An electric field that is parallel with a TFT substrate is formed by a pair of electrodes formed on the TFT substrate. Liquid crystal molecules in a light modulating layer are caused to respond electro-optically to the electric field. The light modulating layer is constituted of a liquid crystal material, an optically active substance, and a dichroic dye. The spiral pitch p [μm] of the light modulating layer, the cell thickness d [μm], the twist angle n of liquid crystal molecules, and the interelectrode interval L [μm] are set in ranges of 1≦p≦15, 1≦d≦10, n≦300°, and L