LED filament with elongated recesses

Abstract

A LED filament (1) comprising: - an elongated carrier (2) with a width, W1, - a first elongated encapsulant (4a) with a height, H1, covering the first major surface (2a) of the elongated carrier (2) and enclosing the plurality of LEDs (3) arranged on the elongated carrier (2), - a second elongated encapsulant (4b) with a height, H2, covering a second major surface (2b), opposite to said first major surface (2a), - a first elongated recess (5a) with a height, H3, and a depth, D1, located at the periphery of the LED filament (1) between the first elongated encapsulant (4a) and the first major surface (2a) of the elongated carrier (2), wherein 0.1≤H3 / H1≤0.7 and 0.2≤(W1- 2*D1) / W1≤0.7 and / or - a second elongated recess (5c) with a height, H4, and a depth, D2, located at the periphery of the LED filament (1) between the second elongated encapsulant (4b) and the second major surface (2b) of the elongated carrier (2), wherein 0.1≤H4 / H2≤0.7 and 0.2≤(W1- 2*D2) / W1≤0.7.

Description

[0001] LED FILAMENT WITH ELONGATED RECESSES

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a LED filament designed to improve its thermal performance and appearance especially for a use as LED filament lamp.

[0004] BACKGROUND OF THE INVENTION

[0005] A trend in lighting is LED filament lamps. A LED filament lamp is a LED lamp which is designed to resemble a traditional incandescent light bulb with a visible filament for aesthetic and light distribution purposes, but with the high efficiency of lightemitting diodes.

[0006] At present, due to the limitations of heat dissipation, the development of high-power LED lamp is restricted.

[0007] SUMMARY OF THE INVENTION

[0008] Hence, it is an object of the present invention to produce a LED filament lamp with an improved thermal performance and appearance.

[0009] To this end, the LED filament is provided with at least one recess located next to the carrier of the LEDs, said recess having specific dimensions and shapes allowing to improve the thermal performance whilst the appearance of the LED filament is enhanced.

[0010] More specifically, the invention relates to a light emitting diode, LED, filament configured to provide, in operation, LED filament light, the LED filament being defined with a longitudinal axis (y), a lateral axis (x) perpendicular to said longitudinal axis (y) and a vertical axis (z) perpendicular to the lateral and longitudinal axes (x,y), said LED filament comprising: an elongated carrier having a first width, Wl, defined along the lateral axis (x); an array of a plurality of LEDs arranged on a first major surface of said elongated carrier, wherein the plurality of LEDs is configured to emit LED light; a first elongated encapsulant having a first height, Hl, defined along the vertical axis (z), said first elongated encapsulant at least partially covering the first major surface of the elongated carrier and at least partly enclosing the plurality of LEDs, the first elongated encapsulant comprising (i) a first luminescent material (e.g. configured to at least partly convert the LED light emitted by said plurality of LEDs into first converted light) and / or (ii) a first light scattering material (e.g. configured to at least partly scatter the LED light emitted by said plurality of LEDs into first scattered light); a second elongated encapsulant having a second height, H2, defined along the vertical axis (z), said second elongated encapsulant at least partially covering a second major surface, opposite to said first major surface, of the elongated carrier, the second elongated encapsulant comprising (iii) a second luminescent material (e.g. configured to at least partly convert the LED light emitted by said plurality of LEDs and / or the first converted light into second converted light) and / or (iv) a second light scattering material (e.g. configured to at least partly scatter LED light emitted by said plurality of LEDs and / or the first scattered light into second scattered light); and wherein said LED filament comprises: (i) a first elongated recess located at the periphery of the LED filament along the lateral axis (x) and between the first elongated encapsulant and the first major surface of the elongated carrier, said first elongated recess having at one side end of the elongated carrier a third height, H3, defined along the vertical axis (z) and having a first depth, DI, defined along the lateral axis (x), wherein 0.1<H3 / Hl<0.7 and 0.2<(Wl-2*Dl) / Wl<0.7 and / or (i) a second elongated recess located at the periphery of the LED filament along the lateral axis (x) and between the second elongated encapsulant and the second major surface of the elongated carrier, said second elongated recess having at the same one side end of the carrier a fourth height, H4, defined along the vertical axis (z) and having a second depth, D2, defined along the lateral axis (x), wherein 0.1<H4 / H2<0.7 and 0.2<(Wl-2*D2) / Wl<0.7. The obtained effect is improved thermal performance whilst the appearance of the LED filament is enhanced. The reason is that the elongated carrier is more exposed to a gas or fluid and thus provides improved cooling via convection whilst the elongated carrier is hided by the elongated encapsulants.

