JPH10339880A - Liquid crystal display device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent a delay difference of a video signal from occurring for each video signal line, thereby ensuring uniformity of luminance on a display surface. SOLUTION: A video signal line for supplying a video signal to each pixel region is formed on a liquid crystal side surface of one of the transparent substrates opposed to each other via a liquid crystal, and an image of the video signal line is formed. In a liquid crystal display device which is formed in the vicinity of a signal supply terminal so as to be bent so as to match a pitch of an electrode of a video drive circuit connected to the video signal supply terminal, the video signal line is connected to a pixel region side. Extending from the first
The first metal layer and the second metal layer are formed so as to partially overlap each other, and include a first metal layer and a second metal layer extending to the video signal supply terminal. The length or width of each of the first metal layers up to each extending end is set such that the wiring resistance of each video signal line formed with the second metal layer is substantially the same.

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 surface of one of a pair of transparent glass substrates which are arranged to face each other with a liquid crystal interposed therebetween. A scanning signal line arranged in the y direction and a video signal line insulated from the scanning signal line and extending in the y direction and arranged in the x direction are formed, and a rectangle surrounded by these signal lines is formed. A pixel region is formed in each region of the shape.

To each pixel region, a thin film transistor turned on by the supply of a scanning signal (voltage) from a scanning signal line, and a video signal (voltage) from a video signal line are applied via the turned on thin film transistor. Pixel electrode to be provided.

It is needless to say that a display area is constituted by an area where these pixel electrodes are gathered.

A scanning signal is supplied to each scanning signal line from a scanning drive circuit externally mounted on or mounted on the transparent glass substrate. Each video signal line is also supplied to the transparent glass substrate. A video signal is supplied from an external or mounted video drive circuit.

Here, the scanning drive circuit is composed of a plurality of semiconductor ICs.
, And each semiconductor IC is responsible for a plurality of adjacent scanning signal lines that are grouped. Similarly, the video drive circuit is also composed of a plurality of semiconductor ICs, and each semiconductor IC is responsible for a plurality of video signal lines adjacent to each other, which are grouped.

For this reason, a portion (terminal portion) of the scanning signal line connected to the scanning drive circuit is provided with each scanning signal extending from the display area in order to match the pitch of each electrode of the scanning driving circuit. Usually, the lines are formed in a pattern converging with each other near the scanning drive circuit.

Similarly, also in the video signal line, portions extending from the display area are formed in a pattern such that they converge in the vicinity of the video drive circuit.

[0009]

In the liquid crystal display device having such a configuration, the resolution has been dramatically improved in recent years, and accordingly, the selection time of the video signal per one video signal line is extremely short. It has become to.

Thus, when each video signal line is formed in the above-described pattern in the vicinity of the video drive circuit, the wiring resistance differs from each video signal line as viewed from the video drive circuit, and the time constant is also different for each video signal line. It is becoming impossible to disregard that the signal lines are different.

This is because, in the video signal supplied to the display area, a delay difference occurs for each of the video signal lines, and unevenness in luminance on the display surface becomes conspicuous.

The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent a delay difference in a video signal from being generated for each video signal line, and thereby to reduce the luminance of a display surface. It is an object of the present invention to provide a liquid crystal display device capable of ensuring uniformity of the liquid crystal display.

[0013]

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, a video signal line for supplying a video signal to each pixel area is formed on a liquid crystal side surface of one of the transparent substrates opposed to each other with a liquid crystal interposed therebetween. In a liquid crystal display device which is formed in the vicinity of a video signal supply terminal so as to be bent to match a pitch of an electrode of a video drive circuit connected to the video signal supply terminal, the video signal line is provided in a pixel region. A first metal layer extending from the side and a second metal layer extending to the video signal supply terminal, and the first metal layer and the second metal layer are formed so as to partially overlap each other. And each of the first and second metal layers is formed such that the wiring resistance of each video signal line is substantially the same.
The length or width up to each extending end of the metal layer is set.

