JP7515353B2 - Manufacturing method of europium-activated β-type sialon phosphor - Google Patents

Description

This disclosure relates to a method for producing europium-activated β-sialon phosphors.

Oxynitride phosphors are known to have little decrease in brightness with increasing temperature and to be highly durable. Among oxynitride phosphors, europium-activated β-sialon is known as a green phosphor that can be excited by ultraviolet light or visible light.

β-SiAlON phosphors can be obtained, for example, by heating a raw material mixture containing silicon nitride powder, aluminum nitride powder, and europium oxide powder under a nitrogen atmosphere. In the course of studying the practical application of β-SiAlON phosphors, there are also studies on improving their brightness.

For example, Patent Document 1 describes a method for producing a β-sialon phosphor, which includes a first heat treatment step in which a mixture containing an aluminum compound, a first europium compound, and silicon nitride is heat-treated to obtain a first heat-treated product, and a second heat treatment step in which the first heat-treated product and a second europium compound are heat-treated in a rare gas atmosphere to obtain a second heat-treated product. Patent Document 2 also proposes a method for producing a β-sialon phosphor, which includes a firing step in which a raw material mixture of a β-sialon phosphor is fired at a temperature of 1820°C to 2200°C in a nitrogen atmosphere to obtain a fired product, and an annealing step in which the fired product is annealed at a temperature of 1100°C or higher in a reducing atmosphere.

JP 2017-002278 A International Publication No. WO 2010/143590

The present disclosure aims to provide a manufacturing method capable of producing europium-activated β-sialon phosphors with excellent internal quantum efficiency.

One aspect of the present disclosure provides a method for producing a europium-activated β-sialon phosphor, comprising: a firing step of obtaining a fired body containing β-sialon from a raw material composition containing a silicon source, an aluminum source, and a europium source, at least one of which is a nitride, by one or more heat treatments; and an annealing step of obtaining an annealed body from a mixture containing the fired body and at least one of silicon and a silicon compound by one or more annealing treatments under an atmosphere containing at least one selected from the group consisting of a rare gas, a reducing gas, and an inert gas, wherein the total amount of the silicon and the silicon compound in the annealing step is 0.001 to 4 mass% with respect to the total amount of the mixture.

In the above-mentioned method for producing a europium-activated β-sialon phosphor, at least one of silicon and a silicon compound is mixed in a predetermined amount when the fired body is annealed, so that a europium-activated β-sialon phosphor having excellent internal quantum efficiency can be produced. The reason why such an effect is obtained is not necessarily clear, but the present inventors speculate as follows. In a europium-activated β-sialon phosphor, divalent europium emits green light, whereas trivalent europium does not emit green light. In the above-mentioned method for producing a europium-activated β-sialon phosphor, silicon or a silicon compound is added in the annealing step, so that silicon acts on europium in the fired body via the gas phase during the annealing treatment, reducing trivalent europium to divalent europium. Therefore, the internal quantum efficiency of the obtained europium-activated β-sialon phosphor can be improved. Additionally, silicon cations supplied via the gas phase can fill vacancies that cause defects in europium-activated β-sialon phosphors, reducing the defects and improving the internal quantum efficiency.

When the atmosphere contains a rare gas, the rare gas may contain argon; when the atmosphere contains a reducing gas, the reducing gas may contain hydrogen; when the atmosphere contains an inert gas, the inert gas may contain nitrogen.

The annealing temperature may be 1000 to 1700°C.

The present disclosure provides a manufacturing method capable of producing europium-activated β-sialon phosphors with excellent internal quantum efficiency.

Embodiments of the present disclosure are described below. However, the following embodiments are merely examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents.

Unless otherwise specified, the materials exemplified in this specification may be used alone or in combination of two or more. When multiple substances corresponding to each component are present in the composition, the content of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified. In this specification, the "steps" may be steps that are independent of each other, or steps that are performed simultaneously.

