Display screen with reduced transitions between sub-pixels

Abstract

The invention relates to a display screen comprising a plurality of pixels including at least a first and a second pixel (1000, 2000) that are in contact, the first pixel comprising at least a first sub-pixel (1100) of a first colour (C1) and a second sub-pixel (1200) of a second colour (C2), and the second pixel comprising at least a first sub-pixel (2100) of the first colour and a second sub-pixel (2200) of the second colour, the first sub-pixels, on the one hand, and the second sub-pixels, on the other hand, being in contact. The screen comprises a set of photoelements (10) comprising a first array (100) of photoelements emitting the first colour and a second array (200) of photoelements emitting the second colour. The first sub-pixels and the second sub-pixels are formed by the first array and the second array of photoelements, respectively.

Description

[0001] "Display screen with reduced transitions between subpixels"

[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 substantially in 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. Typically, an LED makes it possible to emit 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 present structural differences from one sub-pixel to another. These differences create design difficulties: the production of a display screen requires the side-by-side manufacture of nanowires with very precise and, above all, distinct diameters and pitches. 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. It is therefore understandable that the manufacture of a display screen involves a succession of technological steps at the scale of a sub-pixel, which presents significant technical constraints (need for high precision in the alignment of lithography masks, etc.) and can lead to structural defects (edge ​​effects, etc.).

[0006] Moreover, the classic type of arrangement of subpixels within a pixel, illustrated in Figure 12, does not provide optimal performance.

[0007] 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.

[0008] SUMMARY

[0009] To achieve this objective, according to one embodiment, a display screen is provided comprising:

[0010] - a plurality of pixels comprising at least a first pixel and a second pixel, the first pixel and the second pixel being in contact, the first pixel comprising at least a first sub-pixel of a first color, and the second pixel comprising at least a first sub-pixel of the first color, the first sub-pixel of the first pixel and the first sub-pixel of the second pixel being in contact, and

[0011] - a set of photo-elements comprising at least a first continuous array of photo-elements which emits in a first range of wavelengths corresponding to the first color.

[0012] The device is further characterized in that the first subpixel of the first pixel and the first subpixel of the second pixel are both formed by the first array of photoelements.

[0013] A major challenge 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. When a sub-pixel of a given color is formed by a photonic crystal, this photonic crystal has structural characteristics (diameter of the nanowires, 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. The presence of these abrupt transition zones has the disadvantage of breaking the symmetry of the network and, consequently, of creating detrimental edge effects during the growth of the nanowires. 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 highly 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.

[0014] Arranging the subpixels so that subpixels of the same color from neighboring pixels are in contact reduces the number of abrupt transition zones. This is because two subpixels of the same color are formed by photonic crystals with the same structural properties. There are therefore no abrupt transition zones between them.

[0015] If we consider, for example, two pixels each comprising two sub-pixels of two distinct colors, the contact between these pixels being made, as is usually the case, between a sub-pixel of the first pixel of a first color and a sub-pixel of the second pixel of a second color, we can usually count, at the scale of these two pixels, three abrupt transition zones: one within each pixel and one at the interface between the two pixels. By bringing the two pixels into contact at the level of sub-pixels having the same color, i.e. formed by substantially identical photo-element arrays, one of the three abrupt transition zones is eliminated. This reasoning can be extended to the scale of a display screen in its entirety, comprising up to millions of pixels. It is therefore understood that bringing sub-pixels of the same color into contact makes it possible to improve the quality of the photo-element arrays and therefore of the screen itself.

[0016] Furthermore, by bringing two sub-pixels of the same color into contact, a network of photoelements common to both sub-pixels is created. This common network of photoelements has, by definition, dimensions greater than those of a network forming a single sub-pixel. The network forming two neighboring sub-pixels of the same color can thus be formed more easily than two separate networks corresponding to each of the two sub-pixels. The photonic crystal forming the network, by construction also of dimensions greater than the photonic crystals used in the same context in the prior art, also has better performance due to the increase in its dimensions. The proposed arrangement therefore makes it possible to optimize the manufacture of the display screen, to limit the appearance of structural defects and to improve the visual rendering.

