Quantum dot functional microspheres and preparation method and application thereof

Abstract

The present disclosure provides a method for preparing quantum dot functional microspheres, quantum dot functional microspheres and their applications. The method for preparing quantum dot functional microspheres includes: preparing a composition containing quantum dots, surfactant ligands, reactive monomers, crosslinking agents, emulsifiers and initiators, wherein the surfactant ligands have at least two thiol groups; stirring or ultrasonicating the composition to form an emulsion, heating or irradiating the emulsion to cause the emulsion to undergo a polymerization reaction; separating after the reaction to obtain a first quantum dot microsphere, wherein the quantum dots participate in the polymerization reaction through the surfactant ligands, so that the quantum dots and the polymer are chemically bonded; etching the first quantum dot microsphere to obtain a second quantum dot microsphere having a porous structure on the surface; mixing the second quantum dot microsphere with a dispersion containing a quantum dot stabilizing agent, so that at least part of the quantum dot stabilizing agent is adsorbed in the porous structure, to obtain a quantum dot functional microsphere. The quantum dot functional microspheres can have stronger processing stability.

Description

Technical Field

[0001] The present disclosure relates to the technical field of quantum dot photoluminescence, and in particular to a quantum dot functional microsphere and a preparation method thereof, and an optical device containing the same and a preparation method thereof. Background Art

[0002] High-temperature extrusion will lead to a decrease in the quantum yield and life of quantum dot materials, so how to solve the problem of quantum dot failure caused by high temperature is a difficult problem for quantum dot diffusion plates. In addition, the materials used in quantum dot diffusion plates (such as PS, PMMA, PC, PP, etc.) have poor water and oxygen barrier properties, so how to improve the service life of quantum dot materials in the diffusion plate is also another urgent problem to be solved for quantum dot diffusion plates. Summary of the invention

[0003] The purpose of the present disclosure is to provide a quantum dot functional microsphere and a preparation method and application thereof, so as to solve the processing stability of the quantum dot functional microsphere and improve the life of the optical device.

[0004] According to the first aspect of the present disclosure, a method for preparing quantum dot functional microspheres is provided, comprising preparing a composition containing quantum dots, surfactant ligands, reactive monomers, crosslinking agents, emulsifiers and initiators, wherein the surfactant ligands have at least two thiol groups; stirring or ultrasonicating the composition to form an emulsion, heating or irradiating the emulsion to cause a polymerization reaction in the emulsion; separating and obtaining first quantum dot microspheres after the reaction is completed, wherein the quantum dots participate in the polymerization reaction through the surfactant ligands, so that the quantum dots and the polymer are chemically bonded; etching the first quantum dot microspheres to obtain second quantum dot microspheres having a porous structure on the surface; mixing the second quantum dot microspheres with a dispersion containing a quantum dot stabilizing agent, so that at least part of the quantum dot stabilizing agent is adsorbed in the porous structure, to obtain quantum dot functional microspheres.

[0005] Optionally, the reactive monomer includes a first monomer and a second monomer, the first monomer includes one or more of styrene, methyl methacrylate, and isobornyl acrylate, and the second monomer includes one or more of acrylic acid and vinyl acetate; preferably, the mass ratio of the first monomer to the second monomer is 1:1-50:1; more preferably, the polymer of the first quantum dot microspheres includes polystyrene, polymethyl methacrylate, and polyisobornyl acrylate.

[0006] Optionally, the surface active ligand is selected from one or more of pentaerythritol 3-mercaptopropionate, butanediol 3-mercaptopropionate, hexanediol 3-mercaptopropionate, and heptanediol 3-mercaptopropionate; the quantum dot stabilization aid includes one or more of an antioxidant, a ligand-type aid, an anti-ultraviolet absorber, and a light stabilizer; preferably, the crosslinking agent is selected from one or more of divinylbenzene, diene phthalate, and ethylene glycol dimethyl diacrylate; preferably, the emulsifier is selected from one or more of polyvinyl pyrrolidone, polyethylene glycol, and polyvinyl alcohol; preferably, the initiator is selected from an oil-soluble free radical initiator.

[0007] Optionally, the porosity of the second quantum dot microspheres is 10%-50%; preferably, the average pore size of the porous structure of the second quantum dot microspheres is 10-500 nm; preferably, the average particle size of the quantum dot functional microspheres is 50-5000 nm.

[0008] Optionally, the etching treatment includes soaking the first quantum dot microspheres in a solvent; preferably, the solvent includes water, and one or more of methanol, ethanol, isopropanol, and tetrahydrofuran; preferably, the etching treatment time is 12-24 hours; preferably, the etching treatment is followed by separation and purification to obtain the second quantum dot microspheres.

[0009] Optionally, the quantum dots are 1-20 parts by mass, the reactive monomer is 50-100 parts by mass, the cross-linking agent is 1-10 parts by mass, the emulsifier is 0.5-2 parts by mass, and the initiator is 0.05-0.1 parts by mass.

[0010] Optionally, the adsorption process includes: dispersing 20-40 parts by mass of a quantum dot stabilization aid in 200 parts by mass of a liquid to obtain a dispersion containing the quantum dot stabilization aid, and then evenly mixing the dispersion and 10-50 parts by mass of a second quantum dot microsphere. The time to complete the adsorption process is 12-24 hours.