One embodiment of the method for producing a europium-activated β-sialon phosphor includes a sintering step of obtaining a sintered body containing β-sialon from a raw material composition containing a silicon source, an aluminum source, and a europium source, at least one of which is a nitride, by one or more heat treatments, and an annealing step of obtaining an annealed body from a mixture containing the sintered body and at least one of silicon and a silicon compound by one or more annealing treatments under an atmosphere containing at least one selected from the group consisting of a rare gas, a reducing gas, and an inert gas.

The raw material composition contains a compound having an element that is a constituent element of europium-activated β-sialon, and contains at least a silicon source, an aluminum source, and a europium source. In the raw material composition, at least one of the silicon source, the aluminum source, and the europium source is a nitride. The nitride is also a nitrogen source because it has nitrogen that is a constituent element of europium-activated β-sialon. The silicon source means a compound or simple substance having silicon as a constituent element, the aluminum source means a compound or simple substance having aluminum as a constituent element, and the europium source means a compound or simple substance having europium as a constituent element. In this specification, a compound having silicon as a constituent element is also called a silicon compound, a compound having aluminum as a constituent element is also called an aluminum compound, and a compound having europium as a constituent element is also called a europium compound. The silicon compound, the aluminum compound, and the europium compound may each be any of a nitride, an oxide, an oxynitride, and a hydroxide. The raw material composition may further contain β-sialon or europium-activated β-sialon. Here, the β-sialon or europium-activated β-sialon is an aggregate or core material.

Examples of silicon compounds include silicon nitride (Si ₃ N ₄ ) and silicon dioxide (SiO ₂ ). It is preferable to use silicon nitride having a high α fraction. The α fraction of silicon nitride may be, for example, 80 mass% or more, 90 mass% or more, or 95 mass% or more. When the α fraction of silicon nitride is within the above range, primary particle growth can be promoted. It is preferable to use silicon nitride having a small oxygen content. The oxygen content of silicon nitride may be, for example, 3.0 mass% or less, or 1.3 mass% or less. When the oxygen content of silicon nitride is within the above range, the occurrence of defects in the crystal of β-sialon can be suppressed.

Examples of aluminum compounds include aluminum nitride (AlN), aluminum oxide (Al ₂ O ₃ ), and aluminum hydroxide (Al(OH) ₃ ).

Examples of europium compounds include europium oxide (europium oxide), europium nitride (europium nitride), and europium halides. Examples of europium halides include europium fluoride, europium chloride, europium bromide, and europium iodide. The europium compound preferably contains europium oxide. The valence of europium in the europium compound may be divalent or trivalent, and is preferably divalent.

The raw material mixture can be prepared by weighing and mixing each compound. The mixing may be performed by a dry mixing method or a wet mixing method. The dry mixing method may be, for example, a method in which the components are mixed using a V-type mixer or the like. The wet mixing method may be, for example, a method in which a solvent or dispersion medium such as water is added to prepare a solution or slurry, the components are mixed, and then the solvent or dispersion medium is removed.

The heating temperature in the firing process may be, for example, 1800 to 2500°C, 1800 to 2400°C, 1850 to 2100°C, 1900 to 2100°C, 1900 to 2050°C, or 1920 to 2050°C. By setting the heating temperature in the firing process to 1800°C or higher, the grain growth of β-sialon can be promoted and the amount of europium dissolved in solid solution can be made more sufficient. By setting the heating temperature in the firing process to 2500°C or lower, the decomposition of the β-sialon crystals can be sufficiently suppressed.

The heating time in the firing process is preferably long from the viewpoint of promoting the growth of primary particles of β-sialon, but if the heating time is too long, crystal defects may increase, so the heating time may be, for example, 1 to 30 hours, 3 to 25 hours, or 5 to 20 hours.

The raw material mixture may be heated in a nitrogen atmosphere in the firing step, for example. Heating under conditions of high nitrogen partial pressure can suppress the decomposition of silicon nitride at high temperatures. Furthermore, processing at high temperatures can promote particle growth. The raw material mixture may be heated in a pressurized state in the firing step, for example. The pressure may be, for example, 0.010 to 200 MPaG, 0.020 to 200 MPaG, 0.1 to 200 MPaG, 0.1 to 100 MPaG, 0.1 to 50 MPaG, 0.1 to 15 MPaG, or 0.1 to 5 MPaG.

