Wavelength conversion member and white light-emitting element

Abstract

A wavelength conversion member (3) has a phosphor material represented by the general formula (BaxLuzY3-x-y-z)(Al5-xSix)O12:Cey (where x + y + z < 3, x < 3, x > 0, y > 0, z > 0) with a cubic garnet crystal structure with a Ia3d space group.

Description

Wavelength conversion member and white light emitting element

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

[0002] Conventionally, white light sources that combine YAG phosphors with blue LEDs 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, YAG phosphors that are solid-solubilized with Ba and Si have been developed. ３－ｘ－ｙ Ba ｘ Al ５－ｘ Si ｘ O １２ : Ce ｙ (BS-YAG) phosphors have been proposed (see Patent Documents 1 and 2, etc.). These BS-YAG phosphors have the advantages of higher wavelength conversion efficiency at high temperatures and a wider chromaticity range of emission wavelengths than general YAG phosphors.

[0003] International Publication No. 2022 / 168879 Japanese Patent Application Laid-Open No. 2023-144855

[0004] Generally, high-speed on / off operations are required for white light sources used in backlights of image display devices such as liquid crystal display devices, projectors, etc. However, since white light sources using BS-YAG phosphors have a longer emission life than general YAG phosphors, it has been difficult to meet the demand for faster on / off operations.

[0005] The present invention has been made in consideration of the above-mentioned conventional problems, and has an object to provide a wavelength conversion member and a white light emitting element that have a short light emitting life and good wavelength conversion efficiency at high temperatures.

[0006] In order to solve the above problems, the wavelength conversion member of the present invention has a garnet structure with a cubic crystal system and a space group Ia3d, and is represented by the general formula (Ba ｘ Lu ｚ Y ３－ｘ－ｙ－ｚ ) (Al ５－ｘ Si ｘ ) O １２ : Ce ｙ(where x+y+z<3, x<3, x>0, y>0, z>0)

[0007] Such a wavelength conversion member of the present invention has a garnet structure with a cubic crystal system and a space group Ia3d, and is represented by the general formula (Ba ｘ Lu ｚ Y ３－ｘ－ｙ－ｚ ) (Al ５－ｘ Si ｘ ) O １２ : Ce ｙ (where x+y+z<3, x<3, x>0, y>0, z>0) is satisfied, the light-emitting lifetime is short and the wavelength conversion efficiency at high temperatures is good.

[0008] In one embodiment of the present invention, the range of z is 0.04 or more and 0.12 or less.

[0009] In one embodiment of the present invention, the electrode is formed in a plate shape and has a thickness in the range of 0.02 mm to 0.6 mm.

[0010] In one aspect of the present invention, the phosphor material is made of a single crystal plate.

[0011] In one aspect of the present invention, the phosphor material is made of a ceramic plate.

[0012] In one embodiment of the present invention, the element is excited by blue light having a peak wavelength in the range of 430 nm to 480 nm and emits yellow light.

[0013] In one embodiment of the present invention, the emission lifetime at a dominant wavelength of 569 nm is 61 ns or less.

[0014] In order to solve the above problems, the white light emitting element of the present invention is characterized in that any one of the wavelength conversion members described above and a light emitting diode that emits blue light are bonded together at room temperature.

[0015] The present invention can provide a wavelength conversion member and a white light emitting device that have a short light emitting lifetime and good wavelength conversion efficiency at high temperatures.

[0016] FIG. 1 is a schematic cross-sectional view illustrating the structure of a white light emitting element 10 according to a first embodiment. FIG. 2 is a graph showing the results of using an X-ray diffraction device on wavelength conversion member 3 of Example 1. FIG. 3 is a graph showing the emission spectrum of Example 1. FIG. 4 is a graph showing the temperature dependence of wavelength conversion efficiency in each Example and Comparative Example. FIG. 5 is a graph showing the results of luminescence lifetime measurement of Example 6. FIG. 6 is a graph showing the results of using an X-ray diffraction device on wavelength conversion member 3 of Example 7. FIG. 7 is a graph showing the emission spectrum of Example 7. FIG. 8 is a graph showing the results of luminescence lifetime measurement of Example 11.

