Quantum dot photocurable adhesive and method for preparing same, and display device

Abstract

The present application provides a quantum dot photocurable adhesive, a preparation method thereof, and a display device. The quantum dot photocurable adhesive includes a mixed solution and a photocurable adhesive solution, the mixed solution including quantum dots, a light diffusing agent, a functional polymer, and a photocurable adhesive solvent, and the functional polymer is coated on the quantum dots in the mixed solution. The present application can solve the problem of poor performance or structural defects of quantum dots caused by ligand exchange in the conventional liquid phase in the prior art.

Description

[Technical Field]

[0001] This application claims priority based on a Chinese patent application filed on November 29, 2021, bearing application number 202111429693.2 and titled "Quantum dot photocurable adhesive and preparation method thereof, display device." The present application relates to the quantum dot technical field, and in particular to a quantum dot photocurable adhesive and a preparation method thereof, and a display device that uses the quantum dot photocurable adhesive to achieve light color conversion. [Background technology]

[0002] Currently, quantum dots are important low-dimensional semiconductor materials, with all three dimensions less than twice the exciton Bohr radius of the corresponding semiconductor material. Quantum dots also have unique luminescence effects, making them highly applicable in the display industry. Research on quantum dots has made great strides over the past few decades, so analyzing, researching, and optimizing the performance of quantum dot devices is crucial to accelerating their commercialization.

[0003] Conventional quantum dot adhesives are prepared by purifying oil-based quantum dots in an inert olefin atmosphere (e.g., 1-octadecene, liquid paraffin, tetradecene, etc.), then surface-modifying and ligand-exchanging them to dissolve them in PGMEA (propylene glycol methyl ether acetate). The resulting solution is then mixed with a photocurable adhesive (UV adhesive) and a light-diffusing agent to prepare the quantum dot adhesive. QDs synthesized from this oil-based (or oil-based) system have relatively good optical performance and stability. However, dissolving the quantum dots in a PGMEA base, i.e., mixing them with a photoresist (photocurable adhesive), requires the replacement or substitution of the conventional or original ligands, such as MSA (mercaptosuccinic acid) or dihydrolipoic acid. However, conventional ligand exchange significantly destroys the existing ligands on the quantum dots, increasing dangling bonds and defects on the quantum dot surface and degrading their performance. Summary of the Invention [Problem to be solved by the invention]

[0004] In response to the above technical problems, the present application provides a quantum dot photocurable adhesive, a preparation method thereof, and a display device, in order to solve the problem of poor performance or structural defects of quantum dots caused by conventional ligand exchange in the liquid phase in the prior art. [Means for solving the problem]

[0005] To achieve the above object, the present application provides a quantum dot photo-curable adhesive, which includes a mixed solution and a photo-curable adhesive solution, the mixed solution including quantum dots, a light diffusing agent, a functional polymer, and a photo-curable adhesive solvent, and the functional polymer is coated on the outside of the quantum dots in the mixed solution.

[0006] The quantum dots, the light diffusing agent, the functional polymer, and the photocurable adhesive solvent are preferably mixed by ball milling or sand milling.

[0007] The quantum dots are preferably selected from one or a mixture of several of CdSe, CdS, ZnS, CdZnSe, CdZnS, CdZnSeS, ZnSeS, ZnSe, CuInS, CuInSe, InP, and InZnP.

[0008] It is preferable that both the quantum dots and the light diffusing agent are solids.

[0009] The functional polymer is preferably soluble in a propylene glycol methyl ether acetate solvent.

[0010] Preferably, the functional polymer comprises a mixture of one or more of mercaptopropionic acid, styrene maleic anhydride copolymer, phosphate monoesters, phosphate diesters, phosphate triesters, glyceryl phosphate, triethyl phosphate, mercaptosuccinate-acrylate isobornyl, triethyl phosphite, isooctyl phosphate, and triethyl 2-phosphonopropionate.

[0011] In the quantum dot photocurable adhesive, the mass content of the quantum dots is preferably less than 60%.

[0012] The mass content of the quantum dots is preferably 10% to 40%.

[0013] In the quantum dot photocurable adhesive, the mass content of the light diffusing agent is preferably less than 50% and does not exceed the mass content of the quantum dots.

[0014] The mass content of the light diffusing agent is preferably 5% to 30%.

[0015] The photocurable adhesive solution preferably contains a pressure-sensitive adhesive, a photosensitive agent, a functional monomer, a solvent, and an auxiliary.

