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The biggest difference between liquid crystals and plasmas is that they must rely on passive light sources, and plasma televisions are active light-emitting display devices. Currently, mainstream LCD backlight technologies on the market include LED (light emitting diode) and CCFL (cold cathode fluorescent lamp). The LCD is the LCD.. The LCD is the abbreviation of Liquid Crystal Display. The LCD is constructed by placing liquid crystals in two parallel glasses. There are many vertical and horizontal small wires between the two glasses. Controls the rod-like crystal molecules to change direction and refract light to produce images.
The liquid crystal itself does not emit light and can only produce a color change, requiring the backlight source to see the displayed content. Traditional notebook screens use cold cathode fluorescent tubes (CCFLs) as backlights, and LED backlights use LEDs, which is the difference between the two. The white LED is a point light source, and the CCFL tube is a strip light source. Small white LEDs use DC power supplies, which can be used in series and in multiple applications. However, for a few watts or more, appropriate drive circuits must be considered to increase efficiency. CCFL tube must have "high pressure plate" supporting use.
There are several LCD backlight methods, including LED (Light Emitting Diode) and CCFL (Cold Cathode Fluorescent Lamp) or CCFT (Cold Cathode Fluorescent Tube).
The CCFL (Cold Cathode Fluorescent Lamp) backlight is currently the most important backlight product for LCD TVs. Its working principle is that when high voltage is applied to both ends of the lamp, a small number of electrons in the lamp will impact the electrode at high speed to generate secondary electron emission and begin to discharge. After the mercury or inert gas in the tube is impacted by electrons, it excites radiation at 253.7 nm. The UV light generated by the UV light excites the phosphor coated on the inner wall of the tube to generate visible light. CCFL lamp life is generally defined as: In the ambient temperature of 25 °C, with the rated current to drive the lamp, the brightness is reduced to the initial brightness of 50% of the working time length of the lamp life. At present, the nominal life of LCD TV backlight can reach 60000 hours. The CCFL (Cold Cathode Fluorescent Lamp) backlight is characterized by low cost, but the color performance is inferior to the LED backlight.
LED backlight uses light-emitting diodes as a backlight source, which is the most promising alternative to traditional cold cathode fluorescent tubes. Light-emitting diodes are made of several layers of thin, doped semiconductor materials, one layer with an excessive amount of electrons, and the other layer lacking electrons to form positively charged holes. Current passes through during operation, and electrons and holes combine with each other. The energy is released in the form of light radiation. By using different semiconductor materials, light emitting diodes having different light emitting characteristics can be obtained. Light-emitting diodes that have been put into commercial use can provide colors such as red, green, blue, cyan, orange, amber, and white. The main use of mobile phone is white LED backlight, and the LED backlight light source used in LCD TV can be white, it can also be red, green, blue three primary colors, in the high-end products can also be applied multi-color LED backlight to further improve color Expressive, such as six primary color LED backlight light source. The advantage of using LED backlight is that the thickness is thinner, about 5 centimeters, and the color gamut is also very wide. It can reach 105% of the NTSC color gamut. The black luminous flux can be reduced to 0.05 lumens, and the contrast ratio of the LCD TV can reach 10000:1. . At the same time, the LED backlight source also has a lifetime of 100,000 hours. At present, the problems that restrict the development of LED backlights are mainly cost. Because the price is much higher than that of the cold fluorescent lamp light sources, LED backlight light sources can only appear in high-end LCD TVs abroad.