Light-emitting device

Abstract

To provide a light-emitting device in which temperature extinction of a phosphor is suppressed.SOLUTION: The light-emitting device has a light-emitting element and a wavelength conversion part. The wavelength conversion part has a base body made of single crystals and a wavelength conversion member including single crystals. The wavelength conversion member has a first part, a second part, and a third part including the phosphor. The first part and the second part form a film, and the film and the third part form a pair of layers.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure relates to a light-emitting device.

Background Art

[0002] Conventionally, there have been disclosed, for example, in Patent Document 1 and Patent Document 2, light-emitting devices capable of irradiating excitation light emitted from a light-emitting diode or a semiconductor laser element onto a phosphor containing particles made of a phosphor material and outputting visible light.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the output of the excitation light is increased, the amount of heat generated by the phosphor material due to the Stokes shift (energy loss caused by converting light with a short wavelength and high energy per photon into light with a long wavelength and low energy per photon) increases accordingly. When heat accumulates inside the phosphor material and the temperature of the phosphor material rises, a phenomenon called temperature quenching occurs in which the efficiency of wavelength-converting the excitation light decreases. This phenomenon is particularly prominent in a phosphor material in which a large number of phosphor crystal particles are integrated by a transparent resin binder, because the heat conduction between the phosphor crystal particles is hindered by the resin binder having a lower thermal conductivity than the phosphor crystal particles existing between the phosphor crystal particles.

[0005] In addition, when the phosphor material is an aggregate of a large number of phosphor crystal particles, the presence of voids between the particles and grain boundaries hinders heat conduction. Further, when the phosphor material is bonded to a translucent substrate, if the translucent substrate is an aggregate of a large number of particles, the presence of voids between the particles and grain boundaries hinders heat conduction when the heat generated in the phosphor material is transmitted to the substrate and conducted through its interior.

[0006] An object of the present disclosure is to provide a light-emitting device that suppresses temperature quenching of a phosphor.

Means for Solving the Problems

[0007] The light-emitting device according to an embodiment of the present disclosure includes a light-emitting element and a wavelength conversion component. The wavelength conversion component includes a substrate made of a single crystal and a wavelength conversion member containing a single crystal. The wavelength conversion member has a first portion and a second portion containing a phosphor, and the first portion and the second portion form a film.

Effects of the Invention

[0008] It is possible to provide a light-emitting device that improves the heat dissipation performance by heat conduction through the substrate in contact with the phosphor for the heat generated from the phosphor, and suppresses temperature quenching of the phosphor.

Brief Description of the Drawings

[0009]

Figure 1

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Figure 13

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the invention will be described with reference to the drawings as appropriate. However, the embodiments described below are for embodying the technical idea of the present disclosure, and unless otherwise specified, the present disclosure is not limited to the following. In addition, the content described in one embodiment is also applicable to other embodiments. The sizes and positional relationships of the members shown in each drawing may be exaggerated for ease of explanation.

[0011] (First Embodiment) As shown in FIG. 1, the light-emitting device 100 in the first embodiment of the present disclosure includes a light-emitting element 10, a power supply 80 for driving the light-emitting element, a plate-shaped wavelength conversion component 20 including a phosphor on a support base 40, a light-shielding member 50, an optical element 60, a heat sink 70, and a housing 90. The light rays are represented by dashed lines. The light-emitting device 100 emits light in which the light emitted from the light-emitting element and reflected by the wavelength conversion component and the light emitted from the wavelength conversion component 20 having a wavelength different from that of the light emitted from the light-emitting element are mixed.

[0012] (Light-emitting element) The light-emitting element 10 is, for example, an edge-emitting AlInGaN-based laser diode having electrodes on the bottom and top surfaces, and can emit blue laser light (wavelength 440 nm) when energized. The light-emitting element 10 is disposed away from the support base 40, and its emitted light is used as excitation light for the wavelength conversion component 20 placed on the support base 40. Note that the light-emitting element 10 is not limited to a laser diode (semiconductor laser), and solid light-emitting elements such as a light-emitting diode and a superluminescent diode can be suitably used as the light-emitting element 10. The number of the light-emitting elements 10 is not limited to one, and may be plural. In FIG. 1, the light-emitting element 10 is disposed away from the support base 40, but the light-emitting element 10 may be disposed on the support base 40 so that the light emitted from the light-emitting element 10 can irradiate the wavelength conversion component 20.

[0013] (Support base) The material of the support base 40 is, for example, copper (thermal conductivity 398 W / (m·K)). The material of the support base 40 is not limited to copper, and may be a metal material such as a copper alloy, aluminum, or an aluminum alloy, or a material mainly composed of a ceramic such as SiC, SiN, or AlN. It is preferably a material having a thermal conductivity greater than that of the wavelength conversion component 20. This is to efficiently release heat from the wavelength conversion component 20 to the outside. The support base 40 may have wirings, a cooling water channel, or a heat pipe inside, or may be attached to a radiator 70 such as a heat sink fin.

