JPH09244055A - Liquid crystal display - Google Patents

Abstract

(57) Abstract: To prevent occurrence of non-conduction when an electrode on the upper substrate side is pulled out to the lower transparent substrate side. SOLUTION: Polycrystalline silicon is used as a semiconductor layer forming a thin film transistor, and a common electrode formed on the other transparent substrate side is provided with a common electrode at least the surface of which via a sphere. In the liquid crystal display device configured to be drawn out to the conductor layer on the transparent substrate side, the conductor layer is made of the same material as the pixel electrode, and is formed to have unevenness on the surface thereof. It is connected to a low resistance external terminal that applies a voltage from.

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 so-called polycrystalline silicon TFT type liquid crystal display device.

[0002]

2. Description of the Related Art In a so-called TFT type liquid crystal display device, a gate signal is applied to a unit pixel region on a liquid crystal side surface of one transparent substrate (lower transparent substrate) among transparent substrates arranged to face each other with a liquid crystal interposed therebetween. A thin film transistor that is turned on by supplying a scanning signal from the line and a pixel electrode (transparent electrode) to which a pixel signal from the drain signal line is supplied via the turned on thin film transistor are provided.

In this case, the unit pixel region is formed by a region surrounded by gate signal lines and gate signal lines intersecting with each other.

A liquid crystal display device called a polycrystal silicon TFT type uses polycrystal silicon as a semiconductor layer constituting the thin film transistor, but not only that, but also in a display portion of the same transparent substrate. M of the same polycrystalline silicon is provided (in the vicinity of the area that is substantially the display portion)
It is usual to incorporate a drive circuit composed of an IS transistor.

In this case, in manufacturing the liquid crystal display device, in order to reduce the number of steps, the thin film transistor in the display portion and the MIS type transistor forming the drive circuit are formed in parallel.

Further, a common electrode (transparent electrode) common to each unit pixel is formed on the liquid crystal side surface of the other transparent substrate (upper transparent substrate) facing the transparent substrate thus constructed. A connection body for pulling out the common electrode to the transparent substrate side where the gate signal line and the drain signal line are formed is arranged between the transparent substrates.

The connecting body is made of, for example, a resin agent mixed with gold beads, and the gold beads are sandwiched between the common electrode on the upper transparent substrate side and the conductor layer on the lower transparent substrate side. As a result, the common electrode can be drawn out to the lower transparent substrate side.

[0008]

However, in the liquid crystal display device thus constructed, the conductor layer formed on the lower transparent substrate for drawing the common electrode to the lower transparent substrate side as described above is used. It has been pointed out that the connection by the connecting body is defective because it is formed of Al or an alloy mainly containing it.

That is, this Al or an alloy mainly composed of Al has a low resistance and is easy to process, so that it is used as a material for a drain signal line,
This conductor layer is also made of this Al or an alloy mainly containing it.

However, it has been found that this conductor layer is apt to be corroded or contaminated, and that the conduction with the gold beads is often not perfect.

In this case, when the upper transparent substrate is charged, it may cause flicker in display or decrease in contrast.

The present invention has been made under the above circumstances, and an object thereof is to provide a liquid crystal display device capable of preventing the occurrence of non-conduction when the electrode on the upper substrate side is pulled out to the lower transparent substrate side. To provide.

Another object of the present invention is to provide a liquid crystal display device which can achieve the above object without increasing the number of manufacturing steps.

[0014]

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 thin film transistor which is turned on by supplying a scanning signal from a gate signal line to a unit pixel region on the liquid crystal side surface of one of the transparent substrates which are arranged to face each other with the liquid crystal in between, and the thin film transistor. And a pixel electrode to which a pixel signal is supplied from a drain signal line via the thin film transistor, which uses polycrystalline silicon as a semiconductor layer forming the thin film transistor, and is provided on the other transparent substrate side. In a liquid crystal display device configured to lead out the formed common electrode to a conductor layer on the side of the one transparent substrate through at least a spherical body having conductivity, the conductor layer is the same as the pixel electrode. The external end of the low resistance that is made of the above material and has irregularities on its surface and that applies a voltage from the outside. And it is characterized in that it is connected to.