[0017] BRIEF DESCRIPTION OF THE FIGURES

[0018] 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:

[0019] Figure 1 represents a sectional view of an intermediate step in the manufacture of the photoelements included in a display screen according to one of the embodiments of the invention.

[0020] Figures 2A and 2B show embodiments of the invention in which the display screen comprises two pixels each comprising two sub-pixels.

[0021] Figure 3 shows an embodiment of the invention in which the display screen comprises two pixels each comprising three sub-pixels.

[0022] Figures 4, 5 and 6 show embodiments of the invention in which the display screen comprises three pixels.

[0023] Figures 7, 8, 9A and 9B show embodiments of the invention in which the display screen comprises four pixels.

[0024] Figure 10 illustrates a particular embodiment of the invention.

[0025] Figure 11 represents a sectional view of a display screen according to the invention and illustrates in particular control electronics for powering the photo-elements. Figure 12 represents a display screen according to the prior art comprising four pixels and having abrupt transition zones between all the sub-pixels.

[0026] 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.

[0027] DETAILED DESCRIPTION

[0028] 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:

[0029] According to an advantageous embodiment, the first pixel comprises a second sub-pixel of a second color and the second pixel comprises a second sub-pixel of the second color, the second sub-pixel of the first pixel and the second sub-pixel of the second pixel being in contact, the display screen further comprising a second continuous array of photo-elements which emits in a second wavelength range corresponding to the second color, the first wavelength range and the second wavelength range being distinct, the second sub-pixel of the first pixel and the second sub-pixel of the second pixel both being formed by the second array of photo-elements.

[0030] According to one embodiment:

[0031] - the first pixel further comprises a third sub-pixel of a third color,

[0032] - the second pixel further comprises a third sub-pixel of the third color,

[0033] - the photoelement assembly comprises a third continuous photoelement array which emits in a third wavelength range corresponding to the third color, the third wavelength range being distinct from the first wavelength range and the second wavelength range, and the third subpixel of the first pixel and the third subpixel of the second pixel are in contact and both formed by the third photoelement array.

[0034] According to one embodiment, the plurality of pixels comprises at least one third pixel in contact with the first pixel, the first pixel further comprises a third sub-pixel of a third color, the second pixel further comprises a third sub-pixel of the third color, and the third pixel comprises at least one third sub-pixel of the third color, the third sub-pixel of the first pixel and the third sub-pixel of the third pixel being in contact. In this same embodiment, the set of photo elements comprises a third array of photo elements which emits in a third wavelength range corresponding to the third color, the third wavelength range being distinct from the first wavelength range and the second wavelength range. The third sub-pixel of the first pixel and the third sub-pixel of the third pixel are then both formed by the third array of photo elements.

[0035] According to one embodiment, the contact between the first pixel and the second pixel is made along a first contact line and the contact between the first pixel and the third pixel is made along a second contact line, the first contact line and the second contact line being parallel and not coincident.

[0036] According to one embodiment, the contact between the first pixel and the second pixel is made along a first contact line and the contact between the first pixel and the third pixel is made along a second contact line, the first contact line and the second contact line forming an angle, called contact angle, between 5° and 175°, preferably between 30° and 150°.

[0037] In an advantageous example, the contact angle is equal to 120°. This is particularly the case when the pixels each have the shape of a regular hexagon.

[0038] According to one embodiment, the contact between the first pixel and the second pixel is made along a first contact line and the contact between the first pixel and the third pixel is made along a second contact line, the first contact line and the second contact line being perpendicular. Thus, according to an advantageous example, the contact angle is equal to 90°. This is particularly the case when the pixels each have a rectangular or even square shape.

[0039] According to one embodiment, the third pixel further comprises a second sub-pixel of the second color in contact with the second sub-pixel of the first pixel, and the second sub-pixel of the third pixel is formed by the second array of photo-elements.