[0016] The mass content ratio of the light diffusing agent to the quantum dots is preferably 1:100 to 1:1.

[0017] The present application further provides a method for preparing a quantum dot photocurable adhesive, the method comprising: Step S1: mixing quantum dots, a light diffusing agent, a functional polymer, and a photocurable adhesive solvent to prepare a first mixed solution; Step S2 of performing ball milling or sand milling on the first mixed solution under a light-shielded condition to obtain a second mixed solution, in which the quantum dots are coated with the functional polymer outside in the second mixed solution; and step S3 of mixing the second mixed solution with the photo-curable adhesive solution to obtain a quantum dot photo-curable adhesive.

[0018] It is preferable that both the quantum dots and the light diffusing agent are solids.

[0019] In the quantum dot photocurable adhesive, the mass content of the quantum dots is preferably less than 60%.

[0020] In the quantum dot photocurable adhesive, the mass content of the light diffusing agent is preferably less than 50% and does not exceed the mass content of the quantum dots.

[0021] The photocurable adhesive solution preferably contains a pressure-sensitive adhesive, a photosensitive agent, a functional monomer, a solvent, and an auxiliary.

[0022] In step S2, the rotation speed of the ball milling is preferably 500 to 1500 rpm, and the ball milling time is preferably 10 minutes to 5 hours.

[0023] The method for preparing the quantum dots preferably includes: mixing a polar solvent and a non-polar solvent in a predetermined ratio with a quantum dot solution to obtain a turbid quantum dot solution; centrifuging the turbid quantum dot solution and removing the supernatant to obtain a quantum dot solid precipitate; and freeze-drying the obtained quantum dot solid precipitate to remove a low-boiling point reagent remaining on the surface to obtain dry powdered quantum dots.

[0024] The present application further provides a display device, which includes a display substrate and a quantum dot photo-curable adhesive layer provided on the display substrate, wherein the quantum dot photo-curable adhesive layer includes the quantum dot photo-curable adhesive described above. [Effects of the Invention]

[0025] Compared with conventional techniques, the present invention's method for preparing quantum dot photocurable adhesives does not involve the conventional liquid-phase ligand exchange process. Instead, solid quantum dots are mixed with a light diffusing agent, a functional polymer (e.g., a phosphate ester-based polymer), and a photocurable adhesive solvent. The functional polymer coats the surface of the quantum dots, completely covering the entire quantum dots. This ensures good solubility of the quantum dots in the PGMEA solvent, ensuring their inherent optical performance while reducing damage to the quantum dots. Furthermore, the mixed solution is processed by ball milling, ensuring uniform dispersion of the quantum dots in the PGMEA solvent. This method not only solves the problems of dispersion of light diffusing agents such as titanium dioxide in photocurable adhesives, dispersion of quantum dots in photocurable adhesive solvents, and the reduced photoluminescence quantum yield (PLQY) of quantum dots in photoresist-based (photocurable adhesive-based) materials, but also offers a more convenient and rapid process, making it suitable for large-scale production. Furthermore, the solid-liquid reaction process of ball milling overcomes the limitations of liquid-phase reactions. Finally, the prepared quantum dot photocurable adhesive can be formed into a uniform film without graininess, and has high absorption efficiency and conversion efficiency after curing. [Brief explanation of the drawings]

[0026] In order to more clearly describe the technical solutions of the specific embodiments of the present application or the related art, the following briefly introduces drawings that need to be used in the description of the specific embodiments or the prior art. Needless to say, the drawings in the following description are some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work. [Figure 1] 1 is a process flow chart of a method for preparing a quantum dot photocurable adhesive according to an embodiment of the present application. [Figure 2] (A) is a schematic diagram showing the state of the toluene-based quantum dots (bottle on the left) and the prepared quantum dot curing adhesive (bottle on the right) according to Example 1 of the present application, and (B) is a schematic diagram after the quantum dot curing adhesive according to Example 1 of the present application has been spin-coated to form an optical film. [Figure 3] 1A is a schematic diagram of an optical film formed by spin-coating a quantum dot curing adhesive according to Example 2 of the present application, and FIG. 1B is a diagram of the effect of using the quantum dot curing adhesive according to Example 2 of the present application in a micro-LED component. [Figure 4] (A) is a schematic diagram showing the state of toluene-based quantum dots (bottle on the left) and the prepared quantum dot adhesive liquid (bottle on the right) according to Comparative Example 1. (B) is a schematic diagram after spin-coating the quantum dot adhesive liquid according to Comparative Example 1 to form an optical film. (C) is a scanning electron microscope image of the quantum dot adhesive liquid according to Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0027] The following detailed description will be given in conjunction with examples to provide a better understanding of the purpose, structure, configuration and function of the present application.

