Light-emitting device

Abstract

To provide a light-emitting device using quantum dots, particularly green quantum dots, and having high luminous efficiency.SOLUTION: A light-emitting device includes a light-emitting element that emits blue light, a quantum dot that absorbs a portion of blue light emitted by the light-emitting element and emits green light, and at least one of a KSF phosphor, the composition of which is represented by the following general formula (1) and absorbs a portion of the blue light emitted by the light-emitting element to emit red light, and an MGF phosphor, the composition of which is represented by the following general formula (2) and absorbs a portion of the blue light emitted by the light-emitting element to emit red light. A2[M1-aMn4+aF6] (1). (x-a)MgO (a / 2)Sc2O3 yMgF2 cCaF2 (1-b)GeO2 (b / 2)Mt2O3:zMn4+(2).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a light-emitting device, and more particularly to a light-emitting device including a light-emitting element that emits blue light, and quantum dots that absorb a part of the blue light emitted by the light-emitting element and emit green light.

Background Art

[0002] As a light-emitting device that emits white light, there has been conventionally known a light-emitting device including a light-emitting element that emits blue light, a green phosphor (or a yellow-green phosphor that emits yellow-green light) that absorbs a part of the blue light emitted by the light-emitting element and emits green light, and a red phosphor that absorbs a part of the blue light emitted by the light-emitting element and emits red light. Such a light-emitting device that emits white light is used in various applications such as backlights for various displays such as liquid crystal displays and lighting devices.

[0003] In recent years, light-emitting devices in which all or part of the phosphor has been replaced with quantum dots (QD: quantum dot) have been developed. Quantum dots are semiconductor particles having a diameter of several nm to several tens of nm, and like phosphors, absorb light such as blue light emitted by a light-emitting element and emit light different from the absorbed light. There is known a light-emitting device including green quantum dots that absorb blue light emitted by a light-emitting element and emit green light, and red quantum dots that absorb blue light emitted by the light-emitting element and emit red light, without including a green phosphor and a red phosphor. Patent Document 1 also discloses a light-emitting device including a yellow-green phosphor and red quantum dots.

[0004] Quantum dots have the characteristic that their emission peak is sharp, that is, the full width at half maximum of the emission peak is small (narrow). Therefore, when a light-emitting device using quantum dots is combined with a color filter such as a liquid crystal display, it has the advantage of a wider color reproduction range. Furthermore, by matching the peak wavelength of the color filter (the wavelength at which the transmittance is at a peak) with the emission peak of the quantum dots, more light can pass through the color filter. As a result, when the color filter is used, there is less light attenuation and the light extraction efficiency is improved. In particular, since the emission peaks of conventional green phosphors and yellow-green phosphors were broad, these effects can be obtained more significantly by using green quantum dots.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in such a conventional light-emitting device using quantum dots, red quantum dots are used, and for this reason, there is a problem of secondary absorption. That is, a part of the green light (or yellow-green light) emitted by the green quantum dots or green phosphors (or yellow-green phosphors) that have absorbed blue light is absorbed by the red quantum dots and emits red light. When such secondary absorption occurs, there is a problem that the luminous efficiency of the entire light-emitting device decreases. On the other hand, in many applications such as displays and lighting devices, there is a demand for a light-emitting device that can emit brighter light with less power consumption, that is, a light-emitting device with higher luminous efficiency.

[0007] The present invention has been made to meet such demands, and provides a light-emitting device that uses quantum dots, particularly green quantum dots, and has high luminous efficiency.

Means for Solving the Problem

[0008] A light-emitting device comprising: a light-emitting element that emits blue light; quantum dots that absorb a part of the blue light emitted by the light-emitting element and emit green light; a KSF phosphor whose composition is represented by the following general formula (1) and that absorbs a part of the blue light emitted by the light-emitting element and emits red light; and at least one of an MGF phosphor whose composition is represented by the following general formula (2) and that absorbs a part of the blue light emitted by the light-emitting element and emits red light. A2[M 1-a Mn 4+ a F6] (1) (In the formula, A is at least one selected from the group consisting of K + , Li + , Na + , Rb + , Cs + and NH4 + , and M is at least one element selected from the group consisting of Group 4 elements and Group 14 elements, and 0 < a < 0.2 is satisfied.) (x - a)MgO·(a / 2)Sc2O3·yMgF2·cCaF2·(1 - b)GeO2·(b / 2)Mt2O3:zMn 4+ (2) (In the formula, x, y, z, a, b, c satisfy 2.0 ≦ x ≦ 4.0, 0 < y < 1.5, 0 < z < 0.05, 0 ≦ a < 0.5, 0 < b < 0.5, 0 ≦ c < 1.5, and y + c < 1.5, and Mt is at least one selected from Al, Ga, and In.)

