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Thursday, 12 July 2012

LCD (Liquid Crystal Display)


Liquid Crystal is substances that have the ability of reflection and its ability change according to applied voltage to it.
LCD    (liquid crystal display)
LCD is a device that consist of liquid and it
Display information on liquid display.

Construction of LCD

A thin layer liquid crystal is sandwiched between two sheets of glass(the thickness of liquid crystal layer is 10 to 20um).To provide electric field parallel to crystal ,a transparent conducting materiel is applied to inner surface to glass sheet.
Whenever it needed to change the molecular structure of liquid crystal, then this crystal is connected to external voltage through that conducting material.
       Stannic Oxide (Sn02) and Oxide (In2O3) are used to make electrodes.
     Whenever the electric field is present at liquid,
It because opaque.
Thus when voltages are applied to liquid crystal .it does not reflect light.
Display patterns similar LEDs can be created by organizing the molecular into circles. So for application of LEDs the LCD can be also used.

Comparison between LED and LCD

            LED                                                                        LCD
1 It is PN junction diode.
2    It works on the principle of emission light()it produce and emit light).
3  It required more current for operating(nearly 20mA).
4  it works on DC voltage.

5 Consume more power.
6 Response time is less, usually 100 nano second.

7   These are speed.
8 These have lower life.

9  These can be used where power consumption is not a problem.
10  Heavier in weight.
1  It is not a diode.
2  It  works on the principle of reflection of light(it only reflect of light or change its condition).
3  it required less current (about 30 uA).
4  It works on AC voltage of the form of sin wave or square wave (30Hz) . Because if DC is provided, then its life decreases.
5 Consume less power.
6 response times is longer, ussally100 to 300 mile – second.
7 There speed very low.
8 These have longer life.

9  Mostly used in less power devices watch, clocks etc.

10   Lighter is weight and smaller.

Uses of LCDs

Due to consuming very low power to produce electric field, LCDs are commonly used in
1 Pocket size calculators.
2 Digital clocks.
3  Portable computers.
4  Electric type – write display.
5 Small television screens.


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