Thermal inkjet printing. Inkjet printing: in pursuit of quality

Rapidly developing, inkjet printing is expanding into new segments and applications. In the battle for market prospects, research and development in the areas of printheads, inks and specialized compounds. A big advantage when choosing an inkjet printing device will be basic knowledge about manufacturers and technologies of print heads.

Any jet head works on the principle of electronically controlled spraying of liquid droplets onto the desired surface. The two main classes are continuous feed and piezoelectric pulse (drop on demand, DOD) heads, each divided into subclasses.

In continuous inkjet printing, droplets are sprayed continuously, landing either on the material or in a container for recycling and reuse. In DOD equipment, droplet emission depends on certain conditions, and they are formed using a pulse in the ink supply chamber. The types of inkjet DOD printers are determined by the characteristics of pulse generation. The three main categories of technologies on the market are thermal, piezo and continuous flow (electrostatic).

Thermal Inkjet Printing

Thermal inkjet printing technology was first proposed in 1977 by Canon design engineer Ichiro Endo. Since the release of the first desktop printers of this type, thermal printheads have come a long way long haul evolution.

Regardless of design features, thermal printheads are united by the same concept: small droplet size with high speed and nozzle density.

IN compact camera with ink, droplets are formed due to the rapid heating of the resistive element. Rapidly heating up to several hundred degrees, it causes ink molecules to evaporate. A bubble (pressure pulse) forms in the boiling liquid, which forces the ink out of the chamber. As a result, a drop appears at the other end of the nozzle. Once ejected, the vacuum in the chamber is filled with fresh ink from the reservoir and the process repeats.

The disadvantage of the technology is the limited range of compatible liquids: inks for thermal inkjet printers must be developed with evaporation in mind and resistance to high local temperatures. In addition, thermal print heads are negatively affected by the process of so-called cavitation: bubbles constantly form and burst on the surface of the heating element, causing it to wear out. However, modern materials provide thermal jet heads with a fairly long service life.

To reduce droplet size and increase print speed, high-precision technologies are needed to increase the number of nozzles per surface width. Canon FINE printheads offer an impressive capacity of 2,560 nozzles per color (15,360 nozzles per printhead). The nozzles vary in diameter because thermal technology cannot produce droplets of different sizes. Each head has a special combination of 1, 2 and 5 pl nozzles.

Hewlett Packard has achieved impressive nozzle density in the Edgeline printhead. The design, with a print width of 10.8 cm, consists of five silicon chips arranged in a checkerboard pattern.

Physical resolution reaches 1200 dpi at an operating frequency of 48 kHz. A double row of nozzles (10,560 per die) allows Edgeline to apply two colors. When printing in one color, the second row remains as a reserve. Each head, designed to work with water-based or latex ink, has 5 matrices - a total of 52,800 nozzles.

Edgeline is installed in latex printers and roll-to-roll printers from HP. The T300 with a print width of 77 cm includes 70 print heads for each side of the printed canvas. Thus, in double-sided printing mode, 7,392,000 nozzles operate, and the machine applies 148 billion drops to the printed material every second with high precision. All thermal printheads are consumables; their service life depends on the volume of ink passing through them.

Thermal printheads for desktop inkjet printers are also produced by Kodak and Lexmark. Some of the models equipped with them have already been discontinued.

In the wide-format printing market in the segment of inkjet printers with aqueous inks, there is a battle between Canon and HP, the only supplier of latex printers with thermal print heads. And no one other than HP has yet offered a thermal printhead in a single-pass configuration.

Inkjet thermal technologies feel very confident in their niche, but most of the roll and flatbed printers of large and extra-large formats are now represented by models with piezojet print heads.

Piezo technology: drop on demand

Piezoelectric print heads are united by the principle of droplet atomization. Thanks to a wide range of modifications for different materials and applications, they are very popular among inkjet printer manufacturers.

The principle of drop-on-demand technology is based on changing the shape of certain crystals when voltage is applied. As a result, the chamber is deformed, generating an impulse. There are piezoelectric inkjet heads on the market from more than a dozen manufacturers.

