Display pixels including light-emitting diodes and display screens having such display pixels

Abstract

This specification relates to a display pixel (12) including at least first and second light-emitting diodes (LEDs), a first controllable current source (CS_B) supplying a first current to the first light-emitting diode (LED), a second controllable current source (CS_R) supplying a second current to the second light-emitting diode (LED), and an electronic circuit (40) comprising a storage circuit (48) for storing at least first and second color signals (R, B), and a driver circuit (50) configured to control the first controllable current source (CS_B) to supply a first current by pulse width modulation based on the first color signal (B), and to control the second controllable current source (CS_R) to supply a second current by linear commands based on the second color signal (R). i,j Regarding )

Description

[Technical Field]

[0001] This disclosure relates to a display pixel including a light-emitting diode and a display screen having such a display pixel. [Background technology]

[0002] An image pixel corresponds to a unit element of an image displayed by a display screen. In the case of displaying a color image, a display screen generally includes at least three components, also called display subpixels, to display each pixel of the image. These components each emit light radiation called image pixel color components, which are substantially monochromatic (e.g., red, green, and blue). The superposition of the image pixel color components emitted by the three display subpixels provides the observer with a colored perception corresponding to the pixels of the displayed image. In this case, the assembly formed by the three display subpixels used to display the pixels of the image is called a display pixel of the display screen. Each display subpixel may include a light source, in particular a light-emitting diode.

[0003] The display pixels may be arranged as an array, with each display pixel located at the intersection of rows (also called lines) and columns of the array. Electrodes are provided along the rows and columns to connect each display pixel to a control circuit. Generally, each row of display pixels is sequentially selected by signals transmitted along the row electrodes, and the display pixels of the selected row are programmed to display desired image pixels by signals transmitted along the column electrodes.

[0004] It is known that light-emitting diodes (LEDs) can be controlled by pulse width modulation, also known as PWM (Pulse Width Modulation). This type of control involves circulating a continuous current pulse of constant intensity within the LED, where the pulse is periodically repeated and the duty cycle determines the light intensity emitted by the LED. Such control is advantageous because it allows the LED to operate at its optimal operating point, where the efficiency of the LED is maximized, equal to the ratio of the light power emitted by the LED to the power consumed by the LED. Furthermore, pulse width modulation allows the current density flowing through the LED to remain constant. This is advantageous because, in some types of LEDs, the central wavelength of the radiation emitted by the LED can vary depending on the current density flowing through the LED.

[0005] Some of the display subpixels of a display pixel may include a photoluminescent block covering a light-emitting diode (LED). The photoluminescent block contains a light-emitting material that, when excited by light emitted by the associated LED, can emit light of a different wavelength than the light emitted by the associated LED. The photoconversion performance of some types of light-emitting materials, such as quantum dots, may decrease over time depending on the maximum luminous flux the quantum dot receives. Therefore, it may be desirable to command a light-emitting diode covered by such a photoluminescent block to reduce the maximum luminous flux emitted by the LED. [Overview of the project]

[0006] An object of one embodiment is to provide a display pixel including a light-emitting diode and a display screen including such a display pixel that overcomes all or part of the drawbacks of existing display pixels including light-emitting diodes and display screens including such display pixels.

[0007] One embodiment provides a display pixel. The display pixel comprises at least first and second light-emitting diodes, a first controllable current source supplying a first current to the first light-emitting diode, a second controllable current source supplying a second current to the second light-emitting diode, and an electronic circuit, the electronic circuit including a storage circuit for storing at least first and second color signals, and a driver circuit configured to control the first controllable current source to supply a first current by pulse width modulation based on the first color signal, and to control the second controllable current source to supply a second current by linear commands based on the second color signal.

[0008] Such control is advantageous because it allows the first light-emitting diode to operate at its optimal operating point where its efficiency is maximized. Furthermore, pulse-width modulation commands allow the current density flowing through the first light-emitting diode to remain constant. This is advantageous because the central wavelength of the radiation emitted by the first light-emitting diode can vary depending on the current density flowing through it. Additionally, linear commands for the second light-emitting diode are advantageous because they prevent the second light-emitting diode from always emitting the highest intensity radiation, which can be damaging, especially if the second light-emitting diode is covered by a photoluminescent block containing quantum dots.

[0009] According to one embodiment, the display pixel further comprises a third light-emitting diode and a third controllable current source supplying a third current to the third light-emitting diode, wherein a memory circuit is configured to store a third color signal, and a driver circuit is configured to control the third controllable current source to supply a third current by linear commands based on the third color signal. Linear commands of the third light-emitting diode are advantageous because they allow the third light-emitting diode to prevent it from always emitting the highest intensity radiation, which could be damaging, particularly if the third light-emitting diode is covered by a photoluminescence block containing quantum dots.

[0010] According to one embodiment, the first color signal is a digital signal, and the memory circuit includes a first memory cell for storing bits of the first color signal.

[0011] According to one embodiment, the second color signal is a digital signal, and the memory circuit includes a second memory cell for storing bits of the second color signal.

[0012] According to one embodiment, the driver circuit includes a digital-to-analog converter configured to convert a second color signal stored in a second memory cell into an analog control signal for controlling a second controllable current source.

[0013] According to one embodiment, the first color signal is an analog signal, and the memory circuit includes a first capacitor for storing the first color signal.

[0014] According to one embodiment, the second color signal is an analog signal, and the memory circuit includes a second capacitor for storing the second color signal.

[0015] According to one embodiment, each of the first and second light-emitting diodes includes several elemental light-emitting diodes, each including an active region covering a three-dimensional semiconductor element corresponding to a wire-like, conical, frustoconical, or pyramidal element in the nanometer or micrometer range. In the case of such radial three-dimensional light-emitting diodes, the central wavelength of the radiation emitted by the light-emitting diode can vary considerably as a function of the current density passing through the light-emitting diode. A pulse width modulation command allows the current density flowing through the first light-emitting diode to remain constant, which is advantageous when the first light-emitting diode is not covered by a photoluminescent block.

[0016] According to one embodiment, a second light-emitting diode is covered by a first photoluminescence block. According to one embodiment, the first light-emitting diode is configured to emit a first radiation of a first wavelength, the second light-emitting diode is configured to emit a second radiation of a second wavelength, and the first photoluminescence block is configured to convert the second radiation into a third radiation of a third wavelength different from the second wavelength. The first photoluminescence block absorbs the second radiation emitted by the second light-emitting diode and emits a third radiation with a center wavelength different from the center wavelength of the second radiation emitted by the second light-emitting diode. A linear command for the second light-emitting diode can result in a change in the current density supplied to the second light-emitting diode, and as a result, a change in the center wavelength of the second radiation emitted by the second light-emitting diode. However, the first photoluminescence block can emit a third radiation with a fixed center wavelength even if the center wavelength of the second radiation emitted by the second light-emitting diode exhibits dispersion. Therefore, the central wavelength of the third radiation emitted by the first photoluminescence block remains fixed even if the central wavelength of the second radiation emitted by the second light-emitting diode changes.

[0017] According to one embodiment, the first wavelength is equal to the second wavelength by no more than 10%. The first and second light-emitting diodes can, advantageously, be light-emitting diodes manufactured by the same manufacturing method. Therefore, the manufacturing method for the display pixels becomes simpler.