In the liquid crystal display device thus configured, the wiring resistances of the video signal lines formed by the first metal layer and the second metal layer are substantially the same, and the time constant does not vary. become.

For this reason, it is possible to ensure the uniformity of the luminance on the display surface.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] An active matrix type liquid crystal display device called COG (Chip on Grass) which is one embodiment of the liquid crystal display device according to the present invention will be described below with reference to the drawings.

Schematic Configuration of TFT Substrate First, FIG. 2 shows a liquid crystal of a transparent glass substrate 1, which is a so-called TFT substrate, out of a pair of transparent glass substrates disposed to face each other via a liquid crystal. It is a top view which shows the structure of a side surface. Although another transparent glass substrate (referred to as a filter substrate with respect to the TFT substrate) disposed opposite to the TFT substrate is not shown, the transparent glass substrate is disposed opposite to the dashed line frame A in the figure as an outer contour. On the liquid crystal side, a common electrode (transparent electrode) common to each pixel is formed, and a color filter having a different color is formed for each corresponding pixel.

On the surface of the transparent glass substrate 1 on the liquid crystal side, there are formed scanning signal lines (gate signal lines) 2 extending in the x direction in the figure and juxtaposed in the y direction. A video signal line (drain signal line) 3 extending in the y-direction and juxtaposed in the x-direction is formed insulated.

Each rectangular area surrounded by each of the signal lines becomes a pixel area, and a display area is configured by a set of these pixel areas.

A pixel electrode, a thin film transistor, and the like are formed in each of the pixel regions, and the detailed configuration thereof will be described later.

Each scanning signal line 2 has, for example, a left end outside a portion corresponding to the outer contour of another transparent glass substrate disposed oppositely via a liquid crystal (a sealing material is formed in this portion). To the transparent glass substrate 1
Are connected to the electrodes of the semiconductor IC 5 mounted by face-down bonding.

The semiconductor IC 5 functions as a scan drive circuit for supplying a scan signal to the scan signal line 2.

The semiconductor ICs 5 are composed of a plurality, and each semiconductor IC 5 is responsible for a plurality of scanning signal lines 2 which are sequentially grouped by an appropriate number.

Further, a terminal 6 for inputting a signal for driving each of these semiconductor ICs 5 is formed around the transparent glass substrate 1, and this terminal 6 is connected to an electrode of the semiconductor IC. .

That is, a signal from an external circuit, which is an external component of the liquid crystal display device, is input to a semiconductor IC 5 from a terminal 6 formed around the transparent glass substrate 1, and a scanning signal formed by the semiconductor IC 5 Are supplied to the scanning signal line 2.

As is clear from FIG. 1, a portion (terminal portion) of each scanning signal line 2 connected to the semiconductor IC 5.
In order to match the pitch of each electrode of the semiconductor IC 5, each scanning signal line 2 extending from the display area is formed in a pattern converging with each other near the semiconductor IC 5.

Each of the video signal lines 3 has, for example, a portion corresponding to the outer contour of another transparent glass substrate whose lower end is opposed via a liquid crystal (a sealing material is formed on this portion). And is connected to the electrode of the semiconductor IC 7 mounted on the transparent glass substrate 1.

The semiconductor IC 7 functions as a video drive circuit for supplying a video signal to the video signal line 3.

The semiconductor ICs 7 are composed of a plurality, and each semiconductor IC 7 is responsible for a plurality of video signal lines 3 which are sequentially grouped by an appropriate number.

Further, a terminal 8 for inputting a signal for driving each of these semiconductor ICs 7 is formed around the transparent glass substrate 1, and this terminal 8 is connected to an electrode of the semiconductor IC 7. .

That is, a signal from an external circuit serving as an external component of the liquid crystal display device is input to a semiconductor IC 7 from a terminal 8 formed around the transparent glass substrate 1 and a video signal formed by the semiconductor IC 7 is formed. Are supplied to the video signal line 3.

