Light emitting diode display pixel with micro-lenses stacked on light emitting diodes

Abstract

To extract light from light emitting diodes (and thereby improve the efficiency of a display), a microlens stack can be formed over the light emitting diodes. The microlens stack can include a microlens array covered by an additional single microlens. Stacking microlenses in this manner improves the lens optical power without increasing the thickness of the display. The microlens array can be formed from an inorganic material, while the additional single microlens can be formed from an organic material. The additional single microlens can conform to the upper surface of the microlens array. An additional low refractive index layer can be interposed between the light emitting diodes and the microlens array. A diffusion layer can be formed around the light emitting diodes to trap light emitted from the sidewalls of the light emitting diodes.

Description

[0001] This application claims priority to U.S. Patent Application No. 17 / 225,796, filed April 8, 2021, and U.S. Provisional Patent Application No. 63 / 038,318, filed June 12, 2020, the entire contents of which are incorporated herein by reference. Background Technology

[0002] This disclosure relates in general to electronic devices, and more specifically to electronic devices having a display.

[0003] Electronic devices typically include displays. For example, an electronic device may have a light-emitting diode (OLED) display based on light-emitting diode pixels. In this type of display, each pixel includes a light-emitting diode and a thin-film transistor (TFT), which controls the application of signals to the light-emitting diode to generate light. The light-emitting diode may include an OLED layer positioned between an anode and a cathode. To emit light from a given pixel in an OLED display, a voltage can be applied to the anode of the given pixel.

[0004] It is under these circumstances that the implementation scheme described in this paper was developed. Summary of the Invention

[0005] Electronic devices may have a display that includes an array of light-emitting diodes (LEDs). Each LED may be mounted on a substrate and may include an anode and a cathode.

[0006] To extract light from a light-emitting diode (LED) (and thus improve the efficiency of the display), a stack of microlenses can be formed above the LED. This microlens stack can comprise an array of microlenses covered by additional individual microlenses. Stacking microlenses in this manner improves the optical capabilities of the lenses without increasing the thickness of the display.

[0007] The microlens array can be formed from an inorganic material with a high refractive index (such as 2.0). Additional individual microlenses can be formed from an organic material with a lower refractive index than the microlens array (e.g., 1.7). The additional individual microlens can be conformally fitted to the upper surface of the microlens array.

[0008] An additional low-refractive-index layer can be inserted between the light-emitting diode (LED) and the microlens array. This low-refractive-index layer can increase the lens optical capability of the microlens stack and improve recycling efficiency for the display. A low-refractive-index protective layer can be formed above the microlens stack. A diffusion layer can be formed around the LED to trap light emitted from the LED sidewalls. A protective layer can also be formed between the microlens layers. Attached Figure Description

[0009] Figure 1This is a schematic diagram of an exemplary electronic device with a display according to one embodiment.

[0010] Figure 2 This is a schematic diagram of an exemplary display according to one implementation scheme.

[0011] Figure 3 This is a diagram of an exemplary display pixel circuit according to one implementation scheme.

[0012] Figure 4 It is a cross-sectional side view of an exemplary display pixel according to one embodiment, including a light-emitting diode covered by a microlens array and an additional individual microlens.

[0013] Figure 5 It is an exemplary display pixel (such as a microlens array and additional individual microlenses) according to one embodiment. Figure 4 A top view of the display pixels.

[0014] Figure 6 It is a cross-sectional side view of an exemplary display pixel according to one embodiment, including a light-emitting diode covered by a microlens array and an additional individual microlens, but excluding an opaque masking layer.

[0015] Figure 7 It is a cross-sectional side view of an exemplary display pixel according to one embodiment, including a light-emitting diode covered by a microlens array and an additional single microlens having a width greater than that of the microlens array.

[0016] Figure 8 It is a cross-sectional side view of an exemplary display pixel according to one embodiment, comprising a light-emitting diode covered by a microlens array and an additional single microlens having a width smaller than that of the microlens array.

[0017] Figures 9A to 9D This is a cross-sectional side view of an exemplary microlens array showing different possible shapes for the microlenses according to one embodiment. Detailed Implementation

[0018] Figure 1The illustration shows exemplary electronic devices of various types that may have displays. Electronic device 10 may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular phone, a media player or other handheld or portable electronic device, a smaller device (such as a wristwatch, a hanging device, a headset or handset, a device embedded in glasses or other equipment worn on a user's head, or other wearable or micro-devices), a display, a computer monitor containing an embedded computer, a computer monitor not containing an embedded computer, a gaming device, a navigation device, an audio device (e.g., a speaker), an embedded system (such as a system in which electronic equipment with a display is installed in an information kiosk or a car), or other electronic equipment. Electronic device 10 may have the shape of a pair of glasses (e.g., a support frame), may be formed with a helmet-shaped shell, or may have other configurations for helping to mount and secure components of one or more displays on or near a user's head.

[0019] like Figure 1 As shown, the electronic device 10 may include control circuitry 16 for supporting the operation of the device 10. Control circuitry 16 may include memory, such as hard disk drive memory, non-volatile memory (e.g., flash memory configured to form a solid-state drive or other electrically programmable read-only memory), volatile memory (e.g., static random access memory or dynamic random access memory), and so on. Processing circuitry in control circuitry 16 can be used to control the operation of device 10. This processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application-specific integrated circuits, etc.

