Phosphor plate and light-emitting device using same

Abstract

To provide a phosphor plate excellent in luminous efficiency.SOLUTION: A phosphor plate comprises a compound material including an α-type sialon phosphor, and a sintered body containing alumina.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a phosphor plate and a light-emitting device using the same. [Background technology]

[0002] Various developments have been made in the field of phosphor plates. For example, the technology described in Patent Document 1 is known as a technology of this kind. Patent Document 1 describes a SiO 2 A plate-shaped luminescent color conversion member made of inorganic glass dispersed with an inorganic phosphor is disclosed (FIG. 4, claim 1 of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-132923 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, as a result of investigations by the present inventors, it was found that there is room for improvement in terms of luminous efficiency in the plate-shaped luminous color conversion member described in Patent Document 1 above. [Means for solving the problem]

[0005] As a result of further investigation, the inventors found that α-type sialon phosphor and alumina (Al 2 O 3 The inventors have found that by combining and compositing an appropriate material with the phosphor plate, which provides stable luminous efficiency, and have thus completed the present invention.

[0006] According to the present invention, There is provided a phosphor plate made of a composite material including an α-sialon phosphor and a sintered body containing alumina.

[0007] Further, according to the present invention, A group III nitride semiconductor light emitting device; the phosphor plate provided on one surface of the Group III nitride semiconductor light-emitting device; A light emitting device is provided, comprising: Effect of the Invention

[0008] According to the present invention, there are provided a phosphor plate having excellent luminous efficiency and a light emitting device using the same. [Brief description of the drawings]

[0009] The above objects, as well as other objects, features and advantages, will become more apparent from the following preferred embodiments and the accompanying drawings.

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In all drawings, the same components are given the same reference numerals, and the description will be omitted as appropriate. In addition, the drawings are schematic diagrams, and do not correspond to the actual dimensional ratio.

[0012] The phosphor plate of this embodiment will be outlined below. The phosphor plate of this embodiment is constituted by a plate-shaped member made of a composite material including an α-sialon phosphor and a sintered body containing alumina.

[0013] The phosphor plate can function as a wavelength converter that converts irradiated blue light into orange light and emits it.

[0014] According to the findings of the present inventors, the components constituting the composite are α-type sialon phosphor and alumina (Al 2 O 3 It has been discovered that by combining appropriate materials with ZnO, it is possible to realize a phosphor plate that provides stable luminous efficiency.

[0015] Although the detailed mechanism is unclear, it is believed that by appropriately reducing the difference in refractive index between the α-type SiAlON phosphor and alumina, the α-type SiAlON phosphor and glass powder (SiO 2 It is considered that, compared to a composite with alumina, the light emitted from the α-SiAlON phosphor is easier to extract, and the light conversion efficiency is improved. Also, compared to a composite with glass powder, the use of alumina increases the thermal conductivity. This suppresses the decrease in luminescence intensity due to heating, making it possible to apply the phosphor plate of this embodiment to a high-output light-emitting element.

[0016] On the other hand, if the refractive index difference is too small, as in the case of a combination of YAG phosphor and alumina, light scattering becomes difficult, and the phosphor content must be increased to prevent the transmission of blue light.In contrast, the refractive index difference between α-SiAlON phosphor and alumina is appropriately large, which promotes the scattering of blue light and efficiently suppresses the transmission of blue light at a low phosphor content, resulting in the emission of a bright orange color.

[0017] Here, the representative refractive index of each component is as follows: α-type sialon phosphor: about 2, YAG phosphor: about 1.8, Al 2 O 3 : approx. 1.7, SiO 2 : Approximately 1.4 is known.

[0018] According to the above phosphor plate, when irradiated with blue light having a wavelength of 455 nm, the peak wavelength of the wavelength-converted light emitted from the phosphor plate is preferably 585 nm or more and 605 nm or less. Further, according to this, by combining the phosphor plate with a light-emitting element that emits blue light, a light-emitting device that emits orange light with high luminance can be obtained.

[0019] The configuration of the phosphor plate of this embodiment will be described in detail.

[0020] In the composite constituting the above phosphor plate, α-sialon phosphor and alumina are mixed. Mixing means a state in which α-sialon phosphor is dispersed in alumina serving as a base material (matrix phase). That is, the composite may have a structure in which α-sialon phosphor particles are dispersed between and / or within the crystal grains of the (poly)crystals constituted by the base material. These α-sialon phosphor particles may be uniformly dispersed in the base material (alumina sintered body).

