Phosphor plate

Abstract

To provide a phosphor plate capable of obtaining a higher luminous flux in white light using a blue LED or LD.SOLUTION: A phosphor plate 1 includes a plate-shaped fired body 5 having a light incident surface 2 for receiving light and a light emission surface 3 for emitting the light received by the light incident surface, and a glass coating layer 4 formed on the light emission surface of the fired body, wherein the fired body includes (Y1-x-y, Gdx, Cey) 3Al5O12 particles (where 0.018 ≤ x ≤ 0.054 and 0.018 ≤ y ≤ 0.025) and Al2O3 particles, the mean particle size of both particles is 3.0 to 5.0 μ m, the concentration of the (Y1-x-y, Gdx, Cey) 3Al5O12 particles to the total of both particles is 15 to 25vol%, the thickness of the fired body is 90 to 160 μ m, the glass coating layer is formed of an inorganic glass coating material, and the roughness Ra of the glass coating layer is 0.05 to 0.4 μm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a ceramic phosphor plate that converts the wavelength of light emitted from a light-emitting diode (LED) or a laser diode (LD) to produce white light. [Background technology]

[0002] LEDs and LDs have the advantage of longer lifespans and lower power consumption compared to fluorescent lamps, and as a result, they are being widely used as lighting sources for backlights and display panels of small displays, panels for large displays, car headlights, and other general lighting fixtures.

[0003] Among white light lamps that use LEDs and LDs to produce white light, the most promising application for lighting fixtures that require higher heat resistance and durability, such as car headlights, is the combination of a blue LED chip or LD chip with various ceramic phosphors. When a blue LED is used as the light source, the light emitted from the blue LED excites the yellow phosphor in the ceramic phosphor, producing white light through an additive mixture of blue and yellow.

[0004] As such a ceramic phosphor, for example, Patent Document 1 discloses a phosphor plate (Y 1-x-y ,Gd x ,Ce y )3AlO 12 It consists of a sintered body of Al2O3 particles (where 0.07≦x≦0.11, 0.010≦y≦0.015) and Al2O3 particles, (Y 1-x-y ,Gd x ,Ce y )3AlO 12 The average particle size of the particles is 4 μm or more and 6 μm or less, and (Y 1-x-y ,Gd x ,Ce y )3AlO 12The total amount of Al2O3 particles and Y 1-x-y ,Gd x ,Ce y )3AlO 12 The particle concentration is 20vol% or more and 30vol% or less, and the average particle size of Al2O3 particles and (Y 1-x-y ,Gd x ,Ce y )3AlO 12 The ratio of the average particle size of the particles (Al2O3 / (Y 1-x-y ,Gd x ,Ce y )3AlO 12 ) is 1 or more and 2 or less, and the total thickness of the fired body is 150 μm or more and 250 μm or less.

[0005] Patent Document 2 also discloses a wavelength conversion element for forming a reflective layer or anti-reflection film on a wavelength conversion layer to improve reliability and light utilization efficiency. Patent Document 2 discloses a wavelength conversion element having a wavelength conversion layer that converts light of a first wavelength to light of a second wavelength, a planarization layer on at least one surface of the wavelength conversion layer that has a surface roughness smaller than that of the wavelength conversion layer, and an anti-reflection film on the planarization layer that prevents reflection of at least a portion of the light of the first wavelength or the light of the second wavelength. Patent Document 2 also discloses that a glass layer is used as the planarization layer, and that its surface roughness Ra is preferably 100 nm (0.1 μm) or less, more preferably 10 nm (0.01 μm) or less, and even more preferably 5 nm (0.005 μm) or less. It is also disclosed that by providing such a planarization layer on the surface of a wavelength conversion layer made of a sintered phosphor, voids on the surface of the wavelength conversion layer are filled with the planarization layer, and an anti-reflection film compatible with the refractive index of the planarization layer can be formed, thereby improving light utilization efficiency. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-104527 [Patent Document 2] Japanese Patent Publication No. 2022-41839 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, various studies have been conducted on improving LED chips, LD chips, and phosphor materials in order to increase the luminous flux of white light lamps using blue LEDs or LDs. While the phosphor plate described in Patent Document 1 did achieve a reasonable improvement in luminous flux, it did not fully meet the demands of recent years. Against this background, the present invention aims to provide a phosphor plate that can achieve a higher luminous flux in white light lamps using blue LEDs or LDs. [Means for solving the problem]

