JP6692014B2 - Optical wavelength conversion element containing ionic liquid and article containing the optical wavelength conversion element - Google Patents

Description

  The present invention relates to a light wavelength conversion element containing an ionic liquid and an article (a solar cell, a photocatalyst, a photocatalytic hydrogen / oxygen generator, and a light upconversion filter) including the light wavelength conversion element.

  While there is a strong need for alternative energies such as global warming countermeasures and clean energy, there is an urgent need to develop technology to convert sunlight into secondary energy (electric power, hydrogen, etc.) with high efficiency. Expectations for light-secondary energy conversion elements (elements that convert light to secondary energy) such as solar cells and hydrogen-producing photocatalysts that have high light-secondary energy conversion efficiency (light-to-secondary energy conversion efficiency) Is increasing. A light-secondary energy conversion element such as a general solar cell or a hydrogen-generating photocatalyst has a threshold wavelength unique to the light-secondary energy conversion element among light in a wide wavelength range included in sunlight. Only the short wavelength components are used for conversion, and the components with wavelengths longer than the threshold wavelength are unused. Therefore, as one of the technologies to effectively use light in a wide wavelength range included in sunlight, optical up-conversion (that is, by absorbing light with a long wavelength and emitting light with a shorter wavelength, Is being considered).

  Research on optical upconversion using multiphoton absorption of rare earth elements as a means of optical upconversion has a history of over 50 years. However, in the case of multiphoton absorption of rare earth elements, a very high incident light intensity is generally required, and it has been difficult to target weak light such as sunlight as a conversion target.

  Recently, an organic molecule capable of optical up-conversion by absorbing and emitting light was announced.

  Patent Document 1 discloses that in a composition that up-converts photon energy, at least a phthalocyanine, a metal porphyrin, a first component that functions as a photoconductor such as a metal phthalocyanine and absorbs energy in a first wavelength range, and polyfluorene. , Oligofluorene and copolymers thereof, and a second component that functions as a light emitter such as polyparaphenylene and emits energy in the second wavelength range.

  Non-Patent Document 1 describes an optical up-converter using relatively weak light such as sunlight in a toluene solvent utilizing a triplet-triplet annihilation process (hereinafter referred to as "TTA process") in an organic molecule. Has been done.

  There is also a precedent case in which a high molecular weight organic polymer is used as a medium of organic molecules contained in an optical upconverter (Non-Patent Documents 2 and 3).

  Patent Document 2 discloses a system containing at least one polymer and at least one sensitizer containing at least one heavy atom for photo-upconversion, and a triplet energy of the sensitizer. Systems are described whose levels are higher than the triplet energy level of the polymer.

  Non-Patent Document 2 describes an optical up-converter using a polymer of cellulose acetate (molecular weight: about 100,000) as a dispersion medium of organic molecules.

  Non-Patent Document 3 describes an optical up-converter using a soft rubber-like polymer as a medium at room temperature having a glass transition temperature (Tg) of 236K (minus 37 ° C).

  Non-Patent Document 4 describes an optical up-converter using a styrene oligomer (a mixture of styrene trimer and tetramer) as a medium for organic photosensitizing molecules and organic light emitting molecules.

  Non-Patent Document 5 describes metal porphyrins as organic photosensitizing molecules that can be used for light upconversion using the TTA process, and diphenylanthracene, 9,10-bis (phenylethynyl) as organic light emitting molecules. ) Anthracene and 9,10-bis (phenylethynyl) naphthacene are described, and toluene is described as the medium for the organic photosensitizing and organic light emitting molecules.

  In Non-patent Document 6, a boron dipyrromethene (BODIPY) derivative is used as a sensitizer for photo-upconversion using the TTA process, and perylene or 1-chloro-9,10-bis (phenylethynyl) anthracene is used as a medium. It is described that toluene is used as.

  In the optical up-converter using the TTA process, in principle, it is necessary for organic molecules to diffuse energy / collide with each other in order to exchange energy with each other in a medium. Therefore, most of the prior art (Non-Patent Document 1). In 4/5/6), a medium having a high volatility such as a volatile organic solvent such as toluene or benzene or a styrene oligomer was used as a medium. However, highly volatile media such as volatile organic solvents and styrene oligomers have a safety problem due to their flammability, and they also prevent the use of resin materials that dissolve in the media or swell due to the penetration of the media. The problem is that it cannot be used as a container for wavelength conversion elements.

  In addition, in the optical up-converter (Patent Document 2 and Non-Patent Documents 2 and 3) using the TTA process in which a polymer compound such as cellulose acetate or flexible rubber is used as a medium, the polymer compound is flammable. In addition, since it is solid at room temperature (300K) and has low fluidity, there is a problem that the intensity of up-converted light remarkably decreases at room temperature (300K) or lower. In Non-Patent Document 3, optical up-conversion by the TTA process is caused by the fact that the organic molecules responsible for triplet excitation energy inside the medium need to perform diffusion motion / mutual collision and exchange energy between the organic molecules. In the temperature range where the temperature is relatively high and the polymer has sufficient fluidity (> 300K), the upconversion emission intensity increases, but in the temperature range where the temperature is low and the fluidity of the medium is poor (≦ 300K), the upconversion emission intensity is high. Is said to be very weak.

  As a method for solving these problems, the present inventors have proposed a light wavelength conversion element obtained by dissolving and / or dispersing an organic photosensitizing molecule and an organic light emitting molecule in an ionic liquid in a photo upconversion using a TTA process. Therefore, the conventional problems such as the decrease in the intensity of up-conversion light due to the high viscosity of the medium, the flammability of the medium, and the volatility of the medium have been solved (Patent Document 3).

  However, there is a demand for a light wavelength conversion element having a higher light wavelength conversion efficiency (upconversion quantum efficiency) that can be applied to light with a weak intensity of sunlight. There is also a demand for a light wavelength conversion element having good stability over time.

Japanese Patent No. 4518313 Japanese Patent Publication No. 2008-506798 International Publication No. 2012/050137

S. Baluschev, et al. , Physical Review Letters, vol. 97, p. 143903-1 to 143903-3, 2006 A. Monguzzi, et al. , Journal of Physical Chemistry A, vol. 113, p. 1171-1174, 2009 Tanya N.M. Singh-Rachford, et al. , Journal of the American Chemical Society, vol. 131, p. 12007-12014, 2009 T. Miteva, et al. , New Journal of Physics, vol. 10, p. 103002-1 to 10302-10, 2008. S. Baluschev, et al. , New Journal of Physics, vol. 10, p. 013007-1 to 013007-12,2008 W. Wu, et al. , J. Org. Chem. , 2011, 76, p. 7056-7064

  The present invention has been made in view of the above problems, and an object thereof is to have high light wavelength conversion efficiency applicable to weak light such as sunlight intensity and also to have good stability over time, and therefore the sun. A light wavelength conversion element suitable for use in a battery, a photocatalyst, a photocatalyst type hydrogen / oxygen generator, an optical up-conversion filter, and the like, and an article including the light wavelength conversion element (solar cell, photocatalyst, photocatalyst type hydrogen / oxygen generator). , And an optical up-conversion filter).

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a combination of an organic photosensitizing molecule (A) and an organic light emitting molecule (B) showing a TTA process is dissolved in an ionic liquid (C) and It was found that the object can be achieved by using a specific ionic liquid (C) as the ionic liquid (C) in a visually transparent and homogeneous light wavelength conversion element that is / or is dispersed, and completes the present invention. Came to.

  That is, in order to solve the above-mentioned problems, the light wavelength conversion element of the present invention comprises a combination of an organic photosensitizing molecule (A) and an organic light emitting molecule (B) which shows a TTA process in an ionic liquid (C). A visually and homogeneously transparent light wavelength conversion element obtained by dissolving and / or dispersing, wherein the ionic liquid (C) is washed with ultrapure water in a volume 9 times that of the ionic liquid (C). At times, the pH of the water after washing (water separated from the ionic liquid after washing) becomes greater than 5.

  According to the above configuration, when the ionic liquid (C) is washed with ultrapure water having a volume 9 times that of the ionic liquid (C), the pH of the water after washing becomes higher than 5. Therefore, it has a high light wavelength conversion efficiency that can be applied to light with a weak intensity of sunlight, and also has good stability over time. The reason for this is considered as follows. That is, an ionic liquid (for example, some commercially available ionic liquids) having a pH of water after washing of 5 or less when washed with ultrapure water having a volume 9 times that of impurities does not contain impurities including acidic impurities. Since it is contained in a relatively large amount, it is inferior in stability over time, and it is considered that some impurities contained in the ionic liquid cause a decrease in light wavelength conversion efficiency of the light wavelength conversion element. On the other hand, the ionic liquid (C) which is used in the present invention and has a pH of water after washing of more than 5 when washed with 9 times the volume of ultrapure water contains acidic impurities. It is considered that since the content of the impurities is low, the stability with time is good, and the deterioration of the light wavelength conversion efficiency of the light wavelength conversion element due to some impurities contained in the ionic liquid is reduced. Since the light wavelength conversion element of the present invention is based on the TTA process and has a high light wavelength conversion efficiency, it can be applied to light having a weak intensity of sunlight, such as a solar cell, a photocatalyst, and a photocatalyst type. It is suitable for use in hydrogen / oxygen generators, optical up-conversion filters, etc.

  Further, according to the above configuration, conventionally used, flammable and highly volatile organic solvent such as toluene and benzene, and a rubber-like polymer that is flammable and has poor fluidity and a very high viscosity, It is practically safe because it uses an ionic liquid that generally has extremely low vapor pressure, relatively high fluidity, flame retardancy, etc. In addition, the organic photosensitizing molecule (A) and the organic light emitting molecule (B) are sufficiently dissolved and / or dispersed in the ionic liquid (C) to obtain the organic photosensitizing molecule (A) and the organic light emitting molecule ( The TTA process due to the diffusion motion / mutual collision of B) can be sufficiently advanced.

  In the present application documents, “ultra pure water” means water having an electrical resistivity of 15 MΩ · cm or more measured by the measuring method of JIS K 0552. Further, in the present application documents, "visually homogeneous and transparent" means that no two or more layers are visually separated from each other, and to the extent that it can be visually confirmed, it has no solid and is homogeneous, It also means that it is transparent with no turbidity or cloudiness. In addition, in the present application document, “dissolution and / or dispersion” means that either one of dissolution and dispersion is performed, or that dissolution and dispersion are performed at the same time.

  The solar cell of the present invention is characterized by using the light wavelength conversion element. According to the above configuration, since the light wavelength conversion element having a high light wavelength conversion efficiency that can be applied to light having a weak intensity of sunlight is used, a solar cell having a high photoelectric conversion efficiency can be realized.

  Further, the photocatalyst of the present invention is characterized by using the light wavelength conversion element. According to the above configuration, since the light wavelength conversion element having a high light wavelength conversion efficiency applicable to light having a weak intensity of sunlight is used, a photocatalyst having high catalyst efficiency can be realized.

  The photocatalytic hydrogen / oxygen generator of the present invention is characterized by using the light wavelength conversion element. According to the above configuration, since the light wavelength conversion element having a high light wavelength conversion efficiency that can be applied to light with a weak intensity of sunlight is used, a photocatalytic hydrogen / oxygen generator with high hydrogen / oxygen generation efficiency is realized. it can.

  Further, the optical up-conversion filter of the present invention is an optical up-conversion filter that converts light into light of a shorter wavelength, comprising the light wavelength conversion element and a cell serving as a sealing / holding shell thereof, and The wavelength conversion element is characterized in that it is enclosed in the cell.

  According to the above configuration, since the light wavelength conversion element having a high light wavelength conversion efficiency applicable to light having a weak intensity of sunlight is used, an optical up-conversion filter having a high light wavelength conversion efficiency can be realized.

  According to the present invention, a light wavelength conversion element having a high light wavelength conversion efficiency applicable to light as weak as sunlight intensity and having good temporal stability, and an article including the light wavelength conversion element (solar cell, A photocatalyst, a photocatalytic hydrogen / oxygen generator, and an optical up-conversion filter) can be provided.

It is sectional drawing which shows the solar cell which concerns on an example of implementation of this invention. It is sectional drawing which shows the photocatalyst which concerns on an example of implementation of this invention. 5 is a diagram showing an up-conversion emission spectrum of the light wavelength conversion element obtained in Example 1. FIG. 5 is a diagram showing a light absorption spectrum of the light wavelength conversion element obtained in Example 1. FIG. It is a figure which shows the up-conversion emission spectrum of the light wavelength conversion element obtained in Example 2 and Comparative Example 2. 5 is a diagram showing a light absorption spectrum of the light wavelength conversion element obtained in Example 2. FIG. 9 is a diagram showing a light absorption spectrum of a light wavelength conversion element obtained in Comparative Example 2. FIG. It is a figure which shows the standardized up-conversion light emission intensity (peak intensity and integrated intensity) of the light wavelength conversion element of Example 2 and Comparative Example 2. 5 is a diagram showing a light absorption spectrum of a light wavelength conversion element obtained in Example 3. FIG. 5 is a diagram showing an up-conversion emission spectrum of the light wavelength conversion element obtained in Example 3. FIG. 7 is a diagram showing a light absorption spectrum of the light wavelength conversion element obtained in Example 4. FIG. 5 is a diagram showing an up-conversion emission spectrum of the light wavelength conversion element obtained in Example 4. FIG. 9 is a graph showing the relationship between the normalized up-conversion emission intensity of the light wavelength conversion element obtained in Example 5 and the viscosity of the ionic liquid (C) used in the light wavelength conversion element. It is a graph which expanded a part of graph of FIG. FIG. 13 is a diagram showing a light absorption spectrum of a light wavelength conversion element obtained using Ionic Liquid # 14 in Example 5. FIG. 8 is a diagram showing an up-conversion emission spectrum of the light wavelength conversion element obtained using Ionic Liquid # 14 in Example 5. 9 is a diagram showing a light absorption spectrum of a light wavelength conversion element obtained in Example 6. FIG. 7 is a diagram showing an upconversion emission spectrum of the light wavelength conversion element obtained in Example 6. FIG. 9 is a graph showing the relationship between the normalized up-conversion emission intensity of the light wavelength conversion element obtained in Example 7 and the viscosity of the ionic liquid (C) used in the light wavelength conversion element.

