The working principle of the most popular technolo

Technical exchange: working principle of anhydrous printing

release date: Source: China paper industry

in the packaging and printing industry, there are many technologies related to anhydrous printing. Today, China's paper industry will start with anhydrous printing. Let's introduce the relevant contents in detail

toray system

toray waterless printing system consists of three parts: waterless printing plate, specially configured waterless printing ink and printing equipment with a temperature control system

the structure of Toray waterless printing plate is multilayer laminated. The bottom layer is an aluminum base plate, which is coated with a layer of photosensitive polymer material, which is an intermediate layer, and the top layer is a silicone rubber layer after 2 microns. According to the different types of Toray waterless printing plates, the printing resistance ranges from 150000 to 600000 sheets. This data is based on ordinary copper paper. If the surface of the paper is rough, the printing resistance will decline to a certain extent. Toray waterless printing plate is recyclable, which is the same as the traditional recyclable PS version. Toray printing plate is very suitable for all kinds of sheet fed and rotary offset printing machines

the exposure of this kind of printing plate can also use the traditional vacuum printer and light source, and the exposure time is not much different from that of the traditional printing plate. During exposure, the amount of UV light is controlled by the density on the film, so that the light penetrates the silicone layer and irradiates the middle photopolymer layer. The photo reaction on the photopolymer layer is very accurate, and the resolution of the printing plate is very high, which can reach 175 lines/inch, and the range of output points is 0.5% - 99.5%. The following figure shows the imaging mechanism of traditional wet printing plate and anhydrous printing plate

after exposure, the printing plate is developed, and the development process is very simple. (3) The sliding surface between the inlaid steel plate and the lining plate and the dovetail groove surface on the lining plate should be kept clean. The equipment for developing waterless printing plates is different from the traditional development equipment. It uses special chemical reagents and the mechanical structure for processing printing plates. After treatment, the printing plate is an ink repellent silicone layer in the non graphic area. In the graphic area, the silicone tree has been used for many years, and the professional technology grease layer has been removed, leaving the photopolymer material that attaches to the ink. When designing, the printing plate can be designed to selectively absorb and repel ink without using any water and alcohol

the main difference between anhydrous ink and traditional ink is the difference between the resin and connecting material used. The binder of anhydrous printing ink is selected according to its rheology, which is higher than the binder in traditional ink. The principle of water free printing is that the silicone layer in the non graphic area of the printing plate has a low surface energy. If the viscosity of the ink is relatively high, the force of mutual attraction of its own molecules is higher than the force of affinity with silicone, so the material here has a strong ink repellency

the main factor affecting viscosity is temperature. Because there is no water in the printing process, there is no material to cool the surface temperature of the printing plate. Due to friction, the surface temperature of the plate cylinder will continue to rise. At the same time, due to the high viscosity of anhydrous ink, the process of grinding ink in the drum will also cause the temperature of the drum surface to rise

this is why it is necessary to accurately control the temperature on anhydrous printing equipment. The most popular system uses vibration refrigeration technology. During the refrigeration process, the hollow vibration cooling roller in the ink wheel pulls out the coolant. This structure has been used in high-speed rotary offset press for many years. Now after improving it, it is also applied to sheet fed printing equipment. Almost all sheet fed printer manufacturers provide hollow ink vibrating rollers to control the temperature. The following figure shows a typical temperature control system of a water free printing machine. The effect of temperature control varies with the number of ink vibrating rollers

the function of the temperature control system is to circulate the refrigerant through the track of the drum operation to remove the heat generated by the mechanical movement of the printing machine

it is worth noting that this type of system is not designed to cool (or refrigerate) the ink roller, but only to maintain the inherent normal temperature when the printing press operates normally. Only by maintaining a fixed temperature, the viscosity of the ink can be maintained to the best state. The following figure shows the best temperature task window in the temperature control system of water free printing

proofing of waterless printing can be directly completed by film. Note that not all analog systems can reproduce the low expansion rate of waterless printing

some experienced anhydrous printing enterprises provide high-precision samples, and some anhydrous printing enterprises also use the calibrated digital proofing system to produce samples, which also achieved good results

pressek system

pressek pearldry printing system is composed of two parts: printing plate and special formulated anhydrous ink. Their ink is very similar to the ink used by Toray company

according to pressek, whether to install a temperature control system is the choice of printing enterprises. However, in order to obtain a high print resistance, it is recommended to install a temperature control system. The maximum print resistance of pearldry printing plate is 50000. Pearldry plates are also recyclable, with a maximum plate size of 23.75 × 29.4 (four open). The following figure shows the pearldryabl negative printing plate used in waterless printing

like Toray printing plate, the top layer of pearldry printing plate is also a silicon layer that repels ink. In the middle is a photosensitive layer, which can absorb ink and maintain the stability of printing plate size

image and expose the printing plate without film and film development. The imaging technology it uses is called ablation technology. An IR (infrared) laser diode array is used to remove the silicone image layer, and the aluminum or polyester layer under it is exposed so that it can absorb ink. In the process of imaging, the laser processes the image area by rapidly heating the image layer. The resulting gas expansion causes the image to separate from the upper silicone layer, which has only a certain understanding of it. When the printing plate is imaged, the printing plate is stripped and installed on the printing machine. The system can image the printing plate directly on the printing machine (gtp-di or quickmasterdi with 8-opening A3 format), and can also use the pearlsetter plate printer of pressek company to image offline. The size of offline imaging includes 8-open A3 format (15.75 X20) and 4-open A2 format (23.75 x29.4). The format is 40 inches (102CM), and the imaging of the split plate can be completed on the thermal direct plate making machine. With the continuous emergence of other postscript systems, various types of digital proofing systems can be used to proofing waterless printing, such as iris' inkjet printer and 3M's rainbow

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