LED filament comprising elements

Abstract

A LED filament (100) configured to, in operation, emit LED filament light (105), comprising an elongated carrier (110) comprising a first major surface (112), an array of a plurality of LEDs (120) arranged on the first major surface, wherein the plurality of LEDs is configured to emit LED light (125), and an elongated encapsulant (130) comprising a luminescent material and / or a light scattering material. The LED filament further comprises a plurality of elements (200) arranged on at least a part of the elongated encapsulant, wherein the plurality of elements comprises transparent faceted particles (210) and / or transparent lenslets (220) arranged to refract, disperse, reflect and / or diffract the converted light and / or the scattered light into the emitted LED filament light.

Description

[0001] LED filament comprising elements

[0002] FIELD OF THE INVENTION

[0003] The present invention generally relates to light emitting diode, LED, filaments. More specifically, the present invention is related to LED filaments comprising elements.

[0004] BACKGROUND OF THE INVENTION

[0005] The use of light emitting diodes (LED) 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. In particular, LED filament lamps are highly appreciated as they are very decorative.

[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, as the appearance of lamps of this kind are appreciated as they are highly decorative.

[0007] In W02020 / 182925, there is provided a LED filament arrangement comprising at least one LED filament which in turn comprise(s) an array of a plurality of LEDs. The LED filament further comprises a substrate on which the plurality of LEDs is arranged, wherein the substrate surface is arranged to influence the LED light.

[0008] It is an object of the present invention to provide a LED filament which has a decorative lighting effect when the LED filament is in a switched-on state, and a decorative effect in a switched-off state, whilst providing the advantageous properties of LEDs with respect to energy efficiency and light distribution purposes.

[0009] US 2020 / 208009 discloses a LED filament. According to an embodiment, the LED filament comprises an elongated substrate and a plurality of LEDs which are mechanically coupled to the substrate. The LED filament further comprises an at least in part light-transmissive encapsulation which encapsulate the plurality of LEDs and at least partially encapsulates the substrate, and a plurality of at least partially light-reflective particles which are arranged on an outer surface of the encapsulation.

[0010] SUMMARY OF THE INVENTION

[0011] It is of interest to combine the advantageous properties of LEDs with respect energy efficiency, light distribution purposes and / or aesthetics with the aim to provide a LED filament which has a decorative lighting effect when the LED filament is in a switched-on state, and a decorative effect in a switched-off state.

[0012] 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.

[0013] According to the present invention, there is provided a light emitting diode, LED, filament configured to, in operation, emit LED filament light. The LED filament comprises an elongated carrier comprising a first major surface, and an array of a plurality of LEDs arranged on the first major surface, wherein the plurality of LEDs is configured to emit LED light. The LED filament further comprises an elongated encapsulant comprising at least one of a luminescent material configured to at least partly convert the LED light emitted by the plurality of LEDs into converted light and a light scattering material configured to at least partly scatter the LED light into scattered light. The elongated encapsulant at least partially (e.g. at least 80% or at least 90%) covers the first major surface and at least partially encloses the array of the plurality of LEDs. The LED filament further comprises a plurality of elements arranged on at least a part of the elongated encapsulant. The plurality of elements comprises (or is), at least one of, substantial transparent faceted particles, and substantial transparent lenslets, arranged to, at least one of, at least partially refract, at least partially disperse, at least partially reflect, and at least partially diffract, at least one of the converted light and the scattered light into the emitted LED filament light.

[0014] The word transparent in this application is to be understood that it means that at least 70 % of the light emitted by the LED filament will be transmitted through the faceted particles and / or lenslets at a first pass, or preferably at least 85 % of the light. This is also emphasized by the word substantial.

[0015] Thus, the present invention is based on the idea of providing a LED filament comprising a plurality of elements, in the form of transparent faceted particles and / or transparent lenslets, arranged on an elongated encapsulant of the LED filament. During operation of the LED filament, the transparent elements are arranged to refract, disperse, reflect and / or diffract the emitted LED filament light, leading to a decorative and aesthetically appealing lighting effect when the LED filament is in a switched-on state.

[0016] The present invention is advantageous in that the LED filament achieves a decorative lighting effect when the LED filament is in a switched-on state, as well as providing a decorative effect in a switched-off state.

