JPS6230406B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for driving a cholesteric nematic phase change type matrix display liquid crystal panel that can be driven at low voltage and is subjected to vertical alignment treatment that can shorten writing time.

Cholesterol ice cream with vertical alignment treatment
A matrix display liquid crystal panel that uses a nematic phase transition type electro-optic effect has the following advantages compared to a matrix display liquid crystal panel that uses a field effect-twisted nematic type electro-optic effect: It is excellent because 2) it can have a large number of scanning electrodes, and (3) it has good viewing angle characteristics.

The electro-optic effect of the cholesteric-nematic phase transition type mentioned above will be explained. Figure 1 shows the voltage-transmitted light intensity static characteristics of this type. In state 1, liquid crystal molecules form a spiral domain, and in states 2 and 4, liquid crystal molecules form a focal domain.
With Konik orientation, the states of 3-1 and 3-2 are
Liquid crystal molecules are oriented perpendicular to the electrode plane.
In FIG. 1, the voltage V _H is the threshold voltage for phase transition from the cholesteric phase to the nematic phase. States 1 and 4 are states in which displays are accumulated. A case will be described in which the storage state is changed from state 1 to state 4 or from state 4 to state 1. A voltage equal to or higher than V _H is applied to the liquid crystal molecules to shift them from the 1 or 4 state to the 3-1 state. In state 3-1, the voltage applied to the liquid crystal molecules is maintained for several milliseconds.
If a voltage V is applied after setting the state to 0 for ~10-odd milliseconds, the state 3-1 quickly shifts to the state 2. The time for reducing the voltage to zero is set to be longer than the phase transition time from the nematic phase to the cholesteric phase.
If the voltage decreases to V in state 3-1, it passes through state 3-2 and then shifts to state 2, but V/V _H 0.7
If you take it, it will stay in the 3-2 state for a long time (several seconds). If the voltage is changed from V to 0 in state 3-2 and state 2, the voltage shifts to state 1 and 4, respectively, and is accumulated.

A conventional driving method will be described below. In matrix display, a column electrode group and a row electrode group intersect and a voltage is applied to the liquid crystal molecules at the intersection to display a dot-like image. When the row electrode group is line-sequentially scanned, the phase of the voltage applied to the column electrode group is changed depending on whether the display dots on the row electrode group are accumulated in the 1 state or the 4 state during scanning. First, in order to erase the display accumulated in state 1 or state 4, AC pulse voltages with peak value V and duty 1 are applied to the row electrode group and column electrode group, respectively, so that they are in opposite phases to each other. do. An AC pulse voltage with a peak value of 2V and a duty of 1 is applied to all display dots, and by setting the voltage to _2VVH , a transition is made to the state 3-1. Writing of the display starts in the state 3-1, and the voltage for this writing is shown in FIG. In the figure, 5-s and 5-ns indicate the voltages applied to the row electrodes, and 6-s and 6-ns indicate the voltages applied to the column electrodes. 5-s indicates an AC pulse voltage with a peak value V duty of 1 applied to the row electrode during scanning, and 5-ns indicates voltage 0 applied to the row electrode during non-scanning. The scanning time for one row electrode is several
msec to 10-odd msec. 6-s is the display dot on the row electrode during scanning, and 6-ns is the AC pulse voltage of peak value V and duty 1 applied to the column electrode to make the state 2. 6-ns is the display dot on the row electrode during scanning. The figure shows an AC pulse voltage with peak value V and duty 1 applied to the column electrode in order to maintain the state 3-2 on the display dots on the electrodes until the writing of all display dots is completed.

While writing the display, voltage 7 is applied to the selected display dots (dots accumulated in state 4) during scanning, and voltage 9-1 or 9-2 is applied during non-scanning. To non-selected display dots (dots accumulated in a state of 1), voltage 8 is applied during scanning, and voltage 9-1 or 9-2 is applied during non-scanning. After writing is completed, when the voltage applied to the row electrode group and the column electrode group is set to 0, the display dots shift to the 4 or 1 state and are accumulated. The peak value V is the non-selected display dot at 3-2 during the display writing time.
It is set to 0.7≦V/ _VH because it is necessary to maintain the condition. The display writing time corresponds to the above-mentioned scanning time, and this scanning time becomes shorter as the voltage V applied to the display dots immediately before scanning is lower. The conventional drive method has been described above, but
This driving method is limited by V/V _H ≧0.7, so in order to shorten the writing time and drive at low voltage,
There are limits.

An object of the present invention is to provide a method for driving a matrix display liquid crystal panel that can shorten writing time and drive at a lower voltage than conventional driving methods.

The driving method of the present invention is a method of driving a cholesteric nematic phase change matrix display liquid crystal panel subjected to vertical alignment treatment by line sequential scanning, in which a first rectangular wave is applied to the row electrode during scanning, 20~ just before scanning to the row electrode group during non-scanning
Apply 0 volts for 30 msec, and
In the row electrode group during non-scanning, except for the 30msec time,
A second rectangular wave whose phase is shifted by π/2 from the first rectangular wave is applied, and when the intersection with the row electrode during scanning is a selected dot, the first rectangular wave is applied to the column electrode group. , in the case of non-selected dots, a third rectangular wave having an opposite phase to the first rectangular wave is applied.

