Display screen having symmetry elements

Abstract

The invention relates to a display screen comprising an array of pixels (1) which lies in a plane defined by a first direction and a second direction (x, y) and has an elementary pattern (1000) that is the smallest geometric pattern comprising various coloured areas, wherein the entire array of pixels can be obtained by repeating the elementary pattern by translation in the first and second directions by pitches equal to a first dimension (L1) in the first direction and to a second dimension (L2) in the second direction, respectively. The elementary pattern comprises a first pixel (100) and a second pixel (200), each comprising a first sub-pixel (110, 210) of a first color and a second sub-pixel (120, 220) of a second color. The contact between the two pixels defines a plane of symmetry of the elementary pattern.

Description

[0001] "Display screen with elements of symmetry"

[0002] TECHNICAL FIELD

[0003] The present invention relates in particular to the field of microelectronics and optoelectronics technologies. It finds a particularly advantageous but non-limiting application in display technologies and in particular display systems based on LEDs (from the English "Light-Emitting Diode").

[0004] STATE OF THE ART

[0005] A display screen generally comprises a plurality of pixels arranged on a so-called basal plane and emitting independently of one another. Each color pixel generally comprises at least three components for emitting and / or converting a luminous flux, also called sub-pixels. These sub-pixels each emit a luminous flux in substantially a single color (typically red, green and blue). The color of a pixel perceived by an observer comes from the superposition of the different luminous fluxes emitted by the sub-pixels.

[0006] Typically, an LED emits the luminous flux associated with a sub-pixel. An LED may in particular comprise a plurality of active nanowires arranged in a periodic photonic crystal and emitting said luminous flux at the desired wavelength. This photonic crystal is characterized in particular by the diameter of the nanowires and the pitch between the nanowires. Photonic crystals therefore have structural differences from one sub-pixel to another. These differences create design difficulties: the production of a display screen requires the manufacture side by side of nanowires having very precise and, above all, distinct diameters and pitches between them. The dimensions of the areas over which the structural properties of the photonic crystal are constant, i.e. the sub-pixels, are also very small.We therefore understand that the manufacture of a display screen involves a succession of technological stages at the sub-pixel scale, which presents significant technical constraints (need for great precision in the alignment of lithography masks, etc.) and can lead to structural defects (edge ​​effects, etc.).

[0007] Moreover, the classical type of arrangement of subpixels within a pixel and its repetition pixel after pixel by simple translation, illustrated in Figure 8, allows for overall pixel-to-pixel visual uniformity but does not present optimal performance.

[0008] There is therefore a need to optimize the manufacturing of display screens as well as to improve the performance of self-emissive pixels based on nanowires.

[0009] SUMMARY

[0010] To achieve this objective, according to one embodiment, a display screen is provided comprising an array of pixels extending mainly along a plane defined by a first direction and a second direction. The array of pixels has an elementary pattern, which is the smallest geometric pattern comprising different colored areas, the repetition of which by translation in the first direction according to a first pitch equal to the value of a first dimension of the elementary pattern according to the first direction and by translation in the second direction according to a pitch equal to the value of a second dimension of the elementary pattern according to the second direction makes it possible to obtain the array of pixels in its entirety.The pixel array comprises a plurality of pixels comprising at least a first pixel and a second pixel, each pixel of the plurality of pixels comprising at least a first sub-pixel of a first color and a second sub-pixel of a second color distinct from the first color. Each pixel of the plurality of pixels is in contact with at least one other pixel of the plurality of pixels. The display screen is further characterized in that the contact between two pixels in contact is defined by a contact plane defining a plane of symmetry of the elementary pattern.

[0011] An important issue in display technologies concerns the transition zones between adjacent pixels and sub-pixels. Indeed, in display screens, sub-pixels of distinct colors are typically placed next to each other. However, a sub-pixel of a given color is typically formed by a photonic crystal with structural characteristics (nanowire diameter, pitch between neighboring nanowires, etc.) different from those of a photonic crystal forming a neighboring sub-pixel emitting in another color. Abrupt transition zones separate these sub-pixels, as illustrated in Figure 8. The presence of these abrupt transition zones has the disadvantage of breaking the symmetry of the lattice and, consequently, creating detrimental edge effects during nanowire growth.Furthermore, the dimensions of the different photonic crystals forming the different sub-pixels correspond to the dimensions of the latter and are therefore very small. However, the performance level of a photonic crystal is very dependent on the quantity of nanowires constituting it and its dimensions: a small photonic crystal has poorer performance than a larger photonic crystal. Thus, in the current state, and particularly in the case of monolithic screens, in which the dimensions of the sub-pixels are typically very small, the quality of the photonic crystals forming the photo-element arrays is limited. The fact that the elementary pattern of the pixel array has a plane of symmetry makes it possible to reduce the number of abrupt transition zones. Indeed, two sub-pixels of the same color are formed by photonic crystals with the same structural properties.No abrupt transition zone separates them. The juxtaposition of two sub-pixels of the same color induced by symmetry therefore makes it possible to reduce the number of abrupt transition zones. In addition, this juxtaposition makes it possible to form an array of photo-elements with dimensions at least twice those of an array forming a single sub-pixel. This array forming two neighboring sub-pixels of the same color can be formed more easily than two separate arrays corresponding to each of the two sub-pixels. The existence of symmetry within the elementary pattern therefore makes it possible to optimize the manufacture of the display screen and to limit the appearance of structural defects.

