阅读说明：本技术 发光装置的颜色转换层 (Color conversion layer for light emitting devices ) 是由 斯瓦帕基亚·甘纳塔皮亚潘 骆英东 张代化 胡·T·额 朱明伟 奈格·B·帕蒂班德拉 于 2020-05-20 设计创作，主要内容包括：光可固化组合物包括纳米材料、一种或多种(甲基)丙烯酸酯单体和光引发剂,该纳米材料被选择为响应于在紫外或可见光范围内的第二波长带中的辐射的吸收而发射在可见光范围内的第一波长带中的辐射,该光引发剂响应于第二波长带中的辐射的吸收而引发一种或多种(甲基)丙烯酸酯单体的聚合。第二波长带不同于第一波长带。发光装置包括多个发光二极管和与表面接触的固化的光可固化组合物,通过该表面从每个发光二极管发射在紫外或可见光范围内的第一波长带中的辐射。(The photocurable composition includes a nanomaterial selected to emit radiation in a first wavelength band in the visible range in response to absorption of radiation in a second wavelength band in the ultraviolet or visible range, one or more (meth) acrylate monomers, and a photoinitiator that initiates polymerization of the one or more (meth) acrylate monomers in response to absorption of radiation in the second wavelength band. The second wavelength band is different from the first wavelength band. The light emitting device includes a plurality of light emitting diodes and a cured photocurable composition in contact with a surface through which radiation in a first wavelength band in the ultraviolet or visible range is emitted from each light emitting diode.)

1. A photocurable composition comprising:

a nanomaterial selected to emit radiation in a first wavelength band within the visible range in response to absorption of radiation in a second wavelength band within the ultraviolet or visible range, wherein the second wavelength band is different from the first wavelength band;

one or more (meth) acrylate monomers; and

a photoinitiator that initiates polymerization of the one or more (meth) acrylate monomers in response to absorption of radiation in the second wavelength band.

2. The composition of claim 1, wherein the composition comprises:

about 0.1 wt% to about 10 wt% of the nanomaterial;

about 0.5 wt% to about 5 wt% of the photoinitiator; and

about 1 wt% to about 90 wt% of the one or more (meth) acrylate monomers.

3. The composition of claim 2, wherein the composition comprises about 1 wt% to about 2 wt% of the nanomaterial.

4. The composition of claim 2, wherein the composition further comprises a solvent.

5. The composition of claim 4, wherein the composition comprises:

about 0.1 wt% to about 10 wt% of the nanomaterial;

about 0.5 wt% to about 5 wt% of the photoinitiator;

about 1 wt% to about 10 wt% of the one or more (meth) acrylate monomers; and

about 10 wt% to about 90 wt% of the solvent.

6. The composition of claim 5, wherein the composition comprises about 2 wt% to about 3 wt% of the one or more (meth) acrylate monomers.

7. The composition of claim 1, wherein the nanomaterial comprises one or more III-V compounds.

8. The composition of claim 1, wherein the nanomaterial is selected from the group consisting of nanoparticles, nanostructures, and quantum dots.

9. The composition of claim 8, wherein the nanomaterial comprises a quantum dot.

10. The composition of claim 9, wherein each of the quantum dots comprises one or more ligands coupled to the outer surface of the quantum dot, wherein the ligands are selected from the group consisting of thioalkyl compounds and carboxyalkanes.

11. The composition of claim 1, wherein the viscosity of the composition is in the range of about 10cP to about 150cP at room temperature.

12. The composition of claim 1, wherein the surface tension of the composition is in the range of about 20mN/m to about 60 mN/m.

13. A light emitting device comprising:

a plurality of light emitting diodes; and

a cured composition in contact with a surface through which radiation in a first wavelength band in the ultraviolet or visible light range is emitted from each of the light emitting diodes, wherein the cured composition comprises:

a nanomaterial selected to emit radiation in a second wavelength band within the visible range in response to absorption of the radiation in the first wavelength band from each of the light emitting diodes;

a photopolymer; and

a composition of a photoinitiator that initiates polymerization of the photopolymer in response to absorption of radiation in the first wavelength band.