[0040] According to one embodiment, the plurality of pixels comprises at least a fourth pixel in contact with the second pixel and the third pixel, the fourth pixel comprising at least a second sub-pixel of the second color, the second sub-pixel of the second pixel and the second sub-pixel of the fourth pixel on the one hand and the second sub-pixel of the third pixel and the second sub-pixel of the fourth pixel on the other hand being in contact, and the second sub-pixel of the fourth pixel is formed by the second array of photo-elements.

[0041] According to one embodiment, the second pixel further comprises a third sub-pixel of the third color and the fourth pixel further comprises a third sub-pixel of the third color, the third sub-pixel of the second pixel and the third sub-pixel of the fourth pixel being in contact and both being formed by a third continuous secondary array of photo-elements which emits in the third wavelength range.

[0042] According to one embodiment, the third pixel further comprises a first sub-pixel of the first color and the fourth pixel comprises at least one first sub-pixel of the first color, the first sub-pixel of the third pixel and the first sub-pixel of the fourth pixel being in contact and both being formed by a first continuous secondary array of photo-elements which emits in the first wavelength range.

[0043] According to an advantageous example, the first array of photo-elements extends over at least two pixels other than the first pixel and the second pixel.

[0044] According to an advantageous example, each array of photo-elements is common to at least two adjacent pixels, preferably to at least four adjacent pixels.

[0045] According to an advantageous example, each array of photo-elements forming a sub-pixel of the first pixel also forms at least one sub-pixel of at least one pixel adjacent to the first pixel. This may also be the case for any other pixel of the plurality of pixels. According to an advantageous embodiment, 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 4TT sr of the beam emitted by the photo-elements.

[0046] According to a preferred example, the first array of photoelements forms a photonic crystal.

[0047] According to one embodiment, the display screen further comprises a plurality of distinct electrical contacts, each electrical contact being configured to power the photo-elements of an array of photo-elements forming a distinct sub-pixel.

[0048] In one example, photoelements are nanowires.

[0049] 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 carrying out 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.

[0050] According to one embodiment, the display screen comprises at least two separate electrical contacts, one being configured to power the photo-elements of the first array of photo-elements forming the first sub-pixel of the first pixel and the other being configured to power the photo-elements of the first array of photo-elements forming the first sub-pixel of the second pixel.

[0051] In the present invention, the display screen is a single continuous screen having a face configured to display an image at a given time.

[0052] 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.

[0053] 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.

[0054] A wire or nanowire is understood to mean 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 pm (1 pm = 10-6 m).

[0055] The diameter of a nanowire is understood to mean the largest transverse dimension of this nanowire. In the present invention, the 3D structures do not necessarily have a circular cross-section. The 3D structures may in particular have a hexagonal or polygonal cross-section. In particular, in the case of 3D structures based on GaN, this cross-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 cross-section and the diameter of a circumscribed circle of this polygon. In the present patent application, the terms "light-emitting diode", "LED" or simply "diode" are used synonymously. An "LED" may also be understood to mean a "micro-LED". A "micro-LED" is an LED whose dimensions do not exceed 1 mm (1 mm = 10-3 m).

[0056] 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.

[0057] 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.

[0058] 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.

[0059] A substrate, a layer, a device, "based" on a material M, is understood to mean 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.

[0060] A reference frame, preferably orthonormal, comprising the x, y, z axes is shown in the attached figures.

[0061] 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.

[0062] To determine the geometry of 3D structures and the compositions of the different elements (wire, active region, collar for example) of these 3D structures, we can carry out Scanning Electron Microscopy (SEM) or Transmission Electron Microscopy (TEM) analyses or even STEM (Scanning Transmission Electron Microscopy).

[0063] 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, wide angle diffraction HAADF (acronym for "High Angle Annular Dark Field"). The chemical compositions of the different elements can be determined using the well-known EDX or X-EDS method, acronym for "energy dispersive x-ray spectroscopy" which means "energy dispersive analysis of X-ray photons".

[0064] 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).

[0065] 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.

[0066] Cathodoluminescence (CL) and photoluminescence (PL) spectroscopies are well suited to optically characterize the 3D structures described in the present invention.

[0067] The above-mentioned techniques 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.

[0068] A display screen according to one embodiment of the invention will now be described with reference to Figures 1 to 2B.

