Wavelength conversion sintered body and white light-emitting element

Abstract

The present invention provides a wavelength-converting sintered body and a white light-emitting element that can improve the luminescence efficiency of white light and reduce color unevenness. [Solution] General formula Y 3-x-y Ba x Al 5-x Si x O 12 :Ce y A wavelength conversion sintered body (10) characterized by having a phosphor material (11) represented by (where x+y<3, x<5, x>0, y>0) and voids (12) dispersed in the phosphor material (11).

Description

[Technical Field]

[0001] The present invention relates to a wavelength conversion sintered body and a white light-emitting element. [Background technology]

[0002] Conventionally, white light sources combining YAG phosphors and blue LED (Light Emitting Diode) chips have been widely known. However, with the increasing brightness of light sources, thermal quenching occurs due to heat concentration caused by wavelength conversion (Stokes loss) in the YAG phosphor, leading to a decrease in the efficiency of the white light source. Therefore, a YAG phosphor with Ba and Si solid solution was developed. 3-x-y Ba x Al 5-x Si x O 12 :Ce y (BS-YAG) phosphors have been proposed (see Patent Document 1). These BS-YAG phosphors have higher wavelength conversion efficiency at high temperatures and a wider chromaticity range of emission wavelengths than general YAG phosphors. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-119163 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Generally, blue light emitted from a blue LED chip has high directivity in the direction perpendicular to the chip surface. Therefore, wavelength conversion members made of YAG phosphors or BS-YAG phosphors are 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 to secondary light, which is yellow light, and white light is irradiated by the mixture of blue and yellow light. At this time, the yellow light wavelength-converted by the phosphor material has an isotropic Lambertsian light distribution.

[0005] However, when the light transmittance of the wavelength conversion member is high, the blue light from the blue LED chip has a high directivity in the vertical direction and is also extracted vertically from the surface of the wavelength conversion member. On the other hand, the yellow light has a Lambertian light distribution and is likely to be guided laterally in the wavelength conversion member, resulting in a problem that color unevenness is likely to occur in the white light depending on the emission angle. In addition, it was difficult to improve the luminous efficiency because the yellow light wavelength-converted by the phosphor material could not be well mixed with the blue light.

[0006] Therefore, the present invention has been made in view of the above conventional problems, and an object thereof is to provide a wavelength conversion sintered body and a white light emitting device capable of improving the luminous efficiency of white light and reducing color unevenness.

Means for Solving the Problems

[0007] In order to solve the above problems, the wavelength conversion sintered body of the present invention is a phosphor material represented by the general formula Y 3-x-y Ba x Al 5-x Si x O 12 :Ce y (where x + y < 3, x < 5, x > 0, y > 0), and is characterized by having voids dispersed in the phosphor material.

[0008] In such a wavelength conversion sintered body of the present invention, since voids are dispersed in the BS-YAG phosphor, the secondary light wavelength-converted by the phosphor material is scattered by the voids, increasing the ratio of the yellow light extracted from the surface, improving the luminous efficiency of the white light, and reducing color unevenness.

[0009] In addition, in one aspect of the present invention, the voids have an average particle size in the range of 0.01 μm or more and 0.5 μm or less.

[0010] In addition, in one aspect of the present invention, the content of the voids is in the range where the area ratio on the surface of the wavelength conversion sintered body is greater than 0.1% and 1.5% or less.

[0011] Also, in one aspect of the present invention, it is formed into a plate shape and has a thickness in the range of 0.01 mm or more and 0.5 mm or less.

[0012] Further, in order to solve the above problems, the white light emitting device of the present invention is characterized in that any one of the above wavelength conversion sintered bodies is bonded to a light emitting diode that emits blue light.

Advantages of the Invention

[0013] In the present invention, it is possible to provide a wavelength conversion sintered body and a white light emitting device capable of improving the luminous efficiency of white light and reducing color unevenness.