[0014] (Wavelength conversion component) A plan view of the reflective wavelength conversion component 20 placed on the support base 40 is shown in FIG. 2. FIG. 3 is a cross-sectional conceptual view of FIG. 2. The wavelength conversion component 20 absorbs at least a part of the light emitted from the light emitting element 10 as excitation light and emits light having a wavelength different from the wavelength of the excitation light. The wavelength conversion component 20 is joined to the upper surface of the support base 40 via the joining material 30. FIG. 4 shows an enlarged cross-sectional conceptual view of a part of the wavelength conversion component 20. The plate-shaped wavelength conversion component 20 includes a substrate 21 made of a single crystal and a wavelength conversion member 22 containing an inorganic single crystal. In FIG. 4, the wavelength conversion member 22 includes a first inorganic phosphor single crystal 221 and a second inorganic phosphor single crystal 222. Further, a window material shown in another embodiment may be provided. In the reflective wavelength conversion component 20, the incident surface of the excitation light and the surface that emits light having a wavelength different from the wavelength of the excitation light are the same main surface. In FIG. 1, the main surface on the substrate 21 side is the incident surface of the excitation light and is also the surface that emits light having a wavelength different from the wavelength of the excitation light. The main surface on the wavelength conversion member 22 side of the wavelength conversion component 20 is provided with an optical thin film (not shown) for increasing the reflectance of the excitation light and the wavelength-converted light.

[0015] In FIG. 1, the wavelength conversion component 20 is made reflective, but it may be made transmissive as shown in other embodiments. In the transmissive wavelength conversion component 20, the incident surface of the excitation light and the surface that emits light having a wavelength different from the wavelength of the excitation light are different opposing main surfaces. When the main surface on the substrate 21 side is the incident surface of the excitation light, the main surface on the wavelength conversion member 22 side becomes the surface that emits light having a wavelength different from the wavelength of the excitation light, and conversely, when the main surface on the wavelength conversion member 22 side is the incident surface of the excitation light, the main surface on the substrate 21 side becomes the surface that emits light having a wavelength different from the wavelength of the excitation light. It is preferable that the main surface of the wavelength conversion component 20 is provided with an optical thin film for increasing the reflectance or transmittance of the excitation light and / or the wavelength-converted light depending on the usage method.

[0016] It is preferable that the side surface and the bottom surface of the wavelength conversion component 20 are smooth, as this increases the light reflectance at the interface with a light reflecting member (not shown) included in the light shielding member 50. The side surface of the wavelength conversion component 20 and the bottom surface of the wavelength conversion component 20, which is the joint surface with the support base 40, are covered with a light reflecting member. The wavelength-converted light is emitted from the top surface of the wavelength conversion component 20 facing the joint surface with the support base 40.

[0017] In FIG. 3, when the substrate 21 also functions as a window material and the top surface of the wavelength conversion component 20 is the main surface on the substrate 21 side, the side surface of the wavelength conversion component 20 and the main surface on the wavelength conversion member 22 side, that is, the bottom surface of the wavelength conversion component 20, are covered with a light reflecting member. The wavelength conversion component 20 has the main surface on the wavelength conversion member 22 side attached to the support base, and the wavelength-converted light is emitted from the main surface on the substrate 21 side.

[0018] Also, when the main surface on the substrate 21 side is the joint surface with the support base 40, the side surface of the wavelength conversion component 20 and the main surface on the substrate 21 side, that is, the bottom surface of the wavelength conversion component 20, are covered with a light reflecting member. The wavelength conversion component 20 has the main surface on the substrate 21 side attached to the support base 40, and the wavelength-converted light is emitted from the main surface on the wavelength conversion member 22 side, that is, the top surface of the wavelength conversion component 20.

[0019] (Substrate) The substrate 21 is made of, for example, a plate-shaped transparent yttrium aluminum garnet (Y3Al5O 12 (YAG)) single crystal (the plane index of the main surface is (100), and the plate thickness is 150 μm). An optical thin film (not shown) is provided on the main surface on the substrate 21 side of the wavelength conversion component 20 to increase the transmittance of the excitation light and / or the wavelength-converted light. In FIG. 3, a transparent YAG single crystal is used, but a corundum (sapphire, α - Al2O3) single crystal or the like can also be used as the substrate 21.

[0020] (Wavelength conversion member) In FIG. 4, the wavelength conversion member 22 has, for example, a multilayer film (film thickness: 40 μm) including a cerium (Ce)-doped lutetium aluminum garnet single crystal film (Ce:LuAG crystal film) (film thickness: 30 μm), which is a first inorganic phosphor single crystal 221, and a europium (Eu)-doped lutetium aluminum garnet single crystal film (Eu:LuAG crystal film) (film thickness: 10 μm), which is a second inorganic phosphor single crystal 222, formed thereon. Note that the inorganic phosphor crystals are not limited to two types, and two or more types may be used.

[0021] The thermal conductivity of the transparent YAG single crystal of the substrate 21 (13.4 W / (m·K)) is higher than the thermal conductivity of the LuAG single crystal of the wavelength conversion member 22 (8.3 W / (m·K)).

[0022] As the phosphor of the wavelength conversion member 22, an inorganic phosphor crystal that is less likely to deteriorate due to a temperature rise is preferably used. When the wavelength conversion member 22 is formed of a single crystal film, since there are no vacancies or grain boundaries, the thermal conductivity is higher and the mechanical properties are superior to those of a polycrystal. Examples of the inorganic phosphor crystal include crystals of rare earth aluminates, which are very stable chemically and thermally. It has a composition represented by the following formula (I). (Ln 1-n M2 n )3(Al 1-m M1 m )5O 12 (I) (In formula (I), Ln is at least one rare earth element selected from the group consisting of Y, La, Lu, Gd, and Tb, M1 is at least one element selected from Ga and Sc, M2 is an activating component, and is at least one element selected from Ce, Eu, Nd, Yb, Pr, and Cr, and m and n are numbers satisfying 0 ≦ m ≦ 0.02 and 0 < n ≦ 0.1, respectively.)

