Method of producing ceramic sintered body

Abstract

To provide a method of producing a ceramic sintered body.SOLUTION: The method of producing a ceramic sintered body includes: preparing a molded body including a nitride phosphor having a composition including at least one species of alkali earth metal elements M1, and at least one species of metal elements M2 selected from the group consisting of Eu, Ce, Tb and Mn, and Si and N, with the mol ratio of the sum of alkali earth metal elements M1 and metal elements M2 in 1 mol of the composition being 2, the mol ratio of metal elements M2 being a product of a variable y and 2, the variable y being 0.001 or more and smaller than 0.5, the mol ratio of Si being 5, and the mol ratio of N being 8; subjecting the molded body to primary firing to obtain a first sintered body; subjecting the first sintered body to secondary firing while making the first sintered body contact with metallic molybdenum or a solid consisting of an alloy including molybdenum as a main component, to obtain a second sintered body; and subjecting the second sintered body stored in a container including metal with a higher melting point than metallic molybdenum to tertiary firing to obtain a third sintered body.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a ceramic sintered body. [Background technology]

[0002] Some light-emitting devices using LED or LD light-emitting elements are composed of a light-emitting element that is an excitation light source and a member containing a phosphor that absorbs part of the light from the light-emitting element and converts it to a different wavelength. The light-emitting device emits a mixture of light emitted from the light-emitting element and light emitted from the phosphor. Such light-emitting devices are used as light sources for in-vehicle lighting, general lighting, backlights for liquid crystal display devices, illumination, projectors, etc.

[0003] As a member containing a phosphor, Patent Document 1 discloses a sintered body containing a fluoride inorganic binder and a nitride phosphor. [Prior art documents] [Patent documents]

[0004] [Patent Document 2] International Publication No. 2016 / 117623 Summary of the Invention [Problem to be solved by the invention]

[0005] When the sintered body is fired, the fluoride inorganic binder reacts with the nitride phosphor, which may reduce the luminous flux of the sintered body containing the nitride phosphor, adversely affecting the light emission characteristics. An object of the present disclosure is to provide a method for producing a ceramic sintered body capable of emitting light with a high luminous flux. [Means for solving the problem]

[0006] The first aspect is a method for manufacturing a semiconductor device comprising the steps of: 1and at least one metal element M selected from the group consisting of Eu, Ce, Tb and Mn. 2 The composition contains Si and N, and the alkaline earth metal element M 1 and metal element M 2 The total molar ratio of the metal element M 2 a molar ratio of Si is a product of a variable y and 2, the variable y being 0.001 or more and less than 0.5, the molar ratio of Si is 5, and the molar ratio of N is 8; a first firing of the molar body to obtain a first sintered body; a second firing of the first sintered body by contacting the first sintered body with a solid made of molybdenum metal or an alloy containing molybdenum as a main component to obtain a second sintered body; and a tertiary firing of the second sintered body in a container containing a metal having a higher melting point than molybdenum metal to obtain a third sintered body. Effect of the Invention

[0007] According to the present disclosure, it is possible to provide a method for producing a ceramic sintered body capable of emitting light with high luminous flux. [Brief description of the drawings]

[0008] [Figure 1] 2 is a flowchart showing steps of a method for producing a ceramic sintered body. [Diagram 2] 2 is a flowchart showing steps of a method for producing a ceramic sintered body. [Diagram 3] FIG. 1 is a diagram showing area A in the xy chromaticity coordinates of the CIE1931 chromaticity diagram. [Figure 4A] FIG. 1 is a schematic plan view illustrating an example of a light emitting device. [Figure 4B] FIG. 1 is a schematic cross-sectional view showing an example of a light-emitting device. [Figure 5A] 11 is a photograph showing the appearance of a second sintered body after secondary firing according to Example 3. [Figure 5B] 11 is a photograph showing the appearance of a third sintered body after tertiary firing according to Example 3. [Figure 6A]11 is a photograph showing the appearance of a second sintered body after secondary firing in Comparative Example 4. [Figure 6B] 11 is a photograph showing the appearance of the second sintered body after grinding in Comparative Example 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The method for producing a ceramic sintered body according to the present disclosure will be described below. However, the following embodiment is an example for embodying the technical idea of ​​the present invention, and the present invention is not limited to the following method for producing a ceramic sintered body. The relationship between the color name and the chromaticity coordinate, the relationship between the wavelength range of light and the color name of monochromatic light, etc., are in accordance with JIS Z8110.

[0010] The method for producing a ceramic sintered body includes adding at least one alkaline earth metal element M selected from the group consisting of Ba, Sr, Ca, and Mg. 1 and at least one metal element M selected from the group consisting of Eu, Ce, Tb and Mn. 2 The composition contains Si and N, and the alkaline earth metal element M 1 and metal element M 2 The total molar ratio of the metal element M 2 the molar ratio of Si is the product of a variable y and 2, the variable y being 0.001 or more and less than 0.5, the molar ratio of Si is 5, and the molar ratio of N is 8; the molar ratio of Si is 5 and the molar ratio of N is 8; the molar ratio of Si is 5 and the molar ratio of N is 8, ...

[0011] In a method for producing a ceramic sintered body, when a molded body containing a nitride phosphor is obtained and then fired, the sintered body containing crystals having the composition of the nitride phosphor may contain, as impurities, elements contained in the nitride phosphor, and crystals having a composition different from that of the nitride phosphor. The crystals having a composition different from that of the nitride phosphor become impurities, and when these impurities are contained, the density of the obtained sintered body may decrease, and even when the obtained sintered body is irradiated with light, the luminous intensity of the light emitted by the nitride phosphor may decrease, and the luminous flux may decrease.

[0012] For example, a first sintered body obtained by primary firing of a molded body containing a nitride phosphor is more likely to have impurities such as crystals having a composition different from that of the nitride phosphor inside the first sintered body than on the surface of the first sintered body.

[0013] In a method for producing a ceramic sintered body, a molded body containing a nitride phosphor is subjected to a first firing to obtain a first sintered body, and then the obtained first sintered body is brought into contact with a solid made of molybdenum metal or an alloy containing molybdenum to perform a second firing, whereby a gas resulting from decomposition of a crystal having a composition different from that of the nitride phosphor contained in the first sintered body is adsorbed by the molybdenum metal or the alloy containing molybdenum. By the second firing, a gas resulting from decomposition of a crystal having a composition different from that of the nitride phosphor generated inside the first sintered body is adsorbed by a solid made of molybdenum metal or an alloy containing molybdenum, and the decomposed gas is prevented from returning to the sintered body, so that a second sintered body is obtained in which impurities such as crystals having a composition different from that of the nitride phosphor are eliminated or reduced. This is thought to be because impurities such as crystals having a composition different from that of the nitride phosphor react more easily with the molybdenum metal or the alloy containing molybdenum as a main component in contact with the first sintered body than with the crystals having the desired composition of the nitride phosphor contained in the first sintered body, and are more likely to be released from the inside of the first sintered body to the outside.

[0014] Gas produced by decomposition of crystals having a composition different from that of the nitride phosphor produced inside the first sintered body is absorbed by a solid made of molybdenum metal or an alloy containing molybdenum as its main component which is in contact with the first sintered body, but the second sintered body which has been in contact with molybdenum metal or an alloy containing molybdenum as its main component may have some parts of its surface darkened or dulled by the decomposed gas.

[0015] By placing the second sintered body in a container containing a metal with a higher melting point than molybdenum metal and subjecting it to a tertiary firing, the blackening and dullness remaining on the surface of the second sintered body are decomposed and released as gas into the atmosphere, resulting in a high-density third sintered body that is free of blackening and dullness and has the desired body color, as a ceramic sintered body.

[0016] FIG. 1 is a flow chart showing an example of steps of a method for producing a ceramic sintered body. An example of a method for producing a ceramic sintered body will be described with reference to FIG. 1. The method for producing a ceramic sintered body includes preparing a molded body containing a nitride phosphor S101, performing a first firing of the molded body to obtain a first sintered body S102, performing a second firing of the first sintered body to obtain a second sintered body S103, and performing a third firing of the second sintered body S104. The method for producing a ceramic sintered body may include processing the first sintered body or the third sintered body to a desired thickness after obtaining the first sintered body and before obtaining the second sintered body, or after obtaining the third sintered body. The method for producing a ceramic sintered body may include processing the second sintered body to a desired thickness after obtaining the second sintered body and before obtaining the third sintered body.