[0012] BRIEF DESCRIPTION OF THE FIGURES

[0013] The aims, objects, as well as the characteristics and advantages of the invention will emerge more clearly from the detailed description of an embodiment thereof which is illustrated by the following accompanying drawings in which:

[0014] Figure 1 represents an embodiment of the invention in which the pixel array has an elementary pattern comprising two pixels each divided into two sub-pixels.

[0015] Figure 2 represents an embodiment of the invention in which the pixel array has an elementary pattern comprising two pixels each divided into three sub-pixels.

[0016] Figure 3 shows another embodiment of the invention in which the pixel array has an elementary pattern comprising two pixels each divided into three sub-pixels.

[0017] Figure 4 shows an embodiment of the invention in which the pixel array has an elementary pattern comprising four pixels each divided into four sub-pixels.

[0018] Figure 5A represents an embodiment of the invention in which the pixel array has an elementary pattern comprising four pixels each divided into four sub-pixels two by two of the same color.

[0019] Figure 5B represents an embodiment of the invention in which the pixel array has an elementary pattern comprising two pixels each divided into four sub-pixels two by two of the same color.

[0020] Figure 6 shows a cross-sectional view of a photoelement array.

[0021] Figure 7 represents a sectional view of an intermediate step of manufacturing the photoelements included in a display screen according to one of the embodiments of the invention. Figure 8 represents a display screen according to the prior art in which the elementary pattern comprises a single pixel, and without a plane of symmetry at a contact plane between two pixels.

[0022] The drawings are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily to the scale of practical applications. In particular, the dimensions are not representative of reality. DETAILED DESCRIPTION

[0023] Before commencing a detailed review of embodiments of the invention, optional features which may possibly be used in combination or alternatively are set out below:

[0024] According to one embodiment, the plurality of pixels further comprises a third pixel and a fourth pixel.

[0025] According to one embodiment, each pixel of the plurality of pixels further comprises a third sub-pixel of a third color.

[0026] In one example, the third color is distinct from the first color and the second color.

[0027] According to one embodiment, the first sub-pixel of the first pixel and the first sub-pixel of the second pixel on the one hand and the second sub-pixel of the first pixel and the second sub-pixel of the second pixel on the other hand are in contact within the elementary pattern.

[0028] According to one embodiment, each pixel further comprises a fourth sub-pixel of a fourth color.

[0029] In one example, the fourth color is distinct from the first color and the second color.

[0030] In one example, the fourth color is distinct from the third color.

[0031] In one example, the third color is the same as one of the first color and the second color and the fourth color is the same as the other of the first color and the second color.

[0032] According to one embodiment, the first sub-pixel of the first pixel and the first sub-pixel of the second pixel on the one hand and the second sub-pixel of the first pixel and the second sub-pixel of the second pixel on the one hand are powered by separate electrical contacts.

[0033] According to one embodiment, the third sub-pixel of the first pixel and the third sub-pixel of the second pixel are powered by separate electrical contacts.

[0034] According to one embodiment, the fourth sub-pixel of the first pixel and the fourth sub-pixel of the second pixel are powered by separate electrical contacts.

[0035] According to one embodiment, the first sub-pixel of the first pixel, the first sub-pixel of the second pixel and the first sub-pixel of the third pixel are powered by separate electrical contacts.

[0036] According to one embodiment, the first sub-pixel of the first pixel, the first sub-pixel of the second pixel, the first sub-pixel of the third pixel and the first sub-pixel of the fourth pixel are powered by separate electrical contacts.

[0037] It is understood that this principle of distinct electrical contacts between different sub-pixels can be extended mutatis mutandis to any number of pixels and sub-pixels.

[0038] According to an advantageous embodiment, the pixel network is formed by a set of photo-elements.

[0039] According to an advantageous embodiment, the set of photo-elements comprises a plurality of continuous photo-element arrays, each continuous photo-element array extending over at least two adjacent sub-pixels belonging to distinct pixels of the plurality of pixels.

[0040] According to an advantageous embodiment, each continuous network of photo-elements forms a photonic crystal.

[0041] According to an advantageous embodiment, each pixel of the plurality of pixels comprises a plurality of sub-pixels, and the adjacent and same-colored sub-pixels belonging to distinct pixels are formed by a continuous array of photo-elements.

[0042] According to an advantageous example, within the elementary pattern, the first sub-pixels are formed by a first continuous array of photo-elements which emits in a first range of wavelengths corresponding to the first color.

[0043] According to an advantageous example, the second sub-pixels are formed by a second continuous array of photo-elements which emits in a second wavelength range corresponding to the second color.

