LED device having a cyan photoluminescence material and red / green quantum dots

Abstract

To provide fabrications methods for blue color converters installed by self-aligned in-situ curing for micro-LEDs and systems and devices including the blue color converters.SOLUTION: A light-emitting device includes a plurality of light-emitting diodes, a first cured composition over a first subset of the light-emitting diodes, and a second cured composition over a second subset of light-emitting diodes. The first cured composition includes a first photopolymer and a blue photoluminescent material that is an organic, organometallic, or polymeric material, embedded in the first photopolymer. The second cured composition includes a second photopolymer and a nanomaterial embedded in the second photopolymer. The nanomaterial is selected to emit red or green light in response.SELECTED DRAWING: Figure 4E-4H

Description

Technical Field

[0001] The present disclosure generally relates to a method for manufacturing a blue converter attached by self-aligned in-situ curing of micro LEDs, and systems and devices including the blue converter.

Background Art

[0002] Light-emitting diode (LED) panels use an array of LEDs, and individual LEDs provide individually controllable pixel elements. Such LED panels can be used in computers, touch panel devices, personal digital assistants (PDAs), mobile phones, and monitors of televisions, etc.

[0003] LED panels using micron-scale LEDs based on III-V semiconductor technology (also called micro LEDs) have various advantages compared to OLEDs, such as higher energy efficiency, luminance, and lifespan, and fewer material layers in the display stack that can simplify manufacturing. However, there are challenges in manufacturing micro LED panels. Micro LEDs having different colors (e.g., red, green, and blue pixels) need to be manufactured on different substrates through separate processes. Integrating multiple colors of micro LED devices into a single panel generally requires a pick-and-place step of transferring the micro LED devices from their original donor substrate to a destination substrate. This often involves modifications to the LED structure or manufacturing process, such as the introduction of a sacrificial layer to facilitate die release. In addition, stringent requirements for placement accuracy can limit throughput, final yield, or both.

[0004] An alternative approach to avoiding the pick-and-place step is to selectively deposit a color converter (e.g., quantum dots, nanostructures, photoluminescence materials, or organic substances) at specific pixel locations on a substrate fabricated using monochrome LEDs. The monochrome LEDs can generate light of a relatively short wavelength, e.g., violet or blue light, and the color converter can convert this short-wavelength light into light of a longer wavelength, e.g., red or green light for red or green pixels. The selective deposition of the color converter can be carried out using a high-resolution shadow mask or controllable inkjet or aerosol jet printing.

[0005] However, shadow masks are prone to problems regarding alignment accuracy and scalability, and inkjet and aerosol jet technologies have problems with resolution (inkjet), accuracy (inkjet), and throughput (aerosol jet). To manufacture microLED displays, there is a need for new technologies that can precisely and cost-effectively provide different-color color converters on different pixels on a substrate such as a large-area substrate or a flexible substrate. SUMMARY OF THE INVENTION

[0006] The present disclosure generally relates to a method of manufacturing a blue converter attached by self-aligned in-situ curing of microLEDs, and to systems and devices including the blue converter.

[0007] In a general aspect, a light-emitting device includes a plurality of light-emitting diodes, a first cured composition in contact with a surface through which irradiation in a first wavelength range of the UV light range emitted from a subset of the first light-emitting diodes among the plurality of light-emitting diodes passes, and a second cured composition in contact with a surface through which irradiation in a second wavelength range of the UV light or visible light range emitted from a subset of the second light-emitting diodes among the plurality of light-emitting diodes passes. The first cured composition includes a first light polymer and a blue photoluminescence material. The blue photoluminescence material is selected to emit blue light in response to absorption of irradiation in the first wavelength range from each of the light-emitting diodes in a subset of the first light-emitting diodes among the plurality of light-emitting diodes. The blue photoluminescence material, an organic material, an organometallic material, or a polymer material is embedded in the first light polymer. The second cured composition includes a second light polymer and a nanomaterial. The nanomaterial is selected to emit red light or green light in response to absorption of irradiation in the second wavelength range from each of the light-emitting diodes in a subset of the second light-emitting diodes among the plurality of light-emitting diodes. The nanomaterial is embedded in the second light polymer.

[0008] In another aspect, a method of manufacturing a multi-color display includes dispensing a first photocurable fluid onto a display having a backplane and an array of light-emitting diodes electrically integrated with a backplane circuit network of the backplane. The first photocurable fluid includes a blue photoluminescence material selected to absorb ultraviolet light, one or more first monomers, and a first photoinitiator that initiates polymerization of the one or more first monomers in response to absorption of ultraviolet light. A first plurality of light-emitting diodes within the array of light-emitting diodes are activated to illuminate and cure the first photocurable fluid, and a first color conversion layer for converting light from the first plurality of light-emitting diodes to blue light is formed over each of the first plurality of light-emitting diodes, the first color conversion layer having a blue photoluminescence material embedded in a first polymer matrix. Uncured remainder of the first photocurable fluid is removed. Thereafter, a second photocurable fluid is dispensed onto the display. The second photocurable fluid includes a nanomaterial selected to emit red or green light in response to absorption of ultraviolet light, one or more second monomers, and a second photoinitiator that initiates polymerization of the one or more second monomers in response to absorption of ultraviolet light. A second plurality of light-emitting diodes within the array of light-emitting diodes are activated to illuminate and cure the second photocurable fluid, and a second color conversion layer for converting light from the second plurality of light-emitting diodes to light of a different second color is formed over each of the second plurality of light-emitting diodes, the second color conversion layer having nanostructures embedded in a second polymer matrix. Uncured remainder of the second photocurable fluid is removed.

