WO2020161070A1

WO2020161070A1 - An led filament lamp

Info

Publication number: WO2020161070A1
Application number: PCT/EP2020/052607
Authority: WO
Inventors: Rifat Ata Mustafa Hikmet; Ties Van Bommel; Martinus Petrus Joseph PEETERS; Robert Jacob PET
Original assignee: Signify Holding B.V.
Priority date: 2019-02-07
Filing date: 2020-02-03
Publication date: 2020-08-13

Abstract

The present invention relates to an LED-filament lamp comprising an LED-filament configured to emit LED-filament light; and an envelope comprising a light absorbing material configured to absorb light in a wavelength range of 400-440 nm to provide an amber colored appearance, wherein the envelope at least partly encloses the LED-filament, and wherein the light absorbing material is transmissive for substantially all the visible LED-filament light having wavelengths longer than 440 nm.

Description

An LED filament lamp

FIELD OF THE INVENTION

The present inventive concept relates to an LED-filament lamp.

BACKGROUND OF THE INVENTION

In the past, incandescent lamps have been used as a main type of electric light for various applications such as household applications. However, incandescent lamps have several drawbacks such as short life time and low efficiency as they only convert less than 5% of the energy used into visible light. Therefore, over the past years incandescent lamps have been rapidly replaced by other types of lights, e.g. LEDs lamps, which have a much higher efficiency.

It is nevertheless desired to have retrofit lamps which have the same vintage look of the incandescent lamps. A solution for such desire is e.g. to replace the filament of the incandescent lamp with an LED-filament. In order to improve the vintage look of such lamps, a coating is applied onto the lamp’s envelope. However, a drawback of such solution is that the coating absorbs part of light emitted from the LED-filament and results in a lower efficiency than an uncoated vintage look LED-filament lamp.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome at least some of the abovementioned problems.

According to a first aspect, this and other objects are achieved by providing an LED-filament lamp. The LED-filament lamp comprising an LED-filament configured to emit LED-filament light; and an envelope comprising a light absorbing material configured to absorb light in a wavelength range of 400-440 nm to provide an amber colored appearance, wherein the envelope at least partly encloses the LED-filament, and wherein the light absorbing material is transmissive for substantially all the visible LED-filament light having wavelengths longer than 440 nm. Thereby, the light absorbing material does not absorb the LED-filament light and hence does not reduce an efficiency of the LED-filament lamp. The light absorbing material is visible e.g. in an off state with ambient light which comprises light in a wavelength range from 400 to 440 nm wherein the wavelength range of 400-420 nm corresponds to violet light and the wavelength range of 420-440 nm corresponds to short wavelength blue light. This wavelength range (400-440 nm) of the ambient light is absorbed by the light absorbing material to render the lamp to have a vintage look in the off-state. This in turn results into a vintage look LED-filament lamp with an improved efficiency, compared to a vintage look LED lamp with a light absorbing material that absorbs the LED-filament light.

In general, a LED filament is providing LED filament light and comprises a plurality of light emitting diodes (LEDs) arranged in a linear array. Preferably, the LED filament has a length L and a width W, wherein L>5W. The LED filament may be arranged in a straight configuration or in a non-straight configuration such as for example a curved configuration, a 2D/3D spiral or a helix. Preferably, the LEDs are arranged on an elongated carrier like for instance a substrate, that may be rigid (made from e.g. a polymer, glass, quartz, metal or sapphire) or flexible (e.g. made of a polymer or metal e.g. a film or foil).

In case the carrier comprises a first major surface and an opposite second major surface, the LEDs are arranged on at least one of these surfaces. The carrier may be reflective or light transmissive, such as translucent and preferably transparent.

The LED filament may comprise an encapsulant at least partly covering at least part of the plurality of LEDs. The encapsulant may also at least partly cover at least one of the first major or second major surface. The encapsulant may be a polymer material which may be flexible such as for example a silicone. Further, the LEDs may be arranged for emitting LED light e.g. of different colors or spectrums. The encapsulant may comprise a luminescent material that is configured to at least partly convert LED light into converted light. The luminescent material may be a phosphor such as an inorganic phosphor and/or quantum dots or rods.

The LED filament may comprise multiple sub-filaments.

