LED filament

Abstract

The present invention relates to an LED filament 10 for providing an LED filament light 12, comprising an elongated support 14 and a plurality of light emitting diodes 16 arranged on the elongated support, the LED filament being arranged in a coiled-coil configuration.

Description

Technical Field

[0001] The present invention relates to an LED filament for supplying LED (light emitting diode) filament light. The present invention also relates to a lamp or lighting fixture comprising at least one such LED filament. The present invention also relates to a method for manufacturing an LED filament.

Background Art

[0002] The trend in lighting is the LED filament lamp. An LED filament lamp is an LED lamp designed to resemble a conventional incandescent bulb that has a visible filament for aesthetic and light distribution purposes but has the high efficiency of a light emitting diode. The LED filament may be arranged in a straight configuration or in a coil configuration. One example of the latter is disclosed in International Publication No. 2020221653 (A1).

Summary of the Invention

Problems to be Solved by the Invention

[0003] It is an object of the present invention to improve the performance and / or appearance of an LED filament lamp.

Means for Solving the Problems

[0004] According to a first aspect of the present invention, this object and other objects are achieved by an LED filament for supplying LED filament light, comprising an elongated support and a plurality of light emitting diodes arranged on the elongated support, and arranged in a coiled-coil configuration. In particular, the coiled-coil configuration includes a primary coil having a primary diameter D1, the primary coil being coiled into a secondary coil having a secondary diameter D2, the primary coil having a plurality of primary loops, and the secondary coil having a plurality of secondary loops.

[0005] The LED filament of the present invention may be referred to as a coiled coil (or coiled coil) LED filament or a coil-in-coil LED filament. A coil is defined as a structure consisting of a continuous series of loops wound around, that is, a structure including a plurality of loops. Therefore, a coiled coil includes a continuous series of coiled loops.

[0006] The coiled coil configuration of the LED filament of the present invention has several advantages. For example, the coiled coil configuration creates a thicker LED filament while using a thinner LED filament. The reason a thicker LED filament is desired is that more light is emitted from an LED filament having a certain length, or the larger dimensions make it possible to reduce the intensity / brightness (measured on the surface of the LED filament) and prevent / reduce glare. Furthermore, the coiled coil configuration of the LED filament improves thermal management compared to a thicker LED filament supplying the same amount of light, which is due to better fluid (gas, such as air, etc.) flow around the LED filament. Furthermore, the coiled coil configuration of the LED filament provides an improved decorative appearance.

[0007] Note that although a coiled coil filament for an incandescent bulb is known, a coiled coil LED filament is not known.

[0008] The primary diameter D1 may be in the range of 4 mm to 12 mm. If D1 is <4 mm, the filling of the LED filament will be overly dense in order to appropriately handle heat dissipation. If D1 > 12 mm, the compactness of the coiled coil configuration, which has the advantage of high light output in a relatively small space, will be overly slight.

[0009] The secondary diameter D2 may be in the range of 4D1 to 12D1. The secondary diameter D2 may be uniform over the length of the LED filament. Alternatively, the secondary diameter D2 may vary over the length of the LED filament. The secondary diameter D2 may be, for example, (more) small at the ends of the LED filament and (more) large at the longitudinal center of the LED filament.

[0010] The primary coil may have N1 primary loops (or smaller loops, i.e., smaller than the secondary loops), and the secondary coil may have N2 secondary loops (or larger loops, i.e., larger than the primary loops), where N1 ≥ 5N2, preferably N1 ≥ 8N2, more preferably N1 ≥ 10N2, and most preferably N1 ≥ 12N2. N2 is preferably ≥ 3, more preferably N2 ≥ 4, and most preferably N2 ≥ 5. Further, N2 is preferably ≤ 10, more preferably N2 ≤ 8, and most preferably N2 ≤ 7.

[0011] The secondary coil may have a secondary pitch P2 in the range of 2D1 to 10D1.

