LED filament arrangement comprising a plurality of LED filaments

Abstract

There is provided a light emitting diode, LED, filament arrangement (100) for use in a LED filament lamp (900), configured to provide LED filament arrangement light (110). The LED filament arrangement comprises at least two LED filaments (115a, 115b) comprising an elongated carrier (120), a plurality of light emitting diodes, LEDs (130), an elongated primary encapsulant (160) at least partially enclosing the plurality of LEDs, wherein the primary elongated encapsulant comprises luminescent material configured to convert the emitted LED light into converted light (170), wherein the LED filaments are arranged in series, and wherein adjacently arranged LED filaments are mechanically and electrically coupled to each other at a respective coupling region (180). The LED filament arrangement further comprises an elongated secondary encapsulant (200) at least partially wrapping around a main portion of the LED filaments and configured to at least partially transmit and reflect the LED filament light.

Description

[0001] LED filament arrangement comprising a plurality of LED filaments

[0002] FIELD OF THE INVENTION

[0003] The present invention generally relates to a light emitting diode, LED, filament arrangement. More specifically, the present invention relates to a LED filament arrangement comprising a plurality of LED filaments.

[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 of particular interest to provide LED filaments which attain a vintage look, as these decor style LED filaments are very attractive.

[0008] 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, both during operation (on-state) as well as when switched off (off-state). SUMMARY OF THE INVENTION

[0009] 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 during on-state and off-state.

[0010] 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.

[0011] According to the present invention, there is provided a light emitting diode, LED, filament arrangement configured to provide, in an on-state, LED filament arrangement light. The LED filament arrangement is for use in a LED filament lamp.

[0012] The LED filament arrangement comprises at least two LED filaments configured to provide, during operation, LED filament light.

[0013] Each LED filament extends along a length axis, LX, and comprises an elongated carrier having a first major surface, a plurality of light emitting diodes, LEDs, arranged on the first major surface of the elongated carrier, wherein the plurality of LEDs is configured to emit LED light.

[0014] Each LED filament further comprises an elongated primary encapsulant at least partially covering the first major surface of the elongated carrier and at least partially enclosing the plurality of LEDs, wherein the primary elongated encapsulant comprises a luminescent material configured to at least partly convert the emitted LED light into converted light.

[0015] The at least two LED filaments are arranged in series, wherein adjacently arranged LED filaments of the at least two LED filaments are mechanically and electrically coupled to each other at a respective coupling region in such a way that their respective length axes, LX, have a deflection angle in a range from 0 to 80 degrees.

[0016] The LED filament arrangement further comprises an elongated secondary encapsulant enclosing each coupling region and at least partially wrapping around a main portion of the at least two LED filaments, and wherein the elongated secondary encapsulant is configured to at least partially transmit and at least partially reflect the LED filament light. Thus, the present invention is based on the idea of providing a LED filament arrangement comprising two or more LED filaments which are coupled together in an end-to- end manner, wherein an elongated secondary encapsulant is applied over the LED filaments as well as over the coupling region(s) between the LED filaments, and is configured to at least partially transmit and reflect the LED filament light.

[0017] The present invention is advantageous in that the elongated secondary encapsulant at least partially covers a main portion of the LED filaments such that the LED filaments may be perceived as a single filament. This single-filament perception of the LED filament is aesthetically attractive.

[0018] The present invention is further advantageous in that the transmissive and reflective properties of the elongated secondary encapsulant improves the performance and functionality of the LED filament concerning its light distribution, as well as the appearance and the decorative aspect thereof.

[0019] It will be appreciated that the elongated primary encapsulants of the LED filaments may have a yellow-orange color which, by the construction of the LED filament, may be at least partially hidden by the elongated secondary encapsulant. This efficiently and conveniently augments the decorative aspect of the LED filament.

[0020] The present invention is further advantageous in that the properties of the elongated secondary encapsulant may be easily and conveniently customized for desired properties of the light distribution from the LED filament arrangement, as well as the aesthetic appearance of the LED filament arrangement. More specifically, properties of the elongated secondary encapsulant such as e.g. transmissivity, reflectivity, thickness, porosity, etc. may be set or tuned for different purposes. For example, the elongated secondary encapsulant may render a white off-state appearance of the LED filament arrangement, optimize the hiding of the yellow-orange color of the elongated primary encapsulant whilst maintaining an aesthetically attractive LED filament look, etc.

[0021] 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.

[0022] The present invention is further advantageous in that the LED filament arrangement of the present invention comprises relatively few components. The low number of components is advantageous in that the LED filament arrangement is relatively inexpensive to fabricate. Moreover, the low number of components of the LED filament arrangement 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.

[0023] There is provided a light emitting diode, LED, filament arrangement for use in a LED filament lamp, configured to provide, in an on-state, LED filament arrangement light. In embodiments, the LED filament arrangement light may be white light having a correlated color temperature, CCT, in a range from 2000 to 6500 K, and preferably a color rendering index, CRI, of at least 80, or at least 85. The LED filament arrangement comprises at least two LED filaments configured to provide, during operation, LED filament light. Preferably, each LED filament has a length, LF, and a width, WF, wherein LF > 5WF or even LF > 10WF. The LED filament may be arranged in a straight configuration or in a non-straight configuration such as for example a curved configuration, a 2D / 3D spiral or a helix. The LED filament has a light-emitting surface that extends along the length, and preferably at least partly around the axis of elongation. The light-emitting surface is preferably arranged to homogenously emit light and / or to emit light omnidirectionally.

