Phosphor plate and light-emitting device using same

Abstract

A phosphor plate according to the present invention comprises a plate-like composite containing: a parent material; and a phosphor dispersed in the parent material, wherein a main component of the parent material is alumina, and the phosphor includes α-type sialon phosphor and satisfies an L* value of 73.5-85.0, an a* value of 4.4-8.0, and a b* value of 10.8-13.0, in the L*a*b* color coordinates when measured according to JIS Z 8781-4.

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 on phosphor plates up to now. One known example of this type of technology is the technology described in Patent Document 1. Patent Document 1 describes, as an example, a phosphor plate in which YAG:Ce crystal grains and alumina crystal grains are mixed (paragraph 0055 of Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-9470 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as a result of investigations by the present inventors, it has been found that the phosphor plate described in Patent Document 1 has room for improvement in terms of fluorescence intensity. [Means for solving the problem]

[0005] In the above Patent Document 1, sufficient consideration has not been given to a phosphor plate made of a composite containing a base material mainly composed of alumina and a phosphor. The inventors have conducted research and found that in a phosphor plate made of alumina and an α-sialon phosphor, as the color becomes darker, the intensity of the fluorescence decreases accordingly.

[0006] As a result of further investigation, it was found that the decrease in fluorescence intensity can be suppressed by suppressing the blackening of the phosphor plate, and the degree of blackening was * a * b* It was found that stable measurements can be made by using color coordinates as an index. Based on these findings, further research was carried out and the indicator L * a * b * The inventors have found that the fluorescence intensity of the phosphor plate can be improved by setting the color coordinates within an appropriate range, and have completed the present invention.

[0007] According to the present invention, A phosphor plate comprising a plate-shaped composite including a base material and a phosphor dispersed in the base material, The main component of the base material is alumina, the phosphor contains an α-sialon phosphor, The L of the phosphor plate when measured in accordance with JIS Z 8781-4 * a * b * In color coordinates, L * The value is between 73.5 and 85.0, a * The value is between 4.4 and 8.0, and b * The value is between 10.8 and 13.0. A phosphor plate is provided.

[0008] 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: [Effects of the Invention]

[0009] According to the present invention, there are provided a phosphor plate having excellent fluorescence intensity and a light-emitting device using the same. [Brief explanation of the drawings]

[0010]

Figure 1

Figure 2

Figure 3

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are designated by similar reference numerals, and descriptions thereof will be omitted as appropriate. Furthermore, the drawings are schematic diagrams and do not correspond to actual dimensional proportions.

[0012] An outline of the phosphor plate of this embodiment will be described.

[0013] The phosphor plate of this embodiment is composed of a plate-like member having a plate-like composite containing a base material and phosphor dispersed in the base material.

[0014] In the phosphor plate, the main component of the base material is alumina, and the phosphor contains an α-sialon phosphor. Such a phosphor plate can function as a wavelength converter that converts irradiated blue light into orange light and emits it.

[0015] The phosphor plate of this embodiment has an L of the phosphor plate when measured in accordance with JIS Z 8781-4. * a * b * The color coordinates are as follows: * , a * , b * It satisfies the following conditions.

[0016] L * The value must be between 73.5 and 85.0. a * The value must be between 4.4 and 8.0. ·b *The value must be between 10.8 and 13.0.

[0017] According to the inventor's findings, L * a * b * By using the color coordinate as an index, the degree of blackening of the phosphor plate can be stably measured, and the index L * a * b * Color coordinate L * value, a * value, b * It has been found that by setting the value within the above range, the fluorescence intensity of the phosphor plate can be improved.

[0018] L for lightness * The lower limit of L is 73.5 or more, preferably 74.0 or more, and more preferably 75.0 or more. * The upper limit of is 85.0 or less, preferably 84.5 or less, and more preferably 84.0 or less.

[0019] a on the positive side representing the red chromaticity * The lower limit of the value of a is 4.4 or more, preferably 4.5 or more, and more preferably 4.6 or more. * The upper limit of is 8.0 or less, preferably 7.8 or less, and more preferably 7.5 or less.

