Display screen with reduced transitions between sub-pixels

Abstract

Title: Display Screen with Reduced Transitions Between Subpixels The invention relates to a display screen comprising a plurality of pixels, of which at least a first pixel (1000) and a second pixel (2000) are in contact. The first pixel comprises at least a first subpixel (1100) of a first color (C1) and a second subpixel (1200) of a second color (C2), and the second pixel comprises at least a first subpixel (2100) of the first color and a second subpixel (2200) of the second color, the first subpixels on the one hand and the second subpixels on the other being in contact. The screen also comprises an array of photoelements (10) comprising at least a first array of photoelements (100) emitting the first color and a second array (200) of photoelements emitting the second color.The first subpixels are formed by the first array of photoelements, and the second subpixels are formed by the second array of photoelements. Figure for the abbreviation: Fig. 9A.

Description

Title of the invention: Display screen with reduced transitions between sub-pixels. Technical field

[0001] The present invention relates in particular to the field of microelectronics and optoelectronics technologies. Its particularly advantageous, but not limiting, application lies in display technologies, and in particular LED (Light-Emitting Diode) display systems. STATE OF THE ART

[0002] 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 emission and / or light conversion components, also called sub-pixels. These sub-pixels each emit a light flux substantially in a single color (typically red, green, and blue). The color of a pixel perceived by an observer results from the superposition of the different light fluxes emitted by the sub-pixels.

[0003] 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 exhibit structural differences from one sub-pixel to another. These differences lead to design difficulties: manufacturing a display screen requires producing nanowires side by side with very precise and, above all, distinct diameters and pitches. Furthermore, the dimensions of the areas over which the structural properties of the photonic crystal are constant, i.e., the sub-pixels, are very small.It is therefore understandable that the manufacture of a display screen involves a succession of technological steps at the sub-pixel level, 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.).

[0004] Moreover, the classic type of sub-pixel arrangement within a pixel, illustrated in [Fig. 12], does not offer optimal performance.

[0005] There is therefore a need to optimize the manufacturing of display screens and to improve the performance of self-emissive nanowire-based pixels. ABSTRACT

[0006] To achieve this objective, according to one embodiment, a display screen is provided comprising: - 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 subpixel of a first color, and the second pixel comprising at least a first subpixel of the first color, the first subpixel of the first pixel and the first subpixel of the second pixel being in contact, and - a set of photoelements comprising at least a first continuous photoelement array that emits in a first range of wavelengths corresponding to the first color,

[0007] The device is further characterized in that the first sub-pixel of the first pixel and the first sub-pixel of the second pixel are both formed by the first array of photo-elements.

[0008] A significant challenge in display technologies concerns the transition zones between adjacent pixels and sub-pixels. In display screens, sub-pixels of distinct colors are typically placed side by side. When a sub-pixel of a given color is formed by a photonic crystal, this photonic crystal exhibits structural characteristics (nanowire diameter, spacing between neighboring nanowires, etc.) that differ from those of a photonic crystal forming a neighboring sub-pixel emitting in a different color. Abrupt transition zones separate these sub-pixels. The presence of these abrupt transition zones has the disadvantage of disrupting the symmetry of the lattice and, consequently, creating detrimental edge effects during nanowire growth. Furthermore, the dimensions of the various photonic crystals forming the different sub-pixels correspond to the dimensions of the sub-pixels themselves and are therefore very small.However, the performance level of a photonic crystal is highly dependent on the quantity of nanowires it contains and its dimensions: a small photonic crystal performs worse than a larger one. Thus, as things stand, and particularly in the case of monolithic displays, where the dimensions of sub-pixels are typically very small, the quality of the photonic crystals forming the photo-element arrays is limited.

[0009] Arranging the subpixels so that subpixels of the same color belonging to neighboring pixels are in contact reduces the number of abrupt transition zones. Indeed, two subpixels of the same color are formed by photonic crystals with the same structural properties. Therefore, no abrupt transition zone separates them.

[0010] If we consider, for example, two pixels, each comprising two sub-pixels of two distinct colors, the contact between these pixels occurring, as is usually the case, between a sub-pixel of the first pixel of one color and a sub-pixel of the second pixel of a second color, we can typically identify, 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 exhibiting the same color, i.e., formed by arrays of substantially identical photo-elements, we eliminate one of the three abrupt transition zones. This reasoning can be extended to the scale of an entire display screen, comprising up to millions of pixels. It is therefore understandable that bringing sub-pixels of the same color into contact improves the quality of the photo-element arrays and thus of the screen itself.

