Preparation method and application of quantum dot color conversion layer based on microfluidic and polishing technologies

Abstract

The invention discloses a quantum dot color conversion layer preparation method based on a microfluidic and polishing technology, which comprises the following steps: forming a shielding layer with a groove array on the surface of a transparent substrate, constructing different micro-channels through the microfluidic technology, introducing curable quantum dot solutions with different colors into the different micro-channels, and forming a quantum dot color conversion layer on the surface of the transparent substrate. The micro-channels and the corresponding grooves are filled with the quantum dot solution, the quantum dot solution is solidified to form quantum dot layers, the quantum dot layers outside the grooves are removed through the polishing technology, and the quantum dot array located in the groove array is obtained. The invention further discloses an application of the micro-LED full-color display device. According to the method, the multicolor quantum dot color conversion layer with enough thickness can be prepared at one time, the thickness of the quantum dots can be accurately regulated and controlled according to the thickness of the quantum dot film removed through polishing, the quantum dots do not need to be deposited many times, and the technological process is greatly simplified.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor microdisplay, and specifically relates to a method for preparing a quantum dot color conversion layer based on microfluidics and polishing technology and an application thereof. Background Art

[0002] At present, the common display technologies include liquid crystal display (LCD), organic light-emitting diode (OLED), micro-light-emitting diode (Micro-LED) display technology, etc. Compared with the former two, Micro-LED display technology has better luminous performance, such as high brightness, wide color gamut, high contrast, high resolution, fast response speed and long service life, and is called the "next generation display technology."

[0003] At present, there are two main schemes for full-color Micro-LED display: the red, green and blue RGB three-primary color scheme and the quantum dot color conversion scheme. Among them, the quantum dot color conversion scheme combines monochrome blue light or ultraviolet light Micro-LED chips with quantum dot color conversion layers. Only monochrome Micro-LED chips are needed to achieve full-color display, avoiding multiple massive transfers of Micro-LED chips. It is expected to greatly reduce the manufacturing cost of full-color chips, and has attracted widespread attention from academia and industry. At present, the preparation methods of quantum dot color conversion layers proposed by researchers mainly include inkjet printing, photolithography, transfer printing and microfluidics. Among them, the preparation technology of quantum dot color conversion layer based on microfluidics has the advantages of simple preparation process, high raw material utilization rate and high pattern accuracy, and has become one of the hot spots of researchers.

[0004] After the quantum dot solution is introduced into the microfluidic device, the excess quantum dot solution is generally blown out by gas or oil phase fluid to obtain an arrayed quantum dot pattern. However, the thickness of the quantum dots deposited in a single time is relatively thin, which causes the leakage of blue light or ultraviolet light and affects the purity of the excitation light. At the same time, the thinner color conversion layer cannot absorb more ultraviolet light or blue light, resulting in insufficient color conversion efficiency of the device. Therefore, in order to meet the requirements of high-performance color conversion layer construction, multiple deposition processes are required, which increases time and manufacturing costs. Therefore, it is urgent to develop a microfluidic solution that can quickly deposit quantum dots of sufficient thickness, reduce the leakage of background excitation light, improve color conversion efficiency, and thereby improve the display performance of quantum dot color conversion Micro-LED full-color display devices. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for preparing a quantum dot color conversion layer and a full-color Micro-LED display device based on microfluidics and polishing technology. The method has the advantages of simple preparation process, short time, low cost, controllable quantum dot thickness, high color conversion efficiency, etc., which enhances the performance of quantum dot Micro-LED full-color display devices.

[0006] In order to achieve the above purpose, the technical solution of the present invention is:

[0007] A method for preparing a quantum dot color conversion layer based on microfluidics and polishing technology, comprising the following steps:

[0008] 1) forming a shielding layer on a surface of a transparent substrate, and patterning the shielding layer to form a groove array;

[0009] 2) providing a microfluidic cover plate, wherein the microfluidic cover plate comprises a plurality of microchannels; bonding the microfluidic cover plate to one side of the shielding layer of the transparent substrate, so that each microchannel is connected to the plurality of grooves in cooperation with each other;

[0010] 3) introducing curable quantum dot solutions of different colors into different microchannels, so that the quantum dot solutions fill the microchannels and corresponding grooves;

[0011] 4) solidifying the quantum dot solution to form a quantum dot layer;

[0012] 5) Peeling off the microfluidic cover plate, removing the quantum dot layer outside the grooves by polishing technology, and obtaining a quantum dot array located within the groove array.

[0013] Optionally, the curable quantum dot solution includes quantum dots and a liquid component, and the liquid component includes an ultraviolet light-curable resin or a thermosetting resin; in step 4), curing is performed by ultraviolet light irradiation or heating.

