Light emission device and illumination apparatus

A light emission device includes a substrate, a light emission element, and a wavelength converter. The substrate has a first surface. The light emission element is mounted on the first surface and emits excitation light. The wavelength converter is positioned on at least a portion of the first surface and the light emission element. The wavelength converter converts the excitation light into illumination light. The substrate includes at least one of a recess or a projection. The recess has a second surface and a third surface. The second surface is positioned below the first surface. The third surface connects the second surface and the first surface to each other. The projection projects upward from the first surface. The wavelength converter is in contact with at least one of at least a portion of the second surface or at least a portion of the projection.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent Application No. 2020-196995 (filed on Nov. 27, 2020), the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a light emission device and an illumination apparatus.

BACKGROUND OF INVENTION

A known light emission device includes a light emission element positioned in a space surrounded by a frame. The frame is filled with resin to seal the light emission element (see, for example, Patent Literature 1).

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2019-117729

SUMMARY

In one embodiment of the present disclosure, a light emission device includes a substrate, a light emission element, and a wavelength converter6. The substrate has a first surface. The light emission element is mounted on the first surface and emits excitation light. The wavelength converter is positioned on at least a portion of the first surface and the light emission element. The wavelength converter converts the excitation light into illumination light. The substrate includes at least one of a recess or a projection. The recess has a second surface and a third surface. The second surface is positioned below the first surface. The third surface connects the second surface and the first surface to each other. The projection projects upward from the first surface. The wavelength converter is in contact with at least one of at least a portion of the second surface or at least a portion of the projection.

In one embodiment of the present disclosure, an illumination apparatus includes the light emission device and a mount board. The light emission device is mounted on the mount board.

DESCRIPTION OF EMBODIMENTS

Example of Structure of Light Emission Device10

As illustrated inFIGS.1,2, and3, the light emission device10includes an element substrate2, a light emission element3, and a wavelength converter6. The element substrate2has a first surface21and includes recesses22and projections26. The light emission element3is mounted on the first surface21of the element substrate2. The wavelength converter6is positioned above the light emission element3and above the first surface21of the element substrate2. The wavelength converter6covers upper and side surfaces of the light emission element3. The wavelength converter6converts light emitted by the light emission element3into light having a wavelength different from a wavelength of the light emitted by the light emission element3. The light emission device10emits the light converted by the wavelength converter6. InFIG.1and other figures, an upward direction relative to the light emission device10corresponds to a positive Z-axis direction.

The light emission element3emits light having a peak wavelength in a wavelength range of 360 nm or more and 430 nm or less. The wavelength range of 360 nm or more and 430 nm or less is also referred to as a violet light range.

The light emitted from the light emission element3enters the wavelength converter6. The wavelength converter6converts the incoming light into light having a peak wavelength in a wavelength range of 360 nm or more and 780 nm or less, and emits the converted light. The wavelength range of 360 nm or more and 950 nm or less is also referred to as a visible light range. The visible light range includes the violet light range. Visible light includes violet light. The wavelength converter6is excited by the light from the light emission element3, and thereby emits light with a peak wavelength range in the visible light range. The light emitted by the light emission element3is also referred to as excitation light. The light emission element3included in the light emission device10is also referred to as an excitation-light emission element.

The components of the light emission device10will now be described.

The element substrate2is also referred to simply as a substrate. The element substrate2may be made of, for example, an insulative material. The element substrate2may be made of, for example, a ceramic material, such as aluminum oxide (alumina) or mullite, a glass ceramic material, or a composite material of more than one of these materials. The element substrate2may be made of, for example, a polymeric resin material in which fine particles of a metal oxide enabling adjustment of thermal expansion are dispersed. The element substrate2may include aluminum nitride or silicon carbide. Accordingly, the element substrate2can have an increased thermal conductivity, and the light emission device10can have an improved heat dissipation performance.

