Near-infrared light emitting device and method for adjusting the intensity ratio of near-infrared light and visible light

Abstract

A near-infrared light-emitting device (100) comprises a solid-state light-emitting element (1) that emits blue primary light (10), a wavelength conversion body (2) for converting primary light to near-infrared wavelength-converted light (11), and an organic polymer member (3) that transmits mixed light (12) of the primary light and the wavelength-converted light, and the near-infrared light-emitting device (100) outputs mixed light transmitted through the organic polymer member as output light (130). The organic polymer member has a thickness of 3 µm to less than 300 µm and a light transmittance of less than 0.1% at a wavelength of 400 nm or less, a light transmittance at or below the emission peak wavelength of the primary light of less than 1%, a light transmittance of less than 30% at a wavelength of 500 nm or less, and a light transmittance of 75% to less than 100% in a wavelength range of 750 nm to less than 1100 nm, and the light transmittance in units of 10 nm in the wavelength range of 500-750 nm increases as the wavelength increases.

Description

[Technical Field]

[0001] The present invention relates to a near-infrared light emitting device and a method for adjusting the intensity ratio between near-infrared light and visible light. [Background technology]

[0002] Near-infrared light emitting devices that utilize a solid-state light emitting element and a near-infrared phosphor and emit near-infrared light have been known. Many of these near-infrared light emitting devices actually output not only near-infrared light that is invisible to the human eye, but also visible light that is visible to the human eye. Specifically, the near-infrared light emitting device outputs, as visible light, primary light (e.g., blue light) emitted by the solid-state light emitting element and a significant amount of deep red light components on the short wavelength side of the fluorescence emitted by the near-infrared phosphor.

[0003] As such a near-infrared light emitting device, Patent Document 1 discloses a blue light emitting diode and a La 2.98 Gd 0.02 Ga 4.76 Al 0.2 SiO 14 :Cr 0.04 a first light-emitting material which is a near-infrared emitting phosphor, and a Gd 2.85 Sc 1.75 Lu 0.3 GaO 12 :Cr 0.1 and a second luminescent material that is a near-infrared emitting phosphor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 063297 Summary of the Invention

[0005] Conventional near-infrared light-emitting devices such as those described above allow the human eye to recognize visible light, allowing the user to determine whether the device is on or off. However, these near-infrared light-emitting devices have a problem in that the visible light seen by the human eye is generally different from natural light, resulting in an unnatural color tone. For this reason, dye absorption filters or interference filters have been used to adjust the visible light to a color tone closer to natural light. However, using dye absorption filters or interference filters has problems such as increased manufacturing costs and difficulty in thinning the light-emitting unit.

[0006] Another approach is to use a phosphor sheet to convert the visible light into a color tone similar to that of natural light. However, such a phosphor sheet efficiently absorbs the primary light emitted by the solid-state light-emitting element and converts it into visible light, which causes problems such as a decrease in the intensity of near-infrared light and an excessive increase in the intensity of natural light.

[0007] The present invention has been made in consideration of the problems of the prior art. An object of the present invention is to provide a near-infrared light-emitting device that can easily recognize whether the device is on or off, that causes little discomfort when visible light is lit, and that can efficiently output near-infrared light. Another object of the present invention is to provide a method for adjusting the intensity ratio between near-infrared light and visible light.

[0008] To achieve the above object, a near-infrared light emitting device according to a first aspect of the present invention includes a solid-state light emitting element that emits primary light having an emission peak in the wavelength range of 420 nm to less than 500 nm, a wavelength converter that converts the primary light into wavelength-converted light having a fluorescence peak in the wavelength range of 750 nm to less than 2500 nm, and an organic polymer member through which mixed light of the primary light emitted by the solid-state light emitting element and the wavelength-converted light emitted by the wavelength converter is transmitted, and outputs the mixed light transmitted through the organic polymer member as output light. The organic polymer member has a thickness of 3 μm to less than 300 μm, a light transmittance of less than 0.1% for wavelengths of 400 nm or less, a light transmittance of less than 1% for wavelengths of the emission peak of the primary light or less, a light transmittance of less than 30% for wavelengths of 500 nm or less, a light transmittance of 75% to less than 100% in the wavelength range of 750 nm to less than 1100 nm, and a light transmittance in 10 nm increments within the wavelength range of 500 nm to 750 nm that increases with increasing wavelength.

[0009] A near-infrared light emitting device according to a second aspect of the present invention comprises a solid-state light emitting element that emits primary light having an emission peak in a wavelength range of 420 nm or more and less than 500 nm, a wavelength converter that converts the primary light into wavelength-converted light having a fluorescence peak in a wavelength range of 750 nm or more and less than 2500 nm, and an organic polymer member that contains aromatic polyimide and through which mixed light of the primary light emitted by the solid-state light emitting element and the wavelength-converted light emitted by the wavelength converter passes, and outputs the mixed light that has passed through the organic polymer member as output light.

[0010] A method for adjusting the intensity ratio between near-infrared light and visible light according to a third aspect of the present invention includes the steps of transmitting a mixed light of primary light having an emission peak in the wavelength range of 420 nm to less than 500 nm and wavelength-converted light obtained by wavelength-converting the primary light and having a fluorescence peak in the wavelength range of 750 nm to less than 2500 nm through an organic polymer member, and outputting the mixed light transmitted through the organic polymer member as output light. The organic polymer member has a thickness of 3 μm to less than 300 μm, a light transmittance of less than 0.1% for wavelengths of 400 nm or less, a light transmittance of less than 1% for wavelengths of the emission peak of the primary light or less, a light transmittance of less than 30% for wavelengths of 500 nm or less, a light transmittance of 75% to less than 100% in the wavelength range of 750 nm to less than 1100 nm, and a light transmittance in 10 nm increments within the wavelength range of 500 nm to 750 nm that increases with increasing wavelength. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a near-infrared light emitting device according to this embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically illustrating an example of a near-infrared light emitting device according to this embodiment. [Figure 3] FIG. 3 is a cross-sectional view schematically showing another example of the near-infrared light emitting device according to this embodiment. [Figure 4] FIG. 4 is a cross-sectional view schematically showing another example of the near-infrared light emitting device according to this embodiment. [Figure 5] FIG. 5 is a cross-sectional view schematically showing another example of the near-infrared light emitting device according to this embodiment. [Figure 6] FIG. 6 is a cross-sectional view schematically showing another example of the near-infrared light emitting device according to this embodiment. [Figure 7A] FIG. 7A is a graph showing the light transmittance in the wavelength range of 400 nm to 1100 nm for an organic polymer member made of aromatic polyimide. [Figure 7B] FIG. 7B is a graph showing the light transmittance in the wavelength range of 400 nm to 600 nm for an organic polymer member made of aromatic polyimide. [Figure 7C] FIG. 7C is an enlarged graph of the graph of FIG. 7B. [Figure 8A] FIG. 8A is a graph showing the spectral distribution of light output from the near-infrared light emitting devices of Example 1, Comparative Example 1, and Comparative Example 2. FIG. [Figure 8B] FIG. 8B is an enlarged graph of the graph of FIG. 8A. [Figure 9A] 9A is a graph showing the spectral distribution of the light output from the near-infrared light emitting devices of Examples 2 to 6 and Comparative Example 3. FIG. [Figure 9B] FIG. 9B is an enlarged graph of the graph of FIG. 9A. [Figure 10A] FIG. 10A is a diagram showing the color tones of light output from the near-infrared light emitting devices of Examples 3, 5, 7 to 9, and Comparative Example 3 on a CIE chromaticity diagram. [Figure 10B] FIG. 10B is an enlarged view of FIG. 10A. DETAILED DESCRIPTION OF THE INVENTION

[0012] The near-infrared light emitting device and the method for adjusting the intensity ratio between near-infrared light and visible light 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 convenience of explanation and may differ from the actual ratios. Furthermore, the embodiments described below all show preferred specific examples. Therefore, the numerical values, shapes, materials, components, arrangement positions and connection forms of the components shown in the following embodiments are merely examples and are not intended to limit the present embodiment.

[0013] [Near-infrared light emitting device] 1 , a near-infrared light emitting device 100 according to this embodiment includes a solid-state light emitting element 1 that emits primary light 10, and a wavelength converter 2 that receives the primary light 10, then wavelength-converts at least a portion of the primary light 10 into wavelength-converted light 11 and emits the wavelength-converted light 11. The wavelength converter 2 receives the primary light 10 on a main light-receiving surface 2a, and emits primary light 10A and the wavelength-converted light 11 from a main light-emitting surface 2b. The light emitting device 100 then outputs, as output light 13, light components contained in mixed light 12 of the primary light 10A and the wavelength-converted light 11.

