JP2000155337A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a holding capacitor element of a large capacity without affecting an aperture ratio by constituting a first capacitor element of successively laminated first and second electrodes and constituting a second capacitor element of second and third electrodes. SOLUTION: An insulating film 4 is formed to cover a scanning signal line 2 and a holding capacitor line 3 over the entire area on a substrate 1. A video signal line 6 and a pixel electrode 7 are formed on the surface of this insulating film 4. A protective film 8 is formed to cover the pixel electrode 7 and the video signal line 6. A holding capacitor line 9 is formed in superposition on a holding capacitor line 3 on the surface of the protective film 8. The holding capacitor element is composed of the successive laminate of the holding capacitor line 3 (the first electrode), the insulating film 4 (the first insulating film), the pixel electrode 7 (the second electrode), the protective film 8 (the second insulating film) and the holding capacitor line 9 (the third electrode). The first holding capacitor element is composed of the holding capacitor line 3 and the pixel electrode 7 and the second holding capacitor line 7 is composed of the pixel electrode 7 and the holding capacitor line 9.

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 An active matrix type liquid crystal display device extends in the x direction and is juxtaposed in the y direction on a liquid crystal side surface of one of transparent substrates opposed to each other via a liquid crystal. Scanning signal lines, and video signal lines that are insulated from the scanning signal lines and extend in the y-direction and are arranged in parallel in the x-direction, are formed in regions surrounded by these signal lines, respectively.
A switching element driven by supplying a scanning signal (voltage) from one scanning signal line, a pixel electrode to which a video signal from one video signal line (voltage) is applied via the switching element; It is provided with.
For this reason, each pixel of this type of liquid crystal display device has a selection time during which the switching element is turned on and a voltage is input, and a non-selection time during which the switching element is turned off and holding the charge. I do. In this case, a storage capacitor is also formed in each pixel to prevent leakage of accumulated charge when the switching element is in the OFF state.
That is, this storage capacitor element is formed by overlapping a part of the pixel electrode with a part of the storage capacitor line via the dielectric film.

[0003]

However, in the liquid crystal display device having such a configuration, an attempt has been made to increase the overlapping area between the storage capacitor line and the pixel electrode in order to improve the image quality. It has been pointed out that the aperture ratio of the pixel is reduced. Since the overlap region of the storage capacitor line and the pixel electrode is a region that does not contribute to the aperture ratio, increasing the region is because the region that can contribute to the aperture ratio must be reduced. The present invention has been made based on such circumstances, and an object of the present invention is to provide a liquid crystal display device including a storage capacitor having a large capacitance without affecting the aperture ratio.

[0004]

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 includes a capacitor in the pixel, and the capacitor includes a first electrode, a first insulating film, a second electrode, and a second electrode.
, A first electrode, a second electrode, and a third electrode, each of which is a pixel electrode, and a first electrode and a second electrode. The first and second electrodes constitute a first capacitance element, and the second and third electrodes constitute a second capacitance element. In the liquid crystal display device having such a configuration, it is possible to obtain the above-described capacitive element formed of a laminate as a configuration in which two capacitive elements are connected in parallel. This is the first
This means that the capacitance can be increased without increasing the area of the electrode, which must be made of an opaque material, among the first, second, and third electrodes. Therefore,
A large-capacitance element can be obtained without affecting the aperture ratio.

[0005]

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. [Embodiment 1] FIG. 1A is a view showing one embodiment of a liquid crystal display device according to the present invention, and is a plan view showing one pixel thereof. For this reason, the configuration shown in the figure is exactly the same for the vertically adjacent pixels and the left and right adjacent pixels. FIG. 2B is a cross-sectional view taken along line bb of FIG.

The liquid crystal display device shown in FIG. 1 is a so-called vertical electric field type, in which a pixel electrode is formed on a substrate side shown in FIG. A counter electrode (transparent electrode) is formed on a liquid crystal side surface of a substrate (not shown). An electric field is generated in each substrate in the vertical (vertical) direction to control the light transmittance of the liquid crystal, which is why it is called a vertical electric field method.

