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On December 4, 1970, Martin Schadt of Switzerland and Wolfgang Helfrich of Germany – both physicists of the Swiss pharmaceutical company Hoffman-LaRoche – applied for a patent on liquid crystals (LC). That’s right: on the “spinning nematic cell” (Twisted Nematic, TN). With TN technology, they laid the foundation for LCDs in smartphones, computers and televisions as we know them today.
Botanist Friedrich Reinitzer documented the first observation of liquid crystal capacities as early as 1888. However, he only noticed the changing physical states of cholesteryl benzoate at different temperatures. Barnett and Nyman Levin, then employees of the British firm Marconi Wireless Telegraph Co., patented in 1936 that liquid crystals block or let light through, meaning they could be useful in some form as a so-called light valve for displays or screens. It wasn’t until decades later, in the 1960s, that things continued – once again in the UK: Cyril Hilsum, semiconductor physicist, head of the visualization department at the Royal Radar Institute and chair of the electron tube development committee, he conducted the research with George Gray of Hull University on liquid crystals.
Das erste Liquid Crystal Display
The trigger for their efforts was the desire of then British Research Minister John Stonehouse to develop flat screens. RRE chief George MacFarlane told the minister during his inaugural visit that British industry pays more for color cathode tube patents than it costs to develop the Concorde supersonic aircraft. At the time, the Radio Corporation of America (RCA) held all the important patents on colored tubes and in 1968 surprised the world with the first working liquid crystal display.
Martin Schadt, the inventor of LCD technology, received the European Inventor Award in 2013.
(Photo: Armin Kübelbeck, CC BY-SA 3.0)
The type of control chosen by RCA, the dynamic diffusion mode, which George H. Heilmeier, nicknamed the LCD father in professional circles, had developed a year earlier, proved to be a mistake. It was only with Schadt and Helfrich’s TN principle that the technology took the direction that led to today’s quality LC displays. The patent was granted to researchers in 21 countries, but the Federal Republic of Germany refused it. And for those at the top of RCA, the liquid crystal material was too dirty compared to semiconductors – they blocked the development of marketable products with Heilmeier’s invention.
The first commercial applications for liquid crystal displays were in calculators and quartz watch displays. Both products were previously only available with light-emitting diodes, which used a lot of electricity. With quartz wristwatches, this meant that they only revealed the time by pressing a button. With frugal LCDs, however, a permanent display wasn’t a problem.
LCD broker
However, early LCDs reacted slowly, black lines on a gray background wouldn’t even be enough for photorealistic black and white images, let alone color. Another problem: Individual image points (pixels) are checked together in the first “passive” display types. The desired image contents speak to other parts of the screen. Typical windows of graphical computer interfaces, in particular, drew ghost lines across the entire display.
Helps counter the cloudy appearance if liquid crystals are used as light valves. They block the light from a backlight or let it through. The transistors assigned to each pixel help against crosstalk. Anyone who knows the state of integrated circuit manufacturing in the early 1970s can guess what challenges manufacturers were facing. For years a large part of the production process has been waste. Until the turn of the millennium, bad pixels on computer screens were a common nuisance.
Schematic structure of a nematic rotating cell: a vertical polarizing filter layer (1) allows ambient light to pass in one direction only. The glass substrate with indium tin oxide electrodes (2) is part of the actual image converter – together with the liquid crystals (3) and the rear glass plate (4) with an additional layer of electrodes. The rear polarizing filter (5) works in the horizontal direction. A reflective film (for displays for outdoor use) or a light source – the light-emitting diodes on modern screens acts as the light source (6). In many cases, the manufacturer does not install them behind the screen, but to the side of it. Source: Wikimedia Commons
(Image: ed g2s, (CC BY-SA 3.0))
However, flat displays have won their place on or in the computer. There was and there is no alternative for notebooks: only recently have some top models with OLED displays (organic light-emitting diodes) appeared. LC monitors quickly became popular in offices, despite their initially high prices. They take up less space than bulky tube monitors and emit less heat, so air conditioning has less to do. From the late 1980s to the late 1990s, Japanese manufacturer Sharp specialized in LCD for video projectors and home theaters became fashionable in the Western world.
10,000 euros for an LCD TV
It was only after the turn of the millennium that people dared to use LCDs for televisions – production became more stable, it was possible to produce diagonally compatible screens with living rooms. However: nowadays rather tiny screen sizes such as 82cm (32in) or 1.02m (40in) were really expensive – in 2003, Samsung wanted the small sum of 10,000 euros for the LW 40A 13W. Not only this candidate was still far from acceptable quality: dark areas of the picture appeared milky and soggy on LCD TVs at that time, streaked movements, dependence on the viewing angle was extremely strong. Depending on the angle from which the screen was viewed, the visible image would completely flip with a sort of solarization effect. Since about 2010, however, liquid crystal displays have also been good enough to survive as televisions. The only real weakness remains the black display.
Developer LC Schadt received the European Inventor Award in 2013 for his discovery. Others are working around the world to eliminate the latest LCD weaknesses. Whether micro-LEDs or other technologies will win the long-term race is an open question.
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