The film is prepared in vacuum, including the coating of crystalline metal, semiconductor, insulator and other single substance or compound film. Although CVD also uses vacuum methods such as decompression, low pressure or plasma, vacuum coating generally refers to the deposition of thin films by physical methods. There are three types of vacuum coating: evaporation coating, sputtering coating and ion plating.
Vacuum coating technology first appeared in the 1930s, industrial application began in the 1940s and 1950s, and large-scale industrial production began in the 1980s. It has been widely used in electronics, aerospace, packaging, decoration, stamping printing and other industries. Vacuum coating refers to the deposition of a metal or metal compound on the surface of materials (usually non-metallic materials) in the form of vapor phase in vacuum environment, which belongs to physical vapor deposition process. Because the coating is often a metal film, it is also called vacuum metallization. In a broad sense, vacuum coating also includes the vacuum evaporation of polymer and other non-metallic functional films on the surface of metal or non-metallic materials. Among all the plating materials, plastic is the most common, followed by paper coating. Compared with metal, ceramics, wood and other materials, plastics have many advantages, such as abundant sources, easy performance control, convenient processing and so on. Therefore, a wide range of plastics or other polymer materials as engineering decorative structural materials are widely used in automobile, household appliances, daily packaging, industrial decoration and other industrial fields. However, most of the plastic materials have some defects, such as low surface hardness, less gorgeous appearance and low wear resistance. For example, a thin metal film is evaporated on the plastic surface, which can give the plastic a bright metal appearance. The appropriate metal source can also greatly increase the wear resistance of the material surface, and greatly broaden the decorative and application scope of plastics.
The function of vacuum coating is various, which also determines its application is very rich. Generally speaking, the main functions of vacuum coating include giving high metallic luster and mirror effect to the surface of the parts to be coated, making the film have excellent barrier performance on the film materials, and providing excellent electromagnetic shielding and conductive effect.