[0020] Input-output circuitry in device 10, such as input-output device 12, can be used to allow data to be supplied to device 10 and to be supplied from device 10 to external devices. Input-output device 12 may include buttons, joysticks, scroll wheels, touchpads, keypads, keyboards, microphones, speakers, audio generators, vibrators, cameras, sensors, LEDs and other status indicators, data ports, etc. Users can control the operation of device 10 by supplying commands through the input resources of input-output device 12, and can receive status information and other outputs from device 10 using the output resources of input-output device 12.

[0021] Input-output device 12 may include one or more displays, such as display 14. Display 14 may be a touchscreen display including touch sensors for acquiring touch input from a user, or display 14 may be touch-insensitive. The touch sensor of display 14 may be based on an array of capacitive touch sensor electrodes, an acoustic touch sensor structure, a resistive touch element, a force-based touch sensor structure, a light-based touch sensor, or other suitable touch sensor arrangement. The touch sensor for display 14 may be formed by electrodes formed on a common display substrate having display pixels of display 14, or may be formed by a separate touch sensor panel overlapping the pixels of display 14. If desired, display 14 may be touch-insensitive (i.e., the touch sensor may be omitted). Display 14 in electronic device 10 may be a head-up display, which can be viewed without requiring the user to move away from a typical viewpoint, or may be a head-mounted display incorporated into a device worn on the user's head. If desired, display 14 may also be a holographic display for displaying holograms.

[0022] The control circuit 16 can be used to run software, such as operating system code and applications, on the device 10. During operation of the device 10, the software running on the control circuit 16 can display images on the display 14.

[0023] Figure 2 The illustration is shown for example, display 14. Figure 2 As shown, the display 14 may include layers, such as a substrate layer 26. The substrate layer, such as layer 26, may be formed of a rectangular planar material layer or a material layer having other shapes (e.g., circular or other shapes having one or more curved edges and / or straight edges). The substrate layer of the display 14 may include a glass layer, a polymer layer, a silicon layer, a composite film comprising polymeric and inorganic materials, a metal foil, etc.

[0024] Display 14 may have an array of pixels 22 for displaying images to a user, such as a pixel array 28. The pixels 22 in array 28 may be arranged in rows and columns. The edges of array 28 may be straight or curved (i.e., each row and / or column of pixels 22 in array 28 may have the same length or may have different lengths). Any suitable number of rows and columns may exist in array 28 (e.g., ten or more, one hundred or more, or one thousand or more, etc.). Display 14 may include pixels 22 of different colors. For example, display 14 may include red pixels, green pixels, and blue pixels. Pixels of other colors, such as cyan, magenta, and yellow, may also be used.

[0025] The display driver circuit 20 can be used to control the operation of the pixel 28. The display driver circuit 20 may be formed of an integrated circuit, a thin-film transistor circuit, and / or other suitable circuits. Figure 2 An exemplary display driver circuit 20 includes a display driver circuit 20A and additional display driver circuitry such as a gate driver circuit 20B. The gate driver circuit 20B may be formed along one or more edges of the display 14. For example, the gate driver circuit 20B may be arranged along the left and right sides of the display 14, such as... Figure 2 As shown.

[0026] like Figure 2 As shown, the display driver circuit 20A (e.g., one or more display driver integrated circuits, thin-film transistor circuits, etc.) may include communication circuitry for communicating with system control circuitry via signal path 24. Path 24 may be formed by traces or other cables on a flexible printed circuit. Control circuitry may be located on one or more printed circuits in the electronic device 10. During operation, the control circuitry (e.g., Figure 1 The control circuit 16) can provide image data to circuits such as the display driver integrated circuit in circuit 20 for displaying the image on the display 14. Figure 2 The display driver circuit 20A is located at the top of the display 14. This is merely illustrative. The display driver circuit 20A may be located at both the top and bottom of the display 14, or it may be located in other parts of the device 10.

[0027] In order to display an image on pixel 22, display driver circuit 20A can supply corresponding image data to data line D when a control signal is sent to a supporting display driver circuit, such as gate driver circuit 20B, via signal path 30. Utilizing Figure 2 In an exemplary arrangement, the data line D extends vertically through the display 14 and is associated with the corresponding column of the pixel 22.

[0028] The gate driver circuit 20B (sometimes referred to as the gate line driver circuit or the horizontal control signal circuit) may be implemented using one or more integrated circuits, and / or using thin-film transistor circuitry on the substrate 26. Horizontal control lines G (sometimes referred to as gate lines, scan lines, emit control lines, etc.) extend horizontally through the display 14. Each gate line G is associated with a corresponding row of pixels 22. Multiple horizontal control lines, such as gate lines G associated with each row of pixels, may be present if desired. Individually controlled signal paths and / or global signal paths in the display 14 may also be used to transmit other signals (e.g., power signals, etc.).

[0029] Gate driver circuit 20B asserts control signals on gate lines G in display 14. For example, gate driver circuit 20B may receive clock signals and other control signals from circuit 20A on path 30, and in response to the received signals, may sequentially assert gate line signals on gate lines G, starting from the gate line signals G in the first row of pixels 22 in array 28. When each gate line is asserted, data from data line D may be loaded into the corresponding row of the pixel. In this way, control circuits such as display driver circuits 20A and 20B may provide signals to pixel 22 to instruct pixel 22 to display a desired image on display 14. Each pixel 22 may have light-emitting diodes and circuitry (e.g., thin-film circuitry on substrate 26) that respond to control signals and data signals from display driver circuit 20.

