Liquid Crystal Displays. Ernst Lueder. Читать онлайн. Newlib. NEWLIB.NET

Автор: Ernst Lueder
Издательство: John Wiley & Sons Limited
Серия:
Жанр произведения: Техническая литература
Год издания: 0
isbn: 9781119668008
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3.21(b) depicts the pretilt of the π cell pointing in the same direction on both substrates. In this case, the molecules in the centre of the cell experience almost no torque while they relax into the off-stage. The angles by which the relaxing molecules have to be tilted are smaller, resulting in a much higher switching speed.

Schematic illustration of the pretilt angles and the relaxation to the off-state. (a) Of a TN cell; (b) of a p cell.

      As in the HAN cell, the optical anisotropy Δn in the π cell for VLC = 0 changes along the z-axis, which is denoted by Δn(z). As a consequence, the optical retardation R from the input at z = 0 to the output at z = d is

Schematic illustration of the electro-optical response to a square voltage pulse. (a) Of a TN cell with a prolonged relaxation; and (b) of a p cell with a fast relaxation.

      (3.98)equation images

      (3.99)equation images

      A normally white cell has the first transmission maximum at (π/λ)R = (π/2), or

      corresponding to a λ/2-plate. We introduce an effective anisotropy Δneff for the entire optical path in the cell, which is given by

      (3.101)equation images

      (3.102)equation images

      The wide viewing angle inherent to the π cell is discussed in Section 6.3.2.

       3.2.8 Switching dynamics of untwisted nematic LCDs

Schematic illustration of the anchoring of L C molecules at z equals 0 and z equals d.

      with

equation images equation images equation images equation images equation images equation images equation images

      For