Car windows darken upon the push of a button

December 14, 2015 // By Christoph Hammerschmidt
Automotive supplier Continental has developed a glass for car windows whose transparency can be controlled electrically. The technology will improve driving safety, privacy and energy efficiency, the company promises.

The dimmable glass consists of films in which embedded particles can be aligned when a voltage is applied. This effect can be used for targeted darkening of the window. Such films have been available for a long time already. Up to now, however, this technology has only been feasible in the roof area for a small number of high-end cars. Continental now is demonstrating the intelligent activation of the “Suspended Particle Device” film technology also for side and rear windows and the windshield in a test vehicle.

This production-ready film technology is based on embedded particles, which arrange themselves randomly when unpowered and darken the window from outside, while retaining transparency from the inside to the outside. If a voltage is applied, the particles align themselves in parallel, so that the window becomes permeable to light in both directions. The connection to the vehicle system enables the windows to lighten automatically when one approaches the vehicle with a key or smartphone. At present, the technology is still rather expensive given the parts budgets for typical midsize-class family cars. However, promising developments are under way that entitle for hope that the prices will fall rapidly, the company said. In particular technologies, called PDLC (Polymer Dispersed Liquid Crystal), LC (Liquid Crystal) and EC (electrochromism) are mentioned as promising. The latter is already used in cars to darken the exterior or interior mirrors to prevent glare effects. Larger areas, like front screen windows, still have the disadvantage that they require high electrical power to achieve short switching times.

The intelligent Glass Control technology could be used to automatically darken the windows in cases when the driver runs danger to get dazzled or blinded by intensive light sources, like the sun near sunset. Another benefit is that the interior of the vehicle heats up less if the windows are darkened. Plus, the interior remains hidden to outside viewers in the absence of the driver.