WO2025201945A1

WO2025201945A1 - A led filament

Info

Publication number: WO2025201945A1
Application number: PCT/EP2025/057228
Authority: WO
Inventors: Ties Van Bommel; Johannes Petrus Maria Ansems
Original assignee: Signify Holding BV
Current assignee: Signify Holding BV
Priority date: 2024-03-25
Filing date: 2025-03-17
Publication date: 2025-10-02
Anticipated expiration: 2026-09-25

Abstract

A light emitting diode, LED, filament (1) configured to, in operation, emit LED filament light (2) and comprising a first array (3) of a plurality of first LEDs configured to, in operation, emit first LED light (32), a second array (4) of a plurality of second LEDs configured to, in operation, emit second LED light (42), and an elongated carrier (6), the elongated carrier (6) comprising a cross-sectional U-shape forming an elongated cavity (61), a bottom surface (62), a first side surface (63) and a second side surface (64) facing the elongated cavity, and an elongated opening (65) opposite to the bottom surface, the elongated cavity (61) being filled partly or fully with an elongated encapsulant (7), the first array (3) of the plurality of first LEDs being arranged in the elongated cavity (61) on a first one of the bottom surface (62), the first side surface (63) and the second side surface (64), the second array (4) of the plurality of second LEDs being arranged on a second one of the bottom surface (62), the first side surface (63) and the second side surface (64) being different from the first one of the bottom surface (62), the first side surface (63) and the second side surface (64), and the LED filament light (2) comprising at least a part of the first LED light (32) and the second LED light (42), and the elongated opening (65) forms a light exit surface of the LED filament (1).

Description

A LED FILAMENT

FIELD OF THE INVENTION

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

BACKGROUND OF THE INVENTION

A trend in lighting is LED filament lamps. An LED filament lamp is an 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.

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.

Many LED filament configurations have been proposed such as arranging LED arrays on multiple sides of an elongated carrier or special translucent-thermally conductive carriers in order to provide a LED filament providing a homogenously omnidirectional light distribution.

US 2022/0082214 Al discloses a color tunable filament lamp comprising at least one tunable 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. Each tunable white LED filament of the at least one tunable white LED filament comprises first LEDs having a first pre-set correlated color temperature and second LEDs having a second pre-set correlated color temperature lower than the first pre-set correlated color temperature, the first and second pre-set correlated color temperatures defining a sub-range of a correlated color temperature range of the color tunable filament lamp, and the color tunable filament lamp is configured to use the first LEDs and the second LEDs but not the at least one RGB LED filament for target points in said sub-range.

It is desired to improve the optical performance, such as light quality and correlated color temperature, CCT, control and so forth, of LED filaments.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome this problem, and to provide a LED filament with an improved optical performance, such as an improved light quality and correlated color temperature, CCT, control.

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 operation, emit LED filament light, the LED filament comprising a first array of a plurality of first LEDs configured to, in operation, emit first LED light, a second array of a plurality of second LEDs configured to, in operation, emit second LED light, and an elongated carrier, wherein the elongated carrier comprises a cross-sectional U-shape forming an elongated cavity, the elongated carrier comprising a bottom surface, a first side surface and a second side surface facing the elongated cavity, and an elongated opening opposite to the bottom surface, wherein the elongated cavity of the elongated carrier is filled partly or fully with an elongated encapsulant, wherein the first array of the plurality of first LEDs is arranged in the elongated cavity on a first one of the bottom surface, the first side surface and the second side surface, wherein the second array of the plurality of second LEDs is arranged on a second one of the bottom surface, the first side surface and the second side surface being different from the first one of the bottom surface, the first side surface and the second side surface, and wherein the LED filament light comprises at least a part of the first LED light and at least a part of the second LED light, and the elongated opening forms a light exit surface of the LED filament.

