>LCD-Liquid Crystal Displays

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June 19, 2011 by todayscircuits

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What is an LCD/Definition of Liquid Crystal Displays

The liquid-crystal display has the distinct advantage of having a low power consumption than the LED. It is typically of the order of microwatts for the display in comparison to the some order of milliwatts for LEDs. Low power consumption requirement has made it compatible with MOS integrated logic circuit. Its other advantages are its low cost, and good contrast. The main drawbacks of LCDs are additional requirement of light source, a limited temperature range of operation (between 0 and 60° C), low reliability, short oper­ating life, poor visibility in low ambient lighting, slow speed and the need for an ac drive.

Basic structure of an LCD

A liquid crystal cell consists of a thin layer (about 10 u m) of a liquid crystal sand­wiched between two glass sheets with transparent elec­trodes deposited on their inside faces. With both glass sheets transparent, the cell is known as transmittive type cell. When one glass is transparent and the other has a reflective coating, the cell is called reflective type. The LCD does not produce any illumination of its own. It, in fact, depends entirely on illumination falling on it from an external source for its visual effect

Types of LCD/Liquid Crystal Displays.

LCD-Liquid Crystal Displays

Two types of display available are dynamic scatter­ing display and field effect display.

When dynamic scattering display is energized, the molecules of energized area of the display become tur­bulent and scatter light in all directions. Consequently, the activated areas take on a frosted glass appearance resulting in a silver display. Of course, the unenergized areas remain translucent.

Field effect LCD contains front and back polarizers at right angles to each other. Without electrical exci­tation, the light coming through the front polarizer is rotated 90° in the fluid.