Phosphor ceramic and method for producing light emitting device

Abstract

To provide a phosphor ceramic which emits light when excited by excitation light, and a method for producing a light-emitting device.SOLUTION: A method for producing a phosphor ceramic includes preparing a precursor that is either a molded body containing aluminum nitride or a sintered body containing aluminum nitride, and bringing the precursor into contact with a gas containing europium to obtain an aluminum nitride phosphor ceramic having a europium content in a range of more than 0.03% by mass and 1.5% by mass or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a phosphor ceramic and a light emitting device. [Background technology]

[0002] Light-emitting devices that use light-emitting diodes (LEDs) or laser diodes (LDs) as light-emitting elements are used as light sources to replace incandescent bulbs and fluorescent lamps. For example, a light-emitting device that uses an LED and a wavelength conversion member containing a powdered inorganic phosphor and a resin emits a mixed color light of light emitted from the LED and light emitted from the inorganic phosphor excited by the light emitted from the LED. Such light-emitting devices that use an LED and an inorganic phosphor are used not only in the lighting field such as interior lighting and automotive lighting, but also in a wide range of fields such as backlight sources for liquid crystal displays and illumination. Furthermore, light-emitting devices that combine an LD and an inorganic phosphor are used in fields such as light sources for projectors.

[0003] Patent Document 1 discloses a method for producing a sialon phosphor in which, without applying mechanical force to the powder or molding it in advance using a mold or the like, the particle size of the powder aggregates of the mixture is made uniform, and the aggregates are filled as is into a container or the like at a filling rate of 40% or less in bulk density, and then sintered. Patent Document 2 discloses a method for producing a luminescent sintered body, in which aluminum nitride powder, a sintering aid, and a compound containing an element that serves as a luminescent center are mixed and fired. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2006 / 016711 [Patent Document 2] Japanese Patent Application Publication No. 167260 / 1983 Summary of the Invention [Problem to be solved by the invention]

[0005] However, it is difficult to obtain a dense sintered body by the manufacturing methods disclosed in Patent Documents 1 and 2, and there is a demand for an improvement in the thermal conductivity of the sintered body. Therefore, an object of the present invention is to provide a method for manufacturing a phosphor ceramic that has high thermal conductivity and emits light when excited by an excitation light source, and a light emitting device. [Means for solving the problem]

[0006] The present disclosure encompasses the following aspects. A first aspect of the present disclosure is a method for producing a phosphor ceramic, comprising: preparing a precursor which is either a molded body containing aluminum nitride or a sintered body containing aluminum nitride; and contacting the precursor with a gas containing europium to obtain an aluminum nitride phosphor ceramic having a europium content in the range of more than 0.03 mass % to 1.5 mass % or less.

[0007] A second aspect of the present disclosure is a method for manufacturing a light emitting device, including: preparing the phosphor ceramic manufactured by the manufacturing method; preparing an excitation light source; and arranging the phosphor ceramic at a position where it is irradiated with light emitted from the excitation light source. [Effects of the Invention]

[0008] According to the above-described aspects, it is possible to provide a phosphor ceramic having high thermal conductivity and emitting light when excited by excitation light, and a method for manufacturing a light emitting device. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a flowchart showing an example of a method for producing phosphor ceramics. [Figure 2] FIG. 2 is a flowchart showing a method for producing a phosphor ceramic, including an example of a method for producing a precursor. [Figure 3]FIG. 3 is a flowchart showing a method for producing a phosphor ceramic, including an example of a method for producing a precursor. [Figure 4] FIG. 4 is a schematic cross-sectional view showing an example of an embodiment of a light emitting device using an LED element. [Figure 5] FIG. 5 is a schematic cross-sectional view showing an example of an embodiment of a light emitting device using an LD element. [Figure 6] FIG. 6 is a diagram showing the emission spectra of the phosphor ceramics according to Examples 1, 3, and 5 and the ceramic sintered body according to Reference Example 1 when excited with a light source having an emission peak wavelength of 365 nm. [Figure 7] FIG. 7 is a diagram showing the emission spectra of the aluminum nitride phosphor ceramics according to Examples 1, 3 and 5 when excited with a light source having an emission peak wavelength of 400 nm. [Figure 8] FIG. 8 is a diagram showing excitation spectra of the aluminum nitride phosphor ceramics according to Examples 1, 3 and 5. As shown in FIG. [Figure 9] FIG. 9 is a diagram showing XRD spectra of the aluminum nitride phosphor ceramic according to Example 5, the aluminum nitride ceramic according to Comparative Example 1, and AlN, Eu2O3, and Y2O3 registered in the data sheets. [Figure 10] FIG. 10 is an SEM photograph of a backscattered electron image of a cross section of the phosphor ceramic according to Example 5, showing the analyzed portion using SEM-EDX. [Figure 11] FIG. 11 is an SEM photograph of a backscattered electron image of a cross section of the phosphor ceramic according to Example 5, showing the analyzed portion using SEM-EDX. [Figure 12] FIG. 12 is an SEM photograph of a backscattered electron image of a cross section of the phosphor ceramic according to Example 5, showing the analyzed portion using SEM-EDX. [Figure 13] FIG. 13 is an SEM photograph of a backscattered electron image of a cross section of the phosphor ceramic according to Example 5, showing the analyzed portion using the EPMA. [Figure 14]FIG. 14 is an SEM photograph of a backscattered electron image of a cross section of the phosphor ceramic according to Example 5, showing the analyzed portion using the EPMA. [Figure 15] FIG. 15 is an SEM photograph of a backscattered electron image of a cross section of the phosphor ceramic according to Example 5, showing the analyzed portion using the EPMA. DETAILED DESCRIPTION OF THE INVENTION

[0010] The phosphor ceramics, methods for manufacturing the phosphor ceramics, and methods for manufacturing a light-emitting device according to the present disclosure are described below based on embodiments. However, the following embodiments are merely examples for embodying the technical concept of the present invention, and the present invention is not limited to the phosphor ceramics, light-emitting devices, methods for manufacturing the phosphor ceramics, and methods for manufacturing a light-emitting device. In this specification, green light refers to light with a peak emission wavelength of 490 nm or more and 550 nm or less. Furthermore, in this specification, ceramics refers to an aggregate of inorganic non-metallic materials in which multiple powder particles are bonded by sintering. Therefore, ceramics do not include materials that remain in the form of raw powder, such as aluminum nitride powder. In this specification, ceramics are primarily aluminum nitride, and ceramics also include oxides containing aluminum and other elements. In this specification, "primarily aluminum nitride" means that the aluminum nitride content in the ceramic is 90 mass% or more.

[0011] Manufacturing method for phosphor ceramics A method for producing a phosphor ceramic includes preparing a precursor which is either a green body containing aluminum nitride or a sintered body containing aluminum nitride, and contacting the precursor with a gas containing europium to obtain an aluminum nitride phosphor ceramic (hereinafter, also referred to as "AlN phosphor ceramic") having a europium content in the range of more than 0.03 mass% to 1.5 mass% or less. Figure 1 is a flowchart showing an example of a method for producing a phosphor ceramic. The method for producing a phosphor ceramic includes a precursor preparation step S101 and a step S102 of contacting the precursor with a gas containing europium (Eu) to obtain a phosphor ceramic.

[0012] In the method for producing a phosphor ceramic according to this embodiment, by contacting a precursor with a gas containing europium, it is possible to obtain a phosphor ceramic that has high thermal conductivity and emits light when excited by an excitation light source.

[0013] Precursor preparation process The precursor is a molded body containing aluminum nitride or a sintered body containing aluminum nitride. The precursor may be prepared by producing a molded body or a sintered body by the precursor production method described below, or may be prepared using a commercially available aluminum nitride sintered body. Aluminum nitride is the main component of the precursor. For example, it is preferably contained in an amount of 90 mass% or more of the entire precursor.

[0014] In order to prepare a precursor, a method for manufacturing the precursor will be described. The precursor is either a molded body containing aluminum nitride or a sintered body containing aluminum nitride. FIG. 2 is a flowchart showing a method for manufacturing a phosphor, including an example of a method for manufacturing a precursor when the precursor is a molded body containing aluminum nitride. FIG. 3 is a flowchart showing a method for manufacturing a phosphor ceramic, including an example of a method for manufacturing a precursor when the precursor is a sintered body containing aluminum nitride.

[0015] 2 and 3, an example of a method for producing a precursor when the precursor is a molded body or a sintered body will be described. When the precursor is a molded body, the method for producing a molded body includes a raw material mixture preparation step S101a and a molding step S101d. If necessary, the method may include any or all of a kneaded product preparation step S101b, a kneaded product granulation step S101c, and a thermal debinding step S101e. Furthermore, when the precursor is a sintered body, the method further includes a first firing step S101f.

[0016] Raw material mixture preparation process The raw material mixture contains aluminum nitride, and may contain a sintering aid containing a rare earth element other than europium, as required.

[0017] Aluminum nitride The aluminum nitride may be aluminum nitride particles. These aluminum nitride particles can be produced by known production methods. For example, aluminum nitride may be obtained by a combustion synthesis method in which metal aluminum powder is subjected to combustion synthesis in a nitrogen atmosphere or a direct nitridation method, or by a reduction nitridation method in which aluminum oxide powder is heated in nitrogen to reduce it. Alternatively, aluminum nitride may be obtained by the reaction of organoaluminum with ammonia.

[0018] In this specification, the median particle size Da of aluminum nitride particles refers to the particle size corresponding to 50% of the cumulative particle size distribution on a volume basis measured by the Coulter Counter method. The Coulter Counter method is a method based on the Coulter Principle to measure particle size without distinguishing between primary and secondary particles by utilizing the electrical resistance when particles dispersed in an electrolyte aqueous solution pass through a fine aperture. The particle size distribution can be measured using a particle size analyzer (e.g., a CMS, manufactured by Beckman Coulter, Inc.).

