Phosphor, Light-Emitting Device, and Radiation Detector

Abstract

Provided is a phosphor that has a crystal structure belonging to a space group Cmcm, and that has a composition represented by formula (1).　(1): AaBbCcDd (In formula (1), A contains at least one of Na, K, Rb, and Cs. B contains at least one of Cu and Ag. C contains at least one of F, Cl, and Br. D contains I. a, b, c, and d respectively indicate the molar ratios of A, B, C, and D in the entire composition and satisfy: 3.3 ≤ a ≤ 6.8; 2.0 ≤ b ≤ 4.1; 5.2 ≤ c + d ≤ 10.8; 0.5 < c / (c + d) < 1.0; and 1.55 ≤ a / b ≤ 3.4.)

Description

Technical Field

[0001] The present invention relates to a phosphor, particularly a phosphor useful as a scintillator, a light-emitting device using the phosphor, a radiation detector, and a radiation detection device.

Background Art

[0002] As phosphors excited by ultraviolet light or blue light, for example, BaMgAl activated with Mn 10 O 17 , β - sialon - type phosphors activated with Eu, etc. are known. In research and development in these fields, methods for improving fluorescence characteristics have been attempted, such as changing the shape of the emission spectrum by changing the type of luminescent center element, and using phosphors having a specific amount of deviation in the composition formula (Patent Documents 1 - 2).

[0003] As typical scintillators for detecting radiation, Lu2SiO5, Ga3(Ga,Al)5O 12 , Gd2Si2O7, CdWO4, PbWO4, etc. are known. In research and development in these fields, based on the structures of these compounds, methods for improving scintillator characteristics have been attempted, such as substituting matrix atoms with homologous atoms, or co - adding impurity atoms with different valences together with luminescent center atoms (Patent Documents 3 - 6).

[0004] Due to the demand for developing cheaper scintillators, copper - based halides such as Cs3Cu2I5 have been developed, and attempts have been made to activate with In or Tl or substitute Cl for Cs3Cu2I5 for emission wavelength adjustment (Patent Documents 7 - 9).

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

[0006] Among the above phosphors, while showing high luminous efficiency, there are also constituent elements that emit radiation such as Lu, and materials containing harmful substances such as Cd and Pb. However, in recent years, there have been cases where the use of materials containing harmful substances is regulated, and there is a demand for a new phosphor that does not contain harmful substances and has high luminous efficiency.

Summary of the Invention

[0007] The problem to be solved by the present invention is to provide a new phosphor that does not contain harmful substances and has a high emission quantum efficiency. Another problem to be solved by the present invention is to provide a new phosphor that emits light in blue to green by ultraviolet or radiation light, and to provide a light-emitting device and a radiation detector using this phosphor.

[0008] The present inventor has found a new phosphor having a crystal structure different from that of conventional phosphors and a specific composition, and emitting light in blue to green by ultraviolet or radiation light.

[0009] The present invention has the following gist.

[0010] [1] A phosphor having a crystal structure belonging to the space group Cmcm and having a composition represented by the following formula (1). A a B b C c D d ···(1) (In formula (1), A contains one or more of Na, K, Rb, and Cs. B contains one or more of Cu and Ag. C contains one or more of F, Cl, and Br. D contains I. a, b, c, and d respectively represent the molar ratios of A, B, C, and D in the overall composition, satisfying 3.3 ≦ a ≦ 6.8, 2.0 ≦ b ≦ 4.1, 5.2 ≦ c + d ≦ 10.8, 0.5 < c / (c + d) < 1.0, and 1.55 ≦ a / b ≦ 3.4.)

[0011] [2] The phosphor according to [1], having a composition represented by the following formula (2). A a B b C c D d :RE x ···(2) (Formula (2) indicates that a part of any of A, B, C, and D in formula (1) is substituted with an activator element represented by RE. In formula (2), A, B, C, D, a, b, c, and d have the same meanings as in formula (1). RE contains one or more selected from the group consisting of Mn, In, Tl, Ce, Pr, Nd, Sm, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. x represents the total molar ratio of RE, satisfying 0 < x ≦ 0.34.)

[0012] [3] The phosphor according to [1] or [2], having an emission peak wavelength of 440 nm or more and 540 nm or less.

[0013] [4] The phosphor according to any one of [1] to [3], having a luminescence quantum yield of 60% or more when excited by light with a wavelength of 300 nm.

[0014] [5] The phosphor according to any one of [1] to [4], having an excitation peak wavelength of 230 nm or more and 340 nm or less.

[0015] [6] The phosphor according to any one of [1] to [5], when the maximum value of the fluorescence intensity when irradiated with X-rays is taken as 100%, the fluorescence intensity 20 ms after stopping the X-ray irradiation is 7% or less, and the fluorescence intensity 100 ms after stopping the X-ray irradiation is 4% or less.

[0016] [7] The phosphor according to any one of [1] to [6], wherein C in formula (1) is Cl.

[0017] [8] The phosphor according to any one of [1] to [7], wherein B in formula (1) is Cu.

[0018] [9] The phosphor according to any one of [1] to [8], wherein A in formula (1) is Cs.

[0019]

[10] The phosphor according to any one of [1] to [9], wherein the mass ratio of the phase of the composition represented by formula (1) is 50% or more and 100% or less.

[0020]

[11] A phosphor composition containing the phosphor according to any one of [1] to

[10] and having a content of the phosphor of 50% by mass or more.

[0021]

[12] A light-emitting device including the phosphor according to any one of [1] to

[10] or the phosphor composition according to

[11] .

