Introduction to the development and evolution of t

2022-07-25
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Introduction to the development and evolution of flexible carton printing plate

with the improvement of people's quality of life and the improvement of printing and packaging requirements for environmental protection, flexible printing has developed rapidly in the world in recent years. In the field of flexographic printing, there are different types, 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 flexo printing uses different printing equipment to print different substrates with plates of different thickness and hardness

up to now, flexographic printing products are mainly in carton, flexible packaging and label. Three aspects are different consumer goods. Corrugated box printing is gradually developing to a higher level of multi-color and dot. In terms of the use of flexo plates, the carton version accounts for 80%, while flexible packaging, labels and others only account for 20%. According to the incomplete statistics of Shanghai carton industry in the past 10 years, it is growing at a rate of 20% every year. Flexographic printing is preferred by carton printing because the surface of the carton is rough, while general metal plates such as offset aluminum plate or gravure copper plate are difficult to print such substrates. Flexographic printing originated from simple text marks, which is also the best choice for carton printing. Later, this printing method gradually evolved into wide format and narrow format environmental protection printing, which is mainly used to print flexible packaging and trademarks. We see that flexographic plates are evolving day by day, which also makes flexographic products more exquisite, plate making simpler, faster and more environmentally friendly

the following is a brief introduction to the development of flexible carton version

development and evolution of carton flexo: manual engraving rubber plate → casting rubber plate → photosensitive resin plate (digital version, solid/liquid version) → laser direct engraving rubber plate

manual engraving plate, 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 carving knife. This plate making method can only produce simple words and patterns, with a hardness of about 20 ~ 50 degrees. Its raw material is natural rubber or synthetic rubber, which has good elasticity, but the handmade technology is particularly strong, which requires skilled skills and rich experience. Therefore, the printing of this version has great limitations and can only make larger fonts. As it is hand carved, it is a common phenomenon that the formula for calculating the scanning rate in 4.2.2 is irregular. The manual engraving plate is made of low hardness plate. The reproduction of pictures and texts has limitations and is not suitable for dot printing. But it has the advantages of convenience, quickness and low cost. At present, there are simple single laser head engraving simple words in the market instead of manual engraving

for casting rubber plate, the production process is to design drawings first, make metal relief plate, press concave paper or metal template, and press rubber plate through concave template. In the process of heating → pressurizing → vulcanizing → hardening → forming, the water used to make the concave template and the residue during the final processing and forming are polluted, which is non environmental protection. According to the ink used in different substrates, the cast rubber plate is produced into a variety of rubber plates, such as the artificial nitrile rubber plate, which is suitable for solvent ink; Natural rubber version, suitable for water-based alcohol based ink. Generally, the hardness value of the rubber plate is shore 50 degrees, and the general thickness capacity difference is 0.045mm. Due to the complex manufacturing process, it is difficult to control the thickness uniformity of the cast rubber plate, so the thickness uniformity is poor. Generally, the method of polishing the back of the plate is used to achieve a unified thickness. Cast rubber has been gradually eliminated due to cumbersome typesetting, long platemaking time and different thickness. At present, it is difficult to see it in the printing plant

photosensitive resin plate. In 1972, DuPont company of the United States took the lead in launching Cyrel photosensitive resin plate. With its high-resolution image transfer, there are a wide variety of plates with various sizes and thicknesses. It can reproduce 2% ~ 95% of the points at 175 lines/inch. The negative and positive lines are equally excellent. The dynamic load value, displacement value, deformation value, experimental speed and experimental curve are good when overprinting precision. It has excellent ink transfer performance, High printing resistance and good performance, accounting for more than 50% of the global flexible plate market

cyrel photosensitive resin plate composition: it plays an important role in ensuring its quality and improving its reliability. Synthetic rubber, acrylic monomers, photoinitiators, etc. can reproduce small graphics and fine point levels. Exposure only needs negative film. The size is stable, the thickness is uniform, the plate making time is short, the hardness is 34 ~ 42 degrees shore, and the thickness tolerance is 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 treatment (uva+uvc light source)