[0018] According to one embodiment, the first photoluminescence block includes a first quantum dot. The photoconversion performance of the first quantum dot tends to decrease over time depending on the maximum luminous flux received by the first quantum dot. A linear command for the second light-emitting diode advantageously allows limiting the luminous flux on the first quantum dot compared to a pulse-width modulation command. Thus, the first quantum dot is not always subjected to the second radiation from the second light-emitting diode at its highest intensity. Consequently, the durability of the photoconversion performance of the first quantum dot is improved.

[0019] According to one embodiment, a third light-emitting diode is covered by a second photoluminescence block. According to one embodiment, the third light-emitting diode is configured to emit a fourth radiation of a fourth wavelength, and the second photoluminescence block is configured to convert the fourth radiation into a fifth radiation of a fifth wavelength different from the fourth wavelength. The second photoluminescence block absorbs the fourth radiation emitted by the third light-emitting diode and emits a fifth radiation with a center wavelength different from the center wavelength of the fourth radiation emitted by the third light-emitting diode. A linear command for the third light-emitting diode can result in a change in the current density supplied to the third light-emitting diode, which in turn can result in a change in the center wavelength of the fourth radiation emitted by the third light-emitting diode. However, the second photoluminescence block can emit a fifth radiation with a fixed center wavelength even if the center wavelength of the fourth radiation emitted by the third light-emitting diode exhibits dispersion. Therefore, the central wavelength of the fifth radiation emitted by the second photoluminescence block remains fixed even if the central wavelength of the fourth radiation emitted by the third light-emitting diode changes.

[0020] According to one embodiment, the fourth wavelength is equal to the first wavelength by no more than 10%. The first and third light-emitting diodes can, advantageously, be light-emitting diodes manufactured by the same manufacturing method. Thus, the manufacturing method of the display pixels becomes simpler.

[0021] According to one embodiment, the second photoluminescence block includes a second quantum dot. The photoconversion performance of the second quantum dot tends to decrease over time depending on the maximum luminous flux received by the second quantum dot. A linear command for the third light-emitting diode advantageously allows limiting the luminous flux on the second quantum dot compared to a pulse-width modulation command. Thus, the second quantum dot is not always subjected to radiation from the second light-emitting diode at its highest intensity. Consequently, the durability of the photoconversion performance of the second quantum dot is improved.

[0022] According to one embodiment, the display pixel comprises a first integrated circuit including an electronic circuit that includes the memory circuit and the driver circuit.

[0023] According to one embodiment, the display pixel comprises a photoelectronic circuit attached to an integrated circuit, the photoelectronic circuit includes first and second light-emitting diodes.

[0024] One embodiment also, Display pixels as defined above, A first electrode coupled to the driver circuit of the display pixel, A first circuit for transmitting a selection signal onto each first electrode in order to select a display pixel coupled to the first electrode, A second electrode coupled to the electronic circuit of the display pixel, A second circuit for transmitting data signals onto the second electrode and It provides a display screen that includes this feature.

[0025] According to one embodiment, the second circuit is configured to transmit a data signal as an analog signal onto the second electrode.

[0026] According to one embodiment, the second circuit is configured to transmit a data signal as a digital signal onto the second electrode.

[0027] According to one embodiment, the second circuit is configured to transmit data signals, including alternating digital and analog signals, onto the second electrode.

[0028] The aforementioned features and advantages, as well as others, are described in detail in the remainder of the disclosure of specific embodiments, which are given as examples rather than limitations with reference to the accompanying drawings. [Brief explanation of the drawing]

[0029] [Figure 1] A partial and schematic representation of one embodiment of the display screen is shown. [Figure 2] This is a very simplified cross-sectional view of one embodiment of a display pixel. [Figure 3] Figure 1 shows a block diagram of one embodiment of the display pixels of the display screen. [Figure 4] Figure 3 shows a block diagram of one embodiment of the light-emitting circuit for the display pixels. [Figure 5] A block diagram of another embodiment of the light-emitting circuit for the display pixels in Figure 3 is shown. [Figure 6] A block diagram of one embodiment showing a portion of the display pixels in Figure 3 is shown. [Figure 7] A block diagram of another embodiment of some of the display pixels in Figure 3 is shown. [Figure 8] Figure 7 shows an example of a timing diagram of the display pixel signals according to one embodiment of the operation method of the display screen. [Figure 9] A block diagram of another embodiment of some of the display pixels in Figure 3 is shown. [Figure 10] An example of a timing diagram of the display pixel signals in Figure 9, according to another embodiment of the operation method of the display screen, is shown. [Figure 11] A more detailed embodiment of the display pixels shown in Figure 2 is partially and schematically represented. [Figure 12] This represents one embodiment of a three-dimensional light-emitting diode. [Figure 13] Another embodiment of a three-dimensional light-emitting diode is shown. [Modes for carrying out the invention]

[0030] Similar features are designated by the same reference numerals in various figures. In particular, structural and / or functional features common to various embodiments may have the same reference numerals and may have the same structural, dimensional, and material properties.

[0031] For clarity, only the operations and elements useful for understanding the embodiments described herein are illustrated and described in detail.

[0032] In the following disclosures, unless otherwise specified, when referring to absolute position modifiers such as “front,” “back,” “up,” “down,” “left,” and “right,” relative position modifiers such as “above,” “downward,” “higher,” and “lower,” or orientation modifiers such as “horizontal” and “vertical,” it refers to the orientation shown in the diagram.

[0033] Unless otherwise specified, when referring to two elements connected to each other, this means a direct connection with no intermediate elements other than conductors. When referring to two elements coupled to each other, this means that these two elements can be connected or coupled through one or more other elements. Furthermore, a signal that alternates between a first constant state, labeled "0," e.g., a Low logic state, and a second constant state, labeled "1," e.g., a High logic state, is called a "binary signal." The High and Low states of different binary signals in the same electronic circuit may be different. In practice, binary signals can correspond to voltages or currents that may not be perfectly constant in the High or Low states.

[0034] Furthermore, unless otherwise specified, when referring to the voltage at a conductive pad, the difference between the potential at the conductive pad and the reference potential, for example, ground which is considered equal to 0V, is taken into account. If the radiation exhibits a typical "bell" shape spectrum with a maximum value, such as a Gaussian shape, the wavelength of the radiation, or the central or dominant wavelength of the radiation, is called the wavelength at which the spectrum reaches its maximum value.

[0035] Unless otherwise specified, the expressions "about," "approximately," "substantially," and "to the extent of" mean within 10%, preferably within 5%. Furthermore, the expression "substantially constant" means that it changes by less than 10% over time relative to the baseline value.

[0036] A light-emitting diode is said to be a three-dimensional light-emitting diode if it includes a micrometer or nanometer-sized three-dimensional semiconductor element (e.g., a microwire or nanowire) that is covered by an active region and extends in a preferred direction. In particular, a three-dimensional light-emitting diode is said to be radial if its active region extends at least across the sidewalls of the three-dimensional semiconductor element.

