LED filament and LED filament lamp

Abstract

The LED filament has an elongated support having a first individually controllable array of blue LEDs emitting a first blue LED light, a second individually controllable array of blue LEDs emitting a second blue LED light, and a third individually controllable array of blue LEDs emitting a third blue LED light. An elongated encapsulant layer having luminescence particles of a first concentration C1 covers all of the LEDs in the first individually controllable array and all of the LEDs in the second individually controllable array. The blue LEDs in the third individually controllable array are covered by a second encapsulant spot, where (i) the second encapsulant spot does not contain a luminescence material, or (ii) the second encapsulant spot has luminescence particles of a third concentration C3, with C3 < C1. The second encapsulant spot is at least partially covered by the elongated encapsulant layer. Thereby, the light emitted from the LEDs in the third array is exposed to less luminescence.

Description

Technical Field

[0001] The present invention relates to an elongated carrier, an LED filament having a plurality of LEDs attached to the carrier, and an LED filament lamp, i.e., a lamp having an envelope that houses the LED filament and a connector for mechanical and electrical connection of the lamp.

Background Art

[0002] In recent years, LEDs (light emitting diodes) have become a dominant type of light source in many applications due to their excellent energy efficiency. One example is an LED lamp, which has largely replaced incandescent lamps having a heated wire filament within a substantially airtight envelope.

[0003] One disadvantage of LED lamps is that the light emitted may be perceived as different from the light emitted by incandescent lamps. Therefore, various efforts have been made to make LED lamps resemble incandescent lamps. One specific result of these efforts is an LED filament, i.e., a plurality of LEDs disposed on an elongated carrier and covered by a luminescent encapsulant. The light emitted from the LED filament is to a large extent similar to the light emitted by the wire filament in an incandescent lamp.

[0004] A bulb comprising an LED filament (referred to as an LED filament lamp) is designed to resemble a conventional incandescent bulb using one or several visible LED filaments for aesthetic and light distribution purposes. LED filament lamps are becoming increasingly popular and are commercially available as household and commercial lamps.

[0005] Some LED filament lamps are controllable in terms of color point and color temperature. For this purpose, there are LED filaments with two independently controllable strings of blue LEDs, where the LEDs in one of these strings are covered by a small spot of high-luminescence encapsulant. Then, all the LEDs are covered by a general-purpose encapsulant with slightly lower luminescence than the spot. As a result, the two LED strings are exposed to different amounts of luminescence and therefore produce white light with different color temperatures (correlated color temperatures, CCT). By controlling the two strings, the overall color temperature of the LED filament can be controlled.

[0006] A disadvantage of such controllable LED filaments is that the CCT range is quite limited, typically between 2200 and 2700K, and they cannot supply light at higher temperatures. [Overview of the project] [Problems that the invention aims to solve]

[0007] The objective of the present invention is to provide an LED filament with improved controllability of the CCT. [Means for solving the problem]

[0008] This and other objects are achieved by an LED filament that supplies LED filament light and has an elongate support having a plurality of blue LEDs mounted on an attachment surface of the elongate support. The plurality of blue LEDs include a first individually controllable array of blue LEDs that emit a first blue LED light, a second individually controllable array of blue LEDs that emit a second blue LED light, and a third individually controllable array of blue LEDs that emit a third blue LED light. The LED filament further includes an elongate encapsulant layer that covers all of the LEDs in the first individually controllable array and all of the LEDs in the second individually controllable array, the elongate encapsulant layer being formed of a first luminescent material having luminescent particles of a first concentration C1.

[0009] The blue LEDs in the second individually controllable array are covered by a first encapsulant spot formed of a second luminescent material having luminescent particles of a second concentration C2, where C2 > C1. The blue LEDs in the third individually controllable array are covered by a second encapsulant spot, where (i) the second encapsulant spot does not include a luminescent material, or (ii) the second encapsulant spot is formed of a third luminescent material having luminescent particles of a third concentration C3, where C3 < C1. The second encapsulant spot is at least partially covered by the elongate encapsulant layer.

[0010] Here, the "blue" LEDs are intended to mean LEDs configured to emit light within the blue region of the visible light spectrum.