[0017] The present invention is advantageous in that the LED filament is able to provide aesthetically appealing lighting effects such as brilliance, scintillation and / or fire. The brilliance effect, as observed by a user / ob server, is achieved by the LED filament when white light enters from the top of the elements, bounces around, and exits again through the top of the elements. The scintillation effect, which may also be described (or is known) as the sparkle effect, is achieved by flashes of light reflecting off the surfaces of the elements as the LED filament is moved by a user / ob server. The fire effect describes the rainbow colors a user / observer sees due to dispersion of light, and occurs when light enters the elements at an angle, slows down, and disperses into different colors.

[0018] The present invention is further advantageous in that the LED filament is able to provide a reduced yellow appearance, which consequently leads to an exposed white LED filament during operation.

[0019] The present invention is further advantageous in that the LED filament, via its plurality of elements, may achieve an improved thermal management of the LED filament during operation.

[0020] The present invention is further advantageous in that the LED filament is able to combine its aesthetically appealing lighting effects with a desired lighting distribution during operation.

[0021] The present invention is further advantageous in that the LED filament is able to combine aesthetic advantages with the benefits of LED technology, implying a low power consumption, a long operational life, and an increased efficiency related to the ratio between light energy and heat energy.

[0022] The LED filament, which is in operation is configured to emit LED filament light, comprises an elongated carrier comprising a first major surface, and an array of a plurality of LEDs arranged on the first major surface, wherein the plurality of LEDs is configured to emit LED light. By the term “carrier”, it is here meant an element, substrate, printed circuit board, PCB, or the like, arranged to mechanically and / or electrically support the LEDs. Hence, the plurality of LEDs may be arranged, mounted and / or mechanically coupled on / to the first major surface of the elongated carrier (e.g. a substrate), wherein the elongated carrier is configured to mechanically and / or electrically support the LEDs. The LED filament further comprises an elongated encapsulant. By the term “encapsulan ’, it is here meant a material, element, arrangement, or the like, which is configured or arranged to at least partially surround, encapsulate and / or enclose the plurality of LEDs and the elongated carrier. The encapsulant comprises at least one of a luminescent material configured to at least partly convert the LED light emitted by the plurality of LEDs into converted light and a light scattering material configured to at least partly scatter the LED light into scattered light. Hence, the encapsulant comprises the luminescent material and / or the light-scattering material with the properties as described. The light-scattering material may enable forward and / or backward scattering. The light scattering material may comprise a silicone matrix with at least one of AI2O3, BaSCU, TiCL, SiCL, CaF2, CaCCL, and BaTiCL particles. The LED filament further comprises a plurality of elements arranged on at least a part of the elongated encapsulant. In other words, the LED filament may comprise a cover layer, or the like, comprising the plurality of elements arranged on the elongated encapsulant. The (cover layer of the) plurality of elements is hereby arranged or put on, over and / or in front of the encapsulant in order to at least partially protect, hide and / or enclose it. The plurality of elements comprises (or is), at least one of, transparent faceted particles, and transparent lenslets. Hence, the plurality of elements comprises, constitutes, or is, transparent faceted particles and / or transparent lenslets. By “particles”, it is here meant relatively small elements, beads, or the like. By “faceted”, it is meant that the particles comprise relatively small, plane surfaces. By “lenslets”, it is here meant relatively small lenses arranged or configured to optically influence light. The transparent faceted particles and / or transparent lenslets are arranged to, at least one of, at least partially refract, at least partially disperse, at least partially reflect, and at least partially diffract, at least one of the converted light and the scattered light into the emitted LED filament light. Hence, the transparent faceted particles and / or transparent lenslets of the LED filament are arranged to optically influence the converted and / or scattered light, by at least partially refract, at least partially disperse, at least partially reflect, and / or at least partially diffract the converted light and / or the scattered light into the emitted LED filament light.

[0023] According to an example of the present invention, the plurality of elements may be arranged on at least a part of the elongated encapsulant such that the elongated encapsulant is covered for at least 80%, preferably at least 90%, more preferably at least 95%, most preferably at least 98% such as for example 100% or fully covered. Hence, the elongated encapsulant is covered to a relatively high degree of elements. The example is advantageous in that the high degree or level of element coverage of the elongated encapsulant even further contributes to the optical influence of the converted and / or scattered light, which even further contributes to the aesthetically appealing effect of the LED filament during operation.

