Photoresponsive materials and ink compositions

Abstract

To provide a photoresponsive material comprising perovskite-type quantum dots containing at least iodine, having improved durability. [Solution] A photoresponsive material comprising nanoparticles having a perovskite-type crystal structure containing iodine at its sites, and a shell-like ligand having a betaine group and partially coordinating to the nanoparticles, wherein the molar ratio of iodine present at the X-sites on the surface of the nanoparticles is lower than the molar ratio of iodine present at the X-sites inside the nanoparticles.

Description

Technical Field

[0001] The present disclosure relates to a light-responsive material and an ink composition that emit light upon irradiation with light.

Background Art

[0002] Quantum dots having a perovskite crystal structure (perovskite quantum dots) are known to be applicable to organic EL materials and quantum dot light-responsive materials because they have a narrow full width at half maximum and exhibit high color purity in spectroscopic sensitivity characteristics. They also have the characteristic that the emission wavelength can be controlled by changing the halogen composition.

[0003] On the other hand, perovskite quantum dots are likely to have surface defects due to external stimuli such as light, heat, oxygen, and moisture, and the emission quantum yield easily decreases. This is considered to be due to the fact that the particle size of perovskite quantum dots is as small as several to twenty nanometers, resulting in a large specific surface area, and they are composed of ionic crystals and are easily affected by polar substances. Patent Document 1 discloses a technique for improving the stability of perovskite quantum dots by modifying the particle surface with a shell-like ligand exhibiting zwitterionic properties.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When producing photoresponsive materials or light-emitting layers using perovskite-type quantum dots protected by shell-like ligands as described in Patent Document 1, high durability can be obtained with iodine-free compositions such as CsPbBr3. On the other hand, with iodine-containing compositions such as CsPb(Br / I)3, there was room for improvement in durability. Furthermore, the nanoparticles disclosed in Patent Document 1 sometimes suffered from reduced light-emitting performance during manufacturing because a large amount of polar solvent (such as ethyl acetate) was used during purification.

[0006] Therefore, the present invention aims to provide a photoresponsive material comprising perovskite-type quantum dots containing at least iodine, which has improved durability.

[0007] Furthermore, when quantum dots containing photoresponsive nanoparticles are applied to photodetectors and solar cells, the emission quantum yield described in this specification is rephrased as the photoelectric conversion quantum yield related to the generation of charge pairs. In this specification, the emission quantum yield related to the wavelength conversion of light is treated as one form of the conversion quantum yield, including the photoelectric conversion quantum yield related to photoelectric transformation. [Means for solving the problem]

[0008] A photoresponsive material according to an embodiment of the present invention comprises nanoparticles having a perovskite-type crystal structure containing iodine at the X-site, and a shell-like ligand having a betaine group and partially coordinating to the nanoparticle, wherein the molar ratio of iodine present at the X-site on the surface of the nanoparticle is lower than the molar ratio of iodine present at the X-site inside the nanoparticle.

[0009] Furthermore, a photoresponsive material according to another embodiment of the present invention comprises nanoparticles having a perovskite-type crystal structure containing iodine at the X site, and a shell-like ligand having a betaine group and partially coordinating with the nanoparticles, characterized in that the concentration of iodine released from the nanoparticles is higher than the concentration of iodine coordinating with the nanoparticles. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a photoresponsive material comprising a perovskite-type quantum dot containing at least iodine, which has improved photoresistance. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows the schematic configuration of the photoresponsive material according to the first embodiment. [Figure 2] This figure shows a schematic configuration of the ink composition according to the second embodiment. [Figure 3] This figure shows a schematic configuration of a display element equipped with a wavelength conversion layer according to the third embodiment. [Modes for carrying out the invention]

[0012] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. The dimensions, materials, shapes, and relative arrangements of the components described in these embodiments are not intended to limit the scope of the present invention.

[0013] <First Embodiment> A photoresponsive material according to the first embodiment will be described with reference to Figure 1.

[0014] ((Photoresponsive materials)) The photoresponsive material 100 according to this embodiment comprises nanoparticles 10 having a perovskite-type crystal structure containing iodine at the X site, and a shell-like ligand 20 having a betaine group and partially coordinating to the nanoparticle. Furthermore, the molar ratio of iodine present at the X site on the surface of the nanoparticle 10 is configured to be lower than the molar ratio of iodine present at the X site inside the nanoparticle 10. The photoresponsive material 100 has nanoparticles 10 having a perovskite-type crystal structure with a quantum confinement effect and exhibits fluorescence emission, and may therefore be referred to as a luminescent material 100, a fluorescent material 100, a luminescent composition 100, etc.

[0015] (Nanoparticles) The nano-particles 10 employ semiconductor nanocrystals having a perovskite crystal structure with constituent components of an A-site (monovalent cation), a B-site (divalent cation), and an X-site (monovalent anion containing at least an iodide anion as a halide anion). The perovskite crystal structure is also referred to as a perovskite-type structure, an ABX3-type crystal structure, or an ABX3-type structure. Further, a double perovskite crystal structure represented as A2B1B2X6 is also included in the perovskite crystal structure.

[0016] [A-site of Perovskite Crystal Structure] In the A-site of the perovskite crystal structure, a monovalent cation is employed. The monovalent cations employed in the A-site include ammonium cation (NH4 + ), alkylammonium cations having 6 or less carbon atoms, formamidinium cation (HC(NH2)2 + ), guanidinium cation (C(NH2)3 + ), nitrogen-containing organic compound cations such as imidazolium cation, pyridinium cation, and pyrrolidinium cation, and alkali metal cations such as lithium cation (Li + ), sodium cation (Na + ), potassium cation (K + ), rubidium cation (Rb + ), and cesium cation (Cs + ).

[0017] Since these monovalent cations employed in the A-site have a small ionic diameter and are of a size that can fit into the crystal lattice, the perovskite compound can form a stable three-dimensional crystal.

[0018] Preferred examples of the alkylammonium cations having 6 or less carbon atoms include methylammonium cation (CH3NH3 + ), ethylammonium cation (C2H5NH3 + ), propylammonium cation (C3H7NH3 + ), and the like.

[0019] From the viewpoint of obtaining high luminescence efficiency, it is preferable to use at least one of methylammonium cation, formamidinium cation, or cesium cation as the A site, and from the viewpoint of suppressing color change, it is more preferable to use cesium cation as the A site. Two or more monovalent cations may be used in combination as the A site.

[0020] If site A is a cesium cation, cesium salts can be used as raw materials for the synthesis of luminescent nanocrystals, as described later. Such cesium salts may include cesium chloride, cesium bromide, cesium iodide, cesium hydroxide, cesium carbonate, cesium bicarbonate, cesium bicarbonate, cesium formate, cesium acetate, cesium propionate, cesium pivalate, and cesium oxalate, as appropriate. From these candidate cesium salts, an appropriate one can be used depending on the synthesis method.

[0021] If site A is another alkali metal cation, salts or the like obtained by replacing the cesium element in the above-mentioned cesium compound with another alkali metal cation element can be used as raw materials.

[0022] If site A is a nitrogen-containing organic compound cation such as a methylammonium cation, then a neutral compound other than a salt, such as methylamine, can be used as a raw material. Two or more of these raw materials may be used in combination.

[0023] [B site of perovskite crystal structure] The B site of a perovskite crystal structure employs a divalent cation, including either a divalent transition metal cation or a divalent typical metal cation.

