JPH10260431A - Active matrix type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an IPS(in-plane switching) type active matrix liquid crystal display device which can be improved in display contrast. SOLUTION: This active matrix type liquid crystal display device has an array substrate 12 which has signal wires 7 and scanning wires 2 arranged in matrix, TFTs(thin-film transistor) 11 as at least >=1 switching element corresponding to the intersections, a comb-shaped common electrode 8 connected to the TFTs 11, and a comb-shaped common electrode 3 formed meshing with the pixel electrode 8, an opposite substrate 3 which is arranged opposite the array substrate 12, and a liquid crystal layer sandwiched between the array substrate 12 and opposite substrate 13; and the pixel electrode 8 is formed in the same layer with the signal wires 7 and made thicker than the film thickness of the signal wires 7. This simple constitution prevents unoriented light omission nearby a pixel electrode and the reflection of panel external light is suppressed to obtain a high-contrast image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device which can be used as a flat display of AV / OA equipment.

[0002]

2. Description of the Related Art At present, display devices using a liquid crystal have been applied in various fields such as a viewfinder of a video camera, a pocket TV, an information display terminal such as a high-definition projection TV, a personal computer, and a word processor. Active development and commercialization.

In particular, an active matrix type TN (Twisted Nematic) liquid crystal display using a thin film transistor (TFT) as a switching element has a great feature that high contrast is maintained even when a large-capacity display is performed. Has been developed and commercialized as a favorite of large and large-capacity full-color displays for laptop computers and notebook computers, and engineering workstations, which have extremely high market demands.

In such an active matrix type liquid crystal display device, a widely used liquid crystal display mode TN (Twisted Nematic) type has a structure in which liquid crystal molecules are twisted by 90 ° between electrode substrates sandwiching a liquid crystal layer. The panel to be taken is sandwiched between two polarizing plates.

[0005] The two polarizing plates are arranged so that their polarizing axes are orthogonal to each other, and one polarizing plate is parallel or perpendicular to the major axis of the liquid crystal molecules in contact with one substrate. ing. When no voltage is applied, white display is performed. However, when a voltage is applied between two substrates, that is, in a direction perpendicular to the liquid crystal panel, the light transmittance gradually decreases, and black display is performed.

[0006] Such display characteristics are obtained because, when a voltage is applied to the liquid crystal panel, the liquid crystal molecules try to align in the direction of the electric field while untwisting the twisted structure. This is because the polarization state of the incoming light changes and the light transmittance is modulated.

However, even in the same molecular arrangement state, the polarization state of the transmitted light changes depending on the incident direction of the light incident on the liquid crystal panel, so that the light transmittance differs according to the incident direction. That is, the characteristics of the liquid crystal panel have a viewing angle dependency. This viewing angle characteristic causes a luminance inversion phenomenon when the viewpoint is tilted obliquely with respect to the main viewing angle direction (the major axis direction of the liquid crystal molecules in the intermediate layer of the liquid crystal layer).
It is an important issue.

In order to solve this problem, instead of applying an electric field in a direction perpendicular to the substrate as in the TN type liquid crystal display system, an IPS (In) is used in which the direction to be applied to the liquid crystal is substantially parallel to the substrate. -Plane Switching) system, for example, Japanese Patent Publication No. 63-21907 and Japanese Patent Laid-Open No. 6-160.
No. 878 proposes this.

[0009]

FIG. 3A shows a configuration of a pixel portion of an array substrate of a conventional IPS type liquid crystal display device. FIG. 3B is a schematic cross-sectional view of the cross-sectional configuration of the liquid crystal display device taken along a dashed line in FIG.

As shown in FIG. 1, a plurality of scanning lines 2 and signal lines 7 are formed so as to be orthogonal to each other.
A TFT 11 serving as a switching element is provided corresponding to each intersection of the signal wiring 7 and. In one pixel surrounded by two adjacent scanning lines 2 and two adjacent signal lines 7, a plurality of, for example, two pixel electrodes 8 are formed substantially in parallel with the signal lines 7. A plurality of, for example, three common electrodes 3 are formed in a comb shape between the signal wiring 7 and the pixel electrode 8 and between the adjacent pixel electrodes 8, and are engaged with the pixel electrode 8. The storage capacitor section 9 is formed between the pixel electrodes 8 and above the scanning wiring 2.

