Wavelength conversion sintered body and white light emitting element

Abstract

The present invention provides: a wavelength conversion sintered body which is capable of improving the luminous efficiency of white light and is capable of reducing the chromaticity difference with respect to radiation angle; and a white light emitting element. A wavelength conversion sintered body (10) comprises a phosphor material (11) represented by general formula Y3-x-yBaxAl5-xSixO12:Cey (wherein x + y < 3, 0 < x < 3, and 0 < y < 3), and fine particles (12) dispersed in the phosphor material (11). The fine particles (12) are composite oxides of Ba, Si, and Al.

Description

Wavelength conversion sintered body and white light emitting device

[0001] The present invention relates to a wavelength conversion sintered body and a white light emitting device.

[0002] Conventionally, white light sources that combine a YAG phosphor with a blue LED (Light Emitting Diode) chip have been widely known. However, as the brightness of light sources has increased, thermal quenching has occurred due to heat concentration caused by wavelength conversion (Stokes loss) in the YAG phosphor, resulting in a decrease in the efficiency of the white light source. Therefore, Ba-based light sources, which are made by dissolving Ba and Si in a solid solution in the YAG phosphor, have been developed. ａ Y ３－ａ－ｂ Al ５－ａ Si ａ O １２ : Ce ｂ A BS-YAG phosphor has been proposed (see Patent Document 1). This BS-YAG phosphor has the characteristics of having a higher wavelength conversion efficiency at high temperatures than general YAG phosphors, and also having a wider chromaticity range of emission wavelengths.

[0003] Japanese Patent Publication No. 2022-119163

[0004] Generally, blue light emitted by a blue LED chip has high directivity in the direction perpendicular to the chip surface, so a wavelength conversion member made of a YAG phosphor or a BS-YAG phosphor is attached to the chip surface. In the wavelength conversion member, the primary light, which is blue light that reaches the phosphor material, is wavelength-converted into secondary light, which is yellow light, and white light is irradiated as a mixture of the blue and yellow lights. In this case, the yellow light that has been wavelength-converted by the phosphor material has an isotropic Lambertian light distribution.

[0005] However, when the wavelength conversion material has high light transmittance, the blue light from the blue LED chip has high vertical directivity and is extracted vertically from the surface of the wavelength conversion material. In contrast, yellow light has a Lambertian light distribution and is easily guided laterally through the wavelength conversion material, which can lead to chromaticity differences in the white light depending on the radiation angle. Furthermore, the yellow light wavelength-converted by the phosphor material cannot be mixed well with the blue light, making it difficult to improve the luminous efficiency.

[0006] Therefore, the present invention has been made in consideration of the above-mentioned conventional problems, and aims to provide a wavelength conversion sintered body and a white light-emitting element that can improve the luminous efficiency of white light and reduce the chromaticity difference with respect to the normal incidence angle.

[0007] In order to solve the above problems, the wavelength-converting sintered body of the present invention has a structure represented by the general formula Y ３－ｘ－ｙ Ba ｘ Al ５－ｘ Si ｘ O １２ : Ce ｙ (where x+y<3, 0<x<3, 0<y<3) and fine particles dispersed in the phosphor material, wherein the fine particles are a composite oxide of Ba, Si, and Al.

[0008] In such a wavelength-converting sintered body of the present invention, fine particles of a composite oxide of Ba, Si, and Al are dispersed in the phosphor material, so that the secondary light wavelength-converted by the phosphor material is scattered by the fine particles, increasing the proportion of yellow light extracted from the surface, thereby improving the luminous efficiency of white light and reducing the chromaticity difference at normal angles.

[0009] In one aspect of the present invention, the fine particles are composited in the phosphor material.

[0010] In one embodiment of the present invention, the composite oxide is represented by the general formula BaAl ２ Si ｚ O ２ｚ＋４ (where z is a positive integer).

[0011] In one aspect of the present invention, the fine particles have an average particle size in the range of 0.1 μm to 5 μm.

[0012] In one aspect of the present invention, the content of the composite oxide is, in volume percentage, 1% or more and 5% or less of the wavelength-converting sintered body.

[0013] In one aspect of the present invention, the wavelength-converting sintered body is in the form of a plate having a thickness of 0.01 mm or more and 0.5 mm or less.