[0030] Gate driver circuitry 20B may include gate driver circuit blocks, such as gate driver row blocks. Each gate driver row block may include circuitry such as output buffers and other output driver circuitry, register circuitry (e.g., registers that may be linked together to form a shift register), and signal lines, power lines, and other interconnects. Each gate driver row block may provide one or more gate signals to one or more corresponding gate lines in the corresponding pixel row of the pixel array in the effective area of ​​display 14.

[0031] A schematic diagram of an exemplary pixel circuit of the type that can be used for each pixel 22 in array 28 is shown in Figure 3 It is shown in the middle. For example... Figure 3 As shown, display pixel 22 may include a light-emitting diode 38. A positive power supply voltage ELVDD can be provided to a positive power supply terminal 34, and a ground power supply voltage ELVSS can be provided to a ground power supply terminal 36. Diode 38 has an anode (terminal AN) and a cathode (terminal CD). The state of drive transistor 32 controls the amount of current flowing through diode 38, and thus controls the amount of emitted light 40 from display pixel 22. Since the cathode CD of diode 38 is coupled to ground terminal 36, the cathode terminal CD of diode 38 may sometimes be referred to as the ground terminal of diode 38.

[0032] To ensure that transistor 38 remains in the desired state between consecutive data frames, display pixel 22 may include a storage capacitor, such as storage capacitor Cst. A voltage on storage capacitor Cst is applied to the gate of transistor 32 at node A to control transistor 32. One or more switching transistors, such as switching transistor 33, may be used to load data into storage capacitor Cst. When switching transistor 33 is off, data line D is isolated from storage capacitor Cst, and the gate voltage at terminal A is equal to the data value stored in storage capacitor Cst (i.e., the data value from the previous frame of display data displayed on display 14). When a gate line G (sometimes referred to as a scan line) in the row associated with display pixel 22 is determined, switching transistor 33 is turned on, and a new data signal on data line D is loaded into storage capacitor Cst. The new signal on capacitor Cst is applied to the gate of transistor 32 at node A, thereby regulating the state of transistor 32 and adjusting the corresponding amount of light 40 emitted by light-emitting diode 38. If desired, light-emitting diodes (e.g., such as...) used to control display pixels in display 14... Figure 3 The circuitry for operating the display pixel circuitry (including transistors, capacitors, etc.) can be configured in other ways (e.g., including configurations for circuitry to compensate for threshold voltage variations in the drive transistor 32). A display pixel may include additional switching transistors, emitter transistors connected in series with the drive transistor, etc. The capacitor Cst may be located at other desired locations within the pixel (e.g., between the source and gate of the drive transistor). Figure 3 The display pixel circuit is only illustrative.

[0033] To extract light from a light-emitting diode (LED), one or more microlenses can be incorporated above the LED in the display. The one or more microlenses can be used to collimate the light from the LED and ensure that the light is directed vertically toward the viewer. In one embodiment, a single microlens can be formed above each LED to extract light from that LED. However, optimal light extraction may require a large distance between the microlens and the LED (undesirably increasing the thickness of the display). Therefore, each pixel can be covered by both a microlens array and a single microlens formed above the microlens array.

[0034] Figure 4This is a cross-sectional side view of an exemplary display pixel covered by at least two microlenses. As shown, a light-emitting diode (LED) 38 can be formed on a substrate (such as substrate 26). Substrate 26 may include a glass layer, a polymer layer, a silicon layer, a composite film comprising polymers and inorganic materials, a metal foil, etc. The LED 38 can be a microLED (e.g., an LED semiconductor die having a footprint of approximately 10 μm × 10 μm, greater than 5 μm × 5 μm, less than 100 μm × 100 μm, less than 20 μm × 20 μm, less than 10 μm × 10 μm, or other desired sizes). This example is merely illustrative, and the LED 38 could also be an organic light-emitting diode (OLED) comprising multiple OLED layers. The LED can be electrically connected to thin-film circuitry within substrate 26. In one example, the LED can be soldered to the substrate.

[0035] The light-emitting diode (LED) may be surrounded by a diffusion layer 64. The diffusion layer 64 can be used to improve the efficiency of the display. The LED 38 has a top surface 38-U and a sidewall surface 38-S. Ideally, the LED 38 will emit light perpendicularly from the top surface 38-U (e.g., parallel to the Z-axis). However, in practice, the LED 38 may emit some light from the sidewall 38-S (e.g., parallel to the X-axis). The diffusion layer 64 can recapture some of this light by vertically redirecting it.

[0036] The diffusion layer 64 (sometimes referred to as diffuser layer 64, diffuser 64, light redirection layer 64, light scattering layer 64, etc.) comprises multiple light-scattering particles 64-P distributed throughout the matrix material 64-H. The matrix material 64-H can be a transparent polymer (e.g., siloxane). The light-scattering particles 64-P can be formed of a metal oxide (e.g., titanium dioxide) or another desired material. The light-scattering particles 64-P can have a different refractive index than the matrix material 64-H. Light incident on the light-scattering particles can be scattered in random directions. This scattering causes some light to eventually be redirected toward the viewer, thereby improving the efficiency of the display compared to embodiments that omit the diffusion layer (and little or no light from the LED sidewalls is ultimately visible to the viewer).