[0012] The plurality of light-emitting diodes may include blue light-emitting diodes and / or UV light-emitting diodes. The plurality of light-emitting diodes may be covered by an elongated encapsulant. The elongated encapsulant may include a luminescent material configured to at least partially convert the LED light emitted by the blue light-emitting diodes and / or UV light-emitting diodes into converted light. The elongated encapsulant may be flexible. The elongated encapsulant may be a polymer material such as, for example, silicone. The luminescent material may be, for example, a (yellow and / or red) phosphor.

[0013] The plurality of light-emitting diodes may include a first set of first light-emitting diodes and a second set of second light-emitting diodes, and the first set is individually controllable (by a controller) with respect to the second set. The sets may be configured to emit LED light of various colors or spectra, for example. In this way, the coiled coil LED filament may be adjustable, for example, with respect to color and / or color temperature.

[0014] The LED filament may further comprise a ductile element disposed along at least a major portion (>50%, for example >80%) of the length of the elongate support to enable the LED filament to be shaped. "Ductile" means being able to be shaped and dimensionally stable, that is, remaining in the second shape when deformed from the first shape to the second shape. For example, the ductile element may be a (thin) metal wire or strip made of, for example, aluminum or copper. The thickness of the ductile element is preferably in the range of 1 to 5 mm. The ductile element can be disposed in a location where it does not block light, and the ductile element can be disposed, for example, on a second major surface of the elongate support, while the plurality of light-emitting diodes are disposed on the opposite first major surface of the elongate support. The ductile element can be made light-reflective so that at least a portion of the LED filament light can be reflected by the ductile element. The ductile element can be made substantially non-light-absorbing (for example, made of metal or having a reflective coating) so as not to degrade the light output performance of the LED filament. The ductile element can be made non-visible and the ductile element can be integrated, for example, into the elongate support or covered by the aforementioned elongate encapsulant.

[0015] The ductility element may be configured to enable the LED filament to be formed into a first coiled shape corresponding to the above-mentioned primary coil and / or a second coiled shape corresponding to the above-mentioned secondary coil from a basic shape, and the first coiled shape and the second coiled shape are dimensionally stable. The basic shape is typically flat / linear. "Dimensionally stable" may mean in this case that the shape is maintained even after the force used to form the shape is removed.

[0016] Instead of using or in addition to using the ductility element, at least the shape of the primary coil may be fixed by using an adhesive or a thermoplastic polymer, and the thermoplastic polymer can be deformed by heating the LED filament above the glass transition temperature (Tg) and / or melting point (Tm) of the thermoplastic material and then cooling it to room temperature. Regarding the latter technique, a polymer having a high Tg and / or Tm should be selected because when the LED filament is lit, the temperature of the lit LED filament should preferably be below the Tg and / or Tm by at least a difference of 30°C.

[0017] The primary coil may be formed around and attached to a rod, and the rod has one or more of the following properties: (i) (high) reflectivity for reflecting at least a part of the LED filament light, (ii) light diffusibility for diffusing at least a part of the LED filament light, (iii) light convertibility for converting at least a part of the LED filament light, (iv) transparency for functioning as an optical waveguide for guiding at least a part of the LED filament light, and (v) thermal conductivity for functioning as a heat sink. In this way, the rod can facilitate the manufacture of the LED filament and have a beneficial effect on the optical performance and / or thermal performance of the LED filament. The rod is preferably moldable.

[0018] The coiled coil LED filament of the present invention will typically be arranged in a (substantially) linear configuration. Alternatively, the LED filament may be arranged in a triple coil configuration for higher compact light output and / or to simulate the appearance of a glowing 3D filled spherical emitter (similar to the sun).

