Protection for navigation screens has special challenges. GPS screens are very prone to reflections and glare from the sun. To minimize this impact on the display, car manufacturers treat their screens with antireflective coatings. These consist of two thin layers that are designed to cancel out the reflected light while allowing transmitted light through. They create an internal reflective surface that is 1/4 wavelength thick. These two surfaces allow light to be 180° out of phase with light reflecting off the top surface, destructively interfering and canceling out the light intensity.
While this method works well, it is both difficult and expensive to prepare. The coatings must be sputtered in high vacuum using two passes and usually needs a top coating to seal in the rough and brittle surfaces.
A newer method relies on standard photolithographic techniques. A hard patterned surface is created on the substrate to make it behave in the same fashion as the coated system, but at a fraction of the cost. This creates an simple manufacturing method and is prepared efficiently in high volume. The 3-dimensional micro-structured surface has features 200 nanometers in size. These efficiently mimic the two surfaces created by the sputtered coating process allowing for the same destructive interference of incident light with almost no dependence on the viewing angle.
Nanostructured Antireflective Surface
This structure creates greatly diminished reflectance over most of the visible light spectrum
Destructive Interference of Incident Light Using a Structured
Surface Mimics that of Sputtered Coatings
An article1 in LaserFocusWorld discusses the physics of patterned surfaces as antireflection coatings.
Patterned surfaces as optical coatings mimics2 the design of the natural moth eye to prevent reflections at night.
NuShield is pleased to provide a custom designed antireflective, antiglare film. Our films for electronic displays have excellent scratch resistance and optical properties. They are as good as the original antireflective navigation screens in glare reduction and provide superior scratch protection at a reasonable cost. They are designed for a variety of applications.
LaserFocusWorld, April 1997.
Eye Design Book, Chapter 3.
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