14. The apparatus of claim 13, further comprising:

a further plurality of light emitting diodes; and

a further cured composition in contact with a surface through which radiation in the first wavelength band is emitted from each of the further light emitting diodes, wherein the further cured composition comprises:

a further nanomaterial selected to emit radiation in a third wavelength band within the visible range in response to absorption of radiation in the first wavelength band from each of the light emitting diodes;

an additional photopolymer; and

a composition of a further photoinitiator that initiates polymerization of the photopolymer in response to absorption of radiation in the first wavelength band.

15. The device of claim 13, wherein the cured composition has a thickness in a range from about 10nm to about 100 microns.

Technical Field

The present disclosure generally relates to color conversion layers for light emitting devices including organic light emitting devices.

Background

Light Emitting Diode (LED) panels use an array of LEDs, with each LED providing an individually controllable pixel element. Such LED panels may be used in computers, touch panel devices, Personal Digital Assistants (PDAs), cell phones, television monitors, and the like.

Compared to OLEDs, LED panels using micron-sized LEDs (also referred to as micro-LEDs) based on III-V semiconductor technology will have several advantages, such as higher energy efficiency, brightness and lifetime and fewer material layers in the display stack that can be simplified to manufacture. However, challenges exist with the fabrication of micro LED panels. Micro LEDs with different color emissions (e.g., red, green, and blue pixels) need to be fabricated on different substrates by separate processes. The integration of multiple colors of micro LED devices onto a single panel requires a pick and place step to transfer the micro LED devices from the micro LED devices' original donor substrate to the target substrate. This typically involves modifying the LED structure or manufacturing process, for example introducing a sacrificial layer to simplify chip release. Furthermore, strict requirements on placement accuracy (e.g., less than 1um) limit yield, final yield, or both.

An alternative approach to bypassing the pick and place step is to selectively deposit a color converting agent (e.g., quantum dots, nanostructures, photoluminescent material or organic substances) at specific pixel locations on a substrate made of single color LEDs. Monochromatic LEDs can produce light of a relatively short wavelength, such as violet or blue light, and color converters can convert this short wavelength light to longer wavelength light, such as red or green light for red or green pixels. Selective deposition of the color converter can be performed using a high resolution shadow mask or controlled inkjet or aerosol jet printing.

Disclosure of Invention

In a first general aspect, a photocurable composition comprises: a nanomaterial selected to emit radiation in a first wavelength band in the visible range in response to absorption of radiation in a second wavelength band in the ultraviolet or visible range; one or more (meth) acrylate monomers; and a photoinitiator that initiates polymerization of the one or more (meth) acrylate monomers in response to absorption of radiation in the second wavelength band. The second wavelength band is different from the first wavelength band.

Various implementations of the first general aspect may include one or more of the following features.

In some embodiments, the photocurable composition comprises about 0.1 wt% to about 10 wt% of the nanomaterial, about 0.5 wt% to about 5 wt% of the photoinitiator, and about 1 wt% to about 90 wt% of the one or more (meth) acrylate monomers. In some cases, the photocurable composition comprises about 1 wt% to about 2 wt% of the nanomaterial. The photocurable composition may further comprise a solvent.

In certain embodiments, the photocurable composition comprises about 0.1 wt% to about 10 wt% of the nanomaterial, about 0.5 wt% to about 5 wt% of the photoinitiator, about 1 wt% to about 10 wt% of one or more (meth) acrylate monomers, and about 10 wt% to about 90 wt% of the solvent. In some cases, the photocurable composition comprises from about 2 wt% to about 3 wt% of one or more (meth) acrylate monomers.

The nanomaterial typically comprises one or more III-V compounds. In some cases, the nanomaterial is selected from the group consisting of nanoparticles, nanostructures, and quantum dots. Suitable nanostructures include nanoplates, nanorods, nanotubes, nanowires, and nanocrystals. The nanomaterial may be comprised of quantum dots. Each quantum dot typically includes one or more ligands coupled to the outer surface of the quantum dot, wherein the ligands are selected from the group consisting of thioalkyl compounds and carboxyalkanes.

The photocurable composition may comprise one or more crosslinkers, one or more dispersants, one or more stray light absorbers, or any combination of these. The viscosity of the photocurable composition is typically in the range of about 10cP to about 150cP at room temperature. The surface tension of the photocurable composition is typically in the range of about 20mN/m to about 60 mN/m.