By an LED-filament is hereby meant a high efficiency (at least 501m/W) and Omni-directional solid state light source. The LED-filament may emit e.g. white light. An envelope may be made of glass and may be transmissive to all visible wavelengths of light. The envelope may be bulb-shaped having a neck portion and a dome portion similar to those of incandescent lamps i.e. the neck portion may be a bottom portion of the envelope where the envelope is connected to e.g. a cap and the dome portion may be a top portion of the envelope. By a light absorbing material is hereby meant a layer providing a specific color to the LED-filament light e.g. amber color. The light absorbing material may absorb less than 5%, more preferably less than 3%, most preferably less than 2% of the visible LED-filament light. The light absorbing material may absorb less than 10%, more preferably less than 5%, most preferably less than 3% of light in a wavelength range of 440-490 nm of the LED-filament light. In other words, 95% of the visible LED-filament light, more preferably 97%, most preferably 98% of the visible LED-filament light may pass through the light absorbing material i.e. not being absorbed by the light absorbing material. Thereby, an improved vintage look LED-filament lamp i.e. a vintage look LED-filament lamp with an improved efficiency may be achieved.

The light absorbing material may absorb more than 20%, more preferably more than 30%, most preferably more than 40% of the light in the wavelength range from 400 to 440 nm. Thereby, the absorption of the light in the wavelength range of 400-440 nm by the light absorbing material may render the lamp to have a vintage look.

The LED-filament may comprise a plurality of LEDs configured to emit blue light having a peak wavelength (lr) in a range from 450 to 470 nm, preferably 460 nm. Alternatively, or in combination, the LED-filament may comprise a plurality of LEDs configured to emit blue light having a peak wavelength (lr) in a range from 470 to 490 nm. The light absorbing material may be transmissive for wavelengths in a range from 450 to 490 nm. Thereby, the light absorbing material may not absorb the blue light emitted by the LED- filament and hence may not lower an efficiency of the LED-filament lamp.

The LED-filament may further comprise wavelength converting material configured to convert at least part of the blue light emitted from the plurality of LEDs, the converted light and the unconverted blue light may form the LED-filament light. The LED- filament light may be white light. The wavelength converting material may improve a color balance of the emitted LED-filament light, resulting into an improved quality of an obtained color e.g. an improved accuracy of an obtained color.

The light absorbing material may comprise one or more of: perylene dyes; 3- carboxy-6,8-difluoro-7-hydroxycoumarin; and ZnSSe nanoparticles. These materials may not absorb the LED-filament light in a wavelength range of 450-490 nm. For instance, perylene dyes has a sharp cut-off edge at about 440 nm wavelength by which the absorption drops to about zero at 450 nm.

The light absorbing material may be in the form of a coating on a surface of the envelope. Thereby, the coating may comprise one or more of: perylene dyes; 3-carboxy- 6,8-difluoro-7-hydroxycoumarin; and ZnSSe nanoparticles. The coating may be applied onto an interior and/or an exterior surface of the envelope. The coating may be in the form of the light absorbing material in a polymer matrix. Thereby, one or more of: perylene dyes; 3-carboxy-6,8-difluoro-7-hydroxycoumarin; and ZnSSe nanoparticles may be added into a polymer matrix. The obtained polymer matrix may then be used as a coating and be applied onto an interior or exterior surface of the envelope.

The light absorbing material may be an integral part of the envelope. Thereby, the light absorbing material may be comprised in the envelope i.e. the envelope itself may act as the light absorbing material. For instance, the envelope may be made of glass or polymer e.g. PP, PE, PET, PMMA, or PC. The light absorbing material may be in the form of nanoparticles added to the material forming the envelope. Such envelope may be prepared by e.g. injection molding of such materials.

The envelope may comprise scattering material in the form of one or more of: TiCh, BaSCE, and AI2O3. These scattering materials may make the envelope slightly milky and translucent. They may provide a haze and increase the color appearance of the coating. They may increase a path length of the ambient light in the coating and therefore increase the absorption.

The light absorbing material may be applied to an entire light exit area of the envelope. By the light exit area of the envelope is hereby meant the area that light exits the envelope. Thereby, the LED filament light may have to pass through the light absorbing material to exit the lamp. This may in turn result into absorption of the light in the wavelength range of 400-440 nm.