[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 will be denoted by the same reference numerals, and redundant description will be omitted where appropriate. FIG. 1 is a schematic cross-sectional view illustrating the structure of a white light-emitting device 10 according to this embodiment. As shown in FIG. 1, the white light-emitting device 10 according to this embodiment has a light-emitting diode 2 formed on one surface of a substrate 1, and a wavelength conversion member 3 bonded to the upper surface of the light-emitting diode 2 at room temperature. The light-emitting diode 2 also has a light-emitting layer 2a.

[0018] The substrate 1 is a plate-shaped member that holds the light-emitting diode 2 on one surface. The specific configuration of the substrate 1 is not limited, and it may be a growth substrate for growing the crystal of the light-emitting diode 2, or a submount substrate for mounting the light-emitting diode 2. When a growth substrate is used as the substrate 1, it must be made of a material that allows crystal growth of the semiconductor material that constitutes the light-emitting diode 2. When the semiconductor material that constitutes the light-emitting diode 2 is GaN-based, a sapphire substrate, a GsN substrate, a Si substrate, or the like can be used as the substrate 1. Furthermore, when a submount substrate is used as the substrate 1, it is preferable to use a material with good thermal conductivity, and examples of such materials include a single crystal substrate such as AlN or Si, and a ceramic substrate. Furthermore, electrodes and wiring for supplying current to the light-emitting diode 2 may be formed on the substrate 1.

[0019] The light-emitting diode 2 is a semiconductor light-emitting element that emits blue light. The light-emitting diode 2 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 light-emitting diode 2 emits blue light. The light-emitting diode 2 has a structure formed by stacking multiple semiconductor layers and has an internal light-emitting layer 2a. The semiconductor material that constitutes the light-emitting diode 2 is not limited, but a GaN-based semiconductor material having a band gap that allows it to emit blue light can be used. The structure of the light-emitting diode 2 is also not limited, and it may have a known layer structure such as a cladding layer, a current diffusion layer, and a contact layer.

[0020] The light-emitting layer 2a is one of the semiconductor layers included in the light-emitting diode 2, and is a portion that emits blue light by radiative recombination of a current injected into the light-emitting diode 2. In this embodiment, the blue light emitted by the light-emitting layer 2a has a peak wavelength in the range of 430 nm to 480 nm. The semiconductor material that constitutes the light-emitting layer 2a is not limited, but InGaN can be used as an example. The light-emitting layer 2a may also have a known layer structure such as a quantum well structure, a multiple quantum well structure, or an overflow suppression layer.

[0021] The wavelength conversion member 3 is a portion having a phosphor material that is excited by blue light and emits yellow light. The phosphor material of the wavelength conversion member 3 has a garnet structure with a cubic crystal system and a space group Ia3d, and is represented by the general formula (Ba ｘ Lu ｚ Y ３－ｘ－ｙ－ｚ ) (Al ５－ｘ Si ｘ ) O １２ : Ce ｙ and satisfying the relationships x + y + z < 3, x < 3, x > 0, y > 0, and z > 0. More preferably, the value of z of the phosphor material is in the range of 0.04 to 0.12. Such a phosphor material is excited by blue light emitted by the light-emitting diode 2 and having a peak wavelength in the range of 430 nm to 480 nm, and emits yellow light having a peak wavelength in the range of 530 nm to 580 nm. Furthermore, such a phosphor material preferably has an emission lifetime of 61 ns or less at a dominant wavelength of 569 nm, and more preferably has an emission lifetime of 51 ns or less.

