Photoresponsive material and ink composition

Abstract

Provided is a photoresponsive material characterized by comprising nanoparticles having a perovskite-type crystal structure containing iodine at a site, and a shell-shaped ligand having a betaine group and partially coordinated to the nanoparticles, wherein the substance amount ratio of the iodine present at a site X on the surface of the nanoparticles is lower than the substance amount ratio of the iodine present at a site X inside the nanoparticles.

Description

Photoresponsive materials and ink compositions

[0001] This disclosure relates to photoresponsive materials and ink compositions that emit light upon irradiation with light.

[0002] Quantum dots with a perovskite crystal structure (perovskite quantum dots) exhibit a narrow total half-width and high color purity in their spectral sensitivity characteristics, and are therefore known to be applicable to organic EL materials and quantum dot photoresponsive materials. Furthermore, they have the characteristic of allowing control of the emission wavelength by changing the halogen composition.

[0003] On the other hand, perovskite quantum dots are prone to surface defects due to external stimuli such as light, heat, oxygen, and moisture, and their emission quantum yield easily decreases. This is thought to be due to the small particle size of perovskite quantum dots (a few to twenty nanometers) and their large specific surface area, as well as the fact that they are made of ionic crystals and are susceptible to the influence of polar materials. Japanese Patent Publication No. 2023-81338 discloses a technique for improving the stability of perovskite quantum dots by modifying the particle surface with a zwitterionic shell-like ligand.

[0004] Japanese Patent Publication No. 2023-81338

[0005] When producing a photoresponsive material or light-emitting layer using perovskite-type quantum dots protected by a shell-like ligand as described in Japanese Patent Publication No. 2023-81338, CsPbBr ３ High durability can be obtained with iodine-free compositions such as CsPb(Br / I) ３ Compositions containing iodine, such as those mentioned above, had room for improvement in durability. In addition, the nanoparticles disclosed in Japanese Patent Application Publication No. 2023-81338 sometimes suffered from reduced luminescence 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 a perovskite-type quantum dot 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.

[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.

[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.

[0011] This figure shows the schematic configuration of a photoresponsive material according to the first embodiment. This figure shows the schematic configuration of an ink composition according to the second embodiment. This figure shows the schematic configuration of a display element equipped with a wavelength conversion layer according to the third embodiment.

[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 Material)) The photoresponsive material 100 according to this embodiment includes nanoparticles 10 having a perovskite crystal structure containing iodine at the X site, and shell-like ligands 20 having a betaine group and partially coordinated to the nanoparticles. Also, the molar ratio of iodine present at the X site on the surface of the nanoparticles 10 is configured to be lower than the molar ratio of iodine present at the X site inside the nanoparticles 10. Since the photoresponsive material 100 has nanoparticles 10 having a perovskite crystal structure with a quantum confinement effect and has fluorescence emission properties, it may be equivalently referred to as a luminescent material 100, a fluorescent material 100, a luminescent composition 100, etc.

[0015] (Nanoparticles) The nanoparticles 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).

[0016] The perovskite crystal structure is equivalently referred to as a perovskite-type structure, an ABX ３ type crystal structure, an ABX ３ type structure. Also, A ２ B １ B ２ X ６ and the double perovskite crystal structure represented as such is also included in the perovskite crystal structure.

[0017] [A Site of the Perovskite Crystal Structure] The A site of the perovskite crystal structure employs a monovalent cation. The monovalent cations employed at the A site include ammonium cation (NH ４ ＋ ), and alkylammonium cations having 6 or less carbon atoms, formamidinium cation (HC(NH ２ ) ２ ＋ ), guanidinium cation (C(NH ２ ) ３ ＋ ), nitrogen-containing organic compound cations such as imidazolium cation, pyridinium cation, pyrrolidinium cation, etc., and lithium cation (Li ＋), sodium cation (Na ＋ ), potassium cation (K ＋ ), rubidium cation (Rb ＋ ), and cesium cations (Cs ＋ Examples include alkali metal cations such as ).

[0018] Because the monovalent cations employed at these A-sites have small ionic diameters and are small enough to fit within the crystal lattice, the perovskite compound can form a stable three-dimensional crystal.

[0019] A preferred example of an alkylammonium cation having 6 or fewer carbon atoms is the methylammonium cation (CH4). ３ NH ３ ＋ ), ethylammonium cation (C ２ H ５ NH ３ ＋ ), propylammonium cation (C ３ H ７ NH ３ ＋ Examples include:

[0020] 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.

