Liquid-crystal display

"LCD" redirects here. For other uses, see LCD (disambiguation).
Not to be confused with LED.

Layers of a reflective twisted nematic liquid crystal display:
  1. Polarizing filter film with a vertical axis to polarize light as it enters.
  2. Glass substrate with ITO electrodes. The shapes of these electrodes will determine the shapes that will appear when the LCD is switched ON. Vertical ridges etched on the surface are smooth.
  3. Twisted nematic liquid crystal. It normally rotates the light's polarization by 90°. But if the surrounding electrodes are charged, the light's polarization won't be rotated.
  4. Glass substrate with common electrode film (ITO) with horizontal ridges to line up with the horizontal filter.
  5. Polarizing filter film with a horizontal axis. Light whose polarization was rotated by the liquid crystal will pass through, but light that wasn't rotated will be blocked.
  6. Reflective surface to send light back to viewer. (In a backlit LCD, this layer is replaced or complemented with a light source.)

A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers to display information. Liquid crystals do not emit light directly[1] but instead use a backlight or reflector to produce images in color or monochrome.[2]

LCDs are available to display arbitrary images (as in a general-purpose computer display) or fixed images with low information content, which can be displayed or hidden: preset words, digits, and seven-segment displays (as in a digital clock) are all examples of devices with these displays. They use the same basic technology, except that arbitrary images are made from a matrix of small pixels, while other displays have larger elements.

LCDs can either be normally on (positive) or off (negative), depending on the polarizer arrangement. For example, a character positive LCD with a backlight has black lettering on a background that is the color of the backlight, and a character negative LCD has a black background with the letters being of the same color as the backlight.

LCDs are used in a wide range of applications, including LCD televisions, computer monitors, instrument panels, aircraft cockpit displays, and indoor and outdoor signage. Small LCD screens are common in LCD projectors and portable consumer devices such as digital cameras, watches, calculators, and mobile telephones, including smartphones. LCD screens have replaced heavy, bulky and less energy-efficient cathode-ray tube (CRT) displays in nearly all applications.

LCDs are not subject to screen burn-in like on CRTs. However, LCDs are still susceptible to image persistence.[3]

  1. ^ "Bosch's Smart Visor Tracks the Sun While You Drive". IEEE Spectrum. January 29, 2020.
  2. ^ "Definition of LCD". Merriam-Webster.com. Archived from the original on February 25, 2021. Retrieved February 15, 2015.
  3. ^ "LCD Image Persistence". Fujitsu technical support. Fujitsu. Archived from the original on April 23, 2012. Retrieved December 11, 2011.