[0020] b on the positive side represents yellow chromaticity * The lower limit of the value of b is 10.8 or more, preferably 10.9 or more, and more preferably 11.0 or more. * The upper limit of is 13.0 or less, preferably 12.9 or less, and more preferably 12.8 or less.

[0021] L * , a * , b * By setting the values ​​of these to be equal to or greater than the lower limits, the fluorescence intensity of the phosphor plate can be increased. Although the detailed mechanism is not clear, it is believed that the blackening of the phosphor plate containing the α-sialon phosphor and alumina can be suppressed, thereby suppressing the decrease in the fluorescence intensity.

[0022] L * , a * , b * By setting the values ​​of these to be equal to or less than the above upper limits, the function of the wavelength converter to convert irradiated blue light into orange light and emit the orange light can be improved.

[0023] In this embodiment, for example, by appropriately selecting the type and amount of each component contained in the phosphor plate, the method of manufacturing the phosphor plate, etc., the above L * a * b * Among these, the color coordinates can be controlled by appropriately adjusting the specific surface area of ​​the alumina powder, which is the raw material, the heating temperature in the firing process, and the content ratio of the phosphor in the composite. * a * b * This is one of the factors for setting the color coordinates in a desired numerical range.

[0024] Furthermore, according to this embodiment, the phosphor plate containing the α-sialon phosphor and alumina is preferably configured so that when irradiated with blue light having a wavelength of 455 nm, the wavelength-converted light emitted from the phosphor plate has a peak wavelength of 585 nm or more and 605 nm or less. By combining such a phosphor plate with a light-emitting element that emits blue light, a light-emitting device that emits orange light with high brightness can be obtained.

[0025] The phosphor plate of this embodiment will be described in detail below.

[0026] In the composite that constitutes the phosphor plate, a phosphor (α-sialon phosphor) and a base material (alumina) are mixed. Mixing means a state in which the phosphor (α-sialon phosphor) is dispersed in alumina that serves as the 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 (multi)crystals constituted by the base material. These α-sialon phosphor particles may be uniformly dispersed in the base material (alumina sintered body).

[0027] The phosphor may contain an α-sialon phosphor 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)

[0028] 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. n may be, for example, 2.0 or less, 1.0 or less, or 0.8 or less.

[0029] The solid solution composition of α-sialon is such that m Si-N bonds in the unit cell of α-silicon nitride (Si 12 N 16 ) are replaced by Al-N bonds, and n Si-N bonds are replaced by Al-O bonds. In order to maintain electrical neutrality, m / p cations (M, Eu) penetrate and dissolve into the crystal lattice and are represented by the above general formula. In particular, when Ca is used as M, α-sialon is stabilized in a wide composition range, and by replacing a part of it with Eu that serves as a luminescence center, a phosphor that is excited by light in a wide wavelength range from ultraviolet to blue and exhibits visible luminescence from yellow to orange can be obtained.

[0030] Generally, since α-sialon contains a second crystalline 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. The crystalline phase of α-sialon is preferably a single α-sialon phase, and other crystalline phases such as β-sialon, aluminum nitride or its polytypoid, Ca2Si5N8, CaAlSiN3, etc. may be contained.

[0031] Here, if the difference in refractive index is too small, as in the case of a combination of YAG phosphor and alumina, light scattering becomes difficult, and it is necessary to increase the phosphor content in order to prevent transmission of blue light. In contrast, the difference in refractive index between the α-sialon phosphor and alumina is moderately large, which promotes scattering of blue light, and it is thought that the transmission of blue light can be efficiently suppressed even at a low phosphor content, allowing for the emission of bright orange light. The typical refractive indexes of the components are known to be approximately 2.0 for α-sialon phosphor, approximately 1.8 for YAG phosphor, approximately 1.7 for Al2O3, and approximately 1.4 for SiO2.

