JPS5849990A - Liquid crystal display panel driving system - 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 The present invention provides a group of horizontal electrodes arranged parallel to each other (hereinafter referred to as an The present invention relates to a driving method for a liquid crystal display panel having a vertical electrode group (hereinafter abbreviated as Y-axis heavy pole group) and liquid crystals provided at the intersections of the X thin electrode group and each electrode of the Y-axis heavy pole group.

Generally, the structure of the liquid crystal display panel is shown in FIG. That is, as shown in the figure, the X-thin electrode group X1. X2. X3・・・・・・・・・Person and Y thin electrode group intersecting this y11 Yj l Y, I
......Yn, and at the intersection of each electrode of the above two types of electrode groups, the liquid crystal '11 * a12 e ''1B interposed between these two types of electrode groups, respectively.
"1.""""'mn.

Conventionally, to drive a liquid crystal display panel with this configuration,
For example, when addressing the liquid crystal '23 at the intersection of the X2 electrode of the X thin electrode group and the Y3 electrode of the Y axis heavy pole group in FIG. 1, the optical properties of the liquid crystal '23 ( A direct current electric field was applied that was sufficient to change the light transmittance (light transmittance).

However, in the case of the conventional driving method as described above, the electric field applied between the X thin electrode group and the Y axis heavy pole group was a direct current, so the liquid crystal material was electrolyzed by this direct current electric field, and the liquid crystal The drawback was that it shortened its lifespan.

The present invention has been made to solve these drawbacks, and provides a liquid crystal display panel driving system that makes it possible to extend the life of liquid crystal by using an alternating current electric field as the electric field applied to the liquid crystal.

That is, the liquid crystal display panel driving method of the present invention reverses the direction (hereinafter referred to as polarity) of the electric field applied to the liquid crystal interposed between the X-axis heavy pole group and the Y-axis heavy pole group at a predetermined period, This suppresses electrolysis from occurring in the liquid crystal.

Hereinafter, the present invention will be explained in detail using Examples.

FIG. 2 shows the voltage applied to the X-axis heavy pole group and the Y-axis heavy pole group (however, only the Y1 voltage of the Y-axis heavy pole group is shown in the figure) for explaining the first embodiment of the present invention. shows the voltage waveform.

In the same figure, 11 (indicates l horizontal scanning period, each IH
The voltage waveforms applied at each time are shown for the case where the polarity is reversed three times during the above IH with the ground level value or a predetermined DC level value as the boundary. In this case, the above-described voltages are sequentially and alternately applied to the X-axis heavy poles X1 to X1 for each IH, and the above-mentioned voltages are applied to the Y-axis heavy poles only during a predetermined horizontal scanning period.

In other words, in Fig. 1 and Fig. 2, the initial IH off period xl
A predetermined electric field is applied to the liquid crystal alt at the intersection with the X0 electrode, and during the next IH off period, a voltage is applied to the X2 electrode but no voltage is applied to the X1 electrode.
f (during the period, a voltage is applied to the X3 electrode and the X1 electrode, and an electric field is applied to the liquid crystal a13 at the intersection thereof.

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 2/-1 times (l = 2.0 times in the above example) to cause electrolysis of the liquid crystal. This is to suppress the Note that the number of times l of polarity reversal 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 to have the liquid crystal completely follow the display, it is necessary to lengthen the IH off period, but if this is too long, the display will flicker, especially for large screens with a lot of display content. In the case of a panel with a large area, the l frame becomes long, which causes flicker.

Therefore, according to experimental results, the allowable range of the number of polarity reversals is preferably within the range of 1 < io.
For example, p-methoxibe/silysine-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 if one side is the positive side and the other is the negative side with the LH period t, L, ground level value or 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 perfect. This is because since it is an alternating current, it completely satisfies the intended purpose of suppressing the occurrence of electrolysis of the liquid crystal. However, by increasing the number of polarity reversals, even if the number of polarity reversals becomes a decimal number, such as around 1 = 10 times, for example l = 9.5 times, the electrolysis of liquid crystal Of course, it is effective in suppressing the occurrence of.

