Near-infrared light-emitting device, spectroscopic device, and spectroscopic method

Abstract

The near-infrared light-emitting device (100) is configured so as to satisfy the relationship 0.853 MVIS < = MNIR < 1.147 MVIS, where MVIS is the ratio of Imax-VIS-150 to Imax-VIS-30, Imax-VIS-30 is the maximum fluorescence intensity of the visible fluorescence component when the temperature of the wavelength converter (2) is 30 DEG C, Imax-VIS-150 is the maximum fluorescence intensity of the visible fluorescence component when the temperature of the wavelength converter (2) is 150 DEG C, MNIR is the ratio of Imax-NIR-150 to Imax-NIR-30, and MNIR is the ratio of Imax-NIR-150 to Imax-NIR-30. Imax-NIR-30 is the maximum value of the fluorescence intensity of the near-infrared fluorescence component when the temperature of the wavelength converter (2) is 30 DEG C, and Imax-NIR-150 is the maximum value of the fluorescence intensity of the near-infrared fluorescence component when the temperature of the wavelength converter (2) is 150 DEG C.

Description

Technical Field

[0001] The present invention relates to a near-infrared light emitting device, a spectroscopic device using the same, and a spectroscopic method. Background Art

[0002] Conventionally, near-infrared light-emitting devices comprising a solid-state light-emitting element and a wavelength converter are known as light-emitting devices. Patent Document 1 discloses such a near-infrared light-emitting device, in which the wavelength converter comprises a visible phosphor that emits fluorescence with a maximum intensity within the visible wavelength range and a near-infrared phosphor that emits fluorescence with a maximum intensity within the near-infrared wavelength range. Such near-infrared light-emitting devices offer the advantage of being able to accommodate both general observation using visible light and specialized observation using near-infrared light.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2020 / 217671 Summary of the Invention

[0006] However, the temperature quenching of commonly used near-infrared phosphors is greater than that of visible phosphors. Therefore, as the temperature of the phosphor rises due to lighting of the solid-state light-emitting device, the intensity of the near-infrared fluorescence component may decrease relative to the intensity of the visible fluorescence component. Consequently, it may take some time for the output light intensity of the near-infrared light-emitting device to stabilize.

[0007] The present invention has been made in view of the problems of the prior art and has the object of providing a near-infrared light emitting device in which the shape of the spectral distribution changes little with temperature rise of the wavelength converter, and a spectroscopic device and spectroscopic method using the same.

[0008] In order to solve the above-mentioned problems, the near-infrared light-emitting device involved in the embodiment of the present invention comprises: a solid light-emitting element; and a wavelength converter, which includes a visible phosphor that emits visible fluorescence having a maximum fluorescence intensity within the wavelength range of visible light, and a near-infrared phosphor that emits near-infrared fluorescence having a maximum fluorescence intensity within the wavelength range of near-infrared light. The near-infrared light-emitting device emits output light containing visible fluorescence and near-infrared fluorescence. The output light contains a visible fluorescence component having a spectral intensity within the wavelength range of visible light, and a near-infrared fluorescence component having a spectral intensity within the wavelength range of near-infrared light. The near-infrared light-emitting device is configured to satisfy 0.853M VIS ≤M NIR <1.147M VIS Relationship. VIS For I max-VIS-150 Relative to Imax-VIS-30 The ratio of I max-VIS-30 is the maximum fluorescence intensity of the visible fluorescence component when the temperature of the wavelength converter is 30°C. max-VIS-150 M is the maximum fluorescence intensity of the visible fluorescence component when the temperature of the wavelength converter is 150°C. NIR For I max-NIR-150 Relative to I max-NIR-30 The ratio of I max-NIR-30 is the maximum fluorescence intensity of the near-infrared fluorescence component when the temperature of the wavelength converter is 30°C. max-NIR-150 It is the maximum fluorescence intensity of the near-infrared fluorescent component when the temperature of the wavelength converter is 150°C.

[0009] A spectroscopic device according to an embodiment of the present invention includes a near-infrared light emitting device.

[0010] The spectroscopy method according to the embodiment of the present invention utilizes a near-infrared light emitting device. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] [ Figure 1 ] Figure 1 This is a schematic diagram showing an example of the structure of a near-infrared light-emitting device according to one embodiment.

[0012] [ Figure 2 ] Figure 2 This is a schematic diagram showing an example of the structure of a spectroscopic device according to one embodiment.

[0013] [ Figure 3 ] Figure 3 This is a schematic diagram showing an example of the structure of a spectroscopic device according to another embodiment.

[0014] [ Figure 4 ] Figure 4 This is the spectral distribution of the output light emitted from the near-infrared light emitting device of this embodiment.

[0015] [ Figure 5 ] Figure 5 This is a graph showing the temperature quenching of the visible phosphor and near-infrared phosphor used for evaluation.

[0016] [ Figure 6 ] Figure 6 1 and 2 are the fluorescence spectra of the mixed phosphor of Example 2 at various temperatures.

[0017] [ Figure 7 ] Figure 7 1 and 2 are the fluorescence spectra of the mixed phosphor of Example 3 at various temperatures.

[0018] [ Figure 8 ] Figure 8 These are the fluorescence spectra of the mixed phosphor of Example 4 at various temperatures.

[0019] [ Figure 9 ] Figure 9 These are the fluorescence spectra of the mixed phosphor of Example 5 at various temperatures.

[0020] [ Figure 10 ] Figure 10 These are the fluorescence spectra of the mixed phosphor of Example 6 at various temperatures.

[0021] [ Figure 11 ] Figure 11 These are the fluorescence spectra of the mixed phosphor of Example 7 at various temperatures.

[0022] [ Figure 12 ] Figure 12 1 and 2 are fluorescence spectra of the mixed phosphor of Comparative Example 1 at various temperatures.

[0023] [ Figure 13 ] Figure 13 1 and 2 are fluorescence spectra of the mixed phosphor of Comparative Example 2 at various temperatures.

[0024] [ Figure 14 ] Figure 14 It is LiGa5O8:Cr 3+ Near-infrared phosphor and LiGa5O8:Cr of Comparative Example 1 3+ X-ray diffraction pattern of deep red phosphor and X-ray diffraction pattern of LiGa5O8 registered in ICSD (Inorganic Crystal Structure Database).

[0025] [ Figure 15 ] Figure 15 It is LiGa5O8:Cr 3+ Near-infrared phosphor and LiGa5O8:Cr 3+ Fluorescence spectrum of deep red phosphor.

[0026] [ Figure 16 ] Figure 16 It is for LiGa5O8:Cr 3+ Near-infrared phosphor and LiGa5O8:Cr 3+ A graph showing the relationship between the temperature of a deep red phosphor and the maximum fluorescence intensity of the fluorescence emitted by the phosphor. DETAILED DESCRIPTION

[0027] Hereinafter, the near-infrared light emitting device, spectroscopic device, and spectroscopic method according to the present embodiment will be described in detail using the drawings. Furthermore, for ease of explanation, the dimensional ratios in the drawings are exaggerated and may differ from the actual ratios.

[0028] [Near-infrared light-emitting device]

[0029] As mentioned above, the thermal quenching of commonly used near-infrared phosphors is greater than that of visible phosphors. The relatively large thermal quenching of near-infrared phosphors is likely due to their photophysical properties. The following summarizes the reasons for this.

[0030] In the device specifically designed for practical research, the wavelength converter absorbs blue light. The absorbed blue light is then transmitted to the visible phosphor (especially Ce) contained in the wavelength converter. 3+ Activate phosphor or Eu 2+ activated phosphors) and near-infrared phosphors (especially Cr 3+ Each of the activated phosphors is converted into visible light and near-infrared light with longer wavelengths than the absorbed blue light.

[0031] Therefore, the fluorescence of near-infrared phosphors has a larger Stokes shift (the energy difference between light absorption and fluorescence emission) than that of visible phosphors. This also means that the fluorescence of near-infrared phosphors is wavelength-converted light based on electron energy transitions with a large Franck-Condon shift (the shift in the equilibrium position between the ground state and the excited state). 3+ Since the equilibrium position of the excited state of the fluorescent ions of such a near-infrared phosphor is close to the ground state, temperature quenching is easily performed.

[0032] Therefore, in the present disclosure, the temperature quenching of the visible phosphor and the temperature quenching of the near-infrared phosphor are controlled within a predetermined range. This results in the discovery that the spectral distribution of the output light, including visible light from the visible phosphor and near-infrared fluorescence from the near-infrared phosphor, is stable relative to the temperature of the wavelength converter.

[0033] Below, use Figure 1 The near-infrared light-emitting device 100 of this embodiment will be described. Figure 1 FIG. 1 is a schematic diagram showing an example of a near-infrared light emitting device 100 according to an embodiment. Figure 1 As shown, near-infrared light-emitting device 100 includes a solid-state light-emitting element 1 and a wavelength converter 2. Wavelength converter 2 includes a visible phosphor and a near-infrared phosphor. The visible phosphor emits visible fluorescence 22 having a maximum fluorescence intensity within the visible light wavelength range. The near-infrared phosphor emits near-infrared fluorescence 21 having a maximum fluorescence intensity within the near-infrared wavelength range. Near-infrared light-emitting device 100 is configured to emit output light 20 containing visible fluorescence 22 and near-infrared fluorescence 21. Output light 20 includes a visible fluorescence component having a spectral intensity within the visible light wavelength range and a near-infrared fluorescence component having a spectral intensity within the near-infrared wavelength range.