[0011] By covering the LEDs in the third array with encapsulant spots having less luminescence than the third luminescent material, the light emitted from the LEDs in the third array is exposed to less luminescence. As a result, the blue light is wavelength-converted to a smaller extent, resulting in a higher color temperature. The second encapsulant spots may be completely non-luminescent, or they may be luminescent to some extent, but with lower luminescence than the first luminescent material.

[0012] In that case, it is preferable that the concentration C3 of luminescent particles in the third luminescent material is less than 0.8 of the concentration C1 of luminescent particles in the first luminescent material, i.e., C3 / C1 < 0.8. More preferably, C3 / C1 < 0.5, and most preferably, C3 / C1 < 0.3.

[0013] Preferably, the concentration C1 of luminescent particles in the first luminescent material is less than 0.8 of the concentration C2 of luminescent particles in the second luminescent material, i.e., C1 / C2 < 0.8. More preferably, C1 / C2 < 0.5, and most preferably, C1 / C2 < 0.3.

[0014] The second encapsulant spot may be transparent so as not to scatter the light emitted by the blue LED in the third array. In other examples, the second encapsulant spot may be semi-transparent so as to diffuse the light emitted by the blue LED in the third array.

[0015] It should be noted that the light ultimately emitted from the LED filament, referred to as LED filament light, is a mixture of contributions from one or more of the following: the first blue LED light, the first converted light, the second blue LED light, the second converted light, the third blue LED light, and the third converted light.

[0016] The thickness of the second encapsulant spot may be greater than the thickness of the first encapsulant spot so that even less blue light from the LEDs in the third array is converted to a specific wavelength.

[0017] In some embodiments, the elongated encapsulant layer covers all the LEDs in the third individually controllable array. However, in other embodiments, the thickness of the second encapsulant spot is equal to or greater than the thickness of the luminescent encapsulant layer, such that the encapsulant layer does not extend to the entire second encapsulant spot and does not cover the LEDs in the third individually controllable array. In this case, if the second encapsulant spot is non-luminescent, at least some of the light emitted from the blue LEDs in the third array is emitted without any wavelength conversion.

[0018] The first luminescent material may contain green-yellow phosphor particles and red phosphor particles. The second luminescent material may contain red phosphor particles and optionally green-yellow phosphor particles. The third luminescent material may contain green-yellow phosphor particles (if present) and may not contain red phosphor particles.

[0019] It should be noted that the first luminescent material is configured to convert the first blue LED light, the second blue LED light, and / or the third blue LED light at least partially into the first converted light. Similarly, the second luminescent material is configured to convert the second blue LED light at least partially into the second converted light. And finally, the third luminescent material (if present) is configured to convert the third blue LED light at least partially into the third converted light.

[0020] The first blue LED light may have a first primary peak wavelength λ1, the second blue LED light may have a second primary peak wavelength λ2, and the third blue LED light may have a third primary peak wavelength λ3. These primary peak wavelengths may be relatively close to each other, such that |λ2-λ1|≦20nm and / or |λ3-λ2|≦20nm. However, preferably, these primary peak wavelengths are farther apart, such that |λ2-λ1|≧20nm and / or |λ3-λ2|≧20nm. Such separation of these primary peak wavelengths may be advantageous. For example, the first primary wavelength λ1 and the second primary wavelength λ2 may be closer to the excitation maximum of the second luminescent material, thereby resulting in a higher (luminescent) conversion by the first luminescent spot, while the third primary wavelength λ3 may be farther away from the excitation maximum. In this way, (relatively) less third blue LED light is converted into the first conversion light.

[0021] In one embodiment, the support is light-transmitting (e.g., transparent) so that light emitted from the blue LED passes through the support and is emitted outward from the back surface opposite to the mounting surface. In this case, the LED filament may further include a third encapsulant spot disposed on the back surface and aligned with the LED in the second array, a fourth encapsulant spot disposed on the back surface and aligned with the LED in the third array, and a second luminescence encapsulant layer disposed on the back surface and aligned with the first luminescence encapsulant layer.

[0022] The second elongated sealing layer may be formed of a fourth luminescent material having luminescent particles of a fourth concentration C4, and the third sealing spot may be formed of a fifth luminescent material having luminescent particles of a fifth concentration C5, where C5 > C4, and the fourth sealing spot may (i) not contain any luminescent material, or (ii) be formed of a sixth luminescent material having luminescent particles of a sixth concentration C6, where C6 <C4である。

[0023] Note that C1 ≠ C4 and / or C2 ≠ C5 and / or C3 ≠ C6.