That is, in the above case, the number of positive side and negative side differs by one in the case of 1.9.5 times, but this is effective in suppressing the occurrence of electrolysis of the liquid crystal. Moreover, in this case, by alternately giving the difference in the number of positive or negative times to the positive side and the negative side for every 11 (or every l frame, or every l field), the number of polarity inversions 1 is an integer. It is possible to have the same effect as in the case.

Next, FIG. 3 shows a block diagram of an embodiment of a liquid crystal display panel driving device for operating the above driving method according to the present invention.

In the figure, character signals S1, ? encoded from the keyboard l are shown. and a signal S indicating the display position of the characters are sent out as output signals. On the other hand, the signal generating circuit 6 constantly and repeatedly sends out the scanning position signal S, and the coincidence circuit 5 sends out a pulse when the display position signal Sp and the voice scanning position signal S coincide with each other.
The voltage is applied to the gate circuit 2.

In the gate circuit 2, when there is no pulse from the coincidence circuit 5, a refresh memory (refreshmem) is activated.
ory) 3 is added as is to the same memory 3,
The previously applied character signal is repeatedly applied to the character generating circuit 4, but when a pulse is sent from the matching circuit 5, the character signal S of the keyboard l is sent to the refresh memory 3.
to be applied.

The scanning circuit 7 supplies scanning pulses to the character generating circuit 4 and the gated l-line memory circuit 9 based on the output signal of the signal generating circuit 6. The character generation circuit 4 also receives the coded character signal output from the delay circuit 3 and the scanning circuit 7.
A signal corresponding to the shape of the actual character is input to the gated l-line memory circuit 9 by the scanning signal output from the gate. That is, the input applied to the character generation circuit 4 is a signal encoded in 6-bit, G, 8-bit, G, etc., which is converted in the character generation circuit 4 into a signal corresponding to the shape of the character.

The gated l-line memory circuit 9 uses the outputs of the scanning circuit 7 and the character generation circuit 4 to generate 19 characters corresponding to the shape of the character.
The 47 minute signal is held only during the IH period or a period close to IH. Furthermore, the output of the gated l-line memory circuit 9 and the output of the gate signal circuit 8 are the Y-axis multipole group drive circuit lO.
A signal is applied to the Y-axis electrode group in the Y-axis heavy pole group drive circuit 10, and a signal is applied to the Y-axis electrode group of the liquid crystal display panel 13.
Add to the axial heavy pole groups Y1 to Yn.

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 electrode group drive circuit 12. The group drive circuit 12 generates a signal to be supplied to the X-axis multipole group, and the X-axis multipole groups X1 to xIn of the liquid crystal display panel 13 are generated.
Add to.

Next, FIG. 4 is a diagram of an embodiment showing one set of constituent elements of the X-axis electrode group drive circuit 12. Note that the Y-axis heavy pole group driving circuit @lO can also be configured in the same manner as in the diagram.

In Fig. 4, A□ is the input terminal from the gate signal circuit 8, and B
8 is an input terminal from each axis heavy pole group scanning circuit 11, C1 is an output terminal connected to the X axis heavy pole group of the liquid crystal display panel in FIG. 1, AN is an AND circuit, No is a NOT circuit,
Trl and Trl are transistors, R1 and R2
indicates a resistor, and Dl indicates a positive power supply terminal.

Moreover, FIG. 5 shows each input terminal A of the circuit shown in FIG. 4 above.
1 is a waveform diagram showing the signal m,'·B0' applied to B1 and the signal c,' sent out from the output terminal C1 (when l=t).

4 and 5, the input signal A from the gate circuit 8
1' and the input signal from B1'
When ・ is added to the AND circuit AN, the output from the signal ○- is sent to the transistor TB only during the period when the signal B1' is added.
Drive 1. Further, the polarities of the signals B and I are reversed by the NOT circuit No, and applied to the transistor T&2 to drive it.

Therefore, at the output terminal C0, there is a 9 voltage drop in the resistor R0 due to the collector current of the transistor T, and a voltage drop of 9 in the resistor R0 due to the collector current of the transistor T.
Due to the voltage drop across the resistors R1 and R2 due to the collector current of 2, an output signal 01' etc. having the waveform shown in FIG. 5 is obtained.