[0011] Furthermore, by bringing two sub-pixels of the same color into contact, a common photo-element array is created for both sub-pixels. This common photo-element array, by definition, has larger dimensions than an array forming a single sub-pixel. The array forming two adjacent sub-pixels of the same color can thus be formed more easily than two separate arrays, one for each sub-pixel. The photonic crystal forming the array, which is also by design larger than the photonic crystals used in the same context in the prior art, also exhibits better performance due to its increased size. The proposed arrangement therefore optimizes the manufacturing of the display screen, limits the occurrence of structural defects, and improves visual rendering. BRIEF DESCRIPTION OF THE FIGURES

[0012] The aims, objects, features and advantages of the invention will become clearer from the detailed description of an embodiment thereof, which is illustrated by the following accompanying drawings in which:

[0013] [Fig.1] Fig.1 represents a cross-sectional view of an intermediate manufacturing step of the photo-elements included in a display screen according to one of the embodiments of the invention.

[0014] [Fig.2A] Figures 2A and 2B represent embodiments of the invention in which the display screen comprises two pixels, each comprising two sub-pixels.

[0015] [Fig.2B]

[0016] [Fig.3] Fig.3 represents an embodiment of the invention in which The display screen comprises two pixels, each containing three sub-pixels.

[0017] [Fig. 4] Figures 4, 5 and 6 represent embodiments of the invention in which the display screen comprises three pixels.

[0018] [Fig.5]

[0019] [Fig.6]

[0020] [Fig. 7] Figures 7, 8, 9A and 9B represent embodiments of the invention in which the display screen comprises four pixels.

[0021] [Fig.8]

[0022] [Fig.9A]

[0023] [Fig.9B]

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

[0025] [Fig. 11] Fig. 11 represents a cross-sectional view of a display screen according to the invention and illustrates in particular a control electronics enabling the power supply of the photo-elements.

[0026] [Fig. 12] The [Fig. 12] represents a display screen according to the prior art comprising four pixels and having abrupt transition zones between all sub-pixels.

[0027] The drawings are given by way of example and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications. In particular, the dimensions are not representative of reality. DETAILED DESCRIPTION

[0028] Before proceeding with a detailed review of embodiments of the invention, optional features that may be used in combination or alternatively are listed below:

[0029] According to an advantageous embodiment, the first pixel includes a second sub-pixel of a second color and the second pixel includes 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 photo-element array 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 photo-element array.

[0030] According to one embodiment: - the first pixel also includes a third sub-pixel of a third color, - the second pixel also includes a third sub-pixel of the third color, - the photoelement array includes a third continuous photoelement array that emits in a third wavelength range corresponding to the third color, the third wavelength range being distinct from the first and second wavelength ranges, and the third sub-pixel of the first pixel and the third sub-pixel of the second pixel are in contact and both formed by the third array of photo-elements.

[0031] According to one embodiment, the plurality of pixels comprises at least a third pixel in contact with the first pixel; the first pixel further comprises a third subpixel of a third color; the second pixel further comprises a third subpixel of the third color; and the third pixel comprises at least a third subpixel of the third color, the third subpixel of the first pixel and the third subpixel of the third pixel being in contact. In this same embodiment, the set of photoelements comprises a third array of photoelements that emits in a third wavelength range corresponding to the third color, the third wavelength range being distinct from the first and second wavelength ranges. The third subpixel of the first pixel and the third subpixel of the third pixel are then both formed by the third array of photoelements.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] According to one embodiment, the third pixel further comprises a first sub-pixel of the first color and the fourth pixel comprises at least a 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.

[0038] 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.

[0039] 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.

[0040] 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 can also be the case for any other pixel in the plurality of pixels.

[0041] According to an advantageous embodiment, the photo-elements are configured to emit a beam whose intensity along a direction perpendicular to a top 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 over 4ir sr is equal to the total flux over 4ir sr of the beam emitted by the photo-elements.

[0042] According to a preferred example, the first network of photo-elements forms a photonic crystal.

[0043] According to one embodiment, the display screen further comprises a plurality of separate electrical contacts, each electrical contact being configured to power the photo-elements of a photo-element array forming a separate sub-pixel.

[0044] According to one example, the photo-elements are nanowires.

