Optical wavelength conversion medium and composition for forming an optical wavelength conversion medium

Abstract

To provide a light wavelength conversion medium excellent in emission intensity and durability, and also a light wavelength conversion medium-forming composition used for forming that medium.SOLUTION: A conversion medium according to an embodiment comprises a rare earth phosphor comprising a rare earth ion and a nonionic ligand, a nonionic compound substitutable for the nonionic ligand, and a polymer or a solvent.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The embodiments relate to a light wavelength conversion medium with excellent luminescence intensity and durability, and a light wavelength conversion medium forming composition used in its formation. [Background technology]

[0002] Rare-earth phosphors, characterized by their absorption wavelength in the UV region and sharp emission spectra, are expected to be used in optical wavelength conversion media such as light-emitting devices, sensors, security media, and decorative items. For rare-earth phosphors to be applied as optical wavelength conversion media, excellent emission intensity, solubility in polymers and solvents, and durability are desirable. The search for phosphors that simultaneously satisfy these characteristics is currently ongoing. [Overview of the project] [Problems that the invention aims to solve]

[0003] Our investigations have shown that the properties of a light wavelength conversion medium change not only depending on the properties of the phosphor used, but also on the compounds that coexist with that phosphor. The embodiment aims to realize a light wavelength conversion medium with excellent properties by identifying the compounds that coexist with the phosphor in the medium. [Means for solving the problem]

[0004] The optical wavelength conversion medium according to the embodiment is Rare earth phosphors containing rare earth ions and nonionic ligands, A nonionic compound that can be substituted with the aforementioned nonionic ligand, polymer or solvent and It includes.

[0005] Furthermore, the optical wavelength conversion medium formation composition according to the embodiment is Rare earth phosphors containing rare earth ions and nonionic ligands, A nonionic compound that can be substituted with the aforementioned nonionic ligand, polymer or solvent and It includes. [Effects of the Invention]

[0006] According to the embodiment, a light wavelength conversion medium with excellent luminescence intensity and durability, and a composition for forming such a light wavelength conversion medium are provided. [Brief explanation of the drawing]

[0007] [Figure 1] A graph comparing the emission intensity of the optical wavelength conversion media in Example 1 and Comparative Example 1. [Figure 2] Action spectra of the optical wavelength conversion medium according to Example 1 and Comparative Example 1. [Figure 3] A graph showing the durability of the optical wavelength conversion medium according to the embodiment. [Modes for carrying out the invention]

[0008] The embodiments of the present invention will be described in detail below.

[0009] <Light wavelength conversion medium> The optical wavelength conversion medium according to this embodiment is one in which, when irradiated with ultraviolet light, the rare-earth phosphor contained in the medium absorbs ultraviolet light and emits light of a different wavelength than the absorbed light. The rare-earth phosphor is colorless and transparent under indoor light, and emits strong light under ultraviolet or near-ultraviolet light, making it difficult to see under normal conditions, but it becomes visible when irradiated with specific light because it emits light. An optical wavelength conversion medium containing such a phosphor can be used as a security medium by using it for watermarking on certificates and securities. For example, if a barcode is formed using an optical wavelength conversion medium, it becomes difficult to even detect the presence of the barcode under visible light, thus achieving a higher level of security.

[0010] Such optical wavelength conversion media generally include a phosphor and a polymer. In contrast, the optical wavelength conversion media according to the embodiment is A rare earth phosphor containing rare earth ions and nonionic ligands, a nonionic compound capable of substituting the nonionic ligand, a polymer or a solvent is included. This medium may be a molded product of the mixture containing each of the above components, may be formed as a film on an arbitrary plate-like substrate, or may be impregnated in a fibrous substrate.

[0011] The light wavelength conversion medium according to an embodiment exists in a state where the rare earth phosphor (hereinafter sometimes simply referred to as phosphor) and the nonionic compound are dissolved or dispersed in the polymer or the solvent. The molecule of the phosphor contains a nonionic compound as a ligand. Although the phosphor is basically a stable compound, ligand detachment may occur in a state dissolved in a polymer or a solvent, and when a nonionic compound having a structure similar to the nonionic ligand exists in the vicinity of the phosphor, they can substitute each other. Hereinafter, these phosphors, nonionic compounds, and polymers will be described.

