Wavelength conversion member and light source device having the same

Abstract

Provided is a technique for suppressing a decrease in adhesion strength of a reflective film and a decrease in reflectance of the reflective film. A wavelength conversion member 1 includes a phosphor 10 that emits fluorescent light in response to excitation light L1, and a reflective film 20 disposed on the side of a second surface 12 of the phosphor 10. Further, the reflective film 20 includes a metal layer 21 of silver or the like and crystalline oxide particles 22 dispersed in the metal layer 21. Moreover, the melting point of the oxide particles 22 is higher than the melting point of the metal that constitutes the metal layer 21.

Description

Technical Field

[0001] The present invention relates to a wavelength conversion component and a light source device having the same. Background Technology

[0002] Patent Document 1 discloses an optical component comprising: a phosphor; and a reflective film, which is a metal reflective film sintered on the surface of the phosphor and contains a glass component. The glass component is added to a metal such as silver (Ag) to form the reflective film, thereby improving the wettability of the reflective film to the phosphor.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Publication No. 2016-534396 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In Patent Document 1, during the sintering of the reflective film, the glass component contained in the metallic reflective film is heated to a softening temperature. At this temperature, the softened glass component becomes more fluid, sometimes causing it to aggregate or accumulate near the phosphor interface. Furthermore, there is a concern that the glass component might react with the phosphor at the phosphor interface. As a result, the phosphor component deteriorates, and the reflectivity of the reflective film sometimes decreases.

[0008] The purpose of this invention is to provide a technique for suppressing the weakening of the adhesion strength of the reflective film and suppressing the reduction of the reflectivity of the reflective film.

[0009] Solution for solving the problem

[0010] According to a solution of the present invention, a wavelength conversion member is provided, characterized in that it comprises: a phosphor, which is a phosphor that emits fluorescence by excitation light, and has an incident surface on which the excitation light is incident and a back surface facing the incident surface; and,

[0011] A reflective film disposed on the aforementioned back side of the aforementioned phosphor, and having a metal layer and ceramic particles dispersed in the aforementioned metal layer.

[0012] The aforementioned ceramic particles are crystalline, and the melting point of the aforementioned ceramic particles is higher than the melting point of the metal constituting the aforementioned metal layer.

[0013] The effects of the invention

[0014] According to the above scheme, the reflective film has a metal layer and crystalline ceramic particles dispersed in the metal layer. Furthermore, the melting point of the ceramic particles is higher than that of the metal constituting the metal layer. Therefore, the metal layer can be sintered onto the surface of the phosphor by heating to a temperature higher than the melting point of the metal constituting the metal layer. This enhances the adhesion strength of the reflective film. It should be noted that, assuming the metal layer is sintered onto the surface of the phosphor by heating to a temperature higher than the melting point of the metal constituting the metal layer, the ceramic particles do not melt or flow. Therefore, the ceramic particles can be dispersed in the molten metal without agglomerating at the interface with the phosphor. Because the ceramic particles are dispersed in the molten metal, the viscosity of the molten metal increases, maintaining the film shape. This suppresses the decrease in reflectivity of the reflective film. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the light source device 100.

[0016] Figure 2 A flowchart illustrating the manufacturing method of wavelength conversion component 1. Detailed Implementation

[0017] The light source device 100 according to an embodiment of the present invention will be described. It should be noted that in the following description, the light source device 100 is set to a usable state. Figure 1 The state) is used as a reference and is defined as the vertical direction 5 (corresponding to the first direction of this disclosure). Figure 1 As shown, the light source device 100 of this embodiment includes a wavelength conversion member 1 and a light source 2. The light source 2 is a light-emitting diode (LED) or a laser diode (LD), emitting light L1 in a predetermined wavelength range. The wavelength conversion member 1 includes a phosphor 10, which will be described later. When incident with light L1, the phosphor 10 emits light of a different wavelength as fluorescence. In the wavelength conversion member 1, the fluorescence emitted by the phosphor 10, along with light L1 that is detrimental to fluorescence generation in the phosphor 10, is emitted as light L2 in a predetermined direction. The light source device 100 of this embodiment... Figure 1 As shown, this is a reflective light source device used in various optical devices such as headlamps, lighting, and projectors.

[0018] The wavelength conversion component 1 includes: a phosphor 10, a reflective film 20, a bonding layer 30, and a heat dissipation component 40. For example... Figure 1 As shown, the phosphor 10, the reflective film 20, the bonding layer 30, and the heat dissipation component 40 are stacked sequentially from top to bottom.

