JP7606597B2 - Phosphor powder, composite and light-emitting device - Google Patents

Description

The present invention relates to phosphor powders, composites and light-emitting devices.

A fluoride phosphor represented by K ₂ SiF ₆ :Mn (often abbreviated as "KSF phosphor") is known as a phosphor capable of converting blue light emitted from a blue light-emitting diode into red light. This phosphor is efficiently excited by blue light. In addition, the half-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 brightness and excellent color rendering and color reproducibility can be realized.

An example of a prior art for fluoride phosphors is Patent Document 1. Patent Document 1 describes a fluoride phosphor whose composition is expressed by the general formula A ₂ M _(1-n) F ₆ :Mn ⁴⁺ _n , whose bulk density is 0.80 g/cm ³ or more, and whose mass median diameter is 30 μm or less. In the general formula, 0<n≦0.1, the element A is one or more alkali metal elements containing K, and 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.

JP 2019-001897 A

As white LEDs become more widespread, there is a demand for further improvement in the luminescent properties of fluoride phosphors.

The inventors conducted various studies with the goal of obtaining a fluoride phosphor with good luminescence characteristics.

Through their research, the inventors have completed the invention provided below.

The present invention is as follows.

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;
A phosphor powder, in which 65% or more by number of phosphor particles in the phosphor powder are the first phosphor particles.
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.

The present invention also includes the following.

A composite comprising the above phosphor powder and a sealing material that seals the phosphor powder.

The present invention also includes the following.

A light-emitting device comprising a light-emitting element that emits excitation light and the above-mentioned composite that converts the wavelength of the excitation light.

According to the present invention, a fluoride phosphor having good luminescence characteristics is provided.

1A to 1C are diagrams for explaining a truncated hexahedron shape, a cuboctahedron shape, and a truncated octahedron shape. FIG. 1 is a schematic diagram for explaining an example of a light emitting device. 1 is an electron microscope image of a phosphor powder obtained in an example. 1 is an electron microscope image of a phosphor powder obtained in an example. 1 is an electron microscope image of a phosphor powder obtained in an example. 1 is an electron microscope image of a phosphor powder obtained in an example. 1 is an electron microscope image of a phosphor powder obtained in an example. 1 is an electron microscope image of a phosphor powder obtained in an example. 1 is an electron microscope image of a phosphor powder obtained in an example. 1 is an electron microscope image of a phosphor powder obtained in an example. 1 is an electron microscope image of a phosphor powder obtained in an example. 1 is an electron microscope image of a phosphor powder obtained in a comparative example.

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.

<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): 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.

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.

The first phosphor particles are closer to a sphere than cubic phosphor particles. This reduces the specific surface area of the phosphor particles, which is thought to reduce light reflection on the particle surface and result in improved light emission characteristics. In addition, it is thought that the effect of the first phosphor particles being closer to a sphere can be more easily achieved by having the phosphor powder contain 65% or more of the first phosphor particles by number.

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 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), unlike the usual case of crystals being precipitated "slowly." Although the details are unclear, it is presumed 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.

(Composition: Regarding general formula (1))
The element A is one or more alkali metal elements containing K. Specifically, it may 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.

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 element M is high (for example, 50 mol % or more of element M is Si), and it is more preferable that element M is Si alone.

(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.

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.

Incidentally, the crystal system of the first phosphor particles is considered to be a cubic system. And, in the first phosphor particles, the (100) and (111) faces are considered to be exposed.

(Regarding 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.

When the cumulative 50% value in the volume-based particle size distribution curve of the phosphor powder of this embodiment is defined as _D50 , _D50 is preferably 10 μm to 40 μm, more preferably 20 μm to 35 μm. When _D50 is a moderate value, sufficient quantum efficiency can be easily obtained, 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, a uniform and smooth film or sheet can be easily formed.

In addition, when the cumulative 10% value in the volume-based particle size distribution curve of the phosphor powder of this embodiment is _D10 , the cumulative 50% value is _D50 , and the cumulative 90% value is _D90 , ( _D90 - _D10 )/ _D50 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 regarded as an index representing the "width" of the particle size distribution. A narrow width of the particle size distribution of a phosphor powder means that the particle sizes of the phosphor particles in the phosphor powder are relatively "uniform". Therefore, when (D ₉₀ -D ₁₀ )/D ₅₀ is 0.9 or less, for example, 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.

