Light emitting device and lighting device

Abstract

To alleviate a rise in temperature of a wavelength conversion member.SOLUTION: A light emitting device includes a housing, a light emitting element, a wavelength conversion member, a first translucent part and a second translucent part. The housing has a bottom and a side wall. The light emitting device is located at the bottom while surrounded by the side wall, and emits excitation light. The wavelength conversion member is located on the opposite side of the bottom with respect to the light emitting element, and emits fluorescence based on the excitation light. The first translucent part is located between the light emitting element and the wavelength conversion member and has a thermal conductivity lower than that of the housing. The second translucent part is located between the first translucent part and the wavelength conversion member and has a thermal conductivity higher than that of the first translucent part.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a light emitting device and an illumination device. [Background technology]

[0002] Patent Documents 1 and 2 describe techniques relating to lighting devices. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-79934 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-4690 Summary of the Invention [Problem to be solved by the invention]

[0004] There is room for improvement in terms of mitigating the temperature rise of the wavelength conversion member. [Means for solving the problem]

[0005] A light emitting device is disclosed.

[0006] In one embodiment, the light emitting device includes a housing, a light emitting element, a wavelength conversion member, a first light-transmitting portion, and a second light-transmitting portion. The housing has a bottom and sidewalls. The light emitting device is located on the bottom surrounded by the sidewalls and emits excitation light. The wavelength conversion member is located on the opposite side of the bottom from the light emitting element and emits fluorescence based on the excitation light. The first light-transmitting portion is located between the light emitting element and the wavelength conversion member and has thermal conductivity lower than that of the housing. The second light-transmitting portion is located between the first light-transmitting portion and the wavelength conversion member and has thermal conductivity higher than that of the first light-transmitting portion.

[0007] In one embodiment, the lighting device comprises a plurality of light emitting devices. [Effects of the Invention]

[0008] The temperature rise of the wavelength conversion member can be alleviated. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view schematically illustrating a first example of the configuration of a light emitting device. [Figure 2] 1 is a cross-sectional view schematically showing a first example of the configuration of a light-emitting device. [Figure 3] 1A and 1B are diagrams illustrating heat transfer in a light-emitting device. [Figure 4] FIG. 2 is a diagram schematically illustrating a second example of the configuration of a light emitting device. [Figure 5] FIG. 10 is a diagram schematically illustrating a third example of the configuration of the light emitting device. [Figure 6] FIG. 10 is a diagram schematically illustrating a fourth example of the configuration of the light emitting device. [Figure 7] FIG. 10 is a diagram schematically illustrating a fifth example of the configuration of the light emitting device. [Figure 8] FIG. 2 is a diagram schematically illustrating an example of the refractive index of each portion in the light emitting device. [Figure 9] FIG. 2 is a diagram schematically illustrating an example of the configuration of a light-emitting element. [Figure 10] FIG. 10 is a diagram schematically illustrating a light emitting device having a structure in which air is used instead of a second light transmitting portion. [Figure 11] FIG. 1 is a diagram schematically illustrating an example of the configuration of a lighting device. DETAILED DESCRIPTION OF THE INVENTION

[0010] A light-emitting device is known that includes a housing, an LED (Light Emitting Diode) element, and a fluorescent member. The housing has a recess, and the LED element is located within the recess. The fluorescent member has a plate-like shape and is located so as to cover the opening of the recess in the housing. The fluorescent member includes a plate-like transparent member and a plurality of phosphor particles dispersed within the transparent member. The recess in the housing may be filled with a transparent resin that covers the LED element. Excitation light emitted from the LED element passes through the transparent resin and enters the fluorescent member. Each phosphor particle in the fluorescent member absorbs the excitation light and emits fluorescence. The fluorescence is emitted into external space, for example, as illumination light.

[0011] In such a light-emitting device, the phosphor particles generate heat, which causes the temperature of the phosphor particles to rise. If the temperature of the phosphor particles becomes too high, the luminous efficiency of the phosphor particles decreases, which ultimately causes the phosphor particles to lose their light.

[0012] The present inventor has created a light emitting device 1 that can effectively mitigate the temperature rise of the wavelength conversion member. An example of the light emitting device 1 will now be described.

[0013] <Light-emitting device> Fig. 1 is a perspective view that schematically shows a first example of the configuration of light emitting device 1, and Fig. 2 is a cross-sectional view that schematically shows the first example of the configuration of light emitting device 1. Fig. 2 shows a cross section of a portion surrounded by a virtual line in Fig. 1.

[0014] The light emitting device 1 has an emission surface 4a. The light emitting device 1 emits light to the outside from the emission surface 4a. The light is, for example, white light. As shown in FIGS. 1 and 2 , the light emitting device 1 includes a housing 2, a light emitting element 3, a wavelength conversion member 4, a first light-transmitting portion 5, and a second light-transmitting portion 6.

[0015] <Case> The housing 2 includes a bottom 21 and a side wall 22. As shown in FIGS. 1 and 2, the bottom 21 may have a plate-like shape. Specifically, the bottom 21 may have a rectangular plate-like shape. The bottom 21 may have a first surface 21a, a second surface 21b, and a side surface 21c. The second surface 21b is the surface opposite to the first surface 21a. As shown in FIG. 1, the first surface 21a and the second surface 21b may have a rectangular shape. The side surface 21c connects the periphery of the first surface 21a and the periphery of the second surface 21b.

[0016] The sidewall 22 extends from the bottom 21. The sidewall 22 has a tubular shape. As shown in FIG. 1, the sidewall 22 may have a cylindrical shape. The base end of the sidewall 22 is connected to the first surface 21a of the bottom 21. Therefore, the bottom 21 and the sidewall 22 have a concave shape as a whole. Hereinafter, the space surrounded by the bottom 21 and the sidewall 22 will also be referred to as the interior of the housing 2. As will be described later, the light-emitting element 3, the first light-transmitting portion 5, and the second light-transmitting portion 6 are located inside the housing 2. In other words, the sidewall 22 surrounds the light-emitting element 3, the first light-transmitting portion 5, and the second light-transmitting portion 6.

[0017] The housing 2 may be made of a material with high thermal conductivity. The housing 2 may be integrally formed from the same material, or may be formed by combining multiple components. For example, the bottom 21 and the sidewall 22 may be separate bodies fixed to each other by a fixing member. The fixing member may include, for example, a resin, a brazing material, or a solder. The housing 2 may be made of a ceramic material such as aluminum oxide, titanium oxide, zirconium oxide, or yttrium oxide. Alternatively, the housing 2 may be made of a resin material mixed with a powder of a metal oxide such as aluminum oxide, titanium oxide, zirconium oxide, or yttrium oxide. These ceramic or resin materials may be applied to, for example, the sidewall 22. The housing 2 may also be made of a ceramic material such as an aluminum oxide sintered body, a mullite sintered body, an aluminum nitride sintered body, or a silicon nitride sintered body. This ceramic material may be applied to, for example, the bottom 21. When the housing 2 is made of aluminum oxide, the thermal conductivity of the housing 2 is, for example, approximately 29 W / mK.

