JPH06194679A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent the degradation in contrast, the generation of crosstalks, etc., by a fluctuation in common electrode potential by extending a gate insulating film formed on a lower layer electrode clown to a sealing region. CONSTITUTION:A signal wire 2 and a protective film 21 are successively laminated via the gate insulating film 20 on the inside main surface of an insulating substrate 10. Spacers 30 are held between insulating substrates 10 and 11 and a sealing material 31 consisting of an org. resin is filled in a gap. On the other hand, the gate insulating film 20 and the protective film 21 are successively laminated in the sealing regions on the leading out side of scanning lines 3 so as to cover these regions. The spacer 30 is hold between the insulating substrates 10, 11 and the sealing material 31 is filled in the gap. A power substrate 10 where the sealing material 31 is formed in a power feed part. On the other hand, a common electrode 6 formed on the inside main surface of the insulating substrate 11 is extended to the position opposing the power feed terminal 7. The common electrode 6 and the power feed terminal 7 are electrically connected via conductive paste 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode structure of a liquid crystal display device, and more particularly to an electrode structure of a liquid crystal display device using a thin film transistor (hereinafter referred to as TFT) as a switching element.

[0002]

2. Description of the Related Art In recent years, display devices using liquid crystal have a large capacity for TV displays and graphic displays.
Higher density is being promoted. Above all, active matrix type liquid crystal display devices in which a switching element is arranged in each pixel are actively developed and put to practical use.

A conventional technique will be described below by taking an active matrix type liquid crystal display device using a TFT as a switching element as an example. The active matrix liquid crystal display device has a basic configuration in which liquid crystal is provided between an array substrate on which switching elements and display pixel electrodes connected to the switching elements are formed in a matrix and an opposing substrate on which a common electrode is formed. Hold it.

FIG. 7 is a perspective view showing a schematic structure of such a liquid crystal display device. That is, the scanning lines 3 and the signal lines 4 are formed in a matrix on the inner main surface of the array substrate 1,
Display pixel electrodes 6 are connected to the respective intersections via TFTs 5. On the other hand, on the inner main surface of the counter substrate 2, a common electrode 8 is formed over the entire surface, and a light shielding layer 9 is formed so as to surround a region facing the display pixel electrode 6. The array substrate 1 and the counter substrate 2 are several μ
They are arranged opposite to each other with a space of m, and their peripheral portions are sealed with a sealing material containing a spacer such as glass, and a liquid crystal is held in the space.

A power supply terminal 7 is provided outside the sealing area of the array substrate 1. On the other hand, the end of the common electrode 8 extends to a region corresponding to the power supply terminal 7 to form a rectangular power supply part 35, and this power supply part is connected to the power supply terminal 7 and a conductive paste or the like. It is electrically connected.

FIG. 8 is a plan view of one pixel of the liquid crystal display device, and FIG. 9 is a sectional view taken along the line BB of FIG. That is, the gate electrode 42 integrated with the scanning line 3 is formed on the inner main surface of the insulating substrate 10 such as glass, and the semiconductor layer 45, the source electrode 44, and the signal line 4 are formed on the gate electrode 42 via the gate insulating film 20. The integrated drain electrode 43 is sequentially stacked to form T
FT5 is formed. Further, an auxiliary capacitance line 41 is formed in a region adjacent to the TFT 5, and a display pixel electrode 6 connected to the source electrode 44 via the gate insulating film 20 is formed thereon. Further, the protective film 21 is formed in a region except on the display pixel electrode 6, and the alignment film 46 is laminated on the entire surface thereof to form the array substrate 1.

On the other hand, a light-shielding film 9 is formed on the inner main surface of the insulating substrate 11 such as glass so as to surround a region facing the display pixel electrode 6, and a common electrode 8 and an alignment film 47 are sequentially laminated on the entire surface. Thus, the counter substrate 2 is formed.

Next, a general driving method of the above liquid crystal display device will be described. That is, when the selection pulse is applied to the scanning line 3, the TFT 5 becomes conductive and the potential of the display pixel electrode 6 is set to the same potential as the potential of the signal line 4. Next, when a non-selection voltage is applied to the scanning line 3, the TFT 5 becomes non-conductive, and a period until the next selection pulse is applied,
The display pixel electrode 6 holds the written potential. on the other hand,
A predetermined potential is applied to the common electrode 8 from the power supply terminal 7 on the array substrate 1 side through the power supply section 35. And
The light transmittance of the liquid crystal changes according to the potential difference between the display pixel electrode 6 and the common electrode 8, and as a result, image display is performed according to the video signal.

