Quantum dot body, quantum dot composition, and wavelength conversion material and production method thereof

Abstract

This quantum dot body comprises a quantum dot that emits fluorescent light by the action of excitation light. The quantum dot body is characterized in that the quantum dot comprises a semiconductor nanoparticle core and a semiconductor nanoparticle shell that coats the semiconductor nanoparticle core, the surface of the quantum dot is coated with a metal oxide, and the surface of the metal oxide is modified with a phosphonic acid derivative. The quantum dot body is also characterized by having a polymer coating layer on the outermost surface thereof, wherein the polymer coating layer is formed by bonding a reactive substituent in the phosphonic acid derivative to a reactive substituent in a polymer. As a result, there are provided: a quantum dot body which is further improved in stability while maintaining the fluorescence emission characteristics of a quantum dot, and is also further improved in compatibility with a highly polar solvent or a photosensitive resin composition; a quantum dot composition in which the quantum dot body is dispersed in a resin material; a wavelength conversion material obtained by curing the quantum dot composition; and a method for producing the wavelength conversion material.

Description

Quantum dot body, quantum dot composition, wavelength conversion material, and method for producing the same

[0001] The present invention relates to a quantum dot body, a quantum dot composition, a wavelength converting material, and a method for producing the same.

[0002] Quantum dots, which are semiconductor particles with nanometer-sized particle diameters, have discrete energy levels due to the confinement of excitons generated by light absorption in nanometer-sized spaces, and their band gaps depend on the particle diameter. As a result, quantum dots have highly efficient fluorescence emission and sharp emission spectra. Furthermore, because the band gap changes depending on the particle diameter, quantum dots have the advantage of being able to control the emission wavelength, making them promising for use as wavelength conversion materials in solid-state lighting and displays (Patent Document 1).

[0003] Quantum dots containing Cd or Pb are examples of quantum dots that exhibit excellent fluorescence emission properties. However, because Cd and Pb are highly toxic to the human body and the environment, restrictions on their use are being considered around the world, including the European Union's RoHS Directive. Therefore, quantum dots that do not contain these toxic elements are being investigated.

[0004] Furthermore, as a mounting method using quantum dots as a wavelength conversion material, a method has been proposed in which quantum dots are dispersed in a resin material, and a resin composition containing the quantum dots is laminated onto a transparent film, thereby incorporating the resulting material into a backlight unit as a wavelength conversion film (Patent Document 2).

[0005] However, quantum dots are prone to instability due to their small nanometer-sized particle diameter, large specific surface area, high surface energy, and surface activity. Therefore, surface defects are likely to occur on the quantum dot surface due to dangling bonds and oxidation reactions, which cause deterioration of their fluorescence emission properties. Currently available quantum dots have such stability issues, and are known to cause deterioration of their emission properties due to heat, humidity, photoexcitation, and other factors.

[0006] Japanese Patent Application Laid-Open No. 2012-022028 Japanese Patent Application Laid-Open No. 2013-544018 U.S. Patent No. 9708532 Japanese Patent Application Laid-Open No. 2016-111292 Japanese Patent Application Laid-Open No. 2019-536653

[0007] Various studies have been conducted on the stabilization of wavelength conversion materials containing quantum dots.

[0008] One example is gas barrier sealing. Stability is improved by forming an inner layer in which quantum dots are dispersed in an amphiphilic polymer or a compatible polymer, and then dispersing them in another resin layer with low gas permeability. Patent Document 3 discloses a method in which quantum dots (hereinafter also referred to as QDs) are dispersed in a hydrophobic resin layer to form polymer beads, and then the polymer beads are surface-modified to disperse in a hydrophilic polymer. Because hydrophilic polymers tend to have higher gas barrier properties than hydrophobic polymers, QDs are dispersed in such a two-layer or multi-layer structure. However, because the gas barrier properties are insufficient for use in applications that may be subject to high-temperature, high-humidity environments, such as those used in liquid crystal display units, a method is used in which the QD film is sandwiched between gas barrier films to remove the effects of oxygen and water vapor.

[0009] Various methods for producing polymer beads have also been investigated. Patent Document 4 discloses a method in which QD-containing polymer beads are prepared using a polysiloxane having an amino group and a polymerizable functional group, and then a polymer having another polymerizable functional group is mixed with the resulting mixture, emulsified, and then cured. This method uses a polymer containing ligands that coordinate to the QD surface to increase adhesion to the QDs, thereby increasing the concentration of QDs contained within the polymer beads and improving stability. However, this method still provides insufficient stability, and the beads are typically packaged by sandwiching them between barrier films.

[0010] The use of barrier films not only increases costs, but also inevitably increases thickness. Currently, there is a demand for thinner LCD displays, which requires reducing the thickness of wavelength conversion materials, leading to a demand for improved stability without barrier films. Furthermore, when considering color filter applications, patterning is required, making it impractical to provide a protective layer such as a barrier film, and the stability of the quantum dots themselves is essential.

[0011] Patent Document 5 has been published as a study on improving heat resistance and moisture resistance without using a barrier film. In this method, a silazane coating treatment is further performed on the multilayer resin composition using the polymer bead structure of Patent Document 1, thereby improving stability. However, this method has the problem of a decrease in quantum yield when the silazane coating is photocured by irradiation with short ultraviolet light (170 nm).

[0012] Furthermore, when applying quantum dots to color filters, it is important to create a surface state of quantum dots that is suitable for the patterning method. Currently, color filters are manufactured using a photolithography method in which a pigment-containing photosensitive resin composition is applied to a glass substrate, the solvent is dried, and the composition is exposed to UV light through a mask, and uncured portions are removed by alkaline development to form color patterns. This process is repeated to form blue, red, and green patterns. However, photolithography has many problems, such as the uncured portions being wasted, resulting in significant raw material loss, and the process is complicated and requires expensive equipment.

[0013] For this reason, inkjet methods have been investigated in recent years. Inkjet methods are cost-competitive, as they eliminate raw material waste and allow for larger sizes and larger areas to be produced without the need for expensive equipment. However, the technology to create fine nozzles is difficult, and as nozzles become smaller, problems arise such as clogging and unstable ejection. Therefore, both photolithography, which has a proven track record in miniaturization, and inkjet methods, which are cost-competitive, are being investigated.

[0014] However, creating a resin composition containing quantum dots at a high concentration and high dispersion is a challenge for both photolithography and inkjet printing. Resin compositions, with some exceptions, are dispersed in polar solvents such as PGMEA and PGME. Because quantum dots are essentially hydrophobic and difficult to disperse in these solvents and resin materials, they tend to aggregate, making it difficult to create a photosensitive resin composition containing quantum dots at a high concentration and high dispersion. While the addition of a dispersant has been considered as a solution, it has presented problems such as reducing the quantum dot content and altering the properties of the resin after curing.

[0015] The present invention has been made to solve the above problems, and aims to provide a quantum dot body that maintains the fluorescent emission properties of quantum dots while further improving stability and compatibility with highly polar solvents and photosensitive resin compositions, a quantum dot composition in which the quantum dot body is dispersed in a resin material, and a wavelength conversion material obtained by curing the quantum dot composition, as well as a method for producing the same.

[0016] The present invention has been made to achieve the above-mentioned object, and provides a quantum dot body containing quantum dots that emit fluorescence when exposed to excitation light, wherein the quantum dots are composed of a semiconductor nanoparticle core and a semiconductor nanoparticle shell that covers the semiconductor nanoparticle core, the quantum dot surface is coated with a metal oxide, the metal oxide surface is modified with a phosphonic acid derivative, and the quantum dot body has, on its outermost surface, a polymer coating layer formed by bonding between a reactive substituent of the phosphonic acid derivative and a reactive substituent of a polymer.

