LED lamp filament

Abstract

An LED filament (1) configured to emit LED filament light (22) in operation, and comprising: a light transmissive elongate carrier (2) comprising a first main surface (3) and a second main surface (4) opposite the first main surface (3); a plurality of purple light LEDs (7) configured to emit purple light (8) in operation and arranged on the first main surface; a first encapsulation (9) covering the plurality of purple light LEDs (7) and at least a portion of the first main surface (3), and comprising a blue phosphor (10) configured to convert at least a portion of the purple light into blue light (11); a second encapsulant (12) completely covering the first encapsulant (9) and being an elongated encapsulant comprising a first green-yellow phosphor (13) configured to convert a portion of the blue light (11) into first green-yellow light (15) and a first red phosphor (14) configured to convert a portion of the blue light (11) into second green-yellow light (15); and the first red phosphor is configured to convert a portion of the blue light (11) into first red light (16); and a third encapsulation (17) covering at least a portion of the second main surface (4) and being an elongated encapsulation comprising a second green-yellow phosphor (18) and a second red phosphor (19), the second green-yellow phosphor being configured to convert a portion of the blue light (11) into second green-yellow light (20), and the second red phosphor is configured to convert a portion of the blue light (11) into second red light (21), the LED filament light (22) comprising the first green-yellow light (15), the first red light (16), the second green-yellow light (20) and the second red light (21).

Description

Technical Field

[0001] The present invention relates to an LED filament comprising a light-transmitting elongated carrier, the light-transmitting elongated carrier comprising a first main surface and a second main surface opposite to the first main surface.

[0002] As used herein, “violet light” should be understood to encompass light with a peak wavelength in the wavelength range of 380 nm–420 nm. As used herein, “blue light” should be understood to encompass light with a peak wavelength in the wavelength range of 430 nm–490 nm. As used herein, “greenish-yellow light” should be understood to encompass light with a peak wavelength in the wavelength range of 500 nm–580 nm. As used herein, “red light” should be understood to encompass light with a peak wavelength in the wavelength range of 600 nm–680 nm. Background Technology

[0003] The lighting trend is towards LED filament lamps. An LED filament lamp is a type of LED lamp designed to resemble a traditional incandescent bulb, featuring a visible filament for aesthetic and light distribution purposes, but with the high efficiency of a light-emitting diode.

[0004] US 2019 / 0191516 A1 discloses a white light emitting device or LED filament comprising an LED operable to generate excitation light including blue and / or violet light, a first phosphor associated with the LED to generate light with a peak emission wavelength in the range of 500 nm to 575 nm, and a second phosphor associated with a solid-state light emitter to generate light with a peak emission wavelength in the range of 600 nm to 650 nm, wherein the percentage decrease in conversion efficiency corresponding to an increase in excitation photon density exhibited by the second phosphor is greater than the percentage decrease in conversion efficiency corresponding to the same increase in excitation photon density exhibited by the first phosphor.

[0005] The aim is to improve the optical performance and / or appearance of LED filaments.

[0006] The problem of spotting in LED filaments also needs to be addressed, especially when the LED filaments are used in low-brightness (low-luminous-flux) mode. Summary of the Invention

[0007] The object of the present invention is to overcome this problem and to provide an LED filament having at least one of improved performance and improved appearance.

[0008] Another object of the present invention is to provide an LED filament that avoids or at least significantly reduces spots in the LED filament, which are particularly present when the LED filament is used in a low brightness (low luminous flux) mode.

[0009] According to a first aspect of the invention, this and other objectives are achieved by an LED filament configured to emit LED filament light in operation, the LED filament comprising a light-transmitting elongated carrier including a first main surface and a second main surface opposite to the first main surface; and a plurality of violet LEDs configured to emit violet light in operation, the violet light emitted by the plurality of violet LEDs having a wavelength between 380 nm and 420 nm. The plurality of violet LEDs are arranged on the first main surface, having a peak wavelength in the wavelength range of nm; a first package covering the plurality of violet LEDs and at least a portion of the first main surface, the first package including a blue phosphor configured to convert at least a portion of the violet light into blue light; a second package completely covering the first package, the second package being an elongated package including a first green-yellow phosphor and a first red phosphor, the first green-yellow phosphor being configured to convert a portion of the blue light into first green-yellow light, and the first red phosphor being configured to convert a portion of the blue light into first red light; and a third package covering at least a portion of the second main surface of the light-transmitting elongated carrier, the third package being an elongated package including a second green-yellow phosphor and a second red phosphor, the second green-yellow phosphor being configured to convert a portion of the blue light into second green-yellow light, and the second red phosphor being configured to convert a portion of the blue light into second red light, wherein the LED filament light includes the first green-yellow light, the first red light, the second green-yellow light, and the second red light.

