Coated quantum dot material, method for preparing the same, and quantum dot optical device

Abstract

The present disclosure belongs to the technical field of quantum dot materials, and specifically relates to a coated quantum dot material, a preparation method thereof, and a quantum dot optical device. The coated quantum dot material is a coated quantum dot material including a quantum dot core material and an inorganic salt coating agent, the quantum dot core material includes an oil-soluble quantum dot, the inorganic salt coating agent has a solubility in water of less than 0.01g / 100g, a thermal decomposition temperature of more than 300°C, and the ratio of the mass of the quantum dot core material to the molar amount of the inorganic salt coating agent in the coated quantum dot material is 1:0.001 to 1:0.05g / mol. The preparation method includes the steps of: S1: mixing a quantum dot core material, an organic solvent, and an oil-soluble cation precursor to obtain a first mixed solution; S2: heating the first mixed solution to a heating temperature of more than 90°C; and S3: dropping an anionic aqueous solution into the heated first mixed solution. The coated quantum dot material provided in the present application can withstand high temperature processing, has good light resistance, water resistance, and oxygen resistance, and is highly stable.

Description

Technical Field

[0001] Cross-reference to Related Applications This application claims the priority of a Chinese patent application filed with the China National Intellectual Property Administration on September 6, 2021, with an application number of 202111036932.8 and an invention title of "Coated Quantum Dot Material and Its Preparation Method and Quantum Dot Optical Device", and a Chinese patent application filed with the China National Intellectual Property Administration on November 10, 2021, with an application number of 202111328760.1 and an invention title of "Coated Quantum Dot Material and Its Preparation Method and Quantum Dot Optical Device", and all of its content is incorporated herein by reference.

[0002] The present invention belongs to the technical field of quantum dot materials, and specifically relates to a coated quantum dot material, its preparation method, and a quantum dot optical device.

Background Art

[0003] Quantum dots are quasi-zero-dimensional fluorescent semiconductor nanocrystals, and due to their excellent fluorescence properties (such as high quantum yield, continuously adjustable fluorescence emission wavelength, narrow full width at half maximum, etc.), they have great potential for application in the fields of lighting and display. However, during the processing and use process, quantum dot materials are easily affected by conditions such as light, heat, water, and oxygen, and it is difficult to maintain their fluorescence characteristics over a long period. In particular, when forming a quantum dot plate structure, due to the poor high-temperature resistance performance of quantum dots, it is difficult to maintain their good fluorescence performance after performing a high-temperature forming or curing step, which hinders the development of the lighting and display fields.

[0004] Currently, there are mainly two solutions adopted in the industry. One solution is to use a water and oxygen barrier structure to protect the quantum dot material. For example, in the patents initially filed by nanosys and 3M, two layers of oxygen barrier films are pasted outside the quantum dot layer to protect the quantum dot material (CN201480005245.1). However, in this method, the barrier film is expensive and the coating process is complex.

[0005] Another solution is to form a coated quantum dot material to provide protection for the quantum dots. For example, CN108913142A and CN108285792A coat the quantum dot material with a metal oxide to improve its stability. However, during the processing, as the temperature increases, the ligands of the partial quantum dots (e.g., fatty acids, thiols, etc.) are oxidized at high temperatures to produce other organic substances (e.g., sulfonic acid, etc.), which become more acidic and react with the oxide on the quantum dot surface, further affecting the quantum dot material.

[0006] CN108893103A provides a method for coating quantum dots with inorganic salts, employing a one-step method to coat the surface of quantum dots by adsorption, and the performance of the resulting coated quantum dots can be guaranteed to be such that there is no significant optical attenuation after 500 hours of blue light irradiation. However, in practical applications, quantum dot devices are usually required to operate smoothly for more than 1000 hours, and this patent does not disclose the thermal stability of the resulting coated quantum dots.

[0007] To date, conventional technologies have lacked quantum dot materials that meet the needs of high-temperature processing while also possessing good water resistance and oxygen capacity. [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The purpose of this application is to provide a coated quantum dot material, a method for preparing the same, and a quantum dot device in order to overcome the defects of conventional quantum dot materials, such as their inability to withstand high-temperature processing, poor stability, and poor moisture resistance. The coated quantum dot material of this application can withstand high-temperature processing, has good water resistance and oxygen capacity, and has good stability. [Means for solving the problem]

[0009] To achieve the above objective, according to a first aspect, this application provides a coated quantum dot material comprising a quantum dot core material and an inorganic salt coating agent, wherein the quantum dots include oil-soluble quantum dots, the inorganic salt coating agent has a solubility in water of less than 0.01 g / 100 g and a thermal decomposition temperature greater than 300°C, and the ratio of the mass of the quantum dot core material to the molar amount of the inorganic salt coating agent in the coated quantum dot material is 1:0.001 g / mol to 1:0.05 g / mol, preferably 1:0.002 g / mol to 1:0.02 g / mol, and most preferably 1:0.003 g / mol to 1:0.005 g / mol.

