Photon upconversion composition, film, and method for converting to ultraviolet B or ultraviolet C rays.

Abstract

To provide a photon upconversion composition that can convert to ultraviolet B or ultraviolet C rays. [Solution] A compound represented by the following general formula is used. Z is Si or C; R 1 ~R 3 is an alkyl or aryl group; R 4 ~R 8 represents an aliphatic hydrocarbon group bonded by H, D, or sp2 or sp3 carbon atoms. JPEG2026045940000020.jpg31170

Description

[Technical Field]

[0001] The present invention relates to a photon upconversion composition useful as a source of ultraviolet light, a film using the photon upconversion composition, and a method for irradiating the photon upconversion composition with visible light or ultraviolet A light to convert it into ultraviolet B light or ultraviolet C light. [Background technology]

[0002] Photon upconversion is a technology that converts low-energy light into high-energy light, and it is attracting attention as an energy creation technology that can improve the efficiency of solar energy utilization devices, including solar cells and photocatalysts. One known material system in which photon upconversion occurs is a photon upconversion composition that combines a donor, which functions as a sensitizer, and an acceptor, which functions as a light emitter. In this composition, when the donor is excited to an excited singlet state by irradiation with excitation light, it undergoes intersystem crossing to an excited triplet state, and its triplet energy is transferred to the acceptor. In the acceptor, which has become an excited triplet state after receiving the energy, the triplet states of two molecules meet, causing triplet-triplet annihilation, and one of the molecules transitions to an excited singlet state with higher energy than the excited triplet state and emits light (photon upconversion emission). In this composition, the photon upconversion mechanism by triplet-triplet annihilation can convert the irradiated light into light with higher energy (light with a shorter wavelength). Short-wavelength light includes ultraviolet light in the ultraviolet region, such as ultraviolet A (315-400 nm), ultraviolet B (280-315 nm), and ultraviolet C (200-280 nm or less). As a photon upconversion composition that converts to ultraviolet light, a composition containing iridium complex [Ir(C6)(acac)] and bis(triisopropylsilylethynyl)naphthalene has been reported to convert visible light at 445 nm to ultraviolet A at 370 nm or less (see Non-Patent Literature 1). In addition, a composition containing organic delayed fluorescence material (4CzIPN) and bis(triisopropylsilylethynyl)benzene has been reported to convert visible light at 447 nm to ultraviolet B at 309 nm (see Non-Patent Literature 2). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] N. Harada et al., Angew. Chem. Int. Ed. 2021, 60, 142 [Non-Patent Document 2] TJB Zahringer et al., Angew. Chem. Int. Ed. 2023, 62, e202215340 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, photon upconversion compositions that convert light into the ultraviolet region shorter than 309 nm have not yet been developed. Furthermore, general methods or solutions for converting to higher-energy ultraviolet B rays have not yet been provided. In light of these circumstances, the present inventors have diligently conducted research with the aim of providing a photon upconversion composition that converts light into high-energy ultraviolet B and ultraviolet C waves. [Means for solving the problem]

[0005] As a result of intensive studies, the present inventors have found that the problems can be solved by using a compound having a specific structure. The present invention has been proposed based on such findings and specifically has the following configurations.

[0006] [1] A photon upconversion composition containing a compound represented by the following general formula (1). [[ID=�]]General formula (1) [Chemical formula] [In general formula (1), Z represents Si or C, and R 3 , , 3 , 8 , 8 , 3 , 8 , , , , 4 , 1 , 1 , 4 , , <00000^01>, , , 4 , , ~R 3 each independently represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group. R 4 ~R 8 each independently represents a hydrogen atom, a deuterium atom, or an aliphatic hydrocarbon group bonded by an sp2 carbon atom or an sp3 carbon atom.] [2] The photon upconversion composition according to [1], wherein Z is Si. [3] The photon upconversion composition according to [1] or [2], wherein R 1 ~R 3 are each independently a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, or a phenyl group. [4] The photon upconversion composition according to any one of [1] to [3], wherein R 1 ~R 3 are the same group. [5] The photon upconversion composition according to any one of [1] to [4], wherein 1 to 4 of R [[ID=^39]] 4 ~R 8 are each independently an aliphatic hydrocarbon group bonded by an sp2 carbon atom or an sp3 carbon atom. [6] The photon upconversion composition according to any one of [1] to [5], wherein at least one of R 4 ~R 8 is an aliphatic hydrocarbon group having 3 or more carbon atoms bonded by an sp2 carbon atom or an sp3 carbon atom. [7] R 6 A photon upconversion composition according to any one of [1] to [6], wherein the group is an aliphatic hydrocarbon group bonded by sp2 carbon atoms or sp3 carbon atoms. [8] A photon upconversion composition according to any one of [1] to [7], comprising a sensitizer. [9] The photon upconversion composition according to any one of [1] to [8], wherein the sensitizer is a compound represented by the following general formula (2). General formula (2) [ka] [In general formula (2), R 11 ~R 13 Each of these independently represents a hydrogen atom, a deuterium atom, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted amino group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted arylthio group, a substituted phosphinone group, a substituted thiophosphinone group, a substituted phosphinyl group, or a substituted thiophosphinyl group.

