JP7676175B2 - β-type sialon phosphor powder and light-emitting device - Google Patents

Description

The present invention relates to a β-SiAlON phosphor powder and a light-emitting device.

β-SiAlON phosphors are known as phosphors capable of converting blue light emitted from a blue LED (Light Emitting Diode) into light of another color. The chemical composition of β-SiAlON containing Eu as an activator metal is usually represented by the general formula: Si6 _{- zAlzOzN8 -z :} Eu (z is greater than 0).
Various improvements have been made to β-SiAlON phosphors for application in lighting and display devices.

Patent Document 1 describes a method for producing _a phosphor having a general composition formula of Si6 _{- zAlzOzN8 -z} :Re (Re is an activator containing at least one selected from the group consisting of Mn, Ce and Eu, and 0<z<4.2). This production method includes a step of firing the composition represented by the general formula at a temperature of 1500°C to 2200°C inclusive while applying an isotropic pressure of 100 MPa or more in a nitrogen atmosphere, and a step of heating the fired body to 1400°C to 2000°C inclusive in a hydrogen-containing atmosphere to perform an annealing treatment.

Patent Document 2 describes a method for producing β-sialon in which Eu ²⁺ is dissolved in β-sialon represented by Si _6-z Al _z O _z N _8-z . This production method includes a mixing step of mixing raw materials for β-sialon, a firing step of firing the raw materials after the mixing step to form β-sialon, a HIP treatment step of performing HIP (Hot Isostatic Pressing) treatment on the β-sialon after the firing step, an annealing treatment step of annealing the β-sialon after the HIP treatment step, and an acid treatment step of acid treating the β-sialon after the annealing treatment step.

Patent Document 3 describes a β-sialon phosphor represented by the following formula 1, in which D10, D50, and D90 (each in μm) based on volume frequency measured by a laser diffraction/scattering method are 10 μm or less, and the values of D10, D50, and D90 satisfy the relationship of the following formula 2:
Formula 1: Si _12-a Al _a O _b N _16-b : Eu _x (wherein, 0<a≦3;0<b≦3;0<x≦0.1)
Formula 2: (D90-D10)/D50<1.6
(D10, D50, and D90 (each in μm) are measured values obtained by adding 0.5 g of the phosphor to be measured to 100 ml of ion-exchanged aqueous solution containing 0.05 wt % sodium hexametaphosphate, dispersing the solution for 3 minutes using an ultrasonic homogenizer with an oscillation frequency of 19.5±1 kHz and an amplitude of 32±2 μm, with the tip placed in the center of the solution.)

JP 2015-232150 A JP 2011-105532 A International Publication No. 2020/054350

As lighting and display devices using blue LEDs become more widespread and perform better, further improvements are required for β-SiAlON phosphors, such as improving their emission intensity. In particular, there is a demand for improved emission intensity in β-SiAlON phosphors, which emit fluorescence with a relatively short wavelength.

The inventors have conducted various studies with the aim of obtaining a β-SiAlON phosphor with good emission intensity.

As a result of their investigations, the inventors have completed the invention provided below.

The present invention is as follows:

A β-type SiAlON phosphor powder,
In the fluorescence spectrum emitted when the phosphor powder is irradiated with blue light having a wavelength of 455 nm, the peak wavelength is λ _p [nm] and the half-width of the peak is W [nm],
When the absorptance of the phosphor powder at a wavelength of 600 nm is A ₆₀₀ and the absorptance of the phosphor powder at a wavelength of 455 nm is A ₄₅₅ ,
λ _p is 542 nm or less;
A β-sialon phosphor powder, in which the value of X defined in the following mathematical formula (1) is 10 nm or less.
X=(W× _A600 )/( _A455 - _A600 )...(1)

The present invention also provides the following:

A light emitting device including a light emitting source and a wavelength conversion member,
The wavelength conversion member includes a phosphor powder,
The phosphor powder is a light emitting device containing the β-sialon phosphor powder.

The β-SiAlON phosphor powder of the present invention has good emission intensity.

FIG. 1 is a cross-sectional view showing a schematic example of the structure of a light-emitting device.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
In the drawings, similar components are given similar symbols and descriptions thereof will be omitted as appropriate.
In order to avoid complexity, when there are a plurality of identical components in the same drawing, only one of them may be labeled with a reference symbol, and not all of them.
The drawings are for illustrative purposes only. The shapes and dimensional ratios of the components in the drawings do not necessarily correspond to the actual products.

