LED filament

Abstract

The invention relates to a lighting device comprising an elongated carrier, a major white LED filament section, and a minor color LED filament section. The major white light LED filament section comprises a plurality of N first LEDs configured to emit white light with a first CCT. The minor color LED filament section comprises a plurality of M second LEDs configured to emit colored section light with a second CCT. The ratio between the length of the minor color LED filament section and the length of the major white LED filament section ranges from 5% to 30%.

Description

[0001] LED filament

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to the field of solid-state lighting. More particularly, it relates to a Light Emitting Diode (LED) filament comprising LEDs providing light with more than one color and a lighting device comprising such a LED filament.

[0004] BACKGROUND OF THE INVENTION

[0005] Various conventional light sources, such as Edison-type light bulbs, may provide lighting for various lighting applications. However, conventional light sources may have drawbacks, such as high energy consumption, low performance, short operational life, restricted functionality and appearance, limited variety of colors and luminosity, etc. That is why LED filament lamps' performance, functionality and / or appearance have been topics of interest and have been rapidly replacing conventional incandescent lamps.

[0006] A LED filament lamp is an LED lamp which is designed to resemble a traditional incandescent light bulb with a visible filament for aesthetic and light distribution purposes but with higher efficiency, increased operational life, and reduced power consumption of light-emitting diodes. It is desired to improve the performance and / or appearance of LED filaments to be employed in a broader range of lighting applications, such as general lighting.

[0007] To overcome these obstacles and challenges, it is necessary to develop new LED filaments and / or LED filament lamps that have improved performance and functionality without worsening their appearance and increasing their manufacturing complexity and, therefore, their cost.

[0008] It is an object of the present invention to provide a LED filament (lighting device) in which the light emitted by the LED filament light source is used directly for (general) lighting purposes. A further aim of the present invention is improving LED filament lamps' performance, functionality and / or appearance.

[0009] US 2022 / 290820 discloses a LED filament including a linear array of LEDs arranged on a carrier substrate, wherein the linear array is divided into two separate longitudinal sections, a first longitudinal section including only LEDs configured to emit white light, and a second longitudinal section including only LEDs configured to emit color controllable light. The present invention suggests confining the color LEDs to the second longitudinal section of the array, so that the first longitudinal section of the array is capable of emitting homogenous white light of a color temperature in the range of the LEDs in that section.

[0010] In US 2021 / 310617 a LED filament lamp which provides LED filament lamp light is provided. The LED filament lamp comprises at least one LED filament, at least one further LED, at least a partly transmissive envelope, and an optical element. The LED filament light has a first spectral distribution SI with a first color point xl,yl and a first correlated color temperature Tl. The at least one further LED is configured to emit further LED light which has a second spectral distribution S2 with a second color point x2,y2. The optical element is arranged to collimate the further LED light into collimated further LED light. The LED filament lamp light is composed of the LED filament light which has a first spatial distribution (S'l) and the collimated further LED light which has a second spatial distribution (S'2). The first spatial distribution (S' 1) is broader than the second spatial distribution (S'2). The first spectral distribution SI and the second spectral distribution S2 are different and wherein one or more of (i) xl / x2>l. l, and (ii) xl / x2>l. l and yl / y2>l.l with xl / x2>yl / y2 applies.

[0011] SUMMARY OF THE INVENTION

[0012] It is an object of the present invention to provide a LED filament which can present the traditional appearance of a filament in incandescent light bulbs combined with the efficiency of LEDs, whilst at the same time providing improved optical performance.

[0013] This and other objects are achieved by a LED filament having the features in the independent claim. Preferred embodiments are defined in the dependent claims.

[0014] The present invention is related to a LED filament providing LED filament light and comprising: at least one major white LED filament section which comprises a plurality of N first LEDs arranged on a first portion of an elongated carrier, and wherein the at least one major white LED filament section provides white section light; and at least one minor color LED filament section which comprises a plurality of M second LEDs arranged on a second portion different from the first portion of said elongated carrier along the longitudinal axis (LA) of the elongated carrier, and wherein the at least one minor color LED filament section provides colored section light; wherein a ratio, R, between the length (L2) of at least one minor color LED filament section and the length (LI) of the at least one major white LED filament section is in a range from 5% to 30%.

[0015] Thus, the present invention is based on the concept or idea of providing a LED filament having an improved performance, functionality, and / or appearance, by using a section with white light and subtly complementing it with a section with colored light. Thus, a white filament light with a small portion of colored light may be obtained without significantly affecting the color point of the white (section) light. The added colored section light may increase the efficiency of the LED filament, increase the color rendering index of the LED filament light, and / or it may have an aesthetical purpose such as, for example, a warning notice (red / reddish light), a sustainable notice (green / greenish light), etc.

[0016] By the term “first portion” or “first section” it is meant a major white LED filament section. The first section represents the biggest part of the LED filament length, and preferably has a length in a range between 70% and 95% of the length of said LED filament.

[0017] By the term “second portion” or “second section” it is meant a minor colored LED filament section. The second section represents the smallest part of the LED filament length, and preferably has a length in a range between 5% and 30% of the length of said LED filament.

[0018] The color point may refer to a point in the color space defined by the CIE 1931 color space, such as the CIE 1931 XYZ color space. The CIE 1931 color space define quantitative links between distributions of wavelengths in the electromagnetic visible spectrum, and physiologically perceived colors in human color vision. Hence, a color point may have a definition in the color space CIE 1931, wherein the point may be specified by x and y. This is a widely used practice.