[10] The photon upconversion composition according to any one of [1] to [8], wherein the sensitizer is a compound represented by the following general formula (3). General formula (3) [ka] [In general formula (3), R 21 ~R 34 Each of these independently represents a hydrogen atom, a deuterium atom, or a substituted or unsubstituted alkyl group.

[11] A film comprising the photon upconversion composition described in any one of items [1] to

[10] .

[12] Fine particles comprising the photon upconversion composition described in any one of items [1] to

[10] .

[13] A method of irradiating a photon upconversion composition described in any one of items [1] to

[10] with visible light or ultraviolet A to convert it to ultraviolet B or ultraviolet C. [Effects of the Invention]

[0007] According to the present invention, visible light or ultraviolet A rays can be converted to ultraviolet B rays or ultraviolet C rays. [Brief explanation of the drawing]

[0008] [Figure 1] This figure illustrates the UC emission mechanism of the photon upconversion composition of the present invention. [Figure 2] This is the UC emission spectrum obtained when a cyclohexane solution (composition 1) containing compound tBCzP2PO and compound B1 was irradiated with 375 nm excitation light. [Figure 3] This is the UC emission spectrum obtained when a cyclohexane solution (composition 2) containing the compounds tBCzP2PO and B5 was irradiated with 375 nm excitation light. [Modes for carrying out the invention]

[0009] The present invention will be described in detail below. The following descriptions of constituent elements may be based on representative embodiments and specific examples, but the present invention is not limited to such embodiments. In this specification, numerical ranges expressed using "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits. Furthermore, the isotopes of hydrogen atoms present in the molecule of the compound used in the present invention are not particularly limited; for example, all hydrogen atoms in the molecule 1 H is fine, or part or all of it 2 H (Deuterium D) is also acceptable.

[0010] <Photon Upconversion Composition> In this invention, "photon upconversion composition" means a composition that exhibits the ability to convert light irradiated onto the composition (irradiated light) into light of a shorter wavelength. The source light to be converted into "light of a shorter wavelength" is preferably visible light or ultraviolet A light. The destination "light of a shorter wavelength" is preferably ultraviolet B light or ultraviolet C light, and may be light spanning both of these regions. In this specification, "visible light" means light with a wavelength in the range of over 400 nm and up to 800 nm. The ultraviolet light included in the source light and the destination light may be a single light or a composite light including multiple lights with different emission maximum wavelengths. Furthermore, the source light may include visible light and non-visible light, and the destination light may include ultraviolet light and non-ultraviolet light. In this specification, the conversion of irradiated light (excitation light) into shorter wavelength light and subsequent emission by the photon upconversion composition is referred to as "photon upconversion emission" or "UC emission," the light emitted by photon upconversion emission (light with a shorter wavelength than the irradiated light) is referred to as "UC light," and the efficiency of converting irradiated light into UC light is referred to as "upconversion efficiency" or "UC efficiency." Furthermore, "the photon upconversion composition of the present invention" may simply be referred to as "the composition of the present invention."

[0011] (Compounds represented by general formula (1)) The photon upconversion composition of the present invention comprises a compound represented by general formula (1). General formula (1) [ka]

[0012] In general formula (1), Z represents Si or C. In one aspect of the present invention, a compound in which Z is Si is selected. In another aspect of the present invention, a compound in which Z is C is selected.

[0013] R in general formula (1) 1 ~R 3Each of these independently represents a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. 1 ~R 3 They may all be the same or they may all be different. Also, R 1 ~R 3 Two of them may be the same and one may be different. In one preferred embodiment of the present invention, R 1 ~R 3 All of them are identical and represent substituted or unsubstituted alkyl groups. For example, R 1 ~R 3 All of these may be the same and may be an unsubstituted alkyl group having 1 to 6 carbon atoms, for example, a tert-butyl group or an isopropyl group. A triisopropylsilyl group can be preferably exemplified as a group bonded to the carbon atoms constituting the acetylene structure of general formula (1).

[0014] R in general formula (1) 4 ~R 8 Each of these independently represents an aliphatic hydrocarbon group bonded by a hydrogen atom, a deuterium atom, or an sp2 or sp3 carbon atom. An example of an aliphatic hydrocarbon group bonded by an sp2 carbon atom is an α-alkenyl group that does not contain any atoms other than hydrogen, deuterium, or carbon. An example of an aliphatic hydrocarbon group bonded by an sp3 carbon atom is an alkyl group that does not contain any atoms other than hydrogen, deuterium, or carbon. The α-alkenyl group and alkyl group referred to here may also have a cyclic structure. For example, they may be cycloalkyl groups or α-cycloalkenyl groups. In a preferred embodiment of the present invention, R 4 ~R 8 The aliphatic hydrocarbon group that can be adopted is an alkyl group, more preferably an alkyl group having 1 to 6 carbon atoms, such as a methyl group, an ethyl group, an isopropyl group, or a tert-butyl group. 4 ~R 8 The number of aliphatic hydrocarbon groups among them may be any of 0 to 5, for example, it may be 0, 1, or any of 2 to 5.

