LED filament comprising phosphor-converted leds

Abstract

There is provided a light emitting diode, LED, filament (100) comprising an array (150) of a plurality of phosphor-converted light emitting diodes, pc-LEDs (160), wherein each pc-LED of the plurality of pc-LEDs comprises a LED chip (190) configured to emit LED chip light (200) and a phosphor element (210) arranged on the LED chip. The LED filament further comprises a first elongated reflector (250) and a second elongated reflector (260) arranged on either sides of, and adjacent and parallel to, the array of the plurality of pc- LEDs, wherein the first elongated reflector and the second elongated reflector are configured to redirect part of the LED chip light.

Description

[0001] 2024PF80174

[0002] 1

[0003] LED filament comprising phosphor-converted LEDS

[0004] FIELD OF THE INVENTION

[0005] The present invention generally relates to a light emitting diode, LED, filament. More specifically, the present invention relates to a LED filament comprising a plurality of phosphor-converted LEDs, pc-LEDs.

[0006] BACKGROUND OF THE INVENTION

[0007] The use of light emitting diodes, LEDs, for illumination purposes continues to attract attention. Compared to incandescent lamps, fluorescent lamps, neon tube lamps, etc., LEDs provide numerous advantages such as a longer operational life, a reduced power consumption, and an increased efficiency related to the ratio between light energy and heat energy.

[0008] Due to the advantageous aspects of the use of LEDs, the interest has rapidly increased to replace conventional light sources with LEDs in many lighting arrangements. It will be appreciated that this replacement, also called retrofitting, is appreciated and desired by users who wish to have the look of an incandescent bulb. The light source replacement (retrofitting) is often performed by removing the conventional light source(s) from the luminaire (e.g. a lamp holder) of the lighting arrangement and attaching the LEDs, LED arrangement(s) or LED device(s) into the luminaire. One of these concepts is based on LED filaments which are placed in a bulb. The visible LED filament(s) may provide a light distribution which is effective and decorative at the same time, whilst taking advantage of LED technology.

[0009] It is desired to even further improve the performance, functionality and / or appearance of LED filament(s). More specifically, the color of the light provided by a LED device or lamp often varies as a function of the angle of emitted light. This color-over-angle (COA) effect is sometimes significant and can lead to yellow rings at large angles in a far- field, leading to an undesired light distribution and / or an aesthetically inferior LED device (lighting).

[0010] WO 2022 / 268500 discloses a LED filament arrangement for emitting LED filament arrangement light, comprising first and second LED filaments arranged to emit first 2024PF80174

[0011] 2 and second LED filament light wherein the first and second LED filaments elongate along a first axis, A, and comprise first and second arrays of a plurality of first and second LEDs, a carrier arranged to support the first and second LED filaments, at least one structure arranged to at least partially redirect the first and second LED filament light, wherein the at least one structure is arranged adjacent at least one of the first and second LED filaments, and a controller configured to individually control the operation of the first and second arrays of the plurality of first and second LEDs, respectively.

[0012] WO 2024 / 153507 relates to an LED filament comprising: an at least partially light-transmissive elongated carrier; first LEDs configured to emit first LED light and distributed along the carrier on a first surface thereof; a first elongated translucent layer comprising a first luminescent material arranged to at least partly convert said first LED light into first converted light; an elongated reflective layer arranged to at least partially cover said first elongated translucent layer, such that at least part of said first converted light is transmitted through said at least partially light-transmissive elongated carrier; and second LEDs configured to emit second LED light and distributed along the carrier on a second surface thereof, wherein the second LEDs comprise blue LEDs, green LEDs, and red LEDs wherein said second surface of the carrier is free from an encapsulant or comprises an encapsulant being free from a luminescent material.

[0013] SUMMARY OF THE INVENTION

[0014] It is of interest to explore the possibility of combining one or more of the numerous advantages of LED filaments comprising LEDs, whilst improving the LED filaments’ performance and / or functionality via the properties of the light emission and / or distribution from the LED filaments. It is desirable to improve the appearance and / or the decorative aspect of the LED filaments, and in particular the appearance and / or the decorative aspect of the lighting emitted from the LED filaments.

[0015] This and other objects are achieved by providing a LED filament having the features in the independent claim. Preferred embodiments are defined in the dependent claims.

