Liquid crystal display device

The present invention suppresses the increase of consumptive electricity derived from the alternation timing driving of a passive matrix type liquid crystal display device such as an STN system or the like. According to the present invention, the liquid crystal display device which is driven by applying selection voltages to common electrodes during a scanning period of the common electrodes and by applying non-selection voltages during other periods to the common electrodes includes a switching circuit which temporarily short-circuits the common electrode n and the common electrode m during a period shifting from the scanning period of the common electrode n to the scanning period of the common electrode m which succeeds the scanning period of the common electrode n, and makes use of the charge stored in the common electrode n by the application of the selection voltage during the scanning period of the common electrode n for charging the common electrode m.

What is claimed is:

1. A liquid crystal display device comprising:

a liquid crystal panel which juxtaposes a plurality of common electrodes extended in the first direction on one of a pair of substrates sandwiching a liquid crystal layer therebetween and juxtaposes a plurality of segment electrodes extended in the second direction transverse to the first direction on the other of the pair of these substrates,

a common driver having a common voltage output part which applies scanning signals to the plurality of respective common electrodes, and

a segment driver having a segment voltage output part which applies data signals corresponding to display data to the plurality of respective segment electrodes,

wherein the common driver has following functions:

(a) to allocate selection periods sequentially to the plurality of respective common electrodes and to apply a selection voltage to one of the plurality of common electrodes to which non-selection voltage is applied as scanning signals in a period in which the data signals are applied to the plurality of segment electrodes;

(b) to apply the scanning signal to a n.sub.M th one of the plurality of common electrodes to which the Mth selection period (M being a natural number of 2 or more) is allocated performed in sequence of (i) ceasing the application of the non-selection voltage to the nMth of common electrode at a first time when the Mth selection period is started, (ii) starting the application of the selection voltage thereto from the second time coming after the first time, (iii) ceasing the application of the selection voltage thereto at the third time when the Mth selection period expires, and (iv) starting the application of the non-selection voltage thereto from the fourth time coming after the third time;

(c) to comparing polarity of the selection voltages in the Mth selection period and in a (M-1)th selection period allocated prior to the Mth selection period to a n.sub.M-1 th common electrode and applied to the n.sub.M-1 th common electrode, respectively for the non-selection voltage;

(d) to short-circuit a portion of the common voltage output part corresponding to the n.sub.M th common electrode and another portion thereof corresponding to the n.sub.M-1 th common electrode during a period lying between the first time and the second time, when the selection voltage in the Mth selection period and the selection voltage in the (M-1)th selection period have the same polarity, and

(e) not to short-circuit the portion of the common voltage output part corresponding to the n.sub.M th common electrode and the another portion thereof corresponding to the n.sub.M-1 th common electrode during the period lying between the first time and the second time, when the selection voltage in the Mth selection period and the selection voltage in the (M=1)th selection period have the polarities opposite to each other.

2. A liquid crystal display device according to claim 1, wherein the common voltage output part which corresponds to the n.sub.M th common electrode and the common voltage output part which corresponds to the n.sub.M-1 th common electrode are short-circuited in the period after the first time and before the second time.

3. A liquid crystal display device according to claim 1, wherein the period in which the common voltage output part which corresponds to the n.sub.M th common electrode and the common voltage output part which corresponds to the n.sub.M-1 th common electrode are short-circuited expires after the third time and before the fourth time.

4. A liquid crystal display device according to claim 1, wherein, in the liquid crystal panel, the n.sub.M th common electrode and the n.sub.M-1 th common electrode are arranged adjacent to each other.

5. A liquid crystal display device according to claim 1, wherein, in the liquid crystal panel, the n.sub.M th common electrode and the n.sub.M-1 th common electrode are arranged in a spaced-apart manner.