[0037] It should be noted that a diffusion layer (e.g., a top diffuser) may be additionally or alternatively incorporated above lens 56 within the display. For example, the diffusion layer may be formed directly on lens 56 between lens 56 and protective layer 66, protective layer 66 itself may be a diffusion layer, or the diffusion layer may be formed on protective layer 66 between protective layer 66 and polarizer 68, and so on. These examples are merely illustrative. In general, one or more diffusion layers may be incorporated at any desired location within the display stack-up structure.

[0038] Cathode layer 60 can be formed above light-emitting diode and can serve as the cathode terminal for light-emitting diode 38 (e.g. Figure 3 (Cathode terminal CD in the display). The cathode layer can act as the cathode for multiple light-emitting diodes and is thus formed as a cover layer across the display. The cathode layer can be formed of a transparent conductive material (e.g., indium tin oxide).

[0039] An opaque masking layer 58 (sometimes referred to as black masking layer 58, black film 58, opaque film 58, etc.) is formed over substrate 26. The opaque masking layer 58 may have openings that overlap with the light-emitting diode 38. The openings in the opaque masking layer 58 above the light-emitting diode allow light from the light-emitting diode to pass through the opaque masking layer toward the viewer (e.g., in the positive Z direction). Elsewhere (e.g., above the portion of diffuser layer 64 between pixels), the opaque masking layer may block light (e.g., to prevent crosstalk between adjacent pixels). The opaque masking layer 58 may transmit less than 10% of the incident light (at the wavelength associated with the light emitted from LED 38), less than 5% of the incident light, less than 3% of the incident light, less than 1% of the incident light, etc. The opaque masking layer may be formed of any desired material (e.g., organic or inorganic opaque materials).

[0040] Microlenses 54 and 56 may be included to collimate light passing through openings in the opaque shielding layer 58. Microlenses 54 and 56 may be collectively referred to as a microlens stack. First, a microlens array 52 is formed in the openings of the opaque shielding layer 58. The microlens array 52 includes multiple microlenses 54 (e.g., arranged in multiple rows and columns, as an example). Additionally, a single microlens 56 is formed above the microlens array 52. ​​A protective layer 66 is formed above the microlens 56. Including the microlens array 52 in addition to the microlenses 56 allows for the collimation of more light from the LED 38 (e.g., by providing additional lens optics) without increasing the thickness of the display.

[0041] Microlenses 54 and 56 can be formed from any desired material. Microlens 56 can be formed from an organic material (such as an acrylate-based material). Microlens 54 can be formed from an inorganic material (such as silicon nitride). These examples are merely illustrative. In general, both microlenses 54 and 56 can be formed from any desired organic or inorganic material.

[0042] There may be a difference in refractive index between microlens 54 and microlens 56. This difference can be greater than 0.05, greater than 0.1, greater than 0.2, greater than 0.25, greater than 0.3, greater than 0.4, less than 0.4, between 0.2 and 0.4, or any other desired value. Microlens 54 can have a refractive index greater than 1.5, greater than 1.7, greater than 1.8, greater than 1.9, between 1.8 and 2.2, between 1.9 and 2.1, or any other desired value. Microlens 56 can have a refractive index greater than 1.3, greater than 1.4, greater than 1.5, greater than 1.6, greater than 1.7, less than 1.8, less than 1.9, between 1.5 and 1.9, between 1.6 and 1.8, or any other desired value. In one example, microlens 54 is formed of an inorganic material (silicon nitride) having a refractive index of 2.0, and microlens 56 is formed of an organic material (acrylate-based material) having a refractive index of 1.69.

[0043] Microlens 56 may be conformed to (and in direct contact with) the upper surface of microlens 54. Microlens 56 is then covered by a protective layer 66, wherein the protective layer 66 is conformed to (and in direct contact with) the surface of microlens 56. Protective layer 66 may have a lower refractive index than microlens 56, and is therefore sometimes referred to as a low-refractive-index protective layer, low-refractive-index layer, etc. Protective layer 66 may be formed of acrylate-based organic materials or epoxy-based organic materials. These examples are merely illustrative, and in general any desired organic or inorganic material may be used for low-refractive-index protective layer 66. The difference in refractive index between microlens 56 and protective layer 66 may be greater than 0.05, greater than 0.1, greater than 0.2, greater than 0.25, greater than 0.3, greater than 0.4, less than 0.4, between 0.2 and 0.4, or any other desired value. The protective layer 66 may have a refractive index greater than 1.2, greater than 1.3, greater than 1.4, greater than 1.5, between 1.2 and 1.6, between 1.3 and 1.5, or any other desired value. In one example, the protective layer 66 is formed of an epoxy-based material having a refractive index of 1.44.

[0044] An additional layer can be formed on top of the low-refractive-index protective layer 66. For example... Figure 4 As shown, polarizer 68 and transparent cover layer 70 can be formed above the low-refractive-index protective layer. Polarizer 68 can be a linear polarizer or a circular polarizer. Transparent cover layer 70 can be a transparent layer protecting the display (e.g., formed of glass or plastic). If desired, one or more additional layers can be included in the display (e.g., between or above the protective layer 66 and transparent cover layer 70).

