How do LCD (Liquid crystal display.. I think) screens work??

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Offline Seany

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I have just got the book "Naked Science by Christopher Smith" and it fascinated me.. That they have made an LCD tv, which is like a scroll... 0.1mm thick!! You just roll it into a little roll.. And carry it!

What exactly is LCD and how does it work?
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Offline daveshorts

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How do LCD (Liquid crystal display.. I think) screens work??
« Reply #1 on: 10/06/2007 00:39:54 »
I don't know if you have come accross polarisation - Light is a wave, it is quite a strange kind of wave in that if it is coming out of this screen, it can be vibrating left to right, or up to down, or any other angle in between.

A polariser is a piece of plastic which will let only one polarisation of light through it. It behaves a bit like a grill for a wave on a string.

If you have two polarisers on top of each other that are aligned in the same direction quite a lot of light can get through, but if you cross them then none can because one cuts out the left right polarisation and the other the up - down

In an LCD you have two pieces of polariser, and a liquid crystal inside. This is a substance that behaves like a liquid in that all the rod shaped molecules can move around but like a crystal in that they are all aligned in the same direction. It is made with a twist so the molecules twist half way around through the display. This rotates the polarisation of the light so that it can get through. If you apply a voltage between the two sides it will align the molecules between the two plates, they stop twisting and the light can't get through any more. so using electricity you can switch light on and off. Make a couple of million of them and turn them on and off and you have a monitor. Make 20-30 and you have a watch display.