JPH11258626A - Liquid crystal display - Google Patents

Abstract

(57) [Summary] Electrostatic protection measures [Technical solution] One of transparent substrates disposed opposite to each other with a liquid crystal interposed therebetween extends on the liquid crystal side surface and extends in the y direction and in the x direction. A video signal line is provided side by side, and a common signal line is formed at both ends of the video signal line,
One of the common signal lines is commonly connected to video signal lines arranged alternately among the video signal lines, and
The other common signal line is commonly connected to the remaining video signal lines of the video signal lines, and is connected to other video signal lines adjacent to the remaining video signal lines via diodes.

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, for example, a liquid crystal display called an active matrix type.

[0002]

2. Description of the Related Art In an active matrix type liquid crystal display device, a transparent substrate (hereinafter, this substrate is referred to as a TFT substrate) is disposed on a liquid crystal side of one of the transparent substrates disposed to face each other via a liquid crystal. A pixel is formed in each region surrounded by the scanning signal lines extending in the x direction and juxtaposed in the y direction and the video signal lines extending in the y direction and juxtaposed in the x direction. ing.

Each of these pixels is supplied with a thin film transistor which is turned on by a scanning signal (voltage) from a scanning signal line, and a video signal (voltage) from a video signal line via the turned on thin film transistor. And a pixel electrode.

In this case, when manufacturing such a TFT substrate, a transparent substrate larger than a size that can be actually assembled in a liquid crystal display device is prepared, and a region corresponding to a plurality of TFT substrates in the transparent substrate is prepared. After each signal line, thin film transistor, pixel, etc. are formed, each TFT
Cutting for separating each substrate is performed.

Here, when a scanning signal line or a video signal line is formed on the surface of the transparent substrate, a disconnection inspection or the like of the scanning signal line or the video signal line can be performed. Are commonly formed outside the cutting region at the same time.

In the video signal lines, in particular, a common signal line connected to the video signal line is formed at each end of each video signal line, and one common signal line is provided for every other video signal line. The common signal line is commonly connected to the video signal lines, and the other common signal line is commonly connected to the remaining video signal lines.

The intervals between the video signal lines are formed relatively small, and it is determined whether adjacent video signal lines are short-circuited by merely contacting a probe to each of the common signal lines. This is because it can be easily inspected.

[0008]

However, in the production of such a TFT substrate, when cutting a transparent substrate, for example, one common signal line commonly connected to every other video signal line is connected. It has been pointed out that when separated from each of the video signal lines, those video signal lines are completely in a floating state.

In many cases, the transparent substrate is subsequently subjected to a transporting process. During the transport, static electricity enters the floating video signal line, and the characteristics of the thin film transistor connected to the video signal line (characteristics) Vth) will be adversely affected.

The present invention has been made under such circumstances, and an object of the present invention is to provide a liquid crystal display device which is protected from static electricity.

[0011]

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, one of the transparent substrates opposed to each other via the liquid crystal is provided with a surface on the liquid crystal side of the transparent substrate.
Video signal lines extending in the x direction and juxtaposed in the x direction. A common signal line is formed at each end of the video signal line, and one of the common signal lines is one of the video signal lines. Every other video signal line is connected in common with the other video signal lines, and the other common signal line is connected in common with the other video signal lines. It is characterized by being connected to another adjacent video signal line via a diode.

In the liquid crystal display device configured as described above, even when one of the common signal lines is cut off at the time of cutting the transparent substrate, the video signal line separated from the common signal line is connected via a diode. That is, it is still connected to the other common signal line.

For this reason, even if static electricity enters the video signal line, it is diffused to the other common signal line via the diode, so that the characteristics of the thin film transistor connected to the video signal line are changed. This can avoid the adverse effects.

[0015]

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

<< TFT Substrate >> First, FIG. 2 is a plan view schematically showing the structure of one of the pair of transparent substrates (TFT substrate) on the liquid crystal side among a pair of transparent substrates arranged to face each other with the liquid crystal therebetween. .

In FIG. 1, a transparent substrate 1 is provided, and a central portion of the transparent substrate 1 excluding the periphery is a display area (an area surrounded by a dashed line A in the figure).

