JPH08292743A - Liquid crystal display element and driving method therefor - Google Patents

Abstract

PURPOSE: To provide a liquid crystal display element having high display quality by specifying the absolute value of the potential difference between the potential of a source wiring group and the potential of the electrodes of the base plate having counter electrodes. CONSTITUTION: In the driving method of liquid crystal display elements, a potential Vs of a source wiring group has the same polarity with respect to a potential Vc of the electrodes of the base plate having counter electrodes at all the time while the liquid crystal display elements are being driven. Moreover, a potential difference Vdc between the potential Vs and the potential Vc is made larger than the picture element electrode potential at which a liquid crystal display element transmittance becomes 1% and a counter electrode potential difference V1. In other words, the potentials of Vs (Vp ) and Vc satisfy Vs >Vc for odd and even number frames. Furthermore, the potential difference between Vs and Vc becomes 15V during an odd frame and the difference becomes 6V during an even frame. Having the above constitution, a voltage larger than 6V is applied between the picture element electrodes and counter electrodes as one directional electric field in the liquid crystal display elements in which irregular shortcircuited patterns are being generated between a source electrode 2 and a picture element electrode. Therefore, irregular shortcircuited picture elements do not become luminescent spots under a black screen display condition.

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 and a method of driving the same which can be used to realize a high performance and high yield liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been actively approached for large-capacity display typified by image display, and have attracted the most attention as displays capable of realizing low-priced devices.

First, the basic structure of a conventional liquid crystal display device will be described with reference to FIG.

FIG. 3 is a sectional view showing the structure of a conventional liquid crystal display device.

As shown in FIG. 1, a conventional liquid crystal display device has a transparent insulating substrate 7 having an image display area 5 consisting of a switching element group 1, a pixel electrode group 2, an alignment film 3 and a signal wiring electrode group 4. Array substrate A made of transparent common electrode 8
A spacer 10 made of glass fibers or resin fine particles is provided on a counter substrate B made of a transparent insulating substrate 7 ′ having a light shielding layer 9 and an alignment film 3, and a pixel electrode 2 and a transparent common electrode 8 are made to face each other to make a resin adhesive. The liquid crystal composition 12 is filled with the liquid crystal composition 12 in a gap formed by a spacer. The liquid crystal display device configured as above,
Arbitrary information can be displayed by selectively applying a voltage to the pixel electrode group 2 through the switching element 1.

FIG. 4 shows the conventional array substrate A described above.
3 is an enlarged plan view of a unit pixel 5 that constitutes the pixel display region 5 of FIG.

In the array substrate A, a gate electrode wiring 4-1 made of chromium (corresponding to the signal wiring electrode group 4 in FIG. 3) and an insulator made of a silicon nitride film are sandwiched on the glass substrate 7.
The source electrode wiring 4-2 (not shown in FIG. 3) made of aluminum intersects with each other, and the switching element 14 is formed at the intersection of the gate electrode wiring 4-1 and the source electrode wiring 4-2.
As the switching element 14 (corresponding to the switching element group 1 in FIG. 3) made of a thin film transistor having amorphous silicon as a semiconductor layer and the pixel electrode 15 made of indium / tin oxide (corresponding to the pixel electrode group 2 in FIG. 3) Composed.

On the other hand, FIG. 5 shows a conventional timing chart when driving the liquid crystal display element having the above structure.

Here, Vgn indicates the time change of the gate voltage of the nth line, and Vgn + 1 indicates the time change of the gate voltage of the next line (n + 1).

Similarly, Vs represents the time change of the source voltage. The source voltage is the same regardless of the wiring number. The amplitude of Vs is about 10 V at maximum.

Here, one field is the time (frame) for which the gate scanning is completed, and fo is an odd frame and fe.
Is an even frame. Vc is the potential of the counter electrode.

