| 简介 |
PROBLEM TO BE SOLVED : To provide a light emitting device to emit a polychromatic light at high light emitting efficiency.
SOLUTION : When an LED 20 emits a blue light, a part of its energy is absorbed in a fluorescence substance 10, thereby exciting a rare earth element or a transition metal element that is added to a green fluorescent layer 13G and a red fluorescent layer 13R. At the same time, the rare earth element or the transition metal element is newly excited too by an energy that is produced through the recombination of carriers enclosed in the fluorescent layers by the energy. Thus, a green light and a red light are emitted from a green fluorescent layer 13G and a red fluorescent layer 13R. The composition of the fluorescent layer has no electric limit, so that more rare earth or transition metal element can be added in comparison with a case where an electric field is applied to contribute to the improvement in light emitting efficiency. Since a blue light emitted from the LED 20, and a green light and a red light emitted from the fluorescence substance 10, are mixed, a white light produced through three-color mixture that is superior in chromogenic property to two-color mixture can be emitted at a low cost. |
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