New window coating can ease blue moods

Caren B. Les, caren.les@photonics.com

Stuck in the office and feeling blue? Well, open the blinds: A new glass coating could usher in the feel-good light of the outdoors.

Specifically, that’s blue light, which is known to affect a person’s sense of well-being by affecting the balance of hormones. But this wavelength often is blocked or reflected away by standard windows, especially those with heat-insulating and sun-protective glaze treatments.

Our biorhythms are affected not so much by the wavelengths that brighten a room the most, but rather by blue light, said Walther Glaubitt, a researcher at the Fraunhofer Institute for Silicate Research ISC in Würzburg, Germany, where the coating was developed.

There is a nerve connecting the human retina to the hypothalamus, which is the control center for the autonomic nervous system, said researcher Dr. Jörn Probst. Receptors at the end of the nerve connection are sensitive to blue light and convert it to light-and-dark signals, sending them to the part of the brain that functions as our biological clock, where nerve impulses regulate melatonin levels. High levels of melatonin, caused by a lack of light, can lead to sleeping problems, depression and difficulty concentrating.

An innovative window coating allows more mood-lifting light from the blue spectrum to pass through from the outdoors into our indoor spaces. Courtesy of Uniglas GmbH & Co. KG.

“The coating we’ve developed helps people to feel they can perform better and makes it less likely they will fall ill,” Probst said.

The new coating is designed to be especially good at transmitting light in the blue part of the spectrum. “Nobody’s ever made glass like this before,” Glaubitt said. “It makes you feel as if the window is permanently open.”

The treatment consists of a long-lasting, barely noticeable inorganic coating that is only 0.1-µm thick and allows maximum transmission at wavelengths between 450 and 500 nm.

Uniglas GmbH & Co. KG of Montabaur, Germany, is launching a triple-glazed heat-insulating window featuring the new ISC coating. A patent is pending for it under the name Uniglas Vital feel-good glass. This window lets through 79 percent of light at 460 nm; other triple-glazed windows transmit only 66 percent of light at this wavelength.

“Up to now, we’ve only applied our special coating to the side of the glass facing into the cavity between panes,” Glaubitt said. “In the future, we will also be coating the glazing’s exposed surfaces – in other words, the outside and the inside of the window. That will allow us to achieve around 95 percent light transmissivity at 460 nanometers.”