[0018] <Light-emitting element> The light-emitting element 3 is located on the first surface 21a of the bottom 21, surrounded by the side wall 22 of the housing 2. In other words, the light-emitting element 3 is located on the inner bottom surface of the housing 2. The light-emitting element 3 emits excitation light. The excitation light may be monochromatic light such as purple, blue-purple, or blue. More specifically, the excitation light may be, for example, purple light having an intensity peak at a wavelength of 405 nanometers (nm), blue-purple light having an intensity peak at a wavelength of 420 nm, or blue light having an intensity peak at a wavelength of 450 nm.

[0019] The light-emitting element 3 is, for example, a semiconductor light-emitting element. As a specific example, the light-emitting element 3 includes a p-type semiconductor, an n-type semiconductor, and a pair of electrodes that apply a voltage to the semiconductors. The p-type semiconductor layer and the n-type semiconductor layer may be bonded to each other. A first electrode of the pair of electrodes is connected to the p-type semiconductor layer, and a second electrode of the pair of electrodes is connected to the n-type semiconductor layer. The electrodes are made of, for example, metal. When a voltage is applied to the pair of electrodes, excitation light is generated, for example, at the junction between the p-type semiconductor and the n-type semiconductor. The light-emitting element 3 is, for example, an LED element.

[0020] Each electrode of the light emitting element 3 is connected to, for example, a conductive pattern (not shown) provided on the bottom 21 of the housing 2. The conductive pattern is connected to an external power supply through, for example, a conductor (not shown).

[0021] <Wavelength conversion material> The wavelength conversion member 4 is located on the opposite side of the bottom 21 with respect to the light emitting element 3. The wavelength conversion member 4 is fixed to, for example, a side wall 22 of the housing 2. As shown in FIGS. 1 and 2 , the wavelength conversion member 4 may have a plate shape. The wavelength conversion member 4 may have, for example, a disk shape. The periphery of the wavelength conversion member 4 may be fixed to the entire periphery of the side wall 22. By fixing the wavelength conversion member 4 to the side wall 22, the interior of the housing 2 can be sealed.

[0022] The surface of the wavelength conversion member 4 opposite to the light emitting element 3 may correspond to the emission surface 4a. The excitation light from the light emitting element 3 is incident on the wavelength conversion member 4. Conversely, the light emitting element 3 emits the excitation light toward the wavelength conversion member 4. Based on the excitation light, the wavelength conversion member 4 emits fluorescence having a wavelength spectrum different from that of the excitation light. Part of the fluorescence passes through the emission surface 4a and is emitted to the outside.

[0023] For example, the wavelength conversion member 4 includes a plurality of phosphor particles 41 and a binder layer 42. Each of the plurality of phosphor particles 41 is, for example, a phosphor particle that absorbs irradiation with excitation light and emits fluorescence. The plurality of phosphor particles 41 includes, for example, one or more types of phosphor particles 41 that emit fluorescence of one or more types of wavelength spectrums different from the wavelength spectrum of the excitation light in response to irradiation with excitation light. The one or more types of phosphor particles 41 may include, for example, a plurality of types of phosphor particles 41 that emit fluorescence having mutually different wavelength spectra in response to irradiation with excitation light. The plurality of types of phosphor particles 41 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 excitation light. The green phosphor is a phosphor that emits green (G) fluorescence in response to irradiation with excitation light. The blue phosphor is a phosphor that emits blue (B) fluorescence in response to irradiation with excitation light.

[0024] The phosphor constituting the plurality of phosphor particles 41 may be, for example, a phosphor containing a rare earth such as europium (Eu), cerium (Ce) or yttrium (Y) in the form of a compound such as a phosphate, oxide, silicate, nitride, fluoride, aluminate or sulfide.

[0025] The red phosphor may be, for example, a phosphor whose peak wavelength of the fluorescent light emitted in response to irradiation with excitation light is in the range of about 620 nm to 750 nm. Examples of materials for the red phosphor include CaAlSiN3:Eu, Y3O3S:Eu, Y3O3:Eu, and SrCaClAlSiN3:Eu. 2+ Alternatively, CaAlSi(ON)3:Eu, etc. may be used. As the phosphor particles of the red phosphor, for example, phosphor particles that do not contain phosphorus (P) (also called non-phosphorus phosphor particles) or phosphor particles that contain nitride may be used.

[0026] The green phosphor may be, for example, a phosphor whose peak wavelength of fluorescent light emitted in response to irradiation with excitation light is in the range of about 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. As the phosphor particles of the green phosphor, for example, phosphor particles that do not contain phosphorus (P) (non-phosphorus phosphor particles) or phosphor particles that contain nitride may be used.

[0027] As the blue phosphor, for example, a phosphor that emits fluorescent light in response to irradiation with excitation light with a peak intensity in the wavelength range of about 450 nm to 495 nm may be used. 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 may be used. As the phosphor particles of the blue phosphor, for example, phosphor particles containing phosphorus (P) (also called phosphor-based phosphor particles) or phosphor particles containing nitride may be used.

[0028] The particle size of the phosphor particles 41 may be, for example, about 5 micrometers (μm) to 50 μm.

[0029] The phosphor particles 41 generate heat by absorbing the excitation light. This can cause the temperature of the phosphor particles 41 to rise. If the temperature of the phosphor particles 41 rises, the luminous efficiency of the phosphor particles 41 may decrease. The luminous efficiency of the phosphor particles 41 here is, for example, the ratio of the number of photons of the fluorescence from the phosphor particles 41 to the number of photons of the excitation light incident on the phosphor particles 41. If the temperature of the phosphor particles 41 becomes too high, the phosphor particles 41 may quench. Since such a decrease in the luminous efficiency and quenching of the phosphor particles 41 are undesirable, it is desirable to mitigate the temperature rise of the phosphor particles 41.

[0030] The binder layer 42 is translucent to the excitation light and the fluorescence. The binder layer 42 bonds the plurality of phosphor particles 41 together. In other words, the wavelength conversion member 4 has a configuration in which the plurality of phosphor particles 41 are dispersed in the binder layer 42. The binder layer 42 is made of, for example, resin or glass. In other words, the binder layer 42 contains resin or glass. The binder layer 42 may contain glass as a main component. The main component refers to the component that is contained at the highest ratio (also referred to as the content) among the components constituting the substance. Glass is translucent, for example, to transmit the excitation light to the inside of the wavelength conversion member 4 and to radiate the fluorescence emitted by the phosphor particles 41 excited in response to irradiation with the excitation light to the outside of the wavelength conversion member 4. In other words, glass is translucent, for example, to transmit the excitation light and the fluorescence. The binder layer 42 may also be called a glass matrix. If the binder layer 42 is a glass matrix, the binder layer 42 is less susceptible to thermal degradation than a resin.