In the liquid crystal display device having such a configuration, at least the conductor layer in contact with the spherical body having a conductive surface is formed of the same material as the pixel electrode (transparent oxide conductive material) having excellent corrosion resistance. Therefore, in the connection with the sphere, a conductive failure due to corrosion does not occur.

Since the conductor layer has irregularities on its surface, the probability of contamination at the protrusions is low even if it is contaminated. Therefore, this contamination also causes connection to the sphere. The configuration is such that it is less likely that defective conduction will occur.

The transparent oxide conductive material is generally known to have a high resistance, but its area is relatively small, and the external electrode connected thereto is made of another material having a low resistance. If you select, there will be no problem.

As the external electrodes, there are cases where the same material as that used for forming the display portion, that is, the same material as Al or an alloy mainly containing Al is selected. in this case,
By interposing a polycrystalline silicon layer between the transparent conductive layer, which is a conductive oxide, and good conduction can be achieved, there is no problem.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a liquid crystal display device according to the present invention will be described below.

Example 1. First, FIG. 2 is a plan view showing a structure formed on a liquid crystal side surface of one transparent substrate (hereinafter, referred to as a lower transparent substrate) of transparent substrates arranged to face each other with a liquid crystal interposed therebetween. is there.

In the figure, there is a lower transparent substrate 1, and a display portion 2 is formed on this lower transparent substrate 1 occupying most of the area. A vertical scanning circuit 3 is formed on one side (left side in the figure) of the display unit 2, and a video drive circuit 4 is formed on another side (lower side in the figure).

In the display section 2, a plurality of gate signal lines 6 extending in the x direction and arranged in parallel in the y direction in the figure, and insulated from each gate signal line 6 and extending in the y direction and x. A plurality of drain signal lines 7 arranged in parallel in the direction are formed, and a unit pixel is formed in each of rectangular regions surrounded by the signal lines 6 and 7 (for example, a region surrounded by a dotted line A in the drawing). It is like this. The detailed configuration of the unit pixel in this region will be described later.

The gate signal lines 6 are sequentially supplied with scanning signals from the vertical scanning circuit 3, and the drain signal lines 7 are respectively supplied with the video driving circuit 4 in accordance with the timing. From this, pixel signals are supplied at one time.

Each of the vertical scanning circuit 3 and the video driving circuit 4 is formed by a plurality of complementary MIS transistors, and a thin film transistor formed in each pixel region of the display section 2 described later is made of polycrystalline silicon (hereinafter referred to as polysilicon). It is formed of the same polysilicon because of the relationship of ().

Each of the circuits 3 and 4 and the display unit 2 becomes a region covered by the other transparent substrate (not shown) (hereinafter, referred to as upper transparent substrate) through the liquid crystal, and is exposed from the lower transparent substrate. On the surface of the lower transparent substrate, a plurality of electrode terminals 9 connected to each of the circuits 3 and 4 via a wiring layer are formed in parallel.

Here, in a portion corresponding to the periphery of the transparent substrate in the region where the upper transparent substrate is disposed, a sealant for enclosing the liquid crystal disposed between the lower transparent substrate is formed by coating. Further, the upper and lower connectors are arranged at the portions corresponding to the four corners of the transparent substrate.

That is, the region III surrounded by the dotted line in FIG.
Details of (a) are shown in FIG. 3 (a), area III surrounded by a dotted line.
As shown in detail in FIG. 3B, a region Q (sealant application region Q) where the sealant is formed by application has a stripe shape extending along the width direction thereof. The thing is provided with the pattern formed along the extending direction, and the upper and lower connecting body 1 is provided at the end of this sealant application forming area Q.
0 is provided.

The upper and lower connection body 10 is a conductor for drawing out a common electrode common to each unit pixel on one surface of the upper transparent substrate on the liquid crystal side to one of the electrode terminals 9 on the lower transparent substrate 1 side. The specific configuration will be described later in detail.

The upper and lower connecting members 10 are
They are electrically connected to each other through the wiring layer 12 provided on the side opposite to the display portion 2 in the sealant application formation region Q.

