Light-emitting device

Abstract

To provide a light-emitting device that can inhibit a surface of a heat-conductive substrate from being scratched.SOLUTION: A light-emitting device 1 comprises: a heat-conductive substrate 20 including a first region A1 and a second region A2 surrounding the first region A1; and a light-emitting member 10 disposed in the first region A1. The heat-conductive substrate 20 has a surface protective layer 22 disposed in the second region A2. The Mohs hardness of the surface protective layer 22 is higher than the Mohs hardness of gold.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to light emitting devices. [Background technology]

[0002] Light source modules using solid-state light-emitting elements such as LEDs or semiconductor lasers as light sources are used in projectors, endoscopes, vehicle headlamps, lighting devices, liquid crystal display devices, etc. This type of light source module includes, for example, a light source and a phosphor device that emits fluorescence when light emitted by the light source is incident thereon.

[0003] As this type of phosphor device, a light emitting device having a light emitting member made of phosphor ceramics is known (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-154220 Summary of the Invention [Problem to be solved by the invention]

[0005] An example of a conventional light emitting device will be described with reference to Fig. 9. Fig. 9 is a cross-sectional view showing the configuration of a conventional light emitting device 1X.

[0006] As shown in FIG. 9, a light emitting device 1X includes a light emitting member 10X and a thermally conductive substrate 20X that supports the light emitting member 10X.

[0007] The light emitting member 10X has a phosphor substrate 11X made of phosphor ceramics, a light reflecting layer 12X made of a metal such as Ag, and a bonding auxiliary layer 13X made of a metal such as Ag.

[0008] The light emitting member 10X and the thermally conductive substrate 20X are bonded together by a bonding layer 30X, which may be made of Ag paste, AuSn solder, or the like.

[0009] When Ag paste or AuSn solder is used as the bonding layer 30X, gold (Au), which is compatible with the bonding layer 30X, is used as the surface layer of the thermally conductive substrate 20X.

[0010] Specifically, the thermally conductive substrate 20X has a base substrate 21X as a base material, an underlayer 23X made of a nickel-plated film covering the base substrate 21X, and a gold layer 24X made of a gold-plated film covering the underlayer 23X. The gold layer 24X, which is a gold-plated film, is formed on the entire surface of the thermally conductive substrate 20X.

[0011] When the light emitting device 1X configured in this manner is used, the light emitting device 1X is bonded to another member such as a heat dissipation member. In this case, the thermally conductive substrate 20X of the light emitting device 1X is bonded to the heat dissipation member, etc. Therefore, it is preferable that the surface of the thermally conductive substrate 20X is flat.

[0012] However, since the gold layer 24X, which is the surface layer of the thermally conductive substrate 20X, is relatively soft, the gold layer 24X may be scratched during the manufacturing process of the light-emitting device 1X, resulting in poor flatness of the thermally conductive substrate 20X or poor appearance of the thermally conductive substrate 20X.

[0013] For example, when joining the light emitting member 10X to the thermally conductive substrate 20X, the light emitting member 10X is sucked by a suction member such as a collet and transferred onto the thermally conductive substrate 20X, but if the light emitting member 10X falls to a position other than the predetermined position on the thermally conductive substrate 20X due to poor suction or the like, the light emitting member 10X is sucked again and placed in the predetermined position on the thermally conductive substrate 20X. At this time, because the Mohs hardness of the light emitting member 10X is greater than the Mohs hardness of gold, the gold layer 24X of the thermally conductive substrate 20X may be scratched when the light emitting member 10X is sucked again.

[0014] In particular, if the light emitting member 10X has a ceramic phosphor, the Mohs hardness of the ceramic phosphor is greater than that of gold, and therefore the gold layer 24X of the thermally conductive substrate 20X is likely to be scratched when the light emitting member 10X is re-adsorbed.

[0015] Furthermore, since ceramic phosphors are prone to warping, when the light emitting member 10X includes a ceramic phosphor, warping may occur in the light emitting member 10X. In this case, when the light emitting member 10X is re-adsorbed, the warping of the light emitting member 10X may cause the corners of the light emitting member 10X to hit the gold layer 24X of the thermal conductive substrate 20X, which may scratch the gold layer 24X of the thermal conductive substrate 20X.

[0016] Furthermore, the gold layer 24X of the thermally conductive substrate 20X may also be scratched at times other than when the light emitting member 10X is transferred to the thermally conductive substrate 20X. For example, when the thermally conductive substrate 20X and the light emitting member 10X are bonded together with the bonding layer 30X, the light emitting member 10X is set on the bonding layer 30X applied to the thermally conductive substrate 20X. At this time, the light emitting member 10X set on the bonding layer 30X is swung horizontally to remove air bubbles contained in the applied bonding layer 30X. When the light emitting member 10X is swung, the light emitting member 10X may hit the thermally conductive substrate 20X, causing scratches on the gold layer 24X of the thermally conductive substrate 20X.

[0017] Furthermore, the gold layer 24X of the thermal conductive substrate 20X may be scratched at times other than the step of bonding the light emitting member 10X to the thermal conductive substrate 20X. For example, the thermal conductive substrate 20X may be dropped when transferring the thermal conductive substrate 20X, causing scratches on the gold layer 24X of the thermal conductive substrate 20X.

[0018] As described above, in the configuration of the conventional light-emitting device 1X, scratches are formed on the gold layer 24X of the thermally conductive substrate 20X, resulting in poor flatness and poor appearance of the thermally conductive substrate 20X. Poor flatness of the thermally conductive substrate 20X causes problems such as a decrease in the thermal conductivity of the thermally conductive substrate 20X. Furthermore, scratches on the gold layer 24X expose the base layer 23X, resulting in poor appearance of the thermally conductive substrate 20X, which reduces the reliability of the thermally conductive substrate 20X.

