A LED filament lamp showing a flame effect

Abstract

The invention provides a LED filament lamp (1000) comprising a light transmissive envelope (500) and a LED filament (1100) at least partly enclosed by the light transmissive envelope (500), wherein: the light transmissive envelope (500) comprises a light transmissive material (502), wherein the light transmissive envelope (500) comprises a ribbed structure (550) with intermediate relief lines (531) between adjacent elongated convex surfaces (525); wherein the light transmissive envelope (500) comprises an external surface (505) comprising a plurality of facets (540) defined by the ribbed structure (550); wherein the light transmissive envelope (500) comprises an envelope length axis (AE); and wherein the facets (540) are arranged in a spiral-like configuration spiraling about at least part of the envelope length axis (AE); the LED filament (1100) comprises an array of a plurality of solid state light sources (1110) arranged on an elongated carrier (1120), with an encapsulant (1130) covering the plurality of solid state light sources (1110) and at least part of the elongated carrier (1120); wherein the LED filament (1100) is configured to generate filament light; the LED filament lamp (1000) is configured such that (a): a plurality of virtual vectors (Vv) each: (i) start at the envelope length axis (AE), (ii) intersect the LED filament (1100), and (iii) follow a distance from the LED filament (1100) to an intermediate relief line (531) comprised by the light transmissive envelope (500), and (b): a plurality of intersection points (1105') of the virtual vectors (Vv) with the light transmissive envelope (500) define a filament projection (1100') on the light transmissive envelope (500); and the filament projection (1100') provides mutual angles between the filament projection (1100') and the intermediate relief lines (531), wherein at least one of the mutual angles is selected from the range of 10-80°.

Description

[0001] A LED filament lamp showing a flame effect

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a light emitting diode (LED) filament lamp comprising a light transmissive envelope and a LED filament at least partly enclosed by the light transmissive envelope.

[0004] BACKGROUND OF THE INVENTION

[0005] Lighting devices are known in the art. For instance, US2013088880 describes a lighting device including a seat having a first end and a second end opposite the first side, a top surface being formed at the first end; a light source unit installed on the top surface; and a contact cap connected to the second end. The light source further includes a metal core printed circuit board (MCPCB) having a base portion and a plurality of first extension portions extended from and bent along an edge of the base portion to be embedded in the seat, and at least one LED disposed on the base portion.

[0006] US 2022 / 0390075 discloses a LED filament lamp comprising a transparent envelope provided with a transparent optical structure comprising a plurality of individually spaced prismatic grooves and / or ridges that are at least partly aligned along a projection of the at least one LED filament on the transparent envelope.

[0007] SUMMARY OF THE INVENTION

[0008] Incandescent lamps are rapidly being replaced by light emitting diode (LED) based lighting solutions. It may nevertheless be appreciated and desired by users to have retrofit lamps which have the look of an incandescent (candle) bulb. It is desired to further improve the appearance of such (candle) bulb LED lamps, e.g., by providing light having an optical effect. In particular, it may be desirable for (candle) bulb lamps to provide light showing an optical effect, especially a flame effect. However, providing light showing a flame effect may be difficult and / or costly to achieve using LEDs placed in an incandescent candle bulb with a conventional glass design.

[0009] Hence, it is an aspect of the invention to provide an alternative lamp, which preferably further at least partly obviates one or more of above-described drawbacks. The present invention may have as object to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

[0010] One of the concepts is based on LED filaments placed in an incandescent candle bulb, i.e., an incandescent bulb with a candle-like shape. Thereby, a LED lamp may be produced which may be designed to resemble a traditional incandescent light bulb or candle with a visible LED filament for aesthetic and light distribution purposes, but with the high efficiency of LEDs. The appearances of these lamps are highly appreciated as they look highly decorative. For this purpose, one may make use of the infrastructure for producing incandescent lamps based on glass and replace the filament with LEDs emitting visible light.

[0011] According to a first aspect, the invention may provide a light emitting diode (LED) filament lamp comprising a light transmissive envelope and a LED filament. Especially, the LED filament may be at least partly enclosed by the light transmissive envelope. In embodiments, the light transmissive envelope may comprise a light transmissive material. The light transmissive envelope may comprise a ribbed structure. The ribbed structure may especially have intermediate relief lines between adjacent elongated convex surfaces. The elongated convex surfaces may in particular be layered. Further, the light transmissive envelope may comprise an external surface. The external surface may especially comprise a plurality of facets. The plurality of facets may be defined by the ribbed structure. Additionally, the light transmissive envelope may comprise an envelope length axis AE. The facets may be arranged in a spiral-like configuration. The facets may especially be spiraling about at least part of the envelope length axis AE. In embodiments, the LED filament may comprise an array of a plurality of solid state light sources. The solid state light sources may be arranged on an elongated carrier. The LED filament may further comprise an encapsulant. The encapsulant may especially cover the plurality of solid state light sources. Additionally, the encapsulant may cover at least part of the elongated carrier. Furthermore, the LED filament may be configured to generate filament light. The light transmissive envelope may especially be transmissive for at least part of the filament light. In embodiments, the LED filament lamp may be configured such that a plurality of virtual vectors Vv may be defined as follows. Firstly, each of the plurality of virtual vectors Vv may start at the envelope length axis AE, especially at different positions of the envelope length axis AE. Further, each of the plurality of virtual vectors Vv may intersect the LED filament, especially at different positions of the LED filament. Furthermore, each of the plurality of virtual vectors Vv may follow a distance dl from the LED filament to the light transmissive envelope. Especially, the distance dl may be a shortest distance dl from the LED filament to an intermediate relief line comprised by a downstream facet of the light transmissive envelope. The LED filament may further be configured such that the virtual vectors Vv may define a plurality of intersection points of the virtual vectors Vv with the light transmissive envelope. Thereby, the plurality of intersection points of the virtual vectors Vv may define a filament projection on the light transmissive envelope. In embodiments, the filament projection may provide one or more mutual angles a between the filament projection and the intermediate relief lines. At least one of the mutual angles a may especially be selected from the range of 10-80°. Therefore, in embodiments the invention may provide a LED filament lamp comprising a light transmissive envelope and a LED filament at least partly enclosed by the light transmissive envelope, wherein: the light transmissive envelope comprises a light transmissive material, wherein the light transmissive envelope comprises a ribbed structure with intermediate relief lines between adjacent elongated convex surfaces, wherein the light transmissive envelope comprises an external surface comprising a plurality of facets defined by the ribbed structure, wherein the light transmissive envelope comprises an envelope length axis AE, and wherein the facets are arranged in a spiral-like configuration spiraling about at least part of the envelope length axis AE; the LED filament comprises an array of a plurality of solid state light sources arranged on an elongated carrier, with an encapsulant covering the plurality of solid state light sources and at least part of the elongated carrier, wherein the LED filament is configured to generate filament light; the LED filament lamp is configured such that (a): a plurality of virtual vectors Vv each: (i) start at the envelope length axis AE, (ii) intersect the LED filament, and (iii) follow a distance dl from the LED filament to an intermediate relief line comprised by the light transmissive envelope, and (b): a plurality of intersection points of the virtual vectors Vv with the light transmissive envelope define a filament projection on the light transmissive envelope; and the filament projection provides one or more mutual angles a between the filament projection and the intermediate relief lines, wherein at least one of the mutual angles a is selected from the range of 10-80°.

[0012] Hence, specially, the light transmissive envelope may comprise a plurality of facets which spiral from the bottom towards the top (or vice versa) of the light transmissive envelope for providing a twist in the optical effect. Further, the light transmissive envelope may have a ribbed structure comprising intermediate relief lines which may run substantially perpendicular to the envelope length axis (AE), thereby functioning as refractive cylindrical lens structure. The one or more filaments in the lamp (or at least parts thereol) may be oriented at a mutual angle with respect to these relief lines to achieve broadening of the filament light. With the present invention, a LED filament lamp may be provided having a decorative light transmissive envelope which shows an optical effect from a LED filament, especially a flame effect. Especially, the above-described features may lead to formation of a flame effect in the filament lamp. Herein, a flame effect may relate to an optical effect in light mimicking the flame produced by visible combustion of flammable gasses resulting from a fire, e.g., from a candle or wood fire. A flame effect in light may therefore mimic one or more visual properties of a flame. Such visual properties may include one or more of: gradually shaded light (i.e. , lamp light gradually varying in luminance across the lamp surface), warm light, yellow-to-red light, light with a flame-like shape, light with a pointed shape. The LED filament lamp of the present invention may provide light exhibiting a flame effect, i.e., light having one or more of said visual properties. Especially, the present invention may provide light with gradually shaded light (resulting from broadening of the filament light by the ribbed structure), light with desired shapes (e.g., a flame-like shape, or pointed-shape, resulting from the design of the light transmissive envelopes), and light with desired coloring / warmth (resulting from the LED filaments used). The design of the light transmissive envelope having a ribbed structure and configuration of LED filaments may provide a (relatively) straightforward and cost-effective manner of providing light having a flame effect. Therefore in embodiments, the invention may provide an envelope for a LED filament lamp showing a flame effect.

[0013] As indicated above, the invention provides in embodiments a LED filament lamp comprising a light transmissive envelope and a LED filament at least partly enclosed by the light transmissive envelope. Embodiments thereof will be further described herein.

[0014] The LED filament lamp may especially comprise a LED filament. The LED filament may in embodiments comprise an elongated carrier, solid state light sources, and an encapsulant. LED filaments as such are known, and are e.g. described in US 8,400,051 B2, W02020016058, WO2019197394, etc. The LED filament may in embodiments be defined by a first length Li, width W and a thickness T. The LED filament may further comprise a filament axis of elongation AF. The filament axis of elongation AF may especially be a straight axis centered on the direction along which the LED filament is elongated. The filament axis of elongation AF may especially define an axis length LA, i.e., the axis length LA is the length of the LED filament along the filament axis of elongation AF. In some embodiments, the (first length Li of the) LED filament may be straight. In straight embodiments, the first length Li may (essentially) be equivalent to the axis length LA, i.e., the first length Li may follow the filament axis of elongation AF (see also Fig. 2a, embodiment II, and Fig. 2B). In other embodiments, the first length Li may not follow the filament axis of elongation AF. In such embodiments, the first length Li may define a first length axis of elongation AL. Especially, the (first length Li of the) LED filament may be curved. For instance, the LED filament may have a 3D spiraling shape, (like) a helical shape, or another curved shape. In curved embodiments, the axis length LA may be smaller than the first length Li, such as LA / LI < 0.95, especially LA / LI < 0.75, more especially L / LI < 0.35. Especially, the LED filament may have relatively high aspect ratios (Li / W or Li / T), such as at least 10, especially at least 15, such as at least 20, more especially at least 50. Large aspect ratios may better mimic a filament.

[0015] Especially, the elongated carrier may support the solid state light sources. The elongated carrier may e.g. comprise glass or sapphire. In other embodiments, the elongated carrier may comprise a polymeric material. The elongated carrier may be rigid (self- supporting), but may (in polymeric embodiments) also be flexible. In embodiments, the elongated carrier may be translucent or transparent for light, especially visible light. The elongated carrier may have (essentially) similar dimensions to the LED filament. Especially, the elongated carrier may (essentially) define the first length Li and axis length LA of the LED filament. The width W and thickness T of the LED filament may be defined by the elongated carrier as well as other components of the LED filament, e.g., the solid state light sources and an (optional) encapsulant.

[0016] The LED filament may comprise a plurality of solid state light sources arranged in an array on an elongated carrier. The number of solid state light sources in the array may be at least 4, such as at least 8, even more especially at least 12, and may e.g. be up to 100, or yet even larger. Especially, in embodiments the number of solid state light sources in the array may be selected from the range of 10-1000, such as 10-200. The solid state light sources may be arranged in an array over the first length (Li) of the LED filament on the elongated carrier. Hence, over at least part of the length the solid state light sources may be arranged. Hence, the solid state light source may be configured in a ID array over at least part of the length. A first and a last solid state light source may, when measured along the LED filament, have a mutual distance of at least 0.5*Ll, even more especially O.7*L1 (i.e. 70% of the first length). In embodiments, the solid state light source may be configured in two ID arrays, one at one side of the elongated carrier and one at the other side of the elongated carrier. A 2D array of solid state light sources may also be possible. A 2D array of solid state light sources may especially have a (much) smaller number of rows (nl) than the number (n2) of solid state light sources in those respective rows, such as nl / n2 <0.2, like nl / n2 <0.1, especially nl / n2 <0.05.

