Quantum dot body, quantum dot composition, wavelength conversion material, and production methods of those

Abstract

The present invention provides a quantum dot body which includes a quantum dot that produces fluorescence by means of excitation light, wherein: the quantum dot includes a core of a semiconductor nanoparticle and a shell of a semiconductor nanoparticle covering the core of the semiconductor nanoparticle; the surface of the quantum dot is covered with a metal oxide; the surface of the metal oxide is modified with a compound that has a methacryloyloxyethyl group represented by formula (I) and a hydrophilic group; and a polymer coating layer which is formed by bonding the methacryloyloxyethyl group to a reactive substituent of a polymer is provided on the outermost surface. As a result, the present invention provides a quantum dot body which has further improved stability and further improved compatibility with highly polar solvents and photosensitive resin compositions, while maintaining the fluorescence emission characteristics of a quantum dot. (R1 represents a hydrophilic group.)

Description

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

[0001] This invention relates to quantum dots, quantum dot compositions, wavelength conversion materials, and methods for producing the same.

[0002] Quantum dots, composed of semiconductor particles with a particle size of nanoscale, have discrete energy levels due to the confinement of excitons generated by light absorption within nanoscale spaces, and their band gap depends on the particle size. As a result, quantum dots exhibit highly efficient fluorescence emission, and their emission spectra are sharpened. Furthermore, due to the characteristic that the band gap changes with particle size, they have the ability to control the emission wavelength, and are expected to have applications as wavelength conversion materials for solid-state lighting and displays (Patent Document 1).

[0003] Japanese Patent Publication No. 2012-022028, International Publication No. 2011 / 081037

[0004] Quantum dots containing cadmium (Cd) and lead (Pb) are known to exhibit excellent fluorescence properties. However, because Cd and Pb are highly toxic to humans and the environment, restrictions on their use are being considered in various parts of the world, including under the European Union's RoHS directive. Therefore, quantum dots that do not contain these toxic elements are being investigated.

[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 to produce color filters is photolithography, in which a photosensitive resin composition containing pigments is coated onto a glass substrate, the solvent is dried, 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.

[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] (R １ (This 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-Methacryloyloxyethyl trimellitic acid), 4-META (4-Methacryloyloxyethyl 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 both a methacryloyloxyethyl group and a hydrophilic group, thereby enabling the formation of a polymer coating layer more efficiently.

[0022] In this case, 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 may be 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.

[0023] With such a polymer coating layer, oxidation reactions on the quantum dot surface are further suppressed, and the resulting degradation of the quantum dot's fluorescence emission efficiency is also further suppressed. This results in a quantum dot body with improved stability and better compatibility with highly polar solvents and photosensitive resin compositions.

[0024] In this case, the quantum dot composition can be one in which the quantum dots are dispersed in a resin material containing at least one of the same skeletal structures as those contained in the polymer coating layer.

[0025] This results in a quantum dot composition in which the initial value of fluorescence emission efficiency and its degradation over time are suppressed.

[0026] In this case, the wavelength conversion material can include a cured product of the above quantum dot composition.

[0027] This suppresses the initial value and degradation over time of the fluorescence emission efficiency, resulting in a more reliable wavelength conversion material.

[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.

[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.

[0035] This is a schematic cross-sectional view showing an example of the quantum dot body of the present 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] (R １ (This 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 treatment 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 bonding the methacryloyloxyethyl group with a reactive substituent of a 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 Dot) 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] Further, 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, deterioration of the fluorescence emission efficiency can be further suppressed.

[0047] As the material of the semiconductor nanoparticle core 2 of the core / shell semiconductor nanoparticle, those not containing elements such as Cd and Pb from the viewpoint of toxicity are preferable. For example, those selected from the group consisting of II-VI group compounds, III-V group compounds, I-III-VI group compounds, II-IV-V group compounds, and alloys or mixed crystals thereof can be used.

[0048] Specifically, as the material of the semiconductor nanoparticle core 2, ZnS, ZnSe, ZnTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, AgGaS ２ , AgInS ２ , AgGaSe ２ , AgInSe ２ , CuGaS ２ , CuGaSe ２ , CuInS ２ , CuInSe ２ , ZnSiP ２ , and ZnGeP ２ can be mentioned as those selected as single, plural, or mixed crystals from among them. Among these materials, ZnSe, ZnTe, and InP are particularly preferable from the viewpoints of fluorescence emission characteristics and stability.

[0049] Further, the surface of the semiconductor nanoparticle core 2 of the core / shell semiconductor nanoparticle is preferably passivated with an inorganic compound. Thereby, defects on the surface of the core particles are inactivated, the fluorescence emission efficiency is improved, and deterioration of the fluorescence emission efficiency over time is further suppressed.