[0009]

In the above-described liquid crystal display device, the electrodes formed on the counter substrate and the array substrate are intricately capacitively coupled. For this reason, the potentials of the electrodes fluctuate under the influence of mutual potential changes. Figure 10
Shows how the common electrode potential changes due to the change in the signal line potential. The signal line potential takes a different value for each horizontal scanning period in order to supply an independent video signal to each pixel. On the other hand, the common electrode potential changes in the same polarity direction as the potential change at the same time as the signal line potential changes, and then gradually returns to the set potential. Then, when the signal line potential changes in the next horizontal scanning period, the common electrode potential changes again.

In the conventional liquid crystal display device, it takes a considerable time for the common electrode potential to return to the set potential, and the common electrode potential is lower than the set value for a considerable period of one horizontal period. Get lower. Then, the value of the execution voltage applied to the liquid crystal is lowered, the contrast is lowered,
There is a problem that display defects such as crosstalk occur.

The present invention has been made in view of the above technical background.
It is an object of the present invention to realize a good display state by preventing a decrease in contrast and the occurrence of crosstalk due to a change in the common electrode potential.

[0012]

A liquid crystal display device according to a first aspect of the present invention includes a counter substrate having a common electrode formed in a display region on a first insulating substrate and a second insulating substrate. An array substrate having a display pixel electrode connected via a thin film transistor to each intersection of a lower layer electrode and an upper layer electrode laminated via a gate insulating film is formed on the display area so that their electrode forming surfaces face each other. In a liquid crystal display device which is surrounded and sealed at a peripheral portion, and a plurality of power supply terminals are provided outside the sealing region of the array substrate, the lower layer electrode and the upper layer electrode extend to different regions outside the sealing region. While extending, the gate insulating film on the lower electrode extends to at least the sealing region, and the common electrode includes at least a part of the sealing region on the lower electrode side to the power supply terminal. Characterized in that it extends to the area of direction.

A liquid crystal display device according to a second invention of the present invention is formed on a counter substrate having a common electrode formed over the entire display area on the first insulating substrate and on the second insulating substrate. An array substrate having a display pixel electrode connected to each intersection of the lower layer electrode and the upper layer electrode via a thin film transistor is sealed at a peripheral portion so as to surround the display region, and outside the sealing region of the array substrate. In the liquid crystal display layer having a plurality of power supply terminals, a light-shielding layer provided in a region in contact with the common electrode and facing the gap between the display pixel electrodes extends to a region facing the power supply terminal. It is characterized by being present.

[0014]

The inventors of the present invention have made extensive studies on the above problems and found the following. That is, in the conventional liquid crystal display device, the electrical resistance value is extremely high in the connection region between the rectangular power supply portion 35 on the counter substrate side and the common electrode 8. For this reason, the power supply capability to the common electrode is reduced, and it takes a considerable time for the once changed common electrode potential to return to the set potential.

To solve such a problem, for example, it is conceivable to increase the thickness of the electrode forming the connection region to reduce the resistance value. However, such a method is not preferable in a liquid crystal display device. The reason is as follows. That is, the ITO (In
The light transmittance of dium tin oxide) depends greatly on the film thickness, and as the film thickness increases, the light transmittance tends to decrease. Then, the display screen becomes dark and the display quality is significantly deteriorated.

On the other hand, in the liquid crystal display device according to the first aspect of the invention, the common electrode on the counter substrate side is extended to a region including the sealing region on the lower layer electrode side and facing the region where the power supply terminal is provided. To be present, the power feeding path from the power feeding portion to the electrode portion that substantially functions as the common electrode can be expanded. Therefore, the resistance value of the power supply path can be significantly reduced.

At this time, if the common electrode is simply extended to the sealing region, the following problems occur. That is, the spacer contained in the sealing material scrapes the surface of the wiring on the array substrate side, and conductive particles are mixed into the sealing material. Then, a short circuit may occur between the common electrode and the wiring on the array substrate side, and normal display may not be performed.

