Quantum dot-containing composition, wavelength conversion member, and method for manufacturing the quantum dot-containing composition

Abstract

To provide a quantum dot-containing composition capable of improving stability while maintaining the characteristics of quantum dots.SOLUTION: The present invention relates to a quantum dot-containing composition which contains quantum dots capable of emitting fluorescence by excitation light, the quantum dot-containing composition being a mixture of quantum dots and a polymerizable polymer composition, wherein each of the quantum dots has a core-shell structure where an outermost shell comprises ZnS, the surface of each of the quantum dots contains a surface coating layer having a siloxane bond, and the quantum dots have a property such that the intensity of a peak appearing in 1000 to 1200 cm-1 is larger than the intensity of a peak appearing in 2800 to 3000 cm-1 when the quantum dots are subjected to Fourier transform infrared spectroscopy.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a quantum dot-containing composition, a wavelength conversion member, and a method for producing a quantum dot-containing composition. [Background technology]

[0002] In semiconductor nanoparticle single crystals, a strong quantum confinement effect occurs when the crystal size is less than or equal to the Bohr radius of the exciton, resulting in discrete energy levels. Since the energy levels depend on the crystal size, the light absorption and emission wavelengths can be adjusted by changing the crystal size.

[0003] Furthermore, the luminescence produced by exciton recombination in semiconductor nanoparticle single crystals is highly efficient due to the quantum confinement effect, and since this luminescence is basically in the form of emission lines, it is attracting attention because high-brightness, narrow-band emission is possible if a uniform particle size distribution can be achieved. This phenomenon caused by the strong quantum confinement effect in nanoparticles is called the quantum size effect, and semiconductor nanocrystals that utilize this property are being investigated for a wide range of applications as quantum dots (QDs).

[0004] One application of quantum dots is being explored: their use in phosphor materials for displays. If narrow-band, highly efficient light emission can be achieved, it will be possible to reproduce colors that were previously unattainable with existing technologies, making them a promising next-generation display material.

[0005] One type of display currently seeing increased use of quantum dots is the quantum dot liquid crystal display (LCD), which is already being commercialized. Attempts are being made to convert light emitted from white or blue LED backlights to green and red by passing it through a quantum dot-containing wavelength conversion material.

[0006] Because the surface of quantum dots is active and the quantum yield gradually decreases due to moisture and oxygen in the atmosphere, improving the stability of quantum dot-containing wavelength conversion materials is an essential consideration.

[0007] Various studies are being conducted on stabilizing wavelength conversion materials containing quantum dots. One example is gas barrier encapsulation. Stability is improved by forming an inner layer in which quantum dots are dispersed within an amphiphilic polymer or compatible polymer, and then further dispersing them in another resin layer with low gas permeability.

[0008] Patent Document 1 discloses a method for forming polymer beads by dispersing QDs in a hydrophobic resin layer, and then surface-modifying the polymer beads so that they are dispersed in a hydrophilic polymer.

[0009] Hydrophilic polymers tend to have higher gas barrier properties than hydrophobic polymers, which is why QDs are dispersed in such two-layer or multi-layer structures. However, for applications that can be subjected to high temperature and high humidity environments, such as those used in liquid crystal display units, the gas barrier properties are insufficient. Therefore, methods are employed to eliminate the effects of oxygen and water vapor by sandwiching the QD film between gas barrier films.

[0010] Various studies have also been conducted on methods for producing polymer beads. Patent document 2 discloses a method for producing QD-containing polymer beads from a polysiloxane having amino groups and polymerizable functional groups, further mixing in another polymer having polymerizable functional groups, emulsifying, and then curing the mixture.

[0011] This method improves stability by increasing the adhesion to the QDs by introducing ligands that coordinate to the QD surface into the polymer, thereby increasing the concentration of QDs within the polymer beads. However, even with this method, stability is insufficient, and the beads are still implemented by sandwiching them between barrier films. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] U.S. Patent No. 9708532 [Patent Document 2] Japanese Patent Publication No. 2016-111292 [Patent Document 3] Special Publication No. 2019-536653 [Patent Document 4] U.S. Patent Application Publication No. 2019 / 0322926 Specification [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] However, using barrier films not only increases costs but also inevitably increases thickness. Currently, there is a demand for thinner liquid crystal displays, and since it is necessary to reduce the thickness of wavelength conversion components, there is a need for improved stability without barrier films. Furthermore, when considering color filter applications, patterning is required, and it is not practical to provide a protective layer like a barrier film, so the stability of the quantum dots themselves is necessary.

[0014] Patent Document 3 describes a study that improves heat resistance and moisture resistance without using a barrier film. This method involves further applying a silazane coating treatment to a multilayer resin composition using the polymer bead structure described in Patent Document 1, thereby improving stability. However, this method had the problem of reduced quantum yield during photocuring of the silazane coating by irradiation with short ultraviolet light (170 nm).

[0015] Another attempt is documented in Patent Document 4. This method involves coordinating ligands to quantum dots, introducing reactive substituents such as vinyl groups or methacrylic groups to the ligands, then mixing them with a Si-H-containing silicone resin and a curing agent, and curing the mixture by spin-coating and heating to produce a film with improved heat resistance and moisture resistance.

[0016] However, the compatibility between the Si-H-containing silicone resin used and quantum dots is low, and aggregation occurs when attempting to disperse them at high concentrations. Therefore, compatibility must be improved through ligand treatment, but there is a problem that if the balance between hydrophobic groups and hydrophilic groups changes during ligand coordination, aggregation is likely to occur and the quantum yield decreases.

[0017] In addition, when applied to color filters, it is important to form a quantum dot surface state suitable for the patterning method. Currently, the photolithography method has been put into practical use for producing color filters, in which a photosensitive resin composition containing a pigment is applied onto a glass substrate, the solvent is dried, mask exposure is performed by UV irradiation, uncured portions are removed by alkali development to form a color pattern, and this process is repeated to form blue, red, and green patterns.

