Light-emitting device

Abstract

The present invention provides a light-emitting device that can reduce the excitation light contained in the output light and improve fluorescence intensity. [Solution] The light-emitting device 1 for quality inspection comprises a solid-state light-emitting element 10 having an excitation light emission surface 13 for emitting excitation light, a phosphor ceramic layer 20 disposed on the excitation light emission surface 13 and converting excitation light into fluorescence, having an excitation light incident surface 21 into which excitation light is incident, a fluorescence emission surface 22 from which light containing fluorescence is emitted, and a side surface 23, and a sealing resin 30 disposed to surround at least a part of the side surface 23 of the phosphor ceramic layer 20, the light-emitting device 1 emits output light containing fluorescence, the phosphor ceramic layer 20 contains a phosphor in which at least a transition metal element is activated, the thickness of the phosphor ceramic layer 20 is 60 μm or more and 560 μm or less, and the wavelength at which the intensity of the fluorescence spectrum is maximum is 780 nm or more.

Description

[Technical Field]

[0001] This invention relates to a light-emitting device. [Background technology]

[0002] Conventionally, light-emitting devices are known that consist of a light source that emits a primary beam, which is excitation light, and a phosphor that emits near-infrared light. It is also known that light-emitting devices are used for inspection.

[0003] Patent Document 1 discloses an optoelectronic device comprising a semiconductor chip that emits a primary beam during device operation and a conversion element containing a conversion material. The conversion material contains a host material and converts the primary beam emitted from the semiconductor chip during device operation into a secondary beam with a wavelength between 700 nm and 2,000 nm. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special Publication No. 2018-518046 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in light-emitting devices used for quality inspection, if the output light contains a large amount of excitation light, the excitation light may become noise in other inspections or cause discomfort to workers at the inspection site.

[0006] This invention has been made in view of the problems of the prior art described above. The object of this invention is to provide a light-emitting device that can reduce the excitation light contained in the output light and improve the fluorescence intensity. [Means for solving the problem]

[0007] To solve the above problems, a light-emitting device for quality inspection according to an embodiment of the present invention comprises a solid-state light-emitting element having an excitation light emission surface for emitting excitation light. The light-emitting device comprises a phosphor ceramic layer disposed on the excitation light emission surface, which converts excitation light into fluorescence and has an excitation light incident surface on which excitation light is incident, a fluorescence emission surface from which light containing fluorescence is emitted, and a side surface. The light-emitting device comprises a sealing resin disposed to surround at least a portion of the side surface of the phosphor ceramic layer. The light-emitting device emits output light containing fluorescence. The phosphor ceramic layer contains a phosphor in which at least a transition metal element is activated. The thickness of the phosphor ceramic layer is 60 μm or more and 560 μm or less. The wavelength at which the intensity of the fluorescence spectrum is maximum is 780 nm or more. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a light-emitting device that can reduce the excitation light contained in the output light and improve fluorescence intensity. [Brief explanation of the drawing]

[0009] [Figure 1] This is a side cross-sectional view showing an example of a light-emitting device according to one embodiment. [Figure 2] This shows the X-ray diffraction patterns of the reference powder LiMg2Ga9O16:Cr3+ phosphor ceramic and the compound LiGa5O8. [Figure 3] This shows the X-ray diffraction patterns of reference powders for (Ga,Sc)2O3:Cr3+ phosphor ceramics and the compound β-Ga2O3. [Figure 4] This graph shows the relationship between the total thickness of the LiMg2Ga9O16:Cr3+ phosphor ceramic layer and the normalized near-infrared radiation flux. [Figure 5] This graph shows the relationship between the total thickness of the (Ga,Sc)2O3:Cr3+ phosphor ceramic layer and the normalized near-infrared radiation flux. [Figure 6] This graph shows the relationship between the total thickness of the LiMg2Ga9O16:Cr3+ phosphor ceramic layer and the ratio of transmitted blue light emission flux to the total radiant flux. [Figure 7]This graph shows the relationship between the total thickness of the (Ga,Sc)2O3:Cr3+ phosphor ceramic layer and the ratio of transmitted blue light emission flux to the total emission flux. [Figure 8] This is the output light spectrum of a light-emitting device equipped with a LiMg2Ga9O16:Cr3+ phosphor ceramic layer. [Figure 9] This is the output light spectrum of a light-emitting device equipped with a (Ga,Sc)2O3:Cr3+ phosphor ceramic layer. [Figure 10] This graph shows the dependence of the excitation light energy density and excitation light energy on the output light spectrum of a light-emitting device fabricated using a LiMg2Ga9O16:Cr3+ phosphor ceramic layer with a thickness of 187 μm. [Modes for carrying out the invention]

[0010] The light-emitting device according to this embodiment will be described in detail below with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for illustrative purposes and may differ from the actual ratios.

[0011] As shown in Figure 1, the light-emitting device 1 according to this embodiment comprises a solid-state light-emitting element 10, a phosphor ceramic layer 20, a sealing resin 30, and a frame 35.

[0012] The solid-state light-emitting element 10 emits excitation light. The solid-state light-emitting element 10 may include a light-emitting diode (LED) or a laser diode (LD). The solid-state light-emitting element 10 includes a solid-state light-emitting element substrate 11 and an excitation light emission unit 12. The solid-state light-emitting element substrate 11 is a substrate on which the excitation light emission unit 12 is mounted, and may be a printed circuit board. The excitation light emission unit 12 is connected to the solid-state light-emitting element substrate 11.

[0013] The excitation light emission unit 12 emits excitation light. The excitation light emission unit 12 has an excitation light emission surface 13, and the excitation light emission surface 13 emits excitation light. The wavelength of the excitation light is not particularly limited, but the peak wavelength of the excitation light may be 430 nm or more and 460 nm or less, or 445 nm or more and 460 nm or less. By having a peak wavelength of excitation light of 430 nm or more, the color rendering of the light emitted by the light-emitting device 1 can be improved. Also, by having a peak wavelength of excitation light of 460 nm or less, the luminous efficiency of the light-emitting device 1 can be improved. In this specification, "peak" refers to the point where the intensity of the spectrum is maximum. Furthermore, the excitation light is not limited to blue light, but may be ultraviolet light, violet light, green light, red light, or near-infrared light.