A scanning signal line 2 extending in the x direction below the pixel is provided on the surface of the substrate 1 on the liquid crystal side in FIG.
Are formed. Further, a storage capacitance line 3 extending in the x direction is formed at the center of the pixel. This storage capacitance line 3
Are formed of, for example, the same material as that of the scanning signal line 2, and can be formed in the same step as that of the scanning signal line 2.

[0010] An insulating film 4 is formed over the entire area of the substrate 1 so as to cover the scanning signal lines 2 and the storage capacitor lines 3. The insulating film 4 serves as an interlayer insulating film at the intersection of the scanning signal line 2 and the holding capacitor line 3 for a video signal line 6 described later, and as a gate insulating film in a region where the thin film transistor TFT is formed. Function as a dielectric film. First, on the surface of the insulating film 4, a semiconductor layer 5 is formed in a region where the thin film transistor TFT is formed. The semiconductor layer 5 is made of, for example, amorphous Si, and is formed on the scanning signal line 2 so as to overlap a portion close to the video signal line 6. Thus, a part of the scanning signal line 2 also serves as a gate electrode of the thin film transistor TFT.

As shown in FIG. 1, a video signal line 6 extending in the y direction and juxtaposed in the x direction is formed on the surface of the insulating film 4. And the video signal line 6 is
A drain electrode 6 </ b> A formed so as to extend to a part of the surface of the semiconductor layer 5 of the thin film transistor TFT is integrally provided. In this case, the thin film transistor T
An FT source electrode 6B is also formed simultaneously with the formation of the video signal line 6, and this source electrode 6B is
Is formed so as to extend to a part of the formation region.

The surface of the semiconductor layer 5 corresponding to the interface between the drain electrode 6A and the source electrode 6B of the thin film transistor TFT is doped with phosphorus (P) to form a high-concentration layer. , 6B. In this case, the semiconductor layer 5
The high concentration layer is formed in advance on the entire surface of the surface,
After forming the electrodes 6A, 6B, the electrodes 6A, 6B
The above structure can be obtained by etching a high-concentration layer other than the electrode forming region using B as a mask.

Then, a pixel electrode 7 is formed on the insulating film 4. The pixel electrode 7 is connected to the video signal line 6 of the corresponding pixel and the video signal line 6 of the adjacent pixel on the right side in the drawing.
(Not shown), and a source electrode of the thin film transistor TFT formed in a region surrounded by the scanning signal line 2 of the corresponding pixel and the scanning signal line 2 (not shown) of the pixel adjacent to the upper side in the figure. 6B, in other words, the electrical connection is formed. Here, the pixel electrode 7 is formed of a transparent conductive film (for example, Indium-Tin-Oxide). This is because the region where the pixel electrode 7 is formed is a light passing region.

A protective film 8 is formed on the entire surface of the substrate 1 so as to cover the pixel electrodes 7 and the video signal lines 6 and the like. The protective film 8 is superimposed on the storage capacitance line 3 on the surface of the protective film 8. The storage capacitance line 9 is formed. This storage capacitance line 9
Are the storage capacitor lines 9 of the pixels adjacent to the left and right in the figure.
Are connected to each other.

With such a configuration, the storage capacitor element includes the storage capacitor line 3 (first electrode), the insulating film 4 (first insulating film), the pixel electrode 7 (second electrode), and the protective film 8 ( A second insulating film) and a storage capacitor line 9 (third electrode) in this order, and the storage capacitor line 3 and the pixel electrode 7
Is connected to the pixel electrode 7 and the storage capacitor line 9 in the second
And the capacity can be increased. Further, since the first storage capacitor and the second storage capacitor have a laminated structure, the occupied area required for them can be reduced.

