Transparent conductive optical coatings are utilized in markets that require efficient optical transmission along with the need to conduct electricity or dissipate charge. Indium Tin Oxide (ITO) is the most widely known transparent conductive material. It offers good optical performance across the visible band, while providing an impedance range from below 10 Ohms per square to well over 10,000 Ohms per square. There is a direct correlation with the film deposition thickness between optical transmission and impedance targets. Reynard has a long history of balancing the impedance and transmission characteristics of ITO, participating in market needs for heated windows, flat-panel displays, EMI grids, and photovoltaic development. Very high transmission can be achieved with impedance downs to 2K Ohms per square. Low resistance designs of 10 Ohms per square have also been developed that achieves transmission in the 80%-85% range. When combined with an AR coating, the ITO can be index matched to the substrate material on which it is being deposited.
Another solution that Reynard has had much success is with thin metals. For example, gold (Au), can achieve fewer Ohms per square while achieving high optical transmission - even in the IR! However, due to the high cost of Au, it is an unpopular selection when ITO can achieve the required results. Reynard has also successfully deposited materials with silver nanoparticles to achieve conductive coatings. This solution is typically used in hybrid thin film designs where additional optical filtering is required.
ITO and thin metals can be deposited at low-temperature, allowing for deposition on substrate materials such as plastics. These transparent conductive materials can also be patterned using an in-house photolithography process to create patterns from simple match length lines to complex custom grids.