[0009] Implementations of these general aspects may include one or more of the following features.

[0010] The nano material is a first nano material, and the first nano material is selected to emit red light in response to absorption of irradiation in a second wavelength range from each of the light-emitting diodes of a second subset of the plurality of light-emitting diodes. The third cured composition is in contact with a surface through which irradiation in a third wavelength range of UV light or visible light emitted from a third subset of the plurality of light-emitting diodes passes. The third cured composition includes a third polymer and a second nano material. The second nano material is selected to emit green light in response to absorption of irradiation in the third wavelength range from each of the light-emitting diodes of a third subset of the plurality of light-emitting diodes. The second nano material is embedded in the third optical polymer.

[0011] In some cases, the photoluminescence material is an organic material, and the organic material is a free radical. The blue photoluminescence material can be phosphorescent or fluorescent. The blue photoluminescence material generally absorbs ultraviolet light having a maximum wavelength in the range of about 300 nm to about 430 nm. In some cases, the blue photoluminescence material emits blue light having an emission peak in the range of about 420 nm to about 480 nm. The full width at half maximum of the emission peak of the blue photoluminescence material is less than 100 nm. The photoluminescence quantum yield of the blue photoluminescence material generally ranges from 5% to 100%.

[0012] Advantages of the blue converter and systems and devices including the blue converter include high photoluminescence quantum yield, long life, and long storage life.

[0013] Details of one or more embodiments of the subject matter of this disclosure are set forth in the accompanying drawings and the description. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

Brief Description of the Drawings

[0014]

Figure 1A

Figure 1B-1

Figure 1B-2

Figure 1C

Figure 2

Figure 3

Figure 4A-4D

Figure 4E-4H

Figure 5

Figure 6

Figure 7

[0015] Like reference symbols in the various drawings indicate like elements.

Embodiments for Carrying Out the Invention

[0016] Quantum dots can be dispersed in an acrylate formulation for inkjet printing. Subsequently, UV curing is performed, and the quantum dots confined in the polyacrylate matrix can be used as a color conversion layer for advanced displays. However, while red light and green light can be achieved by quantum dots, quantum dots that convert UV light to blue light (e.g., ZeS / Se / Te quantum dots) generally have the drawbacks of low photoluminescence quantum yield (PLQY), short service life, and short shelf life.

[0017] Techniques that can address the problems associated with the lack of a blue converter for micro-LEDs with a UV backlight include using materials other than quantum dots for the blue converter. These blue converters can be included in formulations for micro-LED blue conversion layers formed by self-aligning curing as described in this disclosure.

[0018] Formulations for micro-LED blue conversion layers generally include a blue converter (e.g., not including quantum dots), a reactive component, and a photoinitiator. The formulation may optionally include one or more of a solvent, a functional component (e.g., a high refractive index additive, a surfactant, a light-scattering absorber, or a UV blocker).

[0019] Suitable blue converters include fluorescent and phosphorescent organic molecules, organic radicals, organometallic complexes, and polymers containing one or more of these color converters. The blue converter is selected to have a strong absorption of UV light with a maximum wavelength (λ max ) in the range of about 300 nm to about 430 nm and emit blue light with an emission peak in the range of about 420 nm to about 480 nm. The full width at half maximum (FWHM) of the emission peak is generally less than 100 nm, and the photoluminescence quantum yield (PLQY) is generally in the range of 5% to 100%.

[0020] Examples of suitable blue conversion agents include LUMILUX Blue CD 310, LUMILUX Blue CD 710, and LUMILUX Dispersion Blue CD 910 (available from Honeywell International Inc.). Figure 1A shows the structural formulas of blue fluorescent molecules 4P-NPD, Bepp2, TPA-SBFF, DPAFVF, Ban-(3,5)-CF3, TBPe, DBzA, BITPI, BiPI-1, 4PF, TPI-Py, and PhImA. Figure 1B shows the structural formulas of blue thermally activated delayed fluorescence (TADF) molecules ν-DABNA, DMAC-DPS, CZ-PS, DMTDAc, DMAC-TRZ, Cab-peha-TRZ, Ca-TRZ2, Cz-TRZ3, Cz-TRZ4, BCC-TPTA, DDCzTrz, DPCC-TPTA, DCzTrz, BDPCC-TPTA, Phen-TRZ, TCzTrz, Cz-VPN, CPC, 2PXZ-TAZ, and CC2BP. Figure 1C shows the structural formulas of blue phosphorescent organic complexes and organometallic complexes containing metalloids (boron) and metals (beryllium and iridium).

[0021] Formulations for the red conversion layer and green conversion layer of the micro-LED generally include a red conversion agent or a green conversion agent, a reactive component, and a photoinitiator, respectively. The formulation may optionally include one or more of a solvent, a functional component (e.g., a high refractive index additive, a surfactant, a light-scattering absorber, or a UV blocker).

[0022] Red conversion agents and green conversion agents are substances that emit visible light in a first visible wavelength range in response to absorption of UV irradiation or visible light in a second visible wavelength range. UV irradiation generally has a wavelength in the range of 200 nm to 400 nm. Visible light generally has a wavelength or wavelength range in the range of 500 nm to 800 nm. The first visible wavelength range is different from (e.g., higher in energy than) the second visible wavelength range. That is, the color conversion agent is a material that can convert shorter wavelength light from the micro-LED into longer wavelength light.

