WO2025256965A1

WO2025256965A1 - A led filament comprising a core

Info

Publication number: WO2025256965A1
Application number: PCT/EP2025/065354
Authority: WO
Inventors: Marc Andre De Samber
Original assignee: Signify Holding BV
Current assignee: Signify Holding BV
Priority date: 2024-06-11
Filing date: 2025-06-03
Publication date: 2025-12-18
Anticipated expiration: 2026-12-11

Abstract

A light emitting diode, LED, filament (1; 100; 101) configured to, in an on- state, emit LED filament light (2) and comprising an elongated carrier (3) comprising a first major surface (31) and a second major (32) surface, an array of a plurality of LEDs (4) configured to, in an on-state, emit LED light (41) and being arranged on the first major surface (31), an elongated encapsulant (5) at least partly enclosing the plurality of LEDs (4) and at least partly covering the elongated carrier (3), and an elongated core element (6) being made of a material comprising a strength being at least two times larger than at least the strength of the material of the elongated carrier (3), the LED filament comprising a LED filament diameter (D1), the elongated carrier (3) comprising a carrier width (D2), the elongated core element (6) comprising a core element diameter (D3), wherein an average distance (d) between the elongated carrier (3) and the elongated core element (6) is less than 5 mm and/or less than 2*D2.

Description

A LED filament comprising a core

FIELD OF THE INVENTION

The invention relates to a light emitting diode, LED, filament configured to, in an on-state, emit LED filament light. The invention further relates to a lamp and a luminaire comprising such a LED filament.

As used herein the term “strength” of a material is intended to refer to the ability of the material to withstand an applied load without failure or plastic deformation.

BACKGROUND OF THE INVENTION

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

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

As used herein, the terms carrier and elongated carrier may be used interchangeably, such that the elongated carrier may also simply be denoted carrier.

The LED filament may comprise an encapsulant at least partly covering at least part of the plurality of LEDs. The encapsulant may also at least partly cover at least one of the first major surface and second major surface. The encapsulant may be a polymer material which may be flexible such as for example a silicone. Further, the LEDs may be arranged for emitting LED light, e.g., of different colors or spectrums. The encapsulant may comprise a luminescent material that is configured to convert at least a part of the LED light into converted light. The luminescent material may be a phosphor such as an inorganic phosphor and/or quantum dots or rods (QDs).

The LED filament may comprise multiple sub-filaments. Hitherto, LED filaments have predominantly been used in LED bulbs to mimic incandescent light bulbs. For example, WO 2020/152068 Al discloses a color tunable filament lamp comprising at least one white LED filament adapted to emit white light and at least one RGB LED filament. Each RGB LED filament of the at least one RGB LED filament comprises a plurality of groups, each group comprising a red LED, a green LED and a blue LED. WO 2020/152068 Al also discloses a method of determining a correlated color temperature for at least one white LED filament of such a color tunable filament lamp.

LED filaments now find their way as a dominant light source in multiple lighting applications. It is expected that LED filaments may eventually even take over the role of LED strips, which are Chips on Board (COB) assemblies.

However, the prior art LED filaments are quite fragile structures that need to be handled with care (and expertise), and that need protection from external impact. Hence, its use in bulb products.

There is thus a desire to provide a LED filament that has an improved structural strength and thus is less fragile and allows the use of the LED filaments in stripluminaire applications.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome this problem, and to provide a LED filament that has an improved structural strength and thus is less fragile and allows the use of the LED filaments in strip-luminaire applications.

According to a first aspect of the invention, this and other objects are achieved by means of a light emitting diode, LED, filament configured to, in an on-state, emit LED filament light, the LED filament comprising an elongated carrier comprising a first major surface and a second major surface opposite to the first major surface, an array of a plurality of LEDs configured to, in an on-state, emit LED light and being arranged on the first major surface of the elongated carrier, an elongated encapsulant at least partly enclosing the plurality of LEDs and at least partly covering the elongated carrier, and an elongated core element being made of a material comprising a strength being at least two times larger than at least the strength of the material of the elongated carrier of the LED filament, wherein the LED filament comprises a LED filament diameter, DI, the elongated carrier comprises a carrier width, D2, the elongated core element comprises a core element diameter, D3, and wherein an average distance (d) between the elongated carrier and the elongated core element is less than 5 mm and/or less than 2*D2. Thereby, a LED filament is provided which has an improved structural strength and thus is less fragile and allows the use of the LED filaments in strip-luminaire applications, in which applications the LED filament might be experiencing mechanical loads. Such a LED filament may endure larger mechanical loads, be provided with a longer length, and be used as a self-supporting LED filament.