[0019] According to an embodiment of the present invention, the ratio R is in the range from 7% to 20%. The present embodiment is advantageous in that it provides an optimum ratio of the white section light and the colored section light. Thus, the present embodiment may provide a LED filament providing a more efficient and / or aesthetically pleasing light distribution. The light distribution may refer to the distribution of the LED filament light. In embodiments, the ratio R may be at least 7%. By having a ratio R of at least 7%, the second the at least one minor colored section is visible (from a distance e.g. of at least 3m). In embodiments, the ratio R may be at most 25% or at most 20%. By having a ratio R of at most 20% the color point of the white section light is almost not changed. According to an embodiment of the present invention, the at least one major white LED filament section comprises a first elongated encapsulant covering the plurality of N first LEDs and comprising a first luminescent material configured to at least partly convert first LED light emitted by the plurality of N first LEDs into first converted light and / or a first light scattering material configured to at least partly scatter the first LED light emitted by the plurality of N first LEDs into first scattered light. By the term “encapsulant” it is here meant a cover, enclosure, element, component, part, arrangement, or the like, which is configured or arranged to at least partially cover, surround, encapsulate, and / or enclose at least part of the LED filament. The present embodiment is advantageous in that the homogeneity and / or efficiency of the light distribution provided by the LED filament may be improved.

[0020] According to an embodiment of the present invention, the at least one minorcolored LED filament section comprises a second elongated encapsulant covering the plurality of M second LEDs and comprising a second luminescent material configured to at least partly convert second LED light emitted by the plurality of M second LEDs into second converted light and / or a second light scattering material configured to at least partly scatter the second LED light emitted by the plurality of M second LEDs into second scattered light. The present embodiment is advantageous in that the homogeneity and / or efficiency of the light distribution provided by the LED filament may be improved.

[0021] According to an embodiment of the present invention, the at least one major white LED filament section comprises the first elongated encapsulant covering the plurality of N first LEDs and comprising the first luminescent material configured to at least partly convert the first LED light emitted by the plurality of N first LEDs into the first converted light. Further, the at least one minor-colored LED filament section comprises the second elongated encapsulant covering the plurality of M second LEDs and comprising the second luminescent material configured to at least partly convert the second LED light emitted by the plurality of M second LEDs into the second converted light. Further, at least 80% (or at least 90%) of the first luminescent material is a green phosphor and a red phosphor. Furthermore, the second luminescent material is for at least 80% (or at least 90%) a greenyellow phosphor or for at least 80% (or at least 90%) a red phosphor. The present embodiment is advantageous in that the LED filament provides a more pleasing, homogenous and / or efficient light distribution. Furthermore, the colored green light may provide an indication without significantly effecting the color point of the white light.

[0022] According to an embodiment of the present invention, the LED filament, the at least one colored section light has a luminous flux in a range from 5%-20% of the luminous flux of said LED filament light. The present embodiment is advantageous in that it provides a LED filament with an optimum in the ratio of the white section light and the colored section light. Furthermore, it is advantageous in that the LED filament provides a more pleasing, homogenous and / or efficient light distribution.

[0023] In embodiments, the second elongated encapsulant e.g. the second luminescent material is configured to fully convert the second LED light into the second converted light. Fully convert may mean convert at least 95% or at least 97% of the second LED light.

[0024] According to an embodiment of the present invention, M < 0.5 N. The present embodiment is advantageous in that it provides a further improved optimum in the ratio of the white section light and the colored section light.

[0025] In embodiments the colored section light may be red / reddish light or green / greenish light.

[0026] According to an embodiment of the present invention, the at least one white section light has a first Correlated Color Temperature (CCT1) in a range from 1700K to 6500K, wherein the LED filament light is white light having a filament Correlated Color Temperature (CCTfil) in a range from 1700K to 6500K and a second Color Rendering Index (CRI2) of at least 80 and preferably the LED filament light has a color point (xl,yl) which has a first distance (DI) < 7 SDCM (or < 9 SDCM) to the BBL. In a preferred embodiment, the at least one white section light has a first Correlated Color Temperature (CCT1) in a range from 1600K to 2700K.

[0027] In another preferred embodiment, the white section light may have a color rendering index of at least 85 (>85), or in a more preferred embodiment at least 90 (>90). The BBL may the black body line, or black body locus (BBL), which is the path that such a black body would take in a particular chromaticity space as its temperature increases, wherein the chromaticity space may be the one of the CIE 1931 color space. The SDCM may refer to the standard deviation color matching and / or the MacAdam color steps. The SDCM may indicate the tolerance level where the human eye cannot perceive oscillations. SDCM may define tolerance and color temperature with a number. The lower the number, the less tolerance relative to XY color space.

[0028] The present embodiment is advantageous in that it provides an optimum in the light distribution of the LED filament, which may result in a LED filament that provides a more pleasing, and / or efficient light distribution. Hence, the present embodiment may provide a more optimized compensation for the light from the colored section. According to an embodiment of the present invention, the at least one white section light has a color point (x2,y2) arranged at the other side of the Planckian Black Body Locus (BBL) with respect to a color point (x3,y3) of the colored section light, and preferably has the color point (x2,y2) of the white section light has a second distance (D2) < 12 SDCM to the BBL. The present embodiment is advantageous in that the LED filament provides a more pleasing and / or efficient light distribution.

