Optical modulation method for a liquid crystal layer and liquid crystal device using the method

A liquid crystal device comprising:

• a front polarizing plate, a liquid crystal layer and an optical reflective layer are arranged in this order from the front side of the device, the liquid crystal layer having a thickness determined in reference to a reference liquid crystal layer that is characterized by having one retardation when the reference liquid crystal layer is applied with a predetermined high voltage and an other retardation when the reference liquid crystal layer is applied with a predetermined low voltage, for light that is incident from the front polarizing plate, passes through the reference liquid crystal layer, reflects on the optical reflective layer, passes again through the reference liquid crystal layer and is guided to the front polarizing plate, whereby a bright state and a dark state can be presented based on a predetermined difference between these retardations, wherein
• the thickness of the liquid crystal layer and/or a pre-tilt angle of liquid crystal molecules of the liquid crystal layer is made to be greater than that of the reference liquid crystal layer, so that a same value of the predetermined difference in retardation is obtained by a first retardation obtained by applying the liquid crystal layer with a modified high voltage lower than the predetermined high voltage and a second retardation obtained by applying the liquid crystal layer with a modified low voltage equal to or higher than the predetermined low voltage, or by a first retardation obtained by applying the liquid crystal layer with a modified high voltage equal to or lower than the predetermined high voltage and a second retardation obtained by applying the liquid crystal layer with a modified low voltage higher than the predetermined low voltage is made to be a value of substantially quarter of a wavelength of the light.

A liquid crystal device, comprising:

• a front polarizing plate, a liquid crystal layer and a rear polarizing plate are arranged in this order from the front side of the device, the liquid crystal layer having a thickness determined in reference to a reference liquid crystal layer that is characterized by having one retardation when the reference liquid crystal layer is applied with a predetermined high voltage and an other retardation when the reference liquid crystal layer is applied with a predetermined low voltage, for light that is incident from the rear polarizing plate, passes through the reference liquid crystal layer, and is guided to the front polarizing plate, whereby a bright state and a dark state can be presented based on a predetermined difference between these retardations, wherein
• the thickness of the liquid crystal layer and/or a pre-tilt angle of liquid crystal molecules of the liquid crystal layer is made to be greater than that of the reference liquid crystal layer, so that a same value of the predetermined difference in retardation is obtained by a first retardation obtained by applying the liquid crystal layer with a modified high voltage lower than the predetermined high voltage and a second retardation obtained by applying the liquid crystal layer with a modified low voltage equal to or higher than the predetermined low voltage, or by a first retardation obtained by applying the liquid crystal layer with a modified high voltage equal to or lower than the predetermined high voltage and a second retardation obtained by applying the liquid crystal layer with a modified low voltage higher than the predetermined low voltage is made to be a value of substantially half of a wavelength of the light.