[0019] The phosphor 10 is a plate-shaped sintered ceramic body, comprising: a fluorescent phase containing fluorescent crystalline particles and a transparent phase containing light-transmitting crystalline particles. In the following description, the upper surface of the phosphor 10 (the surface opposite to the reflective film 20) is referred to as the first surface 11, and the lower surface of the phosphor 10 (the surface opposite to the reflective film 20) is referred to as the second surface 12. The fluorescent phase of the phosphor 10 absorbs light L1 incident from the first surface 11 and emits light of a different wavelength. In other words, the fluorescent phase of the phosphor 10 uses the light L1 incident from the first surface 11 as excitation light and emits fluorescence with a wavelength different from the excitation light.

[0020] The transparent phase crystal particles have the composition shown in the chemical formula Al2O3, and the fluorescent phase crystal particles preferably have the chemical formula A3B5O3. 12 The composition shown in Ce (so-called garnet structure) is as follows. It should be noted that "A3B5O" 12 "Ce" refers to Ce being dissolved in A3B5O. 12 In this process, a portion of element A is replaced with Ce.

[0021] Chemical formula A3B5O 12 Elements A and B in Ce are each composed of at least one element selected from the following groups of elements.

[0022] Element A: Lanthanide elements other than Sc, Y, and Ce (Gd may be further included as element A).

[0023] Element B: Al (which may further include Gd as element B)

[0024] By using a ceramic sintered body as the phosphor 10, light scattering at the interface between the fluorescent and transparent phases reduces the angle dependence of light color. This improves color homogeneity.

[0025] like Figure 1 As shown, a reflective film 20 is stacked on the second surface 12 of the phosphor 10. The reflective film 20 reflects the light transmitted in the phosphor 10 and the light generated in the phosphor 10. The reflective film 20 comprises: a metal layer 21 (e.g., silver (Ag), platinum (Pt), aluminum (Al), silver alloy, etc.) and a plurality of crystalline oxide particles 22 dispersed within the metal layer 21. The crystalline oxide particles 22 are an example of the crystalline ceramic particles of the present invention. It should be noted that the crystalline oxide particles 22 are, for example, crystals such as Al2O3, YAG, TiO2, Y2O3, SiO2, Cr2O3, Nb2O5, Ta2O5, etc., and do not contain amorphous oxide particles such as glass.

[0026] A bonding layer 30 is disposed between the reflective film 20 and the heat dissipation component 40, and is formed of AuSn solder containing gold (Au) and tin (Sn). The bonding layer 30 is used to bond the phosphor 10 and the heat dissipation component 40, and to transfer the heat generated in the phosphor 10 to the heat dissipation component 40.

[0027] The heat dissipation component 40 is, for example, a flat plate made of a material with higher thermal conductivity than the phosphor 10, such as copper, copper-molybdenum alloy, copper-tungsten alloy, aluminum, or aluminum nitride. The heat dissipation component 40 dissipates the heat from the phosphor 10 transferred through the bonding layer 30 to the outside.

[0028] Example

[0029] The present invention will be further described below with reference to examples. However, the present invention is not limited to the examples described below.

[0030] [Example 1]

[0031] In Example 1, the wavelength conversion component 1 is fabricated according to the following steps (refer to...). Figure 2 First, the raw materials are weighed in a 6:4 ratio of fluorescent to transparent phase (S11). Next, the weighed raw materials and ethanol are added to a ball mill and pulverized and mixed for 16 hours (S12). It should be noted that pure water can also be used instead of ethanol. Next, the slurry obtained from pulverization and mixing is dried, granulated, and then a binder and water are added (S13). Next, the mixture is kneaded under shear force to produce a blank, which is then formed into a sheet in an extruder (S14). The formed body is fired at approximately 1700°C in an atmospheric atmosphere (S15). The resulting fired body is cut into 250 μm thick pieces, and the surface is mirror-finished to produce the phosphor 10.

[0032] An acrylic binder and solvent are added to silver (Ag) powder (average particle size about 1-100 μm) and alumina (Al2O3) powder (average particle size about 0.1-10 μm) and mixed (S16). When mixing alumina powder and silver powder, the alumina powder is preferably adjusted to about 3-50% by volume, and more preferably to about 5-20% by volume. In this embodiment, the alumina powder is adjusted to about 5% by volume. Next, the resulting slurry is coated on the second surface 12 of the phosphor 10 and dried (S17). Then, in an atmospheric atmosphere, it is heated to a temperature above the melting point of silver (961.8°C) (e.g., 1000°C) (S18). Thus, a reflective film 20 is formed on the second surface 12 of the phosphor 10.

