LCD, TFT and Plasma Television Technologies

Flat-panel televisions replaced the bulky cathode-ray tube by using thin display technologies that form an image across a flat surface. Two distinct technologies dominated the early flat-panel era: the liquid crystal display (LCD), usually built using thin-film transistors (TFT), and the plasma display panel. Both produce a colour picture from a grid of small picture elements, but they work in fundamentally different ways.

An LCD does not emit light itself. Each pixel uses a liquid crystal element, controlled by a thin-film transistor and combined with colour filters and polarising layers, to vary how much light from a backlight passes through. By switching millions of these sub-pixels, the panel builds up a full-colour image. Because the crystals only modulate a separate backlight, LCD televisions are thin, energy-efficient and free from screen burn-in, and the TFT approach gives each pixel its own switching element for sharp, fast images.

A plasma display works on a different principle. Each pixel contains tiny cells filled with a gas that, when energised, forms a plasma and emits ultraviolet light, which in turn excites coloured phosphors to glow, much like miniature fluorescent cells. Because plasma pixels emit their own light, these displays were noted for deep blacks, strong contrast and wide viewing angles, particularly in larger sizes. However, plasma panels generally consumed more power and were prone to burn-in. Over time, improvements in LCD technology and the later rise of organic LED (OLED) displays led to plasma being discontinued, while LCD remains widely used.

Frequently asked questions

How does an LCD television form its picture?

Liquid crystal elements, switched by thin-film transistors, control how much backlight passes through colour filters at each pixel, building up the image.

How does a plasma display differ from an LCD?

A plasma panel's pixels emit their own light from energised gas cells exciting phosphors, whereas an LCD modulates a separate backlight and does not emit light itself.

Why did plasma televisions decline?

Plasma generally used more power and could suffer burn-in, while LCD improved and OLED emerged, leading manufacturers to discontinue plasma panels.