Electric lamp and interference film

Optical interference coatings applied to electric lamps for transmitting, on average, 90% of the visible light radiation in the wavelength range from 400 to 760 nm and for reflecting infrared radiation, comprise three spectrally adjacent multilayer stacks of alternately a first layer (L) of a material having a low refractive index and a second layer (H) of a material having a high refractive index. According to the invention, the reflectance of the interference film amounts, on average, to at least 75% in the wavelength range from 800 to 2200 nm, whereas the transmittance amounts, on average, to at least 90% in the wavelength range from 400 to 760 nm. Preferably, the reflectance of the interference coating amounts, on average, to at least 85% in the wavelength range from 800 to 2500 nm.; The first stack S1 (design wavelength lambda (S1) = 2100 nm) of the interference film as shown in Fig. 2 is based on a design comprising eleven layers of alternately a high and a low refractive index material