Light-emitting element and lighting fixture having the same

Abstract

Provided is a light emitting device and a lighting apparatus having the same. The light emitting device according to one embodiment includes a first light emitting diode chip emitting light of a first peak wavelength, a second light emitting diode chip emitting light of a second peak wavelength longer than the first peak wavelength, a first wavelength conversion material disposed on the first light emitting diode chip for wavelength conversion of the light emitted from the first light emitting diode chip, and a second wavelength conversion material disposed on the second light emitting diode chip for wavelength conversion of the light emitted from the second light emitting diode chip, wherein a peak wavelength of an excitation spectrum of the first wavelength conversion material is closer to the first peak wavelength than the second peak wavelength, and a peak wavelength of an excitation spectrum of the second wavelength conversion material is closer to the second peak wavelength than the first peak wavelength, so that light incident from the first light emitting diode chip to the second wavelength conversion material is blocked, and light incident from the second light emitting diode chip to the first wavelength conversion material is blocked.

Description

[Technical Field]

[0001] The present disclosure relates to a light-emitting element and a lighting device, and more particularly to a light-emitting element that uses a light-emitting diode as a light source and a lighting device having the same. [Background technology]

[0002] In general, indoor lighting devices exhibit a certain spectral power distribution, which is significantly different from the spectral power distribution of sunlight. For example, a light emitting device using blue, green, and red light emitting diodes can realize white light by combining blue, green, and red, but it cannot exhibit a spectral power distribution over a wide wavelength range in the visible range like sunlight, and instead exhibits a distribution with a peak at a specific wavelength.

[0003] The spectrum of blackbody radiation, such as sunlight, is similar to that of conventional white light sources; the higher the color temperature, the higher the intensity in the blue wavelength region. However, as the color temperature increases, the spectrum of white light sources becomes more distinct from that of blackbody radiation. For example, at a temperature of 6500K, the spectrum of blackbody radiation shows a gradual decrease in light intensity from the blue region to the red region.

[0004] The human lens, which has adapted to the solar spectrum, can be damaged by abnormally strong blue wavelength light, which can impair vision. In addition, when retinal cells are exposed to excessive blue energy, abnormal signals are transmitted to the brain, causing abnormal production or suppression of hormones such as cortisol and melatonin, which can have a negative impact on the body's circadian rhythm.

[0005] Recently, various studies have been conducted to provide a white light source that exhibits a spectral power distribution similar to the solar spectrum. However, such a white light source has various drawbacks.

[0006] First, there is a problem of reduced light efficiency of the light source. Since a larger amount of phosphor needs to be wavelength converted compared to conventional light sources, efficiency is reduced due to wavelength conversion. Furthermore, when wavelength conversion of green or red phosphors is performed using light with a wavelength shorter than the blue light emitted from a blue LED, efficiency is reduced due to Stokes shift.

[0007] Meanwhile, phosphors are dispersed in transparent molding materials such as silicone, but as the amount of phosphor increases, it becomes more difficult to block moisture using the transparent molding material. For example, silicone prevents moisture penetration, but a decrease in the silicone mixing ratio drastically reduces the silicone's ability to block moisture penetration.

[0008] Furthermore, phenyl-based silicones, which are suitable for preventing moisture penetration, can easily deform when exposed to light with a wavelength shorter than blue light. For this reason, phenyl-based silicones cannot be used as transparent molding materials in light-emitting devices that use ultraviolet or violet light-emitting diodes. Furthermore, when using light-emitting diodes that emit light with a wavelength shorter than blue light, there are limitations on the selection of housing materials. Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present disclosure is to provide a new technology that can increase the light efficiency of light emitting devices that use various types of phosphors.

[0010] Another object of the present disclosure is to provide a light-emitting device and lighting fixture that can prevent or mitigate damage to the human lens and retina caused by abnormal light in the blue region.

[0011] Another object of the present disclosure is to provide a light emitting device and a lighting apparatus that have a spectral power distribution that corresponds to the spectral power distribution of sunlight, and that can improve light efficiency and reliability. [Means for solving the problem]

[0012] A light emitting device according to an embodiment of the present disclosure includes: a first light emitting diode chip emitting light of a first peak wavelength; a second light emitting diode chip emitting light of a second peak wavelength longer than the first peak wavelength; a first wavelength conversion material disposed on the first light emitting diode chip for wavelength conversion of the light emitted from the first light emitting diode chip; and a second wavelength conversion material disposed on the second light emitting diode chip for wavelength conversion of the light emitted from the second light emitting diode chip. A peak wavelength of an excitation spectrum of the first wavelength conversion material may be closer to the first peak wavelength than the second peak wavelength, and a peak wavelength of an excitation spectrum of the second wavelength conversion material may be closer to the second peak wavelength than the first peak wavelength. Furthermore, light incident from the first light emitting diode chip to the second wavelength conversion material may be blocked, and light incident from the second light emitting diode chip to the first wavelength conversion material may be blocked.

[0013] The light emitting device may further include a third wavelength conversion material disposed on the first light emitting diode chip, and the third wavelength conversion material may convert wavelengths of light emitted from the first light emitting diode chip and light emitted from the first wavelength conversion material. A peak wavelength of an excitation spectrum of the third wavelength conversion material may be closer to a peak wavelength of an emission spectrum of the first wavelength conversion material than the first peak wavelength.

[0014] In one embodiment, the first wavelength conversion material may be a blue phosphor, the second wavelength conversion material may be a green to yellow phosphor, and the third wavelength conversion material may be a red phosphor.

[0015] In one embodiment, the first peak wavelength may be in the range of 410 nm to 440 nm, and the second peak wavelength may be in the range of 440 nm to 470 nm.

[0016] The light emitting device may further include a first housing having a first cavity and a second housing having a second cavity, wherein the first light emitting diode chip may be disposed in the first cavity of the first housing, and the second light emitting diode chip may be disposed in the second cavity of the second housing, and the first cavity and the second cavity may be spaced apart from each other.

