LCD

LCD stands for liquid crystal display, a flat-panel display technology that uses liquid crystal molecules whose orientation controls light transmission. An LCD panel typically consists of a layer of liquid crystal material sandwiched between two polarizers and a backlight. In most consumer LCDs the display pixels are addressed by a thin-film transistor (TFT) array, making it an active-matrix display. Color at each pixel is produced by red, green, and blue subpixels with color filters.

In operation, applying a voltage reorients the liquid crystal molecules, changing how polarized light passes through the second polarizer. Without voltage, the LC molecules twist the plane of polarization, allowing light to pass; with voltage, the twist is reduced, reducing transmission. The result is a pixel that can be turned on or off, or set to intermediate brightness, forming an image. The backlight provides illumination, commonly a white LED array; older displays used cold cathode fluorescent lamps (CCFLs).

LCDs are manufactured as various formats: twisted-nematic (TN), which is fast but with limited viewing angles; in-plane switching (IPS) and vertical alignment (VA) variants improve color accuracy and viewing angles; terms like TFT-LCD refer to active-matrix implementations. Additional variants include transflective LCDs that reflect ambient light to improve readability in bright environments and low-power modes.

Advantages include low power consumption, compact form, and long service life; limitations include moderate contrast, viewing-angle dependence for some types, slower response times for moving images, and the need for a backlight. LCDs are widely used in televisions, computer monitors, laptops, mobile devices, calculators, and instrumentation.