A flexible LED strip filament

Abstract

A LED strip filament (100) is provided configured to, in an on-state, emit LED filament light (2). The LED strip filament (100) comprises a white light-diffusive filament (1) arranged on a LED strip (10). The LED strip (10) comprises an elongated reflective carrier (3), an array of a plurality of LEDs (4), an attachment component (6) and an elongated light- converting encapsulant (5). The elongated reflective carrier (3) comprises a first major surface (31) and a second major surface (32) opposite to the first major surface (31). The array of a plurality of LEDs (4) is configured to, in an on-state, emit LED light (41) and be arranged on the first major surface (31) of the elongated carrier (3). The attachment component (6) is configured for attaching the LED strip filament (100) to an attachment surface (12) and being arranged on the second major surface (32) of the elongated carrier (3). The elongated light-converting encapsulant (5) is at least partly enclosing the plurality of LEDs (4) and at least partly covering the elongated carrier (3). The elongated light- converting encapsulant (5) comprises a luminescent material (51) adapted to convert at least part of the LED light (41) into converted light (42). The LED filament light (2) comprises the converted light (42) and optionally a portion of the LED light (41). The white light-diffusive filament (1) comprises at least one white light-diffusive white, light-diffusive, elongated optics (7), wherein the white, light-diffusive, elongated optics (7) is arranged in direct contact with the elongated encapsulant (5).

Description

[0001] 2024PF80171

[0002] 1

[0003] A flexible LED strip filament

[0004] FIELD OF THE INVENTION

[0005] The invention relates to a flexible light emitting diode, LED, strip filament configured to, in an on-state, emit LED filament light, the LED strip filament comprising a white light-diffusive filament arranged on a LED strip.

[0006] BACKGROUND OF THE INVENTION

[0007] 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.

[0008] The LED filament may be arranged in a straight configuration or in a nonstraight 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).

[0009] 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.

[0010] As used herein, the terms carrier and elongated carrier may be used interchangeably, such that the elongated carrier may also simply be denoted carrier.

[0011] 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).

[0012] The LED filament may comprise multiple sub-filaments. 2024PF80171

[0013] 2

[0014] Typically, LED filaments are rigid elements with very limited, if any, flexibility.

[0015] Most recent LED strips are based on chip-on-board, CoB, technology and comprises an array of a plurality of LEDs arranged at a low pitch and being covered by an elongated encapsulant comprising a luminescent material configured to at least partially convert LED light emitted by said plurality of LEDs into converted light to obtain white light.

[0016] CN 203980145 U discloses a lens for a linear light source to achieve asymmetric light distribution.

[0017] In contrast to LED filaments, a LED strip filament generally comprises a LED filament and an attachment component, for instance based on a glue strip, which is intended for attaching the LED strip filament to a mounting surface of a luminaire.

[0018] It is desired to improve the optical performance and / or the appearance of LED strip filaments.

[0019] In US 2024 / 263751 the invention relates to a LED filament comprising an elongated carrier comprising a first elongated edge portion and a second elongated edge portion arranged at a distance from the first elongated edge portion, a first surface, a second surface arranged opposite to the first surface, the first and the second surfaces being delimited by the first and the second edge portions. The LED filament further comprises a plurality of LEDs distributed along the first surface of the elongated carrier, the plurality of first LEDs being configured to emit a first LED light. The LED filament also comprises a first at least partially light-transmissive elongated layer encapsulating or covering the plurality of first LEDs and at least partially encapsulating or covering the first surface of the elongated carrier and a second elongated reflective layer arranged to asymmetrically encapsulate or cover the first at least partially light-transmissive elongated layer.

[0020] SUMMARY OF THE INVENTION

[0021] It is an object of the present invention to overcome this problem, and to provide an LED strip element with an improved optical performance and / or appearance.

[0022] According to a first aspect of the invention, this and other objects are achieved by a flexible light emitting diode, LED, strip filament. The LED strip filament is configured to, in an on-state, emit LED filament light. The LED strip filament comprises a white light- diffusive filament arranged on a LED strip. The LED strip comprises an elongated carrier, an array of a plurality of LEDs, an attachment component and an elongated light-converting 2024PF80171

[0023] 3 encapsulant. The elongated reflective carrier comprises a first major surface and a second major surface opposite to the first major surface. The array of a plurality of LEDs is configured to, in an on-state, emit LED light and being arranged on the first major surface of the elongated carrier. The attachment component is configured for attaching the LED strip filament to an attachment surface and being arranged on the second major surface of the elongated carrier. The elongated light-converting encapsulant is at least partly enclosing the plurality of LEDs and at least partly covering the first major surface of the elongated carrier. The elongated light-converting encapsulant comprises a luminescent material adapted to convert at least part of the LED light into converted light. The LED filament light comprises the converted light and optionally a portion of the LED light. The white light-diffusive filament comprises at least one white light-diffusive white, light-diffusive, elongated optics, wherein the elongated light-converting encapsulant is arranged between the white, light- diffusive, elongated optics and the elongated carrier.

[0024] Within the meaning of the present invention, the word white is to be interpreted as white, white with a specific CCT, including off-white colors as for example yellowish white or bluish white.

[0025] The light captured by the at least one white, light-diffusive, elongated optics is diffused within the white light-diffusive filament before being emitted as the LED filament light. The at least one white, light-diffusive, elongated optics may enhance the diffusion of the LED filament light outside of the white light-diffusive filament.

[0026] As a result of the light diffusion, the LED strip filament according to the present invention may distribute the LED filament light more uniformly as compared to LED strip filaments without a light-diffusive filament. For instance, hotspots and dark areas may be minimized. For instance, glare may be reduced. The increased uniformity of the LED filament light improves the filament appearance of the LED strip filament.

[0027] The at least one white, light-diffusive, elongated optics may be useful to control the spatial distribution of the LED filament light according to specific requirements.