[0008] The phosphor plate of the present invention is a phosphor plate comprising a plate-shaped fired body having a light incident surface that receives light from a light source and a light emitting surface that is disposed opposite the light incident surface and emits the light received at the light incident surface, and a glass coating layer formed on the light emitting surface of the fired body, wherein the fired body is (Y 1-x-y ,Gd x ,Ce y )3AlO 12 particles (wherein 0.018≦x≦0.054 and 0.018≦y≦0.025) and Al2O3 particles, 1-x-y ,Gd x ,Ce y )3AlO 12 particles and the Al2O3 particles have an overall average particle size of 3.0 μm or more and 5.0 μm or less, and 1-x-y ,Gd x ,Ce y )3AlO 12 The total amount of Al2O3 particles and Y 1-x-y ,Gd x ,Ce y )3AlO 12The particle concentration is 15 vol% or more and 25 vol% or less, the thickness of the fired body is 90 μm or more and 160 μm or less, the glass coating layer is formed from an inorganic glass coating material, and the surface roughness Ra of the glass coating layer surface is 0.05 μm or more and 0.4 μm or less. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a phosphor plate that can obtain a higher luminous flux in a white light lamp using a blue LED or LD. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a phosphor plate according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The phosphor plate of the present invention will be described in detail below with reference to the drawings. The phosphor plate 1 of the present invention comprises a plate-shaped fired body 5 having a light incident surface 2 that receives light from a light source and a light exit surface 3 that is arranged opposite the light incident surface 2 and that emits the light received by the light incident surface 2, and a glass coating layer 4 formed on the light exit surface 3 of the fired body 5.

[0012] The plate-shaped fired body 5 of the phosphor plate 1 is (Y 1-x-y ,Gd x ,Ce y )3AlO 12 particles (hereinafter also referred to as "YAG-based particles") and Al2O3 particles, 1-x-y ,Gd x ,Ce y )3AlO 12The YAG particles and the Al2O3 particles have an overall average particle size of 3.0 μm or more and 5.0 μm or less, and the Gd concentration (x) and Ce concentration (y) in the YAG particles are adjusted to 0.018≦x≦0.054 and 0.018≦y≦0.025. Due to the excellent internal light scattering properties of the sintered body 5 made of such a composite material and having the specific overall average particle size, the Ce concentration (y) in the YAG particles can be increased compared to conventional techniques, and the Gd concentration (x) can be decreased compared to conventional techniques, thereby increasing the efficiency of conversion from blue light to yellow light, and reducing the thickness of the sintered body 5 to 90 μm or more and 160 μm or less, resulting in a higher luminous flux than conventional techniques.

[0013] In this specification, luminous flux refers to the brightness of white light, and refers to the brightness of white light produced by additive color mixing when a blue LED chip is mounted in a light-emitting device and the blue LED is irradiated onto a phosphor plate 1 to emit fluorescence.

[0014] The above (Y 1-x-y ,Gd x ,Ce y )3AlO 12 When the overall average particle size of the Al2O3 particles and the Al2O3 particles is set to 3.0 μm to 5.0 μm and the thickness of the fired body 5 is set to 90 μm to 160 μm, if the Ce concentration (y) is less than 0.018 and the Gd concentration (x) is greater than 0.054, the conversion efficiency from blue light to yellow light is low, resulting in a bluish white color. On the other hand, if the Ce concentration (y) is greater than 0.025 and the Gd concentration (x) is less than 0.018, the color is yellowish white.

[0015] By making the YAG-based particles satisfy the conditions of 0.018≦x≦0.054 and 0.018≦y≦0.025, making the overall average particle size of the YAG-based particles and the Al2O3 particles 3.0 μm or more and 5.0 μm or less, and making the thickness of the fired body 5 90 μm or more and 160 μm or less, it is possible to achieve a white color with little other coloring (high whiteness) and an increased luminous flux.

