Variable-transparency smart glass technology makes it possible to switch “smart” glass instantly from matte to transparent — with one click of a remote control or the press of a button.
The technology is based on a variable-transparency film with an internal liquid-crystal (LC) layer. The film is placed between two layers of glass (triplex), or applied to the glass as a self-adhesive film.
How smart glass works
In its normal state, when the variable-transparency glass is disconnected from the power supply, the liquid crystals of the LC film are oriented randomly in all directions and scatter all light rays passing through it, blocking visibility through the glass in both directions: the glass is matte and highly opaque.
When power is applied, the crystals align perpendicular to the glass and let rays falling in that direction pass without distortion (without scattering): the glass becomes transparent.
The view through smart glass
Variable-transparency smart glass has a high degree of scattering (opalescence): in the matte state, practically no objects can be seen behind it even at a distance of 1–2 cm.
However, if a sharp shadow falls on the glass (when an object is between the light source and the glass, close to the glass, with a darkened room behind it), a vague dark outline of the object can be seen through the glass. This should be taken into account when designing the lighting of rooms with variable-transparency glass.
In the transparent state, the glass slightly scatters rays falling on it at a steep angle: when looking “along” the glass, a slight haze is noticeable.
The matte effect can be changed gradually (by slowly reducing the voltage from about 65 V to 0), but this primarily changes the distance at which objects behind the glass stop being visible. The changes happen quite quickly. This effect can be used in applications where the image is close to the glass — for example, a painting behind smart glass. For shop windows, however, such use is not effective, because the objects visible from the street are usually at roughly the same distance from the glass and would all appear at once.