[0022]

[13] A radiation detector including the phosphor according to any one of [1] to

[10] or the phosphor composition according to

[11] .

[0023]

[14] A radiation inspection apparatus including the radiation detector according to

[13] . [Advantages of the Invention]

[0024] According to the present invention, it is possible to provide a novel phosphor that does not contain harmful substances and has a high luminescence quantum efficiency. In addition, according to the present invention, it is possible to provide a scintillator having a long-wavelength emission peak wavelength suitable for a light receiver. Furthermore, the present invention can provide a novel phosphor that emits light in blue to green by ultraviolet or radiation light, a light-emitting device using this phosphor, a radiation detector, and the like. [Brief Description of the Drawings]

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

[0026] Hereinafter, embodiments of the present invention will be described in detail. The following description is an example (representative example) of the embodiments of the present invention, and the present invention is not limited to the following contents unless it exceeds the gist thereof. In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as a lower limit value and an upper limit value. For example, "A~B" means A or more and B or less.

[0027] [Phosphor] A phosphor according to an embodiment of the present invention (hereinafter, also simply referred to as "phosphor") is a phosphor having a crystal structure belonging to the space group Cmcm and having a composition represented by the following formula (1). A a B b C c D d ···(1) (In formula (1), A contains at least one of Na, K, Rb, and Cs. B contains at least one of Cu and Ag. C contains at least one of F, Cl, and Br. D contains I. a, b, c, and d represent the molar ratios of A, B, C, and D in the overall composition, satisfying 3.3 ≦ a ≦ 6.8, 2.0 ≦ b ≦ 4.1, 5.2 ≦ c + d ≦ 10.8, 0.5 < c / (c + d) < 1.0, and 1.55 ≦ a / b ≦ 3.4.)

[0028] <Crystal system and space group> The crystal system of the phosphor of this embodiment is orthorhombic, and the space group of the crystal structure belongs to No. 63 (C m c m) based on "International Tables for Crystallography (Third, revised edition), Volume A SPACE - GROUP SYMMETRY". Here, the space group can be determined by the conventional method. Specifically, it can be determined by X - ray diffraction measurement using a single crystal or electron beam diffraction.

[0029] <Lattice constant> The lattice constant a of the phosphor of this embodiment is usually 14.36 Å to 19.43 Å, preferably 15.21 Å to 18.59 Å, and more preferably 16.39 Å to 17.40 Å. The lattice constant b of the phosphor of this embodiment is usually 7.77 Å to 10.51 Å, preferably 8.23 Å to 10.05 Å, and more preferably 8.87 Å to 9.41 Å. The lattice constant c of the phosphor of this embodiment is usually 11.93 Å to 16.14 Å, preferably 12.63 Å to 15.44 Å, and more preferably 13.61 Å to 14.45 Å. The lattice constant can be determined according to the conventional method. Specifically, it can be determined by analyzing the results of X - ray diffraction of a single crystal. It can also be determined by performing Rietveld analysis on the results of powder X - ray diffraction and neutron diffraction.

[0030] <Composition ratio> In formula (1) showing the composition of the phosphor of the present embodiment, A is not particularly limited as long as it is an alkali metal element. For example, Li, Na, K, Rb, and Cs can be used. From the viewpoint of stability in the air, the phosphor of the present embodiment contains at least one or more of Na, K, Rb, and Cs as A, and preferably contains Cs.

[0031] The proportion of the above elements contained in A is usually 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more. The upper limit of the proportion of the above elements contained in A is not particularly limited and may be 100% by mass.

[0032] B is not particularly limited as long as it is a monovalent transition element. For example, Cu, Ag, and Au can be used. From the viewpoint of non-scarce elements, the phosphor of the present embodiment contains at least one or more of Cu and Ag as B, and preferably contains Cu.

[0033] The proportion of the above elements contained in B is usually 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more. The upper limit of the proportion of the above elements contained in B is not particularly limited and may be 100% by mass.

[0034] C is not particularly limited as long as it is a halogen excluding iodine. The phosphor of the present embodiment contains at least one or more of F, Cl, and Br as C, preferably contains one or more of Cl and Br, and more preferably contains Cl.

[0035] The proportion of the above elements contained in C is usually 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more. The upper limit of the proportion of the above elements contained in C is not particularly limited and may be 100% by mass.

[0036] D is I (iodine).

[0037] a, b, c, and d represent the molar ratios of A, B, C, and D in the total composition of the phosphor, respectively.

[0038] a is usually 3.3 or more, preferably 4.0 or more, more preferably 4.5 or more, usually 6.8 or less, preferably 6.0 or less, more preferably 5.5 or less.

[0039] b is usually 2.0 or more, preferably 2.4 or more, more preferably 2.7 or more, usually 4.1 or less, preferably 3.6 or less, more preferably 3.3 or less.

[0040] c + d is usually 5.2 or more, preferably 6.4 or more, more preferably 7.2 or more, usually 10.8 or less, preferably 9.6 or less, more preferably 8.8 or less.

[0041] c / (c + d) is usually 0.5 or more, preferably 0.6 or more, more preferably 0.7 or more, usually 1.0 or less, preferably 0.9 or less, more preferably 0.8 or less.

[0042] a / b is usually 1.55 or more, preferably 1.58 or more, more preferably 1.60 or more, even more preferably 1.62 or more, and usually 3.4 or less, preferably 3.0 or less, more preferably 2.5 or less, even more preferably 2.2 or less, even more preferably 2.0 or less, particularly preferably 1.8 or less.