[0010] Using this LED filament, a first encapsulation with blue phosphor was obtained, which essentially functions as a new light source. This results in an LED filament with improved optical performance and / or appearance.

[0011] Furthermore, for this type of LED filament, it is not the LED but the phosphor that becomes the new light source to pump the green-yellow and red phosphors. Since LEDs are point light sources, they are visible when the LED filaments are used in low-brightness mode. Therefore, and further because the first package including the blue phosphor is much larger and more elongated than the LED, an LED filament is provided that avoids or at least significantly reduces spots in the LED filament, which are particularly present when the LED filament is used in low-brightness (low luminous flux) mode.

[0012] The blue phosphor can be configured to completely convert violet light into blue light.

[0013] In this regard, the term "complete conversion" is intended to indicate that at least 95% or at least 97% of the incident light is converted. The resulting effect is a further improvement in the optical performance and appearance of the LED filament. This is because the blue phosphor is the only new light source used in this configuration to pump the green-yellow and red phosphors.

[0014] The purple light emitted by multiple purple LEDs can have a peak wavelength in the wavelength range of 400 nm to 420 nm.

[0015] The result is improved efficiency of the LED filament. This is because using higher wavelength violet light limits Stokes losses.

[0016] The blue phosphor can be a phosphate phosphor, which is configured to be effectively excited by violet light emitted by multiple violet LEDs and includes an emission peak wavelength in the wavelength range of 460-480 nm or 460-490 nm.

[0017] The effect achieved is improved central illumination of the human body by LED filaments. This is because light in this specific wavelength range is suitable for suppressing melatonin production.

[0018] The first green-yellow phosphor and the second green-yellow phosphor can be the same, and the first red phosphor and the second red phosphor can be the same.

[0019] Therefore, an LED filament with a particularly simple structure is provided.

[0020] Alternatively, the first green-yellow phosphor and the second green-yellow phosphor may be different from each other, and / or the first red phosphor and the second red phosphor may be different from each other.

[0021] The effect achieved is due to the improved light quality emitted by the LED filaments. This is because a different spectrum is used, thus providing a more continuous (white) spectrum.

[0022] One or both of the first and second green-yellow phosphors may be included. The luminescent material includes one or more of Y, La, Gd, Tb, and Lu, and one or both of the first and second red phosphors may be doped with tetravalent manganese. The luminescent material of the type wherein M' comprises an alkaline earth cation, M comprises a basic cation, and x is in the range of 0-1, wherein A comprises a tetravalent cation, such as one or more of silicon and titanium, and wherein X comprises a monovalent anion, including at least fluorine.

[0023] Alternatively, or additionally, one or both of the first and second greenish-yellow phosphors include a luminescent material, which may include... The luminescent material is of the type wherein A includes one or more of Y, La, Gd, Tb, and Lu, such as one or more of La and Y in the embodiments. In certain embodiments, as an alternative or addition to the garnet luminescent material, the luminescent material may include The type of luminescent material, wherein A includes one or more of Y, La, Gd, Tb and Lu, such as one or more of La and Y in the embodiments.

[0024] The achieved effect is that the LED filament is equipped with an optimal phosphor system. This is because the aforementioned phosphors, together with the blue phosphor, exhibit optimal light conversion.

[0025] One or both of the first and second green-yellow phosphors can be yttrium aluminum garnet phosphors with an absorption peak close to 450 nm and a main emission wavelength in the wavelength range of 540-560 nm.

[0026] This greenish-yellow phosphor has the advantage of primarily converting blue light and providing the main emission wavelength in the 540-560 nm range.

[0027] One or both of the first and second red phosphors may be KSF phosphors, which are configured to be excited by blue light having the strongest emission peak wavelength at 631 nm and a full width at half maximum (FWHM) of less than 30 nm.

[0028] KSF phosphors can be defined as phosphors doped with tetravalent manganese. The luminescent material comprises an alkaline earth cation, M comprises a basic cation, and x is in the range of 0-1, wherein A comprises a tetravalent cation, such as one or more of silicon and titanium, and X comprises a monovalent anion, including at least fluorine.

[0029] The relevant basic cations (M) are sodium (Na), potassium (K), and rubidium (Rb). Alternatively, lithium and / or cesium may also be used. In a preferred embodiment, M comprises at least potassium. In yet another embodiment, M comprises at least rubidium. The phrase "wherein M comprises at least potassium" means, for example, in molar... Of all the M cations, some include K. + Optionally, the remaining portion includes one or more other monovalent (basic) cations (see also below). In another preferred embodiment, M includes at least potassium and rubidium. Optionally, The luminescent material has a hexagonal phase. In yet another embodiment, The luminescent material has a cubic phase. For x=0, the composition is M2AX6.