[0024] Each LED filament extends along a length axis, LX, and comprises an elongated carrier, a plurality of light emitting diodes, LEDs, arranged on a first major surface of the elongated carrier, wherein the plurality of LEDs is configured to emit LED light. The elongated carrier may, for instance, be a substrate, that may be rigid (made from e.g. a polymer, glass, quartz, metal or sapphire) or flexible (e.g. made of a polymer or metal e.g. a film or foil). The elongated carrier may be reflective or light transmissive, such as translucent and preferably transparent. The plurality of LEDs may be arranged on the first major surface of the elongated carrier in a linear array. By the term “array”, it is here meant a linear arrangement or chain of LEDs, or the like.

[0025] Each LED filament further comprises an elongated primary encapsulant at least partially covering the first major surface of the elongated carrier and at least partially enclosing the plurality of LEDs, wherein the primary elongated encapsulant comprises luminescent material configured to at least partly convert the emitted LED light into converted light. By the term “encapsulant”, it is here meant an elongated material, element, arrangement, or the like, which in the present context is configured or arranged to at least partially cover, surround, encapsulate and / or enclose the first major surface of the elongated carrier and the plurality of LEDs. The encapsulant may be a polymer material which may be flexible such as for example a silicone. The luminescent material of the elongated primary encapsulant may be a phosphor such as an inorganic phosphor and / or quantum dots or rods.

[0026] The at least two LED filaments are arranged in series, wherein adjacently arranged LED filaments of the at least two LED filaments are mechanically and electrically coupled to each other at a respective coupling region in such a way that their respective length axes, LX, have a deflection angle in a range from 0° to 80°. Hence, the two or more (plurality of) LED filaments are arranged one after the other in a row or in series, whereby adjacently arranged LED filaments are mechanically and electrically coupled or connected to each other at a respective coupling region (i.e. each coupling region is provided between two adjacently arranged LED filaments). Hence, by the term “coupling region”, it is here meant a region or part of the LED filament arrangement which may comprise one or more connecting (connector) elements arranged to enable mechanical and / or electrical contact between adjacently arranged LED filaments of the at least two LED filaments of the LED filament arrangement. Furthermore, the at least two LED filaments are coupled such that their respective length axes, LX, have a deflection angle in a range from 0° to 80°. In case the deflection angle is 0°, or substantially 0°, the at least two LED filaments are arranged in series along a common length axis, CLX, of the LED filament arrangement. In case the deflection angle is different from 0°, the at least two LED filaments may form one or more kinks, and may hereby, for example, form a sawtooth shape. In embodiments, the deflection angle may be in a range from 0° to 60°, preferably in a range from 0° to 40°, more preferably in a range from 0° to 20°, and most preferably in a range from 0° to 3°.

[0027] The LED filament arrangement further comprises an elongated secondary encapsulant enclosing each coupling region at least partially wrapping around a main portion of the LED filaments. Alternatively, the elongated secondary encapsulant encloses each coupling region by being arranged at least partially in abutment with a main portion of the LED filaments. According to yet another alternative, the elongated secondary encapsulant encloses each coupling region, is arranged at least partially in abutment with a main portion of the LED filaments and at least partially covers a main portion of the LED filaments. Hence, the LED filaments, of which each comprises an elongated primary encapsulant, are in turn at least partially covered by an elongated secondary encapsulant which is wrapped around a main portion of the LED filaments, wherein the elongated secondary encapsulant furthermore at least partially encloses the coupling region(s) between the LED filaments. The elongated secondary encapsulant is configured to at least partially transmit and at least partially reflect the LED filament light.

[0028] The elongated secondary encapsulant may further be configured to diffuse the converted light, and optionally part of (non-converted) LED light, into the LED filament light. The elongated secondary encapsulant hereby influences the converted light (and optionally part of the LED light) as emitted via the elongated primary encapsulant by diffusing the converted light into the LED filament light as emitted by the LED filament during operation.

[0029] According to an embodiment of the present invention, the elongated secondary encapsulant may fully cover each elongated primary encapsulant. Hence, the elongated secondary encapsulant may hide each elongated primary encapsulant. The present embodiment is advantageous in that the total coverage of all elongated primary encapsulants by the elongated secondary encapsulant provides an even more aesthetically appealing lighting arrangement. For example, the elongated secondary encapsulant may hereby even more efficiently cover any yellow-orange color of the elongated primary encapsulant. Furthermore, by the full coverage of each elongated primary encapsulant, the elongated secondary encapsulant may to an even higher extent attain the look or perception of a singlefilament arrangement. The present embodiment is advantageous in that the total coverage of all elongated primary encapsulants by the elongated secondary encapsulant may provide an even more desirable lighting distribution of the LED filament arrangement during operation.

