JPH0713177A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display device which is high reliability and makes a display of high quality by evading deterioration of a liquid crystal layer and an orientation film due to electric charges accumulated between facing electrodes of a liquid crystal display element and stabilizing the potential of electrodes regarding the image display. CONSTITUTION:The electric charges which are accumulated between the scanning electrode 5 and signal electrode 7 to cause the application of a DC voltage to the liquid crystal layer, etc., are discharged to a 3rd electrode 19 and a 4th electrode 21. In another way, the potential of the main surface of a scanning electrode substrate is held as high as the potential of the main surface of a signal electrode substrate through the liquid crystal layer by the 3rd electrode 19 and 4th electrode 21. In another way, electric charges which are to be accumulated in the scanning electrode 5 and signal electrode 7 are discharged to outside a part which regarding a display on the liquid crystal display element to evade the deterioration of the liquid crystal layer and orientation film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device in which scanning electrodes and signal electrodes are arranged so as to intersect and face each other to form a pixel array in a matrix.

[0002]

2. Description of the Related Art A so-called XY matrix type liquid crystal display device is a strip made of a transparent conductor such as ITO (Indium Tin Oxide) on each main surface of two transparent substrates made of a material such as glass. -Shaped electrodes are arranged in a row, the electrode on one transparent substrate is the scanning electrode, the electrode on the other transparent substrate is the signal electrode, and two electrodes are placed so that these scanning electrodes and signal electrodes intersect and face each other. Transparent substrates are arranged facing each other with a predetermined gap, the liquid crystal composition is injected into the gap and the periphery is sealed with a sealing material to form a liquid crystal layer, and at each intersection of the scanning electrode and the signal electrode. Pixels are formed through the liquid crystal layer.

A scanning pulse having a scanning selection potential is applied to the scanning electrodes to scan-select the scanning electrodes line-sequentially, and a video signal voltage having a selection potential or a non-selection potential is applied to one signal electrode. The image is displayed.

XY using a nematic liquid crystal in general
In the matrix type liquid crystal display device, in order to control the alignment direction of liquid crystal molecules, an alignment film is provided on the main surface of the transparent substrate in contact with the liquid crystal layer so as to cover the scanning electrodes and the signal electrodes.

It is known that the direct current component of the voltage applied to the liquid crystal layer or the alignment film decomposes and deteriorates these components. To avoid this, the liquid crystal display device is driven by an alternating voltage waveform,
That is, it is performed with a voltage waveform whose polarity is inverted around the reference potential. As the reference potential, a scanning non-selection potential of scanning voltage is generally used.

By the way, generally, a dedicated IC called a liquid crystal driver IC such as a signal electrode driving IC and a scanning electrode driving IC is used as a means for outputting an electrode driving voltage waveform of a liquid crystal display element. These receive a plurality of power supply voltages and control signals and output drive voltage waveforms according to the control signals.

However, although the liquid crystal display device uses such a liquid crystal driver IC, a control signal is supplied to the liquid crystal driver IC to control the liquid crystal driver IC when the device is powered on, for example. Before the operation, the power supply voltage is supplied, or when the power of the device is turned off, the power supply voltage is supplied for some time even after the control signal supplied to the liquid crystal driver IC is cut off. A direct current voltage is applied to the element, and there is a problem that the liquid crystal layer and the alignment film are deteriorated by the application of the direct current voltage.

In addition, when the liquid crystal display element is used, static electricity is generated and electric charges are accumulated in the liquid crystal display element, and a DC voltage is applied between the electrodes by the electric charge, which deteriorates the liquid crystal layer and the alignment film. There's a problem.

Taking a liquid crystal display device used for image display as an example, a pixel is formed at each of the intersections of the two electrode substrates facing each other with the liquid crystal layer interposed therebetween.
This pixel portion can be electrically regarded as equivalent to a circuit in which a resistor and a capacitor are connected in parallel.

In a conventional general liquid crystal display device, if the electric resistance formed between the electrodes opposed to each other is low, an effective voltage is not applied at the time of driving, resulting in high current consumption. In addition, the electric resistance formed between both electrodes is set to a sufficiently high value. In addition, low-resistance impurities contained in the liquid crystal layer may cause deterioration of the liquid crystal, and it is said that the larger the resistance of the pixel, the better in order to improve reliability. In addition, the alignment film used for aligning the liquid crystal is often an insulating film having a higher specific resistance than the liquid crystal. The electric resistance formed between the electrodes by such a high resistance liquid crystal layer or alignment film has a very high value.

Therefore, when a voltage is applied to both electrodes of the pixel facing each other as described above, the operation of the liquid crystal driver IC is stopped due to the power switch off or the like, and the charges are left behind on the electrodes facing each other of the pixel. Or when static electricity is generated during use of the device and electric charges are accumulated in the electrodes facing each other, the electric charges may be discharged through the electric resistance formed between both electrodes of the pixel. As described above, since the electric resistance formed between the opposing electrodes of the pixel is high, it takes time, and the DC voltage is continuously applied to the pixel during that time. As a result, not only the liquid crystal and the alignment film are deteriorated and the life of the liquid crystal display device is shortened, but also a display defect may occur in that portion due to the deterioration.