[0012] <Rare earth phosphor> The rare earth phosphor according to an embodiment contains rare earth ions and nonionic ligands. This rare earth phosphor is a phosphor that absorbs light and emits light. Specifically, it is a phosphor that absorbs ultraviolet light, near-ultraviolet light region (400 to 430 nm), and blue light (near 464 nm, corresponding to the F0→D2 transition by Eu(III) ions) and emits light. 7 F0→ 5 D2 transition).

[0013] In an embodiment, the rare earth ions can be appropriately selected to generate fluorescence having a wavelength according to the application, but are preferably lanthanoid ions. More specifically, europium(III) ions or terbium(III) ions are preferred, and europium(III) ions are particularly preferred in order to realize a phosphor having a large spectrum in the red region and excellent color rendering properties.

[0014] Such phosphors containing rare earth ions include a counterion (anion) that ionically bonds to the rare earth ion and a nonionic ligand that forms a coordinate bond.

[0015] Nonionic ligands are compounds that have unpaired electrons and do not produce cations or anions when dissolved in a medium such as water. Such nonionic ligands are preferably selected from the group consisting of phosphine oxide compounds, sulfoxide compounds, and amine compounds. These compounds contain unpaired electrons in their structure, such as P=O bonds and S=O bonds, which form coordinate bonds with rare earth ions. Since rare earth ions have multiple coordination sites, compounds containing multiple bonds with these unpaired electrons are also preferably used. Such compounds bind to rare earth ions as bidentate ligands.

[0016] Specifically, nonionic ligands represented by the following formulas (L-1-1) to (L-3-2) are preferred. [ka] Here, R 1 Each of these is independently a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group, with two R groups bonded to one phosphorus atom, a sulfur atom, or a nitrogen atom. 1 These may bond to each other to form an alicyclic or aromatic ring structure. R 2 This is a substituted or unsubstituted alkylene group or a substituted or unsubstituted arylene group.

[0017] Here, alkyl groups may consist only of carbon and hydrogen, or they may include substituents containing oxygen, nitrogen, or sulfur, such as hydroxyl groups or amino groups. In embodiments, aryl groups may also include elements such as nitrogen or sulfur as constituent elements of the aromatic ring, such as pyridyl groups or thienyl groups, or they may include substituents containing oxygen, nitrogen, or sulfur, such as hydroxyl groups or amino groups.

[0018] R 1 is an alkyl group having 3 to 10 carbon atoms, a fluoroalkyl group having 3 to 10 carbon atoms, an aryl group having 5 to 20 carbon atoms, a fluoroaryl group having 5 to 20 carbon atoms, an alkylaryl group having 6 to 20 carbon atoms, an alkoxyaryl group having 6 to 20 carbon atoms, a heteroaryl group having 5 to 20 carbon atoms, a fluoroaryl group having 6 to 20 carbon atoms and the like are preferable, an alkyl group having 4 to 8 carbon atoms, a fluoroalkyl group having 4 to 8 carbon atoms, an aryl group having 6 to 10 carbon atoms, a fluoroaryl group having 6 to 10 carbon atoms, an alkylaryl group having 7 to 12 carbon atoms, an alkoxyaryl group having 7 to 12 carbon atoms, a heteroaryl group having 6 to 10 carbon atoms, a fluoroaryl group having 6 to 10 carbon atoms and the like are more preferable. Further, at least one R 1 is preferably a substituted phenyl group having a substituent at the ortho position. By having such an ortho-substituted phenyl group, the durability of the phosphor is improved. In particular, it is preferable that all R 1 are ortho-substituted phenyl groups.

[0019] R 2 is preferably an alkylene group having 2 to 8 carbon atoms or an arylene group having 6 to 15 carbon atoms. Incidentally, the number of atoms between two phosphorus atoms, two sulfur atoms, and two nitrogen atoms of R 2 is preferably 2 to 5, and is typically an alkylene group having 3 to 5 carbon atoms.

[0020] R 1 and R 2 may have a linear, branched, or cyclic structure. Further, any one of R 1 is R 2 or another R 1It may bond with a phosphorus atom, a nitrogen atom, or a heteroalicyclic or heteroaromatic ring containing a nitrogen atom.

[0021] Of these, ligands containing phosphine oxide (L-1-1) to (L-1-4) are preferred, and diphosphine dioxide ligand (L-1-2) or tetraphosphine oxide (L-1-3) or (L-1-4) are more preferred.

