Led filament comprising an encapsulant

Abstract

A light emitting diode, LED, filament (100) is provided, configured to provide an LED filament light (110). The LED filament extends along a length axis LX and comprises an elongated carrier (120) and LEDs (130) arranged on a first major surface (145) of the elongated carrier, wherein the LEDs are configured to emit LED light (150). The LED filament further comprises a first elongated encapsulant (200) at least partly covering the elongated carrier and at least partly enclosing the LEDs, wherein the first elongated encapsulant comprises a luminescent material configured to convert the emitted LED light into first converted light (210). The LED filament further comprises a second elongated encapsulant (300) at least partly enclosing the first elongated encapsulant, wherein the second elongated encapsulant comprises a foam (310) comprising a plurality of gas-containing cells and is configured to diffuse the first converted light into the LED filament light.

Description

Technical Field

[0001] This invention generally relates to light-emitting diode (LED) filaments. More specifically, this invention relates to an LED filament comprising an encapsulation arranged to influence emitted LED filament light. Background Technology

[0002] The use of light-emitting diodes (LEDs) for lighting purposes continues to attract attention. Compared to incandescent lamps, fluorescent lamps, and neon lamps, LEDs offer many advantages, such as longer operating life, reduced power consumption, and improved efficiency related to the ratio of light to heat energy.

[0003] Due to the advantages of using LEDs, interest in replacing conventional light sources with LEDs has rapidly increased in many lighting installations. It should be understood that this replacement, also known as retrofitting, is appreciated and desired by users who wish to achieve the look of incandescent bulbs. Light source replacement (retrofitting) is typically performed by removing the conventional light source from the luminaire (e.g., lamp holder) of the lighting installation and attaching an LED, LED unit, or LED device to the luminaire. One of these concepts is based on the LED filament placed within the bulb. While utilizing LED technology, the visible LED filament can provide an efficient and aesthetically pleasing light distribution.

[0004] It is desired to further improve the performance, functionality, and / or appearance of LED filament lamps. More specifically, it is desired to improve the performance and / or functionality of light emission and / or light distribution from LED filament lamps. Another objective is to enhance the appearance and / or decorative qualities of LED filaments and / or LED filament lamps, whether during operation (on-state) or when off (off-state).

[0005] WO 2021 / 052887 discloses an LED filament lamp comprising at least one LED filament having an LED filament length (L) extending from a first end to a second end. The at least one LED filament provides LED filament light and includes an array of multiple LEDs and an encapsulation. The array of multiple LEDs provides LED light and extends along the LED filament length (L). The encapsulation at least partially surrounds the multiple LEDs and includes a light-scattering material. In a direction from the first end to the second end, at least one of (i) the thickness (TL) of the encapsulation and (ii) the concentration (CL) of the light-scattering material in the encapsulation increases along the LED filament length (L) at least two adjacent first LEDs and decreases at least two adjacent second LEDs other than the at least two adjacent first LEDs, and wherein the thickness (TL) and / or concentration (CL) increases first and then decreases at least along a portion of the LED filament length (L). Summary of the Invention

[0006] It is of interest to explore one or more of the many advantages of LED filaments, which include LEDs, by examining the characteristics of light emission and / or distribution of LED filaments, as well as the possibility of improving the appearance and / or decorativeness of LED filaments and / or LED filament lamps during on and off states, while simultaneously improving the performance and / or functionality of LED filaments.

[0007] This and other objectives are achieved by providing an LED filament having the features of the independent claims. Preferred embodiments are defined in the dependent claims.

[0008] According to the present invention, a light-emitting diode (LED) filament is provided, configured to provide LED filament light in an on-state. The LED filament extends along a length axis LX and includes an elongated carrier and a plurality of LEDs disposed on a first main surface of the elongated carrier, wherein the plurality of LEDs are configured to emit LED light. The LED filament also includes a first elongated encapsulation that at least partially covers the elongated carrier and at least partially surrounds the plurality of LEDs, wherein the first elongated encapsulation includes a luminescent material configured to at least partially convert the emitted LED light into first converted light. The LED filament also includes a second elongated encapsulation that at least partially surrounds the first elongated encapsulation, wherein the second elongated encapsulation includes a foam comprising a plurality of gas-containing pores and is configured to diffuse the first converted light into LED filament light. Typically, the foam is a material formed by trapping gas cavities or pores in a solid. It is not necessary to retain the gas in the gas cavities. However, it is desirable to use LED filaments in sealed environments, for example, in bulbs with a relatively high concentration of helium. Helium will also diffuse in the pores, which improves thermal management.