Inkjet technologies have many applications, printing is just one of them. Inkjet printheads are used for marking and coding, postal codes and addresses, document processing, textile printing and marking, engraving, photovoltaics, material deposition and precision liquid dispersion.

Inkjet printheads can be classified by:

compatibility with liquids (aqueous, oily, solvent, UV, acid compositions);
operating temperature;
number of nozzles;
physical permission;
print width;
material of construction;
fixed or variable drop;
smallest drop size;
environmental friendliness

The main difference between inkjet print heads is a fixed or variable droplet size. Fixed drop printers are called binary printers. It is important to understand the differences between technologies and how they work.

Binary printheads produce droplets of a standard volume. There are a lot of options - from 1 pl to 200 pl or more (picoliter - one trillionth of a liter). The main advantage of the technology is that large droplets cover the printed material faster. Another feature of print heads with a fixed droplet size is reduced resolution. Therefore, they are better suited for large format printed products, textile printing and other segments where resolution is not a primary concern.

The smallest drop is provided by the large format printers of the Durst Rho P10 series: Quadro Array print heads with a size of 10 pl offer a resolution of up to 1000 dpi. Inkjet heads with a droplet size of 1 pl are designed not for graphics, but for liquid deposition and printed electronics.

Fixed-drop printheads benefit from their spray frequency, measured in kilohertz (1000 cycles per second). Inkjet printers based on this technology come in 4- and 6-color configurations. When working with large volumes, do not forget that the printing speed of 4 colors is higher than that of 6 colors, and if several print heads are responsible for one color, the printer will generally “fly”.

There is now active debate about which technology is better and why - with a fixed or variable droplet size. But first of all, you need to take into account practical aspects: manufactured products, cost of the printer, economically justified speed.

Variable droplet size printheads can adjust print resolution on the fly. To enlarge the droplet, the system combines several droplets of the base size.

Let's take as an example a printer with a base drop of 6 pl. To get a 12 pl drop, the system sends two pulses to the ink chamber at once: the drops meet in the air and merge into one. The droplet sizes available for a particular printhead are called “levels.”

The 8-level head produces droplets of seven sizes. A piezoelectric head with support for 16 levels will produce 15 droplet sizes. With a base drop size of 6 pl, the available options are obtained by simply multiplying the base drop: 6, 12, 18, 24, 30, 36, 42 pl.

If we analyze the frequency of spraying, it turns out that the formation of variable droplets takes longer, which is quite logical. For a 16-level piezojet head, the base droplet spray speed will be about 28 kHz. If you activate 8 drop options for it, the spray speed will drop to 6.2 kHz. If all 16 options are engaged, the speed is only 2.8 kHz. As we see, when moving from basic level to the maximum possible 16 levels, the number of droplets formed is an order of magnitude less. Printheads with variable droplet size invariably print slower than those with a fixed droplet size. But they increase the resolution of small text and print quality in general.

To increase the performance of variable drop inkjet heads, printer makers are increasing the number of channels per color. The ink channel is a series of nozzles dedicated to a specific ink color - a typical option for scanning and printing systems in one run.

Scanning printing here refers to an inkjet printing method in which a carriage with a print head moves back and forth across the surface of the printed material, and it is fed in a start-stop mode. In some flatbed printers, the image is formed differently: the material reciprocates under a group of print heads that span the entire print width.

Continuous Inkjet - High Speeds

Continuous inkjet technology is a non-contact version of high-speed printing that is used to apply variable information to moving material. Originally designed to add dates, text and barcodes, the modules now offer multi-color printing on roll media. It's hard to believe, but Lord Kelvin was the first to patent this idea in 1867.

The principle of the technology is as follows: a pump supplies liquid ink from a reservoir to many tiny nozzles, forming a continuous stream of droplets at a very high speed. The rate of formation and spraying of droplets is controlled by a vibrating piezoelectric crystal. The speed of its vibration is called the frequency, which in this case varies from 50 to 175 kHz. Each nozzle produces between 50,000 and 175,000 drops per second. They fly through the electrostatic field and, already charged, enter the deflection field, which directs them to the material or to the collection tank for reuse. The bulk of the droplets goes for recycling, and only a small part forms the image on the print. One of the main advantages of this type of inkjet printhead is its high speed.