[0022] The wavelength conversion member 3 is made of a single crystal or ceramic and formed into a plate shape. The thickness of the plate-shaped wavelength conversion member 3 is preferably in the range of 0.02 mm to 0.6 mm, and more preferably in the range of 0.05 mm to 0.6 mm. If the thickness of the wavelength conversion member 3 is thinner than the above range, it is not preferable because it deteriorates in handleability during a process such as bonding to the light-emitting diode 2 by room-temperature bonding. If the thickness of the wavelength conversion member 3 is thicker than the above range, it is not preferable because it is prone to color unevenness.

[0023] Methods for forming the wavelength conversion member 3 as a single crystal plate include the floating zone method (FZ method) and the Czochralski method (CZ method). While specific conditions for the FZ method are not limited, for example, a single crystal of approximately 30 mm can be obtained at a sintering rate of 0.4 mm / min. Furthermore, a high-frequency heating device or a resistance heating device can be used for the CZ method. Furthermore, hot isostatic pressing (HIP) can be used to form the wavelength conversion member 3 as a ceramic plate. While specific conditions for HIP are not limited, for example, 196 MPa, 1550°C to 1650°C, and 2 to 24 hours can be used.

[0024] The method for bonding the wavelength conversion member 3 to the light-emitting diode 2 is not limited, and a method of bonding the wavelength conversion member 3 to the semiconductor layer (GaN) or growth substrate (sapphire) of the light-emitting diode 2 by room temperature bonding can be used.

[0025] Example 1 The phosphor material according to Example 1 is (Ba ０．０５ Lu ０．０４ Y ２．８５ ) (Al ４．９５ Si ０．０５ ) O １２ : Ce ０．０６ First, BaCO ３ (Kanto Chemical Co., Ltd. 99.9%), CeO ２ (99.99% manufactured by Kojundo Kagaku Kenkyusho Co., Ltd.), Y ２ O ３(manufactured by Kojundo Kagaku Kenkyusho Co., Ltd. 99.9%), α-Al ２ O ３ (manufactured by Kojundo Kagaku Kenkyusho Co., Ltd. 99.99%), SiO ２ (Tokuyama SE-8), Lu ２ O ３ Powder raw materials (manufactured by Kojundo Chemical Laboratory Co., Ltd., 99.9%) were prepared. Then, the respective powder raw materials were weighed out so as to have a molar ratio of 0.05:0.06:2.85:2.475:0.05:0.02, and mixed and pulverized to obtain a mixed powder.

[0026] 1 g of the obtained mixed powder was weighed and filled into a φ20 mm mold, and the powder was molded at a molding pressure of 10 MPa to obtain a primary compact. Next, the primary compact was compression molded at a molding pressure of 98 MPa using CIP to obtain a secondary compact. Next, a 1×10 －３ The secondary compact was heated at 1750°C for 24 hours in a nitrogen atmosphere of 196 MPa. The heated secondary compact was then heated for 2 hours by HIP (ultra-high pressure HIP apparatus manufactured by Kobe Steel, Ltd.) under conditions of 196 MPa and 1650°C, to obtain a wavelength conversion member 3 made of a plate-shaped ceramic. The wavelength conversion member 3 obtained was analyzed using ICP atomic emission spectroscopy (ICP analyzer manufactured by Nippon Steel Technology Co., Ltd.), and the results were as follows: ０．０５ Lu ０．０４ Y ２．８５ ) (Al ４．９５ Si ０．０５ ) O １２ : Ce ０．０６ It was confirmed that this was the case.

[0027] Example 2 The phosphor material according to Example 2 is (Ba ０．０１ Lu ０．１２ Y ２．８５ ) (Al ４．９９ Si ０．０１ ) O １２ : Ce ０．０２ The ratio of the powder raw materials is BaCO ３ : CeO ２ :Y ２ O ３ : α-Al ２ O ３ : SiO ２ :Lu ２ O ３The same production method as in Example 1 was used, except that the molar ratio was 0.01:0.02:2.85:2.495:0.01:0.06.