[0024] Divalent transition metal cations include scandium cations (Sc 2+ ), titanium cation (Ti 2 +), vanadium cation (V 2+ ), chromium cation (Cr 2+ ), manganese cation (Mn 2+ ), iron cation (Fe 2+), cobalt cation (Co 2+ ), nickel cation (Ni 2+ ), copper cation (Cu 2+ ), palladium cation (Pd 2+ ), europium cation (Eu 2+ ), ytterbium cation (Yb 2+ ) will be adopted.

[0025] A typical divalent metal cation is the magnesium cation (Mg 2+ ), calcium cation (Ca 2+ ), strontium cation (Sr 2+ ), barium cation (Ba 2+ ), zinc cation (Zn 2+ ), cadmium cation (Cd 2+ ), germanium cation (Ge 2+ ), tin cation (Sn 2+ ), lead cation (Pb 2+ ) may be adopted.

[0026] Among these divalent cations, typical metal cations are preferred in terms of the growth of stable three-dimensional crystals, tin cations or lead cations are more preferred, and lead cations are particularly preferred from the viewpoint of obtaining high luminescence intensity. Two or more of these divalent cations may be used in combination, and the perovskite crystal structure may be a so-called double perovskite type.

[0027] When the B site is a lead cation, lead compounds can be used as raw materials for the synthesis of nanoparticles (luminescent nanocrystals) described later, and an appropriate one can be used depending on the synthesis method. Examples of lead compounds include lead chloride, lead bromide, lead iodide, lead oxide, lead hydroxide, lead sulfide, lead carbonate, lead formate, lead acetate, lead 2-ethylhexanoate, lead oleate, lead stearate, lead naphthenate, lead citrate, lead maleate, and lead acetylacetonate. When the B site is another divalent metal cation, salts of the above-mentioned lead compounds in which the lead element is replaced with another divalent metal cation element can be used as raw materials. Two or more of these raw materials may be used in combination.

[0028] [X-site of perovskite crystal structure] The X-site of the perovskite crystal structure employs monovalent anions, including halide anions, and contains at least an iodide anion. Other halide anions include fluoride anions (F - ), chloride anion (Cl - ), bromide anion (Br - Examples include the following. Among these, chloride anions and bromide anions are preferred from the viewpoint of forming stable three-dimensional crystals and exhibiting strong luminescence in the visible light range. In particular, the inclusion of bromide anions is preferred from the viewpoint of nanoparticle stability.

[0029] Two or more types of halide anions may be used in combination. In particular, when chloride anions, bromide anions, and iodide anions are used in combination, the emission wavelength of the luminescent nanocrystal can be set to a desired wavelength in the visible range, depending on the content ratio of the anion species. That is, when chloride anions, bromide anions, and iodide anions are used in combination, it is preferable because, depending on the content ratio of the anion species, an emission spectrum covering almost the entire visible light range from blue to red can be obtained while maintaining a narrow full width at half maximum.

[0030] The X site may contain monovalent anions other than halide anions. Such monovalent anions other than halide anions include cyanide anions (CN - ), thiocyanate anion (SCN - ), isothiocyanate anion (CNS - Examples include pseudohalide anions such as ). As raw materials for the synthesis of nanoparticles (luminescent nanocrystals) described later, appropriate materials can be selected depending on the synthesis method from salts with A-site and B-site countercations, such as cesium chloride and lead bromide, or salts with other cations.

[0031] The nanoparticles (luminescent nanocrystals) in this embodiment can be manufactured by the following process. The manufacturing method for the nanoparticles 10 may include a hot injection method, in which raw material liquids are mixed at high temperature, and after the formation of fine particles, rapid cooling is performed to obtain a stable product; or a flow synthesis method, in which the raw material liquids are delivered through piping using a pump or the like and mixed. The manufacturing method for the nanoparticles 10 may also employ a ligand-assisted reprecipitation method, in which fine particles are obtained by reprecipitation utilizing the difference in miscibility of the product with the solvent.

[0032] Furthermore, this manufacturing method also employs a room-temperature synthesis method in which, under mild conditions of room temperature, a mixture of non-halogenated raw materials for site A and site B, which do not contain components for site X, is mixed with a separately prepared raw material solution for site X to obtain fine particles. In addition, this manufacturing method is also employed in mechanochemical methods, in which solid raw materials are reacted by mechanical mixing such as milling or ultrasonic treatment to obtain product fine particles, and in situ synthesis methods, in which the raw material solution is coated onto a substrate and then crystals are grown directly to obtain the reactant.

[0033] The particle size of the nanoparticles is preferably between 1 nm and 30 nm in average size, more preferably between 2 nm and 25 nm, and even more preferably between 3 nm and 20 nm. If the average particle size is less than 1 nm, stability may be insufficient. If the average particle size is greater than 30 nm, the quantum confinement effect may not work sufficiently, and the quantum emission yield may decrease.

[0034] The nanoparticle content is preferably 0.01 parts by mass to 50 parts by mass per 100 parts by mass of the total weight of the photoresponsive material, including the medium. If the content is less than 0.01 parts by mass, it may dissolve. If the content is more than 50 parts by mass, dispersibility in the medium may not be ensured.

[0035] The molar ratio of iodine present at the X site on the surface of a nanoparticle is lower than the molar ratio of iodine present at the X site inside the nanoparticle. Here, the surface of the nanoparticle refers to the part of the nanoparticle that is in contact with the medium, and the inside of the nanoparticle refers to the part other than the surface of the nanoparticle. The molar ratio may be a value calculated by [I] / ([I]+[Br]). Here, [X](X=I,Br) refers to the amount of X in the X site on the surface or inside the nanoparticle.

[0036] Furthermore, it is preferable that the conditions of equation (1) are met. [I] 表面 / ([I] 表面 +[Br] 表面 )<[I] 内部 / ([I] 内部 +[Br] 内部 ) Formula (1) Furthermore, it is preferable that the conditions of equation (2) are met. [I] 遊離 / ([I] 遊離 +[Br] 遊離 )>[I] 非遊離 / ([I] 非遊離 +[Br] 非遊離 ) Formula (2) Here's the question: 表面 [Q] represents the amount of substance Q on the surface of the nanoparticle. 内部 This represents the amount of substance Q inside the nanoparticle. Equation (1) shows that the anion X of ABX3 is composed of bromine (Br) and iodine (I) in a BrI mix system AB(I z Br (3-z) This applies to )

[0037] When the perovskite-type anion X, which is a halogen compound, is composed of iodine (I), bromine (Br), and chlorine (Cl), the denominator of equation (1) can be represented as [X].

[0038] Here, the subscript "surface" [Q] represents the amount of anion Q located at the X site on the surface of the nanoparticle 10, and the subscript "internal" [Q] represents the amount of anion Q contained in the internal X site of the nanoparticle 10. Furthermore, the subscript "free" [Q] represents the amount of anion Q that has been released from the nanoparticle 10 and is present in the medium, and the subscript "non-free" [Q] represents the amount of anion Q contained in the X site of the perovskite-type nanoparticle 10.

[0039] (Method for purifying nanoparticles) Nanoparticles synthesized by the above method can be purified by methods such as centrifugation to remove impurities from the synthesis process and then used as raw materials for photoresponsive materials. When centrifugation is performed, it is common practice to add a large excess of a polar solvent such as ethyl acetate to the reaction solution (crude solution) as a poor solvent. However, using a large amount of polar solvent such as ethyl acetate not only increases the amount of centrifugation required, but also causes a decrease in the luminescence properties of the nanoparticles if centrifugation is not performed immediately. This is because the halogen and ligands coordinated to the nanoparticles are desorbed by the polar solvent. Therefore, while purification methods using large amounts of polar solvent are preferred at the laboratory level, they have low applicability to industries requiring large-scale processing. In this embodiment, the amount of polar solvent added during centrifugation is preferably 300 parts or less, and more preferably 100 parts or less, relative to the crude solution. When more than 300 parts of polar solvent are used relative to the crude solution, the luminescence properties of the nanoparticles may decrease as described above. Reducing the amount of polar solvent also reduces the time constraints before starting centrifugation.