[0050] The inorganic compound for performing passivation is not particularly limited, and examples thereof include metal halides. From the viewpoint of improving the fluorescence emission efficiency, GaCl ３ , GaI ３ , GaBr ３ , ZnCl ２ , ZnBr ２, ZnI ２ InCl ３ InBr ３ In I ３ , AgCl, AgBr, AgI, KCl, KBr, KI, NaCl, NaBr, NaI, MgCl ２ MgBr ２ 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 At least one compound selected from the above is particularly preferred.

[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 group II-VI compounds, alloys of group III-V compounds, and mixed crystals.

[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 Oxide) 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 deterioration 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 from the viewpoint of light transmittance, it is preferably 500 nm or less.

[0055] 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 WO ３ ,CrO ３ Ta ２ O ３ , BaTiO ３ , V ２ O ５ , NiO, NbO, Cu ２ O, CuO, MoO ３ Examples include at least one compound selected from the following. From the viewpoint of improving the stability of quantum dots, TiO ２ Al ２ O ３ SiO ２ , ZrO ２ This is preferable.

[0056] (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] (R １ (This represents a hydrophilic group.)

[0061] R in equation (I) above １ The hydrophilic group is not particularly limited, but examples include quaternary ammonium salts, carboxylates, succinates, isocyanates, maleates, hydrogen phosphates, 1,2,4-benzenetricarboxylates, salts of trimellitic anhydrides, phthalates, acetoacetates, and thiocticates. This further improves the affinity to polar solvents and 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-Methacryloyloxyethyl trimethylammonium acid), 4-META (4-Methacryloyl trimethylammonium 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 the reactive substituent of the polymer. This suppresses the deterioration of the fluorescence emission efficiency of the quantum dot over time, further improves stability, and improves 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 sylphenylene 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 is characterized in which quantum dots 1 are 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 the 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 Material] The present invention also provides a wavelength conversion material containing a cured product of the above quantum dot composition. The wavelength conversion material may be used as is or processed. One form is a wavelength conversion film in which the quantum dot composition is dispersed in a resin, which is processed into a sheet and then cured. With such a wavelength conversion material, the quantum dots are dispersed at a high concentration in the resin material without aggregates while maintaining high fluorescence emission characteristics, resulting in improved reliability.

[0076] [Method for Manufacturing Quantum Dots] Next, the method for manufacturing quantum dots according to the present invention will be described. Note that the matters described above 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) There are various methods for manufacturing the core and shell of semiconductor nanoparticles, such as liquid-phase and gas-phase methods, but 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 the hot injection method, in which a precursor species is reacted at high temperature 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 for microwave irradiation include, for example, using Milestone General's flexi WAVE, the method is 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. 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 quantum dot surface 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 to the polar solvent side.

[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 producing quantum dot composition] The present invention also provides a method for producing a quantum dot composition by dispersing the quantum dots produced by the above-described method for producing quantum dots 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.

[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 a skeletal structure with glycidyl (meth)acrylate as a repeating unit, 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 method for manufacturing a wavelength conversion material by curing a quantum dot composition manufactured by the above-described method for manufacturing quantum dot compositions.

[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.

[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 evaluation of the fluorescence emission characteristics of quantum dots in the examples and comparative examples, the emission wavelength, fluorescence emission width at half maximum, and fluorescence emission efficiency (internal quantum yield) of 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 Test) The obtained wavelength conversion material was treated at 85°C and 85% RH (relative humidity) for 500 hours, and its reliability was evaluated by comparing the fluorescence emission efficiency (internal quantum yield) of the wavelength conversion material 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, and the mixture was heated and stirred under reduced pressure at 100°C for 1 hour while dissolving the substances.

[0113] After cooling the flask to room temperature, nitrogen was purged, and 0.50 mL (0.17 mmol) of a 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 the mixture was 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 and degassing. 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] The obtained InP / ZnSe / ZnS precipitate was treated with either toluene or propylene glycol monomethyl ether acetate (PGMEA), both polar solvents. The result showed that the precipitate dispersed in toluene but did not disperse in PGMEA, instead settling. This confirmed that InP / ZnSe / ZnS does not disperse in polar solvents and has a high affinity for non-polar solvents.

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

[0120] (Metal oxide coating process) 10 g of a 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, using a microwave synthesis reactor (Milestone General, flexi WAVE), heating is performed at 2450 MHz at 60°C for 5 minutes to create Al on the InP / ZnSe / ZnS surface. ２ O ３ A coating layer was formed. Ethanol was added to the obtained particles, and the precipitate was removed by centrifugation.

[0122] The resulting InP / ZnSe / ZnS / Al ２ O ３ To the precipitate, polar solvents of hexane or propylene glycol monomethyl ether acetate (PGMEA) were added. As a result, the obtained precipitate dispersed in hexane but did not disperse in PGMEA and settled in InP / ZnSe / ZnS / Al ２ O ３It was confirmed that it does not disperse in polar solvents but has a high affinity for nonpolar solvents.

