Light modulator

Abstract

A bright, and contrasty reflective display can be performed without using polarizer films, and display switching can be performed fast. A ferroelectric liquid crystal is sandwiched between substrates, and electrodes are formed face to face with each other in a direction parallel to the substrates. The ferroelectric liquid crystal, when no electric field is applied to it, goes into a planer state in which a helical axis becomes perpendicular to or almost perpendicular to the substrates, selectively reflecting light of specific wavelengths in a visible region. A driving circuit applies an electric field between the electrodes in a direction perpendicular to or almost perpendicular to the helical axis of the ferroelectric liquid crystal in the planer state. When an electric field equal to or greater than a threshold value is applied, the ferroelectric liquid crystal changes from a planer state due to a low electric field to a homeotropic state in which a helical structure disappears, going into a transparent state, wherein, in the homeotropic state, a cyclic change of refractive index disappears and liquid crystal molecules are arranged in the direction of the electric field. The change in this case is performed fast because the ferroelectric liquid crystal has spontaneous polarization. The ferroelectric liquid crystal may be filled between a pair of transparent substrates each having a transparent electrode formed thereon to apply electric fields in a direction parallel to or almost parallel to the helical axes.