Light-emitting filamentary devices

Abstract

A light emitting device (LED) filament (1), configured to emit an LED filament light upon operation, the LED filament (1) comprising: a phosphor structure (3); a plurality of first LEDs (4) adapted to emit a first LED light upon operation, the plurality of first LEDs (4) being disposed below the phosphor structure (3); a plurality of second LEDs (5) adapted to emit a second LED light upon operation, the second LED light being red light; a plurality of third LEDs (6) adapted to emit a third LED light upon operation, the third LED light being green light; and a plurality of third LEDs (6) adapted to emit a fourth LED light upon operation. the LED filament (1) including: a plurality of fourth LEDs (7) coupled to the plurality of LEDs (4, 5, 6, 7), wherein the fourth LED light is blue light; an electric circuit (11) coupled to the plurality of LEDs (4, 5, 6, 7); and an elongated support (8), wherein the plurality of LEDs (4, 5, 6, 7) are disposed on a first main surface (81) of the elongated support (8); the phosphor structure (3) including a phosphor adapted to generate cold white (CW) light and a phosphor adapted to generate warm white (WW) light, the first LED light includes light having a wavelength of 405 nm or is light having a wavelength of 405 nm, and the phosphor structure (3) is configured to be excited only with light having a wavelength of 405 nm.

Description

[Technical Field]

[0001] The present invention relates to a light emitting device (LED) filament configured to emit an LED filament light in operation, the LED filament comprising: a phosphor structure; a plurality of first LEDs adapted to emit a first LED light in operation, the plurality of first LEDs being disposed below the phosphor structure; a plurality of second LEDs adapted to emit a second LED light in operation, the plurality of second LEDs being disposed below the phosphor structure, the second LED light being red light; a plurality of third LEDs adapted to emit a third LED light in operation, the plurality of third LEDs being disposed below the phosphor structure, the third LED light being green light; a plurality of fourth LEDs adapted to emit a fourth LED light in operation, the plurality of fourth LEDs being disposed below the phosphor structure, the fourth LED light being blue light; electrical circuitry coupled to the plurality of first LEDs, the plurality of second LEDs, the plurality of third LEDs, and the plurality of fourth LEDs; and an elongated support. The present invention relates to an LED filament, including a carrier.

[0002] WO 2022 / 207603 A1 discloses an LED filament lamp including a filament having a first LED filament surface, a second LED filament surface, an intermediate layer, and multiple light sources. The multiple light sources include a first light source associated with the first filament surface that generates a first white light having a first correlated color temperature CCT1, and a second light source associated with the first filament surface that generates a second white light having a second correlated color temperature, where CCT2-CCT1≧500K. The multiple light sources further include a third light source associated with the second filament surface that generates a blue third light, a fourth light source associated with the second filament surface that generates a green fourth light, and a fifth light source associated with the second filament surface that generates a red fifth light. The intermediate layer is configured between at least a portion of the first LED filament surface and at least a portion of the second LED filament surface.

[0003] US 2020 / 3553331A discloses a light emitting system including an LED emitting first radiation characterized by a first wavelength in the range of 390 to 430 nm, a first wavelength conversion material for converting a portion of the first radiation into second radiation characterized by a second wavelength in a second range of about 500 to about 600 nm, and a second wavelength conversion material for converting a portion of the first radiation into third radiation characterized by a third wavelength in a third range of about 600 to about 700 nm. The light spectrum is characterized by a spectral power distribution having an R9 of at least 80 and a violet fraction of at least 0.10.

[0004] As used herein, the terms light emitting device and LED are intended to encompass both LED packages, LED dies and bare LEDs.

[0005] As used herein, warm white (WW) light is intended to refer to light having a color temperature in the range of 2000K to 3300K.

[0006] As used herein, cold white (CW) light is intended to refer to light having a color temperature in the range of 3300K to 5300K.

[0007] As used herein, white light similar to daylight is intended to refer to light having a color temperature in the range of 5300K to 7000K or 5300K to 6500K. [Background technology]

[0008] A current trend in lighting is the use of LED filament lamps, which are LED lamps that contain an LED filament, designed to resemble a traditional incandescent light bulb, with the filament visible for aesthetic and light distribution purposes, but with the high efficiency of light-emitting diodes.

[0009] The LED filament provides LED filament light and includes a plurality of light emitting diodes (LEDs) arranged in a linear array. Preferably, the LED filament has a length L and a width W, where L>5W. The LED filament may be arranged in a straight configuration or in a non-linear configuration, such as a curved configuration, a 2D / 3D swirl, or a spiral. Preferably, the LEDs are arranged on an elongated support, such as a substrate, which may be rigid (e.g., made from a polymer, glass, quartz, metal, or sapphire) or flexible (e.g., made from a polymer or metal, e.g., a film or foil).

[0010] When the support includes a first major surface and an opposite second major surface, the LED is disposed on at least one of these surfaces. The support may be reflective or may be light-transmitting, such as translucent and preferably transparent.

[0011] The LED filament may include an encapsulant at least partially covering 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 polymeric material, such as silicone, which may be flexible. Furthermore, the LEDs may be configured to emit LED light, e.g., of various colors or spectrums. The encapsulant may include a luminescent material configured to at least partially convert the LED light into converted light. The luminescent material may be an inorganic phosphor and / or a phosphor such as quantum dots or quantum rods.

[0012] An LED filament may include multiple sub-filaments.

[0013] Known tunable white filament lamps consist of at least two filaments, one with a low correlated color temperature (CCT) and one with a high CCT. A single filament may also be used that combines low and high CCT emission.