[0014] The primary light 10 emitted by the solid-state light-emitting element 1 is light having an emission peak within a blue wavelength range of 420 nm or more and less than 500 nm, preferably 440 nm or more and less than 470 nm. Specifically, the solid-state light-emitting element 1 is a blue light-emitting element that emits light having a maximum intensity within a wavelength range of 420 nm or more and less than 500 nm, preferably 440 nm or more and less than 470 nm. By irradiating the blue light emitted by the solid-state light-emitting element 1 onto the phosphor of the wavelength converter 2, it is possible to easily obtain near-infrared light components as wavelength-converted light of the phosphor. Furthermore, since the solid-state light-emitting element 1 that emits blue light is easily available, the light-emitting device 100 is advantageous for industrial production.

[0015] The solid-state light-emitting element 1 may be a light-emitting diode. Since the half-width of the light-emitting spectrum of a light-emitting diode is relatively wide, it emits not only a blue light component but also some blue-green to green light component. Therefore, output light 13 containing a green light component can be obtained without using a green phosphor that emits green fluorescence. The solid-state light-emitting element 1 may also be a laser diode. For example, an edge-emitting laser (EEL), a vertical-cavity surface-emitting laser (VCSEL), or the like can be used as the laser diode.

[0016] It is preferable to use a plurality of solid-state light emitting elements 1. This allows the output of the primary light 10 to be increased, resulting in a light emitting device 100 that is advantageous for achieving high output. The light energy density of the primary light 10 emitted by the solid-state light emitting elements 1 is 0.3 W / mm 2It is preferable that the power exceeds 1.0 W / mm 2 In this way, the optical energy density of the primary light 10 is large, and it is possible to emit output light 13 with a relatively high intensity. Note that there is no particular upper limit to the optical energy density of the primary light 10 emitted by the solid-state light emitting element 1, but it is preferably 30 W / mm 2 It can be said that:

[0017] The wavelength-converted light 11 emitted by the wavelength converter 2 is fluorescence having a fluorescence peak in a wavelength range of 750 nm or more and less than 2500 nm, preferably 780 nm or more and less than 1000 nm, and particularly preferably 800 nm or more and less than 950 nm. The wavelength converter 2 preferably contains at least an inorganic phosphor that emits fluorescence. This allows the wavelength converter 2 to be formed using a conventional phosphor that emits fluorescence having a peak in the deep red to near-infrared wavelength range. This makes it possible to produce a light-emitting device 100 that is advantageous for efficient production using existing technology.

[0018] The inorganic phosphor contained in the wavelength converter 2 preferably contains at least a near-infrared phosphor having a fluorescence peak in a wavelength range of 780 nm or more and less than 2500 nm, preferably 780 nm or more and less than 1000 nm, more preferably 800 nm or more and less than 950 nm, which makes it easy to obtain a wavelength converter 2 that emits fluorescence with a high intensity of the near-infrared light component.

[0019] The wavelength converter 2 can be a wavelength converter in which a near-infrared phosphor is sealed with a silicone resin. Alternatively, the wavelength converter 2 can be an all-inorganic wavelength converter in which a near-infrared phosphor is sealed with a low-melting-point glass. Furthermore, the wavelength converter 2 can be an all-inorganic wavelength converter mainly composed of a near-infrared phosphor using a binder or the like. The wavelength converter 2 can also be a sintered body obtained by sintering a near-infrared phosphor, i.e., a fluorescent ceramic.

[0020] The thickness of the wavelength converter 2 is not particularly limited, but the maximum thickness is preferably 100 μm or more and less than 5 mm, and more preferably 200 μm or more and less than 1 mm. Furthermore, the wavelength converter 2 is preferably translucent, which allows the primary light 10 and the light components wavelength-converted inside the wavelength converter 2 to pass through and be emitted.

[0021] The near-infrared phosphor contained in the wavelength converter 2 can be, for example, an inorganic phosphor having a fluorescence peak in a wavelength range of 750 nm or more and less than 1500 nm, particularly 780 nm or more and less than 900 nm. Alternatively, the near-infrared phosphor contained in the wavelength converter 2 can be an inorganic phosphor having a fluorescence peak in a wavelength range of 900 nm or more and less than 1700 nm. It is particularly preferable to use a near-infrared phosphor called a "localized center type," in which light absorption and emission occur through transitions within a single metal ion or ion group. Such near-infrared phosphors are easy to manufacture and procure, making them advantageous for industrial production.

[0022] Typical examples of such near-infrared phosphors include phosphors activated with transition metal ions and phosphors activated with rare earth ions. 3+ The rare earth activated phosphor may be at least one of a Tm activated phosphor and a rare earth activated phosphor. 3+ , Er 3+ , Nd 3+ and Yb 3+ The rare earth activated phosphor may be activated with at least one selected from the group consisting of: 3+ It is preferable that the compound further contains a transition metal ion that has good absorption of blue light, such as:

[0023] Cr 3+There are actually activated phosphors that have a fluorescence peak at a wavelength selected from, for example, 790 nm, 800 nm, 825 nm, 850 nm, 880 nm, 925 nm, 950 nm, 970 nm, and 1035 nm, so it is sufficient to select one that matches the purpose and application from these.

[0024] Rare earth activated phosphor Tm 3+ The activated phosphor has the property of having line-shaped fluorescence peaks at wavelengths of approximately 785 nm, 800 nm, and 820 nm. 3+ The activated phosphor has the property of having line-shaped fluorescent peaks at wavelengths of approximately 970 nm, 1005 nm, 1470 nm, 1530 nm, 1570 nm, 1615 nm, and 1645 nm. 3+ The activated phosphor has the property of having line-shaped fluorescence peaks at wavelengths of 880 nm, 935 nm, 1060 nm, 1105 nm, 1335 nm, and 1420 nm. 3+ The activated phosphor has the property of having line-shaped fluorescent peaks at wavelengths of 970 nm, 1000 nm, and 1025 nm, so it is sufficient to select an appropriate phosphor from these to suit the purpose and application.

[0025] In near-infrared phosphors, the preferred fluorescent ion is Cr. 3+ Cr as a fluorescent ion 3+ By using the above, it is easy to obtain a near-infrared phosphor that absorbs blue light and converts it into near-infrared light components. In addition, depending on the type of host, it is easy to change the light absorption peak wavelength and / or the fluorescence peak wavelength, which is advantageous in changing the excitation spectrum shape and the fluorescence spectrum shape.

[0026] The near-infrared phosphor is Cr 3+ Specifically, the near-infrared phosphor is a phosphor comprising a metal composite oxide activated with Cr, which is a base material selected from the group consisting of borates, phosphates, silicates, aluminates, gallates, germanates, tungstates, and metal oxides. 3+The near-infrared phosphor is preferably a phosphor activated with Cr. The near-infrared phosphor is preferably a phosphor activated with Cr, which has a base of a solid solution of borate, phosphate, silicate, aluminate, gallate, germanate, tungstate or metal oxide. 3+ It is also preferable that the phosphor is activated with CeSc3(BO3)4:Cr. 3+ , (La,Y,Sc)4(BO3)4:Cr 3+ , LaSc3(BO3)4:Cr 3+ , ScBO3:Cr 3+ , KInP2O7:Cr 3+ , SrInP O 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+ , LaLuO3:Cr 3+ , Ba3Sc4O9:Cr 3+ , Zn2SnO4:Cr 3+ , LiIn2SbO6:Cr 3+ , LiSrAlF6:Cr 3+ The near-infrared phosphor may be at least one selected from the group consisting of: Furthermore, the near-infrared phosphor may be a solid solution containing these phosphors as end members.

[0027] From the viewpoint of crystal structure, the near-infrared phosphor can be appropriately selected from, for example, CsCl type and related structures, NaCl type and related structures, ZnS type and related structures, NiAs type and related structures, perovskite type and related structures, spinel and related structures, corundum and related structures, β-tungsten type and related structures, and the like.

[0028] The near-infrared phosphor is preferably a phosphor having a garnet-type crystal structure, which has a proven track record in practical use. The garnet-type crystal structure belongs to a related structure of the β-tungsten type. Cr 3+ The phosphor having a garnet-type crystal structure activated by RE3B'2(AlO4)3:Cr 3+ , RE3B'2(GaO4)3:Cr 3+ Here, RE is a rare earth element, and B' is at least one element selected from Al, Ga, and Sc. In addition, as a near-infrared phosphor, Ln in the crystal constituting the above-mentioned garnet phosphor is used. 3+ -B' 3+ Some of the combinations of M 2+ -Si 4+ Also included are phosphors substituted with a combination of the following. Note that M is an alkaline earth metal, and is at least one element selected from the group consisting of Ca, Sr, and Ba. The near-infrared phosphor may also be a solid solution of the above-mentioned garnet phosphors.