[0017] The term “light source” may refer to a semiconductor light-emitting device, such as a light emitting diode (LEDs), a resonant cavity light emitting diode (RCLED), a vertical cavity laser diode (VCSELs), an edge emitting laser, etc.. The term “light source” may also refer to an organic light-emitting diode, such as a passive-matrix (PMOLED) or an active-matrix (AMOLED). In a specific embodiment, the light source comprises a solid state light source (such as a LED or laser diode). In an embodiment, the light source comprises a LED (light emitting diode). The term LED may also refer to a plurality of LEDs. Further, the term “light source” may in embodiments also refer to a so-called chips-on-board (COB) light source. The term “COB” especially refers to LED chips in the form of a semiconductor chip that is neither encased nor connected but directly mounted onto a substrate, such as a PCB. Hence, a plurality of semiconductor light sources may be configured on the same substrate. In embodiments, a COB is a multi LED chip configured together as a single lighting module. The term “light source” may also relate to a plurality of (essentially identical (or different)) light sources, such as 2-2000 solid state light sources. In embodiments, the light source may comprise one or more micro-optical elements (array of micro lenses) downstream of a single solid state light source, such as a LED, or downstream of a plurality of solid state light sources (i.e. e.g. shared by multiple LEDs).

[0018] In embodiments, the solid state light sources comprise LEDs. Alternatively or additionally, in embodiments the solid state light sources comprise diode lasers. Especially, the solid state light sources comprise LEDs. Therefore, in embodiments, the LED filament comprises an array of a plurality of solid state light sources arranged on an elongated carrier.

[0019] In embodiments, the LED filament may be configured to generate filament light. Especially, the solid state light sources, comprised by the LED filament, may be configured to generate light source light. Thereby, (part ol) the light source light may be comprised by filament light. The encapsulant may diffuse and / or scatter the light source light. Hence, in embodiments, the filament light may comprise the light source light, or may even essentially consist of the light source light. However, in other embodiments, the encapsulant may comprise a luminescent material. The luminescent material may convert at least part of the light source light into luminescent material light. Hence, in embodiments the filament light may comprise luminescent material light, and optionally non-converted light source light. Especially, the filament light may comprise visible light. Hence, in embodiments, the LED filament is configured to generate filament light, which may comprise one or more of light source light and luminescent material light. This will be further elucidated below.

[0020] The terms “light” and “radiation” are herein interchangeably used, unless clear from the context that the term “radiation” does not refer to visible light. The terms “light” and “radiation” may thus especially refer to (at least) visible light. The terms “visible”, “visible light” or “visible emission” and similar terms refer to light having one or more wavelengths in the range of about 380-780 nm. The terms “violet light” or “violet emission” especially relates to light having a wavelength in the range of about 380-440 nm. The terms “blue light” or “blue emission” especially relates to light having a wavelength in the range of about 440-495 nm (including some violet and cyan hues). The terms “green light” or “green emission” especially relate to light having a wavelength in the range of about 495-570 nm. The terms “yellow light” or “yellow emission” especially relate to light having a wavelength in the range of about 570-590 nm. The terms “orange light” or “orange emission” especially relate to light having a wavelength in the range of about 590-620 nm. The terms “red light” or “red emission” especially relate to light having a wavelength in the range of about 620-780 nm. The term “pink light” or “pink emission” refers to light having a blue and a red component. The term “cyan” may refer to one or more wavelengths selected from the range of about 490-520 nm. The term “amber” may refer to one or more wavelengths selected from the range of about 585-605 nm, such as about 590-600 nm. The phrase “light having one or more wavelengths in a wavelength range” and similar phrases may especially indicate that the indicated light (or radiation) has a spectral power distribution with at least intensity or intensities at these one or more wavelengths in the indicate wavelength range. For instance, a blue emitting solid state light source will have a spectral power distribution with intensities at one or more wavelengths in the 440-495 nm wavelength range. Herein, the filament light may at least comprise light at a wavelength selected from the range of 380-780 nm, i.e., visible light. Especially for certain embodiments showing a flame effect, the filament light may at least comprise light at a wavelength selected from the range of 570-780 nm, i.e., yellow light, orange light, amber light, and red light. Hence, the filament light may comprise light of a coloring associated with a flame effect, which may be particularly desired for decorative lighting.

[0021] For other embodiments showing a flame effect, the filament light may comprise white light. The term “white light”, and similar terms, herein, is known to the person skilled in the art. It may especially relate to light having a correlated color temperature (CCT) between about 1500 K and 20000 K, such as between 1800 and 20000 K, especially 2700-20000 K, for general lighting especially in the range of about 2000-7000 K, such as in the range of 2700 K and 6500 K. In embodiments, e.g. for backlighting purposes, or for other purposes, the correlated color temperature (CCT) may especially be in the range of about 7000 K and 20000 K. Yet further, in embodiments the correlated color temperature (CCT) is especially within about 15 SDCM (standard deviation of color matching) from the BBL (black body locus), especially within about 10 SDCM from the BBL, even more especially within about 5 SDCM from the BBL. Especially, the filament light may be relatively warm (white) light, such as selected from the range of 1500 - 3000 K, especially selected from 1500 - 2700 K, most especially selected from the range of 1800-2700 K. The filament light may comprise warm white light associated with a flame effect, which may be particularly desired for decorative lighting or sphere lighting. Hence, in embodiments, the filament light may be white light having a correlated color temperature selected from the range of 1500- 3000 K.

[0022] In embodiments, the LED filament may comprise an encapsulant. The encapsulant may especially cover the plurality of solid state light sources. Further, the encapsulant may cover at least part of the elongated carrier. In general, the encapsulant may be in contact with the elongated carrier and may cover all of the solid state light sources. Hence, in embodiments the encapsulant may be configured over a substantial part of the first length Li of the LED filament (such as over more than 70% of the first length Li) and may be a continuous coating, covering a plurality of solid state light sources, such as at least 2, like at least 5, more especially at least 10, such as in embodiments at least 50% of the total number of solid state light sources in the array, such as at least 75%, especially at least 95%, up to 100%. The encapsulant may be a continuous coating along the first length Li of the LED filament, at one or both sides of the elongated carrier. The solid state light source may have a light emitting surface, such as a LED die. Herein, the phrase “the encapsulant encloses at least part of the solid state light source”, and similar phrases, especially indicate that at least part of the light emitting surface may be enclosed by the encapsulant. Therefore, in embodiments, the LED filament comprises an encapsulant covering the plurality of solid state light sources and at least part of the elongated carrier. More especially, essentially the entire elongated carrier with solid state light sources may be encapsulated with the encapsulant (thereby providing an essentially uniform appearance of the LED filament).

[0023] In embodiments, the encapsulant may be configured to diffuse and / or scatter the light source light. Thereby, the light source light may be provided as diffused and / or scattered light source light. Additionally or alternatively, the encapsulant may comprise a luminescent material configured to convert at least part of the light source light into luminescent material light. In certain further embodiments, the luminescent material may be configured to convert (essentially) all of the light source light into luminescent material light. Therefore, the filament light may in specific embodiments comprise luminescent material light (and optionally unconverted transmitted light source light). Hence, the luminescent material may provide filament light with a desired spectral light distribution (as described above), e.g., white light having a correlated color temperature selected from the range of 1500-3000 K. Therefore, in specific embodiments, the encapsulant comprises a luminescent material configured to convert at least part of the light source light into luminescent material light. Thereby, the filament light comprises luminescent material light and optionally transmitted light source light.

[0024] The term “luminescent material” especially refers to a material that can convert light source light, especially visible radiation, into luminescent material light. In general, the light source light and luminescent material light have different spectral power distributions. Hence, instead of the term “luminescent material”, also the terms “luminescent converter” or “converter” may be applied. In general, the luminescent material light has a spectral power distribution at larger wavelengths than the light source light, which is the case in the so-called down-conversion. In specific embodiments, however the luminescent material light has a spectral power distribution with intensity at smaller wavelengths than the light source light, which is the case in the so-called up-conversion. In embodiments, the “luminescent material” may especially refer to a material that can convert light into e.g. visible and / or infrared light (i.e., light over 780 nm). For instance, in embodiments the luminescent material may be able to convert visible radiation into visible light with a different spectral power distribution. The luminescent material may in specific embodiments also convert visible light into infrared light. Hence, upon excitation with light, the luminescent material emits light. In embodiments, the term “luminescence” may refer to phosphorescence. In embodiments, the term “luminescence” may also refer to fluorescence. Instead of the term “luminescence”, also the term “emission” may be applied. Hence, the terms “light source light” and “luminescent material light” may refer to excitation radiation and emission radiation, respectively. Likewise, the term “luminescent material” may in embodiments refer to phosphorescence and / or fluorescence. The term “luminescent material” may also refer to a plurality of different luminescent materials. Examples of possible luminescent materials are known to the skilled person. Hence, the luminescent material may be configured downstream of the solid state light source(s). The terms “upstream” and “downstream” relate to an arrangement of items or features relative to the propagation of the light from a light generating means (here the especially the light source), wherein relative to a first position within a beam of light from the light generating means, a second position in the beam of light closer to the light generating means is “upstream”, and a third position within the beam of light further away from the light generating means is “downstream”. Hence, the luminescent material may be in (physical) contact with the solid state light sources.

[0025] In embodiments, the LED filament may be at least partly enclosed by a light transmissive envelope. The light transmissive envelope may especially define a cavity, i.e., the light transmissive envelope may be an envelope at least partly enclosing a void volume (or envelope void volume). The cavity of the light transmissive envelope may have at least one opening to the void volume (but more openings are herein not excluded). The light transmissive envelope may provide a desired shape for the LED filament lamp, e.g., a candle bulb shape. The LED filament may in embodiments be arranged within the void volume enclosed by the light transmissive envelope. In embodiments, the light transmissive envelope may comprise an envelope length axis (AE). The envelope length axis AE may especially be a straight axis in the direction of the longest dimension of the light transmissive envelope. That is, when considering the light transmissive envelope as a three-dimensional structure, the envelope length axis AE may be defined in the direction of the longest dimension. The longest dimension (of the three-dimensional structure of the light transmissive envelope) may be longer than any dimension perpendicular to the longest dimension by an aspect ratio of at least 1.2, such as at least 1.5, especially at least 2. Furthermore, the longest dimension (of the three-dimensional structure of the light transmissive envelope) may be longer than any dimension perpendicular to the longest dimension by an aspect ratio of at most 10, such as at most 8.

[0026] The light transmissive envelope may especially comprise a light transmissive material. The light transmissive material may be transmissive for at least part of the filament light, such as the light source light and / or the luminescent material light. In embodiments, the light transmissive material may be transparent for light, especially the filament light. Thereby, the light transmissive envelope may be transmissive for at least part of the filament light. In certain embodiments, the light transmissive envelope may be transmissive for (essentially) all of the filament light. Yet in other embodiments, the light transmissive envelope may be more transmissive to filament light having a desired spectral distribution (as described above) than to other parts of filament light.

[0027] The light transmissive material may comprise one or more materials selected from the group consisting of a transmissive organic material, such as selected from the group consisting of PE (polyethylene), PP (polypropylene), PEN (polyethylene napthalate), PC (polycarbonate), polymethylacrylate (PMA), polymethylmethacrylate (PMMA) (Plexiglas or Perspex), cellulose acetate butyrate (CAB), silicone, polyvinylchloride (PVC), polyethylene terephthalate (PET), including in an embodiment (PETG) (glycol modified polyethylene terephthalate), PDMS (poly dimethylsiloxane), and COC (cyclo olefin copolymer). Especially, the light transmissive material may comprise an aromatic polyester, or a copolymer thereof, such as e.g. polycarbonate (PC), poly (methyl)methacrylate (P(M)MA), polyglycolide or poly glycolic acid (PGA), polylactic acid (PLA), poly caprolactone (PCL), polyethylene adipate (PEA), polyhydroxy alkanoate (PHA), polyhydroxy butyrate (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN); especially, the light transmissive material may comprise polyethylene terephthalate (PET). Hence, the light transmissive material is especially a polymeric light transmissive material. However, in another embodiment the light transmissive material may comprise an inorganic material. Especially, the inorganic light transmissive material may be selected from the group consisting of glasses, (fused) quartz, transmissive ceramic materials, and silicones. Also hybrid materials, comprising both inorganic and organic parts may be applied. Especially, the light transmissive material comprises one or more of PMMA, transparent PC, or glass.

