Electric Lamp

1 . An electric lamp ( 1 ) for a vehicle headlight with low-beam function comprising:

a light source ( 2 ) emitting visible light ( 4 ),

a transparent envelope ( 3 ) having an exterior surface ( 3 ′) and an interior surface ( 3 ″) enclosing said light source ( 2 ),

at least one multilayer structure ( 7 ) provided on the exterior surface ( 3 ′) of the envelope ( 3 ),

wherein a first light ( 5 ) substantially with a bluish-white color transmits the multilayer structure ( 7 ) directly and

a second light ( 6 ) substantially with a yellowish color transmits the multilayer structure ( 7 ) after being reflected at the multilayer structure ( 7 ),

wherein the multilayer structure ( 7 ) being of none light absorbing materials is provided in such a way, that the color of light of a standard light source A being reflected at the multilayer structure ( 7 ) lies within a triangle in the CIE 1931 Yxy color space defined by the x,y coordinates (0.58; 0.42), (0.58; 0.30) and (0.70; 0.30), wherein the lightness Y is in the range of 2.5≦Y≦17.5,

wherein none of the emitted visible light ( 4 ) is absorbed by the multilayer structure ( 7 ).

2 . An electric lamp ( 1 ) as claimed in claim 1 , characterized in that the multilayer structure ( 7 ) being an interference coating comprises at least two layers ( 7 ′, 7 ″) with a first layer ( 7 ′) having a high refractive index n H of n H ≧1.7 and a second layer ( 7 ″) having a low refractive index n L of n L ≦1.6.

3 . An electric lamp ( 1 ) as claimed in claim 1 , characterized in that an illumination distribution ( 10 ) of the lamp on a vertical screen is produced with a bright-dark cut-off ( 11 ), wherein the region (illumination zone ( 12 )) lying below the bright-dark cut-off ( 11 ) is illuminated by the first light ( 5 ) substantially and the bright-dark cut-off ( 11 ) is illuminated by the second light ( 6 ) substantially.

4 . An electric lamp ( 1 ) according to claim 1 , characterized in that the first light ( 5 ) is a bundle of lights leaving the electrical lamp ( 1 ) substantially having peak wavelengths in the range from 400 nm to 600 nm.

5 . An electric lamp ( 1 ) according to claim 1 , characterized in that the second light ( 6 ) is a bundle of lights leaving the electrical lamp ( 1 ) substantially having peak wavelengths in the range from 600 nm to 800 nm.

6 . An electric lamp ( 1 ) according to claim 1 , characterized in that the multilayer structure ( 7 ) comprises a sandwich structure, wherein the first and the second layer ( 7 ′, 7 ″) are positioned alternate to each other.

7 . An electric lamp ( 1 ) according to claim 1 , characterized in that the first layer ( 7 ′) comprises Nb 2 O 5 and/or TiO 2 and/or Ta 2 O 5 and/or ZrO 2 and/or HfO 2 and/or Si 3 N 4 .

8 . An electric lamp ( 1 ) according to claim 1 , characterized in that the second layer ( 7 ″) comprises SiO 2 .

9 . An electric lamp ( 1 ) according to claim 1 , characterized in that the multilayer structure ( 7 ) is provided by CVD, Sputtering, Vaporization or the multilayer structure ( 7 ) is a sol-gel coating.

10 . An electric lamp ( 1 ) according to claim 1 , characterized in that the thickness of the first layer ( 7 ′) is substantially greater than the thickness of the second layer ( 7 ″), wherein the thickness of the multilayer structure ( 7 ) is less than 5 μm.

11 . An electric lamp ( 1 ) according to claim 1 , characterized in that the multilayer structure ( 7 ) comprises four first layers ( 7 ′) of Nb 2 O 5 and four second layers ( 7 ″) of SiO 2 , wherein the thickness of the first layer ( 7 ′) T 1 is in the range of 8 nm≦T 1 ≦25 nm and the thickness of the second layer ( 7 ″) T 2 is in the range of 90 nm≦T 2 ≦210 nm.

12 . An electric lamp ( 1 ) according to claim 1 , characterized in that the multilayer structure ( 7 ) comprises five first layers ( 7 ′) of Si 3 N 4 and five second layers ( 7 ″) of SiO 2 , wherein the thickness of the first layer ( 7 ′) T 1 is in the range of 8 nm≦T 1 ≦25 nm and the thickness of the second layer ( 7 ″) T 2 is in the range of 90 nm≦T 2 ≦200 nm.

13 . A lighting device comprising at least one electric lamp ( 1 ) according to claim 1 .