Computer Printers

Information stored on computer can be read off the screen, but many people find that reading from a computer screen is more physically wearing in terms of eye strain and postural fatigue than reading from the printed page. In the days of mainframe computers, printing was a batch job and required large, durable machines. The development of the first personal computers in the mid-1970s led to the corresponding development of desktop printers.

In the period 1976 to 1979, several types of printer became available. The best print quality was delivered by printers that used the same printing technology as contemporary typewriters. Indeed, some models were converted typewriters that retained the keyboard for dual-purpose use. The print head was a daisy wheel, a disk with spokes and raised characters around the circumference, and the printing medium was a carbon tape. Daisy-wheel printers were comparatively slow and noisy. An acoustic hood could be placed over the printer to deaden the noise, but this made the printer more bulky.

The alternatives to the daisy-wheel printer were cheaper, faster, and quieter, but delivered much lower print quality. In the late 1950s, dot-matrix printers were developed for use with mainframe computers. Dot-matrix printers use carbon tape, but the printer head consists of tiny pins that are selectively used, as instructed by the built-in microprocessor, to form characters. The print quality of desktop models improved somewhat in the early 1980s, when 24-pin heads superseded the original 9-pin heads. The cheapness of dot-matrix printers made them a popular choice where print quality was not the main consideration. Thermal and electro-sensitive printers were quieter still because they were nonimpact printers. Instead of a printer head, they used a stylus and the printing medium, carbon, was impregnated in the paper. The carbon was released in response to electric current flowing through the stylus. The print was fainter and less crisp than that produced by a daisy wheel. Low print quality together with the high cost of the special paper limited the sales of these printers. However, thermal printing is still used in many fax machines.

Two methods of nonimpact printing have proved very successful: the ink-jet printer and the laser printer. The ink-jet printer first appeared on the market in the early 1980s. The Japanese optical and electronics company Canon pioneered “bubble jet” ink printers in 1981. In 1984, the American electronics company Hewlett-Packard introduced the first of its ThinkJet series of ink-jet printers. Ink, supplied in cartridges, is sprayed through a matrix of perforations in the printer head. As with the dot-matrix printer, each character is a composite of dots. In the early days of ink-jet printers, there was a tendency for the ink to “bleed,” creating a fuzzy effect. Bleed-resistant papers were created but these, predictably, were more expensive than ordinary computer paper. By the late 1980s, improvements made to reduce the bleed problem and a steep drop in prices established the ink-jet printer as the favored budget purchase, in place of the dot-matrix printer. Ink-jet printers also have the advantage of compactness. When the notebook generation of portable computers emerged in the late 1980s, complementary portable models of ink-jet printers followed.

The only printer to match the daisy-wheel printer in terms of quality is the laser printer, which has more in common with the photocopier than the typewriter. The world’s first laser printer, the IBM 3800, was introduced by the U.S. office machine giant in 1976, but it took another ten years for the price to fall sufficiently for laser printers to become commercially competitive. Laser printers use powdered ink known as toner and contain a light-sensitive drum, a laser, and a rotating mirror. Where light from the laser beam falls on the electrostatically charged drum, the charge is dissipated; where no light falls, the charge remains and toner is attracted. The toner is transferred to paper and fused in place by heating. While characters and images are formed as patterns of dots, as with dot-matrix and ink-jet printers, the laser printer dots are so small and closely spaced that lines appear to be continuous.

Both ink-jet and laser printing technologies brought another advance—color printing. Canon introduced its first color ink-jet printer in 1982, only a year after its first monochrome model. It is now standard for ink-jet printers to operate as dual monochrome or color printers. Color printing is slightly more expensive because a tri-color ink cartridge has to be replaced more often than a black ink cartridge. Ink-jet models have a huge price advantage over color laser models. Hewlett-Packard, the company that has set the standards in laser printer technology since the launch of its first LaserJet printer in 1984, did not introduce a color model until 1994.

As printer technology changed, different manufacturers became involved. Makers of daisy-wheel printers included major typewriter manufacturers such as IBM and Olivetti as well as Xerox and Tandy/Radio Shack. Since then, Japanese companies have taken over the printer market. Epson became a leading maker of dot-matrix printers, and Canon, with a pedigree in the unrelated field of camera manufacture, is a leading maker of ink-jet printers. In the laser printer field, Japanese companies such as Canon and Panasonic dominate the lower end of the market, but Hewlett Packard of the United States is still a major supplier of top quality models.