New Yellow Phosphor Realizes 10mm Diameter Semispherical White LED (page 2)

Oct 18, 2012
Shinya Saeki, Nikkei Electronics

5 advantages of new white LED

The newly-developed white LED has five major advantages. First, it has a high light flux and is bright. Compared with an existing product using the same purple LED chip and phosphor, its light flux is 25% higher. By applying phosphor particles with a low density, light is prevented from being blocked or scattered.

Second, the brightness of the new white LED is low in the front direction, reducing glare of white LED. Compared with an existing white LED made by combining a blue LED chip and a yellow phosphor (YAG), the light-emitting area and brightness of the new LED are 10 times larger and 1/10, respectively.

Third, the new LED has no directivity because its white light is made by two types of phosphors. And there is no variation in the white light despite its 10mm diameter spherical structure. When a white LED having the same structure was prototyped by using a blue LED chip and yellow phosphor, the straightness of its blue light was so high that the peripheral part turns yellow. Furthermore, when another white LED was made by combining a purple LED chip and red, blue and green phosphors, its blue and green lights were absorbed by the red phosphor, and the peripheral part became red.

Fourth, because of the 10mm diameter spherical structure, the range of its light is wide. When the white LED is used in an LED lighting apparatus, it can brightly light up the entire room, Koito Manufacturing said.

Fifth, because a white LED using the CL_MS phosphor has no directivity, it can have a variety of shapes including not only semispherical shapes but also conical shapes.

Cost advantage

Koito Manufacturing made the CL_MS phosphor with a self-flux method in which part of a crystal's raw material functions as a flux. The process temperature is about 800°C. Because it is an oxide-based phosphor, it does not require high-temperature (2,000°C), high-pressure (10 atm) or controlled atmosphere (oxygen-free condition) treatments. As a result, it is possible to reduce costs, the company said.

The research results were published on the online edition of the British magazine Nature Communications Oct 16, 2012 (local time). They will also be announced at IDW 2012, a trade show on display technologies, which will take place from Dec 4, 2012, in Kyoto.