[0021] (α-sialon phosphor) The α-sialon phosphor of this embodiment includes an α-sialon phosphor containing Eu element represented by the following general formula (1). (M) m(1-x) / p (Eu) mx / 2 (Si) 12-(m+n) (Al) m+n (O) n (N) 16-n ··General formula (1)

[0022] In the above general formula (1), M represents one or more elements selected from the group consisting of Li, Mg, Ca, Y and lanthanide elements (excluding La and Ce), p represents the valence of the M element, 0 < x < 0.5, 1.5 ≤ m ≤ 4.0, 0 ≤ n ≤ 2.0. n may be, for example, 2.0 or less, 1.0 or less, or 0.8 or less.

[0023] The solid solution composition of α-sialon is the unit cell of α-silicon nitride (Si1 2 N 16In this compound, m Si-N bonds are replaced with Al-N bonds, n Si-N bonds are replaced with Al-O bonds, and m / p cations (M, Eu) are inserted into the crystal lattice to form a solid solution in order to maintain electrical neutrality, and it is expressed as shown in the general formula above. In particular, when Ca is used as M, α-SiAlON is stabilized over a wide range of compositions, and by replacing a portion of it with Eu, which acts as the luminescence center, a phosphor is obtained that is excited by light in a wide wavelength range from ultraviolet to blue and emits visible light from yellow to orange.

[0024] In general, since α-sialon has a second crystal phase different from the α-sialon and an amorphous phase that inevitably exists, it is not possible to strictly define the solid solution composition by composition analysis, etc. As the crystal phase of α-sialon, α-sialon single phase is preferable, and other crystal phases include β-sialon, aluminum nitride or its polytypoid, Ca 2 S 5 N 8 , CaAlSiN 3 etc. may be included.

[0025] One method for producing an α-sialon phosphor is to heat and react a mixed powder consisting of a compound of silicon nitride, aluminum nitride, and an interstitial solid solution element in a high-temperature nitrogen atmosphere. In the heating process, some of the components form a liquid phase, and substances move into this liquid phase to produce an α-sialon solid solution. After synthesis, the α-sialon phosphor is formed by sintering multiple equiaxed primary particles to form clumped secondary particles. In this embodiment, a primary particle refers to the smallest particle that has the same crystal orientation within the particle and can exist alone.

[0026] The lower limit of the average particle size of the α-sialon phosphor is preferably 5 μm or more, more preferably 10 μm or more. The upper limit of the average particle size of the α-sialon phosphor is preferably 30 μm or less, more preferably 20 μm or less. The average particle size of the α-sialon phosphor is the dimension of the secondary particles. By making the average particle size of the α-sialon phosphor 5 μm or more, the transparency of the composite can be further improved. On the other hand, by making the average particle size of the α-sialon phosphor 30 μm or less, chipping can be suppressed when cutting the phosphor plate with a dicer or the like.

[0027] Here, the average particle size of the α-sialon phosphor refers to the particle size D50 at which 50% of the particles pass through (accumulated passing fraction) from the small particle size side in the volumetric particle size distribution obtained by measurement using a laser diffraction scattering particle size distribution measurement method (LS13-320, manufactured by Beckman Coulter, Inc.).

[0028] The lower limit of the content of the α-SiAlON phosphor is, for example, 5 Vol% or more, preferably 10 Vol% or more, more preferably 15 Vol% or more, in terms of volume, relative to the entire composite. This can increase the luminous intensity of the thin phosphor plate. Also, the light conversion efficiency of the phosphor plate can be improved. On the other hand, the upper limit of the content of the α-SiAlON phosphor is, for example, 50 Vol% or less, preferably 45 Vol% or less, more preferably 40 Vol% or less, in terms of volume, relative to the entire composite. This can suppress a decrease in the thermal conductivity of the phosphor plate.

[0029] The alumina in the sintered body has low visible light absorption, so that the luminous intensity of the phosphor plate can be increased. In addition, the alumina has high thermal conductivity, so that the heat resistance of the phosphor plate containing alumina can be improved. Furthermore, the alumina has excellent mechanical strength, so that the durability of the phosphor plate can be increased.