  Hereinafter, the present invention will be described in more detail.

  The light wavelength conversion element of the present invention is obtained by dissolving and / or dispersing an organic photosensitizing molecule (A) and an organic light emitting molecule (B), which are combinations showing a TTA process, in an ionic liquid (C). A highly uniform and transparent light wavelength conversion element, wherein when the ionic liquid (C) is washed with ultrapure water having a volume 9 times that of the ionic liquid (C), the pH of the water after washing is It is greater than 5.

  The organic photosensitizing molecule (A) and the organic light emitting molecule (B) can be used without limitation as long as the combination shows the TTA process (emits light based on the TTA process). The absorption wavelength of the organic photosensitizing molecule (A) and the emission wavelength of the organic luminescent molecule (B) can be selected from within the wavelength range of sunlight without limitation. For example, in the light wavelength conversion element of the aspect that up-converts light in the visible to near infrared region, a π-conjugated molecule having a light absorption band in the visible to near infrared region is used as the organic photosensitizing molecule (A). A π-conjugated molecule having an emission band in the visible to near-infrared region can be used as the organic light-emitting molecule (B). As the organic photosensitizing molecule (A) and the organic light emitting molecule (B), aromatic π-electron conjugated compounds, particularly polycyclic aromatic π-electron conjugated compounds, and the like are described in Non-Patent Document 5, for example. Low molecular weight and high molecular weight compounds can be widely used, including existing compounds.

  The organic photosensitizing molecule (A) can be used without limitation as long as it has an absorption maximum wavelength in the wavelength range of sunlight, but usually has an absorption maximum wavelength in the range of 200 to 1000 nm. Are used, and those having an absorption maximum wavelength in the range of 500 to 700 nm are preferably used. As a result, light having a relatively long wavelength, which is not used in a light-secondary energy conversion element such as a general solar cell or a hydrogen generating photocatalyst, is converted into a light having a relatively short wavelength used in a general light-secondary energy conversion element. Light of a wide wavelength range contained in sunlight can be effectively used by the light-secondary energy conversion element.

  As the organic photosensitizing molecule (A), any molecular species that has not been called a dye can be used as long as it has light absorption in the range from the ultraviolet region to the infrared region. Examples of the organic photosensitizing molecule (A) include acenaphthene derivative, acetophenone derivative, anthracene derivative, diphenylacetylene derivative, acridan derivative, acridine derivative, acridone derivative, thioacridone derivative, angelicin derivative, anthracene derivative, anthraquinone derivative, azafluorene. Derivatives, azulene derivatives, benzyl derivatives, carbazole derivatives, coronene derivatives, sumanene derivatives, biphenylene derivatives, fluorene derivatives, perylene derivatives, phenanthrene derivatives, phenanthroline derivatives, phenazine derivatives, benzophenone derivatives, pyrene derivatives, benzoquinone derivatives, biacetyl derivatives, bianthranyl derivatives , Fullerene derivative, graphene derivative, carotene derivative, chlorophyll derivative, chloride Derivative, cinnoline derivative, coumarin derivative, curcumin derivative, dansylamide derivative, flavone derivative, fluorenone derivative, fluorescein derivative, helicene derivative, indene derivative, lumichrome derivative, lumiflavin derivative, oxadiazole derivative, oxazole derivative, periflanthene derivative, perylene derivative , Phenanthrene derivative, phenanthroline derivative, phenazine derivative, phenol derivative, phenothiazine derivative, phenoxazine derivative, phthalazine derivative, phthalocyanine derivative, picene derivative, porphyrin derivative, porphycene derivative, hemiporphycene derivative, subphthalocyanine derivative, psoralen derivative, angelicin derivative, purine Derivatives, pyrene derivatives, pyrromethene derivatives, pyridyl ketone derivatives Body, phenyl ketone derivative, pyridyl ketone derivative, thienyl ketone derivative, furanyl ketone derivative, quinazoline derivative, quinoline derivative, quinoxaline derivative, retinal derivative, retinol derivative, rhodamine derivative, riboflavin derivative, rubrene derivative, squalin derivative, stilbene derivative, tetracene derivative, Pentacene derivative, anthraquinone derivative, tetracenequinone derivative, pentacenequinone derivative, thiophosgene derivative, indigo derivative, thioinzogo derivative, thioxanthene derivative, thymine derivative, triphenylene derivative, triphenylmethane derivative, triaryl derivative, tryptophan derivative, uracil derivative, xanthene derivative , Ferrocene derivatives, azulene derivatives, biacetyl derivatives, terphenyl derivatives, Examples include, but are not limited to, terfuran derivatives, terthiophene derivatives, oligoaryl derivatives, fullerene derivatives, conjugated polyene derivatives, group 14 element-containing condensed polycyclic aromatic compound derivatives, condensed polycyclic heteroaromatic compound derivatives, and the like. is not.

Specific examples of the organic photosensitizer molecule (A) include metal porphyrins (metal complexes of porphyrins); metal tetraazaporphyrins; metal phthalocyanines; iodine derivatives of 3,5-dimethyl-boron dipyrromethene. Boron dipyrromethenes such as iodine derivatives of 3,5-dimethyl-8-phenylboron dipyrromethene; Schiff base metal complexes such as salen metal complexes; metals such as rubidium-bipyridine complexes and iridium-phenanthroline complexes Examples include, but are not limited to, bipyridine complex; metal phenanthroline complex; naphthalenediimides such as N-alkylnaphthalenediimide; acridones such as N-methylacridone. As the metal atom contained in the metalloporphyrins and metal phthalocyanines, Pt, Pd, Ru, Rh, Ir, Zn, Cu or the like can be used. Examples of the metal tetraazaporphyrins include metal tetraazaporphyrins having a structure in which carbon atoms at the 5,10,15,20 positions and R ⁸ bonded thereto in the general formula (5) described below are replaced with nitrogen atoms. ..

  As an example of a compound preferable as the organic photosensitizing molecule (A), a compound having an absorption maximum wavelength in the range of 500 to 700 nm is represented by the following general formula (5).

(In the formula, each R ⁷ represents an arbitrary substituent containing a hydrogen atom, R ⁷ may be the same or different, and any two R ⁷ adjacent to each other may be linked to each other to contain a hydrogen atom. Group may have a 5-membered ring or a 6-membered ring, R ⁸ represents an aryl group having an arbitrary substituent containing a hydrogen atom, R ⁸ may be the same or different, and M is Represents a metal atom)
The compound represented by Here, the "arbitrary substituent containing a hydrogen atom" means a hydrogen atom or an arbitrary substituent excluding a hydrogen atom.

Examples of R ^{7 in} the general formula (5) include a hydrogen atom, an alkyl group (for example, an alkyl group having 1 to 12 carbon atoms), an alkenyl group, an alkynyl group, a halogen atom, a hydroxy group (hydroxyl group), an alkylcarbonyloxy. Group, arylcarbonyloxy group, alkoxycarbonyloxy group, aryloxycarbonyloxy group, carboxylate, alkylcarbonyl group, arylcarbonyl group, alkoxycarbonyl group, aminocarbonyl group, alkylaminocarbonyl group, dialkylaminocarbonyl group, alkylthiocarbonyl group Group, alkoxyl group, phosphate group, phosphonate group, phosphinate group, cyano group, amino group (including alkylamino group, dialkylamino group, arylamino group, diarylamino group, and alkylarylamino group), Silamino group (including alkylcarbonylamino group, arylcarbonylamino group, carbamoyl group, and ureido group), amidino group, imino group, sulfhydryl group, alkylthio group, arylthio group, thiocarboxylic acid group, sulfate group, alkylsulfinyl group, Examples thereof include, but are not limited to, a sulfonate group, a sulfamoyl group, a sulfonamide group, a nitro group, a trifluoromethyl group, a cyano group, an azido group, a heterocycle, an alkylaryl group, or an aryl group or a heteroaryl group. Examples of the substituent which the 5-membered ring or the 6-membered ring formed by connecting two mutually adjacent R ⁷ 's, which may be contained in the general formula (5), with each other have been given as examples of R ⁷ . Substituents may be included, but are not limited to. The 5-membered ring or the 6-membered ring may be linked to another porphyrin ring which may have a substituent. Examples of R ^{8 in} the general formula (5) include, but are not limited to, the substituents mentioned as examples of R ⁷ . Examples of the metal atom contained in the metalloporphyrins and metal phthalocyanines include Pt, Pd, Ru, Rh, Ir, Zn and Cu as the metal atom M in the general formula (5).

  Examples of the metalloporphyrin represented by the general formula (5) include meso-tetraphenyl-tetrabenzoporphyrin metal complex such as meso-tetraphenyl-tetrabenzoporphyrin palladium (CAS number: 119644-64-7), Octaethylporphyrin metal complex such as octaethylporphyrin palladium (CAS number: 24804-00-0) and octa such as meso-tetraphenyl-octamethoxy-tetranaphtho [2,3] porphyrin palladium described in Non-Patent Document 5. An ethylporphyrin metal complex etc. are mentioned. Among these, meso-tetraphenyl-tetrabenzoporphyrin palladium and other meso-tetraphenyl-tetrabenzoporphyrin metal complexes, and octaethylporphyrin palladium and other octaethylporphyrin metal complexes are preferable.

  The organic photosensitizing molecule (A) is more preferably an organic photosensitizing molecule having a structure containing no metal in its structure. As a result, it is possible to avoid the occurrence of environmental pollution due to metal at the time of manufacturing or discarding the light wavelength conversion element.

  Specific examples of the organic photosensitizing molecule having a structure containing no metal include the following general formula (1)

(In the above formula, R ^{1 to} R ⁵ each independently represent an arbitrary substituent containing a hydrogen atom, and adjacent substituents (a pair of R ¹ and R ² , a pair of R ² and R ⁴ , a R ^{2 1} and R ³ pair, R ³ and R ⁴ pair) may be linked to each other to form a 5-membered ring or 6-membered ring having an optional substituent containing a hydrogen atom, and R ⁶ is Represents a halogen atom, an alkyl group having 1 to 5 carbon atoms which may have a substituent, or an alkoxyl group having 1 to 5 carbon atoms which may have a substituent)
Examples thereof include compounds (borondipyrromethenes), C _{70 and the} like.

Examples of R ^{1 to} R ^{5 in} the general formula (1) include hydrogen atom, alkyl group, alkenyl group, alkynyl group, halogen atom, hydroxy group (hydroxyl group), alkylcarbonyloxy group, arylcarbonyloxy group, alkoxy. Carbonyloxy group, aryloxycarbonyloxy group, carboxylate, alkylcarbonyl group, arylcarbonyl group, alkoxycarbonyl group, aminocarbonyl group, alkylaminocarbonyl group, dialkylaminocarbonyl group, alkylthiocarbonyl group, alkoxyl group, phosphate group , Phosphonate groups, phosphinate groups, cyano groups, amino groups (including alkylamino groups, dialkylamino groups, arylamino groups, diarylamino groups, and alkylarylamino groups), acylamino groups (alkylcarbo groups). (Including amino groups, arylcarbonylamino groups, carbamoyl groups, and ureido groups), amidino groups, imino groups, sulfhydryl groups, alkylthio groups, arylthio groups, thiocarboxylic acid groups, sulfate groups, alkylsulfinyl groups, sulfonate groups, sulfamoyl groups. Groups, sulfonamide groups, nitro groups, trifluoromethyl groups, cyano groups, azido groups, heterocycles, alkylaryl groups, or aryl groups or heteroaryl groups, but are not limited thereto. Substituents which may be contained in the general formula (1) and are adjacent to each other (a pair of R ¹ and R ² , a pair of R ² and R ⁴ , a pair of R ¹ and R ³ , a pair of R ³ and R ⁴⁾ Examples of the substituent which the 5-membered ring or the 6-membered ring formed by connecting (a pair with) with each other include the substituents described as examples of R ^{1 to} R ⁵ , but not limited thereto.

R ¹ and R ⁴ in the general formula (1) are each a hydrogen atom, a halogen atom, an aliphatic hydrocarbon group having 1 to 4 carbon atoms which may have a substituent, or a phenyl which may have a substituent. Group, a phenoxy group which may have a substituent, a thienyl group which may have a substituent, a thienoxy group which may have a substituent, the following formula (2)

A 2-carboxyl ethenyl group represented by, or the following formula (3)

It is preferably a 2-carboxyl-2-cyanoethenyl group represented by, more preferably an alkyl group having 1 to 3 carbon atoms which may have a substituent, and an unsubstituted C 1 to 3 carbon group. An alkyl group is more preferable, and an unsubstituted methyl group is most preferable.

R ² and R ³ in the general formula (1) are each a hydrogen atom, a halogen atom, an aliphatic hydrocarbon group having 1 to 4 carbon atoms which may have a substituent, or phenyl which may have a substituent. Group, a phenoxy group which may have a substituent, a thienyl group which may have a substituent, a thienoxy group which may have a substituent, a 2-carboxyl ethenyl group represented by the above formula (2) Or a 2-carboxyl-2-cyanoethenyl group represented by the above formula (3), which is a hydrogen atom, a bromine atom, or an iodine atom (provided that at least one of R ² and R ³ is a bromine atom or It is more preferably an iodine atom), and further preferably a hydrogen atom or an iodine atom (provided that at least one of R ² and R ³ is an iodine atom).