[0014] In this specification, an example is described in which the solid-state light-emitting element 10 includes one excitation light emitting unit 12. However, the solid-state light-emitting element 10 may include a plurality of excitation light emitting units 12. When the solid-state light-emitting element 10 includes a plurality of excitation light emitting units 12, the excitation light emitting units 12 may be arranged side by side in a planar direction on the solid-state light-emitting element substrate 11. The plurality of excitation light emitting units 12 may each emit excitation light having the same wavelength, or they may each emit excitation light having different wavelengths. For example, the plurality of excitation light emitting units 12 may emit excitation light that is a combination of at least two selected from excitation light emitting units 12 that emit ultraviolet light, violet light, blue light, green light, red light, or near-infrared light.

[0015] The energy density of the excitation light is 0.1 W / mm². 2 Preferably, the excitation light energy density is 0.1 W / mm². 2 When the above conditions are met, the object to be inspected can be irradiated with strong light, making it preferable as a light-emitting device 1 for quality inspection. The energy density of the excitation light is 1 W / mm². 2 The above is more preferable. Furthermore, there is no particular upper limit to the energy density of the excitation light, but the energy density of the excitation light is 100 W / mm². 2It may be less than 0.5W. Furthermore, the excitation light energy is preferably 0.5W or higher. When the excitation light energy is 0.5W or higher, a strong light can be irradiated onto the object being inspected, making it preferable as a light-emitting device 1 for quality inspection. The excitation light energy is more preferably 1W or higher, and even more preferably 3W or higher. Furthermore, there is no particular upper limit to the excitation light energy, but the excitation light energy may be less than 200W.

[0016] The phosphor ceramic layer 20 is positioned on the excitation light emission surface 13. The phosphor ceramic layer 20 may be laminated so as to be in direct contact with the excitation light emission surface 13 of the excitation light emission unit 12, or it may be laminated via an adhesive layer. The adhesive layer for bonding the excitation light emission unit 12 and the phosphor ceramic layer 20 is not particularly limited, but may include, for example, at least one of a light-transmitting inorganic adhesive and an organic adhesive.

[0017] The phosphor ceramic layer 20 converts excitation light into fluorescence. Specifically, the phosphor ceramic layer 20 absorbs the excitation light emitted from the excitation light emission unit 12 and emits fluorescence with a longer wavelength than the excitation light. The phosphor ceramic layer 20 has an excitation light incident surface 21 into which the excitation light is incident, a fluorescence emission surface 22 from which light containing fluorescence is emitted, and a side surface 23 connecting the excitation light incident surface 21 and the fluorescence emission surface 22. The excitation light incident surface 21 is in contact with the excitation light emission surface 13 of the excitation light emission unit 12. The fluorescence emission surface 22 is exposed in this embodiment. The side surface 23 is in contact with the sealing resin 30. The fluorescence emission surface 22 may also be in contact with a lens or the like (not shown).

[0018] The external dimensions of the phosphor ceramic layer 20 in a plan view may be approximately the same as the external dimensions of the excitation light emission unit 12 in a plan view. With this configuration, the excitation light and fluorescence guided in the planar direction within the phosphor ceramic layer 20 are less likely to spread beyond the external dimensions of the excitation light emission unit 12. Therefore, a light-emitting device 1 with a high energy density of output light and high brightness can be provided. Note that "approximately the same" means that the external dimensions of the phosphor ceramic layer 20 in a plan view are -20% to +20%, -10% to +10%, -5% to +5%, or -3% to +3% relative to the external dimensions of the excitation light emission unit 12 in a plan view. Note that the external dimensions of the phosphor ceramic layer 20 in a plan view may also be the external dimensions of the excitation light incident surface 21. Also, the external dimensions of the excitation light emission unit 12 in a plan view may also be the external dimensions of the excitation light emission surface 13. In this specification, external dimensions may be interpreted as area.

[0019] The phosphor ceramic layer 20 contains phosphor ceramics. This configuration improves the thermal conductivity of the phosphor ceramic layer 20, making it easier for heat from the phosphor ceramic layer 20 to be dissipated to the outside. As a result, excitation light with a high energy density can be introduced into the phosphor ceramic layer 20, providing an even higher output light-emitting device 1. Furthermore, light containing various wavelength components can be output uniformly. The phosphor ceramic layer 20 may contain 90% or more by mass, 95% or more by mass, or 99% or more by mass of phosphor ceramics. Preferably, the phosphor ceramics contained in the phosphor ceramic layer 20 contain at least crystal grains and pores. This makes it easier for the excitation light and fluorescence to be scattered due to the refractive index difference between the crystal grains and pores, resulting in a light-emitting device 1 that emits output light with less uniformity. Preferably, at least one of the crystal grains of the phosphor ceramics contained in the phosphor ceramic layer 20 has a size of 1 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more. As a result, the phosphor ceramic layer 20 absorbs more excitation light, making it easier to reduce the excitation light contained in the output light.

[0020] The wavelength at which the intensity of the spectrum of the fluorescence emitted from the phosphor ceramic layer 20 is maximum is 780 nm or more. By emitting such fluorescence, quality inspection using near-infrared light can be carried out. The phosphor ceramic layer 20 may contain a near-infrared phosphor having a fluorescence peak within a wavelength range of 780 nm or more and less than 1500 nm. Further, the phosphor ceramic layer 20 may contain a near-infrared phosphor having a fluorescence peak within a wavelength range of 780 nm or more and less than 900 nm.

[0021] The phosphor ceramic layer 20 contains a phosphor activated with at least a transition metal element. The phosphor activated with a transition metal element has a longer fluorescence lifetime and a longer afterglow time compared to the phosphor activated with a rare earth metal element. Therefore, when the solid light-emitting element 10 is driven, for example, even when the power supply becomes unstable and the output of the excitation light temporarily decreases, the fluorescence necessary for inspection is output for a certain period of time. Therefore, the light-emitting device 1 according to the present embodiment can realize stable inspection.