[0015] The following are specific examples of compounds represented by general formula (1). However, the compounds represented by general formula (1) that can be used in the present invention are not limited to the following specific examples. [ka]

[0016] (Mechanism of photon upconversion) The photon upconversion composition of the present invention may contain only one compound represented by general formula (1), or it may contain two or more compounds represented by general formula (1). Furthermore, the photon upconversion composition of the present invention may contain the compound represented by general formula (1) and components other than the compound represented by general formula (1) (hereinafter referred to as "other components"). Examples of other components include donor compounds that provide energy obtained by absorbing excitation light to the compound represented by general formula (1). In the following description, when the photon upconversion composition contains a donor compound, the compound of general formula (1) contained in the composition is referred to as the "acceptor compound". In a photon upconversion composition containing a donor compound and an acceptor compound, it is hypothesized that photon upconversion luminescence occurs via triplet-triplet annihilation through a mechanism such as that shown in Figure 1. The mechanism of this UC luminescence is explained below. Here, the acceptor compound is at its lowest excited singlet energy level S 1,A The lowest excited triplet energy level S of the donor compound 1,D Higher than its lowest excited triplet energy level T 1,A The lowest excited triplet energy level T of the donor compound 1,D The value should be lower than [value]. Furthermore, the excitation light for the donor compound was used as the irradiation light for the composition. In Figure 1, "ISC" indicates intersystem crossing, "TET" indicates triplet energy transfer from the donor compound to the acceptor compound, and "TTA" indicates triplet-triplet annihilation. First, when excitation light is shone onto a photon upconversion composition containing a donor compound and an acceptor compound, as shown in Figure 1, the molecules of the donor compound (donor molecules) absorb the light and enter an excited singlet state (S 1,D After being excited to ), intersystem crossing occurs and an excited triplet state (T 1,D The donor molecule transitions to the excited triplet state (T). The energy of the donor molecule, now in the excited triplet state, is transferred to the acceptor compound molecule (acceptor molecule). This results in the excited triplet state (T). 1,A In the acceptor compound that has reached this state, the triplet states of the two molecules meet, causing triplet-triplet annihilation, and one of the molecules enters an excited singlet state (S 1,A The state transitions to (S). That is, photon upconversion occurs due to triplet-triplet annihilation of the acceptor molecule. The acceptor molecule, now in the excited singlet state, is deactivated by emitting fluorescence (UC light), causing the composition to emit UC light. At this time, the excited singlet state (S) produced by photon upconversion due to triplet-triplet annihilation occurs. 1,A Because the energy level of ) is very high, radiative deactivation from its excited singlet state allows us to obtain UC light with higher energy (shorter wavelength) than the excitation light.

[0017] The donor compound preferably satisfies at least one of the following conditions (A) and (B), and more preferably satisfies both of the following conditions (A) and (B). (A) High absorbance. (B) The absorbance is low in the ultraviolet region, at least in the region that overlaps with the wavelength region of UC light. Compounds that satisfy conditions (A) and (B) can efficiently absorb the irradiated light but do not absorb UC light. Therefore, by using such compounds as donor compounds, the threshold excitation intensity I of the composition can be increased. th This allows for a lower threshold excitation intensity and a higher UC efficiency. th " is the excitation light intensity at the inflection point of a log-log graph showing the dependence of UC emission intensity on excitation light intensity, and corresponds to the excitation light intensity required to maximize UC efficiency. This threshold excitation intensity I thA lower value means that a higher UC efficiency can be obtained with a lower excitation light intensity. In condition (A), "high absorbance" means that the absorption coefficient is 50,000 M. -1 m -1 This means that it is more than that. In condition (B), "low absorbance" means that the absorption coefficient is 40,000 M. -1 cm -1 This means the following:

[0018] The compound represented by general formula (1) is the lowest excited singlet energy level S of the donor compound. 1,D The lowest excitation singlet energy level S is higher than 1,A It possesses the lowest excited triplet energy level T of the donor compound. 1,D Lower than the lowest excited triplet energy level T 1,A It is preferable to have such a compound. It is preferable to select a donor compound that satisfies such conditions and use it in combination with a compound represented by general formula (1) (acceptor compound). The acceptor compound molecule that satisfies these conditions is the lowest excited singlet energy level S of the donor compound. 1,D The lowest excitation singlet energy level S is higher than 1,A By possessing this property, it is possible to emit UC light with a shorter wavelength than the excitation light of the donor compound. Furthermore, molecules of acceptor compounds that satisfy these conditions can reach the lowest excitation triplet energy level T of the donor compound. 1,D Lower than the lowest excited triplet energy level T 1,A By possessing this feature, the excitation triplet energy from the donor compound can be easily received. This allows the UC emission mechanism shown in Figure 1 to function more reliably. Lowest excited singlet energy level S of the acceptor compound 1,A and the lowest excited singlet energy level S of the donor compound 1,D The difference (S 1,A -S 1,D The voltage is preferably 0.3 to 2 eV, more preferably 0.4 to 1 eV, and even more preferably 0.4 to 0.8 eV. Lowest excited triplet energy level T of the donor compound 1,D and the lowest excited triplet energy level T of the acceptor compound 1,A The difference (T 1,D -T 1,A The voltage is preferably 0.01 to 1 eV, more preferably 0.01 to 0.5 eV, and even more preferably 0.01 to 0.2 eV. Lowest excited singlet energy level S 1,A S 1,D and the lowest excited triplet energy level T 1,A , T 1,D For information on the measurement methods, please refer to the section below titled (Measurement Method for Lowest Excited Singlet Energy Level S1 and Lowest Excited Triplet Energy Level T1). These energy levels can also be determined by calculations using density functional theory.

