Image display device

Abstract

An image display device according to one embodiment of the present disclosure comprises: a plurality of display pixels which are arranged in a two-dimensional array form; active layers which are respectively provided to the plurality of display pixels or which are provided straddling the plurality of display pixels; and a photonic crystal layer which is provided to at least some of the plurality of display pixels, which includes a defect in a periodic refractive index distribution that disrupts said periodic refractive index distribution, and in which neither the outer shape of the region having the periodic refractive index distribution nor the structure in the vicinity of the defect has rotational symmetry with respect to rotations of less than 180°.

Description

Image display device

[0001] This disclosure relates to an image display device.

[0002] For example, in Patent Document 1, a light-emitting element is disclosed that uses a defect portion of a photonic crystal layer in which a defect portion that disturbs the periodic refractive index distribution is introduced into the periodic refractive index distribution as a defect cavity.

[0003] Japanese Patent Application Laid-Open No. 2012-253288

[0004] By the way, in a micro-sized display, higher resolution is required.

[0005] It is desirable to provide a high-resolution image display device.

[0006] The image display device according to an embodiment of the present disclosure includes a plurality of display pixels arranged in a two-dimensional array, an active layer provided for each of the plurality of display pixels or across the plurality of display pixels, and at least a part of the plurality of display pixels, including a defect that disturbs the periodic refractive index distribution in the periodic refractive index distribution, and having an outer shape of a region having the periodic refractive index distribution and a structure in the vicinity of the defect both having no rotational symmetry with respect to rotation of less than 180°. It is provided with a photonic crystal layer.

[0007] In the image display device according to an embodiment of the present disclosure, at least a part of a plurality of display pixels arranged in a two-dimensional array is provided with a photonic crystal layer including a defect that disturbs the periodic refractive index distribution in the periodic refractive index distribution, and having an outer shape of a region having the periodic refractive index distribution and a structure in the vicinity of the defect both having no rotational symmetry with respect to rotation of less than 180°. Thereby, the degree of freedom in pixel design is improved.

[0008] Figure 1 is a schematic cross-sectional view (A) and plan view (B) illustrating an example of the configuration of a light-emitting element according to one embodiment of the present disclosure. Figure 2 is a schematic diagram illustrating an example of the overall planar configuration of a display device equipped with the light-emitting element shown in Figure 1. Figure 3 is a schematic planar diagram illustrating an example of the configuration of a display pixel shown in Figure 2. Figure 4 is a schematic planar diagram illustrating an example of the configuration of a general sub-pixel equipped with a photonic crystal. Figure 5 is a diagram showing the emission spectrum of the light-emitting element in the sub-pixel shown in Figure 4, and the extracted X-polarized and Y-polarized components. Figure 6 is a schematic planar diagram illustrating an example of the configuration of a sub-pixel equipped with a photonic crystal shown in Figure 1. Figure 7 is a diagram showing the emission spectrum of the light-emitting element in the sub-pixel shown in Figure 6, and the extracted X-polarized and Y-polarized components. Figure 8 is a schematic planar diagram illustrating another example of the configuration of a sub-pixel equipped with a photonic crystal shown in Figure 1. Figure 9 is a diagram showing the emission spectrum of the light-emitting element in the sub-pixel shown in Figure 8, and the extracted X-polarized and Y-polarized components. Figure 10 is a schematic planar diagram illustrating an example of the layout of sub-pixels in a display device according to Modification 1 of the present disclosure. Figure 11 is a schematic plan view showing an example of the layout of subpixels in a display device according to Modification 2 of the present disclosure. Figure 12 is a schematic plan view showing an example of the configuration of the photonic crystal layer in the subpixels of a display device according to Modification 3 of the present disclosure. Figure 13 is a schematic plan view showing an example of the layout of subpixels in a display device according to Modification 4 of the present disclosure. Figure 14 is a schematic plan view showing an example of the layout of subpixels in a display device according to Modification 5 of the present disclosure. Figure 15 is a schematic plan view showing another example of the layout of subpixels in a display device according to Modification 5 of the present disclosure. Figure 16 is a schematic plan view showing another example of the layout of subpixels in a display device according to Modification 5 of the present disclosure. Figure 17A is a front view showing an example of the appearance of a digital still camera as an application example of the present disclosure. Figure 17B is a rear view showing an example of the appearance of the digital still camera shown in Figure 19A. Figure 18A is a perspective view showing an example of the appearance of a head-mounted display as an application example of the present disclosure. Figure 18B is a perspective view showing an example of the appearance of another head-mounted display as an application example of the present disclosure. Figure 19 is a perspective view showing an example of the appearance of a television apparatus as an application example of this disclosure.