[0030] From the viewpoint of light extraction efficiency, it is desirable that the alumina in the sintered body has few impurities.2 O 3 The purity of the compound can be, for example, 98% wt or more, preferably 99% wt or more.

[0031] The alumina in the sintered body may contain at least one type selected from the group consisting of α-alumina and γ-alumina, which can improve the light conversion efficiency of the phosphor plate.

[0032] The lower limit of the content of the α-sialon phosphor and alumina is, for example, 95 Vol% or more, preferably 98 Vol% or more, more preferably 99 Vol% or more, in terms of volume, relative to the entire composite. In other words, the composite constituting the phosphor plate contains α-sialon phosphor and alumina as main components. This not only improves heat resistance and durability, but also realizes stable luminous efficiency. On the other hand, the upper limit of the content of the α-sialon phosphor and alumina is not particularly limited, but may be, for example, 100 Vol% or less, in terms of volume, relative to the entire composite.

[0033] The lower limit of the thermal conductivity of the phosphor plate is, for example, 10 W / m·K or more, preferably 15 W / m·K or more, and more preferably 20 W / m·K or more. This allows high thermal conductivity to be achieved, and therefore a phosphor plate with excellent heat resistance can be realized. On the other hand, the upper limit of the thermal conductivity of the phosphor plate is not particularly limited, but may be, for example, 40 W / m·K or less.

[0034] In recent years, there has been a trend for phosphors to reach higher temperatures due to the increasing brightness of light sources. Even in such cases, it is possible to stably emit high-brightness orange light by using a phosphor plate with excellent thermal conductivity.

[0035] At least the main surface or both the main surface and the back surface of the phosphor plate may be subjected to a surface treatment, for example, grinding with a diamond grindstone or the like, lapping, polishing, or the like. The surface roughness Ra of the main surface of the phosphor plate is, for example, 0.1 μm or more and 2.0 μm or less, preferably 0.3 μm or more and 1.5 μm or less. On the other hand, the surface roughness Ra of the rear surface of the phosphor plate is, for example, 0.1 μm or more and 2.0 μm or less, and preferably 0.3 μm or more and 1.5 μm or less. By setting the surface roughness to the upper limit or less, it is possible to suppress the light extraction efficiency and the variation in the light intensity in the in-plane direction. By setting the surface roughness to the lower limit or more, it is expected that the adhesion to the adherend can be improved.

[0036] In the phosphor plate, the upper limit of the light transmittance for blue light of 450 nm is, for example, 10% or less, preferably 5% or less, and more preferably 1% or less. This makes it possible to suppress the transmission of blue light through the phosphor plate, thereby enabling the emission of orange light with high brightness. By appropriately adjusting the content of the α-SiAlON phosphor and the thickness of the phosphor plate, the light transmittance for blue light of 450 nm can be reduced. The lower limit of the light transmittance for blue light of 450 nm is not particularly limited, but may be, for example, 0.01% or more.

[0037] The manufacturing process of the phosphor plate of this embodiment will be described in detail.

[0038] The manufacturing method of the phosphor plate of this embodiment can include a step (1) of mixing alumina powder with α-type Sialon phosphor powder containing at least Eu element as the luminescent center, and a step (2) of heating the mixture of alumina powder and α-type Sialon phosphor powder at a temperature of 1300°C or higher and 1700°C or lower to fire a dense composite.

[0039] In step (1), the alumina powder and α-SiAlON phosphor powder used as raw materials are preferably as high purity as possible, and the impurities of elements other than the constituent elements are preferably 0.1% or less. In addition, since the phosphor plate of the present invention is densified by sintering the alumina powder, it is preferable to use a fine alumina powder, and the average particle size of the alumina powder used as a raw material is preferably 1 μm or less. Various methods such as dry and wet methods can be used to mix the raw material powders, but a method that minimizes the pulverization of the α-SiAlON phosphor particles used as a raw material and minimizes the inclusion of impurities from the device during mixing is preferable.

[0040] In step (2), the mixture of alumina powder and α-sialon phosphor powder is sintered at 1300°C to 1700°C. In order to densify the composite, a higher sintering temperature is preferable, but the higher the sintering temperature, the lower the fluorescent properties of the α-sialon phosphor, so the above range is preferable. The sintering method may be normal pressure sintering or pressure sintering, but in order to suppress the deterioration of the properties of the α-sialon phosphor and obtain a dense composite, pressure sintering is preferable, which is easier to densify than normal pressure sintering. Examples of pressure sintering methods include hot press sintering, spark plasma sintering (SPS), and hot isostatic pressure sintering (HIP). In the case of hot press sintering or SPS sintering, the pressure is 10 MPa or more, preferably 30 MPa or more, and preferably 100 MPa or less. The firing atmosphere is preferably a non-oxidizing inert gas atmosphere such as nitrogen or argon, or a vacuum atmosphere, in order to prevent oxidation of the α-sialon.