[0017] Such quantum dot bodies maintain the fluorescent emission properties of the quantum dots, while improving stability and compatibility with highly polar solvents and photosensitive resin compositions.

[0018] In this case, the reactive substituent of the phosphonic acid derivative is preferably one or more of a vinyl group, an acrylic group, a methacrylic group, a hydroxyl group, a phenolic hydroxyl group, an epoxy group, and a glycidyl group.

[0019] This makes it more favorable for forming a polymer coating layer.

[0020] In this case, the reactive substituent of the polymer is preferably one or more of a vinyl group, an acrylic group, a methacrylic group, a hydroxyl group, a phenolic hydroxyl group, an epoxy group, and a glycidyl group.

[0021] This makes it more suitable for forming a polymer coating layer.

[0022] In this case, the polymer coating layer preferably contains at least one skeletal structure identical to the skeletal structure of the main chain of the polymer, and the skeletal structure is preferably a skeletal structure derived from acrylic acid, methacrylic acid, an acrylic acid ester, a methacrylic acid ester, a skeletal structure having glycidyl (meth)acrylate as a repeating unit, a siloxane skeleton, a urethane skeleton, a silphenylene skeleton, a norbornene skeleton, a fluorene skeleton, or an isocyanurate skeleton.

[0023] This allows the introduction of functional groups with large steric hindrance into the polymer coating layer, improving the dispersibility in resin materials containing polymers with the same skeletal structure.

[0024] In this case, a quantum dot composition is provided in which the quantum dot bodies are dispersed in a resin material containing at least one skeletal structure identical to that of the polymer coating layer.

[0025] In such a quantum dot composition, the quantum dots are dispersed in the resin material at a higher concentration with fewer aggregates.

[0026] In this case, a wavelength converting material containing a cured product of the quantum dot composition is provided.

[0027] Such a wavelength converting material maintains the fluorescent emission properties of the quantum dots, has improved stability, and provides a highly concentrated dispersion of quantum dots with improved compatibility with highly polar solvents and photosensitive resin compositions.

[0028] The present invention also provides a method for producing the quantum dot body, which includes the steps of: producing quantum dots each consisting of a semiconductor nanoparticle core and a semiconductor nanoparticle shell covering the semiconductor nanoparticle core; coating the surface of the quantum dot with a metal oxide; modifying the metal oxide surface with a phosphonic acid derivative; and polymerizing a reactive substituent carried by the phosphonic acid derivative with a reactive substituent carried by a polymer by light or heat to form a polymer coating layer.

[0029] Such a method for producing a quantum dot body makes it possible to produce the above quantum dot body.

[0030] In this case, the present invention provides a method for producing a quantum dot composition, which includes a step of dispersing the quantum dot body produced by the method for producing the quantum dot body in a resin material containing at least one skeletal structure that is the same as the skeletal structure of the main chain of the polymer contained in the polymer coating layer.

[0031] Such a method for producing a quantum dot composition makes it possible to produce the above quantum dot composition.

[0032] At this time, there is provided a method for producing a wavelength converting material, which includes a step of curing the quantum dot composition produced by the method for producing a quantum dot composition.

[0033] Such a method for producing a wavelength converting material makes it possible to produce the above wavelength converting material.

[0034] As described above, the quantum dot body of the present invention maintains the fluorescent emission properties of the quantum dots while improving stability and compatibility with highly polar solvents and photosensitive resin compositions. This makes it possible to provide a quantum dot composition in which the quantum dots are dispersed in a resin material at a higher concentration with fewer aggregates, and a wavelength converting material obtained by curing the quantum dot composition.

[0035] 1 is a schematic cross-sectional view showing an example of a quantum dot body of the present invention.

[0036] As a result of extensive research into the above-mentioned problems, it was found that quantum dots consisting of a semiconductor nanoparticle core and a semiconductor nanoparticle shell covering the semiconductor nanoparticle core can be coated with a metal oxide, the surface of the metal oxide modified with a phosphonic acid derivative, and the reactive substituent of the phosphonic acid derivative bonded to the reactive substituent of a polymer, thereby forming a quantum dot body with a polymer coating layer on the outermost surface, thereby improving the stability of the quantum dots.

[0037] Furthermore, it was found that compatibility with resin materials containing polymers can be improved by introducing into the polymer coating layer a skeletal structure that is the same as the skeletal structure of the monomer or polymer of the resin material. This makes it possible to disperse quantum dots in the resin material at a high concentration with fewer aggregates, and it was revealed that wavelength conversion materials can be produced in which quantum dots are dispersed at a high concentration while maintaining high luminescence properties even after curing.

[0038] As a result, it was found that in a reliability test at 85°C and 85% RH without a barrier film, the decrease rate of the internal quantum yield during 500 hours of treatment could be suppressed to within 10%, and stability could be improved.

[0039] That is, the present invention provides a quantum dot body including quantum dots that emit fluorescence when exposed to excitation light, the quantum dots consisting of a semiconductor nanoparticle core and a semiconductor nanoparticle shell covering the semiconductor nanoparticle core, the quantum dot surfaces being coated with a metal oxide, the metal oxide surface being modified with a phosphonic acid derivative, and the quantum dot body having a polymer coating layer on its outermost surface formed by bonding between a reactive substituent of the phosphonic acid derivative and a reactive substituent of a polymer; a quantum dot composition including the quantum dot body dispersed in a resin material containing at least one skeletal structure identical to that of the polymer coating layer; and a wavelength converting material including a cured product of the quantum dot composition and a method for producing the same.

[0040] Hereinafter, embodiments of the present invention will be described. However, in the present invention, the quantum dots, quantum dot bodies, metal oxides, phosphonic acid derivatives, compositions and types of polymer coating layers, and manufacturing methods are not limited to the following embodiments.

[0041] [Quantum dot body] A quantum dot body according to an embodiment of the present invention will be described below with reference to Fig. 1. As shown in Fig. 1, the quantum dot body 1 of the present invention is composed of a quantum dot 2 that emits fluorescence when exposed to excitation light, the quantum dot 2 being composed of a semiconductor nanoparticle core and a semiconductor nanoparticle shell that covers the semiconductor nanoparticle core, a metal oxide layer 3 that covers the surface of the quantum dot 2, a modification layer of a phosphonic acid derivative 4 that modifies the surface of the metal oxide layer 3, and a polymer coating layer 5 that is formed on the outermost surface by bonding of a reactive substituent of the phosphonic acid derivative 4 with a reactive substituent of a polymer.

[0042] Such a quantum dot body 1 suppresses external oxidation reactions on the surface of the quantum dots 2, thereby suppressing deterioration in the fluorescence emission efficiency of the quantum dots, improving stability, and further improving compatibility with highly polar solvents and photosensitive resin compositions.

[0043] (Quantum Dots) The structure of the quantum dots in the present invention is not particularly limited as long as they consist of a semiconductor nanoparticle core and a semiconductor nanoparticle shell. Such quantum dots have excellent fluorescence emission properties and stability. For example, in semiconductor nanoparticles with a core / shell structure in which a nano-sized semiconductor particle serves as the core and a semiconductor particle with a larger band gap and lower lattice mismatch than the core serves as the shell, excitons generated in the shell are confined inside the core particle, thereby further improving fluorescence emission efficiency, and further improving stability because the core surface is covered by the shell.

