Phosphor powder, composite and light-emitting device

Abstract

This fluorescent body powder includes fluorescent body particles having a compositional makeup represented by general formula (1) A2MF6:Mn. The fluorescent body particles include first fluorescent body particles having a shape selected from the group consisting of truncated hexahedron shapes, cuboctahedron shapes, and truncated octahedron shapes. Among the fluorescent body particles in the fluorescent body powder, the proportion of the first fluorescent body particles is 65% or more in terms of the number of particles. In general formula (1), element A is one or more alkali metal elements including K, element M is Si alone, Ge alone, or a combination between Si and at least one element selected from the group consisting of Ge, Sn, Ti, Zr, and Hf, and 0<n≤0.1 is satisfied.

Description

Technical Field

[0001] The present invention relates to a phosphor powder, a composite, and a light-emitting device.

[0002] As a phosphor capable of converting blue light emitted from a blue light-emitting diode into red light, a fluoride phosphor represented by K2SiF6:Mn (often abbreviated as "KSF phosphor") is known. This phosphor is efficiently excited by blue light. Further, the half-value width of the emission spectrum of this phosphor is narrow and sharp. Therefore, by using this phosphor as a red phosphor, a white LED with high luminance, excellent color rendering properties, and color reproducibility can be realized.

[0003] As a prior art of fluoride phosphors, for example, Patent Document 1 can be cited. Patent Document 1 describes a fluoride phosphor having a composition represented by the general formula A2M (1-n) F6:Mn 4+ n having a bulk density of 0.80 g / cm 3 or more and a mass median diameter of 30 μm or less. In the general formula, 0 < n ≦ 0.1, element A is one or more alkali metal elements containing K, and element M is a combination of Si alone, Ge alone, or one or more elements selected from the group consisting of Si and Ge, Sn, Ti, Zr, and Hf.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] With the spread of white LEDs, further improvement in the light-emitting characteristics of fluoride phosphors is required.

[0006] The present inventors have carried out various investigations with the aim of obtaining a fluoride phosphor having good luminescence characteristics. [Means for solving the problem]

[0007] Through investigation, the inventors have completed the invention provided below.

[0008] The present invention is as follows.

[0009] A phosphor powder containing phosphor particles having a composition represented by the following general formula (1): the phosphor particles include first phosphor particles having any shape selected from the group consisting of a truncated hexahedron shape, a cuboctahedron shape, and a truncated octahedron shape; The phosphor powder has phosphor particles, of which 65% or more by number are the first phosphor particles. General formula (1):A2MF6:Mn In the general formula (1), Element A is one or more alkali metal elements containing K, The element M is a single element of Si, a single element of Ge, or a combination of Si and one or more elements selected from the group consisting of Ge, Sn, Ti, Zr, and Hf.

[0010] The present invention also provides the following.

[0011] A composite body comprising the above phosphor powder and a sealant that seals the phosphor powder.

[0012] The present invention also provides the following.

[0013] A light emitting device comprising: a light emitting element that emits excitation light; and the above composite that converts the wavelength of the excitation light. Effect of the Invention

[0014] According to the present invention, a fluoride phosphor having good luminescence characteristics is provided. [Brief description of the drawings]

[0015] [Figure 1] 1A to 1C are diagrams for explaining a truncated hexahedron shape, a cuboctahedron shape, and a truncated octahedron shape. [Diagram 2] FIG. 1 is a schematic diagram for explaining an example of a light emitting device. [Diagram 3] 1 is an electron microscope image of a phosphor powder obtained in an example. [Figure 4] 1 is an electron microscope image of a phosphor powder obtained in an example. [Diagram 5] 1 is an electron microscope image of a phosphor powder obtained in an example. [Figure 6] 1 is an electron microscope image of a phosphor powder obtained in an example. [Figure 7] 1 is an electron microscope image of a phosphor powder obtained in an example. [Figure 8] 1 is an electron microscope image of a phosphor powder obtained in an example. [Figure 9] 1 is an electron microscope image of a phosphor powder obtained in an example. [Figure 10] 1 is an electron microscope image of a phosphor powder obtained in an example. [Figure 11] 1 is an electron microscope image of a phosphor powder obtained in an example. [Figure 12] 1 is an electron microscope image of a phosphor powder obtained in a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The drawings are for illustrative purposes only. The shapes and dimensional ratios shown in the drawings do not necessarily correspond to the actual products.