[0030] According to an example of the present invention, the elongated secondary encapsulant may appear white when the LED filament arrangement is in an off-state. Hence, the properties of the elongated secondary encapsulant may cause the elongated secondary encapsulant to appear white or whitish when the LED filament is in an off-state, i.e. rendering the elongated secondary encapsulant white or whitish (for an observer of the LED filament), when the LED filament is in an off-state (i.e. switched off). The obtained effect is a visually attractive off-state white appearance of the LED filament. More specifically, the LED filament arrangement may hereby attain a vintage look, and it will be appreciated that a decor style LED filament arrangement of this kind is considered very attractive. The present example is further advantageous in that it may also provide an improved optical performance. Hence, the present example is advantageous in that the white color as provided by the elongated secondary encapsulant renders the LED filament attractive for an observer, and that an improved lighting performance also may be attained. According to an example of the present invention, the elongated secondary encapsulant may comprise a light scattering material configured to at least partially diffusely transmit and at least partially diffusely reflect the LED filament light. Hence, the light scattering material of the elongated secondary encapsulant may be configured or arranged to at least partially diffusely transmit and diffusely reflect the LED filament light. By “diffusely transmit”, it is here meant that the light scattering material is configured to transmit the LED filament light whilst providing diffusion of the LED filament light upon transmission. By “diffusely reflect”, it is here meant that the light scattering material is configured to reflect the LED filament light whilst providing diffusion of the LED filament light upon reflection. The present example is advantageous in that the diffusive property of the elongated secondary encapsulant may achieve an omnidirectional, or at least almost omnidirectional, light distribution via the diffusive transmission and reflection. The present example is further advantageous in that the elongated secondary encapsulant’ s reflectivity may even further enhance the effect of masking or hiding a yellow-orange color of the elongated primary encapsulant. The present example is hereby advantageous in that an attractive off-state white LED filament arrangement having an improved optical performance is achieved.

[0031] According to an embodiment of the present invention, the elongated secondary encapsulant may appear white when the LED filament arrangement is in an off-state, and the elongated secondary encapsulant may comprise a light scattering material configured to at least partially diffusely transmit and at least partially diffusely reflect the LED filament light. The present embodiment is advantageous in that the white color as provided by the elongated secondary encapsulant renders the LED filament attractive for an observer, and that an improved lighting performance also may be attained by the light scattering material.

[0032] According to an embodiment of the present invention, the elongated secondary encapsulant may comprise a coating comprising a polymer matrix, wherein the elongated secondary encapsulant is applied onto the elongated primary encapsulant. Alternatively, the elongated secondary encapsulant may constitute (i.e. be) a coating comprising a polymer matrix, wherein the elongated secondary encapsulant (i.e. the coating) is applied onto the elongated primary encapsulant. By “coating”, it is here meant a material, element, or the like, arranged or configured to coat or cover the elongated secondary encapsulant. The present embodiment is advantageous in that the coating comprising (or constituting) the polymer matrix is particularly efficient for light-scattering purposes, consequently leading to an even more appealing LED filament light and / or an even more desired light distribution. According to an example of the present invention, the polymer matrix of the coating may comprise particles of at least one of TiCL, BaSCU, and AI2O3, dispersed in the polymer matrix. Hence, the polymer matrix of the coating of the elongated secondary encapsulant may comprise particles of one or more of TiCL, BaSCU, and AI2O3 dispersed in the polymer matrix. The present example is advantageous in that the mentioned particle compositions are particularly suitable as light-scattering material, thereby even further improving the light distribution properties of the LED filament arrangement.

[0033] According to an embodiment of the present invention, the elongated secondary encapsulant, at each coupling region, may define a respective light-mixing chamber of each coupling region, wherein the light-mixing chamber is arranged to mix LED filament light emitted by the adjacently arranged LED filaments of the respective coupling region. Hence, the elongated secondary encapsulant, which at least partially covers a main portion of the LED filaments and encloses each coupling region, defines (or creates) a light-mixing chamber of each coupling region between adjacently arranged LED filaments. By “light-mixing chamber”, it is here meant that the reflectivity properties of the elongated secondary encapsulant, defining the light-mixing chamber, provide the possibility for the converted light from the (adjacently arranged) LED filaments to reflect and to mix before transmission through (via) the elongated secondary encapsulant as LED filament light.

[0034] According to an embodiment of the present invention, the respective lightmixing chamber comprises a cavity being free from a luminescent material and dispersed reflecting particles. Hence, the light-mixing chamber, which is defined by the elongated secondary encapsulant as it encloses the coupling region(s) between adjacently arranged LED filaments, comprises (defines) a cavity (e.g. a void) which does not contain any luminescent material, nor any (dispersed) reflective particles. Furthermore, according to an example, a respective portion of the elongated secondary encapsulant, at each coupling region, may be free from (dispersed) reflective particles. Hence, the elongated secondary encapsulant may be constructed and arranged in the LED filament arrangement such that it does not contain (dispersed) reflective particles at each coupling region of the LED filament which the elongated secondary encapsulant is arranged to at least partially enclose.

