Phosphor plate

Abstract

The present invention provides a phosphor plate that can obtain a higher luminous flux in a white light source using blue LEDs and LDs. [Solution] The fired body consists of YAG-based phosphor particles and matrix particles made of Al2O3, AlN, or MgO, forming an uneven surface. The uneven surface has protrusions on its apex where the glass coating layer with a thickness of 2 nm to 20 nm is formed. There are 50 to 380 such protrusions in a field of view of 150 μm × 150 μm. The recesses of the uneven surface other than the protrusions are formed with a glass coating layer with an average thickness of 1.5 μm to 3.5 μm. The average thickness of the fired body is 90 μm to 160 μm, and the surface roughness Ra of the glass coating layer surface is 0.05 μm to 0.4 μm.

Description

[Technical Field]

[0001] This invention relates to a phosphor plate made of ceramics that converts the wavelength of light emitted from light-emitting diodes (LEDs) and laser diodes (LDs) to obtain white light. [Background technology]

[0002] LEDs and LDs offer advantages over fluorescent lamps, such as longer lifespan and lower power consumption. Therefore, they are increasingly being used as backlights and display panels for small displays, panels for large displays, car headlights, and other general lighting fixtures.

[0003] Among white light sources that produce white light using LEDs and LDs, the combination of blue LED chips or LD chips with various ceramic phosphors is particularly promising for applications in lighting fixtures requiring higher heat resistance and durability, such as car headlights. 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, resulting in white light emission through additive mixing of blue and yellow light.

[0004] In recent years, various studies have been conducted to improve the phosphor material, LED chip, or LD chip in white light sources using ceramic phosphors and blue LEDs or LDs, in order to increase extraction efficiency as much as possible. As an example of the ceramic phosphor, Patent Document 1 discloses a wavelength conversion member comprising a glass matrix, a phosphor layer containing phosphor particles dispersed in the glass matrix, and a low refractive index layer provided on the surface of the phosphor layer having a refractive index less than or equal to that of the phosphor particles, wherein the low refractive index layer has an uneven structure, and the root mean square slope WΔq of the undulation curve of the uneven structure is 0.1 to 1. In addition, Patent Document 1 describes that the particle diameter of the phosphor particles is preferably 10 μm or more and 50 μm or less. According to such a wavelength conversion member, an improvement in extraction efficiency is recognized, and it is disclosed that by using the phosphor particles, the improvement in extraction efficiency based on the uneven structure can be further enhanced.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Since the wavelength conversion member of Patent Document 1 has a matrix in which phosphor particles are dispersed made of glass such as borosilicate glass, there are problems such as high straight-through transmissivity of the excitation light from the light source and large color separation between the excitation light and the fluorescence. In addition, compared with ceramic materials, the strength is low, and sufficient thinning to increase the light speed cannot be achieved. Furthermore, compared with ceramic materials, the thermal conductivity is low and sufficient heat dissipation cannot be performed, which has been a factor in accelerating the deterioration of the temperature characteristics of the wavelength conversion member.

[0007] As shown in FIG. 4, in the main surface 11a of the phosphor layer 11 of the wavelength conversion member of Patent Document 1, phosphor particles 14 protrude from the surface of the glass matrix 13, and a low refractive index layer 12 having a substantially uniform thickness is provided along the protruding phosphor particles 14, so that the low refractive index layer 12 forms an uneven structure. Since the low refractive index layer 12 is formed with a substantially uniform thickness in this way, combined with the fact that it is the above-mentioned glass matrix, there is a problem that the excitation light easily passes through the wavelength conversion member and sufficient external quantum efficiency by the phosphor particles cannot be obtained.

[0008] Furthermore, in the wavelength conversion member described in Patent Document 1, the thickness of the phosphor layer 11 is preferably as thin as possible, preferably 0.03 mm (30 μm) or more and 0.2 mm (200 μm) or less, and the average particle diameter of the phosphor particles is 10 μm or more. However, with such thickness and phosphor particle size, sufficient internal scattering of light cannot be obtained within the wavelength conversion material, resulting in low conversion efficiency from blue light to yellow light, i.e., external quantum efficiency, and a tendency for the resulting color to be a bluish-white. While it is true that the wavelength conversion member described in Patent Document 1 did show a considerable improvement in extraction efficiency, it did not fully meet the demands of recent years.

