уч[1].пособие по полиграфии_final. Л. В. Красильникова английский язык для полиграфистов
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Ionography In ionography, the charge pattern is generated on the image carrier directly by the imaging unit and a previously generated redistributed homogeneous charge on the imaging surface is not required. Imaging takes place via an ion source, which can be set up with the currently available technology as a page-wide array (e.g., about 310 mm wide) for a resolution of 600dpi. Inking takes place with toners, such as those that are also used for electrophotography. Following transfer to the paper, cleaning of the drum surface with mechanical and electrical equipment is required. The non-conductive dielectric coating of the imaging drum has a very high mechanical hardness, so that cleaning by means of blade systems with surface contact can be carried out simply and efficiently. Fixing already takes place in the nip during toner transfer to the paper by the supply of heat and pressure from the drum (transfixing). Following transfer of the printed image onto the paper, final fixing of the printed image is carried out using a non-contact xenon flash lamp through another brief fusing of the toner via the radiant heat on the paper (flash fusing). The NIP technology of ionography is sometimes also known as electron beam printing. Around 1990, Delphax came on the market with digital printing systems for single-color printing. A printing unit of this type prints at a speed of 90 A4 pages/min. Рис.7 Magnetography Magnetography is a variant of the non-impact printing technologies. A magnetic pattern is applied to the imaging cylinder in accordance with the image. The magnetic fields attract ferrous magnetic powder toner particles via a special inking unit, and the particles are then transferred onto the paper. In principle the magnetography imaging drum is capable of storing a magnetic pattern generated on the surface so that images with the same image content can be printed on paper without re-imaging. In working practice this variation has not yet been put into action, since the circumference of the imaging cylinder is generally smaller than the image-length, but above all because the magnetic pattern is not sufficiently stable to ensure constant print quality. A concept of generating a plate suitable for offset printing on the basis of the imaging cylinder with its hard metallic surface exists. The magnetographical imaging occurs via an imaging system with micro-magnet heads. Then the magnetic toner is applied, which is fused in order to attain a permanent image. The materials on the imaging cylinder surface and the fused toner have to be conditioned so that they are suitable for offset printing. The image is transferred via the blanket cylinder onto the paper using dampening solution and inking up with offset inks. Cleaning equipment must basically consist of mechanical and chemical cleaning components in order to remove the fused toner. Nipson, a leading company in magnetographic printing, calls this concept/technology “Magnetolithography.” Ink Jet The most common non-impact technology used for digital printing systems is ink jet. The ink jet process is a computer to print technology in which ink is sprayed from nozzles, which means that no image carrier is needed. Imaging is done directly onto the substrate. The data of the digital print job is transferred directly to control the imaging unit. In this case the imaging unit is the ink jet system itself, which transfers the ink to the paper via nozzles, mostly directly or in same applications indirectly depending on the technology used. The functional units, imaging system, image carrier, and inking unit are combined into a single module and they transfer the ink directly onto the paper. Ink jet technologies can be classified as continuous ink jet and drop on demand ink jet. The ink used for ink jet printing is usually liquid. An alternative is hot-melt inks which are liquefied by heating. The ink is sprayed onto the substrate where it solidifies after cooling. The continuous ink jettechnology generates a constant stream of small ink droplets, which are charged according to the image and controlled electronically. The charged droplets are deflected by a subsequent electric field, while the uncharged ones flow onto the paper. It means that the imaging signal for charging the droplets corresponds to a negative print image. Continuous ink jet printing usually feeds only a small proportion of the stream of droplets to the substrate. With continuous ink jet generally only a small part of the drop volume covering the sheet in accordance with the print information is applied to the substrate. The large part is fed back into the system. With the so-called “drop on demand ink jet” technology a droplet is only produced if it is required by the image. The most important drop on demand technologies are thermal ink jet and piezo ink jet printing. Thermal ink jet (also known as “bubble jet”) generates the drops by the heating and localized vaporization of the liquid in a jet chamber. With piezo ink jet the ink drop is formed and catapulted out of the nozzle by mechanically deforming the jet chamber, an action resulting from an electronic signal and the piezoelectric properties of the chamber wall. Due to the technical conditions, the possible droplet frequencies are lower with thermal droplet generation than with piezo technology. Ink jet printing represents the most compact technology for transferring information to normal paper in the form of a printed image (comparable to light on photographic paper). It is only necessary to generate a droplet of ink on the basis of image-dependent signals and to spray this droplet directly onto the substrate without an intermediate carrier. Printing systems based on the ink jet technology are usually slow in comparison to conventional printing technologies; they operate at a lower printing speed, especially if imaging is carried out with individual nozzles. Рис.8 Thermography The NIP technology of thermography can be divided into thermal transferand thermal sublimation. In both processes, the ink is applied to a donor (sheet or web) and then transferred to the substrate by the application of heat (or, depending on the system, first to an intermediate carrier which subsequently transfers it to the substrate). In thermal transfer the ink is stored on a