Advantages of the Invention

[0009] A light-emitting device using quantum dots, particularly green quantum dots, can be provided, which has high luminous efficiency.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, it should be noted that the embodiments described below are for embodying the technical idea of the present invention and are not intended to limit the technical scope of the present invention. The configuration described in one embodiment is applicable to other embodiments as well, unless otherwise specified. In the following description, terms indicating a specific direction or position (for example, "up", "down", "right", "left", and other terms including these terms) are used as necessary, but the use of these terms is for facilitating the understanding of the invention with reference to the drawings, and the technical scope of the present invention is not limited by the meanings of these terms. It should be noted that the sizes and positional relationships of the members shown in the respective drawings may be exaggerated for clarity of explanation. Also, parts denoted by the same reference numerals appearing in a plurality of drawings indicate the same parts or members. Further, for example, a member denoted by a reference numeral consisting of a number and an alphabet such as "10A" may have the same configuration as a member denoted by a reference numeral having the same number without an alphabet and a member denoted by a reference numeral having the same number and a different alphabet, unless otherwise specified.

[0012] As a result of intensive studies, the inventor of the present application has found that, instead of using red quantum dots, by using at least one of a KSF phosphor and an MGF phosphor as a red phosphor, a light-emitting device having high luminous efficiency using green quantum dots can be provided. The KSF phosphor and the MGF phosphor, the details of which will be described later, absorb blue light emitted from the light-emitting element and emit red light, but hardly absorb green light emitted from the green quantum dots. That is, secondary absorption does not occur. Therefore, the light-emitting device according to the embodiment of the present invention has high luminous efficiency. Further, the peak in the emission spectrum of the KSF phosphor and the MGF phosphor has a narrow half-value width of about 10 to 20 nm. Therefore, even when passing through a color filter that transmits almost the entire red wavelength range, red with a narrow half-value width can be obtained, so that red light with high color purity can be obtained. The light-emitting devices according to a plurality of embodiments of the present invention will be described in detail below.

[0013] 1. Embodiment 1 FIG. 1 is a schematic cross-sectional view of a light-emitting device 100 according to Embodiment 1 of the present invention. The light-emitting device 100 includes a light-emitting element 1 that emits blue light, green quantum dots 24 that absorb a part of the blue light emitted from the light-emitting element 1 and emit green light, and a red phosphor 14 that absorbs a part of the blue light emitted from the light-emitting element 1 and emits red light. The red phosphor 14 is at least one of a KSF phosphor and an MGF phosphor, the details of which will be described later.

[0014] In the light-emitting device according to the present invention, the positional relationship between the red phosphor 14 and the green quantum dots 24 with respect to the light-emitting element 1 is not particularly limited. That is, (1) the red phosphor 14 may be located closer to the light-emitting element 1 than the green quantum dots 24, (2) the red phosphor 14 may be located farther from the light-emitting element 1 than the green quantum dots 24, and (3) as in Embodiment 2 described later, the red phosphor 14 and the green quantum dots 24 may be located at substantially the same distance from the light-emitting element 1. In Embodiment 1, the red phosphor 14 is located closer to the light-emitting element 1 than the green quantum dots 24.

[0015] The light-emitting device 100 includes a light-emitting element package 10. The light-emitting element package 10 includes a resin package 3 having a bottom surface, side walls, and a cavity that is surrounded by the bottom surface and the side walls and has an open upper portion, a light-emitting element 1 disposed on the bottom surface of the cavity of the resin package 3, and a sealing resin 12 filled in the cavity of the resin package 3. The positive and negative electrodes of the light-emitting element 1 are connected to an external power source via conductive means such as metal wires, metal bumps, and plating, and emit blue light by supplying current (electric power) from the external power source. The sealing resin 12 covers the periphery of the light-emitting element 1 (in the embodiment shown in FIG. 1, the upper surface and the side surface excluding the bottom surface of the light-emitting element 1). The sealing resin 12 contains a red phosphor 14. That is, the red phosphor 14 is dispersedly arranged inside the sealing resin 12. In the embodiment shown in FIG. 1, the red phosphor 14 is uniformly dispersed in the sealing resin 12, but the form of the dispersed arrangement of the red phosphor is not limited to this. The red phosphor 14 may be arranged at a higher density in a part of the sealing resin 12, for example, in the vicinity of the light-emitting element 1. As such an arrangement, there is a so-called sedimentation arrangement in which the dispersion density of the red phosphor is small at the upper part of the sealing resin and high at the bottom of the sealing resin 12 (including directly above the light-emitting element 1). The sedimentation arrangement can be formed, for example, by filling the cavity of the resin package 3 with the sealing resin 12 in which the red phosphor 14 is uniformly dispersed, then leaving the sealing resin 12 uncured for a predetermined time, allowing the red phosphor 14 in the sealing resin 12 to move by gravity, and then curing the sealing resin 12 after the distribution becomes high at the bottom of the sealing resin 12. It may also be sedimented by centrifugal force.

