Vacuum metallizing process

A vacuum coater, also referred to as a vacuum metallizer or barrier coating machine, consists of a vacuum chamber which has been evacuated to, typically, 0.0005 mbar.

Inside this chamber, aluminum wire is fed onto individual, resistance-heated inter-metallic evaporators, where the aluminum becomes molten and evaporates.

The flexible substrate, supported on a chilled process drum, passes over the evaporation source at speeds of up to 1000 m/min. The aluminum vapor condenses onto the substrate and so creates the coating layer.

A plasma treatment unit can also be used as part of a vacuum coater system in order to enhance metal adhesion and/or to improve the substrate's qualities as a barrier against oxygen and water vapor transmission. Here, the surface of the web is hit by plasma just prior to the coating process.

The plasma is formed by applying an electrical voltage to a gas, or combination of gases. In addition to removing moisture and other contaminants, plasma treatment acts to increase the number of nucleation sites by the introduction of polar groups, resulting in a coating with a homogeneous surface morphology and fewer defects.

The vacuum coater is used to deliver aesthetic improvements to flexible substrates and/or to reduce oxygen and water vapor transmission to levels similar to that of glass and metal containers. This delivers improved packaging performance, extends pack shelf life and maintains the quality of the packaged product.

The process can also be used to produce substrates which conduct electricity, save energy, control light transmission or reflection, and which can even help prevent counterfeiting or theft.

Through its General product line, BOBST has formidable expertise in the vacuum coating process and in handling flexible substrates. This has led to the development of high technology vacuum coating and metallizing lines that can be used to produce a wide variety of products.