Editing Fluorescent lamp (section)

==History==
===Physical discoveries===
====Fluorescence====
The [[fluorescence]] of certain rocks and other substances had been observed for hundreds of years before its nature was understood. One of the first to explain it was Irish scientist [[Sir George Stokes, 1st Baronet|Sir George Stokes]] from the [[University of Cambridge]] in 1852, who named the phenomenon "fluorescence" after [[fluorite]], a mineral many of whose samples glow strongly because of impurities.

====Discharge tubes====
By mid-19th century, experimenters had observed a radiant glow emanating from partially evacuated glass vessels through which an [[electric current]] passed. The explanation relied on the nature of electricity and light phenomena as developed by the British scientists [[Michael Faraday]] in the 1840s and [[James Clerk Maxwell]] in the 1860s.<ref>Gribben, John; "The Scientists; A History of Science Told Through the Lives of Its Greatest Inventors"; [[Random House]]; 2004; pp 424–432; {{ISBN|978-0-8129-6788-3}}</ref>

Little more was done with this phenomenon until 1856 when German glassblower [[Heinrich Geissler]] created a [[mercury vacuum pump]] that evacuated a glass tube to an extent not previously possible.  Geissler invented the first gas-discharge lamp, the [[Geissler tube]], consisting of a partially evacuated glass tube with a metal [[electrode]] at either end.  When a high voltage was applied between the electrodes, the inside of the tube illuminated with a [[glow discharge]].  By putting different chemicals inside, the tubes could be made to produce a variety of colors, and elaborate Geissler tubes were sold for entertainment. More important was its contribution to scientific research. One of the first scientists to experiment with a Geissler tube was [[Julius Plücker]], who systematically described in 1858 the luminescent effects that occurred in a Geissler tube. He also made the important observation that the glow in the tube shifted position when in proximity to an [[electromagnetic field]]. [[Alexandre Edmond Becquerel]] observed in 1859 that certain substances gave off light when they were placed in a Geissler tube. He went on to apply thin coatings of luminescent materials to the surfaces of these tubes. Fluorescence occurred, but the tubes were inefficient and had a short operating life.{{sfn|Bright|1949|pp=381–385}}

Inquiries that began with the Geissler tube continued as better vacuums were produced. The most famous was the evacuated tube used for scientific research by [[William Crookes]]. That tube was evacuated by the highly effective mercury [[Sprengel pump|vacuum pump]] created by [[Hermann Sprengel]]. Research conducted by Crookes and others ultimately led to the discovery of the [[electron]] in 1897 by [[J. J. Thomson]] and [[X-rays]] in 1895 by [[Wilhelm Röntgen]]. The [[Crookes tube]], as it came to be known, produced little light because the vacuum in it was too great and thus lacked the trace amounts of gas that are needed for electrically stimulated [[luminescence]].

===Early discharge lamps===
[[Image:Early Cooper Hewitt mercury vapor lamp.jpg|thumb|upright|One of the first [[mercury vapor lamp]]s invented by [[Peter Cooper Hewitt]], 1903. It was similar to a fluorescent lamp without the fluorescent coating on the tube and produced greenish light. The round device under the lamp is the [[ballast (electrical)|ballast]]. ]]

[[Thomas Edison]] briefly pursued fluorescent lighting for its commercial potential. He invented a fluorescent lamp in 1896 that used a coating of [[Scheelite|calcium tungstate]] as the fluorescing substance, excited by [[X-rays]]. Although it received a patent in 1907,<ref>{{patent|US|865367}} ''Fluorescent Electric Lamp''</ref> it was not put into production. As with a few other attempts to use Geissler tubes for illumination, it had a short operating life, and given the success of the incandescent light, Edison had little reason to pursue an alternative means of electrical illumination. [[Nikola Tesla]] made similar experiments in the 1890s, devising high-frequency powered fluorescent bulbs that gave a bright greenish light, but as with Edison's devices, no commercial success was achieved.

One of Edison's former employees created a gas-discharge lamp that achieved a measure of commercial success. In 1895 [[Daniel McFarlan Moore]] demonstrated lamps {{convert|2|to|3|m|ft|sp=us}} in length that used [[carbon dioxide]] or [[nitrogen]] to emit white or pink light, respectively. They were considerably more complicated than an incandescent bulb, requiring both a high-voltage power supply and a pressure-regulating system for the fill gas.<ref name=etheric>{{cite news |title=Mr. Moore's Etheric Light. The Young Newark Electrician's New And Successful Device. |url=https://www.nytimes.com/1896/10/02/archives/mr-moores-etheric-light-the-young-newark-electricians-new-and.html |newspaper=New York Times |date=October 2, 1896 |access-date=2008-05-26 |archive-date=2018-07-25  |archive-url=https://web.archive.org/web/20180725215030/https://www.nytimes.com/1896/10/02/archives/mr-moores-etheric-light-the-young-newark-electricians-new-and.html |url-status=live }} Paid access.</ref>