[0022] The phosphor ceramic layer 20 contains Ti 3+ , V 4+ , Cr 4+ , V 3+ , Cr 3+ , V 2+ , Mn 4+ , Fe 3+ , Co 3+ , Co 2+ and Ni 2+ and may contain a transition metal-activated phosphor activated with at least one selected from the group consisting of transition metals. The phosphor ceramic layer 20 may be a phosphor co-activated with transition metal ions and rare earth ions, or may be a phosphor co-activated with different types of transition metal ions. Such a co-activated phosphor can emit fluorescence containing light of more wavelength components with one phosphor, so that a light-emitting device 1 having a more compact configuration and containing light of more wavelength components can be realized. The rare earth ions to be activated are Nd 3+ , Eu 2+ , Ho 3+ , Er3+ , Tm 3+ and Yb 3+ It may include at least one selected from the group consisting of the following.

[0023] The transition metal element that is activated is Cr 3+ Preferably, it contains Cr as a fluorescent ion. 3+ By using this method, it becomes easier to absorb blue light and convert it into near-infrared light components. Furthermore, it becomes easier to change the light absorption peak wavelength and / or fluorescence peak wavelength depending on the type of matrix, which is advantageous in changing the excitation spectral shape and fluorescence spectral shape.

[0024] The phosphor ceramic layer 20 is made of Cr 3+ It is preferable to include a metal composite oxide activated by . Specifically, the phosphor ceramic layer 20 is based on at least one selected from the group consisting of borate, phosphate, silicate, aluminate, gallate, germanate, tungstate, and metal oxide, and Cr 3+ It is preferable to include a near-infrared phosphor activated by [the specified method].

[0025] The phosphor ceramic layer 20 is made of CeSc3(BO3)4:Cr 3+ 、(La,Y,Sc)4(BO3)4:Cr 3+ LaSc3(BO3)4:Cr 3+ ,ScBO3:Cr 3+ KInP2O7:Cr 3+ Sr3InP3O 12 :Cr 3+ Sr9In(PO4)7:Cr 3+ NaScSi2O6:Cr 3+ Mg2Al4Si5O 18 :Cr 3+ La3(Ga,Gd)5GeO 14 :Cr 3+ La3(Ga,Al)5SiO 14 :Cr 3+ LaMgGa 11 O 19 :Cr 3+ Mg3Ga2GeO8:Cr 3+Li(In,Sc)Ge2O6:Cr 3+ Zn3(Ga,Al)Ge2O 10 :Cr 3+ LiMg2InGe2O8:Cr 3+ NaCa2GaGe5O 14 :Cr 3+ NaGdMgWO6:Cr 3+ (Ga,Sc)2O3:Cr 3+ (Ga,Al)2O3:Cr 3+ LaLuO3:Cr 3+ Ba3Sc4O9:Cr 3+ Zn2SnO4:Cr 3+ LiIn2SbO6:Cr 3+ LiSrAlF6:Cr 3+ LiAl5O8:Cr 3+ LiGa5O8:Cr 3+ LiMg2Ga9O 16 MgGa2O4:Cr 3+ It may include at least one selected from the group consisting of the following.

[0026] The phosphorescent ceramic layer 20 may contain a compound having the same crystal structure as the compound LiGa5O8. The phosphorescent ceramic layer 20 may also contain a compound having the same crystal structure as the compound β-Ga2O3. These phosphors have a wavelength of 780 nm or higher at which the intensity of the fluorescence spectrum is maximum, making them suitable for quality inspection using near-infrared light.

[0027] The thickness of the phosphor ceramic layer 20 may be 60 μm or more and 560 μm or less. When the thickness of the phosphor ceramic layer 20 is 60 μm or more, the proportion of excitation light components included in the output light can be reduced. When the thickness of the phosphor ceramic layer 20 is 560 μm or less, the near-infrared light radiant flux emitted from the light-emitting device 1 can be increased. The thickness of the phosphor ceramic layer 20 may be 90 μm or more, or 100 μm or more. In addition, the thickness of the phosphor ceramic layer 20 may be 550 μm or less, 500 μm or less, 450 μm or less, 400 μm or less, 350 μm or less, 300 μm or less, 250 μm or less, or 200 μm or less.

[0028] The phosphor ceramic layer 20 may contain a compound having the same crystal structure as the compound LiGa5O8. The thickness of the phosphor ceramic layer 20 may be between 60 μm and 300 μm. A light-emitting device 1 equipped with such a phosphor ceramic layer 20 is suitable for quality inspection using near-infrared light, and can particularly reduce the excitation light contained in the output light, thereby reducing unnecessary light for inspection. Examples of compounds having the same crystal structure as the compound LiGa5O8 include LiMg2Ga9O 16 Other examples include MgGa2O4 and solid solutions of MgGa2O4 and LiGa5O8.

[0029] The phosphor ceramic layer 20 may contain a compound having the same crystal structure as the compound β-Ga2O3. The thickness of the phosphor ceramic layer 20 may be between 90 μm and 300 μm. A light-emitting device 1 equipped with such a phosphor ceramic layer 20 is also suitable for quality inspection using near-infrared light, and can particularly reduce the excitation light contained in the output light, thereby reducing the amount of light unnecessary for inspection. In addition to (Ga,Sc)2O3, other examples of compounds having the same crystal structure as the compound β-Ga2O3 include (Ga,Al)2O3.

[0030] The phosphor ceramic layer 20 may include multiple stacked phosphor ceramic layers. This configuration provides a light-emitting device 1 that can uniformly output light containing various wavelength components. Each of the multiple phosphor ceramic layers may contain phosphors that emit fluorescence with different spectral distributions. This broadens the spectrum of fluorescence emitted by each phosphor ceramic layer, resulting in a light-emitting device that can handle quality inspection of various objects. In addition, phosphors other than near-infrared phosphors, such as purple phosphors, blue phosphors, green phosphors, yellow phosphors, or red phosphors, may be placed on the surface or between the layers of the phosphor ceramic layer 20. Furthermore, the phosphors other than near-infrared phosphors may be phosphor ceramics or powdered phosphors.