[0019] (Donor compound) The donor compound used in the photon upconversion composition of the present invention is preferably a compound represented by the following general formula (2) or the following general formula (3). General formula (2) [ka]

[0020] In general formula (2), R 11 ~R 13 Each of these independently represents a hydrogen atom, a deuterium atom, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted amino group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted arylthio group, a substituted phosphinone group, a substituted thiophosphinone group, a substituted phosphinyl group, or a substituted thiophosphinyl group.

[0021] R 11 ~R 13They may all be the same or all be different. Also, R 11 ~R 13 Two of them may be the same and one may be different. For example, R 11 is a substituted or unsubstituted aryl group, and R 12 and R 13 may be substituted amino groups (the two substituents may be bonded to each other to form a cyclic structure). R 11 ~R 13 may all be groups containing a cyclic structure. R 11 ~R 13 Some of them may be aromatic groups and the rest may be non-aromatic groups. R 11 ~R 13 may all be groups containing heteroatoms. As an example of a preferred compound, R 11 is a 4-methoxyphenyl group, and R 12 and R 13 are piperidino groups.

[0022] Hereinafter, specific examples of atoms or groups that R 11 ~R 13 can take are given. However, the atoms or groups that can be adopted in the present invention are not to be construed as being limited by the following specific examples.

[0023]

Chemical formula

[0024]

Chemical formula

[0025]

Chemical formula

[0026]

Chemical formula

[0027] [Chemical formula]

[0028] [Chemical formula]

[0029] General formula (3) [Chemical formula]

[0030] In general formula (3), R 21 ~R 34 each independently represents a hydrogen atom, a deuterium atom, or a substituted or unsubstituted alkyl group. As the alkyl group, for example, an unsubstituted alkyl group can be selected, and for example, an alkyl group having 1 to 6 carbon atoms can be selected. When it is substituted with a substituted or unsubstituted alkyl group, the substitution position is preferably one or more of R 22 ~R 26 , R 29 ~R 33 , for example, it may be one or more of R 22 , R 23 , R 26 , R 29 , R 30 , R 32 , R 33 , and it may also be one or both of R 23 , R 26 . As specific examples of the compound represented by general formula (3), compounds having the following structures can be exemplified. However, the compounds of general formula (3) that can be employed in the present invention should not be construed as being limited by these specific examples. [Chemical formula]

[0031] In this specification, unless otherwise specified, "alkyl group," "alkenyl group," "aryl group," "halogen atom," and "amino group" refer to atoms or substituents within the following ranges. An alkyl group may be linear, branched, or cyclic. For this reason, cycloalkyl groups are included in alkyl groups in this specification. Furthermore, an alkyl group may contain a mixture of two or more of the linear, cyclic, and branched portions. The number of carbon atoms in an alkyl group can be, for example, 1 or more, 2 or more, or 4 or more. The number of carbon atoms can also be 30 or less, 20 or less, 10 or less, 6 or less, or 4 or less. Specific examples of alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, n-pentyl group, isopentyl group, n-hexyl group, cyclopentyl group, cyclohexyl group, and cycloheptyl group. The "alkenyl group" may be linear, branched, or cyclic. Furthermore, two or more of these linear, cyclic, and branched portions may be mixed. The number of carbon atoms in the alkenyl group can be, for example, 2 or more, 4 or more, or 30 or less, 20 or less, 10 or less, 6 or less, or 4 or less. Specific examples of alkenyl groups include ethenyl, n-propenyl, isopropenyl, n-butenyl, isobutenyl, n-pentenyl, isopentenyl, n-hexenyl, isohexenyl, and 2-ethylhexenyl. The "alkynyl group" may be linear, branched, or cyclic. Furthermore, two or more of these components may be mixed. The number of carbon atoms in the alkynyl group can be, for example, 2 or more, or 4 or more. Alternatively, the number of carbon atoms can be 30 or less, 20 or less, 10 or less, 6 or less, or 4 or less. Specific examples of alkynyl groups include the ethynyl group, n-propynyl group, n-butynyl group, n-pentynyl group, and isopentynyl group. The "aryl group" may be a monoring or a fused ring formed by the fusion of two or more rings. If it is a fused ring, the number of fused rings is preferably 2 to 6, and can be selected from, for example, 2 to 4. The number of carbon atoms in the aryl group is preferably 6 to 22, more preferably 6 to 18, even more preferably 6 to 14, and even more preferably 6 to 10. Specific examples of aryl groups include the phenyl group, 1-naphthyl group, 2-naphthyl group, 1-anthracenyl group, 2-anthracenyl group, and 9-anthracenyl group. The "heteroaryl group" may be a monoring or a fused ring formed by the fusion of two or more rings. If it is a fused ring, the number of fused rings is preferably 2 to 6, and can be selected from, for example, 2 to 4. The number of constituent atoms of the ring skeleton of the heteroaryl group is preferably 5 to 22, more preferably 5 to 18, even more preferably 5 to 14, and even more preferably 5 to 10. Specific examples of heteroaryl groups include pyridyl, furyl, thiophenyl, pyrrolyl, oxazolyl, thioxazolyl, and carbazole-9-yl groups. For the alkyl portion of "alkoxy group" and "alkylthio group," please refer to the description of alkyl groups above. For the aryl portion of "aryloxy group" and "arylthio group," please refer to the description of aryl groups above. The "substituted phosphino group," "substituted thiophosphino group," "substituted phosphinyl group," and "substituted thiophosphinyl group" are preferably substituted with two substituents, and examples of substituents include alkyl groups and aryl groups, with aryl groups which may be substituted with alkyl groups being preferred. The "substituted amino group" may be a secondary amino group or a tertiary amino group, but a tertiary amino group is preferred. The substituent of the substituted amino group is preferably an alkyl group, an aryl group, or a heteroaryl group, and more preferably an alkyl group or an aryl group. Examples of substituted amino groups include dialkylamino groups, diarylamino groups, monoalkylamino groups, monoarylamino groups, piperidino groups, pyrrolidino groups, piperazino groups, and morpholino groups. Here, alkyl groups are preferably those with 1 to 20 carbon atoms, and more preferably those with 1 to 10 carbon atoms. Aryl groups are preferably those with 6 to 20 carbon atoms, and more preferably those with 6 to 10 carbon atoms. At least one hydrogen atom of the above-mentioned "alkyl group," "alkenyl group," "alkynyl group," "aryl group," "heteroaryl group," "alkoxy group," "aryloxy group," "alkylthio group," and "arylthio group" may be substituted with a substituent. Examples of substituents include alkyl groups, aryl groups, alkoxy groups, aryloxy groups, halogen atoms (e.g., fluorine atom, chlorine atom, bromine atom), and groups combining these.

