Light-emitting device, backlight unit, and display device

Abstract

A light-emitting device, a backlight unit, and a display device are provided. The light-emitting device includes: a first LED chip that emits light having a peak wavelength in the range of 410 to 430 nm; a second LED chip that emits light having a peak wavelength in the range of 440 to 460 nm; a first quantum dot that converts the light emitted by the first LED chip and the second LED chip into light having a peak wavelength in the range of 510 to 550 nm; and a second quantum dot that converts the light emitted by the first LED chip and the second LED chip into light having a peak wavelength in the range of 610 to 660 nm, wherein in the emission spectrum of the final light, the intensity of the peak wavelength of the first LED chip is 15% or less of the intensity of the peak wavelength of the second LED chip.

Description

[0001] Cross - reference to related applications

[0002] Korean Patent Application No. 10 - 2019 - 0065552, titled "Light - emitting device, backlight unit, and display device", filed with the Korean Intellectual Property Office on June 3, 2019, is incorporated herein by reference in its entirety. Technical field

[0003] The present disclosure relates to a light - emitting device, a backlight unit, and a display device. Background art

[0004] Generally, a white - light emitting device can be manufactured in a form in which various wavelength - converting materials are combined with a blue - light emitting diode (LED) chip. The white - light emitting device can be used as an efficient light source for a display device. For example, quantum dots can be used as wavelength - converting materials for reproducing colors in a display device. Summary of the invention

[0005] According to an exemplary embodiment, a light - emitting device includes: a first LED chip that emits light having a peak wavelength in the range of 410 nm to 430 nm; a second LED chip that emits light having a peak wavelength in the range of 440 nm to 460 nm; a first quantum dot that is disposed on a path of light emitted by the first LED chip and the second LED chip and converts a part of the emitted light into light having a peak wavelength in the range of 510 nm to 550 nm; and a second quantum dot that is disposed on a path of light emitted by the first LED chip and the second LED chip and converts a part of the emitted light into light having a peak wavelength in the range of 610 nm to 660 nm, wherein, in an emission spectrum of the final light, an intensity of the peak wavelength of the first LED chip is equal to 15% or less of an intensity of the peak wavelength of the second LED chip.

[0006] According to an exemplary embodiment, a light - emitting device includes: a first LED chip that emits light having a peak wavelength in the range of 410 nm to 430 nm; a second LED chip that emits light having a peak wavelength in the range of 440 nm to 460 nm; and a wavelength - conversion film having a first quantum dot and a second quantum dot disposed on a path of light emitted by the first LED chip and the second LED chip and converting a part of the emitted light into light having a first peak wavelength and light having a second peak wavelength, respectively, wherein the first peak wavelength is in the range of 510 nm to 550 nm, the second peak wavelength is in the range of 610 nm to 660 nm, and in an emission spectrum of the final light, an intensity of the peak wavelength of the first LED chip is equal to 15% or less of an intensity of the peak wavelength of the second LED chip.

[0007] According to an exemplary embodiment, a backlight unit includes: an LED module having a first LED chip that emits light with a peak wavelength in the range of 410 nm to 430 nm and a second LED chip that emits light with a peak wavelength in the range of 440 nm to 460 nm; and a wavelength conversion film having first quantum dots and second quantum dots disposed on a path of the light emitted through the LED module and converting a part of the emitted light into light with a first peak wavelength and light with a second peak wavelength, wherein the first peak wavelength is in the range of 510 nm to 550 nm, the second peak wavelength is in the range of 610 nm to 660 nm, and in an emission spectrum of the final light, an intensity of the peak wavelength of the first LED chip is 15% or less of an intensity of the peak wavelength of the second LED chip.

[0008] According to an exemplary embodiment, a display device includes: an image display panel having a color filter layer including red, green, and blue color filters; and a backlight unit disposed on a lower surface of the image display panel, wherein the backlight unit includes: an LED module having a first LED chip that emits light with a peak wavelength in the range of 410 nm to 430 nm and a second LED chip that emits light with a peak wavelength in the range of 440 nm to 460 nm; and a wavelength conversion film having first quantum dots and second quantum dots disposed on a path of the light emitted through the LED module and converting a part of the emitted light into light with a first peak wavelength and light with a second peak wavelength, wherein the first peak wavelength is in the range of 510 nm to 550 nm, the second peak wavelength is in the range of 610 nm to 660 nm, and in an emission spectrum of the final light, an intensity of the peak wavelength of the first LED chip is 15% or less of an intensity of the peak wavelength of the second LED chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Features will become apparent to those skilled in the art by describing exemplary embodiments in detail with reference to the accompanying drawings, in which:

[0010] Figure 1 A schematic cross-sectional view of a light-emitting device according to an exemplary embodiment is shown.

[0011] Figure 2 An emission spectrum of light emitted through a first LED chip and a second LED chip of a light-emitting device according to an exemplary embodiment is shown.

[0012] Figure 3 An emission spectrum of the final light in a light-emitting device according to an exemplary embodiment is shown.

[0013] Figure 4 A graph showing relative absorption rates of green quantum dots and red quantum dots according to wavelength is shown.

[0014] Figure 5 A graph showing the conversion efficiency and transmittance of the quantum dot sheet is shown.

[0015] Figure 6 A graph showing the color reproduction rate according to the peak intensity ratio S1' / S2' is shown.

[0016] Figure 7 and Figure 8 A schematic cross-sectional view of a light-emitting device according to each embodiment is shown.

[0017] Figure 9 and Figure 10 A cross-sectional view of an LED chip of a light-emitting device according to an exemplary embodiment is shown.

[0018] Figure 11 A schematic cross-sectional view of a backlight unit (edge-lit type) according to an exemplary embodiment is shown.

[0019] Figure 12 Shows Figure 11 A schematic plan view of an LED module in the backlight unit of.