[0024] According to an embodiment of the present invention, the plurality of elements may constitute at least one layer of elements arranged to at least partially cover the at least a part of the elongated encapsulant. Preferably, the plurality of elements may constitute at least one layer of elements arranged to cover at least 80% or at least 90% of the elongated encapsulant. More preferably, the plurality of elements may constitute at least one layer of elements arranged to fully cover the elongated encapsulant. The present embodiment is advantageous in that the refraction, dispersion, reflection and / or diffraction of the converted and / or scattered light may be even further increased by the layer(s) of elements, thereby further contributing to the aesthetically appealing effect of the LED filament during operation i.e. switched-on-state, but also has an attractive appearance in the switched-off- state.

[0025] According to an embodiment of the present invention, the at least one layer of elements may constitute a retroreflector. By the term “retroreflector”, it is here meant that the layer(s) of elements may reflect light over a relatively wide range of angles of incidence. Explained differently, the retroreflector of the present embodiment achieves a reflection of light via the layer(s) of elements, thereby redirecting the incident light. The present embodiment is advantageous in that the augmented reflective property of the LED filament may provide an even more attractive lighting effect.

[0026] According to an embodiment of the present invention, the LED filament may further comprise a binder layer, wherein the binder layer is, at least one of, transparent, and white reflective, wherein the elements are attached to the elongated encapsulant by the binder layer. Hence, the binder layer is transparent and / or white reflective, wherein the elements are attached to the elongated encapsulant by the binder layer. It is preferred that the binder layer is a non-absorbing layer, i.e. that less than 10%, or even less than 5%, of the light is absorbed. The present embodiment is advantageous in that the binder layer provides a convenient fastening or attachment of the elements to the elongated encapsulant. The present embodiment is further advantageous in that the white reflectiveness and / or transparency of the binder layer may retain, or even augment, the light distribution and / or aesthetical effects of the LED filament. The property of white reflection of the binder layer is particularly advantageous in that a vintage and / or decor style of the LED filament is provided.

[0027] According to an embodiment of the present invention, the binder layer may comprise a polymer matrix, wherein the plurality of elements has a higher refractive index than the polymer matrix, and the plurality of elements is partially covered by the binder layer. It will be appreciated that the plurality of elements may protrude from the binder layer. The polymer matrix preferably comprises silicone. The present embodiment is advantageous in that the higher refractive index of the plurality of elements, which may be at least 1.5, and preferably at least 1.65, compared to the polymer matrix which may have a refractive index of approximately 1.4, yields an improved optical performance of the LED filament.

[0028] According to an embodiment of the present invention, the elongated encapsulant may comprise the luminescent material configured to at least partly convert the LED light emitted by the plurality of LEDs into the converted light, and wherein one of (i) the converted light, and (ii) the converted light and part of the emitted LED light, is white light having a correlated color temperature, CCT, in a range of 1700-6500 K and / or a color rendering index, CRI, of at least 80 or at least 85. The present embodiment is advantageous in that the LED filament may provide white light (cold as well as warm white light) in a convenient manner during operation.

[0029] According to an embodiment of the present invention, a relationship between a thickness, TF, of the LED filament, and the diameter, DE, of the elements, fulfills 0.05-TF < DE < 0.5-TF. Hence, the diameter, DE, of the elements may be as small as 1 / 20 of the thickness, TF, of the LED filament, and as large as half of the thickness, TF, of the LED filament. In embodiments, the thickness, TF, of the LED filament may be in a range from 1 mm to 4 mm. Furthermore, in embodiments, the diameter, DE, of the elements may be in a range from 100 micrometer to 1000 micrometer. The present embodiment is advantageous in that the diameter, DE, of the elements are sufficiently large, yet sufficiently small, to be able to achieve the light distribution properties as well as the aesthetically appealing effect during operation of the LED filament.

[0030] According to an embodiment of the present invention, the plurality of elements may comprise transparent faceted particles, and wherein each transparent faceted particle of the transparent faceted particles comprises at least 7 facets or at least 10 facets or at least 15 facets. The present embodiment is advantageous in that the relatively large amount of facets may even further augment the refraction, dispersion, reflection and / or diffraction of the converted and / or scattered light into the LED filament light. According to an embodiment of the present invention, the plurality of elements comprises transparent faceted particles, and wherein each faceted particle of the transparent faceted particles comprises at least 2 facets at a first portion of the faceted particle facing away from the elongated encapsulant, and at least 2 facets at a second portion of the faceted particle facing the elongated encapsulant. The present embodiment is advantageous in that the refraction, dispersion, reflection and / or diffraction of the converted and / or scattered light may be increased even further, consequently leading to even more aesthetically appealing lighting effects via the LED filament.