[0009] Therefore, the present invention is based on the idea of ​​providing an LED filament comprising a first elongated light-emitting package covered by a (conformally) second elongated (foam) package. This arrangement of the package, and further through the characteristics of the package, improves the performance and / or functionality of the LED filament, as well as its appearance and / or decorative aspects.

[0010] It should be understood that the first elongated (light-emitting) encapsulation of the LED filament can be yellow-orange, and through the construction of the LED filament, the second elongated (foam) encapsulation can conceal this yellow-orange color by encapsulating the first elongated encapsulation provided by the second elongated encapsulation. This effectively and conveniently enhances the appearance and decorative aspects of the LED filament.

[0011] Another advantage of the present invention is that the properties of the foam of the second encapsulation can be easily and conveniently customized for desired characteristics of light distribution from the LED filament and / or the aesthetic appearance of the LED filament. More specifically, foam properties (e.g., thickness, porosity, etc.) can be set or adjusted to optimize the concealment of the yellow-orange color of the first elongated encapsulation while maintaining an aesthetically pleasing LED filament appearance.

[0012] Another advantage of the invention is that the second elongated package is white in the broken state of the LED filament, making the LED filament attractive to the observer.

[0013] In one embodiment, the second elongated package may completely surround the first elongated package.

[0014] Another advantage of the present invention is that the foam of the second elongated encapsulation can improve the thermal management of the LED filament during operation.

[0015] Another advantage of the present invention is that the many advantages of using LED technology can be combined with the attractiveness and appealing characteristics of the disclosed LED filament device.

[0016] Another advantage of the present invention is that the LED filament of the present invention comprises relatively few components. A smaller number of components is advantageous because manufacturing LED filaments is relatively inexpensive. Furthermore, the smaller number of components in the LED filament means easier recycling, especially compared to devices or apparatuses that include a relatively large number of purpose-purpose components, which hinder easy disassembly and / or recycling operations.

[0017] A light-emitting diode (LED) filament is provided, configured to provide LED filament light in an on-state. Preferably, the LED filament has a length L. F and width W F L F >5W FThe LED filament can be arranged in a linear or non-linear configuration, such as, for example, a curved structure, a 2D / 3D spiral, or a helix. The LED filament extends along a length axis LX and includes an elongated carrier and a plurality of light-emitting diodes (LEDs) arranged on a first main surface of the elongated carrier, wherein the plurality of LEDs are configured to emit LED light. The elongated carrier can be, for example, a substrate, which can be rigid (e.g., made of polymer, glass, quartz, metal, or sapphire) or flexible (e.g., made of polymer or metal, such as a film or foil). The elongated carrier can be reflective or translucent, for example, translucent, preferably transparent. The plurality of LEDs can be arranged in a linear array on the elongated carrier. The term "array" herein refers to a linear arrangement or chain of LEDs, etc. The LED filament also includes a first elongated encapsulation that at least partially covers the elongated carrier and at least partially surrounds the plurality of LEDs, wherein the first elongated encapsulation includes a light-emitting material configured to at least partially convert the emitted LED light into first converted light. The term "encapsulation" herein refers to an elongated material, element, device, etc., configured or arranged in this context to at least partially cover, surround, encapsulate, and / or surround an elongated carrier (and, in the case of a first elongated encapsulation, also including a plurality of LEDs). The (first and / or second) encapsulation may be a polymeric material, which may be flexible, such as, for example, silicone. The light-emitting material of the first elongated encapsulation may be a phosphor, such as an inorganic phosphor and / or quantum dots or rods. The LED filament also includes a second elongated encapsulation that at least partially surrounds the first elongated encapsulation. The second elongated encapsulation includes a foam comprising a plurality of gas-containing pores and is configured to diffuse the first converted light and optionally a portion of the (unconverted) LED light into LED filament light. Thus, the second elongated encapsulation at least partially covers, surrounds, encapsulates, and / or surrounds the first elongated encapsulation. Therefore, the foam of the second elongated encapsulation influences the first converted light (and optionally a portion of the LED light) emitted via the first elongated encapsulation by diffusing the first converted light into LED filament light emitted by the LED filament during operation.