[0014] Optionally, in the curable quantum dot solution, the content of quantum dots is 5 to 100 mg / ml.

[0015] Optionally, the quantum dots may be CdSe, CdTe, ZnSe, CuInS, PbS, InP and perovskite, etc. Ultraviolet light curing (UV) resins are mainly composed of oligomers, crosslinking agents, diluents, photosensitizers and other specific additives, such as various acrylic resins, acrylic esterified acrylic resins, polyurethane acrylic resins, etc. Thermosetting resins include polyacrylamide, silicone resins, epoxy resins, isocyanates and polyurethanes, etc.

[0016] Optionally, the microchannel is a strip groove structure, and each strip groove structure has a liquid inlet and a liquid outlet at both ends; a plurality of the microchannels are arranged in parallel and spaced apart on the microfluidic cover plate, and each microchannel corresponds to a row of the grooves.

[0017] Optionally, in step 3), the red quantum dot solution, the green quantum dot solution and the blue quantum dot solution are introduced alternately according to the arrangement order of the microchannels, and are solidified simultaneously in step 4).

[0018] Optionally, the shielding layer is black photoresist, and the groove array is obtained by exposure and development, and the bottom of each groove exposes the surface of the transparent substrate.

[0019] Optionally, in step 1), black photoresist is coated on the surface of the transparent substrate, pre-baked at 100-120°C for 1-3 min, selectively exposed under ultraviolet light for 40-80 s using a patterned photomask, post-baked at 100-120°C for 1-3 min, and after development, flood exposed for 40-80 s, and hardened at 100-120°C for 50-70 min.

[0020] Optionally, the depth of the groove is 1 to 10 μm, and the depth of the strip groove is 20 to 60 μm.

[0021] Optionally, the polishing technology is chemical mechanical polishing, where a softer chemical reaction layer is formed on the surface of the material by a polishing liquid, and under the action of mechanical force, the surface is physically polished by abrasives (such as SiO2, ZrO2 nanoparticles, etc.) in the polishing liquid to remove the chemical reaction layer, thereby achieving the effect of surface flattening.

[0022] A method for preparing a Micro-LED full-color display device, comprising: preparing a quantum dot color conversion layer using the above-mentioned quantum dot color conversion layer preparation method based on microfluidics and polishing technology; bonding one side of a transparent substrate of the quantum dot color conversion layer to a Micro-LED chip, and bonding the other side to a packaging cover plate.

[0023] The beneficial effects of the present invention are:

[0024] (1) Compared with other color conversion layer patterning design schemes based on microfluidic technology, the gas or oil phase blowing process is eliminated, and the preparation process is simple.

[0025] (2) After the curable quantum dots are polished, a multi-color quantum dot color conversion layer of sufficient thickness can be prepared at one time. The thickness of the quantum dots can be precisely controlled by the thickness of the quantum dot film removed by polishing. There is no need to deposit quantum dots multiple times, which greatly simplifies the process flow and saves time and manufacturing costs.

[0026] (3) Quantum dots of sufficient thickness can effectively improve the absorption of blue light or ultraviolet light sources and enhance color conversion efficiency; at the same time, they can reduce the leakage of background light, increase color purity, and enhance the display performance of quantum dot color conversion Micro-LED devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of forming a groove array on a transparent substrate according to an embodiment, wherein (a) is a top view and (b) is a side view;

[0028] Figure 2 is a top view schematic diagram of bonding a patterned transparent substrate and a microfluidic cover plate of an embodiment;

[0029] Figure 3 Schematic diagram of introducing a curable quantum dot solution according to an embodiment, wherein (a) is a top view and (b) is a side view;

[0030] Figure 4 Schematic diagram of the solidification of the quantum dot solution of the embodiment, wherein (a) is a top view and (b) is a side view;

[0031] Figure 5 Schematic diagram of a peeled microfluidic cover plate of an embodiment, wherein (a) is a top view and (b) is a side view;

[0032] Figure 6 Schematic diagram of polishing a quantum dot layer in an embodiment, wherein (a) is a top view and (b) is a side view; a quantum dot color conversion layer is obtained after polishing;

[0033] Figure 7 Schematic diagram of a Micro-LED full-color display device obtained by bonding the quantum dot color conversion layer of the embodiment to the Micro-LED chip. DETAILED DESCRIPTION

[0034] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. The various drawings of the present invention are only for illustration to make it easier to understand the present invention, and the specific proportions can be adjusted according to design requirements. The upper and lower relationships of the relative elements and the definitions of the front / back in the figures described in the text should be understood by those skilled in the art to refer to the relative positions of the components, so they can all be flipped to present the same components, which should all fall within the scope disclosed in this specification.