[0011] According to embodiments of the invention, the following may applies: 0.1<H3 / Hl<0.6 and / or 0.1<H4 / H2<0.6. The obtained effect is improved mechanical strength.

[0012] According to embodiments of the invention, the following may applies: 0.3<(Wl-2*Dl) / Wl<0.7 and / or 0.3<(Wl-2*D2) / Wl<0.7. The obtained effect is further improved mechanical strength. According to embodiments of the invention, the LED filament light may comprise (i) the first converted light and / or the first scattered light, and (ii) the second converted light and / or the second scattered light.

[0013] According to embodiments of the invention, the LED filament light may be white light having a correlated color temperature in a range from 1700K to 6500K and / or a color rendering index of at least 70 (preferably at least 80).

[0014] According to embodiments of the invention, the LED filament may comprise a further array of a plurality of further LEDs arranged on the second major surface of said elongated carrier, wherein the plurality of LEDs is configured to emit further LED light. The second luminescent material may be configured to at least partly convert the further LED light emitted by said plurality of further LEDs into second converted light) and / or the second light scattering material may be configured to at least partly scatter further LED light emitted by said plurality of further LEDs into second scattered light.

[0015] According to embodiments of the invention, the LED filament may have a LED filament length, Lf, of at least 20mm or at least 30mm, a LED filament width, Wf, in a range from 1mm to 6mm, and a LED filament thickness, Tf, in a range from 1mm to 6mm. Preferably Lf>8Wf and Lf>8Tf.

[0016] According to embodiments of the invention, the elongated carrier may be rigid e.g. is made of glass, ceramic or sapphire.

[0017] According to embodiments of the invention, the elongated carrier may have thickness in a range from 0.1mm to 2mm, preferably in a range from 0.3mm to 1 mm. The obtained effect is improved mechanical strength and cooling.

[0018] According to embodiments, the first elongated recess, second elongated recess, third elongated recess and / or fourth elongated recess may be at least 10mm or at least 20mm.

[0019] According to an embodiment of the invention, said LED filament comprises the first elongated recess and the second elongated recess. The obtained effect is further improved thermal performance. The reason is that the cooling is on both sides of the elongated carrier is improved.

[0020] According to an embodiment of the invention, said LED filament comprises a third elongated recess and a fourth elongated recess located at the other periphery of the LED filament along the lateral axis (x), said third and fourth elongated recesses being respectively located between the first elongated encapsulant and the first major surface of the elongated carrier and between the second elongated encapsulant and the second major surface of the elongated carrier, said third elongated recess having at one side end of the elongated carrier a fifth height, H5, defined along the vertical axis (z) and having a third depth, D3, defined along the lateral axis (x), said fourth elongated recess having at one side end of the elongated carrier a sixth height, H6, defined along the vertical axis (z) and having a fourth depth, D4, defined along the lateral axis (x), wherein 0.1<H5 / Hl<0.7 and 0.2<(Wl-2*D3) / Wl<0.7 and wherein 0.1<H6 / H2<0.7 and 0.2<(Wl-2*D4) / Wl<0.7. The obtained effect is even further improved thermal performance whilst the appearance of the LED filament is enhanced. The reason is that the cooling is on both sides of the elongated carrier and on both (edge) sides of the LED filament is improved.