[0028] In addition, in the description of this application, orientations or positional relationships indicated by terms such as "center," "up," "down," "left," "right," "vertical," "horizontal," "inside," and "outside" are based on the orientations or positional relationships shown in the drawings, and are merely for the purpose of conveniently and simply describing this application. They do not indicate or imply that such devices or elements must have a specific orientation or be configured and operated in a specific orientation, and therefore should not be understood as limitations on this application.

[0029] As shown in Figure 1, Figure 1 is a process flow chart of a method for preparing a quantum dot photo-curable adhesive according to an embodiment of the present application. The present application provides a method for preparing a quantum dot photo-curable adhesive, which includes the following steps:

[0030] In step S1, quantum dots, a light diffusing agent, a functional polymer, and a photo-curable adhesive solvent are mixed to form a first mixed solution.

[0031] In step S2, the first mixed solution is subjected to ball milling or sand milling under a light-shielded condition to obtain a second mixed solution. In the second mixed solution, the quantum dots are coated with the functional polymer on their outer surfaces. The ball milling is performed at a rotation speed of 500 to 1500 r / min for a ball milling time of 10 min to 5 h. That is, the outer surfaces of each quantum dot are coated with the functional polymer. The functional polymer is soluble in a propylene glycol methyl ether acetate (PGMEA) solvent.

[0032] In step S3, the second mixed solution is mixed with a photo-curable adhesive solution to obtain a quantum dot photo-curable adhesive, which may be, for example, an ultraviolet-curable adhesive solution.

[0033] Furthermore, it is preferable that both the quantum dots and the light diffusing agent are solid, specifically, for example, in the form of dry powder, thereby realizing a solid-liquid phase reaction and overcoming the limitations of a liquid phase reaction.

[0034] In addition, the method for preparing the quantum dots includes the following steps:

[0035] In step S11, a polar solvent and a non-polar solvent are mixed with the quantum dot solution in a predetermined ratio to obtain a turbid quantum dot solution, and the quantum dot solution is centrifuged to remove the supernatant liquid to obtain a quantum dot solid precipitate.

[0036] In step S12, the obtained quantum dot solid precipitate is freeze-dried to remove the low-boiling point reagent remaining on the surface, thereby obtaining quantum dots in a dry powder form.

[0037] Here, the ratio of the polar solvent to the non-polar solvent can be set according to actual requirements, for example, 2:1, but the present application is not limited thereto.

[0038] In one preferred embodiment, the functional polymer includes a mixture of one or more of, for example, mercaptopropionic acid, styrene-maleic anhydride copolymer, phosphoric acid monoester, phosphoric acid diester, phosphoric acid triester, glyceryl phosphate, triethyl phosphate, mercaptosuccinic acid-isobornyl acrylate, triethyl phosphite, isooctyl phosphate, and triethyl 2-phosphonopropionate. By coating the entire quantum dots with the functional polymer, the quantum dots have good solubility in PGMEA, ensuring the inherent optical performance of the quantum dots while reducing damage to the quantum dots.

[0039] Furthermore, using ball milling or sand milling in step S2 ensures that the quantum dots are uniformly dispersed in the PGMEA solvent. This is because, in general, adding a light-diffusing agent to the photocurable adhesive or PGMEA solvent causes secondary aggregation throughout the system, resulting in significant graininess in the final optical film spin-coated with the quantum dot adhesive. However, during the solid-liquid reaction, solid quantum dots are mixed with a functional polymer (e.g., a phosphate ester-based material), a light-diffusing agent (e.g., titanium dioxide, aluminum oxide, or diamonds), and a photocurable adhesive solvent, followed by ball milling or sand milling. The ball milling or sand milling process ensures that these materials are mixed and uniformly dispersed. This allows for uniform film formation during spin-coating of the prepared quantum dot adhesive, resulting in excellent luminescence performance and a quantum dot yield of 100%.