[0014] WO 2021 / 018646 A1 discloses an LED filament comprising a linear array of LEDs arranged on a carrier substrate, the linear array being divided into two separate longitudinal sections, the first longitudinal section containing only LEDs configured to emit white light and the second longitudinal section containing only LEDs configured to emit color-controllable light. It is proposed to confine colored LEDs to the second longitudinal section of the array so that the first longitudinal section of the array is capable of emitting homogeneous white light of a certain color temperature across the range of LEDs in that section.

[0015] If it is desired to add color to create a full-color light-emitting diode (LED) filament lamp, colored LEDs can be added to the lamp as separate filaments. This is usually undesirable because it results in poor appearance. Alternatively, colored LEDs can be placed on the same surface of the filament substrate, i.e., together with white LEDs. However, if RGB and white LED filament strings are formed on the same printed circuit board (PCB) or flexible printed circuit (FPC) surface of the filament, there can be crosstalk between the cool-white (CW) LED filament string and the warm-white (WW) LED filament string, followed by undesired light crosstalk between the RGB LED filament string and the white LED filament string. Such crosstalk significantly reduces the color gamut produced by this filament in a clear bulb. For example, if light is emitted by a direct blue LED, it can be absorbed by a red-yellow phosphor layer disposed on top of the white LED filament string, causing undesired conversion and thus the generation of undesired red-yellow light. This undesirable red-yellow light emission causes a shift in the filament color point from pure blue to a less saturated color point. Such an unsaturated color appearance is undesirable for color tunable lamps, especially for the highly sought-after color tunable lamps with white-color ambiance.

[0016] Furthermore, saturated colors (especially blue) cannot be produced using filament lamps in which a direct emitter (LED) is coated with a phosphor or phosphor blend. Blue light excites some yellow / green-red phosphors, resulting in a very unsaturated blue. However, phosphors are necessary to produce cool-white and warm-white light with high light quality.

[0017] The problem with high quality white light and high color rendering index (CRI) on the black body locus (BBL) is that next to CW light (color temperature above 4500K or above 3300K) and WW light (color temperature around 2200K or between 2000K and 3300K) on the BBL, a green contribution is needed to create intermediate Correlated Color Temperature (CCT) white light on the BBL (i.e., between 2200K and 4500K). This detracts from the look and feel of the filament, and when looking at the filament, you will see a green emitting LED next to the emitting white channel without any countermeasures, giving a cheap, low-quality image.

[0018] It is therefore desirable to provide a WW-CW filament lamp that, when operated, produces high quality white light at the blackbody locus (BBL) and a high color rendering index (CRI).

[0019] It is further desired to provide a five channel (RGB WW-CW) filament lamp that, in operation, produces saturated colors (red, green and blue) and high quality white light in BBL and a high CRI. Summary of the Invention [Problem to be solved by the invention]

[0020] Thus, it is an object of the present invention to overcome the above-mentioned problems and to provide a WW-CW filament lamp that, when operated, produces high quality white light at the blackbody locus (BBL) and a high color rendering index (CRI).

[0021] It is further desired to provide a five channel (RGB WW-CW) filament lamp that, in operation, produces saturated colors (red, green and blue) and high quality white light in BBL and a high CRI.

[0022] It is also desirable to provide such filament lamps with improved color uniformity when multiple colors are emitted, thus providing a higher color gamut and improved aesthetics of the filament. [Means for solving the problem]

[0023] According to a first aspect of the present invention, this and other objects are a light emitting device (LED) filament configured to emit LED filament light in operation, the LED filament comprising a phosphor structure and a plurality of first LEDs adapted to emit first LED light in operation, the plurality of first LEDs and the phosphor structure being arranged relative to one another such that the phosphor structure receives the first LED light in operation, and a plurality of second LEDs adapted to emit second LED light in operation. a plurality of second LEDs, wherein the second LED light is red light, and the plurality of second LEDs and the phosphor structure are arranged relative to one another such that, in operation, the phosphor structure receives the second LED light; a plurality of third LEDs adapted to emit, in operation, a third LED light, wherein the third LED light is green light, and the plurality of third LEDs and the phosphor structure are arranged relative to one another such that, in operation, the phosphor structure receives the third LED light; and a plurality of fourth LEDs adapted to emit, in operation, a fourth LED light, wherein the fourth LED light is green. the ED light is blue light, and the plurality of fourth LEDs and the phosphor structure are arranged relative to one another such that, in operation, the phosphor structure receives the fourth LED light; an electrical circuit coupled to the plurality of first LEDs, the plurality of second LEDs, the plurality of third LEDs, and the plurality of fourth LEDs; and an elongated support, the plurality of first LEDs, the plurality of second LEDs, the plurality of third LEDs, and the plurality of fourth LEDs being arranged on a first main surface of the elongated support; and the phosphor structure receives the second LED light, the third LED light, and the fourth LED. the first LED light includes at least one of a phosphor adapted to generate a cold white (CW) LED filament light and a phosphor adapted to generate a warm white (WW) LED filament light in combination with one or more of the first LED light, the phosphor structure being configured to convert 10% or less of the second LED light, the third LED light, and the fourth LED light, and the first LED light includes light having a peak wavelength within a range of 380 to 440 nm, 380 to 420 nm, 380 to 410 nm, or 400 to 410 nm, or light having a peak wavelength of 405 nm;Alternatively, the light may be achieved by an LED filament configured to be excited by light having a wavelength corresponding to the wavelength of the first LED light, and the phosphor structure is configured to convert 7% or less, preferably 5% or less, and more preferably 2% or less of the second, third, and fourth LED light.