[0043] By using appropriate elements and ratios for A, B, C, D, a, b, c, and d, a phosphor excellent in emission color and emission efficiency can be obtained.

[0044] The phosphor represented by formula (1) may contain, as an activator, another element RE (also referred to as "activator element") in addition to A, B, C, and D, as represented by the following formula (2). A a B b C c D d :RE x ···(2) (Formula (2) indicates that a part of any of A, B, C, and D in Formula (1) is replaced by an activator element represented by RE. In Formula (2), A, B, C, D, a, b, c, and d have the same meanings as in Formula (1). RE includes one or more selected from the group consisting of Mn, In, Tl, Ce, Pr, Nd, Sm, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. x represents the total molar ratio of RE and satisfies 0 < x ≤ 0.34.)

[0045] The above activator element RE may include one or more selected from the group consisting of Mn, In, Tl, Ce, Pr, Nd, Sm, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. From the viewpoint of obtaining a short fluorescence decay time, the activator element RE preferably contains at least Ce. The proportion of the above elements contained in the activator element RE is usually 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more. The upper limit of this proportion is not particularly limited and may be 100% by mass.

[0046] The activator element may be present in the phosphor in any form. For example, it may be contained in either A or B, or may be contained in both A and B.

[0047] The content of the activator element is not limited. For example, it is usually 1.0% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.2% by mass or less, and may be 0.1% by mass or less, based on the whole phosphor. The lower limit of the content of the activator element is not particularly limited. When expressed in molar ratio, the content of the activator element that replaces a part of any of A, B, C, and D is usually 0.5 or less, preferably 0.4 or less, more preferably 0.34 or less, and still more preferably 0.25 or less. When the activator element is contained in A, the content of the activator element is usually 0.01 mol% or more and 5 mol% or less, preferably 0.1 mol% or more and 2 mol% or less, based on the whole of A. When the activator element is contained in B, the content of the activator element is usually 0.001 mol% or more, usually 5 mol% or less, preferably 1 mol% or less, more preferably 0.1 mol% or less, with respect to the whole of B, and it is preferable that the amount is as small as possible. By containing an appropriate amount of the activator element in the phosphor of the present embodiment, a larger fluorescence intensity can be obtained.

[0048] The phosphor represented by the formula (1) may further contain other elements as long as the effects of the present invention are not impaired.

[0049] The analysis of the elements contained in the phosphor is not particularly limited. For example, it can be carried out by a method of total element analysis using glow discharge mass spectrometry (GDMS).

[0050] The form of the phosphor of the present embodiment is not particularly limited and can be appropriately selected according to each use and purpose. For example, it can be in the form of powder, single crystal, polycrystal, or sintered body. In particular, it can be in the form of powder, single crystal, or sintered body. The form of the phosphor of the present embodiment is, for example, preferably a single crystal or a sintered body block when used in an X-ray CT apparatus. When used for an X-ray detection film for non-destructive inspection, the phosphor of the present embodiment is preferably used as a film in which the powder is dispersed in a resin sheet.

[0051] <Emission characteristics and excitation source> The phosphor of the present embodiment is excited by receiving the energy of the excitation source and emits (luminesces) electromagnetic waves, preferably visible light. As the excitation source, electromagnetic waves such as visible light and ultraviolet rays, ionizing radiation, or current can be used. Examples of the ionizing radiation include X-rays, γ-rays, α-rays, and neutron rays.

[0052] <Emission peak wavelength> The phosphor of this embodiment usually has an emission peak wavelength in the wavelength range of 160 nm to 700 nm. The lower limit of the wavelength range is preferably 350 nm or more, more preferably 440 nm or more, still more preferably 455 nm or more, and the upper limit is preferably 600 nm or less, more preferably 540 nm or less, still more preferably 500 nm or less, and particularly preferably 490 nm or less. When the emission peak wavelength is within the above range, it is preferable because the obtained phosphor exhibits good blue to green colors. The method for measuring the emission spectrum and the emission peak wavelength is not particularly limited. For example, it can be measured using a general spectrofluorophotometer.

[0053] <Emission quantum yield> When the phosphor of this embodiment is excited with ultraviolet light having a wavelength of 300 nm, which is near the excitation peak wavelength, the emission quantum yield is usually 50% or more, preferably 60% or more, more preferably 70% or more, still more preferably 80% or more, and particularly preferably 90% or more. The upper limit of the emission quantum yield is not limited as long as it is within the range of 100% or less, and the higher the better. The higher this emission quantum yield, the more preferable it is in terms of efficiently converting the irradiated light into emitted light. The measurement of the emission quantum yield can be performed, for example, using an absolute PL quantum yield measurement device.

[0054] <Excitation by ultraviolet light or the like, and excitation peak wavelength> The phosphor of this embodiment is preferably excited and emits light by electromagnetic waves in the ultraviolet to visible light region, for example. In this case, the phosphor of this embodiment can be used as a phosphor for use in a light-emitting device, a lighting device, and the like.

[0055] The excitation peak wavelength (absorption maximum wavelength) of the phosphor of this embodiment is usually 200 nm or more, preferably 230 nm or more, more preferably 260 nm or more, usually 400 nm or less, preferably 340 nm or less, and more preferably 320 nm or less. The method for measuring the excitation spectrum and the excitation peak wavelength is not particularly limited. For example, it can be measured using a general spectrofluorophotometer.