[0016] According to the present invention, there is provided a light emitting diode, LED, filament configured to provide, during operation, LED filament light. The LED filament comprises an elongated carrier, an array of a plurality of phosphor-converted light emitting diodes, pc-LEDs, arranged on a first major surface of the elongated carrier and configured to emit phosphor-converted LED light. Each pc-LED of the plurality of pc-LEDs 2024PF80174

[0017] 3 comprises a LED chip configured to emit LED chip light, and a phosphor element arranged on the LED chip. The phosphor element is configured to at least partly convert the LED chip light into converted light, wherein the phosphor-converted LED light comprises one of the converted light, and a combination of the converted light and part of the LED chip light. The LED filament further comprises a first elongated reflector and a second elongated reflector respectively arranged on the first major surface of the elongated carrier and arranged on either sides of, and (substantially) adjacent and (substantially) parallel to, the array of the plurality of pc-LEDs, wherein the first elongated reflector and the second elongated reflector are configured to redirect part of the LED chip light.

[0018] Thus, the present invention is based on the idea of providing a LED filament comprising an array of a plurality of pc-LEDs, wherein each pc-LED comprises a LED chip configured to emit LED chip light. First and second elongated reflectors are arranged on either sides of, and adjacent and parallel to, the array of the plurality of pc-LEDs, wherein the first and second elongated reflectors are configured to redirect part of the LED chip light.

[0019] The present invention is advantageous in that the LED filament achieves an improved color-over-angle (COA). It should be noted that LED devices or lamps in the prior art may suffer from a COA effect which sometimes may be significant, and can lead to yellow rings at large angles in a far-field, leading to an undesired light distribution and / or an aesthetically inferior LED device (lighting). In contrast, by using the first and second elongated reflectors of the LED filament according to the present invention, the COA issue is reduced, or even non-present, during operation of the LED filament.

[0020] The present invention is advantageous in that a desired light distribution and a decorative light effect may be achieved by the LED filament and its configuration of the pc- LEDs and reflectors.

[0021] The present invention is further advantageous in its versatility and customization concerning physical and / or optical properties of the first and second elongated reflectors. Consequently, the light distribution from the LED filament, as well as the aesthetic appearance of the LED filament, may be set or tuned for different purposes.

[0022] The present invention is further advantageous in that the numerous advantages of using LED technology may be combined with the attractiveness and the appealing properties of the LED filament as disclosed.

[0023] The present invention is further advantageous in that the LED filament of the present invention comprises relatively few components. The low number of components is advantageous in that the LED filament arrangement is relatively inexpensive to fabricate. 2024PF80174

[0024] 4

[0025] Moreover, the low number of components of the LED filament implies an easier recycling, especially compared to devices or arrangements comprising a relatively high number of components which impede an easy disassembling and / or recycling operation.

[0026] There is provided a LED filament configured to provide, during operation (i.e. in an on-state), LED filament light. For example, the LED filament light may be white light having a correlated color temperature, CCT, in a range of 1500 to 6500K or 1700K to 2700 K, and may have a color rendering index, CRI, of at least 80, or at least 85. The LED filament may have a length, LF, and a width, WF, wherein LF > 5WF or even LF > 10WF. 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. The LED filament has a light-emitting surface that extends along the length, and preferably at least partly around the axis of elongation. The light-emitting surface is preferably arranged to homogenously emit light and / or to emit light omnidirectionally. The LED filament comprises an elongated carrier, an array of a plurality of phosphor-converted light emitting diodes, pc-LEDs, arranged on a first major surface of the elongated carrier and configured to emit phosphor- converted LED light. The elongated carrier may, for instance, be a substrate, 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). The elongated carrier may be reflective or light transmissive, such as translucent and preferably transparent. By the term “array”, it is here meant a linear arrangement or chain of pc-LEDs, or the like. Each pc-LED of the plurality of pc-LEDs comprises a LED chip configured to emit LED chip light, and a phosphor element arranged on the LED chip. Each pc-LED may be a surface-mounted device (SMD) LED. The phosphor element is configured to at least partly convert the LED chip light into converted light, wherein the phosphor-converted LED light comprises one of the converted light, and a combination of the converted light and part of the LED chip light. Hence, the phosphor- converted LED light comprises the converted light and / or the combination of the converted light and part of the LED chip light. The phosphor element may be a tile or may have a tile shape. The LED filament further comprises a first elongated reflector and a second elongated reflector respectively arranged on the first major surface of the elongated carrier and arranged on either sides of, and adjacent and parallel to, the array of the plurality of pc-LEDs. The first elongated reflector and the second elongated reflector are configured to redirect part of the LED chip light. By “reflector”, it is here meant substantially any element which is configured or able to reflect and / or redirect light, more specifically part of the LED chip light in this case. By “redirect”, it is here meant that at least part of the LED chip light emitted at (very) 2024PF80174

[0027] 5 low angles (e.g. < 20 degrees or < 30 degrees) and (very) high higher angles (e.g. > 150 degrees or > 160 degrees) is redirected, while the LED chip light (substantially) perpendicular to the emission surface of the LED (e.g. angles between 40 and 140 degrees or angles between 50 and 130 degrees) is not redirected.