[0029] The near-infrared phosphor is preferably at least one of a rare earth aluminum garnet phosphor and a rare earth gallium garnet phosphor. Specifically, the near-infrared phosphor is Y3Al2(AlO4)3:Cr 3+ , La3Al2(AlO4)3:Cr 3+ , Gd3Al2(AlO4)3:Cr 3+ , Y3Ga2(AlO4)3:Cr 3+ , La3Ga2(AlO4)3:Cr 3+ , Gd3Ga2(AlO4)3:Cr 3+ , Y3Sc2(AlO4)3:Cr 3+, La3Sc2(AlO4)3:Cr 3+ , Gd3Sc2(AlO4)3:Cr 3+ , Y3Ga2(GaO4)3:Cr 3+ , La3Ga2(GaO4)3:Cr 3+ , Gd3Ga2(GaO4)3:Cr 3+ , Y3Sc2(GaO4)3:Cr 3+ , La3Sc2(GaO4)3:Cr 3+ ,Gd3Sc2(GaO4)3:Cr 3+ It is preferable that the near-infrared phosphor is at least one selected from the group consisting of: Furthermore, the near-infrared phosphor may be a solid solution containing these phosphors as end members.

[0030] As described above, the near-infrared light emitting device 100 according to this embodiment includes, in addition to the solid-state light emitting element 1 and the wavelength converter 2, the organic polymer member 3 through which the mixed light 12 of the primary light 10A emitted by the solid-state light emitting element 1 and the wavelength-converted light 11 emitted by the wavelength converter 2 passes. After the mixed light 12 passes through the organic polymer member 3, the light emitting device 100 outputs the transmitted light as output light 13.

[0031] 2 to 6 schematically show the configurations of near-infrared light emitting devices 100A to 100E according to this embodiment. The light emitting devices 100A to 100E include a plurality of solid-state light emitting elements 1, which are mounted on the surface of a substrate 4. A wavelength converter 2 is disposed opposite the solid-state light emitting elements 1. An organic polymer member 3 is disposed on the wavelength converter 2 on the side opposite the solid-state light emitting elements 1. Therefore, in the light emitting device 100, the solid-state light emitting elements 1, wavelength converter 2, and organic polymer member 3 are stacked in this order.

[0032] As shown in Fig. 2, the organic polymer member 3 can be arranged with a gap between it and the wavelength converter 2. That is, they can be arranged so that there is a gap between the main light receiving surface 3a of the organic polymer member 3 and the main light emitting surface 2b of the wavelength converter 2. Furthermore, as shown in Figs. 3 to 6, the organic polymer member 3 can also be arranged so that it is in close contact with the wavelength converter 2. That is, they can be arranged so that the main light receiving surface 3a of the organic polymer member 3 and the main light emitting surface 2b of the wavelength converter 2 are in contact with each other.

[0033] 4, the organic polymer member 3 can also be arranged so as to encase the solid-state light-emitting element 1 and the wavelength converter 2. In other words, the organic polymer member 3 can be arranged so as to cover the mounting surface of the substrate 4, the side surfaces of the solid-state light-emitting element 1 and the wavelength converter 2, and the main light emission surface 2b of the wavelength converter 2.

[0034] 2, the area of ​​the main light receiving surface 3a of the organic polymer member 3 that receives the mixed light 12 of the primary light 10A and the wavelength-converted light 11 can be larger than that of the main light emitting surface 2b of the wavelength converter 2 that emits the mixed light 12. Furthermore, as shown in FIGS. 3, 5, and 6, the area of ​​the main light receiving surface 3a of the organic polymer member 3 can be substantially the same as that of the main light emitting surface 2b of the wavelength converter 2.

[0035] The wavelength converter 2 can also be arranged spaced apart from the solid-state light-emitting element 1, as shown in Figures 1 and 3. The wavelength converter 2 can also be arranged so as to be in close contact with the solid-state light-emitting element 1, as shown in Figures 2, 4, 5 and 6. The wavelength converter 2 can also be arranged so as to enclose the solid-state light-emitting element 1, as shown in Figure 5.

[0036] The main light receiving surface 2a of the wavelength converter 2 that receives the primary light 10 can have an area larger than that of the main light emitting surface 1b of the solid-state light emitting element 1, as shown in Fig. 3. In addition, the main light receiving surface 2a of the wavelength converter 2 can also have an area substantially the same as that of the main light emitting surface 1b of the solid-state light emitting element 1, as shown in Figs. 2, 4 and 6.

[0037] In the light-emitting device of this embodiment, the organic polymer member 3 can be in the form of a sheet or film. However, such an organic polymer member 3 is prone to becoming wavy. Therefore, as shown in FIGS. 2, 3, and 5, a protective member 5 for fixing the organic polymer member 3 may be provided. The protective member 5 may be, for example, a flat plate. By closely adhering the organic polymer member 3 to the protective member 5, the flatness of the organic polymer member 3 can be maintained. Furthermore, the flatness of the organic polymer member 3 can be maintained even when it is integrated with the solid-state light-emitting element 1 and the wavelength converter 2, as shown in FIG. 6.

[0038] A structure made of an organic compound or an inorganic compound that transmits at least near-infrared rays can be used as the protective member 5. The protective member 5 can be made of a material such as acrylic resin, PET (polyethylene terephthalate) resin, or glass.

[0039] In this embodiment, the organic polymer member 3 contains an aromatic polyimide. An aromatic polyimide has a structure in which aromatic compounds are directly linked by imide bonds. In addition, in an aromatic polyimide, adjacent aromatic rings directly linked by imide bonds have a conjugated structure, forming charge transfer complexes both intramolecularly and intermolecularly. Therefore, aromatic polyimides have the property of absorbing a portion of short-wavelength visible light.

[0040] The aromatic polyimide that can be contained in the organic polymer member 3 can be at least one selected from the group consisting of Kapton (registered trademark) manufactured by DuPont-Toray Co., Ltd., Apical (registered trademark) manufactured by Kaneka Corporation, and Upilex (registered trademark) manufactured by UBE Corporation. Among these, Kapton can be used as the aromatic polyimide. Kapton is made of poly(4,4'-oxydiphenylene-pyromellitimide). Poly(4,4'-oxydiphenylene-pyromellitimide) is a polyimide obtained by polymerizing pyromellitic dianhydride and 4,4'-diaminodiphenyl ether.

[0041] Here, the wavelength dependence of light transmittance in an organic polymer member 3 containing aromatic polyimide will be described. FIG. 7A shows the light transmittance in the wavelength range of 400 nm to 1100 nm for a Kapton sheet, which is an example of an aromatic polyimide sheet, and FIGS. 7B and 7C show the light transmittance in the wavelength range of 400 nm to 600 nm. In FIGS. 7A to 7C, "12 μm (12 × 1)" indicates that one aromatic polyimide sheet having a thickness of 12 μm was used. In addition, "37 μm (12 × 1 + 25 × 1)" indicates that one aromatic polyimide sheet having a thickness of 12 μm and one aromatic polyimide sheet having a thickness of 25 μm were laminated together, resulting in a total thickness of 37 μm. In this specification, the light transmittance of the organic polymer member 3 can be measured in accordance with Japanese Industrial Standard JIS K7361-1.

[0042] 7A and 7B, aromatic polyimides have the property of suppressing the transmission of visible light, particularly light on the short wavelength side (violet and blue light), while hardly suppressing the transmission of near-infrared light components. Furthermore, aromatic polyimides have a light transmittance of essentially 0% within a wavelength range of at least 200 nm or more and less than 400 nm, and maintain a light transmittance at the same level as that of a wavelength of 1100 nm within a wavelength range of at least more than 1100 nm and less than 2000 nm.

[0043] 7B and 7C, the transmittance of visible light through aromatic polyimide decreases as the wavelength decreases, blocking almost all light with a wavelength of approximately 450 nm or less, which coincidentally is almost the same as the peak wavelength of light emitted by a typical commercially available blue light-emitting diode.

[0044] As described above, in the light emitting device 100, mixed light 12 of primary light 10A and wavelength-converted light 11 passes through organic polymer member 3 containing aromatic polyimide, and the transmitted light is output as output light 13. With this configuration, the output of the blue light component of the visible light components of primary light 10A is greatly suppressed, and the intensity of the blue-green to green light component contained in the small amount of primary light 10A is also reduced to a considerable extent. The yellow to red light component and the deep red light component with low luminosity are transmitted through organic polymer member 3. As a result, the spectral distribution in the visible region of output light 13 is such that the intensity of the visible light components in the wavelength region with high luminosity (420 nm or more and less than 660 nm) is extremely reduced, but the intensity remains constant throughout the entire wavelength region. Visible light components in a wavelength range (420 nm or more and less than 660 nm) with high luminosity but low intensity are additively mixed with visible light components in a wavelength range (660 nm or more and less than 780 nm) with low luminosity to form output light 13. In this way, a moderately weak white light is generated by additive color mixing and is visible.

[0045] On the other hand, the near-infrared component of the wavelength-converted light 11 is transmitted through the organic polymer member 3 with almost no absorption. As a result, the synergistic effect of the weak white light and the high-intensity near-infrared light makes it possible to achieve both dim natural light and high-output near-infrared light. Therefore, the light-emitting device 100 has the characteristics of outputting high-output near-infrared light, allowing people to distinguish between the on and off states by the weak white light, and causing almost no discomfort to the surrounding environment when lit.