[0017] 2 is a flow chart showing another example of steps of the method for producing a ceramic sintered body. The method for producing a ceramic sintered body may include processing the first sintered body S202-2 before obtaining the second sintered body S203. The method for producing a ceramic sintered body may include processing the third sintered body S204-2 after obtaining the third sintered body S204-1. The method for producing a ceramic sintered body includes preparing a molded body containing a nitride phosphor S201, primarily firing the molded body to obtain the first sintered body S202-1, secondary firing the first sintered body to obtain the second sintered body S203, and tertiary firing the second sintered body to obtain the third sintered body S204-1, which are the same as the steps shown in FIG. 1. Each step of the method for producing a ceramic sintered body will be described below.

[0018] The method for producing a ceramic sintered body may include preparing a nitride phosphor before preparing a molded body. The nitride phosphor may be a commercially available product or may be produced by the following method.

[0019] The nitride phosphor contains at least one alkaline earth metal element M selected from the group consisting of Ba, Sr, Ca, and Mg. 1 and at least one metal element M selected from the group consisting of Eu, Ce, Tb, and Mn. 2 It is preferable to obtain a raw material mixture containing a second compound containing and a compound containing Si, and heat-treating the raw material mixture in a nitrogen-containing atmosphere at a temperature in the range of 980 ° C. to 1680 ° C. The nitride phosphor may be manufactured by referring to JP2020-083739A.

[0020] The nitride phosphor contains at least one alkaline earth metal element M selected from the group consisting of Ba, Sr, Ca, and Mg. 1 and at least one metal element M selected from the group consisting of Eu, Ce, Tb and Mn. 2 The composition contains Si and N, and the alkaline earth metal element M 1 and metal element M 2The total molar ratio of the metal element M 2 is the product of the variable y and 2, the variable y is 0.001 or more and less than 0.5, the molar ratio of Si is 5, and the molar ratio of N is 8.

[0021] The nitride phosphor preferably has a composition represented by the following formula (I). (M 1 1-y M 2 y )2Si5N8(I) (In formula (I), M 1 is at least one alkaline earth metal element selected from the group consisting of Ba, Sr, Ca and Mg, and M 2 is at least one metal element selected from the group consisting of Eu, Ce, Tb and Mn, and y is a number satisfying 0.001≦y<0.5.

[0022] The nitride phosphor may have a composition represented by the following formula (II): (Ba 1-x-y M 12 x M 2 y )2Si5N8(II) (In formula (II), M 12 is at least one alkaline earth metal element selected from the group consisting of Sr, Ca, and Mg, and M 2 is at least one metal element selected from the group consisting of Eu, Ce, Tb and Mn, and x and y are numbers that satisfy 0≦x<1.0, 0.001≦y<0.5, and 0.001≦x+y<1.0, respectively.

[0023] The product of the variables y and 2 is the content of at least one metal element M selected from the group consisting of Eu, Ce, Tb, and Mn in 1 mole of the chemical composition of the nitride phosphor. 2 The molar ratio of metal element M 2is an activator for the nitride phosphor. From the viewpoint of obtaining a ceramic sintered body with high luminescence intensity, the variable y is preferably in the range of 0.0010 or more and less than 0.5 (0.0010≦y<0.5), more preferably in the range of 0.0015 or more and 0.4 or less (0.0015≦y≦0.4), and may be in the range of 0.0020 or more and 0.3 or less (0.0020≦y≦0.3), or may be in the range of 0.0025 or more and 0.2 or less (0.0025≦y≦0.2). The "molar ratio" indicates the molar amount of an element in 1 mole of the chemical composition contained in the phosphor.

[0024] As represented by formula (II), the composition of the nitride phosphor contains Ba and at least one alkaline earth metal element M selected from the group consisting of Sr, Ca, and Mg. 12 In this case, the product of the variables x and 2 is the amount of alkaline earth metal element M in 1 mole of the nitride phosphor composition. 12 The variable x is influenced by the amount of the activator, but is preferably in the range of 0 to 0.75 (0≦x≦0.75), more preferably in the range of 0.01 to 0.6 (0.01≦x≦0.60), and even more preferably in the range of 0.05 to 0.5 (0.05≦x≦0.50), and may be in the range of 0.06 to 0.45 (0.06≦x≦0.45).

[0025] The nitride phosphor preferably has an average particle size (Fisher Sub-sieve sizer's number) of less than 5.0 μm as measured by the Fisher Sub-sieve sizer (FSSS) method. If the average particle size of the nitride phosphor measured by the FSSS method is less than 5.0 μm, a molded body with few voids can be formed. The average particle size of the nitride phosphor measured by the FSSS method is more preferably 4.5 μm or less, and even more preferably 4.0 μm or less, and may be 0.1 μm or more, or may be 0.5 μm or more. The FSSS method is a type of air permeation method, and is a method in which the specific surface area is measured by utilizing the flow resistance of air to determine the particle size.

[0026] In preparing the molded body, the raw material forming the molded body includes a nitride phosphor. The raw material forming the molded body is preferably made of a nitride phosphor. The content of the nitride phosphor in the raw material forming the molded body is preferably 100 mass%, and may be 95 mass% or more, 97 mass% or more, 98 mass% or more, 99 mass% or more, or 99.5 mass% or more. The raw material or raw material mixture forming the molded body may include a nitride phosphor and a hydride, nitride, carbonate, chloride, imide compound, or amide compound containing an element contained in the nitride phosphor. The raw material or raw material mixture forming the molded body preferably does not include a fluoride or oxide.

[0027] In preparing the molded body, the nitride phosphor or the raw material mixture containing the nitride phosphor is molded into a desired shape to obtain the molded body. The nitride phosphor or the raw material mixture containing the nitride phosphor is preferably a powder, and may be a slurry containing the powder. The molding method of the molded body may be a press molding method in which the powder is pressed to mold the molded body, or a slurry molding method in which a slurry containing the powder is prepared and a molded body is obtained from the slurry. Examples of the press molding method include a mold press molding method and a cold isostatic pressing method (CIP: Cold Isostatic Pressing) specified in No. 2109 of JIS Z2500:2000. The molding method may adopt two types of methods to adjust the shape of the molded body, and CIP molding may be performed after mold press molding. In CIP molding, it is preferable to press the molded body using water as a medium.

[0028] The pressure during die press molding is preferably in the range of 1 MPa to 50 MPa, more preferably in the range of 2 MPa to 20 MPa, and even more preferably in the range of 2 MPa to 15 MPa. If the pressure during die press molding is in the above range, the molded body can be shaped into a desired shape.

[0029] The pressure in the CIP molding is preferably in the range of 50 MPa to 500 MPa, more preferably in the range of 100 MPa to 450 MPa, and even more preferably in the range of 200 MPa to 400 MPa. When the pressure in the CIP molding is in the above range, the density of the molded body can be increased, and a molded body having a substantially uniform density throughout can be obtained, and the density of the sintered body obtained in the subsequent firing step can be increased.

[0030] In the primary firing of the molded body to obtain the first sintered body, the temperature of the primary firing is preferably in the range of 1600°C to 2200°C, more preferably in the range of 1600°C to 2000°C, even more preferably in the range of 1600°C to 1900°C, and even more preferably in the range of 1600°C to 1800°C. When the temperature of the primary firing is in the range of 1600°C to 2200°C, a first sintered body with few voids can be obtained. In this specification, the case of firing an unsintered molded body is referred to as primary firing.

[0031] Examples of primary firing include atmosphere sintering, in which firing is performed in a non-oxidizing atmosphere without applying pressure or load, atmosphere pressure sintering, in which firing is performed under pressure in a non-oxidizing atmosphere, hot press sintering, and spark plasma sintering (SPS).

