Tri-color white light LED lamp

Abstract

The invention relates to a tri-color lamp for generating white light comprising a phosphor composition comprising a phosphor of general formula (Ba1-x-y-z-SrxCay)2SiO4:Euz, wherein 0≦x≦1, 0≦y≦1 and 0<z<1. The phosphor composition may also comprise a red phosphor. The two phosphors can absorb radiation emitted by a light emitting diode, particularly a blue LED. This arrangement provides a mixing of three light sources—light emitted from the two phosphors and unabsorbed light from the LED. The invention also relates to an alternative to a green LED comprising a single green phosphor of general formula (Ba1-x-y-z-SrxCay)2SiO4:Euz, wherein 0≦x≦0 1, 0≦y≦1 and 0<z<1, that absorbs radiation from a blue LED. A resulting device provides green light of high absorption efficiency and high luminous equivalent values.

Description

FIELD OF INVENTION[0001]The present invention relates to a tri-color lamp. The lamp comprises a phosphor composition and a light emitting diode for an excitation energy source. In particular, the lamp employs a blue LED and a mixture of red and green phosphors for the production of white light.BACKGROUND OF THE INVENTION[0002]There is an ongoing need to generate new phosphor compositions to improve efficiency and color quality in luminescent devices, particularly in the production of white light. Phosphors are luminescent materials that can absorb an excitation energy (usually radiation energy) and store this energy for a period of time. The stored energy is then emitted as radiation of a different energy than the initial excitation energy. For example, “down-conversion” refers to a situation where the emitted radiation has less quantum energy than the initial excitation radiation. Thus, the energy wavelength effectively increases, and this increase is termed a “Stokes shift”. “Up-c...

AI Technical Summary

Benefits of technology

[0014]Such a device shows high efficiency, particularly at chip temperature above 150° C., because of the high quenching temperature of such a phosphor.

[0015]Especially, when the phosphor is comprised in a thin film layer the high quenching temperature of the phosphor is of advantage.

Problems solved by technology

Inefficient conversion results when at least a portion of the energy is consumed by non-radiative processes.

Previous tri-color lamps involving a mercury plasma excitation source, however, suffer many disadvantages including: (1) a need for high voltages which can result in gaseous discharge with energetic ions; (2) emission of high energy UV quanta; and (3) correspondingly low lifetimes. Thus, there is an ongoing need for devices that overcome these deficiencies.

The thermal quenching at higher temperatures reduces the LED efficiency, in particular at high chip temperatures.

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