The number of times the heat treatment is performed in the firing step may be one, but may also be, for example, two or more times, such as two to five times, or two to four times. By performing the heat treatment multiple times, it is possible to obtain a europium-activated β-sialon phosphor with superior luminance.

In the firing step, one or more heat treatments are performed. When multiple heat treatments are performed, they are successively referred to as the first heat treatment, the second heat treatment, etc., and the steps of performing each heat treatment may be successively referred to as the first firing step, the second firing step, etc. For example, when the above-mentioned manufacturing method performs two heat treatments in the firing step, the firing step is also said to include a step of first heating a raw material composition containing nitrides to obtain a first heat-treated body, and a second heating the first heat-treated body to obtain a second heat-treated body. In this case, the second heat-treated body corresponds to a fired body containing β-sialon. Before performing multiple heat treatments, the silicon source, the aluminum source, and the europium source may be further mixed and heat-treated.

When the firing step involves two or more heating treatments, the heating temperature, heating time, heating atmosphere, and heating pressure of the first firing step can be the same as those of the above-mentioned heating steps. The heating temperature, heating time, heating atmosphere, and heating pressure of the second firing step and thereafter may be the same as or different from those of the first firing step. However, even if the heating temperature, heating time, heating atmosphere, and heating pressure of the second firing step and thereafter are different from those of the first firing step, they are within the range of conditions shown for the above-mentioned heating steps.

The sintered body obtained in the sintering process has β-SiAlON crystals, and is a solid solution in which an element that serves as the luminescence center is dissolved in part of the crystals, and can emit fluorescence itself. The sintered body obtained in the sintering process may be in the form of a lump, and the particle size may be adjusted by crushing or the like prior to the annealing process.

Next, an annealing step is performed. In this specification, the annealing step refers to a step of annealing a mixture containing the sintered body obtained in the above-mentioned sintering step and at least one of silicon and a silicon compound. The annealing step refers to a heat treatment at a temperature lower than the above-mentioned sintering temperature. In the annealing step, an annealed body is obtained from the mixture by one or more heat treatments.

The silicon compound may be any of those exemplified as components of the raw material composition, and may be the same as or different from the components of the raw material composition. The silicon compound may contain, for example, silicon nitride, silicon monoxide, silicon dioxide, etc., and preferably contains at least one of silicon monoxide and silicon dioxide.

The total amount of silicon and silicon compounds is 0.001 to 4 mass% based on the total amount of the mixture. The lower limit of the total amount of silicon and silicon compounds may be, for example, 0.01 mass% or more, 0.05 mass% or more, 0.1 mass% or more, 0.3 mass% or more, or 0.4 mass% or more based on the total amount of the mixture. By setting the lower limit of the total amount of silicon and silicon compounds within the above range, the internal quantum efficiency of the obtained europium-activated β-type sialon phosphor can be further improved. The upper limit of the total amount of silicon and silicon compounds may be, for example, 3 mass% or less, or 2 mass% or less based on the total amount of the mixture. By setting the upper limit of the total amount of silicon and silicon compounds within the above range, the residue of heterogeneous phases derived from silicon and silicon compounds after acid treatment can be suppressed.

The annealing treatment is performed in an atmosphere containing at least one gas selected from the group consisting of a rare gas, a reducing gas, and an inert gas. By performing the annealing treatment in an atmosphere containing a rare gas, a reducing gas, or an inert gas, the proportion of divalent europium in the europium in the solid solution can be increased.

The rare gas may contain, for example, argon, helium, etc., or may contain argon or may consist of argon. The reducing gas may contain, for example, ammonia, hydrocarbon, carbon monoxide, hydrogen, etc., or may contain hydrogen or may consist of hydrogen. The inert gas may contain, for example, nitrogen, etc., or may consist of nitrogen. The atmosphere of the annealing process may be a mixed gas of two or more of the rare gas, the reducing gas, and the inert gas. When the atmosphere of the annealing process is the mixed gas, the content of the reducing gas may be, for example, 1 to 50 volume % or 4 to 20 volume % based on the total volume of the mixed gas. The content of the inert gas may be, for example, 1 to 50 volume % or 4 to 20 volume % based on the total volume of the mixed gas.