<β-type Sialon phosphor powder>
The β-sialon phosphor powder of this embodiment has the following characteristics.
In the fluorescence spectrum emitted when the β-sialon phosphor powder of this embodiment is irradiated with blue light having a wavelength of 455 nm, the peak wavelength is λ _p [nm] and the half-width of the peak is W [nm].
The absorptance of the β-sialon phosphor powder of this embodiment for light having a wavelength of 600 nm is A ₆₀₀ , and the absorptance of the light having a wavelength of 455 nm is A ₄₅₅ .
_λp is less than or equal to 542 nm.
The value of X defined in the following formula (1) is 10 nm or less.
X=(W× _A600 )/( _A455 - _A600 )...(1)

Just to be clear, the optical absorptances A ₆₀₀ and A ₄₅₅ are dimensionless numbers, so if the half width W is in nm, then X will be in nm.

Light energy is inversely proportional to wavelength. Therefore, normally, when the peak wavelength of the fluorescence spectrum is short, the emission intensity tends to be small. However, the β-SiAlON phosphor powder of this embodiment has a good emission intensity, even though the peak wavelength of the fluorescence spectrum is relatively short (542 nm or less). This is thought to be because the β-SiAlON phosphor powder of this embodiment satisfies the requirement that the value of X defined in formula (1) be 10 nm or less.

Although the details are unclear, the reason why the emission intensity can be increased by designing the β-SiAlON phosphor powder so that the value of X is 10 nm or less can be explained as follows.
The half-width W included in the formula (1) is considered to be related to the amount of impurities and/or defects contained in the phosphor. When the phosphor contains a large amount of impurities and/or defects, W tends to be large. In other words, from the viewpoint of improving the light emission characteristics, it is preferable that W is small.
In addition, based on the inventors' past findings, it is presumed that the absorptance A ₆₀₀ of light with a wavelength of 600 nm is related to the amount of defects and impurities in the phosphor. In other words, from the viewpoint of improving the light emission characteristics, it is considered that a smaller A ₆₀₀ is preferable.
Furthermore, based on the past findings of the present inventors, it is presumed that the absorptance A ₄₅₅ of light with a wavelength of 455 nm is due to absorption by the β-SiAlON itself. Although light with a wavelength of 455 nm is not the excitation light itself, it is considered that a larger A ₄₅₅ is preferable from the viewpoint of improving the light emission characteristics.

In the formula (1), W and _A600 , which are considered to be "smaller the better" from the viewpoint of improving the light-emitting characteristics, are in the numerator, and _A455 , which is considered to be "larger the better" from the viewpoint of improving the light-emitting characteristics, is in the denominator. Also, _A455 in the denominator is subtracted by _A600 , which is considered to be smaller the better.
That is, an X value of 10 nm or less means that W and A ₆₀₀ , which are considered to be smaller in order to improve the light emission characteristics, are small, and A ₄₅₅ , which is considered to be larger in order to improve the light emission characteristics, is large. Therefore, a β-SiAlON phosphor powder having an X value of 10 nm or less is considered to have high light emission intensity.

The present inventors have investigated the performance improvement of β-SiAlON phosphor powder from every viewpoint. Through the investigation, they have concluded that the peak wavelength and the half width of the peak when blue light is irradiated onto the phosphor powder, and the absorption rate when light of a specific wavelength is irradiated onto the phosphor powder, may be related to the emission intensity of the β-SiAlON phosphor powder.
Based on this idea, the inventors further investigated and found that the value of X defined in the formula (1) seems to correlate with the emission intensity. By newly designing a β-SiAlON phosphor powder in which X is 10 nm or less, the emission intensity of the β-SiAlON phosphor powder could be increased.

λ _p may be 542 nm or less, but is preferably 520 nm or more and 542 nm or less, and more preferably 525 nm or more and 541 nm or less.
W is, for example, 55 nm or less, preferably 40 nm or more and 55 nm or less, more preferably 43 nm or more and 52 nm or less, and further preferably 44 nm or more and 51 nm or less. The smaller W is, the better, but the lower limit of W is practically about 40 nm.
A ₆₀₀ is, for example, 0.01 or more and 0.20 or less, preferably 0.01 or more and 0.10 or less, and more preferably 0.03 or more and 0.10 or less.
A ₄₅₅ is, for example, 0.25 or more and 0.90 or less, preferably 0.30 or more and 0.85 or less, more preferably 0.40 or more and 0.80 or less, and further preferably 0.50 or more and 0.80 or less.
For these measurement methods, please refer to the Examples.

The β-sialon phosphor powder of this embodiment can be obtained through an appropriate manufacturing method and manufacturing conditions.
For example, it is preferable to carry out an annealing step in which the sintered product is annealed in a mixed gas atmosphere of hydrogen gas and nitrogen gas to obtain an annealed sintered product, as described below. This makes it easy to set the value of X to 10 nm or less.
It is also preferable to appropriately adjust the number of moles of Al element relative to the number of moles of Si element in the raw material, which makes it easier to set _λp to 542 nm or less.
The production method and conditions will be described in detail later.