[0017] In one embodiment, the first housing may be made of epoxy molding compound, and the second housing may be made of PCT (Polyester Polycyclohexylenedimethylene Terephthalate).

[0018] The light emitting device may further include a first molding part disposed in the first cavity and a second molding part disposed in the second cavity, wherein the first wavelength converting material may be distributed in the first molding part and the second wavelength converting material may be distributed in the second molding part.

[0019] Furthermore, the first molding part may include silicone containing methyl-based silicone as a main component, and the second molding part may include silicone containing phenyl-based silicone as a main component.

[0020] The light emitting device may further include a third wavelength conversion material disposed in the first molding part. The third wavelength conversion material may convert the wavelength of light emitted from the first light emitting diode chip and the first wavelength conversion material, and a peak wavelength of an excitation spectrum of the third wavelength conversion material may be closer to a peak wavelength of an emission spectrum of the first wavelength conversion material than the first peak wavelength.

[0021] Furthermore, the peak wavelength of the emission spectrum of the third wavelength conversion material may be longer than the peak wavelength of the emission spectrum of the second wavelength conversion material.

[0022] In one embodiment, the first wavelength conversion material may be a blue phosphor, the second wavelength conversion material may be a green to yellow phosphor, and the third wavelength conversion material may be a red phosphor.

[0023] The first housing may be coupled to the second housing.

[0024] In one embodiment, the first housing may be surrounded by the second housing.

[0025] In other embodiments, the first housing may be spaced apart from the second housing.

[0026] In one embodiment, the first housing and the second housing may have the same area. In another embodiment, the first housing and the second housing may have different areas.

[0027] A light emitting device according to an embodiment of the present disclosure may include a first light emitting unit including a first light emitting diode chip and a first wavelength conversion material; and a second light emitting unit including a second light emitting diode chip and a second wavelength conversion material. The first light emitting diode chip may emit light having a first peak wavelength, and the second light emitting diode chip may emit light having a second peak wavelength longer than the first peak wavelength. Furthermore, the first light emitting unit may emit first mixed color light having color coordinates located below the Planckian locus on the CIE color coordinate system, and the second light emitting unit may emit second mixed color light having color coordinates located above the Planckian locus on the CIE color coordinate system, and the light emitting device may emit light obtained by mixing the first mixed color light and the second mixed color light.

[0028] Furthermore, the first light emitting unit may further include a third wavelength conversion material, which may convert the wavelengths of light emitted from the first light emitting diode chip and the first wavelength conversion material, and the peak wavelength of the excitation spectrum of the third wavelength conversion material may be closer to the peak wavelength of the emission spectrum of the first wavelength conversion material than the first peak wavelength.

[0029] The first wavelength conversion material may be a blue phosphor, the second wavelength conversion material may be a green to yellow phosphor, and the third wavelength conversion material may be a red phosphor.

[0030] A lighting device according to one embodiment of the present disclosure includes the light-emitting element described above. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a graph showing a typical emission spectrum distribution of a green or yellow garnet-based phosphor. [Figure 2] 1 is a graph showing a typical excitation spectrum distribution of a green or yellow garnet-based phosphor. [Figure 3] 1 is a graph showing a typical emission spectrum distribution of a red CASN-based phosphor. [Figure 4] 1 is a graph showing a typical excitation spectrum distribution of a red CASN-based phosphor. [Figure 5] 1 is a graph showing a typical emission spectrum distribution of a blue halophosphate-based phosphor. [Figure 6] 1 is a graph showing a typical excitation spectral distribution of a blue halophosphate-based phosphor. [Figure 7] 1 is a graph showing the external quantum efficiency of an InGaN-based light-emitting diode as a function of typical wavelength. [Figure 8A] 1 is a schematic plan view illustrating a light emitting device according to an embodiment of the present disclosure. [Figure 8B] 8B is a schematic cross-sectional view taken along line AA' of FIG. 8A. [Figure 9] 1 is a graph showing the emission spectrum distribution of each light-emitting element according to Example 1 and Comparative Example 1. [Figure 10] 10 is a graph showing the emission spectrum distribution of each light-emitting element according to Example 2 and Comparative Example 2. [Figure 11] 10 is a graph showing the emission spectrum distribution of each light-emitting element according to Example 3 and Comparative Example 3. [Figure 12] 1 is a graph illustrating a method for implementing color coordinates of a light emitting device according to each embodiment of the present disclosure. [Figure 13] FIG. 10 is a schematic plan view illustrating a light emitting device according to still another embodiment of the present disclosure. [Figure 14] FIG. 10 is a schematic plan view illustrating a light emitting device according to still another embodiment of the present disclosure. [Figure 15] FIG. 10 is a schematic plan view illustrating a light emitting device according to still another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings. The various embodiments described below are provided as examples to fully convey the concept of the present invention to those skilled in the art. Therefore, the present invention is not limited to the various embodiments described below, and may be embodied in other forms. In the drawings, the width, length, thickness, etc. of elements may be exaggerated for convenience. The same reference numerals refer to the same elements throughout the specification.

[0033] Hereinafter, specific color coordinates refer to color coordinates in the CIE-1931 coordinate system defined by the American National Standards Institute (ANSI), unless otherwise specified.

[0034] To realize a white spectral distribution similar to that of sunlight, it is very important to control the emission intensity of the spectral distribution corresponding to the blue region to the level of sunlight corresponding to the blue region. However, it is very difficult to realize a white region according to the correlated color temperature on the CIE-1931 xy color coordinate system while appropriately controlling the high emission intensity of the blue region to the level of sunlight using a blue LED chip. In order to effectively control the emission intensity of the blue region to the level of sunlight in realizing a white spectral distribution, it is advantageous for the spectral distribution representing blue to be relatively broad and gentle rather than narrow and strong. However, existing methods for realizing a white spectral distribution based on blue LED chips have difficulty appropriately controlling the high emission intensity of the blue region to the level of sunlight due to the narrow and strong spectral distribution emitted from the blue LED.

