Modern inkjet printers can compete with laser printing. Periphery. Ink is faster from a laser

The basis of any process inkjet printing is the process of creating ink droplets and transferring these droplets onto paper or any other inkjet printable media. Controlling the flow of drops allows you to achieve different density and tone of the image.
To date, there are two different approaches to creating a controlled droplet flow. The first method, based on the creation of a continuous flow of drops, is called the method continuous inkjet. The second method of creating a flow of drops provides for the possibility of directly controlling the process of creating a drop at the right time. Systems using this method of droplet flow control are called systems pulse inkjet.

Continuous inkjet printing

The pressurized dye enters the nozzle and separates into droplets by creating rapid pressure fluctuations produced by some electromechanical means. Pressure fluctuations cause a corresponding modulation of the diameter and speed of the dye jet exiting the nozzle, which is separated into individual drops under the influence of surface tension forces.
This method allows you to achieve a very high rate of droplet creation: up to 150 thousand pieces per second for commercial systems and up to a million pieces for special systems. An electrostatic deflection system is used to control the flow of droplets. Drops flying out of the nozzle pass through a charged electrode, the voltage on which changes in accordance with the control signal. The flow of drops then falls into the space between two deflecting electrodes having a constant potential difference. Depending on the previously obtained charge, individual drops change their trajectory in different ways. This effect allows you to control the position of the printed dot, and its presence or absence on paper. In the latter case, the drop is deflected so much that it enters a special trap.
Such systems allow you to print dots with a diameter of 20 microns to one millimeter. A typical dot is 100 microns, which corresponds to a droplet volume of 500 picolitres. Such systems are mainly used in the industrial printing market, in product labeling systems, mass label printing, medicine, etc.

Pulse inkjet printing

This principle of creating a flow of drops provides for the possibility of direct control of the process of creating a drop at a certain time. Unlike continuous systems, there is no constant pressure in the ink volume, and when a drop is needed, pressure pulses are generated. Controlled systems are fundamentally less complicated to manufacture, but their operation requires a device for creating pressure pulses approximately three times more powerful than for continuous systems. The performance of controlled systems is up to 20 thousand drops per second for one nozzle, and the droplet diameter is from 20 to 100 microns, which corresponds to a volume of 5 to 500 picoliters. Depending on the method of creating a pressure pulse in the ink volume, a distinction is made between piezoelectric and thermal inkjet printing.
For implementation piezoelectric method, each nozzle is equipped with a piezoelectric element connected to the ink channel by a diaphragm. Under the influence of an electric field, the piezoelectric element is deformed, due to which the diaphragm is compressed and unclenched, squeezing out a drop of ink through the nozzle. A similar drop generation method is used in Epson inkjet printers.
A positive feature of such inkjet printing technologies is that the piezoelectric effect is well controlled by the electric field, which makes it possible to accurately vary the volume of the resulting droplets, and therefore to a sufficient extent affects the size of the resulting spots on the paper. However, the practical use of drop volume modulation is hampered by the fact that not only the volume, but also the drop velocity changes, which causes point positioning errors when the head moves.
On the other hand, the production of print heads for piezoelectric technology turns out to be too expensive per head, so in Epson printers the print head is part of the printer and can cost up to 70% of the total cost of the entire printer. The failure of such a head requires serious service.

For implementation thermal jet method, each of the nozzles is equipped with one or more heating elements, which, when a current is passed through them, heat up to a temperature of about 600C in a few microseconds. The gas bubble that occurs during sudden heating pushes a portion of the ink forming a drop through the outlet of the nozzle. When the current stops, the heating element cools down, the bubble collapses, and another portion of ink comes from the inlet channel in its place.
The process of creating drops in thermal printheads after a pulse is applied to a resistor is almost uncontrollable and has a threshold dependence of the volume of the evaporated substance on the applied power, therefore, here, dynamic control of the droplet volume, in contrast to piezoelectric technology, is very difficult.
However, thermal printheads have the highest performance to unit cost ratio, so the thermal inkjet printhead is usually part of the cartridge and when the cartridge is replaced with a new one, the printhead is automatically changed. However, the use of thermal printheads requires the development of special inks that can evaporate quite easily without igniting and are not subject to thermal shock damage.

