Inkjet printing method and its application

There are more than 20 kinds of inkjet printing methods. The basic principle is to generate small ink droplets first, and then guide them to the set position, which can be roughly classified into continuous type and intermittent type. The so-called continuous inkjet, regardless of imprinted or non-imprinted, the droplets are generated in a continuous manner, and then the non-printed ink droplets are recovered or dispersed; while the intermittent inkjet produces ink droplets only in the imprinted portion. .

1. Continuous inkjet printing

(1) After the offset ink ink is pressurized and ejected, vibrated, and decomposed into small ink droplets, the electric field will cause the small ink droplets to fly directly after flying over the electric field, whether charged or not. When the electromagnetic field is deviated from the electromagnetic field, the ink droplet with a large charge will be strongly attracted and the meander will be larger. On the contrary, the deflection will be smaller. The uncharged ink droplets will be collected in the ink collection groove.

(2) Printing with ink droplets that are not deviated is similar to the above-mentioned one. The only difference is that the deviated charge is recovered, and instead of deviating the charge, the imprint is formed straight away.

(3) The ink droplets that are not needed for charge separation are still pressurized by the orifice, but the orifices are more slender and have a diameter of about 10-15 μm. The ink droplets that are fine enough to be ejected from the orifice of the tube will be automatically broken down into tiny droplets. These tiny droplets will then pass through the charging ring of the same electrode. Since these ink droplets are quite small, these charged ink droplets will be split into mist again because of the repulsion of same-sex charges. At this time, they lose their directivity and cannot be printed. Conversely, ink that is not charged will not split into imprints. Can be used as a continuous tone printing.

2. Intermittent inkjet printing

(1) Electrostatic pulling draws ink due to electrostatic attraction, and the ink at the injection hole forms a convex half-moon shape, and is juxtaposed with an electrode plate. The surface tension of the embossed ink is affected by the parallel electrode. The high voltage on the board is destroyed and the ink droplets are drawn by electrostatic force. The ink droplets are electrostatically charged and can be deflected vertically or horizontally to a set position or recycled on the mask.

(2) Hot Bubble Inkjet

Instantly heat the ink to expand the gas in the vicinity of the resistor. A small amount of ink will also turn into steam. The ink will be pushed out of the nozzle and let it fly to the surface of the paper to form an imprint. When the ink droplets are ejected, the temperature decreases and the temperature in the ink cartridge quickly decreases. Then, the protruding ink is pulled back into the ink cartridge by capillary principle.

Second, the factors that affect the quality of inkjet prints

1. Color conversion

In nature, all colors are composed of different wavelengths of light. When light passes through the prism, we can see the spectrum of light produced by different wavelengths. The spectrum can be said to be a natural phenomenon of continuous color mixing, but we can use it to define color changes and further manage the colors we need. In television, film, and computer applications, we use color additive methods to handle color changes. All colors can be generated by the overlapping of light of three primary colors (R, G, B), and white light also needs only to overlap three types of light. But for prints, people’s eyes use reflected light to determine the difference in color. When you see a red paper, because the light shines on the paper, the red light in the spectrum is reflected, so you know it is red. . Therefore, in the print, we must use the subtractive method to define the color, which is the so-called C, M, Y three-color model. For colored light, red, green, and blue can be mixed white light, but when using watercolor or paint, the color will be deeper, red, green, and blue are not white. However, since the addition of C, M, and Y colors does not mix pure black, the black is then isolated to form a complete subtractive model of C, M, Y, and K for better performance. Printing quality. The "additive principle" and "subtraction principle" are two major systems in color science. How to accurately convert the color of the light source system (R, G, B) to the color of ink jet or printing system (C, M, Y, K) is a very complex knowledge and is the key to the quality of printing.

2. Resolution

For black-and-white printers, resolution may be the key to determining the quality of prints, but for color printers, color gamut is as important as resolution. DPI resolution is an acronym for DotPer Inch, which indicates how many dots can be printed on l in width. For a black-and-white printing press, the higher the resolution, the finer the color-graded dots printed, and the better the quality of printed products. However, for color printers, the resolution refers to how many ink dots can be printed on the width of l in, regardless of whether ink dots overlap. So for color printers, there are so-called real resolutions and addressing resolutions. (Figure 1)

3. Levels

An output image consists of a number of pixels (or pixels) of different colors and brightness. For example, on a television screen or a computer monitor, beautiful and vivid image quality can be presented, and the image is very realistic. However, the resolution on a computer monitor is only 640 dpi ×480 dpi or 1 600 dpi × 1 200 dpi, and the resolution of the television is even higher. low. Since the color is analogous to the output method, the voltage is used to control the color, so that each point can be displayed in continuous color scale (full tone), so even if the resolution is relatively low, but it still feels very natural and realistic. Therefore, the importance of color gradation is also very obvious. Some printing presses use seven-color printing, in addition to the original C, M, Y, and K colors, plus three colors of light blue, light red, and light black. When color mixing, 7 colors make the picture quality closer to continuous color gradation. As the number of primaries on the graph increases, the image becomes more realistic.