[0018] According to an embodiment of the invention, when the LED filament is in the off state, the plurality of pores in the foam can make the LED filament appear white. Therefore, when the LED filament is in the off state (i.e., off), the plurality of pores in the foam of the second elongated encapsulation are arranged or configured to make the foam appear white (to the observer of the LED filament). The resulting effect is a visually appealing off-state white appearance for the LED filament, while also providing improved optical performance because the white foam redistributes the first converted light into flashes. Therefore, the advantage of this embodiment is that the white color provided by the plurality of pores in the foam makes the LED filament attractive to the observer while providing improved illumination performance.

[0019] According to an embodiment of the invention, the foam may have a pore volume of at least 35% of the total volume of the second elongated encapsulation. "Pore volume" here refers to the void space or pore space of the foam. An advantage of this embodiment is that the relatively large foam porosity or portion of the pore volume produces improved or even optimal light scattering performance, a concealing effect of the yellow-orange hue of the first elongated encapsulation, and / or an attractive white appearance of the LED filament in its off state. Another advantage of this embodiment is that the relatively high level of porosity of the foam results in the outline of the first elongated encapsulation being visible to an observer through the second elongated encapsulation during LED filament operation, thereby resulting in an attractive luminous effect.

[0020] According to embodiments of the present invention, the first elongated package and the second elongated package may comprise the same polymer matrix material. An advantage of this embodiment is that the LED filament is conveniently manufactured from the same polymer matrix material of the first and second elongated packages, resulting in cost and / or time efficiency in the LED filament manufacturing process.

[0021] According to an embodiment of the present invention, in a first direction D1 perpendicular to the length axis LX and parallel to the normal of the first main surface, the first elongated package has a first thickness T1 defined from the elongated carrier to the interface between the first elongated package and the second elongated package. Furthermore, in the first direction D1, the second elongated package may have a second thickness T2 defined from the interface to the light-emitting surface of the second elongated package, wherein... Therefore, the first and second elongated packages may have corresponding thicknesses T1 and T2 along the first direction D1, wherein the thickness T2 of the second elongated package is at least 1.5 times the first thickness T1 of the first elongated package. An advantage of this embodiment is that the second thickness T2 of the second elongated package is thick enough to mask and / or hide the yellow-orange color of the first elongated package. Another advantage of this embodiment is that the second elongated package has a sufficient second thickness T2 to achieve a pure white appearance, while the first elongated package remains relatively thin, resulting in a relatively elongated LED filament. Another advantage of this embodiment is that it achieves sufficient scattering of ambient light and / or the first converted light (and optionally also a portion of the unconverted LED light) during LED filament operation.

[0022] According to an embodiment of the present invention, Therefore, the second thickness T2 of the second elongated package can be less than five times the first thickness T1 of the first elongated package. An advantage of this embodiment is that the second thickness T2 of the second elongated package is thin enough to maintain the filament appearance of the LED filament, thereby maintaining an aesthetically attractive appearance of the LED filament (white in the off state). In the combination of the current and previous embodiments of the LED filament, i.e., the relationship between the thicknesses T1 and T2 of the first and second elongated packages satisfies... The second thickness T2 of the second elongated package is thick enough to mask and / or hide the yellow-orange color of the first elongated package to achieve sufficient scattering of ambient light, first converted light and / or unconverted LED light, while being thin enough to maintain / preserve the aesthetically attractive appearance of the LED filament.

[0023] According to an embodiment of the invention, T1 is in the range of 1 mm to 2 mm (or 0.5 mm to 3 mm), and T2 is in the range of 3 mm to 5 mm (or 2 mm to 6 mm). Preferably, the reflectivity of the second elongated package is in the range of 25% to 48%, particularly 27% to 43%. An advantage of this embodiment is that the thicknesses T1 and T2 of the described first and second elongated packages, together with the reflectivity of the second elongated package, further enhance the masking and / or concealment of the yellow-orange color of the first elongated package, the beneficial optical properties of the LED filament, and the aesthetic appeal of the LED filament. More specifically, an advantage of this embodiment is that it achieves the effect of an attractive off-state white LED filament with improved optical performance. This embodiment provides a relatively elongated and efficient LED filament because only a relatively small portion of the light is lost due to backscattering.