[0037] Figure 1 shows a known example of a display screen 10 in a partial and highly schematic manner. The display screen 10 is, for example, a display screen with 12 display pixels arranged in M ​​rows and N columns. i,j This includes M, an integer ranging from 1 to 8,000, N, an integer ranging from 1 to 16,000, i, an integer ranging from 1 to M, and j, an integer ranging from 1 to N. For example, in Figure 1, M and N are equal to 6. Each display pixel 12 i,j Electrode 14 i The electrode 16 is connected to a source of low reference potential Gnd, for example, to ground. j It is coupled to the source of a high reference potential Vcc via [a specific device]. For example, electrode 14 i The electrodes 16 are shown aligned along the rows in Figure 1. jare shown as being aligned along the columns of Figure 1, and the reverse layout is also possible. The power supply voltage of the display screen corresponds to the voltage between the high reference potential Vcc and the low reference potential Gnd, and is denoted as Vcc like the high reference potential. The power supply voltage Vcc depends in particular on the arrangement of the light emitting diodes and the manufacturing technology of the light emitting diodes. As an example, the power supply voltage Vcc may be on the order of 4V to 5V.

[0038] For each row, the display pixels 12 in the row i,j are coupled to the row electrode 18 i . For each column, the display pixels 12 in the column i,j are coupled to the column electrode 20 j . The display screen 10 is coupled to the row electrodes 18 i and comprises a selection circuit 22 adapted to transmit a selection signal Com onto each of the row electrodes 18 i i . The display screen 10 is coupled to the column electrodes 20 j and comprises a data transmission circuit 24 adapted to transmit a data signal Data onto each of the column electrodes 20 j j . The selection circuit 22 and the control circuit 24 are controlled by a circuit 26 including, for example, a microprocessor.

[0039] Figure 2 is a very simplified cross-sectional view of a known example of the display pixel 12 i,j . Each display pixel 12 i,j ​​The display circuit 32 includes a control circuit 30 covered by the display circuit 32. The display circuit 32 includes light-emitting diodes, preferably at least three light-emitting diode LEDs. The display pixel includes a bottom surface 34 and an upper surface 35 opposite the bottom surface 34, the bottom surface 34 and the upper surface 35 being preferably planar and parallel. The control circuit 30 further includes conductive pads P_Gnd, P_Vcc, P_Col, and P_Row on the bottom surface 34. The control circuit 30 may correspond to an integrated circuit including electronic components, in particular insulated-gate field-effect transistors, also known as MOS transistors, or thin-film transistors, also known as TFTs. Preferably, the display circuit 32 includes only the light-emitting diode LEDs and the conductive elements of these light-emitting diode LEDs, and the control circuit 30 includes all the electronic components necessary to control the light-emitting diode LEDs of the display circuit 32. In a variation, the display circuit 32 may also include other electronic components in addition to the light-emitting diode LEDs. According to one embodiment, each light-emitting diode LED includes several element three-dimensional light-emitting diodes. In Figure 2, the light-emitting diode LEDs are shown as being connected to a common anode. However, it may be desirable to arrange the light-emitting diodes (LEDs) according to a different configuration. For example, the LEDs may be connected to a common cathode or they may be connected independently of each other.

[0040] Each conductive pad P_Gnd, P_Vcc, P_Col, and P_Row corresponds to electrode 14, which is schematically shown in Figure 2. i , 16 j , 18 i , 20 j It is intended to be connected to one of the following. The first conductive pad P_Gnd is coupled to the source of the Low reference potential Gnd. The second conductive pad P_Vcc is coupled to the source of the High reference potential Vcc. The third conductive pad P_Row is coupled to the row electrode 18 i It is coupled with the selection signal Com i The fourth conductive pad P_Col is the column electrode 20. j It is coupled with the data signal Data jThe dimensions of the conductive pads P_Gnd, P_Vcc, P_Col, and P_Row, and the layout of the conductive pads P_Gnd, P_Vcc, P_Col, and P_Row on the bottom surface 34 are shown in the display pixels 12. i,j The design rules and the display pixels 12 within the display screen 10 i,j This is particularly imposed by the assembly method.

[0041] According to one embodiment, the display pixel 12 i,j The system includes a first display subpixel that emits light of a first wavelength, a second display subpixel that emits light of a second wavelength, and a third display subpixel that emits light of a third wavelength. According to one embodiment, the first wavelength corresponds to blue light and is in the range of 430 nm to 490 nm. In this case, the first display subpixel is called a blue display subpixel. According to one embodiment, the second wavelength corresponds to green light and is in the range of 510 nm to 570 nm. In this case, the second display subpixel is called a green display subpixel. According to one embodiment, the third wavelength corresponds to red light and is in the range of 600 nm to 720 nm. In this case, the third display subpixel is called a red display subpixel.

[0042] Figure 3 shows the display pixels 12 of the display screen 10. i,j A block diagram of one embodiment is shown. In the case of a color display screen, the display pixels 12 i,j It includes at least three display subpixels SPix_R, SPix_G, and SPix_B that emit radiation of different colors. For example, display subpixel SPix_B corresponds to the previously defined blue display subpixel, display subpixel SPix_G corresponds to the previously defined green display subpixel, and display subpixel SPix_R corresponds to the previously defined red display subpixel. Each subpixel SPix_R, SPix_G, and SPix_B includes at least one light-emitting diode LED. For each display subpixel SPix_R, SPix_G, and SPix_B, the light-emitting diode LED is coupled in series to controllable current sources CS_R, CS_G, and CS_B. In this example, for each light-emitting diode LED, the anode of the light-emitting diode LED is located at display pixel 12 i,jThe conductive pad P_Vcc receives a high reference potential Vcc, and the cathode of the light-emitting diode LED is coupled to, for example, the terminals of the controllable current sources CS_R, CS_G, CS_B, and the other terminals of the controllable current sources CS_R, CS_G, CS_B are connected to the display pixel 12 i,j The conductive pad P_Gnd receives a low reference potential Gnd. In one variation, the cathode of the light-emitting diode LED receives a low reference potential Gnd, the anode of the light-emitting diode LED is coupled to the terminals of controllable current sources CS_R, CS_G, and CS_B, and the other terminals of the controllable current sources CS_R, CS_G, and CS_B receive a high reference potential Vcc.

[0043] Display pixels 12 i,j The display pixel 12 further includes an electronic circuit 40 for driving controllable current sources CS_R, CS_G, and CS_B for each display sub-pixel SPix_R, SPix_G, and SPix_B. The electronic circuit 40 may include electronic components such as MOS transistors. To power the electronic components of the circuit 40, it may be desirable to use a reduced power supply voltage less than 4V, for example, about 1V or 1.8V, which corresponds to the voltage expected to be applied, for example, between the power supply terminals of a MOS transistor. For this purpose, the display pixel 12 i,j For example, from a high reference potential Vcc, or from a selected signal Com i and data signal j Therefore, it may include a circuit (not shown) for transmitting a reduced power supply voltage Vdd, which is particularly used for the power supply of circuit 40.

[0044] Circuit 40 receives the data signal Data j The conductive pad P_Col receives the selected signal Com. iThe system includes an interface circuit 46 (interface) coupled to a conductive pad P_Row that receives a data signal, and configured to transmit the data signal Data to a memory circuit 48 (color data memory). The memory circuit 48 is configured to store analog or digital color signals R, G, and B based on the received data signal Data. The color signals R, G, and B represent the image pixel color components to be displayed by each display subpixel SPix_R, SPix_G, and SPix_B.