[0030] The relevant alkaline earth cations (M') are magnesium (Mg), strontium (Sr), calcium (Ca) and barium (Ba), especially one or more of Sr and Ba.

[0031] The term "tetravalent manganese" refers to Mn 4+ This is a well-known luminescent ion. In the molecular formula described above, a portion of the tetravalent cation A (such as Si) is replaced by manganese. Therefore, doped with tetravalent manganese... It can also be expressed as The molar percentage of manganese, i.e., the percentage by which it substitutes for the tetravalent cation A, is typically in the range of 0.1-15%, particularly 1-12%, i.e., m is in the range of 0.001-0.15, particularly 0.01-0.12.

[0032] As stated above, X involves monovalent anions, but includes at least fluorine. Other optional monovalent anions may be selected from the group consisting of chlorine (Cl), bromine (Br), and iodine (I).

[0033] In one embodiment, This includes K2SiF6 (also referred to herein as the KSiF system). As described above, in another preferred embodiment, This includes KRbSiF6 (also referred to as the K,Rb system in this paper). As mentioned above, some silicon is replaced by manganese (i.e., the molecular formula can also be described as...). or Where m is as described above, or is described respectively as and Because manganese substitutes for a portion of the main lattice ions and has specific functions, it is also referred to as a "dopant" or "activator." Therefore, hexafluorosilicates are made with manganese (Mn). 4+ Doping or activation.

[0034] In a specific embodiment, the luminescent material may include Alternatively or additionally, in embodiments, the third luminescent material may include Alternatively or additionally, in embodiments, the third luminescent material may include In an embodiment, the third luminescent material may include From the above, we can conclude that "Si, Ti" can represent one or more of Si and Ti.

[0035] KSF-type red phosphors have the advantage of being particularly effectively excited by blue light.

[0036] The light-transmitting elongated carrier can have a transmittance of at least 60% or at least 80% in a wavelength range corresponding to the wavelength range of blue light emitted by the blue phosphor of the first encapsulation.

[0037] The resulting effect is an LED filament with an improved light distribution. The reason is that the new blue light source, i.e., the first encapsulant with blue phosphors, also provides sufficient light of the new blue light source in the opposite direction (i.e., through the carrier).

[0038] The first encapsulant has a minimum first thickness T1 measured perpendicular to the substrate, from the light output surface of the plurality of violet LEDs to the second encapsulant. The second encapsulant has a second thickness T2 of the violet LEDs measured perpendicular to the substrate at the position of the plurality of violet LEDs, from the first encapsulant to the light emitting surface of the second encapsulant, and T1 and T2 can be selected such that T1 > T2. For example, T1 ≥ 1.5 • T2 or T1 ≥ 2 • T2.

[0039] The resulting effect further improves the optical performance and / or appearance of the LED filament. The reason is that the first encapsulant is relatively thick while the second encapsulant is relatively thin.

[0040] The first encapsulant has a minimum first width W1 measured perpendicular to the first thickness T1. The second encapsulant has a second width W2 measured perpendicular to the second thickness T2. The third encapsulant has a third width W3 measured perpendicular to the third thickness T3, and W1, W2, and W3 can be selected such that W1 < W2 and / or W1 < W3. In addition, W2 can be equal to W3.

[0041] The first encapsulant has a first cross-sectional shape, and the first cross-sectional shape can be rectangular or square, with or without rounded corners opposite the contact points with the elongated carrier.

[0042] The second encapsulant has a second cross-sectional shape, and the second cross-sectional shape can be C-shaped or U-shaped to fit around the first encapsulant having the first cross-sectional shape.

[0043] The first encapsulant and the second encapsulant can form a continuous element.

[0044] The third encapsulant has a third cross-sectional shape, and the third cross-sectional shape can be rectangular or square, with or without rounded corners opposite the contact points with the elongated carrier.

[0045] The first green-yellow phosphor has a first concentration C1 in the first encapsulant. The first red phosphor has a second concentration C2 in the first encapsulant. The second green-yellow phosphor has a third concentration C3 in the second encapsulant. The second red phosphor has a fourth concentration C4 in the second encapsulant, and the first, second, third, and fourth concentrations can be selected such that (C1 + C2) / (C3 + C4) ≥ 1.5 or (C1 + C2) / (C3 + C4) ≥ 2.

[0046] The result is an improved appearance for the LED filament.

