Method for producing europium-activated β-sialon phosphor

Abstract

To provide a production method with which a europium-activated β-type sialon phosphor with an excellent internal quantum efficiency can be produced.SOLUTION: An aspect of the disclosure provides a production method which is a production method of a europium-activated β-type sialon phosphor, and has: a sintering step to obtain a sintered compact from a raw material composition containing a silicon source, an aluminum source, and a europium source and including at least one of them as a nitride by one or more heat treatments; and an annealing step to obtain an anneal processed body from a mixture including the sintered compact and a halogen compound having at least one element of Sr and Ba as a constituent element by one or more anneal treatments under an atmosphere including at least one selected from a group consisting of a rare gas, a reductive gas, and an inert gas.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a europium-activated β-sialon phosphor. [Background technology]

[0002] Oxynitride phosphors are known to have little decrease in brightness with increasing temperature and excellent durability. Among oxynitride phosphors, europium-activated β-sialon is known as a green phosphor that can be excited by ultraviolet light, visible light, or the like.

[0003] A europium-activated β-sialon phosphor can be obtained by, for example, 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, efforts are also being made to improve their brightness.

[0004] For example, Patent Document 1 describes a method for producing a β-sialon phosphor, which includes a first heat-treatment step of heat-treating a mixture containing an aluminum compound, a first europium compound, and silicon nitride to obtain a first heat-treated product, and a second heat-treatment step of heat-treating the first heat-treated product and a second europium compound 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 of firing a raw material mixture of the β-sialon phosphor at a temperature of 1820°C to 2200°C in a nitrogen atmosphere to obtain a fired product, and an annealing step of annealing the fired product at a temperature of 1100°C or higher in a reducing atmosphere. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-002278 [Patent Document 2] International Publication No. 2010 / 143590 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present disclosure is to provide a manufacturing method capable of producing a europium-activated β-sialon phosphor with excellent internal quantum efficiency. [Means for solving the problem]

[0007] One aspect of the present disclosure provides a method for producing a europium-activated β-sialon phosphor, the method comprising: a firing step of obtaining a fired body from a raw material composition containing a silicon source, an aluminum source, and a europium source, at least one of which is present as 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 a halogen compound having at least one of Sr and Ba as a constituent element, by one or more annealing treatments in an atmosphere containing at least one selected from the group consisting of a rare gas, a reducing gas, and an inert gas.

[0008] In the above-described method for producing a europium-activated β-sialon phosphor, a halogen compound containing at least one of Sr and Ba as a constituent element is blended in the annealing step, and the annealing treatment is performed in an atmosphere containing at least one selected from the group consisting of a rare gas, a reducing gas, and an inert gas. This allows the production of a europium-activated β-sialon phosphor with excellent internal quantum efficiency. While the reason for this effect is unclear, the inventors speculate as follows: By blending a halide, which would normally be an impurity, into the fired body and firing it, the halide melts and forms a liquid phase, which allows the impurities in the phosphor to be extracted. At the same time, Sr (strontium) and Ba (barium) are incorporated into defects occurring in the phosphor in the fired body, thereby reducing the impurity content and crystal defects. The inventors speculate that these effects improve the internal quantum efficiency of the resulting europium-activated β-sialon phosphor.

[0009] The melting point of the halide may be equal to or lower than 1500° C. By using a compound with a relatively low melting point as the halide, the annealing temperature can be lowered, and the liquid phase as described above can be formed at a relatively low temperature. This makes it easier to extract impurities from the phosphor contained in the fired body, and can further improve the internal quantum efficiency of the europium-activated β-sialon phosphor.

[0010] The total amount of the halogen compounds blended in the annealing step may be 0.001 to 15 mass % based on the total amount of the mixture.

[0011] In the above manufacturing method, 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; and when the atmosphere contains an inert gas, the inert gas may contain nitrogen.