[0023] (Method for manufacturing the wavelength conversion component) As a method for producing an inorganic single crystal, a liquid phase growth method is known, and a transparent inorganic single crystal plate material that becomes the substrate 21 and an inorganic phosphor single crystal plate material contained in the wavelength conversion member 22 can be cut out from an ingot of the liquid phase grown inorganic single crystal. The method for producing the inorganic single crystal plate material is not limited to the liquid phase growth method, and a vapor phase growth method may also be used.

[0024] A transparent single crystal plate material that becomes the substrate 21 and an inorganic phosphor single crystal plate material contained in the wavelength conversion member 22 can be joined by direct bonding, ground and polished to a desired thickness to obtain a wavelength conversion component 20. It is also possible to join a plurality of inorganic phosphor single crystal plate materials contained in the wavelength conversion member 22 by direct bonding. Direct bonding can be performed, for example, by irradiating an argon beam onto the bonding surface of the phosphor single crystal and the bonding surface of the transparent inorganic single crystal in a vacuum, then bringing the bonding surfaces into contact with each other and applying a load for bonding, or by irradiating each bonding surface with plasma for bonding in the atmosphere and then heating.

[0025] The method for obtaining an inorganic phosphor ceramic plate, which is an aggregate of conventional inorganic phosphor crystal grains, requires a number of steps such as preparation of a powder raw material of the inorganic phosphor, molding of the powder, firing of the molded body, slicing of the fired body, and polishing of the fired plate.

[0026] On the other hand, according to the laser CVD method, which is a chemical vapor deposition method described in WO2023 / 017845, an inorganic phosphor crystal film, particularly a metal oxide phosphor crystal film, contained in the wavelength conversion member 22 can be epitaxially formed on a transparent single crystal plate material that becomes the substrate 21. The laser CVD method has a high film formation rate and a large segregation coefficient, so that the concentration of dopants, that is, activating components such as M2:Ce and Eu, can be increased compared with the liquid phase growth method. Uniform thin film formation is possible by controlling the growth time and the supply amount of the source gas, the obtained shape is flat, and it is excellent in mass productivity as a plate-shaped wavelength conversion component 20.

[0027] When growing a metal oxide phosphor crystal film, such as a LuAG crystal film, using an organometallic material as part of the raw material by laser CVD method, while supplying a Lu raw material gas (e.g., lutetium tris(dipivaloylmethanato) vapor and a carrier gas (e.g., Ar gas)), an Al raw material gas (e.g., a mixed gas of aluminum tris(dipivaloylmethanato) vapor and a carrier gas), and oxygen gas (O2) into the reaction chamber, closing the valve provided in the pipe connecting the Ce raw material container and the reaction chamber to stop the supply of the Ce raw material gas (e.g., a mixed gas of cerium tetrakis(dipivaloylmethanato) vapor and a carrier gas) allows the growth of a Ce:LuAG crystal film. By stopping the supply of the Ce raw material gas and opening the valve provided in the pipe connecting the Eu raw material container and the reaction chamber to start the supply of the Eu raw material gas (e.g., a mixed gas of europium tetrakis(dipivaloylmethanato) vapor and a carrier gas), it is possible to easily switch from the growth of the Ce:LuAG crystal film to the growth of the Eu:LuAG crystal film.

[0028] (Light shielding member and light reflecting member) The light reflecting member, which is a part of the light shielding member 50 in FIG. 3 and is arranged adjacent to the wavelength conversion component 20, is, for example, a metal multilayer film containing an Ag film. When joining the metal multilayer film on the bottom surface of the wavelength conversion component 20 and the support base 40 using solder as the bonding material 30, it is preferable that the metal multilayer film includes a barrier layer to prevent a decrease in the light reflectance on the bottom surface on the wavelength conversion member side due to the reaction with the solder. The barrier layer includes, for example, metals such as titanium (Ti), tungsten (W), aluminum (Al), indium (In), tin (Sn), nickel (Ni), platinum (Pt), or alloys of the above materials.

[0029] As the light reflecting member, a metal film such as Ag or Al, a dielectric multilayer film, white cement, a white heat-resistant inorganic adhesive, a white resin, etc. can be used. A metal film with a high light reflectance and a large thermal conductivity can be preferably used as the light reflecting member.

[0030] The light shielding member 50 may include a dark-colored light absorption member to enhance the contrast between the light emitting surface and other regions.

[0031] (Bonding between the wavelength conversion component and the support base) The wavelength conversion component 20 and the support base 40 can be bonded using a bonding material 30. In FIG. 3, the bonding material 30 is an Au-Sn solder with 20 wt% Sn.

[0032] The Au-Sn solder has a eutectic point at 20 wt% Sn (melting point 280°C) and 90 wt% Sn (melting point 217°C), and is suitable because the bond can be maintained even when the temperature of the wavelength conversion component 20 rises to about 200°C. In particular, the Au-Sn solder with 20 wt% Sn has a thermal conductivity of about 57 W / (m·K), so it can be suitably used as the bonding material 30 between the wavelength conversion component 20 and the support base 40.

[0033] Also, for example, a sintered body obtained by sintering a metal paste containing fine metal particles can be used as the bonding material 30 for bonding. The size of the fine metal particles is, for example, nano-size and micron-size, and the metal particles are, for example, silver particles or copper particles. By appropriately setting the sintering conditions, a sintered body having a thermal conductivity of 100 W / (m·K) or more can be obtained. Since silver has a higher reflectance for visible light than copper, a silver sintered body is more preferably used as the bonding material.

[0034] A white heat-resistant inorganic adhesive or a white resin can also be used as the bonding material 30 for bonding between the wavelength conversion component 20 and the support base 40.