[0040] The shell-like ligands described later are thought to preferentially substitute iodine over bromine on the surface of the nanoparticles. This is because iodine has a lower affinity for lead than bromine (HSAB principle) and therefore a lower binding energy. As described above, when purified with a small amount of polar solvent, ligands such as iodine, bromine, oleic acid, and oleylamine are coordinated to the surface of the nanoparticles. However, by applying the shell-like ligands, iodine and oleylamine preferentially detach and become free. As a result, the molar ratio of iodine present at the X-site on the surface of the nanoparticles is lower than the molar ratio of iodine present at the X-site inside the nanoparticles.

[0041] (Shell-shaped ligand) In this embodiment, the shell-shaped ligand 20 has a betaine group and at least a portion of it is coordinated to the surface of the nanoparticle 10. The shell-shaped ligand 20 also comprises a binding portion 30 containing a betaine group and coordinating to the nanoparticle 10, and a polymer portion 40 connected to the binding portion 30. Alternatively, the shell-shaped ligand 20 can be described as containing a copolymer of the binding portion 30 containing a betaine group and coordinating to the nanoparticle 10, and the polymer portion 40 connected to the binding portion 30. The anion Y contained in the betaine group is configured to substitute a portion of the X site of the perovskite-type nanoparticle 10 and coordinate to the surface of the nanoparticle 10. The betaine group provided by the binding portion 30 may be described as a betaine structure. A betaine structure refers to a structure in which positive and negative charges are located at non-adjacent positions within the same molecule, and the molecule as a whole has no charge. Examples of betaine structures include sulfobetaine, phosphobetaine, and carboxybetaine. From the viewpoint of coordination ability with respect to nanoparticles 10, sulfobetaine and phosphobetaine are preferably used.

[0042] The shell-shaped ligand 20 coordinates to the nanoparticles 10 and, from the viewpoint of improving the dispersibility of the nanoparticles in the medium, preferably has an organic group. The organic group may be a linear, branched, or cyclic alkyl group, a linear, branched, or cyclic heteroalkyl group, an aryl group, a heteroaryl group, an aralkyl group, or a heteroaralkyl group. The organic group may also have substituents.

[0043] Because it is easy to effectively form a shell, it is preferable to use a polymer compound as the shell ligand. Furthermore, from the viewpoint of raw material availability and ease of manufacture, it is preferable to use a copolymer obtained by polymerizing at least two types of monomers, each containing a betaine group and an organic group, as the shell ligand.

[0044] From the viewpoint of the stability of nanoparticles in the medium, the weight-average molecular weight of the shell-shaped ligand is preferably 1,000 to 50,000, and more preferably 2,000 to 30,000.

[0045] The method for producing the above polymer compound is not particularly limited as long as a compound with the above structure can be obtained, but for example, it can be produced by the following methods (i) and (ii).

[0046] In other words, (i) a polymer compound can be produced by first producing a monomer containing at least a betaine group, and then polymerizing such monomer. Furthermore, (ii) a polymer compound can be produced by first synthesizing a polymer backbone, and then bonding the betaine group-containing moieties to the polymer backbone by polymer reaction.

[0047] From the standpoint of readily available monomers and control of the amount of functional groups, it is preferable to manufacture the copolymer using the method shown in (i). Below, a method for synthesizing a copolymer having a betaine group and an organic group using the method shown in (i) will be described in detail.

[0048] Monomers used to introduce betaine groups and organic groups into polymer compounds include vinyl ether derivatives, acrylate derivatives, methacrylate derivatives, α-olefin derivatives, and aromatic vinyl derivatives. Among these monomers, acrylate derivatives or methacrylate derivatives are preferred from the viewpoint of ease of monomer production. Examples of monomers having a phosphobetaine group include 2-(methacryloyloxy)ethyl 2-(trimethylammonio)ethyl phosphate (MPC). Examples of monomers having a sulfobetaine group include 3-[[2-(methacryloyloxy)ethyl]dimethylammonio]propane-1-sulfonic acid. Examples of carboxybetaines include 3-[[2-(methacryloyloxy)ethyl]dimethylammonio]propionate. Examples of monomers having organic groups include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, benzyl (meth)acrylate, 3,3,5-trimethylcyclohexyl acrylate, and Trahydrofurfuryl (meth)acrylate, phenoxyethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethyl carbitol (meth)acrylate, isobornyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, (3-ethyloxetan-3-yl)methyl (meth)acrylate, and cyclic trimethylolpropaneformal (meth)acrylate can be used.

[0049] Polymerization methods for the above monomers include radical polymerization and ionic polymerization. Living polymerization can also be used for the purpose of controlling molecular weight distribution or structure. Industrially, radical polymerization is preferred.

[0050] Radical polymerization can be carried out by using a radical polymerization initiator, irradiation with light such as radiation or laser light, a combination of a photopolymerization initiator and light irradiation, or heating. The radical polymerization initiator can be any compound that generates radicals and initiates a polymerization reaction, and is selected from compounds that generate radicals through the action of heat, light, radiation, or oxidation-reduction reactions.

[0051] Examples of radical polymerization initiators include azo compounds, organic peroxides, inorganic peroxides, organometallic compounds, and photopolymerization initiators.

[0052] More specifically, radical polymerization initiators include azo compounds such as 2,2'-azobisisobutyronitrile (AIBN) and 2,2'-azobis(2,4-dimethylvaleronitrile); organic peroxides such as benzoyl peroxide (BPO), tert-butyl peroxypivalate, and tert-butyl peroxyisopropyl carbonate; inorganic peroxides such as potassium persulfate and ammonium persulfate; redox initiators such as hydrogen peroxide-iron(II) salt systems, BPO-dimethylaniline systems, and cerium(IV) salt-alcohol systems; and photopolymerization initiators such as acetophenone systems, benzoin ether systems, and ketal systems. Two or more of these radical polymerization initiators may be used in combination.

[0053] The polymerization temperature of the monomer varies depending on the type of polymerization initiator used, and is not particularly limited. However, polymerization is generally carried out at temperatures between -30°C and 150°C, with a more preferred temperature range being 40°C to 120°C.

[0054] The amount of polymerization initiator used in this process is preferably 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the monomer, and the amount used should be adjusted so that a shell-shaped ligand with the target molecular weight distribution can be obtained.

[0055] Furthermore, any polymerization method can be used, including solution polymerization, suspension polymerization, emulsion polymerization, dispersion polymerization, precipitation polymerization, and bulk polymerization, and is not particularly limited to any particular method.

[0056] The obtained shell-like ligands can be purified as needed. There are no particular restrictions on the purification method, and methods such as reprecipitation, dialysis, and column chromatography can be used.

[0057] The structure of the fabricated shell-like ligand can be identified using various instrumental analyses. Suitable analytical instruments include nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC).

[0058] In the above copolymer, the molar ratio of monomers having betaine groups to monomers having organic groups is preferably 2.0 / 98 or more and 50 / 50 or less. More preferably, this molar ratio is 6 / 94 or more and 45 / 55 or less, and even more preferably 10 / 90 or more and 40 / 60 or less. When the copolymerization composition ratio is within the above range, the coordination of shell-like ligands to nanoparticles is stabilized, and the composition and crystal structure of the luminescent nanocrystals are stabilized. Further copolymerization with other monomers is also possible. The amount of substance may be expressed as molar concentration, and the molar ratio as molar ratio.

