Wavelength conversion member, wavelength conversion device, and light source device

Abstract

To provide a technique for improving light emission intensity for a wavelength conversion member.SOLUTION: A wavelength conversion member comprises a ceramic phosphor which converts the wavelength of incident light, and a reflection film arranged on the ceramic phosphor and including metal reflecting light. The reflection film includes particles formed of a material having a higher fusion point than the metal of the reflection film, and in at least one of particle-containing cross sections as a cross section of the reflection film including cross-sections of particles, the value obtained by dividing a cross-sectional area of a particles by the square of a circumferential length of the particle is 0.02 or larger.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Wavelength conversion members that convert the wavelength of light emitted from a light source have been known for some time. Wavelength conversion members generally include a phosphor that converts the wavelength of incident light and a reflective film that reflects the light that has entered the phosphor in the direction of incidence, and the luminous intensity of the wavelength conversion member is improved by reflecting the light in a predetermined direction with the reflective film. For example, Patent Document 1 discloses a technology for forming a reflective film using a metal to which glass powder has been added. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2016-534396 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even with prior art such as Patent Document 1, there is still room for improvement in the technology for improving the luminous intensity of wavelength conversion members. For example, with the technology of Patent Document 1, when a metal is heated above its melting point to bake a reflective film onto a phosphor, the glass powder added to the metal softens and may react with the phosphor. As a result, if the phosphor deteriorates, the luminous intensity of the wavelength conversion member decreases. Furthermore, if the metal is heated only to a temperature below its melting point to prevent the glass powder from softening, the metal will not be baked onto the phosphor sufficiently, which may reduce the reflective performance of the reflective film and reduce the luminous intensity of the wavelength conversion member.

[0005] An object of the present invention is to provide a technique for improving the luminous intensity in a wavelength conversion member. [Means for solving the problem]

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following aspects.

[0007] (1) According to one aspect of the present invention, there is provided a wavelength conversion member comprising: a ceramic phosphor that converts the wavelength of incident light; and a reflective film disposed on the ceramic phosphor and containing a metal that reflects light, the reflective film containing particles formed from a material having a higher melting point than the metal of the reflective film, wherein in at least one particle-containing cross section of the reflective film that includes a cross section of the particle, the value obtained by dividing the cross-sectional area of ​​the particle by the square of the perimeter of the particle is 0.02 or more.

[0008] According to this configuration, the reflective film containing a light-reflecting metal contains particles formed from a material having a higher melting point than the metal of the reflective film. For example, silver (Ag), which is used as the metal contained in the reflective film, tends to agglomerate when melted. Therefore, when forming the reflective film, it is difficult to spread on the surface of the phosphor, making it difficult to form a uniform reflective film. In the above configuration, a metal containing particles formed from a material having a higher melting point than the metal of the reflective film is used as the raw material for the reflective film applied to the ceramic phosphor. This increases the viscosity of the raw material for the reflective film, making it easier to spread on the surface of the ceramic phosphor, making it easier to form a uniform reflective film. Furthermore, because the melting point of the particles is higher than that of the metal, they do not melt even at temperatures at which the metal melts. This allows the metal to be sufficiently baked onto the ceramic phosphor, and also suppresses reaction between the particles and the ceramic phosphor, thereby suppressing deterioration of the ceramic phosphor. Furthermore, because the particles do not melt even at temperatures at which the metal melts, they are prevented from concentrating at the interface between the ceramic phosphor and the reflective film. This prevents a decrease in the reflectivity of the reflective film. Furthermore, the particles have a particle-containing cross section, which is a cross section of the reflective film including the cross section of the particles, where the cross-sectional area divided by the square of the perimeter is 0.02 or more, and the particles are relatively nearly spherical in shape. This makes it difficult for the particles to aggregate, making it easier to form a homogeneous reflective film. Furthermore, since air bubbles are less likely to adhere to particles with a relatively nearly spherical shape, the formation of voids in the reflective film can be suppressed. This makes it easier to form a homogeneous reflective film with fewer voids. In this way, it is possible to form a homogeneous reflective film while suppressing deterioration of the ceramic phosphor, thereby improving the luminous intensity of the wavelength conversion member.

[0009] (2) In the wavelength conversion member of the above embodiment, the value obtained by dividing the cross-sectional area of ​​the particle by the square of the perimeter of the particle may be 0.02 or more in both the particle-containing cross-section along the stacking direction of the ceramic phosphor and the reflective film and the particle-containing cross-section along a direction perpendicular to the stacking direction. According to this configuration, the value obtained by dividing the cross-sectional area of ​​the particle by the square of the perimeter of the particle is 0.02 or more in both the particle-containing cross-section along the stacking direction of the ceramic phosphor and the reflective film and the particle-containing cross-section along a direction perpendicular to the stacking direction. That is, the value obtained by dividing the cross-sectional area of ​​the particle by the square of the perimeter of the particle is 0.02 or more in both the particle-containing cross-section along the mutually perpendicular directions, and thus the particles have a shape closer to a sphere. This makes it more difficult for the particles to aggregate and for air bubbles to adhere to the particles, making it easier to form a more uniform reflective film. Therefore, the luminous intensity of the wavelength conversion member can be further improved.