[0017] <Phosphor powder> The phosphor powder of this embodiment contains phosphor particles having a composition represented by the following general formula (1): Due to this composition, the phosphor powder of this embodiment converts blue light normally emitted from a blue LED into red light. General formula (1):A2MF6:Mn

[0018] In the general formula (1), Element A is one or more alkali metal elements containing K, The element M is a single element of Si, a single element of Ge, or a combination of Si and one or more elements selected from the group consisting of Ge, Sn, Ti, Zr, and Hf.

[0019] At least a part of the phosphor particles in the phosphor powder of this embodiment is a first phosphor particle having any shape selected from the group consisting of a truncated hexahedron, a cuboctahedron, and a truncated octahedron. Furthermore, among the phosphor particles in the phosphor powder of this embodiment, 65% or more, on a number basis, are first phosphor particles.

[0020] The first phosphor particles are closer to a sphere than the cubic phosphor particles. This reduces the specific surface area of ​​the phosphor particles, which reduces the reflection of light on the particle surface, and is believed to result in improved light emission characteristics. In addition, the phosphor powder contains 65% or more of the first phosphor particles by number, which is believed to make it easier to obtain the effect of the first phosphor particles being closer to a sphere.

[0021] The phosphor powder of this embodiment can be manufactured by using appropriate raw materials and adopting appropriate manufacturing methods and manufacturing conditions. Details will be described later, but for example, when controlling the saturation of an aqueous solution to precipitate phosphor powder, one of the key points is to add water to the system in a short time all at once to instantly increase the saturation. Another key point is the "order" in which each raw material is added to the system. It is believed that the operation of adding water to the system in a short time all at once results in phosphor particles with a shape different from the cubic shape expected from the crystal system (cubic crystal system), which is different from the usual case of "slowly" crystallizing. Although the details are unknown, it is speculated that the relatively close crystal growth rate in the normal direction of each face of the cube and the crystal growth rate in the diagonal direction of the cube are related to the fact that phosphor particles with "rounded corners" are obtained.

[0022] (Composition: General formula (1)) The element A is one or more alkali metal elements containing K. Specifically, it can be K alone, or a combination of K and one or more alkali metal elements selected from Li, Na, Rb, and Cs. From the viewpoint of chemical stability, it is preferable that the content of K in the element A is high (for example, 50 mol % or more of K in the element A), and it is more preferable that the element A is K alone.

[0023] The element M is Si alone, Ge alone, or a combination of Si and one or more elements selected from the group consisting of Ge, Sn, Ti, Zr, and Hf. From the viewpoint of chemical stability, it is preferable that the content of Si in the element M is high (for example, 50 mol % or more of Si in the element M), and it is more preferable that the element M is Si alone.

[0024] (Regarding the shape of phosphor particles) As described above, the phosphor powder of the present embodiment includes first phosphor particles having any shape selected from the group consisting of a truncated hexahedron, a cuboctahedron, and a truncated octahedron. The three-dimensional shapes of the truncated hexahedron, the cuboctahedron, and the truncated octahedron are illustrated in FIG. 1.

[0025] In this embodiment, the first phosphor particles do not have to be "mathematically exact" truncated hexahedral, cuboctahedral, or truncated octahedral shapes. For example, mathematically, among three-dimensional figures resembling a truncated hexahedron, only those having the same length of each side are sometimes defined as truncated hexahedrons. However, in this embodiment, the first phosphor particles also include truncated hexahedron-like phosphor particles having sides of different lengths. In other words, even if the lengths of two sides that should mathematically be the same are not the same, phosphor particles having a pseudo-truncated hexahedral, pseudo-cuboctahedral or pseudo-truncated octahedral shape that can be easily distinguished as a "cubic shape with rounded corners" at a glance in an electron microscope photograph are also included in the first phosphor particles.

[0026] The crystal system of the first phosphor particles is considered to be a cubic system, and the (100) and (111) faces of the first phosphor particles are considered to be exposed.

