LED device with protective layer and manufacturing method thereof

Abstract

A device and a method of forming the device are disclosed herein. The device has a silicone layer disposed on the LED structure, the device further including an inorganic protective layer disposed on a surface of the phosphor layer opposite the LED structure. Methods of forming the device include depositing an inorganic protective layer on a silicone layer using atomic layer deposition.

Description

[0001] Cross - Reference to Related Applications This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 430,862, titled “ALD LAYER TO COVER ADHESIVE SILICONE SURFACES,” filed on Dec. 7, 2022, which is incorporated herein by reference in its entirety. Technical Field

[0002] The present invention generally relates to inorganic layers for protecting pcLEDs and pcLED arrays, light sources including such pcLEDs or pcLED arrays, displays including such pcLED arrays, and visualization systems including such displays. Background Art

[0003] Semiconductor light - emitting diodes and laser diodes (collectively referred to herein as “LEDs”) are among the most efficient light sources currently available. The emission spectrum of an LED typically exhibits a single narrow peak at a wavelength determined by the structure of the device and the composition of the semiconductor material of which it is made. By appropriately selecting the device structure and material system, an LED can be designed to operate at ultraviolet, visible, or infrared wavelengths.

[0004] An LED can be combined with one or more wavelength - converting materials (generally referred to herein as “phosphors”) that absorb the light emitted by the LED and in response emit light at a longer wavelength. For such phosphor - converted LEDs (“pcLEDs”), the fraction of the light emitted by the LED that is absorbed by the phosphor depends on the amount of phosphor material in the optical path of the light emitted by the LED, e.g., on the concentration of the phosphor material in a phosphor layer disposed on or around the LED and the thickness of that layer. A phosphor - converted LED can be designed such that all of the light emitted by the LED is absorbed by one or more phosphors, in which case the emission from the pcLED comes entirely from the phosphors. In such a case, for example, the phosphor can be selected to emit light in a narrow spectral region that is not directly and efficiently generated by the LED. Alternatively, a pcLED can be designed such that only a portion of the light emitted by the LED is absorbed by the phosphor, in which case the emission from the pcLED is a mixture of the light emitted by the LED and the light emitted by the phosphor. By appropriately selecting the LED, the phosphor, and the phosphor composition, such a pcLED can be designed to emit, for example, white light having a desired color temperature and desired color - rendering properties.

[0005] Inorganic LEDs and pcLEDs have been widely used in the manufacture of different types of displays, matrices, and light engines, including: motor vehicle adaptive headlights, augmented reality (AR) displays, virtual reality (VR) displays, mixed reality (MR) displays (AR, VR, and MR systems are referred to herein as visualization systems), smart glasses, and displays for mobile phones, smart watches, monitors, and televisions, as well as flash lighting for cameras in mobile phones. Depending on the size of the matrix or display and its pixel requirements per inch, each LED or pcLED in these architectures can have an area ranging from a few square millimeters down to a few square micrometers (e.g., microLEDs). Summary of the Invention

[0006] In one aspect, the present specification discloses a device that includes a silicone layer disposed on an LED structure, and the device further includes an inorganic protective layer disposed on a surface of the silicone layer opposite to the LED structure. The inorganic protective layer may include a metal oxide. The inorganic protective layer may include at least one of Al2O3, SiO2, CrO2, ZrO2, HfO2, and Ta2O5. The inorganic protective layer may be formed by atomic layer deposition. The inorganic protective layer may have a thickness of less than 100 nm. The inorganic protective layer may be configured to be transparent to wavelengths in the visible light range. The inorganic protective layer may be configured to have optical properties. The silicone layer may have a Shore A hardness of 50 or less. The silicone layer may include a phosphor material to form a phosphor conversion layer. The LED structure may include an LED array, which may include at least two individually addressable light-emitting diodes, and may include a display configured to receive light emitted by the LED array. The LED structure may be a microLED array having at least two individually addressable light-emitting diodes on the same substrate.

[0007] In another aspect, the present specification discloses a method of forming a device, the method including forming a silicone layer on an LED structure and forming an inorganic protective layer on a surface of the silicone layer opposite to the LED structure. Atomic layer deposition may be used to form the inorganic protective layer. The method may further include irradiating the silicone layer with ultraviolet light before atomic layer deposition of the inorganic protective layer. The method may further include exposing the silicone layer to ozone before atomic layer deposition of the inorganic protective layer.

[0008] The devices disclosed herein can be used in, for example, the various devices and applications listed in the background art section above.

[0009] These and other embodiments, features, and advantages of the present invention will become more apparent to those skilled in the art when the following more detailed description of the invention is taken in conjunction with the accompanying drawings, which are briefly described first. Brief Description of the Drawings

[0010] Figure 1 Shows a schematic cross-sectional view of an exemplary pcLED.

[0011] Figure 2A And Figure 2B Shows a schematic cross-sectional view and a top view of a pcLED array, respectively. Figure 2C Shows a schematic top view of an LED wafer from which an LED array such as Figure 2A And Figure 2B The LED arrays shown in can be formed.

[0012] Figure 3A Shows a schematic top view of an electronic board on which an LED or a pcLED array can be mounted, and Figure 3B Similarly shows a pcLED array mounted on the Figure 3A Electronic board.