[0010] (3) In the wavelength conversion member of the above embodiment, the particles in the particle-containing cross section may have an average particle size of 2 μm or more. According to this configuration, the particles in the particle-containing cross section have an average particle size of 2 μm or more. This makes it even more difficult for air bubbles to adhere to the particles, making it easier to form a homogeneous reflective film with fewer voids. Therefore, the luminous intensity of the wavelength conversion member can be further improved.

[0011] (4) In the wavelength conversion member of the above embodiment, the value obtained by dividing the cross-sectional area of ​​the particle by the square of the perimeter of the particle in the particle-containing cross section may be 0.05 or more. According to this configuration, the value obtained by dividing the cross-sectional area of ​​the particle by the square of the perimeter in the particle-containing cross section is 0.05 or more. In other words, the particles have a shape that is closer to a sphere. This makes it even more difficult for air bubbles to adhere to the particles, making it easier to form a homogeneous reflective film with fewer voids. Therefore, the luminous intensity of the wavelength conversion member can be further improved.

[0012] (5) According to another aspect of the present invention, a wavelength converter is provided. This wavelength converter includes the wavelength converter described above, a heat dissipation member that dissipates heat from the ceramic phosphor to the outside, and a bonding layer that bonds the wavelength converter and the heat dissipation member. According to this configuration, the wavelength converter includes the heat dissipation member that dissipates heat from the ceramic phosphor to the outside. This allows the heat generated by the ceramic phosphor that converts the wavelength of incident light to be dissipated by the heat dissipation member, thereby suppressing deterioration of the ceramic phosphor due to heat. Therefore, the luminous intensity of the wavelength converter can be maintained.

[0013] (6) According to yet another aspect of the present invention, there is provided a light source device. This light source device includes the wavelength conversion device described above and a light source that irradiates the ceramic phosphor with light. According to this configuration, the light source device includes a light source that irradiates the ceramic phosphor with light. As a result, the wavelength conversion member, whose luminous intensity has been improved as described above, can more strongly emit light of a wavelength different from external light. Therefore, the luminous intensity of the light source device can be improved.

[0014] The present invention can be realized in various forms, for example, in the form of a device including a wavelength conversion member, a system including a light source device, a method for manufacturing a wavelength conversion member and a light source device, a method for manufacturing a reflective film, etc. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 2 is a cross-sectional schematic view of a wavelength conversion member according to the first embodiment. [Figure 2] FIG. 1 is a schematic diagram of a light source device according to a first embodiment. [Figure 3] FIG. 2 is a first diagram illustrating a particle-containing cross section of a wavelength conversion member. [Figure 4] FIG. 10 is a second diagram illustrating a particle-containing cross section of a wavelength conversion member. [Figure 5] FIG. 2 is an enlarged view of a particle contained in a particle-containing cross section. [Figure 6]FIG. 10 is a diagram illustrating a method for evaluating a wavelength conversion member. [Figure 7] 10A and 10B are diagrams illustrating the results of an evaluation test of a wavelength conversion member. DETAILED DESCRIPTION OF THE INVENTION

[0016] First Embodiment FIG. 1 is a cross-sectional schematic diagram of a wavelength conversion member 1 of the first embodiment. The wavelength conversion member 1 of this embodiment includes a ceramic phosphor 10 and a reflective film 20. When light is incident on the wavelength conversion member 1, it emits light of a different wavelength from the incident light. In FIG. 1, the stacking direction in which the ceramic phosphor 10 and the reflective film 20 are stacked is indicated by a double-ended arrow DL. For ease of explanation, the relationship in size and thickness between the ceramic phosphor 10 and the reflective film 20 in FIG. 1 is illustrated as being different from the actual relationship in size and thickness.

[0017] The ceramic phosphor 10 is a ceramic sintered body, and in this embodiment, is formed in a substantially cylindrical shape. The ceramic phosphor 10 has an incident surface 11 onto which light is incident and a back surface 12 located on the opposite side of the incident surface 11. The ceramic phosphor 10 converts the wavelength of at least a portion of the light incident from the incident surface 11 and emits light of a wavelength different from that of the incident light. The ceramic phosphor 10 is composed of a ceramic sintered body having a fluorescent phase mainly composed of fluorescent crystal particles and a translucent phase mainly composed of translucent crystal particles. The translucent phase crystal particles have a composition represented by the chemical formula Al2O3, and the fluorescent phase crystal particles have a composition represented by the chemical formula A3B5O 12 It is preferable that the composition be represented by the formula A3B5O:Ce (so-called garnet structure). 12 :Ce" is A3B5O 12 This indicates that Ce is dissolved in the solid solution and part of element A is substituted with Ce.

[0018] Chemical formula A3B5O 12 Element A and element B in Ce are each composed of at least one element selected from the following group of elements: Element A: Lanthanides excluding Sc, Y, and Ce (however, element A may also contain Gd) Element B: Al (however, element B may further contain Ga) By using a ceramic sintered body as the ceramic phosphor 10, light is scattered at the interface between the fluorescent phase and the translucent phase, reducing the angular dependency of the light color. This improves the color uniformity. Note that the material of the ceramic phosphor 10 is not limited to the above-mentioned materials.