[0014] In order to solve the above problems, the present invention provides a white light-emitting device comprising any one of the wavelength conversion sintered bodies described above and a light-emitting diode that emits blue light.

[0015] The present invention can provide a wavelength conversion sintered body and a white light emitting device that can improve the luminous efficiency of white light and reduce the chromaticity difference with respect to normal incidence angles.

[0016] FIG. 1 is a schematic cross-sectional view illustrating the structure of a wavelength-converting sintered body 10 according to a first embodiment and a white light-emitting device 100 using the same. FIG. 2 is a schematic diagram illustrating a method for measuring the emitted color and luminous intensity of the white light-emitting device 100. FIG. 3 is a graph illustrating the chromaticity measurement results of the white light-emitting device 100 of the comparative example and Examples 1-5. FIG. 4 is a cross-sectional SEM image of the wavelength-converting sintered body 10 of Example 1. FIG. 5 is a graph illustrating the dependency of the luminous efficiency ratio of the white light-emitting device 100 on the complex oxide volume ratio. FIG. 6 is a graph illustrating the dependency of the luminous efficiency ratio of the white light-emitting device 100 on the plate thickness of the wavelength-converting sintered body 10. FIG. 7 is a graph illustrating the chromaticity measurement results of the white light-emitting device 100 using the comparative example and Examples 6-10.

[0017] (First Embodiment) A first embodiment of the present invention will be described in detail below with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing are denoted by the same reference numerals, and redundant descriptions will be omitted where appropriate. FIG. 1 is a schematic cross-sectional view illustrating the structure of a wavelength-converting sintered body 10 according to this embodiment and a white light-emitting device 100 using the same. As shown in FIG. 1, the white light-emitting device 100 according to this embodiment includes a wavelength-converting sintered body 10 and an LED chip 20 that is bonded to the wavelength-converting sintered body 10 and emits blue light. In the example shown in FIG. 1, the LED chip 20 is mounted on a reflector 30. The wavelength-converting sintered body 10 also includes a sintered phosphor material 11 and fine particles 12 dispersed in the phosphor material 11.

[0018] The wavelength-converting sintered body 10 includes a phosphor material 11 and microparticles 12 made of a composite oxide, and emits yellow light when excited by blue light. The wavelength-converting sintered body 10 is made of ceramic and sintered into a plate shape. The thickness of the plate-shaped wavelength-converting sintered body 10 is preferably in the range of 0.01 mm to 0.5 mm. If the thickness of the wavelength-converting sintered body 10 is thinner than the above-mentioned range, the mechanical strength of the wavelength-converting sintered body 10 will be insufficient, making it difficult to handle, which is undesirable. Furthermore, if the thickness of the wavelength-converting sintered body 10 is thicker than the above-mentioned range, the efficiency of wavelength conversion will decrease, which is undesirable. Hot isostatic pressing (HIP) can be used to form the wavelength-converting sintered body 10 into a ceramic plate.

[0019] The method for bonding the wavelength-converting sintered body 10 to the LED chip 20 is not limited, and a method of bonding the wavelength-converting sintered body 10 to the semiconductor layer (GaN) or growth substrate (sapphire) of the LED chip 20 by room temperature bonding can be used. Alternatively, an adhesive may be applied between the wavelength-converting sintered body 10 and the LED chip 20 to bond the wavelength-converting sintered body 10 and the LED chip 20.

[0020] The phosphor material 11 is represented by the general formula Y ３－ｘ－ｙ Ba ｘ Al ５－ｘ Si ｘ O １２ : Ce ｙ where x + y < 3, 0 < x < 3, and 0 < y < 3 are satisfied. Such phosphor material 11 is excited by blue light emitted by LED chip 20 and having a peak wavelength in the range of 430 nm to 480 nm, and emits yellow light having a peak wavelength of 530 nm to 580 nm. For simplicity, FIG. 1 illustrates an example in which a portion of phosphor material 11 is circled, but in fact most of the volume of wavelength-converting sintered body 10 is made up of phosphor material 11, and fine particles 12 are dispersed in continuous phosphor material 11.