[Embodiment 2] FIG. 2A shows another embodiment of the liquid crystal display device according to the present invention, and is a plan view showing one pixel thereof. For this reason, the configuration of FIG.
The vertically adjacent pixels and the right and left adjacent pixels are exactly the same. FIG. 2B is a cross-sectional view taken along line bb in FIG.

The liquid crystal display device shown in FIG. 1 is of a so-called horizontal electric field type, in which a pixel electrode and a counter electrode are formed adjacent to the pixel electrode on the substrate side shown in FIG. Has become. For this reason, an electrode corresponding to the counter electrode is not formed on a liquid crystal side surface of another substrate (not shown) which is disposed to face the substrate via the liquid crystal. An electric field is generated in each of the substrates in the parallel (lateral) direction to control the light transmittance of the liquid crystal.

On the liquid crystal side surface of the substrate 1 in FIG. 2A, a scanning signal line 2 extending in the x direction below the pixel is provided.
Are formed. A counter voltage signal line 10 extending in the x direction is formed at the center of the pixel. The counter voltage signal line 10 is made of, for example, the same material as the scanning signal line 2, and can be formed in the same process as the scanning signal line 2. This counter voltage signal line 10 also has the function of the storage capacitor line of the liquid crystal display device shown in FIG.

The counter voltage signal line 10 has a counter electrode 11 formed integrally therewith. This counter electrode 1
3 are formed, for example, three each extending vertically in the figure with the counter voltage signal line 10 interposed therebetween. That is, one counter electrode 11 is formed adjacent to a video signal line 6 of the pixel described later, and another one of the other electrodes adjacent to the video signal line 6 of the pixel adjacent to the pixel on the right side in the drawing. The counter electrode 11 is formed, and further, the remaining one counter electrode 11 disposed therebetween is formed.

An insulating film 4 is formed over the entire area of the substrate 1 so as to cover the scanning signal line 2 and the counter voltage signal line 10 (counter electrode 11). The insulating film 4 serves as an interlayer insulating film at an intersection with the scanning signal line 2 and the counter voltage signal line 10 for a video signal line 6 described later.
It functions as a gate insulating film for the region where the thin film transistor TFT is formed and as a dielectric film for the region where the storage capacitor element is formed.

First, a semiconductor layer 5 made of, for example, amorphous Si is formed on the surface of the insulating film 4 in a region where the thin film transistor TFT is formed. The semiconductor layer 5 is formed on the scanning signal line 2 so as to overlap with a portion adjacent to the video signal line 6, and a part of the scanning signal line 2 also serves as a gate electrode of the thin film transistor TFT.

As shown in FIG. 1, a video signal line 6 extending in the y direction and juxtaposed in the x direction is formed on the surface of the insulating film 4. And the video signal line 6 is
A drain electrode 6 </ b> A formed so as to extend to a part of the surface of the semiconductor layer 5 of the thin film transistor TFT is integrally provided. In this case, the thin film transistor T
The source electrode 6B of the FT is formed simultaneously with the formation of the video signal line 6, and this source electrode 6B is connected to the pixel electrode 7 described below.
It is formed integrally with.

The surface of the semiconductor layer 5 corresponding to the interface between the drain electrode 6A and the source electrode 6B of the thin film transistor TFT is doped with phosphorus (P) to form a high concentration layer in the case of FIG. Is the same as

On the insulating film 4, the pixel electrode 7 formed integrally with the source electrode 6B of the thin film transistor TFT is formed as described above. This pixel electrode 7 has two opposing electrodes 11 adjacent on the left side in the figure.
And between the two opposing electrodes 11 adjacent to each other on the right side in the drawing, and are formed adjacent to the respective opposing electrodes, and these pixel electrodes 7 overlap with the opposing voltage signal lines 10. Almost connected to each other at
It has an H 'shape.

Here, the connection portion 7A of the pixel electrode 7 formed so as to overlap with the counter voltage signal line 10 is a storage capacitor element portion, and in order to increase the capacitance as much as possible, the connection portion is It is formed to extend slightly on both sides of each pixel electrode 7.