[0059] The content of the shell-like ligand in the photoresponsive material is preferably 1 to 1000 parts by mass, preferably 5 to 500 parts by mass, and more preferably 10 to 300 parts by mass, with the nanoparticle content being 100 parts by mass. If the content is less than 1 part by mass, the shell effect may not be fully exhibited, and stability may not be improved. If the content is greater than 1000 parts by mass, the solubility and dispersibility of the shell-like ligand in the medium may decrease, and the stability of the photoresponsive material may not be improved. The content of the shell-like ligand in the photoresponsive material can be appropriately adjusted according to the type and application of the nanoparticles and shell-like ligand.

[0060] It comprises a shell-like ligand having a betaine group and at least a portion of which is coordinated to the nanoparticle, The molar ratio of iodine released from nanoparticle 10 is higher than the molar ratio of iodine present in nanoparticle 10.

[0061] The molar ratio may be the value calculated as [I] / ([I]+[Br]). Alternatively, the molar ratio may be the value calculated as [I] / [Br]. Here, [X](X=I,Br) refers to the total amount of X in the nanoparticles.

[0062] As described in the first embodiment, when a shell-shaped ligand is applied to nanoparticles, iodine and oleylamine are preferentially detached and released from the nanoparticles. As a result, the amount of iodine released from the nanoparticles 10 is greater than the amount of bromine released.

[0063] (Measurement of free I and Br concentrations) The concentrations of free I and Br can be measured by wavelength-dispersive X-ray fluorescence analysis (WDXRF). For example, the ZSX100e (manufactured by Rigaku) ​​can be used. First, calibration curves are prepared for I and Br using standard samples. Next, the photoresponsive material is centrifuged and the supernatant is separated. A film-like sample is prepared by photocuring the obtained supernatant, and the concentrations of I and Br released from the nanoparticles 10 can be measured by analyzing it using wavelength-dispersive X-ray fluorescence analysis.

[0064] <Second Embodiment> The ink composition 200 according to the second embodiment will be described with reference to Figure 2.

[0065] To make the ink composition 200 a curing ink composition 200 in response to external stimuli, a polymerizable compound can be dispersed or dissolved in a medium. Alternatively, the ink composition 200 can be directly dispersed or dissolved in the polymerizable compound without using a medium.

[0066] (polymerizable compound) Polymerizable compounds, upon receiving energy from sources such as light, heat, or electromagnetic waves, undergo polymerization reactions, increasing the viscosity of liquid or paste-like intermediates containing themselves and allowing them to harden. Polymerizable compounds that polymerize upon irradiation with light are sometimes referred to as photopolymerizable compounds.

[0067] In order to make the ink composition 200 of this embodiment an ink composition 200 that hardens in response to external stimuli, a polymerizable monomer can also be used as a medium. Polymerizable monomers include UV monomers, UV dimers, UV oligomers, thermopolymerizable monomers, thermopolymerizable dimers, thermopolymerizable oligomers, etc., which may be referred to as photopolymerizable compounds and thermopolymerizable compounds, respectively. These may be used individually or in combination of two or more types.

[0068] Examples of radical polymerizable compounds include monofunctional (meth)acrylate compounds, difunctional (meth)acrylate compounds, trifunctional or more functional (meth)acrylate compounds, hydroxyl group-containing (meth)acrylate compounds, carboxyl group-containing (meth)acrylate compounds, and vinyl compounds.

[0069] Examples of monofunctional (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, benzyl (meth)acrylate, and 3,3,5-trimethylcyclohexyl acrylate. Tetrahydrofurfuryl (meth)acrylate, phenoxyethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethyl carbitol (meth)acrylate, isobornyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, (3-ethyloxetan-3-yl)methyl (meth)acrylate, and cyclic trimethylolpropaneformal (meth)acrylate can be used.

[0070] Examples of difunctional (meth)acrylate compounds include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol 200 di(meth)acrylate, polyethylene glycol 300 di(meth)acrylate, polyethylene glycol 400 di(meth)acrylate, and polyethylene glycol 600 Di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetrapropylene glycol di(meth)acrylate, polypropylene glycol 400 di(meth)acrylate, polypropylene glycol 700 di(meth)acrylate, neopentyl glycol di(meth)acrylate, neopentyl glycol PO-modified di(meth)acrylate, EO-modified bisphenol A di(meth)acrylate, PO-modified bisphenol A di(meth)acrylate, and hydroxypivalic acid neopentyl glycol di(meth)acrylate can be used.

[0071] Examples of trifunctional or more (meth)acrylate compounds include trimethylolpropane triacrylate, trimethylolpropane EO-modified tri(meth)acrylate, trimethylolpropane PO-modified tri(meth)acrylate, glycerin propoxy tri(meth)acrylate, pentaerythritol tri(meth)acrylate, tris(acryloxyethyl) isocyanurate, and EO-modified pentaerythritol tetraacrylate.

[0072] Examples of hydroxyl group-containing (meth)acrylate compounds include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate, as well as 2-hydroxyethyl acryloyl phosphate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, caprolactone-modified 2-hydroxyethyl (meth)acrylate, dipropylene glycol (meth)acrylate, fatty acid-modified glycidyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-hydroxy-3-(meth)acryloyloxypropyl (meth)acrylate, glycerin di(meth)acrylate, and 2-hydroxy-3-acryloyloxypropyl methacrylate.

[0073] Examples of carboxyl group-containing (meth)acrylate compounds include β-carboxyethyl (meth)acrylate, mono(meth)acryloyloxyethyl succinate, and ω-carboxypolycaprolactone mono(meth)acrylate.

[0074] Examples of vinyl compounds that can be used include vinyl acetate, vinyl benzoate, vinyl pivalate, vinyl butyrate, vinyl methacrylate, and N-vinylpyrrolidone.

[0075] Cationic polymerizable compounds can be either photopolymerizable or thermally polymerizable. These may be used individually or in combination of two or more types. Typical cationic polymerizable compounds include, for example, epoxy compounds, oxacene compounds, and vinyl ether compounds.

[0076] The amount of polymerizable compounds, including the radical polymerizable compounds and cationic polymerizable compounds mentioned above, used is preferably 1 to 99 parts by mass, more preferably 5 to 95 parts by mass, and even more preferably 10 to 90 parts by mass, per 100 parts by mass of ink composition 200.

[0077] (Polymerization initiator) Polymerization reactions generally involve the combined use of polymerization initiators and polymerizable compounds. Polymerization initiators are compounds that generate active species to initiate polymerization reactions upon irradiation with active energy rays or heat, and known polymerization initiators can be used. The main active species that initiate polymerization reactions include radical polymerization initiators that generate radicals and cationic polymerization initiators that generate acids, and these may be used in combination. Examples of photoradical polymerization initiators that generate radicals with active energy rays include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl methyl ketal, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butane, oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl Acetophenones such as [phenyl]propanone] and 2-hydroxy-1-[4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl]-2-methylpropan-1-one; benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; phosphines such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; and other phenylglyoxylic methyl esters.

[0078] Among photoradical polymerization initiators, preferred are acetophenones (represented by aminoketones), phosphines, and oxime ester compounds. These can be used individually or in combination depending on the desired properties of the cured product. When using a radical polymerization initiator, the amount used is preferably 0.01 to 100 parts by mass, and more preferably 0.1 to 50 parts by mass, per 100 parts by mass of the total solid content in the composition.