[0032] The first firing is preferably performed in an atmosphere containing nitrogen gas. The second firing and the third firing described later are also preferably performed in an atmosphere containing nitrogen gas. The nitrogen gas-containing atmosphere in the first firing, the second firing and the third firing is preferably an atmosphere containing at least 99% by volume of nitrogen. The nitrogen in the nitrogen gas-containing atmosphere is preferably 99% by volume or more, and more preferably 99.5% by volume or more. The nitrogen gas-containing atmosphere may contain a trace amount of gas such as oxygen in addition to nitrogen, but the oxygen content in the nitrogen gas-containing atmosphere is preferably 1% by volume or less, more preferably 0.5% by volume or less, even more preferably 0.1% by volume or less, even more preferably 0.01% by volume or less, and particularly preferably 0.001% by volume or less. The atmosphere in the firing step may be an atmosphere containing nitrogen having reducing properties, or an atmosphere containing hydrogen gas and nitrogen. When hydrogen gas is contained in the nitrogen-containing atmosphere in the firing step, the content of hydrogen gas in the atmosphere is preferably 1% by volume or more, more preferably 5% by volume or more, and even more preferably 10% by volume or more. The atmosphere for the heat treatment may be a reducing atmosphere using solid carbon in an air atmosphere.

[0033] In obtaining the first sintered body, the molded body is fired in an atmosphere containing nitrogen gas, whereby the first sintered body containing crystals having a composition of a nitride phosphor having high luminescence intensity and having a high relative density can be obtained. 2 When is Eu, divalent Eu that contributes to emission in the nitride phosphor 2+ Due to the increase in the proportion of divalent Eu, a first sintered body having high luminescence intensity can be obtained. 2+ is oxidized to trivalent Eu 3+ However, by first firing the compact in an atmosphere containing nitrogen gas with high reducing power, the trivalent Eu in the nitride phosphor contained in the compact can be reduced. 3+ is divalent Eu 2+ In the nitride phosphor, divalent Eu is reduced to 2+The proportion of the nitride phosphor in the first sintered body increases, and a first sintered body containing crystals having a composition of a nitride phosphor having high luminescence intensity is obtained.

[0034] The atmospheric pressure in the first firing is preferably in the range of 0.1 MPa to 2.0 MPa, more preferably in the range of 0.2 MPa to 1.5 MPa, and even more preferably in the range of 0.5 MPa to 1.2 MPa. The atmospheric pressure in the first firing is preferably a gauge pressure. When the atmospheric pressure in the first firing is within the above range, decomposition of the crystal structure is suppressed, and a first sintered body containing a nitride phosphor having high luminescence intensity is obtained.

[0035] The time for the primary firing may be appropriately selected depending on the atmospheric pressure, and is, for example, from 0.5 hours to 20 hours, and preferably from 1 hour to 10 hours.

[0036] The method for producing a sintered body may include processing the first sintered body after obtaining the first sintered body and before obtaining the second sintered body. By processing the first sintered body, when the first sintered body is subjected to secondary firing, crystals having a composition different from that of the nitride phosphor may be decomposed inside the first sintered body and may be easily released as a gas. In the method for producing a sintered body, processing the first sintered body includes cutting the obtained first sintered body to a desired size. In addition, a known method can be used as a cutting method, and for example, a method using a wire saw or the like can be used. As described later, it is preferable to process the first sintered body so that the thickness of the first sintered body is within a range of 200 μm to 1500 μm.

[0037] The method for producing a ceramic sintered body includes contacting a first sintered body with a solid made of molybdenum metal or an alloy containing molybdenum as a main component and performing a second firing to obtain a second sintered body. The first sintered body is contacted with a solid made of molybdenum metal or an alloy containing molybdenum as a main component and subjected to a second firing, whereby impurities such as crystals having a composition different from that of the nitride phosphor contained inside the first sintered body are decomposed into gas, and the decomposed gas is adsorbed by the molybdenum metal or the alloy containing molybdenum as a main component contacted with the first sintered body, thereby obtaining a second sintered body with reduced impurities. By performing the second firing, impurities such as crystals having a composition different from that of the nitride phosphor contained inside the first sintered body are decomposed into gas and adsorbed by the solid made of molybdenum metal or the alloy containing molybdenum as a main component, and when all the decomposed gas is released to the outside, a second sintered body with a body color in which no blackening or dullness can be confirmed is obtained. By the secondary firing, a part of the gas obtained by decomposing impurities such as crystals having a composition different from that of the nitride phosphor contained inside the first sintered body may remain as blackening or dullness on a part of the surface of the second sintered body. By the secondary firing, a part of the gas obtained by decomposing impurities such as crystals having a composition different from that of the nitride phosphor contained inside the first sintered body may react with molybdenum metal or an alloy containing molybdenum as a main component and remain as blackening or dullness on a part of the surface of the second sintered body. In this specification, the second firing refers to the firing of the first sintered body obtained by firing a molded body in contact with molybdenum metal or an alloy containing molybdenum as a main component.

[0038] In obtaining the second sintered body, the temperature of the secondary firing is preferably in the range of 1650°C to 1800°C, more preferably in the range of 1660°C to 1780°C, even more preferably in the range of 1670°C to 1750°C, and even more preferably in the range of 1675°C to 1725°C. When the temperature of the secondary firing is in the range of 1650°C to 1800°C, impurities such as crystals having a composition different from the composition of the nitride phosphor generated inside the first sintered body can be decomposed and released as gas while suppressing decomposition of the crystal structure having the composition of the nitride phosphor contained in the first sintered body, and the released gas can be adsorbed by molybdenum metal or an alloy containing molybdenum as a main component in contact with the first sintered body. The temperature of the secondary firing is preferably lower than the temperature of the third firing described later.

[0039] The secondary firing is preferably performed in an atmosphere containing nitrogen gas. The atmosphere in which the secondary firing is performed may be the same as or different from the atmosphere in which the primary firing is performed. The nitrogen gas-containing atmosphere in the secondary firing refers to the same atmosphere as the nitrogen gas-containing atmosphere in the primary firing. By performing the secondary firing of the first sintered body in an atmosphere containing nitrogen gas, divalent Eu in the crystal having the composition of the nitride phosphor contained in the first sintered body is reduced. 2+ is oxidized to trivalent Eu 3+ The divalent Eu in the crystal having the composition of the nitride phosphor is suppressed. 2+ By increasing the proportion of the luminescence intensity, the second sintered body can be obtained while maintaining the luminescence intensity.

[0040] The secondary firing is preferably performed at a gauge pressure in the range of 0.2 MPa to 2.0 MPa. When the secondary firing is performed at a gauge pressure in the range of 0.2 MPa to 2.0 MPa, impurities such as crystals having a composition different from that of the nitride phosphor generated inside the first sintered body are easily decomposed and released. The secondary firing may be performed at a gauge pressure in the range of 0.3 MPa to 1.5 MPa, 0.4 MPa to 1.2 MPa, or 0.5 MPa to 1.0 MPa.

[0041] In obtaining the second sintered body, the time for the secondary firing is preferably 1 hour or more and 3 hours or less. When the time for the secondary firing is 1 hour or more and 3 hours or less, it is easy to decompose impurities such as crystals having a composition different from that of the nitride phosphor generated inside the first sintered body and release them as gas while suppressing decomposition of the crystal structure having the composition of the nitride phosphor contained in the first sintered body. The time for the secondary firing may be 1 hour or more and 2 hours or less.

[0042] In obtaining the second sintered body, it is preferable that the first sintered body is a plate-like body and the thickness of the first sintered body is within the range of 200 μm to 1500 μm. In obtaining the second sintered body, if the thickness of the first sintered body is within the range of 200 μm to 1500 μm, even if the inside of the first sintered body contains crystals of a composition different from that of the nitride phosphor, the crystals are decomposed by the secondary firing and are easily released as gas to the outside of the first sintered body or to the surface of the first sintered body close to the outside of the first sintered body. When the first sintered body is a plate-like body, the shape of the plate-like body may be rectangular or circular in plan view. Since crystals having a composition different from that of the nitride phosphor are easily formed inside the first sintered body, by processing the first sintered body so that the thickness is within the range of 200 μm to 1500 μm, the crystals having a composition different from that of the nitride phosphor formed inside the first sintered body are easily decomposed by the secondary firing, and the gas released to the outside can be more easily released, and the impurities contained in the obtained second sintered body can be further reduced.

