White light emitting device

Abstract

A white light emitting device, which is 2 Up to 60mA / mm 2 , preferably from 15A / mm 2 Up to 40mA / mm 2 and more preferably from 20 mA / mm 2 Up to 30mA / mm 2 The device comprises a substrate, at least one string of blue LED chips mounted on the substrate, and a phosphor material composition. The phosphor material composition comprises a narrow-band red phosphor that generates light having a peak emission wavelength in the range from 625 nm to 635 nm. For a CCT from 4000K to 6500K, the weight percentage of the narrow-band red phosphor is between 33 wt.% and 49 wt.%, or for a CCT from 2700K to 3500K, the weight percentage is in an amount from 60 wt.% to 70 wt.%.

Description

Technical Field

[0001] The present invention relates to the field of lighting and display devices. More specifically, the present invention relates to white light emitting devices. Background Art

[0002] Light emitting diodes (LEDs) are widely known as replacements for conventional incandescent light bulbs and / or fluorescent lamps in lighting and display devices. It is desirable to generate white with high color purity at high efficiency.

[0003] There are two main approaches to generating white from LEDs. The first is to use a combination of multiple LEDs of different emitting colors with different intensities. For example, a blue emitting LED, a red emitting LED, and a green emitting LED can be combined to produce white light. However, one problem with this approach is that the spectral power distribution of the component LEDs may be relatively narrow, i.e., may have a full width at half maximum (FWHM) of approximately between 10nm-30nm. Therefore, there is a wavelength range (e.g., 580nm) where it may be difficult to obtain high efficiency.

[0004] Another major approach is to use a monochromatic LED (with emission at a specific wavelength) in combination with a wavelength conversion material (such as a phosphor). In this way, the wavelength conversion material absorbs light of a specific wavelength from the LED and emits light at a different wavelength, typically at a longer wavelength (i.e., lower energy light). For example, a blue LED can be used with a yellow-green phosphor. However, the efficiencies currently achieved using this approach are limited.

[0005] Typical white light emitting devices have efficiencies in the range of 150 lm / W-200 lm / W, and the current density of the LED chips required to achieve these efficiencies is relatively high (typically around 0.2 A / mm 2 Up to 0.5A / mm 2 Therefore, there is a need for a high efficiency white light emitting device using LEDs that does not suffer from the above problems. Summary of the invention

[0006] In view of this, according to the claim, a high-efficiency white light emitting device is provided. In a first aspect of the present invention, a white light emitting device is provided, comprising: a substrate; at least one string of blue LED chips mounted on the substrate, having a dominant wavelength in the range from 445nm to 460nm; and a phosphor material composition, comprising: a yellow-green phosphor material, which generates light with a peak emission wavelength in the range from 520nm to 580nm; and a narrow-band red phosphor material, which generates light with a peak emission wavelength in the range from 625nm to 635nm; wherein for a CCT from 4000K to 6500K, the phosphor material composition includes the narrow-band red phosphor material in an amount from 33wt.% to 49wt.%, or for a CCT from 2700K to 3500K, includes the narrow-band red phosphor material in an amount from 60wt.% to 70wt.%; and wherein the device is suitable for emitting light at a CCT from 10mA / mm 2 Up to 60mA / mm 2 In the range of 15mA / mm 2 Up to 40mA / mm 2 and more preferably from 20 mA / mm 2 Up to 30mA / mm 2 At a blue LED chip input current density within the range of , white light output is generated with an efficiency of at least 230 lm / W.

[0007] Embodiments of the device have high efficiency at low LED input current density. Thus, this provides a white LED that is significantly more efficient than existing LEDs (150-200 lm / W), while also providing the light color required for general lighting applications. For example, the efficiency can be 230 lm / W to 235 lm / W, such as 230 lm / W, 231 lm / W, 232 lm / W, 233 lm / W, 234 lm / W, or 235 lm / W. As described below, embodiments provide this improvement by using a blue LED chip that is more efficient by applying a specific current density, and by using the described amount of narrow-band red phosphor in a wavelength conversion phosphor material (e.g., covering the blue LED chip to modify the wavelength of the light) to improve white spectrum efficiency.

[0008] and white LED device efficiency (Lm / W white ) are shown in the following equation:

[0009] Lm / W white = WPE blue chip xCE phosphor x PE white (1)

[0010] WPEblue chip is the wall socket efficiency,

[0011] CE phosphor is the phosphor conversion efficiency, and

[0012] PE white is the packaging efficiency.

[0013] The efficiency of a device is measured in lumens per watt and can be calculated using standard LED photometric techniques.

[0014] Referring to the first and second components of the white LED device efficiency mentioned in equation (1) above, for different CCT ranges, from 10 mA / mm 2 Up to 60mA / mm 2 The combination of a blue LED chip at a low current density within a range and a phosphor material composition includes a narrow-band red phosphor at a specific weight percentage, which contributes to a high efficiency of at least 230 lm / W in the group. The specific weight percentages of the narrow-band red phosphor materials are important because they determine the ratio of the narrow-band red phosphor material to the yellow-green phosphor material. The white light emitted from the device is composed of components of different colors, which come from the interaction of the blue LED chip with the phosphor material. By incorporating a specific weight percentage of the narrow-band red phosphor material, it has been found that the phosphor material composition provides improved device efficiency for white light emission.

[0015] Narrow-band red phosphor materials can have a FWHM of ≤10 nm over a peak emission wavelength range from 625 nm to 635 nm. The phosphor conversion efficiency of wide red emitter phosphors (i.e., those phosphors having a wider spectral emission profile than narrow-band red phosphors) is typically lower compared to green / yellow-green phosphors. The narrow spectral profile of the narrow-band red phosphor helps to reduce red spectral efficiency losses while maintaining a high color rendering index (CRI). CRI is a measure of color purity and is defined as the ability of a light source to accurately illuminate the color of an object, as if it were illuminated by an incandescent bulb or a natural light source. Therefore, it has been found that a specific combination of materials in the device results in a high efficiency white light emitting device with a high color rendering index.