[0031] The glass constituting the binder layer 42 may be, for example, a low-melting-point glass. For example, an oxide glass having a melting point (Tm) of 200 degrees Celsius (200°C) to 700°C may be used as the low-melting-point glass. The oxide glass serving as the low-melting-point glass has, for example, a glass transition point (Tg) in the range of 100°C to 600°C and a crystallization temperature (Tc) in the range of 150°C to 650°C. For example, a glass containing two or more oxides selected from silicon dioxide (SiO), aluminum oxide (AlO), boron oxide (BO), sodium oxide (NaO), potassium oxide (KO), lithium oxide (LiO), calcium oxide (CaO), barium oxide (BaO), zinc oxide (ZnO), lead monoxide (PbO), and diphosphorus pentoxide (PO) as its main components may be used as the oxide glass. In other words, the oxide glass may contain an oxide of a metal element or an oxide of a metalloid element.

[0032] The binder layer 42 includes, for example, an amorphous phase of glass. This amorphous phase may be, for example, an amorphous phase portion of a low-melting-point glass. The amorphous phase made of glass has translucency, allowing, for example, excitation light and fluorescent light to pass through.

[0033] The heat generated in each phosphor particle 41 is transferred to the outside through the binder layer 42 .

[0034] <1st transparent part> The first light-transmitting portion 5 is located inside the housing 2, and is located between the light-emitting element 3 and the wavelength conversion member 4. The first light-transmitting portion 5 may cover the light-emitting element 3 in a planar view. Here, a planar view means viewing an object with the line of sight along the thickness direction of the bottom 21 of the housing 2. The first light-transmitting portion 5 may be in close contact with the inner surface 22a of the side wall 22 over the entire periphery. The first light-transmitting portion 5 may be in close contact with, for example, the entire surface of the light-emitting element 3, or may be in close contact with the first surface 21a of the bottom 21. The first light-transmitting portion 5 may be located in a state in which it seals the light-emitting element 3. In other words, the first light-transmitting portion 5 covers the entire light-emitting element 3.

[0035] The first light-transmitting portion 5 may be in contact with a part of the inner circumferential surface 22a of the side wall 22 of the housing 2 on the bottom 21 side. The surface of the first light-transmitting portion 5 on the wavelength converting member 4 side may be a flat surface. This surface may be parallel to the first surface 21a of the bottom 21.

[0036] The first light-transmitting portion 5 has insulating properties and light-transmitting properties. For example, the first light-transmitting portion 5 has light-transmitting properties for excitation light. The transmittance of the first light-transmitting portion 5 for the peak wavelength of the excitation light may be, for example, 60% or more, 80% or more, 90% or more, or 95% or more. The first light-transmitting portion 5 may also have light-transmitting properties for fluorescence. The transmittance of the first light-transmitting portion 5 for fluorescence (for example, the minimum value in the visible light range) may be, for example, 60% or more, 80% or more, 90% or more, or 95% or more.

[0037] Furthermore, the thermal conductivity of the first light transmitting portion 5 is lower than the thermal conductivity of the housing 2. The first light transmitting portion 5 is, for example, a solid. The first light transmitting portion 5 is made of, for example, a resin such as a silicone resin, an acrylic resin, or an epoxy resin. When the first light transmitting portion 5 is made of a silicone resin or an epoxy resin, the thermal conductivity of the first light transmitting portion 5 is, for example, about 0.2 W / mk.

[0038] <Second transparent part> The second light-transmitting portion 6 is located inside the housing 2 between the first light-transmitting portion 5 and the wavelength conversion member 4. The second light-transmitting portion 6 may cover the first light-transmitting portion 5 in a planar view. Alternatively, the second light-transmitting portion 6 may be covered by the wavelength conversion member 4 in a planar view. The second light-transmitting portion 6 may be in close contact with the inner circumferential surface 22a of the side wall 22 over the entire periphery. The second light-transmitting portion 6 may be in close contact with, for example, the entire surface of the first light-transmitting portion 5 on the side opposite the bottom portion 21. Alternatively, the second light-transmitting portion 6 may be in close contact with the surface 4b of the wavelength conversion member 4. The surface 4b is the surface opposite the emission surface 4a of the wavelength conversion member 4. At least a portion of the surface 4b is formed by the binder layer 42 of the wavelength conversion member 4. In other words, the second light-transmitting portion 6 may be in contact with the binder layer 42 of the wavelength conversion member 4. When part of the surface 4b of the wavelength conversion member 4 is formed by part of the phosphor particles 41, the second light-transmitting portion 6 may also be in contact with the phosphor particles 41 on the surface 4b of the wavelength conversion member 4. In other words, the second light-transmitting portion 6 may be in direct contact with the wavelength conversion member 4.

[0039] The second light transmitting portion 6 may fill a space surrounded by the first light transmitting portion 5, the sidewall 22, and the wavelength converting member 4. The space may have a truncated cone shape. Furthermore, the first light transmitting portion 5 may fill a portion of the space surrounded by the bottom portion 21, the sidewall 22, and the second light transmitting portion 6 other than the light emitting element 3.

[0040] The second light-transmitting portion 6 has light-transmitting properties. For example, the second light-transmitting portion 6 has light-transmitting properties for excitation light. The transmittance of the second light-transmitting portion 6 for the peak wavelength of the excitation light may be, for example, 60% or more, 80% or more, 90% or more, or 95% or more. The second light-transmitting portion 6 may also have light-transmitting properties for fluorescence. The transmittance of the second light-transmitting portion 6 for fluorescence (for example, the minimum value in the visible light range) may be, for example, 60% or more, 80% or more, 90% or more, or 95% or more.

[0041] The thermal conductivity of the second light-transmitting portion 6 is higher than that of the first light-transmitting portion 5. The thermal conductivity of the second light-transmitting portion 6 may be lower than that of the housing 2. The second light-transmitting portion 6 may be solid or liquid. For example, the second light-transmitting portion 6 is liquid. The second light-transmitting portion 6 contains at least one of ethylene glycol, glycerin, and water. When the second light-transmitting portion 6 is ethylene glycol, the thermal conductivity of the second light-transmitting portion 6 is approximately 0.25 W / mK. When the second light-transmitting portion 6 is glycerin, the thermal conductivity of the second light-transmitting portion 6 is approximately 0.29 W / mK. When the second light-transmitting portion 6 is water (e.g., purified water), the thermal conductivity of the second light-transmitting portion 6 is approximately 0.6 W / mK.

[0042] The thermal conductivity of the second light transmitting portion 6 may be lower than the thermal conductivity of the wavelength conversion member 4. For example, the thermal conductivity of the second light transmitting portion 6 may be lower than the thermal conductivity of the binder layer 42 of the wavelength conversion member 4. The thermal conductivity of the wavelength conversion member 4 (e.g., the binder layer 42) is, for example, 1.0 W / mK.