[0044] According to a preferred example, the photo-elements are configured to emit a beam whose intensity in a direction perpendicular to an upper face of a substrate from which said photo-elements extend is at least 20% greater than the maximum intensity of an emission by a Lambertian light source whose total luminous flux on 4TT sr is equal to the total flux on 4iï sr of the beam emitted by the photo-elements.

[0045] According to an advantageous example, the first array of photoelements forms a photonic crystal. According to an advantageous example, the second array of photoelements forms a photonic crystal.

[0046] In one example, photoelements are nanowires.

[0047] According to an advantageous embodiment, the screen comprises a monolithic support carrying all the pixels of the pixel array. Thus, advantageously, the display screen has been produced from the support without successive cutting and gluing of the latter. The display screen may, for example, have been manufactured, among other things, by epitaxy of photoelements from this single monolithic support.

[0048] In the present invention, the display screen is a single continuous screen having a face configured to display an image at a given time.

[0049] A photoelement is an element capable of emitting a light beam. A photoelement can, for example, be an active 3D structure, such as an active wire or nanowire.

[0050] A 3D structure is said to be active when it includes an active region and is electrically connected, thus allowing it to emit light radiation.

[0051] By wire or nanowire is meant a 3D structure of elongated shape in the longitudinal direction. The longitudinal dimension of the 3D structure, along z in the figures, is greater, and preferably much greater, than the transverse dimensions of the 3D structure, in the xy plane in the figures. The longitudinal dimension is for example at least five times, and preferably at least ten times, greater than the transverse dimensions. A nanowire is a wire having transverse dimensions of less than 2 μm (1 μm = 10-6 m). By diameter of a nanowire is meant the largest transverse dimension of this nanowire. In the present invention, the 3D structures do not necessarily have a circular transverse section. The 3D structures may in particular have a hexagonal or polygonal transverse section. In particular, in the case of 3D structures based on GaN, this section may be hexagonal.The diameter then corresponds to an average diameter calculated from the diameter of a circle inscribed in the polygon of the transverse section and the diameter of a circumscribed circle of this polygon.

[0052] In this patent application, the terms "light-emitting diode", "LED" or simply "diode" are used synonymously. An "LED" can also be understood as a "micro-LED". A "micro-LED" is an LED whose dimensions do not exceed 1 mm (1 mm = 10-3 m).

[0053] In the following, the following abbreviations relating to a material M are possibly used: Mi refers to the intrinsic or unintentionally doped material M, according to the terminology usually used in the field of microelectronics for the suffix -i.

[0054] Mn refers to the material M doped N, N+ or N++, according to the terminology usually used in the field of microelectronics for the suffix -n.

[0055] Mp refers to the material M doped P, P+ or P++, according to the terminology usually used in the field of microelectronics for the suffix -p.

[0056] A substrate, a layer, a device "based on" a material M means a substrate, a layer, a device comprising this material M only or this material M and possibly other materials, for example alloying elements, impurities or doping elements. Thus, a 3D structure based on gallium nitride (GaN) may for example comprise gallium nitride (GaN or GaN-i) or doped gallium nitride (GaN-p, GaN-n). An active region based on gallium-indium nitride (InGaN) may for example comprise gallium-aluminium nitride (AIGaN) or gallium nitride with different aluminium and indium contents (GalnAIN). In the context of the present invention, the material M is generally crystalline.

[0057] A reference frame, preferably orthonormal, comprising the x, y, z axes is shown in the attached figures.

[0058] The terms "substantially", "approximately", "of the order of" mean, when they refer to a value, "within 10%" of that value or, when they refer to an angular orientation, "within 10°" of that orientation. Thus, a direction substantially normal to a plane means a direction presenting an angle of 90±10° with respect to the plane.

[0059] To determine the geometry of 3D structures and the compositions of the different elements (wire, active region, collar for example) of these 3D structures, Scanning Electron Microscopy (SEM) or Transmission Electron Microscopy (TEM) or even Scanning Transmission Electron Microscopy (STEM) analyses can be carried out. TEM or STEM are particularly well suited to the observation and identification of quantum wells - whose thickness is generally of the order of a few nanometers - in the active region. Different techniques listed below in a non-exhaustive manner can be implemented: dark field and bright field imaging, weak beam imaging, and wide-angle diffraction (HAADF) (High Angle Annular Dark Field).

[0060] The chemical compositions of different elements can be determined using the well-known EDX or X-EDS method, an acronym for "energy dispersive x-ray spectroscopy" which means "energy dispersive analysis of X-ray photons".

[0061] This method is well suited for analyzing the composition of small optoelectronic devices such as 3D LEDs. It can be implemented on metallurgical sections within a Scanning Electron Microscope (SEM) or on thin sections within a Transmission Electron Microscope (TEM).

[0062] The optical properties of the various elements, and in particular the main emission wavelengths of GaN-based axial 3D LEDs and / or InGaN-based active regions, can be determined by spectroscopy.

