|LED display panels development history and application fields|
As early as 1923, Lossen.o.w had light emission in the P-N junction with impurities in the study of semiconductor SIC, and the researched light-emitting diode (LED: Light Emitting Diode) has not received much attention. With the rapid development of the electronics industry, especially in the 1960s, display technology has been developed more rapidly, people have researched PDP laser display plasma display panel, LCD liquid crystal display, light-emitting diode (LED), electrochromic display ECD, electrophoresis Display a variety of new display technologies such as EPID. As semiconductor fabrication and processing processes have matured and improved, LEDs have become increasingly dominant in solid-state displays.
LEDs are widely valued and rapidly developed because of their many advantages. For example, high brightness, low operating voltage, low power consumption, easy integration, simple driving, long life, impact resistance and stable performance, etc., the market prospect is extremely broad. At present, LED has developed to high brightness, high weather resistance and luminous density, uniformity of illumination, and full color.
In the early 1980s, with the development of computers, the CGA display method came out. It has four colors of 320*200 resolution. In just 10 years, the display mode has experienced CGA, EGA, SEGA, VGA, SVGA. To the ultra-high resolution development, the display accuracy has been improved from 320*200 to 1600*1250, from four colors to 32-bit true color, and the scanning frequency has been developed from 15.7K to 150K. The working principle of the display is that the signal sent by the receiving host is reduced to light. As the development of people needs a large-screen device, a display device similar to a projector appears. However, due to its own brightness, it cannot be used in a high-brightness environment, so an LED display (screen) appears, and the LED display screen has the characteristics of large viewing angle, high brightness, and bright colors. With the development of technology, LED display applications have been widely used, such as in stadiums, highways, large shopping malls, outdoor advertising and other places are applied to LED display.
According to the survey, two-thirds of the information people receive is obtained through the eyes. Display technology is also used in industrial, military, medical units, public security systems, and even aerospace industries, and plays an important role in the national economy, social life and military fields. Display technology has become an indispensable part of modern human society. technology. In 1970, the earliest GaP, GaAsP homogenous red, yellow, and green low-efficiency LEDs have begun to be used for indicator, digital, and text displays. From this LED, it has entered a variety of application fields, including aerospace, aircraft, automotive, industrial applications, communications, consumer products, etc., covering all sectors of the national economy and thousands of households. As of 1996, LED sales worldwide have reached billions of dollars. Although the LED industry has been limited by color and luminous efficiency for many years, many advantages such as long life and high reliability of GaP and GaAsP LEDs, low operating current, compatibility with TTL and CMOS digital circuits, etc. have been deeply used. The young man. Especially in the last ten years, high brightness and full colorization have always been the frontier topics in the research of LED materials and device technology.
Ultra High Brightness (UHB) is an LED with a luminous intensity of 100 mcd or more, also known as a Candela (cd) LED. The development of high-brightness A1GaInP and InGaN LEDs is progressing rapidly, and has reached the level of performance that conventional materials such as GaA1As, GaAsP, and GaP cannot achieve. In 1991, Toshiba Corporation of Japan and HP Corporation of the United States developed InGaA1P 620nm orange ultra-high brightness LED. In 1992, InGaA1p590nm yellow ultra-high brightness LED was put into practical use. In the same year, Toshiba developed InGaA1P 573nm yellow-green ultra-high brightness LED with a normal light intensity of 2cd. In 1994, Japan Nichia Corporation developed InGaN 450nm blue (green) color ultra-high brightness LED. At this point, the three primary colors of red, green, blue, and orange and yellow LEDs required for color display have reached the candela-level luminous intensity, achieving ultra-high brightness and full color, and making the outdoor full color of the luminous tube. The display becomes a reality.
China's development of LED started in the 1970s, and the industry appeared in the 1980s. There are more than 100 enterprises in the country, and 95% of the manufacturers are engaged in post-package production. The required dies are almost all imported from abroad. Through several "five-year plan" technical transformation, technical research, the introduction of foreign advanced equipment and some key technologies, China's LED production technology has taken a step forward.
Before the 1990s, the growth of LED displays was formed. On the one hand, due to the limitation of LED material devices, the application field of LED display screens has not been widely developed. On the other hand, display screen control technology is basically a communication control method, which objectively affects the display effect. The LED display in this period is widely used in foreign countries. There are few domestic products. The products are mainly red and green. The control method is communication control. The gray level is single point and 4 level gray, and the cost of the product is relatively high.
