JP7821039B2 - Wavelength conversion member and light source device - Google Patents

Description

The present invention relates to a wavelength conversion member and a light source device.

Conventionally, wavelength conversion elements are known that convert excitation light emitted from a light source into fluorescence, which is light of a different wavelength, and emit the converted light. For example, Patent Document 1 discloses a wavelength conversion element comprising a converter, which is a phosphor that emits fluorescence in response to excitation light, and a coating, which is a reflective film, placed on the side of the converter opposite the side irradiated by the excitation light. In such wavelength conversion elements, if the temperature of the converter rises due to heat generated when part of the excitation light incident on the phosphor is converted, the conversion efficiency of converting the excitation light into fluorescence decreases. For this reason, the wavelength conversion element disclosed in Patent Document 1 is equipped with a cooling element as a heat dissipation element to dissipate such heat, and the cooling element is further joined to a heat sink to transfer the heat to the heat sink.

Special table 2016-534396 publication

When heat generated by the conversion of part of the excitation light is transferred to the heat dissipation member, the heat dissipation member thermally expands. However, Patent Document 1 does not take into consideration the thermal expansion of the cooling body, which is the heat dissipation member. Therefore, if the part of the cooling body that is bonded to the heat sink thermally expands when irradiated with excitation light, the contact area between the cooling body and the heat sink decreases, potentially reducing the efficiency of heat dissipation from the phosphor.

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 efficiency of heat dissipation from the phosphor when the heat dissipation member thermally expands.

The present invention has been made to solve at least some of the above-mentioned problems, and can be realized in the following forms.

(1) According to one aspect of the present invention, a wavelength conversion member is provided. This wavelength conversion member comprises: a phosphor that emits fluorescence in response to excitation light, the phosphor having an incident surface onto which the excitation light is incident and a back surface located opposite the incident surface; a reflective film disposed on the back surface of the phosphor; and a heat dissipation member disposed on the side of the reflective film opposite the surface on which the phosphor is disposed, the heat dissipation member dissipating heat generated by the phosphor to the outside, the heat dissipation member having a first surface located on the side of the reflective film and a second surface located opposite the first surface, and the second surface of the heat dissipation member having a recessed portion recessed toward the first surface.

The heat generated when a portion of the excitation light incident on the phosphor is converted is transferred from the phosphor to the heat dissipation member via the reflective film. With this configuration, a recessed portion recessed toward the first surface is formed on the second surface of the heat dissipation member. Therefore, when the heat dissipation member thermally expands due to heat transferred from the phosphor, the shape of the recessed portion changes so that it expands in a direction away from the first surface. Therefore, if a heat sink is disposed on the second surface of the heat dissipation member, the contact area between the heat dissipation member and the heat sink can be increased when the heat dissipation member thermally expands. As a result, the efficiency of heat dissipation from the phosphor can be improved when the heat dissipation member thermally expands.

(2) In the wavelength conversion member of the above aspect, the recessed portion and the phosphor may at least partially overlap each other when the heat dissipation member is viewed through the phosphor.
This configuration shortens the distance from the back surface of the phosphor to the recessed portion compared to a configuration in which the recessed portion and the phosphor do not overlap when viewed through the heat dissipation member from the phosphor side. Therefore, the time from when excitation light begins to be incident on the phosphor to when shape changes due to thermal expansion begin to occur in the recessed portion can be shortened. As a result, when a heat sink is disposed on the second surface of the heat dissipation member, the time from when excitation light begins to be incident on the phosphor to when the contact area between the heat dissipation member and the heat sink begins to increase can be shortened. Furthermore, since the portion of the heat dissipation member facing the back surface of the phosphor is most likely to expand, arranging at least a portion of the recessed portion in such a position can promote shape changes in the recessed portion when irradiated with excitation light.

(3) In the wavelength conversion member of the above aspect, the bottom of the recessed portion that has the greatest depth from the second surface may be included in an overlapping portion between the recessed portion and the phosphor when viewed through the recessed portion.
According to this configuration, the distance from the back surface of the phosphor to the bottom of the recess can be shortened compared to a configuration in which the bottom of the recess is not included in the overlapping portion between the phosphor and the heat dissipation member when viewed through the phosphor. This shortens the time from when excitation light begins to be incident on the phosphor to when shape changes due to thermal expansion begin to occur at the bottom. Because the bottom is the deepest part from the second surface, shape changes at the bottom tend to spread throughout the entire recess. Therefore, by shortening the time when shape changes begin to occur at the bottom, the shape of the recess can be efficiently expanded in a direction away from the first surface.