[0032] (Measurement method for the lowest excited singlet energy level S1 and the lowest excited triplet energy level T1) The lowest excited singlet energy level S1 of the compound used in this invention is obtained by measuring the fluorescence spectrum of the compound in solution and converting the wavelength of the shortest wavelength fluorescence peak to an energy value using the following conversion formula. The lowest excited triplet energy level T1 of the compound used in this invention is obtained by measuring the phosphorescence spectrum of the compound in solution and converting the wavelength of the phosphorescence peak to an energy value using the following conversion formula. The solvent used to prepare the compound in solution should be one that can dissolve the compound (e.g., tetrahydrofuran). The concentration of the solution should be such that spectral measurement is possible (e.g., 100 μM). The emission spectrum can be measured using a xenon lamp as the excitation light source and a JASCO FP-8300 from JASCO Corporation. Conversion formula: S1[eV]=1239.85 / λ F Conversion formula: T1[eV]=1239.85 / λ P In the above equation, λ F λ is the fluorescence peak wavelength [nm], P This is the phosphorescent light peak wavelength [nm].

[0033] (Ratio of donor compound to acceptor compound) When a photon upconversion composition contains a donor compound and an acceptor compound (a compound represented by general formula (1)), the molar ratio of the donor compound to the acceptor compound [(moles of donor compound / moles of acceptor compound) × 100] is preferably 0.01 to 20%, more preferably 0.1 to 10%, and even more preferably 1 to 5%. When the absorbance of the donor compound at the emission wavelength of the acceptor compound is small, the concentration of the donor compound can be increased to allow for greater absorption of excitation light.

[0034] (Other ingredients) The photon upconversion composition of the present invention may further contain other components. Examples of other components include solvents that dissolve donor compounds and acceptor compounds (compounds represented by general formula (1)), matrix materials such as polymers that maintain these compounds dispersed in a solid, and additives such as surfactants. The solvent and polymer can be appropriately selected from known ones. For example, solvents include dimethylformamide, tetrahydrofuran, chloroform, toluene, benzene, and mixtures thereof. Polymers include polystyrene, poly(alkyl methacrylate), poly(alkyl acrylate), poly(N-alkylacrylamide), polyvinyl alcohol, and bioplastics. Bioplastics contain substances derived from renewable organic resources as raw materials and can be appropriately selected from those synthesized chemically or biologically. For example, cellulose and proteins can be used, and it is particularly preferable to use biodegradable biopolymers. In the present invention, two or more of these polymers may be mixed and used. The polymer may have a glass transition temperature of room temperature (25°C) or higher, or a glass transition temperature of less than room temperature. When a polymer with a glass transition temperature of room temperature or higher is used as the matrix material, the film exhibits rigid properties, making molecular diffusion difficult, and energy transfer between compound molecules occurs mainly by energy diffusion. Furthermore, when a polymer with a glass transition temperature below room temperature is used as the matrix material, the film exhibits a soft property, and energy transfer by molecular diffusion can also occur. The glass transition temperature of a polymer can be measured using a differential scanning calorimeter. The method for dispersing donor compounds and acceptor compounds in the polymer is not particularly limited; for example, they may be dispersed by dissolving and mixing them in a common solvent, or the donor compounds and acceptor compounds may be dissolved in a non-volatile solvent, and the resulting solution may be dispersed in the polymer. The non-volatile solvent can be any non-volatile liquid that dissolves the compound well, such as a surfactant (e.g., Triton R X-100) and low molecular weight organic solvents (e.g., hexadecane) can be appropriately selected and used. When the photon upconversion composition contains a solvent, the proportion of the compound represented by general formula (1) to the total amount of the composition is preferably 0.00005 to 0.5% by weight, more preferably 0.00005 to 0.05% by weight, and even more preferably 0.0005 to 0.03% by weight. When the photon upconversion composition contains a polymer, the proportion of the compound represented by general formula (1) to the total amount of the composition is preferably 0.001 to 1% by weight, more preferably 0.01 to 1% by weight, and even more preferably 0.1 to 0.5% by weight.