[0009] Hereinafter, one embodiment of the present disclosure will be described in detail with reference to the drawings. The following description is a specific example of the present disclosure, and the present disclosure is not limited to the following embodiments. Furthermore, the present disclosure is not limited to the arrangement, dimensions, dimensional ratios, etc., of each component shown in each figure. The order of description is as follows: 1. Embodiment (Example of a display device having a photonic crystal layer without rotational symmetry of less than 180°) 2. Modifications 2-1. Modification 1 (Another example of the display pixel configuration) 2-2. Modification 2 (Another example of the display pixel configuration) 2-3. Modification 3 (Another example of the display pixel configuration) 2-4. Modification 4 (Another example of the display pixel configuration) 2-5. Modification 5 (Another example of the display pixel configuration) 3. Application Examples

[0010] <1. Embodiments> Figure 1 schematically shows an example of the cross-sectional configuration (A) of a light-emitting element 10 and the planar configuration (B) of a photonic crystal layer 14 provided on the light-emitting element 10, which constitute a display device (display device 1) according to one embodiment of the present disclosure. Note that Figure 1(A) represents a cross-section of the light-emitting element 10 corresponding to the line I-I' shown in Figure 1(B). Figure 2 schematically shows an example of the overall planar configuration of the display device 1 equipped with the light-emitting element 10 shown in Figure 1. The display device 1 is suitably applicable to electronic devices equipped with an image display device called a so-called LED display (for example, an electronic viewfinder 1124 of a digital still camera 1120, see Figure 17B).

[0011] The display device 1 has a display area 100A and a frame area 100B provided around it. Multiple display pixels P are arranged in a two-dimensional array in the display area 100A. Each of the multiple display pixels P has an emissive layer 12 and a photonic crystal layer 14. The photonic crystal layer 14 contains defects that disrupt the periodic refractive index distribution in at least a portion of the display pixels P, and both the outer shape of the region having the periodic refractive index distribution and the structure near the defects do not have rotational symmetry with respect to rotations of less than 180°.

[0012] Here, the multiple display pixels P correspond to one specific example of "multiple display pixels" as one embodiment of the present disclosure. The light-emitting layer 12 corresponds to one specific example of "active layer" as one embodiment of the present disclosure. The photonic crystal layer 14 corresponds to one specific example of "photonic crystal layer" as one embodiment of the present disclosure.

[0013] [Configuration of the display device] As described above, the display device 1 has a display area 100A in which a plurality of display pixels P are arranged in a two-dimensional array, and a frame area 100B provided around it. Each of the plurality of display pixels P has, for example, a red pixel Pr, a green pixel Pg, and a blue pixel Pb corresponding to RGB, as shown in Figure 3. These red pixel Pr, green pixel Pg, and blue pixel Pb correspond to one of the "first sub-pixel," "second sub-pixel," and "third sub-pixel" in one embodiment of the present disclosure. Hereinafter, unless a particular distinction is necessary, they will simply be referred to as sub-pixels Px. A sub-pixel Px has, for example, a light-emitting element 10 as shown in Figure 1.

[0014] The light-emitting element 10 is a solid-state light-emitting element that emits light in a predetermined wavelength band from its light extraction surface, and is, for example, an LED (Light Emitting Diode) element. An LED element is one which is made by separating the wafer used for crystal growth at the wafer level, and is not a package type covered with independently molded resin or the like that is used in general lighting fixtures. The LED element is, for example, 0.1 μm to 10 μm in size, and is what is called a microLED.

[0015] The light-emitting element 10 is constructed by stacking multiple semiconductor layers. For example, the light-emitting element 10 has a first conductivity layer 11 made of a first conductivity type semiconductor layer, an emissive layer 12, and a second conductivity layer 13 made of a second conductivity type semiconductor layer stacked in this order, with the upper surface (surface 11S2) of the first conductivity layer 11 being the light extraction surface S1. The first conductivity layer 11, the emissive layer 12, and the second conductivity layer 13 are made of, for example, a III-V compound semiconductor. The light-emitting element 10 further has a first electrode 21 on the first conductivity layer 11 side and a second electrode 22 on the second conductivity layer 13 side.

[0016] The first conductivity layer 11 supplies active carriers to the light-emitting layer 12 by doping or the like. The first conductivity layer 11 is formed from, for example, an n-type GaN-based compound semiconductor material and supplies holes as active carriers to the light-emitting layer 12. The first conductivity layer 11 is formed from, for example, an n-type GaN-based semiconductor material. In addition, the first conductivity layer 11 can be formed from, for example, a phosphorus (P)-based compound semiconductor material such as n-type AlGaInP or GaInP, or n-type AlGaAs.

[0017] The first conductive type layer 11 has a pair of opposing surfaces (surface 11S1 and surface 11S2), with surface 11S1 facing the light-emitting layer 12 and surface 11S2 being the light extraction surface S1. The first conductive type layer 11 consists of a plurality of layers, including, for example, a p-type cladding layer (p-cladding layer) and a p-type guide layer (p-guide layer). The p-cladding layer and the p-guide layer are stacked in this order from the light extraction surface S1 side.

[0018] The light-emitting layer 12 emits and amplifies spontaneous emission light, and holes and electrons injected from the first electrode 21 and the second electrode 22 undergo luminescent recombination to generate stimulated emission light. The light-emitting layer 12 has, for example, a multiple quantum well (MQW) structure in which multiple well layers 121 and barrier layers 122 are alternately stacked.

