JP2001021909A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely eliminate display unevenness by separating a conductive layer for connecting an electrostatic protection circuit connected with each drain signal line, via a diode with a common electrode on the side of the other transparent substrate by arranging plural separating parts form the center to the outer contour. SOLUTION: A 3rd and a 4-th electrostatic protection circuits are formed with bi-directional diodes connected across each of the odd-numbered and even- numbered drain signal lines and the common wiring on their both sides. Furthermore, as a guard ring a 6-th electrostatic protection circuit is extended along the upper end side edge of the transparent substrate. Then, this device is provided with conductive layers 25, 26 for connecting these electrostatic protection circuits with the other common electrodes, and these conductive layers 25, 26 are at least divided into the parts 25A-25C, 26A-26C to be connected with each electrostatic protection circuits. Moreover, they are divided by providing plural separating parts from the center of each conductive layers 25, 26 to the outer contours of the conductive layers 25, 26.

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, and more particularly, to a liquid crystal display called an active matrix type.

[0002]

2. Description of the Related Art A liquid crystal display device called an active matrix type extends in the x direction on a liquid crystal side of one of the transparent substrates (TFT substrates) disposed opposite to each other via a liquid crystal. A gate signal line which is arranged in parallel in the y direction and a drain signal line which is insulated from the gate signal line and extends in the y direction and arranged in the x direction are formed.

A region surrounded by each of the signal lines is defined as a pixel region. In the pixel region, a thin film transistor driven by supplying a scanning signal from a gate signal line and an image from a drain signal line via the thin film transistor are provided. A pixel electrode to which a signal is supplied.

An electrostatic protection circuit is formed outside the display area, which is a group of pixel areas. The electrostatic protection circuit is connected to each of the drain signal lines via an electrostatic protection diode. And an electrostatic protection wiring connected to each gate signal line via an electrostatic protection diode.

Further, an electrostatic protection wiring connected to each drain signal line via an electrostatic protection diode is formed on another transparent substrate (filter substrate) which is disposed to face through a liquid crystal and has a constant voltage. To be connected to the opposite electrode held by the counter electrode.

Then, a negative voltage (several tens of volts) with respect to the voltage applied to the counter electrode is applied to an electrostatic protection wiring connected to each gate signal line via an electrostatic protection diode, thereby forming a thin film transistor. Can be lowered.

As a result, the ON current of the thin film transistor can be sufficiently ensured, and the occurrence of display unevenness caused by variations in the voltage applied to the liquid crystal is avoided.

Further, when the filter substrate is charged during the manufacturing process of the liquid crystal display device, it is possible to avoid a potential difference between the thin film transistor and the TFT substrate which causes a shift of the threshold voltage. .

[0009]

In the liquid crystal display device configured as described above, the connection between the electrostatic protection wiring formed on each of the transparent substrates which are arranged to face each other via the liquid crystal and the counter electrode is made. For example, a conductive material containing a large number of conductive beads (resin beads on which metal is plated) is applied between the transparent substrates.

However, even if this conductive material is applied, if the conductive beads contained in the conductive material vary, the connection between them is not sufficient, and display unevenness caused by the variation in the voltage applied to the liquid crystal cannot be avoided. there were.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a liquid crystal display device capable of reliably eliminating display unevenness.

[0012]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, the liquid crystal display device according to the present invention comprises:
A gate signal line extending in one direction and juxtaposed on the liquid crystal side surface of one of the transparent substrates opposed to each other with the liquid crystal interposed therebetween, and a drain insulated by the gate signal line and intersected with the gate signal line A signal line, a thin film transistor driven by supply of a scanning signal from a gate signal line to a pixel region surrounded by the signal line, a pixel electrode to which a video signal from a drain signal line is supplied via the thin film transistor, A first electrostatic protection circuit connected to each of the odd-numbered drain signal lines and a diode and one of the even-numbered drain signal lines and a diode are provided on one side outside the display region formed of a set of pixel regions. A second electrostatic protection circuit connected thereto; and a conductive layer for connecting the first and second electrostatic protection circuits to the common electrode on the other transparent substrate side. At least a part connected to the first electrostatic protection circuit and a part connected to the second electrostatic protection circuit are divided, and the division is made from substantially the center of the conductive layer to the outside of the conductive layer. This is characterized by being provided by providing a plurality of separation portions reaching the contour.