[0043] <Lighting> In such a light emitting device 1, the light emitting element 3 emits excitation light toward the wavelength conversion member 4. The excitation light passes through the first light-transmitting portion 5 and the second light-transmitting portion 6 in this order, and enters the wavelength conversion member 4. The phosphor particles 41 in the wavelength conversion member 4 absorb the excitation light and emit fluorescence. A portion of the fluorescence passes through the emission surface 4a of the wavelength conversion member 4 and is emitted to the outside.

[0044] Another portion of the fluorescence emitted by the wavelength conversion member 4 may travel toward the interior of the housing 2. Furthermore, a portion of the excitation light from the light-emitting element 3 may be reflected by the wavelength conversion member 4. This excitation light travels again inside the housing 2. Therefore, the inner surface 22a of the side wall 22 of the housing 2 may be reflective. For example, a metal layer may be formed on the inner surface 22a of the side wall 22. Examples of materials for the metal layer include tungsten, molybdenum, copper, and silver. A plating layer may be formed on the metal layer. Examples of materials for the plating layer include nickel and gold. This allows a portion of the fluorescence traveling inside the housing 2 to be reflected by the inner surface 22a of the side wall 22, and the reflected fluorescence may pass through the emission surface 4a and be emitted to the outside. Furthermore, a portion of the excitation light reflected by the wavelength conversion member 4 may be reflected by the inner surface 22a of the side wall 22 and be incident on the wavelength conversion member 4 again. As a result, the amount of fluorescence emitted from the emission surface 4a can be increased.

[0045] 2, the inner circumferential surface 22a of the side wall 22 may be inclined with respect to the normal to the first surface 21a of the bottom 21. As an example, the inner circumferential surface 22a of the side wall 22 is inclined so as to widen outward with increasing distance from the bottom 21. In other words, the inner circumferential surface 22a of the side wall 22 is inclined so that the inner diameter of the side wall 22 increases with increasing distance from the bottom 21. The inner circumferential surface 22a may have a shape that follows the side surface of a truncated cone. Such inner circumferential surface 22a of the side wall 22 can reflect the excitation light and fluorescence from the wavelength conversion member 4 toward the wavelength conversion member 4.

[0046] <Fever> As described above, the light-emitting element 3 generates heat when emitting excitation light. When this heat is transferred to the wavelength conversion member 4 through the first light-transmitting portion 5 and the second light-transmitting portion 6, it causes a temperature rise in the phosphor particles 41. Furthermore, as described above, the phosphor particles 41 generate heat when absorbing excitation light. This heat also causes a temperature rise in the phosphor particles 41.

[0047] FIG. 3 is a diagram schematically illustrating heat transfer in the light-emitting device 1. In this embodiment, as described above, the thermal conductivity of the second light-transmitting portion 6 is relatively low. For example, the thermal conductivity of the second light-transmitting portion 6 is lower than both the thermal conductivity of the first light-transmitting portion 5 and the thermal conductivity of the housing 2. Therefore, heat generated in the light-emitting element 3 does not easily pass through the first light-transmitting portion 5. In the example of FIG. 3, the transfer of heat from the light-emitting element 3 to the first light-transmitting portion 5 is schematically illustrated by thin dashed arrows. Here, the amount of heat transfer is schematically indicated by the thickness of the line.

[0048] The thermal conductivity of the housing 2 is higher than that of both the first light-transmitting portion 5 and the second light-transmitting portion 6. As an example, the thermal conductivity of the housing 2 is at least 10 times that of the first light-transmitting portion 5 and the second light-transmitting portion 6. Therefore, the light-emitting device 1 can transfer heat generated in the light-emitting element 3 mainly to the bottom 21 of the housing 2. For example, the heat of the light-emitting element 3 is transferred to the housing 2 through a metal electrode with high thermal conductivity. In the example of FIG. 3, the transfer of heat from the light-emitting element 3 to the bottom 21 is schematically shown by a thick arrow.

[0049] As described above, the heat generated in the light-emitting element 3 is less likely to move toward the first light-transmitting portion 5, and can be moved mainly to the bottom portion 21. This reduces the possibility that the heat generated in the light-emitting element 3 will be transmitted to the wavelength conversion member 4 through the first light-transmitting portion 5 and the second light-transmitting portion 6.

[0050] Meanwhile, part of the heat generated by the phosphor particles 41 is transferred to the side wall 22 of the housing 2 through the binder layer 42 and the second light-transmitting portion 6. Because the thermal conductivity of the second light-transmitting portion 6 is higher than that of the first light-transmitting portion 5, the light-emitting device 1 can more effectively transfer the heat of the phosphor particles 41 to the side wall 22 of the housing 2. In the example of Fig. 3, the transfer of heat from the wavelength conversion member 4 to the side wall 22 is schematically shown by thick arrows.

[0051] As described above, the light emitting device 1 according to this embodiment can reduce heat transfer from the light emitting element 3 to the wavelength conversion member 4 while promoting heat transfer from the wavelength conversion member 4 to the side wall 22. Therefore, the light emitting device 1 can more effectively mitigate the temperature rise of the phosphor particles 41 of the wavelength conversion member 4. This can improve the light emitting efficiency and reliability of the light emitting device 1.

[0052] If the thermal conductivity of the second light-transmitting portion 6 is lower than that of the wavelength conversion member 4, the second light-transmitting portion 6 can more efficiently transfer heat from the wavelength conversion member 4 to the side wall 22 of the housing 2. Therefore, the light emitting device 1 can more effectively mitigate the temperature rise of the phosphor particles 41.

[0053] If the second light-transmitting portion 6 is in direct contact with the surface 4b of the wavelength conversion member 4 and the inner surface 22a of the side wall 22, heat from the wavelength conversion member 4 can be more efficiently transferred to the side wall 22. The second light-transmitting portion 6 being in direct contact with the surface 4b of the wavelength conversion member 4 means that the second light-transmitting portion 6 is in contact with at least one of the binder layer 42 and the phosphor particles 41 of the wavelength conversion member 4.

[0054] When the second light-transmitting portion 6 is liquid, the second light-transmitting portion 6 can transfer heat not only by thermal conduction but also by convection. Therefore, the second light-transmitting portion 6 can more efficiently transfer heat from the wavelength conversion member 4 to the side wall 22 of the housing 2. Therefore, the light-emitting device 1 can more effectively mitigate the temperature rise of the phosphor particles 41.

[0055] When at least one of water, ethylene glycol, and glycerin is used as the liquid, the thermal conductivity of the second light-transmitting portion 6 can be made relatively high. For example, the thermal conductivity of Fluorinert (registered trademark) and Galden (registered trademark), which can be used as the liquid, is 0.07. The thermal conductivity of water, ethylene glycol, and glycerin is higher than that of Fluorinert and Galden.

