Light modulating device

A light modulating device, comprising:

• a first substrate;
• a second substrate;
• a light modulation layer;
• an optically anisotropic layer;
• a first polarization layer;
• a second polarization layer;
• and
• a retardation film,
• wherein each of the first and second substrates has a first surface and a second surface, wherein the first and second surfaces are disposed opposite to each other,
• wherein the first surfaces of the first and second substrates face each other,
• wherein the first and second substrates are each anisotropic substrates having an in-plane phase difference of 500 nm or more for light with a wavelength of 550 nm,
• wherein the light modulation layer is disposed between the first and second substrates;
• wherein the retardation film is formed on the second surface of the first substrate or the second substrate,
• wherein the first polarization layer is formed on the second surface of the first substrate or on the retardation film,
• wherein the second polarization layer is formed on the second surface of the second substrate or on the retardation film,
• wherein the retardation film has an in-plane phase difference in a range of 100 nm to 300 nm for light having a wavelength of 550 nm,
• wherein the retardation film is disposed such that the slow axis of the retardation film and the slow axes of the anisotropic substrates are perpendicular or horizontal to each other,
• wherein the optically anisotropic layer is disposed between at least one of the light modulation layer and the first substrate or between the light modulation layer and the second substrate, wherein the optically anisotropic layer satisfies Equation 3 below:
• nz<ny≈nx [Equation 3]
• wherein, nx is the refractive index of the optically anisotropic layer for light with a wavelength of 550 nm in the slow axis direction, ny is the refractive index of the optically anisotropic layer for light with a wavelength of 550 nm in the fast axis direction, and nz is the refractive index of the optically anisotropic layer in the thickness direction, and
• wherein the slow axis of the retardation film and the absorption axis of the first or second polarization layer that is adjacent to the retardation film are perpendicular to each other.