[0021] If the A site 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.

[0022] If site A is another alkali metal cation, salts of the above-mentioned cesium compound in which the cesium element is replaced with another alkali metal cation element can be used as raw materials.

[0023] 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.

[0024] [B-site of perovskite crystal structure] The B-site of the perovskite crystal structure employs a divalent cation, including a divalent transition metal cation or a divalent typical metal cation.

[0025] 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.

[0026] Divalent typical metal cations include magnesium cations (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.

[0027] 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.

[0028] When the B site is a lead cation, lead compounds can be used as raw materials for the synthesis of the 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.

[0029] [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.

[0030] 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.

[0031] 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 according to the synthesis method from salts with A-site and B-site countercations, such as cesium chloride and lead bromide, or salts with other cations.

[0032] 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.

[0033] 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. Moreover, 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 applied to a substrate and then crystals are grown directly to obtain the reactant.

[0034] The particle size of the nanoparticles is preferably such that the average particle size is 1 nm to 30 nm, more preferably 2 nm to 25 nm, and even more preferably 3 nm to 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.

[0035] The nanoparticle content is preferably 0.01 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the total weight of the photoresponsive material, including the medium. If the content is 0.01 parts by mass or less, it may dissolve. If the content is 50 parts by mass or more, dispersibility in the medium may not be ensured.

[0036] 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.

[0037] Furthermore, it is preferable that the equation (1) is satisfied. [I] 表面 / ([I] 表面 + [Br] 表面 ) < [I] 内部 / ([I] 内部 + [Br] 内部 ) Formula (1)

[0038] Furthermore, it is preferable that the equation (2) is satisfied. [I] 遊離 / ([I] 遊離 + [Br] 遊離 )> [I] 非遊離 / ([I] 非遊離 + [Br] 非遊離 ) Formula (2)

[0039] Here's the question: 表面 [Q] represents the amount of substance Q on the surface of the nanoparticles. 内部 represents the amount of substance Q inside the nanoparticle. Equation (1) is ABX３ The anion X is composed of bromine (Br) and iodine (I) in a BrI mix system AB(I ｚ Br （３－ｚ） This applies to the following:

[0040] 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].

[0041] Here, the subscript "surface" [Q] represents the amount of substance of anion Q located at the X site on the surface of the nanoparticle 10, and the subscript "internal" [Q] represents the amount of substance of anion Q contained in the X site inside the nanoparticle 10. Furthermore, the subscript "free" [Q] represents the amount of substance of anion Q that has been freed from the nanoparticle 10 and is present in the medium, and the subscript "non-free" [Q] represents the amount of substance of anion Q contained in the X site of the perovskite-type nanoparticle 10.

[0042] (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 performing centrifugation, it is common to add a large excess of a polar solvent such as ethyl acetate as a poor solvent to the reaction solution (crude solution). However, when a large amount of polar solvent such as ethyl acetate is used, not only does the amount of centrifugation processing increase, but there is also the problem that the luminescence properties of the nanoparticles will deteriorate if the centrifugation process is not performed immediately. This is because the halogen and ligands coordinated to the nanoparticles are desorbed by the polar solvent. Therefore, although purification methods that use large amounts of polar solvent are preferred at the laboratory level, they have low applicability to industries that require 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 deteriorate as described above. Reducing the amount of polar solvent also reduces the time constraints before starting centrifugation.

[0043] 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.

[0044] (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 nanoparticles 10, sulfobetaine and phosphobetaine are preferably used.

[0045] 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.

[0046] Because it is easy to effectively form a shell, it is preferable to use a polymer compound as the shell-like 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-like ligand.

[0047] 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 or more and 50,000 or less, and more preferably 2,000 or more and 30,000 or less.

[0048] The method for producing the above polymer compound is not particularly limited as long as the above structure is obtained, but it can be produced by, for example, the following methods (i) and (ii).

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] Examples of radical polymerization initiators include azo compounds, organic peroxides, inorganic peroxides, organometallic compounds, and photopolymerization initiators.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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).

[0061] 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.

[0062] 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.

[0063] The nanoparticle has a shell-like ligand having a betaine group and at least a portion of it is coordinated to the nanoparticle, and the molar ratio of iodine released from the nanoparticle 10 is higher than the molar ratio of iodine present in the nanoparticle 10.

[0064] 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.

[0065] 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.

