Quantum dots, quantum dot compositions, and wavelength conversion materials, and methods for manufacturing the same.

Abstract

The objective is to provide quantum dot bodies that maintain the fluorescence emission properties of quantum dots while further improving stability and compatibility with highly polar solvents and photosensitive resin compositions. [Solution] A quantum dot body comprising a quantum dot that emits fluorescence upon excitation light, wherein the quantum dot comprises a core of semiconductor nanoparticles and a shell of semiconductor nanoparticles covering the core of the semiconductor nanoparticles, the surface of the quantum dot is coated with a metal oxide, the surface of the metal oxide is modified with a compound having a methacryloyloxyethyl group and a hydrophilic group represented by the following formula (I) (where R1 represents a hydrophilic group), and the quantum dot body has a polymer coating layer on its outermost surface formed by the bonding of the methacryloyloxyethyl group with a reactive substituent of a polymer. TIFF2026076555000008.tif34166

Description

Technical Field

[0001] The present invention relates to quantum dot bodies, quantum dot compositions, wavelength conversion materials, and methods for producing them.

Background Art

[0002] Quantum dots composed of semiconductor particles with a nanosize particle diameter have discrete energy levels of the semiconductor nanoparticles due to excitons generated by light absorption being confined in a nanosize space, and their band gaps depend on the particle diameter. Therefore, the fluorescence emission of quantum dots is highly efficient and its emission spectrum is sharpened. In addition, due to the characteristic that the band gap changes depending on the particle diameter, it has the feature of being able to control the emission wavelength, and is expected to be applied as a wavelength conversion material for solid lighting and displays (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Examples of quantum dots showing excellent fluorescence emission characteristics include quantum dots containing Cd or Pb. However, since Cd and Pb are highly toxic to the human body and the environment, restrictions on their use are being considered worldwide, starting with the RoHS directive of the European Union. Therefore, quantum dots that do not contain these toxic elements are being studied.

[0005] Furthermore, because quantum dots have a small particle size of nanometers, they have a large specific surface area, high surface energy, and are highly surface-active, making them prone to instability. Therefore, surface defects such as dangling bonds and oxidation reactions easily occur on the quantum dot surface, which degrades their fluorescence emission properties. Currently available quantum dots have these stability issues, and it is known that heat, humidity, and photoexcitation can cause degradation of their emission properties.

[0006] To prevent this degradation, organic or inorganic ligands called ligands are coordinated to the surface of synthesized quantum dots. This ligand coordination and passivation of defects suppresses the degradation of fluorescence emission efficiency.

[0007] Furthermore, as an implementation method using quantum dots as wavelength conversion materials, applications to color filters used in displays and the like have been proposed. When applying quantum dots to color filters, it is important to form a quantum dot surface state suitable for the patterning method. Currently, the main method used for color filters is photolithography, in which a photosensitive resin composition containing pigments is coated onto a glass substrate, the solvent is dried, then a mask is exposed with UV irradiation, and the uncured portion is removed by alkaline development to form a color pattern, and this process is repeated to form blue, red, and green patterns. However, this photolithography method has many problems, such as the significant loss of raw materials due to the uncured portion being wasted, the complicated process, and the use of expensive equipment.

[0008] Therefore, inkjet technology has also been considered in recent years. With inkjet technology, there is no waste of raw materials, and it is possible to manufacture large-scale and large-area products without introducing expensive equipment, making it competitive in terms of cost. However, the technology to create fine nozzles is difficult, and as the nozzles become smaller, problems such as clogging and unstable ejection occur. For miniaturization, both photolithography, which has a proven track record, and inkjet, which is cost-competitive, are being considered.

[0009] In both photolithography and inkjet printing, the challenge lies in creating resin compositions containing quantum dots at high concentrations and with high dispersion. With some exceptions, resin compositions contain quantum dots dispersed in polar solvents such as propylene glycol monomethyl ether acetate (PGMEA) or propylene glycol monomethyl ether (PGME). However, quantum dots are fundamentally hydrophobic and do not disperse easily in these solvents or resin materials, often resulting in aggregation. Therefore, creating photosensitive resin compositions containing quantum dots at high concentrations and with high dispersion is difficult.

[0010] Various studies have been conducted to disperse quantum dots in polar solvents. For example, Patent Document 2 describes a method for producing a composite in which semiconductor nanoparticles are dispersed in silica glass by stepwise reacting a metal alkoxide on the surface of semiconductor nanoparticles to deposit a silica glass layer, enabling the dispersion of the composite in water. However, a problem arose with the composite obtained by this manufacturing method: the fluorescence emission efficiency of the quantum dots was significantly reduced.

[0011] Another method involves using ligands with high affinity for polar solvents and adsorbing them onto the quantum dot surface to improve dispersibility in polar solvents. However, these ligands on the quantum dot surface are removed as soon as the solvent is removed. Therefore, when quantum dots are used as wavelength conversion materials for displays, removing the solvent when mixing the quantum dots with a resin material can lead to problems such as the quantum dots aggregating in the resin, a decrease in the initial fluorescence emission efficiency, and a deterioration in the luminescence efficiency of the composition consisting of quantum dots and resin material over time.

[0012] The present invention has been made to solve the above problems and aims to provide quantum dots that maintain the fluorescence emission characteristics of quantum dots while further improving stability and compatibility with highly polar solvents and photosensitive resin compositions. Furthermore, it aims to provide a quantum dot composition in which the quantum dots are dispersed in a resin material, a wavelength conversion material including a cured product of the quantum dot composition, and methods for manufacturing the same, in which the initial value of the fluorescence emission efficiency and degradation over time are suppressed. [Means for solving the problem]

[0013] The present invention has been made to achieve the above objective, and provides a quantum dot body comprising a quantum dot that emits fluorescence upon excitation light, wherein the quantum dot comprises a core of semiconductor nanoparticles and a shell of semiconductor nanoparticles covering the core of the semiconductor nanoparticles, the surface of the quantum dot is coated with a metal oxide, the surface of the metal oxide is modified with a compound having a methacryloyloxyethyl group and a hydrophilic group represented by the following formula (I), and the quantum dot body has a polymer coating layer on its outermost surface formed by the bonding of the methacryloyloxyethyl group with a reactive substituent of a polymer.

[0014] [ka] (R1 represents a hydrophilic group.)

[0015] Such quantum dot materials maintain the fluorescence emission properties of the quantum dots while improving stability and compatibility with highly polar solvents and photosensitive resin compositions.

[0016] In this case, the hydrophilic group may be selected from quaternary ammonium salts, carboxylates, succinates, isocyanates, maleates, hydrogen phosphates, 1,2,4-benzenetricarboxylates, salts of trimellitic anhydride, phthalates, acetoacetates, and thiocticates.

[0017] This improves the affinity for polar solvents and enhances the dispersibility of quantum dots in polar solvents.

[0018] In this case, the compound having a methacryloyloxyethyl group and a hydrophilic group is bis[2-(methacryloyloxy)ethyl]phosphate, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, mono-2-(methacryloyloxy)ethyl succinic acid, mono[2-(methacryloyloxy)ethyl]maleate, 2-(methacryloyloxy)ethyl isocyanate, (2-methacryloyloxyethyl)trimethylammonium=bis(trifluoromethanesulfonyl)imide, 4-MET(4-Methacryloxyethyl trimellitic acid), 4-META(4-Methacryloxyethyl trimellitic It can be selected from anhydride, mono-2-(methacryloyloxy)ethyl phthalate, bis[[2-(methacryloyloxy)ethyl](methyl)ammonio]propane-1-sulfonic acid, 2-(methacryloyloxy)ethyl acetoacetate, 2-[[2-(methacryloyloxy)ethyl]dimethylammonio]acetic acid, 4-[[2-(methacryloyloxy)ethyl]dimethylammonio]butane-1-sulfonic acid, 3-[[2-(methacryloyloxy)ethyl]dimethylammonio]propionate, 2-methacryloyloxyethyl thioctic acid, and [2-(methacryloyloxy)ethyl]trimethylammonium methylsulfate.

[0019] This further improves the affinity for polar solvents and enhances the dispersibility of quantum dots in polar solvents.

[0020] In this case, the reactive substituent of the polymer can be one or more of the following: vinyl group, acrylic group, methacrylic group, hydroxyl group, phenolic hydroxyl group, epoxy group, or glycidyl group.

[0021] As a result, the reactive substituent of the polymer undergoes a polymerization reaction with the methacryloyloxyethyl group of a compound having a methacryloyloxyethyl group and a hydrophilic group, so that a polymer coating layer can be formed more efficiently.

[0022] At this time, the polymer coating layer contains at least one or more skeleton structures the same as the skeleton structure of the main chain of the polymer, and the skeleton structure is a skeleton structure derived from acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, a skeleton 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] With such a polymer coating layer, the oxidation reaction on the surface of the quantum dots is more suppressed, and the deterioration of the fluorescence emission efficiency of the quantum dots associated therewith is also more suppressed, so that the stability is more improved, and a quantum dot body with better compatibility with a highly polar solvent or a photosensitive resin composition is obtained.