[0028] The at least one white, light-diffusive, elongated optics may focus the LED filament light in a specific direction.

[0029] The light extraction efficiency is hereinafter defined as the fraction of the LED filament light relative to the totality of the LED light. Thus, the extraction efficiency accounts for the portion of the LED light not converted into the converted light and subsequently emitted as the LED filament light, and for the portion of the LED light first converted into the converted light and subsequently emitted as the LED filament light. Any other portion of the 2024PF80171

[0030] 4

[0031] LED light amounts to a light extraction loss. By decreasing the light extraction loss, the light extraction efficiency is increased. Increasing the light extraction efficiency improves the energy efficiency of the LED strip filament.

[0032] Arranging the elongated light-converting encapsulant between the white, light- diffusive, elongated optics and the elongated carrier may increase the light extraction efficiency as compared to LED strip filaments wherein a gap is present between the white, light-diffusive, elongated optics and the elongated encapsulant. Being arranged on the elongated encapsulant, the at least one white, light-diffusive, elongated optics covers, at least partially, the elongated encapsulant. Thus, the at least one white, light-diffusive, elongated optics is configured to capture at least a portion of the converted light and, optionally, a portion of the LED light.

[0033] It should be realized that the converted light and the LED light not captured by the at least one white, light-diffusive, elongated optics may not be diffused within the at least one white, light-diffusive, elongated optics. Thus, the fraction of the converted light and the LED light not captured by the at least one white, light-diffusive, elongated optics may reduce the uniformity in the distribution of the LED filament light, thereby jeopardizing the filament appearance of the LED strip filament. As a consequence, increasing the light extraction efficiency also improves the filament appearance of the LED strip filament.

[0034] The white, light-diffusive, elongated optics may be arranged in direct contact with the elongated encapsulant.

[0035] Arranging the at least one white, light-diffusive, elongated optics in direct contact with the elongated encapsulant may increase the light extraction efficiency as compared to LED strip filaments wherein a gap is present between the at least one white, light-diffusive, elongated optics and the elongated encapsulant. Being arranged in direct contact with the elongated encapsulant, the at least one white, light-diffusive, elongated optics covers, at least partially, the elongated encapsulant. Thus, the at least one white, light- diffusive, elongated optics is configured to capture at least a portion of the converted light and, optionally, a portion of the LED light.

[0036] A reflective layer may be provided on an outer surface of the elongated lightconverting encapsulant between the elongated carrier and the white, light-diffusive, elongated optics.

[0037] The reflective layer may for instance be applied on the left and / or right longitudinal sides of the elongated encapsulant. 2024PF80171

[0038] 5

[0039] Being arranged on the outer surface of the elongated encapsulant between the elongated carrier and the at least one white, light-diffusive, elongated optics, the reflective layer covers, at least partially, a portion of the elongated encapsulant not covered by the at least one white, light-diffusive, elongated optics. Thus, the reflective layer may reduce the light extraction losses. As a result, the efficiency and filament appearance of the LED strip filament may be increased. The elongated light-converting encapsulant may be (in a cross- sectional view) fully enclosed by the one or more reflective layers, the elongated carrier and the elongated optics.

[0040] An elongated, white light-diffuser may be provided on at least a part of an outer surface of the white, light-diffusive, elongated optics. The light-diffuser may for example be a light-diffusive element or a light-diffusive layer or a light-diffusive coating.

[0041] The light-diffuser enhances the diffusion, outside of the white, light-diffusive, elongated optics, of the light captured by the at least one white, light-diffusive, elongated optics. As a result, the filament appearance of the LED strip filament is further improved. Also the light distribution may be further improved.

[0042] One or more of the following may apply to the LED strip filament: the at least one white, light-diffusive, elongated optics may be flexible; the at least one white, light- diffusive, elongated optics may comprise a translucent material comprising a light scattering material; the at least one white, light-diffusive, elongated optics may comprise a translucent material being a silicone.

[0043] The scattering material may for example be bubbles of any one of TiO2, BaSO4, A12O3 and any combination thereof. The silicone may comprise a crosslinked PDMS, crosslinked PDPS, crosslinked PMPS or combinations thereof.

[0044] As a result of the at least one white, light-diffusive, elongated optics being flexible, the at least one white, light-diffusive, elongated optics may be bent or shaped to fit into various fixtures or designs.

[0045] The translucent material allows for the light captured by the at least one white, light-diffusive, elongated optics to be transmitted, at least partially. The light-scattering material may further enhance the diffusion, within the white, light-diffusive, elongated optics, of the light captured by the white, light-diffusive, elongated optics. The lightscattering material may further enhance the diffusion, outside of the white, light-diffusive, elongated optics, of the light captured by the at least one white, light-diffusive, elongated optics. A further effect is that an optimal material and configuration for masking and 2024PF80171

[0046] 6 arrangement is obtained. As a result, the filament appearance of the LED strip filament is further improved.

[0047] The white, light-diffusive, elongated optics may be any one or more of asymmetric and arranged asymmetrically on the elongated encapsulant.

[0048] The asymmetry of the at least one white, light-diffusive, elongated optics itself or the asymmetry in the arrangement of the at least one white, light-diffusive, elongated optics in relation to the elongated encapsulant may facilitate focusing of the LED filament light in a specific direction.

[0049] The elongated carrier may comprise a first longitudinal edge and a second longitudinal edge, wherein the white, light-diffusive, elongated optics extends beyond only one, or beyond both, of the first longitudinal edge and the second longitudinal edge.

[0050] As a result, in case of extending only beyond one longitudinal edge the at least one white, light-diffusive, elongated optics is arranged asymmetrically in relation to the elongated carrier. This arrangement may facilitate focusing of the LED filament light in the direction beyond the only one of the first longitudinal edge and the second longitudinal edge along which the at least one white, light-diffusive, elongated optics extends. In case of extending both edges e.g. symmetrically, the elongated light-converting encapsulant is very well hidden.