[0024] According to an embodiment of the invention, the LED filament may further include a third elongated encapsulation that at least partially surrounds a second main surface of the elongated carrier opposite the first main surface, wherein the third elongated encapsulation comprises foam comprising a plurality of gas-containing pores and is configured to diffuse the first converted light into LED filament light. Therefore, this embodiment implies providing (oppositely arranged) foam-containing second and third elongated encapsulations around (on both sides or entirely around) the first elongated encapsulation. An advantage of this embodiment is that the omnidirectional arrangement of foam associated with the plurality of LEDs of the LED filament results in an attractive off-state white LED filament with improved optical performance.

[0025] In one embodiment, the second and third elongated packages may together completely surround the first elongated package.

[0026] According to an embodiment of the present invention, the elongated carrier may be light transmissive, and the LED filament may further include a fourth elongated encapsulant disposed between the second major surface and the third elongated encapsulant. The fourth elongated encapsulant includes a second luminescent material configured to at least partially convert at least one of the LED light and the first converted light into a second converted light, wherein the third elongated encapsulant is configured to diffuse the second converted light into LED filament light. By the light emission from both sides of the LED filament during operation and the said characteristics of the fourth elongated encapsulant, the advantage of this embodiment is that the effect of an attractive off-state white LED filament with improved optical performance is even further enhanced.

[0027] In an embodiment, the second and third elongated encapsulants may together completely surround the first and fourth elongated encapsulants.

[0028] According to an embodiment of the present invention, in a second direction D2 perpendicular to the length axis LX and parallel to the normal of the second major surface, the third elongated encapsulant may have a third thickness T3 defined from a second interface between the third elongated encapsulant and the fourth elongated encapsulant to the light emitting surface of the third elongated encapsulant, where T3 < T2. It may also be provided that T3 ≤ T2, that is, the third thickness T3 may be smaller than or the same as the second thickness T2 (i.e., T3 = T2). This embodiment even further enhances the effect of an attractive off-state white LED filament with improved optical performance. The reason is that a relatively thin (thinner) third elongated encapsulant can be used for the back side to hide the first elongated encapsulant on the back side, and the third elongated encapsulant has a lighter color due to a lower concentration of (red) phosphor than the (red) phosphor in the first elongated encapsulant, thus ensuring maximum efficiency due to reduced back reflection of the converted light. In the case of using the fourth elongated (luminescent) encapsulant, T3 can still be less than T2. Generally, the phosphor composition in the fourth elongated encapsulant may be different from that in the first elongated encapsulant. The fourth elongated (luminescent) encapsulant may, for example, have a less dark color.

[0029] According to embodiments of the invention, the combination of a second elongated package and a third elongated package forms a tubular shape (or a similar tubular shape) having a length L, a width W perpendicular to the length L, and a thickness T perpendicular to the length L and the width W, wherein L / T > 8 and L / W > 8. Therefore, the tubular shape of the combined structure of the second and third elongated packages provides integration of the package, for example, the package is provided as a single piece (e.g., a monolithic element). An advantage of this embodiment is that the manufacturing of the LED filament is further improved because, for example, by applying extrusion or overmolding, the second and third elongated packages may require only a single manufacturing / processing step, resulting in further improvements in the time and / or cost efficiency of LED filament manufacturing / production. In embodiments, the combination of the second and third elongated packages forming the tubular shape can be flexible. This also allows the LED filament to be easily inserted into the “tube.”

[0030] According to an embodiment of the invention, the gas in at least one of the foams of the second and third elongated encapsulations comprises at least 10 volume percentages of at least one of the following: helium (He) and hydrogen (H2). Therefore, the gas in the foams of the second and / or third elongated encapsulations may comprise at least 10 volume percentages of helium (He) and / or hydrogen (H2). An advantage of this embodiment is that the properties of the foams of the second and / or third elongated encapsulations improve the thermal management (cooling) of the LED filament during operation.

[0031] According to embodiments of the present invention, at least one of the second elongated package and the optional third elongated package is free of scattering particles. Therefore, the second elongated package and / or the third elongated package may be free of scattering particles. An advantage of this embodiment is that the foam properties of the second and / or third elongated packages improve the thermal management (cooling) of the LED filament during operation.

