Liquid crystals were discovered in 1888 by an Austrian botanist named Freidrich Renitzer. The phrase liquid crystal was first used by a German physicist named Otto Lehmann. Liquid crystal is a clear organic material made up of long rod shaped molecules. It was discovered that the substance had the ability to manipulate the path of light waves traveling through it. This property is used in the creation of LCD display devices.

The benefit of liquid crystal display devices over CRT based devices is that LCD devices are less bulky and take almost a third less of the volume per equivalent viewing area, than a conventional CRT. This means LCD technology is a useful component for portable devices like laptops, calculators and mobile phones. Another advantage of LCD technology is that its power usage is significantly less than that of a CRT. However, it is much more costly to manufacture an LCD TV than a CRT TV.

An LCD Televisions is a grouping of LCD elements; each of these elements produces a pixel on the screen. An LCD element consists of two major parts: a layer of liquid crystal between two lightly ridged surfaces with their ridges perpendicular to each other and two optical polarizing filters perpendicular to each other.

The long rod shaped molecules in their normal state position themselves with their axis approximately parallel to each other. As the liquid crystal flows over the finely ridged surface it is possible to manage the alignment of the molecules as they track the position of the grooves. A layer of liquid crystal substance is placed in a container with two finely ridged surfaces whose ridges are perpendicular to each other. Therefore the molecules at the two surfaces are aligned perpendicular to each other and those transitional layers are twisted by intermediate angles.

Natural light waves are positioned at random angles and flow along assorted planes from the light source. An optical polarizing filter or polarizer can separate a single plane of light from the group. The filter acts like a net of finely parallel lines blocking all light, apart from light flowing in an area specific to the lines. The light in this state is said to be polarized. A second polarizer whose lines are perpendicular to the first would block all the polarized light.

The container with ridged surfaces is positioned between two perpendicular polarizing filters. Normally light from the first filter would be blocked by the second filter. However, in this case the liquid crystal material located in-between, twists the plane of light by 90 degrees as it passes through the material. The light is now parallel to the second filter and comes out through it to the eye of the viewer. This creates a light pixel.

A battery linked across the liquid crystal container generates a current through the liquid crystal, and changes the direction of its molecules according to the path of the current flow. This disturbs the pattern of the liquid crystal molecules, so that the molecules at the ridged surfaces are no longer turned by 90 degrees. Polarized light through the first filter gets moved to a different angle by the liquid crystal when it reaches the second filter, through which it can no longer appear. An observer on the other side of the filter does not see any light coming out. This process creates a dark pixel.

Images on the LCD Televisions screen can be displayed using a large number of these cells, each operating as a light or dark pixel. Therefore, on the LCD screen each cell corresponds to one pixel. To display color each cell is made up of three sub-cells with filters over them to produce green, red or blue colored light. By controlling the volume of current in each cell, the intensity of the colored light coming from each of the cells can be manipulated. By combing the 3 primary colors of red, blue and green the entire color spectrum is conveyed to the viewer.



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