R ⁵ in the general formula (1) represents a hydrogen atom, a halogen atom, an aliphatic hydrocarbon group having 1 to 4 carbon atoms which may have a substituent, a phenyl group which may have a substituent, a substituent A phenoxy group which may have a group, a thienyl group which may have a substituent, a thienoxy group which may have a substituent, a 2-carboxyl ethenyl group represented by the formula (2), or the above It is preferably a 2-carboxyl-2-cyanoethenyl group represented by formula (3), more preferably a phenyl group which may have a substituent, and an unsubstituted or alkyl-substituted phenyl group. Is more preferable.

R ⁶ in the general formula (1) is a halogen atom, an alkyl group having 1 to 5 carbon atoms which may have a substituent, or an alkoxyl group having 1 to 5 carbon atoms which may have a substituent. However, it is preferably a fluorine atom.

The organic photosensitizing molecule (A) is preferably a metal porphyrin represented by the general formula (5) or a compound represented by the general formula (1), and in the general formula (1), The compound represented by the formula (1) is more preferable, and in the compound represented by the formula (1), R ^{1 to} R ⁵ in the formula (1) each independently represent a hydrogen atom, a halogen atom or a substituent. An aliphatic hydrocarbon group having 1 to 4 carbon atoms which may have, a phenyl group which may have a substituent, a phenoxy group which may have a substituent, a thienyl group which may have a substituent, A compound which is a thienoxy group which may have a substituent, a 2-carboxylethenyl group represented by the above formula (2), or a 2-carboxyl-2-cyanoethenyl group represented by the above formula (3). More preferably, the following general formula (4)

(In the formula, R ¹ and R ⁴ each independently represent an alkyl group having 1 to 3 carbon atoms which may have a substituent, and R ² and R ³ are each independently hydrogen atom, bromine atom, or iodine. Represents an atom, at least one of R ² and R ³ is a bromine atom or an iodine atom, and R ⁵ represents a phenyl group which may have a substituent)
Most preferably, it is a compound represented by As a result, a light wavelength conversion element having a higher light wavelength conversion efficiency can be realized.

  As the compound represented by the general formula (1), specifically, the following formula

A compound represented by (2-iodo-1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene) (absorption maximum wavelength 510 nm), the following formula

A compound represented by (2,6-diiodo-1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene) (absorption maximum wavelength 529 nm), the following formula

A compound (absorption maximum wavelength 629 nm) represented by the following formula

Compound represented by (absorption maximum wavelength 539 nm), the following formula

A compound (absorption maximum wavelength 557 nm) represented by the following formula

A compound represented by (absorption maximum wavelength 576 nm), the following formula

A compound represented by (absorption maximum wavelengths of 575 nm and 618 nm), the following formula

A compound represented by (absorption maximum wavelength 532 nm), the following formula

And a compound (absorption maximum wavelength 526 nm) represented by These organic photosensitizing molecules (A) may be used alone or in combination of two or more.

  The organic light emitting molecule (B) is not particularly limited as long as it is an organic compound that can emit light up-converted by the TTA process when used together with the organic photosensitizing molecule (A). Can be used. Examples of the organic light-emitting molecule (B) include acenaphthene derivatives, acetophenone derivatives, anthracene derivatives, diphenylacetylene derivatives, acridan derivatives, acridine derivatives, acridone derivatives, thioacridone derivatives, angelicin derivatives, anthracene derivatives, anthraquinone derivatives, azafluorene derivatives, Azulene derivative, benzyl derivative, carbazole derivative, coronene derivative, sumanene derivative, biphenylene derivative, fluorene derivative, perylene derivative, phenanthrene derivative, phenanthroline derivative, phenazine derivative, benzophenone derivative, pyrene derivative, benzoquinone derivative, biacetyl derivative, bianthranyl derivative, fullerene Derivative, graphene derivative, carotene derivative, chlorophyll derivative, chrysene Derivatives, cinnoline derivatives, coumarin derivatives, curcumin derivatives, dansylamide derivatives, flavone derivatives, fluorenone derivatives, fluorescein derivatives, helicene derivatives, indene derivatives, lumichrome derivatives, lumiflavin derivatives, oxadiazole derivatives, oxazole derivatives, periflanthene derivatives, perylene derivatives, Phenanthrene derivative, phenanthroline derivative, phenazine derivative, phenol derivative, phenothiazine derivative, phenoxazine derivative, phthalazine derivative, phthalocyanine derivative, picene derivative, porphyrin derivative, porphycene derivative, hemiporphycene derivative, subphthalocyanine derivative, psoralen derivative, angelicin derivative, purine derivative , Pyrene derivative, pyrromethene derivative, pyridyl ketone derivative , Phenyl ketone derivative, pyridyl ketone derivative, thienyl ketone derivative, furanyl ketone derivative, quinazoline derivative, quinoline derivative, quinoxaline derivative, retinal derivative, retinol derivative, rhodamine derivative, riboflavin derivative, rubrene derivative, squalin derivative, stilbene derivative, tetracene derivative, pentacene Derivatives, anthraquinone derivatives, tetracenequinone derivatives, pentacenequinone derivatives, thiophosgene derivatives, indigo derivatives, thioinzogo derivatives, thioxanthene derivatives, thymine derivatives, triphenylene derivatives, triphenylmethane derivatives, triaryl derivatives, tryptophan derivatives, uracil derivatives, xanthene derivatives, Ferrocene derivative, azulene derivative, biacetyl derivative, terphenyl derivative, -Furan derivative, terthiophene derivative, oligoaryl derivative, fullerene derivative, conjugated polyene derivative, condensed polycyclic aromatic compound derivative containing group 14 element, condensed polycyclic heteroaromatic compound derivative, etc., but not limited to these is not.

  Specific examples of the organic light-emitting molecule (B) include 9,10-diphenylanthracene (CAS number: 1499-10-1) and its derivatives, 9,10-bis (phenylethynyl) anthracene (CAS number). : 10075-85-1) and its derivatives (for example, 1-chloro-9,10-bis (phenylethynyl) anthracene), perylene (CAS number: 198-55-0) and its derivatives (for example, perylene diimide), pyrene and Its derivatives, rubrene and its derivatives, naphthalene and its derivatives (for example, naphthalene diimide, perfluoronaphthalene, 1-cyanonaphthalene, 1-methoxynaphthalene), 9,10-bis (phenylethynyl) naphthacene, 4,4′-bis ( 5-tetraacenyl) -1,1'-biphenyl Emissions, indole, benzofuran, benzothiophene, biphenyl, bifuran, bithiophene, 4,4-difluoro-4-bora -3a, 4a-diaza -s- indacene (boron dipyrromethene) or the like include, but are not limited to. The organic light-emitting molecule (B) is preferably a condensed polycyclic aromatic compound such as perylene, pyrene or anthracene or a derivative thereof. These organic light emitting molecules (B) may be used alone or in combination of two or more.

  The content of the organic photosensitizing molecule (A) and the organic light-emitting molecule (B) in the light wavelength conversion element of the present invention is not particularly limited, but when the light wavelength conversion element is 100 parts by mass, each is usually Is 0.000001 to 10 parts by mass, preferably 0.00001 to 5 parts by mass, and more preferably 0.0001 to 1 part by mass.

  The ionic liquid (C) is a room temperature molten salt composed of cations and anions (a salt in a molten state (liquid state) at room temperature (25 ° C.)). It is generally known that as an ionic liquid, there are at least 1,000,000 or more kinds of compounds depending on the combination of cations and anions. The ionic liquid (C) acts as a medium of the organic photosensitizing molecule (A) and the organic light emitting molecule (B), which are combinations showing the TTA process, and inside thereof, the organic photosensitizing molecule (A) and the organic photosensitizing molecule (A). It allows the diffusion motion of the light emitting molecule (B).

  In the light wavelength conversion element of the present invention, the organic photosensitizing molecule (A) and the organic light emitting molecule (B), which are combinations showing the TTA process, are dissolved and / or dispersed in the ionic liquid (C) and visually observed. Since it needs to be homogeneous and transparent, the ionic liquid (C) has a cation-π interaction with the organic photosensitizing molecule (A) and the organic light emitting molecule (B), and is immiscible with water. Are preferred. In the present specification, the ionic liquid (C) is “immiscible with water”, and at 25 ° C., 50% by mass or less of water may be visually homogeneously and transparently mixed with the ionic liquid (C) (for example, 5% by mass or less of water may be visually homogeneously and transparently mixed with the ionic liquid (C)), but 50% by mass or more of water may not be visually homogeneously and transparently mixed with the ionic liquid (C). means.

  Specific examples of the cation that constitutes the ionic liquid (C) include a nitrogen-containing compound cation, a quaternary phosphonium cation, and a sulfonium cation. Examples of the nitrogen-containing compound cations include heterocyclic aromatic amine cations such as imidazolium cations and pyridinium cations; piperidinium cations, pyrrolidinium cations, pyrazolium cations, thiazolium cations, morpholinium cations. And other heterocyclic aliphatic amine cations; quaternary ammonium cations; aromatic amine cations; aliphatic amine cations; alicyclic amine cations and the like. Examples of the imidazolium cation include 1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-octyl-3-methylimidazolium and the like. 1-alkyl-3-methylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-propyl-2,3-dimethylimidazolium, 1-butyl-2,3-dimethylimidazolium, 1-pentyl- 1-Alkyl-2 such as 2,3-dimethylimidazolium, 1-hexyl-2,3-dimethylimidazolium, 1-heptyl-2,3-dimethylimidazolium, 1-octyl-2,3-dimethylimidazolium , 3-dimethylimidazolium; 1-cyanomethyl-3-methylimidazolium, 1- (2-hydr Kishiechiru) -3-methylimidazolium, and the like. Examples of the pyridinium cation include 1-butylpyridinium, 1-hexylpyridinium, N- (3-hydroxypropyl) pyridinium, and N-hexyl-4-dimethylaminopyridinium. Examples of the piperidinium cation include 1- (methoxyethyl) -1-methylpiperidinium. Examples of the pyrrolidinium cation include 1- (2-methoxyethyl) -1-methylpyrrolidinium and N- (methoxyethyl) -1-methylpyrrolidinium. Examples of the morpholinium cation include N- (methoxyethyl) -N-methylmorpholium and the like. Examples of the quaternary ammonium cations include N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium and N-ethyl-N, N-dimethyl-2-methoxyethylammonium. .. Examples of the quaternary phosphonium cations include tetraalkylphosphonium and tetraphenylphosphonium. Examples of the sulfonium cation include trialkylsulfonium and triphenylsulfonium. One kind of these cations may be present or two or more kinds thereof may be present in the ionic liquid (C).

  Considering the dissolution and dispersion stability of the organic photosensitizing molecule (A) and the organic light emitting molecule (B) in the ionic liquid (C), the cation constituting the ionic liquid (C) is an organic photosensitizing molecule. Those having a “cation-π interaction” between (A) and the organic light emitting molecule (B) are preferable.

The anion constituting the ionic liquid (C) is not particularly limited, and examples thereof include bis (trifluoromethylsulfonyl) imide anion ([N (SO ₂ CF ₃ ) ₂ ] ^- ) and tris (tri). fluoromethyl sulfonyl) methide anion _{([C (SO 2 CF 3} ) 3] -), hexafluorophosphate anion ([PF _6] ^-), tris (pentafluoroethyl) trifluoro phosphate anion ([(C ₂ F _{5) 3} PF ₃ ] ^- ) and other fluorine-containing compound anions; [BR ¹¹ R ¹² R ¹³ R ¹⁴ ] ^- (in this anion structural formula and the following anionic structural formula, R ¹¹ , R ¹² , R ¹³ , and R ¹⁴ Are each independently a group represented by — (CH ₂ ) _n CH ₃ (where n represents an integer of 1 to 9), that is, a linear alkyl group having 1 to 9 carbon atoms, Alternatively, a boron-containing compound anion represented by (representing an aryl group), a bis (fluorosulfonyl) imide anion ([N (FSO ₂ ) ₂ ] ^- ) and the like can be given. In the ionic liquid (C), one kind of these anions may be present, or two or more kinds thereof may be present.

  In general, an ionic liquid is immiscible with water without any upper limit depending on the type of anion composing the ionic liquid, but depending on the type of anion composing the ionic liquid, the ionic liquid is immiscible with water to some extent or a very small amount. Only mix. In the present invention, in consideration of the dissolution / dispersion stability of the organic photosensitizing molecule (A) and the organic light emitting molecule (B) in the ionic liquid (C), the anion of the ionic liquid (C) becomes an ionic liquid. It is preferred that the anion is such that it imparts water immiscibility.