In a second general aspect, a light emitting device includes: a plurality of light emitting diodes; and a curing composition in contact with the surface through which radiation in a first wavelength band in the ultraviolet or visible range is emitted from each light emitting diode. The cured composition comprises: a nanomaterial selected to emit radiation in a second wavelength band within the visible range in response to absorption of radiation in the first wavelength band from each light emitting diode; a photopolymer; and a composition (e.g., fragments) of a photoinitiator that initiates polymerization of the photopolymer in response to absorption of radiation in the first wavelength band. The second wavelength band is different from the first wavelength band.

Implementations of the second general aspect may include one or more of the following features.

The light-emitting device may include an additional plurality of light-emitting diodes and an additional cured composition in contact with a surface through which radiation in a first wavelength band is emitted from each additional light-emitting diode. Additional cured compositions include: a further nanomaterial selected to emit radiation in a third wavelength band in the visible range in response to absorption of radiation in the first wavelength band from each light emitting diode; an additional photopolymer; and a composition of a further photoinitiator that initiates polymerization of the photopolymer in response to absorption of radiation in the first wavelength band. The third wavelength band may be different from the second wavelength band. The thickness of the cured composition is typically in the range of about 10nm to about 100 microns.

Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims.

Various embodiments are described below. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

Drawings

Fig. 1 is a schematic top view of a micro LED array that has been integrated with a backplane.

Fig. 2A is a schematic top view of a portion of a micro LED array.

Fig. 2B is a schematic cross-sectional view of a portion of the micro LED array of fig. 2A.

Fig. 3A to 3H illustrate a method of selectively forming a Color Converter (CCA) layer over a micro LED array.

Fig. 4A to 4C show the formulation of a photocurable fluid.

Fig. 5A to 5E illustrate a method of manufacturing a micro LED array and a partition wall on a base plate.

Fig. 6A to 6D illustrate another method of manufacturing a micro LED array and a partition wall on a base plate.

Like reference symbols in the various drawings indicate like elements.

Detailed Description

As mentioned above, selective deposition of the color converter can be performed using a high resolution shadow mask or controllable inkjet or aerosol jet printing. Unfortunately, shadow masks are prone to problems with alignment accuracy and scalability, while inkjet and aerosol jet technologies suffer from problems with resolution (inkjet), accuracy (inkjet) and throughput (aerosol jet). To manufacture a micro LED display, new techniques are needed to accurately and cost-effectively provide color converters for different colors onto different pixels on a substrate (e.g., a large area substrate or a flexible substrate).

A technique that can address these problems is to coat a substrate with a single color micro LED array with a layer of a light curable fluid containing a Color Converter (CCA) for a first color, then turn on selected LEDs to trigger in situ polymerization and fix the CCA in the vicinity of the selected sub-pixels. The uncured fluid over the unselected sub-pixels can be removed and then the same process can be repeated for CCAs for different colors until all sub-pixels on the chip are covered with a CCA of the desired color. This technique may overcome challenges in alignment accuracy, throughput, and scalability.

Fig. 1 shows a micro LED display 10, the micro LED display 10 comprising an array 12 of individual micro LEDs 14 arranged on a backplane 16 (see fig. 2A and 2B). The micro-LEDs 14 have been integrated with backplane circuitry 18 such that each micro-LED 14 can be individually addressed. For example, backplane circuitry 18 can include a TFT active matrix array with thin film transistors and storage capacitors (not shown) for each micro LED, row address and column address lines 18a, row and column drivers 18b, etc. to drive the micro LEDs 14. Alternatively, the micro-LEDs 14 can be driven by a passive matrix in the backplane circuitry 18. The backplane 16 can be fabricated using well-known CMOS processing.

Fig. 2A and 2B show a portion 12A of the micro LED array 12 having individual micro LEDs 14. All of the micro-LEDs 14 are fabricated with the same structure to produce the same wavelength range (this can be referred to as a "single color" micro-LED). For example, the micro LEDs 14 can generate light in the Ultraviolet (UV) range, such as light in the near-UV range. For example, the micro-LEDs 14 can generate light in the 365 to 405nm range. As another example, the micro LEDs 14 can produce light in the violet or blue range. micro-LEDs are capable of producing light having a spectral bandwidth of 20 to 60 nm.