An average distance, d, between the elongated carrier and the elongated core element may be less than 5 mm, or less than 3 mm, or less than 2 mm, or less than 1 mm. Alternatively, or additionally, an average distance, d, between the elongated carrier and the elongated core element may be chosen to be less than 3*D2, such as less than 2*D2, especially less than 1.5*D2. The average distance, d, between the elongated carrier and the elongated core element may be chosen to be less than 3*D3, such as less than 2*D3, especially less than 1.5*D3.

Additionally, the maximum distance of the elongated carrier to the elongated core element along a light emitting portion of the LED filament may be less than 5 mm, or less than 3 mm, or less than 2 mm, or less than 1 mm.

The LED filament diameter may be equal to or less than 2.5 (D3 + 2*D2), such as equal to or less than 1.5 (D3 + 2*D2), especially equal to or less than (D3 + 2*D2).

Thereby, and especially by providing the elongated core element and fulfilling the relation between the diameters DI and D3 and the width D2, the resulting LED filament is provided with a further improved structural strength.

A typical LED filament as known in the art may have a LED filament diameter of 5 mm or less. The LED filament of this invention may have an overall diameter which is in a similar range. Hence, the LED filament diameter, DI, may be equal to or less than 10 mm, such as less than 5 mm, preferably less than 3 mm. The carrier width, D2, may be equal to or less than 5 mm, such as equal to or less than 3 mm, preferably equal to or less than 2 mm. The core element diameter, D3, may be equal to or less than the carrier width. Especially, the core element diameter, D3, may be less than 3 mm, such as less than 2 mm, preferably less than 1.5 mm. At the same time, the LED filament length, LI, may be larger than 10 cm, such as larger than 20cm, preferably larger than 30 cm.

At least a part of the elongated carrier and the elongated core element may be in physical contact.

Thereby, the resulting LED filament is provided with an even further improved structural strength. The LED filament comprises a LED filament length, LI, the elongated carrier comprises a carrier length, L2, the elongated core element comprises a core element length, L3, and at least one of the following may apply: LI > L3, and L2 > L3.

Thereby, it is prevented that mechanical elongation load on the LED filament would lead to damaging the LED filament, since such an LED filament is protected by the shorter elongated core element.

The elongated core element may be made of a material comprising any one or more of the following: a tensile strength of at least five times the tensile strength of the elongated carrier, or at least seven times the tensile strength of the elongated carrier, a tensile strength of more than 2000 MPa, more than 3000 MPa, or more than 3500 MPa, or about 3600-3700 MPa, a yield strength of more than 2000 MPa, more than 3000 MPa, or more than 3500 MPa, and a Youngs modulus, E, of more than 50 GPa, more than 70 GPa or more than 90 GPa.

Thereby, the resulting LED filament is provided with a particularly high structural strength.

The elongated core element may be made of one or more of aramides, aramid polymers, aramid fibers, aramid polymer fibers, carbon fibers, fibers comprising ultra-high- molecular-weight polyethylene (UHMWPE), silk fibers, banana fibers, spider silk, ramie fibers and composites and/or combinations of any one or more of these.

These materials are all very strong yet still flexible materials, which thus provide the elongated core element, and thus the LED filament, with a high structural strength.

The elongated core element may be made of a combination of two or more materials.

Such an elongated core element may be provided with a further increased structural strength.

The elongated core element may be arranged centrally in the LED filament.

The elongated carrier may be arranged spiraling, curved, or wrapped around the elongated core element in a homogenous or a non-homogenous manner along the length of the elongated core element. Thereby, a LED filament which provides a directionally uniform light output is provided for. Furthermore, such a setup ensures that the elongated core element may be concealed by the elongated carrier in the off-state of the LED filament.

The elongated encapsulant may at least partly enclose the elongated core element.

Thereby, the elongated encapsulant provides a protecting enclosure of the elongated core element, thus increasing the robustness and durability of the LED filament even further. Furthermore, the encapsulant may thereby ensure to improve the concealment of the elongated core element in the off-state of the LED filament.

The elongated core element may extend through the elongated carrier in at least one place.

Thereby, the elongated core element further structurally strengthens the carrier and thereby the LED filament.