Brief Description of the Drawings

[0014] [Figure 1] It is a schematic cross-sectional view for explaining the structure of the wavelength conversion sintered body 10 according to the first embodiment and the white light emitting device 100 using the same. [Figure 2] It is a surface SEM image of the wavelength conversion sintered body 10 in Example 1. [Figure 3] It is a schematic diagram for explaining the method of measuring the emission color and emission intensity of the white light emitting device 100. [Figure 4] It is a graph showing the dependence of the relative emission intensity on the area ratio of voids in the white light emitting device 100. [Figure 5] It is a graph showing the dependence of the relative emission intensity on the plate thickness in the white light emitting device 100.

Modes for Carrying Out the Invention

[0015] (First Embodiment) Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing will be denoted by the same reference numerals, and redundant explanations will be omitted as appropriate. Figure 1 is a schematic cross-sectional view illustrating the structure of the wavelength conversion sintered body 10 and the white light-emitting element 100 using the same according to this embodiment. As shown in Figure 1, in the white light-emitting element 100 according to this embodiment, the wavelength conversion sintered body 10 is bonded to the upper surface of the LED chip 20. In the example shown in Figure 1, the LED chip 20 is mounted on the reflective portion 30. The wavelength conversion sintered body 10 also has a sintered phosphor material 11 and voids 12 dispersed in the phosphor material 11.

[0016] The wavelength conversion sintered body 10 has a phosphor material 11 and voids 12, and is the part that emits yellow light when excited by blue light. The wavelength conversion sintered body 10 is made of ceramic and formed by sintering it into a plate shape. The thickness of the plate-shaped wavelength conversion sintered body 10 is preferably in the range of 0.01 mm to 0.5 mm. If the thickness of the wavelength conversion sintered body 10 is thinner than the above range, the mechanical strength of the wavelength conversion sintered body 10 will be insufficient and handling will deteriorate, which is undesirable. Also, if the thickness of the wavelength conversion sintered body 10 is thicker than the above range, the efficiency of wavelength conversion will decrease, which is undesirable. As a method for forming the wavelength conversion sintered body 10 as a ceramic plate, hot isostatic pressing (HIP) can be used.

[0017] The method for bonding the wavelength conversion sintered body 10 to the LED chip 20 is not limited, and a method of bonding the wavelength conversion 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 conversion sintered body 10 and the LED chip 20 to bond them together.

[0018] The phosphor material 11 has the general formula Y 3-x-y Ba x Al 5-x Si x O 12 :Ce yIt is expressed as such that x+y<3, x<5, x>0, and y>0. Such a phosphor material 11 is excited by blue light with a peak wavelength in the range of 430nm to 480nm emitted from the LED chip 20, and emits yellow light with a peak wavelength of 530nm to 580nm. In Figure 1, for simplicity, a part of the phosphor material 11 is shown enclosed in a circle, but the majority of the volume of the wavelength conversion sintered body 10 is composed of the phosphor material 11, and voids 12 are dispersed in the continuous phosphor material 11.

[0019] The voids 12 are spaces (voids) dispersed within the phosphor material 11 that do not contain the phosphor material 11. The average particle size and content of the voids 12 in the phosphor material 11 can be adjusted by changing the sintering conditions during the sintering process. The method for dispersing the voids 12 in the phosphor material 11 is not limited, but one example is to increase the content by reducing the pressure in the hot isostatic pressing method.

[0020] Furthermore, it is preferable that the average particle size of the void 12 is in the range of 0.01 μm to 0.5 μm. If the average particle size of the void 12 is smaller than the above range, it is undesirable because light scattering due to the difference in refractive index at the interface between the void 12 and the phosphor material 11 is difficult to occur. Also, if the average particle size of the void 12 is larger than the above range, the light that reaches the void 12 is blocked, which is undesirable because the luminescence efficiency of the white light-emitting element 100 decreases.

[0021] The amount of voids 12 contained within the wavelength-converting sintered body 10 is preferably in the range of greater than 0.1% and less than or equal to 1.5% in terms of area ratio on the surface of the wavelength-converting sintered body 10. If the area ratio of voids 12 is smaller than the above range, light scattering in the voids 12 is less likely to occur, which is undesirable. Also, if the area ratio of voids 12 is larger than the above range, the light that reaches the voids 12 is blocked, which is undesirable as it reduces the luminous efficiency of the white light-emitting element 100.