[0031] According to an embodiment of the present invention, the plurality of elements may constitute a stack of at least two layers of elements or at least three layers of elements. Hence, the layers of elements may be arranged on top of each other on the LED filament. The present embodiment is advantageous in that the LED filament hereby provides a convenient and space-saving (slim) arrangement of the plurality of elements in stacks in order to achieve the effects of the present invention. This includes that the filament may also have a part with only one layer or no layer of elements in case the plurality of element covers only a part of the encapsulant.

[0032] According to an embodiment of the present invention, at least one of the plurality of elements having a thermal conductivity of at least 0.7 W / (m-K) (or at least 1 W / (m-K)), and the plurality of elements comprises at least one material selected from the group consisting of glass, sapphire, spinel, A10N, and quartz, is fulfilled. Hence, the plurality of elements has a thermal conductivity of at least 0.7 W / (m-K) (or at least 1 W / (m-K)) and / or the plurality of elements comprises glass, sapphire, spinel, A10N (single crystal aluminum oxide) and / or quartz. The present embodiment is advantageous in that the thermal management of the LED filament during its operation is even further improved, leading to a longer operational life.

[0033] According to an embodiment of the present invention, the elongated carrier is light-transmissive. Furthermore, the elongated encapsulant may at least partially (e.g. at least 80% or at least 90%) cover a second major surface, opposite to the first major surface, of the elongated carrier. The light-transmissive property of the carrier of the present embodiment is advantageous in that the effects of the aesthetical lighting and / or the lighting distribution properties of the LED filament arrangement may be augmented even further. The elongated encapsulant covering the first and second major surfaces may further influence the LED light from the plurality of LEDs arranged on the first major surface due to the carrier being light- transmissive. According to an embodiment of the present invention, the plurality of elements may cover at least 80 % or at least 90 % or at least 95 % of the elongated encapsulant e.g. fully cover the elongated encapsulant. The present embodiment is advantageous in that a relatively large portion of the elongated encapsulant is covered by the plurality of elements, thereby even further augmenting the light distribution properties as well as the aesthetically appealing effect during operation of the LED filament.

[0034] In embodiments, the elongated encapsulant may have a tubular shape and / or may be fully arranged around the elongated carrier and the elongated encapsulant.

[0035] According to an embodiment of the present invention, there is provided a LED filament arrangement configured to, in operation, emit LED filament arrangement light. The LED filament arrangement comprises at least one LED filament according to any one of the preceding claims, wherein the plurality of LEDs comprises a plurality of subsets of LEDs, and a controller coupled to the plurality of subsets of LEDs, wherein the controller is configured to individually control the subsets of LEDs for controlling a level of a sparkling effect of the LED filament arrangement light. By “controller”, it is here meant substantially any unit, device, or the like, which is arranged or configured to control the subset of LEDs. The present embodiment is advantageous in that the controller may conveniently and efficiently control the subsets of LEDs individually for achieving a sparkling effect of the LED filament arrangement light during operation. The sparkling effect may be achieved by directing LED light and / or converted light at different angles onto the plurality of elements.

[0036] According to an embodiment of the present invention, there is provided a LED filament lamp. The LED filament lamp comprises at least one LED filament according to any one of the preceding embodiments or the LED filament arrangement according to the preceding embodiment. The LED filament lamp further comprises a light transmissive envelope at least partially enclosing the LED filament, and a base, wherein the base comprises a connector arranged to mechanically and electrically connect the LED lamp to a socket of a luminaire. By the term “envelope”, it is here meant an enclosing element, such as a cap, cover, or the like, comprising an at least partial translucent and / or transparent material. The present embodiment is advantageous in that the LED filament (or LED filament arrangement) according to the invention may be conveniently arranged in substantially any luminaire, lamp or lighting device, such as a tubular lighting device, a LED filament lamp or a LED filament luminaire, luminaire, lighting system, or the like. The LED filament lamp may further comprise a driver for supplying power to the LEDs of the LED filament. 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.