[0045] The circuit 40 further includes a driver circuit 50 (LED driver) for controlling the associated controllable current sources CS_R, CS_G, and CS_B of each display subpixel SPix_R, SPix_G, and SPix_B. The driver circuit 50 (LED driver) is configured to control the controllable current sources CS_R, CS_G, and CS_B coupled to the light-emitting diode LEDs using analog or digital signals I_red, I_green, and I_blue obtained from the color signals R, G, and B. According to one embodiment, the control circuit 30 can correspond to a single integrated circuit including the circuit 40 for driving the controllable current sources CS_R, CS_G, and CS_B of each display subpixel SPix_R, SPix_G, and SPix_B. More generally, the circuit 40 can be composed of several integrated circuits.

[0046] According to one embodiment, pulse width modulation commands are used to send commands to the current source CS_B of the blue display subpixel SPix_B, while linear commands are used to send commands to the current source CS_G of the green display subpixel SPix_G and to the current source CS_R of the red display subpixel SPix_R. Therefore, the light-emitting diode LED of the blue display subpixel SPix_B is supplied with pulses of current having a constant intensity, and the duration of the pulse depends on the stored color signal B. The light-emitting diode LED of the green display subpixel SPix_G is supplied with currents of different intensity according to the stored color signal G, and the light-emitting diode LED of the red display subpixel SPix_R is supplied with currents of different intensity according to the stored color signal R.

[0047] The constant current intensity flowing through the light-emitting diode (LED) of the blue display subpixel SPix_B is advantageous when it is important to obtain reduced dispersion of the central wavelength of the radiation emitted by the light-emitting diode (LED) of the blue display subpixel SPix_B during operation. In fact, the central wavelength of the radiation emitted by a light-emitting diode usually changes as a function of the current density passing through the LED, and this change is large in the case of radial three-dimensional light-emitting diodes. In this embodiment, since the current density passing through each elemental light-emitting diode remains constant regardless of the color signal B, the central wavelength of the radiation emitted by the elemental light-emitting diodes does not change during operation.

[0048] According to one embodiment, each of the red display subpixels SPix_R and green display subpixels SPix_G includes a photoluminescent block covering the light-emitting diode LED. The photoluminescent block absorbs the radiation emitted by the light-emitting diode LED and emits radiation with a different central wavelength than the central wavelength of the radiation emitted by the light-emitting diode LED. A linear command for the red display subpixels SPix_R and green display subpixels SPix_G can result in a change in the current density supplied to the light-emitting diode LEDs of the red display subpixels SPix_R and green display subpixels SPix_G, and consequently, a change in the central wavelength of the radiation emitted by the light-emitting diode LEDs of the red display subpixels SPix_R and green display subpixels SPix_G. However, the photoluminescent block can emit radiation with a fixed central wavelength even if the central wavelength of the radiation emitted by the light-emitting diode LED exhibits dispersion. Therefore, the central wavelength of the radiation emitted by the photoluminescence block remains fixed, even if the central wavelength of the radiation emitted by the light-emitting diode LEDs of the red display subpixel SPix_R and green display subpixel SPix_G changes due to linear commands for the red display subpixel SPix_R and green display subpixel SPix_G.

[0049] Photoluminescence blocks may contain quantum dots. The light conversion performance of quantum dots tends to decrease over time depending on the maximum luminous flux they receive. Linear commands for the red display subpixel SPix_G and green display subpixel SPix_R advantageously allow for limiting the luminous flux on the quantum dots compared to pulse-width modulation commands. Thus, the quantum dots are not always subjected to radiation from the light-emitting diode LEDs at their highest intensity. Consequently, the durability of the light conversion performance of the quantum dots is improved.

[0050] According to one embodiment, the pulse width modulation command used to issue a command to the current source CS_B of the blue display subpixel SPix_B is a digital pulse width modulation command. In this case, the signal I_blue is a binary signal, and the color signal B is a digital signal.

[0051] Figure 4 shows a block diagram of one embodiment of the display subpixel SPix_B. The controllable current source CS_B includes a switch SW in series with an adjustable current source VCS that supplies a current of controllable intensity. The switch SW is controlled by the signal I_blue. The adjustable current source VCS is controlled by a constant bias signal Bias.

[0052] Figure 5 shows a block diagram of one embodiment of the display subpixel SPix_R. The controllable current source CS_R includes a MOS transistor. The signal I_red corresponds to an analog voltage applied to the gate of transistor CS_R. The display subpixel SPix_G may have the same structure as the display subpixel SPix_R.

[0053] According to one embodiment, each display pixel 12 i,j Data signal received by the conductive pad P_Col jThis is a binary signal that alternates between a Low logic state "0" and a High logic state "1". The Low logic state corresponds to a Low reference potential Gnd, and the High logic state "1" corresponds to a low voltage (e.g., approximately 1V) smaller than the reduced power supply voltage Vdd. In this embodiment, the stored color signals R, G, and B are digital signals.

[0054] Figure 6 shows the data signal. j When the signal is a binary signal and the color signals R, G, and B are digital signals, the display pixel 12 in Figure 3 i,j A block diagram of one embodiment of circuit 40 is shown. The memory circuit 48 includes three registers RR, GR, and BR. Bits of the digital color signal R are stored in the memory cell of register RR, bits of the digital color signal G are stored in the memory cell of register RG, and bits of the digital color signal B are stored in the memory cell of register RB. The driver circuit 50 includes a digital-to-analog converter DAC_R configured to receive the digital color signal R from register RR and convert the digital color signal R into an analog signal corresponding to the signal I_red. The driver circuit 50 also includes a digital-to-analog converter DAC_G configured to receive the digital color signal G from register RG and convert the digital color signal G into an analog signal corresponding to the signal I_green.

[0055] In another embodiment, the stored color signals R and G are analog signals. The storage circuit 48 may include capacitors configured to store the analog color signals R and G. In one embodiment, the circuit 48 is configured to convert data bits for the color signal R into an analog voltage proportional to the data, and the analog voltage is stored across a first capacitor. The voltage across the first capacitor may then correspond to the analog color signal R. The circuit 48 is configured to convert data bits for the color signal G into an analog voltage proportional to the data, and the analog voltage is stored across a second capacitor. The voltage across the second capacitor may then correspond to the analog color signal G.

[0056] According to one embodiment, each display pixel 12 i,j The selection signal Com is received at the conductive pad P_Row. i This is a binary signal that alternates between a Low logic state "0" and a High logic state "1". The Low logic state corresponds to a Low reference potential Gnd, and the High logic state "1" corresponds to a low voltage (for example, approximately 1V) that is smaller than the reduced power supply voltage Vdd.

