Wavelength conversion member and white light-emitting device

Abstract

To provide a wavelength conversion member and white light-emitting device, which feature a short emission lifetime and good wavelength conversion efficiency at high temperature.SOLUTION: A wavelength conversion member (3) disclosed herein comprises a phosphor material that has a cubic crystal system with a garnet structure with the Ia3d space group and is represented by a general formula: (BaxLuzY3-x-y-z)(Al5-xSix)O12:Cey, where x+y+z<3, x<5, x>0, y>0, and z>0.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[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, we have developed YAG phosphors that are solid-solubilized with Ba and Si. 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2022 / 168879 [Patent Document 2] Patent Publication No. 2023-144855 Summary of the Invention [Problem to be solved by the invention]

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

[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. [Means for solving the problem]

[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<5, 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 of 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<5, x>0, y>0, z>0) has a phosphor material with a short emission lifetime and good wavelength conversion efficiency at high temperatures.

[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 device 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. [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic cross-sectional view illustrating the structure of a white light emitting element 10 according to a first embodiment. [Figure 2] 1 is a graph showing the results of using an X-ray diffractometer for wavelength conversion member 3 of Example 1. [Figure 3] 1 is a graph showing an emission spectrum of Example 1. [Figure 4] 10 is a graph showing the temperature dependence of wavelength conversion efficiency in each example and comparative example. [Figure 5] 10 is a graph showing the results of measuring the luminescence lifetime in Example 6. [Figure 6] 10 is a graph showing the results of using an X-ray diffractometer for wavelength conversion member 3 of Example 7. [Figure 7] 10 is a graph showing the emission spectrum of Example 7. [Figure 8] 10 is a graph showing the results of measuring the luminescence lifetime in Example 11. DETAILED DESCRIPTION OF THE INVENTION

[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 explanations 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-like 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), and 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 a light-emitting layer 2a inside. 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 where x+y+z<3, x<5, x>0, y>0, and z>0 are satisfied. More preferably, the value of z in the phosphor material is in the range of 0.04 or more and 0.12 or less. 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 with 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 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 becomes difficult to handle 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 more likely to cause color unevenness.

[0023] Methods for forming the wavelength conversion member 3 into a single crystal plate include the FZ method (Floating Zone method) and the CZ method (Czochralski method). Specific conditions for the FZ method are not limited, but as an example, a single crystal of about 30 mm can be obtained at a sintering rate of 0.4 mm / min. 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 into a ceramic plate. Specific conditions for HIP are not limited, but examples include 196 MPa, 1550°C to 1650°C, and 2 to 24 hours.

[0024] The method for bonding wavelength conversion member 3 to light emitting diode 2 is not limited, and a method of bonding wavelength conversion member 3 to the semiconductor layer (GaN) or growth substrate (sapphire) of 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, the following powder raw materials were prepared: BaCO3 (Kanto Chemical Co., Ltd., 99.9%), CeO2 (Kojundo Chemical Laboratory Co., Ltd., 99.99%), Y2O3 (Kojundo Chemical Laboratory Co., Ltd., 99.9%), α-Al2O3 (Kojundo Chemical Laboratory Co., Ltd., 99.99%), SiO2 (Tokuyama Corporation, SE-8), and Lu2O3 (Kojundo Chemical Laboratory Co., Ltd., 99.9%). Then, each powder raw material was weighed out to a molar ratio of 0.05:0.06:2.85:2.475:0.05:0.02, 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 heating furnace was used to obtain 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 using HIP (ultra-high pressure HIP equipment manufactured by Kobe Steel, Ltd.) under conditions of 196 MPa and 1650°C, to obtain a wavelength conversion member 3 made of plate-shaped ceramic. The wavelength conversion member 3 obtained was analyzed using ICP optical emission spectroscopy (ICP analyzer manufactured by Nippon Steel Technology Co., Ltd.), and the results showed that (Ba 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 same manufacturing method as in Example 1 was used, except that the molar ratio of the powder raw materials was BaCO3:CeO2:Y2O3:α-Al2O3:SiO2:Lu2O3 = 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 0.06The same manufacturing method as in Example 1 was used, except that the molar ratio of the powder raw materials was BaCO3:CeO2:Y2O3:α-Al2O3:SiO2:Lu2O3 = 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 same manufacturing method as in Example 1 was used, except that the molar ratio of the powder raw materials was BaCO3:CeO2:Y2O3:α-Al2O3:SiO2:Lu2O3 = 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 same manufacturing method as in Example 1 was used, except that the molar ratio of the powder raw materials was BaCO3:CeO2:Y2O3:α-Al2O3:SiO2:Lu2O3 = 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 0.01 Y 2,79 )(Al 4.88 Si 0.12 )O 12 :Ce 0.08 The same manufacturing method as in Example 1 was used, except that the molar ratio of the powder raw materials was BaCO3:CeO2:Y2O3:α-Al2O3:SiO2:Lu2O3 = 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 same manufacturing method as in Example 1 was used, except that the molar ratio of the powder raw materials was BaCO3:CeO2:Y2O3:α-Al2O3:SiO2:Lu2O3 = 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. [Table 1]