[0011] According to the second aspect of the present disclosure, a quantum dot functional microsphere is provided, which includes a polymer body, quantum dots dispersed in the polymer body and chemically bonded to the polymer body, the quantum dots have thiol ligands, the polymer body has a polymer cross-linked structure, and the polymer body also has a porous structure. The quantum dot functional microsphere also includes a quantum dot stabilization aid, which is arranged in at least a portion of the porous structure and on the surface of at least a portion of the polymer body.

[0012] Optionally, the polymer of the quantum dot functional microspheres includes polystyrene, polymethyl methacrylate, or polyisobornene acrylate; preferably, the quantum dot stabilization aid includes one or more of an antioxidant, a ligand-type aid, an anti-ultraviolet absorber, and a light stabilizer; preferably, the porosity of the quantum dot functional microspheres is 10%-50%; preferably, the melting temperature of the quantum dot functional microspheres is greater than or equal to 300°C.

[0013] According to a third aspect of the present disclosure, an optical device is provided, the optical device comprising any one of the above-mentioned quantum dot functional microspheres.

[0014] According to the fourth aspect of the present disclosure, a method for preparing an optical device is provided, wherein a mixture comprising quantum dot functional microspheres and blank plastic particles is prepared, wherein the quantum dot functional microspheres are quantum dot functional microspheres obtained by any one of the above preparation methods or any one of the above quantum dot functional microspheres; the mixture is extruded through a melt co-extrusion process, during which the quantum dot functional microspheres are not melted; and an optical device is obtained after cooling, wherein the optical device is an optical film or an optical plate.

[0015] The technical solution of this application combines the advantages of highly cross-linked polymer microspheres and quantum dot stabilizing agents. Quantum dot microspheres are prepared by adjusting the proportion of reactive monomers and surface active ligands participating in polymerization. Quantum dot microspheres with porous structures can be obtained by solvent etching. The additives are adsorbed into the interior and surface of the quantum dot microspheres by static adsorption to achieve local high concentration of quantum dot stabilizing agents to protect the environment. The quantum dot functional microspheres obtained by this preparation method can provide stronger processing stability and better aging life of optical devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting part of the present application are used to provide a further understanding of the present disclosure. The exemplary embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation on the present disclosure. In the drawings:

[0017] Figure 1 The present invention is a flow chart of the preparation of quantum dot functional microspheres according to an embodiment of the present invention.

[0018] Figure 2 The figure is a schematic diagram of the structure of quantum dot functional microspheres according to an embodiment of the present invention.

[0019] Figure 3 This is a scanning electron microscope (SEM) image of the first quantum dot microsphere according to an embodiment of the present disclosure.

[0020] Figure 4 This is a SEM image of the second quantum dot microsphere according to an embodiment of the present disclosure.

[0021] Figure 5This is a SEM image of quantum dot functional microspheres according to an embodiment of the present disclosure.

[0022] Figure 6 The figure is a graph showing the change in relative fluorescence efficiency of two embodiments and a comparative example of the present disclosure over time after aging under specific conditions.

[0023] Explanation of the reference numerals: 1. polymer main body; 2. quantum dot; 3. porous structure (quantum dot stabilizing agent); 4. quantum dot stabilizing agent.

[0024] Note that in the embodiments described below, sometimes the same reference numerals are used in common between different drawings to represent the same parts or parts with the same functions, and their repeated descriptions are omitted. In some cases, similar numbers and letters are used to represent similar items, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0025] For ease of understanding, the position, size, range, etc. of each structure shown in the drawings and the like may not represent the actual position, size, range, etc. Therefore, the present disclosure is not limited to the position, size, range, etc. disclosed in the drawings and the like. DETAILED DESCRIPTION

[0026] Various exemplary embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure.

[0027] The following description of at least one exemplary embodiment is in fact merely illustrative and is in no way intended to limit the present disclosure and its application or use. That is, the structures and methods herein are shown in an exemplary manner to illustrate different embodiments of the structures and methods in the present disclosure. However, those skilled in the art will appreciate that they merely illustrate exemplary ways of the present disclosure that can be implemented, rather than exhaustive ways. In addition, the drawings need not be drawn to scale, and some features may be enlarged to illustrate the details of specific components.

[0028] In addition, technologies, methods, and apparatus known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, such technologies, methods, and apparatus should be considered part of the authorization specification.

[0029] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0030] The words "left", "right", "front", "back", "top", "bottom", "up", "down", "high", "low", etc., in the specification and claims, if present, are used for descriptive purposes and are not necessarily used to describe an unchanging relative position. It should be understood that the words so used are interchangeable under appropriate circumstances, so that the embodiments of the present disclosure described herein, for example, can operate in other orientations than those shown or otherwise described herein. For example, when the device in the drawings is turned over, features previously described as being "above" other features may now be described as being "below" the other features. The device may also be otherwise oriented (rotated 90 degrees or at other orientations), and the relative spatial relationships will be interpreted accordingly.