As is apparent from FIG. 2, a portion (terminal portion) of each video signal line 3 connected to the semiconductor IC 7.
In order to match the pitch of each electrode of the semiconductor IC 7, each video signal line 3 extending from the display area is formed in a pattern converging with each other near the semiconductor IC 7.

Configuration of Pixel Region FIG. 3 is a plan view showing details of the configuration of a pixel region surrounded by scanning signal lines 2 adjacent to each other and video signal lines 3 adjacent to each other. FIG. 4 is a sectional view taken along line VI-VI of FIG.

In FIG. 3, a scanning signal line 2 extending in the x direction and juxtaposed in the y direction is provided on the surface of the transparent glass substrate 1 on the liquid crystal side. This scanning signal line 2 is made of, for example, Al,
The surface is anodized to form an oxide film. However, it is needless to say that the material is not limited to this material and may be another metal layer.

Then, substantially the entire surface of the transparent glass substrate 1 is covered with, for example, Si so as to cover the scanning signal lines 2.
An insulating film 10 made of an N film is formed.

The insulating film 10 serves as an interlayer insulating film in a region where the scanning signal line 2 intersects with the video signal line 3, as a gate insulating film in a region where a thin film transistor TFT described later is formed, and further, as described later. In the formation region of the additional capacitance element Cadd, as a dielectric film,
Each one works.

The island-shaped semiconductor layer 11 is formed on the upper surface of the insulating film and in the region where the thin film transistor is to be formed.

The formation region of the thin film transistor TFT is formed, for example, in the lower left portion of the pixel region in the figure, and is a region that overlaps a part of the scanning signal line 2. Scan signal line 2
Is to have a function as a gate electrode of the thin film transistor TFT.

As the semiconductor layer 11, so-called i-type amorphous Si is used. By forming a drain electrode and a source electrode on the surface of the semiconductor layer 11, a so-called inverted staggered MIS transistor is formed. In this case, the drain electrode and the source electrode are formed simultaneously with the video signal line (therefore, the material is the same).

That is, there is a video signal line 3 extending in the y direction in the figure and juxtaposed in the x direction. A part of the video signal line 3 is extended to form a drain electrode 3D. The source electrode 3S is formed so as to keep a gap corresponding to a predetermined channel length from the drain electrode.

The source electrode 3S is a portion connected to the pixel electrode 13 described later in detail, and an extension for securing this connection region is provided on the pixel region side.

In this case, the video signal line 3 and the drain electrode 3D and the source electrode 3S formed simultaneously with the video signal line 3 are formed by a laminated film of Cr and Al sequentially laminated.

Further, almost the entire surface of the transparent glass substrate 1 covering the video signal lines 3 and the like formed as described above is provided.
For example, a protective film 12 made of a SiN film is formed. This protective film 12 is mainly made of the thin film transistor TF
Avoid direct contact of the liquid crystal with T, thereby
It is possible to prevent the characteristics of the thin film transistor TFT from deteriorating.

A pixel electrode 13 made of ITO (Indium-Tin-Oxide) is formed in a pixel region on the upper surface of the protective film 12. In this case, a contact hole 14 for exposing a part of the extension of the source electrode 3S of the thin film transistor TFT is formed in the protective film 12 in advance, and the pixel electrode 13 is connected to the source electrode 3S through the contact hole 14. Electrical connection can be achieved.

The pixel electrode 13 is a thin film transistor T
It is formed so as to be partially overlapped with another adjacent scanning signal line 2 different from the scanning signal line 2 for driving the FT. As a result, the additional capacitance element Cadd is formed between the scanning signal line 2 and the pixel electrode 13, and the dielectric film includes the insulating film 10 and the protective film 12.

In the pixel region thus configured, the thin film transistor TFT is turned on by the supply of the scanning signal (voltage) from the scanning signal line 2, and the video signal from the video signal line 3 is turned on through the turned on thin film transistor TFT. (Voltage) can be applied to the pixel electrode 13.