[0016] The weight percentage of the narrow band red phosphor material present in the phosphor material composition is specific, depending on the desired correlated color temperature "CCT". The CCT is the temperature of a heated black body radiator having an emission that matches the color of a white light source. CCTs in the range of 2700K to 3500K are described as warm white with a yellower tint. CCTs of 4000K to 6500K are described as neutral white to cool white. Thus, in a first aspect, the device is (i) a device having a CCT from 4000K to 6500K (e.g., emitting light having a CCT from 4000K to 6500K), and the narrow-band red phosphor material is present in the composition in an amount from 33 wt.% to 49 wt.%; or (ii) a device having a CCT from 2700K to 3500K CCT (e.g., emitting light having a CCT from 2700K to 3500K), and the narrow-band red phosphor material is present in the composition in an amount from 60 wt.% to 70 wt.%. It has been found that this narrow range of narrow-band red phosphor materials is particularly efficient.

[0017] In some embodiments, for a CCT from 5000K to 6500K, the phosphor material composition includes the narrow-band red phosphor material in an amount from 33 wt. % to 43 wt. %.

[0018] In some embodiments, the phosphor material composition includes a yellow-green phosphor material in an amount from 44 wt.% to 74 wt.% for a CCT from 4000 K to 6500 K, or in an amount from 22 wt.%-45 wt.% for a CCT from 2700 K to 3500 K. In embodiments, the ratio of the yellow-green phosphor material to the narrow-band red phosphor material contributes to the white light color output, and therefore to the efficiency of the device.

[0019] In some embodiments, for CCT between 4000K and 6500K, the phosphor material composition includes the yellow-green phosphor material in an amount from 51 wt.% to 67 wt.%, and includes the narrow-band red phosphor material in an amount from 33 wt.% to 49 wt.%.

[0020] In some embodiments, for a CCT between 2700K and 3500K, the phosphor material composition further includes a broad-spectrum red phosphor material; and for a CCT between 2700K and 3500K, the phosphor material composition includes: the broad-spectrum red phosphor material in an amount from 1 wt.% to 4 wt.%; the yellow-green phosphor material in an amount from 30 wt.% to 35 wt.%; and the narrow-band red phosphor material in an amount from 64 wt.% to 66 wt.%.

[0021] In an embodiment, a broad spectrum red phosphor material refers to a phosphor having a FWHM value greater than or equal to 30 nm (e.g., this may be 70 nm-90 nm) (at an emission range from 590 nm to 700 nm). The broad spectrum red phosphor material (e.g., a nitride phosphor such as CaAlSiN 3 :Eu 2+ or Sr 2 Si 5 N 8 :Eu 2+ ) is advantageously incorporated into the phosphor composition within a specific CCT range between 2700K-3500K to help provide a warmer white light emission from the device.

[0022] In some embodiments, the phosphor material composition includes the narrow-band red phosphor material in an amount from 60 wt.% to 74 wt.% for a CCT of 2700 K, from 55 wt.% to 69 wt.% for a CCT of 3000 K, from 42 wt.% to 56 wt.% for a CCT of 4000 K, or from 26 wt.% to 40 wt.% for a CCT of 6500 K. These embodiments have been found to be particularly efficient for each respective CCT.

[0023] In some embodiments, the ccy position of the white light output is within a range of 0.02-0.03 above the blackbody curve. The chromaticity of a particular light source may be referred to as a "color point," which has coordinates (ccx, ccy) in a CIE (Commission Internationale de l'éclairage in French, or International Commission on Illumination in English) color space diagram. In the case of white, the "white point" may fall on a locus of chromaticity points corresponding to the color of light emitted by a blackbody radiator heated to a given temperature. This locus is referred to as the blackbody locus or BBL. It has been found that in the device, a specific increase of 0.02-0.03 in the ccy coordinate above the BBL may contribute to improved efficiency. The efficiency of the device is improved because the contribution from the yellow-green phosphor emission is higher than the contribution of the blackbody curve at a specific increase in the ccy coordinate. The yellow-green emission has a high phosphor conversion efficiency, and therefore, as this contribution increases, the overall device efficiency increases.

[0024] In an embodiment, the white light (output) may be above the BBL and at a distance of at least 5 SDCM, preferably at least 7 SDCM, more preferably at least 9 SDCM, even more preferably at least 10 SDCM, most preferably at least 15 SDCM from the BBL. The effect obtained is an improved performance of the white light emitting device according to the present invention. The reason is that high quality white light (output) is obtained with a (relatively) small amount of red light in the white light. In this way, problems with quenching (of the red phosphor) are (further) reduced.

[0025] In an embodiment, the white light (output) may have a color rendering index of at least 80, preferably at least 85, more preferably at least 88, most preferably at least 90. The white light emitting device according to the invention is particularly suitable for achieving such a high quality of light.

[0026] In some embodiments, the substrate and the string of blue LED chips are arranged as an LED filament. In order to generate sufficient lumen output, multiple blue LED chips on the substrate are required, and the LED filament has high design flexibility for chip size and substrate material combinations. Incorporating an LED filament into the device can mimic the traditional configuration of an incandescent bulb, but with greatly improved efficiency. The use of LED filaments in the embodiments is particularly beneficial because the efficiency is significantly improved without the need for, for example, a large heat sink. The efficiency associated with these LED filaments is in part due to the presence of multiple smaller, lower power LED chips than traditional LED filaments. Accordingly, it has been found that the LED filament / multiple filaments can contribute to higher efficiency of the device through lower drive currents.