The pressure during the annealing process may be the same as that during the firing process, but is preferably lower than the pressure conditions during the firing process, and more preferably atmospheric pressure.

The temperature of the annealing treatment needs to be set lower than the heating temperature in the sintering process. The upper limit of the annealing treatment temperature may be, for example, 1700°C or less, or 1680°C or less. By setting the upper limit of the annealing treatment temperature within the above range, further grain growth in the sintered body can be suppressed from occurring, such as aggregation between solid solutions and the formation of secondary particles, resulting in coarsening of the particles. The lower limit of the annealing treatment temperature may be, for example, 1000°C or more, 1100°C or more, 1200°C or more, 1300°C or more, or 1400°C or more. By setting the lower limit of the annealing treatment temperature within the above range, the crystal defect density of the β-type sialon contained in the annealed body can be reduced, and the internal quantum efficiency can be further improved. The annealing treatment temperature can be adjusted within the above range, and may be, for example, 1000 to 1700°C, or 1100 to 1680°C.

The heating time in the annealing treatment may be, for example, 1 to 30 hours, 2 to 25 hours, or 3 to 20 hours, from the viewpoint of further reducing crystal defects in the phosphor contained in the annealed body.

In the annealing step, one or more annealing treatments are performed. When multiple annealing treatments are performed, they are successively referred to as a first annealing treatment, a second annealing treatment, etc., and the steps of performing each annealing treatment may be successively referred to as a first annealing step, a second annealing step, etc. For example, when the above-mentioned manufacturing method performs two annealing treatments in the annealing step, the annealing step is also said to include a step of performing a first annealing treatment on the sintered body to obtain a first annealed body, and a second annealing step of performing a second annealing treatment on the first annealed body to obtain a second annealed body. In this case, the second annealed body corresponds to the above-mentioned annealed body.

When the annealing step involves two or more annealing steps, the annealing temperature, heating time, and heating pressure of the first annealing step can be the same as those of the annealing step described above. The annealing temperature, heating time, and heating pressure of the second annealing step and subsequent steps may be the same as or different from those of the first annealing step. However, even if the annealing temperature, heating time, and heating pressure of the second annealing step and subsequent steps are different from those of the first annealing step, they are within the range of conditions shown for the annealing step described above.

The number of annealing treatments in the annealing step may be one, but may also be, for example, two or more, two to five, or two to four. By performing annealing treatments multiple times, it is possible to reduce the defect density of the crystals of the β-SiAlON contained in the annealed body, and obtain a europium-activated β-SiAlON phosphor with superior internal quantum efficiency.

When annealing is performed multiple times in the annealing step, the silicon and silicon compound may be mixed all at once in the first annealing step, or may be mixed in portions in multiple annealing steps, but is preferably mixed all at once in the first annealing step. Note that when silicon and silicon compounds are mixed in portions, the above description of the total amount of silicon and silicon compounds mixed should be interpreted as the total amount of silicon and silicon compounds mixed in multiple annealing steps.

The method for producing europium-activated β-sialon phosphor may include other steps in addition to the firing step and the annealing step. The other steps may include, for example, a step of treating the annealed body obtained in the annealing step with at least one of an acid and an alkali, a classification step of adjusting the particle size of the annealed body or the annealed body that has been subjected to an acid treatment or the like. The step of treating the annealed body with an acid is called the acid treatment step, and the step of treating the annealed body with an alkali is called the alkali treatment step.

The acid treatment step or alkali treatment step can, for example, reduce the crystal defect density in the phosphor contained in the annealed body, remove silicon present on the surface of the solid solution formed by thermal decomposition of β-sialon, and remove AlN polytypoid, which is a pseudo-polymorph of aluminum nitride (AlN) produced as a by-product during the preparation of the first fired body. The acid may include, for example, hydrofluoric acid and nitric acid. The acid may be a mixed acid of hydrofluoric acid and nitric acid. The alkali may include, for example, sodium hydroxide.