[0031] If the phosphor ceramic layer 20 is stacked on top of multiple phosphor ceramic layers, at least one of the multiple phosphor ceramic layers has a thermal conductivity of 1 Wm -1 K -1 It is preferable that the value be greater than or equal to 3Wm -1 K -1 It is even more preferable that the above conditions are met. This allows the heat generated by the phosphor to be more easily dissipated towards the solid-state light-emitting element 10, resulting in a higher-power light-emitting device 1 with higher-power excitation light incident on the phosphor. Furthermore, all of the multiple phosphor ceramic layers have a thermal conductivity of 1 Wm². -1 K -1 It is preferable that the value be greater than or equal to 3Wm -1 K -1 The above is even more preferable. This makes it easier for the heat generated by the phosphor to be dissipated to the solid-state light-emitting element 10, resulting in a higher-power light-emitting device 1 with higher-power excitation light incident on the phosphor.

[0032] The sealing resin 30 is arranged to surround the side surface 23 of the phosphor ceramic layer 20. This configuration allows the phosphor ceramic layer 20 to be sealed and protected. The sealing resin 30 may be housed within a frame 35 provided on the solid-state light-emitting element substrate 11. The frame 35 is connected to the solid-state light-emitting element substrate 11. The frame 35 may be made of a metal such as aluminum. Inside the frame 35 are the excitation light emission section 12 and the phosphor ceramic layer 20.

[0033] The sealing resin 30 may cover a portion of the surface of the solid-state light-emitting element substrate 11, or it may surround and cover the periphery of the excitation light emission section 12 in the planar direction. The sealing resin 30 may be in direct contact with the side surface 23 of the phosphor ceramic layer 20. The sealing resin 30 may be filled to fill all the space between the excitation light emission section 12 and the frame 35. Alternatively, the sealing resin 30 and the frame 35 may not be in contact, and a space may be provided between the sealing resin 30 and the frame 35. In this embodiment, the phosphor ceramic layer 20 does not protrude from the sealing resin 30, and the entire side surface 23 of the phosphor ceramic layer 20 is in contact with the sealing resin 30. However, a portion of the phosphor ceramic layer 20 may protrude from the sealing resin 30. Furthermore, the sealing resin 30 may be arranged to surround a portion of the side surface 23 of the phosphor ceramic layer 20.

[0034] The sealing resin 30 may include an electrically insulating thermosetting resin. The sealing resin 30 may include at least one selected from the group consisting of, for example, silicone resin, epoxy resin, and phenolic resin. By including these materials in the sealing resin 30, the phosphor ceramic layer 20 is more strongly protected. Therefore, a highly reliable light-emitting device 1 can be provided.

[0035] The sealing resin 30 may reflect at least a portion of the excitation light or fluorescence. This configuration makes it difficult for the fluorescence emitted by the phosphor ceramic layer 20 to spread out from the side surface 23. As a result, a light-emitting device 1 that emits higher brightness output light can be provided. The sealing resin 30 may have light reflectivity that reflects at least one of visible light and near-infrared light. Specifically, the sealing resin 30 may contain a factor that scatters at least one of visible light and near-infrared light. The sealing resin 30 may contain, for example, at least one of pores (air) and metal oxide particles as a factor that scatters at least one of visible light and near-infrared light. These factors may be dispersed in the thermosetting resin. The metal oxide particles may include at least one selected from the group consisting of aluminum oxide (Al2O3) particles, titanium oxide (TiO2) particles, zirconium oxide (ZrO2) particles, and tantalum oxide (Ta2O5) particles.

[0036] The light-emitting device 1 emits output light. The output light contains fluorescence. With this configuration, the light-emitting device 1 can emit near-infrared light. Therefore, the light-emitting device 1 can perform quality inspection using near-infrared light. In addition to fluorescence, the output light may also contain excitation light.

[0037] The light-emitting device 1 is a light-emitting device for quality inspection. The use of the light-emitting device 1 is not particularly limited, but for example, the light-emitting device 1 may be used for food inspection. That is, the object to be inspected by the light-emitting device 1 may be food. Food may be items that people eat, such as ingredients for bento boxes, grains, fruits, vegetables, meat, fish, processed foods, or beverages. The light-emitting device 1 can inspect the quality of the object to be inspected by irradiating it with light suitable for evaluating, for example, the presence or absence of foreign matter, the relative amount of nutritional components, freshness, or moisture content.

[0038] (Note) Based on the above description of embodiments, the following technologies are disclosed.

[0039] (Technology 1) A light-emitting device for quality inspection, comprising: a solid-state light-emitting element having an excitation light-emitting surface for emitting excitation light; a phosphor ceramic layer disposed on the excitation light-emitting surface and converting the excitation light into fluorescence, having an excitation light-incident surface into which the excitation light is incident, a fluorescence-emitting surface from which light containing the fluorescence is emitted, and a side surface; and a sealing resin disposed to surround at least a portion of the side surface of the phosphor ceramic layer, wherein the light-emitting device emits output light containing the fluorescence, the phosphor ceramic layer contains a phosphor in which at least a transition metal element is activated, the thickness of the phosphor ceramic layer is 60 μm or more and 560 μm or less, and the wavelength at which the intensity of the fluorescence spectrum is maximum is 780 nm or more.

[0040] Therefore, it is possible to provide a light-emitting device that can reduce the excitation light contained in the output light and improve fluorescence intensity. Accordingly, the light-emitting device according to this embodiment does not need to be equipped with a filter that absorbs excitation light, and it is possible to suppress an increase in the size of the light-emitting device and an increase in manufacturing costs.