As a countermeasure against such a problem, it has been considered to incorporate a delay circuit to shift the timings of the power supply voltage and the control signal, but it is difficult to set the delay time, and by incorporating such a delay circuit. Manufacturing cost will be high. Further, this delay circuit cannot deal with the problem caused by the DC voltage applied by static electricity.

Further, although the liquid crystal display element is driven by an alternating current, a spike noise-like potential fluctuation occurs due to the interaction of the voltages between the two electrodes facing each other through the capacitance of the pixel, and this potential fluctuation is displayed. There is a problem of causing display defects such as threshold unevenness depending on the pattern and so-called crosstalk.

[0014]

As described above, in the conventional matrix type liquid crystal display device of the multiplex drive system, charges are accumulated between the electrodes facing each other of the liquid crystal display element. There is a problem in that the liquid crystal layer and the alignment film are deteriorated by being applied to the layer and the alignment film, which causes display failure. Further, there is a problem that a display failure such as crosstalk occurs due to a change in the potential due to the interaction of the voltage between the electrodes.

The present invention has been made to solve the above-mentioned problems, and it has been proposed that a liquid crystal layer or an alignment film, which is generated due to charges accumulated between electrodes facing each other of a liquid crystal display element, is generated. An object of the present invention is to provide a liquid crystal display device which realizes high-quality display with high reliability by avoiding deterioration and further stabilizing the potential of electrodes for image display.

[0016]

According to another aspect of the present invention, there is provided a liquid crystal display device comprising a scan electrode substrate having a plurality of scan electrodes arranged in a row, and a signal having a plurality of signal electrodes arranged in a row crossing and facing the scan electrodes. An electrode substrate, a liquid crystal layer sandwiched between the scanning electrode substrate and the signal electrode substrate and forming a pixel at each intersection of the scanning electrode and the signal electrode, and scanning for applying a scanning voltage to the scanning electrode. In a liquid crystal display device having electrode driving means and signal electrode driving means for applying a video signal voltage to the signal electrode, a third electrode facing the signal electrode via the liquid crystal layer is provided on the scanning electrode substrate. Aside from the scanning electrode, a fourth electrode facing the scanning electrode through the liquid crystal layer is arranged side by side on the signal electrode substrate so as to be adjacent to the signal electrode, The third electrode and the fourth electrode And an electrical resistance formed between the third electrode and the signal electrode and an electrical resistance formed between the third electrode and the scanning electrode, It is characterized in that the resistance is set lower than the electric resistance formed between the signal electrode and the scanning electrode.

More specifically, a liquid crystal display device including a two-terminal element electrically connected in series to the liquid crystal layer for each pixel, for example, MIM (Metal Insulator Meta).
The present invention can be applied to a liquid crystal display device using an l) type element.

A scanning non-selection voltage applying means for applying a scanning non-selection voltage output from the scanning electrode driving means to at least one of the third electrode and the fourth electrode may be provided.

Further, another dielectric such as a dielectric made of an ultraviolet curable resin in which carbon fine powder is mixed and dispersed is used in place of the liquid crystal layer between the third electrode and the fourth electrode. You may make it insert.

[0020]

In the liquid crystal display device of the present invention, the third electrode formed on the scanning electrode substrate faces the signal electrode through the liquid crystal layer, and the fourth electrode formed on the signal electrode substrate. Are opposed to the scanning electrodes via the liquid crystal layer. The third electrode and the fourth electrode face each other at the intersecting portion via the liquid crystal layer or the dielectric, and the electric resistance formed between the third electrode and the fourth electrode in this portion is opposite. Since the value is set to a resistance value lower than the value of the electric resistance formed between the scan electrode and the signal electrode for display, the value is accumulated between the scan electrode and the signal electrode and stored in the liquid crystal layer or the like. The electric charges that have been the cause of the application of the DC voltage are released by the third electrode and the fourth electrode. Alternatively, the potential of the main surface of the scanning electrode substrate and the potential of the main surface of the signal electrode substrate are made to be the same potential by the third electrode and the fourth electrode through the liquid crystal layer or a dielectric material instead of the liquid crystal layer.

As described above, by the third electrode and the fourth electrode, the charges that are about to be accumulated in the scanning electrode and the signal electrode are released to the outside of the display-related portion of the liquid crystal display element, or the potential and the signal of the scanning electrode. By making the potential of the electrodes the same, it is possible to eliminate the application of DC voltage and avoid deterioration of the liquid crystal layer and alignment film, resulting in a highly reliable and high-quality liquid crystal display device. can do.

Further, by applying the scanning non-selection voltage to the third electrode or the fourth electrode, it is possible to stabilize the potential at the time of driving the signal electrode group or the scanning electrode group facing each other.

That is, in the conventional liquid crystal display device, the voltage of the scan electrode and the signal electrode varies depending on the display pattern, or the potential varies when the polarity is inverted around the reference voltage. A change in the voltage applied to the signal electrodes causes potential fluctuations, such as spike noise, between the signal electrode group and the scanning electrode group with respect to the electrodes on the opposite side, and electrical resistance exists in these electrodes. As a result, display unevenness called crosstalk occurs due to this. Therefore, in the liquid crystal display device of the present invention, a scanning non-selection voltage is applied to at least one of the third electrode and the fourth electrode, and preferably to both of the third electrode and the fourth electrode, and each of the third electrode and the fourth electrode is respectively applied. An electric capacitance formed between the signal electrode 7 and the scanning electrode 5 facing each other absorbs the above-mentioned potential fluctuation of the electrode to suppress the potential fluctuation when the scanning electrode or the signal electrode is driven, and display unevenness such as crosstalk. Can be eliminated.

