width of 100 μm, a length of 300 μm and a thickness of 10 μm extending from the end of the substrate. After the printing process, the ink composition A was quickly clamped between the optical film on the substrate A2 and the optical film on the substrate A1, and cured by UV radiation. Thus, a display element in which the second wavelength light L2 is green light was produced.

[0207] Also by similar treatment (wherein CsPbBr3 was converted to CsPb(Br 0.35 I 0.65 )3) to produce a display element whose conversion layer emits red light.

[0208] [Example 2]

[0209] A display element was produced similarly to Example 1 except that the thickness of the conversion layer was changed to 3 μm.

[0210] [Example 3]

[0211] A display element was produced similarly to Example 1 except that the thickness of the conversion layer was changed to 1.5 μm.

[0212] [Example 4]

[0213] A display element was produced similarly to Example 1, except that the substrate A1 was changed to the substrate B1 and the substrate A2 was changed to the substrate B2, and the thickness of the conversion layer was changed to 3 μm.

[0214] [Example 5]

[0215] A display element was fabricated similarly to Example 1, except that the conversion layer was printed to extend from the end of the substrate and to have a width of 300 μm, a length of 100 μm, and a thickness of 3 μm.

[0216] [Example 6]

[0217] Similar to Example 1, the CsPbBr3 dispersion was subjected to a dry nitrogen flow to remove the solvent, and was modulated to prepare an ink composition B containing 1 wt% of CsPbBr3 nanocrystals, 89 wt% of 3,3,5-trimethylcyclohexyl acrylate (TMCHA), 5 wt% of 1-hydroxycyclohexyl phenyl ketone (Omnirad 184) and 5 wt% of titanium oxide.

[0218] First, similar to Example 1, printing was performed to form a conversion layer extending from the end of the substrate and having a width of 80 μm, a length of 300 μm, and a thickness of 10 μm. Then, ink composition B was printed adjacent to the conversion layer to form a layer having a width of 20 μm, a length of 300 μm, and a thickness of 10 μm, thereby producing a display element. This structure corresponds to Figure 7B .

[0219] [Example 7]

[0220] A display element was fabricated similarly to Example 6 except that substrate A1 was changed to substrate B1 and substrate A2 was changed to substrate B2, and the thickness of the conversion layer was changed to 3 μm. Figure 7B .

[0221] [Example 8]

[0222] In this example, if FIG. 8A to FIG. 8C As shown, the sub-pixels are stacked in the light extraction direction.

[0223] First, a substrate including an optical layer 34 formed on a quartz substrate and a substrate including an optical layer 36 formed on a quartz substrate are prepared. The optical layer 34 and the optical layer 36 are wavelength selective layers that selectively reflect or transmit light having a specific wavelength. The wavelength selective layer can be formed by a dielectric multilayer film. The dielectric forming the dielectric multilayer film can be an inorganic material, an organic material, or a combination thereof. Examples of organic materials include polyester resins, polyurethane resins, and acrylic resins. The inorganic material can be a fluoride material or an oxide material. Examples of fluoride materials include AlF2 (1.36), MgF2 (1.38), and CaF2 (1.43). Examples of oxide materials include SiO2 (1.45), Al2O3 (1.64), MgO (1.72), Y2O3 (1.88), HfO2 (2.05), SrTiO3 (2.44), and TiO2 (2.49). The numbers in parentheses are reference values ​​of the refractive index.

[0224] The dielectric multilayer film is composed of a multilayer film in which layers of a low-refractive-index material and a high-refractive-index material selected from the above-mentioned materials are alternately stacked.

[0225] When the thickness d of each layer is set to satisfy d = λ0 / 4n (n is the refractive index of each layer at the center wavelength λ0 of the reflection band), the light components reflected at the boundaries between the layers cancel each other out, so that the transmittance decreases and a reflection band is formed. H And the refractive index of the low refractive index material is n L When the width of the central wavelength is W = 2 / π×Sin[(n H -nL ) / (n H +n L )]×λ0 reflection band.

[0226] The dielectric multilayer film of the optical layer 34 is designed to reflect blue light (460 nm) and transmit light emitted from the conversion layer, i.e., green light (530 nm) from the green sub-pixel and red light (630 nm) from the red sub-pixel. The dielectric multilayer film of the optical layer 36 is designed to reflect green light (530 nm) from the green sub-pixel and transmit red light (630 nm) from the red sub-pixel.