Fig. 2B 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 comprises three sub-pixels, one for each color, e.g. one for the blue, green and red channels. Thus, the pixel can include three micro LEDs 14a, 14b, 14 c. For example, the first micro LEDs 14a can correspond to a blue sub-pixel, the second micro LEDs 14b can correspond to a green sub-pixel, and the third micro LEDs 14c can correspond to a red sub-pixel. However, the techniques discussed below are applicable to miniature LED displays using a large number of colors (e.g., four or more colors). In this case, each pixel may include four or more micro LEDs, each corresponding to a respective color. In addition, the techniques discussed below are applicable to miniature LED displays using only two colors.

In general, the single color micro LED14 is capable of producing light in a range of wavelengths having a peak wavelength no greater than that of the highest frequency color intended for the display, e.g., violet or blue light. The color converter can convert this short wavelength light to longer wavelength light, for example, red or green light for a red or green subpixel. If the micro-LEDs generate ultraviolet light, then a color converter can be used to convert the ultraviolet light to blue light for the blue sub-pixel.

Vertical partition walls 20 are formed between adjacent micro LEDs. The partition walls provide optical isolation to aid local polymerization and reduce optical crosstalk during in situ polymerization discussed below. The spacer walls 20 may be photoresist or metal and can be deposited by conventional lithographic processes. As shown in fig. 2A, the walls 20 can form a rectangular array with each micro-LED 14 in a separate recess 22 defined by the walls 20. Other array geometries, such as hexagonal or offset rectangular arrays are also possible. Possible processes for backplane integration and barrier wall formation are discussed in more detail below.

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

Fig. 3A to 3H illustrate a method of selectively forming a Color Converter (CCA) layer over a micro LED array. Initially, as shown in FIG. 3, a first photocurable fluid 30a is deposited over the array of micro LEDs 14 that have been integrated with the backplane circuitry. The first photocurable fluid 30a can have a depth D that is greater than the height H of the partition wall 20.

Referring to fig. 4A-4C, the photocurable fluid (e.g., first photocurable fluid 30a, second photocurable fluid 30b, third photocurable fluid 30C, etc.) includes one or more monomers 32, a photoinitiator 34 for triggering polymerization under illumination at a wavelength corresponding to the emission of the micro-LEDs 14, and a color conversion agent 36 a.

When polymerized, the monomer 32 will increase the viscosity of the fluid 30a, e.g., the fluid 30a can be cured or form a gel-like network structure. Monomer 32 is typically a (meth) acrylate monomer and may include one or more mono (meth) acrylates, di (meth) acrylates, tri (meth) acrylates, tetra (meth) acrylates, or combinations of these. The monomer 32 is provided by a negative photoresist (e.g., 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 monomer 32 may be used as a cross-linking agent or other reactive compound. Examples of suitable crosslinking agents include polyethylene glycol di (meth) acrylates (e.g., diethylene glycol di (meth) acrylate or tripropylene glycol di (meth) acrylate), N' -methylenebis- (meth) acrylamide, pentaerythritol tri (meth) acrylate, and pentaerythritol tetra (meth) acrylate. Examples of suitable reactive compounds include polyethylene glycol (meth) acrylates, vinyl pyrrolidone, vinyl imidazole, styrene sulfonate esters, (meth) acrylamides, alkyl (meth) acrylamides, dialkyl (meth) acrylamides, hydroxyethyl (meth) acrylates, morpholinoethyl acrylate, and vinyl formamide.

The photoinitiator 34 may initiate polymerization in response to radiation such as ultraviolet radiation, ultraviolet-LED radiation, visible radiation, and electron beam radiation. In some cases, the photoinitiator 34 is responsive to ultraviolet or visible radiation. Examples of photoinitiators 34 include Irgacure 184, Irgacure 819, Darocur 1173, Darocur 4265, Darocur TPO, Omnicat 250, and Omnicat 550. Following curing of the photocurable fluid, the compositions of the photoinitiator 34 may be present in the cured photocurable fluid (photopolymer), where these compositions are fragments of the photoinitiator formed during bond cleavage in the photoinitiator in the photoinitiation process.