[0010] Furthermore, the particle size of the quantum dot core material is 3 to 15 nm, and the coating thickness of the inorganic salt coating agent is 0.5 to 20 nm.

[0011] Furthermore, the coated quantum dot material of this application has a quantum yield of 70% or more after thermal processing at a high temperature of 200 to 300°C, and the quantum dot device obtained after thermal processing has an optical attenuation of less than 20%, less than 10%, and more preferably less than 5% after 1000 hours of high-temperature, high-humidity blue light accelerated aging measurement.

[0012] Furthermore, the coated quantum dot material has a quantum yield of 80% or more, and more preferably 90% or more, after being heat-processed at a high temperature of 200-300°C.

[0013] Furthermore, the method for preparing coated quantum dot materials is as follows: S1: A quantum dot core material, an organic solvent, and an oil-soluble cation precursor are mixed to obtain a first mixture, wherein the quantum dot core material contains oil-soluble quantum dots, and the organic solvent has a boiling point higher than that of water. S2: The first mixture is heated, and the heating temperature is higher than 90°C. S3: The step of adding an anionic aqueous solution necessary for growing an inorganic salt dropwise to a heated first mixture and reacting it to obtain a coated quantum dot material.

[0014] According to a second aspect, the present application provides a method for preparing a coated quantum dot material, wherein the coated quantum dot material comprises a quantum dot core material and an inorganic salt coating agent, and the preparation method is S1: A quantum dot core material, an organic solvent, and an oil-soluble cation precursor are mixed to obtain a first mixture, wherein the quantum dot core material contains oil-soluble quantum dots, and the organic solvent has a boiling point higher than that of water. S2: The first mixture is heated, and the heating temperature is higher than 90°C. S3: The step of adding an anionic aqueous solution necessary for growing an inorganic salt dropwise to a heated first mixture and reacting it to obtain a coated quantum dot material.

[0015] Furthermore, in step S1, the ratio of the mass of the quantum dot to the molar amount of the oil-soluble cation precursor is 1:0.001 g / mol to 1:0.05 g / mol, preferably 1:0.002 g / mol to 1:0.02 g / mol, and most preferably 1:0.003 g / mol to 1:0.006 g / mol.

[0016] Furthermore, in step S2, the heating temperature is 100°C or higher. While there are no particular upper limits on the heating temperature, it is desirable to set it to 200°C or lower from the perspective of equipment requirements and energy conservation.

[0017] Furthermore, in step S2, the heating time is 10 to 60 minutes.

[0018] Furthermore, in step S3, the dropping rate is 0.5 to 2 mL / min, preferably 1 to 1.5 mL / min.

[0019] According to a third aspect, the present application provides a coated quantum dot material formed from the preparation method of the second aspect.

[0020] Furthermore, the ratio of the mass of the quantum dot core material to the molar amount of the inorganic salt coating agent in the coated quantum dot material is 1:0.001 g / mol to 1:0.05 g / mol, preferably 1:0.002 g / mol to 1:0.02 g / mol, and most preferably 1:0.003 g / mol to 1:0.005 g / mol.

[0021] Furthermore, the coated quantum dot material, after heat processing at a high temperature of 200-300°C, has a quantum yield of 70% or more, preferably 80% or more, and most preferably 90% or more. The quantum dot device obtained after the heat processing has a light attenuation of less than 20%, preferably less than 10%, and most preferably less than 5% after 1000 hours of high-temperature, high-humidity blue light accelerated aging measurement.

[0022] According to the fourth aspect, the present application provides a quantum dot device comprising a coated quantum dot material as described in the first or third aspect. [Effects of the Invention]