[0043] In obtaining the second sintered body, it is preferable to bring a solid made of molybdenum metal or an alloy containing molybdenum as a main component into contact with the main surface of the first sintered body. By bringing the molybdenum metal or the solid containing molybdenum as a main component into contact with the main surface of the first sintered body, the crystal having a composition different from that of the nitride phosphor contained in the first sintered body in the second firing is easily adsorbed to the gas released by decomposition. The main surface of the first sintered body refers to the surface having the largest area among the surfaces constituting the sintered body. When the first sintered body is a plate-shaped body, it may have two opposing main surfaces.

[0044] In obtaining the second sintered body, the solid made of molybdenum metal or an alloy containing molybdenum as a main component may be a plate-shaped body, a granular body, or a powder. In obtaining the second sintered body, the solid made of molybdenum metal or an alloy containing molybdenum as a main component may be in the shape of a container in which the second sintered body can be placed. The solid made of molybdenum metal or an alloy containing molybdenum as a main component is preferably in the shape of a container or a plate-shaped body because it is easy to contact with the first sintered body and easy to handle. When the solid made of molybdenum metal or an alloy containing molybdenum as a main component is a container, for example, a crucible or boat made of molybdenum metal or an alloy containing molybdenum as a main component can be mentioned. When the solid made of molybdenum metal or an alloy containing molybdenum as a main component has the shape of a container, the main surface of the first sintered body may be placed in contact with the placement surface of the container. In obtaining the second sintered body, when the secondary firing is performed in a furnace, the container in which the first sintered body is placed may be closed with a lid body, or may be open without being closed with a lid body.

[0045] In obtaining the second sintered body, it is preferable that the first sintered body is a plate-shaped body and is sandwiched between two solids made of molybdenum metal or an alloy containing molybdenum as a main component, and the first sintered body is contacted between them. When the first sintered body is a plate-shaped body, it is preferable to sandwich the first sintered body between two molybdenum metals or an alloy containing molybdenum as a main component, so that both of the two opposing main surfaces of the first sintered body are in contact with solids made of molybdenum metal or an alloy containing molybdenum as a main component. When the first sintered body is a plate-shaped body and has two opposing main surfaces, the first sintered body is sandwiched between two molybdenum metals or an alloy containing molybdenum as a main component, so that the first sintered body is in contact with the two opposing main surfaces of the first sintered body. This makes it easier for the gas decomposed by the impurities contained in the first sintered body during the secondary firing to be adsorbed by the molybdenum metal or the alloy containing molybdenum as a main component, and the impurities contained in the second sintered body can be reduced. The two solid bodies made of molybdenum metal or an alloy containing molybdenum as a main component that are in contact with each other and sandwich the first sintered body may be two plate-shaped bodies, one of which may be a container such as a crucible in which the first sintered body can be placed, and the other may be a plate-shaped body.

[0046] In obtaining the second sintered body, the solid made of molybdenum metal or an alloy containing molybdenum as a main component that is to be brought into contact with the first sintered body preferably has an area equal to or greater than the area of ​​the part that is to be brought into contact with the first sintered body. The alloy containing molybdenum as a main component refers to an alloy having the highest molybdenum content among the components contained in the alloy. The content of molybdenum in the alloy containing molybdenum as a main component is preferably 50 mass% or more, more preferably 60 mass% or more, even more preferably 70 mass% or more, even more preferably 80 mass% or more, and particularly preferably 90 mass% or more, based on the total amount of the alloy. The alloy containing molybdenum as a main component may contain at least one element selected from the group consisting of titanium, zirconium, hafnium, niobium, tantalum, tungsten, rhenium, lanthanum, and yttrium.

[0047] In the present specification, the secondary firing does not include hot isostatic pressing (HIP) treatment. The secondary firing does not include hot isostatic pressing (HIP) treatment. Note that the hot isostatic pressing (HIP) treatment may refer to heat treatment performed at a high pressure, for example, of 10 MPa or more, preferably 50 MPa or more and 400 MPa or less. HIP may refer to the hot isostatic pressing (HIP) treatment specified in No. 2112 of JIS Z2500:2000.

[0048] The method for producing a ceramic sintered body includes placing the second sintered body in a container containing a metal with a higher melting point than molybdenum metal and tertiary firing to obtain a third sintered body. In the second sintered body, a part of the gas obtained by decomposing impurities such as crystals having a composition different from that of the nitride phosphor contained inside the first sintered body or a reaction product of the gas reacting with molybdenum metal may remain on the surface of the second sintered body by the secondary firing, resulting in blackening or dullness. Even if blackening or dullness exists on the surface, the second sintered body can be placed in a container containing a metal with a higher melting point than molybdenum metal and tertiary firing to remove the blackening or dullness, thereby obtaining a third sintered body with a desired body color. Even if blackening or dullness does not exist on the surface of the second sintered body, the second sintered body can be placed in a container containing a metal with a higher melting point than molybdenum metal and tertiary firing to obtain a third sintered body with a large relative density. Since the relative density of the third sintered body becomes higher, even if the presence of blackening or dullness on the surface of the second sintered body cannot be visually confirmed, it is believed that gases produced by decomposition of crystals having a composition different from that of the nitride phosphor remaining in the second sintered body, or products of the reaction between the decomposed gases and molybdenum metal, are decomposed by the tertiary firing and released to the outside as gases, etc., resulting in a third sintered body with a high relative density.

[0049] In obtaining the third sintered body, the temperature of the third firing is preferably in the range of 1650°C to 1850°C, more preferably in the range of 1660°C to 1840°C, even more preferably in the range of 1670°C to 1820°C, and even more preferably in the range of 1675°C to 1800°C. When the temperature of the third firing is in the range of 1650°C to 1850°C, the impurities remaining in the second sintered body can be released to the outside as gas while suppressing the decomposition of the crystal having the composition of the nitride phosphor contained in the second sintered body, and the third sintered body having a desired body color and a large relative density can be obtained. The impurities remaining in the second sintered body may refer to a part of the gas decomposed by the crystal having a composition different from the composition of the nitride phosphor, or a product of the reaction between the decomposed gas and molybdenum.

[0050] The temperature of the tertiary firing is preferably higher than that of the secondary firing. If the temperature of the tertiary firing is higher than that of the secondary firing, impurities remaining in the second sintered body are easily released as gas. The temperature difference between the secondary firing and the tertiary firing is preferably 10°C or more higher than the temperature of the secondary firing, preferably 20°C or more higher, more preferably 25°C or more higher, even more preferably 30°C or more higher, even more preferably 40°C or more higher, and particularly preferably 50°C or more higher, and the temperature of the secondary firing may be 150°C or less lower than the temperature of the tertiary firing, 125°C or less lower, or 100°C or less lower.

[0051] The tertiary firing is preferably performed in an atmosphere containing nitrogen gas. The atmosphere in which the tertiary firing is performed may be the same as or different from the atmosphere in which the primary or secondary firing is performed. The nitrogen gas-containing atmosphere in the tertiary firing refers to an atmosphere similar to the nitrogen gas-containing atmosphere in the primary or secondary firing. By subjecting the second sintered body to the tertiary firing in an atmosphere containing nitrogen gas, divalent Eu in the crystal having the composition of the nitride phosphor contained in the second sintered body is reduced. 2+ is oxidized to trivalent Eu 3+ The divalent Eu in the crystal having the composition of the nitride phosphor is suppressed. 2+It is possible to obtain a third sintered body having a high relative density while maintaining the luminescence intensity by increasing the proportion of the sintered body.

[0052] The tertiary firing is preferably performed at a gauge pressure in the range of 0.2 MPa to 2.0 MPa. When the tertiary firing is performed at a gauge pressure in the range of 0.2 MPa to 2.0 MPa, impurities remaining in the second sintered body are easily decomposed and released to the outside. The tertiary firing may be performed at a gauge pressure in the range of 0.3 MPa to 1.5 MPa, or in the range of 0.4 MPa to 1.2 MPa, or in the range of 0.5 MPa to 1.0 MPa. The pressure in the tertiary firing may be the same as or different from the pressure in the first or second firing.