The elongated carrier may comprise at least one through hole, and the elongated core element may extend through the at least one through hole.

Thereby, the further structural strengthening of the carrier is obtained in a simple and straight-forward manner.

The elongated core element may be shaped as a string or a wire.

Thereby, the elongated core element conforms to the overall shape of the LED filament, thus keeping down the size of the LED filament.

The elongated core element may further comprise a plurality of sub core elements. The sub core elements may for example be a plurality of fibers. The sub core elements may be made of the same material or may be made of at least two different materials. The sub core elements may be arranged in the form of a twisted, braided, or intertwined string, thereby even further increasing the strength and maximum length of the filament.

The elongated core element may be flexible such as to allow the LED filament to be bendable or twistable.

Thereby, it becomes possible to provide the strengthened LED filament with a variety of shapes without inflicting any damage to the LED filament.

The elongated core element may be connected to at least one of the elongated carrier and the elongated encapsulant by one or more of an optical grade glue and a silicone.

Thereby, a structurally very simple, yet still very strong, LED filament is provided for. The LED filament may further comprise at least one electrical interface element configured to allow the LED filament to be electrically connected to one or more of a power supply, electrical wiring, a driver, a controller, and a connector to one or more of a power supply, electrical wiring, a driver, and a controller.

The at least one electrical interface element may be arranged at or attached to at least one of two mutually opposite longitudinal ends of the LED filament such as to allow the at least one of the opposite longitudinal ends of the LED filament to be electrically connected to one or more of a power supply, electrical wiring, a driver, a controller, and a connector to one or more of a power supply, electrical wiring, a driver, and a controller.

Thereby electrical connection of the LED filament may be obtained in a particularly simple manner.

Alternatively, or additionally, the LED filament may further comprise at least one mechanical interface element configured to allow the LED filament to be one or more of sealed and mechanically connected to a lamp or a luminaire.

The at least one mechanical interface element may be arranged at or attached to at least one of two mutually opposite longitudinal ends of the LED filament, or at least the elongated core element, such as to allow the at least one of the opposite longitudinal ends of the LED filament to be one or more of sealed and mechanically connected to a lamp or a luminaire.

Thereby mechanical connection of the LED filament may be obtained in a particularly simple manner.

The at least one electrical interface element and the at least one mechanical interface element may be provided in one piece.

Thereby a simpler LED filament with fewer components is provided for.

The LED filament may further comprise a further array of a plurality of LEDs configured to, in an on-state, emit LED light and being arranged on the second major surface of the elongated carrier.

The elongated encapsulant may be an elongated light-converting encapsulant configured to convert at least a part of the LED light into converted light.

The invention further relates to a LED filament lamp comprising a LED filament according to the invention.

The LED filament lamp may further comprise a light transmissive envelope at least partly enclosing the LED filament and a base for electrically and mechanically connecting the LED filament lamp to a socket or a socket of a luminaire. The invention still further relates to a luminaire comprising a LED filament lamp according to the invention.

The invention still further relates to a luminaire comprising a LED filament according to the invention.

It is noted that the invention relates to all possible combinations of features recited in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

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.

Fig. 1 shows a cross-sectional side view of a light emitting diode, LED, filament according to the invention.

Fig. 2 shows a cross-sectional side view of the LED filament according to Fig. 1 and further comprising electrical interface elements.

Fig. 3 shows an enlarged view of the section III of the LED filament according to Fig. 1.

Fig. 4 shows a cross-sectional side view of another LED filament according to the invention.

Fig. 5 shows a cross-sectional side view of the LED filament according to Fig. 4 and further comprising mechanical interface elements.

Fig. 6 shows an enlarged view of the section VI of the LED filament according to Fig. 4.

Fig. 7 shows a perspective view of the LED filament according to Fig. 5 in which the mechanical interface elements form part of one-piece interface elements further comprising electrical interface elements.

Fig. 8 shows a cross-sectional side view of another LED filament according to the invention.

Fig. 9 shows a transversal cross-sectional view of the LED filament according to Fig. 8.

Fig. 10 shows a schematical side view of a luminaire comprising a LED filament according to the invention.

Fig. 11 shows a schematical side view of a lamp comprising a LED filament according to the invention. Fig. 12 shows a schematical side view of another luminaire comprising a lamp and a LED filament according to the invention.