Next, the manufacturing process will be described. Aluminum (Al) is laminated on the glass substrate 1, and the scanning wiring 2 and the common electrode 3 are simultaneously patterned by photolithography. On the scanning wiring 2 and the common electrode 3, a first insulator layer 4 of silicon nitride (SiNx) serving as a gate insulating film of the TFT is laminated. Further, on the first insulator layer 4, a semiconductor layer 5 of amorphous silicon (α-Si) which performs a switching function of the TFT is laminated. afterwards,
Silicon nitride (SiN) as a channel protection film for TFT
x) The second insulator layer 6 is laminated and patterned. Then, three layers of n + amorphous silicon (n + -α-Si), titanium (Ti), and aluminum (Al) are successively deposited to form a collective pattern, and the signal wiring 7 and the pixel electrode 8 are formed.
And the storage capacitor section 9 were formed as shown in the figure. Here, n + amorphous silicon (n + -α-Si) is used for making ohmic contact between the semiconductor layer 5 and the signal wiring 7 and the pixel electrode 8; In order to prevent the semiconductor layer 5 from being diffused. Further, a third insulator layer 10 of silicon nitride (SiNx) is laminated as a TFT protective film.

An alignment film is applied to the array substrate 12 and the counter substrate 13 configured as described above, and a rubbing process is performed. Then, the array substrate 12 and the opposing substrate 13 are bonded with a certain gap therebetween, and liquid crystal is injected between them.
The liquid crystal layer 14 is formed. The opposing substrate 13 has a light shielding film 15 at a position corresponding to the scanning wiring 2 and the signal wiring 7.
The light shielding film 15 does not exist at a position corresponding to the common electrode 3 and the pixel electrode 8.

However, in the above configuration, the signal wiring 7 and the pixel electrode 8 have the same thickness. It is necessary to increase the thickness of the signal wiring 7 in order to provide a margin for disconnection failure and to reduce wiring resistance. Therefore, the pixel electrode 8
The rubbing process is not performed in the vicinity of the pixel electrode 8. For this reason, in the panel display, non-alignment light leakage occurs in that portion, and the contrast is reduced.
Further, since the outermost surface of the pixel electrode 8 is formed of aluminum (Al) having a high reflectivity, light outside the panel is reflected, which causes a problem of further lowering the contrast.

[0014]

An active matrix type liquid crystal display device according to the present invention comprises a plurality of signal wirings and scanning wirings arranged in a matrix, and at least one switching element corresponding to each intersection thereof. A comb-shaped pixel electrode connected to the switching element, an array substrate having a comb-shaped common electrode formed in engagement with the pixel electrode, and an opposing substrate arranged to face the array substrate,
A liquid crystal layer sandwiched between the array substrate and the counter substrate, wherein the pixel electrode is formed in the same layer as the signal wiring, and is thinner than the film thickness of the signal wiring. .

According to the present invention, a rubbing process can be performed even in the vicinity of the pixel electrode, and no non-aligned light escapes in the vicinity of the pixel electrode.

[0016]

DETAILED DESCRIPTION OF THE INVENTION An active matrix type liquid crystal display device according to the present invention comprises a plurality of signal wirings and scanning wirings arranged in a matrix, at least one switching element corresponding to each intersection, and the switching element. An array substrate having a comb-shaped pixel electrode connected to the pixel electrode, a comb-shaped common electrode formed in engagement with the pixel electrode, a counter substrate disposed to face the array substrate, the array substrate and the A liquid crystal layer sandwiched between the opposing substrate and
Since the pixel electrode is formed in the same layer as the signal wiring and has a thickness smaller than the thickness of the signal wiring, even if an alignment film is applied to the array substrate and a rubbing process is performed, the pixel electrode remains in the signal wiring. The rubbing process can be performed even in the vicinity of the pixel electrode because it is thinner than the film thickness of. Therefore, in the panel display, non-aligned light does not escape near the pixel electrode, and a screen with high contrast is obtained.

It is preferable that the pixel electrode and the signal wiring are formed of different conductive materials, and that the outermost surface of the pixel electrode is formed of a conductive material having a lower reflectance than aluminum. Since the electrodes are formed of a transparent conductive material, reflection of light outside the panel is suppressed, and a screen with higher contrast is obtained.

Hereinafter, an active matrix type liquid crystal display device of the present invention will be described based on each embodiment. (Embodiment 1) FIG. 1A schematically shows a plane configuration of a pixel portion of an array substrate according to Embodiment 1 of the present invention, and FIG. 1B is a point of FIG. 1 is a schematic cross-sectional view of a cross-sectional configuration of a liquid crystal display device taken along a chain line.

