LED filament with colored sections

Abstract

There is provided a LED filament (100) comprising a carrier (120), an array of a plurality of LEDs (130) arranged on the carrier, an encapsulant (200) covering the carrier and the plurality of LEDs, wherein the encapsulant comprises luminescent material. The LED filament comprises a plurality of sections (200i), i=l, …, j, configured to emit converted colored light having a peak emission wavelength, λpi, in a wavelength range, λi, being blue, λB, cyan, λC, green, λG, yellow, λY, amber, λA, or red, λR, wherein any first section (200k) is different from any second section (200m). A length, Li, i=l, …, j, of each section is dependent on the wavelength range, λi, of converted light emitted by the section, and / or each section has a distance, Dn, n=l, …, s, between adjacently arranged LEDs of the section, being dependent on the wavelength range, λi, of converted light emitted by the section.

Description

[0001] LED filament with colored sections

[0002] FIELD OF THE INVENTION

[0003] The present invention generally relates to a light emitting diode, LED, filament. More specifically, the present invention relates to a LED filament comprising colored sections.

[0004] BACKGROUND OF THE INVENTION

[0005] 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.

[0006] 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.

[0007] It is desired to even further improve the performance, functionality and / or appearance of LED filament lamps. More specifically, it is desirable to improve the performance and / or functionality of the light emission and / or light distribution from the LED filament lamps. Another purpose is to augment the appearance and / or the decorative aspect of the LED filaments and / or the LED filament lamps.

[0008] WO 2023 / 232594 discloses a LED light source filament arrangement configured to emit LED filament light, the LED light source filament arrangement comprising a first plurality of LED light sources configured to emit first LED light source light, the first LED light source light comprising blue LED light source light, a second plurality of LED light sources configured to emit second LED light source light (6), the second LED light source light comprising red LED light source light, and a luminescent layer covering at least a part of the first plurality of LED light sources and at least a part of the second plurality of LED light sources, the luminescent layer being configured to convert at least 88 percent of the blue LED light source light into converted light, the converted light being one or more of green and yellow light, and the second plurality of LED light sources being arranged in a successional configuration without any LED light sources configured to, in operation, emit LED light source light of other colors than red being provided in the succession of the LED light sources of the second plurality of LED light sources.

[0009] SUMMARY OF THE INVENTION

[0010] 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, and improving the appearance and / or the decorative aspect of the LED filaments and / or the LED filament lamps.

[0011] 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.

[0012] According to the present invention, there is provided a LED filament configured to provide, during operation, LED filament light. The LED filament extends along a length axis, LX, and comprises an elongated carrier, and an array of a plurality of LEDs arranged on a first major surface of the elongated carrier, wherein the plurality of LEDs is configured to emit LED light. The LED filament further comprises an elongated encapsulant at least partially covering the first major surface of the elongated carrier and at least partially enclosing the plurality of LEDs, wherein the elongated encapsulant comprises luminescent material configured to at least partly convert the emitted LED light into converted light. The LED filament further comprises a plurality of sections, arranged along the length axis, LX, wherein each section of the plurality of sections comprises at least three LEDs of the plurality of LEDs, and wherein each section is configured to emit converted light being colored light and having a peak emission wavelength, XPi, in a wavelength range, Xi. The wavelength range, Xi, is one of a blue light wavelength range, XB, of 430 - 470 nm, a cyan light wavelength range, Xc, of 470 - 500 nm, a green light wavelength range, XG, of 500 - 540 nm, a yellow light wavelength range, XY, of 540 - 580 nm, an amber light wavelength range, XA, of 580 - 600 nm, and a red light wavelength range, XR, of 600 - 690 nm. Any first section of the plurality of sections is configured to emit converted light in a first wavelength range, Xk, which is different from a second wavelength range, Xm, of converted light emitted by at least one second section of the plurality of sections. A length, Li, i=l, y, of each section of the plurality of sections is dependent on the wavelength range, Xi, of converted light emitted by the section, and / or each section of the plurality of sections has a distance, Dn, n=l, ... , s, between adjacently arranged LEDs of the section, wherein the distance, Dn, is dependent on the wavelength range, Xi, of converted light emitted by the section.

[0013] Thus, the present invention is based on the idea of providing a LED filament comprising a plurality of sections configured to emit colored light, wherein the length, Li, of the section and / or the distance, Dn, between LEDs of the section, respectively, is (are) dependent on the wavelength range, Xi, of converted light emitted by the section. By this (these) feature(s) of the sections of the LED filament, the performance and / or functionality of the LED filament, as well as the appearance and / or the decorative aspect thereof, are improved.

[0014] The present invention is advantageous in that the colored sections of the LED filament during operation are clearly visible and distinguishable by an observer at a relatively short distance, as well as at a medium distance from the LED filament. This efficiently and conveniently augments the appearance and decorative aspect of the LED filament.

[0015] The present invention is further advantageous in that the LED filament light is observed as white light by an observer at a relatively long distance from the LED filament. Hence, the sum of the colored light from the colored sections of the LED filament during operation of the LED filament is conceived as white light by an observer in the far-field. The LED filament hereby provides decorative and functional lighting during operation.

[0016] It should be noted that due to the luminous flux contributions of the different colors in white light being unequal, also differently colored LED filament sections emit different luminous fluxes. Due to this observation, the LED filament of the present invention having the features of section lengths, Li, and / or distances, Dn, between adjacently arranged LEDs of the sections, being dependent on the wavelength range(s), Xi, of converted light emitted by the section(s), a highly decorative and functional lighting is achieved.

[0017] 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 arrangement as disclosed. 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 is relatively inexpensive to fabricate. 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.

