LCDs (Liquid Crystal Displays) are flat electronic devices commonly used as screens in televisions, computers, smartphones, and display signs. They are designed to produce both still and movable images.

The construction of an LCD screen involves several key components. A thin layer of liquid crystal material is sandwiched between two transparent electrodes on glass substrates. Polarizers are positioned on each side of the liquid crystal layer. Polarizers act as optical filters, allowing light waves of a specific polarization to pass through while blocking others.

Since LCDs do not emit light themselves, a backlight is placed behind the screen to illuminate the display, especially in dark environments. The backlight can be sourced from either Light Emitting Diodes (LED) or Cold Cathode Fluorescent Lamps (CCFL). LED backlights are more popular due to their efficiency and compact size.

To achieve color display, a layer of color filter can be incorporated into the LCD cell. This color filter consists of red, green, and blue (RGB) colors, enabling the LCD to display a wide range of colors. Additionally, a touch panel can be added in front of the LCD screen for interactive functionality.

The discovery of liquid crystals dates back to the 1800s, and over time, they have been modified and improved to suit various applications. Liquid crystals themselves do not emit light but rely on a fluorescent backlight to illuminate the display. This combination of liquid crystals and a backlight has made LCD technology suitable for diverse devices and purposes.