The display area is an area where liquid crystal is interposed between the transparent substrate 2 and the liquid crystal, and the liquid crystal is sealed by a sealing material 3 formed along the periphery of the transparent substrate 2. It is supposed to be.

A scanning signal line 4 extending in the x direction and juxtaposed in the y direction is formed in the display area, and is extended in the y direction while being insulated from the scanning signal line 4. There are formed video signal lines 5 which are arranged side by side in the x direction. Each of the regions surrounded by the scanning signal lines 4 and the video signal lines 5 constitutes a pixel region.

That is, the display area is formed by an aggregate of pixel areas arranged in a matrix.

As shown in FIG. 3 in detail, each pixel region has a thin film transistor TFT turned on by the supply of a scanning signal from the scanning signal line 4 and the video signal line via the turned on thin film transistor TFT. The pixel electrode 6 to which the video signal from the pixel 5 is supplied is formed. In addition to the thin film transistor TFT and the pixel electrode 6, an additional capacitance element Cadd is formed between the pixel electrode 6 and another adjacent scanning signal line 4 different from the scanning signal line 4 for driving the thin film transistor TFT. ing. This additional capacitance element Cadd is a thin film transistor T
Even if the FT is turned off, the video signal is provided to be stored in the pixel electrode 6 for a long time.

Each scanning signal line 4 has one end (left side in the figure) formed to extend outside the display area and is connected to an external terminal 4A, and each video signal line 5 has one end (FIG. (Middle right) is formed to extend outside the display area and is connected to the external terminal 5A.

The other transparent substrate 2 (CF substrate) disposed opposite to the TFT substrate thus formed is provided with a common electrode (transparent electrode) common to each pixel region on its liquid crystal side. Further, one of red, green and blue color filters is formed for each pixel region.

The gap between the transparent substrate 1 and the transparent substrate 2 is regulated by the sealing material 3, and the thickness of the liquid crystal can be set by the sealing material 3.

A liquid crystal enclosing port 8 is formed on a part of one side (the right side in the figure) of the sealing material 3. After the liquid crystal encapsulating port 3 encloses liquid crystal between the transparent substrates 1 and 2, Sealant 9
To be sealed.

<< Pixel Structure >> FIG. 4 is a view showing the structure of the thin film transistor TFT and its vicinity in the structure in the pixel region.

As shown in FIG. 1, first, a scanning signal line 4 is formed on the surface of the transparent substrate 1 so as to extend in the x direction in the figure. The scanning signal line 4 is formed of, for example, an alloy layer of Cr and Mo or a laminate thereof.

An insulating film is provided on the entire surface of the transparent substrate 1 on which the scanning signal lines 4 are formed in order to achieve interlayer insulation between the scanning signal lines 4 and a video signal line 5 described in detail later. Is formed of, for example, a silicon nitride film.

Further, a thin film transistor TFT is formed on an upper surface of the insulating film at one corner of a pixel region surrounded by the scanning signal line 4 and a video signal line 5 described later in detail.

In a region where the thin film transistor TFT is formed, a gate electrode 4G integrally extending from the scanning signal line 4 is formed below the insulating film functioning as a gate insulating film, and a surface of the insulating film is formed. A semiconductor layer 10 made of, for example, amorphous Si is formed so as to extend the gate electrode 4G.

The semiconductor layer 10 is formed so as to extend in substantially the same pattern as the video signal line 5 in a region where the video signal line 5 described later is formed. The video signal line 5 has a laminated structure with the semiconductor layer 10 in order to prevent disconnection and to reduce the capacitance between the scanning signal line 4 and the crossing.

A drain electrode 5D and a source electrode 5S are formed on the surface of the semiconductor layer 10 in the region where the thin film transistor TFT is formed, and these electrodes 5D and 5S are disposed between the gate electrode 4G when viewed from above. And are arranged facing each other.

The interface between the drain electrode 5D and the source electrode 5S on the surface of the semiconductor layer 10 is
A contact layer doped with a high concentration impurity at 0 is formed. This high-concentration impurity layer is formed on the entire surface of the semiconductor layer 10 when the semiconductor layer 10 is formed.
It is formed by etching the impurity layer exposed from D and 5S.