[0053] In obtaining the third sintered body, the time for the tertiary firing is preferably 1 hour or more and 5 hours or less. When the time for the tertiary firing is 1 hour or more and 5 hours or less, the decomposition of the crystal having the composition of the nitride phosphor contained in the second sintered body can be suppressed, while the impurities remaining in the second sintered body can be decomposed and easily released to the outside. The time for the tertiary firing may be 1 hour or more and 4 hours or less, 1 hour or more and 3 hours or less, or 1 hour or more and 2 hours or less.

[0054] In obtaining the third sintered body, the metal having a higher melting point than molybdenum metal is preferably at least one selected from the group consisting of tungsten, tantalum, and rhenium. The container containing a metal having a higher melting point than molybdenum metal preferably contains a metal having a higher melting point than molybdenum metal as a main component. The container containing a metal having a higher melting point than molybdenum metal as a main component means that the content of the metal having a higher melting point than molybdenum metal in the container is the highest. The content of the metal having a higher melting point than molybdenum metal is preferably 50 mass% or more, more preferably 60 mass% or more, even more preferably 70 mass% or more, even more preferably 80 mass% or more, and particularly preferably 90 mass% or more, based on the total amount of the container. Examples of the container containing a metal having a higher melting point than molybdenum metal include a crucible and a boat. In obtaining the third sintered body, when the tertiary firing is performed in a furnace, the container in which the second sintered body is placed may be closed with a lid, or may be open without being closed with a lid.

[0055] In obtaining the third sintered body, it is preferable to tertiarily sinter the second sintered body by placing it in a container containing a metal having a melting point higher than that of molybdenum metal without contacting it with a solid made of molybdenum metal or an alloy containing molybdenum to obtain the third sintered body. If the second sintered body is brought into contact with a solid made of molybdenum metal or an alloy containing molybdenum and tertiary sintering is performed, the third sintered body may not have the desired body color due to a reaction between impurities remaining in the second sintered body and the molybdenum metal or the alloy containing molybdenum, and blackening or dullness may remain on the surface of the third sintered body.

[0056] The third sintered body preferably has a relative density of 95% or more, more preferably 96% or more, even more preferably 97% or more, even more preferably 98% or more, and particularly preferably 99% or more. When the third sintered body has a high relative density, light scattering due to impurities or voids is reduced, and fluorescence with a high luminous flux can be emitted when irradiated with light. When a third sintered body having a high relative density is obtained, even if the third sintered body is subjected to processing such as cutting after obtaining the third sintered body, no cracks or chips are generated, and when a ceramic sintered body made of the third sintered body is used in a light emitting device, the occurrence of color unevenness can be suppressed. The relative density of the third sintered body may be 100% or 99.9% or less.

[0057] The relative density of a sintered body is a value calculated from the apparent density of the sintered body relative to the true density of the sintered body. The relative density of a sintered body is calculated by the following formula (1). The sintered body shown in the following formulas (1) and (2) includes the third sintered body.

[0058]

number

[0059] The true density of the sintered body is the value obtained by multiplying the mass percentage (mass%) of the nitride phosphor by the true density of the nitride phosphor relative to 100 mass% of the sintered body. When the sintered body is formed from a molded body consisting of only the nitride phosphor, the true density of the sintered body is the same as the true density of the nitride phosphor. It becomes degrees.

[0060] The apparent density of a sintered body is the mass of the sintered body divided by the volume of the sintered body determined by Archimedes' method, and is calculated by the following formula (2). In the following formula (2), the volume of the sintered body refers to the volume determined by Archimedes' method.

[0061]

number

[0062] The third sintered body contains at least one alkaline earth metal element M selected from the group consisting of Ba, Sr, Ca, and Mg. 1 and at least one metal element M selected from the group consisting of Eu, Ce, Tb and Mn. 2 The composition contains Si and N, and the alkaline earth metal element M 1 and metal element M 2 The total molar ratio of the metal element M 2 The molar ratio of the nitride phosphor contained in the third sintered body is preferably a product of the variable y and 2, the variable y being 0.001 or more and less than 0.5, the molar ratio of Si being 5, and the molar ratio of N being 8, and more preferably, the third sintered body is composed only of a crystal having the composition of the nitride phosphor. The crystal having the composition of the nitride phosphor contained in the third sintered body preferably has a composition represented by the formula (I). The crystal having the composition of the nitride phosphor contained in the third sintered body more preferably has a composition represented by the formula (II).

[0063] The method for producing a ceramic sintered body may include processing the obtained third sintered body. Processing the third sintered body includes cutting the obtained third sintered body to a desired size, or grinding or polishing it. In addition, a known method can be used as a method for cutting, grinding or polishing, and examples of the method include a method using a surface grinder, blade dicing, laser dicing, wire saw, etc. Among these processes, grinding or polishing is preferable because the processed surface is flat with high accuracy. By processing the third sintered body, a ceramic sintered body of a desired thickness and size can be obtained. The thickness of the ceramic sintered body used as the wavelength conversion member is not particularly limited, but taking into consideration the mechanical strength and wavelength conversion efficiency, it is preferably in the range of 1 μm or more and 1 mm or less, more preferably in the range of 10 μm or more and 800 μm or less, even more preferably in the range of 50 μm or more and 500 μm or less, still more preferably in the range of 95 μm or more and 450 μm or less, or may be in the range of 99 μm or more and 400 μm or less, or may be in the range of 100 μm or more and 400 μm or less, or may be in the range of 120 μm or more and 300 μm or less, or may be in the range of 150 μm or more and 250 μm or less.

[0064] The obtained third sintered body can be a ceramic sintered body used as a wavelength conversion member. The ceramic sintered body used as the wavelength conversion member is preferably irradiated with light having an emission peak wavelength in the range of 380 nm to 570 nm, and converts the wavelength of the irradiated light to emit light having a color tone within an area A defined by the chromaticity coordinates (x, y) of the xy chromaticity coordinates of the CIE 1931 chromaticity diagram, where (x=0.549, y=0.425) is point 1A, (x=0.562, y=0.438) is point 2A, (x=0.589, y=0.411) is point 3A, and (x=0.576, y=0.407) is point 4A, the chromaticity coordinates being (x, y) of (x=0.549, y=0.425) is point 2A, (x=0.562, y=0.438) is point 2A, (x=0.589, y=0.411) is point 3A, and (x=0.576, y=0.407) is point 4A, the chromaticity coordinates being (x, y) of (x=0.549, y=0.425) is point 1A, the chromaticity coordinates being (x=0.562, y=0.438) is point 2A, the chromaticity coordinates being (x=0.589, y=0.411) is point 3A, and the chromaticity coordinates being (x=0.576, y=0.407) is point 4A, the chromaticity coordinates being (x, y) of (x, y) of (x, y) of (x, y) of (x, y) of (x, y) of (x, y) of (x,

[0065] 3 is a diagram showing region A in the xy chromaticity coordinates of the CIE 1931 chromaticity diagram. Light that emits a hue within region A in the chromaticity diagram exhibits an orange emission color.

[0066] The ceramic sintered body obtained by the above-mentioned manufacturing method is combined with a light emitting element such as an LED or an LD. The light emitting device converts the excitation light emitted from the light emitting element by the ceramic sintered body to emit light having a desired emission peak wavelength. The light emitting device emits mixed color light by the light from the light emitting element and the light whose wavelength is converted by the ceramic sintered body. The light emitting device may be used in combination with the ceramic sintered body containing the nitride phosphor and another ceramic sintered body containing a phosphor other than the nitride phosphor.