[0019] The aluminum nitride particles preferably have a median particle size Da in the range of 0.1 μm to 5 μm, more preferably in the range of 0.3 μm to 3 μm, and even more preferably in the range of 0.5 μm to 1.5 μm, which allows for the production of a dense sintered body and a phosphor ceramic with high thermal conductivity.

[0020] The oxygen content of the aluminum nitride particle powder is preferably 2% by mass or less, more preferably 1.5% by mass or less, based on the total amount of the aluminum nitride particle powder. If the oxygen content in the aluminum nitride particle powder is 2% by mass or less, it is possible to reduce Al point defects in the lattice of the aluminum nitride crystals that constitute the base material of the phosphor ceramic, and to reduce the amount of grain boundary phase made of oxide, making it possible to produce a phosphor ceramic with high thermal conductivity. The oxygen content in the aluminum nitride particle powder can be measured using an oxygen / nitrogen analyzer (e.g., EMGA-820, manufactured by Horiba, Ltd.).

[0021] It is preferable that the aluminum nitride particle powder, which is the raw material, does not contain any metal elements other than aluminum. In particular, if the aluminum nitride particle powder contains iron, the resulting phosphor ceramic may be colored black, so it is preferable that the aluminum nitride particle powder does not contain iron. The content of metal elements other than aluminum in the aluminum nitride particle powder is preferably 1% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.1% by mass or less, and particularly preferably 0.01% by mass or less, based on the total amount of the aluminum nitride particle powder. This can reduce coloration of the resulting phosphor ceramic. It can also reduce a decrease in thermal conductivity. The content of metal elements other than aluminum in the aluminum nitride particle powder can be measured using an inductively coupled plasma atomic emission spectroscopy (ICP-AES) device.

[0022] The aluminum nitride particles preferably have a reflectance of 50% or more, more preferably 70% or more, within the wavelength range of 400 nm to 700 nm. If the reflectance of the aluminum nitride particles is 50% or more within the wavelength range of 400 nm to 700 nm, the reflectance of the resulting phosphor ceramic also increases, and the emission intensity of green light when excited by an excitation light source can be increased.

[0023] The content of aluminum nitride particles in the raw material mixture is preferably in the range of 90% to 99.8% by mass, based on 100% by mass of the raw material mixture. By contacting a precursor based on aluminum nitride with a gas containing europium, a phosphor ceramic containing more than 0.03% to 1.5% by mass of europium, having high thermal conductivity, and emitting light when excited by excitation light can be obtained. The content of aluminum nitride particles in the raw material mixture is more preferably in the range of 93% to 99.7% by mass, even more preferably in the range of 95% to 99.6% by mass, and particularly preferably in the range of 95% to 99.5% by mass.

[0024] Sintering aids containing rare earth metals other than europium The raw material mixture may contain a sintering aid. If the raw material mixture contains a sintering aid, the aluminum nitride crystals are tightly bonded together, making it possible to obtain a phosphor ceramic with high thermal conductivity. Examples of sintering aids include compounds containing alkaline earth metal elements and compounds containing rare earth elements other than europium. The sintering aid is preferably a sintering aid containing a rare earth element other than europium. Examples of sintering aids containing a rare earth element other than europium include oxides containing rare earth elements other than europium and fluorides containing rare earth elements other than europium. Specific examples of sintering aids containing rare earth elements other than europium include yttrium oxide (YO), lanthanum oxide (LaO), cerium oxide (CeO), ytterbium oxide (YbO), praseodymium oxide (PrO), neodymium oxide (NdO), samarium oxide (SmO), gadolinium oxide (GdO), dysprosium oxide (DyO), and erbium oxide (ErO). Among sintering aids containing rare earth elements other than europium, yttrium oxide is preferred. This facilitates the formation of a liquid phase with the impurity oxygen contained in the aluminum nitride particles, facilitating the densification of the sintered body.

[0025] The content of the sintering aid in the raw material mixture is preferably 10% by mass or less, or may be 7% by mass or less, 5% by mass or less, 0.05% by mass or more, or 0.1% by mass or more, relative to 100% by mass of the raw material mixture. Furthermore, the raw material mixture may not contain a sintering aid, and the content of the sintering aid in the raw material mixture may be 0% by mass, relative to 100% by mass of the raw material mixture.

[0026] The sintering aid is preferably in powder form. The median particle size De of the sintering aid containing a rare earth element other than europium is preferably in the range of 0.1 μm to 5 μm, more preferably 0.2 μm to 4 μm, and even more preferably 0.3 μm to 3 μm. The median particle size De of the sintering aid relative to the median particle size Da of the aluminum nitride particles is preferably in the range of 0.1 to 20 in particle size ratio De / Da. The median particle size De of the sintering aid refers to the particle size corresponding to 50% of the cumulative particle size distribution on a volume basis measured by the Coulter Counter method. When the particle size ratio De / Da of the median particle size De of the sintering aid relative to the median particle size Da of the aluminum nitride particles is in the range of 0.1 to 20, the particles constituting the raw material mixture are less likely to agglomerate and are more easily dispersed, making it easier to obtain a high-density sintered body. The particle size ratio De / Da of the median particle size De of the sintering aid to the median particle size Da of the aluminum nitride particles is more preferably in the range of 0.2 to 18, even more preferably in the range of 0.3 to 15, and particularly preferably in the range of 0.5 to 10. This makes it less likely that the state will be uneven after mixing with the aluminum nitride particles.

[0027] A raw material mixture containing aluminum nitride and, optionally, a sintering aid containing a rare earth metal other than europium can be obtained by dry mixing or wet mixing. Dry mixing refers to mixing aluminum nitride and each compound in the absence of liquid. Wet mixing refers to mixing raw materials in the presence of an organic solvent or water. Dry mixing is the preferred mixing method. In dry mixing, the mixed powder can contain both large and small sintering aid particles. Relatively large sintering aid particles are thought to be more likely to form localized liquid phases. Localized liquid phases are thought to facilitate rearrangement of aluminum nitride particles, facilitating the formation of a dense sintered body. Furthermore, since aluminum nitride is sensitive to moisture, dry mixing without using moisture is preferred. Furthermore, dry mixing simplifies the manufacturing process compared to wet mixing. For dry mixing, known equipment such as a super mixer, axial mixer, Henschel mixer, ribbon mixer, and rocking mixer can be used. For wet mixing, known equipment such as a ball mill and a media-agitated mill can be used.

[0028] Preparation process of the kneaded material The precursor preparation step may include a step of preparing a kneaded mixture by kneading the raw material mixture with an organic substance. Examples of organic substances include those used as binders, lubricants, and plasticizers. The amount of organic substance contained in the kneaded mixture may be any amount that allows the raw material mixture and the organic substance to be sufficiently mixed without affecting the properties of the resulting sintered body. The amount of organic substance contained in the kneaded mixture may be preferably in the range of 10 to 25 parts by mass per 100 parts by mass of the raw material mixture.

[0029] Examples of organic binders include at least one thermoplastic resin selected from the group consisting of low-density polyethylene, medium-density polyethylene, high-density polyethylene, low-molecular-weight polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, polypropylene, atactic polypropylene, polystyrene, polyacetal, polyamide, and methacrylic resin. In addition to these thermoplastic resins, examples of binders include waxes such as paraffin wax and microcrystalline wax. One type of binder may be used, or two or more types may be used in combination.

[0030] Examples of organic lubricants include hydrocarbon-based lubricants such as liquid paraffin and paraffin wax, and fatty acid-based lubricants such as stearic acid and lauric acid. These lubricants may be used alone or in combination of two or more.

[0031] Examples of organic plasticizers include phthalates, adipic esters, trimellitic esters, etc. One type of plasticizer may be used, or two or more types may be used in combination.

[0032] The kneaded product may contain an auxiliary agent such as a coupling agent to improve the dispersibility of inorganic powders such as aluminum nitride and sintering aids with at least one organic substance selected from the group consisting of binders, lubricants, and plasticizers. The auxiliary agent such as a coupling agent may be added to the kneaded product to the extent that it does not affect the properties of the resulting sintered body.

[0033] The kneaded product can be obtained using a known device.

[0034] Granulation process of kneaded material The precursor preparation step may include a granulation step of granulating the kneaded material. The kneaded material may be granulated into granules or pellets before being formed into a molded body. The granules or pellets of the kneaded material can be obtained using known devices such as a pulverizer, an extruder, or a pelletizer.

[0035] Molding process The precursor preparation process includes a step of molding a raw material mixture, a kneaded product of the raw material mixture, or granulated products of the kneaded product to obtain a molded body. The molded body can be obtained by molding the raw material mixture or the kneaded product using a known method. Known molding methods include injection molding, press molding using a mold, cold isostatic pressing (CIP), extrusion molding, doctor blade molding, and casting. For example, injection molding can form a molded body of a desired shape. When a molded body is formed by injection molding, it is not necessarily necessary to cut the phosphor ceramic into the desired shape after firing the molded body to obtain a phosphor ceramic. Phosphor ceramics containing aluminum nitride as a base material and having high density are very hard and brittle, making them difficult to process, such as cutting. Furthermore, cutting or other processing of phosphor ceramics can cause defects such as chipping. Therefore, injection molding is preferred as a molding method to obtain a molded body, as it is more likely to produce a molded body of a desired shape.