The explanation of the β-SiAlON phosphor powder of this embodiment will continue.

(element composition, etc.)
The composition of a β-sialon phosphor is usually represented by the general formula: Si6 _{- zAlzOzN8 -z :} Eu (z>0). z may be greater than 0, but is usually 4.2 or less. The europium content is preferably 0.1% by mass or more and 2.0% by mass or less.

Mainly from the viewpoint of making _λp 542 nm or less, it is preferable that the value of z is relatively small. Specifically, 0<z≦0.2 is preferable, 0.01≦z≦0.2 is more preferable, 0.01≦z≦0.15 is further preferable, and 0.02≦z≦0.12 is particularly preferable.

From the same viewpoint, it is preferable that the value of z/(6-z), i.e., the number of moles of Al element relative to the number of moles of Si element, is relatively small. Specifically, the value of z/(6-z) is preferably 0.001 or more and 0.05 or less, more preferably 0.002 or more and 0.048 or less, and even more preferably 0.002 or more and 0.045 or less.

By the way, by appropriately adjusting the value of z or z/(6-z), the half-width W also tends to become smaller.

(Median diameter)
The median diameter _D50 of the β-sialon phosphor powder of this embodiment is, for example, 5 μm or more and 30 μm or less, preferably 8 μm or more and 25 μm or less, and more preferably 10 μm or more and 20 μm or less, from the viewpoints of good light emission characteristics and ease of application to various uses.
For the method of measuring the median diameter, see the Examples given later.

(Diffuse Reflectance)
The diffuse reflectance of the β-sialon phosphor powder of this embodiment for light with a wavelength of 800 nm is preferably 96.0% or more and 99.9% or less, more preferably 96.0% or more and 99.0% or less, even more preferably 96.5% or more and 98.5% or less, and particularly preferably 96.5% or more and 98.0% or less.
The value of the diffuse reflectance can reflect the surface properties of the phosphor powder. Although the details are unclear, there are cases where the light emission characteristics are further improved by having an appropriate diffuse reflectance for light with a wavelength of 800 nm.
For the method of measuring the diffuse reflectance, see the Examples given later.

Incidentally, the median diameter of a phosphor powder is usually inversely proportional to the diffuse reflectance of the phosphor powder. In other words, the larger the median diameter, the smaller the diffuse reflectance tends to be. However, in this embodiment, for example, by adopting the manufacturing method described below, it is possible to obtain a β-SiAlON phosphor powder with a relatively large diffuse reflectance even if the median diameter is relatively large.

<Method of manufacturing β-SiAlON phosphor powder>
The β-sialon phosphor powder of this embodiment can be obtained through an appropriate manufacturing method and manufacturing conditions.
The β-sialon phosphor powder of this embodiment preferably has
a raw material mixing step of mixing at least a silicon compound, an aluminum compound, and a europium compound to obtain a raw material mixed powder;
A sintering step of heating the raw material mixed powder at 1800°C or more and 2100°C or less to obtain a sintered product;
an annealing step of annealing the fired product under a mixed gas atmosphere of hydrogen gas and nitrogen gas to obtain an annealed fired product;
It can be produced by a series of steps including the steps of:

Although the details are unclear, in this embodiment, it is speculated that by annealing the fired product in a mixed gas atmosphere of hydrogen gas and nitrogen gas, the decomposition reaction of the β-sialon phosphor is suppressed, thereby reducing defects that adversely affect the luminescence characteristics, and a β-sialon phosphor powder having an X value of 10 nm or less is obtained. As a result, it is speculated that the luminescence intensity is increased compared to a β-sialon phosphor powder having an X value of more than 10 nm that does not undergo such an annealing process.

Each step is explained in detail below.

(Raw material mixing process)
In the raw material mixing step, at least a silicon compound, an aluminum compound, and a europium compound are mixed to obtain a raw material mixed powder. For mixing, various mixers (e.g., a V-type mixer), a mortar, etc. can be used.

The europium compound used as the raw material is not particularly limited. Examples include oxides containing europium, hydroxides containing europium, nitrides containing europium, oxynitrides containing europium, and halides containing europium. These can be used alone or in combination of two or more. Among these, it is preferable to use europium oxide, europium nitride, and europium fluoride alone, and it is more preferable to use europium oxide alone. The europium compound is a material for forming the luminescence center in the β-type sialon.

The raw silicon compound typically includes silicon nitride, and the raw aluminum compound typically includes aluminum nitride. Silicon nitride and aluminum nitride are materials for forming the skeleton of β-sialon.

The raw material mixed powder may further contain aluminum oxide and/or silicon oxide, which are materials for forming the skeleton of the β-sialon.
The raw material mixed powder may further contain β-sialon, which is a material that serves as an aggregate or a core.