[0018] There is provided a LED filament configured to provide, during operation, LED filament light. Preferably, the LED filament has a length, LF, and a width, WF, wherein LF > 5WF. 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 extends along a length axis, LX, and comprises an elongated carrier. 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. The LED filament further comprises an array of a plurality of LEDs arranged on a first major surface of the elongated carrier, wherein the plurality of LEDs is configured to emit LED light. By the term “array”, it is here meant a linear arrangement or chain of LEDs, or the like. The LED filament further comprises an elongated encapsulant at least partially covering the first major surface of the elongated carrier and at least partially enclosing the plurality of 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 elongated carrier and the plurality of LEDs. The elongated encapsulant comprises luminescent material configured to at least partly convert the emitted LED light into converted light. The encapsulant may be a polymer material which may be flexible such as for example a silicone. The luminescent material of the elongated encapsulant may be a phosphor such as an inorganic phosphor and / or quantum dots or rods. The LED filament further comprises a plurality of sections arranged along the length axis, LX, wherein each section of the plurality of sections comprises at least three LEDs of the plurality of LEDs. Hence, each section is a portion or part of the LED filament, and each section hereby comprises three or more LEDs, a part or portion of the elongated carrier and a part or portion of the elongated encapsulant. Each section is configured to emit converted light being colored light and having a peak emission wavelength, XPi, in a wavelength range, Xi, wherein the wavelength range, Xi, is one of a blue light wavelength range, XB, of 430 - 470 nm, a cyan light wavelength range, Xc, of 470 - 500 nm, a green light wavelength range, XG, of 500 - 540 nm, a yellow light wavelength range, XY, of 540 - 580 nm, an amber light wavelength range, XA, of 580 - 600 nm, and a red light wavelength range, XR, of 600 - 690 nm. Hence, the wavelength range, Xi, is a blue light wavelength range, XB, a cyan light wavelength range, Xc, a green light wavelength range, XG, a yellow light wavelength range, XY, an amber light wavelength range, XA, or a red light wavelength range, XR, with the respectively indicated wavelength ranges for each color. By “colored light”, it is here meant that the light is nonwhite light. The “peak emission wavelength” may alternatively be denoted “dominant peak emission wavelength”. Any first section of the plurality of sections is configured to emit converted light in a first wavelength range, Xk, which is different from a second wavelength range, Xm, of converted light emitted by at least one second section of the plurality of sections. Hence, any first section of the plurality of sections is configured to emit converted light in a first wavelength range, Xk, which is different from a second wavelength range, Xm, of converted light emitted by at least one second section of the plurality of sections. In other words, of all sections of the LED filament, there are at least two sections being configured to emit converted light in two different wavelength ranges, Xi. At least one of a length, Li, i=l, ... , 7, of each section of the plurality of sections is dependent on the wavelength range, Xi, of converted light emitted by the section, and each section of the plurality of sections has a distance, Dn, i=n, , s, between adjacently arranged LEDs of the section, wherein the distance, Dn, is dependent on the wavelength range, Xi, of converted light emitted by the section. Hence, for each section of the plurality of sections of the LED filament, the length, Li, i=l, ... , j, of the section is dependent on the wavelength range, Xi, of converted light emitted by the section and / or the distance, Dn, n=l, ... , s, (wherein the distance, Dn, is also denoted as “pitch” or inter-LED distance) between adjacently arranged LEDs of the section is dependent on the wavelength range, Xi, of converted light emitted by the section. It should be noted that j and .s' may be independent of each other, i.e. that the number of lengths, Li, of the sections and the number of distances, Dn, between LEDs of the section are not necessarily the same.

[0019] According to an embodiment of the present invention, the LED filament may comprise at least three sections, wherein any first section of the plurality of sections is configured to emit converted light in a first wavelength range, Xk, any second section of the plurality of sections is configured to emit converted light in a second wavelength range, Xm, and any third section of the plurality of sections is configured to emit converted light in a third wavelength range, Xi, wherein the first, second and third wavelength ranges, Xk,Xm, Xi, are different from each other. Hence the LED filament may comprise at least three sections, wherein each section is configured to emit an individual (distinct, different) color. The present embodiment is advantageous in that a LED filament of at least three sections with different colors is particularly attractive.

[0020] According to an example of the present invention, any first section of the plurality of sections is configured to emit converted light being colored light and having a peak emission wavelength, XPi . in a first wavelength range, Xk, which is different from a second wavelength range, Xm, in which any second (other) section of the plurality of sections is configured to emit converted light being colored light and having a peak emission wavelength, Xpm. Hence, according to this example, each section of the LED filament is configured to emit converted light being colored light and having a peak emission wavelength, XPi, in a wavelength range, Xk, which is different from the emitted converted light being colored light and having a peak emission wavelength, Xpm, in a wavelength range, Xm, of any other section. Hence, in case of a number of j sections of the LED filament, each of the j sections is configured to emit an individual (distinct, different) color. The present embodiment is advantageous in that a LED filament wherein all sections provide distinct, different colors is particularly beneficial for the performance and / or functionality of the LED filament, as well as the appearance and / or the decorative aspect thereof.

[0021] According to an embodiment of the present invention, the LED filament may further comprise at least one ancillary section of the LED filament, arranged along the length axis, LX, wherein the at least one ancillary section comprises at least three LEDs of the plurality of LEDs, and wherein the elongated encapsulant of the at least one ancillary section does not comprise luminescent material. Hence, the ancillary section(s) (e.g. two or more ancillary sections) may comprise or constitute the same kind of features and / or components as the sections of the LED filament, but with the difference that the encapsulant of the sections comprises luminescent material, whereas the encapsulant of the ancillary section(s) is deprived of luminescent material, i.e. does not comprise luminescent material. According to this embodiment, the LED filament may provide converted light via the sections of the LED filament comprising luminescent material, and direct (i.e. non-converted) light via the ancillary section(s) of the LED filament.