[0035] Therefore, in order to realize a white range according to the correlated color temperature on the CIE-1931 xy color coordinate system while maintaining the blue spectral distribution at the same level as sunlight, a new light source capable of expressing a much wider and gentler spectral distribution than a blue light emitting diode chip having a narrow and strong spectral distribution in expressing the blue range, and a wavelength conversion material using the same, are required.

[0036] The three primary colors of light are blue, green, and red, and when these three colors are mixed together, white is expressed. However, when a blue light-emitting diode chip is applied, wavelength conversion materials corresponding to green and red are additionally required, and a specific spectral distribution can be realized by additively mixing the spectral distributions of the respective wavelength conversion materials for green and red and the blue light.

[0037] Meanwhile, when a near-ultraviolet light emitting diode chip that emits visible light close to ultraviolet light, for example, violet light, is applied, a wavelength conversion material for expressing blue is additionally required in addition to wavelength conversion materials corresponding to green and red, and a specific spectral distribution can be realized by additively mixing the blue, green, and red lights emitted from each phosphor with near-ultraviolet light. Whether a blue light emitting diode chip or a near-ultraviolet light emitting diode chip is applied, a spectral distribution design is required in which wavelength conversion materials with appropriate emission spectra required to realize a white spectral distribution are additively mixed with each other to adjust the optical characteristics.

[0038] Each embodiment of the present disclosure discloses a novel method for improving the light efficiency of light-emitting devices that use various types of phosphors. Phosphors have an excitation spectral distribution as well as an emission spectral distribution. When a phosphor is irradiated with light of a wavelength with a high intensity in the excitation spectral distribution, the phosphor can absorb the excitation light and emit wavelength-converted light with high efficiency. In contrast, when a phosphor is irradiated with light of a wavelength with a low intensity in the excitation spectral distribution, the phosphor can absorb the excitation light and emit wavelength-converted light with low efficiency.

[0039] First, the typical emission spectrum distribution and excitation spectrum distribution of each phosphor will be described.

[0040] Fig. 1 is a graph showing a typical emission spectrum distribution of a green or yellow garnet-based phosphor, and Fig. 2 is a graph showing a typical excitation spectrum distribution of a green or yellow garnet-based phosphor. Fig. 1 shows the emission spectrum distribution of the phosphor with excitation light having a wavelength of 450 nm, and Fig. 2 shows the emission intensity of the phosphor at 540 nm depending on the wavelength of the excitation light.

[0041] Generally, green or yellow phosphors have an emission spectrum distribution with a peak wavelength in the range of 500 nm to 600 nm. As shown in FIG. 2, such phosphors have an excitation spectrum distribution with a peak wavelength in the range of 450 nm to 470 nm. That is, green or yellow phosphors convert blue excitation light in the wavelength range of 450 nm to 470 nm into green or yellow light with optimal efficiency. On the other hand, green or yellow phosphors have low excitation spectrum intensity for light in the wavelength range of approximately 420 nm or less, and therefore have significantly lower wavelength conversion efficiency.

[0042] Figure 3 is a graph showing a typical emission spectrum distribution of a red CASN-based phosphor, and Figure 4 is a graph showing a typical excitation spectrum distribution of a red CASN-based phosphor. Figure 3 shows the emission spectrum distribution of the phosphor with excitation light having a wavelength of 450 nm, and Figure 4 shows the emission intensity of the phosphor at 645 nm depending on the wavelength of the excitation light.

[0043] Generally, red phosphors have an emission spectrum distribution with a peak wavelength in the range of 600 nm to 680 nm. Such phosphors have an excitation spectrum distribution with a peak wavelength in the range of 400 nm to 500 nm, as shown in FIG. 4. That is, red phosphors convert excitation light in the wavelength range of 400 nm to 500 nm into red light with optimal efficiency. On the other hand, red phosphors have low excitation spectrum intensity for light in the wavelength range of approximately 500 nm or more, and therefore have significantly low wavelength conversion efficiency.

[0044] FIG. 5 is a graph showing a typical emission spectrum distribution of a blue halophosphate-based phosphor, and FIG. 6 is a graph showing a typical excitation spectrum distribution of a blue halophosphate-based phosphor.

[0045] Generally, blue phosphors have an emission spectrum distribution with a peak wavelength in the range of 440 nm to 480 nm. Such phosphors have an excitation spectrum distribution with a peak wavelength in the range of 400 nm to 425 nm, as shown in Figure 6. That is, blue phosphors convert excitation light in the wavelength range of 400 nm to 425 nm into blue light with optimal efficiency. On the other hand, for light in the wavelength range of about 425 nm or more, the intensity of the excitation spectrum of blue phosphors decreases rapidly as the wavelength increases.

[0046] FIG. 7 is a graph showing the external quantum efficiency of an InGaN-based light-emitting diode as a function of typical wavelength.

[0047] 7, it can be seen that the external quantum efficiency of InGaN-based LEDs is relatively high in the wavelength range of about 390 nm to 470 nm, and is low outside this wavelength range. When using LEDs as light sources, LEDs having peak wavelengths within the above range are generally selected in consideration of optical efficiency.

[0048] For example, a white spectral distribution can be realized by using a blue light emitting diode together with a green or yellow phosphor and a red phosphor. As described with reference to Figures 2 and 4, a blue light emitting diode is suitable as an excitation light source for each of the above phosphors. That is, it has been confirmed that both the green or yellow phosphor and the red phosphor have a strong excitation spectral distribution around 450 nm. Therefore, a desired spectral distribution can be designed with optimal efficiency by applying a blue light emitting diode chip.