[0227] In the example described below, it is assumed that the low refractive index material is SiO2, and the high refractive index material is TiO2. Assuming that the alternating stacking of the SiO2 film and the TiO2 film is defined as once, a multilayer film obtained by repeating the alternating stacking ten times will be described as an example. For incident light with an incident angle of 0 degrees, the thickness of the SiO2 film and the TiO2 film of the optical layer 34 is determined according to the center wavelength of the reflection band. In an example of the optical layer 34, when the center wavelength of the reflection band is 400nm, the thickness of the SiO2 film and the TiO2 film are 69nm and 40nm, respectively, and the total film thickness is 1090nm. In this case, the width of the reflection band is about 133nm. In an example of the optical layer 36, when the center wavelength of the reflection band is 470nm, the thickness of the SiO2 film and the TiO2 film are 81nm and 47nm, respectively, and the total film thickness is 1282nm. In this case, the width of the reflection band is about 156nm. The reflective layer can be made by, for example, sputtering, ion beam deposition or pulsed laser deposition (PLD).

[0228] Similar to Example 1, a green sub-pixel display element including a conversion layer emitting green light is produced by using a substrate on which an optical layer 34 is formed, and a red sub-pixel display element including a conversion layer emitting red light is produced by using a substrate on which an optical layer 36 is formed. The area of ​​the conversion layer is 300 μm×300 μm. Similar to Example 1, a 300 μm×300 μm resin portion containing a light scattering material is formed by using an ink composition obtained by removing CsPbBr3 nanocrystals from ink composition B, thereby producing a blue sub-pixel display element. The red sub-pixel display element, the green sub-pixel display element, and the blue sub-pixel display element are stacked in this order on the Al reflective film to produce the display element.

[0229] [Comparative Example 1]

[0230] A dielectric multilayer mirror that allows blue light to pass through and reflects green and red light is formed on a quartz substrate by ion beam deposition. The dielectric multilayer mirror allows blue light (460nm) incident at an angle of 0 to 30 degrees to pass through, and reflects blue light incident at an angle of more than 30 degrees. The dielectric multilayer mirror reflects green light (530nm) and red light (630nm) incident at any angle. A multilayer film made of SiO2 and TiO2 is used, and a multilayer film with a reflection band having a central wavelength of 580nm, 670nm and 760nm is stacked to form a reflective layer. The film thickness of SiO2 and TiO2 is 100nm and 58nm, 116nm and 67nm, and 131nm and 76nm. The number of repetitions for each band is 5, and the total film thickness of the reflective layer is 2.7μm.

[0231] Similar to Example 1, the CsPbBr3 dispersion was subjected to a dry nitrogen flow to remove the solvent, and was modulated to prepare an ink composition C containing 10 wt% of CsPbBr3 nanocrystals, 75 wt% of 3,3,5-trimethylcyclohexyl acrylate (TMCHA), 5 wt% of 1-hydroxycyclohexyl phenyl ketone (Omnirad 184) and 10 wt% of titanium oxide.

[0232] Similar to Example 1, the above ink composition C was printed on a dielectric multilayer film mirror on a quartz substrate to form a conversion layer with a width of 100 μm, a length of 300 μm and a thickness of 10 μm, thereby manufacturing a display element. This structure corresponds to Figure 3B .

[0233] [Comparative Example 2]

[0234] Similar to Example 1, the same ink composition C as the ink composition used in Comparative Example 1 was printed on a quartz substrate to form a conversion layer having a width of 100 μm, a length of 300 μm, and a thickness of 10 μm, thereby manufacturing a display element. This structure corresponds to Figure 3A .

[0235] [Comparative Example 3]

[0236] Similar to Comparative Example 1, an ink composition D containing 1 wt % of CsPbBr 3 nanocrystals, 84 wt % of 3,3,5-trimethylcyclohexyl acrylate (TMCHA), 5 wt % of 1-hydroxycyclohexyl phenyl ketone (Omnirad 184), and 10 wt % of titanium oxide was prepared.

[0237] Similar to Example 1, the same ink composition D as that used in Comparative Example 1 was printed on a quartz substrate to form a conversion layer having a width of 100 μm, a length of 300 μm, and a thickness of 10 μm, thereby manufacturing a display element. This structure corresponds to Figure 3A .