[0023] In the prior art, generally, the thickness of the coated quantum dot material layer is 0.5 - 20 nm. However, the specific impact of the thickness on the light resistance, heat resistance, water resistance, and oxygen resistance of the quantum dot material is not clear. There may be an obvious difference in the stability performance of coated quantum dot materials with the same coating layer thickness. At the same time, a favorable thickness range beneficial to the stability of coated quantum dots has not been discovered. Currently, there is no relevant research on the relationship between the coating structure parameters of coated quantum dots and the stability of coated quantum dot materials. The inventors of the present application have discovered that by optimizing the ratio of the mass of the quantum dot core material to the molar amount of the inorganic salt coating agent, the light resistance, heat resistance, water resistance, and oxygen resistance of the coated quantum dot material can be effectively improved in the face of the uncertainty between the thickness and stability of the quantum dot material. By forming a specific amount of the coating layer, the high-temperature processing resistance of the quantum dot material can be significantly improved, and it has good light resistance, water resistance, and oxygen resistance, that is, excellent stability. Although the mechanism by which the current ratio of the mass of the quantum dot core material to the molar amount of the inorganic salt coating agent affects the light resistance, heat resistance, water resistance, and oxygen resistance of the coated quantum dots is not clear, one possible reason is that the coating amount of the coating layer that satisfies the above ratio of the mass of the quantum dot core material to the molar amount of the inorganic salt coating agent is more advantageous for forming a coating layer with a density and / or volume that meets the requirements of practical applications, which can well block the contact between water, oxygen, etc. and the quantum dots, prevent the occurrence of disadvantages such as quenching caused by both, and do not significantly affect the optical performance of the quantum dot core material. The coating amount can directly connect the surface of the quantum dots with a sufficient amount of the coating layer on the lattice layer plane, greatly reducing the exposure probability of defects that are prone to be reaction initiation points such as phase transitions existing on the surface of the quantum dots, greatly improving the light resistance and heat resistance of the quantum dots, and reducing the impact of light, heat, etc. on the quantum dot core material; at the same time, the coating amount of the coating agent within the above ratio range does not cause the stress on the contact surface between the inorganic salt structure and the quantum dot structure to be too large, compress the original lattice structure to generate defects, and affect the passage of light.

[0024] The quantum dot material of this application breaks through the technical bottleneck that quantum dot materials cannot withstand high-temperature processing. This material can be directly mixed with pellets such as PS and thermally processed to prepare optical devices such as quantum dot diffusion plates / light guide plates / functional plates, greatly reducing the manufacturing cost, optimizing the preparation process, reducing the loss of quantum yield before and after processing, and improving the optical stability of quantum dot optical devices.

[0025] This application further provides a method for preparing coated quantum dots. The preparation method is to pre-mix a quantum dot with an oil-soluble cation precursor for growing inorganic salts and heat them to adsorb a large amount of cations on the surface of the quantum dots in the oil phase. Further, an anion aqueous solution that is advantageous for the dispersion of the anion precursor is dropped into it; since the temperature in the first mixture is relatively high, close to the boiling point of water, or exceeds the boiling point of water, when dropping a small volume of anion droplets, the water solvent rapidly evaporates, and at the dropped interface, the anion rapidly binds to the cations on the surface of the quantum dots to form a dense inorganic salt coating layer, thereby obtaining a coated quantum dot material with a high ratio of the coating layer to the quantum dot core material. This method can obtain a more dense and / or larger-volume inorganic salt coating layer compared to the preparation process that forms a coating layer and a single-phase coating layer relying only on adsorption. The obtained coated quantum dot material has excellent high-temperature processing resistance compared to the coated quantum dot materials prepared by other liquid-phase methods, and has good light, water, and oxygen resistance capabilities, and high stability.

Brief Description of the Drawings

[0026] The specification drawings constituting a part of this application are used to provide a further understanding of this application. The exemplary embodiments and their descriptions of this application are used to explain this application and do not unduly limit this application. The drawings are as follows.

[0027] [Figure 1] It is a schematic structural diagram of the coated quantum dot material of this application. [Figure 2] It is an electron microscope diagram of the coated quantum dot material of Example 1 of this application. [Figure 3] This is an electron microscope image of the quantum dot material of Comparative Example 1 of this application. [Figure 4] This is a graph of aging measurements for the embodiments and comparative examples of this application. [Modes for carrying out the invention]

[0028] The endpoints and arbitrary values ​​of the ranges disclosed herein are not limited to precise ranges or values, and should be understood to include values ​​close to these ranges or values. Numerical ranges can be obtained by combining the endpoint values ​​of each range, the endpoint values ​​of each range with individual point values, and the individual point values ​​with each other, and these numerical ranges should be considered as specifically disclosed herein.

[0029] In this application, "solubility" means the solubility of the inorganic salt coating agent in water at 20°C.

[0030] As mentioned above, According to a first aspect, the present application provides a coated quantum dot material comprising a quantum dot core material and an inorganic salt coating agent, wherein the quantum dots include oil-soluble quantum dots, the inorganic salt coating agent has a solubility in water of less than 0.01 g / 100 g and a thermal decomposition temperature greater than 300°C, and the ratio of the mass of the quantum dot core material to the molar amount of the inorganic salt coating agent in the coated quantum dot material is 1:0.001 g / mol to 1:0.05 g / mol, preferably 1:0.002 g / mol to 1:0.02 g / mol, and most preferably 1:0.003 g / mol to 1:0.005 g / mol.