[0020] Figure 13 A schematic cross-sectional view of a backlight unit (edge-lit type) according to an exemplary embodiment is shown.

[0021] Figure 14 A schematic cross-sectional view of a backlight unit (direct-lit type) according to an exemplary embodiment is shown.

[0022] Figure 15 Shows Figure 14 A schematic plan view of an LED module in the backlight unit of.

[0023] Figure 16 A schematic exploded perspective view of a display device according to an exemplary embodiment is shown. Detailed Description of the Invention

[0024] Hereinafter, each exemplary embodiment will be described in detail with reference to the accompanying drawings.

[0025] Figure 1 is a schematic cross-sectional view of a light-emitting device according to an exemplary embodiment.

[0026] Referring to Figure 1 , the light-emitting device 100A may include a package 101, a first LED chip 132 and a second LED chip 134 respectively disposed on the package 101, and a wavelength conversion film 150. For example, as Figure 1 shown, the wavelength conversion film 150 may be located above the package 101 and the first LED chip 132 and the second LED chip 134.

[0027] Specifically, the package 101 can be coupled to a pair of lead frames 111 and 112, and can include a recess C that provides a sidewall reflection structure. For example, as Figure 1 shown, a portion of the package 101 can be removed to define a cavity in the package 101 having a flat bottom and curved sidewalls extending from the flat bottom. For example, the cavity can be concave with respect to the package 101 to define the recess C. The first LED chip 132 and the second LED chip 134 can be disposed on the bottom surface of the recess C and can be electrically connected to the lead frames 111 and 112 respectively by wires W. For example, as Figure 1 shown, some portions of the pair of lead frames 111 and 112 can extend through the package 101 to be exposed to the recess C, so that the first LED chip 132 and the second LED chip 134 can be placed, for example, directly on the lead frame 112, while the wires W can extend from each of the first LED chip 132 and the second LED chip 134 to the pair of lead frames 111 and 112. The light-emitting device 100A can further include a resin encapsulation portion 141 disposed in the recess C to surround the first LED chip 132 and the second LED chip 134. For example, the resin encapsulation portion 141 can completely fill the recess C to cover the first LED chip 132 and the second LED chip 134 through the wires W.

[0028] The package 101 can be made of an easily injectable polymer resin. For example, the resin can be an opaque resin or a resin containing highly reflective powder particles (such as Al2O3). In another example, the package 101 can include a ceramic substrate. In this case, heat dissipation through the package 101 can be promoted. In a specific embodiment, the package 101 can be a printed circuit board having a wiring pattern formed thereon.

[0029] The first LED chip 132 and the second LED chip 134 can each include epitaxially grown semiconductor layers (see Figure 9 and Figure 10 ). The first LED chip 132 can emit light having a peak wavelength in the range of 410 nm to 430 nm. For example, the first LED chip 132 can emit near-UV light and violet light. The second LED chip 134 can be a blue LED chip that emits light having a peak wavelength in the range of 440 nm to 460 nm. In some embodiments, the range of the peak wavelength of the second LED chip 134 can be from 445 nm to 460 nm.

[0030] The wavelength conversion film 150 may include a transparent body 151 containing a first quantum dot 154 and a second quantum dot 156. The wavelength conversion film 150 may be disposed on the path of the light (L1 + L2) emitted by the first LED chip 132 and the second LED chip 134. According to an embodiment, the wavelength conversion film 150 may be disposed at a distance from the first LED chip 132 and the second LED chip 134 that generate heat, so as to prevent the first quantum dot 154 and the second quantum dot 156 in the wavelength conversion film 150 from deteriorating due to, for example, the generated heat.

[0031] The transparent body 151 of the wavelength conversion film 150 may include a transparent resin body or a low-temperature sintered glass. For example, the transparent resin body may include epoxy resin, silicone, or a combination thereof.

[0032] The first quantum dot 154 may convert at least a part of the emitted light L1 + L2 into green light, for example, light with a peak wavelength in the range of 510 nm to 550 nm. The second quantum dot 156 may convert at least a part of the emitted light L1 + L2 into red light, for example, light with a peak wavelength in the range of 610 nm to 660 nm. The full width at half maximum of the light (i.e., the final white light L3) converted from the first quantum dot 154 and the second quantum dot 156 may be 40 nm or less.

[0033] For example, the first quantum dot 154 and the second quantum dot 156 may include at least one of InP / ZnS, InP / ZnSe, CdSe / CdS, CdSe / ZnS, PbS / ZnS, InP / ZnSe / ZnS, and InP / GaP / ZnS. In some embodiments, the first quantum dot 154 and the second quantum dot 156 may include at least one of InP / ZnS, InP / ZnSe, and InP / ZnSe / ZnS. The sizes of the first quantum dot 154 and the second quantum dot 156 may be adjusted to meet the desired wavelength conditions.

[0034] The wavelength converted from the quantum dots adopted in this embodiment can be changed by adjusting the diameter (D) of the quantum dots. For example, the diameter of the core of each quantum dot may be about 1 nm to about 30 nm, for example, about 3 nm to about 10 nm. For example, the thickness of the shell surrounding the corresponding core of each quantum dot may be about 0.1 nm to about 20 nm, for example, about 0.5 nm to about 2 nm. By adjusting the diameter of the quantum dots, for example, by adjusting the size of the core and / or shell of the quantum dots, the conversion wavelength can be changed in the range of 510 nm (green) to 660 nm (red). As described above, various colors can be achieved according to the diameter of the quantum dots, and a relatively narrow full width at half maximum (e.g., about 35 nm) can be achieved.

[0035] Thus, quantum dots can achieve various colors according to their sizes, and when used as a substitute for phosphors, quantum dots can be used as red or green phosphors. When quantum dots are used, a relatively narrow full width at half maximum (e.g., about 35 nm) can be achieved.