[0044] Furthermore, the quantum dots may be composed of a semiconductor nanoparticle core and a plurality of semiconductor nanoparticle shells covering the semiconductor nanoparticle core. With such a quantum dot composition, the deterioration of the fluorescence emission efficiency is further suppressed.

[0045] The material for the semiconductor nanoparticle core of the core / shell semiconductor nanoparticles is preferably one that does not contain the elements Cd or Pb from the viewpoint of toxicity, and for example, a material selected from the group consisting of II-VI compounds, III-V compounds, I-III-VI compounds, II-IV-V compounds, and alloys or mixed crystals thereof can be used.

[0046] Specifically, the materials for the semiconductor nanoparticle core include ZnS, ZnSe, ZnTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, and AgGaS. ２ , AgInS ２ , AgGaSe ２ , AgInSe ２ , CuGaS ２ , CuGaSe ２ , CuInS ２ , CuInSe ２ , ZnSiP ２ , and ZnGeP ２ Among these materials, ZnSe, ZnTe, and InP are particularly preferable in terms of fluorescent emission characteristics and stability.

[0047] Furthermore, the surface of the core particle of the core / shell semiconductor nanoparticles is preferably passivated with an inorganic compound, which inactivates defects on the surface of the core particle, improves the fluorescence emission efficiency, and suppresses deterioration of the fluorescence emission efficiency over time.

[0048] The inorganic compound for passivation is not particularly limited, but examples thereof include metal halides. From the viewpoint of improving the fluorescent light emission efficiency, GaCl ３ , GaI ３ , GaBr ３ , ZnCl ２ , ZnBr ２ , ZnI ２ , InCl ３ , InBr ３ , InI ３ , AgCl, AgBr, AgI, KCl, KBr, KI, NaCl, NaBr, NaI, MgCl ２ , MgBr２ , MgI ２ , CaCl ２ , CaBr ２ , CaI ２ , MnCl ２ , MnBr ２ , MnI ２ , FeCl ２ , FeBr ２ , FeI ２ , CuCl ２ , CuBr ２ , CuI ２ , ZrCl ４ , ZrBr ４ , ZrI ４ , GeCl ４ , GeBr ４ , GeI ４ Particularly preferred is at least one compound selected from

[0049] The material for the semiconductor nanoparticle shell is preferably one that does not contain elements such as Cd or Pb from the viewpoint of toxicity, but is also preferably one that has a large band gap and low lattice mismatch with respect to the core material, and can be selected from the group consisting of alloys and mixed crystals of II-VI and III-V group compounds.

[0050] Specific shell materials include those selected from the group consisting of ZnS, ZnSe, ZnTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, and InSb, either singly or in combination, or as mixed crystals. Of these materials, ZnSe and ZnS are particularly preferred in terms of improved fluorescence efficiency and stability.

[0051] (Metal Oxide) The quantum dots of the present invention have their surfaces coated with a metal oxide, which is thought to prevent oxygen and water in the atmosphere from coming into direct contact with the quantum dot surface and suppress oxidation reactions, thereby suppressing deterioration of the fluorescence emission efficiency.

[0052] In the present invention, the "metal oxide coating" on the quantum dot surface may be in the form of a partial or complete coating, as long as the deterioration of the fluorescence emission efficiency over time is suppressed. The coating layer may be a uniform coating layer such as a core / shell structure, or a non-uniform coating layer, or may have a structure in which multiple semiconductor nanoparticles are coated with a metal oxide. The thickness of the metal oxide coating layer is not particularly limited, but is preferably 200 nm or less from the viewpoint of light transmittance.

[0053] In the present invention, the type of metal oxide is not particularly limited, but TiO ２ , ZnO, Al ２ O ３ , SiO ２ , ZrO ２ , Fe ２ O ３ , MgO, Y ２ O ３ , HfO ２ , CeO ２ , In ２ O ３ , SnO ２ , W.O. ３ , CrO ３ , Ta ２ O ３ , BaTiO ３ , V ２ O ５ , NiO, NbO, Cu ２ O, CuO, MoO ３ In order to improve the stability of the quantum dots, at least one compound selected from the group consisting of TiO ２ , Al ２ O ３ , SiO ２ , ZrO ２ is more preferred.

[0054] (Phosphonic Acid Derivative) As described above, in this embodiment, by providing a metal oxide that coats the surface of the quantum dots, water and oxygen in the atmosphere are prevented from coming into direct contact with the quantum dot surface, and deterioration of the fluorescence emission efficiency is suppressed.

[0055] However, after the metal oxide is formed, many hydroxyl groups remain on the outer surface of the metal oxide. When these hydroxyl groups come into contact with water in the atmosphere, hydrogen bonds form on the oxide surface, forming a thin layer of adsorbed water on the nanometer order, known as a hydration layer.

[0056] When the above-mentioned composition in which the surface of quantum dots is coated with a metal oxide is used as a wavelength converting material, the adsorbed water gradually penetrates to the surface of the quantum dots inside due to the long-term exposure to external stimuli such as light and heat, and surface oxidation is promoted, which is thought to cause a deterioration in the fluorescence emission efficiency over long-term use. In order to suppress this deterioration in the fluorescence emission efficiency, it is preferable to remove as many hydroxyl groups as possible from the surface of the metal oxide.

[0057] However, it is difficult to completely remove the hydroxyl groups on the surface of this metal oxide by heating. Heating at approximately 500°C or higher is necessary, although this depends on the composition of the metal oxide. Heating at this temperature range causes changes in the shape of the quantum dots and a deterioration or deactivation of their luminescence efficiency, making it difficult to remove the hydroxyl groups by heating alone.

[0058] Therefore, a modifying agent useful in the present invention, which is necessary for removing hydroxyl groups on the surface of a metal oxide, is a phosphonic acid derivative, and the quantum dot body in the present invention is composed of the quantum dot, a metal oxide that coats the surface of the quantum dot, at least a phosphonic acid derivative that modifies the surface of the metal oxide, and a polymer coating layer, which will be described later.

[0059] In this embodiment, "modification" refers to a state in which phosphonic acid is attached to at least the surface of a metal oxide. The attachment of a phosphonic acid derivative to a surface by "modification" includes partial and full-surface attachment, and refers to a state in which the phosphonic acid derivative is attached to at least a part of the surface.

[0060] The term "adhesion" in the above context may refer to physical adsorption or chemical bonding, and may broadly refer to, for example, covalent bonding, ionic bonding, or hydrogen bonding, or may be a combination of these. Furthermore, as an example, quantum dots, metal oxides, and quantum dot bodies containing phosphonic acid derivatives that modify the metal oxide surface may be in a state in which the organic ligands attached to the metal oxide surface during synthesis and the phosphonic acid derivatives coexist.

[0061] The structure of the phosphonic acid derivative is preferably one represented by at least one of the following formulae (I), (II), (III), and (IV). (In formula (I), R １ is a monovalent organic group having one or more carbon atoms.

[0062] (In formula (II), R ２ is a divalent organic group having one or more carbon atoms.

[0063] (In formula (III), R ３ is a trivalent organic group having one or more carbon atoms.

[0064] (In formula (IV), R ４ is a divalent organic group having one or more carbon atoms.

[0065] In certain embodiments of the compounds of formulas (I) to (IV) of the present invention, the reactive substituents of the metal oxide layer covering the quantum dot surface and the phosphonic acid derivative modifying the surface of the metal oxide layer are bonded to the reactive substituents of the polymer, thereby forming a polymer coating layer on the outermost surface. １ ~R ４ It is preferable that the reactive substituent of the hydroxyl group be one or more of a vinyl group, an acrylic group, a methacrylic group, a hydroxyl group, a phenolic hydroxyl group, an epoxy group, and a glycidyl group, which allows the polymer coating layer to be formed more efficiently.