[0019] According to a second aspect of the present invention, there is provided an (LED) lamp or lighting fixture comprising at least one (coiled coil) LED filament according to the first aspect, arranged behind a light exit window. The lamp further comprises an outer enclosure that at least partially forms the above-described light exit window and at least partially surrounds at least one coiled coil LED filament, and a base for electrically and mechanically connecting the lamp to a socket. The lamp may be, for example, a "giant" light bulb (dimensions ≧ 20 cm). The lighting fixture may be, for example, mountable in a ceiling, in contact with the ceiling, or below the ceiling.

[0020] The at least one coiled coil LED filament may be a plurality of coiled coil LED filaments. The plurality of coiled coil LED filaments may include, for example, at least two coiled coil LED filaments that are intertwined.

[0021] According to a third aspect of the present invention, there is provided a method of manufacturing an LED filament, comprising the steps of preparing a flexible support on which a plurality of light emitting diodes are arranged; coiling the prepared flexible support around a rod to provide an LED filament having a primary coil with a primary diameter D1; and coiling the LED filament having the primary coil into a secondary coil with a secondary diameter D2 to provide an LED filament having a coiled coil configuration. This aspect may exhibit the same or similar features and technical effects as the first aspect, and vice versa.

[0022] It should be noted that the present invention relates to all possible combinations of the features listed in the claims.

Brief Description of the Drawings

[0023] Next, these and other aspects of the present invention will be described in more detail with reference to the accompanying drawings showing embodiments of the present invention.

Figure 1

Figure 2

Figure 3a

Figure 3b

Figure 3c

Figure 3d

Figure 4

Figure 5

[0024] As shown in the figures, the sizes of the layers and regions may be exaggerated for illustrative purposes and are therefore provided to illustrate the general structure of the embodiments of the present invention. Like reference numerals refer to like elements throughout.

Embodiments for Carrying Out the Invention

[0025] Reference will now be made to the accompanying drawings, which show presently preferred embodiments of the invention, and in which the invention will be described more fully hereinafter. 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 so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0026] FIG. 1 shows an LED filament 10 for supplying LED filament light 12 according to an embodiment of the present invention.

[0027] The LED filament 10 includes an elongated flexible support 14 and a plurality of LEDs (light emitting diodes) 16 disposed on the elongated support. See also FIGS. 3a and 3b. In FIG. 1, only some of the LEDs 16 are shown for simplicity.

[0028] According to the present invention, the LED filament 10 is arranged in a coiled coil configuration, as shown, for example, in FIG. 1. Specifically, the coiled coil configuration includes a primary coil 18 having a primary (outer) diameter D1. See also FIG. 3c. Further, the primary coil 18 is coiled into a secondary coil 20 having a secondary diameter D2. The secondary coil 20 has N2 secondary loops. In FIG. 1, N2 is 5. The coiled coil LED filament 10 will typically be arranged in a linear configuration, as also shown in FIG. 1.

[0029] Referring to FIG. 2, the LED filament 10 may be manufactured as follows. In S1, an elongated flexible support 14 is provided, and a plurality of LEDs 16 are arranged on the flexible support 14. Refer also to FIGS. 3a and 3b. The LEDs 16 may be arranged in at least one linear array. Preferably, the elongated flexible support 14 has a length L' and a width W, where L'>20W, preferably L'>40W, more preferably L'>60W, and most preferably L'>80W. The width W of the support 14 of the LED filament 10 may be in the range of 0.5 to 5 mm. The LEDs 16 may be (evenly) distributed over the entire length L' of the support 14. The support 14 may include a first major surface 22a and an opposite second major surface 22b, and the LEDs 16 may be arranged on at least one of these surfaces. In FIG. 3a, the LEDs 16 are arranged on the first major surface 22a. The flexible support 14 may be made of, for example, a polymer or a metal, such as a film or a foil. The support 14 may be a flexible PCB (printed circuit board).