[0024] A second aspect of the present invention relates to an LED filament lamp having an LED filament according to the first aspect of the present invention and a controller configured to individually control a first individually controllable array of the blue LEDs, a second individually controllable array of the blue LEDs, and a third individually controllable array of the blue LEDs so as to change the correlated color temperature of the LED filament light emitted.

[0025] In some embodiments, the lamp further includes an envelope surrounding the LED filament and a connector for mechanically and electrically connecting the LED filament lamp to a socket of a lighting fixture.

[0026] In some embodiments, the lamp further includes an antenna operatively coupled to the controller of the LED filament lamp and configured to receive user input from a remote device, and the controller is configured to individually control the first individually controllable array of the blue LEDs, the second individually controllable array of the blue LEDs, and the third individually controllable array of the blue LEDs based on the user input. BRIEF DESCRIPTION OF THE DRAWINGS <​​​​​​​​​​​​​​​​ [Figure 2c] This is a cross-sectional view of an LED filament according to various embodiments of the present invention. [Figure 2d] This is a cross-sectional view of an LED filament according to various embodiments of the present invention. [Figure 2e] This is a cross-sectional view of an LED filament according to various embodiments of the present invention. [Figure 2f] This is a cross-sectional view of an LED filament according to various embodiments of the present invention. [Figure 2g] This is a cross-sectional view of an LED filament according to various embodiments of the present invention. [Figure 3] This is a perspective view of an LED filament lamp according to an embodiment of the present invention. [Modes for carrying out the invention]

[0028] The LED filament in Figures 1a and 1b has a long, generally flat support 1 on which multiple blue LEDs 2a and 2b are attached. The support 1 may be made of a hard material such as ceramic or metal. Alternatively, the support 1 may be made of a flexible material such as plastic.

[0029] LEDs 2a and 2b are arranged in two LED arrays and are individually connected by their respective conductive paths 3a and 3b provided on the support 1. All LEDs 2a and 2b are further covered by a luminescent encapsulant layer 4, which is formed of a first material, for example, containing phosphor particles. LEDs 2b in the second array are also covered by a luminescent encapsulant spot 5, which is formed of a second material, for example, containing phosphor particles. Layers 4 and spot 5 play a role in wavelength conversion of the light emitted from LEDs 2a and 2b from blue to white.

[0030] The second material (within the spot) has a higher concentration of phosphor particles than the first material (in the layer) such that the light emitted from LED2b in the second array undergoes more wavelength conversion than the light emitted from LED2a in the first array. Therefore, the light emitted from LED2a provides a first higher color temperature T2 (more blue), while LED2b in the second array provides a second lower color temperature T1 (less blue).

[0031] By controlling the two LED arrays separately, the overall color temperature of the LED filament light emitted by the LED filaments can be adjusted between two extreme points T1 and T2.

[0032] Here, embodiments of the present invention will be described with reference to Figures 2a to 2g.

[0033] The LED filament 10 in Figure 2a comprises a support 11 and three arrays 12a, 12b, and 12c of blue LEDs attached to the mounting surface 11a of the support 11. Each LED array has separate electrical connections (not shown) and can be controlled individually.

[0034] In the illustrated example, all LEDs 12a, 12b, and 12c are covered by a luminescence encapsulant layer 14 made of a first luminescence material containing luminescence particles of concentration C1, such as phosphor particles. Furthermore, LED 12b in the second set is covered by an encapsulant spot 15 of a second luminescence material containing luminescence particles of second concentration C2, such as phosphor particles. Layers 14 and spot 15 may be similar to layers 4 and spot 5 in Figure 1a, such that the light emitted from LED 12a has a color temperature T2 and the light emitted from LED 12b has a color temperature T1.

[0035] Furthermore, the LED 12c in the third set is covered by a sealing spot 16 formed of a material having lower luminescence emission than layer 14. Therefore, the light emitted by the LED 12c in the third array undergoes less wavelength conversion than the LEDs 2a and 12b in the first and second arrays, and thus has a higher color temperature T3 (more blue). As a result, the LED filament 10 can be controlled to emit light within a wider color temperature range (T1 to T3).