[0023] The red converter and the green converter can include a photoluminescence material, such as an organic molecule or an inorganic molecule, a nanomaterial (e.g., nanoparticles, nanostructures, quantum dots), or other suitable materials. Suitable nanomaterials generally include one or more III-V compounds. Examples of suitable III-V compounds include CdSe, CdS, InP, PbS, CuInP, ZnSeS, and GaAs. In some cases, the nanomaterial includes one or more elements selected from the group consisting of cadmium, indium, copper, silver, gallium, germanium, hydrides, aluminum, boron, iodides, bromides, chlorine, selenium, tellurium, and phosphorus. In some cases, the nanomaterial includes one or more perovskites.

[0024] Quantum dots can be made uniform or can have a core-shell structure. Quantum dots can have an average diameter in the range of about 1 nm to about 10 nm. One or more organic ligands are generally attached to the outer surface of the quantum dots. The organic ligands facilitate the dispersion of the quantum dots in a solvent. Suitable organic ligands include aliphatic amines, thiols or acid compounds, and the aliphatic portion generally has 6 to 30 carbon atoms. Examples of suitable nanostructures include nanoplatelets, nanocrystals, nanorods, nanotubes, and nanowires.

[0025] The reaction components include monomers, such as (meth)acrylate monomers, and can include one or more mono(meth)acrylates, di(meth)acrylates, tri(meth)acrylates, tetra(meth)acrylates, or combinations thereof. The reaction components can be provided by a negative photoresist, such as an SU-8 photoresist. Examples of suitable mono(meth)acrylates include isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, trimethylcyclohexyl (meth)acrylate, diethyl (meth)acrylamide, dimethyl (meth)acrylamide, and tetrahydrofurfuryl (meth)acrylate. The reaction components can include a crosslinking agent or other reactive compounds. Examples of suitable crosslinking agents include polyethylene glycol di(meth)acrylate (e.g., diethylene glycol di(meth)acrylate or tripropylene glycol di(meth)acrylate), N,N'-methylenebis-(meth)acrylamide, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate. Examples of suitable reactive compounds include polyethylene glycol (meth)acrylate, vinyl pyrrolidone, vinyl imidazole, styrene sulfonate, (meth)acrylamide, alkyl (meth)acrylamide, dialkyl (meth)acrylamide), hydroxyethyl (meth)acrylate, morpholinoethyl acrylate, and vinyl formamide.

[0026] The photoinitiator initiates polymerization in response to irradiation such as UV irradiation, UV-LED irradiation, visible light, and electron beam irradiation. In some cases, the photoinitiator is responsive to UV irradiation or visible light. Suitable photoinitiators include free radical photoinitiators such as bulk curing photoinitiators and surface curing photoinitiators.

[0027] Bulk curing photoinitiators produce free radicals upon exposure to UV irradiation, thereby initiating polymerization. Bulk curing photoinitiators are useful for both surface curing and overall or bulk curing of the dispensed droplets. Bulk curing photoinitiators include benzoin ethers, benzyl ketals, acetylphenones, alkylphenones, phosphine oxides, benzophenone compounds, and thioxanthone compounds.

[0028] Surface curing photoinitiators are activated by UV irradiation to form free radicals by hydrogen abstraction from a second compound, which becomes the actual initiating free radical. This second compound is often called a co-initiator or polymerization synergist and may be an amine synergist. Amine synergists are used to reduce oxygen inhibition, and thus surface curing photoinitiators can be useful for rapid surface curing. Surface curing initiators include benzophenone compounds and thioxanthone compounds. Amine synergists are amines containing active hydrogen. Amine synergists such as amine-containing acrylates can be combined with benzophenone photoinitiators in resin precursor formulations to a) limit oxygen inhibition, b) rapidly cure the droplet or layer surface to fix the dimensions of the droplet or layer surface, and c) enhance the stability of the layer throughout the curing process.

[0029] Examples of suitable photoinitiators include 1-hydroxycyclohexyl phenyl ketone, 4-isopropylphenyl-2-hydroxy-2-methylpropan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2,2-dimethyl-2-hydroxy-acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methylpropiophenone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, bis(2,6-dimethoxy-benzoyl)-2,4,6trimethylphenylphosphine oxide, 2-methyl-1-1[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 3,6-bis(2-methyl-2-morpholino-propionyl)-9-n-octylcarbazole, 2-benzyl-2-(dimethylamino)-1-(4-morpholinyl)phenyl)-1-butanone, benzophenone, 2,4,6-trimethylbenzophenone, isopropylthioxanthone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1phenyl-1-propanone. Suitable blends of commercially available photoinitiators include Darocur 4265, Irgacure 184, Irgacure 250, Irgacure 270, Irgacure 295, Irgacure 369, Irgacure 379, Irgacure 500, Irgacure 651, Irgacure 754, Irgacure 784, Irgacure 819, Irgacure 907, Irgacure 1173, Irgacure 2100, Irgacure 2022, Irgacure 4265, Irgacure TPO, Irgacure TPO-L, Esacure KT37, Esacure KT55, Esacure KTO046, Omnicat 250, and Omnicat 550. Suitable amine synergists include secondary and tertiary amine compounds with or without acrylic groups, such as diethanolamine, triethanolamine, and Genomer 5142.