When the thin film transistor TFT is turned off, the video signal is stored in the pixel electrode 13 by the additional capacitance element Cadd for a long time.

The connecting portion Figure 1 with the semiconductor IC of the video signal lines is a plan view showing the details of the connection portion between the semiconductor IC7 of the video signal line 3.

Although FIG. 2 shows each of the video signal lines 3 connected to one semiconductor IC 7, each of the video signal lines 3 connected to another semiconductor IC 7 has the same configuration. Has become.

Each of the scanning signal lines 3 extending in parallel with each other from the display area side is formed of a laminated film composed of a sequential lamination of Cr and Al, as described above. A shown in FIG. 5A), and extends so as to extend toward the semiconductor IC 7 while changing its running direction.

That is, as shown in FIG.
Among the video signal lines 3 in charge of 7, the video signal line 3 positioned at the center extends as it goes straight, but all the other video signal lines 3 positioned on both sides thereof, respectively. Is bent toward the center video signal line 3 side,
Further, each video signal line 3 is bent again so as to be parallel to each other, and extends to a position facing each electrode 7a of the semiconductor IC 7 as it is.

From this, each video signal line 3 connected to the semiconductor IC 7 has the shortest wiring length in the video signal line 3 located at the center thereof, and is located outside in the video signal lines on both sides thereof. It is in a relationship that it becomes longer sequentially.

Since the line widths of the video signal lines 3 are usually made equal in order to equalize the wiring pitches, their wiring resistances are also the smallest in the video signal line 3 located at the center, and the video signals on both sides thereof are small. The relationship is such that as the signal line is positioned on the outside, it gradually increases.

In this embodiment, in view of this, Cr and Al
Signal line 3 composed of a laminated film formed by sequentially laminating
In the wiring path to the electrode 7a of the semiconductor IC 7,
The configuration is such that it extends halfway in proportion to the length of the wiring path.

That is, since the length of the video signal line 3 at the center is the shortest, the video signal line 3 composed of a laminated film composed of a sequential lamination of Cr and Al is also extended the shortest, and is sequentially extended to the outside. Are arranged so as to extend sequentially longer accordingly.

Then, a video signal line 3 composed of a laminated film composed of these Cr and Al layers in sequence and a semiconductor IC
The connection with each of the electrodes 7 is made via another conductive layer 20 having a higher resistance value than the laminated film.

In the case of the present embodiment, an ITO film formed simultaneously with the formation of the pixel electrode 13 is used as the conductive layer 20, and Cr and Al are formed from the display region beyond the sealing material (dashed-dotted line frame A). The semiconductor IC is completely covered with the video signal line 3 composed of a laminated film of
7 is formed to extend to the position of the corresponding electrode 7a.

It is needless to say that the conductive layer 20 made of the ITO film functions as a part of the video signal line 3. , And also functions reliably as a terminal for connecting to the electrode 7a of the semiconductor IC 7.

Each of the video signal lines 3 including the ITO film has an extremely small difference in wiring resistance caused by a difference in length by adjusting the length of the video signal line made of Cr and Al. It will be configured.

From this, it is possible to prevent a delay difference of a video signal from being generated for each of the video signal lines, thereby making it possible to ensure uniformity of luminance on the display surface.

Embodiment 2 Embodiment 1 described above is directed to a liquid crystal display device in which the pixel electrode 13 in the display section is formed on the upper surface of the protective film 12, that is, the liquid crystal display device in which the pixel electrode 13 is formed as the uppermost layer. It is explained.

However, it goes without saying that the present invention is also applied to a liquid crystal display device in which the pixel electrode is formed as the lowermost layer.

Structure of Pixel Region FIG. 5 is a plan view showing the structure of a pixel region of a liquid crystal display device in which pixel electrodes are formed as the lowermost layer. FIG. 6 is a sectional view taken along the line II in FIG. 6, FIG. 7 is a sectional view taken along the line II-II, and FIG. 7 is a sectional view taken along the line III-III.