[0019] The well layer 121 is a double heterojunction layer sandwiched between barrier layers 122, and highly efficient luminescence recombination is achieved by confining carriers within the layer. The barrier layer 122 is a heterojunction layer formed to confine carriers to the well layer 121, and is a layer having quantum barrier properties. The barrier layer 122 has a larger film thickness than the well layer 121. The luminescent layer 12 (specifically, the well layer 121) has a luminescent region within the layer. The well layer 121 is formed of, for example, InGaN, and the barrier layer 122 is formed of, for example, GaN. In addition, the well layer 121 can be formed of, for example, GaInP or GaAs, and the barrier layer 122 can be formed of, for example, phosphorus (P)-based compound semiconductor materials such as AlGaInP or GaInP, or AlGaAs or GaInN.

[0020] The second conductivity layer 13, like the first conductivity layer 11, supplies active carriers to the light-emitting layer 12 by doping or the like. The second conductivity layer 13 is formed from, for example, a p-type GaN-based compound semiconductor material and supplies holes as active carriers to the light-emitting layer 12. The second conductivity layer 13 is formed from, for example, a p-type GaN-based semiconductor material. In addition, the second conductivity layer 13 can be formed from, for example, a phosphorus (P)-based compound semiconductor material such as p-type AlGaInP or GaInP, or p-type AlGaAs.

[0021] The second conductive layer 13 has a pair of opposing surfaces (surface 13S1 and surface 13S2), with surface 13S1 facing the light-emitting layer 12. The second conductive layer 13 consists of a plurality of layers, including, for example, a p-type cladding layer (p-cladding layer) and a p-type guide layer (p-guide layer). The p-cladding layer and the p-guide layer are stacked in this order from the side opposite to the light extraction surface S1.

[0022] The light-emitting element 10 further includes a photonic crystal layer 14. The photonic crystal layer 14 has a periodic refractive index distribution with a refractive index of approximately the same duration as the wavelength of light, and has a plurality of vacancies 141 arranged in a two-dimensional periodicity within its plane.

[0023] Photonic crystals exist in one, two, or three dimensions, but the photonic crystal layer 14 is made of a two-dimensional slab-type photonic crystal and constitutes, for example, a point-defect type resonator.

[0024] In the photonic crystal layer 14, for example, a plurality of vacancies 141 having rotational symmetry are periodically arranged in a triangular lattice. The photonic crystal layer 14 forms a periodic refractive index distribution in its plane due to the periodic arrangement of the plurality of vacancies 141 in a triangular lattice. The photonic crystal layer 14 further has defects that disrupt the periodic refractive index distribution. A defect refers to a portion where one or more of the plurality of vacancies 141 arranged periodically in a triangular lattice are missing. The photonic crystal layer 14 has a photonic crystal region X that is not a square or a regular hexagon, but has broken rotational symmetry, by shifting a pair of vacancies 141A that are opposite each other across the defect from the six vacancies 141 located at a hexagonal lattice point centered on the defect. The photonic crystal region X has a light confinement effect. The photonic crystal region X includes a cavity defect 142 consisting of a defect in which one vacancy 141 is missing and a pair of vacancies 141A that are shifted away from each other and facing each other across the defect, and a plurality of vacancies 141 around the cavity defect 142, which are located at each point of the triangular lattice necessary to confine light.

[0025] Furthermore, the multiple vacancies 141 having rotational symmetry may be periodically arranged in a square lattice. Also, the method of breaking the rotational symmetry of the photonic crystal region X described above is just one example and is not limited to this.

[0026] The photonic crystal layer 14 is formed for each subpixel Px, for example, within the first conductivity layer 11 (for example, within the n-guide layer). A very strong electric field is generated in the cavity defect 142 where light is confined, and as a result of the interaction between the generated electric field and the light-emitting layer 12, light emission occurs in a resonant mode accompanied by an increase in the spontaneous emission rate of the light-emitting layer 12.

[0027] Figure 4 schematically shows an example of the planar configuration of a subpixel Px' equipped with a photonic crystal that constitutes a typical H1-type cavity consisting of a single point defect, where multiple vacancies 141 are periodically arranged in a triangular lattice. The photonic crystal region X' containing this typical H1-type cavity has a regular hexagonal shape and exhibits 180° rotational symmetry (hexagonal symmetry), as shown in Figure 4. This photonic crystal region X' has a structure that is symmetrical with respect to a 60-degree rotation (hexagonal symmetry, 6-fold rotational symmetry), and the resonant modes are distributed with similar symmetry. Within the photonic crystal region X', electric fields for the X-polarized mode and Y-polarized mode are formed depending on the direction of the dipole in the light-emitting layer, as shown in Figure 4. The X-polarized mode and Y-polarized mode are degenerate to the same wavelength, and as shown in Figure 5, they have peaks of the X-polarized component and Y-polarized component with the same resonant frequency within the emission wavelength of the light-emitting layer 12.