The light absorbing material may absorb less than 5%, more preferably less than 3%, most preferably less than 2% of light in a wavelength range of 490-700 nm of the LED-filament light. Thereby, more than 95%, more preferably more than 97%, most preferably more than 98% of light in the wavelength range of 490-700 corresponding to yellow, green, and red parts of the visible light may pass through the light absorbing material i.e. not being absorbed by the light absorbing material.

An amount of absorption of the light absorbing material may vary across the light exit area of the envelope. For instance, a side face of the envelope may comprise a higher concentration or a thicker layer of the light absorbing material. Thereby this side face of the envelope may be better visible if the lamp is installed in a luminaire, a reflector, or a socket. In this way, the blue light which is directed to a task area e.g. a table is absorbed even less i.e. less than 3%, more preferably less than 2%, most preferably less than 1% of the blue light is absorbed. This may in turn improve readability and alertness. A further scope of applicability of the present invention will become apparent from the detailed description given below. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from this detailed description.

Hence, it is to be understood that this invention is not limited to the particular component parts of the device described as such device may vary. It is also to be understood that the terminology used herein is for purpose of describing particular embodiments only, and is not intended to be limiting. It must be noted that, as used in the specification and the appended claim, the articles "a," "an," and "the," are intended to mean that there are one or more of the elements unless the context clearly dictates otherwise. Thus, for example, reference to "a lamp" or "the lamp" may include several devices, and the like. Furthermore, the words "comprising",“including”,“containing” and similar wordings does not exclude other elements or steps.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiments of the invention. The figures should not be considered limiting the invention to the specific embodiment; instead they are used for explaining and understanding the invention.

Fig. 1 illustrates an example of reflection, transmission and absorption spectrums of an amber coating being used in prior art commercially available LED-filament lamps.

Fig. 2 illustrates a vintage look LED-filament lamp comprising a light absorbing material.

Fig. 3 illustrates an intensity profile of a phosphor converted LED emitting blue light.

Fig. 4 illustrates an absorption profile of perylene with respect to wavelength.

As illustrated in the figures, the sizes of layers and regions are exaggerated for illustrative purposes and, thus, are provided to illustrate the general structures of

embodiments of the present invention. Like reference numerals refer to like elements throughout.

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person.

In connection with FIG 1, an example of reflection, transmission and absorption spectrums of an amber coating being used in prior art commercially available LED-filament lamps is shown. The absorption spectrum (dashed dotted line of FIG 1) shows that a large portion of the blue light, light in the wavelength range of 450-490 nm, is absorbed by the amber coating being used in the commercially available LED-filament lamps. Accordingly, the transmission spectrum (dotted line of FIG 1) shows that a reduced portion of the blue light is transmitted through the amber coating used in the prior art commercially available LED-filament lamps. The reflection spectrum (solid line of FIG 1) shows that the amber coating being used in the commercially available prior art LED- filament lamps reflects a larger portion of blue light than longer wavelengths (wavelengths longer than 490 nm). Thereby, the reflection, transmission and absorption spectrums of FIG 1 show that the amber coating being used in the commercially available prior art LED-filament lamps reduces an efficiency of LEDs emitting blue light.

In connection with FIG 2, an LED-filament lamp 100 is illustrated. The LED filament lamp 100 preferably has a color (correlated) temperature (CCT/CT) in a range of 2000 to 4000 K, more preferably in a range of 2100 to 3000 K, most preferably in a range of 2200 to 2700 K. The LED filament lamp 100 preferably has a color rendering index (CRT) above 70, more preferably above 75, most preferably above 80 such as for example 85. The LED-filament lamp 100 of FIG 2 comprises an LED-filament 110 and an envelope 120 comprising a light absorbing material 130. It should be noted that in FIG 2 the relative dimensions of the shown elements, such as the envelope size, is merely schematic and may, for the purpose of illustrational clarity, differ from a physical structure.

