Travelers passing through Washington D.C.’s Union Station once relied upon ticket agents or mechanical signs to determine where to catch their train. Today, such information is presented on a series of electronic screens scattered throughout the terminal, and people can obtain additional updates using their laptops or cell phones. It is therefore fitting that the National Academy of Engineering (NAE) should choose one of the nation’s busiest train stations as the site to honor four of the people responsible for the development of the liquid crystal display (LCD) and the subsequent proliferation of flat-screen technologies in our homes, offices, and public spaces.
As James D. Shields, the president and C.E.O. of the Draper Laboratories, which endows the prize, pointed out, the work of this year’s recipients certainly met those criteria. “The LCD, as you know, is used by virtually everyone in the modern world on a daily, if not hourly basis,” Shields explained. “It is the medium through which people get information on an endless variety of everyday devices including calculators, clocks, computer monitors, smart phones, and of course, television screens.”
George Heilmeier was one of those researchers. In late 1964, he initiated a series of experiments on the electro-optic properties of liquid crystals. During these investigations, he observed that under a strong electric field, certain transparent liquid crystals scattered light, appearing milky-white until the field was removed. Through the selective application of voltage, this “dynamic scattering” effect could create high-resolution static images and basic moving patterns, such as numeric counters. Heilmeier proceeded to organize an interdisciplinary research team of chemists, physicists, and electrical engineers to incorporate this effect into practical devices and demonstrated the results of their efforts at an RCA press conference in 1968.
Dynamic scattering displays were utilized in the first commercial LCD wristwatches and calculators, but RCA’s failure to invest more heavily in the technology led to the dissolution of the company’s liquid crystal research group. While Heilmeier set aside LCD work to pursue a career in government service, first as a White House Fellow and later as head of the Defense Advanced Research Projects Agency (DARPA), other members of his RCA team remained interested in the subject. One of these was physicist, and fellow Draper Prize winner, Wolfgang Helfrich.
During his time in Princeton, Helfrich devised several theoretical models intended to explain the dynamic scattering effect. He also proposed a new idea for a display, utilizing a helical structure of liquid crystal molecules to control the passage of polarized light, but RCA rejected the idea as a diversion from ongoing work on dynamic scattering.
In 1970, around the same time as Heilmeier’s departure from RCA, Helfrich took a new job at Hoffman-La Roche’s laboratory in Basel, Switzerland. There, he teamed up with solid-state physicist Martin Schadt to create a display based upon the so-called “twisted nematic” effect. Twisted nematic devices, capable of operating at significantly lower power than their dynamic scattering counterparts, soon supplanted the earlier technology and have since become the linchpin of the modern LCD industry. It is, in fact, extremely likely that you are reading this article on a twisted nematic display right now.
But before Helfrich and Schadt’s invention could find a home in your computer monitor or television set, someone had to overcome a longstanding engineering problem. As the number of pixels in a liquid crystal display increases, so too does the complexity of the circuitry required to switch those pixels on and off. Despite some promising preliminary studies by engineers at RCA, this obstacle initially limited LCD use to simpler devices like watches and calculators.
The solution to this dilemma came from Westinghouse researcher, T. Peter Brody. In 1973, Brody and his colleagues built a switching system that positioned a thin-film transistor behind each liquid crystal pixel. This new “active matrix” addressing system made it possible to show high-resolution, moving images on a flat-panel LCD. In 1979, Brody left Westinghouse to form Panelvision, the first company to commercialize active matrix technology in the United States and remained actively involved in the display industry until his death in 2011.
Three decades of additional advances in integrated circuit design and chemical engineering were needed to reconfigure Brody’s black-and-white prototype into the full-color displays we take for granted today, but by the mid-1970s the key technological elements of such devices were in place. Speaking on behalf of the surviving Draper Prize winners and representatives of Brody's family, Wolfgang Helfrich reflected upon the extent to which the LCD had transformed society since he arrived at RCA in the late 1960s. “We've all considered ourselves fortunate,” he observed, “to be involved in the beginning of a technology, which during our lifetimes has become ubiquitous.”
Benjamin Gross is a research fellow at the Chemical Heritage Foundation in Philadelphia. His Ph.D. dissertation at Princeton University looked at the development of the first liquid crystal displays at RCA.
The National Academy of Engineering's Awards Page contains further details about the Draper Prize, including biographies of all previous winners. Additional information on the evolution of LCD technology can be found at this website, hosted by Kent State University.