[0036] Heat degreasing process When the precursor preparation process involves molding the kneaded mixture to obtain a compact, it may include a step of heating and degreasing the molded mixture. Degreasing by heating preferably involves heating in a nitrogen-containing atmosphere at a temperature ranging from 400°C to 700°C. Heating in a nitrogen-containing atmosphere at a temperature ranging from 400°C to 700°C reduces the amount of carbon contained in the compact, enabling degreasing. This prevents a decrease in yield due to cracking of the sintered body caused by carbon remaining in the kneaded mixture. It also prevents oxidation of the sintered body. Depending on the type of organic component, sudden heat generation may occur within the above temperature range. However, heating in a nitrogen-containing atmosphere can prevent such a sudden temperature rise. This prevents deterioration of the firing furnace. In this specification, a nitrogen-containing atmosphere refers to a nitrogen content equal to or greater than the volume percent of nitrogen contained in the air. The nitrogen content in the nitrogen-containing atmosphere is sufficient to be 80% by volume or more, preferably 90% by volume or more, more preferably 99% by volume or more, and even more preferably 99.9% by volume or more. The oxygen content in the nitrogen-containing atmosphere is 0.01% by volume or more and 20% by volume or less, and may be 0.1% by volume or more and 10% by volume or less. The atmospheric pressure for heating is, for example, normal pressure. Alternatively, heating may be performed under a pressurized or reduced pressure environment. A known method can be used for debinding. The carbon content in the molded body obtained by debinding the molded kneaded material is, for example, preferably 1000 ppm or less by mass, more preferably 500 ppm or less. The carbon content of the molded body after debinding can be measured, for example, by non-dispersive infrared (NDIR) spectroscopy. The debinding time for heating may be any time that allows debinding of the organic matter in the kneaded material so that the carbon content in the molded kneaded material is 1000 ppm or less. Specifically, the heating time for debinding (the time for holding the maximum temperature) is preferably 0.1 hours or more and 50 hours or less, and may be appropriately changed depending on the shape of the molded body to be debound.

[0037] First firing process The precursor may be a sintered body containing aluminum nitride. When the precursor is a sintered body containing aluminum nitride, the method may include a step of firing a molded body containing aluminum nitride to obtain a sintered body containing aluminum nitride. In this specification, the step of firing a molded body containing aluminum nitride to obtain a sintered body containing aluminum nitride as a precursor is also referred to as a first firing step. The firing of the molded body is also referred to as first firing. The temperature in the first firing step is also referred to as a first firing temperature. The atmosphere in the first firing step is also referred to as a first firing atmosphere.

[0038] The first firing temperature is preferably in the range of 1700°C or higher and 2050°C or lower. This allows the aluminum nitride particles to be densely bonded together by a liquid phase formed between the aluminum nitride particles, resulting in a sintered body containing aluminum nitride with high thermal conductivity. The first firing temperature is preferably in the range of 1750°C or higher and 2050°C or lower, more preferably in the range of 1800°C or higher and 2050°C or lower, and even more preferably in the range of 1850°C or higher and 2050°C or lower. This further improves the thermal conductivity of the precursor.

[0039] The first firing atmosphere is preferably the nitrogen-containing atmosphere described above. By performing the first firing in a nitrogen-containing atmosphere, aluminum nitride is less likely to decompose and a sintered body with high thermal conductivity can be obtained. Furthermore, in order to stably maintain the nitrogen-containing atmosphere in the first firing atmosphere, a nitrogen-containing gas can be continuously or intermittently supplied.

[0040] The pressure in the first firing atmosphere is, for example, near atmospheric pressure (101.32 kPa), and preferably a gauge pressure of 50 kPa or less. An environment with a gauge pressure of 0 kPa or more and 50 kPa or less can be achieved relatively easily, which improves productivity.

[0041] The first firing time may be any time that allows a dense sintered body to be obtained. Specifically, the first firing time is preferably 0.5 hours or more and 100 hours or less. The first firing time is more preferably 10 hours or more and 70 hours or less, and even more preferably 20 hours or more and 45 hours or less. This allows unnecessary oxygen in the compact to be discharged, resulting in a denser sintered body.

[0042] In the first firing for firing the compact, a carbon furnace is preferably used, which uses carbon as the internal furnace material such as the heating element and heat insulating material, in order to reduce the amount of oxygen in the sintered body. A furnace other than a carbon furnace may also be used as long as it can maintain the first firing temperature.

[0043] The setter and crucible on which the compact is placed are preferably ones that do not deform or decompose at the first firing temperature. The material of the setter or crucible is preferably a nitride such as boron nitride or aluminum nitride. It is preferable to use a setter or crucible made of a material containing a high-purity nitride containing 95% by mass or more.

[0044] The sintered body may further include a step of dividing the sintered body into individual pieces. The shape of the sintered body after division in a plan view may be, for example, substantially circular, substantially rectangular, substantially square, substantially triangular, or any other polygonal shape.

[0045] The precursor is preferably a sintered body containing aluminum nitride. When the precursor is a sintered body containing aluminum nitride, europium is contained in the aluminum nitride sintered body in the step of obtaining a phosphor ceramic, which will be described later, and thereby a phosphor ceramic that emits light when excited by excitation light and has high thermal conductivity can be obtained.

[0046] The aluminum nitride-containing sintered body preferably contains oxygen, with the oxygen content being 0.3 mass% or less. By setting the oxygen content of the aluminum nitride-containing sintered body to 0.3 mass% or less, the thermal conductivity can be further improved. This is because the grain boundary phase formed between aluminum nitride particles in the sintered body can be reduced. Since the grain boundary phase has a lower thermal conductivity than aluminum nitride, reducing this grain boundary phase can improve the thermal conductivity of the aluminum nitride-containing sintered body. Furthermore, by setting the oxygen content of the precursor to 0.3 mass% or less in advance to improve the thermal conductivity, it is possible to maintain a relatively high thermal conductivity even when the precursor is doped with an element that serves as a luminescence center in the process of forming the phosphor ceramics described below. Furthermore, the oxygen content of the aluminum nitride-containing sintered body is more preferably greater than 0 mass% and 0.001 mass% or less. This further improves the thermal conductivity of the resulting sintered body and also provides translucency. For example, if light with a peak wavelength of 380 nm is irradiated onto one side of a 2 mm thick sintered body, light with a peak wavelength of 380 nm can be extracted from the side opposite the irradiated side. This is because the grain boundary phase is reduced, suppressing light absorption by the grain boundary phase. Since the energy gap of aluminum nitride is approximately 6.2 eV, sintered bodies containing aluminum nitride are translucent to light with a peak wavelength of approximately 200 nm or more.

[0047] The thermal conductivity of the sintered body containing aluminum nitride can be, for example, 150 W / m·K or more and 270 W / m·K or less, preferably 200 W / m·K or more and 270 W / m·K or less, and more preferably 220 W / m·K or more and 270 W / m·K or less.

[0048] The oxygen content in the precursor green body or sintered body can be measured after acid decomposition of the sintered body using an oxygen / nitrogen analyzer (for example, EMGA-820, manufactured by Horiba, Ltd.) Note that the oxygen content of the sintered body may be below the detection limit of the oxygen / nitrogen analyzer.

[0049] Process for obtaining phosphor ceramics A precursor that is a molded body containing aluminum nitride or a sintered body containing aluminum nitride can be contacted with a gas containing europium to obtain an aluminum nitride phosphor ceramic having a europium content in the range of more than 0.03 mass % to 1.5 mass %.

[0050] Firing (second firing) process The step of obtaining the phosphor ceramic preferably includes firing the precursor in an atmosphere containing europium at a temperature ranging from the boiling point of metallic europium to less than 2000°C. By firing the precursor in an atmosphere containing europium at a temperature ranging from the boiling point of metallic europium to less than 2000°C, europium is easily doped into the aluminum nitride crystals in the sintered body containing aluminum nitride, making it possible to obtain an aluminum nitride phosphor ceramic that emits light when excited by excitation light. In this specification, the firing in the step of obtaining the phosphor ceramic is also referred to as second firing. The firing temperature in the step of obtaining the phosphor ceramic is also referred to as second firing temperature. The firing atmosphere in the step of obtaining the phosphor ceramic is also referred to as second firing atmosphere.

[0051] The step of obtaining an aluminum nitride phosphor ceramic preferably includes firing a precursor and a europium-containing compound arranged so as not to come into direct contact with the precursor at a temperature ranging from the boiling point of metallic europium to less than 2000° C. A precursor that is an aluminum nitride-containing compact or sintered body is placed in a furnace, and a europium-containing compound is placed in the same furnace so as not to come into contact with the precursor, and fired at a temperature ranging from the boiling point of metallic europium to less than 2000° C., whereby the precursor is doped with europium-containing vapor, and an aluminum nitride phosphor ceramic is obtained that emits light when excited by excitation light.

[0052] The step of obtaining the aluminum nitride phosphor ceramic can include contacting the surface of the precursor with a compound containing europium, and firing the precursor at a temperature ranging from the boiling point of metallic europium to less than 2000° C. This allows for the production of an aluminum nitride phosphor ceramic having a europium content ranging from more than 0.03 mass % to 1.5 mass %.

[0053] In the process of obtaining aluminum nitride phosphor ceramics, a europium source such as a compound containing europium can be placed in the same atmosphere as the precursor, or a gas containing europium can be introduced into the atmosphere for firing. It is sufficient that europium is contained in the atmosphere in which the precursor is second-fired.

[0054] The second firing temperature is above the boiling point of metallic europium and below 2000°C. Specifically, it is preferably within the range of 1530°C or higher and below 2000°C. This makes it easier to dope europium into an aluminum nitride-containing compact or sintered aluminum nitride body when the precursor is brought into contact with a gas containing europium, thereby producing an aluminum nitride phosphor ceramic that absorbs light emitted from an excitation light source and emits light. The second firing temperature is more preferably within the range of 1550°C or higher and 1950°C or lower, even more preferably within the range of 1700°C or higher and 1950°C or lower, and particularly preferably within the range of 1800°C or higher and 1950°C or lower. This allows the resulting aluminum nitride phosphor ceramic to maintain high thermal conductivity while increasing its luminescence intensity.

[0055] The second firing atmosphere is preferably a nitrogen-containing atmosphere. In this specification, a nitrogen-containing atmosphere refers to an atmosphere in which the amount of nitrogen is equal to or greater than the volume percent of nitrogen contained in the atmosphere. The nitrogen content in the nitrogen-containing atmosphere is sufficient to be equal to or greater than 80 volume percent, preferably equal to or greater than 90 volume percent, more preferably equal to or greater than 99 volume percent, and even more preferably equal to or greater than 99.9 volume percent. The oxygen content in the nitrogen-containing atmosphere is equal to or greater than 0.01 volume percent and equal to or less than 20 volume percent, and may be equal to or greater than 0.1 volume percent and equal to or less than 10 volume percent. The atmosphere during the second firing may also be an argon (Ar) atmosphere.