In FIG. 5, a scanning signal line is represented by GL, a video signal line is represented by DL, and a pixel electrode is represented by ITO1.

Here, as shown in FIGS. 7 and 8, the scanning signal line Gl is composed of a conductive layer g1 made of Al, the surface of which is anodized to form an oxide film AOF. . As a result, generation of hillocks, which is a specific phenomenon of Al, is prevented by the oxide film AOF.

The video signal line DL is composed of a laminated film composed of a sequential lamination of Cr and Al. Accordingly, the drain electrode SD2 and the source electrode Sd3 of the thin film transistor TFT are composed of a laminated film composed of the same material. I have.

Gate oxide film G of thin film transistor TFT
Since I is formed by etching with the same pattern as the semiconductor layer AS formed thereon, it is formed without completely covering the pixel electrode ITO1.

In addition, as shown in FIG. 6, since the protective film PSV1 has a structure in which an opening is provided in the region of the pixel electrode ITO1, the light transmittance is improved by the gate oxide film GI and the protective film PSV1. The configuration is not obstructed.

The connection of the source electrode SD1 of the thin film transistor TFT to the pixel electrode ITO1 can be made directly without providing a contact hole in the gate oxide film GI.

[0071] The connection portion between the semiconductor IC of the video signal line 9 is a view corresponding to FIG. 1 is a plan view more specifically shown than FIG.

Also in FIG. 9, the drain video signal drive circuit is configured to be mounted on a transparent substrate by COG (Chip on Grass), and the pixel pitch of the display area and the terminal pitch for connection to the drain video signal drive circuit are provided. Therefore, the layout between the display area and the drain video signal drive circuit mounting portion is arranged so that a part of the drain signal line is arranged in an oblique direction as shown in FIG.

FIG. 10A is a diagram showing only the diagonal wiring portion laid out between the display region of the drain video signal line and the drain video signal drive circuit in FIG.

In the same drawing, the vertical structure (layer structure) of the wiring portion is different from the boundary where a seal material for overlaying two transparent substrates is applied or printed.

That is, the drain video signal drive circuit mounting portion has a two-layer structure of PAS / ITO from the uppermost layer with the transparent substrate film surface facing upward with respect to the sealing material application (printing) portion. In this configuration, no Al / Cr film is used outside the sealing material, so that electrolytic corrosion is prevented from being generated in this portion.

The ITO is formed in the same step as the pixel electrode ITO1, and the PAS is formed as an extension of the protective film PSV1.

The display area side of the sealing material application (printing) portion is PAS from the uppermost layer with the transparent substrate film surface side up.
/ ITO double layer structure, PAS / Al / Cr / I
There is a four-layer structure of TO.

Here, the pattern of the drain signal line having the structure of Al / Cr / (ITO) is shown in FIG.

In this embodiment, Al / Cr
Since the two layers are patterned using the same photomask, the four-layer pattern of PAS / Al / Cr / ITO is formed using three photomasks.

Here, at the time of pattern design, the sheet resistance of the ITO film was set to 20 Ω / □, the sheet resistance of the Al / Cr film was set to 0.09 Ω / □, and the wiring resistance of the diagonal wiring portion was determined to be Al / Cr. ITO three orders of magnitude different from membrane
It greatly depends on the pattern width and length of the film.

Thus, by adjusting the length of the Al / Cr film having a low sheet resistance among the conductive films forming the oblique wiring, the wiring resistance of the drain video signal line is made constant in the substrate. be able to.

In the above-described embodiment, the patterns of the ITO layer and the Al / Cr layer forming the oblique wiring are laid out to have the same width in the previous line. That is, in one diagonal wiring block corresponding to one drain video signal driving circuit, the wiring corresponding to the end of the block having the longest diagonal wiring is ITO having a high sheet resistance.
The layers need to be as long as possible.