Then, the drain electrode 5D and the source electrode 5
S is formed in the same step and with the same material as the video signal line 3.

That is, the video signal line 5 is formed to extend in the y direction in the figure, and at this time, a drain electrode 5D is formed by the extension portion extending from the video signal line 5, and the drain electrode 5D is formed. The source electrode 5S is formed so as to be separated from the electrode 5D.

The source electrode 5S is formed so as to extend to the formation region of the pixel electrode 6 described later in detail, and is configured such that a contact with the pixel electrode 6 can be made in this extending portion.

Here, the video signal line 3 is formed of, for example, the same material as the scanning signal line 2, and is formed of an alloy layer of Mo and Cr. However, the material is not necessarily limited to such a material.

In order to avoid direct contact of the liquid crystal with the thin film transistor TFT, a protective film made of, for example, a silicon nitride film is formed on the entire surface of the transparent substrate 1 thus processed. Is a contact hole 12 exposing a part of the extension of the source electrode 5S.
Are formed.

A pixel electrode 6 made of, for example, an ITO (Indium-Tin-Oxide) film is formed in a pixel region on the upper surface of the protective film. The pixel electrode 6 is connected to the source electrode 5S through the contact hole 12. Electrical connection can be achieved.

<< Transparent Substrate Before Cutting for Each TFT Substrate >> FIG. 1 is a structural view of the main surface of the transparent substrate before the TFT substrate shown in FIG. 2 is separated by cutting. In the figure, for example, two TFT substrates can be formed from one transparent substrate.

This is because one transparent substrate 1A
This is for improving the throughput by processing a plurality of devices simultaneously and then dividing the devices.

Outside the cutting area (area surrounded by a dashed line) of each TFT substrate, a common signal line 40 and a video signal line 5 for commonly connecting the scanning signal lines 4 are connected.
Are commonly formed of the same material as the scanning signal line 4 and the video signal line 5 at the same time.

In this case, in the video signal line 5, in particular, the common signal lines 50A and 50B connected to the video signal line 5 are formed at the respective ends of the video signal lines.

One common signal line 50A (lower side in the figure) is commonly connected to every other video signal line 5 among the video signal lines 5.

The other common signal line 50B (upper side in the figure) is commonly connected to the remaining video signal lines 5, and is connected to the other video signal lines 5 adjacent to the remaining video signal lines 5 and the diode. 14 are connected.

In this case, the diode 14 in this case is provided so that the cathode is connected in the direction of the common signal line 50A (lower side in the figure) which is removed by the first cutting. The diodes 14 are all connected to the video signal line 5 with the same polarity.

As will be described in detail later, each of these diodes 14 is replaced with a corresponding one of the video signal lines 5 connected to the common signal line 50A by cutting.
It has a function of preventing a floating state even if 0A is removed.

The diodes 14 are provided outside the display area (the area where liquid crystal is sealed) in this embodiment. However, the present invention is not limited to this. It goes without saying that it may be inside.

The other end of the video signal line 5 directly connected to the common signal line 50A (without passing through the diode 14) is connected to the inspection pad 5 in front of its external terminal.
B is formed, and a test pad 5B is formed at the other end of the video signal line 5 connected to the common signal line 50B.

Each of these test pads 5B, together with the common signal lines 50A and 50B, is used for checking the disconnection and short-circuit of the video signal line as described below.

<< Disconnection inspection method >> (1) Inspection of disconnection of video signal line One probe is brought into contact with the common signal line 50A, and the other is connected to the inspection pad 5B of the video signal line 5 connected to the common signal line 50A. Are sequentially brought into contact with each other to detect a current flowing therebetween, thereby inspecting whether or not the video signal line 5 is disconnected. The polarity in this case does not matter.

Further, one probe is brought into contact with the common signal line 50B, and the other probe is brought into contact with the test pad 5B of the video signal line 5 connected to the common signal line 50B, so that the probe is interposed therebetween. It detects whether the video signal line is disconnected by detecting the current flowing through the video signal line. The polarity in this case does not matter.

