Optical thin film is composed of thin layered media, such as optical medium material propagating light beam through the interface. The application of optical thin film began in the 1930s. Optical thin film has been widely used in the field of optical and optoelectronic technology, manufacturing various optical instruments. The preparation strip requires high precision.

Optical thin films are defined as: Involved in the process of the propagation path of light, attached to the optical device thickness thin and uniform dielectric film on the surface of the layer, through the layered medium membrane layer reflection, through shot (passbook) and polarization characteristics, in order to achieve what we want in one or multiple wavelengths of light within the scope of all through all light reflection or polarization separation and so on various special form of light.

Optical film is everywhere in our life, from precision and optical equipment, display equipment to the application of optical film in daily life; For example, eyeglasses, digital cameras, various household appliances, or the anti-counterfeiting technology on money can be called an extension of optical film technology. Without optical thin film technology as the development foundation, modern photoelectric, communication or laser technology would not have made progress, which also shows the importance of optical thin film technology research and development.

Optical film refers to the plating or coating of one or more layers of dielectric or metal film or a combination of the two films on optical elements or independent substrates to change the transmission characteristics of light waves, including transmission, reflection, absorption, scattering, polarization and phase change of light. Therefore, it is possible to adjust the transmittance and reflectance of components with different wavebands by proper design, and to make the light with different planes of polarization have different characteristics.

Generally speaking, the production mode of optical film is mainly divided into dry and wet production process. The so-called dry type is no liquid appears in the whole process of processing, such as vacuum evaporation is in a vacuum environment, with electric energy heating solid raw materials, after sublimation into gas attached to a solid substrate surface, complete coating processing.

The gold, silver or metallic packaging film that we see in our daily life is made by dry coating. But under the consideration of actual mass production, the scope of dry coating is less than wet coating.

Wet coating general way is to mix the composition that has all sorts of functions into liquid coating, with different processing method coating is on base material, make liquid coating dry solidify next make it product.