LIQUID CRYSTAL – the material that brought revolution

Liquid crystal devices (LCD) have brought a revolutionary change in electronic display devices; “a place for LCD in all pockets.” The story of this magic liquid ‘liquid crystal’ started in early 1888 when Friedrich Reinitzer discovered a strange phenomenon in a material known as cholesteryl benzoate. This compound had two melting points and it changed to a cloudy liquid at 145 Degree Celsius and then to a clear liquid at 179 Degree Celsius. This cloudy liquid acted as the liquid crystal phase.

As the terminology ‘liquid crystal’ indicates, it has the properties of both solid and liquid. Just imagine a solid that flows! Liquid crystals can flow like a liquid and has an orderly arrangement as that of a crystal. Above 80% of the world’s population spend most of their time in the company of this magic liquid. The liquid crystals are of two types.They are thermotropic liquid crystal and lyotropic liquid crystal. Mostly the liquid crystal displays work with thermotropic liquid crystal. The thermotropics are sensitive to temperature, and the liquid crystal phase will be exhibited only through a certain range of temperature. Liquid crystal molecules are rod- shaped, it is possible to arrange them in lines with the help of an alignment layer, which is usually a polymer. Liquid crystal molecules are dipolar in nature (has a positive and a negative part). When an electric field is applied, the liquid crystal molecules have the ability to align in the direction of the field applied. This property of liquid crystal is being used in display industries.

Not only in mobiles, television and laptop, it is also used in switchable window application. These smart glasses can modulate light and can be used as partition walls, car windows, bathroom doors etc. These smart glasses are made by embedding liquid crystal molecule inside a polymer, which will be opaque. When an electric field is applied, the liquid crystal molecule aligns in the direction of the field and allows the light to pass through, making it transparent. Do you know the soap bubble we play with is also a liquid crystal? They are the lyotropic liquid crystals. They work only at a particular concentration. That’s why when we try to make bubble play at home it becomes a failure. Only the bubble man knows the correct mixing proportion. Thus the liquid crystal has a travelogue along with 7 segment display, LCD display, LED display, smart glass etc.