[0034] The solid-state light-emitting element 1 is configured to emit primary light 10. The output light 20 may also include the primary light 10. The primary light 10 is preferably blue light having a maximum fluorescence intensity in a blue wavelength range of greater than 435 nm and less than 480 nm, particularly greater than 440 nm and less than 470 nm. In this way, both visible phosphors and near-infrared phosphors can be excited by only one solid-state light-emitting element 1. Therefore, the near-infrared light-emitting device 100 is advantageous in simplifying the lighting circuit. In addition, when the primary light 10 can excite the visible phosphor and the near-infrared phosphor with a shorter wavelength of blue light, the technical options for the visible phosphor can be increased. That is, it can be used in combination with any of the green phosphors, yellow phosphors, orange phosphors, and red phosphors described later.

[0035] Solid-state light-emitting element 1 is an element that converts electricity into light. When powered, it converts the supplied electrical energy into light energy. The converted light energy is then emitted from the light extraction surface as primary light 10. Representative examples of solid-state light-emitting element 1 include light-emitting diodes (LEDs) and laser diodes (LDs).

[0036] The wavelength converter 2 includes a visible phosphor and a near-infrared phosphor. The visible phosphor can also be configured to be excited by the primary light 10 emitted by the solid-state light emitting element 1. In addition, the near-infrared phosphor can also be configured to be excited by the primary light 10 emitted by the solid-state light emitting element 1.

[0037] The visible phosphor emits visible fluorescence 22 having a maximum fluorescence intensity within the wavelength range of visible light. The visible phosphor can be at least one selected from the group consisting of a green phosphor that emits light having a maximum fluorescence intensity within a wavelength range of 490 nm to less than 570 nm, a yellow phosphor that emits light having a maximum fluorescence intensity within a wavelength range of 570 nm to less than 585 nm, an orange phosphor that emits light having a maximum fluorescence intensity within a wavelength range of 585 nm to less than 620 nm, and a red phosphor that emits light having a maximum fluorescence intensity within a wavelength range of 620 nm to less than 780 nm. This allows for adjustment of the spectral distribution of the visible fluorescence component. Therefore, the visible fluorescence component of the output light 20 emitted from the near-infrared light-emitting device 100 can be adjusted according to the intended use.

[0038] The visible phosphor may be selected from Ce 3+ Activated garnet phosphor, Eu 2+ Activated alkaline earth metal nitride silicate and Eu 2+At least one phosphor selected from the group consisting of activated alkaline earth metal nitride aluminum silicate. These visible phosphors have a high practical performance as LED lighting. Therefore, these visible phosphors are not only easily available but also provide reliability and ease of use for the near-infrared light-emitting device 100.

[0039] As Ce 3+ Activated garnet phosphors include, for example, those of the general formula RE3Al2(AlO4)3:Ce 3+ The phosphor shown, Ca3Sc2(SiO4)3:Ce 3+ 、Y3Ga2(AlO4)3:Ce 3+ and their solid solutions. In the above general formula, RE represents a rare earth element, for example, at least one rare earth element selected from the group consisting of Sc, Y, La, Tb, Gd and Lu. As the general formula RE3Al2(AlO4)3:Ce 3+ Specifically, the phosphor shown is Lu3Al2(AlO4)3:Ce 3+ 、Y3Al2(AlO4)3:Ce 3+ (YAG) and (Y,Gd)3Al2(AlO4)3:Ce 3+ wait.

[0040] As Eu 2+ Activated alkaline earth metal nitride silicates, for example, Sr2Si5N8:Eu 2+ 、Ca2Si5N8:Eu 2+ and their solid solutions, etc.

[0041] As Eu 2+ Activated alkaline earth metal nitride aluminum silicate, for example, can be given as MAlSiN3:Eu 2+ In the above general formula, M represents magnesium or alkaline earth metal, for example, at least one metal element selected from the group consisting of Mg, Ca, Sr and Ba. 2+ Activated alkaline earth metal nitride aluminum silicate, for example, CaAlSiN3:Eu 2+ (CASN), SrAlSiN3:Eu 2+ 、(Sr,Ca)AlSiN3:Eu 2+ (SCASN) and their solid solutions, etc.

[0042] Among them, the visible phosphor preferably includes at least one phosphor selected from the group consisting of YAG, CASN, and SCASN.

[0043] The near-infrared phosphor emits near-infrared fluorescence 21 having a maximum fluorescence intensity within the wavelength range of the near-infrared ray. The near-infrared fluorescence 21 may also have a spectral intensity at least in the entire range of wavelengths above 700 nm and below 1000 nm. Such a spectral distribution is suitable for detecting the characteristic absorption bands of the stretching vibrations of NH, CH and OH based on spectroscopy. In addition, in a preferred embodiment, the spectral intensity of the spectral distribution at a wavelength of 1000 nm is greater than the spectral intensity at a wavelength of 700 nm. In addition, in a preferred embodiment, the fluorescence is emitted in which the proportion of the near-infrared light component on the wavelength side longer than 750 nm, more preferably longer than 780 nm, is greater than the proportion of the light component on the wavelength side shorter than the above wavelength. Such a spectral distribution is more suitable for the near-infrared light-emitting device 100 for infrared spectroscopy.

[0044] The near-infrared fluorescence 21 may also have a maximum fluorescence intensity within a wavelength range of 800 nm or more and less than 900 nm. Such near-infrared fluorescence 21 may be obtained by using, for example, LiGa5O8:Cr 3+ Near-infrared phosphors and similar near-infrared phosphors emit light as near-infrared phosphors that show a fluorescence characteristic with minimal temperature quenching. Therefore, it has become a popular choice for Ce-based LED lighting. 3+ Activated garnet phosphor and Eu 2+ The near-infrared light emitting device 100 is advantageous in that the wavelength converter 2 is formed by combining an activated visible phosphor with low temperature quenching, such as an alkaline earth metal nitride aluminum silicate phosphor. The near-infrared fluorescence 21 preferably has a maximum fluorescence intensity within a wavelength range of 800 nm to 860 nm.

[0045] The half-maximum width (FWHM) of the spectrum with the maximum fluorescence intensity of near-infrared fluorescence 21 is preferably greater than 180 nm. Therefore, even without using multiple near-infrared phosphors, a near-infrared light component with a spectral distribution over a wide wavelength range of 700 to 1000 nm can be obtained using only a single near-infrared phosphor. This reduces the risk of variations in the shape of the near-infrared fluorescence 21 and the spectral distribution of the near-infrared fluorescence component due to temperature quenching differences when using different types of near-infrared phosphors. The half-maximum width of the spectrum of near-infrared fluorescence 21 can be between 180 nm and 240 nm, or between 200 nm and 220 nm.

[0046] The near-infrared phosphor can be formed by adding at least chromium ions that function as fluorescent ions to the crystals of an inorganic compound having the same spinel-type crystal structure as the compound LiGa5O8. Whether or not the compound has the same spinel-type crystal structure as the compound LiGa5O8 can be determined by measuring the X-ray diffraction pattern using an X-ray diffraction method. Specifically, the XRD pattern of the near-infrared phosphor is substantially the same as the XRD pattern of the compound LiGa5O8 (registration number: 33716) registered in the ICSD.

[0047] The above crystal may contain at least one of an alkali metal of the first group, an element of the thirteenth group, and scandium, and oxygen. y (D 1-x Cr x When )5O8 represents a near-infrared phosphor, A mainly contains an alkali metal, and D mainly contains at least one of a Group 13 element and scandium. Alternatively, D may mainly contain a Group 13 element.

[0048] It should be noted that "A mainly contains an alkali metal" means that A contains 75 mol% or more of the alkali metal. A may contain 90 mol% or more of the alkali metal, 95 mol% or more, or even 100 mol%. Furthermore, "D mainly contains at least one of a Group 13 element and scandium" means that D contains 75 mol% or more of the at least one of the Group 13 element and scandium. D may contain 90 mol% or more of the at least one of the Group 13 element and scandium, 95 mol% or more, or even 100 mol%.

[0049] The alkali metal is preferably at least one element selected from the group consisting of Li, Na, K, Rb and Cs, more preferably at least one of Li and K. The Group 13 element is preferably at least one element selected from the group consisting of Al, Ga and In, more preferably Ga.

[0050] The above crystals preferably have less alkali metals than the stoichiometric composition. That is, relative to the stoichiometric composition, A(D 1- x Cr x )5O8, preferably with a composition lacking element A. This is a way to use crystals with chemical properties similar to LiGa5O8 as near-infrared phosphors. Therefore, it is expected that the same as LiGa5O8:Cr 3+ It has somewhat unique fluorescence properties similar to those of near-infrared phosphors. Furthermore, when applied to spectroscopy, it is expected to enable high-precision non-destructive measurements.

[0051] The near-infrared phosphor is preferably composed of the general formula A y (D1-x Cr x )5O8 represents that A contains an alkali metal as a main component, D contains at least one of a Group 13 element and scandium as a main component, and y is less than 1. When y is less than 1, a near-infrared phosphor with a small proportion of the luminescent component of the bright line can be obtained. y is more preferably less than 0.90, further preferably less than 0.85, and particularly preferably less than 0.83. In addition, y is preferably greater than or equal to 0.70. When y is greater than or equal to 0.70, a heterogeneous β-Ga2O3:Cr 3+ The phosphor is less likely to coexist, making it easier to obtain the desired slightly unique fluorescent properties. y is more preferably 0.75 or greater, and even more preferably 0.77 or greater.

[0052] The crystal preferably contains LiGa5O8 as a main component, with a portion of Ga being substituted by Cr. Here, "the crystal contains LiGa5O8 as a main component" means that the crystal contains 75 mol% or more of LiGa5O8, preferably 90 mol% or more.