In order to make such an action more effective, a liquid crystal is used as a dielectric interposed between the third electrode and the signal electrode group and between the fourth electrode and the scanning electrode group. It is preferable to use a dielectric having a dielectric constant higher than that of the layer, for example, a dielectric made of an ultraviolet curable resin in which carbon fine powder is mixed and dispersed.

The voltage application to the third electrode and the fourth electrode may be performed by the same voltage application circuit, or another circuit may be used.

The operation of the liquid crystal display device of the present invention will be described more specifically with reference to the equivalent circuits shown in FIGS.

FIG. 6 is a diagram schematically showing an equivalent circuit of the liquid crystal display device of the present invention. Here, for simplification of description, a liquid crystal display device in which two signal electrodes and two scanning electrodes and one third electrode and one fourth electrode are provided will be exemplified.

In FIG. 6, the scanning electrodes X1 and X2 face the signal electrodes Y1 and Y2 at a right angle and face each other, and at the facing portions, pixels P11 and P12 that directly perform display via a liquid crystal layer (not shown) or the like. P21 and P22 are formed. The third electrode X3 opposes the signal electrodes Y1 and Y2 at a right angle and opposes the dummy pixels P31 and P32, which are not related to display, through the liquid crystal layer or the like, and the fourth electrode Y3 scans. Dummy pixels P13 and P23 which intersect the electrodes X1 and X2 at a right angle and face each other and which are not related to display through the liquid crystal layer or the like at the facing portions.
Are formed respectively. Further, the third electrode X3 and the fourth electrode Y3 intersect each other at a right angle and face each other, and a dummy pixel P33 which is not related to display is formed at the facing portion via a liquid crystal layer or the like.

On the other hand, the conventional liquid crystal display device which does not have the third electrode X3 and the fourth electrode Y3 can be electrically represented by an equivalent circuit as shown in FIG.

Further, the pixels P11, P12, ...
..P32 and P33 are, as shown in FIG. 6, electric resistance components R11 and R12 formed between the electrodes facing each other, respectively.
... and electric capacitance components C11, C12, ... Can be electrically represented by an equivalent circuit as being connected in parallel.

The scanning electrodes X1 and X2 are connected to scanning electrode driving means (not shown), and the signal electrodes Y1 and Y2 are connected to signal electrode driving means (not shown).

For example, taking only the pixel P11 as an example for description, the switch is turned off in a state where the driving voltage is applied to the pixel P11, and the pixel electrode P1 and the electrode electrodes are steeply connected between the scanning electrode X1 and the signal electrode Y1. Is not connected to the pixel P11 and a voltage is applied to the pixel P11, or the electric connection between the scan electrode X1 and the signal electrode Y1 and the respective electrode driving means is cut so that driving is not performed. At this time, when a charge remains in the pixel P11 due to static electricity from the outside and a voltage is applied, the charge remaining in the pixel P11 is mainly transferred through the electric resistance R11 in the conventional liquid crystal display device as shown in FIG. Had been discharged. However, since the resistance value of the electric resistance R11 is set to be relatively high as described above, it takes time to discharge the electric charge, and the electric charge remains accumulated during that time.
, Y1 was applied with a DC voltage, and the sandwiched liquid crystal layer, alignment film, etc. were deteriorated.

Therefore, in the liquid crystal display device according to the present invention, the electric charge to be accumulated between the opposing electrodes X1 and Y1 is passed only through the electric resistance R11 formed between the scanning electrode X1 and the signal electrode Y1. , The electric resistance R31 formed between the signal electrode Y1 and the third electrode X3 having a lower resistance value than the electric resistance R11, the fourth electrode Y3 and the scanning electrode X1.
And an electrical resistance R13 formed between the third electrode X and
It discharges quickly through the electric resistance R33 formed between 3 and the fourth electrode Y3. Or opposite electrodes X1
, Y1 are made equal to each other through the electric resistance R33 and the like, the time during which the voltage is applied to the pixel P11 is shortened, and the liquid crystal resulting from the DC voltage application due to such residual charge is applied. Suppression of display defects such as deterioration of layers and alignment films and unevenness of threshold value.

By the way, the dummy pixels P13, P23, P3
Since 1, P32, and P33 are pixels that are not related to display, the electric resistance of these dummy pixels may be considerably smaller than that of the pixels P11 ... P22 related to display. In particular, the electric resistance R formed between the third electrode X3 and the fourth electrode Y3
It is preferable that 33 has a very low resistance value in order to quickly bring the third electrode X3 and the fourth electrode Y3 to the same potential, for example, a conductive material such as silver paste which is inexpensive and easy to manufacture. May be used. By thus forming the low-resistance electric resistance R33 between the third electrode X3 and the fourth electrode Y3, the potential difference between the opposing electrode substrates is promptly eliminated, and the direct current voltage is applied. It is possible to avoid deterioration of the liquid crystal layer and the alignment film. As a result, it is possible to prevent the occurrence of display defects.