[0027] The LED filament provides LED filament light and comprises a plurality of light emitting diodes (LEDs) arranged in a linear array. Preferably, the LED filament has a length L and has a width W, wherein L>5W. The LED filament may be arranged in a straight configuration or a non-straight configuration (such as, for example, a bent configuration, a 2D / 3D spiral or a helix). Preferably, the LEDs are arranged on an elongated carrier, such as, for example, a substrate, which may be rigid (e.g., made of polymer, glass, quartz, metal or sapphire) or flexible (e.g., made of polymer or metal (e.g., film or foil)).

[0028] In case the carrier comprises a first main surface and an opposing second main surface, the LEDs are arranged on at least one of these surfaces.The carrier may be reflective or light transmissive, such as translucent and preferably transparent.

[0029] The LED filament may include an encapsulant that at least partially covers at least a portion of the plurality of LEDs. The encapsulant may also at least partially cover at least one of the first major surface or the second major surface. The encapsulant may be a polymer material that may be flexible, such as, for example, silicone. In addition, the LED may be arranged to emit LED light, for example, light of different colors or spectra. The encapsulant may include a luminescent material that is configured to at least partially convert the LED light into converted light. The luminescent material may be a phosphor, such as an inorganic phosphor and / or a quantum dot or a quantum rod.

[0030] An LED filament may include multiple sub-filaments.

[0031] In some embodiments, the LED filament includes a sapphire substrate. Sapphire substrates have been found to be particularly efficient and can help provide additional efficiency to the device.

[0032] Each of the blue LED chips in the device can generate an output flux in the range of 2 lm to 4 lm. For example, one blue LED chip can contribute approximately 3 lm of flux output to the device.

[0033] In some embodiments, the device further comprises an encapsulant over the blue LED chip, the encapsulant comprising the phosphor material composition. The encapsulant can help seal the phosphor material composition in close proximity to the blue LED chip.

[0034] In some embodiments, the yellow-green phosphor material includes yttrium aluminum garnet (YAG), gallium-modified yttrium aluminum garnet GaYAG, or lutetium-modified yttrium aluminum garnet LuYAG. In some embodiments, the narrow-band red phosphor material includes K 2 SiF 6 :Mn 4+ (KSF). KSF phosphors are relatively sensitive to high temperatures because the phosphors tend to degrade at elevated temperatures. One advantage of the present invention is that the LED chip has a relatively low temperature during operation of the white light emitting device due to the relatively low LED chip input current density.

[0035] In some embodiments, for CCT between 4000K and 6500K, the cumulative spectral intensity ratio from 480nm to 600nm is higher than 50% of the total white spectrum from 380nm to 780nm; or for CCT between 2700K and 3500K, the cumulative spectral intensity ratio from 480nm to 600nm is higher than 45% of the total white spectrum.

[0036] In some embodiments, the blue LED chip size is 0.18mm 2 Up to 0.30mm 2It has been found that this is the optimal size range for blue LED chips in devices to help achieve high efficiency.

[0037] In some embodiments, the device includes two or three electrodes provided on the substrate. This type of arrangement may be referred to as a two-finger or three-finger layout. It has been found that by arranging the electrodes on the substrate in this way, the forward voltage V f Generally, the larger the number of electrode tracks / fingers, the higher the V f However, there is a fine balance between the reduction in forward voltage and the increase in inhibition of photoexcitation. Embodiments providing two rails have been found to be particularly efficient.

[0038] In some embodiments, the blue LED chip-to-chip distance is equal to or greater than 0.4 mm. The blue chip emission pattern is omnidirectional, and therefore, efficiency can be greatly improved by making the chip-to-chip distance greater than or equal to 0.4 mm. It has been found that at this distance, the absorption of side-emitting blue light by adjacent chips is reduced. As a result, PE white The distance between the blue LED chips and the chip is preferably greater than or equal to 0.5 mm. The distance between the blue LED chips and the chip is preferably greater than or equal to 0.5 mm. The distance between the blue LED chips and the chip is preferably greater than or equal to 0.5 mm. The distance between the blue LED chips and the chip is preferably greater than or equal to 0.5 mm. The distance between the blue LED chips and the chip is preferably greater than or equal to 0.5 mm.

[0039] In a second aspect, a white light emitting device is provided, comprising: a substrate; at least one string of blue LED chips mounted on the substrate, having a dominant wavelength in the range of 445nm to 460nm, wherein each blue LED chip is separated from an adjacent blue LED chip by a distance from the blue LED chip to the chip; and a phosphor material composition, comprising: a yellow-green phosphor material, which generates light having a peak emission wavelength in the range of 520nm to 580nm; and a narrow-band red phosphor material, which generates light having a peak emission wavelength in the range of 625nm to 635nm, wherein the distance from the blue LED chip to the chip is equal to or greater than 0.4mm. This can be achieved at a power supply of 10mA / mm 2 Up to 60mA / mm 2 In the range of 15 mA / mm 2 Up to 40mA / mm 2 and more preferably within the range of 20 mA / mm 2 Up to 30mA / mm 2At a blue LED chip input current density within the range of, a white light output is generated with an efficiency of at least 230 lm / W.

[0040] In some embodiments, for a CCT from 4000K to 6500K, the phosphor material composition includes a narrow-band red phosphor material in an amount from 26 wt.% to 56 wt.%, or for a CCT from 2700K to 3500K CCT, includes a narrow-band red phosphor material in an amount from 55 wt.% to 74 wt.%.