[0040] The mass ratio of the light diffusing agent to the quantum dots is, for example, 1:100 to 1:1. In the quantum dot photocurable adhesive, the mass content of the light diffusing agent is less than 50%, and the mass content of the diffusing agent does not exceed the mass content of the quantum dots. The mass content of the light diffusing agent is more preferably 5% to 30%. Adding an appropriate amount of light diffusing agent to the quantum dots refracts incident light toward nearby quantum dots, increasing the amount of light irradiated onto the quantum dots. This increases the light utilization rate of the spin-coated quantum dot photocurable adhesive layer, improves the exposure properties of the quantum dot photocurable adhesive, and prevents incomplete exposure and residual quantum dot adhesive from occurring when the quantum dot photocurable adhesive is exposed to light. The light diffusing agent includes organic light diffusing materials and inorganic light diffusing materials. The organic light diffusing material can refract and transmit light to change the propagation direction of the light. Organic light diffusing materials mainly include acrylic and styrene resins, while inorganic light diffusing materials can refract light and change its propagation direction. Inorganic light diffusing materials mainly include inorganic nanoparticles such as nanobarium sulfate, nanocalcium carbonate, nanosilica, and nanotitanium dioxide. Specifically, in this embodiment, the light diffusing agent may be, for example, titanium dioxide (TiO2) inorganic nanoparticles.

[0041] The mass content of the light diffusing agent in quantum dot photo-curable adhesives containing quantum dots of different colors differs for the following reasons: Because red quantum dots have a high conversion rate to blue light, the mass content of the light diffusing agent in quantum dot photo-curable adhesives containing red quantum dots may be low; because green quantum dots have a low conversion rate to blue light, the mass content of the light diffusing agent in quantum dot photo-curable adhesives containing green quantum dots may be high.

[0042] In one preferred embodiment, the quantum dots may be selected from a mixture of one or more of cadmium selenide (CdSe), cadmium sulfide (CdS), zinc sulfide (ZnS), CdZnSe, CdZnS, CdZnSeS, ZnSeS, zinc selenide (ZnSe), CuInS, CuInSe, indium phosphide (InP), and InZnP. The quantum dots may be a uniformly mixed type, a gradiently mixed type, or a core-shell type, i.e., the quantum dots may be uniformly mixed quantum dots, quantum dots mixed with a concentration gradient, or quantum dots with a core-shell structure.

[0043] In addition, in the quantum dot photocurable adhesive, the mass content of the quantum dots is preferably less than 60%. The mass content of the quantum dots is preferably 10% to 40%, which improves film-forming properties of the quantum dot photocurable adhesive and provides superior optical performance.

[0044] In one preferred embodiment, the ligands on the surface of the quantum dots are one or more of ethylxanthogenate, 1-octanoic acid, 1-nonanoic acid, 1-decanoic acid, undecylic acid, dodecylic acid, tridecylic acid, tetradecanoic acid, octadecanoic acid, 1-decanethiol, 1-undecanethiol, 1-dodecanethiol, 1-tetradecanethiol, hexadecylamine, octadecylamine, trioctylamine, octylmercaptan, and dodecylmercaptan. The role of the ligands on the surface of the quantum dots is to increase the hydrophobicity of the quantum dot surface and to reduce the mutual aggregation of quantum dots in a solvent.

[0045] The photocurable adhesive solution includes a pressure-sensitive adhesive, a photosensitive agent, a functional monomer, a solvent, and an auxiliary agent. The solvent in the photocurable adhesive solution is a solvent capable of dissolving the photocurable adhesive, and may be the same as or different from the photocurable adhesive solvent used in step S1.

[0046] In one preferred embodiment, the adhesive is an epoxy resin or an acrylic resin. The epoxy resin may be a monomer or any type of epoxy resin, or any combination thereof. For example, it may be at least one of low-viscosity glycidyl ether epoxy resin, bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, or novolac epoxy resin. The acrylic resin may include, for example, one or a mixture of two or more of isobutyl acrylate, isobornyl methacrylate, or isodecyl acrylate.

[0047] In one preferred embodiment, the auxiliary agent includes one or more of adhesion promoter, coupling agent, dispersant, diluent, or antifoaming agent, and the amount of the auxiliary agent can be increased according to the actual situation during production to improve the stability of the finished product.

[0048] In one preferred embodiment, the functional monomer is an acrylic monomer.

[0049] For example, the adhesive may be an acrylic resin, the functional monomer may be an acrylic monomer, the photosensitizer may be a benzophenone-based photosensitizer, the photocurable adhesive solvent may be a propylene glycol methyl ether acetate (PGMEA) solvent, and the auxiliary may be a diluent that can reduce the viscosity of the solution.