[0028] In embodiments, the light transmissive material (and therefore, the light transmissive envelope) may be transmissive for at least part of the visible light. Especially, the light transmissive envelope may be transmissive for at least part of the filament light. Furthermore, the light transmissive envelope may be >50% transmissive to filament light (especially >70% transmissive, more especially >80% transmissive, most especially >90% transmissive). In specific embodiments, the light transmissive envelope may be transparent for filament light (i.e., 100% transmissive). Especially, the transmission of filament light may be determined under perpendicular radiation of the light transmissive material with filament light (especially filament light comprising visible light). Thereby, the majority (or essentially all) of the filament light may be transmitted by the light transmissive envelope. In further embodiments, the light transmissive material (and therefore, the light transmissive envelope) may be slightly diffuse for at least part of the visible light, i.e., the light transmissive envelope may be reflective for at least part of the visible light in addition to being transmissive for at least part of the visible light. Especially, the light transmissive envelope may be (lightly) reflective for at least part of the filament light. Furthermore, the light transmissive envelope may be <50% reflective to filament light (especially <30% reflective, more especially <20% reflective, most especially <10% reflective). Especially, the reflection of filament light may be determined under perpendicular radiation of the light transmissive material with filament light (especially filament light comprising visible light). Thereby, part of the filament light may be reflected by the light transmissive envelope. Hence, the LED filament lamp may provide diffused light, which may be esthetically desired and / or contribute to the flame effect. Therefore, in such embodiments, the light transmissive material may comprise a (lightly) reflective material. In certain embodiments, the light transmissive material may comprise reflective particles.

[0029] Hence, in specific embodiments, transmission of filament light by the light transmissive envelope may be more than 50% (especially more than 70%, more especially more than 80%, most especially more than 90%), and reflection of filament light by the light transmissive envelope may especially be less than 50% (especially less than 30%, more especially less than 20%, most especially less than 10%). Hence, the majority of the filament light may be transmitted, and at least part of the filament light may be provided as diffuse light.

[0030] In embodiments, the light transmissive envelope may be transparent to filament light. For instance, more than 90% of the filament light may be transmitted through the light transmissive envelope under perpendicular irradiation and less than 10% may be absorbed or scattered. In other embodiments, the light transmissive envelope may be transmissive with a reflectivity to at least part of the filament light selected from the range of (only) 10 - 20% reflection under perpendicular irradiation. Hence, some scattering and / or absorption may be allowed. When less than 10% is reflected under perpendicular irradiation, the light transmissive envelope may be indicated as transparent. With a high transparency, the ribbed structure may provide a lens structure.

[0031] In embodiments, the ribbed structure may be obtained by mechanically carving, etching, (injection) molding, or imprinting on the light transmissive envelope. Alternatively, the ribbed structure may be provided via 3D printing, such as especially FDM (see also below), by which essentially by definition a rib structure may be obtained. In specific embodiments, the light transmissive envelope may be a 3D printed item. In 3D printed embodiments, the 3D printed layers may comprise the elongated convex surfaces. Especially, the 3D printed layers may comprise the elongated convex surfaces as elongated convex outer layer surfaces. Thereby, the 3D printed layers may provide the light transmissive envelope with the ribbed structure. The 3D printing may provide ribbed like stacks, with at a surface between adjacent layers (“ribs”) the relief lines. Therefore, in embodiments, the (3D printed) layers comprise the elongated convex surfaces providing the envelope with the ribbed structure.

[0032] Especially, the light transmissive envelope may be a 3D printed item produced via the use 3D print technologies, such as a polyjet technique, i.e., layer by layer deposition of photo-polymerizable material which is cured after each deposition to form a solid structure, or Fused Deposition Modeling (FDM). Fused deposition modeling (FDM) is an additive manufacturing technology commonly used for modeling, prototyping, and production applications. FDM works on an "additive" principle by laying down material in layers; a plastic filament or metal wire is unwound from a coil and supplies material to produce a part. Possibly, (for thermoplastics for example) the filament is melted and extruded before being laid down. FDM is a rapid prototyping technology. Other terms for FDM are “fused filament fabrication” (FFF) or “filament 3D printing” (FDP), which are considered to be equivalent to FDM. In general, FDM printers use a thermoplastic filament, which is heated to its melting point and then extruded, layer by layer, (or in fact filament after filament) to create a three-dimensional object. FDM printers are relatively fast, low cost and can be used for printing complicated 3D objects. Such printers are used in printing various shapes using various polymers. The technique is also being further developed in the production of LED luminaires and lighting solutions.

[0033] The 3D printing method to produce the light transmissive envelope may especially comprise a 3D printing stage. Basically, the 3D printing stage may comprise feeding 3D printable material, forming an extrudate, and depositing the 3D printable material, to provide a 3D item comprising 3D printed material. Especially, herein the 3D printing stage may comprise layer-wise depositing 3D printable material to provide a plurality of layers of 3D printed material. Hence, by depositing a plurality of layers of 3D printable material in a stacked manner, a 3D item may be provided. In embodiments, the 3D printable material may be provided to a 3D printer, especially to the printer head of a 3D printer. Subsequently, the 3D printable material may be extruded by the printer head through a nozzle and onto a receiver item. For example, in embodiments, the 3D printable material may be deposited on a printing platform. Especially, in embodiments, the 3D printable material may be deposited in a direction such that a string of 3D printable material is provided. By deposition, the 3D printable material becomes 3D printed material. The light transmissive envelope may hence be a 3D printed item produced by layer-wise deposition of the 3D printable material comprising the light transmissive material. Especially, the 3D printed layers may be stacked to produce the light transmissive envelope. Therefore, in specific embodiments, the light transmissive envelope is a 3D printed item. Especially, the light transmissive envelope comprises a plurality of (stacked) (3D printed) layers comprising the light transmissive material.

[0034] Materials that may especially qualify as 3D printable materials may be selected from the group consisting of metals, glasses, thermoplastic polymers, silicones, etc. Especially, the 3D printable material comprises a (thermoplastic) polymer selected from the group consisting of ABS (acrylonitrile butadiene styrene), Nylon (or polyamide), Acetate (or cellulose), PLA (poly lactic acid), terephthalate (such as PET polyethylene terephthalate), Acrylic (polymethylacrylate, Perspex, polymethylmethacrylate, PMMA), Polypropylene (or polypropene), Polycarbonate (PC), Polystyrene (PS), PE (such as expanded- high impact- Polythene (or poly ethene), Low density (LDPE) High density (HDPE)), PVC (polyvinyl chloride) Poly chloroethene, such as thermoplastic elastomer based on copolyester elastomers, polyurethane elastomers, polyamide elastomers polyolefine based elastomers, styrene based elastomers, etc.. Optionally, the 3D printable material may comprise a 3D printable material selected from the group consisting of Urea formaldehyde, Polyester resin, Epoxy resin, Melamine formaldehyde, thermoplastic elastomer, etc... Optionally, the 3D printable material may comprise a 3D printable material selected from the group consisting of a polysulfone. Elastomers, especially thermoplastic elastomers, may especially be interesting as they are flexible and may help obtaining relatively more flexible filaments comprising the thermally conductive material. A thermoplastic elastomer may comprise one or more of styrenic block copolymers (TPS (TPE-s)), thermoplastic polyolefin elastomers (TPO (TPE-o)), thermoplastic vulcanizates (TPV (TPE-v or TPV)), thermoplastic polyurethanes (TPU (TPU)), thermoplastic copolyesters (TPC (TPE-E)), and thermoplastic polyamides (TPA (TPE-A)). Suitable thermoplastic materials are also mentioned in W02017 / 040893. In specific embodiments, the 3D printable material (and the 3D printed material) may comprise one or more of polycarbonate (PC), polyethylene (PE), high-density polyethylene (HDPE), polypropylene (PP), polyoxymethylene (POM), polyethylene naphthalate (PEN), styreneacrylonitrile resin (SAN), polysulfone (PSU), polyphenylene sulfide (PPS), and semi- crystalline polytethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), poly(methyl methacrylate) (PMMA), polystyrene (PS), and styrene acrylic copolymers (SMMA).

[0035] Thereby, either through 3D printing or other means (as described above), the light transmissive envelope may in embodiments be provided with a ribbed structure. In embodiments, the light transmissive envelope may comprise an external surface and an internal surface. The internal surface may be the side of the light transmissive envelope that is facing the void volume and is at least partly enclosed by the cavity of the light transmissive envelope. The external surface may especially be the other side of the light transmissive envelope, i.e., not facing the void volume. The external surface may comprise the ribbed structure. Optionally, the internal surface may comprise a ribbed internal surface, but may also comprise a smooth internal surface. The ribbed structure may especially be defined by elongated convex surfaces and intermediate relief lines (on the external surface). The elongated convex surfaces may be surfaces that are convex (i.e., rounded towards a direction outward from the light transmissive envelope) in a direction parallel to the envelope length axis (AE). Further, the elongated convex surfaces may be elongated in a direction perpendicular to the envelope length axis (AE). The elongated convex surfaces may be arranged adjacent to each other in a direction parallel to the envelope length axis (AE). The intermediate relief lines may be arranged between adjacent elongated convex surfaces. Furthermore, the rounding curve of an elongated convex surfaces towards a direction outward from the light transmissive envelope may start at the two adjacent intermediate relief lines. Thereby, the ribbed structure may be a layered structure (or “stacked structure”) comprising a repeating sequence of (layered) elongated convex surfaces interspersed by intermediate relief lines in a direction parallel to the envelope length axis (AE). In 3D printed embodiments, the ribbed structure may especially be provided during the 3D printing process. Layer by layer printable material may be deposited, by which the 3D printed item may be generated (during the printing stage). The 3D printed item may show characteristic ribbed structures (originating from the deposited 3D printed material filaments).

[0036] In embodiments, the ribbed structure may define a distance d2 between adjacent intermediate relief lines. The distance d2 may especially be selected from the range of 0.2 - 10 mm, such as from the range of 0.4 - 5 mm, especially from the range of 0.5 - 1 mm. The distance d2 may in embodiments (essentially) define the height of an elongated convex surface in the direction parallel to the envelope length axis (AE) that is positioned between two adjacent intermediate relief lines, i.e., across the ribbed structure. In general, the distance d2 may remain the same across and along the ribbed structure (i. e. , both in the directions parallel (across) and perpendicular (along) to the envelope length axis (AE)). However, in some embodiments, the distance d2 may vary across and / or along the ribbed structure. Furthermore, the ribbed structure (especially the intermediate relief lines) may in embodiments define a first thickness Ti of the light transmissive envelope (wall). The first thickness Ti may be the thickness of the light transmissive envelope at the intermediate relief lines. Especially, the first thickness Ti may be a shortest thickness of the light transmissive envelope at the intermediate relief lines. The first thickness Ti may in embodiments be selected from the range of 0.2 - 40 mm, such as from the range of 0.5 - 20 mm, especially from the range of 1 - 10 mm. In general, first thickness Ti at each individual intermediate relief line may remain the same along and across the ribbed structure. However, in some embodiments, the first thickness Ti at each individual intermediate relief line may vary along and across the ribbed structure. Additionally, the ribbed structure (especially the elongated convex surfaces) may in embodiments define a second thickness T2 of the light transmissive envelope. The second thickness T2 may be the thickness of the light transmissive envelope at the elongated convex surfaces. Especially, the second thickness T2 may be a largest thickness of the light transmissive envelope at the elongated convex surfaces. The largest thickness T2 may be especially at the rounded comer of the rounding curve towards a direction outward from the light transmissive envelope of the elongated convex surfaces. The second thickness T2 may in embodiments be selected from the range of 0.5 - 50 mm, such as from the range of 1 - 25 mm, especially from the range of 2 - 15 mm. In general, the second thickness T2 at each individual elongated convex surface may remain the same along and across the ribbed structure. However, in some embodiments, the second thickness T2 at each individual elongated convex surface may vary along and across the ribbed structure. Hence, in embodiments, amongst others at the distance d2, the first thickness Ti, and the second thickness T2, may be selected such as to provide the desired optical effect, especially a flame effect. In 3D printed embodiments, the distance d2, first thickness Ti and second thickness T2 may be determined by the deposition of at least one layer of 3D printed material (originating from the deposited 3D printed material filaments). That is, the height of at least one layer of 3D printed material may determine the distance d2 of the ribbed structure. Further, the largest thickness of at least one layer of 3D printed material may determine the second thickness T2. Furthermore, the smallest thickness between at least two adjacent layers of 3D printed material may determine the first thickness Ti. Thereby, in specific embodiments, the ribbed structure defines a distance d2 between adjacent intermediate relief lines selected from the range of 0.4 - 10 mm (and the distance d2 additionally defines the length of an elongated convex surface along the ribbed structure). Further, the ribbed structure defines a (shortest) first thickness Ti of the light transmissive envelope at the intermediate relief lines selected from the range of 0.2 - 40 mm. Furthermore, the ribbed structure defines a (largest) second thickness T2 of the light transmissive envelope at the elongated convex surfaces selected from the range of 0.5 - 50 mm.