[0035] (Other components) An optical element 60 such as a lens, a radiator 70, or a fan for cooling a power source 80, etc. may be provided outside the main surface of the wavelength conversion component.

[0036] The power supply to the power source for driving the light-emitting element is performed from an external power source such as a commercial power source, a power generation device, various batteries, etc. (not shown).

[0037] (Function and effect) In the first embodiment, since the wavelength conversion member 22 includes an inorganic phosphor single crystal film, there are no voids or grain boundaries between particles that impede heat conduction inside the inorganic phosphor single crystal film, and heat conduction inside the inorganic phosphor single crystal film is efficiently performed, suppressing the temperature rise of the inorganic phosphor single crystal film and suppressing the temperature quenching phenomenon in which the efficiency of wavelength-converting the excitation light decreases. As a result, an improvement in the light output of the light-emitting device 100 can be realized.

[0038] The wavelength conversion member 22 is directly bonded to a substrate 21 made of an inorganic single crystal plate material, and since the thermal conductivity of the substrate 21 is greater than the thermal conductivity of the wavelength conversion member 22, heat generated in the inorganic phosphor single crystal film of the wavelength conversion member 22 easily moves to the substrate 21, there are no voids or grain boundaries between particles that impede heat conduction inside the substrate 21, and heat conduction inside the substrate 21 is performed more efficiently than inside the wavelength conversion member 22, suppressing the temperature rise of the wavelength conversion member 22 and suppressing the temperature quenching phenomenon. As a result, an improvement in the light output of the light-emitting device 100 can be realized.

[0039] By using a material having a thermal conductivity greater than the thermal conductivity of the wavelength conversion component 20 for the support base 40 that serves as a heat dissipation path from the wavelength conversion component 20 and the bonding material 30 between the wavelength conversion component 20 and the support base 40, the heat dissipation property from the wavelength conversion component 20 is improved, the temperature rise of the wavelength conversion member 22 is suppressed, and the temperature quenching phenomenon can be suppressed. As a result, an improvement in the light output of the light-emitting device 100 can be realized.

[0040] The emitted light from a plate formed by sintering a large number of conventional phosphor crystal particles tends to have a wide light distribution like Lambertian light distribution due to scattering by the particles. When the light emitted from the light-emitting device has a wide light distribution, the light emitted from the light-emitting device contains a lot of light that is not utilized as the light emitted from the light-emitting device, so the utilization efficiency of the light emitted from the light-emitting device decreases.

[0041] Inside the wavelength conversion member 22 including the inorganic phosphor single crystal film and inside the substrate 21 made of an inorganic single crystal plate material in the first embodiment of the present disclosure, there are very few grain boundaries and pores, reducing light scattering by the grain boundaries and pores, suppressing the spread of the excitation light, and enabling the provision of a light-emitting device with high luminance.

[0042] Since the single crystal film of the wavelength conversion member 22 is uniform and thin with a film thickness of 100 μm or less, and is disposed on the bottom surface of the wavelength conversion component of the wavelength conversion part on the side of the wavelength conversion member 22 and joined to the support base 40 via a metal multilayer film, when the excitation light is irradiated, the wavelength conversion member 22 in the region irradiated with the excitation light generates heat, and does not generate heat outside the irradiation region, but is quickly exhausted to the support base 40 and not stored in the single crystal film of the wavelength conversion member 22. Also, since the substrate 21 reinforces the mechanical strength of the wavelength conversion component 20 and is firmly joined to the support base 40, the problem of distortion or cracking occurring in the single crystal film of the wavelength conversion member 22 does not occur. Further, since the single crystal film of the wavelength conversion member 22 is uniform and thin, there is little color unevenness, and yellow ringing is less likely to occur even when the light emitted from the light emitting device 100 is irradiated onto the screen.

[0043] Since the wavelength conversion member 22 includes two or more inorganic phosphor single crystal films having different emission wavelengths, for example, a phosphor single crystal film that emits yellow light and a phosphor single crystal film that emits red light, illumination light with high color rendering can be emitted.

[0044] In the first embodiment, when the substrate 21 is a transparent YAG single crystal and the wavelength conversion member 22 is a multilayer film including a Ce:LuAG single crystal film and an Eu:LuAG single crystal film, since the difference in the linear expansion coefficients of the substrate 21 and the wavelength conversion member 22 is small, even when the output of the excitation light is increased, the warping caused by the difference in thermal expansion between the substrate 21 and the wavelength conversion member 22 generated by the heat generation of the wavelength conversion component 20 can be suppressed.

[0045] (Second Embodiment) A plan view of the light emitting device 200 in the second embodiment of the present disclosure is shown in FIG. 5, and a cross-sectional view is shown in FIG. 6. As shown in FIG. 6, the light emitting device 200 includes a light emitting element 10, a plate-shaped wavelength conversion component 20, and a light shielding member 50 including a light reflecting member on the upper surface of the support base 40. The side surface of the light emitting element 10 and the side surface of the wavelength conversion component 20 are covered with a light reflecting member (not shown).

[0046] In FIG. 6, the support base 40 is made of a material mainly composed of AlN ceramic and has a mounting area for the light-emitting element 10. Specifically, the support base 40 has a plate member 41 of AlN ceramic (thermal conductivity 180 W / (m·K)) and a wiring 42 electrically connected to the light-emitting element 10. The wiring 42 includes an upper surface wiring 421, a lower surface wiring 423, and vias 422 electrically connecting the two. Further, it may have a heat sink made of a metal member. In FIG. 6, the support base 40 is made of a material mainly composed of AlN ceramic, but is not limited thereto, and may be made of a material mainly composed of other ceramics such as SiC and SiN, or a polycrystalline diamond material.