[0028] Figure 6 schematically shows an example of the planar configuration of a subpixel Px equipped with a photonic crystal layer 14 of this embodiment. As described above, the photonic crystal layer 14 has a photonic crystal region X that includes a cavity defect 142 consisting of a defect in which a vacancy 141 is missing and a pair of vacancies 141A that are shifted toward each other and facing each other across the defect. The photonic crystal region X has a vertically elongated hexagonal shape, as shown in Figure 6, for example, and has rotational symmetry with respect to a 180° rotation, but its rotational symmetry with respect to 60° and 120° rotations is broken. In this photonic crystal region X, the electric field distribution is distorted. For example, electric fields for the X-polarization mode and the Y-polarization mode are formed around the cavity defect 142, as shown in Figure 7. In other words, in the photonic crystal layer 14, the longitudinal direction of the electric field distribution of the cavity defect 142 coincides with the longitudinal direction of the photonic crystal region X. In the photonic crystal layer 14, the X-polarization mode and the Y-polarization mode are not degenerate and have different resonant frequencies. However, the resonant wavelengths of the X-polarization component and the Y-polarization component are included within the emission wavelength of the light-emitting layer 12, as shown in Figure 7.

[0029] Furthermore, some of the subpixels Px may be configured to utilize either the X-polarization mode or the Y-polarization mode, as shown in Figures 8 and 9, for example. The electric field distribution of the confined light follows the symmetry of the photonic crystal region X. Therefore, subpixels Px that utilize either the X-polarization mode or the Y-polarization mode can be formed by suppressing or pushing out modes that extend in the short-side direction outside the emission wavelength.

[0030] As described above, the photonic crystal layer 14 of this embodiment has a vertically elongated hexagonal photonic crystal region X. In other words, compared to a sub-pixel Px' having a regular hexagonal photonic crystal region X' as shown in Figure 4, the photonic crystal layer 14 of this embodiment can reduce some of the multiple voids 141 necessary for confining light, as shown in Figure 6, thus enabling the formation of a sub-pixel Px with a smaller pixel area.

[0031] Therefore, a sub-pixel Px having a light-emitting element 10 containing this photonic crystal layer 14 can have a horizontally elongated shape. For example, the sub-pixel Px has a rectangular shape (rectangular) with two opposing short sides and two opposing long sides, as shown in Figure 6. As a result, compared to a square-shaped sub-pixel Px' as shown in Figure 4, the area of ​​the margin outside the photonic crystal region X can be reduced.

[0032] The photonic crystal layer 14 only needs to be located at a distance of 1 μm or less from the light-emitting layer 12, and may, for example, be provided within the second conductivity type layer 13. Furthermore, the photonic crystal layer 14 may be provided on the light-emitting layer 12, or it may span across the light-emitting layer 12 and the first conductivity type layer 11, or across the light-emitting layer 12 and the second conductivity type layer 13. The photonic crystal layer 14 may span across the first conductivity type layer 11, the light-emitting layer 12, and the second conductivity type layer 13.

[0033] Furthermore, while Figure 1 and other figures show a structure having a plurality of vacancies 141 arranged at hexagonal lattice points within a horizontally elongated hexagonal photonic crystal region X, the shape of the photonic crystal region and the arrangement of the plurality of vacancies 141 are not limited to this. For example, a structure may be formed by combining a rectangular photonic crystal region X with a plurality of vacancies 141 arranged at square lattice points. The rectangular photonic crystal region X may have, for example, a plurality of vacancies 141 arranged at square lattice points, and a cavity defect 142 consisting of a defect in which one of the vacancies 141 is missing, and a pair of vacancies 141A that are shifted away from each other and facing each other across the defect.

[0034] [Configuration of Display Pixels] As described above, the sub-pixel Px equipped with the photonic crystal layer 14 can have a horizontally elongated shape. The display pixel P has a red pixel Pr, a green pixel Pg, and a blue pixel Pb corresponding to RGB. Each of the red pixel Pr, green pixel Pg, and blue pixel Pb is provided with a light-emitting element 10, and the aforementioned photonic crystal layer 14 is provided for each of the sub-pixels Pr, Pg, and Pb. In other words, each of the red pixel Pr, green pixel Pg, and blue pixel Pb can have a horizontally elongated shape, for example, a rectangular shape having two opposing short sides and two opposing long sides.

[0035] Furthermore, some or all of the red pixels Pr, green pixels Pg, and blue pixels Pb differ in size or shape. For example, the green pixels Pg are larger than the red pixels Pr and blue pixels Pb, depending on the extraction efficiency of each wavelength corresponding to RGB. In the display pixel P, the red pixels Pr, green pixels Pg, and blue pixels Pb are arranged such that, for example, as shown in Figure 3, the shorter sides of the red pixels Pr and blue pixels Pb, which are smaller than the green pixels Pg, face the longer side of the green pixels Pg. In other words, in the display pixel P, the red pixels Pr, green pixels Pg, and blue pixels Pb are arranged such that the smaller red pixels Pr and blue pixels Pb are positioned in the short-side direction of the electric field distribution formed in the photonic crystal layer 14 provided on the green pixels Pg. This allows the red pixels Pr, green pixels Pg, and blue pixels Pb to be arranged densely.