[0057] Figure 7 shows the display pixels 12 of the display screen 10. i,j A block diagram of another embodiment is shown. Display pixel 12 shown in Figure 7 i,j This refers to the display pixel 12 shown in Figure 6. i,j It includes all elements of the interface circuit 46. In the first phase P1, also called the programming phase, the selected signal Com i or data signal j Clock signal Clk and data signal Data j The data signal Data is transmitted to the memory circuit 48, and in the second phase P2, also called the display phase, the selection signal Com is used to control the controllable current source CS_B of the display subpixel SPix_B. i The system is configured to transmit the modulation timing signal PWM from to the driver circuit 50. The modulation timing signal PWM is transmitted during each display phase P2, to the selection signal Com i It can be equal to the clock signal Clk, which is the selected signal Com. i During each programming phase P1 generated from, the selected signal Com i It can be equal to this. The memory circuit 48 is configured to store digital color signals R, G, and B based on the received digital data Data when it is clock-controlled by the clock signal Clk.

[0058] Figure 8 shows one embodiment of a method for displaying an image on a display screen 10, with a display pixel 12 having the structure shown in Figure 7. i,j This shows the timing diagram of the signals received.

[0059] The potentials Vcc and Gnd are substantially constant. The image pixels of the new image to be displayed are shown consecutively from rank 1 to rank M. The duration separating two consecutive selections of the same row on the display screen 10 is called the frame duration T. Signal Com i Knowing that the timing diagram is similar to that of signal Com1, albeit shifted in time, the timing diagrams for signal Com1 and signal Data1 are described in detail for the rank 1 row. For the rank 1 row, display pixels 12 where j changes from 1 to N. 1,j The display of new image pixels by includes a first phase P1 followed by a second phase P2. During phase P1, each display pixel 12 of the rank 1 row 1,j Data signal j The signal is transmitted, and only the signal Data1 is shown in Figure 8. During the second phase P2, each display pixel 12 1,j The light-emitting diode (LED) emits a data signal. j It is controlled by R, G, and B color signals determined based on [the specified criteria].

[0060] During the first phase P1, the selection signal Com1 is set to state "1". Setting the signal Com1 to state "1" for a long duration corresponds to each display pixel 12 in the rank 1 row. 1,j Detected by the interface circuit 46, and therefore the display pixel 12 of this row 1,j This allows selection of one row, but does not select display pixels in other rows. During the first phase P1, the data signal Data j 20 j It is transmitted upwards. Each display pixel 12 1,j Regarding this, the interface circuit 46 receives the data signal Data j The clock signal Clk and data Data are determined based on the pulse. As an example, the data signal Data j Each pulse may have a first duration, or a second duration longer than the first duration. The rising edges of the signal Clk are within a possible constant offset, and the data signal Data jThis can correspond to a sequence of pulses of the same duration that coincides with the rising edge of the pulse. Data is the signal Data j State "0" when the pulse has a first duration, and signal Data j The pulse may correspond to a binary signal in state "1" when it has a second duration. When selected by the signal Com1 in state "1", the interface circuit 46 transmits the data Data stored in circuit 48 in the form of an R, G, B digital signal having bits provided by a successive value of the signal Data, at the rate of the clock signal Clk. The end of the first period P1 of one row corresponds to the beginning of the first period P1 of the next row.

[0061] According to one embodiment, the light-emitting diodes of the display subpixels SPix_B are controlled by pulse width modulation or PWM control. For this purpose, during the second phase P2, the selection signal Com1 is used to clock-control the operation of the circuit 50 for controlling the light-emitting diode LEDs of the display subpixels SPix_B by pulse width modulation, for each display pixel 12 in the rank 1 row. 1,j The interface circuit 46 presents a series of repetitions of pulses in state "1" (PWM signal) transmitted to circuit 50. The number of pulses in the series corresponds to the number of bits in each B digital signal. As an example, if the current source CS_B is as shown in Figure 4, the switch SW is opened and closed at the rate of the PWM pulses according to the value "0" or "1" of each bit of the B color signal, starting from the most significant bit, and this transistor is kept on or off until the next pulse of signal Com1. The duration between two consecutive pulses of signal Com1 is halved each time, so the total duration that the light-emitting diode is on depends on the value of the B color signal. The series of pulses of signal Com1 is repeated until the next first phase P1 of the rank 1 row, with one repetition shown as an example in Figure 8.

[0062] According to another embodiment, each display pixel 12 i,j Data signal received by the conductive pad P_Col jThis is an analog signal. The memory circuit 48 may include a capacitor configured to store the analog color signals R, G, and B.

[0063] Figure 9 shows the display pixels 12 of the display screen 10. i,j A block diagram of another embodiment is shown. Display pixel 12 shown in Figure 9 i,j This refers to the display pixel 12 shown in Figure 6. i,j It includes all elements of the following. According to one embodiment, each display pixel 12 i,j The selection signal Com is received at the conductive pad P_Row. i This is an analog signal. The interface circuit 46 receives the data signal Data in the programming phase P1. j The driver circuit 50 receives the analog signal Data and transmits it to the memory circuit 48, which is configured to provide an analog reference signal REF adapted for PWM control in the display phase P2. The memory circuit 48 includes a capacitor CR for storing the analog color signal R. The analog color signal R may correspond to the voltage across capacitor CR. The memory circuit 48 includes a capacitor CG for storing the analog color signal G. The analog color signal G may correspond to the voltage across capacitor CG. The memory circuit 48 includes a capacitor CB for storing the analog color signal B. The analog color signal B may correspond to the voltage across capacitor CB. The driver circuit 50 is configured to issue commands to the controllable current sources CS_R, CS_G, and CS_B coupled to the light-emitting diode LEDs using control signals obtained from the analog control signals R, G, and B, and, for the current source CS_B of the display subpixel SPix_B, also using a control signal obtained from the analog reference signal REF.

[0064] In one embodiment, the signal Com i This is a display pixel 12 for storing the data signal Data. i,j This allows for both the selection of the display subpixel SPix_B and the transmission of an analog reference signal used for PWM control of the light-emitting diodes.

[0065] FIG. 10 shows, for one embodiment of a method for displaying an image on a display screen 10, the display pixels 12 i,j timing diagram of the signals received. For illustrative purposes, FIG. 10 shows only the signals associated with the rank 1 row and the rank 1 column of the display screen 10.

[0066] In the present embodiment, the potential Vcc and the potential Gnd are not shown in FIG. 10, but are substantially constant during the operation of the display screen 10. Image pixels of a new image to be displayed are sequentially displayed from the rank 1 row to the rank M row. The duration separating two consecutive selections of the same row of the display screen 10 is referred to as a frame duration T. The display pixels 12 of the rank i row, where j varies from 1 to N 1,j The display of new image pixels by means of includes a first phase P1 followed by a second phase P2. During phase P1, the display pixels 12 of the rank i row 1,j receive the analog data signal Data j is transmitted, and only the signal Data1 is shown in FIG. 10. Each display pixel 12 i,j stores the new value of the R, G or B analog color signal based on the received analog data signal Data j . According to one embodiment, the display pixel 12 i,j can continuously receive the data signals Data corresponding to different colors during phase P1. During the second phase P2, each display pixel 12 j 1,j light emitting diodes are controlled from the stored R, G, B color signals.