[0027] (Particle size distribution) When the particle size distribution of the phosphor powder of this embodiment is appropriate, the light emitting characteristics may be improved and the phosphor powder may be easily applied to various applications.

[0028] The cumulative 50% value in the volume-based particle size distribution curve of the phosphor powder of this embodiment is D 50 Then, D 50 is preferably 10 μm or more and 40 μm or less, more preferably 20 μm or more and 35 μm or less. 50 When the value of is appropriate, it is easy to obtain sufficient quantum efficiency, and when it is necessary to mix the phosphor powder with a resin or the like to form a film or sheet containing the phosphor, it is easy to form a uniform and smooth film or sheet.

[0029] In addition, the cumulative 10% value in the volume-based particle size distribution curve of the phosphor powder of this embodiment is D 10 , cumulative 50% value D 50 , cumulative 90% value D 90 Then, (D 90 -D 10 ) / D 50 is preferably 0.9 or less, more preferably 0.75 or less. There is no particular lower limit, but it is, for example, 0.3 or more, specifically 0.5 or more. (D 90 -D 10 ) / D 50 can be considered as an index showing the "width" of the particle size distribution. A narrow particle size distribution of a phosphor powder means that the particle sizes of the phosphor particles in the phosphor powder are relatively "uniform". Therefore, (D 90 -D 10 ) / D 50When the phosphor powder is mixed with a resin or the like to form a film or sheet containing the phosphor, a uniform and smooth film or sheet can be easily formed by keeping the ratio of the phosphor powder to 0.9 or less.

[0030] The volume-based particle size distribution curve can be obtained through measurement by a laser diffraction scattering method. For details of the measurement method, see the examples given later.

[0031] (Proportion of phosphor particles in phosphor powder) In order to obtain a sufficient effect of the first phosphor particles, the phosphor powder may contain more than 65% of the first phosphor particles in terms of number. Specifically, among the phosphor particles in the phosphor powder, preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, and particularly preferably 95% or more are first phosphor particles by number. The upper limit of this value may be 100%. Just to be sure, when 100% of the phosphor particles in the phosphor powder are not first phosphor particles by number, the phosphor powder contains second phosphor particles that do not correspond to the first phosphor particles. The second phosphor particles are similar to the first phosphor particles (composition, etc.) except that the shape is not a truncated hexahedron, a cuboctahedron, or a truncated octahedron. The ratio (by number) of the first phosphor particles in the phosphor powder can be obtained by observing the shapes of at least 50 phosphor particles whose shapes can be confirmed in an image of the phosphor powder taken under a magnified electron microscope.

[0032] <Method of manufacturing phosphor powder> The phosphor powder of this embodiment can be manufactured by using an appropriate material and selecting an appropriate manufacturing method and manufacturing conditions. By selecting an appropriate manufacturing method and manufacturing conditions, it is easy to manufacture a phosphor powder containing a large amount of first phosphor particles. Specific examples of the production methods are described in the Examples section below, but two production methods will be described below as "Production Method 1" and "Production Method 2".

[0033] (Manufacturing method 1) The manufacturing method 1 mainly includes a dissolving step, a Mn source introduction step, and a precipitation step. These steps will be described below. These steps can be performed at room temperature.

[0034] ·Dissolution process In the dissolving step, (i) a raw material containing element A (such as K), (ii) a raw material containing element M (preferably Si), (iii) a raw material containing F, etc. are usually dissolved in hydrofluoric acid (aqueous solution of HF). One raw material may serve as two or more of (i) to (iii). For example, K2SiF6 used in the examples serves as all of the raw materials (i) to (iii). The concentration of hydrogen fluoride in the hydrofluoric acid before dissolving the raw materials is preferably 50 to 60 mass %.

[0035] As the raw material containing the element A, for example, an oxide, hydroxide, fluoride, or carbonate of the element A can be used. The source material containing F can be a fluoride as a source material for other elements (A, M, Mn). F can also be supplied from hydrogen fluoride in hydrofluoric acid used as a solvent.

[0036] A particularly preferred source of material (other than hydrofluoric acid in hydrofluoric acid) for use in the dissolution step is K2SiF6.

