Wavelength conversion member and light source device

Abstract

To provide a technique that can suppress reduction in reflectance of a reflection film, while increasing bonding strength between a phosphor and the reflection film.SOLUTION: A wavelength conversion member comprises: a phosphor that emits fluorescence upon incidence of excitation light, and that has an incidence surface on which the excitation light is incident and a rear face located on an opposite side of the incidence surface; and a reflection film that is arranged on the rear face side of the phosphor, and is composed of a metal layer and particles included inside the metal layer. A melting point of the particles is higher than a melting point of a metal constituting the metal layer. The reflection film has a first surface opposite to the rear face of the phosphor, and a second surface located on an opposite side of the first surface. More particles are included in a side of the second surface than a side of the first surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, wavelength conversion members that convert excitation light irradiated from a light source into fluorescence of a different wavelength and emit the fluorescence have been known. Generally, wavelength conversion members include a phosphor that converts the wavelength of the excitation light and a reflective film arranged on the phosphor opposite to the side irradiated with the excitation light. For example, Patent Document 1 discloses a wavelength conversion member that includes a converter as a phosphor and a metal-containing coating as a reflective film. In this wavelength conversion member, the metal-containing coating contains glass in a metal such as silver, thereby improving the wettability between the silver and the phosphor. [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] In Patent Document 1, when a metal-containing coating is baked onto a converter, the glass contained in the coating is heated to a temperature at which the glass melts. Because the molten glass is fluid, it may aggregate or be unevenly distributed at the phosphor interface, inducing a reaction with the phosphor. As a result, the bonding strength between the phosphor and the reflective film may be reduced, and the reflectance of the reflective film may be reduced.

[0005] The present invention has been made to solve at least some of the above-mentioned problems, and aims to provide a wavelength conversion member and a light source device that can increase the bonding strength between the phosphor and the reflective film while suppressing a decrease in the reflectivity of the reflective film. [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 forms.

[0007] (1) According to one aspect of the present invention, there is provided a wavelength conversion member, comprising: a phosphor that emits fluorescence in response to excitation light, the phosphor having an incident surface on which the excitation light is incident and a back surface opposite the incident surface; and a reflective film disposed on the back surface of the phosphor and made of a metal layer and particles contained within the metal layer, the particles having a melting point higher than that of a metal constituting the metal layer, the reflective film having a first surface facing the back surface of the phosphor and a second surface opposite the first surface, and the particles being contained more abundantly on the second surface side than on the first surface side.

[0008] According to this configuration, the melting point of the particles is higher than that of the metal constituting the metal layer, and such particles are contained in greater numbers on the second surface side than on the first surface side. When manufacturing such a wavelength conversion member, in the process of forming a reflective film on the rear surface of the phosphor, if the material forming the reflective film (including the metal and particles constituting the metal layer) is heated to a temperature equal to or higher than the melting point of the metal constituting the metal layer but lower than the melting point of the particles, the metal constituting the metal layer is melted, and the reflective film can be formed on the rear surface of the phosphor with improved adhesion of the metal layer to the phosphor. This increases the bonding strength between the phosphor and the reflective film. Furthermore, when forming the reflective film on the rear surface of the phosphor, the particles contained on the second surface side are unmelted and are more numerous than those on the first surface side. Therefore, the surface tension acting between the particles and the molten metal conflicts with the surface tension acting between the phosphor and the molten metal, weakening the agglomeration force of the metal to the phosphor and suppressing agglomeration of the molten metal layer. That is, the reflective film can be easily spread along the phosphor, which also contributes to increasing the bonding strength between the phosphor and the reflective film. Furthermore, when the reflective film is formed on the back surface of the phosphor, the particles contained on the first surface side are not melted, just like the particles contained on the second surface side, and there are fewer of them than on the second surface side. This prevents a decrease in the reflectivity of the reflective film caused by a reaction between the melted particles and the back surface of the phosphor or by a large number of particles gathering on the first surface side, reducing the area of the metal layer exposed on the first surface. Therefore, this configuration makes it possible to provide a wavelength conversion member that prevents a decrease in the reflectivity of the reflective film while increasing the bonding strength between the phosphor and the reflective film.