[0066] (Polymer Coating Layer) The quantum dot body of the present invention has a polymer coating layer on the outermost surface by bonding the reactive substituent of the phosphonic acid derivative to the reactive substituent of the polymer.

[0067] The polymer for forming the polymer coating layer is not particularly limited, but a compound having one or more of the following reactive substituents is preferred, which allows the polymer coating layer to be formed more efficiently: a vinyl group, an acrylic group, a methacrylic group, a hydroxyl group, a phenolic hydroxyl group, an epoxy group, and a glycidyl group.

[0068] Furthermore, the polymer coating layer contains at least one skeletal structure that is the same as the skeletal structure of the main chain of the polymer, and the skeletal structure is preferably a skeletal structure derived from acrylic acid, methacrylic acid, an acrylic acid ester, a methacrylic acid ester, a skeletal structure having glycidyl (meth)acrylate as a repeating unit, a siloxane skeleton, a urethane skeleton, a silphenylene skeleton, a norbornene skeleton, a fluorene skeleton, or a compound having an isocyanurate skeleton, and the type, number, ratio, etc. of the introduced structures may be appropriately adjusted so as to prevent aggregation, etc., from occurring when the resin composition and quantum dots are mixed.

[0069] This allows the introduction of functional groups with large steric hindrance into the polymer coating layer, improving the dispersibility in resin materials containing polymers with the same skeletal structure.

[0070] The polymer coating layer is not particularly limited, but is preferably a compound having a siloxane bond from the viewpoint of improving stability.

[0071] [Quantum dot composition] The quantum dot composition of the present invention is a composition in which the quantum dot bodies are dispersed in a resin material containing at least one of the same skeletal structures as the polymer coating layer. The resin material may contain a polymer that is a base polymer and a polymerization initiator, and may also contain an organic solvent, a polymerizable crosslinking agent, a photoacid generator, an antioxidant, a light scattering agent, etc.

[0072] The polymer is selected from polymers derived from acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters, copolymers combining multiple polymers, and polymers having a skeletal structure with glycidyl (meth)acrylate as a repeating unit, a siloxane skeleton, a urethane skeleton, a silphenylene skeleton, a norbornene skeleton, a fluorene skeleton, or an isocyanurate skeleton, depending on the intended use.

[0073] Examples of suitable polymers include acrylic resins, alkyd resins, melamine resins, epoxy resins, silicone resins, polyvinyl alcohol, polyvinylpyrrolidone, polyamides, polyamide-imides, polyimides, and other polyimide precursors and their esterification products, as well as reaction products of tetracarboxylic dianhydrides and diamines. Furthermore, polymerizable substituents are introduced into these polymers, enabling them to be cured when used in combination with a polymerization initiator. Examples of radically polymerizable substituents include vinyl groups, acrylic groups, methacrylic groups, and thiol groups, all of which are suitable for use. Examples of cationically polymerizable substituents include hydroxyl groups, phenolic hydroxyl groups, epoxy groups, glycidyl groups, oxetanyl groups, and isocyanate groups, all of which are suitable for use. Furthermore, a carboxyl group may be introduced to impart alkaline developability.

[0074] It is also preferable that the quantum dot composition of the present invention contains a polymerization initiator. The polymerization initiator may be a thermal or photopolymerization initiator, either of which can be suitably used depending on the base polymer. Examples of photoradical polymerization initiators include those in the Irgacure (registered trademark) series commercially available from BASF, such as Irgacure 290, Irgacure 651, Irgacure 754, Irgacure 184, Irgacure 2959, Irgacure 907, Irgacure 369, Irgacure 379, Irgacure 819, and Irgacure 1173. Examples of the Darocure (registered trademark) series include TPO and Darocure 1173. Other known thermal radical polymerization initiators and photocationic polymerization initiators may also be included.

[0075] The content of the polymerization initiator is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 5 parts by weight, per 100 parts by weight of the polymer to be added. The quantum dot composition of the present invention may contain an organic solvent to improve its coatability. From the viewpoint of compatibility with the quantum dots, organic solvents are preferred, such as ketones, alkylene glycol ethers, alcohols, and aromatic compounds. Examples of suitable solvents include acetone, methyl ethyl ketone, and cyclohexanone from the ketone group; and methyl cellosolve (ethylene glycol monomethyl ether), butyl cellosolve (ethylene glycol monobutyl ether), methyl cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, ethylene glycol monopropyl ether, ethylene glycol monohexyl ether, ethylene glycol dimethyl ether, diethylene glycol ethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, and diethylene glycol methyl ether acetate. Suitable solvents include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, 3-methyl-3-methoxybutanol, and aromatic solvents such as benzene, toluene, and xylene. The quantum dot composition of the present invention may also contain a polymerizable crosslinker, a photoacid generator, an antioxidant, a light scattering agent, and the like, without any particular limitation, as long as the polymerizable coating properties are not affected.

[0076] Such a quantum dot composition has improved dispersibility in a resin material containing a polymer having at least one skeletal structure identical to that of the polymer coating layer, and the quantum dots are dispersed at a high concentration.

[0077] [Wavelength converting material] The present invention also provides a wavelength converting material containing a cured product of the quantum dot composition. The wavelength converting material may be used as is or may be processed. One form of the wavelength converting material is a wavelength conversion film in which the quantum dot composition is dispersed in a resin and processed into a sheet and then cured.

[0078] In such a wavelength conversion material, the quantum dots are dispersed in the resin material at a high concentration without agglomerates while maintaining high light-emitting properties, resulting in improved reliability.

[0079] [Method for manufacturing quantum dot bodies] Next, a method for manufacturing quantum dot bodies of the present invention will be described. The quantum dot bodies of the present invention are manufactured by the steps of: manufacturing quantum dots each consisting of a semiconductor nanoparticle core and a semiconductor nanoparticle shell covering the semiconductor nanoparticle core; coating the surface of the quantum dot with a metal oxide; modifying the metal oxide surface with a phosphonic acid derivative; and polymerizing the reactive substituent of the phosphonic acid derivative with the reactive substituent of the polymer by light or heat to form a polymer coating layer.

[0080] (Step of Producing Quantum Dots) There are various methods for producing the core and shell of semiconductor nanoparticles, such as a liquid phase method or a gas phase method, but the present invention is not particularly limited to these. From the viewpoint of obtaining high fluorescence emission efficiency, it is preferable to use semiconductor nanoparticles obtained by a hot soap method or a hot injection method, in which precursor species are reacted at high temperature in a high-boiling-point nonpolar solvent.

[0081] (Step of Coating the Surface of Quantum Dots with Metal Oxide) The method for forming the metal oxide coating layer is not particularly limited, but from the viewpoint of selectively promoting the reaction on the surface of the quantum dots, a method of reacting a metal oxide precursor in a liquid phase is preferred.

[0082] In the present invention, as an example, a method for forming an oxide coating layer using microwave treatment is exemplified. By using microwaves, the metal oxide precursor is directly heated from the inside, allowing the reaction to proceed selectively in a shorter time, thereby forming a metal oxide layer on the quantum dot surface.

[0083] Here, "microwaves" generally refer to electromagnetic waves having a frequency of 300 MHz to 3 THz. Examples of microwave irradiation methods include, but are not limited to, a method using flexi WAVE manufactured by Milestone General.