[0028] Example 3 The phosphor material according to Example 3 is (Ba ０．０１ Lu ０．０４ Y ２．８９ ) (Al ４．９９ Si ０．０１ ) O １２ : Ce ０．０６ The ratio of the powder raw materials is BaCO ３ : CeO ２ :Y ２ O ３ : α-Al ２ O ３ : SiO ２ :Lu ２ O ３ The same production method as in Example 1 was used, except that the molar ratio was 0.01:0.06:2.89:2.495:0.01:0.02.

[0029] Example 4 The phosphor material according to Example 4 is (Ba ０．１２ Lu ０．０４ Y ２．８ ) (Al ４．８８ Si ０．１２ ) O １２ : Ce ０．０４ The ratio of the powder raw materials is BaCO ３ : CeO ２ :Y ２ O ３ : α-Al ２ O ３ : SiO ２ :Lu ２ O ３ The same production method as in Example 1 was used, except that the molar ratio was 0.12:0.04:2.8:2.44:0.12:0.02.

[0030] Example 5 The phosphor material according to Example 5 is (Ba ０．１２ Lu ０．１２ Y ２．６８ ) (Al ４．８８ Si ０．１２ ) O １２ : Ce ０．０８ The ratio of the powder raw material is expressed as BaCO３ : CeO ２ :Y ２ O ３ : α-Al ２ O ３ : SiO ２ :Lu ２ O ３ The same production method as in Example 1 was used, except that the molar ratio was 0.12:0.08:2.68:2.44:0.12:0.06.

[0031] Example 6 The phosphor material according to Example 6 is (Ba ０．１２ Lu ０．０２ Y ２．７８ ) (Al ４．８８ Si ０．１２ ) O １２ : Ce ０．０８ The ratio of the powder raw materials is BaCO ３ : CeO ２ :Y ２ O ３ : α-Al ２ O ３ : SiO ２ :Lu ２ O ３ The same production method as in Example 1 was used, except that the molar ratio was 0.12:0.08:2.78:2.44:0.12:0.01.

[0032] Comparative Example 1 The phosphor material according to Comparative Example 1 is (Ba ０．１２ Lu ０．１４ Y ２．６６ ) (Al ４．８８ Si ０．１２ ) O １２ : Ce ０．０８ The ratio of the powder raw materials is BaCO ３ : CeO ２ :Y ２ O ３ : α-Al ２ O ３ : SiO ２ :Lu ２ O ３ The same production method as in Example 1 was used, except that the molar ratio was 0.12:0.08:2.66:2.44:0.12:0.07.

[0033] The raw material ratios of Examples 1 to 6 and Comparative Example 1 are shown in Table 1.

[0034] 2 is a graph showing the results of using an X-ray diffractometer for the wavelength conversion member 3 of Example 1. The horizontal axis of the graph represents the diffraction angle, and the vertical axis represents the diffraction intensity. Analysis of the crystal structure from the composition ratio by inductively coupled plasma (ICP) analysis and the X-ray diffraction profile revealed that the crystal system was a cubic garnet structure with a space group of Ia3d.

[0035] (Emission spectrum) Figure 3 is a graph showing the emission spectrum of Example 1. The horizontal axis of the graph represents wavelength, and the vertical axis represents emission intensity. In measuring the emission spectrum, the ceramic plate wavelength conversion member 3 was polished to a thickness of 0.18 mm, and blue light with a peak wavelength of 460 nm was irradiated onto the wavelength conversion member 3 using a fluorescence spectrophotometer (FP-8500 manufactured by JASCO Corporation). In the graph, the peak near 460 nm represents blue light of the excitation light (primary light), and the peak near 530 nm to 580 nm represents yellow light of the secondary light emitted by the wavelength conversion member 3.