Lexmark print head

The print head of a black cartridge of a regular resolution of 600 dpi for early models (Lexmark CJP 1020, 1000, 1100, 2030, 3000, 2050) had 56 nozzles arranged in two zigzag rows. The print head for color cartridges of these models had 48 nozzles divided into three groups of 16 nozzles for each color (Cyan, Magenta, Yellow). The Lexmark CJ 2070 printer used a different printhead that contained 104 monochrome nozzles and 96 color nozzles.
Lexmark inkjet printheads, starting from the 7000 series, use printheads manufactured using laser nozzle-piercing technology (Excimer, Excimer 2). The first models of printheads contained 208 monochrome nozzles and 192 color nozzles.
For the Z51 model and the older model of the Zx2 and Zx3 family, a print head with 400 nozzles was developed. In the Z51 model, only half of the nozzles were used, and the rest worked in hot standby mode, when, as in following models All nozzles were activated at the same time.
The lower and middle models of the Zx2 family use cartridges that are a modification of standard high-resolution cartridges, and the lower and middle models of the Zx3 family use new models of Bonsai cartridges.
Do not leave the print head nozzles open for a long time. If the nozzles are left open, the ink in them dries up and clogs the channels, which leads to printing defects. The cartridge should be left in the printer or in a special box (« garage»). It is also undesirable to touch the nozzles and contacts with your hands, as sebaceous secretions from the skin can spoil the surface.

Print head specifications

Period of meniscus formation:
This is the amount of time it takes for the chamber to refill with ink. It determines the operating frequency of the print head (from 0 to 1200 Hz).

Drop speed:
Low speed results in a continuous location of a point.
High speed results in splashes and streaks.

The mass of a drop is determined:
Heating element size.
Nozzle diameter.
Back pressure.

It has been noticed that in conventional inkjet printers, a drop of ink falling on the paper takes the form of a small triangle, so the lines look jagged on closer inspection. This is due to the fact that the drop is deformed in flight, and when it comes into contact with paper, it spreads. This is especially noticeable in low mode when printing economically. Lexmark offers printers with new, progressive technology printing in which the shape of the nozzles and the speed of the head are balanced so that the drop of ink gives spots, like uniform strokes. This allows you to make the lines smooth, and the print quality is almost indistinguishable from laser printing. In addition, this shape of the spot avoids whitish streaks on the print.

What is ink?

Each manufacturer of inkjet printers develops and improves its ink composition, which is most adapted to the technology produced. At Lexmark, the main components of inkjet inks are:
- Deionized water (85-95% of total volume)
-Pigment or dye
- Solvent (for pigments)
- Humidifier (Humectant)
-surfactant (Surfactant)
- Biocide
-Buffer (pH stabilization)

Pigment or dye. Pigment-based inks (black only) are made from solid particles in a liquid. When such ink gets on paper, the liquid evaporates and is partially absorbed, and the powder sticks to the surface without spreading over it. Therefore, pigment-based inks are waterproof, have poor penetration into paper fibers, but are sensitive to light.
Dye-based inks are generally colored inks. The dye is soluble in water and is absorbed along with it into the thickness of the paper when it dries. Such ink dries faster than pigment ink, is light-resistant, but on the other hand gives more irregularly shaped spots on average than the latter.
Humidifier. The concentration of the humectant affects the viscosity of the ink. This setting should be optimal for this composition ink and the printhead with which it will be used. Indeed, on the one hand, the higher the viscosity, the worse the ink spreads over the surface of the paper, giving a smaller dot size and the clearer the image will be. On the other hand, too much viscosity leads to a long meniscus formation time, which degrades the printing speed. Generally, the ink viscosity is key parameter when defining geometric channels in the print head.
Surface tension affects the wettability of ink on all surfaces it comes into contact with, from the reservoirs in the cartridge to the surface of the paper. Too low static surface tension causes the ink to dry faster on the paper surface, but the average drop volume when the ink is squeezed out of the nozzles is too high. If the surface tension is too high, it will increase the drying time and therefore reduce the image stability when printing.
Acidity level(PH) low acidity leads to low solubility of the ink components in water and, as a result, poor water resistance of the image. The standard acidity level is considered to be in the range from 7.0 to 9.0.
Inside the cartridge there are ink reservoirs, print head nozzles and electrical contacts.
The color cartridge contains 3 separate cells for ink of 3 different colors. The monochrome cartridge contains only one black ink cell.