[0029] According to an embodiment of the present invention, the LED filament light has a color point (xl,yl) which has a first distance (DI) expressed in SDCM to the BBL, wherein the white section light has a color point (x2,y2) which has a second distance (D2) expressed in SDCM to the BBL, and wherein D1<D2. In a preferred embodiment, the difference may be at least 5 SDCM. The present embodiment provides a LED filament wherein the colored section light is correcting the white section light to get a more optimal LED filament light. The present embodiment is further advantageous in that the LED filament provides a more pleasing and / or efficient light distribution.

[0030] According to an embodiment of the present invention, the at least one minorcolored LED filament section is arranged at a first end of said LED filament and / or at a second end of said LED filament. The present embodiment is advantageous in that the LED filament provides a more pleasing and / or efficient light distribution. The present embodiment may provide improved visibility.

[0031] According to an embodiment of the present invention, the at least one minor colored LED filament section comprises at least 5 neighboring LEDs. In a preferred embodiment, the LED filament section comprises at least 7 neighboring LEDs. These embodiments are advantageous in that the visibility may be improved. Furthermore, the LED filament provides a more pleasing and / or efficient light distribution.

[0032] According to an embodiment of the present invention, the at least one major white LED filament section provides the white section light at a first efficiency (El) and a first Color Rendering Index (CRI1), wherein the LED filament provides the LED filament light at a second efficiency (E2) and a second Color Rendering Index (CRI2), and wherein one or more of the following applies: (i) E2>E1 and (ii) CRI2>CRI1. For example, the efficiency may be improved by at least 3% or at least 5%. For example, the CRI may be improved by at least 3 or at least 5 points. The present embodiment is advantageous in that the LED filament provides a more efficient light distribution while also providing a pleasing / desired light distribution. According to an embodiment of the present invention, there is provided a LED filament arrangement comprising a LED filament according to an embodiment of the present invention, and a controller configured to individually control the white section light provided by the at least one major white LED filament section and the colored section light the at least one minor colored LED filament section.

[0033] According to an embodiment of the present invention, there is provided a luminaire, comprising one or more LED filament according to an embodiment of the present invention

[0034] Further objectives of, features of, and advantages with, the present invention will become apparent when studying the following detailed disclosure, the drawings, and the appended claims. Those skilled in the art will realize that different features of the present invention can be combined to create embodiments other than those described in the following.

[0035] BRIEF DESCRIPTION OF THE DRAWINGS

[0036] This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing the preferred embodiment(s) of the invention. The figures presented in this invention are by way of example, and not by way of limitation, in the accompanying drawings, wherein:

[0037] Fig. 1 schematically depicts a LED filament in accordance with an exemplifying embodiment of the present invention, a schematic illustration of a lighting device equipped with an example of LED filament, and some illustrative examples of a length percentage of the first portion and the second portion;

[0038] Fig. 2 schematically depicts a LED filament with no elongated carrier in accordance with an exemplifying embodiment of the present invention;

[0039] Fig. 3 schematically depicts a LED filament with different spacing between LEDs in accordance with an exemplifying embodiment of the present invention;

[0040] Fig. 4 schematically depicts a LED filament in accordance with exemplifying embodiments of the present invention;

[0041] Fig. 5 schematically depicts a LED filament in accordance with exemplifying embodiments of the present invention;

[0042] Fig. 6 schematically depicts a LED filament in accordance with an exemplifying embodiment of the present invention; Fig. 7 schematically depicts two embodiments of LED filaments comprising two rows of LEDs in accordance with an exemplifying embodiment of the present invention;

[0043] Fig. 8 schematically depicts a LED filament comprising two rows of LEDs in accordance with an exemplifying embodiment of the present invention;

[0044] Fig. 9 schematically depicts a LED filament in accordance with an exemplifying embodiment of the present invention;

[0045] Fig. 10 schematically depicts a LED filament in accordance with an exemplifying embodiment of the present invention;

[0046] Fig. 11 schematically depicts a LED filament in accordance with an exemplifying embodiment of the present invention;

[0047] Fig. 12 schematically depicts a lighting device comprising a LED filament in accordance with an exemplifying embodiment of the present invention; and

[0048] Fig. 13 schematically depicts a lighting device comprising more than one LED filament in accordance with an exemplifying embodiment of the present invention.

[0049] DETAILED DESCRIPTION

[0050] Exemplifying embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments are shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, the embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person in the art.

[0051] With reference to Figure 1, a light-emitting diode (LED) filament in accordance with some embodiments will be described.

[0052] The LED filament 100 of Figure 1 comprises a first elongated encapsulant 12, a section 1, i.e. a first major white LED filament section 2, a second elongated encapsulant 22 and a minor color LED filament section 2, i.e. a first minor color LED filament section 2. The at least one major white LED filament section 1 comprises a plurality of N first LEDs 10, which are arranged in a row on a first side of the LED filament 100. The at least one minor color LED filament section 2 comprises a plurality of M second LEDs 20 arranged in a row on a second side of the LED filament 100 along the longitudinal axis (LA) of the elongated carrier 3. The plurality of N first LEDs 10 and of M second LEDs 20 are aligned in one row on the LED filament 100. The N first LEDs 10 are arranged on a first portion 11 of an elongated carrier and provide white section light. Said major white LED filament section 1 comprises a first elongated encapsulant 12 comprising a first luminescent material and / or a scattering material. At least one major white LED filament section 1 comprises a first elongated encapsulant 12 covering the plurality of N first LEDs 10 and comprising a first luminescent material configured to at least partly convert first LED light emitted by the plurality of N first LEDs 10 into first converted light and / or a first light scattering material configured to at least partly scatter the first LED light emitted by the plurality of N first LEDs 10 into first scattered light.