[0047] The reason is that by using a very low concentration in the third encapsulant, its thickness can be increased. In this way, the curvature difference of the encapsulants on both sides is reduced.

[0048] The first package has a minimum thickness T1, measured perpendicularly to the substrate, from the light output surface of the plurality of violet LEDs to the second package. The second package has a second thickness T2, measured perpendicularly to the substrate at the location of the plurality of violet LEDs, from the first package to the light-emitting surface of the second package. The third package has a third thickness T3, measured perpendicularly to the substrate at the location of the plurality of violet LEDs, from the second main surface to the light-emitting surface of the third package. The first, second, and third thicknesses are selected such that 1.3 ≥ T3 / (T1+T2) ≥ 0.7 or 2 ≥ T3 / (T1+T2) ≥ 0.5.

[0049] The result is an improved optical performance and / or appearance of the LED filament. This is because the encapsulation on both sides of the carrier has approximately the same thickness.

[0050] The third encapsulation can completely cover the second primary surface of the light-transmitting, slender carrier.

[0051] In this paper, the term "complete coverage" means covering at least 90% or at least 95% of the available surface area.

[0052] Therefore, LED filaments with a more uniform appearance are provided.

[0053] The elongated carrier also includes a first sub-surface and a second sub-surface opposite to the first sub-surface, the first sub-surface and the second sub-surface being connected to the first main surface and the second main surface, and the first sub-surface and the second sub-surface may be without a second encapsulation and a third encapsulation.

[0054] The result is improved manufacturability of LED filaments. This is because the first, second, and third encapsulants can be provided by dispensing an encapsulation material (e.g., silicone) comprising one or more phosphors.

[0055] The first encapsulation can completely cover the first main surface of the light-transmitting slender carrier.

[0056] In this paper, the term "complete" means at least 90% or at least 95% of the available surface area.

[0057] The effect achieved is improved optical performance of the LED filament. This is due to the new blue light source, i.e., the first encapsulation, which is therefore relatively large.

[0058] The light-transmitting elongated carrier also includes a first sub-surface and a second sub-surface opposite to the first sub-surface, the first sub-surface and the second sub-surface being connected to the first main surface and the second main surface, and the first sub-surface and the second sub-surface being at least partially covered by at least one of a second encapsulation and a third encapsulation.

[0059] The result is an improved appearance for the LED filament. This is because the blue converted light entering the carrier and exiting at the sub-surface is also converted.

[0060] The layer covering the first and second sub-surfaces may be a continuous layer consisting of at least one of the second and third encapsulations or including at least one of the second and third encapsulations.

[0061] In another embodiment, the LED filament light includes a portion of blue light, a first greenish-yellow light having a first spectral distribution having a first full width at half maximum (FWHM1) of at least 80 nm, a second greenish-yellow light having a second spectral distribution having a second full width at half maximum (FWHM2) of at least 80 nm, a first red light having a third spectral distribution having a third full width at half maximum (FWHM3) of less than 40 nm, a second red light having a fourth spectral distribution having a fourth full width at half maximum (FWHM4) of less than 40 nm, and blue light having a fifth spectral distribution having a fifth full width at half maximum (FWHM5) of at least 60 nm. The LED filament light is white light having a correlated color temperature in the range of 1700 K to 6500 K and a color rendering index of at least 85, preferably at least 90.

[0062] The result is that the LED filament can thus emit high-quality white light. This is due to the combination of broadband green-yellow light, narrow-band red light, and fairly broadband blue light.

[0063] In this embodiment, the LED filament light can be white light with a correlated color temperature in the range of 1700K to 6500K and / or a CRI of at least 80. Preferably, the correlated color temperature is in the range of 1700K to 3500K and / or the CRI is at least 85.

[0064] The present invention also relates to an LED lamp comprising at least one LED filament according to the invention. The lamp may include a connector and a housing. The housing may at least partially surround the LED filament (or multiple LED filaments). The connector may be configured to be electrically grounded and mechanically connected to a socket of the luminaire. The luminaire may have a mounting portion for mounting the luminaire to a ceiling or wall.

[0065] More specifically, the present invention also relates to an LED filament lamp, comprising: a connector configured to electrically and mechanically connect the LED filament lamp to a socket of a luminaire; and a housing that at least partially surrounds the LED filament lamp according to the present invention.

[0066] The present invention also relates to a lighting fixture comprising an LED lamp having at least one LED filament according to the present invention.

[0067] It should be noted that the present invention relates to all possible combinations of the features described in the claims. Attached Figure Description

[0068] This and other aspects of the invention will now be described in more detail with reference to the accompanying drawings, which illustrate embodiments of the invention.

