JP2003107525A - Active matrix substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active matrix substrate which can improve the pixel opening rate of a lateral electric field type active matrix substrate and suppress display of a circular stain due to a pinhole formed in a passivation film on a gate line. SOLUTION: The lateral electric field type active matrix substrate has an array substrate having inter-digital pixel electrodes and inter-digital common electrodes formed meshing with the pixel electrodes, an opposite substrate arranged opposite the array substrate and a liquid crystal layer sandwiched between the array substrate and opposite substrate and changes the array of liquid crystal molecules by producing an electric field almost parallel to the array substrate and opposite substrate between them; and a gate line, a common line, a gate insulating film, and a source line are formed in order on the array substrate, the passivation film is formed thereupon, and a flattening insulating film is formed after a shading layer which is electrically connected to none of the gate line, common line, and source line is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix substrate mainly used for a liquid crystal display device.

[0002]

2. Description of the Related Art A liquid crystal display device using a thin film transistor is mainly used for various display devices such as a notebook type personal computer, a portable television and an in-vehicle navigator device as a mainstream of a thin and lightweight display.

One of the performances required of recent liquid crystal display devices
One of them is a wide viewing angle. A liquid crystal mode called an in-plane switching method, that is, an IPS (in-plane switching) method has been considered as one of means for significantly improving this performance.

In the conventional TN (twisted nematic) mode, which is a liquid crystal mode, a screen display is made by utilizing the fact that the orientation of liquid crystal molecules having a refractive index anisotropy changes with respect to a vertical electric field. I am trying. On the other hand, I
The PS method is characterized in that the orientation of the liquid crystal molecules is changed by applying an electric field in the lateral direction to display a screen, and compared with the TN method, the orientation of the liquid crystal molecules and the refractive index anisotropy are improved. It has a feature that it is possible to reduce the viewing angle dependence due to it.

As a conventional liquid crystal display device, FIG.
FIG. 2 is a structural cross-sectional view of a type active matrix substrate.
In FIG. 3, reference numeral 1 denotes an insulating substrate (array substrate) made of glass or the like, on which a gate line 2 made of Al or the like and a common electrode 3 as a pixel electrode made of Al or the like are provided.
And a gate insulating film 5 made of SiNx or the like is formed so as to cover the gate line 2 and the common electrode 3.

Reference numeral 6 denotes a semiconductor layer made of a-Si or the like, 7 denotes a source electrode of the thin film transistor, 9 denotes a drain electrode of the thin film transistor, and 8
Indicates a source line made of Al or the like. Then, the thin film transistor 13 is formed by forming the passivation film 11 so as to cover them.

FIG. 4 is a plan view of an IPS active matrix substrate as seen from above. 4, the parts to which the same numbers are attached are the same as those in FIG. Further, 4 is a common line, 10 is a drain electrode as a pixel electrode, and 12 is an additional capacitance.

[0008]

However, in the structure of the active matrix substrate adopting the conventional IPS method as described above, there is a possibility that a misalignment may occur when the two substrates are bonded together. As a result, the pixel aperture ratio becomes low, and thus there is a potential disadvantage that the light transmittance becomes low as compared with the TN method.

Further, a pinhole may be generated in the passivation film on the gate line, and if a thin film transistor having such a defect is adopted in a liquid crystal display device, an intermediate color (gray) display is made in the liquid crystal display device. There was also a problem that circular spots were generated around the pinhole position. Such circular stains are
Impurities contained in liquid crystal molecules pass through pinholes in the passivation film and contact the gate electrode to be ionized, so that the effective voltage applied to the liquid crystal molecules locally decreases in that region. Is.

In order to solve the above problems, the present invention can improve the pixel aperture ratio in an active matrix substrate adopting the IPS system and can suppress circular spots on the display. It is intended to provide a substrate.

[0011]

In order to achieve the above object, an active matrix substrate according to the present invention is an array having a comb-shaped pixel electrode and a comb-shaped common electrode formed by interlocking with the pixel electrode. A substrate, a counter substrate arranged to face the array substrate, and a liquid crystal layer sandwiched between the array substrate and the counter substrate are provided, and the pixel substrate and the common electrode are substantially parallel to the array substrate and the counter substrate. In a horizontal electric field type active matrix substrate that changes the alignment of liquid crystal molecules by generating an electric field, a gate line, a common line, a gate insulating film, and a source line are sequentially formed on the array substrate, and a passivation film is formed on them. It is characterized in that the planarization insulating film is formed after forming a light shielding layer which is not electrically connected to the gate line, the common line and the source line.