[0021] According to embodiments of the invention, the following may applies: 0.1<H5 / Hl<0.6 and / or 0.1<H6 / H2<0.6. The obtained effect is improved mechanical strength.

[0022] According to embodiments of the invention, the following may applies: 0.3<(Wl-2*D3) / Wl<0.7 and / or 0.3<(Wl-2*D4) / Wl<0.7. The obtained effect is further improved mechanical strength.

[0023] According to an embodiment of the invention, the first elongated recess and the second elongated recess have different dimensions e.g. differences in height and or width of at least 20%. Preferably the first elongated recess has a larger volume than the second elongated recess.

[0024] According to an embodiment of the invention, the third elongated recess and the fourth elongated recess have different dimensions e.g. differences in height and or width of at least 20%. Preferably the third elongated recess has a larger volume than the fourth elongated recess.

[0025] According to an embodiment of the invention, the elongated carrier has a thermal conductivity of at least 1 W / m-K, preferably at least 25 W / m-K, more preferably at least 50 W / m-K, most preferably at least 100 W / m-K.

[0026] According to an embodiment of the invention, the elongated carrier is light- transmissive, preferably the elongated carrier is light scattering. The following may apply (i) the first luminescent material may be configured to at least partly convert the LED light emitted by said plurality of LEDs into first converted light and / or the first light scattering material may be configured to at least partly scatter the LED light emitted by said plurality of LEDs into first scattered light, and (ii) the second luminescent material may be configured to at least partly convert the LED light emitted by said plurality of LEDs and / or the first converted light into second converted light and / or the second light scattering material may be configured to at least partly scatter the LED light emitted by said plurality of LEDs and / or the first scattered light into second scattered light.

[0027] According to an embodiment of the invention, the first elongated encapsulant has a second width, W2, and the second elongated encapsulant has a third width, W3, wherein W2 and / or W3 is the same width as the first width W1 of the elongated carrier. The obtained effect is improved thermal performance whilst the appearance of the LED filament is further enhanced.

[0028] According to an embodiment of the invention, at least one of the first elongated recess, the second elongated recess, the third elongated recess and the fourth elongated recess have respectively a rectangular shape or a tapered shape flaring towards the side end of the elongated carrier.

[0029] According to an embodiment of the invention, a first portion, Pl, on the elongated carrier in the first elongated recess comprises one or more first electrically conductive tracks and / or a second portion, P2, on the elongated carrier in the third elongated recess comprises one or more second electrically conductive tracks.

[0030] According to an embodiment of the invention, said LED filament comprises one or more first electronic components at least partly recessedly arranged in the first recess and electrically and mechanically connected to the one or more first electrically conductive tracks and / or one or more second electronic components at least partly recessedly arranged in the third recess and electrically and mechanically connected to the one or more second electrically conductive tracks. The one or more electronic component may comprise a sensor, a controller and / or a driver. The sensor, controller and driver may be electrically connected to the plurality of LEDs.

[0031] According to an embodiment of the invention, Hl is larger than H2.

[0032] According to an embodiment of the invention, H3 and / or H4 are in a range from 1mm to 5mm, or 1mm to 3mm.

[0033] According to an embodiment of the invention, H5 and / or H6 may be in a range from 1mm to 5mm, or 1mm to 3mm.

[0034] According to an embodiment of the invention, DI and / or D2 may be in a range from 1mm to 5mm, or 1mm to 3mm.

[0035] According to an embodiment of the invention, D3 and / or D4 may be in a range from 1mm to 5mm, or 1mm to 3mm.

[0036] According to an embodiment of the invention, the first encapsulant comprise two layers of distinct material with a first layer covering the first major surface and a second layer covering the first layer and / or the second encapsulant comprise two layers of distinct material with a third layer covering the second major surface and a fourth layer covering the third layer.

[0037] According to an embodiment of the invention, the first layer and the third layer comprise respectively the first and second luminescent material and the second layer and the fourth layer comprise the first or second light scattering material.