[0018] In the photolithography method, uncured portions are wasted, resulting in large raw material loss, complicated processes, and the use of expensive equipment, among other problems. Therefore, inkjet methods have also been studied in recent years.

[0019] The inkjet method is competitive in terms of cost because there is no raw material loss, and it can be produced without introducing expensive equipment for upsizing and large-area production. However, it is difficult to fabricate fine nozzles, and smaller nozzles also cause problems such as clogging and unstable ejection. Currently, both photolithography, which has a proven track record in miniaturization, and inkjet, which is cost-competitive, are being studied.

[0020] On the other hand, for both photolithography and inkjet methods, fabricating a resin composition containing quantum dots with high concentration and high dispersibility is a problem. When dispersing quantum dots at high concentrations, there are problems such as alteration of the properties of the cured resin, for example, curing becomes slower, due to the content of quantum dots.

[0021] The present invention has been made to solve the above problems, and aims to provide a quantum dot-containing composition and a wavelength conversion member that can improve stability while maintaining the properties of quantum dots. Furthermore, the present invention aims to provide a method for producing a quantum dot-containing composition that can improve stability while maintaining the properties of quantum dots. [Means for solving the problem]

[0022] The present invention was made to achieve the above objective, and relates to a quantum dot-containing composition containing quantum dots that emit fluorescence upon excitation light, wherein the quantum dot-containing composition is a mixture of quantum dots and a polymerizable polymer composition, the quantum dot has a core-shell structure with the outermost shell being ZnS, the quantum dot surface contains a surface coating layer having siloxane bonds, and the quantum dot is found to emit fluorescence at 1000-1200 cm⁻¹ by Fourier transform infrared spectroscopy. -1 The peak intensity present is 2800-3000 cm². -1 The present invention provides a quantum dot-containing composition characterized by having a peak intensity greater than that present in [the specified location].

[0023] Such quantum dot-containing compositions make it possible to improve stability while maintaining the properties of the quantum dots.

[0024] In this case, the surface coating layer may have one or more reactive substituents selected from vinyl groups, acrylic groups, methacrylic groups, hydroxyl groups, phenolic hydroxyl groups, and epoxy groups.

[0025] This allows for the introduction of polymerizable polymers and polymerizable substituents into the surface coating layer, making it possible to improve stability while maintaining the properties of quantum dots.

[0026] In this case, the polymer contained in the polymerizable polymer composition may include one or more of the following as substituents that can be polymerized with the reactive substituent: a vinyl group, an acrylic group, a methacrylic group, a hydroxyl group, a phenolic hydroxyl group, or an epoxy group.

[0027] This allows for the polymerization of reactive substituents with polymers, suppressing curing defects during polymer polymerization and improving dispersibility.

[0028] The present invention also provides a wavelength conversion member characterized by being a cured product of the quantum dot-containing composition described above.

[0029] Because such a wavelength conversion member is a cured product of a quantum dot-containing composition that maintains the properties of the quantum dots while improving stability, the wavelength conversion member can also maintain the properties of the quantum dots while improving stability.

[0030] Furthermore, the present invention provides a method for producing a quantum dot-containing composition containing quantum dots that emit fluorescence upon excitation light, comprising: a surface treatment step of heating and mixing a solution in which quantum dots having ZnS formed on their outermost shell are dispersed, a ligand having a substituent capable of forming siloxane bonds and a thiol group, a zinc precursor and a sulfur precursor, thereby coordinating the ligand while forming additional ZnS on the outermost surface of the quantum dots; a surface coating layer formation step, after the surface treatment step, of reacting the substituent capable of forming siloxane bonds with a compound having a reactive substituent capable of forming siloxane bonds to form a surface coating layer having siloxane bonds; and a mixing step, after the surface coating layer formation step, of adding and mixing a polymerizable polymer composition containing the reactive substituent and a polymerizable substituent.

[0031] This manufacturing method allows for the formation of a surface coating layer while simultaneously forming a ZnS shell. By reacting the ZnS shell with a ligand containing substituents capable of forming siloxane bonds, the reduction in luminescence efficiency of quantum dots due to surface treatment is suppressed, inactivating the quantum dots and improving their stability. Furthermore, by arranging polymerizable polymer compositions with polymerizable substituents, not only are curing defects during polymer polymerization suppressed, but dispersibility is also improved. [Effects of the Invention]

[0032] As described above, the quantum dot-containing composition and wavelength conversion member of the present invention make it possible to improve stability while maintaining the properties of the quantum dots. Furthermore, according to the method for producing the quantum dot-containing composition of the present invention, it is possible to improve stability while maintaining the properties of the quantum dots. [Brief explanation of the drawing]

[0033] [Figure 1] The Fourier transform infrared (FT-IR) spectrum of the quantum dot from Example 1 is shown. [Figure 2] The FT-IR spectrum of the quantum dot in Comparative Example 1 is shown. [Figure 3] This shows a flowchart of the method for producing the quantum dot-containing composition of the present invention. [Modes for carrying out the invention]

[0034] The present invention will be described in detail below, but the present invention is not limited to these descriptions.

[0035] As described above, there was a need for a quantum dot-containing composition that could improve stability while maintaining the properties of quantum dots.

[0036] As a result of diligent research into the above-mentioned problems, the present inventors have provided a quantum dot-containing composition containing quantum dots that emit fluorescence upon excitation light, wherein the quantum dot-containing composition is a mixture of quantum dots and a polymerizable polymer composition, the quantum dot has a core-shell structure with the outermost shell being ZnS, the quantum dot surface contains a surface coating layer having siloxane bonds, and the quantum dot has a fluorescence emission of 1000-1200 cm⁻¹ by Fourier transform infrared spectroscopy. -1 The peak intensity present is 2800-3000 cm². -1 We have completed the present invention by discovering that a quantum dot-containing composition characterized by having a peak intensity greater than that present in the original material makes it possible to improve stability while maintaining the properties of the quantum dots.

[0037] Furthermore, as mentioned above, there was a need for a wavelength conversion component that could improve stability while maintaining the properties of quantum dots.

