Light-emitting device

Abstract

To provide an amber light-emitting device that uses an LED and a phosphor to emit amber light, with dramatically improved brightness.SOLUTION: A light-emitting device includes a blue LED, a first phosphor, and a second phosphor, and emits amber light, the first phosphor is excited by the light of the blue LED and emits green to yellow light, the second phosphor is excited by the light of the blue LED, and emits light having an emission peak wavelength greater than the emission peak wavelength of the first phosphor and 625 nm or less, and the emission intensity at an emission wavelength of 650 nm is equal to or less than 60% of the emission intensity at the emission peak wavelength of the light-emitting device.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a light-emitting device that emits amber-colored light.

Background Art

[0002] As an amber-colored light-emitting device, one in which a color glass filter is attached to an incandescent bulb or an AlInGaP-based light-emitting diode (LED chip) has been used. Also, a light-emitting device composed of a blue LED, a YAG phosphor, and a nitride phosphor as described in Patent Document 1 below has been used.

[0003] It is known that the human eye most brightly perceives yellow light with a wavelength of 555 nm (see FIG. 6). In white lighting, blue and red components are also required. However, since the visibility of these wavelengths is low, various techniques have been developed to achieve both color rendering and brightness (see Non-Patent Documents: Non-Patent Documents 1 to 3).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

[0006] AlInGaP-based light-emitting diodes (LED chips) do not require the use of phosphors, but they have problems such as large color changes with current values ​​and poor temperature characteristics. Therefore, it is important to combine blue LEDs with phosphors to produce white, amber, and other colors. In the amber light-emitting device described in Patent Document 1, although the color rendering is high, sufficient brightness could not be obtained in fields where it is important to visually confirm whether the amber light-emitting device is lit or not using an indicator, etc.

[0007] The present invention was made to solve the above problems, and aims to provide an amber-colored light-emitting device that uses LEDs and phosphors to emit amber light, with dramatically improved brightness. [Means for solving the problem]

[0008] The present invention has been made to achieve the above objective, and provides a light-emitting device comprising a blue LED, a first phosphor, and a second phosphor, which emits amber-colored light, wherein the first phosphor emits green to yellow light when excited by the light of the blue LED, and the second phosphor emits light having an emission peak wavelength greater than the emission peak wavelength of the first phosphor and 625 nm or less when excited by the light of the blue LED, and the emission intensity at an emission wavelength of 650 nm is 60% or less of the emission intensity at the emission peak wavelength of the light-emitting device.

[0009] Such a light-emitting device suppresses long-wavelength light emission, which has poor visual sensitivity, and results in an amber-colored light-emitting device with dramatically improved brightness.

[0010] In this case, the amount of the second phosphor relative to the total amount of the first and second phosphors contained in the light-emitting device can be 15% by mass or more.

[0011] This results in an amber-colored light-emitting device with improved brightness.

[0012] In this case, the first phosphor can be one whose emission peak width at half maximum is 110 nm or less.

[0013] By using a phosphor with a narrow half-width, the emission intensity in the deep red region of long wavelengths becomes smaller, resulting in a bright amber-colored light-emitting device.

[0014] In this case, the emission peak wavelength of the light emitted by the second phosphor is 615 nm or less, and the emission intensity at an emission wavelength of 650 nm can be 50% or less of the emission intensity at the emission peak wavelength of the light-emitting device.

[0015] This further suppresses the emission of light with low visual sensitivity at long wavelengths, resulting in an amber-colored light-emitting device with dramatically improved brightness.

[0016] At this time, the amount of the second phosphor with respect to the total amount of the first phosphor and the second phosphor included in the light-emitting device can be 20% by mass or more.

[0017] Thereby, by using a phosphor with a reduced portion having low long-wavelength visual sensitivity, the proportion of the second phosphor in the entire phosphor can be increased, and the brightness of the amber-colored light-emitting device can be further enhanced.

[0018] At this time, the first phosphor can have a particle size of 24 μm or more.

[0019] Thereby, an amber-colored light-emitting device with a further dramatically improved brightness can be obtained.

Advantages of the Invention

[0020] As described above, according to the light-emitting device of the present invention, light emission with low visual sensitivity at long wavelengths is suppressed, and an amber-colored light-emitting device with a dramatically improved brightness can be obtained.