[0036] Furthermore, if each sub-pixel Pr, Pg, and Pb differs in size and shape, the multiple vacancies 141 and their periodic arrangement that constitute the photonic crystal layer 14 formed on each sub-pixel Pr, Pg, and Pb will differ for each. Specifically, the photonic crystal layer 14 provided on each sub-pixel Px has a photonic crystal region X that includes one cavity defect 142 and a plurality of periodically arranged vacancies 141 necessary to obtain at least the light confinement effect. Therefore, the size and periodic arrangement of the multiple vacancies 141 in the photonic crystal layer 14 provided on the red pixel Pr, green pixel Pg, and blue pixel Pb are designed to match the respective sizes and shapes of each.

[0037] Furthermore, Figure 3 is a schematic diagram illustrating this technology, and the arrangement, period, and number of voids 141 are not limited to this. For example, it is obvious that the design could result in a significantly different period for each RGB color.

[0038] [Function and Effects] In this embodiment, the display device 1 has a plurality of display pixels P constituting the display area 100A, each having an emissive layer 12 and a photonic crystal layer 14. The photonic crystal layer 14 contains defects that disrupt the periodic refractive index distribution in at least a portion of the display pixel P, and both the outer shape of the region having the periodic refractive index distribution and the structure near the defects do not have rotational symmetry with respect to rotations of less than 180°. This improves the degree of freedom in pixel design. This will be explained below.

[0039] Optical nanoresonators constructed using photonic crystals can significantly improve the optical controllability of light-emitting elements. However, in so-called microdisplays with pixel pitches of less than 10 μm, for example, visible light is used and current characteristics are important, making it difficult to use high refractive index materials for optical confinement. Therefore, in order to confine light in an optical nanoresonator, a photonic crystal with more than 10 surplus periods is required, which reduces area efficiency.

[0040] In contrast, in this embodiment, a photonic crystal layer 14 is used for multiple display pixels P constituting the display area 100A, which includes a defect in the periodic refractive index distribution that disrupts the periodic refractive index distribution, and both the outer shape of the region having the periodic refractive index distribution and the structure near the defect lack rotational symmetry with respect to rotations of less than 180°. As a result, the photonic crystal region X having a light confinement effect loses its 180° rotational symmetry and takes on a vertically elongated hexagonal shape, for example, as shown in Figure 6, thus reducing some of the multiple voids 141 necessary for confining light. In other words, since it is no longer necessary to make the photonic crystal region X have a symmetrical outer shape, the degree of freedom in pixel design for the shape and arrangement design of each sub-pixel Pr, Pg, and Pb corresponding to RGB constituting the display pixel P can be improved.

[0041] As a result, the display device 1 of this embodiment can improve the area efficiency of the display pixels P in the display area 100A. Therefore, it is possible to provide a high-resolution image display device.

[0042] Next, Modifications 1 to 5 and Application Examples of the present disclosure will be described. Note that components corresponding to the display device 1 in the above embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0043] <2. Modification> (2-1. Modification 1) FIG. 10 schematically shows an example of a planar layout of sub-pixels Px in a display device according to Modification 1 of the present disclosure.

[0044] In the above embodiment, an example is shown in which the green pixel Pg constituting the display pixel P, the red pixel Pr and the blue pixel Pb are configured to be larger than the green pixel Pg, and the short sides of the red pixel Pr and the blue pixel Pb respectively face the long side of the green pixel Pg. However, the present invention is not limited to this.

[0045] In this modification, the red pixel Pr, the green pixel Pg, and the blue pixel Pb constituting the display pixel P are all rectangular shapes of the same size, and the structural portion 23 is arranged in the short side direction of each. The structural portion 23 is, for example, a circuit, a partition wall, an electrode, a contact plug, or the like.

[0046] Note that the two adjacent sub-pixels Px shown in FIG. 10 may be sub-pixels of the same color or sub-pixels of different colors.

[0047] As described above, the present technology enables pixel design without rotational symmetry of three or more times such as a rectangle. Therefore, for example, a structural portion 23 such as a circuit or a partition wall and a flexible arrangement with other sub-pixels Px are possible.

[0048] <(2-2. Modification 2)> FIG. 11 schematically shows an example of a planar layout of sub-pixels Px in a display device according to Modification 2 of the present disclosure.

[0049] In the above embodiment, an example is shown in which the green pixel Pg constituting the display pixel P, the red pixel Pr and the blue pixel Pb are configured to be larger than the green pixel Pg, and the short sides of the red pixel Pr and the blue pixel Pb respectively face the long side of the green pixel Pg. However, the present invention is not limited to this.

[0050] In this modified example, for instance, a green pixel Pg having adjacent X-polarization modes and a blue pixel Pb having adjacent Y-polarization modes are arranged side by side, and a photonic crystal layer 14 is provided across the green pixel Pg and the blue pixel Pb. The photonic crystal layer 14 shares a connecting structure 143 between the green pixel Pg and the blue pixel Pb.