[0038] As a result of diligent research into the above-mentioned problems, the inventors of the present invention have found that a wavelength conversion member, characterized by being a cured product of the quantum dot-containing composition described above, can improve stability while maintaining the properties of quantum dots, and have completed the present invention.

[0039] Furthermore, as mentioned above, there was a need for a method for producing quantum dot-containing compositions that could improve stability while maintaining the properties of quantum dots.

[0040] As a result of diligent research into the above-mentioned problems, the present inventors have found that a method for producing a quantum dot-containing composition containing quantum dots that emit fluorescence upon excitation light can improve stability while maintaining the properties of the quantum dots, and have completed the present invention. This method is characterized by comprising: a surface treatment step of heating and mixing a solution in which quantum dots having ZnS formed on their outermost shell are dispersed, a ligand having a substituent capable of forming siloxane bonds and a thiol group, a zinc precursor and a sulfur precursor, and coordinating the ligand while forming additional ZnS on the outermost surface of the quantum dots; a surface coating layer formation step after the surface treatment step of reacting the substituent capable of forming siloxane bonds with a compound having a reactive substituent capable of forming siloxane bonds to form a surface coating layer having siloxane bonds; and a mixing step after the surface coating layer formation step of adding and mixing a polymerizable polymer composition containing the reactive substituent and a polymerizable substituent.

[0041] The present invention will be described in detail below, but the present invention is not limited to these descriptions. The quantum dot-containing composition of the present invention is a composition containing a surface coating layer containing siloxane bonds formed on the surface of quantum dots that emit fluorescence upon excitation light. More specifically, the quantum dot-containing composition is a mixture of quantum dots and a polymerizable polymer composition. It may also be a mixture of composite particles in which a polymerizable polymer composition and a substituent capable of condensation polymerization is introduced into the surface coating layer, or a mixture thereof.

[0042] (Quantum dots) The external shape of the quantum dots in this invention is not particularly limited, and any form can be used. Quantum dots are mainly nanoparticles with a particle diameter of 10 nm or less, but they can also be nanowires, nanorods, nanotubes, nanocubes, etc., and any shape is applicable.

[0043] If the quantum dots used in the present invention emit fluorescence upon excitation light, any suitable material can be used. For example, as a semiconductor material, one can be selected from the group consisting of Group II-VI, Group III-V, Group IV, Group IV-VI, Group I-III-VI, Group II-IV-V and their mixed crystals or alloys, or compounds having a perovskite structure.

[0044] Specifically, examples include, but are not limited to, compounds containing ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, Si, Ge, Sn, Pb, PbS, PbSe, PbTe, SnS, SnSe, SnTe, AgGaS2, AgInS2, AgGaSe2, AgInSe2, CuGaS2, CuGaSe2, CuInS2, ZnSiP2, ZnGeP2, CdSiP2, CdGeP2, CsPbCl3, CsPbBr3, CsPbI3, CsSnCl3, CsSnBr3, and CsSnI3.

[0045] Furthermore, the quantum dots used in the present invention have a core-shell structure. The shell material capable of forming the core-shell structure is not particularly limited as long as the outermost shell is ZnS, but it is preferable that it has a large band gap and low lattice mismatch compared to the core material, and also preferable that it has a smaller band gap than the outermost shell ZnS, and it is possible to arbitrarily combine the core material and the outermost shell material.

[0046] Specific shell materials include ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, BeS, BeSe, BeTe, MgS, MgSe, MgTe, PbS, PbSe, PbTe, SnS, SnSe, SnTe, CuF, CuCl, CuBr, and CuI. These materials may be selected as a single or multiple mixed crystal, but are not limited to this.

[0047] There are various methods for manufacturing quantum dots, such as liquid-phase and gas-phase methods, and the present invention is not particularly limited in this regard. However, from the viewpoint of exhibiting high fluorescence emission efficiency, it is preferable to use semiconductor nanoparticles obtained by the hot soap method or hot injection method, which involves reacting precursor species at high temperatures in a high-boiling-point nonpolar solvent. It is desirable that the surface has a ligand, which is an organic ligand, coordinated to it in order to impart dispersibility in the nonpolar solvent and reduce surface defects.

[0048] Ligands are preferably aliphatic hydrocarbons from the viewpoint of dispersibility. Examples of such ligands include oleic acid, stearic acid, palmitic acid, myristic acid, lauric acid, decanoic acid, octanoic acid, oleylamine, stearyl(octadecyl)amine, dodecyl(lauryl)amine, decylamine, octylamine, octadecanethiol, hexadecanethiol, tetradecanethiol, dodecanethiol, decanethiol, octanthiol, trioctylphosphine, trioctylphosphine oxide, triphenylphosphine, triphenylphosphine oxide, tributylphosphine, tributylphosphine oxide, etc., and these may be used individually or in combination.

[0049] (Ligands containing a thiol group) Furthermore, it is desirable that the quantum dots of the present invention have a ligand having substituents capable of forming siloxane bonds in addition to the ligands mentioned above. It is desirable that the ligand having substituents capable of forming siloxane bonds has substituents that interact with or adsorb onto the quantum dot surface.

[0050] Substituents that interact or react with the quantum dot surface include amino groups, carboxyl groups, mercapto groups, phosphine groups, phosphine oxide groups, sulfonyl groups, and quaternary ammonium salts. However, the outermost shell is ZnS, and among these, thiol groups are preferred from the viewpoint of coordination and reactivity.

[0051] Furthermore, the quantum dot-containing composition of the present invention contains a surface coating layer having siloxane bonds. For example, the quantum dot surface is coated with a polymer, such as polysiloxane. Therefore, it is desirable that the ligand having substituents that can coordinate to the quantum dot surface has substituents that can form siloxane bonds.

