JPH0895076A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: To prevent interference of signals between drain lines and between the drain lines and a common electrode generated by mixing conductive foreign matter in a sealant at sticking together substrate, and improve the yield, in a liquid crystal display device using a positive stagger type TFT. CONSTITUTION: In a sealant 40 forming area, laminated bodies 14ND, 14D, 15D, 16D constituted of the same material as that of a TFT part N+a-Si, a-Si, gate insulating layers, and gate electrode layers are coated on the upper and lower parts of drain lines 13L. Hereby, even if conductive foreign matter 41 is mixed in the sealant 40, it is insulated by a gate insulating layer 16D, and hence interference of signals between the drain lines 13L and between the drain lines 13L and a common electrode 21 is prevented. In addition, the number of processes is not supplemented, and hence increase of the cost can be avoided.

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 display device which has improved yield by taking measures against foreign matters during the manufacturing process.

[0002]

2. Description of the Related Art Liquid crystal display devices are characterized by thinness, light weight and low power consumption, and are being put to practical use in the fields of OA equipment, AV equipment and the like. In particular, the active matrix type using a thin film transistor (hereinafter abbreviated as TFT) as a switching element can perform static driving with a duty ratio of 100% in a multiplexed manner in principle, and has a large screen and a high-definition moving image display. Is used for.

The active matrix type liquid crystal display device is
It is configured by bonding a substrate (TFT substrate) having display electrodes arranged in a matrix and TFTs connected to each display electrode (TFT substrate) and a substrate having a common electrode (counter substrate) and enclosing a liquid crystal in the gap. . The TFT is a switching element that selects a data signal input to the display electrode, and includes a gate electrode, a drain electrode, a source electrode, and a non-single-crystal semiconductor layer. Each electrode is connected to a gate line, a drain line, and a display electrode, and the non-single crystal semiconductor layer is amorphous silicon (a-Si) or polysilicon (p-Si) and functions as a channel layer. The gate line group is line-sequentially scanned and selected to 1
All the TFTs on the scanning line are turned on, and a data signal synchronized with this is input to each display electrode via each drain line. A voltage is set to the common electrode in synchronization with the scanning signal, and the liquid crystal in the gap is driven by the voltage between the display electrodes facing each other, whereby the light transmittance is adjusted for each display pixel, and each display pixel is adjusted. The combination of the gradation display is visually recognized as a display image.

When a positive stagger type having a gate arranged on the upper layer is used as the TFT, the number of masks is 3 when manufacturing the TFT substrate.
It can be manufactured in one piece, and the cost is low. FIG. 2 is a plan view (a) of a liquid crystal display device using a positive stagger type TFT and a cross-sectional view (b) taken along line BB thereof. On a transparent substrate (10) such as glass, a light shielding layer (11) for preventing light from entering a TFT is formed of Cr or the like, and an interlayer insulating layer (12) is formed so as to cover the light shielding layer (11). Display electrodes (13P) having source electrodes (13S) are arranged in a matrix on the interlayer insulating layer (12), and drain electrodes (13D) are provided between columns of the display electrodes (13P). The drain line (13L) is arranged. All of these are made of ITO. On the source electrode (13S) and the drain electrode (13D), a-Si (14) serving as a channel layer, a gate insulating layer (15) such as SiNx, and a gate electrode (16) such as Al.
G) is laminated to form a TFT. The gate line (16L) is a-Si (14) made of the same material as the TFT part.
And a gate insulating layer (15), and is formed of Al integrally with the gate electrode (16G). In addition, a-Si (14) and the source electrode (1
3S) and a-Si (14) and the drain electrode (13
Between the D), N + type a-Si (14N) whose resistance is lowered by interposing a large amount of impurity ions such as phosphorus is interposed,
Improves ohmic characteristics. The entire surface covering these is subjected to surface treatment by forming an alignment film (17) of polyimide or the like and performing a predetermined rubbing treatment for the purpose of controlling the alignment of the liquid crystal.

On the transparent substrate (20) arranged facing the TFT substrate having such a structure, the common electrode (2) of ITO is formed.
1) is formed on the entire surface, and an alignment film (22) is formed on the surface in the same manner as on the TFT substrate side to serve as a counter substrate. By fixing these TFT substrate and counter substrate at the peripheral edge with a sealing agent such as epoxy resin
m and a liquid crystal (3
0) is injected and the injection port is closed with a sealant to seal the liquid crystal.

[0006]

In the conventional liquid crystal display device, the sealing material (40) is applied to the opposite substrate side on the substrate (10) on which the exposed drain line (13L) is formed at the bonding portion at the peripheral edge. When the conductive foreign substance (41) is mixed in the sealant (40), it is bonded between the drain lines (13L) and between the drain line (13L) and the common electrode (21). There was interference and interference. FIG. 3 shows a plan view (a) of the drain-side peripheral end portion and a cross-sectional view (b) taken along line C-C thereof. The drain line (13L) extends from the pixel portion and is connected to the drain input terminal (13T) at the substrate end, and is bonded to the counter substrate on which the common electrode (21) is formed by the sealant (40).