On the other hand, in the liquid crystal display device of the first invention, since the gate insulating film formed on the lower electrode extends to the sealing region, the lower electrode is scraped by the spacer. It is possible to prevent the conductive particles from being mixed into the sealing material.

Further, in the liquid crystal display device according to the second aspect of the present invention, in order to extend the light-shielding layer having a low resistance such as Cr provided in contact with the common electrode to the power feeding portion, It is possible to significantly reduce the resistance value of the power feeding path to the portion that substantially functions as the common electrode.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. The same numbers are given to the parts corresponding to the configuration of the conventional technique. (Example 1)

FIG. 1 is a perspective view showing a schematic structure of a liquid crystal display device according to an embodiment of the present invention. That is, the scanning lines 1 and the signal lines 2 are formed in a matrix on the inner main surface of the array substrate 1, and the display pixel electrodes 4 are connected to the respective intersections via the TFTs 3. On the other hand, the counter substrate 2
A common electrode 5 is formed on the inner main surface of the. And
The array substrate 1 and the counter substrate 2 are arranged so as to face each other with a space of about 5 μm, and their peripheral portions are sealed, and liquid crystal is sandwiched in the gap. Further, the scanning line 1 and the signal line 2 are extended to the outside of the sealing area and are connected to an external circuit (not shown).

Further, outside the sealing area of the array substrate 1,
A power supply terminal 7 is provided. On the other hand, the end portion of the common electrode 8 extends to a region facing the power supply terminal 7, including the sealing region on the side where the scanning line 3 extends.

FIG. 2 is a diagram for explaining a cross-sectional view of a main part of the liquid crystal display device of FIG. 2A is a perspective view of the liquid crystal display device, FIG. 2B is a cross-sectional view of the sealing area on the signal line leading side, and FIG. 2C is a cross-sectional view of the sealing area on the scanning line leading side. 2D is a cross-sectional view of a portion for feeding power to the common electrode.

The structure in the sealing area on the signal line lead-out side is
It is as follows. That is, on the inner main surface of the insulating substrate 10,
The signal line 2 and the protective film 21 are sequentially stacked via the gate insulating film 20. A spacer 30 is sandwiched between the insulating substrates 10 and 11, and a void is filled with a sealing material 31 made of an organic resin.

On the other hand, in the sealing region on the scanning line lead-out side, the scanning line 3 is formed on the inner main surface of the insulating substrate 10, and the gate insulating film 20 and the protective film 21 are sequentially laminated so as to cover them. There is. On the other hand, the common electrode 6 is formed on the inner main surface of the insulating substrate 11. And the insulating substrates 10 and 1
A spacer 30 is sandwiched between the gaps 1, and a gap is filled with a sealing material 31.

The structure of the power feeding section is as follows. That is, outside the sealing material forming region of the insulating substrate 10,
The power supply terminal 7 is formed, while the common electrode 6 formed on the inner main surface of the insulating substrate 11 extends to a position facing the power supply terminal 7. The common electrode 6 and the power supply terminal 7 are electrically connected via the conductive paste 32. Next, a method of manufacturing the liquid crystal display device of this embodiment will be described. As the structure of the pixel region, the same structure as that shown in FIGS. 8 and 9 was used. First, a Ta film is formed on the insulating substrate 10 by using a sputtering method, and is patterned into a predetermined shape to form the scanning line 3 and the gate electrode 42 integrated with the scanning line 3, the auxiliary capacitance line 41, and the power supply terminal 7. . Then, on the entire surface, Si
An Ox film is formed by using a CVD (Chemical Vapor Deposition) method to form a gate insulating film 20.

Next, an a-Si film is formed by the CVD method and patterned into a predetermined shape to form a semiconductor layer 45. Then, an ITO film is formed by using a sputtering method and patterned into a predetermined shape to form the display pixel electrode 6. Further, an Al film is formed by using the sputtering method, and is patterned into a predetermined shape, so that the signal line 2
A drain electrode 43 and a source electrode 44, which are integrated with, are formed.

Then, S is applied to the area excluding the display pixel electrode 6
The iNx film is formed by the CVD method to form the protective film 21. Further, a polyimide film is applied by printing on the entire surface and a predetermined surface treatment is applied to form an alignment film 46.