[0045] According to an advantageous embodiment, the screen comprises a monolithic substrate carrying all the pixels of the pixel array. Thus, advantageously, the display screen is made from the substrate without successive cutting and gluing of the latter. The display screen may, for example, have been manufactured, among other methods, by epitaxy of photoelements from this single monolithic substrate.

[0046] According to one embodiment, the display screen includes at least two separate electrical contacts, one 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 configured to power the photo-elements of the first array of photo-elements forming the first sub-pixel of the second pixel.

[0047] In the present invention, the display screen is a single continuous screen having one face configured to display an image at a given time.

[0048] A photo-element is understood to be an element capable of emitting a beam of light. A photo-element can, for example, be an active 3D structure, for example an active wire or nanowire.

[0049] A 3D structure is said to be active when it includes an active region and is electrically connected, thus enabling it to emit light radiation.

[0050] A wire or nanowire is defined as a 3D structure elongated along its longitudinal axis. The longitudinal dimension of the 3D structure, along the z-axis in the figures, is greater, and preferably much greater, than the transverse dimensions of the 3D structure in the xy-plane in the figures. For example, the longitudinal dimension is at least five times, and preferably at least ten times, greater than the transverse dimensions. A nanowire is a wire with transverse dimensions less than 2 pm (1 pm = 10⁶ m).

[0051] The diameter of a nanowire is defined as its largest transverse dimension. In the present invention, the 3D structures do not necessarily have a circular cross-section. In particular, the 3D structures may have a hexagonal or polygonal cross-section. Specifically, in the case of GaN-based 3D structures, 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 circumcircle of that polygon.

[0052] In this 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 = 10³ m).

[0053] In the following, the following abbreviations relating to a material M may be used:

[0054] 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.

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

[0056] Mp refers to the material M doped with P, P+ or P++, according to the terminology usually used in the field of microelectronics for the suffix -p.

[0057] A substrate, layer, or device "based on" a material M is understood to mean a substrate, layer, or device comprising only that material M or that material M and optionally other materials, for example, alloying elements, impurities, or dopant 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-aluminum nitride (AlGaN) or gallium nitride with varying aluminum and indium content (GalnAIN). In the context of the present invention, the material M is generally crystalline.

[0058] A coordinate system, preferably orthonormal, comprising the x, y, z axes is shown in the attached figures.

[0059] The terms "approximately," "about," and "in the order of" mean, when referring to a value, "within 10%" of that value, or, when referring to an angular orientation, "within 10°" of that orientation. Thus, a direction substantially normal to a plane means a direction having an angle of 90+10° with respect to the plane.

[0060] To determine the geometry of the 3D structures and the compositions of the different elements (wire, active region, collar for example) of these 3D structures, one can carry out analyses of Scanning Electron Microscopy (SEM) or Transmission Electron Microscopy (TEM or TEM for the English acronym for "Transmission Electron Microscopy") or even Scanning Transmission Electron Microscopy (STEM) (English acronym for "Scanning Transmission Electron Microscopy").

[0061] TEM or STEM are particularly well suited to the observation and identification of quantum wells – whose thickness is generally on the order of a few nanometers – in the active region. Various techniques, listed below in a non-exhaustive manner, can be implemented: dark-field and bright-field imaging, weak beam imaging, and high-angle annular dark field (HAADF) diffraction.

[0062] The chemical compositions of the 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".

[0063] 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).

[0064] The optical properties of the different elements, and in particular the main emission wavelengths of the axial 3D LEDs based on GaN and / or the active regions based on InGaN, can be determined by spectroscopy.

[0065] Cathodoluminescence (CL) and photoluminescence (PL) spectroscopies are well suited to optically characterize the 3D structures described in the present invention.

[0066] The techniques mentioned above make it possible in particular to determine whether an optoelectronic device with an axial 3D wire structure includes InGaN-based quantum wells formed at the top of a GaN-based wire, and a masking layer indicative of an implementation of a MOVPE-type deposition.

[0067] A display screen according to an embodiment of the invention will now be described with reference to Figures 1 to 2B.

[0068] The display screen extends mainly along the xy plane shown in Figures 1 and 2A. It comprises a set of photoelements 10, for example, 3D structures of the nanowire type. These photoelements 10 typically extend from a substrate 2 extending along the xy plane. The substrate has a top face 20 also extending along the xy plane. The substrate 2 can be in the form of a stack comprising, for example, along the z direction, a support 21, a surface layer called a nucleation layer 22, and a masking layer 23, as shown in [Fig. 1].