[0053] Here, the general formula LiGa5O8:Cr 3+ The phosphor represented by (hereinafter referred to as LiGa5O8:Cr 3+ Phosphor) is known as a deep red phosphor that emits a bright line-shaped deep red fluorescent component with a maximum fluorescence intensity around 715 to 720 nm. 3+ The fluorescent properties of the phosphor were evaluated and it was found that it can function as a near-infrared phosphor under specific mixing and synthesis conditions. 3+ Phosphors exhibit the following examples of fluorescence characteristics that are somewhat unique as near-infrared phosphors.

[0054] (1) The fluorescence intensity has a maximum value (fluorescence peak) in a wavelength range of 800 nm to 900 nm, such as around 830 nm.

[0055] (2) It has a fluorescent component in a wide wavelength range of 700 to 1000 nm.

[0056] (3) The fluorescence spectrum is ultra-broad, with the half-width at half maximum of the spectrum at the maximum fluorescence intensity exceeding 180 nm.

[0057] (4) Temperature quenching is small (the maximum fluorescence intensity at a phosphor temperature of 150°C is more than 90% of the maximum fluorescence intensity at 30°C).

[0058] (5) The wavelength conversion efficiency (internal quantum efficiency) of converting the absorbed visible light component into the near-infrared light component exceeds 80% even in the prototype in the early stages of development.

[0059] That is, it was found that LiGa5O8:Cr 3+ The phosphor functions not primarily as a deep red phosphor, but rather as a highly efficient phosphor that emits near-infrared light components with an extremely broad fluorescence spectrum and exhibits minimal temperature quenching. These fluorescence properties, which are rare for near-infrared phosphors, can be effectively utilized in a near-infrared light-emitting device 100 suitable for high-precision non-destructive inspection using spectroscopy, with minimal changes in the spectral distribution shape associated with temperature increases in the wavelength converter 2.

[0060] In order to facilitate the understanding of the present disclosure, the fluorescence intensity maintenance rate, internal quantum efficiency, fluorescence peak wavelength and FWHM of several near-infrared phosphors reported in the report are summarized in Table 1. Table 1 also records the LiGa5O8:Cr 3+ Near-infrared phosphor and LiGa5O8:Cr of Comparative Example 1 3+ Fluorescence properties of deep red phosphors.

[0061] The fluorescence intensity maintenance rate is a value inversely correlated with temperature quenching and is defined as the maximum fluorescence intensity at 150°C relative to the maximum fluorescence intensity at 30°C. The internal quantum efficiency is the photon conversion efficiency of the absorbed visible and near-infrared components. The fluorescence peak wavelength is the wavelength at which the fluorescence intensity reaches its maximum. The full width at half maximum (FWHM) is the full width at half maximum of the spectrum at the fluorescence intensity maximum.

[0062] In addition, in Table 2, for reference, the fluorescence characteristics of representative visible phosphors known for LED lighting are summarized.

[0063] Table 1

[0064]

[0065] Table 2

[0066]

[0067] Generally, for many phosphors, the degree of thermal quenching is correlated with the wavelength conversion efficiency of the phosphor under optimized manufacturing conditions. Therefore, as can be seen from Tables 1 and 2, phosphors with greater fluorescence intensity maintenance tend to exhibit higher internal quantum efficiency.

[0068] Furthermore, the table shows that among phosphors with low fluorescence intensity maintenance rates, some exhibit high internal quantum efficiencies. This is due to differences in the patterns of their temperature quenching characteristics. For example, among phosphors that exhibit temperature quenching, where fluorescence intensity drops sharply above approximately 100°C, data is obtained showing high internal quantum efficiencies at room temperature, such as 30°C, and low fluorescence intensity at 150°C. In other words, phosphors with high internal quantum efficiencies at room temperature are not necessarily those with low temperature quenching (high maximum fluorescence intensity), but phosphors with low temperature quenching can be expected to have high internal quantum efficiencies.

[0069] As can be seen from Tables 1 and 2, the fluorescence intensity maintenance rate of the near-infrared phosphors in Table 1 is much lower than that of the visible phosphors in Table 2, and the majority of the phosphors have large temperature quenching.

[0070] It should be noted that, according to the investigation and evaluation by the inventors, the near-infrared phosphors having a fluorescence intensity maintenance rate exceeding 90% at a phosphor temperature of 150°C are, for example, Ca3Sc2Si3O 12 :Cr 3+ and LiGa5O8:Cr 3+ If we further develop near-infrared phosphors with a fluorescence peak in the wavelength region exceeding 800nm ​​or near-infrared phosphors with a full width half maximum (FWHM) of fluorescence exceeding 180nm from these phosphors, we will only find LiGa5O8:Cr with the unexpected fluorescence characteristics. 3+ Therefore, the LiGa5O8:Cr near-infrared phosphor of the present disclosure is 3+ It is considered to be a near-infrared phosphor that exhibits rare fluorescence properties.

[0071] In addition, LiGa5O8:Cr has a fluorescence intensity maximum in the wavelength region exceeding 800nm, especially around 850nm. 3+ The fluorescence of near-infrared phosphors has a spectral distribution that is relatively close to that of halogen bulbs. Therefore, the use of such near-infrared fluorescent components is suitable for replacing halogen bulbs that emit a lot of heat. In addition, in recent years, it has been discovered that by simply irradiating harvested fruits and vegetables with near-infrared light with a wavelength of around 850nm for a very short time, it is possible to suppress the subsequent loss of freshness and rotting, and to achieve improvements in fruit quality such as maintaining vitamin C, preventing softening, and maintaining gloss. Therefore, LiGa5O8:Cr 3+ The fluorescence of near-infrared phosphors is also suitable for maintaining the freshness of fruits and vegetables as described above.

[0072] On the other hand, one embodiment of LiGa5O8:Cr 3+Near-infrared phosphors emit an ultra-broadband near-infrared light component with a fluorescence spectrum with a half-width at half maximum exceeding 180nm. Therefore, using a single near-infrared phosphor, it is possible to produce a near-infrared light component with a spectral distribution across a wide wavelength range of 700 to 1000nm. This reduces the need to utilize multiple near-infrared light components with different fluorescence peak wavelengths, contributing to technological simplification.

[0073] It should be noted that most near-infrared phosphors, especially those emitting long-wavelength near-infrared light components, show relatively large temperature quenching, or LiGa5O8:Cr 3+ The reason why near-infrared phosphors exhibit such rare fluorescence properties is unclear. It is hoped that the scientific reasons for this will be clarified in the future. In addition, hypotheses include the aforementioned possibility that the equilibrium position of the excited state of the fluorescent ion, which is prone to fluorescing, is close to the ground state.

[0074] The near-infrared fluorescence 21 or near-infrared fluorescence component may also have a sharp peak in the wavelength range of 710 nm to 730 nm. The reason is unclear, but in LiGa5O8:Cr 3+ In the fluorescence spectrum of the near-infrared phosphor, such a peak is generally confirmed. That is, the near-infrared phosphor that emits fluorescence with such a peak is sometimes extremely low in temperature quenching. On the other hand, the near-infrared fluorescence 21 or the near-infrared fluorescence component may not have a peak in the wavelength range of 710nm to 730nm. Alternatively, even if the near-infrared fluorescence 21 or the near-infrared fluorescence component has a peak, the maximum fluorescence intensity in the wavelength range of 800nm ​​to 860nm is set to 1. NIR , set the maximum intensity of the peak to I DR In the case of DR Less than I NIR Here, a peak refers to, for example, Figure 15 The sharp peak near 720nm shown. For example, when the spectral distribution is set to spectral data of each 1nm scale, the spectral data changes by more than 7% / nm within the above wavelength range. The above-mentioned near-infrared phosphor emits fluorescence with a large proportion of near-infrared light components on the wavelength side longer than 800nm. Such a near-infrared phosphor is more suitable for the near-infrared light emitting device 100 for infrared spectroscopy. It should be noted that I DR Can be less than I NIR 1.25 times, less than 1.0 times, and less than 0.8 times.

[0075] Near-infrared phosphor is Cr 3+ Activated phosphor, visible phosphor can be Eu 2+ Activated alkaline earth metal nitride silicate and Eu2+ At least one phosphor selected from the group consisting of activated alkaline earth metal nitride aluminum silicate. 3+ The activated phosphor tends to have an excitation peak (absorption peak) in the orange to red wavelength region with a wavelength of 600 nm or more and less than 650 nm. 2+ Activated alkaline earth metal nitride silicates and alkaline earth metal nitride aluminum silicates tend to have a fluorescence peak in the orange-red wavelength range, between 600 nm and less than 650 nm. Therefore, this approach is advantageous in maintaining a constant ratio of light components absorbed by the near-infrared phosphor when the fluorescence spectrum of the visible phosphor undergoes a long-wavelength shift as temperature rises. This results in a near-infrared light-emitting device 100 that is effective in suppressing fluctuations in the spectral distribution associated with temperature increases.

[0076] The wavelength converter 2 may also include a resin fluorescent film, a fluorescent ceramic, or a composite. The composite may include at least one of a resin fluorescent film and a fluorescent ceramic. The wavelength converter 2 may contain 95% or more, 99% or more, or 100% by mass of an inorganic compound. A wavelength converter 2 containing a higher proportion of inorganic compound exhibits superior thermal conductivity, thereby improving heat dissipation.

[0077] Resin fluorescent films can also be made by dispersing particulate phosphors in a resin. Resin fluorescent films can be formed, for example, by curing a phosphor paste obtained by mixing a resin and a powdered phosphor. Translucent resins can be used as the resin, such as silicone resins. Fluorescent ceramics can also be formed by molding phosphors. Fluorescent ceramics can be formed, for example, by pressurizing and heating phosphor raw materials or phosphor powders to cause them to react and sinter.

