JP7778554B2 - Method for manufacturing β-type sialon phosphor, method for manufacturing wavelength conversion member, and method for manufacturing light-emitting device - Google Patents

Description

The present invention relates to a method for manufacturing a β-sialon phosphor, a method for manufacturing a wavelength conversion member, and a method for manufacturing a light emitting device.

Various developments have been made in β-sialon phosphors. One example of this type of technology is described in Patent Document 1. Patent Document 1 describes a method for producing a β-sialon phosphor, which involves heat-treating a composition containing silicon nitride containing aluminum, oxygen atoms, and europium, mixing the resulting product with a sodium hydroxide solution, performing a first thermal base treatment at 70°C for 3 hours in the atmosphere, and then performing a second thermal base treatment at 200°C for 2 hours in a nitrogen atmosphere (see, for example, Claims 1 and 3, paragraph 0009, Example 6, etc.). The same document also indicates that the first temperature, which is the heating temperature for the first thermal base treatment, is between 50°C and 150°C (paragraph 0051).

JP 2017-110206 A

However, as a result of investigations conducted by the present inventors, it was found that there is room for improvement in terms of thermal degradation resistance in the β-sialon phosphor obtained by the manufacturing method described in Patent Document 1.

The inventors conducted further studies and found that when a fired product of a raw material mixed powder containing Si, Al, and Eu is heated in a basic aqueous solution, the diffuse reflectance of the β-sialon phosphor decreases after a heat degradation test.
Although the detailed mechanism is unclear, it is thought that during the heating process, the surface of the fired product becomes rich in OH groups due to the water present in the basic aqueous solution, which reduces the optical properties of the β-sialon phosphor.

As a result of extensive research based on this knowledge, the inventors discovered that by heating the above-mentioned fired product with a solid basic substance attached to its surface, the decrease in diffuse reflectance of the β-sialon phosphor after a heat degradation test can be suppressed, leading to the completion of the present invention.

According to the present invention,
a preparation step of mixing raw material powders containing silicon, aluminum, and europium, and firing the mixture to prepare a β-sialon phosphor containing europium as a solid solution;
an alkali treatment step of heating the β-sialon phosphor with a solid basic substance attached to its surface;
The present invention provides a method for producing a β-sialon phosphor, comprising:

Further, according to the present invention,
There is provided a method for producing a wavelength conversion member, which includes a step of producing a wavelength conversion member using a β-sialon phosphor obtained by the above-mentioned method for producing a β-sialon phosphor.

Further, according to the present invention,
There is provided a method for manufacturing a light emitting device, which includes a step of mounting a wavelength conversion member obtained by the above-described method for manufacturing a wavelength conversion member on a light emitting surface of a light emitting source.

The present invention provides a method for producing a β-sialon phosphor with excellent resistance to thermal degradation, as well as a wavelength conversion member and a light-emitting device that use the phosphor.

FIG. 2 is a cross-sectional view schematically showing the structure of an LED package used in a reliability test. The results of the reliability test of the LED package are shown.

An overview of the manufacturing method for the β-sialon phosphor of this embodiment will be described.

The method for producing a β-sialon phosphor includes a preparation step in which raw material powders containing silicon, aluminum, and europium are mixed and fired to prepare a β-sialon phosphor containing europium as a solid solution, and an alkali treatment step in which the β-sialon phosphor is heated with a solid basic substance attached to its surface.

According to the inventors' findings, it has been discovered that alkali treatment, in which a solid basic substance is attached to the surface of a β-sialon phosphor and then heated, suppresses the decrease in diffuse reflectance of the β-sialon phosphor after a heat degradation test.

Although the detailed mechanism is unclear, it can be speculated as follows.
An unstable oxide layer containing a large amount of Si—OH is formed on the surface of the β-sialon phosphor, and after a thermal degradation test, excess light absorption due to defects originating from Si—OH increases.
In contrast, by subjecting the surface of a β-sialon phosphor to an alkali treatment in which the surface is heated in the substantial absence of water, Si—OH on the surface is reduced, making it possible to suppress an increase in excess light absorption after a thermal degradation test, and therefore it is thought that this makes it possible to suppress a deterioration in the optical properties of the β-sialon phosphor.