[0069] Figure 1 A schematic cross-sectional view of an embodiment of an LED filament according to the present invention is shown.

[0070] Figure 2 It shows that according to Figure 1 A schematic longitudinal cross-sectional view of an embodiment of an LED filament.

[0071] Figure 3 A graph showing the intensity of an exemplary blue phosphor in an LED filament according to the present invention as a function of wavelength is shown.

[0072] Figure 4 A graph showing the intensity of an exemplary green-yellow phosphor in an LED filament according to the present invention as a function of wavelength is shown.

[0073] Figure 5 A graph showing the intensity of an exemplary red phosphor in an LED filament according to the present invention as a function of wavelength is shown.

[0074] Figure 6 A cross-sectional side view of a lamp including an LED filament according to the present invention is shown.

[0075] As shown in the figures, the dimensions of the layers and regions have been enlarged for illustrative purposes; therefore, the dimensions of the layers and regions are provided to illustrate the general structure of an embodiment of the invention. The same reference numerals consistently denote the same elements. Detailed Implementation

[0076] The invention will now be described more fully below with reference to the accompanying drawings, in which presently preferred embodiments of the invention are illustrated. However, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness and to fully convey the scope of the invention to those skilled in the art.

[0077] First refer to Figure 1 and Figure 2 The LED filament 1 according to the present invention is shown in both transverse and longitudinal cross-sectional views.

[0078] Typically, and regardless of the embodiment, the LED filament 1 is configured to emit LED filament light 22 in operation and includes a light-transmitting elongated carrier 2, a plurality of violet LEDs 7, a first package 9, a second package 12, and a third package 17.

[0079] The light-transmitting elongated carrier 2 and the LED filament 1 typically include a length direction L, a height direction H extending perpendicular to the length direction L, and a width direction W extending perpendicular to both the length direction L and the height direction H. The light-transmitting elongated carrier 2 and the LED filament 1 typically extend in the length direction L. The light-transmitting elongated carrier 2 includes a first main surface 3 and a second main surface 4. Viewed from the height direction H, the second main surface 4 is arranged opposite to the first main surface 3. The elongated carrier 2 also includes a first secondary surface 5 and a second secondary surface 6. Viewed from the width direction W, the second secondary surface is arranged opposite to the first secondary surface 5. The first secondary surface 5 and the second secondary surface 6 connect the first main surface 3 and the second main surface 4. The light-transmitting elongated carrier 2 may be, for example, a printed circuit board (PCB). The light-transmitting elongated carrier 2 may have a transmittance of at least 80% in a wavelength range corresponding to the wavelength range of blue light 11 emitted by the blue phosphor 10 included in the first package 9.

[0080] Multiple violet LEDs 7 are configured to emit violet light 8. The violet light 8 may include a peak wavelength in the wavelength range of 400 nm to 420 nm. The multiple violet LEDs 7 are arranged on the first main surface 3 of the elongated carrier 2. The multiple violet LEDs 7 are typically arranged in one or more rows extending along the length direction L of the elongated carrier—see [link to relevant documentation]. Figure 2 .

[0081] The first package 9 covers a plurality of purple LEDs 7. The first package 9 also covers at least a portion of the first main surface 3 of the elongated carrier 2. Alternatively, the first package 9 may completely cover the first main surface 3 of the light-transmitting elongated carrier 2. The first package 9 includes a blue phosphor 10 (see...). Figure 2 The blue phosphor 10 is configured to convert at least a portion of the violet light 8 into blue light 11. The blue phosphor 10 may be further configured to convert the violet light 8 completely into blue light 11. The first package 9 has a minimum thickness T1, measured perpendicular to the light-transmitting elongated carrier 2, from the light-emitting surface 23 of the plurality of violet LEDs 7 to the second package 12 (see...). Figure 1 ).

[0082] For example, the blue phosphor 10 may be a phosphate phosphor, such as a phosphate phosphor configured to be effectively excited by violet light emitted by a plurality of violet LEDs and including emission peak wavelengths in the 460-480 nm wavelength range. Figure 3 A graph depicting the intensity of such phosphate phosphors as a function of wavelength is shown.

[0083] The second encapsulation 12 completely covers the first encapsulation 9. The first secondary surface 5 and the second secondary surface 6 of the elongated carrier 2 may be without the second encapsulation 12 (see [reference]). Figure 1 Alternatively, the first secondary surface 5 and the second secondary surface 6 of the elongated carrier 2 may be at least partially covered by the second encapsulation 12. The second encapsulation 12 is an elongated encapsulation. The second encapsulation 12 includes a first greenish-yellow phosphor 13 and a first red phosphor 14 (see...). Figure 2 The second package 12 includes a second thickness T2, measured perpendicularly to the light-emitting surface 24 of the elongated carrier 2, from the first package 9 to the second package 12 at the locations of the plurality of violet LEDs 7 (see [link to previous section]). Figure 1 The first thickness T1 of the first package 9 can be selected to be greater than the second thickness T2 of the second package 12.