[0078] The wavelength converter 2 may also contain fluorescent ceramics. The wavelength converter 2 may also contain fluorescent ceramics as a main component. The wavelength converter 2 containing fluorescent ceramics as a main component means that the wavelength converter 2 contains 75% by weight or more of fluorescent ceramics. The wavelength converter 2 may also contain 90% by weight or more of fluorescent ceramics.

[0079] Fluorescent ceramics can contain a near-infrared phosphor as a main component. Fluorescent ceramics containing a near-infrared phosphor as a main component mean that the fluorescent ceramics contain 75% or more of the near-infrared phosphor by weight. Fluorescent ceramics can contain 90% or more, or even 100% by weight, of the near-infrared phosphor. Furthermore, the fluorescent ceramics can be made to contain at least the phosphor with the highest temperature quenching among the phosphors used. This not only improves thermal conductivity but also increases the light absorption rate of the excitation light. This facilitates heat dissipation design, high output, and particularly high output of near-infrared light components and high output of fluorescent components emitted by phosphors with high temperature quenching.

[0080] The output light 20 includes a visible fluorescent component and a near-infrared fluorescent component. The visible fluorescent component has a spectral intensity within the wavelength range of visible light, and the near-infrared fluorescent component has a spectral intensity within the wavelength range of near-infrared light.

[0081] The output light 20 may have spectral intensity at least over the entire wavelength range of 700 nm to 1000 nm. The near-infrared light emitting device 100 emitting such output light 20 is suitable for detecting or analyzing the characteristic absorption bands of stretching vibrations of NH, CH, and OH using spectroscopy.

[0082] The output light 20 preferably does not have the aforementioned peak. Specifically, the spectral distribution within the wavelength range of 700 nm to 1000 nm preferably varies smoothly with wavelength. This suppresses measurement and analysis errors at specific wavelengths, enabling highly reliable evaluation data to be obtained, resulting in a near-infrared light-emitting device 100 that is advantageous for near-infrared spectroscopy. More specifically, when the spectral distribution is provided as spectral data with 1 nm increments, it is preferred that the spectral data within the wavelength range of 700 nm to 1000 nm do not vary by more than 7% / nm, particularly 5% / nm.

[0083] The output light 20 may also have a spectral peak at least in the wavelength range of 800nm ​​to 900nm, in particular, 800nm ​​to 860nm. Such output light 20 is in a form in which the spectral peak in the near-infrared wavelength region is close to the spectral peak of a halogen bulb. Therefore, it becomes easier to use the components and attached software of the conventional spectroscopic device using a halogen bulb. Therefore, it is possible to industrially produce spectroscopic devices without making major design changes. In addition, in recent years, it has been discovered that by simply irradiating harvested fruits and vegetables with near-infrared light of a wavelength of around 850nm for a very short time, it is possible to suppress the subsequent reduction in freshness and decay, and to achieve improvements in fruit quality such as maintenance of vitamin C, suppression of softening, and maintenance of gloss. Therefore, the near-infrared light-emitting device 100 of this embodiment is conducive to maintaining the freshness of fruits and vegetables as described above.

[0084] The half-width at half maximum of the spectrum with the maximum fluorescence intensity within the wavelength range of 800 nm to less than 900 nm can also exceed 180 nm. Therefore, a near-infrared light component with a spectral distribution over a wide wavelength range can be obtained. Therefore, the near-infrared light emitting device 100 is suitable for near-infrared spectroscopy.

[0085] The near-infrared light emitting device 100 is configured to satisfy 0.853M VIS ≤M NIR <1.147M VIS Here, M VIS isI max-VIS-150 Relative to Imax-VIS-30 The ratio (I max-VIS-150 / I max-VIS-30 ). M VIS Indicates the visible light intensity maintenance rate. max-VIS-30 It is the maximum fluorescence intensity of the visible fluorescent component when the temperature of the wavelength converter 2 is 30°C. max-VIS-150 It is the maximum fluorescence intensity of the visible fluorescent component when the temperature of the wavelength converter 2 is 150°C. NIR For I max-NIR-150 Relative to I max-NIR-30 The ratio (I max-NIR-150 / I max-NIR-30 ). M NIR Indicates the near infrared intensity maintenance rate. max-NIR-30 is the maximum fluorescence intensity of the near-infrared fluorescence component when the temperature of the wavelength converter 2 is 30°C. max-NIR-150 This is the maximum fluorescence intensity of the near-infrared fluorescent component when the temperature of the wavelength converter 2 is 150°C.

[0086] That is, a near-infrared phosphor with a small temperature quenching difference from the visible phosphor is used in combination with a visible phosphor. Thus, even if the temperature of the wavelength converter 2 rises over time after the near-infrared light-emitting device 100 is turned on, the intensity ratio of the visible fluorescent component to the near-infrared fluorescent component changes little, and thus the spectral distribution of the output light 20 is stable. Furthermore, the near-infrared light-emitting device 100 can also be configured to meet the preferred 0.90 M VIS ≤M NIR <1.10M VIS , more preferably 0.95M VIS ≤M NIR <1.05M VIS relationship.

[0087] M NIR Preferably, it exceeds 90%. That is, even when the temperature of the wavelength converter 2 rises, the decrease in the fluorescence intensity of the near-infrared fluorescent component is minimal. Such a wavelength converter 2 is obtained by using a near-infrared phosphor that has low temperature quenching and a fluorescence intensity maintenance rate exceeding 90% at a phosphor temperature of 150°C.

[0088] M VIS Preferably, it exceeds 90%. That is, even when the temperature of the wavelength converter 2 rises, the decrease in the fluorescence intensity of the visible fluorescent component is minimal. Such a wavelength converter 2 can be obtained, for example, by using a phosphor with low temperature quenching and a fluorescence intensity maintenance rate exceeding 90%, as shown in Table 2 above, such as a phosphor for LED lighting.

[0089] More preferably M NIR and M VISBoth of these values ​​exceed 90%. In this case, even if the temperature of the wavelength converter 2 rises, the intensity of the output light 20 hardly decreases. Therefore, further increases in the output of the output light 20 can be expected. Such a near-infrared light-emitting device 100 is more suitable for spectrometry. Specifically, such a near-infrared light-emitting device 100 can evaluate the quality of objects such as fruits and vegetables with high precision in a non-destructive manner. In addition, such a near-infrared light-emitting device 100 can also maintain the freshness of fruits and vegetables by irradiating them with near-infrared rays, and can be used to evaluate the quality of materials with uneven body color.

[0090] The near-infrared light emitting device 100 of this embodiment can be widely used in non-destructive inspection using spectroscopy, particularly in quality evaluation of fruits and vegetables, etc. The near-infrared light emitting device 100 can be used as a small, high-performance near-infrared light source, for example.

[0091] As described above, the near-infrared light-emitting device 100 of this embodiment includes a solid-state light-emitting element 1 and a wavelength converter 2. The wavelength converter 2 includes a visible phosphor that emits visible fluorescence 22 having a maximum fluorescence intensity within the wavelength range of visible light, and a near-infrared phosphor that emits near-infrared fluorescence 21 having a maximum fluorescence intensity within the wavelength range of near-infrared light. The near-infrared light-emitting device 100 emits output light 20 containing visible fluorescence and near-infrared fluorescence 21. The output light 20 includes a visible fluorescence component having a spectral intensity within the wavelength range of visible light, and a near-infrared fluorescence component having a spectral intensity within the wavelength range of near-infrared light. The near-infrared light-emitting device 100 is configured to satisfy 0.853M VIS ≤M NIR <1.147M VIS Relationship. VIS For I max-VIS-150 Relative to I max-VIS-30 The ratio of I max-VIS-30 It is the maximum fluorescence intensity of the visible fluorescent component when the temperature of the wavelength converter 2 is 30°C. max-VIS-150 It is the maximum fluorescence intensity of the visible fluorescent component when the temperature of the wavelength converter 2 is 150°C. NIR For I max-NIR-150 Relative to I max-NIR-30 The ratio of I max-NIR-30 is the maximum fluorescence intensity of the near-infrared fluorescence component when the temperature of the wavelength converter 2 is 30°C. max-NIR-150 It is the maximum fluorescence intensity of the near-infrared fluorescent component when the temperature of the wavelength converter 2 is 150°C.

[0092] Even if conventional near-infrared light-emitting devices were intended to non-destructively evaluate the quality of fruits and vegetables using both visible and near-infrared phosphors, the intensity of the near-infrared fluorescent component could decrease relative to the intensity of the visible fluorescent component as the temperature of the phosphors rises due to the lighting of the solid-state light-emitting element 1. Consequently, conventional near-infrared light-emitting devices presented a problem in that they could not accurately evaluate quality within a short period of time after lighting.

[0093] On the other hand, the near-infrared light emitting device 100 of this embodiment is configured to satisfy 0.853M VIS ≤M NIR <1.147M VIS Therefore, even if the temperature of the wavelength converter 2 rises over time after the near-infrared light-emitting device 100 is turned on, the change in the intensity ratio of the visible fluorescence component to the near-infrared fluorescence component is small. Therefore, the shape of the spectral distribution of the near-infrared light-emitting device 100 changes little as the temperature of the wavelength converter 2 rises.

[0094] [Spectroscopic device and spectroscopic method]

[0095] Next, use Figure 2 and Figure 3 The spectroscopic device 200 and the spectroscopic method of this embodiment will be described. The spectroscopic device 200 is, for example, a near-infrared spectroscopic device. The spectroscopic method is, for example, near-infrared spectroscopic method. Figure 2 This is a schematic diagram showing an example of a transmission-type spectroscopic device 200 . Figure 3 1 is a schematic diagram showing an example of a reflective spectroscopic device 200. Figure 2 and Figure 3 As shown, the spectroscopic device 200 includes the near-infrared light emitting device 100. That is, the spectroscopic device 200 relates to spectrometry using the near-infrared light emitting device 100.