[0012] The annealing temperature may be 1000 to 1700°C. [Effects of the Invention]

[0013] According to the present disclosure, a manufacturing method can be provided that can produce a europium-activated β-sialon phosphor with excellent internal quantum efficiency. Here, excellent internal quantum efficiency generally means that the ratio of the number of photons of fluorescent light to the number of photons of excitation light irradiated onto the phosphor is large. Furthermore, a europium-activated β-sialon phosphor with excellent internal quantum efficiency can have improved external quantum efficiency and, therefore, can be made into a highly bright phosphor. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described. 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.

[0015] Unless otherwise specified, the materials exemplified in this specification can be used singly 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.

[0016] One embodiment of a europium-activated β-sialon phosphor is a method for producing a europium-activated β-sialon phosphor, the method comprising: a firing step of obtaining a fired body from a raw material composition containing a silicon source, an aluminum source, and a europium source, at least one of which is present as 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 a halogen compound having at least one of Sr and Ba as a constituent element, by one or more annealing treatments in an atmosphere containing at least one selected from the group consisting of a rare gas, a reducing gas, and an inert gas.

[0017] The raw material composition contains compounds having elements that are constituent elements 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 contains nitrogen, which is a constituent element of europium-activated β-sialon, and therefore also serves as a nitrogen source. The silicon source refers to a compound or element containing silicon as a constituent element, the aluminum source refers to a compound or element containing aluminum as a constituent element, and the europium source refers to a compound or element containing europium as a constituent element. In this specification, a compound containing silicon as a constituent element is also referred to as a silicon compound, a compound containing aluminum as a constituent element is also referred to as an aluminum compound, and a compound containing europium as a constituent element is also referred to as 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, where the β-sialon or europium-activated β-sialon is an aggregate or core material.

[0018] Examples of silicon compounds include silicon nitride (Si3N4) and silicon dioxide (SiO2). It is preferable to use silicon nitride with a high α fraction. The α fraction of silicon nitride may be, for example, 80% by mass or more, 90% by mass or more, or 95% by 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 with a low oxygen content. The oxygen content of silicon nitride may be, for example, 3% by mass or less, or 1.3% by mass or less. When the oxygen content of silicon nitride is within the above range, it is possible to suppress the occurrence of defects in the crystal of β-sialon and the main crystalline phase of the europium-activated β-sialon phosphor.

[0019] Examples of aluminum compounds include aluminum nitride (AlN), aluminum oxide (Al2O3), and aluminum hydroxide (Al(OH)3).

[0020] 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 includes europium oxide. The valence of europium in the europium compound may be divalent or trivalent, and preferably includes divalent.

[0021] The raw material mixture can be prepared by weighing and mixing each compound. Mixing can be performed by a dry mixing method or a wet mixing method. The dry mixing method can be, for example, a method in which each component is mixed using a V-type mixer or the like. The wet mixing method can 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.

[0022] The heating temperature in the firing step 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 step to 1800°C or higher, grain growth of the main crystalline phase of the β-sialon and europium-activated β-sialon phosphor can be promoted, and the amount of europium dissolved in the solid solution can be made more sufficient. By setting the heating temperature in the firing step to 2500°C or lower, decomposition of the β-sialon crystal and the main crystalline phase of the europium-activated β-sialon phosphor can be sufficiently suppressed.

[0023] The heating time in the firing step is preferably long from the viewpoint of promoting primary particle growth of the main crystalline phase of the β-sialon and europium-activated β-sialon phosphor, 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.

[0024] The raw material mixture may be heated in a nitrogen atmosphere in the firing step. Heating under conditions of a high nitrogen partial pressure can suppress decomposition of silicon nitride at high temperatures. Furthermore, treatment at high temperatures can promote particle growth. The raw material mixture may be heated under pressure in the firing step. The pressure may be, for example, 0.01 to 200 MPaG, 0.02 to 200 MPaG, 0.05 to 200 MPaG, 0.1 to 100 MPaG, 0.5 to 100 MPaG, 0.5 to 50 MPaG, 0.5 to 15 MPaG, or 0.5 to 5 MPaG.