[0009] (2) In the wavelength conversion member of the above aspect, the particles may have a specific gravity smaller than that of the metal layer. According to this configuration, particles can be easily unevenly distributed upward in the direction of gravity inside the molten metal layer during manufacturing of the wavelength conversion member. Therefore, when forming a reflective film on the rear surface of the phosphor, by forming a heated metal layer and particles as a reflective film on the rear surface of the phosphor facing upward in the direction of gravity, it is possible to easily unevenly distribute the particles toward the second surface. Therefore, it is possible to accurately provide a wavelength conversion member in which more particles are contained on the second surface side than on the first surface side.

[0010] (3) In the wavelength conversion member of the above aspect, when the length between the first surface and the second surface is defined as the thickness of the reflective film, the particle diameter of the particles may be half or less of the thickness of the reflective film. When the particle diameter of the particles is large, the proportion of the thickness of the metal layer in the thickness of the reflective film becomes relatively small, and the possibility of through-holes being formed in the metal layer increases. In other words, the possibility of forming portions of the reflective film where there is no metal layer when viewed from above increases. With this configuration, it is possible to reduce the possibility of through-holes being formed in the metal layer and to suppress a decrease in the reflective performance of the reflective film.

[0011] (4) In the wavelength conversion member of the above aspect, the material constituting the particles may contain a material contained in the phosphor. This configuration reduces the difference between the thermal expansion coefficient of the particles and the thermal expansion coefficient of the phosphor. Therefore, the temperature ranges in which the particles do not thermally expand excessively and the temperature ranges in which the phosphor does not thermally expand excessively overlap widely, making it possible to set a wide allowable temperature range in which the particles and phosphor do not thermally expand excessively during heating during the manufacturing of the wavelength conversion member or heating due to the thermal conversion of incident excitation light. In other words, this configuration makes it possible to reduce defects caused by excessive thermal expansion of the phosphor or particles, such as cracks, deformation, and peeling between the phosphor and the reflective film. It also makes it possible to suppress compositional changes due to reactions at the interface between the phosphor and the particles.

[0012] (5) The wavelength conversion member of the above aspect may further include a heat dissipation member that is arranged on the second surface side of the reflective film and dissipates heat generated by the phosphor to the outside. According to this configuration, the heat generated when part of the excitation light incident on the phosphor is converted can be dissipated to the outside of the wavelength conversion member by the heat dissipation member. This makes it possible to suppress thermal quenching, which is a decrease in the amount of fluorescence emitted from the phosphor due to an increase in temperature. Therefore, it is possible to suppress a decrease in the amount of fluorescence emitted from the phosphor.

[0013] (6) According to another aspect of the present invention, there is provided a light source device, comprising: the wavelength conversion member according to the above aspect; and a light source that irradiates the excitation light onto the incident surface. According to this configuration, excitation light irradiated from the light source onto the phosphor is emitted as fluorescence from the phosphor. Furthermore, the reflecting film contains more particles on the second surface side than on the first surface side, thereby suppressing a decrease in reflectance. Therefore, the excitation light incident on the phosphor that passes through the phosphor and the fluorescence emitted from the phosphor that travels toward the back surface can be reflected toward the phosphor while suppressing a decrease in their respective intensities. Furthermore, by providing such a reflecting film, a light source device can be provided in which the reflecting film's reflectance is suppressed and the bonding strength between the phosphor and the reflecting film is increased.

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

[0015] [Figure 1] FIG. 2 is an explanatory diagram schematically illustrating a cross-sectional configuration of a wavelength conversion member. [Figure 2] 10 is a flowchart of a method for manufacturing a wavelength conversion member. [Figure 3] 1A to 1C are explanatory diagrams showing a manufacturing process of a wavelength conversion member. DETAILED DESCRIPTION OF THE INVENTION

[0016] FIG. 1 is an explanatory diagram schematically illustrating a cross-sectional configuration of a wavelength conversion member 1 according to one embodiment of the present invention. The wavelength conversion member 1 converts excitation light L1 irradiated from a light source 50, such as a light-emitting diode (LED) or a semiconductor laser (LD), into fluorescence L2 having a wavelength different from that of the excitation light L1 and emits the fluorescence. The wavelength conversion member 1 is used in various optical devices, such as headlamps, lighting devices, and projectors. The wavelength conversion member 1 shown in FIG. 1 is a part of a light source device 100. In addition to the wavelength conversion member 1, the light source device 100 includes a light source 50 that irradiates excitation light L1. The wavelength conversion member 1 includes a phosphor 10, a reflective film 20, a bonding layer 30, and a heat dissipation member 40.