[0096] like Figure 2As shown, a transmission-type spectrometer 200 includes a near-infrared light emitting device 100 and a spectrometer 6. An inspection object 5 is disposed between the near-infrared light emitting device 100 and the spectrometer 6. The near-infrared light emitting device 100 is configured to emit output light 20. The inspection object 5 is disposed so as to be irradiated with the output light 20. The spectrometer 6 is configured to receive transmitted light 11, particularly near-infrared transmitted light, that penetrates the interior of the inspection object 5, of the output light 20 irradiating the inspection object 5. The spectrometer 6 detects and separates the transmitted light 11. The spectrometer 6 may be, for example, a near-infrared spectrometer. The spectrometer 200 may also be an inspection device. The inspection device may also analyze the data separated by the spectrometer 6. The inspection device may also include an analysis unit (not shown) that determines or determines the quality of inspection items such as the internal state and quality of the inspection object 5. The analysis unit may also include a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). The CPU may also read the program and reference data stored in the ROM and perform information processing related to the analysis of the inspection items according to the program.

[0097] like Figure 3 As shown, the reflective spectroscopic device 200 also includes the near-infrared light emitting device 100 and the spectrometer 6. However, in the reflective spectroscopic device 200, the spectrometer 6 is configured to receive reflected light 12, particularly near-infrared reflected light, from the output light 20 irradiated onto the inspection object 5. Other points are the same as those of the transmissive spectroscopic device 200, and therefore their description is omitted.

[0098] The reflective spectrometer 200 may also include a reflective member (not shown), such as a metal plate, particularly a near-infrared reflective member. If the near-infrared fluorescent component of the output light 20 that has passed through the inspection object 5 is reflected by the reflective member and re-transmits the interior of the inspection object 5, near-infrared spectroscopic data unique to the inspection object 5 can be readily obtained, even if the inspection object 5 is, for example, a liquid.

[0099] Furthermore, the transmitted light 11 and the reflected light 12 only need to contain near-infrared fluorescent components. Depending on the form of the inspection object 5, the visible fluorescent component can be transmitted or reflected. In the case of reflecting the visible light component, the visible light component can be separated and utilized for, for example, visual inspection of the inspection object 5.

[0100] The inspection object 5 may also be food. In addition, "food" is a general term for items consumed by humans, such as ingredients for lunch boxes, grains, fruits and vegetables, meat, fish, processed foods, and beverages.

[0101] The spectrometer 200 can also be used as a foreign matter detection device to detect whether the inspection object 5 contains foreign matter. For example, the spectrometer 200 can also be used to detect the presence and condition of foreign matter mixed in food. Furthermore, the spectrometer 200 can also be used as an inspection device other than a foreign matter detection device, such as a quality control device for evaluating the quality of fruits and vegetables. By measuring the amount of near-infrared light transmitted through fruits and vegetables, it is possible to evaluate or measure the sugar content, acidity, or internal disorders of the fruits and vegetables. Therefore, such a spectrometer 200 is suitable for quality management of fruits and vegetables.

[0102] In this manner, spectrometer 200 utilizes at least the near-infrared component contained in output light 20. For example, spectrometer 200 can also detect at least one characteristic absorption band of stretching vibration selected from the group consisting of NH, CH, and OH. Specifically, spectrometer 200 can be configured to obtain near-infrared spectroscopic data such as these characteristic absorption bands. Detecting characteristic absorption bands as analytical data allows for a wide range of uses of spectrometer 200, resulting in high versatility and is therefore preferred.

[0103] As described above, the spectroscopic device 200 includes the near-infrared light-emitting device 100. Furthermore, the spectroscopic method utilizes the near-infrared light-emitting device 100. As described above, the near-infrared light-emitting device 100 exhibits minimal changes in the shape of the spectral distribution as the temperature of the wavelength converter 2 increases. Therefore, the spectroscopic device 200 and the spectroscopic method also exhibit minimal changes in the shape of the spectral distribution as the temperature of the wavelength converter 2 increases. The spectroscopic device 200 and the spectroscopic method of this embodiment can be widely used in foreign matter inspection, quality inspection, and the like.

[0104] Furthermore, in the above embodiment, unless otherwise specified, the spectra of the spectral distribution of the output light 20, the near-infrared fluorescence 21, and the visible fluorescence 22 may be spectra obtained when the primary light 10 (excitation light) has a wavelength of 450 nm. Furthermore, unless otherwise specified, the above spectra may be spectra at 30°C. Specifically, the above spectra may be spectra obtained when the temperature of the phosphor or wavelength converter is 30°C.

[0105] Example

[0106] Hereinafter, the present embodiment will be described in more detail with reference to examples, but the present embodiment is not limited to these examples. It should be noted that evaluation was performed at 30° C. unless otherwise specified.

[0107] (Example 1)

[0108] A near-infrared light-emitting device (wavelength conversion-type light-emitting device) including a solid-state light-emitting element and a wavelength converter was produced using the following components 1) to 4).

[0109] 1) Solid-state light-emitting devices

[0110] High-power blue LED (measured peak wavelength: 460nm) (Product No.: SMBB 450H-1100, Watos OptoSemiconductor Co., Ltd.)

[0111] 2) Wavelength converter

[0112] 2-1)CaAlSiN3:Eu 2+ (CASN) Red phosphor (fluorescence peak wavelength: 651 nm) (Mitsubishi Chemical Corporation)

[0113] 2-2) LiGa5O8:Cr 3+ (LGO) near-infrared phosphor (fluorescence peak wavelength: 833 nm) (produced by the method described below)

[0114] 2-3) Two-component hybrid thermosetting silicone resin (LED sealing material, product name: KER-2600A / B, Shin-Etsu Chemical Co., Ltd.)

[0115] (Fabrication of Wavelength Converter)

[0116] A wavelength converter was produced by laminating a first wavelength converter (one CASN red phosphor sheet) and a second wavelength converter (two LGO near-infrared phosphor sheets) produced as follows.

[0117] (Fabrication of the First Wavelength Converter)

[0118] 0.68 g of CASN red phosphor and silicone resin (1 g of KER-2600A and 1 g of KER-2600B) were mixed using a stirring and degassing device and further degassed. The stirring and degassing device used was manufactured by SHING Co., Ltd., product name: Awatori Rentaro (registered trademark), model: ARE-310. The rotation speed of the stirring and degassing device was approximately 2000 rpm, and the treatment was performed for 3 minutes. In this way, a phosphor paste containing CASN red phosphor and silicone resin was prepared. Using a dispenser (model: ML-5000XII, manufactured by Musashi Engineering Co., Ltd.), the obtained phosphor paste was dropped into a frame with a height of approximately 140 μm. Then, the phosphor paste was heated in an atmosphere at 150°C for 2 hours to cure it. In this way, a resin phosphor film (CASN red phosphor sheet: 10 mm in length × 10 mm in width) with a thickness of approximately 130 μm was formed, and a first wavelength converter was obtained.

[0119] (Fabrication of the Second Wavelength Converter)

[0120] First, LiGa5O8 was synthesized by the following steps: Cr3+ Near-infrared phosphor: Prepare the following compound powders as raw materials.

[0121] 1) Lithium carbonate (Li2CO3): Purity 2N, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0122] 2) Gallium oxide (Ga2O3): Purity 4N, manufactured by Asia Materials Co., Ltd.

[0123] 3) Chromium oxide (Cr2O3): Purity 3N, manufactured by Kojundo Chemical Research Institute Co., Ltd.

[0124] To become Li(Ga 0.97 Cr 0.03 )5O8, that is, the above raw materials are weighed and blended in a manner such that the ratio of the metal elements is the desired. The blended raw materials are dry-mixed using a mortar and pestle to prepare a mixed raw material. The mixed raw material is transferred to an alumina crucible with a lid and fired in an air atmosphere at 1500°C for 4 hours using a box-type electric furnace. The fired product obtained by firing is lightly crushed to prepare LiGa5O8:Cr 3+ (LGO) near-infrared phosphor. The characteristics of LGO near-infrared phosphor will be described later.

[0125] Next, 0.40 g of LGO near-infrared phosphor and silicone resin (1 g of KER-2600A and 1 g of KER-2600B) were mixed with the first wavelength converter using a stirring degassing device and further degassed. In this way, a phosphor paste containing LGO near-infrared phosphor and silicone resin was prepared. Using the above-mentioned dispenser, the obtained phosphor paste was dropped into a frame with a height of about 320 μm. Then, the phosphor paste was heated in an atmosphere at 150°C for 2 hours to cure it. In this way, a resin phosphor film with a thickness of about 300 μm (LGO near-infrared phosphor sheet: 10 mm long × 10 mm wide) was formed to obtain a second wavelength converter.

[0126] (Fabrication of Near-Infrared Light-Emitting Device)

[0127] The blue LED and the second wavelength converter of the stacked wavelength converter are placed opposite each other, and a phosphor sheet is arranged on the main light extraction surface of the blue LED to produce a Figure 1 The near-infrared light-emitting device shown.