[0123] Fluorescence emission characteristics are evaluated using InP / ZnSe / ZnS / Al ２ O ３ The experiment was performed on a hexane dispersion. 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 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, the obtained 1.0 wt% InP / ZnSe / ZnS / Al was placed in a 50 ml vial. ２ O ３ 10 g of a hexane dispersion and 10 ml of bis[2-(methacryloyloxy)ethyl] phosphate solution were added. InP / ZnSe / ZnS / Al bis[2-(methacryloyloxy)ethyl] phosphate ２ O ３ The mass ratio was 10%.

[0126] At this point, hexane and DMF separated into two phases, with the quantum dots dispersed in the hexane, 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 point, the quantum dots had shifted from the hexane, nonpolar solvent, to the DMF side, forming an InP / ZnSe / ZnS / Al ２ O ３ It was confirmed that quantum dots modified with bis[2-(methacryloyloxy)ethyl] phosphate on their surface disperse in polar solvents.

[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. It was 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 the 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.) was 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 / cm. 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] (Preparation of Quantum Dot Composition) 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 Material) A wavelength conversion material was fabricated using the obtained quantum dot composition. The quantum dot composition was vacuum-degassed and coated onto a 50 μm thick polyethylene terephthalate (PET) film, and a 100 μm thick quantum dot-containing resin layer was formed using a bar coater. Furthermore, a PET film was 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 / cm. ２By irradiating light for 20 seconds, the quantum dot-containing resin layer was cured to produce a wavelength conversion material. 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) The same quantum dot manufacturing process as in Example 1 was carried out to produce a toluene dispersion of InP / ZnSe / ZnS.

[0132] (Metal oxide coating process) The same metal oxide coating process on the surface of the quantum dots as in Example 1 was carried out to produce a hexane dispersion of InP / ZnSSe / ZnS / Al ２ O ３

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

[0134] Furthermore, in a nitrogen atmosphere, into a 50 ml vial, 10 g of the obtained 1.0 wt% InP / ZnSSe / ZnS / Al ２ O ３ hexane dispersion and 10 ml of the DMF solution of [2-(methacryloyloxy)ethyl]trimethylammonium chloride were added. The mass ratio of [2-(methacryloyloxy)ethyl]trimethylammonium chloride to InP / ZnSSe / ZnS / Al ２ O ３ was 10%.

[0135] At this time, hexane and DMF were separated into two phases, and InP / ZnSSe / ZnS / Al ２ O ３ ​It was dispersed on the hexane side, which is a non-polar solvent. Next, this solution was heated to 50 °C under a nitrogen atmosphere and stirred for 30 minutes, and then cooled to room temperature. At this time, the quantum dots had phase-transferred from the non-polar solvent hexane to the DMF side, and InP / ZnSe / ZnS / Al ２ O ３ It was confirmed that the quantum dots modified with [2-(methacryloyloxy)ethyl]trimethylammonium chloride on the surface were dispersed in a polar solvent.

[0136] Hexane was further added to the quantum dots subjected to the modification process, and the quantum dots were precipitated by centrifugation. The supernatant was removed, and as a result of adding propylene glycol monomethyl ether acetate (PGMEA) to the obtained quantum dot precipitate, it was confirmed that the quantum dots were dispersed in the PGMEA solvent, which is a polar solvent. The fluorescence emission characteristics of the obtained quantum dots were an emission wavelength of 538 nm, an emission half-width of 43 nm, and an internal quantum yield of 55%.

[0137] (Polymer coating layer formation step) The PGMEA dispersion of the quantum dots subjected to the modification process was added to a flask previously purged with nitrogen, and acrylic resin RA-4101 (manufactured by Negami Sangyo Co., Ltd.) was added at 2 parts by mass with respect to 100 parts by mass of the quantum dot PGMEA dispersion. Further, Irgacure 1173 was added at 1 part by mass with respect to 100 parts by mass of the acrylic resin, and after stirring and mixing, light with a wavelength of 365 nm and an output of 4000 mW / cm ２ was irradiated for 20 seconds using a UV LED irradiation device. After completion of the reaction, hexane was added to precipitate, and after centrifugation, the supernatant was removed and redispersed in PGMEA to form a polymer coating layer, thereby producing a quantum dot body. The fluorescence emission characteristics of the obtained quantum dot body were an emission wavelength of 538 nm, an emission half-width of 43 nm, and an internal quantum yield of 54%.

[0138] (Preparation of Quantum Dot Composition) 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 Material) 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) The same quantum dot manufacturing process as in Example 1 was performed to produce a toluene dispersion of InP / ZnSe / ZnS.