Kodak Stream is an example of continuous inkjet hybrid printing technology. Periodic pulses in the heating modules near each print head nozzle form tiny ink droplets. By adjusting the size and shape of the pulse, the system changes the size of the point and the speed of droplet spraying. Stream technology generates droplets at a frequency of 400 kHz, not inferior in speed to traditional web offset presses. Moreover, Kodak is confident that it is possible to increase the pulse frequency.

The closest competitor to the Prosper digital printing machine is the inkjet roll-to-roll digital printing machine from HP. The theoretical maximum frequency for it is stated at 100 kHz. And for piezoelectric inkjet printers, the standard frequency is 25-40 kHz.

Stream technology is based on MEMS microelectromechanical systems (they were also used in HP Edgeline print heads). Modern MEMS manufacturing technology is similar in principle to integrated circuit manufacturing techniques that are used to create subminiature inkjet structures on silicon. The plate with nozzles is a mechanical element combined with electronics on a common silicon base.

Choose any

Printheads are just one component of complex printing systems. To select the technologies that are best for a particular company, be sure to take technological differences into account. Given the widest selection of offers on modern market, it is important to arm yourself with as much information as possible.

About the author: Jeff Burton ([email protected]), SGIA digital print analyst and consultant for digital print production, color management and product mix, digital equipment and manufacturers. For more than 20 years in the industry, he worked as a production manager, association consultant, and trainer. Author of numerous technical articles and speaker at industry events.

On the same topic:

There are two main printing technologies common in the inkjet printing market: piezoelectric and thermal inkjet.

The differences between these systems are in the method of depositing a drop of ink onto the paper.

Piezoelectric technology was based on the ability of piezocrystals to deform under the influence of electric current. Thanks to the use of this technology, full control of printing is achieved: the size of the drop, the thickness of the jet, the speed of drop ejection onto the paper, etc. are determined. One of the many advantages of this system is the ability to control the size of the droplet, which allows you to obtain prints high resolution.

The reliability of the piezoelectric system has been proven to be significantly higher compared to other inkjet printing systems.

The print quality when using piezoelectric technology is extremely high: even universal, inexpensive models allow you to get prints with almost photographic quality and high resolution. Another advantage of printing devices with a piezoelectric system is the naturalness of color rendering, which becomes really important when printing photographs.

The print heads of EPSON inkjet printers have a high level of quality, which explains their high cost. The piezoelectric printing system ensures reliable operation of the printing device, and the print head rarely fails and is installed on the printer, and is not part of replaceable cartridges.

The piezoelectric printing system was developed by EPSON, it is patented and its use is prohibited by other manufacturers. Therefore, the only printers that use this printing system are EPSON.

Thermal inkjet printing technology used in Canon, HP, Brother printers. Ink is supplied to paper by heating it. The heating temperature can be up to 600°C. The quality of thermal inkjet printing is an order of magnitude lower than piezoelectric printing, due to the inability to control the printing process due to the explosive nature of the drop. As a result of such printing, satellites (satellite drops) often appear, which interfere with obtaining high quality and clarity of prints, leading to distortion. This drawback cannot be avoided, since it is inherent in the technology itself.

Another disadvantage of the thermal inkjet method is the formation of scale in the print head of the printer, since ink is nothing more than a combination of chemicals dissolved in water. The resulting scale clogs the nozzles over time and significantly deteriorates the print quality: the printer begins to streak, color rendition deteriorates, etc.

Due to constant temperature changes in devices using thermal inkjet printing technology, the print head is gradually destroyed (burns out under the influence of high temperature when the thermoelements overheat). This is the main disadvantage of such devices.
The service life of the print head of EPSON printers is the same as the device itself, thanks to the high quality of manufacturing of the PG. Users of devices with thermal inkjet printing will have to buy a new print head each time and replace it, which not only reduces the durability of the printer, but also significantly increases printing costs.
The quality of the print head also matters when using non-original consumables, in particular CISS.

The use of CISS allows the user to increase print volumes by 50%.
The print head of EPSON printers, as has been mentioned more than once in this article, has high quality, due to which an increase in printing volumes does not negatively affect the operation of the printer, but on the contrary allows the user to get maximum savings without deteriorating print quality.