[0036] In this embodiment, in addition to the second LED chip 134 that emits blue light in the range of 440 nm to 460 nm, a first LED chip 132 can be added as an excitation light source that emits violet light in the range less than 430 nm, so as to increase the excited states of the first quantum dot 154 and the second quantum dot 156, thereby greatly improving the light conversion efficiency of the first quantum dot 154 and the second quantum dot 156. Specifically, reference can be made to Figure 4 Describe the effect of improving the light conversion efficiency according to this embodiment. Figure 4 Shows the absorption rates of the first quantum dot 154 and the second quantum dot 156 according to the wavelength.

[0037] Refer to Figure 4 , it can be determined that the light absorption rate within the peak wavelength range A1 (e.g., about 410 nm to about 430 nm) of the first LED chip 132 is higher than the light absorption rate within the peak wavelength range A2 (e.g., about 440 nm to about 460 nm) of the second LED chip 134. For example, the absorption rate at a wavelength of 430 nm can be about 2 to about 3 times that at a wavelength of 450 nm. As described above, compared with the light conversion efficiency of the light (L2) of the second LED chip 134, the light conversion efficiency of the light (L1) of the first LED chip 132 can be greatly improved.

[0038] Therefore, relative to the second LED chip 134 that emits blue light I in the range of about 440 nm to about 460 nm, by adding the first LED chip 132 as the excitation light for the first quantum dot 154 and the second quantum dot 156, the light conversion efficiency of the first quantum dot 154 and the second quantum dot 156 is increased. In addition, as the light conversion efficiency of the first quantum dot 154 and the second quantum dot 156 increases, the content of the first quantum dot 154 and the second quantum dot 56 in the wavelength conversion film 150 can be reduced. That is to say, by adding the first LED chip 132 as the excitation light therein, the extraction efficiency of the light emitted through the wavelength conversion film 150 can be greatly improved to reduce the content of the first quantum dot 154 and the second quantum dot 156.

[0039] For example, when the wavelength conversion film 150 includes the transparent body 151, based on the weight of the transparent resin body of the transparent body 151, the combined weight of the first quantum dots 154 and the second quantum dots 156 may be about 5 wt% to about 30 wt%, for example, about 15 wt% or less. For example, the total weight of the first quantum dots 154 may be greater than the total weight of the second quantum dots 156. For example, the first quantum dots 154 and the second quantum dots 156 may be at least one of InP / ZnS, InP / ZnSe, and InP / ZnSe / ZnS. For example, the first quantum dots 154 and the second quantum dots 156 may include different materials. For example, when the first quantum dots 154 and the second quantum dots 156 are at least one of InP / ZnS, InP / ZnSe, and InP / ZnSe / ZnS respectively, the first quantum dots 154 may be in the range of about 5 wt% to about 10 wt% based on the weight of the transparent resin body, and the second quantum dots 156 may be in the range of about 1 wt% to about 5 wt% based on the weight of the transparent resin body.

[0040] Light having a relatively short wavelength (e.g., the light (L1) of the first LED chip 132) may not contribute to white light (or the color reproducibility of the display device) and may be harmful to the human body. Therefore, the intensity (S1') of the short wavelength peak in the spectrum of the final white light (L3) transmitted through the wavelength conversion film 150 can be adjusted to address this effect.

[0041] Specifically, as Figure 3 shown, in the spectrum of the final white light (L3) emitted from the wavelength conversion film 150, the intensity (S1') of the peak caused by the light (L1) of the first LED chip 132 can be designed to fall within 15% of the intensity (S2') of the peak caused by the light (L2) of the second LED chip 134 (e.g., about 3% to 10%). In other words, while the first LED chip 132 can be implemented as an excitation light source for the quantum dots in the wavelength conversion film 150 at a relatively short wavelength, the intensity (S1') of the emitted violet light (L1) is specifically designed to be lower, e.g., about 15% or less of the intensity (S2') of the blue light (L2) emitted from the second LED chip 134, to minimize any harmful effects of short wavelength light.

[0042] As Figure 2 shown, the light output from the first LED chip 132 and the second LED chip 134 (i.e., the light (L1 and L2)) can be adjusted before passing through the wavelength conversion film 150 to obtain the relative intensity condition of short wavelengths in the spectrum of the final white light (L3). The relative intensity condition of short wavelengths can be satisfied by reducing the light output (S1) from the first LED chip 132 relative to the light output (S2) from the second LED chip 134.

[0043] The first LED chip 132 may have a smaller number and / or smaller size than the second LED chip 134. For example, the number of the first LED chips 132 may be less than the number of the second LED chips 134. Specifically, the first LED chip 132 and the second LED chip 134 may have the same size, the number of the first LED chips 132 may be one, and the number of the second LED chips 134 may be multiple (see Figure 12 and Figure 15 ). In another example, when the same number of the first LED chips 132 and the second LED chips 134 are adopted, the size of the first LED chip 132 may be set to be smaller than the size of the second LED chip 134.

[0044] In this way, by making the outputs between the two kinds of light (L1 and L2) different, before being converted into the final white light (L3), the peak intensity caused by the light (L1) of the first LED chip 132 can be adjusted to be within a range of 15% or less of the peak intensity caused by the light (L2) of the second LED chip 134 (for example, about 3% to 10%).

[0045] As described above, the first LED chip 132 can be adopted to improve the light conversion efficiency of the first quantum dot 154 and the second quantum dot 156. That is to say, since the surrounding optical elements (such as a light guide plate, various optical films, etc.) will increase the absorption loss, the wavelength will become shorter in specific applications (such as in a display device). Therefore, when considering the absorption loss in an application level where a relatively large number of surrounding optical elements are adopted, the first LED chip 132 can be selected to have a wavelength of 410 nm or more.

[0046] For example, as Figure 4 shown, the peak wavelength range (A1) of the first LED chip 132 may be within a range of 410 nm to 430 nm, and the peak wavelength range (A2) of the second LED chip 134 may be within a range of 440 nm to 460 nm. In some embodiments, the peak wavelength range (A2) of the second LED chip 134 may be within a range of 445 nm to 460 nm.