[0056] When the second light-transmitting section 6 contains at least one of water, ethylene glycol, and glycerin, the luminous efficiency of the light-emitting device 1 can be improved. This is because the absorption coefficients of water, ethylene glycol, and glycerin for excitation light and fluorescence are very small. For example, if the first light-transmitting section 5 is made of silicone resin, the absorption coefficient of the first light-transmitting section 5 is approximately 0.1505 (1 / mm). If the binder layer 42 is made of glass, the absorption coefficient of the binder layer 42 is, for example, 0.1393 (1 / m). On the other hand, the absorption coefficient of water can be considered almost zero, and the absorption coefficients of ethylene glycol and glycerin are also smaller than the absorption coefficient of the binder layer 42. Because the absorption coefficients of water, ethylene glycol, and glycerin are smaller than those of the first light-transmitting section 5 and the binder layer 42, the amount of excitation light and fluorescence absorbed by the second light-transmitting section 6 can be reduced. This can improve the luminous efficiency of the light-emitting device 1. Furthermore, since the thermal conductivity of water is higher than that of ethylene glycol and glycerin, by using water as the second light-transmitting portion 6, the light-emitting device 1 can more effectively mitigate the temperature rise of the phosphor particles 41.

[0057] <Volume of the first light-transmitting portion and the second light-transmitting portion> FIG. 4 is a diagram schematically illustrating a second example of the configuration of the light-emitting device 1. As shown in FIG. 4, the volume of the second light-transmitting portion 6 may be larger than the volume of the first light-transmitting portion 5. Furthermore, the thickness T2 of the second light-transmitting portion 6 may be larger than the thickness T1 of the first light-transmitting portion 5. The "thickness" here may be the thickness in the direction normal to the first surface 21a of the bottom portion 21. The thickness T1 of the first light-transmitting portion 5 may be the maximum thickness of the first light-transmitting portion 5, for example, the distance between the interface between the first light-transmitting portion 5 and the second light-transmitting portion 6 and the first surface 21a of the bottom portion 21. Alternatively, the minimum thickness of the first light-transmitting portion 5 may be used as the thickness T1 of the first light-transmitting portion 5. In this case, the thickness T1 of the first light-transmitting portion 5 may be the distance between the interface between the first light-transmitting portion 5 and the second light-transmitting portion 6 and the emission surface 3a of the light-emitting element 3. The emission surface 3a of the light-emitting element 3 here is the surface that contacts the second light-transmitting portion 6 and through which the excitation light passes.

[0058] In this way, since the second light-transmitting portion 6 has a large volume (or thickness) and high thermal conductivity, the second light-transmitting portion 6 can more efficiently transfer heat from the wavelength conversion member 4 to the side wall 22 of the housing 2. Therefore, the light emitting device 1 can further mitigate the temperature rise of the phosphor particles 41.

[0059] When the second light-transmitting portion 6 contains water, if the volume of the second light-transmitting portion 6 is larger than the volume of the first light-transmitting portion 5, the luminous efficiency of the light-emitting device 1 can be improved compared to when the volumes are reversed. This is because, as the volume of the second light-transmitting portion 6, which has a small absorption coefficient, becomes larger, the volume of the first light-transmitting portion 5, which has a large absorption coefficient, becomes relatively smaller, and absorption of excitation light and fluorescence becomes relatively less likely to occur.

[0060] <Sealing> The first light-transmitting portion 5 may be positioned in a state where it seals the light-emitting element 3 from the liquid. For example, the first light-transmitting portion 5 may cover the entire light-emitting element 3. That is, the first light-transmitting portion 5 may be in close contact with the entire light-emitting surface 3a and side surfaces of the light-emitting element 3. This allows the first light-transmitting portion 5 to prevent contact between the second light-transmitting portion 6 (here, the liquid) and the light-emitting element 3. In other words, the first light-transmitting portion 5 can protect the light-emitting element from the liquid. For example, the light-emitting device 1 can reduce the possibility of corrosion occurring in components such as the electrodes of the light-emitting element 3 due to contact with the liquid. This can further improve the reliability of the light-emitting device 1.

[0061] <Interface between the first light-transmitting portion and the second light-transmitting portion> 5 is a diagram schematically illustrating a third example of the configuration of the light emitting device 1. The light emitting device 1 according to the third example differs from the light emitting devices 1 according to the first and second examples in the interface 5a between the first light transmitting portion 5 and the second light transmitting portion 6. The interface 5a may be the surface of the first light transmitting portion 5 facing the light emitting element 3 (for example, the liquid surface), or the surface of the second light transmitting portion 6 facing the wavelength conversion member 4.

[0062] As shown in FIG. 5, the interface 5a between the first light transmitting portion 5 and the second light transmitting portion 6 may be curved. Specifically, the interface 5a may have a convex surface that bulges toward the wavelength conversion member 4. The interface 5a may have an arc-like shape in a cross section perpendicular to the first surface 21a of the bottom portion 21, for example. The interface 5a may have a rotationally symmetric shape. The vertex P1 of the interface 5a may be located opposite the light emitting element 3 (for example, the center). In other words, the vertex P1 may be aligned with the light emitting element 3 in the thickness direction of the wavelength conversion member 4.

[0063] According to the light-emitting device 1 of the third example, the first light-transmitting portion 5 can function as a lens. In other words, the interface 5a functions as a lens surface. Therefore, the excitation light from the light-emitting element 3 is refracted at the interface 5a and travels more widely within the second light-transmitting portion 6. This allows the excitation light to be incident on a wider area of ​​the wavelength conversion member 4. This makes it possible to reduce localized heat buildup in the wavelength conversion member 4.

[0064] 5, the periphery P2 of the interface 5a may be in contact with the inner circumferential surface 22a of the side wall 22. The second light-transmitting portion 6 may be in contact with the entire portion of the inner circumferential surface 22a of the side wall 22 from the periphery P2 to the wavelength conversion member 4. As shown in FIG. 5, the periphery P2 of the interface 5a may be closer to the bottom 21 than to the apex P1 of the interface 5a. In this case, the contact area between the second light-transmitting portion 6 and the side wall 22 is large. This can promote heat transfer from the wavelength conversion member 4 to the side wall 22 through the second light-transmitting portion 6, further improving the heat dissipation of the light-emitting device 1.

[0065] As shown in Fig. 5, the inner peripheral surface 22a of the side wall 22 may be perpendicular to the first surface 21a of the bottom portion 21, or may be inclined as shown in Figs. 2 to 4. Conversely, in Figs. 2 to 4, the inner peripheral surface 22a of the side wall 22 may be perpendicular to the first surface 21a of the bottom portion 21. This also applies to other examples described later.