[0047] In FIG. 6, the light-emitting element 10 is, for example, an AlInGaN-based light-emitting diode with a flip-chip structure on a sapphire substrate, and can emit ultraviolet light when energized. In FIG. 6, the light-emitting element 10 is shown including the sapphire substrate of the growth substrate of the AlInGaN semiconductor multilayer film, but is not limited thereto, and may be one with the growth substrate removed. The light-emitting element 10 has an electrode arrangement surface facing the mounting area of the support base 40, and the surface facing the electrode arrangement surface serves as the mounting surface for the wavelength conversion component 20.

[0048] For the bonding between the support base 40 and the light-emitting element 10, an appropriate conductive adhesive such as solder or plating can be used, or direct bonding can also be employed.

[0049] In FIG. 6, the light-emitting element 10 is composed of one light-emitting diode, but a plurality of light-emitting diodes may be arranged in parallel to form the light-emitting element 10.

[0050] Fig. 7 shows an enlarged conceptual cross-sectional view of the wavelength conversion component 20 in Fig. 6. The wavelength conversion component 20 includes a substrate 21 made of a transparent YAG single crystal plate and a wavelength conversion member 22 containing an inorganic single crystal. The wavelength conversion member 22 has a first portion 223, a second portion 224, and a third portion. In the second embodiment, the first portion 223 and the second portion 224 are inorganic phosphor single crystal films. The first portion 223 of the inorganic single crystal film, the second portion 224 of the inorganic single crystal film, and the third portion that becomes the window member 23 in the inorganic single crystal film are, for example, a Eu:LuAG single crystal film, a Ce:LuAG single crystal film, and a transparent YAG single crystal film epitaxially formed on the substrate 21, respectively. The first portion 223 of the inorganic single crystal film and the second portion 224 of the inorganic single crystal film are arranged side by side in the film thickness direction and form a phosphor film. In the second embodiment, the phosphor film composed of the first portion 223 and the second portion 224 and the third portion constitute a pair of layers.

[0051] The wavelength conversion component 20 has the surface on the substrate 21 side joined to the surface facing the electrode arrangement surface of the light emitting element 10.

[0052] In the second embodiment, the shape and size of the wavelength conversion component 20 are substantially the same as those of the light emitting element 10 in plan view.

[0053] In Fig. 6, the light shielding member 50 including the light reflection member includes a dielectric multilayer film and white cement. Note that the light shielding member 50 can also be used in combination with other materials, such as a white heat-resistant inorganic adhesive, a white resin, etc. The light shielding member 50 may further include cement colored black or the like or a resin containing a heat dissipation filler on the outside. This is to enhance the contrast with the light emitting surface during light emission.

[0054] (Other components) In the second embodiment, the light emitting device 200 may include an optical element such as a light diffusing plate or a lens outside the window member 23 and a driving power source for the light emitting element 10.

[0055] (Method for manufacturing the window member) A wavelength conversion member 22 having a window structure can be manufactured by directly joining a transparent single crystal plate material that becomes the window member 23 and a plate material of an inorganic phosphor crystal. According to the laser CVD method, which is a vapor phase growth method, an inorganic phosphor crystal film and a transparent single crystal film serving as the window member 23 can be sequentially formed epitaxially on a transparent single crystal plate material serving as the substrate 21, and the wavelength conversion member 22 can be obtained.

[0056] (Bonding between the wavelength conversion component and the light emitting element) The wavelength conversion component 20 and the light emitting element 10 can be bonded using an optical path coupling adhesive (not shown) having good light transmittance and refractive index matching. Also, the wavelength conversion component 20 and the light emitting element 10 can be bonded by direct bonding.

[0057] (Function and effect) Since the wavelength conversion member 22 includes a plurality of inorganic single crystal films, there are no voids or grain boundaries between particles that obstruct heat conduction inside each inorganic single crystal film, and heat conduction inside the wavelength conversion member 22 is efficiently performed, suppressing a temperature rise of the wavelength conversion member 22 and suppressing a phenomenon of temperature quenching in which the efficiency of wavelength-converting the excitation light decreases. As a result, an improvement in the light output of the light emitting device 200 can be realized.

[0058] The phosphor crystal film of the wavelength conversion member 22 is directly bonded to the substrate 21 and the window member 23 made of an inorganic single crystal plate material. Since the thermal conductivity of the substrate 21 and the window member 23 is higher than that of the phosphor crystal film, heat generated in the phosphor crystal film easily moves to the substrate 21 and the window member 23, and there are no voids or grain boundaries between particles that obstruct heat conduction inside the substrate 21 and the window member 23. Heat conduction inside the substrate 21 and the window member 23 is more efficient than inside the phosphor crystal film, suppressing a temperature rise of the phosphor crystal film and suppressing the temperature quenching phenomenon. As a result, an improvement in the light output of the light emitting device 200 can be realized.

[0059] When the light-emitting device 200 is driven, the heat generated in the phosphor crystal film by the irradiation of excitation light from the light-emitting element 10 is dissipated not only to the side surface of the phosphor crystal film but also to the surroundings including the support base 40 through the substrate 21 and the window member 23. Heat is radiated from the side surface of the phosphor crystal film to the support base 40 and the surrounding atmosphere through the light-shielding member 50, from the substrate 21 to the support base 40 and the surrounding atmosphere through the light-emitting element 10 or the light-shielding member 50, and from the window member 23 directly or to the support base 40 and the surrounding atmosphere through the light-shielding member 50.