[0025] The number of times of heat treatment in the firing step may be 1, but may also be, for example, 2 or more, such as 2 to 5, or 2 to 4. By performing heat treatment multiple times, a europium-activated β-sialon phosphor with more excellent luminance can be obtained.

[0026] In the firing step, one or more heat treatments are performed. When multiple heat treatments are performed, they are sequentially referred to as a first heat treatment, a second heat treatment, etc., and the steps of performing each heat treatment may be sequentially referred to as a first firing step, a second firing step, etc. For example, when the above-mentioned production method performs two heat treatments in the firing step, the firing step may also be referred to as including a first heat treatment of a raw material composition containing a nitride to obtain a first heat-treated body, and a second heat treatment of the first heat-treated body to obtain a second heat-treated body. In this case, the second heat-treated body corresponds to the fired body containing the β-sialon. Before performing the multiple heat treatments, the silicon source, aluminum source, and europium source may be further mixed and heat-treated.

[0027] When two or more firing steps are performed, 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 step. The heating temperature, heating time, heating atmosphere, and heating pressure of the second firing step and subsequent steps 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 subsequent steps are different from those of the first firing step, they are still within the range of conditions shown for the above-mentioned heating step.

[0028] The fired body obtained in the firing step may be a solid solution having β-sialon crystals, with a luminescence center element dissolved in a portion of the crystals, and may itself be capable of emitting fluorescence. That is, the fired body may contain a europium-activated β-sialon phosphor. The fired body obtained in the firing step may be in the form of a mass, and the particle size may be adjusted by crushing or the like prior to the annealing step.

[0029] Next, an annealing step is performed. In this specification, the annealing step refers to a step of obtaining an annealed body from a mixture containing the fired body obtained in the firing step described above and a halogen compound containing at least one of Sr (strontium) and Ba (barium) as a constituent element. In the annealing step, the annealed body is obtained from the mixture by one or more heat treatments. The internal quantum efficiency of the europium-activated β-sialon phosphor that may be contained in the fired body can also be further improved by undergoing the annealing step.

[0030] The halogen compound containing at least one of Sr (strontium) and Ba (barium) as a constituent element may be used in combination with a plurality of elements or may be used alone, but is preferably used alone because it is easy to control the reaction system during the annealing treatment. Examples of the halogen element constituting the halogen compound include F (fluorine) and Cl (chlorine). The halogen element constituting the halogen compound is preferably Cl, from the viewpoint of further reducing the melting point of the halogen compound and further improving the internal quantum efficiency.

[0031] The upper limit of the melting point of the halogen compound may be, for example, 1500°C or lower, 1450°C or lower, 1400°C or lower, 1350°C or lower, 1300°C or lower, 1250°C or lower, 1200°C or lower, 1150°C or lower, or 1000°C or lower. By using a compound with a relatively low melting point as the halogen compound, the annealing temperature can be lowered and the liquid phase described above can be formed at a relatively low temperature, which makes it easier to extract impurities from the europium-activated β-sialon phosphor in the fired product, thereby further improving the internal quantum efficiency of the resulting europium-activated β-sialon phosphor. The lower limit of the melting point of the halogen compound may be, for example, 800°C or higher or 900°C or higher.

[0032] The boiling point of the halide may be, for example, 1200 to 2500° C., 1200 to 2400° C., 1200 to 2300° C., or 1300 to 2300° C. By using a compound having a boiling point within the above range as the halide, it is possible to more sufficiently prevent the halide from being removed from the system during the annealing treatment.

[0033] The total amount of the halogen compounds may be, for example, 0.001 to 15% by mass, based on the total amount of the mixture. The lower limit of the total amount of the halogen compounds may be, for example, 0.01% by mass or more, 0.05% by mass or more, 0.1% by mass or more, 0.15% by mass or more, or 0.3% by mass or more, based on the total amount of the mixture. When the lower limit of the total amount of the halogen compounds is within the above range, the internal quantum efficiency of the resulting europium-activated β-sialon phosphor can be further improved. The upper limit of the total amount of the halogen compounds may be, for example, 13% by mass or less, 12% by mass or less, or 10% by mass or less, based on the total amount of the mixture. When the upper limit of the total amount of the halogen compounds is within the above range, deterioration of the optical properties of the europium-activated β-sialon phosphor due to a large amount of residual halogen or the like can be more sufficiently suppressed.

