The emergence of the ‘television set’ since the late 1930s has spawned a large amount of developing technologies over the last 7 decades.
Starting initially with a diversion about the current main display techniques, it is hoped in conclusion to relate this to serial and economic trends now and in the future.
The main display technique used since the advent of television is the C.R.T. (cathode ray tube). This consists of a glass tube with a phosphor coating backing to the display surface. Electrons are “fired” at high-speed in a methodical line by line format onto the phosphor surface to produce an optical image visible from the projected image surface or ‘television screen’. This type of television display is typical of the analogue broadcast system although ’set-top’ boxes containing digital to analogue signal conversion are available that convert digital broadcasts signals to analogue display format.
There are several newer types of display technologies now in current use. The main ones being LCD (liquid crystal display) and plasma display technologies.
Plasma Display Technology
The plasma display panel, as it is known, operates as follows. It consists of many tiny cells constructed between two panels of glass. Each cell contains a mixture of noble gases, namely xenon and neon. The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light. This type of display is used often for televisions greater than 32”, and is becoming increasingly popular in home entertainment.
Long electrodes are also sandwiched between the glass plates in front of and behind the cells. The address electrodes sit behind the cells, along the rear glass plate. The transparent display electrodes, which are surrounded by insulating dielectric material and covered by a magnesium oxide protective layer, are mounted in front of the cell, along the front glass plate. Control circuitry charges the electrodes that cross paths at a cell, creating a voltage difference between the front and back and causing the gas to ionise and form a plasma; as the gas ions rush to the electrodes and collide, the photons are emitted.
It would now be wise to describe the operation of an LCD display before contrasting various benefits of differing technologies.