[0022] The present embodiment is advantageous in that the LEDs of the ancillary section(s) may provide light without any light conversion via a luminescent material of an encapsulant, which even further contributes to the versatility and / or the efficiency of the LED filament. According to an embodiment of the present invention, the at least three LEDs of the at least one ancillary section may be arranged to emit ancillary LED light being colored light and having a peak emission wavelength, XPi, in the blue light wavelength range, LB. Hence, the LEDs of the ancillary section(s) may be direct emitting blue LEDs. The present embodiment is advantageous in that the ancillary section(s) may provide blue light from the direct emitting blue LEDs without any light conversion via a luminescent material of an encapsulant, which even further contributes to the efficiency of the LED filament.

[0023] According to an example of the present invention, the at least three LEDs of the at least one ancillary section may be arranged to emit ancillary LED light being colored light and having a peak emission wavelength, XPi, in the red light wavelength range, XR.

[0024] According to an embodiment of the present invention, the LED filament may comprise at least five sections (or six sections). For example, and as according to some embodiments, the at least five sections (or six sections) may comprise at least three sections configured to emit converted light in different wavelength ranges, Xi (i.e. the LED filament may comprise at least three sections of different color), or that all (at least five) sections have different wavelength ranges, Xi, i.e. different color. The present embodiment is advantageous in that this relatively large number of sections of the LED filament, and consequently, this relatively large number or colors of the LED filament, is particularly attractive.

[0025] According to an embodiment of the present invention, a relation between a first length, Li, of any first section of the plurality of sections configured to emit converted light with a first peak emission wavelength, XPk, in a wavelength range, Xk, and a second length, L2, of any second section of the plurality of sections configured to emit converted light with a second peak emission wavelength, Xpm, in a wavelength range, Xm, fulfils Li < L2 if XPk < Xpm, and L2 < Li if Xpm< XPk. Hence, the length, Li, of any section of the plurality of sections of the LED filament is a function of the peak emission wavelength, XPi, in the wavelength range, Xi, of the section, wherein a relatively high peak emission wavelength, XPi, corresponds to a relatively long section length, Li, and vice versa. For example, in case the LED filament comprises at least three sections configured to emit converted light with a (first, second, third) peak emission wavelength, XPk, Xpm, XPi, in a (first, second, third) wavelength range, Xk, Xm, Xi, respectively, the relation between (a first, second, third) length, Li, L2, L3, respectively, of the sections, fulfils Li < L2 if XPk < Xpm, Li < L3 if XPk < XPi, L2 < L3 if Xpm < XPi, and vice versa. For example, in case of a (first) blue section, a (second) green section, and a (third) red section of the LED filament, the (second) green section has a longer length than the (first) blue section, and the (third) red section has a longer length than the (second) green section. The present embodiment is advantageous in that the correlation between the peak emission wavelength, XPi, of the section and the length, Li, of the section even further increases the performance and appearance of the LED filament.

[0026] In embodiments, a (blue) section configured to emit blue light in the (blue) wavelength range, LB, may be the shortest section, i.e. have the shortest section length, Li.

[0027] In embodiments, a (red) section configured to emit red light in the (red) wavelength range, XR, may be the longest section, i.e. have the longest section length, Li.

[0028] According to an embodiment of the present invention, the LED filament may have at least one first section configured to emit one of converted light being colored light and having a peak emission wavelength, XPi, in the blue light wavelength range, B, and direct emitting blue light in the blue light wavelength range, XB. The LED filament may further have at least one second section configured to emit converted light being colored light and having a peak emission wavelength, XPi, in one of the green light wavelength range, XG, and the yellow light wavelength range, XY. The LED filament may further have at least one third section configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the red light wavelength range, R. The LED filament may further have at least one of at least one fourth section configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the amber light wavelength range, XA, and at least one fifth section configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the cyan light wavelength range, Xc. In other words, the LED filament may comprise first section(s) configured to emit converted blue light and / or (other) first section(s) configured to emit direct emitting blue light, whereby the latter first section(s) may be ancillary section(s) arranged to emit ancillary LED light being colored light and having a peak emission wavelength, XPi, in the blue light wavelength range, XB. Furthermore, the LED filament light may comprise second section(s) configured to emit green or yellow light, respectively, as well as third section(s) configured to emit red light. Moreover, the LED filament may comprise fourth and / or fifth section(s) configured to emit amber or cyan light, respectively. Hence, the LED filament may comprise, at least, five different sections configured to emit converted light (and in case of one or more ancillary sections, direct emitting (blue) light). The present embodiment is advantageous in that a particularly attractive and appealing LED filament of many different colors is provided.

[0029] In embodiments, an ancillary section may be the shortest section, i.e. have the shortest section length, Li. Alternatively, in embodiments, an ancillary section may be the longest section, i.e. have the longest section length, Li. According to an embodiment of the present invention, a sum of (the) lengths Llsum,4,5sum of a sum of the lengths, Lisum, of the at least one first section, Li, and a sum of the lengths, L4,5sum, of the at least one of the at least one fourth section, L4, and the at least one fifth section, Ls, and a sum of (the) lengths L2sum,3sum of a sum of the lengths, L2sum, of the at least one second section, L2, and a sum of the lengths, Lssum, of the at least one third section, L3, fulfil Llsum,4,5sum L2sum,3sum. Hence, L lsum,4,5sum Lisum "I" 4,5sum cUld 2sum, 3sum 2sum "I" L3 sum fulfil Llsum,4,5sum L2sum,3sum. The embodiment may further be explained in terms of the section colors of the previous embodiment, whereby Lisum,4,5sum = total length of the blue section(s) + total length of the amber and / or cyan section(s) and L2sum,3sum = total length of the green or yellow section(s) + total length of the red section(s) fulfil Lisum,4,5sum < L2sum,3sum, i.e. that the total length of the blue and amber and / or cyan sections of the LED filament is shorter that the total length of the green or yellow and red sections of the LED filament.