[0019] The reflective film 20 is disposed on the rear surface 12 of the ceramic phosphor 10. The reflective film 20 contains silver (Ag), which is a metal that reflects light, and a plurality of particles 21. The thickness of the reflective film 20 is preferably 10 μm or more and 100 μm or less.

[0020] The silver contained in the reflective film 20 forms a thin film 22 on the rear surface 12, which reflects light that has passed through the ceramic phosphor 10 and light generated by the ceramic phosphor 10. The metal that forms the thin film 22 is not limited to silver, and may be platinum (Pt), aluminum (Al), a silver alloy, or the like.

[0021] The particles 21 contained in the reflective film 20 are made of a material having a higher melting point than silver. In this embodiment, the particles 21 are made of alumina (Al2O3). The material for forming the particles 21 is not limited to alumina, and may be any material having a higher melting point than the metal forming the thin film 22, such as YAG, TiO2, Y2O3, SiO2, Cr2O3, Nb2O5, or Ta2O5. The characteristics of the particles 21 contained in the reflective film 20 will be described in detail later.

[0022] FIG. 2 is a schematic diagram of a light source device 2 of the first embodiment. The light source device 2 of this embodiment includes a wavelength conversion device 3 and a light source 4 that emits light. The wavelength conversion device 3 includes a wavelength conversion member 1, a heat dissipation member 30 that dissipates heat from the wavelength conversion member 1, and a bonding layer 40 that bonds the wavelength conversion member 1 and the heat dissipation member 30. In the wavelength conversion device 3, as shown in FIG. 2, the ceramic phosphor 10 of the wavelength conversion member 1, the reflective film 20 of the wavelength conversion member 1, the bonding layer 40, and the heat dissipation member 30 are stacked in this order. In the light source device 2, light L1 emitted from a light source 4 such as a light-emitting diode (LED) or a semiconductor laser (LD) is irradiated onto the wavelength conversion device 3. When irradiated with light L1, the wavelength conversion device 3 emits light of a different wavelength from the light L1 irradiated onto the wavelength conversion device 3. As a result, the wavelength conversion device 3 emits light L2 of a different color from the light L1 emitted by the light source 4. Such a wavelength converter 3 is used in various optical devices, such as a headlamp, lighting, projector, etc. For convenience of explanation, the relationship between the sizes and thicknesses of the ceramic phosphor 10, the reflective film 20, the heat dissipation member 30, and the bonding layer 40 in the wavelength converter 3 in Fig. 2 is illustrated as being different from the actual relationship between the sizes and thicknesses.

[0023] The heat dissipation member 30 is a flat-plate-shaped member made of a material having higher thermal conductivity than the ceramic phosphor 10, such as copper (Cu), a copper-molybdenum alloy, a copper-tungsten alloy, aluminum (Al), or aluminum nitride (AlN). The heat dissipation member 30 dissipates heat transferred from the ceramic phosphor 10 to the outside of the wavelength conversion device 3 via the bonding layer 40. The heat dissipation member 30 does not have to be a single-layer member made of the above-mentioned materials, and may be a multi-layer member made of the same or different materials. Furthermore, the surface of the heat dissipation member 30 facing the ceramic phosphor 10 may be plated to improve adhesion with the bonding layer 40.

[0024] The bonding layer 40 is disposed between the wavelength conversion member 1 and the heat dissipation member 30. The bonding layer 40 is made of gold and tin, and bonds the ceramic phosphor 10 and the heat dissipation member 30 together. The bonding layer 40 exchanges heat between the ceramic phosphor 10 and the heat dissipation member 30.

[0025] Next, a method for manufacturing the light source device 2 will be described. First, raw materials are weighed so that the fluorescent phase and the translucent phase are, for example, 6:4. The weighed raw materials are placed in a ball mill together with ethanol or pure water and ground and mixed for 16 hours to produce a ceramic phosphor slurry. The ceramic phosphor slurry is dried and granulated, and then a binder and water are added. The mixture is kneaded while applying shear force to produce a clay. The produced clay is formed into a sheet using an extrusion molding machine, and the formed sheet is fired at approximately 1700°C in an air atmosphere. The fired body obtained by firing is cut to a predetermined thickness to produce the ceramic phosphor 10.

[0026] After producing the ceramic phosphor 10, silver powder (average particle size approximately 1 to 100 μm), alumina powder, an acrylic binder, and a solvent are mixed to produce a paste for the reflective film. The produced paste for the reflective film is applied to the rear surface 12 of the ceramic phosphor 10, dried, and then heated to a temperature equal to or higher than the melting point of silver (961.8°C), for example, 1000°C. In this way, the paste for the reflective film is baked onto the rear surface 12 of the ceramic phosphor 10, thereby forming a reflective film 20 on the ceramic phosphor 10 and completing the wavelength conversion member 1.