[0031] In this application, the coated quantum dot material has a coating structure, and specifically, as shown in Figure 1, the inorganic salt coating agent (i.e., B shown in Figure 1) is applied to the outside of the quantum dot (i.e., A shown in Figure 1).

[0032] A coated quantum dot material having a ratio of the mass of the quantum dot core material to the molar amount of the inorganic salt coating agent exhibits excellent resistance to light, heat, water, and oxygen. In any embodiment, the coated quantum dot material has a quantum yield of 70% or more, preferably 80% or more, and more preferably 90% or more, after heat processing at a high temperature of 200-300°C. In another embodiment, the quantum dot device obtained after the heat processing has a light attenuation of less than 20%, preferably less than 10%, and more preferably less than 5%, after 1000 hours of high-temperature, high-humidity blue light accelerated aging measurement. Measurements show that the quantum dot device prepared with the quantum dot material has a light attenuation of less than 20% even after 3500 hours of high-temperature, high-humidity blue light accelerated aging measurement after the heat processing.

[0033] The conditions for the aforementioned high-temperature, high-humidity blue light accelerated aging measurement were 60°C, 90% humidity, and 40W / m². 2 It is 450nm blue light.

[0034] The coated quantum dot material of this application can have the above-mentioned quantum yield and degree of optical attenuation after thermal processing, whereas conventional coated quantum dot materials generally have a quantum yield of less than 70% and an optical attenuation of 40% or more after 1000 hours of high-temperature, high-humidity blue light accelerated aging measurement.

[0035] In this application, there are no specific limitations on the type of quantum dot core material, and any conventional quantum dot material containing oil-soluble quantum dots can be used in this application. The quantum dot material, which is the non-ligand portion of the oil-soluble quantum dot, is selected from at least one of the semiconductor compounds of Groups II-IV, II-VI, II-V, III-V, III-VI, IV-VI, I-III-VI, II-IV-VI, and II-IV-V of the periodic table; and / or at least one of the semiconductor compounds with a core-shell structure consisting of at least two of the semiconductor compounds of Groups II-IV, II-VI, II-V, III-V, III-VI, IV-VI, I-III-VI, II-IV-VI, and IIIV-V; and / or at least one of perovskite nanoparticle materials, metal nanoparticle materials, metal oxide nanoparticle materials, and carbon nanomaterials. The quantum dot core material may be commercially available or synthesized by conventional methods.

[0036] It is understood that the quantum dot core material may contain other non-oil-soluble quantum dot components in addition to oil-soluble quantum dots, and preferably the quantum dot core material consists only of oil-soluble quantum dots.

[0037] The inorganic salt coating agent of this application is not particularly limited as long as it satisfies the above-mentioned requirements for solubility and thermal decomposition temperature.

[0038] Furthermore, the inorganic salt coating agent may be one or more selected from alkaline earth metal salts, group IIIA metal salts, group IVA metal salts, and transition metal salts.

[0039] The alkaline earth metal salt, Group IIIA metal salt, Group IVA metal salt, and transition metal salt mentioned above include one or more selected from sulfates, carbonates, molybdates, borates, and halogen salts of the metals.

[0040] This application does not have specific requirements regarding the particle size of the quantum dot core material and the thickness of the coating layer formed by the inorganic salt coating agent. If the ratio of the mass of the quantum dot core material to the molar amount of the inorganic salt coating agent satisfies the range limited by this application, superior light, heat, water, and oxygen resistance can be obtained compared to the prior art. Furthermore, as described above, the specific influence of thickness on the light, heat, water, and oxygen resistance of quantum dot materials is not clear in this field. Unless the above limitations of this application are met, it is not possible to ensure superior light, heat, water, and oxygen resistance compared to the prior art, regardless of how the thickness is adjusted.

[0041] Preferably, the particle size of the quantum dot core material is 3 to 15 nm, and the thickness of the coating layer formed by the inorganic salt coating agent is 0.5 to 20 nm. The preferred upper limit of thickness given here is taken into consideration from various aspects such as convenience and economy of preparation, and it should be emphasized that even if the thickness is outside the preferred range, the technical effects of this application can be realized as long as the ratio of the mass of the quantum dot core material to the molar amount of the inorganic salt coating agent satisfies the above limitations of this application. Within the above range of particle size of the quantum dot core material and thickness of the coating layer, the coating layer tends to form a coating layer structure with appropriate density compared to the prior art, and good optical performance can be obtained while satisfying excellent light resistance, heat resistance, water resistance, and oxygen resistance.

