US Patent 7220008 Reflective display device

A reflective display device includes a retroreflective layer including a plurality of unit structures that are arranged two-dimensionally on a virtual plane and a modulating layer, which is arranged closer to a viewer than the retroreflective layer is and which is switchable between a first state and a second state that have mutually different optical properties. The reflective display device conducts a display operation by using light that has been reflected back from the retroreflective layer. Each unit structure of the retroreflective layer has a recess defined by three planes that are opposed substantially perpendicularly to each other. The unit structures are arranged so as to face substantially the same direction. An azimuthal direction, which is defined by projecting a normal to one of the three planes onto the virtual plane, and another azimuthal direction, which is defined by projecting a screen downward direction onto the virtual plane, form an angle of less than 30 degrees.