[0069] The support 21 can be made of sapphire, in particular, to limit lattice parameter mismatch with the GaN if the photoelements 10 are based on this material, or of silicon to reduce costs and address technological compatibility issues. In the latter case, it can be in the form of a wafer with a diameter of 200 mm or 300 mm. It serves, in particular, as a support for the 3D structures.

[0070] The nucleation layer 22 is preferably based on AlN. It can alternatively be based on other metal nitrides, for example GaN or AlGaN. It can be formed on the silicon support 21 by epitaxy, preferably by metal-organic vapor phase epitaxy (MOVPE). 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 pm. It preferably has a thickness on the order of The thickness of the nucleation layer can range from a few hundred nanometers, for example around 100 nm or 200 nm, to a few microns, for example on the order of 2 pm. It can also be less than 100 nm thick. Such a thickness helps limit the occurrence of structural defects in the nucleation layer 22. In particular, the growth of this nucleation layer 22 can be pseudomorphic, meaning that epitaxial stresses (related in particular to the difference in lattice parameters between Si and AlN, GaN, or AlGaN) can be elastically relaxed during growth. The crystalline quality of this nucleation layer 22 can thus be optimized.

[0071] 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) onto the nucleation layer 22. It partially masks the nucleation layer 22 and includes openings, preferably circular, 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 zone and / or the second LED and / or the second transition zone, etc. The openings can be distributed regularly within each zone, for example, in the form of an ordered array. Different pitches d, i.e.The distance separating the centers of two adjacent apertures can be defined according to these zones and, in particular, as will be described later, according to the sub-pixels. These apertures can be created, 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 aperture. The lower part of the 3D structure then rests on the nucleation layer of the substrate 2 via its base.

[0072] The set of photo-elements 10 is continuous and is distributed over the entire screen in its dimensions along the x and y directions.

[0073] The term “photo-element” means an active element, that is to say, 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, resulting in light radiation with a principal wavelength. The active region 11 typically comprises a plurality of quantum wells, for example, formed by layers emissive based on GaN, InN, InGaN, AlGaN, AIN, AlInGaN, GaP, AlGaP, AlInGaP, AlGaAs, GaAs, InGaAs, AlInAs, or a combination of several of these materials.

[0075] The set of photoelements 10 comprises a first array 100 of photoelements and a second array 200 of photoelements. An array of photoelements is defined as a subset of the set of photoelements 10. An array of photoelements within the meaning of the invention is continuous, that is to say, the photoelements that compose it are arranged regularly, according to a given spacing, or possibly several given spacings defined in different directions in space. The fact that an array is continuous is also characterized by the fact that all the photoelements that compose it are made of the same material and have the same dimensions (typically the same diameter). In this sense, the photoelements of the same array can be said to be homogeneous and regular. It is understood that the homogeneity and regularity of an array of photoelements must be evaluated by taking into account the manufacturing error margins of the latter.Furthermore, a continuous network has no walls within it.

[0076] Each of these networks forms a photonic crystal and can be defined by several parameters, including: - the emission wavelength, - the lack of network coverage, - the fill rate, also called the openness rate or density, generally between 10 and 90%, - the type of mesh (hexagonal, square...), - 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 photo-elements, and - the dimensions of the nanowires.

[0077] The emission from each of the gratings preferably occurs 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 (referred to as normal to the substrate) is at least 20% greater than the maximum intensity of a Lambertian light emission whose total luminous flux over 4ir sr is equal to the total flux over 4ir sr of the beam emitted by the photoelements. The luminous intensities in question are typically expressed in W.sr 1 (watts per steradians).

[0078] Advantageously, the luminous flux emitted by each of the gratings in a cone defined by an angle of approximately 30° with respect to the normal to the substrate 2 is twice as high, preferably three times as high, and very advantageously four times higher than if the beam came from a Lambertian source. Advantageously, the luminous intensity emitted by each of the gratings along the normal to substrate 2 is twice as high, preferably four times as high, and very advantageously fifteen times as high, as if the beam came from a Lambertian source.

[0079] Emission directed primarily perpendicularly to the upper face 20 of the substrate 2 prevents the photoelements corresponding to a pixel or sub-pixel from illuminating the photoelements of a neighboring pixel or sub-pixel. This ensures isolation of the illumination of the different pixels or sub-pixels without the need for barriers between these elements. This avoids disrupting the continuity and symmetry of the photonic crystals formed by the photoelement arrays. In other words, the fact that the photoelements emit primarily perpendicularly to the upper face 20 of the substrate 2 allows for an increase in the dimensions of the photonic crystals and thus improves their quality.

