Light-emitting device

Abstract

To provide a red light-emitting device that emits red light using a blue light-emitting element (blue LED) and a phosphor, and that has dramatically improved brightness.SOLUTION: A light-emitting device that emits red light includes a blue light-emitting element, a first phosphor, and a second phosphor. The light-emitting device has a peak emission wavelength of 615 nm or more and 690 nm or less. When the emission intensity of the light-emitting device at the peak emission wavelength is taken as 100%, the light-emitting device satisfies all of the following: an emission intensity at an emission wavelength of 580 nm is 20% or less, an emission intensity at an emission wavelength of 700 nm is 50% or less, and the maximum emission intensity at emission wavelengths from 400 nm to 500 nm is 5% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a light emitting device that emits red light. [Background technology]

[0002] As a red light emitting device, an incandescent lamp with a colored glass filter attached or an AlInGaP light emitting diode (LED chip) has been used. In addition, a light emitting device composed of a blue light emitting element (also called a blue LED) and a CaS:Eu phosphor or an oxynitride phosphor has also been proposed, as shown in Patent Document 1 below.

[0003] It is known that the human eye perceives yellow light with a wavelength of 555 nm as the brightest (see Figure 12). For white lighting, blue and red components are also necessary. However, these wavelengths have low luminosity, so various technologies have been developed to achieve both color rendering and brightness (see Non-Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-192614 [Non-patent literature]

[0005] [Non-Patent Document 1] Gregor J. Hoerder et al.,Sr[Li2Al2O2N2]:Eu2+-A high performance red phosphor to brighten the future, NATURE COMMUNICATIONS, volume 10, 1824 (2019) [Non-patent document 2] WA Thornton, Luminosity and Color-Rendering Capability of White Light, Journal of the optical society of america, Vol61 No.9,1971 [Non-patent document 3] M. Koedam and JJOpstelten, Measurement and computer-aided optimization of spectral power distributions, Lighting Research and Technology, Vol3 No.3 1971 Summary of the Invention [Problem to be solved by the invention]

[0006] Although AlInGaP-based light-emitting diodes (LED chips) do not require phosphors, they suffer from problems such as large color changes with current values ​​and poor temperature characteristics. Therefore, it is important to combine blue light-emitting elements (blue LEDs) with phosphors to create light-emitting devices in amber, red, and other colors. The red light-emitting device described in Patent Document 1 is said to have high color rendering properties and be recognizable by people with color vision deficiencies. However, it has not been possible to achieve sufficient brightness in areas where it is important to visually determine whether a red light-emitting device is lit, such as in indicators.

[0007] The present disclosure has been made to solve the above problems, and aims to provide a red light-emitting device that emits red light using a blue light-emitting element (blue LED) and a phosphor, with dramatically improved brightness. [Means for solving the problem]

[0008] The present disclosure has been made to achieve the above object, and provides a light emitting device that includes a blue light emitting element, a first phosphor, and a second phosphor and emits red light, the light-emitting device has an emission peak wavelength of 615 nm or more and 690 nm or less; When the light emitting intensity at the light emitting peak wavelength of the light emitting device is taken as 100%, The emission intensity at an emission wavelength of 580 nm is 20% or less. The emission intensity at an emission wavelength of 700 nm is 50% or less. The maximum emission intensity at an emission wavelength of 400 nm to 500 nm is 5% or less. The present invention provides a light-emitting device that satisfies all of the above.

[0009] Such a light emitting device can suppress emission of long wavelengths with poor visibility, thereby providing a red light emitting device with dramatically improved brightness.

[0010] In this case, when the emission intensity at the emission peak wavelength of the light emitting device is taken as 100%, the emission intensity at an emission wavelength of 580 nm is 5% or less; the emission intensity at an emission wavelength of 700 nm is 40% or less; the maximum emission intensity in the emission wavelength range of 400 nm to 500 nm is 2% or less; The light emitting device can satisfy at least one of the above requirements.

[0011] Such a light emitting device can more effectively suppress long wavelength light emission with poor luminosity and / or can provide a red light emitting device with significantly improved brightness.

[0012] In this case, the light emitting device may be one in which the emission peak wavelength of the first phosphor is less than 635 nm, and the emission peak wavelength of the second phosphor is 635 nm or more.