The element substrate2has the first surface21facing in the positive Z-axis direction. The light emission element3is mounted on the first surface21of the element substrate2. The element substrate2includes first wiring lines31and second wiring lines32for supplying power to the light emission element3. The first wiring lines31extend in a direction crossing the first surface21, and are exposed in plan view of the first surface21. The first wiring lines31may be flush with the first surface21, or project upward from the first surface21. The first wiring lines31are also referred to as via wiring lines. The second wiring lines32extend in a direction along the first surface21. The first wiring lines31may extend to a surface of the element substrate2facing in a negative Z-axis direction (also referred to as a back surface). In this case, the second wiring lines32may be positioned on the back surface of the element substrate2. The second wiring lines32may be positioned both on the back surface of the element substrate2and in the element substrate2. The first wiring lines31and the second wiring lines32may be made of a conductive material, such as tungsten, molybdenum, manganese, or copper. The first wiring lines31and the second wiring lines32may be formed by, for example, preparing metal paste by adding an organic solvent to tungsten powder, printing the metal paste on ceramic green sheets used to form the element substrate2in a predetermined pattern, and stacking and firing the ceramic green sheets. Each of the first wiring lines31and the second wiring lines32may include a plating layer of nickel, gold, or the like formed on a surface thereof to suppress oxidization. The first wiring lines31and the second wiring lines32are also referred to as power-feed wiring lines.

The element substrate2further includes a reflective film40on the first surface21. The reflective film40is positioned on the first surface21to cover at least a portion of the first surface21. The reflective film40may be made of a material obtained by, for example, adding a white material, such as titanium oxide, to a silicone-resin-based material. The reflective film40is not limited to this example, and may be formed to have a reflectance higher than the reflectance of the first surface21. When the reflective film40is positioned on the first surface21, the first surface21does not easily absorb the excitation light emitted from the light emission element3and the illumination light obtained by the wavelength converter6. As a result, the excitation light and the illumination light can be efficiently emitted to the outside of the light emission device10.

The first surface21of the element substrate2includes the recesses22. Each recess22is a space defined by a second surface23and a third surface24. The recess22includes an opening at the same height as the height of the first surface21, and communicates with a space above the recess22through the opening. The recess22may include at least one hole portion.

The second surface23extends in a direction along the first surface21and is positioned deeper into the element substrate2than the first surface21. In other words, the second surface23is positioned below the first surface21. The third surface24connects the first surface21and the second surface23to each other and extends in a direction crossing the first surface21and the second surface23. When, for example, the recess22is rectangular in plan view, the recess22may include more than one third surfaces24. When the recess22is circular in plan view, the third surface24may be cylindrical.

The reflective film40may at least partially cover a portion of the third surface24of the recess22, the portion facing the light emission element3. The reflective film40may cover the third surface24of the recess22over an area connected to a portion of the second surface23. When the reflective film40covers the third surface24of the recess22, the excitation light or the illumination light entering the recess22is reflected toward a region above the element substrate2and is not easily absorbed by the recess22.

The wavelength converter6extends into at least a portion of the recess22. The wavelength converter6is in contact with at least a portion of the second surface23. When the wavelength converter6extends into the recess22and is in contact with at least a portion of the second surface23, the element substrate2and the wavelength converter6can be in contact with each other over a large area. As a result, the wavelength converter6can more strongly adhere to the element substrate2. In other words, the wavelength converter6is not easily removed from the element substrate2. When the wavelength converter6is in contact with at least a portion of the third surface24of the recess22, the wavelength converter6can be in contact with the element substrate2in at least two directions. As a result, the wavelength converter6is not easily removed from the element substrate2even when the wavelength converter6receives an external force.

The wavelength converter6is in direct contact with at least a portion of the second surface23. In other words, the wavelength converter6is in contact with at least a portion of the second surface23without the reflective film40being disposed therebetween. The wavelength converter6generates heat upon conversion of the excitation light into the illumination light. The generated heat is transmitted to the element substrate2and dissipated toward the back surface (surface in the negative Z-axis direction) of the element substrate2. The thickness of the element substrate2at the first surface21is denoted by T1. The thickness is the size of the element substrate2in the Z-axis direction. The thickness of the element substrate2at the second surface23is denoted by T2. Since T2is less than T1, the second surface23is closer to the back surface than the first surface21. Since the second surface23is closer to the back surface than the first surface21, the thermal resistance between the second surface23and the back surface is less than the thermal resistance between the first surface21and the back surface. As a result, the amount of heat dissipated from the wavelength converter6extending to the second surface23to the back surface through the second surface23may be greater than the amount of heat dissipated from the wavelength converter6positioned on the first surface21to the back surface through the first surface21. In other words, when the wavelength converter6is in contact with the second surface23, heat can be more easily dissipated from the wavelength converter6.