[0019] The present invention has been made in view of the above-mentioned problems, and has an object to provide a light-emitting device that can prevent scratches on the surface of a thermally conductive substrate. [Means for solving the problem]

[0020] In order to achieve the above object, one aspect of the light-emitting device of the present invention comprises a thermally conductive substrate including a first region and a second region surrounding the first region, and a light-emitting component arranged in the first region, wherein the thermally conductive substrate has a surface protective layer arranged in the second region, and the Mohs hardness of the surface protective layer is higher than the Mohs hardness of gold. [Effects of the Invention]

[0021] According to the present invention, the surface of the thermally conductive substrate can be protected, and therefore scratches on the surface of the thermally conductive substrate can be prevented. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram showing a configuration of a light-emitting device according to the first embodiment. [Figure 2] FIG. 2 is a diagram showing how light from a light source enters a light-emitting device and output light is emitted from the light-emitting device. [Figure 3] FIG. 3 is a diagram showing a configuration of a light-emitting device according to the second embodiment. [Figure 4] FIG. 4 is a cross-sectional view of a light-emitting device according to a first modification of the second embodiment. [Figure 5] FIG. 5 is a cross-sectional view of a light-emitting device according to Modification 2 of Embodiment 2. As shown in FIG. [Figure 6] FIG. 6 is a cross-sectional view of a light-emitting device according to a third modification of the second embodiment. [Figure 7] FIG. 7 is a diagram showing the configuration of a light-emitting device according to the third embodiment. [Figure 8] FIG. 8 is a diagram showing the configuration of a light-emitting device according to the fourth embodiment. [Figure 9] FIG. 9 is a cross-sectional view showing the configuration of a conventional light-emitting device. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that each of the embodiments described below represents a specific example of the present invention. Therefore, the numerical values, shapes, materials, components, arrangement positions and connection forms of the components, etc. shown in the following embodiments are merely examples and are not intended to limit the present invention. Therefore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concept of the present invention will be described as optional components.

[0024] Furthermore, each figure is a schematic diagram and is not necessarily an exact illustration. Therefore, for example, the scales of the figures do not necessarily match. Furthermore, in each figure, substantially the same components are given the same reference numerals, and redundant explanations are omitted or simplified.

[0025] Furthermore, in this specification, the terms "above," "upper," "below," and "lower" do not refer to the upward direction (vertically upward) and downward direction (vertically downward) in absolute spatial recognition, but are used as terms defined by a relative positional relationship. In the following description, the direction in which the light emitting member 10 is located relative to the thermal conductive substrate 20 is considered to be "above," and the opposite side is considered to be "below." Furthermore, the terms "above" and "lower" are applied not only to the case in which two components are arranged with a gap between them and another component exists between them, but also to the case in which two components are arranged closely together and the two components are in contact with each other.

[0026] (Embodiment 1) First, the configuration of a light-emitting device 1 according to embodiment 1 will be described with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of a light-emitting device 1 according to embodiment 1. Fig. 1(a) is a plan view of the light-emitting device 1, and Fig. 1(b) is a cross-sectional view of the light-emitting device 1 taken along line bb in Fig. 1(a).

[0027] As shown in FIG. 1, the light emitting device 1 includes a light emitting member 10, a thermally conductive substrate 20, and a bonding layer 30 that bonds the light emitting member 10 and the thermally conductive substrate 20 together.

[0028] The light emitting member 10 is a member that emits light. The light emitting member 10 has, as a light emitting member, a phosphor substrate 11. Therefore, the light emitting device 1 is a phosphor device.

[0029] In this embodiment, the light emitting member 10 further includes a light reflecting layer 12 and a bonding auxiliary layer 13 .

[0030] The phosphor substrate 11 is made of a phosphor that emits fluorescence when light is incident on it. Specifically, the phosphor substrate 11 is excited by excitation light and emits fluorescence with a wavelength longer than that of the excitation light. As an example, the phosphor substrate 11 is made of a yellow phosphor. In this case, the phosphor substrate 11 made of the yellow phosphor emits yellow fluorescence using light with a wavelength shorter than that of yellow light (for example, ultraviolet light to blue light) as excitation light. In other words, the phosphor substrate 11 made of the yellow phosphor converts the wavelength of the excitation light to yellow light with a wavelength longer than that of the excitation light. The emission wavelength of the phosphor substrate 11 is not limited to wavelengths in the visible light band, but may be a wavelength in the infrared light range. In this case, the phosphor substrate 11 includes a phosphor that emits light with a wavelength in the infrared light range.

[0031] The phosphor substrate 11 is a phosphor substrate made only of phosphor. In this embodiment, the phosphor substrate 11 is a phosphor plate made of phosphor ceramics. That is, the main component of the phosphor substrate 11 is phosphor ceramics. As an example, the phosphor substrate 11 is made of phosphor ceramics made of sintered polycrystalline phosphor. In this embodiment, the phosphor substrate 11 is made only of phosphor ceramics. That is, the phosphor substrate 11 is a fluorescent member that does not contain a binder.

[0032] In this way, by making the phosphor substrate 11 only from phosphor ceramics, the heat resistance and thermal conductivity of the phosphor substrate 11 can be improved. Furthermore, if the phosphor substrate 11 is a fluorescent material made of phosphor particles and a binder such as silicone, the binder deteriorates, increasing non-luminescent absorption and reducing the conversion efficiency of the phosphor substrate, which converts excitation light into fluorescence. However, by making the phosphor substrate 11 only from phosphor ceramics, the luminous efficiency (conversion efficiency) of the phosphor substrate 11 can be maintained over a long period of time. Furthermore, in this embodiment, the phosphor substrate 11 is made of phosphor ceramics. This reduces the amount of air contained in the phosphor substrate 11 compared to a phosphor substrate made of phosphor particles and a binder such as silicone, thereby improving the thermal conductivity of the phosphor substrate 11. Therefore, heat generated in the phosphor substrate 11 can be efficiently dissipated.

[0033] Furthermore, examples of phosphors that make up phosphor ceramics include YAG (Yttrium Aluminum Garnet) Y3Al5O 12 ), LuAG (Lutetium Aluminum Garnet) Lu3Al5O 12 ), Lu2CaMg2Si3O 12(Lutetium Calcium Magnesium Silicon Garnet) and TAG (Terbium Aluminum Garnet), Gd3Ga5O 12 , (Ga 0.6 Sc 0.4 )2O3, etc. YAG, LuAG, Lu2CaMg2Si3O 12 The dopant to be doped into the phosphor such as TAG can be appropriately selected from Ce, Eu, Cr, and the like.