[0128] The luminous characteristics of the obtained near-infrared light-emitting device were evaluated. When a current of 10 mA (2.6 V) flows through the blue LED chip, blue light is emitted from the blue LED chip as primary light. Then, a part of it is converted into a near-infrared fluorescent component by the second wavelength converter. Furthermore, a part of the primary light that has passed through the second wavelength converter is converted into red light as a visible fluorescent component by the first wavelength converter. Then, a mixed light containing blue light as primary light, a near-infrared fluorescent component, and a visible fluorescent component is emitted from the near-infrared light-emitting device as output light. For reference, the appearance of the output light is purple light, which is light of a hue that is not considered to be white light. In addition, purple light is considered to be light based on the additive mixing of the blue light component of the primary light and the red light component of the near-infrared fluorescent component and the visible fluorescent component.

[0129] Figure 4 : represents the spectral distribution of the output light emitted from the near-infrared light emitting device of this embodiment. Figure 4 It can be seen that the spectral distribution of the output light mainly consists of a light component 10A from the primary light, a light component 20A from the near-infrared phosphor of the second wavelength converter, and a light component 20B from the visible phosphor of the first wavelength converter.

[0130] Depend on Figure 4 As can be seen, by utilizing only a kind of near-infrared phosphor, it is possible to obtain an output light with a fluorescence intensity maximum near 830nm. In addition, by utilizing only a kind of near-infrared phosphor, it is possible not only to have a spectral intensity within a wide wavelength range of more than 700nm and less than 1000nm, but also to obtain an output light with a relatively strong spectral intensity within a wavelength range of more than 700nm and less than 950nm. In addition, by utilizing in combination with the CASN red phosphor as a visible phosphor, it is possible to obtain a near-infrared light emitting device that emits an output light that has a spectral intensity without omission within a wavelength range of more than 570nm and less than 1000nm and a small rate of intensity change relative to the wavelength.

[0131] It should be noted that, as shown in Tables 1 and 2, the temperature quenching of LGO near-infrared phosphor and CASN red phosphor is small, and the near-infrared intensity maintenance rate (M NIR ) exceeds 92% and 90%, and the visible light intensity maintenance rate (M VIS ) is 98%. Therefore, the M of the near-infrared light emitting device VIS With M NIR Meet 0.853M VIS (≈0.836)≤M NIR (≈0.920)<1.147M VIS (=1.124).

[0132] Therefore, even if the wavelength converter temperature rises when the near-infrared light-emitting device is turned on, the spectral shape of the wavelength-converted light from the phosphor at wavelengths longer than approximately 490 nm will change minimally. This makes the near-infrared light-emitting device suitable for spectroscopy, for example, in non-destructive measurement of fruits and vegetables, enabling highly accurate quality assessment within a short period of time after turning on the device.

[0133] It should be noted that the spectral shape of the output light from a near-infrared light-emitting device using a phosphor film containing both visible and near-infrared phosphors can be evaluated using these mixed phosphors, even without forming a near-infrared light-emitting device, as long as the spectral shape consists solely of the wavelength-converted light component of the phosphors. Furthermore, the spectral change of the wavelength-converted light component as the temperature of the phosphor film rises can be determined by examining the temperature dependence of the fluorescence of the mixed phosphor. Therefore, the temperature dependence of the fluorescence spectra of several mixed phosphors containing both visible and near-infrared phosphors was briefly evaluated.

[0134] (Examples 2 to 7 and Comparative Examples 1 and 2)

[0135] The visible and near-infrared phosphors used in the evaluation are summarized in Table 3. Figure 5 The temperature quenching of these phosphors is shown in .

[0136] Table 3

[0137]

[0138] Next, mixed phosphors of Examples 2 to 7 and Comparative Examples 1 and 2 were prepared using the formulations described in Table 4.

[0139] Table 4

[0140]

[0141] Next, in order to show the temperature dependence of the mixed phosphor, the fluorescence spectrum was evaluated when the temperature of the mixed phosphor was changed in increments of 40° C. from 30° C. to 270° C. The wavelength of the excitation light that excited the mixed phosphor was 450 nm.

[0142] Figure 6 1 and 2 are the fluorescence spectra of the mixed phosphor of Example 2 at various temperatures. Figure 7 1 and 2 are the fluorescence spectra of the mixed phosphor of Example 3 at various temperatures. Figure 8 These are the fluorescence spectra of the mixed phosphor of Example 4 at various temperatures. Figure 9 These are the fluorescence spectra of the mixed phosphor of Example 5 at various temperatures. Figure 10 These are the fluorescence spectra of the mixed phosphor of Example 6 at various temperatures. Figure 11These are the fluorescence spectra of the mixed phosphor of Example 7 at various temperatures. Figure 12 1 and 2 are fluorescence spectra of the mixed phosphor of Comparative Example 1 at various temperatures. Figure 13 1 and 2 are fluorescence spectra of the mixed phosphor of Comparative Example 2 at various temperatures.

[0143] All of these data are spectral data that have been normalized using the maximum fluorescence intensity of the visible phosphor for the purpose of visualizing changes in the shape of the spectral distribution. In the figure, the spectral data near 450 nm represents the leakage component of the excitation light.

[0144] according to Figures 6 to 13 , the following trends were confirmed.

[0145] (1) In the mixed phosphors of Comparative Examples 1 and 2, which were a mixture of a visible phosphor with low temperature quenching and a near-infrared phosphor with high temperature quenching, a decrease in the intensity of the near-infrared component was observed as the temperature increased.

[0146] (2) In the mixed phosphors of Examples 2 to 7 in which a visible phosphor with low temperature quenching and a near-infrared phosphor with low temperature quenching are mixed, the intensity of the visible light component and the intensity of the near-infrared light component remain almost unchanged as the temperature rises, or a slight increase in the intensity of the near-infrared light component is observed.

[0147] (3) When the visible phosphor is Ce 3+ In the case of activated garnet phosphor (Examples 4, 5 and 7), the 2+ In comparison of the cases of activated nitride-based phosphors (Examples 2, 3, and 6), the latter shows a smaller spectrum change with increasing temperature. This is summarized in Table 5. In Table 5, "150°C / 30°C" corresponds to M NIR / M VIS .

[0148] Table 5

[0149]

[0150] That is, it was found that in order to suppress the variation in the spectral distribution of the output light accompanying the temperature rise, it is effective to configure the near-infrared light emitting device to satisfy 0.853M VIS ≤M NIR <1.147M VIS The above relationship is particularly effective for changes in spectral distribution within the wavelength range of 600 nm to 980 nm, which is effective for precise evaluation of fruits and vegetables. Furthermore, it was found that the following combination of phosphors is more preferred.

[0151] (1) Combination of a visible phosphor and a near-infrared phosphor with a small temperature quenching difference.

[0152] (2)Being Eu 2+ The activated red phosphor and Cr 3+ Combination of activated near-infrared phosphors.

[0153] It should be noted that in order to suppress the change in the spectral distribution of the output light accompanying the temperature rise, the Eu 2+ The activated red phosphor is then 3+ The reason why the combination of activated near-infrared phosphors can produce effective results is considered to be the following effects. 3+ The activated near-infrared phosphor tends to have an excitation peak (absorption peak) in the orange to red wavelength region with a wavelength of 600 nm or more and less than 650 nm. 2+ Activated red phosphors tend to have a fluorescence peak in the orange-red wavelength range, between 600nm and less than 650nm. Therefore, even if the fluorescence spectrum of visible phosphors undergoes some long-wavelength shift with increasing temperature, the excitation peak of near-infrared phosphors also undergoes some long-wavelength shift. Consequently, the proportion of light components absorbed by near-infrared phosphors does not change significantly with increasing phosphor temperature.

[0154] Furthermore, to suppress the decrease in output light intensity that occurs with temperature increases, it is preferable to use a phosphor with a small absolute value of temperature quenching. Furthermore, when there is a combination of a phosphor whose near-infrared light intensity decreases with temperature and a phosphor whose near-infrared light intensity increases with temperature, the latter is preferred.

[0155] Next, synthesize LiGa5O8:Cr 3+ Deep red phosphor, in order to synthesize LiGa5O8:Cr 3+ Near-infrared phosphors were evaluated for comparison.

[0156] (LiGa5O8:Cr 3+ Synthesis of deep red phosphor)

[0157] Except that the firing temperature is set to 1200℃, the LiGa5O8:Cr 3+ A near-infrared phosphor is prepared in the same manner.

[0158] (LiGa5O8:Cr 3+ Evaluation of phosphors)

[0159] First, an X-ray diffraction pattern was measured by X-ray diffraction using a desktop X-ray diffractometer MiniFlex 600 (Rigaku Corporation), and the crystal phase of the compound constituting the phosphor was identified by comparison with the diffraction pattern of a registered compound crystal.

[0160] Figure 14 It is LiGa5O8:Cr 3+ Near-infrared phosphor and LiGa5O8:Cr 3+ X-ray diffraction pattern of deep red phosphor and X-ray diffraction pattern of LiGa5O8 registered in ICSD (Inorganic Crystal Structure Database). Figure 14 It can be seen that LiGa5O8:Cr 3+ The XRD pattern of the near-infrared phosphor shows that it is similar to that of LiGa5O8:Cr 3+ The XRD pattern of deep red phosphor is the same as that of LiGa5O8:Cr 3+ The near-infrared phosphor has a crystal with the same atomic configuration as the compound LiGa5O8.

[0161] Next, the fluorescence spectrum, temperature quenching, and internal quantum efficiency of the phosphor when excited at an excitation wavelength of 450 nm were evaluated using Quantaurus-QY Plus (extended type, absolute PL quantum yield measurement device with heating mechanism) C13534-02 (manufactured by Hamamatsu Photonics Co., Ltd.).

