Neon lighting

Neon lighting consists of brightly glowing, electrified glass tubes or bulbs that contain rarefied neon or other gases. Neon lights are a type of cold cathode gas-discharge light. A neon tube light is a sealed glass tube with a metal electrode at each end, filled with one of a number of gases at low pressure. A high potential of several thousand volts applied to the electrodes ionizes the gas in the tube, causing it to emit colored light by fluorescence. The color of the light depends on the gas in the tube. Neon lights were named for neon, a noble gas which gives off a popular red light, but other gases and chemicals are used to produce other colors, such as helium (yellow), carbon dioxide (white), and mercury (blue). Neon tubes can be fabricated in curving artistic shapes, to form letters or pictures. They are mainly used to make dramatic, multicolored glowing signage for advertising, called neon signs, which were popular from the 1920s to the 1950s.

The term can also refer to the miniature neon glow lamp, developed in 1917, about seven years after neon tube lighting.

 While neon tube lights are typically meters long, the neon lamps can be less than one centimeter in length and glow much more dimly than the tube lights. Through the 1970s, neon glow lamps were widely used for displays in electronics, for small decorative lamps, and as electronic devices in themselves. While these lamps are now antiques, the technology of the neon glow lamp developed into contemporary plasma displays and televisions.

Georges Claude, a French engineer and inventor, presented neon tube lighting in essentially its modern form at the Paris Motor Show from December 3–18, 1910. Claude, sometimes called "the Edison of France", had a near monopoly on the new technology, which became very popular for signage and displays in the period 1920-1940. Neon lighting was an important cultural phenomenon in the United States in that era; by 1940, the downtowns of nearly every city in the US were bright with neon signage, and Times Square in New York City was known worldwide for its neon extravagances. There were 2000 shops nationwide designing and fabricating neon signs. The popularity, intricacy, and scale of neon signage for advertising declined in the U.S. following the Second World War (1939–1945), but development continued vigorously in Japan, Iran, and some other countries. In recent decades architects and artists, in addition to sign designers, have again adopted neon tube lighting as a component in their works.

Neon lighting is closely related to fluorescent lighting, which developed about 25 years after neon tube lighting. In fluorescent lights, the light emitted by rarefied gases within a tube is used exclusively to excite fluorescent materials that coat the tube, which then shine with their own colors that become the tube's visible, usually white, glow. Fluorescent coatings and glasses are also an option for neon tube lighting, but are usually selected to obtain bright colors.

Neon is a chemical element and an inert gas that is a minor component of the Earth's atmosphere. It was discovered in 1898 by William Ramsay and Morris W. Travers. When Ramsay and Travers had succeeded in obtaining some pure neon from the atmosphere, they explored its properties using an "electrical gas-discharge" tube that was similar to the tubes used today for neon signs. Travers later wrote, "the blaze of crimson light from the tube told its own story and was a sight to dwell upon and never forget." The procedure of examining the colors of the light emitted from gas-discharge (or "Geissler" tubes) was well-known at the time, since the colors of light (the "spectral lines") emitted by a gas discharge tube are, essentially, fingerprints that identify the gases inside.

Immediately following neon's discovery, neon tubes were used as scientific instruments and novelties. However, the scarcity of purified neon gas precluded its prompt application for electrical gas-discharge lighting along the lines of Moore tubes, which used more common nitrogen or carbon dioxide as the working gas, and enjoyed some commercial success in the US in the early 1900s. After 1902, Georges Claude's company in France, Air Liquide, began producing industrial quantities of neon essentially as a byproduct of the air liquefaction business. From December 3–18, 1910, Claude demonstrated two large (12 metres (39 ft) long), bright red neon tubes at the Paris Motor Show. These neon tubes were essentially in their contemporary form. The range of outer diameters for the glass tubing used in neon lighting is 9 to 25 mm; with standard electrical equipment, the tubes can be as long as 30 metres (98 ft). The pressure of the gas inside is in the range 3-20 Torr (0.4-3 kPa), which corresponds to a partial vacuum in the tubing. Claude had also solved two technical problems that substantially shortened the working life of neon and some other gas discharge tubes, and effectively gave birth to a neon lighting industry. In 1915 a US patent was issued to Claude covering the design of the electrodes for gas-discharge lighting; this patent became the basis for the monopoly held in the US by his company, Claude Neon Lights, for neon signs through the early 1930s.

Claude's patents envisioned the use of gases such as argon and mercury vapor to create different colors beyond those produced by neon. In the 1920s, fluorescent glasses and coatings were developed to further expand the range of colors and effects for tubes with argon gas or argon-neon mixtures; generally, the fluorescent coatings are used with an argon/mercury-vapor mixture, which emits ultraviolet light that activates the fluorescent coatings. By the 1930s, the colors from combinations of neon tube lights had become satisfactory for some general interior lighting applications, and achieved some success in Europe, but not in the US. Since the 1950s, the development of phosphors for color televisions has created nearly 100 new colors for neon tube lighting.

Around 1917, Daniel McFarlan Moore, then working at the General Electric Company, developed the miniature neon lamp. The glow lamp has a very different design than the much larger neon tubes used for signage; the difference was sufficient that a separate US patent was issued for the lamp in 1919. A Smithsonian Institution website notes, "These small, low power devices use a physical principle called "coronal discharge." Moore mounted two electrodes close together in a bulb and added neon or argon gas. The electrodes would glow brightly in red or blue, depending on the gas, and the lamps lasted for years. Since the electrodes could take almost any shape imaginable, a popular application has been fanciful decorative lamps. Glow lamps found practical use as electronic components, and as indicators in instrument panels and in many home appliances until the acceptance of Light-Emitting Diodes (LEDs) starting in the 1970s."

Although some neon lamps themselves are now antiques, and their use in electronics has declined markedly, the technology has continued to develop in artistic and entertainment contexts. Neon lighting technology has been reshaped from long tubes into thin flat panels used for plasma displays and plasma television sets.