Japan's gravure printing is mainly used in packaging printing, and its rate is close to 90%. In Europe and the United States, flexo printing dominates most of the market for packaging and printing, and the market is different. Japan's gravure printing has entered a period of maturity today. Flexo printing has also gone from previous low-quality printing, or has changed considerably as a special-purpose image, and has made considerable improvements. Now it is the third largest printing method after offset printing and gravure printing. First, the background of gravure and flexo ink In 1995, Japan's total amount of printing inks was more than 400,000 tons, of which gravure inks accounted for 1/3. Since the late 1960s, gravure inks have rapidly become popular due to the replacement of cellophane with a variety of plastic film materials such as polyethylene, polypropylene, polystyrene, polyester, vinyl chloride, nylon, and so on. Big. However, the rate of growth has slowed since 1985, and its growth rate has been lower in the past five years. The number of flexo inks is still small, but its growth is extremely strong (Table 1). Gravure inks are low-viscosity inks that are colored with a fast-drying organic solvent-soluble resin. In the past, its chromophores mainly used derivatives of natural resins such as nitrocellulose and rosin. However, with the widespread use of various film packaging materials, there has been an increase in the demand for inks that are more adherent and suitable for various applications and can maintain physical properties. All resins that are soluble in solvents can be applied to a variety of gravure inks. In recent years, water-based inks have been actively developed due to environmental requirements and hygiene issues. The history of flexographic printing can be traced back to 1890 when flexographic printing was also referred to as flexographic printing and was limited to rubber flexographic printing. Therefore, it was used in the field of film packaging and was only used as a kraft paper for quite a long period of history. The printing method of the attachment of the bag machine only. In the 1970s, flexo printing was gradually developed in the field of corrugated paper printing, and this area now accounts for 70% of flexo printing. Because flexo printing used rubber stamps at first, it was not possible to make high-quality images. Until 1973, when DuPont developed UV-cured resin plates, it was possible to obtain high-precision prints. The printing inks were also water-based inks. As well as alcoholic ink as the main body. The so-called alcoholicity means that 3 parts of a highly soluble ester-based solvent are mixed with alcohol (because there is very little resin that can be dissolved in a single alcohol solvent), and nitrocellulose, alkyd amine, polyamide, and other resins are used as the vehicle. . However, most resins used for gravure ink cannot be used for flexo printing. Table 1. Changes in the volume and growth rate of major printing inks in the market (Kilotons) Growth rate (times) 85 years 90 years 95 years 85 years 90 years 95 years offset inks 73.7 108.4 119.7 1.47 1.10 1.62 Packaging Gravure Inks 83.2 115.9 121.3 1.39 1.05 1.46 Published Gravure Ink 20.9 25.6 28.5 1.22 1.11 1.36 Metal Plate Ink 28.3 44.1 45.5 1.56 1.03 1.61 News Printing Inks 43.8 50.5 45.7 1.15 0.90 1.04 Rubber Letterpress Flexo Ink 16.5 21.2 25.6 1.28 1.21 1.56 Second, gravure ink 1, concave Development of Printing Inks In addition to the use of lower cost hydrocarbons such as toluene, gravure inks use all fast-drying organic solvents such as esters, ketones, and alcohols. Therefore, gravure printing and ink production are subject to laws and regulations such as fire protection laws and labor safety, and organic solvents such as toluene tend to remain in the printed film. This type of printed matter will cause great harm if used in food packaging. So it is also subject to health laws. 2. Progress of water-based gravure printing inks Water-based gravure printing inks were widely used in the printing of packaging paper and cardboard boxes in the 1970s. Due to the better evaporation drying and absorption drying in paper printing, the drying of water-based inks is better solved and popularized earlier. However, the ink in packaging film printing is water-based, and it has not yet reached a real practical stage. Water-based printing in the field of flexible packaging, adherence to the film, improvement of humidity, and better maintenance of physical properties in various applications, although the requirements for the ink are higher, but the application of such high evaporation energy water-based ink In the middle (the evaporation energy of water is about 5 times that of organic solvents), the matching of desiccant and printing plate system is very important. In addition, due to the reduced lubricating performance caused by water, the frictional resistance increases, and the relative friction between the plate fog and the squeegee and the plate increases, so the