[0016] In particular, by setting the Gd concentration (x) to 0.054 or less and reducing the amount of Gd that causes high-temperature degradation, it is possible to improve the temperature characteristics. Note that the temperature characteristics refer to the temperature dependence of wavelength conversion efficiency, and a decrease in temperature characteristics refers to a decrease in wavelength conversion efficiency as the temperature increases. In the phosphor plate of the present invention, the ratio of Gd concentration (x) / Ce concentration (y) in the phosphor plate is preferably 0.9 to 2.2. By setting the ratio in this range, a phosphor plate with higher whiteness can be obtained.

[0017] Here, the temperature characteristics are calculated by placing the phosphor plate 1 (10 mm x 10 mm) in the center of a 4-inch integrating sphere equipped with a heater, irradiating it with excitation light of 450 nm ± 1 nm in the same manner as in measuring the fluorescence wavelength, measuring the quantum efficiency at 25°C and 200°C from the emission spectrum of the phosphor plate 1, and dividing the quantum efficiency at 200°C by the quantum efficiency at 25°C. 1-x-y ,Gd x ,Ce y )3AlO 12 The Gd concentration (x) and Ce concentration (y) in the particles can be measured by ICP emission spectroscopy.

[0018] If the overall average particle size of the YAG particles and the Al2O3 particles is less than 3.0 μm, the number of grain boundaries becomes too large to obtain sufficient luminous flux, and if it exceeds 5.0 μm, the thickness of the fired body 5 (90 μm to 160 μm) does not provide sufficient internal light scattering, resulting in low efficiency of conversion from blue light to yellow light and a bluish white color. The overall average particle size of the YAG-based particles and the Al2O3 particles can be determined by photographing any portion of the surface of the plate-like sintered body 5 using a laser microscope or a scanning electron microscope, and measuring the imaged YAG-based particles and the Al2O3 particles without distinguishing between them using a linear intercept method. In this case, thermal etching can be performed as necessary to more clearly observe the grain boundaries.

[0019] Furthermore, if the thickness of the fired body 5 is less than 90 μm, sufficient internal light scattering cannot be obtained, the conversion efficiency from blue light to yellow light is low, and the color becomes bluish white, and if the thickness of the fired body 5 exceeds 160 μm, sufficient luminous flux cannot be obtained. The thickness of the fired body 5 can be measured using a micrometer or by standing the fired body 5 upright and observing it under an optical microscope. In the phosphor plate 1 of the present invention, the concentration of YAG-based particles in the fired body 5 is preferably 15 vol% or more and 25 vol% or less, relative to 100 vol% of the total amount of the YAG-based particles and Al2O3 particles. By setting the concentration of YAG-based particles within this range, it is possible to achieve more appropriate internal scattering of light in the fired body 5. The concentration of YAG-based particles can be determined by calculating the ratio of YAG phase to Al2O3 phase using X-ray diffraction (XRD) of the phosphor plate 1.

[0020] In the phosphor plate 1 of the present invention, a glass coating layer 4 made only of an inorganic glass coating material is formed on the light-emitting surface 3 of the fired body 5. The inorganic glass coating material is, for example, perhydropolysilazane, which is a polymer compound that does not contain carbon compounds such as methyl groups or vinyl groups in its side chains. The glass coating layer formed from the organic glass coating material that has been widely used up until now has had a problem with heat resistance. In contrast, inorganic glass coating materials can be used without problems in applications that require higher heat resistance, such as car headlights, and produce a high luminous flux.

[0021] The surface roughness Ra (based on JIS B0601:1994) of the surface of the glass coating layer 4 is 0.05 μm or more and 0.4 μm or less. Patent Document 2 describes that it is preferable that the surface roughness Ra of the planarizing layer formed on one surface of the wavelength conversion element is as small as possible, but with an extremely flat surface with Ra of less than 0.05 μm, the transmittance of blue excitation light increases too much, reducing the conversion efficiency and resulting in a bluish white color.