[0047] The following examples and comparative examples are provided to emphasize the features of one or more embodiments, but it should be understood that the examples and comparative examples are not to be construed as limiting the scope of the embodiments, and the comparative examples are not to be construed as being outside the scope of the embodiments. In addition, it should be understood that the embodiments are not limited to the specific details described in the examples and comparative examples.

[0048] Experimental Example 1

[0049] The peak wavelength of the second LED chip is set to 457 nm, and the peak wavelengths of the first LED chips are sequentially adjusted to 414 nm, 421 nm, 430 nm, 440 nm, 448 nm, and 457 nm. The power conversion efficiency of the wavelength conversion film and the transmittance of the diffusion sheet are measured. In this case, regarding the wavelength conversion film, the first quantum dots and the second quantum dots (green quantum dots and red quantum dots) are respectively set to InP / ZnSe / ZnS to prepare a wavelength conversion film containing a total of 8 wt% of the first quantum dots and the second quantum dots.

[0050] When the peak wavelength of the first LED chip is 414 nm, the power conversion efficiency is expressed as 100% (relative value), and when the peak wavelength of the first LED chip is 457 nm, the transmittance is expressed as 100%. Figure 5 The results of the relative conversion efficiency and transmittance measured according to the wavelength (the wavelength varying based on the first LED chip) are shown in the graph of.

[0051] As Figure 5 shown, and as described above, as the peak wavelength of the first LED chip shortens, the power conversion efficiency increases, but the transmittance of the diffusion sheet decreases. Considering both the increase in power conversion efficiency and the decrease in transmittance, the peak wavelength range of the first LED chip can be in the range of 410 nm to 430 nm.

[0052] Experimental Example 2

[0053] The first LED chip is set to have a peak wavelength of 414 nm, the second LED chip is set to have a peak wavelength of 457 nm, and the same wavelength conversion film as in Experimental Example 1 is used to prepare a white light emitting device. While changing the intensity ratio (S1' / S2') of the peak wavelength based on the finally emitted light, the DCI is measured as the color rendering rate. In Figure 6 the graph of shows the results.

[0054] Referring to Figure 6 , the case where the intensity ratio (S1' / S2') of the peak wavelength is 15% or less is shown to be higher than the case without the first LED chip (DCI = 90.5%), and in particular, when the intensity ratio (S1' / S2') of the peak wavelength is in the range of 3% to 10%, the color rendering rate is higher, about 91%.

[0055] Various modifications can be performed according to the position of the wavelength conversion film (or the first quantum dots and the second quantum dots) and the introduction of additional phosphors. Figure 7 and Figure 8 are schematic cross-sectional views of the light emitting devices according to the respective embodiments.

[0056] Referring to Figure 7 , the light emitting device 100B according to the present embodiment is the same asFigure 1 is similar to the light-emitting device 100A shown, except that a wavelength conversion film 150 is provided. For example, it is directly provided on the upper surface of the resin encapsulation part 141, and a phosphor 145 is introduced into the resin encapsulation part 141. Additionally, unless otherwise specified, the components of this embodiment can be understood by referring to the description of the same or similar components of the Figure 1 light-emitting device 100A shown.

[0057] The phosphor 145 used in this embodiment may further include at least one of a green phosphor and a red phosphor as an additional wavelength conversion material. For example, the green phosphor may include at least one of (Ba,Sr)2SiO4:Eu and β-SiAlON:Eu. The red phosphor may include at least one of (Sr,Ca)AlSiN3:Eu, K2SiF6:Mn, and CaAlSiN3:Eu.

[0058] Since the first quantum dots 154 and the second quantum dots 156 are easily affected by heat, the first quantum dots 154 and the second quantum dots 156 may be arranged to be spaced apart from the first LED chip 132 and the second LED chip 134 respectively to prevent the reliability from deteriorating due to heat. The additional phosphor 145 may be a ceramic material with relatively high heat resistance, so it can be included in the resin encapsulation part 141.

[0059] The wavelength conversion film 150 may be located on the light emission path. In this embodiment, the wavelength conversion film 150 may be arranged to cover the resin encapsulation part 141 on the package 101.

[0060] Refer to Figure 8 According to the light-emitting device 100C of this embodiment, it is similar to the Figure 1 light-emitting device 100A shown, except that the first quantum dots 154 and the second quantum dots 156 are arranged in the resin encapsulation part 141 without using a wavelength conversion film. Additionally, unless otherwise specified, the components of this embodiment can be understood by referring to the description of the same or similar components of the Figure 1 light-emitting device 100A shown.

[0061] The first quantum dots 154 and the second quantum dots 156 may be included in the resin encapsulation part 141 to improve the heat resistance of the first quantum dots 154 and the second quantum dots 156. For example, the resin encapsulation part 141 may be made of epoxy resin, silicone, modified silicone, polyurethane, ethylene oxide, acrylic acid, polycarbonate, polyimide, and combinations thereof. In some embodiments, additional phosphors may also be included in the resin encapsulation part 141, such as Figure 7 the embodiment shown.

[0062] In the above-described embodiment, the lead frames 111 and 112 and the first LED chip 132 and the second LED chip 134 may be electrically connected to each other through a wire W. The first LED chip 132 and the second LED chip 134 may be directly connected to the lead frames 111 and 112 by using conductive bumps in a flip-chip structure.

[0063] As described above, the LED chips applicable to the light-emitting device according to the exemplary embodiment may have various structures. Figure 9 and Figure 10 is a cross-sectional view of the LED chip in the light-emitting device according to the exemplary embodiment.