[0162] Figure 15 It is LiGa5O8:Cr 3+ Near-infrared phosphor and LiGa5O8:Cr 3+ Fluorescence spectrum of deep red phosphor. As shown in Table 1, LiGa5O8:Cr 3+ The fluorescence spectrum of near-infrared phosphor has a maximum fluorescence intensity around 833nm. 3+ The fluorescence spectrum of near-infrared phosphors has a fluorescence component in a wide wavelength range of 700 to 1100 nm. 3+ The FWHM of the fluorescence spectrum of near-infrared phosphors exceeds 214nm and 200nm, and the spectrum width is wide. On the other hand, LiGa5O8:Cr 3+ The fluorescence spectrum of the deep red phosphor has a bright line-shaped fluorescence intensity maximum around 715-720nm, and the FWHM is 4nm. 3+ The fluorescence spectrum of the near-infrared phosphor is similar to that of the conventional LiGa5O8:Cr 3+ The fluorescence spectra of deep red phosphors vary greatly.

[0163] Figure 16 It is for LiGa5O8:Cr 3+ Near-infrared phosphor and LiGa5O8:Cr 3+Deep red phosphor, a graph showing the relationship between the phosphor temperature and the maximum fluorescence intensity (temperature quenching characteristics) emitted by the phosphor. As shown in Table 1, LiGa5O8:Cr 3+ The fluorescence intensity maintenance rate of the near-infrared phosphor exceeds 92% and 90%, and the temperature quenching is very small. On the other hand, LiGa5O8:Cr 3+ The fluorescence intensity maintenance rate of the deep red phosphor was 61%.

[0164] Regarding the internal quantum efficiency, as shown in Table 1, LiGa5O8:Cr 3+ Near-infrared phosphor is 85%, in contrast, LiGa5O8:Cr 3+ The deep red phosphor is 54%. It can be seen that LiGa5O8:Cr 3+ The internal quantum efficiency of the near-infrared phosphor exceeds 80% even in prototypes in the early stages of development.

[0165] Finally, in order to improve the LiGa5O8:Cr 3+ Near-infrared phosphor and LiGa5O8:Cr 3+ To determine the accuracy of compositional information related to differences in deep red phosphors, we analyzed the main component compositions of these phosphors. Using an iCAP7400 Duo (manufactured by Thermo Fisher Scientific), we quantitatively evaluated the composition ratios of Li, Ga, and Cr, the main components of the phosphors, using inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0166] As a result, the composition of the deep red phosphor is Li 0.94 (Ga 0.75 Cr 0.03 )5O 8-α In contrast, the composition of the near-infrared phosphor is Li 0.81 (Ga 0.75 Cr 0.03 )5O 8-α It can be seen that LiGa5O8:Cr 3+ The near-infrared phosphor has a stoichiometric composition of Li(Ga 1-x Cr x )5O8 and a composition that is significantly deficient in Li. These results show that a phosphor that functions as a near-infrared phosphor can be obtained if the amount of Li is small relative to the stoichiometric composition.

[0167] For reference, LiGa5O8:Cr 3+ It is assumed that the near-infrared phosphor exhibits the rare fluorescence characteristics described above.

[0168] LiGa5O8:Cr3+ The near-infrared phosphor is a composition that is Li-deficient relative to the stoichiometric composition. However, it also has similarities to LiGa5O8:Cr 3+ The deep red phosphor has substantially the same crystal structure. If these are taken into consideration, then in LiGa5O8:Cr 3+ In the crystal of near-infrared phosphor, Ga 3+ Part of the valence changes to Ga + , it is possible to maintain the crystal structure.

[0169] That is, the crystal that should have been LiGa(III)3(GaO4)2 becomes X(LiGa(I)Ga(III)2(GaO4)2) (where X satisfies the value of 0<X<1), which is an assumption that the crystal structure of LiGa5O8 is maintained. If it becomes this form, the substitution valence changes to Ga + Ga 3+ The lattice position of Cr 3+ (First Cr 3+ ) have to be in Ga + There is a state where charge strain exists at or near the lattice position. This effect may change the spectral shape and be observed as broad light.

[0170] In addition, the valence does not change after substitution to Ga + Ga 3+ The lattice position of Cr 3+ (Second Cr 3+ ) has a maximum fluorescence intensity (wavelength: about 718 nm) located at a position slightly larger than the first Cr 3+ The maximum fluorescence intensity (wavelength: about 830nm) is on the shorter wavelength side. Therefore, it cannot be denied that the first Cr 3+ Absorbing the second Cr 3+ On the other hand, it is known that Cr 3+ Usually it does not occupy 4 coordination. Therefore, it is speculated that in the crystal of X(LiGa(I)Ga(III)2(GaO4)2), Cr 3+ It exists at the lattice positions of Ga(I) and Ga(III) other than the Ga lattice position of (GaO4).

[0171] Here, the ratio of Ga(I):Ga(III) is 1:2. Therefore, the first Cr 3+ The relative molar number is large, which is regarded as the second Cr 3+ Therefore, it is undeniable that there is a possibility of generating 3+ (bright line luminescence) to the first Cr 3+Through such energy transfer, it is almost impossible to observe the energy transfer from the second Cr 3+ The bright line luminescence caused by the first Cr 3+ This results in a fluorescence spectrum shape dominated by a broad emission component.

[0172] In addition, if the first Cr 3+ Existing in a state with charge strain cannot deny the possibility that the ground state or excited state has a deep potential well. Moreover, if such an electronic state is formed, these electronic states cannot easily change their positions unless they acquire high energy. Therefore, non-luminescent transitions from the excited state to the ground state are difficult to occur, and even at high temperatures, it is possible to exhibit high fluorescence efficiency similar to that at room temperature.

[0173] Furthermore, many near-infrared phosphors exhibit relatively large temperature quenching, which is an essential problem of near-infrared phosphors and may be caused by their photophysical properties.

[0174] The fluorescence of a near-infrared phosphor is, for example, fluorescence that absorbs blue light and converts it into near-infrared light. Therefore, compared to the fluorescence of a visible phosphor, it becomes wavelength-converted light with a larger Stokes shift (the energy difference between light absorption and fluorescence emission). In addition, this also means that it becomes wavelength-converted light generated by electron energy transition with a large Franck-Condon shift (the shift of the equilibrium position between the ground state and the excited state). Therefore, it is speculated that fluorescent ions (such as Cr) that are likely to become near-infrared phosphors 3+ ) is close to the equilibrium position of the excited state of the ground state. Since the fluorescence transition is carried out in this way, it is likely to be easily temperature quenched.

[0175] Homemade LiGa5O8:Cr 3+ In near-infrared phosphors, due to Cr 3+ In such a special environment in LiGa5O8 crystals, it is possible to become a phosphor with both rare fluorescence spectrum and temperature quenching characteristics.

[0176] (Note)

[0177] The following technology is disclosed based on the description of the above embodiments.

[0178] (Technology 1) A near-infrared light-emitting device comprising: a solid-state light-emitting element and a wavelength converter, wherein the wavelength converter includes a visible phosphor that emits visible light fluorescence having a maximum fluorescence intensity within a wavelength range of visible light, and a near-infrared phosphor that emits near-infrared fluorescence having a maximum fluorescence intensity within a wavelength range of near-infrared light, wherein the near-infrared light-emitting device emits output light including the visible light fluorescence and the near-infrared fluorescence, wherein the output light includes a visible fluorescence component having a spectral intensity within the wavelength range of visible light and a near-infrared fluorescence component having a spectral intensity within the wavelength range of near-infrared light, and the near-infrared light-emitting device is configured to satisfy a 0.853M VIS ≤M NIR <1.147M VIS The relationship between the M VIS For I max-VIS-150 Relative to I max-VIS-30 The ratio of I max-VIS-30 is the maximum fluorescence intensity of the visible fluorescent component when the temperature of the wavelength converter is 30° C., and the I max-VIS-150 is the maximum fluorescence intensity of the visible fluorescent component when the temperature of the wavelength converter is 150° C., and the M NIR For I max-NIR-150 Relative to I max-NIR-30 The ratio of I max-NIR-30 is the maximum fluorescence intensity of the near-infrared fluorescent component when the temperature of the wavelength converter is 30° C., I max-NIR-150 It is the maximum fluorescence intensity of the near-infrared fluorescent component when the temperature of the wavelength converter is 150°C.

[0179] With this configuration, even if the temperature of the wavelength converter increases over time after the near-infrared light-emitting device is turned on, the change in the intensity ratio of the visible fluorescent component to the near-infrared fluorescent component is small. Therefore, the shape of the spectral distribution of the near-infrared light-emitting device changes little as the temperature of the wavelength converter increases.

[0180] (Technique 2) The near-infrared light-emitting device according to Technique 1, wherein the half-width at half maximum of the spectrum of the near-infrared fluorescence having the maximum fluorescence intensity exceeds 180 nm. With this configuration, even without using multiple near-infrared phosphors, a near-infrared light component having a spectral distribution within a wide wavelength range of 700 to 1000 nm can be obtained using only one near-infrared phosphor. Therefore, the risk of changes in the shape of the near-infrared fluorescence or the spectral distribution of the near-infrared fluorescence component due to temperature quenching differences when using different types of near-infrared phosphors can be reduced.

[0181] (Technique 3) The near-infrared light-emitting device according to Technique 1 or 2, wherein the near-infrared phosphor is an inorganic compound having a spinel-type crystal structure similar to that of the compound LiGa5O8, to which at least chromium ions functioning as fluorescent ions are added. This configuration utilizes a crystal similar in chemical properties to LiGa5O8, and thus, as a near-infrared phosphor, it is expected to be comparable to LiGa5O8:Cr, which has been shown to exhibit a unique fluorescence spectrum shape and temperature quenching. 3+ Therefore, it is advantageous to combine it with visible fluorescent materials with little temperature quenching, and when applied to spectrometry, it is expected to enable high-precision non-destructive measurements.