[0030] According to an embodiment of the present invention, a relation between a first distance, Di, between adjacently arranged LEDs of any first section of the plurality of sections configured to emit converted light with a first peak emission wavelength, XPi . in a wavelength range, Xk, and a second distance, D2, between adjacently arranged LEDs of any second section of the plurality of sections configured to emit converted light with a second peak emission wavelength, Xpm. in a wavelength range, Xk, fulfils Di < D2 if XPk < Xpm, and D2 < Di if Xpm< XPk. Hence, the pitch or inter-LED distance, Dn, of any section of the plurality of sections of the LED filament is a function of the peak emission wavelength, XPi, in the wavelength range, Xi, of the section, wherein a relatively high peak emission wavelength, XPi, corresponds to a relatively long distance, Dn, between adjacently arranged LEDs, and vice versa. For example, in case the LED filament comprises at least three sections configured to emit converted light with a (first, second, third) peak emission wavelength, XPk, Xpm, XPi, in a (first, second, third) wavelength range, Xk, Xm, Xi, respectively, the relation between (a first, second, third) distance, Di, D2, D3, respectively, between adjacently arranged LEDs of the sections, fulfils Di < D2 if XPk < Xpm, Di < D3 if XPk < XPi, D2 < D3 if Xpm< XPi, and vice versa. The present embodiment is advantageous in that the correlation between the peak emission wavelength, XPi, of the section and the distance, Dn, between adjacently arranged LEDs of the section even further increases the performance and appearance of the LED filament.

[0031] According to an embodiment of the present invention, the elongated carrier may be light-transmissive, and wherein the elongated encapsulant furthermore at least partially covers a second major surface of the elongated carrier, opposite to the first major surface. Hence, the elongated carrier, may cover, at least partially, both sides of the elongated carrier, i.e. that the elongated carrier may cover, at least partly, the first major surface as well as, at least partly, the second major surface. The effect of the elongated carrier being light- transmissive (e.g. translucent and / or transparent), is that the LED light from the plurality of LEDs arranged on the first major surface may be transmitted through the light-transmissive elongated carrier, and be emitted via the second major surface and the portion of the elongated encapsulant partially covering the second major surface. The present embodiment is advantageous in that the LED filament may provide an omnidirectional, or almost omnidirectional, emission of LED filament light. This (almost of fully) omnidirectional LED filament light distribution even further contributes to the light distribution performance and / or aesthetical attractiveness of the LED filament and / or the LED filament light.

[0032] According to an embodiment of the present invention, the LED filament may comprise at least three of at least one first section, at least one second section, at least one third section, at least one fourth section, at least one fifth section and at least one sixth section. The at least one first section may be configured to emit converted light being colored light and having a peak emission wavelength, Xpi, in the blue light wavelength range, LB, wherein the at least one first section comprises BOSE phosphor. The at least one second section may be configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the cyan light wavelength range, Xc, wherein the at least one second section comprises Phosphate phosphor. The at least one third section may be configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the green light wavelength range, G, wherein the at least one third section comprises LuAG phosphor. The at least one fourth section may be configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the yellow light wavelength range, XY, wherein the at least one fourth section comprises YAG phosphor. The at least one fifth section may be configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the amber light wavelength range, XA, wherein the at least one fifth section comprises BSSN phosphor. The at least one sixth section is configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the red light wavelength range, XR, wherein the at least one sixth section comprises one or more of KSiF phosphor, Nitride phosphor and Oxynitride phosphor. Hence, of the LED filament, (the) blue section(s) comprise(s) BOSE phosphor, (the) cyan section(s) comprise(s) BOSE phosphor, (the) green section(s) comprise(s) LuAG phosphor, (the) yellow section(s) comprise(s) YAG phosphor, (the) amber section(s) comprise(s) BSSN phosphor, and (the) red section(s) comprise(s) KSiF phosphor, Nitride phosphor and / or Oxynitride phosphor. The present embodiment is advantageous in that the respective phosphors are efficient for light conversion, i.e. for conversion of light from a (first) wavelength range to a (second) wavelength range. The present embodiment is further advantageous in that the respective phosphors are relatively inexpensive and easily obtainable, thereby contributing to the (cost) efficiency of the LED filament.

[0033] According to an embodiment of the present invention, an order of the plurality of sections, in a direction from a first end portion towards a second end portion, opposite the first end portion, correlates with an increase in a peak emission wavelength, Xpi, in the wavelength range, Xi, in which the respective section is configured to emit converted light. Hence, along the LED filament, from any end portion thereof towards the oppositely arranged end portion, the order of the plurality of sections correlates with an increase (or in the opposite direction, a decrease) in a peak emission wavelength, XPi, in the wavelength range, Xi, in which the respective section is configured to emit converted light. The order of the plurality of sections of the LED filament may hereby follow the order of the rainbow colors. The present embodiment is advantageous in that the order of the plurality of sections according to increasing (decreasing) wavelength is particularly attractive to an observer. Furthermore, in case of combination of one, or both, of the embodiments of increasing length, Li, and increasing distance between LEDs, Dn, of LED filament sections, with increasing peak emission wavelength, Xpi, the LED filament takes on a particularly attractive form with continuously changing properties concerning length, Li, and pitch, Dn, of the sections together with the feature of following the order of the rainbow colors.

[0034] According to an embodiment of the present invention, the LED filament light may be white light having a correlated color temperature, CCT, in a range of 1700K- 6500K, and a color rendering index, CRI, of at least 80. The color rendering index, CRI, may preferably be higher than 85. The present embodiment is advantageous in that the LED filament may provide white light (cold as well as warm white light) in a far field in a convenient manner during operation.

[0035] According to an embodiment of the present invention, there is provided a LED filament arrangement. The LED filament may comprise at least one LED filament according to any one of the preceding embodiments, and a controller coupled to the plurality of sections of the at least one LED filament, wherein the controller is configured to individually control a group of LEDs of the plurality of LEDs belonging to each section of the plurality of sections. Hence, the (group of LEDs of the) sections of the LED filament may be controlled individually by the controller. 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. For example, the controller may provide a relatively high luminous flux for any section, or set of sections, of the plurality of sections, and / or a relatively low luminous flux for any (other) section, or (other) set of sections, of the plurality of sections. The present embodiment 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 and improving the appearance and / or the decorative aspect of the LED filament.