[0030] Optionally, the photocurable composition can contain a solvent. The solvent can be organic or inorganic. Examples of suitable solvents include water, ethanol, toluene, dimethylformamide, methyl ethyl ketone, or combinations thereof. The solvent can be selected to provide the desired surface tension or viscosity to the photocurable composition. The solvent can also improve the chemical stability of other components.

[0031] Optionally, the photocurable composition can contain a light-absorbing agent or a UV blocker. Examples of suitable light-absorbing agents include Disperse Yellow 3, Disperse Yellow 7, Disperse Orange 13, Disperse Orange 3, Disperse Orange 25, Disperse Black 9, Disperse Red 1 acrylate, Disperse Red 1 methacrylate, Disperse Red 19, Disperse Red 1, Disperse Red 13, and Disperse Blue 1. Examples of suitable UV blockers include benzotriazolyl hydroxyphenyl compounds.

[0032] Optionally, the first photocurable composition can include one or more other functional components. As an example, the functional components can affect the optical properties of the color conversion layer. For example, the functional components can include nanoparticles having a sufficiently high refractive index (e.g., at least about 1.7), so that the color conversion layer functions as an optical layer that adjusts the optical path of the output light, for example, providing a microlens. Examples of suitable nanoparticles include TiO2, ZnO2, ZrO2, CeO2, or a mixture of two or more of these oxides. Alternatively, in addition, the nanoparticles can have a refractive index selected such that the color conversion layer functions as an optical layer that reduces total internal reflection losses, thereby improving light extraction. As another example, the functional components can include a dispersant or surfactant that adjusts the surface tension of the photocurable composition. Examples of suitable dispersants or surfactants include siloxanes and polyethylene glycol. As yet another example, the functional components can include a photoluminescence pigment that emits visible light. Examples of suitable photoluminescence pigments include zinc sulfide and strontium aluminate.

[0033] In some cases, the photocurable composition includes approximately up to about 90 wt% of reactive components (e.g., from about 10 wt% to about 90 wt%), from about 0.5 wt% to about 5 wt% of a photoinitiator, and from about 0.1 wt% to about 10 wt% (e.g., from about 1 wt% to about 2 wt%) of a color converter. The photocurable composition can also include a solvent (e.g., up to about 10 wt% of a solvent).

[0034] The photocurable composition can optionally include up to about 5 wt% of a surfactant or dispersant, from about 0.01 wt% to about 5 wt% (e.g., from about 0.1 wt% to about 1 wt%) of a light-scattering absorber, or any combination thereof.

[0035] The viscosity of the photocurable composition is generally in the range of about 10 cP (centipoise) to about 2000 cP (e.g., about 10 cP to about 150 cP) at room temperature. The surface tension of the photocurable composition is generally in the range of about 20 millinewtons per meter (mN / m) to about 60 mN / m (e.g., about 40 mN / m to about 60 mN / m). After curing, the elongation rate at break of the cured photocurable composition is generally in the range of about 1% to about 200%. The tensile strength of the cured photocurable composition is generally in the range of about 1 megapascal (MPa) to about 1 gigapascal (GPa). The photocurable composition can be applied to one or more layers, and the thickness of the cured photocurable composition is generally in the range of about 10 nm to about 100 microns (e.g., about 10 nm to about 20 microns, about 10 nm to about 1000 nm, or about 10 nm to about 100 nm).

[0036] The photocurable composition described in the present disclosure is implemented as a color conversion layer of a display, for example, a micro-LED display described with reference to FIGS. 2 to 7.

[0037] FIG. 2 shows a micro-LED display 10 including an array 12 of single micro-LEDs 14 (see FIGS. 3A and 3B) disposed on a backplane 16. The micro-LEDs 14 are already integrated with the backplane circuit network 18 such that each micro-LED 14 can be individually addressed. For example, the backplane circuit network 18 includes a TFT active matrix array with thin film transistors and storage capacitors (not shown) for each micro-LED, column address lines and row address lines 18a, column drivers and row drivers 18b, etc., and can drive the micro-LEDs 14. Alternatively, the micro-LEDs 14 can be driven by a passive matrix within the backplane circuit network 18. The backplane 16 can be manufactured using a conventional CMOS process.

[0038] Figures 3A and 3B show a portion 12a of a micro-LED array 12 having individual micro-LEDs 14. All of the micro-LEDs 14 are fabricated to have the same structure to generate the same wavelength range (which can be referred to as a "monochromatic" micro-LED). For example, the micro-LED 14 can generate light in the ultraviolet (UV) region, such as in the near-UV region. For example, the micro-LED 14 can generate light in the range of 365 to 405 nm. As another example, the micro-LED 14 can generate light in the violet or blue range. The micro-LED can generate light having a spectral bandwidth of 20 to 60 nm.

[0039] Figure 3B shows a portion of a micro-LED array that can provide a single pixel. Assuming that the micro-LED display is a three-color display, each pixel includes three sub-pixels, one for each color, for example, one for each of a blue channel, a green channel, and a red channel. Thus, a pixel can include three micro-LEDs 14a, 14b, 14c. For example, the first micro-LED 14a can correspond to the blue sub-pixel, the second micro-LED 14b can correspond to the green sub-pixel, and the third micro-LED 14c can correspond to the red sub-pixel. However, the techniques described below are applicable to micro-LED displays that use a number of colors, such as four or five colors. In this case, each pixel can include four or more micro-LEDs where each micro-LED corresponds to a respective color. In addition, the techniques described below are applicable to micro-LED displays that use only two colors.

