A LED filament comprising a LED filament assembly of a plurality of intertwined sub-LED filaments

Abstract

The present invention relates to a light emitting diode, LED, filament (1) configured to provide, in operation, LED filament light, the LED filament having a longitudinal axis, LA, the LED filament (1) comprises a LED filament assembly of a plurality of intertwined sub-LED filaments (2a,2b), said LED filament assembly having in a cross-section perpendicular to the longitudinal axis LA a first diameter D1, D1 being the diameter of a smallest virtual circle encircling the LED-filament assembly, each sub-LED filament (2a,2b) is configured to provide, in operation, respective sub-LED filament light, each sub-LED filament (2a,2b) having a respective sub-LED filament diameter (D2a,D2b), wherein the respective sub-LED filament diameter (D2a, D2b) is in a range of D2min to D2max, wherein 1.5 ≤ D1 / D2max ≤ 3.

Description

[0001] 2023PF80522

[0002] 1

[0003] A LED FILAMENT COMPRISING A LED FILAMENT ASSEMBLY OF A PLURALITY

[0004] OF INTERTWINED SUB-LED FILAMENTS

[0005] FIELD OF THE INVENTION

[0006] The invention relates to intertwined, more specifically twisted, flexible subLED filaments forming a single-LED filament providing CCT and / or CP tunable light.

[0007] BACKGROUND OF THE INVENTION

[0008] A trend in lighting is LED filament lamps. A LED filament lamp is a LED lamp which is designed to resemble a traditional incandescent light bulb with a visible filament for aesthetic and light distribution purposes, but with the high efficiency of lightemitting diodes.

[0009] A recent trend is correlated color temperature (CCT) and / or color point (CP) tunable LED filaments.

[0010] In this respect, the document EP 3 915 338 discloses a color tunable filament lamp comprising at least one tunable white LED filament and at least one RGB (Red Green Blue) filament.

[0011] These tunable LED filaments of different colors or color temperatures are arranged parallel next to each other in straight or helix configuration, forming a wide assembly perceived for the human eye as an assembly of distinct LED filaments. Furthermore, it provides non homogeneous light because the light emitted by one filament is blocked by the light emitted by a neighboring LED filament.

[0012] SUMMARY OF THE INVENTION

[0013] Hence, it is an object of the present invention to produce a tunable LED filament comprising multiple sub-LED filaments with said tunable LED filament perceived as a single LED filament.

[0014] To this end, the LED filament comprises multiple intertwined, or in other words, twisted, coiled, or braided, sub-LED filaments with a tight intertwining.

[0015] More specifically, the invention relates to a light emitting diode, LED, filament configured to provide, in operation, LED filament light, the LED filament having a 2023PF80522

[0016] 2 longitudinal axis, LA, the LED filament comprises a LED filament assembly of a plurality of intertwined sub-LED filaments, said LED filament assembly having in a cross-section perpendicular to the longitudinal axis LA a first diameter DI, DI being the diameter of a smallest virtual circle encircling the LED-filament assembly, each sub-LED filament is configured to provide, in operation, respective sub-LED filament light, each sub-LED filament having a respective sub-LED filament diameter D2, wherein the respective sub-LED filament diameter D2 is in a range of D2min to D2max, wherein 1.5 < Dl / D2max < 3. Although separate sub-filaments are used, because of the dense arrangement, the LED filament assembly is perceived as a single LED filament due to optical integration by the human eye. Hence, a LED filament is provided that has increased light output. Furthermore, the LED filament assembly has an improved mechanical stability or bending stiffness.

[0017] According to embodiments of the invention, the following may apply: 1 < D2max / D2min < 2, preferably 1 < D2max / D2min < 1.5, more preferably 1 < D2max / D2min

[0018] < 1.2, most preferably 1 < D2max / D2min < 1.1. By decreasing the difference in diameters of the sub-filaments, the obtained effect is improved uniformity in the (perceived) thickness of the LED filament assembly.

[0019] According to embodiments of the invention, the following may apply: 2 < Dl / D2max < 2.9, preferably 2 < Dl / D2max < 2.7, more preferably 2 < Dl / D2max < 2.5, most preferably 2 < Dl / D2max < 2.3. By improving the packing of the sub-LED filaments in the LED filament assembly, the obtained effect is further improved uniformity in the (perceived) thickness of the LED filament assembly.