[0024] At this time, the above quantum dot body can be a quantum dot composition dispersed in a resin material containing at least one or more skeleton structures the same as the skeleton structure contained in the polymer coating layer.

[0025] As a result, a quantum dot composition with an initial value of fluorescence emission efficiency and deterioration over time suppressed is obtained.

[0026] At this time, it can be a wavelength conversion material containing a cured product of the above quantum dot composition.

[0027] As a result, an initial value of fluorescence emission efficiency and deterioration over time are suppressed, and a wavelength conversion material with improved reliability is obtained.

[0028] In this case, the above-described method for manufacturing a quantum dot can be a method for manufacturing a quantum dot that includes a quantum dot manufacturing step of manufacturing a quantum dot comprising a semiconductor nanoparticle core and a semiconductor nanoparticle shell covering the semiconductor nanoparticle core; a metal oxide coating step of coating the surface of the quantum dot with a metal oxide; a quantum dot modification step of modifying the surface of the metal oxide with a compound having a methacryloyloxyethyl group and a hydrophilic group represented by formula (I); and a polymer coating layer formation step of forming a polymer coating layer by polymerizing the methacryloyloxyethyl group and a reactive substituent of a polymer using light or heat.

[0029] With this method of manufacturing quantum dots, it is possible to produce quantum dots that maintain the fluorescence emission properties of the quantum dots while improving stability and compatibility with highly polar solvents and photosensitive resin compositions.

[0030] In this case, the quantum dot composition can be manufactured by dispersing the quantum dots produced by the above-described method 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.

[0031] With this method of manufacturing quantum dot compositions, it is possible to produce quantum dot compositions in which the initial value of fluorescence emission efficiency and degradation over time are suppressed.

[0032] In this case, the quantum dot composition produced by the above-described method for manufacturing a quantum dot composition can be cured to produce a wavelength conversion material, which can then be used as a method for manufacturing a wavelength conversion material.

[0033] With this method of manufacturing wavelength conversion materials, the initial value of the fluorescence emission efficiency and its degradation over time are suppressed, making it possible to manufacture wavelength conversion materials with improved reliability. [Effects of the Invention]

[0034] As described above, the quantum dot material of the present invention maintains the fluorescence emission characteristics of the quantum dot while improving stability and improving compatibility with highly polar solvents and photosensitive resin materials. Furthermore, by using the quantum dot material of the present invention to create a quantum dot composition and a wavelength conversion material, the initial value of the fluorescence emission efficiency and the degradation over time are suppressed. Moreover, the method for producing the quantum dot material, quantum dot composition and wavelength conversion material of the present invention makes it possible to produce a quantum dot material having the above effects, a quantum dot composition containing the quantum dot material and a wavelength conversion material. [Brief explanation of the drawing]

[0035] [Figure 1] This is a schematic cross-sectional view showing an example of the quantum dot body of the present invention. [Modes for carrying out the invention]

[0036] The present invention will be described in detail below, but the present invention is not limited to these descriptions.

[0037] As described above, there was a need for quantum dot materials that retained the fluorescence emission properties of quantum dots while further improving stability and compatibility with highly polar solvents and photosensitive resins.

[0038] As a result of diligent research into the above-mentioned problems, the present inventors have found that a quantum dot body containing quantum dots that emit fluorescence upon excitation light comprises a core of semiconductor nanoparticles and a shell of semiconductor nanoparticles covering the core of the semiconductor nanoparticles, the surface of the quantum dot is coated with a metal oxide, the surface of the metal oxide is modified with a compound having a methacryloyloxyethyl group and a hydrophilic group as shown in formula (I) below, and the quantum dot body having a polymer coating layer formed by the bonding of the methacryloyloxyethyl group and a reactive substituent of a polymer on its outermost surface, thereby maintaining the fluorescence emission characteristics of the quantum dot while further improving stability and improving compatibility with highly polar solvents and photosensitive resin materials, and have completed the present invention.

[0039] [ka] (R1 represents a hydrophilic group.)

[0040] Furthermore, it was revealed that the quantum dot composition obtained by dispersing the quantum dots in a resin material, and the wavelength conversion material obtained by curing the quantum dot composition, exhibit high initial fluorescence emission efficiency and suppressed degradation of emission efficiency over time. As a result, it was found that the wavelength conversion material containing the cured quantum dot composition could suppress the rate of decrease in internal quantum yield during 500 hours of processing to within 10% in a reliability test at 85°C and 85%RH without a barrier film, demonstrating improved stability.

[0041] In other words, the present invention relates to a quantum dot body comprising a quantum dot that emits fluorescence upon excitation light, wherein the quantum dot comprises a core of semiconductor nanoparticles and a shell of semiconductor nanoparticles covering the core of the semiconductor nanoparticles, the surface of the quantum dot is coated with a metal oxide, the surface of the metal oxide is modified with a compound having a methacryloyloxyethyl group and a hydrophilic group as shown in formula (I), and the quantum dot body has a polymer coating layer formed by bonding the methacryloyloxyethyl group with a reactive substituent of a polymer on its outermost surface; a quantum dot composition comprising the quantum dot body dispersed in a resin material containing at least one of the same skeletal structures as the skeletal structure contained in the polymer coating layer; and a wavelength conversion material comprising a cured product of the quantum dot composition, and a method for producing the same.

[0042] Embodiments of the present invention will be described below. However, in the present invention, the quantum dots, quantum dot bodies, compounds having methacryloyloxyethyl groups and hydrophilic groups, the composition and type of polymer coating layer, and the manufacturing method are not limited to the following forms.

[0043] [Quantum dot body] Hereinafter, a quantum dot body according to an embodiment of the present invention will be described with reference to Figure 1. As shown in Figure 1, the quantum dot body 1 of the present invention has a structure characterized by having a quantum dot 4 which emits fluorescence upon excitation light, comprising a semiconductor nanoparticle core 2 and a semiconductor nanoparticle shell 3 covering the semiconductor nanoparticle core 2, the surface of which is coated with a metal oxide layer 5, the surface of which is modified with a compound 6 having a methacryloyloxyethyl group and a hydrophilic group as shown in formula (I) above, and an outermost polymer coating layer 7 formed by the bonding of the methacryloyloxyethyl group with a reactive substituent of the polymer.

[0044] As described above, in the quantum dot body 1, the surface of the quantum dot 4 is coated with a metal oxide layer 5, the surface of the metal oxide layer 5 is modified with a compound 6 having a methacryloyloxyethyl group and a hydrophilic group, and further, the methacryloyloxyethyl group is bonded to a reactive substituent of the polymer to form a polymer coating layer 7 on the outermost surface. As a result, the initial value of the fluorescence emission efficiency of the quantum dot body 1 is suppressed while the polymer coating layer 7 is formed, and the quantum dot body 1 of the present invention exhibits high fluorescence emission efficiency. Furthermore, in the quantum dot body 1 of the present invention, oxidation reactions on the surface of the quantum dot 4 from the outside are suppressed by the metal oxide layer 5 and the polymer coating layer 7, so the deterioration of the fluorescence emission efficiency of the quantum dot 4 over time is suppressed, stability is further improved, and compatibility with highly polar solvents and photosensitive resin materials is improved.

[0045] (Quantum dots) The structure of the quantum dot 4 according to the present invention is not particularly limited as long as it includes a semiconductor nanoparticle core 2 and a semiconductor nanoparticle shell 3. Such a quantum dot 4 has excellent fluorescence emission characteristics and stability. For example, in a core / shell structure semiconductor nanoparticle in which a nano-sized semiconductor particle is used as the core and a semiconductor particle with a larger band gap and lower lattice mismatch than the core is used as the shell, the fluorescence emission efficiency is further improved because the excitons generated in the shell are confined inside the core particle, and stability is further improved because the core surface is covered with the shell.

[0046] Furthermore, the quantum dot 4 may include a semiconductor nanoparticle core 2 and a plurality of semiconductor nanoparticle shells 3 covering the semiconductor nanoparticle core 2. With such a quantum dot 4, the degradation of fluorescence emission efficiency is further suppressed.

[0047] As for the material of the semiconductor nanoparticle core 2 of the core / shell semiconductor nanoparticle, it is preferable to use a material that does not contain elements such as Cd or Pb from the viewpoint of toxicity. For example, a material selected from the group consisting of group II-VI compounds, group III-V compounds, group I-III-VI compounds, group II-IV-V compounds, and alloys or mixed crystals thereof can be used.

