Wavelength conversion element, wavelength conversion element manufacturing method and illumination system

Abstract

This wavelength conversion element for converting irradiated excitation light to light having a different wavelength is provided with a wavelength conversion part having a first surface that is irradiated with the excitation light. The wavelength conversion part includes a plurality of phosphor particles, glass, and a plurality of heat-conductive particles. The glass binds together the plurality of phosphor particles. The plurality of heat-conductive particles each include hexagonal boron nitride and are positioned in the glass at interfaces between the plurality of phosphor particles and the glass and / or between two phosphor particles in the plurality of phosphor particles. Between two phosphor particles arranged in a direction along a first surface from among the plurality of phosphor particles, the plurality of heat-conductive particles include first heat-conductive particles positioned along a direction perpendicular to the first surface.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Japanese Application No. 2021-210791 (filed December 24, 2021), the entire disclosure of which is incorporated herein by reference. [Technical Field]

[0002] The present disclosure relates to a wavelength conversion element. , wavelength conversion element manufacturing method and lighting systems. [Background technology]

[0003] Wavelength conversion elements are known that irradiate a phosphor with excitation light and convert the excitation light into light of a different wavelength. For example, Patent Document 1 discloses an emission color conversion member having a configuration in which an inorganic phosphor is dispersed in glass. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4158012 Summary of the Invention

[0005] Wavelength conversion element , wavelength conversion element manufacturing method and a lighting system are disclosed.

[0006] One aspect of the wavelength conversion element includes a wavelength conversion unit having a first surface onto which excitation light is irradiated. The wavelength conversion unit includes a plurality of phosphor particles, glass, and a plurality of thermally conductive particles. The glass bonds the plurality of phosphor particles together. The plurality of thermally conductive particles are located in one or more locations among the glass, the boundary between the plurality of phosphor particles and the glass, and between two phosphor particles in the plurality of phosphor particles, and each contains hexagonal boron nitride. The plurality of thermally conductive particles are arranged in a direction perpendicular to the first surface between two phosphor particles of the plurality of phosphor particles that are aligned in a direction along the first surface. tilted from 0 to 15 degrees relative to the axisa first thermally conductive particle positioned along a direction; tilted within the range of 0 to 15 degrees Located along the direction One or more and thermally conductive particles. In a cross section of the wavelength converting portion taken along an imaginary plane perpendicular to the first surface, each of the first thermally conductive particle and the one or more thermally conductive particles has an elongated rod shape with a longitudinal direction and a lateral direction perpendicular to the longitudinal direction, and is located along a surface of one of the phosphor particles. The longitudinal direction of each of the first thermally conductive particle and the one or more thermally conductive particles is a direction along the surface of the one phosphor particle. One aspect of the method for manufacturing a wavelength conversion element is the method for manufacturing a wavelength conversion element of the above aspect, and includes the steps of: forming a powder mixture of one or more types of phosphor particle powder, glass powder, and thermally conductive particle powder containing hexagonal boron nitride to produce a molded body; and firing the molded body. In the firing step, a pressing force is applied to the molded body in one direction.

[0007] One aspect of the lighting system includes the wavelength conversion element of the above aspect, a light source unit that emits the excitation light, and a lighting unit that emits fluorescence emitted from the wavelength conversion element toward an illumination space in response to irradiation with the excitation light emitted from the light source unit. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of a lighting system according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing an example of the configuration of the wavelength conversion element according to the first embodiment. [Figure 3] FIG. 3 is a conceptual diagram showing an example of a cross-sectional configuration of the wavelength conversion element according to the first embodiment. [Figure 4] FIG. 4 is an image diagram showing an example of positions where a plurality of phosphor particles and a plurality of thermally conductive particles are present in a part of the cross-sectional configuration of the wavelength conversion section according to the first embodiment. [Figure 5] FIG. 5 is a flowchart showing a manufacturing flow of the wavelength conversion element according to the first embodiment. [Figure 6] FIG. 6 is a cross-sectional view showing an example of a wavelength conversion element in the middle of its manufacture. [Figure 7] FIG. 7 is a cross-sectional view showing an example of a wavelength conversion element in the middle of its manufacture. [Figure 8]FIG. 8 is a cross-sectional view showing an example of a wavelength conversion element in the middle of its manufacture. [Figure 9] FIG. 9 is a cross-sectional view showing an example of a wavelength conversion element in the middle of its manufacture. [Figure 10] FIG. 10 is a cross-sectional view showing an example of a wavelength conversion element in the middle of its manufacture. [Figure 11] FIG. 11 is a cross-sectional view schematically showing an image of the state of thermally conductive particles in a pre-sintered body before pressure processing according to one reference example. [Figure 12] FIG. 12 is a cross-sectional view schematically showing an image of the state of thermally conductive particles in a pre-sintered body after pressure processing according to one reference example. [Figure 13] FIG. 13 is a cross-sectional view schematically illustrating an image of the state of thermally conductive particles in the pre-sintered body according to the first embodiment before pressure processing. [Figure 14] FIG. 14 is a cross-sectional view schematically showing an image of the state of thermally conductive particles in the pre-sintered body after pressure processing according to the first embodiment. [Figure 15] FIG. 15 is a perspective view showing an example of the configuration of the wavelength conversion element according to the second embodiment. [Figure 16] FIG. 16 is a cross-sectional view showing an example of the configuration of the wavelength conversion element according to the second embodiment. [Figure 17] FIG. 17 is a flowchart showing a manufacturing flow of the wavelength conversion element according to the second embodiment. [Figure 18] FIG. 18 is a perspective view showing an example of the configuration of the base material according to the second embodiment. [Figure 19] FIG. 19 is a cross-sectional view showing an example of the configuration of the base material according to the second embodiment. [Figure 20] FIG. 20 is an image diagram showing an example of a cross-sectional configuration of a portion XX surrounded by a two-dot chain line in FIG. [Figure 21] FIG. 21 is a cross-sectional view showing the configuration of a substrate according to another first example. [Figure 22] FIG. 22 is a cross-sectional view showing the configuration of a substrate according to another second example. [Figure 23]FIG. 23 is a cross-sectional view showing a configuration example of a wavelength conversion element according to another first example. [Figure 24] FIG. 24 is a cross-sectional view showing a configuration example of a wavelength conversion element according to another first example. [Figure 25] FIG. 25 is a cross-sectional view showing a configuration example of a wavelength conversion element according to another second example. [Figure 26] FIG. 26 is a cross-sectional view showing a configuration example of a wavelength conversion element according to another second example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Wavelength conversion elements are known that irradiate a phosphor with excitation light such as laser light and convert it into light of a different wavelength from the excitation light. Here, for example, if the phosphor includes a red phosphor that emits red fluorescence in response to irradiation with the excitation light, a green phosphor that emits green fluorescence in response to irradiation with the excitation light, and a blue phosphor that emits blue fluorescence in response to irradiation with the excitation light, the wavelength conversion element converts the excitation light into pseudo-white light.

[0010] However, the phosphor may be deteriorated by the temperature rise caused by irradiation with excitation light, for example, when the time during which the phosphor is irradiated with excitation light is prolonged or when the output of the irradiated excitation light is increased.

[0011] Therefore, there is room for improvement in wavelength conversion elements and lighting systems equipped with wavelength conversion elements in terms of reducing deterioration of the wavelength conversion elements.

[0012] Therefore, the inventors of the present disclosure have created a technique that can reduce the deterioration of wavelength conversion elements in wavelength conversion elements and lighting systems equipped with wavelength conversion elements.

[0013] A first embodiment, a second embodiment, and various examples will be described below with reference to the drawings. In the drawings, parts having the same or similar configurations and functions are denoted by the same reference numerals, and redundant explanations will be omitted below. The drawings schematically illustrate various structures and functional configurations. A right-handed XYZ coordinate system is illustrated in Figures 2 to 4, 6 to 14, 16, and 19 to 26. The direction in which the first surface F1 of the wavelength conversion unit 30t faces is the +Z direction, a direction perpendicular to the +Z direction is the +X direction, and a direction perpendicular to both the +Z direction and the +X direction is the +Y direction.

[0014] 1. First Embodiment <1-1. Lighting System> FIG. 1 is a schematic diagram showing an example of the configuration of a lighting system 1 according to a first embodiment. The lighting system 1 is capable of emitting fluorescence L1, which is generated when excitation light L0 is irradiated from a light source unit 2 onto a wavelength conversion element 30 containing a phosphor, as illumination light L2 into a predetermined space (also referred to as an illumination space). The lighting system 1 may emit the illumination light L2 into an indoor space or an outdoor space. In other words, the illumination light L2 emitted by the lighting system 1 may be used indoors or outdoors. Furthermore, multiple lighting systems 1 may each emit the illumination light L2 into the same space, or multiple lighting systems 1 may each emit the illumination light L2 into multiple different spaces.

[0015] As shown in FIG. 1, the lighting system 1 includes, for example, a light source unit 2, a conversion unit 3, and a lighting unit 4.

[0016] The light source unit 2 can emit, for example, excitation light L0. The light source unit 2 has, for example, a light-emitting element. The light-emitting element includes, for example, a laser diode (LD) or a light-emitting diode (LED) chip. The excitation light L0 emitted by the light-emitting element is monochromatic light such as purple, blue-violet, or blue. More specifically, the light-emitting element is, for example, a gallium nitride (GaN) semiconductor laser that emits purple laser light of 405 nanometers (nm). In the example of FIG. 1, the excitation light L0 emitted from the light source unit 2 is transmitted to the conversion unit 3 via an optical transmission path (also referred to as a first optical transmission path) G1 such as an optical fiber. In this case, the light source unit 2 has a connection part to which an end part (also referred to as a first incident end part) of the first optical transmission path G1, to which the excitation light L0 is incident, is connected.