[0031] In the specification and claims, when an element is referred to as being "on", "attached", "connected", "coupled" or "coupled" to another element, the element may be directly on, directly attached, directly connected, directly coupled or directly coupled to another element, or one or more intermediate elements may be present. In contrast, when an element is referred to as being "directly" "on", "directly attached", "directly connected", "directly coupled" or "directly coupled" to another element, there will be no intermediate elements. In the specification and claims, a feature being arranged "adjacent" to another feature may refer to a feature having a portion that overlaps with an adjacent feature or a portion that is located above or below the adjacent feature.

[0032] As used herein, the word "exemplary" means "serving as an example, instance, or illustration" rather than as a "model" to be exactly copied. Any implementation described as exemplary herein is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, the present disclosure is not to be limited by any expressed or implied theory given in the technical field, background, summary, or detailed description.

[0033] As used herein, the term "substantially" is intended to include any minor variations due to design or manufacturing imperfections, device or component tolerances, environmental influences, and / or other factors. The term "substantially" also allows for deviations from a perfect or ideal condition due to parasitic effects, noise, and other practical considerations that may exist in actual implementations.

[0034] In addition, the terms "first", "second" and the like may also be used herein for reference purposes only, and thus are not intended to be limiting. For example, the terms "first", "second" and other such numerical terms referring to structures or elements do not imply a sequence or order unless the context clearly indicates otherwise.

[0035] It should also be understood that when the term “include / comprises” is used in this document, it indicates the presence of the specified features, integers, steps, operations, units and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, units and / or components and / or their combinations.

[0036] In this disclosure, the term "provide" is used in a broad sense to cover all ways of obtaining an object, and thus "providing an object" includes but is not limited to "purchasing", "preparing / manufacturing", "arranging / setting up", "installing / assembling", and / or "ordering" an object, etc.

[0037] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the present disclosure. As used herein, the singular forms "a", "an", and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0038] The inventors found that adding quantum dot stabilizing agents during the thermal processing of quantum dots can protect quantum dots from thermal oxidation degradation during the thermal processing. In addition, these agents can effectively consume the water and oxygen that penetrate during the long-term aging process. However, the uniform addition of quantum dot stabilizing agents often has a poor effect, and the addition of a large amount of quantum dot stabilizing agents will lead to a significant decrease in the mechanical properties of the quantum dot diffusion plate. Polymer-encapsulated quantum dot microspheres are made by suspension polymerization or emulsion polymerization and adjustment of quantum dot surface ligands. This structure is generally a cross-linked system so it can better block water and oxygen, but the ability of simple microsphere coating to block water and oxygen is also limited.

[0039] In a first aspect of the present disclosure, a method for preparing quantum dot functional microspheres is provided, comprising preparing a composition containing quantum dots, surfactant ligands, reactive monomers, crosslinking agents, emulsifiers and initiators, wherein the surfactant ligands have at least two thiol groups; stirring or ultrasonicating the composition to form an emulsion, and then heating or irradiating the emulsion with light to cause a polymerization reaction in the emulsion; separating after the reaction to obtain first quantum dot microspheres, wherein the quantum dots participate in the polymerization reaction through the surfactant ligands, so that the quantum dots and the polymer are chemically bonded; etching the first quantum dot microspheres to obtain second quantum dot microspheres having a porous structure on the surface; mixing the second quantum dot microspheres with a dispersion containing a quantum dot stabilizing agent, so that at least a portion of the quantum dot stabilizing agent is adsorbed in the porous structure, to obtain quantum dot functional microspheres.

[0040] The technical solution of this application combines the advantages of highly cross-linked polymer microspheres and quantum dot stabilizing agents. Quantum dot microspheres are prepared by polymerization with the participation of surface active ligands, and porous quantum dot microspheres can be obtained by solvent etching. The additives are adsorbed into the interior and surface of the quantum dot microspheres by static adsorption to achieve local high concentration of quantum dot stabilizing agents to protect the environment. The quantum dot functional microspheres obtained by this preparation method can provide stronger processing stability and aging life.

[0041] One of the thiol groups in the above-mentioned surfactant ligands coordinates and combines with the surface of the quantum dots during the emulsification process, and another thiol group undergoes a chain transfer reaction with the double bond compound in the composition, that is, the other thiol group is equivalent to a chain transfer agent, so that the quantum dots are chemically bonded to the polymer formed by the polymerization reaction, so that the first quantum dot microsphere formed has a chemically cross-linked structure. The above-mentioned polymerization reaction includes a suspension polymerization reaction or an emulsion polymerization reaction. The cross-linking density of the above-mentioned cross-linked structure can be adjusted by the ratio of the reactive monomer and the cross-linking agent. In the above-mentioned emulsion, a plurality of small droplets are formed, the emulsifier is on the interface of the droplets, and the polarity of the substances inside and outside the droplets is opposite. After the small droplets are solidified, the first quantum dot microspheres are formed. Those skilled in the art can select suitable reaction raw materials according to the requirements for forming the emulsion. In some embodiments, the quantum dots are oil-soluble quantum dots.

[0042] In some embodiments, the reactive monomer includes a first monomer and a second monomer, the first monomer includes one or more of styrene, methyl methacrylate, and isobornyl acrylate, and the second monomer includes one or more of acrylic acid and vinyl acetate. In some embodiments, the mass ratio of the first monomer to the second monomer is 1:1-50:1. In some embodiments, the polymer of the first quantum dot microsphere includes polystyrene, polymethyl methacrylate, and polyisobornyl acrylate. In some embodiments, the porous structure includes a through-hole structure.