[0048] Specifically, the materials for the semiconductor nanoparticle core 2 include those selected as a single, multiple, or mixed crystal from among ZnS, ZnSe, ZnTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, AgGaS2, AgInS2, AgGaSe2, AgInSe2, CuGaS2, CuGaSe2, CuInS2, CuInSe2, ZnSiP2, and ZnGeP2. Among these materials, ZnSe, ZnTe, and InP are particularly preferred in terms of fluorescence emission characteristics and stability.

[0049] Furthermore, it is preferable that the surface of the semiconductor nanoparticle core 2 of the core / shell semiconductor nanoparticle is passivated with an inorganic compound. This inactivates defects on the core particle surface, improving fluorescence emission efficiency and further suppressing the degradation of fluorescence emission efficiency over time.

[0050] The inorganic compound used for passivation is not particularly limited, but examples include metal halides, and at least one compound selected from GaCl3, GaI3, GaBr3, ZnCl2, ZnBr2, ZnI2, InCl3, InBr3, InI3, AgCl, AgBr, AgI, KCl, KBr, KI, NaCl, NaBr, NaI, MgCl2, MgBr2, MgI2, CaCl2, CaBr2, CaI2, MnCl2, MnBr2, MnI2, FeCl2, FeBr2, FeI2, CuCl2, CuBr2, CuI2, ZrCl4, ZrBr4, ZrI4, GeCl4, GeBr4, GeI4 is particularly preferred from the viewpoint of improving fluorescence emission efficiency.

[0051] As for the semiconductor nanoparticle shell 3, it is preferable that it does not contain elements such as Cd and Pb from the viewpoint of toxicity, but it is also preferable that it 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 group II-VI compounds and group III-V compounds.

[0052] Specific shell materials include those selected as single, multiple, or mixed crystals from among ZnS, ZnSe, ZnTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, and InSb. Of these materials, ZnSe and ZnS are particularly preferred in terms of improving fluorescence emission efficiency and stability.

[0053] (Metal oxides) The quantum dot 4 according to the present invention is coated with a metal oxide, which prevents oxygen and water in the atmosphere from directly contacting the quantum dot surface and suppresses oxidation reactions, thereby suppressing the degradation of its fluorescence emission efficiency.

[0054] In this invention, "coating" of the metal oxide on the quantum dot surface can be partial or complete, as long as the degradation of fluorescence emission efficiency over time is suppressed. Furthermore, the coating layer may be uniform, such as a core / shell structure, or non-uniform, and may be a structure in which multiple semiconductor nanoparticles are coated with metal oxide. The thickness of the metal oxide layer 5 is not particularly limited, but is preferably 500 nm or less from the viewpoint of light transmission.

[0055] In the present invention, the type of metal oxide is not particularly limited, but examples include at least one compound selected from TiO2, ZnO, Al2O3, SiO2, ZrO2, Fe2O3, MgO, Y2O3, HfO2, CeO2, In2O3, SnO2, WO3, CrO3, Ta2O3, BaTiO3, V2O5, NiO, NbO, Cu2O, CuO, and MoO3. From the viewpoint of improving the stability of quantum dots, TiO2, Al2O3, SiO2, and ZrO2 are more preferred.

[0056] (A compound having a methacryloyloxyethyl group and a hydrophilic group) In the present invention, a surface modifier useful for improving compatibility with polar solvents and photosensitive resins is compound 6 having a methacryloyloxyethyl group and a hydrophilic group, and the quantum dot body 1 in the present invention includes quantum dots 4, a metal oxide layer 5 coating the surface of the quantum dots 4, and compound 6 having a methacryloyloxyethyl group and a hydrophilic group modifying the surface of the metal oxide layer 5.

[0057] In this invention, "modification" refers to a state in which a compound 6 having a methacryloyloxyethyl group and a hydrophilic group is "adhered" to at least the surface of the metal oxide layer 5. Adhesion to the surface by "modification" includes both partial and complete adhesion, and indicates a state in which it is adhered to at least a part of the surface.

[0058] In the above, "adhesion" may refer to physical adsorption or chemical bonding, and in a broad sense, it may include covalent bonds, ionic bonds, and hydrogen bonds, or combinations thereof. Furthermore, as an example, the quantum dot body 1, which includes quantum dots 4, a metal oxide layer 5, and a compound 6 having a methacryloyloxyethyl group and a hydrophilic group, may be in a state in which at least some of the organic or inorganic ligands that were attached at the time of quantum dot 4 synthesis or metal oxide layer 5 formation are present, as long as it is dispersed in a polar solvent.

[0059] The structure of compound 6 having a methacryloyloxyethyl group and a hydrophilic group in the present invention is represented by the following formula (I).

[0060] [ka] (R1 represents a hydrophilic group.)

[0061] R1 in equation (I) above is not particularly limited as long as it is a hydrophilic group, but examples include quaternary ammonium salts, carboxylates, succinates, isocyanates, maleates, hydrogen phosphates, 1,2,4-benzenetricarboxylates, salts of trimellitic anhydride, phthalates, acetoacetates, and thiocticates. This improves the affinity for polar solvents and enhances the dispersibility of quantum dots in polar solvents.

[0062] The type of compound having a methacryloyloxyethyl group and a hydrophilic group represented by formula (I) above is not particularly limited, but examples include bis[2-(methacryloyloxy)ethyl]phosphate, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, mono-2-(methacryloyloxy)ethyl succinic acid, mono[2-(methacryloyloxy)ethyl]maleate, 2-(methacryloyloxy)ethyl isocyanate, (2-methacryloyloxyethyl)trimethylammonium=bis(trifluoromethanesulfonyl)imide, 4-MET(4-Methacryloxyethyl trimellitic acid), 4-META(4-Methacryloxyethyl trimellitic Examples include anhydride, mono-2-(methacryloyloxy)ethyl phthalate, bis[[2-(methacryloyloxy)ethyl](methyl)ammonio]propane-1-sulfonic acid, 2-(methacryloyloxy)ethyl acetoacetate, 2-[[2-(methacryloyloxy)ethyl]dimethylammonio]acetic acid, 4-[[2-(methacryloyloxy)ethyl]dimethylammonio]butane-1-sulfonic acid, 3-[[2-(methacryloyloxy)ethyl]dimethylammonio]propionate, 2-methacryloyloxyethyl thioctic acid, and [2-(methacryloyloxy)ethyl]trimethylammonium methylsulfate.

[0063] These compounds have the structure shown in formula (I) above and possess hydrophilic groups. By modifying the quantum dot surface, their affinity for polar solvents is further improved, and the dispersibility of quantum dots in polar solvents is further enhanced.

[0064] The amount of compound added as a surface modifier is not particularly limited as long as the compound 6 having a methacryloyloxyethyl group and a hydrophilic group modifies the surface of the metal oxide layer 5. For example, it is preferable that the amount is 50% by mass (wt%) or less relative to the solid mass of the particles consisting of quantum dots 4 and the metal oxide layer 5, as this effectively suppresses aggregation between the composites. It is preferable that the amount is 0.1% by mass (wt%) or more, as this allows the effect of modification on the surface of the metal oxide layer 5 to be sufficiently and stably exerted. Therefore, the amount of surface modifier added is preferably in the range of 0.1 to 50% by mass (wt%) relative to the solid mass of quantum dots 4, and more preferably in the range of 0.5 to 30% by mass (wt%).

[0065] (Polymer coating layer) In the quantum dot body 1 of the present invention, a polymer coating layer 7 is formed on the outermost surface by bonding the methacryloyloxyethyl group of compound 6, which has a methacryloyloxyethyl group and a hydrophilic group, with a reactive substituent of the polymer. This suppresses the degradation of the fluorescence emission efficiency of quantum dots over time, improves stability, and enhances compatibility with highly polar solvents and photosensitive resin compositions.

[0066] The polymer used to form the polymer coating layer 7 is not particularly limited, but it is preferable to use a compound having one or more of the following reactive substituents: vinyl group, acrylic group, methacrylic group, hydroxyl group, phenolic hydroxyl group, epoxy group, or glycidyl group, which allows for more efficient formation of the polymer coating layer 7.

[0067] Furthermore, the polymer coating layer 7 contains at least one skeletal structure identical to the skeletal structure of the main chain of the polymer. The skeletal structure is preferably a compound having a skeletal structure derived from acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, 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. The type, number, and ratio of these structures can be appropriately adjusted so that aggregation does not occur when the resin composition and quantum dots are mixed.

[0068] This allows for the introduction of functional groups with significant steric hindrance into the polymer coating layer 7, resulting in improved dispersibility in resin materials containing polymers with the same skeletal structure. Furthermore, oxidation reactions on the quantum dot surface are further suppressed, and the resulting degradation of the quantum dot's fluorescence emission efficiency is also suppressed, leading to improved stability and greater compatibility with highly polar solvents and photosensitive resin compositions.

[0069] [Quantum dot composition] The quantum dot composition of the present invention comprises quantum dots 1 dispersed in a resin material containing at least one skeletal structure identical to that contained in the polymer coating layer 7. 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, and the like.