The volumetric particle size distribution curve can be obtained through measurements using the laser diffraction scattering method. For details of the measurement method, please refer to the examples below.

(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, if 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 determined 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.

<Method of manufacturing phosphor powder>
The phosphor powder of the present 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 given later, but two production methods will be described below as "Production Method 1" and "Production Method 2".

(Production 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.

Dissolving step 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, K ₂ SiF ₆ 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 %.

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

A particularly preferred source (other than hydrofluoric acid in hydrofluoric _acid ) for use in the dissolution step is _K2SiF6 .

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 later. For example, when _K2MnF6 is used as the raw material containing Mn, dissolution is not completed until about 4 seconds after the introduction, and therefore the solute concentration in the solution may change.

Examples of raw materials containing Mn include hexafluoromanganate, permanganate, oxide (except permanganate), fluoride (except hexafluoromanganate), chloride, sulfate, and nitrate. Among them, fluoride is preferable because Mn can be efficiently substituted at the Si site in the fluoride phosphor and good light emission characteristics can be obtained, and among fluorides, hexafluoromanganate is preferable. Examples of hexafluoromanganate include Na ₂ MnF ₆ , K ₂ MnF ₆ , and Rb ₂ MnF _6. In particular, K ₂ MnF ₆ is preferable because it contains F and K (corresponding to element A) that constitute the fluoride phosphor in addition to Mn.

Precipitation step 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. Here, "as quickly as possible" refers to adding about 1.5 L of water to the system in about 3 seconds, although this depends on the scale of the system. For example, when 1 L of hydrofluoric acid is used in the dissolution step, water is preferably 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.

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, by washing several times with an aqueous solution of hydrofluoric acid before washing with an organic solvent, it is possible to dissolve and remove impurities that have formed in small amounts. The concentration of hydrofluoric acid in the aqueous solution of hydrofluoric acid 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 the 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.

(Production 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.

The dissolving step in the production method 2 can be basically the same as that in the production method 1.

The Mn source introducing step in production method 2 can be basically the same as in production method 1. However, the stirring time (the time from introducing the raw material containing Mn to starting introducing the core particles described below) is preferably 1 to 60 seconds, more preferably 10 to 50 seconds, and further preferably 20 to 40 seconds.

Core Particle Addition Step In the core particle addition step, "core particles" that can serve as nuclei for crystal growth, for example, represented by the composition formula K ₂ SiF ₆ :Mn, are added to 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.
In addition, 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.

The precipitation step in the production method 2 can be basically the same as in the production method 1.

The method for post-processing (separation, recovery, cleaning, etc.) of the phosphor powder obtained in the precipitation process in manufacturing method 2 can basically be the same as in manufacturing method 1.

<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.

Below, an example of a composite and a light-emitting device is described with reference to Figure 2.

FIG. 2 is a schematic diagram of the light emitting device 1. As shown in FIG.
The light emitting device 1 includes a composite body 10 and a light emitting element 20. The composite body 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 composite 10. When the excitation light is blue light, the blue light is wavelength converted to red light by the composite 10 containing phosphor powder.

The composite 10 can be composed of the above-mentioned phosphor powder and a sealant that seals the phosphor powder.
As the encapsulant, 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 preferred from the viewpoints of high transparency and excellent heat resistance. 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% by mass, and preferably 25 to 55% by mass.

The size and shape of the light-emitting element 20 are not particularly limited. Depending on the application of the light-emitting device 1, the light-emitting element 20 can be of any size and shape.

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, improvements, etc. that can achieve the object of the present invention are included in the present invention.

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.