[[File:Peter Cooper Hewitt.jpg|thumb|upright|[[Peter Cooper Hewitt]]]]
Moore invented an electromagnetically controlled valve that maintained a constant gas pressure within the tube, to extend the working life.<ref>{{cite book |title=Modern illuminants and illuminating engineering |last1=Gaster |first1=Leon |last2=Dow |first2=John Stewart |date=1915 |publisher=Whittaker & Co. |url=https://archive.org/details/modernilluminan01dowgoog |pages=[https://archive.org/details/modernilluminan01dowgoog/page/n127 107]–111}}</ref> Although Moore's lamp was complicated, expensive, and required very high voltages, it was considerably more efficient than incandescent lamps, and it produced a closer approximation to natural daylight than contemporary incandescent lamps. From 1904 onwards Moore's lighting system was installed in a number of stores and offices.{{sfn|Bright|1949|pp=221–223}} Its success contributed to [[General Electric]]'s motivation to improve the incandescent lamp, especially its filament. GE's efforts came to fruition with the invention of a [[tungsten]]-based filament. The extended lifespan and improved efficacy of incandescent bulbs negated one of the key advantages of Moore's lamp, but GE purchased the relevant patents in 1912. These patents and the inventive efforts that supported them were of considerable value when the firm took up fluorescent lighting more than two decades later.

At about the same time that Moore was developing his lighting system, [[Peter Cooper Hewitt]] invented the [[mercury-vapor lamp]], patented in 1901 ({{patent|US|682692}}). Hewitt's lamp glowed when an electric current was passed through mercury vapor at a low pressure. Unlike Moore's lamps, Hewitt's were manufactured in standardized sizes and operated at low voltages. The mercury-vapor lamp was superior to the incandescent lamps of the time in terms of [[Efficient energy use|energy efficiency]], but the blue-green light it produced limited its applications. It was, however, used for photography and some industrial processes.

Mercury vapor lamps continued to be developed at a slow pace, especially in Europe. By the early 1930s they received limited use for large-scale illumination. Some of them employed fluorescent coatings, but these were used primarily for color correction and not for enhanced light output. Mercury vapor lamps also anticipated the fluorescent lamp in their incorporation of a ballast to maintain a constant current.

Cooper-Hewitt had not been the first to use mercury vapor for illumination, as earlier efforts had been mounted by Way, Rapieff, Arons, and Bastian and Salisbury. Of particular importance was the mercury-vapor lamp invented by Küch and Retschinsky in [[Germany]]. The lamp used a smaller bore bulb and higher current operating at higher pressures. As a consequence of the current, the bulb operated at a higher temperature which necessitated the use of a quartz bulb. Although its light output relative to electrical consumption was better than that of other sources of light, the light it produced was similar to that of the Cooper-Hewitt lamp in that it lacked the red portion of the spectrum, making it unsuitable for ordinary lighting. Due to difficulties in sealing the electrodes to the quartz, the lamp had a short life.<ref>{{Cite web |url=http://lamptech.co.uk/Documents/M7%20Kuch%20%26%20Retschinsky.htm |title=Article about Küch and Retschinsky lamp |access-date=2020-06-23  |archive-date=2020-06-11  |archive-url=https://web.archive.org/web/20200611162322/http://lamptech.co.uk/Documents/M7%20Kuch%20%26%20Retschinsky.htm |url-status=live }}</ref>

===Neon lamps===
{{main|Neon lamp|Neon lighting}}

The next step in gas-based lighting took advantage of the luminescent qualities of [[neon]], an inert gas that had been discovered in 1898 by isolation from the atmosphere. Neon glowed a brilliant red when used in Geissler tubes.<ref>{{cite book |title=Discovery of the Elements: Third Edition (reprint) |last=Weeks |first=Mary Elvira |author-link=Mary Elvira Weeks |year=2003 |publisher=[[Kessinger Publishing]] |url=https://books.google.com/books?id=SJIk9BPdNWcC&pg=PA287 |page=287 |isbn=978-0-7661-3872-8 }}{{Dead link|date=April 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> By 1910, [[Georges Claude]], a Frenchman who had developed a technology and a successful business for air liquefaction, was obtaining enough neon as a byproduct to support a neon lighting industry.<ref name=Claude1913>{{cite journal |last=Claude |first=Georges |title=The Development of Neon Tubes |journal=The Engineering Magazine |date=November 1913 |pages=271–274 |url=https://books.google.com/books?id=erpMAAAAYAAJ&pg=PA271 |access-date=2016-10-01  |archive-date=2023-04-20  |archive-url=https://web.archive.org/web/20230420064854/https://books.google.com/books?id=erpMAAAAYAAJ&pg=PA271 |url-status=live }}</ref><ref name=vanDulken>{{cite book |title=Inventing the 20th century: 100 inventions that shaped the world : from the airplane to the zipper |last1=van Dulken |first1=Stephen |page=42 |publisher=New York University Press |date=2002 |isbn=978-0-8147-8812-7 |url=https://books.google.com/books?id=aVHRRoQvW60C&pg=PA42}}</ref> While neon lighting was used around 1930 in France for general illumination, it was no more energy-efficient than conventional incandescent lighting. Neon tube lighting, which also includes the use of argon and mercury vapor as alternative gases, came to be used primarily for eye-catching signs and advertisements. Neon lighting was relevant to the development of fluorescent lighting, however, as Claude's improved electrode (patented in 1915) overcame "sputtering", a major source of electrode degradation. Sputtering occurred when ionized particles struck an electrode and tore off bits of metal. Although Claude's invention required [[electrodes]] with a lot of surface area, it showed that a major impediment to gas-based lighting could be overcome.

