The most popular inkjet printing method and its ap

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Ink jet printing methods and their applications

first, there are more than 20 ink jet printing methods. The basic principle is to produce small ink droplets first, and then guide them to the set position, which can be roughly summarized as continuous and intermittent. The so-called continuous inkjet is to produce ink droplets in a continuous manner, whether image or non image, and then recover or disperse the non image ink droplets; Intermittent inkjet only produces ink droplets in the image area

1. continuous ink-jet printing

(1) the printing ink flows through the pressurized jet, vibrates and decomposes into small ink droplets, and then passes through the electric field. Due to the electrostatic effect, the small ink droplets fly straight ahead regardless of whether they are charged or not after flying over the electric field. When passing away from the electromagnetic field, the ink droplets with large charge will be strongly attracted, and the twists and turns will be large; On the contrary, the deflection is small. The uncharged ink drops will accumulate in the ink collecting ditch for recycling

(2) printing with non deviated ink drops is very similar to the above type, the only difference is that the deviated charge is recovered, and the non deviated charge runs straight to form an image

(3) charge and split the unwanted ink drops. The ink flow is still pressurized and ejected from the nozzle, but the tube hole is more slender, with a diameter of about 10 ~ 15 μ m。 The hole of the tube is so thin that the ejected ink drops will automatically decompose into tiny ink drops, and then make these small ink drops pass through the charging ring of the same electrode. Because these ink drops are quite small, these charged ink drops will split into fog again because the same charges repel each other. At this time, it will lose its directionality and cannot be printed. On the contrary, the uncharged ink will not split and form image. It can be used for continuous tone printing

2. Intermittent inkjet printing

(1) ink is sprayed by electrostatic pull due to electrostatic pull. The ink at the spray hole will form a protruding half moon, and then juxtaposed with an electrode plate. The surface tension of the protruding ink will be damaged by the high voltage on the juxtaposed electrode plate, so the ink droplets will be pulled out by electrostatic force. These ink droplets have static electricity, which can be offset vertically or horizontally, shot to the set position or recovered on the shielding plate

(2) hot bubble inkjet

instantly heats the ink, expands the gas near the resistor, and a small amount of ink will turn into steam, squeezing the ink out of the nozzle, making it fly to the paper to form an image. After the ink drops are ejected, the temperature will immediately decrease, so that the temperature in the ink cartridge will soon be low, and then the prominent ink will be pulled back into the ink cartridge by the capillary principle

2. Factors affecting the quality of inkjet printing

1. Color conversion

in nature, all colors are composed of light of different wavelengths. When light passes through a prism, we can see the spectrum of light with different wavelengths. Spectrum can be called a natural phenomenon of continuous color mixing, but we can use it to define color changes and further manage the colors we need. In the application of TV, film and computer, we use additive method to deal with the change of color. All colors can be produced by overlapping the light of three primary colors (R, G, b), including white light, which only needs to be overlapped. But for printed matter, people's eyes judge the color difference by the reflected light. When they see a red paper, because the light source shines on the paper, the red light in the spectrum is reflected, so they know that it is red. Therefore, in print, we must use subtraction to define color, that is, the so-called C, m, y three color model. For colored light, red, green and blue can be mixed to produce white light, but when painting with watercolors or pigments, the color will be darker and darker, and the sum of red, green and blue is not white. However, because the addition of C, m and Y colors cannot mix pure black, black is then separated to form a complete set of C, m, y and K subtraction model, in order to achieve more perfect printing quality. "Addition principle" and "subtraction principle" are two major systems in chromatics. How to accurately convert the color (R, G, b) of the light source system into the color (C, m, y, K) of the inkjet or printing system is a very complex knowledge, which is the key to affect the printing quality

2. Resolution

for black-and-white printing machines, resolution may be the key to determine the quality of prints, However, for color printing, 20 infrared thermometers and measurement standards for calibration were urgently produced and supplied to Hubei (for the two machines that have been issued, the color scale is as important as the resolution. Dpi resolution is the abbreviation of dotper inch, which indicates how many dots can be printed on the width of 1 inch. For black-and-white printing machines, the higher the resolution, the smaller the color scale dots printed, and the better the print quality. But for color printing machines, the resolution refers to how many ink dots can be printed on the width of 1 inch, regardless of whether the ink dots overlap. So for color printing machines There are so-called real resolution and addressing resolution. (as shown in Figure 1)

3. Color scale

an output image is composed of many dots (or pixel) with different colors and brightness. For example, on the TV screen or computer monitor, beautiful and bright image quality can be presented, and the image feels very lifelike. However, the resolution of the computer monitor is only 640 DPI × 480 DPI or 1 600dpi × 1200 DPI, the resolution of TV is lower. Because the color adopts the analog output mode, and uses and controls the color with the enterprise voltage, so that every point can be displayed in a continuous color scale (full tone), so even if the resolution is relatively low, it still feels very natural and realistic. Therefore, the importance of color scale is also very obvious. Some printing machines use seven color printing, in addition to the original four colors of C, m, y and K, plus three colors of light blue, light red and light black. In this way, when mixing colors, the image quality can be closer to the continuous color scale through seven colors. As the number of primary colors on the graph increases, the image becomes more realistic

