What is the printing principle of inkjet and laser printer? How an inkjet printer prints. PC Peripheral World Laser Printer Technology

Suitable for both office and home. To decide whether such a device is needed, you must first understand what this type of device is. "Laser" means that this type of printer prints with a laser, and it also works with dry ink.

The article will talk in more detail about how these devices are arranged, how they work, as well as their main advantages and main disadvantages. All this will help you make the right decision.

Internal arrangement and mechanics

The photoelectric part of xerography is the basis of how the device works. What that laser printer prints on the same principle. Devices are also arranged identically. Unless there are more cartridges in color devices. In the table below - the main nodes laser device, as well as their components.

How it works - 8 steps:

1. The heating part melts the toner;
2. The melted clumps of powder stick to the paper;
3. The scraper removes the remaining toner from the drum;
4. The drum is electrostatically treated and charged (positive or negative);
5. With the help of mirrors, an image appears on the surface of the drum;
6. The drum moves along the magnetic shaft, and the toner puts a picture on it;
7. The drum transfers the image to the paper by rolling over it;
8. rolled through the oven, whereby the image is fixed.

Toner

Toner is a consumable. This is a dry powder (can be black or colored), which is the ink for laser printers. As already described above, it works like this: with the help of static, it (powder) is transferred to a charged photoconductor, due to which an image appears. It is subsequently transferred to paper.

Each manufacturer produces an original . Only with a proprietary dye, the company can guarantee the stable operation of the device. Such qualities as magnetism and dispersion are individual for dyes. Devices are made with the expectation of using a specific toner. Filling the cartridge with an alternative powder of dubious quality, the user risks disrupting the device's performance. If the required toner is not available, you can choose a compatible version with identical properties.

Attention! Attempting to use incompatible products may result in serious equipment malfunctions. You may also void your warranty.

You should be aware that toner can be harmful to health while it is in powder form. It must not be allowed to enter the respiratory tract.

When refilling or removing excess substance, it is extremely important to observe the following precautions:

• use latex gloves;
• wear a respirator or medical mask on your face;
• work with the substance only in a well-ventilated area;
• We recommend using a special vacuum cleaner to remove excess toner.

Even better - do not refill the cartridge yourself, but entrust this business to the pros. Contacting service center, you can not worry that the toner will damage the printer or harm your health.

Laser printers provide higher quality than inkjet printers. The most famous firms - developers of laser printers are Hewlett-Packard, Lexmark.

The principle of operation of a laser printer is based on the method of dry electrostatic image transfer, invented by C.F. Carlson in 1939 and also implemented in copiers. Functional diagram laser printer is shown in fig. 5.6. The main structural element is rotating drum, which serves as an intermediate medium with which the image is transferred to paper.

Rice. 5.6. Functional diagram of a laser printer

Drum is a cylinder covered with a thin film of a light-conducting semiconductor. Typically, zinc oxide or selenium is used as such a semiconductor. A static charge is evenly distributed over the surface of the drum. This is provided by a thin wire or mesh called a corona wire or corona wire. A high voltage is applied to this wire, causing a glowing ionized region around it, called the corona.

Laser, controlled by a microcontroller, generates a thin beam of light reflected from a rotating mirror. The image is scanned in the same way as in a television kinescope: by moving the beam along the line and frame. With the help of a rotating mirror, the beam slides along the cylinder, and its brightness changes abruptly: from full light to complete darkness, and the cylinder is charged in the same stepwise (pointwise) manner. This beam, having reached the drum, changes it electric charge at the point of contact. The size of the charged area depends on the focusing of the laser beam. The beam is focused using a lens. A sign of good focus is the presence of clear edges and corners in the image. For some types of printers, during recharging, the drum surface potential decreases from 900 to 200 V. Thus, on the drum, the intermediate carrier, hidden copy images in the form of an electrostatic relief.

In the next step, the image drum is coated with toner- paint, which is the smallest particles. Under the action of a static charge, the particles are easily attracted to the surface of the drum at the exposed points, and form an image already in the form of a dye relief.

Paper is pulled out of the feed tray and moved to the drum by means of a system of rollers. Just before the drum, the short-ron imparts a static charge to the paper. The paper then comes into contact with the drum and, due to its charge, attracts the particles of toner previously deposited on the drum.

To fix the toner, paper is passed between two rollers with a temperature of about 180 "C. After the end of the printing process, the drum is completely discharged, cleaned of excess particles adhering to the new printing process. The laser printer is page by page, i.e. forms a full page for printing.

