Televisions today have abandoned the more costly and less efficient cathode-ray tubes method of displaying images on the screen. Aside from cost and efficacy, Liquid Crystal Displays are more convenient as the screens are lighter, thinner, and consume less power.

What’s the Science behind LCDs?

Liquid Crystal Displays utilize a semi-solid semi-liquid substance called liquid crystals. They get this seemingly oxymoronic name because they are neither fully liquid nor solid. Their molecules are compact enough to maintain a respectable form as in solids yet they are able to move about freely as in liquids.

These liquid crystals do not transmit light and so require an external light source in order to project the intended image. In the case of simple Liquid Crystal Displays as in calculators and watches, they require the light from outside the device to be reflected by a mirror embedded at the bottom of the screen. In the case of the much more complex LCD televisions, they utilize cold cathode fluorescent lamps (CCFL’s) or colored Light-Emitting Diodes (LED’s) to act as the light source.

LCD technology makes use of liquid crystals in their nematic phase – this is a state wherein the molecules are twisted (Twisted Nematics). It is these TN’s that make the method work. These TN’s are affected by electric currents – untwisting with relation to the voltage to block the passage of light.

From Start to Finish

Now let’s take a look at how these Liquid Crystal Displays work. To most easily understand this concept, let’s tackle first the basics of a simple LCD configuration.

Light is made to pass through a polarized glass filter whose side without the polarizing film is rubbed with a substance containing microscopic grooves to create a particular orientation or direction/alignment. A negative electrode film is placed on top of it before a reversed order of the same layers (electrode-glass filter-polarizing film) but with a positive electrode and in a usually perpendicular (right angle) orientation. Sandwiched between them is a layer of liquid crystals.

Now when the light passes through the first filter and the charged electrode, the liquid crystal untwists and blocks the light that hits the pre-shaped positive electrode plate. When this happens, the screen displays a gray area where the light passes unblocked, and a darkened area the shape of the positive electrode plate where the light is blocked. The end result is you have an image of the shape you intended.

LCDs in the Television Industry

Televisions employ Liquid Crystal Displays to a much larger and more complicated scale. For one thing, they use much larger screens and so use active-matrix components and shutter designs to span the entire screen size. For another, they require sub-pixels and much more articulate electrode plates to display images with curved shapes and distinct colors. Overall, the process is tedious and the light that reaches the viewers is only roughly 8-10% of the original emitted light – all because of complicated blocking mechanisms and switching issues.

Nevertheless, these Liquid Crystal Displays remain to hold a significant advantage over CRT’s in several aspects including image quality. With the advent of improved technologies just around the corner, they will certainly continue to prosper.