[0069] The display screen extends mainly along the xy plane shown in Figures 1 and 2A. It comprises a set of photo-elements 10, for example 3D structures of the nanowire type. These photo-elements 10 typically extend from a substrate 2 extending along the xy plane. The substrate 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, as shown in Figure 1.

[0070] The support 21 may be made of sapphire in particular to limit the mesh parameter mismatch with the GaN if the photo-elements 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 AlN. It may alternatively be based on other metal nitrides, for example GaN or AIGaN. It may be formed on the silicon support 21 by epitaxy, preferably by vapor phase epitaxy with organometallic precursors MOVPE (acronym for “MetalOrganic Vapor Phase Epitaxy”). In a known manner, one or more intermediate buffer layers may 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 may 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 Si and AIN, GaN or AIGaN) 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) 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 the areas corresponding to the first LED and / or the first transition area and / or the second LED and / or the second transition area, etc. The openings can be distributed regularly within each area, for example in the form of an ordered network. Different pitches, iethe distance separating the centers of two adjacent openings, can be defined as a function of said zones and in particular, as will be described further on, as a function of the sub-pixels. These openings can be produced 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 the level of each opening. The lower part of the 3D structure then rests on the nucleation layer of the substrate 2 via its base.

[0073] The set of photo-elements 10 is continuous and is distributed over the entire screen in its dimensions according to the x and y directions.

[0074] 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".

[0075] 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, AHnGaN, GaP, AIGaP, AHnGaP, AIGaAs, GaAs, InGaAs, AllnAs, or a combination of several of these materials.

[0076] The set of photo-elements 10 comprises a first array 100 of photo-elements and a second array 200 of photo-elements. An array of photo-elements is defined as a subset of the set of photo-elements 10. 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 network has no walls within it.

[0077] Each of these networks forms a photonic crystal and can be defined by several parameters, including: the emission wavelength, the network pitch, the filling rate, also called opening rate or density, generally between 10 and 90%, the type of mesh (hexagonal, square, etc.), the refractive index of the material filling the spaces between the nanowires 101 , commonly called “filler”, preferably between 1 and 1.7, the constituent materials of the photoelements, and the dimensions of the nanowires.

[0078] The emission of each of the gratings 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 on 4TT sr is equal to the total flux on 4TT sr of the beam emitted by the photoelements. The luminous intensities in question are typically expressed in W.sr-1 (watts per steradians). 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, as if the beam came from a Lambertian source.Advantageously, the light intensity emitted by each of the gratings according to 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.

[0079] 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.The first array 100 of photo-elements emits in a first wavelength range corresponding to a first color C1 while the second array 200 of photo-elements emits in a second wavelength range corresponding to a second color C2 distinct from the first color.

[0080] The photoelements in the same array have diameters that are substantially equal to a target value. It is understood that, due to inaccuracies resulting from manufacturing processes, it is difficult for the photoelements in the same array to all have a diameter equal to this target value. Variations in the diameter value of a nanowire, for example, due to manufacturing hazards, can be estimated at approximately 10% of the target value. The same applies to the pitch value between two neighboring photoelements. For this reason, not all photoelements emit at exactly the same wavelength. The photoelements in an array of photoelements 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 :.

[0081] Àwo network wavelengths, 2O o of the first array of photo-elements 100 and of the second array of photo-elements 200 are notably defined in this way. Of course, if all the photo-elements do not emit with the same intensity, the different components of the array wavelength, that is to say the wavelengths of the radiation emitted by each of the photo-elements, can be weighted by coefficients relating to their respective intensities.

[0082] The first array of photo-elements 100 and the second array of photo-elements 200 emit radiation corresponding to distinct colors C1 and C2. The two wavelength ranges of the two arrays 100, 200 are considered to be distinct if the array wavelengths λwo, 2O o characterizing them verify the following relation: l^ioo — ^2001 > 30 nm

[0083] In practice, the wavelengths wo, 2O o characterizing the colors C1, C2 of the first network 100 and of the second network 200 respectively belong to very distant ranges. For example, wo is in a range corresponding to a shade of red (between 620 to 800 nm), green (between 520 to 565 nm) or blue (between 430 to 520 nm), and 2Oo in another of these ranges. These ranges are located around the wavelengths set 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 photoelement arrays are close to these values.