[0034] In this embodiment, the phosphor substrate 11 is a fluorescent member made of only phosphor ceramics consisting of sintered YAG doped with Ce. 3+ It is made of YAG phosphor ceramics (refractive index 1.9) containing ZnO, and emits yellow fluorescence.

[0035] In this embodiment, from the viewpoint of conversion efficiency and temperature characteristics, a Ce-doped YAG single-phase polycrystalline material is used for the phosphor substrate 11, but other materials may be mixed in as long as they do not deteriorate in air at 300°C. For example, the object of the present invention can be achieved even if the phosphor substrate 11 is mixed with YAP, yttria, alumina, or the like at a level of a few percent.

[0036] The density of the phosphor substrate 11 is preferably 95% or more and less than 100% of the theoretical density of the phosphor (phosphor ceramic) constituting the phosphor substrate 11. Here, the theoretical density is the density when atoms in the phosphor layer are ideally arranged. The theoretical density is the density when it is assumed that the phosphor substrate 11 has no pores (voids), and is a value calculated using the crystal structure. For example, if the density of the phosphor substrate 11 is 99%, the remaining 1% corresponds to pores. In other words, the higher the density of the phosphor substrate 11, the fewer pores there are. When the density of the phosphor substrate 11 is within the above range, the total amount of fluorescence emitted by the phosphor substrate 11 increases, thereby realizing a light-emitting device 1 that emits a greater amount of light. In this embodiment, since the phosphor substrate 11 has a plurality of pores, the density of the phosphor substrate 11 is less than 100% of the theoretical density. Furthermore, the phosphor ceramic constituting the phosphor substrate 11 in this embodiment has a theoretical density of 4.56 g / cm. 3 Since the phosphor substrate 11 is YAG, the density of the phosphor substrate 11 is 4.32 g / cm 3 More than 4.56g / cm 3 is less than.

[0037] The phosphor substrate 11 has a first surface 11a and a second surface 11b opposite to the first surface 11a. The first surface 11a is the upper surface of the phosphor substrate 11, and the second surface 11b is the lower surface of the phosphor substrate 11.

[0038] The first surface 11a of the phosphor substrate 11 is a surface onto which light from a light source (not shown) is incident. In the present embodiment, the first surface 11a of the phosphor substrate 11 is an exposed surface, but this is not limiting. For example, an anti-reflection film may be formed on the first surface 11a of the phosphor substrate 11. This can prevent light incident on the phosphor substrate 11 from the first surface 11a of the phosphor substrate 11 from being reflected by the first surface 11a, thereby improving the light incidence efficiency into the phosphor substrate 11. As the anti-reflection film, a dielectric multilayer film in which dielectric films are stacked can be used.

[0039] On the other hand, the second surface 11b of the phosphor substrate 11 is the surface on the thermally conductive substrate 20 side. In this embodiment, the second surface 11b of the phosphor substrate 11 is in contact with the upper surface of the light reflecting layer 12.

[0040] The light emitting member 10 is a rectangular, flat-plate member with a constant thickness. Therefore, the first surface 11a and the second surface 11b of the phosphor substrate 11 have a rectangular shape in plan view and are substantially flat (planar) surfaces. Specifically, the first surface 11a and the second surface 11b are polished surfaces. However, the planar shapes of the first surface 11a and the second surface 11b are not limited to rectangular.

[0041] The thickness of the flat phosphor substrate 11 is on the order of microns, less than 200 μm. In this embodiment, the thickness of the phosphor substrate 11 is 100 μm, preferably 80 μm or less. In order to lower the temperature of the phosphor substrate 11 and reduce distortion, the thickness of the phosphor substrate 11 should be 70 μm or less. On the other hand, considering the volume required for the phosphor substrate 11 to efficiently emit light after the light incident on the phosphor substrate 11 is absorbed by the phosphor ceramic, the thickness of the phosphor substrate 11 should be 5 μm or more, more preferably 30 μm or more.

[0042] The light reflecting layer 12 is provided below the phosphor substrate 11. In other words, the phosphor substrate 11 is provided on the light reflecting layer 12. Specifically, the light reflecting layer 12 is provided on the second surface 11b of the phosphor substrate 11.

[0043] The light reflecting layer 12 is provided on the bonding auxiliary layer 13. Therefore, the light reflecting layer 12 is provided between the phosphor substrate 11 and the bonding auxiliary layer 13.

[0044] The light-reflecting layer 12 reflects light from the light source that is incident on the phosphor substrate 11 from the first surface 11a, and also reflects fluorescent light generated by the phosphor substrate 11 that is directed toward the thermally conductive substrate 20. Therefore, the first surface 11a of the phosphor substrate 11 not only functions as an incident surface onto which light from the light source is incident, but also as an exit surface from which light is emitted from the phosphor substrate 11. In this way, the light-emitting device 1 in this embodiment is a reflective light-emitting device, as the light from the light source is reflected by the light-reflecting layer 12 and emitted toward the light source side.

[0045] The light-reflecting layer 12 is a metal film containing a metal such as silver as a main component. In this case, the light-reflecting layer 12, which is a metal film, can be formed by, for example, a vapor deposition method. The light-reflecting layer 12 may also be made of a metal other than silver. For example, the metal that can be used to make the light-reflecting layer 12 may be APC (Ag-Pd-Cu alloy), Al, Pt, Rh, etc.

[0046] The light-reflecting layer 12 is not limited to a metal film. For example, the light-reflecting layer 12 may be a dielectric multilayer film. In this case, a dielectric multilayer film with a reflectance of 90% or more can be formed by stacking multiple dielectric films with different refractive indices. The light-reflecting layer 12 may also be a composite film of a dielectric multilayer film and a metal film. This allows the light-reflecting layer 12 to have high light reflectance over a wide angle with a small number of layers, and can be designed to achieve a more enhanced reflection effect than a metal film alone. For the dielectric multilayer film, silicon oxide can be used as a low-refractive index material, and tantalum oxide, titanium oxide, or niobium oxide can be used as a high-refractive index material. However, from the viewpoints of light resistance and heat resistance, tantalum oxide is preferably used as the high-refractive index material.

