Principle Of Liquid Crystal; Liquid Crystal; Rubbing-Process - Sanyo TI5110LCD Training Manual

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Principle of Liquid Crystal

Training Manual Principle of LCD
2. Principle of Liquid Crystal

2-1 Liquid Crystal

What is Liquid Crystal?
Liquid Crystal is a material whose state is between a solid and liquid. It has characteristics of both solids
and liquids, and generally is a white turbid liquid. Its molecules are normally arranged comparatively
opaque and change to transparent with the application of voltage or heat.
Almost all the materials consist of an organic compound taking the form of a slender stick or a flat plate.
There are three types of liquid crystal as shown in Fig. 4, and they depend on the construction and
arrangement of molecules.
Generally Nematic liquid crystal is used for the display apparatus.
(a) Smectic
Molecules are in layers and arranged parallel to each other. The center of gravity is arranged at random
in the layer.
(b) Nematic
Molecules are not in layers. They are arranged parallel. The center of gravity is able to move freely to the
major axis.
(c) Cholesteric
Molecules are in layers and arranged parallel. The arranging direction of the major axis for the neighbor-
ing layers is shifted gradually.
In order to use liquid crystal for display, it is necessary to regularly arrange the molecules of Nematic

(Rubbing-process).

2-2 Rubbing-process
After chemicals for arranging are put on the glass plate, they are hardened, and then the surface on the
plate is rubbed with a cloth to fix the direction of the gaps that are made. The arranging direction of mole-
cules is settled in the gaps.
This process is used to change the characteristics so the molecules that touch the rubbed surface are
arranged to the major axis of the rubbed direction.
This thin film on the glass plate is called "Alignment film."
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