According to this embodiment, a β-sialon phosphor can be realized that suppresses the reduction in diffuse reflectance after a thermal degradation test and has excellent resistance to thermal degradation. Using such a β-sialon phosphor in a wavelength conversion member or light emitting device can improve reliability under heat.

The β-sialon phosphor of this embodiment is described in detail below.

The β-sialon phosphor of this embodiment is extremely useful as a phosphor for light sources such as light-emitting diodes (hereinafter referred to as LEDs).

Beta-sialon phosphors can, for example, absorb blue light in the wavelength range of 420 nm to 480 nm and emit light with a peak wavelength in the range of more than 480 nm and less than or equal to 800 nm.

The β-sialon phosphor is not particularly limited as long as it can be used as a phosphor, but it is composed of europium-activated β-sialon in which europium is solid-dissolved.

The β-sialon phosphor is represented by the general formula Si _6-z Al _z O _z N _8-z :Eu ²⁺ (0<z≦4.2).
In the general formula Si6 _{- zAlzOzN8 -z} : _Eu2 ⁺ , the z value and the europium content are not particularly limited, but the z value is, for example, more than 0 and not more than 4.2, and from the viewpoint of further improving the luminous intensity of the β-sialon phosphor, preferably 0.005 or more and 1.0 or less.
The content of europium in the β-sialon phosphor is preferably, for example, 0.1% by mass or more and 2.0% by mass or less.

The β-sialon phosphor may be in powder form and configured so that its average particle diameter d50 is, for example, 0.1 μm to 50 μm, preferably 0.25 μm to 40 μm, and more preferably 0.5 μm to 30 μm. By setting it to below the upper limit, variation in the chromaticity of the emitted color can be suppressed. By setting it to above the lower limit, brightness can be improved.

The average particle diameter d50 is a value calculated from the volume average diameter measured by a laser diffraction scattering method.
The measurement was performed in accordance with the particle size distribution measurement method by laser diffraction/scattering described in JIS R 1629:1997 "Method for measuring particle size distribution of fine ceramic raw materials by laser diffraction/scattering method." A particle size distribution measurement device (manufactured by Microtrac-Bell Corporation, product name: "Microtrac MT3300EX II") was used for the measurement. Specifically, 0.1 g of the phosphor to be measured was first added to 100 mL of ion-exchanged water, and the mixture was dispersed for 3 minutes using an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd., product name: "Ultrasonic Homogenizer US-150E", tip size: φ20, amplitude: 100%, oscillation frequency: 19.5 kHz, amplitude: approximately 31 μm) to prepare a measurement sample. The particle size was then measured using the particle size distribution measurement device.

Next, we will explain the method for producing the β-sialon phosphor of this embodiment.

An example of a method for producing a β-sialon phosphor according to this embodiment includes a preparation step of preparing a β-sialon phosphor, and an alkali treatment step of subjecting the surface of the β-sialon phosphor to an alkali treatment.

The preparation step for preparing the β-sialon phosphor may be performed by a known method, but may also include, for example, a firing step of mixing raw material powders containing silicon, aluminum, and europium and firing the mixture to obtain a fired product, and at least one or more post-treatment steps of subjecting the fired product to a crushing/pulverization treatment, classification treatment, annealing treatment, acid treatment, etc. The post-treatment steps can be performed in any order.
The alkali treatment step may be carried out after the classification treatment, or after the acid treatment.

The firing temperature in the firing step is, for example, 1800°C or higher and 2100°C or lower, preferably 1850°C or higher and 2050°C or lower. By setting the firing temperature above the lower limit, the luminescence intensity can be improved. The firing step may be performed multiple times. In addition, part of the raw materials may be added when firing from the second time onwards.

