Both LCD and Plasma TVs are thin and flat. However, the technology used is quite different.
Introduction to the Technology used in Plasma TVs
The fluorescent light bulb forms the basis for this technology. The display in a Plasma TV consists of cells. Each cell consists of two glass panels which are set apart by a thin gap. During manufacture, neon-xenon gas is injected in this gap and the gas is sealed in the form of plasma. When the TV is being used, this gas is charged by electrical means at pre-set intervals. This charged gas then hits against red, green, and blue phosphors, which leads to the formation of an image. Each set of red, green, and blue phosphors is termed a picture element (PIXEL).
The technology in Plasma TVs does remove the need for the heavy picture tube and electron beam scanning that are used in traditional TVs. However, it still uses phosphor burning for image formation. Thus, Plasma TVs continue to have drawbacks such as heat generation and screen burn of stationary images.
Introduction to the Technology used in LCD TVs
LCD TVs use a different technology (you can also refer question #1 for the following discussion).
An LCD panel consists of two layers of glass-like material. These layers are polarized and stuck together. A unique polymer that holds the individual liquid crystals is applied over one layer. Then, electric current is passed through these crystals that either allow or block light, which results in images. LCD crystals are not capable of producing light. Hence, an external source like a fluorescent bulb is required so that the image from the LCD crystal becomes visible.
LCD panels are advantageous over standard CRT and Plasma TVs because they do not involve any lighting up of phosphors. Therefore, they consume less power. In addition, the light source generates less heat than a Plasma or traditional TV. Moreover, there is no chance for radiation from the screen.
Plasma Versus LCD
Advantages of Plasma TVs over LCD TVs
• Bigger screens can be made
• Higher contrast ratio
• Improved ability to display deeper blacks
• Enhanced accuracy with respect to color and saturation
• Improved motion tracking with minimal lag or none at all in the case of fast-moving images
Disadvantages of Plasma TVs over LCD TVs
• Higher chance for burn-in of stationary images
• More heat generation when compared to LCDs
• Performance at higher altitudes is not up to the mark
• Shorter life span of display (8 hours of viewing per day for 9 years, which is approx. 30,000 hours) than LCD. But, technology improvements are leading to increase in this life span to almost 60,000 hours.
LCD Versus Plasma
Advantages of LCD TVs over Plasma TVs
• Zero burn-in of stationary images
• Lower operating temperature
• Good performance even at high altitudes
• Much higher image brightness as against Plasma counterparts
• Longer display life (approx. 60,000 hours, after which all that is required would be replacing only the light source, but not the complete set). This will change depending on environmental factors and usage.
• Lighter than Plasma TVs when comparing same screen sizes
Disadvantages of LCD TVs over Plasma TVs
• Lower contrast ratio
• Display of deep blacks is not as good as seen with Plasma TVs
• Tracking of motion is not very good (lag effects may be seen in fast-moving objects). But, this is being improved now.
• Screen sizes of more than 42 inches are not so common as with Plasma TVs. But, nowadays, LCD TVs of screen size 60 inches are being made.
• Though LCDs do not have the problem of burn-in, the individual pixels can burn out, leading to small, black or white dots on the screen that are visible. Such pixels cannot be rectified. The entire screen needs replacement in such cases, if the pixel burnout becomes annoying.
• More expensive than Plasma TVs of similar sizes (but this is changing at present) particularly when you compare EDTV Plasmas and HDTV-LCD TVs.
For in-depth view comparison between LCD and Plasma, read: Which should I buy: An LCD or a Plasma TV?