[0027] After the wavelength conversion member 1 is completed, AuSn solder foil is sandwiched between the reflective film 20 of the wavelength conversion member 1 and the heat dissipation member 30, and then heated, for example, in a reflow furnace to melt the AuSn solder foil. This bonds the wavelength conversion member 1 and the heat dissipation member 30, completing the wavelength conversion device 3. Finally, the light source 4 is positioned so that light L1 is irradiated onto the incident surface 11 of the wavelength conversion device 3. This completes the light source device 2.

[0028] Next, the characteristics of the particles 21 contained in the reflective film 20 will be described. The particles 21 contained in the reflective film 20 of the wavelength conversion member 1 are made of alumina, which has a higher melting point than the silver contained in the reflective film 20. Generally, when forming a reflective film by baking elemental silver onto a ceramic phosphor in the manufacture of a wavelength conversion member, the silver that is heated and melted on the back surface of the ceramic phosphor tends to agglomerate and does not spread across the back surface of the ceramic phosphor. This can make it difficult to form a homogeneous reflective film from elemental silver. A reflective film paste in which alumina particles are mixed with silver, as in this embodiment, has higher viscosity than molten silver and easily spreads across the back surface 12 of the ceramic phosphor 10, making it easier to form a homogeneous reflective film 20. Furthermore, because the particles 21 have a higher melting point than silver, they do not melt even at temperatures at which silver melts. This allows silver to be sufficiently baked onto the ceramic phosphor 10, improving the adhesion strength between the ceramic phosphor 10 and the reflective film 20 and suppressing reactions between the particles 21 and the ceramic phosphor 10, thereby suppressing deterioration of the ceramic phosphor 10. Furthermore, since the melting point of alumina forming the particles 21 is higher than that of silver, it is possible to prevent the particles 21 from concentrating at the interface between the ceramic phosphor 10 and the reflective film 20. This makes it possible to prevent a decrease in the reflectance of the reflective film 20.

[0029] The particles 21 contained in the reflective film 20 of the wavelength conversion member 1 have a shape that is relatively close to a sphere. Specifically, in at least one particle-containing cross section, which is a cross section of the reflective film 20 including a cross section of the particle 21, the value obtained by dividing the cross-sectional area of ​​the particle 21 by the square of the perimeter of the particle (hereinafter simply referred to as the "cross-sectional area ratio") is 0.02 or more. When the cross-sectional area ratio of the particles 21 is 0.02 or more, the particles 21 are dispersed in molten silver during the production of the wavelength conversion member 1, making it difficult for the particles 21 to aggregate together. This makes it easier to form a homogeneous reflective film 20. Furthermore, when the cross-sectional area ratio of the particles 21 is 0.02 or more, air bubbles are less likely to adhere to the particles 21, making it possible to suppress the generation of voids in the reflective film 20. In this embodiment, the cross-sectional area ratio of the particles 21 is 0.06.

[0030] The particles 21 contained in the reflective film 20 of the wavelength conversion member 1 have an average particle size of 2 μm or more and 50 μm or less in the particle-containing cross section. This makes it even more difficult for air bubbles to adhere to the particles 21 in the molten silver when forming the reflective film 20 of the wavelength conversion member 1, making it easier to form a homogeneous reflective film 20 with fewer voids. In this embodiment, the average particle size of the particles 21 is 7 μm.

[0031] Next, a specific description will be given of a method for calculating the cross-sectional area ratio and average particle size of the particles 21 in this embodiment. In this embodiment, the cross-sectional area ratio and average particle size of the particles 21 described above are calculated using two particle-containing cross sections in the wavelength conversion member 1 that are perpendicular to each other.

[0032] FIG. 3 is a first diagram illustrating particle-containing cross sections in a wavelength conversion member 1. FIG. 3 shows a perspective view of the substantially cylindrical wavelength conversion member 1. For convenience, in FIG. 3, the central axis of the wavelength conversion member 1 is shown as the central axis Ca, and the reflective film 20 is highlighted by hatching. In this embodiment, of the multiple particle-containing cross sections assumed for the wavelength conversion member 1, the cross-sectional area ratio and average particle size of the particles 21 are calculated for both of two cross sections: a particle-containing cross section CS1 along the stacking direction DL in the wavelength conversion member 1, and a particle-containing cross section CS2 along a direction perpendicular to the stacking direction DL.

[0033] FIG. 4 is a second diagram illustrating a particle-containing cross section in the wavelength conversion member 1. FIG. 4 shows a schematic SEM image of the particle-containing cross section CS1 (FIG. 4(a)), and a schematic SEM image of the particle-containing cross section CS2 (FIG. 4(b)). The SEM image in FIG. 4(a) includes a cross section of the ceramic phosphor 10 as well as a cross section of the reflective film 20. In the wavelength conversion member 1 of this embodiment, as shown in FIG. 4, a plurality of particles 21 are dispersed in a thin silver film 22 that forms the reflective film 20. In this embodiment, in the SEM image of the particle-containing cross section CS2 shown in FIG. 4(b), a plurality of particles 21 are dispersed in a thin silver film 22 that forms the reflective film 20. 2 ) the proportion of the particles 21 is preferably 5% or more and 50% or less.