Brief Description of the Drawings

[0021] [Figure 1] An example of the light-emitting device according to the present invention is shown. [Figure 2] The emission spectrum of a phosphor that is excited by the light of a blue LED and emits light from green to yellow is shown. [Figure 3] The emission spectrum of a phosphor that is excited by the light of a blue LED and emits red light is shown. [Figure 4] The results (Examples 3 to 6, Comparative Example 3) of evaluating the peak wavelength dependency of the second phosphor are shown. [Figure 5] The peak wavelength dependency of the first phosphor in the luminous intensity of the light-emitting device is shown. [Figure 6] The sensitivity curve with respect to the wavelength of light in human vision is shown.

Embodiments for Carrying Out the Invention

[0022] The present invention will be described in detail below, but the present invention is not limited to these descriptions.

[0023] As mentioned above, there was a need for an amber-colored light-emitting device that could dramatically improve brightness.

[0024] As a result of diligent research into the above-mentioned problems, the present inventors have found that a light-emitting device comprising a blue LED, a first phosphor, and a second phosphor, which emits amber-colored light, wherein the first phosphor is excited by the light of the blue LED to emit green to yellow light, and the second phosphor is excited by the light of the blue LED to emit light having an emission peak wavelength greater than the emission peak wavelength of the first phosphor and less than or equal to 625 nm, and the emission intensity at an emission wavelength of 650 nm is 60% or less of the emission intensity at the emission peak wavelength of the light-emitting device, thereby suppressing emission at long wavelengths which has poor visual sensitivity and dramatically improving brightness, and have completed the present invention.

[0025] The following explanation will be given with reference to the drawings.

[0026] [Light-emitting device] First, the light-emitting device according to the present invention includes a blue LED, a first phosphor, and a second phosphor, and emits amber-colored light. Furthermore, the light-emitting device, which combines the blue LED, the first phosphor, and the second phosphor, has an emission intensity at an emission wavelength of 650 nm that is 60% or less of the emission intensity at the emission peak wavelength. It is preferable that the emission intensity at an emission wavelength of 650 nm is 50% or less of the emission intensity at the emission peak wavelength of the light-emitting device, as this results in a lower emission intensity in the deep red region of long wavelengths and thus a brighter light.

[0027] Amber refers to the chromaticity range that comprises the long-wavelength region of yellow and the short-wavelength region from yellow to red, as defined in JIS standard Z8110, or the region between the yellow region and the short-wavelength region from yellow to red, as defined in JIS standard Z9101 for safety colors. Specifically, there are JIS standards for amber colors used in vehicles and standards for yellow traffic signals, but in this specification, the range encompassing all of these standards is referred to as amber.

[0028] More specifically, there is the SAE standard (SAE J588) for automotive amber color, which defines amber color as the area enclosed by (x, y) = (0.56, 0.44), (0.54, 0.42), (0.60, 0.39), and (0.61, 0.39) in the chromaticity chart. Similarly, there is the JIS standard (JIS D5500) for automotive amber color, which defines amber color as the area enclosed by (x, y) = (0.571, 0.429), (0.564, 0.429), (0.595, 0.398), and (0.602, 0.398) in the chromaticity chart. Furthermore, there is a CIE standard (CIE DS004 2 / E-1996) for yellow traffic signals, which defines amber as the area enclosed by (x, y) = (0.547, 0.452), (0.536, 0.444), (0.593, 0.387), and (0.613, 0.387) in the chromaticity chart. In this specification, anything that falls within at least one of these ranges is considered amber. Note that the relationship between color names and chromaticity coordinates in this specification is based entirely on the JIS standard (JIS Z8110).

[0029] Figure 1 shows an example of a light-emitting device 100 according to the present invention. The light-emitting device 100 according to the present invention includes, for example, a blue LED 10 arranged on a substrate 40 and a phosphor 1 that absorbs a portion of the light from the blue LED 10 and converts it into light of a different wavelength than the emission wavelength of the blue LED 10. The phosphor 1 includes a first phosphor 1a and a second phosphor 1b, and these first phosphor 1a and second phosphor 1b may be dispersed in a phosphor layer 20 which also functions as a encapsulant made of resin, glass, etc. that covers the blue LED 10, and housed in a package 30. In addition to resin, the phosphor layer 20 may appropriately contain, for example, a filler 2 or additives to improve the dispersibility of the phosphor 1, etc. Furthermore, the package 30 and the substrate 40 may be integrally molded. A detailed explanation follows below.