[0080] The first array of 100 photo-elements emits in a first range of wavelengths corresponding to a first color Ci while the second array of 200 photo-elements emits in a second range of wavelengths corresponding to a second color C2 distinct from the first color.

[0081] The photoelements of the same array have diameters substantially equal to a target value. It is understood that, due to inaccuracies arising from the manufacturing processes, the photoelements of the same array can hardly all have a diameter equal to this target value. Variations in the diameter of a nanowire, for example, due to manufacturing variations can be estimated at approximately 10% of the target value. The same applies to the pitch between two neighboring photoelements. For this reason, not all photoelements emit at exactly the same wavelength. The photoelements of a photoelement array emit within a range of wavelengths characterizing the array. It is understood that an array of N photoelements, each emitting light radiation characterized by a wavelength X; with l <i<N, / ..being within the emission range of the network, and all with the same intensity, emits a global radiation at a network wavelength XréSeau defined by: .

[0082] [Math.l] y __ ^~;=1 1 ■“network— N

[0083] The grating wavelengths Xi00, X200 of the first photo-element grating 100 and the second photo-element grating 200 are defined in particular in this way. Of course, if all the photo-elements do not emit with the same intensity, the different components of the grating wavelength, that is to say the lengths The waves of radiation emitted by each of the photo-elements can be weighted by coefficients relating to their respective intensities.

[0084] The first photo-element array 100 and the second photo-element array 200 emit radiation corresponding to distinct colors Ci and C2. The two wavelength ranges of the two arrays 100, 200 are considered distinct if the grating wavelengths Xi Oo, ^2 00 characterizing them satisfy the following relationship:

[0085] [Math.2] Rioo- ^2ool > 30 nm

[0086] In practice, the wavelengths Xi Oo, M 00 characterizing the colors Ci, C2 of the first 100 grating and the second 200 grating respectively belong to very different ranges. For example, Xi 00 is found 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 X2 oo in another of these ranges. These ranges are located 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 photoelement gratings are close to these values.

[0087] The display screen further comprises a plurality of pixels. This plurality of pixels includes, in particular, a first pixel of 1000 and a second pixel of 2000. The first pixel of 1000 and the second pixel of 2000 are in contact.

[0088] Each pixel in the plurality of pixels comprises at least a first sub-pixel and a second sub-pixel. In particular, a first sub-pixel of the first pixel is defined as 1100, a second sub-pixel of the first pixel as 1200, a first sub-pixel of the second pixel as 2100 and a second sub-pixel of the second pixel as 2200, all represented in [Fig.2A].

[0089] Each sub-pixel displays a color in the visible range. More specifically, the first sub-pixels 1100, 2100 are of the first color Ci and the second sub-pixels 1200, 2200 are of the second color C2.

[0090] As illustrated in Figures 2A and 2B: - the first sub-pixel of the first pixel (1100) and the first sub-pixel of the second (2100) are in contact, and - 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 pixel 1000, 2000 comprises more than two sub-pixels. Figure 2B, on the other hand, represents a scenario in which each pixel 1000, 2000 consists of only two sub-pixels.

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

[0093] A photo-element array thus consists of at least one region, and typically of 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 offers numerous advantages. First, this arrangement reduces the number of transition zones between arrays forming distinct photonic crystals. The number of zones creating symmetry breaks is therefore reduced. Since these zones are responsible for growth defects and losses in optical quality, the quality of the photo-element array, and ultimately that of the display screen, is improved. Furthermore, the formation of the photo-elements is facilitated.Indeed, this process involves successive masking and deposition steps, which become increasingly complex as the gratings get smaller. Specifically, the smaller the areas on which the photoelements are formed, the more precisely the photolithography masks need to be aligned. Furthermore, increasing the dimensions of a continuous photonic crystal of photoelements, and therefore the number of photoelements it contains, improves its ability to discriminate waves based on their wavelength. In other words, the larger the photonic crystal, the better the control over the wavelengths propagating through it. Moreover, increasing the dimensions of the photonic crystal improves its ability to ensure good emission directionality. This plays a significant role, particularly in eliminating the need for walls between sub-pixels and / or adjacent pixels.