Assume that the thermal conductivity of the reflective film40is less than the thermal conductivities of the element substrate2and the wavelength converter6. In this case, the amount of heat dissipated directly from the wavelength converter6to the element substrate2without the reflective film40being disposed therebetween is greater than the amount of heat dissipated from the wavelength converter6to the element substrate2through the reflective film40. Therefore, when the wavelength converter6is in connect with at least a portion of the second surface23without the reflective film40being disposed therebetween, heat can be more easily dissipated from the wavelength converter6.

The depth of the recess22in the element substrate2may be less than the thickness of the element substrate2at the second surface23. In other words, the distance between the first surface21and the second surface23of the element substrate2may be less than the thickness of the element substrate2at the second surface23. In this case, the thickness of the element substrate2at the recess22is equal to or greater than half the thickness of the element substrate2at other portions. As a result, the reduction in the thickness of the element substrate2due to the recess22does not easily affect the strength of the element substrate2.

The first surface21of the element substrate2includes the projections26projecting upward from the first surface21. Each projection26includes a fourth surface27and a fifth surface28. The fourth surface27extends in a direction along the first surface21and is further away from the element substrate2than the first surface21. The fifth surface28extends in a direction crossing the first surface21and the fourth surface27to connect the first surface21and the fourth surface27to each other. A top portion (upper surface) of the projection26is not necessarily flat. The top portion (upper surface) of the projection26may be a curved surface. The top portion of the projection26may include an inclined surface in a region close to the light emission element3. In such a case, light can be more efficiently emitted in an upward direction.

The wavelength converter6is in contact with at least a portion of the projection26. When the wavelength converter6is in contact with the projection26, the element substrate2and the wavelength converter6can be in contact with each other over a large area. As a result, the wavelength converter6can more strongly adhere to the element substrate2. In other words, the wavelength converter6is not easily removed from the element substrate2. The wavelength converter6is in contact with at least a portion of the fifth surface28of the projection26. When the wavelength converter6is in contact with at least a portion of the fifth surface28of the projection26, the wavelength converter6can be in contact with the element substrate2in at least two directions. As a result, the wavelength converter6is not easily removed from the element substrate2even when the wavelength converter6receives an external force.

The reflective film40may cover at least a portion of the fifth surface28of the projection26, the portion being positioned at a side adjacent to the light emission element3. When the reflective film40covers at least a portion of the fifth surface28of the projection26positioned at a side adjacent to the light emission element3, the excitation light or the illumination light reaching the projection26is reflected toward a region above the element substrate2and is not easily absorbed by the projection26. When the fifth surface28of the projection26reflects the excitation light or the illumination light, the excitation light emitted from a side surface of the light emission element3and the illumination light into which the excitation light is converted more easily travel upward than when the projection26is not provided. As a result, light can be more efficiently emitted in an upward direction.

Referring toFIG.3, the depth of the recess22from the first surface21, that is, the distance from the first surface21to the second surface22, is denoted by H1. The height of the projection26from the first surface21, that is, the distance from the first surface21to the top portion of the projection26, is denoted by H2. H2is less than H1. In this case, light traveling from the light emission element3toward the first surface21of the element substrate2does not easily enter the projection26. In other words, emission of the excitation light or the illumination light from the sides of the light emission device10can be reduced. As a result, light can be more efficiently emitted over a wide angle range.

The projection26may be positioned farther from the light emission element3than the recess22. When more than one recesses22and more than one projections26are provided, the projection26closest to the light emission element3may be positioned farther from the light emission element3than the recess22closest to the light emission element3. The recesses22and the projections26may be arranged along concentric circles with the light emission element3at the center. In this case, the projections26are positioned far from the light emission element3, and therefore do not easily absorb the excitation light or the illumination light. As a result, light can be more efficiently emitted.

In the present embodiment, the light emission element3is a light emission diode (LED). The LED emits light to the outside as a result of recombination of electrons and holes in a PN junction between a P-type semiconductor and an N-type semiconductor. The light emission element3is not limited to an LED, and may be other light-emitting devices.

The light emission element3is mounted on the first surface21of the element substrate2. The light emission element3is electrically connected to the first wiring lines31with a brazing material, solder, or the like on the first surface21of the element substrate2. Two first wiring lines31are provided as a pair so that each first wiring line31is connected to one of positive and negative electrodes of the light emission element3. The light emission element3is positioned on the first wiring lines31to cover at least portions of the first wiring lines31in see-through plan view of the first surface21of the element substrate2. The light emission element3may be larger than the first wiring lines31in see-through plan view.