[0036] (Conversion Efficiency) Figure 4 is a graph showing the temperature dependence of wavelength conversion efficiency in each example and comparative example. The horizontal axis of the graph represents the measurement temperature, and the vertical axis represents the conversion efficiency when 25°C is set to 100. The conversion efficiency was measured using the same device as in the measurement of the emission spectrum described above. After measuring only blue light without the wavelength conversion member 3, the results of irradiating the wavelength conversion member 3 with blue light were measured. In addition, the number of photons of absorbed blue light was calculated from the change in the spectrum of blue light before and after wavelength conversion, and the number of photons of yellow light was calculated from the emission spectrum, thereby deriving the conversion efficiency.

[0037] In the graph, the black squares plotted are the measurement results for general YAG, and the white squares plotted are the measurement results for BS-YAG that does not contain Lu. The tilted white squares plotted are the measurement results for Comparative Example 1. In Comparative Example 1, the conversion efficiency was 77% at 200°C, and the conversion efficiency decreased at high temperatures. However, in Examples 1 to 6, the conversion efficiency was maintained at 200°C, equivalent to or greater than that of general YAG (80%).

[0038] (Luminescence lifetime) A luminescence lifetime measurement device (manufactured by Horiba Technoservice Co., Ltd.) was used to measure the luminescence lifetime. The luminescence lifetime was defined as the time from when the luminescence intensity reached its peak value until it was reduced to half. FIG. 5 is a graph showing the luminescence lifetime measurement results for Example 6. The horizontal axis of the graph represents elapsed time (ns), and the vertical axis represents luminescence intensity (a.u.). As shown in the graph, the luminescence intensity reaches its peak value (10,000) at t = 57 ns, and is reduced to half (5,000) at t = 103 ns. Therefore, the luminescence lifetime for Example 6 is calculated to be 46 ns.

[0039] Table 2 shows the composition ratios obtained by ICP analysis, the conversion efficiency at 200° C., and the luminescence lifetime for Examples 1 to 6 and Comparative Example 1. In Comparative Example 1, the conversion efficiency was reduced due to an excess of Lu.

[0040] (Examples 7 to 11, Comparative Example 2) Examples 7 to 11 and Comparative Example 2 are plate-like single crystals represented by the same composition formulas as Examples 1 to 5 and Comparative Example 1, respectively. For Examples 7 to 11 and Comparative Example 2, mixed powders were obtained by mixing and pulverizing powder raw materials at the same molar ratios as Examples 1 to 5, respectively.

[0041] 1 g of the resulting mixed powder was weighed out and placed in a 5 mm diameter sample rod, which was heated to 1800°C and grown by the FZ method. A single crystal growth device manufactured by Crystal Systems Corporation was used to grow the single crystal, growing wavelength conversion members 3 each consisting of a single crystal of approximately 30 mm at a rate of 0.4 mm / min. The resulting wavelength conversion members 3 were crushed into powder and analyzed using ICP atomic emission spectroscopy (with an ICP analyzer manufactured by Nippon Steel Technology Co., Ltd.). The resulting wavelength conversion members 3 were confirmed to have the same composition ratios as those in Examples 1 to 5 and Comparative Example 1, respectively.

[0042] The raw material ratios of Examples 7 to 11 and Comparative Example 2 are shown in Table 3.

[0043] 6 is a graph showing the results of using an X-ray diffractometer for wavelength conversion member 3 of Example 7. The horizontal axis of the graph represents the diffraction angle, and the vertical axis represents the diffraction intensity. Single-crystal wavelength conversion member 3 was crushed into powder, and the composition ratio was determined by ICP analysis and the crystal structure was analyzed from the X-ray diffraction profile. It was found that the crystal system was a cubic garnet structure with a space group of Ia3d.

