A History of Revolutions in Lighting

In 2011, the United Kingdom and the Netherlands phased out the sale of incandescent bulbs. Before that, Australia, Argentina, and Italy had taken the lead in 2010. Afterwards, the list of countries banning sales expanded to include the EU, Canada, and the United States. With 2017, mainland China also phased out incandescent bulbs, and from then on, there would be no more incandescent bulbs in the country.

More than a century ago, in 1879, Edison led humanity into a brand-new "era of light" with a tungsten filament light bulb; more than a century later, the incandescent bulb, which would reach the "ripe old age" of 138 years by 2017, has grown old, ceding the broad stage to the new protagonist—the LED lamp.

The historic tungsten filament bulb

　　Most incandescent bulbs convert 90% of the energy they consume into useless heat, with less than 10% of the energy becoming light.

　　"On October 21, 1879, an American inventor finally lit the world's first practical electric lamp through long and repeated experiments. From then on, the inventor's name, just like the electric lamp he invented, entered countless households. He was Edison, who was later hailed as the 'King of Inventors'."

　　This story spread to countless households. Although some materials also mention an American named Henry Goebel who, before Edison, used carbonized bamboo filaments electrified to produce light, it was still Edison who truly attempted to experiment with more than 1,600 different heat-resistant materials and ultimately used tungsten filament as the bulb filament to produce light over long periods.

　　The tungsten filament bulb is what is traditionally known as the 'incandescent lamp.' In 1906, General Electric invented a method for manufacturing tungsten filaments for electric lamps, ultimately solving the issue of cheap tungsten filament production. Tungsten filament light bulbs entered ordinary households and have been in use ever since.

　　However, the incandescent lamp's rise and fall both stem from the tungsten filament. Subtle differences in electrical resistance along the filament cause uneven temperatures; where resistance is higher, the temperature rises more, causing the tungsten to sublimate faster, which makes the filament thinner, further increasing resistance in a cycle that ultimately causes the filament to burn out. This problem long plagued the lifespan of light bulbs until engineers discovered that replacing the vacuum with inert gas could slow the sublimation of tungsten. Today, most light bulbs are filled with nitrogen, argon, or krypton, with a typical lifespan of around 1,000 hours.

　　A century later, incandescent lamps had to face the dilemma of stepping off the historical stage. Most incandescent lamps convert 90% of their consumed energy into useless heat, with less than 10% becoming light. Such enormous waste sealed the fate of incandescent lamps, which was about to come to an end.

　　For energy conservation and environmental protection, various countries have established timetables for phasing out incandescent lamps: Australia, Argentina, and Italy took the lead in stopping the sale of incandescent lamps in 2010; the United Kingdom and the Netherlands in 2011; the EU and Canada in 2012; the United States in 2014; and mainland China will be the last to stop selling incandescent bulbs in 2017.

　　The Emergence of the Fluorescent Lamp

　　Fluorescent lamps have high luminous efficiency and a large light-emitting area. Their energy efficiency is close to 40%, and the heat they generate is only 1/6 of that of an incandescent lamp of the same brightness.

　　Standing on the shoulders of the 'giant' that was the incandescent lamp, the emergence of fluorescent lamps seemed a natural progression. In 1910, France's A. Claude invented the neon discharge lamp. He filled mercury into the lamp to create a tube emitting blue light, and later coated the inner wall of the tube with phosphor powder to create a tube emitting white light.

　　In 1939, at the New York and Los Angeles World's Fairs, the first practical fluorescent lamp was unveiled. The "fluorescent lamp," an electric light source that uses phosphor to convert the ultraviolet rays generated during low-pressure mercury vapor discharge into visible light, was officially born. Fluorescent lamps are generally made in tubular form, commonly known as "light tubes." They offer high luminous efficiency and a large light-emitting area, with an energy efficiency approaching 40%, while producing only one-sixth of the heat of an incandescent lamp of the same brightness. In addition, fluorescent lamps emit soft light, have a long service life, and can approximate daylight color or various other light colors, making them an excellent indoor lighting source.