[0032] One method for producing an α-sialon phosphor is to heat a mixed powder of silicon nitride, aluminum nitride, and a compound of an interstitial solid solution element in a high-temperature nitrogen atmosphere to cause a reaction. During the heating process, some of the constituent components form a liquid phase, and substances move into this liquid phase, producing an α-sialon solid solution. After synthesis, the α-sialon phosphor consists of multiple equiaxed primary particles sintered to form clumped secondary particles. In this embodiment, the primary particle refers to the smallest particle that has the same crystal orientation within the particle and can exist independently.

[0033] 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. On the other hand, the upper limit of the average particle size of the α-sialon phosphor is preferably 40 μm or less, more preferably 30 μm or less. The average particle size of the α-sialon phosphor is the size 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, while by making the average particle size of the α-sialon phosphor 40 μm or less, chipping can be suppressed when cutting the phosphor plate with a dicer or the like.

[0034] Here, the average particle diameter of the α-sialon phosphor is the particle diameter D at 50% of the cumulative passing fraction (cumulative passing fraction) from the small particle size side in the volume-based particle size distribution obtained by measurement using a laser diffraction scattering particle size distribution measurement method (LS13-320, manufactured by Beckman Coulter). 50 This refers to

[0035] The lower limit of the content of the α-sialon phosphor is, in volume terms, for example, 5 vol% or more, preferably 10 vol% or more, and more preferably 20 vol% or more, based on the entire composite. This can increase the fluorescence intensity of the thin phosphor plate. Also, it can improve the light conversion efficiency of the phosphor plate. On the other hand, the upper limit of the content of the α-sialon phosphor is, in volume terms, for example, 60 vol% or less, preferably 55 vol% or less, and more preferably 50 vol% or less, based on the entire composite. This can suppress a decrease in the thermal conductivity of the phosphor plate. The content of the phosphor may be within the same range as the above upper and lower limits of the content of the α-sialon phosphor.

[0036] The base material contained in the composite may be composed of an alumina sintered body. The alumina in the sintered body has low absorption of visible light, which can increase the fluorescence intensity of the phosphor plate. Furthermore, alumina has high thermal conductivity, which can improve the heat resistance of the phosphor plate containing alumina. Furthermore, alumina also has excellent mechanical strength, which can increase the durability of the phosphor plate.

[0037] From the viewpoint of light extraction efficiency, it is desirable that the alumina in the sintered body has few impurities. For example, the purity of the Al2O3 compound in the alumina in the sintered body can be, for example, 98% wt or more, preferably 99% wt or more.

[0038] The alumina in the sintered body may contain at least one selected from the group consisting of α-alumina and γ-alumina, which can improve the light conversion efficiency of the phosphor plate.

[0039] 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, and more preferably 99 vol% or more, in terms of volume, of the entire composite. This not only improves heat resistance and durability, but also enables stable luminous efficiency to be achieved. 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, of the entire composite. The contents of the phosphor and alumina may be within the same ranges as the above upper and lower limits of the contents of the α-sialon phosphor and alumina.

[0040] 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 for high thermal conductivity and therefore a phosphor plate with excellent heat resistance. 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.

[0041] In recent years, the trend toward higher brightness in light sources has led to a tendency for phosphors to reach higher temperatures. Even in such cases, the use of a phosphor plate with excellent thermal conductivity makes it possible to emit a stable, bright orange light.

[0042] 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, such as grinding with a diamond grindstone or the like, lapping, polishing, or the like.

[0043] An example of a manufacturing process for the phosphor plate of this embodiment will be described.

[0044] The method for manufacturing the phosphor plate of this embodiment can include step (1) of mixing alumina powder with α-sialon phosphor powder containing at least Eu element as the luminescent center, and step (2) of heating the mixture of alumina powder and α-sialon phosphor powder to fire a dense composite.

[0045] In step (1), the alumina powder and α-sialon phosphor powder used as raw materials are preferably as pure as possible, and the impurities of elements other than the constituent elements are preferably 0.1% or less. The raw material powders can be mixed using various methods, including dry and wet methods, but a method that minimizes the pulverization of the α-sialon phosphor particles used as raw material and minimizes the introduction of impurities from the mixing equipment is preferred.