The light emission element3may be mounted on the element substrate2by flip-chip connection. When the light emission element3is mounted by flip-chip connection, the first wiring lines31and the brazing material, solder, or the like are covered by the light emission element3in plan view of the first surface21. When the first wiring lines31and the brazing material, solder, or the like are covered by the light emission element3, the first wiring lines31and the brazing material, solder, or the like do not easily receive the excitation light emitted by the light emission element3or the illumination light obtained by the wavelength converter6. Therefore, the first wiring lines31and the brazing material, solder, or the like do not easily absorb the excitation light or the illumination light. As a result, the light emission device10can more efficiently emit light.

In a comparative example, the light emission element3is mounted on the element substrate2by wire bonding. In such a case, a wire includes at least a portion that is not covered by the light emission element3. In this case, the wire may absorb the excitation light or the illumination light. In the present embodiment, the light emission device10includes the light emission element3mounted on the element substrate2by flip-chip connection. Therefore, absorption of the excitation light or the illumination light is reduced compared to when the light emission element3is mounted by wire bonding as in the comparative example. As a result, the light emission device10can more efficiently emit light.

The number of light emission elements3mounted on the first surface21of the element substrate2is one inFIG.1and other figures. However, the number of light emission elements3is not particularly limited, and may be two or more. When the number of light emission elements3is two or more, the light emission elements3are positioned so as not to overlap in plan view of the first surface21.

The light emission element3may include a light-transmissive base and an optical semiconductor layer formed on the light-transmissive base. The light-transmissive base may include a material on which an optical semiconductor layer can be grown by a chemical vapor deposition method, such as a metal-organic chemical vapor deposition method or a molecular beam epitaxy method. The light-transmissive base may be made of, for example, sapphire, gallium nitride, aluminum nitride, zinc oxide, zinc selenide, silicon carbide, silicon (Si), or zirconium diboride. The light-transmissive base may have a thickness of, for example, 50 μm or more and 1000 μm or less.

The optical semiconductor layer may include a first semiconductor layer formed on the light-transmissive base, a light emission layer formed on the first semiconductor layer, and a second semiconductor layer formed on the light emission layer. The first semiconductor layer, the light emission layer, and the second semiconductor layer may be formed of, for example, a Group III nitride semiconductor, a Group III-V semiconductor, such as gallium phosphide or gallium arsenide, or a Group III nitride semiconductor, such as gallium nitride, aluminum nitride, or indium nitride.

The first semiconductor layer may have a thickness of, for example, 1 μm or more and 5 μm or less. The light emission layer may have a thickness of, for example, 25 nm or more and 150 nm or less. The second semiconductor layer may have a thickness of, for example, 50 nm or more and 600 nm or less.

The wavelength converter6is positioned on the first surface21of the element substrate2. The wavelength converter6fills the space above the light emission element3to seal the light emission element3. The wavelength converter6may be formed by applying a paste on the first surface21of the element substrate2and then curing the paste. Alternatively, the wavelength converter6may be formed by placing a sheet on the first surface21of the element substrate2and then curing the sheet.

The excitation light emitted from the light emission element3directly enters the wavelength converter6. The wavelength converter6converts the incoming excitation light, which is violet light, into light having a peak wavelength in a wavelength range of 360 nm or more and 780 nm or less, and emits the converted light.

The wavelength converter6may include a light-transmissive member60that transmits light and phosphor elements61.

The light-transmissive member60may be made of, for example, an insulative resin material, such as fluorocarbon resin, silicone resin, acrylic resin, or epoxy resin, that transmits light or a glass material that transmits light. The light-transmissive member60may have a refractive index of, for example, 1.4 or more and 1.6 or less.

The light-transmissive member60contains the phosphor elements61. The phosphor elements61may be substantially evenly dispersed in the light-transmissive member60. The phosphor elements61convert the incoming violet light into light with various peak wavelengths.

The phosphor elements61may convert the violet light into, for example, light specified by a spectrum with a peak wavelength in a wavelength range from 400 nm to 500 nm, that is, blue light. In this case, the phosphor elements61may contain a material such as BaMgAl10O17:Eu, (Sr,Ca,Ba)10(PO4)6Cl2:Eu, or (Sr,Ba)10(PO4)6Cl2:Eu.