Each component contained in the raw material powder mixture is preferably in the form of a powder.
In addition, when the prepared raw material mixed powder contains agglomerates, it is preferable to remove the agglomerates by sieving or the like.

The mixing ratio of each raw material may be appropriately adjusted based on the composition of the target β-sialon phosphor.
In this embodiment, by appropriately adjusting the molar ratio of each element in the raw material mixed powder, the emission intensity of the finally obtained β-SiAlON phosphor powder can be further increased.
Specifically, when the number of moles of Si element in the raw mixed powder is defined as M _Si and the number of moles of Al element in the raw mixed powder is defined as M _Al , the value of M _Al /M _Si is preferably 0.001 or more and 0.05 or less, more preferably 0.002 or more and 0.048 or less, and further preferably 0.002 or more and 0.045 or less.
When the value of M _Al /M _Si is 0.05 or less, for example, the peak wavelength of the fluorescence spectrum when the finally obtained β-SiAlON phosphor powder is irradiated with blue light tends to be shorter. This is preferable in that it meets the needs for shorter wavelengths in the market. In addition, when the value of M _Al /M _Si is 0.05 or less, the spectrum of the fluorescence emitted when the finally obtained β-SiAlON phosphor is irradiated with blue light tends to be sharper (i.e., fluorescence closer to monochromatic light is obtained).

Incidentally, the value of M _Al /M _Si corresponds to the value of z/(6-z) in the composition of the finally obtained β-sialon phosphor, in the general formula of the β-sialon phosphor: Si _6-z Al _z O _z N _8-z :Eu (z>0) (when the firing reaction ideally proceeds and all of the raw materials are converted into the β-sialon phosphor).

(Firing process)
In the firing step, the raw material mixed powder obtained in the raw material mixing step is heated at 1800° C. to 2100° C., preferably 1850° C. to 2050° C., to obtain a fired product.
The raw material mixed powder is usually filled into a container made of a material (such as boron nitride) that does not react with the raw material mixed powder during sintering, and then heated.

The firing step is usually carried out in an atmosphere of an inert gas such as nitrogen gas, although a rare gas such as argon may also be used as the inert gas.
The firing process is preferably carried out in an inert gas atmosphere with an absolute pressure of 0.01 MPa to 10 MPa, more preferably in an inert gas atmosphere with an absolute pressure of 0.05 MPa to 5 MPa, and even more preferably in an inert gas atmosphere with an absolute pressure of 0.08 MPa to 1 MPa. The firing reaction is easily promoted by the absolute pressure in the firing process being moderately high. In addition, it is considered that the occurrence of unintended defects in the phosphor is suppressed by the absolute pressure in the firing process not being too high.

The firing process preferably includes a first firing process and a second firing process. A crushing process is preferably carried out between the first firing process and the second firing process. This firing method is preferable from the viewpoint of suppressing excessive agglomeration during firing and promoting a uniform firing reaction.

The crushing step between the first and second firing steps can be carried out, for example, using a supersonic jet mill. The fired material that is not sufficiently small even after crushing may be removed, for example, by sieving. When a sieve is used, the sieve openings are typically 100 μm or less, more preferably 50 μm or less.

The time for the firing step (when the first firing step and the second firing step are performed, the total time for these steps) is preferably from 2 hours to 60 hours, more preferably from 10 hours to 40 hours.
When the first firing step and the second firing step are performed, the time for each of the first firing step and the second firing step is preferably 1 hour or more and 30 hours or less, more preferably 5 hours or more and 20 hours or less.

It is preferable that the fired product obtained in the firing process is subjected to a crushing process before the annealing process. The crushing process increases the surface area of the fired product, which increases the contact area with the mixed gas, and is expected to further improve performance in the annealing process. This crushing process can be performed, for example, using a supersonic jet mill, as in the crushing process between the first and second firing processes.

(Annealing process)
In the annealing step, the fired product obtained in the firing step is annealed in a mixed gas atmosphere of hydrogen gas and nitrogen gas to obtain an annealed fired product.

As long as a β-SiAlON phosphor with good luminous intensity is obtained, the ratio of hydrogen gas to nitrogen gas in the mixed gas is not particularly limited. The ratio of hydrogen gas to nitrogen gas in the mixed gas is, for example, hydrogen gas:nitrogen gas=30:70 to 70:30 by volume, preferably hydrogen gas:nitrogen gas=40:60 to 60:40.

Preferably, the annealing step is performed in a mixed gas atmosphere consisting essentially of only hydrogen gas and nitrogen gas. Specifically, it is preferable that the atmosphere in the annealing step contains essentially only hydrogen gas and nitrogen gas, and the presence ratio of other gases is 1 volume % or less. Ideally, it is preferable that the atmosphere in the annealing step contains only hydrogen gas and nitrogen gas, and does not contain other gases. However, this does not exclude the unavoidable inclusion of other gases than hydrogen gas or nitrogen gas in the atmosphere in the annealing step.