[0034] FIG. 5 is an enlarged view of a particle 21 included in the particle-containing cross section. FIG. 5 is, for example, an enlarged portion of the SEM image of the particle-containing cross section CS1 shown in FIG. 4(a). In this embodiment, for the particle 21 included in the SEM image captured over a certain range including the above-described predetermined area, as shown in FIG. 4, the cross-sectional area Csa, perimeter Pm, and particle size Ps of the particle 21 are measured (see FIG. 5). Specifically, the image processing software WinROOF is used to process the SEM images of the particle-containing cross sections CS1 and CS2, and the cross-sectional area Csa, perimeter Pm, and particle size Ps of the particle 21 are measured from the portion where the particle 21 is present in the SEM image. Here, the cross-sectional area Csa of the particle 21 refers to the area of ​​the portion where the particle 21 is present in the SEM image, and the perimeter Pm of the particle 21 refers to the length of the boundary between the portion where the particle 21 is present and the thin film 22 portion in the SEM image. The particle size Ps of the particle 21 refers to the length of the longest part (maximum particle size) in the part where the particle 21 exists in the SEM image, as shown in Fig. 5. In this embodiment, the cross-sectional area Csa, perimeter Pm, and particle size Ps are measured for each of the particles 21 included in the SEM images of the particle-containing cross sections CS1 and CS2.

[0035] The cross-sectional area ratio of a particle 21 is calculated by dividing the cross-sectional area Csa of one particle 21 by the square of the perimeter Pm. As shown in FIG. 4, when a single SEM image contains multiple particles 21, the cross-sectional area ratio of each of the multiple particles 21 is calculated from the cross-sectional area Csa and perimeter Pm measured for each of the multiple particles 21, and the average cross-sectional area ratio for the single SEM image is calculated from the cross-sectional area ratios of the multiple particles 21 included in the single SEM image. The average cross-sectional area ratio calculated in this manner for a single SEM image is used as the cross-sectional area ratio of the particles included in the reflective film. In this embodiment, the average cross-sectional area ratio calculated using the cross-sectional area ratios of any 10 particles 21 included in a single SEM image is used as the cross-sectional area ratio of the particles 21 included in the reflective film 20. In the wavelength conversion member 1 of this embodiment, in both the particle-containing cross section CS1 along the stacking direction DL of the ceramic phosphor 10 and the reflective film 20 and the particle-containing cross section CS2 along the direction perpendicular to the stacking direction DL, the cross-sectional area ratio (i.e., the cross-sectional area ratio) of the particle 21 divided by the square of the perimeter Pm of the particle 21 is 0.06, which is greater than or equal to 0.05.

[0036] As shown in FIG. 4, when a single SEM image contains multiple particles 21, the average particle size of the particles 21 in the wavelength conversion member 1 is calculated from the particle size Ps measured for each of the multiple particles 21, in the same manner as the method for calculating the cross-sectional area ratio described above. When a single SEM image contains only one particle 21, the particle size of that particle 21 is used as the "average particle size of the particles 21 in the wavelength conversion member 1." When a single SEM image contains multiple particles 21, the value obtained by dividing the standard deviation obtained using the particle sizes Ps of the multiple particles 21 by the average particle size of the particle sizes Ps, i.e., the coefficient of variation, is preferably 10% or more and 30% or less. In the wavelength conversion member 1 of this embodiment, the average particle size of the particles 21 in at least one particle-containing cross section is 2 μm or more.

[0037] Next, an evaluation test of the wavelength conversion member will be described. In this evaluation test, an experiment was conducted using the shape and average particle size of particles dispersed in the reflective film of the wavelength conversion member as variables to evaluate the influence of the characteristics of the particles contained in the reflective film on the luminous intensity. The sample used in this evaluation test was a wavelength conversion member comprising a ceramic phosphor and a reflective film, and was manufactured by the manufacturing method of the wavelength conversion member 1 of this embodiment described above, using a mixture of silver and alumina particles (addition amount: 10% by volume) as the paste for the reflective film.

[0038] FIG. 6 is a diagram illustrating a method for evaluating wavelength conversion members. In this evaluation test, a sample Sp of a wavelength conversion member including a ceramic phosphor s10 and a reflective film s20 was irradiated with laser light Lz1 having a wavelength of 450 nm using a laser light source s3 so that the light was incident perpendicularly on the surface s11 of the ceramic phosphor s10. Of the light emitted from the sample Sp irradiated with the laser light Lz1, the intensity of light L3 emitted at an angle of 45 degrees with respect to the irradiation direction of the laser light Lz1 was measured using a power meter 50 as the emission intensity of the sample Sp. In this evaluation test, the evaluation test was performed on 10 types of samples, and the emission intensity measured for each sample was divided by the emission intensity of a wavelength conversion member including a reflective film (thickness: 120 nm) that did not contain particles to calculate an "emission intensity ratio" for each sample. When the calculated luminescence intensity ratio was 90% or more, the evaluation result was rated as "A." When the calculated luminescence intensity ratio was less than 90% and greater than or equal to 80%, the evaluation result was rated as "B." When the calculated luminescence intensity ratio was less than 80%, the evaluation result was rated as "C."