[0063] Cathodoluminescence (CL) and photoluminescence (PL) spectroscopies are well suited to optically characterize the 3D structures described in the present invention. The techniques mentioned above make it possible in particular to determine whether an optoelectronic device with an axial 3D structure in the form of a wire comprises InGaN-based quantum wells formed on top of a GaN-based wire, and a masking layer indicative of an implementation of a MOVPE-type deposition.

[0064] A monolithic support is a single support made from a single piece.

[0065] A display screen according to a first embodiment of the invention will now be described with reference to figures 1, 6 and 7.

[0066] The display screen extends mainly along the xy plane shown in Figure 1. This plane is defined by a first x direction and a second y direction, preferably perpendicular to each other.

[0067] The display screen comprises a pixel array 1 also extending mainly along the xy plane. The pixels of the pixel array 1 each comprise at least two sub-pixels called first sub-pixels 110, 210 and second sub-pixels 120, 220. A sub-pixel is characterized, among other things, by the color that it can emit. The first sub-pixels 110, 210 of each of the pixels emit a first color C1 while the second sub-pixels 120, 220 emit a second color C2 distinct from the first color C1.

[0068] The color of a sub-pixel can be rendered in different ways. Typically, a sub-pixel is formed, among other things, by an array of photo-elements 10, for example 3D structures of the nanowire type, configured to emit a luminous flux associated with the color in question.

[0069] As illustrated in Figure 7, these photo-elements 10 are typically manufactured by epitaxy and then typically extend from a substrate 2 extending along the xy plane. The substrate 2 has an upper face 20 also extending along the xy plane. The substrate 2 may be in the form of a stack comprising, for example, along the z direction, a support 21, a surface layer called the nucleation layer 22 and a masking layer 23.

[0070] The support 21 may be made of sapphire to limit the mesh parameter mismatch with the GaN if the photoelements 10 are based on this material, or of silicon to reduce costs and for technological compatibility issues. In the latter case, it may be in the form of a wafer with a diameter of 200 mm or 300 mm. It serves in particular as a support for 3D structures.

[0071] The nucleation layer 22 is preferably based on metal nitrides, for example AIN, GaN or AIGaN. It can be formed on the silicon support 21 by epitaxy, preferably by MOVPE (acronym for “MetalOrganic Vapor Phase Epitaxy”). In a known manner, one or more intermediate buffer layers can be arranged between the nucleation layer 22 and the support 21. According to one example, the nucleation layer 22 has a thickness of between 1 nm and 10 μm. It preferably has a thickness of the order of a few hundred nanometers, for example approximately 100 nm or 200 nm, to a few microns, for example of the order of 2 μm. It can also have a thickness of less than 100 nm. Such a thickness makes it possible to limit the appearance of structural defects in the nucleation layer 22.In particular, the growth of this nucleation layer 22 can be pseudomorphic, that is to say that the epitaxial constraints linked in particular to the difference in lattice parameters between the support 21 and the nucleation layer 22 can be elastically released during growth. The crystalline quality of this nucleation layer 22 can thus be optimized.

[0072] The masking layer 23 is preferably made of a dielectric material, for example silicon nitride Si3N4. It can be deposited by chemical vapor deposition CVD (acronym for “Chemical Vapor Deposition”) on the nucleation layer 22. It partially masks the nucleation layer 22 and comprises preferably circular openings exposing areas of the nucleation layer 22. These openings typically have different dimensions, for example different diameters, depending on the areas considered, in particular each of the sub-pixels of the pixel array. The openings can be distributed regularly within each area, for example in the form of an ordered array. Different pitches d, i.e. the distance separating the centers of two adjacent openings, can be defined depending on said areas and in particular, as will be described further on, depending on the sub-pixels.These openings can be made for example by UV or DUV lithography (acronym for Deep UV), by electron beam lithography or by NIL (acronym for Nanoinprint lithography). Such a masking layer 23 allows localized growth of a 3D structure such as a nanowire from the nucleation layer 22 and at each opening. The lower part of the 3D structure then rests on the nucleation layer of the substrate 2 via its base. The photo-elements 10 are distributed over the entire screen in its dimensions according to the x and y directions. The dimensions and limits of a sub-pixel in the xy plane are typically defined by an area of ​​the substrate 2, called the implantation area, from which the photo-elements 10 forming the network of the sub-pixel are grown.

[0073] The term "photo-element" means an active element, i.e. one capable of emitting radiation, but it is understood that each of these elements can be electrically powered or not and thus be "on" or "off".

[0074] An active photoelement 10 or active nanowire 10 comprises an active region 11 and is typically electrically connected. This active region 11 is the site of radiative recombinations of electron-hole pairs making it possible to obtain light radiation having a main wavelength. The active region 11 typically comprises a plurality of quantum wells, for example formed by emissive layers based on GaN, InN, InGaN, AIGaN, AIN, AlInGaN, GaP, AIGaP, AlInGap, AIGaAs, GaAs, InGaAs, AIIIAs, or a combination of several of these materials.