Color converting agents (e.g., 36a, 36b, 36c, etc.) are materials that emit visible radiation in a first visible wavelength band in response to absorption of ultraviolet radiation or visible radiation in a second visible wavelength band. The ultraviolet radiation typically has a wavelength in the range of 200nm to 400 nm. Visible radiation typically has a wavelength or band of wavelengths in the range of 400nm to 800 nm. The first visible wavelength band is different (e.g., more energetic) than the second visible wavelength band. That is, the color conversion agent is a material capable of converting shorter wavelength light from the micro-LEDs 14 to longer wavelength light (e.g., red, green, or blue). In the example shown in fig. 3A-3H, the color conversion agent 36 converts the ultraviolet light from the micro-LEDs 14 to blue light.

The color-converting agent 36 can include a photoluminescent material, such as an organic or inorganic molecule, a nanomaterial (e.g., nanoparticles, nanostructures, quantum dots), or other suitable material. Suitable nanomaterials typically include one or more group 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, arsenic, aluminum, boron, iodide, bromide, chloride, selenium, tellurium, and phosphorus. In some cases, the nanomaterial includes one or more perovskites.

The quantum dots may be uniform or may have a core-shell structure. The quantum dots may have an average diameter in a range of about 1nm to about 10 nm. One or more organic ligands are typically coupled to the outer surface of the quantum dot. The organic ligands promote dispersion of the quantum dots in the solvent. Suitable organic ligands include aliphatic amine, thiol or acid compounds wherein the aliphatic moiety typically has from 6 to 30 carbon atoms. Examples of suitable nanostructures include nanoplates, nanocrystals, nanorods, nanotubes, and nanowires.

Optionally, the photocurable fluid (e.g., 30a, 30b, 30c, etc.) may include a solvent 37. The solvent may be organic or inorganic. Examples of suitable solvents include water, ethanol, toluene, dimethylformamide, methyl ethyl ketone, or combinations of these. The solvent can be selected to provide a desired surface tension and/or viscosity to the photocurable fluid. Solvents can also improve the chemical stability of other compositions.

Optionally, the photocurable fluid may include a stray light absorber or an ultraviolet blocker. Examples of suitable stray light absorbers 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.

Optionally, the first photocurable fluid 30a may include one or more additional functional components 38. As an example, the functional component can affect the optical properties of the color conversion layer. For example, the functional component may comprise nanoparticles having a sufficiently high refractive index (e.g. at least about 1.7) to allow the color conversion layer to act as an optical layer to adjust the optical path of the output light, e.g. to provide microlenses. Examples of suitable nanoparticles include TiO₂、ZnO₂、ZrO₂、CeO₂Or a mixture of two or more of these oxides. Alternatively or additionally, the nanoparticles can have a refractive index selected such that the color conversion layer acts as an optical layer that reduces total reflection losses, thereby improving light extraction. As another example, the functional ingredient may include a dispersant or a surfactant to adjust the surface tension of the fluid 30 a. Examples of suitable dispersants or surfactants include silicones and polyethylene glycols. As yet another example, the functional ingredient may include a photoluminescent pigment that emits visible radiation. Examples of suitable photoluminescent pigments include zinc sulfideAnd strontium aluminate.

In some cases, the photocurable fluid includes about 0.1 wt% to about 10 wt% (e.g., about 1 wt% to about 2 wt%) of a color conversion agent (e.g., nanomaterial), up to about 90 wt% of one or more monomers, and about 0.5 wt% to about 5 wt% of a photoinitiator. The photocurable fluid may also include a solvent (e.g., up to about 10 wt% solvent).

In some cases, the photocurable fluid includes about 0.1 wt% to about 10 wt% (e.g., about 1 wt% to about 2 wt%) of a color conversion agent (e.g., nanomaterial), about 1 wt% to about 10 wt% (e.g., about 2 wt% to about 3 wt%) of one or more monomers, and about 0.5 wt% to about 5 wt% of a photoinitiator. The photocurable fluid may also include a solvent (e.g., up to about 10 wt% solvent).

The photocurable fluid may optionally include from about 0.1 wt% to about 50 wt% of a crosslinker, a reactive compound, or a combination of a crosslinker and a reactive compound. The photocurable fluid may optionally include up to about 5 wt% of a surfactant or a dispersant, about 0.01 wt% to about 5 wt% (e.g., about 0.1 wt% to about 1 wt%) of a stray light absorber, or any combination of these.