[0028] According to an embodiment of the present invention, the first elongated reflector and the second elongated reflector may be configured to, at least one of, reflect part of the LED chip light, and transmit part of the LED chip light. Hence, the first and second elongated reflectors may be configured to reflect and / or transmit part of the LED chip light. According to an example, the first elongated reflector and the second elongated reflector may be diffusers. By “diffuser”, it is here meant that the first and second reflectors are able, arranged or configured to reflect and / or scatter / diffuse light. The diffusers may be translucent and light diffusive. The present embodiment is advantageous in that the first and second reflectors as diffusers may affect or influence the light such that a desired light distribution of the LED chip light is obtained, resulting in a desired distribution and / or appealing aesthetical effect of the LED filament light.

[0029] According to an embodiment of the present invention, the first elongated reflector and the second elongated reflector may have a white appearance. By “white appearance”, it is meant that the first and second elongated reflectors may appear white for an observer. The present embodiment is advantageous in that the first and second elongated reflectors, by their white color, have a particularly appealing appearance, resulting in an attractive LED filament. More specifically, the present embodiment of the white first and second elongated reflectors contributes to a vintage look of the LED filament which is considered particularly attractive.

[0030] According to an embodiment of the present invention, the first elongated reflector and the second elongated reflector may respectively have a first height, Hl, and the array of the plurality of pc-LEDs may have a second height, H2, wherein 0.2-H2 < Hl < 3-H2 or 0.4-H2 < Hl < 2-H2 is fulfilled. The present embodiment is advantageous in that the relation between the first height, Hl, and the second height, H2, may optimize the light distribution of the LED filament light and / or the appearance of the LED filament (light). The present embodiment is further advantageous in that the relation between the first height, Hl, and the second height, H2, may be conveniently customized for light distribution and / or aesthetical appearance purposes.

[0031] According to an embodiment of the present invention, 0.2-H2 < Hl < H2 or 0.3-H2 < Hl < 0.9-H2 may be fulfilled. Hence, the first height, Hl, of the first and second 2024PF80174

[0032] 6 elongated reflectors may be larger than a fifth of the second height, H2, of the array of the plurality of pc-LEDs, and / but smaller than this second height, H2. The present embodiment is particularly advantageous concerning light distribution and / or aesthetical appearance purposes.

[0033] According to an embodiment of the present invention, at least one of the first elongated reflector and the second elongated reflector have a reflectivity, R, in a range of 20 - 50 %, and the first elongated reflector and the second elongated reflector have a transmittivity, T, in a range of 50 - 80 %, may be fulfilled. Hence, the first and second elongated reflectors may have a reflectivity, R, in a range of 20 - 50 %, and / or the first and / or second elongated reflectors may have a transmittivity, T, in a range of 50 - 80 %. The reflectivity, R, and / or the transmissivity, T, can be measured similar to the optical path of the LED chip light through the first and second elongated reflectors.

[0034] According to an example, at least one of the first elongated reflector and the second elongated reflector are white, the first elongated reflector and the second elongated reflector are translucent, the first elongated reflector and the second elongated reflector are light diffusive, the first elongated reflector and the second elongated reflector have a reflectivity, R, in a range of 20 - 50 %, and the first elongated reflector and the second elongated reflector have a transmittivity, T, in a range of 50 - 80 %, may be fulfilled. Hence, in addition to the feature(s) of the first and second elongated reflectors having a reflectivity, R, in a range of 20 - 50 %, and / or the first and / or second elongated reflectors may have a transmittivity, T, in a range of 50 - 80 %, the first elongated reflector and the second elongated reflector may be white, translucent and / or light diffusive.

[0035] According to an embodiment of the present invention, at least a subsection of the first elongated reflector and at least a subsection of the second elongated reflector, which respectively face the array of the plurality of pc-LEDs, are tapered with respect to the elongated carrier. In other words, the subsections of the first and second elongated reflectors facing the array of the plurality of pc-LEDs are tapered, flattened, rounded and / or chamfered. It will be appreciated that the entire (sub)section of the first elongated reflector and / or the entire (sub)section of the second elongated reflector may be tapered or slanted. The present embodiment is advantageous in that the tapered subsections of the first and second elongated reflectors contribute to an even more efficient and / or appealing light distribution, and / or a more attractive appearance of the LED filament.