The bonding between the TFT substrate and the counter substrate is T
Step of applying a sealant (40) on the peripheral edge of the FT substrate, step of spraying a spacer such as glass fiber on the substrate to keep the cell gap constant, and aligning and facing the opposite substrate It is performed by the process of fixing. For example, when there is a conductive foreign substance (41) such as a metal piece when the sealant (40) is applied, this remains in the sealant (40) and is directly bonded to the counter substrate.

Thus, the conductive foreign matter (41) causes
When the drain lines (13L) are connected to each other or the drain line (13L) and the common electrode (21) are connected to each other, interference and interference of data signals occur, resulting in deterioration of display quality.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve this problem. Firstly, two substrates arranged to face each other and the facing surfaces of the two substrates are provided. It is composed of a conductive layer formed in a predetermined pattern, a liquid crystal sandwiched between the two substrates, and an adhesive for bonding the two substrates at the peripheral edge and sealing the liquid crystal. In the liquid crystal display device, an insulating layer formed on the conductive layer is interposed between the adhesive and at least the one substrate.

Secondly, a first substrate and a second substrate which are arranged to face each other, a plurality of display electrodes formed on the facing surface of the first substrate, and a plurality of display electrodes formed between the display electrodes. A drain line, a source electrode integrated with the display electrode, a drain electrode integrated with the drain line, and a semiconductor layer laminated on the source electrode and the drain electrode,
A thin film transistor including an insulating layer and a gate electrode formed of a metal layer, a common electrode formed entirely on the opposite surface of the second substrate, and a thin film transistor sandwiched between the first and second substrates. In a liquid crystal display device comprising a liquid crystal and an adhesive that bonds the first and second substrates together at the peripheral edge and seals the liquid crystal, the drain line is in contact with the adhesive. In the section, a laminated body made of the same material as the insulating layer, the semiconductor layer, and the metal layer is formed.

Thirdly, in the second structure, the laminated body is formed in a line shape integrally extending in a direction intersecting with the drain lines.

[0012]

With the first structure, the insulating layer is interposed between the conductive layer and the adhesive, so that even if a conductive foreign substance is mixed in the adhesive, the conductive layers are adhered to each other and between the patterns. It is possible to prevent signal interference and crosstalk between the substrates. The second
With the above structure, by forming an insulating layer on the drain line at the contact portion with the adhesive, even if a conductive foreign substance is mixed in the adhesive, between the drain lines and between the drain line and the common electrode. Interference and interference are prevented. Furthermore, by forming a laminated body made of the same material as the semiconductor layer, the insulating layer, and the metal layer of the thin film transistor at the contact portion with the adhesive on the drain line, the number of masks required for manufacturing can be increased without increasing the number of masks between drain lines. Also, it is possible to prevent interference and interference between the drain line and the common electrode.

In the third structure, by integrally forming the laminated body coated on each drain line, each drain line is commonly connected by the high-resistance semiconductor layer and the static electricity is diffused. Electric breakdown is prevented.

[0014]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a plan view (a) of a peripheral edge portion of a liquid crystal display device according to the present embodiment and a cross-sectional view (b) taken along line AA thereof. The pixel portion has the same structure as in FIG. Further, in FIG. 1, the same objects as those in FIG. 2 and FIG. 3 of the conventional example are designated by the same reference numerals.

On a transparent substrate (10) such as glass,
An interlayer insulating layer (12) covering the light shielding layer (11) is formed, and a drain line (13L) extending from the pixel portion is formed on the interlayer insulating layer (12). The drain line (13L) is further connected to the drain input terminal (13T) at the end of the substrate. Sealant (40)
In the formation area of TF, cover the dray line (13L) and TF
N + a-Si (14ND), a-Si, the same material as T
(14D), the gate insulating layer (15D), and the gate layer (16D) are laminated. On the drain run (13 L), the sealant (40) is applied to the laminated body (14
ND, 14D, 15D, 16D) are formed in the formation region and are bonded to the common electrode (21) on the counter substrate side.

With this structure, in the step of bonding the substrates, the conductive foreign matter (41) is present and the sealant (4) is present.
0) even if mixed in each drain line (13
Since L) is covered and insulated by the gate insulating layer (15D), interference and interference between the drain lines (13L) and between the drain line (13L) and the common electrode (21) are prevented.