[0022] Furthermore, (L-1-2), (L-2-2), and (L-3-2) are preferably asymmetric in shape. For example, in (L-1-2), asymmetry occurs when the combinations of substituents bonded to each of the two phosphorus atoms are mutually different. When a bidentate ligand containing two unpaired electrons is asymmetric in shape, the ligand field becomes asymmetric, and the quantum yield increases. Since the luminescence intensity of a phosphor is proportional to the product of the quantum yield and the absorption coefficient, a higher quantum yield results in a higher luminescence intensity. Also, when a diphosphine dioxide ligand is asymmetric, its solubility in solvents tends to increase. To make a bidentate ligand asymmetric, it is possible to combine aliphatic hydrocarbon groups with different numbers of carbon atoms, for example, but to increase the distortion of the ligand field, it is preferable to achieve asymmetry by combining aliphatic hydrocarbon groups and aromatic hydrocarbon groups. For example, in (L-1-2), it is preferable that at least one aliphatic hydrocarbon group is bonded to one of the two phosphorus atoms and at least one aromatic hydrocarbon group is bonded to the other phosphorus atom, and it is particularly preferable that two aliphatic hydrocarbon groups are bonded to one phosphorus atom and two aromatic hydrocarbon groups are bonded to the other.

[0023] In the embodiment, the following are examples of preferred nonionic ligands. [ka]

[0024] [ka]

[0025] [ka]

[0026] [ka]

[0027] [ka]

[0028] [ka]

[0029] [ka]

[0030] [ka]

[0031] Furthermore, the rare-earth phosphor contains an arbitrary anion as a counterion. This anion is not particularly limited and may be a halogen ion or acid ion derived from the rare-earth metal salt that is the raw material for the phosphor, or it may be a specific anion used to improve the properties of the phosphor.

[0032] One anion used to improve the properties of a phosphor is a β-diketone ligand. The β-diketone ligand can be arbitrarily selected from those commonly known as phosphor ligands. This β-diketone ligand acts as a counterion to the cation rare-earth ions and also contributes to the formation of the phosphor's ligand field. Furthermore, the rare-earth phosphor according to this embodiment can achieve higher durability when it contains a specific β-diketone ligand.

[0033] A β-diketone ligand is an ionic ligand formed by the removal of one hydrogen atom from a β-diketone compound. β-diketone compounds exhibit keto-enol tautomorphism and can be represented, for example, by the following formula (K). [ka] Here, R 3 Each of these is independently a substituted or unsubstituted alkyl group and a substituted or unsubstituted aryl group, and is preferably a halogen-substituted alkyl group. 3 The C1-C10 alkyl group, the C1-C10 halogenated alkyl group, the phenyl group, the C7-C10 alkylphenyl group, or the C7-C10 halogenated alkylphenyl group are preferred. 3 Of these, fluoroalkyl groups having 1 to 10 carbon atoms are preferred, and fluoroalkyl groups having 1 to 4 carbon atoms are more preferred.

[0034] In the embodiment, the phosphor is preferably having a β-diketone ligand, the β-diketone ligand being an ionic ligand obtained by removing one hydrogen atom from the above-mentioned β-diketone compound.

[0035] In the embodiment, a β-diketone ligand having a halogenated hydrocarbon group is preferable because it results in higher emission intensity. This is because the electron-withdrawing nature of the halogenated hydrocarbon group connects the excited triplet state of the β-diketone ligand with the excited state of the rare earth(III) ion. 5 D0, 5 This is because the energy difference (ΔE) at the D1 level becomes smaller, increasing the energy transfer efficiency from the ligand to the rare earth (III) ion. This linking group is typically bonded to the 1- and / or 3-position of the β-diketone ligand skeleton. Furthermore, β-diketone ligands with an asymmetric shape tend to exhibit higher emission intensity.

[0036] Examples of β-diketone compounds that serve as precursors to such β-diketone ligands include the following: [ka]

[0037] The phosphor according to the embodiment preferably contains a β-diketone ligand as a counterion for a rare earth ion, but may also contain other anions as counterions. Examples of such anions include halogen ions, hydroxyl ions, and carboxylate ions.

[0038] The rare earth phosphor used in the embodiment preferably contains the rare earth ions, nonionic ligands, and ionic ligands described above, and any combination of components may be used as needed. Of these, the phosphor represented by the following formula (1) is preferred. [ka] (In the formula, Each Ar is an independently independent aryl group. Each R is an alkyl group independently. R F Each of these is independently a halogenated hydrocarbon group, n is an integer between 3 and 5. p is an integer of 1 or 2, q is an integer between 1 and 3. M is a rare earth ion, X does not exist when q is 3, and when q is 1 or 2, it is an anion with a valence of 3-q.