A protective film 8 is formed over the entire surface of the substrate 1 so as to cover the pixel electrodes 7 and the video signal lines 6 and the like, and the surface of the protective film 8 holds the counter voltage signal line 10. The storage capacitance line 9 is formed so as to overlap with the capacitance line. The storage capacitor lines 9 are connected to the storage capacitor lines 9 of the pixels adjacent to the left and right sides in the drawing.

With such a configuration, the storage capacitor includes the counter voltage signal line 10 (first electrode), the insulating film 4 (first insulating film), the pixel electrode 7 (second electrode), and the protective film 8. (Second insulating film) and a storage capacitor line 9 (third electrode) in that order.
With the above, the first storage capacitor is replaced with the pixel electrode 7 and the storage capacitor line 9.
Thus, the second storage capacitance element is formed, so that the capacitance can be increased. Further, since the first storage capacitor and the second storage capacitor have a laminated structure, the occupied area required for them can be reduced.

[Embodiment 3] In each of the above embodiments, one end of the storage capacitor line 9 extends to a region outside the display region and is connected to each other in this region. Here, the display area refers to an area composed of an aggregate of pixels, and the outside thereof refers to an area outside the outermost contour of the aggregate. However, the present invention is not limited to this. When the black matrix layer is superimposed on the periphery of the aggregate of the pixels except for the central portion, the superimposed portion of the black matrix layer may be outside the display area. Good (the same applies to the following embodiments). With such a configuration, the potential of the storage capacitor can be stabilized.

[Embodiment 4] FIG. 3 shows another embodiment of the liquid crystal display device according to the present invention, and is a plan view showing one pixel thereof. This figure shows a vertical electric field type liquid crystal display device similar to that shown in FIG. 1, and the configuration is exactly the same for pixels vertically adjacent to it and pixels adjacent to its left and right.

Reference numerals similar to those in FIG. 1 have the same configuration and function. Here, a part different from the configuration in FIG. 1 is a third electrode 9A formed in each pixel. The third electrode 9A is not connected to the third electrode 9A of the pixel adjacent to the left and right in the drawing, but is connected to the third electrode 9A of the pixel adjacent to the top and bottom in the drawing. It has become. The connection of each third electrode 9A of the vertically adjacent pixel in the figure is made by, for example, a wiring layer 9B formed adjacent to the video signal line 6 of the pixel adjacent to the right side in the figure. That is, the third electrode 9A and the wiring layer 9B constitute a storage capacitor line, and this storage capacitor line is common to the pixels arranged in parallel in the y direction (the extending direction of the video signal line 6) in the drawing. It has become.

Unlike such a configuration, for example, when the other storage capacitor line is formed in the extending direction of the scanning signal line 2, the pixels driven by the scanning signal line 2 are turned on / off at the same time. In some cases, the load applied to the storage capacitor line becomes heavy and its potential fluctuates.

When one storage capacitor line of the storage capacitor element of each pixel is formed in the direction in which the video signal line 6 extends, and the other storage capacitor line is also formed in the direction in which the video signal line extends. Coupling between the video signal line 6 and the storage capacitor line may cause so-called vertical smear.

However, one storage capacitor line of the storage capacitor element of each pixel is formed in the direction in which the scanning signal line 2 extends, and the other storage capacitor line (third electrode and wiring layer) is connected to the video signal line 6.
The above-described inconvenience can be avoided when the configuration is formed in the extending direction of the above.

[Embodiment 5] FIG. 4 is a view showing another embodiment of the liquid crystal display device according to the present invention, and is a plan view showing one pixel thereof. This figure shows a liquid crystal display device of the horizontal electric field type similarly to that shown in FIG. 2, and the configuration is exactly the same for pixels vertically adjacent thereto and pixels adjacent to the left and right thereof. In the figure, the same reference numerals as those in FIG. 2 have the same configuration and function.