Inks and colors

The correct transfer of the color of an image to paper is a highly technological process that requires taking into account a considerable number of factors, including a subjective assessment. First of all, the color reproduction of an image depends on the chemical composition of ink and paper, and the architecture of the printer.
A mandatory requirement for ink is a very thin spectral composition, otherwise the colors obtained by mixing will be “dirty”. After drying, the ink must remain transparent, otherwise there will be no natural mixing of colors.
An important factor is also resistance to fading, environmental friendliness and non-toxicity.
It is believed that the optimal composition of the ink is already known. In almost all manufacturers, they represent a suspension of very small particles of mineral pigment. With color inks, the situation is worse, since it is very difficult to select mineral dyes of the desired spectral composition.
Currently, color rendering procedures are based on the so-called color tables, which are used to convert the color space in which the original image was created into some “deformed” color space, which takes into account the peculiarities of rendering colors on paper with ink. Usually, separate color tables are built for each type of paper and are optimized for each individual type of ink and printhead.

Lexmark Drivers

Lexmark printer drivers are ready to print when installed, with automatic object recognition to get good quality images without prior adjustment. Automatic mode also allows you to achieve the optimal combination of quality and speed for printing a document. Setting the driver for special paper or selecting color tables for a more contrast or natural tone of the image is very easy in the Document Quality driver settings section.
Lexmark's Color Fine 2 Series drivers automatically detect the cartridge type, making it much easier to change all systems to a different cartridge type or change from an old one to a new one. characteristic feature drivers of this series is their ability to work with images in sRGB and ICM standards.
sRGB standard proposes that a device-independent color space is used to describe a color image, which is built into Microsoft OC or Internet tools. Using the standardized RGB description of the UTI-R BT.709 color space, this standard allows minimizing the transfer of additional system information associated with the color profile of the equipment on which the image was created along with the image. In the system part of the file with the image, only a reference is given to the standard in which it was created, and the destination position is actively used by the description of the color space provided by the operating system.
ICM standard allows you to more accurately define the variety of generation devices and the display of color images by using color hardware profiles for each type of image generating and display devices. However, this approach implies that the system information associated with the profile of the equipment on which the image is created is transmitted in place with this image.

Photo printing

A serious problem in inkjet printing is the correct reproduction of the light tones of the image. The fact is that conventional color solutions for inkjet printing produce image points of saturated color, so in order to obtain pale shades, ink drops need to be applied quite infrequently. This causes the spots to be so far apart when very light tones are reproduced that graininess becomes noticeable, and there is also a problem with reproduction in high tones.
One of the radical ways to solve this problem is to use additional light-colored inks. In this case, dark tones are obtained by filling with clarified ink. The cartridge with such ink usually replaces the second cartridge (black) and contains clarified Cyan, clarified Magenta and black inks. A light yellow tone is not used, since this color is perceived by the human eye without much difference as yellow.

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inkjet printing is a technology for producing an image using microscopic drops of ink sprayed by the printer's print head onto paper.

The technology of inkjet printing is similar to the technology of matrix printing, since in both the first and second cases the image is formed by dots. Only with matrix printing, the image is applied by hitting the needles on the ink ribbon, and with inkjet printing, by spraying ink onto the paper with the print head.

The most important part of an inkjet printer is printhead, which is an array consisting of many microscopic holes (nozzles, nozzles).