Such a LED filament enables providing high-brightness LED filament light emitted from the elongated opening of said U-shaped elongated carrier. Thereby, a LED filament with an improved optical performance, such as an improved light quality and correlated color temperature, CCT, control, is provided for.

The LED filament may further comprise a third array of a plurality of third LEDs configured to, in operation, emit third LED light, wherein the third array of the plurality of third LEDs is arranged on a third one of the bottom surface, the first side surface and the second side surface being different from the first one and the second one of the bottom surface, the first side surface and the second side surface, and wherein the LED filament light comprises at least a part of the first LED light, at least a part of the second LED light, and at least a part of the third LED light.

Thereby, a LED filament is provided with which omnidirectional light with superior brightness may be emitted from the opening. In such an arrangement, the intensity at the opening may be at least three times the intensity at the other sides of the elongated carrier.

One or more of the first array of a plurality of first LEDs, the second array of a plurality of second LEDs and the third array of the plurality of third LEDs may comprise an array of red, green, and blue LEDs.

Thereby, it becomes possible to provide a LED filament with a tunable color point.

The elongated encapsulant may comprise a luminescent material configured to at least one of converting at least a part of the first LED light into first converted light, converting at least a part of the second LED light into second converted light, and converting at least a part of the third LED light into third converted light.

Thereby, it becomes possible to provide a LED filament with a tunable correlated color temperature, CCT.

At least one of the following may apply: a combination of the first LED light and the first converted light is white light having a first correlated color temperature, CCT1, a combination of the second LED light and the second converted light is white light having a second correlated color temperature, CCT2, and a combination of the third LED light and the third converted light is white light having a third correlated color temperature, CCT3.

Thereby, it becomes possible to provide a LED filament with a tunable color point and/or correlated color temperature, CCT.

The elongated carrier may be light-transmissive.

The elongated encapsulant may comprise any one or more of a silicone polymer, a cross-linked PDMS, a cross-linked PMPS and a cross-linked PDPS. Thereby, extra strength and thus durability is provided to the LED filament.

The elongated encapsulant may comprise any one or more of a light scattering material, BaSCL particles, AIO3 particles, and TiCL particles.

Thereby, an improved mixing of the LED light emitted by the LED arrays is provided. This in turn provides a LED filament light with an improved homogeneity.

The elongated encapsulant may be arranged between the first array of a plurality of first LEDs, the second array of a plurality of second LEDs and, where provided, the third array of the plurality of third LEDs, such that the elongated encapsulant covers the first plurality of LEDs and the second plurality of LEDs and, where provided, the third plurality of LEDs.

Such a configuration enables reducing or even avoiding cross talk, especially between LEDs of different arrays of LEDs.

The elongated carrier comprises a reflectivity, Rl, the elongated encapsulant comprises a reflectivity, R2, and Rl may be at least 40% and may be higher than R2. Preferably, Rl may be higher than R2 by at least 20 %.

Thereby the light losses which may otherwise be inflicted by the carrier are lowered.

The elongated carrier comprises a reflectivity, Rl, a transmissivity, Tl, and an absorption, Al, and at least one of the following may apply: Rl is at least 50 %, Tl is at least 20 %, and Al is less than 3 %.

Thereby the light losses which may otherwise be inflicted by the carrier are lowered considerably.

The elongated carrier further comprises an outer bottom surface and two outer side surfaces facing away from the elongated cavity, and a further elongated encapsulant may be provided on one or more of the outer bottom surface, one or both of the two outer side surfaces, and the elongated opening, and the further elongated encapsulant may comprise one or more of a further luminescent material and a further light scattering material.

Thereby, it becomes possible to provide a LED filament with a further tunable color point and/or correlated color temperature, CCT.

The LED filament may comprise one or more of a first encapsulant arranged between the first array of a plurality of first LEDs and the elongated encapsulant and covering at least a part of the first array of a plurality of first LEDs, a second encapsulant arranged between the second array of a plurality of second LEDs and the elongated encapsulant and covering at least a part of the second array of a plurality of second LEDs, and a third encapsulant arranged between the third array of a plurality of third LEDs and the elongated encapsulant and covering at least a part of the third array of a plurality of third LEDs.