The ambient temperature during the annealing process is, for example, 1100°C or higher and 1800°C or lower, preferably 1300°C or higher and 1750°C or lower. By setting the annealing temperature above the lower limit, the emission intensity can be improved. By setting the annealing temperature below the upper limit, the crystallinity can be improved and a decrease in the emission peak intensity can be suppressed.

The atmospheric gas used during the annealing process is selected from the following: a rare gas of a Group 18 element of the periodic table, such as argon gas, an inert gas, such as nitrogen gas, hydrogen gas, or a mixture of hydrogen gas and argon gas.

The property-improving effect of the annealing process is achieved over a wide range of atmospheric pressures, from reduced to pressurized, but pressures lower than 1 kPa are undesirable because they accelerate the decomposition of the β-sialon phosphor. Furthermore, by pressurizing the atmosphere, it is possible to broaden the range of other conditions required to achieve the annealing effect (lower temperatures, shorter times), but if the atmospheric pressure is too high, the annealing effect will plateau and specialized, expensive annealing equipment will be required. Therefore, considering mass productivity, the preferred atmospheric pressure is 10 MPa or less, and more preferably less than 1 MPa.

The processing time for the annealing step should be between 1 and 24 hours, preferably between 2 and 10 hours, since if it is too short, the effect of improving crystallinity will be low, and if it is too long, the annealing effect will plateau.

Furthermore, the manufacturing method of this embodiment may include an acid treatment step in which the β-sialon phosphor is immersed in an acid solution after the annealing step. This can further improve the properties of the phosphor.

The acid treatment step preferably includes the steps of immersing the β-sialon phosphor in an acid solution, separating the β-sialon phosphor from the acid using a filter or the like, and rinsing the separated β-sialon phosphor with water. The acid treatment removes decomposition products of the β-sialon phosphor crystals that occur during the annealing step, thereby improving the fluorescent properties. Examples of acids used in the acid treatment include hydrofluoric acid, sulfuric acid, phosphoric acid, hydrochloric acid, and nitric acid, either alone or in combination. A mixed acid consisting of hydrofluoric acid and nitric acid is preferred, as it is suitable for removing decomposition products. The temperature of the acid solution during the acid treatment may be room temperature, but to enhance the effectiveness of the acid treatment, it is preferable to heat it to between 50°C and 90°C.

In this manner, a β-sialon phosphor containing europium in solid solution can be obtained.
If necessary, known processes may be added, such as post-treatments as crushing/disintegration, purification, drying, sieving/classification, etc.
The step of adjusting the particle size, such as sieving or classification, may be carried out at any time after the firing step, the annealing step, or the acid treatment step.

The alkali treatment process involves heating the β-sialon phosphor with a solid basic substance attached to its surface.

Examples of basic substances include alkali metal hydroxides, alkali metal carbonates, hydroxides of Group 2 elements of the periodic table, oxides of Group 2 elements of the periodic table, and quaternary ammonium.
An example of the basic substance includes one or more selected from the group _consisting of NaOH, KOH, LiOH, CaO, SrO, _Na2CO3 , and _NaHCO3 .

The solid basic substance may be a basic substance that is solid at room temperature, or may be a basic solution prepared by dissolving the basic substance in a solvent such as water and then removing the solvent at a temperature below 50°C and drying. For example, it may be vacuum dried at a temperature below 50°C.

To attach a solid basic substance to the surface, for example, a powder of β-sialon phosphor may be mixed with a basic substance that is solid at room temperature.
Alternatively, a mixed solution containing a powder of a β-sialon phosphor, a basic substance, and water may be vacuum-dried at a temperature below 50°C to remove the water from the basic substance and adhere the solid basic substance to the surface of the β-sialon phosphor. By removing the solvent such as water at a relatively low temperature below 50°C, the Si—OH groups on the surface of the β-sialon phosphor can be suppressed.

