JPH10148842A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the electrolysis in liquid crystal by providing an electrode having roughly the same potential as that of a common electrode in such a way that it covers one part of a driving circuit area to mitigate the electric field between a driving circuit part and the common electrode opposed to the part. SOLUTION: An insulating film 28 is formed at the liquid crystal side of the vertical scanning circuit 12 and the horizontal circuit of a TFT substrate side and a shielding electrode 40 is formed on the insulating film 28 in such a way that it covers the vertical scanning circuit 12 and the horizontal scanning circuit. This shielding electrode 40 can be constituted with a transparent electrode by being provided concurrently with a process forming a pixel electrode 16. Moreover, it may be formed with an opague matal and in this case, there is the same effect as that at the time when a light shielding film is provided at a position relatively near driving circuits and it is possible to prevent a light entering into driving circuits due to an irregular or the like and a photoelectric current to be generated in the driving circuits due to unwanted lights can be prevented. The shielding electrode 40 is made to be the same potential as that of the common electrode 21 by making it exists along the circuits till a contact part and making it conduct the photoelectric current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and, more particularly, to a liquid crystal panel which generates a DC potential difference between opposing substrates, and more particularly to a thin film transistor (TFT) formed of a polysilicon transistor.
The present invention relates to a technique which is effective when applied to a liquid crystal display device having a drive circuit on a substrate of the (or) type.

[0002]

2. Description of the Related Art As a conventional liquid crystal display device, a simple matrix type liquid crystal display device for driving a pixel at an intersection of stripe-shaped XY electrodes and an active element (for example, a thin film transistor) for each pixel are provided. It is roughly classified into an active matrix type liquid crystal display device that performs a switching operation.

An active matrix type liquid crystal display device is characterized in that, for example, a liquid crystal driving voltage (gradation voltage) is applied to a pixel electrode through an active element such as a thin film transistor (TFT), so that there is no crosstalk between pixels. Unlike the simple matrix type liquid crystal display device, there is no need to use a special driving method for preventing crosstalk, and multi-gradation display is possible.

One of the active matrix type liquid crystal display devices is a TFT type active matrix type liquid crystal display device using an amorphous silicon transistor or a poly silicon transistor (polycrystalline silicon transistor) as a thin film transistor. It has been known.

Hereinafter, in this specification, an amorphous silicon transistor is referred to as an a-SiTr,
P-SiTr as a silicon transistor, a-SiTFT liquid crystal display using a TFT type liquid crystal display using amorphous silicon transistors, and p-SiTFT liquid crystal display using a TFT type liquid crystal display using poly-silicon transistors. It is called a device.

[0006] The a-Si TFT liquid crystal display device is widely used as a display device of a personal computer or a television.

However, in the a-Si TFT liquid crystal display device, it is necessary to provide a driving circuit for driving the liquid crystal around the liquid crystal display panel.

On the other hand, in recent years, a TFT liquid crystal display device using p-SiTr has been developed and commercialized.

In a liquid crystal display panel of a p-SiTFT liquid crystal display device, p-SiTr is formed on a quartz or glass substrate similarly to the liquid crystal display panel of an a-SiTFT liquid crystal display device.
They are arranged and formed in a matrix.

Furthermore, the operating speed of the p-SiTr is aS
Since the operation speed is higher than that of the iTr, in the liquid crystal panel of the p-SiTFT liquid crystal display device, its peripheral circuits can be formed on the same substrate.

FIG. 2A is a schematic block diagram showing a positional relationship of main parts of a liquid crystal display panel (TFT-LCD) used in a p-Si TFT liquid crystal display device, and FIG. FIG. 7B) is a cross-sectional view of FIG.

