Digital Printing and Direct Imaging (3)

The on-demand market is gradually developing and forming in foreign countries. There is no such market in China, but it will develop with the development of technology and economy. The demand for on-demand and personalized is a huge potential market that needs guidance and exploration. Perhaps, for this particular object of our country, we need to use existing on-demand printing/publishing techniques to promote the on-demand market and promote its formation and development.
(4) Key technologies of digital printing In digital printing systems, there are two technologies that are most critical: one is RIP technology, and the other is digital hard copy technology for producing printed matter. Because the two adjacent digital prints may be completely different, that is, 100% variable information, and require a high output speed (should be equivalent to the speed of a traditional sheet-fed offset press), the speed of the RIP is special. Claim. In addition, with the continuous improvement of the quality of digital printing, the resolution has also been increasing. It has grown from the early 200-400 DPI to today's 600-800 DPI (even higher), which further increases the speed and function of the RIP. Claim. The hard copy conversion system is the core of the digital printing machine and is responsible for high-speed conversion of digital pages into high-quality color hard copies, ie prints. This requires that the high speed hard copy system used must meet the following requirements:
● High speed. The printing speed must meet the requirements of thousands of hours per hour;
● High quality. Digital printing should meet or at least approach the quality of conventional offset printing. Otherwise, it would be hard to call print. It may only be called copy or print.
● Plain paper imaging. There is no special requirement for substrates, which can be imaged on common substrates such as paper, film, plastics, etc.
● Low price. The price should be comparable to traditional offset printing.
Although there are many color hard copy systems that can be selected, there are not many hard copy systems that satisfy the above four conditions at the same time. There are mainly listed in Table 1.
Magnetic recording imaging and other four methods. The resolution of an electrophotographic system using dry toner development can reach 600-800 DPI, and up to thousands of DPI can be developed with wet toner, and the number of gradations per pixel can be multi-valued (but limited). If laser scanning imaging with a power of 100 MW is used, the scanning speed in one-dimensional space is 6.35 M/s, and it can be imaged on a common substrate. The coloring agent is a pigment, similar to a traditional offset printing. Inkjet imaging has a resolving power of 300-1500 DPI, the number of tones is multiple (but limited), and the imaging speed is very high. The imaging time for a single pixel is generally 10-4 to -6S (depending on the different inkjet imaging. In the method), the scanning imaging speed in one-dimensional space is 0.63 to 63.5 M/S (scanning at 400 DPI density). However, most ink-jet imaging uses water-based inks, and the color rendering agent is mainly dye-based. The final image formation depends on the interaction between the ink and the substrate. Therefore, inkjet imaging systems generally require the use of special substrates that are matched with the ink in order to achieve the best match in performance between the ink and the substrate.
The use of pigmented plain paper for imaging has always been a direction for the development of inkjet imaging technology. At the same time, it is also a technical difficulty. Electro-aggregation imaging is a new imaging method with very high imaging speed. The formation time of each pixel is 4×10-6S, and the scan imaging speed in one-dimensional space is 15M/S (scan at 400DPI density). This imaging method uses the principle of electrochemical reaction to make the dispersion system agglomerate, so that a water-based reaction ink is converted from a liquid state to a solid state, thereby realizing image recording. Although the current resolution of this system is still very limited and can only reach 400 DPI, each pixel has a tone reproduction capability of up to 256 steps, and therefore has a relatively high quality effect. (To be continued)