[0041] Specifically, the light-emitting device according to this embodiment comprises a solid-state light-emitting element and a phosphor ceramic layer. Therefore, it is possible to irradiate the object to be inspected with output light containing fluorescence. Furthermore, the light-emitting device uses a phosphor ceramic layer. Therefore, compared to a phosphor layer in which phosphors are dispersed in resin, the conversion efficiency from excitation light to fluorescence is high. In addition, the thickness of the phosphor ceramic layer is 60 μm to 560 μm. Therefore, the proportion of excitation light components in the output light can be reduced, and the near-infrared light radiant flux can be increased. On the other hand, if the phosphor ceramic layer absorbs a lot of excitation light, the heat generated in the phosphor ceramic layer will increase, which may lead to a decrease in the input limit (maximum input power) of the light-emitting device and a decrease in the reliability of the light-emitting device. However, since the light-emitting device according to this embodiment is equipped with a sealing resin, it has excellent heat dissipation. Furthermore, the phosphor ceramic layer contains phosphors in which at least transition metal elements are activated, and the wavelength at which the intensity of the fluorescence spectrum is maximum is 780 nm or higher. Therefore, the light-emitting device according to this embodiment has a long afterglow time and is excellent as a light-emitting device for quality inspection using near-infrared light.

[0042] (Technology 2) The light-emitting device according to Technology 1, wherein the phosphor ceramic layer contains a compound having the same crystal structure as the compound LiGa5O8, and the thickness of the phosphor ceramic layer is 60 μm or more and 300 μm or less. In such a light-emitting device, the wavelength at which the intensity of the fluorescence spectrum is maximum is 780 nm or higher, making it suitable for quality inspection using near-infrared light. Furthermore, a light-emitting device equipped with such a phosphor ceramic layer can particularly reduce the excitation light contained in the output light, thereby reducing the amount of light unnecessary for inspection.

[0043] (Technology 3) The light-emitting device according to Technology 1, wherein the phosphor ceramic layer contains a compound having the same crystal structure as compound β-Ga2O3, and the thickness of the phosphor ceramic layer is 90 μm or more and 300 μm or less. In such a light-emitting device, the wavelength at which the intensity of the fluorescence spectrum is maximum is 780 nm or higher, making it suitable for quality inspection using near-infrared light. Furthermore, a light-emitting device equipped with such a phosphor ceramic layer can particularly reduce the excitation light contained in the output light, thereby reducing the amount of light unnecessary for inspection.

[0044] (Technology 4) A light-emitting device according to any one of Technologies 1 to 3, for food inspection. The light-emitting device according to this embodiment can reduce the excitation light contained in the output light. Therefore, it is possible to reduce noise in inspection and reduce the risk of causing discomfort to workers at the inspection site. [Examples]

[0045] The embodiment will be described in more detail below with reference to examples and comparative examples, but the embodiment is not limited to these examples.

[0046] [Example 1] (LiMg2Ga9O 16 :Cr 3+ Synthesis of phosphorescent ceramics) The following compound powders were used as raw materials. • Lithium carbonate (Li2CO3) Magnesium hydroxide (Mg(OH)2) Gallium oxide (Ga2O3) Chromium oxide (Cr2O3)

[0047] LiMg2Ga9O 16 :Cr 3+ The specific composition of the phosphor ceramic is LiMg2(Ga 0.95 Cr 0.05 )9O 16 The following steps were taken. Each phosphor material was weighed using an electronic balance to obtain the above-mentioned composition. Then, each weighed phosphor material was thoroughly mixed using a mortar and pestle. In this way, a mixed material was obtained.

[0048] The above mixed raw materials were molded into a thin cylindrical shape with a thickness of approximately 2 mm using a manual hydraulic press (manufactured by Riken Seiki Co., Ltd.) and a mold (diameter 13 mm). The pressure on the pressure-receiving surface of the mixed raw materials during molding was approximately 20 MPa. In this way, a molded body of the mixed raw materials was obtained. The molding process was repeated under the same conditions to obtain another molded body of the mixed raw materials. Next, the molded body of the mixed raw materials was fired in a box-type atmospheric furnace. The processing temperature was 1400°C and the processing time was several hours. The fired product was a hard, cylindrical solid in which the phosphor raw materials had sintered and densified through a chemical reaction. In other words, the fired product was a ceramic. In this way, LiMg2Ga9O 16 :Cr 3+ We obtained phosphorescent ceramics.

[0049] LiMg2Ga9O obtained in this manner 16 :Cr 3+ The powder X-ray diffraction patterns of phosphor ceramics were measured. As shown in Figure 2, LiMg2Ga9O 16 :Cr 3+ The powder X-ray diffraction pattern of the phosphor ceramic matched the reference powder X-ray diffraction pattern of compound LiGa5O8. Therefore, LiMg2Ga9O 16 :Cr 3+ It can be seen that the phosphorescent ceramics are compounds that have the same crystal structure as the compound LiGa5O8.

[0050] (LiMg2Ga9O 16 :Cr 3+ Processing of phosphorescent ceramics) The top and bottom surfaces of the cylindrical phosphor ceramics after firing were polished using a polishing device (DISCO Corporation, DAG810). The grit size of the polishing blade used was 1400. As a result, phosphor ceramics with a thickness of 78 μm were obtained. Next, the polished phosphor ceramics of varying thicknesses were diced into thin rectangular parallelepipeds using a dicing device (DISCO Corporation, DAD3350). The external dimensions of all the diced pieces, viewed from above, were approximately 3.2 mm in length and 2.6 mm in width. 16 :Cr3+ When the surface of the phosphor ceramics was observed with a scanning electron microscope, it was confirmed that there were crystal grains and pores, and that the crystal grains included those with a size of 20 μm or more.