[0033] Then, with an AuSn solder foil serving as a bonding layer 30 sandwiched between the phosphor 10, which has a reflective film 20 formed on the second surface 12, and the heat dissipation member 40, the wavelength conversion member 1 is fed into a reflow oven to bond the heat dissipation member 40 (S19). Thus, a wavelength conversion member 1, serving as a bond between the phosphor 10 and the heat dissipation member 40, is manufactured. As described above, alumina powder with an average particle size of approximately 0.1 to 10 μm is used; therefore, the average particle size of the alumina particles dispersed in the reflective film 20 of the manufactured wavelength conversion member 1 is approximately 0.1 to 10 μm.

[0034] In Example 1, when the film is a reflective film 20, it is heated to a temperature above the melting point of silver. It should be noted that the melting point of alumina is very high at 2072°C, and the film is not heated to this temperature when forming the reflective film 20. Therefore, when the film is formed as the reflective film 20, the silver particles melt and flow, but the alumina particles are crystalline and therefore do not flow. Thus, the alumina particles can be dispersed in the molten silver without agglomerating at the interface with the phosphor 10. This suppresses the decrease in reflectivity of the reflective film 20 caused by alumina particles agglomerating at the interface with the phosphor 10. Furthermore, the alumina particles dispersed within the reflective film 20 have high light transmittance, thus suppressing the reduction in light intensity caused by light absorption by the alumina particles.

[0035] In Example 1, when the reflective film 20 is formed, silver is sintered onto the surface of the phosphor 10 at a high temperature. Therefore, compared to the case where the reflective film 20 is formed by vapor deposition of silver, the adhesion strength between the reflective film and the phosphor surface can be significantly improved. Furthermore, compared to the case where the reflective film 20 is formed by vapor deposition of silver, a thicker reflective film can be formed. Typically, when the reflective film 20 is formed by vapor deposition of silver onto the surface of the phosphor 10, a thickness of several hundred nm is the limit. In contrast, as described above, when the reflective film 20 is sintered onto the surface of the phosphor 10, the thickness of the reflective film 20 can be increased compared to the case where the reflective film is formed by vapor deposition. In Example 1, the reflective film 20 is formed with a thickness of 5–10 μm. Furthermore, as described above, when the reflective film 20 is sintered onto the surface of the phosphor 10, the reflective film 20 can be formed inexpensively compared to the case where the reflective film is formed by vapor deposition.

[0036] It should be noted that, as described above, when the film is a reflective film 20, if only silver particles are mixed in without alumina particles, the molten silver sometimes partially aggregates when heated to a temperature above the melting point of silver. This partial aggregation of molten silver makes it difficult for the silver to spread across the entire second surface 12 of the phosphor 10. In contrast, as in this embodiment, when alumina particles are dispersed in the molten silver, the viscosity of the molten Ag increases, hindering the partial aggregation of the molten silver, allowing the molten silver to spread across the entire second surface 12 of the phosphor 10.

[0037] [Example 2]

[0038] In Example 2, the oxide particles dispersed inside the reflective film 20 are not alumina particles, but cerium-doped yttrium / aluminum / garnet (YAG:Ce) particles. Otherwise, the wavelength conversion component 1 is manufactured using the same method as in Example 1. In the following description, the cerium-doped yttrium / aluminum / garnet (YAG:Ce) particles will be simply referred to as YAG particles.

[0039] In Example 2, similarly to Example 1, when forming a reflective film 20, silver is sintered onto the surface of the phosphor 10. Therefore, compared to the case where the reflective film 20 is formed by vapor deposition of silver, the adhesion strength between the reflective film and the phosphor surface can be significantly improved, and a reflective film with a thickness of 5–100 μm can be formed. Furthermore, similar to alumina particles, YAG particles act as nuclei attracting the molten silver, thus preventing partial aggregation of the molten silver and allowing the molten silver to spread across the entire second surface 12 of the phosphor 10.

[0040] It should be noted that YAG particles are phosphors that absorb blue light and emit yellow light. Therefore, by dispersing YAG particles inside the reflective film 20, the amount of light inside the reflective film 20 can be increased.