During the alkali treatment process, the β-sialon phosphor is heated in an environment substantially free of water, with a solid basic substance attached to its surface. "Substantially free of water" means that moisture (humidity) contained in the exposure atmosphere outside the solid basic substance is permitted, or moisture in hydrates contained in the solid basic substance is permitted.

In the alkali treatment step, the β-sialon phosphor can be heated from room temperature.
Room temperature may be, for example, 23°C or 25°C.
The upper limit of the heating temperature is not particularly limited, but may be, for example, 400° C. or lower, or 450° C. or lower.

In the alkali treatment step, heating may be performed from room temperature at a temperature rise rate of, for example, 0.1°C/min to 100°C/min, preferably 5°C/min to 50°C/min, and more preferably 1°C/min to 30°C/min.

In the alkali treatment process, the heating atmosphere may be, for example, air, vacuum, or an inert gas atmosphere such as a rare gas or nitrogen.

The method for producing a β-sialon phosphor of this embodiment may further include, after the alkali treatment step, a step of washing the obtained β-sialon phosphor with water.
The water used for washing is removed by drying using a known method.
After the alkali treatment step, post-treatments such as crushing/disintegration, purification, drying, sieving/classification, etc. may be carried out as necessary.

[Wavelength converter, light emitting member]
The light-emitting component of this embodiment comprises a light-emitting element and a wavelength converter that converts light irradiated from the light-emitting element and emits light, and the wavelength converter has the above-mentioned β-sialon phosphor.

An example of a method for manufacturing a wavelength conversion member according to this embodiment includes a step of manufacturing a wavelength conversion member using a β-sialon phosphor obtained by the method for manufacturing a β-sialon phosphor.

The wavelength converter of this embodiment converts light irradiated from a light-emitting element and emits light, and includes the above-mentioned β-sialon phosphor. The wavelength converter may be composed solely of β-sialon phosphor, or may include a host material in which the β-sialon phosphor is dispersed. Known host materials can be used, including, for example, glass, resin, and inorganic materials.

The shape of the wavelength converter is not particularly limited, and it may be configured in a plate shape, or may be configured to encapsulate part of or the entire light-emitting surface of the light-emitting element.

[Light-emitting device]

The light emitting device according to this embodiment includes a light emitting member including a light source (light emitting element) and the wavelength converter.
By combining a light source with a wavelength converter, it is possible to emit light with high luminous intensity.

An example of a method for manufacturing a light-emitting device according to this embodiment includes a step of mounting a wavelength conversion member obtained by the wavelength conversion member manufacturing method on the light-emitting surface of a light source.

An example of a light-emitting device is an LED package. The LED package may include a light source (LED chip), a substrate (lead frame) on which the light source is mounted, and a wavelength converter covering the light source. The LED chip may emit light with a wavelength of 300 nm to 500 nm, which is near-ultraviolet to blue light. The LED chip and lead frame may be electrically connected by bonding wires. The wavelength converter may be covered with a cap made of synthetic resin.

The wavelength converter may contain the β-sialon phosphor, but may also contain other phosphors. Examples of other phosphors include α-sialon phosphor, KSF phosphor, CASN phosphor, SCASN phosphor, and YAG phosphor. These phosphors may be used singly or in combination of two or more.

In the case of a light-emitting device using the above-mentioned β-sialon phosphor, by irradiating near-ultraviolet light or visible light containing wavelengths of 300 nm or more and 500 nm or less as an excitation source, the device exhibits green light emission characteristics with a peak wavelength in the range of 520 nm or more and 560 nm or less. Therefore, by combining a near-ultraviolet LED chip or blue LED chip and β-sialon phosphor as the light source, and further combining them with one or more red-emitting phosphors, blue-emitting phosphors, yellow-emitting phosphors, or orange-emitting phosphors, it is possible to produce white light.

