Liquid crystal displays (LCDs) are mainly divided into LCD backlight types, with LED and CCFL being the two primary backlight technologies.
CCFL backlights are currently the mainstream backlight products for LCD TVs. Their working principle involves a small number of electrons within the lamp tube striking the electrodes at high speed under high voltage, generating secondary electron emission and initiating a discharge. The mercury or inert gas inside the tube is then excited by electron collisions, emitting 253.7nm ultraviolet light. This ultraviolet light excites the phosphor coated on the inner wall of the tube to produce visible light. The lifespan of a CCFL lamp is typically defined as the time it takes for its brightness to decrease to 50% of its initial brightness when driven at rated current at 25°C; its nominal lifespan is up to 60,000 hours. However, the color performance of CCFL backlights is inferior to that of LED backlights.
LED backlights use light-emitting diodes (LEDs) as the backlight source, offering advantages such as low cost and strong color performance. LEDs are made of doped semiconductor materials; during operation, electrons and holes combine, releasing excess energy as light radiation. By using different semiconductor materials, light-emitting diodes (LEDs) with different light-emitting characteristics can be obtained. Commercially available LEDs can provide colors such as red, green, blue, cyan, orange, amber, and white. In LCD TVs, LED backlight sources can be white or based on the three primary colors of red, green, and blue. In high-end products, multi-color LED backlights further enhance color performance, such as six-primary-color LED backlight sources.
The advantages of using LED backlights include thinner profiles (approximately 5 cm), a wider color gamut (105% NTSC), and a black luminous flux reduced to 0.05 lumens, enabling LCD TVs to achieve a contrast ratio of 10000:1. Furthermore, LED backlight sources have a lifespan of up to 100,000 hours.
Currently, the main challenge facing the development of LED backlights is cost. Due to their higher price compared to traditional cold cathode fluorescent lamps (CCFLs), LED backlight sources are currently only used in high-end LCD TVs.