[0066] FIG. 6 is a diagram schematically illustrating a fourth example of the configuration of the light emitting device 1. The light emitting device 1 according to the fourth example differs from the light emitting device 1 according to the third example in the interface 5a between the first light transmitting portion 5 and the second light transmitting portion 6. As shown in FIG. 6, the interface 5a between the first light transmitting portion 5 and the second light transmitting portion 6 may be curved, as in the third example. As shown in FIG. 6, the peripheral edge P2 of the interface 5a may be in contact with the first surface 21a of the bottom portion 21. In other words, the peripheral edge P2 may be located inside the boundary between the inner circumferential surface 22a and the first surface 21a. In other words, the first light transmitting portion 5 may be separated from the side wall 22.

[0067] The second light-transmitting portion 6 may be in contact with the housing 2 over the entire portion of the inner surface 22a of the side wall 22 from the end on the first surface 21a side to the wavelength conversion member 4, and over the entire portion of the first surface 21a outside the periphery P2.

[0068] According to the light emitting device 1 of the fourth example, the second light transmitting portion 6 is in contact with almost the entire inner circumferential surface of the side wall 22. This further promotes heat transfer from the wavelength converting member 4 to the side wall 22 through the second light transmitting portion 6, thereby further improving the heat dissipation of the light emitting device 1. In addition, the heat transfer from the light emitting element 3 to the housing 2 can also be improved.

[0069] Furthermore, a portion of the light from the wavelength conversion member 4 may pass only through the second light transmitting portion 5, be reflected by the first surface 21a of the housing 1, and then pass only through the second light transmitting portion 5 again to be incident on the wavelength conversion member 4. In this path, no reflection loss occurs at the interface 5a between the first light transmitting portion 5 and the second light transmitting portion 6, and therefore optical loss can also be reduced.

[0070] FIG. 7 is a diagram schematically illustrating a fifth example of the configuration of the light-emitting device 1. The light-emitting device 1 according to the fifth example differs from the light-emitting devices 1 according to the first to fourth examples in the interface 5a between the first light-transmitting portion 5 and the second light-transmitting portion 6. As shown in FIG. 7, the interface 5a between the first light-transmitting portion 5 and the second light-transmitting portion 6 may be curved. Specifically, the interface 5a may have a convex surface that bulges toward the light-emitting element 3. The interface 5a may have an arc-like shape in a cross section perpendicular to the first surface 21a of the bottom portion 21. The apex P1 of the interface 5a may be located opposite the light-emitting element 3 (e.g., the center). As shown in FIG. 5, the peripheral edge P2 of the interface 5a may be in contact with the inner circumferential surface 22a of the side wall 22.

[0071] According to the light emitting device 1 of the fifth example, the distance between the light emitting element 3 and the second light transmitting portion 6 is shortened at the vertex P1 of the interface 5a. Therefore, heat from the light emitting element 3 can be transferred to the side wall 22 of the housing 2 via the first light transmitting portion 6.

[0072] <Refractive index> FIG. 8 is a diagram schematically illustrating an example of the refractive index of each part in the light-emitting device 1. FIG. 8 illustrates the refractive index of each part in a cross section, which will be described below. The cross section passes through the light-emitting element 3 and includes a normal to the first surface 21a of the bottom portion 21. As shown in FIG. 8, the refractive index of the first light-transmitting part 5 may be a value between the refractive index of the emission surface 3a of the light-emitting element 3 and the refractive index of the second light-transmitting part 6.

[0073] FIG. 9 is a diagram schematically illustrating an example of the configuration of a light-emitting element 3. In the example of FIG. 9, the light-emitting element 3 includes a support substrate 31, a semiconductor layer 32 formed on the support substrate 31, and a pair of electrodes 33 that apply a voltage to the semiconductor layer 32. The support substrate 31 is translucent to the excitation light. The transmittance of the support substrate 31 with respect to the peak wavelength of the excitation light may be, for example, 60% or more, 80% or more, 90% or more, or 95% or more. The material of the support substrate 31 may be, for example, sapphire, gallium nitride, aluminum nitride, zinc oxide, zinc selenide, silicon carbide, silicon, or zirconium diboride.

[0074] The semiconductor layer 32 includes, for example, a p-type semiconductor layer and an n-type semiconductor layer. These semiconductors are bonded to each other. The pair of electrodes 33 are located, for example, on the opposite side of the semiconductor layer 32 from the support substrate 31. The first electrode 33 is connected to the p-type semiconductor layer, and the second electrode 33 is connected to the n-type semiconductor layer. The light-emitting element 3 is fixed inside the housing 2 with the pair of electrodes 33 located on the bottom 21 side. Conversely, the light-emitting element 3 is fixed inside the housing 2 with the support substrate 31 located on the wavelength conversion member 4 side. The pair of electrodes 33 are connected, for example, to a conductive pattern formed on the first surface 21a of the bottom 21 via a fixing member such as solder.

[0075] The first light-transmitting portion 5 may be in close contact with, for example, the entire light-emitting surface 3a of the light-emitting element 3, the entire side surfaces of the semiconductor layer 32, and the entire pair of electrodes 33. This allows the first light-transmitting portion 5 to protect the light-emitting element 3.

[0076] In such a light-emitting element 3, when a voltage is applied to the pair of electrodes 33, excitation light is generated inside the semiconductor layer 32. Specifically, the excitation light is generated at the junction between the p-type semiconductor layer and the n-type semiconductor layer. The excitation light passes through the support substrate 31 and enters the first light-transmitting portion 5. In this case, the emission surface 3a of the light-emitting element 3 corresponds to the surface of the support substrate 31 opposite to the semiconductor layer 32. Therefore, the refractive index of the emission surface 3a of the light-emitting element 3 corresponds to the refractive index of the support substrate 31. The refractive index of the support substrate 31 is, for example, 1.76 or more. Hereinafter, the refractive index of the emission surface 3a of the light-emitting element 3 will also be referred to as the refractive index of the light-emitting element 3.

[0077] The refractive index of the first light transmitting portion 5 may be smaller than the refractive index of the light emitting element 3. For example, when the first light transmitting portion 5 is made of a silicone resin, the refractive index of the first light transmitting portion 5 is approximately 1.4 or more and 1.55 or less. When the first light transmitting portion 5 is made of an epoxy resin, the refractive index of the first light transmitting portion 5 is approximately 1.5 or more and 1.65 or less.

[0078] The refractive index of the second light-transmitting portion 6 may be smaller than the refractive index of the first light-transmitting portion 5. For example, when the second light-transmitting portion 6 is water, the refractive index of the second light-transmitting portion 6 is approximately 1.33. When the second light-transmitting portion 6 is ethylene glycol, the refractive index of the second light-transmitting portion 6 is approximately 1.43. When the second light-transmitting portion 6 is glycerin, the refractive index of the second light-transmitting portion 6 is approximately 1.46.