[0037] The relief lines may be defined (at the external surface) at the (shortest) first thickness Ti of the light transmissive envelope. Note that essentially equally well the relief lines may be defined (at the external surface) at the (largest) second thickness T2 of the light transmissive envelope.

[0038] In embodiments, the light transmissive envelop may have an absorption length and / or a scatter length of at least the second thickness T2, such as at least twice the second thickness T2. The absorption length may be defined as the length over which the intensity of the light along a propagation direction due to absorption drops with 1 / e. Likewise, the scatter length may be defined as the length along a propagation direction along which light is lost due to scattering and drops thereby with a factor 1 / e.

[0039] In embodiments, the external surface may not be a single continuous surface (e.g., forming a cylinder or cone). Rather, the external surface may especially be segmented. Therefore, the external surface may in embodiments comprise facets, i.e., continuous (essentially polygonal) surfaces segmented from each other configured on the external surface. A facet may thus be defined by a face and a plurality of edges (bordering two or more adjacent facets). In embodiments, the face may be a continuous surface. In some embodiments, the face of at least one facet may be concave. In other embodiments, the face of at least one facet may be convex. Note that one or more facets may also comprise a concave part and a convex part. Especially, the facets may comprise concave parts. The edge may comprise a smallest angle between two faces of at most 85°, such as at most 80°, especially at most 75°. The edge between two faces may especially comprise a relatively sharp comer having the smallest angle between two faces. The edge may comprise a ridge (i.e., a (narrow) relatively raised area) or a groove (i.e., a (narrow) relatively lowered area). The external surface may comprise a plurality of facets, such as n facets. The number of facets n may in embodiments be selected from the range of 2 - 100, such as 3 - 50, especially 3 - 18. The faces may in general be positioned adjacent to each other in a direction perpendicular to the envelope length axis AE. Yet also, in spiraling embodiments, one or more faces may be positioned adjacent to each other in a direction parallel to the envelope length axis AE.

[0040] The facets may especially be defined by the ribbed structure, i.e., each of the plurality facets may comprise at least part of the ribbed structure. Hence, the facets may be ribbed. In certain embodiments, the ribbed structure may define a concave face of at least one facet. In further embodiments, the ribbed structure may define a convex face of one or more facets. In specific embodiments, the ribbed structure may define both at least one concave face and one or more convex faces. Each face may thus comprise a plurality of convex elongated surfaces and intermediate relief lines across the ribbed structure. Each face may comprise at least part of a circumference of the convex elongated surface and intermediate relief lines along the ribbed structure. The circumference may define a circularly equivalent diameter within a plane perpendicular to the envelope length axis (AE). The circumference may especially be defined about the envelope length axis (AE). Further, the circumference may vary in a direction parallel to the envelope length axis (AE). A rotational angle (P) may be defined for each of the faces about the envelope length axis (AE). The rotational angle ( ) of the each of the faces may be at least 20°, such as at least 30°, especially at least 40°. The rotational angle (P) of the one or more facets may be n*360°, such as at most 3*360°, such as at most 2.5*360°, especially at most 2*360°. The rotational angle (P) of the each of the faces may vary in a direction parallel to the envelope length axis (AE). The plurality of facets positioned adjacent to each other along the ribbed structure of the external surface may comprise essentially the entirety of the circumference of the convex elongated surface and intermediate relief lines along the ribbed structure. Hence, the facets may have a ribbed (external) surface.

[0041] One or more facets may be configured on a base side (e.g., a first end, described further below). The one or more facets may hence comprise at least one edge shared with the base side (rather than with an adjacent facet). In embodiments, the base side may generally have a round shape, such as a circle. On the other end across the ribbed structure of the one or more facets may be an apex side. In embodiments, the apex side may be a round shape, such as a circle. The apex side may be a similar shape as the base side. However, the apex side may have different dimensions. Especially, in a candle bulb shape, the apex side may be (essentially) a point. Hence, the (plurality of) faces may have a varying diameter across the external surface. Herein, the facets may especially be configured in a spiral-like configuration. That is, the one or more facets may be rotated (or: “twisted”) relative to the base across the ribbed structure. However, other configurations are herein not excluded. In a spiral-like configuration, the facets may be configured spiraling about (at least part of) the envelope length axis (AE). That is, the central axis of the spiral-like configuration of each facet may (essentially) be equal to (at least part ol) the envelope length axis AE. AS the facets spiral across the external surface, the plurality of facets positioned adjacent to each other along the ribbed structure of the external surface may comprise essentially the entirety of the circumference of the external surface. Thereby, the plurality of facets may provide the external surface of the light transmissive envelope with a desired shape, especially a spiraling (candle bulb) shape. In particular, each facet may provide one or more of a pointed shape or a flame-like shape. The combination of a plurality of facets having such shapes may be used to design a LED filament lamp having, e.g., a torch-like shape, a soft serve ice cream shape, a candle bulb shape, etc. Hence, the design of the facets may further facility a flame effect. Therefore, in embodiments, the light transmissive envelope comprises an external surface comprising a plurality of facets defined by the ribbed structure. Further, the facets are arranged in a spiral-like configuration spiraling about at least part of the envelope length axis AE. In specific embodiments, the plurality of facets is n facets, wherein n is especially selected from the range of 3-18, like at least 4, such as 6-18, like 6-12, though other values may also be possible.

[0042] As indicated above, the invention provides a LED filament lamp comprising a LED filament at least partly enclosed by a light transmissive envelope. In embodiments, the LED filament may be configured within the light transmissive envelope such as to provide a desired optical effect with the filament light. Especially, the LED filament may be configured in such a way as to exhibit a flame effect. To achieve this, the LED filament may be configured in a specific configuration following a set of specifications that will be described below.

[0043] The LED filament may be configured based on the specifications of a plurality of virtual vectors Vv. Each of the plurality of virtual vectors Vv may be defined according to at least the following three specifications. By configuring the LED filament such that a plurality of virtual vectors Vv follow at least these three specifications, the desired optical light effect may be provided. Especially, the plurality of virtual vectors Vv may be used to define a filament projection on the external surface of the light transmissive envelope, with the filament projection having selected mutual angles with the intermediate relief lines. Firstly, each of the plurality of virtual vectors Vv may start at the envelope length axis AE. Especially, each of the plurality of virtual vectors Vv may start at different positions along the envelope length axis AE. Secondly, each of the plurality of virtual vectors Vv may intersect the LED filament. Especially, each of the plurality of virtual vectors Vv may intersect the LED filament at different positions of the LED filament. Thirdly, each of the plurality of virtual vectors Vv may follow a distance dl from the LED filament to an intermediate relief line comprised by the light transmissive envelope. The distance dl may especially be a shortest distance between the LED filament and an intermediate relief line. That is, for each of the plurality of intermediate relief lines, the distance dl may be the shortest distance between the LED filament and that intermediate relief line. However, for different vectors the value of the distance dl is not necessarily the same. In general, each of the plurality of intermediate relief lines may have a single shortest distance from the LED filament. However, it is not excluded that an intermediate relief line may have two or more (essentially equally) shortest distances from the LED filament. The intermediate relief line may in general be an intermediate relief line on the external surface of the light transmissive envelope. Therefore, the shortest distance dl between the LED filament and the intermediate relief line may define an intersection point on the downstream facet, i.e., an intersection point on a facet positioned (directly) downstream of the LED filament. Thus, based on the three specifications, each of the plurality of virtual vectors Vv may start at the envelope length axis AE, follow a direction such that it may intersect the LED filament, and then follow a shortest distance dl to an intermediate relief line on a downstream facet. A single virtual vector Vv may be defined to intersect one LED filament and follow to one facet (i.e., the downstream facet for that LED filament). Further, two or more of the virtual vectors (Vv) may intersect at most one LED filament and follow to at most one facet, such that the virtual vectors (Vv) for that LED filament provide a plurality of intersection points on a plurality of (adjacent) intermediate relief lines on one (downstream) facet. Further, two or more of the virtual vectors (Vv) may intersect at most one LED filament and follow to two or more facets (i.e., the at most one LED filament has two or more downstream facets). Especially, the two or more virtual vectors (Vv) for the at most one LED filament may provide a plurality of intersection points on each of the two or more downstream facets. Moreover, two or more of the virtual vectors (Vv) may intersect two or more LED filaments and follow to at most one facet (i.e., the at most one facet is the downstream facet of two or more LED filaments). Therefore, in embodiments, the LED filament is configured such that a plurality of virtual vectors (Vv) each (i) start at the envelope length axis (AE), (ii) intersect the LED filament, and (iii) follow a (shortest) distance dl from the LED filament to an intermediate relief line comprised by (a downstream facet ol) the light transmissive envelope. Further, for the sake of understanding, a filament projection of the LED filament on the light transmissive envelope may be used. The filament projection may herein be defined by the virtual vectors Vv intersecting with the light transmissive envelope. As each of the plurality of virtual vectors Vv follows a (shortest) distance dl from the LED filament to an intermediate relief line, it follows that there is at least one intersection point on each of those intermediate relief lines with a virtual vector Vv. The plurality of virtual vectors Vv therefore define a plurality of intersection points with the light transmissive envelope. Herein, the plurality of intersection points may define a (two-dimensional) projection of the LED filament on the external surface of the light transmissive envelope. Especially, the (two-dimensional) filament projection may be defined by virtually tracing a path from each of the plurality of intersection points to at least one intersection point on an adjacent intermediate relief line. Therefore, the filament projection may be a (two- dimensional) path tracing intersection points on adjacent intermediate relief lines on the external surface of the light transmissive envelope. Therefore, in embodiments, the LED filament is configured such that a plurality of intersection points of the virtual vectors (Vv) with the light transmissive envelope define a filament projection on the light transmissive envelope. In embodiments, the filament projection may be projected on at least one downstream facet of the light transmissive envelope.

[0044] The filament projection may especially be projected across a plurality of downstream facets of the light transmissive envelope, as the LED filament may have a plurality of downstream facets. In some embodiments with spiraling facets, this may result from a plurality of spiraling facets being arranged downstream of the LED filament, i.e., moving across the ribbed structure, different spiraling facets may be configured downstream of the LED filament. In further embodiments with a LED filament with a 3D spiraling shape, this may result from the spiraling LED filament being arranged closer to a plurality of downstream facets along the first length Li of the LED filament, i.e., moving along the first length Li of the LED filament, different facets may be configured downstream of the LED filament. In embodiments with a filament projection across a plurality of downstream facets, a two-dimensional paths may be traced between the nearest intersection points along the intermediate relief lines within one downstream facet, and one or more two-dimensional paths may be similarly traced on further downstream facets.

