At the drupa exhibition in 1995, computer direct platemaking technology has completely changed the prepress system. Compared with the traditional platemaking process, CTP eliminates the processing of film processing, manual imposition and plate mounting, thus greatly saving the prepress process The time, while greatly reducing pollution. For the average manufacturer, if the purchase of a CTP device requires double the cost, then the benefits of the above advantages of CTP will be twice the benefits.
The high precision of offset printing plate has been the development direction of prepress technology, and until today there have been several branches of technology. At the drupa 2008, these new branch technologies will meet with the audience. In the 4K and 8K format markets, mainly the thermal printing process, the main use of the imprinting unit is ultraviolet laser technology. Both of these processes are plateless printing, and suppliers are seeking solutions for image signal plates that can support inkjet printing.
Which process is the best? Each process has its own characteristics, with advantages and disadvantages. Plate format, operation cycle and plate-making cycle are the key criteria for judging. This is because the investment required to invest in CTP is quite large, but due to the many advantages of CTP technology, the total investment of equipment will be over a period of time. Withdraw.
Ultraviolet laser technology makes platemaking out of the dark room and into the bright age
In the 1990s, the imposition program came out, so that the size of the film can be produced according to the specifications of the printing plate. Taking this as an opportunity, we called it the computer direct film, and the 70x100cm phototypesetting equipment came out. The device belongs to the inner drum structure, because this structure has advantages over the winch structure in terms of the effect and cost of 4-color separation. On this basis, direct plate-making can be carried out, so many suppliers at that time chose the drum-type phototypesetting equipment.
However, the UV digital photosensitive plate in the inner drum structure equipment will not work if there is not enough light exposure. Therefore, the supplier's first research is how to improve the sensitivity of the photosensitive plate. The first-generation photosensitive plates contain anions and halides, which require at least 0.010mj / cm2 of light energy to meet the exposure requirements. This level of plate allows lower energy to complete the exposure. The photosensitive resin plate is also one of the first-generation photosensitive plates, and its sensitivity is only 1/10 of the silver salt plate, which means that it requires an energy requirement of 0.10mj / cm2. The blurred image source only takes up 10% of the total energy, while the other 90% of the energy comes from the pre-heat treatment. Similarly, preheating is also very necessary in the process of making plates.
Different exposure light can be selected according to different layouts, such as argon ion light, neodymium ion light, helium ion light or neon light. All the above light sources are in the visible spectral range, so the process of plate processing must be illuminated by red light or in a completely dark environment. Therefore, the manufacturer must establish a complete spectrum system according to the requirements of plate-making, which will be a huge investment, and the entire operation process must be carried out in a dark room without light.
After a few more years, until Druba in 2000, thermal technology replaced the first-generation photosensitive plate. In Druba 2000, Agfa proposed a new solution to the sensitivity of the silver salt version of the internal drum phototypesetting system: exposure can be completed by UV light at 405 nanometers. Compared with the previous exposure version, this process Allow the process to proceed under a certain color gamut of yellow light. A 05 MW ultraviolet laser emitter is used as the light source. This is very economical and practical, and the technology is applied to the civilian field, and the market potential of CD records is huge. This made many attempts to abandon the manufacture of inner drum equipment dispelled the idea and continue to operate their original industries. In 2002, Fujifilm developed an epoch-making photosensitive resin version containing a 30 megawatt ultraviolet light source. Many market observers predict that this will completely replace thermal technology. So far, this language has not been fully realized, because the principle of the photosensitive resin plate is basically the same, and it needs higher sensitivity. In theory, this is the same as the first-generation photosensitive plate, and the connecting material in the plate structure Unstable chemical drugs are needed and they are very immature. In addition, the preheating unit is also essential. That is to say, the inner drum type equipment is relatively simple compared to the outer drum type equipment, so the UV plate-making machine is more competitive in the folio and quadruple-format plates. Among the 4K and 8K format plates, the main competitor of the UV plate-making equipment is the thermal plate-making machine.
In Canada in 1991, Japan Screen commissioned Creo to develop a plate-making device for offset printing, with no special requirements for sensitivity. They chose the outer drum type, because it can achieve many lasers only a few millimeters away from the plate, and many suppliers in the United States have expressed great interest in this. The first achievement of the research, the Creo3244 plate-making system, uses solid-state YAG lasers and is divided into 480 beams, which can be adjusted on a single drum with an accuracy of 2400dpi.
The success of Creo is that the outer drum structure has a more stable and strong structure for the phototypesetting equipment, but it also has the disadvantages of huge equipment and expensive cost. Therefore, Kodak and Creo jointly developed the second-generation phototypesetting system, which can use photosensitive resin plates and use 830nm wavelength far-infrared laser exposure. During printing, the temperature at the outlet is generally maintained at 110 ° C. The equipment generally does not use chemicals. After the printing is completed, it passes through a heating and drying unit. The temperature is generally 140 ° C. The heating unit molds the dots in the graphic information section, stabilizes the resin by heating, and then forms the printing plate. The general print durability is 200,000. If baked, the print durability can exceed 1 million.
Kodak's well-known DITP Gold system uses a negative plate and is equipped with a semi-automatic typesetting unit. It also has a disc feeder and was put on sale in the fall of 1995.
Another feature of the thermal process is that the exposure process has little effect on the curing of the polymer. The result is that the thermal process has an unprecedented and stable processing flow. Many manufacturers have added thermal plates and have successfully entered the external drum typesetting Equipment market. The treatment process of the positive plate is completely different from that of the negative plate. The non-graphic part is exposed to laser irradiation, and the coating undergoes a chemical reaction, which is peeled off and the hydrophilic part is formed. The unexposed resin is the lipophilic part.
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