[0041] It has been found that the combination of the blue LED chip spacing and the weight percentage of the narrow-band red phosphor material contributes to the high efficiency of the device in this regard. As described above, a specific weight percentage of the narrow-band red phosphor material determines the ratio of the yellow-green phosphor to the narrow-band red phosphor in the phosphor material composition. Moreover, when the blue LED chip spacing distance is greater than or equal to 0.4 mm, the absorption of the lateral emission blue light of another chip is reduced, and according to Equation (1), the packaging efficiency of the device increases. Accordingly, it has been found that at the resulting yellow-green:narrow-band red ratio, when the blue LED chip spacing is greater than or equal to 0.4 mm, the overall efficiency of the device is extremely high.

[0042] In some embodiments, the phosphor conversion efficiency (CE phosphor ) can be improved by optimizing the phosphor formulation to increase the green relative spectral ratio. Since the green spectrum has a higher percentage of the eye sensitivity function weight, the calculated lumen output and efficiency are higher than those of the normal white spectrum. The white spectrum color coordinates are calculated from the spectral ratios of the red / green / blue spectra. A higher green spectral content will result in the LED having a relatively higher y coordinate than the normal white spectrum. In our study, when the y coordinate is shifted 0.011 - 0.030 higher than the center in the y coordinate at 4000K defined by the ANSI standard C78.377, the white LED efficiency can have an improvement of 2 - 5 percentage points.

[0043] The ANSI standard C78.377 is the American National Electric Lamp Standard - Specification for the Chromaticity of Solid State Lighting Products. Referring to Section 4 "Chromaticity", the chromaticity coordinates and the related color temperature (CCT) values used are based on the CIE chromaticity system. And the chromaticity of light is represented by chromaticity coordinates (such as (x, y)). The chromaticity of nominal white light can also be represented by the CCT and the distance from the Planckian locus. In the present disclosure, the CIE 1961 (x - y) diagram is used.

[0044] The coverage of the higher y coordinate color points can be described as follows:

[0045] 0.300 < x < 0.500; and

[0046] -2.3172x 2 +2.3653x–0.170 <y<-2.3172x 2 +2.3653x–0.146.

[0047] This can be done from 10mA / mm 2 Up to 60mA / mm 2 , and preferably at 20mA / mm 2 Up to 30mA / mm 2 At a blue LED chip input current density within the range of , white light output is generated with an efficiency of at least 230 lm / W.

[0048] In some embodiments, the defined higher y coordinate color point coverage can be described by MacAdam ellipses according to ANSI C78.376. MacAdam ellipses are a universal language for defining white color point coverage. Macadam ellipse coverage can be defined using the following parameters, including reference reference point color coordinates (Reference x, Reference y), ellipse parameters (G11 / G12 / G22), SDCM size (K). Since different CCTs have different reference points, the formula for Macadam ellipse coverage is:

[0049] G11*Δx 2 +2G12*Δx*Δy+G22*Δy 2 =1*K

[0050]

[0051]

[0052]

[0053] Δx means the distance in the x direction between the boundary point of the ellipse and the reference point (Reference x);

[0054] Δy refers to the distance in the y direction between the ellipse boundary point and the reference point (Reference y).

[0055] Furthermore, in an embodiment, the correlated color temperature (CCT) is particularly within about 15 SDCM (standard deviation of color matching) from the BBL (blackbody locus), particularly within about 10 SDCM from the BBL, and even more particularly within about 5 SDCM from the BBL (blackbody locus) or the blackbody curve.

[0056] Another way to describe the coverage of a MacAdam ellipse is to use the SDCM size (K), the major axis of the ellipse (a), the minor axis of the ellipse (b), and the ellipse rotation angle (θ). The conversion formulas between G11 / G12 / G22 and a / b / θ are listed below.

[0057] The coverage of the MacAdam ellipse varies with CCT. The following is a comparison of the coverage of the MacAdam ellipse for various CCT ranges.

[0058]

[0059] Example coverage of higher y-coordinate color points surrounding .

[0060] Here, E means the exponent of 10, for example, 5.15E+05=5.15×10 5 .

[0061] The term "luminescent material" in this context relates in particular to inorganic luminescent materials, which are sometimes also indicated as phosphors. These terms are known to the person skilled in the art.

[0062] In an embodiment, quantum dots may be applied and may optionally be embedded in a transmissive matrix, such as, for example, a polymer (such as PMMA or polysiloxane, etc.). Quantum dots are small crystals of semiconductor material, typically having a width or diameter of only a few nanometers. When excited by incident light, the quantum dots emit light whose color is determined by the size and material of the crystal. Therefore, light of a specific color can be produced by adjusting the size of the dots. Most known quantum dots with emission in the visible range are based on cadmium selenide (CdSe) with a shell, such as cadmium sulfide (CdS) and zinc sulfide (ZnS). Cadmium-free quantum dots, such as indium phosphide (InP) and copper indium sulfide (CuInS 2 ) and / or silver indium sulfide (AgInS 2 ). Quantum dots show very narrow emission bands, and therefore they show saturated colors. In addition, the emission color can be easily tuned by adjusting the size of the quantum dots. Any type of quantum dots known in the art can be used in the present invention. However, for reasons of environmental safety and concern, the use of cadmium-free quantum dots or at least quantum dots with a very low cadmium content may be preferred. Instead of quantum dots or in addition to quantum dots, other quantum confinement structures can also be used. In the context of the present application, the term "quantum confinement structure" should be understood as, for example, quantum wells, quantum dots, quantum rods, tripods, tetrapods or nanowires, etc.