[0053] The N first LEDs 10 and M second LEDs 20 may all be the same type of LED. However, the M second LEDs 20 comprises a second elongated encapsulant 22 comprising a second material and / or a second scattering material, such as but not limited to a single phosphor type.

[0054] At least one minor colored LED filament section 2 comprises the second elongated encapsulant 22. The second elongated encapsulant 22 covers the plurality of M second LEDs 20 and comprises a second luminescent material configured to at least partly convert second LED light emitted by the plurality of M second LEDs 20 into second converted light and / or a second light scattering material configured to at least partly scatter the second LED light emitted by the plurality of M second LEDs 20 into second scattered light.

[0055] The N first LEDs 10 are configured to emit white light with a first correlated color temperature (CCT1) in a range between 1500K to 6500K, whereas the M second LEDs 20 are configured to emit any colored light with a second correlated color temperature (CCT2) different from CCT1 in a range between 1500K to 6500K.

[0056] Tools for a CIE 1931 color space may be used for color management of the light to define the resulting light of the LED filament 100. In other words, said tool helps to define the color point (xl,y 1) of the LED filament in the CIE 1931 color spaces.

[0057] The LED filament light has a color point (x 1 ,y 1) which has a first distance (DI) expressed in SDCM to the Planckian Black Body Locus (BBL).

[0058] The white section light has a color point (x2,y2) which has a second distance (D2) expressed in SDCM to the BBL. Preferably, D2>D1.

[0059] The colored section light has a color point (x3,y3) which has a third distance (D3) expressed in SDCM to the BBL.

[0060] The white section light may have a CCT1 in a range from 1500K and 6500K and the LED filament light may be white light having a CCTfil in a range from 1500K to 6500K and a second Color Rendering Index (CRI2) of at least 80, and preferably the LED filament light has a color point (xl,yl) which has a first distance Dl<7 SDCM to the BBL.

[0061] The white section light may have a color point (x2,y2) arranged at the other side of the BBL with respect to a color point (x3,y3) of the colored section light. The color point (x2,y2) of the white section light has preferably a second distance D2<12 SDCM to the BBL.

[0062] The at least one minor color LED filament section 2 has a length in a range from 5% to 30% of the length of the full LED filament 100 (for visibility) and emits colored light having a luminous flux in a range from 5% to 20% of the luminous flux of the LED filament light. Preferably, the M number of M second LEDs 20 is less than half of the N number of N first LEDs 10.

[0063] The white section light has a color point arranged at the other side of the BBL with respect to the colored section light and typically has a second distance (D2) lower or equal to 10 SDCM to the BBL and a CRI of at least 80, preferably higher than 85 and most preferably higher than 90 to compensate for the light of the colored LED filament section(s) 2.

[0064] The major white LED filament section 1 provides the white section light at a first efficiency (El) and a first Color Rendering Index (CRI1), whereas the LED filament 100 provides light at a second efficiency (E2) and a second Color Rendering Index (CRI2). E2 may be higher than El and / or CRI2 may be higher than CRI1 for the reason that the colored section light provided by the at least one minor colored LED filament section 2 improves the efficiency and / or CRI of the LED filament light with respect to the white section light provided by the at least one major white LED filament section 1.

[0065] The second portion 21 may be arranged at an end of the LED filament 100; it typically has three to fifteen neighboring LEDs and has a second elongated encapsulant 22 comprising a second luminescent material and / or second light-scattering material, preferably a single phosphor type and different than the first luminescent material and / or first lightscattering material of the first elongated encapsulant of the first portion 11.

[0066] The minor colored LED filament section 2 may have preferably at least 8 neighboring LEDs, more preferably at least 10 neighboring LEDs, and most preferably at least 12 LEDs.

[0067] By way of example and without any limitation, the colored LEDs may be blue and / or UV LEDs which are covered with a luminescent material, e.g. an encapsulant comprising a luminescent material. The luminescent material may be a phosphor such as an inorganic phosphor or quantum dots / rods. The blue and / or UV light may then be converted by the luminescent material into converted light. For example, a green / yellow phosphor and / or red phosphor may be used to obtain green / yellow and red light, respectively.

[0068] Preferably, the N first LEDs 10 and the M second LEDs 20 are phosphorconverted LEDs. The type, concentration and layer thickness of the phosphor of the N first LEDs 10 may be different from the type, concentration and layer thickness of the phosphor of the M second LEDs 20. LEDs that emit a lower color temperature typically have a higher thickness of phosphor, a higher concentration and / or a phosphor that emits light at higher wavelengths.

[0069] In some embodiments, the first elongated encapsulant 12 and the second elongated encapsulant 22 comprise YAG+KSF phosphor and LuAG phosphor, respectively.

[0070] At least 80% of the first luminescent material is a green phosphor and a red phosphor.

[0071] At least 80% of the second luminescent material is a green phosphor or a red phosphor.

[0072] In some embodiments, the luminescent material and / or light-scattering material of the first and the second elongated encapsulant may be the same but with different thicknesses or concentrations.

[0073] Light emitted by the N first LEDs 10 and light emitted by the M second LEDs 20 arranged on the LED filament 100 together form the light emitted by the LED filament 100.

[0074] The N first LEDs 10 of the at least one major white LED filament section lare electrically connected to the plurality of M second LEDs of the at least one minor color LED filament section 2.

[0075] The first elongated encapsulant 12 and / or the second elongated encapsulant 22 may cover at least part of the LED filament 100. The encapsulant 12 and / or 22 may further cover at least part of the substrate 40.