[0039] In formula (1), the two aryl groups Ar may be the same or different. The aryl group is not limited, but from the viewpoint of solubility and durability of the phosphor, the number of carbon atoms in the aryl group is preferably 5 to 20, and more preferably 5 to 12. The aryl group may contain substituents such as hydroxyl groups and alkoxy groups, and may also contain heteroatoms in the ring, as long as it does not impair the effects of the embodiment. More specifically, the aryl group is preferably phenyl, 2-methylphenyl, 1-ethoxyphenyl, naphthyl, or thienyl, and more preferably phenyl. If phenyl has substituents, the solubility tends to be higher if the substituent is at the 2 position. Alternatively, the two Ar groups may bond to each other to form a ring structure containing a phosphorus atom. Specifically, a structure can be formed in which phenylene is bonded to one phosphorus atom via two hydrocarbon chains.

[0040] In formula (1), the two alkyl groups R may be the same or different. The alkyl group is not limited, but from the viewpoint of solubility and durability of the phosphor, the number of carbon atoms in the alkyl group is preferably 3 to 10, and more preferably 4 to 8. The alkyl group may contain substituents such as hydroxyl groups and alkoxy groups, as long as it does not impair the effects of the embodiment. More specifically, examples of alkyl groups include n-butyl, 1-methylpropyl, t-butyl, n-hexyl, 2-ethylbutyl, and n-octyl. The embodiment also includes cases in which the two R groups bond to each other to form a ring structure containing a phosphorus atom. Specifically, an alkylene chain, particularly an alkylene chain with 3 to 10 carbon atoms, can form a heterocyclic structure bonded to one phosphorus atom.

[0041] In equation (1), the two phosphorus atoms are linked by an alkylene chain with n carbon atoms. n is an integer between 3 and 5, and is preferably 4. High durability can be achieved by keeping n within this range. If n is 2 or less, the positional relationship between the two phosphine oxides is limited, which weakens the coordinate bond of the diphosphine dioxide ligand and reduces the luminescence intensity. On the other hand, if n exceeds 5, one diphosphine dioxide ligand may form a dinuclear complex linked to two rare earth ions, which can reduce solubility.

[0042] In formula (1), the β-diketone ligand has two halogenated hydrocarbon groups R at positions 1 and 3. F It has the following characteristics. Because the β-diketone ligand has a halogenated hydrocarbon group, when the phosphor absorbs light, the energy efficiency from the excited ligand to the rare earth ion is increased, thus enabling high emission intensity. The number of carbon atoms in the halogenated hydrocarbon group is not limited, but in order to achieve high solubility, it is preferable that the number of carbon atoms be 8 or less, and more preferably 1 to 3. Specifically, the halogenated hydrocarbon group is preferably a perfluoroalkyl group, and is particularly preferably CF3, C2F5, or C3F7. Also, two R F The two Rs may be the same or different, but the two Rs F The difference in these factors leads to asymmetric β-diketone ligands, resulting in increased distortion of the ligand field and higher emission intensity, which is desirable.

[0043] It is generally known that in phosphors, equipping the two substituents of a β-diketone ligand with perfluoroalkyl groups improves light resistance and quantum yield. However, it is also known that such a structure reduces solubility in polymers and solvents, leading to decreased transparency of compositions containing the phosphor (phosphors dissolved in polymers or solvents). Reduced transparency of the composition is particularly disadvantageous when applied to security media. In this embodiment, by structuring the diphosphine dioxide ligand in a specific way, it is possible to maintain high solubility while also ensuring the transparency of the composition.

[0044] The phosphor represented by formula (1) has p diphosphine dioxide ligands and q β-diketone ligands, where p is an integer between 1 and 2, and q is an integer between 1 and 3. Most typically, it has one diphosphine dioxide ligand (p=1) and three β-diketone ligands (q=3), and the phosphor forms an 8-coordinate structure. In this case, the charge of the rare earth ion is canceled out by the three β-diketone ligands, so there is no counterion X.

[0045] It is also possible to have two or fewer β-diketone ligands. In this case, generally two diphosphine dioxide ligands can coordinate, but a counterion X is required to cancel out the overall charge of the phosphor. In this case, the counterion may be one divalent anion or two monovalent anions.

[0046] In the embodiment, the phosphor may contain ligands other than diphosphine dioxide ligands or β-diketone ligands, as long as the effects of the embodiment are not impaired.

