Why Are Hydrophobic Coatings Needed?
When applied to a window or other flat optic surface, a hydrophobic coating causes any water landing on the optic to bead up on the surface. This action allows the water to clear off the optic for an unobstructed view and will interfere less with the wavelengths passing through. While rolling off of the surface, the droplets also assist with clearing any small debris on the optics’ surface area.
When you request a hydrophobic coating for your optic materials, this is considered a secondary coating and is applied as an additional process for most AR (anti-reflective) or our dielectric coatings. This can also be applied as a stand-alone option without an optical coating.
Specifying Contact Angles For Hydrophobic Coatings – Contact Angle vs Surface Tension
Hydrophobic coatings create an angled on-surface area instead of a flat surface area. This angle is unrelated to the AOI, so keep that in mind when requesting your coating specifications. We suggest that you work directly with our in-house thin-film engineer, Paul Meier-Wang, to determine what is required for the intended usage of your materials.
Contact Angle is used as a measurement of hydrophobicity.
A High-contact Angle indicates that the surface material is “low wetting” and requires that the droplets will not spread out and roll off of the material more often. This is typically a >90º angle.
When Does Your Application Require A Hydrophobic Coating
Typically, applications that will be used in the field, such as freeway toll sensors, with concerns about year-round weather, humidity, self-cleaning, and anti-freezing, require an additional hydrophobic coating to extend usefulness before a replacement is needed.
Our Markets That Utilize Hydrophobic Coatings
- Industrial – Camera lenses on cell phones and other electronic equipment
- Aerospace – Telescopes and aircraft surfaces
- LiDAR – Components that need to function in all weather conditions
Materials That We Treat With Hydrophobic Coatings
Hydrophobic coatings for all types of surface materials now exist, from concrete to rainwear clothing. At AccuCoat, we can add a second coating on your material for plastic optics and glass lenses to create a protective barrier.
Typical Testing and Specifications of Optical Hydrophobic Coatings from AccuCoat
- Average of Water Contact Angle (>95º) (or tilting angle)
- Average Oil Contact Angle (>70º)
- Ink Pull Test (0-3 Pulls, Needs 2 to Pass Test)