At least one of the first encapsulant, the second encapsulant and the third encapsulant may comprise one or more of a luminescent material and a light scattering material.

Thereby, it becomes possible to provide a LED filament with which each plurality of LEDs may be adjusted in one or both of color point and tunable correlated color temperature, CCT, individually.

The elongated encapsulant may enclose one or more of the first encapsulant, the second encapsulant and, where provided, the third encapsulant partially or fully.

Thereby, a more durable and robust LED filament is provided for.

At least one of the plurality of first LEDs, the plurality of second LEDs and the plurality of third LEDs may be direct-emitting LEDs.

Such a configuration is particularly advantageous for an array of LEDs comprising RGB LEDs. In any event, such a configuration enables avoiding cross talk between LEDs within an array of LEDs.

At least one of the first LEDs of the plurality of first LEDs, the second LEDs of the plurality of second LEDs and, where provided, the third LEDs of the plurality of third LEDs comprises an aspect ratio defined as the ratio of a width to a height of the LED, and the aspect ratio may be equal to or lower than 1 : 1.

Such a configuration enables reducing or even avoiding cross talk between LEDs within an array of LEDs and/or between LEDs of different arrays of LEDs. The cross-sectional U-shape of the elongated carrier may taper in a direction towards the bottom surface.

Thereby, it becomes possible to provide a LED filament with an improved light directionality and with a higher brightness at the light exit surface.

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 according to the invention.

The invention still further relates to a luminaire comprising a LED filament lamp 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 view of a light emitting diode, LED, filament according to the invention.

Figs. 2-6 show cross-sectional views of another light emitting diode, LED, filament according to the invention illustrating different possible colors of LED filament light of a LED filament according to the invention.

Fig. 7 shows a color spectrum illustrating various possible colors of LED filament light of a LED filament according to Figs. 2-6.

Fig. 8 shows a cross-sectional view of another light emitting diode, LED, filament according to the invention.

Fig. 9 shows a cross-sectional view of another light emitting diode, LED, filament according to the invention.

Fig. 10 shows a cross-sectional view of another light emitting diode, LED, filament according to the invention.

Fig. 11 shows a cross-sectional view of another light emitting diode, LED, filament according to the invention. Fig. 12 shows a schematical side view of a lamp comprising a LED filament according to the invention.

Fig. 13 shows a schematical side view of a 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.

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

Generally, and irrespective of the embodiment, the LED filament 1 comprises a plurality of LED arrays 3, 4, 5 configured to, in operation, emit LED light 32, 42, 52, and an elongated carrier 6 comprising a cross-sectional U-shape. The LED filament 1 is configured to, in operation, emit LED filament light 2. The LED filament light 2 comprises at least a part of the LED light 32, 42, 52.

The elongated carrier 6 is U-shaped in cross-section. The U-shape of the elongated carrier 6 forms an elongated cavity 61. The elongated cavity 61 is formed between the legs and the bottom of the U-shape. The elongated carrier 6 comprises a bottom surface 62 and two side surfaces 63, 64 facing the elongated cavity 61. The elongated cavity 61 is formed between the two side surfaces 63, 64 and the bottom surface 62 of the elongated carrier 6. The elongated cavity 61 further comprises an elongated opening 65 opposite to the bottom surface 62. The elongated opening 65 forms a light exit surface of the LED filament 1 through which the LED filament light 2 is emitted. The elongated carrier 6 further comprises an outer bottom surface 66 and two outer side surfaces 67, 68 facing away from the elongated cavity 61. The elongated opening 65, i.e., the light exit surface of the LED filament 1, provides at least 60% or at least 80% of the LED filament light 2. The elongated carrier 6 may be light-transmissive, semi -reflective, semi- diffuse-reflective or a combination thereof. The elongated carrier 6 may be a substrate, such as a printed circuit board. The elongated carrier 6 comprises a reflectivity Rl, a transmissivity T1 and an absorption Al. The reflectivity, Rl, may for instance be at least 50 %. The transmissivity, Tl, may for instance be at least 20 %. The absorption, Al, may for instance be less than 3 %.