[0037] ·Mn source input process In the Mn source introduction step, a raw material containing Mn is introduced into the solution obtained in the dissolution step, and the solution is stirred for, for example, 0.5 seconds to 10 minutes until water is introduced into the system in the precipitation step described below. Incidentally, when K2MnF6 is used as the raw material containing Mn, dissolution is not completed until about 4 seconds after the introduction, and solute concentration in the solution may change.

[0038] Examples of raw materials containing Mn include hexafluoromanganates, permanganates, oxides (except permanganates), fluorides (except hexafluoromanganates), chlorides, sulfates, and nitrates. Among them, fluorides are preferred because they can efficiently substitute Mn for the Si site in the fluoride phosphor and provide good luminescence characteristics, and among fluorides, hexafluoromanganates are preferred. Examples of hexafluoromanganates include Na2MnF6, K2MnF6, and Rb2MnF6. In particular, K2MnF6 is preferred because it contains F and K (corresponding to element A) that constitute fluoride phosphors in addition to Mn.

[0039] ·Precipitation process In the precipitation step, an appropriate amount of water is added to the system as quickly as possible. This causes the system to rapidly become supersaturated, and phosphor particles having the composition represented by general formula (1) are precipitated. "As quickly as possible" here means that, although it depends on the scale of the system, for example, when 1 L of hydrofluoric acid is used in the dissolution step, preferably about 1.5 L of water is added to the system in about 3 seconds. This operation of suddenly bringing the system into a supersaturated state is thought to result in phosphor particles with shapes that differ from the cubic shapes expected from the crystal lattice structure, unlike the usual "slow" crystal precipitation. Although the details are unclear, it is speculated that the relatively close crystal growth speed in the normal direction of each face of the cube and the crystal growth speed in the diagonal direction of the cube are related to the fact that phosphor particles with "rounded corners" are obtained.

[0040] The phosphor powder obtained in the precipitation process is recovered by solid-liquid separation such as by filtration, and washed with an organic solvent such as methanol, ethanol, or acetone. If fluoride phosphor powder is washed with water, a part of it may be hydrolyzed to produce a brown manganese compound, which may deteriorate the properties of the phosphor. For this reason, it is preferable to use an organic solvent in the washing process. Furthermore, washing with an aqueous hydrofluoric acid solution several times before washing with an organic solvent can dissolve and remove trace amounts of impurities. The concentration of hydrofluoric acid in the aqueous hydrofluoric acid solution used for washing is preferably 5% by mass or more from the viewpoint of suppressing decomposition of the fluoride phosphor, and is preferably 60% by mass or less from the viewpoint of solubility of the phosphor powder. After the washing step, it is preferable to dry the phosphor powder to thoroughly evaporate the washing liquid. In addition, classification may be performed using a sieve with a specified mesh size, and coarse particles may be removed.

[0041] (Manufacturing method 2) Although manufacturing method 2 differs from manufacturing method 1, it is similar to manufacturing method 1 in that phosphor particles having a composition represented by general formula (1) are precipitated by rapidly bringing the system into a supersaturated state. Manufacturing method 2 mainly includes a dissolving step, a Mn source introduction step, a core particle introduction step, and a precipitation step. These steps are described below. These steps can be performed at room temperature.

[0042] ·Dissolution process The dissolving step in the production method 2 can be basically the same as in the production method 1.

[0043] ·Mn source input process The Mn source introduction step in Production Method 2 can be basically the same as in Production Method 1. However, the stirring time (the time from introduction of the raw material containing Mn to the start of introduction of the core particles described below) is preferably 1 to 60 seconds, more preferably 10 to 50 seconds, and further preferably 20 to 40 seconds.

[0044] ·Nuclear particle injection process In the core particle introduction step, for example, "core particles" that can serve as nuclei for crystal growth and are represented by the composition formula K2SiF6:Mn are introduced into the system. As the core particle, for example, the phosphor particle obtained as in the above-mentioned (Production Method 1) can be used. However, the core particle may or may not contain the first phosphor particle. When core particles are obtained by the manufacturing method 1, it is preferable that the time between the Mn source introduction step and the precipitation step is short (about 1 second). Although it is merely speculation, it is speculated that obtaining core particles in this manner makes it easier to form a chemical structure in the core particles that is suitable for obtaining phosphor particles having a truncated hexahedral, cuboctahedral, or truncated octahedral shape.