For example, a combination of a β-sialon phosphor that exhibits green color and a KSF-based phosphor that exhibits red color can be used favorably in a backlight LED suitable for a high color rendering TV or the like.
Below, examples of reference forms are given.
1. A preparation step of mixing raw material powders containing silicon, aluminum, and europium, and firing the mixture to prepare a β-sialon phosphor containing europium in solid solution;
an alkali treatment step of heating the β-sialon phosphor with a solid basic substance attached to its surface;
A method for producing a β-sialon phosphor, comprising:
2. A method for producing the β-sialon phosphor of 1.,
The method for producing a β-sialon phosphor, wherein the alkali treatment step involves heating from room temperature.
3. A method for producing the β-sialon phosphor according to 2.,
In the alkali treatment step, the temperature is increased from room temperature at a rate of 0.1° C./min to 100° C./min.
4. A method for producing the β-sialon phosphor according to any one of 1. to 3.,
In the alkali treatment step, the heating atmosphere is an air atmosphere, a vacuum atmosphere, a rare gas atmosphere, or a nitrogen gas atmosphere.
5. A method for producing the β-sialon phosphor according to any one of 1. to 4.,
The method for producing a β-sialon phosphor further comprises, after the alkali treatment step, a step of washing the obtained β-sialon phosphor with water.
6. A method for producing the β-sialon phosphor according to any one of 1. to 5.,
The method for producing a β-sialon phosphor , wherein the solid basic substance comprises one or more selected from the group consisting of NaOH, KOH, LiOH, CaO, SrO, Na ₂ CO ₃ , and NaHCO ₃ .
7. A method for producing a wavelength conversion member, comprising the step of producing a wavelength conversion member using a β-sialon phosphor obtained by the method for producing a β-sialon phosphor according to any one of 1. to 6.
8. A method for manufacturing a light emitting device, comprising the step of mounting a wavelength conversion member obtained by the method for manufacturing a wavelength conversion member according to 7. on a light emitting surface of a light emitting source.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the descriptions in these examples.

<Preparation of β-SiAlON phosphor>

(Comparative Example 1)
(1) Each raw material was weighed into a container so that silicon nitride (Si ₃ N ₄ ) was 98.4 mass%, aluminum nitride (AlN) was 1.0 mass%, and europium oxide (Eu ₂ O ₃ ) was 0.6 mass%, and mixed using a V-type mixer (manufactured by Tsutsui Scientific Machinery Co., Ltd.) to obtain a mixture. The obtained mixture was passed through a sieve with a mesh size of 250 μm to remove agglomerates, thereby obtaining a raw material composition. Agglomerates that did not pass through the sieve were pulverized, and the particle size was adjusted so that they could pass through the sieve.

(2) 200 g of the raw material composition prepared as described above was weighed into a cylindrical boron nitride container with a lid (a molded product made by Denka Company Limited, primarily composed of boron nitride (product name: Denka Boron Nitride N-1), inner diameter: 10 cm, height: 10 cm). The container was then placed in an electric furnace equipped with a carbon heater, and the temperature was raised to 2000°C under a nitrogen gas atmosphere (pressure: 0.90 MPaG). The mixture was then heated at 2000°C for 10 hours (sintering process). After heating, the sample, which had become loosely agglomerated in the container, was placed in a mortar and crushed. After crushing, the sample was passed through a sieve with 250 μm openings to obtain a powdery first sintered body.

(3) Next, the first fired body was packed into a cylindrical boron nitride container, and the container was placed in an electric furnace equipped with a carbon heater. The temperature was raised to 1450°C in an argon gas atmosphere (pressure: 0.025 MPaG), and heating was continued at this temperature for 5 hours (annealing process). After heating, the loosely aggregated particles remaining in the container were crushed in a mortar and mortar, and then passed through a 250 μm sieve to obtain powder.

(4) Next, the powder obtained in (3) was added to a mixed acid of hydrofluoric acid (concentration: 50% by mass) and nitric acid (concentration: 70% by mass) (a 1:1 volumetric mixture of hydrofluoric acid and nitric acid), and acid treatment was performed for 30 minutes while stirring at 75°C. After the acid treatment, the stirring was stopped, the powder was allowed to settle, and the supernatant and fine powder refined by the acid treatment were removed. Distilled water was then added and the mixture was stirred again. The stirring was stopped, the powder was allowed to settle, and the supernatant and fine powder were removed. This procedure was repeated until the pH of the aqueous solution was 8 or less and the supernatant was transparent. The resulting precipitate was filtered, dried, and passed through a sieve with 250 μm openings, yielding the europium-activated β-sialon phosphor of Comparative Example 1.