[0043] The stirring includes mechanical stirring, air flow stirring, manual stirring, etc., and the mechanical stirring includes vortexing. In some embodiments, the composition is sonicated for 20-40 minutes using an ultrasonic probe (preferably greater than or equal to 100 W) to form an emulsion.

[0044] In some embodiments, heating the emulsion to polymerize the emulsion comprises: raising the temperature of the emulsion to 50-80° C., and polymerizing the emulsion for 12-48 hours under stirring at 400-800 rpm to form a stable emulsion.

[0045] In some embodiments, the light is ultraviolet light.

[0046] In some embodiments, the microspheres are separated by centrifugation. In some embodiments, after separation, the surface of the first quantum dot microspheres is further cleaned to remove the emulsifier and the raw materials not involved in the reaction, thereby obtaining the first quantum dot microspheres.

[0047] In some embodiments, the quantum dots in the composition are in the form of quantum dot powder, and the ligands of the quantum dots in this state include fatty acid radical ligands, which may be oleate, stearate, and the like.

[0048] In some embodiments, the quantum efficiency of the quantum dots is greater than or equal to 70%, preferably greater than or equal to 80%.

[0049] In some embodiments, the types of quantum dots include core-shell compounds formed by one or more II-VI main group compounds, including but not limited to CdSe, CdTe, MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe and CdS, or core-shell compounds formed by one or more III-V main group compounds, including but not limited to GaN, GaP, GaAs, InN, InP and InAs. Quantum dots may also include other elements.

[0050] In some embodiments, the average size of the quantum dots is 5-30 nm. In some embodiments, the fluorescence half-maximum width (FWHM) of the quantum dots is less than 30 nm.

[0051] In some embodiments, the surface active ligand is an organic ligand, the number of C of which is greater than or equal to 2, so that at least one thiol group is not easy to bind to the surface of the quantum dot (due to steric hindrance). In some embodiments, the surface active ligand is selected from one or more of pentaerythritol 3-mercaptopropionate, butanediol 3-mercaptopropionate, hexanediol 3-mercaptopropionate, and heptanediol 3-mercaptopropionate.

[0052] In some embodiments, the quantum dot stabilization agent includes one or more of an antioxidant, a ligand-based agent, an ultraviolet absorber, and a light stabilizer.

[0053] In some embodiments, the antioxidant is a phenolic antioxidant, including but not limited to 2,6-di-tert-butyl-p-cresol, 4,6-bis(octylthiomethyl)-o-cresol, N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetrakis[β-(3.5-di-tert-butyl, 4-hydroxyphenyl)propionate], 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane, 1,3,5-trimethyl, 2,4,6,-tris(3,5,-di-tert-butyl, 4-hydroxybenzyl)benzene. In some embodiments, the antioxidant is a thioester antioxidant, including but not limited to dioctadecyl thiodipropionate, ditridecyl thiodipropionate, 3-(dodecylthio)propionic acid-2,2-bis[[3-(dodecylthio)-propionyloxy]methyl]-1,3-propylene glycol ester, 4,4'-thiobis(6-tert-butyl-m-cresol), and 4,4'-thiobis(6-tert-butyl-2-methylphenol).

[0054] In some embodiments, the ultraviolet absorber includes but is not limited to one or more of 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2-(2ˊ-hydroxy-5ˊ-methylphenyl)benzotriazole, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octyloxybenzophenone, 2-(2'-hydroxy-3',5'-di-tert-phenyl)-5-chlorobenzotriazole, and 4-benzoyloxy-2,2,6,6-tetramethylpiperidine.

[0055] In some embodiments, the light stabilizer is not limited to poly(4-hydroxyethyl-2,2,6,6-tetramethyl-1-piperidinylethanol) succinate, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacic acid, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacic acid ester, poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinylethanol) succinate, poly{[6-[(1,1,3,3-tetramethylbutyl)amino]]-1,3 ,5-triazine-2,4-[(2,2,6,6,-tetramethyl-piperidinyl)imino]-1,6-hexanediamine[(2,2,6,6-tetramethyl-4-piperidinyl)imino]}, poly{[N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine]-[2,4,6-trichloro-1,3,5-triazine and N-butyl-1-butylamine]-[N-butyl-2,2,6,6-tetramethyl-4-piperidinamine]}.

[0056] In some embodiments, the ligand auxiliary agent is selected from one or more of zinc oleate, magnesium oleate, calcium stearate, magnesium stearate, etc. The ligand auxiliary agent can be bound to the surface of the quantum dots to provide stability for the quantum dots. In some embodiments, the above composition also includes other auxiliary agents.

[0057] In some embodiments, the crosslinking agent is selected from one or more of divinylbenzene, diene phthalate, and ethylene glycol dimethyl diacrylate.

[0058] In some embodiments, the emulsifier is selected from one or more of polyvinyl pyrrolidone, polyethylene glycol, and polyvinyl alcohol. In some embodiments, the initiator is selected from an oil-soluble free radical initiator, and the oil-soluble free radical initiator includes but is not limited to one of azobisisobutyronitrile, dibenzoyl peroxide, and the like.