[0084] In this case, the coating step is preferably carried out in the presence of quantum dots and a metal oxide precursor, and the metal oxide precursor in the presence of the quantum dots is irradiated with microwaves to coat the surfaces of the semiconductor nanoparticles with the metal oxide, thereby efficiently forming a metal oxide coating layer and suppressing deterioration of the fluorescence emission efficiency.

[0085] In this case, it is preferable to select one or more of polar solvents, non-polar solvents, and ionic liquids as the dispersion medium for the quantum dots and metal oxide precursor, and form the coating layer in that solvent.

[0086] The solvent used in the coating step is preferably one or more of toluene, hexane, cyclohexane, benzene, and diethyl ether, as these non-polar solvents can further improve the dispersibility of semiconductor nanoparticles (quantum dots).

[0087] If the solvent is a non-polar solvent, a microwave-absorbing heating element called Weflon, a type of PTFE resin containing a carbon component manufactured by Milestone, may optionally be used during the coating process.

[0088] The precursor of the metal oxide is not particularly limited, but it is preferable to use one or more selected from metal alkoxides, metal halides, and metal complexes. From the viewpoint of stability, silicon alkoxides, aluminum alkoxides, zirconium alkoxides, and titanium alkoxides are particularly preferable as the metal oxide precursor.

[0089] In this case, it is preferable to use a catalyst to promote the reaction of the metal oxide precursor during the coating step. In particular, when a metal alkoxide is used, it is desirable to use a catalyst to promote the sol-gel reaction. Examples of the catalyst include an acidic aqueous solution and a basic aqueous solution, and a basic aqueous solution is particularly preferable from the viewpoint of the film thickness of the coating layer.

[0090] Furthermore, a surfactant may be added during the coating step from the viewpoint of dispersibility of the metal oxide precursor. The surfactant is not particularly limited, but examples thereof include quaternary ammonium salts such as cetyltrimethylammonium bromide, which are cationic surfactants; carboxylates and sulfonates, which are anionic surfactants; and polyethylene alkyl ethers and cetyltrimethylammonium bromide, which are nonionic surfactants. Cationic surfactants are particularly preferred from the viewpoint of dispersibility of the metal oxide precursor.

[0091] It is also preferable to carry out the coating step in the presence of alcohol. If coating is carried out in the presence of alcohol, the dispersibility of the metal oxide precursor is better. Furthermore, when a surfactant is added, dissolving it in a polar solvent such as alcohol can further improve the dispersibility.

[0092] In this case, the reaction temperature in the microwave irradiation treatment varies depending on the solvent, but is preferably 40 to 200°C, more preferably 50 to 110°C, from the viewpoint of preventing deterioration of the fluorescence emission efficiency.

[0093] Although microwave treatment is used as an example of the metal oxide coating step in this embodiment, there are no particular limitations on the method as long as the quantum dot surfaces are "coated" with a metal oxide layer.

[0094] (Step of modifying the metal oxide surface with a phosphonic acid derivative) The phosphonic acid derivative is a stable compound and does not self-polymerize, so it does not precipitate in the bulk and selectively adheres to and modifies the metal oxide surface or the quantum dot surface.

[0095] In particular, on the surface of a metal oxide, heat treatment at several tens of degrees causes a dehydration condensation reaction between the hydroxyl groups of the metal oxide and the phosphonic acid derivative, thereby removing the hydroxyl groups on the surface of the metal oxide and modifying the metal oxide surface with the phosphonic acid derivative.

[0096] Furthermore, the OH group of the phosphonic acid derivative is bonded to the dangling oxygen bond on the surface of the metal oxide. ＋ Since protons are continuously donated, the above dehydration condensation reaction is repeated, and the surface of the metal oxide is densely modified with the phosphonic acid derivative.

[0097] The heating temperature when modifying the quantum dot surface or metal oxide surface with the phosphonic acid derivative is not particularly limited, but for efficient modification, the heating temperature is preferably in the range of 50 to 300° C., more preferably in the range of 80 to 200° C. Within such a range, the quantum dot surface can be modified more efficiently.

[0098] The amount of the phosphonic acid derivative added as the surface modifier is not particularly limited as long as it is within the range in which the phosphonic acid derivative modifies the quantum dot surface or the metal oxide surface; for example, an amount of 50 wt % or less relative to the solid weight of the quantum dots is preferable because it can effectively suppress aggregation of the quantum dots and precipitation of the phosphonic acid derivative; and an amount of 0.01 wt % or more allows the effect of modification on the quantum dot surface or the metal oxide surface to be sufficiently and stably exerted; therefore, the added weight of the surface modifier is preferably in the range of 0.01 to 50 wt % relative to the solid weight of the quantum dots, and more preferably in the range of 0.05 to 40 wt %.

[0099] (Step of Forming Polymer Coating Layer) The reactive substituent of the phosphonic acid derivative that has modified the metal oxide surface and the reactive substituent of the polymer are polymerized by light or heat to form a polymer coating layer on the outermost surface.

[0100] The polymer for forming the polymer coating layer is not particularly limited, but it is preferable to use a compound having one or more of the following reactive substituents: a vinyl group, an acrylic group, a methacrylic group, a hydroxyl group, a phenolic hydroxyl group, an epoxy group, and a glycidyl group.

[0101] The polymer coating layer also contains at least one skeletal structure that is the same as the skeletal structure of the main chain of the polymer. Examples of the skeletal structure include a skeletal structure derived from acrylic acid, methacrylic acid, an acrylic acid ester, or a methacrylic acid ester, a skeletal structure having glycidyl (meth)acrylate as a repeating unit, a siloxane skeleton, a urethane skeleton, a silphenylene skeleton, a norbornene skeleton, a fluorene skeleton, or a compound having an isocyanurate skeleton. The type, number, and ratio of the skeletal structures to be introduced may be appropriately adjusted so as to prevent aggregation, etc., when the resin composition and quantum dots are mixed.

[0102] Such a method for producing a quantum dot body makes it possible to produce a quantum dot body that maintains the fluorescent emission properties of the quantum dots, has improved stability, and has improved compatibility with highly polar solvents and photosensitive resin compositions.

[0103] [Method for producing quantum dot composition] Next, a method for producing a quantum dot composition will be described, which comprises dispersing the quantum dot bodies produced by the above-described method for producing quantum dot bodies in a resin material containing at least one skeletal structure identical to the skeletal structure of the main chain of the polymer contained in the polymer coating layer. The resin material can be a polymer base polymer and a polymerization initiator, and may also contain an organic solvent, a polymerizable crosslinking agent, a photoacid generator, an antioxidant, a light scattering agent, etc.

[0104] Suitable examples of the polymer include polymers derived from acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters, copolymers combining multiple polymers, and polymers having a skeletal structure with glycidyl (meth)acrylate as a repeating unit, a siloxane skeleton, a urethane skeleton, a silphenylene skeleton, a norbornene skeleton, a fluorene skeleton, and an isocyanurate skeleton. The polymer to be used may be selected appropriately depending on the application.

[0105] Furthermore, these polymers have polymerizable substituents introduced into them, and can be cured by using them in combination with a polymerization initiator. The polymerization initiator can be a thermal or photopolymerization initiator, and either can be suitably used depending on the base polymer. In addition, known thermal radical polymerization initiators and photocationic polymerization initiators may also be used.

[0106] The content of the polymerization initiator is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 5 parts by mass, per 100 parts by mass of the polymer to be added. An organic solvent may be used to improve the coatability of the quantum dot composition. Furthermore, other agents such as a polymerizable crosslinker, a photoacid generator, an antioxidant, and a light scattering agent may also be used, with no particular limitations provided that they do not affect the coatability of the polymerizable material.