(4) In the wavelength conversion member of the above aspect, the inner surface of the recess may be a curved surface.
According to this configuration, the stress acting on the inner surface of the recessed portion during thermal expansion of the heat dissipation member can be prevented from concentrating at a specific location, thereby preventing cracks from occurring on the inner surface of the recessed portion.

(5) In the wavelength conversion member of the above aspect, the depth from the second surface to the bottom may be 30 μm or less, and the gradient from the outer edge of the recess on the second surface side to the bottom may be 20 μm/mm or less, based on the second surface.
With this configuration, when a heat sink is disposed on the second surface of the heat dissipation member, good contact between the heat dissipation member and the heat sink can be achieved when the heat dissipation member thermally expands and the shape of the recess changes, thereby further increasing the efficiency of heat dissipation from the phosphor when the heat dissipation member thermally expands.

(6) According to another aspect of the present invention, there is provided a light source device, the light source device including 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 heat dissipation member constituting the wavelength conversion member has a recessed portion recessed toward the first surface. When the heat dissipation member thermally expands due to heat transferred from the phosphor upon irradiation with excitation light from the light source, the shape of the recessed portion changes to expand away from the first surface. Therefore, when a heat sink is disposed on the second surface of the heat dissipation member, the contact area between the heat dissipation member and the heat sink can be increased during thermal expansion of the heat dissipation member. Therefore, by including such a heat dissipation member, a light source device can be provided that improves the efficiency of heat dissipation from the phosphor when irradiated with excitation light from the light source.

The present invention can be realized in various forms, such as wavelength conversion members, light source devices, light-emitting devices, lighting, devices including these, and methods for manufacturing these.

FIG. 1 is an explanatory diagram showing a cross-sectional configuration of a wavelength conversion member according to one embodiment of the present invention. FIG. 1 is a plan view of a wavelength conversion member according to an embodiment of the present invention. FIG. 10 is an explanatory diagram schematically illustrating a cross-sectional configuration of a wavelength conversion member of a comparative example. 10 is an explanatory diagram showing a state in which a heat dissipation member of a comparative example is thermally expanded; FIG. 10A and 10B are explanatory views showing a state in which the heat dissipation member of the embodiment of the present invention is thermally expanded; FIG. 10 is an explanatory diagram showing test results when irradiating with an excitation light laser. FIG. 10 is an explanatory diagram for explaining "depth" and "gradient."

Figure 1 is an explanatory diagram schematically illustrating the cross-sectional configuration of a wavelength conversion member 1 according to one embodiment of the present invention. Mutually orthogonal X, Y, and Z axes are illustrated in Figure 1. These X, Y, and Z axes are common to all subsequent figures. The cross section shown in Figure 1 corresponds to the XZ cross section of the wavelength conversion member 1. 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 of a wavelength different from that of the excitation light L1 and emits the fluorescence. Wavelength conversion members 1 are used in various optical devices, such as headlamps, lighting fixtures, and projectors. The wavelength conversion member 1 shown in Figure 1 is 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 and a heat sink 60. The wavelength conversion member 1 includes a phosphor 10, a reflective film 20, a bonding layer 30, and a heat dissipation member 40.

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 opposite the incident surface 10F. The ceramic sintered body constituting the phosphor 10 includes a fluorescent phase mainly composed of fluorescent crystal particles and a translucent phase mainly composed of translucent crystal particles. The crystal particles of the translucent phase are _Al2O3 ( _{alumina). On the other hand, the crystal particles of the fluorescent phase preferably have a composition represented by A3B5O12 : Ce} (a _so -called garnet structure ₎ . _A3B5O12 :Ce indicates that Ce is dissolved in _A3B5O12 , substituting a portion of _the element _{A with} Ce.

The element A and the element B in A ₃ B ₅ O ₁₂ :Ce are each composed of at least one element selected from the following group of elements:
Element A: Lanthanides other than Sc, Y, and Ce (however, element A may further 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 color of the light. This improves the color uniformity. Note that the material of the phosphor 10 is not limited to the above-mentioned materials.

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. Examples of metals that make up the reflective film 20 include silver (Ag), platinum (Pt), aluminum (Al), and silver alloys. In this embodiment, the metal that makes up the reflective film 20 is silver (Ag). The reflective film 20 also has one surface 20F and another surface 20B. The one surface 20F is the surface of the reflective film 20 on which the phosphor 10 is disposed. The other surface 20B is the surface opposite the one surface 20F.