[0038] The invention also relates to a LED filament lamp comprising an envelope at least partly enclosing the LED filament as described above and a base for electrically and mechanically connecting said lamp to a socket of a luminaire.

[0039] Further objectives of, features of, and advantages with, the present invention will become apparent when studying the following detailed disclosure, the drawings and the appended claims. Those skilled in the art will realize that different features of the present invention may be combined to create embodiments other than those described in the following.

[0040] BRIEF DESCRIPTION OF THE DRAWINGS

[0041] 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.

[0042] Figs.1-4 show cross-section views of the LED filament according to different embodiments of the invention.

[0043] Figs.5(a)-(c) schematically represent different variants for manufacturing the LED filament with recesses according to the invention.

[0044] Fig.6 shows a lamp provided with the LED filament according to the invention.

[0045] DETAILED DESCRIPTION

[0046] Figs.1-4 show a LED, for light emitting diode, filament according to the invention for different embodiments. The LED filament 1 comprises an array with a plurality of LEDs 3 arranged on an elongated carrier 2. The carrier 2 comprises a first major surface 2a and a second major surface 2b opposite to the first major surface 2a, with the plurality of LEDs 3 arranged on said first major surface 2a.

[0047] The LED filament 1 comprises a first elongated encapsulant 4a at least partially covering the first major surface 2a of the elongated carrier 2 and at least partly enclosing the plurality of LEDs 3. The first elongated encapsulant 4a may be made up of a first luminescent material configured to at least partly convert the LED light emitted by said plurality of LEDs 3 into a first converted light. In addition or in alternative, the first elongated encapsulant 4a may be made up of a first light scattering material configured to at least partly scatter the LED light emitted by said plurality of LEDs 3 into a first scattered light. The LED filament 1 further comprises a second elongated encapsulant 4b at least partially covering the second major surface 2b. The second elongated encapsulant 4b is made up of a second luminescent material configured to at least partly convert the LED light emitted by said plurality of LEDs 3 and / or the first converted light into a second converted light. In addition or in alternative, the second elongated encapsulant 4b is made up of a second light scattering material configured to at least partly scatter LED light emitted by said plurality of LEDs 3 and / or the first scattered light into a second scattered light. For example, the first and second luminescent materials may be a phosphor such as an inorganic phosphor and / or quantum dots or rods and the first and second scattering material may comprise for example BaSCU, AI2O3 and / or TiCL particles. Alternatively, as represented in figure 3, the first and second elongated encapsulant 4a, 4b can be made up of two layers 4al,4a2 and 4bl,4b2. The first layer 4al,4bl may comprise the luminescent material while the second layer 4a2,4b2 may comprise the light scattering material to create an OFF-state white appearance.

[0048] According to the invention, the LED filament comprises at least one elongated recess. It may be an elongated recess 5a, called first elongated recess, at one side end of the LED filament’s width with said first recess 5a located between the first elongated encapsulant 4a and the first major surface 2a of the elongated carrier 2 or it may be an elongated recess 5c, called second elongated recess, located between the second elongated encapsulant 4b and the second major surface 2b at one side end of the LED filament’s width. Preferably, the LED filament comprises the first and second elongated recesses 5a, 5c. Preferably, they are located on the same side end of LED filament’s width for allowing a larger gap for improved cooling. More preferably, the LED filament comprises a third elongated recess 5b and a fourth elongated recess 5d located on the other side end of the LED filament’s width for improved light homogeneity. The third elongated recess 5b is located between the first elongated encapsulant 4a and the first major surface 2a of the elongated carrier 2 and the fourth elongated recess 5d is located between the second elongated encapsulant 4b and the second major surface 2b. Said LED filament is defined with a longitudinal axis (y), a lateral axis (x) perpendicular to said longitudinal axis (y) and a vertical axis (z) perpendicular to the lateral and longitudinal axes (x,y) as represented in figure 1 with : the elongated carrier 2 having a first width, Wl, defined along the lateral axis (x); the first elongated encapsulant 4a having a first height, Hl, defined along the vertical axis (z), said first height Hl being the maximum height if the height of the encapsulant is not constant; and having a second width, W2, defined along the lateral axis (x); the second elongated encapsulant 4b having a second height, H2, defined along the vertical axis (z), and having a third width, W3, defined along the lateral axis (x); the first elongated recess 5a having at one side end of the carrier’s width a third height, H3, defined along the vertical axis (z) and having a first depth, DI, defined along the lateral axis (x), the second elongated recess 5c having at one side end of the carrier’s width a fourth height, H4, defined along the vertical axis (z) and having a second depth, D2, defined along the lateral axis (x), the third elongated recess 5b having at one side end of the carrier’s width a fifth height, H5, defined along the vertical axis (z) and having a third depth, D3, defined along the lateral axis (x), the fourth elongated recess 5d having at one side end of the carrier’s width a sixth height, H6, defined along the vertical axis (z) and having a fourth depth, D4, defined along the lateral axis (x).