Due to the characteristics of printing devices using thermal inkjet technology, an increase in printing volumes can lead to the failure of the PG printer.

As observations show, to obtain maximum savings with perfect print quality, it is more advisable to use EPSON printing devices with CISS. EPSON printers operate with a continuous ink supply system more consistently than printing devices from other manufacturers.

The development of thermal technology began in 1984 by HP and Canon. At first, business was slow and required a lot of money. And only in the 1990s. managed to achieve an acceptable level of quality, speed and cost. Later to HP and Canon with the aim further work Lexmark joined in on thermal printers and this led to the creation of today's high resolution printers. As the name implies, thermal (or electrothermal) jet formation is based on an increase in the temperature of liquid ink under the influence of an electric current. This temperature increase is provided by a heating element located in the ejection chamber. In this case, some of the ink evaporates, and a build-up in the chamber quickly increases. overpressure, and a small drop of ink is ejected from the ejection chamber through a precision nozzle. Within one second, this process is repeated many times.

Thermal droplet ejection system . Print quality, speed and efficiency are determined by many factors, but the main factors determining the behavior of ink at the required temperatures and pressures are the configuration of the ejection chamber, as well as the diameter and precision of the nozzle. The behavior of ink when heated and ejected from the nozzle, along with the characteristics of the ink itself (its viscosity, surface tension, ability to evaporate, etc.), is also influenced by the characteristics of the channel leading to the nozzle and the point of exit into the nozzle. Of great importance for ensuring the correct ejection of ink from the nozzle are also the nature of the change in the ink meniscus in the nozzle after ejection and the refilling of the ejection chamber.

Mechanics of creating a thermal jet . Stages of drop formation and ejection.

Stage 1 - Creating overpressure . The formation of the thermal ink jet begins in the print head of the cartridge. The electrical impulse generates a heat flux on the heating elements equivalent to more than two billion watts per square meter. This is about 10 times more than the flux on the surface of the Sun! Fortunately, since the duration of the thermal pulse is only 2 millionths of a second, although the temperature during this time increases at a rate of 300 million degrees per second, the surface of the heating element only manages to heat up to approximately 600°C during this time.

Stage 2 - Forming an ink drop . Since the heating is extremely fast, in reality the temperature at which the ink can no longer exist as a liquid is reached only in a layer less than one millionth of a millimeter thick. At this temperature (approximately 330°C), a thin layer of ink begins to evaporate and a bubble is pushed out of the nozzle. The steam bubble is formed at a very high temperature, and therefore the steam pressure in it is enormous - about 125 atmospheres, i.e. four times the pressure created in modern gasoline internal combustion engines.

Stage 3 - Cooling the chamber. Such a bubble, possessing enormous energy, acts like a piston, throwing ink from the nozzle onto the page at a speed of 500 inches per second. The resulting drop weighs only 18 billionths of a gram! Based on commands from the printer driver, 400 nozzles can be activated simultaneously in any combination.

Step 4 - Filling the chamber . Refilling the ejection chamber takes less than 100 millionths of a second, after which the chamber is ready for use again. In Lexmark thermal inkjet printers, the cycle of forming and ejecting an ink drop, cooling and reheating the chamber can be repeated up to 12,000 times per second.

Impressive facts . Here are some data characterizing the process of bubble formation. Heat flow at the surface:
heating element = 109 W/m2
Sun = 108 W/m2
Heating in a thin layer to a temperature of 600°C
Melting point of aluminum = 660°C
Initial pressure in the bubble - 125 atm
This is the pressure in the ocean at a depth of 1,000 m

Differences between "bubble jet" and "ink jet". Although inkjet technology was originally created by HP and Canon, the term "bubble jet" has now become associated with Canon, essentially separate from the "inkjet" technology being developed by Lexmark and HP. However, in reality both of these terms refer to almost identical systems. The only major difference between them is that in Canon's "bubble jet" system, the vector of the process of ink evaporation and bubble formation does not coincide with the direction of the axis passing through heating element and the nozzle, and is oriented at an angle of 90° to it.

