The deposit of thin films is often used to change glass properties. For example, the optical properties of glass products, such as light transmission or reflection, can be adjusted by applying suitable coating layer systems.
Coated glass plays a major role in a number of applications such as heat-reflection coating systems on window panes to lower heating costs; solar protection coatings to reduce air conditioning costs in countries with high-intensity solar radiation; coated car windows to reduce thermal increases in the interior; and mirrors used both in home furniture and the automobile industry. There are several processes regarding how to apply coating on a surface. However, in order to be applied to glass surfaces coatings must meet several criteria: compatibility with glass properties, ability to form uniform films over large surfaces, ability to be produced economically, operating safety and environmental friendliness. Due to these restrictions, primary glass manufacturing companies today use physical vapor deposition (PVD) and chemical vapor deposition (CVD). We will be concentrating on PVD, also known as the sputtering process.
The basic PVD process works by passing an electrical current through ionised gas, thus bombarding the surface of a metal cathode with ions. The atoms of the desired metal are vaporised and then deposited in a thin film on the surface of glass. The invention of the ?planar magnetron? in 1971 increased the effectiveness of the process. This is often called a ?soft coat?, because the coating is more susceptible to damage than is hard coat glass when glazed in monolithic forms. Due to its fragility, this soft-coated glass has special handling and processing requirements. Today sputtering is the most important flat-glass process in use.