[0040] Generally, the monochromatic micro-LED 14 can generate light in a wavelength range having a peak of a wavelength equal to or less than the wavelength of the highest frequency color intended for the display, for example, purple light or blue light. The color conversion agent can convert this short-wavelength light into light of a longer wavelength, for example, red light or green light for red or green sub-pixels. When the micro-LED generates UV light, the color conversion agent can be used to convert the UV light into blue light for blue sub-pixels.

[0041] The vertical isolation wall 20 is formed between adjacent micro-LEDs. The isolation wall provides optical isolation that helps to localize polymerization and reduce optical crosstalk during in-situ polymerization described later. The isolation wall 20 can be a photoresist or a metal and can be deposited by a conventional lithography process. As shown in FIG. 3A, the wall 20 can form a rectangular array having each micro-LED 14 within individual recesses 22 defined by the wall 20. Other array shape dimensions, for example, hexagonal or offset rectangular arrays are also possible. Possible processes for backplane integration and isolation wall formation are described in more detail below.

[0042] The wall can have a height H of about 3 to 20 μm. The wall can have a width W of about 2 to 10 μm. The height H can be greater than the width W, for example, the wall can have an aspect ratio of 1.5:1 to 5:1. The height H of the wall is sufficient to block light from reaching an adjacent micro-LED from one micro-LED.

[0043] FIGS. 4A-4H show a method of selectively forming a color conversion layer on a micro-LED array. First, as shown in FIG. 4A, a first photocurable composition 30a is deposited on an array of micro-LEDs 14 that is already integrated with the backplane circuit network. The first photocurable composition 30a can have a depth D greater than the height H of the isolation wall 20.

[0044] As shown in FIGS. 5A to 5C, the photocurable composition (e.g., the first photocurable composition 30a, the second photocurable composition 30b, the third photocurable composition 30c, etc.) includes a polymerizable component 32, a photoinitiator 34 that triggers polymerization under illumination with a wavelength corresponding to the light emission of the micro-LED 14, and a color converter 36a. The polymerizable component 32 includes the antioxidant-inhibiting additives and reaction components described herein.

[0045] After curing of the photocurable composition, the components of the photoinitiator 34 may be present in the cured photocurable composition (photopolymer), in which case this component is a fragment of the photoinitiator formed during the breaking of the bond of the photoinitiator in the photoinitiation process.

[0046] Returning to FIG. 4A, the first photocurable composition 30a can be deposited on the display over the micro-LED array by a spin-on method, dipping, spray coating, or an inkjet process. The inkjet process can be more efficient in the consumption of the first photocurable composition 30a.

[0047] Next, as shown in FIG. 4B, the circuit network of the backplane 16 is used to selectively activate the first plurality of micro-LEDs 14a. This first plurality of micro-LEDs 14a corresponds to the sub-pixels of the first color. In particular, the first plurality of micro-LEDs 14a corresponds to the sub-pixels for the color of the light generated by the color converter in the photocurable composition 30a. For example, assuming that the color converter in the fluid 30a converts the light from the micro-LED 14 into blue light, only these micro-LEDs 14a corresponding to the blue sub-pixels are turned on. Since the micro-LED array is already integrated with the backplane circuit network 18, power can be supplied to the micro-LED display 10, and a control signal can be applied by a microprocessor to selectively turn on the micro-LEDs 14a.

[0048] As shown in FIGS. 4B and 4C, activation of the first plurality of micro LEDs 14a causes in-situ curing of the first photocurable composition 30a, generating illumination A (see FIG. 4B) that forms a first solidified color conversion layer 40a (see FIG. 4C) on each activated micro LED 14a. That is, the fluid 30a cures to form the color conversion layer 40a, but only on the selected micro LEDs 14a. For example, the color conversion layer 40a for converting blue light can be formed on each micro LED 14a.

[0049] In some implementations, the illumination from the selected micro LEDs 14a does not reach the other micro LEDs 14b, 14c. In such situations, the isolation walls 20 may not be necessary. However, even when the spacing between the micro LEDs 14 is small enough, the isolation walls 20 can effectively block the illumination A from the selected micro LEDs 14a from reaching areas above those other micro LEDs that are within the penetration depth of the illumination from the other micro LEDs. The isolation walls 20 can also be included, for example, simply as an insurance against illumination reaching areas above other micro LEDs.

[0050] The drive current and drive time of the first plurality of micro LEDs 14a can be selected for an appropriate photon dosage for the photocurable composition 30a. The power per subpixel for curing the fluid 30a is not necessarily the same as the power per subpixel in the display mode of the micro LED display 10. For example, the power per subpixel in the curing mode can be made higher than the power per subpixel in the display mode.

[0051] As shown in FIG. 4D, when curing is completed and the first solidified color conversion layer 40a is formed, the remaining uncured first photocurable composition is removed from the display 10. As a result, the other micro LEDs 14b, 14c remain exposed for the next deposition step. In some implementations, the uncured first photocurable composition 30a can be easily washed away from the display using a solvent such as water, ethanol, toluene, dimethylformamide, or methyl ethyl ketone, or a combination thereof. When the photocurable composition 30a includes a negative photoresist, the wash fluid can include a photoresist developer for the photoresist.

