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HISTORY OF TECHNOLOGY, TECHNOLOGY, OBJECTS AROUND US
Printers. History of invention and production
Directory / The history of technology, technology, objects around us A printer (Printer, from the English. print - printing) is an external peripheral device of a computer designed to output text or graphic information stored in a computer to a solid physical medium, usually paper, in small print runs (from units to hundreds) without creating a printed form . This distinguishes printers from printing equipment and risographs, which, due to the printing form, are faster and cheaper in large runs (hundreds or more copies). A printer is a high-tech printing device designed primarily to work with a computer. The printer is designed to convert information stored in a computing device from digital form to analog form for an accessible understanding of this information by the user and its subsequent long-term storage. Other printing devices have also become widespread, such as multifunction devices (MFPs), which combine the functions of a printer, scanner, copier and telefax in one device. Such a combination is rational from the technical and economic side, and also convenient to use. The entire range of manufactured printers is almost exhausted by four principles of operation: printers based on impact technologies, printers based on electrographic technologies, printers based on inkjet technologies, printers based on thermal technologies. Other printing methods are highly specialized or experimental.
The oldest printing technology is electrographic. The first such copier was invented before World War II. But it took a long time before printers were created based on this technology. The principle of their operation is that a charge corresponding to the desired image is induced on the surface of the photosensitive unit. This charge attracts the toner powder to the appropriate points. The toner is then transferred directly to the paper or to an intermediate carrier from which it is already deposited on the paper. The toner is literally baked to the paper in a special heater to make the image stable. According to the method of charging, printers of this type are divided into laser and LED. The operation of laser printers is similar to the process of photocopying. The only difference is that instead of a lamp, a thin laser beam is used, which hits the surface of the photoconductor through a mirror prism. As the prism rotates, the beam moves along the drum, and a string is formed. When the drum turns, the lines change. As a result, groups of electrostatic charges are formed on the surface of the drum, corresponding to a given image. Next, the toner is recharged and fed to the drum, and the image is transferred to a sheet of paper or film and fixed in an electric heating device - a "stove". That is why the sheets that come out of the laser printer are warm.
The laser printer guarantees high quality printing, it works quickly and almost silently. True, the cost of a replacement cartridge, which includes a toner container and the photoconductor itself, is quite high. The most widespread are printers that print up to 12-16 pages per minute, as well as faster ones (20-24 pages). By using toners of different colors, you can get images that look like photographs. However, color printing speed is slower and the cost per copy is higher. The LED printer has a line of a large number of pulsed LEDs - electrical devices that emit light. LEDs are located along the surface of the photoconductor, one for each dot. The combination of the LED signals on the line forms the image. This allows you to reduce the number of moving parts and optical devices in the design of the printer. The print quality of such printers is high, the image at the edges of the sheet is not distorted. In impact technologies, an ink ribbon is placed between the printing element of the printer and the paper - usually in a cartridge equipped with a ribbon rewind mechanism. The printing element strikes the ink ribbon, causing the dye to fall onto the paper. There are two fundamentally different options. The first - the printing element is designed in the form of a finished sign (symbol). It was widely used in the past because it provided crisp printing of text characters at high speed. There were no requirements for printing graphic information for devices of this type; graph plotters were used for this purpose. With the expansion of the scope of computers, printing with ready-made characters gradually lost its position, since it is impossible to change the size of characters with it, the character set is limited, and the possibilities of graphic printing are minimal. The second option - the printing element synthesizes the applied information "on the go" from dots during the printing process. Each point is formed by the impact of the needle. Almost all modern printers using impact technology synthesize an image from dots. The needles of the percussion mechanism form a kind of matrix. That is why we call such printers dot matrix printers. Typically, the needles are placed in a head that moves across the paper feed direction. After the head forms a horizontal stripe of the image, the paper advances to the width needed to print the next stripe. To increase the speed of impact printers, the size of the matrix of needles is increased up to the width of the sheet, while the printing unit itself remains stationary. These are called line matrix printers.
The advantages of dot matrix printers include low operating costs, high resistance to external conditions, as well as the ability to print on thick and multilayer papers. However, dot-matrix printers have limited graphic printing capabilities and minimal color capabilities. Basically, these printers are used in industry, transport, the financial sector, trade, utilities. The most common printers today are based on inkjet technology. Here, the crushed dye in the form of droplets is sprayed onto the material - most often paper. Typically, as with dot-matrix printers, the print head moves across the media feed direction to form an image stripe, and then the media shifts to print the next stripe. However, instead of needles, the head has many nozzles for ejecting paint. If only a black (monochrome) cartridge is used, the image will be in black and white. A set of color cartridges allows you to get high-quality color images.
In inkjet technology, two varieties have developed, thermal inkjet, in which the ink is activated and ejected under the action of heat, and piezoelectric, where ink is ejected under pressure created by the vibration of the membrane. Inkjet printers are cheaper than laser printers. In addition, according to environmentalists, they are "cleaner", because they work almost silently and emit less ozone, a strong oxidizing agent that is harmful to health. The inkjet printer is small in size, so it can be easily carried from one place to another. However, an inkjet printer also has disadvantages: the print speed is lower than that of a laser printer, and the "ink" has to be changed frequently. The "thermal printing technologies" group includes printers that are quite different in nuances of technology and design, for which the thermal principle of operation is fundamentally important. With inkless technology using thermal paper, the image is formed by direct contact of the print head with the paper. Heating the surface of the head causes the corresponding dots on the paper to "colour". Advantages of inkless thermal printers: excellent scalability and low operating costs. Disadvantages of inkless thermal printers: limited graphics capabilities, as well as poor print durability. With conventional thermal transfer, the dye is on the ribbon, similar to how it is implemented in dot-matrix printers. However, its transfer to paper is not due to impact, but under the influence of heating of the desired points on the surface of the head. A special case of thermal transfer is sublimation printing, in which the dye is sublimated into a gaseous state and absorbed into the pores on the surface of a special paper, after which the image is usually fixed (for example, a protective layer is applied). In most cases, thermal transfer printers can optionally print on heat-sensitive paper without the use of dye, although this possibility is usually not advertised. At the same time, the print quality is approximately the same as that of a thermal fax machine. In recent years, solid ink technology has developed rapidly. In this case, the ink heated to melting is applied to an intermediate carrier - a printing drum, from where it gets onto the paper. Advantages of solid ink technology: high color quality, high print speed, relatively low operating costs. The disadvantages of this technology include a rather high cost. However, in the future they should become a dangerous competitor to laser color printers in this respect as well. Author: Musskiy S.A.
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