[0051] (LiMg2Ga9O 16 :Cr 3+ )(Fabrication of a light-emitting device using phosphor ceramics) LiMg2Ga9O with a thickness of 78 μm after dicing 16 :Cr 3+ The phosphor ceramics were mounted on an LED (solid-state light-emitting device) having an excitation light-emitting surface. As the LED, one having an excitation light-emitting surface with a rectangular shape of approximately 3.2 mm in length and approximately 2.6 mm in width was used. Specifically, first, an adhesive made of silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd.) that transmits visible light was applied in an appropriate amount to the excitation light-emitting surface using a dispenser (manufactured by Musashi Engineering, Inc., 350PCSmart). Then, the LiMg2Ga9O 16 :Cr 3+ phosphor ceramics were placed on the excitation light-emitting surface using a manual die bonder so that the contour of the excitation light-emitting surface and the contour of the phosphor ceramics approximately matched. Then, using a dryer, the above adhesive was thermally cured. The thermal curing conditions were 1 hour at 100 °C and 3 hours at 150 °C.

[0052] Next, a light-reflective resin (manufactured by Shin-Etsu Chemical Co., Ltd.) in which TiO2 particles were dispersed in silicone resin was applied in an appropriate amount using a dispenser (manufactured by Musashi Engineering, Inc., 350PCSmart) so as to surround the phosphor ceramics in plan view. That is, the above light-reflective resin was applied so as to contact the side surface of the phosphor ceramics. Then, using a dryer, the light-reflective resin was thermally cured. The thermal curing conditions were 1 hour at 150 °C. In this way, a light-emitting device as shown in FIG. 1 with a phosphor ceramics layer thickness of 78 μm was obtained.

[0053] [Example 2] A light-emitting device was fabricated in the same manner as in Example 1 except that the thickness of the phosphor ceramics layer was 102 μm.

[0054] [Example 3] A light-emitting device was fabricated in the same manner as in Example 1, except that the thickness of the phosphor ceramic layer was 202 μm.

[0055] [Example 4] On the upper surface of the phosphor ceramic layer with a thickness of 202 μm in the light-emitting device of Example 3, a phosphor ceramic with a thickness of 102 μm obtained in the polishing / dicing process of Example 2 was laminated without using an adhesive. In this way, a light-emitting device with a substantially phosphor ceramic layer thickness of 304 μm was fabricated.

[0056] [Example 5] On the upper surface of the phosphor ceramic layer with a thickness of 202 μm in the light-emitting device of Example 3, two phosphor ceramics with a thickness of 102 μm obtained in the polishing / dicing process of Example 2 were laminated without using an adhesive. In this way, a light-emitting device with a substantially phosphor ceramic layer thickness of 406 μm was fabricated.

[0057] [Example 6] On the upper surface of the phosphor ceramic layer with a thickness of 202 μm in the light-emitting device of Example 3, three phosphor ceramics with a thickness of 102 μm obtained in the polishing / dicing process of Example 2 were laminated without using an adhesive. In this way, a light-emitting device with a substantially phosphor ceramic layer thickness of 508 μm was fabricated.

[0058] [Comparative Example 1] On the upper surface of the phosphor ceramic layer with a thickness of 202 μm in the light-emitting device of Example 3, four phosphor ceramics with a thickness of 102 μm obtained in the polishing / dicing process of Example 2 were laminated without using an adhesive. In this way, a light-emitting device with a substantially phosphor ceramic layer thickness of 610 μm was fabricated.

[0059] [Example 7] ((Ga,Sc)2O3:Cr 3+ (Synthesis of phosphor ceramics) The following compound powders were used as raw materials. Gallium oxide (Ga2O3) • Scandium oxide (Sc2O3) Chromium oxide (Cr2O3)

[0060] In addition, the following compound powders were used as reaction accelerators. • Boron oxide (H3BO3) • Silicon dioxide (SiO2)

[0061] (Ga,Sc)2O3:Cr 3+ The specific composition of the phosphor ceramics is (Ga 0.605 Sc 0.39 Cr 0.005 The mixture was set to 2O3. Each phosphor raw material and each reaction accelerator was weighed using an electronic balance to achieve the above composition. Then, each weighed phosphor raw material and each reaction accelerator was placed in a plastic container along with an appropriate amount of alumina balls (3 mm in diameter). An appropriate amount of ethanol as a mixed solvent was then added to the container, and the mixture was wet-mixed using a planetary ball mill (PULVERISETTE5, manufactured by Fritsch Japan Co., Ltd.). After that, the alumina balls were removed using a filter, and a slurry-like mixed raw material was obtained in which each phosphor raw material and each reaction accelerator was mixed with the solvent. The slurry-like mixed raw material was then transferred to a metal container lined with a Nafuron sheet and dried at 150°C using a dryer to evaporate the solvent. In this way, the dried mixed raw material was obtained.

[0062] To ensure that the dried mixed raw materials would become a physically stable molded product in subsequent processes, a binder was added to the dried mixed raw materials. Specifically, the dried mixed raw materials were placed in a mortar, and a 2.5% by weight solution of polyvinyl alcohol was added as a binder, at a rate of 20% by weight relative to the weight of the dried mixed raw materials, using a dropper. Subsequently, the dried mixed raw materials and the 2.5% by weight solution of polyvinyl alcohol were thoroughly mixed using a pestle. In this way, a mixed raw material suitable for molding was obtained.

[0063] The above mixed raw materials were molded into a cylindrical shape using a manual hydraulic press (manufactured by Riken Seiki Co., Ltd.) and a mold (diameter 50 mm). The pressure applied to the pressure-receiving surface of the mixed raw materials during molding was approximately 20 MPa. In this way, a molded body of the mixed raw materials was obtained. Next, the molded body of the mixed raw materials was fired in a box-type atmospheric furnace. The processing temperature was 1400°C and the processing time was 4 hours. The fired product after firing was a hard, cylindrical solid in which the phosphor raw materials had sintered and densified through a chemical reaction. In other words, the fired product after firing was a ceramic. In this way, (Ga,Sc)2O3:Cr 3+ We obtained phosphorescent ceramics.