[0075] As mentioned previously, a sub-pixel is typically formed by an array of photoelements 10 as just described. Such an array consists of a photonic crystal that can be described by several parameters and in particular:

[0076] • the emission wavelength,

[0077] • no network,

[0078] • the filling rate, also called opening rate or density, generally between 10 and 90%,

[0079] • the type of mesh (hexagonal, square, etc.),

[0080] • the refractive index of the material filling the spaces between the photo-elements 10, commonly called “filler”, preferably between 1 and 1.7,

[0081] • the constituent materials of the photo-elements 10, and

[0082] • the dimensions of the photo-elements 10.

[0083] The photo-element arrays 10 forming the first sub-pixels 110, 210 emit in a first wavelength range corresponding to the first color C1, while the photo-element arrays 10 forming the second sub-pixels 120, 220 emit in a second wavelength range corresponding to the second color C2.

[0084] An array of photo-elements within the meaning of the invention is continuous, that is to say that the photo-elements that compose it are arranged regularly, according to a given pitch, possibly several given pitches defined in different directions of space. The fact that an array is continuous is also characterized by the fact that all the photo-elements that compose it are based on the same material and have the same dimensions (typically the same diameter). In this sense, it can be said that the photo-elements of the same array are homogeneous and regular. It is understood that the homogeneity and regularity of an array of photo-elements is to be evaluated by taking into account the margins of error in manufacturing the latter. Furthermore, a continuous array does not have any walls within it. The emission of each of the arrays is preferably mainly in a direction perpendicular to the upper face 20 of the substrate 2.According to an advantageous example, the photoelements are configured to emit a beam whose intensity in a direction perpendicular to the upper face 20 of the substrate 2 (called normal to the substrate) is at least 20% greater than the maximum intensity of a Lambertian light emission whose total luminous flux over 4 sr is equal to the total flux over 4 sr of the beam emitted by the photoelements. The luminous intensities in question are typically expressed in W.sr-1.

[0085] Advantageously, the luminous flux emitted by each of the gratings in a cone defined by an angle of substantially 30° relative to the normal to the substrate 2 is twice as high, preferably three times as high, and very advantageously four times as high, than if the beam came from a Lambertian source. Advantageously, the luminous intensity emitted by each of the gratings along the normal to the substrate 2 is twice as high, preferably four times as high, and very advantageously fifteen times as high, than if the beam came from a Lambertian source.

[0086] An emission directed mainly perpendicular to the upper face 20 of the substrate 2 makes it possible to prevent the photo-elements corresponding to a pixel or sub-pixel from illuminating the photo-elements of a neighboring pixel or sub-pixel. Thus, isolation of the illumination of the different pixels or sub-pixels is guaranteed without the need to create walls between these elements. This avoids breaking the continuity and symmetry of the photonic crystals formed by the arrays of photo-elements. In other words, the fact that the photo-elements emit mainly perpendicular to the upper face 20 of the substrate 2 makes it possible to increase the dimensions of the photonic crystals and therefore to improve their quality.

[0087] The photoelements of the same array have diameters substantially equal to a target value. It is understood that, due to inaccuracies resulting from the manufacturing processes, it is difficult for the photoelements 10 of the same array to all have a diameter equal to this target value. Variations in the value of the diameter of a nanowire, for example, due to manufacturing hazards, can be estimated at approximately 10% of the target value. The same applies to the value of the pitch between two neighboring photoelements. For this reason, not all the photoelements 10 emit at exactly the same wavelength. The photoelements 10 of an array of photoelements 10 emit in a range of wavelengths characterizing the array.We understand that a network of N photo-elements each emitting light radiation characterized by a wavelength Ài with 1 <i<N, Ài étant compris dans la plage d’émission du réseau, et tous avec une même intensité, émet un rayonnement global à une longueur d’onde de réseau Àréseau définie par :.

[0088] The so-called grating wavelengths characterizing the light rays emitted by the gratings forming the first sub-pixels 110, 210 (À1) and the second sub-pixels 120, 220 (À2) are notably defined in this way. Of course, if all the photo-elements 10 do not emit with the same intensity, the different components of the grating wavelength, that is to say the wavelengths of the radiation emitted by each of the photo-elements 10, can be weighted by coefficients relating to their respective intensities.

[0089] The first sub-pixels and the second sub-pixels emit radiation corresponding to distinct colors C1 and C2. The two wavelength ranges of the two gratings 100, 200 are considered to be distinct if the wavelengths of gratings λ1, λ2 characterizing them satisfy the following relationship: — -^2001 > 30 nm

[0090] In practice, the wavelengths λ1 , λ2 characterizing the colors C1 , C2 of the first sub-pixels and the second sub-pixels respectively belong to very distant ranges. For example, λ1 is in a range corresponding to a shade of red (between 620 and 800 nm), green (between 520 and 565 nm) or blue (between 430 and 520 nm), and λ2 in another of these ranges. These ranges are around the wavelengths fixed by the International Commission on Illumination (CIE) for the three physical primary colors: 700 nm for red, 536.1 nm for green and 435.8 nm for blue. Ideally, the wavelengths emitted by the photo-element arrays are close to these values.