[0041] [Example 3]

[0042] In Example 3, when mixing alumina powder and silver powder, alumina powder with an average particle size of about 5 to 50 μm was used, and a reflective film 20 with a thickness of 10 to 150 μm was formed. Otherwise, the wavelength conversion member 1 was manufactured in the same manner as in Example 1. Because alumina powder with an average particle size of about 5 to 50 μm was used, the average particle size of the alumina particles dispersed in the reflective film 20 of the manufactured wavelength conversion member 1 was about 5 to 50 μm. It was confirmed that the wavelength conversion member 1 of Example 3 also exhibited the same effect as the wavelength conversion member 1 of Example 1.

[0043] <Effects of the Implementation Method>

[0044] The wavelength conversion member 1 of this embodiment includes: a phosphor 10 that emits fluorescence from excitation light L1; and a reflective film 20 disposed on the second surface 12 side of the phosphor 10. Thus, for example, as... Figure 1 As shown, light emitted from phosphor 10 in a direction different from the direction of light L2 emission (e.g., light propagating downwards) is reflected upwards by reflective film 20, thus increasing the amount of light emitted by wavelength conversion member 1. Furthermore, reflective film 20 has a metal layer 21 such as silver and crystalline oxide particles 22 dispersed in the metal layer 21. Moreover, the melting point of oxide particles 22 is higher than the melting point of the metal constituting metal layer 21. Therefore, the metal layer can be sintered onto the surface of phosphor 10 at a temperature higher than the melting point of the metal constituting metal layer 21. This enhances the adhesion strength of reflective film 20 to phosphor 10. It should be noted that, assuming the metal layer 21 is sintered onto the surface of phosphor 10 at a temperature higher than the melting point of the metal constituting metal layer 21, the oxide particles 22 do not melt and do not flow; therefore, the oxide particles 22 do not aggregate at the interface with phosphor 10 and can be dispersed in the molten metal. The oxide particles 22 are dispersed in the molten metal, thus increasing the viscosity of the molten metal and preventing it from partially agglomerating. This, in turn, helps to prevent a decrease in the reflectivity of the reflective film 20.

[0045] In the above embodiments, the oxide particles 22 (e.g., alumina particles or YAG particles) are transparent. This suppresses the reduction in light intensity caused by light absorption by the oxide particles 22. Other transparent oxide particles include, for example, alumina particles, YAG particles, TiO2, Y2O3, SiO2, Cr2O3, Nb2O5, Ta2O5, etc.

[0046] In the above embodiments, when the oxide particle 22 is an oxide particle that emits light upon excitation (e.g., YAG particle), the oxide particle 22 emits light, thus increasing the amount of light inside the reflective film 20. Other examples of luminescent oxide particles besides YAG particles include LuAG (lutetium / aluminum / garnet).

[0047] In the above embodiment, the wavelength conversion member 1 includes a heat dissipation member 40 that dissipates heat from the phosphor 10 to the outside. Therefore, the heat generated when the phosphor 10 emits fluorescence from the excitation light can be effectively dissipated to the outside, thus suppressing extinction caused by a temperature rise in the phosphor 10. Consequently, the reduction in the amount of light emitted by the wavelength conversion member 1 can be suppressed.

[0048] In the above embodiment, the light source device 100 includes a light source 2 that irradiates light L1 onto the phosphor 100. As described above, the reflective film 20 has a thicker film than a reflective film formed by vapor deposition, which improves the adhesion strength of the reflective film 20 to the phosphor 10. This improves the heat resistance of the reflective film 20, thereby increasing the brightness of the light L1 incident on the phosphor 100 and improving the luminous intensity of the light source device 100.

[0049] <Change Method>

[0050] The above embodiments and examples are merely examples and can be modified as appropriate. For example, the materials of the phosphor 10 and the reflective film 20 are not limited to the materials described above, and suitable materials can be used. The bonding layer 30 is not limited to AuSn solder formed of gold and tin, but can also be solder formed of other materials, or it can be formed by sintering fine powders of silver, copper (Cu), etc. The heat dissipation component 40 can be a single-layer structure formed of the above materials, or it can be a multi-layer structure formed of the same or different materials. In addition, the surface of the heat dissipation component 40 can be plated with gold, nickel, etc. In addition, in order to improve the adhesion with the bonding layer 30, and / or to prevent oxidation of the reflective film 20, a metal film (e.g., a thin film of gold (Au), a thin film of nickel (Ni), etc.) can be formed between the bonding layer 30 and the reflective film 20.

[0051] In the above embodiment, the metal layer 21 of the reflective film 20 is formed of silver, but the present invention is not limited to such a solution. As the metal layer 21, metals other than silver can be used (e.g., silver alloys, platinum, aluminum, etc.).

