High-tech and Operational Points of Flexographic Printing (I)

Flexographic printing derived from letterpress printing has been developed and improved for more than 100 years. It constantly absorbs advanced technology and improves the quality of printing. Today, excellent flexo printing products are completely comparable to offset printing, marking the beginning of a new milestone in flexo printing. . In recent years, flexo printing has grown at an alarming rate of 70% per year, and now accounts for more than 20% of the global printing market. According to experts' predictions, by 2005, the flexo printing market is expected to rank second in all printing formats. Looking at the remarkable improvement of the quality of flexo printing, the key is the application of high technology, so that the overall level of technology and material quality continue to increase.

I. Digitization and Laser Technology in Plate Making

The high technology of plate making is the laser technology that emerged from the 1960s when the core technology of computer-to-plate (also called laser direct-to-plate or digital direct-to-plate (CTP)) technology was pushed. After the 1990s, with the development of computer technology and equipment materials, CTP technology has matured and continuously demonstrated its superiority, accelerating the research and development and industrialization of CTP technology. According to statistics, in the United States by 1997, 65% of large-scale printing plants had used CTP technology. From 1995 to 2002, the rate of application of CTP increased at a rate of more than one time per year. Computer direct plate making speeds up the plate making, increases the printing plate quantity and the printing quality, is advantageous to the environmental protection, is advantageous to escapes the darkroom operation and so on merit. Today, CTP technology has shown its superiority in lithography, and its market share is constantly expanding. With the improvement of its technology and CTP plate quality, its market prospect is very broad. It can also be said that it is an important direction for the future development of the printing industry. Using CTP technology, not only can be printed on paper, but also printed on other substrates, such as the use of a variety of plastic film and composite film, metal foil, wood, glass, ceramics, textiles and so on.

Digital direct platemaking was first studied in other printing processes. Flexo platemaking is the last printing method to transition to non-film platemaking in various layouts. This is because the flexographic plate has a certain thickness. It is necessary to use digital high-speed laser to directly obtain three-dimensional dots on the plate material. The difficulty can be achieved. It is 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, not only have poor stability but also have high costs. In addition, the temperature and humidity all have a certain influence on the film, and sometimes it is necessary to prevent the film from being rubbed. Injuries, 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 parts of the tone may not be reproduced. Since the smaller dots are not easily printed, they can only be rough. The number of screen lines is printed. 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 etched 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. (At this time, 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.

The application of CTP technology can well solve some of the problems caused by materials and technical problems in the conventional filmmaking. For example, excessive back-exposure time results in inconsistent relief of lower substrate thickness, lack of back exposure or main exposure time resulting in line distortion and dot loss, over-exposure of main exposure time resulting in lighter shades, and inaccuracy of post-exposure errors resulting in excessive plate hardness. , Insufficient wash time caused by the lower relief thickness of the substrate, wash plate for a long time, the brush pressure caused by line deformation and dot loss, not photosensitive material is not completely dissolved caused by the lighter shade and so on. With the continuous deepening and improvement of the research on CTP technology and related technical materials, its superiority will become more apparent. It not only saves time, manpower, materials and other resources, improves the quality of printed matter, reduces environmental pollution, but also The optimization of the process flow and the ease of forming continuous production lines with a high degree of automation, combined with advanced computer technology, can be confident that CTP technology will bring a new revolution in flexo printing.

(to be continued)