With this structure, since the light-shielding layer is provided on the array substrate, the precision of preventing light leakage between pixels is higher in process than the case where the light-shielding layer is provided on the counter substrate, that is, the color filter side. Therefore, it is possible to suppress the decrease in the aperture ratio due to the misalignment when the two substrates are bonded together.

Further, even if a pinhole is generated in the passivation film, it is possible to suppress the generation of a circular spot due to the pinhole because it is covered with the light shielding layer and the flattening insulating film. .

Further, since a flattening film is formed on each of the gate, source and common wirings to flatten the unevenness of the array surface, the unevenness of the wirings creates a region where the orientation is insufficient during rubbing. It is possible to prevent the domain from being generated.

Further, by adopting a structure in which the light shielding layer is not electrically connected to each wiring, it becomes possible to prevent liquid crystal alignment disorder, and the above problems (improvement of aperture ratio and suppression of circular stain). Can be solved.

Further, in the active matrix substrate according to the present invention, the light shielding layer is preferably made of an insulating material. This is because it is possible to prevent the alignment disorder of the liquid crystal due to the voltage applied between the drain or the common electrode and the light-shielding layer, which can occur when the light-shielding layer is made of a conductive material.

Further, the active matrix substrate according to the present invention preferably has a color layer formed for each pixel.

[0018]

DETAILED DESCRIPTION OF THE INVENTION An active matrix substrate according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an active matrix substrate according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes an insulator substrate (array substrate) made of glass or the like, on which a gate line 2 made of Al or the like and a common electrode 3 made of Al or the like as a pixel electrode are arranged. A gate insulating film 5 made of a SiNx film or the like is formed so as to cover them.

Reference numeral 6 denotes a semiconductor layer made of a-Si or the like, 7 denotes a source electrode of the thin film transistor, 9 denotes a drain electrode of the thin film transistor, and 8
Indicates the source line. Then, the thin film transistor 13 is formed by forming the passivation film 11 made of SiNx so as to cover these.

In the present embodiment, the light-shielding layer 14 which was conventionally formed on the counter substrate is formed on the above-described insulator substrate (array substrate). The light shielding layer 14 is made of an insulating organic pigment or the like. If the light-shielding layer 14 is made of a conductive material, the light-shielding layer 14 will be in a floating state. Therefore, depending on the driving conditions of the liquid crystal display device and the pattern of the light-shielding layer 14, the liquid crystal alignment disorder may occur. Because. Reference numeral 15 indicates a color layer, and 16 indicates a flattening insulating film made of acrylic resin or the like.

FIG. 2 shows a plan view of the active matrix substrate according to the embodiment of the present invention. Figure 2
2 shows a gate line, 3 shows a common electrode as a pixel electrode, and 4 shows a common line. 6 is a semiconductor layer, 7 is a source electrode of a thin film transistor, 8
Is the source line, 9 is the drain electrode of the thin film transistor,
Reference numeral 10 indicates a drain electrode as a pixel electrode, and 12 indicates an additional capacitance.

Further, the color layer 14 is formed for each pixel as shown by a broken line, and the insulating light-shielding layer 15 is formed as a grid in accordance with the pixel as shown by a chain line. Shows.

As shown in FIGS. 1 and 2, in the active matrix substrate according to this embodiment, a gate line 2, a common line 3, a gate insulating film 5, and a source line 8 are formed on an insulator substrate (array substrate) 1. Are sequentially formed to form a passivation film 11, and then a color layer 15 made of organic pigments of red, green, and blue is formed for each pixel by a pigment dispersion method. After that, a light-shielding layer 14 made of an insulating black organic pigment is formed in a grid pattern in accordance with the pixels, and a planarization insulating film 16 made of acrylic resin is used as an overcoat.
Is formed.

With this structure, the light-shielding layer 14 is provided on the array substrate 1 and the color layer 15 is formed for each pixel. Therefore, the light-shielding layer 14 is provided on the counter substrate, that is, on the color filter side. It can be expected that the accuracy of preventing light leakage between pixels will be higher in the process than that of the structure in which. When the light is shielded from the counter substrate side, the accuracy of the deviation of the light shielding region due to the bonding of the array substrate and the counter substrate is generally 2 to 3 μm, whereas the light shielding on the array substrate 1 is performed. This is because, in the case of the present embodiment in which the layer 14 is provided, since the deviation of the light-shielding region depends on the manufacturing accuracy in the photo process, the accuracy of the photomask overlay deviation becomes 1 micron or less.

Therefore, a light shielding layer is formed on the array side,
By using a transparent substrate (for example, a glass substrate) as the counter substrate, it is possible to suppress a decrease in the aperture ratio, which occurs in the conventional active matrix type liquid crystal display device due to a misalignment when the two substrates are bonded together. It is considered possible.