The process of operation of a laser printer from the moment a command is received from a computer to the output of a printed sheet can be divided into several interrelated stages, during which such functional components of the printer are involved as CPU; scan processor; mirror motor control board; beam brightness amplifier; temperature control unit; sheet feed control unit; paper feed control board; interface board; power unit; control panel buttons and indication board; additional RAM expansion cards. In fact, the functioning of a laser printer is similar to a computer: the same central processing unit, on which the main functions of interconnection and control are concentrated; RAM, where data and fonts are located, interface boards and a control panel board that communicate the printer with other devices, a print unit that outputs information to a sheet of paper.

The history of laser printers began in 1938 with the development of dry ink printing technology. Chester Carlson, while working on inventing a new way to transfer images to paper, used static electricity. The method was called electrography and was first used by the Xerox Corporation, which released the Model A copier in 1949. However, for this mechanism to work, some operations had to be done manually. 10 years later, the fully automatic Xerox 914 was created, which is considered the prototype of modern laser printers.

The idea to "draw" what should be printed later directly on the copy drum with a laser beam belongs to Gary Starkweather. Since 1969, the company has been developing and in 1977 released the Xerox 9700 serial laser printer, which printed at a speed of 120 pages per minute.

The device was very large, expensive, intended exclusively for enterprises and institutions. And the first desktop printer was developed by Canon in 1982, a year later - new model LBP-CX. HP partnered with Canon to launch the Laser Jet series in 1984 and immediately took the lead in the home laser printer market.

Currently, monochrome and color printers are produced by many corporations. Each of them uses its own technologies, which may differ significantly, but general principle The operation of a laser printer is typical for all devices, and the printing process can be divided into five main stages.

Photoconductor charge

The print drum (Optical Photoconductor, OPC) is a metal cylinder coated with a photosensitive semiconductor on which an image is formed for subsequent printing. Initially, the OPC is supplied with a charge (positive or negative). You can do this in one of two ways using:

• coronator (Corona Wire), or coronator;
• charge roller (Primary Charge Roller, PCR), or charging shaft.

Corotron is a block of wire and a metal frame around it.

The corona wire is a tungsten filament with a carbon, gold or platinum coating. Under the action of high voltage between the wire and the frame, a discharge occurs, a luminous ionized area (crown), an electric field is created that transfers a static charge to the photoconductor.

Usually, a wire cleaning mechanism is built into the unit, since its contamination greatly degrades print quality. Using a corotron has certain disadvantages: scratches, accumulation of dust, toner particles on the filament or bending of the filament can lead to an increase in the electric field in this place, a sharp decrease in the quality of printouts, and possibly damage to the surface of the drum.

In the second version, the supporting structure with the heating element inside is wrapped by a flexible film made of a special heat-resistant plastic. The technology is considered less reliable, used in printers for small businesses and home use where large loads of equipment are not expected. To prevent the sheet from sticking to the oven and twisting it around the shaft, a bar with paper separators is provided.

Color print

Four primary colors are used to form a color image:

• black,
• yellow,
• purple,
• blue.

Printing is carried out according to the same principle as black and white, but first the printer breaks the picture to be obtained into monochrome images for each of the colors. In the process of work, color cartridges transfer their drawings to paper, and their imposition on each other gives the final result. There are two color printing technologies.

Multipass

With this method, an intermediate carrier is used - a shaft or a toner transfer belt. In one revolution, one of the colors is applied to the tape, then another cartridge is fed into the right place and the second image is superimposed on top of the first image. In four passes, a complete image is formed on the intermediate carrier, which is transferred to paper. The print speed of a color image in printers using this technology is four times slower than a monochrome one.

single pass

The printer includes a complex of four separate printing mechanisms under common control. The color and black cartridges are lined up, each with a separate laser unit and transfer roller, and the paper passes under the photoconductors, sequentially collecting all four monochrome images. Only after that the sheet enters the oven, where the toner is fixed on the paper.

Print with pleasure.

Many believe that the laser printer is so named because it burns images onto paper with a laser. However, one laser is not enough to get a quality print.

The most important element of a laser printer is the photoconductor. It is a cylinder covered with a photosensitive layer. Another required component toner is a coloring powder. Its particles are fused into a sheet of paper, leaving the desired image on it.