[0049] According to the invention, the recesses and the carrier have to meet some requirements in terms of dimensions to get the improved thermal performance and appearance of the LED filament.

[0050] In a preferred embodiment, the LED filament comprises the first elongated recess 5a and / or the second elongated recess 5c with dimensions satisfying the following relationships:

[0051] 0.1<H3 / Hl<0.7 and 0.2<(Wl-2*Dl) / Wl<0.7 and / or

[0052] 0.1<H4 / H2<0.7 and 0.2<(Wl-2*D2) / Wl<0.7.

[0053] In the embodiment with the third elongated recess 5b and the fourth elongated recess 5d, the following relationships have to be satisfied: 0.1<H5 / Hl<0.7 and 0.2<(Wl-2*D3) / Wl<0.7 and

[0054] 0.1<H6 / H2<0.7 and 0.2<(Wl-2*D4) / Wl<0.7.

[0055] Typically, H3, H4, H5 and / or H6 are in a range from to 1mm to 3mm, and DI, D2, D3 and / or D4 are in a range from 1mm to 3 mm.

[0056] Preferably, the first elongated recess and the second elongated recess have different dimensions so that . . . (what ’s the technical reason?). Preferably, the third elongated recess and the fourth elongated recess have different dimensions for the same reason.

[0057] The recesses may adopt different shapes. In figure 1, the recesses have a tapered shape flaring towards the side end of the elongated carrier for an improved light distribution. In figure 2, the recesses have a rectangular shape for best thermal performance.

[0058] The carrier 2 is configured to mechanically and / or electrically support the plurality of LEDs 3. Preferably, the carrier is light transmissive and more preferably it is light scattering for an improved appearance. To optimize the thermal performance, the carrier has a thermal conductivity of at least 1 W / m-K, preferably at least 25 W / m-K, more preferably at least 50 W / m-K, most preferably at least 100 W / m-K.

[0059] The carrier may comprise on a portion Pl and / or P2 of its first major surface 2a one or more electrically conductive tracks 7,8, said portion Pl and P2 being respectively located in the first elongated recess 5a and in the third elongated recess 5b (figure 4). The electrically conductive tracks 7,8 are electrically and mechanically connected to one or more electronic components 9a, 9b at least partly recessedly arranged in the first 5a or third recess 5b. Said one or more electronic components 9a, 9b can be a sensor, a controller and / or a driver. To accommodate these electronic components and conductive tracks on the first major surface 2a of the carrier, the height Hl of the first encapsulant 4a is preferably higher than the height H2 of the second encapsulant 4b. The sensor, controller and driver may be electrically connected to the plurality of LEDs.

[0060] In addition, preferably, the first elongated encapsulant 4a has a second width, W2, and the second elongated encapsulant has a third width, W3, wherein W2 and / or W3 is the same width as the first width, Wl, of the elongated carrier 2 in order to fully cover it.