[0067] During the first phase P1, the selection signal Com i is set to a High level and is substantially constant, thus forming a voltage pulse. The signal Com i pulses are detected by the interface circuit 46 of each display pixel 12 in the rank i row i,j , and thus the display pixels 12 in this row i,j ​makes it possible to select, while the display pixels of other rows are not selected. According to one embodiment, the duration of each pulse is shorter than the duration of a frame divided by the number of rows to be selected, preferably shorter than 100 μs. During the first phase P1, the data signal Data j is transmitted to the column electrodes 20 j . Each data signal Data j may correspond to an analog signal that can take a constant value from a minimum value to a maximum value. The interface circuit 46 transmits the signal Data j in the form of an R, G, or B signal having a value corresponding to the signal Data to the display pixel 12 1,j the signal Data stored in the circuit 50 j , and the signal R stored by the display pixel 12 1,1 1,1 and the current I flowing through the light emitting diode of the display sub-pixel SPix_B of the display pixel 12 1,1 LED1,1 is shown in FIG. 10 as an example. The end of the first phase P1 of a certain row may correspond to the start of the first phase P1 of the next row.

[0068] According to one embodiment, the light emitting diode of the display sub-pixel SPix_B of the display pixel 12 1,j is controlled by pulse width modulation. For this purpose, during the first portion P2_ON of the second phase P2, the selection signal Com i changes periodically, and each display pixel 12 in the row of rank i i,j ​​The interface circuit 46 presents a series of identical patterns detected by the interface circuit 46. The interface circuit 46 transmits the series of patterns to the circuit 50 as an analog reference signal REF for controlling the light-emitting diode LED of the display subpixel SPix_B by pulse width modulation. As an example, in Figure 10, each pattern includes a rising voltage ramp followed by a falling voltage ramp. According to another example, each pattern includes only one rising voltage ramp or only one falling voltage ramp. In general, each pattern includes a determined voltage fluctuation curve, e.g., an exponential growth curve, a sine curve, etc. The shape of the pattern may include, for example, eye sensitivity compensation, in particular gamma correction. The pattern repetition frequency for each phase P2_OFF allows for 1 to 1,000 pattern cycles per phase P2_OFF.

[0069] Display pixels 12 i,j The circuit 50 controls the light-emitting diode LED of the display subpixel SPix_B based on a comparison between the stored B analog signal and the analog reference signal REF. For example, the current source CS_B of the display subpixel SPix_B is turned off when the stored B analog signal is greater than the analog reference signal REF, and as a result the current I supplied to the light-emitting diode is turned off. LED When this becomes zero, the current source CS_B for the display subpixel SPix_B is turned on when the stored B analog signal is smaller than the analog reference signal REF, and as a result, a constant non-zero current I is supplied to the light-emitting diode. LED1,1 You can obtain this.

[0070] During the second part of the second phase P2, P2_OFF, the selected signal Com i The LED is maintained at a constant level, for example, a Low level, and therefore the light-emitting diode LED of the display subpixel SPix_B of the display pixels in that row is off. The duration of the second part P2_OFF can vary from 0% to 100% of the duration of the second phase P2. In particular, the second part P2_OFF may not exist. According to one embodiment, the duration of each phase P2 is equal to the duration of the frame Tframe, which is reduced by the duration of phase P1.

[0071] During the display phase P2, the driver circuit 50 uses the obtained control signals I_red and I_green (which may correspond to analog control signals R and G) to send commands to the controllable current sources CS_R and CS_G coupled to the light-emitting diode LEDs of the display subpixels SPix_R and SPix_B.

[0072] According to another embodiment, each display pixel 12 i,j Data signal received by the conductive pad P_Col j A is a digital signal for transmitting color signal B, and analog signals for transmitting color signals G and R. Therefore, color signal B is a digital signal, and the memory circuit 48 can include a register for storing the digital color signal B. Furthermore, color signals R and G are analog signals, respectively. The memory circuit 48 can include capacitors configured to store the analog color signals R and G.

[0073] Figure 11 shows a display pixel 12 containing microwires or nanowires. i,j This is a partially simplified cross-sectional view of one embodiment. Display pixel 12 i,j From bottom to top of Figure 11, - A substrate 60 including opposing surfaces 62, 64, wherein the upper surface 62 is preferably flat at least at the level of the light-emitting diode, - Made of a material that promotes wire growth, a seed layer 66 is placed on the surface 62, - An insulating layer 68 that covers the seed layer 66 and includes an opening 70 that exposes a portion of the seed layer 66, - A light-emitting diode LED (six light-emitting diodes are shown), where each light-emitting diode LED is in contact with the seed layer 66 through one of the apertures 70, - An insulating layer 74 extending from the lower side of the light-emitting diode LED and extending onto the insulating layer 68 between the light-emitting diode LEDs, - An electrode is formed to cover each light-emitting diode LED, and a layer 76 extends further on the insulating layer 74 between the light-emitting diode LEDs, - A reflective conductive layer 78 extending on the layer 76 between light-emitting diodes (LEDs), wherein, as one modification, the conductive layer 78 may be interposed between the electrode layer 76 and the insulating layer 74 between the light-emitting diodes (LEDs), - Dielectric protective layer 80 extending over layers 76 and 78, - A photoluminescent block 82 covering the light-emitting diode assemblies of the display subpixels SPix_R and SPix_G, -A block 84 that is transparent to radiation emitted by the light-emitting diode of the display subpixel SPix_B, and the transparent block 84 may be omitted. -A wall 88 between blocks 82 and 84, where each wall 88 is opaque to radiation emitted by light-emitting diodes (LEDs), -One, two, or three color filters 90 covering at least a portion of blocks 82, 84, for example, a single yellow filter, two filters (the first being a yellow filter and the second a red filter), or three filters (the first being a red filter, the second a green filter, and the third a blue filter), with one, two, or three color filters 90, where a single filter 90 covering two blocks is shown as an example, and Includes.

[0074] According to one embodiment, each light-emitting diode can be a three-dimensional light-emitting diode. According to one embodiment, the light-emitting diode LED includes a semiconductor layer made of a III-V compound, such as GaN, AlN, InN, InGaN, AlGaN, or AlInGaN, or a semiconductor layer made of a II-VI compound.

[0075] A three-dimensional light-emitting diode (LED) includes a three-dimensional semiconductor element, such as a wire-like, conical, frustoconical, or pyramidal element, particularly a microwire or nanowire, on which the active region of the LED extends. The terms "microwire" or "nanowire" refer to a three-dimensional structure with an elongated shape in a preferred direction, where at least two dimensions, called small dimensions, are 5 nm to 2.5 μm (preferably 50 nm to 2.5 μm), and a third dimension, called large dimensions, is at least 1 times (preferably at least 2 times) the largest of the small dimensions. In certain embodiments, the small dimensions may be about 3 μm or less, preferably 100 nm to 3 μm, more preferably 1 μm to 1.5 μm. In certain embodiments, the height of each microwire or nanowire may be 500 nm or more, preferably 1 μm to 50 μm.

[0076] Figure 12 shows display pixels 12 i,j This is a partial and schematic cross-sectional view of one embodiment of a light-emitting diode LED. According to one embodiment, each light-emitting diode LED includes a wire 90 in contact with a seed layer 66 through one of the openings 70, and a shell 92 which includes a stack of semiconductor layers covering the sidewalls and top of the wire 90. Such a configuration is called a radial type. The assembly formed by each wire 90 and the associated shell 92 constitutes a light-emitting diode LED.