[0079] (solvent) Polymerizable compounds may contain a solvent as needed. Suitable solvents include, for example, alkanes such as pentane and hexane, cycloalkanes such as cyclopentane and cyclohexane, esters such as ethyl acetate, butyl acetate, and benzyl acetate, ethers such as diethyl ether and tetrahydrofuran, ketones such as cyclohexanone and acetone, and alcohols such as methanol, ethanol, isopropanol, butanol, and hexanol. Monoacetate compounds such as diethylene glycol monoethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, and dipropylene glycol methyl ether acetate, diacetate compounds such as 1,4-butanediol diacetate and propylene glycol diacetate, and triacetate compounds such as glyceryl triacetate can also be used.

[0080] Because the solvent can be easily removed before the polymerizable compound hardens, a solvent with a boiling point of 300°C or lower is used. The term "solvent" is sometimes replaced with "coagulant."

[0081] (Other additives) In this embodiment, the ink composition 200 may be mixed with, if necessary, oxygen removers, antioxidants, scattering agents such as titanium dioxide, surfactants, antifungal agents, light stabilizers, and other additives that impart various properties.

[0082] <Third Embodiment> The wavelength conversion layer according to the third embodiment will be described using Figure 3.

[0083] (Wavelength conversion layer) The wavelength conversion layer in this embodiment is a component formed by curing an ink composition 200 containing a photoresponsive material 100 in a codispersed state and a polymerizable compound 50, as shown in Figure 3, on a substrate. Since the wavelength conversion layer takes the form of a layer supported by other components, it may be referred to as the wavelength conversion layer 520 as shown in Figure 3. Support configurations include a laminated configuration and a dispersed configuration dispersed in a matrix material. The wavelength conversion layer 520 can be formed by coating the ink composition 200 onto a support component (substrate) and curing it to form a film, sheet, or patterned pixels.

[0084] (Method for forming a wavelength conversion layer) The method for forming the wavelength conversion layer 520 is not particularly limited. For example, one method involves coating an ink composition onto a substrate, pre-drying as needed, and then curing the film by heat treatment or irradiation with active energy rays as needed. The thickness of the cured wavelength conversion layer is preferably 0.1 to 200 μm, more preferably 1 to 100 μm.

[0085] In active energy ray irradiation, the active energy rays are electromagnetic waves such as thermal rays, ultraviolet rays, visible light, near-infrared rays, and electron beams that reduce fluidity and accelerate hardening through polymerization, crosslinking, drying, etc., which are appropriately selected. As the light source for providing active energy rays, a light source having a main emission wavelength in the wavelength range of 100 to 450 nm is preferred. Examples of such light sources include ultra-high pressure mercury lamps, high pressure mercury lamps, medium pressure mercury lamps, mercury xenon lamps, metal halide lamps, high-power metal halide lamps, xenon lamps, pulsed emission xenon lamps, deuterium lamps, fluorescent lamps, ND-YAG third harmonic lasers, HE-CD lasers, nitrogen lasers, XE-Cl excimer lasers, XE-F excimer lasers, semiconductor-pumped solid-state lasers, and LED lamp light sources having emission wavelengths of 365 nm, 375 nm, 385 nm, 395 nm, and 405 nm.

[0086] (Wavelength conversion element) The wavelength conversion element 520e comprises a first optical conversion layer 520p and a second optical conversion layer 520s, the optical conversion layer 520 having different halogen compositions with respect to the halogen X located at the X site.

[0087] Figure 3 shows the cross-sectional structure of the display element 500 according to the third embodiment.

[0088] The display element 500 has a light-emitting layer 510, a dielectric multilayer film 517, and a wavelength conversion layer 520 stacked in the stacking direction D1. In the stacking direction D1, the downstream side corresponds to the side where the user viewing the image drawn on the display element is positioned. The wavelength conversion layer 520 is separated from the wavelength conversion layer corresponding to adjacent elements by a black matrix BM that separates pixels.

[0089] As described above, the ink composition 200 is cured together with the polymerizable compound 50 by a polymerization treatment such as photopolymerization. Upon curing, the ink composition 200 constitutes the wavelength conversion layer 520 of the display element 500, which satisfies predetermined dimensions. That is, the wavelength conversion layer 520 is a layer that has been solidified by curing together with the polymerizable compound 50.

[0090] The light-emitting layer 510 corresponds to a light source that emits light L1 at a first wavelength λ1. The wavelength conversion layer 520 has an optical coupling surface 522 on the side of the light-emitting layer 510 that optically couples with the light-emitting layer 510, and an extraction surface 524 on the opposite side of the light-emitting layer 510 that extracts secondary light L2 converted by the wavelength conversion layer 520.

[0091] In this embodiment, the wavelength conversion layer 520 receives primary light L1 with wavelength λ1 that propagates through the dielectric multilayer film 917. The dielectric multilayer film 517 provides the display element 500 with the spectral transmission characteristics of the primary light from the light-emitting layer 510 and the spectral reflection characteristics of the secondary light L2 with wavelength λ2 emitted in the wavelength conversion layer 520. The wavelength λ2 of the secondary light L2 is longer than the wavelength λ1 of the primary light L1.

[0092] The dielectric multilayer film 917 can be replaced with another optical element that is light-transmitting for the first wavelength λ1 emitted by the light-emitting layer 510. Furthermore, another optical element (not shown) can be placed in front of the extraction surface 524 (opposite the light-emitting layer 510).

[0093] ((Storage method)) Since luminescent nanoparticles having a perovskite crystal structure are susceptible to degradation of their luminescence properties due to external stimuli such as light and heat, it is preferable to store the photoresponsive material according to this embodiment in a refrigerator or darkroom where external light is blocked. Doing so reduces degradation of the photoresponsive material according to this embodiment due to light and heat during storage.

[0094] ((Measurement, analysis method)) Various physical property measurements can be performed as follows.

[0095] (Measurement of molecular weight distribution of shell-shaped ligands) The molecular weight distribution of shell ligands can be calculated in terms of monodisperse polymethyl methacrylate by gel permeation chromatography (GPC). Molecular weight measurement by GPC can be performed, for example, as shown below.

[0096] The sample is added to the eluent listed below to achieve a sample concentration of 1% by mass, and the solution is allowed to stand at room temperature for 24 hours to dissolve. This solution is then filtered through a solvent-resistant membrane filter with a pore diameter of 0.45 μm to obtain the sample solution, which is then measured under the following conditions. Equipment: Agilent 1260 Infinity System (manufactured by Agilent Technologies) Column: PFG analytical linear M column (manufactured by PSS) Eluent: 2,2,2-trifluoroethanol Flow rate: 0.2ml / min Oven temperature: 40℃ Sample injection volume: 20 μL To calculate the molecular weight distribution of the sample, a molecular weight calibration curve prepared using standard polymethyl methacrylate resin (EasiVial PM Polymer Standard Kit, Agilent Technologies) is used.

[0097] (Compositional analysis of shell-shaped ligands) The compositional analysis of shell ligands can be performed using nuclear magnetic resonance (NMR). For example, using the ECA-600 (600 MHz) manufactured by JEOL Ltd., 1H-NMR and 13C-NMR spectra are measured. The measurements are performed at 25°C in a deuterated solvent containing tetramethylsilane as an internal standard. The chemical shift value is read as the ppm shift value (δ value) with the internal standard tetramethylsilane set to 0. Measuring shell ligands purified using preparative GPC dissolved in an NMR solvent such as methanol reduces the influence of other components. The signal originating from the betaine group is observed at lower magnetic fields compared to the signal originating from the organic group. By comparing the signal intensity from the organic group and the signal intensity from the betaine group, the molar ratio (copolymerization ratio) of monomers containing the betaine group and monomers containing the organic group can be determined.