[0013] This makes it possible to stably suppress long-wavelength light emission with poor visibility and dramatically improve brightness.

[0014] In this case, the light emitting device may be such that the first phosphor is a LuAG phosphor, a YAG phosphor, a SCASN phosphor, or a KSF phosphor.

[0015] This makes it possible to stably suppress long-wavelength light emission with poor visibility and dramatically improve brightness.

[0016] In this case, the light emitting device may be one in which the amount of the first phosphor relative to the total amount of the first phosphor and the second phosphor is 20 mass % or more.

[0017] This results in a red light emitting device with improved brightness.

[0018] In this case, the light emitting device may be one in which the emission half widths of the first phosphor and the second phosphor are 80 nm or less.

[0019] Such a light emitting device can more effectively suppress long wavelength light emission with poor visibility, resulting in a red light emitting device with dramatically improved brightness.

[0020] In this case, the second phosphor may have an excitation spectrum intensity of 70% or more at a wavelength of 580 nm, when the maximum intensity of the excitation spectrum at wavelengths of 250 to 600 nm is taken as 100%.

[0021] Such a light emitting device can more effectively suppress long wavelength light emission with poor visibility, resulting in a red light emitting device with dramatically improved brightness. [Effects of the Invention]

[0022] As described above, the light emitting device of the present disclosure provides a red light emitting device with dramatically improved brightness by suppressing long wavelength light emission with poor luminosity. [Brief explanation of the drawings]

[0023] [Figure 1] 1 illustrates an example of a light emitting device according to the present disclosure. [Figure 2] The figure shows the emission spectrum of a phosphor that emits green to yellow light when excited by light from a blue light-emitting element (blue LED). [Figure 3] The figure shows the emission spectrum of a phosphor that is excited by light from a blue light-emitting element (blue LED) and emits red light. [Figure 4] The results of evaluating the peak wavelength dependency of the first phosphor (Comparative Examples 2 to 4 and Examples 1 to 4) are shown below. [Figure 5] 1 shows the emission spectra of the light emitting devices of Comparative Examples 1 and 2 and Example 1. [Figure 6] The results of evaluating the peak wavelength dependency of the first phosphor (Comparative Example 2, Examples 5 to 8) are shown below. [Figure 7] 1 shows the emission spectra of the light emitting devices of Comparative Example 2 and Examples 5 and 8. [Figure 8] The results of evaluating the peak wavelength dependency of the first phosphor (Comparative Example 2, Example 9) are shown. [Figure 9] 1 shows the emission spectra of the light emitting devices of Comparative Example 2 and Example 9. [Figure 10] 1 shows an example of the excitation spectrum of a second phosphor. [Figure 11] 1 is a diagram illustrating a chromaticity range of red. [Figure 12] This shows the sensitivity curve for light wavelengths in human vision. [Figure 13] 1 shows the temperature characteristics of an AlInGaP-based red LED and a red light emitting device that combines an InGaN-based blue LED of the present disclosure with two types of phosphors. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present disclosure will be described in detail below, but the present disclosure is not limited thereto.

[0025] As described above, there has been a demand for a red light emitting device that emits red light using a blue light emitting element (blue LED) and a phosphor, with dramatically improved brightness.

[0026] As a result of extensive research into the above-mentioned problems, the present inventors have discovered a light emitting device that emits red light and includes a blue light emitting element, a first phosphor, and a second phosphor, the light-emitting device has an emission peak wavelength of 615 nm or more and 690 nm or less; When the light emitting intensity at the light emitting peak wavelength of the light emitting device is taken as 100%, The emission intensity at an emission wavelength of 580 nm is 20% or less. The emission intensity at an emission wavelength of 700 nm is 50% or less. The maximum emission intensity at an emission wavelength of 400 nm to 500 nm is 5% or less. The present inventors have found that a light emitting device that satisfies all of the above requirements can suppress emission of long wavelengths with poor luminosity and achieve a red light emitting device with dramatically improved brightness, thereby completing the present disclosure.

[0027] The following description will be made with reference to the drawings.

