Twisted Nematic Display:

Working:

    The top glass plate is rotated through 90o and hence the molecules are also twisted through 90o.

Without field,

    The light is passed through the polarizer, then through the molecules and finally through the analyzer. Here the field view appears bright, because the plane of polarization is rotated through 90o by the crossed position of polarizer and analyzer and another 90o by twisted molecules.

With field:

Now the field is applied, the twisted molecules come to normal position and this only 90o rotation of plane of polarization between polarizer and analyzer. Therefore, there is no transmission of light and the display appears black and white background.

    When the electric field is switched off, once again the molecules return back to their twisted position and so display is bright and erased.