[0060] Further, by using a material having the same coefficient of linear expansion as that of the substrate 21 for the window member 23, warping of the wavelength conversion component 20 due to thermal expansion of the wavelength conversion component 20 when the wavelength conversion component 20 generates heat can be suppressed.

[0061] Since the shape and size of the wavelength conversion component 20 are substantially the same as those of the light-emitting element 10 in plan view, the irradiation region of the excitation light becomes the entire wavelength conversion member 22, and there is no problem that distortion or cracks occur in the phosphor crystal film due to the temperature difference between the excitation light irradiation region and the non-irradiation region.

[0062] (Third Embodiment) The light-emitting device in the third embodiment of the present disclosure is the same as that in the first embodiment except for the wavelength conversion component 20.

[0063] FIG. 8 is a schematic diagram of the wavelength conversion component 20 in the third embodiment, where (a) is a plan conceptual diagram and (b) is a partially enlarged conceptual diagram. FIG. 9 is a cross-sectional conceptual diagram of FIG. 8.

[0064] In FIG. 9, the wavelength conversion component 20 includes, for example, a wavelength conversion member 22 including a eutectic film composed of a substrate 21 of a plate material of a transparent sapphire single crystal, a first portion 223 of a Ce:YAG single crystal, and a second portion 224 of an α-Al2O3 single crystal having a corundum structure. In FIG. 8, the first portion 223 and the second portion 224 are visible through the substrate 21. The substrate 21 has an m-plane or an a-plane as a main plane. The substrate 21 has a thermal conductivity greater than that of the first portion 223 of the wavelength conversion member 22. The eutectic film of the wavelength conversion member 22 includes a periodic structure in which the first portion 223 and the second portion 224 are alternately arranged periodically in a direction perpendicular to the film thickness of the eutectic film. That is, the eutectic film has a structure in which columns composed of α-Al2O3 crystals arranged periodically penetrate a Ce:YAG crystal film. The periodic structure inside the eutectic film forms a two-dimensional slab-type photonic crystal. The first portion 223 of the wavelength conversion member 22 includes a phosphor crystal that absorbs a part of the excitation light and generates light having a longer wavelength than the excitation light. The second portion 224 preferably has translucency with respect to the excitation light and the light wavelength-converted by the first portion 223. This is to improve the luminous efficiency of the light-emitting device.

[0065] (Method for manufacturing wavelength conversion component) An epitaxial first inorganic phosphor crystal thin film 221 is formed on a plate material of a transparent single crystal serving as the substrate 21 by a laser CVD method, which is a vapor phase growth method. By electron beam lithography and dry etching such as RIE, a dot pattern in which a plurality of circular holes penetrating the first inorganic phosphor crystal thin film 221 are arranged in a triangular lattice is formed, and the transparent single crystal of the substrate is exposed in dots. Again, a eutectic film composed of the first portion 223 and the second portion 224 is formed on the substrate 21 on which the dot pattern of the first inorganic phosphor crystal thin film 221 is formed by the laser CVD method. The first portion 223 grows on the first inorganic phosphor crystal thin film 221, the second portion 224 grows on the exposed transparent single crystal of the substrate 21, and the periodically arranged dot pattern is inherited by the eutectic film to form a two-dimensional slab-type photonic crystal.

[0066] (Function and effect) Since the first portion 223 of the wavelength conversion member 22 is made of an inorganic phosphor single crystal film, there are no inter-particle voids or grain boundaries that impede heat conduction inside the first portion 223. Heat conduction inside the first portion 223 is efficiently performed, suppressing the temperature rise of the first portion 223 and suppressing a phenomenon called temperature quenching in which the efficiency of wavelength-converting the excitation light decreases. As a result, improvement of the light output of the light-emitting device can be realized.

[0067] Since the second portion 224 of the wavelength conversion member 22 is disposed directly on the substrate 21 through the first portion 223 of the wavelength conversion member 22, the second portion 224 of the wavelength conversion member 22 conducts the heat generated in the first portion 223 and helps to dissipate the heat from the wavelength conversion member 22 to the outside, such as a heat dissipation component, through the substrate 21. Although the thermal conductivity of the first portion 223 and the thermal conductivity of the second portion 224 may be equal, it is preferable that the thermal conductivity of the second portion 224 is larger than the thermal conductivity of the first portion 223. This is because it is easy to suppress the occurrence of temperature quenching in the first portion 223.

[0068] The first portion 223 of the wavelength conversion member 22 is directly bonded to a substrate 21 made of an inorganic single crystal plate material, and since the thermal conductivity of the substrate 21 is larger than the thermal conductivity of the first portion 223, the heat generated in the first portion 223 easily moves to the substrate 21. There are no inter-particle voids or grain boundaries that impede heat conduction inside the substrate 21, and heat conduction inside the substrate 21 is performed more efficiently than inside the wavelength conversion member 22, suppressing the temperature rise of the first portion 223 and suppressing the temperature quenching phenomenon. As a result, improvement of the light output of the light-emitting device can be realized.

[0069] Specifically, the thermal conductivity of a sapphire single crystal, that is, an α-Al2O3 single crystal having a corundum structure, is about 42 W / (m·K), which is greater than that of a YAG single crystal, about 13.4 W / (m·K). Therefore, even when the Ce:YAG crystal film is thicker than 100 μm, the columns made of α-Al2O3 crystals penetrating the Ce:YAG crystal film conduct the heat generated in the Ce:YAG crystal film to the substrate, suppressing the temperature rise of the YAG crystal film. Since the columns made of α-Al2O3 crystals are epitaxially formed with the sapphire single crystal substrate 21, there is no grain boundary between the two, and heat conduction is efficiently performed. As a result, the temperature rise of the wavelength conversion component 20 can be suppressed, the temperature quenching phenomenon can be suppressed, and as a result, the light output of the light emitting device can be improved.