As the ionic liquid (C), a combination of the specific example of the anion and the specific example of the cation can be used. As the ionic liquid (C), more specifically, for example, 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (CAS number: 174899-82-2, for example, the manufacturer is Ionic Liquids Technologies). (A commercially available product of GmbH is available), 1-propyl-2,3-dimethylimidazolium bis (trifluoromethylsulfonyl) imide (CAS number: 169051-76-7, for example, a commercial product of Ionic Liquids Technologies GmbH or a manufacturer Is commercially available from Merck KGaA), 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (CAS number: 174899-83-3, for example, the manufacturer is Ionic Liq. Commercial products of ids Technologies GmbH and commercial products of manufacturer Merck KGaA are available), 1-propyl-2,3-dimethylimidazolium tris (trifluoromethylsulfonyl) methide (CAS number: 169051-77-8, for example, manufacturer) Commercially available from Covalent Associates Inc.), N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imide (CAS number: 464927-84-2, For example, a commercially available product (product number: 11468-55) manufactured by Nisshinbo Co., Ltd. and sold by Kanto Kagaku Co., Ltd., 1-hexyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (CAS) is available. No .: 38215 -50-7, for example, the manufacturer can obtain a commercial product of Merck KGaA), 1-octyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (CAS number: 178631-04-4, for example, the manufacturer is Nisshinbo Spinning Co., Ltd. The distributor is a commercial product of Kanto Chemical Co., Inc. (product number: 49514-85), 1-ethyl-2,3-dimethylimidazolium bis (trifluoromethylsulfonyl) imide (CAS number: 174899). -90-2, for example, a commercial item (product number: 49515-52) available from Kanto Chemical Co., Inc., 1-butyl-2,3-dimethylimidazolium bis (trifluoromethylsulfonyl) imide (CAS) No .: 350493-08-2, for example, the manufacturer is Ionic Liquids Tec. commercial products of Nologies GmbH and manufacturers can obtain commercial products of Merck KGaA), ethyldimethylpropylammonium bis (trifluoromethylsulfonyl) imide (CAS number: 258273-77-7, for example, manufacturers obtain commercial products of Merck KGaA). Possible), 1-ethyl-3-methylimidazolium tris (pentafluoroethyl) trifluorophosphate (CAS number: 377739-43-0, for example, a commercial product of the manufacturer Merck KGaA is available), 1-hexyl-3- Methylimidazolium tris (pentafluoroethyl) trifluorophosphate (CAS number: 713512-19-7, for example, a commercial product of the manufacturer Merck KGaA is available), 1-butyl-1-methylpyrrolidinium bis (tri) Luoromethylsulfonyl) imide (CAS number: 223437-11-4, for example, a commercial product of the manufacturer Merck KGaA is available), 1-butyl-1-methylpyrrolidinium tris (pentafluoroethyl) trifluorophosphate (CAS) No .: 851856-47-8, such as a commercial product of the manufacturer Merck KGaA), methyltri-n-octylammonium bis (trifluoromethylsulfonyl) imide (CAS number: 375395-33-8, for example, the manufacturer Merck KGaA). Commercially available product), 1-ethyl-3-methylimidazolium tris (trifluoromethylsulfonyl) methide, 1-butyl-3-methylimidazolium tris (trifluoromethylsulfonyl) methide, 1-hexyl-3- Methyl Midazolium tris (trifluoromethylsulfonyl) methide, 1-octyl-3-methylimidazolium tris (trifluoromethylsulfonyl) methide, 1-butyl-2,3-dimethylimidazolium tris (trifluoromethylsulfonyl) methide, N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium tris (trifluoromethylsulfonyl) methide, 1-butyl-3-methylimidazolium tris (pentafluoroethyl) trifluorophosphate, 1-octyl -3-Methylimidazolium tris (pentafluoroethyl) trifluorophosphate, 1-propyl-2,3-dimethylimidazolium tris (pentafluoroethyl) trifluorophosphate, 1-butyl-2,3-dimethylimidazo Lithium tris (pentafluoroethyl) trifluorophosphate, N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium tris (pentafluoroethyl) trifluorophosphate, 1-ethyl-3-methylimidazolium hexafluoro Phosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-hexyl-3-methylimidazolium hexafluorophosphate, 1-octyl-3-methylimidazolium hexafluorophosphate, 1-propyl-2,3-dimethyl Imidazolium hexafluorophosphate, 1-butyl-2,3-dimethylimidazolium hexafluorophosphate, N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium hexaflu Rohosufeto, 1-ethyl-3-methylimidazolium ^{[BR 11 R 12 R 13 R} 14] -, 1- butyl-3-methylimidazolium ^{[BR 11 R 12 R 13 R} 14] -, 1- hexyl -3 -Methylimidazolium [BR ¹¹ R ¹² R ¹³ R ¹⁴ ] ^- , 1-octyl-3-methylimidazolium [BR ¹¹ R ¹² R ¹³ R ¹⁴ ] ^- , 1-Propyl-2,3-dimethylimidazolium [BR ¹¹ R ¹² R ¹³ R ¹⁴ ] ^- , 1-butyl-2,3-dimethylimidazolium [BR ¹¹ R ¹² R ¹³ R ¹⁴ ] ^- , N, N-diethyl-N-methyl-N- (2-methoxyethyl ) ammonium ^{[BR 11 R 12 R 13 R} 14] -, 1- butyl pyridinium hexafluorophosphate, 1-hexyl pyridinium hexafluorophosphate, 1-cyanomethyl-3-methylimidazolium bi (Trifluoromethylsulfonyl) imide, N-hexyl-4-dimethylaminopyridinium bis (trifluoromethylsulfonyl) imide, 1- (2-hydroxyethyl) -3-methylimidazolium bis (trifluoromethylsulfonyl) imide, N -(3-hydroxypropyl) pyridinium bis (trifluoromethylsulfonyl) imide, N-ethyl-N, N-dimethyl-2-methoxyethylammonium tris (pentafluoroethyl) trifluorophosphate, 1- (2-hydroxyethyl) -3-Methylimidazolium tris (pentafluoroethyl) trifluorophosphate, N- (3-hydroxypropyl) pyridinium tris (pentafluoroethyl) trifluorophosphate, N- (methoxyethyl) -N- Tylmorpholium tris (pentafluoroethyl) trifluorophosphate, 1- (2-methoxyethyl) -1-methyl-pyrrolidinium tris (pentafluoroethyl) trifluorophosphate, 1- (methoxyethyl) -1-methyl Piperidinium tris (pentafluoroethyl) trifluorophosphate, 1- (methoxyethyl) -1-methylpiperidinium bis (trifluoromethylsulfonyl) imide, N- (methoxyethyl) -1-methylpyrrolidinium bis ( Examples thereof include, but are not limited to, trifluoromethylsulfonyl) imide and N- (methoxyethyl) -N-methylmorpholium bis (trifluoromethylsulfonyl). These ionic liquids (C) may be used alone or in combination of two or more.

  In the present invention, considering the stability of dissolution / dispersion of the organic photosensitizing molecule (A) and the organic light emitting molecule (B) in the ionic liquid (C), the organic light A combination of a cation having a “cation-π interaction” between the sensitizing molecule (A) and the organic light emitting molecule (B) and an anion that imparts immiscibility to the ionic liquid is preferable, and the ionic liquid (C) is preferable. Also, a water-immiscible one is preferable.

  As the ionic liquid (C), among the specific examples listed above, 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1-propyl-2,3-dimethylimidazolium bis ( Trifluoromethylsulfonyl) imide, 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1-propyl-2,3-dimethylimidazolium tris (trifluoromethylsulfonyl) methide, N, N-diethyl -N-methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imide, 1-hexyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1-octyl-3-methylimidazolium Bis (trifluoromethylsulfonyl) imi , 1-ethyl-2,3-dimethylimidazolium bis (trifluoromethylsulfonyl) imide, 1-butyl-2,3-dimethylimidazolium bis (trifluoromethylsulfonyl) imide, ethyldimethylpropylammonium bis (trifluoromethyl) Sulfonyl) imide, 1-ethyl-3-methylimidazolium tris (pentafluoroethyl) trifluorophosphate, 1-hexyl-3-methylimidazolium tris (pentafluoroethyl) trifluorophosphate, 1-butyl-1-methylpyrrolid Dinium bis (trifluoromethylsulfonyl) imide, 1-butyl-1-methylpyrrolidinium tris (pentafluoroethyl) trifluorophosphate, and methyltri-n-octylammonium bis (trif Oro methylsulfonyl) imide is particularly preferable.

  The viscosity of the ionic liquid (C) at 26 ° C. is usually 10 mPa · s or more, preferably 50 mPa · s or more, and more preferably 70 mPa · s or more. Thereby, a light wavelength conversion element having higher light wavelength conversion efficiency can be realized.

  The ionic liquid (C) contained in the light wavelength conversion element of the present invention is such that when the ionic liquid is washed with 9 times its volume of ultrapure water, the pH of the water after washing becomes higher than 5. Thereby, a light wavelength conversion element having higher light wavelength conversion efficiency and better stability over time can be realized. As a method for measuring the pH of water after washing when the ionic liquid (C) is washed with 9 times its volume of ultrapure water, the volume of the ionic liquid (C) is 9 times its volume (volume ratio). A method is used in which after adding ultrapure water (9 times its volume) and stirring, the aqueous layer is separated and the pH of the aqueous layer is measured.

  Commercially available ionic liquids often show an acidity of 5 or less after washing when the ionic liquid is washed with 9 times its volume of ultrapure water. When such a commercially available ionic liquid is used, by removing impurities from the commercially available ionic liquid, the pH of the water after washing is higher than 5 when washed with 9 times its volume of ultrapure water. It is necessary to obtain such an ionic liquid (C) and use the ionic liquid (C).

  As a method for removing impurities from the ionic liquid, for example, (1) a method of treating the ionic liquid with activated carbon, (2) a method of washing the ionic liquid with water, and (3) a method of washing the ionic liquid with an organic solvent ( For example, refer to JP 2012-144441 A), (4) The ionic liquid crystallized by dissolving the ionic liquid in a solvent to obtain a solution, then lowering the temperature of the solution to crystallize the ionic liquid from the solution. Is separated from the solution by filtration (recrystallization method; see, for example, JP 2010-184902 A), (5) A column filled with a filler such as alumina after the ionic liquid is dissolved in a solvent to obtain a solution. Method of passing the solution through the column (column method; for example, JP 2005-314332 A), (6) Method of treating ionic liquid with metal hydride (JP 2005-89313 A) Irradiation), and the like. You may use combining these methods. As the method (2), for example, water (preferably ultrapure water) is added to the ionic liquid, and the mixture is stirred and then the water layer is removed by repeating the washing treatment until the pH of the water after washing becomes higher than 5. Then, a method of distilling off (drying) water by heating under reduced pressure can be used.

  The light wavelength conversion element of the present invention is a solution or dispersion prepared by dissolving and / or dispersing the organic photosensitizing molecule (A) and the organic light emitting molecule (B) in the ionic liquid (C) using a generally known technique. Can be produced by the method of obtaining In the above method, if necessary, other additives are mixed with the organic photosensitizing molecule (A) and the organic light emitting molecule (B) in the ionic liquid (C) by using a commonly known technique to prepare a solution or A dispersion may be obtained. In the method, if necessary, a known disperser such as an ultrasonic disperser, a bead mill, a homogenizer, a wet jet mill, a ball mill, an attritor, a sand mill, a roll mill, or a microwave disperser may be used alone or in combination. Alternatively, the organic photosensitizing molecule (A) and the organic light emitting molecule (B) may be finely pulverized and finely dispersed to obtain a solution or a dispersion liquid.

  As another method for producing the light wavelength conversion element of the present invention, for example, first, the organic photosensitizing molecule (A) and the organic light emitting molecule (B) are dissolved and / or dispersed in a volatile organic solvent, Next, the resulting solution and / or dispersion is stirred and mixed with the ionic liquid (C) to form a visually homogeneous and transparent solution and / or dispersion, which is further reduced in pressure from the solution and / or dispersion. Then, a method of removing the volatile organic solvent to a trace amount or less can also be used. According to this method, it is easy to obtain a light wavelength conversion element in a homogeneous and transparent mixed state, and it is possible to obtain a light wavelength conversion element with high stability and high light wavelength conversion efficiency. Therefore, the light wavelength conversion element of the present invention is obtained. More preferable as a method.

  The volatile organic solvent used in the above method can dissolve and / or disperse the organic photosensitizing molecule (A) and the organic light emitting molecule (B), and can be mixed with the ionic liquid (C) homogeneously and transparently, Further, there is no particular limitation as long as it is a volatile organic solvent that can be removed to a trace amount under reduced pressure. Here, the "trace amount" is an amount in which the volatile organic solvent mixed in the ionic liquid (C) can be detected only at a noise level or lower based on the measurement of the light absorption spectrum. The volatile organic solvent is preferably a volatile organic solvent capable of dissolving the organic photosensitizing molecule (A) and the organic light emitting molecule (B). As the volatile organic solvent, an aromatic solvent such as toluene, benzene or xylene can be used. When a volatile organic solvent capable of dissolving the organic photosensitizing molecule (A) and the organic light emitting molecule (B) is used, the volatile organic solvent is adjusted to the solubility of the organic photosensitizing molecule and the organic light emitting molecule. Can be selected as appropriate.

  As the means for stirring and mixing, known techniques or devices such as ultrasonic waves, bubbling, a stirrer, a liquid feed pump, a crusher, a bead mill, a homogenizer, a wet jet mill, and a microwave can be used. These means may be used alone or in combination of two or more kinds.

  The light wavelength conversion element of the present invention has a water content of preferably 1% by mass or less, more preferably 0.1% by mass or less, further preferably 0.01% by mass or less, Most preferably, it is 0.001 mass% or less. Thereby, a light wavelength conversion element having higher light wavelength conversion efficiency can be realized.

  The oxygen concentration of the light wavelength conversion element of the present invention is preferably 100 mass ppm or less, more preferably 10 mass ppm or less, still more preferably 1 mass ppm or less, and 0. Most preferably, it is 1 mass ppm or less. Thereby, a light wavelength conversion element having higher light wavelength conversion efficiency can be realized.

  The light wavelength conversion element of the present invention is a visually homogeneous and transparent solution and / or dispersion, and further has good stability. The light wavelength conversion element of the present invention can be used for a solar cell, a photocatalyst, a photocatalytic hydrogen / oxygen generator, an optical up-conversion filter, and the like.