[0036] According to an embodiment of the present invention, the elongated carrier may have a white appearance. By “white appearance”, it is here meant that the elongated 2024PF80174

[0037] 7 carrier may appear white for an observer. The present embodiment is advantageous in that the elongated carrier, by its white color, has a particularly appealing appearance, resulting in an attractive LED filament. More specifically, the present embodiment of a white elongated carrier contributes to a vintage look of the LED filament which is considered particularly attractive.

[0038] According to an embodiment of the present invention, the elongated carrier may comprise a diffuser being light-transmissive and configured to transmit at least one of part of the LED chip light, and part of the converted light. Hence, the elongated carrier is configured to transmit part of the LED chip light and / or part of the converted light. The present embodiment is advantageous in that the light-transmissive diffuser may achieve an (almost) omnidirectional light distribution, which may result in an even further desired LED filament light as emitted and / or an aesthetically appealing lighting effect.

[0039] According to an embodiment of the present invention, the LED filament may further comprise an elongated encapsulant at least partially covering the first major surface of the elongated carrier and at least partially covering the array of the plurality of pc-LEDs. By the term “encapsulant”, it is here meant an elongated material, element, arrangement, or the like, which in the present context is configured or arranged to at least partially cover, surround, encapsulate and / or enclose the first major surface of the elongated carrier and the array of the plurality of pc-LEDs. The encapsulant may be a polymer material which may be flexible such as for example a silicone. The luminescent material of the elongated primary encapsulant may be a phosphor such as an inorganic phosphor and / or quantum dots or rods.

[0040] According to an embodiment of the present invention, the elongated encapsulant may comprise a polymer matrix being transparent.

[0041] According to an embodiment of the present invention, the pc-LEDs may cover a surface area, Ai, of a total surface area, A2, of the first major surface, wherein Ai <= 0.2-A2 is fulfilled. Hence, the pc-LEDs may cover less than a fifth of the first major surface. The present embodiment is advantageous in that a relatively large area of the first major surface may transmit and / or reflect the LED chip light.

[0042] According to an embodiment of the present invention, the phosphor element may comprise a green-yellow phosphor and / or a red phosphor. The green-yellow phosphor may be configured to at least partially convert the LED chip light into green-yellow converted light. The red phosphor may be configured to at least partially convert the LED chip light into red converted light. 2024PF80174

[0043] 8

[0044] According to an embodiment of the present invention, the phosphor element may comprise at least one of a green-yellow phosphor of the type AsBsOn Ce, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc, and an orange-red phosphor comprising at least one of at least one nitride phosphor, at least one oxynitride phosphor, and a red phosphor of the type M’xM2-2xAX6 doped with tetravalent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x is selected from the range of 0 - 1, wherein A comprises a tetravalent cation, wherein X comprises a monovalent anion, at least comprising fluorine. Hence, the phosphor element may comprise a green-yellow phosphor of the type AsBsO Ce and / or an orange-red phosphor comprising (a) nitride phosphor(s), (an) oxynitride phosphor and / or a red phosphor. The present embodiment is advantageous in that the LED filament, via the green-yellow phosphor, the orange-red phosphor or the red phosphor of the phosphor element provides a more pleasing, homogenous and / or efficient light distribution and high quality of light.

[0045] In embodiments, the first elongated reflector and the second elongated reflector may not cover the plurality of pc-LEDs.

[0046] In embodiments, at least 60% or at least 80% of the converted light may not impinge on the first elongated reflector and the second elongated reflector. The obtained effect is improved efficiency.

[0047] In embodiments, the first elongated reflector and the second elongated reflector have a first height, Hl, and wherein each of the first elongated reflector and the second elongated reflector has a first width, Wl, measured at the LED chips and perpendicular to the elongation direction of the elongated carrier, and wherein the following may applies: W1>H1 or W1>1.5 H1. The obtained effect is improved efficiency and / or (off- state) white appearance.

[0048] In embodiments, the first elongated reflector and the second elongated reflector may partially cover the first major surface. The obtained effect is improved thermal management.

[0049] In embodiments, the first elongated reflector and the second elongated reflector may not cover edges of the elongated carrier.

[0050] In embodiments, the first elongated reflector and the second elongated reflector may not cover a second major surface, opposite to the first major surface, of the elongated carrier. 2024PF80174

[0051] 9

[0052] According to an embodiment of the present invention, there is provided a LED filament arrangement. The LED filament arrangement comprises at least one LED filament according to any one of the preceding embodiments, wherein the plurality of pc-LEDs comprises a first subset of pc-LEDs emitting first subset light, and a second subset of pc- LEDs emitting second subset light being different from the first subset light with respect to at least one of color point, CP, and correlated color temperature, CCT, from the first subset light. The LED filament arrangement further comprises a controller configured to individually control the first and second subsets of pc-LEDs to vary the color point, CP, of the LED filament light. Hence, the LED filament of the LED filament arrangement comprises a first and a second subset of pc-LEDs, wherein the first and second subset of pc-LEDs differ in color point, CP, and / or correlated color temperature, CCT.