Here, the part different from the configuration of FIG. 2 is the third electrode 9A formed in each pixel. This third electrode 9A
Are not connected to the third electrode 9A of the pixel adjacent to the left and right in the figure, but are connected to the third electrode 9A of the pixel adjacent to the top and bottom in the figure. The connection of each third electrode 9A of the vertically adjacent pixel in the figure is made by, for example, a wiring layer 9B formed adjacent to the video signal line 6 of the pixel adjacent to the right side in the figure. That is, a storage capacitor line is formed by the third electrode 9A and the wiring layer 9B, and the storage capacitor line is common to the pixels adjacent in the y direction (the extending direction of the video signal line 6) in the drawing. I have.

The liquid crystal display device thus configured has the same effects as those of the fourth embodiment, and also has the effects specific to the configuration of the in-plane switching method. That is, in the configuration of the vertical electric field method described in the fourth embodiment, an electric field having a component parallel to the substrate may be generated between the storage capacitor line formed in the extending direction of the video signal line 6 and the pixel electrode, A so-called domain occurs in that part.

However, in this embodiment, since the light transmittance of the liquid crystal is controlled by the electric field of the component parallel to the substrate 1, such inconvenience does not occur. Further, as shown in the figure, the storage capacitor line formed in the extending direction of the video signal line 6 can be formed so as to overlap with the counter electrode 11, so that there is no fear that the aperture ratio is reduced. To play.

[Embodiment 6] In each of the above embodiments,
Each storage capacitor line extends to the outside of the display area, and is commonly connected to each other. With such a configuration, the potential of the storage capacitor can be stabilized.

Embodiment 7 In this embodiment, in each pixel, the first electrode (holding capacitance line) and the third electrode (holding capacitance line) are connected to each other by, for example, through holes. is there. That is, for example, FIG.
As shown in FIG. 5, which is a diagram corresponding to FIG. 5, a through-hole is formed in the protective film 8 and the insulating film 4 in this portion by using the area of the gap between the video signal line 6 and the pixel electrode 7, and And the third electrode are connected to each other.
By providing a new storage capacitance line different from this storage capacitance line in addition to the conventional storage capacitance line, the new storage capacitance line is inevitable to intersect with the scanning signal line 2 or the video signal line 6. There is a concern that the load on the scanning signal line 2 or the video signal line 6 will increase, thereby causing distortion in the signal waveform and causing smear. However, with the above-described configuration, the number of storage capacitance lines that intersect the scanning signal lines 2 or the video signal lines 6 is substantially one, so that the fear of occurrence of smear can be avoided.

[Embodiment 8] For the same purpose as in Embodiment 7, for example, as shown in FIG. 6 corresponding to FIG. 2, a gap between the video signal line 6 and the connection portion 7A of the pixel electrode 7 is formed. Is used to form a through hole in the protective film 8 and the insulating film 4 in this portion, and the first electrode (counter voltage signal line) and the third electrode (holding capacitance line) are connected to each other. I have.

[Embodiment 9] On the premise of the configuration shown in Embodiments 7 and 8, a first electrode and a third electrode are connected in each pixel, and a scanning signal line is extended. The storage capacitor lines are connected by connecting the pixels in the existing direction.
With such a configuration, the potential of the storage capacitor can be stabilized.

[Embodiment 10] On the premise of the configuration shown in Embodiments 7 and 8, a first electrode and a third electrode are connected in each pixel, and a video signal line is extended. The storage capacitor lines are connected by connecting the pixels in the existing direction. With such a configuration, the potential of the storage capacitor can be stabilized.

[Embodiment 11] In the structure of each of the above embodiments, one of the first electrode and the third electrode is made of ITO. In the case of a vertical electric field type liquid crystal display device, one electrode may be formed in the same step as the pixel electrode. In this case, an increase in the number of manufacturing steps can be avoided. Also,
A horizontal electric field type liquid crystal display device, wherein an IT for preventing electrolytic corrosion is provided on the surface of an external terminal of the video signal line 6 or the scanning signal line 2.
When the O film is covered, one electrode may be formed in the same step as the ITO film. If you do this,
An increase in the number of manufacturing steps can be avoided.