As illustrated in the figures, the sizes of layers and regions are exaggerated for illustrative purposes and, thus, are provided to illustrate the general structures of embodiments of the present invention. Like reference numerals refer to like elements throughout.

DETAILED DESCRIPTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person.

Figs. 1-2 shows cross-sectional side views of a light emitting diode, LED, filament 1 according to the invention, and Fig. 3 shows an enlarged view of section III shown in Fig.1 of the LED filament 1.

Referring first to Figs. 1 and 3, generally, and irrespective of the embodiment, the LED filament 1 is configured to, in an on-state, emit LED filament light 2. Generally, and irrespective of the embodiment, the LED filament 1 comprises an elongated carrier 3, an array of a plurality of LEDs 4, an elongated encapsulant 5 and an elongated core element 6. Together, the elongated carrier 3, the array of a plurality of LEDs 4, and the elongated encapsulant 5 are in the following denoted LED filament body 10. Further, the LED filament 1 comprises a LED filament diameter DI and a LED filament length LI (cf. Figs. 1 and 4).

The elongated carrier 3 comprises a first major surface 31 and a second major 32 surface opposite to the first major surface 31. The elongated carrier 3 comprises a carrier width D2 and a carrier length L2 (cf. Figs. 1 and 4). The elongated carrier 3 may be any suitable substrate such as a printed circuit board (PCB). The elongated carrier 3 may be made from such materials as for example glass, ceramic, sapphire, copper and FPC (polymers like polyimide, PET).

The array of a plurality of LEDs 4 are configured to, in an on-state, emit LED light 41. The array of a plurality of LEDs 4 are arranged on the first major surface 31 of the elongated carrier 3. The elongated encapsulant 5 is for the sake of simplicity not shown on Figs. 1 and 2. Reference is instead made to Fig. 3. The elongated encapsulant 5 encloses the plurality of LEDs 4 at least partly. The elongated encapsulant 5 further covers the elongated carrier 3, and particularly the first major surface 31 thereof, at least partly. The elongated encapsulant 5 may be an elongated light-scattering encapsulant configured to scatter at least a part of the LED light 41. Alternatively, or additionally, the elongated encapsulant 5 may be an elongated light-converting encapsulant configured to convert at least a part of the LED light 41 into converted light 42 (cf. Fig. 3). In this case the LED filament light 2 comprises LED light 41 and/or converted LED light 42. The elongated encapsulant 5 may for instance comprise a phosphor or other light converting material or element(s) 51 (cf. Fig. 3).

As shown in Fig. 3, another elongated encapsulant 5’ may optionally be provided covering the elongated carrier 3, and particularly the second major surface 32 thereof, at least partly. As also shown in Fig. 3, the LED filament 1 may further optionally comprise a further array of a plurality of LEDs 4’ configured to, in an on-state, emit LED light 41’. The further array of a plurality of LEDs 4’ is arranged on the second major surface 32 of the elongated carrier 3. The elongated encapsulant 5’ may further enclose the further plurality of LEDs 4’ at least partly. It is feasible that the encapsulant 5 and the further encapsulant 5’ may be two identical encapsulants or one and the same encapsulant. Alternatively, it is feasible that the encapsulant 5 and the further encapsulant 5’ may be mutually different encapsulants. When the LED filament 1 comprises a further array of a plurality of LEDs 4’, the LED filament light 2 comprises both the LED light 41 and the LED light 41’. When the LED filament 1 further comprises a further encapsulant 5’ being a light converting encapsulant configured to convert the LED light 41’ into converted light (not shown), the LED filament light 2 may further comprise such converted LED light.

The elongated core element 6 may be arranged centrally in the LED filament 1. The elongated core element 6 is made of a material comprising a strength being larger than, and in particular at least two times larger than, the strength of the material of the LED filament 1, and in particular the strength of the elongated carrier 3 of the LED filament 1. The elongated core element 6 comprises a core element diameter D3 and a core element length L3.

An average distance d (cf. Fig. 3) between the elongated carrier 3 and the elongated core element 6 is less than 5 mm, or less than 3 mm, or less than 2 mm, or less than 1 mm. Additionally, or alternatively, the average distance d between the elongated carrier 3 and the elongated core element 6 is less than 1.5 times the carrier width D2 or may be less than 1.5 times the core element diameter D3. Additionally, the LED filament diameter DI, the carrier width D2 and the core element diameter D3 may be chosen such as to fulfill the relation DI < 1.5 (D3 + 2*D2). Additionally or alternatively, at least a part of the elongated carrier 3 and the elongated core element 6 are in physical contact.