On the other hand, an ITO film is formed on the insulating substrate 11 by a sputtering method to have a thickness of 200 to 400 Å and is patterned into a shape shown in FIG. 1 to form a common electrode 6. Then, a polyimide film is applied by printing on the entire surface and a predetermined surface treatment is performed to form an alignment film 47. The array substrate 1 and the counter substrate 2 thus obtained are sealed with a sealant 3 containing a spacer 30 in the peripheral portion.
Seal with 1. At this time, a conductive paste is applied on the power supply terminal 7 in advance and connected to the power supply unit on the counter substrate side.
Thus, the liquid crystal display device of this example was obtained.

In the liquid crystal display device of the present embodiment, the resistance value of the power feeding path from the power feeding portion to the region substantially functioning as the common electrode can be significantly reduced, so that the common electrode potential is kept at a predetermined potential. The recovery time could be shortened significantly, and no crosstalk or contrast reduction was observed due to fluctuations in the common electrode potential. In order to make the resistance value of the power feeding path similar to that of the present embodiment in the shape of the conventional common electrode, it is necessary to form the common electrode to be twice or more thick. Then, the light transmittance is reduced by about 10%, and the display quality is significantly impaired. Further, since it takes a considerable time to form the common electrode, the production efficiency will be significantly reduced.

On the other hand, in the liquid crystal display device of this embodiment, a liquid crystal display device having extremely good display characteristics could be obtained without significantly changing the manufacturing process of the conventional liquid crystal display device.

Further, since the gate insulating film extends right above the scanning line, the surface of the scanning line is prevented from being scraped by the spacer particles, and the short circuit between the scanning line and the common electrode in the sealing region is prevented. can do.

Further, by extending the gate insulating film also to the lead-out portion of the signal line, the substrate spacing can be made equal in the lead-out portion of the scanning line and the signal line. Therefore, it is possible to prevent the variation in the substrate interval.

In this embodiment, the liquid crystal display device in which the scanning line serves as the lower layer electrode has been described, but the present invention is not limited to such a configuration, and for example, the signal line is the lower layer electrode and the scanning line is the upper layer electrode. Needless to say, it can be applied when used as an electrode. (Example 2)

Another example of the liquid crystal display device of the present invention will be described below. The liquid crystal display device of this embodiment is characterized in that a light-shielding layer that is in contact with the common electrode is formed on the counter substrate, and the light-shielding layer is extended to the power feeding portion of the common electrode. FIG. 3 is a perspective view showing a schematic structure of the liquid crystal display device of the present embodiment and corresponds to FIG. 1 of the first embodiment. Further, FIG. 4 is a cross-sectional view of the power feeding portion and corresponds to FIG. 2D of the first embodiment.

Next, a method of manufacturing the liquid crystal display device of the liquid crystal display device of this embodiment will be described. The array substrate 1 is obtained in the same manner as in the above embodiment. On the other hand, the counter substrate is manufactured as follows. That is, a Cr film is formed on the insulating substrate 11 by a sputtering method to have a thickness of about 1000 Å and patterned into a predetermined shape to form the light shielding layer 9. Then, an ITO film is formed thereon to have a thickness of 200 to 400 Å and patterned into a shape shown in FIG. 3 to form a common electrode 8. In this way, the power feeding portion is formed by stacking the Cr film and the ITO film. Further, an alignment film is formed on this to obtain the counter substrate of this embodiment. Then, in the same manner as in Example 1, a liquid crystal display device of this example was obtained.

In the liquid crystal display device of this embodiment, the resistance of the common electrode hardly depends on the ITO film thickness, and in this embodiment, the common electrode film thickness can be made as thin as possible so that ITO can be stably formed. . Therefore, the time required for the common electrode potential to return to the set potential can be significantly shortened, and the occurrence of crosstalk and the decrease in contrast due to the fluctuation of the common electrode potential were not observed. Further, the light transmittance of the common electrode of the present embodiment is improved by about 10% as compared with the common electrode conventionally formed with a film thickness of about 800 to 1000 angstroms.