[0013] Figure 4A Shows a schematic cross-sectional view of a pcLED array arranged relative to a waveguide and a projection lens. Figure 4B Shows an arrangement similar to that of Figure 4A In the absence of a waveguide.

[0014] Figure 5 Schematically shows an exemplary camera flash system.

[0015] Figure 6 Schematically shows an exemplary display system.

[0016] Figure 7 Shows a block diagram of an exemplary visualization system.

[0017] Figure 8A Shows a cross-section of a pcLED device with a thin inorganic protective layer, and Figure 8B Is Figure 8A An enlarged view of the region marked "B" in.

[0018] Figure 9 Shows a prototype two-part atomic layer deposition (ALD) reaction for forming Al2O3 using trimethylaluminum (TMA).

[0019] Figure 10 Shows a method for forming a pcLED device with a thin inorganic protective layer.

[0020] Figure 11 Shows a cross-section of an LED device with a silicone lens having a thin inorganic protective layer. Detailed Description

[0021] The following detailed description should be read with reference to the accompanying drawings, in which like reference numerals refer to like elements throughout the different figures. The drawings, which are not necessarily to scale, depict alternative embodiments and are not intended to limit the scope of the invention. The detailed description illustrates, by way of example, not by way of limitation, the principles of the invention.

[0022] Figure 1 An example of a single pcLED 100 is shown, which includes a light-emitting semiconductor diode (LED) structure 102 disposed on a substrate 104, and a phosphor layer 106 (which may also be referred to herein as a wavelength conversion structure) disposed on the LED. The light-emitting semiconductor diode structure 102 generally includes an active region disposed between an n-type layer and a p-type layer. Applying a suitable forward bias across the diode structure causes light to be emitted from the active region. The wavelength of the emitted light is determined by the composition and structure of the active region.

[0023] For example, the LED can be a Group III nitride LED that emits ultraviolet, blue, green, or red light. LEDs formed from any other suitable material system and emitting light of any other suitable wavelength can also be used. Other suitable material systems can include, for example, Group III phosphide materials, Group III arsenide materials, and II-IV materials.

[0024] Any suitable phosphor material can be used to form the phosphor layer 106, depending on the desired optical output and color specifications from the pcLED. The phosphor layer can, for example, include phosphor particles dispersed in a binder material or bonded to each other with a binder material, or can be or include a sintered ceramic phosphor plate. In the phosphor layer 106, where the phosphor particles are dispersed in a binder material (also referred to as a matrix material or matrix), silicone resin is often used for the matrix material due to its good light extraction properties and general availability of the material.

[0025] Figures 2A - 2B A cross-sectional view and a top view of an array 200 of pcLEDs 100 including a phosphor layer 106 disposed on a substrate 202 are shown, respectively. Such an array can include any suitable number of pcLEDs arranged in any suitable manner. In the illustrated example, the array is depicted as being formed monolithically on a shared substrate, but alternatively, an array of LEDs or pcLEDs can be formed from individually mechanically separated LEDs or pcLEDs. The substrate 202 can optionally include CMOS circuitry for driving the LEDs and can be formed from any suitable material.

[0026] Although Figures 2A - 2BA three-by-three array of nine pcLEDs is shown, but such an array can include, for example, dozens, hundreds, or thousands of LEDs or pcLEDs. The width (e.g., side length) of each LED or pcLED in the array plane can be, for example, less than or equal to 1 millimeter (mm), less than or equal to 500 micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, or less than or equal to 10 micrometers. The LEDs in such an array can be spaced apart from each other by streets or lanes, which have a width in the array plane of, for example, hundreds of micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, less than or equal to 10 micrometers, or less than or equal to 5 micrometers. Although the example shown depicts rectangular LEDs or pcLEDs arranged in a symmetric matrix, the LEDs or pcLEDs and the array can have any suitable shape or arrangement and do not all need to have the same shape or size. For example, the LEDs or pcLEDs located in the central portion of the array may be larger than the LEDs or pcLEDs located in the peripheral portion of the array. Alternatively, the LEDs or pcLEDs located in the central portion of the array can be smaller than the LEDs or pcLEDs located in the peripheral portion of the array.

[0027] Figure 2C A schematic top view of a portion of an LED wafer 210 is shown, from which an LED array such as Figure 2A and Figure 2B the LED arrays shown in Figure 2C can be formed. An enlarged 3×3 portion of the wafer is also shown. In the example wafer, each LED or pcLED 111 having a side length (e.g., width) of W1 is arranged in a square matrix, with the center-to-center distance between adjacent LEDs or pcLEDs being D1 and separated by a lane 113 having a width of W2. W1 can be, for example, less than or equal to 1 millimeter (mm), less than or equal to 500 micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, or less than or equal to 10 micrometers. W2 can be, for example, hundreds of micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, less than or equal to 10 micrometers, or less than or equal to 5 micrometers. D1 = W1 + W2.

[0028] For example, an array can be formed by cutting the wafer 210 into individual LEDs or pcLEDs and arranging the die on a substrate. Alternatively, the array can be formed from the entire wafer 210 or by dividing the wafer 210 into smaller LED or pcLED arrays.

[0029] LEDs or pcLEDs having dimensions (e.g., side length) in the array plane less than or equal to about 50 micrometers are generally referred to as microLEDs, and an array of such microLEDs can be referred to as a microLED array.