[0020] According to embodiments of the invention, a maximum distance between sub-LED filaments may be less than D2max, such as less than 0.8-D2max, preferably less than 0.5-D2max, at the cross-section perpendicular to the longitudinal axis LA.

[0021] According to embodiment of the invention, the plurality of intertwined sub- LED filaments comprises n sub-LED filaments. The smallest virtual circle encircles a first cross-section area Al and each of the n sub-LED filaments has a respective sub-LED filament cross section area, A2a, . . . , An. The n sub-LED filament cross section areas sum up into a combined sub-LED filament cross section area, SAn, For the sum SAn of all the n sub- LED filament cross section areas 0.5 < SAn / Al < 1, such as 0.6 < SAn / Al < 1, preferably 0.7

[0022] < SAn / Al < 1 applies.

[0023] This further improves the density of packing of the sub-LED filaments in the LED filament by minimizing empty spaces between the sub-LED filaments. Thereby further improved uniformity in the (perceived) thickness of the LED filament assembly is achieved. 2023PF80522

[0024] 3

[0025] According to embodiments of the invention, each sub-LED filament has a length La, Lb, determined along the elongation direction of each sub-LED filament, and 0.75 < La / Lb < 1.25, such as 0.8 < La / Lb < 1.2, especially 0.9 < La / Lb < 1.1.

[0026] In other words, the sub-LED filaments have a similar length, such that a neat LED filament is formed upon intertwining the sub-LED filaments in which each sub-LED filament extends through substantially the whole LED filament assembly.

[0027] According to embodiments of the invention, each sub-LED filament of the plurality of intertwined sub-LED filaments is twisted. The obtained effect is improved homogenous LED filament light having improved mixed sub-LED filament light.

[0028] According to embodiments of the invention, each sub-LED filament of the plurality of intertwined sub-LED filaments comprises an array of a plurality of LEDs arranged on an elongated carrier, each LED of the plurality of LEDs comprises a respective light output surface facing away from the longitudinal axis LA. The obtained effect is improved efficiency. The reason is that the emission directions of the plurality of LEDs is directed in a direction facing away from the LED filament assembly.

[0029] According to embodiments of the invention, the plurality of intertwined sub- LED filaments are mutually fixed by a glue or a clamp. The obtained effect is a reliable and robust LED filament assembly which is perceived as a single LED filament.

[0030] According to embodiments of the invention, the plurality of intertwined sub- LED filaments comprises three sub-LED filaments, four sub-LED filaments or five sub-LED filaments.

[0031] According to embodiments of the invention, the respective sub-LED filament light of at least two sub-LED filaments or at least three sub-LED filaments mutually differs in terms of color and / or correlated color temperature. The obtained effect is improved spectral light distribution and / or light quality. The reason is that multiple different spectral light distributions can be combined.

[0032] According to embodiments of the invention, the plurality of intertwined sub- LED filaments comprises one of the following:

[0033] (i) a first sub-LED filament configured to provide, in operation, first sub-LED filament light having a first correlated color temperature (CCT1) and a second sub-LED filament configured to provide, in operation, second sub-LED filament light having a second correlated color temperature (CCT2) at least 300K (or at least 700K) different from the first correlated color temperature; 2023PF80522

[0034] 4

[0035] (ii) a first sub-LED filament configured to provide, in operation, red sub-LED filament light, a second sub-LED filament configured to provide, in operation, green sub- LED filament light, and a third sub-LED filament configured to provide, in operation, blue sub-LED filament light;

[0036] (iii) a first sub-LED filament configured to provide, in operation, red sub-LED filament light, a second sub-LED filament configured to provide, in operation, green sub- LED filament light, a third sub-LED filament configured to provide, in operation, blue sub- LED filament light, and a fourth sub-LED filament configured to provide, in operation, fourth sub-LED filament light having a first correlated color temperature (CCT1);

[0037] (iv) a first sub-LED filament configured to provide, in operation, red sub-LED filament light, a second sub-LED filament configured to provide, in operation, green sub- LED filament light, a third sub-LED filament configured to provide, in operation, blue sub- LED filament light, a fourth sub-LED filament configured to provide, in operation, fourth sub-LED filament light having a first correlated color temperature (CCT1), and a fifth sub- LED filament configured to provide, in operation, fifth sub-LED filament light having a second correlated color temperature (CCT2) at least 300K (or at least 700K) different from the first correlated color temperature. The obtained effect is that such LED filament assembly can be used for color and / or correlated color temperature control.