[0051] In embodiments, the LED strip filament, e.g. the elongated light-converting encapsulant, has in an off-state of the LED filament, a white appearance.

[0052] The white, light-diffusive, elongated optics may comprise a first part and a second part opposite to the first part, wherein one or more of the following applies: the first part may comprise a surface structure or surface roughness, and / or the second part may comprise a smooth surface structure or a reflective layer configured to provide total reflection or total internal reflection, TIR, such as to redirect light towards the first part.

[0053] The first part may extend beyond one of the first longitudinal edge and the second longitudinal edge. The second part may extend beyond (another) one of the first longitudinal edge and the second longitudinal edge. The first part may be arranged at the left side of the LED strip filament and the second part may be arranged at the right side of the LED strip filament.

[0054] The surface structure or surface roughness that the first part may comprise is useful to enhance the diffusion, within the white, light-diffusive, elongated optics, of the light captured by the white, light-diffusive, elongated optics. The surface structure or surface roughness that the first part may comprise is also useful to enhance the diffusion, outside of 2024PF80171

[0055] 7 the white, light-diffusive, elongated optics, of the light captured by the at least one white, light-diffusive, elongated optics. As a result, the filament appearance of the LED strip filament is further improved.

[0056] The smooth surface structure or reflective layer that the second part may comprise is useful to focus the LED filament light in a specific direction, i.e. towards the first part.

[0057] The elongated carrier comprises a first width, Wl, the elongated lightconverting encapsulant comprises a second width, W2, and the white light-diffusive filament comprises a third width, W3, wherein one or more of the following may apply: (i) W3 > 1.2*W2 or W3 > 1.5*W2, and (ii) W3 > 1.2*W1 or W3 > 1.5*W1. It may additionally, or alternatively, also apply that (ii) W3 < 3*W1 or W3 < 3*W1.

[0058] Thereby it becomes possible to hide the colored elongated encapsulant and / or to hide LED strip. As a result, the filament appearance of the LED strip filament is improved.

[0059] It may apply that 0.7 < W2 / W1 < 1.3. The effect is that the hiding of the LED strip is improved.

[0060] The LED, strip filament comprises a first height, Hl, and the white light- diffusive filament comprises a second height, H2, and the following may apply: O.95*H1 > H2 > O.6*H1. The effect is that the hiding of the LED strip is improved even further.

[0061] The LED strip comprises a first width, Wl, and a first height, Hl, the white light-diffusive filament comprises a second width, W2, and a second height, H2, and the following may apply: W2 > Wl, or W2 > 2*W1, and H2 > Hl, or H2 > 2*H1.

[0062] The second width W2 of the white light-diffusive filament being larger than the first width Wl of the LED strip facilitates covering, at least partially, of the elongated encapsulant by the at least one white, light-diffusive, elongated optics. Thereby it becomes possible to hide the colored elongated encapsulant and / or to hide LED strip. As a result, the light extraction efficiency may be increased, thereby improving the energy efficiency and filament appearance of the LED strip filament.

[0063] The second height H2 of the white light-diffusive filament being larger than the first height Hl of the LED strip may facilitate focusing of the LED filament light in a specific direction, i.e. in the direction of the second height H2.

[0064] The LED strip comprises a first width, Wl, and a first height, Hl, the white light-diffusive filament comprises a second width, W2, and a second height, H2, and the following may apply: Hl is in a range from 1 mm to 3 mm and Hl is in a range from 3 mm to 6 mm, or the following may apply: H2 / W2 < 2. 2024PF80171

[0065] 8

[0066] The elongated encapsulant and / or the elongated carrier comprises a first diameter, DI, the white light-diffusive filament comprises a second diameter, D2, and one or more of the following may apply: DI is in a range from 1 mm to 3 mm and DI is in a range from 3 mm to 6 mm, or D2 / W2 < 2.

[0067] The white light-diffusive elongated optics may comprise a transparent core and a white, light-diffusive cladding.

[0068] As a result, the light captured by the at least one white, light-diffusive, elongated optics may be reflected / scattered, at least partially, at the interface between the transparent core and the white, light-diffusive cladding. This at least partial reflection enhances the diffusion within the white, light-diffusive, elongated optics of the light captured by the white, light-diffusive, elongated optics, thereby improving the filament appearance of the LED strip filament.

[0069] The reflectivity of the white, light-diffusive, elongated optics may be in a range from 10 % to 50% or 15 % to 40 %. The LED strip filament may have, in an off-state of the LED filament, a white appearance.

[0070] Thereby a LED strip filament with good hiding characteristics and also high efficiency and light distribution is obtained.

[0071] One or more of the following may apply to the LED strip filament: the light- diffusive cladding may comprise a first thickness, Tl, on its top and a second thickness, T2, at its sides, wherein Tl > T2; the light-diffusive cladding may comprise a first refractive index, nl, and the transparent core may comprise a second refractive index, n2, wherein nl < n2.

[0072] The first thickness Tl being larger than the second thickness T2 may facilitate focusing of the LED filament light in a specific direction, i.e. towards the top of the light- diffusive cladding.

[0073] The first refractive index nl being smaller of the second refractive index n2 facilitates guiding of light within the core. In other terms, the white light-diffusive filament serves as an optical waveguide for the light captured by the at least one white, light-diffusive, elongated optics. It should be realized that the white light-diffusive filament has an axis of elongation. Thus, the light captured by the white, light-diffusive, elongated optics is guided, primarily, along the axis of elongation of the white light-diffusive filament within the transparent core of the white light-diffusive filament by total internal reflection. This light guiding enhances the uniformity of the LED filament light, thereby improving the filament appearance of the LED strip filament. 2024PF80171

[0074] 9

[0075] The atachment component comprises a width, W3, the elongated carrier comprises a width, W4, and W3 may be equal to W4.

