George Heilmeier, one of the principal creators of the liquid-crystal display (LCD) technology that made it possible to hang television sets on walls and carry computers in coat pockets, died April 21 at a hospital in Plano, Tex., near Dallas. He was 77.

He died after a stroke, according to his daughter, Beth Jarvie.

Dr. Heilmeier, the son of a janitor, was the first member of his family to finish high school. He went on to achieve widespread recognition for helping to pave the way toward the slender and graceful, yet prodigiously powerful, electronic devices that characterize modern life.

In 2006, he won Japan’s Kyoto Prize for achievements benefiting humanity; two years ago, he shared the Draper Prize, awarded by the National Academy of Engineering. Both are regarded as equivalents of the Nobel Prize.

The “liquid crystal” description of the materials that ­Dr. Heilmeier worked with appeared at first to be an oxymoron. Crystals carry an image of rigidity and regularity — almost exactly the opposite of liquids.

But liquid crystals can be made, and some have a particularly valuable property: They can scatter light when subjected to an electrical field. By this property, they lend themselves to incorporation in devices that translate invisible electrical signals into visible light.

Others had studied the electro-optical properties of liquid crystals and had speculated on how the crystals could be used in a display, said Benjamin Gross, a historian of science whose doctoral thesis dealt with the development of LCD technology.

But, Gross said, “George Heilmeier was the first person to transform that idea into a practical technology.”

Dr. Heilmeier organized a research group at RCA to develop clocks and similar devices using the technology. The crystal property on which his work was based was known as dynamic scattering, and the first LCD watches and calculators made use of that property.

Later, a new form of liquid-crystal display, known as the twisted nematic display, largely replaced the dynamic scattering equipment. But in a very real sense, Gross said, Dr. Heilmeier’s displays marked the beginning of the modern LCD industry.

Today’s slim, flat screens are in many ways suggestive of the video walls that appeared decades ago in memorable visions of the future created by Ray Bradbury, the celebrated author of science fiction and fantasy works.

They also formed part of the early wishes of David Sarnoff, the communications pioneer who built RCA, where much of Dr. Heilmeier’s work was done. It was Sarnoff who in the early 1950s, when TV sets were hulking items that housed massive cathode-ray tubes, proposed that sets that could hang on a wall, like a painting.

Although he brought dreams to life, Dr. Heilmeier was also a hard-headed realist. His list of questions to be put to anyone proposing a new product was widely circulated in the engineering world as an example of no-nonsense decision-making.

The questions were on the order of, “Who cares?...what difference will it make?” and “How much will it cost? How long will it take?

In 1975, Dr. Heilmeier joined the Defense Department as head of the Defense Advanced Research Projects Agency. DARPA has acquired a reputation for developing weapons and military devices that turn up on battlefields and in news reports decades after they were conceived, such as radar-eluding stealth technology and smart bombs.

After two years at DARPA, Dr. Heilmeier returned to private industry, first with Dallas-based Texas Instruments and later at Bellcore, a research company in Morristown, N.J.

George Harry Heilmeier was born May 22, 1936, in Philadelphia. He attended the University of Pennsylvania on scholarship, receiving a bachelor’s degree in electrical engineering in 1958.

While working at RCA, he obtained three graduate degrees at Princeton University, including a doctorate in 1962.

Dr. Heilmeier’s daughter said “it was the Christian character of my dad” as well as his ability to put his head down and push forward with the work at hand that played major roles in his contributions.

In addition to his daughter, Beth Jarvie, Dr. Heilmeier is survived by his wife of 52 years, the former Janet Faunce; and three grandchildren.

Dr. Heilmeier’s many honors included the National Medal of Science in 1991; the Optical Society of America’s Edwin H. Land Medal; and the Medal of Honor from the Institute of Electrical and Electronics Engineers.

He seemed to lack pretense or self-consciousness when discussing his accomplishments. Asked by the Dallas Morning News what it was like “to invent something,” Dr. Heilmeier said, “We knew we were on to something.”

He said RCA executives came to see his invention, and “they would ooh and aah and whatnot.”