[0047] Specific examples of phosphors that can be used in the embodiments include, for example, (1-1) to (1-58) below. Of these, (1-1) to (1 to 16) and (1-48) to (1-58) are preferred, and (1-1) to (1 to 11) are more preferred.

[0048] [ka]

[0049] [ka]

[0050] [ka]

[0051] [ka]

[0052] [ka]

[0053] [ka]

[0054] [ka]

[0055] [ka]

[0056] <Nonionic compounds> The optical wavelength conversion medium according to this embodiment further contains a nonionic compound that can substitute for the nonionic ligand contained in the phosphor. As a result, even if a nonionic ligand is detached from the phosphor molecule, a substitute nonionic compound is present near the rare earth ions, so the ligand field of the phosphor is maintained, and the properties of the phosphor are maintained at a high level. Since the nonionic compound can substitute for the nonionic ligand that constitutes the phosphor, it may not be possible to clearly distinguish between the nonionic ligand and the nonionic compound. However, even in that case, the total amount of nonionic ligand and nonionic compound must be constant, and this total amount must exceed the stoichiometric amount based on the rare earth ions contained in the optical conversion medium.

[0057] Such nonionic compounds can be selected from the same nonionic ligands as described above. The nonionic ligand and the nonionic compound contained in the phosphor contained in the photoconversion medium may be the same or different. Alternatively, two or more different nonionic compounds may be mixed and used. However, since the properties of the phosphor, such as the emission wavelength, may change when ligand exchange occurs, it is preferable that the nonionic ligand and the nonionic compound are the same. On the other hand, cost reduction may be possible by combining a nonionic compound different from the nonionic ligand contained in the complex. For example, if the complex uses diphosphine as the nonionic ligand, Ji When oxides are present, using monophosphine oxide as a nonionic compound allows for the production of photoconversion media at a lower cost.

[0058] The amount of nonionic compound in the photoconversion medium according to the embodiment is not particularly limited, as long as it contains nonionic compounds, but it is preferable to contain 0.01 to 100 molar equivalents, and more preferably 0.1 to 50 molar equivalents, relative to rare earth ions. Taking the case where the phosphor is represented by formula (1) as an example, the phosphor molecule of formula (1) contains p moles of nonionic ligand (p equivalents relative to rare earth ions), so the total amount of nonionic ligand and nonionic compound contained in the photoconversion medium is preferably p + 0.01 to p + 100 moles. Typically, it is preferable that p in formula (1) is 1, so the total amount of nonionic ligand and nonionic compound contained in the photoconversion medium is preferably 1.01 to 101 equivalents.

[0059] Furthermore, for ligand exchange, it is preferable that the distance between the rare earth ions and the nonionic ligands be short. For this reason, a high concentration of rare earth ions in the medium is preferable, but if the concentration of rare earth ions, i.e., the concentration of the phosphor, is too high, there is a possibility of a decrease in luminescence intensity due to concentration quenching. For this reason, the rare earth ion content in the medium is preferably 1 × 10⁻⁶ -7 A concentration of approximately 1 mol / L is preferable.

[0060] <Polymer or solvent> In the embodiment, the light conversion medium contains a phosphor and a nonionic compound dissolved or dispersed in a polymer or solvent. The polymer or solvent used here is preferably highly transparent in order to efficiently transfer the light incident on the light conversion medium to the phosphor and to efficiently release the light emitted from the phosphor to the outside.

[0061] Examples of such polymers include polyacrylic acid, polymethacrylic acid, polystyrene, polycarbonate, polyester, polyolefin, polyvinyl chloride, polyvinyl acetate, and copolymers thereof. Among these polymers, polymethyl methacrylate, polycarbonate, polystyrene, acrylic, diethylene glycol bisallyl carbonate, poly-4-methylpentene-1, alicyclic polyolefin resins, alicyclic acrylic resins, and copolymers thereof are preferably used.

[0062] Furthermore, phosphors containing phosphine oxide ligands and β-diketone ligands are stable even under strongly acidic conditions, and therefore tend to maintain high durability even when dispersed or dissolved in acidic polymers. Thus, acidic polymers can also be used as polymers. Examples of such acidic polymers include polymers having carboxyl groups or sulfonic acid groups, such as alkyd polymers like linseed oil-modified maleic acid alkyd polymers and acrylic-modified alkyd polymers, as well as polyacrylic acid and polystyrene sulfonic acid. Acidic cation exchange resins can also be used as polymers.

