How Liquid Crystals In LCD Displays Works

[Carl Fredrik Ahl]

Hi,

I know that liquid crystals align with the electric field and therefore are able to either let the backlight through or not depending on if the there are electricity or not. What I wonder is why do the liquid crystals align with the electric field and why does the protons of the backlight wants to go in the direction of the liquid crystals?

Source: 



 

[Strange]

23 minutes ago, Carl Fredrik Ahl said:

why do the liquid crystals align with the electric field

Because they have an uneven distribution of charges across the molecule (or part of the molecule) - in other words a dipole. In some cases, I think the presence of the electric field can creates the dipole (by moving charges from one part of the molecule to another). 

Then the electric field causes the molecule to change its alignment, or in some case its rotation.

25 minutes ago, Carl Fredrik Ahl said:

why does the protons of the backlight wants to go in the direction of the liquid crystals?

(Photon, not proton.)

The photons will go in all directions from the source. Some will go through the LCD layer. 

The LCD has a polarised filter one each side. Normally light passes though because both filters have the same alignment. Apply a voltage and the LCD twists the polarisation of the light (because the photons interact with the asymmetric charges in the molecules) so it no longer passes through the second filter.

 

[Carl Fredrik Ahl]

18 hours ago, Strange said:

(Photon, not proton.)

Spelling mistake or auto corect, sorry. I ment photons.

 

18 hours ago, Strange said:

Apply a voltage and the LCD twists the polarisation of the light (because the photons interact with the asymmetric charges in the molecules) so it no longer passes through the second filter.

Yeah I know this but I wonder why it twists. What makes it twist explained in atomic level? Thx for the answer btw. I totally forgot that the electric field attract or repell the charges in atoms