| 摘要 |
PURPOSE:To improve observation without the sharp increase of power consumption even at a position reduced at its lighting condition by changing the negative/positive display of liquid crystal when the quantity of light is reduced to less than a prescribed value. CONSTITUTION:Since the output of a lighting switch 1 is in the ''1'' level when the peripheral is bright, a signal generator 2 sends a signal supplied to an input terminal 2b as it is. Consequently, voltage between control electrodes 42 and 44 is zero and the polarizing direction of polarizing plates 41, 48 is determined so that the display at that time is positive display. When the periphery becomes dark and the light is reduced to less than the prescribed value, a threshold circuit 12 sends a ''0'' level signal. consequently, the signal generator 2 inverts the signal supplied to the terminal 2b and sends the inverted signal, so that voltage is applied between the control electrodes 42 and 44. Consequently, the orientation of a liquid crystal layer 43 is turned to a direction parallel to the electric field, its optical activity disappears and a liquid crystal display part 4 showing positive display is turned to negative display. Thus, the liquid crystal display part 4 shows positive display at the bright time and negative display at the dark time. |