[0070] The periodic structure inside the eutectic film forming the two-dimensional slab-type photonic crystal can narrow the light distribution of the emitted light, thereby improving the front luminance. The light coupling rate with optical elements such as lenses is improved, and the conversion efficiency from the power to the light of the light emitting device is improved.

[0071] (Fourth Embodiment) The light emitting device according to the fourth embodiment of the present disclosure is the same as the second embodiment except for the wavelength conversion component 20.

[0072] FIG. 10 is a schematic diagram of the wavelength conversion component 20 in the fourth embodiment, where (a) is a plan view and (b) is a partially enlarged view. FIG. 11 is a cross-sectional view of FIG. 10.

[0073] In FIG. 10, the wavelength conversion component 20 includes, for example, a substrate 21 made of a transparent sapphire single crystal plate material and a wavelength conversion member 22. The wavelength conversion member 22 includes a eutectic film of a first portion 223 of an inorganic phosphor single crystal and a second portion 224 of an inorganic single crystal, and a window member 23 of an α-Al2O3 single crystal film. For example, the inorganic phosphor single crystal of the first portion 223 is a Ce:YAG single crystal, and the inorganic single crystal of the second portion 224 is an α-Al2O3 single crystal. In FIG. 10, the first portion 223 and the second portion 224 of the wavelength conversion member 22 are visible through the window member 23. The wavelength conversion member 22 has a structure in which columns (first portion 223) made of periodically arranged Ce:YAG crystals penetrate an α-Al2O3 crystal film (second portion 224). The substrate 21 has an m-plane or an a-plane as its main plane. The substrate 21 has a thermal conductivity greater than that of the phosphor single crystal, and the window member 23 also has a thermal conductivity greater than that of the phosphor single crystal. The first portion 223 and the second portion 224 form a film as a eutectic that alternately and periodically aligns in a direction perpendicular to the thickness direction of the film, and a pair of layers composed of the eutectic film and the third portion 23 are included in the wavelength conversion member 22.

[0074] (Method for manufacturing wavelength conversion component) An epitaxial first inorganic phosphor crystal thin film 221 is formed on the transparent single crystal plate material that will be the substrate 21 by laser CVD, which is a vapor phase growth method. By electron beam lithography and dry etching such as RIE, the first inorganic phosphor crystal thin film 221 is removed leaving a triangular lattice dot pattern to expose the substrate 21, and a triangular lattice dot pattern composed of islands of a plurality of first inorganic phosphor crystal thin films 221 is formed on the substrate 21. Again, a eutectic composed of the first portion 223 and the second portion 224 is formed on the substrate 21 on which the dot pattern of the first inorganic phosphor crystal thin film 221 is formed by laser CVD. The first portion 223 grows on the first inorganic phosphor crystal thin film 221, and the second portion 224 grows on the exposed transparent single crystal of the substrate 21, and the periodically arranged dot pattern is inherited by the eutectic film to form a two-dimensional photonic crystal.

[0075] Furthermore, a transparent inorganic single crystal film serving as the window member 23 can be formed on the eutectic crystal film by direct bonding or by a laser CVD method, which is a vapor phase growth method.

[0076] (Function and Effect) Since the columnar first portion 223 is an inorganic phosphor single crystal, there are no inter-particle voids or grain boundaries inside the first portion that impede heat conduction, and heat conduction inside the first portion 223 is performed efficiently.

[0077] The heat generated in the columnar first portion 223 is dissipated to the outside through the substrate 21, the second portion 224, and the window member 23 surrounding the columnar first portion 223. Each of the substrate 21, the second portion 224, and the window member 23 has a higher thermal conductivity than the thermal conductivity of the first portion 223, and there are no inter-particle voids or grain boundaries inside any of them that impede heat conduction. Heat conduction inside the substrate 21, the second portion 224, and the window member 23 is performed more efficiently than inside the first portion 223, preventing heat from being stored in the first portion 223 and causing the temperature of the first portion 223 to rise excessively, and suppressing temperature quenching of the phosphor crystals contained in the first portion 223.

[0078] The periodic structure inside the eutectic crystal film of the wavelength conversion member 22 forms a two-dimensional photonic crystal. When the wave number of light traveling perpendicular to the side surface of the columnar first portion 223 satisfies the Bragg reflection condition, that light cannot exist inside the eutectic crystal film. That is, the light existing in the wavelength conversion member 22 has a wave number vector parallel to the extending direction of the columnar first portion 223. That is, by having a two-dimensional photonic crystal structure, the light extraction efficiency from the wavelength conversion component 20 is improved, and the light distribution of the emitted light can be narrowed.

[0079] The refractive index of the first part 223 is higher than that of the second part 224. For example, when a Ce:YAG single crystal is used for the first part 223, its refractive index is 1.82 to 1.86. For example, when an α-Al2O3 single crystal is used for the second part 224, the refractive index of the second part 224 is 1.76 to 1.77. The light that undergoes total reflection at the interface between the first part 223 and the second part 224 and propagates inside the first part 223 is radiated into the substrate 21 of single crystal transparent sapphire or the window member 23 of the α-Al2O3 single crystal film at the end of the columnar first part 223. The light that passes through the interface between the first part 223 and the second part 224 and enters the second part 224 refracts at the interface according to Snell's law and travels toward the window member 23 side or the substrate 21 side, reducing the light heading toward the side surface of the wavelength conversion component 20. The light that travels toward the substrate 21 side at the bottom surface on the substrate 21 side of the wavelength conversion component 20 is reflected toward the window member 23 side by the optical thin film. Thus, the proportion of the light exiting from the top surface on the window member 23 side can be increased, improving the light emission efficiency of the light emitting device.