[0049] However, as described above, white light produced by combining a blue LED and a phosphor exhibits excessively high emission intensity in the blue region, as shown in Figure 2, and therefore has a spectral distribution different from that of white light similar to sunlight. To solve this problem, a near-ultraviolet LED may be used as the light source, but a wavelength conversion material, i.e., a blue phosphor, is still required to express blue.

[0050] Meanwhile, the wavelength of the near-ultraviolet light emitting diode is selected to excite the blue, green, yellow, and red phosphors used together with the near-ultraviolet light emitting diode. In selecting the emission wavelength of the near-ultraviolet light emitting diode, since the blue region is expressed by the wavelength conversion material, the wavelength emitted from the near-ultraviolet light emitting diode should not be the dominant emission wavelength in the blue region, the efficiency of the radiant power of the light emitting diode chip expressed in mW should be maximized, and physical deterioration of each element constituting the light emitting device should be minimized. Furthermore, possible adverse effects on the human body should also be considered.

[0051] First, the peak wavelength of light emitted from a near-ultraviolet light emitting diode must be 440 nm or less so that it does not have a dominant emission wavelength in the blue region and can excite the blue phosphor. Furthermore, to maximize the efficiency of the light emitting diode's radiant output (expressed in mW), the peak wavelength of the near-ultraviolet light emitting diode may be 390 nm or more, or even 400 nm or more, or even 410 nm or more, as can be seen from FIG. 7. For example, a near-ultraviolet light emitting diode can exhibit good luminous efficiency within the range of 400 nm to 430 nm.

[0052] Meanwhile, phosphors, which correspond to wavelength conversion materials, are excited by light in a high-energy range based on physical laws and typically emit light in a low-energy range. When ions corresponding to the luminescent center of the phosphor receive energy equivalent to the excitation energy, the phosphor undergoes an energy loss process, expressed as the Stokes shift, and emits light with lower energy than the excitation energy. Furthermore, the quantum efficiency of a phosphor is maximized when there is a specific difference between the excitation energy and the emission energy. This means that it is necessary to select a phosphor that can maximize the efficiency of the excitation wavelength and emission wavelength, taking into account the Stokes shift characteristics of the phosphor material itself.

[0053] The emission and excitation spectral power distributions of halophosphate phosphors, which are representative wavelength conversion materials in the blue region, are shown in Figures 5 and 6. Referring to the excitation spectral power distribution in Figure 6, it can be seen that the efficiency of the excitation spectral power distribution decreases sharply as the wavelength increases beyond 420 nm.

[0054] Therefore, in applying a near-ultraviolet light emitting diode, the emission wavelength and phosphor of the near-ultraviolet light emitting diode, not only a blue phosphor but also a green or yellow phosphor and a red phosphor must be selected so as to realize a white spectral distribution through interaction with the phosphor and to optimize the output light efficiency for applied electrical energy, i.e., the light efficiency of the light emitting device expressed in lm / W.

[0055] In the prior art, a near-ultraviolet light emitting diode is used as a light source in combination with a blue phosphor, a green or yellow phosphor, and a red phosphor, i.e., the near-ultraviolet light emitting diode is used as an excitation light source for the blue phosphor, the green or yellow phosphor, and the red phosphor.

[0056] 1 and 2, which show the emission spectral distribution and excitation spectral distribution of the YAG phosphor, a typical wavelength conversion material in the green to yellow region, it is clear that in the excitation spectral distribution of the YAG phosphor, the efficiency in the 400-420 nm region, which corresponds to the emission wavelength of a near-ultraviolet light-emitting diode, drops sharply compared to the blue wavelength region of 450-460 nm. In other words, the Stokes shift characteristics of the YAG phosphor, which is a wavelength conversion material in the green to yellow region, are not suitable for maximum-efficiency wavelength conversion when applied to a near-ultraviolet light-emitting diode.

[0057] It is also possible to consider a case where a near-ultraviolet light emitting diode excites a blue phosphor to emit blue light, and the blue light emitted from the blue phosphor excites a green or yellow phosphor. However, even in this case, the energy of the light emitted from the near-ultraviolet light emitting diode experiences energy loss in the blue phosphor and then experiences energy loss again in the green or yellow phosphor, so a decrease in energy conversion efficiency cannot be prevented.

[0058] Meanwhile, in the excitation and emission spectral distributions of the CASN-based red phosphor shown in Figures 3 and 4, the main emission wavelength of the red phosphor is located at approximately 640 nm to 650 nm. However, referring to Figure 2 showing the white spectral distribution implemented on a blue LED chip, it can be seen that the wavelength having the maximum emission distribution in the red region shifts to around 630 nm as the color temperature increases. The reason why the main emission wavelength of the red wavelength-converted CASN-based phosphor differs from the main emission wavelength of the white spectral distribution is due to the energy interaction between the phosphors, and this is thought to be due to the following reasons.

[0059] That is, in a method for implementing a white spectral distribution based on a blue LED, light emitted from the blue LED is first simultaneously absorbed by the green-to-yellow phosphor and the red phosphor, undergoing an energy conversion process, and the converted light is emitted. The red phosphor absorbs the energy emitted from the blue LED and the green-to-yellow phosphor, and then emits red light after an appropriate energy conversion process. The excitation spectral distribution of the red phosphor shown in FIG. 4 overlaps significantly with the emission spectral distribution of the green-to-yellow phosphor shown in FIG. 1. That is, the red phosphor absorbs not only the energy emitted from the blue LED but also the energy emitted from the green-to-yellow phosphor, resulting in energy interference between the green-to-yellow phosphor and the red phosphor. As a result, the white spectral distribution for each correlated color temperature shown in FIG. 2 does not exhibit the original emission spectral distributions of the green-to-yellow and red phosphors, but shifts to a region between the green-to-yellow and red regions of the original emission distribution.

