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LCD Technology

LCD Technology

Introduction

The LCD, or “Liquid Crystal Display”, is ubiquitous in the world around us, in electronic devices such as digital clocks and watches, microwave ovens, laptop computers, and most recently in television screens. The nature of LCD technology means that manufacturers can do away with the CRT, or “Cathode Ray Tube” – a bulky, power-hungry piece of equipment that is responsible for the depth, weight, and power consumption, of a traditional television set – so that televisions can be flatter, lighter and more energy efficient. This, in turn, means that television screens can be much larger; the largest CRT television screen ever made measured 38″, diagonally, whereas LCD makes screen sizes measuring 108″, or more, a real possibility.

How LCD Technology Works

The first step in explaining how LCD technology works is to explain what liquid crystals are, because the name itself appears to be a contradiction. Liquid crystals are a state of matter whose order is, as their name suggests, intermediate between that of a liquid and that of a crystal. They are typically rod-shaped molecules, about 25 *ngstr*ms (*), or 25 * 10-10 metres, in length, and can be fluid like a crystal, or display different physical properties along different axes like a crystal. Their important characteristic, however, is that their ordering is a function of temperature, and they react, predictably, to an applied electrical current, in such a way as to control the passage of light.

An LCD panel consists of two glass plates, polarised so that only light in one plane or the other is allowed to pass, with a “sandwich” of liquid crystal molecules between them. In a TFT (“Thin Film Transistor”) panel, a matrix of tiny transistors and capacitors is arranged on the glass substrate, so that the voltage to each individual picture element, or “pixel”, can be controlled very precisely. When voltage is applied, the liquid crystal molecules orientate themselves in one direction, permitting light, and effectively switching the pixel “on”. A colour filter is used to apply colour to each pixel, and so a complete image is built up on the secreen.

LCD Technology Then, Now & in the Future

The discovery of the effect of electricity on liquid crystal molecules, and the passage of light through them, is credited to Richard Williams of RCA (“Radio Corporation of America”) in 1962, and his work was followed up by another RCA employee, George Heilmeier, who actually predicted that a colour LCD panel of modern proportions was a possibility. The first commercial LCD product, a pocket calculator, is credited to Sharp in 1973, and it was Sharp again, some years later, in 1988, who demonstrated the first, full colour, full motion LCD panel. Sharp also produced the first wall hanging LCD television in 1991, when several of the major electronic manufacturers began investing heavily in LCD technology, and so began the path to the technology that we know today.

There are still one or two inherent problems with LCD technology that have yet to be fully solved, even in modern times. The first of these is the viewing angle – that is, the maximum angle either side of the “head-on” position, in the horizontal and vertical planes, at which images can be viewed acceptably – which in some LCD television screens is limited to 120* or 130*. This does not compare favourably with the 160* viewing angle typically available in Plasma television screens, and may result in a loss of colour depth and contrast if the screen is not viewed from directly in front. Similarly, poor contrast ratio – that is, the difference between the darkest (black) and the lightest (white) colour that can be displayed on a screen, simultaneously – is often cited as another drawback of LCD technology.

The consumer electronics market is changing at a breathtaking pace, with new technologies and products appearing on an almost daily basis, but the future for LCD televisions looks assured. Demand for LCD technology is still sky-high, with LCD televisions dominating the market in Western Europe, and Sharp, and other manufacturers keen to promote their latest models, now just 2″ thick at their thickest point. Apparently, up to 100 million European households are still waiting to replace their existing CRT televisions with LCD models, so their remains huge potential in the marketplace.