[0028] [Light-emitting device] FIG. 1 shows an example of a light-emitting device 100 according to the present disclosure. The light-emitting device 100 according to the present disclosure includes, for example, a blue light-emitting element (blue LED) 10 disposed on a substrate 40, and a phosphor 1 that absorbs a portion of light from the blue light-emitting element (blue LED) 10 and converts the light into light with a wavelength different from the wavelength of light emitted by the blue light-emitting element (blue LED) 10. The phosphor 1 includes a first phosphor 1a and a second phosphor 1b. The first phosphor 1a and the second phosphor 1b may be dispersed in a phosphor layer 20 that also functions as a sealant made of resin, glass, or the like that covers the blue light-emitting element (blue LED) 10, and may be housed in a package 30. In addition to the resin, the phosphor layer 20 may contain, as appropriate, additives such as a filler 2 and additives for improving the dispersibility of the phosphor 1. The package 30 and the substrate 40 may also be molded integrally. This will be described in detail below.

[0029] First, the light emitting device according to the present disclosure includes a blue light emitting element (blue LED), a first phosphor, and a second phosphor, and emits red light having an emission peak wavelength of 615 nm or more, more preferably 630 nm or more, and 690 nm or less.

[0030] Here, we will explain the chromaticity range of red. JIS Standard Z5500:1995 specifies the chromaticity range for red used in automobile taillights and stoplights. Specifically, Table 4 of JIS Standard Z5500:1995 specifies that the chromaticity coordinates of red are y≦0.335, z≦0.008. Using z=1-xy, the chromaticity coordinates are as shown in Figure 11. JIS Standard Z9103:2018 also specifies the chromaticity coordinates of safety signs and other items, but this specification focuses on the chromaticity coordinate range of traffic lights, which have particularly high color purity. Specifically, Table 6 of JIS Standard Z9103:2018 specifies the chromaticity coordinates of the four points: (0.710, 0.290), (0.690, 0.290), (0.660, 0.320), and (0.680, 0.320). In this specification, the range encompassing all of these standards is defined as red.

[0031] The chromaticity coordinates of the red region targeted by the light-emitting device described in Patent Document 1 are four points: (0.54, 0.234), (0.54, 0.302), (0.631, 0.35), and (0.68, 0.3). Referring to FIG. 11, it can be seen that these are different from the red region targeted by the light-emitting device according to the present disclosure.

[0032] As a result of extensive research by the inventors into light-emitting devices that emit red light using blue light-emitting elements (blue LEDs) and phosphors, it was discovered that by using two types of phosphors to adjust the emission intensity at a specified emission wavelength, it is possible to obtain a red light-emitting device with dramatically improved brightness.

[0033] The light emitting device according to the present disclosure has the following characteristics: (A) The emission intensity at an emission wavelength of 580 nm is 20% or less; (B) the emission intensity at an emission wavelength of 700 nm is 50% or less; (C) The maximum emission intensity at an emission wavelength of 400 nm to 500 nm is 5% or less; A light emitting device that satisfies all of the above conditions (A) to (C) is obtained by combining a blue light emitting element (blue LED) with two types of phosphors, a first phosphor and a second phosphor, that convert light from the blue light emitting element (blue LED).

[0034] Note that "when the emission intensity at the emission peak wavelength of the light-emitting device is taken as 100%, the emission intensity at the emission wavelength λnm is X% or less" can also be expressed as "the emission intensity at the emission wavelength λnm is X% or less of the emission intensity at the emission peak wavelength of the light-emitting device."

[0035] In a light-emitting device, if light leakage from the blue light-emitting element (blue LED) becomes significant, it becomes difficult to achieve characteristics further to the right (X-axis) of the chromaticity coordinates, resulting in a red color with poor color purity. Therefore, if the light-emitting device has a (A) emission intensity at an emission wavelength of 580 nm of 20% or less and (C) a maximum emission intensity at an emission wavelength of 400 nm to 500 nm of 5% or less, assuming that the emission intensity at the peak emission wavelength of the light-emitting device is 100%, the yellow light output from the light-emitting device and the leakage of light from the blue light-emitting element (blue LED) can be suppressed, resulting in a red color with good color purity. Furthermore, if the light-emitting device has a (B) emission intensity at an emission wavelength of 700 nm of 50% or less, assuming that the emission intensity at the peak emission wavelength of the light-emitting device is 100%, the emission intensity in the long-wavelength deep red region will be reduced, resulting in a brighter light. Thus, by satisfying all of the above (A), (B), and (C), a red light-emitting device with dramatically improved brightness can be achieved.