[0056] The second firing may be carried out, for example, at normal pressure or in a pressurized environment. When the second firing is carried out in a pressurized environment, the atmospheric pressure in the second firing is preferably in the range of 0.01 MPa to 0.1 MPa in gauge pressure, may be in the range of 0.01 MPa to 0.09 MPa in gauge pressure, or may be in the range of 0.01 MPa to 0.08 MPa in gauge pressure.

[0057] The time for the second firing may be set appropriately so long as the amount of europium doped into the aluminum nitride phosphor ceramic is in the range of more than 0.03% by mass and not more than 1.5% by mass, for example, from 0.1 to 20 hours, or from 0.5 to 10 hours.

[0058] The compound containing europium may be, for example, an oxide, nitride, hydroxide, or halide. Examples of the compound containing europium include europium oxide (Eu2O3), europium nitride (EuN), and europium(III) fluoride (EuF3). It is preferable to use europium oxide as the compound containing europium because it is stable at room temperature or in the air.

[0059] In the step of obtaining aluminum nitride phosphor ceramics, the europium-containing gas is preferably a europium-containing gas obtained by reducing europium oxide. Examples of methods for reducing europium oxide include placing a precursor and europium oxide in a carbon furnace and firing them at a temperature above the boiling point of metallic europium but below 2000°C to reduce the europium oxide to a europium-containing gas. Other examples include placing a reducing agent such as carbon in a furnace containing the precursor and europium oxide and firing them at a temperature above the boiling point of metallic europium but below 2000°C to reduce the europium oxide to a europium-containing gas.

[0060] The amount of europium charged per 1 g of aluminum nitride precursor was 1.4 mg / cm, calculated as a compound containing europium. 3 More than 14mg / cm 3 The amount of europium to be added per gram of aluminum nitride precursor is preferably 1.7 mg / cm in terms of a compound containing europium. 3 More than 11mg / cm 3 Preferably, 2.0 mg / cm or less 3 More than 10mg / cm 3 It can be placed within the following range:

[0061] The amount of europium charged per 1 g of aluminum nitride precursor is, for example, 1.2 mg / cm 3 More than 12mg / cm 3 The amount of the compound containing europium in the furnace may be within the following range: The amount of the compound containing europium per gram of aluminum nitride is preferably 1.5 mg / cm 3 in terms of the europium content per unit volume. 3 More than 10mg / cm 3 The amount is preferably in the range of 1.7 mg / cm 3 More than 9.0mg / cm 3The amount is within the following range: By this, an aluminum nitride phosphor ceramic can be obtained.

[0062] The europium content in the resulting aluminum nitride phosphor ceramic is in the range of more than 0.03 mass% to 1.5 mass% or less. This results in an aluminum nitride phosphor ceramic that emits light when excited by excitation light. The europium content in the aluminum nitride phosphor ceramic is preferably in the range of 0.05 mass% to 1.1 mass%, more preferably in the range of 0.05 mass% to 0.8 mass%, and even more preferably in the range of 0.1 mass% to 0.7 mass%. This makes it possible to improve the luminescence intensity of the aluminum nitride phosphor sintered body while maintaining high thermal conductivity, thereby achieving both.

[0063] The aluminum nitride phosphor ceramic preferably emits green light. Specifically, it is preferable that the aluminum nitride phosphor ceramic emits green light when irradiated with excitation light having an emission peak wavelength in the range of 200 nm to 480 nm, preferably 280 nm to 480 nm. The aluminum nitride phosphor ceramic preferably emits green light from the same surface as the incident surface onto which the excitation light is incident, and the incident light preferably passes through the aluminum nitride phosphor ceramic and exits from the surface opposite the incident surface, also emitting green light. When excitation light passes through the aluminum nitride phosphor ceramic and exits, the exiting light may not be green light but may be light having an emission peak wavelength in a wavelength range other than green light.

[0064] The obtained aluminum nitride phosphor ceramic preferably not only emits light from the incident surface on which excitation light is incident, but also from the surface opposite to the surface on which the excitation light is incident, after the incident light has passed through the aluminum nitride phosphor ceramic. The aluminum nitride phosphor ceramic preferably emits green light from the surface on which excitation light is incident, and preferably the light that passes through the aluminum nitride phosphor ceramic and is emitted from the surface opposite to the incident surface also emits green light. When excitation light passes through the aluminum nitride phosphor ceramic and is emitted, the emitted light may not be green light, but may be light having an emission peak wavelength in a wavelength range other than green light.

[0065] Aluminum nitride phosphor ceramics The aluminum nitride phosphor ceramic contains aluminum nitride, europium, and oxygen, with the oxygen content being 2.5 mass% or less and the europium content being greater than 0.03 mass% and less than 1.5 mass%. The aluminum nitride phosphor ceramic is preferably obtained by the aforementioned manufacturing method. The amounts of europium (Eu) and yttrium (Y) in the aluminum nitride phosphor ceramic can be measured using an inductively coupled plasma atomic emission spectroscopy (ICP-AES). The amount of oxygen (O) can be measured using an oxygen / nitrogen analyzer.

[0066] The aluminum nitride phosphor ceramic has a europium content of more than 0.03 mass% and not more than 1.5 mass%. This allows europium to be doped into the aluminum nitride crystal phase, and the europium doped into the aluminum nitride crystal phase serves as the luminescence center, absorbing light emitted from an excitation light source and emitting light. The europium content in the aluminum nitride phosphor ceramic is preferably in the range of 0.05 mass% to 1.1 mass%, more preferably in the range of 0.08 mass% to 0.9 mass%, and even more preferably in the range of 0.1 mass% to 0.7 mass%. This allows the aluminum nitride phosphor sintered body to improve luminescence intensity while maintaining high thermal conductivity, achieving both of these.

[0067] The aluminum nitride phosphor ceramic contains aluminum nitride, europium, and oxygen, with the oxygen content being 0.7% by mass or less and the europium content being in the range of more than 0.08% by mass and 0.9% by mass or less. This allows the aluminum nitride phosphor ceramic to emit light upon receiving light emitted from an excitation light source, with europium serving as the luminescence center. It can also emit light from the side opposite to the side receiving light from the excitation light source. Furthermore, since aluminum nitride is the base material, it can have high thermal conductivity.

[0068] The aluminum nitride phosphor ceramic preferably emits light having an emission peak wavelength in the range of 500 nm to 550 nm when exposed to light from an excitation light source. The aluminum nitride phosphor ceramic preferably emits green light when exposed to light from an excitation light source. The aluminum nitride phosphor ceramic preferably emits green light when exposed to excitation light having an emission peak wavelength in the range of 200 nm to 480 nm. If the europium content in the aluminum nitride phosphor ceramic is 0.03 mass% or less, a luminescent ceramic cannot be obtained. If the europium content in the aluminum nitride phosphor ceramic exceeds 1.5 mass%, the amount of europium is too high, which may result in absorption of light in the green wavelength range and reduced luminous efficiency.

[0069] The aluminum nitride phosphor ceramic contains oxygen, and the oxygen content is 2.5% by mass or less. This allows for the production of aluminum nitride phosphor ceramics with high thermal conductivity. The aluminum nitride phosphor ceramic preferably has an oxygen content of 1.0% by mass or less, more preferably 0.7% by mass or less, and particularly preferably 0.5% by mass or less. This reduces the grain boundary phase composed of oxides containing nitrogen and aluminum compared to when the oxygen content is outside the above range. A small grain boundary phase is preferable in terms of luminescence properties and heat dissipation. From the perspective of luminescence properties, light emitted from an excitation light source and / or fluorescence with europium as the luminescence center can be easily extracted to the outside of the aluminum nitride phosphor ceramic. Furthermore, the reduced grain boundary phase improves the light transmittance of the aluminum nitride phosphor ceramic, allowing light to pass through the aluminum nitride phosphor ceramic and exit from the surface opposite to the light incident surface. From the viewpoint of heat dissipation, the proportion of the aluminum nitride crystalline phase, which has a high thermal diffusivity, in the aluminum nitride phosphor ceramic can be relatively higher than the proportion of the grain boundary phase, which contains nitrogen, aluminum, and oxygen and has a low thermal diffusivity. This improves the thermal diffusivity of the aluminum nitride phosphor ceramic, and increases its thermal conductivity. The proportion of the crystalline phase in the entire aluminum nitride phosphor ceramic may be, for example, 95% to 99.9% by volume, or 97% to 99.9% by volume.

[0070] The aluminum nitride phosphor ceramic may contain aluminum nitride crystalline phases with a size of, for example, 8 μm or more and 30 μm or less. The aluminum nitride phosphor ceramic may also contain aluminum nitride crystalline phases with a size of 10 μm or more and 20 μm or less. Crystal phases with these sizes can be contained in the aluminum nitride phosphor ceramic as highly pure crystalline phases, for example, when oxygen contained in the aluminum nitride phosphor ceramic is sufficiently removed. This improves the thermal conductivity of the aluminum nitride phosphor ceramic. The average size of the aluminum nitride crystalline phase is, for example, 6 μm or more and 20 μm or less. The size of the aluminum nitride crystalline phase can be determined, for example, by examining the size of the aluminum nitride crystalline phase in an arbitrary region of a cross-sectional SEM image observed at 1000x magnification. The arbitrary region is, for example, a 127 μm × 88 μm region. A line is drawn on the obtained image, and the length from grain boundary to grain boundary of the aluminum nitride crystalline phase that overlaps with this line is measured.