[0091] The photonic crystals formed by the arrays of photoelements are preferably sized and configured to amplify the emission of the photoelements. For a given photonic crystal, this amplification is effective in the wavelength range corresponding to the color emitted by said photonic crystal. As will become apparent later, this color corresponds to that of the sub-pixel formed by the photonic crystal in question.

[0092] As mentioned previously, the emission by the first sub-pixels 110, 210 and the second sub-pixels 120, 220 of the colors C1 and C2 respectively is notably enabled by the dimensioning of their respective arrays of photo-elements 10. As illustrated in FIG. 7, the photo-elements 111, 211 forming the first sub-pixels 110, 210 have first target diameters d10 and are spaced apart by a first target pitch p10. In the same way, the photo-elements 121, 221 forming the second sub-pixels 120, 220 have second target diameters d20 and are spaced apart by a second target pitch p20.

[0093] The pixel network 1 has the particularity of being able to be defined by an elementary pattern 1000 whose repetition in the first direction x and in the second direction y makes it possible to reconstitute the entire network.

[0094] More precisely, as shown in Figure 1, a first dimension L1 of the elementary pattern 1000 is defined along the first direction x and a second dimension L2 of the elementary pattern 1000 along the second direction y. The pixel array 1 is then made up of a repetition of the elementary pattern 1000 according to a first pitch of a value of L1 along the first direction x and according to a second pitch of a value of L2 along the second direction y. In other words, the pixel array 1 can be obtained by repetition of the elementary pattern 1000 at each node of a network whose basic vectors are defined by the following formulas: h ~ iy ~ 2llyll The elementary pattern 1000 is characterized not only by its geometric shape but also by the colored areas, corresponding to sub-pixels, that it contains. Thus, in the definition of the elementary pattern 1000, two areas are considered identical only if they have the same shape and can emit the same color.

[0095] The elementary pattern 1000 comprises at least a first pixel 100 and a second pixel 200, as shown in FIG. 1. The first pixel 100 comprises at least a first sub-pixel 110 of the first color C1 and a second sub-pixel 120 of the second color C2. The second pixel 200 also comprises at least a first sub-pixel 210 of the first color C1 and a second sub-pixel 220 of the second color C2. The first pixel 100 and the second pixel 200 are in direct contact. By “contact between two pixels” is meant the contact at the substrate 2 between the implantation zones defining the limits in the xy plane of each of the two pixels. There is typically no physical contact between photo-elements 111, 121 forming the first pixel 100 and photo-elements 211, 221 forming the second pixel. The contact between the first pixel 100 and the second pixel 200 is made according to a plane called the contact plane 12.This contact plane 12 defines a plane of symmetry of the elementary pattern 1000. Indeed, as represented in FIG. 1, the first sub-pixel of the first pixel 110 and the first sub-pixel of the second pixel 210 on the one hand and the second sub-pixel of the first pixel 120 and the second sub-pixel of the second pixel 220 on the other hand are symmetrical with respect to the contact plane 12, both from the geometric point of view and from the colors emitted by each of the sub-pixels.

[0096] Due to this symmetry, sub-pixels emitting the same color - in Figure 1: the first sub-pixel of the first pixel 110 and the first pixel of the second sub-pixel 210, both emitting the first color C1 - are in contact. Thus, two arrays of photo-elements 111, 211 having substantially identical structural characteristics - here a first target diameter d10 and a first target pitch or spacing p10 - are in contact. In this way, an array of photo-elements 111, 211 is formed with dimensions twice those of an array of photo-elements forming a single sub-pixel 110, 210.

[0097] Furthermore, by definition of the elementary pattern 1000, the latter is repeated at a pitch L1 along the first direction x and at a pitch L2 along the second direction y. This implies, due to the internal symmetry of the elementary pattern 1000, the contact of other networks having the same structural characteristics. It can be noted for example in FIG. 1 that, due to the repetition of the elementary pattern 1000 in the second direction y, the second sub-pixels 120, 220 are in contact with sub-pixels of other pixels emitting the same color and therefore sized in a similar manner.Furthermore, if, as is the case in the illustration of Figure 1, the sub-pixels extend in the first direction x over the entire dimension L1 of the elementary pattern 1000, then, due to the repetition of the elementary pattern 1000 in this same first direction x, each of the sub-pixels is in contact with sub-pixels of adjacent pixels along x having the same structural characteristics. It can be seen in this same Figure 1 that similar photo-element arrays are thus formed extending from one end of the display screen to the other along the first direction x. The same considerations can apply mutatis mutandis to the case where the contact plane 12 defining the symmetry of the elementary pattern 1000 extends parallel to the yz plane rather than to the xz plane.

