CCFLs

CCFLs, or cold-cathode fluorescent lamps, are a type of gas-discharge lamp used primarily for backlighting liquid-crystal displays such as computer monitors, televisions, and laptop screens. They consist of glass tubes filled with a noble gas (commonly argon) and a small amount of mercury, with phosphor-coated inner walls. When an alternating high voltage is applied by an external inverter and ballast, the gas ionizes and emits ultraviolet light, which excites the phosphor to produce visible light. The cold cathode designation refers to the absence of a heated filament at the cathode, unlike traditional fluorescent tubes.

A typical CCFL backlight is driven by a dedicated inverter that supplies high voltage AC to start and sustain the discharge. CCFL tubes come in several sizes and are wired in series within an LCD module. They require ballast to regulate current and a stable power supply. In the display era before LEDs, CCFLs provided relatively uniform brightness and good color rendering over large panels, but they are less energy efficient than modern LED backlights and require more components.

Disadvantages include sensitivity to aging, which causes lumen depreciation and color shifts; the need for hazardous mercury and high-voltage drivers; and constraints on thickness and form factor. Lifetimes are on the order of 20,000 to 60,000 hours, depending on usage and cooling. With the rise of LED backlighting in the 2010s, CCFLs have become largely obsolete in new consumer devices, though they may still appear in older equipment and some signage applications.