[0022] For this reason, in the present invention, an appropriate degree of roughness is provided to the glass coating layer 4 to prevent a decrease in whiteness (the smaller the deviation from the CIE chromaticity coordinates (0.33, 0.33), the higher the whiteness). In the present invention, by setting the surface roughness Ra of the glass coating layer 4 surface to 0.05 μm or more and 0.4 μm or less, the CIE chromaticity coordinates of the white light emitted from the surface of the glass coating layer can be made closer to (0.33, 0.33) (reducing color unevenness) and the light extraction efficiency can be improved.

[0023] The fact that the glass coating layer is made of an inorganic glass coating material can be confirmed by the C / Si molar ratio value obtained by analyzing the cross section using energy dispersive X-ray analysis (EDS). When an organic glass coating material such as organopolysiloxane is used, the C / Si molar ratio is 5 or more, whereas when an inorganic glass coating agent such as perhydropolysilazane is used, the C / Si molar ratio is 1 or less, even taking into account measurement errors such as when carbon tape is used to fix the sample in the EDS analysis and contamination such as hydrocarbons.

[0024] The average thickness of the glass coating layer 4 is preferably 0.1 μm to 3 μm, more preferably 0.3 μm to 2 μm. By setting the thickness within this range, the surface roughness of the glass coating layer 4 can be more reliably set to 0.05 μm to 0.4 μm, thereby achieving both improved light extraction efficiency and improved color unevenness. The average thickness of the glass coating layer 4 was measured as follows. That is, an arbitrary cross section in the thickness direction of the phosphor plate on which the glass coating layer was formed was imaged using a scanning electron microscope (SEM) with a field of view of 10 μm vertical x 12 μm horizontal, and the area of ​​the glass coating layer was determined by image processing. This area was then divided by 12 μm to obtain the thickness. The same image was taken at 10 different locations, and the average value was used as the average thickness.

[0025] For example, spin coating can be used as a method for forming the glass coating layer 4. In the spin coating method, a uniform polysilazane layer is formed over the entire surface of the substrate by rotating the fired body 5 at high speed, onto which perhydropolysilazane (PHPS) dissolved in an organic solvent has been dropped, and then a dense glass coating film is obtained by heat treating (baking) the fired body 5 at 400 to 500°C for 50 to 70 minutes in an oxidizing atmosphere.

[0026] An example of a method for producing the phosphor plate 1 of the present invention will be described below. Yttrium (III) oxide (Y2O3), cerium (IV) oxide (CeO2), gadolinium (III) oxide (Gd2O3), and aluminum oxide (Al2O3) are mixed and formed into a sheet, which is then degreased and pressed to create a green molded product of the desired shape. Next, the green molded product is cut into 1.0 x 10 -2 The fired body 5 is obtained by firing under a vacuum atmosphere of medium to low vacuum of not more than Pa. The fired body 5 is a fired body made of YAG particles and Al2O3 particles.

[0027] Next, the surface of the fired body 5 is glass coated. As described above, the glass coating is carried out by using a method such as spin coating. [Example]

[0028] The present invention will be specifically described below based on examples, but the present invention is not limited to the examples shown below. [Example 1] [Preparation of Chip Phosphor Plate] [1][(Y 1-x-y ,Gd x ,Ce y )3AlO 12 +Al2O3] Preparation of fired body Cerium (IV) oxide powder with an average particle size of 0.4 μm and a purity of 99.9%, yttrium (III) oxide powder with an average particle size of 1.0 μm and a purity of 99.9%, gadolinium (III) oxide powder with an average particle size of 0.7 μm and a purity of 99.9%, and aluminum oxide powder with an average particle size of 0.3 μm and a purity of 99.9% were mixed in a predetermined blending ratio to obtain a raw material powder. 1-x-y ,Gd x ,Ce y )3AlO 12 The weights of the yttrium (III) oxide powder, gadolinium (III) oxide powder, cerium (IV) oxide powder, and aluminum oxide powder were adjusted so that the Gd concentration and Ce concentration in the (+Al2O3) sintered body 5 would be the compositions shown in Table 1.