[0070] The aforementioned polymers are selected as appropriate for the application from polymers derived from acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, copolymers combining multiple polymers, polymers containing glycidyl (meth)acrylate as a repeating unit, siloxane skeletons, urethane skeletons, silphenylene skeletons, norbornene skeletons, fluorene skeletons, and isocyanurate skeletons.

[0071] Examples include acrylic resins, alkyd resins, melamine resins, epoxy resins, silicone resins, polyvinyl alcohol, polyvinylpyrrolidone, polyamides, polyamide-imides, polyimide precursors and their esterification products, and reaction products of tetracarboxylic dianhydrides and diamines. These polymers are also given polymerizable substituents, and curing is possible when used in combination with polymerization initiators. Radical polymerizable substituents include vinyl groups, acrylic groups, methacrylic groups, and thiol groups, all of which can be suitably used. Cationic polymerizable substituents include hydroxyl groups, phenolic hydroxyl groups, epoxy groups, glycidyl groups, oxetanyl groups, and isocyanate groups, all of which can be suitably used. In addition, carboxyl groups may be introduced to impart alkali developability.

[0072] Furthermore, the quantum dot composition of the present invention may also preferably contain a polymerization initiator. The polymerization initiator may be a thermal or photopolymerization initiator, and either can be suitably used in conjunction with the base polymer. Examples of photoradical polymerization initiators include the Irgacure® 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 Darocure® series include TPO and Darocure 1173. In addition, known thermal radical polymerization initiators and photocationic polymerization initiators may also be included.

[0073] The polymerization initiator content is preferably 0.1 to 10 parts by mass, and more preferably 0.2 to 5 parts by mass, per 100 parts by mass of polymer added. The quantum dot composition of the present invention may contain an organic solvent to improve its coatability. From the viewpoint of compatibility with quantum dots, an organic solvent is preferred as the solvent, for example, ketones, alkylene glycol ethers, alcohols, and aromatic compounds. From the ketone group, acetone, methyl ethyl ketone, cyclohexanone, etc. From the alkylene glycol ether group, methyl cellosolve (ethylene glycol monomethyl ether), butyl cellosolve (ethylene glycol monobutyl ether), methyl acetate cellosolve, ethyl acetate cellosolve, butyl acetate cellosolve, 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 acetate monomethyl ether, diethylene glycol acetate Suitable solvents include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, 3-methyl-3-methoxybutanol, etc. from the alcohol group, and benzene, toluene, xylene from the aromatic solvent group. Furthermore, the quantum dot composition of the present invention may also contain polymerizable crosslinking agents, photoacid generators, antioxidants, light scattering agents, etc., and there are no particular limitations as long as the coatability of the quantum dot composition is not affected.

[0074] Such quantum dot compositions have improved dispersibility in resin materials containing polymers that include at least one of the same skeletal structures as those contained in the polymer coating layer 7, allowing for high-concentration dispersion of quantum dots 4.

[0075] [Wavelength conversion materials] Furthermore, the present invention provides a wavelength conversion material containing a cured product of the above-mentioned quantum dot composition. The wavelength conversion material may be used as is or processed. One example is a wavelength conversion film in which the quantum dot composition is dispersed in a resin, which is formed by processing it into a sheet and then curing it. With such wavelength conversion materials, quantum dots are dispersed at high concentrations in the resin material without aggregates, while maintaining high fluorescence emission characteristics, resulting in improved reliability.

[0076] [Manufacturing method for quantum dots] Next, a method for producing quantum dots according to the present invention will be described. Note that the above-mentioned explanations regarding quantum dots, quantum dot compositions, and wavelength conversion materials may be omitted.

[0077] The present invention provides a method for producing a quantum dot, comprising: a quantum dot production step for producing a quantum dot comprising a semiconductor nanoparticle core and a semiconductor nanoparticle shell covering the semiconductor nanoparticle core; a metal oxide coating step for coating the surface of the quantum dot with a metal oxide; a quantum dot modification step for modifying the surface of the metal oxide with a compound having a methacryloyloxyethyl group and a hydrophilic group represented by formula (I); and a polymer coating layer formation step for forming a polymer coating layer by polymerizing the methacryloyloxyethyl group and a reactive substituent of a polymer using light or heat.

[0078] (Quantum dot manufacturing process) While there are various methods for manufacturing the core and shell of semiconductor nanoparticles, such as liquid-phase and gas-phase methods, the present invention is not particularly limited. From the viewpoint of obtaining high fluorescence emission efficiency, it is preferable to use semiconductor nanoparticles obtained by the hot soap method or hot injection method, in which precursor species are reacted at high temperatures in a high-boiling-point nonpolar solvent.

[0079] (Metal oxide coating process) The method for forming the metal oxide coating layer is not particularly limited, but from the viewpoint of selectively promoting the reaction on the quantum dot surface, a method of reacting the metal oxide precursor in a liquid phase is preferred.

[0080] In this invention, one example is a method for forming an oxide coating layer using microwave treatment. By using microwaves, the metal oxide precursor is directly heated from within, allowing the reaction to proceed selectively in a shorter time, and enabling the formation of a metal oxide layer on the quantum dot surface.

[0081] Here, "microwaves" generally refers to electromagnetic waves with frequencies ranging from 300 MHz to 3 THz. While methods of microwave irradiation include, for example, using Milestone General's flexi WAVE, they are not particularly limited.

[0082] In the metal oxide coating process, it is preferable to perform the process in the presence of quantum dots and a metal oxide precursor, and to coat the surface of the semiconductor nanoparticles with metal oxide by irradiating the metal oxide precursor in the presence of quantum dots with microwaves. This allows for the efficient formation of the metal oxide coating layer and suppresses the deterioration of fluorescence emission efficiency.

[0083] In this case, it is preferable to select one or more of the following as the dispersion medium for the quantum dots and metal oxide precursor: a polar solvent, a nonpolar solvent, or an ionic liquid, and to form the coating layer in that solvent.

[0084] Furthermore, it is preferable that the solvent used in the metal oxide coating process be one or more of the following solvents: toluene, hexane, cyclohexane, benzene, and diethyl ether. These nonpolar solvents can further improve the dispersibility of semiconductor nanoparticles (quantum dots).

[0085] Furthermore, if the solvent is a nonpolar solvent, a microwave-absorbing heating element called Weflon, a type of PTFE resin containing carbon components manufactured by Milestone, may be optionally used during the coating process.

[0086] While not particularly limited, it is preferable to use one or more metal oxide precursors 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 preferred as metal oxide precursors.

[0087] In this process, it is preferable to use a catalyst to accelerate the reaction of the metal oxide precursor during the coating process. In particular, when using a metal alkoxide, it is preferable to use a catalyst to accelerate the sol-gel reaction. Examples of catalysts include acidic aqueous solutions or basic aqueous solutions, with basic aqueous solutions being particularly preferred from the viewpoint of coating layer thickness.

[0088] Furthermore, a surfactant may be added during the metal oxide coating process from the viewpoint of dispersibility of the metal oxide precursor. The surfactant is not particularly limited, but examples include cationic surfactants such as quaternary ammonium salts like cetyltrimethylammonium bromide, anionic surfactants such as carboxylates and sulfonates, and nonionic surfactants such as polyoxyethylene alkyl ethers and cetyltrimethylammonium bromide. Cationic surfactants are particularly preferred from the viewpoint of dispersibility of the metal oxide precursor.

[0089] Furthermore, it is preferable to carry out the metal oxide coating process in the presence of alcohol. Coating in the presence of alcohol results in better dispersibility of the metal oxide precursor. In addition, if a surfactant is added, dispersibility can be further improved by dissolving it in a polar solvent such as alcohol.

[0090] In this case, the reaction temperature during microwave irradiation treatment varies depending on the solvent, but from the viewpoint of stably maintaining fluorescence emission efficiency, 40 to 200°C is preferred, and 50 to 110°C is more preferred.

[0091] While microwave processing is used as an example for the metal oxide coating process in this embodiment, the method is not particularly limited as long as the quantum dot surface is "coated" with a metal oxide layer.

[0092] (Quantum dot modification process) The method for modifying the surface of a metal oxide layer with a compound having a methacryloyloxyethyl group and a hydrophilic group is not particularly limited, as long as the compound is modified on the metal oxide surface. As an example, a system consisting of two phases, a polar solvent and a nonpolar solvent, is used in which particles with a metal oxide coating layer formed on the surface of quantum dots are dispersed in a nonpolar solvent and a polar solvent in which a compound having a methacryloyloxyethyl group and a hydrophilic group is dispersed is mixed by strong stirring or the like, and the quantum dots modified with the compound having a methacryloyloxyethyl group and a hydrophilic group are extracted into the polar solvent.