Further, the voltage Vp (not shown) of the pixel electrode is
It is an alternating voltage having an amplitude of 12 V, with 6 V in the positive direction and 6 V in the negative direction, with Vc as the center.

During normal operation, the pixel electrode group 2 is selectively applied with 6 V, which is the potential difference between Vp and Vc, through the switching element 1, so that, for example, the brightness of black display (see FIG. 6) is increased. The obtained information can be displayed. Here, FIG. 6 shows the light transmittance characteristics of the voltage Vlc applied to the liquid crystal in the normally white mode liquid crystal display element.

On the other hand, in the conventional driving method, the median values Vsc and Vc of Vs are set to about 1V to 3V. Therefore, the potentials of Vs and Vc are V during an odd frame.
s> Vc, and Vc> Vs for even frames. further,
The potential difference between Vs and Vc is 6V to 8V in an odd frame and 4V to 2V in an even frame.

[0015]

However, in the conventional method of driving the liquid crystal display element, the source wiring 4 shown in FIG. 4 is used.
-2 and the pixel electrode 15 are electrically short-circuited due to formation of an irregular pattern during manufacturing (for example, a substantially square portion with reference numeral 16 in FIG. 4), the source signal is directly applied to the pixel electrode. To be done. Therefore, the potential difference between the pixel electrode 15 and the counter electrode becomes irregular.

The liquid crystal applied voltage Vlc applied to the liquid crystal in the normally white mode liquid crystal display element shown in FIG. 6 is represented by the root mean square value of the potential difference between the pixel potential Vp and the counter potential Vc.

As shown in FIG. 4, consider a case where a Vs signal amplitude for black display is applied when an irregular short circuit occurs in a pixel in the image display area.

Here, due to an irregular short circuit, Vp becomes Vs
Becomes equal to

Therefore, the potential difference between Vp and Vc is odd frame 6V, even frame 4V (maximum odd frame 8V, even frame 2V) as described in the prior art, and the root mean square value of Vlc is 3.6V. (4.1V).

Therefore, as can be seen from FIG. 6, a perfect black display state cannot be displayed. Pixels in which the above-mentioned irregular short circuit occurs have higher brightness than normal pixels. There is a problem that it becomes a so-called bright spot and remarkably deteriorates the image quality. That is, the yield is lowered and the cost is increased.

Therefore, in consideration of such problems in the conventional liquid crystal display element, the present invention eliminates the defect of becoming a bright spot even when an irregular short circuit occurs, and further improves the display quality as compared with the conventional one. It is an object of the present invention to provide an excellent liquid crystal display device.

It is another object of the present invention to provide a method for driving a liquid crystal display device which can solve the above-mentioned conventional problems.

[0023]

According to a first aspect of the present invention, there are provided a switching element group including thin film transistors, a source wiring electrode group and a gate wiring electrode group connected to the switching element group, and the switching element group. A substrate having a matrix-shaped image display region having a connected pixel electrode group and a substrate having at least a transparent counter electrode are opposed to each other on their electrode surface sides, and a predetermined gap is maintained. Placed,
A method of driving a liquid crystal display device, in which a liquid crystal composition is filled in the gap, wherein an absolute value of a potential difference between a potential Vs of the source wiring group and a potential Vc of an electrode of the substrate with the counter electrode is a pixel electrode. And a method of driving the liquid crystal display element in which the value is equal to or larger than the absolute value of the potential difference Vl between the opposite electrodes.

According to a second aspect of the present invention, a switching element group including thin film transistors, a source wiring electrode group and a gate wiring electrode group connected to these switching element groups, and a pixel electrode connected to the switching element group are provided. A substrate having a matrix-shaped image display region having a group and a substrate with a counter electrode having at least transparency, and the electrode surface sides of the respective substrates are opposed to each other and are arranged while maintaining a predetermined gap. In a liquid crystal display device having a liquid crystal composition filled therein, the absolute value of the potential difference between the potential Vs of the source wiring group and the potential Vc of the electrode of the substrate with the counter electrode is between the pixel electrode and the counter electrode. The liquid crystal display element is set to a value equal to or larger than the absolute value of the potential difference Vl.