Close-up photo of an inkjet print head nozzle

At piezoelectric printing A piezocrystal is located above the nozzle of the print head, which bends under the influence of an electric current and pushes an ink drop out of the nozzle onto the paper. The stronger the current charge, the more the piezocrystal bends, and the larger the size of the extruded drop. By adjusting the charge of the electric current, you can control the size of the ink drops. Piezoelectric printing technology is used in Epson inkjet printers.

A schematic representation of the principle of operation of piezoelectric printers is presented below.

Working principle of piezo inkjet print head

At bubble inkjet printing the smallest thermoelements (microheaters, thin-film resistors) are placed in the nozzles of the print head, to which electrical impulses with a duration of 7-10 microseconds are applied. When heated, the thermoelements heat up the ink until ink-air bubbles form. Bubbles, increasing in volume, push ink drops out of the nozzle. After that, the heating stops and a new portion of ink is drawn into the nozzle. The fuser turns on and off at an incredible rate, ejecting approximately 24,000 ink drops per second from each print head nozzle.

Thermal inkjet printing similar in nature to bubble inkjet printers, with the only difference being that in bubble inkjet printers the heating elements are built into the nozzles of the printhead, while in thermal inkjet printers they are located directly behind the nozzles. Otherwise, thermal inkjet printing resembles bubble inkjet printing: the heating element heats the ink to the evaporation temperature. The ink boils, increases in volume, bubbles and is pushed out of the cavity of the nozzles onto the paper carrier.

A schematic representation of the principle of operation of thermal inkjet printers is shown in the following figure.

Working principle of thermal inkjet print head

Inkjet printers operate with microscopic ink droplets with a volume of about one picoliter. The diameter of the ink drop is about 13 microns. Approximately 10,000 such ink drops are placed in 1 mm3. Since the droplet diameter is larger than the print pitch, the droplets overlap when forming an image. Millions of ink droplets are involved in the formation of the image, so the image is very rich and high quality.

Drops of ink on paper

Color inkjet printing uses several different color cartridges. The number of such cartridges ranges from 4 to 8.

Inkjet printer with six individual color ink cartridges

Mixing color ink in various proportions allows you to get many shades. Inkjet printers provide more high quality color printing than laser printers. True, unlike laser printers, ink is consumed quite quickly when printing color images and photographs. In addition, inkjet printers print images more slowly than laser printers. But the cost of color inkjet printers is much lower than the cost of color laser printers.

Inkjet technology appeared in the mid-1980s as a result of an attempt to get rid of the shortcomings of the two dominant printing methods at that time: dot matrix and laser (electrographic). Laser printing was unacceptably expensive, and color was not yet dreamed of (and even now, although color laser printers have become available, they have no chance to bypass inkjet printers in the field of photo prints). And inkjet printing emerged as a cheap alternative for printing office documents, devoid of the disadvantages of dot-matrix printers - slow, noisy and producing low-quality prints.

The idea, which, apparently, almost simultaneously (around 1985) came to the minds of engineers from Hewlett-Packard and Canon, was to replace the needle that hits the paper in dot-matrix printers through the ink layer on the ribbon with a drop of liquid ink. The volume of the drop should be calculated so that it does not spread and creates a point of a certain diameter. This technology got real life when they came up with a convenient way to form a dosed drop - thermal.

The thermal inkjet printing method is actually monopolized by Canon and Hewlett-Packard, which own most of the patents for this technology, the rest of the companies only license it, making their own small changes. While HP uses the term "thermal inkjet" (thermal ink-jet) printing method, and Canon prefers the term "bubble-jet" (bubble-jet).

Although there are differences between them, they are fundamentally identical.

On fig. 1 shows the process of thermal inkjet printing in the form of a conditional cinegram of the cycle of the nozzle (sometimes called ejectors). A miniature heating element is built into the chamber wall (highlighted in red in the top frame), which heats up very quickly to a high temperature (500 °C). The ink boils (second frame), a large vapor bubble forms in them (the next two frames) and the pressure rises sharply - up to 120 atmospheres, which causes the ink to be pushed out through the nozzle at a speed of more than 12 m / s in the form of a drop with a volume of about 2 picolitres (this is two thousandths from a billionth of a litre). The heating element is switched off by this moment, and the bubble collapses due to pressure drop (bottom frames). Everything happens very quickly - in a few microseconds. The ink is fed into the nozzle due to capillary forces (which is much slower), and after filling the nozzle with a new portion, the system is ready to work. The entire cycle takes approximately 100 ms, that is, the frequency of drops is 10 kHz, and in modern printers - twice as much.