[0017] The phosphor 10 emits fluorescence L2 when irradiated with excitation light L1. The phosphor 10 has an incident surface 10f and a back surface 10b. The incident surface 10f is the surface onto which the excitation light L1 is incident. The back surface 10b is the surface located opposite the incident surface 10f. The ceramic sintered body constituting the phosphor 10 includes a fluorescent phase mainly made up of fluorescent crystal particles, and a translucent phase mainly made up of translucent crystal particles. The translucent phase's crystal particles are Al2O3 (alumina). On the other hand, the fluorescent phase's crystal particles are made up of 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] 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 Gd) By using a ceramic sintered body as the 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 phosphor 10 is not limited to the above-mentioned materials.

[0019] The reflective film 20 is disposed on the rear surface 10b side of the phosphor 10, and reflects, toward the phosphor 10, excitation light L1 incident on the phosphor 10 that has passed through the phosphor 10, and fluorescence L2 emitted from the phosphor 10 that is directed toward the rear surface 10b. The reflective film 20 has a first surface 20f and a second surface 20b. The first surface 20f is a surface facing the rear surface 10b of the phosphor 10. The second surface 20b is a surface located opposite the first surface 20f.

[0020] The reflective film 20 is composed of a metal layer 21 and particles 22. Examples of metals that constitute the metal layer 21 include silver (Ag), platinum (Pt), aluminum (Al), and silver alloys. In this embodiment, the metal that constitutes the metal layer 21 is silver (Ag). The particles 22 are contained within the metal layer 21. Examples of particles 22 include ceramic particles such as Al2O3, YAG, TiO2, Y2O3, SiO2, Cr2O3, Nb2O5, and Ta2O5, and metal particles such as Ni, W, Mo, Cr, and Nb. In this embodiment, the particles 22 are Al2O3. That is, the material that constitutes the particles 22 is Al2O3, which is the same as the crystalline particles of the translucent phase of the phosphor 10. Therefore, the material that constitutes the particles 22 includes the material contained in the phosphor 10. The volume ratio of the particles 22 in the reflective film 20 to the volume of the metal layer 21 is preferably 0.1 to 20.0%. Furthermore, when the length between the first surface 20f and the second surface 20b is defined as the thickness of the reflective film 20, the thickness is preferably 1 to 100 μm, and the particle diameter of the particles 22 is preferably 0.5 to 50 μm. In this embodiment, the particle diameter of the particles 22 is half or less of the thickness of the reflective film 20. The particle diameter value is the average value of particle diameters of 100 random particles 22 among the particles 22 observed in a cross-sectional image taken with a scanning electron microscope (SEM).

[0021] Furthermore, in the reflective film 20, the melting point of the particles 22 is higher than the melting point of the metal constituting the metal layer 21. In this embodiment, the melting point of Al2O3 constituting the particles 22 is 2072°C, and the melting point of silver (Ag) constituting the metal layer 21 is 961.8°C. Furthermore, the specific gravity of the particles 22 is lower than the specific gravity of the metal layer 21.