[0098] (Content of shell-shaped ligands) The content of shell-like ligands in the photoresponsive material and ink composition 200 can all be determined from the weight of shell-like ligands isolated using preparative GPC. Alternatively, it can be determined from TG-DTA measurement and integrated intensity of NMR.

[0099] (Crystal structure analysis of nanoparticles, composition ratio analysis of X-sites) The crystal structure and composition of nanoparticles can be analyzed using an X-ray diffractometer (XRD). For example, by measuring the X-ray diffraction pattern using a RINT 2100 (manufactured by Rigaku), it is possible to analyze whether the nanoparticles have a perovskite-type crystal structure. Furthermore, by utilizing the fact that the interstitial distance of the crystal differs depending on the composition ratio of the X-sites, the composition ratio of the X-sites can be analyzed.

[0100] (Method for confirming that shell-like ligands are coordinated to nanoparticles) Infrared spectroscopy (IR) can be used to confirm whether shell-like ligands are coordinated to nanoparticles. A dispersion containing nanoparticles and shell-like ligands is mixed with a poor solvent as needed, precipitated by centrifugation, and then the supernatant is removed and the precipitate is dried. Shell-like ligands not bound to the nanoparticles are removed along with the supernatant. The IR spectrum of the obtained solid is measured, and if a signal originating from the betaine group is observed, it can be confirmed that the nanoparticle shell-like ligands are coordinated. In this case, the signal originating from the betaine group may shift by several nanometers due to coordination.

[0101] Furthermore, coordination can be confirmed by transmission electron microscopy (TEM) observation. Normally, photoresponsive nanoparticles with a perovskite crystal structure are observed in a regularly arranged form. However, when shell ligands are coordinated, the arrangement appears disordered due to steric repulsion between the shell ligands themselves and between the shell ligands and the substrate. This can also be used to confirm coordination.

[0102] (Nanoparticle content) The content of nanoparticles 10 in both the photoresponsive material 100 and the ink composition 200 can be measured using ICP emission spectroscopy and NMR. The amount of Pb is measured from the emission intensity of ICP emission spectroscopy, and the amount of ligands is measured from the signal intensity of NMR. The content of nanoparticles 10 can be measured from the crystal structure and composition information of nanoparticles 10 obtained by XRD as described above. [Examples]

[0103] The present disclosure will be further described below by a first set of examples, but will not be limited thereto.

[0104] [Production of polymer compound a] A reaction vessel equipped with a condenser, stirrer, thermometer, and nitrogen inlet tube was prepared. 10.7 parts of 2-(methacryloyloxy)ethyl 2-(trimethylammonio)ethyl phosphate (MPC), 45.4 parts of hexyl methacrylate (HMA), 4.1 parts of azobisisobutyronitrile, and 900 parts of n-butanol were charged into the reaction vessel. Furthermore, nitrogen bubbling was performed in the reaction vessel for 30 minutes. The resulting reaction mixture was heated under a nitrogen atmosphere at 65°C for 8 hours to complete the polymerization reaction. After cooling the reaction mixture to room temperature, the solvent was removed by vacuum distillation. The resulting residue was dissolved in chloroform and purified by dialysis using a dialysis membrane (Spectra / Por7 MWCO 1kDa, Spectrum Laboratories). After removing the solvent by vacuum distillation, the mixture was dried under reduced pressure at 50°C and below 0.1kPa to obtain polymer compound 1-a, a copolymer of MPC and EHMA.

[0105] When the obtained polymer compound 1-a was analyzed using the above analytical method, it was confirmed that the weight-average molecular weight (Mw) was 10,800, and that structural units derived from MPC were present in 12 mol% of the total monomer units.

[0106] [Production of polymer compound b] Polymer compound b was prepared in the same manner as polymer compound a, except that 17.0 parts of MPC and 41.8 parts of HMA were used instead of 10.7 parts of MPC and 45.4 parts of HMA. When the obtained polymer compound 1-a was analyzed using the analytical method described above, it was confirmed that the weight-average molecular weight (Mw) was 11,200 and that structural units derived from MPC accounted for 19 mol% of the total monomer units.

[0107] Table 1 shows the composition ratio and weight-average molecular weight (Mw) of polymer compounds a and b manufactured as described above.

[0108] [Table 1]

[0109] [Preparation of polymer compound solutions] (Preparation of a toluene solution of polymer compound a) In a reaction vessel equipped with a stirrer, thermometer, and reflux condenser, 1 part of polymer compound a and 99 parts of toluene were charged, and the temperature was raised to 110°C and heated for 5 minutes. After confirming that polymer compound a was completely dissolved, it was cooled to room temperature to obtain a toluene solution of polymer compound a.

[0110] (Preparation of a toluene solution of polymer compound b) A toluene solution of polymer compound b was obtained in the same manner as the preparation of a toluene solution of polymer compound a, except that polymer compound b was used in the preparation of a toluene solution of polymer compound a.

[0111] [Manufacturing of nanoparticle dispersions] (Manufacturing of nanoparticle a dispersion) Ten parts of cesium carbonate, twenty-seven parts of oleic acid, and thirty-eight parts of 1-octadecene were placed in a flask, heated to 120°C, and degassed for 30 minutes using a vacuum pump. The mixture was then heated to 150°C under a stream of dry nitrogen and held for 30 minutes to obtain a cation raw material solution.

[0112] Separately, 10 parts of lead(II) bromide and 493 parts of 1-octadecene were placed in a flask, the liquid temperature was heated to 120°C, and the mixture was degassed for 1 hour using a vacuum pump. 89 parts of oleic acid and 81 parts of oleylamine were added, and the mixture was degassed again for 30 minutes using a vacuum pump. After that, the liquid temperature was increased to 185°C using a nitrogen flow to obtain the lead raw material solution.

[0113] 40 parts of cation stock solution were added to the entire volume of the lead stock solution, and the mixture was cooled on ice after 5 seconds. 35 parts of ethyl acetate were added, and centrifugation (10,000 rpm, 15 minutes) was started after 5 minutes, and the supernatant was removed. The resulting residue was dispersed in hexane and analyzed by XRD. The resulting particles had a perovskite-type crystalline structure, and their composition was CsPb(Br 0.4 I 0.6 The result was 3. Furthermore, when the weight of the material at temperatures above 400°C was analyzed by TG-DTA as perovskite-type nanoparticles, 60% of the total solid content was found to be perovskite-type nanoparticles. The perovskite-type nanoparticles were dispersed in hexane to obtain a nanoparticle dispersion a so that the amount of perovskite-type nanoparticles was 1% by weight.

[0114] (Manufacturing of nanoparticle b dispersion) In the preparation of nanoparticle dispersion a, a hexane dispersion of nanoparticles was obtained in the same manner as in the preparation of nanoparticle dispersion a, except that 35 parts of ethyl acetate were not added. XRD analysis revealed that the obtained particles had a perovskite-type crystalline structure, and the composition was CsPb(Br 0.4 I 0.6 The result was 3. Furthermore, when the weight of the material at temperatures above 400°C was analyzed by TG-DTA as perovskite-type nanoparticles, 61% of the total solid content was found to be perovskite-type nanoparticles. The perovskite-type nanoparticles were dispersed in hexane to obtain nanoparticle b dispersion, with the amount of perovskite-type nanoparticles being 1% by weight.

