The era of the tube
For most of the twentieth century, a television was a box with a glass tube inside. In a cathode-ray tube (CRT), an electron gun fires a beam at a phosphor-coated screen, and magnetic fields sweep it across line after line. Karl Ferdinand Braun built an early cathode ray tube in 1897, and the same family of cathode ray tubes was adapted for television in the 1920s and 1930s. It was a successful design. The tubes were bright, produced rich contrast, and could be manufactured in large numbers.
It also had a built-in limitation. A tube has to be deep enough for the beam to reach the corners of the screen, so a larger picture meant a deeper, much heavier set. The glass was thick, since it had to hold a vacuum. Consumer CRT sets reached roughly 30 to 40 inches diagonally at the high end, and the biggest were very heavy. Beyond that size, projection systems took over. A cabinet that took up a corner of a room was normal.
Early ideas for flat screens
Engineers imagined a flat television, a picture hung on the wall, long before it was practical. Several technologies were studied through the middle of the century.
Plasma displays began at the University of Illinois in 1964, where Donald Bitzer, Gene Slottow and colleagues built a small panel. In plasma, each pixel is a tiny cell containing gas. An electric charge turns the gas into plasma that emits ultraviolet light, which excites a phosphor to glow in red, green or blue. The early panels were monochrome and used in computer terminals.
Liquid crystal displays (LCDs) do not make light themselves. Liquid crystals are materials whose molecules can be twisted by an electric field, changing how they pass polarized light. Research in the 1960s, including work at RCA, showed that this effect could form images, and in the early 1970s the twisted nematic design made practical, low-power displays. These first appeared in calculators and digital watches. Making a large, fast, full-color display with them was a far harder problem, and it took decades of improvement in materials and manufacturing.
Plasma and LCD on the market
Large flat-screen displays reached consumers in the late 1990s. Plasma was first. Fujitsu and other makers launched wall-hanging plasma sets of around 40 inches in 1997 and 1998, at prices that were very high and out of reach for most households. Early LCD televisions were small, and mostly sold as portable or kitchen sets.
For several years, plasma had the edge in large sizes, with strong contrast and wide viewing angles, while LCD had advantages in weight, power use and sizes below about 40 inches. Over the 2000s, improvements in LCD manufacturing made bigger panels affordable. LCD makers expanded production lines, and costs fell fast. By around 2007 or 2008, LCD sets were selling in greater numbers than CRT sets in many markets, and plasma lost ground to LCD in the larger sizes as well. Some major manufacturers stopped making plasma sets in the early-to-mid 2010s.
LED backlights and OLED
Another change came in lighting. Early LCD televisions used fluorescent tubes for backlighting. From the late 2000s, makers switched to light emitting diodes, which allowed thinner cabinets, lower power use and, in some designs, adjusting the backlight in zones to improve dark scenes. These sets were often marketed as “LED televisions”, although the screens were still LCD panels with an LED backlight.
Organic light-emitting diode (OLED) panels take a different approach. Each pixel makes its own light, which allows true black and very thin panels. OLED televisions reached the consumer market in the 2010s, mainly at the high end, and they compete with improved LCD systems. Quantum-dot films and mini-LED backlights are among later refinements. The competition continues and the details change quickly.
What changed in the living room
The switch to flat panels altered how people arranged their homes.
- Furniture: The bulky television cabinet and its deep corner shelf gave way to low stands and wall mounts. Many households put the screen over a fireplace or on a bracket.
- Size: Because panels were lighter per inch, screens of 50 inches and more became common. Rooms were rearranged for larger pictures and more distant viewing.
- Shape: Old sets used a 4:3 shape. Wide-screen sets with a 16:9 ratio matched digital broadcasts and films, and made letterboxed pictures less common.
- Sources: Thin sets were designed with HDMI and other digital inputs for game consoles, disc players and streaming boxes.
- Resolution: High-definition and later 4K displays became standard, with more pixels than a CRT could show clearly.
The disposal of old sets also became an issue. Old CRT sets contain leaded glass, and many places now have recycling rules for them.
Not the end of the story
The television is now partly a computer, with built-in apps and an internet connection. The shapes of rooms, the habits of viewers and the technology inside the panel all continue to change, and the CRT, which dominated the century before, has become a rare item. Yet some of its ideas survive: a modern display still builds an image from a grid of colored points, refreshed many times each second.