The imaging drum and toner hopper are most often part of the same one-piece cartridge, which in addition has many other important parts - the charge and developer rollers, the cleaning blade and the waste toner bin.

Now let's look at how this all happens in more detail.

Printer steps

An electronic document is sent for printing. In this moment printed circuit board processes it, and the laser sends digital pulses to the cartridge. By charging the photoconductor with negative particles, the laser transfers an image or text to it that needs to be printed.

When the laser beam hits the drum, it removes the charge and uncharged zones remain on its surface. Each toner particle is negatively charged and in contact with the drum unit, the toner adheres to uncharged fragments under the influence of static electricity. This is called image development.

A special roller with a positive charge presses a sheet of paper against the photoconductor. Because oppositely charged particles attract, the toner sticks to the paper.

Next, the paper with toner is heated to a temperature of about 200 degrees using a thermal shaft of the so-called stove. Due to this, the toner expands and the image is firmly fixed on the paper. Therefore, documents freshly printed on a laser printer are always warm.

The last step is to charge the photoconductor and clean it of any remaining toner using a cleaning blade and waste toner box.

This is how the printing process works. The laser paints the future image with charged particles. The photoconductor catches and transfers the ink powder to the paper. Toner adheres to paper due to static electricity and fuses to it.

The copier works on the same principle.

Benefits of a laser printer

It is believed that the print speed of a laser printer is higher than that of an inkjet printer. On average, this is 27-28 prints per minute. Therefore, they are used for printing a large number documents.

The device does not make much noise during operation. The print quality is very high at a low print cost, which is achieved due to the low consumption and price of the toner. The cost of most models of laser printers is also quite affordable.

For many years there has been a debate about whether a laser printer is harmful to health. Particles of toner used in laser printing, are so small that they easily penetrate the human body, settle and accumulate in the respiratory tract. With constant contact with toner for 15-20 years, headaches, asthma and other diseases can develop.

However, printer manufacturers assure that there is no harm in daily use of the printer. Production technologies are constantly being improved, and cartridges are tested in laboratories.

Danger can arise only when you try to open and refill the cartridge yourself. Toner particles can get into the lungs and are very poorly excreted from the body, so it is better to entrust the refilling of the printer to specialists.

The speed, service life and print quality of laser printers are really on top. This device is indispensable in the work and everyday life of many users and is not as whimsical as capricious inkjet printers, who often have problems with printing when refilling.

If you still got not the most successful model of a laser printer and you did not use it much at all, then do not despair. KupimToner buys back new printers from different brands, as well as accessories for them, offering a decent price.

Before answering the question of how a laser type printer works, it should be noted that the first image obtained by C. Carlson using static electricity and dry ink dates back to 1938. But the first prototype of a modern laser device was created in the mid-50s of the last century. It should be added that the principle of operation of a laser printer is based on the process of the so-called. laser scanning. After the document is scanned, the ink is applied and transferred, as well as the finished image is fixed. A similar principle of laser printing allows you to print text and graphics on plain paper at a fairly high speed. You can learn more about how a laser printer prints below.

If we talk about what a laser printer device is, then it must be said that any model of such a device consists of a photoconductor, a laser unit, a transfer unit and a fixing unit. In addition, cartridges, depending on the model, use magnetic shaft or developing roller. Paper is fed to print using a special node responsible for this action.

To answer in more detail the question of how a laser-type printer works, it is also necessary to talk about the paint (toner) used in this office equipment. So, the toner is a substance consisting of very small particles of polymer coated with a dye, with the inclusion of magnetite. In addition, it includes the so-called. charge regulator. Depending on the manufacturer, all such powders differ in such indicators as density, dispersion, grain size, magnity, etc. For this reason, refilling a laser printer with any random powder paint is not worth it, because. this will degrade the print quality.

Office equipment of this type, as a monochrome printer / MFP, has found wide application for personal use, i.e. Houses. Its main advantage lies in the affordable cost, which is due to the fact that such devices do not need a large amount of software resources or memory. All they need is a controller that will allow them to carry out the most basic function, which is to print all kinds of documents. In general, it can be used to print plain text or some black and white charts and diagrams where the presence of color does not play a big role. Other advantages of monochrome laser-type devices are low cost for consumables, withstanding heavy loads and the ability to print a large number of pages. But such a printer device does not allow it to print color photographs and complex schemes. In addition, such a device does not have high print quality.