[0046] Aromatic polyimides are known as essential materials for cutting-edge industries, possessing high mechanical strength and excellent heat resistance (-269 to +400°C). Aromatic polyimides also have excellent electrical insulation (380 to 400 kV / mm) and chemical resistance, and a low thermal expansion coefficient for an organic material. Furthermore, because aromatic polyimides are synthetically synthesized organic materials, they are inexpensive compared to optical filters and other materials that use inorganic materials. As mentioned above, such aromatic polyimides are widely known as "Kapton," and films and adhesive tapes are commercially available. Therefore, this configuration makes the light-emitting device 100 advantageous for manufacturing and providing reliable, inexpensive products.

[0047] As can be seen from Figures 7B and 7C, a sheet made of aromatic polyimide and having a thickness of 12 to 100 µm substantially blocks light components with wavelengths of 450 nm or less. In other words, the sheet blocks light components with wavelengths of 450 nm or less so that the light transmittance for wavelengths of 400 nm or less is less than 0.1%. The wavelength of 450 nm corresponds approximately to the peak wavelength of primary light 10 from a blue LED.

[0048] Furthermore, an aromatic polyimide sheet having a thickness of 12 μm to 100 μm, particularly a sheet having a thickness of 25 μm to 100 μm, has a light transmittance of less than 1%, particularly less than 0.1%, for light components with wavelengths of 450 nm or less.The sheet also has a light transmittance of less than 30% for light components with wavelengths of 500 nm or less, which decreases to less than 20% or less than 10% as the thickness increases.

[0049] A sheet made of aromatic polyimide and having a thickness of 12 μm to 100 μm has a light transmittance of 75% or more and less than 100% for wavelengths of 750 nm or more and less than 1100 nm. When the sheet has a thickness of less than 50 μm, the light transmittance is 80% or more for wavelengths of 750 nm or more and less than 1100 nm.

[0050] A sheet made of aromatic polyimide and having a thickness of 12 μm to 100 μm has a light transmittance in 10 nm increments within a wavelength range of 500 nm to 750 nm, which increases with increasing wavelength.

[0051] Considering the variation in the properties of aromatic polyimides and improvement techniques, it is believed that aromatic polyimides having a thickness of 3 μm or more and less than 300 μm, particularly 10 μm or more and less than 120 μm, will have light transmission properties similar to those shown in FIGS. 7B and 7C.

[0052] As described above, in the light-emitting device 100 of this embodiment, a member containing aromatic polyimide can be used as the organic polymer member 3. Furthermore, it is preferable to use a member containing aromatic polyimide as a main component as the organic polymer member 3, and it is preferable to use a member made of aromatic polyimide. However, the organic polymer member 3 of this embodiment is not limited to a member containing aromatic polyimide, and a light-emitting device that can emit both dim white light and high-output near-infrared light can also be obtained by using a member having the following properties:

[0053] Specifically, the light emitting device 100 of this embodiment can use an organic polymer member 3 that has all of the following characteristics (1) to (6): (1) a thickness of 3 μm or more and less than 300 μm; (2) a light transmittance of less than 0.1% for wavelengths of 400 nm or less; (3) a light transmittance of less than 1% for wavelengths of the emission peak of primary light 10; (4) a light transmittance of less than 30% for wavelengths of 500 nm or less; (5) a light transmittance of 75% or more and less than 100% in the wavelength range of 750 nm or more and less than 1100 nm; (6) the light transmittance in 10 nm increments within the wavelength range of 500 nm or more and less than 750 nm increases with increasing wavelength. Note that (3) the light transmittance of less than the emission peak wavelength of primary light 10 is more preferably less than 0.1%; and (4) the light transmittance of less than 500 nm is preferably less than 20%, more preferably less than 10%.

[0054] In the light emitting device 100 of this embodiment, the wavelength converter 2 may be configured not to include a visible phosphor that emits fluorescence with a fluorescence peak in the wavelength range of 380 nm or more and less than 780 nm. In this configuration, the light emitting device can be configured only with the solid-state light emitting element 1, the wavelength converter 2 made of a near-infrared phosphor, and the organic polymer member 3, thereby simplifying the structure of the device. This reduces the labor required for managing the components. Furthermore, it is possible to suppress lot-to-lot variations in the color tone of the mixed light 12 and the output light 13.

[0055] On the other hand, in the light emitting device 100 of this embodiment, the wavelength converter 2 may be configured to include a visible phosphor that emits fluorescence having a fluorescence peak in a wavelength range of 500 nm or more and less than 780 nm. In particular, the wavelength converter 2 may be configured to include a visible phosphor that emits fluorescence having a fluorescence peak in at least one of the wavelength ranges of green from 500 nm to less than 560 nm and reddish-orange to deep red from 600 nm to less than 780 nm. This configuration makes the light emitting device 100 advantageous for controlling the color tone of the output light 13 visible to the human eye.

[0056] In the light emitting device 100 of this embodiment, the wavelength converter 2 may have a mixed light emitting surface (main light emitting surface 2b), and the mixed light emitting surface may be configured to emit mixed light 12. In this way, simply covering the mixed light emitting surface of the wavelength converter 2 with the organic polymer member 3 allows the mixed light 12 to pass through the organic polymer member 3. Therefore, the light emitting device 100 is advantageous in reducing the area of ​​the output light emitting surface 3b of the organic polymer member 3.

[0057] In the light emitting device 100 of this embodiment, the wavelength converter 2 is preferably configured to absorb at least a part of the primary light 10 and convert it into wavelength-converted light 11, and to transmit the unabsorbed primary light 10. With this configuration, the wavelength converter 2 and the organic polymer member 3 are stacked above the main light emitting surface 1b of the solid-state light emitting element 1, thereby outputting output light 13 having both visible light and near-infrared light components. This configuration also makes the light emitting device 100 advantageous for reducing the area of ​​the output light emitting surface 3b.

[0058] In the light emitting device 100 of this embodiment, the wavelength converter 2 preferably has a flat light output surface (main light emission surface 2b) for the mixed light 12. This allows the conventional sheet-like organic polymer member 3 to be easily attached to the wavelength converter 2. This makes it easy to integrate the wavelength converter 2 and the organic polymer member 3, resulting in a light emitting device 100 that is advantageous in terms of compactness.

[0059] In the light emitting device 100 of this embodiment, the wavelength converter 2 can be a resin fluorescent film in which particles of a near-infrared phosphor are dispersed in a translucent resin. Such a resin fluorescent film is an orthodox technology used in LED lighting sources. This makes the light emitting device 100 advantageous for manufacturing without worrying about issues in industrial production. Furthermore, it becomes possible to easily manufacture a light emitting device 100D configured such that the wavelength converter 2 encases the solid-state light emitting element 1, as shown in FIG. 5.

[0060] In the light emitting device 100 of this embodiment, the wavelength converter 2 may be made of fluorescent ceramics. Fluorescent ceramics are sintered bodies made by sintering a near-infrared phosphor, and have excellent heat resistance and thermal conductivity. Therefore, this configuration makes the light emitting device 100 advantageous for achieving high output.

[0061] In the light-emitting device 100 of this embodiment, the organic polymer member 3 can be in the form of a sheet or film. In this case, the thickness of the organic polymer member 3 is reduced, resulting in a light-emitting device 100 that is advantageous for thinning. In addition, in this case, the organic polymer members 3 can be easily stacked and do not become bulky. Therefore, the light-emitting device 100 is advantageous for adjusting the transmittance of visible light. The thickness of the organic polymer member 3 is preferably 3 μm or more and less than 300 μm, more preferably 10 μm or more and less than 100 μm, and even more preferably 20 μm or more and 75 μm or less.

[0062] In the light-emitting device 100 of this embodiment, the wavelength converter 2 and the organic polymer member 3 may be bonded with a light-transmitting adhesive material. This integrates the wavelength converter 2 and the organic polymer member 3, thereby suppressing color shifts in the output light 13 due to misalignment between them. Furthermore, even if the organic polymer member 3 deteriorates, the deteriorated organic polymer member 3 can be peeled off and a new organic polymer member 3 can be bonded. Note that either a silicone resin or an acrylic resin can be used as the adhesive material.

[0063] Here, the refractive index of the aromatic polyimide that can be contained in the organic polymer member 3 is 1.65 or more and 1.70 or less, which is higher than the refractive index of air (1.0) and the refractive index of silicone resin and acrylic resin (1.40 or more and 1.55 or less). Therefore, a refractive index step occurs at the boundary between the aromatic polyimide and air, the boundary between the aromatic polyimide and silicone resin, and the boundary between the aromatic polyimide and acrylic resin, which may reduce the light extraction efficiency.