[0038] According to embodiments of the invention, the LED filament comprises a core extending along the longitudinal axis LA, the plurality of sub-LED filaments being arranged around the core. The obtained effect is an improved LED filament assembly in terms of mechanical and / or thermal performance.

[0039] According to embodiments of the invention, the core has one or more of the following features:

[0040] (i) the core is flexible,

[0041] (ii) the core has a reflectivity of at least 70%,

[0042] (iii) the core is translucent,

[0043] (iv) the core has a thermal conductivity of at least 10W / m-K. The obtained effect is an improved LED filament assembly in terms of optical, mechanical and / or thermal performance.

[0044] According to embodiments of the invention, the pitch angle a of the sub-LED filaments with respect to the longitudinal axis LA is in a range from 30 to 60 degrees, preferably in a range from 30 to 50 degrees, more preferably in a range from 30 to 45 2023PF80522

[0045] 5 degrees, most preferably in a range from 30 to 40 degrees. The obtained effect is even further improved uniformity in the (perceived) thickness of the LED filament assembly.

[0046] According to embodiments of the invention, the LED filament comprises a translucent shell extending along the longitudinal axis LA, the plurality of sub-LED filaments being at least partly enclosed by the translucent shell. The translucent shell may be transparent. Such shell provides (ingress) protection without increasing the diameter of the Tight source’. The reason is that a transparent shell does (almost) not redirect / diffuse the LED filament light. The translucent shell may be diffusive / light scattering to improve the mixing of the sub-LED filament light.

[0047] In embodiments, the LED filament light may be white light having a correlated color temperature in a range from 1700K to 6500K and / or a color rendering index of at least 80 or at least 85.

[0048] In embodiments, the sub-LED filament light may be (i) white light having a correlated color temperature in a range from 1700K to 6500K and / or a color rendering index of at least 80 or at least 85, Red light, Green light or Red light.

[0049] In embodiments, the LED filament may comprise an elongated carrier. The plurality of LEDs may be arranged on a first major surface of the elongated carrier. The elongated carrier may be reflective or translucent e.g. transparent or light diffusive. A first elongated encapsulant may cover at least part of the first major surface and at least party enclose the plurality of LEDs. A second elongated encapsulant may cover at least part of a second major surface opposite to the first major surface. Alternatively the first elongated encapsulant may also cover at least a portion of the second major surface of the elongated carrier. The first elongated encapsulant may comprise (i) a first luminescent material configured to at least partly convert LED light emitted by the plurality of LEDs into first converted light and / or (ii) a first light scattering material configured to at least partly scatter LED light emitted by the plurality of LEDs into first scattered light. The second elongated encapsulant may comprise (i) a second luminescent material configured to at least partly convert LED light emitted by the plurality of LEDs into second converted light and / or (ii) a second light scattering material configured to at least partly scatter LED light emitted by the plurality of LEDs into second scattered light. The (sub) LED filament light may comprise one or more of the first converted light, the second converted light, the first scattered light, the second scattered light, and (part of) the LED light.

[0050] In embodiments, the LED filament may have a non-circular cross-section. Said LED filament may have a length L, a width W and a thickness T. The LED filament 2023PF80522

[0051] 6 length L may be at least 5 cm, preferably at least 10 cm, more preferably at least 15 cm, most preferably at least 20 cm. The LED filament width W may be in a range 1 to 10 mm, preferably in a range from 2 to 9 mm, more preferably in a range from 3 to 8 mm, most preferably in a range from 4 to 7 mm. The LED filament thickness T may be in a range 1 to 10 mm, preferably in a range from 2 to 9 mm, more preferably in a range from 3 to 8 mm, most preferably in a range from 4 to 7 mm. L may be at least 10 times W and at least 10 times T.

