Big touch screens, like those used on smart phones and portable media devices, are great … unless the sun is out. Then the glare can be a killer, rendering some devices next to useless. Scientists have developed a test for analyzing reflection-resistant coatings to make using touch screen devices easier. The research also includes defining a better smudge-resistant coating to deter ugly fingerprints and scratches from screens and surfaces.

Consumer electronics companies value the appearance and functionality of their ubiquitous devices and, hence, have created them with smudge, scratch and reflective resistant coatings, reported Dr Steven R. Carlo and colleagues at the 238th National Meeting of the American Chemical Society.

And while these coatings are effective, their structure and mechanisms are poorly understood, said Carlo, whose colleagues developed a test to determine the chemical composition and effectiveness of smudge and reflective resistant materials. They believe this will lead to a better understanding of the chemistry of these coatings, allowing improved formulations and performance.

"Surfaces are particularly important in consumer products. This work investigates how products can be modified to reduce smudging and reflections. These modifications can offer improved resistance to fingerprints, anti-reflection properties or enhanced physical resistance," Carlo explains.

The basis of anti-smudge coatings is a compound called perfluoro alkyl ether, a derivative of Teflon with added ether groups to enhance its repellent effects. Anti-reflective materials use alternating layers of material, including silica and aluminum, to bend and diffuse light to reduce glare.

Since traditional chemical techniques could not be used on these super-thin coatings, Carlo and his team used depth profile X-ray photoelectron spectroscopy (XPS) - a tool for comparing the chemistry of these coatings to predict their performance.

The data allowed them to compare chain length, degree of branching and the hydrocarbon and fluoroether content of various samples. The fluoroether content has a key effect in enhancing the desired effect. Anti-reflective coatings need alternating layers, which have differences in their refractive index (RI), a measure of how fast light travels through a material.

XPS allowed the scientists to visualize the multi-layer structure and the chemical species present in each layer - the greater number of alternate layers in a coating, the greater the anti-reflection qualities. Also, more silica and aluminum layers provide better glare reduction.