Researchers solve screen glare nightmare with 'moth-eye' antireflective film

£$% ambient... light! Can't see.. darn.. phone... screen

A new anti-glare film could help us see our phones a little bit better on a bright day.

"Ambient light is everywhere," says Jiun-Haw Lee, an electrical engineer at National Taiwan University in Taipei.

Natural light lowers the contrast of display screens, making them appear much darker. That's because when light from the sun hits glass, some of it reflects.

Commercial multilayer antireflection films available from the tech shop combine layers that each reflect light waves in such a way that the reflecting waves interfere, cancelling each other out. By using a moth-eye-nanostructure film that scatters light, however, researchers reduced reflection down to about 0.23 per cent, from about 1 per cent available with commercial films.

While it might not seem like such an improvement at first, Lee told The Register that leads to about a 3 per cent improvement in display contrast.

The researchers created the 2 x 2cm film by imprinting a 200-nanometre-thick moth-eye pattern on a plastic film. Moth eyes are shaped in such a way that they scatter light instead of reflecting it back – researchers have previously experimented with using them to optimise the absorption properties of solar cells, for example.

To fabricate the new film, first the researchers submerged solid silicon dioxide nanoparticles (about 100nm diameter) in a watery liquid, which assembled into a hexagon shape when heated. They then dunked this hexagon into a liquid plastic, which they stamped onto a plastic, scratch-resistant film. When they applied UV light, the liquid solidified.

The idea is that when light hits the film, the pattern makes light scatter away instead of reflecting back. Placing the film on part of a 10" monitor and applying a point-source light (sort of like a LED lamp), the team realised that the reflection was only about 0.23 per cent.

Lee says the hydrophobic film is applicable to any kind of display or phone. It's unnoticeable to the touch because of its nano-thickness and will last as long as the film used.

A paper describing the work appeared last week in Optica.

Michael Walls, a physicist at Loughborough University in the UK who has studied thin, antireflective films for spectacles and solar cells, said that the reflection rate is impressive. However, he points out the nanostructure would cause dirt and grease from fingers to accumulate much more quickly than normal.

Lee says the next step is to try different shapes to try to improve the reflection percentage. ®


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