JPS60258590A - Driving of liquid display panel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a horizontal electrode group (hereinafter abbreviated as an X-thin electrode group).
, a vertical electrode group arranged to intersect each of the X-axis heavy pole groups (hereinafter abbreviated as the Y-axis heavy pole group), and each electrode of the X-axis heavy pole group and the Y-axis heavy pole group. The present invention relates to a method of driving a liquid crystal display panel having liquid crystals provided at the intersections of , and particularly to a method suitable for driving a large-sized liquid crystal display panel with a large number of display contents.

[Background of the invention]

Generally, the structure of a liquid crystal display panel is as shown in FIG. In other words, as shown in the same figure, the X-axis heavy pole group
□, X2. X3・・・・・・・・・Y-axis heavy pole group that intersects XTn and Kohire I Y 1+ Y 21 ” :I
l......Y, and liquid crystals a1□+a12*a13, respectively, interposed between the two types of electrode groups at the intersections of the respective electrodes of the two types of electrode groups.
...a In n.

Conventionally, to drive a liquid crystal display panel with this configuration,
For example, when addressing the liquid crystal a 23 at the intersection of the X2 electrode of the X-axis heavy pole group and the X3 electrode of the Y-axis heavy pole group in FIG. A DC electric field sufficient to change the light transmittance was applied.

However, when using such a conventional drive method.

Since the electric field applied between the X-axis heavy pole group and the Y-axis heavy pole group was a direct current, there was a drawback that the liquid crystal material was electrolyzed by the direct current electric field, shortening the life of the liquid crystal.

[Purpose of the invention]

The present invention was made to solve these drawbacks, and by changing the electric field applied to the liquid crystal to an alternating current electric field, it is possible to drive a large liquid crystal display panel with a long life and flicker-free operation even with a large display content. The present invention provides a method for driving a liquid crystal display panel.

[Summary of the invention]

The feature of the present invention is that by changing the levels of both the scanning voltage applied to the X-axis heavy pole group and the signal voltage applied to the Y-axis heavy pole group, the electric field due to the difference between the two voltages can be applied to the desired liquid crystal. the direction of the electric field (hereinafter referred to as polarity) is 1.
The reason is that the inversion is performed at a cycle of a frame (or one field) or a plurality of frames (or a plurality of fields). In the present invention, since an electric field is applied to the liquid crystal provided at the intersection due to the difference between the scanning voltage and the signal voltage, the duty changes depending on the number of electrodes scanned within the frame period. Since it is possible to use an alternating current electric field without lengthening the horizontal scanning period, it is suitable when there is a lot of content to be displayed and it is difficult to perform polarity reversal within one horizontal scanning period. Even a large liquid crystal display panel can be driven with a long life and without flickering, and the frequency component of the electric field applied to the liquid crystal can be lowered, which is advantageous in terms of power consumption. Moreover, by changing the levels of both the scanning voltage and the signal voltage, the polarity of the electric field due to the difference between the two electrodes is reversed at the above-mentioned period and applied to the liquid crystal, so the range of fluctuation in the level of the signal voltage required to reverse the polarity of the electric field is It has the advantage that it can be made small and a drive circuit with low breakdown voltage can be used.

Furthermore, the present invention is characterized by equalizing the absolute value of the electric field applied to the liquid crystal in two adjacent cycle periods to create a complete alternating current electric field, thereby completely canceling the direct current component and causing electrolysis of the liquid crystal. The aim is to more completely suppress the occurrence of

Another feature of the present invention is that the scanning voltage and the signal voltage each have four levels, and at the time of addressing, the highest level or the lowest level is alternately applied at the above-mentioned period,
During non-addressing, one of the remaining levels is applied alternately at the above-mentioned period, and in each frame (or each field), both the scanning voltage and the signal voltage are applied to the liquid crystal during non-addressing, and one of the voltages is applied to the electric field. The purpose is to make the electric field applied to the liquid crystal at the time of address the opposite polarity, and to invert the polarity of these electric fields at the above-mentioned period to improve the contrast.

[Embodiments of the invention]

First, the present invention will be explained in detail. First, the present invention in which the polarity of electrodes is inverted within one horizontal scanning period will be explained in detail.

Figure 2 shows the voltage waveforms applied to the X-axis multipole group and the Y-axis multipole group (however, only the X1 electrode of the Y-axis multipole group is shown in the figure) to explain this reference example. .

