How plasma tv display works

How plasma tv display works

Plasma tv was made as an improvement to the existing CRT TVs then. How CRT TVs work  when converting signals is not different from the plasma tv especially the analog type. This type of display uses plasma as a source of light. To create plasma, gases are ionized where the number of electrons is increased causing an imbalance of charges. So, plasma was used to replace the beam of electrons from the old CRT TVs.

What is plasma

Before we learn How plasma tv display works, we shall first define what is plasma. In addition to the three state states of matter, there is the plasma state. In 2001, three scientists earned the Nobel peace prize for discovering the fifth state of matter-Bose Einstein condensate. The plasma state is a state that is acquired by heavily ionizing gas molecules to create anions and cations. The anions and cations can conduct electricity

History of plasma display

While the plasma tv became very popular very recently, the idea and the technology of plasma is as own as computers dynamic RAM. It may even be older than that.  Its research has shown that the idea of a flat-screen was proposed in 1936 by a Hungarian engineer. However, the prototype came to be in 1964 which was co-developed by Gene Slottow and Donald Bitzer from the University of Illinois.

First plasma

The first plasma screens displayed output orange color instead of the white color as the CRT TVs did.  So they were orange and black screens.  What made these screens very popular is that they did not need any circuitry or memory to have their images refreshed. However, CRT displays were back on business after the discovery of semiconductor memory which made them more affordable. in the 1970s a single plasma display used to cost $2,500. Nonetheless, plasma screens remain suitable for areas such as stock exchange because of their thinness.

Still, in the same period, there was the seven-segment plasma display called the panaplex display.  They were common in calculators, cash registers, pinball machines, navigation equipment among many other places. In other words, anything the previously used numitron display adopted the Panaplex display technology. But now, we have LED almost everywhere instead of plasma.

Black monochrome

In the 1980s an orange on black monochrome display was introduced in the market by IBM. It only a 19-inch screen, very big by their standards then. Before the decade came to an end, the displays became widely employed on portable computers that depended on the alternating current power supply. Example of such computers includes the Compaq portable 386 and IBM P75. Unfortunately, IBM shut the largest plasma screen factory in the world in the same decade. However, this was a smart move because the competition was quite high from the LCD active-matrix display.  IBM choose to produce mainframe computers instead.

Full-color plasma display

The first full-color plasma display came to market in 1992, a 21-inch screen. It was created by Fujitsu company. The same company introduces 42-inch full-color display panel in 1995. You will be shocked to know it was until 1997 that flat screens were commercially available, and this credited to Philips company. However, the screens were costly, once went for up to $ 15000. It was not until the 2000s that the price dropped to $ 10, 000.

In early 2000, the first 60 -inch plasma display was announced by plasmaco. Plasmaco company was purchased by Panasonic in 1996 after the two companies performed a joint project.  The acquisition cost the parent company only $ 26,000,000.

By the late 2000s, researchers noted that the plasma screens were no longer the top sale display but LCD screens were. The largest plasma display screen ever created was 150-inch by Panasonic. It was a popular belief then that LCD was only suited for small screens. Among the benefits that plasma screen owners enjoyed include wider viewing angles. Secondly, once you had a plasma screen you enjoy a greater color spectrum, unlike the CRT. Thirdly, your tv had a faster response and finally, there was an increased color contrast.

Out of market

Since 2010, plasma displays are no longer popular. People are now going for LED displays since they are lighter, have higher power efficiencies, and are more affordable. In 2014, Panasonic announced they would no longer produce plasma screens any longer.  LG and Samsung did the same in 2015. The technology was interesting but soon it will be out of the market. People are looking forward to the most promising technology, OLED displays.

Initially, the first plasma display panels were not TVs. They were meant to just display video signal. So, if you needed to watch television, you needed a separate tuner system. However, today almost all plasma display panels you will go for in the market have tunes so they are technically plasma TVs.

How plasma display panel works

Below is a plasma display panel (PDP). The component in the middle of the layers has 3 cell compartments called a pixel. Each of the three cells has 15% neon gas and other gases. The cells contain primary colors, each cell for a single color either blue, red or green. A cell appears as shown in the figure below.

How plasma tv display works
Plasma cell

There are thousands of such cells on a single plasma television set. The cells are sandwiched between electrodes but between the electrodes and the cells are dielectric materials.   Each of the three cells has power provided by the electrodes. When dielectric layers are used, there is more charge that gathers between cells and electrodes.

How plasma tv display works
vertical array of the plasma cell
Electrodes

Electrodes on the placed vertically and horizontally depending on their location relative to the cells. The vertical electrodes are on the display side of the cells and are transparent; they are called transparent display electrodes. They have a coat of magnesium oxide.  The horizontally placed electrodes are placed behind the cells and are not transparent; they are called address electrodes.