[0036] According to an embodiment of the present invention, there is provided a LED filament lamp, comprising one of at least one LED filament according to any one of the preceding embodiments, and the LED filament arrangement according to the preceding embodiment. The LED filament lamp further comprises a light-transmissive envelope (or cover) 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. Hence, the LED filament lamp comprises either one or more LED filaments or a LED filament arrangement, which in turn comprises one or more LED filaments. 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 arrangement and / or via the feature(s) of the lamp.

[0037] 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.

[0038] BRIEF DESCRIPTION OF THE DRAWINGS

[0039] 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.

[0040] Fig. 1 shows a LED filament lamp according to the prior art,

[0041] Fig. 2 schematically shows a LED filament according to an exemplifying embodiment of the present invention,

[0042] Figs. 3a and 3b schematically show LED filaments according to exemplifying embodiments of the present invention, and

[0043] Fig. 4 shows a LED filament lamp comprising LED filaments according to an exemplifying embodiment of the present invention. DETAILED DESCRIPTION

[0044] 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 and / or aspect of the LED filaments 20 and / or the LED filament lamps 10.

[0045] Fig. 2 schematically shows a LED filament 100 according to an exemplifying embodiment of the present invention. The LED filament 100 is configured to provide (emit), during operation, LED filament light 110. The LED filament light 110 may be white light having a correlated color temperature, CCT, in a range of 1700K-6500K, and a color rendering index, CRI, of at least 80. The LED filament 100 extends along a length axis, LX, and comprises an elongated carrier 120. An array of a plurality of LEDs 130 is arranged on a first major surface 145 of the elongated carrier 120. It should be noted that the LED filament 100 may comprise substantially any number of array(s) of the plurality of LEDs 130. The plurality of LEDs 130 is configured to emit LED light 150. The LED filament 100 further comprises an elongated encapsulant 160 at least partially covering or enclosing the first major surface 145 of the elongated carrier 120 and at least partially enclosing the plurality of LEDs 130. The elongated encapsulant 120 comprises luminescent material configured to at least partly convert the emitted LED light 150 into converted light 170. Although not shown, a concentration of the luminescent material in the elongated encapsulant 160 may vary over the length of the LED filament 100.

[0046] The LED filament 100 further comprises a plurality of sections 200i, i=l, ... ,j, arranged along the length axis, LX, of the LED filament 100. In Fig. 2, six sections 200i, i=l, ... ,6, are indicated, but it should be noted that the number of sections 200i is substantially arbitrary, as long as there is a plurality (i.e. at least two) sections 200i. Each section 200i of the plurality of sections 200i comprises at least three LEDs 130 of the plurality of LEDs 130. Each section 200i hereby constitutes a portion or part of the LED filament 100, and each section 200i comprises three or more LEDs 130, a part or portion of the elongated carrier 120 and a part or portion of the elongated encapsulant 160. Each section 200i is configured to emit converted light being colored light and having a peak emission wavelength, XPi, in a wavelength range, Xi. The peak emission wavelength, XPi, in a wavelength range, Xi, is further illustrated in the insert figure, wherein the peak emission wavelenght, XPi, constitutes a dominant peak emission wavelength, XPi. The wavelength range, Xi, is one of a blue light wavelength range, B, of 430 - 470 nm, a cyan light wavelength range, Xc, of 470 - 500 nm, a green light wavelength range, G, of 500 - 540 nm, a yellow light wavelength range, Y, of 540 - 580 nm, an amber light wavelength range, XA, of 580 - 600 nm, and a red light wavelength range, R, of 600 - 690 nm. Hence, the wavelength range, Xi, is a blue light wavelength range, XB, a cyan light wavelength range, Xc, a green light wavelength range, XG, a yellow light wavelength range, XY, an amber light wavelength range, XA, or a red light wavelength range, XR. Any first section 200k of the plurality of sections 200i is configured to emit converted light in a wavelength range, Xk, which is different from a wavelength range, Xm, of converted light emitted by at least one second section 200mof the plurality of sections 200i. Hence, any first section 200k of the plurality of sections 200 is configured to emit converted light in a (first) wavelength range, Xk, which is different from a (second) wavelength range, Xm, of converted light emitted by at least one second section 200mof the plurality of sections 200i. In other words, of all sections 200i of the LED filament, there are at least two sections being configured to emit converted light in two different wavelength ranges, Xk. According to the example of Fig. 2, all six sections 200i, i=1...6, are arranged to emit converted light of a different color, namely blue, cyan, green, yellow amber, and red. Explained in general terms, any first section 200k of the plurality of sections 200i is configured to emit converted light being colored light and having a peak emission wavelength, XPi, in a wavelength range, Xk, which is different from a wavelength range, Xm, of converted light emitted by any second section 200mof the plurality of sections 200i.

[0047] In Fig. 2, a length, Li, i=l, ... , y, of each section 200i of the plurality of sections 200i is dependent on the wavelength range, Xi, of converted light emitted by the section 200i. For example, a relation between a first length, Li, of any first section 200k of the plurality of sections 200i configured to emit converted light with a first peak emission wavelength, XPk, in a wavelength range, Xk, and a second length, L2, of any second section 200m of the plurality of sections 200i configured to emit converted light with a second peak emission wavelength, Xpm, in a wavelength range, Xm, fulfils Li < L2 if XPk < Xpm, or L2 < Li if XPm < XPk. Hence, if the peak emission wavelength, XPi, is relatively high, the length, Li, is relatively long, and vice versa. For the example of the six sections 200i, 6, in Fig. 2, the (first) blue section 200i, having a relatively small peak emission wavelength, XPi, accordingly has a relatively short length, Li. For the other sections 200i, seen from left to right, the length, Li, of the respective section 200i increases, and the (sixth) red section 200e, having a relatively large peak emission wavelength, XPi, accordingly has a relatively long length, Le. It should be noted that the increase in length, Li, may be gradual (as in Fig. 2), or that the increase in length, Li, may be progressive.

