LCD modes
The various LCD modes for negative and positive cells in STN and TN modes are shown here:

Negative modes are only suitable for use in either transflective or transmissive modes.

Silver-mode STN uses an optical film to give a more neutral background than green-mode STN.

Polarizers
Basic TN and STN displays use a reflective rear polarizer which gives good contrast when there is sufficient ambient light. Light from the front passes through the display and is then reflected back by the mirror attached to the rear polarizer.

For low-light viewing, a transmissive or transflective rear polarizer must be specified.

Transmissive displays depend on backlighting to be visible. Transflective is a compromise - light from a backlight will allow the display to be read in the dark whilst allowing the display to operate in the reflective mode when there is enough ambient light. This means the backlight can be switched off to conserve power when not needed.

Backlights can be in the form of an array of LEDs, CFL tubes, incandescent lamps or thin EL panels.

We can advise on the suitability of each type in your specific application.