[0046] The upper limit of the BET specific surface area of ​​the alumina powder used as the raw material is, for example, 10.0 m 2 / g or less, preferably 9.0m 2 / g or less, more preferably 8.0m 2 / g or less, more preferably 6.0m 2 / g. This can prevent the phosphor plate from becoming black. On the other hand, the lower limit of the BET specific surface area of ​​the alumina powder is, for example, 0.1 m 2 / g or more, preferably 0.5m 2 / g or more, more preferably 1.0m 2 / g or more, more preferably 2.0m 2 This increases the sinterability of the alumina powder and allows the formation of a dense composite.

[0047] In step (2), the mixture of alumina powder and α-sialon phosphor powder is fired at 1300°C to 1700°C. The heating temperature in the sintering step is preferably 1500°C or higher. To densify the composite, a higher firing temperature is preferable, but if the firing temperature is too high, the phosphor and alumina will react, reducing the fluorescence intensity of the phosphor plate, so the above range is preferred.

[0048] The firing method may be either pressureless sintering or pressure sintering, but pressure sintering is preferred because it is easier to densify than pressureless sintering in order to suppress deterioration in the properties of the α-sialon phosphor and to obtain a dense composite.

[0049] Examples of pressure sintering methods include hot press sintering, spark plasma sintering (SPS), hot isostatic pressure sintering (HIP), etc. 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.

[0050] 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.

[0051] In this way, the phosphor plate of this embodiment is obtained. The surface of the plate-like composite in the obtained phosphor plate may be subjected to known surface treatments such as polishing, plasma treatment, and surface coating treatment, as long as the effects of the present invention are not impaired.

[0052] The light emitting device of this embodiment will be described.

[0053] The light emitting device of this embodiment includes a group III nitride semiconductor light emitting element (light emitting element 20) and the above-described 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, or may be disposed via a light-transmitting member or a spacer.

[0054] The phosphor plate 10 arranged on the light emitting element 20 may be a disc-shaped phosphor plate 100 (phosphor wafer) shown in FIG. 1, but may also be an individual piece of the phosphor plate 100. 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. After phosphor plate 100 is obtained through the above manufacturing process, the thickness can be appropriately adjusted by grinding or the like. The disk-shaped phosphor plate 100 is more durable and easier to transport than a rectangular one because chipping and cracking at the corners are less likely to occur.

[0055] An example of the semiconductor device is shown in Figures 2(a) and 2(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.

[0056] 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 light-emitting device 110 may have either a face-up type or a face-down type structure. The light-emitting device 120 in FIG. 2(b) also 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 heat fusion. Furthermore, the light emitting device 110 and the light emitting device 120 may be entirely sealed with a transparent sealing material.

[0057] Note that individualized phosphor plates 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 the light-emitting elements 20 with phosphor plates 10 may be diced into individual pieces. Alternatively, a 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 diced into individual pieces all at once.

[0058] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. Examples of reference configurations are appended below. 1. A phosphor plate comprising a plate-like composite including a base material and a phosphor dispersed in the base material, where the main component of the base material is alumina, the phosphor includes an α-sialon phosphor, when measured in accordance with JIS Z 8781-4, the L * a * b * color coordinate of the phosphor plate, L * the value is 73.5 or more and 85.0 or less, a * the value is 4.4 or more and 8.0 or less, and b * the value is 10.8 or more and 13.0 or less, a phosphor plate. 2. The phosphor plate according to 1., where the content of the phosphor is 5 Vol% or more and 60 Vol% or less in the entire composite, a phosphor plate. 3. The phosphor plate according to 1. or 2., where the total value of the content of the α-sialon phosphor and the alumina is 95 Vol% or more and 100 Vol% or less in the entire composite, a phosphor plate. 4. The phosphor plate according to any one of 1. to 3., where the thermal conductivity of the phosphor plate is 10 W / m·K or more and 40 W / m·K or less, a phosphor plate. 5. The phosphor plate according to any one of 1. to 4., (M) m(1-x) / pwhere the α-sialon phosphor includes an α-sialon phosphor represented by the following general formula (1), a phosphor plate. mx / 2 (Eu) 12-(m+n) (Al) m+n (O) n (N) 16-n (Si) ·· 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. ​ ​ ​ ​ [Example]

[0059] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the descriptions of these examples.