One or more of the following relations between the core element length L3 and each of the LED filament length LI and the carrier length L2 may be fulfilled: LI > L3 and L2 > L3, such that the core element only is subjected to elongation stress.

Suitable materials for the elongated core element 6 includes aramides, aramid polymers, aramid fibers, aramid polymer fibers, carbon fibers and composites and/or combinations of any one or more of these. Exemplary aramid polymers include for instance Kevlar, Twaron, Nomex, New Star, and Teijinconex prepared from diamine and diacid (or equivalent) precursors. Nomex, Teijinconex, and New Star contain predominantly metalinkages. They are called poly-metaphenylene isophthalamides (MPIAs). By contrast, Kevlar and Twaron both predominantly contain para-linkages. They are called p-phenylene terephthalamides (PPTAs). Aramides typically exhibit a tensile strength of above 3000 MPa (for instance around 3700 MPa for Kevlar) a yield strength of above 3000 (for instance around 3600 MPa for Kevlar) and a Young’s modulus of between 70 and 112 GPa.

It is noted that Young's modulus, E, quantifies the relationship between tensile or compressive stress, c, (force per unit area) and axial strain, a, (proportional deformation) in the linear elastic region of a material, such that E = o/e.

Another suitable material for the elongated core element 6 is fibers comprising ultra-high-molecular-weight polyethylene (UHMWPE). One example is the Dyneema® Composite Fabric (DCF), also known as Cuben Fiber (CTF3), which is a high-performance non-woven composite material used in high-strength, low-weight applications. It is made of a thin sheet of UHMWPE laminated between two sheets of polyester.

Other suitable materials for the elongated core element 6 include silk fibers, banana fibers, spider silk and ramie fibers. Banana fibers are derived from the pseudo-stems of banana plants. Ramie fibers are made from the Chinese nettle plant.

Alternatively, or additionally, the elongated core element 6 may be made of any suitable material comprising a tensile strength of more than 3000 MPa, or more than 3500 MPa, such as about 3600-3700 MPa, and/or a yield strength of more than 3000 MPa, or more than 3500 MPa, and/or a Youngs modulus, E, of more than 50 GPa, more than 70 GPa or more than 90 GPa. As shown in Fig. 1, the LED filament body 10, or at least the elongated carrier 3 of the LED filament 1, is arranged spiraling around the elongated core element 6. Alternatively, the LED filament body 10, or at least the elongated carrier 3 of the LED filament 1, may be arranged curved or wrapped around the elongated core element 6. Whether arranged spiraling, curved, or wrapped around the elongated core element 6, the LED filament body 10, or at least the elongated carrier 3, may be arranged so in a homogenous or a non-homogenous manner along the length L3 of the elongated core element 6. Alternatively, or additionally, the elongated encapsulant 5 may at least partly enclose the elongated core element 6. It is in a further alternative feasible that the LED filament body 10, or at least the elongated carrier 3, may be arranged twisted, spiraling, curved, or wrapped around the core element 6 and only attached (or sealed) at both opposite longitudinal ends of the core element 6.

The elongated core element 6 may be shaped as a string or a wire or a rod. The elongated core element 6 may also be flexible such as to allow the LED filament 1 to be bendable or twistable.

Referring now specifically to Fig. 2, the LED filament 1 further comprises two optional electrical interface elements 9, one at each longitudinal end of the LED filament 1. The electrical interface elements 9 are configured to allow the LED filament 1 to be electrically connected to one or more of a power supply, electrical wiring 404 (cf. Fig. 12), a driver 402 (cf. Figs. 9 and 11), a controller 305 (cf. Fig. 11), and a connector 406 (cf. Fig. 10) to one or more of a power supply, electrical wiring, a driver, and a controller.

Figs. 4-5 shows cross-sectional side views of another LED filament 100 according to the invention, and Fig. 6 shows an enlarged view of section VI shown in Fig.4 of the LED filament 100. The LED filament 100 differs from the LED filament 1 shown in Figs. 1-3 and described above in virtue of the following features.