[0059] In some embodiments, the porosity of the second quantum dot microsphere is 10%-50%. In some embodiments, the average pore size of the porous structure of the second quantum dot microsphere is 10-500 nm. In some embodiments, the average pore size of the porous structure of the second quantum dot microsphere is 20-300 nm. Porosity and pore size can be adjusted by the ratio between different reactive monomers. In some embodiments, the average particle size of the quantum dot functional microsphere is 50-5000 nm. In some embodiments, the average particle size of the quantum dot functional microsphere is 200-1200 nm. The average particle size can be adjusted by the ratio of reactive monomers and emulsifiers.

[0060] In some embodiments, the etching process includes soaking the first quantum dot microspheres with a solvent. In some embodiments, the solvent includes water and one or more of methanol, ethanol, isopropanol, and tetrahydrofuran. In some embodiments, the solvent is a combination of ethanol, water, and isopropanol, preferably, the volume ratio of the three is 2:1:1.

[0061] In some embodiments, the etching treatment time is 12-24 hours. In some embodiments, the etching treatment is followed by separation and purification to obtain the second quantum dot microspheres.

[0062] In some embodiments, the quantum dots are 1-20 parts by mass, the reactive monomer is 50-100 parts by mass, the crosslinking agent is 1-10 parts by mass, the emulsifier is 0.5-2 parts by mass, and the initiator is 0.05-0.1 parts by mass.

[0063] In some embodiments, the adsorption process includes: dispersing 20-40 parts by mass of an auxiliary agent in 200 parts by mass of a liquid to obtain an auxiliary agent-containing dispersion, and then evenly mixing the dispersion and 10-50 parts by mass of second quantum dot microspheres. The time to complete the adsorption process is 12-24 hours.

[0064] In some embodiments, the melting temperature of the prepared quantum dot functional microspheres is greater than or equal to 300° C. The melting temperature is relatively high due to the highly cross-linked structure.

[0065] According to a second aspect of the present disclosure, a quantum dot functional microsphere is provided, which includes a polymer body, quantum dots dispersed in the polymer body and chemically bonded to the polymer body, the quantum dots have thiol ligands, the polymer body has a polymer cross-linked structure, and the polymer body also has a porous structure. The quantum dot functional microsphere also includes a quantum dot stabilization aid, which is disposed in at least a portion of the porous structure and on the surface of at least a portion of the polymer body. Figure 2 A structural diagram of quantum dot functional microspheres is shown.

[0066] In some embodiments, the quantum dot has a thiol ligand, wherein the thiol ligand has one or more thiol groups coordinated to the surface of the quantum dot. In some embodiments, the quantum dot stabilization aid completely covers the polymer host.

[0067] In some embodiments, the polymer of the quantum dot functional microspheres includes polystyrene, polymethyl methacrylate, or polyisobornene acrylate. In some embodiments, the quantum dot stabilizing agent includes one or more of an antioxidant, a ligand auxiliary, an anti-ultraviolet absorber, and a light stabilizer.

[0068] In some embodiments, the porosity of the quantum dot functional microspheres is 10%-50%. In some embodiments, the average pore size of the porous structure is 10-500 nm. In some embodiments, the average particle size of the quantum dot functional microspheres is 50-5000 nm.

[0069] In some embodiments, the melting temperature of the quantum dot functional microspheres is greater than or equal to 300°C.

[0070] According to a third aspect of the present disclosure, an optical device is provided, which comprises any one of the above-mentioned quantum dot functional microspheres.

[0071] Quantum dot functional microspheres have good stability due to their high degree of cross-linking; in addition, the adsorbed quantum dot stabilization agent has a relatively high concentration locally on the quantum dots, which can protect the quantum dots from being etched by high temperature and water oxygen during the melt extrusion process and significantly improve the service life of the quantum dots.

[0072] The fourth aspect of the present disclosure provides a method for preparing an optical device, preparing a mixture comprising quantum dot functional microspheres and blank plastic particles, wherein the quantum dot functional microspheres are quantum dot functional microspheres obtained by any of the above preparation methods or any of the above quantum dot functional microspheres; extruding the mixture through a melt co-extrusion process, during which the quantum dot functional microspheres are not melted; and obtaining an optical device after cooling, wherein the optical device is an optical film or an optical plate.

[0073] On the one hand, the adsorbed quantum dot stabilizing agent has a relatively high concentration locally in the quantum dots, which can protect the quantum dots from being etched by high temperature and water oxygen during the melt extrusion process, and significantly increase the service life of the quantum dots. On the other hand, since the quantum dot stabilizing agent is dispersed in the quantum dot functional microspheres, it is not necessary to add a large amount of additives or only a small amount of additives during the preparation of optical devices, and the mechanical properties of the optical devices can be better maintained. In addition, the quantum dot functional microspheres and the polymer derived from the blank plastic particles can also form a "sandbag structure", which improves the toughness of the optical devices.

[0074] Quantum dot functional microspheres will not melt at the selected process temperature due to their high degree of cross-linking. However, after melt co-extrusion, their shape may not be maintained and there may be slight deformations, but overall they are still spherical.

[0075] In some embodiments, the optical plate is a quantum dot diffusion plate. In some embodiments, the blank plastic particles are one or more of PS, PC, PP or PMMA. In some embodiments, the mixture further comprises other additives.