[0060] <Creating a phosphor plate> (Test Example 1) As a raw material for the phosphor plate of Test Example 1, alumina powder (AHP200, manufactured by Nippon Light Metal Co., Ltd., BET specific surface area: 6.0 m) was used. 2 / g), Ca-α sialon phosphor (Alonbright YL-600B, manufactured by Denka Co., Ltd., average particle size D 50 :15μm) was used.

[0061] 7.857 g of alumina powder and 2.833 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 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 is alumina:Ca-α sialon phosphor=70:30 volume %.

[0062] Approximately 11 g of the raw material powder mixture was filled into a carbon die with an inner diameter of 30 mm and fitted with a carbon lower punch, and an upper carbon punch was then fitted to sandwich the raw material powder in place. A 0.127 mm thick carbon sheet (GRAFOIL, manufactured by GraTech) was placed between the raw material powder mixture and the carbon jig to prevent adhesion.

[0063] The hot press jig filled with this raw material powder mixture was placed in a multipurpose high-temperature furnace (Fuji Denpa Kogyo Co., Ltd., Hi-Multi 5000) equipped with a carbon heater. The furnace was evacuated to a vacuum of 0.1 Pa or less, and while maintaining the reduced pressure, the upper and lower punches were pressed at a 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. A fired product with an outer diameter of 30 mm was then recovered, 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 2 mm.

[0064] The BET specific surface area of ​​the alumina powder was measured based on JIS Z 8830:2013. The bulk density of the phosphor plate of Test 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 Test Example 1 was 99.9%. The phosphor plate of Test Example 1 was polished and observed under an SEM, and as a result, it was observed that Ca-α sialon phosphor particles were dispersed in the alumina matrix phase.

[0065] (Test Example 2) Alumina powder was mixed with AKP-3000 (Sumitomo Chemical Co., Ltd., BET specific surface area: 4.5 m 2 A circular phosphor plate having a thickness of 2 mm was obtained in the same manner as in Test Example 1, except that the concentration of the phosphor was changed to 1 / g.

[0066] (Test Example 3) Alumina powder was mixed with AKP-20 (Sumitomo Chemical Co., Ltd., BET specific surface area: 4.3 m 2 A circular phosphor plate having a thickness of 2 mm was obtained in the same manner as in Test Example 1, except that the concentration of the phosphor was changed to 1 / g.

[0067] (Test Example 4) Alumina powder was prepared using AA-03 (Sumitomo Chemical Co., Ltd., BET specific surface area: 5.2 m 2 A circular phosphor plate having a thickness of 2 mm was obtained in the same manner as in Test Example 1, except that the concentration of the phosphor was changed to 1 / g.

[0068] (Test Example 5) Alumina powder was prepared using TM-DAR (manufactured by Taimei Chemical Industry Co., Ltd., BET specific surface area: 14.5 m 2 A circular phosphor plate having a thickness of 2 mm was obtained in the same manner as in Test Example 1, except that the concentration of the phosphor was changed to 1 / g.

[0069] (Test Example 6) Alumina powder was prepared using AKP-53 (manufactured by Sumitomo Chemical Co., Ltd., BET specific surface area: 11.7 m 2 A circular phosphor plate having a thickness of 2 mm was obtained in the same manner as in Test Example 1, except that the concentration of the phosphor was changed to 1 / g.

[0070] [Color] The color of the phosphor plate obtained in each test example was measured using an ultraviolet-visible spectrophotometer (V-550) manufactured by JASCO Corporation, equipped with an integrating sphere device (ISV-469). Base correction was performed using a standard white plate (Spectralon manufactured by Labsphere). The phosphor plate was set and measurements were performed in the wavelength range of 300 to 850 nm, and the color (L) was calculated in accordance with JIS Z 8781-4:2013. * , a * , b * The results are shown in Table 1.

[0071] Based on the results of the color tone in Table 1, Test Examples 1 to 4 were designated as Examples 1 to 4, and Test Examples 5 and 6 were designated as Comparative Examples 1 and 2.