[0036] In one embodiment, the spot 16 is formed of a completely non-luminescent material, which may be, for example, transparent or diffusive. In another embodiment, the spot 16 is formed of a third luminescent material containing luminescent particles of a third concentration C3, such as phosphor particles.

[0037] As an example, the first luminescent material in layer 14 may include green to yellow phosphor particles and red phosphor particles. The second luminescent material in spot 15 may have red phosphor particles and optionally green to yellow phosphor particles. The third luminescent material (when present in spot 16) may have green to yellow phosphor particles and may not contain red phosphor particles.

[0038] As shown in Figure 2b, the spot 16 covering the LED 12c may have a thickness D2 greater than the thickness D1 of the spot 15. As a result, the light emitted from the LED 12c passes through a smaller portion of the luminescence layer 14 and undergoes even less wavelength conversion. In fact, as shown in Figure 2c, the spot 16 may have a thickness D2 that matches the thickness D3 of the layer 14. Or, even further, as shown in Figure 2d, it may exceed the thickness D3 of the layer 14.

[0039] Looking at Figure 2e, the LED filament 10e is similar to the filament in Figure 2d, except that the encapsulant spot 18 surrounds the LED 12c and tapers toward the LED 12c. For example, the spot 18 may taper conically or pyramidically. Such shapes can ensure even lower levels of wavelength conversion.

[0040] Figure 2f shows an LED filament similar to the LED filament in Figure 2d, but with additional individually controllable LED arrays emitting different colored light; in the illustrated example, an array of red LEDs 12d and an array of green LEDs 12e. The additional controllable LED arrays can further improve the color temperature control of the LED filament. Furthermore, the additional LED arrays offer a significant improvement in color control possibilities, which can be particularly beneficial in combination with improved color temperature control.

[0041] Figure 2g shows that the support 11 is transparent, meaning that the light emitted by LEDs 12a, 12b, and 12c also passes through the support and is emitted from the LED filaments on the back surface 11b opposite to the mounting surface 11a. To ensure that the light emitted on the back surface has the same or at least the same color temperature as the light emitted on the front surface, a luminescence layer 19 similar to layer 14 is also provided on the back surface. Furthermore, luminescence spots 20 and 21 corresponding to spots 15 and 16 are provided on the back surface, aligned with LEDs 12b and 12c, respectively. Since the amount of light reaching the back surface is less than the amount of light emitted from the front surface, the thickness of spots 20 and 21 and the thickness of layer 19 may be smaller than the corresponding thicknesses of spots 15 and 16 and layer 14. In other examples, the thickness may be the same, but the concentrations of phosphor particles C4 in layer 19 and / or C5 and C6 in spots 15 and 16 may differ from concentrations C1, C2, and C3, respectively.

[0042] The LED filament lamp 30 in Figure 3 generally includes a light-transmitting envelope 31 and a connector 32 configured to electrically and mechanically connect the lamp to a socket 33. The connector 32 is here a threaded connector conforming to an existing light bulb socket standard, such as E27. The envelope 32 may be made of glass or plastic and may be transparent (clear) or diffusive depending on the desired illumination. One or more LED filaments 10, four in the illustrated example, are arranged within the envelope 32, as in one of the examples in Figures 2a to 2g.

[0043] The lamp 30 further includes a driver circuit 34 for driving an individually controllable LED array and a controller 35 for controlling the driver circuit 35. The controller 35 can receive control signals remotely via an antenna 36. Control signals can be generated by user input from a remote device, such as a handheld device like a smartphone.

[0044] Those skilled in the art will see that the present invention is by no means limited to the preferred embodiments described above. On the contrary, many modifications and changes are possible within the scope of the appended claims. For example, the present invention is not limited to blue LEDs and luminescent encapsulants. The principle of the present invention is broadly applicable to any type of LED in which different arrays of LEDs undergo different amounts of wavelength conversion.