[0056] <Afterglow upon X-ray excitation> The phosphor of this embodiment is preferably excited and emits light by radiation. In this case, the phosphor of this embodiment can also be used as a scintillator. When the phosphor of this embodiment is irradiated with X-rays, assuming the maximum value of the fluorescence intensity is 100%, the fluorescence intensity 20 ms after stopping the X-ray irradiation is usually 10% or less, preferably 7% or less, more preferably 5% or less. Further, the fluorescence intensity 100 ms after stopping the X-ray irradiation is usually 5% or less, preferably 4% or less, more preferably 3% or less. The lower limit of this fluorescence intensity is not particularly limited and is usually 0% or more. The smaller the fluorescence intensity after stopping the X-ray irradiation, for example, the higher the time resolution when used in a diagnostic apparatus using radiation, the sharper the image can be obtained, and the radiation exposure can be reduced, which is preferable. This fluorescence intensity can be measured by the method described in the examples below.

[0057] The phosphor of this embodiment may be a single phase or may contain a plurality of phases, as long as the overall composition is represented by the formula (1). When the phosphor of this embodiment contains a plurality of phases, the phosphor of this embodiment usually contains a phase having the composition represented by the formula (1).

[0058] The proportion of the phase having the composition represented by the formula (1) in the phosphor of this embodiment is usually 40% or more, preferably 50% or more, more preferably 60% or more, still more preferably 70% or more, even more preferably 80% or more, particularly preferably 90% or more, most preferably 95% or more, and especially preferably 98% or more on a mass basis. The upper limit of the proportion of the phase having the composition represented by the formula (1) in the phosphor of this embodiment is not particularly limited, and the higher the better, but it is usually 100% or less. When the phosphor of this embodiment is a single phase, the mass ratio is 100% or approximately 100%.

[0059] [Phosphor composition containing phosphor] <Phosphor composition> The phosphor of this embodiment can also be used as the phosphor of this embodiment and a phosphor composition containing a substance different from the phosphor (hereinafter, may be referred to as "the phosphor composition of this embodiment").

[0060] The substance different from the phosphor of this embodiment is an arbitrary inorganic material and / or organic material. For example, CsCl, CuCl, CsCuCl3, CsCu2Cl3, Cs2CuCl4, Cs3Cu2Cl5, and solid solutions and hydrates of these compounds with halogens other than chlorine, CsI, CuI, CsCu2I3, CsCu9I 10 and solid solutions and hydrates of these compounds with halogens other than iodine, etc. can be mentioned.

[0061] Regarding the characteristics of the phosphor composition of this embodiment, preferably, at least the part composed of the phosphor of this embodiment exhibits characteristics equivalent to or better than those when the phosphor of this embodiment is used alone. More preferably, the entire phosphor composition also exhibits characteristics equivalent to or better than those when the phosphor of this embodiment is used alone. By using together a substance different from the phosphor of this embodiment, a diverse phosphor composition having the characteristics of both can be obtained.

[0062] The manufacturing method of the phosphor composition of this embodiment is not particularly limited. For example, it can be obtained during the process of the step of manufacturing the phosphor of this embodiment. Alternatively, in the manufacturing process of the phosphor of this embodiment, it can also be obtained by appropriately adjusting the elemental ratio of the raw materials and / or the conditions of the manufacturing process. Further, it can also be obtained by appropriately adding a substance different from the phosphor of this embodiment after the manufacturing process of the phosphor of this embodiment is completed.

[0063] <Content ratio of phosphor> The content rate of the phosphor of the present embodiment with respect to the total mass of the phosphor composition of the present embodiment is usually 20% by mass or more, preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% or more. The upper limit of the content rate of the phosphor of the present embodiment with respect to the total mass of the phosphor composition of the present embodiment is not particularly limited, but is usually less than 100%. When the content rate of the phosphor of the present embodiment in the phosphor composition of the present embodiment is within the above range, it is expected that the performance of the part composed of the phosphor of the present embodiment included in the phosphor composition of the present embodiment, or the entire phosphor composition of the present embodiment, exhibits characteristics at least equivalent to those when the phosphor of the present embodiment is used alone. The method for measuring the content rate of the phosphor in the phosphor composition is not particularly limited. For example, it can be determined by performing Rietveld analysis on the results of powder X-ray diffraction and neutron diffraction.

[0064] [Method for manufacturing phosphor] The method for manufacturing the phosphor of the present embodiment (hereinafter, may also be referred to as "the present manufacturing method") is not particularly limited as long as the phosphor of the present embodiment can be obtained. For example, methods including the following steps 1 and 2, and preferably further including the following steps 3 and 4 can be mentioned. Step 1: A raw material mixing step of weighing raw materials so as to obtain a target composition and sufficiently mixing them to obtain a raw material mixture Step 2: A synthesis step of filling the obtained raw material mixture into a heat-resistant container and performing heat treatment under a predetermined temperature and a predetermined atmosphere to obtain a synthetic powder Step 3: A pressure molding step of pressure molding the obtained synthetic powder to obtain a pressure molded body Step 4: A firing step of firing the obtained pressure molded body under a predetermined temperature and a predetermined atmosphere, and processing and washing the fired product as necessary to obtain a sintered body

[0065] [Raw material preparation step] The present manufacturing method may include a step of preparing raw materials (raw material preparation step). The raw materials to be used are not particularly limited as long as the phosphor of the present embodiment can be manufactured. For example, oxides, halides, inorganic acid salts, etc. of each constituent atom can be used.

[0066] As the A source in formula (1), for example, one or more of LiF, LiCl, LiBr, LiI, NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, CsF, CsCl, CsBr, CsI and their hydrates can be used. The purity of each is usually 90% or more, preferably 99% or more, and the upper limit is not particularly limited.