[0009] Against this backdrop, the present invention aims to provide a phosphor plate that can achieve higher conversion efficiency from blue light to yellow light and higher whiteness in a white light source using blue LEDs and LDs. [Means for solving the problem]

[0010] The phosphor plate of the present invention comprises a plate-shaped fired body having a light incident surface for receiving light from a light source and a light emission surface positioned opposite the light incident surface and emitting light received on the light incident surface, and a glass coating layer formed on the light emission surface of the fired body, wherein the fired body consists of YAG-based phosphor particles and matrix particles made of Al2O3, AlN, or MgO, the overall average particle size of the phosphor particles and the matrix particles is 3.0 μm or more and 5.0 μm or less, the light emission surface of the fired body has an uneven surface made of the phosphor particles and the matrix particles, the uneven surface has a plurality of protrusions on its tops, the glass coating layer with an average thickness of 2 nm or more and 20 nm or less is formed thereon The material includes protrusions made of body particles and protrusions made of matrix particles, and when observed from above the light-emitting surface, there are 50 to 380 such protrusions in a field of view of 150 μm × 150 μm, and when observed from above the light-emitting surface, the total area of ​​the multiple protrusions in a field of view of 150 μm × 150 μm is 16% to 35% of the area of ​​the field of view, and the glass coating layer with an average thickness of 1.5 μm to 3.5 μm is formed in the recesses of the uneven surface other than the multiple protrusions, the average thickness of the fired body in the direction from the light-incident surface to the light-emitting surface is 90 μm to 160 μm, the glass coating layer is formed of an inorganic glass coating material, and the surface roughness Ra of the glass coating layer surface is 0.05 μm to 0.4 μm.

[0011] In the phosphor plate of the present invention, a higher conversion efficiency from blue light to yellow light and a higher degree of whiteness can be obtained in a white light source using blue LEDs and LDs. [Effects of the Invention]

[0012] According to the present invention, a phosphor plate with higher external quantum efficiency and higher whiteness can be provided in a white light source using blue LEDs and LDs. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic diagram showing a phosphor plate, which is one embodiment of the present invention. [Figure 2] Figure 2 is an observation photograph taken from above the light-emitting surface of a phosphor plate, which is one embodiment of the present invention. [Figure 3] Figure 3 is a schematic diagram of the AA cross-section (light-emitting surface side only) at an arbitrary point in an observation photograph taken from above the light-emitting surface of a phosphor plate, which is one embodiment of the present invention. [Figure 4] Figure 4 is a schematic diagram of the wavelength conversion member shown in Patent Document 1. [Modes for carrying out the invention]

[0014] The phosphor plate of the present invention will be described in detail below with reference to Figures 1 to 3. 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 emission surface 3 that is positioned opposite the light incident surface 2 and emits the light received by the light incident surface 2, and a glass coating layer 4 formed on at least the light emission surface 3 of the fired body 5.

[0015] The plate-shaped fired body 5 in the phosphor plate 1 consists of YAG-based phosphor particles 6 and matrix particles 7 made of Al2O3, AlN, or MgO, and the overall average particle size (hereinafter also referred to as the overall average diameter) of the phosphor particles 6 and the matrix particles 7 is 3.0 μm or more and 5.0 μm or less. The overall average particle size of the YAG-based phosphor particles and the Al2O3 particles can be determined by photographing any portion of the surface of the plate-shaped fired body 5 using a laser microscope or scanning electron microscope, and measuring the YAG-based phosphor particles and Al2O3 particles without distinguishing between them using a linear intercept method. In this case, if necessary, thermal etching can be performed to observe the grain boundaries more clearly. The light-emitting surface 3 of the fired body 5 has an uneven surface formed thereon, consisting of the phosphor particles 6 and the matrix particles 7, and the glass coating layer 4 is formed on this uneven surface so as to have an average thickness of 2 nm to 20 nm above the top of the surface (at the top of the protrusions 8 of the uneven surface).

[0016] As shown in Figure 3, the plurality of protrusions include protrusions made of the phosphor particles 6 and protrusions made of the matrix particles 7. In other words, multiple protrusions 8 are formed, and one of these protrusions is made of either the phosphor particles 6 or the matrix particles 7, and the protrusion 8 as a whole is made of both the phosphor particles 6 and the matrix particles 7. When observed from above the light-emitting surface, there are between 50 and 380 protrusions 8 in a field of view of 150 μm × 150 μm. The firing body 5, made of such a composite material and having a specific overall average particle size, exhibits good internal light scattering properties. By having a specific number of protrusions 8 per unit area on the uneven surface, each with a glass coating layer of a specific average thickness, appropriate reflection of blue light can be obtained, thereby increasing the conversion efficiency from blue light to yellow light. Furthermore, the average thickness of the firing body 5 in the direction from the light incident surface to the light emission surface can be reduced to 90 μm or more and 160 μm or less, resulting in a higher luminous flux compared to the conventional technology. Furthermore, the YAG-based phosphor particles mentioned above refer to (Y 1-x-y ,Gd x Ce y )3Al5O1 2 pairs (where 0.000≦x≦0.060 and 0.008≦y≦0.030) It is a particle composed of the same elements.