In the figure, IH indicates one horizontal scanning period, and the voltage waveform applied for each [H] is the case where the polarity is reversed three times between IHs, with the ground level value or a predetermined direct paddle level value as the boundary. Show about. In this case, X thin electrode
1 to XTn are sequentially and alternately applied with the above voltages for each IH, and the above voltages are applied to the Y thin electrodes only during a predetermined horizontal scanning period.

That is, in FIG. 1 and FIG. 2, in the first period 11-1, the liquid crystal a is located at the intersection of the X1 electrode and the Y□ group electrode.

An electric field is applied due to the difference between the voltages applied to both electrodes, and in the next IH period, a voltage is applied to the X2 electrode, but no voltage is applied to the Y1 electrode, and furthermore, in the next IH period, an electric field is applied to the Y□ group electrode voltage is applied, and the liquid crystal a at the intersection
23 shows that an electric field is applied.

In this way, when applying an electric field to a predetermined liquid crystal during the IH period, the polarity of the electric field is generally reversed 2Q-1 times (Q = 2.0 times in the above example) to prevent electrolysis of the liquid crystal. It is something to suppress. Note that the number of polarity reversals Q indicates a real number of 1 or more.

In general, the larger the number of polarity inversions, the better from the viewpoint of preventing electrolysis in the liquid crystal, but if it is too large, the response of the liquid crystal will not be able to follow.

In addition, in order to increase the number of inversions and have the liquid crystal completely follow the display, it is necessary to lengthen the ],H period, but if this is made too long, the display will flicker.
Particularly in the case of a large-area panel with many display contents, the j-frame becomes long, causing flicker.

Therefore, according to experimental results, the allowable range of the number of polarity inversions is preferably within the range of 1 α≦10. This tolerance range is
For example, p-methoxybenzylidine-p-n-butyl-
It can be applied to all common liquid crystals such as aniline.

Further, it is desirable that the appropriate number of reversals is an integer. This means that during the lH period, if one side is on the positive side and the other is on the negative side with the ground level value or a predetermined DC level value as the boundary, the number of times it will be on the positive side and the number of times it will be on the negative side will be equal, and it will be a complete alternating current. This is because the occurrence of electrolysis of the liquid crystal can be completely suppressed. However, this can be solved by increasing the number of polarity reversals, such as around Q=10 times, for example, Q=
Of course, even if the number of polarity reversals becomes a decimal number when the number of polarity inversions is increased, such as 9.5 times, it is effective in suppressing the occurrence of electrolysis of the liquid crystal.

In other words, in the case of item 2, the number of times the positive side is positive and the number of times the negative side is different by one in the case of Ω = 9.5 times, but it is effective in suppressing the occurrence of electrolysis of the liquid crystal. be. Moreover, in this case, each LH, or each frame, or each field.

By alternately applying the difference in the number of positive or negative times to the positive side and the negative side, the same effect as when the number Q of polarity inversions is an integer can be achieved.

Next, FIG. 3 shows a block diagram of a liquid crystal display panel driving device for carrying out the driving method of this reference example.

In the figure, a signal S of coded characters and a signal SP indicating the display position of the characters are sent out from the keyboard 1 as output signals. On the other hand, the signal generating circuit 6 constantly repeatedly sends out the scanning position signal Ss, and the matching circuit 5 sends out a pulse to apply it to the gate circuit 2 when the display position signal SP and the scanning position signal S8 match.

In the gate circuit 2, when there is no pulse from the coincidence circuit 5, the refresh memory (refreshmem
ory) 3 is directly applied to the same memory 3, and the previously applied character signal is repeatedly applied to the character generating circuit 4. However, when a pulse is sent from the coincidence circuit 5,
Refresh the character signal Sk of keyboard 1 in memory 3
to be applied.

The scanning circuit 7 supplies scanning pulses to the character generating circuit 4 and the gated one-line memory circuit 9 based on the output signal of the signal generating circuit 6. Further, the character generation circuit 4 generates a signal corresponding to the shape of the actual character by using the coded character signal output from the refresh memory 3 and the scanning signal output from the scanning circuit 7 to a gated one-line memory circuit 9. Enter.

That is, the input applied to the character generation circuit 4 is a 6-bit or 8-bit coded signal, which is converted into a signal corresponding to the shape of the character in the character generation circuit 4.