[0063] Furthermore, preferred solvents include a) esters, such as ethyl acetate and butyl acetate; b) alcohols, such as methyl alcohol, ethyl alcohol, and propyl alcohol; c) glycols, such as ethylene glycol and propylene glycol; d) ketones, such as acetone and dimethyl ketone; e) sulfoxides, such as dimethyl sulfoxide; f) alkanes, such as hexane and octane; g) halogenated alkanes, such as perfluorocyclohexane and carbon tetrachloride; and mixtures thereof.

[0064] <Composition for forming a light wavelength conversion medium and a method for manufacturing a light wavelength conversion medium using the same> The optical wavelength conversion medium according to the embodiment comprises the aforementioned phosphor, nonionic compound, and polymer. The composition for forming this medium comprises each component and, optionally, other solvents or additives.

[0065] One embodiment of a composition for forming a light wavelength conversion medium (hereinafter sometimes simply referred to as "the composition") includes a solvent in addition to the phosphor, nonionic compound, and polymer described above. As the solvent, a suitable one can be selected from generally known organic solvents. Specifically, examples include esters such as ethyl acetate, aliphatic fluorinated hydrocarbons such as perfluoropentane, aromatic hydrocarbons such as toluene or xylene, and alcohols such as ethanol, methanol, isopropanol, and butanol. Such a composition can be applied to a substrate or impregnated into a fibrous support, and then the solvent is evaporated by heating or other means to form a light wavelength conversion medium supported on the substrate or support. Any substrate can be selected, such as paper, plastic, cloth, nonwoven fabric, or ceramics. Furthermore, the application method is not particularly limited. When the light wavelength conversion medium is used as a security medium, it is common to form an identifiable mark by drawing or transferring a certain shape onto the substrate by printing or other means.

[0066] Furthermore, the composition may include the aforementioned phosphor, nonionic compound, and polymer, but may not contain a solvent. If a thermosetting polymer, which is liquid at room temperature and hardens upon heating, is used as the polymer, a light wavelength conversion medium can be formed by heating after coating or impregnation. Alternatively, if a thermoplastic polymer, which is liquid at high temperatures and hardens at room temperature, is used as the polymer, a light wavelength conversion medium can be formed by coating or impregnating with a high-temperature composition and then cooling it. In addition, a crosslinking agent or polymerization initiator can be combined with the composition and hardened after coating or impregnation to form a light wavelength conversion medium.

[0067] Furthermore, by molding the composition on a substrate or inside a container and then peeling it off, a molded body of a light wavelength conversion medium (fluorescent film) without a support can be obtained.

[0068] When preparing these compositions, it is common practice to blend the rare earth complex and the additional nonionic compound with a polymer or the like. However, instead, a salt containing rare earth ions and an excess amount of the nonionic compound may be blended with a polymer or the like to form a rare earth phosphor in the composition.

[0069] The composition may optionally contain additives such as surfactants, defoamers, preservatives, and pH adjusters. Furthermore, when the composition according to the embodiment is used as a security medium, it is preferable that it is colorless and transparent, as low visibility under visible light is desirable. However, dyes and pigments may be combined as needed. Additionally, to maintain the stability of the rare-earth phosphor, the rare-earth phosphor and nonionic compound may be encapsulated in microcapsules or the like before formulation.

[0070] The following describes examples of embodiments, but the embodiments are not limited thereto.

[0071] <Example 1> A composition was prepared by dissolving the rare earth phosphors shown in formulas (1-3) in an acrylic resin to a concentration of 10% by mass, and then adding 1 molar equivalent of the diphosphine dioxide compound shown in formula (A). This composition was molded and then cured to create a fluorescent film. The excitation spectrum and action spectrum of the obtained fluorescent film were measured. The results are shown in Figures 1 and 2.

[0072] <Comparative Example 1> A fluorescent film was prepared by preparing a composition in the same manner as in Example 1, except that the diphosphine dioxide compound shown in formula (A) was not included. The action spectrum of the obtained fluorescent film was measured. The results are shown in Figures 1 and 2.

[0073] <Rating> Figures 1 and 2 show that the fluorescent film according to Example 1 has a higher emission intensity and a higher quantum yield on the short-wavelength ultraviolet side compared to the medium of Comparative Example 1.

