What is the working principle of the printer?

According to the working principle, photocopiers can be divided into photochemical copying, thermal copying and electrostatic copying. Electrostatic copying is the most widely used copying technology at present.

A copier is a device that obtains copies with the same magnification, enlargement or reduction from written, drawn or printed manuscripts. The advantage of the copier is its fast copying speed and simple operation. The main difference from traditional movable type printing, stencil mimeograph and offset printing is that it can obtain copies directly from the original without other intermediate means such as plate making. It's cheaper to make several copies.

At the beginning of the 20th century, blueprint method and diazo method were mainly used to copy documents and drawings. Diazo method is more convenient and faster than blueprint method, and has been widely used. Later, dye transfer, silver salt diffusion transfer and thermal replication appeared.

1938, Carlson of the United States rubbed a zinc plate coated with sulfur with cotton cloth in a dark room to make it charged, and then covered it with a transparent manuscript with images on it. After exposure, sprinkle with lycopodium powder to present the original appearance. This is the original way of xerography.

1950, the first hand-operated ordinary paper electrostatic copier with selenium as light conductor came out; 1959, a 9 14 copier with more perfect performance appeared. Since then, the research and production of photocopiers have developed rapidly. Electrostatic copying has become the most widely used copying method.

In the 1960s, we began to study color copying, and the method used was basically decomposition of three primary colors, and adding black became four-color copying. At the end of 1970s, a research report on the color imaging of electrophoretography was published at the third international electrostatic photography conference, which was a step forward than the previous method. In the 1990s, the laser color copier reappeared.

According to the working principle, photocopiers can be divided into photochemical copying, thermal copying and electrostatic copying.

Photochemical copy includes direct copy, blueprint copy, diazo copy, dye transfer and diffusion transfer. Direct photocopying method uses Gao Fancha photographic paper instead of photosensitive film to shoot the manuscript, which can be enlarged or reduced; Blueprint method is to coat iron salt on the surface of copy paper, and the original is a single sheet of translucent material, which is stacked together for exposure and developed to form an image with white characters on a blue background; Diazo method is similar to blueprint method. The surface of copy paper is coated with diazonium compounds, and after exposure, it is developed in liquid or gaseous ammonia to produce dark images. Dye transfer printing method is to combine the front of the manuscript with a translucent negative coated with photosensitive emulsion, and then transfer it to paper after liquid development and exposure; Diffusion transfer method is similar to dye transfer method. After exposure, stick the negative on the copy paper coated with drug film. After liquid development, the silver salt on the negative film diffuses to the copy paper to form a black image.

Thermal copy is to paste the copy paper coated with thermal sensitive materials on a single original and receive infrared or heat source irradiation. The heat absorbed by the image part is transferred to the surface of the copy paper, which darkens the tone of the heat-sensitive material and forms a copy. This copying method is now mainly used for fax machines to receive faxes.

Electrostatic copying is the most widely used copying technology at present. It is made of selenium, zinc oxide, cadmium sulfide and organic photoconductor, which are charged in the dark to accept the exposure of the original image to form an electrostatic latent image, and then developed, transferred and fixed.

There are two kinds of xerography: direct method and indirect method. The direct method is to form an electrostatic latent image on paper coated with photoconductive materials, and then develop it with liquid or powder developer. After the image is fixed on the surface of the paper, it becomes a copy. Indirect method first forms a latent image on the surface of photoconductor and develops it, then transfers the image to ordinary paper and becomes a copy after fixing. After 1970s, indirect method became the mainstream and development direction of xerography.

The electrostatic copier mainly has three parts: the illumination of the manuscript and the focusing imaging part; Forming a latent image on the photoconductor and developing the latent image; The paper feeding, conveying and fixing parts of copy paper.

The manuscript is placed on a transparent manuscript table, and the manuscript table or light source moves at a uniform speed to scan the manuscript. The original image is focused by an optical system consisting of several mirrors and lenses and imaged on the surface of the photoconductor. The optical system can image at the same magnification, magnification or reduction.

Most substrates covered with photoconductive materials are round, called photoconductive drums, and some are in the form of flat or endless belts. When copying at the same magnification, the scanning speed of the original is the same as the linear speed of the photoconductor. The light guide material has high resistance in the dark. When it passes through the charging electrode, the air is ionized by the high voltage of the electrode, and the free ions are rapidly and uniformly deposited on the surface of the film under the action of the electric field, so that it has a uniform electrostatic charge.

When the photoconductor is exposed by light from the manuscript system, its resistivity decreases rapidly, and the surface charge disappears or partially disappears with the intensity of light, thus forming an electrostatic latent image on the film. After development, the electrostatic latent image becomes a visible image.

Development methods are divided into dry method and wet method, of which dry method is widely used. Dry development usually adopts magnetic brush method, and under the action of electric field force, developing toner with opposite polarity to latent image charge is added to the surface of photoreceptor. The amount of adsorbed toner increases or decreases with the charge of latent image, so a layered toner image appears.

The paper feeding mechanism sends a single sheet or a roll of copy paper to the transfer position and contacts the toner image on the surface of the photoconductor. Under the action of the electric field force of the transfer electrode, the toner on the photoconductor surface is attracted to the paper. After the copy paper is separated from the surface of the photoconductor, it enters the fuser. After hot pressing, cold pressing or heating, the resin contained in the toner melts and adheres to the paper, becoming a permanent copy image.

After the toner image is transferred, the photoconductor continues to move through the cleaning part. The residual untransferred toner is removed by a brush or an elastic scraper, and then the residual charge on the surface of the photoconductor is eliminated by a depolarizer or an illumination source. When the photoconductor enters the charging area again, the next copying cycle begins.

With the rapid development of photocopying technology, the properties of photoconductive materials are constantly improved, and there are more and more varieties. The control performance of photocopiers is constantly improving. Most machines can automatically and manually feed paper, and some can automatically copy on both sides. The application scope of photocopiers is expanding day by day, and the continuous adoption of various new technologies has gradually exceeded the scope of simply copying documents and drawings as they are.

Nowadays, copier has been combined with modern communication technology, computer and laser technology, and has become an important part of information network. It can be used as a terminal for reading and recording information in the process of short-distance or long-distance data transmission, and it is an indispensable link in modern office automation.