[0064] Referring to Figure 9 , the LED chip 10A according to the present embodiment may include a substrate 11 and a semiconductor stack S disposed on the substrate 11. The semiconductor stack S may include a first-conductive-type semiconductor layer 14, an active layer 15, and a second-conductive-type semiconductor layer 16 arranged in order on the substrate 11. A buffer layer 12 may be additionally disposed between the substrate 11 and the first-conductive-type semiconductor layer 14.

[0065] The substrate 11 may be an insulating substrate, such as sapphire, but is not limited thereto. In addition to the insulating substrate, the substrate 11 may be a conductive substrate or a semiconductor substrate. For example, in addition to sapphire, the substrate 11 may be SiC, Si, MgAl2O4, MgO, LiAlO2, LiGaO2, or GaN. Concave and convex portions P may be formed on the upper surface of the substrate 11. The concave and convex portions P may improve the quality of the single crystal to be grown while improving the light extraction efficiency.

[0066] The buffer layer 12 may be In x Al y Ga 1-x-y N (0 ≤ x < 1, 0 ≤ y < 1). For example, the buffer layer 12 may be GaN, AlN, AlGaN, or InGaN. As needed, multiple layers may be combined, or the composition may be gradually changed.

[0067] The first-conductive-type semiconductor layer 14 may be a nitride semiconductor layer satisfying n-type In x Al y Ga 1-x-y N (0 ≤ x < 1, 0 ≤ y < 1, 0 ≤ x + y < 1), and the n-type impurity may be Si. For example, the first-conductive-type semiconductor layer 14 may include n-type GaN. The second-conductive-type semiconductor layer 16 may be a p-type In x Al y Ga 1-x-yA nitride semiconductor layer of N(0≤x<1, 0≤y<1, 0≤x + y<1), and the p-type impurity can be Mg. For example, the semiconductor layer 16 of the second conductivity type can be implemented as a single-layer structure, but can have a multi-layer structure with different compositions for each layer, as in this embodiment.

[0068] The active layer 15 can be a multi-quantum well (MQW) structure in which quantum well layers and quantum barrier layers are alternately stacked. For example, the quantum well layer and the quantum barrier layer can be In x Al y Ga 1-x-y N(0≤x≤1, 0≤y≤1, 0≤x + y≤1). In a specific example, the quantum well layer can be In x Ga 1-x N(0<x≤1), and the quantum barrier layer can be GaN or AlGaN. The thicknesses of the quantum well layer and the quantum barrier layer can be respectively in the range of about 1 nm to about 50 nm. The active layer 15 is not limited to the multi-quantum well structure, but can be a single quantum well structure.

[0069] The first electrode 19a and the second electrode 19b can be respectively arranged on the mesa etching region of the semiconductor layer 14 of the first conductivity type and the semiconductor layer 16 of the second conductivity type to be on the same surface (the first surface). For example, the first electrode 19a can include Ag, Ni, Al, Cr, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au, etc., and can be adopted as a structure with a single layer or two or more layers. In some embodiments, the second electrode 19b can be a transparent electrode, for example, a transparent conductive oxide or a transparent conductive nitride, or can include graphene. The second electrode 19b can include, for example, at least one of Al, Au, Cr, Ni, Ti, and Sn.

[0070] Referring to Figure 10 , it can be understood that the LED chip 10B according to this embodiment is similar to the Figure 9 shown LED chip 10A, except for the electrode structure and its related structures. Additionally, unless otherwise specified, the elements of this embodiment can be understood by referring to the description of the same or similar elements of the Figure 9 shown LED chip 10A.

[0071] As Figure 10As shown, the LED chip 10B may include a first electrode 22 and a second electrode 24 respectively connected to a semiconductor layer 14 of a first conductivity type and a semiconductor layer 16 of a second conductivity type. The first electrode 22 may include a connection electrode portion 22a connected to the semiconductor layer 14 of the first conductivity type through the semiconductor layer 16 of the second conductivity type and the active layer 15, and a first electrode pad 22b connected to the connection electrode portion 22a. The connection electrode portion 22a may have the same structure as a conductive via. The connection electrode portion 22a may be surrounded by an insulating portion 21 to be electrically separated from the active layer 15 and the semiconductor layer 16 of the second conductivity type. The connection electrode portion 22a may be disposed in a region where the semiconductor stack S is etched. In the connection electrode portion 22a, the number, shape, spacing, or the contact area thereof with the semiconductor layer 14 of the first conductivity type may be appropriately designed to reduce the contact resistance. In addition, the connection electrode portions 22a may be arranged in multiple rows and columns on the semiconductor stack S to increase the current. The second electrode 24 may include an ohmic contact layer 24a on the semiconductor layer 16 of the second conductivity type and a second electrode pad 24b.

[0072] The connection electrode portion 22a and the ohmic contact layer 24a may include a conductive material having a single-layer or multi-layer structure, which has ohmic characteristics with respect to the semiconductor layer 14 of the first conductivity type and the semiconductor layer 16 of the second conductivity type respectively. For example, the connection electrode portion 22a and the ohmic contact layer 24a may be formed by a process of depositing or sputtering at least one of metals (such as Ag, Al, Ni, Cr) and transparent conductive oxides (TCOs) (such as ITO).

[0073] The first electrode pad 22b and the second electrode pad 24b may be respectively connected to the connection electrode portion 22a and the ohmic contact layer 24a to serve as external terminals of the LED chip 10B. For example, the first electrode pad 22b and the second electrode pad 24b may be Au, Ag, Al, Ti, W, Cu, Sn, Ni, Pt, Cr, NiSn, TiW, AuSn, or their eutectic metals.

[0074] The first electrode 22 and the second electrode 24 can be arranged in the same direction and can be mounted in a lead frame or the like in a so-called flip-chip form. The two electrodes 22 and 24 can be electrically separated from each other by an insulating portion 21. The insulating portion 21 can be any material having electrical insulation properties. For example, a material having a relatively low light absorption rate can be used. For example, silicon oxide or silicon nitride can be used. If necessary, a reflective material can be dispersed in the light-transmitting material to form a reflective structure. Alternatively, the insulating portion 121 can be a multilayer reflective structure in which a plurality of insulating films having different refractive indices are alternately stacked. For example, the multilayer reflective structure can be a distributed Bragg reflector (DBR) in which a first insulating film having a first refractive index and a second insulating film having a second refractive index are alternately stacked.