[0071] The aluminum nitride phosphor ceramic may contain at least one rare earth element other than europium, and the content of the rare earth element other than europium may be 0.5 mass% or less. When a sintering aid containing a rare earth element other than europium is contained in an aluminum nitride molded body, the aluminum nitride phosphor ceramic may contain the rare earth element contained in the sintering aid. If the content of the rare earth element other than europium in the aluminum nitride phosphor ceramic is 0.5 mass% or less, the grain boundary phase is reduced, and the light transmittance of the aluminum nitride phosphor ceramic is improved.

[0072] The rare earth elements, excluding europium, contained in the aluminum nitride phosphor ceramic form oxides. These oxides may contain nitrogen and aluminum. The oxides containing the rare earth elements, excluding europium, form grain boundary phases between the aluminum nitride crystal phases. When the sintering aid is yttrium oxide, an oxide containing yttrium may be formed in the grain boundary phase.

[0073] Furthermore, europium doped into the sintered body containing aluminum nitride forms an oxide. This oxide may contain nitrogen and aluminum. The oxide containing europium may form a grain boundary phase between aluminum nitride crystal phases. In the aluminum nitride phosphor ceramic, a grain boundary phase is formed between aluminum nitride crystal phases, and the grain boundary phase may contain an oxide phase containing yttrium and an oxide phase containing europium. The oxide phase containing yttrium and the oxide phase containing europium may each form a grain boundary phase separately, or the oxide phase containing yttrium and the oxide phase containing europium may be combined to form a single grain boundary phase.

[0074] Europium exists in the aluminum nitride crystalline phase and the grain boundary phase in the aluminum nitride phosphor ceramic. The amounts of europium and yttrium present in the aluminum nitride crystalline phase or grain boundary phase of an aluminum nitride phosphor ceramic can be determined by cutting the aluminum nitride phosphor ceramic so that its cross section is exposed, and analyzing specific locations on the cross section using, for example, an electron probe microanalyzer (EPMA), a scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDX). EPMA can be performed using a field emission electron probe microanalyzer (e.g., model JXA-8500F, manufactured by JEOL Ltd.). SEM and EDX can be performed using an SEM-EDX device (e.g., model SU8230, manufactured by Shimadzu Corporation, and a silicon drift detector (SDD device), manufactured by Horiba, Ltd.). The amount of europium contained in the grain boundary phase is higher than the amount of europium contained in the aluminum nitride crystalline phase. For example, in any cross section of an aluminum nitride phosphor ceramic, three to five arbitrary locations in the grain boundary phase can be selected, the amount of europium in the grain boundary phase at the selected locations can be detected, and the arithmetic average value can be measured as the amount of europium present in the grain boundary phase. On the other hand, it is presumed that europium in the aluminum nitride crystalline phase is doped as an activator element. Therefore, since the amount of europium in the aluminum nitride crystalline phase is so small that it is below the detection sensitivity of EDX and EPMA, it may not be possible to measure it.

[0075] The thermal diffusivity of aluminum nitride phosphor ceramics measured by the laser flash method at 25°C is 80 mm 2 The aluminum nitride phosphor ceramic has a thermal diffusivity of 65 mm / s or more as measured by the laser flash method. 2 / s or more, 80 mm 2 / s or more is preferable, and 85m 2 / s or more is more preferable, and 90 mm 2 It is more preferable that the thermal diffusivity is 95 mm / s or more.2 / s or more is even more preferable. Thermal conductivity is calculated by the product of thermal diffusivity, specific heat capacity, and density. Therefore, aluminum nitride phosphor ceramics with high thermal diffusivity also have high thermal conductivity and excellent heat dissipation. Furthermore, the thermal diffusivity of aluminum nitride phosphor ceramics is lower than that of single crystal aluminum nitride, and is 136.3 mm 2 / s or less.

[0076] The thermal diffusivity α of aluminum nitride phosphor ceramics can be measured at 25°C using a laser flash analyzer (e.g., LFA447, manufactured by NETZSCH) by the laser flash method on a sample measuring, for example, 10 mm long x 10 mm wide x 2 mm thick. In this specification, the specific heat capacity Cp of aluminum nitride (AlN) is 0.72 KJ / kg·K. The apparent density of aluminum nitride phosphor ceramics can be calculated using the volume measured by Archimedes' method according to the following formula (1). In formula (1), aluminum nitride phosphor ceramics are referred to as AlN phosphor ceramics.

[0077]

number

[0078] The thermal conductivity λ of the aluminum nitride phosphor ceramic can be calculated from the product of the measured thermal diffusivity α, specific heat capacity Cp, and density ρ (apparent density), specifically, by the following formula (2).

[0079]

number

[0080] The apparent density of aluminum nitride phosphor ceramics is 2.5 g / cm 3 (0.0025kg / m 3 The apparent density of the aluminum nitride phosphor ceramic is preferably 2.9 g / cm or more.3 More preferably, it is 3.0 g / cm or more. 3 More preferably, it is 3.1 g / cm or more. 3 This allows for improved thermal conductivity. The apparent density of the aluminum nitride phosphor ceramic is less than the theoretical density, 3.5 g / cm. 3 It may be the following:

[0081] The thermal conductivity of the aluminum nitride phosphor ceramic is, for example, 150 W / m·K or more and 250 W / m·K or less, preferably 150 W / m·K or more and 200 W / m·K or less, more preferably 210 W / m·K or more and 250 W / m·K or less, and particularly preferably 220 W / m·K or more and 250 W / m·K or less.

[0082] The excitation spectrum of the aluminum nitride phosphor ceramic preferably has intensity in the range of 280 nm to 480 nm. Furthermore, it preferably has an intensity of 55% or more of the maximum intensity of the excitation spectrum in the range of 420 nm to 440 nm. Furthermore, it preferably has an intensity of 70% or more of the maximum intensity of the excitation spectrum in the range of 420 nm to 440 nm. This allows the aluminum nitride phosphor ceramic to be efficiently excited in the range of 420 nm to 440 nm. For example, in the excitation spectrum of the aluminum nitride phosphor ceramic, the rate of change in the range of 305 nm to 325 nm is smaller than the rate of change in the range of 325 nm to 345 nm. When the oxygen content in the aluminum nitride phosphor ceramic is 1 mass% or less and the europium content is 1.1 mass% or less, preferably when the oxygen content in the aluminum nitride phosphor ceramic is 0.7 mass% or less and the europium content is 0.08 mass% to 0.9 mass%, for example, the excitation spectrum of the aluminum nitride phosphor ceramic, in the range of 370 nm to 385 nm, has a maximum and minimum intensity within a range of ±5% of the average intensity in that range. Furthermore, the excitation spectrum of the aluminum nitride phosphor ceramic can have a peak wavelength in the range of 385 nm to 410 nm.

[0083] The aluminum nitride phosphor ceramic preferably emits green light having an emission peak wavelength in the range of 500 nm to 550 nm when excited by an excitation light source. The emission peak wavelength of light excited by the aluminum nitride phosphor ceramic with the excitation light source may be in the range of 510 nm to 540 nm. The aluminum nitride phosphor ceramic may be doped with an element other than europium as the emission center to emit blue or red light. The full width at half maximum (FWHM) of the emission spectrum of the aluminum nitride phosphor ceramic is 100 nm or less, 90 nm or less, or 85 nm or less.

[0084] When the oxygen content of the aluminum nitride phosphor ceramic is 1 mass% or less and the europium content is 1.1 mass% or less, or preferably when the oxygen content of the aluminum nitride phosphor ceramic is 0.7 mass% or less and the europium content is 0.08 mass% to 0.9 mass%, the peak wavelength of the excitation light source can be 340 nm to 440 nm. Furthermore, the peak wavelength of the excitation light source is preferably 360 nm to 430 nm, and particularly preferably 385 nm to 410 nm. Since the aluminum nitride phosphor ceramic can be excited in a wavelength range where the excitation spectrum of the aluminum nitride phosphor ceramic is highly intense, more efficient excitation is possible.

[0085] Light-emitting device manufacturing method A method for manufacturing a light-emitting device includes preparing a phosphor ceramic manufactured by the above-described manufacturing method, preparing an excitation light source, and arranging the phosphor ceramic at a position where it is irradiated with light emitted from the excitation light source.

[0086] Light-emitting device The light emitting device includes a phosphor ceramic and an excitation light source. The light emitting device emits light emitted from at least the phosphor ceramic excited by the excitation light source to the outside. The light emitting device may emit mixed color light including the light from the excitation light source and the luminescent color emitted from the phosphor ceramic excited by the excitation light source to the outside.

[0087] The excitation light source is, for example, a light-emitting element that emits light having an emission peak wavelength in the range of 280 nm or more and less than 480 nm. The peak wavelength of the excitation light source is preferably in the range of 325 nm or more and 445 nm or less, more preferably in the range of 345 nm or more and 430 nm or less, and even more preferably in the range of 360 nm or more and 430 nm or less. This allows the aluminum nitride phosphor ceramic to be excited at a wavelength with a high intensity excitation spectrum, thereby enabling efficient excitation of the aluminum nitride phosphor ceramic.

[0088] Light-emitting device using LED elements FIG. 4 is a schematic cross-sectional view showing an example of an embodiment of a light emitting device.

[0089] The excitation light source may be a light-emitting element having an emission peak wavelength in the range of 280 nm to 480 nm. The light-emitting element may be a semiconductor light-emitting element having an emission peak wavelength in the range of 280 nm to 480 nm. The light-emitting element may be a light-emitting diode element (hereinafter also referred to as "LED element").

[0090] Light-emitting element The LED elements 1 are arranged on wiring 5 provided on the substrate 2. The wiring 5 includes an anode and a cathode. The LED elements 1 can be selected according to the emission color, wavelength, size, number, and purpose. Examples of semiconductor light-emitting elements having an emission peak wavelength in the range of 280 nm to 480 nm include Group III nitride semiconductors (In X Al Y Ga 1-X-Y N, 0≦X, 0≦Y, X+Y≦1) can be used. The LED element 1 can have, for example, a pair of positive and negative electrodes on the same side. The LED element 1 can be flip-chip mounted on the wiring 5, for example, by bumps. When the LED element 1 is flip-chip mounted on the wiring 5, the surface opposite the surface on which the pair of electrodes is formed becomes the light extraction surface. Note that one LED element 1 may be used per light-emitting device. The LED element 1, together with the phosphor ceramic 3, may be surrounded by a light-reflecting member 4. A light-reflecting member 4 may also be arranged between multiple LED elements 1.