[0052] Ligands having substituents capable of forming siloxane bonds include compounds containing alkoxysilanes such as trimethoxysilyl, triethoxysilyl, dimethoxymethylsilyl, diethoxymethylsilyl, dimethylmethoxysilyl, and ethoxydimethylsilyl groups, compounds having silazane bonds, compounds having Si-OH bonds, compounds having Si-X (X: halogen) bonds, and carboxylic acids. However, it is preferable to use ligands containing alkoxysilanes, silazanes, or Si-OH groups because the reaction can proceed under mild conditions without the generation of acid as a byproduct.

[0053] (Surface coating layer) The surface coating layer of the quantum dot-containing composition of the present invention has siloxane bonds. More specifically, it is desirable that the quantum dot surface is coated with a polymer of polysiloxane. Therefore, it is desirable to form a polysiloxane-containing quantum dot surface polymer coating layer by reacting a substituent capable of forming siloxane bonds contained in a ligand having a thiol group that can coordinate to the quantum dot with a compound having a reactive substituent that can form siloxane bonds.

[0054] Furthermore, it is desirable that the surface coating layer of the present invention has at least one reactive substituent that can polymerize with the polymerizable polymer composition described later. It is desirable that the substituent that can polymerize with the polymer is contained in the surface coating layer by forming a covalent bond with it.

[0055] By forming covalent bonds, substituents that can polymerize with the polymer are less likely to detach during subsequent purification operations compared to cases where the molecule forms aggregates with surface-coated quantum dots or is contained in a way that coordinates to the quantum dot surface or surface coating layer.

[0056] Furthermore, examples of reactive substituents that can polymerize with polymers include vinyl groups, acrylic groups, methacrylic groups, hydroxyl groups, phenolic hydroxyl groups, epoxy groups, sulfonyl groups, carboxyl groups, and thiol groups. However, substituents that are not too acidic and do not coordinate too easily with quantum dots are preferable because they can reliably suppress aggregation. Specifically, vinyl groups, acrylic groups, methacrylic groups, hydroxyl groups, phenolic hydroxyl groups, and epoxy groups are preferred.

[0057] (Focus of FT-IR) As shown in Figure 1, the surface-coated quantum dots are measured by FT-IR at 1000-1200 cm⁻¹. -1 The peak intensity present is 2800-3000 cm². -1 It is greater than the peak intensity present in [location].

[0058] As shown in Figure 2, 1000~1200cm -1 The peak intensity present is 2800-3000 cm². -1 If the peak intensity is below the present value, the properties of the quantum dot, such as internal quantum efficiency, may deteriorate, or its stability may worsen.

[0059] (Polymerizable polymer composition) The quantum dot-containing composition of the present invention is a mixture of quantum dots and a polymerizable polymer composition, the polymerizable polymer composition consisting of, for example, 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.

[0060] Suitable polymers include polymers derived from acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters, as well as copolymers combining multiple polymers, polymers with glycidyl (meth)acrylate as a repeating unit, and polymers containing siloxane skeletons, urethane skeletons, silphenylene skeletons, norbornene skeletons, fluorene skeletons, and isocyanurate skeletons. The polymer used may be selected as appropriate for the application.

[0061] 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.

[0062] Furthermore, these polymers preferably have reactive substituents and polymerizable substituents, and when used in combination with a polymerization initiator, curing becomes possible. Radical polymerizable substituents include vinyl groups, acrylic groups, methacrylic groups, thiol groups, etc., and all of these can be suitably used. Cationic polymerizable substituents preferably include one or more of hydroxyl groups, phenolic hydroxyl groups, and epoxy groups. Other examples include glycidyl groups, oxetanyl groups, isocyanate groups, etc., and all of these can be suitably used. In addition, carboxyl groups may be introduced to impart alkali developability.

[0063] Furthermore, the quantum dot-containing 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 depending on 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.

[0064] 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.

[0065] The quantum dot-containing composition of the present invention may contain a solvent to improve its applicability. From the viewpoint of compatibility with quantum dots, organic solvents are preferred as solvents, such as ketones, alkylene glycol ethers, alcohols, and aromatic compounds. From the ketone group, examples include acetone, methyl ethyl ketone, cyclohexanone, etc. From the alkylene glycol ether group, examples include 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 group of alcohols, and benzene, toluene, and xylene from the group of aromatic solvents.

[0066] Furthermore, the quantum dot-containing composition in the present invention may also contain polymerizable crosslinking agents, photoacid generators, antioxidants, light scattering agents, etc., and is not particularly limited as long as it does not affect the coatability of the quantum dot-containing composition.

[0067] (Method for manufacturing quantum dot-containing composition) The quantum dot-containing composition of the present invention can be manufactured by the method shown in Figure 3. First, quantum dots with ZnS formed on the outermost shell that emit fluorescence upon excitation light are fabricated, or if they have already been fabricated, the fabricated quantum dots are prepared and dispersed in a solution (S0 in Figure 3). Examples of quantum dot manufacturing methods include the liquid-phase method and the gas-phase method already described.

[0068] Next, the solution containing dispersed quantum dots, a ligand having substituents and thiol groups capable of forming siloxane bonds, and a solution containing a zinc precursor and a sulfur precursor are heated and mixed to coordinate the ligand while forming additional ZnS on the outermost surface of the quantum dots (S1 in Figure 3, surface treatment step).

[0069] The reason for coordinating the ligand while forming ZnS in this way is as follows. When coordinating a ligand having a thiol group with a substituent capable of forming a siloxane bond, it is common practice to disperse quantum dots, to which ligands containing long-chain hydrocarbons are coordinated, in a hydrophobic solvent, and then perform ligand exchange by mixing them with a ligand having a thiol group that can coordinate to the quantum dot surface along with the substituent capable of forming a siloxane bond. The ligand exchange reaction conditions, such as the amount of ligand added, heating temperature, time, and light irradiation, are appropriately changed depending on the type of ligand. However, it has been found that this method results in a certain decrease in quantum yield.

[0070] Therefore, by mixing ligands with zinc precursor and sulfur precursor solutions when forming the ZnS shell, ligands can be introduced without reducing the quantum yield, and more ligands can be introduced than by performing ligand exchange.

