LED will lighten up 21st century. But safety poses a challenge               健康面の安全性が課題―21世紀を灯すLED―


 Japan exploded in joy this year when three Japanese scientists were jointly awarded the Nobel Prize for physics. The Royal Swedish Academy of Sciences announced on October 7 that Isamu Akasaki, professor of Meijo University, Hiroshi Amano, professor of Nagoya University, and Shuji Nakamura, professor of University of California were named the 2014 recipients for their contribution to the invention of blue light-emitting diode (LED) and its practical application. Akasaki and Amano were credited with their study of the basic LED technology and Nakamura with the key role he played in turning it into a product.


Energy-saving lamps



The main reason cited for their award was not the invention of blue LED itself. It was in 1993 that Nakamura invented bright blue light beams. The announcement by the academy attributed the award to their “invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources"



LED lamps are more efficient than conventional light devices such as incandescent and fluorescent light bulbs. In other words, they emit as much brightness as the conventional lamps but consume less electric power as they yield less heat energy when turning electric energy into light energy. For these reasons, LED lamps had been expected to become an energy-saving light source in the next generation. Three primary light colors are essential to make white light. However, while red and green LED lights had been invented in early days, only blue LED had not been. The study and invention by the three Japanese scientists won the high acclaim for making both the production and practical application of white LED possible.


Blue light



People today benefit from blue LED not only as lamps but as many other devices seen everywhere in daily life. This is because it has made light emit a variety of colors. One familiar example is electronic message boards at stations, airports and stadiums. Before blue LED was invented, the messages had been displayed only in olive green, red and orange colors. Now, however, blue and white light colors are routinely used and their brightness is increasing. The official website of Nobel Prize says, “Incandescent light bulbs lit the 20th century; the 21st century will be lit by LED lamps.” Indeed LED lights will make people’s life brighter and more comfortable.



Yet, LED is not quite without problem. Blue light essential to produce white light is the shortest in wavelength among visible light rays and is known to have a strong energy. It is called "blue light." It can hardly be absorbed by the eyeball’s cornea and lens. The strong ray, therefore, directly reaches the retina, posing some risks to health such as eyestrain and sleep rhythm disorder. The latter problem can happen particularly when the eye is exposed to the ray just before one goes to the bed.



A more serious problem is dazzling caused by the strong directivity of LED lights. Coupled with the strong energy of blue light, this can damage the retina before one actually realizes it. These problems have been widely taken up in society. In particular, some pundits say that LED lights can badly affect the children’s learning environment.



Energy-saving LED lights are still at their development stage and face a major challenge in addressing those health problems.



(Written by: Naoto Takeda)