[0079] Light is reflected at the boundary between materials with different refractive indices. For example, excitation light can be reflected at the boundary between the light-emitting element 3 and the first light-transmitting section 5 (e.g., the emission surface 3a), and can also be reflected at the boundary between the first light-transmitting section 5 and the second light-transmitting section 6. The excitation light reflected at each boundary can be reflected by the housing 2 and can eventually enter the wavelength conversion member 4. However, due to reflection, the path that the excitation light must take to enter the wavelength conversion member 4 becomes longer, and the amount of excitation light absorbed by materials along that path increases. Therefore, as the reflectance at each boundary increases, the amount of excitation light that penetrates into the wavelength conversion member 4 decreases.

[0080] The reflectance R at the interface for light incident perpendicularly to the interface is expressed by the following equation using the refractive indices n1 and n2 of the different materials.

[0081] R=(n1-n2) 2 / (n1+n2) 2 ···(1) As can be seen from equation (1), the smaller the refractive index difference (n1-n2), the smaller the reflectance R. Conversely, the larger the refractive index difference, the larger the reflectance R.

[0082] When the refractive index of the first light-transmitting portion 5 is outside the range between the refractive index of the light-emitting surface 3 a of the light-emitting element 3 and the second light-transmitting portion 6, either the difference Δn1 between the refractive index of the first light-transmitting portion 5 and the refractive index of the light-emitting element 3 or the difference Δn2 between the refractive index of the first light-transmitting portion 5 and the second light-transmitting portion 6 becomes large. In contrast, when the refractive index of the first light-transmitting portion 5 is a value between the refractive index of the light-emitting surface 3 a of the light-emitting element 3 and the second light-transmitting portion 6, the differences Δn1 and Δn2 can be reduced more uniformly. Because reflectance is proportional to the square of the refractive index difference, uniformly reducing the differences Δn1 and Δn2 can effectively reduce the reflectance at each interface. This allows for a further improvement in the amount of excitation light incident on the wavelength conversion member 4.

[0083] The refractive index of the surface 4b of the wavelength conversion member 4 may be greater than the refractive index of the second light transmitting portion 6, and may also be greater than the refractive index of the first light transmitting portion 5. Here, the refractive index of the surface 4b of the wavelength conversion member 4 may be considered to be the refractive index of the binder layer 42. The refractive index of the wavelength conversion member 4 (e.g., the binder layer 42) may be, for example, about 1.69.

[0084] FIG. 10 is a schematic diagram illustrating a light-emitting device 1A having a structure in which air is used instead of the second light-transmitting portion 6. The refractive index of air is 1.0. Consider the ratio of the amount of excitation light entering the wavelength conversion member 4 to the amount of excitation light emitted by the light-emitting element 3. The inventors calculated the ratios for the light-emitting device 1 and the light-emitting device 1A. This calculation was performed using optical simulation. Water was used as the second light-transmitting portion 6. In the calculation, the refractive index of water was set to 1.33, and the absorption coefficient of water was set to zero. The refractive index of air was set to 1, and the absorption coefficient of air was set to zero. As a result of the calculation, the ratio for the light-emitting device 1A was 55.8%, while the ratio for the light-emitting device 1 was 60.8%. This indicates that the ratio can be improved by using a material for the second light-transmitting portion 6 whose refractive index is closer to that of the wavelength conversion member 4 than that of air.

[0085] Furthermore, when the luminous efficiency of the phosphor particles 41 of the light emitting device 1 and the light emitting device 1A was measured, the luminous efficiency of the phosphor particles 41 of the light emitting device 1A was 79%, while the luminous efficiency of the phosphor particles 41 of the light emitting device 1 was 94%. This is thought to be due in part to the mitigation of the temperature rise of the phosphor particles 41 due to the heat dissipation effect of the second light-transmitting portions 6.

[0086] <Another example> The refractive index of the second light transmitting section 6 may be a value between the refractive index of the binder layer 42 of the wavelength conversion member 4 and the refractive index of the first light transmitting section 5. This makes it possible to uniformly reduce the difference between the refractive index of the binder layer 42 and the refractive index of the second light transmitting section 6, and the difference between the refractive index of the second light transmitting section 6 and the first light transmitting section 5. This makes it possible to further improve the amount of excitation light that enters the wavelength conversion member 4.

[0087] <Lighting equipment> FIG. 11 is a diagram schematically illustrating an example of the configuration of a lighting device 100. The lighting device 100 includes a light-emitting device 1. Light is emitted from the light-emitting device 1 to the outside of the lighting device 100. The lighting device 100 may be used indoors or outdoors. In the former case, the lighting device 100 may be placed on a ceiling or a wall inside the room.

[0088] As shown in FIG. 11, the lighting device 100 includes a light emitting device 1, a lens system 15, and a housing 11.

[0089] The housing 11 may have a side wall 12, a first member 13, and a second member 14. The side wall 12 may have a tubular shape (for example, a cylindrical shape). The first member 13 is located at a first peripheral edge on one side of the side wall 12. The first member 13 has, for example, a plate-like shape, and the peripheral edge of the first member 13 is connected to the first peripheral edge of the side wall 12. The second member 14 is located at a second peripheral edge on the other side of the side wall 12. The second member 14 has, for example, a plate-like shape, and the peripheral edge of the second member 14 is connected to the second peripheral edge of the side wall 12. The internal space of the housing 11 is formed by the side wall 12, the first member 13, and the second member 14.

[0090] The light emitting device 1 may be located in the first member 13. The light emitting device 1 may be disposed to penetrate the first member 13. The light emitting device 1 emits fluorescent light toward the internal space of the housing 4.

[0091] The housing 11 has an illumination opening 11a that allows fluorescence from the light emitting device 1 to pass toward the illumination space. In other words, the illumination opening 11a is an opening that connects the internal space of the housing 11 with the external illumination space. As shown in Fig. 11 , the illumination opening 11a may be formed in the second member 14. The illumination opening 11a may penetrate the second member 14 in a direction along the central axis of the side wall 12.

[0092] Lens system 15 is located in the internal space of housing 4 on the path of the fluorescence from light emitting device 1. Lens system 15 passes the fluorescence from light emitting device 1 toward the outside of housing 4. Lens system 15 includes lens 16, and focuses the fluorescence from light emitting device 1 on a virtual image plane on the side opposite light emitting device 1, i.e., on the opening 4a side. In other words, lens system 15 may be an imaging optical system that forms a light source image of light emitting device 1 as a real image on the image plane.

[0093] 11, the lens system 15 may be composed of a single lens 16, or may be composed of multiple lenses 16. The lens 16 may be a spherical biconvex lens. The lens 16 is formed of a material containing at least one of glass such as optical glass and resin such as acrylic resin.

[0094] Although the lighting device has been described in detail above, the above description is merely an example in all respects, and this disclosure is not limited thereto. Furthermore, the various examples described above can be combined and applied as long as they are not mutually contradictory. It is understood that countless examples not illustrated can be envisioned without departing from the scope of this disclosure.