[0047] The bonding auxiliary layer 13 is a layer that assists in bonding the light emitting member 10 and the thermally conductive substrate 20 by the bonding layer 30. Therefore, the bonding auxiliary layer 13 is provided on the thermally conductive substrate 20 side of the light emitting member 10. Specifically, the bonding auxiliary layer 13 is provided below the light reflecting layer 12.

[0048] The bonding auxiliary layer 13 is preferably made of a material that is easily bonded to the bonding layer 30. The light reflecting layer 12 is a metal film containing metal as a main component. For example, if the bonding layer 30 is made of Ag, the bonding auxiliary layer 13 is preferably made of Ag or Au. Furthermore, if the bonding layer 30 is made of a eutectic solder such as AuSn or SnAgCu, the bonding auxiliary layer 13 is preferably made of Au. The bonding auxiliary layer 13, which is a metal film, can be formed by, for example, a vapor deposition method.

[0049] The thermally conductive substrate 20 to which the light emitting member 10 is joined has the function of conducting and dissipating heat generated in the light emitting member 10. In other words, the thermally conductive substrate 20 is a heat dissipation substrate. Specifically, the thermally conductive substrate 20 is a heat spreader that spreads the heat generated in the light emitting member 10 in a planar direction to dissipate the heat and conducts the heat to a heat sink connected to the thermally conductive substrate 20. The thermally conductive substrate 20 also functions as a support substrate that supports the light emitting member 10. Therefore, it is preferable that the thermally conductive substrate 20 be a rigid body having higher rigidity than the light emitting member 10.

[0050] The thermally conductive substrate 20 has a base substrate 21 and a surface protection layer 22. In this embodiment, the thermally conductive substrate 20 further has an underlayer 23 and a gold layer 24.

[0051] The thermally conductive substrate 20 includes a first region A1 and a second region A2 surrounding the first region A1. The first region A1 in the thermally conductive substrate 20 is a region in which the gold layer 24 is provided. That is, the first region A1 in the thermally conductive substrate 20 is defined by the gold layer 24. In this embodiment, the gold layer 24 has a rectangular shape in a planar view, and therefore the first region A1 also has a rectangular shape in a planar view. The first region A1 is a central region that includes the center of the thermally conductive substrate 20. Therefore, the gold layer 24 is provided in an approximately central region of the surface protection layer 22.

[0052] The second region A2 in the thermally conductive substrate 20 is adjacent to the first region A1. Therefore, the boundary between the first region A1 and the second region A2 is the outline of the gold layer 24. In this embodiment, the second region A2 is a region other than the first region A1.

[0053] The base substrate 21 is a substrate that serves as the core of the thermally conductive substrate 20. Because the thermally conductive substrate 20 has the function of conducting heat generated in the light emitting member 10, the base substrate 21 is preferably made of a material with high thermal conductivity. Specifically, the thermal conductivity of the base substrate 21 is preferably higher than that of the light emitting member 10. In particular, the thermal conductivity of the base substrate 21 is preferably higher than that of the phosphor substrate 11, which is the heat source. This allows the heat generated in the light emitting member 10 to be efficiently conducted to the thermally conductive substrate 20. As an example, the thermal conductivity of the base substrate 21 is preferably 100 W / mK or higher.

[0054] Specifically, the base substrate 21 is a metal substrate made of a metal material. For example, a copper substrate (Cu substrate), a silver substrate (Ag substrate), an APC (Ag-Pd-Cu alloy) substrate, etc. can be used as the base substrate 21. In the present embodiment, the base substrate 21 is a copper substrate.

[0055] The base substrate 21 is a flat plate with a substantially uniform thickness. In the present embodiment, the shape of the base substrate 21 in a plan view is rectangular. The thickness of the base substrate 21 is preferably thicker than the thickness of the light emitting member 10. In the present embodiment, the thickness of the base substrate 21 is 400 μm or more. As an example, the thickness of the base substrate 21 is 30 times or more the thickness of the light emitting member 10. The thickness of the base substrate 21 may be 1 mm or more, or may be 3 mm or more. Furthermore, the width of the base substrate 21 is, for example, approximately 3 to 20 times the width of the light emitting member 10 (more specifically, the width of the phosphor substrate 11), and the thickness of the base substrate 21 is thinner than the width of the base substrate 21.

[0056] In order to efficiently conduct the heat generated by the light emitting member 10 to the heat sink, it is preferable that the heat conducted from the light emitting member 10 to the thermally conductive substrate 20 be conducted laterally within the thermally conductive substrate 20. For this reason, it is preferable that the thickness of the base substrate 21 is large, but if the thickness of the base substrate 21 is about five times the spot size (width) of the excitation light irradiated on the light emitting member 10, the effect of thermal conductivity will be reduced. Note that the width of the light emitting member 10 is set to be equal to (or greater than) the spot size (width) of the excitation light.

[0057] The surface protective layer 22 is the outermost layer of the thermally conductive substrate 20 and is a layer that protects the thermally conductive substrate 20. The Mohs hardness of the surface protective layer 22 is higher than that of gold. As a material for the surface protective layer 22, for example, a material having a Mohs hardness higher than that of gold (2.5) can be selected from the materials in Table 1 below. Furthermore, the Mohs hardness of the surface protective layer 22 is preferably 3 or higher.

[0058] [Table 1]

[0059] Specifically, the surface protective layer 22 may be made of a metal such as chromium (Cr), nickel (Ni), palladium (Pd), rhodium (Rh), platinum (Pt), titanium (Ti), or tungsten (W). In this embodiment, the base substrate 21 is a copper substrate, the underlayer 23 is a nickel layer, and a gold layer 24 is formed on the surface protective layer 22, as described below. Therefore, the surface protective layer 22 is a chromium layer made of chromium. Chromium not only has high Mohs hardness but also excellent corrosion resistance. The chromium layer, which is the surface protective layer 22, is, for example, a chromium plating film formed by a plating method. The surface protective layer 22 may also be formed by a method other than plating. The surface protective layer 22 may also be made of a material other than a metal. For example, the surface protective layer 22 may be made of an inorganic material such as SiO2 or Al2O3.