Therefore, the Al / Cr layer having a lower sheet resistance than the ITO layer is laid out so as to be the longest at the end of the block, and the Al / Cr layer is formed so that no Al / Cr is formed outside the sealing material. ing. At the center of the block, the Al / Cr layer is laid out so as to be the shortest.

FIG. 11 is an enlarged view of a portion A in FIG. FIG. 12 shows B in FIG.
The section is enlarged. From this, it becomes clear that the length of the Al / Cr layer is gradually changing.

In the above-described embodiment, the difference in the wiring resistance caused by the difference in the length of the video signal line is reduced by adjusting the length of the video signal line made of Cr and Al. Needless to say, the present invention is not limited to this.

For example, it goes without saying that this may be performed by changing the width of the video signal line composed of Cr and Al extending from the display area.

That is, within the range of the width of the ITO film, the width of the video signal line at the central portion may be minimized, and the width may be sequentially increased outside the central portion. Further, it goes without saying that the entire wiring resistance of the video signal line may be made the same by setting the length and the width.

In the above-described embodiment, the video signal lines formed in the display area are formed by using a laminated film composed of Cr and Al in order. However, the present invention is limited to such materials and the laminated structure. It goes without saying that it may be formed of another material or a single layer structure.

In the above-described embodiment, the ITO film is used in the portion where the video signal line can be connected to the semiconductor IC. However, the present invention is not limited to this material and is suitable for forming the terminal portion. It goes without saying that another metal layer may be used.

Further, in this embodiment, the so-called COG type is described, but it is needless to say that the present invention is not limited to this.

In the portion where the video signal line extending from the display area beyond the sealant is connected to the video drive circuit (semiconductor IC), the video signal line is made to coincide with the electrode pitch of the video drive circuit. This is because the present invention can be applied as long as the patterns are bent and converged with each other.

[0092]

As is apparent from the above description,
ADVANTAGE OF THE INVENTION According to the liquid crystal display device by this invention, it can prevent that the delay difference of a video signal arises for every line of a video signal line, and can thereby ensure the uniformity of the brightness | luminance of a display surface.

[Brief description of the drawings]

FIG. 1 is a plan view of an essential part showing one embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is a schematic plan view showing one embodiment of a TFT substrate of the liquid crystal display device according to the present invention.

FIG. 3 is a plan view showing one embodiment of a pixel region of the liquid crystal display device according to the present invention.

FIG. 4 is a sectional view taken along line VI-VI of FIG. 3;

FIG. 5 is a plan view showing another embodiment of the pixel region of the liquid crystal display device according to the present invention.

FIG. 6 is a sectional view taken along the line II of FIG. 5;

FIG. 7 is a sectional view taken along line II-II in FIG.

FIG. 8 is a sectional view taken along line III-III in FIG.

FIG. 9 is a plan view of a principal part showing another embodiment of the liquid crystal display device according to the present invention.

FIG. 10 is an explanatory view showing a part of the plan view shown in FIG. 9;

FIG. 11 is an enlarged view of a portion A in FIG.

FIG. 12 is an enlarged view of a portion B in FIG.

[Explanation of symbols]

1: transparent glass substrate, 3: video signal line, 7: semiconductor IC
(Image drive circuit), 20 ... conductive layer (ITO film).

Claims (2)

[Claims] An image signal line for supplying an image signal to each pixel region is formed on a liquid crystal side surface of one of the transparent substrates opposed to each other with a liquid crystal interposed therebetween. In a liquid crystal display device which is formed in the vicinity of a video signal supply terminal so as to be bent so as to match a pitch of an electrode of a video drive circuit connected to the video signal supply terminal, the video signal line is a pixel region A first metal layer extending from the side and a second metal layer extending to the video signal supply terminal, and the first metal layer and the second metal layer are formed so as to partially overlap each other. And the length of each video signal line formed by the first metal layer and the second metal layer to the extending end of each first metal layer so that the wiring resistance is substantially the same. Or, the feature is that the width is set Liquid crystal display device. 2. The liquid crystal display device according to claim 1, wherein the second metal layer is made of an ITO film.