The annealing temperature in the annealing step is not particularly limited as long as a β-SiAlON phosphor with good luminescence intensity is obtained. The annealing temperature is preferably 1350°C or higher and 1750°C or lower, more preferably 1400°C or higher and 1700°C or lower, and even more preferably 1420°C or higher and 1680°C or lower. By selecting an appropriate annealing temperature, a β-SiAlON phosphor with higher luminescence intensity can be obtained and unintended decomposition of the β-SiAlON phosphor can be suppressed.

The annealing step is preferably carried out in an atmosphere where the pressure is controlled to be relatively low. Specifically, the annealing step is preferably carried out in an atmosphere where the absolute pressure is preferably 0.001 MPa or more and 1 MPa or less, more preferably 0.005 MPa or more and 0.8 MPa or less, and even more preferably 0.01 MPa or more and 0.5 MPa or less. Although the details are unclear, by carrying out the annealing step in an atmosphere where the pressure is controlled to be relatively low, there is a tendency to obtain a β-SiAlON phosphor with greater luminescence intensity.

The time for the annealing step is preferably 1 hour or more, and more preferably 4 hours or more, from the viewpoint of obtaining a sufficient effect of the annealing.
The time for the annealing step is preferably 25 hours or less, and more preferably 20 hours or less, from the viewpoints of reducing energy costs and suppressing unintended decomposition of the fired product.

(Acid treatment process)
The method for producing a β-sialon phosphor powder according to the present embodiment preferably includes an acid treatment step in which the annealed fired product is brought into contact with an acid. By carrying out the acid treatment step, impurities and heterogeneous phases (phases that do not contribute to light emission or have low light emission efficiency) on the surface of the fired product can be removed or reduced, and the light emission intensity can be further increased in some cases.

In the acid treatment step, for example, an aqueous solution containing one or more acids selected from hydrofluoric acid, sulfuric acid, phosphoric acid, hydrochloric acid, and nitric acid can be used. From the viewpoint of increasing the efficiency of removing impurities and heterogeneous phases, two or more acids may be used in combination. In this embodiment, it is preferable to use hydrofluoric acid and nitric acid in combination.

The acid treatment step can usually be carried out by placing the fired product in an aqueous acid solution and stirring for a few minutes to a few hours (for example, 10 minutes to 6 hours). After stirring is complete, it is desirable to separate the precipitated fired product by filtration and to wash away any substances adhering to the β-SiAlON phosphor powder with water.

<Light Emitting Device>
The light emitting device of the present embodiment includes a light source and a wavelength conversion member. The wavelength conversion member includes a phosphor powder, and this phosphor powder includes the above-mentioned β-sialon phosphor powder.

FIG. 1 is a cross-sectional view showing a schematic example of the structure of a light-emitting device 10. As shown in FIG.
The light emitting device 10 includes an LED chip as a light emitting source 12, a first lead frame 13 on which the light emitting source 12 is mounted, a second lead frame 14, a wavelength conversion member 15 that covers the light emitting source 12, a bonding wire 16 that electrically connects the light emitting source 12 and the second lead frame 14, and a synthetic resin cap 19 that covers these. The wavelength conversion member 15 includes a phosphor 18 and a sealing resin 17 in which the phosphor 18 is dispersed.

A recess 13b is formed in the upper portion 13a of the first lead frame 13 for mounting a light emitting diode chip as the light source 12. The recess 13b has a generally funnel shape with a hole diameter gradually expanding from its bottom surface upward, and the inner surface of the recess 13b is a reflective surface. The electrode on the lower surface of the light emitting source 12 is die bonded to the bottom surface of this reflective surface. The other electrode formed on the upper surface of the light emitting source 12 is connected to the surface of the second lead frame 14 via a bonding wire 16.

Various types of LED chips can be used as the light-emitting source 12, and LED chips that emit near-ultraviolet to blue light with wavelengths of 300 nm to 500 nm are particularly preferred.

The phosphor 18 used in the wavelength conversion member 15 of the light emitting device 10 is a phosphor particle contained in the β-sialon phosphor powder of this embodiment. From the viewpoint of controlling the light wavelength of the light emitting device 10, the phosphor 18 may further contain, in addition to the β-sialon phosphor, a phosphor such as an α-sialon phosphor, a KSF phosphor, CaAlSiN ₃ , or a simple substance or a mixture of YAG. Examples of elements that are dissolved in these phosphors include europium (Eu), cerium (Ce), strontium (Sr), calcium (Ca), and manganese (Mn). These phosphors may be used alone or in combination of two or more.
Among these, in the present embodiment, a KSF phosphor having manganese as a solid solution is preferable. By using a combination of a β-SiAlON phosphor that emits green light and a KSF phosphor that emits red light, it is possible to configure, for example, a backlight LED suitable for a high color rendering TV or the like.
By combining the light emitting source 12 and the wavelength conversion member 15, it is possible to emit light having a high emission intensity.