The elongated cavity 61 is filled partly or fully with an elongated encapsulant 7. For instance, the elongated cavity 61 is filled with the elongated encapsulant 7 up to at least 60% or at least 80% of the elongated carrier 6. The elongated encapsulant 7 may comprise a silicone polymer, a cross-linked PDMS, a cross-linked PMPS, a cross-linked PDPS or any combination thereof. The elongated encapsulant 7 is arranged between the LED arrays 3, 4, 5. The elongated encapsulant 7 comprises a reflectivity R2. The reflectivity, Rl, of the elongated carrier 6 may be higher than the reflectivity, R2, of the elongated encapsulant 7, such as higher than R2 by at least 20 %. The elongated encapsulant 7 may comprise a light scattering material 71 configured to scatter the LED light 32, 42, 52. The light scattering material 71 may for instance be BaSCL particles, AIO3 particles, TiCL particles or any combination thereof. In principle, however, the elongated encapsulant 7 may be omitted.

The plurality of LED arrays 3, 4, 5 are arranged is arranged in the elongated cavity 61. The plurality of LED arrays 3, 4, 5 are arranged is arranged such that one LED array 5 is arranged on the bottom surface 62 and one LED array 3, 4 is arranged on each side surface 63, 64 of the elongated carrier 6.

An optional further elongated encapsulant 8 is provided on or at one or more of the outer bottom surface 66, one or both of the two outer side surfaces 67, 68, and the elongated opening 65. As shown on Fig. 1, the further elongated encapsulant 8 comprises a first part 81 provided on or at the outer bottom surface 66, a second part 82 provided on or at the outer side surface 67, a third part 83 provided on or at the outer side surface 68, and a fourth part provided on or at the elongated opening 65. One or more of the parts 81-84 of the further elongated encapsulant 8 may be omitted. The further elongated encapsulant 8 may be configured to scatter at least a part of any LED light 91-93 (cf. Figs. 2 and 3) emitted through the respective surface 66-69 or opening 65. Alternatively, or additionally, the further elongated encapsulant 8 may be configured to convert at least a part of any LED light 91-93 emitted through the respective surface 66-69 or opening 65. The further elongated encapsulant 8 may thus comprise a light converting material, a light scattering material or a combination thereof.

The LEDs of each LED array 3, 4, 5 of the plurality of LED arrays is configured to, in operation, emit LED light 32, 42, 52, respectively. The LED light 32, 42, 52 may have mutually different colors, mutually different correlated color temperatures or a combination thereof. The LEDs of each LED array 3, 4, 5 of the plurality of LED arrays may be direct-emitting LEDs. The LEDs of each LED array 3, 4, 5 of the plurality of LED arrays each comprise a height aspect ratio and a width aspect ratio. The height aspect ratio may be chosen to be lower than the width aspect ratio, for instance by at least one.

The plurality of LED arrays 3, 4, 5 comprises a first LED array 3, a second LED array 4 and a third LED array 5. The first LED array 3 provides light with a first correlated color temperature, CCT. The second LED array 4 provides light with a second CCT. The second CCT may be being lower than the first CCT. The third LED array 5 provides light with a third CCT. As shown in Fig. 1 all three LED arrays 3, 4, 5 comprise one row of LEDs.