[0017] If the average thickness of the glass coating layer 4 formed above the protrusions 8 exceeds 20 nm above the top, or if the number of protrusions 8 in a field of view of 150 μm × 150 μm is less than 50 when observed from above the light-emitting surface 3, the amount of blue light reflected at the light-emitting interface 3 and returning to the phosphor plate is insufficient, resulting in a low conversion efficiency from blue light to yellow light. By limiting the number of the protrusions 8 to 380 or less, it is possible to achieve both a higher luminous flux and improved conversion efficiency from blue light to yellow light, in other words, an improved external quantum efficiency. Furthermore, by setting the average thickness of the glass coating layer 4 to 2 nm or more, it is possible to reduce the occurrence of chipping defects in the dicing process when manufacturing phosphor chips from phosphor plates.

[0018] The aforementioned protrusion 8 consists of both the phosphor particles 6 and the matrix particles 7. In particular, the protrusions of the matrix particles reflect a large amount of blue light, which greatly contributes to improving the external quantum efficiency. Furthermore, when observed from above the light-emitting surface 3, it is preferable that the total area of ​​the protrusions in a field of view of 150 μm × 150 μm is between 16% and 35% of the field of view area. This makes it possible to more reliably achieve both a higher luminous flux and improved external quantum efficiency.

[0019] In this specification, luminous flux refers to the brightness of white light, and it 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 shone onto a phosphor plate 1 to cause fluorescence emission.

[0020] If the overall average particle size of the phosphor particles 6 and the matrix particles 7 is less than 3.0 μm, there will be too many grain boundaries, and a sufficient luminous flux cannot be obtained. Furthermore, if the overall average particle size of the phosphor particles 6 and the matrix particles 7 exceeds 5.0 μm, sufficient internal light scattering cannot be obtained at the average thickness of the calcined body 5 (90 μm to 160 μm), resulting in low conversion efficiency from blue light to yellow light and a bluish-white color.

[0021] In the phosphor plate 1 of the present invention, the glass coating layer 4 with an average thickness of 1.5 μm or more and 3.5 μm or less is formed in the recesses other than the protrusions on the uneven surface. If the average thickness of the glass coating layer formed above the recesses other than the aforementioned protrusions is less than 1.5 μm, the transmission of blue and yellow light from the recesses will be poor, and sufficient light flux (extraction efficiency) cannot be obtained. Furthermore, if the average thickness of the glass coating layer formed above the recesses other than the convex portions exceeds 3.5 μm, the amount of blue and yellow light absorbed in those recesses increases, and a high luminous flux (extraction efficiency) cannot be obtained. Furthermore, as shown in Figure 3, the recessed portion may have irregularities caused by protrusions 9 that do not correspond to the protrusions 8 on which the glass coating layer with an average thickness of 2 nm to 20 nm is formed above its apex. The presence of these irregularities enhances light scattering and reduces color unevenness.

[0022] The average thickness of the glass coating layer 4 was measured as follows. Specifically, an arbitrary cross-section in the thickness direction of a phosphor plate with a glass coating layer was imaged using a scanning electron microscope (SEM) with a field of view of 10 μm vertically and 12 μm horizontally. The area of ​​the glass coating layer was determined by image processing, and this value was divided by 12 μm to obtain the thickness. The same imaging was performed at 10 different locations, and the average value was taken as the average thickness.

[0023] Furthermore, if the average thickness of the fired body 5 is less than 90 μm, sufficient internal light scattering cannot be obtained, resulting in low conversion efficiency from blue light to yellow light and a bluish-white color. On the other hand, if the average thickness of the fired body 5 exceeds 160 μm, sufficient luminous flux cannot be obtained. The average thickness of the fired body 5 can be measured using a micrometer, or by placing the fired body 5 upright and using an optical microscope.

[0024] Furthermore, the YAG-based phosphor particles are present in the calcined body, (Y 1-x-y ,Gd x Ce y )3Al5O 12 The particles are preferably composed of the following elements (where 0.018 ≤ x ≤ 0.054 and 0.018 ≤ y ≤ 0.025), and it is preferable to use Al2O3 particles as the matrix particles. This makes it possible to more reliably obtain higher external quantum efficiency and higher whiteness at the average thickness of the sintered body 5. In the phosphor plate 1 of the present invention, it is preferable that the concentration of phosphor particles in the fired body 5 is 15 vol% or more and 25 vol% or less, relative to the total amount of phosphor particles and matrix particles of 100 vol%. By setting the concentration of YAG particles within the aforementioned range, the internal light scattering properties in the calcined body 5 can be made more appropriate. The concentration of the phosphor particles can be determined by calculating the ratio of the YAG phase to the Al2O3 phase, AlN phase, or MgO phase by X-ray diffraction (XRD) of the phosphor plate 1.