In the liquid crystal display device constructed as described above, for example, a conductor containing a large number of conductive beads is applied on the upper surface of the conductive layer in order to establish conduction with the counter electrode on the other transparent substrate side. However, even if the application of the conductive beads varies, the probability that the conductive beads are present on the upper surface of each of the divided conductive layers increases, and the conduction with the counter electrode can be reliably achieved. To play.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the liquid crystal display device according to the present invention will be described below with reference to the drawings.

FIG. 1 is an equivalent circuit diagram showing one embodiment of the liquid crystal display device according to the present invention. The figure is an equivalent circuit diagram, but is a diagram corresponding to an actual geometric arrangement.

FIG. 1 is a plan view of a transparent substrate 1 on a liquid crystal side of a transparent substrate 1 which is a so-called TFT substrate among transparent substrates disposed to face each other with a liquid crystal interposed therebetween.

In FIG. 1, a gate signal line 2 extending in the x direction and juxtaposed in the y direction is formed, and a drain signal line 3 extending in the y direction and juxtaposed in the x direction. Are formed.

Each rectangular area surrounded by these signal lines constitutes a pixel area, and a display area is constituted by an aggregate of these pixel areas.

In each pixel region, a switching element (thin film transistor TFT) driven by the supply of a scanning signal from the gate signal line 2 and a video signal from a drain signal line 3 are supplied via the switching element. A pixel element PIX and a capacitive element Cadd provided between the pixel electrode PIX and another gate signal line 2 adjacent to the gate signal line for driving the switching element are formed.

The capacitance element Cadd has a function of, for example, keeping the video signal stored in the pixel electrode PIX for a relatively long time when the switching element is turned off.

Further, an electrostatic protection circuit, which will be described in detail later, is formed around the display area composed of the pixel area configured as described above, and covers the display area and the electrostatic protection circuit. Then, a transparent substrate (shown by a dotted frame 4 in the figure) called a so-called filter substrate is arranged.

Although not shown, a transparent substrate 1 and a sealing material for sealing a liquid crystal between the transparent substrate 1 and the gap between the transparent substrate 1 and the liquid crystal are provided between the transparent substrate 1 and the sealing material (reference numeral in FIG. 2). 35) are formed.

The left end of each gate signal line 2 in the figure is a transparent substrate 4
In other words, the gate terminal 2A is formed to extend beyond the sealing material to the outside of the opposing region, and to supply a scanning signal to the extending portion.

The gate terminal 2 A is connected to an output bump of a scanning drive circuit 6 composed of a semiconductor integrated circuit (IC). Is mounted on the transparent substrate 1 so as to be connected to the input terminal 8 provided on the transparent substrate 1.

Similarly, the lower end in the drawing of each drain signal line 3 extends to the outside of the opposing region of the transparent substrate 4, in other words, beyond the sealing material, and supplies a video signal to the extending portion. Terminal 3A is formed.

The drain terminal 3A is connected to an output bump of a video signal drive circuit 11 composed of a semiconductor integrated circuit (IC) mounted on the transparent substrate 1.
The video signal drive circuit 11 is mounted on the transparent substrate 1 such that its input bumps are connected to input terminals 11 provided around the transparent substrate 1.

As described above, an electrostatic protection circuit is provided in a region facing the transparent substrate 4 and outside the display region.

This static electricity protection circuit comprises a gate signal line 2
Thin-film transistors connected via gate electrodes when static electricity enters some of them
And a circuit for preventing electrostatic breakdown (or characteristic deterioration) of the thin film transistor TFT connected to the drain signal line 3 via a drain electrode when static electricity enters some of the drain signal lines 3. Or a circuit for preventing characteristic deterioration).

