In the history of the printing industry in recent years, the rise of the flexographic printing process is one of the most striking events. A century ago, flexographic printing was only a very insignificant and insignificant printing process. At that time, it was also referred to as “animation printing,†because aniline inks were used. With the application of new materials and improved printing conditions, the flexographic printing process has rapidly emerged. It completely abolished the aniline ink, replaced by solvent-based inks and water-based inks, and the quality of printed matter has been significantly improved and improved. Today's flexo printing process is no longer the same, it has developed into another major printing process following embossing, offset printing and gravure printing. In developed regions such as the Americas and Europe, flexographic printing accounts for about 15% of the total printing market. In the packaging industry, flexographic printing has become the dominant printing technology. In China, the proportion of flexo printing is less than 5%. Flexo printing has great potential for development in China. According to relevant personage predictions, flexographic printing will still maintain a good momentum of growth. In the printing market of corrugated cartons, labels, flexible packaging, paper bags and folding cartons, flexographic printing has grown rapidly, and its market share will continue to rise.
First, the development status of flexo printing Anilox roller technology leading the way With the improvement of anilox roller processing technology and precision, the quality level of flexographic printing process is also constantly improved. Ten years ago, the number of screen lines of anilox rollers was generally limited to the standard of 360-440 lines/inch, but today it has reached 800 lines/inch, and it may be even higher. The higher the number of anilox roller screens is, the thinner the transferred ink layer is, so it is necessary to use ink with a higher and stronger hiding power, and it is not possible to dry on such fine anilox rollers, otherwise Cause paste version.
In addition, flexo printing has also promoted the development of high-speed flexographic printing presses, but this has some difficulties for flexographic printing systems using water-based inks because high-speed printing presses require a high concentration of pigments in the ink, and The ink is required to have good transfer properties.
UV ink technology is one of the best in flexographic printing. Ultraviolet (UV) UV-drying inks began in the middle of the 20th century. However, they have not been developed for nearly 20 years, and they will continue to maintain an astonishing growth rate. In the flexographic printing of trademarks and labels, almost a quarter of the business is printed using UV inks.
UV inks have no pollution, and there is no problem of volatilization of water and solvents at all. There is no solvent volatilization in the printing process, so the bright color of the printed matter, the small dot enlargement rate, and the good reducibility, the quality of the printed matter can be comparable to the offset printing products. Therefore, the application of UV technology makes flexographic printing completely competitive and competing with offset printing.
Water-based inks are widely used in flexographic printing. Water-based inks have the widest range of applications and they have an absolute advantage. For example, water-based inks are used in the printing of corrugated boxes, paper bags, paper products, milk cartons, and the like. However, in the printing compounding of plastic films, although the growth rate of water-based inks is relatively slow, it still maintains a certain growth trend. In addition, water-based inks are expected to show new growth points in folding carton printing and some current gravure printing businesses.
In recent years, the voice of environmental protection has been high, and governments of various countries are also continuing to take measures to protect the environment on which human beings depend for survival. They have successively formulated a series of laws and regulations to intensify efforts to control and reduce the emission of organic volatile substances; environmental protection organizations also Ozone emissions are being strictly limited, which ultimately will affect the emissions of VOCs (organic volatiles) into the atmosphere. Such measures have promoted the promotion and application of water-based inks.
The production level of flexographic printing presses has increased dramatically as the proportion of flexographic printing in the printing market has grown and the range of applications has grown wider, which has led to a significant increase in the development level of flexo printing machinery. In recent years, some well-known European and American flexographic press manufacturers have adopted sleeve technology, closed squeegee, digital plate cylinder, digital (gearless) transmission technology, UV technology, and non-stop roll change when developing new equipment. Device and tension control technology, computer control technology, and predictive diagnostic technology have successfully developed high-quality, high-level flexographic presses. Digital printing systems such as W&H's eight-color satellite flexo press, Cerutti's flexographic flexo press, BHS' Flexline Vario, Flexlin Conpact flexo presses, and CMR's flexless presses are all examples of flexo printing today. The higher level of the machine.
Second, the new breakthroughs in flexo technology Flexo-digital digital plate-making flexo platemaking is the last transition in a variety of layouts to non-film plate printing, this is because the flexographic plate has a certain thickness, to digital information through High-speed laser directly exposed on the plate to obtain three-dimensional dots, the difficulty can be imagined much higher than the lithography. However, all the constraints of the traditional platemaking methods, such as the use of multi-channel image processing with film processing, are not only poor in stability, but also have high costs. In addition, the temperature and humidity have more or less influence on the film, and sometimes it is necessary to beware of the film. Scratches, scratches, etc.; when the film and the plate are exposed, the image quality may be impaired due to light diffusion or poor adhesion, and the subtle tones cannot be reproduced. Since the smaller dots are not easily printed, they can only be used. Print the number of coarse screen lines. Therefore, flexographic printing can only be found in the production of low quality products.