[0060] Therefore, not only the conversion efficiency of wavelength conversion of light emitted from a light source such as a blue light emitting diode or a near-ultraviolet light emitting diode by a red phosphor, but also the conversion efficiency of wavelength conversion of light emitted from a green to yellow phosphor by a red phosphor must be considered.

[0061] Hereinafter, light emitting devices with maximized light efficiency according to embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0062] FIG. 8A is a schematic plan view illustrating a light emitting device 100 according to an embodiment of the present disclosure, and FIG. 8B is a schematic cross-sectional view taken along line AA' of FIG. 8A.

[0063] 8A and 8B, a light emitting device 100 according to an embodiment of the present disclosure includes two light emitting units. For example, the first light emitting unit may include a first housing 20a, a first light emitting diode chip 30a, a first molding part 40a, a first wavelength converting material 50a, and a third wavelength converting material 50c. The second light emitting unit may include a second housing 20b, a second light emitting diode chip 30b, a second molding part 40b, and a second wavelength converting material 50b.

[0064] The first housing 20a and the second housing 20b may be disposed adjacent to each other or may be bonded to each other. For example, the first and second housings 20a and 20b may be formed of epoxy molding compound (EMC), silicone molding compound (SMC), PCT (Polyester Polycyclohexylenedimethylene Terephthalate), or ceramic. EMC has excellent light resistance and impact resistance, particularly for the light emitting device 100 including a light emitting diode chip with a short wavelength light source. Therefore, as an example, the first and second housings 20a and 20b may be formed of EMC. However, the present disclosure is not limited thereto. For example, the first housing 20a may be formed of EMC, and the second housing 20b may be formed of PCT. PCT has a high reflectivity for blue light and may therefore be appropriately used for a housing in which the second light emitting diode chip 30b with a wavelength of 440 nm or more is mounted.

[0065] The first light emitting diode chip 30a may emit light having a first peak wavelength in a range of about 410 nm to about 440 nm. The first light emitting diode chip 30a may be formed of a gallium nitride-based semiconductor layer. The first light emitting diode chip 30a may be mounted in a cavity of the first housing 20a.

[0066] The second light emitting diode chip 30b emits light with a longer wavelength than the first light emitting diode chip 30a. The second light emitting diode chip 30b may emit light with a second peak wavelength, for example, in the range of 440 nm to 470 nm. The second light emitting diode chip 30b may be mounted in a cavity of the second housing 20b.

[0067] The first molding part 40a covers the first LED chip 30a. The first molding part 40a can fill the cavity of the first housing 20a. The first molding part 40a can include wavelength conversion materials 50a and 50c. The first molding part 40a can include silicone. For example, the first molding part 40a can be formed of a high-refractive index silicone containing a large amount of phenyl-based silicone together with methyl-based silicone, a medium-refractive index silicone containing a small amount of phenyl-based silicone in methyl-based silicone, or a low-refractive index silicone containing no phenyl-based silicone in methyl-based silicone. Methyl-based silicone has better light resistance to short-wavelength light such as near-ultraviolet light and better impact resistance than phenyl-based silicone. Therefore, the first molding part 40a can contain methyl-based silicone as a main component and also phenyl-based silicone, but the content of phenyl-based silicone needs to be appropriately controlled, for example, it can be 10 wt% or less of the methyl-based silicone.

[0068] The second molding part 40b covers the second light emitting diode chip 30b. The second molding part 40b may fill the cavity of the second housing 20b. The second molding part 40b may include a wavelength converting material 50b. The second molding part 40b may include silicone. For example, the second molding part 40b may include a larger amount of phenyl-based silicone than the first molding part 40a. The second molding part 40b may have a higher refractive index than the first molding part 40a. Since phenyl-based silicone has a relatively high refractive index, it may maximize the light extraction efficiency of the light emitting diode chip 30b.

[0069] The first wavelength conversion material 50a converts the wavelength of the light emitted from the first light emitting diode chip 30a. The first wavelength conversion material 50a may have a peak wavelength longer than the first peak wavelength. For example, the first wavelength conversion material 50a may be a blue phosphor. Examples of blue phosphors include BAM-based, halophosphate-based, and aluminate-based phosphors, such as BaMgAl 10 O 17 :Mn 2+ , BaMgAl 12 O 19 :Mn 2+ or (Sr,Ca,Ba)PO4Cl:Eu 2+ The first wavelength conversion material 50a is not limited to a phosphor, but may be a quantum dot, a perovskite, or the like. The first wavelength conversion material 50a may have a peak wavelength in the range of, for example, 440 nm to 500 nm.

[0070] The second wavelength conversion material 50b converts the wavelength of the light emitted from the second light emitting diode chip 30b. The second wavelength conversion material 50b may have a peak wavelength longer than the second peak wavelength. For example, the second wavelength conversion material 50b may be a green to yellow phosphor. Examples of green or yellow phosphors include LuAG (Lu3(Al,Gd)5O 12 :Ce 3+ ), YAG(Y(Al,Gd)O 12 :Ce 3+ ), Ga-LuAG((Lu,Ga)3(Al,Gd)5O 12 :Ce 3+ ), Ga-YAG ((Ga,Y)3(Al,Gd)5O 12 :Ce 3+ ), LuYAG ((Lu,Y)3(Al,Gd)5O 12 :Ce 3+ ), Ortho-Silicate ((Sr,Ba,Ca,Mg)2SiO4:Eu 2+ ), Oxynitride ((Ba,Sr,Ca)Si2O2N2:Eu 2+), or Thio Gallate (SrGa2S4:Eu 2+ The second wavelength-converting material 50b may be a quantum dot or a perovskite. The second wavelength-converting material 50b may have a peak wavelength in the range of 500 nm to 600 nm, for example.