[0064] Therefore, when the incident surface (main light receiving surface 3a) of the organic polymer member 3 for the mixed light 12 comes into contact with a low refractive index material having a smaller refractive index than the incident surface, it is preferable to arrange an intermediate refractive index material on the incident surface, which has a refractive index smaller than that of the organic polymer member 3 and a refractive index larger than that of the low refractive index material. Also, when the exit surface (output light emitting surface 3b) of the organic polymer member 3 for the output light 13 comes into contact with a low refractive index material having a smaller refractive index than the incident surface, it is preferable to arrange an intermediate refractive index material on the exit surface, which has a refractive index smaller than that of the organic polymer member 3 and a refractive index larger than that of the low refractive index material. This configuration reduces the refractive index difference, making it possible to increase the extraction efficiency of the output light 13.

[0065] Specifically, when the organic polymer member 3 is in close contact with the wavelength converter 2 containing a silicone resin as a main component via an adhesive material, the adhesive material can be an intermediate refractive index material. Preferably, the adhesive material has a refractive index greater than 1.55 and less than 1.65, and is, for example, an epoxy resin.

[0066] Furthermore, when the organic polymer member 3 is in contact with an air layer, an intermediate refractive index material can be disposed on the surface in contact with the air layer (output light emitting surface 3b). In this case, the refractive index of the intermediate refractive index material is preferably less than 1.65, and more preferably 1.40 or more and less than 1.55. For example, by using a polyimide tape whose surface has been pre-coated with a silicone resin, the intermediate refractive index material can be disposed on the output light emitting surface 3b of the organic polymer member 3.

[0067] The intermediate refractive index material is preferably a material that transmits at least near-infrared rays.

[0068] In the light-emitting device 100 of this embodiment, the main light emission surface 2b of the wavelength converter 2 for the mixed light 12 is preferably rectangular when viewed along the stacking direction (the vertical direction in FIG. 1 ) of the solid-state light-emitting element 1, the wavelength converter 2, and the organic polymer member 3. Furthermore, the main light emission surface 2b of the wavelength converter 2 is preferably rectangular, and more preferably square, when viewed along the stacking direction. In this case, a plate- or sheet-shaped organic polymer member can be used by simply cutting it, resulting in a light-emitting device 100 that is advantageous for industrial production. Furthermore, the organic polymer member 3 that is simply cut can cover the entire main light emission surface 2b without excess or deficiency, so that output light 13 with little color unevenness can be obtained.

[0069] In the light-emitting device 100 of this embodiment, the mixed light 12 preferably contains a blue light component in the wavelength range of 430 nm or more and less than 490 nm, a green light component in the wavelength range of 490 nm or more and less than 550 nm, and a red light component in the wavelength range of 640 nm or more and less than 770 nm. The blue light component is preferably a light component in the wavelength range of 440 nm or more and less than 470 nm. The green light component is preferably a light component in the wavelength range of 510 nm or more and less than 540 nm. The red light component is preferably a light component in the wavelength range of 640 nm or more and less than 700 nm. In this case, since the mixed light 12 contains light components of the three primary colors of light, it is possible to output white light obtained by additively mixing these colors as the output light 13.

[0070] In the light-emitting device 100 of this embodiment, the maximum intensity of the mixed light 12, which is visible light having a wavelength of 380 nm or more and less than 780 nm, can be smaller than the maximum intensity of the near-infrared light having a wavelength of 780 nm or more and less than 2500 nm. Furthermore, the maximum intensity of the mixed light 12, which is visible light, can be 10% or more and less than 50%, or even 30% or more and less than 40%, of the maximum intensity of the near-infrared light. This makes the light-emitting device 100 advantageous for outputting high-power near-infrared light. Furthermore, the light-emitting device 100 is advantageous for outputting output light 13 that combines visible light that is dimly visible to the human eye with high-power near-infrared light.

[0071] In the light-emitting device 100 of this embodiment, the output light 13 preferably has a correlated color temperature of 2000 K or more and less than 10,000 K, more preferably 2500 K or more and less than 7,000 K. The output light 13 also preferably has an average color rendering index Ra of 65 or more and less than 100, more preferably 75 or more and less than 100. This allows the light-emitting device 100 to emit visible light similar to natural light, making it advantageous for notifying people of the on / off state without causing discomfort. Note that output light 13 with such a correlated color temperature can be achieved when the thickness of the organic polymer member 3 is approximately 35 μm or more and less than 120 nm. Also, output light 13 with such an average color rendering index Ra can be achieved when the thickness of the organic polymer member 3 is approximately 15 μm or more and less than 120 nm.

[0072] The light emitting device 100 of this embodiment can be used in a configuration in which the output light 13 is directly irradiated onto the object to be irradiated. It can also be used in a configuration in which the output light 13 is indirectly irradiated onto the object to be irradiated. In the case of indirect irradiation, the output light 13 is irradiated onto a reflector that reflects near-infrared rays or a light diffuser that diffuses near-infrared rays. Then, the object to be irradiated is irradiated with near-infrared rays reflected by the reflector or near-infrared rays diffused by the light diffuser. With this configuration, the object to be irradiated is irradiated with diffused near-infrared rays, so that the near-infrared rays can be irradiated from multiple directions without unevenness in intensity or color tone. The reflector and light diffuser may be made of an inorganic or organic material, as appropriate.

[0073] The light-emitting device 100 of this embodiment can be widely used in electronic devices and equipment systems that use near-infrared rays. Furthermore, electronic devices and equipment systems configured using the light-emitting device 100 allow people to recognize the on / off state of the near-infrared rays without feeling any discomfort. This makes it possible to prevent people from forgetting to turn off the near-infrared rays. Furthermore, even if people forget to turn off the near-infrared rays, they can be gently reminded without damaging the lighting environment of the space.

[0074] As described above, the near-infrared light emitting device 100 of this embodiment includes a solid-state light emitting element 1 that emits primary light 10 having an emission peak in the wavelength range of 420 nm or more and less than 500 nm. The light emitting device 100 further includes a wavelength converter 2 that converts the primary light 10 into wavelength-converted light 11 having a fluorescence peak in the wavelength range of 750 nm or more and less than 2500 nm. The light emitting device 100 further includes an organic polymer member 3 through which mixed light 12 of primary light 10A emitted by the solid-state light emitting element 1 and wavelength-converted light 11 emitted by the wavelength converter 2 passes. The light emitting device 100 outputs the mixed light 12 that has passed through the organic polymer member 3 as output light 13. The organic polymer member 3 has the following characteristics (1) to (6). (1) The thickness is 3 μm or more and less than 300 μm. (2) The light transmittance for wavelengths of 400 nm or less is less than 0.1%. (3) The light transmittance of the primary light 10 at or below the wavelength of the emission peak is less than 1%. (4) The light transmittance for wavelengths of 500 nm or less is less than 30%. (5) The light transmittance in the wavelength range of 750 nm or more and less than 1100 nm is 75% or more and less than 100%. (6) The light transmittance in 10 nm increments within the wavelength range of 500 nm to 750 nm increases as the wavelength becomes longer.

[0075] In the light-emitting device 100, the organic polymer member 3 has the property of suppressing the transmission of visible light, particularly light on the short wavelength side (violet light and blue light), while hardly suppressing the transmission of near-infrared light components. Therefore, when mixed light 12 of primary light 10A and wavelength-converted light 11 passes through the organic polymer member 3, the output of the blue light component of primary light 10A is greatly suppressed, and only the blue-green to green light component slightly contained in primary light 10A and the red light component slightly contained in wavelength-converted light 11 are transmitted. As a result, the visible light components transmitted through the organic polymer member 3 become weak white light through additive color mixing, which can be visually recognized. On the other hand, the near-infrared light component of wavelength-converted light 11 is transmitted without being absorbed by the organic polymer member 3. In this way, the light-emitting device 100 has a configuration that combines dim visible light and strong near-infrared light, allowing visual recognition of the on and off states.

[0076] The near-infrared light emitting device 100 of this embodiment includes a solid-state light emitting element 1 that emits primary light 10 having an emission peak in the wavelength range of 420 nm or more and less than 500 nm. The light emitting device 100 further includes a wavelength converter 2 that converts the primary light 10 into wavelength-converted light 11 having a fluorescence peak in the wavelength range of 750 nm or more and less than 2500 nm. The light emitting device 100 further includes an organic polymer member 3 containing aromatic polyimide, through which mixed light 12 of primary light 10A emitted by the solid-state light emitting element 1 and wavelength-converted light 11 emitted by the wavelength converter 2 passes. The light emitting device 100 outputs the mixed light 12 that has passed through the organic polymer member 3 as output light 13.

[0077] Aromatic polyimides have the property of suppressing the transmission of light on the short wavelength side (violet and blue light) while hardly suppressing the transmission of near-infrared light components. Therefore, by using aromatic polyimides as the organic polymer member 3, the light-emitting device 100 can achieve both dim visible light and strong near-infrared light, making it possible to visually recognize the on and off states. Aromatic polyimides also have high mechanical strength and excellent heat resistance. Aromatic polyimides also have excellent electrical insulation and chemical resistance, and a low thermal expansion coefficient for an organic material. Furthermore, because aromatic polyimides are artificially synthesized organic materials, they are inexpensive. Therefore, by using aromatic polyimides as the organic polymer member 3, a highly reliable and inexpensive light-emitting device can be obtained.