[0035] According to an embodiment of the present invention, the respective cavity may comprise one of silicone and gas. Alternatively, the respective cavity may comprise another light transmissive material, e.g. (a) transparent polymer.) Hence, the respective cavity may comprise silicone or gas. For example, the respective cavity may comprise crosslinked polydimethylsiloxane (PDMS). In case the respective cavity comprises gas, the gas may be air or helium (He).

[0036] According to an embodiment of the present invention, the LED filament arrangement may comprise N LED filaments, wherein 3 < N < 5. Hence, the LED filament arrangement may comprise between three and five LED filaments arranged in series, e.g. along a common length axis, CLX, of the LED filament arrangement.

[0037] According to an example of the present invention, adjacent ends of the elongated primary encapsulants of the LED filaments are separated by a distance di, and at least one of the following is fulfilled: (i) di < 0.2-Li, and (ii) di < 4-Ti, Li being a length of any of the LED filaments, and Ti being a thickness of any of the LED filaments.

[0038] Hence, adjacent LED filaments may be arranged in series such that they are spaced apart by a distance, di, which is smaller than a fifth of the length, Li, of any of the LED filaments. Preferably di < 0.15-Li, more preferably di < 0.1 -Li, and most preferably di < 0.05-Li. It should be noted that the distance, di, may constitute a length dimension of the light-mixing chamber(s), as the light-mixing chamber(s) may be defined by the elongated secondary encapsulant at each coupling region according to an embodiment of the present invention. The present example is advantageous in that the aesthetic appearance of the LED filament arrangement is optimized.

[0039] According to an example of the present invention, a distance, di, between adjacent ends of adjacent LED filaments along a common length axis, CLX, of the LED filament arrangement, and a thickness, Ti, of any of the LED filaments, may fulfil di < 4-Ti. Hence, the distance, di, between adjacent ends of adjacent LED filaments along the common length axis, CLX, may be smaller than four times the thickness, Ti. Preferably di < 3-Ti, more preferably di < 2-Ti, most preferably di < Ti. The present example is advantageous in that the aesthetic appearance of the LED filament arrangement is optimized.

[0040] According to an embodiment of the present invention, a distance, di, between adjacent ends of the elongated primary encapsulants of adjacent LED filaments along a common length axis, CLX, of the LED filament arrangement, and at least one of a length, Li, of any of the LED filaments, whereby di < 0.2-Li, and a thickness, Ti, of any of the LED filaments, whereby di < 4-Ti, is fulfilled. Hence, the distance, di, between adjacent ends of adjacent LED filaments along the common length axis, CLX, may be smaller than a fifth of the length, Li, of any of the LED filaments and / or smaller than four time the thickness, Ti, of any of the LED filaments. The present embodiment is advantageous in that the aesthetic appearance of the LED filament arrangement is optimized.

[0041] According to an embodiment of the present invention, the elongated secondary encapsulant fully covers each elongated primary encapsulant, wherein the elongated secondary encapsulant has a first portion at the coupling region and a second portion different from the first portion, the first portion having a diameter Di, and the second portion having a diameter D2, and wherein 0.7-Di < D2 < 1.3-Di.

[0042] Hence, the diameter, Di, of a respective portion of the elongated secondary encapsulant, at each coupling region, and the diameter, D2, of a part of the elongated secondary encapsulant, different from the respective portion of the elongated encapsulant, at each coupling region, may be similar, or may even be (approximately) the same. Preferably, 0.8-Di < D2 < 1.2-Di, more preferably 0.9-Di < D2 < 1.1-Di, and most preferably 0.95-Di < D2 < 1.05-Di. As the width (diameter) of the LED arrangement along the common length axis, CLX, of the LED filament is approximately the same, the present embodiment is advantageous in that the impression of a single LED filament is increased even further.

[0043] According to an embodiment of the present invention, the LED filament arrangement may further comprise an elongated third encapsulant arranged between the elongated primary encapsulant and the elongated secondary encapsulant, wherein the elongated third encapsulant encloses each coupling region. In embodiments, the elongated third encapsulant may fully cover or fully enclose the elongated primary encapsulant. In embodiments, the elongated second encapsulant may fully cover or fully enclose the elongated third encapsulant. In embodiments, the elongated third encapsulant may have a thickness 0.5 to 2 times the thickness of the elongated first encapsulant. In embodiments, the elongated third encapsulant may have a thickness 0.5 to 2 times the thickness of the elongated second encapsulant. Preferably, the elongated third encapsulant is translucent, more preferably transparent.

[0044] According to an embodiment of the present invention, the elongated carrier may be light transmissive, wherein the elongated primary encapsulant and the elongated secondary encapsulant may at least partially cover a second major surface, opposite the first major surface, of the elongated carrier. The present embodiment is advantageous in that the light transmissive elongated carrier may achieve an (almost) omnidirectional light distribution of the LED filament arrangement. The present embodiment is further advantageous in that the elongated primary and secondary encapsulants may influence the light transmitted via the second major surface, due to the light transmissive property of the elongated carrier, thereby even further enhancing the aesthetical appearance of the LED filament arrangement during operation.