[0071] Next, after the surface treatment step, a substituent capable of forming siloxane bonds is reacted with a compound that is capable of forming siloxane bonds and has a reactive substituent to form a surface coating layer having siloxane bonds (S2 in Figure 3, surface coating layer formation step).

[0072] Specifically, a reaction is carried out to form a polysiloxane with quantum dots to which thiols having substituents capable of forming siloxane bonds are coordinated, which were introduced in the surface coating layer formation process, thereby forming a surface coating layer containing siloxane bonds.

[0073] While the sol-gel method is a suitable general method for forming polysiloxane bonds, quantum dots are susceptible to acidic conditions and moisture. Therefore, a sol-gel method under basic conditions or a sol-gel method using a Lewis acid catalyst is preferred, and more preferably, a non-hydrolysis sol-gel method using diphenylsilanediol or tetramethyldisiloxanediol, or a Lewis acid-promoted sol-gel reaction (LANHSG) using an alkoxysilane with a Lewis acid-catalyzed reactive substituent is preferred.

[0074] Furthermore, it is desirable that the surface coating layer of the present invention has at least one substituent that can polymerize with the polymer contained in the polymerizable polymer composition, or a skeletal structure with a similar structure. It is desirable that the substituent that can polymerize with the polymer, or the compound having a similar skeletal structure, be contained in the surface coating layer by forming covalent bonds. There are no particular restrictions on the method of forming covalent bonds, but for example, a suitable method is to introduce substituents that can form siloxane bonds into substituents that can polymerize with the polymer, or into a compound having a similar skeletal structure, and add them during the non-hydrolyzable sol-gel reaction described above, thereby containing them in the surface coating layer by forming covalent bonds, or to introduce substituents that can polymerize with the polymer contained in the polymerizable polymer composition during the non-hydrolyzable sol-gel reaction described above, and then introduce them into the surface coating layer by reacting the polymer or monomer thereafter.

[0075] After the surface coating layer formation step, a polymerizable polymer composition containing reactive substituents and polymerizable substituents is added and mixed to obtain a quantum dot-containing composition (S3 in Figure 3, mixing step). Specifically, after forming the surface coating layer, unreacted substances are removed by purification, and the resulting product is mixed with a polymerizable polymer composition, thereby producing a quantum dot-containing composition. By forming the surface coating layer, the compatibility with the polymerizable polymer composition is improved, and a quantum dot-containing composition in which quantum dots are uniformly dispersed without aggregation can be produced.

[0076] (Wavelength conversion member comprising quantum dot-containing composition) The wavelength conversion member of the present invention is a resin composition which is a cured product of the quantum dot-containing composition produced by the above method. The form of the wavelength conversion member in the present invention is not particularly limited, and examples include a wavelength conversion film in which quantum dots are dispersed in a polymerizable polymer composition obtained by processing into a sheet shape and then curing, and a wavelength conversion color filter patterned as an inkjet or resist material.

[0077] The method for producing (manufacturing) the wavelength conversion member is not particularly limited. For example, the wavelength conversion member can be obtained by applying the quantum dot-containing composition to a transparent film such as PET or polyimide or a substrate material, curing the composition, and then performing lamination processing.

[0078] For application to a transparent film, spraying methods such as spray coating and inkjet coating, spin coating and bar coating can be used.

[0079] The method for curing the quantum dot-containing composition can be performed, for example, by heating the film coated with the quantum dot-containing composition at 60°C for 2 hours, and then heating at 150°C for 4 hours. Alternatively, the quantum dot-containing composition may be cured by photopolymerization reaction. For example, curing can be performed by irradiation with light having a wavelength of 365 nm and an output of 4000 mW / cm 2 for 20 seconds using a UVLED irradiation device, and the curing method is not particularly limited and can be appropriately changed according to the application.

[0080] Here, it is preferable that a polymerizable substituent that can polymerize with the polymer in the quantum dot-containing composition is introduced into the surface coating layer, because this enables production of a wavelength conversion member having high reliability after curing and free from aggregation and curing inhibition. [Examples]

[0081] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited thereto. In this example, an InP / ZnSe / ZnS core-shell type quantum dot was used as the quantum dot material.

[0082] ~Example 1~ (Quantum dot core synthesis process) 0.23 g (0.9 mmol) of palmitic acid, 0.088 g (0.3 mmol) of indium acetate, and 10 mL of 1-octadecene were added to a flask. The mixture was heated to 100°C under reduced pressure and stirred, and degassed for 1 hour while dissolving the raw materials.

[0083] Subsequently, nitrogen was purged into the flask, and 0.75 mL (0.15 mmol) of a solution prepared by mixing tritrimethylsilylphosphine with trioctylphosphine to a 0.2 M solution was added. The temperature was then raised to 300°C, and it was confirmed that the solution changed color from yellow to red, indicating the formation of core particles.

[0084] (Quantum dot shell layer synthesis process) Next, 2.85 g (4.5 mmol) of zinc stearate and 15 mL of 1-octadecene were added to another flask. Under reduced pressure, the mixture was heated at 100°C with stirring and degassed for 1 hour to prepare a 0.3 M zinc stearate octadecene solution. 3.0 mL (0.9 mmol) of this solution was added to the reaction solution after core synthesis and cooled to 200°C.

[0085] Next, 0.474 g (6 mmol) of selenium and 4 mL of trioctylphosphine were added to another flask and heated to 150°C to dissolve, preparing a 1.5 M selentrioctylphosphine solution. The reaction solution after the core synthesis step, which had been cooled to 200°C, was then heated to 320°C over 30 minutes, and 0.1 mL of selentrioctylphosphine solution was added in increments of 0.6 mL (0.9 mmol) at 320°C for 10 minutes before being cooled to room temperature. 0.44 g (2.2 mmol) of zinc acetate was added and dissolved by heating and stirring under reduced pressure at 100°C.

[0086] The flask was again purged with nitrogen and heated to 230°C. 0.98 mL (4 mmol) of 1-dodecanethiol was added and held for 1 hour. The resulting solution was cooled to room temperature to prepare a core-shell type quantum dot-containing solution.