[0050] The present application also provides a quantum dot photocurable adhesive, which includes a mixed solution and a photocurable adhesive solution, the mixed solution including quantum dots, a light diffusing agent, a functional polymer, and a photocurable adhesive solvent, the functional polymer coating the quantum dots in the mixed solution. The quantum dots, the light diffusing agent, the functional polymer, and the photocurable adhesive are mixed by ball milling or sand milling. The photocurable adhesive solution is, for example, a UV-curable adhesive solution.

[0051] The quantum dot photocurable adhesive is preferably prepared by the above-described method for preparing a quantum dot photocurable adhesive. Specifically, quantum dots, a light diffusing agent, a functional polymer, and a photocurable adhesive solvent are first mixed together. The mixed solution is then subjected to ball milling or sand grinding under light-shielded conditions to obtain the mixed solution. Finally, the mixed solution is mixed with a photocurable adhesive solution to obtain the quantum dot photocurable adhesive.

[0052] In one preferred embodiment, the functional polymer is soluble in propylene glycol methyl ether acetate (PGMEA), and more preferably includes a mixture of one or more of, for example, mercaptopropionic acid, styrene-maleic anhydride copolymer, phosphoric acid monoester, phosphoric acid diester, phosphoric acid triester, glyceryl phosphate, triethyl phosphate, mercaptosuccinic acid, isobornyl acrylate, triethyl phosphite, isooctyl phosphate, and triethyl 2-phosphonopropionate. In the present application, by coating the entire quantum dots with the functional polymer, the quantum dots have good solubility in PGMEA, ensuring the inherent optical performance of the quantum dots while reducing damage to the quantum dots.

[0053] Furthermore, it is preferable that both the quantum dots and the light diffusing agent are solid, specifically, for example, in the form of dry powder, thereby realizing a solid-liquid phase reaction and overcoming the limitations of a liquid phase reaction.

[0054] Furthermore, the mass content ratio of the light diffusing agent to the quantum dots is, for example, 1:100 to 1:1. In the quantum dot photo-curable adhesive, the mass content of the light diffusing agent is less than 50% and does not exceed the mass content of the quantum dots. The mass content of the light diffusing agent is more preferably 5% to 30%.

[0055] In one preferred embodiment, the quantum dots may be selected from a mixture of one or more of cadmium selenide (CdSe), cadmium sulfide (CdS), zinc sulfide (ZnS), CdZnSe, CdZnS, CdZnSeS, ZnSeS, zinc selenide (ZnSe), CuInS, CuInSe, indium phosphide (InP), and InZnP. The quantum dots may be a uniformly mixed type, a gradiently mixed type, or a core-shell type, i.e., the quantum dots may be uniformly mixed quantum dots, quantum dots mixed with a concentration gradient, or quantum dots with a core-shell structure.

[0056] In addition, in the quantum dot photocurable adhesive, the mass content of the quantum dots is preferably less than 60%, and more preferably 10% to 40%, which improves film-forming properties and optical performance of the quantum dot photocurable adhesive.

[0057] In one preferred embodiment, the ligands on the surface of the quantum dots are one or more of ethylxanthogenate, 1-octanoic acid, 1-nonanoic acid, 1-decanoic acid, undecylic acid, dodecylic acid, tridecylic acid, tetradecanoic acid, octadecanoic acid, 1-decanethiol, 1-undecanethiol, 1-dodecanethiol, 1-tetradecanethiol, hexadecylamine, octadecylamine, trioctylamine, octylmercaptan, and dodecylmercaptan. The role of the ligands on the surface of the quantum dots is to increase the hydrophobicity of the quantum dot surface and to reduce the mutual aggregation of quantum dots in a solvent.

[0058] The photocurable adhesive solution includes a pressure-sensitive adhesive, a photosensitive agent, a functional monomer, a solvent, and an auxiliary agent. The solvent in the photocurable adhesive solution is a solvent capable of dissolving the photocurable adhesive, and may be the same as or different from the photocurable adhesive solvent used in step S1.

[0059] In one preferred embodiment, the adhesive is an epoxy resin or an acrylic resin. The epoxy resin may be a monomer or any type of epoxy resin, or any combination thereof. For example, it may be a mixture of one or more of low-viscosity glycidyl ether epoxy resin, bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, or novolac epoxy resin. The acrylic resin may include, for example, one or a mixture of two or more of isobutyl acrylate, isobornyl methacrylate, or isodecyl acrylate.