improved squeegee system is not available for the entire printing system. The missing part (above right). Although the water-based gravure ink has entered the stage of use, it has yet to gain further popularity. This is because the promotion of the use of water-based inks not only enhances the performance of existing dryers, but also requires high-precision shallow holes. Printing plates, etc., and the improvement of the entire printing system requires considerable investment. In the near future, the gravure printing will be completely separated from the organic solvent. Now a variety of printing tests are being carried out. It can be assured that the printing industry will soon usher in the era of full use of water-based inks. Third, the flexographic printing ink 1, flexographic ink directional flexo ink is not completely different from the gravure ink, but more similar. However, due to the different printing systems, there is a difference in printability with gravure printing. Basically, flexo printing uses water-based inks and alcohol-based inks. Water-based flexo inks have long been used for the printing of corrugated paperboard and paper bags, while waterborne inks for flexible packaging film printing are still under development. Flexographic printing of packaging films now uses alcohol solvent inks, but it is difficult to maintain its physical properties to suit multi-purpose film packaging materials, especially after various composite processing and cooking processes. Another reason why flexo inks are rarely used in packaging film printing is because the print quality is far less than that of gravure printing. The quality of the two printed images is shown in Table 2. The films used in flexible packaging are basically oleophilic, hydrocarbons such as toluene are easy to adhere to, and the gravure ink is also good in transferability, and flexible printing inks mainly composed of polar solvents such as water and alcohols, It is difficult to ink the film, which has the disadvantages of poor transferability and poor leveling. In color printing, it is extremely difficult to handle large-format dot gains with high-precision image processing techniques. In addition to these deficiencies, coupled with many factors of flexo printing, it is necessary for the entire printing system to carry out precise management and transformation of operations. The new choice for flexographic printing is the use of universal UV (ultraviolet curing) inks (the so-called universal inks, which are suitable for printing from paper to film), which have entered the practical stage in Europe and the United States, and some have reported good results. The UV ink has good printability, does not change the physical properties during printing, and can be printed with higher viscosity (viscous as honey). Therefore, dot enlargement is greatly reduced in color printing, thereby improving print quality. In addition, after the use of UV inks, there is no problem of the discharge of solvents, which is conducive to environmental protection. In short, the trend of UV ink will cause constant concern. 2. Problems of flexo-printing water-based inks Flexo printing is called kiss touch. Light-press printing and light-press printing inks have a great influence on the quality of printed images. Water-based ink In the printing of hydrophilic paper, there is no major obstacle in the transfer of the ink, but it is difficult to apply ink to a strong, oil-repellent film, and it is prone to ink-moistening. The ink remaining on the printing plate is Become blocked version of the reasons. In addition, the flexo printing ink has a smaller transfer amount than the gravure ink, and the ink path is long, and the ink scatters due to evaporation during the transfer, resulting in a change in the composition of the ink, resulting in blockage, poor transfer, and poor leveling. Therefore, the re-solubility is good, the change on the machine is small, the ink, adhesion is good, can maintain its physical properties in various uses, and good drying water-based ink is the current demand. However, the contradiction is that both the printability and the physical properties must be maintained. The opposite is true for the functional requirements of the ink. Therefore, the difficulty in designing water-based inks is conceivable. Table 2: Comparison of Gravure Printing and Flexographic Printing Quality Gravure Printing Flexographic Printing (Including Thick Lines) Uniformity and Goodness (Good Inking) • Variation in Fluid Viscosity, Flowability, Moisture, and Easiness Pinholes · Increased printing pressure to improve the ink squeezing at the edge of the field · Good (no ink squeezing occurs) · Indentation is too large and occurs when there is too much ink · Fine anilox roller is used to increase the viscosity of the ink and it is expected to improve the edge of the field Part of fluffy, good (does not occur) · Small print pressure, easy to occur when the amount of ink is small · Stamping caused by deformation of the surface of the printing