[0017] The conversion unit 3 includes, for example, a wavelength conversion element 30. The wavelength conversion element 30 can convert the irradiated excitation light L0 into light with a wavelength different from that of the excitation light L0. The wavelength conversion element 30 includes, for example, a phosphor that emits fluorescence with a wavelength different from that of the excitation light L0 in response to irradiation with the excitation light L0. If the wavelength conversion element 30 includes, for example, phosphors that emit red (R), green (G), and blue (B) fluorescence in response to irradiation with purple excitation light L0, the purple excitation light L0 is converted into pseudo-white light in the wavelength conversion element 30. In the example of FIG. 1, the fluorescence L1 emitted from the wavelength conversion element 30 in response to irradiation with the excitation light L0 is transmitted to the illumination unit 4 via an optical transmission path G2 (also referred to as a second optical transmission path) such as an optical fiber. The conversion unit 3 also includes, for example, a housing in which the wavelength conversion element 30 is fixed. In this case, the housing has, for example, a first opening connected to an end (also referred to as a first exit end) of the first optical transmission line G1 from which the excitation light L0 is emitted, and a second opening connected to an end (also referred to as a second entrance end) of the second optical transmission line G2 into which the fluorescence L1 is incident. An optical element such as a mirror may be arranged inside the housing to collect the fluorescence L1 emitted from the wavelength conversion element 30 in response to irradiation with the excitation light L0, onto the second entrance end of the second optical transmission line G2.

[0018] The illumination unit 4 can emit, for example, fluorescence L1 emitted from the wavelength conversion element 30 in response to irradiation with excitation light L0 emitted from the light source unit 2 toward a predetermined illumination space. The illumination unit 4 has, for example, a main body and an optical element. In this case, the main body has, for example, a connection portion to which an end portion (also referred to as a second emission end portion) of the second optical transmission path G2 from which the fluorescence L1 is emitted is connected. For example, a cylindrical member can be used for the main body. For example, the optical element is attached to the main body and emits the fluorescence L1 emitted from the second emission end portion of the second optical transmission path G2 as illumination light L2 toward the predetermined illumination space.

[0019] The lighting system 1 may also include, for example, a control device 5 for controlling the operation of the light source unit 2. The control device 5 includes, for example, a control unit 51 and a driving unit 52. The control unit 51 can comprehensively manage the operation of the control device 5 by controlling the other components of the control device 5. The control unit 51 includes, for example, a central processing unit (CPU) 511 and a storage unit 512. The storage unit 512 includes a non-transitory recording medium readable by the CPU 511, such as a read-only memory (ROM) and a random access memory (RAM). The storage unit 512 stores a program Pg1 for controlling the control device 5, etc. Various functions of the control unit 51 are realized by the CPU 511 executing the program Pg1 stored in the storage unit 512. The driving unit 52 can drive the light source unit 2, for example, in response to an instruction from the control unit 51. The driving unit 52 can drive the light source unit 2 and cause the light source unit 2 to output excitation light L0 by, for example, supplying power from a power source to the light source unit 2. For example, the control unit 51 controls whether or not power is supplied from the power source to the light source unit 2 via the drive unit 52, thereby controlling the timing at which the light source unit 2 emits the excitation light L0.

[0020] <1-2. Configuration of wavelength conversion element> FIG. 2 is a cross-sectional view showing an example of the configuration of the wavelength conversion element 30 according to the first embodiment. FIG. 2 schematically illustrates the periphery of a first output end of the first optical transmission line G1 and the periphery of a second input end of the second optical transmission line G2. As shown in FIG. 2, the wavelength conversion element 30 includes a wavelength conversion section 30t and a substrate 30b. The cross-sectional structure of the wavelength conversion section 30t has a complex structure with intricate microstructures, but a schematic illustration of the structure is omitted in FIG. 2 for convenience.

[0021] The wavelength conversion unit 30t has a surface (also referred to as a first surface) F1 onto which the excitation light L0 is incident. The wavelength conversion unit 30t also has a surface (also referred to as a second surface) F2 located on the opposite side from the first surface F1. The wavelength conversion unit 30t has, for example, a plate-like or film-like shape having a thickness along the direction from the second surface F2 to the first surface F1. The base material 30b has a surface (also referred to as a third surface) F3 on which the wavelength conversion unit 30t is arranged. Specifically, the second surface F2 of the wavelength conversion unit 30t is fixed to the third surface F3. In the example of FIG. 2, the first surface F1 faces the +Z direction, the second surface F2 faces the -Z direction, and the third surface F3 faces the +Z direction. For example, a plate-like member is used for the base material 30b. For example, a disk-like member or a member that is rectangular in plan view is used for the plate-like member.

[0022] The base material 30b is a member to which the wavelength converting portion 30t is fixed. The base material 30b has, for example, a higher thermal conductivity than the wavelength converting portion 30t. This allows the base material 30b to function as, for example, a heat sink that dissipates heat from the wavelength converting portion 30t.

[0023] Fig. 3 is an image diagram schematically illustrating an example of a cross-sectional configuration of the wavelength conversion element 30 according to the first embodiment. Fig. 3 shows an image of a cross section drawn based on a scanning electron microscope (SEM) photograph of the cross section of the wavelength conversion section 30t.

[0024] As shown in Fig. 3, the wavelength converting unit 30t includes a plurality of phosphor particles 31, glass 32, and a plurality of thermally conductive particles 33. In Fig. 3, the base material 30b is hatched with diagonal lines slanting upward to the right, the plurality of phosphor particles 31 are hatched with diagonal lines slanting upward to the left, the glass 32 is hatched with sandy hatching, and the plurality of thermally conductive particles 33 are depicted with thick straight lines or solid lines.

[0025] Each of the plurality of phosphor particles 31 is, for example, a particle of a phosphor (also referred to as a phosphor particle) that emits fluorescence in response to irradiation with the excitation light L0. The plurality of phosphor particles 31 includes, for example, one or more types of phosphor particles that emit fluorescence of one or more wavelength spectra different from the wavelength spectrum of the excitation light L0 in response to irradiation with the excitation light L0. The one or more types of phosphor particles may include, for example, multiple types of phosphor particles that emit fluorescence having mutually different wavelength spectra in response to irradiation with the excitation light L0. The multiple types of phosphor particles include, for example, red phosphor particles, green phosphor particles, and blue phosphor particles. The red phosphor is a phosphor that emits red (R) fluorescence in response to irradiation with the excitation light L0. The green phosphor is a phosphor that emits green (G) fluorescence in response to irradiation with the excitation light L0. The blue phosphor is a phosphor that emits blue (B) fluorescence in response to irradiation with the excitation light L0. The phosphor constituting the plurality of phosphor particles 31 may be, for example, a phosphor containing a rare earth such as Eu (europium), Ce (cerium), or Y (yttrium) in the form of a compound such as phosphate, oxide, silicate, nitride, fluoride, aluminate, or sulfide. The particle size of the phosphor particles 31 may be, for example, about 5 micrometers (μm) to 50 μm.

[0026] The plurality of phosphor particles 31 include, for example, two phosphor particles 31 aligned in a direction along the first surface F1. The two phosphor particles 31 aligned in a direction along the first surface F1 face each other in the direction along the first surface F1 without sandwiching any other phosphor particle 31 therebetween. In the first embodiment, the direction along the first surface F1 is a direction along the XY plane. In the cross-sectional configuration of FIG. 3, the direction along the first surface F1 is a direction along the ±X directions.

[0027] Here, the direction along the first surface F1 is not limited to a direction extending parallel to the first surface F1. For example, the direction along the first surface F1 may include a direction inclined within a range of 0 to 15 degrees with respect to the first surface F1, or may include a direction inclined within a range of 0 to 30 degrees with respect to the first surface F1. In other words, the direction along the first surface F1 is not limited to a direction extending parallel to the XY plane. For example, the direction along the first surface F1 may include a direction inclined within a range of 0 to 15 degrees with respect to the XY plane, or may include a direction inclined within a range of 0 to 30 degrees with respect to the XY plane. In the cross-sectional structure of FIG. 3, the direction along the first surface F1 may include a direction inclined within a range of 0 to 15 degrees with respect to a virtual line (also referred to as a virtual line) parallel to the X axis, or may include a direction inclined within a range of 0 to 30 degrees with respect to a virtual line parallel to the X axis.

[0028] For example, focusing on the upper right portion of the wavelength conversion unit 30t in FIG. 3, the plurality of phosphor particles 31 includes a first phosphor particle P1 and a second phosphor particle P2 as two phosphor particles 31 aligned in a direction along the first surface F1. The first phosphor particle P1 and the second phosphor particle P2 face each other in a direction along the first surface F1 without any other phosphor particles 31 sandwiched between them. Furthermore, focusing on the center portion of the left side of the wavelength conversion unit 30t in FIG. 3, the plurality of phosphor particles 31 includes a third phosphor particle P3 and a fourth phosphor particle P4 as two phosphor particles 31 aligned in a direction along the first surface F1. The third phosphor particle P3 and the fourth phosphor particle P4 face each other in a direction along the first surface F1 without any other phosphor particles 31 sandwiched between them.

[0029] The glass 32, for example, bonds the plurality of phosphor particles 31 together. The glass 32 is located, for example, between the plurality of phosphor particles 31 and between the phosphor particles 31 and the substrate 30b. The glass 32 has the function of directly conducting heat from the phosphor particles 31 in the portions in direct contact with the phosphor particles 31. Here, the surfaces of the phosphor particles 31 may be covered with a coating layer. In this case, the state in which the glass 32 is in direct contact with the phosphor particles 31 includes a state in which the coating layer covering the phosphor particles 31 is in direct contact with the glass 32. The glass 32 is transparent, for example, to transmit the excitation light L0 to the inside of the wavelength conversion unit 30t and to radiate the fluorescence L1 emitted by the phosphor particles 31 excited in response to irradiation with the excitation light L0 to the outside of the wavelength conversion unit 30t. When excitation light L0 is irradiated onto the first surface F1 of the wavelength conversion section 30t, the heat caused by the irradiation of excitation light L0 onto the multiple phosphor particles 31 and the glass 32 is conducted to the base material 30b via the glass 32, etc., and dissipated.