[0060] In one preferred embodiment, the auxiliary agent includes one or more of adhesion promoter, coupling agent, dispersant, diluent, or antifoaming agent, and the amount of the auxiliary agent can be increased according to the actual situation during production to improve the stability of the finished product.

[0061] In one preferred embodiment, the functional monomer is an acrylic monomer.

[0062] For example, the adhesive may be an acrylic resin, the functional monomer may be an acrylic monomer, the photosensitizer may be a benzophenone-based photosensitizer, the photocurable adhesive solvent may be a propylene glycol methyl ether acetate (PGMEA) solvent, and the auxiliary may be a diluent that can reduce the viscosity of the solution.

[0063] The present application also provides a display device, which includes a display substrate and a quantum dot photo-curable adhesive layer provided on the display substrate, the quantum dot photo-curable adhesive layer including the quantum dot photo-curable adhesive described above. By providing the quantum dot photo-curable adhesive layer on the display substrate, light color conversion is realized.

[0064] In one embodiment of the present application, a quantum dot photoresist layer (or photocurable adhesive layer) is provided on a display substrate, and the quantum dot photocurable adhesive layer is formed by spin-coating the quantum dot photocurable adhesive. Specifically, when forming the quantum dot photocurable adhesive layer, a quantum dot photocurable adhesive layer containing red quantum dots is formed in the red pixel dot region, a quantum dot photocurable adhesive layer containing green quantum dots is formed in the green pixel dot region, and no quantum dot photocurable adhesive layer is formed in the blue pixel dot region.

[0065] In addition, the specific process of forming a quantum dot photo-curable adhesive layer containing green quantum dots in the green pixel dot region can refer to the specific process of forming a quantum dot photo-curable adhesive layer containing red quantum dots in the red pixel dot region, and the examples of the present application will not be described in detail here.

[0066] The display device may be a display device using technologies such as LCD, OLED, QLED, mini LED, micro LED, etc. The display device can be applied to any product or component having a display function, such as a monitor, laptop computer, tablet computer, electronic paper, mobile phone, television, VR display, digital photo frame, navigator, AR display, or in-vehicle display.

[0067] The present application will now be further described with reference to specific examples.

[0068] [Example 1] First, acetone (acetone:toluene = 2:1) was added to 1 g of toluene-based green Cd-based quantum dots. The resulting product was centrifuged and the supernatant removed to obtain a solid quantum dot precipitate. The solid quantum dot precipitate was then vacuum freeze-dried to remove any low-boiling point reagents remaining on the surface, yielding a quantum dot powder. Next, the quantum dot powder was added to 0.3 g of triethyl phosphite, 0.1 g of titanium dioxide, and 7 ml of PGMEA solvent, mixed, and ball milled at a ball milling speed of 1000 r / min for 3 hours. After completion, the resulting mixture was mixed with 2 ml of UV adhesive (ultraviolet light-curing adhesive) to obtain quantum dot photocuring adhesive No. 1.

[0069] [Example 2] First, 1 g of toluene-based red Cd-based quantum dots was mixed with acetone (acetone:toluene = 2:1), and the supernatant was removed to obtain a solid quantum dot precipitate. The solid quantum dot precipitate was then freeze-dried to remove any low-boiling reagents remaining on the surface, yielding a quantum dot powder. Next, the quantum dot powder was mixed with 0.4 g of isooctyl phosphate, 0.15 g of titanium dioxide, and 4 ml of PGMEA solvent, and ball milled at a rotation speed of 1000 r / min for 3 hours. After milling, the resulting mixture was mixed with 1 ml of UV adhesive to obtain quantum dot photocurable adhesive No. 2.

[0070] [Example 3] First, 1.4 g of toluene-based green Cd-based quantum dots and 0.2 g of red Cd-based quantum dots were mixed with acetone (acetone:toluene = 2:1), and the supernatant was removed to obtain a solid precipitate of quantum dots. The solid precipitate of quantum dots was then freeze-dried to remove any remaining low-boiling reagents on the surface, yielding a quantum dot powder. The quantum dot powder was then ball-milled with 0.2 g of triethyl phosphite, 0.28 g of isooctyl phosphate, 0.3 g of titanium dioxide, and 8 mL of PGMEA solvent at a ball milling speed of 1000 r / min for 3 h. After completion, the resulting mixture was mixed with 2 mL of UV adhesive to obtain quantum dot photocurable adhesive No. 3.