Such an autonomously controlled nozzle is part of the print head located on a carriage moving across the sheet, similar to the print unit of a dot matrix printer. With a nozzle diameter of 10 microns, the placement density is 2500 nozzles per inch; in one head there can be from several hundred to several thousand nozzles. In modern high-speed devices, fixed heads began to be used - in order to eliminate the slowest stage in the entire process of the transverse movement of the carriage. For example, HP produces high-performance photo kiosks in which the heads are arranged in blocks across the entire width of the sheet.

On Canon printers, the thermal element is located on the side of the camera (as in Fig. 1), while on HP (and Lexmark) it is on the back. Perhaps this difference is due to the original ideas: according to corporate legend, a Canon engineer dropped a soldering iron on a paint syringe (that is, the syringe heated up from the side), and HP researchers borrowed the principle from an electric kettle, which is heated from the end. Like it or not, the lateral arrangement allows Canon to mount two thermal elements per nozzle, which improves performance and manageable droplet size, but complicates and increases the cost of design.

Canon's more expensive "bubble" heads are reusable and built into the printer. HP heads are easier to manufacture, because they were traditionally built directly into the cartridge and thrown away with it. This is much more convenient, as it guarantees print quality (the head simply does not have time to work out the resource) and high reliability of the assembly. However, with this approach, improving the heads leads to a rise in the cost of cartridges, so many modern HP printers have separate heads, like Epson or Canon. For example, the Photosmart Pro B9180, today's flagship of HP's "home" photo printers, has replaceable individual heads, while its cheaper analogue, the Photosmart Pro B8353, has cartridge-integrated heads.

Until a certain period, the word "printing" was associated either with the work of a printing house, or with laser regulars in large offices. Inkjet printing was different in that it was a process of transferring an image or text using a nozzle plate and liquid dye.

It would seem that the concept of inkjet printing began to come into use only recently, after inkjet printers became available to the average user. However, the history of their development covers almost 200 years.

The figure below illustrates the evolution of inkjet printing from its inception to the present.

Stages of development of inkjet printing

Theoretical developments

The theoretical basis of inkjet printing technology goes back to 1833. It was then that Felix Savard, a French physicist and inventor, revealed an interesting pattern: as a result of liquid spraying through holes with a microscopic diameter (nozzles), perfectly even drops are formed. And only 45 years later, in 1878, this phenomenon was mathematically described by Lord Reilly, Nobel Prize winner.

However, earlier, in 1867, William Thompson patented the idea of ​​a continuous ink supply (Continuous Ink Jet). He used electrostatic forces to control the spraying of ink and liquid dye onto paper. Based on this principle, William Thompson designed the recorders necessary for the operation of electric telegraphs.

Continuous printing

Significant for inkjet printing technology was 1951 - Siemens received a patent for an inkjet printer, the first of its kind. It was based on the technology of continuous ink supply. A little later, many global manufacturers of printing equipment adopted this technology and continued to improve it.

The forerunners of modern inkjet printers were rather bulky, equipped with various cylinders, pumps and other moving parts, whimsical to use and, moreover, cost big money. Such printers worked very slowly, and not without drawbacks: they could leak ink when printing, which was not very convenient and safe.

Print on demand

The process originated in the 60s of this century, when a professor from Stanford University managed to obtain ink drops of the same volume and equally spaced from each other. To do this, he used pressure waves produced due to the movement of a piezoceramic element. Such a system was called “Drop-on-demand”, translated from English as “drops on demand”. Technology has made it possible to move away from the use complex system ink recycling, charging system, and eliminate droplet rejection.

