Bio-inspired antireflection film makes displays more readable under the sun

July 03, 2017 // By Julien Happich
Finding their inspiration in nature, an international team of researchers has investigated the use of a moth-eye-like nanostructure as an antireflection surface that would enhance any display readability under a bright sun.

The researchers first developed a numerical model to simulate and optimize the optical behaviours of micro-dimples as found on a moth's eyes (optimized to catch all available light at night and reduce glare).


The moth-eye-like nanostructures as seen from
above (left) and from the side (right).
Image Credit: Shin-Tson Wu, College of Optics
and Photonics, University of Central Florida.

In a promising paper titled "Broadband antireflection film with moth-eye-like structure for flexible display applications" published in the Optica journal, the researchers reveal a flexible substrate nano-imprinted with dimples about 100 nanometres in diameter then layered with a thin hard-coating film. Self-assembled nanospheres were used to create the imprint master, a fabrication process that is easily scalable to large film sizes, claim the researchers who hope their new flexible AR film will make it into the multi-billion smartphone market.

The result is a flexible anti-reflection (AR) film with a luminous reflectance under 0.23% and exhibiting less than 1% haze. That’s an order of magnitude lower than the iPhone’s surface reflection measured at 4.4 percent and turns any display panel (rigid or fixed) into a sunlight readable unit.

Such an efficient AR film also removes the need for adaptive brightness control, which brightens the display's output under bright light but also drains battery power.

The film was proven to have good mechanical characteristics (pencil hardness over 3H), making it suitable for touch panels, while being flexible to a bending radius of 8mm. To top it up, the researchers waterproofed the film with a fluoroalkyl coating to raise hydrophobicity. With a water contact angle over 100°, water-based liquids just slides off the screen and help keep it clean.