[0016] The light-emitting element package 10 has its upper surface as the emission surface and emits blue light and red light. More specifically, a part of the blue light emitted from the light-emitting element 1 passes through the encapsulating resin 12 and is emitted outward from the upper surface of the encapsulating resin 12. A part of the blue light emitted from these light-emitting element packages 10 may be reflected by the side surface and / or the bottom surface of the resin package 3 when traveling inside the encapsulating resin 12 and then emitted from the upper surface of the encapsulating resin 12. Another part of the blue light emitted from the light-emitting element 1 is absorbed by the red phosphor 14 while traveling inside the encapsulating resin 12, and the red phosphor 14 emits red light. Then, the red light emitted from the red phosphor 14 passes through the encapsulating resin 12 and is emitted outward from the upper surface of the encapsulating resin 12. A part of the red light emitted by these red phosphors 14 may be reflected by the side surface and / or the bottom surface of the resin package 3 when traveling inside the encapsulating resin 12 and then emitted from the upper surface of the encapsulating resin 12.

[0017] Outside the encapsulating resin 12, that is, in FIG. 1, a green quantum dot-containing layer 20 is disposed on the upper part of the encapsulating resin 12 (or the resin package 3). The green quantum dot-containing layer 20 includes a light-transmitting material 22 and green quantum dots 24. That is, the green quantum dots 24 are dispersedly arranged in the light-transmitting material 22. The green quantum dot-containing layer 20 may have any form. One of the preferred forms is a sheet shape (or film shape) as shown in FIG. 1. This is because the thickness of the green quantum dot-containing layer 20 can be made uniform and color unevenness can be suppressed.

[0018] By having such a configuration, in the light-emitting device 100, the red phosphor 14 is located closer to the light-emitting element 1 than the green quantum dots 24. By disposing a KSF phosphor or an MGF phosphor having a particle size (or diameter) as large as, for example, 20 to 50 μm near the light-emitting element and disposing green quantum dots 24 having a particle size (or diameter) of, for example, 2 to 10 nm near the light-emitting element 1, light scattering, particularly light scattering of green light by the red phosphor 14, can be suppressed. As a result, the light extraction efficiency (that is, the luminous efficiency) can be further improved. Regarding the improvement of the light extraction efficiency, details will be described after explaining the configuration of Embodiment 2 described below.

[0019] Most of the red light emitted from the upper surface of the light-emitting element package 10 enters the interior from the lower surface of the green quantum dot-containing layer 20, passes through the light-transmitting material 22 of the green quantum dot-containing layer 20, and then exits outside from above the upper surface of the green quantum dot-containing layer 20. Most of the blue light emitted from the upper surface of the light-emitting element package 10 enters the interior from the lower surface of the green quantum dot-containing layer 20. A part of the blue light that has entered the interior from the lower surface of the green quantum dot-containing layer 20 passes through the light-transmitting material 22 of the green quantum dot-containing layer 20 and then exits outside from above the upper surface of the green quantum dot-containing layer 20. Another part of the blue light that has entered the interior from the lower surface of the green quantum dot-containing layer 20 is absorbed by the green quantum dots 24, and the green quantum dots 24 emit green light. Most of the green light emitted by the green quantum dots 24 travels inside the light-transmitting material 22 and exits outside from above the upper surface of the green quantum dot-containing layer 20. As a result, outside the upper surface of the green quantum dot-containing layer 20, blue light, red light, and green light are mixed to obtain white light.

[0020] Note that a part of the green light emitted by the green quantum dots 24 travels downward, exits from the lower surface of the green quantum dot-containing layer 20, and enters the interior of the encapsulating resin 12 from the upper surface of the light-emitting element package 10. However, the red phosphor 14, which is at least one of the KSF phosphor and the MGF phosphor, hardly absorbs green light. Therefore, for example, after being reflected by the inner surface of the resin package 3, it exits from the upper surface of the light-emitting element package 10, enters from the lower surface of the green quantum dot-containing layer 20, and there is green light that exits from the upper surface of the green quantum dot-containing layer 20. The presence of such green light contributes to the improvement of the extraction efficiency of the light-emitting device 100.

[0021] In the embodiment shown in FIG. 1, the green quantum dot-containing layer 20 and the encapsulating resin 12 (or the resin package 3) are separated. Thereby, an effect can be obtained that more reliably suppresses the heat generated by the light-emitting element 1 from being transmitted to the heat-sensitive green quantum dots 24. However, not limited to this, the green quantum dot-containing layer 20 and the encapsulating resin 12 (or resin package 3) may be in contact with each other. In this case, more light emitted from the light-emitting element package 10 enters the green quantum dot-containing layer 20, making it possible to further improve the extraction efficiency. Also, even if the green quantum dot-containing layer 20 and the encapsulating resin 12 (or resin package 3) are in contact with each other, since the light-emitting element 1 and the green quantum dots 24 are separated from each other to some extent, the effect of suppressing the thermal degradation of the green quantum dots 24 can be obtained.