[0060] The surface protective layer 22 is disposed in the second region A2 of the thermally conductive substrate 20. The surface protective layer 22 may be disposed in a portion of the second region A2, or may be disposed in the entire region of the second region A2. The surface protective layer 22 may also be disposed in a region other than the second region A2. In this embodiment, the surface protective layer 22 is disposed not only in the second region A2 but also in the first region A1. Specifically, the surface protective layer 22 is provided in the entire region of the thermally conductive substrate 20. Specifically, the surface protective layer 22 is formed so as to cover the entire surface of the base layer 23. The surface protective layer 22 has a constant thickness, but this is not limited to this.

[0061] The thickness of the surface protection layer 22 is, for example, 5 μm. From the viewpoint of scratch resistance, the thickness of the surface protection layer 22 is preferably 1% or more of the thickness of the phosphor substrate 11.

[0062] The underlayer 23 is a layer that serves as a base when the surface protection layer 22 is formed. Therefore, the surface protection layer 22 is formed on the underlayer 23. The underlayer 23 is formed on the base substrate 21. In this embodiment, the underlayer 23 is formed so as to cover the entire surface of the base substrate 21.

[0063] The underlayer 23 can be made of metal. In this embodiment, the underlayer 23 is a nickel layer made of nickel. The underlayer 23, which is a nickel layer, is, for example, a nickel plating film formed by a plating method. The underlayer 23 may be formed by a method other than plating. Furthermore, the underlayer 23 has a constant thickness, but this is not limiting.

[0064] The thickness of the underlayer 23 is, for example, 1 μm, but since it is sufficient that the underlayer 23 adheres closely to the surface protection layer 22, the thickness of the underlayer 23 can be set in the range of 100 nm to 10 μm.

[0065] The gold layer 24 is a layer made of gold (Au) and is provided on the surface protection layer 22. Specifically, the gold layer 24 is provided partially on the surface protection layer 22.

[0066] The gold layer 24 is, for example, a gold plating film formed by a plating method. In this case, the gold layer 24, which is a gold plating film, is formed using the surface protection layer 22, which is a chrome plating film, as a base layer. The gold layer 24 is formed in a partial region on the surface protection layer 22 by a partial plating method. The gold layer 24 has a uniform thickness, but this is not limiting.

[0067] The thickness of the gold layer 24 is, for example, 200 nm, but is not limited to this. The gold layer 24 may have any thickness as long as it can ensure close contact between the gold layer 24 and the bonding layer 30.

[0068] In this embodiment, the shape of the gold layer 24 in plan view is rectangular. However, the shape of the gold layer 24 in plan view is not limited to a rectangle, and may be a circle or a polygon other than a rectangle.

[0069] The light emitting member 10 and the thermally conductive substrate 20 are bonded together by a bonding layer 30. The bonding layer 30 is a layer for bonding the light emitting member 10 and the thermally conductive substrate 20 together, and is present between the light emitting member 10 and the thermally conductive substrate 20. In other words, the bonding layer 30 exists as an adhesive layer between the light emitting member 10 and the thermally conductive substrate 20. In this embodiment, the bonding layer 30 bonds the bonding auxiliary layer 13 of the light emitting member 10 to the gold layer 24 of the thermally conductive substrate 20.

[0070] The bonding layer 30 is preferably made of a bonding material with high thermal conductivity, such as a thermally conductive adhesive. The bonding layer 30 can be made of a metal paste (e.g., Ag nanopaste) made of a metal such as Ag or Cu, a eutectic solder such as AuSn solder or SnAgCu solder, or a resin material containing a highly thermally conductive filler. Due to their high thermal conductivity, Ag paste or AuSn solder is desirable for the bonding layer 30, and Ag paste with a volume percentage of 95% is particularly desirable.

[0071] The bonding layer 30 and the light emitting member 10 are disposed on the gold layer 24 of the thermally conductive substrate 20. That is, the bonding layer 30 and the light emitting member 10 are disposed in the first region A1 of the thermally conductive substrate 20. Therefore, the gold layer 24 and the bonding layer 30 are largely covered by the light emitting member 10. In this embodiment, the outline of the gold layer 24 roughly coincides with the outline of the bonding layer 30 and the light emitting member 10. Therefore, in the light emitting device 1, the surfaces of the gold layer 24 and the bonding layer 30 are almost not exposed. However, the surface of the gold layer 24 is exposed when the light emitting member 10 is mounted on the thermally conductive substrate 20.

[0072] The outline of each of the gold layer 24 and the bonding layer 30 does not have to coincide with the outline of the light emitting member 10. For example, in the present embodiment, the gold layer 24, the bonding layer 30, and the light emitting member 10 each have a rectangular shape in plan view. In this case, the width of the gold layer 24 may be greater than the width of the bonding layer 30, and a portion of the gold layer 24 may protrude from the bonding layer 30. Furthermore, the width of the bonding layer 30 and / or the gold layer 24 may be greater than the width of the light emitting member 10, and a portion of the bonding layer 30 and / or the gold layer 24 may protrude from the light emitting member 10. For example, the width of the gold layer 24 may be 0.5 to 2 times the width of the light emitting member 10.

[0073] Next, an example of use of the light emitting device 1 according to the first embodiment will be described with reference to Fig. 2. Fig. 2 is a diagram showing an example of use of the light emitting device 1 according to the first embodiment. Fig. 2 shows how light from a light source 2 enters the light emitting device 1 and output light is emitted from the light emitting device 1. The light source 2 and the light emitting device 1 form a light source module.

[0074] 2, light L1 emitted from a light source 2 is incident on the light-emitting device 1. Specifically, the light L1 emitted from the light source 2 is incident on a light-emitting member 10 of the light-emitting device 1. The light source 2 is, for example, a laser light source having a semiconductor laser that emits laser light as the light L1. Therefore, the light-emitting member 10 of the light-emitting device 1 is irradiated with the laser light.