As is best seen in Fig. 6, the elongated core element 6 is extending through the LED filament body 10, and in particular the elongated carrier 3, in at least one place. More particularly, the elongated carrier 3 comprises at least one through hole 7. The elongated core element 6 extends through the at least one through hole 7. In this way, and especially if the elongated carrier 3 comprises a plurality of through holes 7, the central core element 6 may be stitched or led through the LED filament body 10, and in particular the elongated carrier 3. For instance, the central core element 6 may be stitched or led through the LED filament body 10 by using a machine that creates the through hole(s) 7 with a needle or another suitable tool. Alternatively, the central core element 6 may be stitched or led through the LED filament body 10 my using a wiring machine that feeds the central core element 6 through pre-punched through holes 7 in the elongated carrier 3.

As is best seen in Fig. 5, the LED filament further 100 further comprises two optional mechanical interface elements 13, one at each longitudinal end of the LED filament 1. The mechanical interface elements 13 may be configured to allow the LED filament 100 to be sealed at the longitudinal ends such as to protect the LED filament 100 against external influences. Alternatively, or additionally, the mechanical interface elements 13 may be configured to allow the LED filament 100 to be mechanically connected to a lamp or a luminaire. The mechanical interface elements 13 may be attached to each longitudinal end of the LED filament 100, or at least each longitudinal end of the elongated core element 6.

Referring to Fig. 7, it is noted that in case of a LED filament 100 comprising both electrical interface element(s) 9 and mechanical interface element(s) 13, it is feasible to provide an electrical interface element 9 and a mechanical interface element 13 as an integrated element or a one-piece element. Whether the electrical interface element 9 forms part of a one-piece element or not, the electrical interface element 9 may further comprise suitable electronic components 91 such as a converter or a controller.

As is best seen in Figs. 4 and 5, the elongated core element 6 is furthermore connected to the LED filament body 10, and in particular to at least one of the elongated carrier 3 and the elongated encapsulant 5, by a silicone 8 or another optically suitable encapsuling material. The encapsuling material or silicone 8 comprises an encapsuling material diameter D4 and an encapsuling material length L4 (cf. Fig. 4). The following relation between the core element length L3 and the encapsulating material length L4 may be fulfilled: L4 > L3. Additionally, or alternatively, the average distance d between the elongated carrier 3 and the elongated core element 6 may be chosen to be less than half the encapsulating material diameter D4.

Fig. 8 shows a cross-sectional side view of another LED filament 101 according to the invention, and Fig. 9 shows a transversal cross-sectional view of the LED filament 101. The LED filament 101 differs from the LED filaments 1 and 100 shown in Figs. 1-6 and described above in virtue of the following features.

As is best seen in Fig. 9, the LED filament body 10 is wrapped around the elongated core element 6. The elongated core element 6 is connected to the LED filament body 10, and in particular to at least one of the elongated carrier 3 and the elongated encapsulant 5, by an optical grade glue 14. The optical grade glue 14 is arranged between the elongated core element 6 and the LED filament body 10. In one application, LED filaments 1, 100, 101 according to the invention may be used as a freely hanging strip. Such free hanging strips are particularly advantageous in various business-to-customer applications, one examples being suspended LED strips that need protection against mechanical loads because of gravitational forces and external loads from, e.g., ventilation in the room.

Other applications in which LED filaments 1, 100, 101 according to the invention may be used include luminaires and lamps of various types, as will be described further below with reference to Figs. 10-12.

Fig. 10 shows a cross-sectional side view of an exemplary luminaire 200. The luminaire 200 may be a ceiling-mounted or wall-mounted luminaire. The luminaire 200 comprises a LED filament 1, 100, 101 according to any embodiment of the invention.

The luminaire 200 further comprises a reflector or casing or screen 203. The casing 203 comprises a light exit surface 205, an opposite surface 207 configured for abutment with a mounting surface and two end surfaces 208 and 209. The light exit surface 205 may optionally comprise a light diffusing and/or light redirecting element (not shown).

The LED filament 1, 100, 101 may optionally comprise electrical and mechanical interface element(s) 9’. The luminaire 200 may optionally comprise a socket or connection element 206 configured for connection to the LED filament 1, 100, 101 or where provided the interface element(s) 9’ of the LED filament 1, 100, 101.

The luminaire 200 may further comprise a driver 202 configured for controlling the LED filament 1, 100, 101. Alternatively, or additionally, the LED filament 1, 100, 101 may comprise a controller, which may or may not be separate from the driver 202. As shown in Fig. 10, the driver 202 is arranged on the casing 203 of the luminaire 200. The driver may also be arranged within or incorporated into the casing 203. The luminaire 200 further comprises an electrical wiring (not shown) for connection to a source of electricity, such as a mains.

