LED-filaments and LED-filament lamps utilizing manganese-activated fluoride red photoluminescence material
An LED-filament comprising: a partially light-transmissive substrate; a plurality of 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 plurality of 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 can further comprise 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. An LED-filament comprising:
a partially light-transmissive substrate having a front face and a back face;
a plurality of blue LED chips mounted on the front face of the substrate, wherein a portion of the light emitted by the blue LED chips travels through the substrate and out of the back face of the substrate;
a first broad-band green photoluminescence material, a first broad-band red photoluminescence material, and a narrow-band manganese-activated fluoride red photoluminescence material covering the plurality of blue LED chips and the front face of the substrate; and
a second broad-band green photoluminescence material and a second broad-band red photoluminescence material covering the back face of the substrate;
wherein there is no narrow-band manganese-activated fluoride red photoluminescence material covering the back face of the substrate.
2. The LED-filament of claim 1 , wherein a content ratio of the first broad-band red photoluminescence material with respect to the total of the narrow-band manganese-activated fluoride red photoluminescence material and the first broad-band red photoluminescence material is at least one of: at least 20 wt %; at least 30 wt %; and at least 40 wt %.
3. The LED-filament of claim 1 , comprising a first layer having the narrow-band manganese-activated fluoride red photoluminescence material disposed on the plurality of blue LED chips; and a second layer having the first broad-band green photoluminescence material disposed on the first layer; and the first broad-band red photoluminescence material is in at least one of: the first layer and the second layer.
4. The LED-filament of claim 3 , wherein the first layer comprises a uniform thickness layer on at least a principle light emitting face of at least one of the LED chips.
5. The LED-filament of claim 3 , wherein the first layer comprises particles of a light scattering material.
6. The LED-filament of claim 1 , comprising a layer comprising a mixture of the narrow-band manganese-activated fluoride red photoluminescence material, the first broad-band green photoluminescence material, and the first broad-band red photoluminescence material.
7. The LED-filament of claim 6 , wherein the layer further comprises particles of a light scattering material.
8. The LED-filament of claim 1 , wherein the narrow-band manganese-activated fluoride red photoluminescence material is at least one of: K 2 SiF 6 :Mn 4+ , K 2 GeF 6 :Mn 4+ , and K 2 TiF 6 :Mn 4+ .
9. The LED-filament of claim 1 , wherein at least one of the first broad-band red photoluminescence material and the second broad-band red photoluminescence material comprises a rare-earth-activated red photoluminescence material.
10. The LED-filament of claim 9 , wherein the rare-earth-activated red photoluminescence material is at least one of: a nitride-based phosphor material having a general composition AAlSiN 3 :Eu 2+ where A is at least one of Ca, Sr or Ba; a sulfur-based phosphor material having a general composition (Ca 1-x Sr x )(Se 1-y S y ):Eu 2+ where 0≤x≤1 and 0<y≤1; and a silicate-based phosphor material having a general composition (Ba 1-x Sr x ) 3 SiO 5 :Eu 2+ where 0≤x≤1.
11. The LED-filament of claim 1 , wherein the substrate has a transmittance of at least one of: from 2% to 70%, from 30% to 50%, and from 10% to 30%.
12. The LED-filament of claim 1 , wherein the partially light-transmissive substrate comprises a material selected from the group consisting of: alumina, silica, magnesium oxide, sapphire, quartz glass, diamond, silicon oxide.