The classification step may be performed, for example, by either a wet classification method or a dry classification method. Examples of wet classification include an elutriation classification method in which the annealed body is added to a mixed solvent containing ion-exchanged water and a dispersant (e.g., sodium hexametaphosphate, etc.) or a mixed solvent containing ion-exchanged water and ammonia water, stirred, and then allowed to stand to remove particles with small particle sizes.

The europium-activated β-sialon phosphor obtained by the above-mentioned manufacturing method may contain β-sialon as a main crystal, or may be composed of β-sialon. The europium-activated β-sialon phosphor may contain a different phase within a range _that does not impair the gist of the present disclosure. The europium-activated β-sialon phosphor may have a composition represented by the composition formula Si6 _{- ZAlZOZN8 -Z} :Eu. In the above composition formula, z may be 0.0<z≦4.2, or 0.0<z≦0.5. The composition of the europium-activated β-sialon phosphor can be adjusted by changing the components and composition ratio of the raw material composition.

The 50% cumulative diameter (D50) in the volume-based cumulative particle size distribution of the europium-activated β-sialon phosphor obtained by the above-mentioned manufacturing method may be adjusted according to the use of the phosphor. The 50% cumulative diameter (D50) in the volume-based cumulative particle size distribution of the europium-activated β-sialon phosphor may be, for example, 0.1 to 50 μm, 3 to 40 μm, or 6 to 30 μm. D50 can be controlled, for example, by adjusting the conditions such as the heating temperature and heating time during phosphor manufacturing, as well as by classification, etc.

In this specification, D50 refers to the particle diameter when the cumulative value from the small particle diameter reaches 50% of the total in the volume-based particle diameter distribution curve measured by the laser diffraction/scattering method. The distribution curve for the particle diameter of the phosphor is performed in accordance with the particle diameter distribution measurement method by the laser diffraction/scattering method described in JIS R 1629:1997 "Method for measuring particle diameter distribution by the laser diffraction/scattering method for fine ceramic raw materials". A particle diameter distribution measuring device can be used for the measurement. Specifically, first, 0.1 g of the phosphor to be measured is put into 100 mL of ion-exchanged water, a small amount of sodium hexametaphosphate is added, and the measurement sample is subjected to dispersion processing for 3 minutes using an ultrasonic homogenizer. The particle size is measured using a particle diameter distribution measuring device, and D50 is determined from the obtained particle size distribution. D50 is also called the median diameter and means the average particle diameter of the target particles. As a particle size distribution measuring device, for example, "Microtrac MT3300EX II" (product name) manufactured by Microtrac Bell Co., Ltd. can be used. As an ultrasonic homogenizer, for example, "Ultrasonic Homogenizer US-150E" (product name, tip size: φ20, Amplitude: 100%, oscillation frequency: 19.5 KHz, amplitude: approximately 31 μm) manufactured by Nippon Seiki Seisakusho Co., Ltd. can be used.

The europium-activated β-sialon phosphor obtained by the above-mentioned manufacturing method has excellent internal quantum efficiency. The internal quantum efficiency of the europium-activated β-sialon phosphor can be, for example, more than 80%, 81% or more, 82% or more, 83% or more, or 84% or more.

In this specification, the internal quantum efficiency refers to the quantum efficiency obtained when the phosphor is excited with near-ultraviolet light having a wavelength of 455 nm. Specifically, the internal quantum efficiency is determined by measuring it using the method described in the examples of this specification.

The europium-activated β-sialon phosphor may be used alone or in combination with other phosphors. The europium-activated β-sialon phosphor has excellent internal quantum efficiency, and is therefore suitable for use in light-emitting devices such as LEDs. The phosphor may be dispersed in a cured resin. The cured resin is not particularly limited, and may be, for example, a resin used as a sealing resin for light-emitting devices.

Although several embodiments have been described above, the present disclosure is in no way limited to the above-mentioned embodiments. Furthermore, the contents of the descriptions of the above-mentioned embodiments can be mutually applied.

The contents of this disclosure will be described in more detail below with reference to examples and comparative examples. However, this disclosure is not limited to the following examples.