[0037] BRIEF DESCRIPTION OF THE DRAWINGS

[0038] 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.

[0039] Fig. 1 shows a LED filament lamp according to the prior art,

[0040] Fig. 2 schematically shows a LED filament according to an exemplifying embodiment of the present invention,

[0041] Figs. 3a and 3b schematically show elements of a LED filament according to exemplifying embodiments of the present invention,

[0042] Fig. 4 schematically shows a LED filament according to an exemplifying embodiment of the present invention, and

[0043] Fig. 5 schematically shows a LED filament lamp according to an exemplifying embodiment of the present invention.

[0044] DETAILED DESCRIPTION

[0045] 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. LED filament lamps 10 of this kind are able to produce warm white light. However, it is of interest to improve the properties of the light emitted from the LED filaments 20 as well as augmenting the appearance and / or the decorative aspect of the LED filaments 20 and / or the LED filament lamps 10.

[0046] Fig. 2 schematically shows a LED filament 100 according to an exemplifying embodiment of the present invention. The LED filament 100 is configured to emit LED filament light 105. The LED filament 100 comprises an elongated carrier 110 extending in a first direction, A. The elongated carrier 110 comprises a first major surface 112. The LED filament 100 comprises an array of a plurality of LEDs 120 arranged on the first major surface 112, wherein the plurality of LEDs 120 is configured to emit LED light 125. The elongated carrier 110 may be an element, substrate, printed circuit board, PCB, or the like, arranged to mechanically and / or electrically support the plurality of LEDs 120. Hence, the plurality of LEDs 120 may be arranged, mounted and / or mechanically coupled on / to the first major surface 112 of the elongated carrier 110, wherein the elongated carrier 110 is configured to mechanically and / or electrically support the LEDs 120. The LED filament 100 further comprises an elongated encapsulant 130. The encapsulant 130 at least partially surrounds, encapsulates and / or encloses the plurality of LEDs 120 and the elongated carrier 110. The encapsulant 130 comprises a luminescent material configured to at least partly convert the LED light 125 emitted by the plurality of LEDs 120 into converted light and / or a light scattering material configured to at least partly scatter the LED light 125 into scattered light. The thickness, TF, of the LED filament 100 may be in a range from 1 mm to 4 mm.

[0047] The LED filament 100 further comprises a plurality of elements 200 arranged on at least a part of the elongated encapsulant 130. It should be noted that the distribution, size, form, etc. of the plurality of elements 200 are schematically indicated as examples, and that the plurality of elements 200 may have many different sizes and / or forms. The plurality of elements 200 comprises transparent faceted particles (e.g. transparent faceted elements, beads, or the like) and / or transparent lenslets. By “lenslets”, it is here meant relatively small lenses arranged to optically influence light.

[0048] The word transparent in this application is to be understood that it means that at least 70 % of the light emitted by the LED filament will be transmitted through the faceted particles and / or lenslets at a first pass, or preferably at least 85 % of the light. This is also emphasized by the word substantial.

[0049] The plurality of elements 200, i.e. the transparent faceted particles and / or the transparent lenslets, are arranged to, at least one of, at least partially refract, at least partially disperse, at least partially reflect, and at least partially diffract, at least one of the converted light and the scattered light into the emitted LED filament light 105. Hence, the transparent faceted particles and / or transparent lenslets of the plurality of elements 200 are arranged to, at least partially refract, at least partially disperse, at least partially reflect, and / or at least partially diffract the converted light and / or the scattered light into the emitted LED filament light 105. The plurality of elements 200 may constitute at least one layer of elements, e.g. arranged as a stack of layers, arranged to at least partially cover the elongated encapsulant 130. Furthermore, in case that the plurality of elements 200 are arranged in (a) layer(s), this (these) layer(s) may constitute a retroreflector. The LED filament may further comprise a binder layer (not shown). The plurality of elements 200 may hereby be attached to the elongated encapsulant 130 by the binder layer, which may be transparent and / or white reflective. The binder layer is preferably a non-absorbing layer, i.e. that less than 10%, or even less than 5%, of the light is absorbed. The binder layer may furthermore comprise a polymer matrix (which e.g. may comprise silicone), with a refractive index of approximately 1.4, whereas the plurality of elements 200 has a higher refractive index than the polymer matrix, such as at least 1.5 or at least 1.65. The plurality of elements 200, which for example may comprise glass, sapphire, spinel, A10N, and / or quartz, may furthermore have a thermal conductivity of at least 0.7 W / (m-K).