[0091] Phosphor ceramics The phosphor ceramic 3 is made of the aluminum nitride phosphor ceramic described above. The phosphor ceramic 3 can be arranged to cover the surface 1a of the LED element 1, which serves as the light extraction surface. For example, the surface 3b of the phosphor ceramic 3 may be arranged to cover the surface 1a of the LED element 1. When the phosphor ceramic 3 is arranged to cover the surface 1a of the LED element 1, which serves as the light extraction surface, the phosphor ceramic 3 is excited by the light emitted from the LED element 1, causing the phosphor ceramic 3 to emit light. The phosphor ceramic emits, for example, green light. The surface 3a of the phosphor ceramic 3 may be flush with the surface 4a of the light-reflecting member 4 or may protrude from the light-reflecting member 4a. Furthermore, the phosphor ceramic 3 has high thermal conductivity and can dissipate heat to the outside of the light-emitting device 100. The phosphor ceramic 3 is arranged in contact with the surface 1a of the LED element 1, which serves as the light extraction surface, and may be bonded thereto by an adhesive, direct bonding, or the like. When the LED element 1 and the phosphor ceramic 3 are directly bonded together, the thickness of the phosphor ceramic 3 used in the light emitting device 100 is, for example, in the range of 50 μm or more and 500 μm or less, or may be in the range of 60 μm or more and 450 μm or less, or may be in the range of 70 μm or more and 400 μm or less.

[0092] Light-emitting device using LD element FIG. 5 is a schematic cross-sectional view showing an example of an embodiment of a light-emitting device using a laser diode element.

[0093] The light emitting device 200 includes an LD element 12 and a phosphor ceramic 13 in a package member 15. The phosphor ceramic 13 is disposed at a position where it is irradiated with laser light emitted from the LD element 12, either directly or via an optical member or the like. The LD element 12 may be disposed in the package member 15 directly or via a submount 16. The phosphor ceramic 13 has a first main surface 13a and a second main surface 13b located opposite the first main surface 13a. The LD element 12 is disposed on the first main surface 13a side, and light emitted from the LD element 12 is directly irradiated onto the first main surface 13a of the phosphor ceramic 13. The phosphor ceramic 13 may also be provided with a light reflective film and / or a light reflective member 14, either in contact with or not in contact with the surface other than the light incident surface. For example, when emitting light reflected by the phosphor ceramic 13, a light-reflecting film and / or a light-reflecting member 14 can be disposed on the surface of the phosphor ceramic 13 opposite to the surface where excitation light enters and from which light is extracted. The package member 15 may be composed of, for example, a base and a light-extraction window 15a.

[0094] laser diode element The excitation light source can be an LD element. The LD element is made of, for example, a group III nitride semiconductor (In X Al Y Ga 1-X-Y Examples of suitable laser diodes include elements having a semiconductor layer structure (N, 0≦X, 0≦Y, X+Y≦1). For example, an LD element having a peak oscillation wavelength in the range of 280 nm to 480 nm can be used. Also, an LD element having a peak oscillation wavelength in the range of preferably 325 nm to 445 nm, more preferably 340 nm to 430 nm can be used. It is particularly preferable to use an LD element having a peak oscillation wavelength in the range of 360 nm to 430 nm. This allows the aluminum nitride phosphor ceramic to be excited by light with a peak wavelength that has a high intensity excitation spectrum, thereby enabling efficient excitation of the aluminum nitride phosphor ceramic. The full width at half maximum of the emission spectrum of the LD element is, for example, 5 nm or less, preferably 3 nm or less.

[0095] It is preferable to place the LD element and the phosphor ceramic at positions apart from each other, which allows the heat emitted from each component to have separate dissipation paths, allowing the heat to be dissipated efficiently from each component.

[0096] Submount Examples of materials for the submount include aluminum nitride, silicon carbide, a composite material of copper and diamond, a composite material of aluminum and diamond, etc. The composite material of copper and diamond and the composite material of aluminum and diamond contain diamond, and therefore have excellent heat dissipation properties.

[0097] Phosphor ceramics The phosphor ceramic is excited by the light irradiated from the LD element and emits light. The phosphor ceramic is the aluminum nitride phosphor ceramic described above. Because phosphor ceramic has high thermal diffusivity and thermal conductivity, it can dissipate heat generated by the phosphor ceramic and reduce the decrease in luminous efficiency due to temperature rise.

[0098] Light-reflecting film and / or light-reflecting member The light-reflecting film and / or light-reflecting member preferably has a reflectance of 60% or more for the irradiated laser light and / or the light emitted from the phosphor ceramic, and may have a reflectance of 90% or more. Since aluminum nitride phosphor ceramics having an oxygen content of 1 mass% or less and a europium content of 0.08 mass% to 0.7 mass% are translucent, providing the light-reflecting film and / or light-reflecting member can reflect light that would otherwise be lost through transmission, thereby improving the light extraction efficiency.

[0099] The phosphor ceramic may be, for example, in the form of a plate. The plate-shaped member has two flat surfaces that are parallel to and face each other. Taking into consideration heat dissipation and ease of handling, the thickness of the phosphor ceramic may be in the range of 50 μm to 1000 μm, 50 μm to 500 μm, or 80 μm to 350 μm. The phosphor ceramic may also have a thickness that varies partially.

[0100] Package material The package member is preferably formed using a material with good heat dissipation properties, such as a metal including copper, a copper alloy, or an iron alloy, or a ceramic including aluminum nitride or aluminum oxide. The base and / or the light extraction window constituting the package member may have various shapes, such as a substantially circular, elliptical, or polygonal planar shape. The light extraction window of the package member can be formed from, for example, glass, sapphire, or the like.

[0101] The light emitting device in this embodiment is not limited to the above light emitting device, and examples thereof include a light emitting device in which phosphor ceramics are provided outside a package containing a light emitting element to convert wavelength, and a so-called CAN package type light emitting device. [Example]

[0102] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0103] Example 1 Precursor preparation process Aluminum nitride (AlN) powder and yttrium oxide (YO) powder were dry-mixed to obtain a raw material mixture. The aluminum nitride particles accounted for 95% by mass of the raw material mixture, and the yttrium oxide particles accounted for 5% by mass. The aluminum nitride particles had a median particle size Da of 1.1 μm, and the yttrium oxide particles had a median particle size De of 0.7 μm. The particle size ratio De / Da of De to Da was 0.64. 15 parts by mass of paraffin wax was added to 100 parts by mass of the raw material mixture as a binder, and the mixture was kneaded using a kneader to obtain a kneaded product. The kneaded product was then placed in an injection molding machine and molded into a shape measuring 13 mm long x 13 mm wide x 3 mm thick. The molded kneaded product was then heated and degreased in a nitrogen flow atmosphere (100% nitrogen gas by volume) at 500°C and atmospheric pressure (101.32 kPa) for 3 hours to obtain a green body. The carbon content in the compact was 500 ppm or less, and the oxygen content in the sintered body, measured by the method described below, was 2.2 mass %.

[0104] Process for obtaining aluminum nitride phosphor ceramics The obtained precursor compact (1.8 g) containing aluminum nitride was placed on a boron nitride setter installed in a boron nitride crucible, and 0.3 g of europium oxide (Eu2O3) powder was added to the same crucible (the europium oxide content was 16.7 mass% relative to the mass of the precursor, and the europium content in the europium oxide per 1 g of aluminum nitride was 3.6 mg / cm3). 3 ) was introduced into the mixture, which was then placed in a carbon furnace and subjected to a second firing in a nitrogen-containing atmosphere (100% by volume of nitrogen gas) at 1900°C and a gauge pressure of 0.03 MPa for 2 hours, thereby obtaining the aluminum nitride phosphor ceramic of Example 1 in which europium was doped into the aluminum nitride crystal phase.

[0105] Example 2 Precursor preparation process In the precursor preparation step, a molded body prepared under the same conditions as in Example 1 was placed on a boron nitride setter installed in a boron nitride crucible, which was then placed in a carbon furnace and subjected to a first firing at 1950°C, 0.03 MPa, and 35 hours in a nitrogen-containing atmosphere (100% by volume of nitrogen gas), to obtain a sintered body as a precursor containing aluminum nitride. The oxygen content in the sintered body, measured by the method described below, was below the detection limit.

[0106] Process for obtaining aluminum nitride phosphor ceramics The obtained sintered body (1.8 g) containing aluminum nitride, which is the precursor, was placed on a boron nitride setter installed in a boron nitride crucible, and 0.15 g of europium oxide (Eu2O3) powder was added to the same crucible (e.g., the europium oxide content was 8.3 mass% relative to the mass of the precursor, and the europium content in the europium oxide per 1 g of aluminum nitride was 1.8 mg / cm3). 3 ) was introduced into the mixture, which was then placed in a carbon furnace and subjected to a second firing in a nitrogen-containing atmosphere (100% by volume of nitrogen gas) at 1800°C and a gauge pressure of 0.03 MPa for 2 hours, thereby obtaining an aluminum nitride phosphor ceramic of Example 2 in which europium was doped into the aluminum nitride crystal phase.

[0107] Example 3 An aluminum nitride phosphor ceramic of Example 3 was obtained in the same manner as in Example 2, except that the temperature of the second firing was set to 1900°C in the step of obtaining an aluminum nitride phosphor ceramic.