[0045] like Figure 4As shown, in some configurations, a layer 62 can be interposed between the light-emitting diode 38 and the microlens 54. Layer 62 (sometimes referred to as transparent layer 62, low-refractive-index layer 62, low-refractive-index protective layer 62, protective layer 62, etc.) can be formed of organic materials (e.g., epoxy-based or acrylate-based materials) or inorganic materials (e.g., silicon dioxide). Layer 62 can have a transparency greater than 80%, greater than 90%, greater than 95%, greater than 99%, or any other desired transparency. The low-refractive-index layer 62 can provide several performance advantages to the display. First, the presence of the low-refractive-index layer 62 increases the distance between the microlenses 54 and 56 and the light-emitting diode 38 (due to the thickness 72 of layer 62). This increased distance results in improved lens optics for the microlenses 54 and 56, leading to better collimation of light from the LED 38. A specific thickness 72 of layer 62 can be selected to optimize microlens performance. The thickness 72 can be less than 3 micrometers, less than 2 micrometers, less than 1.5 micrometers, less than 1 micrometer, greater than 1 micrometer, greater than 0.5 micrometers, between 1 micrometer and 3 micrometers, between 1 micrometer and 2 micrometers, or any other desired value.

[0046] The difference in refractive index between microlens 56 and protective layer 62 can be greater than 0.05, greater than 0.1, greater than 0.2, greater than 0.25, greater than 0.3, greater than 0.4, less than 0.4, between 0.2 and 0.4, or any other desired value. The difference in refractive index between microlens 54 and protective layer 62 can be greater than 0.1, greater than 0.2, greater than 0.4, greater than 0.5, greater than 0.6, less than 0.7, between 0.5 and 0.7, or any other desired value. Protective layer 62 can have a refractive index greater than 1.2, greater than 1.3, greater than 1.4, greater than 1.5, between 1.2 and 1.6, less than 1.6, less than 1.5, between 1.3 and 1.5, or any other desired value.

[0047] In addition to increasing the spacing between the microlens and the LED, the protective layer 62 can also improve light recycling in the display (and thus increase efficiency). When the protective layer 62 has a low refractive index, more light will be recycled (due to the smaller escape cone caused by the low refractive index). This example is merely illustrative. In another possible implementation, the protective layer 62 may be formed of the same material as the microlens 54 or another material with a higher refractive index. In this type of implementation (where the refractive index in layer 62 is high), the improvement in recycling efficiency may be less due to the additional separation provided by the thickness 72, but the optical capabilities of the lens are still improved.

[0048] Each microlens can have any desired size. Microlens 56 can have a height (sometimes referred to as thickness) 74 greater than 3 micrometers, greater than 4 micrometers, greater than 5 micrometers, greater than 10 micrometers, greater than 15 micrometers, less than 15 micrometers, less than 10 micrometers, between 3 and 10 micrometers, between 4 and 6 micrometers, between 10 and 15 micrometers, or any other desired quantity. Microlens 56 can have a width (sometimes referred to as diameter) 76 greater than 5 micrometers, greater than 10 micrometers, greater than 15 micrometers, greater than 20 micrometers, less than 20 micrometers, less than 15 micrometers, between 10 and 20 micrometers, between 10 and 15 micrometers, or any other desired quantity. Each microlens 54 can have a height (sometimes referred to as thickness) 80 greater than 0.1 micrometers, greater than 0.3 micrometers, greater than 0.5 micrometers, greater than 1 micrometer, greater than 2 micrometers, less than 5 micrometers, less than 2 micrometers, between 0.3 and 2 micrometers, between 0.5 and 1 micrometer, or any other desired quantity. Each microlens 54 may have a width (sometimes referred to as diameter) 78 greater than 0.5 micrometers, greater than 1 micrometer, greater than 2 micrometers, greater than 3 micrometers, greater than 5 micrometers, less than 5 micrometers, less than 3 micrometers, between 1 micrometer and 3 micrometers, or any other desired amount.

[0049] Figure 5 This illustrates an exemplary pixel (such as a microlens array covered by a single microlens) Figure 4 A top view (pixels). As shown, the microlens array 52 includes multiple microlenses 54. Figure 5 The microlenses 54 are arranged in uniform rows and columns. This example is merely illustrative. The microlenses may alternatively be arranged in other (regular or irregular) patterns. For example, the area occupied by the microlens array may be circular or another desired shape. Individual microlenses 56 are then formed above the microlens array 52. ​​As shown, the entire microlens array 52 is composed of overlapping microlenses 56. The microlenses 56 may conform to and contact the upper surface of each microlens in the microlens array 52. ​​The microlenses 54 in the array 52 are coplanar.

[0050] LED 38 is laterally surrounded by a diffusion layer 64 (e.g., surrounding all sides in the XY plane). Figure 4 The examples in the text are merely illustrative. Figure 6An alternative configuration is shown, in which the light-emitting diode 38 is laterally surrounded by layer 82. In some cases, layer 82 may be an optically transparent passivation layer formed of a transparent polymer. In this case, layer 82 may have a transparency greater than 80%, greater than 90%, greater than 95%, greater than 99%, etc. Alternatively, layer 82 may be an opaque layer that blocks incident light (e.g., a black masking layer, a black mask, an opaque mask, etc.). In this case, layer 82 may have a transparency less than 20%, less than 10%, less than 5%, less than 1%, etc. Figure 6 It also shows how one can optionally omit the source from Figure 4 58. Opaque masking layer.