[0022] In the embodiment shown in FIG. 1, the light-emitting element package 10 has its mounting surface as the bottom surface (lower surface), and is a top-view type light-emitting element package in which the surface on the side opposite to the light extraction surface is the mounting surface (for example, the upper surface is the light extraction surface and the lower surface is the mounting surface). However, not limited to this, the light-emitting element package 10 may be configured as a so-called side-view type in which the surface adjacent to the light extraction surface is the mounting surface. Also, in the embodiment shown in FIG. 1, the light-emitting element package 10 including the resin package 3 is used, but not limited to this. Instead of the light-emitting element package 10, a so-called package-less form in which a phosphor layer containing the red phosphor 14 is formed on the surface of the light-emitting element 1 without using a resin package may be used.

[0023] Next, details of each element of the light-emitting device 100 will be shown. 1) Light-emitting element The light-emitting element 1 may be any known light-emitting element as long as it emits blue light (the emission peak wavelength is in the range of 435 to 465 nm), and may be a blue LED chip. The light-emitting element 1 may include a semiconductor laminate, and preferably includes a nitride semiconductor laminate. The semiconductor laminate (preferably a nitride semiconductor laminate) may have, in order, a first semiconductor layer (for example, an n-type semiconductor layer), a light-emitting layer, and a second semiconductor layer (for example, a p-type semiconductor layer). As a preferable nitride semiconductor material, specifically, In X Al Y Ga 1-X-YN (0 ≤ X, 0 ≤ Y, X + Y ≤ 1) may be used. The film thickness and layer structure of each layer may be those known in the art.

[0024] 2) Red phosphor The red phosphor 14 is at least one of a KSF phosphor and an MGF phosphor. The KSF phosphor and the MGF phosphor have the advantage of hardly absorbing green light and thus hardly causing secondary absorption. Further, it is characterized in that the full width at half maximum of the emission peak is 35 nm or less, preferably 10 nm or less. Hereinafter, the KSF phosphor and the MGF phosphor will be described in detail.

[0025] (KSF phosphor) The KSF phosphor is a red phosphor whose emission wavelength peak is in the range of 610 to 650 nm. Its composition is represented by the following general formula (1). A2[M 1-a Mn 4+ a F6] (1) (In the formula, A is at least one selected from the group consisting of K + , Li + , Na + , Rb + , Cs + and NH4 + ; M is at least one element selected from the group consisting of Group 4 elements and Group 14 elements; and a satisfies 0 < a < 0.2.)

[0026] The full width at half maximum of the emission peak of the KSF phosphor is 10 nm or less. Regarding this KSF phosphor, reference may be made to Japanese Patent Application No. 2014-122887 previously filed by the applicant of the present application.

[0027] An example of a method for manufacturing a KSF phosphor will be described. First, KHF2 and K2MnF6 are weighed so as to obtain a desired composition ratio. The weighed KHF2 is dissolved in an HF aqueous solution to prepare Solution A. Also, the weighed K2MnF6 is dissolved in an HF aqueous solution to prepare Solution B. Further, an aqueous solution containing H2SiF6 is prepared so as to have a desired composition ratio to obtain Solution C containing H2SiF6. Then, while stirring Solution A at room temperature, Solutions B and C are each added dropwise. After subjecting the obtained precipitate to solid-liquid separation, it is washed with ethanol and dried, whereby a KSF phosphor can be obtained.

[0028] (MGF phosphor) MGF is a red phosphor that emits deep red fluorescence. That is, the peak of its emission wavelength is 650 nm or longer on the longer wavelength side than that of the KSF phosphor, and it is a phosphor activated by Mn 4+ An example of the composition formula is 3.5MgO·0.5MgF2·GeO2:Mn 4+ represented by. The full width at half maximum of the MGF phosphor is 15 nm or more and 35 nm or less.

[0029] In the MGF phosphor, part of the Mg element of MgO in its composition may be substituted with other elements such as Li, Na, K, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, V, Nb, Ta, Cr, Mo, W, etc., and the luminous efficiency may also be improved by substituting part of the Ge element in GeO2 with other elements such as B, Al, Ga, In, etc. Preferably, by substituting both elements of Mg and Ge with both elements of Sc and Ga, respectively, the luminous intensity of light in the wavelength region of 600 to 670 nm, which is called deep red, can be further improved.