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

Returning to fig. 3A, the first photocurable fluid 30a can be deposited on the display over the array of micro LEDs by spin coating, dip coating, spray coating, or ink jet processes. The inkjet process can be more efficient in the consumption of the first photocurable fluid 30 a.

Next, as shown in FIG. 3B, the circuitry of the backplane 16 is used to selectively activate the first plurality of micro LEDs 14 a. The first plurality of micro-LEDs 14a corresponds to a first color sub-pixel. In particular, the first plurality of micro LEDs 14a correspond to sub-pixels for converting the color in the photocurable fluid 30a into the color of the resulting light. For example, assuming that the color conversion component in the fluid 30a will convert light from the micro-LEDs 14 to blue light, only the micro-LEDs 14a corresponding to the blue sub-pixels are turned on. Because the micro LED array is already integrated with the backplane circuitry 18, power can be supplied to the micro LED display 10 and a control signal can be applied by the microprocessor to selectively turn on the micro LEDs 14 a.

Referring to fig. 3B and 3C, activation of the first plurality of micro-LEDs 14a generates illumination a (see fig. 3B) that results in-situ curing of the first photocurable fluid 30a to form a first cured color conversion layer 40a over each activated micro-LED 14a (see fig. 3C). In short, the fluid 30a is cured to form the color conversion layer 40a, but only on selected micro LEDs 14 a. For example, a color conversion layer 40a for converting into blue light can be formed on each of the micro LEDs 14 a.

In some embodiments, curing is a self-limiting process. For example, illumination from the micro-LEDs 14a, such as ultraviolet illumination, can have a limited penetration depth into the photocurable fluid 30 a. Thus, while FIG. 3B shows illumination A reaching the surface of photocurable fluid 30a, this is not required. In some embodiments, the illumination from the selected micro LED14 a does not reach the other micro LEDs 14b, 14 c. In this case, the partition wall 20 may not be necessary.

However, if the spacing between the micro-LEDs 14 is small enough, the partition wall 20 can positively block illumination a from selected micro-LEDs 14a from reaching areas that would be above other micro-LEDs within the penetration depth from such other micro-LED illumination. For example, the partition wall 20 can also be included only as a guarantee to prevent the illumination from reaching the area above the other micro LEDs.

The drive current and drive time for the first plurality of micro-LEDs 14a can be selected to provide the photocurable fluid 30a with an appropriate photon dose. The power for each sub-pixel of the curing fluid 30a need not be the same as the power for each sub-pixel in the display mode of the micro LED display 10. For example, the power for each sub-pixel for the curing mode can be higher than the power for each sub-pixel for the display mode.

Referring to fig. 3D, when curing is complete and the first cured color conversion layer 40a is formed, the remaining uncured first photocurable fluid is removed from the display 10. This exposes the other micro LEDs 14b, 14c for subsequent deposition steps. In some embodiments, the uncured first photocurable fluid 30a is simply rinsed from the display with a solvent such as water, ethanol, toluene, dimethylformamide, or methyl ethyl ketone, or a combination of these. If the photocurable fluid 30a comprises a negative photoresist, the rinsing fluid can comprise a photoresist developer for the photoresist.

Referring to fig. 3E and 4B, the process described above with respect to fig. 3A-3D is repeated, but with respect to the second photocurable fluid 30B and with respect to the activation of the second plurality of micro-LEDs 14B. After rinsing, a second color conversion layer 40b is formed over each of the second plurality of micro LEDs 14 b.

The second photocurable fluid 30b is similar to the first photocurable fluid 30a, but includes a color conversion agent 36b to convert the shorter wavelength light from the micro-LEDs 14 to a different second color, longer wavelength light. The second color may be, for example, green.

The second plurality of micro-LEDs 14b corresponds to a sub-pixel of a second color. In particular, the second plurality of micro-LEDs 14b correspond to sub-pixels for the color of light produced by the color conversion component in the second photocurable fluid 30 b. For example, assuming that the color conversion component in the fluid 30a will convert light from the micro-LEDs 14 to green light, only those micro-LEDs 14b corresponding to the green sub-pixels are turned on.

Referring to fig. 3F and 4C, optionally, the process described above with respect to fig. 3A-3D is repeated again, but with respect to the third photocurable fluid 30C and with respect to the activation of the third plurality of micro-LEDs 14C. After rinsing, a third color conversion layer 40c is formed over each third plurality of micro LEDs 14 c.

