Plasma TVs: great technology in a dead end

Flat and bigger than picture tube TVs: In the autumn of 1996 Philips and its subsidiary Grundig presented their first flat-screen TVs, from January 1997 they could actually be bought. A Fujitsu plasma panel with a diagonal of 1.06 meters (42 inches) and wide VGA resolution (852 x 480 pixels) was used as the screen. Whoever wanted to watch TV flat had to be well-heeled: Both companies wanted 30,000 D-Marks each for their technology demonstration.

The data give it away: the screen could not even fully display the SD TV signals common in Europe at the time with 576 visible lines. The quality of the flat debut was also otherwise modest: the image was noisy, the contrast and brightness were so-so. Even laypeople saw at first glance: Flat TVs were not a competition for the then-dominant picture tubes - they were just big and flat.

No tube competition

Still, these TVs and the screen technology used in them heralded the flat-panel era around the world. Philips and Grundig were not alone: ​​in other parts of the world, other manufacturers installed the Fujitsu panel or competing products. Hitachi, LG, Mitsubishi, NEC, and Samsung, among others, produced this type of screen at the plasma heyday; The technical leaders were Pioneer and Panasonic. They took an extra year with their plasma screens, but then dominated this market segment. The Panasonic TC-42 PD 1 E appeared at the radio exhibition in 1997 - it also only offered Wide VGA resolution, but a much better picture than the competition at the time. At a price of 32,000 DM, however, it was also outrageously expensive.

But over several generations, the humble beginnings became an ever better display technology, which for a long time was superior to the competing screens based on liquid crystal (LCD). So why did this type of screen disappear eight years ago?

The history of plasma goes as far back as that of LCDs. Technically, the screens are related to the fluorescent tubes. In the pixels of the plasma, the noble gas is ignited by a spark, which generates UV light. This hits a phosphor layer that generates the visible image. The first plasma screens were part of the main computer Plato IV in 1964; the neon used in them defined the orange color of the luminescent layer.

No flattened picture tube

Phosphorus? Tension? That sounds very similar to the principle of the picture tube - in it an electron beam fires the luminous layer and thus produces the TV picture. But there is one fundamental difference: The brightness of the picture tube is determined by the voltage of the electron beam - if a pixel is to shine brighter, more voltage is applied to the luminescent layer. A plasma pixel, on the other hand, only knows on and off - its brightness cannot be regulated via the (ignition) voltage.

Fortunately, the human eye is sluggish. You can not only fool him into movements, but also brightness levels. If the pixels are switched on and off differently often using pulse width modulation (PWM), the currently required brightness can be displayed. This is how the adventurous frequency specifications for plasma TVs came about. In the case of picture tubes, doubling the refresh rate from 50 to 100 Hertz (Hz) produced a calmer picture. The plasma panels actually only showed 50 Hz. But because they did this in twelve steps to display the different brightness levels, the manufacturers advertised "600 Hz".

Despite the PWM technology, the plasma panels did not manage to reproduce all shades of the TV picture - this was only possible through artificially interspersed noise ("dithering"). At first, the algorithms for the display control were quite crude; accordingly, the noise made itself noticeably disturbing. Many early plasma displays also showed a kind of solarization effect at certain image brightnesses.

Intoxicating pictures

In this stone age flat-screen TV, plasma-sized liquid crystal displays (LCD) were simply not available. And those who existed also had massive teething troubles. The panels were too sluggish for TV pictures; accordingly smeared movements; the Solarization effects could also be clearly seen on them.

Plasma screens were the quickest way to eliminate the problems of the first generation. They also have fundamental advantages: As an active display, your image is independent of the viewing angle. LCDs, on the other hand, are light valves that control the glow of a light source. This changes the image impression depending on the viewing angle. Another weakness of LCDs is related to their principle: They never completely block the light from their backlighting; dark parts of the image, therefore, appear rather cloudy-gray. The plasma screens, on the other hand, were soon able to achieve almost perfect black - "almost" because they would not work without a certain basic voltage and therefore brightness; On some models, the dithering was also noticeable in dark areas.

Better with 2D and 3D

Nevertheless: For the typical TV situation with rather subdued light, plasmas were ideal and qualitatively most likely at eye level with picture tubes. But that's not all: with the attempts to establish 3D in the TV market, which began in 2009, they also demonstrated their superiority in interaction with LCD shutter glasses. With this 3D technology, LCD TVs tend to have ghost contours.

But nothing helped. The Koreans said goodbye to their plasma panels; in Japan only Pioneer and Panasonic made plasma - in 2008 Panasonic took over the panel business (and a large part of the developers) from Pioneer, becoming the last advocate of the technology.

One reason for the decline of the plasma panels was their supposedly high power consumption, said Rainer Zwing, formerly responsible for the improvement of plasma TVs at Thomson (now: Technicolor) and today managing director of the video software company CRS iiMotion, in an interview: "Very few consumers understood that the information on the nameplates initially stated the maximum power consumption and not the actual average consumption. LCDs of the same size, as long as neon tubes acted as background light, were at a similar level as plasmas in TV operation - often enough even lightly about that."

Dirk Schulze, who was part of the company's product marketing department when the Panasonic TC-42 PD 1 E was launched and is now marketing director for TV and home AV, agrees: "The EU's Ecodesign Directive was a nail in the coffin for plasma technology. As a result, the energy efficiency of plasma TVs was rated with C or D. Unfortunately, it was not clear to consumers that in practice this only meant additional electricity costs of 10 to 20 euros per year. "

Power consumption overrated

The sales situation in the store also worked against plasma TVs. Most of the shops are rather bright; the customers stand further away from the screens than they later sit away at home. Practically all TV manufacturers, therefore, implement a brightly colored shop image mode that should signal from a distance: "Buy me!" Compared to the LCDs, the background light of which can be almost unlimited, the plasmas fell behind.

Connoisseurs knew about these pseudo weaknesses and continued to buy plasmas for their home theaters - but the majority of customers opted for LCD. When the industry wanted to lure customers with UHD resolution (3840 x 2160 pixels) after the failed 3D attempt, the game was over: Panasonic still made headlines with a 3.81 meter UHD plasma. But in the typical living room screen diagonals (1.40 / 1.65 meters; 55/65 inches), UHD with plasma is not feasible. The light output would be too low; the power consumption is too high. In addition, the LCDs had caught up: thanks to light-emitting diodes as background light, their power consumption was now below that of plasma TVs even under realistic conditions, black and viewing angle dependency had improved. The LC panels tumbled and tumbled off the production lines at low prices.

Happiness and glass ...

Two further weak points of plasmas: It doesn't work without glass - it's heavy and prone to breakage. And if you don't use the displays as a television, but as a computer monitor or information display; If one and the same motif is on the screen for a long time, it is branded.

Rainer Zwing mentions another reason why, in his opinion, Plasma failed. "In contrast to LCD technology, there was never a comparable exchange between the initially numerous manufacturers in the plasma sector, technical details were fearfully guarded. LCD manufacturers, on the other hand, often patented their technologies - but competitors could use them or better alternatives to develop."

The plasma TV phase only lasted 17 years - but its end heralded the triumph of organic light-emitting diodes (OLED). Panasonic man Schulze: "It's a shame that plasma couldn't hold up - but OLED TVs with their self-luminous pixels are their legitimate successors."

Post a Comment