[0075] The multilayer reflective structure can be stacked by repeatedly stacking (2 to 100 times) a plurality of insulating films having different refractive indices. For example, the multilayer reflective structure can be stacked by repeatedly stacking 3 to 70 times (for example, repeatedly stacking 4 to 50 times). The plurality of insulating films of the multilayer reflective structure can be oxides or nitrides respectively, such as SiO2, SiN, SiO x N y , TiO2, Si3N4, Al2O3, TiN, AlN, ZrO2, TiAlN, TiSiN, and combinations thereof. The first insulating layer and the second insulating layer can be determined to have refractive indices in the range of about 1.4 to about 2.5. The refractive indices of the first insulating layer and the second insulating layer can be less than the refractive index of the semiconductor layer 14 of the first conductivity type and the refractive index of the substrate 11, or can be less than the refractive index of the semiconductor layer 14 of the first conductivity type, but greater than the refractive index of the substrate 11.

[0076] The light-emitting device according to the above embodiment can be advantageously used as a light source for a backlight unit and a display device.

[0077] Figure 11 is a schematic cross-sectional view of a backlight unit (side-injection type) according to an exemplary embodiment. Figure 12 is Figure 11 a schematic plan view of an LED module in the backlight unit of

[0078] Referring to Figure 11 , the backlight unit 1200 according to the present embodiment can include a light guide plate 1233 and an LED module 1220 that radiates light onto a side surface of the light guide plate 1233. The light of the LED module 1220 can be incident on the light guide plate 1233 to be converted into a surface light source. The backlight unit 1200 can further include a reflective layer 1234 disposed on a lower surface of the light guide plate 1233, so that the light passing through the light guide plate 1233 can be emitted in an upward direction.

[0079] The LED module 1220 may include a circuit board 1201 and a plurality of light sources 1210 mounted thereon. As Figure 12 shown, the LED module 1220 may include a strip-shaped circuit board 1201 and a plurality of light sources 1210 arranged longitudinally. It can be understood that, except for the wavelength conversion film 150, the plurality of light sources 1210 may be the same as Figure 1 the light-emitting device 100A. That is to say, except for the structure of the wavelength conversion film, each single light source among the plurality of light sources 1210 may be substantially the same as a light-emitting device 100A. For example, it includes a first LED chip 132 and a second LED chip 134. As Figure 11 shown, the wavelength conversion film 1250 may be spaced apart from the plurality of light sources 1210 and may be disposed on the upper surface of the light guide plate 1233. For example, the wavelength conversion film 1250 may be parallel to the light guide plate 1233 to completely overlap the light guide plate 1233.

[0080] The wavelength conversion film 1250 may include a transparent body containing a first quantum dot QD1 and a second quantum dot QD2. As described above, the first quantum dot QD1 may convert at least a part of the emitted light into green light, for example, light with a peak wavelength in the range of 510 nm to 550 nm, and the second quantum dot QD2 may convert at least a part of the emitted light into red light, for example, light with a peak wavelength in the range of 610 nm to 660 nm.

[0081] For example, each of the plurality of light sources 1210 may include one first LED chip 1205A and two second LED chips 1205B arranged in a package 1211, as Figure 12 shown. By arranging the number of the first LED chips 1205A to be less than the number of the second LED chips 1205B, in the final emission spectrum of the light, the intensity of the peak wavelength of the first LED chip 1205A may be maintained at 15% or less of the intensity of the second LED chip 1205B.

[0082] Referring to Figure 13 , the backlight unit 1300 according to the present embodiment may be a side-entry backlight unit and may include a light guide plate 1333 and an LED module 1320 disposed on the side surface of the light guide plate 1333. A wavelength conversion member 1350 corresponding to the wavelength conversion film may be disposed between the side surface of the light guide plate 1333 and the LED module 1320. In some embodiments, the light emitted by the LED module 1320 may be guided into the light guide plate 1333 through a reflection structure 1301.

[0083] In this embodiment, the wavelength conversion member 1350 employed may include a transparent body containing a first quantum dot and a second quantum dot, in a manner the same as or similar to that of the wavelength conversion film. As described above, the first quantum dot may convert at least a portion of the emitted light into green light, for example, light having a peak wavelength in the range of 510 nm to 550 nm, and the second quantum dot may convert at least a portion of the emitted light into red light, for example, light having a peak wavelength in the range of 610 nm to 660 nm.

[0084] Figure 14 is a schematic cross-sectional view of a backlight unit (direct-lit type) according to an exemplary embodiment, Figure 15 is Figure 14 a schematic plan view of an LED module in the backlight unit of

[0085] Referring to Figure 14 , the backlight unit 1500 according to this embodiment may be an example of a direct-lit type backlight unit. The backlight unit 1500 may include a light guide plate 1533, a wavelength conversion film 1550 disposed on the upper surface of the light guide plate 1533, and an LED module 1520 disposed on the lower surface of the wavelength conversion film 1550. Additionally, the backlight unit 1500 may introduce a diffusion film 1560 between the light guide plate 1533 and the LED module 1520. Various optical films (e.g., polarizing films) etc. may be employed in addition to the diffusion film.