An optional encapsulant 31, 41, 51 may be arranged between at least one of the LED arrays 3, 4, 5 and the elongated encapsulant 7. The encapsulant 31, 41, 51 encloses the at least one of the LED arrays 3, 4, 5. The elongated encapsulant 7 encloses the encapsulant 31, 41, 51 at least partially, and as shown fully. One or more of the encapsulants 31, 41, 51 may be configured to scatter at least a part of the LED light 32, 42, 52. Alternatively, or additionally, the one or more of the encapsulants 31, 41, 51 may be configured to convert at least a part of the LED light 32, 42, 52. The encapsulants 31, 41, 51 may thus comprise a light converting material, a light scattering material or a combination thereof. The encapsulants 31, 41, 51 may be identical, or as shown on Fig. 1 mutually different, at least in virtue of their respective light scattering and/or light converting properties.

It is also feasible to emit one of the LED arrays 3, 4, 5. In other words, it is feasible that the LED filament 1 may comprise only two LED arrays. For example, the LED filament 1 may comprise a first array 3 of a plurality of first LEDs configured to, in operation, emit first LED light 32 and a second array 4 of a plurality of second LEDs configured to, in operation, emit second LED light 42. The first array 3 of the plurality of first LEDs is then arranged in the elongated cavity 61 on a first one of the bottom surface 62, the first side surface 63 and the second side surface 64, and the second array 4 of the plurality of second LEDs is arranged on a second one of the bottom surface 62, the first side surface 63 and the second side surface 64 being different from the first one of the bottom surface 62, the first side 63 surface and the second side surface 64. The LED filament light 2 then comprises at least a part of the first LED light 32 and the second LED light 42.

Turning now to Figs. 2-6, cross-sectional views of other LED filaments 100- 104 according to the invention is shown, each illustrating a different possible color of LED filament light obtainable with a LED filament according to the invention. The various colors and/or color temperatures of light obtained as illustrated in Figs. 2-6 are also illustrated in the color spectrum shown in Fig. 7.

All of the LED filaments 100-104 shown in Figs. 2-6 differ from the LED filament 1 described above in relation to Fig. 1 in that the LED array 5, which is arranged on the bottom surface 62, is an array of red, green, and blue, RGB, LEDs 5a, 5b and 5c, respectively.

The LED filament 100 shown in Fig. 2 is configured or controlled to emit LED filament light 2 being cool white light. The LED filament 101 shown in Fig. 3 is configured or controlled to emit LED filament light 2 being warm white light (marked W in Fig. 7). The LED filament 102 shown in Fig. 4 is configured or controlled to emit LED filament light 2 being red light (marked R in Fig. 7). The LED filament 103 shown in Fig. 5 is configured or controlled to emit LED filament light 2 being green light (marked G in Fig. 7). The LED filament 104 shown in Fig. 6 is configured or controlled to emit LED filament light 2 being blue light (marked B in Fig. 7).

Fig. 8 shows a cross-sectional view of another light emitting diode, LED, filament 105 according to the invention. The LED filaments 105 differs from the LED filaments 1 and 100-104 described above in relation to Figs. 1-6 in virtue of the following features.

The arrays of LEDs 3, 4 and 5 are identical LEDs. That is, LEDs configured to emit LED light 32, 42, 52 having the same color, the same color temperature or both. Furthermore, the encapsulants 31, 41, 51 are, if provided, identical at least in terms of their light scattering properties or light converting properties or both.

Fig. 9 shows a cross-sectional view of another light emitting diode, LED, filament 106 according to the invention. The LED filament 106 differs from the LED filaments 1 and 100-105 described above in relation to Figs. 1-6 and 8 in virtue of the following features.

The arrays of LEDs 3, 4 and 5 are identical. More particularly, the arrays of LEDs 3, 4 and 5 are each an array of RGB, LEDs 3a, 3b, 3c, 4a, 4b, 4c and 5a, 5b and 5c, respectively. Furthermore, the encapsulants 31, 41, 51 are, if provided, identical at least in terms of their light scattering properties or light converting properties or both.