[0052] As shown in FIGS. 4E and 5B, the processes described above with reference to FIGS. 4A - 4D are repeated, except that a second photocurable composition 30b is used and a second plurality of micro LEDs 14b are activated. After washing, a second color conversion layer 40b is formed over each of the second plurality of micro LEDs 14b.

[0053] The second photocurable composition 30b is similar to the first photocurable composition 30a, but includes a color conversion agent 36b that converts shorter wavelength light from the micro LED 14 to longer wavelength light of a different second color. The second color can be, for example, green.

[0054] The second plurality of micro LEDs 14b correspond to sub - pixels of the second color. In particular, the second plurality of micro LEDs 14b correspond to sub - pixels for the color of the light generated by the color conversion agent in the second photocurable composition 30b. For example, assuming that the color conversion agent in the fluid 30a converts the light from the micro LED 14 to green light, only these micro LEDs 14b corresponding to the green sub - pixels are turned on.

[0055] As shown in FIGS. 4F and 5C, optionally, the processes described above with reference to FIGS. 4A-4D are repeated, provided that a third photocurable composition 30c is used and a third plurality of micro-LEDs 14c are activated. After rinsing, a third color conversion layer 40c is formed over each of the third plurality of micro-LEDs 14c.

[0056] The third photocurable composition 30c is similar to the first photocurable composition 30a, but includes a color conversion agent 36c that converts shorter wavelength light from the micro-LED 14 to longer wavelength light of a different third color. The third color can be, for example, red.

[0057] The third plurality of micro-LEDs 14c correspond to sub-pixels of the third color. In particular, the third plurality of micro-LEDs 14c correspond to sub-pixels for the color of light produced by the color conversion agent in the third photocurable composition 30c. For example, assuming that the color conversion agent in the fluid 30c converts light from the micro-LED 14 to red light, only these micro-LEDs 14c corresponding to the red sub-pixels are turned on.

[0058] In this specific embodiment shown in FIGS. 4A-4F, the color conversion layers 40a, 40b, 40c are deposited for each color sub-pixel. This is necessary, for example, when the micro-LED generates ultraviolet light.

[0059] However, the micro-LED 14 may generate blue light instead of UV light. In this case, the coating of the display 10 with the photocurable composition containing the blue conversion agent can be skipped, and the process can be carried out using the photocurable composition for the green and red sub-pixels. For example, as shown in FIG. 4E, a plurality of one set of micro-LEDs are left without the color conversion layer. The process shown by FIG. 4F is not carried out. For example, the first photocurable composition 30a can include the green CCA and a first plurality of the micro-LEDs 14a can correspond to the green sub-pixels, and the second photocurable composition 30b can include the red CCA and a second plurality of the micro-LEDs 14b can correspond to the red sub-pixels.

[0060] Assuming that the fluids 30a, 30b, 30c contain a solvent, some of the solvent can be trapped in the color conversion layers 40a, 40b, 40c. As shown in FIG. 4G, this solvent can be evaporated, for example, by exposing the micro-LED array to heat by an IR lamp or the like. The evaporation of the solvent from the color conversion layers 40a, 40b, 40c can shrink these layers so that the final layers become thinner.

[0061] The removal of the solvent and the shrinkage of the color conversion layers 40a, 40b, 40c can increase the concentration of the color conversion agent, for example, quantum dots, thereby enhancing the color conversion efficiency. On the other hand, by including the solvent, the flexibility of the chemical formulation of other components of the photocurable composition, for example, the color conversion agent or the crosslinkable component, can be enhanced.

[0062] Optionally, as shown in FIG. 4H, a UV blocking layer 50 can be deposited over all of the micro LEDs 14. The UV blocking layer 50 can block UV light that is not absorbed by the color conversion layer 40. The UV blocking layer 50 can be a Bragg reflector or simply a material that selectively absorbs UV light (e.g., a benzotriazolyl hydroxyphenyl compound). The Bragg reflector can reflect UV light back to the micro LED 14, thus increasing energy efficiency. Other layers such as a stray light absorption layer, a photoluminescence layer, and a high refractive index layer can optionally also include materials that can be deposited over the micro LED 14.

[0063] Accordingly, as described herein, the photocurable composition is selected to emit irradiation in a first wavelength range of the visible light range in response to absorption of irradiation in a second wavelength range of the UV light or visible light range, a color conversion agent, a reactive component (e.g., one or more monomers), and a photoinitiator that initiates polymerization of the active component in response to absorption of irradiation in the second wavelength range. The second wavelength range is different from the first wavelength range.

[0064] In some implementations, the light emitting device includes a plurality of light emitting diodes and a cured composition in contact with a surface through which irradiation in a first wavelength range of the UV light or visible light range emitted from each of the light emitting diodes passes. The cured composition includes a nanomaterial selected to emit irradiation in a second wavelength range of the visible light range in response to absorption of irradiation in the first wavelength range from each of the light emitting diodes, a photopolymer, and a component (e.g., a fragment) of a photoinitiator that initiates polymerization of the photopolymer in response to absorption of irradiation in the first wavelength range. The second wavelength range is different from the first wavelength range.