[0093] The type of nonpolar solvent is not particularly limited, as long as the particles with the metal oxide coating formed on the quantum dot surface are dispersed without settling. Similarly, the polar solvent is not particularly limited, as long as the compound having methacryloyloxyethyl groups and hydrophilic groups is eluted without precipitation. Furthermore, even if the polar and nonpolar solvents do not mix and separate into two phases, the type of solvent is not limited, as long as the resulting quantum dots are dispersed on the polar solvent side.

[0094] The heating temperature when modifying the quantum dot surface with a compound having a methacryloyloxyethyl group and a hydrophilic group is not particularly limited, but a heating temperature in the range of 30 to 100°C is preferred for efficient modification. Within this range, the metal oxide layer surface can be modified more efficiently.

[0095] (Polymer coating layer formation process) The method for forming a polymer coating layer on the outermost surface of a quantum dot is not particularly limited, as long as it involves a polymerization reaction between the methacryloyloxyethyl group of a compound having a methacryloyloxyethyl group and a hydrophilic group and a reactive substituent of a polymer.

[0096] Furthermore, the polymer can be used in combination with a polymerization initiator. Polymerization initiators include thermal or photopolymerization initiators, and either can be suitably used depending on the polymer. In addition, known thermal radical polymerization initiators or photocationic polymerization initiators may be used.

[0097] Furthermore, in the step of forming the polymer coating layer, in addition to compounds having methacryloyloxyethyl groups and hydrophilic groups, polymers, and polymerization initiators, organic solvents, polymerizable crosslinking agents, photoacid generators, etc., may also be included, and can be adjusted as appropriate to efficiently advance the polymerization reaction.

[0098] According to this method for manufacturing quantum dots, which includes a "quantum dot manufacturing process," a "metal oxide coating process," a "quantum dot modification process," and a "polymer coating layer formation process," it is possible to manufacture quantum dots that maintain the fluorescence emission properties of the quantum dots while improving stability and compatibility with highly polar solvents and photosensitive resin compositions.

[0099] [Method for manufacturing quantum dot compositions] The present invention also provides a method for producing a quantum dot composition by dispersing quantum dots produced by the above-described method in a resin material containing at least one skeletal structure identical to the skeletal structure of the main chain of a polymer contained in a polymer coating layer.

[0100] The resin material can consist of a polymer as the base polymer and a polymerization initiator, and may also contain organic solvents, polymerizable crosslinking agents, photoacid generators, antioxidants, light scattering agents, etc.

[0101] The polymers can preferably include polymers derived from acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, copolymers combining multiple polymers, polymers containing glycidyl (meth)acrylate repeating units, siloxane skeletons, urethane skeletons, silphenylene skeletons, norbornene skeletons, fluorene skeletons, and isocyanurate skeletons, and the polymer used may be selected as appropriate for the application.

[0102] Furthermore, these polymers have polymerizable substituents introduced into them, and can be cured by using them in combination with a polymerization initiator. Polymerization initiators include thermal or photopolymerization initiators, and either can be suitably used depending on the base polymer. In addition, known thermal radical polymerization initiators or photocationic polymerization initiators may be used.

[0103] The polymerization initiator content is preferably 0.1 to 10 parts by mass, and more preferably 0.2 to 5 parts by mass, per 100 parts by mass of polymer added. Organic solvents may be used to improve the coatability of the quantum dot composition. In addition, polymerizable crosslinking agents, photoacid generators, antioxidants, light scattering agents, etc., may be used, and there are no particular restrictions as long as they do not affect the coatability of the quantum dot composition.

[0104] According to this method for manufacturing quantum dot compositions, it is possible to produce quantum dot compositions in which the dispersibility of quantum dots in a resin material is improved.

[0105] [Method for manufacturing wavelength conversion materials] The present invention also provides a manufacturing method for producing a wavelength conversion material by curing a quantum dot composition produced by the above-described method for producing a quantum dot composition.

[0106] The method for manufacturing the wavelength conversion material is not particularly limited, but for example, a wavelength conversion material can be obtained by coating a resin composition, in which a quantum dot composition is dispersed in a resin, onto a transparent film such as PET or polyimide, curing it, and then laminating it.

[0107] The transparent film can be coated using spray or inkjet methods, or with spin coating, bar coating, or doctor blade methods, forming a resin layer. The thickness of the resin layer and the transparent film is not particularly limited and can be selected as appropriate depending on the application.

[0108] According to this method for manufacturing wavelength conversion materials, even after curing the quantum dot composition, it is possible to disperse the quantum dots in the resin material without aggregation while maintaining high fluorescence emission efficiency, thereby enabling the production of a wavelength conversion material with improved reliability. [Examples]

[0109] The present invention will be described in detail below with reference to examples, but this is not intended to limit the present invention.

[0110] (Measurement of emission wavelength, emission width at half maximum, and fluorescence emission efficiency) For the fluorescence emission characteristics of the quantum dots in the examples and comparative examples, the emission wavelength, fluorescence emission full width at half maximum, and fluorescence emission efficiency (internal quantum yield) of the quantum dots at an excitation wavelength of 450 nm were measured using the quantum efficiency measurement system (QE-2100) manufactured by Otsuka Electronics Co., Ltd.

[0111] (Reliability testing) The obtained wavelength conversion materials were treated at 85°C and 85%RH (relative humidity) for 500 hours, and their reliability was evaluated by comparing the fluorescence emission efficiency (internal quantum yield) of the wavelength conversion materials before and after treatment.

[0112] [Example 1] (Quantum dot manufacturing process) 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 added to a flask. The mixture was heated and stirred under reduced pressure at 100°C for 1 hour while dissolving the substances, and the gas was removed.

[0113] After cooling the flask to room temperature, nitrogen was purged, and 0.50 mL (0.17 mmol) of 10 vol% (tris)trimethylsilylphosphine / octadecene solution was added to the flask. The flask was heated to 300°C and stirred for 20 minutes to synthesize InP semiconductor core particles.

[0114] Next, after cooling the flask to 200°C, 0.10 mL (0.02 mmol) of gallium(III) chloride / octadecene solution was added and heated for 20 minutes.

[0115] Furthermore, after heating the flask to 240°C, 4.0 mL (1.2 mmol) of 0.30 M zinc stearate / octadecene solution was added and stirred for 30 minutes. Then, 0.60 mL (0.90 mmol) of 1.5 M selenium / trioctylphosphine solution was added to the flask and stirred for 30 minutes.

[0116] Next, after cooling the flask 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, it was heated to 230°C, and 0.48 mL (2.0 mmol) of 1-dodecanethiol was added and stirred for 40 minutes.

[0117] The resulting solution was cooled to room temperature, ethanol was added, and the quantum dots, consisting of an InP core, a ZnSe shell, and a ZnS shell, were precipitated by centrifugation, and the supernatant was removed.

[0118] To the obtained InP / ZnSe / ZnS precipitate, either toluene or propylene glycol monomethyl ether acetate (PGMEA) was added as a polar solvent. As a result, the obtained precipitate dispersed in toluene but did not disperse in PGMEA and instead settled, confirming that InP / ZnSe / ZnS does not disperse in polar solvents and has a high affinity for nonpolar solvents.

[0119] Fluorescence emission characteristics were evaluated using an InP / ZnSe / ZnS toluene dispersion. The obtained quantum dots exhibited an emission wavelength of 536 nm, a emission width at half maximum of 41 nm, and an internal quantum yield of 81%.

[0120] (Metal oxide coating process) 10 g of the toluene dispersion of the obtained 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 reaction vessel.

[0121] Subsequently, an Al2O3 coating layer was formed on the InP / ZnSe / ZnS surface by heating at 60°C for 5 minutes at 2450 MHz using a microwave synthesis reactor (flexi WAVE, manufactured by Milestone General). Ethanol was added to the resulting particles, and the supernatant was removed by centrifugation.

[0122] The obtained InP / ZnSe / ZnS / Al2O3 precipitate was treated with either hexane or propylene glycol monomethyl ether acetate (PGMEA), both polar solvents. The results showed that the precipitate dispersed in hexane but settled in PGMEA, confirming that InP / ZnSe / ZnS / Al2O3 does not disperse in polar solvents and has a high affinity for non-polar solvents.

[0123] Fluorescence emission characteristics were evaluated using a hexane dispersion of InP / ZnSe / ZnS / Al2O3. The obtained quantum dots exhibited an emission wavelength of 537 nm, a emission width at half maximum of 42 nm, and an internal quantum yield of 65%.

[0124] (Quantum dot modification process) Under a nitrogen atmosphere, 10 mg of bis[2-(methacryloyloxy)ethyl phosphate was weighed into a 20 ml vial, and 10 ml of dimethylformamide (DMF) was added and stirred to prepare a bis[2-(methacryloyloxy)ethyl phosphate] solution.