[0077] The shell 92 may include a stack of several layers, particularly an active layer 94 and a junction layer 96. The active layer 94 is the layer from which most, preferably all, of the radiation supplied by the light-emitting diode LED originates. For example, the active layer 94 may include confinement means such as a single quantum well or multiple quantum wells. The junction layer 96 may include a stack of semiconductor layers that are the same III-V material as the wire 90, but with the opposite conductivity type to that of the wire 90.

[0078] Figure 13 shows display pixels 12 i,jThis is a partial and schematic cross-sectional view of another embodiment of the light-emitting diode LED. The light-emitting diode LED shown in Figure 13 includes all the elements of the light-emitting diode LED shown in Figure 12, differing in that the shell 92 is located only on top of the wire 90. Such a configuration is called the axial type.

[0079] The formation of the light-emitting diode LEDs shown in Figures 12 and 13, i.e., the growth of the wire 90 within the aperture 70 and the formation of the shell 92 covering the wire 90, can be carried out, for example, by metal-organic chemical vapor deposition (MOCVD) or any other suitable method.

[0080] The substrate 60 may correspond to the previously disclosed control circuit 30.

[0081] The seed layer 66 is made of a material that promotes wire growth. For example, the material forming the seed layer 66 may be a nitride, carbide, or boride of a transition metal from group IV, V, or VI of the periodic table, or a combination of these compounds. According to one embodiment, the seed layer 66 may be omitted. According to another embodiment, the seed layer 66 may be replaced, for example, by a seed pad formed at the bottom of the opening 70.

[0082] Each insulating layer 68, 74, and 80 is made of a dielectric material, such as silicon oxide (SiO2) or silicon nitride (Si x N y In the formula, x is approximately equal to 3 and y is approximately equal to 4, for example, Si3N4), silicon oxynitride (especially with the general formula SiO2 x N y These can be made of materials such as Si2ON2, aluminum oxide (Al2O3), hafnium oxide (HfO2), titanium dioxide (TiO2), or diamond. The insulating layers 68, 74, and 80 may have a single-layer structure or be a stack of two or three or more layers. If the insulating layer 68 corresponds to a stack of at least two layers, the upper layer of the stack is an insulating type made of, for example, a dielectric material.

[0083] The conductive layer 78 preferably corresponds to a metal layer, such as aluminum, silver, copper, gold, or zinc. The thickness of the conductive layer 78 may be in the range of 0.01 μm to 1,000 μm.

[0084] The electrode layer 76 is capable of passing electromagnetic radiation emitted by the light-emitting diode. The material forming the electrode layer 76 may be a transparent conductive material such as indium tin oxide (ITO), aluminum zinc oxide, or gallium zinc oxide, or graphene. The thickness of the electrode layer 76 may be in the range of 0.01 μm to 10 μm.

[0085] According to one embodiment, each photoluminescence block 82 is positioned opposite one of the light-emitting diodes or an assembly of light-emitting diodes. Each photoluminescence block 82 includes a light-emitting element that, when excited by light emitted by the associated light-emitting diode LED, can emit light of a different wavelength than the light emitted by the associated light-emitting diode LED. According to one embodiment, the display pixel 12 i,j The device includes at least two types of photoluminescence blocks 82. Each photoluminescence block 82 of the first type can convert radiation supplied by a light-emitting diode into first radiation of a first wavelength, and each photoluminescence block 82 of the second type can convert radiation supplied by a light-emitting diode that it covers into second radiation of a second wavelength.

[0086] According to one embodiment, the light-emitting diode can emit blue light, i.e., radiation having a wavelength in the range of 430 nm to 480 nm. According to one embodiment, the first wavelength corresponds to green light and is in the range of 510 nm to 570 nm. According to one embodiment, the second wavelength corresponds to red light and is in the range of 600 nm to 720 nm.

[0087] The aspect ratio of block 82, i.e., the ratio of the height to the maximum width of the block, may be in the range of 0.01 to 10, preferably 0.05 to 2.

[0088] According to one embodiment, each photoluminescent block 82 contains, for example, particles of at least one photoluminescent material in a transparent matrix. An example of a photoluminescent material is YAG:Ce or YAG:Ce 3+ It is yttrium aluminum garnet (YAG), also known as trivalent cerium ion-activated yttrium aluminum garnet (YAG). The average particle size of conventional photoluminescent materials is generally over 5 μm.

[0089] According to one embodiment, each photoluminescent block 82 includes a matrix in which single crystal particles of a semiconductor material in the nanometer range, which are hereafter also referred to as semiconductor nanocrystals or nanoluminescent particles, are dispersed. The internal quantum efficiency QY of the photoluminescent material int QY is equal to the ratio of the number of photons emitted to the number of photons absorbed by the photoluminescent material. int This is more than 5%, preferably more than 10%, and more preferably more than 20%.

[0090] According to one embodiment, the average size of the nanocrystals is in the range of 0.5 nm to 1000 nm, preferably 0.5 nm to 500 nm, more preferably 1 nm to 100 nm, and particularly 2 nm to 30 nm. For dimensions less than 50 nm, the photoconversion properties of semiconductor nanocrystals depend essentially on quantum confinement phenomena. In this case, the semiconductor nanocrystals correspond to quantum dots.

[0091] According to one embodiment, the semiconductor material for the semiconductor crystal is selected from the group comprising cadmium selenide (CdSe), indium phosphide (InP), cadmium sulfide (CdS), zinc sulfide (ZnS), zinc selenide (ZnSe), cadmium telluride (CdTe), zinc telluride (ZnTe), cadmium oxide (CdO), zinc cadmium oxide (ZnCdO), zinc cadmium sulfide (CdZnS), zinc cadmium selenide (CdZnSe), indium silver sulfide (AgInS2), PbScX3 type perovskites where X is a halogen atom, particularly iodine (I), bromine (Br), or chlorine (Cl), and mixtures of at least two of these compounds. According to one embodiment, the semiconductor material for the semiconductor nanocrystal is selected from the materials described in the publication of Le Blevenec et al., Physica Status Solidi (RRL)-Rapid Research Letters, Vol. 8, No. 4, pp. 349-352, April 2014.

[0092] According to one embodiment, the dimensions of the semiconductor nanocrystal are selected according to the desired wavelength of radiation emitted by the semiconductor nanocrystal. For example, CdSe nanocrystals with an average size of about 3.6 nm can convert blue light to red light, and CdSe nanocrystals with an average size of about 1.3 nm can convert blue light to green light. According to another embodiment, the composition of the semiconductor nanocrystal is selected according to the desired wavelength of radiation emitted by the semiconductor nanocrystal.

[0093] The matrix is ​​at least partially, preferably more than 80%, transparent to radiation emitted by photoluminescent particles and / or light-emitting diodes (LEDs). The matrix is ​​made of, for example, silica. The matrix is ​​made of, for example, any at least partially transparent polymer, particularly silicone, acrylic resin or poly(methyl methacrylate) (PMMA) type, or polylactic acid (PLA). The matrix may be made of a at least partially transparent polymer, in particular, used with a three-dimensional printer. The matrix may correspond to photosensitive or non-photosensitive glass (SOG, spin-on glass) deposited by centrifugal coating. According to one embodiment, the matrix contains 2% to 90%, preferably 10% to 60% by weight of nanocrystals, for example, about 30% by weight of nanocrystals.