[0034] The annealing treatment is carried out in an atmosphere containing at least one gas selected from the group consisting of a rare gas, a reducing gas, and an inert gas, and by carrying out 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.

[0035] 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 for the annealing step may be a mixed gas of two or more of the rare gas, the reducing gas, and an inert gas. When the mixed gas is used as the atmosphere for the annealing step, the content of the reducing gas may be, for example, 1 to 50 vol% or 4 to 20 vol% based on the total volume of the mixed gas at standard conditions. The content of the inert gas may be, for example, 1 to 50 vol% or 4 to 20 vol% based on the total volume of the mixed gas at standard conditions.

[0036] The pressure during the annealing treatment may be the same as that during the firing step, but is preferably lower than the pressure conditions during the firing step, and more preferably atmospheric pressure.Specifically, the pressure during this treatment may be, for example, 0.01 to 100 MPaG, 0.02 to 100 MPaG, 0.02 to 50 MPaG, 0.02 to 30 MPaG, 0.02 to 15 MPaG, 0.02 to 10 MPaG, or 0.02 to 5 MPaG.

[0037] The annealing temperature must be set lower than the heating temperature in the sintering process. The upper limit of the annealing temperature may be, for example, 1700°C or lower, 1650°C or lower, 1600°C or lower, 1550°C or lower, or 1500°C or lower. By setting the upper limit of the annealing temperature within the above range, the halide compound is removed from the system, and further grain growth in the sintered body can be prevented from proceeding, resulting in aggregation between solid solutions, the formation of secondary particles, and the like, resulting in particle coarsening. The lower limit of the annealing temperature may be, for example, 1000°C or higher, 1100°C or higher, 1200°C or higher, 1300°C or higher, or 1400°C or higher. Setting the lower limit of the annealing temperature within the above range melts the halide compound to form a liquid phase, thereby enabling more sufficient extraction of impurities in a mixture containing the sintered body into the liquid phase. Setting the lower limit of the annealing temperature within the above range also reduces the density of crystal defects contained in the annealed body. This can further improve the internal quantum efficiency of the resulting europium-activated β-sialon phosphor.The annealing temperature can be adjusted within the above-mentioned range, and may be, for example, 1000 to 1700°C, or 1100 to 1680°C.

[0038] 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 more sufficiently extracting impurities in the mixture and further reducing crystal defects in the phosphor contained in the annealed body.

[0039] In the annealing step, one or more annealing treatments are performed. When multiple annealing treatments are performed, they are sequentially referred to as a first annealing treatment, a second annealing treatment, etc., and the steps of performing each annealing treatment may be sequentially referred to as a first annealing treatment, a second annealing treatment, 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 fired body to obtain a first annealed body, and 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.

[0040] When the annealing step includes 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 can 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 still within the range of conditions shown for the annealing step described above.

[0041] The number of annealing treatments in the annealing step may be one, but may also be two or more, for example, two to five, or two to four. By performing annealing treatments multiple times, impurities in the crystals contained in the annealed body can be extracted more sufficiently, the defect density in the crystals can be reduced, and a europium-activated β-sialon phosphor with better internal quantum efficiency can be obtained.

[0042] When annealing is performed multiple times in the annealing step, the above-mentioned halogen compound may be blended all at once in the first annealing step, or may be blended in portions over multiple annealing steps, but is preferably blended all at once in the first annealing step. Note that when the above-mentioned halogen compound is blended in portions, the above description of the blending amount of the halogen compound should be interpreted as the total amount of the halogen compound blended over multiple annealing steps.

[0043] The method for producing a europium-activated β-sialon phosphor may include other steps in addition to the firing step and the annealing step. Examples of such other steps include a step of treating the annealed body obtained in the annealing step with at least one of an acid and an alkali, and 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.