[0045] According to an example of the present invention, the elongated primary encapsulant and the elongated secondary encapsulant may comprise a same polymer matrix material. The present embodiment is advantageous in that the LED filament arrangement is conveniently produced by the same polymer matrix material of the elongated primary and secondary encapsulants, consequently leading to cost- and / or time-efficiency of the production process of the LED filament arrangement.

[0046] According to an example of the present invention, the elongated primary encapsulant, in a first direction, B, perpendicular to the length axis, LX, has a first thickness, Ti, and the elongated secondary encapsulant, in the first direction, B, has a second thickness, T2, wherein T2 > 1.5-Ti. Hence, the elongated primary and secondary encapsulants may have respective thicknesses, Ti, T2, along the first direction, B, wherein the second thickness, T2, of the elongated secondary encapsulant is thicker than the first thickness, Ti, of the elongated primary encapsulant, by at least a factor 1.5. The present example is advantageous in that the second thickness, T2, of the elongated secondary encapsulant is thick enough to mask and / or hide the yellow-orange color of the elongated primary encapsulant(s). The present embodiment is further advantageous in that the elongated secondary encapsulant has a sufficient second thickness, T2, for obtaining its desired properties while the elongated primary encapsulant is kept relatively thin, resulting in a relatively slim LED filament arrangement.

[0047] According to an embodiment of the present invention, T2 < 5-Ti. Hence, the second thickness, T2, of the elongated secondary encapsulant may be less than five times as thick as the first thickness, Ti, of the elongated primary encapsulant. The present embodiment is advantageous in that the second thickness, T2, of the elongated secondary encapsulant is thin enough to retain / maintain the filament look of the LED filament arrangement, thereby retaining / maintaining the aesthetically attractive appearance of the (off-state white) LED filament arrangement. In case of a combination of the present and previous embodiments of the LED filament arrangement, i.e. that the relation between the thicknesses, Ti, T2, of the elongated primary and secondary encapsulants fulfils 1.5-Ti < T2 < 5-Ti, the second thickness, T2, of the elongated secondary encapsulant is thick enough to mask and / or hide the yellow- orange color of the elongated primary encapsulant, to achieve a sufficient scattering of ambient light, the converted light and / or non-converted LED light, whilst at the same time being thin enough to retain / maintain the aesthetically attractive appearance of the LED filament arrangement.

[0048] According to an embodiment of the present invention, Ti is in a range from 1 mm to 2 mm, T2 is in a range from 3 mm to 5 mm, and the reflectivity of the elongated secondary encapsulant is in a range from 25% to 48%. The present embodiment is advantageous in that the described thicknesses, Ti, T2, of the elongated primary and secondary encapsulants, respectively, together with the elongated secondary encapsulant’ s reflectivity, even further enhance the effects of masking and / or hiding the yellow-orange color of the elongated primary encapsulant, the beneficial optical properties of the LED filament arrangement, as well as the aesthetical attractiveness of the LED filament arrangement. More specifically, the present embodiment is advantageous in that the effect of an attractive off- state white LED filament arrangement having an improved optical performance is achieved.

[0049] According to an example of the present invention, the elongated secondary encapsulant may have a length, Ls, and a thickness, Ts, wherein Ls > 5-Ts.

[0050] According to an example of the present invention, the elongated secondary encapsulant may have a length, Ls, a width, Ws, wherein Ls > 5 Ws.

[0051] According to an example of the present invention, the elongated secondary encapsulant may have a width, Ws, in a range from 2 mm to 12 mm.

[0052] According to an embodiment of the present invention, the elongated secondary encapsulant may have a length, Ls, a width, Ws, and a thickness, Ts, wherein Ls > 5-Ts, Ls > 5 Ws and Ws is in a range from 2 mm to 12 mm. Preferably, Ls > 7-Ts and Ls > 5-Ws, more preferred Ls > 9-Ts and Ls > 9-Ws, and most preferred Ls > 10-Ts and Ls > 10-Ws. Preferably, Ws is in a range from 2 mm to 10 mm, more preferably 2 mm to 8 mm, and most preferably 2 mm to 7 mm.

[0053] According to an embodiment of the present invention, there is provided a LED filament device. The LED filament arrangement may comprise at least one LED filament arrangement according to any one of the preceding embodiments, and a transparent tube enclosing the at least one LED filament arrangement. The present embodiment is advantageous in that the attractiveness of the off-state white appearance of the LED filament arrangement is enhanced even further due to the (modest) reflective properties of the transparent tube. The present embodiment is further advantageous in that the transparent tube provides an ingress protection of the LED filament arrangement. According to an embodiment of the present invention, there is provided a LED filament lamp. The LED filament lamp comprises one of at least one LED filament arrangement according to any one of the preceding embodiments, and the LED filament device according to the previous embodiment. The LED filament lamp further comprises a light-transmissive envelope at least partly enclosing the at least one LED filament arrangement, and a connector for electrically and mechanically connecting the LED filament lamp to a socket of a luminaire. Hence, the LED filament lamp comprises one or more LED filament arrangements, which in turn comprises a plurality of LED filaments. The present embodiment is advantageous in that the LED filament lamp, comprising the LED filaments, 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.

