Twisted nematic liquid crystal display device

DETAILED DESCRIPTION The present invention relates to a twisted nematic liquid crystal display device comprising a first transparent electrode which has been subjected to orientation treatment in a first direction and second transparent electrode, which has been subjected to orientation treatment in a second direction.
A liquid crystal layer, the major axes of the molecules of which are subjected to a twisted orientation (e.
g.
90.
degree.
), is located between said first and second electrodes.
A first transparent polarizing plate having a direction of polarization coinciding with the first direction is located outside the first electrode.
A second transparent polarizing plate having a direction of polarization coinciding with the first direction is located outside the second electrode.
In such a device, when no voltage is applied between the two electrodes, light incident on the first polarizing plate is not able to pass through the liquid crystal layer due to the twisted orientation of the major axes of the molecules of the liquid crystal layer.
However, when an excitation voltage is applied between the two electrodes, the major axes of the molecules of the liquid crystal layer are re-orientated so as to lie parallel to the electric field and light incident on the first polarizing plate is able to pass through the liquid crystal layer and out through the second polarizing plate.
According to the invention, the display device is characterized in that the optical path length difference (.
DELTA.
nd) of the liquid crystal layer, which is equal to the product of the thickness (d) of the liquid crystal layer and the double refraction index (.
DELTA.
n) of the liquid crystal layer, has a value such that 1.
4 .
mu.
m .
ltoreq.
.
DELTA.
nd.
ltoreq.
1.
7 .
mu.
m.