LCDBacklights

LCD backlights are light sources that illuminate the liquid-crystal layer of an LCD display. Because the liquid crystals themselves do not emit light, a separate illumination system is required to produce visible images.

Historically, backlights used CCFLs (cold cathode fluorescent lamps). Since the 2000s, LED backlights have largely displaced CCFLs due to higher efficiency, longer life, and better color control. Backlights are typically edge-lit LED or full-array (direct-lit) LED, with full-array designs often supporting local dimming for improved contrast.

Edge-lit configurations place LEDs along the panel edges, with light guided across the panel by a light guide plate and diffusers. Full-array backlights place LEDs behind the LCD area, sometimes enabling local dimming in zones to adjust brightness independently and improve black levels.

LED backlights offer higher energy efficiency, thinner panel profiles, wider color gamuts, and better color control. They also avoid the mercury used in CCFLs. Local dimming and greater peak brightness can enhance contrast, but edge-lit systems can suffer from non-uniformity or blooming if not well designed.

Common concerns include flicker from dimming methods, aging that can shift brightness or color temperature, and uniformity issues such as backlight bleed. Lifespan for LED backlights is typically tens of thousands of hours, with brightness commonly specified in nits.

Applications include televisions, computer monitors, laptops, and many flat-panel displays. The choice of backlight architecture influences display thickness, energy use, and image quality.