(2) Inspection of short circuit between adjacent video signal lines One probe is brought into contact with the common signal line 50A, and the other probe is brought into contact with the common signal line 50B to detect a current flowing between them. By doing so, it is checked whether or not a short circuit has occurred between adjacent video signal lines.

In this case, it is necessary to apply a reverse voltage to the diode, and the common signal line 50A must have a higher potential than the common signal line 50B.

<< Method of Assembling Liquid Crystal Display Panel >> Next, one embodiment of a method of assembling a liquid crystal display panel using the above-described transparent substrate 1A before cutting will be described with reference to FIG.

Step 1 (FIG. 7A) The transparent substrate 1A shown in FIG. 1 is prepared. In this case, a CF substrate 2A is attached to the transparent substrate 1A via a sealing material 3 (see FIG. 2) so as to cover the main surface.

Then, a portion corresponding to the side of each TFT substrate on which the liquid crystal sealing hole 8 is formed (shown by a dashed line XX in the drawing: corresponding to a two-dot chain line X'-X 'in FIG. 1).
The cutting is performed on the transparent substrates 1A and 1B along the line.

By performing this cutting, the cutting surfaces of the TFT substrate 1 and the CF substrate 2 are flush with each other in the portion where the liquid crystal sealing hole 8 is formed, and the sealing is easy when the liquid crystal is sealed. Will be able to

Step 2 (FIG. 6B) In each of the parts separated by the above cutting,
Only the transparent substrate 2A corresponding to the CF substrate is formed into a predetermined shape by cutting a portion indicated by a chain line in the figure.

By this cutting, the transparent substrate 1A
Terminal 4A of the scanning signal line 4 and its common signal line 40 and the external terminal 5A of the video signal line 5 formed on the surface of
And the common signal lines 50A and 50B are exposed.

Step 3 (FIG. 10C) The side of the video signal line 5 opposite to the side on which the external terminal 5A is formed is cut along the dashed line in the figure.

In this case, as shown in FIG.
The cutting surface of the TFT substrate 1 (transparent substrate 1A) can be made substantially flush with the end surface of the CF substrate 2 with the cutter 90 contacting the end surface of the CF substrate 2.

The common signal line 50A is cut off from the video signal line 5 by this cutting. FIG. 7 shows the state of the transparent substrate 1A on the TFT substrate side in this case.

In the prior art, every other video signal line 5 connected to the common signal line 50A is completely floated by this cutting. However, in this embodiment, the video signal line 5 is connected via the diode 14. It is characterized in that it is still connected to the common signal line 50B.

That is, after this step, usually, the process proceeds to the next step after the transfer step.
Even if static electricity infiltrates the video signal line 5, it is diffused to the common signal line 50B via the diode 14, and the effect of avoiding the adverse effect of deteriorating the characteristics of the thin film transistor TFT can be obtained.

When the video signal line 5 is in a floating state and static electricity enters the video signal line 5,
As a rule of thumb, it has been confirmed that the video signal line 5 is negatively charged. Therefore, the diode 14 is connected to the common signal line 50B side as a cathode, and
Is diffused toward the common signal line 50B via the diode 14.

From this, the video signal line 5 may be positively charged depending on the environment. In this case, the diode 14 may be connected so that the polarity of the diode 14 is reversed.

In this case, in the short-circuit test between adjacent video signal lines 5, if the potential difference due to the voltage applied to the common signal lines 50A and 50B is set to be opposite to the above-mentioned case, It can be done without any trouble.

In the embodiment described above, the diode 1
4 are arranged so as to have the same polarity. However, depending on the transport condition or state after cutting, there may be a case where different electric charges are charged by being grouped for each adjacent video signal line 5. In this case, it is effective to set the polarity of the diode 14 accordingly.

Step 4 (FIG. 4D) The TFT substrate is cut along the dashed line in the figure to obtain the shape shown in FIG.

Step 5 (FIG. 10E) Thereafter, liquid crystal is sealed through the liquid crystal sealing hole 9 and the sealing hole is closed with the sealing agent 9 to complete the liquid crystal display panel.

<< Diode >> FIG. 1 is a plan view showing an embodiment of the diode described above.

In the figure, a common signal line 50B running in the x direction in the figure is provided, and a plurality of video signal lines 5 are formed integrally with the common signal line 50B while running in the y direction in the figure. I have.