[0050] Fig. 3a schematically shows an element 200 (in 2D) of a LED filament according to an exemplifying embodiment of the present invention. It is also referred to Fig. 2 and the associated text for an increased understanding of the features and / or properties of the element(s) 200 and of the LED filament comprising these element(s) 200. It should be noted that the size, form, etc. of the element 200 is schematically indicated in Fig. 3a as an example, and that the element 200 may have many different sizes and / or forms. In other words, the element 200 is exemplified as being star-shaped, but the element 200 may alternatively have the form of a diamond, pyramid, etc. In Fig 3a, the element 200 has the form of a faceted particle. A relationship between a thickness, TF, (indicated in Fig. 2) of the LED filament, and the diameter, DE, of the element 200, fulfills 0.05-TF < DE < 0.5-TF. Hence, the diameter, DE, of the element 200 may be as small as 1 / 20 of the thickness, TF, of the LED filament, and as large as half of the thickness, TF, of the LED filament. For example, the thickness, TF, of the LED filament may be in a range from 1 mm to 4 mm and / or the diameter, DE, of the element 200 may be in a range from 100 micrometer to 1000 micrometer.

[0051] According to the exemplified element 200 in form of a faceted particle, it may comprise at least 7 facets 220, i.e. relatively small and even surfaces. The element 200 may comprise at least 2 facets 220 at a first portion 300 of the element 200 facing away from the elongated encapsulant of the LED filament, and at least 2 facets at a second portion 310 of the element 200 facing the elongated encapsulant of the LED filament.

[0052] Fig. 3b schematically shows an element 200 of a LED filament of the present invention. Here, the element 200 in the form of a transparent, faceted particle, has a diamondshape with a base 400, a tip 410 opposite the base 400, and a central section 420 between the base 400 and the tip 410, wherein a diameter of the central section, Des, is larger than a diameter of the base, DB. The element 200 of the LED filament may provide a brilliance effect, as observed by a user / ob server, during operation of the LED filament as shown in the leftmost image of Fig. 3b. The brilliance effect is achieved by the LED filament when white light 450 enters from the top (base 400) of the element 200, bounces around, and exits again through the top (base 400) of the element 200. The scintillation effect, which may also be described (or is known) as the sparkle effect, is achieved by flashes of light reflecting off the surfaces of the element 200 as the LED filament is moved by a user / ob server. The rightmost image of Fig. 3b schematically indicates a fire effect via the element 200 of the LED filament. The fire effect describes the rainbow colors 470 a user / observer sees due to dispersion of light, and occurs when light 450 enters the element 200 at an angle, slows down, and disperses into different colors 470.

[0053] Fig. 4 schematically shows a LED filament 100 according to an exemplifying embodiment of the present invention. It should be noted that the LED filament 100 shown in Fig. 4 has several features in common with the LED filament 100 shown in Fig. 2, and it is hereby referred to Fig. 2 and the associated text for an increased understanding of the features, properties and / or functions of the LED filament 100. The LED filament 100 of Fig. 4, schematically shown to be held in the palm of a hand, comprises a plurality of elements 200 arranged on the elongated encapsulant 130 of the LED filament 100, wherein the plurality of elements 200 are arranged to, at least partially refract, disperse, reflect, and / or diffract the LED light emitted by the plurality of LEDs, as converted and / or the scattered via the encapsulant 300, into the emitted LED filament light.

[0054] Fig. 5 schematically shows a LED filament lamp 600. The LED filament lamp 600 comprises at least one LED filament 100 according to any one of the preceding embodiments. It will be appreciated that the disclosed arrangement of LED filaments 100 in Fig. 5 is merely exemplifying, and that the LED filament lamp 600 may comprise substantially any arrangement of one or more LED filaments 100. The LED filament lamp 600 further comprises a light transmissive envelope 610 at least partially enclosing the LED filament(s) 100, and a base 620, wherein the base 620 comprises a connector arranged to mechanically and electrically connect the LED lamp to a socket of a luminaire. The LED filament lamp 600 may further comprise a driver for supplying power to the LEDs of the LED filament 100. The LED filament lamp 600 may alternatively comprise a LED filament arrangement configured to, in operation, emit LED filament arrangement light. The LED filament arrangement may comprise at least one LED filament 100, wherein the plurality of LEDs of the LED filament(s) 100 comprises a plurality of subsets of LEDs. The LED filament arrangement may further comprise a controller coupled to the plurality of subsets of LEDs, wherein the controller is configured to individually control the subsets of LEDs for controlling a level of a sparkling effect of the LED filament arrangement light.