[0051] If desired, a passivation layer (sometimes called a protective layer) 53 may optionally be included between each adjacent microlens layer. The passivation layer may have any desired refractive index (e.g., greater than 1.2, greater than 1.3, greater than 1.4, greater than 1.5, greater than 1.6, greater than 1.7, greater than 1.8, greater than 1.9, between 1.8 and 2.2, between 1.9 and 2.1, less than 1.8, less than 1.9, between 1.5 and 1.9, between 1.6 and 1.8, between 1.2 and 1.6, between 1.3 and 1.5, etc.). This example is merely illustrative. Generally, the passivation layer may optionally be included on the upper and / or lower surfaces of each microlens layer (e.g., in direct contact with the upper and / or lower surfaces of each microlens layer). Figure 6 The passivation layer 53 is adapted to the upper surface of the microlens 54 of the microlens array 52. ​​The lower surface of the microlens 56 is then adapted to the upper surface of the passivation layer 53.

[0052] The arrangement of opaque shielding layers described so far (e.g., in Figure 4 and Figure 6 (The following is merely illustrative.) Besides including (as in...) Figure 4 (in Chinese) or omitted (as in...) Figure 6 In addition to the (middle) implementation, in embodiments where the opaque masking layer is included in the pixel, the opaque masking layer may have a different occupied area.

[0053] like Figure 7 As shown, the area occupied by the microlens array 52 can have a width of 84. Figure 4 and Figure 6 In this array, the width 84 of the array 52 is approximately equal to the width of the microlens 56. In other words, the width 84 can be approximately the width of the microlens 56 (…). Figure 4 Within 15%, 10%, 5%, or 1% of the width of 76. In contrast, in Figure 7In this case, the width 84 differs from the width of the microlens 56 by a larger amount (e.g., greater than 20%, greater than 40%, greater than 60%, etc.). In other words, the width of the microlens 56 can be 1.5 times or more, 2.0 times or more, between 1.3 times and 2.5 times larger than the array width 84.

[0054] exist Figure 4 and Figure 7 In this example, the opaque masking layer 58 defines an opening completely occupied by the microlens array 52. ​​In other words, there is no gap between the microlens 54 and the opaque masking layer 58. This example is merely illustrative. Gaps may exist between the opaque masking layer 58 and the edges of the microlens array 52 if desired. Figure 7 In addition to the entire microlens array 52, the microlens 56 also overlaps and directly contacts a portion of the opaque shielding layer 58 vertically. Figure 7 A method is also shown in which the low-refractive-index protective layer 62 between the LED 38 and the microlens array 52 can be optionally omitted.

[0055] Figure 8 An alternative arrangement is shown in which the width 84 of the microlens array 52 is greater than the width 76 of the microlens 56. In this case, the microlens array 52 is partially covered by the microlens 56 (instead of as in...). Figure 4 , Figure 6 and Figure 7 (Completely covered). In this embodiment, microlens 56 remains the only microlens formed above array 52. Figure 7 In this context, a width of 84 can differ from a width of 76 by more than 20%, 40%, 60%, etc. In other words, a width of 84 can be 1.5 times or more, 2.0 times or more, or between 1.3 and 2.5 times larger than a width of 76.

[0056] exist Figure 4 and Figures 6 to 8 The example depicts a larger single microlens formed above multiple smaller microlenses. This example is merely illustrative. The positions of the microlenses can be switched if desired (e.g., forming an array of smaller microlenses above larger microlenses). Generally, two or more layers of microlenses may be included, with each microlens layer comprising one or more microlenses of any desired size.

[0057] exist Figure 4 and Figures 6 to 8 In the image, the microlenses 54 of array 52 are depicted as having a curved upper surface. Figure 9AThis type of arrangement is illustrated in detail. As shown, each microlens has a curved upper surface 90°. Each curved upper surface can have a consistent radius of curvature or inconsistent radii of curvature. The width, height, center-to-center spacing (pitch), radius of curvature, and contact angle (e.g., the angle at which the curved upper surface of a given microlens intersects the curved upper surface of an adjacent microlens) of the microlens can be adjusted to optimize display performance.

[0058] Figure 9A The examples shown are merely illustrative. In general, each microlens 54 can have any desired shape. For example... Figure 9B As shown, each microlens 54 (sometimes referred to as a focusing feature 54) can have a triangular cross-sectional shape (e.g., associated with a pyramidal shape, a triangular prism shape, etc.). Each microlens can have surfaces that intersect at an angle 92 and can intersect relative to adjacent microlenses at an angle 94. The width, height, center-to-center spacing between microlenses, angles 92 and 94 can be adjusted to optimize display performance. Figure 9B In the example, each microlens has an isosceles triangular cross-section. This example is merely illustrative. Microlenses can have any other type of triangular cross-sectional shape if desired.