[0030] In a pcLED array, all pcLEDs can be configured to emit light of substantially the same spectrum. Alternatively, the pcLED array can be a multicolor array, where different pcLEDs in the array can be configured to emit light of different spectra (colors) by employing different phosphor compositions. Similarly, in an array of direct-emitting LEDs (i.e., LEDs that do not have their wavelengths converted by a phosphor), all LEDs in the array can be configured to emit light of substantially the same spectrum, or the array can be a multicolor array that includes LEDs configured to emit light of different colors.

[0031] Each LED or pcLED in the array can be individually operable (addressable) and / or can be operable as part of a group or subset of LEDs or pcLEDs in the array (e.g., adjacent).

[0032] An LED or pcLED array, or portions of such an array, can be formed as a segmented monolithic structure, where each LED or pcLED is electrically isolated or partially electrically isolated from one another by trenches and / or insulating materials, but the electrically isolated or partially electrically isolated segments remain physically connected to one another through other portions of the semiconductor structure. For example, in such a monolithic structure, the active region and a first semiconductor layer of a first conductivity type (n or p) on one side of the active region can be segmented, and a second unsegmented semiconductor layer of the opposite conductivity type (p or n) is located on the side of the active region opposite the first semiconductor layer. The second semiconductor layer can then physically and electrically connect the segmented structures to one another on one side of the active region, where the segmented structures are otherwise electrically isolated from one another and can thus be operated individually as separate LEDs.

[0033] Thus, an LED or pcLED array can be or include a monolithic multicolor matrix of individually operable LED or pcLED light emitters. The LEDs or pcLEDs in the monolithic array can be, for example, microLEDs as described above.

[0034] A single individually operable LED or pcLED or a group of adjacent such LEDs or pcLEDs can correspond to a single pixel (picture element) in a display. For example, a group of three individually operable adjacent LEDs or pcLEDs that includes a red emitter, a blue emitter, and a green emitter can correspond to a single color-tunable pixel in a display.

[0035] As Figures 3A - 3BAs shown, an LED or pcLED array 200 can be mounted, for example, on an electronic board 300 that includes a power and control module 302, a sensor module 304, and an attachment area 306. The power and control module 302 can receive power and control signals from an external source as well as signals from the sensor module 304, and the power and control module 302 controls the operation of the LED / pcLED based on these signals. The sensor module 304 can receive signals from any suitable sensor (such as from a temperature or light sensor). Alternatively, the array 200 can be mounted on a separate board (not shown) from the power and control module and the sensor module.

[0036] Each LED or pcLED can optionally be combined or arranged in combination with a phosphor layer positioned adjacent to the LED or pcLED or a lens or other optical element disposed on the phosphor layer of the LED or pcLED. Such optical elements not shown in the figures can be referred to as "primary optical elements". Additionally, as Figures 4A - 4B shown, the array 200 (e.g., mounted on the electronic board 300) can be arranged in combination with secondary optical elements such as waveguides, lenses, or both for use in the intended application. In Figure 4A this case, the light emitted by the pcLED 100 is collected by the waveguide 402 and directed to the projection lens 404. For example, the projection lens 404 can be a Fresnel lens. Such an arrangement can be suitable for use, for example, in motor vehicle headlights. In Figure 4B this case, the light emitted by the pcLED 100 is directly collected by the projection lens 404 without using an intervening waveguide. This arrangement can be particularly suitable when the LEDs or pcLEDs can be spaced close enough to each other, and can also be used in motor vehicle headlights as well as in camera flash applications. For example, micro-LED display applications can use an optical arrangement similar to the Figures 4A - 4B optical arrangement depicted.

[0037] In another exemplary arrangement, a central block of LEDs or pcLEDs in the array can be associated with a single common (shared) optical device, and the edge LEDs or pcLEDs in the array located at the periphery of the central block are each associated with a corresponding individual optical device.

[0038] Generally speaking, depending on the desired application, any suitable optical element arrangement can be used in combination with the LED and pcLED arrays described herein.

[0039] The LED and pcLED arrays as described herein can be used in applications that require or benefit from fine-grained intensity, spatial, and temporal control of light distribution. Such applications can include, but are not limited to, precise special patterning of the emitted light from individual LEDs or pcLEDs or from groups (e.g., blocks) of LEDs or pcLEDs. Depending on the application, the emitted light can be spectrally distinct, time-adaptive, and / or environment-responsive. Such arrays can provide pre-programmed light distributions in various intensity, spatial, or temporal patterns. The emitted light can be at least partially based on received sensor data and can be used for optical wireless communication. Associated electronics and optics can be distinct at the level of individual LEDs / pcLEDs, groups, or devices.

[0040] Arrays of individually operable LEDs or pcLEDs can be used in combination with lenses, lens systems, or other optical devices or optical systems (e.g., as described above) to provide illumination suitable for a particular purpose. For example, in operation, such an adaptive illumination system can provide illumination that changes color and / or intensity across an illuminated scene or object and / or aims in a desired direction. Beam focusing or steering of the light emitted by the LED or pcLED array can be electronically performed by activating the LEDs or pcLEDs in groups of different sizes or sequentially activating the LEDs or pcLEDs to allow dynamic adjustment of the beam shape and / or direction without moving the optics or changing the focus of the lenses in the lighting device. A controller can be configured to receive data indicating the position and color characteristics of objects or people in a scene and control the LEDs or pcLEDs in the array based on this information to provide illumination suitable for the scene. Such data can be provided by, for example, an image sensor, an optical (e.g., laser scanning) sensor, or a non-optical (e.g., millimeter wave radar) sensor. Such adaptive illumination is becoming increasingly important for motor vehicles (e.g., adaptive headlights), mobile device cameras (e.g., adaptive flash), and AR, VR, and MR applications (such as the applications described below).