For the first time, on-demand printing was used in 1977 in the PT-80 printers from Siemens, and some time later (1978) in the Silonics printer. Later this way printing continued its evolution: the technology developed and became the basis of more and more new models of inkjet printers for commercial use.

The most expensive part in a printer was, and still is, the printhead. It was impossible to “painlessly” replace it, as it happened with the cartridge. Therefore, users found new interaction algorithms. For example, to prevent clogging of the nozzles of the print head with air bubbles or dried ink residues, they tried to use the printer even when it was not particularly necessary. And all in order to prevent a long downtime of the printing device.

Back in the 70s of the twentieth century, the prerequisites for color printing appeared. The Swedish professor Herz has found a way to reproduce all sorts of shades of gray thanks to the method of regulating the density of the droplets. This made it possible to print not only text, but also various images, transmitting gray gradations.

bubble seal

We owe the technology of bubble printing to Canon. In the late 70s, its specialists showed the world the technology of inkjet printing, previously unknown - "Bubble Jet" or "bubble printing". The principle of operation of these inkjet printers is as follows: a microscopic thermoelement is placed in the nozzle, which instantly heats up to 500 ° C as soon as a current acts on it. When heated, the ink boils, air bubbles (bubbles) are formed inside the chamber, under the influence of which equal volumes of ink are pushed out of the nozzle onto the paper. As soon as the ink stops heating and cools to its previous temperature, the bubbles burst, and the next portion of ink is drawn into the nozzle. This ensures uninterrupted printing.

The principle of bubble inkjet printing technology

As soon as Canon introduced bubble jet technology at the Grand Fair in 1981, it immediately caught the public's attention. And already in 1985, the Canon BJ-80 saw the light, the first monochrome bubble printer. Three years later, the Canon BJC-440 appeared, the first large format printer to use the same technology. He could already print in color at 400 dpi.

The cost of printing with bubble inkjet technology is relatively low. However, the cost of maintaining the printer increases because the print head is built into the ink cartridges and not the printer. But there is also back side medals: the device remains operational if a non-original cartridge is used.

Thermal printing

The era of thermal printing began towards the end of the 90s, although HP and Canon began developing it as early as 1984. The thing is that it was not possible to achieve the necessary combination of quality and cost of printing, as well as the speed of work. A little later, Lexmark joined the giants of the industry. In this tandem, these largest companies achieved high resolution printing and created a semblance of modern printers.

The resulting technology became known as "thermal printing" (thermal inkjet). This technology was used by HP's first line of inkjet printers, the ThinkJet.

HP THinkJet Inkjet Printers

The principle of thermal printing is to increase the volume of ink when heated. The temperature of the heating element inside the print head was raised by the heating element. Ink located close to the heating element begins to evaporate when heated. Bubbles are formed that push out a certain amount of them from the nozzle. The pressure drop causes the same volume of ink to enter the print head. This process is repeated with a high cyclicity of up to 12,000 refuelings per second. The printhead based on thermal inkjet technology consists of a large number of microscopic nozzles and ejection chambers.

HP has chosen an unusual course - it has made a replacement print head, which is part of the cartridge and is thrown away with it without much regret. This step solved the printer's durability problem.

The principle of operation of a thermal printer

Bubble and thermal inkjet printers were affordable, compact, quiet, and provided a wide color range, which flooded the market for affordable printers and almost drove dot-matrix printers out of the market.

Piezoelectric seal

The technology of the piezoelectric printing system (Piezoelectric Ink Jet) appeared in 1993 thanks to Epson, which was the first to use it in their printers. The principle of piezoelectric printing is based on the property of piezocrystals to change their volume and shape under the influence of current. In the structure of the cartridge, one of the walls is a piezoelectric plate. It bends under the influence of current and thereby reduces the volume of the ink chamber. As a result, a certain amount of ink is pushed out of the nozzle.

The principle of piezoelectric printing technology

The advantage of a stationary print head is its efficiency, because it does not have to be changed as often as cartridges. However, there is a small chance that when you change the cartridge, air may get into the print head and clog the nozzles, affecting print quality.