[0115] (Manufacturing of nanoparticle-C dispersion) In the preparation of nanoparticle dispersion a, a hexane dispersion of nanoparticles was obtained using the same procedure as for nanoparticle dispersion a, except that centrifugation was started at 15 minutes instead of 5 minutes. XRD analysis revealed that the obtained particles had a perovskite-type crystalline structure, and the composition was CsPb(Br 0.4 I 0.6 The result was 3. Furthermore, when the weight of the material at temperatures above 400°C was analyzed by TG-DTA as perovskite nanoparticles, 60% of the total solid content was found to be perovskite nanoparticles. The perovskite nanoparticles were dispersed in hexane so that the amount of perovskite nanoparticles was 1% by weight to obtain a nanoparticle dispersion c.

[0116] (Manufacturing of nanoparticle d dispersion) In the preparation of nanoparticle dispersion a, a hexane dispersion of nanoparticles was obtained in the same manner as in the preparation of nanoparticle dispersion a, except that 2000 parts of ethyl acetate were added instead of 35 parts of ethyl acetate. Analysis by XRD revealed that the obtained particles had a perovskite-type crystalline structure, and the composition was CsPb(Br 0.42 I 0.58The result was 3. Furthermore, when the weight of the material at temperatures above 400°C was analyzed by TG-DTA as perovskite-type nanoparticles, 63% of the total solid content was found to be perovskite-type nanoparticles. The perovskite-type nanoparticles were dispersed in hexane to obtain a nanoparticle dispersion d so that the amount of perovskite-type nanoparticles was 1% by weight.

[0117] (Manufacturing of nanoparticle-e dispersion) In the preparation of nanoparticle dispersion a, a hexane dispersion of nanoparticles was obtained in the same manner as in the preparation of nanoparticle dispersion a, except that 2000 parts of ethyl acetate were added instead of 35 parts of ethyl acetate, and centrifugation was started at 15 minutes instead of 5 minutes. Analysis by XRD revealed that the obtained particles had a perovskite-type crystalline structure, and the composition was CsPb(Br 0.43 I 0.57 The result was 3. Furthermore, when the weight of the material at temperatures above 400°C was analyzed by TG-DTA as perovskite-type nanoparticles, 60% of the total solid content was found to be perovskite-type nanoparticles. The perovskite-type nanoparticles were dispersed in hexane to obtain a nanoparticle dispersion e, with the amount of perovskite-type nanoparticles being 1% by weight.

[0118] [Table 2]

[0119] [Preparation of photoresponsive materials] (Example 1) 529 parts of a dispersion of nanoparticles a were placed in a container, and the solvent was removed by distillation under reduced pressure. 50 parts of a toluene solution of polymer compound a were added, and the mixture was heated at 60°C for 5 minutes to obtain photoresponsive material 1.

[0120] (Example 2) Photoresponsive material 2 was obtained in the same manner as photoresponsive material 1, except that 50 parts of toluene solution were changed to 150 parts of toluene solution.

[0121] (Example 3) Photoresponsive material 3 was obtained in the same manner as photoresponsive material 1, except that 50 parts of toluene solution were changed to 250 parts of toluene solution.

[0122] (Example 4) Photoresponsive material 4 was obtained in the same manner as photoresponsive material 1, except that 50 parts of toluene solution were changed to 350 parts of toluene solution.

[0123] (Example 5) A photoresponsive material 5 was obtained in the same manner as photoresponsive material 4, except that a toluene solution of polymer compound b was used instead of a toluene solution of polymer compound a.

[0124] (Example 6) A photoresponsive material 6 was obtained in the same manner as photoresponsive material 3, except that a nanoparticle b dispersion was used instead of a nanoparticle a dispersion.

[0125] (Example 7) A photoresponsive material 7 was obtained in the same manner as photoresponsive material 3, except that a nanoparticle c dispersion was used instead of a nanoparticle a dispersion.

[0126] (Example 8) A photoresponsive material 8 was obtained in the same manner as photoresponsive material 3, except that a nanoparticle d dispersion was used instead of a nanoparticle a dispersion.

[0127] (Comparative Example 1) A photoresponsive material 9 was obtained in the same manner as photoresponsive material 3, except that a dispersion of nanoparticles e was used instead of a dispersion of nanoparticles a.

[0128] (Comparative Example 2) Photoresponsive material 10 was obtained in the same manner as photoresponsive material 3, except that 250 parts of toluene solution were not added.

[0129] Table 3 shows the type and concentration of the nanoparticle dispersion, the concentration of nanoparticles in the nanoparticle dispersion, the concentration of materials other than nanoparticles in the nanoparticle dispersion, the type and concentration of the toluene solution of the polymer compound, and the concentration of the polymer compound in the toluene solution of the polymer compound for photoresponsive materials 1 to 10.

[0130] [Table 3]

[0131] [Preparation of Titanium Oxide Dispersion] Forty parts of titanium dioxide JR-403 (manufactured by Teika), one part of Ajisper PB821 (manufactured by Ajinomoto® Fine Techno), sixty parts of 3,3,5-trimethylcyclohexyl acrylate (TMCHA) (manufactured by Osaka Organic Chemical Industry, trade name Viscoat #196), and glass beads (1 mm in diameter) were placed in a container and dispersed using paint conditioner for four hours to obtain a titanium dioxide dispersion.

[0132] [Preparation of ink composition] (Example 9) Ink composition 1 was obtained by blending 8.0 parts of photoresponsive material 1, 11 parts of titanium dioxide dispersion, 28 parts of TMCHA, 2.5 parts of 1,6-hexanediol diacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name HDDA), and 1.4 parts of polymerization initiator (manufactured by IGMresins, trade name OmniradTPO).

[0133] (Example 10) Ink composition 2 was obtained in the same manner as ink composition 1, except that 9.0 parts of photoresponsive material 2 were used instead of 8.0 parts of photoresponsive material 1, and 31 parts of TMCHA were used instead of 32 parts of TMCHA.

[0134] (Example 11) Ink composition 3 was obtained in the same manner as ink composition 1, except that 10.0 parts of photoresponsive material 3 were used instead of 8.0 parts of photoresponsive material 1, and 30 parts of TMCHA were used instead of 32 parts of TMCHA.

[0135] (Example 12) Ink composition 4 was obtained in the same manner as ink composition 1, except that 11.5 parts of photoresponsive material 4 were used instead of 8.0 parts of photoresponsive material 1, and 29 parts of TMCHA were used instead of 32 parts of TMCHA.

[0136] (Example 13) An ink composition 5 was obtained in the same manner as with photoresponsive material 4, except that photoresponsive material 5 was used instead of photoresponsive material 4.

[0137] (Example 14) An ink composition 6 was obtained in the same manner as with photoresponsive material 3, except that photoresponsive material 6 was used instead of photoresponsive material 3.

[0138] (Example 15) An ink composition 7 was obtained in the same manner as with photoresponsive material 3, except that photoresponsive material 7 was used instead of photoresponsive material 3.

[0139] (Example 16) An ink composition 8 was obtained in the same manner as with photoresponsive material 3, except that photoresponsive material 8 was used instead of photoresponsive material 3.

[0140] (Comparative Example 3) An ink composition 9 was obtained in the same manner as with photoresponsive material 3, except that photoresponsive material 9 was used instead of photoresponsive material 3.

[0141] (Comparative Example 4) Ink composition 10 was obtained in the same manner as ink composition 1, except that 7.5 parts of photoresponsive material 10 were used instead of 8.0 parts of photoresponsive material 1, and 33 parts of TMCHA were used instead of 28 parts of TMCHA.

[0142] Table 4 shows the type and concentration of photoresponsive material, titanium dioxide concentration, type and concentration of polymerizable compound, and polymerization initiator concentration for ink compositions 1 to 10.