[0067] As the B source, for example, one or more of CuF, CuCl, CuBr, CuI, AgF, AgCl, AgBr, AgI, AuF, AuCl, AuBr, AuI and their hydrates can be used. The purity of each is usually 90% or more, preferably 99% or more, and the upper limit is not particularly limited.

[0068] As the C source and D source, they can be introduced as F, Cl, Br, I in the above A source, B source, and the following activator element sources.

[0069] Similarly, oxides, halides, inorganic acid salts, etc. can be used for the activator element. For example, regarding Ce, one or more of CeO2, CeI3, Ce2O3, Ce(NO3)3, etc. can be used. The purity of these raw materials is usually 90% or more, preferably 99% or more, and the upper limit is not particularly limited.

[0070] <Raw material mixing step> This manufacturing method may include a step of mixing raw materials to obtain a raw material mixture (raw material mixing step). The method of mixing raw materials is not particularly limited, and generally used methods are applicable. For example, a dry mixing method and a wet mixing method can be mentioned.

[0071] Examples of the dry mixing method include mixing using a mortar or a ball mill.

[0072] As a wet mixing method, for example, a solvent or dispersion medium such as water is added to the raw materials, and they are mixed using a mortar and pestle to form a dispersed solution or slurry state, and then dried by spray drying, heat drying, natural drying, or the like.

[0073] <Synthesis step> This manufacturing method may include a step (synthesis step) of heat-treating the above raw material mixture to obtain synthetic powder.

[0074] In the synthesis step, the raw material mixture can be filled into a heat-resistant container such as a crucible or a tray and heat-treated to obtain synthetic powder. The material of the heat-resistant container is not particularly limited as long as it has low reactivity with each raw material. For example, platinum-based containers such as Pt, RtRh alloy with 30 mass% of Rh content, Ir, and silicate glass containers can be mentioned. The atmosphere during heat treatment is not particularly limited, and examples include a reducing atmosphere such as a hydrogen atmosphere, a hydrogen-noble gas mixed atmosphere; an air atmosphere; a nitrogen atmosphere; a reduced pressure atmosphere, etc. When heat treatment in the air is carried out in a reducing atmosphere, in addition to platinum-based containers, Mo, W-based containers, etc. can also be used. From the viewpoint of suppressing oxidation during firing, an atmosphere that does not contain air is more preferable.

[0075] The synthetic powder obtained in this step may be used to obtain a sintered body by a firing step, or can be used as a phosphor powder as it is.

[0076] Regarding the temperature and time of heat treatment in the synthesis step, there is no particular limitation as long as the phosphor of this embodiment can be obtained. The temperature and time of heat treatment are preferably set to the temperature and time at which each mixed raw material reacts sufficiently. The temperature is usually 100°C or higher, preferably 200°C or higher, and usually 600°C or lower, preferably 500°C or lower. The time is usually 1 hour or longer, preferably 3 hours or longer, and usually 100 hours or shorter.

[0077] The synthesized powder obtained in the above synthesis step may be sieved. The mesh size (opening) of the sieve is usually 500 μm or less, preferably 200 μm or less. By sieving, aggregation of the powder can be eliminated, and a phosphor with uniform quality can be obtained.

[0078] <Pressing and forming step> This manufacturing method may include a step (pressing and forming step) of obtaining a pressed and formed body by pressing and forming the synthesized powder obtained in the above synthesis step. The method and conditions of pressing and forming are not particularly limited. For example, it can be carried out by uniaxial pressing or cold isostatic pressing. The pressure during pressing and forming can be, for example, 1 MPa or more, preferably 30 MPa or more. There is no particular limitation on the upper limit of the pressing and forming pressure, but it is usually 400 MPa or less, preferably 300 MPa or less. By appropriately performing pressing and forming, voids after sintering are reduced and light transmittance is improved.

[0079] <Pre-sintering step> This manufacturing method may include a step (pre-sintering step) of obtaining a pre-sintered product by pre-sintering the synthesized powder obtained in the above synthesis step or the pressed and formed body obtained in the above pressing and forming step. The temperature, pressure, time, and atmosphere during pre-sintering are not particularly limited as long as the phosphor of this embodiment can be obtained. The pre-sintering temperature is usually 150 °C or more, preferably 200 °C or more, and usually 500 °C or less, preferably 350 °C or less. The pre-sintering pressure is usually 10 -5 Pa or more, preferably 10 -3 Pa or more, usually 10 MPa or less, preferably 2 MPa or less. The pre-sintering time is usually 1 hour or more, preferably 2 hours or more, and usually 50 hours or less. The pre-sintering atmosphere is preferably an inert atmosphere such as an argon atmosphere or a nitrogen atmosphere.

[0080] <Sintering step> This manufacturing method may include a step (sintering step) of obtaining a sintered product (sintered body) by further heating (sintering) the synthesized powder obtained in the above synthesis step, the pressed and formed body obtained in the pressing and forming step, or the pre-sintered product obtained in the pre-sintering step under pressure. The pressurization method and conditions in the firing process are not particularly limited. For example, it can be carried out by hot isostatic pressing (HIP). Hot pressing treatment may be performed before firing.

[0081] The conditions during firing are not particularly limited as long as the phosphor of the present embodiment can be obtained. The firing temperature is usually 150 °C or higher, preferably 200 °C or higher, and usually 500 °C or lower, preferably 350 °C or lower. The firing pressure is usually 10 MPa or higher, preferably 30 MPa or higher, and usually 300 MPa or lower, preferably 200 MPa or lower. The firing time is usually 0.5 hours or longer, preferably 1 hour or longer, and usually 20 hours or shorter, preferably 10 hours or shorter.