[0045] ·Precipitation process The precipitation step in the production method 2 can be basically the same as in the production method 1.

[0046] The method of post-treatment (separation and recovery, washing, etc.) of the phosphor powder obtained in the precipitation step in Production Method 2 can be basically the same as in Production Method 1.

[0047] <Composite and Light-Emitting Device> The composite of this embodiment includes the above-mentioned phosphor powder and a sealant that seals the phosphor powder. Moreover, the light emitting device of the present embodiment includes a light emitting element that emits excitation light, and the above-mentioned composite that converts the wavelength of the excitation light. The light emitting device of this embodiment is preferably used as, for example, a backlight for a display.

[0048] An example of the composite and the light emitting device will be described below with reference to FIG.

[0049] FIG. 2 is a schematic diagram of the light emitting device 1. As shown in FIG. The light emitting device 1 includes a composite 10 and a light emitting element 20. The composite 10 is provided in contact with an upper portion of the light emitting element 20. The light emitting element 20 is typically a blue LED. Terminals are provided on the bottom of the light emitting element 20. When the terminals are connected to a power source, the light emitting element 20 can emit light. The excitation light emitted from the light emitting element 20 is wavelength converted by the complex 10. When the excitation light is blue light, the blue light is wavelength converted to red light by the complex 10 containing phosphor powder.

[0050] The composite 10 can be composed of the above-mentioned phosphor powder and a sealant that seals the phosphor powder. As the sealing material, for example, various curable resin materials (materials that are cured by heat and / or light) can be used. Any curable resin material can be used as long as it is sufficiently transparent and can provide the optical properties required for a display or lighting device. Examples of the sealing material include silicone resin materials. Regarding silicone resin materials, curable materials are supplied by Toray Dow Corning Co., Ltd., Shin-Etsu Chemical Co., Ltd., etc., and silicone resin materials are preferable from the viewpoints of high transparency and excellent heat resistance. In addition, examples of the sealing material include epoxy resin materials and urethane resin materials. The amount of the phosphor powder particles in the composite 10 is, for example, 10 to 70 mass %, and preferably 25 to 55 mass %.

[0051] There is no particular limitation on the size or shape of the light-emitting element 20. Depending on the application of the light-emitting device 1, the light-emitting element 20 can have any size or shape.

[0052] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of the present invention are included in the present invention. EXAMPLES

[0053] The embodiments of the present invention will be described in detail based on Examples and Comparative Examples. It should be noted that the present invention is not limited to the Examples.

[0054] <Raw materials> The following raw materials were used: HF: Aqueous solution with a concentration of 55% by mass manufactured by Stella Chemifa Corporation K2SiF6: manufactured by Morita Chemical Co., Ltd. K2MnF6: Prepared by the method described in paragraph 0042 of JP2019-1897A KHF2: Special grade reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. SiO2: FB-50R manufactured by Denka Co., Ltd. KSF core particles: Produced as follows:

[0055] (KSF Core Particle Manufacturing Method) KSF core particles were produced according to the following procedure. (1) At room temperature, 655 g of K2SiF was added to 1000 mL of a 55% by mass HF aqueous solution contained in a Teflon (registered trademark) beaker and stirred for 10 minutes. This produced a homogeneous solution. (2) While continuing to stir, 65.9 g of K2MnF was added to the beaker. (3) One second after the addition of K2MnF6, 1500 mL of ion-exchanged water was added to the beaker at a rate of 500 mL / s. This caused the precipitation of a yellow solid to begin. Stirring was then continued for 5 minutes. (4) After stirring, the solution was left to stand to precipitate the yellow solids. After the precipitation was confirmed, the supernatant was removed, and the yellow solids were washed with hydrofluoric acid having a concentration of about 24% by mass, and then washed with methanol. The washed solids were filtered to separate and recover the solids, and further dried to evaporate and remove the remaining methanol. After drying, a nylon sieve with 75 μm openings was used to classify and recover only the yellow powder that passed through this sieve.