[0143] [Table 4]

[0144] The abbreviations used in Table 4 are shown below. TMCHA: 3,3,5-Trimethylcyclohexyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) HDDA: 1,6-Hexanediol diacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) <Measurement of the ratio of free I and Br> Ink compositions 1-10 were centrifuged (15000 rpm, 60 minutes), and the supernatant was separated. Using the obtained supernatant, a liquid film was prepared on a glass substrate (3 cm × 3 cm), and cured using a 365 nm wavelength LED lamp to form a 1 mm thick cured film. Wavelength-dispersive XRF was measured to quantify the concentrations of free I and Br, and the molar ratio of iodine freed from the perovskite nanocrystals R1 = [I] free / ([Br] free +[I] free ) was calculated. Here [X] free (X=I,Br) represents the concentration of free X. Equipment: Wavelength-dispersive X-ray fluorescence analyzer (Rigaku, ZSX100e) Measurement conditions: Tube Rh (rhodium), tube voltage 30kV, tube current 120mA Measurement mode: EZscan, Target elements: B~U Spectroscopic crystal: LiF1 <Measurement of the ratio of I and Br coordinated in nanoparticles> 1 to 10 parts of the inky composition were centrifuged (15000 rpm, 60 minutes), and the supernatant was removed. 95 parts of TMCHA and 5 parts of OmniradTPO were added to the resulting residue and redispersed. A liquid film was prepared on a glass substrate (3 cm × 3 cm) and cured using a 365 nm wavelength LED lamp to form a 1 mm thick cured film. Wavelength-dispersive XRF was measured to quantify the concentrations of coordinated I and Br, and the molar ratio of non-free iodine contained in the perovskite nanocrystal R2 = [I] coordinate / ([Br] coordinate +[I] coordinate ) was calculated. Here [X] coordinate (X=I,Br) represents the concentration of X coordinated to the nanoparticles.

[0145] The results are shown in Table 5.

[0146] [Table 5]

[0147] [Manufacturing of wavelength conversion layer] The obtained ink compositions 1 to 10 were used to spin-coat glass substrates (10 cm × 10 cm). Each of the spin-coated glass substrates with ink compositions 1 to 10 was then exposed to a total light intensity of 400 mJ / cm² using a belt-conveyor type ultraviolet irradiation device (high-pressure mercury lamp, 120 W / cm²). 2 A cured film with a thickness of 10 μm was formed on the glass substrate by irradiating it with ultraviolet light in such a manner. After this, a barrier film was laminated on the surface of the cured film to obtain wavelength conversion layers 1 to 10.

[0148] <Evaluation of wavelength conversion layers 1-10> The following evaluations were performed on the obtained wavelength conversion layers ~10. The results are shown in Table 6.

[0149] [Light resistance evaluation] For each wavelength conversion layer 1-10, the wavelength is 450 nm and the intensity is 100,000 cd / m². 2 The emission peak wavelength, total halfwidth, and absolute emission quantum yield (PLQY) were measured after 16 hours of irradiation with blue light.

[0150] <Measurement conditions> Measurement device: Absolute PL quantum yield analyzer C9920-03 (manufactured by Hamamatsu Photonics) Excitation light wavelength: 460nm Excitation light integration range: Excitation light wavelength ±10 nm Emission integration range: (excitation light wavelength + 20) nm to 770 nm The evaluation criteria are as follows.

[0151] <Evaluation Criteria> The following criteria were used for evaluation. A: PLQY value is 80% or higher after 16 hours of blue light irradiation. B: PLQY value after 16 hours of blue light irradiation is between 70% and 80%. C: PLQY value after 16 hours of blue light irradiation is between 60% and 70%. D: PLQY value less than 60% after 16 hours of blue light irradiation

[0152] [Table 6]

[0153] According to Table 6, the wavelength conversion layer in this embodiment exhibits a long emission peak wavelength, a narrow full width at half maximum, and high PLQY immediately after fabrication and after irradiation with B light. This is thought to be because the shell-shaped ligand having a betaine group effectively coordinates to the perovskite-type nanoparticles containing iodine at the X site in the ink composition of this embodiment. When a large amount of ethyl acetate is used for purification and centrifugation is started after 5 minutes, as in Example 16, the emission peak wavelength becomes slightly shorter and the PLQY becomes slightly lower. When a large amount of ethyl acetate is used for purification and centrifugation is started after 15 minutes, as in Comparative Example 3, the emission peak wavelength becomes shorter and the PLQY becomes lower. When a shell-shaped ligand is not used, as in Comparative Example 4, the PLQY after irradiation with B light becomes very low. [Explanation of symbols]

[0154] 10 nanoparticles 20 Shell-shaped ligands 100 Photoresponsive materials

Claims

1. Nanoparticles having a perovskite-type crystal structure containing iodine at the X site, A shell-shaped ligand having a betaine group and at least a portion of which is coordinated to the nanoparticles, A photoresponsive material in which the molar ratio of iodine present at the X-site on the surface of the nanoparticle is lower than the molar ratio of iodine present at the X-site inside the nanoparticle.

2. Nanoparticles having a perovskite-type crystal structure containing iodine at the X site, A shell-shaped ligand having a betaine group and at least a portion of which is coordinated to the nanoparticles, The molar ratio of iodine released from the aforementioned nanoparticles is higher than the molar ratio of non-free iodine contained in the nanoparticles, resulting in a photoresponsive material.

3. The photoresponsive material according to claim 1 or 2, wherein the shell-shaped ligand comprises a binding portion containing the betaine group and coordinating to the nanoparticles, and a polymer portion connected to the binding portion.

4. The photoresponsive material according to claim 1 or 2, wherein the shell-shaped ligand comprises a copolymer of a binding portion containing the betaine group and coordinating to the nanoparticles, and a polymer portion connected to the binding portion.

5. The photoresponsive material according to claim 1 or 2, wherein the shell-like ligand is coordinated to the surface of the nanoparticles.

6. The photoresponsive material according to claim 1 or 2, wherein the shell-shaped ligand has an anion that substitutes for a portion of the iodine located at the X site and is coordinated to the surface of the nanoparticles.

7. The photoresponsive material according to claim 1 or 2, wherein the nanoparticle contains bromine at the X site.

8. The photoresponsive material according to claim 7, wherein the molar ratio of iodine corresponds to [I] / ([I]+[Br]). Here, [Q] represents the amount of substance Q.

9. A photoresponsive material according to claim 1 that satisfies the following formula (1). [I] 表面 / ( [I] 表面 + [Br] 表面 ) < [I] 内部 / ( [I] 内部 + [Br] 内部 ) Formula (1)

10. The photoresponsive material according to claim 2, satisfying the following formula (2). [I] 遊離 / ( [I] 遊離 + [Br] 遊離 ) > [I] 非遊離 / ( [I] 非遊離 + [Br] 非遊離 ) Formula (2)

11. An ink composition comprising a photoresponsive material according to claim 1 or 2 and a polymerizable compound.

12. The ink composition according to claim 11, comprising a polymerization initiator.

13. The ink composition according to claim 12, wherein the polymerizable compound comprises a photopolymerizable compound that undergoes a polymerization reaction upon irradiation with light, and the polymerization initiator comprises a photopolymerization initiator that generates an active species that initiates the polymerization reaction.

14. A photoconversion layer comprising the ink composition according to claim 11 and a cured product of the polymerizable compound.

15. A wavelength conversion element comprising, as the light conversion layer according to claim 14, a first light conversion layer and a second light conversion layer having different halogen compositions with respect to the halogen located at the X site.

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