[0024] Such a phosphor structure is useful for generating cool white and warm white light with high light quality. Because the phosphor structure is not excited by blue light (up to 450 nm), or is excited only to a relatively low extent, the direct blue channel (i.e., the fourth light emitted by the fourth LEDs) is transmitted through the phosphor layer without being converted. Thus, when the first LEDs are activated and emit the first light, the phosphor structure is excited and together emits white light. When one (or more) of the second, third, and fourth LED (red, green, and blue) dies are activated and emit LED light, the red, green, and / or blue LED light is transmitted through the phosphor structure without generating (undesirable) emission. Thus, when using an LED filament according to the present invention, it is possible to provide LED filament light with high-quality white light and saturated colors, as described above. Additionally, the phosphor scatters the red, green, and / or blue LED light, thereby improving the color uniformity of the LED filament light and improving or increasing the color gamut of the LED filament light. The term "phosphor" may refer to a single phosphor material or a combination of two or more phosphor materials.

[0025] In terms of other than the peak wavelength of the first LED light, it should be noted that in one embodiment, the difference between the peak wavelength of the fourth LED light, i.e., the blue light, and the peak wavelength of the first LED light is ensured to be greater than 40 nm, greater than 45 nm, or greater than 50 nm. Considering the fact that the peak wavelength of the fourth LED light is most often approximately 460 nm in practice, the maximum peak wavelength of the first LED light should therefore be less than 410 nm. In one embodiment, the first LED is adapted to emit a first LED light having a peak wavelength of 405 nm during operation.

[0026] This allows the conversion rate of green light by the phosphor structure to be more moderate, especially when combined with a green LED under a phosphor structure, such as the above-mentioned third LEDs, and no longer needs to be less than 5%, especially since saturated green is not required to be able to follow the black body locus (BBL).It is therefore possible to provide a WW-CW filament lamp that produces high-quality white light at the black body locus (BBL) and a high color rendering index (CRI) during operation.

[0027] In one embodiment, the first LED is adapted to emit a first LED light, when in operation, having a peak wavelength within ±2 nm, ±5 nm, ±10 nm, or ±20 nm of 405 nm.

[0028] Using a first light having a peak wavelength within ±2 nm, ±5 nm, ±10 nm or ±20 nm of 405 nm, or even at 405 nm, has the advantage that if some of the first light leaks through the phosphor layer (this light is largely invisible), it may excite some optical brighteners, for example optical brighteners in fabrics or paper, leading to a better white perception (Crisp White).

[0029] In one embodiment, the plurality of first LEDs, the plurality of second LEDs, the plurality of third LEDs and the plurality of fourth LEDs are arranged in a sequence where the first LED is followed by a group including the second LED, the third LED and the fourth LED.

[0030] Such a group including the second LED, the third LED and the fourth LED is also known as a Red-Green-Blue-group or an RGB-group. The order of the three LEDs in the RGB-group may be, for example, RGB or BRG or any other suitable order.

[0031] Thus, a WW-CW LED filament is obtained that, in operation, produces high-quality white light at the blackbody locus (BBL) and a high color rendering index (CRI). Furthermore, such an LED filament has improved color homogeneity when multiple colors are emitted, and thus also improved aesthetics of the LED filament.

[0032] In one embodiment, the LED filament comprises a single filament string.

[0033] This provides a four-channel LED filament with a particularly simple construction.

[0034] In one embodiment, the LED filament includes a first filament string and a second filament string, and the phosphor structure is arranged on the first filament string and the second filament string such that one of the first filament string and the second filament string includes a phosphor adapted to generate cold white (CW) light in combination with one or more of the second LED light, the third LED light, and the fourth LED light, and the other of the first filament string and the second filament string includes a phosphor adapted to generate warm white (WW) light in combination with one or more of the second LED light, the third LED light, and the fourth LED light.

[0035] This provides a 5-channel (RGB WW-CW) LED filament that produces saturated colors (red, green and blue) and high-quality white light at the blackbody locus (BBL) and a high color rendering index (CRI).

[0036] In one embodiment, the phosphor adapted to generate WW light includes a red phosphor disposed below a phosphor adapted to generate CW light of the same type as the phosphor adapted to generate CW light included in one of the first and second filament strings that includes a phosphor adapted to generate CW light.

[0037] This allows the same production methods to be used as those used in Chip-On-Board (COB) technology to manufacture the LED filaments according to the invention, which makes the manufacture of the LED filaments particularly simple.

[0038] In one embodiment, each of the first filament string and the second filament string includes a plurality of first LEDs adapted to emit a first light in operation, and the plurality of first LEDs and the phosphor structure are arranged relative to each other such that the phosphor structure receives the first light in operation.

[0039] This provides high quality white light in the BBL with increased intensity.

[0040] In one embodiment, each of the first filament string and the second filament string includes: a plurality of second LEDs adapted to emit a second LED light in operation, the second LED light being red light, and the plurality of second LEDs and the phosphor structure being arranged relative to one another such that the phosphor structure receives the second LED light in operation; a plurality of third LEDs adapted to emit a third LED light in operation, the third LED light being green light, and the plurality of third LEDs and the phosphor structure being arranged relative to one another such that the phosphor structure receives the third LED light in operation; and a plurality of fourth LEDs adapted to emit a fourth LED light in operation, the fourth LED light being blue light, and the plurality of fourth LEDs and the phosphor structure being arranged relative to one another such that the phosphor structure receives the fourth LED light in operation.

[0041] This provides an LED filament structure in which the first filament string and the second filament string are essentially identical, thus providing a simplified production process.

