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Liquid Crystal Display (LCD) stands for Liquid Crystal Display. Liquid crystals are transparent substances exhibiting both sold and liquid matter properties. Light passing through liquid crystal follows the alignment of the molecules that make them up. Applying electricity changes their molecular alignment thus changing the way light passes through them, and by putting these individual displays together you can create a display screen which is tremendously smaller then our CRT (Cathode Ray Tube) monitors.
There are two main principles applied in making LCD. The first principle consists of sandwiching liquid crystals between two finally grooved surfaces where the groves on one surface are perpendicular to the groves on the other. Since molecules on one surface are aligned north to south and the molecules on the other surface are aligned east to west. Then the molecules in between are forced into a twisted state of 90 degrees. Applying a voltage to the liquid crystal rearranges the molecules vertically allowing light to pass through. The second principle of the LCD relies on the properties of polarizing filters and light itself. Natural light waves are orientated at random angles. A polarized filter is simply a set of incredibly fine parallel lines. These lines act like a net, blocking all light waves apart from those orientated parallel to the lines. A second polarizing filter with lines arranged perpendicular (at 90 degrees) to the first would therefore totally block this already polarized light. Light would only pass through the second polarizes if its lines were exactly parallels with the first, or if the light itself had been twisted to match the second polarizes. The LCD consists of two polarizing filters with their lines arranged at 90 degrees to each other. When a voltage is applied the liquid crystals in-between twist and realign the lines vertically which then causes a block in the light. In other words if there is no voltage applied the light will be able to pass through, but if there is a voltage applied the light will be blocked. Controlling the different amounts of light passing through the liquid crystals allows the LCD to create color display. A LCD pixel consists of three different elements, each of which can create 64 shades of light.
With more and more people buying computers a need for better technology has aroused creating a market for efficient and more compact computers. One of the major components of a PC is its display (monitor). With the introduction of this new technology a display that is smaller but not equivalent in all aspect to the CRT monitor has been created.
One of the major differences between the CRT and the LCD are their physical size. A CRT consists of a cathode ray tube that requires a large amount of space as opposed to a LCD that is based on a very thin screen. This reason you can use the LCD many places where a CRT would be unfit (i.e. Laptops, small work area ). Having a small physical appearance doesn t mean a cut back on display size. Unlike CRT monitors, the diagonal measurement of a LCD is the same as its viewable area, so there s no loss of the traditional inch or so behind the monitor s faceplate or bezel. The combination makes any LCD a match for a CRT 2 to 3 inches larger. CRT monitors are capable of displaying unlimited amount of colors. In contrast to CRT monitors a LCD can display less then or equal to unlimited colors depending on the type of the LCD monitor you buy. CRT monitors are able to display multiple resolutions while a LCD will only work well in one resolution. Another issue with the LCD monitor is the viewing angel. A CRT screen can be looked at from a very wide angle, practically from the side, but a LCD monitor has a much smaller viewing angle, needed to be viewed more directly from the front. From the side, the image on a LCD screen can seem to disappear, or invert colors. As LCD technology becomes more advanced, these problems hopefully will be solved. The LCD is also an energy saver and does not emit harmfully radiation as the CRT monitors do.
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