[0039] FIG. 7 is a diagram illustrating the results of the evaluation test of the wavelength conversion member. 2 " indicates the value (cross-sectional area ratio) obtained by dividing the cross-sectional area of ​​the alumina particles in the particle-containing cross section of sample Sp by the square of the perimeter of the alumina particles, and "average particle diameter" indicates the average particle diameter of the alumina particles in the particle-containing cross section of sample Sp. "Csa / Pm" of each sample 2" and "average particle size of particles" were calculated in the same manner as the calculation methods for the cross-sectional area ratio and average particle size of particles 21 in wavelength conversion member 1 of the present embodiment.

[0040] As shown in Figure 7, Csa / Pm 2 It was found that the emission intensity ratio of Sample 1 and Sample 2, where Csa / Pm is 0.01, is less than 80% (evaluation: C). 2 It was revealed that in Samples 3 to 10 where the ratio was 0.02 or more, the emission intensity ratio was 80% or more (evaluation: B or A). This is because in Samples 3 to 10, the shape of the alumina particles contained in the reflective film s20 was relatively close to spherical, so that when the reflective film s20 was formed in the production of the wavelength conversion member sample, the alumina particles were easily dispersed and air bubbles were less likely to adhere to the alumina particles.

[0041] In addition, when comparing the emission intensity ratios of samples 4, 5, and 6, which have the same average particle size of alumina particles contained in the reflective film s20, Csa / Pm 2 It was found that the larger the Csa / Pm, the larger the emission intensity ratio. 2 Sample 4 with a Csa / Pm of 0.02 2 When comparing samples 5 and 6 with Csa / Pm of 0.05 or more, 2 It was found that the emission intensity ratio becomes significantly larger when Csa / Pm becomes 0.05 or more. 2 Csa / Pm is 0.02 compared to sample 4. 2 This is because the shape of the alumina particles contained in the reflective film s20 of samples 5 and 6, in which the value is 0.05 or more, is closer to a sphere, making it easier for the alumina particles to disperse and more difficult for air bubbles to adhere to the alumina particles.

[0042] Csa / Pm 2It was revealed that for Sample 3 and Sample 4, where the average particle size of the alumina particles is 0.02, Sample 4, where the average particle size of the alumina particles is 2 μm, has a larger emission intensity ratio than Sample 3, where the average particle size of the alumina particles is 1 μm. This is because the larger the particle size of the alumina particles, the less likely it is that air bubbles will adhere to the alumina particles when the reflective film s20 is formed, and therefore the generation of voids in the reflective film s20 can be suppressed.

[0043] Csa / Pm 2 It was found that for samples 6 to 10 with a Csa / Pm ratio of 0.06, samples 7 to 10 with an average alumina particle size of 4 μm or more had a larger emission intensity ratio than sample 6 with an average alumina particle size of 2 μm. This is because the Csa / Pm 2 Similar to the relationship between Sample 3 and Sample 4 where the particle size is 0.02, the larger the particle size of the alumina particles, the less likely it is that air bubbles will adhere to the alumina particles when forming the reflective film s20, thereby suppressing the generation of voids in the reflective film s20.

[0044] According to the wavelength conversion member 1 of this embodiment described above, the reflective film 20 containing silver that reflects light contains particles 21 formed from alumina, which has a higher melting point than silver. Generally, silver tends to agglomerate when melted, so when forming a reflective film, it is difficult for the silver to spread on the surface of the phosphor, making it difficult to form a homogeneous reflective film. In the wavelength conversion member 1, a metal containing particles 21 formed from alumina, which has a higher melting point than silver, is used as the reflective film paste applied to the ceramic phosphor 10. This increases the viscosity of the raw material for the reflective film 20, making it easier to spread on the back surface 12 of the ceramic phosphor 10, and therefore making it easier to form a homogeneous reflective film 20. Therefore, the luminous intensity of the wavelength conversion member 1 can be improved.

[0045] Furthermore, in the wavelength conversion member 1 of this embodiment, the particles 21 have a higher melting point than silver, and therefore do not melt even at temperatures at which silver melts. This allows silver to be sufficiently baked onto the ceramic phosphor 10, and also suppresses the reaction between the particles 21 and the ceramic phosphor 10, thereby suppressing deterioration of the ceramic phosphor 10. Generally, when the raw materials for a reflective film contain metal and particles, if the particles melt during film formation, the molten particles may move through the molten metal and concentrate at the interface between the ceramic phosphor and the reflective film, reducing the reflectivity of the reflective film. However, in the wavelength conversion member 1, the particles 21 do not melt even at temperatures at which silver melts, and therefore the particles 21 can be prevented from concentrating at the interface between the ceramic phosphor 10 and the reflective film 20. This prevents a decrease in the reflectivity of the reflective film 20.