[0082] The atmosphere during firing is not particularly limited as long as the phosphor of the present embodiment can be obtained. Considering the stability of materials, reaction vessels, furnace materials, etc., it is preferable to perform firing under an appropriate atmosphere as appropriate. Specific atmospheres include, for example, inert atmospheres such as argon atmosphere and nitrogen atmosphere.

[0083] The firing process may optionally include a pretreatment process (a process for performing washing, drying, vacuum degassing, etc.), a post-treatment process (a process for performing washing, drying, etc.), and the like.

[0084] <Single crystal growth process> When obtaining the phosphor as a single crystal, for example, the raw material mixture, or the sintered body obtained by the above firing process or the following annealing process is heated and melted, and a single crystal is grown from the melt to obtain it.

[0085] In this case, the temperature of the heat melting treatment is usually 200 to 600 °C, preferably 300 to 500 °C. The pressure is not particularly limited as long as it is within the pressure range in which the raw material mixture or the sintered body obtained by the above firing process or the following annealing process does not decompose. For example, it can be carried out at normal pressure. The material of the container used for heat melting is not particularly limited as in the case of the synthesis process. Examples include platinum-based metals such as Pt, RtRh alloy with 30 mass% Rh content, Ir, and silicate glass.

[0086] The container and atmosphere during single crystal production can be appropriately selected from the same viewpoints as in the production of the sintered body. There is no particular limitation on the method of growing a single crystal, and general Czochralski method, Bridgman method, micro-pulling down method, EFG method, zone melting method, etc. can be used. For the purpose of lowering the melting point, a flux method or the like can also be used. When growing a large crystal, the Czochralski method and the Bridgman method are preferable.

[0087] <Annealing process> In the case of obtaining the phosphor of the present embodiment as a sintered body in this manufacturing method, the fired product obtained by the firing process may be used as the sintered body as it is, but after the firing process, a process of annealing the fired product (annealing process) may be included for the purpose of repairing crystal defects. By performing annealing, light absorption due to crystal defects is reduced, and a sintered body with higher translucency can be obtained.

[0088] Various conditions such as temperature, pressure, time, and atmosphere in the annealing process are not particularly limited as long as the phosphor of the present embodiment can be obtained. The annealing temperature is usually 100 °C or higher, preferably 150 °C or higher, and usually 390 °C or lower, preferably 300 °C or lower. The annealing pressure is usually 10 MPa or higher, preferably 20 MPa or higher, and usually 300 MPa or lower, preferably 200 MPa or lower. The annealing time is usually 0.5 hours or longer, preferably 1 hour or longer, and usually 20 hours or shorter, preferably 10 hours or shorter. The annealing atmosphere is preferably an inert atmosphere such as an argon atmosphere or a nitrogen atmosphere.

[0089] <Film production process> When obtaining the phosphor as a film, for example, methods such as I and II below can be used. I: A method of weighing raw materials so as to obtain a target composition, dissolving the weighed raw materials in a solvent, applying the obtained solution to a substrate, and heating the coating film at a predetermined temperature and in a predetermined atmosphere to precipitate crystals II: A method of preparing raw materials so as to obtain a target composition and depositing them on a substrate at a predetermined temperature and in a predetermined atmosphere The substrate during film production can be appropriately selected.

[0090] The solvent for dissolving the raw materials is not particularly limited as long as it can dissolve or disperse the raw materials. For example, one or more of 2-methoxyethanol, 2-ethoxyethanol, dimethyl ether, methyl ethyl ether, acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, dimethyl sulfoxide, N,N-dimethylformamide, acetonitrile, tetrahydrofuran, hexane, cyclohexane, methylcyclohexane, ethylcyclohexane, toluene, xylene, etc. can be used. The concentration of the raw materials in the solution can be adjusted as appropriate. For example, a concentration of 0.05 to 1.0 mol / L in terms of the obtained phosphor is preferable.

[0091] <Phosphor powder> The method for obtaining the phosphor of this embodiment as a powder is not particularly limited. For example, a method of obtaining the synthetic powder obtained in the above synthesis step as a powder phosphor as it is; a method of pulverizing the sintered body obtained by the above firing step or annealing step; a method of pulverizing the single crystal obtained by the single crystal growth step; etc. can be mentioned. The method of the pulverization is not particularly limited.

[0092] [Uses of the phosphor] The use of the phosphor of this embodiment is not particularly limited. For example, due to the property of being excited by ultraviolet rays or the property of emitting light in blue to green, it can be used as a light-emitting element. Further, it can be used in a light-emitting device including such a light-emitting element.

[0093] Examples of the light-emitting device include a lighting device, an image display device, and an automobile headlamp. As the light-emitting device such as a lighting device or an image display device, an LED device such as an LED lighting device or an LED image display device, an EL device such as an EL lighting device or an EL image display device, and a fluorescent lamp are known. More specifically, a white light-emitting diode, a lighting fixture including a plurality of white light-emitting diodes, a backlight for a liquid crystal panel, etc. can be mentioned, but it is not particularly limited thereto.

[0094] Examples of the image display device include a fluorescent display tube (VFD), a field emission display (FED), a plasma display panel (PDP), a cathode ray tube (CRT), a liquid crystal display (LCD), etc., but it is not particularly limited thereto.