However, the pixels P13, P23,
If the electric resistances R13, R23, R31, and R32 of P31 and P32 are too low, those electric resistances and the third and fourth electric resistances
An electrical short circuit may occur between the scanning electrodes or between the signal electrodes via the electrodes of (1), and display failure may occur. Therefore, it is desirable that the electric resistances R13, R23, R31, and R32 be set to a resistance value that is effectively and sufficiently higher than the electric resistance when driving the scan electrodes and the signal electrodes so that such display defects do not occur. .

By the way, when the third electrode X3 and the fourth electrode Y3 are not electrically connected to a power source (driving voltage applying means) such as a liquid crystal driver IC or the like and are electrically released (floating state), When the power is turned on, the initial potentials of these electrodes are indefinite, so that a large potential difference is generated between the scan electrode X1 and the signal electrode Y1 and a voltage may be applied. In driving, the third electrode X3 and the fourth electrode Y3 are left unreversed when the polarity is reversed. Furthermore, the third electrode X3, the fourth
The potential of the electrode Y3 of each of the signal electrodes Y1 and
A change occurs due to the change in the potential of the scan electrode X1, which causes malfunction in some cases. Therefore,
In order to prevent such a problem, the third electrode X3 and the fourth electrode X3
It is sufficient to apply the scanning non-selection potential of the scanning voltage, that is, the same potential as the reference potential of the liquid crystal applied voltage, to at least one, preferably both, of the electrodes Y3.

In this way, when the power is turned on, the third
Since the initial potentials of the electrode X3 and the fourth electrode Y3 are always set to the scanning non-selection potential, the potential difference between the scanning electrode X1 and the signal electrode Y1 is eliminated. Further, when the liquid crystal is driven, the potential averaged over a long time of the scanning electrode X1 and the signal electrode Y1 relating to the display becomes the reference potential, but since this reference potential is always applied to the third electrode X3 and the fourth electrode Y3, The third electrode X3 and the fourth electrode Y3 can suppress the potential fluctuation caused by the potential fluctuations of the scanning electrode X1 and the signal electrode Y1 facing each other as compared with the floating state. That is, adding the third electrode X3 and the fourth electrode Y3 to the conventional liquid crystal display device as shown in FIG.
Pixels P11, P12, P2 for displaying C3, C13, C23 and C33
It is equivalent to connecting 1 and P22 in parallel. At this time, the electric capacitances C31, C32, C33, C13, C23 and C33 are set to the pixel P.
11, P12, P21, P22 capacitance C11, C12, C21, C
The capacitance is set to be equal to or larger than that of 22, and the scanning non-selection voltage is supplied to the third electrode X3 and the fourth electrode Y3, so that both electrodes X1 of the pixels P11, P12, P21, P22,
It is possible to effectively suppress the potential fluctuations that occur between Y1, X2 and Y2.

[0038]

Embodiments of the liquid crystal display device of the present invention will be described in detail below with reference to the drawings.

(Embodiment 1) FIG. 1 is a diagram showing a configuration of a liquid crystal display device according to a first embodiment of the present invention, FIG. 2 (a) is a sectional view showing the liquid crystal display element (liquid crystal cell), and FIG. (B) is the top view. This liquid crystal display device includes a liquid crystal display element 10
0 is connected to the scan electrode driving unit 200, the signal electrode driving unit 300, and the power supply circuit 600.

In the liquid crystal display element 100, a large number of strips of a transparent conductive film made of ITO (indium tin oxide) are arranged in parallel on the main surfaces of the scanning electrode substrate 1 and the signal electrode substrate 3 which are made of a glass substrate, which face each other. The scan electrodes 5 and the signal electrodes 7 are formed, and the scan electrodes 5 and the signal electrodes 7 are formed.
Pixels P11, P12, and
... The scanning electrode substrate 1 and the signal electrode substrate 3 are arranged such that Pmn is formed and a pixel array of a matrix of m × n matrix is formed, both substrates 1 and 3 are combined with a gap provided, and a liquid crystal is provided in the gap. A liquid crystal layer 9 is obtained by encapsulating the composition. Insulating films 11 and 13 and alignment films 15 and 17 are provided on the main surface of scan electrode substrate 1 and the main surface of signal electrode substrate 3 so as to cover scan electrode 1 and signal electrode 3, respectively, over substantially the entire area of the pixel array. Is formed with a thickness of 1000 angstroms.

On the main surface of the scanning electrode substrate 1, a third electrode 19 made of ITO is arranged in parallel with the scanning electrode 5 at a slight distance from the scanning electrode 5, and the signal electrode substrate 3 is also provided.
A fourth electrode 21 made of ITO is provided in parallel with the signal electrode 7 on the main surface thereof at a slight distance from the signal electrode 7.

