Home Computer What is LCD (Liquid Crystal Display)? How it works

What is LCD (Liquid Crystal Display)? How it works


We use things with LCD every day. Because of its advantages over LCDs, LCDs are dominant. They draw thinner, lighter and less power. In 1888, Friedrich Reinitzer discovered the liquid crystal. The Austrian biochemist observed that upon melting of cholesterol benzoate, a cloudy liquid was obtained which hardened as the temperature increased. The liquid eventually crystallized after turning blue on cooling. In 1968 RCA saw experimental LCD.

Electricity, light, liquid crystals

Solids, liquids, gases are the three general states of matter. Solids contain molecules that all point in the same way. Their position against each other remains the same. However, the molecules in the liquid point in all directions. Substances also exist that have a position between liquid and solid. Their molecules show the properties of both liquid and solid molecules. Liquid crystals, therefore, are neither liquid nor solid.

With experiments it is true that liquid crystals are more liquid than solids. Liquid crystals are sensitive to temperature. So it is used to make thermometers.

The liquid crystal receives the effect of electric current. Twisted nematics is a type of liquid crystal. They are definitely untwisted when lightning strikes them. LCDs use twisted nematics to approximate the light path.

LCD type

Liquid crystals are generally classified as thermotropic or lyotropic. Thermotropic liquid crystals respond to changes in temperature. They also, to some extent, respond equally to pressure. Lyotropic liquid crystals are formed in the production of detergents and soaps. The type of solvent they are mixed with determines the reaction of lyotropic liquid crystals. The main differences are in isotropic or nematic thermotropic liquid crystals. When the former are randomly arranged, the latter molecules are clearly patterned in one order.


In the nematic phase, the direction of the atoms depends on the pointer. Anything from a magnetic field to a surface that has a microscopic groove can be a pointer. Liquid crystals in the nematic phase can be further classified by how the molecules relate to each other. Smectic arrangement forms layers of atoms. There is diversity in this phase. In a main type, the molecules in a layer are tilted at an angle from the previous layer. Working or chiral nematic type molecules move from one layer to another. This gives a spiral structure.


FLCs or ferroelectric liquid crystals use liquid crystal materials that contain chiral molecules in a semantic C type configuration. The spiral character of these molecules allows micro switching response time which makes FLC responsive to liquid displays. SSFLCs or surface stable ferroelectric liquid crystals bring controlled pressure through the use of glass plates. This compresses the atomic spiral to speed up the switching.

A simple LCD

The following features make LCD construction possible

  • Light is polarizable;
  • Liquid crystals modify polarized light;
  • Electricity changes the liquid crystal structure;
  • Electricity that conducts transparent matter.

Take two sheets of polarized glass. The polymer forming microscopic groove can remain on the side of the glass without polarizing film on it. The polarized film and grooves face in the same direction. We then add a coating of nematic liquid crystal to a filter. The first layers of atoms are aligned with the approach of the filter. The groove causes this. Next, add another piece of glass with polarizing film to the first sheet at right angles. The twisting atoms are aligned until the topmost layer is at a 90 degree angle to the bottom. This way the top layer matches the polarized glass filters. By striking the first filter, the light becomes polarized.

When light passes through successive layers, the atoms change the plane of light vibration. Is the alignment with the final layer of atoms. If the second polarized glass filter matches the final layer, light passes through.