[0032] According to embodiments of the invention, at least one of the foams of the second elongated encapsulation and the third elongated encapsulation comprises at least one of a silicone polymer. According to another embodiment of the invention, the foam cells may have an open-cell structure, meaning the foam may include interconnected adjacent cells. According to yet another embodiment of the invention, the foam cells may have a pore volume of at least 35% of the total volume of the foams of the second elongated encapsulation and the third elongated encapsulation. Therefore, the foams of the second elongated encapsulation and / or the third elongated encapsulation may comprise a silicone polymer, foam cells with an open-cell structure, and / or foam cells having a pore volume (porosity) of at least 35% of the total volume of the foams of the second elongated encapsulation and / or the third elongated encapsulation. The open-cell structure of the foam cells is advantageous because it improves the thermal management of the LED filament during operation through gas flow. The use of a silicone polymer is advantageous because it has improved lifespan. The use of a silicone polymer is further advantageous because unwanted browning (which can occur with other polymers) can be avoided, thereby further contributing to LED filament attraction. Foam cells with a pore volume of at least 35% of the total foam volume result in optimal performance in terms of light scattering by the LED filament, concealment of the yellow-orange color of the first elongated encapsulation, and white attraction of the LED filament in its off state.

[0033] In the embodiments, at least one of the first, second, third, and fourth elongated encapsulations may include a polymer matrix of silicone resin, such as polydimethylsiloxane PDMS, polymethylphenylsiloxane PMPS, or polydiphenylsiloxane PDPS.

[0034] According to an embodiment of the present invention, an LED filament device is provided. The LED filament device may include at least one LED filament according to any of the foregoing embodiments, and a transparent tube surrounding the at least one LED filament. An advantage of this embodiment is that the attractiveness of the white appearance of the LED filament in its off state is further enhanced due to the (moderate) reflective properties of the transparent tube. Another advantage of this embodiment is that the transparent tube provides inlet protection for the LED filament.

[0035] According to embodiments of the present invention, an LED filament lamp is provided, comprising at least one LED filament according to any of the foregoing embodiments and one of the LED filament devices according to the foregoing embodiments. The LED filament lamp further includes a light-transmitting housing (or cover) that at least partially surrounds at least one LED filament, and a connector for electrically and mechanically connecting the LED filament lamp to a socket of a luminaire. Thus, the LED filament lamp comprises one or more LED filaments or LED filament devices, and the LED filament device further comprises one or more LED filaments. An advantage of this embodiment is that the LED filament lamp comprising (multiple) LED filaments combines aspects of desired light emission and aesthetic appearance provided via the LED filament device and / or via (multiple) features of the lamp.

[0036] According to an example of the invention, the LED filament device or LED filament lamp may further include a controller configured to control the luminous flux of the LED filament light. In the case of multiple LED filaments, the controller can control each LED filament individually. "Controller" herein refers to any device, unit, etc., capable of controlling the luminous flux via wired or wireless technology. An advantage of this embodiment is that the controller can conveniently and effectively control (multiple) LED filaments, thereby further improving light emission from the LED filaments and enhancing the appearance and / or decorative aspects of the LED filaments.

[0037] Other objects, features, and advantages of the invention will become apparent upon studying the following detailed disclosure, drawings, and appended claims. Those skilled in the art will recognize that different features of the invention can be combined to produce embodiments different from those described in the detailed description and the examples below.

[0038] In one example, the foam can be white and / or can have a white appearance.

[0039] In one example, the second elongated encapsulation may have a reflectivity of at least 20%.

[0040] In one example, the second elongated encapsulation may have a reflectivity of up to 65%.

[0041] In one example, the second elongated package may be positioned at a distance D other than zero relative to the first elongated package (e.g., D > 50 micrometers and / or D < 1000 micrometers).

[0042] In one example, the foam as a whole can be white and / or have a white appearance. This is because when light enters the foam, it must pass through multiple (e.g., at least 7, preferably at least 8, more preferably at least 11, most preferably at least 15) (microscopic) pores (also called foam), i.e., multiple surfaces. These surfaces cause the light to scatter in different directions, which makes the foam appear white.

[0043] In one example, multiple pores can have an (average) diameter of less than 1 mm, for example, in the range of 5 to 500 micrometers or 50 to 500 micrometers.

[0044] In one example, the foam and / or multiple pores comprise a polymer matrix material. The polymer matrix material may be a non-light-absorbing polymer (i.e., less than 5% absorption). The polymer matrix material may be translucent, for example, a transparent polymer. The polymer matrix material may include PMMA, PET, PC, and / or silicone.