[0029] To this raw powder (100 wt%), 30 wt% ethanol, 10 wt% polyvinyl butyral (PVB) binder, and 3 wt% succinic acid plasticizer were added, and the mixture was ground and mixed for 50 hours in a ball mill using aluminum oxide balls to prepare a slurry. This slurry was used to form green sheets of a predetermined thickness by a doctor blade method. At this time, the thickness of the formed green sheets and the number of layers were adjusted so that the resulting fired body 5 had the thickness shown in Table 1. Specifically, 80 μm green sheets were prepared and two of these were layered. The obtained green sheet (laminate) was degreased in air at 600°C for 120 minutes, calcined in air at 1200°C for 90 minutes, and then -2 The mixture was baked at 1680°C for 360 minutes in a vacuum atmosphere of 0.05 Pa or less. 1-x-y ,Gd x ,Ce y )3AlO 12 A fired body 5 consisting of Al2O3 particles and Al2O3 particles was obtained. Note that the thickness after firing was 100 μm as shown in Table 1 due to shrinkage.

[0030] [2] Formation of a glass coating layer on the surface of the fired body A mixed solution of perhydropolysilazane and dibutyl ether (Sanwa Chemical Co., Ltd., Sancelazane ANN120-20) was uniformly applied by spin coating onto the surface of the fired body 5. Then, the fired body 5 was baked at 450°C for 60 minutes to form a glass coating layer 4 with a thickness of 1.5 μm on the surface of the fired body 5.

[0031] [3] Cutting The fired body 5 on which the glass coating layer 4 was formed was cut into 1 mm x 1 mm pieces by dicing to produce chip-shaped phosphor plates.

[0032] [Evaluation of Chip Phosphor Plates] [1] Gd and Ce concentrations By ICP emission spectrometry, the (Y 1-x-y ,Gd x ,Ce y )3AlO 12 The Gd concentration (x) and Ce (y) concentrations were determined for five fired bodies consisting of Al2O3 particles and Al2O3 particles.

[0033] [2](Y 1-x-y ,Gd x ,Ce y )3AlO 12 particle concentration The ratio of YAG phase to Al2O3 phase was calculated by X-ray diffraction (XRD) of the phosphor plate. 1-x-y ,Gd x ,Ce y )3AlO 12 (Y 1-x-y ,Gd x ,Ce y )3AlO 12 The concentration of the particles was measured.

[0034] [3] Overall average particle size of YAG particles and Al2O3 particles An arbitrary portion of the opposite side of the chip phosphor plate, on which the glass coating layer was not formed, was photographed using a laser microscope, and the imaged YAG-based particles and Al2O3 particles were measured using the linear intercept method without distinguishing between them to determine the average particle size of the YAG-based particles and Al2O3 particles as a whole. The overall average particle size shown in Table 1 represents the average value of the overall average particle size obtained by photographing five different arbitrary portions.

[0035] [4] Room temperature luminous flux The chip phosphor plate was fixed onto a blue LED chip (light-emitting area 1 mm square, emission wavelength 450 nm) with silicone resin. The emitted light was collected using a 4-inch integrating sphere, and the emission spectrum at room temperature was measured using a visible-near-infrared fiber multichannel spectrometer (manufactured by Ocean Photonics, product name USB4000-VIS-NIR-ES). The luminous flux was calculated from the obtained emission spectrum. The same type of LED chip was sealed with commercially available YAG:Ce phosphor powder (Mitsubishi Chemical High-Technica Corporation, product name P46-Y3) impregnated at 20 vol% in commercially available phenyl silicone resin (Dow Corning, product name OE-6630), and the relative luminous flux value was calculated with the luminous flux set at 100. A relative luminous flux value of 127 or higher was deemed to have produced bright white light, and a value of 121 or lower was deemed to have been insufficient.

[0036] [5] Temperature characteristics The LED chip phosphor plates were arranged in three rows, vertically, horizontally, and diagonally, in a 3x3 array using commercially available phenyl silicone resin (Dow Corning, product name OE-6630). These were then placed in the center of a 4-inch integrating sphere equipped with a heater. Similar to the fluorescence wavelength measurement, excitation light of 450 nm ± 1 nm was irradiated, and the quantum efficiency at 25°C and 200°C was measured from the emission spectrum of the phosphor plate. The quantum efficiency at 200°C divided by the quantum efficiency at 25°C was used to determine the temperature dependence of wavelength conversion efficiency. A quantum efficiency of 84 or higher was considered to be excellent in terms of temperature dependence, while a value of 81 or lower was considered to be poor.