[0075] Light L1 emitted from the light source 2 is incident on the light emitting member 10 of the light emitting device 1 as excitation light. As a result, the phosphor substrate 11 of the light emitting member 10 is excited by the light L1 from the light source 2, and fluorescence of a predetermined color is generated in the phosphor substrate 11. That is, part of the light L1 (excitation light) from the light source 2 is wavelength converted in the phosphor substrate 11 to become light L2 of a predetermined wavelength (wavelength-converted light). Then, light L2, which is the fluorescence generated in the phosphor substrate 11, and part of the light L1 from the light source 2 that was incident on the phosphor substrate 11 and did not undergo wavelength conversion are mixed, and this mixed light is emitted from the phosphor substrate 11 as output light La.

[0076] In this embodiment, a light-reflecting layer 12 is provided on the light-emitting member 10. Therefore, light L1 from the light source 2 is absorbed by the phosphor substrate 11 and emits light L2 (fluorescence), while traveling up to the light-reflecting layer 12, and after being reflected by the light-reflecting layer 12, continues to travel toward the light source 2 and is emitted from the first surface 11a of the phosphor substrate 11 to the outside of the phosphor substrate 11 as output light La.

[0077] For example, if the light source 2 is a laser light source that emits blue laser light and the phosphor substrate 11 is a phosphor plate made of a yellow phosphor made of YAG phosphor ceramics, the light L2, which is yellow light generated by the phosphor substrate 11, and the light L1, which has not been wavelength-converted by the phosphor substrate 11, are reflected by the light-reflecting layer 12 and mixed together to become white light, which is then emitted from the first surface 11a of the phosphor substrate 11.

[0078] As described above, the light-emitting device 1 according to this embodiment includes a thermally conductive substrate 20 including a first region A1 and a second region A2 surrounding the first region A1, and a light-emitting member 10 disposed in the first region A1. The thermally conductive substrate 20 has a surface protection layer 22 disposed in the second region A2, and the Mohs hardness of the surface protection layer 22 is higher than that of gold. Specifically, the Mohs hardness of the surface protection layer 22 is preferably 3 or higher.

[0079] With this configuration, the surface of the thermally conductive substrate 20 can be protected by the surface protection layer 22, which has a high Mohs hardness, and therefore, it is possible to prevent scratches on the surface of the thermally conductive substrate 20. Specifically, in this embodiment, the entire surface of the thermally conductive substrate 20 except for the region that is bonded to the light emitting member 10 is covered by the surface protection layer 22. This makes it possible to effectively prevent scratches on the surface of the thermally conductive substrate 20.

[0080] Furthermore, in the light-emitting device 1 according to this embodiment, the thermally conductive substrate 20 has a gold layer 24 partially disposed on the surface protective layer 22, the first region A1 in the thermally conductive substrate 20 is the region where the gold layer 24 is disposed, and the light-emitting member 10 is disposed above the gold layer 24.

[0081] With this configuration, even if a relatively soft gold layer 24 is provided on the thermal conductive substrate 20, the gold layer 24 is provided partially and the area (second area A2) other than the area (first area A1) where the gold layer 24 is provided is covered with the surface protection layer 22, so that scratches on the surface of the thermal conductive substrate 20 can be further prevented.

[0082] Furthermore, since phosphor ceramic has a higher Mohs hardness than resin phosphor, if light-emitting member 10X has phosphor substrate 11X made of phosphor ceramic, as in the conventional light-emitting device 1X of Figure 6, there is a risk that gold layer 24X may be scratched by light-emitting member 10X. However, as in the light-emitting device 1 of this embodiment, gold layer 24 is partially provided and the area other than the area where gold layer 24 is provided is covered with surface protective layer 22, so that scratches on the surface of thermally conductive substrate 20 can be effectively prevented even if light-emitting member 10 has phosphor substrate 11 made of phosphor ceramic.

[0083] (Embodiment 2) Next, a light-emitting device 1A according to embodiment 2 will be described with reference to Fig. 3. Fig. 3 is a diagram showing the configuration of the light-emitting device 1A according to embodiment 2. Fig. 3(a) is a plan view of the light-emitting device 1A, and Fig. 3(b) is a cross-sectional view of the light-emitting device 1A taken along line bb in Fig. 3(a).

[0084] As shown in FIG. 3, a light emitting device 1A according to this embodiment differs from the light emitting device 1 according to the first embodiment in the configuration of a thermally conductive substrate 20A.

[0085] Specifically, in the light-emitting device 1 according to the first embodiment, the thermally conductive substrate 20 has an underlayer 23, and the base substrate 21 is covered with two layers, the underlayer 23 and the surface protective layer 22. In contrast, in the light-emitting device 1A according to the present embodiment, the thermally conductive substrate 20A does not have an underlayer 23, and the base substrate 21 of the thermally conductive substrate 20A is covered only with the surface protective layer 22. In other words, the surface protective layer 22 directly covers the base substrate 21.

[0086] Furthermore, while the surface protection layer 22 in the first embodiment is a chromium layer, the surface protection layer 22 in the present embodiment is a nickel layer. Therefore, the light-emitting device 1A according to this embodiment has a structure in which the outermost chromium layer does not exist in the light-emitting device 1 according to the first embodiment.

[0087] As described above, in the light-emitting device 1A according to this embodiment, the surface of the thermally conductive substrate 20A is protected by the surface protection layer 22 having a high Mohs hardness, so that scratches on the surface of the thermally conductive substrate 20A can be prevented.

[0088] The thickness of the surface protection layer 22 is, for example, 6 μm. From the viewpoint of scratch resistance, the thickness of the surface protection layer 22 is preferably 1% or more of the thickness of the phosphor substrate 11, and is desirably, for example, 2 μm or more. Furthermore, from the viewpoint of suppressing defects in the outer shape due to distortion of the surface protection layer 22, the thickness of the surface protection layer 22 is desirably 20 μm or less.