  The solar cell of the present invention uses the light wavelength conversion element of the present invention.

  An example of the solar cell of the present invention will be described based on FIG. As shown in FIG. 1, a solar cell according to an example of the present invention includes a photoelectric conversion layer (solar cell layer) 1 and a strip-shaped light-receiving surface electrode provided on a surface of the photoelectric conversion layer 1 on a light incident side. 7, a transparent back electrode 2 laminated on the back surface of the surface of the photoelectric conversion layer 1 on the light incident side, a transparent insulating film 3 laminated on the back surface of the surface of the transparent back electrode 2 on the light incident side, The up-conversion layer 4 using the light wavelength conversion element of the present invention, which is laminated on the back surface of the insulating film 3 on the light incident side, and the back surface of the up conversion layer 4 on the light incident side surface. The light reflection film 5 is provided.

  The photoelectric conversion layer 1 is not particularly limited, and an organic photoelectric conversion layer such as a dye-sensitized solar cell or an organic thin film solar cell, a compound semiconductor photoelectric conversion layer, a silicon photoelectric conversion layer, or the like can be used. it can.

The light-receiving surface electrode 7 and the light-reflecting film 5 can be formed of a metal such as Ag, Al, Ti, Cr, Mo, W, Ni or Cu. The transparent back electrode 2 can be formed of a transparent conductor such as ITO (Indium Tin Oxide), SnO ₂ or ZnO. The transparent insulating film 3 can be formed of a resin such as polyethylene terephthalate, polycarbonate, polyimide resin, acrylic resin, and polyether nitrile.

  Like the optical up-conversion filter of the present invention described later, the up-conversion layer 4 may be formed of a cell and a light wavelength conversion element enclosed in the cell, or may be formed of only a light wavelength conversion element. May be. When the up-conversion layer 4 is formed only of the light wavelength conversion element, the transparent insulating film 3, the up-conversion layer 4, and the light reflection film 5 may be sealed at their peripheral edges with a sealing member such as a sealing resin. Good.

  With the configuration of FIG. 1, the incident light 6 from the sun is up-converted by the up-conversion layer 4 (converted into light of a shorter wavelength), whereby the intensity of light in the wavelength range that the photoelectric conversion layer 1 can use for power generation. It is possible to further improve the power generation efficiency of the solar cell.

  Although the up-conversion layer 4 is disposed between the transparent insulating film 3 and the light-reflecting film 5 in the configuration of FIG. 1, the up-conversion layer 4 may be disposed at the light-incident side of the light-receiving surface electrode 7 or the like. You may change to another arrangement position like this. In that case, a transparent insulating film may be provided between the up-conversion layer 4 and the light-receiving surface electrode 7.

  Moreover, in the solar cell of FIG. 1, the light-receiving surface electrode 7 may be replaced with a transparent electrode formed on the entire surface of the photoelectric conversion layer 1 on the light incident side. Moreover, in the solar cell of FIG. 1, the transparent insulating film 3 may be omitted. However, when the up-conversion layer 4 is formed of only the light wavelength conversion element, the transparent insulating film 3 is provided in order to avoid contact between the light wavelength conversion element and the transparent back electrode 2. It is preferable to arrange it between the two. Further, in the solar cell of FIG. 1, when the arrangement position of the up-conversion layer 4 is changed to the light incident side of the light-receiving surface electrode 7 and the transparent insulating film 3 is omitted, the transparent back electrode 2 is used as a light reflecting electrode. Alternatively, the light reflection film 5 may be omitted.

  The photocatalyst of the present invention uses the light wavelength conversion element of the present invention. For example, by arranging a photocatalyst layer in place of the light-receiving surface electrode 7, the photoelectric conversion layer 1, the transparent back electrode 2 and the transparent insulating film 3 in the solar cell of FIG. 1, it is possible to realize a photocatalyst with high catalytic efficiency. You can

  As shown in FIG. 2, a photocatalyst according to an example of the present invention is a glass channel in which a photocatalyst-added water 10 (photocatalyst layer) is contained and a space other than the photocatalyst-added water 10 is filled with a gas 9. 8, an up-conversion layer 4 formed on the side and bottom surfaces of the glass channel 8, a light reflection film 5 formed on the outer surface of the up-conversion layer 4, and for supporting the light reflection film 5. The mechanical support 11 is formed on the outer surface of the light reflection film 5.

  With the configuration shown in FIG. 2, the incident light 6 from the sun is up-converted by the up-conversion layer 4 (converted into light having a shorter wavelength), whereby the photocatalyst added to the water 10 can be used for the catalytic reaction. It is possible to increase the intensity of light and further improve the conversion efficiency of the photocatalyst.

  The photocatalytic hydrogen / oxygen generator of the present invention uses the light wavelength conversion element of the present invention. For example, by arranging a photocatalyst layer in place of the light-receiving surface electrode 7, the photoelectric conversion layer 1, the transparent back electrode 2 and the transparent insulating film 3 in the solar cell of FIG.・ Oxygen generator can be realized.

  The optical up-conversion filter of the present invention is an optical up-conversion filter that converts light into light having a shorter wavelength, and includes the light wavelength conversion element and a cell.

  The cell is not particularly limited as long as it is a cell that can transmit light. For example, two glass plates made of quartz glass, borosilicate glass or the like are superposed and their peripheral portions are fused. A cell having a bonded structure can be used.

  The light wavelength conversion element is preferably encapsulated in the cell in an oxygen concentration of 100 mass ppm or less, more preferably 10 mass ppm or less in the cell. It is more preferably encapsulated in the cell in a state of 1 mass ppm or less, and most preferably encapsulated in the cell in a state of 0.1 mass ppm or less. When the light wavelength conversion element is enclosed in the cell in a state where the oxygen concentration is 100 mass ppm or less, the oxygen concentration is kept low. As a result, it is possible to realize an optical up-conversion filter that stably exhibits a high optical wavelength conversion efficiency that can be applied to light with a weak intensity of sunlight.

  The optical up-conversion filter is obtained by, for example, injecting a light wavelength conversion element into a cell, performing deoxidation treatment until the oxygen concentration becomes 100 mass ppm or less, if necessary, and then sealing the cell by a method. Obtainable. Examples of the deoxidizing method include a method of decompressing the light wavelength conversion element using a vacuum pump such as a rotary pump or a turbo molecular pump, and an inert gas such as nitrogen gas or argon gas in the light wavelength conversion element. And a method of decompressing (vacuum degassing) using a vacuum pump after freezing the light wavelength conversion element (freezing vacuum degassing method) and the like.

  The light up-conversion filter can be used as the up-conversion layer 4 of the solar cell, photocatalyst, and photocatalytic hydrogen / oxygen generator.

  In addition, in articles such as a solar cell using the light wavelength conversion element of the present invention, a photocatalyst, a photocatalytic hydrogen / oxygen generator, an optical up-conversion filter, an oxygen getter is provided to reduce the oxygen concentration of the light wavelength conversion element. May coexist. Further, in articles such as a solar cell, a photocatalyst, a photocatalytic hydrogen / oxygen generator, and an optical up-conversion filter using the light wavelength conversion element of the present invention, a water absorbing material for reducing the oxygen concentration of the light wavelength conversion element. May coexist.

  Next, the present invention will be described in more detail by way of examples. The present invention is not limited to the following examples. The ultrapure water used in the following production examples of the ionic liquid (C) is as follows.

[Production of ultrapure water]
In the following production example of the ionic liquid (C), ultrapure water produced by an ultrapure water production apparatus (manufacturer: Merck KGaA, model number: Direct-Q (registered trademark) UV3) was used as the ultrapure water.

[Synthesis Example 1 of Organic Photosensitizing Molecule (A)]
According to the method described in Non-Patent Document 6, the following formula

で表される有機光増感分子（Ａ）（２−ヨード−１，３，５，７−テトラメチル−８−フェニル−４，４−ジフルオロボラジアザインダセン）を合成した。得られた化合物の同定は、以下のＮＭＲスペクトルにより行った。
¹Ｈ ＮＭＲ（４００ＭＨｚ，ＣＤＣｌ₃)：δ ７．５１−７．４８（ｍ，３Ｈ），７．２７−７．２５（ｍ，２Ｈ），６，０４（ｓ，１Ｈ），２．６３（ｓ，３Ｈ），２．５７（ｓ，３Ｈ），１．３８（ｓ，６Ｈ）
¹³Ｃ ＮＭＲ（１００ＭＨｚ，ＣＤＣｌ₃)：δ １５７．９，１５４．７，１４５．３，１４３．４，１４１．７，１３５．０，１３２．０，１３１．１，１２９．８，１２９．５，１２９．４，１２８．０，１２２．５，８４．４，１６．８，１６．０，１４．９，１４．７
〔有機光増感分子（Ａ）の合成例２〕
非特許文献６に記載の方法で、下記式

The organic photosensitizing molecule (A) (2-iodo-1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene) represented by the following formula was synthesized. The obtained compound was identified by the following NMR spectrum.
¹ H NMR (400 MHz, CDCl ₃ ): δ 7.51-7.48 (m, 3H), 7.27-7.25 (m, 2H), 6, 04 (s, 1H), 2.63 ( s, 3H), 2.57 (s, 3H), 1.38 (s, 6H)
¹³ C NMR (100 MHz, CDCl ₃ ): δ 157.9, 154.7, 145.3, 143.4, 141.7, 135.0, 132.0, 131.1, 129.8, 129.5. , 129.4, 128.0, 122.5, 84.4, 16.8, 16.0, 14.9, 14.7.
[Synthesis Example 2 of Organic Photosensitizing Molecule (A)]
According to the method described in Non-Patent Document 6, the following formula

で表される有機光増感分子（Ａ）（２，６−ジヨード−１，３，５，７−テトラメチル−８−フェニル−４，４−ジフルオロボラジアザインダセン）を合成した。得られた化合物の同定は、以下のＮＭＲスペクトルにより行った。
¹Ｈ ＮＭＲ（４００ＭＨｚ，ＣＤＣｌ₃）：δ ７．５４−７．５１（ｍ，３Ｈ），７．２６−７．２４（ｍ，２Ｈ），２．６５（ｓ，６Ｈ），１．３８（ｓ，６Ｈ）
¹³Ｃ ＮＭＲ（１００ＭＨｚ，ＣＤＣｌ₃）：δ １５６．９，１４５．５，１４１．５，１３４．４，１２９．７，１２９．６，１２７．９，８５．８，１７．１，１６．２
〔イオン液体（Ｃ）の作製例１〕
非水混和性のイオン液体である１−プロピル−２，３−ジメチルイミダゾリウムビス（トリフルオロメチルスルホニル）イミド（ＣＡＳ番号：１６９０５１−７６−７；以下「イオン液体＃１」と称する）の市販品（製造元：Ｉｏｎｉｃ Ｌｉｑｕｉｄｓ Ｔｅｃｈｎｏｌｏｇｉｅｓ ＧｍｂＨ）をガラスバイアル瓶にとり、そのイオン液体＃１の市販品にその９倍の体積の超純水を加え、汎用のマグネチックスターラーおよび撹拌子を用いて撹拌し静置した（その９倍の体積の超純水により洗浄した）。このとき、ガラスバイアル瓶の内容物は、ガラスバイアル瓶の底部にある当該イオン液体層と、その上にある水層とに分離した。その後、水層を取得し、水層のｐＨ（洗浄後の水のｐＨ）を測定したところ、水層のｐＨは３．９であった。

The organic photosensitizing molecule (A) represented by (2,6-diiodo-1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene) was synthesized. The obtained compound was identified by the following NMR spectrum.
¹ H NMR (400 MHz, CDCl ₃ ): δ 7.54 to 7.51 (m, 3H), 7.26 to 7.24 (m, 2H), 2.65 (s, 6H), 1.38 ( s, 6H)
¹³ C NMR (100 MHz, CDCl ₃ ): δ 156.9, 145.5, 141.5, 134.4, 129.7, 129.6, 127.9, 85.8, 17.1, 16.2
[Preparation Example 1 of Ionic Liquid (C)]
Commercially available non-water-miscible ionic liquid, 1-propyl-2,3-dimethylimidazolium bis (trifluoromethylsulfonyl) imide (CAS number: 169051-76-7; hereinafter referred to as "ionic liquid # 1") The product (manufacturer: Ionic Liquids Technologies GmbH) is placed in a glass vial, and 9 times the volume of ultrapure water is added to the commercial product of the ionic liquid # 1, and the mixture is stirred by using a general-purpose magnetic stirrer and a stirrer. (It was washed with 9 times its volume of ultrapure water). At this time, the content of the glass vial was separated into the ionic liquid layer at the bottom of the glass vial and the water layer above it. After that, when the aqueous layer was obtained and the pH of the aqueous layer (pH of water after washing) was measured, the pH of the aqueous layer was 3.9.

  On the other hand, 1 ml of this commercial product of ionic liquid # 1 is placed in a glass vial having an internal capacity of about 8 ml, 30 mg of activated carbon is added to the commercial product of ionic liquid # 1, and a vacuum drying oven (manufacturer: Yamato Scientific Co., Ltd., model number: ADP200) In vacuo at 140 ° C. for 3 hours. After taking out the glass vial from the vacuum drying oven, centrifugation was performed to obtain a supernatant portion containing almost no activated carbon. The supernatant portion thus obtained was passed through a disposable syringe filter (manufacturer: Merck KGaA, model number: IC Millex (registered trademark) -LG) having a pore size of about 0.2 μm to remove residual activated carbon, and a glass vial having an internal capacity of about 20 ml. Poured in. A washing operation of adding 9 times the volume of ultrapure water to the contents of the glass vial, stirring for 5 minutes using a general-purpose magnetic stirrer and stirrer, leaving it for a few minutes, and then removing the water layer. Repeated 3 times. When the pH of the aqueous layer removed by the third washing operation (pH of water after washing) was measured, the pH of the aqueous layer was 6.5.