In the case of a light-emitting device 10 using a β-type sialon phosphor, by irradiating near-ultraviolet light or visible light containing a wavelength of 300 nm or more and 500 nm or less as an excitation source as the light emission source 12, it has green light emission characteristics with a peak in the wavelength range of 520 nm or more and 550 nm or less. Therefore, by using a near-ultraviolet LED chip or blue LED chip and a β-type sialon phosphor as the light emission source 12, and further combining it with a single or mixed substance of a red-emitting phosphor, a blue-emitting phosphor, a yellow-emitting phosphor, or an orange-emitting phosphor with a wavelength of 600 nm or more and 700 nm or less, it is possible to obtain white light.

The light emitting device 10 tends to have good brightness because it contains a β-SiAlON phosphor with improved emission intensity.

The above describes the embodiments of the present invention, but 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 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 prepared and used:
Si ₃ N ₄ : α-type silicon nitride powder (SN-E10 grade) manufactured by Ube Industries
AlN: Aluminum nitride powder (F grade) manufactured by Tokuyama Corporation
Eu ₂ O ₃ : Europium oxide powder (RU grade) manufactured by Shin-Etsu Chemical Co., Ltd.

<Production of β-type Sialon phosphor powder>
A β-type Sialon phosphor powder was produced according to the following procedure.
(1) Raw Material Mixing Process Using a V-type mixer (Tsutsui Rikagaku Kikai S-3), the above raw materials were mixed in the ratios (mass%) shown in the table below to obtain a mixture. The mixture was then passed through a sieve with a mesh size of 250 μm to remove aggregates. In this way, a raw material mixed powder was obtained.

(2) Firing step (2-1) First firing step 200 g of the raw material mixed powder was filled into a cylindrical boron nitride container with a lid having an inner diameter of 10 cm and a height of 10 cm. Then, in an electric furnace equipped with a carbon heater, heat treatment was performed at 1950° C. for 15 hours in a nitrogen atmosphere of 0.8 MPa.
(2-2) Crushing Step The powder obtained in (2-1) above was pulverized using a supersonic jet pulverizer (PJM-80SP, manufactured by Nippon Pneumatic Mfg. Co., Ltd.), and the pulverized material obtained was then passed through a nylon sieve with an opening of 45 μm to obtain a pulverized and sintered powder.
(2-3) Second Firing Step The pulverized and sintered powder obtained in (2-2) above was again packed into a cylindrical boron nitride container with a lid and an inner diameter of 10 cm and a height of 10 cm. Then, in an electric furnace equipped with a carbon heater, heat treatment was performed at 1950° C. for 15 hours in a nitrogen atmosphere of 0.8 MPa.
(2-4) Crushing Step The powder obtained in (2-3) above was pulverized using a supersonic jet pulverizer (PJM-80SP, manufactured by Nippon Pneumatic Mfg. Co., Ltd.), and the pulverized material obtained was then passed through a nylon sieve with an opening of 45 μm to obtain a pulverized and sintered powder.

(3) Annealing step The pulverized and sintered powder obtained in (2-4) above was annealed under the conditions described in the "Annealing conditions" section of the table below, using as the atmospheric gas the gas described in the "Atmospheric gas (annealing step)" section of the table below (Example: mixed gas of hydrogen gas and nitrogen gas, Comparative example: hydrogen gas alone, nitrogen gas alone, or argon gas). As a result, an annealed sintered product was obtained.

(4) Acid Treatment Step After the annealing step, the fired product was allowed to cool to room temperature and then placed in an acid aqueous solution of 25 vol% 50% hydrofluoric acid, 25 vol% 70% nitric acid, and 50 vol% water, and stirred at 75° C. for 30 minutes.
After the stirring was completed, the mixture was left to stand for a while, and the fired product that had precipitated was washed with water, filtered, and dried to obtain a β-SiAlON phosphor powder.

<Composition analysis>
The ratios of Si, Al, O, N and Eu in the phosphor powders of each of the Examples and Comparative Examples were determined by the following analytical methods: In the composition analysis, the relative molar amount was assumed to be Si+Al=6 (mol) in consideration of the general formula: _{Si6 - zAlzOzN8 -z} :Eu (z>0).
The amounts of Si, Al and Eu were determined based on the results of analysis using an ICP emission spectrometer (Rigaku Corporation, CIROS-120).
O and N were calculated using the analysis results obtained using an oxygen/nitrogen analyzer (EMGA-920, manufactured by Horiba, Ltd.).