The former electrostatic protection circuit includes a first electrostatic protection circuit 14 extending in the y direction in the drawing so as to intersect (insulate) each gate signal line 2 on each of the left and right sides of the display area. And a second electrostatic protection circuit 15.

The first electrostatic protection circuit 14 is provided between each gate signal line 2 and a common wiring on both sides of each gate signal line 2 at the intersection with each gate signal line 2. A bidirectional diode D is connected and configured.

Similarly, the second electrostatic protection circuit 15 is provided between each gate signal line 2 and a common wiring on both sides of the gate signal line 2 at the intersection with each gate signal line 2. The bidirectional diodes D are connected to each other.

In the electrostatic protection circuit thus configured, for example, when static electricity enters some of the gate signal lines 2, all of the other gate signal lines 2 are connected via the bidirectional diode D and the common wiring. , Thereby avoiding electrostatic breakdown of the thin film transistor TFT.

The latter electrostatic protection circuit comprises a third electrostatic protection circuit 16 and a fourth static electricity protection circuit 16 extending in the x direction in the drawing so as to cross (insulate) each drain signal line 3 above the display area. The circuit 17 is composed of an electrical protection circuit 17.

The third electrostatic protection circuit 16 is connected between each drain signal line 3 and a common wiring on both sides of the drain signal line 3 at the intersection with each even-numbered drain signal line 3. And a bidirectional diode D
Are connected and configured.

Similarly, the fourth electrostatic protection circuit 17 connects each of the drain signal lines 3 and the common wiring on both sides of the drain signal lines 3 at the intersection with each of the odd-numbered drain signal lines 3. In between, bidirectional diodes D
Are connected and configured.

For example, when static electricity intrudes into some of the drain signal lines 3, the static electricity protection circuit having the above-mentioned configuration is connected to the other drain signal lines 3 via the bidirectional diode D and the common wiring. In addition, as will be described in detail later, it is also diffused to the common electrode on the side of the transparent substrate 4 which is a filter substrate, thereby avoiding electrostatic breakdown and the like of the thin film transistor TFT.

The bidirectional diode D is formed in parallel with the MIS type thin film transistor TFT in each pixel region, and has the same structure except that the source electrode and the gate electrode of the thin film transistor TFT are connected to each other. It is similar.

Then, the scanning drive circuit 6 for the gate signal line 2
A fifth electrostatic protection circuit 20 is formed outside the second electrostatic protection circuit 14 on the side opposite to the side connected to.

The fifth electrostatic protection circuit 20 is provided on the transparent substrate 1
, And has a function as a guard ring that reliably prevents static electricity from the right side of the transparent substrate 1 from entering the gate signal line 2 side.

The fifth electrostatic protection circuit 20 is provided on the side of the gate signal line 2 opposite to the side connected to the scanning drive circuit 6 because the left side of the transparent substrate 1 on which the scanning drive circuit 6 exists is provided. From the scanning drive circuit 6
This makes it difficult for the gate signal line 2 to directly enter the gate signal line 2.

Similarly, the sixth electrostatic protection circuit 21 is provided outside the third and fourth electrostatic protection circuits 16 and 17 on the opposite side of the drain signal line 3 connected to the video signal drive circuit 10.
Are formed.

The sixth electrostatic protection circuit 21 includes a transparent substrate 1
Of the transparent substrate 1, and the static electricity from the upper side of the transparent substrate 1
It has a function as a guard ring that reliably prevents intrusion into the side.

The reason why the sixth electrostatic protection circuit 21 is provided on the side of the drain signal line 3 opposite to the side connected to the video signal drive circuit 10 is that the lower end of the transparent substrate 1 on which the video signal drive circuit 10 exists. This is because even if static electricity enters from the side, it is difficult for the static electricity to directly enter the drain signal line 3 due to the presence of the video signal drive circuit 10.