[0076] The width W3 of the atachment component being the same as the width W4 of the elongated carrier reduces the volume of the LED strip filament, thereby improving the miniaturization thereof.

[0077] The LED strip filament may comprise a controller configured to (individually) control (subsets of one or more LEDs of) the plurality of LEDs.

[0078] Thus, the LED strip filament may be CCT tunable, i.e., the correlated color temperature (CCT) of the LED filament light may be tuned by individually controlling the LEDs of the plurality of LEDs. For example, the CCT may be varied by at least 500 K, e.g. from a CCT below 2500K to a CCT above 2700 K.

[0079] The invention further relates to a LED filament lamp comprising a flexible LED strip filament according to the invention.

[0080] The LED filament lamp may further comprise a light transmissive envelope at least partly enclosing the flexible LED strip filament and a base for electrically and mechanically connecting the LED filament lamp to a socket or a socket of a luminaire.

[0081] The invention still further relates to a luminaire comprising a LED filament lamp according to the invention.

[0082] The invention still further relates to a luminaire comprising a flexible LED strip filament according to the invention.

[0083] It is noted that the invention relates to all possible combinations of features recited in the claims.

[0084] BRIEF DESCRIPTION OF THE DRAWINGS

[0085] 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.

[0086] Fig. 1 shows a cross-sectional view of a flexible light emitting diode, LED, strip filament according to the invention.

[0087] Fig. 2 shows a cross-sectional view of a variant of the flexible LED strip filament according to Fig. 1.

[0088] Fig. 3 shows a cross-sectional view of another the flexible LED strip filament according to Fig. 1.

[0089] Fig. 4 shows a cross-sectional view of another flexible LED strip filament according to the invention. 2024PF80171

[0090] 10

[0091] Fig. 5 shows a cross-sectional view of a variant of the flexible LED strip filament according to Fig. 4.

[0092] Fig. 6 shows a cross-sectional view of the flexible LED strip filament according to Fig. 4 mounted on an attachment surface.

[0093] Fig. 7 shows a cross-sectional view of the flexible LED strip filament according to Fig. 5 mounted on an attachment surface.

[0094] Figs. 8-10 show cross-sectional views of different variations of the flexible LED strip filament according to Fig. 4.

[0095] Fig. 11 shows a schematical side view of a lamp comprising a LED filament according to the invention.

[0096] Fig. 12 shows a schematical side view of a luminaire comprising a lamp and a LED filament according to the invention.

[0097] 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.

[0098] DETAILED DESCRIPTION

[0099] 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.

[0100] Fig. 1 shows a cross section of an LED strip filament 100 according to a first embodiment of the present invention.

[0101] The LED strip filament 100 is configured to, in an on-state, emit LED filament light 2. The LED strip filament 100 comprises a white light-diffusive filament 1 arranged on a LED strip 10. The LED strip 10 comprises an elongated, reflective carrier 3, an array of a plurality of LEDs 4, an attachment component 6 and an elongated light-converting encapsulant 5.

[0102] The elongated, reflective carrier 3 comprises a first major surface 31 and a second major surface 32 opposite to the first major surface 31. The elongated, reflective 2024PF80171

[0103] 11 carrier 3 may comprise electrical wiring configured to provide the array of a plurality of LEDs 4 with electrical power.

[0104] The array of a plurality of LEDs 4 is configured to, in an on-state, emit LED light 41. The array of a plurality of LEDs 4 is arranged on the first major surface 31 of the elongated carrier 3.

[0105] The attachment component 6 is configured for attaching the LED strip filament 100 to an attachment surface 12 (cf. Fig. 6). The attachment component 6 is further configured for being arranged on the second major surface 32 of the elongated carrier 3.

[0106] The elongated light-converting encapsulant 5 is enclosing the plurality of LEDs 4 and covering the elongated carrier 3. Particularly, the elongated light-converting encapsulant 5 covers at least a part of the first major surface 31 of the elongated carrier 3. The elongated light-converting encapsulant 5 comprises a luminescent material 51 adapted to convert at least part of the LED light 41 into converted light 42. The LED filament light 2 comprises the converted light 42 and, optionally, a portion of the LED light 41.

[0107] The white light-diffusive filament 1 comprises a white, light-diffusive, elongated optics 7. The elongated light-converting encapsulant 5 is arranged between the white, light-diffusive, elongated optics 7 and elongated carrier 3. Optionally, the white, light- diffusive, elongated optics 7 is arranged in direct contact with the elongated encapsulant 5. The cross-sectional shape of the white light-diffusive filament 1 may for instance be circular or oval.

[0108] It should be realized that the LED light 41 may be emitted, in principle, in all directions, including directions away from the elongated encapsulant 5 or the white, light- diffusive, elongated optics 7. At least a portion of the LED light 41 is absorbed by the luminescent material 51 and subsequently converted into the converted light 42.

[0109] It should be realized that being reflective, the elongated carrier 3 is configured to reflect at least a portion of the LED light 41 emitted by the plurality of LEDs 4 in directions away from the elongated encapsulant 5 or the white, light-diffusive, elongated optics 7 back towards the elongated encapsulant 5 or the white, light-diffusive, elongated optics 7. At least a portion of the LED light 41, directly emitted towards the elongated encapsulant 5 or redirected towards the elongated encapsulant 5 by the elongated carrier 3, is converted into the converted light 42 by the luminescent material 51. Thus, the elongated carrier 3 being reflective increases the fraction of LED light 41 that is converted into the converted light 42. 2024PF80171

[0110] 12

[0111] Being arranged in direct contact with the elongated encapsulant 5, the white, light-diffusive, elongated optics 7 covers, at least partially, the elongated encapsulant 5. Thus, the white, light-diffusive, elongated optics 7 is configured to capture at least a portion of the converted light 42 and, optionally, a portion of the LED light 41 not converted into the converted light 42.