[0025]

According to the present invention, the substrate having the matrix-shaped image display area includes the switching element group including the thin film transistors, the source wiring electrode group and the gate wiring electrode group connected to the switching element group, and the switching element group. A pixel electrode group connected to the substrate, the substrate with the counter electrode is at least transparent, the electrode surface sides of the substrates are opposed to each other, and are arranged with a predetermined gap, and the liquid crystal is placed in the gap. A liquid crystal display device filled with a composition, wherein the potential V of the source wiring group is
The absolute value of the potential difference between s and the potential Vc of the electrode of the substrate with the counter electrode is set to be equal to or larger than the absolute value of the potential difference Vl between the pixel electrode and the counter electrode.

For example, in the method of driving the liquid crystal display element of the present invention set as described above, the source wiring and the pixel electrode are formed with an irregular pattern during manufacturing while driving the liquid crystal display element as usual. In an abnormal state where an electrical short circuit occurs and the source signal is directly applied to the pixel electrode, even in the case of black screen display, a pixel in which an abnormal short circuit occurs has a black display of the same degree as that of a normal pixel. Brightness is obtained. That is, it does not become a bright spot and does not impair the image quality. Thereby, for example, the yield of the liquid crystal display element can be improved, the cost can be reduced, and further, the display performance can be dramatically improved.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a timing chart of each voltage in a liquid crystal display element of an embodiment according to the present invention. The same embodiment will be described with reference to the drawing, and a liquid crystal display element according to another invention. The driving method of is also described at the same time.

Here, the structure of the liquid crystal display element of this embodiment is basically the same as that of FIGS. 3 and 4 described above.

Further, Vgn, Vgn + 1, Vs, fo, f
The definitions of e and Vc are the same as in the timing chart of the conventional driving method (see FIG. 5).

In the driving method of the present invention, the difference between the median value of Vs Vsc and Vc is set to 11V. The structure of the liquid crystal display element of the present invention is the same as the conventional structure shown in FIGS.

FIG. 2 shows the transmittance characteristics when a DC voltage is applied to the liquid crystal of a normally white mode liquid crystal display element. As can be seen from the figure, the transmittance becomes almost 1% or less at 6V or higher. This is in a relationship equivalent to about 6V which is the voltage V1 that can obtain a transmittance of 1% of a normal liquid crystal driving voltage.

The operation of the present embodiment having the above-mentioned structure will be described below.

That is, as shown in FIG. 1, the potentials of Vs (that is, Vp) and Vc are Vs> Vc in both odd frames and even frames. Further, the potential difference between Vs and Vc is 15V in an odd frame and 6V in an even frame.

As a result, the source electrode 3 in FIG.
In the liquid crystal display element in which the irregular short circuit pattern 12 of the pixel electrode 5 is generated, 6 V or more is constantly applied between the pixel electrode and the counter electrode by the electric field in one direction, and the black screen display Even in this case, the irregular short-circuited pixel does not become a bright spot (see FIG. 2).

As described above, in the above embodiment, as a method of driving the liquid crystal display element, the potential Vs of the source wiring group always has the same polarity as the potential Vc of the electrode of the substrate with the counter electrode while driving the liquid crystal display element. , The potential difference Vd between Vs and Vc
The value c is larger than the pixel electrode potential V1 at which the liquid crystal transmittance is 1% and the counter electrode potential difference V1.

As described above, according to the present embodiment, while driving the liquid crystal display element as in the conventional case, the source electrode is directly short-circuited by forming an irregular pattern of the source electrode, and the source signal is directly applied to the pixel electrode. In the irregular state, even in the case of a black screen display, a pixel in which an irregular short circuit occurs can obtain a brightness of black display similar to that of a normal pixel.