<Ingredients>
The following raw materials were used:
HF: 55% by mass aqueous solution manufactured by Stella Chemifa Corporation K ₂ SiF ₆ : manufactured by Morita Chemical Industries, Ltd. K ₂ MnF ₆ : prepared by the method described in paragraph 0042 of JP2019-1897A KHF ₂ : special grade reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. SiO ₂ : FB-50R manufactured by Denka Co., Ltd.
KSF core particles: Produced as follows

(Method of manufacturing KSF core particles)
KSF core particles were produced according to the following procedure.
(1) At room temperature, 55 g of K ₂ SiF ₆ was added to 1000 mL of a 55% by mass aqueous HF solution contained in a Teflon (registered trademark) beaker, and the mixture was stirred for 10 minutes to obtain a homogeneous solution.
(2) While continuing to stir, 5.9 g of K ₂ MnF ₆ was added to the beaker.
(3) One second after the addition of K ₂ MnF ₆ , 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 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 a mesh size of 75 μm was used to classify and recover only the yellow powder that passed through the sieve.

<Production of phosphor powder>
(Example 1-1)
The phosphor powder was produced according to the following procedure.
(1) At room temperature, 50 g of K ₂ SiF ₆ was added to 1000 mL of a 55% by mass aqueous HF solution contained in a Teflon (registered trademark) beaker, and the mixture was stirred for 10 minutes to obtain a homogeneous solution.
(2) While continuing to stir, 6 g of K ₂ MnF ₆ 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 precipitation of a yellow solid to begin. Stirring was then continued for 5 minutes.

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 a mesh size of 75 μm was used to classify and recover only the yellow powder that passed through the sieve.
In this manner, a phosphor powder was obtained.

(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 K ₂ MnF ₆ 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

(Example 2-1)
The phosphor powder was produced according to the following procedure.
(1) At room temperature, 50 g of K ₂ SiF ₆ was added to 1000 mL of a 55% by mass aqueous HF solution contained in a Teflon (registered trademark) beaker, and the mixture was stirred for 10 minutes to obtain a homogeneous solution.
(2) While continuing stirring, 6 g of K ₂ MnF ₆ 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.

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.

(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: 9 g
Example 2-4: 9.5 g
Example 2-5: 10g
Example 2-6: 10.5 g
Example 2-7: 11 g
Example 2-8: 11.5 g
Example 2-9: 12g

Comparative Example
The phosphor powder was produced according to the following procedure.
(1) At room temperature, 87.9 g of SiO ₂ was added to 1000 mL of a 55% by mass aqueous HF solution contained in a Teflon (registered trademark) beaker, and the mixture was stirred for 15 minutes, thereby obtaining a homogeneous solution.
(2) While continuing stirring, 19.6 g of K ₂ MnF ₆ 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 311 g of KHF ₂ to 1500 mL of a 55% by mass HF aqueous solution and stirring for 15 minutes) was added to the beaker in (2) above at a rate of 500 mL/s. This caused precipitation of a yellow solid to begin. Stirring was then continued for 5 minutes.

After the stirring was completed, the precipitation process, washing process of the solid matter, separation and recovery, drying process, sieving, etc. were carried out in the same manner as in Example 1-1. As a result, phosphor powder was obtained.

<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 K ₂ SiF ₆ crystal. From this, it was confirmed that K ₂ SiF ₆ :Mn was obtained in a single phase.

<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 placed therein. The container was then placed in a homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd., product name US-150E) whose output had been adjusted in advance to "Altitude: 100%", and pretreatment was carried out for 3 minutes.
A volumetric particle size distribution curve was obtained for the solution thus prepared using a laser diffraction/scattering particle size distribution analyzer (manufactured by Microtrackbell, product name MT3300EXII). From the obtained curve, _D10 , _D50 , and _D90 were calculated, and further ( _D90 - _D10 )/ _D50 was calculated.

<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 shapes could be confirmed were randomly selected, and each particle was judged to have (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.

<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 separated to a wavelength of 455 nm 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, a concave cell was filled with the phosphor powder obtained in each Example 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 absorption rate (= (Qex-Qref)/Qex x 100), internal quantum efficiency (= Qem/(Qex-Qref) x 100), and external quantum efficiency (= Qem/Qex x 100) were calculated.

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

As shown in the table above, phosphor particles containing 65% or more by number of first phosphor particles having any shape selected from the group consisting of truncated hexahedral, cuboctahedral, and truncated octahedral shapes exhibited good light-emitting characteristics.

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.

1 Light emitting device 10 Composite 20 Light emitting element

Claims (3)

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

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