Ink cartridges. The reservoirs from which ink is supplied to the print head can be divided into two design types. First, the monoblock system, which combines a built-in ink tank and an ejection unit, is widely used. It has the advantage that every time the ink tank is changed, the print head is also replaced, which helps maintain high print quality. In addition, it is simpler in design and easier to replace. In the second, more complex system, the print head is separated from the ink reservoir, and here only this reservoir is replaced when it is empty.

Manufacturing of print heads. The manufacture of a print head is a complex process carried out at the microscopic level, where the measurement accuracy is determined in microns. The basic materials used to make the ejection chamber, ink channel, electronic control circuitry and heating elements are similar to those used in the semiconductor industry, where the thinnest conductive metal and insulating layers are precision laser processed. This technology requires large investments in both development and production, and this is one of the main reasons that very few companies decide to act in this area.

An example of a monoblock cartridge. The foam in the ink reservoir acts as a sponge to absorb liquid ink so that ink is continuously supplied to the print head without unwanted leakage from the cartridge due to gravity or leakage of ink from the print head itself. At the base of the monobloc cartridge are the electrical contacts and the print head - a key element of the entire inkjet printing process; ink is supplied to the print head through a set of channels coming from the reservoir.

Location and number of nozzles . The print head is a collection of many microassemblies consisting of ejection chambers and associated nozzles, arranged in a checkerboard pattern to increase the vertical density of the nozzles. With this arrangement of nozzles, the number of nozzles at a distance of half an inch (approximately 1.27 cm) can reach 208, as is the case, for example, in the black cartridges of Lexmark Z models, so that a resolution of 1.44 million dots can be achieved.

Prospects. Print quality is determined by many factors, but the main ones are dot size, vertical dot density and drop frequency through the nozzle; These indicators are the main criteria for further work on print heads, be they thermal or piezoelectric heads. Thermal heads have some advantages over electromechanical heads because the key technology used to make them is similar to that used to make microprocessor chips and other semiconductor electronics products. Rapid progress in these areas is benefiting thermal technology, and we can expect even higher resolutions and faster printing speeds to be achieved in the coming years.

Advantages and disadvantages. Thermal inkjet printing has several advantages over its competing piezo technology. For example, the simplicity of the design and the close analogy with semiconductor manufacturing: this means that the marginal cost of production here will be lower than for competing technology. The configuration of the ejection chambers allows the placement of nozzles closer friend to each other, which makes it possible to achieve higher resolution.

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 a picture or text using a plate of nozzles 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 spans almost 200 years.

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

Stages of development of inkjet printing

Theoretical developments

The theoretical foundations of inkjet printing technology go back to 1833. It was then that Felix Savard, a French physicist and inventor, discovered an interesting pattern: as a result of spraying liquid 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 laureate.

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

Continuous printing

The year 1951 was significant for inkjet printing technology - 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 predecessors of modern inkjet printing devices were quite bulky, equipped with various cylinders, pumps and other moving parts, difficult to use and, moreover, expensive big money. Such printers worked very slowly, and were not without their drawbacks: they could leak ink when printing, which was not very convenient or safe.

Print on demand

The process originated in the 60s of this century, when a professor from Stanford University managed to obtain identical in volume and distant from each other by equal distance ink drops. To do this, he used pressure waves produced by the movement of a piezoceramic element. This 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 recirculation, charging system, and eliminate droplet deflection.

Printing on demand was first used in 1977 in PT-80 printing devices from Siemens, and some time later (1978) in a Silonics printer. Later this method 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 the printer was, and still is, the print head. It was impossible to replace it “painlessly”, as was the case with the cartridge. Therefore, users found new interaction algorithms. For example, in order to prevent the print head nozzles from clogging with air bubbles or dried ink residues, they tried to use the printer even when there was no particular need for it. And all in order to prevent long-term downtime of the printing device.

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

Bubble Seal

We owe our bubble printing technology to Canon. In the late 70s, its specialists introduced the world to a previously unknown inkjet printing technology - “Bubble Jet” or “bubble printing”. The operating principle 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 current is applied to it. When heated, the ink boils, air bubbles form inside the chamber, under the influence of which they are pushed out of the nozzle onto the paper. equal volumes ink. 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 continuous printing.