[0067] The light-emitting element preferably has an emission peak wavelength in the range of 365 nm to 650 nm, more preferably has an emission peak wavelength in the range of 380 nm to 570 nm, and even more preferably has an emission peak wavelength in the range of 400 nm to 550 nm. The light-emitting element is, for example, a nitride-based semiconductor (In X Al Y Ga 1-X-Y It is preferable to use a semiconductor light emitting element using a semiconductor light emitting element having a wavelength of 0≦X, 0≦Y, X+Y≦1. By using a semiconductor light emitting element as the excitation light source, it is possible to obtain a light emitting device that is highly efficient, has high linearity of output with respect to input, and is stable against mechanical shock.

[0068] 4A and 4B show a configuration example of a light emitting device using a ceramic sintered body as a wavelength conversion member. FIG. 4A is a schematic plan view of the light emitting device 100. FIG. 4B is a schematic cross-sectional view of the light emitting device 100 shown in FIG. 4A along the line IV-IV'. The light emitting device 100 includes a light emitting element 10 having an emission peak wavelength in the range of 365 nm to 650 nm, and a wavelength conversion member 51 that is excited by light from the light emitting element 10 and emits light. The light emitting element 10 is flip-chip mounted on the substrate 1 via a bump that is a conductive member 61. The wavelength conversion member 51 is disposed on the light emitting surface of the light emitting element 10 via an adhesive layer 80. The light emitting element 10 and the wavelength conversion member 51 have their sides covered by a covering member 90 that reflects light. The light emitting element 10 can receive power from the outside of the light emitting device 100 via the wiring and conductive member 61 formed on the substrate 1, and can cause the light emitting device 100 to emit light. The light emitting device 100 may include a semiconductor element 11 such as a protective element for protecting the light emitting element 10 from being destroyed by application of an excessive voltage. The semiconductor element 11 may be mounted on the substrate 1 via a conductive member 61. A covering member 90 is disposed so as to cover the semiconductor element 11, for example. Each member used in the light emitting device will be described below. For details, the disclosure of JP 2014-112635 A may be referred to.

[0069] The adhesive layer is preferably made of a material that can optically connect the light emitting element and the wavelength conversion member. The material constituting the adhesive layer is preferably at least one resin selected from the group consisting of epoxy resin, silicone resin, phenolic resin, and polyimide resin. The light emitting element and the wavelength conversion member may be directly bonded without the adhesive layer.

[0070] Examples of the semiconductor element provided in the light emitting device as required include a transistor for controlling the light emitting element and a protective element for suppressing the destruction or performance deterioration of the light emitting element due to the application of an excessive voltage. An example of the protective element is a Zener diode. When the light emitting device includes a covering member, it is preferable to use an insulating material as the material of the covering member. More specifically, examples of the insulating material include phenol resin, epoxy resin, bismaleimide triazine resin (BT resin), polyphthalamide (PPA) resin, and silicone resin. A colorant, a phosphor, and a filler may be added to the covering member as required. The light emitting device may use bumps as the conductive member. The bump material may be Au or its alloy, and other conductive members may be eutectic solder (Au-Sn), Pb-Sn, lead-free solder, and the like.

[0071] An example of a method for manufacturing a light emitting device will be described. For details, refer to the disclosures of, for example, JP 2014-112635 A or JP 2017-117912 A. The method for manufacturing a light emitting device preferably includes a step of arranging a light emitting element, a step of arranging a semiconductor element as necessary, a step of preparing a wavelength conversion member, a step of bonding the light emitting element and the wavelength conversion member, and a step of arranging a covering member.

[0072] For example, in the step of arranging the light-emitting element, the light-emitting element is arranged on the substrate. The light-emitting element and the semiconductor element are, for example, flip-chip mounted on the substrate. In addition, in the step of preparing the wavelength conversion member, a wavelength conversion member made of a ceramic sintered body obtained by the above-mentioned manufacturing method is prepared. Next, in the step of bonding the light-emitting element and the wavelength conversion member, the prepared wavelength conversion member is placed opposite the light-emitting surface of the light-emitting element, and the wavelength conversion member is bonded to the light-emitting element by an adhesive layer. Next, in the step of arranging the covering member, the side surfaces of the light-emitting element and the wavelength conversion member are covered with the covering member. This covering member is for reflecting the light emitted from the light-emitting element, and when the light-emitting device also includes a semiconductor element, it is preferable to arrange the semiconductor element so that it is embedded in the covering member. In this manner, the light-emitting device shown in FIG. 4A and FIG. 4B can be manufactured. EXAMPLES

[0073] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0074] Example 1 Preparation of nitride phosphors Alkaline earth metal element M contained in nitride phosphor 1 Ba and Sr are used as the metal element M 2 Eu was used as the starting material. Ba3N2, Sr3N2, EuN, and Si3N4 were used as the starting materials. Each compound was weighed in a glove box in an inert gas atmosphere so that the molar ratio of each element was Ba:Sr:Eu:Si=1.120:0.873:0.007:5, and each compound was mixed to obtain a raw material mixture. The obtained raw material mixture was filled into a crucible, and heat-treated at 1600°C for 5 hours in an atmosphere containing 99.9% by volume or more of nitrogen and the remainder being oxygen (0.1% by volume or less), with a gas pressure of 0.9 MPa in gauge pressure, to obtain a fired product. The particles of the fired product obtained were sintered together, so they were dispersed, and then sieved to remove coarse particles and fine particles, and the remaining particles were separated into 100% by volume (Ba 0.56 Sr 0.4365 EU 0.0035 A nitride phosphor having a composition of 2Si5N8 was obtained. The average particle size (Fisher sub-sieve sizer's number) of the obtained nitride phosphor was measured by the FSSS method using a Fisher Sub-Sieve Sizer Model 95 (manufactured by Fisher Scientific). The average particle size of the nitride phosphor measured by the FSSS method was 1.0 μm.

[0075] Preparing the molded body The obtained nitride phosphor was filled into a mold, and pressed at a pressure of 2 MPa to form a cylindrical molded body with a diameter of 28.5 mm and a thickness of 10 mm. Further, CIP molding was performed at a pressure of 352.8 MPa to form a cylindrical molded body with a diameter of 25 mm and a thickness of 9 mm. The molded body was composed only of the above-mentioned nitride phosphor, and was 100% by mass of nitride phosphor.

[0076] Obtaining the first sintering The obtained compact was placed in a sintering furnace (manufactured by Fuji Electric Industrial Co., Ltd.) and held at 1675°C and 0.9 MPa for 1 hour in an atmosphere containing 99.9% by volume or more of nitrogen and the remainder being oxygen (0.1% by volume or less) to perform primary sintering, thereby obtaining a first sintered body. Furthermore, the first sintered body was sliced ​​to a thickness of 720 μm with a wire saw, and the first sintered body was processed.

[0077] Obtaining the second sintering A crucible made of molybdenum metal and two plate-shaped bodies made of molybdenum metal (with a molybdenum purity of 99.9% by mass) measuring 30 mm in length, 30 mm in width, and 0.2 mm in thickness were prepared. The main surfaces of the plate-shaped bodies made of molybdenum metal were brought into contact with the two circular main surfaces of the obtained first sintered body with a diameter of 25 mm, respectively, and the first sintered body sandwiched between the two plate-shaped bodies made of molybdenum metal was placed in the crucible. The first sintered body sandwiched between the two plate-shaped bodies made of molybdenum metal was placed in a firing furnace (manufactured by Fuji Electric Industrial Co., Ltd.) together with the crucible, and secondary firing was performed by holding at 1675°C and 0.9 MPa for 2 hours in an atmosphere containing 99.9% by volume or more of nitrogen and the remainder being oxygen (0.1% by volume or less), to obtain a second sintered body.

[0078] Obtaining the third sintering A crucible (tungsten content 99.9 mass%) containing tungsten metal having a higher melting point than molybdenum metal was prepared. The second sintered body obtained was removed from the plate-like body made of molybdenum metal and placed in a crucible containing tungsten metal without contacting the plate-like body made of molybdenum metal, and the crucible was placed in a firing furnace (manufactured by Fuji Electric Industrial Co., Ltd.) and held at 1750°C and 0.9 MPa for 1 hour in an atmosphere containing 99.9 volume% or more of nitrogen and the remainder being oxygen (0.1 volume% or less), to perform tertiary firing, thereby obtaining a third sintered body. Both sides of the main surface of the obtained third sintered body were ground using a surface grinder so as to have the thickness shown in Table 1, and the third sintered body was processed to obtain a ceramic sintered body according to Example 1. The thicknesses of the ceramic sintered bodies according to the examples and comparative examples are shown in Table 1.

