Liquid crystal displays (LCDs) are widely used as a display for computer terminals, calculators, security systems and other apparatus. It is known that the scattering characteristic of the liquid crystal depends upon the viewing angle at which an observer views the liquid crystal. Accordingly, many liquid crystal displays are pivotable so that the user may adjust the viewing angle for maximum contrast. For example, U.S. Pat. No. 4,680,674 to Moore describes a modular computer system in which the liquid crystal display is hinged to provide for adjustment of viewing angle, and U.S. Pat. No. 4,443,819 to Funada et al. discloses a liquid crystal TV which is pivotable about its rod antenna to provide adjustment. Unfortunately, a hinge or pivot may create reliability problems, and increase cost and complexity. Furthermore, not all applications of LCD displays will permit a hinged or pivoted display.
It is also known that the viewing angle of a liquid crystal display may be controlled by a bias voltage applied to the liquid crystal. It is therefore common for liquid crystal displays to include a bias input for receiving a bias voltage to control the viewing angle, and a potentiometer or variable resistor to adjust the bias voltage. For example, U.S. Pat. No. 4,744,103 to Dahlquist et al. discloses a telephone which includes an LCD display and a potentiometer for adjusting the viewing angle, and U.S. Pat. No. 4,319,237 to Matsuo et al. discloses a combination of fixed and variable resistors for adjusting the viewing angle of an LCD display.
Unfortunately, a potentiometer is susceptible to contamination and wear, and a potentiometer knob or a thumb screw may be accidently moved. To avoid accidental movement, a recessed adjustment screw may be provided, in which case a screwdriver is needed to adjust the screw. Moreover, present day microprocessor controlled devices, e.g. microwave ovens, video cassette recorders or security systems, avoid the use of any knobs or dials in favor of keyboard-style pushbuttons.