[0084] 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.

[0085] The display screen further comprises a plurality of pixels. This plurality of pixels notably comprises a first pixel 1000 and a second pixel 2000. The first pixel 1000 and the second pixel 2000 are in contact.

[0086] Each of the pixels of the plurality of pixels comprises at least a first sub-pixel and a second sub-pixel. This notably defines a first sub-pixel of the first pixel 1100, a second sub-pixel of the first pixel 1200, a first sub-pixel of the second pixel 2100 and a second sub-pixel of the second pixel 2200, all represented in FIG. 2A.

[0087] Each subpixel has a color in the visible range. More precisely, the first subpixels 1100, 2100 are of the first color C1 and the second subpixels 1200, 2200 are of the second color C2.

[0088] As illustrated in Figures 2A and 2B:

[0089] - the first subpixel of the first pixel 1100 and the first subpixel of the second 2100 are in contact, and

[0090] - the second sub-pixel of the first pixel 1200 and the second sub-pixel of the second pixel 2200 are also in contact.

[0091] Figure 2A illustrates an embodiment in which each of the pixels 1000, 2000 comprises more than two sub-pixels. Figure 2B represents a case where each of the pixels 1000, 2000 consists of only two sub-pixels.

[0092] The display screen can be characterized by its set of photo-elements or by its set of pixels. These two sets are however entirely linked because the different sub-pixels are formed by the different arrays of photo-elements. More precisely, the first sub-pixels 1100, 2100 are in particular formed by the first array of photo-elements 100 and the second sub-pixels 1200, 2200 are in particular formed by the second array of photo-elements 200. This correspondence is found in particular in the fact that the first array 100 emits radiation at a first array wavelength Xwo corresponding to the first color C1 and that the first sub-pixels 1100, 2100 are of this first color C1. The same applies to the color C2 of the second sub-pixels 1200, 2200, generated by the second array 200.

[0093] An array of photo-elements is thus made up of at least one region, and typically a plurality of regions forming at least one pair of adjacent sub-pixels. These regions are continuous and are made up of photo-elements having substantially identical structural characteristics, apart from manufacturing errors. In the prior art, an array corresponds to only a single region itself corresponding to a single sub-pixel. Thus, the dimensions of the arrays are optimized. This has many advantages. First of all, this arrangement makes it possible to reduce the number of transition zones between arrays forming distinct photonic crystals. 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 array of photo-elements and ultimately that of the display screen is improved. In addition, the formation of the photo-elements is facilitated.Indeed, the latter is done by successive masking and deposition steps, which are all the more complex to carry out as the networks are of small dimensions. In particular, the smaller the dimensions of the areas on which to form photo-elements, the more it is necessary for the photolithography masks to be precisely aligned. In addition, increasing the dimensions of a continuous photonic crystal of 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 the photonic crystal is extended, the better the control and amplification of the wavelengths propagating there. 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.

[0094] 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.

[0095] According to one embodiment, the set of photo-elements comprises a third array 300 of photo-elements. The structural properties of the first and second arrays 100, 200 can be applied mutatis mutandis to the third array 300. The third array 300 of photo-elements emits in a third wavelength range corresponding to a third wavelength λ300 and a third color C3. Preferably, the third wavelength λ300 is in the third range among the previously cited wavelength ranges. For example, if the first color C1 corresponded to a shade of red and the second color C2 to a shade of blue, then the third color C3 typically corresponds to a shade of green.

[0096] This third array 300 of photo-elements makes it possible to form a plurality of third sub-pixels. Figure 3 in particular illustrates an embodiment in which the first pixel 1000 comprises a third sub-pixel called the third sub-pixel of the first pixel 1300 and the second pixel 2000 comprises a third sub-pixel called the third sub-pixel of the second pixel 2300. The second sub-pixels 1200, 2200 on the one hand and the third sub-pixels 1300, 2300 on the other hand are advantageously in contact.