[0125] Furthermore, under a nitrogen atmosphere, 10 g of the obtained 1.0 wt% InP / ZnSe / ZnS / Al2O3 hexane dispersion and 10 ml of bis[2-(methacryloyloxy)ethyl phosphate] solution were added to a 50 ml vial. The mass ratio of bis[2-(methacryloyloxy)ethyl phosphate] to InP / ZnSe / ZnS / Al2O3 was 10%.

[0126] At this time, hexane and DMF separated into two phases, and the quantum dots were dispersed in the hexane, which is a nonpolar solvent. Next, this solution was heated to 50°C under a nitrogen atmosphere, stirred for 30 minutes, and then cooled to room temperature. At this time, the quantum dots migrated from the hexane, which is a nonpolar solvent, to the DMF side, and it was confirmed that quantum dots modified with bis[2-(methacryloyloxy)ethyl] phosphate on the surface of InP / ZnSe / ZnS / Al2O3 were dispersed in the polar solvent.

[0127] The modified quantum dots were further precipitated by adding hexane and centrifuging. After removing the supernatant, propylene glycol monomethyl ether acetate (PGMEA) was added to the resulting quantum dot precipitate. The results confirmed that the quantum dots dispersed in the polar solvent PGMEA. The fluorescence emission properties of the obtained quantum dots were an emission wavelength of 537 nm, an emission width at half maximum of 42 nm, and an internal quantum yield of 60%.

[0128] (Polymer coating layer formation process) The PGMEA dispersion of modified quantum dots was added to a flask that had been pre-purged with nitrogen, and 2 parts by mass of methacrylic-modified silicone oil X-32-3817-3 (manufactured by Shin-Etsu Chemical Co., Ltd.) were added per 100 parts by mass of the quantum dot PGMEA dispersion. After stirring and degassing, the mixture was irradiated with a UV LED while stirring, at a wavelength of 365 nm and an output of 4000 mW / cm². 2 The material was irradiated with light for 20 seconds. After the reaction was complete, hexane was added to precipitate the material, and after centrifugation, the supernatant was removed and dispersed again in PGMEA to form a polymer coating layer and produce quantum dots. The fluorescence emission characteristics of the obtained quantum dots were an emission wavelength of 537 nm, an emission width at half maximum of 42 nm, and an internal quantum yield of 59%.

[0129] (Manufacturing of quantum dot compositions) Quantum dots dispersed in PGMEA and methacrylic-modified silicone oil X-32-3817-3 (manufactured by Shin-Etsu Chemical Co., Ltd.) were weighed and mixed so that the quantum dots accounted for 20 wt% of the non-volatile content. After mixing, the solvent was removed to obtain the quantum dot composition.

[0130] (Manufacturing of wavelength conversion materials) A wavelength conversion material was fabricated using the obtained quantum dot composition. The quantum dot composition was degassed under vacuum and coated onto a 50 μm thick polyethylene terephthalate (PET) film. A 100 μm thick quantum dot-containing resin layer was formed using a bar coater. A PET film was then laminated onto this resin layer. This film was then irradiated with a UV LED at a wavelength of 365 nm and an output of 4000 mW / cm². 2 A wavelength conversion material was fabricated by curing a quantum dot-containing resin layer by irradiating it with light for 20 seconds. The fluorescence emission characteristics of the obtained wavelength conversion material were an emission wavelength of 537 nm, an emission half-width of 42 nm, and an internal quantum yield of 53%.

[0131] [Example 2] (Quantum dot manufacturing process) A toluene dispersion of InP / ZnSe / ZnS was produced using the same quantum dot manufacturing process as in Example 1.

[0132] (Metal oxide coating process) A metal oxide coating process on the quantum dot surface was performed in the same manner as in Example 1 to produce a hexane dispersion of InP / ZnSe / ZnS / Al2O3.

[0133] (Quantum dot modification process) Under a nitrogen atmosphere, a 75 wt% aqueous solution of [2-(methacryloyloxy)ethyl]trimethylammonium chloride was used to weigh 10 mg of [2-(methacryloyloxy)ethyl]trimethylammonium chloride into a 20 ml vial. 10 ml of dimethylformamide (DMF) was then added and stirred to prepare a DMF solution of [2-(methacryloyloxy)ethyl]trimethylammonium chloride.

[0134] Furthermore, under a nitrogen atmosphere, 10 g of the obtained 1.0 wt% InP / ZnSe / ZnS / Al2O3 hexane dispersion and 10 ml of DMF solution of [2-(methacryloyloxy)ethyl]trimethylammonium chloride were added to a 50 ml vial. The mass ratio of [2-(methacryloyloxy)ethyl]trimethylammonium chloride to InP / ZnSe / ZnS / Al2O3 was 10%.

[0135] At this time, hexane and DMF separated into two phases, with InP / ZnSe / ZnS / Al2O3 dispersed in the hexane, which is a nonpolar solvent. Next, this solution was heated to 50°C under a nitrogen atmosphere, stirred for 30 minutes, and then cooled to room temperature. At this time, the quantum dots migrated from the hexane, which is a nonpolar solvent, to the DMF, and it was confirmed that quantum dots modified with [2-(methacryloyloxy)ethyl]trimethylammonium chloride on the surface of InP / ZnSe / ZnS / Al2O3 dispersed in the polar solvent.

[0136] The modified quantum dots were further precipitated by adding hexane and centrifuging. After removing the supernatant, propylene glycol monomethyl ether acetate (PGMEA) was added to the resulting quantum dot precipitate. The results confirmed that the quantum dots dispersed in the polar solvent PGMEA. The fluorescence emission properties of the obtained quantum dots were an emission wavelength of 538 nm, an emission width at half maximum of 43 nm, and an internal quantum yield of 55%.

[0137] (Polymer coating layer formation process) The PGMEA dispersion of modified quantum dots was added to a flask that had been pre-purged with nitrogen, and 2 parts by mass of acrylic resin RA-4101 (manufactured by Negami Sangyo Co., Ltd.) were added per 100 parts by mass of the quantum dot PGMEA dispersion. Furthermore, 1 part by mass of Irgacure1173 was added per 100 parts by mass of acrylic resin, and after stirring and mixing, the mixture was irradiated using a UV LED irradiation device at a wavelength of 365 nm and an output of 4000 mW / cm². 2 The material was irradiated with light for 20 seconds. After the reaction was complete, hexane was added to precipitate the material, and after centrifugation, the supernatant was removed and dispersed again in PGMEA to form a polymer coating layer and produce quantum dots. The fluorescence emission characteristics of the obtained quantum dots were an emission wavelength of 538 nm, an emission width at half maximum of 43 nm, and an internal quantum yield of 54%.

[0138] (Manufacturing of quantum dot compositions) A solution of quantum dots dispersed in PGMEA and acrylic resin RA-4101 (manufactured by Negami Sangyo Co., Ltd.) were weighed so that the quantum dots constituted 20 wt% of the non-volatile content. Irgacure 1173 was weighed at 1 part by mass per 100 parts by mass of the non-volatile content of the acrylic resin and mixed. After mixing, the PGMEA solvent was removed by vacuum distillation to obtain the quantum dot composition.

[0139] (Manufacturing of wavelength conversion materials) A wavelength conversion material was fabricated using the obtained quantum dot composition in the same manner as in Example 1. The fluorescence emission characteristics of the obtained wavelength conversion material were an emission wavelength of 538 nm, an emission half-width of 43 nm, and an internal quantum yield of 50%.

[0140] [Example 3] (Quantum dot manufacturing process) A toluene dispersion of InP / ZnSe / ZnS was produced using the same quantum dot manufacturing process as in Example 1.

[0141] (Metal oxide coating process) A metal oxide coating process on the quantum dot surface was performed in the same manner as in Example 1 to produce a hexane dispersion of InP / ZnSe / ZnS / Al2O3.

[0142] (Quantum dot modification process) Under a nitrogen atmosphere, 10 mg of mono[2-(methacryloyloxy)ethyl]maleate was weighed into a 20 ml vial, and 10 ml of dimethylformamide (DMF) was added and stirred to prepare a mono[2-(methacryloyloxy)ethyl]maleate acid solution.

[0143] Furthermore, under a nitrogen atmosphere, 10 g of the obtained 1.0 wt% InP / ZnSe / ZnS / Al2O3 hexane dispersion and 10 ml of mono[2-(methacryloyloxy)ethyl]maleate acid solution were added to a 50 ml vial. The mass ratio of mono[2-(methacryloyloxy)ethyl]maleate to InP / ZnSe / ZnS / Al2O3 was 10%.

[0144] At this time, hexane and dimethylformamide separated into two phases, and InP / ZnSe / ZnS / Al2O3 was dispersed in the hexane side, which is a nonpolar solvent. Next, this solution was heated to 50°C under a nitrogen atmosphere, stirred for 30 minutes, and then cooled to room temperature. At this time, the quantum dots had shifted to the dimethylformamide side, which is a polar solvent, and it was confirmed that the quantum dots were dispersed, yielding InP / ZnSe / ZnS / Al2O3 quantum dots modified with mono[2-(methacryloyloxy)ethyl]maleate.