[0087] (Surface treatment process) (3-mercaptopropyl)triethoxysilane (Tokyo Chemical Industries, Ltd.) was used as a ligand having substituents capable of forming siloxane bonds and substituents capable of coordinating to the quantum dot surface. A zinc precursor solution was prepared by dissolving 0.45 g (2 mmol) of zinc bromide in 2.4 mL of trioctylphosphine.

[0088] Next, 0.064 g (2 mmol) of sulfur was dissolved in a mixed solution of 1.1 mL of 1-dodecanethiol and 1.1 mL of (3-mercaptopropyl)triethoxysilane to prepare a sulfur precursor solution. The core-shell type quantum dot-containing solution obtained in the quantum dot shell layer synthesis step was heated to 210°C, and 1.25 mL of the zinc precursor solution and 1.3 mL of the sulfur precursor solution were added.

[0089] After the reaction was complete, ethanol was added to precipitate the reactants, and the supernatant was removed by centrifugation. The same purification process was repeated, and a solution was prepared in which quantum dots, each coordinated with a ligand having substituents capable of forming siloxane bonds, were dispersed in toluene.

[0090] (Surface coating layer formation process) Triethoxyvinylsilane (4.0 mmol), diphenylsilanediol (6 mmol), barium hydroxide monohydrate (0.15 mmol), and a toluene solution containing dispersed quantum dots after the surface treatment process were added to a flask purged with nitrogen, and the mixture was heated and stirred at 65°C for 24 hours. After the reaction was complete, the mixture was cooled to room temperature, ethanol was added to precipitate the reactants, and the mixture was centrifuged. The supernatant was removed and dispersed in toluene.

[0091] (Fourier transform infrared spectroscopy) FT-IR measurement involves directly dropping a dispersion containing semiconductor nanoparticles (quantum dots) onto a detection unit using a diamond ATR (Attenuated Total Reflection), allowing it to dry completely, and then measuring at 400-4000 cm⁻¹. -1 Measurements were taken with 20 cumulative measurements within the specified measurement range. As shown in Figure 1, the 1000-1200 cm⁻¹ values ​​originating from the Si-O bond were measured. -1 The intensity of peak A present in this area is 2800-3000 cm. -1 We confirmed that the intensity of peak B, which originates from the CH bond present in the region, is greater than that of peak B.

[0092] (Quantum dot-containing composition mixing process) The solution obtained after the surface coating layer formation process, dispersed in toluene, and methacrylic-modified silicone oil X-32-3817-3 (Shin-Etsu Chemical Co., Ltd.) were weighed and mixed so that the quantum dots were present at a non-volatile content ratio of 20 wt%. After mixing, the solvent was removed using an evaporator to obtain a quantum dot-containing composition.

[0093] (Manufacturing process for wavelength conversion components) A wavelength conversion component was fabricated using the obtained quantum dot-containing composition. The quantum dot-containing composition was degassed using a stirring degasser, poured onto a PET film, and a thin film was formed using a bar coater. Next, the formed thin film was irradiated in a nitrogen atmosphere using a UV LED irradiation device at a wavelength of 365 nm and an output of 4000 mW / cm². 2 By irradiating the quantum dot-containing resin layer with light for 20 seconds, a wavelength conversion component with a thickness of 50 μm was fabricated by photocuring.

[0094] (Measurement of emission wavelength, emission width at half maximum, and luminous efficiency) In the examples and comparative examples, the fluorescence emission characteristics of the quantum dots were evaluated using the quantum efficiency measurement system (QE-2100) manufactured by Otsuka Electronics Co., Ltd., to measure the emission wavelength, fluorescence full width at half maximum, and fluorescence emission efficiency (internal quantum efficiency) of the quantum dots at an excitation wavelength of 450 nm.

[0095] (Reliability testing) The obtained wavelength conversion material was treated at 85°C and 85%RH (relative humidity) for 250 hours, and its reliability was evaluated by measuring the fluorescence emission efficiency of the treated wavelength conversion material.

[0096] ~Comparison Example 1~ The quantum dot shell layer synthesis process was carried out in the same manner as in Example 1 to obtain a solution in which quantum dots were dispersed.

[0097] (Surface treatment process) (3-mercaptopropyl)triethoxysilane (Tokyo Chemical Industries, Ltd.), a ligand having substituents capable of forming siloxane bonds and substituents capable of coordinating to the quantum dot surface, was added (3.0 mmol) to a solution containing dispersed quantum dots and stirred for 24 hours. After the reaction was complete, the quantum dots were purified by adding ethanol to precipitate them, as in Example 1, and then dispersed in toluene. In other words, unlike Example 1, no additional ZnS was formed during the surface treatment process.

[0098] (Surface coating layer formation process) Triethoxyvinylsilane (4.0 mmol), diphenylsilanediol (6 mmol), barium hydroxide monohydrate (0.15 mmol), and a toluene solution containing dispersed quantum dots after the surface treatment process were added to a flask purged with nitrogen, and the mixture was heated and stirred at 65°C for 24 hours. After the reaction was complete, the mixture was cooled to room temperature, ethanol was added to precipitate the reactants, and the mixture was centrifuged. The supernatant was removed and dispersed in toluene.

[0099] (Fourier transform infrared spectroscopy) FT-IR measurement involves directly dropping a dispersion containing semiconductor nanoparticles (quantum dots) onto a detection unit using a diamond ATR (Attenuated Total Reflection), allowing it to dry completely, and then measuring at 400-4000 cm⁻¹. -1 Measurements were taken with 20 cumulative measurements within the specified measurement range. As shown in Figure 2, the 1000-1200 cm⁻¹ originating from the Si-O bond... -1 The intensity of peak A present in this area is 2800-3000 cm. -1 The intensity of peak B, which originates from the CH bond present in the region, was smaller.