[0098] These adjacencies of similar networks (within the elementary pattern 1000 or between two repetitions of the elementary pattern 1000) have many advantages. First of all, this makes it possible to reduce the number of abrupt transition zones 5 between distinct photonic networks. This therefore reduces the number of zones creating symmetry breaks. Since these zones are responsible for growth defects and losses in optical quality, the quality of the photo-element network 10 and ultimately that of the display screen is improved. In addition, the formation of the photo-elements 10 is facilitated. Indeed, the latter is done by successive masking and deposition steps, which are all the more complex to carry out as the identical photo-element networks are of small dimensions. In particular, the smaller the dimensions of the implantation zones, the more it is necessary for the photolithography masks to be precisely aligned.Furthermore, increasing the dimensions of a continuous photonic crystal of 10 photo-elements, and therefore the number of photo-elements that compose it, makes it possible to improve its capacity to discriminate waves according to their wavelength. In other words, the more extended the photonic crystal, the better the control and amplification of the wavelengths propagating therein. Furthermore, increasing the dimensions of the photonic crystal makes it possible to improve its capacity to ensure good emission directionality. This plays an important role, in particular, in the possibility of doing without walls between sub-pixels and / or adjacent pixels.

[0099] A photonic crystal can operate as such from three rows of photoelements. The greater the number of rows of photoelements forming the photonic crystal, the better the quality of the photonic crystal will be obtained. Thus, advantageously, the photonic crystals are each formed by at least 10 rows, preferably 20 rows, and even more preferably 50 rows of photoelements.

[0100] Figures 2 to 5B illustrate other embodiments of the present invention. All are characterized by the fact that the elementary pattern 1000 has at least one plane of symmetry. In each of these examples, the existence of this plane or these planes of symmetry and the repetition of the elementary pattern 1000 in the xy plane allow the reduction of the number of abrupt transition zones 5 and the optimization of the manufacture of the photo-element arrays 10.

[0101] Figure 2 illustrates an embodiment in which each of the two pixels 100, 200 of the elementary pattern 1000 further comprises a third sub-pixel 130, 230 emitting a third color C3 advantageously distinct from the first color C1 and the second color C2. In this example, within the elementary pattern 1000, only the first sub-pixel of the first pixel 110 and the first pixel of the second pixel 210 are in contact. In the embodiment illustrated in Figure 3, the second sub-pixel of the first pixel 120 and the second sub-pixel of the second pixel 220 are also in contact along the contact plane 12.

[0102] Another embodiment will now be described with reference to Figure 4. In this example, the elementary pattern 1000 further comprises a third pixel 300 and a fourth pixel 400. Each pixel 100, 200, 300, 400 comprises a first sub-pixel 110, 210, 310, 410, a second sub-pixel 120, 220, 320, 420, a third sub-pixel 130, 230, 330, 430 and a fourth sub-pixel 140, 240, 340, 440, respectively emitting the first color C1, the second color C2, a third color C3 and a fourth color C4. In this embodiment, the four colors C1, C2, C3 and C4 are distinct from each other. The photo-element arrays forming the third sub-pixels 130, 230, 330, 430 have a third target diameter d30 and a third spacing p30, while the photo-element arrays forming the fourth sub-pixels 140, 240, 340, 440 have a fourth target diameter d40 and a fourth spacing p40.

[0103] The following contact plans are defined:

[0104] • A first contact plane 12 between the first pixel 100 and the second pixel 200, defining a first plane of symmetry of the elementary pattern 1000,

[0105] • A second contact plane 23 between the second pixel 200 and the third pixel 300, defining a second plane of symmetry of the elementary pattern 1000,

[0106] • A third contact plane 34 between the third pixel 300 and the fourth pixel 400, defining a third plane of symmetry of the elementary pattern 1000,

[0107] • A fourth contact plane 14 between the first pixel 100 and the fourth pixel 400, defining a fourth plane of symmetry of the elementary pattern 1000.

[0108] It is noted in Figure 4 that, due to these internal symmetries in the elementary pattern 1000, an array of photo-elements emitting the third color C3 is formed from the four third sub-pixels 130, 230, 330, 430, with dimensions four times greater than those of an array of photo-elements forming a single third sub-pixel 130, 230, 330, 430. It is also noted that, due to the repetition of the elementary pattern 1000 in the xy plane, the other sub-pixels are also in contact with similar sub-pixels (i.e. emitting the same color), but this time belonging to neighboring elementary patterns.

[0109] Figure 5A illustrates an embodiment very similar to that of Figure 4, but in which the colors are identical two by two (apart from slight nuances due to manufacturing defects). In the example illustrated, the first color C1 and the third color C3 on the one hand and the second color C2 and the fourth color C4 are identical.

[0110] In an embodiment illustrated in Figure 5B, the elementary pattern 1000 comprises two pixels 100, 200 each comprising four sub-pixels two by two of the same color. The two sub-pixels 100, 200 are in contact along a contact plane 12 defining a plane of symmetry of the elementary pattern 1000. Here again, the symmetry within the elementary pattern 1000 and the repetition of the elementary pattern 1000 in the xy plane ensure the adjacency of identical sub-pixels two by two.

[0111] It should be noted that the choice of the number of subpixels within the pixels, their arrangement and the colors they emit depends on the intended display applications.