[0145] The modified quantum dots were further precipitated by adding hexane and centrifuging. After removing the supernatant, propylene glycol monomethyl ether acetate (PGMEA) was added to the resulting quantum dot precipitate. The results confirmed that the quantum dots dispersed in the polar solvent PGMEA. The fluorescence emission properties of the obtained quantum dots were an emission wavelength of 537 nm, an emission width at half maximum of 42 nm, and an internal quantum yield of 58%.

[0146] (Polymer coating layer formation process) Next, the PGMEA dispersion of the modified quantum dots was added to a flask that had been pre-purged with nitrogen, and 2 parts by mass of the isocyanuric acid derivative DA-MGIC (manufactured by Shikoku Chemicals, Inc.) were added per 100 parts by mass of the quantum dot PGMEA dispersion. Furthermore, 1 part by mass of Irgacure1173 was added per 100 parts by mass of DA-MGIC, and after stirring and mixing, the mixture was treated with a UV LED irradiation device at a wavelength of 365 nm and an output of 4000 mW / cm². 2 The material was irradiated with light for 20 seconds. After the reaction was complete, hexane was added to precipitate the material, and after centrifugation, the supernatant was removed and dispersed again in PGMEA to form a polymer coating layer and produce quantum dots. The fluorescence emission characteristics of the obtained quantum dots were an emission wavelength of 537 nm, an emission width at half maximum of 42 nm, and an internal quantum yield of 55%.

[0147] (Manufacturing of quantum dot compositions) A dispersion of quantum dots dispersed in epoxy-containing silicone resin (CAS No. 2253674-54-1, manufactured by Shin-Etsu Chemical Co., Ltd.) and PGMEA was weighed and mixed so that the quantum dots constituted 20 wt% of the non-volatile content. 2 parts by mass of photoacid generator CPI-310FG and 20 parts by mass of crosslinking agent THI-DE were weighed and mixed with 100 parts by mass of the non-volatile content of the silicone resin. After mixing, the PGMEA solvent was removed by vacuum distillation to obtain the quantum dot composition.

[0148] (Manufacturing of wavelength conversion materials) A wavelength conversion material was fabricated using the obtained quantum dot composition. The quantum dot composition was degassed under vacuum, coated onto a 5 mm thick glass substrate, and after removing the solvent, a 100 μm thick quantum dot-containing resin layer was formed using a bar coater. A PET film was then laminated onto this resin layer. This film was then irradiated with a UV LED at a wavelength of 365 nm and an output of 4000 mW / cm². 2 A quantum dot-containing resin layer was cured by irradiating it with light for 20 seconds, and then a wavelength conversion material was fabricated by heating it at 120°C for 5 minutes. The fluorescence emission characteristics of the obtained wavelength conversion material were an emission wavelength of 537 nm, an emission half-width of 42 nm, and an internal quantum yield of 50%.

[0149] [Comparative Example 1] The same quantum dot manufacturing process as in Example 1 was carried out, but without the metal oxide coating process on the quantum dot surface, surface modification with a compound having methacryloyloxyethyl groups and hydrophilic groups, and the formation of a polymer coating layer, the quantum dots were mixed with a resin material. Methacrylic-modified silicone oil X-32-3817-3 (manufactured by Shin-Etsu Chemical Co., Ltd.) was weighed into the toluene dispersion after the quantum dot manufacturing process so that the quantum dots were present at a non-volatile content ratio of 20 wt%, and mixed. After mixing, the solvent was removed to obtain a quantum dot composition.

[0150] A wavelength conversion material was fabricated using the obtained quantum dot composition by the same manufacturing method as in Example 1. The fluorescence emission characteristics of the obtained wavelength conversion material were a wavelength of 544 nm, an emission half-width of 47 nm, and an internal quantum yield of 28%.

[0151] [Comparative Example 2] A quantum dot manufacturing process similar to that of Example 1 was carried out, and a metal oxide coating process on the quantum dot surface similar to that of Example 1 was performed. The mixture was then mixed with a resin material without surface modification with a compound having methacryloyloxyethyl groups and hydrophilic groups, or without forming a polymer coating layer. Methacrylic-modified silicone oil X-32-3817-3 (manufactured by Shin-Etsu Chemical Co., Ltd.) was weighed and mixed into a hexane dispersion of the quantum dots up to the metal oxide coating step, with the amount being such that the solid material of the quantum dots up to the metal oxide coating step was 20 wt% based on the non-volatile content ratio. After mixing, the solvent was removed to obtain a quantum dot composition.

[0152] A wavelength conversion material was fabricated using the obtained quantum dot composition by the same manufacturing method as in Example 1. The fluorescence emission characteristics of the obtained wavelength conversion material were a wavelength of 544 nm, an emission half-width of 47 nm, and an internal quantum yield of 34%.

[0153] [Comparative Example 3] A quantum dot manufacturing process similar to that of Example 1 was carried out, a metal oxide coating process on the quantum dot surface similar to that of Example 1 was performed, and surface modification with a compound having methacryloyloxyethyl groups and hydrophilic groups similar to that of Example 1 was performed. The quantum dots were then mixed with a resin material without forming a polymer coating layer. Methacrylic-modified silicone oil X-32-3817-3 (manufactured by Shin-Etsu Chemical Co., Ltd.) was weighed and mixed into the PGMEA dispersion of the quantum dots up to the surface modification step, with a non-volatility ratio such that the solid material of the surface-modified quantum dots was 20 wt%. After mixing, the solvent was removed to obtain a quantum dot composition.

[0154] A wavelength conversion material was fabricated using the obtained quantum dot composition by the same manufacturing method as in Example 1. The fluorescence emission characteristics of the obtained wavelength conversion material were a wavelength of 541 nm, an emission half-width of 44 nm, and an internal quantum yield of 39%.

[0155] Table 1 shows the results for Examples 1-3 and Comparative Examples 1-3. It shows the fluorescence emission characteristics of quantum dots, quantum dots coated with a metal oxide layer, quantum dots surface-modified with a compound having a methacryloyloxyethyl group and a hydrophilic group, and quantum dots with a polymer coating (quantum dot bodies), as well as the fluorescence emission characteristics of the wavelength conversion material, the microscopic observation results of the wavelength conversion material, and the internal quantum yield (fluorescence emission efficiency) value after reliability testing of the wavelength conversion material.

[0156] [Table 1]

[0157] From the results in Table 1, it was found that the wavelength conversion materials of Comparative Examples 1 to 3 showed a significant decrease in the initial value of the internal quantum yield, a large shift in the emission wavelength to longer wavelengths, and an expansion of the full width at half maximum, based on their emission characteristics in quantum dot dispersions. On the other hand, it was confirmed that the wavelength conversion materials of Examples 1 to 3 suppressed the decrease in the initial value of the internal quantum yield, and maintained their emission characteristics in terms of wavelength and full width at half maximum, based on their emission characteristics in quantum dot dispersions.

[0158] Furthermore, microscopic observation revealed that the wavelength conversion materials of Comparative Examples 1-3 contained more aggregates of quantum dots approximately 1-50 μm in size than the wavelength conversion materials of Examples 1-3. This suggests that the quantum dots in Comparative Examples 1-3 aggregated within the resin material due to their low compatibility with the photosensitive resin. As a result of this aggregation, the internal quantum yield of the wavelength conversion materials in Comparative Examples 1-3 decreased significantly, and the wavelength shifted to longer wavelengths, leading to an expansion of the full width at half maximum.

[0159] On the other hand, the wavelength conversion materials of Examples 1-3 were found to have small and few aggregates. This is thought to be because the polymer coating layer in Examples 1-3 introduced significant steric hindrance, improving compatibility with highly polar PGMEA and photosensitive resin materials, thereby effectively suppressing the aggregation of quantum dots. This improved dispersion of quantum dots in the resin material was confirmed. As a result of this improved dispersion, the wavelength conversion materials of Examples 1-3 are thought to have suppressed the decrease in the initial value of the internal quantum yield and to have maintained their wavelength and full width at half maximum characteristics.

[0160] Furthermore, regarding the reliability test results for the wavelength conversion material (treated at 85°C and 85%RH for 500 hours), it can be seen that the decrease in internal quantum yield over time was suppressed to within 10% for Examples 1-3, indicating improved stability compared to Comparative Examples 1-3. This is thought to be because the oxidation reaction on the quantum dot surface was suppressed by the coating of the metal oxide layer and the formation of the polymer coating layer in the quantum dot bodies of Examples 1-3, thus maintaining the internal quantum yield. In Comparative Example 1, it is thought that the ligands and modifiers on the quantum dot surface desorbed over time under high temperature and high humidity conditions, causing the oxidation reaction on the quantum dot surface to proceed and significantly reducing the internal quantum yield. In Comparative Examples 2 and 3, because a polymer coating layer was not formed on the outermost surface, the oxidation reaction on the quantum dot surface could not be completely suppressed, resulting in a gradual decrease in the internal quantum yield.