[0030] The MGF phosphor is a phosphor represented by the following general formula (2). (x-a)MgO·(a / 2)Sc2O3·yMgF2·cCaF2·(1-b)GeO2·(b / 2)Mt2O3:zMn 4+ (2) (wherein x, y, z, a, b, and c satisfy 2.0 ≤ x ≤ 4.0, 0 < y < 1.5, 0 < z < 0.05, 0 ≤ a < 0.5, 0 < b < 0.5, 0 ≤ c < 1.5, and y + c < 1.5, and Mt is at least one selected from Al, Ga, and In.)

[0031] In General Formula (2), by setting 0.05 ≤ a ≤ 0.3 and 0.05 ≤ b < 0.3, the luminance of the further-emitted red light can be improved. For the MGF phosphor, reference may be made to Japanese Patent Application No. 2014-113515 previously filed by the applicant of the present application.

[0032] An example of the method for manufacturing the MGF phosphor according to an embodiment of the present invention will be described. First, MgO, MgF2, Sc2O3, GeO2, Ga2O3, and MnCO3 are weighed so as to have a desired composition ratio as raw materials. After mixing these raw materials, the mixed raw materials are filled into a crucible and then fired at 1000 to 1300 ° C in the atmosphere to obtain them.

[0033] 3) Green quantum dots The green quantum dots 24 are semiconductor materials, for example, compound semiconductors such as II-VI group, III-V group, or IV-VI group, more specifically, CdSe, core-shell type CdS x Se 1-x / ZnS, GaP, and other nano-sized particles. The green quantum dots 24 have, for example, a particle size (average particle size) of 1 to 20 nm. The green quantum dots 24 emit green light whose peak of the emission wavelength is in the range of 510 to 560 nm. The full width at half maximum of the emission peak of the green quantum dots 24 is 40 nm or less, preferably 30 nm or less and is small. The green quantum dots may be surface-modified or stabilized with a resin such as PMMA (polymethyl methacrylate). In this case, the particle size means the particle size of the core portion made of a semiconductor material, excluding the portion of the resin or the like attached for surface modification and stabilization.

[0034] 4) Translucent material The light-transmitting material 22 can transmit blue light, green light, and red light. Among the light emitted from the light-emitting element 1 and incident on the light-transmitting material 22, the light-transmitting material preferably transmits 60% or more, more preferably 70% or more, 80% or more, or 90% or more. Preferred examples of the light-transmitting material 22 include high-strain-point glass, soda glass (Na2O·CaO·SiO2), borosilicate glass (Na2O·B2O3·SiO2), forsterite (2MgO·SiO2), lead glass (Na2O·PbO·SiO2), and alkali-free glass. Alternatively, organic polymers (having forms of polymer materials such as flexible plastic films, plastic sheets, and plastic substrates composed of polymer materials) exemplified by polymethyl methacrylate (polymethyl methacrylate, PMMA), polyvinyl alcohol (PVA), polyvinyl phenol (PVP), polyethersulfone (PES), polyimide, polycarbonate (PC), polyethylene terephthalate (PET), polystyrene (PS), polyethylene naphthalate (PEN), cyclic amorphous polyolefin, polyfunctional acrylate, polyfunctional polyolefin, unsaturated polyester, epoxy resin, and silicone resin can be mentioned.

[0035] 5) Encapsulation resin The encapsulation resin 12 can transmit blue light and red light, and preferably can also transmit green light. Among the light emitted from the light-emitting element 1 and incident on the light-transmitting material 22, the encapsulation resin preferably transmits 60% or more, more preferably 70% or more, 80% or more, or 90% or more. Preferred examples of the encapsulation resin 12 include silicone resin, silicone-modified resin, epoxy resin, epoxy-modified resin, phenol resin, polycarbonate resin, acrylic resin, TPX resin, polynorbornene resin, or hybrid resins containing one or more of these resins. Among them, silicone resin or epoxy resin is preferred, and silicone resin having particularly excellent light resistance and heat resistance is more preferred.

[0036] 6) Resin package The resin package 3 may be made of any type of resin. Preferred resins include thermoplastic resins containing at least one of aromatic polyamide resins, polyester resins, and liquid crystal resins, or thermosetting resins containing at least one of epoxy resins, modified epoxy resins, phenolic resins, silicone resins, modified silicone resins, hybrid resins, acrylate resins, urethane resins, etc. The resin package 3 is preferably made of a white resin. This is because more of the light that reaches the resin package 3 among the light traveling inside the encapsulating resin 12 can be reflected.