[0045] In one example, the foam can be either closed-cell or open-cell foam. In closed-cell foam, the gas forms discrete cavities, each completely surrounded by a solid material (e.g., a polymer matrix material). In open-cell foam, the cavities are interconnected.

[0046] In one example, the foam could be solid foam.

[0047] In one example, the foam can be flexible (e.g., able to be easily bent without breaking) or rigid (e.g., cannot be bent or forced to deform).

[0048] In one example, the foam can have a curved shape, such as a spiral.

[0049] In one example, the foam may not contain luminescent materials, (light-absorbing) dyes, and / or (light-scattering) particles.

[0050] In one example, the foam could be a sponge-like material. Attached Figure Description

[0051] This and other aspects of the invention will now be described in more detail with reference to the accompanying drawings, which illustrate embodiments of the invention.

[0052] Figure 1 An LED filament lamp according to the prior art is shown.

[0053] Figure 2 An LED filament device according to an exemplary embodiment of the present invention is schematically illustrated.

[0054] Figure 3 An LED filament device comprising at least one LED filament is schematically shown according to an exemplary embodiment of the present invention.

[0055] Figure 4 An LED filament lamp is shown, which includes an LED filament according to an exemplary embodiment of the present invention. Detailed Implementation

[0056] Figure 1An LED filament lamp 10 according to the prior art is shown, which includes a plurality of LED filaments 20. This type of LED filament lamp 10 is very popular because it is highly decorative and offers many advantages compared to incandescent lamps, such as longer operating life, reduced power consumption, and increased efficiency related to the ratio between light and heat energy. However, it is of interest to improve the characteristics of the light distribution emitted from the LED filaments 20, and even further enhance the decorative appearance and / or aspects of the LED filaments 20 and / or the LED filament lamp 10.

[0057] Figure 2 A cross-section of an LED filament 100 according to an exemplary embodiment of the present invention is schematically shown. The LED filament 100 is configured to provide (emit) LED filament light 110. The LED filament 100 extends along a length axis LX and includes an elongated carrier 120. An array of a plurality of LEDs 130 is arranged on a first main surface 145 of the elongated carrier 120. It should be noted that the LED filament 100 may substantially comprise any number of arrays of a plurality of LEDs 130. The plurality of LEDs 130 preferably comprises more than 5 LEDs, more preferably more than 8 LEDs, and even more preferably more than 10 LEDs. The plurality of LEDs 130 may be direct-emitting LEDs that provide color. The plurality of LEDs 130 are configured to emit LED light 150. The LED filament 100 also includes a first elongated encapsulation 200 that at least partially surrounds the elongated carrier 120 and at least partially surrounds the plurality of LEDs 130. The first elongated package 200 includes a light-emitting material configured to at least partially convert emitted LED light 150 into first converted light 210. The light-emitting material of the first elongated package 200 may be a light-scattering material, for example, including… A polymer matrix of and / or TiO2 particles. The luminescent material of the first elongated package 200 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 also be, for example, a (blue) green / yellow and / or red phosphor. Although not shown, the concentration of the luminescent material in the first elongated package 200 may vary along the length of the LED filament 100.

[0058] The LED filament 100 also includes a second elongated package 300 that at least partially surrounds the first elongated package, wherein the second elongated package 300 includes a foam 310. The foam 310 includes a plurality of gas-containing pores. The average diameter of the plurality of pores is 1-100 μm. The gas in the foam 310 of the second elongated package 300 may include at least 10 volume percent of helium (He) and / or hydrogen (H2). The second elongated package 300 may be free of scattering particles. Furthermore, since the plurality of pores in the foam 310 may have an average diameter in the range of 1-100 μm, the thickness of the foam 310 is chosen such that it spans at least 5, preferably at least 10, more preferably at least 15, and most preferably at least 20 pores in each cross-section.