[0089] Although the light emitting member 10 is not warped in this embodiment, this is not limiting. Specifically, as shown in FIG. 4, the light emitting member 10 may be warped convexly downward. In this case, the light emitting member 10 is bonded to the bonding layer 30 such that the protruding portion of the light emitting member 10 is embedded in the bonding layer 30. Therefore, no gap is formed between the end of the light emitting member 10 and the bonding layer 30. By warping the light emitting member 10 convexly downward, the scratch resistance of the thermal conductive substrate 20A can be improved. In other words, even if the light emitting member 10 falls onto a location other than the location of the gold layer 24 of the thermal conductive substrate 20A due to poor suction or the like when bonding the light emitting member 10 to the thermal conductive substrate 20A, scratches on the thermal conductive substrate 20A can be suppressed. Note that, as long as the light emitting member 10 is warped convexly downward, the gold layer 24 may be formed on the entire surface of the thermal conductive substrate 20A. In other words, if the light emitting member 10 is warped so as to be convex downward, even if the light emitting member 10 falls onto the thermal conductive substrate 20A when joining the light emitting member 10 to the thermal conductive substrate 20A, scratches on the surface of the thermal conductive substrate 20A can be minimized.

[0090] Furthermore, in this embodiment, the entire surface of the base substrate 21 is covered with the surface protective layer 22, but this is not limiting. Specifically, as shown in Fig. 5, the surface protective layer 22 may be formed on the top and back surfaces of the base substrate 21, and the surface protective layer 22 may not be formed on the side surfaces of the base substrate 21. With this configuration, a plurality of base substrates 21 each having the surface protective layer 22 formed on the top and back surfaces can be cut out from a mother substrate (large size) in which the surface protective layer is formed on the top and back surfaces of a copper substrate. In other words, it becomes possible to cut out multiple thermal conductive substrates 20A in a state in which the gold layer 24 is not formed.

[0091] Furthermore, in the present embodiment, the gold layer 24 of the thermally conductive substrate 20A is formed only on the upper surface of the surface protective layer 22, but this is not limited thereto. Specifically, as shown in FIG. 6, the gold layer 24A may be formed on the side and rear surfaces of the surface protective layer 22. In other words, it is not necessary for the gold layer to be formed only on the upper surface of the surface protective layer 22, which is not covered by the light emitting member 10. In this way, by forming the gold layer 24A on the rear surface of the surface protective layer 22, the thermally conductive substrate 20A can be easily bonded to a heat spreader with a bonding material, thereby improving heat dissipation. The gold layer 24A may have the same thickness as the gold layer 24 on the upper surface, but this is not limited thereto.

[0092] The modifications shown in FIGS. 4 to 6 can also be applied to other embodiments.

[0093] (Embodiment 3) Next, a light-emitting device 1B according to embodiment 3 will be described with reference to Fig. 4. Fig. 4 is a diagram showing the configuration of the light-emitting device 1B according to embodiment 3. Fig. 4(a) is a plan view of the light-emitting device 1B, and Fig. 4(b) is a cross-sectional view of the light-emitting device 1B taken along line bb in Fig. 4(a).

[0094] As shown in FIG. 4, a light emitting device 1B according to this embodiment differs from the light emitting device 1 according to the first embodiment in the configuration of a thermally conductive substrate 20B.

[0095] Specifically, in the light-emitting device 1 according to the first embodiment, the base substrate 21 of the thermally conductive substrate 20 is a single-metal substrate (specifically, a copper substrate) made of a single metal, but in the light-emitting device 1B according to the present embodiment, the base substrate 21B of the thermally conductive substrate 20B is an alloy substrate made of multiple alloys. Everything except the base substrate 21B is the same as in the first embodiment.

[0096] The alloy substrate base substrate 21B may be, for example, a copper-carbon composite substrate (Cu-C substrate). Note that the alloy substrate constituting base substrate 21B is not limited to a Cu-C substrate, and may be a copper-tungsten composite substrate (Cu-W substrate), a copper-molybdenum substrate (Cu-Mo substrate), a magnesium silicon carbide substrate (Mg-SiC substrate), or the like.

[0097] As described above, in the light-emitting device 1B according to this embodiment, the surface of the thermally conductive substrate 20B is protected by the surface protection layer 22 having a high Mohs hardness, so that scratches on the surface of the thermally conductive substrate 20B can be prevented.

[0098] An alloy substrate is a mixture of various elements, and the bonds at the interfaces between the elements are weak, making it prone to chipping and peeling. For example, a copper-carbon composite substrate (Cu-C substrate) is prone to chipping of the carbon portion. The surface protection layer 22 can prevent such chipping and peeling.

[0099] Furthermore, in the light-emitting device 1B according to the present embodiment, the base substrate 21B of the thermally conductive substrate 20B is an alloy substrate with excellent thermal conductivity, such as a Cu-C substrate, which improves the thermal conductivity of the thermally conductive substrate 20B, thereby enabling the heat generated in the light-emitting member 10 to be conducted to the thermally conductive substrate 20B more efficiently.

[0100] (Fourth embodiment) Next, a light emitting device 1C according to embodiment 4 will be described with reference to Fig. 5. Fig. 5 is a diagram showing the configuration of the light emitting device 1C according to embodiment 4. Fig. 5(a) is a plan view of the light emitting device 1C, and Fig. 5(b) is a cross-sectional view of the light emitting device 1C taken along line bb in Fig. 5(a).

[0101] As shown in FIG. 5, a light emitting device 1C according to this embodiment differs from the light emitting device 1 according to the first embodiment in the configuration of a thermally conductive substrate 20C.

[0102] Specifically, in the light-emitting device 1 according to the first embodiment, the surface protection layer 22 of the thermally conductive substrate 20 is provided across the first region A1 and the second region A2, and the surface protection layer 22 is present below the gold layer 24 provided in the first region A1. In other words, the gold layer 24 is provided above the surface protection layer 22.

[0103] In contrast, in the light-emitting device 1C of the present embodiment, the surface protective layer 22C of the thermally conductive substrate 20C is provided only in the second region A2 of the first region A1 and the second region A2, and is not provided in the first region A1. Therefore, in the present embodiment, the surface protective layer 22C does not exist under the gold layer 24. The surface protective layer 22C covers the base substrate 21C so as to have an opening in the first region A1. The surface protective layer 22C is a surface oxide layer formed by oxidizing the surface layer of the base substrate 21C. As an example, the base substrate 21C is an aluminum substrate (Al substrate), and the surface protective layer 22C is an aluminum oxide layer made of aluminum oxide (Al2O3).