Hereinafter, the present invention will be explained in detail using examples. In the embodiment, a driving method using AC pulse voltage will be described. First, in order to erase the display accumulated in the 1 state or the 4 state, a peak value V ₁ and a duty 1 are applied to the row electrode group and the column electrode group, respectively.
AC pulse voltages are applied in opposite phases to each other. As a result, all displayed dots have a peak value of 2V ₁ ,
AC pulse voltage of duty 1 is applied, 2V ₁
By setting ≧V _H , the state shifts to 3-1. Writing of the display starts in the state 3-1, and the writing voltage is shown in FIG. In the figure, 10-s, 10ns, 11 is the row electrode, 12
-s, 12-ns is the voltage applied to the column electrodes. 10-s indicates the AC pulse voltage with peak value V ₁ and duty 1 applied to the row electrode during scanning, and 10-ns indicates the peak value V ₁ and duty 1 applied to the row electrode during non-scanning. It shows an AC pulse voltage whose phase is π/2 ahead of 10-S,
A voltage of 11, instead of a 10-ns voltage, is applied to the row electrode for a fixed period of 20 to 30 msec just before the row electrode is scanned. 12-s is the AC pulse voltage of peak value V 1 and duty ₁ applied to the column electrode to make the display dots on the row electrodes in the 2 state during scanning, and 12-ns is the voltage applied to the row electrodes during scanning. The peak value applied to the column electrode in order for the upper display dot to maintain the state of 3-2 until the writing of all display dots is completed.
V ₁ indicates a duty 1 AC pulse voltage. These 10-s, 10-ns, 11, 12-s, 1
A combined voltage of 2-ns will be applied to each display dot. That is, while writing the display, the selected display dots (dots accumulated in state 2) are applied with voltage 14 during scanning, and during non-scanning, voltage 13-1 or voltage 13-1 is applied for a fixed period of 20 to 30 msec. immediately before scanning. 13-2 is applied, and at other non-scanning times, voltage 16-1 or 16-2 is applied. On the other hand, to non-selected display dots (dots accumulated in state 4), voltage 15 is applied during scanning, and during non-scanning, voltage 13-1 or 13-2 is applied for a certain period of 20 to 30 msec immediately before scanning. During non-scanning, voltage 16-1 or 16-2 is applied. In this example V ₁
to 1/2V _H. In this case, the voltage applied to the non-selected display dots is √2V ₁ , or 0.707V _H , except for 20 to 30 msec immediately before scanning, so the non-selected display dots remain in the state of 3-2 until the end of writing. can be kept. On the other hand, since the voltage applied to the selected display dot is 0.5 V _H for 20 to 30 msec immediately before scanning, the scanning time per dot is halved compared to the conventional driving method. (When V ₁ /V _H is 0.5 and 0.7, the scanning time is twice as different.) The present invention has been explained above using an embodiment, but in the conventional driving method, the driving voltage is 0.7 V _H or more. On the other hand, in the driving method of the present invention, the driving voltage is 0.5V _H or more, so compared to the conventional driving method, according to the driving method of the present invention,
The writing time can be cut in half, and the drive voltage can be reduced by half.
Can be reduced by 30%.

As above, the present invention has been explained in detail with reference to examples. In the examples, 13-
1, 13-2, 14, 15, 16-1, 16-2
driving voltages, but these voltages can also be generated in other ways. For example, it can be generated by applying a DC pulse voltage to the row and column electrodes.

[Brief explanation of the drawing]

Figure 1 shows the voltage-transmitted light intensity static characteristics to explain the electro-optical characteristics of a cholesteric-nematic phase change type liquid crystal panel, Figure 2 shows the voltage generated by the conventional driving method, and Figure 3 FIG. 2 is a diagram showing voltages generated by the driving method of the embodiment for explaining the present invention. 7, 8, 14, 15 are voltages applied to the display dots during scanning, 9-1, 9-2, 13-1, 1
3-2, 16-1, and 16-2 are voltages applied to display dots during non-scanning.

Claims (1)

[Claims] 1. In a method of driving a cholesteric nematic phase change matrix display liquid crystal panel subjected to vertical alignment treatment by line sequential scanning, a first rectangular wave is applied to the row electrodes during scanning, and the row electrodes during non-scanning are 0 volt was applied to the group for 20 to 30 msec immediately before scanning, and the phase was shifted by π/2 with respect to the first rectangular wave to the row electrode group during non-scanning, excluding the 20 to 30 msec period. A second rectangular wave is applied to the column electrode group, and when the intersection with the row electrode during scanning is a selected dot, the first rectangular wave is applied to the column electrode group, and when the intersection is an unselected dot,
A method for driving a matrix display liquid crystal panel, comprising applying a third rectangular wave having an opposite phase to the first rectangular wave.