Re-orientation of the dye (red) by the liquid crystal (yellow) results in a change in light transmission.
In light absorptive e-Tint systems, a dichroic guest dye is added to the liquid crystal host. The dichroism of the dye results in an absorbance that is orientation dependent. These dyes are specifically designed and fabricated to have a tight alignment with the liquid crystal host. Therefore, reorientation of the host by an applied field results in a reorientation of the dye and in subsequent change in the absorbance of the system. In effect, the system behaves as a molecular version of a blind. Non-polarizer based systems have advantages over conventional polarizer based systems in that they offer the opportunity to shift the transmission window as needed. For example, for eyewear applications, the mixture can achieve clear state transmissions of > 70% which is not achievable by polarizer based systems.
Light absorbing e-Tint®
AlphaMicron is the recognized leader in guest-host systems and has invented and commercialized its e-Tint technology for sports eyewear, military and automotive applications. Polarizer-based refractive systems The inherent birefringence of liquid crystals means that the index of refraction seen by an incident light depends on the relative angle between the polarization of the light and the long axis of the liquid crystal molecules. This property allows the liquid crystal film to be used as a polarization rotator. Since we can alter the orientation of the molecules with an applied field, we can control the degree of polarization rotation. In this way, we can alter the transmission of a light between a pair of crossed polarizers. This type of device can provide an exceptionally good light blocking and fast response time. But, the clear state transmission is less than 45% (because of the polarizers). AlphaMicron has demonstrated the first polarizer based devices on curved flexible plastic substrates for intense light protection.