[0161] As described above, according to the embodiments of the present invention, the quantum dot material of the present invention maintains fluorescence emission characteristics while improving compatibility with highly polar solvents and photosensitive resin materials. The quantum dot composition using this quantum dot material has quantum dots dispersed in the resin material without aggregation. The wavelength conversion material using this quantum dot composition was confirmed to have high reliability, with suppressed degradation of fluorescence emission efficiency (internal quantum yield) over time under high temperature and high humidity conditions.

[0162] This specification includes the following embodiments: [1]: A quantum dot body comprising a quantum dot that emits fluorescence upon excitation light, wherein the quantum dot comprises a core of semiconductor nanoparticles and a shell of semiconductor nanoparticles covering the core of the semiconductor nanoparticles, the surface of the quantum dot is coated with a metal oxide, the surface of the metal oxide is modified with a compound having a methacryloyloxyethyl group and a hydrophilic group as shown in formula (I) below, and the quantum dot body has a polymer coating layer on its outermost surface formed by bonding the methacryloyloxyethyl group with a reactive substituent of a polymer. [ka] (R1 represents a hydrophilic group.) [2]: The quantum dot body of [1], wherein the hydrophilic group is selected from quaternary ammonium salts, carboxylates, succinates, isocyanates, maleates, hydrogen phosphates, 1,2,4-benzenetricarboxylates, salts of trimellitic anhydride, phthalates, acetoacetates, and thiocticates. [3]: The compound having a methacryloyloxyethyl group and a hydrophilic group is bis[2-(methacryloyloxy)ethyl]phosphate, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, mono-2-(methacryloyloxy)ethyl succinic acid, mono[2-(methacryloyloxy)ethyl]maleate, 2-(methacryloyloxy)ethyl isocyanate, (2-methacryloyloxyethyl)trimethylammonium=bis(trifluoromethanesulfonyl)imide, 4-MET(4-Methacryloxyethyl trimellitic acid), 4-META(4-Methacryloxyethyl trimellitic A quantum dot body of the above [1] or [2], comprising being selected from anhydride, mono-2-(methacryloyloxy)ethyl phthalate, bis[[2-(methacryloyloxy)ethyl](methyl)ammonio]propane-1-sulfonic acid, 2-(methacryloyloxy)ethyl acetoacetate, 2-[[2-(methacryloyloxy)ethyl]dimethylammonio]acetic acid, 4-[[2-(methacryloyloxy)ethyl]dimethylammonio]butane-1-sulfonic acid, 3-[[2-(methacryloyloxy)ethyl]dimethylammonio]propionate, 2-methacryloyloxyethyl thioctic acid, and [2-(methacryloyloxy)ethyl]trimethylammonium methylsulfate. [4]: The quantum dot body according to [1], [2], or [3], wherein the reactive substituent of the polymer is one or more of the following: vinyl group, acrylic group, methacrylic group, hydroxyl group, phenolic hydroxyl group, epoxy group, or glycidyl group. [5]: The quantum dot body according to [1], [2], [3] or [4] above, wherein 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, acrylic acid ester, methacrylic acid ester, a skeletal structure having glycidyl (meth)acrylate as repeating units, a siloxane skeleton, a urethane skeleton, a sylphenylene skeleton, a norbornene skeleton, a fluorene skeleton, or an isocyanurate skeleton. [6]: A quantum dot composition in which the quantum dot bodies described in [1], [2], [3], [4], or [5] above are dispersed in a resin material containing at least one of the same skeletal structures as those contained in the polymer coating layer. [7]: A wavelength conversion material comprising a cured product of the quantum dot composition described in [6] above. [8]: A method for producing a quantum dot according to [1], [2], [3], [4] or [5] above, comprising: a quantum dot production step for producing a quantum dot comprising a core of semiconductor nanoparticles and a shell of semiconductor nanoparticles covering the core of the semiconductor nanoparticles; a metal oxide coating step for coating the surface of the quantum dot with a metal oxide; a quantum dot modification step for modifying the surface of the metal oxide with a compound having a methacryloyloxyethyl group and a hydrophilic group represented by formula (I) above; and a polymer coating layer formation step for forming a polymer coating layer by polymerizing the methacryloyloxyethyl group and a reactive substituent of a polymer by light or heat. [9]: A method for producing a quantum dot composition, comprising dispersing the quantum dots produced by the method for producing quantum dots described in [8] above 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.

[10] : A method for producing a wavelength conversion material, comprising curing a quantum dot composition produced by the method for producing a quantum dot composition described in [9] above to produce a wavelength conversion material.

[0163] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention. [Explanation of Symbols]

[0164] 1...Quantum dot body, 2...Semiconductor nanoparticle core, 3...Semiconductor nanoparticle shell 4...Quantum dots, 5...Metal oxide layer, 6... Compounds having a methacryloyloxyethyl group and a hydrophilic group, 7…Polymer coating layer.

Claims

1. A quantum dot body containing quantum dots that emit fluorescence upon excitation light, The quantum dot comprises a core of semiconductor nanoparticles and a shell of semiconductor nanoparticles covering the core of the semiconductor nanoparticles. The surface of the quantum dot is coated with a metal oxide. The surface of the metal oxide is modified with a compound having a methacryloyloxyethyl group and a hydrophilic group, as shown in formula (I) below. A quantum dot body characterized by having a polymer coating layer on its outermost surface, formed by the bonding of the methacryloyloxyethyl group with a reactive substituent of the polymer. 【Chemistry 1】 (R １ (This represents a hydrophilic group.)

2. The quantum dot body according to claim 1, characterized in that the hydrophilic group is selected from quaternary ammonium salts, carboxylates, succinates, isocyanates, maleates, hydrogen phosphates, 1,2,4-benzenetricarboxylates, salts of trimellitic anhydride, phthalates, acetoacetates, and thiocticates.

3. The compounds having a methacryloyloxyethyl group and a hydrophilic group include bis[2-(methacryloyloxy)ethyl]phosphate, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, mono-2-(methacryloyloxy)ethyl succinic acid, mono[2-(methacryloyloxy)ethyl]maleate, 2-(methacryloyloxy)ethyl isocyanate, (2-methacryloyloxyethyl)trimethylammonium=bis(trifluoromethanesulfonyl)imide, 4-MET (4-Methacryloyloxyethyl trimethylammonium acid), 4-META (4-Methacryloyloxyethyl trimethylammonium The quantum dot body according to claim 1, characterized in that it is selected from anhydride, mono-2-(methacryloyloxy)ethyl phthalate, bis[[2-(methacryloyloxy)ethyl](methyl)ammonio]propane-1-sulfonic acid, 2-(methacryloyloxy)ethyl acetoacetate, 2-[[2-(methacryloyloxy)ethyl]dimethylammonio]acetic acid, 4-[[2-(methacryloyloxy)ethyl]dimethylammonio]butane-1-sulfonic acid, 3-[[2-(methacryloyloxy)ethyl]dimethylammonio]propionate, 2-methacryloyloxyethyl thioctic acid, and [2-(methacryloyloxy)ethyl]trimethylammonium methylsulfate.

4. The quantum dot body according to claim 1, characterized in that the reactive substituent of the polymer is one or more of the following: vinyl group, acrylic group, methacrylic group, hydroxyl group, phenolic hydroxyl group, epoxy group, and glycidyl group.

5. The quantum dot body according to claim 1, wherein 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, acrylic acid ester, methacrylic acid ester, a skeletal structure having glycidyl (meth)acrylate as a repeating unit, a siloxane skeleton, a urethane skeleton, a sylphenylene skeleton, a norbornene skeleton, a fluorene skeleton, or an isocyanurate skeleton.

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

7. A wavelength conversion material characterized by comprising a cured product of the quantum dot composition described in claim 6.

8. A method for manufacturing a quantum dot body according to any one of claims 1 to 5, A quantum dot manufacturing process for producing a quantum dot comprising a semiconductor nanoparticle core and a semiconductor nanoparticle shell covering the semiconductor nanoparticle core, A metal oxide coating step in which the surface of the quantum dot is coated with a metal oxide, A quantum dot modification step is performed by modifying the surface of the metal oxide with a compound having a methacryloyloxyethyl group and a hydrophilic group represented by formula (I), A method for producing a quantum dot, comprising a polymer coating layer formation step, in which the methacryloyloxyethyl group and a reactive substituent of the polymer are polymerized by light or heat to form a polymer coating layer.

9. A method for producing a quantum dot composition, characterized by dispersing quantum dots produced by the method for producing quantum dots described in claim 8 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.

10. A method for producing a wavelength conversion material, characterized by curing a quantum dot composition produced by the method for producing a quantum dot composition described in claim 9.

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