[0022] 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) formed thereon, and by applying a voltage to both electrodes, a current is injected and blue light is emitted. The LED chip 20 has a structure formed by stacking multiple semiconductor layers and has a light-emitting layer inside. The semiconductor material constituting the LED chip 20 is not limited, but a GaN-based semiconductor material with a band gap capable of emitting blue light can be used. Furthermore, the structure of the LED chip 20 is not limited and may have known layer structures such as a growth substrate, cladding layer, current diffusion layer, and contact layer.

[0023] The LED chip 20 emits blue light when the current injected into the LED chip 20 undergoes light recombination in the light-emitting layer. In this embodiment, the blue light emitted by the LED chip 20 has a peak wavelength in the range of blue light between 430 nm and 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 known layer structures such as a quantum well structure, a multiple quantum well structure, or an overflow suppression layer.

[0024] The reflective section 30 is a component that mounts the LED chip 20 and reflects light from the LED chip 20 and the wavelength conversion sintered body 10. The specific configuration of the reflective section 30 is not limited; it may be a resin plate with a reflective film formed on its surface, or it may be made by processing metal to form a recess. Figure 1 shows an example in which the LED chip 20 is mounted on the reflective section 30. The LED chip 20 may also be directly mounted on a wiring board or the like, or mounted on a component such as a submount. When using a submount substrate, it is preferable to use a material with good thermal conductivity, and as an example, single crystal substrates such as AlN or Si, or ceramic substrates can be used. In addition, electrodes and wiring for supplying current to the LED chip 20 may be formed on the reflective section 30 and the wiring board.

[0025] In the white light-emitting element 100 shown in Figure 1, blue light (primary light) emitted from the light-emitting layer of the LED chip 20 is incident on the wavelength-converting sintered body 10 (solid arrow in the figure). The primary light that reaches the wavelength-converting sintered body 10 is partially converted to yellow light (secondary light) by the phosphor material 11 (dashed arrow in the figure). The blue light that is not converted is transmitted through the wavelength-converting sintered body 10 and extracted from the top surface. The converted yellow light spreads isotropically within the wavelength-converting sintered body 10, propagating not only upwards but also to the sides and downwards. The yellow light incident on the void 12 is scattered by the refractive index difference with the phosphor material 11, increasing the amount of light that propagates upwards. This improves the luminescence efficiency of the white light extracted from the top of the white light-emitting element 100 and also improves color uniformity.

[0026] (Comparative example) The wavelength conversion sintered body 10 in the comparative example is based on the general formula Y 3-x-y Ba x Al 5-x Si x O 12 :Ce y This ceramic is made of a BS-YAG phosphor that satisfies x+y<3, x<5, x>0, and y>0. First, powdered raw materials of Y2O3 (99.9% from Kojunkagaku Kenkyusho Co., Ltd.), CeO2 (99.99% from Kojunkagaku Kenkyusho Co., Ltd.), BaCO3 (99.9% from Kanto Kagaku Co., Ltd.), α-Al2O3 (99.99% from Kojunkagaku Kenkyusho Co., Ltd.), and SiO2 (SE-8, 99.9% from Tokuyama Corporation) were prepared. Then, each powdered raw material was weighed to have a molar ratio of Y:Ce:Ba:Al:Si = 2.91:0.05:0.04:4.96:0.04, and mixed and ground in a mortar to obtain a mixed powder.

[0027] The obtained mixed powder was filled into a mold with a thickness of t=1 mm and a diameter of φ15 mm, and pressure was applied to obtain a primary molded body. Next, using CIP, the primary molded body was compression molded at a molding pressure of 250 MPa to obtain a secondary molded body. Then, the secondary molded body was placed in an alumina container (Nikkatoh SSA-S B1) and heated in air at 1550°C for 10 hours. After the secondary molded body cooled, it was placed in a carbon container and further pressure sintered for 2 hours using HIP (Kobe Steel ultra-high pressure HIP device) under conditions of Ar atmosphere, 150 MPa, and 1550°C to obtain a translucent wavelength conversion sintered body 10 made of plate-shaped ceramic. The obtained wavelength conversion sintered body 10 was polished to a thickness of 0.2 mm, cut into a square of 1 mm, and bonded to an LED chip 20 at room temperature to obtain a comparative example white light-emitting element 100.