The development of the neon light also was significant for the last key element of the fluorescent lamp, its fluorescent coating.{{sfn|Bright|1949|pp=369–374}} In 1926 Jacques Risler received a French patent for the application of fluorescent coatings to neon light tubes.{{sfn|Bright|1949|p=385}} The main use of these lamps, which can be considered the first commercially successful fluorescents, was for advertising, not general illumination. This, however, was not the first use of fluorescent coatings; Becquerel had earlier used the idea and Edison used calcium tungstate for his unsuccessful lamp.<ref>{{Cite book |url=https://books.google.com/books?id=XcRPQcc0vU0C&q=Becquerel+%22Fluorescent+Lamp%22+Coating&pg=PA283 |title=Building Systems for Interior Designers – Corky Binggeli – Google Books |access-date=2016-06-05 |isbn=9780470228470 |last1=Binggeli |first1=Corky |year=2010 |publisher=John Wiley & Sons |archive-date=2023-04-20  |archive-url=https://web.archive.org/web/20230420064855/https://books.google.com/books?id=XcRPQcc0vU0C&q=Becquerel+%22Fluorescent+Lamp%22+Coating&pg=PA283 |url-status=live }}</ref><ref>{{Cite book |url=https://books.google.com/books?id=0i-SmPtmJDIC&q=Becquerel+%22Fluorescent+Coating%22&pg=PT163 |title=Uncle Tungsten: Memories of a Chemical Boyhood – Oliver Sacks – Google Books |date=2011-06-16 |access-date=2016-06-05 |isbn=9780330537216 |last1=Sacks |first1=Oliver |publisher=Pan Macmillan |archive-date=2023-04-20  |archive-url=https://web.archive.org/web/20230420064854/https://books.google.com/books?id=0i-SmPtmJDIC&q=Becquerel+%22Fluorescent+Coating%22&pg=PT163 |url-status=live }}</ref><ref>{{cite web |url=http://www.ies.org/lighting/history/timeline-of-lighting.cfm |title=Discover Lighting! History > Milestones in Lighting |publisher=Ies.org |access-date=2016-06-05 |archive-url=https://web.archive.org/web/20160604153528/http://www.ies.org/lighting/history/timeline-of-lighting.cfm |archive-date=2016-06-04 |url-status=dead }}</ref> Other efforts had been mounted, but all were plagued by low efficiency and various technical problems. Of particular importance was the invention in 1927 of a low-voltage “metal vapor lamp” by Friedrich Meyer, Hans-Joachim Spanner, and [[Edmund Germer]], who were employees of a German firm in [[Berlin]]. A German patent was granted but the lamp never went into commercial production.

===Commercialization of fluorescent lamps===
All the major features of fluorescent lighting were in place at the end of the 1920s. Decades of invention and development had provided the key components of fluorescent lamps: economically manufactured glass tubing, inert gases for filling the tubes, electrical ballasts, long-lasting electrodes, mercury vapor as a source of luminescence, effective means of producing a reliable electrical discharge, and fluorescent coatings that could be energized by ultraviolet light. At this point, intensive development was more important than basic research.