[0053] According to an embodiment of the present invention, there is provided a LED filament lamp. The LED filament lamp comprises one of at least one LED filament according to any one of the preceding embodiments and a LED filament arrangement according to the preceding embodiment. The LED filament lamp further comprises a light-transmissive envelope at least partly enclosing the at least one LED filament, and a connector for electrically and mechanically connecting the LED filament lamp to a socket of a luminaire. The present embodiment is advantageous in that the LED filament lamp, comprising the LED filament(s), combines the aspects of a desired light emission and aesthetical appearance provided via the LED filament(s) and / or via the feature(s) of the lamp.

[0054] According to an example of the present invention, the LED filament device or the LED filament lamp may further comprise a controller configured to control the luminous flux of the LED filament light. The controller may control each LED filament individually. By “controller”, it is here meant any device, unit, or the like, which is able to control the luminous flux either by wire or via wireless technology. The present example is advantageous in that the controller may conveniently and efficiently control the LED filament(s), thereby even further ameliorating the light emission from the LED filament(s) and improving the appearance and / or the decorative aspect of the LED filament(s).

[0055] 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 can be combined to create embodiments other than those described in the following. 2024PF80174

[0056] 10

[0057] BRIEF DESCRIPTION OF THE DRAWINGS

[0058] 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.

[0059] Fig. 1 shows a LED filament lamp according to the prior art, Figs. 2a-c, and 3a-c schematically show LED filaments according to exemplifying embodiments of the present invention,

[0060] Fig. 4 schematically shows a LED filament arrangement according to an exemplifying embodiment of the present invention, and

[0061] Fig. 5 is a view of a LED filament lamp according to an exemplifying embodiment of the present invention.

[0062] DETAILED DESCRIPTION

[0063] Fig. 1 shows a LED filament lamp 10 according to the prior art, comprising a plurality of LED filaments 20. LED filament lamps 10 of this kind are highly appreciated as they are very decorative, as well as providing numerous advantages compared to incandescent lamps such as a longer operational life, a reduced power consumption, and an increased efficiency related to the ratio between light energy and heat energy. However, it is of interest to improve the properties of the light distribution emitted from the LED filaments 20, and to even further augment the decorative appearance of the LED filaments 20 and / or the LED filament lamps 10. More specifically, the color of the light provided by a LED filament lamp may vary as a function of the angle of emitted light. This color-over-angle (COA) effect is sometimes significant and can lead to yellow rings at large angles in a far- field, leading to an undesired light distribution and / or an aesthetically inferior LED filament lamp 10.

[0064] Fig. 2a schematically shows a cross-section of a LED filament 100 according to an exemplifying embodiment of the present invention. The LED filament 100, which is shown in cross-section perpendicular to a length axis, Lx, of the LED filament 100, is configured to provide, during operation, LED filament light 110. Preferably, the LED filament 100 has a length, L, and a width W, wherein L > 5W. The width, W, may for example be in a range from 0.5 to 5 mm. The LED filament 100 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. The LED filament 110 comprises an elongated carrier 140 and an array of a plurality of phosphor-converted light emitting diodes, LEDs 160 arranged on a first major surface 170 of the elongated carrier 140. The elongated carrier 140 may, for instance, 2024PF80174

[0065] 11 be a substrate, 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). The elongated carrier 140 may be reflective or light transmissive, such as translucent and preferably transparent.

[0066] It should be noted that the LED filament 100 may comprise substantially any number of pc-LEDs 160 arranged in one or more arrays. The plurality of pc-LEDs 160 preferably comprises more than 5 pc-LEDs, more preferably more than 8 pc-LEDs, and even more preferred more than 10 pc-LEDs.

