Most industrial TFTs today have an edge LED backlight. The backlight illuminates the entire surface of the TFT, so if we reduce the brightness of the backlight, it affects the entire TFT surface at the same time.
A VA display (Vertical Aligement) consists of two linear polarizing filters rotated 90° to each other and some other stuff. Between the filters are two transparent electrodes (a pixel electrode and a common counter electrode). These usually consist of a glass plate with an ITO layer (indium tin oxide) applied. On top of this is the orientation layer. The elongated liquid crystals are embedded in between.