In the gated one-line memory circuit 9, a signal for one line corresponding to the shape of a character is held by the outputs of the scanning circuit 7 and the character generating circuit 4 only for the IH period or a period close to the IH. Furthermore, the output of the gated one-line memory circuit 9 and the output of the gate signal circuit 8 are the same as those of the Y-axis multipole group drive circuit 10.
and generates a signal to be applied to the Y-phase electrode group in the Y-axis heavy pole group drive circuit 10, and
Add to the fine electrode groups Y1 to Yo.

On the other hand, the X-axis heavy pole group scanning circuit 11 is operated by the signal from the signal generation circuit 6, and its output and the output of the gate signal circuit 8 are input to the X-axis heavy pole group drive circuit 12. A signal to be supplied to the X narrow electrode group is generated in the heavy pole group drive circuit 12 and applied to the X phase electrode group X1 to Xm of the liquid crystal display panel 13.

Next, FIG. 4 shows a circuit showing one set of components of the X-axis heavy pole group drive circuit 12. Note that the Y-axis heavy pole group drive circuit 10
can also be configured in the same way as in the same figure.

In Fig. 4, A□ is the input terminal from the gate signal circuit 8, and B
1 is an input terminal from the xIII electrode group scanning circuit 11, C
1 is an output terminal connected to the X thin electrode group of the liquid crystal display panel in FIG. 1, AN is an AND circuit, No is a NOT circuit, Tr□ and T1□ are transistors, R1 and R2 are resistors, and D is a positive electrode. The power supply terminal is shown.

Further, FIG. 5 is a waveform diagram showing the case where each person in the circuit shown in FIG. 4 is 1).

4 and 5, the input signal A from the gate circuit 8
□ and the input signal B from the X-axis heavy pole group scanning circuit 11,
/ is applied to the AND circuit AN, the output from the signals A and ' is applied to the transistor T only during the period when the signal B is applied.
Drive R1. Further, the polarity of the signal B1/ is inverted by the NOT circuit No, and is applied to the transistor 'r0□2 to drive it.

Therefore, the output terminal C1 receives an output signal 01' with the waveform shown in FIG. 5 due to the voltage drop in the resistor R□ due to the collector current of the transistor R3□ and the voltage drop in the resistors R1 and R2 due to the collector current of the transistor T82. is obtained.

Note that this reference example is not limited to the use of the circuit shown in Figure 4; in short, any circuit configuration may be used as long as the output signal 01' as shown in Figure 5 can be obtained. .

Further, in FIG. 5, it goes without saying that the DC component of the output signal C may be changed depending on the circuit configuration.

In the reference example explained above, since the polarity of the electric field is reversed within one horizontal scanning period, it is possible to sufficiently eliminate the possibility of electrolysis occurring within the liquid crystal. Therefore, there is a risk of flickering in the liquid crystal display, and in the case of a large liquid crystal display panel with many display contents, it may be difficult to perform polarity reversal once within one horizontal scanning period. The present invention has been made based on the above points, and it is an object of the present invention to provide a driving method that can drive a large liquid crystal display panel with a large number of contents to be displayed with a long life and without flickering.

FIG. 6 shows voltage waveforms applied to the X thin electrode group and the Y phase electrode group (however, only the Y1 electrode is shown in the figure) for explaining the first embodiment of the present invention. As in the case of Fig. 2, this means that I H
A voltage (scanning voltage) is applied sequentially to the Y-axis heavy pole group Y1.
A voltage (signal voltage) corresponding to the information to be displayed is applied to each of ~Yn, for example, a voltage is applied to Yl during the 1st H period and the 3rd H period, and the display is performed on the liquid crystals a11 and 8□3 in FIG. It is something that can be done. That is, in this embodiment, the levels of the scanning voltage applied to the X thin electrode group and the signal voltage applied to the Y phase electrode group are changed as shown in Figure E, and an electric field due to the difference in pressure between the two electrodes is applied to the liquid crystal, and the polarity of this electric field is changed. is inverted every frame or every predetermined plurality of frames (FIG. 6 shows a case where the polarity is inverted every frame).