Note that the present invention is not limited to the use of the circuit shown in FIG. 4; in short, any circuit configuration may be used as long as the output signal C1' as shown in FIG. 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.

Next, FIG. 6 shows voltage waveforms applied to the X-axis heavy pole group and the Y-axis electrode group (however, only the Y1 electrode is shown in the figure) for explaining the second embodiment of the present invention. . As in the case of FIG. 2, a voltage is applied sequentially to the X thin electrodes X1 to
By applying a voltage to the H period and the third H period, the liquid crystal shown in FIG.
11 and 'Is to perform display. That is, in the second embodiment, the polarity of the electric field applied to the liquid crystal is reversed every 1 frame, or every predetermined plurality of frames (FIG. 6 shows a case where the polarity is reversed every 1 frame), as shown in the figure. ).

As explained in the first embodiment, 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 frame or multiple frames before changing the polarity of the electric field. It is something that is reversed. 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. When the allowable range was determined experimentally, it was found that the number of frames M is preferably within the range of 1<M<10.

Incidentally, in order to realize the second embodiment, the configuration previously shown in FIGS. 3 and 4 can be used as is. In addition, the input terminal A1 in FIG. FIG. 7 shows an example of the signals sent to B1 and output terminal C□, respectively. That is, the signal A1' in FIG. 7 is applied to the input terminal A□ in FIG. 4, and the input terminal B1! In this case, it is sufficient to apply B11, and C1' can be obtained as an output signal.

Furthermore, in this second embodiment, a case has been described in which the direction of the electric field applied to the liquid crystal is reversed every M frames.
Of course, the direction of the electric field may be similarly reversed every N fields.

In this case as well, when the allowable range of the number of fields N is determined experimentally, it is preferably within the range of l<N and 10.

Comparing the second embodiment with the first embodiment, in which the polarity of the electric field is reversed for each IH, in the first embodiment, the polarity is reversed in a short time, so electrolysis occurs within the liquid crystal. However, since the lH period is long, and the l frame period is also long, there is a possibility that flickering may occur in the liquid crystal display. On the other hand, the second
In the embodiment, flickering can be prevented by shortening the IH period, but the polarity reversal time of the electric field applied to the liquid crystal becomes longer, and there is a possibility that electrolysis cannot be completely prevented from occurring.

Next, FIG. 8 shows voltage waveforms applied to the X moving electrode group and the Y moving electrode group (however, only the Y1 electrode is shown in the figure) for explaining the third embodiment of the present invention. . Note that the voltage waveforms in the figure are for the liquid crystals '11 and 'Is as shown in FIG.
This is for when displaying.

As shown in the figure, in the third embodiment, the direction of the electric field applied to the liquid crystal is changed every 1 frame (or field) or a predetermined plurality of frames (or fields), as described in the second 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 of the opposite polarity 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 the contrast. In other words, this embodiment shows that the present invention can be applied to a known method in which contrast is improved by applying a bias voltage of the opposite polarity after the drive voltage disappears.

In this case, as shown in FIG. 8, for example, in the first frame, a predetermined electrode of the X-moving electrode group has +h1 on the liquid crystal located at the intersection of the X-moving electrode group and the Y-moving electrode group to be addressed. A voltage of -h0 is applied to the Y thin electrode, while a voltage of -h2 is applied to the X moving electrode group and a voltage of +h2 is applied to the Y moving electrode group. , the LCD addressed by this has 2h
.

voltage is applied to the unaddressed liquid crystal for 2 h,
Alternatively, a voltage of -h2 is applied. However, in this case, the difference between the applied voltages is hl > h
2, and in Figure 8 above, h2=i
The case where h□ is shown is shown.

As shown in FIG. 6, the addressed X thin electrodes and Y
If voltage h1 is applied to the thin electrode and all other X-axis and Y-axis electrodes are grounded, the address along either the X thin electrode or the Y thin electrode that intersects the liquid crystal being addressed. Voltage h□ is also applied to the liquid crystal that is not
Contrast may be weakened.