[0052] In the above embodiments, alumina particles and YAG particles can be used as the crystalline oxide particles contained in the reflective film 20, but the present invention is not limited to such a solution. The particles dispersed inside the metal layer 21 of the reflective film 20 are not necessarily alumina particles or YAG particles, as long as they are crystalline ceramic particles with a melting point higher than that of the metal constituting the metal layer 21 of the reflective film 20. As crystalline ceramic particles, suitable oxides, nitrides, carbides, borides, and surface-ceramized metal particles other than alumina particles and YAG particles can be used, for example. It should be noted that, as described above, the crystalline ceramic particles do not contain amorphous oxide particles such as glass.

[0053] Oxide particles are stable in an atmospheric atmosphere. Therefore, when crystalline oxide particles are used as crystalline ceramic particles as in the above embodiment, firing can be carried out in an atmospheric atmosphere where the firing temperature can be easily adjusted, as in the process of S18 described above.

[0054] As crystalline ceramic particles, particles of the ceramic sintered body constituting the phosphor 10 can be used. When there is a difference in the coefficient of thermal expansion between the reflective film 20 and the phosphor 10, there is a concern that the reflective film 20 may peel off from the phosphor 10 due to heat release during the use of the wavelength conversion member 1. In contrast, using crystalline ceramic particles of the ceramic sintered body constituting the phosphor 10 reduces the difference in their coefficients of thermal expansion, thus suppressing peeling. Furthermore, when ceramic particles come into contact with the phosphor, their composition may change. However, using crystalline ceramic particles of the ceramic sintered body constituting the phosphor 10 suppresses this compositional change.

[0055] Furthermore, in the above embodiments, the reflective film 20 is directly sintered onto the second surface 12 of the phosphor 10, but this disclosure is not limited to such a scheme. For example, a film such as a sealing film or a high-reflectivity film can be formed between the second surface 12 of the phosphor 10 and the reflective film 20. The sealing film or high-reflectivity film can be formed from niobium oxide, titanium oxide, lanthanum oxide, tantalum oxide, yttrium oxide, gadolinium oxide, tungsten oxide, hafnium oxide, aluminum oxide, silicon oxide, chromium oxide, etc. It should be noted that the sealing film or high-reflectivity film can be a single-layer film formed from the above materials, or it can be a multilayer film formed from the same or different materials. When the second surface 12 of the phosphor 10 is formed into such a high-reflectivity film, the adhesion strength between the reflective film 20 and the phosphor 10 (and the high-reflectivity film) can be enhanced, similar to embodiments 1 and 2 above.

[0056] The embodiments and modifications thereof of the invention have been described above, but the scope of protection of the invention is not limited to the scope described above. It will be apparent to those skilled in the art that various modifications or improvements can be made to the above embodiments. The claims also clearly indicate that such modifications or improvements can be included within the scope of protection of the invention.

[0057] The manufacturing method shown in the instruction manual and accompanying drawings does not specify the order of execution for each process. Furthermore, they can be executed in any order as long as the output of previous processes is not used for subsequent processes. For convenience, even if terms such as "first," "next," etc. are used, it should not be interpreted as meaning that they must be performed in that order.

[0058] Explanation of reference numerals in the attached figures

[0059] 1 Wavelength conversion component

[0060] 10. Fluorescent cells

[0061] 20 Reflective film

[0062] 21 Metal Layer

[0063] 22 Oxide Particles

[0064] 30 Bonding layer

[0065] 40 heat dissipation components

Claims

1. A wavelength conversion component, characterized in that, have: A phosphor, which emits fluorescence upon excitation light and has an incident surface on which the excitation light is incident and a back surface facing the incident surface; and, The reflective film is disposed on the back side of the phosphor and has a metal layer and ceramic particles dispersed in the metal layer. The ceramic particles are crystalline, and their melting point is higher than that of the metal constituting the metal layer. The ceramic particles are the particles of the ceramic sintered body that constitute the phosphor.

2. The wavelength conversion component according to claim 1, characterized in that, The ceramic particles are oxide particles.

3. The wavelength conversion component according to claim 1, characterized in that, The ceramic particles are translucent.

4. The wavelength conversion component according to any one of claims 1 to 3, characterized in that, The ceramic particles are oxide particles that emit light when excited.

5. The wavelength conversion member according to any one of claims 1 to 3, further comprising a heat dissipation member disposed on the side of the reflective film opposite to the phosphor, and dissipating heat from the phosphor.

6. A light source device, comprising: The wavelength conversion component according to claim 5; and, A light source that irradiates the incident surface of the phosphor with the excitation light.

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