[Embodiment 12] In the structure of each of the above embodiments, a reference voltage is applied to the storage capacitor line, and this reference voltage is supplied from an external drive circuit. By doing so, the potential of the storage capacitor line can be stabilized, and the image quality can be improved.

In each of the embodiments described above, the capacitor is composed of the first electrode, the first insulating film, the second electrode, the second insulating film,
It is composed of a sequential laminated body with a third electrode, of which the second
Are configured as pixel electrodes. But,
The first electrode or the third electrode is not limited to this.
Needless to say, this electrode may be a pixel electrode.

[0044]

As is apparent from the above description,
ADVANTAGE OF THE INVENTION According to the liquid crystal display device by this invention, it becomes possible to provide a large capacity | capacitance storage element, without affecting an aperture ratio.

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram showing another embodiment of the pixel of the liquid crystal display device according to the present invention.

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

FIG. 4 is a configuration diagram showing another embodiment of the pixel of the liquid crystal display device according to the present invention.

FIG. 5 is a configuration diagram showing another embodiment of the pixel of the liquid crystal display device according to the present invention.

FIG. 6 is a configuration diagram showing another embodiment of the pixel of the liquid crystal display device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Scan signal line, 3 ... Storage capacity line (1st electrode), 4 ... Insulating film (1st insulating film), 5 ... Semiconductor layer, 6
... video signal line, 7 ... pixel electrode (second electrode), 8 ... protective film (second insulating film), 9 ... storage capacitor line (third electrode).

Claims (10)

[Claims] 1. A pixel having a capacitor in a pixel, the capacitor comprising a layered structure of a first electrode, a first insulating film, a second electrode, a second insulating film, and a third electrode. And any one of the first electrode, the second electrode, and the third electrode is a pixel electrode, and the first electrode and the second electrode form a first capacitor with the second electrode. A liquid crystal display device, comprising a second capacitor with the third electrode. 2. A scanning signal line extending in the x-direction and juxtaposed in the y-direction on a liquid crystal side surface of one of the transparent substrates opposed to each other with the liquid crystal interposed therebetween. Extend x
2. The liquid crystal display device according to claim 1, wherein the video signal lines arranged in the direction and pixels are formed in a region surrounded by the signal lines. 3. The storage capacitor line according to claim 2, wherein the remaining electrodes other than the pixel electrode are respectively connected to those of the pixels in the extending direction of the scanning signal line to form a storage capacitor line. Liquid crystal display device. 4. The storage capacitor line according to claim 2, wherein the remaining electrodes other than the pixel electrode are respectively connected to those of the pixels in the extending direction of the video signal line to form a storage capacitor line. Liquid crystal display device. 5. The remaining electrode except for the pixel electrode,
One electrode is connected to those in the pixel in the direction in which the scanning signal line extends to form a storage capacitor line, and the other electrode is connected to those in the pixel in the direction in which the video signal line extends to form a storage capacitor line. 3. The liquid crystal display device according to claim 2, wherein the liquid crystal display device comprises a line. 6. The storage capacitor line according to claim 3, wherein each of the storage capacitor lines extends to a position outside a display region configured as an aggregate of pixels, and is connected outside the display region. The liquid crystal display device according to any one of the above. 7. The liquid crystal display device according to claim 1, wherein the remaining electrodes other than the pixel electrode are connected in the pixel. 8. The liquid crystal display device according to claim 1, wherein one of the remaining electrodes other than the pixel electrode is made of ITO. . 9. The liquid crystal display device according to claim 3, wherein a reference voltage is supplied to the storage capacitor line. 10. The liquid crystal display device according to claim 9, wherein the reference voltage is formed by a driving circuit.