[0035] 1. Preparation of morphological patterned microarray structure. In this embodiment, a glass substrate with a thickness of 1 mm is selected as the transparent substrate 1, and a black photoresist is spin-coated at 500 rpm for 40 seconds as the shielding layer 2. After pre-baking at 110°C for 2 minutes, selective exposure is performed using a photomask to achieve patterning, exposure is performed under 365nm ultraviolet light for 60 seconds, and post-baking is performed at 110°C for 2 minutes. Development is performed in a KOH solution with a mass fraction of 0.42% for 10 to 15 seconds, and then flood exposure is performed for 60 seconds. After hardening at 110°C for 1 hour, a groove array is formed in the shielding layer 2, which includes a plurality of grooves 2a arranged in an array, and the bottom of the grooves 2a exposes the transparent substrate 1, that is, the depth of the grooves 2a is the same as the thickness of the shielding layer 2, which is 3μm. Figure 1 The groove 2a is, for example, a square groove with a side length of 10 μm.

[0036] 2. Bonding of patterned transparent substrate and microfluidic cover plate. In this embodiment, polydimethylsiloxane (PDMS) is used to prepare the microfluidic cover plate 3. The microfluidic cover plate 3 includes a plurality of microchannels 3a. The microchannels are strip-shaped groove structures. Each strip-shaped groove structure has a liquid inlet and a liquid outlet at both ends. The plurality of microchannels 3a are arranged in parallel and spaced apart on the microfluidic cover plate 3. The microfluidic cover plate 3 is bonded to one side of the shielding layer 2 of the transparent substrate 1, so that each microchannel 3a corresponds to a row of grooves 2a and is connected. Figure 2 shown.

[0037] 3. Pass the curable quantum dot solution. Use the syringe pump to simultaneously pass the photocurable red CdSe / ZnS, green CdSe / ZnS, and blue CdZnS / ZnS quantum dot solutions into the constructed microchannel 3a. Specifically, according to the arrangement order of the microchannel 3a, alternately pass the red quantum dot solution, the green quantum dot solution, and the blue quantum dot solution to fill the microchannel and the corresponding grooves. The top view of the quantum dot solution is shown in FIG. Figure 3 (a) shows the side view. Figure 3 (b) shows that the red quantum dots R, green quantum dots G, and blue quantum dots B, the microchannels that pass through the same color quantum dot solution can be controlled by the same injection pump, achieving multi-color and multi-channel simultaneous injection, which is convenient for large-scale and efficient preparation. In this embodiment, the photocurable quantum dot solution includes red CdSe / ZnS, green CdSe / ZnS, blue CdZnS / ZnS quantum dots, cyclohexyl methacrylate (CHMA), 2-isopropylthioxanthone (ITX), and pentaerythritol triacrylate (PETA).

[0038] 4. Curing of quantum dot solution. UV curing is performed for 60 seconds under UV ultraviolet irradiation (preferably on the transparent side of the microfluidic cover plate). The acrylic monomer (CHMA), photoinitiator (ITX) and crosslinking agent (PETA) work together to quickly form a cured polymer material through free radical polymerization reaction, so that the quantum dot solution is cured. The top view schematic diagram is as follows Figure 4 (a) shows the side view. Figure 4 As shown in (b), the simultaneous solidification of R\G\B quantum dots can be achieved.

[0039] 5. Peel off the microfluidic cover plate 3. After the quantum dot solution is completely solidified, peel off the microfluidic cover plate 3 to obtain a continuous red, green and blue quantum dot layer R / G / B consistent with the microchannel pattern. The top view schematic diagram is as follows: Figure 5 (a) shows the side view. Figure 5 (b) as shown.

[0040] 6. Polishing the surface of the quantum dot layer. Use a chemical mechanical polisher to polish the surface of the continuous quantum dot layer prepared above, thinning the thickness of the quantum dots to expose the microarray structure, that is, exposing the surface of the shielding layer 2, and obtaining an independently dispersed quantum dot array of red, green and blue colors with a thickness consistent with the depth of the groove 2a, and obtaining an RGB quantum dot color conversion layer, the top view of which is shown in FIG. Figure 6 (a) shows the side view. Figure 6 (b) as shown.