The third electrode 19 and the fourth electrode 21 are not covered with the insulating films 11 and 13 and the alignment films 15 and 17. This is formed between the third electrode 19 and the signal electrode 7 via the liquid crystal layer 9, and between the fourth electrode 21 and the scanning electrode 19 via the liquid crystal layer 9. The electric resistance and the electric resistance formed between the third electrode 19 and the fourth electrode 21 via the liquid crystal layer 9 are controlled by the insulating films 11 and 13 and the alignment films 15 and 17 having high resistance values.
This is because the resistance is not provided, so that the resistance is lower than the electrical resistance formed between the scan electrode 1 and the signal electrode 3.

These two substrates are placed facing each other with a space of about 7 μm and bonded together with a sealant / adhesive 23 made of epoxy resin, and a liquid crystal composition is sealed in the space to form a liquid crystal layer 9 and a liquid crystal display. The element 100 is formed.

At this time, as shown in FIG. 3, a portion where the third electrode 19 and the signal electrode 7 face each other, a portion where the fourth electrode 21 and the scanning electrode 5 face each other, and a portion where the third electrode 19 and the third electrode 19 touch each other. The portion of the electrode 4 facing the electrode 21 is inside the sealant / adhesive 23, and the liquid crystal layer 9 is interposed between the electrodes.

Here, the specific resistance of the liquid crystal layer 9 is about 10 ¹² Ω · cm.
On the other hand, the insulating films 11 and 13 and the alignment films 15 and 17
Has a specific resistance of about 10 ¹⁶ Ω · cm or more.
The resistance value between the electrode 19 and the fourth electrode 21, the resistance value between the third electrode 19 and the signal electrode 7, and the resistance value between the fourth electrode 21 and the scanning electrode 5 are All signal electrodes 7
It is smaller than the resistance value between the scanning electrode 5 and the scanning electrode 5.

The substrate size of the liquid crystal display element is A4 size, and the number of pixels (the number of dots) is 640 × 400 dots. That is, the total number of scanning electrodes 19 is 400, and the total number of signal electrodes 21 is 640.
Each scanning electrode 5 is individually connected to the scanning electrode driving unit 200, and each signal electrode 7 is connected to the signal electrode driving unit 300.

The power supply circuit 600 includes the scan electrode driving section 200.
And a power supply which is connected to the signal electrode drive unit 300 and supplies a power supply voltage which is a source of a scan voltage applied to the scan electrode 5 to the scan electrode drive unit 200 and a source of a video signal voltage which is applied to the signal electrode 7. The voltage is supplied to the signal electrode driving unit 300.

The scan electrode drive section 200 includes a shift register 25, a frame inversion circuit 27 and a drive circuit array 29.
The main part of the scanning electrode 5 is configured to output a scanning pulse having a selection potential for each line of the scanning electrode per frame period and apply the scanning pulse to the scanning electrode 5.

While the scan pulse (scan selection voltage) is applied to one scan electrode, the scan non-select voltage (reference voltage) is applied to the other remaining scan electrodes to set the scan non-select potential. Retained. The scanning voltage applied to the scanning electrode 5 is composed of such a scanning selection voltage and a scanning non-selection voltage.

On the other hand, the signal electrode driving section 300 is mainly composed of a shift register 31, a latch circuit 33, a frame inverting circuit 35 and a driving circuit array 37, and the signal information introduced into the shift register 31 is latched by the latch circuit 3.
3 and the like, serial-parallel conversion is performed, and a video signal voltage is applied via the frame inversion circuit 35 and the drive circuit array 37, and applied in parallel to each line of the signal electrode group 7 at the same time. That is, when the pixel is turned on, the video signal voltage applied to the signal electrode corresponding to the pixel at the corresponding time is set as the selection potential, and when turned off, the non-selection potential is set. As a result, when the scanning electrode 5 of the liquid crystal display element is at the selection potential, the pixel at the intersection where the signal electrode 7 is at the selection potential is in the ON state, and the other pixels are in the OFF state.

As described above, in the liquid crystal display device according to the first embodiment, the third electrode made of ITO is provided on the main surface of the scanning electrode substrate 1 in parallel with the scanning electrode 5 with a slight distance from the scanning electrode 5. Electrodes 19 are arranged side by side, and a fourth electrode 21 made of ITO is arranged side by side on the main surface of the signal electrode substrate 3 in parallel with the signal electrode 7 with a small distance from the signal electrode 7. The third electrode 19 and the fourth electrode 21 are not covered with the insulating films 11 and 13 and the alignment films 15 and 17 having a high resistance value, and the liquid crystal is interposed between the third electrode 19 and the signal electrode 7. Electrical resistance formed via the layer 9 and between the fourth electrode 21 and the scanning electrode 19 Electrical resistance formed via the liquid crystal layer 9 and between the third electrode 19 and the fourth electrode 21 The electric resistance formed through the liquid crystal layer 9 between the scanning electrode 1 and the signal electrode 3 is It is set to a lower resistance than the electrical resistance is. By setting in this way, the charges accumulated between the scanning electrode 5 and the signal electrode 7 and causing the direct current voltage to be applied to the liquid crystal layer 9 and the like are transferred to the third electrode 19 and the fourth electrode. It is quickly absorbed by the electrode 21 and escaped to a portion other than the pixel array portion. Alternatively, the scanning electrode substrate 1 is formed by the third electrode 19 and the fourth electrode 21 via the liquid crystal layer 9.
The potential of the main surface (amount of accumulated charges) and the potential of the main surface of the signal electrode substrate 3 (amount of accumulated charges) are set to the same potential (the same amount). In this way, the application of the charge DC voltage can be canceled and the deterioration of the liquid crystal layer or the alignment film can be avoided, and as a result, a liquid crystal display device with high reliability and high display quality can be realized.