4. Print head control

The dots of ink are sprayed onto the paper through nozzles. In general, the nozzles and the print head are made together, so the technology of the print head itself is very important, and the left and right print heads are the ink jet technology, cantilever gears and transmission belts of the printing presses. The precision.

5. ink

Ink can be divided into dye type (D y eType) and pigment type (Pigment Type). The color saturation of dye ink is good, but the water resistance is not good; while the color saturation of pigment ink is not as good as that of dye ink. , but good water resistance. At present, inkjet inks are mostly dye-based, such as Epson and Canon's C, M, Y, and K all-color dye inks. The ink of the ink jet printer must have enough surface tension to prevent the ink from spouting when ejected. In addition, the ink must also be fast-drying to prevent haziness on the paper. Therefore, the ink itself is also one of the factors that affect the print quality.

6. Substrate materials

The quality of the print has an important relationship with the paper used, just like washing photos. Different papers can have different effects. In the case of an inkjet printer, since the fibers of each paper are different, the adsorption capability of the ink is also different. Of course, the effects exhibited are also different. Glossy photo quality is of course best for photo paper; ordinary documents are printed on plain paper or inkjet paper.

Third, the application of inkjet printing

Since inkjet printing is a non-contact, pressureless, non-printing digital printing method, it has unparalleled advantages over traditional printing. It has nothing to do with the material and shape of the substrate. In addition to paper and plates, it can also use metals, ceramics, glass, silk, textiles, etc., and it has strong adaptability. At the same time, inkjet printing does not require film, baking, imposition, printing and other processes, and has been widely used in the printing field.

1. Lottery printing

Sports lottery tickets, welfare lottery tickets, and various commercial papers with variable numbers such as random numbers, bar codes, and two-dimensional codes, etc., can be ink jet printed. Inkjet printing can adapt to a variety of different thicknesses of paper, while the ink can penetrate the paper fiber, to prevent the winning information on the lottery ticket being altered to prevent fraud.

2. Large format inkjet

In the area of ​​large-format printing, inkjet printers are used. In fact, it is another definition of inkjet printers. Usually refers to large-format and ultra-large format inkjet printers. Generally, the width is more than 1 m, and the maximum can reach 3~. 5 m, mainly for the production of large-format posters, promotional items, outdoor advertising, etc. For example, a large-format advertising printing plant in Germany printed the world's largest inkjet newspaper using the VUTEk Ultra Vu 3300 inkjet printer. With the prosperity of the market economy and the expansion of commodity circulation, the inkjet printing of outdoor advertising will show a significant increase.

3. Digital proofing

When DTP has just emerged, digital proofing uses continuous inkjet and thermal sublimation methods. With the advent of large format inkjet printers, large format inkjet printers are now widely used as proofing devices. With inkjet technology, not only less investment, faster, but also the output image quality and final product quality similar to meet customer requirements.

4. Personalized printing

With the prosperity of the economy and the improvement of people’s living standards, there are many personalized albums, commemorative albums, desk calendars, calendars, etc. These prints, which require less print, require shorter time, and have lower costs, use inkjet printers or inkjet printers. It is more appropriate.

In addition, inkjet printing can be used in the direct mail printing market. With the continuous development of inkjet technology, inkjet printers are not only widely used in advertising, photography and other industries due to their good image quality and high speed, but also in applications such as trademark printing, packaging and printing, and security printing. Has become an indispensable output device.

Fourth, the relationship between inkjet printing and screen printing

As a complement to screen printing, the advantages of wide-format inkjet printing are obvious. As a new high-tech printing method, inkjet printing provides a very effective method and approach for the challenges faced by screen printing companies.

Supporting wide-format inkjet printing equipment will accelerate the development of a broader, high-value-added market for screen printers, such as: printing of medium- and short-length adhesive-backed materials, tight sales point poster printing, medium and short-term delivery Version of hard materials and some special applications such as printing. Inkjet printing not only provides a good market for screen printing companies, but also allows the company to provide its customers with "one-stop service" to attract more customers.

Ink jet printing is directly printed by a digital file (standard format), no plate making is required, and a business can be printed within a few minutes after receiving an order. The inkjet printing process is convenient and efficient, and the documents are queued for printing. If a printing machine is equipped with a drying system, the former job is also online and the next job has already started printing.

Inkjet printing saves space and manpower, and management of the printing process is easier. Inkjet printing can be printed according to the exact amount needed for the job, completely avoiding the waste of printed materials during the color calibration process. Wide-format inkjet printing can also provide proofing support for screen printing processes by providing fast, high quality and accurate proofing on the final material.

Although inkjet printing has its unique advantages, it does not pose a direct threat to screen printing. On the contrary, it is precisely complementary to screen printing. Screen printing companies can comprehensively consider plate making time, cost, and printing quantity, and select the appropriate printing method according to the type of business (faster, faster