[0076] Hereinafter, the embodiments are described in more detail with reference to specific examples. However, they are illustrative examples of the present disclosure, and the present disclosure is not limited thereto.

[0077] Embodiment 1

[0078] PS quantum dot functional microspheres

[0079] Step 1: Mix 5 parts of quantum dot powder, 40 parts of the first monomer (styrene), 10 parts of the second monomer (acrylic acid), 1 part of the surfactant ligand (3-mercaptopropionate butanediol), 5 parts of the cross-linking agent (divinylbenzene), 0.5 parts of the emulsifier (polyvinyl pyrrolidone) and 0.05 parts of the initiator (azobisisobutyronitrile), and emulsify with a 200W probe ultrasound for 30 minutes to obtain an emulsion.

[0080] Step 2: The emulsion was heated to 55° C. and reacted for 24 h under stirring at 400 rpm to obtain the first quantum dot microspheres.

[0081] Step 3: Wash the first quantum dot microspheres twice with acetone to remove the emulsifier on the surface of the microspheres and the monomers that did not participate in the reaction; add them to ethanol / water / isopropanol (volume ratio of 2:1:1) and stir for 24 hours for etching, then wash them twice with ethanol and water respectively to obtain the second quantum dot microspheres, whose porosity is about 30% and the pore size is 20-100 nm.

[0082] Step 4: Add 20 parts of the second quantum dot microspheres into a toluene solution containing 100 parts of an auxiliary agent (2,6-di-tert-butyl-p-cresol: poly(4-hydroxyethyl-2,2,6,6-tetramethyl-1-piperidinethanol) ester = 1:1) and stir for 24 hours to obtain PS quantum dot functional microspheres (average particle size of 800 nm).

[0083] Step 5: The prepared PS quantum dot functional microspheres are melt-coextruded with PS matrix resin particles and diffusion masterbatch through an extruder, and the processing temperature is 180°C to 230°C, and then cooled to obtain a diffusion plate containing quantum dot microspheres.

[0084] Embodiment 2

[0085] PMMA quantum dot functional microspheres

[0086] Step 1: Mix 5 parts of quantum dot powder, 20 parts of the first monomer (methyl methacrylate), 20 parts of the first monomer (styrene), 10 parts of the second monomer (acrylic acid), 2 parts of the surfactant ligand (3-mercaptopropionate butanediol), 10 parts of the crosslinker (divinylbenzene), 1 part of the emulsifier (polyvinyl pyrrolidone) and 0.05 parts of the initiator (azobisisobutyronitrile), and emulsify with a 200W probe ultrasound for 20 minutes to obtain an emulsion.

[0087] Step 2: The emulsion was heated to 60° C. and reacted for 24 h under stirring at 400 rpm to obtain the first quantum dot microspheres.

[0088] Step 3: Wash the first quantum dot microspheres twice with acetone to remove the emulsifier on the surface of the microspheres and the monomers that have not participated in the reaction; add them to ethanol / water / isopropanol (volume ratio of 2:1:1) and stir for 24 hours, then wash them twice with ethanol and water respectively to obtain the second quantum dot microspheres, whose porosity is about 40% and the pore size is 15-60nm.

[0089] Step 4: Add 20 parts of quantum dot porous microspheres into a toluene solution containing 100 parts of an additive (2,6-di-tert-butyl-p-cresol: poly(4-hydroxyethyl-2,2,6,6-tetramethyl-1-piperidinethanol) ester = 1:1) and stir for 24 hours to obtain PMMA quantum dot functional microspheres (average particle size of 480 nm).

[0090] Step 5: The prepared PMMA quantum dot functional microspheres are melt-coextruded with PS matrix resin particles and diffusion masterbatch through an extruder at a processing temperature of 210°C to 240°C, and then cooled to obtain a diffusion plate containing quantum dot microspheres.

[0091] Embodiment 3

[0092] The difference from Example 1 is that the mass of the first monomer styrene in step 1 is 30 parts, the second monomer is changed to 20 parts of vinyl acetate, the reaction temperature in step 2 is changed to 65°C for 30 hours, and the etching solvent in step 3 is methanol / water / isopropanol (2:1:0.5). The second quantum dot microspheres obtained have a microsphere porosity of about 47% and a pore size of 200-300nm. The average particle size of the PS quantum dot functional microspheres obtained in step 4 is 1000nm.

[0093] Embodiment 4

[0094] The difference from Example 1 is that in step 1, the first monomer is changed to 45 parts of isobornene acrylate, the second monomer is 5 parts of acrylic acid, the reaction temperature in step 2 is changed to 60°C for 24 hours, and the etching solvent in step 3 is tetrahydrofuran / water / isopropanol (1:1:1). The second quantum dot microspheres obtained have a porosity of about 15% and a pore size of 10-80 nm. The average particle size of the PS quantum dot functional microspheres obtained in step 4 is 400 nm.

[0095] Embodiment 5

[0096] The difference from Example 1 is that in step 1, the mass of the first monomer styrene is 20 parts, isobornene acrylate is 15 parts, the second monomer is changed to 15 parts of vinyl acetate, the reaction temperature in step 2 is changed to 55°C for 48 hours, and the etching solvent in step 3 is the same as that in Example 4. The second quantum dot microspheres obtained have a porosity of about 22% and a pore size of 80-220nm. The average particle size of the PS quantum dot functional microspheres obtained in step 4 is 650nm.