The introduction of a flexographic platesetter directly exposes the image to the flexographic plate, overcoming the above-mentioned disadvantages caused by the use of the film. The flexographic plate used for direct plate making is different from the ordinary plate, and its surface Re-applied a layer of ablative layer - synthetic carbon film, this synthetic carbon film can also avoid dust particles. When the laser scans, the patch at the spot is melted to evaporate without leaving any traces, which is equivalent to leaving an extremely clear picture on the surface, and then the back of the flexo is still exposed as usual. , (The exposure time determines the thickness of the plate). The main exposure (the light source passes through the opening of the synthetic film that has been eroded and direct exposure of the underlying photopolymer, so that there is no scattering or diffuse reflection, so the edges of the dots are sharper and sharper. Moreover, the digital version Even if the material is exposed for a long period of time, it will not cause the dot shape to blur. Finally, the etching process is performed.
In the history of more than 100 years of modern printing technology of flexo printing and screening, screening technology has increased from 30 to 40 years ago in optical screening to electronic screening. The size of outlets ranges from coarse to fine outlets, and the distribution of outlets is from regular to non-existent. The random distribution of rules, all these technical improvements and reforms, eliminates moiré, makes the tone more flat, and the print reproduction range is expanded. In general, the purpose is to improve the printing quality. However, corresponding to this, it is necessary to develop compatible recording speeds and higher resolution devices. However, the development of things tends to undergo unexpected changes. As a result of reverse thinking, some famous merchants are already working hard to develop low-resolution screen-printing screening technologies. According to past experience, in order to reproduce a certain tone in a device with a low resolution, the necessary resolution is 10 times or more than the number of lines (for example, the number of screen lines for 100 lines, the output resolution should be above 1000 DPI. The resolution of a 150-175 network cable generally requires a resolution of 2000-3000 DPI.) Now the new Intelli DotSpeedScreen screening technology from OPTRonICS International Corporation and Turbo Screening developed by Saturn Asia Pacific Co., Ltd. have achieved high resolution lines with low resolution output (eg, 150-175 lines at 1000 DPI). Among the most realistic touches on flexo printing, Samba Screen by BARCO and Hybrid Screen by PPC are both the latest screening methods for flexo printing. For flexo printing, since the dots of the highlights are not easily printed, the reproduction of the highlights is not complete. The above two screening methods are used, and this problem can be completely improved.
Ink Transfer System and New Generation of Anilox Rollers In order to stably supply low viscosity (5-500) ink to the flexographic layout, the anilox roller transfer system is the ideal printing method. In general, the anilox roll is sculpted on the surface of ceramics. According to the different types of cells, it has cubic, conical, oblique, and other shapes. According to the shape, the number of lines, the depth, etc., the ink supply amount and the ink holding amount are calculated. High-quality ceramic magnetic anilox roller has strong wear resistance. From its processing, laser engraving uses conventional carbon dioxide laser engraving method and YAG laser engraving method using multiple impacts, and the latter is currently a type of mesh engraving. The highest preparation method is that each mesh is struck twice by a laser beam, the first hits the engraving, and the second hit increases the depth of the mesh. Double-clicking on the shaped mesh creates a smooth wall with a fast and uniform ink transfer, ensuring print quality. In terms of its composition, the anilox roller inking system has two methods. One is to use a counter roll method in which the peripheral speed is very slow, and the other is a squeegee method in which an ink is scraped with a squeegee like gravure. The anilox roller blade installation method clockwise and counterclockwise. Recently, the ink slot squeegee method was introduced. The two positive and negative squeegees are not only accurate, but also maintain ink volume. Since the ink tank is used, the scattering and evaporation of the ink can be suppressed, and the ink supply can be stabilized according to the printing speed.
In recent years, a newly developed graphite carbon fiber material has gained popularity in the manufacturing industry due to its light and hard characteristics. Invented in 1994, the carbon fiber core was soon applied to the flexo-printed anilox roller core, becoming a new generation of more advantageous anilox roller. Although steel rolls have long been the most preferred material for anilox rolls due to their physical properties such as strength, mechanical processing properties and durability, they are replaced by such carbon fiber roll cores instead of the conventional steel roll cores. Its strength is 2 times that of steel rollers and its weight is 1/10 that of steel rollers.
The anilox roller of this carbon fiber core has been tried out and has the following advantages:
1. Due to the special lightness of the carbon fiber anilox roll, it is easy to handle in the roll change and labor is reduced.
2. The carbon fiber anilox roll is not easily damaged during roll change, which saves a large amount of money for re-engraving the new roll.
3. In the driving part of the printing machine, the total weight of the carbon fiber anilox roller is 1/10 of the weight of the steel roller, which is beneficial to reduce the friction between the rollers and the service life of the anilox roller is accordingly increased, thereby reducing the downtime. , increased productivity.
When the speed of the printing press reached 3000 sheets per hour, the difference between the steel roll and the carbon fiber anilox roll was even more obvious. The steel core anilox roll beats a lot and in its center part, it is not able to maintain the solid image while the carbon fiber The anilox roller, however, can maintain a solid image across the roller surface. Although the carbon fiber anilox roller is light and hard, its offset is less than 1/10 of the steel core roller. The greatest benefit of this feature has greatly improved the printing quality of large flexographic printing presses.