[0052] In embodiments, the sub-LED filaments may have a non-circular crosssection. In this case, the sub-LED filament diameter D2 may be the diameter of a smallest virtual circle encircling the sub-LED filament. Said sub-LED filaments may have a length L, a width W and a thickness T. The sub-LED filament length L may be at least 5 cm, preferably at least 10 cm, more preferably at least 15 cm, most preferably at least 20 cm. The sub-LED filament width W may be in a range 0.5 to 3 mm. The sub-LED filament thickness T may be in a range 0.5 to 3 mm. L may be at least 10 times W and at least 10 times T.

[0053] The invention also relates to a LED filament arrangement comprising the LED filament as described aforementioned, the LED filament arrangement further comprises a controller configured to individually control the sub-LED filament light provided, during operation, by the sub-LED filaments. For example, when using a (relatively) cool-white (CW) sub-LED filament and a (relatively) warm-white (WW) sub-LED filament, the controller may be configured to individually control the WW sub-LED filament and the CW sub-LED filament. In this way, the correlated color temperature (CCT) of the LED filament can be altered. Said CW LED filament may have a first correlated color temperature, CCT1 of >3000K. Said CW LED filament may have a second correlated color temperature, CCT2 of <2700K with preferably I CCT1-CCT2 I >500K or >1000K. For example, when using a red, green and blue sub-LED filament, the controller may be configured to individually control the red, green and blue sub-LED filaments. In this way, the color point of the LED filament may be altered e.g. with a Ax in color coordinates of at least 0.05 and / or with a Ay in color coordinates of at least 0.05 (e.g. in a CIE 1931 Color Space). In similar vein, a red, green, blue and white sub-LED filament may be combined and individually controlled by the controller.

[0054] The invention also relates to a LED filament lamp or a LED filament luminaire comprising the LED filament or the LED filament arrangement as described hereabove. The LED filament lamp may comprise a (transparent) envelope at least partly enclosing said LED filament. The LED filament lamp may comprise a connector for 2023PF80522

[0055] 7 electrically and / or mechanically connecting the LED filament lamp to a socket (of a luminaire). The luminaire may comprise a light exit window e.g. a transparent plate to exit the LED filament light (as luminaire light). Said LED filament lamp and / or luminaire may further comprise an antenna.

[0056] Further objectives of, features of, and advantages with, the present invention will become apparent when studying the following detailed disclosure, the drawings and the appended claims. Those skilled in the art will realize that different features of the present invention may be combined to create embodiments other than those described in the following.

[0057] BRIEF DESCRIPTION OF THE DRAWINGS

[0058] This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiment(s) of the invention.

[0059] Fig. 1 shows a schematic view of the LED filament according to one variant of the invention with two zooms of the LEDs on the carrier.

[0060] Fig. 2 shows a schematic view of the LED filament according to another variant of the invention with one sub-LED filament having a larger diameter than the other one.

[0061] Fig. 3 shows three schematic cross-sectional views of different variants of the LED filament according to the invention.

[0062] Fig. 4 shows the LED filament of Fig. 1 twisted on a core according to an embodiment of the invention.

[0063] Fig. 5 shows three LED filaments with different pitch angles a.

[0064] Fig. 6 shows a cross-sectional view of the elongated carrier with the LEDs surrounded by an encapsulant.

[0065] Fig. 7 shows a lamp provided with the LED filament according to the invention.

[0066] Fig .8 shows a luminaire comprising several lamps.

[0067] DETAILED DESCRIPTION

[0068] Fig. 1 shows a LED, for light emitting diode, filament according to the invention. The LED filament 1 comprises multiple sub-LED filaments 2a, 2b intertwined around a longitudinal axis LA. The term intertwined is used but other appropriate terms could be braided, coiled, or twisted. In the example illustrated, only two sub-LED filaments are 2023PF80522

[0069] 8 represented but the number of sub-LED filaments could be of 3, 4, 5 or more (Fig. 3). Preferably, the LED filament 1 comprises at least three sub-filaments 2a, 2b, 2c.