  Finally, the water layer remaining in the glass vial was removed as much as possible with a glass Pasteur pipette (manufacturer: Fisher Scientific Inc., product number: 5-5351-01). The contents (ionic liquid layer) of the glass vial were dried in a forced convection drying oven (sold by: Advantech Toyo Co., Ltd., Toyo Seisakusho, model number: DRM320DB) at 70 ° C. overnight, and then vacuum dried oven ( The same as the one used for the previous vacuum drying) was vacuum dried at 120 ° C. for 3 hours to obtain an ionic liquid (C), an ionic liquid # 1.

[Production Example 2 of Ionic Liquid (C)]
1-Butyl-2,3-dimethylimidazolium bis (trifluoromethylsulfonyl) imide, which is a non-water-miscible ionic liquid in place of the commercially available ionic liquid # 1 used in Preparation Example 1 of ionic liquid (C) (CAS number: 350493-08-2; hereinafter referred to as "ionic liquid # 2"), except that a commercially available product (manufacturer: Ionic Liquids Technologies GmbH) is used, the same treatment as in Preparation Example 1 of the ionic liquid (C) ( Washing (stirring and removal of the water layer) with ultrapure water having a volume 9 times the volume of the ionic liquid was repeated 3 times). As a result, the pH of the aqueous layer removed by the third washing operation (pH of water after washing) became 6.4, and ionic liquid # 2 that was ionic liquid (C) was obtained.

[Production Example 3 of Ionic Liquid (C)]
By performing the same treatments as those in Preparation Examples 1 and 2 of the ionic liquid (C), the ionic liquid # 1 and the ionic liquid # 2, which are the ionic liquid (C), were obtained. In addition, 1-ethyl-3-methylimidazolium bis (trifluoromethyl), which is an ionic liquid that is completely immiscible with water, is used instead of the commercially available ionic liquid # 1 used in Preparation Example 1 of ionic liquid (C). Sulfonyl) imide (CAS number: 174899-82-2; hereinafter referred to as “ionic liquid # 3”) (manufacturer: Ionic Liquids Technologies GmbH), 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl). ) Imide (CAS number: 174899-83-3; hereinafter referred to as “ionic liquid # 4”) (manufacturer: Ionic Liquids Technologies GmbH), 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) Imide (CAS number: 17489 -83-3; commercially available product (manufacturer: Merck KGaA), hereinafter referred to as "ionic liquid # 5", ethyldimethylpropylammonium bis (trifluoromethylsulfonyl) imide (CAS number: 258273-77-7; hereinafter referred to as "ion" Liquid # 6 ") (commercial product: Merck KGaA), 1-propyl-2,3-dimethylimidazolium bis (trifluoromethylsulfonyl) imide (CAS number: 169051-76-7; hereinafter referred to as" ionic liquid "). # 7 ”) (commercial name: Merck KGaA), 1-ethyl-3-methylimidazolium tris (pentafluoroethyl) trifluorophosphate (CAS number: 377739-43-0; hereinafter referred to as“ ionic liquid # 8 ”). ")) Commercial product (manufacturer: Merck KGaA , 1-hexyl-3-methylimidazolium tris (pentafluoroethyl) trifluorophosphate (CAS number: 713512-19-7; hereinafter referred to as “ionic liquid # 9”) (manufacturer: Merck KGaA), 1 -Butyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl) imide (CAS number: 223437-11-4; hereinafter referred to as "ionic liquid # 10") commercial product (manufacturer: Merck KGaA), 1-butyl -2,3-Dimethylimidazolium bis (trifluoromethylsulfonyl) imide (CAS number: 350493-08-2; hereinafter referred to as "ionic liquid # 11") commercial product (manufacturer: Merck KGaA), 1-hexyl- 3-methylimidazolium bis (trifluoromethylsulfonyl) Commercially available imide (CAS number: 382150-50-7; hereinafter referred to as “ionic liquid # 12”) (manufacturer: Merck KGaA), 1-butyl-1-methylpyrrolidinium tris (pentafluoroethyl) trifluorophosphate. (CAS number: 851856-47-8; hereinafter referred to as “ionic liquid # 13”) (manufacturer: Merck KGaA), and methyltri-n-octylammonium bis (trifluoromethylsulfonyl) imide (CAS number: 375395). 33-8; hereinafter, referred to as “ionic liquid # 14”), except that each of the commercially available products (manufacturer: Merck KGaA) is used, by performing the same process as in Preparation Example 1 of the ionic liquid (C), the ionic liquid is obtained. (C) Ionic liquid # 3, ionic liquid # 4, ionic liquid # 5 , Ionic liquid # 6, ionic liquid # 7, ionic liquid # 8, ionic liquid # 9, ionic liquid # 10, ionic liquid # 11, ionic liquid # 12, ionic liquid # 13, and ionic liquid # 14 were obtained.

  To a portion of each of the obtained ionic liquids (C), ionic liquids # 1 to # 14, 9 times the volume of ultrapure water was added, and a general-purpose magnetic stirrer and stirrer were used. After stirring for a minute and standing still for a few minutes, the aqueous layer was obtained and the pH of the aqueous layer (pH of water after washing) was measured. In all cases, the pH of the aqueous layer was higher than 5.

[Confirmation of dissolution stability of organic photosensitizing molecule (A) in ionic liquid (C)]
Organic Photosensitizer Molecule (A) Organic Photosensitizer Molecule (A) Obtained in Synthesis Example 2 (2,6-diiodo-1,3,5,7-tetramethyl-8-phenyl-4,4- The following experiment was carried out in order to confirm that (difluoroboradiazaindacene) can be dissolved and / or dispersed in the ionic liquid (C) visually and homogeneously and transparently, and that the state is kept stable. I went.

  First, three glass vials having an internal volume of about 8 ml were prepared, and the pH of the washing water was preliminarily adjusted to be higher than 5 in each of the glass vials according to Preparation Example 1 of the ionic liquid (C). Ion liquid # 1, which is ionic liquid (C), ionic liquid # 3, and ionic liquid # 12 were put in 300 μl each.

Then, the organic photosensitizing molecule (A) (2,6-diiodo-1,3,5) obtained in Synthesis Example 2 of the organic photosensitizing molecule (A) was placed in each of these three glass vials. , 7-Tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene) was dissolved in toluene at a concentration of 3 × 10 ⁻⁴ M, and 100 μl of each solution was added. Then, the contents of these glass vials are repeatedly sucked and exhaled using a glass Pasteur pipette (manufacturer: Fisher Scientific Inc., product number: 5-5351-01) to homogenize visually. And it was a transparent mixed solution. Then, these glass vials were capped, and stirred and homogenized for about 7 minutes with an ultrasonic bath sonicator (manufacturer: Branson Ultrasonics Corp., model number: Model 3510). Then, remove the lid of each glass vial, put each glass vial in a vacuum container, and use a scroll pump (manufacturer: Edwards Co., Ltd., model number: XDS35i, design ultimate pressure: 1 Pa or less) at room temperature for about 8 hours. A vacuum treatment was performed. As a result, a visually homogeneous and transparent single layer solution and / or dispersion (liquid) in which toluene was removed to a trace amount or less was obtained.

  Next, in order to confirm the stability of these liquids, these three glass vials were stored by standing still in a shelf in the air and at room temperature which was not exposed to light, and after 162 hours, they were taken out from the shelf and confirmed. The liquid remained visually homogeneous and clear. Further, a small amount of each of these three types of liquid was dropped on a slide glass and observed with a microscope at an objective lens magnification of 10 times and 50 times. As a result of observation, solid precipitation such as fine crystals was not observed at all in any liquid, and the organic photosensitizing molecule (A) obtained in Synthesis Example 2 of the organic photosensitizing molecule (A) was visually homogeneous. In addition, it was confirmed that the state of being dissolved and / or dispersed in the ionic liquid (C) was kept transparent and stable.

[Example 1]
(Fabrication of light wavelength conversion element)
At room temperature, 400 μl of ionic liquid # 1 which is the ionic liquid (C) obtained in Preparation Example 1 of ionic liquid (C) was placed in a glass vial having an internal volume of about 8 ml. Subsequently, in ionic liquid # 1 which is this ionic liquid (C), meso-tetraphenyl-tetrabenzoporphyrin palladium (CAS number: 119654-64-7) as an organic photosensitizing molecule (A) was added in toluene. About 20 μl of a solution dissolved at a concentration of 2 × 10 ⁻⁴ M and perylene (CAS number: 198-55-0) as an organic light emitting molecule (B) were dissolved at a concentration of 4 × 10 ⁻³ M in toluene. About 300 μl of solution was added. This resulted in a visually inhomogeneous mixed liquid. For this visually inhomogeneous mixed liquid, a glass Pasteur pipette (same as that used in Preparation Example 1 of ionic liquid (C)) was used to "suck By repeating "vomiting", a visually homogeneous and transparent mixed solution was obtained. Then, the glass vial was capped, and stirred and homogenized with an ultrasonic bath sonicator (manufacturer: Branson Ultrasonics Corp., model number: Model 3510) for about 10 minutes.

After that, the lid of the glass vial is removed, the glass vial is placed in a vacuum container, and decompressed for about 8 hours at room temperature using a scroll pump (manufacturer: Edwards Co., Ltd., model number: XDS35i, design ultimate pressure: 1 Pa or less). Processed. As a result, the volatile component, toluene, was removed to a trace amount or less, and a visually homogeneous and transparent one-layer solution and / or dispersion (liquid) was obtained. Furthermore, this glass vial was placed in a vacuum chamber (made of aluminum, a cylindrical custom-made product with an internal size of 10 cm in diameter and 6 cm in height) installed in a glove box filled with argon, and a special lid was installed. After sealing the vacuum chamber with, a turbo molecular pump (manufacturer: Pfeiffer Vacuum Technology AG, model number: HiCube 80, substantial ultimate pressure: about 10 ⁻⁴ to 10 ⁻⁵ Pa) overnight, about 10 ⁻⁴ to 10 ^−5. By vacuuming at a vacuum degree of Pa, residual oxygen molecules were thoroughly removed, and a visually homogeneous and transparent liquid as a light wavelength conversion element was obtained.

(Evaluation of up-conversion emission of light wavelength conversion element)
Then, in the same glove box, the lid of the vacuum chamber is opened, and in the same glove box, as in the method described in Patent Document 3, a part of the liquid (light wavelength conversion element) has an internal dimension of 1 mm × 1 mm. It was injected into a square quartz tube with an outer size of 2 mm x 2 mm and a length of about 25 mm, which was closed at one end and about 3/4 of its total length, and the open end of the quartz tube was sealed with lead solder and sealed in the quartz tube. A sample for up-conversion luminescence evaluation was obtained. This up-conversion luminescence evaluation sample comprises a light wavelength conversion element and a quartz tube as a cell, and the light wavelength conversion element is sealed in the quartz tube in a state where the oxygen concentration is 100 mass ppm or less. And corresponds to the optical up-conversion filter of the present invention.

  The prepared sample for evaluation of up-conversion emission was fixed to a dedicated sample holder and emitted as a excitation light from a continuous light laser light emitter (manufacturer: CVI Melles Griot Inc., model number: 25LHP928-249). Wavelength: 632.8 nm, spot diameter: approx. 0.8 mm, output power: approx. 28 mW, hereafter referred to as "continuous light laser emission # 1"), and a bright blue up-conversion emission (wavelength near 475 nm) was visually observed. (Maximum peak) was observed. Then, the up-conversion luminescence from the same sample for evaluation of up-conversion luminescence was taken out by a condenser lens in a direction perpendicular to the incident excitation light, and the taken-up up conversion luminescence was analyzed by another lens with a spectroscope (manufacturer: Roper Scientific GmbH). , A model number: SP-2300i) with an electron-cooled silicon CCD detector (manufacturer: Roper Scientific GmbH, model number: Pixis100BR) that is focused on the entrance slit and installed after the spectroscope. The strength was measured. The measured up-conversion emission spectrum is shown in FIG. When this intensity was monitored with respect to time, the intensity of the up-conversion emission from the sample for up-conversion emission evaluation did not change during the irradiation time of continuous light laser emission # 1 (several minutes). Has a high stability against irradiation with continuous light laser emission # 1.

(Measurement of light absorption spectrum of light wavelength conversion element)
In addition, the remaining liquid (light wavelength conversion element) that was not used in the preparation of the up-conversion emission evaluation sample was put into a thin quartz cell having a thickness of 1 mm to obtain a light absorption spectrum measurement sample. The light absorption spectrum of the light absorption spectrum measurement sample was measured with an ultraviolet-visible near-infrared spectrophotometer (manufacturer: Shimadzu Corporation, model number: UV-3600). The measured light absorption spectrum is shown in FIG.

[Comparative Example 1]
Instead of the ionic liquid # 1 which is the ionic liquid (C) obtained by the method of Preparation Example 1 of the ionic liquid (C), a commercial product of the ionic liquid # 1 used in Preparation Example 1 of the ionic liquid (C) ( Visually as a light wavelength conversion element for comparison by the same procedure as in Example 1 except that the pH of the water after washing was 3.9 as it is after washing with 9 times the volume of ultrapure water. An upper homogeneous and transparent liquid was prepared, a comparative up-conversion luminescence evaluation sample was prepared in the same procedure as in Example 1, and subsequently the up-conversion luminescence intensity was measured under the same conditions as in Example 1.