[0044] 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, a pseudopolymorph of aluminum nitride (AlN) formed as a by-product during preparation of the 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.

[0045] The classification step may be performed by, for example, either a wet classification method or a dry classification method. Examples of wet classification include elutriation classification, in which the annealed body is added to a mixed solvent containing ion-exchanged water and a dispersant (e.g., sodium hexametaphosphate) or a mixed solvent containing ion-exchanged water and aqueous ammonia, stirred, and then allowed to stand to remove particles with a small particle size.

[0046] The europium-activated β-sialon phosphor obtained by the above manufacturing method may contain, as a main crystal, a crystal having the same crystal structure as β-sialon, or may be composed of a crystal having the same crystal structure as β-sialon. The europium-activated β-sialon phosphor may contain heterogeneous phases as long as the gist of the present disclosure is not impaired. The europium-activated β-sialon phosphor contains Si 6-Z Al Z O Z N 8-Z :Eu and may have a composition represented by the compositional formula. In the above compositional formula, z may be 0.0 < z < 4.2, may be 0.0 < z < 2.0, or may be 0.0 < z ≤ 0.5. The composition of the europium-activated β-sialon phosphor can be adjusted by changing the components and composition ratios of the raw material composition.

[0047] In the composition of the europium-activated β-sialon phosphor, the contents of nitrogen atoms (N) and oxygen atoms (O) can be quantified by an oxygen-nitrogen analyzer, and the contents of europium (Eu), silicon (Si), and aluminum (Al) can be confirmed by performing elemental quantitative analysis using an ICP emission spectrometer.

[0048] The 50% cumulative diameter (D50) in the volume-based cumulative particle size distribution of the europium-activated β-sialon phosphor obtained by the above manufacturing method may be adjusted according to the use of the phosphor and the like. 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 conditions such as the heating temperature and heating time during phosphor production, and by classification and the like.

[0049] In this specification, D50 refers to the particle size at which the cumulative value from the smallest particle size reaches 50% of the total in the volume-based particle size distribution curve measured by laser diffraction / scattering. The particle size distribution curve for phosphors is measured in accordance with the particle size distribution measurement method using laser diffraction / scattering described in JIS R 1629:1997, "Method for Measuring Particle Size Distribution of Fine Ceramics Raw Materials by Laser Diffraction / Scattering." A particle size distribution analyzer can be used for the measurement. Specifically, 0.1 g of the phosphor to be measured is first placed in 100 mL of ion-exchanged water, a small amount of sodium hexametaphosphate is added, and the sample is dispersed using an ultrasonic homogenizer for 3 minutes. The particle size is measured using a particle size distribution analyzer, and D50 is determined from the resulting particle size distribution. D50, also known as the median diameter, refers to the average particle size of the target particles. An example of a particle size distribution analyzer is the "Microtrac MT3300EX II" (product name) manufactured by Microtrac Bell Corporation. As the 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.

[0050] The europium-activated β-sialon phosphor obtained by the above-mentioned method has reduced impurities and a sufficiently reduced rate of crystal defects, and therefore has excellent absorptivity for light with a wavelength of 455 nm. The absorptivity of the phosphor for light with a wavelength of 455 nm can be, for example, 74% or more, 76% or more, or 78% or more.

[0051] The europium-activated β-sialon phosphor obtained by the above-mentioned production method has reduced impurities and a sufficiently reduced proportion of crystal defects, so that the phosphor's absorption of light with a wavelength of 800 nm is suppressed to a low level. The europium-activated β-sialon phosphor's lower limit of diffuse reflectance for light with a wavelength of 800 nm can be 95% or more, 96% or more, or 97% or more. The europium-activated β-sialon phosphor has suppressed absorption of light with a wavelength of 800 nm and is less affected by defects and heterophases, which are non-luminescent components, so that it can have superior internal quantum efficiency.