[0063] In particular, the luminescent material is configured to convert at least a portion of the light source light into luminescent material light having an emission band having a wavelength in one or more of (a) a green light spectrum wavelength range and (b) a yellow light spectrum wavelength range, wherein the luminescent material comprises A3 B 5 O 12 : Ce type (garnet) luminescent material, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc. Therefore, the luminescent material light can be, for example, green light or yellow light (or in a specific embodiment, even orange light (depending on the composition of the garnet and the concentration of cerium). However, other embodiments are also possible, see below. In an embodiment, 0.05%-10%, even more particularly 0.05%-5%, such as 0.1%-5% of the A element comprises Ce. In particular, in an embodiment, 0.1%-3%, such as up to 2%, such as selected from the range of 0.1%-1.5%, such as at least more than 0.5% of the A element comprises Ce.

[0064] Alternatively or additionally, the luminescent material may be, for example, M 2 Si 5 N 8 :Eu 2+ and / or MAlSiN 3 :Eu 2+ and / or Ca 2 AlSi 3 O 2 N 5 :Eu 2+ etc., wherein M includes one or more of Ba, Sr and Ca, and in the embodiment, particularly includes at least Sr. In a specific embodiment, the first luminophore may include a luminophore selected from (Ba, Sr, Ca)S:Eu, (Ba, Sr, Ca)AlSiN 3 :Eu and (Ba, Sr, Ca) 2 Si 5 N 8 :Eu. In these compounds, europium (Eu) is substantially or exclusively divalent and replaces one or more of the indicated divalent cations. Generally, Eu will be present in an amount not exceeding 10% of the cations; its presence will be particularly in the range of about 0.5% to 10%, more particularly in the range of about 0.5% to 5%, relative to the cation(s) it replaces. The term ":Eu" indicates that a portion of the metal ions is replaced by Eu (in these examples by Eu 2+ For example, assuming CaAlSiN 3 :Eu contains 2% Eu, so the correct chemical formula can be (Ca 0.98 Eu 0.02 )AlSiN 3 .

[0065] Any of the above aspects may be provided alone or in combination with any of the above embodiments.

[0066] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

[0068] Figure 1 A schematic diagram of a white light emitting device according to an embodiment of the present invention is shown.

[0069] Figure 2 A schematic diagram of a white light emitting device according to an embodiment of the present invention is shown.

[0070] Figure 3A The substrate and blue LED string are shown as the LED filament in the device, and

[0071] Figure 3B A device configured as an LED filament bulb according to one embodiment of the present invention is shown.

[0072] Figure 4A-4B Two and three interdigitated electrode tracks are shown respectively on a substrate of a white light emitting device.

[0073] Figure 5A Shown is a graph of efficiency versus current density for a white light emitting device comprising an array of blue LED chips.

[0074] Figure 5B Shown is a graph of the wall plug efficiency (WPE) of a series of blue LED chips (without phosphor covering over the LED chips) versus the current density of the current flowing through the chips.

[0075] Figure 6 A- Figure 6 C shows a graph of relative radiant power versus wavelength for a device including a phosphor material composition comprising: in 6A) only a green phosphor; Figure 6 In B) a green phosphor and a broad-spectrum red phosphor; and in 6C) a green phosphor and a narrow-band red phosphor.

[0076] Fig. 7A and Figure 7B Spectral power distributions for two different devices are shown; in FIG. 7a ), the device has a ccy on the blackbody locus, and in FIG. 7b ), the device has a ccy about 0.03 above the blackbody locus according to one embodiment of the present invention;

[0077] Figure 8 The human eye sensitivity function for different colors is shown;

[0078] Fig. 9 and Fig.10 shows the defined upper y color coordinate coverage above the ANSI C78.377 bin range; and

[0079] Fig.11 The parameters of the MacAdam ellipse are shown. DETAILED DESCRIPTION

[0080] In one aspect, a white light emitting device is provided, comprising: a substrate; at least one string of blue LED chips mounted on the substrate, having a dominant wavelength in the range of from 445 nm to 460 nm; and a phosphor material composition comprising: a yellow-green phosphor material, which generates light with a peak emission wavelength in the range of from 520 nm to 580 nm; and a narrow-band red phosphor material, which generates light with a peak emission wavelength in the range of from 625 nm to 635 nm; wherein for a CCT from 4000K to 6500K, the phosphor material composition includes the narrow-band red phosphor material in an amount from 33 wt.% to 49 wt.%, or for a CCT from 2700K to 3500K, includes the narrow-band red phosphor material in an amount from 60 wt.% to 70 wt.%; and wherein the device is suitable for emitting light at a power of from 10 mA / mm 2 Up to 60mA / mm 2 At an input current density of blue LED chips within the range, white light output is generated with an efficiency of at least 230 lm / W.

[0081] In embodiments, the weight percentage of phosphor material in the phosphor material composition of a device may vary and depend on the desired CCT.

[0082] For the narrow-band red phosphor, for a CCT from 4000K to 6500K, the weight percentage is from 26 wt.% to 56 wt.%. For example, the weight percentage can be from 33 wt.% to 49 wt.%. In some embodiments, the weight percentage can also be from 44 wt.% to 54 wt.%. In other embodiments, for a CCT of 4000K, this can be 49%. For a CCT from 5000K to 6000K, the weight percentage can also be from 33 wt.% to 43 wt.%, and in other embodiments, 38 wt.%. For a CCT from 2700K to 3500K, the weight percentage of the narrow-band red phosphor is from 55 wt.% to 74 wt.%. For example, the weight percentage can be from 64 wt.% to 66 wt.%. More specifically, the weight percentage of the narrow-band red phosphor material for the corresponding CCT can be: for 2700K, between 60wt.% and 74wt.%, and in another embodiment, 67wt.%; for 3000K, between 55wt.% and 69wt.%, and in another embodiment, 62wt.%; for 4000K, between 42wt.% and 56wt.%, and in another embodiment, 49wt.%; and for 6500K, between 26wt.% and 40wt.%, and in another embodiment, 33wt.%.