[0094] The thickness of the photoluminescence block 82 depends on the concentration of the nanocrystals and the type of nanocrystals used. The height of the photoluminescence block 82 is preferably greater than the height of the wire 71 and less than or equal to the height of the wall 88. In the top view, each photoluminescence block 82 may correspond to a square, rectangle, L-shaped polygon, etc., having an area that may be equal to the area of ​​a square with sides of 1 μm to 100 μm, preferably 3 μm to 15 μm.

[0095] According to one embodiment, an opaque wall 88 reflects radiation emitted by a light-emitting diode LED. The wall 88 is at least partially made of at least one reflective material. The reflective material may be a combination of at least two metallic materials, particularly iron, copper, aluminum, tungsten, silver, titanium, hafnium, zirconium, or compounds thereof. Preferably, the wall 88 is made of a material that is compatible with the manufacturing method carried out in microelectronics. Preferably, the wall 88 is made of aluminum or silver.

[0096] The height of the wall 88, measured along a direction perpendicular to the surface 62, is in the range of 300 nm to 200 μm, preferably 3 μm to 15 μm. The thickness of the wall 88, measured along a direction parallel to the surface 62, is in the range of 100 nm to 50 μm, preferably 0.5 μm to 10 μm.

[0097] According to one embodiment, the wall 88 may be made of a reflective material or may be covered with a coating that reflects the wavelength of radiation emitted by the photoluminescent block 82 and / or light-emitting diode. Preferably, the wall 88 surrounds the photoluminescent block 82. In this case, the wall 88 reduces crosstalk between adjacent photoluminescent blocks 82.

[0098] Various embodiments and modifications have been described. Those skilled in the art will understand that certain features of these various embodiments and modifications may be combined, and other modifications will be conceivable to those skilled in the art.

[0099] Finally, the practical implementation of the described embodiments and modifications is within the capabilities of those skilled in the art based on the functional descriptions given above.

[0100] This application claims priority to French Patent Application No. 23 / 09903, filed on 19 September 2023, entitled “Display Pixel Including Light-Emitting Diode and Display Screen Having Such Display Pixel,” which is incorporated herein by reference to the maximum extent permitted by law.

Claims

1. At least first and second light-emitting diodes (LEDs), A first controllable current source (CS_B) that supplies a first current to the first light-emitting diode (LED), A second controllable current source (CS_R) supplies a second current to the second light-emitting diode (LED), Electronic circuit (40) and The electronic circuit (40) is provided with, A memory circuit (48) for storing at least first and second color signals (R, B), A driver circuit (50) is configured to control the first controllable current source (CS_B) to supply the first current by pulse width modulation based on the first color signal (B), and to control the second controllable current source (CS_R) to supply the second current by a linear command based on the second color signal (R). Display pixels (12 ｉ，ｊ ).

2. The display pixel according to claim 1, further comprising a third light-emitting diode (LED) and a third controllable current source (CS_G) for supplying a third current to the third light-emitting diode (LED), wherein the memory circuit (48) is configured to store a third color signal (G), and the driver circuit (50) is configured to control the third controllable current source (CS_G) to supply the third current by a linear command based on the third color signal (G).

3. The display pixel according to claim 1 or 2, wherein the first color signal (B) is a digital signal, and the memory circuit (48) includes a first memory cell (RB) for storing bits of the first color signal (B).

4. The display pixel according to any one of claims 1 to 3, wherein the second color signal (R) is a digital signal, and the memory circuit (48) includes a second memory cell (RR) for storing bits of the second color signal (R).

5. The display pixel according to claim 4, wherein the driver circuit (50) includes a digital-to-analog converter (DAC_R) configured to convert the second color signal (R) stored in the second memory cell (RR) into an analog control signal (I_red) for controlling the second controllable current source (CS_R).

6. The display pixel according to claim 1 or 2, wherein the first color signal (B) is an analog signal, and the memory circuit (48) includes a first capacitor (CB) for storing the first color signal (B).

7. The display pixel according to claim 1 or 2, wherein the second color signal (R) is an analog signal, and the memory circuit (48) includes a second capacitor (CR) for storing the second color signal (B).

8. The display pixel according to any one of claims 1 to 7, wherein each of the first and second light-emitting diodes (LEDs) comprises several element light-emitting diodes, each including an active region (94) covering a three-dimensional semiconductor element (90) corresponding to a wire-like, conical, frustoconical, or pyramidal element in the range of nanometers or micrometers.

9. The display pixel according to any one of claims 1 to 8, wherein the second light-emitting diode (LED) is covered by a first photoluminescence block (82).

10. The display pixel according to claim 9, wherein the first light-emitting diode (LED) is configured to emit a first radiation of a first wavelength, the second light-emitting diode (LED) is configured to emit a second radiation of a second wavelength, and the first photoluminescence block (82) is configured to convert the second radiation into a third radiation of a third wavelength different from the second wavelength.

11. The display pixel according to claim 10, wherein the first wavelength is equal to the second wavelength by no more than 10%.

12. The display pixel according to any one of claims 9 to 11, wherein the first photoluminescent block (82) includes a first quantum dot.

13. The display pixel according to claim 2, wherein the third light-emitting diode (LED) is covered by a second photoluminescent block (82).

14. The display pixel according to claims 10 and 13, wherein the third light-emitting diode (LED) is configured to emit a fourth radiation of a fourth wavelength, and the second photoluminescence block (82) is configured to convert the fourth radiation into a fifth radiation of a fifth wavelength different from the fourth wavelength.

15. The display pixel according to claim 14, wherein the fourth wavelength is equal to the first wavelength by no more than 10%.

16. The display pixel according to any one of claims 13 to 15, wherein the second photoluminescent block (82) includes a second quantum dot.

17. A display pixel according to any one of claims 1 to 16, comprising a single integrated circuit (30) including the electronic circuit (40) which includes the memory circuit (48) and the driver circuit (50).

18. The display pixel according to claim 17, comprising an optoelectronic circuit (32) attached to the integrated circuit (30), wherein the optoelectronic circuit (32) includes the first and second light-emitting diodes (LEDs).

19. Display pixels (12) according to any one of claims 1 to 18 ｉ，ｊ )and, The aforementioned display pixels (12 ｉ，ｊ The first electrode (18) is coupled to the driver circuit (50) of the above. ｉ )and, The display pixel (12) coupled to the first electrode ｉ，ｊ To select ), a selection signal (Com) is applied to each first electrode. ｉ A first circuit (22) for transmitting ) and The aforementioned display pixels (12 ｉ，ｊ The second electrode (20) is coupled to the aforementioned electronic circuit (40) of ) ｊ )and, A data signal (Data ｊ ) on the second electrode, and a second circuit (24) for transmitting A display screen (10) including the display screen.

20. The second circuit (24) has the second electrode (20 ｊ ) on the data signal (Data ｊ The display screen according to claim 19, configured to transmit ) as an analog signal.

21. The second circuit (24) has the second electrode (20 ｊ ) on the data signal (Data ｊ The display screen according to claim 19, configured to transmit ) as a digital signal.

22. The second circuit (24) has the second electrode (20 ｊ ) The data signal (Data) includes alternating digital and analog signals ｊ The display screen according to claim 19, configured to transmit )

Images