Such a liquid crystal display device is manufactured as follows. First, Cr is deposited on a transparent substrate (10) such as glass to a thickness of about 2000 Å by sputtering, and this is etched to form a light-shielding layer (1
1) is formed. Subsequently, a silicon nitride film is formed by CVD to form an interlayer insulating layer (12), and a light shielding layer (11)
Is covered. Next, on the interlayer insulating layer (12), IT
By sputtering O to a thickness of about 1000Å, N
+ a-Si (14N) is sequentially laminated to a thickness of about 200 to 300Å, and these films (12, 14N) are etched to form a display electrode (13P), a drain line (13L) and a source electrode (13S). ) And a drain electrode (13D) are formed. Next, on the substrate on which the source / drain wirings (13) are formed, a-Si (14) is laminated to a thickness of about 500 to 1000 Å by plasma CVD, and then the gate insulating layer (15) is formed by plasma CVD. Is deposited to a thickness of 2000 to 4000 Å, and then Al to be the gate wiring (16) is deposited to a thickness of about 4000 Å by sputtering. Al, SiNx, and a-S sequentially laminated in this way
The i and N + a-Si are formed by etching in a pattern of the gate line (16L) and the gate electrode (16G) and a pattern of covering the drain line (13L) in the sealant (40) forming region at the edge of the substrate. The unnecessary portion is removed by etching using the resist as a mask. As a result, a TFT in which N + a-Si (14N), a-Si (14), a gate insulating layer (15) and a gate electrode (16G) are laminated on the source and drain electrodes (13S, 13D), And A on the stack of SiNX and a-Si
and a drain line (13L) in the sealant (40) forming region is formed.
L +) has N + a-Si (14ND) and a-Si (14ND).
D), gate insulating layer (15D) and gate layer (16D)
Is formed.

In FIG. 1, each laminate (14ND, 1
4D, 15D, 16D) are provided separately for each drain line (13L), but may be integrally formed. In this case, since the gate layer (15D) is floating, it serves as a countermeasure against static electricity on the drain input side. That is, in order to leave at least the gate insulating layer (15D) on the drain line (13L), the stacked body (14N
D, 14D, 15D, 16D), but this laminated body (14ND, 14D, 15D, 16D)
, The drain lines (13L) are commonly connected by a high resistance a-Si (14D).
L) to fulfill the function of preventing electrostatic breakdown.

As described above, in the region where the sealant (40) is formed, N + a-Si, a is formed on the drain line (13L).
-Laminate (14ND, consisting of Si, SiNX and Al)
14D, 15D, 16D) to cover the drain lines (13L) and between the drain lines (13L).
L) and the common electrode (21) can be prevented from interfering with each other and interference, and such a laminate (14ND, 14ND)
Since D, 15D, 16D) are formed at the same time when the gate wiring (16) is patterned, an increase in manufacturing cost can be avoided.

[0020]

As is apparent from the above description, according to the present invention,
Without increasing the cost, signal interference and interference between the drain lines and between the drain lines and the common electrode, which are caused by foreign substances during the manufacturing process, were prevented, and reliability was improved. In addition, a structure that also serves as a measure against electrostatic breakdown is possible, and the yield is further improved.

[Brief description of drawings]

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

2A and 2B are a plan view and a cross-sectional view of a pixel portion of a liquid crystal display device.

3A and 3B are a plan view and a cross-sectional view illustrating problems of a conventional liquid crystal display device.

[Explanation of symbols]

 10, 20 Substrate 11 Light-shielding layer 12 Interlayer insulating film 13, 21 ITO 14 a-Si 15 SiNX 16 Al 17, 22 Alignment film 21 Common electrode 30 Liquid crystal 40 Sealant 41 Conductive foreign matter

Claims (3)

[Claims] 1. A pair of substrates arranged to face each other, a conductive layer formed in a predetermined pattern on the facing surfaces of the two substrates, and a liquid crystal sandwiched between the two substrates. A liquid crystal display device comprising an adhesive that bonds the two substrates together at a peripheral edge portion and seals the liquid crystal, wherein the adhesive is on the conductive layer between at least the one substrate. A liquid crystal display device characterized in that an insulating layer formed on the substrate is interposed. 2. A first substrate and a second substrate arranged to face each other, a plurality of display electrodes formed on the facing surface of the first substrate, and a drain formed between the display electrodes. Line, a source electrode integrated with the display electrode, a drain electrode integrated with the drain line, and a gate electrode composed of a semiconductor layer, an insulating layer, and a metal layer stacked on the source electrode and the drain electrode Thin film transistor, a common electrode formed entirely on the opposing surface of the second substrate, a liquid crystal sandwiched between the first and second substrates, and the first and the second liquid crystal at the peripheral edge. A liquid crystal display device comprising: an adhesive that bonds the two substrates together and seals the liquid crystal; and the insulating layer, the semiconductor layer, and the semiconductor layer on the drain line at a contact portion with the adhesive. The liquid crystal display device, wherein a stack of serial metal layer and the same material is formed. 3. The liquid crystal display device according to claim 2, wherein the stacked body is formed in a line shape integrally extending in a direction intersecting with the drain lines.