Principle of bubble jet printing technology

As soon as Canon introduced bubble jet technology at the Grand Fair in 1981, the public immediately became interested. And already in 1985, the Canon BJ-80, the first monochrome bubble printer, saw the light of day. 3 years later, the Canon BJC-440 appeared, the first large format printer using the same technology. He could already print in color with a resolution of 400 dpi.

Printing costs with bubble inkjet technology are relatively low. However, printer maintenance costs increase because the print head is built into the ink cartridges rather than into the printer. But there is also the other side of the coin: 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 back in 1984. The whole point is that it was not possible to achieve the required combination of quality and cost of printing, as well as speed. A little later, Lexmark joined the industry giants. In this tandem, these largest companies achieved high resolution printing and created something similar to modern printers.

The resulting technology became known as “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 increased under the influence of the heating element. Ink located close to the heating element begins to evaporate when heated. Bubbles are formed, which push a certain number of them out of the nozzle. As a result of the decrease in pressure, the same volume of ink enters the print head. This process is repeated with high cyclicity up to 12 thousand refills per second. The print head based on thermal inkjet technology consists of large quantity microscopic nozzles and ejection chambers.

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

The working principle of a thermal printer

Bubble and thermal inkjet printers had an affordable price, were compact, operated silently and provided a wide color range, thanks to which they flooded the market of affordable printing devices and practically ousted dot matrix printers from the market.

Piezoelectric printing

Piezoelectric Ink Jet technology appeared in 1993 thanks to Epson, which was the first to use it in its 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.

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 changing a cartridge, air may enter the print head and clog the nozzles, affecting print quality.

Modern traditions

Advances in technology have now made inkjet printers even more popular. They are purchased for both office and home use due to their affordable price and compactness. Sometimes users buy inkjet printers for color printing as a complement to monochrome laser printers. There is an opinion that laser devices are faster and cheaper when printing text documents, while inkjet devices are faster and cheaper when printing color photographs.

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

Advantages of inkjet printers.

The most important advantage of inkjet printing devices is the high quality of color printing. You can recreate vivid and realistic photos with excellent rendering small parts and halftones. In addition, inkjet printers are practically silent, do not require a long time to warm up, and are available in a wide range of model range and are available in different modifications.

Disadvantages of inkjet printers.

The main reason for not using an inkjet printer is the high cost of original cartridges, the fragility of prints due to fading or spreading of ink when liquid gets in, as well as clogged print heads. Although the solutions to all these shortcomings are very simple. Blockages can be eliminated by standard head cleaning, and prints can be made more durable by using pigment ink. But alternative consumables and ink, which at the moment achieved high quality indicators. The difference from the original ink is no more than 2-5%, due to which the difference in printing results is indistinguishable to the naked eye.

You can read a lot of news about the development of modern printers, MFPs and plotters.

The core of any inkjet printing process is the process of creating droplets of ink and transferring those droplets onto paper or any other inkjet-compatible media. Controlling the flow of droplets allows you to achieve different density and tonality of the image.
Today, there are two different approaches to creating a controlled droplet flow. The first method, based on creating a continuous flow of droplets, is called the method continuous inkjet printing. The second method of creating a flow of drops provides the ability to directly control the process of creating a drop in right moment time. Systems using this method of controlling droplet flow are called systems pulse inkjet printing.