[0028] (Example 1) The wavelength conversion sintered body 10 according to Example 1 is based on the general formula Y 3-x-y Ba x Al 5-x Si x O 12 :Ce y The ceramic is represented by a BS-YAG phosphor satisfying x+y<3, x<5, x>0, and y>0, in which voids 12 made of BaAl2Si2O8 are dispersed. A wavelength conversion sintered body 10 was obtained using the same manufacturing method as the comparative example, except that the HIP conditions were 125 MPa and 1550°C for 2 hours of pressure sintering, and the white light-emitting element 100 of Example 1 was obtained.

[0029] (Example 2) The wavelength conversion sintered body 10 according to Example 2 is based on the general formula Y 3-x-y Ba x Al 5-x Si x O 12 :Ce y The ceramic is represented by a BS-YAG phosphor satisfying x+y<3, x<5, x>0, and y>0, in which voids 12 made of BaAl2Si2O8 are dispersed. A wavelength conversion sintered body 10 was obtained using the same manufacturing method as the comparative example, except that the HIP conditions were 100 MPa and 1550°C for 2 hours of pressure sintering, and the white light-emitting element 100 of Example 2 was obtained.

[0030] (Example 3) The wavelength conversion sintered body 10 according to Example 3 is based on the general formula Y 3-x-y Ba x Al 5-x Si x O 12 :Ce y The ceramic is represented by a BS-YAG phosphor satisfying x+y<3, x<5, x>0, and y>0, in which voids 12 made of BaAl2Si2O8 are dispersed. A wavelength conversion sintered body 10 was obtained using the same manufacturing method as the comparative example, except that the HIP conditions were 75 MPa and 1550°C for 2 hours of pressure sintering, and the white light-emitting element 100 of Example 3 was obtained.

[0031] (Example 4) The wavelength conversion sintered body 10 according to Example 4 is based on the general formula Y 3-x-y Ba x Al 5-x Si x O 12 :Ce y The ceramic is represented by a BS-YAG phosphor satisfying x+y<3, x<5, x>0, and y>0, in which voids 12 made of BaAl2Si2O8 are dispersed. A wavelength conversion sintered body 10 was obtained using the same manufacturing method as the comparative example, except that the HIP conditions were 50 MPa and 1550°C for 2 hours of pressure sintering, and the white light-emitting element 100 of Example 4 was obtained.

[0032] (Example 5) The white light-emitting element 100 of Example 5 was obtained in the same manner as in Example 3, except that the wavelength-converting sintered body 10 was polished to a thickness of 0.5 mm.

[0033] (Example 6) The white light-emitting element 100 of Example 6 was obtained in the same manner as in Example 3, except that the wavelength-converting sintered body 10 was polished to a thickness of 0.05 mm.

[0034] The surface of the wavelength conversion sintered bodies 10 obtained in the comparative examples and Examples 1 to 6 described above was mirror-polished and annealed for 2 hours at 1270°C in air. For mirror polishing, the surfaces were roughly polished using water-resistant abrasive paper #400, #800, and #1200 manufactured by IMT Co., Ltd. at 150 rpm × 20 N each, and then polished with artificial polycrystalline diamond of 9 μm, 3 μm, and 1 μm manufactured by Harzock Japan Co., Ltd. at 150 rpm × 20 N each. Figure 2 is a surface SEM image of the wavelength conversion sintered body 10 in Example 1. As shown in Figure 2, it can be confirmed that multiple black voids 12 are dispersed between the phosphor material 11. When 30 voids 12 were arbitrarily selected from this surface SEM image and their particle size was measured, the particle size was found to be between 0.01 μm and 0.5 μm.

[0035] The polished surface of the wavelength-converting sintered body 10 was observed using SEM, and void 12 image analysis was performed on the 2000x observation surface to calculate the area ratio of voids 12 in the wavelength-converting sintered body 10 and obtain the content (void ratio). The obtained content (void ratio) was 0.1% for the comparative example, 0.3% for Example 1, 0.5% for Example 2, 1.0% for Example 3, 1.5% for Example 4, 1.0% for Example 5, and 1.0% for Example 6.