[0061] The LED filament with at least one recess can be manufactured according to the processes schematically represented in figure 5. The encapsulants can be pre-shaped with the recesses and subsequently attached, e.g. glued onto the LEDs 3 as represented in figure 5a. Alternatively, at least one part of the first and major surfaces 2a, 2b are covered with molds 6 having the shape of the recess (figure 5b). Next, the encapsulant 4a, 4b is dispensed and cross-linked and subsequently the molds 6 are removed obtaining said elongated recess 5a, 5b. Another approach represented in figure 5c is to apply two layers 4al, 4a2 with the first layer 4a 1 covering the LEDs 3 and the second layer 4a2 covering the first layer 4a 1 with said second layer 4a2 pre-shaped with the recesses.

[0062] Finally, the invention also relates to a LED filament lamp 10 represented in figure 6. It comprises an envelope 11 at least partly enclosing the LED filament 1 according to the invention and a base 12 for electrically and mechanically connecting said lamp 10 to a socket 13 of a luminaire.

Claims

CLAIMS:

1. A light emitting diode, LED, filament (1) configured to provide, in operation,LED filament light, the LED filament (1) being defined with a longitudinal axis (y), a lateral axis (x) perpendicular to said longitudinal axis (y) and a vertical axis (z) perpendicular to the lateral and longitudinal axes (x,y), said LED filament (1) comprising: an elongated carrier (2) having a first width, Wl, defined along the lateral axis (x); an array of a plurality of LEDs (3) arranged on a first major surface (2a) of said elongated carrier (2), wherein the plurality of LEDs (3) is configured to emit LED light; a first elongated encapsulant (4a) having a first height, Hl, defined along the vertical axis (z), said first elongated encapsulant (4a) at least partially covering the first major surface (2a) of the elongated carrier (2) and at least partly enclosing the plurality of LEDs (3), the first elongated encapsulant (4a) comprising (i) a first luminescent material and / or (ii) a first light scattering material; a second elongated encapsulant (4b) having a second height, H2, defined along the vertical axis (z), said second elongated encapsulant (4b) at least partially covering a second major surface (2b), opposite to said first major surface (2a), of the elongated carrier (2), the second elongated encapsulant (4b) comprising (iii) a second luminescent material and / or (iv) a second light scattering material; and wherein said LED filament (1) comprises: (i) a first elongated recess (5a) located at the periphery of the LED filament (1) along the lateral axis (x) and between the first elongated encapsulant (4a) and the first major surface (2a) of the elongated carrier (2), said first elongated recess (5a) having at one side end of the elongated carrier (2) a third height, H3, defined along the vertical axis (z) and having a first depth, DI, defined along the lateral axis (x), wherein 0.1<H3 / Hl<0.7 and 0.2<(Wl-2*Dl) / Wl<0.7 and / or (ii) a second elongated recess (5c) located at the periphery of the LED filament (1) along the lateral axis (x) and between the second elongated encapsulant (4b) and the second major surface (2b) of the elongated carrier (2), said second elongated recess (5c) having at the same one side end of the carrier (2) a fourth height, H4, defined along the vertical axis (z) and having a seconddepth, D2, defined along the lateral axis (x), wherein 0.1<H4 / H2<0.7 and 0.2<(Wl- 2*D2) / Wl<0.7.

2. The LED filament (1) according to the previous claim, wherein said LED filament (1) comprises the first elongated recess (5a) and the second elongated recess (5c).

3. The LED filament (1) according to claim 2, wherein said LED filament (1) comprises a third elongated recess (5b) and a fourth elongated recess (5d) located at the other periphery of the LED filament (1) along the lateral axis (x), said third and fourth elongated recesses (5b, 5d) being respectively located between the first elongated encapsulant (4a) and the first major surface (2a) of the elongated carrier (2) and between the second elongated encapsulant (4b) and the second major surface (2b) of the elongated carrier (2), said third elongated recess (5b) having at one side end of the elongated carrier (2) a fifth height, H5, defined along the vertical axis (z) and having a third depth, D3, defined along the lateral axis (x), said fourth elongated recess (5d) having at one side end of the elongated carrier (2) a sixth height, H6, defined along the vertical axis (z) and having a fourth depth, D4, defined along the lateral axis (x), wherein 0.1<H5 / Hl<0.7 and 0.2<(Wl-2*D3) / Wl<0.7 and wherein 0.1<H6 / H2<0.7 and 0.2<(Wl-2*D4) / Wl<0.7.