[0042] In one embodiment, the first LED, second LED, third LED and fourth LED on the first filament string and the second filament string, respectively, are arranged relative to each other such that the same LEDs, e.g., the respective first LEDs, of each filament string are arranged offset relative to each other in the longitudinal direction of the LED filament.

[0043] This provides a filament lamp with improved color uniformity and color gamut when multiple colors are emitted, and thus improved aesthetics of the filament.

[0044] In one embodiment, the LED filament includes at least a first filament string and a second filament string, wherein a plurality of first LEDs and phosphor structures adapted to emit first LED light in operation are disposed on the first filament string, a plurality of second LEDs adapted to emit second LED light in operation, a plurality of third LEDs adapted to emit third LED light in operation, and a plurality of fourth LEDs adapted to emit fourth LED light in operation are disposed on the second filament string.

[0045] This provides a five-channel LED filament with a particularly simple construction.

[0046] In one embodiment, the LED filament includes one or more further filament strings, wherein a further plurality of second LEDs adapted to emit a second LED light in operation are disposed on at least one further filament string of the one or more further filament strings, a further plurality of third LEDs adapted to emit a third LED light in operation are disposed on at least one further filament string of the one or more further filament strings, and a further plurality of fourth LEDs adapted to emit a fourth LED light in operation are disposed on at least one further filament string of the one or more further filament strings.

[0047] This provides more saturated and intense colored (RGB) light.

[0048] In one embodiment, the phosphor structure is of a type that, when exposed to light, emits light in the yellow-red wavelength region and is not excited by light in the green-blue wavelength region.

[0049] In one embodiment, the phosphor structure is of a type that, when exposed to light, emits light in one or more of the yellow and red wavelength regions, and is not excited by light in one or more of the green and blue wavelength regions.

[0050] In one embodiment, the phosphor structure is of a type that is not excited by light in the blue wavelength region.

[0051] In one embodiment, the phosphor structure is of a type that is not excited by light having a wavelength in the range of 550 nm to 610 nm.

[0052] Any of these embodiments allows for the provision of high quality white light over a wide CCT range.

[0053] In one embodiment, the phosphor structure includes at least one phosphor selected from the group including a violet pumped blue (VB) phosphor, such as (Sr,Ca,Ba)5(PO4)3Cl:Eu2+, a violet pumped green (VG) phosphor, such as (Ba,Sr)MgAl10O17:Mn2+,Eu2+, and a violet pumped red phosphor, such as Mg8Ge2O11F2:Mn4+. In a particular embodiment, the phosphor includes an A3B5O12:Ce type phosphor, where A in some embodiments includes one or more of Y, La, Gd, Tb, and Lu, particularly (at least) one or more of Y, Gd, Tb, and Lu, and B in some embodiments includes one or more of Al, Ga, In, and Sc. In particular, A may comprise one or more of Y, Gd and Lu, in particular one or more of Y and Lu. In particular, B may comprise one or more of Al and Ga, more in particular at least Al, such as essentially only Al. Thus, a particularly suitable phosphor is a cerium comprising garnet material.

[0054] These are all particularly suitable yellow / green / red phosphors that exhibit low (royal) blue absorption.

[0055] In one embodiment, the phosphor structure comprises at least one phosphor selected from the group comprising quantum dot materials with violet absorption and green, yellow or orange / red emission.

[0056] These are all particularly suitable yellow / green / red quantum dot type phosphors that exhibit low (royal) blue absorption.

[0057] In one embodiment, the LED filament further includes an encapsulant that at least partially surrounds the plurality of LEDs and, if provided, the elongated support.

[0058] This provides a particularly strong and durable LED filament.

[0059] In one embodiment, at least one of the phosphor adapted to generate CW light and the phosphor adapted to generate WW light forms part of the encapsulant.

[0060] This provides an LED filament with a particularly simple and compact construction.

[0061] In one embodiment, the encapsulant further comprises a light-transmitting material.

[0062] The invention also relates to a luminaire or lamp comprising a light-emitting device according to the invention.

[0063] The term "blue light" or "blue emission" particularly relates to light having a wavelength in the range of about 440-495 nm (including some purple and cyan hues). The term "green light" or "green emission" particularly relates to light having a wavelength in the range of about 495-570 nm. The term "yellow light" or "yellow emission" particularly relates to light having a wavelength in the range of about 570-590 nm. The term "orange light" or "orange emission" particularly relates to light having a wavelength in the range of about 590-620 nm. The term "red light" or "red emission" particularly relates to light having a wavelength in the range of about 620-780 nm. The term "pink light" or "pink emission" refers to light having blue and red components. The term "cyan" may refer to one or more wavelengths selected from the range of approximately 490 to 520 nm. The term "amber" may refer to one or more wavelengths selected from the range of approximately 585 to 605 nm, such as approximately 590 to 600 nm. The phrase "light having one or more wavelengths in a wavelength range" and similar phrases may specifically indicate that the indicated light (or radiation) has a spectral power distribution with intensities at at least one or more wavelengths within the indicated wavelength range. For example, a blue-emitting solid-state light source has a spectral power distribution with intensities at one or more wavelengths within the wavelength range of 440 to 495 nm.