[0041] 7. Bonding with UV Micro-LED chip. One side of the transparent substrate 1 of the prepared quantum dot color conversion layer is bonded with the corresponding UV Micro-LED chip 4, and the other side is bonded with the packaging cover plate 5 to obtain a quantum dot color conversion Micro-LED full-color display device, such as Figure 7 As shown. The ultraviolet light Micro-LED chip 4 includes a plurality of Micro-LED units 4a, and a Micro-LED driving substrate located thereunder, including conventional structures such as a driving circuit, a P-type substrate, an N-type electrode, a buffer insulating layer, a multi-quantum well, and a metal electrode. The array of Micro-LED units 4a corresponds one-to-one to the RGB quantum dot array, and the bottom ultraviolet light excites the quantum dots to realize full-color photoluminescence display.

[0042] In addition, in other embodiments, when the curable quantum dot solution adopts a thermosetting resin, curing is performed by heating to achieve a similar technical effect.

[0043] In addition, in other embodiments, a similar method for preparing a quantum dot color conversion layer can be used to form an R / G quantum dot array and blank B pixel points, and photoluminescent full-color display can be achieved through excitation of a blue light Micro-LED chip.

[0044] The above embodiments are only used to further illustrate a method and application of preparing a quantum dot color conversion layer based on microfluidics and polishing technology of the present invention, but the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a quantum dot color conversion layer based on microfluidics and polishing technology, characterized in that: The following steps are involved: 1) forming a shielding layer on a surface of a transparent substrate, and patterning the shielding layer to form a groove array; 2) providing a microfluidic cover plate, wherein the microfluidic cover plate comprises a plurality of microchannels; bonding the microfluidic cover plate to one side of the shielding layer of the transparent substrate, so that each microchannel is connected to the plurality of grooves in cooperation with each other; 3) introducing curable quantum dot solutions of different colors into different microchannels, so that the quantum dot solutions fill the microchannels and corresponding grooves; 4) solidifying the quantum dot solution to form a quantum dot layer; 5) Peeling off the microfluidic cover plate, removing the quantum dot layer outside the grooves by polishing technology, and obtaining a quantum dot array located within the groove array.

2. The method for preparing a quantum dot color conversion layer based on microfluidics and polishing technology according to claim 1, characterized in that: The curable quantum dot solution includes quantum dots and a liquid component, wherein the liquid component includes an ultraviolet light curable resin or a thermosetting resin; in step 4), curing is performed by ultraviolet light irradiation or heating.

3. The method for preparing a quantum dot color conversion layer based on microfluidics and polishing technology according to claim 1, characterized in that: In the curable quantum dot solution, the content of quantum dots is 5 to 100 mg / mL.

4. The method for preparing a quantum dot color conversion layer based on microfluidics and polishing technology according to claim 1, characterized in that: The microchannel is a strip groove structure, and each strip groove structure has a liquid inlet and a liquid outlet at both ends; a plurality of the microchannels are arranged in parallel and spaced apart on the microfluidic cover plate, and each microchannel corresponds to a row of the grooves.

5. The method for preparing a quantum dot color conversion layer based on microfluidics and polishing technology according to claim 4, characterized in that: In step 3), the red quantum dot solution, the green quantum dot solution and the blue quantum dot solution are introduced alternately according to the arrangement order of the microchannels, and are solidified simultaneously in step 4).

6. The method for preparing a quantum dot color conversion layer based on microfluidics and polishing technology according to claim 1, characterized in that: The shielding layer is black photoresist, and the groove array is obtained by exposure and development, and the bottom of each groove exposes the surface of the transparent substrate.

7. The method for preparing a quantum dot color conversion layer based on microfluidics and polishing technology according to claim 6, characterized in that: In step 1), a black photoresist is coated on the surface of the transparent substrate, pre-baked at 100-120° C. for 1-3 min, selectively exposed under ultraviolet light for 40-200 s using a patterned photomask, post-baked at 100-120° C. for 1-5 min, and after development, flood exposed for 40-200 s, and hardened at 100-120° C. for 50-70 min.

8. The method for preparing a quantum dot color conversion layer based on microfluidics and polishing technology according to claim 1, characterized in that: The depth of the groove is 1-10 μm, and the depth of the strip groove is 20-60 μm.

9. The method for preparing a quantum dot color conversion layer based on microfluidics and polishing technology according to claim 1, characterized in that: The polishing technology adopts chemical mechanical polishing, using a polishing liquid to form a chemical reaction layer on the surface of the quantum dot layer, and under the action of mechanical force, the surface is physically ground by the abrasive in the polishing liquid to remove the chemical reaction layer.

10. A method for preparing a Micro-LED full-color display device, characterized in that: include: The quantum dot color conversion layer is prepared by the method for preparing a quantum dot color conversion layer based on microfluidics and polishing technology as described in any one of claims 1 to 9; One side of the transparent substrate of the quantum dot color conversion layer is bonded to the Micro-LED chip, and the other side is bonded to the packaging cover.

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