[0059] The foam 310 of the second elongated package 300 is configured to diffuse the converted light 210 and optionally a portion of the LED light 150 into LED filament light 110. Therefore, the second elongated package 300 at least partially covers, surrounds, encapsulates, and / or surrounds the first elongated package 200. Thus, the foam 310 of the second elongated package 300 influences the first converted light 210 (and optionally a portion of the LED light 150) emitted via the first elongated package 200 by diffusing the first converted light 210 into LED filament light 110 emitted by the LED filament 100 during operation. When the LED filament 100 is in the off state, a plurality of pores in the foam 310 can make the LED filament 100 appear white. Therefore, the plurality of pores in the foam 310 of the second elongated package 300 are arranged or configured to make the foam 310 appear white (to the observer of the LED filament 100) when the LED filament 100 is in the off state (i.e., off). Foam 310 may have at least 35% of the total pore volume of the second elongated encapsulation 300. Foam 310 may comprise a silicone polymer, preferably a cross-linked silicone polymer (preferably polydimethylsiloxane, PDMS, polydiphenylsiloxane PDPS, and / or polymethylphenylsiloxane PMPS). The second elongated encapsulation 300 may be flexible by using silicone or polyurethane rubber (PUR), or rigid by using a ceramic material. The first elongated encapsulation 200 and the second elongated encapsulation 300 may comprise the same polymer matrix material.

[0060] In a first direction D1 perpendicular to the length axis LX and parallel to the normal of the first main surface 145 of the LED filament 100, the first elongated package 200 has a first thickness T1. The first thickness T1 is defined from the elongated carrier to the interface 400 between the first elongated package 200 and the second elongated package 300. Furthermore, the second elongated package 300 may have a second thickness T2 in the first direction D1. The second thickness T2 is defined from the interface 400 between the first elongated package 200 and the second elongated package 300 to the light-emitting surface 410 of the second elongated package 300. The relationship between the first and second thicknesses of the first elongated package 200 and the second elongated package 300 can respectively satisfy… The relationship between the first and second thicknesses T1 and T2 can be further satisfied. Numerically, T1 can be in the range of 1 mm to 2 mm, T2 can be in the range of 3 mm to 5 mm, and the reflectivity of the second elongated package 300 can be in the range of 25% to 48%.

[0061] The LED filament 100 may further include a third elongated encapsulation 500 that at least partially surrounds a second main surface 545 of the elongated carrier 120 opposite to the first main surface 145. The third elongated encapsulation 500 includes a foam 310 comprising a plurality of gas-containing pores and is configured to diffuse the first converted light 210 into LED filament light 110. The gas in the foam 310 of the third elongated encapsulation 500 may include at least 10 volume percent helium (He) and / or hydrogen (H2). The third elongated encapsulation 500 may be free of scattering particles.

[0062] The elongated carrier 120 may be light-transmitting, and the LED filament 100 may further include a fourth elongated package 600 disposed between the second main surface 545 and the third elongated package 500. The fourth elongated package 600 includes a second light-emitting material configured to at least partially convert LED light 150 and / or the first converted light 210 into second converted light 610, wherein the third elongated package 500 is configured to diffuse the second converted light 610 into LED filament light 110. The third elongated package 500 may have a third thickness T3 in a second direction D2 perpendicular to the length axis LX and parallel to the normal to the second main surface 545. The third thickness T3 is defined from the second interface 700 between the third elongated package 500 and the fourth elongated package 600 to the light-emitting surface 710 of the third elongated package 500, wherein T3 ≤ T2. The combination of the second elongated package 300 and the third elongated package 500 can form a tubular shape having a length L, a width W perpendicular to the length L, and a thickness T perpendicular to the length L and the width W, wherein L / T>8 and L / W>8.

[0063] Figure 3An LED filament assembly 800 is schematically shown. The LED filament assembly 800 includes at least one LED filament 100 according to any of the foregoing embodiments. The LED filament assembly 800 also includes a transparent tube 810, for example made of glass, which surrounds the LED filament 100. It should be noted that the transparent tube 810 may be in physical contact with or physically separated from the LED filament(s) 100.

[0064] Figure 4 An LED filament lamp 900 according to an embodiment of the present invention is schematically shown. The LED filament lamp 900 can be configured as essentially any type of lamp or luminaire, including one or more LED filaments 100 as described in any of the above embodiments. The LED filament lamp 900 also includes a light-transmitting housing 910, exemplified as a bulb shape. The light-transmitting housing 910 at least partially surrounds (multiple) of the LED filaments 100. The LED filament lamp 900 also includes a connector 920 for electrically and mechanically connecting the LED filament lamp 900 to a socket of the luminaire. Although not shown, the LED filament lamp 900 may also include a controller configured to control the luminous flux of the LED filament light. In the case of multiple LED filaments, the controller can control each LED filament individually.