Example 1
[Preparation of europium-activated β-sialon phosphor]
The raw materials were weighed and placed in a container so that the silicon nitride (Si ₃ N ₄ ) was 96.0 mass%, aluminum nitride (AlN) was 2.8 mass%, aluminum oxide (Al ₂ O ₃ ) was 0.5 mass%, and europium oxide (Eu ₂ O ₃ ) was 0.7 mass%, and mixed using a V-type mixer (manufactured by Tsutsui Rikagaku Kikai Co., Ltd.) to obtain a mixture. The obtained mixture was passed through a sieve with a mesh size of 250 μm to remove aggregates, thereby obtaining a raw material composition. The aggregates that did not pass through the sieve were pulverized and the particle size was adjusted so that they would pass through the sieve.

200 g of the raw material composition prepared as described above was weighed out and placed in a cylindrical boron nitride container with a lid (boron nitride molded body (product name: Denka Boron Nitride N-1), manufactured by Denka Co., Ltd., inner diameter: 10 cm, height: 10 cm). The container was then placed in an electric furnace equipped with a carbon heater, and heated to 2020°C under a nitrogen gas atmosphere (pressure: 0.90 MPaG), and heated at the heating temperature of 2020°C for 8 hours (firing process). After heating, the sample that had become loosely aggregated lumps in the container was taken in a mortar and crushed. After crushing, the sample was passed through a sieve with 250 μm openings to obtain a powdered first fired body.

Next, the mixture was adjusted so that the first fired body was 99.9 mass% as a standard and silicon dioxide (SiO ₂ ) was 0.1 mass%, and this was filled into a cylindrical boron nitride container, which was then 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 performed at the heating temperature of 1450°C for 3 hours (annealing process). After heating, the lumps in which the particles were loosely aggregated in the container were crushed in a mortar and passed through a 250 μm sieve to obtain a powder.

Next, the obtained powder was added to a mixed acid of hydrofluoric acid (concentration: 50% by mass) and nitric acid (concentration: 70% by mass) (hydrofluoric acid and nitric acid mixed in a volume ratio of 1:1), and acid treatment was performed for 30 minutes while stirring at a temperature of 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. Then, distilled water was further 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 operation was repeated until the pH of the aqueous solution was 8 or less and the supernatant was transparent, and the obtained precipitate was filtered and dried to obtain a europium-activated β-type sialon phosphor.

(Comparative Example 1)
A europium-activated β-type sialon phosphor was obtained in the same manner as in Example 1, except that silicon dioxide was not added in the annealing step and only the first fired body was annealed.

(Example 2 and Comparative Example 2)
A europium-activated β-sialon phosphor was obtained in the same manner as in Example 1, except that the amount of silicon dioxide added in the annealing step was changed as shown in Table 1.

Example 3
A europium-activated β-sialon phosphor was obtained in the same manner as in Example 1, except that elemental silicon was used in place of silicon dioxide in the annealing step.

Example 4
A europium-activated β-sialon phosphor was obtained in the same manner as in Example 1, except that in the annealing step, silicon dioxide was replaced with silicon elemental, and the amount of silicon elemental was changed as shown in Table 1.

Example 5
A europium-activated β-sialon phosphor was obtained in the same manner as in Example 1, except that silicon monoxide was used instead of silicon dioxide in the annealing step.

Example 6
A europium-activated β-sialon phosphor was obtained in the same manner as in Example 1, except that silicon monoxide was used instead of silicon dioxide in the annealing step and the blending amount of silicon monoxide was changed as shown in Table 1.

(Example 7)
A europium-activated β-type SiAlON phosphor was obtained in the same manner as in Example 1, except that the atmosphere in the annealing step was changed from an argon gas atmosphere to a hydrogen gas atmosphere, and the treatment temperature in the annealing step was changed to 1650° C. in an electric furnace equipped with a metal heater.

(Example 8)
Except for changing the blending amount of silicon dioxide in the annealing step as shown in Table 1, the same procedure as in Example 7 was carried out to obtain europium-activated β-sialon phosphors.

