Roll-to-roll vacuum coating equipment has seen significant development over the past 30 years. Coated products are widely used in decoration, packaging, capacitors, and other fields, and can coat various thin films with optical, electrical, electromagnetic, and conductive properties. Its applications are very broad, with common substrates including PE, PET, PI, PP, OPP, BOPP, paper, foam plastics, and fabrics. Generally, plastic-based film materials have a moisture content of 1%–2%, while paper has an even higher moisture content, typically 5%–7%, and even after coating and drying, the moisture content remains around 3%. Due to the high moisture content of the substrates, coating chambers have evolved from the initial single-chamber design to the current double-chamber or multi-chamber structures.
Evaporation sources can be resistive, inductive, electron beam, or magnetron sputtering. Dual-chamber structures are widely used, and their advantages are: ① They can vapor-deposit paper substrates with large outgassing volumes while ensuring coating quality. A large amount of gas released from the paper is exhausted from the winding chamber. Because the gap between the winding chamber and the vapor deposition chamber is very narrow, the released gas is unlikely to enter the vapor deposition chamber; ② Single-chamber structures require a large exhaust system to ensure the working pressure during vapor deposition, while the vapor deposition chamber in a dual-chamber structure has a smaller gas volume, allowing for the use of a small extraction unit, reducing equipment costs and saving energy; ③ Separate extraction of the winding chamber and the vapor deposition chamber shortens extraction time.
In addition to the general structures of vacuum coating equipment, roll-to-roll vacuum coating equipment must have a winding mechanism to achieve continuous coating. Because the substrate being coated is paper or plastic, which requires a large amount of gas release, the vacuum chamber can be either single-chamber or multi-chamber.