In FIG. 2, 11 is a display area, 12 is a vertical scanning circuit, 13 is a horizontal scanning circuit, 19 is a liquid crystal,
Reference numeral 5 denotes a sealing material for filling a liquid crystal 19 between two transparent substrates and bonding the substrates, and reference numeral 21 denotes a common electrode. Thus, in the p-Si TFT liquid crystal display device, the display region 11
Vertical scanning circuit unit 1 which is a peripheral driving circuit on the same substrate as
2. The horizontal scanning circuit unit 13 is formed.

FIG. 2 shows a sealing material 15 in a gap between two substrates.
There is a region in which the liquid crystal 19 is sealed (hereinafter referred to as a liquid crystal sealing region), and the vertical scanning circuit unit 1 is provided outside the liquid crystal sealing region.
2. The horizontal scanning circuit section 13 is formed.

[0014]

In the liquid crystal display device having such a configuration, the drive circuit section (vertical scan circuit section 12 and horizontal scan circuit section 13) is provided outside the liquid crystal sealing area as described above. Therefore, the wiring connecting the drive circuit section and the display area is provided below the sealant 15. Generally, in the liquid crystal panel, a spacer having a size approximately equal to the gap is mixed in the sealing material 15 in order to make the gap between the TFT substrate 10 and the color filter substrate 20 uniform. Therefore, the TFT substrate 10 and the color filter substrate 20
When the sealing material 15 is combined at a fixed interval, the sealing material 15 is cured while being pressed until the interval between the two substrates becomes constant, but by this pressing, the wiring under the sealing material 15 is changed by a spacer or the like. There is a danger of damage due to pressurization.

In order to prevent breakage of the wiring below the sealing material 15, it is conceivable to provide a drive circuit in the liquid crystal sealing region. However, in this configuration, when the liquid crystal display panel is driven, a DC voltage such as a power supply voltage or a ground voltage is applied to the drive circuit unit, and the drive output voltage is considered as an average value between the opposing common electrode. Is applied, and a constant DC potential difference is generated between the drive circuit unit and the common electrode.

For this reason, an electric field based on the DC potential difference in the liquid crystal sealing region causes electrolysis of metals, organic substances, and the like constituting the drive circuit portion and mixes them as impurities in the liquid crystal.
These impurities cause a problem that the image quality is poor.

An object of the present invention is to solve such a problem, and one object of the present invention is to alleviate an electric field between a driving circuit portion and a common electrode facing the driving circuit portion to prevent electrolysis in a liquid crystal. An object of the present invention is to provide a liquid crystal display device having a structure that can be obtained.

Another object is to apply pressure to the sealing material,
An object of the present invention is to provide a liquid crystal display device having a structure in which a wiring connecting a driving circuit portion and a display region is not damaged.

[0019]

The following is a brief description of an outline of a typical invention among the inventions disclosed in the present application. That is, (1) a first substrate, a second substrate, a liquid crystal sandwiched between the first substrate and the second substrate, and a matrix formed on the first substrate and arranged in a matrix. A pixel region formed of a plurality of switching elements, a driving circuit region for driving the switching elements, and a common electrode formed on the second substrate, and covering at least a part of the driving circuit region. Then, a liquid crystal display device having a configuration in which an electrode having substantially the same potential as the common electrode is provided.

(2) A first substrate, a second substrate, a liquid crystal sandwiched between the first and second substrates, and a matrix formed on the first substrate. A pixel region including a plurality of switching elements arranged, a driving circuit region for driving the switching elements, a common electrode formed on the second substrate, and the first substrate and the second substrate are electrically connected. The liquid crystal display device has a contact portion that is electrically connected and a wiring that electrically connects the common electrode and the contact portion.

In the liquid crystal display device configured as described above,
Since the potential of the electrode provided above the drive circuit and the potential of the common electrode become the same, the electric field applied to the liquid crystal is alleviated.
Electrolysis in the liquid crystal can be prevented.

[0022]

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

In all the drawings for describing the embodiments of the present invention, components having the same function are denoted by the same reference numerals, and their repeated description will be omitted.