4. The LED filament (1) according to claims 2 or 3, wherein the first elongated recess (5a) and the second elongated recess (5c) have different dimensions, and / or when referring to claim 3 the third elongated recess (5b) and the fourth elongated recess (5d) have different dimensions, preferably the first elongated recess has a larger volume than the second elongated recess.

5. The LED filament (1) according to any one of the previous claims, wherein the elongated carrier (2) has a thermal conductivity of at least 1 W / m-K, preferably at least 25 W / m-K, more preferably at least 50 W / m-K, most preferably at least 100 W / m-K.

6. The LED filament (1) according to any one of the previous claims, wherein the elongated carrier (2) is light-transmissive, and wherein the following applies (i) the first luminescent material is configured to at least partly convert the LED light emitted by said plurality of LEDs into a first converted light and / or the first light scattering material is configured to at least partly scatter the LED light emitted by said plurality of LEDs into afirst scattered light, and (ii) the second luminescent material is configured to at least partly convert the LED light emitted by said plurality of LEDs and / or the first converted light into a second converted light) and / or the second light scattering material is configured to at least partly scatter the LED light emitted by said plurality of LEDs and / or the first scattered light into a second scattered light.

7. The LED filament (1) according to any one of the previous claims, wherein the first elongated encapsulant (4a) has a second width, W2, and the second elongated encapsulants (4b) has a third width, W3, wherein W2 and / or W1 is the same width as the first width, Wl, of the elongated carrier (2).

8. The LED filament (1) according to any one of the previous claims, wherein at least one of the first elongated recess (5a), the second elongated recess (5c), the third elongated recess (5b) and the fourth elongated recess (5d) have respectively a rectangular shape or a tapered shape flaring towards the side end of the elongated carrier (2).

9. The LED filament (1) according to any one of the previous claims, wherein a first portion, Pl, on the elongated carrier (2) in the first elongated recess (5a) comprises one or more first electrically conductive tracks (7) and / or a second portion, P2, on the elongated carrier (2) in the third elongated recess (5b) comprises one or more second electrically conductive tracks (8).

10. The LED filament (1) according to claim 9, wherein the LED filament (1) comprises one or more first electronic components (9a) at least partly recessedly arranged in the first recess (5a) and electrically and mechanically connected to the one or more first electrically conductive tracks (7) and / or one or more second electronic components (9b) at least partly recessedly arranged in the third recess (5b) and electrically and mechanically connected to the one or more second electrically conductive tracks (8).

11. The LED filament (1) according to claim 9, wherein Hl is larger than H2.

12. The LED filament (1) according to any one of the previous claims, wherein H3 and / or H4 are in a range from to 1mm to 3mm, and wherein DI and / or D2 are in a range from 1mm to 3 mm.

13. The LED filament (1) according to any one of the previous claims 2 to 11, wherein the first encapsulant (4a) comprise two layers (4al,4a2) of distinct material with a first layer (4al) covering the first major surface (2a) and a second layer (4a2) covering the first layer (4al) and / or the second encapsulant (4b) comprise two layers (4bl,4b2) of distinct material with a third layer (4b 1) covering the second major surface (2b) and a fourth layer (4b2) covering the third layer (4b 1).

14. The LED filament (1) according to the previous claim, wherein the first layer (4al) and the third layer (4b 1) comprise respectively the first and second luminescent material and the second layer (4a2) and the fourth layer (4b2) comprise the first or second light scattering material.

15. A LED filament lamp (10) comprising an envelope (11) at least partly enclosing the LED filament (1) according to any one of the previous claims and a base (12) for electrically and mechanically connecting said lamp (10) to a socket (13) of a luminaire.

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