[0036] Furthermore, when the emission intensity at the emission peak wavelength of the light-emitting device is taken as 100%, if any of the following (a), (b), or (c) is satisfied, it is more preferable because it results in a red light-emitting device that more effectively suppresses emission with poor luminosity at long wavelengths and / or further dramatically improves brightness. (a) The emission intensity at an emission wavelength of 580 nm is 5% or less. (b) The emission intensity at an emission wavelength of 700 nm is 40% or less. (c) The maximum emission intensity at an emission wavelength of 400 nm to 500 nm is 2% or less.

[0037] (a) If the emission intensity at an emission wavelength of 580 nm is 5% or less, the yellow light output from the light-emitting device can be more effectively suppressed, resulting in the emission of red light with better color purity. (b) If the emission intensity at an emission wavelength of 700 nm is 40% or less, brightness will be further dramatically improved. (c) If the maximum emission intensity at an emission wavelength of 400 nm to 500 nm is 2% or less, light leakage from the blue light-emitting element (blue LED) can be more effectively suppressed, resulting in the emission of red light with better color purity.

[0038] (Blue light emitting element) The blue light-emitting element (blue LED) 10 according to the present disclosure is not particularly limited as long as it emits blue light. For example, an element with an emission peak wavelength in the range of 380 to 480 nm can be used. Such blue light-emitting elements (blue LEDs) are high-quality and low-cost and are relatively easily available.

[0039] The blue light-emitting element (blue LED) preferably has an emission half-width of 80 nm or less. This effectively suppresses long-wavelength emission with poor visibility, resulting in a red light-emitting device with dramatically improved brightness. The emission half-width of the blue light-emitting element is more preferably narrow, more preferably 50 nm or less, and even more preferably 30 nm or less.

[0040] (First phosphor) As the first phosphor, for example, an oxide phosphor, a sulfide phosphor, an oxynitride phosphor, a nitride phosphor, a fluoride phosphor, or a quantum dot phosphor can be used.

[0041] The oxide phosphor is, for example, (Y,Gd)3(Al,Ga)5O 12 : Ce, Lu3(Al,Ga)5O 12 :Ce, (Ba,Sr,Ca)2SiO4:Eu, Ca8Mg(SiO4)4Cl2:Eu, SrLi3AlO4:Eu, (Sr,Ba)3(Si,Ge)O5:Eu, etc.

[0042] The sulfide phosphor is, for example, a phosphor such as SrGa2S4:Eu.

[0043] Examples of oxynitride phosphors include β-SiAlON:Eu (β-sialon), Ca-α-SiAlON:Eu (α-sialon), (Ba, Sr, Ca)Si2N2O2:Eu, and Sr[Li2Al2O2N2]:Eu.

[0044] The nitride phosphor is, for example, (La,Y)3Si6N 11 :Ce, (Sr,Ca)AlSiN3:Eu, (Ba,Sr,Ca)2Si5N8:Eu and other phosphors.

[0045] The fluoride phosphor is, for example, a phosphor such as K2SiF6:Mn.

[0046] Quantum dot phosphors are phosphors whose cores include, for example, CdSe, (Cs,FA,MA)(Pb,Sn)(F,Cl,Br,I)3 (FA is formamidinium, MA is methylammonium), InP, and (Ag,Cu)(In,Ga)(S,Se)2.

[0047] As described in Patent Document 1, a red phosphor is required to obtain red light emission. However, in the present disclosure, the first phosphor can be a green to red phosphor with a wavelength longer than the peak wavelength of the blue light emitting element (blue LED) and shorter than the peak wavelength of the blue light emitting element (for example, a red phosphor with an emission peak wavelength shorter than 635 nm). For example, the first phosphor can be Lu3(Al,Ga)5O 12 LuAG phosphor, (Y,Gd)3(Al,Ga)5O, represented by Ce 12 It is preferable to use a YAG phosphor represented by (Sr,Ca)AlSiN3:Eu, a SCASN phosphor represented by (Sr,Ca)AlSiN3:Eu, or a KSF phosphor represented by K2SiF6:Mn, because such phosphors emit light efficiently with light from a blue light-emitting element.