[0030] Each of the plurality of thermally conductive particles 33 is located, for example, in one or more of the following locations: within the glass 32, at the boundary between the plurality of phosphor particles 31 and the glass 32, and between two phosphor particles 31. Each of the plurality of thermally conductive particles 33 has better thermal conductivity than the glass 32. For example, boron nitride (also known as hexagonal boron nitride or h-BN) having a hexagonal crystal structure is used for each of the plurality of thermally conductive particles 33. The thermally conductive particles 33 have the function of directly conducting heat from the phosphor particles 31 in the portions that are in direct contact with the phosphor particles 31, and the function of indirectly conducting heat from the phosphor particles 31 via the glass 32 in the portions that are in contact with the glass 32. Particles of hexagonal boron nitride, for example, have a plate-like shape and are known to exhibit high thermal conductivity in the direction along the plate surface (also referred to as the direction along the ab plane or the direction along the (002) plane) (see, for example, Natsumi Torase, Junichi Tatami, Motoyuki Iijima, and Takumi Takahashi, "Preparation of Nitride Phosphor Particle-Dispersed h-BN / Glass Composite," Journal of the Society of Powder Technology, Vol. 57, No. 3, 2020, pp. 137-143). Therefore, the thermally conductive particles 33 have high thermal conductivity in the direction along the plate surface. The length of each of the plurality of thermally conductive particles 33 along the plate surface may be, for example, approximately 1 μm to 10 μm, or approximately 5 μm to 6 μm.

[0031] The thermally conductive particles 33 include a thermally conductive particle (also referred to as a first thermally conductive particle) 33a located between two of the phosphor particles 31 aligned in a direction along the first surface F1 and perpendicular to the first surface F1. In other words, for example, two phosphor particles 31 facing each other in the direction along the first surface F1 without sandwiching another phosphor particle 31 sandwich the first thermally conductive particle 33a in the direction along the first surface F1. The plate surface of the first thermally conductive particle 33a is located in the direction perpendicular to the first surface F1. Here, glass 32 may or may not be present between the two phosphor particles 31 and the first thermally conductive particle 33a. In the first embodiment, the direction perpendicular to the first surface F1 is the ±Z direction, which is the thickness direction of the wavelength conversion unit 30t.

[0032] Here, the state in which the thermally conductive particles 33 are positioned along the direction perpendicular to the first surface F1 is not limited to a state in which an imaginary plane (also referred to as a virtual plane) perpendicular to the first surface F1 and the plate surface of the thermally conductive particles 33 completely coincide. In the cross-sectional structure of Fig. 3, the state in which the thermally conductive particles 33 are positioned along the direction perpendicular to the first surface F1 is not limited to a state in which an imaginary line parallel to the Z axis and the plate surface of the thermally conductive particles 33 completely coincide. For example, the state in which the thermally conductive particles 33 are positioned along the direction perpendicular to the first surface F1 may include a state in which the plate surface of the thermally conductive particles 33 coincides with an imaginary plane tilted at an angle of 0 to 15 degrees with respect to the imaginary plane perpendicular to the first surface F1, or may include a state in which the plate surface of the thermally conductive particles 33 coincides with an imaginary plane tilted at an angle of 0 to 30 degrees with respect to the imaginary plane perpendicular to the first surface F1. In the cross-sectional structure of Figure 3, the state in which the thermally conductive particles 33 are positioned along a direction perpendicular to the first face F1 may include a state in which a virtual line inclined within a range of 0 degrees to 15 degrees with respect to the Z axis coincides with the plate surface of the thermally conductive particles 33, or a state in which a virtual line inclined within a range of 0 degrees to 30 degrees with respect to the Z axis coincides with the plate surface of the thermally conductive particles 33.

[0033] 3, the plurality of thermally conductive particles 33 includes a first thermally conductive particle 33a located along the ±Z direction between a first phosphor particle P1 and a second phosphor particle P2 as two phosphor particles 31 aligned in the ±X direction. The plurality of thermally conductive particles 33 also includes a first thermally conductive particle 33a located along the ±Z direction between a third phosphor particle P3 and a fourth phosphor particle P4 as two phosphor particles 31 aligned in the ±X direction.

[0034] In the first embodiment, the first thermally conductive particles 33a have, for example, a plate surface extending in the direction from the first surface F1 to the second surface F2. In other words, the first thermally conductive particles 33a have, for example, a plate surface extending in the thickness direction of the wavelength conversion unit 30t. Therefore, for example, the first thermally conductive particles 33a can increase the thermal conduction in the wavelength conversion unit 30t in the direction from the first surface F1 to the second surface F2. In other words, the first thermally conductive particles 33a can increase the thermal conduction in the thickness direction of the wavelength conversion unit 30t. This can improve, for example, the heat dissipation performance of the wavelength conversion unit 30t. As a result, for example, the temperature rise of the multiple phosphor particles 31 when the first surface F1 of the wavelength conversion unit 30t is irradiated with excitation light L0 can be reduced. Therefore, for example, the phosphor particles 31 are less likely to deteriorate, and deterioration of the wavelength conversion element 30 can be reduced.

[0035] Fig. 4 is an image showing an example of the positions where a plurality of phosphor particles 31 and a plurality of thermally conductive particles 33 are present in a part of the cross-sectional configuration of the wavelength conversion unit 30t according to the first embodiment. Fig. 4 shows an image of only the positions where three phosphor particles 31 and a plurality of thermally conductive particles 33 around the three phosphor particles 31 are present, based on a scanning electron microscope (SEM) photograph of the cross section of the wavelength conversion unit 30t. For convenience, Fig. 4 omits the presence of glass 32. In Fig. 4, as in Fig. 3, the plurality of phosphor particles 31 are hatched using diagonal lines slanting upward to the left, and the plurality of thermally conductive particles 33 are depicted by thick straight or solid lines.

[0036] 4, for example, the plurality of thermally conductive particles 33 may include one or more thermally conductive particles (also referred to as second thermally conductive particles) 33b in contact with the surface of one of the plurality of phosphor particles 31. If this configuration is adopted, for example, heat dissipation from one phosphor particle 31 to the glass 32 or the like via the one or more second thermally conductive particles 33b can be increased. This can reduce, for example, the temperature rise of the phosphor particles 31. As a result, deterioration of the phosphor particles 31 can be reduced, and deterioration of the wavelength conversion element 30 can be reduced.

[0037] Here, for example, one or more second thermally conductive particles 33b may be in contact with the surfaces of all of the phosphor particles 31 in the wavelength conversion section 30t, or one or more second thermally conductive particles 33b may be in contact with the surfaces of two or more of the phosphor particles 31 in the wavelength conversion section 30t. In other words, the number of phosphor particles 31 having surfaces in contact with one or more second thermally conductive particles 33b is not limited to one. For example, the more phosphor particles 31 having surfaces in contact with one or more second thermally conductive particles 33b, the more the degradation of the phosphor particles 31 is reduced, and the more the degradation of the wavelength conversion element 30 can be reduced.

[0038] Here, for example, in a cross section of the wavelength converting section 30t taken along an imaginary plane (also referred to as a virtual plane) perpendicular to the first surface F1, as shown in FIG. 4, each of the one or more second thermally conductive particles 33b may have an elongated rod-like shape having a longitudinal direction and a lateral direction. The lateral direction may be a direction perpendicular to the longitudinal direction. In the example of FIG. 4, the cross section of the wavelength converting section 30t taken along an imaginary plane perpendicular to the first surface F1 is a plane along the XZ plane. In this cross section, for example, the longitudinal direction of each of the one or more second thermally conductive particles 33b may be a direction along the surface of one phosphor particle 31 with which the one or more second thermally conductive particles 33b are in contact. If this configuration is adopted, for example, the area on the surface of one phosphor particle 31 where one or more second thermally conductive particles 33b are in contact may be increased, thereby increasing heat dissipation from one phosphor particle 31 to the glass 32 or the like via the one or more second thermally conductive particles 33b. This can reduce, for example, the temperature rise of the phosphor particles 31. As a result, deterioration of the phosphor particles 31 can be reduced, and deterioration of the wavelength conversion element 30 can be reduced.

[0039] The cross section of the wavelength converting unit 30t taken along an imaginary plane perpendicular to the first surface F1 may be a cross section of the wavelength converting unit 30t inclined at an angle ranging from 0 to 15 degrees with respect to the imaginary plane perpendicular to the first surface F1, or may be a cross section of the wavelength converting unit 30t inclined at an angle ranging from 0 to 30 degrees with respect to the imaginary plane perpendicular to the first surface F1. In other words, the cross section of the wavelength converting unit 30t taken along an imaginary plane perpendicular to the first surface F1 is not limited to the cross section of the wavelength converting unit 30t perpendicular to the first surface F1.

[0040] Here, for example, in a cross section of the wavelength conversion unit 30t taken along an imaginary plane perpendicular to the first surface F1, one or more second thermally conductive particles 33b may be in contact with 10% to 70% of the surface area of ​​one phosphor particle 31. If this configuration is adopted, for example, by having one or more second thermally conductive particles 33b in contact with 10% or more of the surface area of ​​one phosphor particle 31, heat dissipation from one phosphor particle 31 to the glass 32 or the like via one or more second thermally conductive particles 33b can be increased. This can reduce, for example, the temperature rise of the phosphor particle 31. As a result, deterioration of the phosphor particle 31 and therefore deterioration of the wavelength conversion element 30 can be reduced. Furthermore, for example, by having one or more second thermally conductive particles 33b in contact with 70% or less of the surface area of ​​one phosphor particle 31, the area of ​​the surface of one phosphor particle 31 in contact with the glass 32 is ensured, and the strength of the bond between the multiple phosphor particles 31 via the glass 32 can be ensured to a certain extent. This can improve, for example, the durability of the wavelength conversion unit 30t. Therefore, deterioration of the wavelength conversion element 30 can be reduced and the durability of the wavelength conversion element 30 can be improved.