[0022] As shown in FIG. 1, the particles 22 are contained in greater numbers on the second surface 20b side than on the first surface 20f side. Such a distribution of the particles 22 can be confirmed by analyzing a cross-sectional image taken with a scanning electron microscope (SEM). Specifically, such a distribution of the particles 22 can be confirmed by comparing the distribution of the particles 22 near the first surface 20f with the distribution of the particles 22 near the second surface 20b in an image of a cross section (such as the cross section shown in FIG. 1) perpendicular to the incident surface 10f of the phosphor 10. The distribution of the particles 22 near the first surface 20f is expressed by the value obtained by dividing the cross-sectional area of the particles 22 present within a range from the first surface 20f to a depth of 10% of the thickness of the reflective film 20 (the length between the first surface 20f and the second surface 20b) by the cross-sectional area of the metal layer 21 present within the same range. Meanwhile, the distribution of particles 22 in the vicinity of the second surface 20b is similarly expressed by the value obtained by dividing the cross-sectional area of particles 22 present within a range from the second surface 20b to a depth that is 10% of the thickness of the reflective film 20 by the cross-sectional area of metal layer 21 present within the same range. Note that FIG. 1 is a diagram that schematically shows the distribution of particles 22 within the reflective film 20, and the particles 22 contained on the first surface 20f side and the particles 22 contained on the second surface 20b side do not need to be distributed at equal intervals, and particles 22 may also be contained in a portion of the reflective film 20 closer to the center between the first surface 20f and the second surface 20b. Of course, the ratio of particles 22 contained on the first surface 20f side to particles 22 contained on the second surface 20b side does not need to be the ratio shown in FIG. 1.

[0023] The bonding layer 30 is disposed between the reflective film 20 and the heat dissipation member 40 (described later), and bonds the reflective film 20 and the heat dissipation member 40 together. The bonding layer 30 is formed of AuSn solder containing gold (Au) and tin (Sn). Note that the bonding layer 30 is not limited to AuSn solder, and may be solder such as Sn-Pb solder, Sn-Ag-Cu solder, Sn-Zn-Bi solder, Sn-Cu solder, or Sn-Ag-In-Bi solder. Alternatively, the bonding layer 30 may be formed by sintering fine powder of silver (Ag), copper (Cu), or the like.

[0024] The heat dissipation member 40 is disposed on the second surface 20b side of the reflective film 20, and dissipates heat generated in the phosphor 10 to the outside of the wavelength conversion member 1. In this embodiment, the heat dissipation member 40 is disposed on the surface of the bonding layer 30 opposite to the surface bonded to the reflective film 20. Examples of materials that can be used to form the heat dissipation member 40 include materials that have higher thermal conductivity than the phosphor 10, such as copper, copper-molybdenum alloy, copper-tungsten alloy, and aluminum, and in this embodiment, the material that forms the heat dissipation member 40 is copper.

[0025] FIG. 2 is a flowchart of a method for manufacturing the wavelength conversion member 1. FIGS. 3A to 3D are explanatory diagrams showing the manufacturing steps of the wavelength conversion member 1. In manufacturing the wavelength conversion member 1, first, as shown in FIG. 3A, a phosphor 10 is prepared (step S10). Specifically, the phosphor 10 is prepared by grinding and mixing materials that form the bases of the fluorescent phase and the translucent phase with ethanol to form a slurry, drying the slurry, granulating the slurry, adding a binder and water, and kneading the mixture to form a clay. A molded product made from the clay is then fired. Next, as shown in FIG. 3B, a first paste 21pf is applied to the back surface 10b of the phosphor 10 (step S20). Specifically, the first paste 21pf is applied to the back surface 10b of the phosphor 10, with the back surface 10b of the phosphor 10 facing upward in the direction of gravity. The first paste 21pf is prepared in advance by mixing the metal powder and particles 22 that make up the metal layer 21 with an acrylic binder and a solvent.

[0026] Next, as shown in FIG. 3(C), a second paste 21pb is applied to the surface of the first paste 21pf opposite the back surface 10b (step S30). The second paste 21pb is the same as the first paste 21pf except that it contains more particles 22 than the first paste 21pf. A laminate LM is a laminate in which the phosphor 10, the first paste 21pf, and the second paste 21pb are stacked. Next, the laminate LM is heated at a temperature equal to or higher than the melting point of the metals contained in the first and second pastes 21pf and 21pb but lower than the melting point of the particles 22. As a result, the first paste 21pf and the second paste 21pb fuse together, forming a reflective film 20 on the back surface 10b of the phosphor 10 as shown in FIG. 3(D) (step S40). When the first paste 21pf and the second paste 21pb fuse together, the specific gravity of the particles 22 contained in each paste is smaller than the specific gravity of the metal contained in the paste, so some of the particles 22 contained in the first paste 21pf move toward the second paste 21pb (not shown in FIG. 3(D)). The amount of movement of the particles 22 is adjusted by the heating temperature and heating time. Then, the reflective film 20 and the heat dissipation member 40 are bonded via the bonding layer 30 (step S50), thereby completing the method for manufacturing the wavelength conversion member 1.