[0066] (Measurement of the concentration of free I and Br) The concentration 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 concentration of I and Br released from the nanoparticles 10 can be measured by analyzing it using wavelength-dispersive X-ray fluorescence analysis.

[0067] <Second Embodiment> The ink composition 200 according to the second embodiment will be described with reference to Figure 2.

[0068] 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.

[0069] (Polymerizable Compounds) Polymerizable compounds can undergo polymerization reactions upon receiving energy such as light, heat, or electromagnetic waves, increasing the viscosity of liquid or paste-like intermediates containing themselves and causing them to harden. Polymerizable compounds that undergo polymerization reactions upon irradiation with light are sometimes referred to as photopolymerizable compounds.

[0070] 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 that are UV-curable, thermally polymerizable monomers, thermally polymerizable dimers, thermally polymerizable oligomers, etc., which may be referred to as photopolymerizable compounds and thermally polymerizable compounds, respectively. These may be used individually or in combination of two or more types.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] Examples of carboxyl group-containing (meth)acrylate compounds include β-carboxyethyl (meth)acrylate, mono(meth)acryloyloxyethyl succinate, and ω-carboxypolycaprolactone mono(meth)acrylate.

[0077] Examples of vinyl compounds that can be used include vinyl acetate, vinyl benzoate, vinyl pivalate, vinyl butyrate, vinyl methacrylate, and N-vinylpyrrolidone.

[0078] 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.

[0079] 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 the ink composition 200.

[0080] (Polymerization Initiators) Polymerization reactions generally involve the combined use of polymerization initiators and polymerizable compounds. Polymerization initiators are compounds that generate active species that 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 using 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], 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.

[0081] Among photoradical polymerization initiators, preferred are acetophenones, phosphines, and oxime ester compounds, typified by aminoketones. 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.

[0082] (Solvent) Polymerizable compounds may contain a solvent as needed. Examples of solvents include 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.

[0083] 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."

[0084] (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.

[0085] <Third Embodiment> The wavelength conversion layer according to the third embodiment will be described using Figure 3.

[0086] (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 laminated configurations and dispersed configurations in a matrix material. The wavelength conversion layer 520 can be formed by coating the ink composition 200 onto a support member (substrate) and curing it to form a film, sheet, or patterned pixels.

[0087] (Method for forming the 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 necessary, and then curing the film by heat treatment or irradiation with active energy rays as necessary. The thickness of the cured wavelength conversion layer is preferably 0.1 to 200 μm, more preferably 1 to 100 μm.

[0088] In active energy ray irradiation, the active energy rays are appropriately selected electromagnetic waves that reduce fluidity and accelerate hardening through polymerization, crosslinking, drying, etc., such as thermal rays, ultraviolet rays, visible light, near-infrared rays, and electron beams. 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.

[0089] (Wavelength conversion element) The wavelength conversion element 520e comprises a first photoconversion layer 520p and a second photoconversion layer 520s, the first and second photoconversion layers 520p having different halogen compositions with respect to the halogen X located at the X site.

[0090] Figure 3 shows the cross-sectional structure of the display element 500 according to the third embodiment.

[0091] 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 coincides with 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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 (on the opposite side of the light-emitting layer 510).

[0096] (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 can reduce degradation of the photoresponsive material according to this embodiment due to light and heat during storage.

[0097] (Measurement and Analysis Methods) Various physical property measurements can be performed as follows.

[0098] (Molecular weight distribution measurement of shell 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 as shown below, for example.

[0099] The sample was added to the eluent listed below to achieve a sample concentration of 1% by mass, and the solution was allowed to stand at room temperature for 24 hours to dissolve. The solution was then filtered through a solvent-resistant membrane filter with a pore diameter of 0.45 μm to obtain the sample solution, which was then measured under the following conditions: Instrument: Agilent 1260 Infinity System (Agilent Technologies) Column: PFG Analytical Linear M Columns (PSS) Eluent: 2,2,2-Trifluoroethanol Flow rate: 0.2 ml / min Oven temperature: 40°C Sample injection volume: 20 μL

[0100] 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.

[0101] (Compositional Analysis of Shell-Shaped Ligands) The compositional analysis of shell-shaped 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 measurement is 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. When shell-shaped ligands purified using preparative GPC are dissolved in an NMR solvent such as methanol and measured, the influence of other components is less pronounced. Signals originating from betaine groups are observed on the lower magnetic field side compared to signals originating from organic groups. By comparing the signal intensity from organic groups and signals originating from betaine groups, the molar ratio (copolymerization ratio) of monomers containing betaine groups and monomers containing organic groups can be determined.