Each of the other video signal lines 5 is formed with a diode 14 interposed therebetween.

This diode 14 is a thin film transistor T
The FT has a configuration similar to that of the FT. By connecting the gate electrode to the source electrode (electrode positioned on the display region side), a current flows from the source electrode to the drain electrode (electrode positioned on the common signal line 50B side). Flows, and no current flows in the opposite direction.

That is, first, the gate electrode 14G is formed on the surface of the transparent substrate. This gate electrode 14G
Are arranged so as to intersect with a video signal line 5 (particularly indicated as 5S in the figure) to be described later.
4G 'is formed outside the area of the intersection.

Then, an insulating film is formed over the entire area of the transparent substrate so as to cover the gate electrode 14G. The insulating film on the gate electrode 14G has the function of a gate insulating film in the thin film transistor structure.

The semiconductor layer 10 is formed in an island shape on the portion of the gate electrode 14G which intersects the video signal line 5S. In this case, the semiconductor layer 10 is provided on the video signal line 5.
It has a shape having a protruding portion along the traveling direction of S. When the video signal line 5S is formed later, the video signal line 5S is formed even if a portion of the step due to the semiconductor layer 10 is partially disconnected.
This is to prevent the disconnection of S.

The video signal line 5S is connected to the semiconductor layer 1
0 (separate (physical)).
Thereby, the semiconductor layer 10 of the video signal line 5S on the display area side
The upper end has the function of the source electrode 14S, and the end of the video signal line 5S on the side of the common signal line 50B on the semiconductor layer 10 has the function of the drain electrode 14D.

The video signal line 5S on the display area side has an extended portion in a part thereof, and this extended portion is an electrode terminal 14S 'for connecting to the terminal portion of the gate electrode 14G. It has become.

That is, a protective film is formed over the entire area of the transparent substrate processed as described above.
A conductive film 20 made of, for example, an ITO film is formed to connect the terminals through a contact hole exposing a part of the electrode terminal 14G 'of the gate electrode 14G and a part of the electrode terminal 14S' of the source electrode 14S. .

<< Manufacturing Method >> FIGS. 9 and 10 are process diagrams showing one embodiment of a method of manufacturing the diode.

FIG. 9 is a cross-sectional view taken along the line AA ′ of FIG. 8, and FIG. 10 is a cross-sectional view taken along the line BB ′ of FIG.

The manufacture of this diode is performed in parallel with the manufacture of each pixel in the display area, and will be described together with the manufacture of this pixel. FIG. 11 is a view showing one embodiment of the manufacturing process of the pixel.
It is sectional drawing in the -T 'line.

Step 1. A transparent substrate 1A is prepared, and a gate electrode 14G made of, for example, an alloy layer of Cr and Mo is formed on the surface of the transparent substrate 1A (FIGS. 9A and 10).
(A)).

The gate electrode 14G is formed of the same material and in the same process as the gate electrode 4G (scanning signal line 4) of the thin film transistor TFT in the pixel region (FIG. 11A).

Step 2. An insulating film 21 is formed on the entire surface of the transparent substrate 1A so as to cover the gate electrode 14G. Further, after the semiconductor layer 10 is formed over the entire surface of the insulating film 12, the semiconductor layer 10 is selectively etched into a pattern shown in FIG. 8 by using a photolithography technique (FIGS. 9B and 10B). b)).

The insulating film 21 and the semiconductor layer 10 are
The insulating film 21 and the semiconductor layer 10 in the pixel region are formed of the same material and in the same process (FIG. 11).
(B)).

Step 3. For example, a metal layer made of an alloy of Cr and Mo is formed over the entire area, and the metal layer is selectively etched into a pattern shown in FIG. Thus, the source electrode 14S and the drain electrode 14D are formed at the end of the video signal line 5 on the semiconductor layer 10 (FIGS. 9C and 10C).

In the formation of the video signal line 5, the source electrode 5S and the drain electrode 5D of the thin film transistor TFT are simultaneously formed in the pixel region (FIG. 11).
(C)).

In this step, the thin film transistor TFT and the video signal line 5 connected to the thin film transistor TFT are formed.