As explained in the reference example, there is a limit to the ability of the liquid crystal to follow changes in the direction of the electric field, so it takes a long time to scan one or more frames and then reverses the polarity of the electric field. be. However, in this embodiment, if the period for reversing the polarity of the electric field applied to the liquid crystal is M frames, if the number of frames M is too large, the effect of suppressing electrolysis of the liquid crystal will be reduced. Experimentally determining the allowable range, the number M of flares 1z is 1≦
It has been found that the range of M≦10 is preferable.

Incidentally, in order to realize this embodiment, the configuration previously shown in FIGS. 3 and 4 can be used as is. Also the fourth
FIG. 7 shows an example of signals input and output to the input terminals A□, B□ and the output terminal C1 in the figure. That is, the signal A1' in FIG. 7 is added to the input terminal A1 in FIG. 4, and
Input terminal B.

It is sufficient to apply B1# to , and C1# can be obtained as an output signal.

Further, in this embodiment, a case has been described in which the direction of the electric field applied to the liquid crystal is reversed every M frames, but it goes without saying that the direction of the electric field may be similarly reversed every N fields. Also in this case, when determining the allowable range of the number of fields N, it is preferable that it be within the range of 1≦N≦10.

This example is based on the reference example, that is, the polarity reversal of the electric field is L.
When compared with the case where the calculation is performed every H, there is no difference in the effective value applied to each liquid crystal between the two methods, but the frequency components of the electric field actually applied to the liquid crystal are significantly different between the two methods. For example, if the frame frequency is set to fF so as not to cause flicker to the eyes, the effective frequency component OP of the electric field applied to the liquid crystal is
In the case of the reference example (when Q=1) -fF≦fOP≦MfF However, M is given by the number of scanning lines, but when the polarity is changed every frame as in this embodiment, the following is true. Therefore, in the case of the reference example, the frequency fluctuation width is small and the threshold fluctuation due to frequency fluctuation can be reduced.
Although this is advantageous in terms of operating margin, it is disadvantageous in terms of power consumption because the frequency component becomes high. On the other hand, this embodiment has an advantage in terms of power consumption because the frequency components can be lowered compared to the reference example.

Furthermore, in this embodiment, by changing the levels of both the scanning voltage and the signal voltage, the polarity of the electric field due to the difference between the two voltages is reversed, so the range of variation in the level of the signal voltage required for reversing the polarity of the electric field is reduced. This has the advantage that the breakdown voltage of the drive circuit can be lowered.

Next, FIG. 8 shows the voltage waveforms applied to the X-axis heavy pole group and the Y-axis heavy pole group (however, only the Y1 electrode is shown in the figure) for explaining the second embodiment of the present invention. show. Note that the voltage waveforms in the figure are for the liquid crystals A, A, and A, as shown in FIG.
This is for when displaying.

As shown in the figure, in the second embodiment, the direction of the electric field applied to the liquid crystal is changed every frame (or field) or a predetermined plurality of frames (or fields), as described in the first embodiment. The method of reversing the polarity (Figure 8 shows the case where the polarity is reversed every frame) is the same, but in this example, a voltage was applied to each electrode to cause the required liquid crystal to display. Later, when the voltage becomes zero and the liquid crystal display stops, a bias voltage is applied to that electrode. In this way, the difference in the strength of the electric field applied to each of the non-addressed liquid crystal and the addressed liquid crystal is increased, thereby improving contrast.

That is, as shown in FIG. 8, for example, in the first frame, a predetermined electrode of the X-axis multipole group is located on the liquid crystal located at the intersection of the X-axis multipole group and the Y-axis multipole group to be addressed. A voltage of +h1 is applied to the electrode, and a voltage of -h1 is applied to the Y-axis electrode, whereas a voltage of -h2 is applied to the X-axis multipole group and a voltage of +h2 is applied to the Y-axis multipole group. A voltage is applied, and the liquid crystal addressed by this has +2
A voltage of h1 is applied, and a voltage of -2 is applied to the unaddressed liquid crystal.
A voltage of h2 or (hx h2) is applied, and in the next adjacent frame, a voltage of -h□ is applied to the X-axis @pole, and a voltage of +h1 is applied to the Y thin electrode.
For those that are not addressed, a voltage of +h2 is applied to the X-axis heavy pole group, a voltage of -h2 is applied to the Y-axis heavy pole group, and a voltage of -2h1 is applied to the liquid crystal that is addressed. +2h2 or (hz
hz) is applied, so that the absolute value is equal between two adjacent frames, and the voltage
Even for liquid crystals where both the thin electrode and the Y thin electrode are not addressed,
One of the X thin electrode and the Y thin electrode is applied to the liquid crystal to be addressed. The voltage ±(hi hz) and the opposite polarity voltage 2k+
2 is applied to increase the relative brightness of the addressed liquid crystal, thereby improving the contrast.