[0097] Embodiment 6

[0098] The difference from Example 1 is that in step 1, the emulsifier is changed to 1 part of polyethylene glycol, the cross-linking agent divinylbenzene is 10 parts, the emulsification time is 25 minutes, the porosity of the second quantum dot microspheres obtained in step 3 is 28%, the pore size is 10-80nm, and the average particle size of the microspheres obtained in step 4 is 450nm.

[0099] Embodiment 7

[0100] The difference from Example 1 is that in step 1, the emulsifier is changed to 2 parts of polyethylene glycol, the cross-linking agent divinylbenzene is 15 parts, the emulsification time is 20 minutes, the reaction time in step 2 is 30 hours at 60°C, the porosity of the second microspheres obtained in step 3 is 20%, the pore size is 10~60nm, and the average particle size of the microspheres obtained in step 4 is 200nm.

[0101] Embodiment 8

[0102] The difference from Example 1 is that the auxiliary agent solution in step 4 is changed to 100 parts (4,4'-thiobis(6-tert-butyl-2-methylphenol:bis(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate=4:1).

[0103] Embodiment 9

[0104] The difference from the first embodiment is that the base resin in step 5 is changed to PC (polycarbonate). The processing temperature in step 5 is 220°C to 250°C.

[0105] Comparative Example 1

[0106] Step 1: Mix 5 parts of quantum dots, 50 parts of the first monomer (styrene), 1 part of the surfactant ligand (3-mercaptopropionate butylene glycol ester), 5 parts of the cross-linking agent (divinylbenzene), 0.5 parts of the emulsifier (polyvinyl pyrrolidone) and 0.05 parts of the initiator (azobisisobutyronitrile), and emulsify with 200W probe ultrasound for 30 minutes to obtain an emulsion.

[0107] Step 2: The emulsion was heated to 55° C. and reacted for 24 h under stirring at 400 rpm to obtain the first quantum dot microspheres.

[0108] Step 3: Wash the first quantum dot microspheres twice with acetone to remove the emulsifier on the surface of the microspheres and the monomers that have not participated in the reaction; wash them twice with ethanol for later use.

[0109] Step 4: Add 20 parts of quantum dot microspheres into a toluene solution containing 100 parts of (2,6-di-tert-butyl-p-cresol: poly(4-hydroxyethyl-2,2,6,6-tetramethyl-1-piperidinethanol) succinate = 1:1) and stir for 24 hours to obtain the target quantum dot microspheres.

[0110] Step 5: The prepared quantum dot microspheres are melt-coextruded with PS matrix resin particles and diffusion masterbatch through an extruder at a processing temperature of 180°C to 230°C, and a diffusion plate containing quantum dot microspheres is obtained after cooling.

[0111] Comparative Example 2

[0112] 100 parts of the prepared quantum dot powder, 100 parts of an antioxidant and a light stabilizer equivalent to the quantum dots, PS matrix resin particles, and diffusion masterbatch are melt-coextruded through an extruder at a processing temperature of 180°C to 230°C, and a diffusion plate containing quantum dot microspheres is obtained after cooling.

[0113] The quantum dot diffusion plates obtained in the examples and comparative examples were tested for fluorescence efficiency, and the results are shown in Table 1.

[0114] Table 1

[0115] Sample No. Fluorescence efficiency Comparative Example 1 20% Comparative Example 2 15% Embodiment 1 40% Embodiment 2 50% Embodiment 3 44% Embodiment 4 48% Embodiment 5 52% Embodiment 6 50% Embodiment 7 38% Embodiment 8 42% Embodiment 9 35%

[0116] The quantum dot diffusion plates obtained in Examples 1 and 2 and Comparative Example 1 were placed at 60°C, 90% relative humidity, and 20mW blue light (450nm) illumination. Samples were taken out at specific time intervals for fluorescence efficiency testing to obtain relative efficiency changes. The aging test results are shown in Figure 6 .

[0117] The method for testing the fluorescence efficiency of quantum dots is: using a 450nm blue LED as the backlight source, using an illuminometer to test the blue backlight spectrum and the spectrum through the quantum dot diffusion plate, and using the integral area of ​​the spectrum to calculate the fluorescence efficiency. The ratio of the quantum efficiency after a specific time to the initial efficiency changes according to this ratio to obtain the relative efficiency.

[0118] From Table 1, Table 2 and Figure 6 It can be seen that the quantum dot functional microspheres using the technical solution described in this application significantly improve the stability of the quantum dot diffusion plate, thereby maintaining a good fluorescence efficiency.

[0119] The quantum dot diffusion plates obtained in the embodiment and the comparative example were subjected to cantilever beam test according to the national standard GB / T1843-2008. The results are shown in Table 2. It can be seen that the impact resistance of the PS diffusion plate containing quantum dot microspheres is significantly improved. The results are shown in Table 2. It can be seen that the impact strength of the embodiment is significantly increased, which improves the toughness of the optical device.

[0120] Table 2

[0121] Sample No. <![CDATA[Impact strength (J / cm 2 ).]]> Comparative Example 2 8.0 Embodiment 1 12.5 Embodiment 2 12.0

[0122] Although some specific embodiments of the present disclosure have been described in detail by way of example, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present disclosure. The various embodiments disclosed herein may be combined in any manner without departing from the spirit and scope of the present disclosure. It should also be understood by those skilled in the art that various modifications may be made to the embodiments without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.

