Patent ID: 8330709

Claim:
An illuminating device comprising: a light guide plate; a light source arranged on a side face of the light guide plate; and a light modulation device that is arranged on a surface or an inside of the light guide plate and that is bonded to the light guide plate, wherein the light modulation device has a pair of transparent substrates that is distanced from each other and arranged opposite to each other, a pair of electrodes provided on each surface of the pair of transparent substrates, and a light modulation layer provided in a gap between the pair of transparent substrates, the light modulation layer has a first region and a second region that have optical anisotropy and that have each response speed to an electric field different from each other, the first region has a structure in which an optical axis of the first region is in parallel with a light incident face into which light of the light source enters of side faces of the light guide plate and crosses with the surface of the transparent substrates at a first angle when a voltage is not applied between the pair of electrodes, and has a structure in which the optical axis of the first region is in parallel with the light incident face and crosses with the surface of the transparent substrates at a second angle larger than the first angle when a voltage is applied between the pair of electrodes, and the second region has a structure in which an optical axis of the second region is in parallel with the light incident face and crosses with the surface of the transparent substrates at the first angle without relation to presence of voltage application between the pair of electrodes.