FIG. 4A is a plan view showing an embodiment of the structure of the unit pixel, and FIG. 4B is a sectional view taken along the line VII (b) -VII (b) of FIG. Shows.

In each of the figures, first, on the surface of the transparent substrate 1, a first polysilicon layer 14 is formed on an upper part in a pixel region (a region surrounded by a gate signal line 6 and a drain signal line 7 described later). ing. This first polysilicon layer 1
Reference numeral 4 is such that both ends thereof extend to the respective formation regions of the adjacent drain signal lines 7.

The first polysilicon layer 14 is a semiconductor layer of the thin film transistor TFT, a wiring layer for connecting the drain region of the semiconductor layer to the drain signal line, and a storage capacitor Cstg connected to the source region of the semiconductor layer. One of the electrodes is configured.

Then, the gate signal line 6 is formed by the second polysilicon layer 16 doped with impurities all over to have conductivity. A part of the gate signal line 6 is extended and formed so as to straddle the first polysilicon layer 14, so that the gate signal line 6 also constitutes the gate electrode 6A of the thin film transistor TFT.

In this case, in the thin film transistor TFT, the gate insulating film is interposed between the thin film transistor TFT and the first polysilicon layer 14 under the gate electrode 6A. The gate insulating film is formed of the first polysilicon layer 14. It is composed of a silicon oxide film formed by heat-treating its surface after formation. Then, the first polysilicon layer 14 in the region other than the region where the gate electrode 6A is formed is doped with impurities by using the gate electrode 6A as a mask (thus, at this time, the gate signal line 6 is also electrically conductive). One of the drain region, the source region, the wiring, and the storage capacitor is formed.

Further, the transparent substrate 1 processed in this way
An insulating film 18 made of, for example, a PSG film is formed on the surface of the first polysilicon layer 1 extending to a part of the formation region of the drain signal line 7.
4A, a contact hole 18A for exposing one end thereof and a contact hole 18B for exposing a part of the first polysilicon layer 14 running in a part of a formation region of a pixel electrode 22 described later are formed. There is.

A drain signal line 7 is formed on the surface of the insulating film 18, so that the drain signal line 7 is connected to the thin film transistor TFT through the contact hole 18A.
Connected to the drain region of.

The drain signal line 7 on the left side of the figure among the drain signal lines 7 is formed so as to be overlapped with the extension portion on the other end side of the first polysilicon layer 14, and the overlap portion has the storage capacitance Cstg. It is configured to also serve as the other electrode. In this case, the dielectric film of the storage capacitor Cstg becomes the insulating film 18.

The drain signal line 7 is made of aluminum containing syrincon as its material.

Further, a protective film 20 made of, for example, a SiN film is formed on the surface of the transparent substrate processed in this way, and the protective film 20 has a pixel electrode 22 forming region, which will be described in detail later, and the above-mentioned region. An opening 20A for exposing the contact hole 18B exposing the first polysilicon layer 14 is formed.

In the area of the opening 20A of the protective film 20, the pixel electrode extending to the periphery of the protective film 20 is formed of a transparent conductive film made of an oxide of In and Sn, for example. There is.

Since the thin film transistor TFT in each unit pixel region adopts the above-described structure,
As described above, the complementary MIS transistor forming the vertical scanning circuit 3 and the video driving circuit 4 has almost the same structure as the thin film transistor TFT, but the manufacturing process is also almost the same. There is.

Therefore, the material layers sequentially laminated from the front surface side of the lower transparent substrate 1 are substantially the same around the lower transparent substrate 1. Therefore, it goes without saying that the structure of the sealant application region Q and the laminated structure of each material of the structure of the connection body, which will be described next, are substantially restricted by the laminated structure described above.

FIG. 1 is a sectional view taken along line I-I of FIG.

In the figure, on the surface of the lower transparent substrate 1, a polysilicon layer 16 is formed in the formation region of the upper and lower connecting members 10 and the wiring portion 12 connecting the upper and lower connecting members 10 to other upper and lower connecting members 10. ing. The polysilicon layer 16 is formed at the same time when the second polysilicon layer 16 (for forming the gate signal line 6) in the display section 2 is formed, and therefore has a conductivity. It is like this.