[0112] As illustrated in Figure 6, the display screen advantageously comprises electrical contacts 3 for electrically powering the photo-elements 10. These electrical contacts 3 may be common to a plurality of photo-elements 10. Preferably, photo-elements 10 belonging to arrays forming distinct sub-pixels are powered separately. Thus, even if the arrays forming two neighboring sub-pixels have been formed simultaneously and form a continuous set of similar photo-elements, the two sub-pixels remain independent from an electrical point of view. It may indeed be necessary for the rendering of the image for both sub-pixels to be lit, both sub-pixels to be extinguished, or only one to be lit. These electrical contacts 3 are connected to control electronics 4 for controlling the switching on or off of the photo-elements 10 according to the display requirements.The representation in Figure 6 of the control electronics 4 is purely illustrative. In particular, the assignment of the various transistors to the various photo-elements as well as their connections are in no way limiting. For example, the photo-elements are also typically connected at another pole to an electrical connection not shown for reasons of clarity.

[0113] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention.

Claims

Claims 1. Display screen comprising a pixel array (1) extending mainly along a plane defined by a first direction (x) and a second direction (y), having an elementary pattern (1000), which is the smallest geometric pattern comprising different colored areas whose repetition by translation in the first direction (x) according to a first pitch equal to the value of a first dimension (L1) of the elementary pattern (1000) according to the first direction (x) and by translation in the second direction (y) according to a pitch equal to the value of a second dimension (L2) of the elementary pattern (1000) according to the second direction (y) makes it possible to obtain the pixel array (1) in its entirety, comprising a plurality of pixels comprising at least a first pixel (100) and a second pixel (200), each pixel of the plurality of pixels comprising at least a first sub-pixel (110, 210) of a first color and a second sub-pixel (120,220) of a second color distinct from the first color and each pixel among the plurality of pixels being in contact with at least one other pixel of the plurality of pixels, characterized in that the contact between two pixels in contact is defined by a contact plane defining a plane of symmetry of said elementary pattern (1000)., 2. Display screen according to the preceding claim wherein the plurality of pixels further comprises a third pixel (300) and a fourth pixel (400).

3. A display screen according to any preceding claim wherein each pixel of the plurality of pixels further comprises a third sub-pixel (130, 230) of a third color.

4. Display screen according to the preceding claim in which the third color is distinct from the first color and the second color.

5. Display screen according to the preceding claim in which the first sub-pixel of the first pixel (110) and the first sub-pixel of the second pixel (210) on the one hand and the second sub-pixel of the first pixel (120) and the second sub-pixel of the second pixel (220) on the other hand are in contact within the elementary pattern (1000).

6. Display screen according to any one of the three preceding claims wherein each pixel further comprises a fourth sub-pixel (140, 240) of a fourth color.

7. Display screen according to the preceding claim in which the fourth color is distinct from the first color and the second color.

8. Display screen according to the preceding claim in combination with any one of claims 3 to 5 in which the fourth color is distinct from the third color.

9. The display screen of claim 6 wherein the third color is identical to one of the first color and the second color and the fourth color is identical to the other of the first color and the second color.

10. Display screen according to any one of the preceding claims in which the first sub-pixel of the first pixel (110) and the first sub-pixel of the second pixel (210) on the one hand and the second sub-pixel of the first pixel (10) and the second sub-pixel of the second pixel (220) on the other hand are powered by separate electrical contacts.

11. Display screen according to any one of the preceding claims in which the pixel array (1) is formed by a set of photo-elements.

12. Display screen according to the preceding claim in which the set of photoelements comprises a plurality of continuous photoelement arrays, each continuous photoelement array extending over at least two adjacent sub-pixels belonging to distinct pixels of the plurality of pixels.

13. Display screen according to the preceding claim in which each continuous array of photo-elements forms a photonic crystal.

14. A display screen according to any one of claims 11 to 13 wherein each pixel of the plurality of pixels comprises a plurality of sub-pixels, and wherein the adjacent and same-colored sub-pixels belonging to distinct pixels are formed by a continuous array of photo-elements.

15. Display screen according to any one of claims 11 to 14 wherein, within the elementary pattern (1000), the first sub-pixels (110, 210) are formed by a first continuous array of photo-elements which emits in a first range of wavelengths corresponding to the first color.

16. Display screen according to any one of claims 11 to 15 wherein the second sub-pixels (120, 220) are formed by a second continuous array of photoelements which emits in a second wavelength range corresponding to the second color.

17. Display screen according to either of the two preceding claims, in which the photo-elements are configured to emit a beam whose intensity in a direction perpendicular to an upper face (20) of a substrate (2) from which said photo-elements extend is at least 20% greater than the maximum intensity of an emission by a Lambertian light source whose total luminous flux over 4TT sr is equal to the total flux over 4TT sr of the beam emitted by the photo-elements.

18. Display screen according to any one of claims 11 to 17 in which the photo-elements are nanowires.

19. Display screen according to any one of the preceding claims comprising a monolithic support carrying all of the pixels of the pixel array (1).

Images