1. Vacuum coating refers to a method of heating metal or nonmetal materials under high vacuum to make them evaporate and condense on the surface of plated parts (metal, semiconductor or insulator) to form a thin film. Such as vacuum aluminum plating and vacuum chromium plating.
2. Optical coating refers to the process of coating a layer (or layers) of metal (or dielectric) film on the surface of optical parts. The purpose of coating on the surface of optical parts is to reduce or increase the requirements for light reflection, beam splitting, color separation, filtering and polarization. Commonly used coating methods include vacuum coating (a physical coating) and chemical coating.
Second, the principle of difference.
1. Vacuum coating is an important aspect of vacuum application. It is a new thin film preparation technology based on vacuum technology, which absorbs a series of new technologies such as electron beam, molecular beam, ion beam, plasma beam, radio frequency and magnetron by physical or chemical methods. To provide scientific research and practical production. Simply put, it is a method of evaporating or sputtering metal, alloy or compound in vacuum to solidify and deposit it on the plated object (called substrate, substrate or matrix).
2. Interference of light is widely used in thin film optics. The common method of optical thin film technology is to coat a thin film on the glass substrate by vacuum sputtering, which is generally used to control the reflectivity and transmittance of the substrate to the incident beam to meet different needs. In order to eliminate the reflection loss on the surface of optical parts and improve the imaging quality, it is necessary to plate one or more transparent dielectric films, which are called antireflection films or antireflection films.
With the development of laser technology, there are different requirements for the reflectivity and transmittance of thin films, which promotes the development of multilayer high reflection films and broadband antireflection films. In order to meet the needs of various applications, highly reflective films are used to manufacture polarizing reflective films, dichroic films, luminescent films and interference filters. After coating on the surface of optical parts, light is reflected and transmitted on the film for many times, forming multi-beam interference. By controlling the refractive index and thickness of the film, different intensity distributions can be obtained, which is the basic principle of interference coating.
Third, the difference between methods and materials.
1, vacuum coating material:
(1) Vacuum evaporation: clean the substrate to be coated and put it into the coating room. After vacuumizing, the membrane material is heated to a high temperature to make the vapor reach about 13.3Pa, so that the vapor molecules fly to the surface of the substrate and condense to form a membrane.
(2) cathode sputtering coating: the substrate to be coated is placed on the reverse side of the cathode, and inert gas (such as argon) is introduced into the vacuum chamber, and the pressure is kept at about 1.33 ~ 1.3 Pa. Then, connecting the cathode to a 2000V DC power supply will trigger a glow discharge, and positively charged argon ions will impact the cathode to emit atoms, and the sputtered atoms will be deposited in an inert atmosphere.
(3) Chemical vapor deposition: the process of obtaining deposited films by thermal decomposition of selected metal compounds or organic compounds.
(4) Ion plating: In essence, ion plating is an organic combination of vacuum evaporation plating and cathode sputtering plating, which has both technological characteristics. Table 6-9 lists the advantages and disadvantages of various coating methods.
2. Optical coating materials
(1) magnesium fluoride: colorless tetragonal powder with high purity. The optical film prepared with it can improve the transmittance without collapse.
(2) Silicon dioxide: colorless and transparent crystal with high melting point, high hardness and good chemical stability. The purity is high, and the high-quality silicon dioxide coating prepared from it has good evaporation state and no collapse point. According to the use requirements, it can be divided into ultraviolet, infrared and visible light.
(3) Zirconia: white heavy crystal, high refractive index, high temperature resistance, stable chemical properties and high purity. It can be used to prepare high quality zirconia coating without collapse.