PVD Vacuum: evaporation Roll to Roll winding coating equipment
Winding vacuum coating machine has made great development in the past 30 years. Its coating products are widely used in decoration, packaging, capacitors and other fields, and can be coated with optical, electrical, electromagnetic and conductive films. PE, PET, PI, PP, OPP, BOPP, paper, foam and cloth are used. Generally, the water content of plastic base film material is 1% ~ 2%, and the paper has a greater water content, which is generally 5% ~ 7%. After drying by coating, the water content is still 3%. Due to the high water content of substrate, the coating chamber developed from the original single chamber to the current double or multi-chamber structure. Evaporation sources can be resistive, inductive, electronic and magnetron sputtering. Double-chamber structure is widely used, and its advantages are: the paper substrate can be steamed and plated with a large amount of air release, and the coating quality can be guaranteed. A large amount of gas from the paper is drained from the reel room. As the gap between the coiling chamber and the evaporating chamber is very small, the gas discharged is not easy to enter the evaporating chamber. A large exhaust system is required in the single-chamber structure to guarantee the working pressure during evaporation, while a small gas volume in the double-chamber structure can be equipped with a small pump set to reduce equipment cost and save energy. The winding room and the evaporation room are separately pumped, which can shorten the pumping time.
The winding vacuum coater has to have a winding mechanism in order to realize continuous coiling except for all the structures of the general coater. As the coated substrate is paper or plastic with large air release, the structure of the vacuum chamber is divided into single chamber and multiple chamber. The structure of the winding double-chamber vacuum plating machine is shown in figure 10-10.
Several issues to be considered in the design of winding mechanism:
1. To improve winding speed. The winding speed is the linear speed of the strip substrate moving. It is a main technology of winding mechanism. The winding speed of early domestic coating machine was only 10m/min, and now it is only 80m/min ~ 120m/min. Among foreign EW series products of Japan, the winding speed has reached 300m/min, Germany L. The coating machine produced by H company has reached 600m/min. It can be seen that with the development of coating technology, the winding speed needs to be improved.
2. The problem of constant linear velocity of strip substrates. This problem is also important because only the winding mechanism can guarantee the constant wire speed of the strip substrate, so that the coating thickness of the substrate can be uniform. This is particularly important for the preparation of functional membranes (such as capacitor membranes) for strip substrates.
3. The problem of deviation and crimp of strip substrates. With the improvement of winding speed, the strip substrate will be deflected and deflected in the process of winding coating, which will seriously cause the fracture of the substrate and interrupt the production, which will not only affect the production efficiency, but also waste materials. Therefore, this problem should be fully considered in the design of winding mechanism.
The vacuum extraction system of coiling film machine is divided into two groups: the upper chamber and the lower chamber. The upper room is the base material winding room, which requires a low vacuum degree, and is a rotz pump unit or a rotz pump unit and a mechanical pump unit. General vacuum evaporation chamber to reached to 1 x10 pa ^ - 3-2 x 10 ^ - 3 pa, working pressure is 1 x 10 ^ - 2 pa - 2 x 10 ^ - 2 pa, and the vacuum is usually an order of magnitude lower than evaporation chamber. Sometimes the coiling coating machine is mainly used as an augmentation pump (a kind of oil diffusion pump). Although its ultimate pressure is not as good as that of oil diffusion pump, its pumping speed range extends to the direction of high pressure by an order of magnitude, which is very suitable for such evaporation coating process.
At present, crucible is used to evaporate most of the evaporation sources of winding film plating machine in China, and its materials include boron nitride, graphite, molybdenum, etc. Due to its good electrical and thermal properties and long service life, boron nitride is widely used in coiling coating machine. The heating power of each crucible is 6kW - 8kW, and the heating voltage is 10V - 12V. The number of crucible is determined by the width of substrate. The wider the width the more crucible. Four crucibles at 500mm width, 7 at 800mm and 12 at 1300mm. The distribution of crucible is not uniform, the middle part is more spaced, and the spacing is small at the edge of substrate. Some of the outermost crucible overlapped with the width of substrate.
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