[0071] [Comparative Example 1] Using the conventional preparation method, 0.5 g of toluene-based green Cd-based quantum dots were mixed with ethanol (ethanol:toluene = 2:1) to obtain a precipitate. The precipitate was freeze-dried for 2 hours, and the powder was dispersed in 5 ml of ethanol (ultrasonic dispersion). 50 mg of triethyl phosphite was added, and the mixture was sonicated for 3 hours to precipitate. After vacuum freeze-drying, the mixture was dispersed in 7 ml of PGMEA solvent, and 0.1 g of titanium dioxide and 2 ml of UV adhesive were added and mixed to obtain quantum dot adhesive solution No. 4.

[0072] Comparative Example 2 Using the conventional preparation method, 1 g of toluene-based red Cd-based quantum dots was mixed with ethanol (ethanol:toluene = 2:1) to obtain a precipitate. The precipitate was freeze-dried for 2 hours, and the powder was dispersed in 5 ml of ethanol (ultrasonic dispersion). 0.4 g of isooctyl phosphate was added, and the mixture was sonicated for 3 hours to precipitate the powder. After vacuum freeze-drying, the mixture was dispersed in 4 ml of PGMEA solvent, and 0.15 g of titanium dioxide and 1 ml of UV adhesive were added and mixed to obtain quantum dot adhesive solution No. 5.

[0073] The quantum dot photo-curable adhesives according to the present application obtained in Examples 1 to 3 and the quantum dot adhesive solutions obtained in Comparative Examples 1 and 2 were spin-coated to form optical films, and tests were conducted. The test results are shown in Table 1 below and Figures 2A to 4C. Figure 2A is a schematic diagram showing the toluene-based quantum dots (bottle on the left) and the prepared quantum dot curable adhesive (bottle on the right) according to Example 1 of the present application. Figure 2B is a schematic diagram of the quantum dot curable adhesive according to Example 1 of the present application after spin-coating to form an optical film. Figure 3A is a schematic diagram of the quantum dot curable adhesive according to Example 2 of the present application after spin-coating to form an optical film. Figure 3B is a diagram showing the effect of using the quantum dot curable adhesive according to Example 2 of the present application in a micro-LED component. FIG. 4A is a schematic diagram showing the state of the toluene-based quantum dots (bottle on the left) and the prepared quantum dot adhesive liquid (bottle on the right) according to Comparative Example 1; FIG. 4B is a schematic diagram showing the quantum dot adhesive liquid according to Comparative Example 1 after spin-coating to form an optical film; and FIG. 4C is a scanning electron microscope image of the quantum dot adhesive liquid according to Comparative Example 1.

[0074] [Table 1]

[0075] As shown in Table 1 and Figures 2A to 4C, the quantum dot photocurable adhesive obtained using the preparation method of this application is more uniform, less destructive to the quantum dots, and maintains a high quantum dot PLQY (photoluminescence quantum yield) of 99%. The resulting quantum dot photocurable adhesive layer is grain-free and has a blue light absorption rate of 100%. The initial quantum dot efficiency refers to the liquid PLQY tested after conventional quantum dot synthesis in an oil phase.

[0076] Specifically, for example, the device prepared by the conventional method of Comparative Example 1 exhibited poor performance and a grainy appearance (Figure 4(C)). Furthermore, as shown in Figure 4(B), the spin-coated film had a white surface and low efficiency. In contrast, the quantum dot photocurable adhesives prepared by the method of the present application (Examples 1 and 2) exhibited a smooth, uniform spin-coated film, as shown in Figure 2(B) and Figure 3(A). The prepared micro-LED devices also exhibited good performance (Figure 3(B)) and no grainy appearance.

[0077] The present invention avoids the conventional liquid-phase ligand exchange process for preparing quantum dot photocurable adhesives. Instead, solid quantum dots are mixed with a light-diffusing agent, a functional polymer (e.g., a phosphate ester-based polymer), and a photocurable adhesive solvent. The functional polymer coats the surface of the quantum dots, completely covering the entire quantum dots. This ensures good solubility of the quantum dots in the PGMEA solvent, ensuring their inherent optical performance while minimizing damage to the quantum dots. Furthermore, ball milling the mixed solution ensures uniform dispersion of the quantum dots in the PGMEA solvent. This application not only solves the problems of dispersion of light-diffusing agents such as titanium dioxide in photocurable adhesives, dispersion of quantum dots in photocurable adhesive solvents, and reduced photoluminescence quantum yield (PLQY) of quantum dots in photoresist-based (photocurable adhesive-based) adhesives, but also provides a more convenient and rapid process, making it suitable for large-scale production. Furthermore, the solid-liquid reaction of ball milling overcomes the limitations of liquid-phase reactions. Finally, the prepared quantum dot photocurable adhesive can be formed into a uniform film without graininess, and has high absorption efficiency and conversion efficiency after curing.

