A liquid crystal display (LCD) consists basically of liquid crystals which are able to influence the polarization direction of light.

The basic element of this display technique is the so-called Schadt-Helfrich-cell. The liquid crystals show characteristics of solids as well as of liquids. In addition, they are arranged spirally under a twisted angle of 90 degrees. This is called twisted nematic (TN).

Before entering into the liquid crystals, the light is polarized by the polarizer. When the display is turned off, the polarization direction of the incoming light changed through the transposition of the crystals (TN!); the display looks translucent/black (normally white/black mode).

If an electric voltage is now impressed on the electrodes, the transposition of the crystals is suspended. That way, the polarization direction of the light is no longer changed – the light cannot pass through the second polarizer (which is arranged opposite the first). Therefore, the light is reflected and we see a picture.

The electronically controlled pixels, which each consist of 3 sub-pixels, are responsible for the different colors. The sub-pixels correspond to the colors red, green, blue, out of which all needed colors can be mixed.

With modern displays, the transposition degree of the crystals is increased which enables a higher contrast.

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