Patent ID: 7982828

Claim:
A polarization switching liquid crystal element having TN liquid crystal retained between two transparent substrates for transmitting at least visible polarized light with the polarized light transmission axis selectively rotated by 90 degrees when a voltage is selectively applied to said TN liquid crystal, wherein a phase difference u of said TN liquid crystal is defined by the following equation: u= 2 ×Δn×d/λ where Δn is the refractive index anisotropy of said TN liquid crystal, d is the thickness of said TN liquid crystal, and λ is the wavelength of said polarized light and a transmittance T of said polarization switching liquid crystal element measured with polarization plates on the incident and outgoing sides is defined by the following equation: T =(½)×sin 2 {π(1 +u 2 ) 1/2 /2}/(1 +u 2 ), and wherein the phase difference u includes a value 1.7 and the transmittance T is 0.1 or lower when the λ ranges from 400 nm to 700 nm.