The bonding layer 30 is disposed between the reflective film 20 and the heat dissipation member 40 (described below), and bonds the reflective film 20 and the heat dissipation member 40 together. The bonding layer 30 is formed from AuSn solder, which contains gold (Au) and tin (Sn). Note that the bonding layer 30 is not limited to AuSn solder, and may be formed by sintering fine powders of silver (Ag), copper (Cu), or other metals, for example.

The heat dissipation member 40 is disposed on the other surface 20B side and dissipates heat generated by the phosphor 10 to the outside of the wavelength conversion member 1. In this embodiment, the heat dissipation member 40 is disposed on the other surface 20B side of the reflective film 20 via the bonding layer 30. Examples of materials that can be used to form the heat dissipation member 40 include copper, copper-molybdenum alloy, copper-tungsten alloy, aluminum, and aluminum nitride, which have higher thermal conductivity than the phosphor 10. In this embodiment, the material that forms the heat dissipation member 40 is copper.

The heat dissipation member 40 has a first surface 40F and a second surface 40B. The first surface 40F is located on the reflective film 20 side. The second surface 40B is located on the opposite side of the first surface 40F. A heat sink 60 is disposed on the second surface 40B. A recess 42 is formed on the second surface 40B, recessed toward the first surface 40F. Specifically, the recess 42 is recessed toward the first surface 40F to a depth of 50% or less of the length from the second surface 40B to the first surface 40F. Here, the depth refers to the length in the direction from the second surface 40B toward the first surface 40F (the length in the +Z-axis direction in FIG. 1). In addition, in this embodiment, the recess 42 is formed on the second surface 40B, and thus a space S defined by the recess 42 and the heat sink 60 exists between the heat dissipation member 40 and the heat sink 60. The bottom 42B is the portion of the recess 42 that is deepest from the second surface 40B. The outer edge ED will be explained using Figure 2 below.

Figure 2 is a plan view of the wavelength conversion member 1. That is, Figure 2 shows the wavelength conversion member 1 as viewed from the +Z-axis direction. In Figure 2, the wavelength conversion member 1 is viewed in a see-through manner, and the circular dashed line indicates the outer edge ED (also shown in Figure 1) of the recess 42 on the second surface 40B side. The position of the bottom 42B is indicated by a dot. The recess 42 and the phosphor 10 at least partially overlap when the heat dissipation member 40 is viewed in a see-through manner from the phosphor 10 side (the +Z-axis direction side in Figures 1 and 2). In this embodiment, as shown in Figure 2, when the heat dissipation member 40 is viewed in a see-through manner from the phosphor 10 side, the recess 42 and the phosphor 10 overlap in a positional relationship where the phosphor 10 is included inside the recess 42. Furthermore, the bottom 42B is included in the overlapping portion between the recess 42 and the phosphor 10 when viewed in a see-through manner. The overlapping portion refers to the portion where the phosphor 10 and the recessed portion 42 overlap when viewed through the heat dissipation member 40 from the phosphor 10 side, and in this embodiment, this corresponds to the inner portion of the region of the phosphor 10 that extends along the XY plane (shown in Figure 2). More specifically, in this embodiment, the bottom 42B is positioned opposite the center position of the phosphor 10 when viewed from the +Z axis direction, as shown in Figure 2, and this opposing position is the center position of the recessed portion 42 when viewed from the +Z axis direction.

Also, as shown in FIG. 1, the inner surface of the recessed portion 42 is a curved surface. More specifically, in this embodiment, the inner surface of the recessed portion 42 is a curved surface that approaches the first surface 40F as it moves from the outer edge ED toward the bottom 42B. In other words, the inner surface of the recessed portion 42 is deepest at its center position (corresponding to the bottom 42B) when viewed from the +Z axis direction.

Figure 3 is an explanatory diagram showing a schematic cross-sectional configuration of a wavelength conversion member 1c of a comparative example. The wavelength conversion member 1c shown in Figure 3 constitutes a light source device 100c together with a light source 50. The wavelength conversion member 1c is the same as the wavelength conversion member 1 of the embodiment described in Figures 1 and 2, except that it includes a heat dissipation member 40c that corresponds to the heat dissipation member 40 without the recessed portion 42.