[0071] The peak wavelength of the excitation spectrum of the second wavelength conversion material 50b is closer to the second peak wavelength of the second light emitting diode chip 30b than to the first peak wavelength of the first light emitting diode chip 30a. Therefore, when the second wavelength conversion material 50b is excited by the light emitted from the second light emitting diode chip 30b, the optical efficiency can be increased and the optical loss due to the Stokes shift can be reduced compared to when the second wavelength conversion material 50b is excited by the light emitted from the first light emitting diode chip 30a.

[0072] The third wavelength conversion material 50c can convert the wavelength of light emitted from the first light emitting diode chip 30a and the first wavelength conversion material 50a. The third wavelength conversion material 50c can emit light having a peak wavelength longer than the peak wavelength of the second wavelength conversion material 50b. For example, the third wavelength conversion material 50c can be a red phosphor. Examples of red phosphors include nitride, sulfide, fluoride, oxyfluoride, and oxynitride phosphors, and more specifically, CASN (CaAlSiN3:Eu 2+ ), (Ba,Sr,Ca)2Si5N8:Eu 2+ , (Ca,Sr)S2:Eu 2+ ), or (Sr,Ca)2SiS4:Eu 2+ The third wavelength conversion material 50c may be a quantum dot or a perovskite. The third wavelength conversion material 50c may have a peak wavelength in the range of 600 nm to 700 nm, for example.

[0073] The peak wavelength of the excitation spectrum of the third wavelength conversion material 50c may be closer to the peak wavelength of the first wavelength conversion material 50a than the first peak wavelength of the first light emitting diode chip 30a, thereby reducing efficiency loss when light emitted from the first light emitting diode chip 30a is converted by the first wavelength conversion material 50a and then converted again by the third wavelength conversion material 50c.

[0074] Meanwhile, the second wavelength converting material 50b is disposed outside the path of light emitted from the first light emitting diode chip 30a so that the light emitted from the first light emitting diode chip 30a cannot excite the second wavelength converting material 50b in the second housing 20b. Also, the first and third wavelength converting materials 50a, 50c are disposed outside the path of light emitted from the second light emitting diode chip 30b so that the light emitted from the second light emitting diode chip 30b cannot excite the first and third wavelength converting materials 50a, 50c in the first housing 20a. For this purpose, the cavity of the first housing 20a and the cavity of the second housing 20b may be separated from each other by a partition wall.

[0075] According to the embodiment of the present disclosure, a light emitting device 100 that can realize more intense white light because the light efficiency is high even when white light of the same color temperature is realized under the same input power is provided. That is, it is possible to maximize lm / W, which indicates the output light efficiency for the applied electrical energy.

[0076] In this embodiment, first to third wavelength converting materials 50a, 50b, and 50c are arranged to realize white light, but the present disclosure is not limited thereto. That is, the present disclosure may be applied to a light emitting device using two or more wavelength converting materials with different excitation and emission spectra, and these two or more wavelength converting materials are excited by respective light emitting diode chips having different peak wavelengths. This reduces light loss due to the Stokes shift and enables wavelength conversion with optimal efficiency for each wavelength converting material. Furthermore, since housing materials and molding part materials suitable for each light emitting diode chip can be selected, the reliability and light efficiency of the light emitting device can be further improved.

[0077] Meanwhile, in this embodiment, the wavelength conversion materials 50a, 50b, and 50c disposed in the first and second housings 20a and 20b are mainly described. However, in addition to these wavelength conversion materials 50a, 50b, and 50c, other wavelength conversion materials may be added to the first housing 20a and / or the second housing 20b. For example, Mn 4+ An activating fluoride phosphor may be added to the first housing 20a or the second housing 20b.

[0078] White light emitting devices using conventional near-ultraviolet light emitting diodes and white light emitting devices according to the embodiments of the present disclosure were fabricated at various color temperatures, and the relative luminance, color coordinates, correlated color temperature (CCT), and color rendering index (CRI) are shown in Table 1.

[0079] [Table 1]

[0080] The conventional light emitting devices were fabricated using a single light emitting diode chip and blue, green to yellow, and red phosphors, and emitted white light having correlated color temperatures of Comparative Examples 1 to 4 under a driving current of 100 mA.

[0081] The white light emitting device of the present disclosure includes a first LED chip and a second LED chip disposed in a first housing and a second housing, respectively, a blue phosphor and a red phosphor disposed in the first housing, and a green to yellow phosphor disposed in the second housing. When the first LED chip and the second LED chip are driven so that the sum of their driving currents is 100 mA, the white light emitting device emits white light having a correlated color temperature similar to that of a conventional light emitting device. The first LED chip and the conventional single LED chip both have peak wavelengths of about 410 nm to 440 nm, and the second LED chip has a peak wavelength of about 440 nm to 470 nm.

[0082] Referring to Table 1, under the same total current condition, Comparative Example 1 and Example 1 realized white light having a correlated color temperature of about 5000K, but the light emitting device of Example 1 exhibited 20% higher brightness than the light emitting device of Comparative Example 1. Comparative Example 2 and Example 2 realized white light having a correlated color temperature of about 4000K, but the light emitting device of Example 2 exhibited 25% higher brightness than the light emitting device of Comparative Example 2. Comparative Example 3 and Example 3 realized white light having a correlated color temperature of about 3000K, but the light emitting device of Example 3 exhibited 30% higher brightness than the light emitting device of Comparative Example 3. Comparative Example 4 and Example 4 realized white light having a correlated color temperature of about 2700K, but the light emitting device of Example 4 exhibited 34% higher brightness than the light emitting device of Comparative Example 4.

[0083] FIG. 9 is a graph showing the emission spectrum distribution of each light-emitting element according to Example 1 and Comparative Example 1, FIG. 10 is a graph showing the emission spectrum distribution of each light-emitting element according to Example 2 and Comparative Example 2, and FIG. 11 is a graph showing the emission spectrum distribution of each light-emitting element according to Example 4 and Comparative Example 4.