[0086] The LED module 1520 may include a circuit board 1501 and a plurality of light sources 1510 mounted on the circuit board 1501. The circuit board 1501 may have an area substantially corresponding to that of the light guide plate 1533, for example, the backlight unit. As Figure 15 shown, the LED module 1520 may include a circuit board 1501 and the plurality of light sources 1510 arranged in multiple rows and columns. It can be understood that, except for the wavelength conversion film 150, the plurality of light sources 1510 may be the same as Figure 1 the light-emitting device 100A of Figure 14 shown. As

[0087] The wavelength conversion film 1550 may include a transparent body containing a first quantum dot QD1 and a second quantum dot QD2. As described above, the first quantum dot QD1 may convert at least a portion of the emitted light into green light, for example, light having a peak wavelength in the range of 510 nm to 550 nm, and the second quantum dot QD2 may convert at least a portion of the emitted light into red light, for example, light having a peak wavelength in the range of 610 nm to 660 nm.

[0088] Each of the plurality of light sources 1510 may include a first LED chip 1505A and three second LED chips 1505B arranged in a rectangular shape on a package 1511, as Figure 15 shown. By arranging the number of the first LED chips 1505A to be less than the number of the second LED chips 1505B, in the final emission spectrum of light, the intensity of the peak wavelength of the first LED chip 1505A may be maintained at 15% or less of the intensity of the peak wavelength of the second LED chip 1505B.

[0089] Figure 16 is a schematic exploded perspective view of a display device according to an exemplary embodiment.

[0090] Referring to Figure 16 , the display device 2000 according to the present embodiment may include a backlight unit 2200, an optical sheet 2300, and an image display panel 2400 (e.g., a liquid crystal panel).

[0091] The backlight unit 2200 may include a bottom case 2210, a reflector 2220, a light guide plate 2240, and an LED module 2230 disposed on at least one side surface of the light guide plate 2240. The LED module 2230 may include a circuit board 2001 and a plurality of light sources 2005 arranged on the circuit board 2001. Each of the plurality of light sources may be a light emitting device according to the above embodiment. The plurality of light sources 2005 employed in this embodiment may be side - entry light emitting devices in which the light emitting window is mounted on the side surface.

[0092] In some embodiments, the backlight unit 2200 may be replaced by any one of the backlight units 1200, 1300, and 1500 shown in Figure 11 , Figure 13 and Figure 14 . For example, a wavelength conversion film may be used to position (e.g., arrange) the first quantum dots and the second quantum dots on the light emitting path (e.g., the surface of the light guide plate) to be separated from the LED module that causes heat generation.

[0093] The optical sheet 2300 may be disposed between the light guide plate 2240 and the image display panel 2400. The optical sheet 2300 may include various sheets, such as a diffusion sheet, a prism sheet, and / or a protective sheet.

[0094] The image display panel 2400 may display an image using the light emitted through the optical sheet 2300. For example, the image display panel 2400 may include an array substrate 2420, a liquid crystal layer 2430, and a color filter layer 2440. The array substrate 2420 may include pixel electrodes arranged in a matrix form, thin - film transistors for applying a driving voltage to the pixel electrodes, and signal lines for operating the thin - film transistors.

[0095] The color filter layer 2440 may include a transparent substrate, color filters, and a common electrode. The color filter layer 2440 may include filters that selectively allow light of specific wavelengths in the white light emitted by the backlight unit 2200 to pass through. The liquid crystal layer 2430 may be rearranged by an electric field formed between the pixel electrode and the common electrode to control the light transmittance. The light with the controlled light transmittance may pass through the color filters of the color filter layer 2440 to display an image. The image display panel 2400 may further include a driving circuit unit that processes an image signal, etc.

[0096] By summarizing and commenting, quantum dots can be used as wavelength conversion materials for generating white light in display devices. However, when red quantum dots and green quantum dots are mixed with the blue light emitted by a blue LED chip, the light conversion efficiency of the blue light is relatively low, while the loss of the blue light is relatively high, resulting in a relatively large power loss. In addition, the quantum dots may deteriorate due to the heat generated by the LED chip.

[0097] Accordingly, an exemplary embodiment provides a light-emitting device in which the light loss can be reduced and the power efficiency can be improved by increasing the light conversion efficiency of quantum dots used as wavelength conversion materials. The exemplary embodiment also provides a backlight unit and a display device including the light-emitting device having reduced light loss and improved power efficiency.

[0098] That is, according to the exemplary embodiment, in addition to the second LED chip that emits blue light, the light-emitting device further includes a first LED chip that emits near-UV or violet light (not blue light of a higher wavelength) as excitation light for the quantum dots to increase the light conversion efficiency of the quantum dots. Therefore, in the wavelength conversion film, the concentration of the quantum dots can be reduced while the light extraction efficiency can be increased.

[0099] In addition, according to the exemplary embodiment, in the spectrum of the final white light, the peak of the first LED chip can be designed to be 15% or less of the peak intensity of the blue light to improve the power efficiency and minimize the harm of short-wavelength light to the human body.

[0100] Exemplary embodiments have been disclosed herein. Although specific terms have been used, they have been used and interpreted in a general and descriptive sense only and not for the purpose of limitation. In some cases, unless otherwise specifically stated, one of ordinary skill in the art will be clear that, as of the filing of the present application, the features, characteristics, and / or elements described in connection with a particular embodiment can be used alone or in combination with the features, characteristics, and / or elements described in connection with other embodiments. Accordingly, those skilled in the art should understand that various changes can be made to the form and details without departing from the spirit and scope of the invention as set forth in the appended claims.

Claims

1. A light-emitting device, comprising: at least one first light-emitting diode chip that emits first light having an emission peak wavelength in the range of 414 nm to 430 nm; at least one second light-emitting diode chip that emits second light having an emission peak wavelength in the range of 440 nm to 460 nm; a first quantum dot on a path of the light emitted by the at least one first light-emitting diode chip and the at least one second light-emitting diode chip, the first quantum dot converting a first portion of the first light and the second light emitted by the at least one first light-emitting diode chip and the at least one second light-emitting diode chip into light having a peak wavelength in the range of 510 nm to 550 nm; and a second quantum dot on a path of the light emitted by the at least one first light-emitting diode chip and the at least one second light-emitting diode chip, the second quantum dot converting a second portion of the first light and the second light emitted by the at least one first light-emitting diode chip and the at least one second light-emitting diode chip into light having a peak wavelength in the range of 610 nm to 660 nm, wherein, in an emission spectrum of the final light emitted from the first quantum dot and the second quantum dot, an intensity of the peak wavelength of the at least one first light-emitting diode chip is equal to 15% or less of an intensity of the peak wavelength of the at least one second light-emitting diode chip.