[0041] Here, for example, one or more second thermally conductive particles 33b may be in contact with 10% to 70% of the surface area of ​​each of all of the phosphor particles 31 present in the wavelength conversion unit 30t, or one or more second thermally conductive particles 33b may be in contact with 10% to 70% of the surface area of ​​two or more of the phosphor particles 31 present in the wavelength conversion unit 30t. In other words, the number of phosphor particles 31 having one or more second thermally conductive particles 33b in contact with 10% to 70% of their surface area is not limited to one. For example, the greater the number of phosphor particles 31 having one or more second thermally conductive particles 33b in contact with 10% to 70% of their surface area, the more likely it is that deterioration of the wavelength conversion element 30 will be reduced and the durability of the wavelength conversion element 30 will be improved.

[0042] Here, for example, in a cross section of the wavelength conversion unit 30t taken along an imaginary plane perpendicular to the first surface F1, as shown in FIG. 4, each of the plurality of thermally conductive particles 33 may have an elongated rod shape having a longitudinal direction and a lateral direction. The lateral direction may be a direction perpendicular to the longitudinal direction. In this cross section, for example, the plurality of thermally conductive particles 33 may include two or more thermally conductive particles 33 that are aggregated and in contact with each other in the lateral direction. If this configuration is adopted, for example, the aggregated two or more thermally conductive particles 33 may increase the heat transfer and heat conduction of the two or more thermally conductive particles in the lateral direction, thereby increasing heat dissipation from the plurality of phosphor particles 31. For example, if the short sides of the two or more aggregated thermally conductive particles 33 are aligned along the direction from the first surface F1 to the second surface F2, the two or more aggregated thermally conductive particles 33 can increase the thermal conduction in the wavelength conversion unit 30t in the direction from the first surface F1 to the second surface F2. In other words, the two or more aggregated thermally conductive particles 33 can increase the thermal conduction in the thickness direction of the wavelength conversion unit 30t. This can improve the heat dissipation performance of the wavelength conversion unit 30t, for example. As a result, for example, the temperature rise of the multiple phosphor particles 31 when the first surface F1 of the wavelength conversion unit 30t is irradiated with excitation light L0 can be reduced. Therefore, for example, the phosphor particles 31 are less likely to deteriorate, and deterioration of the wavelength conversion element 30 can be reduced.

[0043] Here, for example, in two adjacent thermally conductive particles 33 among the two or more aggregated thermally conductive particles 33, the longitudinal direction of the second thermally conductive particle 33 may be positioned along the longitudinal direction of the first thermally conductive particle 33. Also, in two adjacent thermally conductive particles 33 among the two or more aggregated thermally conductive particles 33, the second thermally conductive particle 33 may be in contact with the entire longitudinal area of ​​the first thermally conductive particle 33, or the second thermally conductive particle 33 may be in contact with a partial longitudinal area of ​​the first thermally conductive particle 33.

[0044] Furthermore, in the first embodiment, for example, the second surface F2 of the wavelength conversion unit 30t, which is located on the opposite side of the first surface F1, is fixed to a base material 30b that functions as a heat sink. In this case, the presence of the first thermally conductive particles 33a positioned along the direction from the first surface F1 toward the base material 30b can increase heat dissipation from the wavelength conversion unit 30t through the base material 30b. This can reduce, for example, the temperature rise of the multiple phosphor particles 31 when the first surface F1 of the wavelength conversion unit 30t is irradiated with excitation light L0. As a result, for example, the phosphor particles 31 are less likely to deteriorate, and deterioration of the wavelength conversion element 30 can be reduced.

[0045] 3, for example, the plurality of thermally conductive particles 33 may include thermally conductive particles (also referred to as third thermally conductive particles) 33c located along the third surface F3 of the base material 30b. This configuration, for example, can increase heat transfer from the wavelength conversion unit 30t over a wider area of ​​the third surface F3 of the base material 30b to which the wavelength conversion unit 30t is fixed, thereby increasing heat dissipation from the wavelength conversion unit 30t. This can reduce the temperature rise of the phosphor particles 31 when the first surface F1 of the wavelength conversion unit 30t is irradiated with excitation light L0. As a result, for example, the phosphor particles 31 are less susceptible to degradation, and degradation of the wavelength conversion element 30 can be reduced.

[0046] Here, glass 32 may or may not be present between the third surface F3 and the third thermally conductive particles 33c. Here, the state in which the thermally conductive particles 33 are positioned along the third surface F3 is not limited to a state in which an imaginary plane parallel to the third surface F3 and the plate surface of the thermally conductive particles 33 completely coincide. In the cross-sectional structure of FIG. 3 , the state in which the thermally conductive particles 33 are positioned along the third surface F3 is not limited to a state in which an imaginary line parallel to the X-axis and the plate surface of the thermally conductive particles 33 completely coincide. For example, the state in which the thermally conductive particles 33 are positioned along the third surface F3 may include a state in which an imaginary plane tilted at an angle of 0 to 15 degrees relative to the third surface F3 coincides with the plate surface of the thermally conductive particles 33, or a state in which an imaginary plane tilted at an angle of 0 to 30 degrees relative to the third surface F3 coincides with the plate surface of the thermally conductive particles 33. In the cross-sectional structure of Figure 3, the state in which the thermally conductive particles 33 are positioned along the third surface F3 may include a state in which a virtual line inclined within a range of 0 to 15 degrees with respect to the X axis coincides with the plate surface of the thermally conductive particles 33, or a state in which a virtual line inclined within a range of 0 to 30 degrees with respect to the X axis coincides with the plate surface of the thermally conductive particles 33.

[0047] The wavelength converting unit 30t may have, for example, a void. The void is a portion of the wavelength converting unit 30t that is empty of any of the phosphor particles 31, the glass 32, and the thermally conductive particles 33. The void may be located, for example, between two phosphor particles 31, within the glass 32, between the phosphor particle 31 and the glass 32, between two thermally conductive particles 33, between the phosphor particle 31 and the thermally conductive particle 33, or between the glass 32 and the thermally conductive particle 33.

[0048] <1-3. Method for manufacturing wavelength conversion element> Fig. 5 is a flow chart showing a manufacturing flow of the wavelength conversion element 30 according to the first embodiment. Fig. 6 to Fig. 10 are cross-sectional views showing examples of states during the manufacturing of the wavelength conversion element 30. Hereinafter, the manufacturing method of the wavelength conversion element 30 will be described using Fig. 6 to Fig. 10 with reference to Fig. 5.

[0049] First, as shown in FIG. 6, a substrate 30b is prepared (step S1). The substrate 30b may be made of, for example, a metal material. Examples of the metal material include copper (Cu), aluminum (Al), magnesium (Mg), gold (Au), silver (Ag), iron (Fe), chromium (Cr), cobalt (Co), beryllium (Be), molybdenum (Mo), tungsten (W), and alloys. For example, if Cu, Al, Mg, Fe, Cr, Co, or Be is used as the metal material, the substrate 30b can be easily fabricated by a casting method such as die casting. For example, if Al, Mg, Ag, Fe, Cr, or Co is used as the metal material, the reflectance of visible light on the surface of the substrate 30b can be increased. The reflectance of visible light may be improved by mirror-polishing the surface of the substrate 30b by physical polishing, chemical polishing, or the like.

[0050] The base material 30b may be made of a non-metallic material such as aluminum nitride (AlN), gallium nitride (GaN), silicon carbide (SiC), silicon nitride (Si3N4), carbon (C), sapphire (Al2O3), magnesia (MgO), or garnet. The non-metallic material may be, for example, a crystalline material or an amorphous material. Examples of crystalline non-metallic materials include SiC and Si3N4. These non-metallic materials have low reflectivity for visible light. Therefore, when AlN is used, an optical reflective film may be formed on the surface. The shape and size of the base material 30b may be appropriately determined depending on the size of the wavelength conversion element 30. For example, when the base material 30b is rectangular in plan view, the thickness of the base material 30b may be set to approximately 0.1 millimeters (mm) to 5 mm, and the length and width of the base material 30b may be set to approximately 0.5 mm to 30 mm.

[0051] Next, as shown in FIG. 7, a mask 30m having an opening 30o corresponding to the planar shape of the wavelength converting portion 30t is superimposed on the third surface F3 of the base material 30b, which is the main surface on which the wavelength converting portion 30t is formed (step S2). The mask 30m may be made of aluminum, for example. In this case, the opening 30o having the desired planar shape can be formed by etching or other processes. The thickness of the mask 30m is set to be greater than the thickness of the wavelength converting portion 30t. For example, if the thickness of the wavelength converting portion 30t is 0.1 mm, the thickness of the mask 30m is set to 0.15 mm to 0.2 mm. Here, for example, the material of the mask 30m may be resin. There are no limitations on the material of the mask as long as it is possible to form the opening 30o having the desired shape and is strong enough to withstand the subsequent powder filling process.

[0052] Next, as shown in Figure 8, a powder (also called mixed powder) that is a thorough mixture of one or more types of phosphor particle powder (also called phosphor powder), glass powder (also called glass powder), and thermally conductive particle powder (also called thermally conductive powder) is filled into the opening 30o of the mask 30m to form a powder filler PW (step S3).

[0053] Here, in the mixed powder, for example, the content of phosphor powder is about 45 weight percent (wt%) to 85 wt%, the content of glass powder is about 10 wt% to 45 wt%, and the content of thermally conductive powder is about 1 wt% to 20 wt%.

[0054] The phosphor powder includes, for example, particles of a red phosphor, particles of a green phosphor, and particles of a blue phosphor.

[0055] The red phosphor may be, for example, a phosphor whose peak wavelength of fluorescence emitted in response to irradiation with excitation light L0 is in the range of approximately 620 nm to 750 nm. Examples of materials for the red phosphor include CaAlSiN3:Eu, Y2O2S:Eu, Y2O3:Eu, and SrCaClAlSiN3:Eu. 2+ Alternatively, CaAlSi(ON)3:Eu or the like is applied.