Then, an insulating film 18 made of a PSG film is formed so as to cover the polysilicon layer 16 as well, and this insulating film 18 is one of the polysilicon layers 16 below it in the formation region of the upper and lower connectors 10. An opening 18C for exposing the portion is formed, and in the formation area of the wiring portion 12, the opening 18C is intermittently provided along the extending direction thereof.
D is formed. The insulating film 18 is formed simultaneously with the formation of the insulating film 18 in the display unit 2.

Further, on the insulating film 18, along the extending direction of the polysilicon layer 16, and the polysilicon layer 1 is formed.
6, an Al (1% Si) layer 17 is formed so as to overlap with No. 6, and as a result, the wiring portion 12 is formed on the polysilicon layer 16 and the A layer.
1 (1% Si) layer 17 and each opening 18D of the insulating film 18
It is configured as a side-by-side structure that is intermittently connected through. The Al (1% Si) layer 17 is formed at the same time as the Al (1% Si) layer (for forming the drain signal line 7) in the display section 2.

The surface processed in this way has
The protective film 20 formed by directly extending the protective film 20 formed in the display unit 2 is formed.
In No. 0, the opening 20B is formed at a portion corresponding to the formation region of the upper and lower connecting bodies 10.

A transparent conductive film 22A made of an oxide of In and Sn is formed in the opening 20B of the protective film 20 so as to cover even the periphery of the opening 20B. As a result, the transparent conductive film 22A is formed. A polysilicon layer (that is, the wiring portion 1) is formed through an opening 18C previously formed in the insulating film 18.
2) It has a function as an electrode terminal connected to 16.

Further, on the transparent conductive film 22A, the upper and lower connectors 10 which are interposed between the upper transparent substrate and the upper transparent substrate are arranged. The upper and lower connectors 10 are, for example, epoxy adhesive 10B mixed with so-called gold beads 10A. Here, the gold bead 10A is a true sphere (diameter, 8.
(0 μm) surface is gold-plated.

It should be noted that the gold beads 10A are not necessarily limited to such a structure, and may be those coated with silver paste on the surface or metal particles such as Cr and Ni. There is no end.

On the liquid crystal side surface of the upper transparent substrate 100, an Al (1% Si) layer 101, an insulating film 102, and a common electrode 103 are sequentially formed. Transparent conductive film 2 through gold beads 10A
It is configured to be pulled out to 2A.

Although not shown, the transparent conductive film 22A is formed so as to extend to the external terminal 9. Here, the external terminal 9 is made of, for example, Al.
Since it is known that it is difficult to establish conduction between them when they are formed of a (1% Si) layer, the problem can be solved by interposing a polysilicon layer, for example.

With this structure, since the transparent conductive layer 22A that is in contact with the gold beads 10A is made of a material having excellent corrosion resistance, a conductive defect due to corrosion will occur in the connection with the spherical body. Will disappear.

Since the transparent conductive layer 22A has irregularities on its surface, the probability that contamination will occur at the protrusions of the transparent conductive layer 22A is low. The structure is such that a conductive defect is less likely to occur in the connection with.

The transparent conductive layer 22A is generally known to have a high resistance, but its area is made relatively small, and the external electrode 9 connected thereto has a low resistance material made of another material. If you select, there will be no problem.

As the external electrode 22A, the display unit 2 is used.
There is a case where the material used for forming the film, that is, Al (1% Si) is selected, and in this case also, good conduction is achieved by interposing a polycrystalline silicon layer between the transparent conductive layer 22A and the transparent conductive layer 22A. The problem goes away because you can.

FIG. 5 is a sectional view taken along line VV of FIG.

In the figure, a polysilicon layer 16 is first formed on the surface of the transparent substrate 1 in the sealant application region Q. The polysilicon layer 16 has a stripe shape extending in the width direction of the sealant application region Q.
A plurality of patterns are arranged side by side in the extending direction of the sealant application region Q.

The polysilicon layer 16 is formed simultaneously with the formation of the second polysilicon layer 16 (for forming the gate signal line 6) in the display section 2. Therefore, the polysilicon layer 16 has conductivity.