[0021] The particles 12 are composed of a composite oxide of Ba, Si, and Al, and are particles that scatter light when dispersed in the phosphor material 11. Preferably, the particles 12 are composited in the phosphor material 11 and have the general formula BaAl ２ Siｚ O ２ｚ＋４ (where z is a positive integer). The particles 12 are formed by precipitating excess Ba, Si, and Al contained in the raw material as a composite oxide when sintering the phosphor material 11. There is no particular limitation on the method for precipitating the composite oxide as the particles 12. For example, a compound represented by the general formula Y ３－ｘ－ｙ Ba ｘ Al ５－ｘ Si ｘ O １２ : Ce ｙ , x + y < 3, 0 < x < 3, 0 < y < 3), and then sintering the phosphor material 11 expressed as follows: Ba, Si, and Al raw materials are increased in amounts approximately 1.01 to 1.06 times greater than the stoichiometric ratio for sintering the phosphor material 11 expressed as x + y < 3, 0 < x < 3, 0 < y < 3.

[0022] Furthermore, it is preferable that the average particle diameter of the particles 12 is in the range of 0.1 μm to 5 μm. If the average particle diameter of the particles 12 is smaller than the above range, it is difficult for light to be scattered due to the difference in refractive index at the interface between the particles 12 and the phosphor material 11, which is undesirable. If the average particle diameter of the particles 12 is larger than the above range, the light that reaches the particles 12 is blocked, which is undesirable as it reduces the luminous efficiency of the white light-emitting element 100.

[0023] The content of the composite oxide microparticles 12 contained in the wavelength-converting sintered body 10 is preferably 1% to 5% by volume of the wavelength-converting sintered body 10. If the content of the microparticles 12 is smaller than the above range, light scattering by the microparticles 12 is unlikely to occur, which is undesirable. On the other hand, if the content of the microparticles 12 is larger than the above range, light that reaches the microparticles 12 is blocked, which is undesirable as it reduces the luminous efficiency of the white light-emitting element 100.

[0024] The LED chip 20 is a semiconductor light-emitting element that emits blue light and corresponds to a light-emitting diode in the present invention. The LED chip 20 has an anode electrode (not shown) and a cathode electrode (not shown). When a voltage is applied to both electrodes, a current is injected and the LED chip 20 emits blue light. The LED chip 20 has a structure formed by stacking multiple semiconductor layers and has an internal light-emitting layer. The semiconductor material constituting the LED chip 20 is not limited, but a GaN-based semiconductor material having a band gap capable of emitting blue light can be used. The structure of the LED chip 20 is also not limited, and the LED chip 20 may have a known layer structure, such as a growth substrate, cladding layer, current diffusion layer, and contact layer.

[0025] The LED chip 20 emits blue light by radiative recombination in the light-emitting layer of the LED chip 20 due to the current injected into the LED chip 20. In this embodiment, the blue light emitted by the LED chip 20 has a peak wavelength in the range of 430 nm to 480 nm. The semiconductor material constituting the light-emitting layer of the LED chip 20 is not limited, but InGaN can be used as an example. The light-emitting layer may also have a known layer structure such as a quantum well structure, a multiple quantum well structure, or an overflow suppression layer.

[0026] The reflector 30 is a member that mounts the LED chip 20 and reflects light from the LED chip 20 and the wavelength-converting sintered body 10. The specific configuration of the reflector 30 is not limited, and it may be a resin plate with a reflective film formed on its surface, or a metal with a recess formed by processing. While FIG. 1 shows an example in which the LED chip 20 is mounted on the reflector 30, the LED chip 20 may be mounted directly on a wiring substrate or on a member such as a submount. When a submount substrate is used, it is preferable to use a material with good thermal conductivity, such as a single-crystal substrate such as AlN or Si, or a ceramic substrate. Furthermore, electrodes and wiring for supplying current to the LED chip 20 may be formed on the reflector 30 or the wiring substrate.

[0027] In the white light-emitting element 100 shown in FIG. 1 , blue light (primary light) emitted from the light-emitting layer of the LED chip 20 enters the wavelength-converting sintered body 10, and part of the blue light is wavelength-converted to yellow light (secondary light) in the phosphor material 11. The blue light that has not been wavelength-converted passes through the wavelength-converting sintered body 10 and is extracted from the top surface. The wavelength-converted yellow light spreads isotropically within the wavelength-converting sintered body 10 and travels not only upward but also sideways and downward. The yellow light that enters the composite oxide microparticles 12 is scattered due to the difference in refractive index with the phosphor material 11, increasing the amount of light traveling upward. This improves the luminous efficiency of the white light extracted upward from the white light-emitting element 10 and reduces color unevenness.