[0078] Although the present application has been described through the above-mentioned related examples, the above-mentioned examples are merely examples of implementing the present application. Furthermore, the technical configurations of different embodiments of the present application described above can be combined with each other as long as they are not inconsistent with each other. The disclosed examples do not limit the scope of the present application. Any changes and modifications that do not deviate from the spirit and scope of the present application are within the scope of patent protection of the present application.

Claims

1. A quantum dot photocurable adhesive, The quantum dot photocurable adhesive includes a mixed solution and an ultraviolet curable adhesive solution, the mixed solution includes quantum dots, titanium dioxide, isooctyl phosphate or triethyl phosphite, and a propylene glycol methyl ether acetate solvent, and the isooctyl phosphate or triethyl phosphite in the mixed solution coats the entire quantum dots. A quantum dot photocurable adhesive characterized by:

2. The quantum dots are selected from one or a mixture of several of CdSe, CdS, ZnS, CdZnSe, CdZnS, CdZnSeS, ZnSeS, ZnSe, CuInS, CuInSe, InP, and InZnP; 2. The quantum dot photocurable adhesive according to claim 1.

3. The quantum dots and the titanium dioxide are both solids.

2. The quantum dot photocurable adhesive according to claim 1.

4. In the quantum dot photocurable adhesive, the mass content of the quantum dots is less than 60%.

2. The quantum dot photocurable adhesive according to claim 1.

5. The mass content of the quantum dots is 10% to 40%; 5. The quantum dot photocurable adhesive according to claim 4.

6. In the quantum dot photocurable adhesive, the mass content of the titanium dioxide is less than 50% and does not exceed the mass content of the quantum dots; 2. The quantum dot photocurable adhesive according to claim 1.

7. The mass content of the titanium dioxide is 5% to 30%. The quantum dot photocurable adhesive according to claim 6 .

8. The mass content ratio of the titanium dioxide to the quantum dots is 1:100 to 1:1; 2. The quantum dot photocurable adhesive according to claim 1.

9. A method for preparing a quantum dot photocurable adhesive, comprising: Step S1: mixing quantum dots, titanium dioxide, isooctyl phosphate or triethyl phosphite, and propylene glycol methyl ether acetate solvent to prepare a first mixed solution; Step S2 of ball milling the first mixed solution under a light-shielding condition to obtain a second mixed solution, in which the isooctyl phosphate or triethyl phosphite in the second mixed solution covers the entire quantum dots; and step S3 of mixing the second mixed solution with the ultraviolet curable adhesive solution to obtain a quantum dot photocurable adhesive. A method for preparing a quantum dot photocurable adhesive.

10. The quantum dots and the titanium dioxide are both solids. The method for preparing the quantum dot photocurable adhesive according to claim 9 .

11. In the quantum dot photocurable adhesive, the mass content of the quantum dots is less than 60%. The method for preparing the quantum dot photocurable adhesive according to claim 9 .

12. In the quantum dot photocurable adhesive, the mass content of the titanium dioxide is less than 50% and does not exceed the mass content of the quantum dots; The method for preparing the quantum dot photocurable adhesive according to claim 9 .

13. In step S2, the rotation speed of the ball milling is 500 to 1500 rpm, and the ball milling time is 10 minutes to 5 hours. The method for preparing the quantum dot photocurable adhesive according to claim 9 .

14. The method for preparing quantum dots includes: Mixing a polar solvent and a non-polar solvent with a quantum dot solution in a predetermined ratio to obtain a turbid quantum dot solution, centrifuging the turbid quantum dot solution, and removing the supernatant to obtain a quantum dot solid precipitate; and freeze-drying the obtained quantum dot solid precipitate to remove the low-boiling point reagent remaining on the surface, thereby obtaining quantum dots in a dry powder form. The method for preparing the quantum dot photocurable adhesive according to claim 9 .

15. A display device, The display substrate includes a quantum dot photocurable adhesive layer provided on the display substrate, and the quantum dot photocurable adhesive layer includes the quantum dot photocurable adhesive according to any one of claims 1 to 8. A display device characterized by:

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