[0037] 2. Embodiment 2 FIG. 2 is a schematic cross-sectional view of a light-emitting device 100A according to Embodiment 2 of the present invention. In the above-described light-emitting device 100, the encapsulating resin 12 contained the red phosphor 14. However, in the light-emitting device 100A, instead of the encapsulating resin 12 containing the red phosphor 14, the light-transmissive material 22 contains the red phosphor 14. Therefore, inside the light-transmissive material 22, the red phosphor 14 and the green quantum dots 24 are arranged, whereby the red phosphor 14 and the green quantum dots 24 are located at approximately the same distance from the light-emitting element 1.

[0038] The light-emitting element package 10A may have the same configuration as the light-emitting element package 10 of Embodiment 1, except that the encapsulating resin 12 does not contain the red phosphor 14. Also, the green quantum dot-containing layer 20A may have the same configuration as the green quantum dot-containing layer 20 of Embodiment 1, except that it contains the red phosphor 14 in addition to the green quantum dots 24.

[0039] As described above, in the light-emitting device 100 according to Embodiment 1, the red phosphor 14 is located closer to the light-emitting element 1 than the green quantum dots 24, and in the light-emitting device 100A according to Embodiment 2, the red phosphor 14 and the green quantum dots 24 are located at approximately the same distance from the light-emitting element 1. Each embodiment has different advantages. The advantages will be described below.

[0040] 1) Advantages of the light-emitting device 100 FIG. 3 is a schematic cross-sectional view for explaining the advantages of the light-emitting device 100. FIG. 3(a) is a schematic cross-sectional view showing an embodiment in which the red phosphor 14 is disposed inside the encapsulating resin 12, and FIG. 3(b) is a schematic cross-sectional view showing an embodiment in which the red phosphor 14 is disposed inside the light-transmissive material 22. As described above, the particle size of the red phosphor 14 is 20 to 50 μm, and the particle size of the green quantum dots 24 is 2 to 10 nm, with a difference in particle size of about two orders of magnitude. FIGS. 3(a) and 3(b) are schematic diagrams for more clearly showing the advantages of the light-emitting device 100 based on this difference in particle size. Compared with FIGS. 1 and 2, the difference in particle size between the red phosphor 14 and the green quantum dots 24 is more clearly shown.

[0041] Reference numeral 114 in FIG. 3(a) schematically shows (a part of) the red light emitted by the red phosphor 14X, which is one of the plurality of red phosphors 14, and reference numeral 124 schematically shows (a part of) the green light emitted by the green quantum dot 24X, which is one of the plurality of green quantum dots 24. Similarly, reference numeral 114A in FIG. 3(b) schematically shows (a part of) the red light emitted by the red phosphor 14Y, which is one of the plurality of red phosphors 14, and reference numeral 124A schematically shows (a part of) the green light emitted by the green quantum dot 24Y, which is one of the plurality of green quantum dots 24.

[0042] As shown in FIG. 3(b), when the red phosphor 14 with a large particle size is disposed in the light-transmissive material 22, the green light 124A emitted from the green quantum dot 24Y is scattered by the red phosphor 14 existing in its path and does not reach the upper surface of the green quantum dot-containing layer 20A. (In FIG. 3(b), the red light 114A exits outward from the upper surface of the green quantum dot-containing layer 20A, but the green light 124A does not reach the upper surface of the green quantum dot-containing layer 20A.) Such scattering of a part of the green light due to the presence of the red phosphor 14 with a large particle size in the green quantum dot-containing layer 20A can be a factor causing a slight decrease in the light-emitting efficiency.

[0043] In contrast, as shown in FIG. 3(a), the green quantum dot-containing layer 20 does not contain red phosphors 14 with large particle sizes, and except for the light-transmitting material 22, it only contains green quantum dots 24. Then, the possibility that the green light traveling through the green quantum dot-containing layer 20 is scattered by the green quantum dots 24 with extremely small particle sizes is quite low (in FIG. 3(a), the red light 114 and the green light 124 are coming out of the upper surface of the green quantum dot-containing layer 20 to the outside). Therefore, higher luminous efficiency can be obtained.

[0044] 2) Advantages of the light-emitting device 100A The green quantum dot-containing layer 20A of the light-emitting device 100A contains both the red phosphor 14 and the green quantum dots 24 as described above. Although the red phosphor 14 has less deterioration due to heat compared to the green quantum dots 24, by adopting such a configuration, it is possible to suppress the heat generated by the light-emitting element 1 from being transmitted to the red phosphor 14, and the deterioration of the red phosphor 14 can be more reliably suppressed. Also, since the red phosphor 14 and the green quantum dots 24 are arranged inside the light-transmitting material 22, it is only necessary to arrange the wavelength conversion material in the light-transmitting material 22, and it is not necessary to arrange the red phosphor 14 in the encapsulating resin 12, so the manufacturing process becomes simpler.