The LED-filament 110 shown in FIG 2 is configured to emit the LED-filament light. The LED-filament 110 may comprise one or more LEDs configured to emit blue light in the wavelength range of 450-490 nm. The LED-filament 110 shown in FIG 2 comprises two filament portions 110a and 110b arranged in a longitudinal direction L of the envelope 120. The LED-filament 110 of FIG 1 is designed in a way that it looks similar to the wire filament of traditional incandescent lamps i.e. the two filament portions 110a and 110b resemble the two wires attached to a thin metal filament of traditional incandescent lamps. The LED-filament 110 may have coiled, spring, or meander shape arranged in the

longitudinal direction L of the envelope 120. Each filament portion 110a or 110b shown in FIG 2 comprises an LED. However, it should be noted that the LED-filament portions 110a and 110b may comprise any further number of LEDs. The filament portions 110a and 110b may be tilted with respect to the longitudinal direction L at angles up to 25 degrees, for example 20 degrees. The LED-filament may comprise a carrier having an elongated body and a plurality of LEDs which are mechanically coupled to the carrier. The carrier may be transparent. The carrier may be a glass, sapphire or quartz substrate. The LEDs may be encapsulated with an encapsulant. The encapsulant may cover a first surface of the carrier on which the LEDs are mounted. The encapsulant may also encapsulate a second surface of the carrier, opposite the first surface.

The LED-filament 110 may comprise a wavelength converting material configured to convert at least part of the blue light emitted from the plurality of LEDs such that the converted light and the unconverted blue light may form the LED-filament light. The encapsulant may comprise the wavelength converting material to convert at least part of the LED light into a converted light.

The envelope 120 shown in FIG 2 partly encloses the LED-filament 110. The envelope 120 shown in FIG 2 is a transparent bulb and has a neck portion and a dome portion. The neck portion of the envelope 120 is attached to a cap 140. The neck portion of the envelope 120 shown in FIG 2 has a smaller dimension i.e. a smaller diameter with respect to the dome portion. However, it should be noted that the envelope 120 may have various shapes and dimensions. For instance, the envelope 120 may be configured such that a diameter of the neck portion may gradually increase toward the dome portion or the diameter of the neck portion may abruptly increase toward the dome portion. The envelope 120 may be configured such that a diameter of the neck portion increases gradually toward a middle portion (a portion between the neck and the dome portions) and decreases gradually toward the dome portion i.e. a candle-shape envelope. The envelope 120 may have a cylindrical shape such that a diameter of the neck portion may be the same as the diameter of the dome portion. The envelope 120 may be made e.g. from glass, polymer or any other suitable material. Some examples of a polymer material are PP, PE, PET, PMMA, or PC polymers. The envelope 120 is preferably transmissive to all visible wavelengths of light. The envelope may comprise a scattering material in the form of one or more of: TiCh, BaSCE, and AI2O3. These scattering materials may make the envelope slightly milky and translucent or may provide a haze and increase the color appearance of the coating. They may e.g. increase a path length of the ambient light in the coating and therefore increase the absorption.

The cap 140 shown in FIG 2 is a right-hand threaded metal base, so-called Edison screw, traditionally used for incandescent lamps. The cap 140 is attached to the neck portion of the envelope 120 i.e. a diameter of the cap 140 matches a diameter of the neck portion. The cap 140 may be screwed into a matching lamp holder. The cap 140 may have various shapes or be made of various types of materials with different colors providing that it can be electrically connected to e.g. a lamp holder. The cap may have pins to allow it to be connected into electric plugs or a matching lamp holder. The cap may comprise a driver to adapt the incoming current and voltage to the specific requirement of the lamp. The driver is electrically connected to the cap and to the LED light source. The driver may also be electrically connected to a controller and the cap, and the controller is connected to the LED light source.

As shown in FIG 2, the envelope 120 comprises a light absorbing material 130. The light absorbing material is substantially transmissive for blue light with

wavelengths in a range from 450 to 490 nm i.e. the absorption spectrum of the colored material 130 is outside the emission spectrum of the LED-filament light. The light absorbing material may be transmissive for 95% of the LED-filament light. It is more preferred that the colored material 130 provides 97% or more transparency for the LED-filament light. The light absorbing material 130 may be configured such that it may absorb light preferably below 450 nm. It may be more preferred to configure a light absorbing material 130 that absorbs light below 445 nm. It may be most preferred to configure a light absorbing material 130 that absorbs light below 440 nm. The light absorbing material 130 may absorb light in the wavelength range of 400-440 nm.

