Chapter 16: Monitors and Displays^391
Electrode The common electrode plane for the assembly. The electrodes in an
LCD are transparent.
Liquid crystal A layer of TN liquid crystal.
Electrode A layer of glass with one or more smaller electrodes attached.
Polarizing film Another layer of polarizing film at a right angle to the other
layer of polarizing film.With no current flowing through the LCD assembly, any light entering the front (or the
to pin Figure 16-12) will pass through to the mirror and be reflected back out of the assembly.
However, when electricity is applied to the electrodes, the liquid crystals between them
untwist and block the light from passing through it. The result is that the areas where
power was applied now show through the front of the LCD as darkened or black areas.
In a simple LCD, like that on a wristwatch, a top layer of electrodes forms all of the
sections used to create the numbers to be displayed. When the electrodes are energized in
a certain pattern, the liquid crystal darkens and the viewer sees it as the time. Figure 16-13
illustrates the pattern or electrodes that would be used to display numbers. As the
electrodesections are energized, that portion of the display turns black and numbers
form, as in Figure 16-14.
LCD Light Sources
Liquid crystals do not produce light, so any light source must come from outside. There
are two types of LCD light sources: reflective and transmissive. A reflective LCD reflects
the light entering through its polarized filters using only the light available from its envi-
ronment. A transmissive LCD, which is the type used in portable computers and
Figure 16-13. The pattern of electrodes used to produce a number on an LCD