[0042] Preferably, the method for preparing the coated quantum dot material includes the steps of: S1: mixing a quantum dot core material, an organic solvent, and an oil-soluble cation precursor to obtain a first mixture, wherein the quantum dot core material contains oil-soluble quantum dots and the organic solvent has a boiling point higher than that of water; S2: heating the first mixture to a heating temperature higher than 90°C; and S3: dropping an aqueous anion solution necessary for growing an inorganic salt into the heated first mixture and reacting it to obtain a coated quantum dot material. The selective range of specific processes is the same as the preparation method provided in the second aspect of this application; specifically, please refer to the subsequent descriptive sections relating to the second aspect.

[0043] The preparation of coated quantum dot materials by liquid-phase method has advantages such as a simple process and ease of industrialization. The above preparation method is only one method for preparing the coated quantum dot material provided in this application, and the coated quantum dot material of this application may be prepared by other methods, and this application is not limited thereto.

[0044] According to a second aspect, the present application provides a preparation method for preparing a coated quantum dot material comprising a quantum dot core material and an inorganic salt coating agent, the preparation method being: S1: A quantum dot core material, an organic solvent, and an oil-soluble cation precursor are mixed to obtain a first mixture, wherein the quantum dot core material contains oil-soluble quantum dots, and the organic solvent has a boiling point higher than that of water. S2: The first mixture is heated, and the heating temperature is higher than 90°C. S3: The step of adding an anionic aqueous solution necessary for growing an inorganic salt dropwise to a heated first mixture and reacting it to obtain a coated quantum dot material.

[0045] In the second embodiment, the selective range of the quantum dot core material and the inorganic salt coating agent is the same as that of the quantum dot core material and the inorganic salt coating agent in the first embodiment described above, and therefore no further explanation is provided here.

[0046] In this application, in step S1, a first oil phase mixture is formed in an organic solvent with the quantum dot core material and the oil-soluble cation precursor. By utilizing the high solubility of the oil-soluble quantum dots and the oil-soluble cation precursor in the organic solvent, a large amount of cations can be adsorbed onto the surface of the quantum dot core material, which is advantageous because it allows for the subsequent dropwise addition of anions to grow a large amount of inorganic salt.

[0047] Furthermore, in step S1, the ratio of the mass of the quantum dot to the molar amount of the oil-soluble cation precursor is 1:0.001 g / mol to 1:0.05 g / mol, preferably 1:0.002 g / mol to 1:0.02 g / mol, and most preferably 1:0.003 g / mol to 1:0.006 g / mol.

[0048] The above-mentioned ratio of quantum dots to oil-soluble cation precursors is advantageous because it allows for the appropriate and uniform adsorption of cations onto the quantum dot surface.

[0049] In this application, the organic solvent is not particularly limited, as long as its boiling point is higher than that of water. Those skilled in the art can select an appropriate organic solvent depending on the solubility of the quantum dot and the oil-soluble cation precursor. The selected organic solvent may or may not undergo a coordination reaction with the quantum dot core material. Non-limiting examples of organic solvents include liquid paraffin, aromatic hydrocarbons, long-chain alkanes, fatty acids, and octadecene.

[0050] The amount of organic solvent used should be sufficient to adequately mix the quantum dot core material and the oil-soluble cation precursor, and a person skilled in the art can appropriately select the amount of the quantum dot core material and the oil-soluble cation precursor used.

[0051] According to this application, there are no limitations on the mixing method of each raw material in step S1. They may be mixed directly in one step, two of the raw materials may be mixed first and then mixed with another raw material, or they may be mixed in a batch manner.

[0052] In one specific embodiment, in step S1, quantum dots and an oil-soluble cation precursor can be added to an organic solvent, respectively, to obtain a quantum dot core material solution and an oil-soluble cation precursor solution, and then the two can be mixed. In another specific embodiment, the oil-soluble cation precursor may be added to the organic solvent first, and then the quantum dots may be added, or the quantum dot core material may be added to the organic solvent first, and then the oil-soluble cation precursor may be added.

[0053] In another specific preferred embodiment, the method includes first preparing a quantum dot core material into a quantum dot oil solution before performing step S1.

[0054] In the above preferred embodiment, the quantum dot core material is mixed with an oil-soluble cation precursor and an organic solvent in the form of a quantum dot oil solution, which is advantageous due to the uniform adsorption of the quantum dot core material and the cation.