[0070] Each sub-LED filament 2a, 2b has a respective diameter D2a,D2b, said diameter D2a,D2b may include the thickness of a carrier, one or more encapsulants and one or more LEDs as described hereafter. The LED filament 1 has a diameter D measured in a direction perpendicular to the longitudinal axis LA.

[0071] The sub-LED filament and / or the LED filament could have a non-circular cross-section. For this reason, the diameter D2a,D2b, the diameter D and the diameter DI described hereafter are more generally defined as the smallest virtual diameter that could be drawn around respectively the sub-LED filament and the LED filament. This definition allows to cover circular and non-circular cross-sections.

[0072] The respective diameter D2a,D2b may be identical as shown in Fig. 1 or different with a minimum diameter D2min for the sub-filament 2a and a maximum D2max for the sub-filament 2b as shown in Fig. 2. As a consequence, the diameter D of the LED filament 1 may be constant or variable along the longitudinal axis LA. According to the invention, a diameter DI in the direction perpendicular to the longitudinal axis LA is defined, with said diameter DI being the smallest diameter of the LED filament. According to the invention, the ratio between DI and D2max is comprised between 1.5 and 3 (1.5<D1 / D2max<3), preferably between 2 and 2.9, more preferably between 2 and 2.7, most preferably between 2 and 2.5, and even more preferably between 2 and 2.3, to obtain a dense arrangement. Preferably, the ratio between D2max and D2min is comprised between 1 and 2 (l<D2min / D2max<2), more preferably between 1 and 1.5, most preferably between 1 and 1.2 and even more preferably between 1 and 1.1. D2min could also be equal to D2max allowing to form a LED filament with a constant diameter D and so with a helical shape. Preferably, as represented in Fig. 4, the pitch angle a of the sub-LED filaments 2a, 2b with respect to the longitudinal axis LA is in a range from 30 to 60 degrees for a better optical integration. Preferably it is in a range from 30 to 50 degrees, more preferably in a range from 30 to 45 degrees, most preferably in a range from 30 to 40 degrees. Fig. 5 represents the LED filament with a decreasing pitch angle a from the upper view to the lower view.

[0073] The LED filament may have a length L, a width W and a thickness T, with W being equal to T and corresponding to the diameter DI for a circular cross-section. The LED filament length L may be at least 5 cm, preferably at least 10 cm, more preferably at least 15 cm, most preferably at least 20 cm. The LED filament width W may be in a range 1 to 10 mm, preferably in a range from 2 to 9 mm, more preferably in a range from 3 to 8 mm, most 2023PF80522

[0074] 9 preferably in a range from 4 to 7 mm. The LED filament thickness T may be in a range 1 to 10 mm, preferably in a range from 2 to 9 mm, more preferably in a range from 3 to 8 mm, most preferably in a range from 4 to 7 mm. L may be at least 10 times W and at least 10 times T.

[0075] The sub-LED filament may have a length L, a width W and a thickness T, with W being equal to T and corresponding to the diameter D2a,D2b for a circular cross-section. The sub-LED filament length L may be at least 5 cm, preferably at least 10 cm, more preferably at least 15 cm, most preferably at least 20 cm. The sub-LED filament width W may be in a range 0.5 to 3 mm. The sub-LED filament thickness T may be in a range 0.5 to 3 mm. L may be at least 10 times W and at least 10 times T.

[0076] Fig. 3 shows three schematic cross-sectional views of different variants of the LED filament according to the invention. The plurality of intertwined sub-LED filaments comprises n sub-LED filaments 2a-2n. The smallest virtual circle encircles a first crosssection area Al and each of the n sub-LED filaments 2a-2n has a respective sub-LED filament cross section area, A2a-An. For a sum S of all the n sub-LED filament cross section areas 0.5 < S / Al < 1, such as 0.6 < S / Al < 1, preferably 0.7 < S / Al < 1 applies.

[0077] The sub-LED filaments 2a, 2b may be twisted around a core 5 extending along the longitudinal axis LA (Fig. 4). Said core 5 may for example be a rod or a wire. The core can fulfill one or more of the following features: being flexible for improved reliability, being reflective with a reflectivity of at least 70% for preventing crosstalk, being translucent for improved homogeneous light, being metallic with a thermal conductivity of at least lOW / m.K for improved cooling. The core 5 may be included in the final LED filament 1 but could alternatively be removed after having twisted the multiple sub-LED filaments.