[0072] [Table 1]

[0073] The obtained phosphor plate was evaluated based on the following evaluation items.

[0074] [Crystal structure analysis] The diffraction patterns of the phosphor plates of Examples 1 to 4 were measured using an X-ray diffractometer (product name: Ultima IV, manufactured by Rigaku Corporation), and it was confirmed that a crystalline phase existed in the alumina sintered body. This crystalline phase contained α-alumina and Ca-α-sialon phosphor as the main phase, with a small amount of γ-alumina mixed in.

[0075] [Evaluation of optical properties] The phosphor plates obtained in each Example and Comparative Example were further ground using a surface grinder to obtain circular phosphor plates having the plate thicknesses shown in Table 1, and then the fluorescence intensity was measured according to the following procedure. The optical characteristics of the phosphor plate were measured using a chip-on-board (COB) LED package 130. Figure 3 is a schematic diagram of an apparatus (LED package 130) for measuring the emission spectrum of phosphor plate 100. First, the phosphor plate 100 of each example and comparative example and the aluminum substrate (substrate 30) on which the recess 70 was formed were 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. Next, a blue LED (light-emitting element 20) was mounted inside the recess 70 of the substrate 30 as a blue light source. Thereafter, a circular phosphor plate 100 was placed above 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) LED package 130) shown in FIG.

[0076] Using a total luminous flux measurement system (HalfMoon / φ1000 mm 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.

[0077] The maximum fluorescence intensity (W / nm) of orange light with wavelengths between 585 nm and 605 nm was determined from the obtained emission spectrum. Table 1 shows the relative values ​​(%) of the maximum fluorescence intensity of other Examples and Comparative Examples, normalized to Example 1 as 100%.

[0078] The phosphor plates of Examples 1 to 4 were shown to be superior in fluorescence intensity to those of Comparative Examples 1 and 2.

[0079] This application claims priority based on Japanese Patent Application No. 2019-120859, filed on June 28, 2019, the disclosure of which is incorporated herein by reference in its entirety. [Explanation of symbols]

[0080] 10 Phosphor Plate 20 Light-emitting element 30 boards 40 Solder 50 electrodes 60 Bonding Wire 70 recess 100 phosphor plates 100 Light-emitting device 120 Light-emitting device 130 LED package

Claims

1. A phosphor plate comprising a plate-shaped composite including a base material and a phosphor dispersed in the base material, The main component of the base material is alumina, the phosphor contains an α-sialon phosphor, the content of the α-sialon phosphor in the entire composite is 20 Vol% or more and 60 Vol% or less; The thickness of the phosphor plate is 0.227 mm or less, The L of the phosphor plate when measured in accordance with JIS Z 8781-4 based on the following procedure ＊ a ＊ b ＊ In color coordinates, L ＊ The value is 75.0 or more and 85.0 or less, a ＊ The value is 4.4 or more and 8.0 or less, and b ＊ The value is 10.8 or more and 13.0 or less, Phosphor plate. (procedure) Using an ultraviolet-visible spectrophotometer equipped with an integrating sphere device, base correction is performed using a standard white plate (Spectralon), the phosphor plate is set in the device, and measurement is performed in the wavelength range of 300 to 850 nm under the condition of measurement mode: reflectance, and the color tone (L*, a*, b*) of the phosphor plate is calculated in accordance with JIS Z 8781-4:2013.

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

3. 3. The phosphor plate according to claim 1, The phosphor plate has a thermal conductivity of 10 W / m·K or more and 40 W / m·K or less.

4. The phosphor plate according to any one of claims 1 to 3, The phosphor plate contains an α-sialon phosphor 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 form (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.)

5. The phosphor plate according to any one of claims 1 to 4, A phosphor plate used as a wavelength converter that converts irradiated blue light into orange light and emits it.

6. a group III nitride semiconductor light emitting device; the phosphor plate according to any one of claims 1 to 5 provided on one surface of the group III nitride semiconductor light-emitting device; A light emitting device comprising:

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