Golden View Display wants you to make an informed choice among our LCD products. The tech center provides you with most of the information you will need to understand liquid crystal displays.
In this section, we will explain everything ranging from the
properties of liquid crystal molecules to the basic principle
of display technology by using TN type liquid crystals as an
example.
The parallel arrangement of liquid crystal molecules along
grooves, when coming into contact with grooved surface in
a fixed direction, liquid crystal molecules line up parallelly
along the grooves.
Natural state
Molecules are
arranged in a
loosely ordered
fashion with
their long axes
parallel. |
When coming
into contact
with a finely
grooved
surface
(alignment
layer). |
Molecules line up parallel along grooves. |
When liquid crystals are sandwiched between upper and lower
plates, they line-up with grooves pointing in directions 'a' and
'b,' respectively. The molecules along the upper plate point in direction 'a' and
those along the lower plate in direction 'b,' thus forcing the liquid
crystals into a twisted structural arrangement./ (figure shows
a 90-degree twist) (TN type liquid crystal) |
 |
 |
Light travels through the spacing of the molecular arrangement.
The light also "twists" as it passes through the twisted liquid
crystals. Light passes through liquid crystals, following the direction in which
the molecules are arranged. When the molecule arrangement is twisted
90 degrees as shown in the figure, the light also twists 90 degrees as
it passes through the liquid crystals.
Light bends 90 degrees as it follows the twist of the molecules |
Molecules rearrange themselves when voltage is appliedWhen voltage is applied to the liquid crystal structure,
the twisted light passes straight through.
The molecules in liquid crystals are easily rearranged by applying
voltage or another external force. When voltage is applied,
molecules rearrange themselves vertically (along with the electric
field) and light passes straight through along the arrangement of
molecules. |
 |
 |
Blocking light with two polarizing filters.
When voltage is applied to a combination of two polarizing filters
and twisted liquid crystal, it becomes a LCD display.
Light passes when two polarizing filters are arranged with
polarizing axes as shown at left figure.
Light is blocked when two polarizing filters are arranged with
polarizing axes as shown at right figure. |
TN type LCDs
A combination of polarizing filters and twisted liquid crystal creates
a liquid crystal display.
When two
polarizing filters
are arranged
along
perpendicular
polarizing axes,
light entering from above is re-
directed 90
degrees along the helix arrangement
of the liquid crystal molecules so that
it passes through
the lower filter. |
 |
When voltage is
applied, the liquid
crystal molecules
straighten out of their helix pattern and
stop redirecting the
angle of the light,
thereby preventing
light from passing
through the lower
filter. |
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|
This figure depicts the principle behind typical twisted nematic
(TN) liquid crystal displays. In a TN type LCD, liquid crystals in
which the molecules form a 90-degree twisted helix, are
sandwiched between two polarizing filters. When no voltage is
applied, light passes; when voltage is applied, light is blocked
and the screen appears black. In other words, the voltage acts
as a trigger causing the liquid crystals to function like the shutter
of a camera.
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