[0052] The term "diffuse reflectance" as used herein refers to a value determined from the diffuse reflectance spectrum of a europium-activated β-sialon phosphor measured using a UV-visible spectrophotometer. The diffuse reflectance is determined by the procedure described in the Examples of this specification. The UV-visible spectrophotometer may be, for example, a "V-550" (product name) manufactured by JASCO Corporation.

[0053] The europium-activated β-sialon phosphor obtained by the above-described production method has excellent internal quantum efficiency, which can be, for example, more than 82%, 83% or more, 84% or more, 85% or more, 86% or more, or 87% or more.

[0054] The internal quantum efficiency in this specification refers to the quantum efficiency obtained when a phosphor is excited with 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.

[0055] The europium-activated β-sialon phosphor may be used alone or in combination with other phosphors. Because europium-activated β-sialon phosphors have excellent internal quantum efficiency, they are suitable for use in light-emitting devices such as LEDs. The phosphor may be dispersed in a curable resin. The curable resin is not particularly limited, and may be, for example, a resin used as a sealing resin for light-emitting devices.

[0056] Although several embodiments have been described above, the present disclosure is not limited to the above embodiments. Furthermore, the descriptions of the above embodiments can be applied to each other. [Example]

[0057] The present disclosure will be described in more detail below with reference to examples and comparative examples, although the present disclosure is not limited to the following examples.

[0058] Example 1 [Preparation of europium-activated β-sialon phosphor] The raw materials were weighed into a container so that the silicon nitride (Si3N4) was 96.0 mass%, aluminum nitride (AlN) was 2.8 mass%, aluminum oxide (Al2O3) was 0.5 mass%, and europium oxide (Eu2O3) was 0.7 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 250 μm openings to remove aggregates, thereby obtaining a raw material composition. The aggregates that did not pass through the sieve were crushed and the particle size was adjusted so that they would pass through the sieve.

[0059] 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 Co., Ltd., primarily composed of boron nitride (trade 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 heated to 2020°C under a nitrogen gas atmosphere (pressure: 0.90 MPaG). The mixture was then heated at 2020°C for 8 hours (sintering step). After heating, the sample, which had become loosely agglomerated lumps in the container, was placed in a mortar and crushed. After crushing, the mixture was passed through a sieve with 250 μm openings to obtain a powdered sintered product.

[0060] Next, strontium fluoride (SrF2) was blended with the sintered body to prepare a mixture. The blending amount of strontium fluoride was adjusted to 0.100 mass% based on the total amount of the mixture. The resulting mixture was filled 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 1450°C for 3 hours (annealing step). After heating, the loosely aggregated particles in the container were crushed in a mortar and passed through a 250 μm sieve to obtain powder.

[0061] Next, the obtained powder was added to a mixed acid of hydrofluoric acid (concentration: 50% by mass) and nitric acid (concentration: 70% by mass) (a mixture of hydrofluoric acid and nitric acid 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. Thereafter, more distilled water was 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, and the resulting precipitate was filtered and dried to obtain a europium-activated β-sialon phosphor.

[0062] (Examples 2 and 3) A europium-activated β-sialon phosphor was obtained in the same manner as in Example 1, except that the amount of strontium fluoride added was changed as shown in Table 1.

[0063] Examples 4 to 6 A europium-activated β-sialon phosphor was obtained in the same manner as in Example 1, except that anhydrous strontium chloride (SrCl2) was used instead of strontium fluoride and the amount of strontium chloride added was changed as shown in Table 1.

[0064] Examples 7 to 9 A europium-activated β-sialon phosphor was obtained in the same manner as in Example 1, except that barium fluoride (BaF2) was used instead of strontium fluoride and the amount of barium fluoride added was changed as shown in Table 1.

[0065] Examples 10 to 12 A europium-activated β-sialon phosphor was obtained in the same manner as in Example 1, except that anhydrous barium chloride (BaCl2) was used instead of strontium fluoride and the amount of barium chloride added was changed as shown in Table 1.

[0066] (Comparative Example 1) A europium-activated β-sialon phosphor was obtained in the same manner as in Example 1, except that strontium fluoride was not added in the annealing step and only the fired body was annealed.

