Plasma display
A plasma display panel ( PDP english for Plasma Display Panel ) is a color flat-panel that generates the different colored light using phosphors, which are excited by the light generated by gas discharge plasma.
Plasma screens are mainly used as large ( 42 inches measured diagonally) television display devices. Here they compete with liquid crystal displays ( "LCD" ); Cathode ray tubes were never built in these sizes.
Operation
Plasma (from the Greek " structure " ) is ionized gas, which contains neutral particles and free ions, excited atoms and electrons. Due to spontaneous emission of excited atoms plasmas emit visible light and ultraviolet radiation.
In plasma screen is made of the emission of UV rays through a low-pressure plasma advantage. The operation is similar to a fluorescent lamp. In such lamps, the phosphors are excited by ultraviolet radiation of the mercury plasma in the emission of visible light. In plasma displays are used, however noble gases.
Construction of the color monitor
Between two glass plates there are very many small chambers. Three chambers result from the color display a pixel, a so-called pixels.
Each of the three chambers is illuminated in one of the three primary colors red, green and blue. The colors are caused by additive color mixing, ie by mixing the three primary colors ( eg yellow by mixture of green and red light, which is accomplished with plasma screen by lighting of the respective chambers ). Each chamber is filled with a noble gas mixture of neon and xenon, with the pressure is substantially lower than the normal atmospheric pressure, so it is a " near- vacuum ". Some manufacturers also mix in helium. The proportion of xenon is about 3 % to 5 %.
For forming an image, each individual chamber is " ignited " with an associated transistor, i.e., the gas is ionized briefly, it becomes a plasma. The basic colors in the chambers are generated by different phosphors ( phosphors), as soon as the ultraviolet radiation emitted by the plasma (Vacuum Ultraviolet range 140 to 190 nm) is incident on the phosphors. The ultraviolet itself is not visible. The phosphors convert the VUV radiation into visible light with the different depending on the fluorescent color.
Each color is produced by another fluorescent: BaMgAl10O17: Eu2 ( blue), Zn2SiO4: Mn2 ( green) and (Y, Gd) BO3: Eu3 ( red; may also depend on Y ( V, P) O4: Eu3 or Y2O2S: Eu3 be generated ). To produce not only the discrete states "on" ( lit ) and "off", but also intermediate brightness levels, the chambers at frequent intervals ( intervals ) can be ignited. The time of ignition is varied in order to vary the brightness. The longer a chamber is ignited, the brighter it shines.
The gas between the two glass plates is heavily diluted by low plasma temperatures are possible. The ignition voltage of several hundred volts is required. On the lower dielectric layer ( glass plate, that is an insulating layer ) is seated a Reihen-/Adress-Elektrodenstreifen that enables together with the upper electrodes of the control lines of each chamber ( each chamber is located at the crossing point of an address, and a top electrode). In the chamber itself contains a phosphor ( applied to the dielectric layer and the barrier ) and the gas mixture or the plasma. A protective layer has the function of protecting the upper dielectric layer and the transparent electrode located there. The two electrodes may generate a gas discharge in the chamber only with a pulse voltage applied to them due to the dielectric layers, they be protected - the pulse parameters determine the brightness of each color emitted.
Plasma screens are manufactured using sandwich construction.
The address electrodes are vertical and the line electrodes arranged horizontally. By the so- formed grid ( also known as matrix ), one can control the different chambers with the multiplexing method. While one might each only control a set with only one electrode layer, it is with a grid ( each intersection point corresponds to a chamber ) possible to control each chamber separately.
The blue phosphor has a lower stability with VUV radiation.
History and Future
The first functional plasma screen was developed in 1964 by Donald L. Bitzer and H. Gene Slottow for the mainframe system Plato IV of the University of Illinois. Plasma screens over CRT monitors had the advantage that they could be directly controlled digitally; Moreover, they were quite durable and space saving. For several years, plasma displays have therefore been widely used in the mainframe sector. Monochrome plasma screens or displays like the one pictured plasma monitor of the PLATO V use, as opposed to color-capable plasma screens no different colored phosphors. It is used per pixel, only one chamber, which is filled with a rare gas of neon. This results in the orange - red color. The operation is based on the glow discharge and is identical to a glow lamp.