[0112] The light captured by the white, light-diffusive, elongated optics 7 is diffused within the white light-diffusive filament 1 before being emitted by or from the LED strip filament 100 as the LED filament light 2.

[0113] The light extraction efficiency is hereinafter defined as the fraction of the LED filament light 2 relative to the totality of the LED light 41. Thus, the extraction efficiency accounts for the portion of the LED light 41 not converted into the converted light 42 and subsequently emitted as the LED filament light 2, and for the portion of the LED light 41 first converted into the converted light 42 and subsequently emitted as the LED filament light 2. Any other portion of the LED light 41 amounts to a light extraction loss. By decreasing the light extraction loss, the light extraction efficiency is increased.

[0114] Being reflective, the elongated carrier 3 increases the fraction of LED light 41 that is converted into the converted light 42, thereby increasing the light extraction efficiency.

[0115] It should be realized that the attachment surface 12 (not shown in Fig. 1, but shown in Fig. 6) may be a mounting surface of a luminaire. The attachment surface 12 may also be a wall, a ceiling, or a similar surface.

[0116] In the embodiment shown in Fig. 1, a reflective layer 8 is provided on an outer surface 52 of the elongated encapsulant 5 between the elongated carrier 3 and the white, light-diffusive, elongated optics 7. The reflective layer 8 extends between the elongated carrier 3 and the white, light-diffusive, elongated optics 7. More particularly, the reflective layer 8 is provided on a left and right longitudinal side of the outer surface 52 of the elongated encapsulant 5 between the elongated carrier 3 and the white, light-diffusive, elongated optics 7.

[0117] The reflective layer 8 covers the portion of the elongated encapsulant 5 not covered by the white, light-diffusive, elongated optics 7. The reflective layer 8 is configured to reflect back towards the elongated encapsulant 5 or the white, light-diffusive, elongated optics 7 at least a portion of the converted light 42 and the LED light 41 propagating in directions away from the elongated encapsulant 5. Thus, the reflective layer 8 is configured to reduce the light extraction loss. 2024PF80171

[0118] 13

[0119] In the embodiment shown in Figs. 4 and 6, no reflective layer is provided on the LED strip filament 103. Instead, the white, light-diffusive, elongated optics 7 is arranged to fully cover the elongated encapsulant 5. As will be described in further detail further below, the white, light-diffusive, elongated optics 7 is asymmetric. Otherwise, the LED strip filament 103 is the same as the LED strip filament 100 shown in Fig. 1.

[0120] It should be realized that the arrangements described above is beneficial for the light extraction efficiency. In fact, the fraction of the converted light 42 and the LED light 41 that is not captured by the white, light-diffusive, elongated optics 7 is reduced as compared to the case wherein a portion of the elongated encapsulant 5 were not covered by the white, light-diffusive, elongated optics 7 and, at the same time, no reflective layer similar to the reflective layer 8 in Fig. 2 were present.

[0121] Fig. 2 shows another LED strip filament 101 according to the invention. The LED strip filament 101 is similar to the LED strip filament 100 shown in Fig. 1 and described above, but differs therefrom in virtue of the following features.

[0122] As shown in Fig. 2, the white light-diffusive filament 1 of the LED strip filament 101 comprises a white light-diffusive layer 9 provided on an outer surface 71 of the white, light-diffusive, elongated optics 7.

[0123] Thus, the light captured by the white, light-diffusive, elongated optics 7 may be refractive at the interface between the white, light-diffusive, elongated optics 7 and the white light-diffusive layer 9, and subsequently diffused within the light-diffusive layer 9 before being emitted as the LED filament light 2.

[0124] In the embodiments in Fig. 1, Fig. 2 and Fig. 6, the white, light-diffusive, elongated optics comprises a translucent material, e.g. a silicone or a crosslinked PDMS, a crosslinked PDPS, a crosslinked PMPS or a combination thereof. The translucent material comprises a light scattering material. The light scattering material may comprise particles or bubbles of any one of TiO2, BaSO4, A12O3 and any combination thereof. It should be realized that materials such as silicone or crosslinked PDMS are flexible. Therefore, they may be bent or shaped to fit into various fixtures or designs.

[0125] Figs. 4 and 6 show another LED strip filament 103 according to the invention. Other LED strip filaments 104, 105, 106 and 107 according to the invention and similar to that in Fig. 4 are illustrated in Fig. 5, Fig. 7, Fig. 8, Fig. 9 and Fig. 10. In the following, the embodiments illustrated in the figures from Fig. 4 to Fig. 10 will be described.

[0126] As shown in the figures from Fig. 4 to Fig. 10, all of the LED strip filament 103-107 comprise a white, light-diffusive, elongated optics 7 which is asymmetric. In other 2024PF80171

[0127] 14 terms, the cross section of the white, light-diffusive, elongated optics 7 shown in the figures from Fig. 4 to Fig. 10, or any other respective cross section of the white, light-diffusive, elongated optics 7 parallel to that shown in the respective figure, does not have a symmetry axis. As a result, the white, light-diffusive, elongated optics 7 is also asymmetric in relation to the elongated encapsulant 5.

[0128] It should be realized that, alternatively, the white, light-diffusive, elongated optics 7 may be symmetric, but arranged asymmetrically on the elongated encapsulant 5.

[0129] In either case, the asymmetry of the white, light-diffusive, elongated optics 7 in relation to the elongated encapsulant 5 facilitates focusing of the LED filament light 2 in a specific direction, as further illustrated later.