The first surface 40cF and second surface 40cB of the heat dissipation member 40c correspond to the first surface 40F and second surface 40B of the heat dissipation member 40 of the embodiment. The second surface 40cB of the heat dissipation member 40c does not have a recess 42 formed therein. Therefore, in the wavelength conversion member 1c of the comparative example, there is no space S (see Figure 1) between the heat dissipation member 40c and the heat sink 60.

Figure 4 is an explanatory diagram showing the state of the heat dissipation member 40c thermally expanding in the wavelength conversion member 1c of the comparative example. The heat generated by the conversion of a portion of the excitation light L1 incident on the phosphor 10 from the light source 50 is transferred from the phosphor 10 to the heat dissipation member 40c via the reflective film 20 and the bonding layer 30, causing the heat dissipation member 40c to thermally expand. At this time, the second surface 40cB of the heat dissipation member 40c expands in a direction away from the first surface 40cF. The expanded portion ex shown in Figure 4 is the portion of the second surface 40cB that expands in a direction away from the first surface 40cF due to thermal expansion. Because the wavelength conversion member 1c of the comparative example does not have the space S (see Figure 1), the expansion portion ex occurs when the phosphor 10 is irradiated with the excitation light L1. This reduces the contact area between the heat dissipation member 40c and the heat sink 60, which may reduce the efficiency of heat dissipation from the phosphor 10.

Figure 5 is an explanatory diagram showing the state of the heat dissipation member 40 during thermal expansion in the wavelength conversion member 1 of the embodiment described in Figures 1 and 2. As in Figure 4, heat generated by conversion of a portion of the excitation light L1 incident on the phosphor 10 from the light source 50 causes thermal expansion of the heat dissipation member 40. At this time, the shape of the recess 42 formed on the second surface 40B of the heat dissipation member 40 changes so that it expands in a direction away from the first surface 40F. The expanded portion EX shown in Figure 5 is the portion of the recess 42 that expands in a direction away from the first surface 40F due to thermal expansion. The expansion portion EX is generated when the phosphor 10 is irradiated with excitation light L1, thereby reducing the space S (see Figure 1) and increasing the contact area between the heat dissipation member 40 and the heat sink 60, thereby improving the efficiency of heat dissipation from the phosphor 10.

Figure 6 is an explanatory diagram of test results showing the "maximum temperature" of phosphor 10 when irradiated with an excitation laser light for wavelength conversion members (Examples 1 to 9, Comparative Example 1) manufactured by adjusting the parameters related to the recessed portion 42 described in Figures 1 and 2. Examples 1 to 9 and Comparative Example 1 are wavelength conversion members manufactured by adjusting the "depth" and "gradient" shown in Figure 6 as various parameters related to the recessed portion 42. The "maximum temperature" and "determination" shown in Figure 6 will be discussed later.

Figure 7 is an explanatory diagram illustrating the "depth" and "gradient" shown in Figure 6. The dashed-dotted line DL in Figure 7 is a line passing through the end OT of the second surface 40B in the cross section of the heat dissipation member 40. "Depth" refers to the depth DP from the dashed-dotted line DL to the bottom 42B. "Gradient" refers to the gradient from the outer edge ED of the recess 42 to the bottom 42B (the value obtained by dividing the depth DP by the length LG, described below), based on the dashed-dotted line DL. The length LG refers to the minimum length from position P, which is the depth DP away from the bottom 42B toward the second surface 40B, to the outer edge ED. In this embodiment, because the bottom 42B is located at the center of the recess 42 when viewed from the +Z axis direction (see Figure 2), the length from position P to the outer edge ED is constant at any position on the outer edge ED.

Returning to the explanation of Figure 6, Examples 1 to 9 are wavelength conversion members manufactured with a "depth" adjusted to a range of 3 to 50 μm and a "gradient" adjusted to a range of 1 to 25 μm/mm. In other words, Examples 1 to 9 correspond to wavelength conversion member 1 (see Figure 1) in which recesses 42 are formed. On the other hand, Comparative Example 1 is a wavelength conversion member manufactured with a "depth" adjusted to 0 μm and a "gradient" adjusted to 0 μm/mm. In other words, Comparative Example 1 corresponds to wavelength conversion member 1c (see Figure 3) in which recesses 42 are not formed.