[0141] (Metal oxide coating process) The same metal oxide coating process on the quantum dot surface as in Example 1 was performed, resulting in InP / ZnSe / ZnS / Al ２ O ３ A hexane dispersion was prepared.

[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, the obtained 1.0 wt% InP / ZnSe / ZnS / Al was placed in a 50 ml vial. ２ O ３ 10 g of a hexane dispersion and 10 ml of mono[2-(methacryloyloxy)ethyl]maleate acid solution were added. The InP / ZnSe / ZnS / Al of mono[2-(methacryloyloxy)ethyl]maleate was added. ２ O ３ The mass ratio was 10%.

[0144] At this time, hexane and dimethylformamide separate into two phases: InP / ZnSe / ZnS / Al ２ O ３ The quantum dots were dispersed on 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 moved to the dimethylformamide side, which is a polar solvent, and it was confirmed that the quantum dots were dispersed, and the InP / ZnSe / ZnS / Al modified with mono[2-(methacryloyloxy)ethyl]maleate was found. ２ O ３ We obtained quantum dots.

[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 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 Irgacure 1173 was added per 100 parts by mass of DA-MGIC, 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 / cm. 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 half-width of 42 nm, and an internal quantum yield of 55%.

[0147] (Preparation 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 PGMEA was weighed and mixed so that the quantum dots accounted for 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 Material) 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 / cm. 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, a emission half-width of 47 nm, and an internal quantum yield of 28%.

[0151] [Comparative Example 2] The same quantum dot manufacturing process as in Example 1 was carried out, and the same metal oxide coating process on the quantum dot surface as in Example 1 was carried out. The mixture was then mixed with a resin material without surface modification with a compound having a methacryloyloxyethyl group and a hydrophilic group, 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 quantum dots that had undergone the metal oxide coating process, with a non-volatility ratio such that the solid material of the quantum dots that had undergone the metal oxide coating was 20 wt%. 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, a emission half-width of 47 nm, and an internal quantum yield of 34%.

[0153] [Comparative Example 3] The same quantum dot manufacturing process as in Example 1 was carried out, the same metal oxide coating process on the quantum dot surface as in Example 1 was carried out, and the surface was modified with a compound having a methacryloyloxyethyl group and a hydrophilic group as in Example 1. The mixture was 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 quantum dots up to the surface modification step 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 of 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 the reliability test of the wavelength conversion material.

[0156]

[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 the quantum dot dispersion. 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 the quantum dot dispersion.

[0158] Furthermore, microscopic observation revealed that the wavelength conversion materials of Comparative Examples 1 to 3 contained more aggregates of quantum dots approximately 1 to 50 μm in size than the wavelength conversion materials of Examples 1 to 3. This is thought to be because the quantum dots in Comparative Examples 1 to 3 had low compatibility with the photosensitive resin, causing them to aggregate within the resin material. As a result of this aggregation, the internal quantum yield of the wavelength conversion materials of Comparative Examples 1 to 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 to 3 were found to have small and few aggregates. This is thought to be because the polymer coating layer in Examples 1 to 3 introduced significant steric hindrance, improving compatibility with highly polar PGMEA and photosensitive resin materials, thereby effectively suppressing the aggregation of quantum dots, and thus improving the dispersibility of quantum dots in the resin material. As a result of this improved dispersibility, the wavelength conversion materials of Examples 1 to 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 to 3, indicating improved stability compared to Comparative Examples 1 to 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 to 3, thereby 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, since a polymer coating layer was not formed on the outermost surface, the oxidation reaction on the quantum dot surface could not be completely suppressed, and the internal quantum yield gradually decreased.

[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 represented by the following formula (I), 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. (R １(where 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-Methacryloyloxyethyl trimethylammonium acid), 4-META (4-Methacryloyloxyethyl trimethylammonium 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 silphenylene skeleton, a norbornene skeleton, a fluorene skeleton, or an isocyanurate skeleton. [6]: The quantum dot body according to [1], [2], [3], [4], or [5] above, dispersed in a resin material containing at least one skeletal structure that is the same as the skeletal structure contained in the polymer coating layer. [7]: A wavelength conversion material comprising a cured product of the quantum dot composition according to [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 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 the polymer by light or heat. [9]: A method for producing a quantum dot composition, comprising dispersing the quantum dot produced by the method for producing a quantum dot according to [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 the quantum dot composition produced by the method for producing a quantum dot composition according to [9] above.

[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.

Claims

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 represented by the following formula (I), and the quantum dot body is characterized in that it has a polymer coating layer on its outermost surface formed by the bonding of the methacryloyloxyethyl group with a reactive substituent of a polymer. (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 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-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 of the same skeletal structures as 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 producing a quantum dot according to any one of claims 1 to 5, comprising: a quantum dot production step of producing 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 by light or heat.

9. A method for producing a quantum dot composition, characterized by dispersing the 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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