[0104] Furthermore, in the thermal conductive substrate 20C of the present embodiment, in addition to the gold layer 24, a first intermediate layer 25 and a second intermediate layer 26 are also provided in the first region A1. The first intermediate layer 25 is partially provided on the base substrate 21C, and the second intermediate layer 26 is laminated on the first intermediate layer 25. The second intermediate layer 26 is provided on the entire upper surface of the first intermediate layer 25. As an example, the first intermediate layer 25 is a zinc layer made of zinc (Zn), and the second intermediate layer 26 is a nickel layer made of nickel (Ni). Specifically, the first intermediate layer 25 is a zinc-plated film formed on the base substrate 21C by a selective plating method, and the second intermediate layer 26 is a nickel-plated film formed by a plating method using the first intermediate layer 25 as a base layer.

[0105] The gold layer 24 is formed on the second intermediate layer 26. The gold layer 24 can be formed by a plating method. Specifically, the gold layer 24 is a gold plating film.

[0106] As described above, in the light emitting device 1C according to the present embodiment, the surface of the thermally conductive substrate 20C is protected by the surface protection layer 22C having a high Mohs hardness, so that the surface of the thermally conductive substrate 20C can be prevented from being scratched.

[0107] The surface protection layer 22C, which is the surface oxidation layer of the base substrate 21C, can be formed by stacking the first intermediate layer 25, the second intermediate layer 26, and the gold layer 24 on the base substrate 21C, and then annealing or anodizing the surface of the base substrate 21C to oxidize the surface of the base substrate 21C and form the surface protection layer 22.

[0108] The thickness of the surface protection layer 22C is set to 10 nm from the viewpoint of scratch resistance, but is not limited to this thickness. The surface protection layer 22C exhibits scratch resistance as long as the thickness is 1 nm or more.

[0109] (Variation) Although the light emitting device and the like according to the present invention have been described based on the embodiments, the present invention is not limited to the above-described embodiments.

[0110] For example, the base substrate of the thermally conductive substrate may be one other than those described in the above embodiments 1 to 4. Specifically, the base substrate of the thermally conductive substrate may be a silicon carbide substrate (SiC substrate), an aluminum nitride substrate (AlN substrate), a silicon substrate (SS substrate), or the like. In this case, the aluminum nitride substrate or the silicon substrate does not need to be a single crystal substrate, and may be a polycrystalline substrate.

[0111] Furthermore, in the above-described first to fourth embodiments, the light emitting member 10 is a phosphor substrate 11 made only of phosphor ceramics, i.e., a phosphor substrate 11 containing no binder, but this is not limiting. For example, the light emitting member 10 may be a mixture of phosphor ceramics and other materials. Specifically, the light emitting member 10 may contain particles and / or binders having light scattering (light diffusing) properties in addition to the phosphor ceramics.

[0112] In addition, in the first to fourth embodiments, the planar shapes of the light emitting member 10 and the bonding layer 30 are rectangular, but this is not limited thereto. The planar shapes of the light emitting member 10 and the bonding layer 30 may be polygonal (triangle, hexagon, etc.) other than rectangular.

[0113] Furthermore, in the above-described first to fourth embodiments, the light emitting member 10 has the light reflecting layer 12, but this is not limiting. That is, the light emitting member 10 does not have to have the light reflecting layer 12. Furthermore, the light emitting member 10 has the bonding auxiliary layer 13, but this is not limiting. That is, the light emitting member 10 does not have to have the bonding auxiliary layer 13.

[0114] In addition, in the above-described first to fourth embodiments, the light source 2 that emits light to be incident on the light-emitting devices 1 to 1C is a laser light source that emits laser light, but this is not limiting. Specifically, the light source 2 may be another solid-state light-emitting element such as an LED, or may be an optical device that emits light other than a solid-state light-emitting element.

[0115] In addition, the present invention also includes forms obtained by applying various modifications to the above-described embodiments that a person skilled in the art would conceive, and forms realized by arbitrarily combining the components and functions of the embodiments within the scope of the present invention. Furthermore, the present invention also includes any combination of two or more claims from the multiple claims set forth in the claims at the time of filing, provided that there is no technical contradiction. For example, when a dependent claim set forth in the claims at the time of filing is made into a multiple claim or multiple multiple claims that cite all of the superordinate claims within the scope of the technical contradiction, the present invention also includes all combinations of claims included in that multiple claim or multiple multiple multiple claims. [Explanation of symbols]

[0116] 1, 1A, 1B, 1C Light-emitting devices 10. Light-emitting member 11 Phosphor substrate 12 Light reflective layer 20, 20A, 20B, 20C Thermal Conductive Substrate 22, 22C Surface Protective Layer 24 gold layers A1, First Domain A2, Second Field

Claims

1. a thermally conductive substrate including a first region and a second region surrounding the first region; a light emitting member disposed in the first region, the thermally conductive substrate has a surface protection layer disposed in the second region; The Mohs hardness of the surface protective layer is higher than the Mohs hardness of gold. Light-emitting device.

2. The Mohs hardness of the surface protective layer is 3 or more. The light emitting device of claim 1 .

3. The surface protection layer is made of Cr, Ni, Pd, Rh, Pt, Ti, W, SiO ２ , Al ２ O ３ It is composed of a material including at least one selected from the following: The light emitting device of claim 1 .

4. the thermally conductive substrate has a gold layer partially provided on the surface protection layer; the first region is a region where the gold layer is provided, The light-emitting member is provided above the gold layer. The light-emitting device according to any one of claims 1 to 3.

5. The gold layer has a rectangular shape in a plan view, The width of the gold layer is 1 to 10 times the width of the light-emitting member. The light-emitting device of claim 4 .

6. The light-emitting member has a phosphor substrate made of a phosphor ceramic. The light-emitting device according to any one of claims 1 to 3.

7. The light emitting member further has a light reflecting layer, The phosphor substrate is provided on the light-reflecting layer. The light-emitting device of claim 6.

Images