During metallization, highly-pure metals are evaporated in a vacuum and deposited on the substrates to be coated. Depending on the metal used and on the thickness of the deposited layer, it is possible to produce mirrors, absorbers or even partly-transparent or decorative coatings in this way. In general, the coatings produced by these means are also provided with a transparent protective layer, likewise vapour-deposited in a vacuum. This prevents subsequent oxidation of the metals and protects them from mechanical damage. The products to be coated can be made of glass, metal, ceramic or plastic.
Vapour-deposition of pure metals or mixtures of metals and oxides allows absorbent coatings to be produced. These coatings “swallow” a large proportion of the incident radiated energy and convert it into heat. Specific selection of the metals used, the mixing ratios and the layer thicknesses generated allow the absorptive effect to be reinforced in the desired wavelength ranges. This makes absorption values › 90 % feasible.
Various metals naturally have good reflectivity. which can be used for making metal mirrors. To achieve this, the pure metals are evaporated in a vacuum and deposited on a substrate in the form of thin layers. In order to use the high level of reflectivity of the pure metals, these are likewise provided with an additional transparent protective layer under a high vacuum in order to prevent subsequent oxidation. Aluminium is commonly used for the UV and VIS range, silver for the VIS range and gold for the IR range. Depositing very thin layers of metal on a transparent substrate likewise facilitates the production of partly-transparent layers/beam splitter coatings.