On the display side, the outermost part is a glass later where your image is shown. As was described earlier, the gas is ionized which then excites phosphor that produces light.  When we looked at how CRT TVs work, we saw that a beam of electrons or cathode rays causes the phosphor to produce light.  However, plasma technology uses voltage to ionize gas the causes plasma to occur and the plasma itself excites the phosphor. This is how  plasma tv display works.

Types of phosphors

Do you remember we said the three produces one of the primary colors, one for each cell? There are different phosphors for each color. The green light is produced by the following phosphor SrAl12O19:Mn, BaAl12O19:Mn, and Zn2SiO4:Mn.  Blue light is given out by (Y,Gd)(V,P)O4 and BaMgAl14O23:Eu. Finally, for you to have a red light, you will have to use any of the following phosphors; (Y,Gd)BO3:Eu, YBO3:Eu, and Y2O3:Eu.

You could be wondering since we have only three colors only how are we able to see the rest of the colors such as purple? When your plasma tv screen needs to produce any other color other than the primary colors, the intensity of each of the primary colors is varied.  The figure below shows a cross-section of a cell.

How plasma tv display works
A closer look at the plasma cell
How colors are produced

You are also wondering now that images have several colors, how does each pixel know which color to display? It is simple.  There is a control box that allows power to flow through each electrode at certain intersections when the pixel needs to be illuminated. Once the power flows through the electrodes, the gas becomes ionized, and hence the plasma is created. The current from the electrode has passed through the cells where electrons and protons move according.

It is during this movement the ionized gas molecules collide with the moving electrons causing energy to create. The electrons on the ion acquire a brief excited state. When they calm down ( become less excited) they is an energy that is then released, the ultraviolet photon.  It is these UV photons that cause the phosphor to emit light after getting excited. So, when you see a motion picture on your plasma tv, the cells are turned on and off regularly to change color.

Attributes of Plasma display panels (PNP)
Light weight

There are some advantages that plasma displays have over other forms of display such as the CRT and LCD. For starters, plasma is not as bulky and heavy as the CRT tv is.  They do not have an extended backside like the CRT tv. Additionally, there is no dangerous high voltage that is included when the design plasma display-CRT has accelerating anodes at 1500V. however, it is estimated that plasma and CRT consume an almost equal amount of power.

Brighter image

Plasma display panels give brighter images than both the CRT and LCD screens. If you remember, we had said earlier that plasma tv has higher refresh rates than both the CRT and LCD. So, you will never see motion blur because of faster reaction time.

Disadvantages

There are cons that you will suffer when using a plasma tv. The first disadvantage is that image is burnt on the screen if it held on for a long time a phenomenon called image burn-in. It occurs since phosphor tends to get overheated and then lose its luminosity. In the long run, the decline in the luminosity causes image quality to decline as well. This is bound to happen if a cell output a bright color for a prolonged time.  If this happens, you should turn off your screen to allow cells to discharge.

Other than the above disadvantages, there is an additional drawback that the plasma tv had, they were very expensive. However, this is not a problem anymore now that better and cheaper display panels from LED are available in the market.

Current trends on tv

Our discussion on how plasma tv display works will not be complete  if we do not look into current trends. You have realized that display screens are becoming thinner, more efficient and even affordable.  While the plasma display panel are enticingly interesting, it is being phased out since the major manufacturers stopped manufacturing them since 2015.

Unless you are tech geek seeking technology as a hobby, do not go buying one; you won’t find one and if you are lucky you might get a second hand one at a lofty price. While plasma brought about major improvement of the CRT, they prices were prohibitively high and just a few numbers of people and organization could afford them.

What is difference between LCD and plasma display

Now that we know How plasma tv display works, we shall look into some of the advantages and disadvantages of plasma. LCD and plasma display work in different ways. Technically, Plasma tv or monitors were awfully expensive, far expensive than LCD. The plasma panels are known for their faster refresh rate than LCD so you will not experience blurred motion. This is why plasma displays were favored in sports and movie applications. Though there has been improve of LCD`s refresh rates, they are still slower than plasma tv.

LCD do not consume as much power as their plasma counter parts do. A plasma screen consumes between 300 -700 W while the LCD consumes between 50-250 W. OLED display consumes between 15-60W.

It also goes without saying the plasma tv are heavier than LCD and hence they are more fragile. So, be careful when carrying one from one point to another.

The currently people are going for LED because they are lighter, has high refresh rates and consumes less power than LCD, Plasma and CRT. Today, you might not get a CRT on the market easily.

Most tv in the market can be used as monitors and vise versa.  This is because of the rise of need for gaming monitors. Furthermore, technology has allowed manufacturers to ensure that monitors can be integrated with other equipment such as the xbox, play station among others.

 

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