[0059] Figure 9C Another example of a microlens shape that can be used in pixel 22 is shown. Figure 9C In this configuration, each microlens has a planar upper surface 96 parallel to the lower surface 98. This can be referred to as a columnar microlens. The width of the upper surface 96, the width of the lower surface 98, the center-to-center spacing between microlenses, the height of the microlenses, and the contact angle between adjacent microlenses can be adjusted to optimize display performance.

[0060] exist Figure 9D Another possible arrangement for the microlens array 52 is shown in the figure. Figure 9D Examples of microlenses with different cross-sectional shapes incorporated in a single display are shown. As shown, microlenses 54-1 and 54-4 can have a cross-sectional shape of right triangles. These cross-sectional shapes can be symmetrical about a vertical axis. Additionally, the microlens array 52 includes microlenses 54-2 and 54-3 with a cross-sectional shape of right trapezoids (trapezoidal with at least two right angles). The cross-sectional shapes of microlenses 54-2 and 54-3 can also be symmetrical about a vertical axis (e.g., the same vertical axis as microlenses 54-1 and 54-4).

[0061] If needed, Figures 9A to 9D The microlens shape shown (or any other desired microlens shape) can be used in any of the foregoing embodiments. For example... Figure 4 and Figures 6 to 8As shown in either of these examples, each pixel in the display may be covered by one or more microlenses. The microlens arrangement for each pixel may be the same across the display, or different pixels may have different microlens arrangements. Figure 4 and Figures 6 to 8 The features can be used in any combination. For example, any pixel may optionally include or omit the low refractive index layer 62, may use a diffusion layer, an opaque layer, or a transparent polymer around the LED 38, may optionally include or omit the opaque shielding layer 58, may have stacked microlenses with any desired width and height, may include microlenses and a protective layer formed of any desired material, may include protective layers between microlens layers, and so on. Similarly, any of these combinations may use microlenses 54 of any shape (e.g., as in...). Figure 9A , Figure 9B , Figure 9C or Figure 9D middle).

[0062] In an illustrative example, the microlens stack above each pixel can be optimized based on the wavelength of the light emitted by each pixel. Consider an example where the display includes red, blue, and green light-emitting diodes (LEDs). Instead of all pixels in the display having the same microlens stack, each color of LED could be covered by the same microlens stack. In this case, all red pixels would have the same first microlens stack, all green pixels would have the same second microlens stack, and all blue pixels would have the same third microlens stack. Alternatively, two colors could use the same stack, and the third color could use a different stack. For example, all blue and green pixels could have the same first microlens stack, and all red pixels could have the same second microlens stack.

[0063] Additionally, this paper illustrates an example of at least two stacked microlens layers. In other possible arrangements, three or more microlens layers may be included in the microlens stack to obtain additional lens optical capabilities. In these types of arrangements, three or more microlenses may be vertically overlapped.

[0064] According to one embodiment, a display is provided, the display including a substrate, a light-emitting diode formed on the substrate, and a microlens array formed above the light-emitting diode, the microlens array including a plurality of first microlenses and second microlenses, the microlens array having a first width, and second microlenses conforming to and covering the microlens array, the second microlenses having a second width greater than the first width.

[0065] According to another embodiment, each microlens in the first microlens has a third width less than the second width and a first height, and the second microlens has a second height greater than the first height.

[0066] Each microlens in the first microlens is formed of a first material having a first refractive index, and the second microlens is formed of a second material having a second refractive index less than the first refractive index.

[0067] According to another implementation scheme, the first material is an inorganic material, and the second material is an organic material.

[0068] According to another implementation, the difference between the first refractive index and the second refractive index is greater than 0.2.

[0069] According to another embodiment, the display includes a low refractive index layer interposed between a light-emitting diode and a microlens array, the low refractive index layer having a third refractive index that is less than the second refractive index and the first refractive index.

[0070] According to another implementation, the difference between the third refractive index and the first refractive index is greater than 0.5.

[0071] According to another embodiment, the display includes a protective layer formed above and conforming to the second microlens, the protective layer having a third refractive index less than the second refractive index and the first refractive index.

[0072] According to another implementation, the difference between the third refractive index and the second refractive index is greater than 0.2.

[0073] The display includes a diffusion layer formed adjacent to the sidewall of the light-emitting diode.

[0074] According to another embodiment, the diffusion layer comprises light-scattering microparticles distributed throughout the transparent polymer material.

[0075] According to another embodiment, the display includes an opaque shielding layer formed above the substrate, and the microlens array is formed in an opening in the opaque shielding layer.

[0076] According to another embodiment, the display includes an opaque shielding layer formed above the substrate, a microlens array formed in an opening in the opaque shielding layer, and the opaque shielding layer formed above and in direct contact with an indium tin oxide layer, the indium tin oxide layer forming part of the light-emitting diode.

[0077] According to another embodiment, the display includes an opaque shielding layer formed above the substrate (the microlens array is formed in an opening in the opaque shielding layer), an indium tin oxide layer forming part of the light-emitting diode, and a protective layer interposed between the indium tin oxide layer and the microlens array.

[0078] According to another implementation, the second width is more than 1.5 times greater than the first width.

[0079] According to another embodiment, each of the first microlenses has a curved upper surface.

[0080] According to another embodiment, each of the first microlenses has a triangular cross-sectional shape.