[0055] The organic solvent used in preparing the quantum dot oil solution may be the same as or different from the organic solvent used in the subsequent mixing of the quantum dot core material and the oil-soluble cation precursor, but it is preferable that they be the same.

[0056] In this application, by controlling the heating in step S2 so that the temperature of the first mixture approaches or exceeds the boiling point of water, and by combining this with the dropwise addition of the anion aqueous solution in step S3, the aqueous solvent is rapidly evaporated during the dropwise addition process, and at the interface where the anions are added, the anions rapidly combine with the cations on the quantum dot surface to grow and form an inorganic salt coating layer.

[0057] The preparation method described above, compared to conventional methods, utilizes both adsorption and ionic bond generation simultaneously to grow a larger, denser, and more stable inorganic salt coating agent, thereby forming a coating structure on the surface of the quantum dots. This results in the coated quantum dot material possessing comprehensive performance characteristics including resistance to high temperatures, humidity, oxidation, and light irradiation.

[0058] Preferably, the heating temperature in step S2 is 100°C or higher.

[0059] In this application, preferably, the heating time in step S2 is 10 to 60 minutes.

[0060] The above preferred heating conditions are advantageous for the adsorption of the oil-soluble cation precursor and the quantum dot core material, and the selection of the heating temperature is also advantageous for the rapid evaporation of the aqueous solvent during dropwise addition and for the growth reaction of the inorganic salt.

[0061] In this application, preferably, in step S2, the heating is carried out under an inert atmosphere. The inert atmosphere may be argon gas or nitrogen gas. This preferred approach is more advantageous in preventing the quantum dot core material from coming into contact with oxygen in the air and oxidizing before it is coated with the inorganic salt.

[0062] More preferably, in step S2, the heating is carried out under stirring. The stirring is advantageous for mass transfer, on the one hand, to sufficiently adsorb the cation precursor onto the quantum dot core material, and on the other hand, to make the temperature distribution more uniform.

[0063] According to this application, preferably, in step S3, the dropping rate is 0.5 to 2 mL / min, more preferably 1 to 1.5 mL / min. If the dropping rate is too fast, the degree of supersaturation at the interface is too high, and the formed sparingly soluble salt tends to self-nucleate and not grow on the surface of the quantum dot. If the dropping rate is too slow, the solvent temperature is higher than the boiling point of water, so the solvent evaporates too quickly, which is unfavorable for chemical reactions at the interface. The preferred specific dropping rate scheme of this application can encourage the formation of an appropriate amount of coating layer at the dropped interface, further improving the light, heat, water, and oxygen resistance of the resulting coated quantum dot material.

[0064] In this application, a person skilled in the art can select specific types of cation precursors and anion aqueous solutions that form sparingly soluble inorganic salts depending on the type of inorganic salt coating agent. In particular, in this application, it is necessary to use an oil-soluble cation precursor, which is advantageous due to its adsorption to cations on the quantum dot surface.

[0065] Preferably, the oil-soluble cation precursor is one or more selected from oil-soluble alkaline earth metal salt precursors, oil-soluble IIIA metal salt precursors, oil-soluble IVA metal salt precursors, and oil-soluble transition metal salt precursors.

[0066] The specific types of the oil-soluble alkaline earth metal salt precursor, oil-soluble IIIA metal salt precursor, oil-soluble IVA metal salt precursor, and oil-soluble transition metal salt precursor can be any type that can prepare the inorganic salt coating agent. For example, the oil-soluble alkaline earth metal salt, oil-soluble IIIA metal salt precursor, oil-soluble IVA metal salt precursor, and oil-soluble transition metal salt are preferably selected from stearates, phosphonates, oleates, oleylamine salts, etc., that contain alkaline earth metals, IIIA metals, IVA metals, and transition metals.

[0067] In this application, the anion in the anionic aqueous solution is determined by the type of target inorganic salt, and the cation in the anionic aqueous solution may be any cation that does not affect the growth of the inorganic salt, such as sodium ions, potassium ions, and ammonium ions.

[0068] In this application, the concentration of the anion in the aqueous anion solution is not particularly limited, as long as it can be ensured that the anion is sufficiently soluble and is advantageous for the rapid evaporation of the aqueous solvent in the aqueous anion solution during the dropwise addition process. For example, the anion concentration of the aqueous anion solution may be 0.05 to 10 mol / L.

[0069] The amount of the anionic aqueous solution used should be sufficient to ensure adequate reaction between the cation and anion in the oil-soluble cation precursor. Preferably, according to this application, the method further includes, in step S3, continuing to maintain temperature for 15 to 120 minutes after the dropwise addition is complete. During the continued temperature maintenance process, the cation and anion can continue to react, thereby ensuring that sufficient reaction products are obtained.