(Comparative Example 2)
In the same manner as in Comparative Example 1, the powder of the β-sialon phosphor obtained in (4) was heated in an air atmosphere at a heating rate of 10°C/min, heated at 105°C for 10 hours (heating step), and passed through a sieve with 250 μm openings to obtain a europium-activated β-sialon phosphor of Comparative Example 2.

(Comparative Example 3)
A europium-activated β-sialon phosphor of Comparative Example 3 was obtained in the same manner as in Comparative Example 2, except that the heating temperature in the heating step was changed to 175° C. and the heating time was changed to 1 hour.

(Comparative Example 4)
In the same manner as in Comparative Example 1, the powder of the β-sialon phosphor obtained in (4) was mixed with a 50 mass % aqueous solution of sodium hydroxide, and then the mixed solution was filtered. After filtration, the mixed solution was kept at 30°C for 1 day in a vacuum atmosphere without heating, and then washed with water to remove any basic substances remaining on the surface. The mixture was then dried and passed through a sieve with an opening of 250 μm, thereby obtaining a europium-activated β-sialon phosphor of Comparative Example 4.

(Comparative Example 5)
In the same manner as in Comparative Example 1, the powder of the β-sialon phosphor obtained in (4) was mixed with a 50 mass % aqueous sodium hydroxide solution, and the mixed solution was then heated in an air atmosphere at a temperature increase rate of 10°C/min and heated at 100°C for 1 hour (heating step), followed by washing with water to remove any basic substances remaining on the surface, drying, and passing through a sieve with an opening of 250 μm to obtain a europium-activated β-sialon phosphor of Comparative Example 5.

(Comparative Example 6)
A europium-activated β-sialon phosphor of Comparative Example 6 was obtained in the same manner as in Comparative Example 5, except that the heating temperature in the heating step was changed to 200°C.

(Comparative Example 7)
A europium-activated β-sialon phosphor of Comparative Example 7 was obtained in the same manner as in Comparative Example 5, except that the heating temperature in the heating step was changed to 300°C.

(Comparative Example 8)
In the same manner as in Comparative Example 1, the powder of the β-sialon phosphor obtained in (4) was mixed with a 40% by mass aqueous solution of sodium chloride (aqueous solution of a non-basic substance), and then this mixed solution was filtered. The residue was vacuum dried at 45°C to obtain a dried powder. The dried powder was heated at a heating rate of 10°C/min and heated at 300°C for 1 hour (heating step), then washed with water, dried, and passed through a sieve with an opening of 250 μm, thereby obtaining a europium-activated β-sialon phosphor of Comparative Example 8.

(Comparative Example 9)
In the same manner as in Comparative Example 1, the powder of the β-sialon phosphor obtained in (4) was mixed with a 20 mass % aqueous sodium hydroxide solution, and the mixed solution was heated at 70°C for 3 hours in an air atmosphere. The slurry-like residue was then continuously heated at 200°C for 2 hours (heating step), washed with water, dried, and passed through a sieve with an opening of 250 μm to obtain a europium-activated β-sialon phosphor of Comparative Example 9.
It was confirmed that water remained in the slurry residue after heating at 70° C. for 3 hours.

Example 1
In the same manner as in Comparative Example 1, the powder of the β-sialon phosphor obtained in (4) was mixed with a 50% by mass aqueous solution of sodium hydroxide, and then the mixed solution was filtered. The residue was vacuum dried at 45°C to obtain a dried powder. The dried powder was then heated at 45°C for 10 hours in a vacuum atmosphere (alkali treatment step), washed with water, dried, and passed through a sieve with an opening of 250 μm, thereby obtaining the europium-activated β-sialon phosphor of Example 1.