[0067] Each pc-LED of the plurality of pc-LEDs 160 comprises a LED chip 190 configured to emit LED chip light 200, and a phosphor element 210 arranged on the LED chip 190. The phosphor element 210 is configured to at least partly convert the LED chip light 200 into converted light 220. The phosphor-converted LED light 180 comprises the converted light 220 and / or a combination of the converted light 220 and part of the LED chip light 200. The LED filament 100 further comprises a first elongated reflector 250 and a second elongated reflector 260. The first elongated reflector 250 and the second elongated reflector 260 are respectively arranged on the elongated carrier 140 and arranged on either sides of, and adjacent and parallel to, the array of the plurality of pc-LEDs 160. The first elongated reflector 250 and the second elongated reflector 260 are configured to redirect part of the LED chip light 200. Here, the cross-section of the first elongated reflector 250 and the second elongated reflector 260 is bulb-shaped (hemispherical), but it should be noted that other shapes or forms of the cross-section is feasible. The first and second elongated reflector 250, 260 may comprise a silicone polymer e.g. a cross-linked silicone polymer such as crosslinked PDMS, crosslinked PDPS and crosslinked PMPS, or combinations thereof.

[0068] In Fig. 2a, the first and second elongated reflectors 250, 260 respectively have a first height, Hl, wherein the array of the plurality of pc-LEDs 160 has a second height, H2. The relation between the first height, Hl, of the first and second elongated reflectors 250, 260 and the second height, H2, of the array of the plurality of pc-LEDs 160 fulfills 0.2-H2 < Hl < 3-H2, such as 0.2-H2 < Hl < H2. According to Fig. 2a, 0.5-H2 < Hl < 0.8-H2, such as Hl ~ 0.65-H2, i.e. that the first height, Hl, of the first and second elongated reflectors 250, 260 is lower than (below) the second height, H2, of the array of the plurality of pc-LEDs. Hl may be in a range from 0.3 to 3 mm. H2 may be in a range from 0.3 to 3 mm.

[0069] Fig. 2b schematically shows a portion of a LED filament 100 according to Fig. 2a and according to an exemplifying embodiment of the present invention. More specifically, the portion of the LED filament 100, as shown in cross-section parallel to the length axis, Lx, of the LED filament 100, shows the array 150 of the plurality of pc-LEDs 160 as arranged on 2024PF80174

[0070] 12 the elongated carrier 140. It should be noted that the number of arrays 150 and / or the number of pc-LEDs is arbitrary. The first elongated reflector 250 and the second elongated reflector 260 of the LED filament 100 are respectively arranged on the first major surface of the elongated carrier 140 and arranged on either sides of, and adjacent and parallel to, the array 150 of the plurality of pc-LEDs 160.

[0071] Fig. 2c schematically shows a cross-section of a LED filament 100 according to an exemplifying embodiment of the present invention. It will be appreciated that the LED filament 100 shown in Fig. 2c has many features and / or functions in common with the LED filament 100 of Fig. 2a, and it is referred to Fig. 2a for references, as well as for an increased understanding of the LED filament 100.

[0072] In Fig. 2c, the first and second elongated reflectors 250, 260 respectively have a first height, Hl, wherein the array of the plurality of pc-LEDs 160 has a second height, H2. The relation between the first height, Hl, of the first and second elongated reflectors 250, 260 and the second height, H2, of the array of the plurality of pc-LEDs fulfills 0.2-H2 < Hl < 3-H2. According to Fig. 2c, H2 < Hl < 1.5-H2, such as Hl ~ 1.25-H2, i.e. that the first height, Hl, of the first and second elongated reflectors 250, 260 is higher than the second height, H2, of the array of the plurality of pc-LEDs.

[0073] Figs. 3a and 3b schematically show cross-sections of a LED filament 100 according to an exemplifying embodiment of the present invention. It will be appreciated that the LED filament 100 shown in Figs. 3a and 3b has many features and / or functions in common with the LED filament 100 of Figs. 2a and 2b, and it is referred to Figs. 2a and 2b for references, as well as for an increased understanding of the LED filament 100. It should be noted that any feature(s) and / or function(s) of the LED filament 100 shown in Figs. 3a and 3b may be combined with the LED filament 100 shown in Figs. 2a and 2b, and vice versa.

[0074] The LED filament 100 of Fig. 3a comprises an (elongated) encapsulant 300 at least partially covering the first major surface of the elongated carrier and at least partially covering the array of the plurality of pc-LEDs. The encapsulant 300 may comprise a polymer matrix being transparent. The elongated encapsulant 300 may comprise a luminescent material. Although not shown, a concentration of the luminescent material in the encapsulant 300 may vary over the length of the LED filament 100. The encapsulant 300 may furthermore comprise a light-scattering material configured to scatter at least part of the phosphor-converted LED light. The light-scattering material may comprises light scattering particles e.g. BaSCU, TiCL and / or AI2O3 particles. The encapsulant may comprise a silicone 2024PF80174

[0075] 13 polymer e.g. a cross-linked silicone polymer such as crosslinked PDMS, crosslinked PDPS and crosslinked PMPS, or combinations thereof.