[0078] The intertwined sub-LED filaments are fixed to each other with a flexible glue. The glue may be a silicone, e.g. cross-linked polydimethylsiloxane preferably with a light scattering material.

[0079] The tunable sub-LED filament 2a, 2b comprises an elongated flexible carrier 4 and a plurality of LEDs 3a, 3b arranged along the carrier 4 as shown in Fig. 1. The flexible carrier 4 may for example be made of a polymer or metal, e.g. a film or foil. The carrier 4 may be a flexible PCB (printed circuit board). The LEDs are radially facing outwards from the LED filament. The plurality of LEDs 3a, 3b may be arranged on a first major surface 4a of the elongated carrier 4 (Fig. 6). The elongated carrier may be reflective or translucent e.g. transparent or light diffusive. A first elongated encapsulant 15 may cover at least part of the first major surface 4a and at least party enclose the plurality of LEDs 3 a, 3b. A second 2023PF80522

[0080] 10 elongated encapsulant 16 may cover at least part of a second major surface 4b opposite to the first major surface 4a. Alternatively the first elongated encapsulant may also cover at least a portion of the second major surface of the elongated carrier. The first elongated encapsulant may comprise (i) a first luminescent material configured to at least partly convert LED light emitted by the plurality of LEDs into first converted light and / or (ii) a first light scattering material configured to at least partly scatter LED light emitted by the plurality of LEDs into first scattered light. The second elongated encapsulant may comprise (i) a second luminescent material configured to at least partly convert LED light emitted by the plurality of LEDs into second converted light and / or (ii) a second light scattering material configured to at least partly scatter LED light emitted by the plurality of LEDs into second scattered light. The (sub) LED filament light may comprise one or more of the first converted light, the second converted light, the first scattered light, the second scattered light, and (part of) the LED light.

[0081] The LED filament according to the invention provides CCT and / or CP tunable light. To this end, at least two sub-LED filaments 2a, 2b have a different color and / or color temperature. The following architectures for the colors and / or color temperatures of the multiple sub-LED filaments can be achieved: there are at least two sub-LED filaments 2a, 2b with a first sub-LED filament configured to provide, in operation, a first sub-LED filament light having a first correlated color temperature (CCT1) and a second sub-LED filament configured to provide, in operation, a second sub-LED filament light having a second correlated color temperature (CCT2) at least 300K different from the first correlated color temperature. For example, it may a first sub-LED filament emitting a warm white light and a second sub-LED filament emitting a cold white light; there are at least three sub-LED filaments 2a, 2b, 2c with a first sub-LED filament configured to provide, in operation, red sub-LED filament light, a second sub-LED filament configured to provide, in operation, green sub-LED filament light, and a third sub- LED filament configured to provide, in operation, blue sub-LED filament light; there are at least four sub-LED filaments 2a, 2b, 2c, 2d with a first sub-LED filament configured to provide, in operation, red sub-LED filament light, a second sub-LED filament configured to provide, in operation, green sub-LED filament light, a third sub-LED filament configured to provide, in operation, blue sub-LED filament light, and a fourth sub- LED filament configured to provide, in operation, fourth sub-LED filament light having a first correlated color temperature (CCT1); 2023PF80522

[0082] 11 there are at least five sub-LED filaments 2a, 2b, 2c, 2d, 2e with a first sub-LED filament configured to provide, in operation, red sub-LED filament light, a second sub-LED filament configured to provide, in operation, green sub-LED filament light, a third sub-LED filament configured to provide, in operation, blue sub-LED filament light, a fourth sub-LED filament configured to provide, in operation, fourth sub-LED filament light having a first correlated color temperature (CCT1), and a fifth sub-LED filament configured to provide, in operation, fifth sub-LED filament light having a second correlated color temperature (CCT2) at least 300K different from the fourth correlated color temperature. For example, the fourth and fifth sub-LED filaments may respectively emit a warm white light and a cold white light.

