What is a Flat Screen?

Flat screen are slowly replacing the conventional CRT monitors, as they are bulky. These were introduced for use on battery-operated portable computers, as these consume very little power. Liquid Crystal Display (LCD) monitors use flat screen. In an LCD, the image is formed by so-called liquid crystals. These are long rod-like molecules which though solid can flow like a liquid.

Each pixel on the screen consists of a microscopic electrode positioned below several of these molecules. As the output from the computer scans the screen a row at a time, it activates each of these pixels in turn, switching it on or off. When a pixel is on, the crystals twit in such a way that they block out the light. When it is off, they let the light through.

Color LCDs require very fast liquid crystals. In what is called passive matrix display there are three screens, colored red, green and blue, which are placed on top of each other. Below the three screens are the thousands of pixel electrodes, which generate light. The pixels in each screen act as filters for this light. If a pixel is to be red, for example, the green and blue filters above it are turned on, blocking out those colors but the red filter is off, allowing the red light through. By turning the filters on and off in other combinations, other colors can be obtained. Active matrix screens are difficult to manufacture and are very expensive. They are available with only a few top-of-the-range computers.