That is, it is prevented from becoming a bright spot and the image quality is not impaired. As a result, it has been confirmed that the yield of the liquid crystal display device can be improved, the cost can be reduced, and the display performance can be dramatically improved.

In the above embodiment, the potential difference between Vsc and Vc is set to 11V, but the potential difference is not limited to this, and may be 11V or more, for example, and the same effect can be obtained.

Further, in the above embodiment, the relationship between the potential Vs of the source wiring group and the potential Vc of the electrode of the substrate with the counter electrode is described as the case where the potential difference between Vsc and Vc is 11V. Not limited to, for example, Vsc and V
The potential difference of c is 1 V as in the case described with reference to FIG.
Of course, the amplitude may be set to about 3V and the amplitude of Vs may be set to a larger value. Specifically, the amplitude may be set to about 18V. Even in this case, the absolute value of the potential difference between the potential Vs of the source wiring group and the potential Vc of the electrode of the substrate with the counter electrode is set to be equal to or larger than the absolute value of the potential difference Vl between the pixel electrode and the counter electrode. Therefore, the same effect can be obtained.

Further, in the above embodiment, the driving method in the case where Vs is inverted every frame is explained, but the present invention is not limited to this, and it is inverted every row (so-called row inversion).
Also in the driving method, the same action can be realized by setting the potential difference between Vsc and Vc to 11 V or more.

[0042]

As is apparent from the above description, the present invention has an advantage that the display quality of the liquid crystal display device is much better than the conventional one.

[Brief description of drawings]

FIG. 1 is a timing chart of a driving method of a liquid crystal display element according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a direct current voltage and a transmittance characteristic of a normally white mode liquid crystal display element according to an embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of a liquid crystal display element of a conventional example and a liquid crystal display element of this example.

FIG. 4 is an enlarged plan view of a pixel display region of an active matrix substrate of a conventional example and this example.

FIG. 5 is a timing chart when driving a liquid crystal display element of a conventional example.

FIG. 6 is a diagram showing a relationship between voltage and transmittance characteristics of a conventional normally white mode liquid crystal display element.

[Explanation of symbols]

 1 switching element group 2 pixel electrode group 3 alignment film 4 signal wiring electrode group 5 image display area 7, 7'transparent insulating substrate 8 transparent common electrode 9 light-shielding layer 10 spacer 11 resin adhesive 12 liquid crystal composition A array substrate B facing Substrate Vg Gate voltage Vs Source voltage Vc Counter voltage

Claims (2)

[Claims] 1. A matrix having a switching element group including thin film transistors, a source wiring electrode group and a gate wiring electrode group connected to the switching element group, and a pixel electrode group connected to the switching element group. A liquid crystal in which a substrate having an image display region and a substrate with a counter electrode are arranged such that the electrode surface sides of the respective substrates face each other and a predetermined gap is maintained, and the gap is filled with a liquid crystal composition. A method of driving a display element, wherein the absolute value of the potential difference between the potential Vs of the source wiring group and the potential Vc of the electrode of the substrate with the counter electrode is the same as the absolute value of the potential difference Vl between the pixel electrode and the counter electrode. A method for driving a liquid crystal display device, wherein the value is larger than that. 2. A matrix-like structure having a switching element group including thin film transistors, a source wiring electrode group and a gate wiring electrode group connected to the switching element group, and a pixel electrode group connected to the switching element group. A substrate having an image display region and a substrate with a counter electrode are provided, and the electrode surface sides of the respective substrates face each other and are arranged while maintaining a predetermined gap, and the gap is filled with a liquid crystal composition. In the liquid crystal display device, the absolute value of the potential difference between the potential Vs of the source wiring group and the potential Vc of the electrode of the substrate with the counter electrode is equal to or greater than the absolute value of the potential difference Vl between the pixel electrode and the counter electrode. A liquid crystal display device characterized by being set to a large value.