[0056] The green phosphor may be, for example, a phosphor whose peak wavelength of fluorescence emitted in response to irradiation with excitation light L0 is in the range of approximately 495 nm to 570 nm. Examples of materials for the green phosphor include β-sialon (β-SiAlON:Eu), SrSi2(O,Cl)2N2:Eu, and (Sr,Ba,Mg)2SiO4:Eu2. 2+ , ZnS:Cu,Al or Zn2SiO4:Mn, etc. are applied.

[0057] The blue phosphor used is, for example, a phosphor whose peak wavelength of fluorescence emitted in response to irradiation with excitation light L0 is in the range of about 450 nm to 495 nm. The material of the blue phosphor is, for example, (Ba,Sr)MgAl 10 O 17 :Eu, BaMgAl 10 O 17 :Eu, (Sr, Ca, Ba) 10 (PO4)6Cl2:Eu, (Sr,Ba) 10 (PO4)6Cl2:Eu or α-sialon, etc., are applied.

[0058] The phosphor powder may have a variety of particle size distributions, for example, the phosphor powder may contain phosphor particles with a 50% particle size (D50) in the range of 0.1 μm to 100 μm, or may contain phosphor particles with a D50 in the range of 10 μm to 30 μm.

[0059] The glass powder may be, for example, a powder of low-melting-point glass that is transparent after sintering. The low-melting-point glass may be oxide glass with a melting point of 200 degrees Celsius (200°C) to 700°C. The low-melting-point glass may be, for example, glass containing, as its main components, a plurality of components selected from tin oxide, zinc oxide, boron oxide, bismuth oxide, boron oxide, vanadium oxide, tellurium oxide, and phosphoric acid. The low-melting-point glass may also contain, for example, an oxide of an alkali metal. Specifically, the glass powder may be tin-phosphate-based low-melting-point glass.

[0060] The glass powder may have a variety of particle size distributions, similar to the particle size distribution of the phosphor powder. For example, the glass powder may contain glass particles with a D50 in the range of 0.1 μm to 100 μm, or may contain glass particles with a D50 in the range of 10 μm to 20 μm.

[0061] The thermally conductive powder may be, for example, a powder of hexagonal boron nitride (h-BN) particles, which have a plate-like shape.

[0062] The thermally conductive powder may have a variety of particle size distributions. For example, the thermally conductive powder may contain thermally conductive particles with a 50% particle size (D50) in the range of 1 μm to 10 μm, or may contain thermally conductive particles with a D50 in the range of 5 μm to 6 μm.

[0063] The phosphor powder, glass powder, and thermally conductive powder can be mixed by a vibration method, a rotary shaking method, etc. Furthermore, a medium may be used when mixing the phosphor powder, glass powder, and thermally conductive powder, and the medium can be used in various ways, such as a dry method in which the powders are mixed directly, or a wet method in which the powders are mixed with a solvent or binder.

[0064] Next, as shown in FIG. 9, the mask 30m is removed from the substrate 30b on which the powder filler PW has been formed (step S4), and the powder filler PW is heated to form a pre-sintered body PS (step S5). The heating temperature is set to a temperature equal to or higher than the melting point of the glass powder but lower than the temperature at which the phosphor particles lose their fluorescent function. For example, the heating temperature may be about 260°C to 600°C, or 350°C to 450°C.

[0065] The heating of the powder filler PW and the pre-sintered body PS and the pressurization process described below can be performed, for example, in a common chamber. This chamber may or may not be a vacuum container. For example, if the chamber is a vacuum container, the chamber can be evacuated during heating. For example, heating the chamber in a vacuum state reduces the generation of bubbles when the glass powder melts. The heating and pressurization of the powder filler PW and the pre-sintered body PS can be performed, for example, in the atmosphere. The heating and pressurization of the powder filler PW and the pre-sintered body PS can be performed, for example, using a multipurpose high-temperature sintering furnace or a heater block and hand press.

[0066] 10, after the heating temperature reaches the set temperature, the pre-sintered body PS is subjected to pressure processing on the substrate 30b while maintaining the set temperature (step S6). The pressure during the pressure processing can be set to a pressure that does not physically crush the phosphor particles and cause them to lose their fluorescent function. For example, the pressure during the pressure processing is set to 20 kgf / cm. 2 to 300 kgf / cm 2 The pressure is set to about 2 MPa to about 30 MPa. Here, the pre-sintered body PS is maintained in a pressurized state at a pressure that satisfies this pressure condition for a period of, for example, 1 second to 10 minutes. Then, the pre-sintered body PS is cooled while maintaining the pressure applied to the pre-sintered body PS during pressurization (step S7), and the pressure is released when the temperature of the pre-sintered body PS drops below the melting point of the glass powder. As a result, the pre-sintered body PS becomes the wavelength conversion section 30t.

[0067] Through the above steps, the wavelength conversion element 30 can be manufactured.

[0068] Here, let us assume that a reference example is adopted in which the content of phosphor powder is approximately 5 wt%, the content of glass powder is approximately 75 wt% to 94 wt%, and the content of thermally conductive powder is 1 wt% to 20 wt% in the above mixed powder.

[0069] Fig. 11 is a cross-sectional view showing a schematic image of the state of thermally conductive particles 33 in a pre-sintered body PS according to a reference example before pressure processing. Fig. 12 is a cross-sectional view showing a schematic image of the state of thermally conductive particles 33 in a pre-sintered body PS according to a reference example after pressure processing. In Figs. 11 and 12, the phosphor particles are not shown because the content of the phosphor particles in the pre-sintered body PS is low.

[0070] As shown in Figure 11, in the pre-pressurized sintered body PS, the plate-shaped thermally conductive particles 33 are positioned in random directions. During pressurization, the heating temperature of the pre-sintered body PS is equal to or higher than the melting point of the glass powder, causing the glass to melt and become fluid. When pressurization is performed on the pre-sintered body PS in this state, applying a pressing force in the -Z direction, as shown in Figure 12, each of the plate-shaped thermally conductive particles 33 is positioned in a direction perpendicular to the direction of the pressing force. This allows each of the plate-shaped thermally conductive particles 33 to be arranged in a direction perpendicular to the thickness direction of the pre-sintered body PS.

[0071] Fig. 13 is a cross-sectional view schematically showing an image of the state of the thermally conductive particles 33 in the pre-sintered body PS according to the first embodiment before pressure processing. Fig. 14 is a cross-sectional view schematically showing an image of the state of the thermally conductive particles 33 in the pre-sintered body PS according to the first embodiment after pressure processing. In Figs. 13 and 14, since the pre-sintered body PS has a high content of the plurality of phosphor particles 31, each of the plurality of phosphor particles 31 is shown as a regular pentagon hatched with diagonal lines slanting upward to the left.

[0072] As shown in FIG. 13 , in the pre-pressurized sintered body PS, the plate-like thermally conductive particles 33 are positioned in random directions. During pressurization, the heating temperature of the pre-pressurized body PS is equal to or higher than the melting point of the glass powder, causing the glass to melt and become fluid. In this state, the pre-pressurized body PS is subjected to pressurization applying a pressure in the -Z direction. In this case, as shown in FIG. 14 , even after the pre-pressurized body PS is subjected to pressurization applying a pressure in the -Z direction, the presence of the phosphor particles 31 allows the plate-like thermally conductive particles 33 to maintain their random orientation. This allows the thermally conductive particles 33 to include, for example, first thermally conductive particles 33a arranged in a direction parallel to the thickness direction of the pre-sintered body PS. As a result, in the wavelength conversion section 30t, the first thermally conductive particles 33a have a plate surface along a direction perpendicular to the first surface F1, and therefore, the thermal conduction in the thickness direction from the first surface F1 to the second surface F2 in the wavelength conversion section 30t can be increased.

[0073] 14, the thermally conductive particles 33 may include one or more second thermally conductive particles 33b in contact with the surfaces of the phosphor particles 31 in the pre-sintered body PS after the pressure processing. For example, if the content of the phosphor particles 31 in the pre-sintered body PS is relatively high when the pre-sintered body PS is subjected to pressure processing, the number of locations where the spacing between the phosphor particles 31 is narrow may increase. This may increase the number of one or more second thermally conductive particles 33b in contact with the surfaces of the phosphor particles 31 in the pre-sintered body PS after the pressure processing. Here, for example, if the content of the thermally conductive particles 33 in the pre-sintered body PS is relatively high when the pre-sintered body PS is subjected to pressure processing, the number of one or more second thermally conductive particles 33b in contact with the surfaces of the phosphor particles 31 in the pre-sintered body PS after the pressure processing may increase.

[0074] Here, for example, in the cross section of the pre-sintered body PS after the pressure processing, the longitudinal direction of each of one or more second thermally conductive particles 33b may be in a direction along the surface of one phosphor particle 31 with which the one or more second thermally conductive particles 33b are in contact, as shown in Fig. 4. For example, when the pre-sintered body PS is subjected to pressure processing, if the content of multiple phosphor particles 31 in the pre-sintered body PS is relatively high, the number of locations where the spacing between the multiple phosphor particles 31 is narrow may increase. This may result in, for example, an increase in the number of one or more second thermally conductive particles 33b in contact with one phosphor particle 31 and having their longitudinal direction along the surface of the single phosphor particle 31 in the cross section of the pre-sintered body PS after the pressure processing. Here, for example, when the pre-sintered body PS is subjected to pressure processing, if the content of multiple thermally conductive particles 33 in the pre-sintered body PS is relatively high, the number of one or more second thermally conductive particles 33b that are in contact with one phosphor particle 31 and have a longitudinal direction along the surface of the one phosphor particle 31 can increase in the cross section of the pre-sintered body PS after pressure processing.

[0075] 4, for example, one or more second thermally conductive particles 33b may be in contact with 10% to 70% of the surface area of ​​one phosphor particle 31 in the cross section of the pre-sintered body PS after the pressure processing. For example, if the content of multiple thermally conductive particles 33 in the pre-sintered body PS is relatively high when the pre-sintered body PS is subjected to pressure processing, the number of phosphor particles 31 in which one or more second thermally conductive particles 33b are in contact with 10% to 70% of the surface area in the cross section of the pre-sintered body PS after the pressure processing can increase.