[0041] The light emitting device of this embodiment will be described.

[0042] The light emitting device of this embodiment includes a group III nitride semiconductor light emitting element (light emitting element 20) and the above phosphor plate 10 provided on one surface of the group III nitride semiconductor light emitting element. The group III nitride semiconductor light emitting element includes an n-layer, a light emitting layer, and a p-layer, each of which is made of a group III nitride semiconductor such as AlGaN, GaN, or InAlGaN-based material. A blue LED that emits blue light can be used as the group III nitride semiconductor light emitting element. The phosphor plate 10 may be disposed directly on one surface of the light emitting element 20, but may also be disposed via a light transparent member or a spacer.

[0043] The phosphor plate 10 arranged on the light emitting element 20 may be a disk-shaped phosphor plate 100 (phosphor wafer) shown in FIG. 1, but an individual piece of the phosphor plate 100 may also be used. Fig. 1 is a schematic diagram showing an example of the configuration of a phosphor plate. The thickness of phosphor plate 100 shown in Fig. 1 may be, for example, 100 μm or more and 1 mm or less. The thickness of phosphor plate 100 can be appropriately adjusted by grinding or the like after it is obtained by the above-mentioned manufacturing process. The disk-shaped phosphor plate 100 is more durable and easier to transport than a rectangular one because chipping and cracking at the corners is suppressed.

[0044] An example of the above-mentioned semiconductor device is shown in Figures 2(a) and (b). Figure 2(a) is a cross-sectional view showing a schematic configuration of a flip-chip type light-emitting device 110, and Figure 2(b) is a cross-sectional view showing a schematic configuration of a wire-bonding type light-emitting device 120.

[0045] 2(a) includes a substrate 30, a light-emitting element 20 electrically connected to the substrate 30 via solder 40 (die-bonding material), and a phosphor plate 10 provided on the light-emitting surface of the light-emitting element 20. The flip-chip type light-emitting device 110 may have either a face-up type or a face-down type structure. Moreover, the light-emitting device 120 in FIG. 2(b) includes a substrate 30, a light-emitting element 20 electrically connected to the substrate 30 via a bonding wire 60 and an electrode 50, and a phosphor plate 10 provided on the light-emitting surface of the light-emitting element 20. In FIG. 2, the light emitting element 20 and the phosphor plate 10 are attached by a known method, and may be attached by, for example, a silicone adhesive or by a method such as heat fusion. Furthermore, the light emitting device 110 and the light emitting device 120 may be entirely sealed with a transparent sealing material.

[0046] Incidentally, the individualized phosphor plate 10 may be attached to the light emitting elements 20 mounted on the substrate 30. A plurality of light emitting elements 20 may be attached to a large-area phosphor plate 100, and then each light emitting element 20 with phosphor plate 10 may be diced into individual pieces. Alternatively, the large-area phosphor plate 100 may be attached to a semiconductor wafer having a plurality of light emitting elements 20 formed on its surface, and then the semiconductor wafer and phosphor plate 100 may be collectively diced into individual pieces.