[0056] <Production of phosphor powder> (Example 1-1) The phosphor powder was produced according to the following procedure. (1) At room temperature, 650 g of K2SiF was added to 1000 mL of a 55% by mass HF aqueous solution contained in a Teflon (registered trademark) beaker and stirred for 10 minutes. This produced a homogeneous solution. (2) While continuing to stir, 66 g of K2MnF was added to the beaker and stirred for 1 second. (3) Next, 1500 mL of ion-exchanged water was poured into the beaker at a rate of 500 mL / s. This caused the precipitation of a yellow solid to begin. Stirring was then continued for 5 minutes.

[0057] After the stirring was completed, the solution was left to stand to precipitate the yellow solids. After the precipitation was confirmed, the supernatant was removed, and the yellow solids were washed with hydrofluoric acid having a concentration of about 24% by mass, and then washed with methanol. The washed solids were filtered to separate and recover the solids, and further dried to evaporate and remove the remaining methanol. After the drying process, a nylon sieve with 75 μm openings was used to classify and recover only the yellow powder that passed through the sieve. In this manner, a phosphor powder was obtained.

[0058] (Examples 1-2 to 1-7) A phosphor powder was obtained in the same manner as in Example 1-1, except that the stirring time between the addition of K2MnF6 and the start of the addition of 1500 mL of ion-exchanged water was changed from 1 second to the following time: Example 1-2: 2 seconds Example 1-3: 3 seconds Example 1-4: 5 seconds Example 1-5: 30 seconds Example 1-6: 60 seconds Example 1-7: 300 seconds

[0059] (Example 2-1) The phosphor powder was produced according to the following procedure. (1) At room temperature, 650 g of K2SiF was added to 1000 mL of a 55% by mass HF aqueous solution contained in a Teflon (registered trademark) beaker and stirred for 10 minutes. This produced a homogeneous solution. (2) While continuing to stir, 66 g of K2MnF was added to the beaker and stirred for 10 seconds. (3) Next, 8 g of KSF core particles were added to the beaker and stirred for 2 minutes. (4) Next, 1500 mL of ion-exchanged water was poured into the beaker at a rate of 500 mL / s. This caused the precipitation of a yellow solid to begin. Stirring was then continued for 5 minutes.

[0060] After the stirring was completed, precipitation treatment, washing treatment of the solid matter, separation and recovery, drying treatment, sieving, etc. were carried out in the same manner as in Example 1-1. In this manner, a phosphor powder was obtained.

[0061] (Examples 2-2 to 2-9) A phosphor powder was obtained in the same manner as in Example 2-1, except that the amount of KSF core particles added in the above (3) was changed from 8 g to the amount described below. Example 2-2: 8.5 g Example 2-3: 9g Example 2-4: 9.5 g Example 2-5: 10g Example 2-6: 10.5 g Example 2-7: 11g Example 2-8: 11.5 g Example 2-9: 12g

[0062] (Comparative Example) The phosphor powder was produced according to the following procedure. (1) At room temperature, 87.9 g of SiO2 was added to 1000 mL of a 55% by mass HF aqueous solution contained in a Teflon (registered trademark) beaker and stirred for 15 minutes. This gave a homogeneous solution. (2) While continuing to stir, 19.6 g of K2MnF6 was added to the beaker and stirred for 30 seconds. (3) A solution prepared in a Teflon (registered trademark) beaker other than the beaker in (2) above (prepared by adding 2311 g of KHF to 1500 mL of HF aqueous solution with a concentration of 55% by mass and stirring for 15 minutes) was added to the beaker in (2) above at a rate of 500 mL / s. This caused the precipitation of a yellow solid to begin. Stirring was then continued for 5 minutes.

[0063] After the stirring was completed, the same procedures as in Example 1-1 were carried out, such as precipitation treatment, washing treatment of the solid matter, separation and recovery, drying treatment, and sieving, etc. In this manner, a phosphor powder was obtained.

[0064] <Identification: Crystal phase measurement, composition measurement, etc.> For the phosphor powder (yellow powder) obtained in each example, an X-ray diffraction pattern was obtained using an X-ray diffractometer. The obtained X-ray diffraction pattern was the same as that of K2SiF6 crystal. From this, it was confirmed that K2SiF6:Mn was obtained in a single phase.

