In the1970s, the earliest homogeneous red, yellow and green LEDs with low luminous efficiency GaP and GaAsP have been applied to indicator lamps, digital and text displays. Since then, LED has entered a variety of application fields, including aerospace, aircraft, automobiles, industrial applications, communications, consumer products and so on. Covering all sectors of the national economy and thousands of households. By 1996, the global sales of LED have reached several billion dollars. Although LED has been limited by color and luminous efficiency for many years, GaP and GaAsP LED have many advantages, such as long life, high reliability, low working current and compatibility with TTL and CMOS digital circuits, so they have been ignored by users. In the 1990s, high brightness and full color have been the frontier topics of LED materials and device technology research. Ultra-high brightness (UHB) refers to the LED whose luminous intensity reaches or exceeds 100mcd, also known as Candeira LED. The development of high brightness A 1GaInP and InGaN LED has made rapid progress, and now it has reached the performance level that conventional materials GaA 1As, GaAsP and GaP can't. 199 1 In 2001, Toshiba Corporation of Japan and Hewlett-Packard Company of the United States developed InGaA 1P 620nm orange ultra-high brightness LED, and 1992 InGaA 1p590nm yellow ultra-high brightness LED was put into practical use. In the same year, Toshiba developed InGaA 1P 573nm yellow-green ultra-high brightness LED with normal light intensity of 2cd. 1994 InGaN 450nm blue (green) ultra-high brightness LED was developed by Niya Company of Japan. At this point, all the red, green, blue, orange and yellow LEDs required for color display have reached the Candeira-class luminous intensity, achieving ultra-high brightness and full color, making the outdoor full-color display of light-emitting tubes a reality. The development of LED in China began in 1970s, and the industry appeared in 1980s. There are about 100 enterprises in China, 95% of which are engaged in back packaging production, and almost all the required molds are imported from abroad. Through several "five-year plans" of technical transformation, technical research, the introduction of foreign advanced equipment and some key technologies, China's LED production technology has taken a step forward.