[0102] (Shell-like ligand content) The shell-like ligand content in the photoresponsive material and ink composition 200 can be determined from the weight of shell-like ligands isolated using preparative GPC. It can also be determined from TG-DTA measurement and integrated intensity of NMR.

[0103] (Crystal structure analysis of nanoparticles, analysis of X-site composition ratio) The crystal structure analysis and composition analysis of nanoparticles can be performed 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.

[0104] (Method for confirming the coordination of shell-like ligands to nanoparticles) Whether or not shell-like ligands are coordinated to nanoparticles can be confirmed using infrared spectroscopy (IR). 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 nm due to coordination.

[0105] 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-like ligands are coordinated, the arrangement appears disordered due to steric repulsion between the shell-like ligands themselves and between the shell-like ligands and the substrate. This can also be used to confirm coordination.

[0106] (Nanoparticle Content) The content of nanoparticles 10 in the photoresponsive material 100 and the ink composition 200 can both 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 ligand is measured from the signal intensity of NMR. The content of nanoparticles 10 can be measured from the crystal structure and composition information of the nanoparticles 10 obtained by XRD as described above.

[0107] The present disclosure will be described in more detail below by a first set of embodiments, but this will not limit the present disclosure.

[0108] [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 (MPC) phosphoric acid, 45.4 parts of hexyl methacrylate (HMA), 4.1 parts of azobisisobutyronitrile, and 900 parts of n-butanol were charged into the reaction vessel. Nitrogen bubbling was then 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 the reaction mixture was cooled to room temperature, the solvent was removed by reduced pressure distillation. The resulting residue was dissolved in chloroform and purified by dialysis using a dialysis membrane (Spectrum Laboratories, Spectra / Por7 MWCO 1kDa). After removing the solvent by reduced pressure distillation, polymer compound 1-a, a copolymer of MPC and EHMA, was obtained by drying under reduced pressure at 50°C and 0.1 kPa or less.

[0109] 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 MPCs were present in 12 mol% of the total monomer units.

[0110] [Preparation of polymer compound b] Polymer compound b was prepared in the same manner as the preparation of 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 were present in 19 mol% of the total monomer units.

[0111] Table 1 shows the composition ratio and weight-average molecular weight (Mw) of polymer compounds a to b manufactured as described above.

[0112]

[0113] [Preparation of Polymer Compound Solution] (Preparation of Toluene Solution of Polymer Compound a) One part of polymer compound a and 99 parts of toluene were charged into a reaction vessel equipped with a stirrer, thermometer, and reflux condenser, 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.

[0114] (Preparation of 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.

[0115] [Preparation of Nanoparticle Dispersion] (Preparation of Nanoparticle a Dispersion) 10 parts cesium carbonate, 27 parts oleic acid, and 388 parts 1-octadecene were placed in a flask, the liquid temperature was heated to 120°C, and the mixture was 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.

[0116] Separately, 10 parts of lead(II) bromide and 493 parts of 1-octadecene were placed in a flask, heated to 120°C, and 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.

[0117] 40 parts of cation stock solution were added to the entire amount of 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 obtained residue was dispersed in hexane and analyzed by XRD. The resulting particles had a perovskite-type crystalline structure, and the composition was CsPb(Br ０．４ I ０．６ ) ３ Furthermore, analysis of the perovskite-type nanoparticles by weight at temperatures above 400°C using TG-DTA revealed that 60% of the total solid content consisted of perovskite-type nanoparticles. The perovskite-type nanoparticles were dispersed in hexane to obtain a nanoparticle a dispersion, with the amount of perovskite-type nanoparticles being 1% by weight.

[0118] (Preparation of nanoparticle b dispersion) 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. Analysis by XRD revealed that the obtained particles had a perovskite-type crystalline structure and a composition of CsPb(Br ０．４ I ０．６ ) ３ Furthermore, analysis of the perovskite-type nanoparticles by weight at temperatures above 400°C using TG-DTA revealed that 61% of the total solid content consisted of perovskite-type nanoparticles. The perovskite-type nanoparticles were dispersed in hexane to obtain a nanoparticle b dispersion, with the amount of perovskite-type nanoparticles being 1% by weight.