[0064] (Ga,Sc)2O3:Cr obtained in this way 3+ The powder X-ray diffraction pattern of phosphor ceramics was measured. As shown in Figure 3, (Ga,Sc)2O3:Cr 3+ The powder X-ray diffraction pattern of the phosphor ceramic matched the reference powder X-ray diffraction pattern of compound β-Ga2O3. Therefore, (Ga,Sc)2O3:Cr 3+ It can be seen that the phosphorescent ceramics are compounds with the same crystal structure as the compound β-Ga2O3. Note that (Ga,Sc)2O3:Cr 3+ The difference in peak positions between β-Ga2O3 and β-Ga2O3 is because they are composed of different elements while maintaining the same crystal structure.

[0065] ((Ga,Sc)2O3:Cr 3+ Processing of phosphorescent ceramics) The top and bottom surfaces of the cylindrical phosphor ceramics after firing were polished using a polishing device (DISCO Corporation, DAG810). The grit size of the polishing blade used was 1400. As a result, phosphor ceramics with a thickness of 92 μm were obtained. Next, the polished phosphor ceramics were diced into thin rectangular parallelepiped shapes using a dicing device (DISCO Corporation, DAD3350). The external dimensions in plan view after dicing were all approximately 3.2 mm in length and 2.6 mm in width. 3+When the surface of the phosphorescent ceramic was observed using a scanning electron microscope, it was confirmed that crystal grains and pores were present, and that some of the crystal grains were larger than 1 μm in size.

[0066] ((Ga,Sc)2O3:Cr 3+ Fabrication of a light-emitting device using phosphorescent ceramics. (Ga,Sc)2O3:Cr with a thickness of 92 μm after dicing. 3+ A phosphorescent ceramic was mounted on an LED (solid-state light-emitting device) having an excitation light emission surface. The LED used had a rectangular excitation light emission surface approximately 3.2 mm long and 2.6 mm wide. Specifically, first, an appropriate amount of a visible light-transmitting silicone resin adhesive (manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to the excitation light emission surface using a dispenser (Musashi Engineering Co., Ltd., 350PCSmart). After dicing, (Ga,Sc)2O3:Cr 3+ The phosphorescent ceramic was placed on the excitation light emission surface using a manual die bonder, so that the contour of the phosphorescent ceramic approximately matched the contour of the excitation light emission surface. The adhesive was then heat-cured using a drying oven. The heat-curing conditions were 100°C for 1 hour, followed by 150°C for 3 hours.

[0067] Next, a light-reflective resin (manufactured by Shin-Etsu Chemical Co., Ltd.), in which TiO2 particles are dispersed in a silicone resin, was applied in an appropriate amount using a dispenser (Musashi Engineering Co., Ltd., 350PCSmart) so as to surround the phosphor ceramics in a plan view. In other words, the light-reflective resin was applied so as to be in contact with the side surface of the phosphor ceramics. After that, the light-reflective resin was heat-cured using a drying oven. The heat-curing conditions were 150°C for 1 hour. In this way, a light-emitting device with a phosphor ceramic layer thickness of 92 μm was obtained.

[0068] [Example 8] In the light-emitting device of Example 7, a phosphor ceramic layer with a thickness of 92 μm was laminated onto the upper surface of the phosphor ceramic layer with a thickness of 92 μm obtained in the polishing / dicing process of Example 7, without using an adhesive. In this way, a light-emitting device with a phosphor ceramic layer thickness of substantially 184 μm was fabricated.

[0069] [Example 9] Two layers of phosphor ceramics, each 92 μm thick and obtained from the polishing / dicing process of Example 7, were laminated onto the upper surface of the phosphor ceramic layer, which had a thickness of 92 μm, without the use of adhesive. In this way, a light-emitting device with a phosphor ceramic layer thickness of substantially 276 μm was fabricated.

[0070] [Example 10] Three layers of phosphor ceramics, each 92 μm thick, obtained from the polishing / dicing process of Example 7, were laminated onto the upper surface of the phosphor ceramic layer, which had a thickness of 92 μm, without the use of adhesive. In this way, a light-emitting device with a phosphor ceramic layer thickness of 368 μm was fabricated.

[0071] [Example 11] In the light-emitting device of Example 7, four phosphor ceramics with a thickness of 92 μm, obtained in the polishing / dicing process of Example 7, were laminated onto the upper surface of the phosphor ceramic layer with a thickness of 92 μm without using an adhesive. In this way, a light-emitting device with a phosphor ceramic layer thickness of substantially 460 μm was fabricated.

[0072] [Example 12] In the light-emitting device of Example 7, five phosphor ceramics with a thickness of 92 μm, obtained in the polishing / dicing process of Example 7, were laminated onto the upper surface of the phosphor ceramic layer with a thickness of 92 μm without using an adhesive. In this way, a light-emitting device with a phosphor ceramic layer thickness of substantially 552 μm was fabricated.

[0073] [Comparative Example 2] Six phosphor ceramics, each 92 μm thick and obtained from the polishing / dicing process of Example 7, were laminated onto the upper surface of the phosphor ceramic layer, which had a thickness of 92 μm, without the use of adhesive. In this way, a light-emitting device with a phosphor ceramic layer thickness of 644 μm was fabricated.

[0074] [Evaluation of the optical properties of light-emitting devices] The fabricated light-emitting device was placed in an integrating sphere (approximately 50 cm in diameter) connected to a multi-channel spectrometer, and the output light spectrum, excitation light flux (blue light flux), and fluorescence light flux (near-infrared light flux) of the device were measured by ignition. The input current was 0.2 A. The energy of the excitation light at an input current of 0.2 A was 1.38 W. The energy density of the excitation light at an input current of 0.2 A was 0.17 W / mm². 2 That was the case.

[0075] Figure 4 shows LiMg2Ga9O 16 :Cr 3+ This graph shows the relationship between the total thickness of the phosphor ceramic layer and the normalized near-infrared radiation flux. Figure 5 shows (Ga,Sc)2O3:Cr 3+ This graph shows the relationship between the total thickness of the phosphor ceramic layer and the normalized near-infrared radiation flux. Figure 6 shows LiMg2Ga9O 16 :Cr 3+ This graph shows the relationship between the total thickness of the phosphorescent ceramic layer and the ratio of the transmitted blue light emission flux to the total emission flux. Figure 7 shows (Ga,Sc)2O3:Cr 3+ This graph shows the relationship between the total thickness of the phosphorescent ceramic layer and the ratio of the transmitted blue light emission flux to the total radiant flux. Figure 8 shows LiMg2Ga9O 16 :Cr 3+ This is the output light spectrum of a light-emitting device equipped with a phosphor ceramic layer. Figure 9 shows (Ga,Sc)2O3:Cr 3+ This is the output light spectrum of a light-emitting device equipped with a phosphorescent ceramic layer.