[0076] 4, the cross section of the pre-sintered body PS after the pressure processing may include two or more thermally conductive particles 33 that are aggregated and in contact with each other in the direction along the short side of the thermally conductive particles 33. For example, if the content of the thermally conductive particles 33 in the pre-sintered body PS is relatively high when the pre-sintered body PS is subjected to pressure processing, the number of two or more thermally conductive particles 33 that are aggregated and in contact with each other in the direction along the short side of the thermally conductive particles 33 may increase in the cross section of the pre-sintered body PS after the pressure processing.

[0077] Furthermore, for example, as shown in Fig. 13, the thermally conductive particles 33 that were located between the phosphor particles 31 and the third surface F3 of the base material 30b near the base material 30b in the pre-pressure-processed temporary sintered body PS may become third thermally conductive particles 33c located along the third surface F3 by the pressurization, as shown in Fig. 14. As a result, for example, heat transfer from the wavelength converting unit 30t may increase in a wider area of ​​the third surface F3 of the base material 30b to which the wavelength converting unit 30t is fixed, and therefore heat dissipation from the wavelength converting unit 30t may increase.

[0078] In the above manufacturing method, when the base material 30b is made of a material that easily forms an oxide film, such as aluminum, the base material 30b and the wavelength converting portion 30t are bonded by an oxidation bond. In other words, the base material 30b and the wavelength converting portion 30t are bonded by an oxidation bond in which oxygen in the oxide film formed on the surface of the base material 30b by heating bonds with oxygen in the oxide glass.

[0079] Furthermore, in the above manufacturing method, when the substrate 30b is made of a material that is difficult to oxidize and bond, the surface of the substrate 30b may be provided with minute irregularities, for example, several micrometers in size, and the glass may be entangled therein to enhance the bonding strength between the substrate 30b and the wavelength converting section 30t through an anchoring effect. In other words, the surface of the substrate 30b may have an irregular shape (minute irregularities). For example, the size of the minute irregularities referred to here may be such that the low-melting-point glass that is liquefied upon heating flows and penetrates the minute irregularities. In this case, the size of the minute irregularities may be set to, for example, 0.1 μm to 50 μm. Furthermore, the size of the minute irregularities may be set to a size that allows phosphor particles to penetrate the minute irregularities. In this case, the size of the minute irregularities may be set to, for example, 5 μm to 50 μm. The size of the minute irregularities (irregularities of the irregular shape) of the substrate 30b here refers to, for example, the dimension between the bottom (lowest point) of the concave portion of the minute irregularities and the top (highest point) of the convex portion in the thickness direction of the substrate 30b.

[0080] Furthermore, when a material that cannot be expected to form an oxidative bond or an anchor effect is used for the material of the base material 30b, the wavelength converting portion 30t and the base material 30b may be prepared separately. Here, for example, instead of forming the wavelength converting portion 30t on the base material 30b, a powder filler PW may be formed separately from the base material 30b, the powder filler PW may be heated to form a pre-sintered body PS, and the pre-sintered body PS may be subjected to a pressure process to obtain the wavelength converting portion 30t. In this case, a metal multilayer film may be formed on the surface of the wavelength converting portion 30t facing the base material 30b, and the wavelength converting portion 30t and the base material 30b may be joined by soldering.

[0081] An example of the multilayer film is a multilayer film (also referred to as a Ti / Pt / Au multilayer film) in which thin films of titanium (Ti), platinum (Pt), and gold (Au) are stacked in this order from the wavelength converting section 30t side. This multilayer film can be formed to a thickness of several to several hundred nanometers by, for example, sputtering or vapor deposition. Here, Ti has good bonding properties with oxide glass. Au is a material with good wettability with solder material. The Pt film functions as a barrier film that reduces peeling of the Ti film from the wavelength converting section 30t by the molten solder material when the solder material melts. The multilayer film may be, for example, a multilayer film (also referred to as a Cr / Pt / Au multilayer film) in which thin films of chromium (Cr), Pt, and Au are stacked in this order from the wavelength converting section 30t side, or a multilayer film (also referred to as a Cr / Ni / Au multilayer film) in which thin films of Cr, nickel (Ni), and Au are stacked in this order from the wavelength converting section 30t side. Here, for example, the thickness of the Ti thin film may be about 0.1 μm, the thickness of the Pt thin film may be about 0.2 μm, and the thickness of the Au thin film may be about 0.2 μm.

[0082] As the solder material, for example, tin (Sn)-phosphorus (P)-copper (Cu) solder or Au-Sn solder can be used.

[0083] <1-4. Other Configurations of Wavelength Conversion Element> 3, the wavelength conversion element 30 may employ a configuration (also referred to as configuration A) in which, for example, the first thermally conductive particle 33a has a length along the direction perpendicular to the first surface F1 that is longer than the distance along the first surface F1 between two phosphor particles 31 aligned in the direction along the first surface F1. In other words, in the wavelength conversion section 30t, for example, the length along the direction perpendicular to the first surface F1 of the first thermally conductive particle 33a may be longer than the distance along the first surface F1 between two phosphor particles 31 that sandwich the first thermally conductive particle 33a. Here, the distance along the first surface F1 between two phosphor particles 31 aligned in the direction along the first surface F1 may be the distance between portions of the two phosphor particles 31 that face each other with the first thermally conductive particle 33a sandwiched between them. The length of the first thermally conductive particle 33a along the direction perpendicular to the first face F1 includes the length of the first thermally conductive particle 33a in the longitudinal direction along the plate surface.

[0084] 3, the length Le1 in the ±Z direction of the first thermally conductive particle 33a sandwiched between the first phosphor particle P1 and the second phosphor particle P2 is longer than the distance D1 in the ±X direction between the first phosphor particle P1 and the second phosphor particle P2. For example, when the distance D1 is approximately 0.5 μm to 5 μm, the length Le1 may be approximately 1 μm to 10 μm, or may be approximately 5 μm to 6 μm.

[0085] For example, when pressurizing the pre-sintered body PS as in the above-described manufacturing method, if the content of the phosphor particles 31 in the pre-sintered body PS is relatively high, the spacing between the phosphor particles 31 may become narrow. This allows the formation of the above-described structure A. Therefore, for example, if the above-described structure A is employed, when manufacturing a wavelength conversion element 30 having the structure A, the content of the phosphor particles 31 in the pre-sintered body PS may be relatively high, and the spacing between the phosphor particles 31 may become narrow. This allows, for example, an increase in the number of thermally conductive particles 33 that maintain their orientation along the pressing direction of the pre-sintered body PS between the phosphor particles 31 during pressurization of the pre-sintered body PS. In other words, the above-described structure A can be said to be a structure suitable for, for example, providing first thermally conductive particles 33a positioned along a direction perpendicular to the first surface F1 in order to improve the heat dissipation performance of the wavelength conversion unit 30t.

[0086] 3, the wavelength conversion element 30 may employ a configuration (also referred to as configuration B) in which a plurality of thermally conductive particles 33 are arranged along the surfaces of a plurality of phosphor particles 31. If configuration B is employed, for example, the number of first thermally conductive particles 33a positioned along the direction perpendicular to the first surface F1 in the wavelength conversion section 30t may increase. This may improve the heat dissipation performance of the wavelength conversion section 30t, for example.

[0087] For example, when pressurizing the pre-sintered body PS as in the above-described manufacturing method, if the content of the phosphor particles 31 in the pre-sintered body PS is relatively high, the number of locations where the spacing between the phosphor particles 31 is narrow may increase. This may result in, for example, capillary action causing molten glass to flow between the phosphor particles 31. As a result, the above-described configuration B may be formed. Therefore, for example, if the above-described configuration B is employed, when manufacturing a wavelength conversion element 30 having the configuration B, the content of the phosphor particles 31 in the pre-sintered body PS may be relatively high, and the number of locations where the spacing between the phosphor particles 31 is narrow may increase. This may result in, for example, an increase in the number of first thermally conductive particles 33a aligned along the surfaces of the phosphor particles 31 due to capillary action causing molten glass to flow between the phosphor particles 31 during pressurization of the pre-sintered body PS. As a result, for example, in the wavelength conversion unit 30t, the number of first thermally conductive particles 33a positioned along the direction perpendicular to the first surface F1 may increase between the phosphor particles 31. In other words, the above configuration B can be said to be a configuration suitable for having a large number of first thermally conductive particles 33a positioned along a direction perpendicular to the first surface F1, for example, in order to improve the heat dissipation performance of the wavelength conversion section 30t.

[0088] Here, the wavelength conversion element 30 may employ a configuration (also referred to as configuration C) in which the plurality of phosphor particles 31 includes polyhedral phosphor particles 31, as shown in FIG. 3. In the example of the central portion on the left side of the wavelength conversion section 30t in FIG. 3, the third phosphor particle P3 and the fourth phosphor particle P4 both have a polyhedral structure. A narrow gap exists between the third phosphor particle P3 and the fourth phosphor particle P4. Therefore, for example, when the pre-sintered body PS is subjected to pressure processing as described above, a plurality of thermally conductive particles 33 may be arranged in a continuous form in the narrow gap between the third phosphor particle P3 and the fourth phosphor particle P4.

[0089] Therefore, for example, if the above-mentioned configuration C is adopted, the number of elongated gaps formed between the thermally conductive particles 33 may increase when the pre-sintered body PS is subjected to pressure processing, and the number of the thermally conductive particles 33 aligned along the direction perpendicular to the first surface F1 may increase. This may improve the heat dissipation performance of the wavelength conversion unit 30t, for example. For example, if β-sialon (β-SiAlON:Eu) is used as the green phosphor, the shape of the phosphor particles 31 of the green phosphor may be a polyhedron such as a hexahedron.