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

[0055] Further objectives of, features of, and advantages with, the present invention will become apparent when studying the following detailed disclosure, the drawings and the appended claims. Those skilled in the art will realize that different features of the present invention can be combined to create embodiments other than those described in the following.

[0056] BRIEF DESCRIPTION OF THE DRAWINGS

[0057] 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.

[0058] Fig. 1 shows a LED filament lamp according to the prior art,

[0059] Fig. 2 schematically shows a LED filament arrangement according to an exemplifying embodiment of the present invention,

[0060] Fig. 3 schematically shows a lighting device comprising at least one LED filament arrangement according to an exemplifying embodiment of the present invention. Fig. 4 shows a LED filament lamp comprising a LED filament arrangement according to an exemplifying embodiment of the present invention.

[0061] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0062] 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.

[0063] Fig. 2 schematically shows a cross-section of a LED filament arrangement 100 according to an exemplifying embodiment of the present invention. The LED filament arrangement 100 for use in a LED filament lamp is configured to provide (emit), in an on- state, LED filament arrangement light 110. The LED filament arrangement 100 comprises at least two LED filaments 115a-d. In Fig. 2, the LED filament arrangement 100 is exemplified as having four LED filaments 115a-d, but it should be noted that the number of LED filaments 115a-d is substantially arbitrary. For example, the LED filament arrangement 100 may comprise (exactly) two LED filaments 115a-d. According to another example, the LED filament arrangement 100 may comprise N LED filaments, wherein 2 < N < 7 or 3 < N < 5. The LED filaments 115a-d are configured to provide, during operation, LED filament light 118. Each LED filament 115a-d 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 each LED filament 115a-d may comprise substantially any number of array(s) of the plurality of LEDs 130. The plurality of LEDs 130 preferably comprises more than 5 LEDs, more preferably more than 8 LEDs, and even more preferred more than 10 LEDs. The plurality of LEDs 130 may be direct emitting LEDs which provide a color. The plurality of LEDs 130 is configured to emit LED light 150. Each LED filament 115a-d further comprises an elongated primary encapsulant 160 which at least partially covers the first major surface 145 of the elongated carrier 120 and at least partially encloses the plurality of LEDs 130. The elongated primary encapsulant 160 comprises a luminescent material configured to at least partly convert the emitted LED light 150 into converted light 170. The luminescent material of the elongated primary encapsulant 160 may be a light-scattering material, e.g. a polymer matrix comprising BaSCU, AI2O3 and / or TiCE particles. The luminescent material of the elongated primary encapsulant 160 may be a phosphor such as an inorganic phosphor (e.g. YAG, LuAG, ECAS, KSiF, etc.) and / or quantum dots or rods. The phosphor may further be e.g. a (blue) green / yellow and / or red phosphor. Although not shown, a concentration of the luminescent material in the elongated primary encapsulant 160 may vary over the length of the LED filament(s) 115a-d.

[0064] The at least two LED filaments 115a-d are arranged in series along a common length axis, CLX, of the LED filament arrangement 100. Adjacently arranged LED filaments 115a-d of the at least two LED filaments are mechanically and electrically coupled to each other at a respective coupling region 180a-c in such a way that their respective length axes, LX, have a deflection angle in a range from 0° to 80°. According to the example of Fig. 2, the four LED filaments 115a-d are arranged one after the other in a row or in series, whereby adjacently arranged LED filaments 115a-d are mechanically and electrically coupled or connected to each other at a respective coupling region 180a-c. Here, the deflection angle is 0°, or substantially 0°, such that the at least two LED filaments 115a-d are arranged in series in an aligned manner. According to one or more alternatives not shown in Fig. 2, the at least two LED filaments 115a-d may form kinks in case the deflection angle is different from 0°, and may, for example, for a sawtooth shape. In more general terms, the LED filament arrangement 100 comprises N LED filaments 115a-d (whereby N > 2) and N-l coupling region(s) 180a-c (whereby N > 1), wherein a (single) coupling region 180a-c is respectively provided between two adjacently arranged LED filaments 115a-d of the at least two LED filaments 115a-d. The coupling regions 180a-c of the LED filament arrangement 100 each comprises a connecting (connector) element 250 (e.g. an electrical wire) arranged to enable electrical contact between adjacently arranged LED filaments 115a-d of the LED filament arrangement 100. The connecting (connector) element 250, or any other element, may furthermore provide mechanical contact between adjacently arranged LED filaments 115a-d of the LED filament arrangement 100. The LED filament arrangement 100 further comprises an elongated secondary encapsulant 200 which encloses each coupling region 180a-c. Furthermore, the elongated secondary encapsulant 200 at least partially covers a main portion of the at least two LED filaments 115a-d. Alternatively, the elongated secondary encapsulant 200 encloses each coupling region 180a-c, is arranged at least partially in abutment with a main portion of the at least two LED filaments 115a-d and at least partially covers a main portion of the at least two LED filaments 115a-d. According to an example, the elongated secondary encapsulant 200 may fully cover each elongated primary encapsulant 160 of the respective LED filaments 115a-d. The LED filament arrangement 100 may even comprise an elongated third encapsulant (not shown) arranged between the elongated primary encapsulant 160 and the elongated secondary encapsulant 200. The elongated third encapsulant may enclose each coupling region.