[0081] According to another embodiment, each microlens in the first microlens has a columnar cross-sectional shape with parallel upper and lower surfaces.

[0082] According to another embodiment, the display includes a protective layer inserted between the microlens array and the second microlens.

[0083] According to one embodiment, a display is provided, the display including a substrate, a light-emitting diode formed on the substrate, a plurality of coplanar microlenses formed of an inorganic material (the light-emitting diode is at least partially overlapped by the plurality of coplanar microlenses), and an additional microlens formed of an organic material, the additional microlens covering all of the plurality of coplanar microlenses.

[0084] According to another embodiment, the inorganic material has a first refractive index greater than 1.9, and the organic material has a second refractive index less than 1.8.

[0085] According to another embodiment, the display includes a protective layer that covers the additional microlens and has a third refractive index of less than 1.5 and a second refractive index of greater than 1.6.

[0086] According to one embodiment, a display is provided, the display including a substrate, a light-emitting diode formed on the substrate, a transparent layer formed above the light-emitting diode, a microlens array formed above the transparent layer (the transparent layer being interposed between the light-emitting diode and the microlens array), and an additional microlens overlapping the light-emitting diode, the microlens array being interposed between the transparent layer and the additional microlens, and the additional microlens having a first refractive index that is lower than a second refractive index of the microlens array and greater than a third refractive index of the transparent layer.

[0087] The foregoing description is merely illustrative, and various modifications can be made by those skilled in the art without departing from the scope and substance of the described embodiments. The aforementioned embodiments can be implemented independently or in any combination.

Claims

1. A display, the display comprising: substrate; A light-emitting diode, wherein the light-emitting diode is formed on the substrate; A microlens array formed above the light-emitting diode, wherein the microlens array includes a plurality of first microlenses, and wherein the microlens array has a first width; A second microlens, which is conformable to and covers the microlens array, wherein the second microlens has a second width greater than the first width, wherein each of the first microlenses is formed of a first material having a first refractive index, and wherein the second microlens is formed of a second material having a second refractive index less than the first refractive index; and A low refractive index layer is inserted between the light-emitting diode and the microlens array, wherein the low refractive index layer has a third refractive index that is less than the second refractive index and the first refractive index.

2. The display according to claim 1, wherein each of the first microlenses has a third width and a first height that are less than the second width, and wherein the second microlens has a second height that is greater than the first height.

3. The display according to claim 1, wherein the first material is an inorganic material and the second material is an organic material.

4. The display according to claim 1, wherein the difference between the first refractive index and the second refractive index is greater than 0.

2.

5. The display according to claim 4, wherein the difference between the third refractive index and the first refractive index is greater than 0.

5.

6. The display according to claim 4, further comprising: A protective layer is formed above and conforms to the second microlens, wherein the protective layer has a fourth refractive index that is less than the second refractive index and the first refractive index.

7. The display according to claim 6, wherein the difference between the fourth refractive index and the second refractive index is greater than 0.

2.

8. The display according to claim 1, further comprising: A diffusion layer is formed adjacent to the sidewall of the light-emitting diode.

9. The display of claim 8, wherein the diffusion layer comprises light-scattering microparticles distributed throughout the transparent polymer material.

10. The display according to claim 8, further comprising: An opaque shielding layer is formed above the substrate, wherein the microlens array is formed in an opening in the opaque shielding layer.

11. The display according to claim 1, further comprising: An opaque shielding layer is formed above the substrate, wherein the microlens array is formed in an opening in the opaque shielding layer, and wherein the opaque shielding layer is formed above and in direct contact with the indium tin oxide layer, the indium tin oxide layer forming a portion of the light-emitting diode.

12. The display according to claim 1, wherein the second width is greater than 1.5 times the first width.

13. The display of claim 1, wherein each of the first microlenses has a curved upper surface.

14. The display of claim 1, wherein each of the first microlenses has a triangular cross-sectional shape.

15. The display of claim 1, wherein each of the first microlenses has a columnar cross-sectional shape with parallel upper and lower surfaces.

16. The display according to claim 1, further comprising: A protective layer is inserted between the microlens array and the second microlens.

17. A display, the display comprising: substrate; A light-emitting diode, wherein the light-emitting diode is formed on the substrate; A plurality of coplanar microlenses, the plurality of coplanar microlenses being formed of an inorganic material, wherein the light-emitting diode is at least partially overlapped by the plurality of coplanar microlenses, wherein the inorganic material has a first refractive index greater than 1.9; and An additional microlens, the additional microlens being formed of an organic material, wherein the additional microlens covers all of the plurality of coplanar microlenses, and wherein the organic material has a second refractive index of less than 1.

8.

18. The display according to claim 17, further comprising: A protective layer covering the additional microlens and having a third refractive index of less than 1.5, wherein the second refractive index is greater than 1.

6.

19. A display, the display comprising: substrate; A light-emitting diode, wherein the light-emitting diode is formed on the substrate; A transparent layer is formed above the light-emitting diode; A microlens array is formed above the transparent layer, wherein the transparent layer is interposed between the light-emitting diode and the microlens array; and An additional microlens overlaps with the light-emitting diode, wherein the microlens array is interposed between the transparent layer and the additional microlens, and wherein the additional microlens has a first refractive index that is lower than a second refractive index of the microlens array and greater than a third refractive index of the transparent layer.

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