The STN (super twisted nematic) type liquid crystal display device of the first embodiment as described above was driven. Specifically, T9822 and T98231 manufactured by Toshiba, which are liquid crystal driver ICs, were used as the scan electrode driving unit 200 and the signal electrode driving unit 300, respectively, and were connected to the liquid crystal display element by the TAB method. This liquid crystal display device has a duty ratio of 1/400, a bias ratio of 1/21, and a frame frequency of 70H.
At z, it was multiplexed driven using the N-line inversion method.

Turn off (disconnect) the power supply voltage of the power supply circuit 600
Before performing the scanning electrode driving unit 200 and the signal electrode driving unit 3
By cutting off the control signal of 00, the liquid crystal display element 10
After applying a direct current to 0 for about 10 minutes, inputting the power supply voltage and the control signal again to drive this liquid crystal display device and verifying the display quality, the display unevenness due to the application of the direct current voltage was slight. There was no visual problem at all.

(Example 2) The third electrode 19 and the fourth electrode 21 of the liquid crystal display device of the first example were connected to the third electrode driving section 400 and the fourth electrode driving section 500, respectively. .

The third electrode driving section 400 and the fourth electrode driving section 500 are also connected to the power supply circuit 600 so that the scanning non-selection voltage is supplied from the power supply circuit 600.
A liquid crystal display device of the second embodiment was prepared with the other configurations being the same as those of the liquid crystal display device of the first embodiment. The structure is shown in FIG.

The third electrode driving section 400 is mainly composed of a frame inverting circuit 39 and a driving circuit array 41, and applies a voltage when scanning is not selected to the third electrode 5. Similarly, the fourth electrode drive section 500 is mainly composed of the frame inversion circuit 43 and the drive circuit array 45, and applies a voltage when scanning is not selected to the third electrode 5.

As the third electrode driving section 400 and the fourth electrode driving section 500, a T type manufactured by Toshiba, which is a liquid crystal driver IC, is used.
9822 is used, which is a liquid crystal display device 10 by the TAB method.
Connected to 0. By not inputting the latch signal, the latch circuit is prevented from operating, and all the output terminals are short-circuited to collectively output the scanning non-selection voltage to the third electrode 19 and the fourth electrode 21. did.

Since the liquid crystal display device of the second embodiment is constructed as described above, the scanning non-selection voltage is applied to the third electrode 19 or the fourth electrode 21, and the signal electrodes facing each other. 7 or the potential of the scanning electrode 5 can be stabilized. That is, the third electrode 19 and the fourth electrode 2 thereof
The electric capacitances formed between the signal electrodes 7 and the scanning electrodes 5 facing each other absorb the potential fluctuations of the scanning electrodes 5 and the signal electrodes 7 facing each other, thereby causing the occurrence of display unevenness such as crosstalk. It can be resolved.

The STN type liquid crystal display device of the second embodiment as described above is used in the duty ratio 1/400, bias ratio 1/21,
The frame frequency was 70 Hz, and multiplex driving was performed using the N line inversion method.

The liquid crystal display device is driven by inputting direct current to the liquid crystal display element by cutting off the control signal before cutting off the power supply voltage and leaving it for about 10 minutes, and then inputting the power supply voltage and the control signal again. Then, the display quality was verified, and as a result, it was possible to suppress the display unevenness due to the application of the DC voltage and to make it even smaller than that in the first embodiment, and there was no visual problem at all, and a good display was obtained. The result was that it could be realized.

(Embodiment 3) In order to make the action of stabilizing the potential of the scanning electrode 5 or the signal electrode 7 in the liquid crystal display device of the second embodiment more effective, the third electrode 19 and Between the electrodes, which have a higher dielectric constant than the liquid crystal layer 9 and are opposed to each other via the dielectric, as a dielectric inserted between the signal electrode 7 and the fourth electrode 21 and the scanning electrode 5. A dielectric may be used so that the electric resistance formed in the above is lower than the electric resistance formed between the scanning electrode 5 and the signal electrode 7 via the liquid crystal layer 9. As such a dielectric, for example, a dielectric made of an ultraviolet curable resin in which carbon fine powder is mixed and dispersed is suitable.

Therefore, as shown in FIGS. 4A and 4B, a portion where the third electrode 19 and the fourth electrode 21 face each other and a portion where the scanning electrode 5 and the signal electrode 7 face each other are set. It is arranged so as to be outside the sealing material / adhesive 49, and along the outer periphery of the sealing material / adhesive 49, between the third electrode 19 and the fourth electrode 21, between the third electrode 19 and the signal electrode. UV-curing resin UV-1000 (manufactured by Sony Chemical Co.) 47, in which carbon fine powder is mixed and dispersed, is inserted as a dielectric between the electrode 7 and the fourth electrode 21 and the scanning electrode 5, and ultraviolet rays are emitted.
The liquid crystal display element 700 is prepared by irradiating and curing for 2 minutes.
This liquid crystal display element 700 is replaced in place of the liquid crystal display element 100 used in the liquid crystal display device of the second embodiment,
A liquid crystal display device of the example of was prepared.