[0130] It should be realized that, when referring to the asymmetry of the white, light- diffusive, elongated optics 7 or the asymmetry of the arrangement of the white, light- diffusive, elongated optics 7, it is the asymmetry of a cross section of the white, light- diffusive, elongated optics 7, or the asymmetry of the arrangement of a cross section of the white, light-diffusive, elongated optics 7, that is referred to. The cross section is the respective cross section shown in the figures from Fig. 4 to Fig. 11, or any other equivalent respective cross section, i.e. a cross section parallel to the respective cross section shown in the respective figure.

[0131] As shown in the figures from Fig. 4 to Fig. 10, the elongated carrier comprises a first longitudinal edge 33 and a second longitudinal edge 34. The second longitudinal edge 34 is parallel to the first longitudinal edge 33.

[0132] As further shown in the figures from Fig. 4 to Fig. 7, the white, light-diffusive, elongated optics 7 of the LED strip filaments 103 and 104 extends beyond only the first longitudinal edge 33. As a result, the white, light-diffusive, elongated optics 7 is arranged asymmetrically in relation to the elongated carrier 3. This arrangement facilitates focusing of the LED filament light 2 in the direction beyond the first longitudinal edge 33 along which the white, light-diffusive, elongated optics 7 extends.

[0133] It should be realized that the LED strip filament 103 shown in Fig. 4 is similar to the LED strip filament 104 shown in Fig. 5, the only difference being the shape of the white, light-diffusive, elongated optics 7. As shown in Fig. 4 and Fig. 5, the white, light- diffusive, elongated optics 7 comprises a first part 72, extending beyond the first longitudinal edge 33, and a second part 73, opposite to the first part 72. Neither the first part 72 nor the second part 73 extends beyond the second longitudinal edge 34. In embodiment in Fig. 4, the second part 73 has a side parallel to the second longitudinal edge 34. In the embodiment in 2024PF80171

[0134] 15

[0135] Fig. 5, the second part 73 has a side arranged diagonally with respect to the second longitudinal edge 34.

[0136] In Fig. 7, the LED strip filament 104 shown in Fig. 5is shown mounted on an attachment surface 12 to which the attachment component 6 is configured for attaching the LED strip filament 104.

[0137] Fig. 8 shows an LED strip filament 105 which is similar to, but differs from, the LED strip filament 103 shown in Fig. 4 in virtue of the following.

[0138] As shown in Fig. 8, the white, light-diffusive, elongated optics 7 comprises a first part 72, extending beyond the first longitudinal edge 33, and a second part 73, opposite to the first part 72 and extending beyond the second longitudinal edge 34. The second part 73 comprises a smooth surface 75 configured to provide total internal reflection (TIR) such as to redirect light towards the first part 72.

[0139] In other terms, the second part 73 comprises a smooth surface 75 inside the white, light-diffusive, elongated optics 7. The smooth surface 75 is inclined with respect to the second long longitudinal edge 34 in such a way that a light ray incident on a point of the smooth surface from inside the white, light-diffusive, elongated optics 7, at an angle of incidence larger than a critical angle, undergoes TIR. The angle of incidence is the angle between an axis, orthogonal to the smooth surface 75 at the point of incidence, and the light ray. The critical angle is the angle of incidence above which TIR occurs. The critical angle depends on the smooth surface 75 and the medium outside the white, light-diffusive, elongated optics 7 at the interface with the smooth surface 75. The inclination of the smooth surface 75 is such that a light ray undergoing TIR is redirected towards the first part 72.

[0140] Fig. 9 shows an LED strip filament 106 which is similar to, but differs from the LED strip filament 105 shown in Fig. 8 in virtue of the following.

[0141] The first part 72 of the white, light-diffusive, elongated optics 7 of the LED strip filament 106 comprises a surface roughness 74. The light captured by the white, light- diffusive, elongated optics 7 may be refracted at the interface between the white, light- diffusive, elongated optics 7 and the medium outside the white, light-diffusive, elongated optics 7. The surface roughness 74 enhances the scattering of light incident on the surface roughness 74 from inside the white, light-diffusive, elongated optics 7 as compared to light incident on other surfaces of the white, light-diffusive, elongated optics 7 from inside the white, light-diffusive, elongated optics 7. Thus, the surface roughness is useful to enhance the diffusion, within the white, light-diffusive, elongated optics 7, of the light captured by the white, light-diffusive, elongated optics 7. 2024PF80171

[0142] 16

[0143] It should be realized that the light refracted to the medium outside the white, light-diffusive, elongated optics 7 may undergo further scattering when impinging on the surface roughness 74 in the medium outside the white, light-diffusive, elongated optics 7. Thus, the surface roughness is useful to enhance the diffusion, outside the white, light- diffusive, elongated optics 7, of the light captured by the white, light-diffusive, elongated optics 7.

[0144] Fig. 10 shows an LED strip filament 107 which is similar to, but differs from the LED strip filament 105 shown in Fig. 8 in virtue of the following.

[0145] Instead of the smooth surface 75, the second part 73 comprises a reflective layer 76 configured to provide total reflection such as to redirect light towards the first part 72. The reflective layer 76 may be any type of mirror, such as a dielectric mirror or a metallic mirror, configured to totally reflect back towards the first part 72 light incident on the reflective layer 76 from inside the white, light-diffusive, elongated optics 7.

[0146] Referring back to the embodiment in Fig. 2, it is shown that the LED strip filament 100 comprises a first height Hl, and that the LED strip 10 comprises a first width, Wl, and a third height, H3. The first width W1 and the third height H3 are defined along respective directions perpendicular to each other.

