LED-Filaments and LED-Filament Lamps
An LED-filament includes a partially light-transmissive substrate; blue LED chips mounted on a front face of the substrate; first broad-band green to red photoluminescence materials and a first narrow-band manganese-activated fluoride red photoluminescence material covering the blue LED chips and the front face of the substrate; and second broad-band green to red photoluminescence materials covering the back face of the substrate. The LED-filament may further include a second narrow-band manganese-activated fluoride red photoluminescence material on the back face of the substrate in an amount that is less than 5 wt % of a total red photoluminescence material content on the back face of the substrate.
1 . (canceled)
2 . An LED-filament comprising:
an at least partially light-transmissive substrate;
an array of LED chips on a front face of the substrate;
a first layer containing a narrow-band red phosphor, wherein the first layer is in direct contact with and covers all of the LED chips of the array;
a second layer containing a first broad-band green phosphor and a first broad-band red phosphor, wherein the second layer is in direct contact with and covers the first layer; and
a third layer containing a second broad-band green phosphor and a second broad-band red phosphor covering a back face of the substrate.
3 . The LED-filament of claim 2 , wherein the third layer contains no narrow-band red phosphor, or wherein the third layer contains a narrow-band red phosphor in an amount up to 5 wt % of a total red phosphor content of the third layer.
4 . The LED-filament of claim 2 , wherein a content ratio of the first broad-band red phosphor with respect to the total of the narrow-band red phosphor and the first broad-band red phosphor is at least one of: at least 20 wt %; at least 30 wt %; and at least 40 wt %.
5 . The LED-filament of claim 2 , wherein the peak emission wavelength of the first broad-band red phosphor is shorter than at least one of: the peak emission wavelength of the second broad-band red phosphor, and the peak emission wavelength of the narrow-band red phosphor.
6 . The LED-filament of claim 5 , wherein the peak emission wavelength of the first broad-band red phosphor is about 615 nm.
7 . The LED-filament of claim 5 , wherein the peak emission wavelength of the second broad-band red phosphor is from about 620 nm to about 650 nm.
8 . The LED-filament of claim 2 , further comprising a layer containing particles of a light scattering material, wherein the layer is in contact with at least one of: the first layer, the second layer, and the third layer.
9 . The LED-filament of claim 8 , wherein light scattering material is selected from the group consisting of: zinc oxide, titanium dioxide, barium sulfate, magnesium oxide, silicon dioxide, aluminum oxide, zirconium oxide, and mixtures thereof.
10 . The LED-filament of claim 2 , wherein the narrow-band red phosphor is at least one of: K 2 SiF 6 :Mn 4+ , K 2 GeF 6 :Mn 4+ , and K 2 TiF 6 :Mn 4+ .
11 . The LED-filament of claim 2 , wherein the substrate has a transmittance of one of: from 20% to 100%, from 2% to 70%, from 30% to 50%, and from 10% to 30%.
12 . The LED-filament of claim 2 , wherein the LED-filament has a luminous efficacy of at least 150 lm/W.
13 . The LED-filament of claim 2 , wherein the first layer is on at least one light emitting face of the LED chips, or is on each light emitting face of the LED chips.
14 . The LED-filament of claim 2 , wherein at least one of the first layer, the second layer, and the third layer comprises particles of a light scattering material.
15 . The LED-filament of claim 14 , wherein light scattering material is selected from the group consisting of: zinc oxide, titanium dioxide, barium sulfate, magnesium oxide, silicon dioxide, aluminum oxide, zirconium oxide, and mixtures thereof.
16 . An LED-filament lamp comprising an LED-filament,
wherein the LED-filament comprises:
an at least partially light-transmissive substrate;
an array of LED chips on a front face of the substrate;
a first layer containing a narrow-band red phosphor, wherein the first layer is in direct contact with and covers all of the LED chips of the array;
a second layer containing a first broad-band green phosphor and a first broad-band red phosphor, wherein the second layer is in direct contact with and covers the first layer; and
a third layer on a back face of the substrate containing a second broad-band green phosphor and a second broad-band red phosphor.
17 . The LED-filament lamp of claim 16 , wherein the third layer contains no narrow-band red phosphor or wherein the third layer contains a narrow-band red phosphor in an amount up to 5 wt % of a total red phosphor content of the third layer.
18 . The LED-filament lamp of claim 16 , wherein the peak emission wavelength of the first broad-band red phosphor is shorter than at least one of: the peak emission wavelength of the second broad-band red phosphor, and the peak emission wavelength of the narrow-band red phosphor.
19 . The LED-filament lamp of claim 16 , wherein the peak emission wavelength of the first broad-band red phosphor is about 615 nm and/or the peak emission wavelength of the second broad-band red phosphor is from about 620 nm to about 650 nm.
20 . The LED-filament lamp of claim 16 , further comprising a layer containing particles of a light scattering material, wherein the layer is in contact with at least one of: the first layer, the second layer, and the third layer.
21 . The LED-filament lamp of claim 16 , wherein the narrow-band red phosphor is at least one of: K 2 SiF 6 :Mn 4+ , K 2 GeF 6 :Mn 4+ , and K 2 TiF 6 :Mn 4+ .