[Embodiment 1] FIG. 1A is a schematic block diagram showing the positional relationship of each part of a liquid crystal display device according to an embodiment (Embodiment 1) of the present invention.
FIG. 1B is a cross-sectional view taken along line AA ′ of FIG.

In FIG. 1, 10 is a TFT substrate, 20 is a color filter substrate, 11 is a display area, 12 is a vertical scanning circuit section, 13 is a horizontal scanning circuit section, 15 is a sealant, 17
Is a contact portion, 21 is a common electrode, and 19 is a liquid crystal.
Thus, the vertical scanning circuit section 12 and the horizontal scanning circuit section 13
Are formed in a liquid crystal sealing region surrounded by the sealing material 15. Therefore, there is no need to provide a wiring for connecting the drive circuit portion and the pixel portion under the sealing material 15, and the wiring is not damaged by the pressure of the sealing material 15.

FIG. 3 is a schematic plan view showing the TFT substrate 10 of the liquid crystal display device of the present invention.

In FIG. 3, the TF in the display area 11
On the surface of the T substrate 10 on the liquid crystal side, for example, a TFT substrate 10
A gate signal line 50 extending in the horizontal direction and juxtaposed in the vertical direction, and a drain signal line 51 extending in the vertical direction and juxtaposed in the horizontal direction insulated from these gate signal lines 50. Is formed. A pixel region is formed near the intersection of each of these signal lines. A plurality of pixel regions are arranged in a matrix to form a display region 11.
In FIG. 3, only one pixel region is shown by an equivalent circuit for simplicity, and the other is omitted. 23 is a thin film transistor, 25 is a liquid crystal capacity, and 26 is a storage capacity. The thin film transistor 23 is turned on / off by a scanning signal from a gate signal line 50, and a video signal from a drain signal line 51 is written and held as a liquid crystal driving voltage (gradation voltage) to a pixel electrode via the thin film transistor 23. The pixel electrode forms one electrode of the liquid crystal capacitor 25, and the common electrode 21 shown in FIG. 1 forms the other electrode.

Reference numeral 14 denotes a group of connection terminals for connecting to an external circuit, which are generally formed around the TFT substrate 10. Various signals to the vertical scanning circuit 12 and the horizontal scanning circuit 13 are transmitted from the connection terminal group 14 via the wiring layer 53. The number of the wiring layers 53 for connecting the drive circuit section and the connection terminal group 14 is smaller than that of the wiring for connecting the drive circuit section and the pixel section, and there is a margin in the wiring width. High tolerance to pressure. As shown in FIG. 1, the common electrode 21 is provided on the color filter substrate 20, so that the connection terminals 14 and the common electrode 21 are electrically connected to each other through the distance between the TFT substrate 10 and the color filter substrate 20. It is necessary to provide a conductive member as described above. Therefore, a contact portion 17 is provided, and the common electrode 2 is provided.
A conductive paste or the like is provided between the first contact portion 1 and the contact portion 17 to perform electrical connection.

FIG. 4A is a schematic plan view showing the shape of the color filter of the color filter substrate 20, and FIG. 4B is a sectional view taken along the line CC 'of FIG. 4A. FIG. 4A omits a common electrode and the like for description. On the liquid crystal side surface of the color filter substrate 20, for example, a color filter 27 that transmits light of a specific wavelength such as red, blue, and green corresponds to each pixel portion provided on the TFT substrate 10 (not shown). Around the color filter 27, a black mask 22 that prevents unnecessary light from passing is provided. On a substantially entire surface of the color filter substrate 20, a common electrode 21 made of a transparent conductive material such as ITO (Indium-tin-oxide) is formed. Reference numeral 28 denotes a protective film.

FIG. 5 shows the positional relationship among the common electrode 21, the pixel electrode 16, and the driving circuit (the vertical scanning circuit 12 in the figure). 18 is a pixel portion, 28 is a protective film, 52 is a drive circuit portion semiconductor layer, 53 is a drive circuit wiring, 55 is a pixel portion semiconductor layer, 51 is a drain signal line, 50 is a gate signal line, and 50 is a gate signal line.
0 is a color filter substrate, 21 is a common electrode, and 22 is a black mask. Note that the thickness of each layer is described as being thicker than the actual size for easy understanding, and liquid crystals, alignment films, and the like are omitted.