4. print head control

ink dots are sprayed onto the paper through the nozzle. Generally speaking, the nozzle 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 inkjet technology, the precision of the cantilever gear and the transmission belt of the printing machine

5. ink

ink can be divided into dye type and pigment type. Dye type ink has good color saturation, but poor water resistance; Although the color saturation of pigment ink is not as good as that of dye ink, it has good water resistance. At present, inkjet inks are mostly dye inks, such as Epson and Canon's C from single-1 process control to all factory automation, m, y, K four-color all use dye inks. The ink of an inkjet printer must have sufficient surface tension to prevent the ink from splashing out when ejected. In addition, the ink must also be fast drying to prevent blooming on the paper. Therefore, the ink itself is also one of the factors affecting the printing quality

6. substrate material

printing quality is closely related to the paper used, just like developing photos, different photo papers can achieve different effects. In terms of inkjet printing machines, because each paper fiber is different, the adsorption capacity of ink is also different. Of course, the effect is also different. Of course, photo paper is the best quality for glossy photos; Ordinary documents can be printed on ordinary paper or inkjet paper

III. application of inkjet printing

because inkjet printing is a digital printing method without contact, pressure and printing plate, it has incomparable advantages over traditional printing. It has nothing to do with the material and shape of the substrate. In addition to paper and printing plate, it can also use metals, ceramics, glass, silk, textiles, etc., with strong adaptability. At the same time, inkjet printing does not need film, baking, plate making, plate printing and other processes, and has been widely used in the printing field

1. Lottery printing

sports lottery, welfare lottery, as well as various commercial bills with random numbers, bar codes, QR codes and other variable data, can be printed by inkjet. Ink jet printing can adapt to various paper thicknesses, and ink can penetrate into paper fibers, which can prevent the winning information on the lottery from being altered and fraud

2. Large format inkjet

inkjet machine is used in the field of large format inkjet. In fact, it is another definition of inkjet printer, which usually refers to large format and super large format inkjet printer. The general width is more than 1 m, and the maximum volume can reach 3 ~ 5 m. It is mainly used to make large format posters, promotional materials, outdoor advertisements, etc. For example, a large format advertising printing plant in Germany uses Witt's ultra large format inkjet printer vutek ultra Vu 3300 to print the world's largest inkjet newspaper. With the prosperity of market economy and the expansion of commodity circulation, the ink-jet printing of outdoor advertising will show a sharp upward trend

3. digital proofing

when DTP was just emerging, digital proofing adopted continuous inkjet and thermal sublimation. With the emergence of large-scale inkjet printers, large-scale inkjet printers have been widely used as proofing equipment. Using inkjet technology, not only the investment is small, the speed is fast, but also the output image quality is similar to the final product quality, which can meet the requirements of customers

4. Personalized printing

with the prosperity of the economy and the improvement of people's living standards, there are many personalized photo albums, commemorative books, desk calendars, wall calendars, etc. these prints with small printing volume, short time requirements and low cost are more suitable to use inkjet printers or inkjet printers

in addition, inkjet printing can be used in the direct mail printing market. With the continuous development of ink-jet technology, ink-jet printing machine, with its characteristics of good image quality and fast speed, is not only widely used in advertising, photography and other industries, but also has become an indispensable output device in trademark printing, packaging printing, anti-counterfeiting printing and other applications

IV. The relationship between inkjet printing and block printing

as a supplement to block printing, the advantages of wide width 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 printing enterprises

supporting wide width inkjet printing equipment will accelerate printing enterprises to expand a broader and high value-added market field, such as: medium and short version of back glue material printing, point of sale poster printing with tight delivery time, medium and short version of hard materials and printing for some special applications, etc. Inkjet printing not only provides a favorable market for printing enterprises, but also enables this enterprise to provide "one-stop service" for their customers, so as to attract more customers

inkjet printing is directly printed by digital documents (standard format) without plate making. A business can be printed within minutes after receiving an order. The process of ink-jet printing is convenient and efficient, and documents are printed in queues. If a printing machine is equipped with a drying system, the previous live part is still dry, and the next live part has begun to print

inkjet printing saves space and manpower, and the printing process is easier to manage. Ink jet printing can print according to the exact quantity required by live parts, which can completely avoid the waste of printing materials in the process of traditional printing and color correction. By providing fast, high-quality and accurate proofs on the final materials, wide width inkjet printing can also be used for plate printing

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