However, the technical progress and reduced manufacturing costs helped in the 1970s, the CRT monitor as a computer display unit for breakthrough. Plasma screens have since been used only for a few special purposes.
When at the beginning of the 1980s the first laptops were developed, attacked some early manufacturers, including GRiD, Toshiba and Chicony, the equipment of their portable computers to the plasma screen technology back, as it allowed very flat and compact housing forms at appropriate large screen size and ergonomic point of view (angle of view, contrast) was the first liquid crystal displays far superior. The high power consumption of plasma displays, however, made a stand alone operation largely impossible; also their use remained limited to expensive equipment for cost reasons. Since high-resolution color plasma screens were not technically possible and get great strides in the development of better LCDs, laptops, plasma disappeared around 1990 from the market.
At about the same time began several consumer electronics companies with the development of color plasma screens for televisions. The first color plasma display with a screen diagonal of 21 inches was launched in 1992 by Fujitsu; to the development of market-ready displays elapsed after a few years.
The first television with plasma screen Pioneer 1997 brought to the market. For commercial breakthrough for the technology carried the Olympic Winter Games in 1998: A Japanese TV station then needed large flat screens for the in-house HDTV service.
According to reports from radio amateurs send plasma screens from broadband electromagnetic radiations interfere with the reception in the medium and short wave range in the near vicinity. They themselves are - unlike tube sets - insensitive to magnetic fields. Therefore, one can also place speaker systems with non- shielded magnet next to the screen without causing picture interference.
The power consumption of a plasma screen hangs - unlike LCD TVs - heavily on the visual from and behaves dynamically: A subject consumes far less power than a light.
Earlier it was indicated that plasma displays visible after losing an average of 30,000 hours on luminosity (which had some buyers tend to an LCD ); today (2011) is called a value of 60,000 hours.
Market situation
Today, plasma screens play a minor role compared to LCD TVs on the market. In 2007, of the 4.4 million sold 3.9 million flat panel LCDs.
In 2012, the market share of plasma screens stood at only 5.7%. This represents a decline to 2011 by 23%.
The low market share is also due to the fact that plasma screens are available only from a size of 42 "( about 106 cm).
In early 2008 announced the TV manufacturer Pioneer, the future also offer LCD TVs and no longer produce its plasma panels themselves and to relate these future Panasonic (Matsushita ). In September 2008, Hitachi announced adjust to the panel manufacturing. After Pioneer in February 2009 announced the production of plasma and LCD TVs completely set, remained with Panasonic the last Japanese manufacturer of plasma TVs. Panasonic will also be set up to end of March 2014 its production of plasma TVs.
Was Panasonic in 2009 is still the world's largest manufacturers of plasma displays (39 % market share, followed by Samsung with 31% and LG with 22 % ), the market share was in 2012 only 16.5 %, which is far behind its main competitor Samsung ( 51.9 %).
The electronics markets call mainly four characteristics of flat panel displays: the size, the price, the maximum resolution ( HD ready or Full HD) and contrast. Principle related advantages of plasma technology are the vertically and horizontally almost unlimited wide viewing angles without color and contrast impairments and the extremely short response time of each image cell, which is in the nanosecond range. The higher contrast has long been regarded as the main advantage of plasma screens, as they reached a contrast of 15,000:1 compared to a maximum of 1000:1 with an LCD. Today reach plasma screens 5,000,000:1 and more.
Alternatives to plasma screens
Possible alternatives to plasma screen depend strongly on the application.
As a "normal" TV LCD TV with CCFL or LED backlight are often chosen as an alternative. Conventional CRT screens (English: Cathode Ray Tube) can not be produced in such large formats, as required to achieve the mechanical stability of screen material ( glass thickness) increases sharply. Given the overall depth and convergence errors ( color shifts ) and linearity error are increasingly more difficult to control ( distortion ).
For large screens an alternative is the projection (projector ) on a white wall or a special screen. The images thus produced a lower contrast than the images on an LCD or even more so than that of a plasma TV.
2011, the OLED screen technology has been known by several smartphones. TV manufacturers want to bring the first TVs to the market in late 2012.
Plasma Addressed Liquid Crystal ( PALC abbreviation ) is a technique for flat panel displays, the elements of the plasma screens, LCDs (Liquid Crystal Displays ) and TFT-LCDs contains or combines. It uses plasma switch (instead of a TFT screen transistors) to control an LCD screen.