Coated film refers to evenly coating silicone oil on the surface of the film to improve the surface properties of the PET film to improve the adaptability of printing and the bonding force of the vacuum aluminum plating layer. Corona treatment is usually used to improve the surface tension of the film. However, the corona method has problems such as timeliness. Especially in high-temperature and high-humidity environments, the film tension after corona treatment is easily attenuated. However, the chemical coating method does not have such problems, so it is favored by the printing industry and the aluminum plating industry.