Akai LCT-4216 Service Manual page 43

LCD basic display theory.
When an electrical field is applied to the LC planes, the LC molecules re-align
themselves so that they are parallel to the electrical field. This electrical process
is known as twisted nematic field effect or TNFE. In this alignment, polarized
light is not twisted as it passes through the LC material (see Diagram 3A and
3B). If the front polarizer is oriented perpendicular to the rear polarizer, light will
pass through the energized display but will be blocked by the rear polarizer. An
LCD in this form is acting as a light shutter.
Displays with variable characters are created by selectively etching away the
conductive surface that was originally deposited on the glass. Etched areas
become the display's background; unetched areas become the display's
characters.
Diagram 3A. The "off" state of a TN LCD-the LC molecules form a twist and therefore
cause polarized light to twist as it passes through.
Diagram 3B. The "on" state-the electrical field re-aligns the LC molecules so they do
not twist the polarized light.