The phosphor elements61may convert the violet light into, for example, light specified by a spectrum with a peak wavelength in a wavelength range from 450 nm to 550 nm, that is, blue green light. In this case, the phosphor elements61may contain a material such as (Sr,Ba,Ca)5(PO4)3Cl:Eu or Sr4Al14O25:Eu.

The phosphor elements61may convert the violet light into, for example, light specified by a spectrum with a peak wavelength in a wavelength range from 500 nm to 600 nm, that is, green light. In this case, the phosphor elements61may contain a material such as SrSi2(O,Cl)2N2:Eu, (Sr,Ba,Mg)2SiO4:Eu2+, ZnS:Cu,Al, or Zn2SiO4:Mn.

The phosphor elements61may convert the violet light into, for example, light specified by a spectrum with a peak wavelength in a wavelength range from 600 nm to 700 nm, that is, red light. In this case, the phosphor elements61may contain a material such as Y2O2S:Eu, Y2O3:Eu, SrCaClAlSiN3:Eu2+, CaAlSiN3:Eu, or CaAlSi(ON)3:Eu.

The phosphor elements61may convert the violet light into, for example, light specified by a spectrum with a peak wavelength in a wavelength range from 680 nm to 800 nm, that is, near-infrared light. The near-infrared light may include light with a wavelength range from 680 nm to 2500 nm. In this case, the phosphor elements61may contain a material such as 3Ga5O12:Cr.

The combination of the types of the phosphor elements61included in the wavelength converter6is not particularly limited. The material contained in the phosphor elements61is not limited to the above-described materials, and various other materials may be contained.

As described above, the phosphor elements61convert the violet light entering the wavelength converter6from the light emission element3into light with a peak wavelength different from that of the violet light. The peak wavelength of the converted light may be included in a visible light range. The converted light may have a plurality of peak wavelengths depending on the combination of the phosphor elements61included in the wavelength converter6. For example, when the phosphor elements61contain a material emitting blue fluorescent light, a material emitting blue green fluorescent light, and a material emitting green fluorescent light, the converted light has wavelengths of blue, blue green, and green as peak wavelengths. When the phosphor elements61contain only one type of material, the converted light has a peak wavelength of that material. The phosphor elements61are not limited to these examples, and may contain materials in various combinations. The color of light emitted from the wavelength converter6is determined on the basis of the types of materials contained in the phosphor elements61. In other words, the converted light may have various spectra.

In the present embodiment, the light emission device10is capable of emitting light having various spectra depending on the combination of the materials contained in the phosphor elements61. For example, the light emission device10is capable of emitting light with a spectrum of direct light from the sun, a spectrum of sunlight that has reached a predetermined depth in the sea, a spectrum of candlelight, a spectrum of light of a firefly, or the like. In other words, the light emission device10is capable of emitting light in various colors. The light emission device10is capable of emitting light at various color temperatures.

As described above, in the present embodiment, the light emission device10includes the element substrate2including at least one of the recess22or the projection26positioned on the first surface21. The wavelength converter6is in contact with at least one of at least a portion of the second surface23or at least a portion of the projection26. Thus, the wavelength converter6is not easily removed from the element substrate2. The wavelength converter6is simply placed on the element substrate2and is not easily removed from the element substrate2. As a result, in the present embodiment, the light emission device10includes a simple structure, and the reliability thereof can be maintained or improved. When the element substrate2includes both the recess22and the projection26, the possibility of removal of the wavelength converter6can be further reduced. When at least one of the recess22or the projection26is positioned on the first surface21, the light emission device10can more efficiently emit light.

Other Embodiments of Light Emission Device10

The area of the opening of the recess22may be less than the area of the second surface23. For example, as illustrated inFIG.4, a length (L1) of the opening of the recess22in sectional view may be shorter than a length (L2) of the second surface23in sectional view. In plan view of the element substrate2, an edge of the opening of the recess22may be positioned inside an edge of the second surface23. An angle (θ1) between the second surface23and the third surface24defining the recess22may be acute. The shape illustrated inFIG.4is also referred to as an inverse-tapered shape.

As illustrated inFIG.5, the recess22may include at least two sections in sectional view. The recess22may include an upper section (section closer to the first surface21) and a lower section (section farther from the first surface21). The area of the lower section may be smaller than the area of the upper section in plan view of the element substrate2. The shape illustrated inFIG.5is also referred to as a cavity shape.