[0100] (Quantum dot-containing composition mixing process) The solution obtained after the surface coating layer formation process, dispersed in toluene, and methacrylic-modified silicone oil X-32-3817-3 (Shin-Etsu Chemical Co., Ltd.) were weighed and mixed so that the quantum dots were present at a non-volatile content ratio of 20 wt%. After mixing, the solvent was removed using an evaporator to obtain a quantum dot-containing composition.

[0101] (Manufacturing process for wavelength conversion components) A wavelength conversion component was fabricated using the obtained quantum dot-containing composition. The quantum dot-containing composition was degassed using a stirring degasser, poured onto a PET film, and a thin film was formed using a bar coater. Next, the formed thin film was irradiated in a nitrogen atmosphere using a UV LED irradiation device at a wavelength of 365 nm and an output of 4000 mW / cm². 2 A wavelength conversion component with a thickness of 50 μm was fabricated by photocuring a quantum dot-containing resin layer by irradiating it with light for 20 seconds. Compared to Example 1, aggregates were observed, and the quantum yield was lower.

[0102] ~Example 2~ A toluene solution containing dispersed quantum dots was prepared in the same manner as in Example 1, up to the surface treatment step.

[0103] (Surface coating layer formation process) In a flask purged with nitrogen, [(3-triethoxysilyl)propyl] succinic anhydride (Tokyo Chemical Industries, Ltd.) (4.0 mmol), diphenylsilanediol (6 mmol), barium hydroxide monohydrate (0.15 mmol), and a toluene solution containing dispersed quantum dots after the surface treatment process were added, and the mixture was heated and stirred at 65°C for 24 hours. After the reaction was complete, the mixture was cooled to room temperature, ethanol was added to precipitate the reactants, centrifugation was performed, the supernatant was removed, and the mixture was dispersed in toluene.

[0104] (Quantum dot-containing composition mixing process) The solution after the surface coating layer formation process, dispersed in toluene, and the acrylic resin RA-4101 (Negami Sangyo Co., Ltd.) were weighed so that the quantum dots were present at 20 wt% in terms of non-volatile content. Five parts by mass of the photoradical generator Irgacure1173 were added to 100 parts by mass of the acrylic resin non-volatile content and mixed. After mixing, the toluene solvent was removed by vacuum distillation to obtain a quantum dot-containing composition.

[0105] (Method for fabricating wavelength conversion components) A wavelength conversion component was fabricated using the obtained quantum dot-containing composition. The quantum dot-containing composition was degassed under vacuum, and a 20cm x 10cm square, 500μm thick PTFE-coated mold was poured with a solid content of 20%. The mixture was then heated on a hot plate at 120°C for 1 hour to evaporate the solvent and create a quantum dot-containing resin layer. A portion of the layer was cut off and developed with a PGMEA solution to confirm that no residual film remained.

[0106] Subsequently, the remaining quantum dot-containing resin layer is irradiated in a nitrogen atmosphere using a UV LED irradiation device with a wavelength of 365 nm and an output of 4000 mW / cm². 2 A wavelength conversion component with a thickness of 100 μm was fabricated by photocuring it by irradiating it with light for 20 seconds.

[0107] ~Comparative Example 2~ A toluene solution containing dispersed quantum dots was prepared using the same method as in Comparative Example 1 up to the surface treatment step, and the wavelength conversion component was prepared using the same method as in Example 2 for the rest of the process.

[0108] ~Example 3~ Up to the surface treatment step, a toluene solution containing dispersed quantum dots was prepared in the same manner as in Examples 1 and 2.

[0109] (Surface coating layer formation process) In a flask purged with nitrogen, tris[3-(trimethoxysilyl)propyl] isocyanurate (1.0 mmol), diphenylsilanediol (6 mmol), barium hydroxide monohydrate (0.15 mmol), and a toluene solution containing dispersed quantum dots after the surface treatment process were added, and the mixture was heated and stirred at 65°C for 24 hours. After the reaction was complete, the mixture was cooled to room temperature, ethanol was added to precipitate the reactants, and the mixture was centrifuged. The supernatant was removed and dispersed in toluene.

[0110] (Quantum dot-containing composition mixing process) An epoxy-containing silicone resin (Shin-Etsu Chemical Co., Ltd., CAS No. 2253674-54-1) and a solution obtained after the surface coating layer formation process, dispersed in toluene, were weighed and mixed so that the quantum dots constituted 20 wt% of the non-volatile content. For every 100 parts by mass of the silicone resin non-volatile content, 2 parts by mass of the photoacid generator CPI-310FG (Sunapro Co., Ltd.) and 20 parts by mass of the crosslinking agent THI-DE were weighed and mixed. After mixing, the toluene solvent was removed by vacuum distillation to obtain a quantum dot-containing composition.

[0111] (Manufacturing method for wavelength conversion components) A wavelength conversion component was fabricated using the obtained quantum dot-containing composition. The quantum dot-containing composition was degassed under vacuum, and a 20cm x 10cm square, 500μm thick PTFE-coated mold was poured with a solid content of 20%. The mixture was then heated on a hot plate at 120°C for 1 hour to evaporate the solvent and create a quantum dot-containing resin layer. A portion of the layer was cut off and developed with a PGMEA solution to confirm that no residual film remained.

[0112] Subsequently, the remaining quantum dot-containing resin layer is irradiated in a nitrogen atmosphere using a UV LED irradiation device with a wavelength of 365 nm and an output of 4000 mW / cm². 2A wavelength conversion component with a thickness of 100 μm was fabricated by photocuring it by irradiating it with light for 20 seconds.

[0113] ~Comparative Example 3~ A toluene solution containing dispersed quantum dots was prepared using the same method as in Comparative Example 1 up to the surface treatment step, and the wavelength conversion component was prepared using the same method as in Example 3 for the rest of the process.

[0114] ~Example 4~ Up to the surface treatment step, a toluene solution containing dispersed quantum dots was prepared in the same manner as in Examples 1, 2, and 3.