The drive circuit is composed of a set of complementary MOS transistors. Each of these transistors has the same substrate as a thin film transistor whose semiconductor layer (drive circuit section semiconductor layer 52) is made of polycrystalline silicon and whose pixel section semiconductor layer 55 is made of polycrystalline silicon in the display region 11. Formed on top. The drive circuit wiring 53 wired in the drive circuit is made of a metal such as aluminum and is used as a power supply line and a signal line. For this reason, a certain voltage is supplied to the drive circuit wiring 53, and a DC potential difference is generated between the common electrode 21 and the common electrode 21 on the average of the entire drive circuit.

[Embodiment 2] FIG. 6 is a sectional view showing a liquid crystal display device according to an embodiment (Embodiment 2) of the present invention.

In the second embodiment of the present invention, the common electrode 21
Are formed except for the portion facing the drive circuit section. A transparent conductive film such as ITO for forming the common electrode 21 can be formed over the entire surface of the color filter substrate 20 and selectively etched to form a desired shape. As described above, in the case of Embodiment 2 of the present invention, although a voltage is supplied to the drive circuit, no specific voltage is generated on the surface opposite to the liquid crystal, so that the electrolysis in the liquid crystal is not performed. Can be prevented.

FIG. 7 shows the color filter substrate 20 shown in FIG.
FIG. 5 is a schematic plan view showing the shape of a common electrode 21 provided on the liquid crystal side surface of FIG. Since the common electrode 21 is one of the electrodes for driving the liquid crystal, the common electrode 21 is provided on the entire surface of the display area corresponding to each pixel. However, in order to prevent the generation of a DC potential, the common electrode 21 21 has been removed. Therefore, conventionally, the common electrode 21 is
The contact portion wiring 54 which is unnecessary since it was formed to extend from the common electrode 21 to the contact portion 17 is formed.

[Embodiment 3] FIG. 8 is a sectional view showing a liquid crystal display device according to an embodiment (Embodiment 3) of the present invention.

In FIG. 8, the insulating film 2 is provided on the liquid crystal side of the vertical scanning circuit 12 and the horizontal scanning circuit 13 on the TFT substrate side.
8 is formed, and the vertical scanning circuit 12 is further formed on the insulating film 28.
Then, the shield electrode 40 is formed so as to cover the horizontal scanning circuit 13. By providing this shielding electrode 40 at the same time as the step of forming the pixel electrode, it is possible to configure the transparent electrode. It may also be made of an opaque metal, in which case
This has the same effect as providing a light-shielding film at a position relatively close to the drive circuit, and can prevent light from entering the drive circuit due to irregular reflection in the liquid crystal and the like, which is generated in the drive circuit due to unnecessary light. Photocurrent and the like can be prevented.

The shielding electrode 40 extends to the contact portion 17 and is made conductive, so that the same potential as that of the common electrode 21 can be obtained.

FIG. 9 is a schematic plan view showing the shape of the shielding electrode 40 on the TFT substrate 10. The shielding electrode 40 is formed so as to cover the vertical scanning circuit 12 and the horizontal scanning circuit 13, and is formed so as to extend to the contact portion 17.

Although an electric field is generated between the drive circuit and the shield electrode 40, as described above, the common electrode 21 and the shield electrode 4
The potential is equal to 0, and the presence of electrodes having substantially the same potential across the liquid crystal can prevent a DC electric field from being generated in the liquid crystal.

As described above, the present invention has been specifically described based on the embodiments of the present invention. However, the present invention is not limited to the embodiments of the present invention, and various modifications may be made without departing from the gist of the present invention. It goes without saying that you get it.