Continuous Inkjet Printing

The pressurized dye enters the nozzle and is separated into droplets by generating rapid pressure fluctuations produced by some electromechanical means. Pressure fluctuations cause a corresponding modulation of the diameter and speed of the dye jet emerging from the nozzle, which is divided into individual droplets under the influence of surface tension forces.
This method allows you to achieve very high speed creating droplets: 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 droplet flows. Droplets flying out of the nozzle pass through a charged electrode, the voltage on which changes in accordance with the control signal. The flow of droplets then enters the space between two deflecting electrodes that have a constant potential difference. Depending on the charge received previously, individual drops change their trajectory in different ways. This effect allows you to control the position of the printed dot, as well as its presence or absence on the paper. In the latter case, the drop is deflected so much that it ends up in a special catcher.
Such systems allow printing dots with a diameter from 20 microns to one millimeter. A typical dot size is 100 microns, which corresponds to a droplet volume of 500 picoliters. 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 droplets allows for the possibility of directly controlling the process of creating a droplet at a certain time. Unlike systems continuous action, there is no constant pressure in the volume of ink, and if it is necessary to create a drop, pressure pulses are generated. Controlled systems are fundamentally less complex to manufacture, but their operation requires a device for generating pressure pulses approximately three times more powerful than for continuous systems. The productivity of controlled systems is up to 20 thousand drops per second for one nozzle, and the diameter of the drops is from 20 to 100 microns, which corresponds to a volume from 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, a piezoelectric element is installed in each nozzle, 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 contracts and expands, squeezing a drop of ink through the nozzle. A similar drop generation method is used in Epson inkjet printers.
A positive property of such inkjet printing technologies is that the piezoelectric effect is well controlled electric field, which makes it possible to quite accurately vary the volume of the resulting droplets, and therefore sufficiently influences the size of the resulting spots on the paper. However, the practical use of drop volume modulation is complicated by the fact that not only the volume but also the speed of the drop changes, which causes point positioning errors when the head is moving.
On the other hand, the production of printheads for piezoelectric technology turns out to be too expensive per head, so in Epson printers the printhead is part of the printer and can cost up to 70% of the total cost of the entire printer. Failure of such a head requires serious service.

For implementation thermojet method, each of the nozzles is equipped with one or more heating elements, which, when current is passed through them, are heated to a temperature of about 600C in a few microseconds. A gas bubble that appears during sudden heating pushes a portion of ink through the nozzle outlet, forming a drop. When the current stops, the heating element cools down, the bubble collapses, and another portion of ink from the input channel takes its place.
The process of creating droplets in thermal print heads after applying a pulse to a resistor is almost uncontrollable and has a threshold dependence of the volume of evaporated substance on the applied power, so here dynamic control droplet volume, unlike piezoelectric technology, is very difficult.
However, thermal printheads have the highest performance-to-cost per unit production ratio, so the thermal inkjet printhead is usually part of the cartridge and when replacing the cartridge with a new one, the printhead is automatically replaced. However, the use of thermal print heads requires the development of special inks that can evaporate fairly easily without ignition and are not subject to destruction due to thermal shock.

Lexmark printhead

Regular 600 dpi black cartridge print head 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 print head, which contained 104 monochrome nozzles and 96 color nozzles.
For the production of print heads for Lexmark inkjet printers, starting from the 7000 series, print heads are used that are manufactured using laser nozzle flashing technology (Excimer, Excimer 2). The first printhead models contained 208 monochrome nozzles and 192 color nozzles.
For the Z51 model and the older model of the Zx2 and Zx3 family, its own 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, like in the following models, all the nozzles were simultaneously used.
The junior and mid-range models of the Zx2 family use cartridges that are modifications of standard high-resolution cartridges, while the junior and mid-range models of the Zx3 family use new models of Bonsai cartridges.
Do not leave the print head nozzles open for long periods of time. If the nozzles are left open, the ink in them dries out 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.

Printhead Specifications

Period of meniscus formation:
This is the period of time required to refill the chamber with ink. It defines operating frequency print head (from 0 to 1200 Hz).

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

The mass of the drop is determined by:
The size of the heating element.
Nozzle diameter.
Back pressure.

It has been noticed that in conventional inkjet printers, a drop of ink hitting the paper takes the shape of a small triangle, so the lines look jagged upon closer inspection. This is due to the fact that the drop is deformed in flight, and when it comes into contact with paper, it blurs. This is especially noticeable in low mode during economical printing. Lexmark offers printers with a new, advanced printing technology in which the shape of the nozzles and the speed of the head are balanced so that a drop of ink produces spots like even strokes. This results in smooth lines and print quality almost indistinguishable from laser printing. In addition, this shape of the spot allows you to avoid whitish streaks on the print.

What is ink?