[0119] (Preparation of nanoparticle dispersion c) A hexane dispersion of nanoparticles was obtained in the same manner as in the preparation of nanoparticle dispersion a, except that 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 a composition of CsPb(Br ０．４ I ０．６ ) ３ Furthermore, analysis of the perovskite-type nanoparticles by weight at temperatures above 400°C using TG-DTA revealed that 60% of the total solid content consisted of perovskite-type nanoparticles. The perovskite-type nanoparticles were dispersed in hexane to obtain a nanoparticle dispersion c, with the amount of perovskite-type nanoparticles being 1% by weight.

[0120] (Production of nanoparticle d dispersion) In the production of the nanoparticle dispersion a, a hexane dispersion of nanoparticles was obtained in the same manner as in the production of the nanoparticle dispersion a, except that 2000 parts of ethyl acetate was added instead of 35 parts of ethyl acetate. When analyzed by XRD, the obtained particles had a perovskite-type crystal structure, and the composition was CsPb(Br ０．４２ I ０．５８ ). ３ Also, when the weight at 400 °C or higher was analyzed as perovskite-type nanoparticles by TG-DTA, 63% of the total solid content was perovskite-type nanoparticles. The nanoparticles were dispersed in hexane so that the amount of perovskite-type nanoparticles was 1% by weight, and a nanoparticle d dispersion was obtained.

[0121] (Production of nanoparticle e dispersion) In the production of the nanoparticle dispersion a, a hexane dispersion of nanoparticles was obtained in the same manner as in the production of the nanoparticle dispersion a, except that 2000 parts of ethyl acetate was added instead of 35 parts of ethyl acetate, and centrifugation was started 15 minutes later instead of starting centrifugation after 5 minutes. When analyzed by XRD, the obtained particles had a perovskite-type crystal structure, and the composition was CsPb(Br ０．４３ I ０．５７ ). ３ Also, when the weight at 400 °C or higher was analyzed as perovskite-type nanoparticles by TG-DTA, 60% of the total solid content was perovskite-type nanoparticles. The nanoparticles were dispersed in hexane so that the amount of perovskite-type nanoparticles was 1% by weight, and a nanoparticle e dispersion was obtained.

[0122]

[0123] [Preparation of photo-responsive material] (Example 1) 529 parts of the nanoparticle a dispersion was placed in a container, and the solvent was distilled off under reduced pressure. 50 parts of a toluene solution of the polymer compound a was added thereto, and it was heated at 60 °C for 5 minutes to obtain a photo-responsive material 1.

[0124] (Example 2) A photo-responsive material 2 was obtained in the same manner as the photo-responsive material 1, except that 50 parts of the toluene solution was changed to 150 parts of the toluene solution.

[0125] (Example 3) A 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.

[0126] (Example 4) A 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.

[0127] (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.

[0128] (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.

[0129] (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.

[0130] (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.

[0131] (Comparative Example 1) A photoresponsive material 9 was obtained in the same manner as photoresponsive material 3, except that a nanoparticle e dispersion was used instead of a nanoparticle a dispersion.

[0132] (Comparative Example 2) A photoresponsive material 10 was obtained in the same manner as photoresponsive material 3, except that 250 parts of toluene solution were not added.

[0133] 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.

[0134]

[0135] [Preparation of Titanium Dioxide Dispersion] 40 parts of titanium dioxide JR-403 (manufactured by Teika), 1 part of Ajisper PB821 (manufactured by Ajinomoto® Fine Techno), 60 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 4 hours to obtain a titanium dioxide dispersion.

[0136] [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).

[0137] (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.

[0138] (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.

[0139] (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.

[0140] (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.

[0141] (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.

[0142] (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.

[0143] (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.

[0144] (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.

[0145] (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.

[0146] 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.

[0147]

[0148] The abbreviations in Table 4 are as follows: 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.)

[0149] <Measurement of the ratio of free I and Br> Ink compositions 1 to 10 were centrifuged (15,000 rpm, 60 minutes), and the supernatant was separated. Using the obtained supernatant, a liquid film was prepared on a glass substrate (3 cm x 3 cm), and a cured film with a thickness of 1 mm was formed by curing with a 365 nm wavelength LED lamp. 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. Apparatus: wavelength-dispersive X-ray fluorescence analyzer (Rigaku, ZSX100e) Measurement conditions: tube target Rh (rhodium), tube voltage 30 kV, tube current 120 mA Measurement mode: EZscan, measured elements: B - U Spectroscopy crystal: LiF1

[0150] <Measurement of the ratio of I and Br coordinated to nanoparticles> 10 parts of ink compositions 1 - 10 were centrifuged (15000 rpm, 60 minutes), and the supernatant was removed. 95 parts of TMCHA and 5 parts of Omnirad TPO were added to the obtained residue and redispersed. A liquid film was formed on a glass substrate (3 cm × 3 cm) and cured using an LED lamp with a wavelength of 365 nm to form a cured film with a thickness of 1 mm. Wavelength-dispersive XRF was measured to quantify the concentrations of coordinated I and Br, and the molar ratio of non-free iodine contained in perovskite-type nanocrystals R2 = [I]coordinate / ([Br]coordinate + [I]coordinate) was calculated. Here, [X]coordinate (X = I, Br) represents the concentration of X coordinated to the nanoparticles.