The "maximum temperature" shown in Figure 6 refers to the highest temperature of the phosphor 10 measured by thermography during one minute of irradiation of the phosphor 10 in a wavelength conversion member (Examples 1-9, Comparative Example 1) placed on a heat sink 60 with an excitation laser beam (wavelength 450 nm) having a spot diameter of 1 mm. The lower this "maximum temperature," the higher the heat transfer efficiency of the heat generated in the phosphor 10 upon irradiation with the excitation laser beam, which is transferred from the phosphor 10 to the heat dissipation member 40c and heat sink 60 via the reflective film 20 and bonding layer 30. In particular, in wavelength conversion members 1 having recesses 42, such as those in Examples 1-9, the lower the "maximum temperature," the greater the increase in the contact area between the heat dissipation member 40 and the heat sink 60 due to irradiation with the excitation laser beam, thereby improving the efficiency of heat dissipation from the phosphor 10. The "evaluation" shown in Figure 6 is a rating for the "maximum temperature," and is indicated by three levels: A, B, and C. If the "maximum temperature" was less than 80°C, it was rated as A; if it was between 80°C and 100°C, it was rated as B; and if it was 100°C or higher, it was rated as C.

In Comparative Example 1, the "maximum temperature" was 103°C, resulting in a "C" rating. Furthermore, in Examples 1, 2, and 6, the "maximum temperatures" were 88°C, 83°C, and 81°C, respectively, resulting in a "B" rating. In Examples 3-5 and 7-9, the "maximum temperatures" were 75°C, 74°C, 68°C, 62°C, 64°C, and 73°C, respectively, resulting in a "A" rating. Therefore, the results shown in Figure 6 confirm that, compared to Comparative Example 1, in the case of wavelength conversion members 1 (see Figure 1) fabricated with the combinations of "depth" and "gradient" shown in at least Examples 1-9, the contact area between the heat dissipation member 40 and the heat sink 60 increases during irradiation with an excitation laser beam, improving the efficiency of heat dissipation from the phosphor 10. Furthermore, the results of Examples 1-9 shown in Figure 6 confirm that a "gradation" of "A" is achieved when the "depth" is 30 μm or less and the "gradient" is 20 μm/mm or less. That is, from the results shown in Figure 6, it was confirmed that it is preferable for the recesses 42 formed in the wavelength conversion member 1 to have a "depth" of 30 μm or less and a "gradient" of 20 μm/mm or less.

As described above, according to the wavelength conversion member 1 of this embodiment, the second surface 40B of the heat dissipation member 40 has a recessed portion 42 recessed toward the first surface 40F. Therefore, when the heat dissipation member 40 thermally expands due to heat transferred from the phosphor 10, the shape of the recessed portion 42 changes so that it expands in a direction away from the first surface 40F (see FIG. 5). Therefore, if a heat sink 60 is disposed on the second surface 40B of the heat dissipation member 40, the contact area between the heat dissipation member 40 and the heat sink 60 can be increased when the heat dissipation member 40 thermally expands. As a result, the efficiency of heat dissipation from the phosphor 10 can be improved when the heat dissipation member 40 thermally expands.

Furthermore, in the wavelength conversion member 1 of this embodiment, as shown in FIG. 2, the recessed portion 42 and the phosphor 10 at least partially overlap when viewed through the heat dissipation member 40 from the phosphor 10 side. Therefore, compared to a configuration in which the recessed portion 42 and the phosphor do not overlap when viewed through the heat dissipation member 40 from the phosphor 10 side, the distance from the back surface 10B of the phosphor 10 to the recessed portion 42 can be shortened. Therefore, the time from when the excitation light L1 begins to be incident on the phosphor 10 to when the recessed portion 42 begins to change shape due to thermal expansion can be shortened. As a result, when a heat sink 60 is disposed on the second surface 40B of the heat dissipation member 40, the time from when the excitation light L1 begins to be incident on the phosphor 10 to when the contact area between the heat dissipation member 40 and the heat sink 60 begins to increase can be shortened. Furthermore, since the portion of the heat dissipation member 40 facing the rear surface 10B of the phosphor 10 is most likely to expand, arranging at least a portion of the recess 42 in such a position can promote the change in shape of the recess 42 when irradiated with excitation light L1.