[0147] More specifically, the cross section of the elongated carrier 3 is rectangular. This rectangle has a width along a direction parallel to the first major surface 31, the width being the first width WL The third height H3 is the maximum extension of the cross section of the LED strip filament 10 along a direction perpendicular to the first major surface 31, from a first point on the perimeter of the lower portion of the white, light-diffusive, elongated optics 7 to a second point on the perimeter of attachment component 6. Furthermore, the elongated light-converting encapsulant 5 comprises a second width, W2, parallel ti the first width WL

[0148] As also shown in Fig. 2, the white light-diffusive filament 1 comprises a third width, W3, and a second height, H2. The third width W3 and the second height H2 are defined along respective directions perpendicular to each other.

[0149] More specifically, the cross section of white, light-diffusive, elongated optics 7 has a lower portion, in direct contact with the elongated encapsulant 5, and an upper portion, opposite to the lower portion. The upper portion has a semicircular shape. This semicircle has a diameter, the diameter being the third width W3. The third width W3 is defined along a direction parallel to the first major surface 31. The second height H2 is the maximum extension of the cross section of the white, light-diffusive, elongated optics 7 2024PF80171

[0150] 17 along a direction perpendicular to the first major surface 31, from a first point on the perimeter of the upper portion to a second point on the perimeter of the lower portion.

[0151] It should be realized that the cross section of the white, light-diffusive, elongated optics 7 may, alternatively, have a difference shape, e.g. any of the respective shapes of the embodiments shown in the figures from Fig. 4 to Fig. 10.

[0152] The first width W1 and the third width W3 are chosen such that W3 is larger than Wl. Alternatively, the first width W1 and the third width W3 may be chosen such that W3 is larger than twice Wl.

[0153] The first height Hl and the second height H2 may be chosen such that O.95*H1 > H2 > O.6*H1. Alternatively, or additionally, the third height H3 and the second height H2 are chosen such that H2 is larger than H3. Alternatively, or additionally, the third height H3 and the second height H2 may be chosen such that H2 is larger than twice H3.

[0154] In the embodiment in Fig. 2, the third height H3 is 1.5 mm and H2 is 2 mm. Alternatively, H3 may be in a range from 1 mm to 3 mm, and H2 may be in a range from 3 mm to 6 mm. Alternatively, H2 may be smaller than twice W3.

[0155] Furthermore, Wl, W2 and W3 may be chosen such that W3 > 1.2*W2, or preferably such that W3 > 1.5*W2. Alternatively, or additionally, W3 and Wl may be chosen such that W3 > 1.2*W1, or preferably such that W3 > 1.5*W1. 9. Alternatively, or additionally, Wl and W2 may be chosen such that 0.7 < W2 / W1 < 1.3.

[0156] Finally, Fig. 3 shows an LED strip filament 102 which is similar to, but differs from the LED strip filament 101 shown in Fig. 2 in virtue of the following.

[0157] Fig. 3 shows an embodiment similar to that in Fig. 2, the only difference being that the white, light-diffusive, elongated optics 7 comprises a transparent core 13 and a light- diffusive cladding 14.

[0158] More specifically, the white, light-diffusive, elongated optics 7 comprises the transparent core 13. The light-diffusive cladding 14 is arranged on an outer surface 71 of the transparent core 13.

[0159] The reflectivity of the light-diffusive cladding 14 is in a range from 20 % to 50 %. In other terms, the light captured by the white, light-diffusive, elongated optics 7, when incident on the interface between the transparent core 13 and the light-diffusive cladding 14 from inside the transparent core 13, experiences a reflectivity in the range from 20 % to 50 2024PF80171

[0160] 18

[0161] As shown in Fig. 3, the light-diffusive cladding 14 comprises a first thickness, Tl, on its top and a second thickness, T2, at its sides. The first thickness T1 is larger than the second thickness T2.

[0162] The light-diffusive cladding 14 comprises a first refractive index, nl, and the transparent core comprises a second refractive index, n2. The first refractive index nl is smaller than the second refractive index n2.

[0163] It should be realized that the white light-diffusive filament 1 has an axis of elongation. As a result of nl being smaller than n2, the light captured by the white, light- diffusive, elongated optics 7 is guided by TIR, primarily, along the axis of elongation of the white light-diffusive filament 1 within the transparent core 13 of the white light-diffusive filament 1.

[0164] Referring back, collectively, to Fig. 1, Fig. 2 and Fig. 3, it is therein shown that the attachment component 6 comprises a width, W3. The elongated carrier comprises a width, W4. The width W3 and the width W4 are equal.

[0165] Alternatively, the width W3 and the width W4 may be different. For instance, the width W3 may be larger than the width W4.

[0166] As illustrated in Fig. 1, the LED strip filament 100 comprises a controller 11 configured to individually control the LEDs of the plurality of LEDs 4. Any LED strip element 100-107 according to the invention may comprise such a controller 11.

[0167] By individually controlling the LEDs of the plurality of LEDs 4, the correlated color temperature (CCT) of the LED filament light 2 may be tuned. Thus, the LED strip filament is CCT tunable. The plurality of LEDs 4 may comprise blue LEDs and red LEDs.

[0168] The controller 11 may be configured to control wirelessly the LEDs of the plurality of LEDs 4.

[0169] Fig. 11 shows an exemplary lamp 300 comprising a flexible LED strip filament 100 according to any embodiment of the invention. In the embodiment shown, the flexible LED strip filament 100 comprises a substantially straight flexible LED strip filament. The flexible LED strip filament of such a lamp may in other embodiments be a flexible LED strip filament with another shape, such as, but not limited to, spiral-shaped, helix-shaped, meandering, twisted, flat and combinations thereof.

[0170] The lamp 300 further comprises a driver or controller 305 configured for controlling the plurality of LEDs 4 of the flexible LED strip filament 100. The controller 305 is configured to power the plurality of LEDs 4 via electrical circuitry (not visible on the figures) of the flexible LED strip filament 100. The flexible LED strip filament 100 may also 2024PF80171

[0171] 19 comprise a controller, which may or may not be separate from the controller 305. In other words, the controller 305 and the controller 11 of the flexible LED strip filament 100 may be integrated into one and the same driver or controller, or they may be mutually separate units.