[0079] Example 2 A ceramic sintered body according to Example 2 was obtained in the same manner as in Example 1, except that the secondary firing was performed at the temperature shown in Table 1 in obtaining the second sintered body.

[0080] Examples 3 and 4 In preparing the nitride phosphor, (Ba 0.56 Sr 0.4375 EU 0.0025 The ceramic sintered bodies of each Example were obtained in the same manner as in Example 1, except that a nitride phosphor having a composition of N2Si5N8 was obtained and that in obtaining the second sintered body, secondary firing was performed at each temperature shown in Table 1.

[0081] Examples 5 to 7 In preparing the nitride phosphor, (Ba 0.56 Sr 0.4385 EU 0.0015 The ceramic sintered bodies of each Example were obtained in the same manner as in Example 1, except that a nitride phosphor having a composition of N2Si5N8 was obtained and that in obtaining the second sintered body, secondary firing was performed at each temperature shown in Table 1.

[0082] Examples 8 and 9 In obtaining the third sintered body, the ceramic sintered bodies according to each Example were obtained in the same manner as in Example 1, except that the tertiary firing was performed at the temperature shown in Table 1.

[0083] Comparative Example 1 A ceramic sintered body according to Comparative Example 1 was obtained in the same manner as in Example 1, except that in obtaining the second sintered body, the first sintered body was placed in a crucible containing tungsten metal without being brought into contact with a plate-shaped body made of molybdenum metal, and subjected to secondary firing.

[0084] Comparative Examples 2 and 3 In obtaining the second sintered body, the ceramic sintered bodies according to each comparative example were obtained in the same manner as in Comparative Example 1, except that the secondary firing was performed at each temperature shown in Table 1.

[0085] Comparative Example 4 Except for not carrying out the tertiary firing, a ceramic sintered body according to Comparative Example 4 was obtained in the same manner as in Example 1. In Table 1, the symbol "-" indicates that the tertiary firing was not carried out.

[0086] Comparative Example 5 A ceramic sintered body according to Comparative Example 5 was obtained in the same manner as in Example 2, except that the tertiary firing was not performed.

[0087] The following measurements were carried out on each of the ceramic sintered bodies of the Examples and Comparative Examples. The results are shown in Table 1.

[0088] Relative Density (%) The relative density of each of the ceramic sintered bodies in the Examples and Comparative Examples was calculated by the above-mentioned formulas (1) and (2). The true density of the ceramic sintered body is the true density of the nitride phosphor forming each of the molded bodies in the Examples and Comparative Examples, and the true density of the nitride phosphor is 4.33 g / cm 3 It is.

[0089] Chromaticity coordinates (x, y) Each ceramic sintered body of the examples and comparative examples was mounted on a light-emitting element (LED) with an emission peak wavelength of 455 nm to prepare a sample light-emitting device. In each sample light-emitting device, a current of 1 A was passed through the light-emitting element to irradiate each ceramic sintered body with excitation light, and the chromaticity coordinates (x, y) of the CIE1931 color system of the fluorescence emitted from each ceramic sintered body was measured using a multichannel spectrometer (Hamamatsu Photonics K.K., product name: PMA-12).

[0090] Relative luminous flux (%) In each light-emitting device sample using each ceramic sintered body of the examples and comparative examples, a current of 1A was passed through the light-emitting element to irradiate each ceramic sintered body with excitation light, and the fluorescent luminous flux (lm) emitted from each ceramic sintered body was measured using a total luminous flux measuring device. The luminous flux of Comparative Example 3, which had the lowest secondary firing temperature, was set to 100%, and the fluorescent luminous flux emitted from each ceramic sintered body was calculated as a relative luminous flux (%).

[0091] [Table 1]

[0092] The ceramic sintered bodies according to Examples 1 to 9 have a high relative density of 95% or more and a high relative luminous flux compared to the ceramic sintered bodies according to Comparative Examples 1 to 5. The ceramic sintered bodies according to Examples 1 to 9 emitted orange fluorescent light when irradiated with light from the light emitting element. From this result, the ceramic sintered bodies according to Examples 1 to 9 were obtained by subjecting the main surface of the first sintered body to contact with two molybdenum metals and subjecting it to secondary firing, thereby decomposing the impurities contained in the first sintered body and releasing them as gas, and then placing it in a crucible containing tungsten and subjecting it to tertiary firing at a temperature higher than that of the secondary firing, thereby obtaining a ceramic sintered body made of a third sintered body having a high relative density, a desired body color, and emitting fluorescence of a desired color.

[0093] The ceramic sintered bodies according to Examples 1 to 4, 8 and 9 emitted fluorescence with a luminescent color within region A in the xy chromaticity coordinates of the CIE1931 chromaticity diagram.

[0094] The ceramic sintered bodies according to Examples 1 to 7 and 9 had a relative density of 97% or more, a higher relative density, no blackening or dullness on the surface, and a desired body color. The ceramic sintered body according to Example 8 had a small temperature difference of 25°C between the second firing temperature and the third firing temperature, and therefore the amount of decomposed impurities escaping as gas in the third firing was small, resulting in a relative density of 95% or more. The ceramic sintered body according to Example 8 had a desired body color and a high relative luminous flux.

[0095] The ceramic sintered bodies according to Examples 5 to 7 had different compositions of nitride phosphors from those of Examples 1 to 4, 8 and 9, and emitted fluorescence having a desired color tone, although the emission color was not within the region A.

[0096] FIG. 5A is an external photograph showing the main surface of the second sintered body after the second firing in Example 3, and FIG. 5B is an external photograph showing the main surface of the third sintered body after the third firing in Example 3. As shown in FIG. 5A, in Example 3, the main surface of the second sintered body after the second firing was darkened or dull, with part of the gas obtained by decomposing impurities such as crystals having a composition different from the composition of the nitride phosphor contained inside the first sintered body or a reaction product obtained by reacting the gas with molybdenum metal remaining on the surface of the second sintered body. As shown in FIG. 5B, in Example 3, the main surface of the third sintered body after the third firing is such that the second sintered body is placed in a container containing a metal having a melting point higher than that of molybdenum metal and the darkening or dullness remaining on the surface of the second sintered body is decomposed and released into the atmosphere as gas, and a third sintered body having a desired body color without darkening or dullness of the body color is obtained.

[0097] In the ceramic sintered bodies according to Comparative Examples 1 to 3, the first sintered body is placed in a crucible containing tungsten and subjected to the secondary firing without contacting the first sintered body with a solid made of molybdenum metal or an alloy containing molybdenum as a main component, and therefore the amount of gas released as a result of decomposition of impurities contained in the first sintered body is small, and the relative density of the obtained ceramic sintered bodies is lower than that of the ceramic sintered bodies according to Examples 1 to 9. The ceramic sintered bodies according to Comparative Examples 1 to 3 have a lower relative density than that of Examples 1 to 9, and the relative luminous flux is also lower than that of the ceramic sintered bodies according to Examples 1 to 9.

[0098] In the ceramic sintered bodies of Comparative Examples 4 and 5, the second firing is performed by contacting the first sintered body with a solid made of molybdenum metal or an alloy containing molybdenum as the main component. However, since the third firing is not performed, the blackening and dullness generated by the gas generated by the decomposition of impurities contained in the first sintered body during the second firing is not removed, and at least a part of the body color of the ceramic sintered body turns black, and the relative luminous flux is very low at 20.7% or 0%.

[0099] FIG. 6A is an external photograph showing the main surface of the second sintered body after the second firing in Comparative Example 4, and FIG. 6B is an external photograph showing the main surface of the second sintered body after grinding without the third firing in Comparative Example 4. As shown in FIG. 6A, in Comparative Example 4, the main surface of the second sintered body after the second firing was dull because a part of the gas obtained by decomposing impurities such as crystals having a composition different from the composition of the nitride phosphor contained inside the first sintered body or a reaction product obtained by reacting the gas with molybdenum metal remained on the surface and inside of the second sintered body. As shown in FIG. 6B, since the third firing was not performed in Comparative Example 4, even if the second sintered body was ground, dullness remained on the surface and inside of the second sintered body, and the ceramic sintered body became black and the relative luminous flux was reduced.