[0108] Example 4 In the process of obtaining aluminum nitride phosphor ceramics, 0.3 g of europium oxide powder (16.7 mass% of europium oxide relative to the mass of the precursor, 3.6 mg / cm of europium oxide contained in europium oxide per 1 g of aluminum nitride) was added to a sintered body (1.8 g) that was a precursor produced under the same conditions as in Example 2. 3 An aluminum nitride phosphor ceramic of Example 4 was obtained in the same manner as in Example 2, except that ) was introduced.

[0109] Example 5 An aluminum nitride phosphor ceramic of Example 5 was obtained in the same manner as in Example 4, except that the temperature of the second firing was set to 1900°C in the step of obtaining an aluminum nitride phosphor ceramic.

[0110] Example 6 An aluminum nitride phosphor ceramic of Example 6 was obtained in the same manner as in Example 4, except that the temperature of the second firing was set to 1950°C in the step of obtaining an aluminum nitride phosphor ceramic.

[0111] Example 7 In the process of obtaining aluminum nitride phosphor ceramics, 0.7 g of europium oxide powder (38.9 mass% of europium oxide relative to the mass of the precursor, the content of europium in europium oxide per 1 g of aluminum nitride was 8.4 mg / cm) was added to a sintered body (1.8 g) that was a precursor produced under the same conditions as in Example 2. 3 An aluminum nitride phosphor ceramic of Example 7 was obtained in the same manner as in Example 2, except that the second firing temperature was set to 1900°C.

[0112] Example 8 An aluminum nitride phosphor ceramic of Example 8 was obtained in the same manner as in Example 5, except that in the step of obtaining an aluminum nitride phosphor ceramic, the second firing was performed in an Ar atmosphere.

[0113] Example 9 In the process of obtaining aluminum nitride phosphor ceramics, 0.7 g of europium oxide powder (38.9 mass% of europium oxide relative to the mass of the precursor, the content of europium in europium oxide per 1 g of aluminum nitride was 8.4 mg / cm) was added to a sintered body (1.8 g) that was a precursor produced under the same conditions as in Example 2. 3 An aluminum nitride phosphor ceramic of Example 9 was obtained in the same manner as in Example 2, except that the second firing temperature was set to 1950°C.

[0114] Comparative Example 1 A molded body (1.8 g) produced under the same conditions as the precursor of Example 1 was placed on a boron nitride setter installed in a boron nitride crucible, which was then placed in a carbon furnace and fired at 1900°C and 0.03 MPa gauge pressure for 2 hours in a nitrogen-containing atmosphere (100% nitrogen gas by volume) without introducing europium oxide powder, to produce ceramics containing aluminum nitride of Comparative Example 1 (hereinafter also referred to as "aluminum nitride ceramics"). The aluminum nitride ceramic of Comparative Example 1 does not emit light even when excited with light from an excitation light source.

[0115] Reference example 1 In the process of obtaining aluminum nitride phosphor ceramics, 0.3 g of europium oxide powder (16.7 mass% of europium oxide relative to the mass of the precursor, 3.6 mg / cm of europium oxide contained in europium oxide per 1 g of aluminum nitride) was added to a sintered body (1.8 g) that was a precursor produced under the same conditions as in Example 2. 3 ) was introduced and the second firing temperature was set to 2000°C, the same procedure as in Example 2 was carried out to obtain an aluminum nitride ceramic of Reference Example 1 having a europium content of 0.03 mass%.

[0116] Reference example 2 A sintered body containing aluminum nitride was obtained as a precursor under the same conditions as in Example 2. This was designated Reference Example 2. The oxygen content in the sintered body, measured by the method described below, was below the detection limit.

[0117] (size of aluminum nitride crystal phase) The size of the aluminum nitride crystalline phase was examined for each sample of the aluminum nitride phosphor ceramic of Example 5 and the aluminum nitride ceramic of Comparative Example 1. The size of the aluminum nitride crystalline phase was examined in a 127 μm × 88 μm region of a cross-sectional SEM image observed at 1000x magnification. Multiple lines were drawn on the obtained image, and the length from grain boundary to grain boundary of the aluminum nitride crystalline phase that overlapped with each line was used as the size of the aluminum nitride crystalline phase, and the average value was calculated. The average size of the aluminum nitride crystalline phase in the aluminum nitride phosphor ceramic of Example 5 was approximately 7.4 μm. The average size of the aluminum nitride crystalline phase in the aluminum nitride ceramic of Comparative Example 1 was approximately 3.8 μm.

[0118] (Apparent density) The mass and volume of each sample of the aluminum nitride phosphor ceramics of the Examples, the aluminum nitride ceramics of Comparative Example 1, and the aluminum nitride ceramics of the Reference Examples, measuring 10 mm in length, 10 mm in width, and 2 mm in thickness, were measured, and the apparent density was calculated based on the above formula (1). The volume was measured by Archimedes' method. The results are shown in Table 1.

[0119] (thermal diffusivity) The thermal diffusivity α of each aluminum nitride phosphor ceramic of the Examples, the aluminum nitride ceramic of Comparative Example 1, and each aluminum nitride ceramic of the Reference Examples was measured at 25°C by the laser flash method using a laser flash analyzer (LFA447, manufactured by NETZSCH) for each sample measuring 10 mm long x 10 mm wide x 2 mm thick. The results are shown in Table 1.

[0120] (thermal conductivity) For each aluminum nitride phosphor ceramic sample in the Examples, the aluminum nitride ceramic in Comparative Example 1, and each aluminum nitride ceramic sample in the Reference Example, the thermal conductivity λ was calculated based on the measured apparent density, thermal diffusivity α, and specific heat capacity Cp of the aluminum nitride phosphor ceramic. The specific heat capacity Cp was calculated using the specific heat capacity of aluminum nitride, which is 0.72 kJ / kg K. The results are shown in Table 1.

[0121] (Europium (Eu) and yttrium (Y) content) The content of europium (Eu) or yttrium (Y) in each aluminum nitride phosphor ceramic of the Examples, the aluminum nitride ceramic of Comparative Example 1, and each aluminum nitride ceramic of the Reference Example was measured using an inductively coupled plasma atomic emission spectrometry (ICP-AES) device after acid decomposition of the aluminum nitride phosphor ceramic or aluminum nitride ceramic. The results are shown in Table 1.

[0122] (Oxygen (O) content) The amount of oxygen (O) in each aluminum nitride phosphor ceramic of the Examples, the aluminum nitride ceramic of Comparative Example 1, and each aluminum nitride ceramic of the Reference Example was measured using an oxygen / nitrogen analyzer. The results are shown in Table 1.

[0123] (Emission color, emission spectrum) The aluminum nitride phosphor ceramics of Examples 1, 3, and 5, and the aluminum nitride ceramic sample of Reference Example 1, were irradiated with excitation light having peak emission wavelengths of 365 nm and 400 nm, respectively, to confirm the emission color of the aluminum nitride phosphor ceramics. Using a quantum efficiency measurement device (QE-2000, manufactured by Otsuka Electronics Co., Ltd.), the samples were irradiated with excitation light having peak emission wavelengths of 365 nm and 400 nm, and the emission spectra were measured at room temperature (25°C ± 5°C). The emission spectra of the aluminum nitride phosphor ceramics of Examples 1, 3, and 5, when irradiated with excitation light having a peak emission wavelength of 365 nm, and the emission spectrum of the aluminum nitride ceramic of Reference Example 1, are shown in FIG. 6. The emission spectra of the aluminum nitride phosphor ceramics of Examples 1, 3, and 5, when irradiated with excitation light having a peak emission wavelength of 400 nm, are shown in FIG. 7. It was confirmed that the aluminum nitride phosphor ceramics had a peak emission wavelength in the range of 500 nm to 550 nm, and emitted green light, regardless of whether the peak emission wavelength of the excitation light was 365 nm or 400 nm. The color tone of the emitted light from each aluminum nitride phosphor ceramic of the Examples when irradiated with excitation light having a peak emission wavelength of 365 nm was also visually confirmed. The color tone of the light transmitted through each aluminum nitride phosphor ceramic of the Examples and emitted from the surface opposite to the light incident surface when irradiated with excitation light having a peak emission wavelength of 380 nm was also visually confirmed. Furthermore, 2 mm thick samples of each aluminum nitride phosphor ceramic of the Examples were visually confirmed for the translucency of incident light. The results are shown in Table 1.

[0124] (Excitation spectrum) The excitation spectra of the aluminum nitride phosphor ceramics according to Examples 1, 3, and 5 were measured using a spectrofluorometer (F-4500, manufactured by Hitachi High-Tech Science Corporation), and the results are shown in FIG.

[0125] [Table 1]

[0126] The aluminum nitride phosphor ceramics according to Examples 1 to 9 had a europium (Eu) content in the range of more than 0.03 mass% to 1.5 mass% or less, and emitted light when exposed to light emitted from an excitation light source. The aluminum nitride phosphor ceramics according to Examples 2 to 8 had an oxygen content of 0.5 mass% or less, and were confirmed to have high thermal conductivity of 200 (W / m K) or more and translucency. The aluminum nitride phosphor ceramic according to Example 1 had a high oxygen content of 2.2 mass%, and when irradiated with an excitation light source with an emission peak wavelength of 380 nm, no light emission could be visually confirmed on the surface opposite the excitation light source incident surface. This is presumably due to the presence of a large grain boundary phase containing oxides.

[0127] The aluminum nitride ceramics of Comparative Example 1, which was not subjected to a second firing by contact with a gas containing europium, and the aluminum nitride ceramics of Reference Example 1, in which the amount of europium in the ceramic was 0.03 mass %, did not emit light when exposed to light from the excitation light source.