[0097] According to one embodiment, the plurality of pixels comprises a third pixel 3000 in contact with the first pixel 1000. This third pixel 3000 comprises at least one third sub-pixel 3300 in contact with and formed by the same third array of photo-elements 300 as the third sub-pixel of the first pixel 1300.

[0098] As illustrated in Figures 4 and 5, the first pixel 1000 and the second pixel 2000 are in contact and this contact is made along a straight line called the first contact line 12. The contact between the first pixel 1000 and the third pixel 3000 is made along a straight line called the second contact line 13. According to an example illustrated in Figure 4, the first contact line 12 and the second contact line 13 are parallel. In this case, the second pixel 2000 and the third pixel 3000 are located on either side of the first pixel 1000. According to an example illustrated in Figure 5, the first contact line 12 and the second contact line 13 are perpendicular. In the typical case of square-shaped pixels, the second pixel 2000 and the third pixel 3000 border adjacent sides of the first pixel 1000.

[0099] This pooling of the third array of photo-elements 300 between the third sub-pixel of the first pixel 1300 and the third sub-pixel of the third pixel 3300 has the same advantages as the pooling of the first array 100 and the second array 200 between the first sub-pixels 1100, 2100 and second sub-pixels 1200, 2200. It is understood that combining these contactings of sub-pixels of the same color and these poolings of photonic crystals makes it possible to increasingly reduce the number of abrupt transitions 5 between sub-pixels such as those represented for example in FIG. 12.

[0100] Still with the aim of pooling the photo-element networks, the third pixel 3000 may comprise a second sub-pixel 3200 in contact with the second sub-pixel of the first pixel 1200. The second network 200 then forms not only the second sub-pixel of the first network 1200, the second sub-pixel of the second network 2200 but also the second sub-pixel of the third network 3200 (as illustrated in FIG. 6). The corresponding photonic crystal therefore extends over three sub-pixels 1200, 2200, 3200.

[0101] According to one embodiment, the plurality of pixels comprises a fourth pixel 4000 in contact with the first pixel 1000 and with the third pixel 3000. As illustrated in FIG. 7, this fourth pixel 4000 comprises at least one second sub-pixel 4200 in contact with the second sub-pixel of the first pixel 1200 and with the second sub-pixel of the third pixel 3200. The second network 200 then forms the second sub-pixels 1200, 2200, 3200, 4200 of all four pixels 1000, 2000, 3000, 4000.

[0102] As illustrated in Figure 8, according to one embodiment, the second pixel 2000 and the fourth pixel 4000 each comprise a third sub-pixel 2300, 4300. These two sub-pixels are in contact and are both formed by a third secondary network 300' of photo-elements having the same characteristics as the third network 300. The third secondary network 300' and the third network 300 can in particular be manufactured simultaneously.

[0103] As illustrated in Figures 9A and 9B, according to one embodiment, the third pixel 3000 and the fourth pixel 4000 each comprise a first sub-pixel 3100, 4100. These two sub-pixels are in contact and are both formed by a first secondary array 100' of photoelements having the same characteristics as the first array 100. The first secondary array 100' and the first array 100 may in particular be manufactured simultaneously. Figure 9A envisages that the pixels consist of only three sub-pixels. Figure 9B illustrates an embodiment in which the pixels comprise a fourth sub-pixel, which may for example be formed by an array of photoelements shared with a sub-pixel of a neighboring pixel not shown.

[0104] Figure 10 illustrates a particular embodiment in which some pixels are of a single color and adjoin sub-pixels of the same color and belonging to adjacent pixels. For example, as illustrated, the third pixel 3000 is entirely formed by the first array 100, which also forms the first sub-pixel of the first pixel 1100 and the first sub-pixel of the second pixel 2100.