At this time, the specific resistance of the ultraviolet curable resin 47 is about 10 ⁸ Ω · cm, whereas the specific resistance of the liquid crystal layer 9 is about 10 ¹² , and the insulating films 11 and 13 and the alignment film are formed. 15,
The specific resistance of No. 17 was about 10 ¹⁶ Ωcm or more. Thus, the electrical resistance between the third electrode 19 and the fourth electrode 21, the electrical resistance between the third electrode 19 and the signal electrode 7, and the electrical resistance between the third electrode 19 and the scanning electrode 5 The electric resistances of all are lower than the electric resistance between the signal electrode 7 and the scanning electrode 5. In addition, at this time, the third electrode 19 and the fourth electrode 21, the third electrode 19 and the signal electrode 7, and the fourth electrode 21 and the scanning electrode 5 are connected via the ultraviolet curable resin 47. The electric capacity formed between them was about 3 nF per cm ² . On the other hand, the electric capacity formed between the scanning electrode and the signal electrode via the liquid crystal layer 9 was about 1 nF per cm ² .

This liquid crystal display device has a duty ratio of 1/40.
0, bias ratio 1/21, frame frequency 70 Hz, multiplex drive using the N line inversion method showed less display unevenness depending on the display pattern than in the first and second embodiments. The display was obtained. Furthermore, by cutting off the control signal before cutting off the power supply voltage, applying direct current to the liquid crystal display element and leaving it for about 10 minutes, inputting the power supply voltage and control signal again, and driving the liquid crystal display device. Almost no display unevenness due to the application of the DC voltage was observed, and a display better than that of the second embodiment was obtained.

As the dielectric 47, when the electric resistance is too low, the dielectric between the third electrode and the opposing signal electrode and between the fourth electrode and the opposing scanning electrode is used. A current leaks through the body 47, causing a display defect when driving the liquid crystal. Further, even when the dielectric constant is too high, the scanning voltage or the video signal voltage becomes dull due to the electric capacity formed between the electrodes facing each other via the dielectric 47, and the display quality is deteriorated. Therefore, the electric resistance of the dielectric 47 is about 100 times or more the electric resistance value of the signal electrode and the scanning electrode, and the total sum of the electric capacities at respective intersections does not exceed the total sum of the electric capacities of the pixel part Just set it.

(Embodiment 4) In the third embodiment, the third
The electrode driving unit 400 and the fourth electrode driving unit 500 are used as one circuit. This circuit is a T9822 manufactured by Toshiba as in the third embodiment, and the liquid crystal display element 100 is formed by the TAB method.
, And the latch circuit is not operated by not inputting a latch signal, and all the output terminals are short-circuited to collectively apply the scanning non-selection voltage to the third electrode 19 and the fourth electrode 21. I did it.

With such a simple structure,
The manufacturing (material) cost could be reduced as compared with the third embodiment.

Further, by providing a connection portion made of silver paste at the intersection of the third electrode 19 and the fourth electrode 21, the resistance value between the third electrode 19 and the fourth electrode 21 is reduced.
When it is lowered to 10Ω, the display unevenness due to the application of the DC voltage can be suppressed to be even smaller than that in the case of the third embodiment, and there is no visual problem at all, and a good display can be realized. Results were obtained.

(Embodiment 5) The material of the third electrode 19 and the fourth electrode 21 of the liquid crystal display device of the fourth embodiment is IT.
When displaying was performed on the liquid crystal display device of the fifth embodiment in which O was changed to Al (aluminum), display unevenness depending on the display pattern was suppressed and the display was made even smaller than in the case of the fourth embodiment. , The display quality could be further improved. Further, it was confirmed that even after applying the DC voltage similar to that in the fourth embodiment, the display unevenness was hardly seen, and good display quality could be maintained.

(Embodiment 6) As shown in FIG. 5, instead of the XY simple matrix type liquid crystal display element 100 used in the liquid crystal display device of the first embodiment and the liquid crystal display device of the second embodiment. A liquid crystal display device of the sixth embodiment was obtained by using the MIM nonlinear element type liquid crystal display element 500.

FIG. 5A is an enlarged view of the MIM element 503 formed on the signal electrode substrate 501. A signal film 509 made of tantalum 505 and tantalum oxide 507 is formed by forming a conductive film made of metal tantalum having a projection for each pixel on the signal electrode substrate 501 and anodizing the surface. . Further signal electrode 509
Pixel electrode 511 made of ITO so that it does not overlap with 1
An island-shaped electrode 513 made of metallic chrome is formed so as to be formed for each pixel so as to overlap the protrusion of the signal electrode 509 and a part of the pixel electrode 511. 5B is a cross-sectional view of the signal electrode substrate 501 taken along the line AA ′ in FIG. This shows a state in which the MIM element 503 is formed by the tantalum 505, the tantalum oxide 507, and the island-shaped electrode 513 of metallic chromium, and is connected to the pixel electrode 511. Furthermore, a fourth electrode 515 made of metallic chromium is formed on the signal electrode substrate 501 in parallel with the signal electrode 509.