[0045] Furthermore, the LED filament may be configured such that the filament projection provides mutual angles (a) between the filament projection and the intermediate relief lines. A mutual angle (a) may herein relate to an angle between the two-dimensional path of the filament projection and an intermediate relief line. Especially, a mutual angle (a) may be defined at an intersection point of the intermediate relief line. Further, a mutual angle (a) may be a smallest angle between the filament projection and an intermediate relief line. Furthermore, a mutual angle (a) may be defined on the external surface of the light transmissive envelope. Therefore, two or more intersection points of the virtual vectors Vv with the intermediate relief lines may define at least two mutual angles (a) as the smallest angle between the path of the filament projection (defined by the two or more intersection points) and an intermediate relief line on the external surface. That is, two or more intersection points may be necessary to define a path of the filament projection, and a mutual angle (a) may be defined at each of the two or more intersection points. Therefore, in specific embodiments, the filament projection on at least one of the downstream facets may provide a plurality of mutual angles (a) between the filament projection and the intermediate relief lines (at the intersection points). In embodiments, at least one of the mutual angles (a) may be selected from the range of 5 - 85°, such as from the range of 8 - 82°, especially from the range of 10 - 80°. Furthermore, in specific embodiments, one or more of the mutual angles (a) may be selected from the range of 15 - 75°, such as from the range of 20 - 70°, especially from the range of 25 - 65°. When filament light from the LED filament reaches the ribbed structure with defined mutual angles (a) between the filament projection and the intermediate relief lines, the elongated convex surfaces may act as refractive cylindrical lenses for the filament light. Thereby, the desired optical effect may be provided to the filament light. Especially, the filament light may be provided as broadened filament light, such as gradually shaded filament light. Hence, the configuration of a LED filament having a filament projection with mutual angles (a) selected from a specified range may provide filament light having a flame effect.

[0046] In embodiments with a plurality of mutual angles (a) on at least one of the downstream facets, at least 35% of the plurality of mutual angles (a) (on the at least one of the downstream facets) may be individually selected from the ranges specified above, such as at least 50%, especially at least 65%, most especially at least 80%. Two or more of the plurality of mutual angles (a) (on the at least one of the downstream facets) may be equal, i.e., the path of the projection is relatively constant. However, at least two more of the plurality of mutual angles (a) (on the at least one of the downstream facets) may be different, i.e., the path of the projection may change across the external surface (comprised by the facet). Relatively constant mutual angles (a) across the filament projection may especially provide a gradually shaded light effect. Varying mutual angles (a) may especially provide an acutely shaded light effect.

[0047] Therefore, in embodiments, the filament projection provides mutual angles (a) between the filament projection and the intermediate relief lines, and at least one of the mutual angles (a) is selected from the range of 10-80°. Further, in specific embodiments, the filament projection on at least one of the (downstream) facets provides a plurality of mutual angles (a) between the filament projection and the intermediate relief lines, and at least 80% of the plurality of mutual angles (a) may be individually selected from the range of 10-80°. In certain embodiments, one or more of the mutual angles (a) may be selected from the range of 20-70°. With angles about 90°, the flame effect may not be achieved and the light of the filament(s) may only appear broader or elongated.

[0048] Summarizing, in embodiments the LED filament may be configured as described above: defining a plurality of virtual vectors Vv to intersect with the LED filament and the intermediate relief lines, thereby projecting a filament projection on the external surface of the light transmissive envelope, such that mutual angles (a) selected from specified ranges are provided between the filament projection and the intermediate relief lines. Hence, with such configuration of the LED filament relative to the ribbed structure, the LED filament lamp of the present invention may provide filament light with a desired optical effect. Especially, with such configuration the elongated convex surfaces may act as refractive cylindrical lenses for the filament light. Thereby, the desired optical effect may be provided to the filament light. Herein, the LED filament lamp may be designed specifically to achieve the desired optical effect. Especially, the configuration of the LED filament within the LED filament lamp and the dimensions of the ribbed structure may be designed to result in an optical effect (especially a flame effect) when viewing the LED filament lamp. Such lamps may be designed in a manner that they act as a decorative ensemble. Both the configuration of the LED filament and the ribbed structure may be designed specifically to achieve the mutual angles (a) selected from specified ranges are provided between the filament projection and the intermediate relief lines. In particular, such mutual angles (a) may provide vertical broadening (seen as a flame effect) of the filament light when viewing the LED filament lamp. If the LED filaments are not configured with such mutual angles (a), then when placed into the light transmissive the optical effect may only result in elongation of the filament light rather than the desired flame effect.

[0049] Especially, the LED filament may be designed and configured specifically to provide the mutual angles (a) selected from specified ranges with a specific ribbed structure. Vice versa, the light transmissive envelope may be designed specifically to have a ribbed structure providing the mutual angles (a) selected from specified ranges with a certain LED filament. Furthermore, a curved LED filament, such as especially a 3D spiraling LED filament (described further below), may easily be configured to provide the mutual angles (a) selected from specified ranges with a wide range of (different) light transmissive envelopes. Moreover, a spiraling light transmissive envelope, especially having spiraling facets providing a candlelight bulb shape, may easily be configured to provide the mutual angles (a) selected from specified ranges with a wide range of (different) LED filaments. Therefore, a LED filament lamp designed to comprise a curved LED filament, such as a spiral-like filament, or a spiraling light transmissive envelope may provide a (relatively) straightforward design and cost-effective manner of providing light having a flame effect. In particular, a LED filament lamp comprising both a curved LED filament, such as a spiral-like filament, and a spiraling light transmissive envelope may bypass specific configurations of the LED filament and the ribbed structure and readily provide light having a flame effect from (essentially) all viewing angles and (essentially) all configurations.

[0050] In specific embodiments, the LED filament lamp may comprise a plurality of LED filaments, such as at least 2 LED filaments, especially at least 3 LED filaments, such as at least 4 LED filaments. Furthermore, the LED filament lamp may comprise a plurality of LED filaments, such as at most 10 LED filament, especially at most 8 LED filaments, such as at most 6 LED filaments. Herein, each of the plurality of LED filaments may be configured as specified above. In particular, each of the plurality of LED filaments may define their own set of a plurality of virtual vectors Vv relative to the intermediate relief lines (as described above for each individual LED filament). Thereby, a filament projection may be defined for each of the plurality of LED filaments. Each of the plurality of LED filaments may have different downstream facets. However, the plurality of LED filaments may share downstream facets. In some embodiments, the filament projections of different LED filaments may in some embodiments partially overlap or intersect. Especially, this may in certain embodiments result from a plurality of spiraling facets around the plurality of LED filaments. Further, in other embodiments, this may result from a plurality of spiraling LED filaments being arranged sharing or overlapping the same plurality of downstream facets. Hence, a plurality of LED filaments may especially facilitate achieving or enhancing a flame effect on a plurality of downstream facets, and the desired optical effect may be present from more (especially all) viewing angles. Further specific embodiments of the invention may provide further specifications to achieve or enhance the flame effect in the filament light. Especially, such embodiments may further facilitate achieving or enhancing one of the visual properties of a flame effect as described above. Such specific embodiments will be described below.

[0051] In certain embodiments, the filament axis of elongation (AF) and the envelope length axis (AE) (as described above) may not be configured in a single plane. Both the filament axis of elongation (AF) and the envelope length axis (AE) may herein be straight ID axes. The LED filament may be configured such that the filament axis of elongation (AF) and the envelope length axis (AE) are not configured within a single plane. Therefore, such configuration of the LED filament may facilitate achieving a filament projection on the external surface providing mutual angles (a) selected from specified ranges. Hence, the LED filament may thereby provide a slanted filament projection on the external surface. Should the filament axis of elongation (AF) and the envelope length axis (AE) be configured within the same plane, the desired optical effect may be diminished or absent (especially when viewed from that plane) as the filament projection may provide mutual angles (a) outside of the specified ranges (i.e., the LED filament may provide a straight filament projection on the external surface, especially when the filament is straight, and with mutual angles (a) of 90°). Hence, with this configuration, the desired optical effect may be present from more (especially all) viewing angles. Therefore, in specific embodiments, the filament axis of elongation (AF) and the envelope length axis (AE) may not be configured in a single plane. However, when the filament is curved, such as in the case of a spiraling filament, then a plurality of the mutual angles (a) may be within the indicated range of about 10-80°.

[0052] As described above, the LED filament may be curved. In specific embodiments, the LED filament may comprise a three-dimensional (3D) spiraling shape. For instance, the LED filament may have a 3D spiraling shape, such as in embodiments a helical shape, or another curved shape. Especially, in embodiments the LED filament may have a helical-like shape. Furthermore, the filament projection for a curved shape may facilitate achieving a filament projection on the external surface providing mutual angles (a) selected from specified ranges. Hence, the curved LED filament may thereby provide a slanted filament projection on the downstream faces.

[0053] In certain embodiments, the LED filament lamp may comprise a second light transmissive envelope. The second light transmissive envelope may comprise any light transmissive material as described above for the light transmissive envelope. In specific embodiments, the second light transmissive envelope may (also) be a 3D printed item, e.g., a FDM 3D printed item or a stereolithography (SLA) 3D printed item. Preferably, the second light transmissive envelope may comprise a transparent material, especially glass or quartz. The second light transmissive envelope may be a tube at least partly enclosing a second void volume. Especially, the second light transmissive envelope may have a tube-like shape. The second light transmissive may especially at least partly enclose the LED filament. That is, the LED filament may be placed within the second void volume at least partly enclosed by the second light transmissive envelope. The light transmissive envelope may itself at least partly enclose the second light transmissive envelope, i.e., the second light transmissive envelope may be placed within the void volume at least partly enclosed by the light transmissive envelope. Therefore, the light transmissive envelope at least partly enclosed the second light transmissive envelope which at least partly encloses the LED filament. Hence, the second light transmissive envelope may provide an enclosure for the LED filament e.g. for (electrical) safety reasons. Further, the second light transmissive envelope may shield the LED filament from external hazards and may be especially applicable for outdoor lighting. Therefore, in further embodiments, the LED filament lamp comprises a second light transmissive envelope. Especially, the second light transmissive envelope may at least partly enclose the LED filament, and the light transmissive envelope may at least partly enclose the second light transmissive envelope. Especially, the second light transmissive envelope is essentially transparent for the filament light.

[0054] The present invention may especially be applicable for a candle bulb shaped lamp, as a flame effect may especially be appreciated in such candle bulb lamps. Furthermore, the shape of candle bulb lamps may facilitate providing light exhibiting a flame effect. Therefore, the following specific embodiments may especially relate to (candle) bulb lamps.

[0055] In further embodiments, the LED filament lamp may comprise a support part. The support part may comprise a base structure, e.g., a screw base structure or a twist-lock base structure. The support may further comprise electrically conductive elements, e.g., electrically conductive wiring. The support part may be designed to safely and conveniently provide electrical connectivity to the LED filament lamp. Therefore, the support part may further comprise electrical safety elements. Further, the support part may optionally provide connecting elements to a control system. The LED filament may especially be functionally coupled to the support part, i.e., the support part may provide electrical connectivity (and optionally connection to a control system) to the LED filament. The control system may herein comprise a system providing electronic control and / or ballast control. The term “controlling” and similar terms especially refer at least to determining the behavior or supervising the running of an element. Hence, herein “controlling” and similar terms may e.g. refer to imposing behavior to the element (determining the behavior or supervising the running of an element), etc., such as e.g. measuring, displaying, actuating, opening, shifting, changing temperature, etc.. Thereby, the control system may herein in embodiments provide electronic control and / or ballast control, i.e., imposing a desired electronic and / or electrical ballast on the LED filament lamp to safely provide filament light with the desired optical effect.

[0056] Beyond that, the term “controlling” and similar terms may additionally include monitoring. Hence, the term “controlling” and similar terms may include imposing behavior on an element and also imposing behavior on an element and monitoring the element. The controlling of the element can be done with a control system, which may also be indicated as “controller”. The control system and the element may thus at least temporarily, or permanently, functionally be coupled. The element may comprise the control system. In embodiments, the control system and element may not be physically coupled. Control can be done via wired and / or wireless control. The term “control system” may also refer to a plurality of different control systems, which especially are functionally coupled, and of which e.g. one control system may be a master control system and one or more others may be slave control systems. A control system may comprise or may be functionally coupled to a user interface.

[0057] The control system may also be configured to receive and execute instructions from a remote control. In embodiments, the control system may be controlled via an App on a device, such as a portable device, like a Smartphone or I-phone, a tablet, etc.. The device is thus not necessarily coupled to the lighting system, but may be (temporarily) functionally coupled to the lighting system.

[0058] Optionally, the control system may comprise a slave control system. Hence, in embodiments the control system may (also) be configured to be controlled by an App on a remote device. In such embodiments the control system of the lighting system may be a slave control system or control in a slave mode. For instance, the lighting system may be identifiable with a code, especially a unique code for the respective lighting system. The control system of the lighting system may be configured to be controlled by an external control system which has access to the lighting system on the basis of knowledge (input by a user interface of with an optical sensor (e.g. QR code reader) of the (unique) code. The lighting system may also comprise means for communicating with other systems or devices, such as on the basis of Bluetooth, Thread, WIFI, LiFi, ZigBee, BLE or WiMAX, or another wireless technology.