[0065] <Particle size distribution measurement by laser diffraction scattering method> 30 mL of ethanol was measured into a 50 mL beaker, and 0.03 g of phosphor powder was added thereto. Next, the container was placed in a homogenizer (manufactured by Nippon Seiki Seisakusho, product name US-150E) whose output had been adjusted to "Altitude: 100%" in advance, and pretreatment was carried out for 3 minutes. The volume-based particle size distribution curve was obtained for the solution thus prepared using a laser diffraction scattering type particle size distribution analyzer (manufactured by Microtrackbell, product name MT3300EXII). 10 , D 50 and D. 90 Then, (D 90 -D 10 ) / D 50 asked for.

[0066] <Counting the ratio of first phosphor particles> The phosphor powder obtained in each Example was photographed with an electron microscope. From the photographed image, 50 particles whose shape could be confirmed were randomly selected, and each particle was judged as to whether it had (i) any shape selected from the group consisting of a truncated hexahedron, a cubic octahedron, and a truncated octahedron, or (ii) any other shape. Then, the ratio (number basis) of the first phosphor particles in the phosphor powder was calculated.

[0067] <Evaluation of light emission characteristics (quantum efficiency, etc.)> A standard reflector (Spectralon, product name, manufactured by Labsphere) with a reflectance of 99% was set at the side opening (φ10 mm) of an integrating sphere (φ60 mm). Monochromatic light, which was split into 455 nm wavelengths from a light emission source (Xe lamp), was introduced into this integrating sphere via an optical fiber, and the spectrum of the reflected light was measured with a spectrophotometer (MCPD-7000, product name, manufactured by Otsuka Electronics Co., Ltd.). At this time, the number of excitation light photons (Qex) was calculated from the spectrum in the wavelength range of 450 to 465 nm. Next, the phosphor powder obtained in each Example was filled in a concave cell so that the surface was smooth, and the cell was set in the opening of an integrating sphere, and monochromatic light with a wavelength of 455 nm was irradiated, and the excitation reflected light and fluorescence spectra were measured by a spectrophotometer. The number of excitation reflected light photons (Qref) and the number of fluorescence photons (Qem) were calculated from the obtained spectrum data. The number of excitation reflected light photons was calculated in the same wavelength range as the number of excitation light photons, and the number of fluorescence photons was calculated in the range of 465 to 800 nm. From the obtained three types of photon numbers, the absorptivity (=(Qex-Qref) / Qex×100), internal quantum efficiency (=Qem / (Qex-Qref)×100), and external quantum efficiency (=Qem / Qex×100) were calculated.

[0068] The above results are summarized in Tables 1 and 2. Moreover, SEM images of each phosphor powder are shown in FIGS.

[0069] [Table 1]

[0070] [Table 2]

[0071] As shown in the above table, phosphor particles containing 65% or more by number of first phosphor particles having any shape selected from the group consisting of truncated hexahedron, cuboctahedron, and truncated octahedron showed good light-emitting characteristics.

[0072] This application claims priority based on Japanese Patent Application No. 2021-052745, filed on March 26, 2021, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0073] 1 Light emitting device 10 Complex 20 Light emitting element

Claims

1. A phosphor powder containing phosphor particles having a composition represented by the following general formula (1): the phosphor particles include first phosphor particles having any shape selected from the group consisting of a truncated hexahedron shape, a cuboctahedron shape, and a truncated octahedron shape; Among the phosphor particles in the phosphor powder, 65% or more by number are the first phosphor particles, a cumulative 50% value D50 in a volume-based particle size distribution curve is 20 μm or more and 40 μm or less; A phosphor powder in which (D 90 -D 10 ) / D 50 is 0.9 or less, where D 10 is the cumulative 10% value, D 50 is the cumulative 50% value, and D 90 is the cumulative 90% value in a volume-based particle size distribution curve. General formula (1): A ２ MF ６ :Mn In general formula (1), Element A is one or more alkali metal elements containing K, The element M is Si alone, Ge alone, or a combination of Si with one or more elements selected from the group consisting of Ge, Sn, Ti, Zr, and Hf.

2. A composite comprising the phosphor powder according to claim 1 and an encapsulant that encapsulates the phosphor powder.

3. A light emitting device comprising: a light emitting element that emits excitation light; and the composite according to claim 2 that converts the wavelength of the excitation light.

Images