[0048] As the first phosphor, it is preferable to use LuAG phosphor, which has a higher internal quantum efficiency and a narrower emission half-width than YAG, because this makes it possible to fabricate a highly reliable and inexpensive red light-emitting device.

[0049] It is also preferable to use a nitride-based red phosphor as the first phosphor.

[0050] It is also preferable to use a phosphor with a half-width of 80 nm or less as the first phosphor. In particular, the KSF phosphor has an extremely small half-width of 9 nm, which can reduce the long-wavelength portion with low luminosity (deep red emission), thereby providing a red light-emitting device with dramatically improved brightness. In addition, when a KSF phosphor is used as the first phosphor, in order to suppress leakage of blue light from a blue light-emitting element (blue LED), it is preferable that the ratio of the amount of the first phosphor to the total amount of the first phosphor and the second phosphor be 50 mass% or more.

[0051] If the leakage of blue light from the blue light-emitting element (blue LED) can be suppressed, it is possible to stably produce characteristics further to the right (X-axis direction) of the chromaticity coordinates, resulting in a red color with good color purity. For this reason, it is effective to have the first phosphor play the role of efficiently absorbing blue light.

[0052] (Second phosphor) As the second phosphor, for example, an oxide phosphor, a sulfide phosphor, a nitride phosphor, or a quantum dot phosphor can be used.

[0053] The oxide phosphor is, for example, a phosphor such as 3.5MgO·0.5MgF2·GeO2:Mn.

[0054] The sulfide phosphor is, for example, a phosphor such as CaS:Eu.

[0055] Examples of nitride phosphors include (Sr,Ca)AlSiN3:Eu, CaAlSiN3:Eu, (Ba,Sr,Ca)2Si5N8:Eu, and Sr[LiAl3N4]:Eu.

[0056] Quantum dot phosphors are phosphors whose cores include, for example, CdSe, (Cs,FA,MA)(Pb,Sn)(F,Cl,Br,I)3 (FA is formamidinium, MA is methylammonium), InP, and (Ag,Cu)(In,Ga)(S,Se)2.

[0057] The second phosphor according to the present disclosure may have a peak emission wavelength longer than that of the first phosphor, for example, a phosphor that is excited by light from a blue light-emitting element (blue LED) and emits red light with a peak emission wavelength of 635 nm or more.

[0058] It is preferable to use a second phosphor having an emission half-width of 80 nm or less. Specifically, nitride-based red phosphors, which have been developed in recent years, are preferable, and it is more preferable to use a highly reliable SCASN phosphor.

[0059] Furthermore, it is preferable that the second phosphor absorbs the emission of the first phosphor. An example of the excitation spectrum of the second phosphor is shown in FIG. 10. Since emission other than red is particularly unnecessary for the light-emitting device according to the present disclosure, it is preferable that the emission of wavelengths below 580 nm be as small as possible. From this perspective, it is more preferable that the second phosphor has an excitation spectrum intensity of 70% or more at a wavelength of 580 nm, where the maximum intensity of the excitation spectrum at wavelengths of 250 to 600 nm is taken as 100%. It is believed that such a second phosphor can suppress the emission of the first phosphor at wavelengths below 580 nm. It is also more preferable that the second phosphor has an excitation spectrum intensity of 70% or more at a wavelength of 580 nm from the emission peak wavelength of the blue light-emitting element. It is believed that such a second phosphor can satisfactorily excite the second phosphor with light from the blue light-emitting element and suppress the emission of the first phosphor at wavelengths below 580 nm.

[0060] (Combination of phosphors, etc.) The combination of the first phosphor and the second phosphor is not particularly limited as long as it satisfies all of the above (A), (B), and (C).

[0061] Figures 2 and 3 show the emission spectra of phosphor materials that can be suitably used for the first phosphor and the second phosphor. Figure 2 shows the emission spectrum of a phosphor that is excited by light from a blue light-emitting element (blue LED) to emit green to yellow light. Figure 3 shows the emission spectrum of a phosphor that is excited by light from a blue light-emitting element (blue LED) to emit red light.

