Since it was invented by Thomas Edison in 1879, the incandescent filament lamp had played the leading part in the illumination field for more than a century. However, in the 1990s, Nichia Corporation made a breakthrough by succeeding in the practical use and mass-production of blue LED for the first time in the world and achieved a paradigm shift in the illumination field by the practical use and mass-production of white LED. This case is about the essential patent for the blue LED.