[0105] It is understood that the principle of bringing sub-pixels of the same color into contact and of pooling photonic crystals of the same structure can be extended to a number of pixels greater than four. This idea is also applicable regardless of the number of sub-pixels included in each of the pixels. The distribution of the different photo-element arrays will be a function of the geometry of the pixel and the arrangement of the sub-pixels within the pixels. It should be noted that a highly optimized screen can be obtained by repeating the patterns previously described. For example, by repeating in the xy plane the pattern consisting of the four pixels illustrated in Figure 9A, continuous sets of similar photo-elements (of the type forming the third array 300 and the third secondary array 300') are created extending over four sub-pixels and no longer just two.Similarly, continuous sets of photoelements of the type of those in the first array 100 can be obtained.

[0106] Regardless of the number of pixels and subpixels and the arrangement of subpixels within each pixel, the goal is always to limit the number of contacts between subpixels of different colors.

[0107] As illustrated in Figure 11, the display screen advantageously comprises electrical contacts 3 for electrically powering the photo-elements. These electrical contacts 3 may be common to a plurality of photo-elements. Preferably, photo-elements 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 array of 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.

[0108] These electrical contacts 3 are connected to control electronics 4 for controlling the switching on or off of the photo-elements according to the display requirements. The representation in Figure 11 of the control electronics 4 is purely illustrative. In particular, the allocation of the different transistors to the different 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.

[0109] Figure 11 further illustrates the juxtaposition of three pixels 1000, 2000, 3000. In particular, there is a sectional view of the first sub-pixel of the second pixel 2100, the first sub-pixel of the first pixel 1100, the second sub-pixel of the first pixel 1200 and the second sub-pixel of the third pixel 3200. The first array 100 is formed of photo-elements having a first target diameter d100 and a first target pitch between them p100. The second array 200 is formed of photo-elements having a second target diameter d200 and a second target pitch between them p200. As illustrated, each of these arrays forms two adjacent sub-pixels belonging to neighboring pixels: the first array 100 forms the first sub-pixel of the second pixel 2100 and the first sub-pixel of the first pixel 1100, while the second array 200 forms the second sub-pixel of the first pixel 1200 and the second sub-pixel of the third pixel 3200.

[0110] 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 plurality of pixels comprising at least a first pixel (1000) and a second pixel (2000), the first pixel (1000) and the second pixel (2000) being in contact, the first pixel (1000) comprising at least a first sub-pixel (1100) of a first color (C1) and the second pixel (2000) comprising at least a first sub-pixel (2100) of the first color (C1), the first sub-pixel of the first pixel (1100) and the first sub-pixel of the second pixel (2100) being in contact, and • a set of photo-elements (10) comprising at least a first continuous array of photo-elements (100) which emits in a first wavelength range corresponding to the first color (C1), characterized in that the first sub-pixel of the first pixel (1100) and the first sub-pixel of the second pixel (2100) are both formed by the first array of photo-elements (100).

2. Display screen according to the preceding claim wherein the first pixel (1000) comprises a second sub-pixel (1200) of a second color (C2) and the second pixel (2000) comprises a second sub-pixel (2200) of the second color (C2), the second sub-pixel of the first pixel (1200) and the second sub-pixel of the second pixel (2200) being in contact, the display screen further comprising a second continuous array (200) of photo-elements which emits in a second wavelength range corresponding to the second color (C2), the first wavelength range and the second wavelength range being distinct, the second sub-pixel of the first pixel (1200) and the second sub-pixel of the second pixel (2200) both being formed by the second array of photo-elements (200).

3. Display screen according to the preceding claim in which: • the first pixel (1000) further comprises a third sub-pixel (1300) of a third color (C3), • the second pixel (2000) further comprises a third sub-pixel (2300) of the third color (C3), • the set of photo-elements comprises a third continuous array of photo-elements (300) which emits in a third wavelength range corresponding to the third color (C3), the third wavelength range being distinct from the first wavelength range and the second wavelength range, and in which the third sub-pixel of the first pixel (1300) and the third sub-pixel of the second pixel (2300) are in contact and both formed by the third array of photo-elements (300).