[0062] It is preferable to select the first phosphor and the second phosphor from among the phosphors shown in Figures 2 and 3. As described above, by combining a blue light-emitting element (blue LED) with the first phosphor and the second phosphor and adjusting the emission intensity at a predetermined emission wavelength, it is possible to obtain a red light-emitting device with dramatically improved brightness.

[0063] In particular, it is preferable to use a combination in which the first phosphor has an emission peak wavelength of less than 635 nm and the second phosphor has an emission peak wavelength of 635 nm or more.

[0064] As described above, it is preferable to have the first phosphor absorb blue light and the second phosphor absorb the light emitted by the first phosphor. In this case, the first phosphor is required to have high luminous efficiency. Specifically, it is preferable that the blue light absorption rate is 70% or more and the internal quantum efficiency is 80% or more.

[0065] Furthermore, if phosphors with emission half-widths of 80 nm or less are used as both the first and second phosphors, the emission intensity in the long-wavelength deep red region will be reduced, resulting in a bright red light emitting device.

[0066] However, if the ratio of the amount of the first phosphor to the total amount of the first phosphor and the second phosphor is 50 mass% or less, the emission of the first phosphor will not appear in the red light-emitting device (it will be absorbed by the second phosphor), and therefore the half-value width of the first phosphor may be 80 nm or more. The amount of the first phosphor to the total amount of the first phosphor and the second phosphor is more preferably 20 mass% or more, and even more preferably 30 mass% or more.

[0067] Furthermore, the difference between the peak wavelength of the first phosphor and the peak wavelength of the second phosphor is preferably less than 20 nm, and more preferably less than 10 nm. [Example]

[0068] The present disclosure will be specifically described below using examples, but the present disclosure is not limited thereto.

[0069] A 3528mm (3.5mm x 2.8mm) bathtub-shaped SMD (surface mount device) mounted with a blue LED with a peak emission wavelength of 447nm was prepared as a light-emitting device. The phosphor was mixed with silicone resin, applied in a predetermined amount, and its optical properties were evaluated. Because blue LEDs vary in output, the luminous intensity was corrected so that the light output at If = 65mA was 25mW / sr. First and second phosphors with various physical properties were prepared, and these were combined to fabricate and evaluate light-emitting devices. In Comparative Examples 1 and 2, only one type of phosphor was used, and the luminous intensity evaluation result of Comparative Example 2 (SCASN (641nm)) was used as the reference (luminous intensity: 100%). The phosphors used in these Examples and Comparative Examples are listed in Table 1. The optical properties of the phosphor powders were measured using the integrating sphere unit of a JASCO FP-6500 spectrophotometer.

[0070] [Table 1]

[0071] (Examples 1 to 4, Comparative Examples 1 to 4) First, we will explain the results of evaluating the dependency of the luminous intensity of the light-emitting device on the peak wavelength of the first phosphor. Table 2 shows the details of each material, the composition of each material, and the evaluation results. In Table 2, "Ip580" indicates the emission intensity at an emission wavelength of 580 nm relative to the emission intensity at the emission peak wavelength of the light-emitting device. Furthermore, "Ip700" indicates the emission intensity at an emission wavelength of 700 nm relative to the emission intensity at the emission peak wavelength of the light-emitting device. Furthermore, "Ip400-500" indicates the highest emission intensity at an emission wavelength of 400 nm to 500 nm relative to the emission intensity at the emission peak wavelength of the light-emitting device. Note that the phosphor ratios and phosphor concentrations are based on mass (the same applies to Tables 3 and 4).

[0072] Here, it is desirable that the total concentration of the phosphors is 30% or more. By making the phosphor concentration relatively high in the light emitting device, it is possible to suppress leakage of blue light from the blue light emitting element (blue LED).