[0030] (Blue LED) The blue LED 10 according to the present invention is not particularly limited, but one with an emission peak wavelength in the range of 380 to 480 nm can be used. Such blue LEDs are readily available in high quality and low cost.

[0031] (First phosphor) The first phosphor according to the present invention emits green to yellow light when excited by light from a blue LED. Figure 2 shows the emission spectrum of the first phosphor 1a that emits green to yellow light when excited by light from a blue LED. As the first phosphor 1a, for example, a YAG-based phosphor, a LuAG-based phosphor, a SiAlON-based phosphor, or a silicate-based phosphor can be used. A YAG-based phosphor is, for example, Y3(Al,Ga)5O 12 : These are phosphors such as Ce. LuAG-based phosphors include, for example, Lu3(Al,Ga)5O 12These are phosphors such as Ce. SiAlON-based phosphors include, for example, β-SiAlON:Eu (β-sialon) and Ca-α-SiAlON:Eu. Silicate-based phosphors include (Ba,Sr)2SiO4:Eu and Ca8Mg(SiO4)4Cl2:Eu. As described in Patent Document 1, YAG-based phosphors are common, but as shown in Figure 2, LuAG phosphors have a narrower emission width at half maximum and lower emission intensity in the deep red region compared to YAG phosphors. Furthermore, Eu-emitting phosphors such as β-sialon phosphors have an even narrower emission width at half maximum.

[0032] Here, it is preferable to use a first phosphor 1a whose emission peak full width at half maximum is 110 nm or less. Among the phosphors shown in Figure 2, LuAG and β-sialon are examples of such phosphors. If such a material is used as the first phosphor 1a, the emission intensity in the deep red region of long wavelengths will be reduced, resulting in a bright amber-colored light-emitting device.

[0033] Furthermore, it is preferable that the first phosphor 1a has a particle size of 24 μm or more. Using such a first phosphor results in an amber-colored light-emitting device with dramatically improved brightness.

[0034] (Second phosphor) The second phosphor according to the present invention is excited by light from a blue LED and emits light having an emission peak wavelength greater than that of the first phosphor and 625 nm or less. Figure 3 shows the emission spectrum of a phosphor that emits red light when excited by light from a blue LED. From among such phosphors, the second phosphor 1b according to the present invention is selected and used in combination with the first phosphor 1a described above. As the second phosphor, one that emits light having an emission peak wavelength of 615 nm or less is particularly preferred.

[0035] Furthermore, as phosphors that emit red light, phosphors such as CaAlSiN3:Eu, known as CASN, (Sr,Ca)AlSiN3:Eu, known as SCASN, and (Ba,Sr,Ca)2Si5N8:Eu, known as the 258 series, can be used. Conventionally, phosphors with a wide half-width were used for red light, but in recent years, development of phosphors with a narrow half-width has progressed. Compared to α-sialon, which is known as a phosphor for amber light, SCASN-type phosphors with low emission intensity in the deep red region have been developed. As the second phosphor according to the present invention, it is preferable to use one with low emission intensity in the deep red region.

[0036] (Combination of phosphors) The combination of the first and second phosphors is not particularly limited, but a combination of LuAG and SCASN is preferred. Because such a combination has a narrow full width at half maximum, it is possible to reduce the long-wavelength region with low luminous sensitivity (deep red emission), and furthermore, an amber-colored light-emitting device with dramatically improved brightness can be provided.

[0037] The amount of the second phosphor relative to the total amount of the first and second phosphors contained in the light-emitting device is preferably 15% by mass or more, and more preferably 20% by mass or more. This results in an amber-colored light-emitting device with improved brightness. [Examples]

[0038] The present invention will be described in detail below with reference to examples, but this is not intended to limit the present invention.

[0039] As a light-emitting device, a bathtub-shaped SMD (Surface Mount Device) of size 3528 (3.5 mm x 2.8 mm) was prepared, with a blue LED with a peak emission wavelength of 447 nm mounted on it. A phosphor was mixed with silicone resin, a predetermined amount was applied, and its optical properties were evaluated. Since there are individual differences in output of the blue LEDs, the luminous intensity was corrected so that the light output at If = 65 mA was 25 mW / sr. Various phosphors with different physical properties were prepared as the first and second phosphors, and these were combined to create a light-emitting device for evaluation, and the evaluation was carried out. In Comparative Example 1, only one type of phosphor (α-SiAlON) was used, and the evaluation result of this luminous intensity was used as the standard. Table 1 shows the various phosphors used in this example and comparative example.