[0090] <1-5. Summary of the First Embodiment> In the wavelength conversion element 30 according to the first embodiment, for example, in the wavelength conversion section 30t, the plurality of thermally conductive particles 33 include a first thermally conductive particle 33a located between two of the plurality of phosphor particles 31 aligned in a direction along the first surface F1 and perpendicular to the first surface F1. This allows, for example, the first thermally conductive particle 33a to increase thermal conduction in the wavelength conversion section 30t in a direction perpendicular to the first surface F1. In other words, for example, the first thermally conductive particle 33a can increase thermal conduction in the thickness direction of the wavelength conversion section 30t. This can improve, for example, the heat dissipation performance of the wavelength conversion section 30t. As a result, for example, the temperature rise of the plurality of phosphor particles 31 when the first surface F1 of the wavelength conversion section 30t is irradiated with excitation light L0 can be reduced. Therefore, for example, deterioration of the wavelength conversion element 30 can be reduced.

[0091] Furthermore, for example, by reducing deterioration in the wavelength conversion element 30, deterioration in the lighting system 1 including this wavelength conversion element 30 can be reduced.

[0092] <2. Other embodiments> The present disclosure is not limited to the first embodiment described above, and various modifications and improvements are possible without departing from the gist of the present disclosure.

[0093] <2-1. Second embodiment> In the first embodiment, for example, the base material 30b may be a base material having various structures on which the wavelength converting portion 30t is arranged.

[0094] Fig. 15 is a perspective view showing an example of the configuration of the wavelength conversion element 30 according to the second embodiment. Fig. 16 is a cross-sectional view showing an example of the configuration of the wavelength conversion element 30 according to the second embodiment.

[0095] 15 and 16, the wavelength conversion element 30 may be modified to a wavelength conversion element 30A in which a wavelength conversion portion 30t is located in a recess 30r of a substrate 30bA. The recess 30r has a third surface F3 as a bottom surface and a fourth surface F4 as a side surface. The second surface F2 of the wavelength conversion portion 30t is fixed to the third surface F3 of the recess 30r. The side surface of the wavelength conversion portion 30t contacts the fourth surface F4 of the recess 30r.

[0096] With this configuration, excitation light L0 that is scattered inside the wavelength conversion unit 30t and is not converted into fluorescence L1 is reflected by the fourth surface F4, which serves as the side surface of the recess 30r of the base material 30bA, and returns to the inside of the wavelength conversion unit 30t, where it can be converted into fluorescence L1. Furthermore, because the side surface of the wavelength conversion unit 30t is in contact with the fourth surface F4 of the recess 30r, heat generated in the wavelength conversion unit 30t is dissipated from the fourth surface F4 to the outside via the base material 30b, and the temperature rise in the wavelength conversion unit 30t can be reduced.

[0097] 17 is a flowchart showing a manufacturing flow of the wavelength conversion element 30A according to the second embodiment. Hereinafter, the manufacturing method of the wavelength conversion element 30A will be described with reference to FIG.

[0098] First, a substrate 30bA as shown in FIGS. 18 and 19 is prepared (step S11). FIG. 18 is a perspective view showing an example of the configuration of the substrate 30bA according to the second embodiment. FIG. 19 is a cross-sectional view showing an example of the configuration of the substrate 30bA according to the second embodiment. The substrate 30bA has an overall disk-like shape and has a recess 30r on a first plate surface. For example, the depth of the recess 30r of the substrate 30bA is set to 0.01 mm to 1 mm, and the thickness of the substrate 30bA below the bottom surface of the recess 30r is set to 0.05 mm to 10 mm. The depth of the recess 30r is set to be greater than the thickness of the wavelength converting section 30t. For example, if the thickness of the wavelength converting section 30t is 0.1 mm, the depth of the recess 30r is set to 0.15 mm to 0.2 mm. Furthermore, for example, the diameter of the substrate 30bA is set to 0.5 mm to 30 mm, and the diameter of the recess 30r is set to 0.1 mm to 10 mm.

[0099] The material of the substrate 30bA is a material with a thermal expansion coefficient close to that of the wavelength converting unit 30t. For example, a metal or inorganic material with a thermal expansion coefficient within ±50% of the thermal expansion coefficient of the low-melting-point glass that is the material of the glass 32 of the wavelength converting unit 30t may be used. For example, when a metal material is used for the substrate 30bA, aluminum or an aluminum alloy may be used as the metal material. For example, when a material with high light reflectivity, such as aluminum, is used for the substrate 30bA, the surface of the substrate 30bA may be polished to a mirror finish by physical polishing or chemical polishing to improve the visible light reflectance of the surface of the substrate 30bA. Furthermore, when a metal material is used for the substrate 30bA, the substrate 30bA may be formed by, for example, cutting using a machining process or molding using a die-casting method.

[0100] Alternatively, ceramics may be used as the material for the substrate 30bA. In this case, the substrate 30bA may be formed using laminated ceramics, or by powder pressure molding. For example, a ring-shaped green sheet with a through-hole (corresponding to the recess 30r) and a disk-shaped green sheet without a through-hole are stacked and sintered to form the substrate 30bA from laminated ceramics. Alternatively, the substrate 30bA may be formed by powder pressure molding, for example, by filling a first mold with ceramic powder having a cylindrical opening, applying pressure to the ceramic powder filled in the first mold using a second mold for forming a recess (corresponding to the recess 30r). For example, the substrate 30bA may be formed by mixing ceramic powder with wax, a binder, or the like, and applying pressure to form a molded body with a recess (corresponding to the recess 30r), and then sintering the molded body. Examples of ceramics that can be used as the material for the substrate 30bA include alumina, aluminum nitride, silicon nitride, mullite, and zirconia.

[0101] Alternatively, the base material 30bA may be formed of ceramic and metal. For example, the base material 30bA may be formed by bonding a ring-shaped member (metal member) made of metal such as aluminum or an aluminum alloy to a disc-shaped ceramic substrate using a bonding material. In this case, the through-hole of the ring-shaped member forms the recess 30r. Examples of the bonding material include brazing material primarily composed of silver (Ag) and copper (Cu). Alternatively, the bonding material may be brazing material primarily composed of aluminum (Al), solder primarily composed of tin (Sn), silver (Ag), and copper (Cu), or a resin bonding material such as epoxy, silicone, or acrylic. The thermal conductivity of the base material 30bA may be enhanced by adding a highly thermally conductive filler such as silver (Ag), aluminum nitride (AlN), or boron nitride (BN) to the resin bonding material.

[0102] The base material 30bA may be formed by bonding a ceramic substrate and a ceramic ring-shaped member with a bonding material, instead of forming the base material 30bA from laminated ceramics by co-firing. In this case, the bonding material described above can also be used.

[0103] 17, next, a powder (mixed powder) obtained by thoroughly mixing one or more types of phosphor particle powder (phosphor powder), glass powder, and thermally conductive particle powder (thermally conductive powder) is filled into the recess 30r to form a powder filler (step S12). Here, the contents of the phosphor powder, glass powder, and thermally conductive powder in the mixed powder, as well as the materials, compositions, and mixing methods of the phosphor particles, glass powder, and thermally conductive particles, will be omitted because they overlap with those in the first embodiment.

[0104] Next, the powder filler is heated together with the base material 30bA in which the powder filler is filled in the recesses 30r to form a pre-sintered body (step S13).

[0105] Next, after the heating temperature reaches the set temperature, the pre-sintered body is subjected to pressure processing on the base material 30bA while the set temperature is maintained (step S14).

[0106] The explanation of the heating and pressurizing of the powder packing body overlaps with the explanation in the first embodiment, and therefore will be omitted.

[0107] Next, the pre-sintered body is cooled while maintaining the pressure applied during pressurization (step S15), and the pressure is released when the temperature of the pre-sintered body becomes lower than the melting point of the glass powder. As a result, the pre-sintered body becomes the wavelength converting portion 30t.

[0108] The wavelength conversion element 30A can be manufactured by the above steps. In addition, for example, since the powder filler is formed in the recess 30r of the base material 30bA, step S2 of superposing a mask on the base material and step S4 of removing the mask are not required in the manufacturing method of the wavelength conversion element 30 according to the first embodiment described using the manufacturing flow of Fig. 5, and therefore the manufacturing process can be simplified.

[0109] FIG. 20 is a conceptual diagram illustrating an example of the cross-sectional configuration of the portion XX surrounded by the two-dot chain line in FIG. 16. Here, in the wavelength conversion element 30A, for example, the plurality of thermally conductive particles 33 may include thermally conductive particles (also referred to as fourth thermally conductive particles) 33d located along the fourth surface F4 of the base material 30bA. If this configuration is adopted, for example, heat transfer from the wavelength conversion unit 30t can be increased not only on the third surface F3 of the base material 30bA to which the wavelength conversion unit 30t is fixed but also over a wider area of ​​the fourth surface F4, thereby increasing heat dissipation from the wavelength conversion unit 30t. This can further reduce the temperature rise of the phosphor particles 31 when the first surface F1 of the wavelength conversion unit 30t is irradiated with excitation light L0. As a result, for example, deterioration of the wavelength conversion element 30 can be further reduced.

[0110] Here, glass 32 may or may not be present between the fourth surface F4 and the fourth thermally conductive particle 33d. Here, the state in which the thermally conductive particles 33 are positioned along the fourth surface F4 is not limited to a state in which an imaginary plane parallel to the fourth surface F4 and the plate surface of the thermally conductive particle 33 are completely aligned. In the cross-sectional structure of FIG. 20 , the state in which the thermally conductive particles 33 are positioned along the fourth surface F4 is not limited to a state in which an imaginary line parallel to the Z axis and the plate surface of the thermally conductive particle 33 are completely aligned. For example, the state in which the thermally conductive particles 33 are positioned along the fourth surface F4 may include a state in which an imaginary plane tilted at an angle of 0 to 15 degrees relative to the fourth surface F4 is aligned with the plate surface of the thermally conductive particle 33, or a state in which an imaginary plane tilted at an angle of 0 to 30 degrees relative to the fourth surface F4 is aligned with the plate surface of the thermally conductive particle 33. In the cross-sectional structure of Figure 20, the state in which the thermally conductive particles 33 are positioned along the fourth surface F4 may include a state in which a virtual line inclined within a range of 0 to 15 degrees relative to the Z axis coincides with the plate surface of the thermally conductive particles 33, or a state in which a virtual line inclined within a range of 0 to 30 degrees relative to the Z axis coincides with the plate surface of the thermally conductive particles 33.

