Special Coating Assures Better Viewing
Scratches on plastic displays make them more difficult to read. Reflections from the surface also disturb viewing. Using the so-called PICVD technique, special multi-layer coatings can be applied to plastic surfaces. The pulsed plasma produces scratch-resistant, low-reflecting surfaces in a single step.
The PICVD technique (Plasma Impulse Chemical Vapour Deposition) was used previously to coat glass. Schott HiCotec has now modified the technique in such a way that strongly adhering, homogeneous coatings can be applied to plastic parts.
The component to be coated is placed in a vacuum chamber into which the gaseous coating material is introduced. The plasma is ignited in the chamber by microwaves. As a result, oxides are deposited on the surface. Cyclical repetition of the process produces a multi-layer coating. Very low processing temperatures are involved – extremely dense and homogeneous coatings can be generated even at room temperature with the pulsed plasma technique. Applications in the plastics sector include display coverings for car radios and navigation systems.
Multi-layer system absorbs reflections
A typical multi-layer system comprises an adhesive layer, an anitscratrch layer, an antireflecting layer and a hydrophobic layer that can be cleaned easily. All four layers can be applied in a single process step via PICVD.
The adhesive layer assures that the subsequent layers adhere strongly to the display as the temperature varies. The antiscratch layer protects the display against mechanical damage. The antireflecting layer consists of alternating layers of silicon dioxide and titanium dioxide. Each of these layers is only fractions of a micrometer thick. The display surface reflects less than one percent of the incident light. This is hardly perceptible by the viewer. The final layer assures that the display covering can be cleaned with a tissue without the need for a cleaning agent.