25 August 2009

Touchscreens become glare, smudge resistant

Touchscreen users rejoice, there is now a way to reduce their tendency to smudge and cut sunlight glare.

Smudge, scratch, and reflective resistant coatings have become standard on high-end touchscreen cell phones and MP3 players. These coatings are effective. However, their structure and mechanisms are under study and not understood, so Steven R. Carlo, Ph.D., Paul Verghese, Ming Wu, and colleagues from the American Chemical Society developed a test to determine the chemical composition and effectiveness of smudge and reflective resistant materials. The test could also lead to a better understanding of the chemistry of these coatings and allow improved formulations and performance, Carlo said.

Scientists developed a test for evaluating and improving the performance of smudge- and glare-resistant screens.

“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 said.

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 layers, to bend and diffuse light to reduce glare.

Since traditional chemical techniques would not work 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 efficacy. Anti-reflective coatings need alternating layers, which have differences in their refractive index (RI), a measure of how fast light travels through a material. Fluorocarbons in general have low RI and offer anti-smudge properties. XPS allowed the scientists to visualize the multi-layer structure and the chemical species present in each layer. In general, the greater the number of layers there are in a coating, the greater the anti-reflective properties. Carlo and his team also discovered more silica and aluminum layers led to better glare reduction.

For related information, go to www.isa.org/manufacturing_automation.