[0107] According to this method for producing a quantum dot composition, the dispersibility in a resin material containing a polymer having at least one skeletal structure identical to that of the polymer coating layer is improved, and it is possible to produce a quantum dot composition in which quantum dots are dispersed at a high concentration.

[0108] [Method for producing wavelength converting material] The present invention also provides a method for producing a wavelength converting material by a step of curing a quantum dot composition produced by the above-mentioned method for producing a quantum dot composition.

[0109] The method for producing the wavelength converting material is not particularly limited. For example, a resin composition in which a quantum dot composition is dispersed in a resin can be applied to a transparent film such as PET or polyimide, cured, and laminated to obtain the wavelength converting material.

[0110] The resin layer can be formed by coating onto the transparent film using a spraying method such as a spray or inkjet method, a spin coat method, a bar coater method, or a doctor blade method. The thickness of the resin layer and the transparent film is not particularly limited and can be selected appropriately depending on the application.

[0111] According to such a method for producing a wavelength converting material, even after curing the quantum dot composition, it is possible to disperse the quantum dots in a resin material at a high concentration without forming aggregates, while maintaining high luminescence properties, and it is possible to produce a wavelength converting material with improved reliability.

[0112] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0113] (Measurement of Emission Wavelength, Emission Half Width, and Emission Efficiency) In the examples and comparative examples, the fluorescence emission properties of the quantum dots were evaluated by measuring the emission wavelength, fluorescence emission half width, and fluorescence emission efficiency (internal quantum yield) of the quantum dots at an excitation wavelength of 450 nm using a quantum efficiency measurement system (QE-2100) manufactured by Otsuka Electronics Co., Ltd.

[0114] (Reliability Test) The obtained wavelength converting material was treated under conditions of 85° C. and 85% RH (relative humidity) for 500 hours, and the fluorescence emission efficiency (internal quantum yield) of the wavelength converting material before and after the treatment was compared to evaluate its reliability.

[0115] Example 1 (Step of Producing Quantum Dots) 0.070 g (0.24 mmol) of indium acetate, 0.256 g (0.72 mmol) of palmitic acid, and 4.0 mL of 1-octadecene were placed in a flask, and the mixture was heated and stirred at 100° C. under reduced pressure to dissolve the indium acetate and degass for 1 hour.

[0116] After cooling the flask to room temperature and purging with nitrogen, 0.50 mL (0.17 mmol) of a 10 vol% (tris)trimethylsilylphosphine / octadecene solution was added to the flask, and the flask was heated to 300°C and stirred for 20 minutes to synthesize InP semiconductor core particles.

[0117] Next, the flask was cooled to 200° C., and then 0.10 mL (0.02 mmol) of a gallium (III) chloride / octadecene solution was added, followed by heating for 30 minutes.

[0118] The flask was then heated to 240°C, and 4.0 mL (1.2 mmol) of a 0.30 M zinc stearate / octadecene solution was added, followed by stirring for 30 minutes. 0.60 mL (0.90 mmol) of a 1.5 M selenium / trioctylphosphine solution was then added to the flask, followed by stirring for 30 minutes.

[0119] Next, after the flask was cooled to room temperature, 0.22 g (1.1 mmol) of zinc acetate was added, and the mixture was heated and stirred under reduced pressure at 100°C for 1 hour while dissolving. After purging the flask with nitrogen, the mixture was heated to 230°C, and 0.48 mL (2.0 mmol) of 1-dodecanethiol was added, followed by stirring for 30 minutes.

[0120] The resulting solution was cooled to room temperature, ethanol was added, and the mixture was centrifuged to precipitate quantum dots consisting of an InP core, a ZnSe shell, and a ZnS shell, and the supernatant was removed.

[0121] Toluene was further added to the precipitate to disperse it, and ethanol was added again, followed by centrifugation. The supernatant was removed and the precipitate was redispersed in toluene to prepare an InP / ZnSe / ZnS toluene dispersion.

[0122] (Step of Coating the Surface of Quantum Dots with Metal Oxide) 10 g of the obtained toluene dispersion of 1.0 wt % InP / ZnSe / ZnS quantum dots, 0.10 g of aluminum isopropoxide, 50 μL of 25% aqueous ammonia solution, and 0.010 g / 100 μL of cetyltrimethylammonium bromide / ethanol solution were mixed and placed in a high-pressure reactor.

[0123] Thereafter, a microwave synthesis reaction apparatus (flexi WAVE, manufactured by Milestone General Co.) was used to heat the mixture at 2450 MHz at 60° C. for 5 minutes, thereby forming Al on the InP / ZnSe / ZnS surface. ２ O ３ The resulting nanoparticles were added with ethanol, precipitated by centrifugation, and the supernatant was removed. Toluene or octadecene was added and the nanoparticles were redispersed by ultrasonic irradiation. The fluorescence emission characteristics of the InP / ZnSe / ZnS / Al nanoparticles dispersed in toluene were evaluated. ２ O ３was measured.

[0124] (Step of Modifying Metal Oxide Surface with Phosphonic Acid Derivative) In a nitrogen atmosphere, 11 mg of vinylphosphonic acid (VPA) was weighed into a 20 ml vial, and 5 ml of toluene and 1 ml of ethanol were added and stirred to prepare a hexadecylphosphonic acid solution.

[0125] Further, in a nitrogen atmosphere, the obtained 1.0 wt % InP / ZnSe / ZnS / Al ２ O ３ 10 g of the octadecene dispersion and 6 ml of the VPA solution were added to the flask. Then, the flask was heated and stirred at 50° C. under reduced pressure, and degassed for 10 minutes.

[0126] Next, the flask was purged with nitrogen, heated to 150° C., and stirred for 3 hours to obtain InP / ZnSe / ZnS / Al ２ O ３ In contrast, vinylphosphonic acid-modified InP / ZnSe / ZnS / Al ２ O ３ / VPA was obtained.

[0127] The resulting solution was cooled to room temperature, ethanol was added, and the mixture was centrifuged to precipitate the vinylphosphonic acid-modified quantum dots. The supernatant was removed, and the precipitate was dispersed in toluene. Ethanol was added again, the mixture was centrifuged, the supernatant was removed, and the precipitate was redispersed in toluene.

[0128] (Step of forming a polymer coating layer) The obtained InP / ZnSe / ZnS / Al ２ O ３ The toluene dispersion of 100 parts by mass of quantum dots / VPA was added to a flask that had been purged with nitrogen, and 2 parts by mass of methacrylic-modified silicone oil X-32-3817-3 (Shin-Etsu Chemical Co., Ltd.) was added per 100 parts by mass of the toluene dispersion of quantum dots. After stirring, mixing, and degassing, the mixture was irradiated with UV LED at a wavelength of 365 nm and an output of 4000 mW / cm while stirring. ２After the reaction was completed, ethanol was added to cause precipitation, and after centrifugation, the supernatant was removed and the mixture was dispersed again in toluene to form a polymer coating layer, thereby producing quantum dots.

[0129] (Production of quantum dot composition) The quantum dots dispersed in toluene and methacrylic modified silicone oil X-32-3817-3 (Shin-Etsu Chemical Co., Ltd.) were weighed and mixed so that the quantum dots contained 20 wt% in terms of nonvolatile content. After mixing, the solvent was removed to obtain a quantum dot composition.