[0028] Comparative Example The wavelength-converting sintered body 10 according to the comparative example is a sintered body having a general formula Y ３－ｘ－ｙ Ba ｘ Al ５－ｘ Si ｘ O １２ : Ce ｙ The ceramic is made of a BS-YAG phosphor, which satisfies the following conditions: x+y<3, 0<x<3, 0<y<3. ２ O ３ (99.9% manufactured by Kojundo Kagaku Kenkyusho Co., Ltd.), CeO ２ (99.99% manufactured by Kojundo Kagaku Kenkyusho Co., Ltd.), BaCO ３ (Kanto Chemical Co., Ltd., 99.9%), α-Al ２ O ３ (manufactured by Kojundo Kagaku Kenkyusho Co., Ltd. 99.99%), SiO ２ (SE-8, 99.9% by Tokuyama Corporation) were prepared as powder raw materials. Each powder raw material was weighed out so as to have a molar ratio of Y:Ce:Ba:Al:Si=2.91:0.05:0.04:4.96:0.04, and mixed and pulverized in a mortar to obtain a mixed powder.

[0029] The resulting mixed powder was filled into a mold with a thickness of t = 1 mm and a diameter of 15 mm, and pressure was applied to obtain a primary compact. Next, using cold isostatic pressing (CIP), the primary compact was compression-molded at a molding pressure of 250 MPa to obtain a secondary compact. Next, the secondary compact was placed in an alumina crucible (Nikkato Corporation SSA-S B1) and heated at 1550 ° C for 4 hours in air. After cooling the secondary compact, it was further pressure-sintered for 2 hours using hot isostatic pressing (HIP) (Kobe Steel, Ltd. ultra-high pressure HIP apparatus) under conditions of an Ar atmosphere, 100 MPa, and 1550 ° C to obtain a plate-shaped ceramic translucent wavelength-converting sintered body 10. The obtained wavelength-converting sintered body 10 was polished to a thickness of 0.2 mm, cut into 1 mm square pieces, and bonded to an LED chip 20 at room temperature to obtain a white light-emitting element 100 of the comparative example.

[0030] Example 1 The wavelength-converting sintered body 10 according to Example 1 was a sintered body having a general formula Y ３－ｘ－ｙ Ba ｘ Al ５－ｘ Si ｘ O １２ : Ce ｙ and the BS-YAG phosphor satisfies the following conditions: x+y<3, 0<x<3, 0<y<3. ２ Si ２ O ８ The ceramic is a ceramic in which composite oxide fine particles 12 consisting of Y, Ce, Ba, Al, and Si are dispersed. A wavelength-converting sintered body 10 was obtained using the same manufacturing method as in the comparative example, except that the molar ratio of the powder raw materials was set to Y:Ce:Ba:Al:Si=2.91:0.05:0.07:5.02:0.10, and thus a white light-emitting device 100 of Example 1 was obtained.

[0031] Example 2 The wavelength-converting sintered body 10 according to Example 2 was a sintered body of the general formula Y ３－ｘ－ｙ Ba ｘ Al ５－ｘ Si ｘ O １２ : Ce ｙ and the BS-YAG phosphor satisfies the following conditions: x+y<3, 0<x<3, 0<y<3. ２ Si ２ O ８The ceramic is a ceramic in which composite oxide fine particles 12 consisting of Y, Ce, Ba, Al, and Si are dispersed. A wavelength-converting sintered body 10 was obtained using the same manufacturing method as in Example 1, except that the molar ratio of the powder raw materials was set to Y:Ce:Ba:Al:Si=2.91:0.05:0.05:4.98:0.06, and thus a white light-emitting device 100 of Example 2 was obtained.