From this, the thin film transistor TFT
The common signal lines 50A and 50B are formed at the same time in order to prevent static electricity from entering through the video signal line 5. Static electricity is diffused by the common signal lines 50A and 50B and is protected from the thin film transistor TFT.

Step 4. A protective film 22 is formed over the entire area, and the protective film 22 has an electrode terminal 14G 'of the gate electrode 14G.
9 and a contact hole for exposing a part of the electrode terminal 14G ′ of the source electrode 14S (FIG. 9).
(D), FIG. 10 (d)).

The protective film 22 serves as the protective film 2 in the pixel region.
The contact hole is formed in the same step as the contact hole in the pixel region while the contact hole is formed in the same material and in the same step as FIG. 2 (FIG. 11D).

Step 5. An ITO film is formed over the entire area, and this I
The conductive layer 10 is formed by selectively etching the TO layer into the pattern shown in the figure using the photolithography technique (FIGS. 9E and 10E).

The conductive layer 10 is formed in the same step as the pixel electrode 6 in the pixel area (FIG. 11E).

As described above, according to the liquid crystal display device of this embodiment, even if one of the common signal lines is cut off when the transparent substrate is cut, the video signal line separated from the common signal line is a diode. And is still connected to the other common signal line.

For this reason, even if static electricity enters the video signal line, the static electricity is diffused to the other common signal line via the diode, so that the characteristics of the thin film transistor connected to the video signal line are changed. This can avoid the adverse effects.

[0099]

As is apparent from the above description, the liquid crystal display device according to the present invention provides sufficient protection against static electricity.

[Brief description of the drawings]

FIG. 1 is a plan view showing one embodiment of a liquid crystal display device (before cutting a transparent substrate) according to the present invention.

FIG. 2 is a plan view showing one embodiment of a liquid crystal display device (after cutting a transparent substrate) according to the present invention.

FIG. 3 is an equivalent circuit diagram showing one embodiment of a pixel of the liquid crystal display device according to the present invention.

FIG. 4 is a plan view showing one embodiment of a pixel of the liquid crystal display device according to the present invention.

FIG. 5 is a process diagram showing one embodiment of a method of assembling a liquid crystal display device according to the present invention.

FIG. 6 is an explanatory view showing the effect of the method for assembling a liquid crystal display device according to the present invention.

FIG. 7 is a plan view showing the shape of a transparent substrate (TFT substrate side) in one step of a method of assembling a liquid crystal display device according to the present invention.

FIG. 8 is a plan view showing one embodiment of a diode incorporated in the liquid crystal display device according to the present invention.

FIG. 9 is a process diagram showing one embodiment of a method of manufacturing the diode, and is a cross-sectional view taken along line AA ′ of FIG.

FIG. 10 is a process view showing one embodiment of the method for manufacturing the diode, and is a cross-sectional view taken along the line BB ′ of FIG.

11 is a process view showing one embodiment of a method for manufacturing a thin film transistor in a pixel region, and is a cross-sectional view taken along line TT ′ of FIG. 4;

[Explanation of symbols]

1A transparent substrate, 4 scanning signal line, 5 video signal line, 5A external terminal (video signal line), 5B inspection pad (video signal line), 40 common signal line (scanning) Signal lines), 50A, 50B ... common signal lines (video signal lines),
TFT: A thin film transistor.

Claims (4)

[Claims] An image signal line extending in the y-direction and juxtaposed in the x-direction is provided on a liquid crystal side surface of one of the transparent substrates opposed to each other via a liquid crystal, A common signal line is formed at each end of the video signal line. One of the common signal lines is commonly connected to every other video signal line among the video signal lines, and the other is shared. The communication line is connected in common with the remaining video signal lines of the video signal lines, and is connected to other video signal lines adjacent to the remaining video signal lines via diodes. Liquid crystal display device. 2. The liquid crystal display device according to claim 1, wherein the diode is provided in a region where liquid crystal is sealed. 3. The liquid crystal display device according to claim 1, wherein one common signal line is a signal line separated from a video signal line earlier than the other common signal line. 4. The liquid crystal display device according to claim 1, wherein the diodes are all connected to the video signal lines with the same polarity.