[0076] Some embodiments may have LEDs arranged on more than one surface or side, such as on two opposite surfaces of the substrate 40. In some embodiments, the encapsulants 12 and / or 22 may cover the sides of the substrate 40 on which LEDs are arranged and the LEDs on those sides. In some embodiments, the encapsulants 12 and / or 22 may encapsulate all sides of the substrate 40 of the LED filament 100.

[0077] The elongated encapsulants 12 and / or 22 may comprise a polymer. The encapsulants 12 and / or 22 may comprise a silicone-based material. The elongated encapsulants 12 and / or 22 may comprise diffusing material for spreading the light. For example, the elongated encapsulants 12 and / or 22 may include scattering particles, such as one or more barium sulfate (BaSO4), aluminium oxide (A12O3), and titanium dioxide (TiO2) particles. The elongated encapsulants 12 and / or 22 are / is at least partially light-transmissive, such as translucent or transparent.

[0078] The elongated encapsulant 12, 22 and / or the substrate 40 may be partially light transmissive. For example, the elongated encapsulants 12, 22 and the substrate 40 be translucent or transparent. The elongated encapsulants 12, 22 and the substrate 40 may be at least partially curved. The elongated encapsulants 12, 22 and the substrate 40 may be at least partially straight. The elongated encapsulants 12, 22 and the substrate 40 may be rigid. The elongated encapsulants 12, 22 and the substrate 40 may be flexible.

[0079] The major white LED filament section 1 comprises the first elongated encapsulant 12 covering the plurality of N first LEDs 10 and comprising the first luminescent material configured to at least partly convert the first LED light emitted by the plurality of N first LEDs 10 into the first converted light.

[0080] The minor colored LED filament section 2 comprises the second elongated encapsulant 22 covering the plurality of M second LEDs 20 and comprising the second luminescent material configured to at least partly convert the second LED light emitted by the plurality of M second LEDs 20 into the second converted light.

[0081] With reference to Figure 2, a LED filament 300 in accordance with some embodiments will be described.

[0082] Figure 2 is a top view of a LED filament 300. The LED filament 300 may be equivalent to the LED filament 100 described with reference to Figure 1. The LED filament 300 comprises only a substrate 40 without any elongated encapsulant to encapsulate the substrate 40, and the LEDs are arranged on one or both portions of the LED filament 300.

[0083] With reference to Figure 3, a LED filament 400 in accordance with some embodiment will be described. The LED filament 400 may be equivalent to the LED filament 100 described with reference to Figure 1, except that the distance between the N first LEDs 10, as well as the distance between the M second LEDs 20 are dissimilar. The N first LEDs 10 arranged at a first end of the LED filament 100 may have a first distance between each N first LEDs 10, and the M second LEDs 20 may have a second distance between each M second LEDs 20. The first distance may be shorter or longer than the second distance. For example, M second LEDs 20 may be placed / arranged at a distance shorter to each other on one end of the LED filament 100 compared to the distance between the N first LEDs 10 at the other opposite end of the LED filament 400. In other words, the LEDs may be spaced at a distance that starts short from one end and increases gradually or in a certain pattern. The spacing pattern or distance between the N first LEDs may differ from the spacing pattern or distance between the M second LEDs 20. The end with shorter or longer spacing between LEDs may be at the very end of the LED filament 400, on the side of the other portion, in the middle or in any part of the LED filament 400. Any possible combination of the technical features recited above may be envisaged.

[0084] With reference to Figure 4, the lengths of the different regions will be described. Figure 4 is a schematic illustration of a LED filament 500, which may be equivalent to the LED filament 100 described with reference to Figure 1. In Figure 4 the at least one major white LED filament section 1 has a first length LI and the at least one minor color LED filament 2 has a second length L2.

[0085] In some embodiments, a ratio R between the length L2 of at least one minor color LED filament section 2 and the length LI of the at least one major white LED filament section 1 is in a range from 5% to 30%. The ratio R may be in the range from 5% to 18%.

[0086] In some embodiments, a ratio of the first length LI to the length of the LED filament is in the range of 70%-95%, whereas the remaining length is kept for the second length L2 representing between 5% and 30%.

[0087] In some embodiments, the major white LED filament section 1 (LI) may have at least 51% of the total length of the LED filament 500, whereas the minor single color LED filament section 2 (L2) may have no more than 49% of the total length of the LED filament 500.

[0088] With reference to Figure 5, a LED filament in accordance with some embodiments will be described.

[0089] Figure 5 is a schematic illustration of a LED filament 600. The LED filament 600 may be equivalent to the LED filament 100, described with reference to Figure 1, except that there is more than one combination of the at least one major white LED filament section 1 and the at least one minor color LED filament section 2, which may be arranged differently and in diverse combinations.

[0090] The at least one major white LED filament section 1 and the at least one minor color LED filament section 2 may be alternated identically or with different numbers and / or sizes and / or types. For example, the M second LEDs 20’ of the second section 2’ may be different than the M second LEDs 20 of the at least one minor color LED filament section 2. It is to be understood that there may be three or more different configurations for the at least one major white LED filament section 1 and the at least one minor color LED filament section 2. For example, the at least one minor color LED filament section 2 may have have three different configurations 2, 2’ and 2”, wherein each configuration may be different in terms of number of LEDs 20, size / type of LEDs 20 and distance between LEDs 20. The same applies for the N first LEDs 10, 10’, 10” of the different configurations of the at least one major white LED filament section 1, 1’ and 1”. It is to be understood that the first portion and the second portion may be alternated accordingly, i.e. according to the different arrangements / configurations of the first section 1 and the second section 2.