The third photocurable fluid 30c is similar to the first photocurable fluid 30a, but includes a color conversion agent 36c to convert the shorter wavelength light from the micro-LEDs 14 to a different third color, longer wavelength light. The third color may be, for example, red.

The third plurality of micro-LEDs 14c corresponds to a sub-pixel of a 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 component in the third photocurable fluid 30 c. For example, assuming that the color conversion component in the fluid 30c converts light from the micro-LEDs 14 to red light, only those micro-LEDs 14c corresponding to the red sub-pixels are turned on.

In this particular example shown in fig. 3A to 3F, a colour conversion layer 40a, 40b, 40c is deposited for each colour sub-pixel. This is necessary, for example, when micro LEDs generate ultraviolet light.

However, the micro LEDs 14 may generate blue light instead of ultraviolet light. In this case, the application of the display 10 by the light curable fluid containing the blue color converter can be skipped and the process can be performed using the light curable fluids for the green and red sub-pixels. Leaving a plurality of micro-LEDs without a color conversion layer, for example, as shown in fig. 3E. The processing shown in fig. 3F is not performed. For example, the first light curable fluid 30a may include a green CCA and the first plurality of micro-LEDs 14a may correspond to green sub-pixels, and the second light curable fluid 30b may include a red CCA and the second plurality of micro-LEDs 14b may correspond to red sub-pixels.

Assuming that the fluids 30a, 30b, 30c comprise solvents, some of the solvents may be trapped in the color conversion layers 40a, 40b, 40 c. Referring to fig. 3G, the solvent can be evaporated, for example, by exposing the micro LED array to heat (e.g., by an IR lamp). Evaporation of the solvent from the color conversion layers 40a, 40b, 40c can result in shrinkage of the layers, making the final layers thinner.

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 (e.g., quantum dots), thereby providing higher color conversion efficiency. On the other hand, including a solvent may allow for greater flexibility in the chemical formulation of other components of the photocurable fluid (e.g., in the color conversion agent or crosslinkable component).

Alternatively, as shown in fig. 3H, an ultraviolet blocking layer 50 can be deposited on top of all of the micro-LEDs 14. The ultraviolet blocking layer 50 can block ultraviolet light that is not absorbed by the color conversion layer 40. The ultraviolet blocking layer 50 may be a bragg reflector or may simply be a material that selectively absorbs ultraviolet light (e.g., a benzotriazolyl hydroxyphenyl compound). The bragg reflector may reflect the ultraviolet light back to the micro-LEDs 14, thereby improving energy efficiency. Other layers (e.g., stray light absorbing layers, photoluminescent layers, and high refractive index layers) include materials that are also optionally deposited on the micro-LEDs 14.

Accordingly, as described herein, a photocurable composition includes a nanomaterial selected to emit radiation in a first wavelength band in the visible range in response to absorption of radiation in a second wavelength band in the ultraviolet or visible range, one or more (meth) acrylate monomers, and a photoinitiator that initiates polymerization of the one or more (meth) acrylate monomers in response to absorption of radiation in the second wavelength band. The second wavelength band is different from the first wavelength band.

In some embodiments, a light emitting device includes a plurality of light emitting diodes, and a cured composition in contact with a surface through which radiation in a first wavelength band in the ultraviolet or visible range is emitted from each light emitting diode. The cured composition comprises: a nanomaterial selected to emit radiation in a second wavelength band within the visible range in response to absorption of radiation in the first wavelength band from each light emitting diode; a photopolymer; and a composition (e.g., fragments) of a photoinitiator that initiates polymerization of the photopolymer in response to absorption of radiation in the first wavelength band. The second wavelength band is different from the first wavelength band.

In certain embodiments, the light-emitting device comprises an additional plurality of light-emitting diodes and an additional cured composition in contact with a surface through which radiation in the first wavelength band is emitted from each additional light-emitting diode. Additional cured compositions include: a further nanomaterial selected to emit radiation in a third wavelength band within the visible range in response to absorption of radiation in the first wavelength band from each light emitting diode; an additional photopolymer; and a composition of a further photoinitiator that initiates polymerization of the photopolymer in response to absorption of radiation in the first wavelength band. The third wavelength band may be different from the second wavelength band.