[0041]

The effects obtained by the typical inventions disclosed in the present application will be briefly described as follows.

(1) The electric field between the drive circuit section and the common electrode facing the drive circuit section is relaxed to prevent electrolysis in the liquid crystal.

(2) To provide a liquid crystal display device having a structure in which wiring is not damaged by pressurization of a sealing material.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a liquid crystal display device according to an embodiment of the present invention. FIG. 1A is a schematic block diagram.
FIG. 1B is a cross-sectional view taken along line AA ′ of FIG.

FIG. 2 is a schematic configuration diagram of a conventional liquid crystal display device.
(A) is a schematic block diagram, and (b) of FIG.
Sectional drawing in the -B 'line.

FIG. 3 is a schematic plan view showing a TFT substrate of a liquid crystal display device according to an embodiment of the present invention.

FIG. 4 is a schematic configuration diagram illustrating a color filter substrate of a liquid crystal display device according to an embodiment of the present invention;
FIG. 4A is a schematic plan view, and FIG.
Sectional drawing in line C '.

FIG. 5 is a schematic cross-sectional view of a liquid crystal display device which is an embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view of a liquid crystal display device which is an embodiment of the present invention.

FIG. 7 is a schematic plan view showing the shape of a common electrode of a color filter substrate of a liquid crystal display device according to an embodiment of the present invention.

FIG. 8 is a schematic cross-sectional view of a liquid crystal display device which is an embodiment of the present invention.

FIG. 9 is a schematic plan view showing the shape of a shielding electrode of a liquid crystal display device according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... TFT board, 11 ... Display area, 12 ... Vertical scanning circuit, 13 ... Horizontal scanning circuit, 14 ... Connection terminal group, 15 ... Seal material, 16 ... Pixel electrode, 17 ... Contact part, 18 ...
Pixel section, 19: liquid crystal, 20: color filter substrate, 21
... common electrode, 22 ... black mask, 23 ... thin film transistor, 25 ... liquid crystal capacitance, 26 ... storage capacitance, 27 ... color filter, 28 ... protective film, 40 ... shielding electrode, 41 ... insulating film, 50 ... gate signal line, 51 ... Drain signal line, 52
... A drive circuit part semiconductor layer, 53. a wiring layer, 54. a contact part wiring, 52. a pixel part semiconductor layer.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Haruhisa Iida 3300 Hayano Mobara-shi, Chiba Pref.Electronic Device Division, Hitachi, Ltd. 72) Inventor Toshihiro Sato 3300 Hayano Mobara-shi, Chiba Pref.Electronic Device Division, Hitachi, Ltd.

Claims (3)

[Claims] A first substrate, a second substrate, a liquid crystal interposed between the first substrate and the second substrate, and a first liquid crystal interposed between the first substrate and the second substrate.
Having a pixel region formed of a plurality of switching elements arranged in a matrix, a driving circuit region for driving the switching elements, and a common electrode formed on the second substrate; A liquid crystal display device comprising an electrode having substantially the same potential as the common electrode so as to cover at least a part of the drive circuit region. A first substrate, a second substrate, a liquid crystal interposed between the first substrate and the second substrate, and a first liquid crystal interposed between the first substrate and the second substrate.
Having a pixel region formed of a plurality of switching elements arranged in a matrix, a driving circuit region for driving the switching elements, and a common electrode formed on the second substrate; A liquid crystal display device comprising: an electrode electrically connected to the common electrode in the drive circuit region. 3. A first substrate, a second substrate, a liquid crystal sandwiched between the first substrate and the second substrate, and a first liquid crystal interposed between the first substrate and the second substrate.
A pixel region formed on the substrate and including a plurality of switching elements arranged in a matrix, a driving circuit region for driving the switching element, a common electrode formed on the second substrate, A liquid crystal display device comprising: a contact portion that electrically connects the first substrate and the second substrate; and a wiring that electrically connects the common electrode and the contact portion.