[0238] <Brightness Evaluation>

[0239] Blue light with a peak emission wavelength of 460nm is guided as excitation light via an optical fiber, and the emitted light is focused by a lens and enters the conversion layer from the side. The amount of blue light (intensity×area) remains constant. The intensity of blue light per unit area increases as the film thickness decreases. For Example 5, the intensity is greater. An integrating sphere is placed just above the conversion layer, and a multi-channel spectrometer C10027-01 (Hamamatsu Photonics) is used to measure the integral value of the emission spectrum for green light at 530nm±30nm and the integral value of the emission spectrum for red light at 630nm±30nm as brightness.

[0240] Table 1 shows the brightness of green and red.

[0241] [Table 1]

[0242]

[0243] When the specific refractive index difference Δ of the waveguide is Δ=1.5, the brightness of green and red increases with decreasing film thickness (Examples 1-3). This may be because the waveguide mode is reduced.

[0244] When the film thickness of the waveguide is constant at 3 μm, the brightness of green and red increases with decreasing specific refractive index difference Δ (Examples 2 and 4). This is probably because the waveguide mode is reduced.

[0245] Regardless of whether the blue light is incident in the long side direction or the short side direction, the brightness is substantially constant (Examples 2 and 5).

[0246] When the scattering portion is provided at the end, the brightness of green and red increases. This is probably because the light in the waveguide mode is scattered at the light scattering portion and extracted as light in the emission mode (Examples 6 and 7).

[0247] When the multilayer structure is used, the brightness of green and red increases. This is because the area of ​​the conversion layer increases by 3 times (Example 8).

[0248] In both Example 1 and Comparative Example 1, the film thickness is 10 μm, and a reflective layer is provided on the lower surface. In Comparative Example 1, although the concentration of the luminescent nanocrystal is 10 wt%, the brightness of green and red is relatively small. This means that Example 1 has a higher light extraction efficiency. When the concentration of the luminescent nanocrystal is set to 1 wt% as in Example 1, the brightness of green and red further decreases (Comparative Example 2). In addition, when a reflective layer is not provided on the lower surface, the brightness of green and red decreases (Comparative Example 3).

[0249] The present invention is not limited to the above-described embodiments, and various changes and modifications may be made without departing from the spirit and scope of the present invention. In order to make the public aware of the scope of the present invention, the following claims are attached.

[0250] This application claims the benefit of Japanese Patent Application No. 2022-087838, filed May 30, 2022, which is hereby incorporated by reference herein in its entirety.

[0251] 100 display components

[0252] 10A light emitting layer array

[0253] 10 Luminous Layer

[0254] 20A conversion layer array

[0255] 20First conversion layer

[0256] 22 first coupling portion

[0257] 24First Extraction Section

[0258] 26First conversion unit

[0259] 28 first reflection part

Claims

1. A display element, comprising: a light-emitting layer array comprising a plurality of light-emitting layers arranged in a two-dimensional manner and emitting light of a first wavelength; as well as A conversion layer array, comprising a plurality of first conversion layers, the plurality of first conversion layers comprising a first coupling portion, a first extraction portion and a first reflection portion, the first coupling portion being optically coupled to a portion of the plurality of light emitting layers, the first extraction portion and the first reflection portion facing each other to alternately reflect the light of the first wavelength received via the first coupling portion and guide the light of the first wavelength in a direction away from the first coupling portion, the plurality of first conversion layers emitting light of a second wavelength obtained as a result of wavelength conversion of the light of the first wavelength via the first extraction portion.

2. The display element according to claim 1, wherein The plurality of first conversion layers include first photoresponsive nanoparticles for converting light of the first wavelength into light of the second wavelength.

3. The display element according to claim 1 or 2, wherein: The spectral reflectivity of the first extraction portion with respect to the light of the first wavelength is higher than the spectral reflectivity with respect to the light of the second wavelength.

4. The display element according to any one of claims 1 to 3, wherein: The spectral transmittance of the first extraction portion with respect to the light of the second wavelength is higher than the spectral transmittance with respect to the light of the first wavelength.

5. The display element according to any one of claims 1 to 4, wherein: The second wavelength is longer than the first wavelength.

6. The display element according to any one of claims 1 to 5, wherein: A spectral reflectance of the first reflecting portion with respect to the light of the second wavelength is higher than a spectral reflectance of the first extracting portion with respect to the light of the second wavelength.