donor and is transferred to the substrate by the application of heat. The ink on the donor may be wax or a special polymer (resin). In thermal sublimation the ink is transferred from the donor to the substrate by diffusion. The heat melts the ink and initiates a diffusion process onto the paper. This requires a special coating on the substrate to take on the diffused colorants. Thermal transfer is based on the ink melting onto the carrier film when heated. The liquefied ink is transferred to the substrate under low pressure. In the simple binary process, the optical density of the print is set in advance by producing the donor with a specified thickness of layer, pigment concentration, and hue. When the heating element is switched off there is no ink transfer. The use of micromechanical and microelectronic techniques in the mechanical design of the thermal head facilitates finely controlled heating of the image area. This makes it possible to transfer different quantities of ink. Due to the composition of the ink layer, however, the ink concentration of the transfer remains constant, although the dot size may vary. It means that smaller or larger amounts of ink can be transferred by defined melting. In thermal sublimation, the ink evaporates locally through the application of heat, which triggers sublimation. In physical terms, sublimation is the vaporization of a solid without the intermediate formation of a liquid. Depending on the thermal energy supplied to the pixel/dot, a different amount of ink is transferred to the substrate. The printing material must be treated with a special coating into which the ink penetrates by means of diffusion. With this method several gray values can be produced per dot depending on the quantity of ink diffused. The process is controlled by the temperature and/or the duration of the heating signal. In contrast to thermal transfer with variable pixel size, here the diameter of the dot remains roughly the same although the color density changes. Electrography Non-impact printing processes based on electrography use an electric field to transfer the image information onto the substrate. If the paper has a dielectric coating it is possible to write the latent charge image directly onto the paper. A simple three-stage printing process of imaging, inking, and fixing becomes possible. Due to the air gapbetween paper and writing electrode high field intensities are required. For an efficient, precise charge formation while imaging, the writing electrode (stylus) may be in contact with the coated paper surface. Imaging head and paper surface must be resistant to wear and exhibit good sliding properties. The imaging electrode is brought into contact with the paper under light pressure. After imaging, the paper web comes into contact with the liquid toner, which is kept at a constant color concentration in a closed circuit. Paper surface and liquid toner act together in such a way that the toner is only attracted to the charged areas of the paper surface. In a subsequent process, similar to other NIP technologies with liquid toner (e.g., with electrophotography or ionography) the toner image must be fixed on the paper in a fusing unit. Electrography is seen to some extent as an independent NIP technology. Photography The non-impact printing technology of photography is the conversion of analog photography into the digital generation of the image. For this, photographic papersare used that are imaged via digitally addressed laser systems. Specially coated paperis used for photography as in electrography. Image setuptakes place by imaging with three wavelengths for the colors Red, Green, and Blue. The required hue in the image is produced through the intensity control of the individual laser light sources. Gas lasers or semiconductor lasers can be used as light sources. With the help of proofing system large-format color pictures can be produced. The resolution for this system is up to 4000 dpi. An external drum system provides the imaging using an imaging system with axial movement. The imaging process is followed by a development process that is compatible with the photographic paper used. Due to the high imaging resolution it is possible to reproduce the screen structuresof the color separations for offset printing. Photographic papers might have surface structureswhich can differ from the paper quality specifications in print production. In particular, adaptation of paper white has led to enhancements in photographic paper for use in proof printing. In the case of large-format digital imaging systems for photography (photofinishing), the structurescorrespond to those of computer to film or computer to plate applications. “X”- Graphy New types of non-impact printing technologies that cannot be attributed to known technologies are classified under “X”-Graphy NIP technology. Selected new technologies are: • TonerJet Printing Technology; •Direct Imaging Printing Technology; • Elcography. It will be common to all new technologies for special physical effects to be employed, often in conjunction with new developments in the chemical structure of the inks and the use of additives to implement computer to print technologies. ESSENTIAL VOCABULARY Words and Word Combinations
ACTIVITIES 1. Find words and word combinations of the essential vocabulary in the text and translate the sentences they are used in into Russian. 2. Answer the following questions:
3. Match the term with the definition:
4. Find the statement true or false: 1. Electrophotography is the least widespread non-impact printing technology. 2. The toner may be transferred directly onto the paper, although in some cases it may also be transferred via intermediate systems, in the form of a drum or a belt. 3. The mechanical cleaning, which removes particles of toner, can not be done by means of brushes or suction. 4. Ink jet technologies can be classified as continuous ink jet and drop on demand ink jet. 5. Non-impact printing processes based on electrography use an electric field to transfer the image information onto the substrate. 6. Photographic papers might have surface structureswhich can differ from the paper quality specifications in print production. 7. With the help of proofing system large-format black-and-white pictures can be produced. 5. Match the two halves of the phrases and use them in the sentences of your own:
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