4. Display screen according to claim 2, wherein the plurality of pixels comprises at least one third pixel (3000) in contact with the first pixel (1000), the first pixel (1000) further comprises a third sub-pixel (1300) of a third color (C3), the second pixel (2000) further comprises a third sub-pixel (2300) of the third color (C3), and the third pixel (3000) comprises at least one third sub-pixel (3300) of the third color (C3), the third sub-pixel of the first pixel (1300) and the third sub-pixel of the third pixel (3300) being in contact, and wherein the set of photo elements comprises a third array of photo elements (300) which emits in a third wavelength range corresponding to the third color (C3), the third wavelength range being distinct from the first wavelength range and the second wavelength range, and wherein the third sub-pixel of the first pixel (1300) and the third sub-pixel of the third pixel (3300) are both formed by the third array of photo elements (300).

5. Display screen according to the preceding claim in which the contact between the first pixel (1000) and the second pixel (2000) is made along a first contact line (12) and the contact between the first pixel (1000) and the third pixel (3000) is made along a second contact line (13), the first contact line (12) and the second contact line (13) being parallel and not coincident.

6. Display screen according to claim 4 wherein the contact between the first pixel (1000) and the second pixel (2000) is made along a first contact line (12) and the contact between the first pixel (1000) and the third pixel (3000) is made along a second contact line (13), the first contact line (12) and the second contact line (13) forming an angle, called contact angle, between 5° and 175°, preferably between 30° and 150°.

7. Display screen according to the preceding claim in which the contact angle is equal to 90°.

8. Display screen according to claim 6 wherein the contact angle is equal to 120°.

9. Display screen according to any one of claims 4 to 8 wherein the third pixel (3000) further comprises a second sub-pixel (3200) of the second color (C2) in contact with the second sub-pixel of the first pixel (1200), and wherein the second sub-pixel of the third pixel (3200) is formed by the second array of photo-elements (200).

10. Display screen according to the preceding claim wherein the plurality of pixels comprises at least one fourth pixel (4000) in contact with the second pixel (2000) and the third pixel (3000), the fourth pixel (4000) comprising at least one second sub-pixel (4200) of the second color (C2), the second sub-pixel of the second pixel (2200) and the second sub-pixel of the fourth pixel (4200) on the one hand and the second sub-pixel of the third pixel (3200) and the second sub-pixel of the fourth pixel (4200) on the other hand being in contact, and wherein the second sub-pixel of the fourth pixel (4200) is formed by the second array of photo-elements (200).

11. Display screen according to the preceding claim in which the second pixel (2000) further comprises a third sub-pixel (2300) of the third color (C3) and the fourth pixel (4000) further comprises a third sub-pixel (4300) of the third color (C3), the third sub-pixel of the second pixel (2300) and the third sub-pixel of the fourth pixel (4300) being in contact and both being formed by a third continuous secondary array of photo-elements (300') which emits in the third wavelength range.

12. Display screen according to the preceding claim wherein the third pixel (3000) further comprises a first sub-pixel (3100) of the first color (C1) and the fourth pixel (4000) comprises at least one first sub-pixel (4100) of the first color (C1), the first sub-pixel of the third pixel (3100) and the first sub-pixel of the fourth pixel (4100) being in contact and both being formed by a first continuous secondary array of photo-elements (100') which emits in the first wavelength range.

13. Display screen according to any one of the preceding claims wherein the first array of photo-elements (100) extends over at least two pixels other than the first pixel (1000) and the second pixel (2000).

14. Display screen according to any one of the preceding claims in which each array of photo-elements is common to at least two adjacent pixels, preferably to at least four adjacent pixels.

15. A display screen according to any preceding claim wherein each array of photo-elements forming a sub-pixel of the first pixel also forms at least one sub-pixel of at least one pixel adjacent to the first pixel.

16. Display screen according to any one of the 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.

17. A display screen according to any preceding claim wherein the first array of photoelements forms a photonic crystal.

18. Display screen according to any one of the preceding claims further comprising a plurality of electrical contacts (3) configured to power the set of photo-elements (10), the photo-elements of photo-element arrays forming distinct sub-pixels being powered by distinct electrical contacts (3).

19. Display screen according to any one of the preceding claims in which the photo-elements are nanowires.

20. Display screen according to any one of the preceding claims comprising a monolithic support (21) carrying all of the photo-elements of the set of photo-elements (10).

Images