[0091] In other embodiments, there may be one or more alternating pairs of white LED filament sections 1 and color LED filament sections 2. Further, in other embodiments, different types of LEDs, as well as elongated encapsulants 12, 22 for one or more sections and portions may be used. In these cases, the luminescent material and / or light scattering material for one or more sections and portions, may be altered or / and changed partially or fully for one or more section and portions.

[0092] Figure 6 is a schematic illustration of a LED filament 700. The LED filament 700 may be equivalent to the LED filament 100 described with reference to Figure 1, except that there is more than one type of LEDs in the at least one major white LED filament section 1 and / or the at least one minor color LED filament section 2.

[0093] The at least one major white LED filament section 1 of the LED filament 700 comprises at least two types of LEDs 10 and 10a. The more than one type of LEDs 10 and 10a may be spaced irregularly. Additionally, each LED and / or each type of LED may be controlled separately. Each LED 10, 10a in the first portion 1 may be of a different type, as illustrated by the different patterns filling each LED 10, 10a.

[0094] The at least one minor color LED filament section 2 of the LED filament 700 comprises at least two types of LEDs 20 and 20a. The more than one type of LEDs 20 and 20a may be spaced irregularly. Additionally, each LED and / or each type of LED may be controlled separately. Each LED 20, 20a in the first section 1 may be of a different type, as illustrated by the different patterns filling each LED 20, 20a.

[0095] With reference to Figure 7, a LED filament in accordance with some embodiments will be described.

[0096] Figure 7 is a schematic illustration of a LED filament 800 in two possible embodiments (a) and (b). The LED filaments 800 and 800’ may be equivalent to the LED filament 100, described with reference to Figure 1, except that the LEDs of the at least one major white LED filament section 1 and the at least one minor color LED filament section 2 are arranged in more than one parallel row. The first row in the LED filament 800 comprises, from left to right in the present illustration, eight first LEDs in a first major white LED filament section 1, and three second LEDs in a first minor color LED filament section 2. The second row is, in the present configuration, arranged below the first row on the substrate and separate from (e.g. parallel with) the first row. The second row comprises, from left to right in the present illustration of Figure 7a, three second LEDs in a second minor color LED filament section 2’, and eight first LEDs in a second major white LED filament section L. In Figure 7, the first row and the second row are connected in in series. However, the first row and the second row may be connected in parallel. If the LED filament comprises more than two rows, a mix of electrical connections (e.g. in series or in parallel) may be used. Additionally, each row may be controlled or connected separately. The connection may be from one side or more than one side of the LED filament (Figure 7).

[0097] The LED filament 800’ is similar to LED filament 800 except that the sequence of the second row is reversed, from right to left in the present illustration of Figure 7b, three second LEDs in the second minor color LED filament section 2’, and eight first LEDs in the second major white LED filament section L. In other words, there is no limitation on the sequence, order, or arrangement of the sections, portions or / and the rows in the LED filament 800.

[0098] In other embodiments, the LEDs may be arranged in more than two rows, and the LEDs may be arranged in any other directions, forms, and ways (parallel, inclined, curved, crossed, circular, etc.). Using a combination of any arrangement described herein may also be possible.

[0099] With reference to Figure 8, a LED filament in accordance with some embodiments will be described.

[0100] Figure 8 shows a schematic illustration of a LED filament 900. The LED filament 900 may be equivalent to the LED filaments 100 or 800, described with reference to Figure 1 or Figure 7.

[0101] The LED filament 900 is similar to LED filament 800 except that the first and second major white LED filament sections 1 and 1’, and the second minor color LED filament sections 2 and 2’ are arranged parallel to each other but connected in series. In other words, the connection between the first and second row when the major white LED filament sections 1, 1’ and the minor color LED filament sections 2, 2’ are arranged in parallel, goes from a first minor color LED filament section 2 to a second major white LED filament section 1’, while in Figure 7b the connection goes from a first minor color LED filament section 2 to a second major white LED filament section L.

[0102] With reference to Figure 9, a LED filament in accordance with some embodiments will be described.

[0103] Figure 9 is a schematic illustration of a LED filament 1000. The LED filament 1000 may be equivalent to the LED filament 100, described with reference to Figure 1, except that the arrangement and number of first portions(s) 1 and second portion(s) is different.

[0104] The LED filament 1000 comprises four major white LED filament sections 1 and four minor color LED filament sections 2 respecting the length ratio between the two said sections. In other words, the major white LED filament sections 1 may represent between 70% and 95% of the total LED filament to leave the remaining part for the minor color LED filament sections 2, i.e. between 30% and 5%. The major white LED filament sections 1 may be arranged parallel, juxtaposed, side by side, or in general, adjacent in any way to the minor color LED filament sections 2 without necessarily being connected between one, two, or more of the minor color LED filament sections 2. Again, it is possible to connect and control each section or each type of section separately.

[0105] With reference to Figure 10, a LED filament in accordance with some embodiments will be described.

[0106] Figure 10 is a schematic illustration of a LED filament 1100. The LED filament 1100 may be equivalent to the LED filament 100, described with reference to Figure 1, except that the minor color LED filament section(s) 1 and the minor color LED filament section(s) 2 are connected in parallel.

[0107] The major white LED filament section(s)l and the minor color LED filament section(s) 2 may be connected to one or more controllers with one or more means of connection. There is no limitation for the arrangement, position, or placement of the portion in the substrate 40. Other arrangements to use the area of the substrate 40 in a more efficient way may also be possible. It is obvious to the person skilled in the art that many combinations are possible to arrange the one or more sections 1 and 2 in the substrate of the LED filament to improve, for example, the CCT or luminosity of the filament.