In 1990-1995, this stage was a period of rapid development of LED displays. In the 1990s, the global information industry grew at a high speed, and information technology continued to break through in various fields. LED displays have also seen new results in LED materials and control technologies. Blue LED chip successfully developed, full-color LED display enters the market; technology development in the field of electronic computers and microelectronics, video control technology appears in the field of display control technology, display gray level achieves 16 gray levels and 64 levels Grayscale graying, the dynamic display effect of the display is greatly improved. At this stage, the development of LED display screens in China is very fast. From the initial enterprises, the annual output value of tens of millions of yuan to dozens of enterprises, the annual output value is several hundred million yuan. The product application fields involve financial securities, sports and airports. , railways, stations, road traffic, commercial advertising, postal and telecommunications and many other fields, especially the development of the securities stock industry in 1993 has led to a substantial increase in the LED display market. The mainstream product situation of LED display in the field of flat panel display has basically taken shape, and the LED display industry has become an emerging high-tech industry.
Since 1995, the development of LED display has entered a period of overall improvement and improvement of the industrial structure. At the same time, the internal competition of the LED display industry has intensified, and many small and medium-sized enterprises have been formed. The prices of products have fallen sharply, and the application fields are broader. The products have experienced a series of new problems in terms of quality and standardization. The relevant departments have developed LED displays. Attention has been paid to and proper regulation and guidance have been carried out, and work in this area is gradually deepening. After several years of development, China's LED display industry has basically formed a number of key enterprises with a certain scale. According to incomplete statistics, by the end of 1998, there were more than 20 enterprises with annual sales of more than 10 million yuan, and their total sales amounted to about 600 million yuan, accounting for more than 85% of the total market. There are more than 100 enterprises engaged in LED display in the country, employing nearly 6,000 people. The annual sales of the industry is nearly 800 million yuan. The growth rate in 1996 and 1997 has remained at around 40%. In 1998, it fell slightly. In the domestic market, the domestic LED display market share is nearly 100%, and there are basically no similar products in foreign countries. The 43rd World Table Tennis Championships main venue Tianjin Sports Center, Beijing-Kowloon Railway, Beijing West Railway Station, Capital Airport, Pudong Airport And so on, all of them won the bid by domestic representative enterprises. The technical level is relatively ahead.
The application of LED displays involves many areas of social economy, including:
Securities trading, financial information display. The LED display board in this field accounts for more than 50% of the domestic LED display demand in previous years, and is still the main demand industry for LED display. LED displays are widely used by the Shanghai Stock Exchange, the Shenzhen Stock Exchange and tens of thousands of securities and financial institutions throughout the country.
Airport flight dynamic information display. The requirements for information display in civil aviation airport construction are very clear. LED display is the preferred product of Flight Information Display System (FIDS), Capital Airport, Shanghai Pudong International Airport, Haikou Meilan Airport, Zhuhai Airport, Xiamen Gaoqi Airport, Shenzhen Huangtian Airport, Guangzhou Baiyun Airport and dozens of new and renovated airports in China have selected domestic LED display products.
Port and station passenger guidance information display. The information system and broadcasting system with the LED display as the main body, the train arrival and disclosure system, and the ticket information system together constitute the automation system of the passenger transportation hub, Beijing Railway Station, Beijing West Railway Station, Nanchang Station, Dalian Port and other important domestic railway stations and ports. All products and systems provided by domestic manufacturers are installed.
The stadium information is displayed. The LED display sign has replaced the traditional light bulb and CRT display. The Tianjin Sports Center, the main venue of the 43rd World Table Tennis Championships, adopted the domestic color video LED display for the first time, which was widely praised. Shanghai Sports Center, Dalian Stadium and many other domestic important The stadium has adopted LED display screens as the main means of information display.
Road traffic information display. The rise of Intelligent Transportation Systems (ITS), in the fields of urban transportation, highways, etc., LED display screens as variable information boards, speed limit signs, etc., instead of foreign similar products, have been widely adopted.
The dispatching command center information is displayed. Power dispatching, vehicle dynamic tracking, vehicle dispatch management, etc. are also gradually adopting high-density LED displays.
Business promotion and information display in service areas such as postal, telecommunications, shopping malls and other shopping centers. Domestically produced LED displays play a role in information display in service areas throughout the country.
Advertising media new products. In addition to a single large indoor and outdoor display as advertising media, cluster LED display advertising systems have appeared in some cities in China; the train LED display advertising system has also been adopted and promoted in dozens of passenger trains nationwide.