[0045] Note that as described above, in the light-emitting device 100A, the light-transmitting material 22 of the green quantum dot-containing layer 20A contains the red phosphor 14, and the encapsulating resin 12 of the light-emitting element package 10A does not contain the red phosphor 14, but both the light-transmitting material 22 of the green quantum dot-containing layer 20A and the encapsulating resin 12 of the light-emitting element package 10A may contain the red phosphor 14.

[0046] 3. Embodiment 3 FIG. 4 is a schematic cross-sectional view showing a liquid crystal display 200 using a light-emitting device 100B according to Embodiment 3 of the present invention. The light-emitting device 100B includes a light-emitting element package 10, a green quantum dot-containing layer 20, and a light guide plate 52 disposed between the light-emitting element package 10 and the green quantum dot-containing layer 20. In the embodiment shown in FIG. 4, a light guide plate 52 is disposed between the encapsulating resin 12 of the light-emitting element package 10 and the green quantum dot-containing layer 20. More specifically, the encapsulating resin 12 is disposed to face one side surface of the light guide plate 52, and the green quantum dot-containing layer 20 is disposed to face the upper surface of the light guide plate 52. In the embodiment shown in FIG. 4, the light-emitting element package 10 is of a top view type, but is not limited thereto, and may have other forms such as the above-described side view type.

[0047] The light-emitting device 100B may include a reflector 51 on the lower surface of the light guide plate 52 so as to reflect upward the light that has reached the lower surface of the light guide plate 52 among the light incident from the light-emitting element package 10 to the light guide plate 52 and direct it toward the upper surface of the light guide plate 52.

[0048] In the embodiment shown in FIG. 4, the light-emitting element package 10 is disposed at a distance from the light guide plate 52, but is not limited thereto. For example, the light-emitting element package 10 and the light guide plate 52 may be brought into contact with each other by bringing the encapsulating resin 12 or the resin package 3 into contact with the side surface of the light guide plate 52. The green quantum dot-containing layer 20 may be disposed in contact with the upper surface of the light guide plate 52, or may be disposed at a distance from the light guide plate 52.

[0049] A lower polarizing film 53A is disposed on the green quantum dot-containing layer 20. A liquid crystal cell 54 is disposed on the lower polarizing film 53A, and a color filter array 55 is disposed on the liquid crystal cell 54. The color filter array 55 includes a plurality of types of color filter portions corresponding to different colors that transmit only light of a specific color, such as a red color filter portion 55A, a green color filter portion 55B, and a blue color filter portion 55C. An upper polarizing film 53B is disposed on the color filter array 55.

[0050] Next, the operation of the liquid crystal display 200 will be described. A part of the blue light emitted by the light-emitting element 1 comes out of the encapsulating resin 12. Also, a part of the blue light emitted by the light-emitting element 1 is absorbed by the red phosphor 14 disposed within the encapsulating resin 12, and red light is emitted from the red phosphor 14, and this red light comes out of the encapsulating resin 12. That is, purple light mixed with blue light and red light is emitted from the light-emitting element package 10, and this purple light (blue light + red light) enters the green quantum dot-containing layer 20 through the light guide plate 52. A part of the blue light that has entered the green quantum dot-containing layer 20 is absorbed by the green quantum dots 24, and the green quantum dots 24 emit green light. As a result, white light mixed with blue light, green light, and red light is emitted from the upper surface of the green quantum dot-containing layer 20, and this white light enters the lower polarizing film 53A. A part of the white light (blue light + green light + red light) that has entered the lower polarizing film 53A passes through the lower polarizing film 53A and enters the liquid crystal cell 54. A part of the white light that has entered the liquid crystal cell 54 passes through the liquid crystal cell 54 and reaches the color filter array 55.