[0095] By combining the phosphor of this embodiment with phosphors that exhibit light emission of other colors such as yellow, green, and red, such as YAG:Ce, a β-sialon type phosphor activated with Eu, CASN:Eu, etc., it can be used for a white light-emitting element and a light-emitting device.

[0096] The phosphor of this embodiment can also be used, for example, as a scintillator material in a radiation detector. The radiation detector can be used, for example, in the fields of radiation medicine, physics, physiology, chemistry, mineralogy such as for medical diagnosis or safety inspection X-ray CT, for medical diagnosis positron CT (PET), for cosmic ray observation, for underground resource exploration, and further for oil exploration.

[0097] When used for the application of a radiation detector, the form of the phosphor of this embodiment is not particularly limited, and it can be any of a powder, a single crystal, and a sintered body. The phosphor of this embodiment can be used as a radiation detector by combining it with a light receiver. Examples of the light receiver used in the radiation detector include a position-sensitive photomultiplier tube (PS-PMT), a silicon photomultiplier (Si-PM), a photodiode (PD), or an avalanche photodiode (APD).

[0098] Furthermore, the phosphor of this embodiment can be used as a radiation inspection device by being equipped with these radiation detectors. Examples of the radiation inspection device include non-destructive inspection devices such as detectors for non-destructive testing, detectors for resource exploration, and detectors for high energy physics, and diagnostic devices such as medical image processing devices. Examples of medical image processing devices include positron emission tomography (PET) devices, X-ray CT, and SPECT. Examples of PET types include two-dimensional PET, three-dimensional PET, time-of-flight (TOF) PET, and depth-of-infrared (DOI) PET. These can also be used in combination. EXAMPLES

[0099] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0100] [Example 1] <Cs5Cu3Cl6I2蛍光体の製造> CsI ​​(purity 99.999%), CsCl (purity 99.9%), and CuCl (purity 99.99%) manufactured by Sigma-Aldrich were mixed in a molar ratio of Cs:Cu:Cl:I = 5:3:6:2 to obtain a raw material mixture. The obtained raw material mixture was placed in a glass tube and then sealed under reduced pressure. Next, the glass tube in which the raw material mixture was sealed was placed in a tubular furnace and held at 400°C for 12 hours, and then cooled over 24 hours to obtain a bulk sample.

[0101] A transparent block-shaped crystal with a side length of about 100 μm was extracted from a part of the obtained bulk sample. X-ray diffraction intensity was collected from this block-shaped crystal using a single crystal X-ray structure analyzer (Rigaku, R-AXIS RAPIDII) equipped with a MoKα source and a graphite monochromator, and crystal structure analysis was performed. The obtained crystal was confirmed to be a new compound Cs5Cu3Cl6I2, which belongs to the space group Cmcm and has the crystal parameters and atomic coordinates shown in Table 1. For reference, FIG. 1 shows the powder XRD pattern calculated from the structural analysis results when a CuKα radiation source was used.

[0102]

Table 1

[0103] <Powder XRD measurement> Next, the above-mentioned massive sample was pulverized to obtain a powder sample (phosphor of Example 1). For the phosphor of Example 1, powder XRD was measured using an X-ray diffractometer equipped with a CuKα ray source (D8 Advance, manufactured by Bruker). The obtained XRD pattern is shown in Fig. 2. As is clear from the comparison with Fig. 1, the phosphor of Example 1 was a single phase of Cs5Cu3Cl6I2 belonging to the space group Cmcm.

[0104] <Measurement of emission spectrum and excitation spectrum> Using a spectrofluorometer (F-4500, manufactured by Hitachi, Ltd.), the emission spectrum and excitation spectrum of the phosphor of Example 1 were measured. The results are shown in Fig. 3. The excitation spectrum is the measurement result obtained by monitoring the emission at 462 nm. The emission spectrum is the measurement result when excited at 300 nm. The emission peak wavelength of the phosphor of Example 1 was 462 nm, and the excitation peak wavelength was 271 nm. Using an absolute PL quantum yield measurement device (L9799-02, manufactured by Hamamatsu Photonics), the emission quantum yield of the phosphor of Example 1 when excited with light of wavelength 300 nm was measured. As a result, the emission quantum efficiency was as good as 95%. It was found that the phosphor of Example 1 has high emission efficiency upon ultraviolet excitation and is an excellent blue-green phosphor for ultraviolet excitation.

[0105] <Evaluation of scintillation characteristics and afterglow intensity> In the powder XRD measurement, the phosphor of Example 1 clearly showed luminescence under X-ray irradiation. Next, after filling 200 mg of the phosphor of Example 1 into a quartz petri dish, the sample was irradiated with X-rays under the conditions of 100 kV, 20 mAs, and 16 mGy / s, and the fluorescence intensity during X-ray irradiation and after stopping X-ray irradiation was measured with a photomultiplier tube. The results are shown in Fig. 4. The fluorescence intensity after stopping X-ray irradiation was 3.9% after 20 ms and 2.1% after 100 ms, with the fluorescence intensity during X-ray irradiation taken as 100%. The calculated density derived from single crystal structure analysis was 4.05 g / cm 3 . The effective atomic number calculated from the composition formula is 50.0. It can be seen that the phosphor of Example 1 exhibits blue-green luminescence and has a high radiation shielding ability.