In 1934, [[Arthur Compton]], a renowned physicist and GE consultant, reported to the GE lamp department on successful experiments with fluorescent lighting at [[General Electric Company plc|General Electric Co., Ltd.]] in Great Britain (unrelated to General Electric in the United States). Stimulated by this report, and with all of the key elements available, a team led by George E. Inman built a prototype fluorescent lamp in 1934 at [[General Electric]]'s [[Nela Park]] (Ohio) engineering laboratory. This was not a trivial exercise; as noted by Arthur A. Bright, "A great deal of experimentation had to be done on lamp sizes and shapes, cathode construction, gas pressures of both argon and mercury vapor, colors of fluorescent powders, methods of attaching them to the inside of the tube, and other details of the lamp and its auxiliaries before the new device was ready for the public."{{sfn|Bright|1949|pp=388–391}}

In addition to having engineers and technicians along with facilities for R&D work on fluorescent lamps, General Electric controlled what it regarded as the key patents covering fluorescent lighting, including the patents originally issued to Hewitt, Moore, and Küch. More important than these was a patent covering an [[electrode]] that did not disintegrate at the gas pressures that ultimately were employed in fluorescent lamps. Albert W. Hull of GE's Schenectady Research Laboratory filed for a patent on this invention in 1927, which was issued in 1931.<ref>{{ref patent| country=US |number=1790153 |status=patent |title=Electrical Discharge Device and Method of Operation |gdate=1931-01-27 |fdate=1927-10-15 |invent1=Albert W. Hull |invent2= |assign1=General Electric Company }}</ref> General Electric used its control of the patents to prevent competition with its incandescent lights and probably delayed the introduction of fluorescent lighting by 20 years. Eventually, war production required 24-hour factories with economical lighting, and fluorescent lights became available.

While the Hull patent gave GE a basis for claiming [[legal]] rights over the fluorescent lamp, a few months after the lamp went into production the firm learned of a U.S. patent application that had been filed in 1927 for the aforementioned "metal vapor lamp" invented in Germany by Meyer, Spanner, and Germer. The patent application indicated that the lamp had been created as a superior means of producing ultraviolet light, but the application also contained a few statements referring to fluorescent illumination. Efforts to obtain a U.S. patent had met with numerous delays, but were it to be granted, the patent might have caused serious difficulties for GE. At first, GE sought to block the issuance of a patent by claiming that priority should go to one of their employees, Leroy J. Buttolph, who according to their claim had invented a fluorescent lamp in 1919 and whose patent application was still pending. GE also had filed a patent application in 1936 in Inman's name to cover the “improvements” wrought by his group. In 1939 GE decided that the claim of Meyer, Spanner, and Germer had some merit, and that in any event a long interference procedure was not in their best interest. They therefore dropped the Buttolph claim and paid $180,000 to acquire the Meyer, et al. application, which at that point was owned by a firm known as Electrons, Inc. The patent was duly awarded in December 1939.<ref>{{ref patent| country=US |number=2182732 |status=patent |title=Metal Vapor Lamp |gdate=1939-12-05 |fdate=1927-12-19  |invent1=Friedrich Meyer |invent2=Hans-Joachim Spanner |invent3=Edmund Germer |assign1=General Electric Company }}</ref>  This patent, along with the Hull patent, put GE on what seemed to be firm legal ground, although it faced years of legal challenges from [[Sylvania Electric Products]], Inc., which claimed [[Patent infringement|infringement]] on patents that it held.

Even though the patent issue was not completely resolved for many years, General Electric's strength in manufacturing and marketing gave it a pre-eminent position in the emerging fluorescent light market. Sales of "fluorescent lumiline lamps" commenced in 1938 when four different sizes of tubes were put on the market. They were used in fixtures manufactured by three leading corporations: [[Lightolier]], [[Artcraft Fluorescent Lighting Corporation]], and Globe Lighting.  The Slimline fluorescent ballast's public introduction in 1946 was by Westinghouse and General Electric and Showcase/Display Case fixtures were introduced by Artcraft Fluorescent Lighting Corporation in 1946.<ref>''Electrical Consultant'', Vol. 50, p. 4, 1946</ref><ref>''Westinghouse Engineer'', Vol. 12–13, p. 141, 1952</ref>  During the following year, GE and [[Westinghouse Electric Corporation (1886)|Westinghouse]] publicized the new lights through exhibitions at the [[1939 New York World's Fair|New York World's Fair]] and the [[Golden Gate International Exposition]] in San Francisco. Fluorescent lighting systems spread rapidly during World War II as wartime manufacturing intensified lighting demand. By 1951 more light was produced in the United States by fluorescent lamps than by incandescent lamps.<ref>{{cite web|url=https://americanhistory.si.edu/lighting/20thcent/prec20.htm|title=Lighting A Revolution: 20th Century Store-room|website=americanhistory.si.edu|access-date=2019-04-26 |archive-date=2018-11-09 |archive-url=https://web.archive.org/web/20181109144831/http://americanhistory.si.edu/lighting/20thcent/prec20.htm|url-status=live}}</ref>

In the first years [[zinc orthosilicate]] with varying content of [[beryllium]] was used as greenish phosphor. Small additions of magnesium tungstate improved the blue portion of the spectrum, yielding acceptable white. After the discovery that [[Berylliosis|beryllium was toxic]], halophosphate-based phosphors dominated.{{sfn|Van Broekhoven|2001|p=[https://books.google.com/books?id=klE5qGAltjAC&pg=PA97 97–98]}}