[0035] (Usefulness of photon upconversion compositions) The photon upconversion composition of the present invention is preferably free of heavy metals. In this invention, "heavy metals" in "heavy metal-free" refers to heavy metals with a specific gravity of 4 g / cm³. 3 This refers to the metals mentioned above. "Heavy metal-free" means that the compound is substantially free of heavy metals in any form, whether as constituent elements or as elemental heavy metals, and does not exclude the presence of heavy metals as unavoidable impurities. Here, "substantially free of heavy metals" means that the heavy metal content in the composition is 0.1 ppm or less. The photon upconversion composition of the present invention exhibits high UC efficiency at low excitation light intensity even without containing heavy metals. Therefore, the photon upconversion composition of the present invention has the characteristics of having a low environmental impact and being easy to use industrially due to the stable supply of raw materials. At the same time, the photon upconversion composition of the present invention can efficiently convert irradiated light such as visible light and ultraviolet A waves into ultraviolet B waves and ultraviolet C waves and emit light at practical levels of excitation light intensity. Therefore, the photon upconversion composition of the present invention can be effectively used as a source of ultraviolet light in various situations where ultraviolet light is utilized. For example, by applying a film of the photon upconversion composition of the present invention to a transparent body such as transparent glass or a transparent resin board and exposing it to sunlight, ultraviolet light can be obtained inexpensively. When this ultraviolet light is used to activate a photocatalyst, the photocatalyst can be made to work energy-efficiently, and the efficiency of artificial photosynthesis and other processes utilizing the photocatalyst can be increased. For example, it can greatly contribute to improving the fuel efficiency of fuel cell vehicles that produce hydrogen from water and sunlight by acting on a photocatalyst and then use that hydrogen to generate electricity in a fuel cell. The transparent body to which the film is applied only needs to be an object that can transmit at least a portion of the UC light (preferably 10% or more, more preferably 50% or more, even more preferably 90% or more, and particularly preferably 99% or more), and it is sufficient if it can transmit at least a portion of the UC light in the wavelength range that is particularly to be utilized. When applying the film to a transparent body, it may be directly attached to the surface of the transparent body, laminated on the surface of the transparent body, or stacked on the surface of the transparent body in a removable manner. It may also be sandwiched between two transparent bodies. Furthermore, by selecting a lens with a light-gathering function as the transparent body, the UC light can be focused to a specific spot by applying the film, thereby achieving even more efficient use of energy. Ordinary glass transmits visible light and ultraviolet A rays, but not ultraviolet B rays or ultraviolet C rays. Therefore, by irradiating the photon upconversion composition of the present invention, which is placed in a glass container, with visible light and ultraviolet A rays from outside the glass container, the converted ultraviolet B rays and ultraviolet C rays can be trapped inside the glass container. As a result, the converted ultraviolet B rays and ultraviolet C rays can be utilized in an energy-efficient manner. For example, they can be used to advance chemical reactions (bond activation, Diels-Alder reaction).

[0036] <film> Next, the film of the present invention will be described. The film of the present invention contains the photon upconversion composition of the present invention. For a description of the photon upconversion composition of the present invention, please refer to the description in the <Photon Upconversion Composition> section above. Embodiments of the present invention include a film formed from a photon upconversion composition and a film formed from a photon upconversion composition in layers on a substrate. In the latter embodiment, the film may consist only of the layered photon upconversion composition, or it may consist of the layered photon upconversion composition and a substrate. The method for forming the photon upconversion composition into a film is not particularly limited, and known film forming methods such as calendering, extrusion, and inflation molding can be used. The method for forming the layered photon upconversion composition is also not particularly limited, and either a dry process or a wet process may be used. The substrate is also not particularly limited, and for example, materials such as glass, transparent plastic, quartz, and silicon can be used. The photon upconversion composition used for the film is preferably one that contains a compound represented by general formula (1) and a polymer, or a compound represented by general formula (1) (acceptor compound), a donor compound, and a polymer, because it facilitates molding and film formation and allows control of the film's mechanical properties. The polymer used in the composition can be appropriately selected from known film polymers, such as polystyrene, poly(alkyl acrylate), poly(alkyl methacrylate), poly(N-alkylacrylamide), epoxy resin, and polyvinyl alcohol. Furthermore, when using a hydrophilic polymer such as polyvinyl alcohol, it is preferable to add a surfactant to the composition to improve the dispersibility of the compound. The film of the photon upconversion composition may be a single-layer or multi-layer structure. When the film is multi-layer, it is preferable that at least adjacent layers have different compositions from each other.