[0065] In some implementation manners, the light-emitting device includes a plurality of additional light-emitting diodes and an additional cured composition in contact with a surface through which irradiation in a first wavelength range emitted from each of the additional light-emitting diodes passes. The additional cured composition includes an additional CCA selected to emit irradiation in a third wavelength range in the visible light range in response to absorption of irradiation in the first wavelength range from each of the light-emitting diodes, an additional optical polymer, and components of an additional photoinitiator that initiates polymerization of the optical polymer in response to absorption of irradiation in the first wavelength range. The third wavelength range may be different from the second wavelength range.

[0066] Figures 6A-6E show a method of manufacturing a micro-LED array and isolation walls on a backplane wiring board. As shown in Figure 6A, the process starts with a wafer 100 providing a micro-LED array. The wafer 100 includes a substrate 102, such as a silicon or sapphire wafer, on which a first semiconductor layer 104 having a first doping on top, an active layer 106, and a second semiconductor layer 108 having a second reverse doping are deposited. For example, the first semiconductor layer 104 can be an N-type doped gallium nitride (n-GaN) layer, the active layer 106 can be a multiple quantum well (MQW) layer 106, and the second semiconductor layer 107 can be a P-type doped gallium nitride (p-GaN) layer 108.

[0067] As shown in Figure 6B, the wafer 100 is etched to divide the layers 104, 106, 108 into individual micro-LEDs 14 including a plurality of first, second, and third micro-LEDs 14a, 14b, 14c corresponding to the first, second, and third colors. In addition, conductive contacts 110 can be deposited. For example, a p-type contact 110a and an n-type contact 110b can be deposited on the n-GaN layer 104 and the p-GaN layer 108, respectively.

[0068] Similarly, the backplane 16 is manufactured to include a circuit network 18 and electrical contacts 120. The electrical contacts 120 can include a first contact 120a, for example, a driving contact, and a second contact 120b, for example, a grounding contact.

[0069] As shown in FIG. 6C, the micro-LED wafer 100 is aligned with and arranged to contact the backplane 16. For example, the first contact 110a can contact the first contact 120a, and the second contact 110b can contact the second contact 120b. The micro-LED wafer 100 can be lowered to contact the backplane or vice versa.

[0070] Next, as shown in FIG. 6D, the substrate 102 is removed. For example, a silicon substrate can be removed from the substrate 102 by polishing, for example, chemical mechanical polishing. As another example, a sapphire substrate can be removed by a laser lift-off process.

[0071] Finally, as shown in FIG. 6E, the isolation wall 20 is formed on the backplane 16 (to which the micro-LEDs 14 are already attached). The isolation wall can be formed by conventional processes such as deposition of photoresist, patterning of the photoresist by photolithography, and development to remove the portion of the photoresist corresponding to the recess 22. The resulting structure can be used as the display 10 for the process described with respect to FIGS. 4A - 4H.

[0072] FIGS. 7A - 7D show another method of manufacturing a micro-LED array and isolation walls on a backplane. This process can be similar to the process described above with respect to FIGS. 6A - 6E, but differs in the following respects.

[0073] As shown in FIG. 7A, the process begins with a wafer 100 that provides a micro-LED array and a backplane 16, similar to the process described above.

[0074] As shown in FIG. 7B, a partition wall 20 is formed on the backplane 16 (where the micro-LEDs 14 are not yet attached).

[0075] In addition, the wafer 100 is etched to divide the layers 104, 106, 108 into individual micro-LEDs 14 including a plurality of first, second, and third micro-LEDs 14a, 14b, 14c. However, the recess 130 formed by this etching process is deep enough to accommodate the partition wall 20. For example, the etching can continue such that the recess 130 extends into the substrate 102.

[0076] Next, as shown in FIG. 7C, the micro-LED wafer 100 is aligned with the backplane 16 and arranged to contact the backplane 16 (or vice versa). The partition wall 20 fits into the recess 130. In addition, the contacts 110 of the micro-LEDs are electrically connected to the contacts 120 of the backplane 16.

[0077] Finally, as shown in FIG. 7D, the substrate 102 is removed. As a result, the micro-LEDs 14 and the partition wall 20 remain on the backplane 16. The resulting structure can be used as the display 10 for the process described with respect to FIGS. 4A - 4H.

[0078] Terms related to arrangements such as vertical and lateral are used. However, such terms refer to relative arrangements and not absolute arrangements with respect to gravity. For example, lateral refers to a direction parallel to the substrate surface, and vertical refers to a direction perpendicular to the substrate surface.

[0079] It will be appreciated by those skilled in the art that the foregoing examples are illustrative and not limiting. For example: ·While the above description focuses on micro LEDs, the present technique can be applied to other displays comprising other types of light emitting diodes, particularly other microscale light emitting diodes, e.g., displays comprising LEDs having a width of less than about 10 microns. ·While the above description assumes that the color conversion layers are formed in the order of blue, green, red, other orders, e.g., blue, red, green, are also possible. Additionally, other colors, e.g., orange and yellow, are possible.

[0080] It should be understood that various modifications can be made without departing from the spirit and scope of the present disclosure.