[0130] (Production of wavelength converting material) A wavelength converting material was produced using the obtained quantum dot composition. The quantum dot composition was vacuum degassed and applied to a polyethylene terephthalate (PET) film with a thickness of 50 μm, and a quantum dot-containing resin layer with a thickness of 100 μm was formed using a bar coater. A PET film was then attached to the resin layer for lamination. This film was then exposed to a UV LED irradiation device with a wavelength of 365 nm and an output of 4000 mW / cm. ２ The quantum dot-containing resin layer was cured by irradiating it with light of 1000 kJ / cm for 20 seconds, thereby producing a wavelength converting material.

[0131] Comparative Example 1: The quantum dot production process was carried out in the same manner as in Example 1, and the resin composition was mixed without performing the metal oxide coating, surface modification with phosphonic acid, and polymer layer formation processes. Methacrylic-modified silicone oil X-32-3817-3 (Shin-Etsu Chemical Co., Ltd.) was weighed and mixed into the toluene dispersion after the quantum dot production process so that the quantum dots contained 20 wt% in terms of nonvolatile content. After mixing, the solvent was removed to obtain a quantum dot composition. The wavelength conversion material was produced in the same manner as in Example 1.

[0132] (Comparative Example 2) The quantum dot production process and metal oxide coating were performed in the same manner as in Example 1, and the resin composition was mixed without performing the surface modification with phosphonic acid and the polymer layer formation process. Methacrylic-modified silicone oil X-32-3817-3 (Shin-Etsu Chemical Co., Ltd.) was weighed and mixed into the toluene dispersion after the metal oxide coating layer formation process so that the quantum dots contained 20 wt% in terms of nonvolatile content. After mixing, the solvent was removed to obtain a quantum dot composition. The wavelength conversion material was produced in the same manner as in Example 1.

[0133] Example 2 The same process as in Example 1 was carried out up to the step of forming the metal oxide coating layer.

[0134] (Step of Modifying Metal Oxide Surface with Phosphonic Acid Derivative) Next, under a nitrogen atmosphere, 31 mg of 11-phosphonoundecyl acrylate was weighed into a 20 ml vial, and 5 ml of toluene and 1 ml of ethanol were added and stirred to prepare a hexadecylphosphonic acid solution.

[0135] Further, in a nitrogen atmosphere, the obtained 1.0 wt % InP / ZnSe / ZnS / Al ２ O ３ 10 g of the octadecene dispersion and 6 ml of 11-phosphonoundecyl acrylate solution were added to the flask. Then, the flask was heated and stirred at 50° C. under reduced pressure, and degassed for 10 minutes.

[0136] Next, the flask was purged with nitrogen, heated to 150° C., and stirred for 3 hours to obtain InP / ZnSe / ZnS / Al ２ O ３ In contrast, InP / ZnSe / ZnS / Al modified with 11-phosphonoundecyl acrylate ２ O ３The resulting solution was cooled to room temperature, ethanol was added, and the mixture was centrifuged to precipitate the quantum dots modified with 11-phosphonoundecyl acrylate, after which the supernatant was removed. Toluene was added to the precipitate, and the mixture was dispersed. Ethanol was added again, the mixture was centrifuged, the supernatant was removed, and the mixture was redispersed in toluene.

[0137] (Step of forming a polymer coating layer) The obtained InP / ZnSe / ZnS / Al ２ O ３ A toluene dispersion of 11-phosphonoundecyl acrylate was added to a flask that had been previously purged with nitrogen, and 2 parts by mass of acrylic resin RA-4101 (Negami Industries Co., Ltd.) was added per 100 parts by mass of the quantum dot toluene dispersion. Furthermore, 1 part by mass of Irgacure 1173 was added per 100 parts by mass of the acrylic resin, and after stirring and mixing, the mixture was irradiated with a UVLED irradiation device at a wavelength of 365 nm and an output of 4000 mW / cm. ２ After the reaction was completed, ethanol was added to cause precipitation, and after centrifugation, the supernatant was removed and the mixture was dispersed again in toluene to form a polymer coating layer, thereby producing quantum dots.

[0138] (Production of quantum dot composition) A solution of quantum dot bodies dispersed in toluene and acrylic resin RA-4101 (Negami Sangyo Co., Ltd.) were weighed out so that the quantum dot bodies were contained in a nonvolatile content ratio of 20 wt%, and 1 part by mass of Irgacure 1173 was weighed out and mixed for 100 parts by mass of the nonvolatile content of the acrylic resin. After mixing, the toluene solvent was removed by distillation under reduced pressure to obtain a quantum dot composition.

[0139] (Production of Wavelength Converting Material) A wavelength converting material was produced in the same manner as in Example 1 using the obtained quantum dot composition.

[0140] Comparative Example 3 A quantum dot composition and a wavelength converting material were prepared by carrying out the quantum dot production process in the same manner as in Example 2, without carrying out the metal oxide coating, surface modification with phosphonic acid, and polymer coating layer formation processes. Acrylic resin RA-4101 (Negami Sangyo Co., Ltd.) was weighed and mixed into the toluene dispersion after the quantum dot production process so that the quantum dots contained 20 wt % in terms of nonvolatile content. After mixing, the solvent was removed to obtain a quantum dot composition. The wavelength converting material was prepared in the same manner as in Example 2.

[0141] Example 3 In the same manner as in Example 2, the steps up to the surface modification step with a phosphonic acid derivative were carried out.

[0142] (Step of forming a polymer coating layer) Next, the obtained InP / ZnSe / ZnS / Al ２ O ３ A toluene dispersion of 11-phosphonoundecyl acrylate was added to a flask that had been previously purged with nitrogen, and 2 parts by mass of an isocyanuric acid derivative DA-MGIC (Shikoku Chemical Industry Co., Ltd.) was added per 100 parts by mass of the quantum dot toluene dispersion. Furthermore, 1 part by mass of Irgacure 1173 was added per 100 parts by mass of DA-MGIC, and after stirring and mixing, the mixture was irradiated with a UVLED irradiation device at a wavelength of 365 nm and an output of 4000 mW / cm. ２ After the reaction was completed, ethanol was added to cause precipitation, and after centrifugation, the supernatant was removed and the mixture was dispersed again in toluene to form a polymer coating layer, thereby producing quantum dots.

[0143] (Production of quantum dot composition) A dispersion of quantum dots dispersed in epoxy-containing silicone resin (CAS No. 2253674-54-1, manufactured by Shin-Etsu Chemical Co., Ltd.) and toluene was weighed and mixed so that the quantum dots contained 20 wt% in terms of nonvolatile content. 2 parts by mass of photoacid generator CPI-310FG and 20 parts by mass of crosslinker THI-DE were weighed and mixed per 100 parts by mass of silicone resin nonvolatile content. After mixing, the toluene solvent was removed by distillation under reduced pressure to obtain a quantum dot composition.

[0144] (Production of wavelength converting material) A wavelength converting material was produced using the obtained quantum dot composition. The quantum dot composition was vacuum degassed and applied to a 5 mm thick glass substrate. After removing the solvent, a quantum dot-containing resin layer with a thickness of 100 μm was formed using a bar coater. A PET film was then attached to the resin layer for lamination. This film was then irradiated with UV LED light at a wavelength of 365 nm and an output of 4000 mW / cm. ２ The quantum dot-containing resin layer was cured by irradiating it with light for 20 seconds, and then heated at 120° C. for 5 minutes to prepare a wavelength converting material.