comparison between photosensitive resin plate and engraving rubber plate: the photosensitive resin plate has a small shrinkage and will not produce telescopic deformation during plate making. It can make accurate printing plates with good dimensional stability. The photosensitive resin plate making process is relatively simple, and the reproduction accuracy of the original is high. The side of the photosensitive resin plate is flat and straight. Compensation 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 printing pressure, printing times and recovery degree. 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 plate 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 has large elasticity, the contact with the substrate is uniform, and the printed ink color is also uniform, but the image level reproducibility is poor, and the point enlargement is significant; Small elasticity leads to high hardness, which is suitable for printing high-level point four-color graphics and text; 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 ± 0.03 mm. Depending on the printing equipment, plates with different thickness specifications should be selected, generally 0.7 mm ~ 7mm can be selected at that time. Finally, the depth of the relief. Improper relief of the printing plate will cause the ink to paste the plate or parts of the picture and text to be damaged due to pressure; The stability of polymer directly affects the printing effect and printing resistance of plate

the liquid photosensitive resin version began to rise in the late 1980s, and occupied the Asia Pacific markets such as Japan and Malaysia as well as the manual engraving version. A printing plate made of liquid photosensitive resin is called a 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 1 hour to complete all the work, and the raw material cost is more than half lower than that of the solid Version (calculated according to the liquid version polymer lf32/37 produced in Australia), but this material can only print short-term products. Later, the new TF series of high-quality photosensitive liquid raw materials were introduced. Due to the increased cost, it is difficult to see them in the market. The limitation of liquid plate is that it can not make large size plates. Due to the reason of its technological process, the large format plate making process will lead to the uneven thickness of plates, which is the most difficult problem for users to solve. Many waste products are also caused from this. In addition, the production of plates with different thicknesses requires the replacement of many cumbersome raw materials, so the production of thin plates is relatively less

the Cyrel digital image came out at the end of the 1990s. It solves the problems of film vacuum absorption in the production of ordinary photosensitive resin plates and the enlargement of text edges during the photosensitive process. It is a new breakthrough in photosensitive resin plates. The plate surface 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, the laser burns the black film to form the graphic, and then the main exposure → plate washing → drying → post-treatment process is carried out to complete plate making. It is characterized by high printing contrast, anti white words are not easy to be filled in, and the point enlargement is controlled to the minimum, which can obtain high resolution, save tedious preparation work, solve the problem of vacuum absorption, and solve the problem of determining the exposure time according to the image and text. At present, there are nearly 10 CDI plate making systems in Chinese Mainland. It is believed that more such devices will enter the ranks of flexo plate making in the future

laser engraving rubber plate directly, and laser technology has been used in the printing field since the 1990s. The laser engraving ceramic roller is a new breakthrough in flexo printing. In recent years, the laser engraving rubber plate is used to replace the photosensitive resin plate. The advantage is that the computer inputs the graphic information to directly engrave, eliminating the procedures of vacuum exposure and plate washing of output film. The direct engraving seamless sleeve version simplifies the plate pasting time. Because the plate base is made of fiber cloth, the size is very stable, the printing resistance is high, the plate making process is simple, the picture and text accuracy is high, the plate making time is short and the efficiency is high. By using the laser engraving roller technology, the British Luscher company has improved the direct engraving of rubber plate by laser, with 300wco2 beam, two laser heads producing 0.7m2 per hour, and can engrave on the sleeve plate, which can simplify the time of plate pasting. Rubber plate direct engraving technology has been listed as the most advanced flexographic plate making process in the European and American markets. However, due to its sophisticated equipment, high cost, and imported raw materials, the price of engraving rubber plate is also higher than that of photosensitive resin plate, so it is still a process to put it into use in the Chinese Mainland market. (end)

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