What are the key technologies to improve the quality of flexographic plates?
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Since the launch of Drupa 1995, the flexographic direct plate-making technology has been receiving much attention from the industry and has become a mainstream flexographic plate-making technology.
From traditional film-making to computer-to-plate, the flexographic plate-making technology has indeed achieved a qualitative leap, which has improved the quality of flexographic plate making to a new level.
However, the development of flexographic direct plate making technology has not been rapid for more than 10 years.
On the one hand, the user is reluctant to accept the increase in the cost of the plate making; on the other hand, in the process of direct plate making in the flexographic plate, the influence of the oxygen in the air on the shape of the dot during the main exposure cannot be realized. : 1 copy, and the top of the high-gloss dot is round. The dome dot is sensitive to printing pressure and is prone to wear. After printing for a period of time, a relatively serious dot gain phenomenon tends to occur, and when a non-absorbent material such as a film is printed, the solid density is insufficient and the ink layer is easily caused. Unevenness, the phenomenon of ink coverage is not real, white spots, etc., and the phenomenon of "washing board" is easily generated in the direct printing of corrugated cardboard.
In recent years, the widely-recognized flat-top dot plate-making technology has emerged to solve the above problems. It has opened a door for Flexo to participate in market competition more broadly at a higher starting point.
The core of the flat top dot plate making technology is to isolate the influence of oxygen on the shape of the dot during the main exposure process, thereby achieving a 1:1 copy of the graphic. In addition, the flat top dot plate making technology has many advantages. In addition to being able to effectively solve the above problems and improve printing quality, the performance in improving printing stability is also remarkable. Because compared with the ordinary flexographic direct plate making technology, the printing plate made by the flat top dot plate making technology has higher wear resistance of the high-gloss small dots, and the dot gain is also easier to control, which is for the orders with large printing volume. It is very important to say.
Undoubtedly, the flat top dot plate making technology further improves the quality of the flexographic plate making on the basis of the direct plate making technology, and effectively compensates for the inherent shortcomings of flexo printing, and the quality of flexo printing has once again made a leap.
At present, the suppliers that can provide flat-top dot plate-making technology in the world mainly include Flint, DuPont, Esko, Kodak, and Meidemei. The technical principles and implementation methods of each are different.
In the actual use process, the flat top outlet generally shows a higher printing durability and a smoother gradient dot, which has gained wide consensus in the field of paper packaging printing. For flexible packaging users, the use of solid screening technology to enhance the density of ink in the field is the most striking technological advancement of flat-top dot technology.
Extensive testing has shown that this technology is widely applicable to the printing of most non-absorbent materials in aqueous inks and alcohol-soluble inks. After the aspherical mirror engraving technique with reduced aberrations, it is theoretically possible to engrave a laser spot having a minimum diameter of 6 μm on the surface of the plate, and to form minute pits on the surface of the finished plate, and the improved micro-cavity screening The technology has increased the density of film printing to a new level, while the smoothness of the field has been significantly improved.
With the increase of user groups, the limitations of flat-top dot technology have gradually emerged. The biggest problem is the stability of the screening technology, which is the problem of repeated reproduction of micro-cavity dots. Since the size and shape of these micro-cavities have been completely impossible to measure with conventional inspection equipment, it is often necessary to rely on a large number of monochrome tests at the printing house to determine the engraving parameters for production. Although this method helps to visually measure changes in printing density, it is limited by the actual production situation of the printing house, and there is a certain delay in time. At the same time, fluctuations in the printing environment will also have a greater impact on the final solid density. The impact makes it difficult to analyze the cause of the problem. In the actual printing production, the parameter-determined field screening technology will also undergo considerable changes in printing density. After the fluctuation of the printing process is excluded, the influencing factors of the plate-making process also need to be systematically analyzed and controlled.
Since 2014, DuPont, Flint, and Medmei have invested in research and development. Currently, flat top dot plates are introduced without any additional equipment and auxiliary materials, that is, traditional engraving and plate making equipment are used. Flat-top outlets such as DuPont's EPR and ESP laser versions, Flint's NEF and FTF laser versions, and Med's ITP laser version can be produced.
During the test and production trials, it was found that the repeatability of the self-contained flat top dot plate was greatly improved, especially in the field printing section. Taking DuPont plate as an example, EPR is a flat top dot plate with a smooth surface. ESP is based on a flat top dot plate. A matte coating is added to the surface of the plate to carry more ink for improvement. Ink transfer. During the actual production test, we found that the ESP plate on the matte surface has an excellent improvement on the ink transfer in the field. The ESP plate on the matte surface is printed better than the ordinary laser plate, especially for paper printing, using ESP plate The secondary printing can achieve the effect of two printings of the ordinary laser plate, and the ink transfer ability can be seen.
Through extensive testing, we also noticed that ESP plates on matte surfaces can greatly increase the density of printing in the field, and because of its high surface energy, EPR plates and ESP plates can effectively reduce the paste problem for partial film printing. . DuPont Cyrel® Easy technology simplifies flexographic plate making and guarantees excellent print quality. The printing test was extremely successful and greatly accelerated the commercialization process.