[0151] The results are shown in Table 5.

[0152]

[0153] [Manufacture of wavelength conversion layer] Spin coating was performed on a glass substrate (10 cm × 10 cm) using the obtained ink compositions 1 - 10. For each glass substrate on which the spin-coated ink compositions 1 - 10 were formed, using a belt conveyor type ultraviolet irradiator (high-pressure mercury lamp 120 W / cm2 lamp), ultraviolet light was irradiated so that the integrated light quantity was 400 mJ / cm ２ to form a cured film with a thickness of 10 μm on the glass substrate. Thereafter, a barrier film was laminated on the surface of the cured film to obtain wavelength conversion layers 1 - 10.

[0154] <Evaluation of wavelength conversion layers 1 - 10> The obtained wavelength conversion layers 1 - 10 were evaluated as follows. The results are shown in Table 6.

[0155] [Light resistance evaluation] For each of the wavelength conversion layers 1 - 10, at a wavelength of 450 nm and an intensity of 100,000 cd / m ２The emission peak wavelength, total halfwidth, and absolute emission quantum yield (PLQY) were measured after 16 hours of irradiation with blue light.

[0156] <Measurement Conditions> Measurement device: Absolute PL quantum yield analyzer C9920-03 (Hamamatsu Photonics) Excitation light wavelength: 460 nm Excitation light integration range: Excitation light wavelength ± 10 nm Emission integration range: (Excitation light wavelength + 20) nm to 770 nm

[0157] The evaluation criteria are as follows.

[0158] <Evaluation Criteria> The following criteria were used for evaluation: A: PLQY value of 80% or higher after 16 hours of blue light irradiation B: PLQY value of 70% or higher but less than 80% after 16 hours of blue light irradiation C: PLQY value of 60% or higher but less than 70% after 16 hours of blue light irradiation D: PLQY value of less than 60% after 16 hours of blue light irradiation

[0159]

[0160] According to Table 6, the wavelength conversion layer according to this embodiment has a long emission peak wavelength, exhibits a narrow full width at half maximum, and has high PLQY both immediately after fabrication and after irradiation with B light. This is thought to be because, in the ink composition according to this embodiment, the shell-shaped ligand having a betaine group is effectively coordinated to the perovskite-type nanoparticles containing iodine at the X site. As in Example 16, when a large amount of ethyl acetate is used for purification and centrifugation is started after 5 minutes, the emission peak wavelength becomes slightly shorter and the PLQY becomes slightly lower. As in Comparative Example 3, when a large amount of ethyl acetate is used for purification and centrifugation is started after 15 minutes, the emission peak wavelength becomes shorter and the PLQY becomes lower. As in Comparative Example 4, when no shell-shaped ligand is used, the PLQY after irradiation with B light becomes very low.

[0161] The present invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are attached to make the scope of the invention public.

[0162] This application claims priority based on Japanese Patent Application No. 2024-208063, filed on November 29, 2024, and all of its contents are incorporated herein by reference.

[0163] 10 Nanoparticles 20 Shell-shaped ligands 100 Photoresponsive material

Claims

1. A photoresponsive material comprising: nanoparticles having a perovskite-type crystalline structure containing iodine at the X-site; and a shell-like ligand having a betaine group and at least a portion of which is coordinated 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.

2. A photoresponsive material comprising nanoparticles having a perovskite-type crystalline structure containing iodine at the X site, and a shell-like ligand having a betaine group and at least a portion of which is coordinated to the nanoparticles, wherein the molar ratio of iodine freed from the nanoparticles is higher than the molar ratio of non-free iodine contained in the nanoparticles.

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 nanoparticles contain 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. The photoresponsive material according to claim 1, satisfying 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, which satisfies 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 includes a photopolymerizable compound that undergoes a polymerization reaction upon irradiation with light, and the polymerization initiator includes 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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