  As a result, the up-conversion emission intensity of this comparative up-conversion emission evaluation sample was very weak by visual observation, and was significantly weaker than the up-conversion emission intensity of the up-conversion emission evaluation sample obtained in Example 1. Met. Moreover, when the time change of the up-conversion emission intensity of the comparative up-conversion emission evaluation sample was monitored, the up-conversion emission intensity started to decrease rapidly immediately after the continuous light laser emission # 1 irradiation was started, and After about 10 seconds, the up-conversion emission almost disappeared. Therefore, it was found that the above-mentioned sample for evaluation of up-conversion emission for comparison was extremely unstable with respect to the irradiation of continuous light laser emission # 1.

  As can be seen from the results of Example 1 and Comparative Example 1, the optical wavelength conversion element of Example 1, which is the optical wavelength conversion element of the present invention, had good stability of up-conversion emission. That is, a commercial product of the ionic liquid # 1 used in Preparation Example 1 of the ionic liquid (C) (the pH of water after cleaning becomes 3.9 when washed with 9 times the amount of ultrapure water) Is replaced with ionic liquid # 1 which is the ionic liquid (C) (the pH of the water after cleaning becomes higher than 5 when washed with 9 times the amount of ultrapure water). We have succeeded in improving the stability of the wavelength conversion element to a form suitable for application.

[Example 2]
In place of the ionic liquid # 1 which is the ionic liquid (C) prepared in the preparation example 1 of the ionic liquid (C), an ionic liquid # 2 which is the ionic liquid (C) prepared in the preparation example 2 of the ionic liquid (C) is used. A visually homogeneous and transparent liquid as a light wavelength conversion element was prepared by the same procedure as in Example 1 except that it was used, and an up-conversion emission evaluation sample and a light absorption spectrum measurement sample were prepared by the same procedure as in Example 1. Then, subsequently, the up-conversion emission spectrum, the up-conversion emission intensity (peak intensity and integrated intensity), and the light absorption spectrum were measured under the same conditions as in Example 1. The measured up-conversion emission spectrum and light absorption spectrum are shown in FIGS. 5 and 6, respectively.

[Comparative Example 2]
Except that the commercial product of the ionic liquid # 2 used in the preparation example 2 of the ionic liquid (C) is used as it is, instead of the ionic liquid # 1 which is the ionic liquid (C) obtained in the preparation example 1 of the ionic liquid (C). Is a visually uniform and transparent liquid as a light wavelength conversion element for comparison, which is manufactured by the same procedure as in Example 1, and a sample for up-conversion luminescence evaluation for comparison and a light for comparison are manufactured by the same procedure as in Example 1. A sample for measuring an absorption spectrum was prepared, and subsequently, an up-conversion emission spectrum, an up-conversion emission intensity (peak intensity and integrated intensity), and a light absorption spectrum were measured under the same conditions as in Example 1. The measured up-conversion emission spectrum and light absorption spectrum are shown in FIGS. 5 and 7, respectively.

  In order to compare the up-conversion luminescence intensity of the sample for up-conversion luminescence evaluation of Example 2 and the up-conversion luminescence intensity of the sample for up-conversion luminescence evaluation of Comparative Example 2, the up-conversion luminescence intensity of these samples was increased. The up conversion emission intensity (peak intensity and integrated intensity) of the sample for conversion emission evaluation was standardized as 1. In FIG. 8, the up-converted emission intensities (peak intensity and integrated intensity) of the samples for evaluation of up-conversion emission of Example 2 and Comparative Example 2 thus standardized are shown on the vertical axis. The magnitude of these up-conversion emission intensity is proportional to the up-conversion quantum efficiency (light wavelength conversion efficiency).

The preparation of the comparative up-conversion luminescence evaluation sample in this comparative example was carried out simultaneously in the same batch in the same batch as the preparation of the up-conversion luminescence evaluation sample in Example 2. Further, the measurement of the up-conversion emission intensity of the comparative up-conversion emission evaluation sample in this comparative example was performed under the same optical measurement conditions on the same day as the measurement of the up-conversion emission intensity of the up-conversion emission evaluation sample in Example 2. Went below. Therefore, in this comparative example, it is possible to quantitatively compare the measurement result of the up-conversion emission intensity with the result in Example 2, as shown in FIG. In the light wavelength conversion element of the second embodiment, which is the light wavelength conversion element according to the present invention, which uses the ionic liquid # 2 which is the ionic liquid (C) in which the pH of the water after cleaning becomes higher than 5, Up of the light wavelength conversion element of Comparative Example 2 which is a light wavelength conversion element for comparison using a commercially available ionic liquid # 2 in which the pH of water after washing becomes 5 or less when washed with double amount of ultrapure water It was found that the up-conversion emission intensity improved (improved) to about 1.4 times the conversion emission intensity was obtained. As described above, from the comparison between Example 1 and Comparative Example 1 and the comparison between Example 2 and Comparative Example 2, the advantages and improvement effects of using the ionic liquid (C) in the light wavelength conversion element are apparent. became.

[Example 3]
(Fabrication of light wavelength conversion element)
Ionic Liquid # 2 (400 μl) obtained in Preparation Example 2 of Ionic Liquid (C) in place of Ionic Liquid # 1 (400 μl) which is Ionic Liquid (C) obtained in Preparation Example 1 of Ionic Liquid (C) Was used in place of about 20 μl of a solution of meso-tetraphenyl-tetrabenzoporphyrin palladium dissolved in toluene at a concentration of 2 × 10 ⁻⁴ M, and was obtained in Synthesis Example 1 of the organic photosensitizing molecule (A). The organic photosensitizing molecule (A) (2-iodo-1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene) in toluene at a concentration of 6 × 10 ⁻⁴ M A visually homogeneous and transparent liquid as a light wavelength conversion element was obtained in the same manner as in Example 1 except that about 40 μl of the solution dissolved in 2 was used. Subsequently, an up-conversion emission evaluation sample and a light absorption spectrum measurement sample were prepared by the same procedure as in Example 1, and subsequently, the light absorption spectrum was measured under the same conditions as in Example 1. The measured light absorption spectrum is shown in FIG.

(Measurement of up-conversion quantum efficiency of optical wavelength conversion element)
The up-conversion quantum efficiency (light wavelength conversion efficiency) of the sample for evaluation of up-conversion emission produced in this example is as follows based on the reference method as in the measuring method described in [0099] of Patent Document 3. Measured.

  First, the sample for evaluation of up-conversion emission produced in this example was fixed to the same sample holder as used in Example 1, and a continuous light laser emitter (manufacturer: Abal OptoTek Co., Ltd.) was used as excitation light. (AOTK), model number: Action532S) emitted continuous light laser emission (wavelength: 532 nm, spot diameter: about 0.8 mm, output power: about 30 mW), and upconversion emission of a sample for evaluation of upconversion emission. Spectra were measured and recorded with an electronically cooled silicon CCD (Charge Coupled Device) detector (same as used in Example 1) installed after the spectrometer (same as used in Example 1). The measured up-conversion emission spectrum is shown in FIG.

Subsequently, 9,10-bis (phenylethynyl) anthracene (CAS number: 10075-85-, which is a dye known to have a fluorescence quantum efficiency of about 85% in a nonpolar solvent such as toluene or benzene). A toluene solution having a concentration of 1 × 10 ⁻⁵ M of 1) was prepared. This solution was poured into a square quartz tube of one end closed having a size of 1 mm × 1 mm, an outer size of 2 mm × 2 mm, and a length of about 25 mm, which was the same as that used in Example 1 and this example, about 3/4 of its total length. The open end was sealed with lead solder to obtain a reference sample. Then, this reference sample was fixed to the same sample holder used in Example 1, and emitted as excitation light from a continuous-wave laser light emitter (manufacturer: World Star Tech Inc., model number: TECBL-30GC-405). Continuous light laser emission (wavelength: 405 nm, spot diameter: about 0.8 mm, output power: about 1 mW), and the fluorescence emission spectrum of the reference sample was measured by a spectroscope (the same as that used in Example 1). It was measured and recorded with an electronically cooled silicon CCD detector (same as used in Example 1) installed later.

  The up-conversion emission spectrum of the sample for up-conversion emission evaluation and the fluorescence emission spectrum of the reference sample recorded in this way are dependent on the diffraction efficiency wavelength of the diffraction grating mounted in the spectrometer and the electron-cooled silicon CCD detector. The wavelength dependence of detection sensitivity was corrected, and the distortion of the recorded spectral shape was corrected. Then, based on the information on the absorbance and excitation light intensity of the sample at the excitation wavelength for each of the spectra (upconversion emission spectrum and fluorescence emission spectrum) after correction of the upconversion emission evaluation sample and the reference sample, those skilled in the art usually The upconversion quantum efficiency of the sample for evaluation of upconversion emission was determined by using the relational expression used.

  From the above procedure, the up-conversion quantum efficiency of the light wavelength conversion element manufactured in this example was found to be 20.1%.

[Example 4]
Synthesis of Organic Photosensitizing Molecule (A) Organic Photosensitizing Molecule (A) Obtained in Synthesis Example 1 (2-Iodo-1,3,5,7-tetramethyl-8-phenyl-4,4-difluorobora) Diazaindacene) was dissolved in toluene at a concentration of 6 × 10 ⁻⁴ M in place of about 40 μl of the solution, and the organic photosensitizing molecule (A) obtained in Synthesis Example 2 of the organic photosensitizing molecule (A) was replaced. About 20 μl of a solution of (2,6-diiodo-1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene) dissolved in toluene at a concentration of 3 × 10 ⁻⁴ M. Using the same procedure as in Example 3, except that the above was used, a visually homogeneous and transparent liquid as a light wavelength conversion element was obtained.

  Then, a sample for evaluation of upconversion emission and a sample for measuring light absorption spectrum were prepared by the same procedure as in Example 3 except that the light wavelength conversion element prepared in this example was used. The spectrum and upconversion quantum efficiency were measured. FIG. 11 shows the measured light absorption spectrum, and FIG. 12 shows the upconversion emission spectrum. As a result, the up-conversion quantum efficiency of the light wavelength conversion element manufactured in this example was found to be 16.8%.

[Comparison between Examples 3 and 4 and Non-Patent Document 6]
In Non-Patent Document 6, as the organic photosensitizing molecule and the organic light emitting molecule, each was obtained in Synthesis Example 1 of the same type of molecule as used in Example 3, that is, each organic photosensitizing molecule (A). A light wavelength conversion element is prepared using an organic photosensitizing molecule (A) (2-iodo-1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene) and perylene. However, a classical organic solvent (acetonitrile) is used as a medium for the light wavelength conversion element. In Non-Patent Document 6, it is reported that the optical wavelength conversion element is irradiated with continuous light laser emission having a wavelength of 532 nm as excitation light, and the measurement is performed, and that the up-conversion quantum efficiency is 2.4%. ..

  Further, in Non-Patent Document 6, as the organic photosensitizing molecule and the organic light emitting molecule, the same kind of molecule as that used in Example 4, that is, each obtained in Synthesis Example 2 of the organic photosensitizing molecule (A) was obtained. Wavelength conversion using the obtained organic photosensitizing molecule (A) (2,6-diiodo-1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene) and perylene Elements have been made, but a classical organic solvent (acetonitrile) is used as the medium for the light wavelength conversion element. In Non-Patent Document 6, it is reported that the optical wavelength conversion element is irradiated with continuous-wave laser light having a wavelength of 532 nm as excitation light for measurement, and the upconversion quantum efficiency was 5.4%. ..

  Although the conditions for measurement in Example 3 and Example 4 and Non-Patent Document 6 are not completely the same, a simple comparison is not necessarily easy, but the up-conversion quantum obtained in Example 3 and Example 4 is not always easy. The efficiencies (20.1% and 16.8%) are about an order of magnitude higher than the upconversion quantum efficiencies (2.4% and 5.4%) measured in Comparative Examples 3 and 4, indicating a significant improvement. It can be judged that (improvement) was obtained.

[Example 5]
Subsequently, as an ionic liquid (C), ionic liquids having various viscosities were studied, and as a result of earnestly examining the effect of the type on the optical wavelength conversion efficiency (upconversion quantum efficiency) of the optical wavelength conversion element, surprisingly, , It was revealed for the first time that the viscosity of the ionic liquid is a very important factor in the design that controls the light wavelength conversion efficiency of the light wavelength conversion element.

(Measurement of viscosity of ionic liquid (C))
Ionic liquid (C) produced in Production Example 3 of ionic liquid (C) used in this example, ionic liquid # 1, ionic liquid # 2, ionic liquid # 3, ionic liquid # 4, ionic liquid # 5, the ionic liquid # 6, the ionic liquid # 7, the ionic liquid # 8, the ionic liquid # 9, the ionic liquid # 10, the ionic liquid # 11, the ionic liquid # 12, the ionic liquid # 13, and the ionic liquid # 14. , Cone / plate type viscometer (manufacturer: Brookfield Engineering Laboratories, Inc., model number: R / S Plus). As a result, the viscosity of ionic liquid # 1 at 26 ° C. was 86.8 mPa · s, the viscosity of ionic liquid # 2 at 26 ° C. was 94.5 mPa · s, and the viscosity of ionic liquid # 3 at 26 ° C. was 28.4 mPa · s. , The viscosity of ionic liquid # 4 at 26 ° C. is 45.7 mPa · s, the viscosity of ionic liquid # 5 at 26 ° C. is 47.0 mPa · s, the viscosity of ionic liquid # 6 at 26 ° C. is 70.3 mPa · s, The viscosity of Liquid # 7 at 26 ° C. is 87.3 mPa · s, the viscosity of Ionic Liquid # 8 at 26 ° C. is 57.9 mPa · s, and the viscosity of Ionic Liquid # 9 at 26 ° C. is 86.7 mPa · s, Ionic Liquid # The viscosity of 10 at 26 ° C. is 71.8 mPa · s, the viscosity of ionic liquid # 11 at 26 ° C. is 94.7 mPa · s, and the viscosity of ionic liquid # 12 at 26 ° C. 64.8mPa · s, the viscosity at 26 ° C. ionic liquid # 13 viscosity at 200mPa · s, 26 ℃ ionic liquid # 14 was 584mPa · s.