[0083] The tunable sub-LED filaments are electrically connected to a controller 12 schematically represented in Fig. 7, to individually control the light emitted by the different sub-LED filaments. For example, when using a (relatively) cool-white (CW) sub-LED filament and a (relatively) warm-white (WW) sub-LED filament, the controller may be configured to individually control the WW sub-LED filament and the CW sub-LED filament. In this way, the correlated color temperature (CCT) of the LED filament can be altered. Said CW LED filament may have a first correlated color temperature, CCT1 of >3000K. Said CW LED filament may have a second correlated color temperature, CCT2 of <2700K with preferably I CCT1-CCT2 I >500K or >1000K. For example, when using a red, green and blue sub-LED filament, the controller may be configured to individually control the red, green and blue sub-LED filaments. In this way, the color point of the LED filament may be altered e.g. with a Ax in color coordinates of at least 0.05 and / or with a Ay in color coordinates of at least 0.05 (e.g. in a CIE 1931 Color Space). In similar vein, a red, green, blue and white sub-LED filament may be combined and individually controlled by the controller.

[0084] The LED filament 1 may comprise a translucent, e.g. light-scattering, shell 6 for off-state white appearance and better optical integration. The translucent shell may be transparent. The shell 6 may be a tube extending along the longitudinal axis LA and covering at least partially the sub-LED filaments 2a, 2b as represented in Fig. 4.

[0085] The invention also relates to a LED filament lamp 10 represented in Fig. 7. It comprises an envelope 11 at least partly enclosing the LED filament 1 according to the invention and a base 13 with the controller 12 to individually control the sub-LED filament light emitted in operation by the different sub-LED filaments. The LED filament lamp may comprise a connector (not represented) for electrically and / or mechanically connecting the LED filament lamp to a socket of a luminaire. 2023PF80522

[0086] 12

[0087] The invention also relates to a luminaire 17 shown in Fig. 8 comprising several LED filament lamps 10. The luminaire may comprise a light exit window (not represented) e.g. a transparent plate to exit the LED filament light as luminaire light. Said LED filament lamp and / or luminaire may further comprise an antenna (not represented). The LED filament 1 according to the invention may be manufactured by the method comprising the steps of :

[0088] Providing a plurality of sub-LED filaments 2a, 2b having a respective diameter D2a,D2b with the respective sub-LED filaments diameters D2a,D2b being in a range from D2min to D2max, Intertwining said plurality of sub-LED filaments 2a, 2b in a direction around the longitudinal axis LA to obtain the LED filament 1 with the minimum diameter DI in the direction perpendicular to the longitudinal axis LA, said intertwining being carried out so that Dl / D2max is comprised between 1.5 and 3.

Claims

2023PF8052213CLAIMS:

1. A light emitting diode, LED, filament (1) configured to provide, in operation, LED filament light, the LED filament having a longitudinal axis, LA, the LED filament (1) comprising a LED filament assembly of a plurality of intertwined sub-LED filaments (2a, 2b), said LED filament assembly having in a cross-section perpendicular to the longitudinal axis LA a first diameter DI, DI being the diameter of a smallest virtual circle encircling the LED- filament assembly, each sub-LED filament (2a, 2b) is configured to provide, in operation, respective sub-LED filament light, each sub-LED filament (2a, 2b) having a respective sub- LED filament diameter, D2a,D2b, wherein the respective sub-LED filament diameter, D2a, D2b is in a range of D2min to D2max, wherein 1.5 < Dl / D2max < 3, and wherein 1 < D2max / D2min < 1.5.

2. The LED filament (1) according to claim 1, wherein each sub-LED filament (2a, 2b) has a length La, Lb, and wherein 0.8 < La / Lb < 1.2.

3. The LED filament (1) according to any one of the preceding claims, wherein the plurality of intertwined sub-LED filaments comprises n sub-LED filaments (2a,..., 2n), wherein the smallest virtual circle encircles a first cross-section area Al, wherein each of the n sub-LED filaments (2a, . . . ,2n) has a respective sub-LED filament cross section area,A2a, . . . , An, summing up into a combined sub-LED filament cross section area, S An, and wherein 0.5 < SAn / Al < 1.