Fig. 5A to 5E illustrate a method of manufacturing a micro LED array and a partition wall on a base plate. Referring to fig. 5A, the process begins with a wafer 100 that will provide an array of micro LEDs. The wafer 100 includes a substrate 102, such as a silicon or sapphire wafer, on which substrate 102 a first semiconductor layer 104 having a first doping, an active layer 106, and a second semiconductor layer 108 having a second opposite doping are disposed. For example, the first semiconductor layer 104 may be an n-doped gallium nitride (n-GaN) layer, the active layer 106 may be a Multiple Quantum Well (MQW) layer 106, and the second semiconductor layer 107 may be a p-doped gallium nitride (p-GaN) layer 108.

Referring to fig. 5B, the wafer 100 is etched to divide the layers 104, 106, 108 into individual micro LEDs 14, including first, second, and third pluralities of micro LEDs 14a, 14B, 14c corresponding to the first, second, and third colors. In addition, conductive contacts 110 can be deposited. For example, p-contact 110a and n-contact 110b can be deposited on n-GaN layer 104 and p-GaN layer 108, respectively.

Similarly, backplane 16 is fabricated to include circuitry 18 and electrical contacts 120. The electrical contacts 120 can include a first contact 120a, such as a drive contact, and a second contact 120b, such as a ground contact.

Referring to fig. 5C, the micro LED chip 100 is aligned and placed in contact with the bottom plate 16. For example, the first contact 110a can contact the first contact 120a, and the second contact 110b can contact the second contact 120 b. The micro LED chip 100 may be lowered into contact with the backplane, or vice versa.

Next, referring to fig. 5D, the substrate 102 is removed. For example, the silicon substrate can be removed by polishing the substrate 102, such as by chemical mechanical polishing. As another example, the sapphire substrate can be removed by a laser lift-off process.

Finally, referring to fig. 5E, a partition wall 20 is formed on the bottom plate 16 (to which the micro-LEDs 14 have been attached). The partition walls may be formed by conventional processes such as deposition of photoresist, patterning of the photoresist by photolithography, and removal of portions of the photoresist corresponding to the grooves 22 by development. The resulting structure can then be used as a display 10 for the process described in fig. 3A-3H.

Fig. 6A to 6D illustrate another method of manufacturing a micro LED array and a partition wall on a base plate. This process may be similar to the process discussed above with respect to fig. 5A-5E, except as described below.

Referring to fig. 6A, the process begins similarly to the process described above, wherein the wafer 100 will provide the micro LED array and the backplane 16.

Referring to fig. 6B, a partition wall 20 is formed on the bottom plate 16 (the micro LED14 is not yet attached to the bottom plate 16).

In addition, the wafer 100 is etched to divide the layers 104, 106, 108 into individual micro-LEDs 14, including first, second, and third pluralities of micro-LEDs 14a, 14b, 14 c. 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.

Next, as shown in fig. 6C, the micro LED chip 100 is aligned and placed in contact with the bottom plate 16 (or vice versa). The partition wall 20 is fitted into the groove 130. In addition, the contacts 110 of the micro-LEDs are electrically connected to the contacts 120 of the backplane 16.

Finally, referring to fig. 6D, the substrate 102 is removed. This leaves the micro-LEDs 14 and the partition wall 20 on the bottom plate 16. The resulting structure can then be used as a display 10 for the process described with respect to fig. 3A-3H.

Terms of orientation, such as vertical and lateral, have been used. However, it should be understood that these terms refer to relative positioning, not absolute positioning with respect to gravity. For example, lateral is a direction parallel to the substrate surface, while vertical is a direction orthogonal to the substrate surface.

Those skilled in the art will appreciate that the foregoing examples are illustrative and not limiting. For example:

although the above description focuses on micro-LEDs, the techniques can be applied to other displays with other types of light emitting diodes, particularly displays with other micro-LEDs, for example, LEDs spanning less than about 10 microns.

Although the above description assumes that the order of formation of the colour conversion layer is blue, then green, then red, other orders are possible, for example blue, then red, then green. In addition, other colors are possible, such as orange and yellow.

It will be understood that various modifications may be made without departing from the spirit and scope of the disclosure.