New Discovery of Flexo Platemaking Technology (I)

The printing quality of the flexographic printing plate largely depends on the quality of the flexographic plate material. In recent years, the quality of the flexographic plate material has been greatly improved. The improvement of the quality of the plate and the appearance of the thin plate process have laid a good foundation for improving the quality of the flexographic printing. Flexible plate-making technology is also changing from analog to digital. Like offset printing and gravure printing, it is gradually transitioning to a computer-less plate-making method without a film. The advent of a flexographic computer-to-plate system has made it possible to expose digital image files directly to flexographic plates. It effectively reduces dot gain and guarantees the quality of printed products, and some of the prints have reached or are close to offset or gravure levels.

Development of flexo plate

1) Demand drives the development of flexo plates

Flexographic plates have undergone development from the flexo->photoresin->digital photopolymer plates. In flexo printing, the media system used is very extensive, such as various types of plates, plates of different thicknesses, plates of different substrates, double-stick tapes with different adhesiveness, and cushioning materials with different elasticities, etc. And so on, they can be combined to form a variety of different combinations. People have always been eager to have a special plate, do not need film, can use computer to produce fine gradation plates directly; the quality of platemaking has nothing to do with graphics, and there is no dot enlargement in plate making; the ink transfer performance of plates is good, and Adapt to the conditions of tropical, subtropical and continental climates. It is based on this demand that a digital photosensitive resin plate emerged, which is a new type of thinner plate material for flexographic printing, the surface of which has a black protective layer, and the protective layer can be used by CTP equipment. The emitted laser is ablated. It can also have very stable performance in different climates. Even after a few million prints, the ink transfer performance remains constant and consistent. Market demand has promoted the development of the plate. This plate improves the quality of flexographic printing.

When using traditional flexographic printing methods, the printing pressure needs to be adjusted slightly higher in order to eliminate the influence of the printing plate (washing and developing), which inevitably results in the expansion of the dots. In general, the greater the deformation of the printing plate, the greater the phenomenon of screen dot enlargement after printing and the quality of the final printing product. Therefore, the traditional flexible printing plate can only print low-line images and thick graphics. Can not print fine text. In order to reduce the deformation of the printing plate and improve the quality of the final printed matter, people took corresponding measures to improve and perfect the exposure tolerance of the digital photosensitive resin plate, achieved good printing effect, and improved the quality of the printed matter.

2) Development Trend of Flexible Plates

Due to the market's influence on the quality requirements of printed products, the development of the flexo version tends to be thin. Because under normal circumstances, the low hardness of the thick printing plate printing quality is poor and the printing pressure is high, and the high hardness thin printing plate printing quality is good, suitable for printing the advanced coating paper, the price is relatively cheaper. The thin printing plate has almost no distortion after printing, reducing the height of the image bulges, improving the stability of the image, and increasing the latitude of the copied image. Thin plates can also improve the stability of plate positioning. As a result, thinner plates have now appeared. With the rapid development of thin plates, new gasket materials are also emerging. Meet the development requirements of flexographic printing.

2 Technological development of computer-based flexo

The direct computer-based flexo edition is divided into: a computer-directed flexographic system and a computer-directed sleeve printing system. There are two ways to directly make a flexographic system by computer, one is a laser imaging system flexographic version, and the other is a direct laser engraving plate.

1) Laser Imaging Flexo System

The laser imaging flexo version uses a computer-to-plate system to control YAG lasers with digital signals to generate infrared light. After black coated synthetic film is used for photolithography, the black film is ablated to form a negative image. The plate-making method is the same as the exposure step, plate-washing, drying, post-exposure and other processing steps to make a flexographic plate. Such as Esko Graphic's CDI (Cyrel Digital Imager) computer direct imaging system. In the process of imaging and plate making of this system, except for the use of plate and digital imaging technology and the traditional flexo plate making process, other equipment and processes are the same as the traditional ones.

Advantages of adopting CDI: simple process; short equipment time; realizing non-film direct plate making; exposure time has nothing to do with the type of graphics and dot density, overcomes the defects of the traditional plate-making exposure time determined by the graphic; not easy to appear dirty and bad spots The phenomenon eliminates the phenomenon of dot expansion caused by the diffusion of light in the conventional filmmaking process; fine and clear high-quality flexo printing plates can be obtained with tiny YAG laser energy; as no film is used, the plate making cost is reduced, and printing is improved. Product quality.

2) Laser Direct Engraving Platemaking System

The laser direct engraving plate uses the image signal control laser of the electronic system to directly sculpt on a single sheet or sleeve flexo plate to form a flexographic printing plate. The plate making process is fully digitalized, and the engraved plate needs only to be cleaned with warm water, and it can be immediately printed on the machine, which reflects the advantages of high-precision, simple and rapid plate making process. The laser direct engraving flexo plates mainly include: laser-engraved rubber plate, seamless rubber plate cylinder and seamless rubber sleeve plate. You can sculpt lines or stencils. It is mainly used for flexo printing of paper, plastics and stickers, as well as preprinting and direct printing of corrugated paper. The rubber material specially developed for laser engraving in China has also been successfully used. The printing plate made of it has better printing durability than ordinary flexible plates.

The advantages of laser direct engraving flexography are mainly reflected in: no need for drying and rinsing, eliminating the need for flushing and saving a lot of cost; since it is no longer necessary to dry the printing plate (generally, the normal flexo drying time is as long as 2-3h), it can be significant. Reducing plate-making time; engraving flexographic plates to ensure plate quality is stable, and in the process of photopolymer plate printing, printing plate expansion and drying defects can easily cause plate thickness deviation; direct engraving flexographic plates no longer need digital laser exposure plate-making system Some of the equipment needed (such as exposure machines, processor, dryers, and post-processors) can reduce investment.