[Evaluation of europium-activated β-SiAlON phosphor]
For each of the europium-activated β-sialon phosphors prepared in Examples 1 to 8 and Comparative Examples 1 and 2, the absorptance, internal quantum efficiency, external quantum efficiency, and chromaticity X when irradiated with excitation light having a wavelength of 455 nm were evaluated by the methods described below. The results are shown in Table 1. Table 1 also shows, as a reference example, the measurement results of a standard sample of a β-sialon phosphor (manufactured by Sialon Corporation, NIMS Standard Green lot No. NSG1301).

<Absorptivity, Internal Quantum Efficiency, and External Quantum Efficiency>
The absorptance (excitation light absorptance), internal quantum efficiency, and external quantum efficiency of the phosphor when irradiated with excitation light of 455 nm wavelength were calculated by the following procedure. First, the phosphor to be measured was filled in a concave cell so that the surface was smooth, and the cell was attached to the opening of an integrating sphere. Monochromatic light having a wavelength of 455 nm was split from a Xe lamp, which is a light emission source, and introduced into the integrating sphere as excitation light for the phosphor using an optical fiber. The monochromatic light, which is the excitation light, was irradiated onto the phosphor to be measured, and the fluorescence spectrum was measured. A spectrophotometer (manufactured by Otsuka Electronics Co., Ltd., product name: MCPD-7000) was used for the measurement.

The emission intensity of the phosphor was determined from the obtained fluorescence spectrum data. The number of reflected excitation light photons (Qref) and the number of fluorescent photons (Qem) were also calculated from the obtained fluorescence spectrum data. The number of reflected excitation light photons was calculated in the same wavelength range as the number of excitation light photons, and the number of fluorescent photons was calculated in the range of 465 to 800 nm. 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 that time, the number of excitation light photons (Qex) was calculated from the spectrum in the wavelength range of 450 to 465 nm.

From the above calculation results, the absorptance of the 455 nm excitation light, the internal quantum efficiency, and the external quantum efficiency of the phosphor to be measured were calculated based on the following formulas.
Absorption rate of 455 nm excitation light=((Qex-Qref)/Qex)×100
Internal quantum efficiency = (Qem / (Qex - Qref)) x 100
External quantum efficiency = (Qem/Qex) x 100
From the above formula, the relationship between the external quantum efficiency, the absorptance of the 455 nm excitation light, and the internal quantum efficiency can be expressed as follows:
External quantum efficiency = 455 nm light absorptance x internal quantum efficiency

<Chromaticity X>
The chromaticity X was determined by calculating the CIE chromaticity coordinate x value (chromaticity X) in the XYZ color system defined in JIS Z8781-3:2016 from the spectral data in the wavelength range of 465 to 780 nm of the fluorescence spectrum in accordance with JIS Z8724:2015.

The measured values of the phosphor's absorptance, internal quantum efficiency, external quantum efficiency, and chromaticity X may vary if the manufacturer of the measuring device, production lot number, etc., changes. Therefore, the values measured by the measurement method described in this specification are used as the various measured values. However, if the manufacturer of the measuring device, production lot number, etc., is changed, each measured value can be corrected using the measured value of the standard sample of the β-type Sialon phosphor described above as the reference value. As the standard sample for obtaining the reference value, the standard sample of the β-type Sialon phosphor listed above as Reference Example 1 can be used.

The present disclosure provides a manufacturing method capable of producing europium-activated β-sialon phosphors with excellent internal quantum efficiency.

Claims (2)

a sintering step of obtaining a sintered body containing a β-sialon from a raw material composition containing a silicon source, an aluminum source, and a europium source, with at least one of them being in the form of a nitride, by one or more heat treatments;
and an annealing step of obtaining an annealed body from a mixture containing the sintered body and at least one of silicon and a silicon compound by one or more annealing treatments under an atmosphere containing at least one selected from the group consisting of a rare gas and a hydrogen gas,
The annealing temperature is 1000 to 1700° C.,
a total amount of the silicon and the silicon compound in the annealing step is 0.001 to 0.5 mass % based on a total amount of the mixture ;
The method for producing a europium-activated β-sialon phosphor , wherein the silicon compound is at least one selected from the group consisting of oxides and hydroxides . 2. The method for producing a europium-activated β-sialon phosphor according to claim 1, wherein when the atmosphere contains a rare gas, the rare gas contains argon.