[0025] The phosphor plate 1 of the present invention has a glass coating layer 4 formed of an inorganic glass coating material on at least the light-emitting surface 3 of the fired body 5. The inorganic glass coating material is, for example, a perhydropolysilazane, and consists of a polymer compound that does not contain carbon compounds such as methyl groups or vinyl groups in its side chains. Conventional glass coating layers formed using organic glass coating materials have had issues with heat resistance. In contrast, by using inorganic glass coating materials, it is possible to use them without problems even in applications requiring higher heat resistance, such as car headlights, and to obtain high luminous flux.

[0026] Furthermore, the surface roughness Ra (according to JIS B 0601:1994) of the glass coating layer 4 surface is 0.05 μm or more and 0.4 μm or less. Patent Document 1 states that it is preferable for the arithmetic mean roughness Ra of the low refractive index layer formed on one surface of the wavelength conversion member to be as small as possible. However, on a very flat surface with Ra less than 0.05 μm, the transmittance of blue excitation light increases too much, reducing the external quantum efficiency and resulting in a bluish-white color.

[0027] Therefore, in this invention, the glass coating layer 4 is given an appropriate roughness to prevent a decrease in whiteness (the smaller the deviation from the CIE chromaticity coordinate (0.33, 0.33), the higher the whiteness). In this 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 4 can be brought closer to (0.33, 0.33) (reduction of color unevenness), and the light extraction efficiency can be improved.

[0028] Furthermore, the fact that the glass coating layer 4 is made of an inorganic glass coating material can be confirmed by the molar ratio of C / Si obtained by analyzing its cross-section using energy-dispersive X-ray spectroscopy (EDS). When using organic glass coating materials such as organopolysiloxane or organopolysilazane, the molar ratio of C / Si is 5 or more, whereas when using inorganic glass coating materials such as perhydropolysilazane, the molar ratio of C / Si is 1 or less, even including measurement errors such as when carbon tape is used for sample fixation in the EDS analysis and contamination by hydrocarbons.

[0029] For example, a spin coating method can be used to form the glass coating layer 4. In the spin coating method, a uniform polysilazane layer is formed on the entire substrate by rapidly rotating a sintered body 5 to which perhydropolysilazane (PHPS) dissolved in an organic solvent has been dropped, and then a dense glass film is obtained by heat treatment (baking) at 400-500°C in an oxidizing atmosphere.

[0030] An example of a method for manufacturing 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, formed into a sheet, dried, and then die-cut by press to produce green molded products of a predetermined shape. Next, the green molded products are degreased and further processed to 1.0 × 10 -2 A calcined body 5 is obtained by calcining in a vacuum atmosphere of medium to low vacuum (Pa or less). The calcined body 5 is composed of YAG-based phosphor particles and Al2O3 matrix particles.

[0031] Next, the surface of the fired body 5 is glass-coated. The glass coating is performed by using a method such as the spin coating method as described above.

Example

[0032] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to the examples shown below. [Example 1] [Preparation of chip-shaped phosphor plates] [1] Preparation of a fired body of [YAG-based phosphor particles + Al2O3 matrix particles] (Y 1-x-y ,Gd x ,Ce y )3Al5O 12 A fired body composed of YAG-based phosphor particles and Al2O3 matrix particles was prepared as follows. 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 at a predetermined blending ratio, and the weights of yttrium(III) oxide powder, gadolinium(III) oxide powder, cerium(IV) oxide powder, and aluminum oxide powder were adjusted so that the Gd concentration (x) in the ((Y 1-x-y ,Gd x ,Ce y )3Al5O 12 +Al2O3) fired body was 0.036 and the Ce concentration (y) was 0.020. In Table 1, it is simply described as "YAG-based".

[0033] To this raw material powder, ethanol, a polyvinyl butyral (PVB)-based binder at 10 wt%, and a succinic acid-based plasticizer at 2 wt% were added, and pulverization and mixing were performed for 50 hours using a ball mill with aluminum oxide balls to prepare a slurry. Using this slurry, a green sheet of a predetermined thickness was formed by the doctor blade method. At this time, the thickness of the green sheet to be formed and the number of layers were adjusted so that the resulting fired body had the thickness shown in Table 1 (average thickness in the direction from the light incident surface to the light emission surface of the fired body). Specifically, two 80 μm green sheets were prepared and laminated. The resulting green sheet (laminated) was degreased in air at 600°C for 1 hour, and then processed into a 1.0 × 10⁻⁶ sheet. -2 The product is baked at 1680°C for 20 hours under a vacuum atmosphere of Pa or less, (Y 1-x-y ,Gd x Ce y )3Al5O 12 A calcined body consisting of particles and Al2O3 particles was obtained. As shown in Table 1, the thickness of the obtained calcined body was 100 μm due to shrinkage during calcination.