[0032] Example 3 The wavelength-converting sintered body 10 according to Example 3 was a sintered body having a general formula Y ３－ｘ－ｙ Ba ｘ Al ５－ｘ Si ｘ O １２ : Ce ｙ and the BS-YAG phosphor satisfies the following conditions: x+y<3, 0<x<3, 0<y<3. ２ Si ２ O ８ The ceramic is a ceramic in which composite oxide fine particles 12 consisting of Y, Ce, Ba, Al, and Si are dispersed. A wavelength-converting sintered body 10 was obtained using the same manufacturing method as in Example 1, except that the molar ratio of the powder raw materials was set to Y:Ce:Ba:Al:Si=2.91:0.05:0.09:5.06:0.14, and thus a white light-emitting device 100 of Example 3 was obtained.

[0033] Example 4 A white light emitting device 100 of Example 4 was obtained in the same manner as in Example 1, except that the wavelength conversion sintered body 10 was polished to a thickness of 0.05 mm.

[0034] Example 5 A white light emitting device 100 of Example 5 was obtained in the same manner as in Example 1, except that the wavelength conversion sintered body 10 was polished to a thickness of 0.5 mm.

[0035] FIG. 2 is a schematic diagram illustrating a method for measuring the luminous color and luminous intensity of the white light-emitting element 100. As shown in FIG. 2, a measuring device (MCPD1000 manufactured by Otsuka Electronics Co., Ltd.) having a light-receiving unit 40 and a spectrometer 50 was used to measure the chromaticity and luminous intensity of the white light-emitting elements 100 of the comparative example and Examples 1-5 placed on a stage ST. The white light-emitting element 100 had the LED chip 20 facing the stage ST, and the wavelength-converting sintered body 10 facing the light-receiving unit 40. For the measurement, a current of 500 mA was applied to the white light-emitting element 100 for 10 minutes, and the light-receiving unit 40 was placed 5 cm above the center of the wavelength-converting sintered body 10. The relative luminous intensity, where the luminous intensity of the comparative example is taken as 1, was 1.1 for Example 1, 1.05 for Example 2, 1.00 for Example 3, 1.05 for Example 4, and 1.00 for Example 5.

[0036] FIG. 3 is a graph showing the chromaticity measurement results of the white light-emitting element 100 of the comparative example and examples 1-5. The measurement device and measurement method shown in FIG. 2 were used to measure the chromaticity. The solid-line frame shown in the graph indicates the chromaticity range of the vehicle headlight. All of examples 1-5 were within the chromaticity range of the vehicle headlight. In Table 1, the results of the chromaticity judgment of the comparative example, in which the chromaticity was outside the chromaticity range of the vehicle headlight, are indicated by "-", and the results of the chromaticity judgment of examples 1-5, in which the chromaticity was within the chromaticity range of the vehicle headlight, are indicated by "◯".

[0037] FIG. 4 is a cross-sectional SEM image of the wavelength conversion sintered body 10 of Example 1. The light gray portion in FIG. 4 is the phosphor material 11 made of BS-YAG, and the dark gray portion dispersed in the phosphor material 11 is the fine particles 12 made of a composite oxide of Ba, Si, and Al. Thirty fine particles 12 were randomly selected from this cross-sectional SEM image, and their particle sizes were measured. The particle sizes were 0.1 μm or more and 5 μm or less. Furthermore, when the fine particles 12 were analyzed using an energy-dispersive X-ray fluorescence analysis (EDX: Energy-dispersive X-ray spectroscopy) device, it was found that the fine particles 12 were BaAl ２ Si ２ O ８ Furthermore, EDX analysis revealed that the phosphor material 11 was made of BS-YAG and the phosphor material 12 was made of BaAl ２ Si ２ O８ The molar ratio of the particles 12 consisting of BaAl: (number of moles of particles) / {(number of moles of phosphor)+(number of moles of particles)} and the weight ratio of the particles: (weight of particles) / {(weight of phosphor)+(weight of particles)} were calculated. ２ Si ２ O ８ Based on the specific gravity of 3.37 of the phosphor and the specific gravity of the BS-YAG phosphor (4.55), the volume percentage of the microparticles 12 in the wavelength-converting sintered body 10, i.e., the volume ratio: (volume of microparticles) / {(volume of phosphor)+(volume of microparticles)} was calculated.

[0038] Table 1 shows the results of the molar ratio, weight ratio, volume ratio, plate thickness, luminous efficiency ratio, and chromaticity evaluation of the particles 12 in the comparative example and Examples 1 to 5.