[0064] The invention relates to all possible combinations of the features recited in the claims. [Brief explanation of the drawings]

[0065] This and other aspects of the present invention will now be described in more detail with reference to the accompanying drawings, which illustrate one or more embodiments of the present invention. As shown in the figures, the sizes of layers and regions may be exaggerated for illustrative purposes and are thus provided to illustrate the general structure of embodiments of the present invention. Like reference numerals refer to like elements throughout. [Figure 1] 1 shows a top view of a first embodiment of a light-emitting device according to the present invention; [Figure 2] 2 shows a top view of a second embodiment of a light-emitting device according to the present invention; [Figure 3] 3 shows a cross-sectional side view of the light-emitting device according to FIG. 2. [Figure 4] 3 shows a top view of a third embodiment of a light-emitting device according to the present invention; [Figure 5] 1 shows a graph illustrating the emission and excitation spectra of several yellow / green / red phosphors with low (royal) blue absorption with normalized intensity as a function of wavelength. [Figure 6] 1 shows a graph illustrating the emission and excitation spectra of several yellow / green / red quantum dot (QD) type phosphors with low (royal) blue absorption with normalized intensity as a function of wavelength. [Figure 7] 1 shows a schematic cross-sectional side view of a lamp including a light-emitting device according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0066] The present invention is described more fully hereinafter with reference to the accompanying drawings, in which presently preferred embodiments of the invention are shown. However, the present 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, so that the scope of the disclosure will be fully conveyed to those skilled in the art.

[0067] 1 shows a top view of one embodiment of a light emitting device (LED) filament 1 according to the present invention. Generally, regardless of the embodiment, the LED filament 1 includes a filament string 2 including a phosphor structure 3 and a plurality of first LEDs 4.

[0068] It should be noted that the inventive concept described herein of reducing crosstalk between blue light and phosphor by using a phosphor that is not excited by blue light is not limited to being applicable to light emitting devices having a filament shape, but may also be applied to light emitting devices having, for example, chip-on-board (COB), LED strips or other suitable shapes.

[0069] The first LED 4 is adapted to emit a first LED light during operation. The first LED light includes or is light having a wavelength of 405 nm. The first LED 4 may be adapted to emit a first LED light during operation having a peak wavelength of 405 nm. The first LED 4 may be adapted to emit a first LED light during operation having a peak wavelength within ±2 nm, ±5 nm, ±10 nm, or ±20 nm of 405 nm, for example. The first LED 4 and the phosphor structure 3 are positioned relative to each other such that the phosphor structure 3 receives the first LED light during operation. The phosphor structure 3 is positioned in a light-receiving relationship with the first LED 4. The first LED 4 is positioned below the phosphor structure 3. The phosphor structure 3 may at least partially cover the first LED 4.

[0070] The LED filament 1 may further include a plurality of second LEDs 5. The second LEDs 5 are adapted to emit second LED light, in operation, where the second LED light is red light. The second LEDs 5 are red (R) LEDs. The second LEDs 5 and the phosphor structure 3 are arranged relative to each other such that, in operation, the phosphor structure 3 receives the second LED light. The phosphor structure 3 is arranged in a light-receiving relationship with the second LEDs 5. The second LEDs 5 are arranged below the phosphor structure 3. The phosphor structure 3 may at least partially cover the second LEDs 5.

[0071] The LED filament 1 may further include a plurality of third LEDs 6 adapted to emit a third LED light, in operation, where the third LED light is green light. The third LEDs 6 are green (G) LEDs. The third LEDs 6 and the phosphor structure 3 are arranged relative to each other such that, in operation, the phosphor structure 3 receives the third LED light. The phosphor structure 3 is arranged in a light-receiving relationship with the third LEDs 6. The third LEDs 6 are arranged below the phosphor structure 3. The phosphor structure 3 may at least partially cover the third LEDs 6.

[0072] The LED filament 1 may further include a plurality of fourth LEDs 7 adapted to emit a fourth LED light, in operation, where the fourth LED light is blue light. The fourth LEDs 7 are blue (B) LEDs. The fourth LEDs 7 and the phosphor structure 3 are arranged relative to each other such that, in operation, the phosphor structure 3 receives the fourth LED light. The phosphor structure 3 is arranged in a light-receiving relationship with the fourth LEDs 7. The fourth LEDs 7 are arranged below the phosphor structure 3. The phosphor structure 3 may at least partially cover the fourth LEDs 7.

[0073] Thus, in a more generalized sense, the first LED 4 may be said to be adapted to emit, in operation, a first LED light that is violet or UV light.

[0074] In the embodiment shown, there are three first LEDs 4, three second LEDs 5, three third LEDs 6 and three fourth LEDs 7. The number of LEDs 4, 5, 6, 7 may be adapted to fit the length of the LED filament 1.

[0075] In the illustrated embodiment, the LED filament 1 comprises one filament string 2. Thus, all LEDs 4, 5, 6, 7 are arranged on one and the same filament string 2 of the LED filament 1.

[0076] The LEDs 4, 5, 6, and 7 of the LED filament 1 may be arranged in the following sequence: first LED 4, second LED 5, third LED 6, and fourth LED 7. Alternatively, the LEDs 4, 5, 6, and 7 of the LED filament 1 may be arranged in the following sequence: first LED 4, fourth LED 7, second LED 5, and third LED 6. More generally, the LEDs 4, 5, 6, and 7 of the LED filament 1 may be arranged in the following sequence: first LED 4, followed by a group including the second LED 5, the third LED 6, and the fourth LED 7, i.e., an RGB group, where the three LEDs of the RGB group may be arranged in any suitable order, e.g., RGB or BRG.

[0077] The LEDs 4, 5, 6, 7 of the LED filament 1 are disposed on a surface 81 of a support 8. The support is not visible in FIG. 1 but is best seen in FIG. 3. Surface 81 is a first major surface 81 of the support 8. The support 8 is an elongated support 8. The elongated support 8 may be a substrate. The elongated support 8 or substrate may be a printed circuit board (PCB).