On the other hand, in this embodiment, 2h1 or
-h2, that is, when h2=h□ as described above, only the voltage h□ is applied, and 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 a long life and the above-mentioned good contrast, a display device with a long life and good contrast can be obtained.

Furthermore, the driving method of this embodiment can drive the liquid crystal display panel 13 shown in FIG.
The following circuit is required.

FIG. 9 shows a circuit of one embodiment, where A2 is an input terminal from the gate signal circuit 8 shown in FIG. 3, and B2 is an input terminal from the scanning circuit 11 for X-thin electrode group. The output terminal to the X dynamic electrode group of panel 13, ANl is 7
AN is an AND circuit with two inhibit terminals, AN3 is an AND circuit with one inhibit terminal, T
, 1 to Tr3 are transistors, R3 to R5 are resistors, and B2 is a positive power supply terminal. Note that resistance R3 to R5
It is assumed that there is a relationship of R, )R3)R4 between the resistance values.

FIG. 10 shows the signals A2' and -B2/ applied to the input terminals A2 and B2 of the circuit shown in FIG. 9 above, and the signal C2' sent to the output terminal C2 (when l=1). In this waveform diagram, it is possible to easily obtain the output signal C2' at the output terminal C2 by using the input signals A2' and B2'.

Furthermore, the value of h2 is not limited to i of hl, and it is also possible to make the voltages applied to the X electrode group and the Y electrode group asymmetric.

As explained above, according to the liquid crystal display panel driving method according to the present invention, by alternately reversing the polarity of the electric field applied to the liquid crystal, it is possible to easily utilize the liquid crystal with a long life. Furthermore, as described in the third embodiment above,
Contrast can also be improved by applying an appropriate voltage to the unaddressed liquid crystal. Furthermore, by using the configurations shown in the second and third embodiments of the present invention, it is possible to drive a large liquid crystal display panel with a large number of display contents with a long life and without flickering. This method has great advantages.

In the above description of the present invention, only the case where the liquid crystal is driven by a voltage source has been described in detail, but the present invention can also be applied to the case where the liquid crystal is driven by a current source by partially changing the circuit. It is.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the configuration of a general liquid crystal display panel.
2 is a waveform diagram for explaining the first embodiment of the present invention, FIG. 3 is a block diagram for explaining the present invention, and FIG. 4 is a diagram of the X-axis electrode group drive circuit shown in FIG. 3 above. A circuit diagram showing one set of constituent elements, FIG. 5 is a voltage waveform diagram for explaining FIG. 4,
FIG. 6 is a voltage waveform diagram applied to the X and Y electrodes in the second embodiment of the present invention, FIG. 7 is an explanatory voltage waveform diagram of the above embodiment, and FIG. 8 is a diagram of the voltage waveforms applied to the X and Y electrodes in the second embodiment of the present invention. FIG. 9 is a diagram of voltage waveforms applied to the X and Y electrodes; FIG. 9 is a circuit diagram showing one set of components of the X-axis electrode group drive circuit of the third embodiment; FIG.
This figure is a voltage waveform diagram for explaining the operation of FIG. 9 above. 1: Keyboard, 2: Gate circuit, 3: Reflation, memory, 4: Character generation circuit, 5-matching circuit, 6: Signal generation circuit, 7: Scanning circuit, 8: Gate signal circuit, 9: L line with gate Memory circuit, 10: Y-axis heavy pole group drive circuit, l
1: X-axis electrode group scanning circuit, 12: X-axis electrode group drive circuit, 13: Liquid crystal display panel. Base 1 Koeta Y2 ″f3---Cold Y. 2nd figure

Claims (1)

[Claims] 1. A plurality of X thin electrodes that are parallel to each other, a plurality of Y thin electrodes that intersect each of the X thin electrodes and are parallel to each other, and each of the above X thin electrodes and each Y thin electrode. In a driving method of a liquid crystal display panel that uses a liquid crystal display panel equipped with a liquid crystal provided at an intersection point, selects the X thin electrode and the Y thin electrode and applies an electric field to the required liquid crystal to display information. 1. A liquid crystal display panel driving method, wherein the polarity of the electric field is reversed by selecting a unipolar voltage having a plurality of levels greater than a predetermined level.