[0041] Figure 5 An example camera flash system 500 including an LED or pcLED array and an optical (e.g., lens) system 502 is schematically shown. The example camera flash system 500 can be or include an adaptive illumination system as described above, in which the LEDs or pcLEDs in the array can be individually operable or operable in groups. In operation of the camera flash system, the illumination from some or all of the LEDs or pcLEDs in the array and the optical system 502 can be adjusted (deactivated, operated at full intensity, or operated at an intermediate intensity). As described above, the array can be a monolithic array or include one or more monolithic arrays. As described above, the array can be a microLED array.

[0042] The flash system 500 also includes an LED driver 506 controlled by a controller 504, such as a microprocessor. The controller 504 may also be coupled to a camera 507 and a sensor 508 and operate according to instructions and profiles stored in a memory 510. The camera 507 and the LED or pcLED array and lens system 502 may be controlled by the controller 504 to, for example, match the illumination provided by the system 502 (i.e., the field of view of the illumination system) to the field of view of the camera 507, or to otherwise adapt the illumination provided by the system 502 to the scene observed by the camera as described above. The sensor 508 may include, for example, a position sensor (e.g., a gyroscope and / or an accelerometer) and / or other sensors that may be used to determine the position and orientation of the system 500.

[0043] Figure 6 An example display system 600 is schematically illustrated, which includes an array 610 of individually or group-operable LEDs or pcLEDs, a display 620, a light-emitting array controller 630, a sensor system 640, and a system controller 650. As described above, the array 610 may be a monolithic array or include one or more monolithic arrays. The array may be monochromatic. Alternatively, the array may be a multicolor array, where different LEDs or pcLEDs in the array are configured to emit different colors of light, as described above. Thus, the array may be or include a monolithic multicolor matrix of individually operable LED or pcLED light emitters, which may be, for example, microLEDs as described above. An individual or group of adjacent individually operable LEDs or pcLEDs in the array may correspond to a single pixel (image element) in the display. For example, a group of three individually operable adjacent LEDs or pcLEDs including a red emitter, a blue emitter, and a green emitter may correspond to a single color-tunable pixel in the display. Similarly, to provide redundancy in the case of a defective LED or pcLED, a group of six individually operable adjacent LEDs or pcLEDs including two red emitters, two blue emitters, and two green emitters may correspond to a single color-tunable pixel in the display. The array 610 may be used to project light in a graphic pattern or an object pattern, which may, for example, support an AR / VR / MR system.

[0044] Sensor inputs are provided to the sensor system 640, while power and user data inputs are provided to the system controller 650. In some embodiments, the modules included in the system 600 may be compactly arranged in a single structure, or one or more elements may be individually mounted and connected via wireless or wired communication. For example, the array 610, the display 620, and the sensor system 640 may be mounted on a headset or glasses, where the light-emitting array controller and / or the system controller 650 are separately mounted.

[0045] System 600 may incorporate a variety of optical devices (not shown) to couple the light emitted by array 610 into display 620. Any suitable optical devices may be used for this purpose.

[0046] Sensor system 640 may include, for example: external sensors that monitor the environment, such as cameras, depth sensors, or audio sensors; and internal sensors that monitor the position of the AR / VR / MR headset, such as accelerometers or two-axis or three-axis gyroscopes. Other sensors may include, but are not limited to, barometric pressure, stress sensors, temperature sensors, or any other suitable sensors required for local or remote environmental monitoring. In some embodiments, control inputs through the sensor system may include detected touches or taps, gesture inputs, or controls based on the position of the headset or display.

[0047] In response to data from sensor system 640, system controller 650 may send images or instructions to light array controller 630. Changes or modifications to the images or instructions may also be made through user data input or automatic data input as needed. User data input may include, but is not limited to, data input provided by audio instructions, tactile feedback, eye or pupil positioning, or a connected keyboard, mouse, or game controller.

[0048] As described above, AR, VR, and MR systems can be more generally referred to as examples of visualization systems. In a virtual reality system, the display may present a view of a scene (such as a three-dimensional scene) to the user. The user may move within the scene, such as by repositioning the user's head or by walking. The virtual reality system may detect the user's movement and change the view of the scene to account for the movement. For example, when the user rotates the user's head, the system may present a view of the scene that changes in the direction of view to match the user's gaze. In this way, the virtual reality system can simulate the user's presence in a three-dimensional scene. Additionally, the virtual reality system may receive tactile sensory input, such as from a wearable position sensor, and may optionally provide tactile feedback to the user.

[0049] In an augmented reality system, a display can incorporate elements from the user's surrounding environment into the view of a scene. For example, an augmented reality system can add text captions and / or visual elements to the view of the user's surrounding environment. For example, a retailer can use an augmented reality system to show a user what a piece of furniture would look like in a room in the user's home by combining a visualization of the piece of furniture over a captured image of the user's surrounding environment. As the user walks around in the user's room, the visualization interprets the user's movement and changes the visualization of the furniture in a manner consistent with that movement. For example, an augmented reality system can place a virtual chair in the room. The user can stand in front of the location of the virtual chair in the room to view the front side of the chair. The user can move within the room to an area behind the location of the virtual chair to view the back side of the chair. In this way, an augmented reality system can add elements to a dynamic view of the user's surrounding environment.