plate Fine hollow lines, text reproduction · Better · Partially appear jagged jagged · Easy to fine · Too much ink is prone to stacking ink · The hollow lines can be slightly roughened to improve the reproduction of fine text (including thin lines) · Dots appear at the edges, jagged · Good, Straight lines · Too much ink is generated Stacking ink · Fine Cables can be printed with clear lines. Bar code reproduction. Edge mesh. Good. Overprinting. Thicker printing density. Ink density. Available printing plate ink hole depth adjustment. Ink density. Available anilox roller ink hole volume adjustment register. Accuracy and color control Institutional registration · Easy to stretch, thickness varies · Accuracy depends on the sticker · Printed with CI machine is not allowed in the case of limited printing plate fog · Non-image part of the plate due to the accuracy, poor squeegee, ink viscosity, etc. Unfavorable, easy to occur, good (does not occur), blockage, good (does not occur), appropriate printing pressure, minimal ink transfer, ink drying balance, ink re-dissolvability, tone adjustment, image superposition, good, poor dry balance Occurs when attention is paid • When the ink drips • When the speed increases The overprinting of the solid part occurs • Good printing pressure is higher • The dry balance is balanced Color printing • Good (175 lines/inch) • Need to pay attention to the blocking plate, squeegee ink marks, printing Fog and thick lines are good, for example: 85 lines/inch. 100 to 150 lines. Fashionable. Note that blockage occurs. Need to use fine line anilox roller Color tone performance. Good ink hue balance. Concentration through ink Hole size, depth performance, technology accumulation, high light area, good dot network expansion, and highlight reproduction, most of which need to be modified. The ink hue balance, the concentration of a concentration of the network performance, less accumulated technology, technology-related Problems 1, Ceramic anilox ceramic anilox flexo printing applications for more than ten years of history, can be said to be improving and stable ceramic anilox flexo printing quality trump card. Although chrome rollers and laser-engraved ceramic rollers have their own market, it is predicted that the large market is gradually turning to ceramic roller applications. Initially, the ceramic roller causes poor printing due to the unevenness of the ink holes, and uneven roller thickness results in abnormal abrasion of the blade, or pinholes and the like. Now the ceramic roller has been able to maintain a stable quality, but the printing ink often occurs due to ink blocking and lighter or uneven failure, so the cleaning and management after printing can not be ignored. Once the clogging of the ink clogging occurs, ultrasonic cleaning can be used to restore the capacity of the ink cisterns and can be used as new. Because of the superior hardness of the ceramic roller manufacturing process, there has been no report of deterioration of the anilox roller due to wear. So a ceramic roller has at least 10 years of wear resistance. On the face of it, the cost is higher than that of the chrome roll, but considering its durability, it is not only cheap, but also the image quality is greatly improved. In fact, the durability of the ceramic roller is completely unproblematic. In addition, the ceramic roller can be renewed, and the diamond layer can be used to grind the ceramic layer and then sprayed. It is very easy to change the volume of the ink hole. Moreover, the ceramic anilox roller is engraved with a laser, so the ink hole capacity is changed. Convenient, according to the content of the printing selection of the number of lines and anilox roller suitable for ink hole capacity. Recently, there have been used thinner thread anilox rolls. Anilox rollers of 1 inch 500 or 600 lines in Japan are also in use. However, although the number of anilox roller heights is beneficial to the improvement of the printing quality, the thinning of the anilox roller brings about a reduction in the capacity of ink holes. Along with this, the high density of the ink is required, and the density of the ink itself has a certain limit. In the general package printing, at least the ink cavity capacity of at least 3 cm3/m2 is required. The ceramic anilox roll is not only used in flexographic printing, but also can be used as a gravure solid printing roll, an ink fountain roll without an ink key printing machine, a coating roll for an adhesive or a coating, etc., due to its advantages of being hard to wear. 2. The control method of the closed-type ink-jet flexo printing ink has two-roller extrusion method, common ink-squeeze type, and closed reversed ink scraping method. In recent years, the latter has gradually increased. Extrusion can be used for high-density printing, but due to changes in printing speed and ink viscosity, the amount of ink transferred also changes, still easily lead to unstable print quality. general
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