[0145] Comparative Example 4: A quantum dot composition and a wavelength converting material were prepared by carrying out the quantum dot production process in the same manner as in Example 3, without carrying out the metal oxide coating, surface modification with phosphonic acid, and polymer coating layer formation processes. An epoxy-containing silicone resin (CAS No. 2253674-54-1, manufactured by Shin-Etsu Chemical Co., Ltd.) was weighed and mixed into the toluene dispersion after the quantum dot production process so that the quantum dots were contained at 20 wt% in terms of nonvolatile content. Two parts by mass of photoacid generator CPI-310FG and 20 parts by mass of crosslinker THI-DE were weighed and mixed per 100 parts by mass of silicone resin nonvolatile content. After mixing, the toluene solvent was removed by distillation under reduced pressure to obtain a quantum dot composition. The wavelength converting material was prepared in the same manner as in Example 3.

[0146] The results of Examples 1 to 3 and Comparative Examples 1 to 4 are shown in Table 1. Table 1 shows the fluorescence emission properties of quantum dots, quantum dots coated with a metal oxide layer, quantum dots surface-modified with phosphonic acid, quantum dots (quantum dot bodies) after the formation of a polymer coating layer, and wavelength converting materials, as well as the fluorescence emission efficiency (internal quantum yield) of the wavelength converting materials after reliability evaluation.

[0147]

[0148] The results in Table 1 show that, compared to the Examples, the Comparative Examples have a lower internal quantum yield of the wavelength converting material, a large shift in the emission wavelength to longer wavelengths, and an increased half-value width.

[0149] Furthermore, when observed using a microscope, many aggregates of about 1 to 50 μm were observed in the wavelength converting materials of Comparative Examples 1 to 4, which is thought to have resulted in a decrease in quantum yield. On the other hand, the wavelength converting materials of Examples have small aggregates and a small number of them, which is thought to have suppressed the decrease in quantum yield. This is thought to be because the formation of the polymer coating layer in Examples allows the introduction of large steric hindrance, effectively suppressing aggregation, and the improvement in dispersibility of the quantum dot composition was confirmed.

[0150] Furthermore, when the results of the reliability test (treated at 85°C and 85% RH for 500 hours) were compared, it was found that the stability of the Examples was improved over that of the Comparative Examples, and that the decrease in quantum yield was suppressed.

[0151] As described above, according to the examples of the present invention, it was confirmed that the quantum dot composition using the quantum dot body of the present invention exhibits high stability, and that the wavelength converting material using this exhibits suppressed deterioration in fluorescence emission efficiency under high temperature and high humidity conditions, and is highly reliable.

[0152] This specification includes the following aspects. [1]: A quantum dot body containing quantum dots that emit fluorescence when exposed to excitation light, the quantum dots consisting of a semiconductor nanoparticle core and a semiconductor nanoparticle shell covering the semiconductor nanoparticle core, the quantum dot surfaces coated with a metal oxide, the metal oxide surface modified with a phosphonic acid derivative, and the quantum dot body having, on its outermost surface, a polymer coating layer formed by bonding between a reactive substituent of the phosphonic acid derivative and a reactive substituent of a polymer. [2]: The quantum dot body of [1] above, wherein the reactive substituent of the phosphonic acid derivative is one or more of a vinyl group, an acrylic group, a methacrylic group, a hydroxyl group, a phenolic hydroxyl group, an epoxy group, and a glycidyl group. [3]: The quantum dot body of [1] or [2] above, wherein the reactive substituent of the polymer is one or more of a vinyl group, an acrylic group, a methacrylic group, a hydroxyl group, a phenolic hydroxyl group, an epoxy group, and a glycidyl group. [4]: The quantum dot body according to [1], [2], or [3] above, wherein the polymer coating layer contains at least one skeletal structure identical to the skeletal structure of the main chain of the polymer, and the skeletal structure is a skeletal structure derived from acrylic acid, methacrylic acid, an acrylic acid ester, a methacrylic acid ester, a skeletal structure having glycidyl (meth)acrylate as a repeating unit, a siloxane skeleton, a urethane skeleton, a silphenylene skeleton, a norbornene skeleton, a fluorene skeleton, or an isocyanurate skeleton. [5]: A quantum dot composition comprising the quantum dot body according to [1], [2], [3], or [4] above dispersed in a resin material containing at least one skeletal structure identical to the polymer coating layer. [6]: A wavelength converting material comprising a cured product of the quantum dot composition according to [5] above.[7]: A method for producing a quantum dot body according to [1], [2], [3], or [4], comprising the steps of producing quantum dots each consisting of a semiconductor nanoparticle core and a semiconductor nanoparticle shell covering the semiconductor nanoparticle core, coating the surface of the quantum dot with a metal oxide, modifying the surface of the metal oxide with a phosphonic acid derivative, and polymerizing a reactive substituent carried by the phosphonic acid derivative with a reactive substituent carried by a polymer by light or heat to form a polymer coating layer. [8]: A method for producing a quantum dot composition, comprising the step of dispersing the quantum dot body produced by the method for producing a quantum dot body according to [7] in a resin material containing at least one skeletal structure identical to the skeletal structure of the main chain of the polymer contained in the polymer coating layer. [9]: A method for producing a wavelength conversion material, comprising the step of curing the quantum dot composition produced by the method for producing a quantum dot composition according to [8].

[0153] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. A quantum dot body comprising a quantum dot that emits fluorescence when excited by excitation light, the quantum dot comprising a semiconductor nanoparticle core and a shell of semiconductor nanoparticles covering the semiconductor nanoparticle core, the quantum dot surface being coated with a metal oxide, the metal oxide surface being modified with a phosphonic acid derivative, and the quantum dot body having, on its outermost surface, a polymer coating layer formed by bonding between a reactive substituent of the phosphonic acid derivative and a reactive substituent of a polymer.

2. The quantum dot body according to claim 1, characterized in that the reactive substituent of the phosphonic acid derivative is one or more of a vinyl group, an acrylic group, a methacrylic group, a hydroxyl group, a phenolic hydroxyl group, an epoxy group, and a glycidyl group.

3. The quantum dot body according to claim 2, characterized in that the reactive substituent of the polymer is one or more of a vinyl group, an acrylic group, a methacrylic group, a hydroxyl group, a phenolic hydroxyl group, an epoxy group, and a glycidyl group.

4. The quantum dot body described in claim 3, characterized in that the polymer coating layer contains at least one skeletal structure that is the same as the skeletal structure of the main chain of the polymer, and the skeletal structure is a skeletal structure derived from acrylic acid, methacrylic acid, an acrylic acid ester, or a methacrylic acid ester, a skeletal structure having glycidyl (meth)acrylate as a repeating unit, a siloxane skeleton, a urethane skeleton, a silphenylene skeleton, a norbornene skeleton, a fluorene skeleton, or an isocyanurate skeleton.

5. A quantum dot composition comprising the quantum dot body according to any one of claims 1 to 4 dispersed in a resin material containing at least one skeletal structure identical to that of the polymer coating layer.

6. A wavelength converting material comprising a cured product of the quantum dot composition according to claim 5.

7. A method for producing a quantum dot body as described in claim 1, comprising the steps of: producing a quantum dot consisting of a semiconductor nanoparticle core and a shell of semiconductor nanoparticles covering the semiconductor nanoparticle core; coating the surface of the quantum dot with a metal oxide; modifying the metal oxide surface with a phosphonic acid derivative; and polymerizing a reactive substituent of the phosphonic acid derivative with a reactive substituent of a polymer by light or heat polymerization reaction to form a polymer coating layer.

8. A method for producing a quantum dot composition, comprising a step of dispersing quantum dot bodies produced by the method for producing quantum dot bodies described in claim 7 in a resin material containing at least one skeletal structure identical to the skeletal structure of the main chain of the polymer contained in the polymer coating layer.

9. A method for producing a wavelength conversion material, comprising a step of curing a quantum dot composition produced by the method for producing a quantum dot composition according to claim 8.

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