[0050] Figure 7 A general block diagram of an example visualization system 710 is shown. The visualization system 710 can include a wearable housing 712, such as a head-mounted headset or goggles. The housing 712 can mechanically support and house the elements detailed below. In some examples, one or more of the elements detailed below can be included in one or more additional housings that can be separate from the wearable housing 712 and coupled to the wearable housing 712 wirelessly and / or via a wired connection. For example, a separate housing can reduce the weight of the wearable goggles, such as by including a battery, a radio, and other elements. The housing 712 can include one or more batteries 714 that can power any or all of the elements detailed below. The housing 712 can include circuitry that can be electrically coupled to an external power source, such as a wall outlet, to charge the battery 714. The housing 712 can include one or more radios 716 to communicate wirelessly with a server or network via a suitable protocol, such as WiFi.

[0051] The visualization system 710 can include one or more sensors 718, such as optical sensors, audio sensors, tactile sensors, thermal sensors, gyroscopic sensors, time-of-flight sensors, triangulation-based sensors, and so on. In some examples, one or more sensors can sense the user's location, position, and / or orientation. In some examples, one or more sensors 718 can generate a sensor signal in response to the sensed location, position, and / or orientation. The sensor signal can include sensor data corresponding to the sensed location, position, and / or orientation. For example, the sensor data can include a depth map of the surrounding environment. In some examples, such as for an augmented reality system, one or more sensors 718 can capture real-time video images of the surrounding environment near the user.

[0052] The visualization system 710 may include one or more video generation processors 720. The one or more video generation processors 720 may receive scene data representing a three-dimensional scene from a server and / or a storage medium, such as a set of position coordinates of objects in the scene or a depth map of the scene. The one or more video generation processors 720 may receive one or more sensor signals from one or more sensors 718. In response to the scene data representing the surrounding environment and at least one sensor signal representing the location and / or orientation of the user relative to the surrounding environment, the one or more video generation processors 720 may generate at least one video signal corresponding to a view of the scene. In some examples, the one or more video generation processors 720 may generate two video signals, one for each eye of the user, the two video signals respectively representing views of the scene as seen from the left and right eyes of the user. In some examples, the one or more video generation processors 720 may generate more than two video signals and combine these video signals to provide one video signal for both eyes, two video signals for both eyes, or other combinations.

[0053] The visualization system 710 may include one or more light sources 722 that may provide light for a display of the visualization system 710. Suitable light sources 722 may include any of the LEDs, pcLEDs, LED arrays, and pcLED arrays discussed above, such as those discussed above with respect to the display system 600.

[0054] The visualization system 710 may include one or more modulators 724. The modulator 724 may be implemented in one of at least two configurations.

[0055] In a first configuration, the modulator 724 may include circuitry that may directly modulate the light source 722. For example, the light source 722 may include an array of light-emitting diodes, and the modulator 724 may directly modulate the electrical power, voltage, and / or current directed to each light-emitting diode in the array to form modulated light. The modulation may be performed in an analog manner and / or a digital manner. In some examples, the light source 722 may include an array of red light-emitting diodes, an array of green light-emitting diodes, and an array of blue light-emitting diodes, and the modulator 724 may directly modulate the red light-emitting diodes, green light-emitting diodes, and blue light-emitting diodes to form modulated light to produce a particular image.

[0056] In a second configuration, the modulator 724 can include a modulation panel, such as a liquid crystal panel. The light source 722 can produce uniform illumination or near-uniform illumination to illuminate the modulation panel. The modulation panel can include pixels. Each pixel can selectively attenuate a corresponding portion of the modulation panel area in response to an electrical modulation signal to form modulated light. In some examples, the modulator 724 can include multiple modulation panels that can modulate different colors of light. For example, the modulator 724 can include a red modulation panel that can attenuate red light from a red light source, such as a red light-emitting diode, a green modulation panel that can attenuate green light from a green light source, such as a green light-emitting diode, and a blue modulation panel that can attenuate blue light from a blue light source, such as a blue light-emitting diode.

[0057] In some examples of the second configuration, the modulator 724 can receive uniform white light or near-uniform white light from a white light source, such as a white light-emitting diode. The modulation panel can include wavelength-selective filters on each pixel of the modulation panel. The panel pixels can be arranged in groups (such as three or four groups), where each group can form a pixel of a color image. For example, each group can include panel pixels with a red filter, panel pixels with a green filter, and panel pixels with a blue filter. Other suitable configurations can also be used.

[0058] The visualization system 710 can include one or more modulation processors 726 that can receive video signals (such as from one or more video generation processors 720) and, in response, can generate electrical modulation signals. For configurations in which the modulator 724 directly modulates the light source 722, the electrical modulation signal can drive the light source 722. For configurations in which the modulator 724 includes a modulation panel, the electrical modulation signal can drive the modulation panel.

[0059] The visualization system 710 can include one or more beam combiners 728 (also referred to as beam splitters 728) that can combine different color beams to form a single multi-color beam. For configurations in which the light source 722 can include multiple light-emitting diodes of different colors, the visualization system 710 can include one or more wavelength-sensitive (e.g., dichroic) beam splitters 728 that can combine different colors of light to form a single multi-color beam.