The light-shielding layer is made of, for example, A other than Cr.
A metal such as 1 can be used. At this time, if the surface of the light-shielding layer is oxidized, contact failure may occur. Therefore, as described above, ITO may be coated on the light shielding layer of the power feeding unit. In addition, the light shielding layer is C
A two-layer structure of rO / Cr may be used, and CrO may be removed at the power feeding portion to connect with the conductive paste. (Example 3)

A modification of the second embodiment will be shown below. That is,
In the second embodiment, the power feeding portion is formed by the laminated structure of the common electrode and the light shielding layer. However, depending on the film forming conditions, the adhesion strength between these films may be reduced and the sealing portion may be broken. is there.

In consideration of this point, the liquid crystal display device of the present embodiment is intended to improve the strength of the power feeding portion. FIG. 5 is an enlarged view of the counter substrate in the power feeding portion of the liquid crystal display device of this embodiment, and FIG. 6 is a line B in FIG.
A sectional view along B ′ is shown. That is, in the power feeding portion, the light shielding layer is formed in a mesh shape, and ITO is laminated on the light shielding layer to form a predetermined shape to form a common electrode. The formation of the light shielding layer can be realized by using a normal PEP process. Hereinafter, in the same manner as in Example 2, the liquid crystal display device of the present invention was obtained.

In the liquid crystal display device of the present embodiment, in addition to the effect of the liquid crystal display device of the second embodiment, film peeling between the common electrode and the light-shielding layer in the power feeding portion is unlikely to occur and the yield can be greatly improved. did it.

[0042]

As described in detail above, in the liquid crystal display device of the present invention, the resistance value of the power feeding path from the power feeding portion of the common electrode to the display area can be significantly reduced, and therefore the following effects can be obtained. To be That is, since the recovery time after the change of the common electrode potential caused by the capacitive coupling between the wiring on the array substrate and the common electrode can be significantly shortened, it is possible to reduce the occurrence of display defects such as reduction in contrast and crosstalk. . Moreover, a bright display screen can be obtained without impairing the light transmittance of the common electrode. Thus, a liquid crystal display device having extremely good display characteristics can be realized without significantly changing the manufacturing process of the conventional liquid crystal display device.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a liquid crystal display device of the first invention.

FIG. 2 is a cross-sectional view showing a main part structure of the liquid crystal display device of FIG.

FIG. 3 is a perspective view showing an embodiment of the liquid crystal display device of the second invention.

FIG. 4 is a cross-sectional view showing a main part structure of the liquid crystal display device of FIG.

FIG. 5 is a plan view showing still another example of the liquid crystal display device of the second invention.

6 is a cross-sectional view taken along the line BB ′ of FIG.

FIG. 7 is a perspective view showing an example of a conventional liquid crystal display device.

FIG. 8 is a plan view of one pixel of the liquid crystal display device.

9 is a cross-sectional view taken along the line CC ′ of FIG.

FIG. 10 is a chart showing an example of drive waveforms of a liquid crystal display device.

[Explanation of symbols]

 1 ... Array substrate 2 ... Counter substrate 3 ... Scan line 4 ... Signal line 5 ... TFT 6 ... Display pixel electrode 7 ... Power supply terminal 8 ... Common electrode 9 ... Shading layer

Claims (2)

[Claims] 1. An intersection of a counter substrate having a common electrode formed in a display region on a first insulating substrate and a lower layer electrode and an upper layer electrode laminated on a second insulating substrate via a gate insulating film. An array substrate having a display pixel electrode connected to a portion via a thin film transistor is sealed in a peripheral portion surrounding the display region so that their electrode forming surfaces face each other,
In the liquid crystal display device, in which a plurality of power supply terminals are provided outside the sealing region of the array substrate, the lower layer electrode and the upper layer electrode extend to different regions outside the sealing region, and on the lower layer electrode. The gate insulating film extends at least to the sealing region, and the common electrode extends to a region facing the power supply terminal including at least a part of the sealing region on the lower layer electrode side. A liquid crystal display device characterized by the above. 2. A thin film transistor is provided at each intersection of a counter substrate having a common electrode formed on the entire surface of a display region on a first insulating substrate and a lower layer electrode and an upper layer electrode formed on a second insulating substrate. A liquid crystal display layer in which an array substrate having display pixel electrodes connected to each other is sealed at a peripheral portion so as to surround the display region, and a plurality of power supply terminals are provided outside the sealing region of the array substrate. The liquid crystal display device according to claim 1, wherein a light shielding layer provided in a region in contact with the common electrode and facing a gap between the display pixel electrodes extends to a region facing the power supply terminal.