The luminaire 200 illustrates an application example in a simple luminaire structure in which no further mechanical support of the LED filament 1, 100, 101 is required. The LED filament 1, 100, 101 is connected mechanically and electrically on both inside surfaces 210 and 211 of the end surfaces 208 and 209 of the luminaire 200. The luminaire 200 may have a fully open structure, which only serves as a holder for the LED filament 1, 100, 101.

Fig. 11 shows an exemplary lamp 300 comprising a LED filament 1, 100, 101 according to any embodiment of the invention. In the embodiment shown, the LED filament 1, 100, 101 comprises a substantially straight LED filament. The LED filament of such a lamp may in other embodiments be a LED filament with another shape, such as, but not limited to, spiral-shaped, helix-shaped, meandering, twisted, flat and combinations thereof.

The lamp 300 further comprises a driver or controller 305 configured for controlling the plurality of LEDs 4 of the LED filament 1, 100, 101. The controller 305 is configured to power the plurality of LEDs 4 via electrical circuitry (not visible on the figures) of the LED filament 1, 100, 101. The LED filament 1, 100, 101 may also comprise a controller, which may or may not be separate from the controller 305. In other words, the controller 305 and the controller of the LED filament 1, 100, 101 may be integrated into one and the same driver or controller, or they may be mutually separate units.

The lamp 300 further comprises an envelope 301 at least partially enveloping the at least one LED filament 1, 100, 101. The lamp 300 further comprises a cap 303. As shown in Fig. 11, the controller 305 is arranged within the envelope 301. When comprising a cap 303, the controller 305 may also be arranged inside the cap 303 such that it is hidden from view. The lamp 300 further comprises threading 302 for connection to a socket, and a terminal 304 for connection to a source of electrical energy.

The envelope 301 of the lamp 300 may further and optionally be provided with a coating (not shown), such as a reflective coating, covering at least a part of the envelope 301.

Turning finally to Fig. 12, another exemplary luminaire in the form of a pendant 400 is shown. The pendant 400 comprises a LED filament 1, 100, 101 according to any embodiment of the invention. The LED filament 1, 100, 101 is as shown in Fig. 11 provided within a lamp 300 in the form of a light bulb. The LED filament 1, 100, 101 as shown in Fig. 12 comprises a substantially straight LED filament.

As is also mentioned above, the light bulb further comprises a transparent envelope (cf. transparent envelope 301 of lamp 300) at least partially enveloping the at least one LED filament 1, 100, 101. The transparent envelope may be shaped in any feasible shape, for example such as to resemble the shape of any one of a standard light bulb, a globe light bulb, a candlelight bulb, a customized light bulb and even a spiral light bulb. The transparent envelope may comprise a luminescent material. The transparent envelope may be a glass envelope.

The pendant 400 further comprises a socket 401 for connecting the lamp 300, and thereby the LED filament 1, 100, 101, to the pendant 400. The socket 401 is adapted to cooperate with the base 303 of the lamp 300. The socket 401 may comprise a threading adapted to cooperate with the threading 302 of the lamp 300. The socket 401 may comprise a terminal adapted to cooperate with the terminal 304 of the lamp 300. The pendant 400 further comprises a reflector or screen 403.

The pendant 400 may further comprise a driver 402 configured for controlling the LED filament 1, 100, 101. The driver 402 may or may not be the same unit as the controller 305 described above. In other words, the driver 402 and the controller 305 may be integrated into one and the same driver or controller, or they may be mutually separate units. Alternatively, or additionally, the LED filament 1, 100, 101 may also comprise a controller, which may or may not be separate from one or both of the driver 402 and the controller 305.

As shown in Fig. 12, the driver 402 is arranged on a reflector or screen 403 of the pendant 400. The driver may also be arranged within or incorporated into the reflector or screen 403. The pendant 400 further comprises an electrical wiring 404 for connection to a source of electricity, such as a mains.