Furthermore, an insulating film 18 is formed on the surface of the transparent substrate 1 including these polysilicon layers 16 as well.
The insulating film 18 is formed with an opening 18E exposing the central portion of the polysilicon layer 16 excluding the peripheral portion. The insulating film 18 is the insulating film 18 in the display unit 2.
Is formed at the same time as the formation of.

On the upper surface of the polysilicon layer 16 exposed from the opening 18E of the insulating film 8, Al (1% Si) is formed.
The layer 17 is formed, and the peripheral portion of the Al (1% Si) layer 17 is overlapped with the periphery of the opening 18E of the insulating film 18 and is formed in substantially the same pattern as the polysilicon layer 16. Also in this case, the Al (1% Si) layer 17 is
It is formed simultaneously with the Al (1% Si) layer 17 (for forming the drain signal line 7) in the display section 2.

Then, the protective film 20 formed in the display section 2 is formed in the sealant application region Q processed in this way.
The protective film 20 is formed by extending as it is.

A glass fiber 31 is mixed in the seal coating material 30 interposed between the upper transparent substrate 100 and the upper transparent substrate 100, and the upper transparent substrate 100 and the lower transparent substrate 100 are transparent depending on the diameter of the glass fiber 31, as shown in the figure. The gap with the substrate 1 and thus the layer thickness of the liquid crystal is defined. In this case, the gold beads 10A in the upper and lower connectors 10 are
The glass fiber 31 will be slightly crushed according to the diameter of the glass fiber 31.

As described above, the unevenness is formed as described above along the extending direction of the sealant application forming region of the lower transparent substrate 1, because the unevenness causes distortion in each transparent substrate. This is because this distortion can bring about an action of making it difficult for the gap variation due to the external force of each transparent substrate to occur.

Embodiment 2 FIG . FIG. 6 is a configuration diagram showing another embodiment of the liquid crystal display device of the present invention and corresponds to FIG.

The structure different from that of FIG. 1 is that the conductive layer on the side of the lower transparent substrate 1 in contact with the gold beads 10A is the polysilicon layer 16.
In this configuration, the transparent conductive layer 22A is not interposed.

Also in this case, the polysilicon layer 16
Since is a material having excellent corrosion resistance, it has the same effect as that of the first embodiment.

Example 3. FIG. 7 is a block diagram showing another embodiment of the liquid crystal display device of the present invention and corresponds to FIG.

A structure different from that shown in FIG. 1 is that, as an alternative to the gold beads, it is made of Cr or an alloy mainly containing Cr and has a plurality of protrusions formed on the surface thereof.

The conductive layer on the side of the lower transparent substrate 1 which comes into contact with such a conductor made of Cr or the like is made of Al or an alloy containing it as a main component.

In this case, even if the conductive layer made of Al or an alloy mainly composed of Al is corroded, the protrusions formed on the surface of the conductor penetrate through the corroded surface. Since they are arranged, it is possible to sufficiently secure their conductivity.

Therefore, the structure is not limited to that of this embodiment, and the conductor is made of Al or an alloy mainly composed of Al and the conductive layer is made of Cr or an alloy mainly composed of Cr. Needless to say, it can be used as a material.

[0074]

As is apparent from the above description,
According to the liquid crystal display device of the present invention, it is possible to prevent the occurrence of non-conduction when the electrode on the upper substrate side is pulled out to the lower transparent substrate side.

Further, the above effect can be obtained without increasing the number of manufacturing steps.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a main part of a liquid crystal display device according to the present invention.

FIG. 2 is a plan view showing a configuration of a liquid crystal side surface of a so-called lower substrate of the liquid crystal display device according to the present invention.

FIG. 3 is a plan view showing details of a partial region in FIG.

FIG. 4 is a plan view and a sectional view showing an embodiment of a thin film transistor incorporated in a liquid crystal display device according to the present invention.

5 is a cross-sectional view taken along the line VV of FIG.

FIG. 6 is a cross-sectional view showing another embodiment of the main part of the liquid crystal display device according to the present invention.

FIG. 7 is a cross-sectional view showing another embodiment of the main part of the liquid crystal display device according to the present invention.