[0065] The elongated secondary encapsulant 200 is configured to at least partially transmit and at least partially reflect the LED filament light 118. The elongated secondary encapsulant 200 may appear white when the LED filament arrangement 100 (and accordingly, the LED filaments 115a-d) is (are) in an off-state. The elongated secondary encapsulant 200 may comprise a light scattering material configured to at least partially diffusely transmit and at least partially diffusely reflect the LED filament light 118. The elongated secondary encapsulant 200 may comprise a coating comprising a polymer matrix, wherein the elongated secondary encapsulant 200 is applied onto the elongated primary encapsulant 160. The polymer matrix may comprise particles of at least one of TiCL, BaSCU, and AI2O3, dispersed in the polymer matrix. The elongated secondary encapsulant may have a length, Ls, a width, Ws, and a thickness, Ts, wherein Ls > 5-Ts, Ls > 5 Ws and Ws is in a range from 2 mm to 12 mm.

[0066] In Fig. 2, the LED filament arrangement 100 is exemplified such that the elongated secondary encapsulant 200 thereof, at each coupling region 180a-c, defines a respective light-mixing chamber 300 of each coupling region 180a-c. Each light-mixing chamber 300 is arranged to mix the LED filament light 118 emitted by the adjacently arranged LED filaments 115a-c of the respective coupling region 180a-c. Hence, the elongated secondary encapsulant 200, which at least partially covers a main portion of the LED filaments 115a-c and encloses each coupling region 180a-c, defines (or creates) a respective light-mixing chamber 300 of each coupling region 180a-c between adjacently arranged LED filaments 115a-c. Furthermore, according to this example of the LED filament arrangement 100, the respective light-mixing chamber 300 comprises a cavity 310 being free from a luminescent material and (dispersed) reflective particles. The cavity 310 may comprise silicone or a gas. For example, the cavity 310 may comprise crosslinked polydimethylsiloxane (PDMS), or in the case of gas, the cavity 310 may comprise air or helium (He). Furthermore, a respective portion of the elongated secondary encapsulant 200, at each coupling region 180a-c, may be free from (dispersed) reflective particles. The adjacently arranged LED filaments 115a-d may have a distance, di, between adjacent ends 410a, 410b of the elongated primary encapsulants 160 of these LED filaments 115a-d. This distance, di, along the common length axis, CLX, and a length, Li, of any of the LED filaments 115a-d, may fulfil di < 0.2-Li. Hence, adjacent LED filaments 115a-d may be arranged in series such that they are spaced apart by a distance, di, which is smaller than a fifth of the length, Li, of any of the LED filaments. As indicated in Fig. 2, the distance, di, may constitute a length dimension of the light-mixing chamber(s) 300, as the light-mixing chamber(s) 300 may be defined by the elongated secondary encapsulant 200 at each coupling region 180.

[0067] The distance, di, between adjacent ends 410a, 410b of adjacent LED filaments 115a-d along the common length axis, CLX, of the LED filament arrangement 100 and a thickness, Ti, of any of the LED filaments 115a-d, may fulfil di < 4-Ti. Hence, the distance, di, between adjacent ends 410a, 410b of adjacent LED filaments 115a-d along the common length axis, CLX, may be smaller than four times the thickness, Ti, of any of the LED filaments 115a-d.

[0068] The LED filament arrangement 100 may further comprise a transparent tube 810, e.g. by glass, enclosing the LED filaments 115a-d, constituting a LED filament device. It should be noted that the transparent tube 810 may be in physical contact with the LED filaments 115a-d or be physically separated from the LED filaments 115a-d.

[0069] Fig. 3 schematically shows a lighting device with a plurality of LED filament arrangements 100. Here, the number of LED filament arrangements 100 is four, but it will be appreciated that the number of LED filament arrangements 100 is substantially arbitrary. One of the LED filament arrangements 100 is indicated as having four LED filaments 115a-d, in accordance with Fig. 2, but is should be noted that the number is substantially arbitrary. Furthermore, the different LED filament arrangements 100 in Fig. 3 may each have a different number of LED filaments. Each LED filament arrangement 100 further comprises an elongated secondary encapsulant 200 which at least partially covers a main portion of the LED filaments 115a-d.

[0070] Fig. 4 schematically shows a LED filament lamp 900 according to an embodiment of the present invention. The LED filament lamp 900, which may constitute substantially any kind of lamp or luminaire, comprises one or more LED filament arrangements 100 according to any one of the previously described embodiments. The LED filament lamp 900 further comprises a light-transmissive envelope 910, which is exemplified as being bulb-shaped. The light-transmissive envelope 910 at least partially encloses the LED filament arrangement(s) 100. The LED filament lamp 900 further comprises a connector 920 for electrically and mechanically connecting the LED filament lamp 900 to a socket of a luminaire. The LED filament lamp 900 may further comprise a controller 930 configured to control the luminous flux of the LED filament light. The controller 930 is schematically indicated by a dashed rectangle in the connector 920, but it should be noted that the controller 930 may be arranged at substantially any position or place. The controller 930 may, for example, be able to control each LED filament of the LED filament arrangement 100 individually. 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 arrangement 100, the elongated primary encapsulant 160, the elongated secondary encapsulant 200, etc., may have different shapes, dimensions and / or sizes than those depicted / described.