[0048] It should be noted that there may be other relations between the lengths, Li, i=l, ... , 7, of the sections 200i of the LED filament 100. For example, a sum Lisum,4,5sum of a sum of the lengths, Lisum, of the at least one first section, Li, and a sum of the lengths, L4sum, of the at least one of the at least one fourth section, L4, and the at least one fifth section, Ls, and wherein a sum L2sum,3sum of a sum of the lengths, L2sum, of the at least one second section, L2, and a sum of the lengths, Lssum, of the at least one third section, L3, may fulfil Lisum,4,5sum < L2sum,3sum. Applied to the exemplifying LED filament 100 of Fig. 2, this means that the sum of the first (blue) section(s) lengths, Li, and the (yellow) section(s) lengths, L4, and / or the (amber) section(s) lengths, Ls, is shorter than the sum of the second (cyan) section(s) lengths, L2, and the (green) section(s) lengths, L3.

[0049] In Fig. 2, each section 200i, i=l, ... , 6 of the plurality of sections 200i has a distance, Dn, n=l, , s, between adjacently arranged LEDs 130 of the section 200i. Here, j=6=s. The distance, Dn, is dependent on the wavelength range, Xi, of converted light emitted by the section 200i. For example, a relation between a (first) distance, Di, between adjacently arranged LEDs 130 of any first section 200k of the plurality of sections 200i configured to emit converted light with a peak emission wavelength, XPi, in a wavelength range, Xk, and a (second) distance, D2, between adjacently arranged LEDs 130 of any second section 200k of the plurality of sections 200i configured to emit converted light with a peak emission wavelength, XPi, in a wavelength range, Xk, fulfils Di < D2 if XPk < Xpmand D2 < Di if Xpm< XPk. Hence, if the peak emission wavelength, XPi, is relatively high, the pitch or inter-LED distance, Dn, is relatively large, and vice versa. For the example of the six sections 200i, i=l, ... ,6, in Fig. 2, the (first) blue section 200i, having a relatively small peak emission wavelength, XPi, in the blue wavelength range, XB, accordingly has a relatively short inter- LED distance, Di. For the other sections 200i, seen from left to right, the distance or LED pitch, Dn, of the respective section 200i increases, and the (sixth) red section 2006, having a relatively large peak emission wavelength, XPi, in the red wavelength range, XR, accordingly has a relatively large distance or LED pitch, De.

[0050] In Fig. 2, the first section 200i may comprise BOSE phosphor, the second section 2002 may comprise Phosphate phosphor, the third section 200s may comprise LuAG phosphor, the fourth section 2004 may comprise YAG phosphor, the fifth section 200s may comprise BSSN phosphor, and / or the sixth section 200e one or more of KSiF phosphor, Nitride phosphor and Oxynitride phosphor.

[0051] In Fig. 2, an order of the plurality of sections 200i, in a direction from a first end portion (e.g. left end portion) towards a second end portion (e.g. right end portion), opposite the first end portion, correlates with an increase in a peak emission wavelength, XPi, in the wavelength range, Xi, in which the respective section 200i is configured to emit converted light. Hence, and as shown in Fig. 2, the order of the plurality of sections 200i of the LED filament 100 follows the order of the rainbow colors.

[0052] The LED filament 100 of Fig. 2 may furthermore comprise at least one ancillary section 200x(not shown) of the LED filament 100, arranged along the length axis, LX, wherein the at least one ancillary section 200xcomprises at least three LEDs 130 of the plurality of LEDs 130, and wherein the elongated encapsulant 160 of the at least one ancillary section 200xdoes not comprise luminescent material. For example, the LEDs 130 of the at least one ancillary section 200xmay be arranged to emit ancillary LED light being colored light and having a peak emission wavelength, XPi, in the blue light wavelength range, LB.

[0053] Figs. 3a and 3b schematically show LED filaments 100 according to exemplifying embodiments of the present invention. It should be noted that the LED filaments 100 of Figs. 3a and 3b have many features and functions in common with the LED filament 100 as exemplified in Fig. 2, and some references have been omitted in Figs. 3a and 3b for this reason. Hence, it is also referred to Fig. 2 and the associated text for an understanding of Figs. 3a and 3b.

[0054] In Fig. 3a, the LED filament 100 comprises three sections 200i, i=l, arranged along the length axis, LX, of the LED filament 100. Each section 200i comprises at least three LEDs 130 of the plurality of LEDs 130, a part or portion of the elongated carrier 120, and a part or portion of the elongated encapsulant 160. Each section 200i is configured to emit converted light being colored light and having a peak emission wavelength, XPi, in a wavelength range, Xi. The wavelength ranges, Xi, in the example of Fig. 3a, are a blue light wavelength range, XB, of 430 - 470 nm, a green light wavelength range, XG, of 500 - 540 nm, and a red light wavelength range, XR, of 600 - 690 nm. Any (first) section 200k of the plurality of sections 200i is hereby configured to emit converted light in a wavelength range, Xk, which is different from a wavelength range, Xm, of converted light emitted by any other (second) section 200mof the plurality of sections 200i. In Fig. 3a, a length, Li, i=l, ... , 3, of each section 200i of the plurality of sections 200i is dependent on the wavelength range, Xi, of converted light emitted by the section 200i. The (first, leftmost) blue section 200i, configured to emit converted colored light with a peak emission wavelength, XPi, in the blue light wavelength range, XB, has a shorter length, Li, compared to the (relatively) longer length, L2, of the (second, middle) green section 2OO2, configured to emit converted green light with a peak emission wavelength, XPi, in the green light wavelength range, G. The (third, rightmost) red section 200s, configured to emit converted colored light with a peak emission wavelength, XPi, in the red light wavelength range, XR, has the (relatively) longest length, L3, i.e. longer than the length, Li, of the blue section 200i and the length, L2, of the green section 2002.