[0076] According to the embodiment of the LED filament 100 in Fig. 3a, the first elongated reflector 250 and the second elongated reflector 260 have a reflectivity, R, in a range of 20 - 50 %, and a transmittivity, T, in a range of 50 - 80 %. Furthermore, a subsection 270 of the first elongated reflector 250 and a subsection 280 of the second elongated reflector 260, which subsections 270, 280 respectively face the array of the plurality of pc-LEDs, are tapered with respect to the elongated carrier. Alternatively, the entire section of the first elongated reflector 250 and / or the entire section of the second elongated reflector 260 may be tapered or slanted. According to the embodiment of the LED filament 100 in Fig. 3 a, the pc- LEDs cover a surface area, Ai, of a total surface area, A2, (not shown) of the first major surface, wherein Ai <= 0.2-A2 is fulfilled. Furthermore, according to an embodiment of the present invention, the phosphor element 210 may comprise a green-yellow phosphor of the type AsBsOn Ce, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc, and / or an orange-red phosphor comprising at least one nitride phosphor, at least one oxynitride phosphor and / or a red phosphor.

[0077] Fig. 3b schematically shows a cross-section of a LED filament 100 according to an exemplifying embodiment of the present invention. It will be appreciated that the LED filament 100 shown in Fig. 3b corresponds to the LED filament 100 of Fig. 3a, albeit the height of the first and second elongated reflectors of the LED filament 100 is larger compared to the LED filament 100 of Fig. 3a.

[0078] Fig. 3c schematically shows a cross-section of a LED filament 100 according to an exemplifying embodiment of the present invention. It will be appreciated that the LED filament 100 shown in Fig. 3c corresponds to the LED filament 100 of Fig. 3a, albeit the entire section of the first elongated reflector 250 and / or the entire section of the second elongated reflector 260 may be tapered or slanted.

[0079] Fig. 4 schematically shows a LED filament arrangement 500 according to an exemplifying embodiment of the present invention. The LED filament arrangement 500 comprises at least one LED filament 100 according to any one of the preceding embodiments, and it is hereby referred to one or more of the previous figures and / or associated texts for references, features and / or functions of the LED filament 100. The plurality of pc-LEDs of the LED filament 100 of the LED filament arrangement 500 comprises a first subset 510a of pc-LEDs emitting first subset light 520a, and a second subset 510b of pc-LEDs emitting second subset light 520b. It will be appreciated that the number 2024PF80174

[0080] 14 and / or position of the pc-LEDs of the first and / or second subsets 510a, 510b is arbitrary. The first subset light 520a differs from the second subset light 520b with respect to color point, CP, and / or correlated color temperature, CCT. Hence, and as indicated in Fig. 4, a first color point, CPI, of the first subset light 520a may differ from a second color point, CP2, of the second subset light 520b and / or a first correlated color temperature, CCT1, of the first subset light 520a may differ from a second correlated color temperature, CCT2, of the second subset light 520b. The LED filament arrangement 500 further comprises a controller 530 configured to individually control the first and second subsets 520a, 520b of pc-LEDs to vary the color point, CP, of the LED filament light. It should be noted that the controller 530 is schematically indicated in Fig. 4, and that its position may be on the LED filament 100, or separated from the LED filament 100. Furthermore, the controller 530 may be connected or coupled to the LED filament 100 via wire or wirelessly.

[0081] Fig. 5 schematically shows a LED filament lamp 900 according to an embodiment of the present invention. The LED filament lamp 900, which may constitute substantially any kind of lamp or luminaire, comprises one or more LED filaments 100 according to any one of the previously described embodiments or a LED filament arrangement 500 according to the previously described embodiment. The LED filament lamp 900 further comprises a light-transmissive envelope 910, which is exemplified as being bulbshaped. The light-transmissive envelope 910 at least partially encloses the LED filament(s) 100. The LED filament lamp 900 further comprises a connector 920 for electrically and mechanically connecting the LED filament lamp 900 to a socket of a luminaire. The LED filament lamp 900 may further comprise the controller 530 according to the previously described embodiment configured to individually control the first and second subsets of pc- LEDs to vary the color point, CP, of the LED filament light. The controller 530 is schematically indicated by a dashed rectangle in the connector 920, but it should be noted that the controller 530 may be arranged at substantially any position or place. The controller 530 may, for example, be able to control each LED filament 100 individually.

[0082] 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. For example, one or more of the LED filament 100, the first elongated reflector 250, the second elongated reflector 260, etc., may have different shapes, dimensions and / or sizes than those depicted / described.