[0034] [2] Formation of a glass coating layer on the surface of the fired body A mixed solution of perhydropolysilazane and dibutyl ether (SanCelazan ANN120-20, manufactured by Sanwa Chemical Co., Ltd.) was uniformly applied to the surface of the fired body by spin coating. Subsequently, a glass coating layer 4 was formed on the surface of the fired body by baking at 450°C for 1 hour. On the uneven surface of the fired body, the glass coating layer with an average thickness of 2 nm to 20 nm was formed above the peaks. The average thickness of the glass coating layer above the convex portions was 13 nm, while the average thickness of the glass coating layer above the concave portions other than the convex portions was 2.2 μm. The molar ratio of C / Si in the perhydropolysilazane at this time was 0.3. The surface roughness of the glass coating layer on the exit surface was 0.15 μm.

[0035] [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.

[0036] [Evaluation of chip-shaped phosphor plates] [1] Gd concentration and Ce concentration ICP emission analysis revealed that the chip-shaped phosphor plate (Y 1-x-y ,Gd x Ce y )3Al5O 12 The Gd concentration (x) and Ce concentration (y) of the calcined body portion consisting of particles and Al2O3 particles were determined, and it was confirmed that both were at the above-mentioned set concentrations. Upon verification, it was confirmed that the Gd concentration (x) in the fired body was 0.036 and the Ce concentration (y) was 0.020. Furthermore, it was confirmed that the Gd concentration (x) in the fired body of the other examples and comparative examples was 0.036 and the Ce concentration (y) was 0.020 in the fired body.

[0037] [2](Y 1-x-y ,Gd x Ce y )3Al5O 12 Particle concentration The ratio of the YAG phase to the Al2O3 phase is calculated by X-ray diffraction (XRD) of the phosphor plate, and (Y 1-x-y ,Gd x Ce y )3Al5O 12 (Y) 1-x-y ,Gd x Ce y )3Al5O 12 The concentration of the particles was measured. The measurement results showed that (Y 1-x-y ,Gd x Ce y )3Al5O 12 (Y) 1-x-y ,Gd x Ce y )3Al5O 12 The particle concentration was 20 vol%. Note that other examples and comparative examples are also provided (Y 1-x-y ,Gd x Ce y )3Al5O 12 (Y) 1-x-y ,Gd x Ce y )3Al5O 12The particle concentration was 20 vol%.

[0038] [3] Average thickness of the glass coating layer above the protrusion After pre-treating an arbitrary cross-section in the thickness direction of a phosphor plate with a glass coating layer formed on it using a focused ion beam method, the thickness of the glass coating layer above the convex portion, where an average thickness of 2 nm to 20 nm was formed, was measured using a transmission electron microscope (JEOL Ltd., product name JEM-2100) at a magnification of 400kx. Ten such images were taken at different locations, and the average value was taken as the average thickness of the glass coating layer above the convex portion.

[0039] [4] Number of protrusions per unit area (field of view 150 μm × 150 μm) and ratio of total area The surface shape (light-emitting surface) of a phosphor plate with a glass coating layer was observed by acquiring a brightness image from above the light-emitting surface using a confocal microscope (magnification 1200x). At this time, multiple white, island-like protrusions were observed on the uneven surface of the fired body, where the glass coating layer with an average thickness of 2 nm to 20 nm was formed above its apex. Areas that were not observed as white islands were defined as recesses. Since there is a difference in brightness contrast between the protrusions and recesses, the difference between the protrusions and recesses can be made clear by processing the image, such as by binarization. The number of these visible island-like areas was counted within a 150 μm × 150 μm field of view, and this was used to determine the number of protrusions within that 150 μm × 150 μm field of view. Furthermore, the total area of ​​these visible island-like portions was calculated using image processing, and this was divided by the total area of ​​the image to obtain the ratio of the total area of ​​the convex portions. Figure 2 shows a confocal microscope image of the phosphor plate from Example 1 at a field of view of 150 μm × 150 μm. There were 200 white, island-like protrusions.