The MIM element thus formed is shown in FIG.
A sixth liquid crystal display device was manufactured in which the signal electrode substrate as shown in (c) was used and the operation mode of the liquid crystal was changed from STN type to TN type.

The MIM type liquid crystal display device of the sixth embodiment as described above is provided with a duty ratio of 1/400, a bias ratio of 1/5,
The frame frequency was 70 Hz, and multiplex driving was performed using the N line inversion method. By cutting the control signal before cutting the power supply voltage, a direct current is applied to the liquid crystal display element
After leaving it for 10 minutes, the power supply voltage and control signal were input again to drive this liquid crystal display device, and the display quality was verified. The result was that it was possible.

(Comparative Example 1) In the first example, the third electrode and the fourth electrode were removed from the liquid crystal display element 100, and a liquid crystal display element 800 having the same structure as the conventional one was prepared and used. An experiment was conducted to drive the liquid crystal display device under the same drive conditions as in the first embodiment.

As in the first embodiment, after turning off the control signal before turning off the power supply voltage and leaving the electric charge in the liquid crystal display element 800 so that the direct current voltage is applied, it is left for 10 minutes. Then, when the liquid crystal display element 800 was driven again by inputting the power supply voltage and the control signal and the display quality thereof was verified, the brightness of the portion where DC was considered to be applied was lowered and display unevenness occurred. In addition, display unevenness that occurs depending on the display pattern during driving, so-called crosstalk,
It occurred more remarkably than in the first embodiment.

Although the STN type liquid crystal display element is used as the liquid crystal display element in the above embodiments, the present invention is not limited to this. Besides this, for example, normal TN (Twisted Nema)
A tic) type liquid crystal display element may be used.

The use of the liquid crystal display element is not necessarily limited to the image display. It goes without saying that it can also be used for a liquid crystal display element for displaying characters, for example.

[0078]

As described above in detail, according to the present invention, the deterioration of the liquid crystal layer or the alignment film caused by the charges accumulated between the electrodes facing each other in the liquid crystal display element. It is possible to provide a liquid crystal display device that realizes highly reliable and high-quality display by avoiding the above and further stabilizing the potential of the electrode for image display.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a sectional view (a) and a plan view (b) showing a structure of a liquid crystal display element according to a first embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 4 is a sectional view (a) and a plan view (b) showing a structure of a liquid crystal display element according to a third embodiment of the present invention.

FIG. 5 is a diagram showing a structure of a liquid crystal display element according to a sixth embodiment of the present invention.

FIG. 6 is an equivalent circuit diagram schematically showing the operation of the liquid crystal display device of the present invention.

FIG. 7 is an equivalent circuit diagram schematically showing the operation of a conventional liquid crystal display device.

[Explanation of symbols]

1 ... Scan electrode substrate, 3 ... Signal electrode substrate, 5 ... Scan electrode,
7 ... Signal electrode, 9 ... Liquid crystal layer, 11, 13 ... Insulating film, 1
5, 17 ... Alignment film, 19 ... Third electrode, 21 ... Fourth electrode, 23 ... Sealing material / adhesive, 25, 31 ... Shift register, 27, 35 ... Frame inversion circuit, 29, 37 ... Driving Circuit array, 100 ... Liquid crystal display element, 200 ... Scan electrode drive section, 300 ... Signal electrode drive section, 400 ... Third electrode electrode drive section, 500 ... Fourth electrode electrode drive section, 600 ...
Power supply circuit

Claims (4)

[Claims] 1. A scan electrode substrate having a plurality of scan electrodes arranged in a row, a signal electrode substrate having a plurality of signal electrodes arranged in a row crossing and facing the scan electrodes, the scan electrode substrate and the signal electrode. A liquid crystal layer sandwiched between a substrate and forming a pixel at each intersection of the scanning electrode and the signal electrode, a scanning electrode driving unit for applying a scanning voltage to the scanning electrode, and a video signal voltage for the signal electrode. In a liquid crystal display device having a signal electrode driving means for applying a voltage, a third electrode facing the signal electrode through the liquid crystal layer is arranged in parallel on the scanning electrode substrate so as to be adjacent to the scanning electrode. A fourth electrode facing the scanning electrode via the liquid crystal layer is juxtaposed on the signal electrode substrate so as to be adjacent to the signal electrode, and the third electrode and the fourth electrode Electrical resistance formed between and An electric resistance formed between the third electrode and the signal electrode and an electric resistance formed between the third electrode and the scan electrode are formed between the signal electrode and the scan electrode. A liquid crystal display device characterized by being set to a resistance lower than the electric resistance of the liquid crystal display. 2. The liquid crystal display device according to claim 1, further comprising a two-terminal element electrically connected in series to the liquid crystal layer for each pixel. 3. A scanning non-selection voltage applying means for applying a scanning non-selection voltage output from the scanning electrode driving means to at least one of the third electrode and the fourth electrode. The liquid crystal display device according to claim 1 or 2. 4. The dielectric material other than the liquid crystal layer is interposed between the third electrode and the fourth electrode, and the dielectric material according to claim 1, 2, or 3. Liquid crystal display device.