[0100] An embodiment according to the present disclosure includes the following method for producing a ceramic sintered body. [Section 1] At least one alkaline earth metal element M selected from the group consisting of Ba, Sr, Ca and Mg 1 and at least one metal element M selected from the group consisting of Eu, Ce, Tb and Mn. 2 The composition contains Si and N, and the alkaline earth metal element M 1 and metal element M 2 The total molar ratio of the metal element M 2 a molar ratio of Si is 5 and a molar ratio of N is 8; and A first sintering process is performed on the molded body to obtain a first sintered body. contacting the first sintered body with a solid made of molybdenum metal or an alloy containing molybdenum as a main component and subjecting it to secondary firing to obtain a second sintered body; and placing the second sintered body in a container containing a metal having a melting point higher than that of molybdenum metal and subjecting it to a tertiary firing to obtain a third sintered body. [Section 2] In obtaining the secondary sintered body, the temperature of the secondary firing is within the range of 1650° C. or more and 1800° C. or less; In obtaining the tertiary sintered body, the temperature of the tertiary firing is in the range of 1650° C. or more and 1850° C. or less, and is higher than the temperature of the secondary firing; Item 2. The method for producing a ceramic sintered body according to item 1, wherein the second firing and the third firing are carried out in a nitrogen-containing atmosphere at a gauge pressure in the range of 0.2 MPa to 2.0 MPa. [Section 3] Item 3. The method for producing a ceramic sintered body according to item 1 or 2, wherein in obtaining the second sintered body, the first sintered body is a plate-like body, and the thickness of the first sintered body is in the range of 200 μm or more and 1500 μm or less. [Section 4] Item 4. The method for producing a ceramic sintered body according to item 3, wherein a solid made of molybdenum metal or an alloy containing molybdenum as a main component is brought into contact with a main surface of the first sintered body in obtaining the second sintered body. [Section 5] Item 5. The method for producing a ceramic sintered body according to any one of items 1 to 4, wherein in obtaining the second sintered body, the solid made of molybdenum metal or an alloy containing molybdenum as a main component is a plate-shaped body. [Section 6] Item 6. The method for producing a ceramic sintered body according to any one of items 1 to 5, wherein in obtaining the second sintered body, the first sintered body is a plate-shaped body, and the first sintered body is sandwiched and contacted between two solids made of the molybdenum metal or an alloy containing molybdenum as a main component. [Section 7] 7. The method for producing a ceramic sintered body according to any one of items 1 to 6, wherein the time for the secondary firing is 1 hour or more and 3 hours or less in obtaining the second sintered body. [Section 8] 8. The method for producing a ceramic sintered body according to any one of items 1 to 7, wherein the time for the tertiary firing is 1 hour or more and 5 hours or less in obtaining the third sintered body. [Section 9] 9. The method for producing a ceramic sintered body according to any one of items 1 to 8, wherein in obtaining the third sintered body, the third sintered body has a relative density of 97% or more. [Section 10] Item 10. The method for producing a ceramic sintered body according to any one of items 1 to 9, wherein the metal having a melting point higher than that of the molybdenum metal in obtaining the third sintered body is at least one selected from the group consisting of tungsten, tantalum and rhenium. [Section 11] Item 11. The method for producing a ceramic sintered body according to any one of items 1 to 10, wherein the nitride phosphor has a composition represented by the following formula (1): (M 1 1-y M 2 y )2Si5N8(I) (In formula (I), M 1 is at least one alkaline earth metal element selected from the group consisting of Ba, Sr, Ca and Mg, and M 2 is at least one metal element selected from the group consisting of Eu, Ce, Tb and Mn, and y is a number satisfying 0.001≦y<0.5. [Industrial Applicability]

[0101] The ceramic sintered body obtained by the manufacturing method of the present disclosure can be used as a wavelength conversion member capable of converting the wavelength of light emitted from an LED or LD in light emitting devices used as light sources for in-vehicle use, general lighting, backlighting of liquid crystal display devices, illumination, projectors, etc. In addition, the ceramic sintered body obtained by the manufacturing method of the present disclosure emits light when irradiated with excitation light, and can be used as a material for solid scintillators. [Explanation of symbols]

[0102] 1: substrate, 10: light emitting element, 11: semiconductor element, 51: wavelength conversion member, 61: conductive member, 80: adhesive layer, 90: covering member, 100: light emitting device.

Claims

1. At least one alkaline earth metal element M selected from the group consisting of Ba, Sr, Ca and Mg １ and at least one metal element M selected from the group consisting of Eu, Ce, Tb and Mn. ２ The composition contains Si and N, and the alkaline earth metal element M １ and metal element M ２ The total molar ratio of the metal element M ２ a molar ratio of Si is 5 and a molar ratio of N is 8; and A first sintering process is performed on the molded body to obtain a first sintered body. contacting the first sintered body with a solid made of molybdenum metal or an alloy containing molybdenum as a main component and subjecting it to secondary firing to obtain a second sintered body; and placing the second sintered body in a container containing a metal having a melting point higher than that of molybdenum metal and subjecting it to a third firing to obtain a third sintered body.

2. In obtaining the secondary sintered body, the temperature of the secondary firing is within a range of 1650° C. or more and 1800° C. or less; In obtaining the tertiary sintered body, the temperature of the tertiary firing is in the range of 1650° C. or more and 1850° C. or less, and is higher than the temperature of the secondary firing; 2. The method for producing a ceramic sintered body according to claim 1, wherein the second firing and the third firing are carried out in an atmosphere containing nitrogen at a gauge pressure in the range of 0.2 MPa to 2.0 MPa.

3. 3. The method for producing a ceramic sintered body according to claim 1 or 2, wherein in obtaining the second sintered body, the first sintered body is a plate-like body, and the thickness of the first sintered body is in the range of 200 μm or more and 1500 μm or less.

4. 4. The method for producing a ceramic sintered body according to claim 3, wherein in obtaining the second sintered body, a main surface of the first sintered body is brought into contact with a solid made of molybdenum metal or an alloy containing molybdenum as a main component.

5. 3. The method for producing a ceramic sintered body according to claim 1, wherein in obtaining the second sintered body, the solid body made of molybdenum metal or an alloy containing molybdenum as a main component is a plate-shaped body.

6. 3. The method for producing a ceramic sintered body according to claim 1 or 2, wherein in obtaining the second sintered body, the first sintered body is a plate-shaped body, and the first sintered body is sandwiched and contacted between two solids made of the molybdenum metal or an alloy containing molybdenum as a main component.

7. The method for producing a ceramic sintered body according to claim 1 or 2, wherein in obtaining the second sintered body, the second firing is performed for a period of time ranging from 1 hour to 3 hours.

8. The method for producing a ceramic sintered body according to claim 1 or 2, wherein in obtaining the third sintered body, the tertiary firing is performed for a period of time ranging from 1 hour to 5 hours.

9. 3. The method for producing a ceramic sintered body according to claim 1, wherein in obtaining the third sintered body, the third sintered body has a relative density of 97% or more.

10. The method for producing a ceramic sintered body according to claim 1 or 2, wherein in obtaining the third sintered body, the metal having a melting point higher than that of the molybdenum metal is at least one selected from the group consisting of tungsten, tantalum and rhenium.

11. The method for producing a ceramic sintered body according to claim 1 or 2, wherein the nitride phosphor has a composition represented by the following formula (1): (M １ １－ｙ M ２ ｙ ) ２ Si ５ N ８ (I) (In formula (I), M １ is at least one alkaline earth metal element selected from the group consisting of Ba, Sr, Ca and Mg, M ２ is at least one metal element selected from the group consisting of Eu, Ce, Tb and Mn, and y is a number that satisfies 0.001≦y<0.5.

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