[0083] For the yellow-green phosphor material, the yellow-green phosphor weight material percentage may be from 44 wt.% to 74 wt.% for a CCT from 4000K to 6500K. For a CCT from 2700K to 3500K, the yellow-green phosphor weight percentage may be from 22 wt.% to 45 wt.%.

[0084] Thus, for a CCT of 4000K, an example of weight percentages in embodiments of the present invention may be 49 wt. % narrow band red phosphor and 51 wt. % yellow-green phosphor, and for a CCT of 6500K, 33 wt. % narrow band red phosphor and 67 wt. % yellow-green phosphor.

[0085] The weight percentage of the broad spectrum red phosphor material may be from 1 wt.% to 4 wt.%. For example, the weight percentage may be 3 wt.%. Therefore, for a CCT of 2700K, an example of a device including a broad red phosphor according to an embodiment of the present invention may include: 67 wt.% of a narrow band red phosphor; 30 wt.% of a yellow-green phosphor and 3 wt.% of a broad spectrum red phosphor. For a CCT of 3000K, an example of another device including a broad red phosphor according to an embodiment of the present invention may include: 62 wt.% of a narrow band red phosphor; 35 wt.% of a yellow-green phosphor and 3 wt.% of a broad spectrum red phosphor.

[0086] Embodiments for devices including LED filaments may include single or multiple LED filaments arranged in a variety of ways. For example, single or multiple LED filaments may be arranged in various shapes such as spiral(s), coil(s), ring(s), or rod(s) within a bulb or any alternative housing shape such as a cube, cylinder, or ellipsoid. The LED filament may include various types of substrates such as glass or ceramic or sapphire. In particular, sapphire substrates in LED filaments may provide an additional 1%-2% efficiency gain due to their increased transparency (compared to glass or ceramic substrates), which contributes to more backside white light output.

[0087] Embodiments including two- or three-finger layouts may be arranged in a variety of ways, and a device may include a single two- or three-finger layout or multiple two- or three-finger layouts.

[0088] The size of the blue LED chips in the embodiments of the present invention may also vary. In some cases, the size is between 0.18 mm 2 -0.30mm 2 In some embodiments, the chip size is 0.2 mm 2 .

[0089] The present invention will be described with reference to the accompanying drawings. Figure 1 A first embodiment of the present invention is shown in FIG. A white light emitting device 1 includes a blue LED chip 2 mounted on a substrate 3. A phosphor material composition including a yellow-green phosphor material 4 and a narrow-band red phosphor material 5 is deposited on the blue LED chip 2. The blue LED chip 2 and the phosphor material composition of the device are sealed inside the device by a sealant 7. Wiring 6 is provided to connect the blue LED 2.

[0090] exist Figure 1 In a specific implementation of the embodiment of , the device has a CCT of 4000K, and the phosphor material composition includes 49 wt. % of the narrow-band red phosphor 5 and 51 wt. % of the yellow-green phosphor 4 .

[0091] Figure 2 Another embodiment of the present invention is shown in FIG. A white light emitting device 101 includes a blue LED chip 102 mounted on a substrate 103. The phosphor material composition includes: a yellow-green phosphor material 104, a narrow-band red phosphor material 105, and a wide-spectrum red phosphor material 108 deposited on the blue LED chip 102. The blue LED chip 102 and the phosphor material composition of the device are sealed inside the device by a sealant 107. Wiring 106 is provided to connect the blue LED 102.

[0092] exist Figure 2 In a specific implementation of the embodiment of , the device has a CCT of 2700K, and the phosphor material composition of this embodiment includes: 67 wt % of a narrow band red phosphor, 30 wt % of a yellow-green phosphor, and 3 wt % of a broad spectrum red phosphor.

[0093] Figure 3A The LED filament 200 of a white light emitting device is shown. The LED filament 200 includes a substrate 203 and a string of blue LED chips 202. The string of blue LED chips 202 is mounted on the substrate 203. Each blue LED chip 202 has a 0.18 mm 2 Up to 0.30mm 2 size, and is separated from the adjacent blue LED chip 202 by a distance d of at least 0.4 mm.

[0094] Figure 3B Another embodiment of the present invention is shown, wherein the white light emitting device 204 comprises Figure 3A Four of the LED filaments 200 are LED filaments. In alternative embodiments, a different number of LED filaments may be used. Although not depicted, the device 204 also includes a phosphor material composition including a yellow-green phosphor material and a narrow-band red phosphor material deposited over the blue LED chip 016. As shown in FIG. 3 b , it shows a plurality of LED filaments 200 arranged in a bulb-shaped housing to mimic the appearance of a traditional incandescent bulb. The substrate 203 is a sapphire substrate.

[0095] Alternatively, in various embodiments, Figure 3A and Figure 3B The device 3 includes an alternative phosphor material composition, which includes: a yellow-green phosphor material, a narrow-band red phosphor material, and a broad-spectrum red phosphor material, which are deposited on a blue LED chip. The device has a CCT of 2700K, and the phosphor material composition of this embodiment includes: 67wt% narrow-band red phosphor, 30wt.% yellow-green phosphor, and 3wt.% broad-spectrum red phosphor.

[0096] Figure 4A Two electrodes are shown arranged as two interdigitated elongated tracks 310 on a substrate 302 of a white light emitting device 300. This arrangement of electrode tracks is referred to as a two-finger layout. Two solder pads 311 are arranged on the substrate 302 and connected to the interdigitated electrode tracks 310. Alternatively, Figure 4B 4 shows three electrodes arranged as three interdigitated elongated tracks 410 on a substrate 402 of a white light emitting device 400. This arrangement is referred to as a three-finger layout. Two solder pads 411 are arranged on the substrate 402 and connected to the interdigitated electrode tracks 410. In an embodiment, the white light emitting device may include Figure 4A and Figure 4B The two-finger layout 300 or the three-finger layout 400 of the embodiment can be used. Such devices 300 and 400 can also include a blue LED chip mounted on a substrate. A phosphor material composition including a yellow-green phosphor material and a narrow-band red phosphor material is deposited on the blue LED chip. The device has a CCT of 4000K, and the phosphor material composition of these embodiments includes 49 wt.% of a narrow-band red phosphor and 51 wt.% of a yellow-green phosphor.

