The hottest talk about the development of flexo pr

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In other words, the development of flexo printing plate

flexo printing has developed rapidly in recent years with its unique printing method. With the improvement of people's quality of life, the environmental protection demand of printing and packaging has increased. In the field of flexographic printing, there are different types of printing processes, such as direct multi-color printing of cartons, pre printing of cartons, flexible packaging printing, film printing (plastic bags, tablecloths, etc.), trademark printing, coating of LCD conductive liquid in the electronic industry, etc. the above flexographic printing uses different printing equipment and plates with different thickness and hardness to print different substrates

so far, flexographic printing products are mainly in cartons, flexible packaging and labels. Because the three are different consumer goods, using Chinese menus and windows standard graphic operations, corrugated box printing is gradually developing towards a higher level of color multi-color dots. In terms of the use of flexographic plates, cartons account for 80%, while flexible packaging, labels and others account for only 20%, And it has adapted to the relatively large pull force in the past 0 years. According to the incomplete statistics of Shanghai carton industry, it has increased at a rate of 20% every year. The reason why flexographic printing is selected as the first choice for carton printing is that the rough surface of cartons, while general metal plates such as offset aluminum base plate and gravure copper plate are difficult to print such cause prints. Therefore, flexographic printing originated from carton printing with simple text marks, which is also the best choice for carton printing. Later, this printing method gradually evolved into wide and narrow format environmental protection printing, mainly making flexible packaging and trademarks. Therefore, we also clearly see the essential equipment of flexo printing - flexo plate is evolving day by day, which makes flexo printing more exquisite, plate making more simple, fast and convenient, and more environmentally friendly. With the rapid development of flexographic printing, the following is a brief introduction to the development of flexible carton printing

the development and evolution of flexible edition: Hand Carved rubber Edition - cast rubber Edition - photosensitive resin (digital edition, solid/liquid Edition) - laser directly carved rubber edition

hand carved version, which is simple to make, belongs to rubber products. It is made by transferring pictures and texts on the front of the plate and then carving with a knife. This method of plate making can only produce simple words and patterns, with a hardness of about Xiao's. Its raw material is natural rubber or synthetic rubber, which has good elasticity, but it is highly skilled in manual production, which requires skilled skills and rich experience. Therefore, the printing of this version has great limitations and can only make larger fonts. It is a common phenomenon that the font is irregular because it is hand carved. Manual engraving plate is a low hardness plate, and the reproduction of graphics and texts has limitations, which is not suitable for dot printing. But it has the advantages of convenience, quickness and low cost. At present, there are simple single laser heads on the market to carve simple words instead of manual carving

the production process of the word casting rubber plate is to first design the drawing, make the metal relief plate and press the concave paper or metal template, press the rubber plate through the concave template, heat the rubber - pressurize - sulfur - harden - form, and the water for making the concave template and the residue during the final processing and forming are contaminated, which is a non environmental protection process. The cast rubber plate can produce a variety of rubber plates according to the inks of different substrates, including artificial nitrile rubber (suitable for solvent inks), natural rubber (suitable for water-based alcohol based inks), hardness value: 50 Shore, and the general thickness capacity difference is 0.045mm. Due to the complex production process, the uniformity of the thickness of the cast rubber plate is difficult to control, so the uniformity of the thickness is poor, and the method of polishing the back of the plate is generally used to achieve a unified thickness. Due to the problems of cumbersome typesetting, long platemaking time and different thickness, cast rubber has been difficult to see in the printing plant before the 5 experimental steps, and is gradually eliminated

photosensitive resin plate. In 1972, DuPont company of the United States took the lead in launching Cyrel photosensitive resin plate. With its transfer of high-resolution images, there are a wide range of plates, with flat sheets of various sizes and thicknesses; Under the condition of 175 lines per inch, 2% - 95% points can be reproduced. The negative line and the positive line are equally excellent, with extraordinary overprint accuracy, excellent ink transfer performance, extremely high printing resistance, and excellent performance accounting for more than 50% of the global plate market. Cyrel photosensitive resin plate is composed of synthetic rubber, acrylic monomer, photoinitiator, etc., which can reproduce fine graphics and fine dot level graphics and texts. Exposure requires negative film completion, with stable size, uniform thickness, high precision, short plate making time, shore hardness, and thickness tolerance of 0.03mm. Plate making process: back exposure (UV-A light source) - main exposure (UV-A light source) - cleaning (75% tetrachloroethylene + 25% n-butanol) - drying (60 ℃) - post-processing (uva+uvc light source)