Claims

CLAIMS:

1. A LED filament arrangement (100) comprising two LED filaments (115a, 115b) for emitting LED filament light (118), each LED filament (115a, 155b) extending along a length axis, and comprising: an elongated carrier (120) having a first major surface (145), a plurality of LEDs (130) for emitting LED light (150), the plurality of LEDs (130) being arranged on the first major surface (145), an elongated primary encapsulant (160) at least partially covering the first major surface (145) and at least partially enclosing the plurality of LEDs (130), the elongated primary encapsulant (160) comprising a luminescent material for at least partly converting the LED light (150) into converted light (170), wherein the two LED filaments (155a, 155b) are arranged in series and mechanically and electrically coupled to each other at a coupling region (180) in such a way that their respective length axes have a deflection angle in a range from 0 to 80 degrees, wherein the LED filament arrangement (100) further comprises an elongated secondary encapsulant (200) enclosing the coupling region (180) and at least partially wrapping around a main portion of the two LED filaments (155a, 155b), and wherein the elongated secondary encapsulant (200) is configured to at least partially transmit and at least partially reflect the LED filament light (188).

2. The LED filament arrangement (100) according to claim 1, wherein the elongated secondary encapsulant (200) fully covers each elongated primary encapsulant (160).

3. The LED filament arrangement (100) according to claim 1 or 2, wherein the elongated secondary encapsulant (200) appears white when the LED filament arrangement (100) is in an off-state, and wherein the elongated secondary encapsulant (200) comprises a light scattering material for at least partially diffusely transmitting and at least partially diffusely reflecting the LED filament light (188).

4. The LED filament arrangement (100) according to any one of the preceding claims, wherein the elongated secondary encapsulant (200) comprises a coating having a polymer matrix, and wherein the elongated secondary encapsulant (200) is applied onto the elongated primary encapsulant (160).

5. The LED filament arrangement (100) according to any one of the preceding claims, wherein, at the coupling region (180), the elongated secondary encapsulant (200) defines a light-mixing chamber (300), and wherein the light-mixing chamber (300) is arranged to mix the LED filament light (118).

6. The LED filament arrangement (100) according to claim 5, wherein the light mixing chamber (300) comprises a cavity (310), and wherein the cavity (310) is free from a luminescent material and from reflective particles.

7. The LED filament arrangement (100) according to claim 6, wherein the cavity (310) comprises one of silicone and a gas.

8. The LED filament arrangement (100) according to any one of the preceding claims, wherein the LED filament arrangement (100) comprises N LED filaments, and wherein 3 < N < 5.

9. The LED filament arrangement (100) according to any one of the preceding claims, wherein adjacent ends (410a, 410b) of the elongated primary encapsulants (160) of the LED filaments (115a, 115b) are separated by a distance di, and wherein at least one of the following is fulfilled: di < 0.2-Li, and di < 4-Ti,Li being a length of any of the LED filaments (155a, 155b), and Ti being a thickness of any of the LED filaments (155a, 155b).

10. The LED filament arrangement (100) according to any one of the preceding claims, wherein the elongated secondary encapsulant (200) fully covers each elongated primary encapsulant (160), wherein the elongated secondary encapsulant (200) has a firstportion at the coupling region (180) and a second portion different from the first portion, the first portion having a diameter Di, and the second portion having a diameter D2, and wherein 0.7-Di < D2< 1.3-Di.

11. The LED filament arrangement (100) according to any one of the preceding claims, wherein the LED filament arrangement (100) further comprises an elongated third encapsulant arranged between the elongated primary encapsulant (160) and the elongated secondary encapsulant (200), and wherein the elongated third encapsulant encloses the coupling region (180).

12. The LED filament arrangement (100) according to any one of the preceding claims, wherein the elongated carrier (120) is light transmissive, wherein the elongated carrier (120) has a second major surface opposite the first major surface (145), and wherein the elongated primary encapsulant (160) and the elongated secondary encapsulant (200) at least partially cover the second major surface.

13. The LED filament arrangement (100) according to any one of the preceding claims, wherein the elongated secondary encapsulant (200) has a length Ls, a width Ws, and a thickness Ts, and wherein Ls > 5-Ts, Ls > 5 Ws, and Ws is in a range from 2 mm to 12 mm.

14. A LED filament device comprising the LED filament arrangement (100) according to any one of the preceding claims, wherein the LED filament device further comprises a transparent tube (810) enclosing the LED filament arrangement (100).

15. A LED filament lamp (900) comprising the LED filament arrangement (100) according to any one of claims 1-13, wherein the LED filament lamp (900) further comprises a light-transmissive envelope (910) enclosing the LED filament arrangement (100), and a connector (920) for electrically and mechanically connecting the LED filament lamp (900) to a socket of a luminaire.

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