[0128] As shown in Figures 6 and 7, the aluminum nitride phosphor ceramics of Examples 1, 3, and 5 were confirmed to emit green light, with peak emission wavelengths in the green light wavelength range of 500 nm to 550 nm, regardless of whether the peak wavelength of the excitation light was 365 nm or 400 nm. The aluminum nitride phosphor ceramic of Example 5 exhibited approximately 10 times higher emission intensity with excitation light having a peak emission wavelength of 365 nm and approximately 13.6 times higher emission intensity with excitation light having a peak emission wavelength of 400 nm than the aluminum nitride phosphor ceramic of Example 1. This is thought to be because, for example, the aluminum nitride phosphor ceramic of Example 5 has a lower oxygen content and less absorption by the grain boundary phase compared to the aluminum nitride phosphor ceramic of Example 1. Furthermore, the aluminum nitride ceramic of Reference Example 1 did not emit light when exposed to excitation light, despite having a europium content of 0.03 mass%.

[0129] 8, the aluminum nitride phosphor ceramics according to Examples 3 and 5 had portions with higher intensity in the range of 380 nm or more than the excitation spectrum of the aluminum nitride phosphor ceramic according to Example 1. The excitation spectrum of the aluminum nitride phosphor ceramic according to Example 5 had a peak wavelength in the range of 385 nm or more and 410 nm or less.

[0130] (X-ray diffraction pattern) X-ray diffraction patterns were measured for the aluminum nitride phosphor ceramic of Example 5 and the aluminum nitride ceramic of Comparative Example 1 using an X-ray diffractometer (SmartLab, manufactured by Rigaku Corporation) with an X-ray source of CuKα radiation (λ = 0.15418 nm, tube voltage 45 kV, tube current 40 mA). The resulting X-ray diffraction (XRD) patterns, which show the diffraction intensity versus the diffraction angle (2θ), are shown in FIG. 9. From top to bottom, FIG. 9 shows the X-ray diffraction pattern for the aluminum nitride phosphor ceramic of Example 5 and the X-ray diffraction pattern for the aluminum nitride ceramic of Comparative Example 1. For reference, the X-ray diffraction (XRD) patterns for AlN, Eu2O3, and YO3 registered in the Inorganic Crystal Structure Database (ICSD) are also shown.

[0131] As shown in FIG. 9, the XRD patterns of the aluminum nitride phosphor ceramic of Example 5 and the aluminum nitride ceramic of Comparative Example 1 have peaks at approximately the same positions as the diffraction angle 2θ of the XRD pattern of AlN, confirming that the aluminum nitride phosphor ceramic of Example 5 and the aluminum nitride ceramic of Comparative Example 1 have approximately the same structure as AlN.

[0132] (Elemental analysis of aluminum nitride phosphor ceramics: SEM-EDX analysis) The surface of the aluminum nitride phosphor ceramic according to Example 5 was polished using a cross-section polisher (CP) and then coated with carbon. The cross-section of the aluminum nitride phosphor ceramic was then observed and quantitatively analyzed using a backscattered electron image. The quantitative analysis was performed using a SEM-EDX device (SU8230, manufactured by Hitachi, Ltd., SDD detector). The N, O, Al, Y, and Eu elements in the aluminum nitride phosphor ceramic were analyzed using semi-quantitative analysis. The total of the analytical values ​​for N, O, Al, Y, and Eu in the aluminum nitride phosphor ceramic at each measurement point was set to 100% by mass, and the content (mass%) of each element was calculated. The results, rounded to one decimal place, are shown in Table 2. Note that as a result of rounding, the total amount of N, O, Al, Y, and Eu in the aluminum nitride phosphor ceramic may not equal 100% by mass. In Figures 10 to 15, crosses indicate the approximate analysis locations. In Figure 10, p1 indicates an analysis location in the aluminum nitride crystal phase. p2 indicates an analysis location where the aluminum nitride crystal phase and the grain boundary phase cannot be clearly distinguished. In Figure 11, p3 and p4 indicate analysis locations at different positions in one grain boundary phase. In Figure 12, p5 and p6 indicate analysis locations in different grain boundary phases, respectively.

[0133] [Table 2]

[0134] In two locations (p1 and p2) in the backscattered electron image of the cross section of the aluminum nitride phosphor ceramic according to Example 5 shown in FIG. 10, the ratio of nitrogen to aluminum was almost the same as that of aluminum nitride, confirming the formation of an aluminum nitride crystalline phase. The aluminum nitride phosphor ceramic according to Example 5 was excited by light from an excitation light source and emitted light, so it contained Eu, which acts as the luminescence center. However, the amount of Eu contained in the aluminum nitride crystalline phase was below the detection limit of SEM-EDX. In four locations (p3, p4, p5, and p6) in the grain boundary phase in the backscattered electron image of the cross section of the aluminum nitride phosphor ceramic according to Example 5 shown in FIGS. 11 and 12, there were some areas rich in Eu and some areas rich in Y. The brighter locations p3 and p5 in the grain boundary phase contained a lot of Eu, while the darker locations p4 and p6 in the grain boundary phase contained a lot of Y. It is presumed that the locations p3 and p5 in the grain boundary phase are where a grain boundary phase composed of an oxide containing a lot of Eu is formed. In FIGS. 11 and 12, it was presumed that the grain boundary phase consisting of oxides containing a large amount of Y was formed at the locations p4 and p6 in the grain boundary phase.

[0135] (Elemental analysis of aluminum nitride phosphor ceramics: EPMA analysis) The aluminum nitride phosphor ceramic of Example 5 was surface-finished using a cross-section polisher (CP) and then coated with carbon. The cross-section of the aluminum nitride phosphor ceramic was then observed and quantitatively analyzed using a backscattered electron microscope (EPMA) (JXA-8500F, manufactured by JEOL Ltd.). Quantitative analysis was performed on the elements nitrogen (N), oxygen (O), aluminum (Al), yttrium (Y), and europium (Eu) at each measurement point in the aluminum nitride crystalline phase and each measurement point in the grain boundary phase of the aluminum nitride phosphor ceramic. The total of the analytical values ​​for N, O, Al, Y, and Eu at each measurement point was set to 100% by mass, and the content (mass%) of each element was calculated. The results, rounded to two decimal places, are shown in Table 2. Figures 13 to 15 are SEM photographs of backscattered electron images of the cross-section of the aluminum nitride phosphor ceramic of Example 5. In Fig. 13, p7 indicates the analyzed location in the aluminum nitride crystal phase, and p10 indicates the analyzed location in the grain boundary phase. In Fig. 14, p8 and p9 indicate the analyzed locations in the aluminum nitride crystal phase, and p12 indicates the analyzed location where it was not possible to distinguish between the aluminum nitride crystal phase and the grain boundary phase. In Fig. 15, p11 indicates the analyzed location in the grain boundary phase.

[0136] [Table 3]

[0137] At three locations (p7, p8, and p9) in the aluminum nitride crystal phase shown in FIGS. 13 and 14, Eu was below the detection limit (0.01 mass%). The aluminum nitride phosphor ceramic according to Example 5 was excited by light from an excitation light source and emitted light, so it contained Eu, which serves as the luminescence center. However, the Eu contained in the aluminum nitride crystal phase was below the detection limit of EPMA. At two locations (p10 and p11) in the grain boundary phase shown in FIGS. 13 and 15, some grain boundary phases contained Eu, while others did not. It was presumed that a grain boundary phase composed of an oxide such as Al-ON-Eu had been formed in the grain boundary phase where Eu was detected. At two locations (p10 and p11) in the grain boundary phase in the backscattered electron images of the cross section of the aluminum nitride phosphor ceramic according to Example 5 shown in FIGS. 13 and 15, Y was not measured, and its concentration was below the detection limit (0.01 mass%). It was confirmed that Eu was detected at measurement point p12 in the backscattered electron image of the cross section of the aluminum nitride phosphor ceramic according to Example 5 shown in FIG. [Industrial Applicability]

[0138] The aluminum nitride phosphor ceramic according to this embodiment can be used in semiconductor packages. It can also be used in combination with a light-emitting element such as an LED or LD, which serves as an excitation light source, as a wavelength conversion material for lighting devices for automobiles or general lighting, or for backlights of liquid crystal display devices. It can also be used as an ultraviolet light detector. [Explanation of symbols]

[0139] 1: LED element, 2: substrate, 3, 13: aluminum nitride phosphor ceramic, 4, 14: light reflecting member, 5: wiring, 12: LD element, 15: package member, 16: submount, 100, 200: light emitting device.

Claims

1. Providing a precursor which is either a compact comprising aluminum nitride or a sintered body comprising aluminum nitride; and contacting the precursor with a gas containing europium to obtain an aluminum nitride phosphor ceramic having a europium content in the range of more than 0.03 mass % to 1.5 mass % or less.

2. 2. The method for producing a phosphor ceramic according to claim 1, wherein the step of obtaining the aluminum nitride phosphor ceramic comprises firing the precursor in an atmosphere containing europium at a temperature ranging from the boiling point of metallic europium to less than 2000°C.

3. 3. The method for producing a phosphor ceramic according to claim 2, wherein the step of obtaining the aluminum nitride phosphor ceramic comprises firing the precursor and a compound containing europium arranged so as not to come into direct contact with the precursor at a temperature in the range of not less than the boiling point of the metallic europium and less than 2000°C.

4. The amount of europium charged per 1 g of the precursor was 1.2 mg / cm ３ 12mg / cm or more ３ The method for producing a phosphor ceramic according to claim 1 , wherein the content of the phosphor ceramic is within the following range:

5. The method for producing a phosphor ceramic according to claim 1 , wherein the precursor is a sintered body containing the aluminum nitride.

6. the sintered body containing aluminum nitride contains oxygen, 6. The method for producing a phosphor ceramic according to claim 5, wherein the oxygen content is 0.3 mass % or less.

7. 7. The method for producing a phosphor ceramic according to claim 1, wherein the europium-containing gas is obtained by reducing europium oxide.

8. 8. The method for producing a phosphor ceramic according to claim 1, wherein the precursor is obtained by firing aluminum nitride particles and a sintering aid containing a rare earth element other than europium.

9. Preparing a phosphor ceramic manufactured by the manufacturing method according to any one of claims 1 to 8; providing an excitation light source; and disposing the phosphor ceramic at a position where it is irradiated with light emitted from the excitation light source.

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