[0097] Figure 5A The efficiency curve of a white light emitting device including a series of blue LED chips at applied current density is shown. It has been found through experiments that the range of applied current density that gives the best efficiency of the device according to the embodiment of the invention is 10mA / mm 2 -60mA / mm 2 and preferably between 20 mA / mm 2 -30mA / mm 2 and in some embodiments, it is 25 mA / mm 2 After this range, the efficiency of the device drops. When used with the particular phosphor material compositions and / or other efficiency improvements disclosed herein, it has been found that the efficiency can unexpectedly be further improved at this current density to provide increased lm / W output. Figure 5B Figure 1 shows the wall plug efficiency (WPE) curves for a series of blue LED chips (without phosphor covering the LED chips) at applied current density. Figure 5A Compared to the curves in Figure 2, the WPE (of the blue LED chip) decreases much more slowly than the efficiency (of the white light emitting device) as the current density increases beyond the peak value, e.g. Figure 5A Medium, about 10mA / mm 2 and 60mA / mm 2 Both reach 230lm / W, but Figure 5B Medium, 60mA / mm 2WPE is higher than 10mA / mm 2 The WPE of the white light emitting device is shown in Figure 1, with a gap of G. The reason for this rapid decrease in efficiency with respect to current density in a white light emitting device is the thermal sensitivity of the narrow band red phosphor material (e.g., KSF phosphor). The combination of the phosphor composition according to the present disclosure and the setting of a specific current density together promote an increased lm / W output of up to 230 lm / W.

[0098] Figure 6 A shows the spectral power distribution of a device not according to the invention, which comprises only yellow-green phosphor material in the phosphor material composition. Relatively high efficiency can be achieved using only yellow-green phosphor material, but this is detrimental to the color rendering index. Figure 6 B shows the spectral power distribution of a device not according to the present invention, the device comprising a phosphor material composition comprising both a green phosphor material and a broad red phosphor material. Figure 6 Compared to the distribution of the device shown in A, the color rendering index properties are improved. Figure 6 C shows the spectral power distribution of a device according to the present invention having a green phosphor and a narrow band red phosphor in the phosphor material composition. In this example, the color rendering index properties of the device are greatly improved, and the red radiant powder appears much higher than the other two devices.

[0099] Radiant power is measured in Watts and is defined as the amount of light emitted from a light source regardless of the direction from which the light is emitted at each wavelength. In an embodiment, radiant power measurements are performed using a spectrophotometer or spectroradiometer connected to an integrating sphere.

[0100] Fig. 7A The spectral power distribution of a device not according to an embodiment of the present invention is shown for a CCT of 4000K. Figure 7B The spectral power distribution of a device according to one embodiment of the present invention is shown. Due to the incorporation of a narrow band red phosphor within a specific phosphor weight percentage range at a CCT of 4000K, it can be seen that the device has a much higher efficiency.

[0101] Examples of phosphor material compositions within devices

[0102] The following is an example of an apparatus according to an embodiment of the present invention, having Figure 5A The current density and resulting efficiency are shown in .

[0103] Table 1

[0104]

[0105] These examples include the preferred amount of narrow-band red phosphor material in the device for a given CCT. It has been found that the resulting ratio of narrow-band red phosphor to yellow-green phosphor within the phosphor material composition exhibits the highest device efficiency at low blue LED chip input current density within a specific range. This contributes to the overall device efficiency due to the increase in phosphor conversion efficiency as described in reference to equation (1).

[0106] By incorporating other above-mentioned features into the device, such as LED filament, blue LED chip spacing greater than 0.4 mm, and two-finger layout (in addition to the preferred narrow-band red phosphor material weight percentages in Table 1), the efficiency of the device can be further improved to above 230 lm / W. This is due to the corresponding increase in wall socket efficiency and packaging efficiency as discussed with reference to equation (1).

[0107] Accordingly, it has been found that, at the specific weight percentages given in Table 1, including: 0.2 mm 2 chip size; two-finger layout; chip spacing greater than 0.5mm, and 0.025A / mm 2 The device with lower input current density of blue LED chip can have the highest maximum white LED efficiency point.

[0108] These examples include the preferred amount of narrow-band red phosphor material in the device for a given CCT. It has been found that the resulting ratio of narrow-band red phosphor to yellow-green phosphor within the phosphor material composition exhibits the highest device efficiency at low blue LED chip input current density within a specific range. This contributes to the overall device efficiency due to the increase in phosphor conversion efficiency as described in reference to equation (1).

[0109] By incorporating other above-mentioned features into the device, such as LED filament, blue LED chip spacing greater than 0.4 mm, and two-finger layout (in addition to the preferred narrow-band red phosphor material weight percentages in Table 1), the efficiency of the device can be further improved to above 230 lm / W. This is due to the corresponding increase in wall socket efficiency and packaging efficiency as discussed with reference to equation (1).

[0110] Figure 8 The human eye sensitivity function for different colors is shown. The green spectrum has the highest weight percentage compared to red or blue.