[0059] Through a slave control system, the filament light may be provided with desired properties. Especially, the slave control system may control one or more properties of the filament light selected from radiant flux, color point, and correlated color temperature (CCT). Thereby, the slave control system may control providing filament light having desired light properties of the filament light. Especially, the slave control system may provide desired filament light having a flame effect.

[0060] The system, or apparatus, or device (such a the herein described LED filament lamp), may execute an action in a “mode” or “operation mode” or “mode of operation” or “operational mode”. The term “operational mode may also be indicated as “controlling mode”. Likewise, in a method an action or stage, or step may be executed in a “mode” or “operation mode” or “mode of operation” or “operational mode”. This does not exclude that the system, or apparatus, or device may also be adapted for providing another controlling mode, or a plurality of other controlling modes. Likewise, this may not exclude that before executing the mode and / or after executing the mode one or more other modes may be executed. In specific embodiments, the slave control system may have an operational mode to change the one or more properties of the filament light being controlled. Thereby, a continually changing filament light having a flame effect may be provided, e.g., having a dancing or flickering flame effect. Such dancing or flickering flame effect may be particularly aesthetically pleasing as it further mimics a natural flame.

[0061] However, in embodiments a control system may be available, that is adapted to provide at least the controlling mode. Would other modes be available, the choice of such modes may especially be executed via a user interface, though other options, like executing a mode in dependence of a sensor signal or a (time) scheme, may also be possible. The operation mode may in embodiments also refer to a system, or apparatus, or device, that can only operate in a single operation mode (i.e. “on”, without further tunability).

[0062] Hence, in embodiments, the control system may control in dependence of one or more of an input signal of a user interface, a sensor signal (of a sensor), and a timer. The term “timer” may refer to a clock and / or a predetermined time scheme.

[0063] In embodiments, the light transmissive envelope may comprise a first end and a second end. As defined above, the light transmissive envelope may define a cavity. The opening of the cavity may especially be at the first end. The first end may be configured in contact with the support part. Especially, in embodiments the first end may be configured functionally coupled to the support part. The second end may be the part of the light transmissive envelope most remote from the support part. Therefore, in specific embodiments, the LED filament lamp comprises a support part. Especially, the LED filament is functionally coupled to the support part. Further, the light transmissive envelope comprises a first end, configured in contact with the support part and a second end, remote from the support part.

[0064] Together, the first end and the second end may define a height Hl of the light transmissive envelope. Furthermore, the light transmissive envelope may define a width W of the light transmissive envelope in a direction perpendicular to the envelope length axis (AE). Especially, the width W may increase along the envelope length axis (AE) in a direction from the first end to the second end over at least part of the height Hl to a maximum width WM. In embodiments, the width W may be related to an outer perimeter (Po) of the light transmissive envelope (i.e. , the width W may essentially be the diameter and the outer perimeter (Po) the circumference of the circularly equivalent shape of the light transmissive envelope). Especially, the maximum width WM may relate to a largest outer perimeter (POL) of the light transmissive envelope.

[0065] In certain embodiments, the external surface may comprise an outer perimeter Po. The outer perimeter Po of the external surface may especially be defined in a plane perpendicular to the envelope length axis (AE). The outer perimeter Po of the external surface may be conformal to the facets defined on the external surface, i.e., the outer perimeter Po may not be perfectly circular but may follow the contours defined by the facets (as may be especially the case for a candle bulb lamp). Hence, the ribbed structure (i.e. the intermediate relief lines between adjacent elongated convex surfaces) may follow the outer perimeter Po. The outer perimeter Po of the external surface may in some embodiments (especially a candle bulb lamp) vary (in radius) across the envelope length axis (AE). The external surface may therefore further comprise a largest outer perimeter (POL). Therefore, in further embodiments, the external surface comprises a largest outer perimeter (POL) configured in a plane perpendicular to the envelope length axis (AE), and the largest outer perimeter (POL) is conformal to the facets.

[0066] Moving further along the envelope length axis (AE) in a direction from the first end to the second end, the width W may subsequently decrease over at least part of the height HL Thereby, the LED filament lamp may have the shape of a bulb lamp, especially when the maximum width WM is reached at the half of the height Hl (such as between 45 - 55% along the height Hl) and when the maximum width WM is similar to the height Hl . In further embodiments, the LED filament lamp may have the shape of a candle bulb lamp, such as when the maximum width WM is reached between 10 - 50% of the height Hl, such as between 15 - 45% of the height Hl, especially between 20 - 40% of the height Hl. More specifically, the LED filament lamp may have the shape of a candle bulb lamp when the maximum width WM is smaller than the height Hl, such as WM / Hl < 0.8, especially WM / Hl < 0.6, preferably WM / Hl < 0.4. Therefore, the shape of the LED filament lamp may define the height Hl and the width W. Desired shapes such as a (candle) bulb shape may define different dimensions. Such shapes may be especially desirable for use of light with a flame effect. Thereby, in certain embodiments, the first end and the second end define a height (Hl) of the light transmissive envelope. Especially, along the envelope length axis (AE), in a direction from the first end to the second end, the light transmissive envelope increases in width (W) over at least part of its height (Hl) to a maximum width (WM). Furthermore, the width (W) decreases over at least part of its height (Hl) in a direction from the maximum width (WM) to the second end.

[0067] In further embodiments, the facets may provide one or more top angles (am) between the facets and the envelope length axis (AE). Especially, the top angles (am) may be defined at the second end. Each facet at the second end may define one top angle (am) with the envelope length axis (AE) at the second end. Therefore, in embodiments with a plurality of (spiraling) facets, the facets may provide a plurality of top angles (am) at the second end. The one or more top angles (am) may be selected from the range of 5 - 90°, such as from the range of 10-82.5°, especially from the range of 15 - 75°. In embodiments wherein the LED filament lamp has a “classic bulb”-like shape, the light transmissive envelope may comprise a flattened top comprising the second end. For a flattened top, the one or more top angles (a.1 2) may be selected from the range of 45 - 90°, such as from the range of 50 - 82.5°, especially from the range of 55 - 75°. In embodiments of a candle bulb shape LED filament lamp, the light transmissive envelope may comprise a pointed tip comprising the second end. For a pointed tip, the one or more top angles (am) may be selected from the range of 5 - 45°, such as from the range of 10 - 40°, especially from the range of 15 - 35°. Therefore, the second end and especially the top angles (am) may further define desired shapes. Examples thereof may be a flattened top for a “classic bulb”-like shape, a pointed top for a (candle) bulb shape, and further varieties. Such shapes may be especially desirable for use of light with a flame effect, as a pointed tip may provide a pointed shape or flame-like shape, to the light. Therefore, in specific embodiments, the light transmissive envelope comprises a pointed tip (with a top angle (am) selected from the range of 5-25°). Further, the pointed tip comprises the second end.

[0068] In certain embodiments, one or more of the facets may have a facet height H2. The facet height H2 may be defined in a plane parallel to the envelope length axis (AE). The facet height H2 may especially be defined in a plane parallel to the height Hl. The one or more facets may in such embodiments spiral over the facet height H2 (especially around the envelope length axis (AE), as described above). In some embodiments, the one or more facets may spiral across (essentially) the entire height Hl of the light transmissive envelope. Therefore, in specific embodiments the facet height H2 may be essentially the same as the height Hl. In other embodiments, the one or more facets may be shorter than the entire height Hl of the light transmissive envelope. However, the facet height H2 may in general not be shorter than 0.5*Hl. Therefore, in such embodiments, the following may apply: O.5<H2 / H1<1, such as O.65<H2 / H1<1, especially O.75<H2 / H1<1. It should be noted that the one or more facets themselves may have a facet length LF. AS the one or more facets spiral around the envelope length axis (AE), the facet length LF may in embodiments be larger than the facet height H2. In specific embodiments, the facet length LF may be larger than or equal to the height Hl, i.e., LF > Hl > H2. In other embodiments, the facet length Lpmay be smaller than or equal to the height Hl, i.e., Hl > LF > H2. Thereby, one or more facets may spiral around the (candle) bulb lamp. The one or more facets may spiral about at least part of the envelope length axis (AE).SUCII facets may provide different viewing angles to the filament light with the flame shape. Furthermore, such facets may enhance the pointed shape or flame-like shape of the filament light. Therefore, in specific embodiments, one or more of the facets have a facet height (H2), and the one or more facets spiral over the facet height (H2). Especially, in such embodiments, the following applies: O.5<H2 / H1<1. In further such embodiments, the one or more facets spiral about at least part of the envelope length axis (AE) over a rotational angle ( ) of at least 30°.

[0069] In yet a further aspect, the invention also provides a luminaire comprising the LED filament lamp as defined herein. The luminaire may further comprise a housing, optical elements, louvres, etc. etc... The lamp or luminaire may further comprise a housing enclosing the light generating system. The lamp or luminaire may comprise a light window in the housing or a housing opening, through which the filament light may escape from the housing.

[0070] The LED filament lamp may be part of or may be applied in e.g. office lighting systems, household application systems, shop lighting systems, home lighting systems, accent lighting systems, spot lighting systems, theater lighting systems, fiber-optics application systems, projection systems, self-lit display systems, pixelated display systems, segmented display systems, warning sign systems, medical lighting application systems, indicator sign systems, decorative lighting systems, portable systems, automotive applications, (outdoor) road lighting systems, urban lighting systems, green house lighting systems, horticulture lighting, digital projection, or LCD backlighting. The LED filament lamp (or luminaire) may be part of or may be applied in e.g. optical communication.

[0071] BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

[0073] Fig. 1A-C schematically depict some general aspects of a 3D printer and of an embodiment of 3D printed material;

[0074] Fig. 2A-B schematically depict embodiments of LED filaments and configurations thereof;

[0075] Fig. 3A-C schematically depict embodiments of filament projections of LED filaments on ribbed structures;

[0076] Fig. 4A-D schematically depict embodiments of light transmissive envelopes;

[0077] Fig. 5A-B schematically depict cross-sectional views of embodiments of light transmissive envelopes;

[0078] Fig. 6 schematically depicts embodiments of applications. The schematic drawings are not necessarily to scale.

[0079] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0080] Fig. 1A-C schematically depict some general aspects of a 3D printer and of an embodiment of 3D printed material. In specific embodiments, the light transmissive envelope 500 may be a 3D printed item 1. In embodiments, the light transmissive envelope 500 may comprise a plurality of (stacked) layers 322 comprising the light transmissive material 502. In embodiments, the layers 322 may comprise the elongated convex surfaces 525 (as elongated convex (outer) layer surfaces 525) providing the envelope 500 with the ribbed structure 550.

[0081] Fig. la schematically depicts some aspects of the 3D printer. Reference 500 indicates a 3D printer. Reference 530 indicates the functional unit configured to 3D print, especially FDM 3D printing; this reference may also indicate the 3D printing stage unit. Here, only the printer head for providing 3D printed material, such as an FDM 3D printer head is schematically depicted. Reference 501 indicates the printer head. The 3D printer of the present invention may especially include an optical fiber providing system 602, see also further below. Reference 502 indicates a printer nozzle. Reference 320 indicates a filament of printable 3D printable material 201.

[0082] Instead of a filament also pellets may be used as 3D printable material 201. Both can be extruded via the printer nozzle 502.

[0083] For the sake of clarity, not all features of the 3D printer 500 have been depicted, only those that are of especial relevance for the present invention (see further also below). Reference 321 indicates extrudate (of 3D printable material 201).

[0084] The 3D printer 500 is configured to generate a 3D item 1 by layer-wise depositing on a receiver item 550, which may in embodiments at least temporarily be cooled, a plurality of layers 322 wherein each layer 322 comprises 3D printable material 201, such as having a melting point Tm. The 3D printable material 201 may be deposited on a substrate 1550 (during the printing stage). By deposition, the 3D printable material 201 has become 3D printed material 202. 3D printable material 201 escaping from the nozzle 502 is also indicated as extrudate 321. Reference 401 indicates thermoplastic material.

[0085] The 3D printer 500 may be configured to heat the filament 320 material upstream of the printer nozzle 502. This may e.g. be done with a device comprising one or more of an extrusion and / or heating function. Such device is indicated with reference 573, and is arranged upstream from the printer nozzle 502 (i.e. in time before the filament material leaves the printer nozzle 502). The printer head 501 may (thus) include a liquefier or heater. Reference 201 indicates printable material. When deposited, this material is indicated as (3D) printed material, which is indicated with reference 202.