[0084] The first green-yellow phosphor 13 is configured to convert a portion of the blue light 11 into first green-yellow light 15. The first green-yellow phosphor 13 may, for example, include... The luminescent material is of the type wherein A includes one or more of Y, La, Gd, Tb, and Lu. The first encapsulant 9 includes a first greenish-yellow phosphor 13 of a first concentration of C1. For example, the first greenish-yellow phosphor 13 may be a yttrium aluminum garnet phosphor having an absorption peak close to 450 nm and a main emission wavelength in the range of 540-560 nm. Figure 4 The graph shows the intensity of such a yttrium aluminum garnet phosphor as a function of wavelength.

[0085] The first red phosphor 14 is configured to convert a portion of the blue light 11 into first red light 16. The first red phosphor 14 may be doped with tetravalent manganese. The luminescent material is of the type where M' represents an alkaline earth cation, M represents a basic cation, and x is in the range of 0-1, where A represents a tetravalent cation, such as one or more of silicon and titanium, and where X represents a monovalent anion, including at least fluorine. The first encapsulation 9 includes a first red phosphor 14 with a second concentration of C2. As an example, the first red phosphor 14 may be a KSF phosphor configured to be excited by blue light having the strongest emission peak wavelength at 631 nm and a full width at half maximum (FWHM) of less than 30 nm. Figure 5A graph depicting the intensity of such a KSF phosphor as a function of wavelength is shown.

[0086] The third encapsulation 17 covers at least a portion of the second primary surface 4 of the light-transmitting elongated carrier 2. The first secondary surface 5 and the second secondary surface 6 of the elongated carrier 2 may be without the third encapsulation 17 (see [link to documentation]). Figure 1 Alternatively, the first secondary surface 5 and the second secondary surface 6 of the elongated carrier 2 may be at least partially covered by the third encapsulation 17. The third encapsulation 17 is an elongated encapsulation. The third encapsulation 17 includes a second greenish-yellow phosphor 18 and a second red phosphor 19 (see...). Figure 2 The third package 17 includes a third thickness T3, measured perpendicularly to the light-transmitting elongated carrier 2 at the locations of the plurality of violet LEDs 7, from the second main surface 4 to the light-emitting surface 25 of the third package 17 (see [reference]). Figure 1 We can choose a first thickness T1, a second thickness T2, and a third thickness T3 such that the relation 1.3 ≥ T3 / (T1+T2) ≥ 0.7 is satisfied.

[0087] The second green-yellow phosphor 18 is configured to convert a portion of the blue light 11 into second green-yellow light 20. The second green-yellow phosphor 18 may be different from the first green-yellow phosphor 13. Alternatively, the second green-yellow phosphor 18 may be the same as the first green-yellow phosphor 13. The second green-yellow phosphor 18 may, for example, include... The luminescent material is of the type, wherein A includes one or more of Y, La, Gd, Tb, and Lu. The second encapsulant 12 includes a second greenish-yellow phosphor 18 of a third concentration of C3. For example, the second greenish-yellow phosphor 18 may be a yttrium aluminum garnet phosphor having an absorption peak close to 450 nm and a main emission wavelength in the wavelength range of 540-560 nm. Figure 4 A graph depicting the intensity of such a yttrium aluminum garnet phosphor as a function of wavelength is shown.

[0088] The second red phosphor 19 is configured to convert a portion of the blue light 11 into second red light 21. The second red phosphor 19 may be different from the first red phosphor 14. Alternatively, the second red phosphor 19 may be the same as the first red phosphor 14. The second red phosphor 19 may be doped with tetravalent manganese. The luminescent material is of the type wherein M' represents an alkaline earth cation, M represents a basic cation, and x is in the range of 0-1, wherein A represents a tetravalent cation, such as one or more of silicon and titanium, and wherein X represents a monovalent anion, including at least fluorine. As an example, the first red phosphor 14 may be a KSF phosphor configured to be excited by blue light having the strongest emission peak wavelength at 631 nm and a full width at half maximum (FWHM) of less than 30 nm. Figure 5A graph showing the intensity of such a KSF phosphor as a function of wavelength is shown. The second encapsulation 12 may include a second red phosphor 19 at a fourth concentration C4. The first concentration C1, the second concentration C2, the third concentration C3, and the fourth concentration C4 can be selected such that the relationship (C1+C2) / (C3+C4) ≥ 1.5 is satisfied.