It is noted that the pendant 400 shown in Fig. 12 as well as the luminaire 200 shown in Fig. 10 are only two examples of a luminaire according to the invention. Any suitable type of luminaire may be envisaged, such as but not limited to, a standing luminaire, a wall hung luminaire, a chandelier, a reading luminaire, an outdoor luminaire, and a table luminaire. Another feasible example is a track lighting luminaire comprising multiple parallel LED filaments 1, 100, 101. Another feasible example is a tubular LED lamp, TLED. Other feasible examples are semi-transparent and transparent light panels, as well as light panels being look-through in an off state, in which a plurality of LED filaments 1, 100, 101 are connected via bus bar connectors. For TLEDs and light panels it is preferred to employ LED filaments 1, 100, 101 in which the filament is minimally visible in the off-state.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. 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 measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.

Claims

CLAIMS:

1. A light emitting diode, LED, filament (1; 100; 101) configured to, in an on- state, emit LED filament light (2), the LED filament comprising: an elongated carrier (3) comprising a first major surface (31) and a second major (32) surface opposite to the first major surface; an array of a plurality of LEDs (4) configured to, in an on-state, emit LED light (41) and being arranged on the first major surface (31) of the elongated carrier; an elongated encapsulant (5) at least partly enclosing the plurality of LEDs and at least partly covering the elongated carrier; and an elongated core element (6) being made of a material comprising a strength being at least two times larger than at least the strength of the material of the elongated carrier (3) of the LED filament; wherein the LED filament comprises a LED filament diameter, DI, the elongated carrier (3) comprises a carrier width, D2, the elongated core element (6) comprises a core element diameter, D3, and wherein an average distance (d) between the elongated carrier (3) and the elongated core element (6) is less than 5 mm and/or less than 2*D2, wherein the LED filament comprises a LED filament length, LI, in an elongation direction, wherein LI > 5 D1, and wherein the elongated core element (6) is made of a material comprising any one or more of the following: a tensile strength of more than 2000 MPa, a yield strength of more than 2000 MPa, and a Youngs modulus, E, of more than 50 GPa.

2. A LED filament according to claim 1, wherein DI < 1.5 (D3 + 2*D2).

3. A LED filament according to any one of the above claims, wherein at least a part of the elongated carrier (3) and the elongated core element (6) are in physical contact.

4. A LED filament according to any one of the above claims, wherein the elongated carrier (3) comprises a carrier length, L2, wherein the elongated core element (6) comprises a core element length, L3, and wherein at least one of the following applies:

LI > L3, and

L2 > L3.

5. A LED filament according to any one of the above claims, wherein DI < 10 mm, and wherein LI > 10 cm.

6. A LED filament according to any one of the above claims, wherein the elongated core element (6) is made of one or more of aramides, aramid polymers, aramid fibers, aramid polymer fibers, carbon fibers, fibers comprising ultra-high-molecular-weight polyethylene (UHMWPE), silk fibers, banana fibers, spider silk, ramie fibers and composites and/or combinations of any one or more of these.

7. A LED filament according to any one of the above claims, wherein the elongated carrier (3) is arranged spiraling, curved or wrapped around the elongated core element (6).

8. A LED filament according to any one of the above claims, wherein the elongated encapsulant (5) further at least partly encloses the elongated core element (6).

9. A LED filament according to any one of the above claims, wherein the elongated core element (6) is extending through the elongated carrier (3) in at least one place.

10. A LED filament according to any one of the above claims, wherein the elongated carrier (3) comprises at least one through hole (7), and wherein the elongated core element (6) is extending through the at least one through hole (7).

11. A LED filament according to any one of the above claims, wherein the elongated core element (6) is shaped as a string or a wire.

12. A LED filament according to any one of the above claims, wherein the elongated encapsulant (5) comprises one or more of a luminescent material configured to at least partly convert the LED light (41) into converted light, and a light scattering material configured to at least partly scatter the LED light (41) into scattered light.

13. A LED filament according to any one of the above claims, wherein the elongated core element (6) is connected to at least one of the elongated carrier (3) and the elongated encapsulant (5) by one or more of an optical grade glue (14) and a silicone (8).

14. A LED filament according to any one of the above claims, wherein the LED filament further comprises one or more of the following: at least one electrical interface element (9) configured to allow the LED filament to be electrically connected to one or more of a power supply, electrical wiring, a driver, a controller, and a connector (406) to one or more of a power supply, electrical wiring, a driver, and a controller, and at least one mechanical interface element (13) configured to allow the LED filament to be one or more of sealed and mechanically connected to a lamp or a luminaire.

15. A LED filament lamp (300) or a luminaire (400) comprising a LED filament (1) according to any one of the preceding claims.