[0067] (Comparative Examples 2 and 3) A europium-activated β-sialon phosphor was obtained in the same manner as in Example 1, except that magnesium fluoride (MgF2) was used instead of strontium fluoride and the blending amount of magnesium fluoride was changed as shown in Table 1.

[0068] (Comparative Examples 4 and 5) A europium-activated β-sialon phosphor was obtained in the same manner as in Example 1, except that calcium fluoride (CaF2) was used instead of strontium fluoride and the amount of calcium fluoride added was changed as shown in Table 1.

[0069] (Comparative Example 6) A europium-activated β-sialon phosphor was obtained in the same manner as in Example 1, except that strontium oxide (SrO) was used instead of strontium fluoride and the amount of strontium oxide added was changed as shown in Table 1.

[0070] (Comparative Example 7) A europium-activated β-sialon phosphor was obtained in the same manner as in Example 1, except that barium oxide (BaO) was used instead of strontium fluoride and the amount of barium oxide blended was changed as shown in Table 1.

[0071] <Absorption rate, internal quantum efficiency> The light absorptance (excitation light absorptance) and internal quantum efficiency of the europium-activated β-sialon phosphor when irradiated with excitation light having a wavelength of 455 nm were calculated by the following procedure. The results are shown in Table 1.

[0072] First, the phosphor to be measured was filled into a concave cell so that the surface was smooth, and the cell was attached to the opening of the integrating sphere. Monochromatic light with a wavelength of 455 nm was split from a Xe lamp, which served as a light source, and introduced into the integrating sphere using an optical fiber as excitation light for the phosphor. This monochromatic 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.

[0073] 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 fluorescence 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 fluorescence 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. The number of excitation light photons (Qex) was calculated from the spectrum in the wavelength range of 450 to 465 nm.

[0074] From the above calculation results, the absorptance of the 455 nm excitation light and the internal quantum efficiency of the phosphor to be measured were calculated based on the following formulas. Absorbance of 455 nm excitation light = ((Qex-Qref) / Qex) x 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 455 nm excitation light, and the internal quantum efficiency can be expressed as follows: External quantum efficiency = 455nm light absorption rate × internal quantum efficiency

[0075] <Diffuse reflectance for 800 nm light> The diffuse reflectance of the europium-activated β-sialon was measured using an integrating sphere device (product name: ISV-469) attached to an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name: V-550). After baseline correction using a standard reflector (Spectralon (registered trademark)), a solid sample holder filled with the phosphor powder to be measured was attached to the spectrophotometer, and the diffuse reflectance was measured in the wavelength range of 500 to 850 nm. Of the measurement results, the diffuse reflectance value at 800 nm was particularly used. The results are shown in Table 1.

[0076] [Table 1]

[0077] For reference, the melting points and boiling points of the halogen compounds used in the examples and comparative examples are shown in Table 2.

[0078] [Table 2] [Industrial Applicability]

[0079] According to the present disclosure, it is possible to provide a manufacturing method capable of manufacturing a europium-activated β-sialon phosphor with excellent internal quantum efficiency.

Claims

1. A method for producing a europium-activated β-sialon phosphor, comprising the steps of: a firing step of obtaining a fired body from a raw material composition containing a silicon source, an aluminum source, and a europium source, wherein the raw material composition contains at least one of the silicon source, the aluminum source, and the europium source as a nitride, by one or more heat treatments; an annealing step of obtaining an annealed body from a mixture containing the sintered body and a halogen compound containing at least one of Sr and Ba as a constituent element by one or more annealing treatments under an argon atmosphere; The melting point of the halogen compound is 1500°C or less, The annealing temperature is 1400 to 1700°C.

2. The method according to claim 1, wherein the melting point of the halogen compound is 873 to 1463°C.

3. 3. The method according to claim 1, wherein the total amount of the halogen compounds in the annealing step is 0.001 to 15 mass % based on the total amount of the mixture.

4. The manufacturing method according to any one of claims 1 to 3, wherein the annealing temperature is 1400 to 1450°C.

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