Chester Carlson, the inventor of photocopying, was originally a patent attorney, as well as a part-time researcher and inventor. His job at the patent office in New York required him to make a large number of copies of important papers. Carlson, who was arthritic, found this to be a painful and tedious process. This motivated him to conduct experiments with photoconductivity. Carlson used his kitchen for his “electrophotography” experiments, and, in 1938, he applied for a patent for the process. He made the first photocopy using a zinc plate covered with sulfur. The words “10-22-38 Astoria” were written on a microscope slide, which was placed on top of more sulfur and under a bright light. After the slide was removed, a mirror image of the words remained. Carlson tried to sell his invention to some companies but failed because the process was still underdeveloped. At the time, multiple copies were most commonly made at the point of document origination, using carbon paper or manual duplicating machines, and people did not see the need for an electronic machine. Between 1939 and 1944, Carlson was turned down by over 20 companies, including IBM and General Electric—neither of which believed there was a significant market for copiers.
In 1944, the Battelle Memorial Institute, a non-profit organization in Columbus, Ohio, contracted with Carlson to refine his new process. Over the next five years, the institute conducted experiments to improve the process of electrophotography. In 1947, Haloid Corporation (a small New York-based manufacturer and seller of photographic paper) approached Battelle to obtain a license to develop and market a copying machine based on this technology.
Haloid felt that the word “electrophotography” was too complicated and did not have good recall value. After consulting a professor of classical language at Ohio State University, Haloid and Carlson changed the name of the process to “xerography”, which was derived from Greek words that meant “dry writing”. Haloid called the new copier machines “Xerox Machines” and, in 1948, the word “Xerox” was trademarked. Haloid eventually changed its name to Xerox Corporation.
In 1949, Xerox Corporation introduced the first xerographic copier called the Model A. Defeating computer leader IBM, Xerox became so successful that, in North America, photocopying came to be popularly known as “xeroxing”. Xerox has actively fought to prevent “Xerox” from becoming a genericized trademark. While the word “Xerox” has appeared in some dictionaries as a synonym for photocopying, Xerox Corporation typically requests that such entries be modified and that people not use the term “Xerox” in this way.
In the early 1950s, Radio Corporation of America (RCA) introduced a variation on the process called Electrofax, whereby images are formed directly on specially coated paper and rendered with a toner dispersed in a liquid.
During the 1960s and through the 1980s, Savin Corporation developed and sold a line of liquid-toner copiers that implemented a technology based on patents held by the company.
Before the widespread adoption of xerographic copiers, photo-direct copies produced by machines such as Kodak’s Verifax were used. A primary obstacle associated with the pre-xerographic copying technologies was the high cost of supplies: a Verifax print required supplies costing US$0.15 in 1969, while a Xerox print could be made for $0.03 including paper and labour. The coin-operated Photostat machines still found in some public libraries in the late 1960s made letter-size copies for $0.25 each, at a time when the minimum wage for a US worker was $1.65 per hour; the Xerox machines that replaced them typically charged $0.10.
Xerographic copier manufacturers took advantage of a high perceived value of the 1960s and early 1970s and marketed paper that was “specially designed” for xerographic output. By the end of the 1970s, paper producers made xerographic “run ability” one of the requirements for most of their office paper brands.
Some devices sold as photocopiers have replaced the drum-based process with inkjet or transfer film technology.
Among the key advantages of photocopiers over earlier copying technologies is their ability:
- to use plain (untreated) office paper;
- to implement duplex (or two-sided) printing;
- to scan several pages automatically with an ADF; and,
- eventually, to sort and/or staple output.
Coloured toner became available in the 1950s, although full-colour copiers were not commercially available until 3M released the Colour-in-Colour copier in 1968, which used a dye sublimation process rather than conventional electrostatic technology. The first electrostatic colour copier was released by Xerox (the 6500) in 1973. Colour photocopying is a concern to governments, as it facilitates counterfeiting currency and other documents: for more information, see Counterfeiting section.
There is an increasing trend for new photocopiers to implement digital technology, thereby replacing the older analogue technology. With digital copying, the copier effectively consists of an integrated scanner and laser printer. This design has several advantages, such as automatic image quality enhancement and the ability to “build jobs” (that is, to scan page images independently of the process of printing them). Some digital copiers can function as high-speed scanners; such models typically offer the ability to send documents via email or to make them available on file servers.
A major advantage of digital copier technology is “automatic digital collation”. For example, when copying a set of 20 pages 20 times, a digital copier scans each page only once, then uses the stored information to produce 20 sets. In an analogue copier, either each page is scanned 20 times (a total of 400 scans), making one set at a time, or 20 separate output trays are used for the 20 sets.
Low-end copiers also use digital technology but tend to consist of a standard PC scanner coupled to an inkjet or low-end laser printer, both of which are far slower than their counterparts in high-end copiers. However, low-end scanner-inkjets can provide colour copying at a lower upfront purchase price but with a much higher cost per copy. Combined digital scanner-printers sometimes have built-in fax machines and are known as multifunction printers.