[0078] Note that this embodiment can also be regarded as a novel method for making a person aware of the on / off state of the near-infrared light emitting device 100 that exclusively emits near-infrared rays. Specifically, this embodiment can also be regarded as a method for checking the on / off state of the near-infrared light emitting device 100 that emits near-infrared rays, characterized in that mixed light 12 of near-infrared rays and visible light whose intensity is lower than that of near-infrared rays is transmitted through the organic polymer member 3, and output as white light.

[0079] [Method for adjusting the intensity ratio of near-infrared and visible light] Next, a method for adjusting the intensity ratio between near-infrared rays and visible light according to this embodiment will be described.

[0080] As described above, the organic polymer member 3 has the property of suppressing the transmission of visible light, particularly light on the short wavelength side (violet light and blue light), while hardly suppressing the transmission of near-infrared light. Therefore, by transmitting a mixture of near-infrared light and visible light through the organic polymer member 3, it is possible to efficiently transmit near-infrared light while significantly suppressing the output of visible light, particularly violet light and blue light.

[0081] In this way, by transmitting a mixed light of near-infrared light and visible light through the organic polymer member 3, the transmission of visible light, particularly violet light and blue light, is suppressed, and therefore it becomes possible to adjust the intensity ratio between near-infrared light and visible light by using the organic polymer member 3. Therefore, this embodiment can also be regarded as a novel method for adjusting the intensity ratio between near-infrared light and visible light for a mixed light of near-infrared light and visible light.

[0082] Specifically, this embodiment is a method for adjusting the intensity ratio between near-infrared rays and visible light in a near-infrared light-emitting device 100 that outputs near-infrared rays and visible light that is weaker in intensity than the near-infrared rays, and is a method for adjusting the intensity ratio between near-infrared rays and visible light, characterized in that mixed light 12 of near-infrared rays and visible light is output by transmitting it through an organic polymer member 3.

[0083] The method for adjusting the intensity ratio of near-infrared light to visible light according to this embodiment includes a step of transmitting mixed light 12, which is made of primary light 10 having an emission peak in the wavelength range of 420 nm or more and less than 500 nm, and wavelength-converted light 11 obtained by wavelength-converting primary light 10 and having a fluorescence peak in the wavelength range of 750 nm or more and less than 2500 nm, through an organic polymer member 3. The adjustment method further includes a step of outputting mixed light 12 transmitted through organic polymer member 3 as output light 13. Organic polymer member 3 has the following characteristics (1) to (6). (1) The thickness is 3 μm or more and less than 300 μm. (2) The light transmittance for wavelengths of 400 nm or less is less than 0.1%. (3) The light transmittance of the primary light 10 at or below the wavelength of the emission peak is less than 1%. (4) The light transmittance for wavelengths of 500 nm or less is less than 30%. (5) The light transmittance in the wavelength range of 750 nm or more and less than 1100 nm is 75% or more and less than 100%. (6) The light transmittance in 10 nm increments within the wavelength range of 500 nm to 750 nm increases as the wavelength becomes longer.

[0084] As described above, the organic polymer member 3 can suppress the transmission of light on the short wavelength side as the thickness increases. Specifically, as shown in Fig. 7, when the organic polymer member 3 is made of aromatic polyimide, the light transmittance of visible light with wavelengths of 380 nm or more and less than 780 nm decreases as the thickness of the organic polymer member 3 increases, and the light transmittance decreases particularly as the wavelength becomes shorter. In this way, as the thickness of the organic polymer member 3 increases, light on the short wavelength side is blocked, and the correlated color temperature of the output light 13 transmitted through the organic polymer member 3 can be lowered.

[0085] Thus, as the thickness of the organic polymer member 3 increases, the light transmittance of visible light decreases, and the light transmittance decreases particularly as the wavelength becomes shorter. Therefore, it is possible to adjust the color tone of visible light by adjusting the thickness of the organic polymer member 3. Therefore, this embodiment can also be regarded as a novel method for adjusting the color tone of visible light, which is a mixture of near-infrared light and visible light.

[0086] Specifically, this embodiment is a method for adjusting the color tone of visible light in a near-infrared light-emitting device 100 that outputs near-infrared light and visible light, and is a method for adjusting the color tone of output light 13, characterized in that mixed light 12 of near-infrared light and visible light is transmitted through an organic polymer member 3 and output. [Example]

[0087] Hereinafter, the present embodiment will be described in more detail with reference to examples and comparative examples, but the present embodiment is not limited to these examples.

[0088] [Example 1] First, a near-infrared light emitting device of Example 1 was fabricated using the following components. (1) Dimmable LED base light; Panasonic Corporation, product number: NDNN52500 DK9, power consumption 14W (2) Near-infrared LED package; externally sourced, surface-mounted (SMD) type, 3mm x 3mm, power consumption 460mW (3) Polyimide adhesive tape (organic polymer component); thickness 50 μm

[0089] The LED base light is a lighting fixture with a structure in which 32 white LED packages of two types with different light colors are arranged alternately at equal intervals in a straight line. The two types of white LED packages are daylight white and warm white, and all are SMD type. The LED base light has a control circuit that independently controls the power input to the daylight white and warm white LEDs, which allows the color of the white light emitted by the LED base light to be controlled.

[0090] A near-infrared LED package is an LED package that combines a blue LED and a near-infrared phosphor. Generally, a prototype can be procured by communicating the desired specifications (spectral distribution, driving voltage / current, size, etc.) to a manufacturer with the manufacturing technology for LED packages that use inorganic phosphors and requesting a prototype. Note that hereinafter, "near-infrared LED package" will also be referred to as "near-infrared LED."

[0091] Polyimide adhesive tape is known as "Kapton (registered trademark) tape" and is an adhesive tape containing aromatic polyimide. Such polyimide adhesive tapes with different thicknesses and tape widths are commercially available as general-purpose products. Note that, hereinafter, "polyimide adhesive tape" will also be referred to as "polyimide tape."

[0092] Specifically, first, the lighting globe attached to the front of the LED base light was removed, exposing the total of 64 white LEDs that the LED base light has. The lighting globe of the LED base light is designed to be easily detached. Next, all of the 64 white LEDs, the incandescent white LEDs (32 pieces), were removed. Next, 32 near-infrared LEDs were installed in their place. A lighting test was then conducted to confirm that there were no electrical connection problems with the replaced near-infrared LEDs. After that, polyimide tape was applied so as to completely cover the light output surface of the near-infrared LEDs (32 pieces).

[0093] In this way, the light emitting device of this example was obtained, which is equipped with a white LED that emits daylight white light and a near-infrared LED that emits near-infrared light, and can independently control the light output of daylight white and near-infrared. In this example, to simplify the device configuration, the detached lighting globe is not attached, but it can also be configured with the lighting globe attached.

[0094] [Comparative Example 1] The light emitting device of this example was obtained by the same steps as in Example 1, except that no polyimide tape was attached to the light output surface of the near-infrared LED.

[0095] Comparative Example 2 The light emitting device of this example was obtained by the same process as in Example 1, except that a YAG fluorescent film (thickness: 150 μm) was attached to the light output surface of the near-infrared LED instead of polyimide tape.

[0096] The YAG phosphor film was fabricated as follows: First, Y3Al5O 12 :Ce 3+ A YAG phosphor powder represented by the general formula (I) and a transparent silicone resin were prepared. The fluorescent color of the YAG phosphor was yellow-green. Next, the YAG phosphor powder and the transparent silicone resin were weighed out to a volume ratio of 10% and 90% (weight ratio: YAG:agent A:agent B ≈ 1:1:1), and then mixed to obtain a phosphor paste (total amount: approximately 3 g). The obtained phosphor paste was then poured into a mold and thermally cured at a temperature of 100 to 150°C to obtain a YAG phosphor film.

[0097] [Evaluation of Light-Emitting Devices of Example 1 and Comparative Examples 1 and 2] The near-infrared light-emitting device of Example 1 obtained as described above was energized and turned on, and the spectral distribution of its output light was evaluated. However, for convenience, the following explanation will be given for the case where the white LED is turned off using the dimming function of the lighting fixture and only the near-infrared LED is turned on. Note that the near-infrared light-emitting device of Example 1 can also turn on the white LED using the dimming function of the lighting fixture. Furthermore, the intensity ratio between the near-infrared light and the white light can be changed, and the output intensity of the near-infrared light can also be adjusted.