Claims

2024PF8017415CLAIMS:

1. A light emitting diode, LED, filament (100) configured to provide, during operation, LED filament light (110), the LED filament comprising an elongated carrier (140), an array (150) of a plurality of phosphor-converted light emitting diodes, pc- LEDs (160), arranged on a first major surface (170) of the elongated carrier and configured to emit phosphor-converted LED light (180), wherein each pc-LED of the plurality of pc-LEDs comprises a LED chip (190) configured to emit LED chip light (200), and a phosphor element (210) arranged on the LED chip, wherein the phosphor element is configured to at least partly convert the LED chip light into converted light (220), wherein the phosphor-converted LED light comprises one of the converted light, and a combination of the converted light and part of the LED chip light, a first elongated reflector (250) and a second elongated reflector (260) respectively arranged on the first major surface of the elongated carrier and arranged on either sides of, and adjacent and parallel to, the array of the plurality of pc-LEDs, wherein the first elongated reflector and the second elongated reflector are configured to redirect part of the LED chip light, wherein the first elongated reflector, the second elongated reflector and the elongated carrier have a white appearance.

2. The LED filament according to claim 1, wherein the first elongated reflector and the second elongated reflector are configured to, at least one of, reflect part of the LED chip light, and transmit part of the LED chip light.

3. The LED filament according to claim 1 or 2, wherein the first elongated reflector (250) and the second elongated reflector (260) have a first height, Hl, and wherein2024PF8017416 each of the first elongated reflector (250) and the second elongated reflector (260) has a first width, Wl, measured at the LED chips and perpendicular to the elongation direction of the elongated carrier, and wherein W1>H1.

4. The LED filament according to any one of the preceding claims, wherein the first elongated reflector and the second elongated reflector respectively have a first height, Hl, and the array of the plurality of pc-LEDs has a second height, H2, whereinO.2-H2 < H1 < 3-H2 is fulfilled.

5. The LED filament according to claim 4, whereinO.2-H2 < H1 < H2 is fulfilled.

6. The LED filament according to any one of the preceding claims, wherein at least one of the first elongated reflector and the second elongated reflector have a reflectivity, R, in a range of 20 - 50 %, and the first elongated reflector and the second elongated reflector have a transmittivity, T, in a range of 50 - 80 %, is fulfilled.

7. The LED filament according to any one of the preceding claims, wherein at least a subsection (270) of the first elongated reflector and at least a subsection (280) of the second elongated reflector, which respectively face the array of the plurality of pc-LEDs, are tapered with respect to the elongated carrier.

8. The LED filament according to any one of the preceding claims, wherein at least 60% of the converted light (220) does not impinge on the first elongated reflector and the second elongated reflector.

9. The LED filament according to any one of the preceding claims, wherein the elongated carrier comprises a diffuser being light-transmissive and configured to transmit at least one of2024PF8017417 part of the LED chip light, and part of the converted light.

10. The LED filament according to any one of the preceding claims, further comprising an elongated encapsulant (300) at least partially covering the first major surface of the elongated carrier and at least partially covering the array of the plurality of pc-LEDs.

11. The LED filament according to claim 10, wherein the elongated encapsulant comprises a polymer matrix being transparent.

12. The LED filament according to any one of the preceding claims, wherein the pc-LEDs cover a surface area, Ai, of a total surface area, A2, of the first major surface, whereinAi < 0.2- A2is fulfilled.

13. The LED filament according to any one of the preceding claims, wherein the phosphor element comprises at least one of a green-yellow phosphor of the type AsBsOn Ce, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc, and an orange-red phosphor comprising at least one of at least one nitride phosphor, and at least one oxynitride phosphor, and a red phosphor of the type M’xM2-2xAX6 doped with tetraval ent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x is selected from the range of 0 - 1, wherein A comprises a tetraval ent cation, wherein X comprises a monovalent anion, at least comprising fluorine.

14. A LED filament arrangement (500), comprising at least one LED filament according to any one of the preceding claims, wherein the plurality of pc-LEDs comprises a first subset (510a) of pc-LEDs emitting first subset light (520a), and2024PF8017418 a second subset (510b) of pc-LEDs emitting second subset light (520b) being different from the first subset light with respect to at least one of color point, CP, and correlated color temperature, CCT, from the first subset light, and a controller (530) configured to individually control the first and second subsets of pc-LEDs to vary the color point, CP, of the LED filament light.

15. A LED filament lamp (900a-d), comprising one of at least one LED filament according to any one of claims 1-13, and a LED filament arrangement according to claim 14, a light-transmissive envelope (910) at least partly enclosing the at least one LED filament, and a connector (920) for electrically and mechanically connecting the LED filament lamp to a socket of a luminaire.

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