| 摘要 |
The present invention provides a polarization switching liquid crystal element 1 having TN liquid crystal 7 retained between two transparent substrates 2 a and 2 b 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 the TN liquid crystal 7 , wherein a phase difference u of said TN liquid crystal 7 is defined by the following equation: u= 2 xDeltanxd/lambda, where Deltan is the refractive index anisotropy of said TN liquid crystal 7 , d is the thickness of said TN liquid crystal 7 , and lambda 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)xsin<SUP>2</SUP>{pi(1+u<SUP>2</SUP>)<SUP>1/2</SUP>/2}/(1+u<SUP>2</SUP>), and wherein the phase difference u includes a value 1.7 and the transmittance T is 0.1 or lower when the lambda ranges from 400 nm to 700 nm. Then, a polarization switching liquid crystal element having a high response speed and reduced wavelength-dependency can be realized using inexpensive and highly durable TN liquid crystal without increasing parts cost.
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