[0055] 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 elongated carrier 110, the LEDs 120, 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, in operation, emit LED filament light (105), comprising an elongated carrier (110) comprising a first major surface (112), an array of a plurality of LEDs (120) arranged on the first major surface, wherein the plurality of LEDs is configured to emit LED light (125), an elongated encapsulant (130) comprising at least one of a luminescent material configured to at least partly convert the LED light emitted by the plurality of LEDs into converted light and a light scattering material configured to at least partly scatter the LED light into scattered light, wherein the elongated encapsulant at least partially covers the first major surface and at least partially encloses the array of the plurality of LEDs, and a plurality of elements (200) arranged on at least a part of the elongated encapsulant, wherein the plurality of elements comprises, at least one of, substantial transparent faceted particles (210), and substantial transparent lenslets (220), arranged to, at least one of, at least partially refract, at least partially disperse, at least partially reflect, and at least partially diffract, at least one of the converted light and the scattered light into the LED filament light., and wherein the plurality of elements constitutes a stack of at least two layers of elements.

2. The LED filament according to claim 1, wherein the plurality of elements constitutes at least one layer of elements arranged to at least partially cover the at least a part of the elongated encapsulant.

3. The LED filament according to claim 2, wherein the at least one layer of elements constitutes a retroreflector.

4. The LED filament according to any one of the preceding claims, further comprising a binder layer, wherein the binder layer is, at least one of, transparent, and white reflective, wherein the elements are attached to the elongated encapsulant by the binder layer.

5. The LED filament according to claim 4, wherein the binder layer comprises a polymer matrix, wherein the plurality of elements has a higher refractive index than the polymer matrix, and the plurality of elements is partially covered by the binder layer.

6. The LED filament arrangement according to any one of the preceding claims, wherein the elongated encapsulant comprises the luminescent material configured to at least partly convert the LED light emitted by the plurality of LEDs into the converted light, and wherein one of(i) the converted light, and(ii) the converted light and part of the emitted LED light, is white light having a correlated color temperature, CCT, in a range of 1700-6500K and a color rendering index, CRI, of at least 80.

7. The LED filament according to any one of the preceding claims, wherein a relationship between a thickness, TF, of the LED filament, and the diameter, DE, of the elements, fulfills 0.05-TF < DE < 0.5-TF.

8. The LED filament according to any one of the preceding claims, wherein the plurality of elements comprises transparent faceted particles (210), and wherein each transparent faceted particle of the transparent faceted particles comprises at least 7 facets.

9. The LED filament according to any one of the preceding claims, wherein the plurality of elements comprises transparent faceted particles (210), and wherein each faceted particle of the transparent faceted particles comprisesat least 2 facets at a first portion (300) of the faceted particle facing away from the elongated encapsulant, and at least 2 facets at a second portion (310) of the faceted particle facing the elongated encapsulant.

10. The LED filament according to any one of the preceding claims, wherein at least one of the plurality of elements having a thermal conductivity of at least 0.7 W / (m-K), and the plurality of elements comprises at least one material selected from the group consisting of glass, sapphire, spinel, A10N and quartz, is fulfilled.

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

12. The LED filament arrangement according to any one of the preceding claims, wherein the plurality of elements covers at least 80 % of the elongated encapsulant.

13. A LED filament arrangement configured to, in operation, emit LED filament arrangement light (000), comprising at least one LED filament according to any one of the preceding claims, wherein the plurality of LEDs comprises a plurality of subsets of LEDs, and a controller coupled to the plurality of subsets of LEDs, wherein the controller is configured to individually control the subsets of LEDs for controlling a level of a sparkling effect of the LED filament arrangement light.

14. A LED filament lamp (600), comprising at least one LED filament according to any one of claims 1-12 or the LED filament arrangement according to claim 13,a light transmissive envelope (610) at least partially enclosing the LED filament, and a base (620), wherein the base comprises a connector arranged to mechanically and electrically connect the LED lamp to a socket of a luminaire.

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