[0080] (Fifth Embodiment) The light emitting device in the fifth embodiment of the present disclosure is the same as the fourth embodiment except for the wavelength conversion member 22.

[0081] FIG. 12 is a schematic diagram of the wavelength conversion component 20 in the fifth embodiment, where (a) is a plan view concept, and (b) is a partial enlarged view concept. FIG. 13 is a cross-sectional view concept of FIG. 12.

[0082] In FIG. 11, the wavelength conversion member 22 has, for example, a pair of layers including a eutectic film composed of a first portion 223 of a Ce:YAG single crystal and a second portion 224 of an α - Al2O3 single crystal and a third portion 225 of an α - Al2O3 single crystal film, and has one or more pairs of such layers. That is, the wavelength conversion component 20 is a laminate of a substrate 21 / the first eutectic film / the first third portion 225 / the second eutectic film / the second third portion 225 / the third eutectic film / the third third portion 225 / ··· / the nth eutectic film / the nth third portion 225 (also serving as the window member 23) (n is a natural number). In the eutectic film composed of the first portion 223 and the second portion 224, the first portion 223 and the second portion 224 are arranged alternately in a direction perpendicular to the thickness direction of the film. In FIG. 12, the nth first portion 223 and the nth second portion 224 are visible through the window member 23.

[0083] In the fourth embodiment, the substrate 21 of the single crystal transparent sapphire has an m - plane or an a - plane as the main plane, but in the fifth embodiment, the plane orientation of the main plane of the single crystal transparent sapphire may be other plane orientations.

[0084] (Method for manufacturing a wavelength conversion component) When growing a eutectic film composed of, for example, Ce:YAG crystal and α-Al2O3 crystal by laser CVD method, while supplying Y source gas (for example, tris(dipivaloylmethanato)yttrium vapor and carrier gas (for example, Ar gas)), Al source gas (for example, a mixed gas of tris(dipivaloylmethanato)aluminum vapor and carrier gas), and oxygen gas (O2) into the reaction chamber under the control of the supply amount of each source gas, if Ce source gas (for example, a mixed gas of tetrakis(dipivaloylmethanato)cerium vapor and carrier gas) is supplied into the reaction chamber, a eutectic film composed of Ce:YAG crystal and α-Al2O3 crystal will grow. If the valve provided in the pipe connecting the Y source container and the reaction chamber and the valve provided in the pipe connecting the Ce source container and the reaction chamber are closed simultaneously, since the supply of Al source gas and oxygen gas continues, an α-Al2O3 crystal film will grow. Again, if the valve provided in the pipe connecting the Y source container and the reaction chamber and the valve provided in the pipe connecting the Ce source container and the reaction chamber are opened simultaneously, a eutectic film will grow. Again, if both valves are closed, an α-Al2O3 crystal film will grow. By opening and closing the valves a predetermined number of times, the above-mentioned laminate is formed. Note that since the YAG single crystal film that is the starting point of the growth of the first part 223 is not arranged, the arrangement and shape of the first part 223 in the second part 224 are left to nature.

[0085] (Function and Effect) Due to the three-dimensional distribution of the first part 223, the light traveling inside the wavelength conversion member 22 is repeatedly reflected and refracted at the boundary between the first part 223 and the second part 224 and at the boundary between the first part 223 and the third part 23, and the wavelength conversion member 22 is provided with the effect of scattering light.

Industrial Applicability

[0086] The light-emitting device of the present disclosure can be suitably used for various light sources such as light sources for lighting and projectors, and light sources for headlamps for moving bodies such as automobiles, ships, and airplanes.

Explanation of Reference Numerals

[0087] 10 Light-emitting element 20 Wavelength conversion component 21 Substrate 22 Wavelength conversion member 221 First inorganic phosphor single crystal 222 Second inorganic phosphor single crystal 223 First part 224 Second part 225 Third part 23 Window member 30 Bonding material 40 Support base 41 Ceramic plate material 42 Wiring 421 Top surface wiring 422 Via 423 Bottom surface wiring 50 Light shielding member 60 Optical element 70 Heat sink 80 Power supply for driving light emitting element 90 Housing 100, 200 Light emitting device

Claims

1. A wavelength conversion component comprising a substrate made of a single crystal and a wavelength conversion member containing a single crystal, wherein the wavelength conversion member has a first portion of a single crystal, a second portion of the single crystal, and a third portion of a single crystal film, the first portion and the second portion form a film, and having one or more pairs of layers composed of the film and the third portion, a wavelength conversion component.

2. The wavelength conversion component according to claim 1, wherein the first portion and the second portion are arranged side by side in the thickness direction of the film. The wavelength conversion component according to claim 1.

3. The wavelength conversion component according to claim 1, wherein the first portion and the second portion are arranged alternately in a direction perpendicular to the thickness direction of the film. The wavelength conversion component according to claim 1.

4. The wavelength conversion component according to claim 3, wherein the first portion and the second portion are arranged periodically. The wavelength conversion component according to claim 3.

5. The wavelength conversion component according to claim 3, having two or more pairs of the pair of layers. The wavelength conversion component according to claim 3.

6. A light emitting device comprising a solid light emitting element that emits excitation light, and the wavelength conversion component according to any one of claims 1 to 5 that absorbs the excitation light.

Images