[0078] An electrical circuit 11 is coupled to the LEDs 4, 5, 6, 7, such as to supply electrical energy to the LEDs 4, 5, 6, 7. The electrical circuit 11 is not visible in Figure 1 but is shown in Figure 2. The electrical circuit 11 may be disposed on or within the elongated support 8. The electrical circuit 11 may include one or more electrical tracks, for example one track for each of the first, second, third and fourth LEDs.

[0079] The phosphor structure 3 may be part of or form part of the encapsulant 9, best shown in FIG. 3 . The encapsulant 9 at least partially surrounds the LEDs 4, 5, 6, 7 and the elongated support 8. Furthermore, the encapsulant 9 may optionally include a light-transmitting material. The light-transmitting material of the encapsulant 9 may be a polymer, such as silicone, that can withstand high-intensity light and heat. The phosphor structure 3 may be encapsulated by the encapsulant 9, such as being disposed below the encapsulant 9, or being disposed within or forming part of the encapsulant 9. Alternatively, the phosphor structure 3 may be disposed on top of the encapsulant 9, such as on an outer surface of the encapsulant 9.

[0080] 1 is an example of how an RGB+white filament can be made in accordance with the present invention. In operation, a first LED 4 and phosphor structure 3 are used to provide white LED filament light. Second, third, and fourth LEDs 5, 6, 7 may be used to generate LED filament light with different correlated color temperatures (CCTs), such as the CCT provided by the second, blue LED 5 and phosphor structure 3, and / or to generate colored light with a very large color gamut.

[0081] In operation, when the first LED 4 is turned on, the phosphor structure 3 is excited, and the first LED 4 and the phosphor structure 3 together emit white LED filament light. When one (or more) of the second, third, and fourth LEDs 5, 6, and 7 is in operation, the light from the second, third, and fourth LEDs is transmitted by the phosphor structure 3 without generating (undesirable) luminescence. In this way, an LED filament capable of obtaining high-quality white light and saturated colors is provided. Furthermore, the phosphor structure 3 scatters the light from the second, third, and fourth LEDs, which enhances the color uniformity of the LED filament light. The LED filament 1 shown in FIG. 1 is a four-channel filament.

[0082] Regardless of the embodiment, the phosphor structure 3 generally includes one or both of a phosphor adapted to generate cold white (CW) light and a phosphor adapted to generate warm white (WW) light, and the phosphor structure 3 is configured to be excited only with light having a wavelength corresponding to the wavelength or wavelength range of the first LED light, for example, a wavelength of 405 nm. The phosphor structure 3 may also optionally include a phosphor adapted to generate daylight-like white light. Generally, it is acceptable for the phosphor structure 3 to be adapted to or capable of converting, for example, 5% or less of the light from the second, third, and fourth LEDs 5, 6, and 7. For example, if 5% of the blue light (i.e., the fourth LED light) is absorbed and converted by the phosphor structure, the color purity will decrease by about 3% to about 95%, and if 10% is absorbed and converted, the color purity will decrease to about 92%. More specifically, a maximum of 10% conversion is acceptable, preferably a maximum of 5% conversion, and more preferably a maximum of 2% conversion.

[0083] The phosphor structure 3 may be of a type that, when exposed to light, emits light in the yellow-red wavelength region and is not or hardly excited by light in the green-blue wavelength region. The phosphor structure 3 may be of a type that is not or hardly excited by light in the blue wavelength region. The phosphor structure may be of a type that is not or hardly excited by light in the wavelength region of 550 nm to 610 nm.

[0084] Suitable phosphors for phosphor structure 3 include, but are not necessarily limited to, those listed below. Phosphor structure 3 may include one or more of these phosphors. The phosphors listed below are non-limiting examples of phosphors that emit in the yellow-red region and are not (or are barely) excited using (royal) blue light. Suitable phosphors include, for example, quantum dot materials with violet absorption and green, yellow, or orange / red emission. Suitable phosphors include, for example, violet-pumped blue (VB) phosphors such as (Sr,Ca,Ba)5(PO4)3Cl:Eu2+, violet-pumped green (VG) phosphors such as (Ba,Sr)MgAl10O17:Mn2+,Eu2+, and violet-pumped red phosphors such as Mg8Ge2O11F2:Mn4+.

[0085] The graph in Figure 5 shows the normalized intensity as a function of wavelength for each of the three phosphor materials listed above. The graph in Figure 6 shows the normalized intensity as a function of wavelength for three different quantum dot materials that emit green, yellow, and orange / red light, respectively. In the graphs, the abbreviation "EXC" refers to the excitation spectrum of the material, and the abbreviation "EMI" refers to the emission spectrum of the material. The graphs in Figures 5 and 6 show phosphor materials that emit in the yellow-red region and are not, or are barely, excited by (royal) blue light.

[0086] Turning now to Figure 2, there is shown a top view of a light emitting device (LED) filament 100 according to another embodiment of the present invention. Figure 3 shows a cross-sectional side view of the LED filament 100. The LED filament 100 of Figure 2 differs from the LED filament 1 of Figure 1 described above in the following features:

[0087] The LED filament 100 includes a first filament string 2a and a second filament string 2b. A phosphor structure 3 is disposed on the first filament string 2a and the second filament string 2b. The phosphor structure 3 includes two portions 3a and 3b, one of which, in the illustrated embodiment, is portion 3a, includes a phosphor adapted to generate cold white (CW) light. The other of which, in the illustrated embodiment, is portion 3b, includes a phosphor adapted to generate warm white (WW) light. Thus, one of the first filament string 2a and the second filament string 2b, in the illustrated embodiment, is the first filament string 2a, includes a phosphor adapted to generate cold white (CW) light, and the other of the first filament string 2a and the second filament string 2b, in the illustrated embodiment, is the second filament string 2b, includes a phosphor adapted to generate warm white (WW) light.

