LED-Filaments and LED-Filament Lamps

Abstract

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+ .