The light absorbing material 130 shown in FIG 2 is in the form of a coating and covers an exterior surface of the envelope 120. The light absorbing material 130 may also, or alternatively, be applied onto an interior surface of the envelope 120. The light absorbing material 130 may cover an entire interior and/or an entire exterior surface of the envelope 120. The light absorbing material 130 may cover a part of an interior and/or a part of an exterior surface of the envelope 120. For instance, the light absorbing material 130 may not be applied onto a neck portion of the envelope 120. For illustrative purpose, FIG 2 shows that the light absorbing material 130 is applied non-symmetrically onto the exterior surface of the envelope 120. However, the light absorbing material 130 may be applied symmetrically onto an interior and/or an exterior surface of the envelope 120. The light absorbing material 130 in the form of a coating may be applied uniformly onto an exterior and/or an interior surface of the envelope 120 i.e. the coating may have a uniform thickness everywhere. The light absorbing material 130 in the form of a coating may be applied non-uniformly i.e. the coating may be applied with various thicknesses or various patterns across an interior and/or exterior surface of the envelope 120. The light absorbing material 130 may render a color such as an amber-yellow color. The amber-yellow color may provide a vintage look.

The light absorbing material may comprise one or more of: perylene dyes; 3- carboxy-6,8-difluoro-7-hydroxycoumarin; and ZnSSe nanoparticles. In the case of a coating, the coating may be in the form of a polymer matrix such that the polymer matrix comprises one or more of the abovementioned materials. The light absorbing material may be an integral part of the envelope 120 i.e. the envelope 120 itself may act as the light absorbing material 130. In this case, the envelope 120 itself comprises one or more of the

abovementioned materials. These materials are configured such that they absorb light in the wavelength range 400-440 nm. Therefore, these materials do not absorb light in the wavelength range of 450- 490 nm. These nanoparticles may be added to the material forming the envelope 120. Such envelope may be prepared by e.g. injection molding of such materials.

FIG 3 shows an example of an intensity profile of a white LED that may be used together with a light absorbing material 130 to provide a vintage look with an improved efficiency. The intensity profile shown in FIG 3 is related to a phosphor converted LED. The material forming such LED may comprise gallium nitride (GaN). It may alternatively comprise indium gallium nitride (InGaN). FIG 3 shows a peak wavelength (lr) in a range from 450 to 470 nm with a maximum at 460 nm. This peak may be emitted from GaN or InGaN material. FIG 3 also shows a broader spectrum in a range roughly from 500-700 nm. This broader spectrum may be emitted e.g. from cerium-doped yttrium aluminium garnet (Ce: YAG) being used as a phosphor. Alternatively, a blue light LED may be used having a peak wavelength (lr) in a range from 470 to 490 nm with a maximum at 480 nm.

FIG 4 shows an example of an absorption profile of a light absorbing material 130. The absorption profile shown in FIG 4 is related to perylene. FIG 4 shows molar extinction coefficient of perylene with respect to a wavelength range comprising the wavelength range of blue light. FIG 4 shows that perylene absorbs light in the wavelength range of 400-440 nm and hence renders an amber-yellow color. FIG 4 also shows that perylene has a sharp cut-off edge at about 440 nm such that the absorption drops to about zero at 450 nm. By using a material with absorption profile similar to perylene, a shift in a color point is preferably below 5 standard deviation color matching (SDCM). It is more preferred to have a shift below 3 SDCM in the color point. It is most preferred to have a shift below 2 SDCM in the color point.

The LED-filament lamp 100 may be included in a lamp fixture. The lamp fixture may comprise the LED-filament lamp 100, a reflector and a socket configured to receive a cap of the LED-filament lamp 100. The reflector may be arranged such that it may not enclose a dome portion of an envelope of the lamp. However, the reflector may be configured to at least partly enclose a neck portion of an envelope of the lamp. Thereby, the reflector may reflect light emitted from the neck portion of the envelope to provide an improved visibility of objects. The lamp fixture may be connected e.g. to a room ceiling such that light emitted from the neck portion of the lamp becomes directed vertically downwards e.g. onto a room floor after being reflected by the reflector.