[0037] Furthermore, another embodiment of the film of the present invention is an impregnated film in which a liquid material of a compound represented by general formula (1) is impregnated into a porous film. The liquid material can be a solution in which the compound represented by general formula (1) is dissolved, a solution in which the compound represented by general formula (1) (acceptor compound) and a donor compound are dissolved, a melt obtained by heating and melting the compound represented by general formula (1), or a melt obtained by heating a mixture of the compound represented by general formula (1) and a donor compound. The melt obtained by heating the mixture may be a mixture in which a solid acceptor compound is dispersed in the melt of the donor compound, or both the acceptor compound and the donor compound may be in a melted state. Of these, the film impregnated with the solution is preferred because it is easier to obtain a stable product. As the porous film, an organic porous film in which an organic filler is dispersed in a matrix polymer can be used, and commercially available products such as microporous film (manufactured by 3M) can be used. In addition, PTFE membrane film (manufactured by Tokyo Glass Instruments Co., Ltd.), polyethylene porous sheet (manufactured by Flon Chemical Co., Ltd.), etc. can also be used. In one aspect of the present invention, a polyolefin film, preferably a polypropylene film, can be used as the porous film. In one aspect of the present invention, a porous film with a pore size of 0.3 μm or less, preferably 0.2 μm or less, and more preferably 0.1 μm or less can be used. In one aspect of the present invention, a porous film with a moisture permeability of 10,000 g / m² 2 Films with a permeability of 24 hours or more, or with an air permeability of 200 seconds / 100 ml or more, can be used. In one aspect of the present invention, a porous film can be used that absorbs and retains organic liquids internally, but does not allow water to pass through.

[0038] The thickness of the film of the present invention is preferably 10 nm to 1 cm, more preferably 100 nm to 500 μm, and even more preferably 1 μm to 100 μm. If the layers of the photon upconversion composition are multilayered, their total thickness shall be within the above thickness range.

[0039] Furthermore, the film of the present invention may consist only of a film containing the photon upconversion composition of the present invention, or it may have other layers or films. An example of other films is an oxygen barrier film. When an oxygen barrier film is used, it is preferable to cover and seal the entire film containing the photon upconversion composition with the oxygen barrier film. The oxygen barrier film can be a polyvinyl alcohol film or a film of a copolymer of vinyl alcohol and other monomers, and for example, an ethylene-vinyl alcohol copolymer film can be preferably used. Another example of other layers is a layer having a microlens array. By forming a layer having a microlens array on a film containing the photon upconversion composition of the present invention and irradiating it with excitation light through the layer having the microlens array, the photon upconversion luminescence efficiency can be improved. The lens diameter, pitch, and arrangement of the microlens array can be adjusted to improve the photon upconversion luminescence efficiency. The lens diameter that determines the curvature of each lens in the arrangement can be selected, for example, from a range of 10 μm or more, 50 μm or more, 100 μm or more, or from a range of 200 μm or less, 160 μm or less, or 130 μm or less.

[0040] <Methods for converting to ultraviolet B or ultraviolet C rays> Next, we will explain a method of converting visible light or ultraviolet A rays into ultraviolet B rays or ultraviolet C rays. The conversion method of the present invention involves irradiating the photon upconversion composition or film of the present invention with visible light or ultraviolet A light to convert it into ultraviolet B light or ultraviolet C light. For a description of the photon upconversion composition of the present invention and definitions of visible light and ultraviolet light, please refer to the description in the <Photon Upconversion Composition> section above, and for a description of the film of the present invention, please refer to the description in the <Film> section above. To convert visible light or ultraviolet A to ultraviolet B or ultraviolet C using the method of the present invention, first, the photon upconversion composition or film of the present invention is irradiated with visible light or ultraviolet A. The visible light or ultraviolet A to be irradiated may be a single light having a maximum emission wavelength at a specific wavelength in the visible to ultraviolet A region, a composite light composed of multiple lights with different maximum emission wavelengths, a composite light composed of lights with continuous wavelengths in the visible region, or a composite light composed of lights with continuous wavelengths in the ultraviolet A region. In addition, the light irradiated onto the composition may include other types of light besides visible light and ultraviolet A. Examples of irradiation sources include sunlight, LEDs, Xe lamps, and lasers. The irradiation intensity is 0.1 to 1000 mW / cm². 2 Preferably, the value is 0.5 to 100 mW / cm². 2 It is more preferable that the power is 1-50 mW / cm². 2 It is even more preferable that this is the case. The irradiation time is not particularly limited; for example, it should be 1 minute or more. In the method of the present invention, irradiation with visible light or ultraviolet A waves causes the photon upconversion composition or film of the present invention to emit ultraviolet B or ultraviolet C waves as unintended emission light. This emission only needs to be observed in the ultraviolet B or ultraviolet C wave region. Here, "observed in the ultraviolet B or ultraviolet C wave region of ultraviolet light" means that the emission maximum wavelength of the ultraviolet light is within the range of ultraviolet B or ultraviolet C waves, or the emission maximum wavelength is near ultraviolet B or ultraviolet C waves, and an emission intensity of 50% or more of the intensity at that emission maximum wavelength is observed in the ultraviolet B or ultraviolet C wave region. [Examples]