[0037] [6] Whiteness The chip-shaped phosphor plate was fixed with silicone resin on top of a blue LED chip (light-emitting area 1 mm square, emission wavelength 450 nm). The chromaticity (CIE_x, CIE_y) of the light emitted from the phosphor plate in the vertical direction (0°) in the CIE 1931 color space was measured. When both ΔCIE_x and ΔCIE_y were 0.02 or less relative to the white chromaticity (0.33, 0.33), the whiteness was judged to be excellent, and when greater than 0.02, it was judged to be poor.

[0038] [comprehensive evaluation] If all of the evaluation items [3] to [5] were excellent, the evaluation was marked with a "○", if there was one poor evaluation, the evaluation was marked with a "△", and if there were two or more poor evaluations, the evaluation was marked with an "×". The results are shown in Table 1.

[0039] [Examples 2 and 3] [Comparative Examples 1 and 2] Chip-type phosphor plates were produced in the same manner as in Example 1, except that the composition of the raw material powder (gadolinium (III) oxide powder concentration, cerium (IV) oxide powder concentration) was changed and the Gd concentration and Ce concentration of the fired body were changed as shown in Table 1. The composition of the phosphor plate and the results of evaluation in the same manner as in Example 1 are shown in Table 1. It was found that Comparative Example 1, which had a high Ce concentration, had a small room temperature luminous flux and inferior white light brightness, while Comparative Example 2, which had a high Gd concentration, had inferior temperature dependence of wavelength conversion efficiency (temperature characteristics, which are the luminous flux at high temperatures) from room temperature to 200°C.

[0040] [Examples 4 and 5] [Comparative Examples 3 and 4] (Y 1-x-y ,Gd x ,Ce y )3AlO 12 (Y 1-x-y ,Gd x ,Ce y )3AlO 12 Chip phosphor plates were produced in the same manner as in Example 1, except that the particle concentration was changed as shown in Table 1. The composition of the phosphor plate and the results of evaluation in the same manner as in Example 1 are shown in Table 1. (Y 1-x-y ,Gd x ,Ce y )3AlO 12 In Comparative Example 3, where the particle concentration was less than 15 vol%, the brightness decreased due to increased internal scattering, and in Comparative Example 4, where the particle concentration was more than 25 vol%, the whiteness decreased due to decreased internal scattering.

[0041] [Examples 6 to 8] [Comparative Examples 5 and 6] A phosphor plate was produced in the same manner as in Example 1, except that the thickness of the green sheet formed by the doctor blade method was changed and the thickness of the fired body was changed as shown in Table 1. The composition of the phosphor plate and the results of evaluation in the same manner as in Example 1 are shown in Table 1. In Comparative Example 5, in which the thickness of the fired body was less than 90 μm, bright white light was obtained but the whiteness was poor. On the other hand, in Comparative Example 6, in which the thickness of the fired body was more than 160 μm, the brightness was poor.

[0042] [Examples 9 and 10], [Comparative Examples 7 and 8] A phosphor plate was produced in the same manner as in Example 1, except that the firing temperature and time were changed and the overall average particle size of the fired body was changed as shown in Table 1. The composition of the phosphor plate and the results of evaluation in the same manner as in Example 1 are shown in Table 1. In Comparative Example 7, where the fired body had an overall average particle size of less than 3.0 μm, sufficient luminous flux was not obtained. On the other hand, in Comparative Example 8, where the fired body had an overall average particle size of more than 5.0 μm, sufficient internal light scattering was not obtained, resulting in low efficiency of conversion from blue light to yellow light and a bluish white color.

[0043] Comparative Example 9 In Comparative Example 9, a phosphor plate was produced in the same manner as in Example 1, except that the raw material for forming the glass coating layer 4 was changed from perhydropolysilazane, an inorganic glass coating material, to organopolysilazane (Sancelazane, product name #2000-20, manufactured by Sanwa Chemical Co., Ltd.). The composition of the phosphor plate and the results of evaluation in the same manner as in Example 1 are shown in Table 1. Comparative Example 9, in which the glass coating layer 4 was formed using organopolysiloxane, an organic glass coating material (cross-sectional C / Si molar ratio of 7.0), had poor heat resistance, film peeling occurred during use, and the brightness of the white light was poor.