[0115] (Surface coating layer formation process) In a flask purged with nitrogen, triethoxysilylpropyl methacrylate (4.0 mmol), diphenylsilanediol (6 mmol), barium hydroxide monohydrate (0.15 mmol), and a toluene solution containing dispersed quantum dots after the surface treatment process were added and heated and stirred at 65°C for 24 hours. After the reaction was complete, the mixture was cooled to room temperature, ethanol was added to precipitate the reactants, centrifugation was performed, the supernatant was removed, and the mixture was dispersed in toluene.

[0116] (Quantum dot-containing composition mixing process) A phenol-crosslinkable silicone resin (Shin-Etsu Chemical, CAS No. 916059-41-1) and a solution obtained after the surface coating layer formation process, dispersed in toluene, were weighed and mixed so that the non-volatile content ratio contained 20 wt% quantum dots. For every 100 parts by mass of the silicone resin non-volatile content, 2 parts by mass of the photoacid generator CPI-310FG (Sunapro) and 20 parts by mass of the crosslinking agent THI-DE were weighed and mixed. After mixing, the toluene solvent was removed by vacuum distillation to obtain a quantum dot-containing composition.

[0117] (Method for fabricating wavelength conversion components) A wavelength conversion component was fabricated using the obtained quantum dot-containing composition. The quantum dot-containing composition was degassed under vacuum, and a 20cm x 10cm square, 500μm thick PTFE-coated mold was poured with a solid content of 20%. The mixture was then heated on a hot plate at 120°C for 1 hour to evaporate the solvent and create a quantum dot-containing resin layer. A portion of the layer was cut off and developed with a PGMEA solution to confirm that no residual film remained.

[0118] Subsequently, the remaining quantum dot-containing resin layer is irradiated in a nitrogen atmosphere using a UV LED irradiation device with a wavelength of 365 nm and an output of 4000 mW / cm². 2 A wavelength conversion component with a thickness of 100 μm was fabricated by photocuring it by irradiating it with light for 20 seconds.

[0119] ~Comparative Example 4~ A toluene solution containing dispersed quantum dots was prepared using the same method as in Comparative Example 1 up to the surface treatment step, and the wavelength conversion component was prepared using the same method as in Example 4 for the rest of the process.

[0120] Table 1 shows the results of comparing Examples 1-4 with Comparative Examples 1-4.

[0121] [Table 1]

[0122] Table 1 shows the emission wavelength, fluorescence full width at half maximum, and internal quantum efficiency after quantum dot synthesis, surface treatment, surface coating layer formation, mixing (quantum dot-containing composition), and after curing of the quantum dot-containing composition (wavelength conversion member), as well as the rate of decrease in internal quantum efficiency during reliability testing and the presence or absence of aggregates in the wavelength conversion member. Table 1 also shows the FT-IR results after surface coating layer formation.

[0123] As shown in Table 1, in all of the examples, peak A of the FT-IR after the formation of the surface coating layer was larger than peak B, whereas in the comparative example, peak B was larger than peak A, and the internal quantum efficiency after the surface treatment process, after the formation of the surface coating layer, and after the creation of the quantum dot-containing composition was also inferior.

[0124] Furthermore, compared to the examples, the comparative example shows a decrease in internal quantum efficiency after the fabrication of the wavelength conversion member, and the emission wavelength also exhibits a larger shift to longer wavelengths. This is thought to be due to insufficient dispersion stability in the comparative example, which led to the formation of aggregates.

[0125] Furthermore, when comparing the reliability test results (treated at 85°C and 85%RH for 250 hours) of the examples and comparative examples, the stability was similar due to the formation of a surface coating layer, but the comparative examples showed greater degradation than the examples.

[0126] Thus, in the examples, in reliability tests conducted at 85°C and 85%RH without a barrier film, the rate of decrease in internal quantum efficiency during 250 hours of processing (the rate of decrease in internal quantum efficiency after processing) could be kept within 10%, demonstrating that stabilization is possible.

[0127] As described above, the quantum dot-containing composition of the present invention exhibits high internal quantum efficiency and stability, and also has good film quality after curing, confirming its applicability to quantum dot-containing resists and quantum dot-containing inkjet inks.

[0128] 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-containing composition containing quantum dots that emit fluorescence upon excitation light, The quantum dot-containing composition is a mixture of quantum dots and a polymerizable polymer composition, wherein the quantum dot has a core-shell structure, the outermost shell is ZnS, and the quantum dot surface contains a surface coating layer having siloxane bonds. The aforementioned quantum dots were found to have a range of 1000–1200 cm⁻¹ by Fourier transform infrared spectroscopy. －１ The peak intensity present is 2800-3000 cm². －１ A quantum dot-containing composition characterized by having a peak intensity greater than that present in [the specified location].

2. The quantum dot-containing composition according to claim 1, characterized in that the surface coating layer has one or more reactive substituents selected from vinyl groups, acrylic groups, methacrylic groups, hydroxyl groups, phenolic hydroxyl groups, and epoxy groups.

3. The quantum dot-containing composition according to claim 2, characterized in that the polymer contained in the polymerizable polymer composition contains one or more of the following as a substituent that can be polymerized with the reactive substituent: a vinyl group, an acrylic group, a methacrylic group, a hydroxyl group, a phenolic hydroxyl group, or an epoxy group.

4. A wavelength conversion member characterized by being a cured product of a quantum dot-containing composition according to any one of claims 1 to 3.

5. A method for producing a quantum dot-containing composition containing quantum dots that emit fluorescence upon excitation light, A surface treatment step involves heating and mixing a solution containing quantum dots in which ZnS is formed on the outermost shell, a ligand having substituents and thiol groups capable of forming siloxane bonds, a zinc precursor, and a sulfur precursor, thereby coordinating the ligand while forming additional ZnS on the outermost surface of the quantum dots. After the surface treatment step, a surface coating layer formation step is performed to form a surface coating layer having siloxane bonds by reacting a substituent capable of forming siloxane bonds with a compound having a reactive substituent capable of forming siloxane bonds. A method for producing a quantum dot-containing composition, characterized by comprising a mixing step of adding and mixing a polymerizable polymer composition containing the reactive substituent and a polymerizable substituent after the surface coating layer formation step.

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