The reflector may be made from various types of materials with various colors and may have various shapes such as round, square or cylindrical shape. For instance, the reflector may have a tapered cylindrical shape and be made from Aluminum having a mirror look. The reflector may have single, double or multi-layers e.g. an interior mirror-like Aluminum layer and an exterior fabric layer. The reflector may also be made of silver. A silver layer can be produced on the surface by the reduction of a silver salt. The silver reflector may also be produced by sintering of silver nano-particles.

The socket may be formed in various shapes and from different materials or combination of different materials providing that it has a matching holder to receive the lamp cap 140. The socket may be connected to the reflector e.g. by having at least one attachment to a portion of the reflector. The socket may have pins to allow it to be connected into electric plugs or a matching holder. The socket may have a driver to adapt the incoming current and voltage to the specific requirement of the LED-filament lamp 100.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

Claims

CLAIMS:

1. An LED-filament lamp (100) comprising:

an LED-filament (110) configured to emit LED-filament light; and an envelope (120) comprising a light absorbing material (130) configured to absorb light in a wavelength range of 400-440 nm to provide an amber colored appearance, wherein the envelope (120) at least partly encloses the LED-filament (110), and

wherein the light absorbing material (130) is transmissive for substantially all the visible LED-filament light having wavelengths longer than 440 nm.

2. The LED-filament lamp (100) according to claim 1, wherein the light absorbing material (130) absorbs less than 5%, more preferably less than 3%, most preferably less than 2% of the visible LED-filament light.

3. The LED-filament lamp (100) according to claim 1 or 2, wherein the light absorbing material absorbs less than 10%, more preferably less than 5%, most preferably less than 3% of light in a wavelength range of 440-490 nm of the LED-filament light.

4. The LED-filament lamp (100) according to anyone of claims 1-3, wherein the light absorbing material absorbs more than 20%, more preferably more than 30%, most preferably more than 40% of the light in the wavelength range from 400 to 440 nm.

5. The LED-filament lamp (100) according to anyone of claims 1-4, wherein the

LED-filament (110) comprises a plurality of LEDs configured to emit blue light having a peak wavelength (lr) in a range from 450 to 470 nm, preferably 460 nm, and wherein the light absorbing material (130) is transmissive for wavelengths in a range from 450 to 490 nm.

6. The LED-filament lamp (100) according to anyone of claims 1-4, wherein the

LED-filament (110) comprises a plurality of LEDs configured to emit blue light having a peak wavelength (lr) in a range from 470 to 490 nm, and wherein the light absorbing material (130) is transmissive for wavelengths in a range from 450 to 490 nm.

7. The LED-filament lamp (100) according to claim 5 or 6, wherein the LED- filament (110) further comprises wavelength converting material configured to convert at least part of the blue light emitted from the plurality of LEDs, the converted light and the unconverted blue light forming the LED-filament light.

8. The LED-filament lamp (100) according to anyone of claims 1-7, wherein the light absorbing material (130) comprises one or more of: perylene dyes; 3-carboxy-6,8- difluoro-7-hydroxycoumarin; and ZnSSe nanoparticles.

9. The LED-filament lamp (100) according to anyone of claims 1-8, wherein the light absorbing material (130) is in the form of a coating on a surface of the envelope (120).

10. The LED-filament lamp (100) according to claim 9, wherein the coating is in the form of the light absorbing material in a polymer matrix.

11. The LED-filament lamp (100) according to anyone of claims 1-10, wherein the light absorbing material (130) is an integral part of the envelope (120).

12. The LED-filament lamp (100) according to anyone of claims 1-11, wherein the envelope (120) comprises scattering material in the form of one or more of: TiCh, BaSCE, and AI2O3.

13. The LED-filament lamp (100) according to anyone of claims 1-12, wherein the light absorbing material (130) is applied to an entire light exit area of the envelope (120).

14. The LED-filament lamp (100) according to anyone of claims 1-13, wherein the light absorbing material absorbs less than 5%, more preferably less than 3%, most preferably less than 2% of light in a wavelength range of 490-700 nm of the LED-filament light.

15. The LED-filament lamp (100) according to anyone of claims 1-14, wherein an amount of absorption of the light absorbing material (130) varies across the area of the envelope (120).