Each inkjet printer manufacturer develops and improves its own ink composition, which is most adapted to the equipment being produced. Lexmark's main inkjet ink components are:
-Deionized water (85-95% of total volume)
-Pigment or dye
- Solvent (for pigments)
-Humectant
-Surfactant
-Biocide
-Buffer (pH stabilization)

Pigment or dye. Pigment-based inks (black only) are made from solid particles suspended in a liquid. When such ink gets on paper, the liquid evaporates and is partially absorbed, and the powder adheres to the surface without spreading over it. Therefore, pigment-based inks are water-resistant, have weak penetration into paper fibers, but are sensitive to light.
Dye-based inks are typically colored inks. The dye is soluble in water and is absorbed along with it into the thickness of the paper when it dries. Such inks dry faster than pigment inks, are lightfast, but produce average stains irregular shape more than the last ones.
Humidifier. The concentration of the humidifier affects the viscosity of the ink. This parameter should be optimal for the given ink composition and the print head with which they 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 high a viscosity results in a prolonged meniscus formation time, which degrades printing speed. Typically, the ink viscosity is key parameter when determining geometric channels in the print head.
Surface tension affects the wettability of ink on all surfaces with which it comes into contact, from the reservoirs in the cartridge to the surface of the paper. If the statistical surface tension is too low, the ink dries faster on the paper surface, but the average drop volume when squeezing ink out of the nozzles is too high. Too high a surface tension increases drying time and therefore reduces the durability of the image when printed.
Acidity level(PH) low acidity leads to low solubility of ink components in water and, as a result, poor water resistance of the image. The standard acidity level is 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 ink cells for three different colors. A monochrome cartridge contains only one cell of black ink.

Ink and colors

Correctly transferring the color of an image onto paper is a highly technological process that requires taking into account a considerable number of factors, including subjective assessment. First of all, the color reproduction of the image depends on chemical composition ink and paper, printer architecture.
A mandatory requirement for ink is a very fine spectral composition, otherwise the colors obtained when mixed will be “dirty”. Once dry, the ink must remain transparent, otherwise there will be no natural color mixing.
An important factor is also resistance to fading, environmental friendliness and non-toxicity.
It is believed that the optimal composition of ink is already known. Almost all manufacturers use them as a suspension of very small particles of mineral pigment. With colored inks the situation is worse, since it is very difficult to find the right mineral dyes spectral composition.
Currently, color rendering procedures are based on so-called color tables, which are used to convert the color space in which the original image was created into a “deformed” color space that takes into account the peculiarities of how colors are rendered on paper by ink. Typically, separate color tables are built for each type of paper and optimized for each separate type ink and print heads.

Lexmark Drivers

Lexmark printer drivers are ready to print once installed, with automatic object recognition to help you get good quality images without pre-setting. Automatic mode also allows you to achieve the optimal combination of document print quality and speed. Driver settings for special paper or selecting color tables for a more contrasting or natural tone of the image is very simple in the “Document Quality” section of the driver settings.
Lexmark Color Fine 2 Series drivers allow you to automatically detect the type of cartridge, thereby significantly simplifying the procedure for configuring all systems to a different type of cartridge or replacing an old one with a new one. Characteristic feature drivers of this series is their ability to work with images in the sRGB and ICM standards.
sRGB standard proposes that a device-independent color space built into the Microsoft OS or Internet tools is used to describe a color image. Using the standardized RGB description of the UTI-R BT.709 color space, this standard allows us to minimize the transmission along with the image of additional information associated with the color profile of the equipment on which the image was created. The system part of the image file only provides a reference to the standard in which it was created, and the destination position is actively used by the color space description provided by the operating system.
ICM standard allows you to more accurately define the diversity of color image generation and display devices by using color hardware profiles for each type of image generation and display device. However, this approach implies that system information associated with the profile of the equipment on which the image was created is stored in place with this image.

Photo printing

A major challenge 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 saturated color dots, so to obtain pale shades you need to apply drops of ink quite rarely. This causes the spots to be so far apart when transmitting very light tones that the grain in the image becomes noticeable, and also causes problems with the rendering of highlights.
One of radical ways The solution to this problem is to use additional light-colored inks. In this case, dark tones are obtained by filling with lightened ink. A cartridge with such ink usually replaces the second cartridge (black) and contains lightened Cyan, lightened Magenta and black inks. A light yellow tone is not used because this color is perceived by the human eye without much difference as yellow.