[0060] The visualization system 710 can direct modulated light towards the observer's eyes in at least one of two configurations. In a first configuration, the visualization system 710 can act as a projector and can include suitable projection optics 730 that can project the modulated light onto one or more screens 732. The screen 732 can be positioned at a suitable distance from the user's eyes. The visualization system 710 can optionally include one or more lenses 734 that can position a virtual image of the screen 732 at a suitable distance from the eyes, such as a close-focus distance, such as 500 mm, 750 mm, or another suitable distance. In some examples, the visualization system 710 can include a single screen 732 such that the modulated light can be directed towards both of the user's eyes. In some examples, the visualization system 710 can include two screens 732 such that the modulated light from each screen 732 can be directed towards the respective eye of the user. In some examples, the visualization system 710 can include more than two screens 732. In a second configuration, the visualization system 710 can direct the modulated light directly into one or both eyes of the observer. For example, the projection optics 730 can form an image on the retina of one eye of the user, or on the retina of each of the user's two eyes.

[0061] For some configurations of the augmented reality system, the visualization system 710 can include at least a partially transparent display such that the user can view the user's surrounding environment through the display. For such a configuration, the augmented reality system can generate enhanced modulated light corresponding to the surrounding environment rather than the surrounding environment itself. For example, in an example where a retailer displays a chair, the augmented reality system can direct the modulated light corresponding to the chair rather than the rest of the room towards the screen or towards the user's eyes.

[0062] As described above with respect to Figure 1 Silicone is commonly used as the matrix material between the phosphor converter grains in the phosphor layer 106 of the pcLED. Under operation, the LED releases heat. Due to the different coefficients of thermal expansion (abbreviated herein as "CTE") of the interacting materials in the pcLED, such as the surface of the LED structure 102 in contact with the phosphor layer 106 and the phosphor particles with the matrix material, degradation of the pcLED can occur. Such degradation can include, for example, structural degradation such as delamination of the layers and / or cracking within the layers.

[0063] To prevent delamination and cracking in pcLEDs, highly flexible silicone resins with low Shore hardness values are particularly suitable for use as matrix materials in phosphor layers. Such silicone resins with low Shore hardness values can include silicone resins having a Shore hardness of, for example, 50 or lower on the Shore A hardness scale (i.e., hardness ≤ 50A), or silicone resins having a Shore hardness of less than 30 (i.e., hardness < 30A), for example.

[0064] However, silicone resins with low Shore hardness values (e.g., hardness ≤ 50A, or hardness < 30A) tend to have a sticky surface, and dust particles, fluff, and other debris may adhere to the sticky surface of the silicone resin matrix material of the phosphor layer. Such dust particles, fluff, and other debris can cause problems in LED applications (and especially LED arrays) because the dust, fluff, and / or debris adhering to the surface of the phosphor layer 106 can obscure and block the light from individual LEDs and cause device failure due to the blocked light. In particular, in microLEDs, since each LED is small, a single dust particle can block the light emitted from an individual LED or group of LEDs in the array, and in a display system including a microLED array, for example, the blocked light can significantly affect the quality of light projection. Therefore, it is necessary to prevent the accumulation of dust, fluff, and other debris on the LED surface (and especially the microLED surface). Thus, in order to effectively use highly flexible silicone resins with low Shore hardness in pcLEDs, a method for preventing the adhesion of dust, fluff, and other debris from the pcLED surface is needed.

[0065] Figure 8A A cross-section of a pcLED device with a thin inorganic protective layer is shown, and Figure 8B is Figure 8A an enlarged view of the region marked "B" in

[0066] In Figure 8A , the pcLED device 800 includes an LED structure 802. The LED structure 802 can be an individual LED, such as, for example, the LED structure 102 described with reference to Figure 1 . The LED structure 802 can be an LED array or a microLED array, such as, for example, the array 200 described with reference to Figure 2A or the LED wafer 210 described with reference to Figure 2C . The LED structure 802 can be disposed on a substrate 804.

[0067] The phosphor layer 806 may be disposed on the LED structure 802. The phosphor layer 806 may include a phosphor material disposed in a matrix material. The phosphor material may be, for example, any phosphor particles having wavelength conversion properties known to those of ordinary skill in the art. The matrix material may be, for example, silicone. The silicone used as the matrix material for the phosphor layer 806 may be a silicone material having a low Shore hardness (e.g., a Shore A hardness of 50 or less, or for example less than 30, as described above).

[0068] As Figure 8A and Figure 8B shown in [references], the thin inorganic protective layer 820 may be disposed on the silicone matrix material of the phosphor layer 806 such that the lower surface 822 of the inorganic protective layer 820 is disposed on the surface 810 of the phosphor layer 806 opposite to the LED structure 802. The thin inorganic protective layer 820 may be in direct contact with the phosphor layer 806 and enclose the silicone matrix material of the phosphor layer 806. For example, the inorganic protective layer 820 may cover any area of the silicone layer that transmits light emitted from the LED structure and may be exposed to the surrounding environment (e.g., air (air that may contain dust, fluff, and other debris)). The inorganic protective layer 820 protects the phosphor layer 806 from collecting such dust, fluff, and debris by preventing dust, fluff, and other debris from adhering to the matrix material of the phosphor layer 806. The upper surface 824 of the inorganic protective layer 820 may be in contact with the surrounding environment (e.g., air), or may be disposed under a lens or other features required for the application in which the pcLED device 800 is used.