[0089] The LED filament light 22 may include, or be a combination of, a first green-yellow light 15, a first red light 16, a second green-yellow light 20, and a second red light 21. Furthermore, the LED filament light 22 may include a portion of blue light 11. The first green-yellow light 15 may have a first spectral distribution having a first full width at half maximum (FWHM1) of at least 80 nm. The second green-yellow light 20 may have a second spectral distribution having a second full width at half maximum (FWHM2) of at least 80 nm. The first red light 16 may have a third spectral distribution having a third full width at half maximum (FWHM3) of less than 40 nm. The second red light 21 may have a fourth spectral distribution having a fourth full width at half maximum (FWHM4) of less than 40 nm. The blue light may have a fifth spectral distribution having a fifth full width at half maximum (FWHM5) of at least 60 nm. The LED filament light 22 may be white light having a correlated color temperature in the range of 1700 K to 6500 K and a color rendering index of at least 85 or at least 90.

[0090] at last, Figure 6 An exemplary lamp 40 is shown, comprising an LED filament 1 according to any embodiment of the invention. In the illustrated embodiment, the LED filament 1 is a substantially straight LED filament. In other embodiments, the LED filament 1 of such a lamp may be an LED filament having other shapes, such as, but not limited to, spiral, helical, zigzag, twisted, flat, and combinations thereof.

[0091] Lamp 40 also includes a driver or controller 41 configured to control LEDs 3 of LED filament 1. Controller 41 is configured to supply power to a plurality of violet LEDs 7 via circuitry of LED filament 1 (not visible in the figure). Controller 41 may also be configured to control at least one of the CCT and CRI of LED filament light 22. Controller 41 may also be configured to control other parameters related to the violet LEDs 7 and LED filament light 22.

[0092] The lamp 40 also includes a casing 42 that at least partially encloses at least one LED filament 1. The lamp 40 also includes a cap 43. (As...) Figure 6As shown, the controller 41 is arranged within the housing 42. When the cap 43 is included, the controller 41 can also be arranged inside the cap 43, making it visually concealed. The lamp 40 also includes threads 44 for connecting to a socket and terminals 45 for connecting to an electrical source.

[0093] The housing 42 of the lamp 40 may also, and optionally, be provided with a coating (not shown) covering at least a portion of the housing 42, such as a reflective coating.

[0094] Those skilled in the art will recognize that the present invention is by no means limited to the preferred embodiments described above. Rather, many modifications and variations are possible within the scope of the appended claims.

[0095] Furthermore, by studying the accompanying drawings, the disclosure, and the appended claims, those skilled in the art can understand and implement variations of the disclosed embodiments in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. The fact that certain measures are recited in mutually different dependent claims does not imply that combinations of these measures cannot be advantageously used.

Claims

1. An LED filament (1) configured to emit LED filament light (22) during operation, said LED filament comprising: The light-transmitting elongated carrier (2) includes a first main surface (3) and a second main surface (4) opposite to the first main surface. A plurality of violet LEDs (7) are configured to emit violet light (8) during operation, wherein the violet light (8) emitted by the plurality of violet LEDs has a peak wavelength in the wavelength range of 380 nm to 420 nm, and the plurality of violet LEDs are arranged on the first main surface. A first package (9) covers at least a portion of the plurality of purple LEDs (7) and the first main surface, the first package including a blue phosphor (10) configured to convert at least a portion of the purple light into blue light (11). A second encapsulation (12) completely covers the first encapsulation (9). The second encapsulation is an elongated encapsulation comprising a first green-yellow phosphor (13) and a first red phosphor (14), the first green-yellow phosphor being configured to convert a portion of the blue light into first green-yellow light (15), and the first red phosphor being configured to convert a portion of the blue light into first red light (16). A third encapsulation (17) covers at least a portion of the second main surface (4) of the light-transmitting elongated carrier. The third encapsulation is an elongated encapsulation comprising a second green-yellow phosphor (18) and a second red phosphor (19), wherein the second green-yellow phosphor is configured to convert a portion of the blue light into second green-yellow light (20), and the second red phosphor is configured to convert a portion of the blue light into second red light (21). The LED filament light (22) includes the first green-yellow light (15), the first red light (16), the second green-yellow light (20), and the second red light (21).

2. The LED filament of claim 1, wherein the blue phosphor is configured to completely convert the purple light into blue light.

3. The LED filament according to any one of the preceding claims, wherein the purple light (8) emitted by the plurality of purple LEDs has a peak wavelength in the wavelength range of 400 nm to 420 nm.