[0088] The phosphor adapted to generate WW light, which is comprised here in the second part 3b of the phosphor structure 3, in this embodiment comprises a red phosphor arranged below the phosphor adapted to generate CW light, which phosphor adapted to generate CW light is of the same type as the phosphor adapted to generate CW light comprised in the first part 3a of the phosphor structure 3.

[0089] Each of the first filament string 2a and the second filament string 2b may include first, second, third and fourth LEDs 4, 5, 6, 7 arranged in a similar manner as described above for the LED filament 1 shown in Figure 1. Furthermore, it is also feasible to arrange the first filament string 2a and the second filament string 2b (or the respective LEDs 4, 5, 6, 7 on the first filament string 2a and the second filament string 2b) relative to each other such that the same LEDs of each filament string, e.g., the first LED 4, are arranged offset relative to each other in the longitudinal direction L of the filament strings 2a, 2b.

[0090] Alternatively, a plurality of first LEDs 4 adapted to emit a first LED light in operation may be arranged on the first filament string 2a, and a plurality of second LEDs 5 adapted to emit a second LED light in operation, a plurality of third LEDs 6 adapted to emit a third LED light in operation, and a plurality of fourth LEDs 7 adapted to emit a fourth LED light in operation may be arranged on the second filament 2b.

[0091] In any case, it is also feasible to provide an LED filament 100 that includes more than two filament strings in which the LEDs are arranged as described in any of the above variations.

[0092] Turning now to Figure 4, there is shown a top view of a light emitting device (LED) filament 101 according to yet another embodiment of the present invention. The LED filament 101 of Figure 4 differs from the LED filaments described above in connection with Figures 1-3 in the following features.

[0093] The LED filament 101 includes a filament string 2 according to any of the above embodiments. In Figure 4, the filament string 2 according to the embodiment shown in Figure 1 is shown as an example.

[0094] The LED filament 101 includes one or more additional filament strings, three additional filament strings 2d, 2e, and 2f in the illustrated embodiment. A further plurality of second LEDs 5a adapted to emit a second LED light in operation is arranged on the further filament string 2d. A further plurality of third LEDs 6a adapted to emit a third LED light in operation is arranged on the further filament string 2e. A further plurality of fourth LEDs 7a adapted to emit a fourth LED light in operation is arranged on the further filament string 2f.

[0095] Thus, Figure 4 shows an embodiment in which an LED filament 1, 101 according to any of the above embodiments described in relation to Figures 1 to 3 may be used together with blue, green and red LEDs 5, 6, 7 arranged on separate filaments or filament strings 2d, 2e, 2f.

[0096] It should be noted that in the embodiment shown in Figure 4, each further filament string 2d-2f includes only one of the further second, third and fourth LEDs 5a-7a. In other variants, each further filament string 2d-2f may include two or more of the further second, third and fourth LEDs 5a-7a, for example an RGB group. Combinations are also possible. In yet another variant, only the first LED 4 may be arranged on the filament string 2.

[0097] 7 shows an exemplary lamp 12 including an LED filament 1 according to any embodiment of the present invention. In the illustrated embodiment, the LED filament 1 is a substantially linear LED filament. In other embodiments, the LED filament 1 of such a lamp may be an LED filament of another shape, such as, but not limited to, spiral-shaped, helix-shaped, meandering, twisted, flat, and combinations thereof.

[0098] The lamp 12 further includes a driver or controller 17 configured to control the LED filament light source of the LED filament 1. The controller 17 is configured to power the plurality of LEDs 20 via an electrical circuit 21 of the LED filament 1. The controller 17 may further be configured to control at least one of a CCT of the LED filament light source light and a CRI of the LED filament light source light. The controller 17 may also be configured to control other parameters associated with the LED filament light source and the LED filament light source light.

[0099] Lamp 12 further includes an envelope 13 that at least partially surrounds at least one LED filament 1. Lamp 12 further includes a cap 14. As shown in Figure 7, a controller 17 is disposed within envelope 13. If cap 14 is included, controller 17 may be disposed inside cap 14 so as to be hidden from view. Lamp 12 further includes threads 15 for connection to a socket and terminals 16 for connection to a source of electrical energy.

[0100] The envelope 13 of the lamp 12 may further optionally include a coating 18 , such as a reflective coating, covering at least a portion of the envelope 13 .

[0101] Those skilled in the art will recognize that the present invention is by no means limited to the preferred embodiments described above: on the contrary, many modifications and variations are possible within the scope of the appended claims.

[0102] Furthermore, variations to the disclosed embodiments can be understood by those skilled in the art, from a study of the drawings, the disclosure, and the appended claims, and can be implemented 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 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.

