Directview LCD Training 9 Theory
THEORY
THEORY
This section covers what Liquid Crystals are and how an LCD Display works.
LIQUID CRYSTALS
In school you learned that matter has three distinct states; solid, liquid, and gas. However, there are
states of matter that may fall between these states, like liquid crystals. Basically they are crystals
that hold their orientation (shape) but can flow similar to liquids. Their molecules point in same
direction with respect to each other like in a solid, but they are free to change position like in a
liquid. Think of a handful of pencils. They collectively hold their shape at rest, but change shape when
you squeeze or let go of them.
There are different phases and types of liquid crystals that perform differently. Small amounts of
pressure, heat, and/or electricity can cause liquid crystals to change in some way. For LCDs we are
interested in the electricity aspect, but pressure and heat are side effects that have to be dealt with.
This is why LCDs have a limited operating range and distort when you press on the screen.
LIQUID CRYSTAL DISPLAY
A Liquid Crystal Display is composed of a light source (backlight), a Liquid Crystal Panel, and a driving
circuit. We start with a light source at the back of the panel composed of thin fluorescent bulbs
(CCFLs - Cold Cathode Flouresent Lamps). This light passes through filters to help create a uniform
light source. Then the light passes through the Liquid Crystal Panel which is composed of thousands
of pixels that control the flow of light throught the panel to make images.
SOLID LIQUID LIQUID CRYSTAL
Data Driver IC
Printed Circuit Board
Gate Driver IC
Inverter
Driving
Circuit
Power Supply
for Video Signal
Pixel Array & Wiring
Liquid Crystal
Panel
Polarizer
CF Panel
Liquid Crystal
TFT Panel
Lamp
Prism
Diffuser
Light Guide
Backlight Unit
Polarizer
Reflector
Inverter
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