Fig. 10 shows a cross-sectional view of another light emitting diode, LED, filament 107 according to the invention. The LED filament 107 differs from the LED filaments 1 and 100-106 described above in relation to Figs. 1-6 and 8-9 in virtue of the following features.

The arrays of LEDs 3 and 5 are identical LEDs. That is, the LEDs are configured to emit LED light 32 and 52 having the same color, the same color temperature or both. The array of LEDs 4 arranged on the side surface 64 is an array of RGB LEDs. Furthermore, the encapsulants 31, 41, 51 are, if provided, mutually different at least in terms of their light scattering properties or light converting properties or both.

Fig. 11 shows a cross-sectional view of another light emitting diode, LED, filament 108 according to the invention. The LED filament 108 differs from the LED filaments 1 and 100-107 described above in relation to Figs. 1-6 and 8-10 in virtue of the following features.

The cross-sectional U-shape of the elongated carrier 6 tapers in a direction towards the bottom surface 62. The side surfaces 63 and 64 extend in an angle P being larger than 90 degrees with the bottom surface 62. As shown in Fig. 11, the side surfaces 63 and 64 are straight. It is also feasible that the side surfaces 63 and 64 may be curved. Still further, it is also feasible that the corner sections or transitions 621 and 622 between the bottom surface 62 and the respective side surfaces 63 and 64 may be rounded rather than, as shown on Fig. 11, angled.

Fig. 12 shows an exemplary lamp 300 comprising a LED filament 1, 100-108 according to any embodiment of the invention. In the embodiment shown, the LED filament 1 is 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, spiralshaped, helix-shaped, meandering, twisted, flat and combinations thereof.

The lamp 300 further comprises a driver or controller 305 configured for controlling the LEDs 32, 42, 52 of the LED filament 1. The controller 305 is configured to power the LEDs 32, 42, 52 via electrical circuitry (not visible on the figures) of the LED filament 1. The LED filament 1 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 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. The lamp 300 further comprises a cap 303. As shown in Fig. 12, 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. 13, an exemplary luminaire in the form of a pendant 400 is shown. The pendant 400 comprises a LED filament 1, 100-107 according to any embodiment of the invention. The LED filament 1 is as shown in Fig. 13 provided within a lamp 300 in the form of a light bulb. The LED filament 1 as shown in Fig. 13 is 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. 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, 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. 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 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. 13, 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. 13 is only one example 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.

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) configured to, in operation, emit LED filament light (2), the LED filament comprising: a first array (3) of a plurality of first LEDs configured to, in operation, emit first LED light (32), a second array (4) of a plurality of second LEDs configured to, in operation, emit second LED light (42), and an elongated carrier (6), wherein the elongated carrier (6) comprises a cross-sectional U-shape forming an elongated cavity (61), the elongated carrier (6) comprising a bottom surface (62), a first side surface (63) and a second side surface (64) facing the elongated cavity, and an elongated opening (65) opposite to the bottom surface, wherein the elongated cavity (61) of the elongated carrier is filled partly or fully with an elongated encapsulant (7), wherein the first array (3) of the plurality of first LEDs is arranged in the elongated cavity (61) on a first one of the bottom surface (62), the first side surface (63) and the second side surface (64), wherein the second array (4) of the plurality of second LEDs is arranged on a second one of the bottom surface (62), the first side surface (63) and the second side surface (64) being different from the first one of the bottom surface, the first side surface and the second side surface, and wherein the LED filament light (2) comprises at least a part of the first LED light (32) and at least a part of the second LED light (42), and the elongated opening (65) forms a light exit surface of the LED filament (1).

2. A LED filament according to claim 1, and further comprising a third array (5) of a plurality of third LEDs configured to, in operation, emit third LED light (52), wherein the third array (5) of the plurality of third LEDs is arranged on a third one of the bottom surface (62), the first side surface (63) and the second side surface (64) being different from the first one and the second one of the bottom surface, the first side surface and the second side surface, and wherein the LED filament light (2) comprises at least a part of the first LED light (32), at least a part of the second LED light (42), and at least a part of the third LED light (52).