[0094] A photonic crystal can function as such with three rows of photoelements. The greater the number of rows of photoelements forming the photonic crystal, the higher the quality of the photonic crystal obtained. Thus, advantageously, the photonic crystals are each formed by at least 10 rows, preferably 20 rows, and preferably even 50 rows of photoelements.

[0095] According to one embodiment, the photo-element array comprises a third 300 photo-element array. The structural properties of the first and second arrays 100, 200 can be applied mutatis mutandis to the third 300 array. The third 300 photo-element array emits in a third wavelength range corresponding to a third wavelength X300 and a third color C3. Preferably, the third wavelength X300 is found in the third range among the previously mentioned wavelength ranges. For example, if the first color Ci 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 of 300 photo-elements allows the formation of a plurality of third sub-pixels. Figure 3, in particular, illustrates an embodiment in which the first pixel 1000 comprises a third sub-pixel, referred to as the third sub-pixel of the first pixel 1300, and the second pixel 2000 comprises a third sub-pixel, referred to as the third sub-pixel of the second pixel 2300. The second sub-pixels 1200 and 2200, on the one hand, and the third sub-pixels 1300 and 2300, on the other hand, are advantageously in contact.

[0097] According to one embodiment, the plurality of pixels includes a third pixel 3000 in contact with the first pixel 1000. This third pixel 3000 includes at least a 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 along a straight line called the first contact line 12. The contact between the first pixel 1000 and the third pixel 3000 is along a straight line called the second contact line 13. According to an example illustrated in [Fig. 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 [Fig. 5], the first contact line 12 and the second contact line 13 are perpendicular. In the typical case of square pixels, the second pixel 2000 and the third pixel 3000 border adjacent sides of the first pixel 1000.

[0099] This sharing 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 sharing of the first array 100 and of the second network 200 between the first sub-pixels 1100, 2100 and second sub-pixels 1200, 2200. It is understood that combining these contacts of sub-pixels of the same color and these sharing of photonic crystals makes it possible to reduce more and more the number of abrupt transitions 5 between sub-pixels such as represented for example on the [Fig. 12].

[0100] Still with the aim of sharing photo-element arrays, the third pixel 3000 can include a second sub-pixel 3200 in contact with the second sub-pixel of the first pixel 1200. The second array 200 then forms not only the second sub-pixel of the first array 1200, the second sub-pixel of the second array 2200, but also the second sub-pixel of the third array 3200 (as illustrated in [Fig. 6]). The corresponding photonic crystal thus extends over three sub-pixels 1200, 2200, and 3200.

[0101] According to one embodiment, the plurality of pixels includes 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 includes at least a second subpixel 4200 in contact with the second subpixel of the first pixel 1200 and with the second subpixel of the third pixel 3200. The second array 200 then forms the second subpixels 1200, 2200, 3200, 4200 of the set of four pixels 1000, 2000, 3000, 4000.

[0102] As illustrated in [Fig.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 array 300' of photo-elements having the same characteristics as the third array 300. The third secondary array 300' and the third array 300 can in particular be manufactured simultaneously.

[0103] As illustrated in Figures 9A and 9B, in 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 can, in particular, be manufactured simultaneously. Figure 9A shows 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 certain pixels are of a single color and are adjacent to sub-pixels of the same color belonging to adjacent pixels. For example, as illustrated, the third pixel 3000 is formed entirely by the first network 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 subpixels of the same color into contact and sharing 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 subpixels contained in each pixel. The distribution of the different photoelement arrays will depend on the pixel geometry and the arrangement of the subpixels within the pixels. It should be noted that a highly optimized screen can be obtained by repeating the patterns described above. For example, by repeating in the xy plane the pattern formed by the four pixels illustrated in [Fig. 9A], continuous sets of similar photoelements (of the type forming the third array 300 and the third secondary array 300') are created, extending over four subpixels and no longer just two.Similarly, continuous sets of photoelements of the type of those in the first 100-network can be obtained.

[0106] Regardless of the number of pixels and sub-pixels and the arrangement of sub-pixels in each of the pixels, the objective is always to limit the number of contacts between sub-pixels of different colors.

[0107] As illustrated in [Fig. 11], the display screen advantageously includes electrical contacts 3 for supplying power to the photoelements. These electrical contacts 3 can be common to a plurality of photoelements. Preferably, photoelements belonging to arrays forming distinct subpixels are supplied separately. Thus, even if the arrays forming two adjacent subpixels were formed simultaneously and constitute a continuous array of photoelements, the two subpixels remain electrically independent. Indeed, it may be necessary for image rendering that both subpixels be illuminated, that both subpixels be off, or that only one be illuminated.