[0069] The inorganic protective layer 820 may be formed of a material that is optically transparent to the wavelengths of light emitted by the LED structure 802 and the phosphor layer 806. For example, when the LED structure 802 and the phosphor layer 806 are configured to emit visible light, the material forming the inorganic protective layer may be transparent to wavelengths between 380 nm and 780 nm. Similarly, if the LED structure 802 and the phosphor layer 806 are configured to emit near-infrared light or infrared light, the inorganic protective layer 820 may be transparent in the near-infrared light (800 - 2500 nm) and / or infrared light (3000 - 25000 nm) wavelength ranges.

[0070] Examples of inorganic materials that can be used to form the inorganic protective layer 820 include, for example, Al2O3, SiO2, CrO2, ZrO2, HfO2, and Ta2O5. Depending on the application, a combination of two or more inorganic materials can be used. Such a combination can be used, for example, to form an inorganic protective layer that is a mixture of two or more inorganic materials in a single layer. The inorganic protective layer 820 can also be formed as a multi-layer, i.e., a first inorganic material layer, such as, for example, Al2O3; followed by a second inorganic material layer, such as, for example, Ta2O5. Such a multi-layer inorganic protective layer 820 can include multiple layers and multiple inorganic materials.

[0071] Figure 8B The thickness T of the inorganic protective layer 820 between the lower surface 822 and the upper surface 824 is shown. The inorganic protective layer 820 can have any thickness T and can, for example, be up to one micron thick. However, in practice, film integrity under thermal or elastic stress after deposition may limit the maximum thickness. To prevent dust, lint, and other debris from adhering to the silicone matrix material of the phosphor layer 806, the inorganic protective layer 820 only needs to be thick enough to shield the silicone matrix material. Using a thin inorganic protective layer 820 to protect the phosphor layer 806 from dust, lint, and debris without significantly increasing the size, weight, and depth of the pcLED device 800. Thus, the inorganic protective layer 820 can, for example, have a thickness T of less than 100 nm or, for example, less than 50 nm. For example, the inorganic protective layer 820 can have a thickness T in the range of 20 - 30 nm.

[0072] The inorganic protective layer 820 can also be formed to have certain optical properties. For example, the inorganic protective layer 820 can act as an anti-reflection filter. Such an anti-reflection filter can be formed by a single layer having a thickness T of a quarter wavelength (e.g., using a reference wavelength of 550 nm). Or a multi-layer can be used, for example, a multi-layer structure having alternating high refractive index materials and low refractive index materials, where each individual layer is a quarter wavelength thick. The inorganic protective layer 820 can also be designed for spectral selection, for example, a low wavelength pass filter, a high wavelength pass filter, or a bandpass filter formed by a combination of a low wavelength pass filter and a high wavelength pass filter. In another example, the inorganic protective layer 820 can be formed to have semi-reflective optical properties over a larger spectral range (e.g., 380 to 780 nm), which can be used to change the appearance of the LED's "off" state.

[0073] The inorganic protective layer 820 can be formed on the phosphor layer 806 using an atomic layer deposition (ALD) process. ALD is a pulsed chemical vapor deposition (CVD) process that allows for the growth of thin layers by applying one atomic layer of material per cycle. This process is self-limiting, allowing for very controlled and conformal coatings or layers.

[0074] The ALD reaction is divided into (at least) two parts. In the first step, a metal (oxide) precursor is fed into the reactor and adsorbs reactive groups on the surface and / or reacts with reactive groups on the surface, and then substantially all unreacted or unadsorbed precursor molecules are removed by purging the reactor. In the second step, an oxygen source is fed into the reactor and reacts with the metal source on the particle surface, and then the reactor is purged to substantially remove all remaining oxygen source molecules and hydrolysis products formed by the condensation reaction. A prototypical two-part ALD reaction for forming Al2O3 using trimethylaluminum (TMA) is in Figure 9 illustrated.

[0075] Due to the self-limiting nature of the surface reaction, these two steps result in the formation of atomic layers (or monolayers). These atomic layer reaction steps are repeated multiple times to form the final ALD layer.

[0076] ALD can be performed at low temperatures (50 °C - 350 °C) and is thus compatible with a variety of materials, which include, for example, LED and pcLED materials, and especially silicone resins used as matrix materials in the phosphor layer 806. Typical purge times are in the range of 2 seconds to 60 seconds.

[0077] The term metal oxide precursor particularly indicates a precursor of a metal oxide. The precursor itself may not be a metal oxide, but may include, for example, metal organic molecules. Thus, metal (oxide) precursors, especially for ALD, typically may include metal halides, alkoxides, amides, and other metal (organic) compounds.

[0078] The inorganic protective layer 820 can be, for example, Al2O3. The Al2O3 layer can be deposited by using Al(CH3)3 (TMA), AlCl3, or HAl(CH3)2 precursors in combination with water, ozone, or an oxygen source. Additional details for forming an Al2O3 coating using ALD can be found in Dillon, Ott, Way, and George, Surface Science, 322 (1995) 230 - 242 illustrated.

