LCDdisplays

LCD displays are flat-panel screens that use liquid crystals sandwiched between polarizing layers to control light. The crystals do not emit light themselves; they modulate light from a backlight to form images. By applying electric fields across the liquid crystal layer, the orientation of the crystals changes the polarization of light, which is then filtered to create color and brightness at each pixel.

A modern LCD typically uses an active-matrix backplane with thin-film transistors (TFTs), one transistor per pixel, enabling rapid switching and higher resolution. Light from a separate backlight passes through the liquid crystal layer and color filters before reaching the viewer. The majority of backlights today are white LEDs, though older designs used cold cathode fluorescent lamps (CCFL). The result is a bright, thin panel suitable for integration into monitors, televisions, and mobile devices.

Panel technologies include twisted nematic (TN), vertical alignment (VA), and in-plane switching (IPS). TN panels are fast and inexpensive but offer limited viewing angles and color accuracy. IPS panels provide broader viewing angles and more accurate colors, while VA panels offer higher contrast ratios. The choice affects color fidelity, response time, and viewing experience.

Key characteristics include resolution, color gamut, contrast, brightness, response time, and viewing angle. LCDs are generally more energy-efficient than cathode-ray tubes and avoid burn-in, but require backlighting and can exhibit backlight bleed or color shift at extreme angles. Compared with self-emitting technologies like OLED, LCDs remain a cost-effective option for large displays and high resolutions.

Applications span computer monitors, televisions, mobile devices, and instrumentation, with ongoing improvements in contrast, color reproduction, and power efficiency.