[0047] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can also be adopted. 1. A phosphor plate comprising a composite body including an α-sialon phosphor and a sintered body containing alumina. 2. The phosphor plate according to 1., wherein the thermal conductivity of the phosphor plate is 10 W / m·K or more and 40 W / m·K or less. 3. The phosphor plate according to 1. or 2., wherein the content of the α-sialon phosphor is 5 Vol% or more and 50 Vol% or less in terms of volume with respect to the entire composite body. 4. The phosphor plate according to any one of 1. to 3., wherein the total value of the contents of the α-sialon phosphor and the alumina is 95 Vol% or more and 100 Vol% or less in terms of volume with respect to the entire composite body. 5. The phosphor plate according to any one of 1. to 4., wherein the α-sialon phosphor includes an α-sialon phosphor containing Eu element represented by the following general formula (1). (M) m(1-x) / p (Eu) mx / 2 (Si) 12-(m+n) (Al) m+n (O) n (N) 16-n ·· General formula (1) (In the above general formula (1), M represents one or more elements selected from the group consisting of Li, Mg, Ca, Y, and lanthanide elements (excluding La and Ce), p represents the valence of the M element, 0 < x < 0.5, 1.5 ≤ m ≤ 4.0, and 0 ≤ n ≤ 2.0.) 6. The phosphor plate according to any one of 1. to 5., wherein the alumina includes one or more selected from the group consisting of α-alumina and γ-alumina. 7. The phosphor plate according to any one of 1. to 6., wherein the average particle diameter D50 of the α-sialon phosphor in the composite body is 5 μm or more and 30 μm or less. 8. The phosphor plate according to any one of 1. to 7., wherein the surface roughness Ra on the main surface of the phosphor plate is 0.1 μm or more and 2.0 μm or less. 9. The phosphor plate according to any one of 1. to 8., which is used as a wavelength converter that converts irradiated blue light into orange light and emits light. 10. The phosphor plate according to any one of 1. to 9., wherein the light transmittance at 450 nm blue light is 10% or less. 11. A light-emitting device comprising a group-III nitride semiconductor light-emitting element and the phosphor plate according to any one of 1. to 10. provided on one surface of the group-III nitride semiconductor light-emitting element. ​ EXAMPLES

[0048] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the description of these examples.

[0049] Example 1 Alumina powder (TM-DAR, manufactured by Taimei Chemical Industry Co., Ltd.) and Ca-α sialon phosphor (Alonbright YL-600B, manufactured by Denka Co., Ltd., average particle size D50: 15 μm) were used as raw materials for the phosphor plate of Example 1. 7.857 g of alumina powder and 2.833 g of Ca-α sialon phosphor powder were weighed out and dry mixed in an agate mortar. The mixed raw materials were passed through a nylon mesh sieve with 75 μm openings to break up agglomerates, and a raw material mixed powder was obtained. The true density of the raw materials (alumina: 3.97 g / cm 3 , Ca-α SiAlON phosphor: 3.34 g / cm 3 ) the compounding ratio calculated was alumina:Ca-α SiAlON phosphor=70:30 volume %.

[0050] Approximately 11 g of the raw material powder mixture was filled into a carbon die with an inner diameter of 30 mm and a carbon lower punch set in place, and then an upper carbon punch was set to sandwich the raw material powder in place. A carbon sheet (GRAFOIL, manufactured by GraTech) with a thickness of 0.127 mm was set between the raw material powder mixture and the carbon jig to prevent adhesion.

[0051] The hot press jig filled with the raw material powder mixture was set in a multipurpose high-temperature furnace (Hi-Multi 5000, manufactured by Fuji Electric Industrial Co., Ltd.) with a carbon heater. The inside of the furnace was evacuated to 0.1 Pa or less, and while maintaining the reduced pressure, the upper and lower punches were pressed with a press pressure of 55 MPa. While maintaining the pressurized state, the temperature was raised to 1600°C at a rate of 5°C per minute. After reaching 1600°C, heating was stopped, the material was slowly cooled to room temperature, and the pressure was released. Then, a fired product with an outer diameter of 30 mm was collected, and the outer periphery was ground using a surface grinder and a cylindrical grinder to obtain a circular phosphor plate with a diameter of 25 mm and a thickness of 1.5 mm. The bulk density of the phosphor plate of Example 1 was measured by a method in accordance with JIS-R1634:1998 and found to be 3.729 g / cm 3 The theoretical density of the mixture calculated from the true density and blending ratio of the raw materials was 3.781 g / cm 3 Therefore, the relative density of the phosphor plate of Example 1 was 98.6%. The phosphor plate of Example 1 was polished and observed with an SEM, and as a result, it was observed that Ca-α SiAlON phosphor particles were dispersed in the alumina matrix phase. In addition, the surface roughness Ra of the main surface of the phosphor plate in Example 1 was 1.0 μm, and the surface roughness Ra of the back surface opposite the main surface was 1.0 μm, as measured using a surface roughness measuring device (Mitutoyo, SJ-400) in accordance with JIS B0601:1994.