[0039] FIG. 5A is a graph showing the dependence of the luminous efficiency ratio of the white light-emitting element 100 on the volume ratio of the complex oxides, and FIG. 5B is a graph showing the dependence of the luminous efficiency ratio of the white light-emitting element 100 on the plate thickness of the wavelength-converting sintered body 10.

[0040] The horizontal axis of Fig. 5A shows the volume ratio of microparticles 12 in wavelength conversion sintered body 10, and the vertical axis shows the relative luminous efficiency when the luminous intensity of the comparative example is set to 1. In Fig. 5A, the measurement results of Examples 1-3 are plotted to form an approximate curve, and the luminous efficiency is improved compared to BS-YAG alone when the volume ratio of the composite oxide is in the range of 0.01 to 0.05 (volume percentage is in the range of 1% to 5%).

[0041] 5B, the horizontal axis represents the plate thickness of the polished wavelength conversion sintered body 10, and the vertical axis represents the relative luminous efficiency when the luminous intensity of the comparative example is set to 1. In FIG. 5B, the measurement results of Examples 1, 4, and 5 are plotted to form an approximate curve, and the luminous efficiency is improved compared to BS-YAG alone in the plate thickness range of 0.05 mm or more and 0.5 mm or less.

[0042] Example 6 The wavelength-converting sintered body 10 according to Example 6 was a sintered body having a general formula Y ３－ｘ－ｙ Ba ｘ Al ５－ｘ Si ｘ O １２ : Ce ｙand the BS-YAG phosphor satisfies the following conditions: x+y<3, 0<x<3, 0<y<3. ２ SiO ６ The ceramic is a ceramic in which composite oxide fine particles 12 consisting of Y, Ce, Ba, Al, and Si are dispersed. A wavelength-converting sintered body 10 was obtained using the same manufacturing method as in Example 1, except that the molar ratio of the powder raw materials was set to Y:Ce:Ba:Al:Si=2.91:0.05:0.07:5.02:0.07, and thus a white light-emitting device 100 of Example 6 was obtained.

[0043] Example 7 The wavelength-converting sintered body 10 according to Example 7 was a sintered body having a general formula Y ３－ｘ－ｙ Ba ｘ Al ５－ｘ Si ｘ O １２ : Ce ｙ and the BS-YAG phosphor satisfies the following conditions: x+y<3, 0<x<3, 0<y<3. ２ SiO ６ The ceramic is a ceramic in which composite oxide fine particles 12 consisting of Y, Ce, Ba, Al, and Si are dispersed. A wavelength-converting sintered body 10 was obtained using the same manufacturing method as in Example 1, except that the molar ratio of the powder raw materials was set to Y:Ce:Ba:Al:Si=2.91:0.05:0.05:4.98:0.05, and thus a white light-emitting device 100 of Example 7 was obtained.

[0044] Example 8 The wavelength-converting sintered body 10 according to Example 8 was a sintered body having a general formula Y ３－ｘ－ｙ Ba ｘ Al ５－ｘ Si ｘ O １２ : Ce ｙ and the BS-YAG phosphor satisfies the following conditions: x+y<3, 0<x<3, 0<y<3. ２ SiO ６ The ceramic is a ceramic in which composite oxide fine particles 12 consisting of Y, Ce, Ba, Al, and Si are dispersed. A wavelength-converting sintered body 10 was obtained using the same manufacturing method as in Example 1, except that the molar ratio of the powder raw materials was set to Y:Ce:Ba:Al:Si=2.91:0.05:0.10:5.08:0.10, and thus a white light-emitting device 100 of Example 8 was obtained.

[0045] Example 9 A white light emitting device 100 of Example 9 was obtained in the same manner as in Example 6, except that the wavelength conversion sintered body 10 was polished to a thickness of 0.05 mm.

[0046] Example 10 A white light emitting device 100 of Example 10 was obtained in the same manner as in Example 6, except that the wavelength conversion sintered body 10 was polished to a thickness of 0.5 mm.

[0047] As in Examples 1-5, the chromaticity and luminous intensity of the white light-emitting elements 100 of Examples 6-10 were measured using the measuring device shown in Fig. 2. The relative luminous intensity, assuming that the luminous intensity of the comparative example was 1, was 1.1 for Example 6, 1.05 for Example 7, 1.00 for Example 8, 1.05 for Example 9, and 1.00 for Example 10.