As for color laser printers, their advantages are good printing speed and the ability to print color schemes, images and photographs. But keep in mind that such a printing device is quite expensive, which, in turn, significantly narrows its availability. Its other disadvantages are low profitability due to the high cost. Supplies, high power consumption, and insufficient color image quality. Those. such a device is not suitable for printing professional photos.

But all types of laser printers, as a rule, have the same principle of operation. The only difference is in their cost and functionality and parameters such as the resolution of a laser printer, for example. As for the printing process itself, it can be divided into five key stages, described below.

The first stage: the formation of a photodrum charge (photoshaft)

To answer the question of how a laser printer works and how it works, it should be said that one of its main devices is a print drum coated with a special semiconductor that has high photosensitivity. It is on it that at the first stage an image is formed, intended for further printing. To do this, this part is supplied with a charge with a plus or minus sign. This is done, as a rule, with the help of a coronator (coronator) or a charging shaft (charge roller). The first is a block consisting of a wire around which there is a metal frame, the second is a metal shaft covered with foam rubber or conductive rubber.

The first way to give the photoshaft a certain charge using a coronator is that under the action of voltage between the frame and the wire (tungsten filament coated with platinum/gold/carbon), a discharge is formed. After that, an electric field is formed, which, in turn, transfers a static-type charge to the photoconductor.

The use of a coronator has a number of disadvantages, which are that the accumulation of ink / dust particles on its filament or its bending can lead to a sharp decrease in print quality, an increase in the electric type field in a certain place, and even damage to the surface of the photoconductor.

As for the second method, the charge roller in contact with the drum supplies its surface, which is highly photosensitivity, with a certain charge. At the same time, the voltage on the roller is an order of magnitude lower, which, in turn, solves the problem with the appearance of ozone. But in order to carry out the transfer of charge, contact is necessary. Consequently, the printer parts in this case wear out faster.

Stage two: exposure

The purpose of this stage is to form an invisible image of dots on the surface of a photodrum with increased photosensitivity, and without the use of a static charge. To do this, a thin laser beam shines on a four- or hexagonal mirror, after which it is reflected and hits the so-called. spreading lens. He sends it to a specific place on the surface of the drum. Next, a system consisting of several lenses and mirrors moves the laser beam along the photo shaft, resulting in the formation of a line. Because printing is carried out using dots, the laser is constantly turned on and off. The charge is also removed in a pointwise manner. After the line comes to an end, the photo roller starts to turn by means of a stepping motor and the exposure procedure continues.

Third stage: development

Another shaft in the laser printer cartridge is a metal tube, inside of which there is a magnetic core. A magnet inside the compartment attracts toner to the surface of the shaft and, rotating, takes it out. A special dosing blade allows you to adjust the thickness of the dye layer and thus prevent its uniform distribution.

After that, the ink gets between the photoconductor and the magnetic roller. In areas that have been exposed, the toner begins to be attracted to the surface of the phototube, and in charged areas it is repelled. The ink remaining on the magnetic roller usually travels further and passes through the hopper again. As for the toner that has moved to the surface of the drum, it makes the image on it visible, after which it follows on, i.e. to paper.

Fourth stage: transfer

A sheet of paper that was fed into the device passes under the photo roller. In this case, under the paper is the so-called. an image transfer roller that helps to bring the toner present on the surface of the drum onto the surface of the paper. A charge with a plus sign is applied to the core of the roller, made of metal, which is transferred to the paper through the rubber coating. The microscopic particles of toner transferred to the surface of the sheet adhere to it solely due to static attraction. All powder particles, paper fluff and dust remaining on the photoconductor are sent using a squeegee or wiper to a hopper specially designed for waste. As soon as the photoconductor completes the entire cycle, the charge roller / corotron again contributes to the restoration of charge on its surface and the whole work is repeated again.

Fifth stage: fixing

The toner used in laser printers must have the ability to melt at high temperatures. Only due to this property can it finally be fixed on the surface of the paper.

To do this, the sheet is pulled between two shafts, one of which presses it, and the other warms it up. Thanks to this, microscopic particles of the coloring matter are, as it were, fused into the structure of the page. After leaving the oven, the powder solidifies quickly enough, as a result of which the printed picture or text becomes quite stable.

It should also be added that the top roller, which heats up a sheet of paper, is in the form of a thermal film or a Teflon roller. In this case, the second option is considered more durable and reliable. However, it is expensive and is used most often in devices that must withstand heavy loads. The first option is less reliable, and is usually used for printers designed for small offices and home use.