[0027] As described above, in the wavelength conversion member 1 of this embodiment, the melting point of the particles 22 is higher than the melting point of the metal constituting the metal layer 21, and such particles 22 are contained in greater amounts on the second surface 20b side than on the first surface 20f side. When manufacturing such a wavelength conversion member 1, in the step of forming the reflective film 20 on the back surface 10b of the phosphor 10, if the material that forms the reflective film 20 (including the metal constituting the metal layer 21 and the particles 22) is heated to a temperature equal to or higher than the melting point of the metal constituting the metal layer 21 and lower than the melting point of the particles 22 (corresponding to step S40 in FIG. 2 ), the metal constituting the metal layer 21 is melted, and therefore the reflective film 20 can be formed on the back surface 10b of the phosphor 10 in a state in which the adhesion of the metal layer 21 to the phosphor 10 is improved. Therefore, the bonding strength between the phosphor 10 and the reflective film 20 can be increased. Furthermore, when the reflective film 20 is formed on the rear surface 10b of the phosphor 10, the particles 22 contained on the second surface 20b side are not melted and are present in greater numbers than on the first surface 20f side. Therefore, the surface tension acting between the particles 22 and the molten metal is counterbalanced by the surface tension acting between the phosphor 10 and the molten metal, weakening the force of aggregation of the metal relative to the phosphor 10 and suppressing aggregation of the molten metal layer 21. This allows the reflective film 20 to be easily spread along the phosphor 10, thereby also enhancing the bonding strength between the phosphor 10 and the reflective film 20. Furthermore, when the reflective film 20 is formed on the rear surface 10b of the phosphor 10, the particles 22 contained on the first surface 20f side are not melted, just like the particles 22 contained on the second surface 20b side, and are present in fewer numbers than on the second surface 20b side. This makes it possible to suppress a decrease in the reflectance of the reflective film 20, which occurs when the molten particles 22 react with the back surface 10b of the phosphor 10 or when many particles 22 gather on the first surface 20f side, reducing the area of the metal layer 21 exposed on the first surface 20f. Therefore, the wavelength conversion member 1 of the present embodiment can provide a wavelength conversion member 1 that suppresses a decrease in the reflectance of the reflective film 20 while increasing the bonding strength between the phosphor 10 and the reflective film 20.

[0028] Furthermore, in the wavelength conversion member 1 of this embodiment, the particles 22 are made of Al2O3. Since Al2O3 has high light transmittance, it is possible to prevent the particles 22 from absorbing the excitation light or fluorescence that reaches the reflective film 20 side, and therefore it is possible to prevent a decrease in the reflectance of the reflective film 20.

[0029] Furthermore, in the wavelength conversion member 1 of this embodiment, the specific gravity of the particles 22 is smaller than the specific gravity of the metal layer 21, and therefore the particles 22 can be easily unevenly distributed upward in the direction of gravity inside the molten metal layer 21 during the manufacture of the wavelength conversion member 1. Therefore, when forming the reflective film 20 on the rear surface 10b of the phosphor 10, by forming the heated metal layer 21 and the particles 22 as the reflective film 20 on the rear surface 10b of the phosphor 10 facing upward in the direction of gravity (see FIG. 3), the particles 22 can be easily unevenly distributed on the second surface 20b side. As a result, it is possible to accurately provide a wavelength conversion member 1 in which more particles 22 are contained on the second surface 20b side than on the first surface 20f side.