However, in this case, the difference between the applied voltages is h, > h2
It is assumed that the following relationship exists, and FIG. 8 above shows the case where h2=h1.

As shown in FIG. 6, the addressed X thin electrodes and Y
If a voltage h□ is applied to the lill electrode and all other X and Y axis electrodes are grounded, address along either the X thin electrode or the Y thin electrode that intersects the liquid crystal being addressed. The voltage h1 is also applied to the liquid crystal that is not displayed, and the contrast may become weaker.

On the other hand, in this embodiment, when 2h2 or -h1 is applied, the contrast can be improved compared to the embodiment shown in FIG.

As described above, by the driving method shown in FIG. 8, which is characterized by long life and good contrast as described in item 1, a display device with long life and good contrast can be obtained.

Further, according to the driving method of this embodiment, it is possible to drive the liquid crystal display panel 13 shown in FIG. is necessary.

FIG. 9 shows the circuit of one embodiment, Δ2 is the input terminal from the signal circuit 8 shown in FIG. is an output terminal to the X-axis heavy pole group of the liquid crystal display panel 13, ANl is an AND circuit, AN2 is an AND circuit with two inhibit terminals, ΔN3 is an AND circuit with one inhibit terminal,
'J''r' l~Tr3 are transistors, R3
~R is a resistor, and B2 is a positive power supply terminal. Note that the resistance R
It is assumed that there is a relationship between the resistance values of R3 to R5: Rs ) R3>R,4.

FIG. 10 shows the signals A2' and 82' applied to the input terminals A2 and B2 of the circuit shown in FIG. 9 above, and the signal C2' (in the case of 1=1) sent to the output terminal C2. In the waveform diagram, by using input signals A2' and 82', it is easy to obtain output signal C2' at output terminal C2.

Furthermore, 1) the value of h2 in η is not limited to -h of hl, and it is also possible to make the voltages applied to the X electrode group and the Y electrode group asymmetrical.

〔Effect of the invention〕

As explained below, according to the liquid crystal display panel driving method according to the present invention, the polarity of the electric field applied to the liquid crystal is reversed at the cycle of one frame (or one field) or multiple frames (or multiple fields). Even a large liquid crystal display panel with many display contents can be driven with a long life and without flickering, and the frequency component of the electric field applied to the liquid crystal can be lowered, which is advantageous in terms of power consumption. Moreover, since the polarity of the electric field applied to the liquid crystal is reversed by changing both the levels of the scanning voltage and the signal voltage, it is possible to reduce the range of variation in the level of the blanking voltage required for reversing the polarity of the electric field.
This has the advantage that the withstand voltage of the drive circuit can be lowered.

In addition, by equalizing the absolute value of the electric field applied to the liquid crystal in two adjacent cycle periods to create a complete alternating current electric field, the direct current component is completely canceled and the occurrence of electrolysis of the liquid crystal is more completely suppressed. be able to.

Furthermore, as described in the second embodiment, contrast can also be improved by applying an appropriate voltage to the unaddressed liquid crystal.

Note that the driving method for reversing the polarity of the electric field applied to the liquid crystal for each frame is described in the Proceedings of the IEEE.
) Vol, 59. No, 11, P, 157'4-
As is clear from the liquid crystal display panel shown in FIGS. 19 and 20, the driving method described in this document uses an active element such as a diode or FET at the intersection of each electrode. This is the so-called switch matrix method, in which a liquid crystal element and a capacitor connected in parallel to the liquid crystal element are connected to this active element, and these active elements are turned on and off to drive the liquid crystal. 1, that is, in the driving method of this document, the active element of the diode or FET is turned on by the scanning pulse applied to the scanning electrode, and at the same time only the signal pulse applied to the signal electrode is applied to the liquid crystal. Also charges the capacitor. At this time, the liquid crystal is in a selected (display) state. Even if the active element is turned off in a non-selected state, the liquid crystal cell maintains its display state due to discharge from the storage capacitor until the next selective scan is performed. In this way, the storage capacitor functions as a frame memory, and the liquid crystal panel of the above-mentioned document operates at substantially 100% duty. therefore,
This liquid crystal panel does not have the problem of flicker that is a problem of the present invention, and furthermore, by providing an active element at each intersection,
Since this is turned on and off to drive the liquid crystal, there is no problem with crosstalk. The switch-matrix method described in the above document can completely prevent crosstalk, and in principle can be expected to have the same operating margin as static drive, but it requires the formation of an active element such as a diode or FET at each intersection of the matrix. However, it is difficult to produce completely defect-free panels, and it is also expensive.