[0051] Each of the blue light, green light, and red light that has reached the color filter array 55 can pass through the corresponding filter portion. For example, the red light passes through the red color filter portion 55A, the green light passes through the green color filter portion 55B, and the blue light passes through the blue color filter portion 55C. A part of each of the blue light, green light, and red light that has passed through the color filter array 55 passes through the upper polarizing film 53B. Thereby, the liquid crystal display 200 can display a desired image. As described above, the red light emitted by the red phosphor 14 and the green light emitted by the green quantum dots 24 have a narrow half-value width at the emission peak, and thus have high color purity. Also, since more light can pass through the red color filter portion 55A and the green color filter portion 55B, the efficiency can be improved. The present invention includes the following aspects. Aspect 1: A light-emitting element that emits blue light, Quantum dots that absorb a part of the blue light emitted by the light-emitting element and emit green light, A KSF phosphor whose composition is represented by the following general formula (1) and which absorbs part of the blue light emitted by the light-emitting element and emits red light, and an MGF phosphor whose composition is represented by the following general formula (2) and which absorbs part of the blue light emitted by the light-emitting element and emits red light, and at least one of them, A light-emitting device characterized by including . A2[M 1-a Mn 4+ a F6] (1) (In the formula, A is at least one selected from the group consisting of K + , Li + , Na + , Rb + , Cs + and NH4 + . M is at least one element selected from the group consisting of Group 4 elements and Group 14 elements, and a satisfies 0 < a < 0.2.) (x - a)MgO·(a / 2)Sc2O3·yMgF2·cCaF2·(1 - b)GeO2·(b / 2)Mt2O3:zMn 4+ (2) (In the formula, x, y, z, a, b, and c satisfy 2.0 ≦ x ≦ 4.0, 0 < y < 1.5, 0 < z < 0.05, 0 ≦ a < 0.5, 0 < b < 0.5, 0 ≦ c < 1.5, and y + c < 1.5. Mt is at least one selected from Al, Ga, and In.) Aspect 2: A sealing resin that covers the light-emitting element, A quantum dot-containing layer that includes a light-transmitting material and the quantum dots and is disposed outside the sealing resin, The light-emitting device according to Aspect 1, characterized by including . Aspect 3: The light-emitting device according to Aspect 2, characterized in that the sealing resin contains the KSF phosphor. Aspect 4: The light-emitting device according to Aspect 2 or 3, characterized in that the quantum dot-containing layer is a sheet and is separated from the sealing resin. Aspect 5: The light-emitting device according to aspect 3 or 4, characterized in that a light guide plate is disposed between the sealing resin and the quantum dot-containing layer. Aspect 6: The light-emitting device according to aspect 5, characterized in that the sealing resin is disposed to face one side surface of the light guide plate, and the quantum dot-containing layer is disposed to face the upper surface of the light guide plate. Aspect 7: The light-emitting device according to aspect 2, characterized in that the KSF phosphor is disposed in the quantum dot-containing layer.

Description of reference numerals

[0052] 1 Light-emitting element 3 Resin package 10, 10A Light-emitting element package 12 Sealing resin 14 Red phosphor 20, 20A, Green quantum dot-containing layer 22 Translucent material 24, 24X, 24Y Green quantum dots 51 Reflector 52 Light guide plate 53A Lower polarizing film 53B Upper polarizing film 54 Liquid crystal cell 55 Color filter array 55A Red color filter section 55B Green color filter green 55C Blue color filter section 100, 100A, 100B Light-emitting device 114, 114A Red light 124, 124A Green light 200 Liquid crystal display

Claims

1. a red phosphor that absorbs a portion of the blue light emitted by the light-emitting element and emits red light; a green quantum dot that absorbs a portion of the blue light emitted by the light-emitting element and emits green light; A light-transmitting material; The green quantum dot-containing layer, wherein the half-width of the emission peak of the red phosphor is 35 nm or less.

2. The green quantum dot-containing layer of claim 1 , wherein the light-transmitting material is an organic polymer.

3. The green quantum dot-containing layer according to claim 1 , wherein the light-transmitting material is polymethylmethacrylate resin.

4. The green quantum dot-containing layer according to any one of claims 1 to 3, wherein the emission wavelength peak of the green quantum dots is 510 to 560 nm.

5. The green quantum dot-containing layer according to any one of claims 1 to 4, wherein the half-value width of the emission peak of the green quantum dots is 40 nm or less.

6. The green quantum dot-containing layer according to any one of claims 1 to 5, wherein the green quantum dots have a particle size of 1 to 20 nm.

7. a red phosphor that absorbs a portion of the blue light emitted by the light-emitting element and emits red light; a green quantum dot that absorbs a portion of the blue light emitted by the light-emitting element and emits green light; A light-transmitting material; The green quantum dot-containing layer, wherein the red phosphor is at least one of a KSF phosphor and a MGF phosphor.

8. 8. The green quantum dot-containing layer according to claim 7, wherein the red phosphor is a KSF phosphor, and the composition of the KSF phosphor is represented by the following general formula (1): A 2 [M 1-a Mn 4+ a F 6 ] (1) (Wherein, A is K + , Li + , Na + , Rb + , Cs + and N.H. 4 + M is at least one element selected from the group consisting of Group 4 elements and Group 14 elements, and a satisfies 0<a<0.

2.

9. 8. The green quantum dot-containing layer according to claim 7, wherein the red phosphor is an MGF phosphor, and the composition of the MGF phosphor is represented by the following general formula (2): (x-a)MgO・(a / 2)Sc 2 O 3 ・yMgF 2 ・cCaF 2 ・(1-b)GeO 2 ・(b / 2)Mt 2 O 3 :zMn 4+ (2) (In the formula, x, y, z, a, b, and c satisfy 2.0≦x≦4.0, 0<y<1.5, 0<z<0.05, 0≦a<0.5, 0<b<0.5, 0≦c<1.5, and y+c<1.5, and Mt is at least one selected from Al, Ga, and In.)

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