[0108] Figure 11 is a schematic illustration of a LED filament 1200. The LED filament 1200 may be equivalent to the LED filament 100, described with reference to Figure 1. In Figure 12, the minor color LED filament sections 2 are arranged perpendicular to the major white LED filament sections 1. It is to be understood that the at least one minor color LED filament section 2 may be arranged at an angle relative at least one major white LED filament section 1.

[0109] With reference to Figure 12, a lighting device in accordance with some embodiments will be described.

[0110] Figure 12 is a schematic illustration of a lighting device 1400 in accordance with some embodiments. The lightning device 1400 may be a luminaire or lamp. The lighting device 1400 comprises a LED filament 1301, which may be equivalent to any LED filament described in relation to any of the preceding Figures. The lighting device 1400 further comprises an at least partially light-transmissive envelope 1302, a base 1303, a controller 1304 and a connector 1305.

[0111] The LED filament 1301 is arranged to extend away from a plane defined by the base 1303. In other embodiments, however, the LED filament 1301 may be arranged in different orientations.

[0112] The envelope 1302 envelops the LED filament 1301. The envelope 1302 is at least partially light-transmissive to couple out the light emitted by the LED filament 1301, i.e. to transmit light outside the envelope 1302. The envelope 1302 has a reflectivity for wavelengths of light emitted by the LED filament 1301, which may be less than 20%; Specifically, the reflectivity of the envelope 1302 for wavelengths emitted by the LED filament 1301 may be less than 15%. More specifically, the reflectivity of the envelope 1302 for wavelengths of light emitted by the LED filament 1301 may be less than 10%. For example, the envelope 1302 may be at least partially light-transmissive, i.e. transparent.

[0113] The envelope 1302 is mounted on the base 1303. The base 1303 may comprise electrical connectors 1305 for connecting the lighting device 1400 to a luminaire socket. The base 1303 may be adapted to be connected with, for example, an Edison socket or a bayonet socket. The base 1303 may, for example, comprise a cap, such as an E5, E10, El l, E12, E14, El 7, E26, E27, E29, E39, E40 base, or an automotive light base, or the like base, or a bayonet base. The base 1303 may further comprise a housing. In some embodiments, the controller 1305 may be arranged within the housing.

[0114] The LED filament 1301 is connected to the controller 1304 by means of a connector 1305. The connector 1305 may comprise holding means for holding the LED filament 1301. The connector 1304 may further comprise electrical connections for supplying power to the LED filament 1301. The controller 1304 is configured to control a power supply to the N first LEDs 10 of the at least one major white LED filament section 1, and a power supply to the M second LEDs 20 of at least one minor color LED filament section 2.

[0115] The controller 1304 may be configured to control the power supply of the N first LEDs 10 of the at least one major white LED filament section 1, and the power supply to the M second LEDs 20 of the at least one minor color LED filament section 2 of the LED filament 1301 individually. Through control of the power supply of the LEDs the brightness of each one of the sets of N first LEDs 10 and M second LEDs 20 may be controlled.

[0116] The ratio of power between the N first LEDs 10 and the M second LEDs 20 is of particular interest, as a change in the ratio of emittance between the LEDs of the different types may change the color temperature of the combined light. The controller 1304 may control the color temperature of the light emitted by the lighting device 1400 in a range extending from the CCT1 of the N first LEDs 10 (no power supplied to the M second LEDs 20) to the CCT2 of the M second LEDs 20 (no power supplied to the N first LEDs 10).

[0117] The controller 1304 may be configured to operate the LED filament 1301 in different modes. The N first LEDs 10 or the M second LEDs 20 may be switched on separately or switched on together. Further, the controller 1304 may vary the luminosity and / or CCT of each type of LEDs 10, 20.

[0118] Each LED of the N first LEDs 10 may provide a first luminous flux while each LED of the M second LEDs 20 may provide a second luminous flux. In case the N first and M second LEDs are switched on, it is preferable that the M second LEDs of the major white LED filament section 2 emit colored light having a luminous flux in a range from 5% to 20% of the luminous flux of the LED filament light.

[0119] With reference to Figure 13, a lighting device in accordance with some embodiments will be described.

[0120] Figure 13 is a schematic illustration of a lighting device 1500, which may be equivalent to the lighting device 1400 described with reference to Figure 12, except that it comprises more than one LED filament, more precisely three LED filaments 1401, 1402, 1403, which may be equivalent to any LED filaments described with reference to the preceding Figures.

[0121] The lighting device 1500 comprises an envelope 1404 mounted on a base 1405. Inside the envelope 1404, three different types of LED filaments 1401, 1402, 1403 are arranged parallel to one another and extending away (substantially perpendicularly) from the plane defined by the base 1405 of the lighting device 1500. The LED filaments 1401, 1402, 1403 may be connected to a controller via connections in the envelope 1404 or inside the base 1405.

[0122] The LED filaments may be in one or more rows arranged in parallel or in any other direction. There is no limitation on the number of LED filaments 1401, 1402, 1403 that can be arranged inside the envelope 1404 or the lighting device 1500.

[0123] In the present embodiment, the three LED filaments 1401, 1402, 1403 start from the at least one major white LED filament section 1. In other words, the major white LED filament section(s) 1 is (are) placed from the base side. However, in other embodiments, the at least one minor color LED filament section 2 of the LED filament may be placed at the side of the base 1405. Other placements toward the base 1405, such as but not limited to parallel, perpendicular, or inclined to the base 1405 are also possible.