<Various characteristics>
(Peak wavelength λ _p , half width W, and absorptance A ₄₅₀ of light with a wavelength of 455 nm)
The phosphor powder of each Example or Comparative Example was filled into a concave cell so that the surface was smooth, and attached to the opening of an integrating sphere. Monochromatic light separated to a wavelength of 455 nm from a light emission source (Xe lamp) was introduced into the integrating sphere using an optical fiber as excitation light for the phosphor. This monochromatic light was irradiated onto a phosphor sample, and the fluorescence spectrum of the sample was measured using a spectrophotometer (MCPD-7000 manufactured by Otsuka Electronics Co., Ltd.). From the obtained spectral data, the number of photons of the excitation reflected light (Qref) was calculated. The number of photons of the excitation reflected light was calculated in the same wavelength range as the number of photons of the excitation light.
In addition, using the same device, a standard reflector with a reflectance of 99% (Spectralon (registered trademark) manufactured by Labsphere) was attached to the opening of the integrating sphere to measure the spectrum of excitation light with a wavelength of 455 nm. At this time, the number of excitation light photons (Qex) was calculated from the spectrum in the wavelength range of 450 to 465 nm.
The absorptance A ₄₅₅ of light with a wavelength of 455 nm was calculated by the following formula.
A ₄₅₅ = ((Qex-Qref)/Qex)

The wavelength showing the highest intensity in the range of 465 nm to 800 nm in the obtained fluorescence spectrum was determined as the peak wavelength _λp .
In addition, the half-width (full width at half maximum) W was defined as the difference between the wavelength on the long wavelength side and the wavelength on the short wavelength side at which the intensity is half the intensity of the peak wavelength in the spectrum appearing in the wavelength range of 465 nm to 800 nm of the obtained fluorescence spectrum.

Incidentally, when a standard sample of β-sialon phosphor (NIMS Standard Green lot No. NSG1301, manufactured by Sialon Corporation) was measured by the above measurement method, _A455 was 0.744, the peak wavelength was 543 nm, and the half width was 53 nm. The measured values of _A455 , peak wavelength, and half width may vary if the manufacturer of the measuring device, production lot number, etc. are changed. Therefore, when the manufacturer, production lot number, etc. of the measuring device are changed, the measured values of the standard sample are used as the reference value and each measured value is corrected.

(Absorptance _A600 of light with a wavelength of 600 nm)
A standard reflector with a reflectance of 99% (Spectralon (registered trademark) manufactured by Labsphere) was set at the opening of the integrating sphere. Monochromatic light separated into wavelengths of 600 nm from a light emission source (Xe lamp) was introduced into the integrating sphere via an optical fiber. The reflected light spectrum was then measured with a spectrophotometer (MCPD-7000 manufactured by Otsuka Electronics Co., Ltd.). At this time, the number of incident light photons (Qex(600)) was calculated from the spectrum in the wavelength range of 590 nm to 610 nm.

Next, the concave cell was filled with β-SiAlON phosphor powder so that the surface was smooth, and set in the opening of the integrating sphere. Then, monochromatic light with a wavelength of 600 nm was irradiated, and the incident reflected light spectrum was measured by a spectrophotometer. The incident reflected light photon number (Qref(600)) was calculated from the obtained spectrum data. The incident reflected light photon number (Qref(600)) was calculated in the same wavelength range as the incident light photon number (Qex(600)). From the obtained two types of photon numbers, the absorptance A ₆₀₀ of light with a wavelength of 600 nm was calculated based on the following formula.
A ₆₀₀ = ((Qex(600)-Qref(600))/Qex(600))

Incidentally, when a standard sample of a β-sialon phosphor (NIMS Standard Green lot No. NSG1301, manufactured by Sialon Corporation) was measured by the above measurement method, _A600 was 0.076. Since the value of _A600 may vary when the manufacturer of the measuring device, the production lot number, etc. are changed, when the manufacturer of the measuring device, the production lot number, etc. are changed, each measured value was corrected by using the measured value of the standard sample as the reference value.

(Calculation of X)
From the A ₄₅₅ , A ₆₀₀ and W thus determined, X was calculated according to the formula (1).

(Diffuse reflectance of light with a wavelength of 800 nm)
Measurements were performed using an integrating sphere device (ISV-469) attached to a JASCO UV-Visible spectrophotometer (V-550). Specifically, baseline correction was performed using a standard reflector (Spectralon (registered trademark)), and a solid sample holder filled with phosphor powder was attached to a predetermined position on the device to measure diffuse reflectance in the wavelength range of 500 nm to 850 nm. The diffuse reflectance of light with a wavelength of 800 nm was then calculated.