[0073] A specific example of the composition of Example 1 is shown below. An InGaN-based blue chip with an emission peak wavelength of 447 nm and a green phosphor Lu3Al5O 12 :Ce 3+ (hereafter abbreviated as LuAG) and red phosphor (Sr,Ca)AlSiN3:Eu 2+ A red light-emitting device was fabricated using the phosphor. A thermosetting silicone resin and Aerosil were used to prevent the phosphor from settling. The compounding ratios are shown below. Silicone resin A (main agent) 0.5000g Silicone resin B (hardener) 0.5000g Aerosil 0.0150g LuAG (544 nm) phosphor 0.2747 g SCASN (641 nm) phosphor 0.5101 g

[0074] [Table 2]

[0075] FIG. 4 also shows the evaluation results (Comparative Examples 2 to 4 and Examples 1 to 4) of the dependency of the luminous intensity of the light-emitting device (the "relative value" of "brightness" in Table 2) on the peak wavelength of the first phosphor. Note that Comparative Example 1 has an extremely low luminous intensity that is outside the range of the scale of FIG. 4, and is therefore not shown in FIG. 4. As can be seen from Table 2 and FIG. 4, Examples 1 to 4 obtained red light-emitting devices with higher luminous intensity (brighter) than the comparative examples. It was also found that a preferable condition is that the device contains a first phosphor with an emission peak wavelength of less than 635 nm and that the internal quantum efficiency of the first phosphor is 80% or higher.

[0076] The emission spectra of the light-emitting devices of Comparative Examples 1 and 2 and Example 1 are shown in Figure 5. Because Comparative Examples 1 and 2 use a single type of phosphor, they directly reflect the characteristics of the phosphor powder (Table 2). When comparing Comparative Example 2 and Example 1, there does not appear to be a significant difference in the emission spectra in the upper graph of Figure 5, but a closer look at the lower graph of Figure 5 reveals that Example 1 is slightly shifted to the shorter wavelength side.

[0077] As can be seen from the upper diagram of Figure 5, the emission spectrum of the first phosphor, which is the green phosphor to the short-wavelength red phosphor, has almost no effect on the emission spectrum of the red light-emitting element. This is thought to be because the ratio of the first phosphor is lower than the ratio of the second phosphor, and the emission of the first phosphor is absorbed by the second phosphor and converted into red emission of the second phosphor.

[0078] (Examples 5 to 8) Furthermore, the evaluation results (for Examples 5 to 8) of the peak wavelength dependency of the first phosphor when the emission peak wavelength of the first phosphor was changed between 609 and 637 nm are shown in Table 3. The dependency of the luminous intensity of the light emitting device (the "relative value" of "brightness" in Table 3) on the peak wavelength of the first phosphor is shown in FIG. 6, and the emission spectra of the light emitting devices of Examples 5 and 8, together with that of Comparative Example 2, are shown in FIG.

[0079] [Table 3]

[0080] As can be seen from Table 3 and Fig. 6, red light-emitting devices with higher luminosity (brighter) than the comparative example were obtained in Examples 5 to 8. When comparing the emission spectra of Comparative Example 2 with those of Examples 5 and 8, there does not appear to be a significant difference in the emission spectra in the upper diagram of Fig. 7, but referring to the enlarged lower diagram of Fig. 7, it can be seen that Examples 5 and 8 are shifted to the shorter wavelength side.

[0081] (Examples 9 and 10) The evaluation results of Examples 9 and 10, in which KSF was used as the first phosphor, are shown in Table 4. The evaluation results of the luminous intensity of the light emitting device (Example 9) are shown in FIGS.

[0082] [Table 4]

[0083] As shown in Table 4 and FIG. 8, it can be seen that when the KSF phosphor was used as the first phosphor, a red light emitting device with higher luminosity (brighter) than the comparative example was obtained.

[0084] Furthermore, when comparing the emission spectra of Comparative Example 2 and Example 9, as shown in Figure 9, the sharp emission spectrum of KSF is clearly visible in the emission spectrum of the red light-emitting device. This is thought to be because the ratio of KSF, the first phosphor, is higher than the ratio of the second phosphor. In this way, by using a phosphor with a small emission half-width as the first phosphor and increasing the ratio of the first phosphor, a red light-emitting device with higher luminosity (brighter) than the Comparative Example was obtained.

[0085] 13 shows the temperature characteristics of a red light-emitting device (Example 10) that combines an AlInGaP red LED and the disclosed InGaN blue LED with two types of phosphors. The luminous intensity at 150°C compared to room temperature of 25°C drops to about 20% for the AlInGaP red LED, but remains above 80% for Example 10, demonstrating that this is a red light-emitting device with excellent brightness and temperature characteristics.