Claims

1. LED filament that supplies light, A long, slender support, A plurality of blue LEDs are attached to the mounting surface of the elongated support, A first individually controllable array of blue LEDs emitting first blue LED light, A second individually controllable array of blue LEDs emitting a second blue LED light, and A plurality of blue LEDs, including a third individually controllable array of blue LEDs that emit third blue LED light, An LED filament comprising an elongated sealing layer covering all LEDs in the first individually controllable array and all LEDs in the second individually controllable array, the elongated sealing layer being formed of a first luminescent material having luminescent particles of a first concentration C1, The blue LEDs in the second individually controllable array are covered by a first encapsulant spot formed of a second luminescent material having luminescent particles of a second concentration C2, wherein C2 > C1. The blue LEDs in the third individually controllable array are covered by the second encapsulant spot, (i) The second sealing spot does not contain luminescent material, or (ii) The second sealing spot is formed by a third luminescent material having luminescent particles of a third concentration C3, where C3 < C1. An LED filament in which the second encapsulant spot is at least partially covered by the elongated encapsulant layer.

2. The LED filament according to claim 1, wherein C1 / C2 < 0.5 and / or C3 / C1 < 0.

5.

3. The second sealing spot does not contain luminescent material. The LED filament according to claim 1 or 2, wherein the second sealing material spot is translucent or contains a light scattering material.

4. The LED filament according to any one of claims 1 to 3, wherein the thickness of the second encapsulant spot is greater than the thickness of the first encapsulant spot.

5. The LED filament according to any one of claims 1 to 4, wherein the elongated sealing layer covers all LEDs in the third individually controllable array.

6. The LED filament according to any one of claims 1 to 4, wherein the thickness of the second encapsulant spot matches the thickness of the luminescent encapsulant layer, or exceeds the thickness of the luminescent encapsulant layer.

7. The LED filament according to any one of claims 1 to 6, wherein the first luminescent material comprises green to yellow phosphor particles and red phosphor particles, and / or the second luminescent material comprises red phosphor particles and optionally comprises green to yellow phosphor particles.

8. The LED filament according to any one of claims 1 to 7, wherein the second encapsulant spot is formed by a third luminescent material having luminescent particles of a third concentration C3, and the third luminescent material contains green to yellow phosphor particles but does not contain red phosphor particles.

9. The LED filament according to any one of claims 1 to 8, wherein the first blue LED light has a first main peak wavelength λ1, the second blue LED light has a second main peak wavelength λ2, and the third blue LED light has a third main peak wavelength λ3, and |λ2-λ1| ≥ 20 nm and / or |λ3-λ2| ≥ 20 nm.

10. The elongated support is light-transmitting such that light from the blue LED is emitted from the back surface opposite to the mounting surface, and the LED filament is A third encapsulating material spot is disposed on the rear surface and is aligned with the blue LED of the second individually controllable array, A fourth encapsulating material spot is disposed on the rear surface and is aligned with the blue LED of the third individually controllable array, The LED filament according to any one of claims 1 to 9, further comprising a second elongated luminescence encapsulant layer disposed on the back surface and aligned with the first luminescence encapsulant layer.

11. The second elongated sealing layer is formed of a fourth luminescent material having luminescent particles of a fourth concentration C4, The third sealing spot is formed by a fifth luminescent material having luminescent particles of fifth concentration C5, where C5 > C4. The fourth sealing spot, (i) Does not contain luminescent material, or (ii) The LED filament according to claim 10, formed from a sixth luminescent material having luminescent particles of sixth concentration C6, wherein C6 < C4.

12. The LED filament according to claim 11, wherein C1 ≠ C4 and / or C2 ≠ C5 and / or C3 ≠ C6.

13. An LED filament according to any one of claims 1 to 12, An LED filament lamp having a controller configured to individually control a first individually controllable array of blue LEDs, a second individually controllable array of blue LEDs, and a third individually controllable array of blue LEDs, in order to change the correlated color temperature of the LED filament light.

14. An envelope that at least partially surrounds the LED filament, The LED filament lamp according to claim 13, further comprising a connector for mechanically and electrically connecting the LED filament lamp to a socket of a lighting fixture.

15. The LED filament lamp according to claim 13 or 14, further comprising an antenna functionally coupled to the controller of the LED filament lamp and configured to receive user input from a remote device, wherein the controller is configured to individually control a first individually controllable array of blue LEDs, a second individually controllable array of blue LEDs, and a third individually controllable array of blue LEDs based on the user input.

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