[0055] In Fig. 3a, each section 200i of the plurality of sections 200i has a distance, Dn, n=l, ... , 3, between adjacently arranged LEDs 130 of the section 200i. The distance, Dn, is dependent on the wavelength range, Xi, of converted light emitted by the section 200i. For the example of the three sections 200i, i=l, ... ,3, in Fig. 3a, the (first) blue section 200i has a relatively short pitch or intra-LED distance, Di, whereas the distances, D2, D3, for the (second) green section 2OO2 and the (third) red section 2OO3, respectively, increase. Hence, for the sections 200i, seen from left to right of the LED filament 100, the pitch or inter LED distance, Dn, of the respective section 200i increases, whereby the (third) red section 2OO3, having a relatively large peak emission wavelength, XPi, accordingly has a relatively large pitch or inter-LED distance, D3.

[0056] The LED filament 100 of Fig. 3b has many features, components and functions in common with the LED filament 100 of Fig. 3a, and it is also referred to Fig. 3a and the associated text. In Fig. 3b, however, the LED filament 100 comprises four sections 200i, i=l, ... ,4, arranged along the length axis, LX, of the LED filament 100. The sections 200i are configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the blue light wavelength range, B, of 430 - 470 nm, the green light wavelength range, G, of 500 - 540 nm, the yellow light wavelength range, XY, of 540 - 580 nm, and the red light wavelength range, XR, of 600 - 690 nm. In Fig. 3b, the length, Li, 4, of each section 200i of the plurality of sections 200i is dependent on the wavelength range, Xi, of converted light emitted by the section 200i. The (first, leftmost) blue section 200i, configured to emit converted colored light with a peak emission wavelength, XPi, in the blue light wavelength range, XB, has a shorter length, Li, compared to the (relatively) longer length, L2, of the (second) green section 2OO2, configured to emit converted green light with a peak emission wavelength, XPi, in the green light wavelength range, XG. The (third) yellow section 2003, configured to emit converted colored light with a peak emission wavelength, XPi, in the yellow light wavelength range, XY, has a longer length, L3, than Li and L2. The (fourth) red section 2004, configured to emit converted colored light with a peak emission wavelength, XPi, in the red light wavelength range, R, has the (relatively) longest length, L4, i.e. a length which is longer than the length, Li, of the blue section 200i, the length, L2, of the green section 2OO2, and the length, L3, of the yellow section 2OO3.

[0057] In Fig. 3b, each section 200 of the plurality of sections 200 has a distance, Dn, n=l, ... , 4, between adjacently arranged LEDs 130 of the section 200i. The distance, Dn, is dependent on the wavelength range, Xi, of converted light emitted by the section 200i. For the example of the four sections 200i, i=l, in Fig. 3a, the (first) blue section 200i has a relatively short pitch or intra-LED distance, Di, whereas the distances, D2, D3, D4 for the (second) green section 2OO2, the (third) yellow section 2OO3, and the (fourth) red section 2004, respectively, increase. Hence, for the sections 200i, seen from left to right, the distance, Dn, of the respective section 200i increases, whereby the (fourth) red section 2004, having a relatively large peak emission wavelength, XPi, accordingly has a relatively large pitch or inter-LED distance, D4.

[0058] Fig. 4 schematically shows a LED filament lamp 600 according to an embodiment of the present invention. The LED filament lamp 600, 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. According to this example, the LED filament lamp 600 comprises two LED filaments 100, but it should be noted that the number of LED filaments 100 is arbitrary. The LED filaments 100 form part of a LED filament arrangement, which further comprises a controller 510. The controller 510 is configured to individually control a group of LEDs belonging to each section of the plurality of sections on the LED filaments 100. According to the example of Fig. 4, the controller 510 may individually control the LEDs of the (three) sections of the first LED filament, and individually control the LEDs of the (three) sections of the second LED filament. The controller 510 may hereby control / vary the CCT of the LED filament light from the respective LED filaments 100.

[0059] The LED filament lamp 600 further comprises a light-transmissive envelope 610, which is exemplified as being bulb-shaped. The light-transmissive envelope 610 at least partially encloses the LED filament(s) 100. The LED filament lamp 600 further comprises a connector 620 for electrically and mechanically connecting the LED filament lamp 600 to a socket of a luminaire. The controller 510 of the LED filament lamp 600 is exemplified as being arranged in the connector 620, but it should be noted that the controller 510 may be arranged substantially anywhere in the LED filament lamp 600.

[0060] 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 encapsulant 200, the second elongated encapsulant 300, etc., may have different shapes, dimensions and / or sizes than those depicted / described.

Claims

CLAIMS:

1. A light emitting diode, LED, filament (100) configured to provide, during operation, LED filament light (110), the LED filament extending along a length axis, LX, and comprising an elongated carrier (120), an array of a plurality of light emitting diodes, LEDs (130) arranged on a first major surface (145) of the elongated carrier, wherein the plurality of LEDs is configured to emit LED light (150), an elongated encapsulant (160) at least partially covering the first major surface of the elongated carrier and at least partially enclosing the plurality of LEDs, wherein the elongated encapsulant comprises luminescent material configured to at least partly convert the emitted LED light into converted light (170), a plurality of sections (2000, i=l, y, of the LED filament, arranged along the length axis, LX, wherein each section of the plurality of sections comprises at least three LEDs of the plurality of LEDs, and wherein each section is configured to emit converted light being colored light and having a peak emission wavelength, XPi, in a wavelength range, Xi, wherein the wavelength range, Xi, is one of a blue light wavelength range, XB, of 430 - 470 nm, a cyan light wavelength range, Xc, of 470 - 500 nm, a green light wavelength range, XG, of 500 - 540 nm, a yellow light wavelength range, XY, of 540 - 580 nm, an amber light wavelength range, XA, of 580 - 600 nm, and a red light wavelength range, XR, of 600 - 690 nm, wherein any first section (200k) of the plurality of sections is configured to emit converted light in a first wavelength range, Xk, which is different from a second wavelength range, Xm, of converted light emitted by at least one second section (200m) of the plurality of sections, wherein at least one of a length, Li, i=l, , y, of each section of the plurality of sections is dependent on the wavelength range, Xi, of converted light emitted by the section, andeach section of the plurality of sections has a distance, Dn, n=l, s, between adjacently arranged LEDs of the section, wherein the distance, Dn, is dependent on the wavelength range, Xi, of converted light emitted by the section, and wherein the LED filament comprising at least three sections, wherein any first section of the plurality of sections is configured to emit converted light in a first wavelength range, Xk, any second section of the plurality of sections is configured to emit converted light in a second wavelength range, Xm, and any third section of the plurality of sections is configured to emit converted light in a third wavelength range, Xi, wherein the first, second and third wavelength ranges, Xk, Xm, Xi, are different from each other.