[0040] [5] Average thickness of the glass coating layer above the recess The thickness of the glass coating layer above the recess was measured by imaging an arbitrary cross-section in the thickness direction of a phosphor plate with a glass coating layer formed on it using a scanning electron microscope (SEM) at 10,000x magnification. Ten such imagings were performed at different locations, and the average value was taken as the average thickness of the glass coating layer above the recess. As shown in Figure 3, in any cross-section, if there is a protrusion 8 on the upper part of which the glass coating layer with an average thickness of 2 nm to 20 nm is formed, and a protrusion 9 (irregularity) that does not fall into this category exists between the protrusion 8 and the protrusion 8, the thickness of the glass coating layer on the upper part of the recess was measured using the thickest portion t.

[0041] [6] Overall average particle size of phosphor particles and matrix particles Any portion of the uncoated surface of the chip-shaped phosphor plate can be photographed using a laser microscope or scanning electron microscope, and the YAG-based phosphor particles and Al2O3 particles (matrix particles) can be measured and determined using a linear intercept method without distinguishing between them. In this process, thermal etching can be performed as needed to observe the grain boundaries more clearly. Furthermore, when evaluating the glass-coated surface of the chip-shaped phosphor plate, the glass coating layer can be removed by surface grinding and mechanical polishing, followed by thermal etching, and then imaging using a laser microscope or scanning electron microscope.

[0042] [7] Average thickness of the sintered body The average thickness of the chip-shaped phosphor plate (sintered body) can be measured using a micrometer or by placing the phosphor plate upright and using an optical microscope. This measurement was performed at 10 different locations, and the average value was taken as the average thickness of the phosphor plate.

[0043] [8] Room temperature luminous flux The aforementioned chip-shaped phosphor plate was fixed to a blue LED chip (emission area 1 mm square, emission wavelength 450 nm) with silicone resin. After focusing the emitted light with a 4-inch integrating sphere, the emission spectrum at room temperature was measured using a visible-to-near-infrared fiber multichannel spectrometer (Ocean Photonics, product name USB4000-VIS-NIR-ES). The luminous flux was calculated from the obtained emission spectrum. The relative luminous flux value was calculated when the luminous flux of a commercially available YAG:Ce phosphor (manufactured by Mitsubishi Chemical High-Technica, product name P46-Y3) powder was contained in 20 vol% commercially available phenyl silicone (manufactured by Dow Corning, product name OE-6630) resin and sealed on the same type of LED chip was set to 100. When the relative luminous flux value was 127 or higher, bright white light was obtained; when it was 121 or lower, it was deemed insufficient.

[0044] [9] External quantum efficiency LED chip-shaped phosphor plates were arranged in a 3x3 configuration using commercially available phenyl silicone resin (Dow Corning, product name OE-6630), with three chips arranged vertically, horizontally, and diagonally. Excitation light of 450 nm ± 1 nm was irradiated onto the plates, and the ratio of photons emitted as fluorescence to the total number of irradiated photons was calculated. Similar to room temperature luminous flux, the relative value was calculated using the value obtained when commercially available YAG:Ce phosphor (manufactured by Mitsubishi Chemical High-Technica, product name P46-Y3) powder was contained in 20 vol% of commercially available phenyl silicone (manufactured by Dow Corning, product name OE-6630) resin and sealed, with the value set to 100. If the relative value is 10⁵ or higher, it is determined that the external quantum efficiency is excellent.

[0045]

[10] Whiteness The aforementioned chip-shaped phosphor plate was fixed onto a blue LED chip (light-emitting area 1 mm square, light-emitting wavelength 450 nm) with silicone resin. The chromaticity (CIE_x, CIE_y) in the vertical direction (0°) of the light emitted from the phosphor plate was measured in the CIE1931 color space. For a whiteness index of (0.33, 0.33), if both ΔCIE_x and ΔCIE_y were 0.02 or less, the whiteness was judged to be excellent; if they were greater than 0.02, it was judged to be inferior.

[0046] [comprehensive evaluation] If all of the evaluation items [6] to [8] were excellent, the result was marked with "○"; if there was one inferior value (evaluation), it was marked with "△"; and if there were two or more inferior values ​​(evaluations), it was marked with "×". The results are shown in Table 1.

[0047] [Examples 2 and 3] [Comparative Examples 1 and 2] A phosphor plate was prepared using the same method as in Example 1, except that the firing temperature was changed and the overall average particle size of the fired body was changed as shown in Table 1. The results of the evaluation, which was performed in the same manner as in Example 1, are shown in Table 1. In Comparative Example 1, where the overall average particle size of the calcined body was less than 3.0 μm (2.5 μm), sufficient luminous flux could not be obtained. On the other hand, in Comparative Example 2, where the overall average particle size of the calcined body exceeded 5.0 μm (5.6 μm), sufficient internal light scattering was not obtained, resulting in low conversion efficiency from blue light to yellow light and a bluish-white color. In contrast, the phosphor plates of Examples 2, 1, and 3, in which the overall average particle size of the calcined body was 3.0 μm to 5.0 μm, all showed excellent values ​​(evaluations) among [6] room temperature luminous flux, [7] external quantum efficiency, and [8] whiteness.