[0044] [Comparative Example 10] A phosphor plate was produced in the same manner as in Example 1, except that the spin coating was repeated three times. The composition of the phosphor plate and the results of evaluation in the same manner as in Example 1 are shown in Table 1. The surface roughness Ra of the glass coating layer 4 surface was 0.01 μm, and in Comparative Example 10, where Ra was small, the color was slightly bluish white.

[0045] [Example 11] A phosphor plate was prepared in the same manner as in Example 1, except that the spin coating was repeated twice. The composition of the phosphor plate and the results of evaluation in the same manner as in Example 1 are shown in Table 1. The phosphor plate of Example 11, in which the surface roughness Ra of the glass coating layer 4 surface was 0.05 μm, which was larger than 0.01 μm in Comparative Example 10, had high room temperature luminous flux, good temperature characteristics, and high whiteness, similar to the other Examples.

[0046] [Example 12] A phosphor plate was produced in the same manner as in Example 1, except that the ratio of perhydropolysilazane in the mixed solution of perhydropolysilazane and dibutyl ether was set to 2 / 3. The composition of the phosphor plate and the results of evaluation in the same manner as in Example 1 are shown in Table 1. The phosphor plate of this Example 10, in which the surface roughness Ra of the glass coating layer 4 was 0.40 μm, which was smaller than the 0.41 μm of Comparative Example 11 described later, had a high room temperature luminous flux, good temperature characteristics, and high whiteness, similar to the other Examples.

[0047] [Comparative Example 11] A phosphor plate was prepared in the same manner as in Example 2, except that the ratio of perhydropolysilazane in the mixed solution of perhydropolysilazane and dibutyl ether was halved. The composition of the phosphor plate and the results of evaluation in the same manner as in Example 1 are shown in Table 1. In Comparative Example 11, in which the surface roughness Ra was 0.41 μm, which was greater than 0.020 μm, the emitted light was scattered significantly, and the luminous flux was insufficient.

[0048] [Reference example] As a conventional example, ((Y 1-x-y ,Gd x ,Ce y )3AlO 12 +Al2O3) (x=0.070; y=0.012) fired body (corresponding to Patent Document 1) was used to prepare a phosphor plate having a thickness of 200 μm without providing a glass coating layer 4, and evaluated in the same manner as in Example 1. As shown in Table 1, the phosphor plate of the reference example was inferior to the phosphor plate of the present invention in both room temperature luminous flux and temperature characteristics.

[0049] The above experiments confirmed that the phosphor plate of the present invention can provide a higher luminous flux and excellent whiteness in a white light LED.

[0050] [Table 1] [Explanation of symbols]

[0051] 1 phosphor plate 2 light incidence surface 3 light exit surface 4 layers of glass coating 5. Fired body

Claims

[Claim 1] a plate-shaped fired body having a light incident surface that receives light from a light source and a light emitting surface that is disposed opposite the light incident surface and that emits the light received at the light incident surface; A phosphor plate having a glass coating layer formed on the light emitting surface of the fired body, The fired body (Y 1-x-y , Gd x , Ce y ) 3 Al 5 O 12 particles (where 0.018≦x≦0.054 and 0.018≦y≦0.025) and Al 2 O 3 It consists of particles, The (Y 1-x-y , Gd x , Ce y ) 3 Al 5 O 12 Particles and the Al 2 O 3 The particles have an overall average particle size of 3.0 μm or more and 5.0 μm or less, The (Y 1-x-y , Gd x , Ce y ) 3 Al 5 O 12 Particles and Al 2 O 3 With respect to the total amount of particles (100 vol%), (Y 1-x-y , Gd x , Ce y ) 3 Al 5 O 12 The particle concentration is 15 vol% or more and 25 vol% or less, The thickness of the fired body is 90 μm or more and 160 μm or less, The glass coating layer is formed of an inorganic glass coating material, and the surface roughness Ra of the glass coating layer is 0.05 μm or more and 0.4 μm or less.

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