Claims

1. A light emitting device (LED) filament configured to emit LED filament light when operated, the LED filament comprising: a phosphor structure; a plurality of first LEDs adapted to emit first LED light in operation, the plurality of first LEDs and the phosphor structure being positioned relative to one another such that the phosphor structure receives the first LED light in operation; a plurality of second LEDs adapted to emit second LED light in operation, the second LED light being red light, the plurality of second LEDs and the phosphor structure being positioned relative to one another such that the phosphor structure receives the second LED light in operation; a plurality of third LEDs adapted to emit third LED light in operation, the third LED light being green light, the plurality of third LEDs and the phosphor structure being positioned relative to one another such that the phosphor structure receives the third LED light in operation; a plurality of fourth LEDs adapted to emit fourth LED light in operation, the fourth LED light being blue light, the plurality of fourth LEDs and the phosphor structure being positioned relative to one another such that the phosphor structure receives the fourth LED light in operation; an electrical circuit coupled to the plurality of first LEDs, the plurality of second LEDs, the plurality of third LEDs, and the plurality of fourth LEDs; an elongated support, wherein the plurality of first LEDs, the plurality of second LEDs, the plurality of third LEDs, and the plurality of fourth LEDs are disposed on a first main surface of the elongated support; Including, the phosphor structure includes at least one of a phosphor adapted to generate cold white (CW) light and a phosphor adapted to generate warm white (WW) light in combination with one or more of the second LED light, the third LED light, and the fourth LED light; the phosphor structure is configured to convert 10% or less of the second LED light, the third LED light, and the fourth LED light; the first LED light includes or is light having a peak wavelength in the range of 380 to 440 nm, 380 to 410 nm, or 400 to 410 nm, or light having a peak wavelength of 405 nm, and the phosphor structure is configured to be excited by light having a wavelength corresponding to the wavelength of the first LED light.

2. 2. The LED filament of claim 1, wherein the plurality of first LEDs, the plurality of second LEDs, the plurality of third LEDs, and the plurality of fourth LEDs are arranged in a sequence of a first LED followed by a group including a second LED, a third LED, and a fourth LED.

3. 3. The LED filament of claim 1, wherein the LED filament comprises a single filament string.

4. 3. The LED filament of claim 1, wherein the LED filament includes a first filament string and a second filament string, and the phosphor structure is arranged on the first filament string and the second filament string such that one of the first filament string and the second filament string includes a phosphor adapted to produce cold white (CW) light in combination with one or more of the second LED light, the third LED light, and the fourth LED light, and the other of the first filament string and the second filament string includes a phosphor adapted to produce warm white (WW) light in combination with one or more of the second LED light, the third LED light, and the fourth LED light.

5. 5. The LED filament of claim 4, wherein the phosphor adapted to produce the WW light comprises a red phosphor disposed below a phosphor adapted to produce the same type of CW light as the phosphor adapted to produce the CW light included in the one of the first and second filament strings that includes the phosphor adapted to produce the CW light.

6. 6. The LED filament of claim 4, wherein each of the first filament string and the second filament string comprises a plurality of first LEDs adapted to emit a first light, in operation, the plurality of first LEDs and the phosphor structure being arranged relative to one another such that, in operation, the phosphor structure receives the first light.

7. 7. The LED filament of claim 4, wherein each of the first filament string and the second filament string comprises: a plurality of second LEDs adapted to emit, in operation, a second LED light, wherein the second LED light is red light, and the plurality of second LEDs and the phosphor structure are arranged relative to one another such that, in operation, the phosphor structure receives the second LED light; a plurality of third LEDs adapted to emit, in operation, a third LED light, wherein the third LED light is green light, and the plurality of third LEDs and the phosphor structure are arranged relative to one another such that, in operation, the phosphor structure receives the third LED light; and a plurality of fourth LEDs adapted to emit, in operation, a fourth LED light, wherein the fourth LED light is blue light, and the plurality of fourth LEDs and the phosphor structure are arranged relative to one another such that, in operation, the phosphor structure receives the fourth LED light.

8. the LED filaments include at least a first filament string and a second filament string; the plurality of first LEDs adapted to emit first LED light in operation and the phosphor structure are disposed on the first filament string; 3. The LED filament of claim 1, wherein the plurality of second LEDs adapted to emit second LED light, when operated, the plurality of third LEDs adapted to emit third LED light, and the plurality of fourth LEDs adapted to emit fourth LED light, when operated, are arranged on the second filament string.

9. the LED filament includes one or more additional filament strings; a plurality of additional second LEDs adapted to emit second LED light in operation are disposed on at least one additional filament string of the one or more additional filament strings; a plurality of additional third LEDs adapted to emit third LED light in operation are disposed on at least one additional filament string of the one or more additional filament strings; 9. The LED filament of claim 1, wherein a further plurality of fourth LEDs adapted to emit fourth LED light in operation are disposed on at least one further filament string of the one or more further filament strings.

10. 10. An LED filament according to any one of claims 1 to 9, wherein the phosphor structure is of a type that, when exposed to light, emits light in any one or more of the yellow and red wavelength regions and is not excited by light in any one or more of the green and blue wavelength regions.

11. 11. An LED filament according to any one of claims 1 to 10, wherein the phosphor structure is of a type that is not excited by light having a wavelength in the blue region.

12. 12. An LED filament according to any one of claims 1 to 11, wherein the phosphor structure is of a type that is not excited by light in the wavelength range of 550 nm to 610 nm.

13. 13. The LED filament of claim 1, wherein the phosphor structure comprises at least one phosphor selected from the group comprising: Purple pump blue phosphor, (Sr,Ca,Ba)5(PO4)3Cl:Eu2+, Purple pump green phosphor, (Ba, Sr) MgAl10 O17: Mn2+, Eu2+, Purple pump red phosphor, Mg8Ge2O11F2:Mn4+.

14. 14. An LED filament according to any one of claims 1 to 13, wherein the phosphor structure comprises at least one phosphor selected from the group comprising quantum dot materials with violet absorption and green, yellow or orange / red emission.

15. 15. A luminaire or lamp comprising an LED filament according to any one of claims 1 to 14.

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