[0051] When the photonic crystal layer 14 extends around the photonic crystal region X, the photonic crystal layer 14 comes to have a connection structure 143 around the photonic crystal region X that includes a plurality of vacancies 141B having a planar shape without rotational symmetry, as shown in Figure 11, for example. The connection structure 143 has the effect of, for example, prohibiting both red light that propagates in a specific direction and has a specific polarization, and blue light that propagates in another specific direction and has a specific polarization. In other words, the connection structure 143 does not necessarily constitute a perfect optical band gap that prohibits all wavenumber components and all polarization components.

[0052] Thus, in this modified example, the photonic crystal layer 14 is provided across multiple sub-pixels Px, and the connecting structure 143 is shared between adjacent sub-pixels Px. This makes it possible to suppress color mixing between adjacent sub-pixels Px from which light of different wavelength bands is extracted, without providing physical separation structures such as partitions. Furthermore, since the connecting structure 143 simultaneously contributes to the light confinement of adjacent sub-pixels Px, the total area occupied by the photonic crystal region X in the display pixel P can be reduced.

[0053] (2-3. Modification 3) Figure 12 schematically shows an example of the configuration of the photonic crystal layer 14A in the subpixel Px of the display device according to Modification 3 of the present disclosure.

[0054] In the above embodiment, an example was shown in which each sub-pixel Px constituting the display pixel P includes one cavity defect 142 and a plurality of periodically arranged vacancies 141 necessary to obtain at least a light confinement effect, but the embodiment is not limited thereto.

[0055] This modified example has multiple cavity defects 142 within the pixel. The multiple cavity defects 142 within the pixel may include not only H1 type cavities but also other types of cavities such as H0 type cavities that do not use point defects.

[0056] (2-4. Modification 4) Figure 13 schematically represents an example of the layout of sub-pixels Px in a display device according to Modification 4 of the present disclosure.

[0057] The above modifications 1 to 3 can be combined with each other. In this modified example, the display pixel P1 consists of multiple red pixels Pr, green pixels Pg, and blue pixels Pb of different sizes, arranged so that the long side of the largest green pixel Pg is opposite to the short sides of the red pixels Pr and blue pixels Pb, and the structural part 23 is positioned in the direction of the long side of the smallest blue pixel Pb. The display pixel P1 is further provided with a photonic crystal layer 14 extending over the red pixels Pr, green pixels Pg, and blue pixels Pb, and the green pixels Pg shares a PBG 143 between the red pixels Pr and blue pixels Pb.

[0058] Even in a display device equipped with such a display pixel P1, the same effects as in the above embodiment can be obtained.

[0059] (2-5. Modification 5) Figures 14 to 16 schematically represent an example of the layout of sub-pixels Px in a display device according to Modification 5 of the present disclosure.

[0060] In the above embodiment, an example was shown in which each sub-pixel Px constituting the display pixel P includes one cavity defect 142 and a plurality of periodically arranged vacancies 141 necessary to obtain at least a light confinement effect, but the embodiment is not limited thereto.

[0061] For example, as shown in Figure 14, the display pixel P2 may include a sub-pixel Px (e.g., a green pixel Pg) having a photonic crystal layer 14 that maintains rotational symmetry. For example, as shown in Figure 15, the display pixel PP3 may include a sub-pixel Px (e.g., a green pixel Pg) having a photonic crystal layer 14 that does not have cavity defects 142. For example, as shown in Figure 16, the display pixel P3 may include a sub-pixel Px (e.g., a green pixel Pg) in which a photonic crystal layer 14 is not formed.

[0062] The display device 1 of this disclosure can improve the area efficiency of the display pixels P in the display area 100A, even if some or all of the multiple display pixels P constituting the display area 100A are any of the above-mentioned display pixels P2 to P4. Therefore, it is possible to provide a high-resolution image display device.

[0063] <3. Application Examples> (Application Example 1) Figure 17A is a front view showing an example of the external appearance of a digital still camera (electronic device) 1120. Figure 17B is a rear view showing an example of the external appearance of a digital still camera 1120. The digital still camera 1120 is a single-lens reflex type with interchangeable lenses. The digital still camera 1120 has an interchangeable shooting lens unit (interchangeable lens) 1121 located approximately in the center of the front of the camera body 1122, and a grip portion 1123 for the photographer to hold on the left side of the front.

[0064] A monitor 1126 is located slightly to the left of the center of the back of the camera body 1122. An electronic viewfinder (eyepiece) 1124 is located above the monitor 1126. The photographer can determine the composition by looking through the electronic viewfinder 1124 and viewing the light image of the subject guided by the shooting lens unit 1121. The electronic viewfinder 1124 is equipped with a display device 1.

[0065] (Application Example 2) The image display device of the present disclosure (for example, display device 1) is also applicable to a head-mounted display (hereinafter referred to as HMD). The head-mounted display 1130A can be used for VR (Virtual Reality), AR (Augmented Reality), MR (Mixed Reality), or SR (Substitutional Reality), etc.