[0084] 9, 10, and 11, it can be seen that the light emitting devices of the examples exhibit similar emission spectrum distributions to the light emitting devices of the comparative examples, but exhibit relatively higher emission intensities across most wavelength ranges in the visible region. Furthermore, by disposing the red phosphor together with the blue phosphor, the peak wavelength in the red region shifts to a shorter wavelength side compared to the conventional light emitting device, which can further increase the overall brightness of the light emitting device.

[0085] FIG. 12 is a graph illustrating a method for implementing color coordinates of a light emitting device according to each embodiment of the present disclosure.

[0086] The light emitting device 100 according to this embodiment emits two mixed light beams having color coordinates in a first region BR and a second region BY, and realizes a desired final mixed light beam by mixing the two mixed light beams. The first region BR may be located below the Planckian locus PL, and the second region BY may be located above the Planckian locus PL. For example, a first light emitting unit including a first light emitting diode chip 30a, a blue phosphor 50a, and a red phosphor 50c may be used to emit a first mixed light beam having color coordinates in the first region BR, and a second light emitting unit including a second light emitting diode chip 30b and green to yellow phosphors 50b may be used to emit a second mixed light beam having color coordinates in the second region BY. Light with desired color coordinates can be realized by mixing the first mixed light beam and the second mixed light beam. The color coordinates and intensities of the first mixed light beam and the second mixed light beam may be adjusted so that the final mixed light beam has color coordinates on the Planckian locus. For example, by adjusting the color coordinates in the first region BR and the color coordinates in the second region BY and their intensities, white light having a desired color temperature can be realized.

[0087] In this embodiment, a light emitting device 100 that emits white light of a desired color temperature is described, but the present disclosure is not limited to white light, and the light emitting device 100 can also emit other mixed color light such as cyan light.

[0088] FIG. 13 is a schematic plan view illustrating a light emitting device 200 according to still another embodiment of the present disclosure.

[0089] 13, the light emitting device 200 according to this embodiment is substantially similar to the light emitting device 100 described with reference to FIGS. 8A and 8B, but differs in that the first housing 20a and the second housing 20b are spaced apart from each other. The first housing 20a and the second housing 20b may be formed through different processes, which allows for flexible selection of materials for the first and second housings 20a and 20b. As a result, the first housing 20a and the first housing 20b may be formed of materials suitable for the first and second light emitting diode chips 30a and 30b. For example, the first housing 20a may be formed of EMC, and the second housing 20b may be formed of PCT.

[0090] Furthermore, each molding part 40a, 40b may be formed of a material suitable for the first light emitting diode chip 30a and the second light emitting diode chip 30b. For example, the first molding part 40a may be formed of silicone containing methyl-based silicone as a main component, and the second molding part 40b may be formed of silicone containing phenyl-based silicone as a main component.

[0091] FIG. 14 is a schematic plan view illustrating a light emitting device 300 according to still another embodiment of the present disclosure.

[0092] 14, the light emitting device 300 according to this embodiment is substantially similar to the light emitting device 100 described with reference to FIGS. 8A and 8B, but differs in that the first housing 20a is surrounded by the first housing 20b. The first housing 20a may be formed first, and then the second housing 20b may be formed to surround the first housing 20a. Alternatively, the second housing 20b may be formed first, and then the first housing 20a may be formed within the second housing 20b. The materials of the first housing 20a and the second housing 20b may be selected to suit the first and second light emitting diode chips 30a and 30b, respectively. For example, the first housing 20a may be formed of EMC, and the second housing 20b may be formed of PCT.

[0093] Furthermore, each molding part 40a, 40b may be formed of a material suitable for the first light emitting diode chip 30a and the second light emitting diode chip 30b. For example, the first molding part 40a may be formed of silicone containing methyl-based silicone as a main component, and the second molding part 40b may be formed of silicone containing phenyl-based silicone as a main component.

[0094] FIG. 15 is a schematic plan view illustrating a light emitting device 400 according to still another embodiment of the present disclosure.

[0095] 15, a light emitting device 400 according to this embodiment is substantially similar to the light emitting device 100 described with reference to FIGS. 8A and 8B, but differs in the relative sizes of the first housing 20a and the second housing 20b. As shown in FIG. 15, the first housing 20a may be larger than the first housing 20b, which allows more phosphor to be disposed in the cavity of the first housing 20a and allows more wavelength conversion of light emitted from the first light emitting diode chip 30a than light emitted from the second light emitting diode chip 30b.

[0096] According to each embodiment of the present disclosure, a plurality of LED chips are adopted to maximize wavelength conversion efficiency by taking into consideration the wavelength conversion efficiency of each phosphor having a different excitation spectrum. Furthermore, when different types of phosphors are mixed, each phosphor may be selected to prevent light emitted from one phosphor from being wavelength-converted with low efficiency by another phosphor. For example, a red phosphor is mixed with a blue phosphor, but not with a green phosphor, thereby suppressing a decrease in light efficiency.

[0097] According to each embodiment of the present disclosure, wavelength conversion efficiency is maximized, and further, the housing material and molding part material that are optimal for each light-emitting diode chip can be selected, thereby significantly increasing the light emission brightness compared to light-emitting devices according to conventional technology.

[0098] The light-emitting elements 100, 200, 300, and 400 of the present disclosure may be used for illumination and thus may be installed in a lighting fixture. In particular, by employing the light-emitting elements of the present disclosure, a lighting fixture that emits white light similar to sunlight with high efficiency can be provided.

[0099] Although various embodiments of the present invention have been described above, the present invention is not limited to these embodiments and can be modified in various ways. Furthermore, elements introduced in a particular embodiment may be applied to other embodiments without departing from the spirit of the invention.