[0065] Those skilled in the art will recognize that the present invention is by no means limited to the preferred embodiments described above. Rather, many modifications and variations are possible within the scope of the appended claims. For example, one or more of the LED filament 100, the first elongated package 200, the second elongated package 300, etc., may have a shape, size, and / or size different from those depicted / described.

Claims

1. A light-emitting diode (LED) filament (100) configured to provide LED filament light (110) in an on-state, the LED filament extending along a length axis LX and comprising... Slender carrier (120). Multiple light-emitting diodes (LEDs) (130) are arranged on the first main surface (145) of the elongated carrier, wherein the multiple LEDs are configured to emit LED light (150). A first elongated package (200) at least partially covers the elongated carrier and at least partially surrounds the plurality of LEDs, wherein the first elongated package includes a light-emitting material configured to at least partially convert the emitted LED light into first converted light (210), and A second elongated package (300) at least partially surrounds the first elongated package, wherein the second elongated package includes a foam (310) comprising a plurality of gas-containing pores and configured to diffuse the first converted light into the LED filament light. When the LED filament is in the off state, the plurality of pores in the foam make the LED filament appear white.

2. The LED filament of claim 1, wherein the foam has at least 35% of the total volume of the second elongated encapsulation in terms of pore volume.

3. The LED filament according to any one of the preceding claims, wherein the first elongated encapsulation and the second elongated encapsulation comprise the same polymer matrix material.

4. The LED filament according to any one of the preceding claims, The first elongated package has a first thickness T1 in a first direction D1 that is perpendicular to the length axis LX and parallel to the normal of the first main surface, defined from the elongated carrier to the interface (400) between the first elongated package and the second elongated package. The second elongated package has a second thickness T2 in the first direction D1, defined from the interface to the light-emitting surface (10) of the second elongated package. in .

5. The LED filament according to claim 4, wherein... .

6. The LED filament according to claim 4 or 5, wherein T1 is in the range of 1mm to 2mm. T2 is in the range of 3mm to 5mm, and The reflectivity of the second elongated package is in the range of 25% to 48%.

7. The LED filament according to any one of the preceding claims further comprises a third elongated package (500) that at least partially surrounds a second main surface (545) of the elongated carrier opposite to the first main surface, wherein the third elongated package comprises a foam comprising a plurality of gas-containing pores and is configured to diffuse the first converted light into the light of the LED filament.

8. The LED filament according to claim 7, wherein The elongated carrier is light-transmitting, and the LED filament further includes: A fourth elongated package (600) is disposed between the second main surface and the third elongated package, wherein the fourth elongated package includes a second light-emitting material configured to at least partially convert at least one of the LED light and the first converted light into a second converted light (610), wherein the third elongated package is configured to diffuse the second converted light into the LED filament light.

9. The LED filament according to claim 8, wherein the third elongated package has a third thickness T3 in a second direction D2 perpendicular to the length axis LX and parallel to the normal of the second main surface, defined from the second interface (700) between the third elongated package and the fourth elongated package to the light-emitting surface (710) of the third elongated package, wherein T3 <T2。 10. The LED filament according to any one of claims 7 to 9, wherein the combination of the second elongated encapsulation and the third elongated encapsulation forms a tubular shape, the tubular shape having: Length L, The width W perpendicular to the length L, and The thickness T is perpendicular to the length L and the width W, where L / T > 8 and L / W > 8.

11. The LED filament according to any one of claims 7 to 10, wherein The gas in at least one of the foams of the second elongated package and the third elongated package comprises at least 10% by volume of at least one of helium (He) and hydrogen (H2); and At least one of the second elongated package and the third elongated package does not have scattering particles.

12. The LED filament according to any one of claims 7 to 11, wherein at least one of the foams of the second elongated encapsulation and the third elongated encapsulation comprises at least one of the following: Silicone polymer, Foam cells with open-cell structure, and Foam cells comprising at least 35% of the total pore volume of at least one of the foam having the second elongated encapsulation and the foam having the third elongated encapsulation.

13. An LED filament device (800), comprising: At least one LED filament according to any one of the preceding claims A transparent tube (810) surrounding the at least one LED filament.

14. An LED incandescent lamp (900) comprising one of the following: At least one LED filament according to any one of claims 1 to 12, and The LED filament device according to claim 13, A light-transmitting housing (910) that at least partially surrounds the at least one LED filament, and A connector (920) is used to electrically and mechanically connect the LED filament lamp to a socket of the luminaire.

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