[0111] Fig. 9 and Fig.10The higher y color coordinate coverage above the ANSI C78.377 bin range is shown as defined to achieve higher efficiency in white. The "bin range" refers to the chromaticity specifications for SSL products defined in Annex A "Seven-Step Quadrangle" of ANSI C78.377. Fig. 9 The CIE 1931 diagram shows upper and lower color ranges with higher ccy coordinates than the ANSI C78.377 bin range. Fig.10 , the CIE 1931 diagram shows an example of a MacAdam ellipse range according to ANSI standard C78.376 that has a higher ccy coordinate than the ANSI C78.377 bin range.

[0112] Fig.11 The parameters a / b / θ of the Macadam ellipse are shown.

[0113] By studying the drawings, the disclosure and the appended claims, those skilled in the art can understand and implement variations to the disclosed embodiments when implementing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0114] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0115] If the term "suitable for" is used in the claims or the specification, it should be noted that the term "suitable for" is intended to be equivalent to the term "configured to".

[0116] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A white light emitting device, comprising: a substrate; at least one string of blue LED chips, mounted on the substrate and having a peak wavelength in the range from 445 nm to 460 nm; and a phosphor material composition, comprising: a yellow-green phosphor material that generates light having a peak emission wavelength in the range from 520 nm to 580 nm; and a narrow-band red phosphor material that generates light having a peak emission wavelength in the range from 625 nm to 635 nm; wherein for a CCT from 4000K to 6500K, the phosphor material composition comprises the narrow-band red phosphor material in an amount from 33 wt.% to 49 wt.%, or for a CCT from 2700K to 3500K, the phosphor material composition comprises the narrow-band red phosphor material in an amount from 60 wt.% to 70 wt.%; and The device is suitable for the 2 Up to 60mA / mm 2 At a blue LED chip input current density within the range of , white light output is generated with an efficiency of at least 230 lm / W.

2. The device according to claim 1, wherein the input current density of the blue LED chip is 20 mA / mm 2 Up to 30mA / mm 2 within the range.

3. The device according to claim 1 or claim 2, wherein for a CCT from 5000K to 6500K, the phosphor material composition comprises the narrow-band red phosphor material in an amount from 33 wt.% to 43 wt.

4. The device according to claim 1 or claim 2, wherein for a CCT from 4000K to 6500K, the phosphor material composition comprises the yellow-green phosphor material in an amount from 44 wt.% to 74 wt.%, or for a CCT from 2700K to 3500K, the phosphor material composition comprises the yellow-green phosphor material in an amount from 22 wt.% to 45 wt.

5. The device according to claim 1 or claim 2, wherein for a CCT from 4000K to 6500K, the phosphor material composition comprises the yellow-green phosphor material in an amount from 51 wt.% to 67 wt.% and comprises the narrow-band red phosphor material in an amount from 33 wt.% to 49 wt.

6. The device according to claim 1 or claim 2, in, for a CCT between 2700K and 3500K, the phosphor material composition further comprises a broad-spectrum red phosphor material; and wherein, for a CCT between 2700K and 3500K, the phosphor material composition comprises: the broad-spectrum red phosphor material in an amount from 1 wt.% to 4 wt.%; the yellow-green phosphor material in an amount from 30 wt.% to 35 wt.%; and the narrow-band red phosphor material in an amount from 64 wt.% to 67 wt.

7. A white light emitting device, comprising: a substrate; at least one string of blue LED chips, mounted on the substrate and having a peak wavelength in the range from 445 nm to 460 nm; and a phosphor material composition, comprising: a yellow-green phosphor material that generates light having a peak emission wavelength in the range from 520 nm to 580 nm; and a narrow-band red phosphor material that generates light having a peak emission wavelength in the range from 625 nm to 635 nm; The device is suitable for the 2 Up to 60mA / mm 2 A white light output is generated at an efficiency of at least 230 lm / W at a blue LED chip input current density within a range of , and wherein the color point (x, y) of the white light output is within the following range relative to the chromaticity specification for SSL products defined in the 7-step quadrilateral of Annex A of ANSI Standard C78.377: 0.300 < x < 0.500; and <h2 style=";text-align:left;direction:ltr">-2.3172x<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +2.3653x-0.170 <y<-2.3172x <h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +2.3653x–0.146; where x and y are the chromaticity coordinates according to the CIE 1931 color diagram.

8. The device of claim 7, wherein the color point of the white light output ranges above a black body locus and is at least 5 SDCM from the black body locus.

9. A device according to claim 7 or claim 8, wherein the device is adapted to operate at from 15 mA / mm 2 Up to 40mA / mm 2 At a blue LED chip input current density within the range of , white light output is generated with an efficiency of at least 230 lm / W.

10. A device according to claim 1 or claim 2 or claim 7 or claim 8, wherein the ccy position of the white light output is in the range of 0.02-0.03 above the black body curve.

11. The device of claim 1 or claim 2 or claim 7 or claim 8, wherein the substrate and the at least one string of blue LED chips are arranged as an LED filament.

12. The device of claim 1 or claim 2 or claim 7 or claim 8, wherein the yellow-green phosphor material comprises YAG, GaYAG or LuYAG; and wherein the narrow-band red phosphor material comprises K2SiF6:Mn 4 + .

13. The device according to claim 1 or claim 2 or claim 7 or claim 8, wherein for CCT between 4000K and 6500K, the cumulative spectral intensity ratio from 480nm to 600nm is higher than 50% of the total white spectrum from 380nm to 780nm; or Wherein for CCT between 2700K and 3500K, the cumulative spectral intensity ratio from 480nm to 600nm is higher than 45% of the total white spectrum.

14. The device according to claim 1 or claim 2 or claim 7 or claim 8, wherein the size of the blue LED chip is 0.18 mm 2 Up to 0.30mm 2 within the range.

15. The device of claim 1 or claim 2 or claim 7 or claim 8, wherein the distance from the blue LED chip to the chip is equal to or greater than 0.4 mm.

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