[0030] Furthermore, in the wavelength conversion member 1 of this embodiment, the particle diameter of the particles 22 is equal to or less than half the thickness of the reflective film 20. When the particle diameter of the particles 22 is large, the proportion of the thickness of the metal layer 21 in the thickness of the reflective film 20 becomes relatively small, and the possibility of through holes being formed in the metal layer 21 increases. In other words, the possibility of forming portions of the reflective film 20 where there is no metal layer 21 when viewed from above increases. Therefore, in the wavelength conversion member 1, it is possible to reduce the possibility of through holes being formed in the metal layer 21, and to suppress a decrease in the reflective performance of the reflective film.

[0031] Furthermore, in the wavelength conversion member 1 of this embodiment, the material constituting the particles 22 includes the material contained in the phosphor 10. This allows for a small difference between the thermal expansion coefficients of the particles 22 and the phosphor 10. Therefore, the temperature ranges in which the particles 22 do not thermally expand excessively and the temperature ranges in which the phosphor 10 does not thermally expand excessively overlap widely. This allows for a wide allowable temperature range in which the particles 22 and the phosphor 10 do not thermally expand excessively during heating during the manufacture of the wavelength conversion member 1 or heating due to thermal conversion of the incident excitation light L1. In other words, the wavelength conversion member 1 is less susceptible to defects caused by excessive thermal expansion of the phosphor 10 or the particles 22, such as cracks, deformation, and peeling between the phosphor and the reflective film. Furthermore, compositional changes due to reactions at the interface between the phosphor 10 and the particles 22 can be suppressed.

[0032] Furthermore, the wavelength conversion member 1 of this embodiment is provided with a heat dissipation member 40 that dissipates heat generated in the phosphor 10 to the outside. Therefore, the heat generated when part of the excitation light L1 incident on the phosphor 10 is converted can be dissipated to the outside of the wavelength conversion member 1 by the heat dissipation member 40. This makes it possible to suppress thermal quenching, in which the amount of fluorescence from the phosphor 10 decreases due to a temperature rise. Therefore, it is possible to suppress a decrease in the amount of fluorescence emitted from the phosphor 10.

[0033] Furthermore, according to the light source device 100 of this embodiment, excitation light L1 irradiated from the light source 50 onto the phosphor 10 is emitted as fluorescence L2 from the phosphor 10. Furthermore, the reflective film 20 contains more particles on the second surface 20b side than on the first surface 20f side, thereby suppressing a decrease in reflectance. Therefore, it is possible to reflect the excitation light and fluorescence toward the phosphor 10 while suppressing a decrease in the intensity of the excitation light L1 incident on the phosphor 10 that has passed through the phosphor 10 and the fluorescence L2 emitted from the phosphor 10 that is directed toward the back surface. Furthermore, by providing such a reflective film 20, the light source device 100 not only suppresses a decrease in the reflectance of the reflective film 20 but also enhances the bonding strength between the phosphor 10 and the reflective film 20.

[0034] <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.

[0035] In the above embodiment, the reflective film 20 is disposed in direct contact with the rear surface 10b of the phosphor 10 as shown in FIG. 1 , but this is not limiting. For example, as long as the reflective film 20 is disposed on the rear surface 10b side of the phosphor 10, another structure may be disposed between the reflective film 20 and the phosphor 10. Examples of such another structure include an adhesive film and an enhanced reflection film. Even when such a structure is disposed between the reflective film 20 and the phosphor 10, the reflective film 20 can be formed with improved adhesion to the structure and the phosphor 10.

[0036] As described in the above embodiment, the particles 22 are not limited to Al2O3. For example, the particles 22 may be YAG. When the particles 22 made of YAG are included in the reflective film 20, they can absorb blue light contained in the excitation light or fluorescent light that has reached the reflective film 20 side, and emit yellow light.

[0037] In the above embodiment, the material constituting particles 22 was Al2O3, which is the same as the crystal particles of the translucent phase of phosphor 10, but is not limited to this. The material constituting particles 22 only needs to contain at least a portion of the materials contained in phosphor 10, and may further contain a material different from the materials contained in phosphor 10. Furthermore, if the materials contained in phosphor 10 are not contained in the materials constituting particles 22, it is preferable that the material constituting particles 22 contains a material having a thermal expansion coefficient equivalent to that of the material contained in phosphor 10.