[0074] [ka]

[0075] <Example 2> A fluorescent film was prepared by dissolving the rare earth phosphors shown in formula (1-4) in an acrylic resin to a concentration of 10% by mass, and then adding 1 molar equivalent of the diphosphine dioxide compound shown in formula (A). This fluorescent film was irradiated with 70,000 lux of light, and the emission spectral intensity was measured at irradiation times of 0, 24, 48, and 168 hours. The results are shown in Figure 3. Figure 3 shows the relative values ​​with the emission spectral intensity at 0 hours of light irradiation set to 1.

[0076] <Comparative Example 2> A fluorescent film was prepared by dissolving the rare earth phosphor shown in formula (1-13) in an acrylic resin to a concentration of 10% by mass. The emission spectral intensity of this fluorescent film was measured for varying light irradiation times, similar to the procedure in Example 2. The results are shown in Figure 3.

[0077] [ka]

[0078] <Durability evaluation> The medium in Comparative Example 2, which does not contain a nonionic compound, tends to have poor durability and a rapid degradation of luminescence intensity upon light irradiation.

[0079] <Transparency Assessment> The transparency of the fluorescent films of Examples 1 and 2 and Comparative Examples 1 and 2 was visually evaluated. The fluorescent films of Examples 1 and 2 were transparent, and no turbidity was observed. On the other hand, the fluorescent film of Comparative Example 1 showed slight turbidity, and the fluorescent film of Comparative Example 2 was more turbid than that of Comparative Example 1. This difference in transparency is thought to be dependent on solubility, and it can be seen that the solubility of the phosphor tends to improve when there is an excess of phosphine oxide.

[0080] <Evaluation of variation in luminescence intensity within a plane> In fluorescent films, if the solubility of the phosphor is insufficient, the variation in emission intensity within the film becomes large when the fluorescent film is irradiated with excitation light under the same conditions. In Examples 1-2 and Comparative Examples 1-2, a 3 cm square region was created within each fluorescent film, and this region was divided into nine 1 cm square regions. Each 1 cm square region was excited with light of a wavelength of 330 nm, and the spectral area of ​​the emission spectrum was measured to determine the variation in emission intensity of each region. The variations in the fluorescent films of Examples 1-2 and Comparative Examples 1-2 were less than 3%, less than 3%, approximately 10%, and approximately 30%, respectively.

[0081] As described above, several embodiments have been explained, but these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, and modifications are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

Claims

1. Rare earth phosphors containing rare earth ions and nonionic ligands, A nonionic compound that can be substituted with the aforementioned nonionic ligand, polymer or solvent and A light wavelength conversion medium containing, The nonionic ligand and the nonionic compound are selected from the group consisting of phosphine oxide compounds, sulfoxide compounds, and amine compounds. The rare earth phosphor is a complex having a structure in which the nonionic ligand is coordinately bonded to the rare earth ion. A light wavelength conversion medium in which the nonionic compound and the nonionic ligand have the same structure.

2. The nonionic ligand and the nonionic compound are of formulas (L-1-1) to (L-3-2): 【Chemistry 1】 (In the formula, R １ However, each is independently a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group, with two R groups bonded to one phosphorus atom, a sulfur atom, or a nitrogen atom. １ These may bond to each other to form an alicyclic or aromatic ring structure. R ２ (However, it is a substituted or unsubstituted alkylene group or a substituted or unsubstituted arylene group.) A light wavelength conversion medium according to claim 1, represented by any one of the following.

3. The optical wavelength conversion medium according to claim 2, wherein the nonionic ligand and the nonionic compound are represented by any of the formulas (L-1-1) to (L-1-4).

4. R １ However, each independently, Alkyl alkyl groups having 3 to 10 carbon atoms, Fluoroalkyl groups having 3 to 10 carbon atoms, Aryl groups having 5 to 20 carbon atoms, Fluoroaryl groups with 5 to 20 carbon atoms Alkylaryl groups having 6 to 20 carbon atoms, Alkoxyaryl groups with 6 to 20 carbon atoms Heteroaryl groups having 5 to 20 carbon atoms, and A light wavelength conversion medium according to claim 2 or 3, selected from the group consisting of fluoroaryl groups having 6 to 20 carbon atoms.

5. R １ The optical wavelength conversion medium according to any one of claims 2 to 4, wherein at least one of the members is a substituted phenyl group having a substituent in the ortho position.

6. The optical wavelength conversion medium according to any one of claims 1 to 5, wherein the nonionic ligand and the nonionic compound are diphosphine dioxides.

