Hydrophobic Coatings

Hi, I’m Ehren, Product Engineer at Edmund Optics, and I have with me our TECHSPEC Hydrophobic Coated Window. A hydrophobic coating means water repellant. Although in this case we have a water repellant coating applied to a window, the same coating can be applied to many of our optics. This coating will cause water droplets to form on contact with your optic, instead of being absorbed or spread out across the optic. What are the benefits of liquid beading up on your optic? The less liquid that’s in contact with your optic’s surface, means that more unobstructed incident light can pass through your lens, or your window, or any of our hydrophobic coated surfaces. It also facilitates cleaning. As water beads up and rolls off of the surface, it collects unwanted particles, leaving behind a much cleaner optic. Hydrophobic surfaces are specified according to what is called their contact angle. The contact angle has no relation to the anti-reflection coating’s angle of incidence specification. Instead, the contact angle is defined by the physical contact made by the water, the optic, and the surrounding air. An optic without a hydrophobic coating doesn’t repel liquid, therefore creating an acute contact angle. A hydrophobic coated optic causes liquid to bead up and create a large, obtuse contact angle. The large contact angles cause less of the liquid to be in contact with the optic’s surface. In the case of our TECHSPEC Hydrophobic Coated Windows, contact angles are larger than 107 degrees, even after mild abrasion. Our hydrophobic coating is a secondary coating and can be applied to almost any of our anti-reflective or dielectric coatings. For more information on using our hydrophobic coating in your application, please visit the following link.