[0052] Example 2 The raw materials for the phosphor plate of Example 2 were the same alumina powder and Ca-α sialon phosphor as those of Example 1. 6.701 g of alumina powder and 3.777 g of Ca-α sialon phosphor were weighed and dry mixed in an agate mortar. The compounding ratio calculated from the true density of the raw materials was alumina:Ca-α sialon phosphor=60:40 volume %. The method for producing the phosphor plate of Example 2 is similar to the method for producing the phosphor plate of Example 1, except that the compounding ratio of the alumina powder and the Ca-α SiAlON phosphor is different. The bulk density of the phosphor plate of Example 2 was measured in the same manner as in Example 1, and was found to be 3.665 g / cm 3 The theoretical density of the raw material mixture was 3.717 g / cm 3 Therefore, the relative density of the phosphor plate of Example 2 was 98.6%. The surface roughness Ra of the main surface of the phosphor plate in Example 2 was 1.0 μm, and the surface roughness Ra of the rear surface opposite to the main surface was 1.1 μm.

[0053] Comparative Example 1 As a raw material for the phosphor plate of Comparative Example 1, SiO 2 Powder (FB-9DC grade, manufactured by Denka Co., Ltd.) and Ca-α SiAlON phosphor (Alonbright YL-600B, manufactured by Denka Co., Ltd.) were used. 2 4.354 g of the powder and 2.723 g of Ca-α Sialon phosphor powder were weighed and dry mixed in an agate mortar. The mixed raw materials were passed through a nylon mesh sieve with 75 μm openings to obtain a raw material mixed powder. The compounding ratio calculated from the true density of the raw materials was SiO 2 :Ca-α SiAlON phosphor=70:30 volume %. Approximately 7 g of the raw material mixed powder was filled into a carbon die for hot pressing in the same manner as in Example 1, and hot press sintering was performed in a multipurpose high-temperature furnace. The inside of the furnace was evacuated to a vacuum of 0.1 Pa or less, and while maintaining the reduced pressure, the temperature was raised from room temperature at a rate of 20°C per minute, and at 800°C, nitrogen gas was introduced into the furnace. Nitrogen gas was introduced into the furnace, and the atmospheric pressure inside the furnace was set to 0.1 MPa·G. After the introduction of nitrogen gas, the temperature was raised to 1375°C at a rate of 5°C per minute, and maintained at 1375°C for 15 minutes. Thereafter, the temperature was lowered to room temperature at a rate of 5°C per minute, and the pressure was released. Then, a fired product with an outer diameter of 30 mm was collected and processed in the same manner as in Example 1 to obtain a circular phosphor plate with a diameter of 25 mm and a thickness of 1.5 mm.

[0054] [Thermal conductivity measurement] The thermal conductivity of the phosphor plates of Examples 1 and 2 and Comparative Example 1 at room temperature (25° C.) was measured by a flash method in accordance with JIS1611:2010. Thermal diffusivity: Measured using a xenon flash analyzer (LFA447, Netsch Japan Co., Ltd.). Specific heat capacity: Measured in accordance with JIS K7123 using a DSC measuring device (DSC8000, manufactured by PerkinElmer). Bulk density: Measured according to the method of JIS-R1634:1998. Thermal conductivity (W / m K) = bulk density (g / cm 3 ) × thermal diffusivity (m 2 / s) × specific heat capacity (J / (kg K)) The thermal conductivity of the phosphor plate of Example 1 was 18 W / m·K, the thermal conductivity of the phosphor plate of Example 2 was 15 W / m·K, and the thermal conductivity of the phosphor plate of Comparative Example 1 was 1.9 W / m·K.

[0055] [Crystal structure analysis] The phosphor plates of Examples 1 and 2 were ground in a mortar to prepare powder samples, and the diffraction pattern of the obtained samples was measured using an X-ray diffractometer (product name: Ultima IV, manufactured by Rigaku Corporation). As a result, it was confirmed that a crystalline phase was present in the alumina sintered body. This crystalline phase contained α-alumina as the main phase, with a small amount of γ-alumina mixed in.

[0056] [Evaluation of optical properties] The optical characteristics of the phosphor plate were measured using a chip-on-board (COB) type LED package 130. FIG. First, the obtained circular phosphor plate 100 having a thickness of 1.5 mm was processed to have a thickness of 0.25 mm. Next, an aluminum substrate (substrate 30) having a recess 70 formed therein was prepared. The diameter φ of the bottom surface of the recess 70 was set to 13.5 mm, and the diameter φ of the opening of the recess 70 was set to 16 mm. Inside the recess 70 of the substrate 30, a blue LED (light-emitting element 20) was mounted as a blue light source. Thereafter, a circular phosphor plate 100 was placed on the blue LED so as to cover the opening of the recess 70 of the substrate 30, thereby producing the device (chip-on-board (COB) type LED package 130) shown in FIG.