[0124] In other embodiments, the LED filaments 1401, 1402, 1403 may be arranged differently within the envelope 1404. For example, the LED filaments 1401, 1402, 1403 may be arranged in the same direction. Alternatively, the LED filaments 1401, 1402, 1403 may be arranged in different directions and orientations.

[0125] 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.

[0126] It is noted that other embodiments using all possible combinations of features recited in the above-described embodiments may be envisaged. Thus, the present disclosure also relates to all possible combinations of features mentioned herein. Any embodiment described herein may be combinable with other embodiments also described herein, and the present disclosure relates to all combinations of features.

[0127] Although features and elements are described above in particular combinations, each feature or element can be used alone without the other features and elements or in various combinations with or without other features and elements.

[0128] Additionally, variations to the described embodiments can be understood and effected by the skilled person in practicing the claimed invention from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements, and the indefinite articles “a” and “an” do not exclude a plurality. The mere fact that certain features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage.

Claims

CLAIMS:

1. A LED filament (100) providing LED filament light and comprising: at least one major white LED filament section (1) which comprises a plurality of N first LEDs (10) arranged on a first portion (11) of an elongated carrier (3), and wherein the at least one major white LED filament section (1) provides white section light; and at least one minor color LED filament section (2) which comprises a plurality of M second LEDs (20) arranged on a second portion (21) different from the first portion of said elongated carrier (3) along the longitudinal axis (LA) of the elongated carrier, and a second elongated encapsulant (22) covering the plurality of M second LEDs (20) comprising a second luminescent material of which 80% is a green phosphor or 80% is a red phosphor, configured to at least partly convert second LED light emitted by the plurality of M second LEDs (20) into second converted light, wherein the at least one minor color LED filament section (2) provides colored section light that is red / reddish light or green / greenish light; wherein a ratio, R, between the length (L2) of at least one minor color LED filament section (2) and the length (LI) of the at least one major white LED filament section (1) is in a range from 5% to 30%.

2. The LED filament (100) according to claim 1, wherein R is in the range from 7% to 20%.

3. The LED filament (100) according to claim 1 or 2, wherein the at least one major white LED filament section (1) comprises a first elongated encapsulant (12) covering the plurality of N first LEDs (10) and comprising a first luminescent material configured to at least partly convert first LED light emitted by the plurality of N first LEDs (10) into first converted light and / or a first light scattering material configured to at least partly scatter the first LED light emitted by the plurality of N first LEDs (10) into first scattered light.

4. The LED filament (100) according to any one of the preceding claims, wherein the second elongated encapsulant (22) comprising a second light scattering material configured to at least partly scatter the second LED light emitted by the plurality of M second LEDs (20) into second scattered light.

5. The LED filament (100) according to claim 3 and 4, wherein: the at least one major white LED filament section (1) comprises the first elongated encapsulant (12) covering the plurality of N first LEDs (10) and comprising the first luminescent material configured to at least partly convert the first LED light emitted by the plurality of N first LEDs (10) into the first converted light, wherein at least 80% of the first luminescent material is a green-yellow phosphor and a red phosphor.

6. The LED filament (100) according to any one of the preceding claims, wherein the at least one colored section light has a luminous flux in a range from 5%-20% of the luminous flux of said LED filament light.

7. The LED filament (100) according to any one of the preceding claims, wherein M < 0.5 N.

8. The LED filament (100) according to any one of the preceding claims, wherein: the at least one white section light has a first Correlated Color Temperature (CCT1) in a range from 1700K to 6500K; and wherein the LED filament light is white light having a filament Correlated Color Temperature (CCTfil) in a range from 1700K to 6500K and a second Color Rendering Index (CRI2) of at least 80, and the LED filament light has a color point (xl,yl) which has a first distance (DI) < 7 SDCM to the BBL.

9. The LED filament (100) according to any one of the preceding claims, wherein the at least one white section light has a color point (x2,y2) arranged at the other side of the Planckian Black Body Locus (BBL) with respect to a color point (x3,y3) of the colored section light, and has the color point (x2,y2) of the white section light has a second distance (D2) < 12 SDCM to the BBL.

10. The LED filament (100) according to any one of the preceding claims, wherein: the LED filament light has a color point (xl,yl) which has a first distance (DI) expressed in SDCM to the BBL; the white section light has a color point (x2,y2) which has a second distance (D2) expressed in SDCM to the BBL; and wherein DI <D2.

11. The LED filament (100) according to any one of the preceding claims, wherein the at least one minor colored LED filament section (2) is arranged at a first end of said LED filament (100) and / or wherein the at least one major white LED filament section (1) is arranged at a second end of said LED filament (100).

12. The LED filament (100) according to any one of the preceding claims, wherein the at least one minor colored LED filament section (2) comprises at least 5 neighboring LEDs.

13. The LED filament according to any one of the preceding claims, wherein: the at least one major white LED filament section (1) provides the white section light at a first efficiency (El) and a first Color Rendering Index (CRI1); the LED filament (100) provides the LED filament light at a second efficiency (E2) and a second Color Rendering Index (CRI2); and one or more of the following applies: (i) E2>E1 and (ii) CRI2>CRI1.

14. A LED filament arrangement comprising a LED filament according to any one of the preceding claims and a controller configured to individually control the white section light provided by the at least one major white LED filament section and the colored section light the at least one minor color LED filament section.

15. A lamp or luminaire comprising one or more LED filaments according to any one of claims 1 to 13 or the LED filament arrangement according to claim 14.

Images