4. The LED filament according to any one of the preceding claims, wherein the blue phosphor (10) is a phosphate phosphor, the phosphate phosphor being configured to be effectively excited by the purple light emitted by the plurality of purple LEDs and including an emission peak wavelength in the wavelength range of 460 nm to 480 nm.

5. The LED filament according to any one of the preceding claims, wherein one or both of the following are applicable: The first greenish-yellow phosphor (13) and the second greenish-yellow phosphor (18) are different from each other, and The first red phosphor (14) and the second red phosphor (19) are different from each other.

6. The LED filament according to any one of the preceding claims, wherein: The first greenish-yellow phosphor and / or the second greenish-yellow phosphor include Luminescent materials of the type wherein A includes one or more of Y, La, Gd, Tb, and Lu; and The first red phosphor and / or the second red phosphor are doped with tetravalent manganese. The luminescent material of the type wherein M' comprises an alkaline earth cation, M comprises a basic cation, and x is in the range of 0-1, wherein A comprises a tetravalent cation, such as one or more of silicon and titanium, and wherein X comprises a monovalent anion, including at least fluorine.

7. The LED filament according to any one of the preceding claims, wherein the light-transmitting elongated carrier has a transmittance of at least 80% in a wavelength range corresponding to the wavelength range of the blue light (11) emitted by the blue phosphor of the first package.

8. The LED filament according to any one of the preceding claims, wherein the first package (9) includes a minimum thickness (T1) measured perpendicular to the light-emitting surface (23) of the plurality of violet LEDs (7) to the second package, wherein the second package (12) includes a second thickness (T2) measured perpendicular to the light-emitting surface (24) of the plurality of violet LEDs to the light-emitting surface (24) of the second package, and wherein T1>T2.

9. The LED filament according to any one of the preceding claims, wherein the first green-yellow phosphor has a first concentration (C1) in the first encapsulation (9), the first red phosphor has a second concentration (C2) in the first encapsulation (9), the second green-yellow phosphor has a third concentration (C3) in the second encapsulation (12), and the second red phosphor has a fourth concentration (C4) in the second encapsulation (12), wherein .

10. The LED filament according to any one of the preceding claims, wherein the first package (9) has a minimum thickness (T1) measured perpendicularly to the light-emitting surface (23) of the plurality of violet LEDs (7) to the second package, the second package (12) has a second thickness (T2) measured perpendicularly to the light-emitting surface (24) of the plurality of violet LEDs (7) to the light-emitting surface (24) of the second package (9) to the location of the plurality of violet LEDs (7) and perpendicularly to the light-emitting surface (25) of the third package (17) and perpendicularly to the light-emitting surface (25) of the third package (7), wherein .

11. The LED filament according to any one of the preceding claims, wherein the elongated carrier (2) further comprises a first sub-surface (5) and a second sub-surface (6) opposite to the first sub-surface, the first sub-surface and the second sub-surface connecting the first main surface and the second main surface, and wherein the first sub-surface (5) and the second sub-surface (6) are without the second encapsulation (12) and the third encapsulation (17).

12. The LED filament according to any one of claims 1 to 9, wherein the first encapsulation (9) completely covers the first main surface of the light-transmitting elongated carrier.

13. The LED filament according to any one of claims 1 to 9 and 11, wherein the light-transmitting elongated carrier (2) further comprises a first sub-surface (5) and a second sub-surface (6) opposite to the first sub-surface, the first sub-surface and the second sub-surface connecting the first main surface and the second main surface, and wherein the first sub-surface (5) and the second sub-surface (6) are at least partially covered by at least one of the second encapsulation (12) and the third encapsulation (17).

14. The LED filament according to any one of the preceding claims, wherein: The LED filament light (22) includes a portion of the blue light; The first greenish-yellow light has a first spectral distribution with a first full width at half maximum (FWHM1) of at least 80 nm; the second greenish-yellow light has a second spectral distribution with a second full width at half maximum (FWHM2) of at least 80 nm; the first red light has a third spectral distribution with a third full width at half maximum (FWHM3) of less than 40 nm; the second red light has a fourth spectral distribution with a fourth full width at half maximum (FWHM4) of less than 40 nm; the blue light has a fifth spectral distribution with a fifth full width at half maximum (FWHM5) of at least 60 nm; and... The LED filament light (22) is white light with a correlated color temperature in the range of 1700K to 6500K and a color rendering index of at least 85, wherein the color rendering index is preferably at least 90.

15. An LED filament lamp, comprising: A connector is configured to electrically and mechanically connect the LED filament lamp to a socket in the luminaire; And a casing that at least partially surrounds the LED filament (1) according to any one of the preceding claims.

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