[0066] Figure 18A is a perspective view showing the external appearance of a head-mounted display (electronic device) 1130A. The head-mounted display 1130A has, for example, a glasses-shaped display unit 1132 with ear hooks 1131 on both sides for attachment to the user's head. The display unit 1132 includes a display device 1.

[0067] Figure 18B is a perspective view showing the appearance of another head-mounted display (electronic device). The head-mounted display is a smart glasses 1130B that displays various information on eyeglasses 1133. The smart glasses 1130B comprises a main body, an arm 1135, and a lens barrel 1136. The main body 1134 is connected to the arm 1135. The main body 1134 is detachable from the eyeglasses 1133. The main body 1134 contains a control board and a display unit for controlling the operation of the smart glasses 1130B. The main body 1134 and the lens barrel 1136 are connected to each other via the arm 1135. The lens barrel 1136 emits image light emitted from the main body 1134 via the arm 1135 towards the lens 1137 of the eyeglasses 1133. This image light enters the human eye through the lens 1137. As shown in Figure 18B, the wearer of the smart glasses 1130B can see not only the surrounding environment but also various information emitted from the lens barrel 1136, just like with regular glasses. The main body 1134 is equipped with a display device 1.

[0068] (Application Example 3) Figure 19 is a perspective view showing an example of the appearance of a television device (electronic device) 1140. This television device 1140 has, for example, a video display screen section 1141 including a front panel 1142 and a filter glass 1143. The video display screen section 1141 is equipped with a display device 1.

[0069] The present disclosure has been described above with reference to embodiments, modifications 1 to 5, and application examples. However, the present disclosure is not limited to the above embodiments, and various modifications are possible. For example, two or more of the above modifications 1 to 5 may be combined.

[0070] Furthermore, although the above embodiments show examples in which the light-emitting layer 12 is formed using a compound semiconductor material, the invention is not limited to this. The light-emitting layer 12 may be formed using, for example, organic electroluminescence (EL).

[0071] Furthermore, the effects described herein are merely examples and are not limited to those described; other effects may also occur.

[0072] The present technology can also take the following configurations. According to the present technology with the following configurations, the degree of freedom in pixel design is improved, making it possible to provide a high-resolution image display device. (1) An image display device comprising: a plurality of display pixels arranged in a two-dimensional array; an active layer provided on each of the plurality of display pixels or spanning the plurality of display pixels; and a photonic crystal layer provided on at least a portion of the plurality of display pixels, which includes a defect in the periodic refractive index distribution that disrupts the periodic refractive index distribution, and the outer shape of the region having the periodic refractive index distribution and the structure near the defect both lack rotational symmetry with respect to rotations of less than 180°. (2) The image display device according to (1), wherein the plurality of display pixels include a first sub-pixel, and the first sub-pixel has a light-emitting region that includes a photonic crystal region that is not square or a regular hexagon. (3) The image display device according to (2), wherein the photonic crystal layer includes one or more of the defects in the first sub-pixel. (4) The image display device according to (2) or (3), wherein the first sub-pixel includes one or more types of the defects. (5) The image display device according to any one of (2) to (4), wherein the longitudinal direction of the photonic crystal region coincides with the longitudinal direction of the electric field distribution generated within the photonic crystal region. (6) The image display device according to any one of (2) to (5), wherein the photonic crystal layer has a plurality of vacancies that form the periodic refractive index distribution, and the photonic crystal region includes the plurality of vacancies arranged at the positions of square lattice points or hexagonal lattice points, and one or more pairs of the vacancies shifted from the positions of the square lattice points or hexagonal lattice points. (7) The image display device according to any one of (2) to (6), wherein the light extracted from the photonic crystal region includes the resonance wavelengths of the X-polarization component and the Y-polarization component, respectively, in the emission spectrum of the active layer. (8) The image display device according to any one of (2) to (7), wherein the plurality of display pixels further include a second sub-pixel having a different light emission color from the first sub-pixel, and the first sub-pixel and the second sub-pixel differ in size or shape.(9) The image display device according to (8), wherein the photonic crystal layer has a plurality of vacancies that form the periodic refractive index distribution, and the plurality of vacancies arranged in the first sub-pixel and the second sub-pixel are arranged with different periodicities from each other. (10) The image display device according to (8) or (9), wherein the photonic crystal layer is provided across the first sub-pixel and the second sub-pixel. (11) The image display device according to (10), wherein the photonic crystal layer has a plurality of vacancies that form the periodic refractive index distribution, the plurality of vacancies arranged in the first sub-pixel and the second sub-pixel have a planar shape with rotational symmetry, and the plurality of vacancies between adjacent first sub-pixels and second sub-pixels have a planar shape without rotational symmetry. (12) The image display device according to any one of (8) to (11), wherein the plurality of display pixels further include a third sub-pixel having a different light emission color from the first sub-pixel and the second sub-pixel, and the first sub-pixel, the second sub-pixel and the third sub-pixel differ in size or shape from one another. (13) The image display device according to (12), wherein the first sub-pixel, the second sub-pixel and the third sub-pixel each have a rectangular shape with two opposing short sides and two opposing long sides. (14) The image display device according to (13), wherein the first sub-pixel is larger than the second sub-pixel and the third sub-pixel, and the second sub-pixel and the third sub-pixel are arranged such that the long side of the first sub-pixel and the short sides of the second sub-pixel and the third sub-pixel, respectively, face each other. (15) The image display device according to any one of (12) to (14), wherein the photonic crystal layer has a plurality of vacancies that form the periodic refractive index distribution, and the plurality of vacancies arranged in the first sub-pixel, the second sub-pixel, and the third sub-pixel are arranged with different periodicities from each other.(16) The image display device according to any one of (1) to (15), wherein the display pixel has an light-emitting element comprising the active layer, a first semiconductor layer having a first conductivity type, and a second semiconductor layer having a second conductivity type different from the first conductivity type, and provided on the opposite side of the active layer from the first semiconductor layer, and the photonic crystal layer is formed on at least a part of the first semiconductor layer or the second semiconductor layer.