When the wavelength converter6is disposed in the recess22including one of the structures illustrated inFIGS.4and5, the wavelength converter6is not easily removed from the first surface21of the element substrate2. In other words, the wavelength converter6can more strongly adhere to the element substrate2. The space in the recess22may have a cross-sectional area less than that of the second surface23at least at a location between the first surface21and the second surface23in the height direction. In other words, the space in the recess22may have a constricted shape in sectional view. Also in this case, the wavelength converter6is not easily removed from the first surface21of the element substrate2.

As illustrated inFIG.6, the recess22may be structured such that an angle (θ2) between the third surface24positioned at a side far from the light emission element3(side in the positive Y-axis direction inFIG.6) and the second surface23is obtuse. When the recess22is rectangular in plan view, the third surface24at the side far from the light emission element3is one of multiple third surfaces24facing the third surface24connected to the light emission element3in sectional view. When the recess22is circular in plan view, the third surface24at the side far from the light emission element3is the third surface24in a region facing a region connected to the light emission element3. When the excitation light or the illumination light enters the recess22including the structure illustrated inFIG.6from the light emission element3, the entering light is reflected by the third surface24. Since the angle (θ2) between the third surface24at the side far from the light emission element3and the second surface23is obtuse, the light entering in a direction from the light emission element3is easily reflected upward. As a result, the light emission device10can emit a greater amount of light to the outside. In other words, the light emission device10can more efficiently emit light.

As illustrated inFIG.7, the recess22may be groove-shaped and surround the light emission element3in plan view of the element substrate2. The recess22may extend discontinuously instead of extending along the entire periphery of the light emission element3. For example, the recess22may be groove-shaped and extend in one direction, such as the X-axis direction or the Y-axis direction. When the recess22is groove-shaped, the wavelength converter6can extend into the recess22over a larger area. As a result, the wavelength converter6can more strongly adhere to the element substrate2.

As illustrated inFIG.8, the element substrate2may include at least a first layer201and a second layer202. The number of layers is not limited to two, and may be three or more. In other words, the element substrate2may include at least two layers. Assume that the boundary between the first layer201and the second layer202is exposed in the space in the recess22. The boundary between the first layer201and the second layer202may include small gaps. The light-transmissive member60extending into the recess22may include intrusive portions601extending into the gaps at the boundary between the first layer201and the second layer202. In other words, at least a portion of the wavelength converter6may extend into a space between adjacent ones of the layers of the element substrate2. When the light-transmissive member60includes the intrusive portions601, the wavelength converter6including the light-transmissive member60is not easily removed from the element substrate2including the recess22. In other words, the wavelength converter6can more strongly adhere to the element substrate2.

The light emission device10emits the illumination light toward a region above (in the positive Z-axis direction from) the wavelength converter6on the first surface21of the element substrate2. The light emission device10may emit the illumination light sideways (in the X-axis direction or Y-axis direction) from the wavelength converter6. Thus, light can be more efficiently emitted.

The light emission device10may be obtained by forming two or more light emission devices10on the element substrate2and then separating the light emission devices10from each other by dicing the element substrate2. Alternatively, the light emission device10may be obtained by mounting a plurality of light emission elements3on the element substrate2, placing or applying the wavelength converter6, and then separating the light emission devices10from each other. The element substrate2may be divided such that one light emission device10includes one light emission element3, or such that one light emission device10includes two or more light emission elements3.

As illustrated inFIGS.9,10, and11, the first surface21of the element substrate2may further include a second recess29. The second recess29is positioned below the light emission element3. In other words, the second recess29is positioned to overlap the light emission element3in plan view of the first surface21. The second recess29may have a depth less than the depth of the recess22positioned not to overlap the light emission element3as illustrated inFIG.9, equal to the depth of the recess22as illustrated inFIG.10, or greater than the depth of the recess22as illustrated inFIG.11. When the second recess29is provided, the wavelength converter6can extend into the second recess29below the light emission element3. Therefore, the wavelength converter6serves as a joining material for joining the light emission element3and the element substrate2to each other and increases the bonding strength between the light emission element3and the element substrate2. When the depth of the second recess29is equal to the depth of the recess22, the recesses do not receive uneven stress upon application of heat to the wavelength converter6and other components, and cracks or the like are not easily formed in the element substrate2. When the depth of the second recess29is greater than the depth of the recess22, a larger amount of joining material is provided at a location overlapping the light emission element3, and the bonding strength can be increased accordingly. When the depth of the second recess29is less than the depth of the recess22, the bonding strength can be increased, and the bonding strength can be increased with less possibility of deformation of the substrate compared to when the depth is large. Accordingly, the light emission element3can be stably mounted.

