The term 'liquid crystals' refers to the two crucial characteristics of these materials. They are liquids (organic) and at the same time, they have qualities typical of crystals. That is why a thin layer of liquid crystal in a display reacts when voltage is applied. By varying the voltage, you can control the way each pixel of the display looks like, which means you can create images.
The design principle of the display is illustrated in the figure below. Liquid crystal is placed between transparent diodes whose surfaces twist the optical axis by 90°. The thing is placed between crossed polarizers and illuminated. The incoming light is polarized by the first polarizer and enters the liquid crystal; the polarization plane of the outgoing light is rotated by 90°, and thus it passes through the analyzer and the display pixel is bright.
Application of voltage causes crystal deformation, as a result of which a single axis structure is formed whose optical axis is parallel to the direction of light which does not rotate the plane of polarization. Then, the light exiting the liquid crystal is absorbed by the analyzer. The pixel turns dark. After the voltage is switched off, intermolecular forces cause the molecules to return to the original configuration of a 'twisted nematic' and brighten the pixel. The three pixels presented in the figure have color filters. They constitute a single element of the image. In the situation shown in the figure, the red pixel will be bright, the green pixel will be slightly darker, whereas the blue one will remain dark. The element of the image will be of the resultant color.
There are tens of thousands of liquid-crystal substances and still new ones are produced. Their properties are studied all around the world. This can be done by way of experiments and measurements. Also, phenomena related to them can be studied with the aid of computations. And the latter is exactly what scientists of the Institute of Physics in Lodz University of Technology do. Computations allow them to determine e.g. what qualities a liquid crystal should have for the display in which it will be used to meet particular performance requirements or to find out how a device with a selected liquid-crystal material will perform.