[0041] The features of the present invention will be further described in detail below with reference to examples and comparative examples. The materials, amounts used, proportions, processing content, processing procedures, etc., shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following specific examples. In the following examples, a spectrophotometer (JASCO: V-670) was used to measure the absorption spectrum, and a spectrofluorometer (JASCO: FP-8300) was used to measure the emission spectrum. A multichannel spectrometer (Otsuka Electronics: MCPD-9800) was used to measure the emission spectrum.

[0042] [Donor and acceptor compounds used in the examples] The donor and acceptor compounds used in this example are shown below. Donor compounds [ka]

[0043] Acceptor compound [ka]

[0044] The donor compound tBCzP2PO exhibited absorption in the ultraviolet A region, with an emission maximum wavelength of 384 nm. The lowest excitation triplet energy was 3.3 eV. The lowest excited singlet energies of the acceptor compounds were 14.59 eV for compound B and 4.43 eV for compound B5, both of which were high values.

[0045] (Example 1) Preparation and evaluation of a photon upconversion composition containing compound tBCzP2PO and compound B1 A solution (composition 1) was prepared by dissolving compound tBCzP2PO and compound B1 in cyclohexane in a glove box under an Ar atmosphere. Here, the concentration of compound tBCzP2PO was 300 μM and the concentration of compound B1 was 5 mM. The prepared composition 1 was irradiated with 375 nm excitation light, and the UC emission spectrum was measured in an Ar atmosphere with a 350 nm long-wavelength cut-off filter placed between the sample and the spectrometer. The results are shown in Figure 2. For composition 1, UV emission was observed in the ultraviolet B region.

[0046] (Example 2) Preparation and evaluation of a photon upconversion composition containing compound tBCzP2PO and compound B5 A cyclohexane solution of compound tBCzP2PO and compound B5 (Composition 2) was prepared in the same manner as in Example 1, except that compound B5 was used instead of compound B1. The UC emission spectrum was measured after irradiation with excitation light. The results are shown in Figure 3. UV emission was also observed in the ultraviolet B region for Composition 2. [Industrial applicability]

[0047] The photon upconversion composition of the present invention can convert visible light or ultraviolet A to ultraviolet B or ultraviolet C. Because it enables upconversion to short-wavelength regions that were previously impossible to convert, the present invention has high industrial applicability.

Claims

1. A photon upconversion composition comprising a compound represented by the following general formula (1). General formula (1) 【Chemistry 1】 [In general formula (1), Z represents Si or C, and R １ ~R ３ Each of these independently represents a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. ４ ~R ８ Each of these independently represents an aliphatic hydrocarbon group bonded by a hydrogen atom, a deuterium atom, or an sp2 or sp3 carbon atom.

2. The photon upconversion composition according to claim 1, wherein Z is Si.

3. R １ ~R ３ The photon upconversion composition according to claim 1, wherein each of them is independently a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, or a phenyl group.

4. R １ ~R ３ The photon upconversion composition according to claim 1, wherein the two groups are the same.

5. R ４ to R ８ The photon upconversion composition according to claim 1, wherein 1 to 4 of them are each independently an aliphatic hydrocarbon group bonded by an sp2 carbon atom or an sp3 carbon atom.

6. R ４ ~R ８ The photon upconversion composition according to claim 1, wherein at least one of them is an aliphatic hydrocarbon group having 3 or more carbon atoms bonded by an sp2 carbon atom or an sp3 carbon atom.

7. R ６ The photon upconversion composition according to claim 1, wherein is an aliphatic hydrocarbon group bonded by sp2 carbon atoms or sp3 carbon atoms.

8. A photon upconversion composition according to claim 1, comprising a sensitizer.

9. The photon upconversion composition according to claim 1, wherein the sensitizer is a compound represented by the following general formula (2). General formula (2) 【Chemistry 2】 [In general formula (2), R １１ ~R １３ Each of these independently represents a hydrogen atom, a deuterium atom, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted amino group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted arylthio group, a substituted phosphinone group, a substituted thiophosphinone group, a substituted phosphinyl group, or a substituted thiophosphinyl group.

10. The photon upconversion composition according to claim 1, wherein the sensitizer is a compound represented by the following general formula (3). General formula (3) 【Transformation 3】 [In general formula (3), R ２１ ~R ３４ Each of these independently represents a hydrogen atom, a deuterium atom, or a substituted or unsubstituted alkyl group.

11. A film comprising the photon upconversion composition according to any one of claims 1 to 10.

12. Fine particles comprising the photon upconversion composition according to any one of claims 1 to 10.

13. A method for converting a photon upconversion composition according to any one of claims 1 to 10 into ultraviolet B or ultraviolet C by irradiating it with visible light or ultraviolet A waves.

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