[0044] (Emission spectrum) Figure 7 is a graph showing the emission spectrum of Example 7. The horizontal axis of the graph represents wavelength, and the vertical axis represents emission intensity. In measuring the emission spectrum, the single crystal wavelength conversion member 3 was polished to a thickness of 0.18 mm, and blue light with a peak wavelength of 460 nm was irradiated onto the wavelength conversion member 3 using a fluorescence spectrophotometer (FP-8500 manufactured by JASCO Corporation). In the graph, the peak near 460 nm represents blue light of the excitation light (primary light), and the peak near 530 nm to 580 nm represents yellow light of the secondary light emitted by the wavelength conversion member 3.

[0045] (Luminescence lifetime) A luminescence lifetime measurement device (manufactured by Horiba Technoservice Co., Ltd.) was used to measure the luminescence lifetime. The luminescence lifetime was defined as the time from when the luminescence intensity reached its peak value until it was reduced to half. FIG. 8 is a graph showing the luminescence lifetime measurement results for Example 11. The horizontal axis of the graph represents elapsed time (ns), and the vertical axis represents luminescence intensity (a.u.). As shown in the graph, the luminescence intensity reaches its peak value (10,000) at t = 58 ns, and is reduced to half (5,000) at t = 104 ns. Therefore, the luminescence lifetime for Example 11 is calculated to be 46 to 47 ns.

[0046] Table 4 shows the composition ratios obtained by ICP analysis, the conversion efficiency at 200° C., and the luminescence lifetime for Examples 7 to 11 and Comparative Example 2. In Comparative Example 2, the conversion efficiency was reduced due to an excess of Lu.

[0047] As described above, the wavelength conversion member 3 and the white light emitting element 10 of this embodiment have a garnet structure with a cubic crystal system and a space group Ia3d, and are represented by the general formula (Ba ｘ Lu ｚ Y ３－ｘ－ｙ－ｚ ) (Al ５－ｘ Si ｘ ) O １２ : Ce ｙ (where x+y+z<3, x<5, x>0, y>0, z>0) has a phosphor material having a short emission lifetime and good wavelength conversion efficiency at high temperatures.

[0048] Second Embodiment Next, a second embodiment of the present invention will be described. Description of content that overlaps with the first embodiment will be omitted. In the first embodiment, an example was shown in which the plate-shaped wavelength conversion member 3 was bonded to the light-emitting diode 2 at room temperature, but the plate-shaped wavelength conversion member 3 may also be disposed at a distance from the light-emitting diode 2. Alternatively, the wavelength conversion member 3 may be formed into fine particles and dispersed in a translucent sealing resin, and the light-emitting diode 2 may be sealed with the sealing resin.

[0049] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. The technical scope of the present invention also includes embodiments obtained by appropriately combining the technical means disclosed in different embodiments. This application claims priority based on Japanese Patent Application No. 2024-078887, filed May 14, 2024, the contents of which are incorporated herein by reference.

Claims

1. The crystal system is a cubic system, the space group is Ia3d, and the garnet structure has the general formula (Ba ｘ Lu ｚ Y ３－ｘ－ｙ－ｚ ) (Al ５－ｘ Si ｘ ) O １２ : Ce ｙ (where x+y+z<3, x<3, x>0, y>0, z>0) 2. A wavelength conversion member according to claim 1, wherein the range of z is 0.04 or more and 0.12 or less.

3. The wavelength conversion member according to claim 1, which is formed in a plate shape and has a thickness in the range of 0.02 mm to 0.6 mm.

4. A wavelength conversion member according to claim 1, characterized in that the phosphor material is made of a single crystal plate.

5. A wavelength conversion member according to claim 1, characterized in that the phosphor material is made of a ceramic plate.

6. A wavelength conversion material according to claim 1, characterized in that it is excited by blue light having a peak wavelength in the range of 430 nm to 480 nm and emits yellow light.

7. A wavelength conversion member according to claim 6, characterized in that the emission lifetime at a dominant wavelength of 569 nm is 61 ns or less.

8. A white light emitting element comprising the wavelength conversion material according to any one of claims 1 to 7 and a light emitting diode that emits blue light, bonded at room temperature.

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