(Fabrication of light wavelength conversion element)
In place of the ionic liquid # 1 which is the ionic liquid (C) prepared in the preparation example 1 of the ionic liquid (C), the ionic liquid # 1 which is the ionic liquid (C) prepared in the preparation example 3 of the ionic liquid (C) , Ionic liquid # 2, ionic liquid # 3, ionic liquid # 4, ionic liquid # 5, ionic liquid # 6, ionic liquid # 7, ionic liquid # 8, ionic liquid # 9, ionic liquid # 10, ionic liquid # 11. , 14 types of light wavelength conversion elements were produced by the same procedure as in Example 1 except that the ionic liquid # 12, the ionic liquid # 13, and the ionic liquid # 14 were used.

(Measurement of up-conversion emission intensity of light wavelength conversion element)
Using the above 14 kinds of light wavelength conversion elements, 14 kinds of samples for evaluation of up-conversion emission were manufactured by the same procedure as in Example 1, and subsequently, the up-conversion emission intensity was measured under the same conditions as in Example 1. ..

  Using the up-conversion emission intensity of an up-conversion luminescence evaluation sample prepared using ionic liquid (C) as ionic liquid (C), the other up-conversion luminescence evaluation samples prepared with ionic liquid (C) The effect of the viscosity of the ionic liquid on the upconversion efficiency was examined by relatively standardizing the upconversion emission intensity.

  The 14 types of ionic liquids (C) in Production Example 3 of ionic liquid (C) and the 14 types of samples for evaluation of upconversion luminescence in this example were produced under the same conditions. The upconversion emission intensities of these 14 types of upconversion emission evaluation samples were also measured under the same optical measurement conditions, and all the measurements in this example were performed at an environmental temperature of 26 ± 1 ° C. .. Therefore, it is possible to quantitatively compare the measurement results of the upconversion emission intensity among these 14 types of samples for evaluating the upconversion emission.

  In order to confirm reproducibility, the up-conversion luminescence evaluation sample prepared from the ionic liquid # 13 was tested three times, and the up-conversion luminescence evaluation sample prepared from the ionic liquid # 14 was tested twice. The preparation of the conversion luminescence evaluation sample and the upconversion luminescence intensity measurement were repeated.

  In the graph of FIG. 13, the viscosity at 26 ° C. of the ionic liquids # 1 to # 14, which are the ionic liquids (C), is plotted on the horizontal axis for evaluation of up-conversion emission prepared from the ionic liquid # 2 that is the ionic liquid (C). The vertical axis represents the upconversion emission intensity of all the samples for evaluation of upconversion emission, which is standardized with the upconversion emission intensity of the sample being 1. Further, FIG. 14 shows a graph obtained by enlarging a plot portion of the sample for up-conversion luminescence evaluation prepared from the ionic liquids # 1 to 13 which is the ionic liquid (C) in the graph of FIG. In FIG. 13 and FIG. 14, the plot of each up-conversion emission evaluation sample is shown by the type of ionic liquid used for its production.

  It should be noted that the measured values of the absorbances of the up-conversion emission evaluation samples at the excitation wavelength (632.8 nm) were slightly different from each other, but in order to remove this influence, correction was made to the fluctuations of the measured absorbance values. I went. The values on the vertical axis in FIGS. 13 and 14 are values after this correction.

  From the results of FIGS. 13 and 14, the relative upconversion emission intensity of the light wavelength conversion element (which is proportional to the upconversion quantum efficiency) and the viscosity of the ionic liquid (C) used in the light wavelength conversion element are shown. It was discovered that there was a clear and strong correlation between them. Further, at least in the ranges of the horizontal axes of FIGS. 13 and 14, it is possible to achieve higher upconversion emission intensity (that is, higher upconversion quantum efficiency) by using the ionic liquid (C) having higher viscosity. It was revealed. From this, it became clear for the first time that the viscosity of the ionic liquid used in the light wavelength conversion element is a very important factor controlling efficiency in the design of the light wavelength conversion element.

(Measurement of up-conversion quantum efficiency of optical wavelength conversion element)
In the present example, for the up-conversion emission evaluation sample prepared using the ionic liquid (C), the ionic liquid # 14, the same continuous light laser light emitter as that used in Example 1 was emitted as the excitation light. The optical absorption spectrum and the up-conversion emission were obtained by the same procedure as in Example 3 except that the continuous light laser emission # 1 (wavelength: 632.8 nm, spot diameter: about 0.8 mm, output power: about 28 mW) was irradiated. The spectrum was measured and the up-conversion quantum efficiency (light wavelength conversion efficiency) of the light wavelength conversion element was measured. FIG. 15 shows the measured light absorption spectrum, and FIG. 16 shows the up-conversion emission spectrum. As a result, the up conversion quantum efficiency of the light wavelength conversion element was found to be 15.4%.

[Example 6]
(Fabrication of light wavelength conversion element)
Ionic Liquid # 14 (400 μl) obtained in Production Example 3 of Ionic Liquid (C) in place of Ionic Liquid # 1 (400 μl) which is Ionic Liquid (C) obtained in Production Example 1 of Ionic Liquid (C) Was used instead of a solution of meso-tetraphenyl-tetrabenzoporphyrin palladium in toluene at a concentration of 2 × 10 ⁻⁴ M as the organic photosensitizing molecule (A), and octaethylporphyrin palladium was concentrated in toluene. A solution prepared by dissolving 4 × 10 ⁻⁴ M was used, and 9,10-diphenylanthracene was replaced by a solution prepared by dissolving perylene as an organic luminescent molecule (B) in toluene at a concentration of 4 × 10 ⁻³ M in toluene. A visually homogeneous and transparent liquid as a light wavelength conversion element was obtained in the same manner as in Example 1 except that a solution dissolved therein at a concentration of 4 × 10 ⁻³ M was used. Subsequently, a sample up-conversion for light absorption spectrum measurement and a sample for emission evaluation were prepared by the same procedure as in Example 1, and the light absorption spectrum was measured under the same conditions as in Example 1. The measured light absorption spectrum is shown in FIG.

  Then, the up-conversion emission spectrum was measured using the above-mentioned sample for evaluation of up-conversion emission by the same procedure as in Example 3 except that the light wavelength conversion element produced in this example was used. The measured up-conversion emission spectrum is shown in FIG.

  In addition, the same procedure as in Example 3 was performed except that the upconversion quantum efficiency was measured under the condition of an output power of 30 mW using the above-mentioned sample for evaluation of upconversion emission, and the output power of continuous light laser emission was changed to 20 mW. By the same procedure as in Example 3, the upconversion quantum efficiency under the condition of the output power of 20 mW was measured using the above sample for evaluation of upconversion emission. As a result, it was found that the optical wavelength conversion element manufactured in this example had an upconversion quantum efficiency of 31.3% under an output power of 30 mW and an upconversion quantum efficiency of 29.2% under an output power of 20 mW.

[Example 7]
(Measurement of viscosity of ionic liquid (C))
Ionic liquid (C) produced in Production Example 3 of ionic liquid (C) used in this example, ionic liquid # 1, ionic liquid # 2, ionic liquid # 3, ionic liquid # 4, ionic liquid # 5, the ionic liquid # 9, the ionic liquid # 10, the ionic liquid # 12, the ionic liquid # 13, and the ionic liquid # 14 were measured using a cone / plate viscometer (the same as that used in Example 5). Was measured at 20 ° C.

(Fabrication of light wavelength conversion element)
In place of the ionic liquid # 14 which is the ionic liquid (C) obtained in Preparation Example 2 of the ionic liquid (C), the ionic liquid #C which is the ionic liquid (C) prepared in Preparation Example 3 of the ionic liquid (C) 1, ionic liquid # 2, ionic liquid # 3, ionic liquid # 4, ionic liquid # 5, ionic liquid # 9, ionic liquid # 10, ionic liquid # 12, ionic liquid # 13 and ionic liquid # 14 are used respectively. Except for the above, 10 types of light wavelength conversion elements were produced by the same procedure as in Example 6.

(Measurement of up-conversion emission intensity of light wavelength conversion element)
Using the above 10 kinds of light wavelength conversion elements, 10 kinds of samples for evaluation of up-conversion emission were manufactured by the same procedure as in Example 1, and subsequently, the up-conversion emission intensity was measured under the same conditions as in Example 3. ..

  Using the up-conversion emission intensity of an up-conversion luminescence evaluation sample prepared using ionic liquid (C) as ionic liquid (C), the other up-conversion luminescence evaluation samples prepared with ionic liquid (C) The effect of the viscosity of the ionic liquid on the upconversion efficiency was examined by relatively standardizing the upconversion emission intensity.

  In addition, the measurement of the up-conversion emission intensity of these 10 types of samples for evaluation of up-conversion emission was also performed under the same optical measurement conditions, and all the measurements in this example were performed at an environmental temperature of 20 ± 1 ° C. .. Therefore, it is possible to quantitatively compare the measurement results of the upconversion emission intensity among these 10 types of samples for evaluating the upconversion emission.

  In the graph of FIG. 19, the ionic liquid (C) ionic liquid # 1, ionic liquid # 2, ionic liquid # 3, ionic liquid # 4, ionic liquid # 5, ionic liquid # 9, ionic liquid # 10, ionic liquid # 10. With the viscosities of # 12, ionic liquid # 13, and ionic liquid # 14 at 20 ° C. as the abscissa, the upconversion luminescence intensity of the upconversion luminescence evaluation sample prepared from ionic liquid # 2, which is ionic liquid (C), The vertical axis indicates the upconversion emission intensity of all the samples for evaluation of upconversion emission standardized as 1. In FIG. 19, a plot of each up-conversion emission evaluation sample is shown by the type of ionic liquid used for its production.

  From the results of FIG. 13, FIG. 14, and FIG. 19, the viscosity of the ionic liquid (C) used in the light wavelength conversion element regardless of the types of the organic photosensitizing molecule (A) and the organic light emitting molecule (B). It has been found that the relative upconversion emission intensity of the light wavelength conversion element (which is proportional to the upconversion quantum efficiency) increases with increasing.

1 Solar Cell Layer 2 Transparent Back Electrode 3 Transparent Insulation Film 4 Up-Conversion Layer 5 Light Reflecting Film 7 Light-Receiving Surface Electrode 8 Glass Channel 9 Gas 10 Water with Photocatalyst 11 Mechanical Support

Claims (9)

An organic photosensitizing molecule (A) and an organic luminescent molecule (B), which are combinations showing a triplet-triplet annihilation process, are dissolved and / or dispersed in an ionic liquid (C) and are visually homogeneous and transparent. A light wavelength conversion element,
The absorption maximum wavelength of the organic photosensitizing molecule (A) is in the range of 500 to 700 nm,
The ionic liquid (C) becomes a viscosity at 26 ° C. is 45.7mPa · s or more, and, when washing the ionic liquid (C) in ultrapure water 9 times the volume of its water after washing optical wavelength conversion elements, characterized in that the pH of greater than 5.   The light wavelength conversion element according to claim 1, wherein the organic photosensitizing molecule (A) contains no metal in its structure. The organic photosensitizing molecule (A) has the following general formula (1)

(In the above formula, R ^{1 to} R ⁵ each independently represent an arbitrary substituent containing a hydrogen atom, and adjacent substituents (a pair of R ¹ and R ² , a pair of R ² and R ⁴ , a R ^{2 1} and R ³ pair, R ³ and R ⁴ pair) may be linked to each other to form a 5-membered ring or 6-membered ring having an optional substituent containing a hydrogen atom, and R ⁶ is Represents a halogen atom, an alkyl group having 1 to 5 carbon atoms which may have a substituent, or an alkoxyl group having 1 to 5 carbon atoms which may have a substituent)
The light wavelength conversion element according to claim 1 or 2, which is a compound represented by: R ^{1 to} R ⁵ in the general formula (1) each independently have a hydrogen atom, a halogen atom, an optionally substituted aliphatic hydrocarbon group having 1 to 4 carbon atoms, or a substituent. A phenyl group which may have a substituent, a phenoxy group which may have a substituent, a thienyl group which may have a substituent, a thienoxy group which may have a substituent, the following formula (2)

A 2-carboxyl ethenyl group represented by, or the following formula (3)

The light wavelength conversion element according to claim 3, which is a 2-carboxyl-2-cyanoethenyl group represented by: The organic photosensitizing molecule (A) has the following general formula (4)

(In the formula, R ¹ and R ⁴ each independently represent an alkyl group having 1 to 3 carbon atoms which may have a substituent, and R ² and R ³ are each independently hydrogen atom, bromine atom, or iodine. Represents an atom, at least one of R ² and R ³ is a bromine atom or an iodine atom, and R ⁵ represents a phenyl group which may have a substituent)
The light wavelength conversion element according to any one of claims 1 to 4, which is a compound represented by the formula (5).   A solar cell using the light wavelength conversion element according to claim 1.   A photocatalyst using the light wavelength conversion element according to claim 1.   A photocatalytic hydrogen / oxygen generator using the light wavelength conversion element according to claim 1. An optical up-conversion filter that converts light into light of shorter wavelength,
An optical wavelength conversion element according to any one of claims 1 to 5,
With cells,
An optical up-conversion filter, wherein the light wavelength conversion element is enclosed in the cell.

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