[0070] According to a third aspect, the present application provides a coated quantum dot material obtained by preparing a coated quantum dot material using the method for preparing coated quantum dot materials described in a second aspect.

[0071] Preferably, the coated quantum dot material can obtain a coated structure having a sufficient amount of coating layer similar to that of the first embodiment, and has excellent high-temperature processability and stability against light, heat, water, and oxygen.

[0072] According to the fourth aspect, the present application provides a quantum dot device comprising a coated quantum dot material as described in the first or third aspect.

[0073] This application does not limit the form of existence of the quantum dot device and includes, but is not limited to, any form of quantum dot device in the field of lighting and display, such as quantum dot diffusers / light guides / functional plates, etc.

[0074] This application does not limit the method for obtaining the coated quantum dot device from the quantum dot material, and can be carried out using conventional methods, for example, by directly mixing the coated quantum dot material with pellets such as PS and processing them into a quantum dot device.

[0075] The present disclosure will be described in more detail below with reference to examples.

[0076] Example 1 Select CdSe / ZnS oily quantum dots, purify them, and then take 3g for use.

[0077] 300 mL of liquid paraffin was placed in a flask, 0.01 mol of barium stearate and 3 g of the above quantum dots were added to obtain the first mixture, argon gas was passed through it, it was stirred (1000 r / min), heated to 120°C, and kept warm for 30 minutes.

[0078] Next, 10 mL of sodium sulfate aqueous solution was added dropwise, setting the sulfate ion concentration to 1 mol / L and the dropping rate to 1 mL / min.

[0079] After the dropping was complete, the material was kept warm for 1 hour and purified to obtain a coated quantum dot material with a barium sulfate shell layer on the surface.

[0080] Figure 2 shows an electron microscope image of the obtained coated quantum dot material.

[0081] Comparative Example 1 The 3g quantum dot material selected and purified in Example 1.

[0082] Figure 3 shows an electron microscope image of the obtained quantum dot material.

[0083] Comparative Example 2 3 g of quantum dot material, obtained by selection and purification according to the method of Example 1, was dissolved in 300 mL of liquid paraffin, heated to 120°C, 0.01 mol of barium sulfate was added, and the mixture was thoroughly reacted and stirred. After purification, a quantum dot material with a barium sulfate shell layer on the surface was obtained.

[0084] Comparative Example 3 3 g of water-soluble CdSe / ZnS quantum dots, 300 mL of aqueous solution, and 0.01 mol of barium chloride were added to a flask.

[0085] Argon gas was passed through the mixture, and it was stirred (1000 r / min). 10 mL of sodium sulfate aqueous solution (sodium sulfate concentration 1 mol / L) was added dropwise, with the dropping rate set to 1 mL / min.

[0086] After the dropping was complete, stirring was continued for 1 hour, and the material was purified to obtain a quantum dot material with a barium sulfate shell layer on the surface.

[0087] Example 2 The procedure was carried out according to the method of Example 1, except that the amount of barium stearate used was 0.005 mol and the amount of sodium sulfate aqueous solution (concentration the same as in Example 1) used was 5 mL.

[0088] Example 3 The procedure was carried out according to the method of Example 1, except that the amount of barium stearate used was 0.05 mol and the amount of sodium sulfate aqueous solution (concentration the same as in Example 1) used was 50 mL.

[0089] Example 4 The procedure followed the method of Example 1, except that the dropping rate was 2 mL / min.

[0090] Example 5 The procedure followed the method of Example 1, except that the dropping rate was 0.5 mL / min.

[0091] Table 1 shows the partial test parameters and measurement results for the above examples and comparative examples.

[0092] Measurement method The coated quantum dot materials obtained in the examples and comparative examples were mixed with PS granule pellets at 250°C, and quantum dot PS devices were fabricated by extruding plates using a microextruder and a plate vulcanizer. Next, the following measurements were performed.

[0093] Each of the above quantum dot PS devices underwent high-temperature, high-humidity, blue light accelerated aging (60°C, 90% humidity, 40W / m²). 2 The normalized time-varying luminance curve obtained by applying blue light (blue light wavelength 450 nm) is shown in Figure 4.

[0094] Quantum yield measurements were performed on the coated quantum dot material before processing and on the quantum dot PS optical device obtained after processing. The quantum yield of the PS quantum dot devices prepared from the coated quantum dot materials of the above examples and comparative examples before processing was 95% in all cases. The results for the quantum yield of each example and comparative example after processing are shown in Table 1.