Furthermore, in the wavelength conversion member 1 of this embodiment, as shown in FIG. 2, the bottom 42B is included in the overlapping portion between the recessed portion 42 and the phosphor 10 when viewed through the phosphor 10. Therefore, compared to a configuration in which the bottom 42B of the recessed portion 42 is not included in the overlapping portion between the recessed portion 42 and the phosphor 10 when the heat dissipation member 40 is viewed through the phosphor 10, the distance from the back surface 10B of the phosphor 10 to the bottom 42B of the recessed portion 42 can be shortened. This shortens the time from when excitation light L1 begins to be incident on the phosphor 10 to when shape changes due to thermal expansion begin to occur in the bottom 42B. Because the bottom 42B is the deepest part from the second surface 40B, shape changes in the bottom 42B tend to spread throughout the recessed portion 42. Therefore, by shortening the time when shape changes begin to occur in the bottom 42B, the shape of the recessed portion 42 can be efficiently expanded in the direction away from the first surface 40F.

Furthermore, in the wavelength conversion member 1 of this embodiment, as shown in FIG. 2 , in the overlapping portion between the recess 42 and the phosphor 10 when viewed through a transmittance lens, the bottom 42B is positioned opposite the center position of the phosphor 10 when viewed from the +Z-axis direction, and this opposing position is the center position of the recess 42 when viewed from the +Z-axis direction. When excitation light L1 is irradiated onto the center position of the phosphor 10 when viewed from the +Z-axis direction, heat generated by the conversion of a portion of the excitation light L1 tends to concentrate at that center position. Therefore, by arranging the bottom 42B at a position opposite such a center position, the heat generated and concentrated at the center position of the phosphor 10 when irradiated with excitation light L1 can be used to change the shape of the bottom 42B. Furthermore, because the bottom 42B is positioned at the center position of the recess 42 when viewed from the +Z-axis direction, shape changes of the bottom 42B due to thermal expansion can be more easily spread throughout the entire recess 42.

Furthermore, in the wavelength conversion member 1 of this embodiment, the inner surface of the recessed portion 42 is curved. This prevents the stress acting on the inner surface of the recessed portion 42 during thermal expansion of the heat dissipation member 40 from concentrating in a specific location, thereby preventing cracks from occurring on the inner surface of the recessed portion 42.

Furthermore, it is preferable that the recesses 42 formed in the wavelength conversion member 1 have a depth of 30 μm or less and a gradient of 20 μm/mm or less. In a wavelength conversion member 1 having recesses 42 with such depths and gradients, when a heat sink 60 is placed on the second surface 40B of the heat dissipation member 40, good contact between the heat dissipation member 40 and the heat sink 60 can be achieved when the heat dissipation member 40 thermally expands and the shape of the recesses 42 changes. As a result, the efficiency of heat dissipation from the phosphor 10 can be further improved when the heat dissipation member 40 thermally expands.

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 heat dissipation member 40 constituting the wavelength conversion member 1 has a recessed portion 42 recessed toward the first surface 40F. Therefore, when the heat dissipation member 40 thermally expands due to heat transferred from the phosphor 10 upon irradiation with excitation light L1 from the light source 50, the shape of the recessed portion 42 changes to expand in a direction away from the first surface 40F. Therefore, if a heat sink 60 is disposed on the second surface 40B of the heat dissipation member 40, the contact area between the heat dissipation member 40 and the heat sink 60 can be increased during thermal expansion of the heat dissipation member 40. Therefore, by including such a heat dissipation member 40, the light source device 100 improves the efficiency of heat dissipation from the phosphor 10 when the light source 50 irradiates excitation light L1.

<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.

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 limited to this. For example, as long as the reflective film 20 is disposed on the rear surface 10B side of the phosphor 10, other components may be disposed between the reflective film 20 and the phosphor 10. Examples of other components include an adhesive film or an enhanced reflection film that improves adhesion. In addition, an adhesive film or protective layer may also be disposed between the reflective film 20 and the bonding layer 30.

In the above embodiment, when the heat dissipation member 40 is viewed through from the phosphor 10 side, the recess 42 and the phosphor 10 overlap in a positional relationship where the phosphor 10 is contained within the recess 42, but this is not limited to this. For example, when the heat dissipation member 40 is viewed through from the phosphor 10 side, the recess 42 and the phosphor 10 may only partially overlap, or the recess 42 and the phosphor 10 may overlap in a positional relationship where the recess 42 is contained within the phosphor 10.