[0038] In the above embodiment, the particles 22 are made of Al2O3 and the metal layer 21 is made of silver (Ag), but this is not limiting. For example, the particles 22 and the metal layer 21 may each be made of multiple materials. In such a case, the melting point of the particles 22 being higher than the melting point of the metal that makes up the metal layer 21 means that the melting point of the material that makes up the particles 22 with the lowest melting point is higher than the melting point of the material that makes up the metal layer 21 with the highest melting point.

[0039] In the above embodiment, the reflective film 20 is formed from two types of paste (first and second pastes 21pf and 21pb) with different particle contents, but this is not limiting. For example, the reflective film 20 may be formed from one type of paste or three or more types of paste, as long as the paste contains the metal that constitutes the metal layer 21 and particles 22 with a specific gravity smaller than that of the metal.

[0040] 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.

[0041] The present invention can also be realized in the following forms. [Application example 1] A wavelength conversion member, a phosphor that emits fluorescence when exposed to excitation light, the phosphor having an incident surface onto which the excitation light is incident and a back surface located opposite to the incident surface; a reflective film disposed on the rear surface side of the phosphor and composed of a metal layer and particles contained within the metal layer; the melting point of the particles is higher than the melting point of the metal constituting the metal layer; The reflective film is a first surface of the phosphor that faces the back surface; a second surface located opposite the first surface, A wavelength conversion member, characterized in that the particles are contained in greater amounts on the second surface side than on the first surface side. [Application example 2] The wavelength conversion member according to Application Example 1, A wavelength conversion member, wherein the particles have a specific gravity smaller than that of the metal layer. [Application example 3] The wavelength conversion member according to Application Example 1 or Application Example 2, A wavelength conversion member, characterized in that, when the length between the first surface and the second surface is defined as the thickness of the reflective film, the particle diameter of the particles is equal to or less than half the thickness of the reflective film. [Application example 4] The wavelength conversion member according to any one of Application Examples 1 to 3, A wavelength conversion member, wherein the material constituting the particles includes a material contained in the phosphor. [Application example 5] The wavelength conversion member according to any one of Application Examples 1 to 4, further comprising: A wavelength conversion member comprising a heat dissipation member disposed on the second surface side of the reflective film, for dissipating heat generated by the phosphor to the outside. [Application Example 6] A light source device, The wavelength conversion member according to any one of Application Examples 1 to 5, a light source that irradiates the excitation light onto the incident surface. [Explanation of symbols]

[0042] 1...Wavelength conversion material 10...Phosphor 10f…Incidence surface 10b…Back side 20…Reflection film 20f…First page 20b…Second side 21...Metal layer 21pf...First paste 21pb...Second paste 22…Particle 30...Joining layer 40...Heat dissipation member 50...Light source 100...Light source device

Claims

1. A wavelength conversion member, a phosphor that emits fluorescence when exposed to excitation light, the phosphor having an incident surface onto which the excitation light is incident and a back surface located opposite to the incident surface; a reflective film disposed on the rear surface side of the phosphor and composed of a metal layer and particles contained within the metal layer; the melting point of the particles is higher than the melting point of the metal constituting the metal layer; The reflective film is a first surface facing the back surface of the phosphor; a second surface located opposite the first surface, A wavelength conversion member, characterized in that the particles are contained in greater amounts on the second surface side than on the first surface side.

2. The wavelength conversion member according to claim 1 , A wavelength conversion member, wherein the particles have a specific gravity smaller than that of the metal layer.

3. The wavelength conversion member according to claim 2, A wavelength conversion member, characterized in that, when the length between the first surface and the second surface is defined as the thickness of the reflective film, the particle diameter of the particles is equal to or less than half the thickness of the reflective film.

4. The wavelength conversion member according to claim 3, A wavelength conversion member, wherein the material constituting the particles includes a material contained in the phosphor.

5. The wavelength conversion member according to claim 4, further comprising: A wavelength conversion member comprising a heat dissipation member disposed on the second surface side of the reflective film and configured to dissipate heat generated by the phosphor to the outside.

6. A light source device, The wavelength conversion member according to any one of claims 1 to 5, a light source that irradiates the excitation light onto the incident surface.

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