[0030] The LEDs 16 may be, for example, blue LEDs and / or UV LEDs, although other LEDs such as RGB LEDs may be used instead. Further, the LEDs 16 and the first major surface 22a may be covered by an elongated flexible encapsulant 24. The encapsulant 24 may be, for example, a silicone material. The encapsulant 24 may include a luminescent material configured to at least partially convert the LED light 26 emitted by the blue LEDs and / or UV LEDs 16 into converted light 28. The LED light 26 and / or the converted light 28 may form the LED filament light 12. The luminescent material may be, for example, an inorganic phosphor and / or a phosphor such as quantum dots or quantum rods.

[0031] Further, the LEDs 16 may include a first set of first LEDs and a second set of second LEDs, and the first set is individually controllable by a controller (not shown) with respect to the second set. In this way, the LED filament 10 may be adjustable, for example, with respect to color and / or color temperature.

[0032] The support body 14 may be provided with a ductile (formable) element 30. The ductile element 30 enables the LED filament 10 to be formed and also enables it to maintain a new shape. The ductile element 30 may be arranged along at least a major part of the length L' of the support body 14, preferably along the (substantially) entire length L' of the support body 14. The ductile element 30 can be arranged, for example, on the second main surface 22b of the support body 14 as shown in FIGS. 3a and 3b. In this way, the ductile element 30 does not block the LED light emitted by the LED 16 arranged on the opposite first main surface 22a. Alternatively, the ductile element 30 can be integrated into the support body 14, that is, provided inside the support body 14. In this way, in addition to not blocking the LED light emitted by the LED 16, the ductile element 30 may also be invisible to the user / observer. In another alternative, the ductile element 30 can be covered by the encapsulant 24 so as to be non-visible. For example, the ductile element 30 may be a thin * metal wire or strip made of, for example, aluminum or copper. Therefore, the (metal) ductile element 30 may be light-reflective and / or substantially non-light-absorbing. * The thickness of the ductile element 30 is preferably in the range of 1 to 5 mm.

[0033] In step S1, the unfinished LED filament 10' has a basic shape that is typically flat / linear as shown in FIG. 3a.

[0034] In S2, the unfinished LED filament 10', which includes the support 14, is preferably coiled around the rod 32 to provide an unfinished LED filament 10'' having a primary coil 18 with a primary diameter D1. When the LED 16 is arranged only on the first main surface 22a, the support 14 may be coiled such that the first main surface 22a having the LED 16 is present outside the primary coil 18. The advantage of this is that light is emitted in a direction away from the LED filament 10, and therefore, less light is absorbed, improving the LED filament light 12. Furthermore, such a configuration is more reliable because the possibility of the electrical connection being broken is low. The primary coil 18 may also be attached to the rod 32. In step S2, the ductile element 30 enables the LED filament 10' to be shaped from a basic shape (Figure 3a) into a first coiled shape corresponding to the above-mentioned primary coil 18, and this first coiled shape is dimensionally stable.

[0035] The rod 32 may be at least one of (i) reflective, (ii) light diffusive, (iii) light converting, (iv) transmissive, (v) thermally conductive, and (vi) formable. The rod 32 may be (i) highly reflective, and preferably, the reflectivity R > 80%. Regarding (ii), the rod 32 may have a reflectivity R > 80%. Regarding (iii), the rod 32 may be configured to convert at least 10% of the LED filament light. Regarding (iv), the rod 32 preferably has a transmissivity > 80%, and more preferably is transparent. Regarding (v), the rod preferably has a thermal conductivity > 100 W / mK, more preferably > 200 W / mK, and most preferably > 250 W / mK.

[0036] The rod 32 may be included within the final / completed LED filament 10 and may therefore be arranged within the LED filament lamp 100 or the lighting fixture, or alternatively, it is possible that it is removed after step S2 and is not included within the final / completed LED filament 10.