The fifth electrostatic protection circuit 20 and the sixth
The electrostatic protection circuit 21 has a conductive layer 25 for drawing a common electrode (transparent electrode) common to each pixel region on the liquid crystal side surface of the transparent substrate 4 as a filter substrate to the transparent substrate 1 as a TFT substrate. Are connected to each other so that even if static electricity enters, the static electricity is more easily diffused.

In the case of this embodiment, the conductive layer 25 is composed of three separated conductive layers 25A, 25B, and 25C, and the fifth electrostatic protection circuit 20 and the sixth static protection circuit 20 are connected through the conductive layer 25A. And an electrical protection circuit 21.

As described above, these conductive layers 25A, 25A,
5B and 25C are connected to a counter electrode connected to, for example, the ground potential in each case.
It is possible to greatly reduce the influence of static electricity entering the electrostatic protection circuit 20 and the sixth electrostatic protection circuit 21 on others.

The counter electrode (transparent electrode) on the transparent substrate 4 side is T
As a conductive layer to be drawn out to the transparent substrate 1 side which is an FT substrate, a conductive layer 26, a conductive layer 27, and a conductive layer 28 are formed together with the conductive layer 25 on each of the squares of the display area. , And three conductive layers 26A, 26B, and 26C separated from each other, like the conductive layer 25.

The third electrostatic protection circuit 16 has one end connected to the conductive layer 25C and the other end connected to the conductive layer 26C, and the fourth electrostatic protection circuit 17 has one end connected to the conductive layer 25B.
The other end is connected to the conductive layer 26B, and the sixth electrostatic protection circuit 21 has one end connected to the conductive layer 25A and the other end connected to the conductive layer 26A.

Thus, at the stage when the assembly of the TFT substrate and the filter substrate is completed, the third electrostatic protection circuit 16
The fourth static electricity protection circuit 17, the fifth static electricity protection circuit 20, and the sixth static electricity protection circuit 21 are used with being grounded, respectively, so that the reliability for static electricity protection is increased.

Before assembling the TFT substrate and the filter substrate, in other words, in the case where the TFT substrate is handled in a state of only the TFT substrate, the fifth electrostatic protection circuit 2 formed to be connected to each other is formed.
The other electrostatic protection circuits (first to fourth electrostatic protection circuits) except the 0th and sixth electrostatic protection circuits 21 are formed electrically independently.

The reason is that, before assembly with the filter substrate, an inspection for disconnection or short circuit of the gate signal line 2 and the drain signal line 3 is usually performed, so that the inspection at that time is not hindered. To do that.

Here, as described above, the conductive layers 25 and 26 are each composed of a divided conductive layer. However, in an actual configuration, as shown in FIG. Ingenuity has been devised.

For example, in the case of the conductive layer 25, a plurality of separation portions extending from the approximate center of the conductive layer 25 to the outer contour of the conductive layer 25 are provided, so that the conductive layer 25 is divided into the conductive layers 25A, 25B, and 25C. .

It is preferable that the respective areas of these conductive layers 25A, 25B, 25C are substantially equal, but they need not be strict.

Therefore, in addition to the conductive layer 25 shown in FIG. 3, a layer shown in FIGS. 4A and 4B may be used.

In the case of the conductive layer 26 as well, similarly to the conductive layer 25, by providing a plurality of separation portions extending from the approximate center to the outer contour of the conductive layer 26, each conductive layer 26A, 26
B and 26C.

In this embodiment, the third electrostatic protection circuit 16, the fourth electrostatic protection circuit 17, and the sixth electrostatic protection circuit 21 (fifth electrostatic protection circuit 20) are each grounded. The conductive layer 25 (and the conductive layer 26)
Is divided into three parts, respectively. However, the number of divisions is not limited as required, and it is needless to say that the number may be four or five.

On the upper surfaces of the conductive layers 25 and 26 thus configured, a large number of conductive beads (for example, a resin bead surface plated with metal) are provided in order to achieve conduction with the counter electrode on the filter substrate side. Is applied, but even if the application of these conductive beads varies,
The probability that the conductive beads are present on the upper surface of each of the divided conductive layers is increased, and the effect that the conduction with the counter electrode can be surely achieved can be achieved.

FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1, and is a cross-sectional view showing the filter substrate and the backlight BL. The members shown in FIG. 1 are denoted by the same reference numerals in FIG.

On the liquid crystal side surface of the transparent substrate 31 on the filter substrate side, a black matrix BM is formed so as to define each pixel area.
A color filter 32 is formed in the opening.

Then, a flat film 33 is formed so as to cover the black matrix BM and the color filter 32, and on the upper surface thereof, a counter electrode 34 made of a transparent electrode is formed in common for each pixel region.

The counter electrode 34 is drawn out to the TFT substrate via the conductor 39 and the conductive film 26.

Here, as described above, the conductor 39 has been described as being formed by coating and including a large number of conductive beads formed by plating metal on the surface of resin beads. It is needless to say that the paste material may be a paste material containing a conductive metal powder such as gold and silver.

In the figure, reference numeral 35 denotes a sealant, 36 denotes an alignment film, and 37 denotes a deflection plate.

[0066]

As is apparent from the above description,
According to the liquid crystal display device of the present invention, display unevenness can be eliminated.

[Brief description of the drawings]

FIG. 1 is an equivalent circuit diagram showing one embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

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

FIG. 4 is an explanatory view showing another embodiment of the liquid crystal display device according to the present invention.

[Explanation of symbols]

2 ... gate signal line, 3 ... drain signal line, 14 ... first electrostatic protection circuit (first electrostatic protection circuit), 15 ... second electrostatic protection circuit (first electrostatic protection) Circuit), 16... Third electrostatic protection circuit (second electrostatic protection circuit), 17... Fourth electrostatic protection circuit (second electrostatic protection circuit), 20. Protection circuit (third electrostatic protection circuit), 21... Sixth electrostatic protection circuit (third electrostatic protection circuit), 25, 2
6, 27, 28: conductive layer, TFT: thin film transistor, PIX: pixel electrode, Cadd: capacitive element.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09G 3/20 680 G09G 3/36 3/36 G02F 1/136 500 (72) Inventor Masaaki Matsuda Mobara, Chiba 3300 Hayano, Hitachi, Ltd.Display Group, Hitachi, Ltd. F-term within the display group of the factory (reference) 2H092 GA37 GA38 GA39 GA60 GA64 HA13 HA16 JB52 JB58 JB79 MA11 NA01 NA14 PA03 PA04 PA08 PA09 2H093 NA16 NC09 NC11 NC62 NC81 ND05 ND40 5C006 AA22 BB16 BC06 BF36 EC01 FA20 5C080 ADD DD03 5C094 AA03 AA21 AA23 AA31 AA48 BA03 BA43 CA19 DA12 DB02 D B04 DB05 EA02 EA04 EA05 EA07 EA10 EB02 FA01 FA02 FB12 GB01 GB10

Claims (1)

[Claims] 1. A gate signal line extending in one direction and juxtaposed on a liquid crystal side surface of one of transparent substrates opposed to each other via a liquid crystal and insulated by the gate signal line. A thin film transistor driven by the supply of a scanning signal from the gate signal line, and a video signal from the drain signal line via the thin film transistor are supplied to a drain signal line intersecting the pixel line and a pixel region surrounded by the signal line. A pixel electrode, a first electrostatic protection circuit connected to each of the odd-numbered drain signal lines via a diode, and an even-numbered drain signal line on one side outside the display region comprising a set of pixel regions; And a second electrostatic protection circuit connected via a diode; and a conductive layer for connecting the first and second electrostatic protection circuits to a common electrode on the other transparent substrate side. Is divided into at least a portion connected to the first electrostatic protection circuit and a portion connected to the second electrostatic protection circuit, and the division is performed from substantially the center of the conductive layer. A liquid crystal display device comprising: a plurality of separation portions reaching an outer contour of a conductive layer.