[0086] As described above, according to the examples of the present disclosure, it was possible to obtain a red light emitting device with high luminosity that suppresses long wavelength light emission with poor luminosity and dramatically improves brightness.

[0087] The present specification includes the following aspects. [1]: A light emitting device that includes a blue light emitting element, a first phosphor, and a second phosphor and emits red light, the light-emitting device has an emission peak wavelength of 615 nm or more and 690 nm or less; When the light emitting intensity at the light emitting peak wavelength of the light emitting device is taken as 100%, The emission intensity at an emission wavelength of 580 nm is 20% or less. The emission intensity at an emission wavelength of 700 nm is 50% or less. The maximum emission intensity at an emission wavelength of 400 nm to 500 nm is 5% or less. A light-emitting device that satisfies all of the above. [2]: When the emission intensity at the emission peak wavelength of the light-emitting device is taken as 100%, the emission intensity at an emission wavelength of 580 nm is 5% or less; the emission intensity at an emission wavelength of 700 nm is 40% or less; the maximum emission intensity in the emission wavelength range of 400 nm to 500 nm is 2% or less; The light emitting device according to [1] above, which satisfies at least one of the following conditions. [3]: The light emitting device according to the above [1] or [2], wherein the first phosphor has an emission peak wavelength of less than 635 nm, and the second phosphor has an emission peak wavelength of 635 nm or more. [4]: The light emitting device according to [1], [2] or [3] above, wherein the first phosphor is a LuAG phosphor, a YAG phosphor, a SCASN phosphor or a KSF phosphor. [5]: The light emitting device according to [1], [2], [3] or [4], wherein the amount of the first phosphor relative to the total amount of the first phosphor and the second phosphor is 20 mass % or more. [6]: The light emitting device according to [1], [2], [3], [4] or [5] above, wherein the emission half width of the first phosphor and the second phosphor is 80 nm or less. [7]: The light emitting device according to [1], [2], [3], [4], [5] or [6], wherein the second phosphor has an excitation spectrum intensity of 70% or more at a wavelength of 580 nm when the maximum intensity of the excitation spectrum at wavelengths of 250 to 600 nm is taken as 100%.

[0088] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Explanation of symbols]

[0089] 1...phosphor, 1a...first phosphor, 1b...second phosphor, 2...filler, 10... Blue light emitting element (blue LED), 20... Phosphor layer, 30... Package, 40...substrate, 100...light-emitting device.

Claims

1. A light emitting device that includes a blue light emitting element, a first phosphor, and a second phosphor and emits red light, the light-emitting device has an emission peak wavelength of 615 nm or more and 690 nm or less; When the light emitting intensity at the light emitting peak wavelength of the light emitting device is taken as 100%, The emission intensity at an emission wavelength of 580 nm is 20% or less, The emission intensity at an emission wavelength of 700 nm is 50% or less, The maximum emission intensity at an emission wavelength of 400 nm to 500 nm is 5% or less, A light-emitting device characterized by satisfying all of the above.

2. When the emission intensity at the emission peak wavelength of the light-emitting device is taken as 100%, the emission intensity at an emission wavelength of 580 nm is 5% or less; the emission intensity at an emission wavelength of 700 nm is 40% or less; the maximum emission intensity in the emission wavelength range of 400 nm to 500 nm is 2% or less; 2. The light emitting device according to claim 1, wherein at least one of the following is satisfied.

3. 2. The light emitting device according to claim 1, wherein the first phosphor has an emission peak wavelength of less than 635 nm, and the second phosphor has an emission peak wavelength of 635 nm or more.

4. 2. The light emitting device according to claim 1, wherein the first phosphor is a LuAG phosphor, a YAG phosphor, a SCASN phosphor, or a KSF phosphor.

5. 2. The light emitting device according to claim 1, wherein the amount of the first phosphor relative to the total amount of the first phosphor and the second phosphor is 20 mass % or more.

6. 2. The light emitting device according to claim 1, wherein the emission half widths of the first phosphor and the second phosphor are 80 nm or less.

7. The light emitting device according to any one of claims 1 to 6, characterized in that the second phosphor has an excitation spectrum intensity of 70% or more at a wavelength of 580 nm when the maximum intensity of the excitation spectrum at wavelengths of 250 to 600 nm is 100%.

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