(Median diameter _D50 )
The median diameter _D50 was measured using a particle size measuring device using a laser diffraction/scattering method, Microtrac MT3300EXII (Microtrac Bell Co., Ltd.). The measurement procedure was as follows.
(1) 0.5 g of phosphor powder was added to 100 mL of an aqueous solution of ion-exchanged water mixed with 0.05% by mass of sodium hexametaphosphate, and a dispersion treatment was performed for 3 minutes using an ultrasonic homogenizer, Ultrasonic Homogenizer US-150E (Nihon Seiki Seisakusho Co., Ltd.), with an amplitude of 100%, an oscillation frequency of 19.5±1 kHz, a tip size of 20φ, and an amplitude of 32±2 μm, by placing the tip in the center of the liquid.
(2) After that, the particle size distribution was measured using the above-mentioned device.
(3) From the obtained particle size distribution, the median diameter D ₅₀ (unit: μm) was determined.

(Emission Intensity)
The peak intensity of the β-sialon phosphor powder was measured using a spectrofluorophotometer (Hitachi High-Technologies Corporation, F-7000) calibrated by the Rhodamine B method and a standard light source as follows.

First, the phosphor powder was packed into a dedicated solid sample holder.
Next, the fluorescent spectrum was measured by irradiating the phosphor powder with excitation light split to a wavelength of 455 nm using a spectrofluorometer, and the peak intensity was calculated from the obtained fluorescent spectrum.
The peak intensity varies depending on the measuring device and conditions, so the units are arbitrary. The measuring conditions are the same in each example and comparative example, and the measurements in each example and comparative example were performed consecutively. The table below shows the intensity when the peak intensity of the β-SiAlON phosphor powder in Example 1 is taken as 100%.

The various information is summarized in the table below.

As shown in the above table, the emission intensity of the β-SiAlON phosphor powder having _λp of 540 nm or less and X value of 10 nm or less was greater than that of the β-SiAlON phosphor powder having _λp of 540 nm or less but X value of more than 10 nm. Specifically, by comparing Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3, that is, the examples and comparative examples having the same elemental composition and the same peak wavelength but different X values due to different manufacturing conditions, it can be understood that the emission intensity can be increased by designing the β-SiAlON phosphor powder so that the X value is 10 nm or less.
Just to be clear, generally, the emission intensity tends to increase as the peak wavelength increases (is longer). Therefore, it should be noted that the fact that the emission intensity of Comparative Example 3 (peak wavelength: 540 nm) is greater than that of Example 1 (peak wavelength: 527 nm) and Example 2 (peak wavelength: 529 nm) does not mean that the invention is ineffective.

10 Light emitting device 12 Light emitting source (LED chip)
13 First lead frame 13a Upper portion 13b Recess 14 Second lead frame 15 Wavelength conversion member 16 Bonding wire 17 Sealing resin 18 Phosphor powder 19 Cap

Claims (6)

A β-type SiAlON phosphor powder,
In the fluorescence spectrum emitted when the phosphor powder is irradiated with blue light having a wavelength of 455 nm, the peak wavelength is λ _p [nm] and the half-width of the peak is W [nm],
When the absorptance of the phosphor powder at a wavelength of 600 nm is A ₆₀₀ and the absorptance of the phosphor powder at a wavelength of 455 nm is A ₄₅₅ ,
λ _p is 529 nm or less;
The value of X defined by the following formula (1) is 10 nm or less,
The median diameter _D50 measured by a laser diffraction/scattering method is 10.2 μm or more;
A β-type sialon phosphor powder represented by the composition formula Si6 _{- zAlzOzN8 -z} :Eu ( 0.02≦z≦0.12 ) _.
X=(W× _A600 )/( _A455 - _A600 )...(1) β-SiAlON phosphor powder according to claim 1,
A β-sialon phosphor powder having a median diameter _D50 of 20 μm or less as determined by a laser diffraction/scattering method. 3. The β-sialon phosphor powder according to claim 1,
A β-SiAlON phosphor powder having a diffuse reflectance of 96.0% or more and 99.9% or less for light with a wavelength of 800 nm. A light emitting device including a light emitting source and a wavelength conversion member,
The wavelength conversion member includes a phosphor powder,
A light emitting device, wherein the phosphor powder comprises the β-sialon phosphor powder according to any one of claims 1 to 3 . 5. The light emitting device according to claim 4 ,
The light emitting device, wherein the light emitting source includes an LED chip that emits light having a wavelength of 300 nm or more and 500 nm or less. 6. The light emitting device according to claim 4 ,
The light emitting device, wherein the phosphor powder further contains KSF phosphor powder containing manganese as a solid solution.

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