[0111] Here, the wavelength conversion element 30A shown in Figure 15 has a configuration in which a recess 30r having a circular planar shape is provided on the upper surface of a disk-shaped substrate 30bA, but the substrate 30bA is not limited to a disk shape, and the planar shape of the recess 30r is not limited to a circle.

[0112] Here, the shape of the internal space of the recess 30r of the substrate 30bA is not limited to a plate or columnar shape. The shape of the internal space of the recess 30r of the substrate 30bA may be, for example, a cone or pyramid shape, as shown in FIG. 21, or a hemispherical or semi-ellipsoidal shape, as shown in FIG. 22. FIG. 21 is a cross-sectional view showing the configuration of a substrate 30bA according to another first example. FIG. 22 is a cross-sectional view showing the configuration of a substrate 30bA according to another second example. In these cases, the substrate 30bA may not have a fourth surface F4 as a side surface of the recess 30r, as long as it has a third surface F3 as the bottom surface of the recess 30r.

[0113] When the base material 30bA shown in Fig. 21 is used, for example, the first surface F1 of the wavelength converting portion 30t may be a flat surface along the XY plane as shown in Fig. 23, or the first surface F1 of the wavelength converting portion 30t may be a surface parallel to the third surface F3 as shown in Fig. 24. In other words, the first surface F1 of the wavelength converting portion 30t may be a surface recessed in a cone-like or pyramidal shape along the third surface F3 as shown in Fig. 24. From another perspective, the wavelength converting portion 30t may have a cone-like or pyramidal shape corresponding to the shape of the recess 30r as shown in Fig. 23, or may have a plate-like shape curved along the third surface F3 as shown in Fig. 24.

[0114] When the base material 30bA shown in Fig. 22 is used, for example, the first surface F1 of the wavelength converting section 30t may be a flat surface along the XY plane as shown in Fig. 25, or may be a surface parallel to the third surface F3 as shown in Fig. 26. In other words, the first surface F1 of the wavelength converting section 30t may be a surface recessed into a hemispherical or semi-ellipsoidal shape along the third surface F3 as shown in Fig. 26. From another perspective, the wavelength converting section 30t may have a hemispherical or semi-ellipsoidal shape corresponding to the shape of the recess 30r as shown in Fig. 25, or may have a plate-like shape curved along the third surface F3 as shown in Fig. 26.

[0115] The wavelength converting section 30t having a recessed first surface F1 shown in Figures 24 and 26 can be realized, for example, by pressing a pre-sintered body with a pressing body having a convex portion corresponding to the shape of the third surface F3 during pressure processing.

[0116] <3.Other> In each of the above embodiments, for example, each of the one or more types of phosphor particles corresponding to the multiple phosphor particles 31 may be a single type of phosphor particle that emits fluorescence having one wavelength spectrum in response to irradiation with excitation light L0.

[0117] Furthermore, for example, the multiple types of phosphor particles included in the multiple phosphor particles 31 may include at least a first type of phosphor particles that emit a first fluorescence having a first wavelength spectrum in response to irradiation with excitation light L0, and a second type of phosphor particles that emit a second fluorescence having a second wavelength spectrum different from the first wavelength spectrum in response to irradiation with excitation light L0. The first type of phosphor particles and the second type of phosphor particles may be, for example, two types of phosphors selected from a red phosphor, a green phosphor, and a blue phosphor.

[0118] Furthermore, for example, the multiple types of phosphor particles included in the multiple phosphor particles 31 may include a third type of phosphor particles that emit a third fluorescence having a third wavelength spectrum different from both the first wavelength spectrum and the second wavelength spectrum in response to irradiation with excitation light L0. The first type of phosphor particles, the second type of phosphor particles, or the three types of phosphor particles may be phosphor particles that emit fluorescence of various colors in response to irradiation with excitation light L0, such as blue-green phosphor particles or yellow phosphor particles.

[0119] The blue-green phosphor is a phosphor that emits blue-green fluorescence in response to irradiation with excitation light L0. The yellow phosphor is a phosphor that emits yellow fluorescence in response to irradiation with excitation light L0. For example, the blue-green phosphor is a phosphor that emits fluorescence in response to irradiation with excitation light L0 with a peak wavelength in the range of about 495 nm. The material of the blue-green phosphor is, for example, (Sr,Ba,Ca)5(PO4)3Cl:Eu or Sr4Al. 14 O 25 For example, the yellow phosphor may be a phosphor whose peak wavelength of fluorescence emitted in response to irradiation with excitation light L0 is in the range of approximately 570 nm to 590 nm. For example, the yellow phosphor may be a material such as SrSi2(O,Cl)2N2:Eu. Here, the ratio of the elements in parentheses can be set arbitrarily as long as it is within the range of the molecular formula.

[0120] Furthermore, for example, the multiple types of phosphor particles contained in the plurality of phosphor particles 31 may include four or more types of phosphor particles.

[0121] In each of the above embodiments, for example, the light source unit 2 and the conversion unit 3 may be positioned close to each other. In this case, the excitation light L0 emitted from the light source unit 2 may be directly irradiated onto the wavelength conversion elements 30, 30A of the conversion unit 3, or may be irradiated via an optical element such as a collimator lens.

[0122] In each of the above embodiments, for example, the wavelength conversion element 30 may have a wavelength conversion portion 30t without having a base material 30b. In this case, the glass 32 included in the wavelength conversion portion 30t is located, for example, at least between a plurality of phosphor particles 31. Here, for example, a powder filler PW is formed using a mold or the like separately from the base material 30b, and the powder filler PW is heated to form a pre-sintered body PS, and the pre-sintered body PS is subjected to pressure processing, thereby obtaining the wavelength conversion portion 30t as a wavelength conversion element.

[0123] It goes without saying that all or part of the components constituting each of the above-described embodiments and examples can be combined as appropriate within the scope of not causing any contradiction. [Explanation of symbols]

[0124] 1. Lighting system 2 Light source section 3. Conversion section 30,30A Wavelength conversion element 30b,30bA base material 30t Wavelength conversion unit 31 Phosphor particles 32 Glass 33 Thermally conductive particles 33a First thermally conductive particles 33b Second thermally conductive particles 33c Third thermal conductive particles 4. Lighting section D1 Distance F1 front page F2 2nd side F3 3rd page F4 4th side L0 excitation light L1 fluorescence L2 illumination light Le1 length P1 First phosphor particles P2 Second phosphor particles P3 Third phosphor particle P4 Fourth phosphor particle

Claims

1. a wavelength converting unit having a first surface onto which the excitation light is irradiated, The wavelength converting portion is a plurality of phosphor particles; glass bonding the plurality of phosphor particles together; a plurality of thermally conductive particles each including hexagonal boron nitride, each located in one or more of the following locations: within the glass; at a boundary between the plurality of phosphor particles and the glass; and between two phosphor particles in the plurality of phosphor particles; the plurality of thermally conductive particles include, between two phosphor particles of the plurality of phosphor particles aligned in a direction along the first surface, a first thermally conductive particle positioned along a direction inclined within a range of 0 to 15 degrees with respect to an axis perpendicular to the first surface, and one or more thermally conductive particles positioned along a direction inclined within a range of 0 to 15 degrees with respect to the first surface; a wavelength conversion element in which, in a cross section of the wavelength conversion unit along an imaginary plane perpendicular to the first surface, the first thermally conductive particle and the one or more thermally conductive particles each have an elongated rod-like shape having a longitudinal direction and a lateral direction perpendicular to the longitudinal direction, and are located along a surface of one of the plurality of phosphor particles, and the longitudinal direction of the first thermally conductive particle and the one or more thermally conductive particles is a direction along the surface of the one phosphor particle.

2. The wavelength conversion element according to claim 1, A wavelength conversion element, wherein the first thermally conductive particle has a length along a direction perpendicular to the first surface that is longer than a distance between the two phosphor particles in the direction along the first surface.

3. 3. The wavelength conversion element according to claim 1, The plurality of thermally conductive particles are arranged along the surfaces of the plurality of phosphor particles.

4. 3. The wavelength conversion element according to claim 1, A wavelength conversion element, wherein the plurality of thermally conductive particles include one or more second thermally conductive particles in contact with a surface of one of the plurality of phosphor particles.

5. The wavelength conversion element according to claim 4, A wavelength conversion element, wherein in a cross section of the wavelength conversion portion along an imaginary plane perpendicular to the first surface, the one or more second thermally conductive particles are in contact with an area of ​​10% to 70% of the surface of one of the phosphor particles.

6. 3. The wavelength conversion element according to claim 1, A wavelength conversion element, wherein in a cross section of the wavelength conversion portion along an imaginary plane perpendicular to the first surface, each of the plurality of thermally conductive particles has an elongated rod-like shape having a longitudinal direction and a lateral direction perpendicular to the longitudinal direction, and the plurality of thermally conductive particles include two or more thermally conductive particles that are aggregated in a state of contact with each other in a direction along the lateral direction.

7. 3. The wavelength conversion element according to claim 1, A wavelength conversion element, wherein the content of the plurality of phosphor particles in the wavelength conversion portion is 45 weight percent to 85 weight percent.

8. 3. The wavelength conversion element according to claim 1, a substrate; the wavelength converting portion has a second surface located on the opposite side to the first surface, The substrate has a third surface to which the second surface is fixed.

9. 3. A method for manufacturing a wavelength conversion element according to claim 1 or 2, comprising: a step of forming a molded body by molding a powder mixture of one or more types of phosphor particle powder, glass powder, and thermally conductive particle powder containing hexagonal boron nitride; and a step of firing the molded body, In the step of firing the molded body, a pressing force is applied to the molded body in one direction.

10. The wavelength conversion element according to claim 1 or 2; a light source unit that emits the excitation light; an illumination unit that emits fluorescence emitted from the wavelength conversion element in response to irradiation with the excitation light emitted from the light source unit toward an illumination space.

Images