[0040] [Table 1]

[0041] First, we will explain the results of the evaluation of the dependence of the luminous intensity of the light-emitting device on the peak wavelength of the second phosphor. Table 2 shows the details of each material, the composition of each material, and the evaluation results. In Table 2, "Ip650" indicates the emission intensity at an emission wavelength of 650 nm as a percentage of the emission intensity at the emission peak wavelength of the light-emitting device. Figure 4 shows the evaluation results of the dependence of the luminous intensity of the light-emitting device ("Luminous Intensity (Relative Value)" in Table 2) on the peak wavelength of the second phosphor (Examples 3 to 6, Comparative Example 3).

[0042] [Table 2]

[0043] As shown in Examples 1-6 of Table 2 and Figure 4, if a second phosphor that emits light with an emission peak wavelength of 625 nm or less is used, and the emission intensity at an emission wavelength of 650 nm is 60% or less of the emission intensity at the emission peak wavelength of the light-emitting device, then the luminous intensity (relative value) will be 100% or more. Furthermore, from the results of Examples 3-6, it can be seen that if the emission peak wavelength of the second phosphor is 615 nm or less (Examples 4, 5) and Ip650 is 50% or less (Examples 4-6), the luminous intensity (relative value) will be even higher. In addition, it can be seen that if the amount of the second phosphor relative to the total amount of the first and second phosphors (the "red ratio" in Table 2) is 15% by mass or more (Example 5), and even more so, 20% by mass or more (Example 4), the luminous intensity (relative value) will be even higher.

[0044] Next, we will describe the results of evaluations using the same second phosphor but with different conditions for the first phosphor. Table 3 shows the details of each material, its composition, and the evaluation results. Figure 5 shows the results of the evaluation of the dependence of the luminous intensity (relative value) of the light-emitting device on the peak wavelength of the first phosphor.

[0045] [Table 3]

[0046] As shown in Examples 7-9 of Table 3, it can be seen that using a first phosphor with a full width at half maximum of 110 nm or less increases the luminous intensity (relative value) of the light-emitting device. On the other hand, as shown in Figure 5, it can be seen that the dependence of the luminous intensity of the light-emitting device on the peak wavelength of the first phosphor is small.

[0047] Next, we will explain the results of evaluating the second phosphor using the same material but varying the particle size of the first phosphor (dependence on the particle size of the first phosphor). Table 4 shows the details of each material, its composition, and the evaluation results.

[0048] [Table 4]

[0049] As shown in Table 4, the larger the particle size of the first phosphor, the higher the luminous intensity (relative value) of the light-emitting device. In particular, it is desirable to use particles with a particle size of 24 μm or larger.

[0050] As described above, according to the embodiments of the present invention, a light-emitting device with high luminosity (bright) amber color was obtained.

[0051] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0052] 1...Phosphor, 1a...First phosphor, 1b...Second phosphor, 2...Filler 10...Light-emitting element, 20...Phosphor layer, 30...Package, 40...Substrate 100... Light-emitting device.

Claims

1. A light-emitting device comprising a blue LED, a first phosphor, and a second phosphor, which emits amber-colored light, The first phosphor is at least one of a LuAG-based phosphor or an Eu-emitting phosphor, which is excited by the light of the blue LED and emits green to yellow light, and has a full width at half maximum of 110 nm or less of the emission peak. The second phosphor is excited by the light from the blue LED and emits light having an emission peak wavelength greater than that of the first phosphor and less than or equal to 615 nm. A light-emitting device characterized in that the emission intensity at an emission wavelength of 650 nm is 50% or less of the emission intensity at the emission peak wavelength of the light-emitting device.

2. The light-emitting device according to claim 1, characterized in that the amount of the second phosphor relative to the total amount of the first phosphor and the second phosphor contained in the light-emitting device is 15% by mass or more.

3. The light-emitting device according to claim 1 or 2, characterized in that the amount of the second phosphor relative to the total amount of the first phosphor and the second phosphor contained in the light-emitting device is 20% by mass or more.

4. The light-emitting device according to any one of claims 1 to 3, characterized in that the first phosphor has a particle size of 24 μm or more.

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