Claims

1. A method for manufacturing a light emitting diode (LED) comprising: a first plurality of light emitting diodes and a second plurality of light emitting diodes, each light emitting diode of the plurality of light emitting diodes configured to emit radiation within a wavelength range of a UV range; a first cured composition in contact with a surface through which radiation emitted from the first plurality of light emitting diodes passes, A first optical polymer, and a quantum dot-free blue photoluminescent material selected to emit blue light in response to absorption of said radiation in said wavelength range from each light emitting diode of said first plurality of light emitting diodes; the first cured composition comprising: a second cured composition in contact with a surface through which radiation emitted from the second plurality of light emitting diodes passes, a second optical polymer, and quantum dots embedded within the second optical polymer, the quantum dots selected to emit red or green light in response to absorption of the radiation within the wavelength range from each light emitting diode of the second plurality of light emitting diodes. the second cured composition comprising 2. A light emitting device comprising:

2. the quantum dots include first quantum dots selected to emit red light in response to absorption of the radiation in the wavelength range from each light emitting diode of the second plurality of light emitting diodes; The light emitting device comprises: a third cured composition in contact with a surface through which radiation emitted from a third plurality of light emitting diodes of the plurality of light emitting diodes passes, a third optical polymer, and second quantum dots of a different composition than the first quantum dots embedded within the third optical polymer, the second quantum dots selected to emit green light in response to absorption of the radiation in the wavelength range from each light emitting diode of the third plurality of light emitting diodes; the third cured composition comprising The light emitting device of claim 1 further comprising:

3. 10. The light-emitting device of claim 1, wherein the blue photoluminescent material is an organic material, an organometallic material, or a polymeric material.

4. 10. The light emitting device of claim 1, wherein the blue photoluminescent material is phosphorescent.

5. The light emitting device of claim 1 , wherein the blue photoluminescent material is fluorescent.

6. 10. The light emitting device of claim 1, wherein the blue photoluminescent material absorbs ultraviolet radiation having a maximum wavelength in the range of about 300 nm to about 430 nm.

7. 10. The light emitting device of claim 1, wherein the blue photoluminescent material emits blue light having an emission peak in the range of about 420 nm to about 480 nm.

8. 8. The light emitting device of claim 7, wherein the full width at half maximum of the emission peak of the blue photoluminescent material is less than 100 nm.

9. 10. The light emitting device of claim 1, wherein the photoluminescence quantum yield of the blue photoluminescent material ranges from 5% to 100%.

10. The blue photoluminescent material is 4P-NPD, Bepp 2 , TPA-SBFF, DPAFVF, Ban-(3,5)-CF3, TBPe, DBzA, BITPI, BiPI-1, 4PF, TPI-Py, PhImA, v-DABNA, DMAC-DPS, CZ-PS, DMTDAc, DMAC-TRZ, Cab-pH-TRZ, Ca-TRZ2, Cz-TRZ3, Cz-TRZ4, BCC-TPTA, DDCzTrz, DPCC-TPTA, DCzTrz, BDPCC-TPTA, Phen-TRZ, TCzTrz, Cz-VPN, CPC, 2PXZ-TAZ, and CC2BP.

11. dispensing a first photocurable fluid onto a display having a backplane and an array of light emitting diodes electrically integrated with backplane circuitry of the backplane, the first photocurable fluid comprising a quantum dot-free blue photoluminescent material selected to absorb ultraviolet light, one or more first monomers, and a first photoinitiator that initiates polymerization of the one or more first monomers in response to absorption of the ultraviolet light; activating a first plurality of light emitting diodes in the array of light emitting diodes to illuminate and cure the first light curable fluid and forming a first color conversion layer over each of the first plurality of light emitting diodes for converting light from the first plurality of light emitting diodes to blue light, the first color conversion layer having the blue photoluminescent material free of quantum dots embedded in a first polymer matrix; removing any uncured remainder of the first photocurable fluid; and thereafter, dispensing a second light curable fluid over the display, the second light curable fluid comprising quantum dots selected to emit red or green light in response to absorption of the ultraviolet light, one or more second monomers, and a second photoinitiator that initiates polymerization of the one or more second monomers in response to absorption of the ultraviolet light; activating a second plurality of light emitting diodes in the array of light emitting diodes to illuminate and cure the second light curable fluid and forming a second color conversion layer over each of the second plurality of light emitting diodes for converting light from the second plurality of light emitting diodes to a different second color of light, the second color conversion layer having the quantum dots embedded in a second polymer matrix; removing any uncured remainder of the second photocurable fluid; and A method for producing a multi-color display comprising:

12. The method of claim 11 , wherein the one or more first monomers and the one or more second monomers are both (meth)acrylate monomers.

13. The method of claim 11 , wherein the one or more first monomers and the one or more second monomers have the same chemical structure.

14. 12. The method of claim 11, wherein the one or more first photoinitiators and the one or more second photoinitiators have the same chemical structure.

15. The quantum dots include first quantum dots selected to emit red light in response to absorption of ultraviolet light; The method further comprises: dispensing a third light curable fluid onto the display, the third light curable fluid comprising second quantum dots of a different composition than the first quantum dots selected to emit green light in response to absorption of ultraviolet light, one or more third monomers, and a third photoinitiator that initiates polymerization of the one or more third monomers in response to absorption of ultraviolet light; activating a third plurality of light emitting diodes in the array of light emitting diodes to illuminate and cure the third light curable fluid and forming a third color conversion layer over each of the third plurality of light emitting diodes to convert light from the third plurality of light emitting diodes to green light, the third color conversion layer having the second quantum dots embedded in a third polymer matrix; removing any uncured remainder of the third photocurable fluid; and The method of claim 11 further comprising:

16. The method of claim 11 , wherein the blue photoluminescent material is an organic material, an organometallic material, or a polymeric material.

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