[0108] These electrical contacts 3 are connected to a control electronics 4 which controls the switching on or off of the photoelements according to display requirements. The representation of the control electronics 4 in [Fig. 11] is for illustrative purposes only. In particular, the assignment of the different transistors to the different photoelements and their connections are not in any way limiting. For example, the photoelements are also typically connected at another terminal to an electrical connection not shown for clarity.

[0109] Figure 11 further illustrates the juxtaposition of three pixels 1000, 2000, and 3000. It includes, in particular, a cross-sectional view of the first subpixel of the second pixel 2100, the first subpixel of the first pixel 1100, the second subpixel of the first pixel 1200, and the second subpixel of the third pixel 3200. The first 100 array is The second array, consisting of photoelements with a first target diameter d 100 and a first target spacing between them plOO, is composed of photoelements with a second target diameter d200 and a second target spacing between them p200. As illustrated, each of these arrays forms two adjacent subpixels belonging to neighboring pixels: the first 100 array forms the first subpixel of the second pixel 2100 and the first subpixel of the first pixel 1100, while the second 200 array forms the second subpixel of the first pixel 1200 and the second subpixel 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

1. Demands Display screen including: a plurality of pixels comprising at least a first pixel (1000), a second pixel (2000) and a third pixel (3000), the first pixel (1000) and the second pixel (2000) on the one hand and the first pixel (1000) and the third pixel (3000) on the other hand being in contact, the first pixel (1000) comprising at least a first subpixel (1100) of a first color (C1), a second subpixel (1200) of a second color (C2) and a third subpixel (1300) of a third color (C3), the second pixel (2000) comprising at least a first subpixel (2100) of the first color (C1), a second subpixel (2200) of the second color (C2) and a third subpixel (2300) of the third color (C3), the third pixel (3000) comprising at least a first subpixel (3100) of the first color (Ci), a second sub-pixel (3200) of the second color (C2) and a third sub-pixel (3300) of the third color (C3),the first subpixel of the first pixel (1100) and the first subpixel of the second pixel (2100) being in contact, the second subpixel of the first pixel (1200) and the second subpixel of the second pixel (2200) being in contact, the third subpixel of the first pixel (1300) and the third subpixel of the third pixel (3300) being in contact, and, a set of photoelements (10) comprising at least: i. a first continuous array of photo-elements (100) which emits in a first range of wavelengths corresponding to the first color (Ci), the first sub-pixel of the first pixel (1100) and the first sub-pixel of the second pixel (2100) both being formed by the first array of photo-elements (100), ii. a second continuous photo-element array (200) which emits in a second range of wavelengths corresponding to the second color (C2), the first range of wavelengths wavelengths and the second range of wavelengths being distinct, the second subpixel of the first pixel (1200) and the second subpixel of the second pixel (2200) are both formed by the second array of photo-elements (200), iii.a third array of photoelements (300) which emits in a third range of wavelengths corresponding to the third color (C3), the third range of wavelengths being distinct from the first range of wavelengths and the second range of wavelengths, the third subpixel of the first pixel (1300) and the third subpixel of the third pixel (3300) both being formed by the third array of photoelements (300), characterized in that 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 perpendicular.

2. Display screen according to the preceding claim wherein the third pixel (3000) further comprises a second sub-pixel (3200) of the second color 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 photoelements (200).

3. Display screen according to the preceding claim wherein the plurality of pixels comprises at least a fourth pixel (4000) in contact with the second pixel (2000) and the third pixel (3000), the fourth pixel (4000) comprising at least a second sub-pixel (4200) of the second color, 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).

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

5. Display screen according to the preceding claim in which the fourth pixel (4000) comprises at least a first sub-pixel (4100) of the first color, 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.

6. 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).

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

8. Display screen according to any one of the preceding claims 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.

9. Display screen according to any one of the preceding claims wherein the photo-elements are configured to emit a beam whose intensity along 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 4ir sr is equal to the total flux over 4ir sr of the beam emitted by the photo-elements.

10. Display screen according to any one of the preceding claims wherein the first array of photo-elements forms a photonic crystal.

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

12. Display screen according to any one of the preceding claims wherein the photo-elements are nanowires.

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

Images