Claims

1. A method for preparing quantum dot functional microspheres, characterized in that: A composition containing quantum dots, surface active ligands, reactive monomers, crosslinking agents, emulsifiers and initiators is prepared, wherein the surface active ligands have at least two thiol groups; after stirring or ultrasonicating the composition to form an emulsion, the emulsion is heated or illuminated to cause a polymerization reaction in the emulsion; after the reaction is completed, a first quantum dot microsphere is separated to obtain the quantum dots, wherein the quantum dots participate in the polymerization reaction through the surface active ligands, so that the quantum dots and the polymer are chemically bonded; the first quantum dot microsphere is etched to obtain a second quantum dot microsphere having a porous structure on the surface; the second quantum dot microsphere is mixed with a dispersion containing a quantum dot stabilizing agent, so that at least part of the quantum dot stabilizing agent is adsorbed in the porous structure to obtain the quantum dot functional microsphere, wherein the reactive monomer includes a first monomer and a second monomer, the first monomer includes one or more of styrene, methyl methacrylate and isobornyl acrylate, and the second monomer includes one or more of acrylic acid and vinyl acetate; the quantum dot stabilizing agent includes an antioxidant; and the melting temperature of the quantum dot functional microsphere is greater than or equal to 300°C.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the first monomer to the second monomer is 1:1-50:

1.

3. The preparation method according to claim 1, characterized in that: The crosslinking agent is selected from one or more of divinyl benzene, diene phthalate, and ethylene glycol dimethyl diacrylate.

4. The preparation method according to claim 1, characterized in that: The emulsifier is selected from one or more of polyvinyl pyrrolidone, polyethylene glycol and polyvinyl alcohol.

5. The preparation method according to claim 1, characterized in that: The initiator is selected from oil-soluble free radical initiators.

6. The preparation method according to claim 1, characterized in that: The porosity of the second quantum dot microspheres is 10%-50%.

7. The preparation method according to claim 1, characterized in that: The average pore size of the porous structure of the second quantum dot microspheres is 10-500 nm.

8. The preparation method according to claim 1, characterized in that: The average particle size of the quantum dot functional microspheres is 50-5000nm.

9. The preparation method according to claim 1, characterized in that: The etching process includes soaking the first quantum dot microspheres in a solvent.

10. The preparation method according to claim 9, characterized in that: The solvent includes water, and one or more of methanol, ethanol, isopropanol, and tetrahydrofuran.

11. The preparation method according to claim 1, characterized in that: The etching treatment time is 12-24 hours.

12. The preparation method according to claim 1, characterized in that: After the etching treatment, separation and purification are performed to obtain the second quantum dot microspheres.

13. The preparation method according to claim 1, characterized in that: The quantum dots are 1-20 parts by mass, the reactive monomer is 50-100 parts by mass, the cross-linking agent is 1-10 parts by mass, the emulsifier is 0.5-2 parts by mass, and the initiator is 0.05-0.1 parts by mass.

14. The preparation method according to claim 1, characterized in that: The adsorption process includes: dispersing 20-40 parts by mass of the quantum dot stabilization aid in 200 parts by mass of liquid to obtain a dispersion containing the quantum dot stabilization aid, and then evenly mixing the dispersion and 10-50 parts by mass of the second quantum dot microspheres. The time to complete the adsorption process is 12-24 hours.

15. The preparation method according to claim 1, characterized in that: The quantum dot stabilization aid further includes one or more of a ligand aid, an anti-ultraviolet absorber and a light stabilizer.

16. A quantum dot functional microsphere prepared according to the preparation method according to any one of claims 1 to 15, characterized in that: The quantum dot functional microspheres include a polymer body, quantum dots dispersed in the polymer body and chemically bonded to the polymer body, the quantum dots have thiol ligands, the polymer body has a polymer cross-linked structure, the polymer body also has a porous structure, the quantum dot functional microspheres also include a quantum dot stabilization aid, the quantum dot stabilization aid is arranged in at least a portion of the porous structure and on the surface of at least a portion of the polymer body; the polymer of the quantum dot functional microspheres includes polystyrene, polymethyl methacrylate, or polyisobornene acrylate; the quantum dot stabilization aid includes an antioxidant, and the melting temperature of the quantum dot functional microspheres is greater than or equal to 300°C.

17. The quantum dot functional microsphere according to claim 16, characterized in that: The porosity of the quantum dot functional microspheres is 10%-50%.

18. An optical device, characterized in that: The optical device comprises the quantum dot functional microspheres according to any one of claims 16 to 17.

19. A method for preparing an optical device, characterized in that: A mixture comprising quantum dot functional microspheres and blank plastic particles is prepared, wherein the quantum dot functional microspheres are the quantum dot functional microspheres obtained according to any one of the preparation methods of claims 1 to 15 or the quantum dot functional microspheres according to any one of claims 16 to 17; the mixture is extruded by a melt co-extrusion process, during which the quantum dot functional microspheres are not melted; and the optical device is obtained after cooling, wherein the optical device is an optical film or an optical plate.

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