[0037] The primary diameter D1 may be in the range of 4 mm to 12 mm. Furthermore, the primary coil 18 may have N1 primary loops. N1 may be ≧5N2, preferably N1≧8N2, more preferably N1≧10N2, and most preferably N1≧12N2. Therefore, when N2 = 5 as shown in FIG. 1, the primary coil 18 can have more than 60 primary loops.

[0038] In S3, the unfinished LED filament 10'' (regardless of the presence or absence of the rod 32) is coiled into a secondary coil 20 having a secondary diameter D2 in order to provide the (final / finished) LED filament 10 having a coiled coil configuration. In other words, the coiled LED filament 10' obtained in step S2 is then coiled, for example, into a spiral / helical shape in order to obtain the coiled coil LED filament 10. In step S3, the ductility element 30 enables the LED filament 10'' to be shaped into a second coiled shape corresponding to the above-described secondary coil 20, and the second coiled shape is dimensionally stable.

[0039] The secondary diameter D2 may be in the range of 4D1 to 12D1. Therefore, when D1 = 4 mm, the secondary diameter D2 may be as small as about 16 mm. Also, when D1 = 12 mm, the secondary diameter D2 may be as large as about 144 mm. The secondary diameter D2 is typically uniform over the length L of the LED filament 10, as shown in FIG. 3d.

[0040] N2 (i.e., the number of secondary loops of the secondary coil 20) is preferably ≧3, more preferably N2≧4, and most preferably N2≧5. Furthermore, N2 is preferably ≦10, more preferably N2≦8, and most preferably N2≦7.

[0041] Furthermore, the secondary pitch P2 of the secondary coil 20 may be in the range of 2D1 to 10D1. Therefore, when D1 = 4 mm, the secondary pitch P2 may be as small as about 8 mm. Also, when D1 = 12 mm, the pitch P may be as large as about 120 mm.

[0042] In an embodiment, the primary pitch P1 of the primary coil 18 (see FIG. 3c) may be much smaller than the secondary pitch P2. Preferably, P2 is at least 8 times P1, more preferably, P2 is at least 10 times P1, and most preferably, P2 is at least 12 times P1.

[0043] In an embodiment, the primary pitch P1 may be much smaller than the secondary pitch P2, but not overly long. Preferably, P2 is at most 30 times P1.

[0044] The length L of the LED filament 10 may be at least 20 cm, preferably at least 40 cm, more preferably at least 60 cm, and most preferably at least 80 cm.

[0045] FIG. 4 shows an LED filament 10''' for supplying LED filament light 12 according to another embodiment of the present invention. The LED filament 10''' includes an elongated support (14) and LEDs (16) disposed on the elongated support, and the LED filament 10''' is arranged in a triple coil-shaped coil configuration. That is, the coiled coil LED filament 10 may be coiled again into a tertiary coil. The tertiary coil may have a tertiary (outer) diameter D3. For this embodiment, the method of FIG. 2 can include an additional step (S4) of coiling to provide the tertiary coil.

[0046] FIG. 5 shows an LED lamp 100 including a coiled coil LED filament 10. The LED lamp 100 further includes an outer enclosure 102 surrounding the coiled coil LED filament 10, and a base 104 for electrically and mechanically connecting the LED lamp 100 to an external socket (not shown). The LED lamp 100 may be a retrofit bulb. The LED lamp 100 may be a large bulb, and the diameter or height or width of the outer enclosure 102 is ≧ 20 cm.

[0047] The outer enclosure 102 forms a light-emitting window of the LED lamp 100. The outer enclosure 102 may be, for example, transparent. In this case, the outer enclosure 102 has a spherical or globe (G) shape, but other shapes such as a general type (A) or tubular (T) are equally possible.

[0048] The coiled coil LED filament 10 is arranged in a linear vertical configuration in FIG. 5, but it may also be arranged, for example, in a horizontal configuration (i.e., perpendicular to the longitudinal axis of the lamp 100). Furthermore, a second coiled coil LED filament 10a may be intertwined with the (first) LED filament 10.