[0086] Reference 572 indicates a spool or roller with material, especially in the form of a wire, which may be indicated as filament 320. The 3D printer 500 transforms this in an extrudate 321 downstream of the printer nozzle which becomes a layer 322 on the receiver item or on already deposited printed material. In general, the diameter of the extrudate 321 downstream of the nozzle 502 is reduced relative to the diameter of the filament 320 upstream of the printer head 501. Hence, the printer nozzle 502 is sometimes (also) indicated as extruder nozzle. Arranging layer 322 by layer 322 and / or layer 322 on layer 322, a 3D item 1 may be formed. Reference 575 indicates the filament providing device, which here amongst others includes the spool or roller and the driver wheels, indicated with reference 576. Reference Ax indicates a longitudinal axis or filament axis. Printing may especially occur along a printing direction, which may especially coincide with the longitudinal axis Ax. Further, reference S indicates a direction for the layer-wise deposition (i.e. , a building direction), such that a stack 340 of layers 322 of 3D printed material 202 may be provided.

[0087] Reference 300 schematically depicts a control system. The control system may be configured to control the 3D printer 500. The control system 300 may be comprised or functionally coupled to the 3D printer 500. The control system 300 may further comprise or be functionally coupled to a temperature control system configured to control the temperature of the receiver item 550 and / or of the printer head 501. Such temperature control system may include a heater which is able to heat the receiver item 550 to at least a temperature of 50 °C, but especially up to a range of about 350 °C, such as at least 200 °C.

[0088] Alternatively or additionally, in embodiments the receiver plate may also be moveable in one or two directions in the x-y plane (horizontal plane). Further, alternatively or additionally, in embodiments the receiver plate may also be rotatable about z axis (vertical). Hence, the control system may move the receiver plate in one or more of the x-direction, y- direction, and z-direction.

[0089] Alternatively, the printer 500 can have a head that can also rotate during printing. Such a printer 500 has an advantage that the printed material 202 cannot rotate during printing.

[0090] Layers are indicated with reference 322, and have a layer height H and a layer width W.

[0091] Note that the 3D printable material 201 is not necessarily provided as filament 320 to the printer head 501. Further, the filament 320 may also be produced in the 3D printer 500 from pieces of 3D printable material 201. Hence, the nozzle 502 may effectively produce from particulate 3D printable material 201 a filament 320, which upon deposition is indicated as layer 322 (comprising 3D printed material 202). Note that during printing the shape of the extrudate 321 may further be changed, e.g. due to the nozzle 502 smearing out the 3D printable material 201 / 3D printed material 202. Fig. lb schematically depicts that also particulate 3D printable material 201 may be used as feed to the printer nozzle 502.

[0092] Reference D indicates the diameter of the nozzle 502 (through which the 3D printable material 201 is forced). However, the nozzle 502 is not necessarily circular. Fig. lb schematically depicts in 3D in more detail the printing of the 3D item 1 under construction. Here, in this schematic drawing the ends of the layers in a single plane are not interconnected, though in reality this may in embodiments be the case.

[0093] Reference H indicates the height of a layer. Layers are indicated with reference 322. Here, the layers have an essentially circular cross-section. Often, however, they may be flattened, such as having an outer shape resembling a flat oval tube or flat oval duct (i.e. a circular shaped bar having a diameter that is compressed to have a smaller height than width, wherein the sides (defining the width) are (still) rounded).

[0094] Hence, Fig. la schematically depict some aspects of a fused deposition modeling 3D printer 500, comprising (a) a first printer head 501 comprising a printer nozzle 502, (b) a filament providing device 575 configured to provide a filament 320 comprising 3D printable material 201 to the first printer head 501, and optionally (c) a receiver item 550, which can be used to provide a layer of 3D printed material 202.

[0095] Fig. lb schematically depict some aspects of a fused deposition modeling 3D printer 500 (or part thereol), comprising a first printer head 501 comprising a printer nozzle 502, and optionally a receiver item (not depicted), which can be used to which can be used to provide a layer of 3D printed material 202. Such fused deposition modeling 3D printer 500 may further comprise a 3D printable material providing device, configured to provide the 3D printable material 201 to the first printer head.

[0096] In Figs, la-lb, downstream of the nozzle 502, the filament 320 with 3D printable material becomes, when deposited, layer 322 with 3D printed material 202. In Fig. lb, by way of example the extrudate is essentially directly the layer 322 of 3D printed material 202, due to the short distance between the nozzle 502 and the 3D printed material (or receiver item (not depicted).

[0097] Fig. 1c schematically depicts a stack 340 of 3D printed layers 322, each having a layer height H and a layer width W. Note that in embodiments the layer width and / or layer height may differ for two or more layers 322. The layer width and / or layer height may also vary within a layer. Reference 252 in Fig. 1c indicates the item surface of the 3D item (schematically depicted in Fig. 1c).

[0098] Referring to Figs, la-lc, the filament of 3D printable material that is deposited leads to a layer having a height H (and width W). Depositing layer 322 after layer 322, the 3D item 1 is generated. Fig. 1c very schematically depicts a single-walled 3D item 1. Reference 25 may refer to reflective particles, see also above and further below. Fig. 2A-B schematically depict embodiments of configurations of the LED filament 1100 generating lamp light 1001. Fig. 2A schematically depicts embodiments wherein the LED filament 1100 may be configured to generate filament light 1101. The LED filament 1100 may in embodiments have a first length Li, a width W and a thickness T. Further, the LED filament 1100 may have a filament axis of elongation AF and an axis length LA (defined along the filament axis of elongation AF). Although the light transmissive envelope 500 is not depicted in the embodiments of Fig. 2A for clarity purposes, an envelope length axis (AE) comprised by a light transmissive envelope 500 is depicted in the embodiments of Fig. 2A.

[0099] Fig. 2A schematically depicts in embodiment (I) a plurality of LED filaments 1100 configured in a plane parallel to the envelope length axis (AE). Such configuration of LED filaments may likely not result in a filament projection (1100’) wherein at least one of the mutual angles (a) is be selected from the range of 10-80° (and therefore, the configuration of LED filaments in embodiment (I) is not according to the present invention). In particular, in embodiment (I) the mutual angles (a) may be 90° as the filament projection 1100’ is perpendicular to the intermediate relief lines 531 and elongated convex structures 525 of the ribbed structure 550 (as schematically depicted in Fig. 3A). Hence, the filament light 1101 may not comprise the desired optical effect.

[0100] Embodiment (II) depicts a plurality of LED filaments 1100 configured according to the present invention (i.e., the LED filament is configured such that at least one of the mutual angles (a) may be selected from the range of 10-80°, as schematically depicted in Fig. 3B). Furthermore, the left side of embodiment (II) depicts a side view perspective, whereas the right side of embodiment (II) depicts a top view perspective. Especially, in the embodiment (II) 4 straight LED filaments 1100 are shown, arranged surrounding axis of elongation (AE) and partially overlapping from a side view perspective and a top view perspective. In embodiments, the filament axis of elongation (AF) and the envelope length axis (AE) of the LED filaments 1100 may not be configured in a single plane.

[0101] Embodiment (III) depicts a plurality of LED filaments 1100 in a 3D spiraling shape, especially a helical-like shape. Especially, 2 helical LED filaments 1100 are depicted arranged surrounding axis of elongation (AE). In an alternative embodiment (not depicted), a single helical LED filament 1100 may be arranged spiraling around the axis of elongation (AE). Note that in the embodiments with the spiraling shape, it may not be a problem when the filament axis of elongation AF and the envelope length axis AE are configured within the same plane, the desired optical effect. Fig. 2B schematically depicts a LED filament 1100 comprising solid state light sources 1110 and an encapsulant 1130. The LED filament 1100 may comprise an array of a plurality of solid state light sources 1110 arranged on an elongated carrier 1120, with an encapsulant 1130 covering the plurality of solid state light sources 1110 and at least part of the elongated carrier 1120. In embodiments, the solid state light sources 1110 may be configured to generate light source light 1111. In embodiments, the encapsulant 1130 may comprise a luminescent material 1135 configured to convert at least part of the light source light 1111 into luminescent material light 1131. In embodiments, the filament light 1101 may comprise luminescent material light 1131 and optionally transmitted light source light 1111. In embodiments, the filament light 1101 may be white light having a correlated color temperature selected from the range of 1500-6500 K.

[0102] Fig. 3A-C schematically depict embodiments of filament projections 1100’ of LED filaments 1100 on ribbed structures 550 (with a view from the external surface 505). In embodiments, the light transmissive envelope 500 may comprise a facet 540 comprising at least part of the ribbed structure 550 with intermediate relief lines 531 between adjacent (layered) elongated convex surfaces 525. In embodiments, the LED filament lamp 1000 may be configured such that a plurality of intersection points 1105’ of virtual vectors (Vv) (as schematically depicted in Fig. 4A and Fig. 5A) with the light transmissive envelope 500 define a filament projection 1100’ on the light transmissive envelope 500. In embodiments, the filament projection 1100’ provides mutual angles (a) between the filament projection 1100’ and the intermediate relief lines 531.

[0103] Fig. 3 A schematically depicts the filament projections of embodiment (I) in Fig. 2A (therefore, not according to the present invention). The mutual angles (a) between the filament projections 1100’ and the intermediate relief lines 531 may be 90° as the filament projection 1100’ is parallel to the intermediate relief lines 531. Hence, the desired optical effect may not be achieved (as only lengthening of the projection lines may be achieved).

[0104] Fig. 3B schematically depicts the filament projections of a plurality of LED filaments 1100 (according to the present invention). In embodiments, at least one of the mutual angles (a) may be selected from the range of 10-80°. In embodiments, the filament projection on at least one of the (downstream) facets 540 may provide a plurality of mutual angles (a) between the filament projection and the intermediate relief lines. Herein depicted are two mutual angles ai and oa. In embodiments, one or more of the mutual angles (a) may be selected from the range of 20-70°. Hence, the desired optical effect of a gradually shaded light may be achieved.

[0105] Fig. 3C schematically depicts the filament projection of embodiment (III) in Fig. 2A (i.e., a 3D spiraling shape, especially a helical LED filament 1100). Herein depicted are four mutual angles ai, 012, as, and a4. In embodiments, at least 80% of the mutual angles (a) may be individually selected from the range of 10-80°.

[0106] In such embodiments, the (curved) LED filament may especially comprise a plurality of downstream facets. This may be achieved by designing the facets of the light transmissive envelope and by configuration of the (curved) LED filament near the plurality of facets. Especially, the (curved) LED filament may thereby provide a slanted filament projection on a plurality of downstream facets. Especially, different parts of the LED filament along the circumference of the 3D spiraling (or helical-like) shape may via different vectors be related to different downstream facets. However, theoretically finishing a 360° turn along the 3D spiraling (or helical-like) shape of the LED filament may again have the same downstream facet. Therefore, in such embodiments, a (two-dimensional) path may be traced between the nearest intersection points along the intermediate relief lines within one downstream facet, and one or more (two-dimensional) paths may be similarly traced on further downstream facets. Hence, a 3D spiraling LED filament may especially facilitate achieving or enhancing a flame effect on a plurality of downstream facets, and the desired optical effect may be present from more (especially all) viewing angles. Therefore, in certain embodiments, the LED filament comprises a 3D spiraling shape (such as a helical shape).

[0107] Fig. 4A-D schematically depict embodiments of light transmissive envelopes 500. In embodiments, the light transmissive envelope 500 may comprise a light transmissive material 502. Therefore the light transmissive envelope 500 may be transmissive for at least part of the filament light 1101. In embodiments, the light transmissive envelope 500 may comprise an external surface 505 comprising a plurality of facets 540 defined by the ribbed structure 550. In embodiments, the light transmissive envelope 500 may comprise an envelope length axis (AE). In embodiments, the facets 540 may be arranged in a spiral-like configuration spiraling about at least part of the envelope length axis (AE). In embodiments, the LED filament lamp 1000 may be configured such that a plurality of virtual vectors (Vv) each: (i) start at the envelope length axis (AE), (ii) intersect the LED filament 1100, and (iii) follow a (shortest) distance dl from the LED filament 1100 to an intermediate relief line 531 comprised by (a downstream facet 540 ol) the light transmissive envelope 500. In embodiments, the external surface 505 may comprise a largest outer perimeter (POL) configured in a plane perpendicular to the envelope length axis (AE). In embodiments, the largest outer perimeter (POL) may be conformal to n facets 540. In embodiments, n may be selected from the range of (2-100, more especially) 3-18.