[0073] This application claims priority based on Japanese Patent Application No. 2024-170781, filed with the Japan Patent Office on 30 September 2024, and all contents of that application are incorporated herein by reference.

[0074] Those skilled in the art will understand that various modifications, combinations, subcombinations, and changes can be conceived depending on design requirements and other factors, and that these fall within the scope of the attached claims and their equivalents.

Claims

1. An image display device comprising: a plurality of display pixels arranged in a two-dimensional array; an active layer provided on each of the plurality of display pixels or spanning the plurality of display pixels; and a photonic crystal layer provided on at least a portion of the plurality of display pixels, which includes a defect in the periodic refractive index distribution that disrupts the periodic refractive index distribution, and both the shape of the region having the periodic refractive index distribution and the structure near the defect lack rotational symmetry with respect to rotations of less than 180°.

2. The image display device according to claim 1, wherein the plurality of display pixels include a first sub-pixel, and the first sub-pixel has a light-emitting region that includes a photonic crystal region that is not square or hexagonal.

3. The image display device according to claim 2, wherein the photonic crystal layer includes one or more of the defects within the first subpixel.

4. The image display device according to claim 2, wherein the first subpixel includes one or more types of defects.

5. The image display device according to claim 2, wherein the longitudinal direction of the photonic crystal region coincides with the longitudinal direction of the electric field distribution generated within the photonic crystal region.

6. The image display device according to claim 2, wherein the photonic crystal layer has a plurality of vacancies that form the periodic refractive index distribution, and the photonic crystal region includes the plurality of vacancies arranged at the positions of square lattice points or hexagonal lattice points, and one or more pairs of the vacancies shifted from the positions of the square lattice points or hexagonal lattice points.

7. The image display device according to claim 2, wherein the light extracted from the photonic crystal region includes the resonant wavelengths of the X-polarized component and the Y-polarized component, respectively, in the emission spectrum of the active layer.

8. The image display device according to claim 2, wherein the plurality of display pixels further include a second sub-pixel having a different light emission color from the first sub-pixel, and the first sub-pixel and the second sub-pixel differ in size or shape.

9. The image display device according to claim 8, wherein the photonic crystal layer has a plurality of vacancies that form the periodic refractive index distribution, and the plurality of vacancies arranged in the first subpixel and the second subpixel are arranged with different periodicities from each other.

10. The image display device according to claim 8, wherein the photonic crystal layer is provided over the first sub-pixel and the second sub-pixel.

11. The image display device according to claim 10, wherein the photonic crystal layer has a plurality of vacancies that form the periodic refractive index distribution, the plurality of vacancies arranged in the first subpixel and the second subpixel have a rotationally symmetric planar shape, and the plurality of vacancies between adjacent first subpixels and second subpixels have a planar shape that does not have rotational symmetry.

12. The image display device according to claim 8, wherein the plurality of display pixels further include a third sub-pixel having a different light emission color from the first sub-pixel and the second sub-pixel, and the first sub-pixel, the second sub-pixel and the third sub-pixel differ from each other in size or shape.

13. The image display device according to claim 12, wherein the first sub-pixel, the second sub-pixel, and the third sub-pixel each have a rectangular shape with two opposing short sides and two opposing long sides.

14. The image display device according to claim 13, wherein the first sub-pixel is larger than the second sub-pixel and the third sub-pixel, and the second sub-pixel and the third sub-pixel are arranged such that the long side of the first sub-pixel faces the short side of the second sub-pixel and the third sub-pixel, respectively.

15. The image display device according to claim 12, wherein the photonic crystal layer has a plurality of vacancies that form the periodic refractive index distribution, and the plurality of vacancies arranged in the first sub-pixel, the second sub-pixel, and the third sub-pixel are arranged with different periodicities from one another.

16. The image display device according to claim 1, wherein the display pixel has an light-emitting element comprising the active layer, a first semiconductor layer having a first conductivity type, and a second semiconductor layer having a second conductivity type different from the first conductivity type, and provided on the opposite side of the active layer from the first semiconductor layer, and the photonic crystal layer is formed on at least a part of the first semiconductor layer or the second semiconductor layer.

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