How LCD ( liquid crystal display ) works

LCDs are most common part of our day to day life. we can see it in computer, laptops, digital clocks, mobiles and many other electronics devices. LCDs are common because they offer some real advantages over other display technologies. They are thinner and lighter and draw much less power than cathode ray tubes (CRTs)


But why it is called liquid crystal display? from name 'liquid crystal', We think of a crystal as a solid material like quartz, usually as hard as rock, and a liquid is obviously different.

How could any material combine the two stats? As we know there are three common stats of matter: solid, liquid and gaseous. Solids act the way they do because their molecules always maintain their orientation and stay in the same position with respect to one another. The molecules in liquids are just the opposite: They can change their orientation and move anywhere in the liquid.

But there are some substance that have some special properties that their molecules tend to maintain their orientation, like the molecules in a solid, but also move around to different positions, like the molecules in a liquid.This means that liquid crystals are neither a solid nor a liquid. by to a little heat it change its state from solid to liquid.

There are several categories of liquid crystal substance like in solid and liquids depends upon temperature and particular nature of substance. Liquid crystal have several distinct Phases and one of them is called "nematic phase". Which make possible LCDs.

One of feature of liquid crystals that they are affected by electric current . One of liquid crystal of nematic phase called twisted nematics (TN) is naturally twisted. Applying an electric current to these liquid crystals will untwist them to varying degrees, depending on the current's voltage. LCDs use these liquid crystals
because they react predictably to electric current in such a way as to control light passage.

A simple LCD is shown in fig. and working can also understand by given image. LCD use two glass filter but on perpendicular angle of plane of polarization. and between them liquid crystal is applied.

working of LCD

Two transparent electrode is attached on both side of liquid crystal in this case shape of 8. Electrode is used to apply voltage to make liquid crystal untwisted. when voltage is applied liquid crystal they get untwisted and the plane of polarization of light is unaffected, when light reached to second filter, plane of polarization are perpendicular and light not passes and like a dark number on LCD.

But when voltage is not applied they remain twisted and change the plane of polarization which same as second filter and that area are looking lighten then other..

it is simply one but there are many types of LCDs which works a little different.
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