[0098] FIG. 8A is a graph showing the spectral distribution of output light emitted by the near-infrared light-emitting devices of Example 1, Comparative Example 1, and Comparative Example 2. For reference, FIG. 8B shows an enlarged view of the visible region of the spectral distribution of FIG. 8A. As shown in FIGS. 8A and 8B, the spectral distribution of output light emitted by the light-emitting device of Example 1 consisted of a very weak visible light component with intensity in the wavelength range of 400 nm or more and less than 610 nm and a strong near-infrared component located in the near-infrared region (780 nm to 2.5 μm). The wavelength range of 400 nm or more and less than 610 nm is a region in the visible region (380 to 780 nm) where scotopic sensitivity is relatively high. The visible light component had light components throughout the entire wavelength range of at least 420 nm to less than 780 nm, and the near-infrared component had light components throughout the entire wavelength range of at least 780 nm to less than 1100 nm. Therefore, the visible light component of the output light emitted by the light emitting device of Example 1 could be seen as a faint white light that glowed dimly in the dark.

[0099] Here, we investigated the ratio of the maximum intensity of the dark-place high luminosity component, which is a light component with a wavelength of 400 nm or more and less than 610 nm, to the near-infrared component. As a result, we found that the maximum intensity of the dark-place high luminosity component was 0.27% of the maximum intensity of the near-infrared component, which is less than 0.3%, let alone 1%.

[0100] Next, the spectral distribution of the dark-place high luminosity component and near-infrared component in the output light of Example 1 will be described. As shown in Figure 8B, the dark-place high luminosity component was relatively strong in the light component (blue) within the wavelength range of 460 nm or more and less than 500 nm. The intensity fluctuation range of the light component (blue-green to red) within the wavelength range of 500 nm or more and less than 610 nm was small, with the minimum intensity exceeding 80% of the maximum intensity. Furthermore, the intensity of the visible light component with a wavelength longer than 610 nm increased as the wavelength increased.

[0101] On the other hand, as shown in Figure 8A, the intensity of the near-infrared component gradually increased with increasing wavelength, at least within the wavelength range of 780 nm or more and less than 1100 nm. The near-infrared component had its maximum intensity within the wavelength range of 800 nm or more and less than 950 nm (especially less than 900 nm). Furthermore, the intensity of the near-infrared component gradually decreased above 950 nm.

[0102] In addition, the near-infrared component in the output light of the light emitting device of Example 1 is Cr when compared with the desired specifications communicated to the near-infrared LED package manufacturer and known technology. 3+ It is highly likely that the fluorescence is due to the electron energy transition of the trivalent chromium ion of the activated phosphor.

[0103] Next, the differences between the output light of the light emitting device of Example 1 and the output light of the light emitting devices of Comparative Examples 1 and 2 will be described. As shown in Figures 8A and 8B, in the spectral distribution of the output light of Comparative Example 1, the maximum intensity of near-infrared light near a wavelength of 840 nm was approximately 106% of that of Example 1. On the other hand, in the spectral distribution of the output light of Comparative Example 1, the maximum intensity of the blue light component near a wavelength of 450 nm was 9275% (93 times) of that of Example 1. Furthermore, in Comparative Example 1, there were fewer visible light components (green to red) other than blue light, resulting in visible light components biased toward blue.

[0104] For this reason, the light emitting device of Example 1 emitted output light that combined white light that glows dimly in the dark with strong near-infrared light, while the light emitting device of Comparative Example 1 emitted relatively strong blue light and strong near-infrared light. From these results, it was found that Comparative Example 1 output a strong bluish light that tends to be uncomfortable when turned on, whereas Example 1 had the advantageous effect of outputting a dim white light that appears natural.

[0105] 8A and 8B, in the spectral distribution of the output light of Comparative Example 2, the maximum intensity of near-infrared light near a wavelength of 840 nm was approximately 95% of that of Example 1. On the other hand, the maximum intensity of the blue light component near a wavelength of 450 nm was 1192% (12 times) of that of Example 1. Furthermore, the intensities of visible light components (green to red) other than blue light in Comparative Example 2 were relatively high; for example, the maximum intensity within the wavelength range of 500 nm or more and less than 650 nm was 1737% (17 times) of that of Example 1.

[0106] For this reason, Example 1 emits output light that combines a dim white light and strong near-infrared light, while Comparative Example 2 emits relatively strong white light and relatively weak near-infrared light. From these results, it was found that Comparative Example 2 outputs bright white light and weak near-infrared light when lit, while Example 1 has the advantageous effect of appearing dim and natural.

[0107] Here, the spectral distribution of the output light of the near-infrared light emitting device according to this embodiment is determined substantially by the total thickness of the polyimide tapes, regardless of the thickness of each polyimide tape or the number of layers stacked. Therefore, the spectral distribution of the output light of the near-infrared light emitting device was evaluated by changing the total thickness of the polyimide tapes.

[0108] [Example 2] A light-emitting device having the configuration shown in FIG. 1 was fabricated using one near-infrared LED used in Example 1 and polyimide tape. Specifically, polyimide tape (Kapton tape) was attached so as to cover the entire light output surface of the near-infrared LED used in Example 1. In this example, multiple sheets of polyimide tape were laminated to a total thickness of 35 μm. In this way, the light-emitting device of this example was obtained, in which polyimide tape was provided on the surface of the near-infrared LED.

[0109] [Examples 3 to 6] The light emitting devices of Examples 3, 4, 5 and 6 were obtained by the same process as in Example 2, except that the polyimide tapes were laminated so that the total thickness of the polyimide tapes was 50 μm, 85 μm, 100 μm and 160 μm, respectively.

[0110] Comparative Example 3 The light emitting device of this example was obtained by the same steps as in Example 2, except that no polyimide tape was attached to the light output surface of the near-infrared LED.

[0111] [Evaluation of Light-Emitting Devices of Examples 2 to 6 and Comparative Example 3] The light emitting devices of Examples 2 to 6 and Comparative Example 3 obtained as described above were energized and turned on under the same conditions, and then the spectral distribution of the output light was evaluated.

[0112] FIG. 9A is a graph showing the spectral distribution of output light emitted by the light-emitting devices of Examples 2 to 6 and Comparative Example 3. For reference, FIG. 9B shows an enlarged view of the visible region of the spectral distribution of FIG. 9A. As seen in FIGS. 9A and 9B, the spectral distribution of output light emitted by the light-emitting devices of Examples 2 to 6, similar to that of Example 1, consisted of a very weak visible light component in the visible region (380 to 780 nm) and a strong near-infrared component in the near-infrared region (780 nm to 2.5 μm). The visible light component had a light component spanning at least the entire wavelength range of 510 nm to less than 780 nm, and the near-infrared component had a light component spanning at least the entire wavelength range of 780 nm to less than 1100 nm.

[0113] In Examples 2, 3, 4, and 5, the visible light components were in the wavelength ranges of 410 nm, 430 nm, 450 nm, and 460 nm or more, respectively. Therefore, although there were differences in light color, the visible light components of the output light emitted by the light-emitting devices of Examples 2 to 6 could be seen as a faint white light that glowed dimly in the dark.

[0114] Here, the ratio of the maximum intensity of the dark-place high luminosity light component, which is a light component with a wavelength of 400 nm or more and less than 610 nm, to the near-infrared component was examined. As a result, the maximum intensity of the dark-place high luminosity light component in Examples 2, 3, 4, 5, and 6 was 2.98%, 0.31%, 0.10%, 0.09%, and 0.08% of the maximum intensity of the near-infrared component, respectively. In other words, the maximum intensity of the dark-place high luminosity light component in Examples 2, 3, 4, 5, and 6 was less than 3% of the maximum intensity of the near-infrared component. Note that this intensity ratio was less than 0.5% in Examples 3 to 6, and 0.1% or less in Examples 4 to 6.

[0115] Next, the spectral distributions of the dark-place high luminosity light component and near-infrared component in the output light of Examples 2 to 6 will be described. As shown in Figure 9B, the dark-place high luminosity light component of Examples 2 to 4 had a peak in the wavelength range of 400 nm or more and less than 500 nm, and the light component (blue) in the wavelength range of 460 nm or more and less than 500 nm was relatively strong. The light component (blue-green to red) in the wavelength range of 550 nm or more and less than 610 nm had a small intensity fluctuation range, with the minimum intensity exceeding 80% of the maximum intensity. Note that the intensity of visible light components with wavelengths longer than 610 nm increased as the wavelength increased.

[0116] In contrast, the dark-place high luminosity light components of Examples 5 and 6 did not have a peak in the wavelength range of 400 nm or more and less than 610 nm. Furthermore, the dark-place high luminosity light components had a higher maximum intensity in the wavelength range of 500 nm or more and less than 610 nm than the maximum intensity of the light components in the wavelength range of 400 nm or more and less than 500 nm. Furthermore, the dark-place high luminosity light components with wavelengths longer than 550 nm increased in intensity as the wavelength increased. Note that, as in Examples 2 to 4, the intensity of the visible light components with wavelengths longer than 610 nm increased as the wavelength increased.

[0117] On the other hand, the near-infrared components of Examples 2 to 6 exhibited the same spectral distribution as that of Example 1, as can be seen from FIGS. 8A and 9A.