4. The LED filament (1) according to any one of the preceding claims, wherein each sub-LED filament (2a, 2b) of the plurality of intertwined sub-LED filaments (2a, 2b) is twisted.

5. The LED filament (1) according to any one of the preceding claims, wherein each sub-LED filament (2a, 2b) of the plurality of intertwined sub-LED filaments (2a, 2b) comprises an array of a plurality of LEDs (3a, 3b) arranged on an elongated carrier (4), each2023PF8052214LED of the plurality of LEDs (3a, 3b) comprises a respective light output surface facing away from the longitudinal axis LA.

6. The LED filament (1) according to any one of the preceding claims, wherein the plurality of intertwined sub-LED filaments (2a, 2b) are mutually fixed by a glue or clamp.

7. The LED filament (1) according to any one of the preceding claims, wherein the plurality of intertwined sub-LED filaments (2a, 2b) comprises three sub-LED filaments (2a, 2b, 2c), four sub-LED filaments (2a, 2b, 2c, 2d) or five sub-LED filaments (2a, 2b, 2c, 2d, 2e).

8. The LED filament (1) according to any one of the preceding claims, wherein the respective sub-LED filament light of at least two sub-LED filaments (2a, 2b) mutually differs in terms of color and / or correlated color temperature.

9. The LED filament (1) according to any one of the preceding claims, wherein the plurality of intertwined sub-LED filaments (2a, 2b) comprises one of the following:(i) a first sub-LED filament configured to provide, in operation, first sub-LED filament light having a first correlated color temperature (CCT1) and a second sub-LED filament configured to provide, in operation, second sub-LED filament light having a second correlated color temperature (CCT2) at least 300K different from the first correlated color temperature (CCT1);(ii) a first sub-LED filament configured to provide, in operation, red sub-LED filament light, a second sub-LED filament configured to provide, in operation, green sub- LED filament light, and a third sub-LED filament configured to provide, in operation, blue sub-LED filament light;(iii) a first sub-LED filament configured to provide, in operation, red sub-LED filament light, a second sub-LED filament configured to provide, in operation, green sub- LED filament light, a third sub-LED filament configured to provide, in operation, blue sub- LED filament light, and a fourth sub-LED filament configured to provide, in operation, fourth sub-LED filament light having a first correlated color temperature (CCT1);(iv) a first sub-LED filament configured to provide, in operation, red sub-LED filament light, a second sub-LED filament configured to provide, in operation, green sub- LED filament light, a third sub-LED filament configured to provide, in operation, blue sub- LED filament light, a fourth sub-LED filament configured to provide, in operation, fourth2023PF8052215 sub-LED filament light having a first correlated color temperature (CCT1), and a fifth subLED filament configured to provide, in operation, fifth sub-LED filament light having a second correlated color temperature (CCT2) at least 300K different from the first correlated color temperature.

10. The LED filament (1) according to any one of the preceding claims, further comprising a core (5) extending along the longitudinal axis LA, wherein the plurality of sub- LED filaments (2a, 2b) is arranged around the core (5).

11. The LED filament (1) according to claim 10, wherein one or more of the following applies:(v) the core (5) is flexible,(vi) the core (5) has a reflectivity of at least 70%,(vii) the core (5) is translucent,(viii) the core (5) has a thermal conductivity of at least 10W / m-K.

12. The LED filament (1) according to any one of the preceding claims, wherein the pitch angle a of the sub-LED filaments (2a, 2b) with respect to the longitudinal axis LA is in a range from 30 to 60 degrees.

13. The LED filament (1) according to any one of the preceding claims, further comprising a translucent shell (6) extending along the longitudinal axis LA, wherein the plurality of sub-LED filaments (2a, 2b) is at least partly enclosed by the translucent shell (6).

14. A LED filament arrangement comprising the LED filament (1) according to any one of the preceding claims, the LED filament arrangement further comprising a controller (12) configured to individually control the sub-LED filament light provided, during operation, by the sub-LED filaments (2a, 2b).

15. A LED filament lamp (10) or a LED filament luminaire (17) comprising the LED filament (1) according to any one of the claims 1-13 or the LED filament arrangement according to claim 14.

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