2. The LED filament according to claim 1, further comprising at least one ancillary section (200x) of the LED filament, arranged along the length axis, LX, wherein the at least one ancillary section comprises at least three LEDs of the plurality of LEDs, and wherein the elongated encapsulant of the at least one ancillary section does not comprise luminescent material.

3. The LED filament according to claim 2, wherein the at least three LEDs of the at least one ancillary section is arranged to emit ancillary LED light being colored light and having a peak emission wavelength, XPi, in the blue light wavelength range, XB.

4. The LED filament according to any one of the preceding claims, comprising at least five sections.

5. The LED filament according to any one of the preceding claims, wherein a relation between a first length, Li, of any first section (200k) of the plurality of sections configured to emit converted light with a peak emission wavelength, XPk, in a wavelength range, Xk, and a second length, L2, of any second section (200m) of the plurality of sections configured to emit converted light with a peak emission wavelength, Xpm, in a wavelength range, Xm, fulfilsL 1 L2 if XPk Xpm, and L2 L 1 if Xpm Xpk.

6. The LED filament according to any one of the preceding claims, comprising at least one first section configured to emit one of converted light being colored light and having a peak emission wavelength,XPi, in the blue light wavelength range, LB, and direct emitting blue light in the blue light wavelength range, LB, at least one second section configured to emit converted light being colored light and having a peak emission wavelength, XPi, in one of the green light wavelength range, XG, and the yellow light wavelength range, XY, at least one third section configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the red light wavelength range, XR. and at least one of at least one fourth section configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the amber light wavelength range, XA, and at least one fifth section configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the cyan light wavelength range, Xc.

7. The LED filament according to claim 6, wherein a sum of lengths Lisum,4,5sum of a sum of the lengths, Lisum, of the at least one first section, Li, and a sum of the lengths, L4sum, of the at least one of the at least one fourth section, L4, and the at least one fifth section, Ls, and and wherein a sum of lengths L2sum,3sum of a sum of the lengths, L2sum, of the at least one second section, L2, and a sum of the lengths, Lssum, of the at least one third section, L3, fulfil Llsum,4,5sum L2sum,3sum.

8. The LED filament according to any one of the preceding claims, whereina relation between a first distance, Di, between adjacently arranged LEDs of any first section (200k) of the plurality of sections configured to emit converted light with a first peak emission wavelength, XPi . in a wavelength range, Xk, and a second distance, D2, between adjacently arranged LEDs of any second section (200k) of the plurality of sections configured to emit converted light with a second peak emission wavelength, Xpm. in a wavelength range, Xm, fulfilsD 1 < D2 if Xpk < pm, and D2 < D 1 if Xpm < Xpk.

9. The LED filament according to any one of the preceding claims, wherein the elongated carrier is light-transmissive, and wherein the elongated encapsulant at least partially covers a second major surface (310) of the elongated carrier, opposite to the first major surface.

10. The LED filament according to any one of the preceding claims, comprising at least three of at least one first section (200i) configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the blue light wavelength range, XB, wherein the at least one first section comprises BOSE phosphor, at least one second section (2OO2) configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the cyan light wavelength range, Xc, wherein the at least one second section comprises Phosphate phosphor, at least one third section (2OO3) configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the green light wavelength range, XG, wherein the at least one third section comprises LuAG phosphor, at least one fourth section (2OO4) configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the yellow light wavelength range, XY, wherein the at least one fourth section comprises YAG phosphor, at least one fifth section (200s) configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the amber light wavelength range, XA, wherein the at least one fifth section comprises BSSN phosphor, andat least one sixth section (200e) configured to emit converted light being colored light and having a peak emission wavelength, XPi, in the red light wavelength range, XR, wherein the at least one sixth section comprises one or more of KSiF phosphor, Nitride phosphor and Oxynitride phosphor.

11. The LED filament according to any one of the preceding claims, wherein an order the plurality of sections, in a direction from a first end portion towards a second end portion, opposite the first end portion, correlates with an increase in a peak emission wavelength, XPi, in the respective wavelength range, Xi, in which the respective section is configured to emit converted light.

12. The LED filament according to any one of the preceding claims, wherein the LED filament light is white light having a correlated color temperature, CCT, in a range of 1700K- 6500K, and a color rendering index, CRI, of at least 80.

13. A LED filament arrangement (500), comprising at least one LED filament according to any one of the preceding claims, a controller (510) coupled to the plurality of sections of the at least one LED filament, wherein the controller is configured to individually control a group of LEDs belonging to each section of the plurality of sections.

14. A LED filament lamp (600), comprising one of at least one LED filament according to any one of claims 1-12, and a LED filament arrangement according to claim 13, a light-transmissive envelope (610) at least partly enclosing the at least oneLED filament, and a connector (620) for electrically and mechanically connecting the LED filament lamp to a socket of a luminaire.

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