[0076] As shown in Figure 4, the light-emitting device with a phosphor ceramic layer thickness of 610 μm in Comparative Example 1 had a small proportion of near-infrared light emission flux. On the other hand, the light-emitting devices with phosphor ceramic layer thicknesses of 78 μm to 508 μm in Examples 1 to 6 had a larger proportion of near-infrared light emission flux compared to Comparative Example 1. Furthermore, as can be seen from Figure 4, it was confirmed that there is a maximum value of normalized near-infrared light emission flux when the total thickness of the phosphor ceramic layer is between 102 μm and 202 μm.

[0077] Furthermore, as shown in Figure 5, the light-emitting device with a phosphor ceramic layer thickness of 644 μm in Comparative Example 2 exhibited a smaller proportion of near-infrared light emission flux. On the other hand, the light-emitting devices with phosphor ceramic layer thicknesses of 92 μm to 552 μm in Examples 7 to 12 exhibited a larger proportion of near-infrared light emission flux compared to Comparative Example 2. In addition, as can be seen from Figure 5, it was confirmed that a maximum value of normalized near-infrared light emission flux exists when the total thickness of the phosphor ceramic layer is between 92 μm and 276 μm.

[0078] As can be seen from Figures 4 and 5, in all phosphor ceramic layers, a radiant flux of 80% or more of the maximum radiant flux was obtained by keeping the total thickness to 300 μm or less. Furthermore, although phosphor ceramic layers with a film thickness of less than 60 μm were not evaluated due to the characteristics of the film thickness control device, it can be confirmed from Figures 4 and 5 that a near-infrared radiant flux of 80% or more of the maximum radiant flux was obtained.

[0079] Furthermore, as shown in Figures 6 and 7, the ratio of transmitted blue light emission flux to the total emission flux decreased as the total thickness of the phosphor ceramic layer increased. In particular, as shown in Figure 6, LiMg2Ga9O 16 :Cr 3+ It can be seen that by making the total thickness of the phosphor ceramic layer 60 μm or more, the ratio of transmitted blue light emission flux to the total emission flux can be reduced to 60% or less. Also, (Ga,Sc)2O3:Cr 3+ It can be seen that by increasing the total thickness of the phosphor ceramic layer to 90 μm or more, the ratio of transmitted blue light emission flux to the total emission flux can be reduced to 60% or less.

[0080] As shown in Figures 8 and 9, LiMg2Ga9O 16 :Cr 3+ Phosphor ceramic layer and (Ga,Sc)2O3:Cr 3+ In light-emitting devices equipped with a phosphorescent ceramic layer, the wavelength at which the fluorescence spectrum intensity was maximum was 780 nm or higher. Furthermore, it was confirmed that in these light-emitting devices, increasing the thickness of the phosphorescent ceramic layer reduced the intensity of the excitation light, which had a peak around 450 nm.

[0081] Figure 10 shows LiMg2Ga9O with the same composition as Example 1 but a thickness of 187 μm. 16 :Cr 3+ This graph shows the dependence of the excitation light energy density and excitation light energy on the output light spectrum of a light-emitting device fabricated using a phosphor ceramic layer. As shown in Figure 10, the ratio of excitation light intensity to fluorescence intensity in the output light spectrum remained almost unchanged regardless of the excitation light energy density and excitation light energy. In other words, even if the excitation light energy density and energy are increased, it is possible to reduce the excitation light components that are unnecessary for inspection by keeping the thickness of the phosphor ceramic layer within a predetermined range.

[0082] From these results, it can be seen that when the thickness of the phosphor ceramic layer is between 60 μm and 560 μm, it is possible to reduce the excitation light contained in the output light and improve the fluorescence intensity.

[0083] Although this embodiment has been described above, this embodiment is not limited to these, and various modifications are possible within the scope of the gist of this embodiment. [Explanation of Symbols]

[0084] 1. Light-emitting device 10 Solid-state light-emitting devices 13 Excitation light emission surface 20. Phosphorescent ceramic layer 21 Excitation light incident surface 22 Fluorescence-emitting surface 23 Side view 30 Sealing Resin

Claims

1. A solid-state light-emitting element having an excitation light emitting surface that emits excitation light, A phosphor ceramic layer is disposed on the excitation light emission surface, converts the excitation light into fluorescence, and has an excitation light incidence surface into which the excitation light is incident, a fluorescence emission surface from which light containing the fluorescence is emitted, and a side surface. A sealing resin is disposed so as to surround at least a portion of the side surface of the phosphor ceramic layer, A light-emitting device comprising, The light-emitting device emits output light including the fluorescence, The aforementioned phosphor ceramic layer contains a phosphor in which at least a transition metal element has been activated. The thickness of the phosphor ceramic layer is 60 μm or more and 560 μm or less. A light-emitting device for quality inspection, wherein the wavelength at which the intensity of the fluorescence spectrum is maximum is 780 nm or higher.

2. The aforementioned phosphor ceramic layer is a compound LiGa ５ O ８ It contains a compound that has the same crystal structure as, The light-emitting device according to claim 1, wherein the thickness of the phosphor ceramic layer is 60 μm or more and 300 μm or less.

3. The aforementioned phosphor ceramic layer is compound β-Ga ２ O ３ It contains a compound that has the same crystal structure as, The light-emitting device according to claim 1, wherein the thickness of the phosphor ceramic layer is 90 μm or more and 300 μm or less.

4. A light-emitting device according to any one of claims 1 to 3, for use in food inspection.

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