[0118] Next, the differences between the output light of the light emitting devices of Examples 2 to 6 and the output light of the light emitting device of Comparative Example 3 will be described. As shown in FIGS. 9A and 9B, the spectral distribution of the output light of Comparative Example 3 was compared with the spectral distributions of Examples 2, 3, 4, 5, and 6, with the maximum intensity of near-infrared light around a wavelength of 840 nm being 105%, 110%, 114%, 119%, and 132%, respectively. Meanwhile, the maximum intensity of the dark-place high luminosity light component of Comparative Example 3 was 1308% (13 times), 13334% (133 times), 40337% (403 times), 51736% (517 times), and 61946% (619 times), respectively, compared with Examples 2, 3, 4, 5, and 6. Furthermore, Comparative Example 3 contained fewer visible light components (green to red) other than blue light, resulting in a visible light component biased toward blue.

[0119] For this reason, Examples 2 to 6, and particularly Examples 3 to 6, emit output light that combines white light that glows dimly in the dark with strong near-infrared light, while Comparative Example 3 emits relatively strong blue light and strong near-infrared light. From these results, it was found that Comparative Example 3 outputs a strong bluish light that tends to be uncomfortable when turned on, while Examples 2 to 6 have the advantageous effect of appearing dimly white and natural.

[0120] [Examples 7 to 9] The light emitting devices of Examples 7, 8 and 9 were obtained by the same process as in Example 2, except that the polyimide tapes were laminated so that the total thicknesses were 25 μm, 37 μm and 75 μm, respectively.

[0121] [Evaluation of Light-Emitting Devices of Examples 7 to 9] The light emitting devices of Examples 7 to 9 obtained as described above were energized and turned on under the same conditions as Examples 2 to 6, and then their output light was evaluated. Specifically, the light color (correlated color temperature) of the output light, the chromaticity x and y on the CIE chromaticity diagram and the deviation from blackbody radiation (deviation duv), and the general color rendering index Ra were evaluated. In addition, the light emitting devices of Example 3 (total thickness 50 μm), Example 5 (total thickness 100 μm), and Comparative Example 3 were also evaluated for the light color (correlated color temperature) of the output light, the chromaticity x and y on the CIE chromaticity diagram and the deviation from blackbody radiation (deviation duv), and the general color rendering index Ra.

[0122] 10A and 10B are diagrams showing the color tones of the output light of the light-emitting devices of Examples 3, 5, 7 to 9 and Comparative Example 3 on the CIE chromaticity diagram. For reference, Figs. 10A and 10B also show the ranges of white light color types (daylight, neutral white, white, warm white, and incandescent) on the CIE chromaticity diagram. Table 1 also shows the numerical data for correlated color temperature, chromaticity coordinates x and y, deviation duv, and general color rendering index Ra.

[0123] [Table 1]

[0124] As shown in FIGS. 10A and 10B and Table 1, in Examples 3, 5, and 7 to 9 in which the thickness of the polyimide tape was 25 μm or more and 100 μm or less, white output light was obtained.

[0125] It was observed that the white output light had a tendency for the correlated color temperature to decrease and the general color rendering index to increase as the thickness of the polyimide tape increased. In this example, by changing the thickness of the polyimide tape, the correlated color temperature could be controlled within a range of approximately 2000K or more and less than 9000K. In other words, the correlated color temperature could be controlled within a range from incandescent color to daylight color. Furthermore, the general color rendering index Ra could be controlled within a range of approximately 45 or more and less than 85.

[0126] In particular, Examples 3, 9, and 5 emitted output light with a low color temperature of 3000 K or less, which is more easily visible in the dark, and further resulted in an average color rendering index Ra exceeding 75. Furthermore, a low color temperature of less than 2200 K is considered to have an average color rendering index exceeding 80. For this reason, it was found that the light emitting device of this embodiment, which emits output light with such a low color temperature, is preferable in terms of making illuminated objects appear more natural.

[0127] It should be noted that the deviation duv is important. In the light-emitting device of this embodiment, even when the thickness of the polyimide tape was changed, there was no significant deviation from the locus of blackbody radiation. In other words, the deviation duv was always within the range of 0.00±0.02, and it was found that this embodiment can produce white light that is close to natural light.

[0128] In this way, by using an aromatic polyimide tape or an aromatic polyimide film, it is possible to provide a light-emitting device that outputs high-power near-infrared rays and that allows the on / off state of the near-infrared rays to be visually recognized in the dark as a soft, natural white light.

[0129] Although the present embodiment has been described above, the present embodiment is not limited to this, and various modifications are possible within the scope of the gist of the present embodiment.

[0130] The entire contents of Patent Application No. 2022-070021 (filing date: April 21, 2022) are incorporated herein by reference. [Industrial Applicability]

[0131] According to the present disclosure, it is possible to provide a near-infrared light-emitting device that can easily recognize whether the light is on or off, that causes little discomfort when visible light is lit, and that can efficiently output near-infrared rays, and a method for adjusting the intensity ratio between near-infrared rays and visible light. [Explanation of symbols]

[0132] 1 Solid-state light-emitting device 2 Wavelength converter 3 Organic polymer materials 10,10A primary light 11 Wavelength conversion light 12 mixed light 13 Output light 100, 100A, 100B, 100C, 100D, 100E Near-infrared light emitting device

Claims

1. a solid-state light-emitting element that emits primary light having an emission peak in a wavelength range of 420 nm or more and less than 500 nm; a wavelength converter that converts the primary light into wavelength-converted light having a fluorescence peak in a wavelength range of 750 nm or more and less than 2500 nm; an organic polymer member (excluding an organic polymer member containing a phosphor) through which mixed light of primary light emitted by the solid-state light emitting element and wavelength-converted light emitted by the wavelength converter is transmitted; Equipped with The organic polymer member is The thickness is 3 μm or more and less than 300 μm, a light transmittance of less than 0.1% at a wavelength of 400 nm or less, a light transmittance of less than 1% at a wavelength of the emission peak of the primary light, and a light transmittance of less than 30% at a wavelength of 500 nm or less; The light transmittance in the wavelength range of 750 nm or more and less than 1100 nm is 75% or more and less than 100%, The light transmittance in 10 nm increments within the wavelength range of 500 nm or more and 750 nm or less increases as the wavelength becomes longer, The near-infrared light emitting device outputs the mixed light that has passed through the organic polymer member as output light.

2. The near-infrared light emitting device according to claim 1 , wherein the organic polymer member includes an aromatic polyimide.

3. 3. The near-infrared light emitting device according to claim 1, wherein the solid-state light emitting element is a light emitting diode.

4. 3. The near-infrared light emitting device according to claim 1, wherein the wavelength converter includes a near-infrared phosphor that emits fluorescence having a fluorescence peak in a wavelength range of 780 nm or more and less than 2500 nm.

5. 3. The near-infrared light emitting device according to claim 1, wherein the wavelength converter does not contain a visible phosphor that emits fluorescence having a fluorescence peak in a wavelength range of 380 nm or more and less than 780 nm.

6. The near-infrared light emitting device according to claim 1 , wherein the organic polymer member is in the form of a sheet or a film.

7. 3. The near-infrared light emitting device according to claim 1, wherein the organic polymer member has a thickness of 10 μm or more and less than 100 μm.

8. 3. The near-infrared light emitting device according to claim 1, wherein the output light comprises white light.

9. The output light comprises a visible light component having a wavelength of 380 nm or more and less than 780 nm and a near-infrared component having a wavelength of 780 nm or more and less than 2500 nm, 3. The near-infrared light emitting device according to claim 1, wherein a maximum intensity of a light component with high luminosity in a dark place, which is a light component with a wavelength of 400 nm or more and less than 610 nm, is less than 3% of a maximum intensity of the near-infrared component.

10. A method for adjusting the intensity ratio of near-infrared light to visible light, comprising: a step of transmitting a mixed light of primary light having an emission peak in a wavelength range of 420 nm or more and less than 500 nm and wavelength-converted light obtained by wavelength-converting the primary light and having a fluorescence peak in a wavelength range of 750 nm or more and less than 2500 nm through an organic polymer member (excluding organic polymer members containing a phosphor); a step of outputting the mixed light transmitted through the organic polymer member as output light; and The organic polymer member is The thickness is 3 μm or more and less than 300 μm, a light transmittance of less than 0.1% at a wavelength of 400 nm or less, a light transmittance of less than 1% at a wavelength of the emission peak of the primary light, and a light transmittance of less than 30% at a wavelength of 500 nm or less; The light transmittance in the wavelength range of 750 nm or more and less than 1100 nm is 75% or more and less than 100%, A method in which the light transmittance in 10 nm increments within a wavelength range of 500 nm or more and 750 nm or less increases as the wavelength becomes longer.

11. The output light comprises a visible light component having a wavelength of 380 nm or more and less than 780 nm and a near-infrared light component having a wavelength of 780 nm or more and less than 2500 nm, The method according to claim 10 , wherein the maximum intensity of a light component with high luminosity in a dark place, which is a light component with a wavelength of 400 nm or more and less than 610 nm, is less than 3% of the maximum intensity of the near-infrared component.

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