[0106] [Example 2] CsI was added to 2-methoxyethanol to a final concentration of 0.30 mol / L, CsCl to a final concentration of 0.45 mol / L, and CuCl to a final concentration of 0.45 mol / L, and then stirred until the raw materials were dissolved to prepare a Cs, Cu, Cl, I solution with a concentration of 0.15 mol / L in terms of Cs5Cu3Cl6I2. Next, the obtained solution was dropped onto a quartz substrate and spin-coated under the conditions of 500 rpm for 5 seconds and 4000 rpm for 30 seconds, and then baked at 100 °C to prepare a Cs5Cu3Cl6I2 thin film (the phosphor of Example 2).

[0107] For the phosphor of Example 2, in the same manner as in Example 1, the emission spectrum and emission quantum yield when excited with ultraviolet light of wavelength 300 nm were measured. The phosphor results are shown in Fig. 5. The phosphor of Example 2 showed an emission peak wavelength at 472 nm and exhibited blue-green luminescence as in Example 1. The emission quantum efficiency of the phosphor of Example 2 was as good as 72%.

[0108] [Reference Example 1] CsI ​​(purity 99.999%) and CuI (purity 99.999%) manufactured by Sigma-Aldrich were mixed in a molar ratio of Cs:Cu:I=3:2:5 to obtain a raw material mixture. The obtained raw material mixture was placed in a glass tube and then sealed under reduced pressure. Next, the glass tube in which the raw material mixture was sealed was placed in a box furnace and held at 300°C for 100 hours, and then cooled to room temperature over 3 hours to obtain a bulk sample. The obtained bulk sample was pulverized to obtain a powder sample (phosphor of Reference Example 1). The powder XRD measurement result of the phosphor of Reference Example 1 is shown in Fig. 6. The powder sample of Reference Example 1 was a single phase of Cs3Cu2I5 belonging to the space group Pnma.

[0109] Next, the emission spectrum and excitation spectrum of the phosphor of Reference Example 1 were measured using a spectrofluorophotometer (Hitachi, F-4500). The results are shown in FIG. The excitation spectrum was measured by monitoring the emission at 439 nm, and the emission spectrum was measured when excited at 302 nm. The phosphor of Reference Example 1 had an emission peak wavelength of 440 nm and an excitation peak wavelength of 303 nm. The luminescence quantum yield of the phosphor of Reference Example 1 was 81% when excited at 300 nm, indicating that the phosphor of Reference Example 1 is a phosphor that emits blue light when excited by ultraviolet light.

[0110] As described above, the present invention can provide a novel phosphor that does not contain harmful substances and has high luminescence quantum efficiency. Furthermore, the present invention can provide a scintillator having a long emission peak wavelength suitable for a photoreceiver. Furthermore, the present invention can provide a novel phosphor that emits blue to green light when exposed to ultraviolet light or radiation, and a light-emitting device and a radiation detector that use this phosphor.

[0111] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2020-072369 filed on April 14, 2020, the entire disclosure of which is incorporated herein by reference.

Claims

1. A phosphor having a crystal structure belonging to the space group Cmcm and having a composition represented by the following formula (1). A ａ B ｂ C ｃ D ｄ ...(1) (In formula (1), A contains any one or more of Na, K, Rb, and Cs. B contains any one or more of Cu and Ag. C contains any one or more of F, Cl, and Br. D contains I. a, b, c, and d respectively represent the molar ratios of A, B, C, and D in the overall composition, and satisfy 3.3 ≦ a ≦ 6.8, 2.0 ≦ b ≦ 4.1, 5.2 ≦ c + d ≦ 10.8, 0.5 < c / (c + d) < 1.0, and 1.55 ≦ a / b ≦ 3.4.)

2. The phosphor according to claim 1, having a composition represented by the following formula (2). A ａ B ｂ C ｃ D ｄ : RE ｘ ... (2) (Formula (2) indicates that a part of any of A, B, C, and D in formula (1) is substituted with an activator element represented by RE. In formula (2), A, B, C, D, a, b, c, and d have the same meanings as in formula (1). RE contains one or more selected from the group consisting of Mn, In, Tl, Ce, Pr, Nd, Sm, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. x represents the total molar ratio of RE and satisfies 0 < x ≦ 0.34.)

3. The phosphor according to claim 1 or 2, having an emission peak wavelength of 440 nm or more and 540 nm or less.

4. The phosphor according to any one of claims 1 to 3, having an emission quantum yield of 60% or more when excited by light with a wavelength of 300 nm.

5. The phosphor according to any one of claims 1 to 4, having an excitation peak wavelength of 230 nm or more and 340 nm or less.

6. The phosphor according to any one of claims 1 to 5, wherein when the maximum value of the fluorescence intensity when irradiated with X-rays is taken as 100%, the fluorescence intensity 20 ms after stopping the irradiation of X-rays is 7% or less, and the fluorescence intensity 100 ms after stopping the irradiation of X-rays is 4% or less.

7. The phosphor according to any one of claims 1 to 6, wherein C in formula (1) is Cl.

8. The phosphor according to any one of claims 1 to 7, wherein B in formula (1) is Cu.

9. The phosphor according to any one of claims 1 to 8, wherein A in formula (1) is Cs.

10. The phosphor according to any one of claims 1 to 9, wherein the mass ratio of the phase having the composition represented by formula (1) is 50% or more.

11. A phosphor composition containing the phosphor according to any one of claims 1 to 10 and having a content of the phosphor of 50% by mass or more.

12. A light-emitting device comprising the phosphor according to any one of claims 1 to 10 or the phosphor composition according to claim 11.

13. A radiation detector comprising the phosphor according to any one of claims 1 to 10 or the phosphor composition according to claim 11.

14. A radiation inspection apparatus comprising the radiation detector according to claim 13.

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