| 摘要 |
PURPOSE:To expand the life of an active matrix type liquid crystal display device by reading out a voltage being impressed to a liquid crystal display picture element at present at the time of refreshing operation, inverting and amplifying the voltage and applying the inverted and amplified voltage to the picture element again. CONSTITUTION:The capacity levels C14, C16 of dummy cells 8, 9 are precharged to intermediate potential levels '1', '-1' respectively by precharge voltage generating circuits 10, 11. When signals (a), (c) are turned to 'H' at time t1, prescribed switch elements are closed, a scanning signal line (m) is connected to dummy lines na, nb to make both the signal lines equal potential and disconnected at time t2. At time t3, the scanning electrode l1 of a picture element 1 and the line (b) are turned to 'H', prescribed elements are closed, respective potential levels of the C14, C16 are divided by respective capacity values and stray capacity values and the potential of C3 is also divided by floating capacity CA. The voltage of the scanning line (m) is compared with that of the dummy lines na, nb by comparators 6, 7 respectively, the compared values are converted into ternary value by a ternary conversion output circuit 12 on the basis of the prescribed method, and at time t5, the dummy lines na, nb are connected to the scanning signal line (m) by a signal (d). Since an alternate voltage is applied to a capacity C in an element 1 on the basis of the ternary conversion output (k) during the period until an element 2 is turned off and an AC field can be impressed to a liquid crystal element 4 every refreshing operation, the life of the display device can be expanded.
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