[0046] Furthermore, according to the wavelength conversion member 1 of this embodiment, the particles 21 have a shape that is relatively close to spherical, with the cross-sectional area Csa divided by the square of the perimeter Pm at particle-containing cross sections CS1 and CS2, which are cross sections of the reflective film including the cross sections of the particles 21, being 0.02 or more. This makes the particles 21 less likely to aggregate, making it easier to form a homogeneous reflective film 20. Furthermore, since air bubbles are less likely to adhere to the particles 21 that are relatively close to spherical in shape, it is possible to suppress the generation of voids in the reflective film 20. This makes it easier to form a homogeneous reflective film 20 with fewer voids. Therefore, the luminous intensity of the wavelength conversion member 1 can be improved.

[0047] Furthermore, in the wavelength conversion member 1 of this embodiment, the particle-containing cross section CS1 along the stacking direction DL of the ceramic phosphor 10 and the reflective film 20 and the particle-containing cross section CS2 along the direction perpendicular to the stacking direction DL both have a value of 0.02 or more when the cross-sectional area Csa of the particle 21 is divided by the square of the perimeter Pm of the particle 21. That is, the particle 21 has a shape that is even closer to a sphere because the value of the cross-sectional area Csa of the particle 21 divided by the square of the perimeter Pm of the particle 21 is 0.02 or more when the particle-containing cross section CS1 is along the stacking direction DL of the ceramic phosphor 10 and the reflective film 20. This makes it even more difficult for the particles 21 to aggregate and for air bubbles to adhere to the particles 21, making it easier to form a more uniform reflective film 20. Therefore, the luminous intensity of the wavelength conversion member 1 can be further improved.

[0048] Furthermore, according to the wavelength conversion member 1 of this embodiment, the average particle size of the particles 21 in the particle-containing cross sections CS1 and CS2 is 2 μm or more. This makes it even more difficult for air bubbles to adhere to the particles 21, making it easier to form a homogeneous reflective film 20 with even fewer voids. Therefore, the luminous intensity of the wavelength conversion member 1 can be further improved.

[0049] Furthermore, in the wavelength conversion member 1 of this embodiment, the particle 21 has a value of 0.05 or more when the cross-sectional area Csa is divided by the square of the perimeter Pm in the particle-containing cross sections CS1 and CS2. That is, the particle 21 has a shape that is even closer to a sphere. This makes it even more difficult for air bubbles to adhere to the particle 21, making it easier to form a homogeneous reflective film 20 with fewer voids. Therefore, the luminous intensity of the wavelength conversion member 1 can be further improved.

[0050] Furthermore, the wavelength converter 3 of this embodiment includes a heat dissipation member 30 that dissipates heat from the ceramic phosphor 10 to the outside. This allows the heat generated by the ceramic phosphor 10, which converts the wavelength of incident light, to be dissipated by the heat dissipation member 30, thereby suppressing deterioration of the ceramic phosphor 10 due to heat. This allows the emission intensity of the wavelength converter 3 to be maintained.

[0051] Furthermore, according to the light source device 2 of this embodiment, the light source device 2 includes a light source 4 that irradiates light onto the ceramic phosphor 10. As a result, the wavelength conversion member 1 with improved emission intensity can more strongly emit light of a wavelength different from external light, thereby improving the emission intensity of the light source device 2.

[0052] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0053] [Variation 1] In the above-described embodiment, the wavelength conversion device 3 includes the wavelength conversion member 1, the bonding layer 40, and the heat dissipation member 30, and the wavelength conversion member 1 includes the ceramic phosphor 10 and the reflective film 20. However, the configurations of the wavelength conversion member 1 and the wavelength conversion device 3 are not limited to these. They may also include a sealing film, a plating layer, or the like.

[0054] [Variation 2] In the above embodiment, the cross-sectional area ratio of the particles 21 in the wavelength conversion member 1 is 0.05 or more. However, the cross-sectional area ratio of the particles 21 may be 0.02 or more. If the cross-sectional area ratio is 0.02 or more, the particles have a shape that is relatively close to a sphere, so that the particles are less likely to aggregate with each other and air bubbles are less likely to adhere to the particles.

[0055] [Variation 3] In the above embodiment, the cross-sectional area ratio of the particles 21 is 0.05 or more in both the particle-containing cross section CS1 along the stacking direction DL of the wavelength conversion member 1 and the particle-containing cross section CS2 along the direction perpendicular to the stacking direction DL. However, the particle-containing cross sections for calculating the cross-sectional area ratio of the particles 21 are not limited to these. It is sufficient that at least one of the particle-containing cross sections has a cross-sectional area ratio of 0.02 or more. The same applies to the average particle diameter.

[0056] [Variation 4] In the above-described embodiment, the average cross-sectional area ratio calculated using the respective cross-sectional area ratios of any 10 particles 21 included in one SEM image of the reflective film 20 was used as the cross-sectional area ratio of the particles 21 included in the reflective film 20. The number of particles 21 used to calculate the average cross-sectional area ratio is not limited to 10, but is preferably 10 or more.