[0048] [Examples 4-6][Comparative Examples 3, 4] The thickness of the green sheet formed by the doctor blade method was changed, and the fired body average A phosphor plate was prepared using the same method as in Example 1, except that the thickness was changed as shown in Table 1. The results of the evaluation, which was performed in the same manner as in Example 1, are shown in Table 1. In Comparative Example 3, where the average thickness of the fired body was less than 90 μm (70 μm), bright white light was obtained, but the whiteness was inferior. On the other hand, in Comparative Example 4, where the average thickness of the fired body was greater than 160 μm (180 μm), the brightness was inferior. In contrast, the phosphor plates of Examples 4 to 6, in which the average thickness of the fired body was 90 μm to 160 μm, all showed excellent values ​​(evaluations) among [6] room temperature luminous flux, [7] external quantum efficiency, and [8] whiteness.

[0049] [Examples 7-9][Comparative Examples 5, 6] A phosphor plate was prepared using the same method as in Example 1, except that the spin rate of the spin coating was changed, the ratio of perhydropolysilazane in the mixed solution of perhydropolysilazane and dibutyl ether was changed, the number of protrusions on the uneven surface of the light-emitting surface of the fired body was changed, the thickness of the glass coating layer above the recesses was changed, and the total area ratio of the protrusions, the average thickness of the glass coating layer above the recesses, and the surface roughness of the light-emitting surface of the phosphor plate were changed. The results of the evaluation, which was performed in the same manner as in Example 1, are shown in Table 1. In Comparative Example 5, where the number of protrusions was less than 50 (40), the total area ratio of the protrusions was less than 16% (15%), the thickness of the glass coating layer above the recesses exceeded 3.5 μm (4.0 μm), and the surface roughness Ra of the emission surface of the phosphor plate was less than 0.05 μm (0.03 μm), the external quantum efficiency was inferior. On the other hand, in Comparative Example 6, where the number of protrusions exceeded 380 (390), the total area ratio of the protrusions exceeded 35% (36%), the average thickness of the glass coating layer above the recesses was less than 1.5 μm (0.9 μm), and the surface roughness Ra of the emission surface of the phosphor plate was greater than 0.4 μm (0.5 μm), the external quantum efficiency was excellent, but the brightness (luminous flux) was inferior. In contrast, the phosphor plates of Examples 4 to 6, in which the number of protrusions was set to 50 to 380, the total area ratio of the protrusions to 16% to 35%, the average thickness of the glass coating layer above the recesses to 3.5 μm to 1.5 μm, and the surface roughness Ra of the emission surface of the phosphor plate to 0.05 μm to 0.4 μm, all showed excellent values ​​(evaluations) among [6] room temperature luminous flux, [7] external quantum efficiency, and [8] whiteness.

[0050] [Examples 10-12], [Comparative Examples 7, 8] Comparative Example 7 involved preparing a phosphor plate using the same method as in Example 1, except that the glass coating surface of the prepared phosphor plate was polished using a mirror-finish shot blasting machine (product name SMAP; manufactured by Toyo Polishing Materials Co., Ltd.). In the other Examples 10-12 and Comparative Example 8, phosphor plates were prepared using the same method as in Example 1, except that the ratio of perhydropolysilazane in the mixed solution of perhydropolysilazane and dibutyl ether was changed, and the thickness of the glass coating layer above the recess was also changed. The results of the evaluation, which was performed in the same manner as in Example 1, are shown in Table 1. In Comparative Example 7, where the average thickness of the glass coating layer above the protrusion was less than 2 nm (or not formed), the brightness was inferior. On the other hand, in Comparative Example 8, which exceeded 20 nm (30 nm), the brightness was superior, but the external quantum efficiency was inferior.

[0051] [Comparative Example 11] Comparative Example 11 was prepared using the same method as in Example 1, except that the raw material used to form the glass coating layer 4 was changed from perhydropolysilazane, an inorganic glass coating material, to organopolysilazane, an organic glass coating material. The results of the evaluation, which was performed in the same manner as in Example 1, are shown in Table 1. Comparative Example 11, in which the glass coating layer 4 was formed using organopolysilazane, an organic glass coating material (with a cross-sectional molar ratio of C / Si of 7.0), exhibited poor heat resistance, film peeling during use, and inferior brightness of white light.

