Liquid Crystal Display (LCD)

Liquid Crystal Display or LCD is the technology mostly used for flat panel screens like laptop, calculator or even desktop monitor. It is based on blocking the light rather than emitting it unlike other display technologies. The LCD technology creates images by sandwiching an electrically reactive substance between two electrodes. Liquid crystals contain two sheets of polarizing material with liquid solution between them. When electric current passes through the liquid, it causes the crystals to align so that light can not pass through them.

Each crystal acts like switch, allowing light to pass through or blocking the light. Liquid crystals are rod-shaped molecules in the display that spiral when exposed to an electrical charge. This will produce the desired image. Liquid color of the image can be changed by increasing or reducing supply of electric current into the crystal cells.

Color LCDs use two display grids for producing color- passive matrix and active matrix. The active matrix also called thin film transistor (TFT) has a transistor located at each pixel transaction and controls the pixel when electricity is applied. They consume less power and so in an active matrix power can be witched off or on more frequently thereby enhancing screen refresh time. But this technology is quite expensive.

On the other hand, passive matrix technology makes use of a grid of bound conductors, with pixels located at every crossing of this grid. Whenever a current sweeps throught two of the grid's conductors, the luminosity of the pixels will change.

This technology is less expensive. Recent development in passive matrix technology using CSTN and DSTN technologies has enabled it to produce color images that can rival active matrix displays.