the difference between the photosensitive resin plate and the carved rubber is that the photosensitive resin plate has a small shrinkage and will not produce telescopic deformation during plate making. It can make a printing plate with accurate size and good dimensional stability. Photosensitive resin plate making process is simple, and the reproduction accuracy of the original is high. The side of the photosensitive resin plate is straight, so the compensation problem can be considered in time when making the base plate, and there is no need to polish the back of the plate. Even if it is thinner than the rubber plate, it can make a high-precision printing plate

how to determine the quality of the photosensitive resin version? The first is to look at hardness and elasticity. Hardness will directly affect the pressure, printing times and recovery degree during printing. The hardness of printing plate is a key index of printing plate. Different equipment and different substrates must be equipped with plates with different hardness. The hardness of the resin version depends on the hardness of the photopolymer, which can be controlled by adding a hardness control agent. Elasticity is the inverse index of hardness, that is, the higher the hardness, the smaller the elasticity. If the printing plate is elastic, the contact with the substrate is uniform, and the ink color printed is also uniform, but the reproducibility of the image hierarchy is poor, and the point enlargement is relatively significant; Small elasticity leads to high hardness, which is suitable for printing high-level point and four-color graphics and texts; Secondly, the uniformity of plate thickness is an important indicator of plate quality. Take DuPont Cyrel photosensitive resin plate as an example: the error range of its thickness can be controlled within +/- 0.03mm. Printing equipment selects plates with different thickness specifications, generally 0.7mm-7mm for selection. Finally, the depth of the relief. Improper relief of the printing plate will lead to the damage of the ink paste or the part of the picture and text due to pressure; The stability of the polymer directly affects the printing effect and printing resistance of the plate

photosensitive resin liquid edition, which began to rise in the late 1980s, and hand carved edition occupy the Asia Pacific markets such as Japan and Malaysia. The printing plate made of liquid photosensitive resin is called liquid photosensitive resin plate. Its plate making process is: flow spreading - back mask exposure - front exposure - back full exposure - recovery of unhardened resin - Development - drying and post exposure. The production of the liquid version takes only 1 hour to complete all the work, and the raw material cost is reduced by more than half compared with the solid Version (calculated according to the liquid version polymer lf32/37 produced in Australia), but this material can only print short orders. Later, the new TF series of high-quality photosensitive liquid raw materials were introduced, which was difficult to see in the market due to the increased cost. The limitation of liquid plate is that it can't make large size plates. Due to the reason of its technological process, large format plate making process will lead to the uniformity of plate thickness, so this is also the most difficult problem for users to solve. Many waste products are also caused from this. In addition, making plates with different thicknesses requires replacing many cumbersome raw materials, so the production of thin plates is relatively less

the advent of DuPont Cyrel digital image in the late 1990s solved the problem of film vacuum absorption in the production of ordinary photosensitive resin plate, and solved the problems of UV light passing through the film time point during the photosensitive process, expanding the text edge and hypertrophy, which is a new breakthrough in photosensitive resin plate. The surface of this plate is coated with a layer of black photosensitive polymer film to replace the negative film of traditional plate making. During plate making, the film is omitted, the computer inputs the graphic data, and the laser burns the black film to form the graphic, and then the main exposure - plate washing - drying - post-processing process is carried out to complete plate making. Its characteristics are high printing contrast, anti white words are not easy to be filled, the dot expansion is minimized, and high resolution high light spots can be obtained, When it comes to price work, it saves tedious preparations, solves the problem of vacuum absorption, and solves the problem of determining the exposure time according to the image and text. At present, there are 8 to 10 CDI plate making systems in Chinese Mainland. It is believed that more such advanced equipment will enter the ranks of flexo plate making in the future

blanket direct laser plate making began to be used in the printing field in the 1990s. Laser engraving ceramic roller is a new breakthrough in flexo printing. In recent years, laser engraving rubber plate instead of photosensitive resin plate has been used. Its advantage is that the computer inputs graphic information and directly engraves it, eliminating the procedures of output film vacuum exposure and plate washing. The direct engraving seamless sleeve version simplifies the plate pasting time. Because the plate base is fiber cloth, the size is very stable, the printing resistance is high, the plate making process is simple, the graphic accuracy is high, the plate making time is short, and the efficiency is high. Using laser engraving roller technology, British Luscher company has improved the direct plate making of laser blanket, with 300W CO2 beam and 2 laser heads of 0.7 square meters per hour. And it can be engraved on the sleeve plate, which can simplify the time of pasting the plate. Blanket direct engraving technology has been listed as the most advanced flexographic plate making process in the European and American markets. However, due to the high precision cost of its equipment, and the price of imported raw materials for carving rubber blanket is also higher than that of photosensitive resin version, there is still a long way to go before it is put into use in the Chinese Mainland market

Author: Wen Xiaolin of Shenzhen JiuHeng Equipment Co., Ltd.

source: International Printing

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