[0052] [Example 16] A phosphor plate was prepared using the same method as in Example 1, except that the matrix particles were changed to AlN and the calcined body was prepared as follows. Specifically, 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%, aluminum oxide powder with an average particle size of 0.3 μm and a purity of 99.9%, and aluminum nitride powder with an average particle size of 1.0 μm and a purity of 99.9% are mixed in a predetermined ratio, ((Y 1-x-y ,Gd x Ce y )3Al5O 12 The weights of yttrium(III) oxide powder, gadolinium(III) oxide powder, cerium(IV) oxide powder, and aluminum oxide powder were adjusted so that the Gd concentration (x) in the calcined AlN body was 0.036 and the Ce concentration (y) was 0.020. Subsequently, the green sheet obtained by the same method as in Example 1 was degreased in air and then 1.0 × 10⁻⁶ -2 The product is fired at 1750°C under a vacuum atmosphere of Pa or less, (Y 1-x-y ,Gd x Ce y )3Al5O 12 A calcined body consisting of particles and AlN particles was obtained. [8] Room temperature luminous flux, [9] External quantum efficiency, and

[10] Whiteness all showed excellent values ​​(evaluations). The results are shown in Table 1.

[0053] [Example 17] A phosphor plate was prepared using the same method as in Example 1, except that the matrix particles were changed to MgO and the calcined body was prepared as follows. 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%, aluminum oxide powder with an average particle size of 0.3 μm and a purity of 99.9%, and magnesium oxide powder with an average particle size of 0.1 μm and a purity of 99.9% are mixed in a predetermined ratio, ((Y 1-x-y ,Gd x Ce y )3Al5O 12The weights of yttrium(III) oxide powder, gadolinium(III) oxide powder, cerium(IV) oxide powder, and aluminum oxide powder were adjusted so that the Gd concentration (x) in the calcined body (+MgO) was 0.036 and the Ce concentration (y) was 0.020. Subsequently, the green sheet obtained by the same method as in Example 1 was degreased in air and then 1.0 × 10⁻⁶ -2 The mixture is fired at 1600°C under a vacuum atmosphere of Pa or less, (Y 1-x-y ,Gd x Ce y )3Al5O 12 A calcined body consisting of particles and MgO particles was obtained. [8] Room temperature luminous flux, [9] External quantum efficiency, and

[10] Whiteness all showed excellent values ​​(evaluations). The results are shown in Table 1.

[0054] According to the above experiment, it was confirmed that the phosphor plate of the present invention can obtain a higher luminous flux in a white light LED, and that it has high external quantum efficiency and whiteness, resulting in a better conversion efficiency from blue light to yellow light.

[0055] [Table 1] [Explanation of Symbols]

[0056] 1. Phosphor plate 2 Light incidence surface 3 Light exit surface 4. Glass coating layer 5. Firing body 6. Phosphorescent particles 7 Matrix particles 8. A convex portion on the upper part of the apex where a glass coating layer with an average thickness of 2 nm to 20 nm is formed. 9. A convex portion on the upper part of the apex on which the glass coating layer with an average thickness of 2 nm to 20 nm is formed, and a convex portion between the convex portion and the convex portion that does not fall under this category.

Claims

[Claim 1] A plate-shaped fired body having a light incident surface that receives light from a light source, and a light emission surface positioned opposite the light incident surface and emitting the light received by the light incident surface, A phosphor plate comprising a glass coating layer formed on the light-emitting surface of the fired body, The calcined body contains YAG-based phosphor particles and Al 2 O 3 It consists of matrix particles made of AlN or MgO, The overall average particle size of the phosphor particles and the matrix particles is 3.0 μm or more and 5.0 μm or less. The light-emitting surface of the fired body has an uneven surface formed on it, consisting of the phosphor particles and the matrix particles. The uneven surface has a plurality of protrusions on its uppermost part where the glass coating layer with an average thickness of 2 nm to 20 nm is formed. The plurality of protrusions include protrusions made of phosphor particles and protrusions made of matrix particles, and when observed from above the light-emitting surface, there are 50 to 380 protrusions in a field of view of 150 μm × 150 μm, and when observed from above the light-emitting surface, the total area of ​​the plurality of protrusions in a field of view of 150 μm × 150 μm is 16% to 35% of the area of ​​the field of view. The glass coating layer with an average thickness of 1.5 μm to 3.5 μm is formed in the recesses other than the multiple protrusions of the uneven surface. The average thickness of the fired body in the direction from the light incident surface to the light emission surface is 90 μm or more and 160 μm or less. A phosphor plate characterized in that the glass coating layer is formed of 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.

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