Example of Structure of Illumination Apparatus100

As illustrated inFIG.12, in one embodiment, an illumination apparatus100includes at least one light emission device10and emits light emitted from the light emission device10as illumination light. When the illumination apparatus100includes a plurality of light emission devices10, the illumination apparatus100may control the intensities of light emitted from the light emission devices10individually or in association with each other. The spectra of light emitted from the light emission devices10may be the same or differ from each other. The illumination apparatus100may control the intensities of light emitted from the light emission devices10in association with each other to control the spectrum of light obtained by combining light emitted from the light emission devices10. The light obtained by combining light emitted from the light emission devices10is also referred to as combined light. The illumination apparatus100may emit the combined light as the illumination light. The illumination apparatus100may select at least one or more of the light emission devices10and cause the selected light emission devices10to emit illumination light.

The illumination apparatus100may further include a mount board110on which the light emission devices10are mounted. The illumination apparatus100may further include a housing120and a pair of end plates130. The housing120includes a groove-shaped portion in which the mount board110is placed. The end plates130cover end portions at short sides of the housing120. The number of light emission devices10mounted on the mount board110may be one or two or more. The light emission devices10may be arranged on the mount board110in one line, or in a grid pattern or a staggered pattern. The arrangement of the light emission devices10is not limited to these examples. The light emission devices10may be mounted on the mount board110in various types of arrangements.

The mount board110may include a circuit board including a wiring pattern. The circuit board may include, for example, a printed board, such as a rigid board, a flexible board, or a rigid-flexible board. The circuit board may include a drive circuit that controls the light emission device10.

The mount board110functions to dissipate heat emitted by the light emission devices10to the outside. The mount board110may be made of, for example, a metal material, such as aluminum, copper, or stainless steel, an organic resin material, or a composite material containing these materials.

The mount board110may have an elongated rectangular shape in plan view. The shape of the mount board110is not limited to this, and may be various other shapes.

The illumination apparatus100may further include a lid portion140for enclosing the mount board110and the light emission device10disposed in the housing120. The lid portion140may be made of a light-transmissive material to allow transmission of the illumination light emitted from the light emission devices10to the outside of the illumination apparatus100. The lid portion140may be made of, for example, a resin material, such as acrylic resin, or glass. The lid portion140may have an elongated rectangular shape in plan view. The shape of the lid portion140is not limited to this, and may be various other shapes. The illumination apparatus100may further include a sealing member provided between the lid portion140and the housing120. In this case, water, dust, or the like does not easily enter the housing120. As a result, the illumination apparatus100has improved reliability irrespective of the environment in which the illumination apparatus100is installed. The illumination apparatus100may further include an absorbent in the housing120.

The drawings illustrating the embodiments of the present disclosure are schematic. In the drawings, dimensional ratios or the like may differ from the actual ones.

Although embodiments of the present disclosure have been described based on the drawings and examples, the present disclosure is not limited to the above-described embodiments. Note that various modifications or alterations are possible by those skilled in the art based on the present disclosure. Therefore, note that those modifications or alterations are included in the scope of the present disclosure. For example, functions or the like included in each component or the like may be rearranged without any logical inconsistencies, and a plurality of component or the like may be combined together or divided. Other changes are also possible without departing from the spirit of the present disclosure.

In the present disclosure, terms such as “first” and “second” are identifiers for distinguishing components. In the present disclosure, the numbers of components distinguished by the terms such as “first” and “second” may be interchanged with each other. For example, the identifier “first” of the first surface21and the identifier “second” of the second surface23may be interchanged with each other. The identifiers are interchanged simultaneously. The components are distinguishable even after their identifiers are interchanged. The identifiers may be omitted. Components whose identifiers are omitted are distinguished by reference signs. In the present disclosure, description of identifiers such as “first” and “second” alone is not to be used for interpretation of the order of components or as basis for assuming that identifiers of smaller numbers are present.

In the present disclosure, the X axis, the Y axis, and the Z axis are provided for convenience of description, and are interchangeable. Components of the present disclosure have been described by using the orthogonal coordinate system including the X axis, the Y axis, and the Z axis. Positional relationships between the components of the present disclosure are not limited to orthogonal relationships.