[0049] Those skilled in the art will understand that the present invention is in no way limited to the above-described preferred embodiments. Rather, many modifications and variations are possible within the scope of the appended claims. For example, the coiled coil LED filament 10 may also be included within a lighting fixture.

[0050] Furthermore, by considering the drawings, the present disclosure, and the appended claims, variations to the disclosed embodiments can be understood by those skilled in the art and can be accomplished when implementing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain means are recited in mutually different dependent claims does not indicate that a combination of these means cannot be advantageously used.

Claims

1. An LED filament for supplying LED filament light, comprising: an elongated support; a plurality of light-emitting diodes disposed on the elongated support, The LED filament is arranged in a coiled coil configuration, and the coiled coil configuration includes a primary coil having a primary diameter D １ and the primary coil is coiled into a secondary coil having a secondary diameter D ２ , an LED filament.

2. The primary diameter D １ is in the range of 4 mm to 12 mm, the LED filament according to claim 1.

3. The secondary diameter D ２ is 4·D １ to 12·D １ The LED filament according to claim 1 or 2, wherein the range is as described above.

4. The primary coil has N １ primary loops, the secondary coil has N ２ secondary loops, and N １ ≥ 5 · N ２ The LED filament according to claim 1 or 2.

5. The secondary coil has a secondary pitch P in the range of 2·D １ to 10·D １ and is the LED filament according to claim 1 or 2. ２ ​

6. wherein the plurality of light-emitting diodes includes blue light-emitting diodes and / or UV light-emitting diodes, the plurality of light-emitting diodes is covered by an elongated encapsulant, and the elongated encapsulant is configured to at least partially convert the LED light emitted by the blue light-emitting diodes and / or the UV light-emitting diodes into converted light, the LED filament according to claim 1 or 2, comprising a luminescent material.

7. wherein the plurality of light-emitting diodes includes a first set of first light-emitting diodes and a second set of second light-emitting diodes, and the first set is individually controllable with respect to the second set, the LED filament according to claim 1 or 2.

8. The LED filament according to claim 1 or 2, further comprising a ductile element disposed along at least a major portion of the length of the elongated support to enable the LED filament to be shaped.

9. The ductile element is configured to enable the LED filament to be shaped into a first coiled shape corresponding to the primary coil and / or a second coiled shape corresponding to the secondary coil from a basic shape, and the first coiled shape and the second coiled shape are dimensionally stable, the LED filament according to claim 8.

10. The primary coil is formed around and attached to a rod, the rod having one or more of the following properties: reflectivity for reflecting at least a portion of the LED filament light; light diffusibility for diffusing at least a portion of the LED filament light; light convertibility for converting at least a portion of the LED filament light; transparency for functioning as an optical guide for guiding at least a portion of the LED filament light; and thermal conductivity for functioning as a heat sink, the LED filament according to claim 1 or 2.

11. The LED filament according to claim 1 or 2, wherein the LED filament is arranged in a triple-coiled coil configuration.

12. A lamp or lighting fixture comprising at least one coiled coil LED filament according to claim 1 or 2, disposed behind a light exit window.

13. The lamp or lighting fixture according to claim 12, wherein the at least one coiled coil LED filament is a plurality of coiled coil LED filaments.

14. The lamp or lighting fixture according to claim 13, wherein the plurality of coiled coil LED filaments includes at least two coiled coil LED filaments that are intertwined.

15. A method of manufacturing an LED filament, comprising: preparing a flexible support, wherein a plurality of light emitting diodes are disposed on the flexible support; Primary diameter D １ To provide an LED filament having a primary coil having a primary diameter D, a step of coiling the prepared flexible support around a rod; To provide an LED filament having a coiled coil configuration, the LED filament having the primary coil is coiled into a secondary coil having a secondary diameter D ２ and a step of forming the coil into a secondary coil having a secondary diameter D. A method including this step is provided.

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