3. A LED filament according to any one of the above claims, wherein one or more of the first array (3) of a plurality of first LEDs, the second array (4) of a plurality of second LEDs and the third array (5) of the plurality of third LEDs comprises an array of red, green, and blue LEDs.

4. A LED filament according to any one of the above claims, wherein the elongated encapsulant (7) comprises a luminescent material configured to at least one of: converting at least a part of the first LED light (32) into first converted light, converting at least a part of the second LED light (42) into second converted light, and converting at least a part of the third LED light (52) into third converted light.

5. A LED filament according to any one of the above claims, wherein at least one of the following applies: a combination of the first LED light (32) and the first converted light is white light having a first correlated color temperature, CCT1; a combination of the second LED light (42) and the second converted light is white light having a second correlated color temperature, CCT2; and a combination of the third LED light (52) and the third converted light is white light having a third correlated color temperature, CCT3.

6. A LED filament according to any one of the above claims, wherein the elongated carrier (6) is light-transmissive.

7. A LED filament according to any one of the above claims, wherein the elongated encapsulant (7) is arranged between the first array (3) of a plurality of first LEDs, the second array (4) of a plurality of second LEDs and, where provided, the third array (5) of the plurality of third LEDs, such that the elongated encapsulant (7) covers the first plurality of LEDs and the second plurality of LEDs and, where provided, the third plurality of LEDs.

8. A LED filament according to any one of the above claims, wherein the elongated carrier (6) comprises a reflectivity (Rl), wherein the elongated encapsulant (7) comprises a reflectivity (R2), and wherein Rl is at least 40% and is higher than R2, or wherein Rl is higher than R2 by at least 20 %.

9. A LED filament according to any one of the above claims, wherein the elongated carrier (6) comprises a reflectivity, Rl, a transmissivity, Tl, and an absorption, Al, and wherein at least one of the following applies:

Rl is at least 50 %, Tl is at least 20 %, and Al is less than 3 %.

10. A LED filament according to any one of the above claims, wherein the elongated carrier (6) further comprises an outer bottom surface (66) and two outer side surfaces (67, 68) facing away from the elongated cavity (61), and wherein a further elongated encapsulant (8) is provided on one or more of the outer bottom surface, one or both of the two outer side surfaces, and the elongated opening (65), and wherein the further elongated encapsulant comprises one or more of a further luminescent material and a further light scattering material.

11. A LED filament according to any one of the preceding claims, comprising one or more of a first encapsulant (31) arranged between the first array (3) of a plurality of first LEDs and the elongated encapsulant (7) and covering at least a part of the first array (3) of a plurality of first LEDs, a second encapsulant (41) arranged between the second array (4) of a plurality of second LEDs and the elongated encapsulant (7) and covering at least a part of the second array (4) of a plurality of second LEDs, and a third encapsulant (51) arranged between the third array (5) of a plurality of third LEDs and the elongated encapsulant (7) and covering at least a part of the third array (5) of a plurality of third LEDs.

12. A LED filament according to claim 11, wherein at least one of the first encapsulant (31), the second encapsulant (41) and the third encapsulant (51) comprises one or more of a luminescent material and a light scattering material.

13. A LED filament according to any one of the above claims, wherein at least one of the first LEDs of the plurality of first LEDs, the second LEDs of the plurality of second LEDs and, where provided, the third LEDs of the plurality of third LEDs comprise an aspect ratio defined as the ratio of a width to a height of the LED, and wherein the aspect ratio is equal to or lower than 1 : 1.

14. A LED filament according to any one of the above claims, wherein the cross- sectional U-shape of the elongated carrier (6) tapers in a direction towards the bottom surface (62).

15. A LED filament lamp (300) or a luminaire (400) comprising a LED filament

(1) according to any one of the preceding claims.