[0048] 6 is a graph showing the chromaticity measurement results of the white light-emitting element 100 using the comparative example and examples 6-10. The measurement device and measurement method shown in FIG. 2 were used for measuring the chromaticity. The solid line frame shown in the graph indicates the chromaticity range of the vehicle headlight. All of examples 6-10 were within the chromaticity range of the vehicle headlight.

[0049] Similarly to Examples 1-5, cross-sectional SEM images of the wavelength-converting sintered bodies 10 of Examples 6-10 were taken (not shown). Thirty particles 12 were randomly selected from the cross-sectional SEM images, and the particle sizes were measured. The particle sizes were found to be 0.1 μm or more and 5 μm or less. Furthermore, energy dispersive X-ray spectroscopy (EDX analysis) revealed that the particles 12 of Examples 6-10 were BaAl ２ SiO ６ Furthermore, EDX analysis revealed that the phosphor material 11 was made of BS-YAG and the phosphor material 12 was made of BaAl ２ SiO ６ The molar ratio of the particles 12 consisting of BaAl: (number of moles of particles) / {(number of moles of phosphor)+(number of moles of particles)} and the weight ratio of the particles: (weight of particles) / {(weight of phosphor)+(weight of particles)} were calculated. ２ SiO ６ Based on the specific gravity of the microparticles (2.38) and the specific gravity of the BS-YAG phosphor (4.55), the volume percentage of the microparticles 12 in the wavelength-converting sintered body 10, i.e., the volume ratio: (volume of microparticles) / {(volume of phosphor)+(volume of microparticles)} was calculated.

[0050] The molar ratio, weight ratio, volume ratio, plate thickness, luminous efficiency ratio, and chromaticity evaluation results of the microparticles 12 in the comparative example and examples 6-10 are shown in Table 2. In Table 2, the results of the chromaticity evaluation of the comparative example, in which the chromaticity was outside the chromaticity range of the vehicle headlight, are indicated by "-", and the results of the chromaticity evaluation of examples 6-10, in which the chromaticity was within the chromaticity range of the vehicle headlight, are indicated by "◯".

[0051] As described above, in the wavelength conversion sintered body 10 and white light emitting element 100 of the present invention, the fine particles 12 which are a composite oxide of Ba, Si, and Al are dispersed in the phosphor material 11, so that the secondary light wavelength-converted by the phosphor material 11 is scattered by the fine particles 12, increasing the proportion of yellow light extracted from the surface, thereby improving the luminous efficiency of white light and reducing the chromaticity difference with respect to the normal angle of incidence.

[0052] Second Embodiment Next, a second embodiment of the present invention will be described. Details that overlap with those of the first embodiment will not be described. In the first embodiment, an example was shown in which the plate-shaped wavelength-converting sintered body 10 was bonded to the LED chip 20 at room temperature. However, the plate-shaped wavelength-converting sintered body 10 may be disposed at a distance from the LED chip 20.

[0053] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0054] This application claims priority based on Japanese Patent Application No. 2024-095304, filed June 12, 2024, the contents of which are incorporated herein by reference.

Claims

1. General formula Y ３－ｘ－ｙ Ba ｘ Al ５－ｘ Si ｘ O １２ : Ce ｙ (where x+y<3, 0<x<3, 0<y<3) and fine particles dispersed in the phosphor material, wherein the fine particles are a composite oxide of Ba, Si, and Al.

2. A wavelength-converting sintered body according to claim 1, characterized in that the fine particles are composited in the phosphor material.

3. The wavelength converting sintered body according to claim 1, wherein the composite oxide has the general formula BaAl ２ Si ｚ O ２ｚ＋４ (where z is a positive integer).

4. A wavelength-converting sintered body according to claim 1, wherein the fine particles have an average particle size in the range of 0.1 μm to 5 μm.

5. A wavelength-converting sintered body according to claim 1, characterized in that the content of said composite oxide is, in volume percentage, 1% or more and 5% or less of the wavelength-converting sintered body.

6. The wavelength-converting sintered body according to claim 1, characterized in that it is in the form of a plate having a thickness of 0.01 mm or more and 0.5 mm or less.

7. A white light emitting device comprising the wavelength conversion sintered body according to any one of claims 1 to 6 and a light emitting diode that emits blue light.

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