　　Reducing the diameter of fluorescent lamp tubes improves luminous efficiency and gave rise to the "energy-saving lamp." The formal name for energy-saving lamps is rare-earth tri-color compact fluorescent lamps, which were born in the 1970s at Philips in the Netherlands. Energy-saving lamps are similar in size to incandescent lamps and use the same socket interface, so they can directly replace incandescent lamps. While delivering the same light output, these lamps consume only 1/5 to 1/4 of the electricity of ordinary incandescent lamps, saving substantial lighting energy and costs—hence the name "energy-saving lamp."

　　HID Lamps Lighting Up the Night

　　A standard HID lamp produces more than three times the luminous flux of an ordinary lamp, with color temperatures ranging from 3000K to over 12000K. It is suitable for nighttime lighting and street lighting.

　　While fluorescent lamps were being developed, another branch of light bulbs was also evolving. In 1932, high-pressure mercury lamps went on sale, marking the beginning of HID (High Intensity Discharge) lamps.

　　In 1961, Gilbert Reiling of General Electric filed the first patent for a metal halide lamp—a lamp suitable for commercial, street, and industrial lighting. Three years later, in 1964, it was exhibited at the World's Fair, stunning audiences worldwide.

　　Shortly afterward, General Electric introduced its high-pressure sodium lamp in 1965. The HID lamp family began to expand significantly. Xenon lamps broke with the tungsten-filament incandescent principle invented by Edison: high-pressure inert xenon gas is filled inside quartz arc tubes to replace the traditional filament, with mercury and carbon compounds at the two electrodes. A ballast delivers a 23,000-volt high-pressure current to stimulate the xenon to emit light.

　　The luminous flux of a standard HID lamp is over three times that of an ordinary lamp, and the color temperature of HID lamps ranges from 3000K to over 12000K. The light color around 6000K is the closest match to noon sunlight, offering the highest acceptance and comfort for the human eye. When such lighting is used for vehicle night illumination and street lighting, it effectively reduces driver visual fatigue, and the increased brightness of vehicle lights also significantly expands the visible range in front of the vehicle, thereby creating safer driving conditions.

　　LED, the Fourth-Generation Light Source

　　Some have pointed out that high-brightness LEDs will rank among the greatest inventions in human history since Edison's incandescent light bulb.

　　As we entered the 21st century, a new leading player began to emerge on the lighting stage: the LED lamp.

　　What is LED? LED stands for Light Emitting Diode, the English abbreviation for light-emitting diode. In fact, it appeared very early: the red light-emitting diode first emerged in 1964, followed by the yellow LED. It wasn't until 1994 that blue and green LEDs were successfully developed. In 1996, the Japanese company Nichia successfully developed the white LED.

　　With its inherent characteristics—such as energy efficiency, long lifespan, vibration resistance, fast response, and cold light source—LED is widely used in indicator lights, signal lights, display screens, landscape lighting, and other fields. It can be seen everywhere in our daily lives: home appliances, telephones, dashboard lighting, automotive fog lights, traffic signals, and more.

　　Initially, due to limitations such as poor brightness and high cost, LEDs could not be promoted as a general lighting source. In recent years, however, with deeper research into semiconductor luminescent materials, continuous improvements in LED manufacturing processes, and the development and application of new materials (nitride crystals and phosphors), breakthrough progress has been made in ultra-high-brightness LEDs of various colors. Their luminous efficiency has increased nearly 1,000-fold, and all colors of the visible light spectrum have been achieved in terms of chromaticity. Most importantly, the emergence of ultra-high-brightness white LEDs has made it possible for LED applications to cross over into the high-efficiency lighting source market. It has been said that high-brightness LEDs will be one of humanity's greatest inventions since Edison's invention of the incandescent light bulb.

　　"Compared with traditional lighting, current LED lighting still has many shortcomings. For example, LED light sources have high surface brightness, which can cause glare if the optical design is poor; LED lighting products have poor interchangeability, with products from different companies not being interchangeable; LED lighting products lack standards, and testing methods are still incomplete; LED lighting products are very expensive, and their cost-performance ratio is not yet ideal." Professor Zhou Taiming of the Department of Light Sources and Lighting Engineering at Fudan University pointed out in his analysis, "However, LED lighting produces no ultraviolet radiation and contains no mercury; compared with traditional lighting, LED lighting is more environmentally friendly and produces less light pollution."