[0036] Figure 3 is a schematic diagram illustrating the method for measuring the emission color and emission intensity of a white light-emitting element 100. As shown in Figure 3, in this embodiment, 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 emission intensity of the white light-emitting element 100 placed on a stage ST. The white light-emitting element 100 was positioned with the LED chip 20 facing the stage ST and the wavelength conversion 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 at a distance of 5 cm directly above the center of the wavelength conversion sintered body 10. The relative emission intensities, with the emission intensity of Example 1 set to 1, were 0.98 for the comparative example, 1.1 for Example 2, 1.12 for Example 3, 1.06 for Example 4, 1.01 for Example 5, and 1.05 for Example 6.

[0037] Table 1 shows the void content (void ratio), plate thickness, luminescence intensity ratio, and chromaticity determination results for the comparative example and Examples 1-6. [Table 1]

[0038] Figure 4 is a graph showing the dependence of the relative luminescence intensity on the void area ratio in the white light-emitting element 100. The horizontal axis of Figure 4 shows the void content (void ratio) of voids 12 in the wavelength-converting sintered body 10, and the vertical axis shows the relative luminescence efficiency when the luminescence intensity of Example 1 is set to 1. In Figure 4, the measurement results using the white light-emitting element 100 of Comparative Example 1, which was polished to a plate thickness of 0.2 mm, and Examples 1-4 are plotted to create an approximate curve, showing that the luminescence intensity improves when the void content of voids 12 is greater than 0.1% and less than or equal to 1.5%.

[0039] Figure 5 is a graph showing the plate thickness dependence of the relative luminescence intensity in the white light-emitting element 100. The horizontal axis of Figure 5 represents the plate thickness of the polished wavelength-converting sintered body 10, and the vertical axis represents the relative luminescence efficiency when the luminescence intensity of the comparative example is set to 1. In Figure 5, the measurement results using the white light-emitting element 100 of Examples 3, 5, and 6, in which the void content 12 is 1%, are plotted and an approximation curve is drawn, showing that the luminescence intensity improves in the plate thickness range of 0.01 mm to 0.5 mm.

[0040] As described above, in the wavelength-converting sintered body 10 and white light-emitting element 100 of the present invention, the voids 12 are dispersed in the phosphor material 11, which scatters the secondary light whose wavelength has been converted by the phosphor material 11 in the voids 12, increasing the proportion of yellow light extracted from the surface, thereby improving the luminescence efficiency of white light and reducing color unevenness.

[0041] (Second Embodiment) Next, a second embodiment of the present invention will be described. Details that overlap with the first embodiment will be omitted. In the first embodiment, an example was shown in which a plate-shaped wavelength conversion sintered body 10 was bonded to an LED chip 20 at room temperature. However, the plate-shaped wavelength conversion sintered body 10 may be placed at a distance from the LED chip 20.

[0042] The present invention is not limited to the embodiments described above, 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. [Explanation of Symbols]

[0043] 100... White light-emitting element 10...Wavelength conversion sintered body 11…Phosphor materials 12...Void 20…LED chips 30…Reflector 40...Light receiving section 50...Spectrometer

Claims

1. General formula Y ３－ｘ－ｙ Ba ｘ Al ５－ｘ Si ｘ O １２ : Ce ｙ (Here, the range satisfies x + y < 3, x < 5, x > 0, y > 0) A phosphor material represented by, A wavelength conversion sintered body characterized by having voids dispersed in the phosphor material.

2. A wavelength conversion sintered body according to claim 1, The wavelength conversion sintered body is characterized in that the void has an average particle size in the range of 0.01 μm to 0.5 μm.

3. A wavelength conversion sintered body according to claim 1, The wavelength conversion sintered body is characterized in that the content of the voids is in the range of greater than 0.1% and less than or equal to 1.5% in terms of area ratio on the surface of the wavelength conversion sintered body.

4. A wavelength conversion sintered body according to claim 1, A wavelength conversion sintered body characterized by being formed into a plate shape and having a thickness in the range of 0.01 mm to 0.5 mm.

5. A wavelength conversion sintered body according to any one of claims 1 to 4, A white light-emitting element characterized by having light-emitting diodes that emit blue light bonded to it.

Images