[0108] In embodiments, the LED filament lamp, the one or more facets 540 spiral about at least part of the envelope length axis (AE) over a rotational angle (P) of at least 30°.

[0109] In general, the intermediate relief lines 531 and convex elongated surfaces 525 of the ribbed structure 550 may be arranged perpendicular to the envelope length axis (AE).

[0110] Herein, the facets 540 may be defined by a face and a plurality of edges (bordering two or more adjacent facets). The edge between two faces may especially comprise a relatively sharp comer having the smallest angle between two faces. The edge may comprise a ridge or a groove.

[0111] Fig. 4A depicts a top-down view perspective of such embodiments, especially showing how the plurality of virtual vectors (Vv) each: (i) start at the envelope length axis (AE), (ii) intersect the LED filament 1100, and (iii) follow a (shortest) distance dl from the LED filament 1100 to an intersection point 1105’ on the external surface 505.

[0112] Fig. 4B depicts a side view perspective of such embodiments. Further, Fig. 4B depicts facets 540 having a facet length LF. In embodiments, the light transmissive envelope 500 may comprise a first end 501 and a second end 502. In embodiments, the first end 501 and the second end 502 define a height (Hl) of the light transmissive envelope 500. In embodiments, the facets 540 provide one or more top angles (am) between the facets 540 and the envelope length axis (AE) at the second end. In embodiments, the light transmissive envelope 500 may comprise a pointed tip 507 (with a top angle (am) selected from the range of 5-82.5°). Further, the pointed tip 507 may comprise the second end 502. In embodiments, along the envelope length axis (AE), in a direction from the first end 501 to the second end 502, the light transmissive envelope 500 increases in width (W) over at least part of its height (Hl) to a maximum width (WM), and decreases over at least part of its height (Hl) in a direction from the maximum width (WM) to the second end 502.

[0113] Fig. 4C depicts a side view of candle bulb embodiments. In the depicted embodiments, one or more of the facets 540 may have a facet height (H2). In embodiments, O.5<H2 / H1<1. In embodiments, the one or more facets 540 spiral over the facet height (H2). Herein, the facet height H2 essentially equals the height HL Especially, Fig. 4C depicts an embodiment with a pointed tip 507 at the second end 502 (with top angles (a.1 2) selected from the range of 5-45°). Fig. 4D depicts a side view perspective of a “classic bulb” embodiments. Especially, Fig. 4D depicts an embodiment with a flattened tip 506 at the second end 502 (with top angles (a.1 2) selected from the range of 45-82.5°).

[0114] Fig. 5A-B schematically depict cross-sectional views of embodiments of light transmissive envelopes 500 (especially having a light transmissive envelope wall).

[0115] Fig. 5A depicts embodiments that may comprise a support part 600. In embodiments, the LED filament 1100 may be functionally coupled to the support part 600. In embodiments, the light transmissive envelope 500 may comprise (a) a first end 501, configured (functionally coupled and) in contact with the support part 600.

[0116] The embodiment may especially comprise a second light transmissive envelope 1500. In embodiments, the second light transmissive envelope 1500 at least partly encloses the LED filament 1100. In embodiments, the light transmissive envelope 500 at least partly encloses the second light transmissive envelope 1500.

[0117] Furthermore, the embodiments in Fig. 5A depicts a helical-shaped LED filament 1100 finishing a 360° turn along the 3D spiraling (or helical-like) shape of the LED filament, thereby again having the same downstream facet.

[0118] Fig. 5B depicts embodiments wherein the ribbed structure 550 defines a distance d2 between adjacent intermediate relief lines 531 selected from the range of 0.4 - 10 mm (more preferably 0.5-5mm, most preferably 0.5-lmm) (wherein the distance d2 additionally may define the height of an elongated convex surface 525). In embodiments, a (shortest) first thickness Ti of the light transmissive envelope 500 at the intermediate relief lines 531 selected from the range of 0.2 - 40mm. In embodiments, a (longest) second thickness T2 of the light transmissive envelope 500 at the elongated convex surfaces 525 selected from the range of 0.5 - 50 mm. Herein, the ribbed structure 550 may especially comprise 3D printed layers 322.

[0119] Fig. 6 schematically depicts an embodiment of a luminaire 2 comprising the light generating system 1000 as described above. Reference 301 indicates a user interface which may be functionally coupled with the control system 300 comprised by or functionally coupled to the light generating system 1000. Fig. 6 also schematically depicts an embodiment of lamp 1 comprising the light generating system 1000. Reference 3 indicates a projector device or projector system, which may be used to project images, such as at a wall, which may also comprise the light generating system 1000. Hence, Fig. 6 schematically depicts embodiments of a lighting device 1200 selected from the group of a lamp 1, a luminaire 2, a projector device 3, a disinfection device, a photochemical reactor, and an optical wireless communication device, comprising the light generating system 1000 as described herein. In embodiments, such lighting device may be a lamp 1, a luminaire 2, a projector device 3, a disinfection device, or an optical wireless communication device. Lighting device light escaping from the lighting device 1200 is indicated with reference 1201. Lighting device light 1201 may essentially consist of system light 1001, and may in specific embodiments thus be system light 1001. Reference 1300 refers to a space, such as a room.

[0120] The term “plurality” refers to two or more. The terms “substantially” or “essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term “essentially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term “comprise” also includes embodiments wherein the term “comprises” means “consists of’. The term “and / or” especially relates to one or more of the items mentioned before and after “and / or”. For instance, a phrase “item 1 and / or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term "comprising" may in an embodiment refer to "consisting of but may in another embodiment also refer to "containing at least the defined species and optionally one or more other species". Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0121] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The devices, apparatus, or systems may herein amongst others be described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation, or devices, apparatus, or systems in operation. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

[0122] The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim, or a system claim, enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. In yet a further aspect, the invention (thus) provides a software product, which, when running on a computer is capable of bringing about (one or more embodiments ol) the method as described herein.

[0123] The invention also provides a control system that may control the device, apparatus, or system, or that may execute the herein described method or process. Yet further, the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by the device, apparatus, or system, controls one or more controllable elements of such device, apparatus, or system.

[0124] The invention further applies to a device, apparatus, or system comprising one or more of the characterizing features described in the description and / or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and / or shown in the attached drawings.

[0125] The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.

Claims

CLAIMS:

1. A LED filament lamp comprising a light transmissive envelope (500) and a LED filament (1100) at least partly enclosed by the light transmissive envelope (500), wherein: the light transmissive envelope (500) comprises a light transmissive material (502), wherein the light transmissive envelope (500) comprises a ribbed structure (550) with a repeating sequence of parallel intermediate relief lines (531) between adjacent elongated convex surfaces (525); wherein the light transmissive envelope (500) comprises an external surface (505) comprising a plurality of facets (540), each facet comprising at least part of the ribbed structure (550); wherein the light transmissive envelope (500) comprises an envelope length axis (AE); and wherein the facets (540) are arranged in a spiral-like configuration spiraling about at least part of the envelope length axis (AE); the LED filament (1100) comprises an array of a plurality of solid state light sources (1110) arranged on an elongated carrier (1120), with an encapsulant (1130) covering the plurality of solid state light sources (1110) and at least part of the elongated carrier(l 120); wherein the LED filament (1100) is configured to generate filament light (1101); the LED filament lamp (1000) is configured such that (a): a plurality of virtual vectors (Vv) each: (i) start at the envelope length axis (AE), (ii) intersect the LED filament (1100), and (iii) follow a distance (dl) from the LED filament (1100) to an intermediate relief line (531) comprised by the light transmissive envelope (500), and (b): a plurality of intersection points (1105’) of the virtual vectors (Vv) with the light transmissive envelope (500) define a filament projection (1100’) on the light transmissive envelope (500); and the filament projection (1100’) provides mutual angles (a) between the filament projection (1100’) and the intermediate relief lines (531), wherein at least one of the mutual angles (a) is selected from the range of 10-80°.

2. The LED filament lamp (1000) according to claim 1, wherein the filament projection (1000’) on at least one of the facets (540) provides a plurality of mutual angles (a) between the filament projection (1100’) and the intermediate relief lines, wherein at least3. The LED filament lamp (1000) according to any one of the preceding claims, wherein the intermediate relief lines (531) are oriented substantially perpendicular to the envelope length axis (AE).

4. The LED filament lamp (1000) according to any one of the preceding claims, wherein the LED filament (1100) comprises a filament axis of elongation (AF), and wherein the filament axis of elongation (AF) and the envelope length axis (AE) are not configured in a single plane.

5. The LED filament lamp (1000) according to any one of the preceding claims, wherein the LED filament (1100) comprises a 3D spiraling shape.

6. The LED filament lamp (1000) according to any one of the preceding claims, wherein the external surface (505) comprises a largest outer perimeter (POL) configured in a plane perpendicular to the envelope length axis (AE); wherein the largest outer perimeter (POL) is conformal to n facets (540), wherein n is selected from the range of 3-18.

7. The LED filament lamp (1000) according to any one of the preceding claims, wherein the light transmissive envelope (500) comprises (a) a first end (501) and (b) a second end (502), remote from the support part (600), wherein the first end (501) and the second end (502) define a height (Hl) of the light transmissive envelope (500); wherein along the envelope length axis (AE), in a direction from the first end (501) to the second end (502), the light transmissive envelope (500) increases in width (W) over at least part of its height (Hl) to a maximum width (WM), and decreases over at least part of its height (Hl) in a direction from the maximum width WM) to the second end (502).

8. The LED filament lamp (1000) according to claim 7, wherein the light transmissive envelope (500) comprises a pointed tip (507), wherein the pointed tip (507) comprises the second end (502).

9. The LED filament lamp (1000) according to any one of the preceding claims 7-8, wherein one or more of the facets (540) have a facet height (H2), wherein O.5<H2 / H1<1; and wherein the one or more facets (540) spiral over the facet height (H2), wherein the one ormore facets (540) spiral about at least part of the envelope length axis (AE) over a rotational angle (P) of at least 30°.

10. The LED filament lamp (1000) according to any one of the preceding claims, wherein one of the following applies: (a) the light transmissive envelope (500) is transparent to filament light (1101); or (b) the light transmissive envelope (500) is transmissive with a reflectivity to at least part of the filament light (1101) selected from the range of 10 - 20% reflection under perpendicular irradiation.

11. The LED filament lamp (1000) according to any one of the preceding claims, wherein the solid state light sources (1110) are configured to generate light source light (1111), wherein the encapsulant (1130) comprises a luminescent material (1135) configured to convert at least part of the light source light (1111) into luminescent material light (1131), wherein the filament light (1101) comprises luminescent material light (1131) and optionally transmitted light source light (1111); wherein the filament light (1101) is white light having a correlated color temperature selected from the range of 1500-3000 K.

12. The LED filament lamp (1000) according to any one of the preceding claims, wherein the ribbed structure (550) defines: (i) a distance (d2) between adjacent intermediate relief lines (531) selected from the range of 0.4 - 10 mm; (ii) a first thickness (Ti) of the light transmissive envelope (500) at the intermediate relief lines (531) selected from the range of 0.2 - 40 mm; and (iii) a second thickness (T2) of the light transmissive envelope (500) at the elongated convex surfaces (525) selected from the range of 0.5 - 50 mm.

13. The LED filament lamp (1000) according to any one of the preceding claims, comprising a second light transmissive envelope (1500), wherein the second light transmissive envelope (1500) at least partly encloses the LED filament (1100), and wherein the light transmissive envelope (500) at least partly encloses the second light transmissive envelope (1500).

14. The LED filament lamp (1000) according to any one of the preceding claims, comprising a plurality of LED filaments (1100).

15. The LED filament lamp (1000) according to any one of the preceding claims, wherein the light transmissive envelope (500) is a 3D printed item (1); wherein the light transmissive envelope (500) comprises a plurality of layers (322) comprising the light transmissive material (502), wherein the layers (322) comprise the elongated convex surfaces (525) providing the envelope (500) with the ribbed structure (550).

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