[0057] Using a total luminous flux measurement system (HalfMoon / φ1000mm integrating sphere system, manufactured by Otsuka Electronics Co., Ltd.), the emission spectrum on the surface of phosphor plate 100 was measured when the blue LED of the manufactured LED package 130 was turned on. The measurement results are shown in FIG.

[0058] Fig. 4 shows the emission spectra when the phosphor plates of Examples 1 and 2 and Comparative Example 1 were used. The emission intensity on the vertical axis of Fig. 4 is a relative value when the maximum emission intensity of Example 1 is set to 100. In the emission spectrum, the maximum emission intensity of orange light (Orange) with a wavelength of 595 nm to 605 nm is represented as T O The maximum emission intensity of blue light (Blue) with a wavelength of 445 nm to 465 nm is defined as T B When the amount of blue light transmitted from the blue LED is T B / T O It was defined as follows.

[0059] 4, the peak wavelength of the emission spectrum was about 600 nm in Examples 1 and 2 and Comparative Example 1. However, it was found that the emission intensity at the peak wavelength in Examples 1 and 2 was higher than that in Comparative Example 1. In addition, in all of Examples 1 and 2 and Comparative Example 1, a slight spectrum originating from the transmitted light of the blue LED was observed around a wavelength of 450 nm. However, the transmittance T B / T O It was found that the value was comparable to that of Comparative Example 1. In addition, in the phosphor plate of Example 1, the light transmittance of blue light at a wavelength of 450 nm was 1.5%, which indicates that the transmission of blue light was sufficiently suppressed. It was found that by using the phosphor plates of Examples 1 and 2, a light emitting device having excellent fluorescent intensity of orange light and excellent luminous efficiency for converting blue light to orange light could be realized.

[0060] This application claims priority based on Japanese Patent Application No. 2018-189141, filed on October 4, 2018, the disclosure of which is incorporated herein in its entirety.

Claims

1. A phosphor plate made of a composite material including an α-SiAlON phosphor and a sintered body including alumina, The α-sialon phosphor includes an α-sialon phosphor containing Eu element represented by the following general formula (1): The thermal conductivity of the phosphor plate is 10 W / m K or more and 40 W / m K or less, The content of the α-sialon phosphor is 15 Vol% or more in terms of volume with respect to the entire composite, A phosphor plate having a relative density of 98.6% or more. (M) ｍ（１－ｘ）／ｐ (Eu) ｍｘ／２ (Si) １２－（ｍ＋ｎ） (Al) ｍ＋ｎ (O) ｎ (N) １６－ｎ ・・General formula (1) (In the above general formula (1), M represents one or more elements selected from the group consisting of Li, Mg, Ca, Y, and lanthanide elements (excluding La and Ce), p represents the valence of the M element, 0<x<0.5, 1.5≦m≦4.0, and 0≦n≦2.0.)

2. 2. The phosphor plate of claim 1, A phosphor plate, wherein a total content of the α-sialon phosphor and the alumina is 95 Vol % or more and 100 Vol % or less in terms of volume with respect to the entire composite.

3. 2. The phosphor plate of claim 1, The phosphor plate, wherein the alumina comprises at least one selected from the group consisting of alpha alumina and gamma alumina.

4. 2. The phosphor plate of claim 1, The average particle diameter D50 of the α-sialon phosphor in the composite is 5 μm or more and 30 μm or less.

5. 2. The phosphor plate of claim 1, The phosphor plate has a surface roughness Ra of 0.1 μm or more and 2.0 μm or less on a main surface thereof.

6. 2. The phosphor plate of claim 1, A phosphor plate used as a wavelength converter that converts irradiated blue light into orange light and emits it.

7. 2. The phosphor plate of claim 1, A phosphor plate having a light transmittance of 10% or less for blue light of 450 nm.

8. A group III nitride semiconductor light emitting device; The phosphor plate according to any one of claims 1 to 7 provided on one surface of the Group III nitride semiconductor light-emitting device; A light emitting device comprising:

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