Furthermore, since only the signal pulses applied to the signal electrodes are applied to the liquid crystal, the fluctuation range of the signal pulses required to invert the polarity of the electric field applied to the liquid crystal is large, and a high-voltage driving circuit is required. However, the driving method of the present invention does not require active elements such as diodes or FETs or storage capacitors at each intersection, and can drive a large liquid crystal display panel with a long life and without flickering even with a large display content. By inverting the polarity of the electric field applied to the liquid crystal by changing both the levels of the scanning voltage and the signal voltage, it is possible to reduce the range of variation in the level of the signal voltage required to invert the polarity of the electric field. This has the advantage that the withstand voltage of the drive circuit can be lowered compared to the drive method of the above-mentioned document.

In addition, a two-frequency drive method has been considered that prevents crosstalk by applying a high frequency that does not cause the liquid crystal to respond when it is not selected, but since this drive method uses high frequencies, the drive voltage is high and the power consumption is large. Put it away.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the configuration of a general liquid crystal display panel;
Fig. 2 is a waveform diagram for explaining a reference example, Fig. 3 is a block diagram for explaining the same, and Fig. 4 is a circuit showing one set of components of the X-axis multipole group drive circuit shown in Fig. 3 above. Figure 5 is the 4th
A voltage waveform diagram for explaining the diagram, FIG. 6 is the first diagram of the present invention.
Voltage waveform diagram applied to the X and Y electrodes in Example 7
The figure is an explanatory voltage waveform diagram of this embodiment, and FIG. 8 is a voltage waveform diagram applied to the X and Y electrodes in the second embodiment of the present invention.
FIG. 9 is a circuit diagram showing one set of components of the X-axis heavy pole group drive circuit of the second embodiment, and FIG. 10 is a voltage waveform diagram for explaining the operation of FIG. 9. ■=Keyboard, 2: Gate circuit. 3: Refresh memory, 4: Character generation circuit. 5: matching circuit, 6: signal generation circuit, 7: scanning circuit. 8-1 signal circuit, 9: 1-line memory circuit with gate, 10: Y-axis heavy pole group drive circuit, 11: X-axis heavy pole group scanning circuit, 12: X-axis heavy pole group drive circuit. l3: Liquid crystal display panel 1st figure 2nd low (1M heat factor 3rd figure -/ φth 5th figure 2nd mouth 7th figure g] 15 2 b≧) //2 %, o field

Claims (1)

[Claims] 1. A first electrode group, a second electrode group that intersects with each of the first electrode groups, and 2. At each intersection of the first and second electrode groups. Using a liquid crystal display panel equipped with a liquid crystal, a scanning voltage is sequentially applied to the first electrode group for selection, and a signal voltage is applied to each of the second electrode group according to information to be displayed. In a driving method for displaying information by applying an electric field to a required liquid crystal, by changing the levels of both the scanning voltage and the signal voltage, the polarity of the electric field due to the difference between the two voltages can be changed for one frame (or one field) or Multiple frames (or multiple fields)
A method for driving a liquid crystal display panel characterized by inverting the display panel at a period of . 2. A method for driving a liquid crystal display panel according to claim 1, characterized in that the absolute value of the electric field is made equal in two adjacent cycle periods. 3. In claim 2, the scanning voltage and the signal voltage each have four levels, and at the time of addressing, the highest level or the lowest level is alternately applied at the above-mentioned period, and each frame (or each The electric field applied to the liquid crystal when both voltages are not addressed and the electric field applied to the liquid crystal when one of the voltages is addressed are made to have opposite polarities within the field), and the polarity of these electric fields is set at the above period. A method for driving a liquid crystal display panel, which is characterized by inverting the display panel.