[0095] [Table 1]

[0096] The quantum dot core material selected in the examples and comparative examples was a CdSe / ZnS core-shell type quantum dot. Due to the protection of the ZnS shell layer, the inorganic salt coating applied outside the ZnS shell layer had little effect on the quantum yield. Therefore, the quantum yield before heat processing in each example and comparative example was 95%. After heat processing, there was a clear difference in the quantum yield between each example and comparative example. This is due to the different protective capabilities of the quantum dot core material by the different coating layers, that is, the coated quantum dot materials exhibited different heat resistance due to the different inorganic salt coating layers.

[0097] As can be seen from Figure 4 and Table 1, compared to the comparative example, the coated quantum dot material prepared by the preparation method provided in this application shows a significantly improved coating amount compared to the inorganic salt coating agent in the prior art. The coated quantum dot material, in which the ratio of the mass of the quantum dot core material to the molar amount of the inorganic salt coating agent is within the limited range of this application, exhibits excellent high-temperature resistance and good resistance to light, moisture, and oxygen after high-temperature processing, i.e., it has good stability.

[0098] Furthermore, by comparing Example 1 with Examples 2-3, it is possible to obtain a coated quantum dot material with a more favorable ratio of the mass of the quantum dot core material to the molar amount of the inorganic salt coating agent by adjusting the raw material blending ratio, thereby further improving the heat resistance, moisture resistance, light resistance, and oxygen stability of the coated quantum dot material.

[0099] Furthermore, by comparing Example 1 with Examples 4-5, it is possible to obtain a coated quantum dot material with a more favorable ratio of the mass of the quantum dot core material to the molar amount of the inorganic salt coating agent according to the preferred dropping rate scheme of this application, and to further improve the heat resistance, moisture resistance, light resistance, and oxygen resistance of the coated quantum dot material.

[0100] The above description is merely a preferred embodiment of the present application and does not limit it, and to those skilled in the art, the present application is subject to various modifications and changes. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application should be included within the scope of protection of the present application.

Claims

1. A method for preparing a coated quantum dot material, wherein the coated quantum dot material comprises a quantum dot core material and an inorganic salt coating agent, and the preparation method is S1: A first mixture is obtained by mixing a quantum dot core material, an organic solvent, and an oil-soluble cation precursor, wherein the quantum dot core material is a CdSe / ZnS oil-soluble quantum dot, the organic solvent has a boiling point higher than that of water, and the oil-soluble cation precursor is barium stearate. S2: The first mixture is heated, and the heating temperature is higher than 90°C. S3: Adding an anionic aqueous solution necessary for growing an inorganic salt dropwise to a heated first mixture and reacting it to obtain a coated quantum dot material, wherein the anionic aqueous solution is an aqueous sodium sulfate solution, and the process includes these steps. The inorganic salt coating agent is barium sulfate. In S1, the ratio of the mass of the quantum dot core material to the molar amount of the oil-soluble cation precursor is 1 g:0.001 mol to 1 g:0.05 mol. The oil-soluble quantum dots are quantum dots that can be dispersed in an oily solvent. The oil-soluble cation precursor is a method for preparing a coated quantum dot material, which is a cation precursor that can be dispersed in an oily solvent.

2. The method for preparing a coated quantum dot material according to claim 1, characterized in that the organic solvent is at least one of liquid paraffin, aromatic hydrocarbons, long-chain alkanes, fatty acids, or octadecene.

3. The method for preparing a coated quantum dot material according to claim 1, characterized in that the anion concentration of the aqueous anion solution is 0.05 mol / L to 10 mol / L.

4. The method for preparing a coated quantum dot material according to claim 1, wherein in S1, the ratio of the mass of the quantum dot core material to the molar amount of the oil-soluble cation precursor is 1 g:0.002 mol to 1 g:0.02 mol.

5. The method for preparing a coated quantum dot material according to claim 1, wherein in S1, the ratio of the mass of the quantum dot core material to the molar amount of the oil-soluble cation precursor is 1 g:0.003 mol to 1 g:0.006 mol.

6. The method for preparing a coated quantum dot material according to claim 1, wherein in S2, the heating temperature is 100°C or higher.

7. The method for preparing a coated quantum dot material according to claim 1, wherein in S2, the heating time is 10 min to 60 min.

8. The method for preparing a coated quantum dot material according to claim 1, wherein in S3, the dropping rate is 0.5 mL / min to 2 mL / min.

9. The method for preparing a coated quantum dot material according to claim 1, wherein in S3, the dropping rate is 1 mL / min to 1.5 mL / min.

10. The method for preparing a coated quantum dot material according to claim 1, further comprising, in S3, continuing to maintain heat for 15 min to 120 min after the dropping is completed.

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