[0172] The lamp 300 further comprises an envelope 301 at least partially enveloping the at least one flexible LED strip filament 100. 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.

[0173] 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.

[0174] Turning finally to Fig. 12, an exemplary luminaire in the form of a pendant 400 is shown. The pendant 400 comprises a flexible LED strip filament 100 according to any embodiment of the invention. The flexible LED strip filament 100 is as shown in Fig. 12 provided within a lamp 300 in the form of a light bulb. The flexible LED strip filament 100 as shown in Fig. 12 comprises a substantially straight flexible LED strip filament.

[0175] 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 flexible LED strip filament 100. 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.

[0176] The pendant 400 further comprises a socket 401 for connecting the lamp 300, and thereby the flexible LED strip filament 100, 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.

[0177] The pendant 400 may further comprise a driver 402 configured for controlling the flexible LED strip filament 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. 2024PF80171

[0178] 20

[0179] Alternatively, or additionally, the flexible LED strip filament 100 may also comprise a controller 11 , which may or may not be separate from one or both of the driver 402 and the controller 305.

[0180] 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.

[0181] It is noted that the pendant 400 shown in Fig. 12 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.

[0182] 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.

[0183] 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

2024PF8017121CLAIMS:

1. A flexible light emitting diode, LED, strip filament (100) configured to, in an on-state, emit LED filament light (2), the LED strip filament (100) comprising a white light- diffusive filament (1) arranged on a LED strip (10), wherein the LED strip (10) comprises: an elongated carrier (3) comprising a first major surface (31) and a second major (32) surface opposite to the first major surface (31), 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 (3), an attachment component (6) configured for attaching the LED strip filament (100) to an attachment surface (12) and being arranged on the second major surface (32) of the elongated carrier (3), and an elongated light-converting encapsulant (5) at least partly enclosing the plurality of LEDs (4) and at least partly covering the first major surface of the elongated carrier (3), the elongated light-converting encapsulant (5) comprising a luminescent material (51) adapted to convert at least part of the LED light (41) into converted light (42), the LED filament light (2) comprising the converted light (42) and optionally a portion of the LED light (41), and wherein the white light-diffusive filament (1) comprises a white, light- diffusive, elongated optics (7), wherein the elongated light-converting encapsulant (5) is arranged between the white, light-diffusive, elongated optics (7) and elongated carrier (3), and wherein the elongated carrier (3) has a first width, Wl, the elongated lightconverting encapsulant (5) has a second width, W2, and the white light-diffusive filament (1) has a third width, W3, wherein one or more of the following applies:W3 > L2*W2, preferably W3 > L5*W2, andW3 > L2*W1, preferably W3 > L5*W1.

2. A LED strip filament (100) according to claim 1, wherein a reflective layer (8) is provided on an outer surface (52) of the elongated light-converting encapsulant (5) between the elongated carrier (3) and the white, light-diffusive, elongated optics (7).2024PF80171223. A LED strip filament (100) according to claim 1 or 2, wherein an elongated, white, light-diffuser (9) is provided on at least a part of an outer surface (71) of the white, light-diffusive, elongated optics (7).

4. A LED strip filament (100) according to claim 1 or 2, wherein the white, light- diffusive elongated optics (7) comprises a transparent core (13) and a white, light-diffusive cladding (14).

5. A LED strip filament (100) according to claim 4, wherein one or more of the following applies: the light-diffusive cladding (14) comprises a first thickness, Tl, on its top and a second thickness, T2, at its sides, wherein Tl > T2, and the light-diffusive cladding (14) comprises a first refractive index, nl, and the transparent core comprises a second refractive index, n2, wherein nl < n2.

6. A LED strip filament (100) according to any one of the above claims, wherein the following applies: the white, light-diffusive, elongated optics (7) is flexible, the white, light-diffusive, elongated optics (7) comprises a translucent material comprising a light scattering material, and the white, light-diffusive, elongated optics (7) comprises a translucent material being a silicone.

7. A LED strip filament (100) according to any one of the above claims, wherein the white, light-diffusive, elongated optics (7) is one or more of asymmetric and arranged asymmetrically on the elongated encapsulant (5).

8. A LED strip filament (100) according to any one of the above claims, wherein the elongated carrier (3) comprises a first longitudinal edge (33) and a second longitudinal edge (34), and wherein the white, light-diffusive, elongated optics (7) extends beyond only one, or beyond both, of the first longitudinal edge (33) and the second longitudinal edge (34).2024PF80171239. A LED strip filament (100) according to any one of the above claims, wherein the white, light-diffusive, elongated optics (7) comprises a first part (72) and a second part (73) opposite to the first part (72), wherein one or more of the following applies: the first part (72) comprises a surface structure or surface roughness (74), and the second part (73) comprises a smooth surface structure or a reflective layer (75) configured to provide total reflection or total internal reflection, TIR, such as to redirect light towards the first part (72).

10. A LED strip filament (100) according to any one of the above claims, wherein 0.7 < W2 / Wl < 1.3.

11. A LED strip filament (100) according to any one of the above claims, wherein the LED, strip filament (100) has a first height, Hl, and the white light-diffusive filament (1) has a second height, H2, wherein O.95*H1 > H2 > O.6*H1.

12. A LED strip filament (100) according to any one of the preceding claims, wherein the reflectivity of the white, light-diffusive, elongated optics (7) is in a range from 15 % to 40 %, wherein the LED strip filament has, in an off-state of the LED filament, a white appearance.

13. A LED strip filament (100) according to any one of the above claims, and further comprising a controller (11) configured to individually control subsets of one or more LEDs of the plurality of LEDs (4).

14. A LED filament lamp (300) or a luminaire (400) comprising a LED strip filament (100) according to any one of the preceding claims.

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