7. The display element according to claim 2, wherein: The first conversion layer has a first optical gradient, so that the optical density of the photoresponsive nanoparticles increases with the increase of the distance from the first coupling portion in the direction of the layer surface.

8. The display element according to any one of claims 1 to 7, wherein: The conversion layer array also includes a plurality of second conversion layers, the plurality of second conversion layers including a plurality of second coupling portions, a second extraction portion, and a second reflection portion, the plurality of second coupling portions being optically coupled to the plurality of light emitting layers in regions other than regions where the light emitting layer array is optically coupled to the plurality of first conversion layers, the second extraction portions and the second reflection portions facing each other to alternately reflect the light of the first wavelength received via the plurality of second coupling portions and guide the light of the first wavelength in a direction away from the second coupling portions, the plurality of second conversion layers emitting light of a third wavelength obtained as a result of wavelength conversion of the light of the first wavelength via the second extraction portions.

9. The display element according to claim 8, wherein: The plurality of second conversion layers include second photoresponsive nanoparticles for converting light of the first wavelength into light of the third wavelength.

10. The display element according to claim 8 or 9, wherein: The spectral reflectance of the second extraction portion with respect to the light of the first wavelength is higher than the spectral reflectance with respect to the light of the third wavelength.

11. The display element according to any one of claims 8 to 10, wherein: The spectral transmittance of the second extraction portion with respect to the light of the third wavelength is higher than the spectral transmittance with respect to the light of the first wavelength.

12. The display element according to any one of claims 8 to 11, wherein: The third wavelength is longer than the first wavelength and the second wavelength.

13. The display element according to any one of claims 8 to 12, wherein: A spectral reflectance of the second reflecting portion with respect to the light of the third wavelength is higher than a spectral reflectance of the second extracting portion with respect to the light of the third wavelength.

14. The display element according to claim 9, wherein: The second conversion layer has a second optical gradient, so that the optical density of the photoresponsive nanoparticles increases with the increase of the distance from the second coupling portion in the layer surface direction.

15. The display element according to any one of claims 1 to 14, wherein: The conversion layer array also includes a plurality of third conversion layers, the plurality of third conversion layers including a third coupling portion, a third extraction portion and a third reflection portion, the third coupling portion being optically coupled to the plurality of light emitting layers in an area other than an area where the light emitting layer array is optically coupled to the plurality of first conversion layers or the plurality of second conversion layers, the third extraction portion and the third reflection portion facing each other to alternately reflect the light of the first wavelength received via the third coupling portion and guide the light of the first wavelength in a direction away from the third coupling portion, the plurality of third conversion layers emitting at least one of the light of the first wavelength and the light of a fourth wavelength obtained as a result of wavelength conversion of the light of the first wavelength via the third extraction portion.

16. The display element according to claim 15, wherein: The plurality of third conversion layers include third photoresponsive nanoparticles for converting light of the first wavelength into light of the fourth wavelength, the fourth wavelength being closer to the first wavelength than the second wavelength and the third wavelength.

17. The display element according to claim 15 or 16, wherein: The spectral reflectance of the third extraction portion with respect to the light of the first wavelength is higher than the spectral reflectance with respect to the light of the fourth wavelength.

18. The display element according to any one of claims 15 to 17, wherein: The spectral reflectance of the third extraction portion with respect to the light of the first wavelength is higher than the spectral reflectance with respect to the light of the fourth wavelength.

19. The display element according to any one of claims 15 to 18, wherein: The fourth wavelength is longer than the first wavelength.

20. The display element according to any one of claims 15 to 19, wherein: A spectral reflectance of the third reflecting portion with respect to the light of the fourth wavelength is higher than a spectral reflectance of the third extracting portion with respect to the light of the fourth wavelength.

21. The display element according to any one of claims 15 to 20, wherein: The plurality of third conversion layers change propagation directions in optical propagation paths from each of the third coupling sections to the third extraction section, but do not perform wavelength conversion on the light of the first wavelength.

22. The display element according to any one of claims 1 to 21, wherein: The first coupling portion does not overlap with the first extraction portion when viewed along an axis parallel to the layer thickness direction.

23. The display element according to any one of claims 8 to 14, wherein: The first extraction portion and the second extraction portion include non-overlapping portions when viewed along an axis parallel to a layer thickness direction.

24. The display element according to any one of claims 8 to 14, wherein: The first extraction portion and the second extraction portion include overlapping portions when viewed along an axis parallel to a layer thickness direction.

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