[0034] (crystal structure) 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 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) 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. The emission spectrum was measured by polishing the ceramic plate wavelength conversion member 3 to a thickness of 0.18 mm, irradiating the wavelength conversion member 3 with blue light having a peak wavelength of 460 nm, and using a fluorescence spectrophotometer (FP-8500 manufactured by JASCO Corporation). The peak near 460 nm in the graph represents blue excitation light (primary light), and the peak near 530 nm to 580 nm represents yellow secondary light emitted by the wavelength conversion member 3.

[0036] (conversion efficiency) 4 is a graph showing the temperature dependence of wavelength conversion efficiency in each example and comparative example. The horizontal axis of the graph shows the measurement temperature, and the vertical axis shows 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 blue light alone without the wavelength conversion member 3, the wavelength conversion member 3 was irradiated with blue light and the results were measured. Furthermore, the number of photons of the absorbed blue light was calculated from the change in the spectrum of the blue light before and after wavelength conversion, and the number of photons of the yellow light was calculated from the emission spectrum, thereby deriving the conversion efficiency.

[0037] In the graph, the black squares plot the measurement results for a typical YAG, and the white squares plot the measurement results for a BS-YAG that does not contain Lu. The tilted white squares plot 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, at least at 80%, equivalent to that of a typical YAG.

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

[0039] Table 2 shows the results of the composition ratios obtained by ICP analysis, the conversion efficiency at 200° C., and the luminous lifetime for Examples 1 to 6 and Comparative Example 1. [Table 2]

[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 in the same molar ratios as Examples 1 to 5, respectively.

[0041] 1 g of the obtained mixed powder was weighed out and placed in a φ5 mm sample rod, and heated to 1800°C to grow a single crystal by the FZ method. A single crystal growth device manufactured by Crystal Systems Corporation was used to grow the single crystal, and wavelength conversion member 3 consisting of a single crystal of about 30 mm was obtained at a rate of 0.4 mm / min. The obtained wavelength conversion member 3 was crushed into powder and analyzed using ICP atomic emission spectroscopy (ICP analyzer manufactured by Nippon Steel Technology Co., Ltd.), which confirmed that the composition ratios were the same as those of 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. [Table 3]

[0043] (crystal structure) 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 system, and the space group was Ia3d, a garnet structure.

[0044] (Emission spectrum) 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, 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 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 excitation light (primary light), and the peak near 530 nm to 580 nm represents yellow light of secondary light emitted by wavelength conversion member 3.

[0045] (luminescence lifetime) FIG. 8 is a graph showing the results of measuring the luminescence lifetime of Example 11. The horizontal axis of the graph represents elapsed time (ns), and the vertical axis represents luminescence intensity (au). A luminescence lifetime measurement device (manufactured by Horiba Technoservice Co., Ltd.) was used to measure the luminescence lifetime. As shown in the graph, the luminescence intensity reaches a peak value (10,000) at t = 58 ns, and the luminescence intensity is reduced to half (5,000) at t = 104 ns. Therefore, the luminescence lifetime of Example 6 is calculated to be 46 to 47 ns.

[0046] Table 4 shows the results of the composition ratios obtained by ICP analysis, the conversion efficiency at 200° C., and the luminous lifetime for Examples 7 to 11 and Comparative Example 2. [Table 4]

[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 with 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. Descriptions that overlap with those of 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 spaced apart 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. 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]

[0050] 10...White light emitting element 1...Substrate 2...Light-emitting diode 2a...Emitting layer 3...Wavelength conversion material

Claims

1. The crystal system is a cubic garnet structure with a space group of Ia3d, 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) A wavelength conversion member comprising a phosphor material represented by the formula:

2. The wavelength conversion member according to claim 1 , A wavelength conversion member characterized in that the range of z is 0.04 or more and 0.12 or less.

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

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

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

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

7. The wavelength conversion member according to claim 6, A wavelength conversion member having an emission lifetime of 61 ns or less at a dominant wavelength of 569 nm.

8. A wavelength conversion member according to any one of claims 1 to 7; A white light emitting device characterized in that a light emitting diode that emits blue light is bonded at room temperature.

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