2. The light-emitting device according to claim 1, wherein, The number of the at least one first light-emitting diode chip is less than the number of the at least one second light-emitting diode chip.

3. The light-emitting device according to claim 2, wherein, The size of the at least one first light-emitting diode chip is equal to the size of the at least one second light-emitting diode chip, the number of the at least one first light-emitting diode chip is one, and the number of the at least one second light-emitting diode chip is plural.

4. The light-emitting device according to claim 1, wherein, The size of the at least one first light-emitting diode chip is less than the size of the at least one second light-emitting diode chip.

5. The light-emitting device according to claim 1, wherein, The peak wavelength of the at least one second light-emitting diode chip is in the range of 445 nm to 460 nm.

6. The light-emitting device according to claim 1, wherein, In an emission spectrum of the final light emitted from the first quantum dot and the second quantum dot, an intensity of the peak wavelength of the at least one first light-emitting diode chip is in the range of 3% to 10% of an intensity of the peak wavelength of the at least one second light-emitting diode chip.

7. The light-emitting device according to claim 1, wherein, Each of the first quantum dot and the second quantum dot includes at least one of InP / ZnS, InP / ZnSe, CdSe / CdS, CdSe / ZnS, PbS / ZnS, InP / ZnSe / ZnS, and InP / GaP / ZnS.

8. The light-emitting device according to claim 1, further comprising a wavelength conversion film on a path of the light emitted by the at least one first light-emitting diode chip and the at least one second light-emitting diode chip, the wavelength conversion film including a transparent resin body having the first quantum dot and the second quantum dot, and the final light being directly emitted from the wavelength conversion film.

9. The light-emitting device according to claim 8, wherein, Each of the first quantum dots and the second quantum dots includes at least one of InP / ZnS, InP / ZnSe, and InP / ZnSe / ZnS. The first quantum dots account for 5 wt% to 10 wt% of the transparent resin body, and the second quantum dots account for 1 wt% to 5 wt% of the transparent resin body.

10. A light-emitting device, comprising: A first light-emitting diode chip that emits first light having an emission peak wavelength in the range of 414 nm to 430 nm; A second light-emitting diode chip that emits second light having an emission peak wavelength in the range of 440 nm to 460 nm; and A wavelength conversion film on a path of light emitted by the first light-emitting diode chip and the second light-emitting diode chip. The wavelength conversion film includes first quantum dots and second quantum dots to convert a part of the light emitted by the first light-emitting diode chip and the second light-emitting diode chip into light having a first peak wavelength and light having a second peak wavelength, respectively. Wherein, the first peak wavelength is in the range of 510 nm to 550 nm, the second peak wavelength is in the range of 610 nm to 660 nm, and in an emission spectrum of the final light directly emitted from the wavelength conversion film, an intensity of the peak wavelength of the first light-emitting diode chip is equal to 15% or less of an intensity of the peak wavelength of the second light-emitting diode chip.

11. The light-emitting device according to claim 10, wherein, The number of the first light-emitting diode chips is less than the number of the second light-emitting diode chips.

12. The light-emitting device according to claim 10 further comprises: A resin encapsulation part surrounding the first light-emitting diode chip and the second light-emitting diode chip, and the wavelength conversion film is spaced apart from the resin encapsulation part.

13. The light-emitting device according to claim 12, wherein, The resin encapsulation part includes at least one phosphor of a green phosphor and a red phosphor.

14. The light-emitting device according to claim 13, wherein, The green phosphor includes at least one of (Ba,Sr)2SiO4:Eu and β-SiAlON:Eu.

15. The light-emitting device according to claim 13, wherein, The red phosphor includes at least one of (Sr,Ca)AlSiN3:Eu, K2SiF6:Mn, and CaAlSiN3:Eu.

16. A backlight unit, comprising: A light-emitting diode module, comprising: A first light-emitting diode chip that emits first light having an emission peak wavelength in the range of 414 nm to 430 nm, and A second light-emitting diode chip that emits second light having an emission peak wavelength in the range of 440 nm to 460 nm; and A wavelength conversion film on a path of light emitted by the first light-emitting diode chip and the second light-emitting diode chip. The wavelength conversion film includes first quantum dots and second quantum dots to convert a part of the light emitted from the light-emitting diode module into light having a first peak wavelength and light having a second peak wavelength, respectively. Wherein, the first peak wavelength is in the range of 510 nm to 550 nm, the second peak wavelength is in the range of 610 nm to 660 nm, and in an emission spectrum of the final light directly emitted from the wavelength conversion film, an intensity of the peak wavelength of the first light-emitting diode chip is equal to 15% or less of an intensity of the peak wavelength of the second light-emitting diode chip.

17. The backlight unit according to claim 16, wherein: the light emitting diode module includes a plurality of light sources having the first light emitting diode chip and the second light emitting diode chip, and in each of the plurality of light sources, the number of the first light emitting diode chips is less than the number of the second light emitting diode chips.

18. The backlight unit according to claim 16, further comprising: A light guide plate having an edge supporting the light emitting diode module, and the wavelength conversion film is located on the upper surface of the light guide plate.

19. The backlight unit according to claim 16, further comprising: A light guide plate having a lower surface supporting the light emitting diode module, and the wavelength conversion film is located on the upper surface of the light guide plate.

20. The backlight unit according to claim 16, wherein, The peak wavelength of the second light emitting diode chip is in the range of 445 nm to 460 nm.

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