[0182] (Technique 4) The near-infrared light-emitting device according to any one of Techniques 1 to 3, wherein the near-infrared fluorescence has a peak within the wavelength range of 710 nm to 730 nm. Near-infrared phosphors that emit fluorescence with such a peak may have minimal temperature quenching. Therefore, a near-infrared light-emitting device with minimal temperature quenching may be provided.

[0183] (Technique 5) A near-infrared light-emitting device according to any one of Techniques 1 to 4, wherein the visible phosphor is at least one phosphor selected from the group consisting of a green phosphor that emits light having a maximum fluorescence intensity within a wavelength range of 490 nm to less than 570 nm, a yellow phosphor that emits light having a maximum fluorescence intensity within a wavelength range of 570 nm to less than 585 nm, an orange phosphor that emits light having a maximum fluorescence intensity within a wavelength range of 585 nm to less than 620 nm, and a red phosphor that emits light having a maximum fluorescence intensity within a wavelength range of 620 nm to less than 780 nm. This configuration allows for adjustment of the spectral distribution of the visible fluorescence component. Therefore, the visible fluorescence component of the output light emitted from the near-infrared light-emitting device can be adjusted according to the intended use.

[0184] (Technique 6) The near-infrared light emitting device according to any one of Techniques 1 to 5, wherein the visible phosphor is selected from Ce 3+ Activated garnet phosphor, Eu 2+ Activated alkaline earth metal nitride silicate and Eu 2+ At least one phosphor selected from the group consisting of activated alkaline earth metal nitride aluminum silicates. These visible phosphors have a high practical performance in LED lighting. They are not only easily available but also reliable and easy to use.

[0185] (Technique 7) The near-infrared light emitting device according to any one of Techniques 1 to 6, wherein the near-infrared phosphor is Cr 3+The activated phosphor is a visible phosphor activated by Eu 2+ Activated alkaline earth metal nitride silicate and Eu 2+ A phosphor selected from at least one of an activated alkaline earth metal nitride aluminum silicate. Such a near-infrared light-emitting device is advantageous in maintaining a constant ratio of light components absorbed by the near-infrared phosphor when the fluorescence spectrum of the visible phosphor shifts toward longer wavelengths as the temperature rises. This advantageously suppresses fluctuations in the spectral distribution associated with temperature increases.

[0186] (Technique 8) The near-infrared light-emitting device according to any one of Techniques 1 to 7, wherein the wavelength converter comprises a fluorescent ceramic. This configuration not only improves the thermal conductivity of the wavelength converter but also increases the optical absorption rate of the excitation light. This facilitates heat dissipation design and high output.

[0187] (Technique 9) The near-infrared light-emitting device according to any one of Techniques 1 to 8, wherein the visible phosphor and the near-infrared phosphor are excited by the primary light emitted by the solid-state light-emitting element. This configuration allows the visible phosphor and the near-infrared phosphor to be excited by a single solid-state light-emitting element. This facilitates the simplification of the lighting circuit.

[0188] (Technique 10) The near-infrared light-emitting device according to any one of Techniques 1 to 9, wherein the output light has a spectral intensity at least across the entire wavelength range of 700 nm to 1000 nm. Such output light includes light components in the characteristic absorption bands of the stretching vibrations of NH, CH, and OH. Therefore, such a near-infrared light-emitting device is suitable for detecting the characteristic absorption bands of the stretching vibrations of NH, CH, and OH using spectrometry.

[0189] (Technique 11) A near-infrared light-emitting device according to any one of Techniques 1 to 10, wherein the output light has a spectral peak at least within the wavelength range of 800 nm to 900 nm. Such output light has a spectral peak in the near-infrared wavelength region close to that of a halogen bulb. Consequently, the components and accompanying software of conventional spectroscopic devices that utilize halogen bulbs can be readily utilized. Consequently, spectroscopic devices can be industrially produced without major design changes.

[0190] (Technique 12) A spectroscopic device comprising the near-infrared light-emitting device according to any one of Techniques 1 to 11. This spectroscopic device utilizes the fact that the shape of the spectral distribution of the near-infrared light-emitting device changes little with increasing temperature of the wavelength converter. Therefore, it is a spectroscopic device capable of performing high-precision spectroscopy.

[0191] (Technique 13) A spectroscopic method utilizing the near-infrared light-emitting device described in any one of Techniques 1 to 11. This spectroscopic method utilizes a near-infrared light-emitting device whose spectral distribution changes little with increasing temperature of a wavelength converter. Therefore, high-precision spectroscopic method can be achieved.

[0192] The entire contents of Japanese Special Application No. 2023-010886 (filing date: January 27, 2023) are hereby incorporated by reference.

[0193] As mentioned above, the contents of this embodiment have been described based on the examples, but this embodiment is not limited thereto, and it is obvious to those skilled in the art that various modifications and improvements can be made within the scope of the gist of this embodiment.

[0194] Industrial applicability

[0195] According to the present disclosure, it is possible to provide a near-infrared light-emitting device in which the shape of the spectral distribution changes less with a temperature increase of a wavelength converter, and a spectroscopic device and a spectroscopic method using the same.

[0196] Reference numerals

[0197] 1Solid-state light-emitting element

[0198] 2Wavelength converter

[0199] 10 One Light

[0200] 20 Output Light

[0201] 21 Near-infrared fluorescence

[0202] 22 Visible fluorescence

[0203] 100 Near-infrared light-emitting device

[0204] 200 Spectrometer

Claims

1. A near-infrared light-emitting device comprising a solid-state light-emitting element and a wavelength converter, wherein the wavelength converter comprises a visible phosphor that emits visible fluorescence having a maximum fluorescence intensity within a wavelength range of visible light, and a near-infrared phosphor that emits near-infrared fluorescence having a maximum fluorescence intensity within a wavelength range of near-infrared light, wherein: The near-infrared light emitting device emits output light containing the visible fluorescence and the near-infrared fluorescence, The output light includes a visible fluorescent component having a spectral intensity in the wavelength range of visible light and a near-infrared fluorescent component having a spectral intensity in the wavelength range of near-infrared light. The near-infrared light emitting device is configured to meet 0.853M VIS ≤M NIR <1.147M VIS relationship, The M VIS For I max-VIS-150 Relative to I max-VIS-30 The ratio of I max-VIS-30 is the maximum fluorescence intensity of the visible fluorescent component when the temperature of the wavelength converter is 30° C., and the I max-VIS-150 is the maximum fluorescence intensity of the visible fluorescent component when the temperature of the wavelength converter is 150° C., The M NIR For I max-NIR-150 Relative to I max-NIR-30 The ratio of I max-NIR-30 is the maximum fluorescence intensity of the near-infrared fluorescent component when the temperature of the wavelength converter is 30° C., I max-NIR-150 is the maximum fluorescence intensity of the near-infrared fluorescent component when the temperature of the wavelength converter is 150°C.

2. The near-infrared light emitting device according to claim 1, wherein The half-maximum width of the spectrum of the near-infrared fluorescence having the maximum fluorescence intensity exceeds 180 nm.

3. The near-infrared light emitting device according to claim 1 or 2, wherein: The near-infrared phosphor is obtained by adding at least chromium ions functioning as fluorescent ions to the crystals of an inorganic compound having the same spinel crystal structure as the compound LiGa5O8.

4. The near-infrared light emitting device according to any one of claims 1 to 3, wherein The near-infrared fluorescence has a sharp peak in a wavelength range of 710 nm to 730 nm.

5. The near-infrared light emitting device according to any one of claims 1 to 4, wherein The visible phosphor is at least one phosphor selected from the group consisting of a green phosphor that emits light having a maximum fluorescence intensity within a wavelength range of greater than 490 nm and less than 570 nm, a yellow phosphor that emits light having a maximum fluorescence intensity within a wavelength range of greater than 570 nm and less than 585 nm, an orange phosphor that emits light having a maximum fluorescence intensity within a wavelength range of greater than 585 nm and less than 620 nm, and a red phosphor that emits light having a maximum fluorescence intensity within a wavelength range of greater than 620 nm and less than 780 nm.

6. The near-infrared light emitting device according to any one of claims 1 to 5, wherein The visible phosphor is selected from Ce 3+ Activated garnet phosphor, Eu 2+ Activated alkaline earth metal nitride silicate, and Eu 2+ At least one phosphor selected from the group consisting of activated alkaline earth metal nitride aluminosilicates.

7. The near-infrared light emitting device according to any one of claims 1 to 6, wherein The near-infrared phosphor is Cr 3+ The activated phosphor is a visible phosphor activated by Eu 2+ Activated alkaline earth metal nitride silicate and Eu 2+ A phosphor of at least one of activated alkaline earth metal nitride aluminum silicates.

8. The near-infrared light-emitting device according to any one of claims 1 to 7, wherein The wavelength converter includes a fluorescent ceramic.

9. The near-infrared light-emitting device according to any one of claims 1 to 8, wherein The visible phosphor and the near-infrared phosphor are excited by the primary light emitted by the solid-state light emitting element.

10. The near-infrared light-emitting device according to any one of claims 1 to 9, wherein The output light has spectral intensity at least in the entire wavelength range of 700 nm to 1000 nm.

11. The near-infrared light-emitting device according to any one of claims 1 to 10, wherein The output light has a spectral peak at least in a wavelength range of 800 nm to 900 nm. 12 . A spectroscopic device comprising the near-infrared light-emitting device according to claim 1 .

13. A spectroscopic method using the near-infrared light emitting device according to any one of claims 1 to 11.

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