In the above embodiment, the bottom 42B of the overlapping portion between the recess 42 and the phosphor 10 when viewed through the phosphor 10 is positioned opposite the center of the phosphor 10 as viewed from the phosphor 10 side, and this opposite position is the center of the recess 42 as viewed from the phosphor 10 side, but this is not limited to this. For example, the bottom 42B may be positioned at a position different from the position opposite the center of the phosphor 10, and this position may be the center of the recess 42 as viewed from the phosphor 10 side. Alternatively, the bottom 42B may be positioned opposite the center of the phosphor 10 as viewed from the phosphor 10 side, and this opposite position may be a position different from the center of the recess 42 as viewed from the phosphor 10 side.

In the above embodiment, the inner surface of the recessed portion 42 was a curved surface that approached the first surface 40F from the outer edge ED toward the bottom 42B, but this is not limited to this. For example, if the inner surface of the recessed portion 42 is curved, the shape may be any shape. Furthermore, the inner surface of the recessed portion 42 does not have to be a curved surface; for example, the shape of the recessed portion 42 may be a rectangular parallelepiped. Furthermore, only a portion of the inner surface of the recessed portion 42 may be curved; for example, the shape of the recessed portion 42 may be a truncated cone.

In the above embodiment, one recessed portion 42 is formed on the second surface 40B, but this is not limited to this. For example, two or more recessed portions 42 may be formed on the second surface 40B. Furthermore, the depth, slope, and size of the outer edge of such recessed portions 42 may be the same as or different from each other.

This aspect has been described above based on embodiments and variations, but 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 its spirit or the scope of the claims, and equivalents are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

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 back surface side of the phosphor;
a heat dissipation member that is disposed on a surface of the reflective film opposite to a surface on which the phosphor is disposed, and that dissipates heat generated by the phosphor to the outside,
The heat dissipation member is
a first surface located on the reflective film side;
a second surface located opposite the first surface,
The wavelength conversion member, wherein the second surface of the heat dissipation member has a recess formed thereon that is recessed toward the first surface.
[Application Example 2]
The wavelength conversion member according to Application Example 1,
The wavelength conversion member, wherein the recessed portion and the phosphor at least partially overlap each other when the heat dissipation member is viewed through the heat dissipation member from the phosphor side.
[Application Example 3]
The wavelength conversion member according to Application Example 1 or Application Example 2,
A wavelength conversion member, characterized in that a bottom portion of the recessed portion that has the greatest depth from the second surface is included in an overlapping portion between the recessed portion and the phosphor when viewed through the recessed portion.
[Application Example 4]
The wavelength conversion member according to any one of Application Examples 1 to 3,
The wavelength conversion member, wherein the inner surface of the recess is a curved surface.
[Application Example 5]
The wavelength conversion member according to any one of Application Examples 1 to 4,
a depth from the second surface to the bottom is 30 μm or less;
a gradient from an outer edge of the recessed portion on the second surface side to the bottom, with the second surface as a reference, of 20 μm/mm or less.
[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.

DESCRIPTION OF SYMBOLS 1... Wavelength conversion member 10... Phosphor 10F... Incident surface 10B... Rear surface 20... Reflective film 20F... One surface 20B... Other surface 30... Bonding layer 40... Heat dissipation member 40F... First surface 40B... Second surface 42... Recessed portion 42B... Bottom portion 50... Light source 60... Heat sink 100... Light source device

Claims (5)

A light source device ,
a light source that irradiates excitation light;
a phosphor that emits fluorescence when exposed to the 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 back surface side of the phosphor;
a heat dissipation member that is disposed on a surface of the reflective film opposite to a surface on which the phosphor is disposed, and that dissipates heat generated by the phosphor to the outside,
The heat dissipation member is
a first surface located on the reflective film side;
a second surface located opposite the first surface,
a recessed portion recessed toward the first surface is formed on the second surface,
A heat sink is disposed on the second surface,
A light source device , characterized in that a space defined by the recess and the heat sink exists between the heat dissipation member and the heat sink . The light source device according to claim 1 ,
The light source device , wherein the recessed portion and the phosphor at least partially overlap each other when viewed through the heat dissipation member from the phosphor side. 3. The light source device according to claim 2,
A light source device characterized in that the bottom of the recessed portion, which has the greatest depth from the second surface, is included in the overlapping portion between the recessed portion and the phosphor when viewed through the light source device. The light source device according to claim 3,
The light source device , wherein the inner surface of the recessed portion is a curved surface. The light source device according to claim 4,
a depth from the second surface to the bottom is 30 μm or less;
a gradient from the outer edge of the recessed portion on the second surface side to the bottom, with the second surface as a reference, of 20 μm/mm or less.