7. The optical wavelength conversion medium according to claim 6, wherein the nonionic ligand is a diphosphine dioxide in which the combinations of substituents bonded to each of the two phosphorus atoms are mutually different.

8. The optical wavelength conversion medium according to any one of claims 1 to 5, wherein the nonionic ligand and the nonionic compound are tetraphosphine tetraoxide.

9. The optical wavelength conversion medium according to any one of claims 1 to 8, wherein the rare earth ion is europium(III) ion or terbium(III) ion.

10. The optical wavelength conversion medium according to any one of claims 1 to 9, wherein the rare earth phosphor comprises a β-diketone ligand.

11. The optical wavelength conversion medium according to claim 10, wherein the β-diketone ligand comprises a halogenated hydrocarbon group.

12. The optical wavelength conversion medium according to any one of claims 1 to 11, wherein the polymer is selected from the group consisting of polyacrylic acid, polymethacrylic acid, polystyrene, polycarbonate, polyester, polyolefin, polyvinyl chloride, polyvinyl acetate, and copolymers thereof.

13. The optical wavelength conversion medium according to any one of claims 1 to 12, wherein the polymer is selected from the group consisting of polymethyl methacrylate, polycarbonate, polystyrene, acrylic, diethylene glycol bisallyl carbonate, poly-4-methylpentene-1, alicyclic polyolefin resin, alicyclic acrylic resin, and copolymers thereof.

14. The optical wavelength conversion medium according to any one of claims 1 to 13, wherein the solvent is selected from the group consisting of esters, alcohols, glycols, ketones, sulfoxides, alkanes, halogenated alkanes, and mixtures thereof.

15. The optical wavelength conversion medium according to any one of claims 1 to 14, comprising the nonionic compound in an amount of 0.01 to 100 molar equivalents relative to the rare earth ions.

16. The content of the aforementioned rare earth ions is 1 × 10⁻⁶ relative to the total amount of the light wavelength conversion medium. －７ A light wavelength conversion medium according to any one of claims 1 to 15, wherein the concentration is ~1 mol / l.

17. Rare earth phosphors containing rare earth ions and nonionic ligands, A nonionic compound that can be substituted with the aforementioned nonionic ligand, polymer or solvent and A composition for forming a light wavelength conversion medium, comprising: The nonionic ligand and the nonionic compound are selected from the group consisting of phosphine oxide compounds, sulfoxide compounds, and amine compounds. The rare earth phosphor is a complex having a structure in which the nonionic ligand is bonded to the rare earth ion. A composition for forming an optical wavelength conversion medium, wherein the nonionic compound and the nonionic ligand have the same structure.

18. Rare earth phosphors containing rare earth ions and nonionic ligands, A nonionic compound that can be substituted with the aforementioned nonionic ligand, polymer or solvent and A light wavelength conversion medium comprising the rare earth phosphor, wherein the rare earth phosphor is of formula (1) 【Chemistry 2】 (In the formula, Each Ar is an independently independent aryl group. Each R is independently an alkyl group. R Ｆ Each of these is independently a halogenated hydrocarbon group, n is an integer between 3 and 5. p is an integer of 1 or 2, q is an integer between 1 and 3. M is a rare earth ion, X does not exist when q is 3, and when q is 1 or 2, it is an anion with a valence of 3-q. A medium for converting optical wavelengths, represented by the symbol.

19. Rare earth phosphors containing rare earth ions and nonionic ligands, A nonionic compound that can be substituted with the aforementioned nonionic ligand, polymer and Includes, The nonionic ligand and the nonionic compound are selected from the group consisting of phosphine oxide compounds, sulfoxide compounds, and amine compounds. The rare earth phosphor is a complex having a structure in which the nonionic ligand is coordinately bonded to the rare earth ion. A composition for forming a light wavelength conversion medium is prepared in which the nonionic compound and the nonionic ligand have the same structure. A method for producing a light wavelength conversion medium, comprising curing the aforementioned composition.

20. A method for producing an optical wavelength conversion medium according to claim 19, wherein the composition is prepared by blending the salt containing the rare earth ions and an excess amount of the nonionic compound with the polymer or the like.

21. A method for producing an optical wavelength conversion medium according to claim 19 or 20, wherein the composition is applied to a substrate or impregnated into a fibrous support and then cured.

22. A method for producing a light wavelength conversion medium according to any one of claims 19 to 21, wherein the composition further contains a solvent, and the composition is cured by evaporating the solvent by heating.

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