[Explanation of symbols]

16 ... Polysilicon layer, 22 ... Pixel electrode, 22A ...
... Conductor layer, 10 ... Upper and lower connectors, 10A ... Gold beads.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masayasu Edo 3300 Hayano, Mobara-shi, Chiba Electronic device division, Hitachi, Ltd. (72) Inventor Takuo Kaito 3300 Hayano, Mobara-shi, Chiba Hitachi, Ltd. Electronic device (72) Inventor Satoshi Mitsuhashi 3300, Hayano, Mobara-shi, Chiba Hitachi, Ltd. Electronic Devices Division (72) Inventor, Taminito Nakagome 3300, Hayano, Mobara-shi, Chiba Hitachi, Ltd. Electronic Devices Division

Claims (9)

[Claims] 1. A thin film transistor which is turned on by supplying a scanning signal from a gate signal line to a unit pixel region on a liquid crystal side surface of one of the transparent substrates which are arranged to face each other with a liquid crystal interposed therebetween, and a thin film transistor which is turned on. And a pixel electrode to which a pixel signal is supplied from a drain signal line via the thin film transistor, wherein polycrystalline silicon is used as a semiconductor layer forming the thin film transistor, and the other transparent substrate side is provided. In a liquid crystal display device configured to lead out the formed common electrode to a conductor layer on the side of the one transparent substrate through at least a spherical body having conductivity, the conductor layer is the same as the pixel electrode. It is made of the above materials and has irregularities on its surface, and it is connected to an external terminal with low resistance that applies voltage from the outside. A liquid crystal display device characterized by being provided. 2. A thin film transistor which is turned on by supplying a scanning signal from a gate signal line to a unit pixel region on a liquid crystal side surface of one of the transparent substrates arranged to face each other with a liquid crystal interposed therebetween, and the thin film transistor. And a pixel electrode to which a pixel signal is supplied from a drain signal line via the thin film transistor, wherein polycrystalline silicon is used as a semiconductor layer forming the thin film transistor, and the transparent substrate on the other transparent substrate side. In a liquid crystal display device configured to draw out the formed common electrode to a conductor layer on the side of the one transparent substrate through at least a spherical body having conductivity, the conductor layer is formed of polycrystalline silicon. And a liquid crystal display device characterized in that the liquid crystal display device is connected to a low resistance external terminal for applying a voltage from the outside. 3. A thin film transistor which is turned on by supplying a scanning signal from a gate signal line to a unit pixel region on a liquid crystal side surface of one of the transparent substrates arranged to face each other with a liquid crystal interposed therebetween, and the thin film transistor. And a pixel electrode to which a pixel signal is supplied from a drain signal line via the thin film transistor, wherein polycrystalline silicon is used as a semiconductor layer forming the thin film transistor, and the other transparent substrate side is provided. In a liquid crystal display device configured to lead the formed common electrode to a conductor layer on the side of the one transparent substrate via a conductor, the conductor has a shape having a plurality of protrusions on its surface. In addition, as each material of the conductor and the conductive layer, one of them is Al or an alloy mainly containing it, and the other is Cr or The liquid crystal display device characterized by being formed of an alloy which mainly Les. 4. A sphere for drawing out a common electrode formed on the other transparent substrate side to a conductor layer on one transparent substrate side,
The liquid crystal display device according to any one of claims 1 and 2, wherein the surface of the polymer beads is coated with silver paste or Au, or is made of Ni or Cr metal particles. 5. The liquid crystal display device according to claim 1, wherein the conductive layer made of the same material as the pixel electrode is made of an oxide of In and Sn. 6. The low-resistance external terminal to which a voltage is applied from the outside is formed of Al or an alloy mainly containing Al, and an intervening layer is provided between the external layer and the conductive layer to improve conduction. The liquid crystal display device according to claim 1, wherein: 7. The liquid crystal display device according to claim 6, wherein the intervening layer is made of polycrystalline silicon. 8. The liquid crystal display device according to claim 6, wherein the intervening layer is made of amorphous silicon. 9. The liquid crystal display device according to claim 6, wherein the intervening layer is made of Cr.