[0079] In additional embodiments, the inorganic protective layer can be formed by ALD using precursors and methods understood by those of ordinary skill in the art from another material - such as SiO2, SnO2, CrO2, ZrO2, HfO2, Ta2O5, TiO2, ZnO, TiN, TaN, V2O5, PtO2, B2O3, CdS. The inorganic protective layer 820 can be formed from a combination of metal oxide materials by forming a multilayer structure as described above.

[0080] Figure 10A method of forming a pcLED device with a thin inorganic protective layer is shown. At S10, a phosphor layer is formed on an LED structure using methods known to those of ordinary skill in the art. The phosphor layer includes a phosphor material disposed in a silicone matrix material. The upper surface of the phosphor layer opposite the LED structure is the cured silicone of the matrix material.

[0081] At S20, the LED structure with the phosphor layer is placed in an ALD reactor, and an inorganic protective layer is formed using the ALD process as disclosed above. Before the start of atomic layer deposition, a short activation treatment can be applied to the silicone surface of the phosphor layer, such as by using ultraviolet radiation and / or exposure to ozone, which can increase the accessibility of -OH groups on the surface of the phosphor layer.

[0082] The advantage of forming a thin inorganic protective layer using ALD is that it can be performed at a low enough temperature so that the formed phosphor layer and LED structure are not damaged or altered by the ALD process. For example, an inorganic protective layer made of Al2O3 can be deposited at a temperature of 150 °C (+ / - 5 °C), and many silicones that can be used as matrix materials in the phosphor conversion layer are stable at this temperature, so forming the inorganic protective layer does not affect the phosphor conversion layer.

[0083] Such an ALD protective layer for protecting a phosphor layer formed of a silicone matrix material as described in FIG. 8 above can be used anywhere in an LED device where a low Shore hardness silicone material is used to protect such a silicone layer. That is, the silicone layer protected by the inorganic protective layer does not need to be a phosphor layer including a phosphor material. For example, Figure 11 Device 1100 is shown, which has an LED structure 1170, a lens 1180 having optical properties formed of a low Shore hardness silicone, and an inorganic protective layer 1190 disposed on and in contact with the lens 1180.

[0084] The LED structure 1170 can be any of the above LED structures. The LED structure 1170 can include an intermediate layer (not shown) between the light-emitting surface of the LED within the LED structure 1170 and the lens 1180. For example, a phosphor layer or other lens can be included in the LED structure 1170.

[0085] The lens 1180 receives light or a portion of the light emitted by the LED within the LED structure 1170. Although the lens 1180 is shown as a representative convex shape in Figure 11 it is not limited to this shape and can have any useful shape for the desired optical properties.

[0086] An inorganic protective layer 1190 is disposed on the surface 1181 of the lens 1180 and is used to protect the lens 1180 formed of a low Shore hardness silicone resin from dust, fluff, and other debris, as described above. The inorganic protective layer 1190 can be formed using the materials, methods, and thicknesses described above. One advantage of using ALD to form such an inorganic protective layer is that the ALD method can be used to form a layer that conforms to the shape of the underlying silicone resin layer (i.e., the ALD layer can be conformal).

[0087] This disclosure is illustrative and not restrictive. Given this disclosure, further modifications will be apparent to those skilled in the art and are intended to fall within the scope of the appended claims.

Claims

1. A device, comprising: A silicone layer disposed on an LED structure; And An inorganic protective layer disposed on a surface of the silicone layer opposite to the LED structure.

2. The device according to claim 1, wherein the inorganic protective layer comprises a metal oxide.

3. The device according to claim 2, wherein the inorganic protective layer comprises at least one of Al2O3, SiO2, CrO2, ZrO2, HfO2, and Ta2O5.

4. The device according to claim 1, wherein the inorganic protective layer is formed by atomic layer deposition.

5. The device according to claim 1, wherein the thickness of the inorganic protective layer is less than 100 nm.

6. The device according to claim 1, wherein the inorganic protective layer is configured to be transparent to wavelengths within the visible light range.

7. The device according to claim 1, wherein the silicone matrix material has a Shore A hardness of 50 or less.

8. The device according to claim 1, wherein the silicone layer comprises a phosphor material.

9. The device according to claim 1, wherein the silicone layer is formed as a lens.

10. The device according to claim 1, wherein the inorganic protective layer is configured to have optical properties.

11. The device according to claim 10, wherein the LED structure comprises an LED array, the array comprising at least two individually addressable light-emitting diodes.

12. The device according to claim 11, further comprising a display configured to receive light emitted by the LED array.

13. A method of forming a device, the method comprising: Forming a silicone layer on an LED structure; And Forming an inorganic protective layer on a surface of the silicone layer opposite to the LED structure.

14. The method according to claim 13, wherein forming the inorganic protective layer comprises using atomic layer deposition.

15. The method according to claim 14, further comprising irradiating the silicone layer with ultraviolet light before atomic layer deposition of the inorganic protective layer.

16. The method according to claim 14, further comprising exposing the silicone layer to ozone before atomic layer deposition of the inorganic protective layer.

17. The method according to claim 13, wherein the inorganic protective layer comprises a metal oxide.

18. The method according to claim 13, wherein the inorganic protective layer comprises at least one of Al2O3, SiO2, CrO2, ZrO2, HfO2, and Ta2O5.

19. The method according to claim 13, wherein the thickness of the inorganic protective layer is less than 100 nm.

20. The method according to claim 13, wherein the inorganic protective layer is configured to be transparent to wavelengths within the visible light range.

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