Modern traditions

The development of technology has now made inkjet printers even more popular. They are purchased for both office and for home use thanks to them affordable price and compactness. Sometimes users buy inkjet printers for color printing as an addition to monochrome laser printers. There is an opinion that laser devices can print text documents faster and cheaper, while inkjet devices can print color photographs.

Currently, 4600x1200 dpi is considered the print resolution standard for modern inkjet printers. But there are already devices that surpass this indicator. Other features of inkjet printers include borderless printing, as well as a built-in LCD display or a port for reading memory cards.

Benefits of inkjet printers

The most basic trump card of inkjet printers is the high quality of color printing. You can recreate bright and realistic photos with excellent rendering of fine details and midtones. In addition, inkjet printers are almost silent, do not require a long warm-up time, are presented in a wide range of model range and are available in different versions.

Disadvantages of inkjet printers

The main reason for refusing to use an inkjet is the high cost of original cartridges, the fragility of prints due to fading or spreading of ink when liquid enters, and clogged print heads. Although the solutions to all these shortcomings are very simple. Clogs can be overcome with standard head cleaning, and prints can be made more durable using pigment inks. But alternative ones will help to avoid overpayment for original cartridges. expendable materials and inks, which have reached high quality levels so far. The difference from the original ink is no more than 2-5%, due to which the difference in print results is indistinguishable to the naked eye.

A lot of news from the development of modern printers, MFPs and plotters can be read.

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Technology thermal inkjet printing based on the property of ink to expand in volume when heated. The heated ink, increasing in volume, pushes microscopic ink droplets into the nozzles of the print head of the printer, which form an image on paper. AT general view thermal inkjet printing technology is shown below.

Thermal Inkjet Technology

Thermal inkjet printing is the most popular inkjet printing technology and is used in 75% of inkjet printers.

Share of printers using thermal inkjet printing technology

The largest contribution to the development of thermal inkjet printing technology was made by corporations Canon and HP, who independently developed two printing technologies in the 1970s: Bubble Jet (Canon) and Thermal Inkjet(H.P.).

Thermal Inkjet Technologies

Bubble Jet thermal inkjet technology was introduced to the public in 1981 at the Grand Fair. In 1985 using innovative technology The legendary Canon BJ-80 monochrome printer was released, in 1985 - the first Canon BJC-440 color printer.

Schematic representation of Bubble Jet inkjet printing technology

The essence of technology Inkjet Bubble Jet is as follows. A thermistor (heater) is built into each nozzle of the print head for instant heating of the ink, which at temperatures above 500 ° C, evaporating, form a bubble that pushes the ink drop out. Then the thermistor turns off, the ink cools and the bubble disappears, and the low pressure zone draws in a new portion of ink.

Interestingly, the ink heats up to a temperature of 500°C in just 3 microseconds, and drops fly out of the nozzle at a speed of 60 km/h. Every second in each nozzle of the print head, the ink heating and cooling cycle is repeated 18,000 times.

The second inkjet printing technology - Thermal Inkjet - began to be developed by HP in 1984, but the first ThinkJet printer based on this printing technology was introduced into mass production much later.

Schematic representation of Thermal Inkjet technology

Thermal Inkjet Technology is based on the same printing principle as Bubble Jet technology, with the only difference being that in printers using Bubble Jet technology, thermistors are located in the microscopic nozzles of the print head, while in printers using Thermal Inkjet technology, they are located directly behind the nozzle.

Thus, Bubble Jet and Thermal Inkjet technologies differ only in details.

The main advantages of thermal inkjet printing over piezo inkjet printing are the absence of moving mechanisms and stable operation. Along with this, thermal inkjet printing has one significant drawback: it does not allow you to control the size and shape of ink droplets. In addition, when ink drops fly out of the print head nozzle, satellite drops (satellites) that form when the ink boils escape with them. The appearance of such "satellites" can be triggered by the unstable vibration of the ink mass during its ejection from the nozzle. It is the satellite drops that cause the formation of an undesirable contour (“ink fog”) around the print and mixing colors in graphic files.