Example 2
A europium-activated β-sialon phosphor of Example 2 was obtained in the same manner as in Example 1, except that in the alkali treatment step, instead of "heating at 45°C for 10 hours in a vacuum atmosphere," the obtained dry powder was heated in an air atmosphere at a temperature increase rate of 10°C/min from 25°C and then heated to 100°C for 1 hour.

(Examples 3 to 16 and 19)
Europium-activated β-sialon phosphors of Examples 3 to 16 and 19 were obtained in the same manner as in Example 2, except that the conditions in the alkali treatment step were changed to those shown in Table 1.
Examples 17 and 18
Powdered _Na2CO3 or _NaHCO3 was mixed with the powder of the β-sialon phosphor obtained in (4) in the same manner as in Comparative Example ₁ to obtain a powdered mixture (dry powder). The obtained powdered mixture was heated in an air atmosphere from 25°C at a heating rate of 10°C/min to 300°C for 1 hour, then washed with water, dried, and passed through a sieve with 250 μm openings to obtain europium-activated β-sialon phosphors of Examples 17 and 18.

The β-sialon phosphors of each example and comparative example were evaluated for the following characteristics and evaluation items.

(Diffuse reflectance before and after thermal degradation test)
The diffuse reflectance of the β-sialon phosphor was measured using an ultraviolet-visible spectrophotometer (V-550) manufactured by JASCO Corporation equipped with an integrating sphere device (ISV-469).
Baseline correction was performed using a standard reflector (Spectralon), and a solid sample holder filled with β-sialon phosphor was set, and the diffuse reflectance was measured in the wavelength range of 500 to 850 nm.
The diffuse reflectance (%) at 500 nm was measured.
Furthermore, 4 g of the β-sialon phosphor was placed in a porcelain crucible with a lid (manufactured by Kenis, capacity 30 mL), the lid was closed, and a heat treatment (thermal degradation test) was carried out in an air atmosphere at 250°C for 5 hours (heat increase rate 10°C/min). After that, the sample was passed through a sieve with 250 μm openings, and the diffuse reflectance (%) at 500 nm was measured in the same manner.
Table 1 shows the diffuse reflectance (%) at 500 nm before and after the thermal degradation test.

Measured values for 500 nm diffuse reflectance may fluctuate if the manufacturer of the measuring device, production lot number, etc., changes. Therefore, the values measured using the measurement methods described in this specification are used as various measured values. However, if the manufacturer of the measuring device, production lot number, etc., changes, each measured value can be corrected using the measured value from a standard sample of β-sialon phosphor as the reference value.

When the 500 nm diffuse reflectance of a standard sample of β-sialon phosphor (manufactured by Sialon Corporation, NIMS Standard Green lot No. NSG1301) was measured using the above-mentioned measurement method, the 500 nm diffuse reflectance was found to be 80.4%.

From the above, the β-sialon phosphors of Examples 1 to 19 exhibited higher diffuse reflectance after the thermal degradation test than Comparative Examples 1 to 9, demonstrating superior resistance to thermal degradation.