Further, even if pinholes occur in the passivation film 11, they are covered with the color layer 15, the light-shielding layer 14, and the flattening insulating film 16, so that circular spots caused by the pinholes occur. It is also possible to suppress the phenomenon that occurs.

Furthermore, since a flattening film is formed on each of the gate, source, and common wirings to flatten the unevenness of the array surface, the unevenness of the wirings causes a region with insufficient orientation during rubbing. It is also possible to prevent the occurrence of a domain that operates.

Further, by adopting a structure in which the light shielding layer is not electrically connected to each wiring, it becomes possible to prevent the alignment disorder of the liquid crystal. That is, in the IPS type liquid crystal display device, when the light-shielding layer has a predetermined potential, a horizontal electric field is generated between the light-shielding layer and the drain or the common electrode, which causes liquid crystal orientation disorder, and the liquid crystal display device is used as a display element. It is expected that control will not be possible. Therefore,
Since the light-shielding layer is not electrically connected to any of the common gate source electrodes, the alignment disorder of the liquid crystal due to the horizontal electric field does not occur,
It is considered necessary that the light shielding layer is not electrically connected to any electrode of the common gate source.

Further, even when the light-shielding layer is not electrically connected, if the light-shielding layer itself is made of a conductive material, the light-shielding layer will be in a floating state, so that the liquid crystal display device. Depending on the driving conditions and the pattern of the light-shielding layer, the light-shielding layer may fluctuate to a predetermined potential and the liquid crystal orientation may be disturbed. Therefore, by using an insulating material such as an organic pigment or a resin for the light shielding layer, it becomes possible to more reliably prevent the above-mentioned disordered alignment of the liquid crystal.

[0031]

As described above, the active matrix substrate according to the present invention has the conventional structure because the color layer and the light shielding layer are provided on the array substrate.
It is possible to suppress a decrease in the aperture ratio due to a misalignment when the two substrates are bonded together.

Further, even if a pinhole is generated in the passivation film, the color layer, the light-shielding layer, and the flattening insulating film are covered, so that the generation of the circular stain caused by the pinhole can be suppressed.

Furthermore, since a flattening film is formed on each of the gate, source, and common wirings to flatten the unevenness of the array surface, the unevenness of the wiring creates a region where the orientation is insufficient during rubbing. Can be prevented.

Further, the structure in which the light shielding layer is not electrically connected to each wiring can prevent the liquid crystal alignment disorder between the pixel electrode and the light shielding layer.

[Brief description of drawings]

FIG. 1 is a sectional view of an active matrix substrate according to an embodiment of the present invention.

FIG. 2 is a plan view of an active matrix substrate according to an embodiment of the present invention.

FIG. 3 is a sectional view of an active matrix substrate according to a conventional IPS method.

FIG. 4 is a plan view of a conventional IPS active matrix substrate.

[Explanation of symbols]

1 Insulator substrate 2 gate lines 3 common electrode 4 common line 5 Gate insulation film 6 semiconductor layers 7 Source electrode of thin film transistor 8 source lines 9 Drain electrode of thin film transistor 10 Drain electrode as pixel electrode 11 Passivation film 12 additional capacity 13 thin film transistor 14 color layers 15 Light-shielding layer 16 Planarization insulating film

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H091 FA02Y FA34Y GA07 GA11                       GA16 LA16                 2H092 GA14 JA34 JA37 JA41 JB51                       JB57 JB58 NA07                 5C094 AA03 AA06 BA03 BA43 CA19                       CA24 DA09 DA15 EA04 EA07                       EB02 HA08                 5F110 AA30 BB01 CC07 DD02 EE03                       FF03 GG02 GG15 NN03 NN24                       NN27 NN49 NN72 QQ19

Claims (3)

[Claims] 1. An array substrate having a comb-shaped pixel electrode and a comb-shaped common electrode formed by interlocking with the pixel electrode; an opposite substrate arranged to face the array substrate; A liquid crystal layer sandwiched between a substrate and the counter substrate is provided, and an array of liquid crystal molecules is changed between the pixel electrode and the common electrode by generating an electric field substantially parallel to the array substrate and the counter substrate. In the lateral electric field type active matrix substrate, a gate line, a common line, a gate insulating film, and a source line are sequentially formed on the array substrate, and a passivation film is formed on them, and the gate line, the common line, An active matrix substrate, wherein a light-shielding layer that is not electrically connected to the source line is formed and then a planarization insulating film is formed. 2. The active matrix substrate according to claim 1, wherein the light shielding layer is made of an insulating material. 3. The active matrix substrate according to claim 1, wherein a color layer is formed for each pixel.