[0095] This disclosure includes the following:

[0096] In one embodiment, (1) a light emitting device can include a housing having a bottom and sidewalls, a light emitting element located on the bottom surrounded by the sidewalls and emitting excitation light, a wavelength conversion member located on the opposite side of the bottom from the light emitting element and emitting fluorescence based on the excitation light, a first light-transmitting portion located between the light emitting element and the wavelength conversion member and having a thermal conductivity lower than that of the housing, and a second light-transmitting portion located between the first light-transmitting portion and the wavelength conversion member and having a thermal conductivity higher than that of the first light-transmitting portion.

[0097] (2) In the light-emitting device of (1) above, the second light-transmitting portion can contain a liquid.

[0098] (3) In the light-emitting device of (2) above, the liquid may contain at least one of water, ethylene glycol, and glycerin.

[0099] (4) In the light emitting device of (2) or (3), the first light transmitting portion includes a solid and can be positioned in a state where the light emitting element is sealed from the liquid.

[0100] (5) In the light emitting device according to any one of (2) to (4), the first light transmitting portion includes a solid and can cover the entire light emitting element.

[0101] (6) In the light emitting device according to any one of (1) to (5), the second light transmitting portion can be in contact with an inner circumferential surface of the side wall.

[0102] (7) In the light emitting device according to any one of (1) to (6) above, the first light transmitting portion can be in contact with an inner circumferential surface of the side wall.

[0103] (8) In the light emitting device of any one of (1) to (7), the second light-transmitting portion can be filled in a space surrounded by the first light-transmitting portion, the side wall, and the wavelength conversion member.

[0104] (9) In the light emitting device according to any one of (1) to (8), the second light transmitting portion may have a larger volume than the first light transmitting portion.

[0105] (10) In any one of the light-emitting devices (1) to (9) above, the refractive index of the first light-transmitting portion may be a value between the refractive index of the light-emitting element and the refractive index of the second light-transmitting portion.

[0106] (11) In any one of the light-emitting devices (1) to (10) above, the wavelength conversion member may include a plurality of phosphor particles and a binder layer bonding the plurality of phosphor particles together, and the refractive index of the binder layer may be greater than the refractive index of the second light-transmitting portion.

[0107] (12) In any one of the light-emitting devices (1) to (11) above, the wavelength conversion member may include a plurality of phosphor particles and a binder layer bonding the plurality of phosphor particles together, and the refractive index of the second light-transmitting portion may be a value between the refractive index of the binder layer and the refractive index of the first light-transmitting portion.

[0108] (13) In any one of the light-emitting devices (1) to (12) above, the wavelength conversion member may include a plurality of phosphor particles and a binder layer bonding the plurality of phosphor particles together, and the refractive index of the second light-transmitting portion may be smaller than the refractive index of the binder layer and the refractive index of the first light-transmitting portion, and larger than the refractive index of air.

[0109] (14) In any one of the light-emitting devices (1) to (13), the wavelength conversion member may include a plurality of phosphor particles and a binder layer bonding the plurality of phosphor particles together, and the binder layer may be mainly composed of glass.

[0110] (15) In the light-emitting device according to any one of (1) to (14), the excitation light can include purple light.

[0111] (16) An illumination device can include any one of the light-emitting devices described in (1) to (15) above, and a lens system that transmits the fluorescence emitted from the light-emitting device to the outside. [Explanation of symbols]

[0112] 1. Light-emitting device 100 lighting equipment 2. Case 21 Bottom 22 Side wall 3. Light-emitting device 4 Wavelength conversion material 41 Phosphor particles 42 binder layer 5 1st transparent part 6 2nd transparent part

Claims

1. a housing having a bottom and a sidewall; a light-emitting element located at the bottom and surrounded by the sidewall, the light-emitting element emitting excitation light; a wavelength conversion member that is located on the opposite side of the bottom portion with respect to the light emitting element and that emits fluorescence based on the excitation light; a first light-transmitting portion located between the light-emitting element and the wavelength conversion member and having a thermal conductivity lower than a thermal conductivity of the housing; a second light transmitting portion located between the first light transmitting portion and the wavelength converting member, the second light transmitting portion having a thermal conductivity higher than that of the first light transmitting portion; A light emitting device comprising:

2. 2. The light emitting device according to claim 1, The second light-transmitting portion includes a liquid.

3. 3. The light emitting device according to claim 2, The light-emitting device, wherein the liquid contains at least one of water, ethylene glycol, and glycerin.

4. 4. The light emitting device according to claim 2, The light emitting device, wherein the first light transmitting portion includes a solid and is positioned in a state where the light emitting element is sealed from the liquid.

5. 4. The light emitting device according to claim 2, The light-emitting device, wherein the first light-transmitting portion includes a solid and covers the entire light-emitting element.

6. 4. The light emitting device according to claim 1, The second light-transmitting portion is in contact with an inner circumferential surface of the side wall.

7. 4. The light emitting device according to claim 1, The first light transmitting portion is in contact with an inner circumferential surface of the side wall.

8. 4. The light emitting device according to claim 1, the second light-transmitting portion fills a space surrounded by the first light-transmitting portion, the sidewall, and the wavelength conversion member.

9. 4. The light emitting device according to claim 1, A light emitting device, wherein the volume of the second light transmitting portion is larger than the volume of the first light transmitting portion.

10. 4. The light emitting device according to claim 1, A light emitting device, wherein the refractive index of the first light transmitting portion is a value between the refractive index of the light emitting element and the refractive index of the second light transmitting portion.

11. 4. The light emitting device according to claim 1, the wavelength conversion member includes a plurality of phosphor particles and a binder layer that bonds the plurality of phosphor particles together; a refractive index of the binder layer greater than a refractive index of the second light-transmitting portion;

12. 4. The light emitting device according to claim 1, the wavelength conversion member includes a plurality of phosphor particles and a binder layer that bonds the plurality of phosphor particles together; a refractive index of the second light-transmitting portion having a value between a refractive index of the binder layer and a refractive index of the first light-transmitting portion;

13. (Including the case where the second light-transmitting portion is water) 4. The light emitting device according to claim 1, the wavelength conversion member includes a plurality of phosphor particles and a binder layer that bonds the plurality of phosphor particles together; a refractive index of the second light-transmitting portion is smaller than the refractive index of the binder layer and the refractive index of the first light-transmitting portion, and is larger than the refractive index of air.

14. 4. The light emitting device according to claim 1, the wavelength conversion member includes a plurality of phosphor particles and a binder layer that bonds the plurality of phosphor particles together; A light-emitting device, wherein the binder layer is primarily made of glass.

15. 4. The light emitting device according to claim 1, A light-emitting device, wherein the excitation light includes purple light.

16. 4. An illumination device comprising: the light-emitting device according to claim 1; and a lens system that transmits the fluorescence emitted from the light-emitting device to the outside.

Images