[0057] [Variation 5] In the above-described embodiment, the particles 21 contained in the reflective film 20 in the particle-containing cross section have an average particle size of 2 μm or more and 50 μm or less. However, the average particle size of the particles may be smaller than 2 μm or larger than 50 μm. By making the average particle size of the particles 2 μm or more and 50 μm or less, when forming the reflective film of the wavelength conversion member, it becomes even more difficult for air bubbles to adhere to the particles in the molten silver, making it easier to form a homogeneous reflective film with fewer voids.

[0058] [Variation 6] In the above-described embodiment, the average particle size of the particles 21 is calculated from the SEM image of the particle-containing cross section by taking the length of the longest part of the portion in the SEM image where the particles 21 are present as the particle size of one particle 21. However, the method of calculating the average particle size of the particles 21 is not limited to this. The reflective film 20 formed on the ceramic phosphor 10 may be dissolved to recover the particles 21 contained in the reflective film 20, and the particle size of each of the recovered particles may be measured before calculating the average particle size of the particles 21.

[0059] This aspect has been described above based on embodiments and modifications. However, the above-described embodiments are intended to facilitate understanding of this aspect and are not intended to limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0060] [Application example 1] A wavelength conversion member, a ceramic phosphor that converts the wavelength of incident light; a reflective film disposed on the ceramic phosphor and containing a metal that reflects light; the reflective film contains particles formed of a material having a melting point higher than that of a metal of the reflective film; In at least one particle-containing cross section, which is a cross section of the reflective film including a cross section of the particle, the value obtained by dividing the cross-sectional area of ​​the particle by the square of the perimeter of the particle is 0.02 or more. A wavelength conversion member characterized by: [Application example 2] The wavelength conversion member according to Application Example 1, In both the particle-containing cross section along the stacking direction of the ceramic phosphor and the reflective film and the particle-containing cross section along the direction perpendicular to the stacking direction, the value obtained by dividing the cross-sectional area of ​​the particle by the square of the perimeter of the particle is 0.02 or more. A wavelength conversion member characterized by: [Application example 3] The wavelength conversion member according to Application Example 1 or Application Example 2, In the particle-containing cross section, the average particle size of the particles is 2 μm or more. A wavelength conversion member characterized by: [Application example 4] The wavelength conversion member according to any one of Application Examples 1 to 3, In the particle-containing cross section, the value obtained by dividing the cross-sectional area of ​​the particle by the square of the perimeter of the particle is 0.05 or more. A wavelength conversion member characterized by: [Application example 5] A wavelength conversion device, The wavelength conversion member according to any one of Application Examples 1 to 4, a heat dissipation member that dissipates heat from the ceramic phosphor to the outside; a bonding layer that bonds the wavelength conversion member and the heat dissipation member together, A wavelength conversion device characterized by: [Application Example 6] A light source device, The wavelength conversion device according to Application Example 5, a light source that irradiates the ceramic phosphor with light; A light source device characterized by: [Explanation of symbols]

[0061] 1...Light source device 2...Wavelength conversion material 3...Light source 4...Wavelength conversion device 10...Ceramic phosphor 20…Reflection film 21...Particle 30...Heat dissipation member 40...Joining layer CS1,CS2…Particle-containing cross section Csa…Cross-sectional area DL: stacking direction Pm…Perimeter length

Claims

1. A wavelength conversion member, a ceramic phosphor that converts the wavelength of incident light; a reflective film disposed on the ceramic phosphor and having a thin film formed of a metal that reflects light; the reflective film is formed from a material having a melting point higher than that of the metal forming the thin film, and contains particles dispersed within the thin film; In at least one particle-containing cross-section, which is a cross-section of the reflective film including a cross-section of the particle and a cross-section of the thin film, a value obtained by dividing the cross-sectional area of ​​the particle by the square of the perimeter of the particle is 0.02 or more; The proportion of the particles in an area of ​​1 mm 2 is 5% or more and 50% or less. A wavelength conversion member characterized by:

2. The wavelength conversion member according to claim 1 , a value obtained by dividing the cross-sectional area of ​​the particle by the square of the perimeter of the particle is 0.02 or more in both the particle-containing cross-section along the stacking direction of the ceramic phosphor and the reflective film and the particle-containing cross-section along the direction perpendicular to the stacking direction; A wavelength conversion member characterized by:

3. The wavelength conversion member according to claim 1 or 2, In the particle-containing cross section, the average particle size of the particles is 2 μm or more. A wavelength conversion member characterized by:

4. The wavelength conversion member according to claim 1 or 2, In the particle-containing cross section, the value obtained by dividing the cross-sectional area of ​​the particle by the square of the perimeter of the particle is 0.05 or more. A wavelength conversion member characterized by:

5. A wavelength conversion device, The wavelength conversion member according to claim 1 or 2; a heat dissipation member that dissipates heat from the ceramic phosphor to the outside; a bonding layer that bonds the wavelength conversion member and the heat dissipation member together, A wavelength conversion device characterized by:

6. A light source device, The wavelength conversion device according to claim 5 , a light source that irradiates the ceramic phosphor with light; A light source device characterized by:

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