Claims

1. a first light emitting diode chip that emits light of a first peak wavelength; a second light emitting diode chip emitting light of a second peak wavelength longer than the first peak wavelength; a first wavelength conversion material disposed on the first light emitting diode chip for converting the wavelength of light emitted from the first light emitting diode chip; a second wavelength conversion material disposed on the second light emitting diode chip and converting the wavelength of light emitted from the second light emitting diode chip; a peak wavelength of the excitation spectrum of the first wavelength conversion material is closer to the first peak wavelength than the second peak wavelength; a peak wavelength of the excitation spectrum of the second wavelength conversion material is closer to the second peak wavelength than the first peak wavelength; light incident on the second wavelength conversion material from the first light emitting diode chip is blocked; The light emitting device is configured such that light from the second light emitting diode chip is blocked from being incident on the first wavelength conversion material.

2. further comprising a third wavelength conversion material disposed on the first light emitting diode chip; the third wavelength conversion material converts wavelengths of light emitted from the first light emitting diode chip and light emitted from the first wavelength conversion material; The light emitting device of claim 1 , wherein a peak wavelength of the excitation spectrum of the third wavelength conversion material is closer to a peak wavelength of the emission spectrum of the first wavelength conversion material than the first peak wavelength.

3. the first wavelength conversion material is a blue phosphor; the second wavelength conversion material is a green to yellow phosphor; The light-emitting device according to claim 2 , wherein the third wavelength conversion material is a red phosphor.

4. the first peak wavelength is in the range of 410 nm to 440 nm; The light-emitting device according to claim 1 , wherein the second peak wavelength is in the range of 440 nm to 470 nm.

5. a first housing having a first cavity; a second housing having a second cavity; the first light emitting diode chip is disposed in a first cavity of the first housing; the second light emitting diode chip is disposed in a second cavity of the second housing; The light emitting device of claim 1 , wherein the first cavity and the second cavity are spaced apart from each other.

6. the first housing is formed from an epoxy molding compound; The light emitting device according to claim 5, wherein the second housing is made of PCT (Polyester Polycyclohexylenedimethylene Terephthalate).

7. a first molding part disposed within the first cavity; a second molding part disposed in the second cavity; the first wavelength converting material is distributed within the first molding portion; The light emitting device of claim 5 , wherein the second wavelength conversion material is distributed within the second molding portion.

8. the first molding part includes silicone containing methyl silicone as a main component, The light emitting device of claim 7 , wherein the second molding part includes silicone containing phenyl-based silicone as a main component.

9. further comprising a third wavelength converting material disposed within the first molding portion; the third wavelength conversion material converts wavelengths of light emitted from the first light emitting diode chip and light emitted from the first wavelength conversion material; The light emitting device of claim 7 , wherein a peak wavelength of the excitation spectrum of the third wavelength conversion material is closer to a peak wavelength of the emission spectrum of the first wavelength conversion material than the first peak wavelength.

10. The light-emitting device according to claim 9 , wherein a peak wavelength of the emission spectrum of the third wavelength-converting material is longer than a peak wavelength of the emission spectrum of the second wavelength-converting material.

11. the first wavelength conversion material is a blue phosphor; the second wavelength conversion material is a green to yellow phosphor; The light-emitting device according to claim 9 , wherein the third wavelength conversion material is a red phosphor.

12. The light emitting device of claim 5 , wherein the first housing is coupled to the second housing.

13. The light emitting device of claim 12 , wherein the first housing is surrounded by the second housing.

14. The light emitting device of claim 5 , wherein the first housing is spaced apart from the second housing.

15. The light emitting device of claim 5 , wherein the first housing and the second housing have different areas.

16. a first light-emitting unit including a first light-emitting diode chip and a first wavelength conversion material; a second light-emitting unit including a second light-emitting diode chip and a second wavelength conversion material; the first light emitting diode chip emits light of a first peak wavelength; the second light emitting diode chip emits light having a second peak wavelength longer than the first peak wavelength; the first light-emitting unit emits a first mixed color light having a color coordinate located below the Planckian locus on the CIE color coordinate system; the second light-emitting unit emits second mixed color light having color coordinates located above the Planckian locus on the CIE color coordinate system; a light-emitting element that emits light obtained by mixing the first mixed color light and the second mixed color light;

17. the first light-emitting unit further includes a third wavelength-converting material; the third wavelength conversion material converts wavelengths of light emitted from the first light emitting diode chip and light emitted from the first wavelength conversion material; The light emitting device of claim 16 , wherein a peak wavelength of the excitation spectrum of the third wavelength conversion material is closer to a peak wavelength of the emission spectrum of the first wavelength conversion material than the first peak wavelength.

18. the first wavelength conversion material is a blue phosphor; the second wavelength conversion material is a green to yellow phosphor; The light-emitting device of claim 17 , wherein the third wavelength-converting material is a red phosphor.

19. a light-emitting element; The light-emitting element is a first light emitting diode chip that emits light of a first peak wavelength; a second light emitting diode chip emitting light of a second peak wavelength longer than the first peak wavelength; a first wavelength conversion material disposed on the first light emitting diode chip for converting the wavelength of light emitted from the first light emitting diode chip; a second wavelength conversion material disposed on the second light emitting diode chip and converting the wavelength of light emitted from the second light emitting diode chip; a peak wavelength of the excitation spectrum of the first wavelength conversion material is closer to the first peak wavelength than the second peak wavelength; a peak wavelength of the excitation spectrum of the second wavelength conversion material is closer to the second peak wavelength than the first peak wavelength; light incident on the second wavelength conversion material from the first light emitting diode chip is blocked; The light from the second light emitting diode chip is blocked from entering the first wavelength conversion material.

20. the light emitting device further includes a third wavelength conversion material disposed on the first light emitting diode chip; the third wavelength conversion material converts wavelengths of light emitted from the first light emitting diode chip and light emitted from the first wavelength conversion material; 20. The lighting device of claim 19, wherein a peak wavelength of the excitation spectrum of the third wavelength-converting material is closer to a peak wavelength of the emission spectrum of the first wavelength-converting material than the first peak wavelength.

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