<Reliability test>
The reliability of the LED packages incorporating the alkali-treated phosphor particles of each example and the phosphor particles of each comparative example was evaluated as follows: The results obtained by the reliability test are shown in FIG.
The LED package used was one conforming to the structure of the light emitting device shown in FIG.
The alkali-treated phosphor particles or phosphor particles were mounted on the LED package by wire-bonding the lead frame to the electrode on the top of the LED located at the bottom of the recessed case, and then injecting the alkali-treated phosphor particles or phosphor particles mixed with liquid silicone resin (KER6150, manufactured by Shin-Etsu Chemical Co., Ltd.) into the recessed case using a microsyringe. The phosphor concentration in the phosphor + resin was 10.5 wt%. After mounting the alkali-treated phosphor particles or phosphor particles, the package was left to stand for 15 hours in a room temperature, low humidity environment (MacDry MCU-201A, manufactured by ERC), and then cured at 150°C for 1 hour. The LED used had a peak emission wavelength of 448 nm and a chip size of 1.0 mm x 0.5 mm.
The luminous flux of the LED packages equipped with the alkali-treated phosphor particles of each Example and each Comparative Example obtained in the above manner was measured, and the initial value L0 was designated. Furthermore, after leaving the LED packages illuminated at 300 mA at 85°C and 85% RH for 250 hours, the LED packages were removed and dried at room temperature, and the luminous flux L1 was measured, and the reliability coefficient M (= L1/L0 × 100) was calculated. The reliability test requires a reliability coefficient M of 80% or more. This value can only be achieved with highly reliable alkali-treated phosphor particles.
It was confirmed that the LED packages incorporating the alkali-treated phosphor particles of Examples 3 and 4 met the above-mentioned pass criteria.

REFERENCE SIGNS LIST 10 Light emitting device 20 Light emitting element 30 Heat sink 40 Case 50 First lead frame 60 Second lead frame 70 Bonding wire 72 Bonding wire 80 Composite 82 Alkali-treated phosphor particles 84 Sealant

Claims (10)

a preparation step of preparing a β-sialon phosphor containing europium as a solid solution, the preparation step including a firing step of mixing raw material powders containing silicon, aluminum, and europium and firing the mixture to obtain a fired product, and a post-treatment step of further performing at least one of a crushing/pulverizing treatment, a classification treatment, an annealing treatment, and an acid treatment on the fired product after the firing step;
an alkali treatment step of heating the β-sialon phosphor with a solid basic substance attached to its surface;
A method for producing a β-sialon phosphor, comprising: a preparation step of mixing raw material powders containing silicon, aluminum, and europium, and firing the mixture to prepare a β-sialon phosphor containing europium as a solid solution;
an alkali treatment step of heating the β-sialon phosphor with a solid basic substance attached to the surface thereof,
The β-sialon phosphor has the general formula Si _6-z Al _z O _z N _8-z :Eu ²⁺ (0<z≦4.2) a preparation step of mixing raw material powders containing silicon, aluminum, and europium, and firing the mixture to prepare a β-sialon phosphor containing europium as a solid solution;
an alkali treatment step of heating the β-sialon phosphor with a solid basic substance attached to the surface thereof,
In the alkali treatment step, the heating temperature is 450° C. or less. A method for producing the β-sialon phosphor according to any one of claims 1 to 3, comprising the steps of :
The method for producing a β-sialon phosphor, wherein the alkali treatment step involves heating from room temperature. A method for producing the β-sialon phosphor according to any one of claims 1 to 4 ,
In the alkali treatment step, the temperature is increased from room temperature at a rate of 0.1° C./min to 100° C./min. A method for producing the β-sialon phosphor according to any one of claims 1 to 5 ,
In the alkali treatment step, the heating atmosphere is an air atmosphere, a vacuum atmosphere, a rare gas atmosphere, or a nitrogen gas atmosphere. A method for producing the β-sialon phosphor according to any one of claims 1 to 6 , comprising the steps of:
The method for producing a β-sialon phosphor further comprises, after the alkali treatment step, a step of washing the obtained β-sialon phosphor with water. A method for producing the β-sialon phosphor according to any one of claims 1 to 7 , comprising the steps of:
The method for producing a β-sialon phosphor, wherein the solid basic substance comprises one or more selected from the group consisting of NaOH, KOH, LiOH, CaO, SrO, Na ₂ CO ₃ , and NaHCO ₃ . A method for producing a wavelength conversion member, comprising the step of producing a wavelength conversion member using a β-sialon phosphor obtained by the method for producing a β-sialon phosphor according to any one of claims 1 to 8 . A method for manufacturing a light emitting device, comprising the step of mounting a wavelength conversion member obtained by the method for manufacturing a wavelength conversion member according to claim 9 on a light emitting surface of a light emitting source.