On the glass array substrate 1 shown in FIG. 1, a plurality of scanning wirings 2 and signal wirings 7 are formed so as to be orthogonal to each other, and a TFT 11 serving as a switching element corresponding to each intersection of the scanning wirings 2 and the signal wirings 7. Is provided. In one pixel surrounded by two adjacent scanning lines 2 and two adjacent signal lines 7, a plurality of, for example, two pixel electrodes 8 are formed substantially in parallel with the signal lines 7.

Between the signal wiring 7 and the pixel electrode 8 and between the adjacent pixel electrodes 8, a plurality of, for example, three common electrodes 3 are provided.
Are formed in a comb shape and are in mesh with the pixel electrode 8.
The storage capacitor section 9 is formed between the pixel electrodes 8 and above the scanning wiring 2.

The manufacturing process is as follows. Scan wiring 2
As shown in the figure, a pattern is formed on the glass substrate 1 in a substantially parallel manner at predetermined intervals by photolithography using aluminum. At the same time, a common electrode 3 that is substantially parallel to each other is patterned between two adjacent scanning lines 2.

The thickness of the scanning wiring 2 and the common electrode 3 is 1
The thickness is 50 nm, and the material is not limited to aluminum, and a conductive single-layer film or a multilayer film such as chromium (Cr) or a metal containing aluminum as a main component may be used.

On the scanning wiring 2 and the common electrode 3, a first insulating material such as silicon nitride (SiNx), which serves as a gate insulating film of the TFT 11 functioning as a switching element, is used.
An insulator layer 4 is laminated. Further, the first insulator layer 4
A semiconductor layer 5 made of, for example, amorphous silicon (α-Si), which controls the switching function of the TFT, is stacked on the substrate.
After that, a second insulator layer 6 of silicon nitride (SiNx) is laminated and patterned as a channel protective film of the TFT. And n + amorphous silicon (n + -α-S
i), two layers of titanium (Ti) are successively deposited, and a collective pattern is formed by dry etching;
And the storage capacitor section 9 were formed as shown in the figure. A pixel electrode 8 is formed between two mutually adjacent common electrodes 3 so as to be substantially parallel to the common electrode 3. Here, titanium (T
The film thickness of i) was 100 nm.

Further, aluminum (Al) is
The pattern was formed by wet etching so that the signal wiring 7 was substantially perpendicular to the scanning wiring 2 and substantially parallel to the scanning wiring 2 by using this.

On the scanning line 2 with the first insulator layer 4 and the semiconductor layer 5 interposed therebetween, a storage capacitor section 9 is formed so as to overlap the two pixel electrodes 8. The storage capacitor section 9 is provided to hold the voltage supplied to the pixel. Then, a third insulator layer 10 of, for example, silicon nitride (SiNx) was laminated as a protective film.

An alignment film was applied to the array substrate 12 and the counter substrate 13 configured as described above, and a rubbing process was performed. Then, the array substrate 12 and the counter substrate 13 were bonded together with a gap of 3 μm therebetween, and liquid crystal was injected between them to form a liquid crystal layer 14. As described above, the pixel electrode 8 is 200 nm thinner than the signal wiring 7, so that rubbing can be performed in the vicinity of the pixel electrode 8, and the pixel electrode 8 is formed of titanium having a lower reflectance than aluminum. . When a lighting image inspection of this liquid crystal display device was performed, it was confirmed that there was no non-alignment light leakage near the pixel electrode 8 and an image with high contrast was obtained.

The pixel electrode 8 has a thickness of 30 to 200 n.
m and the material is tantalum other than titanium (T
a), a conductive material having a lower reflectance than aluminum, such as chromium (Cr) or molybdenum (Mo), or indium-tin oxide (ITO) as a transparent conductive material may be used.

This configuration is effective even when the common electrode 3 is formed in the same layer as the signal wiring 7 by applying the items related to the pixel electrode 8 to the common electrode 3. (Embodiment 2) FIG. 2 (a) schematically shows a planar configuration of a pixel portion of an array substrate according to (Embodiment 2) of the present invention, and FIG. 2 (b) is a point of FIG. 2 (a). 1 is a schematic cross-sectional view of a cross-sectional configuration of a liquid crystal display device taken along a chain line. A description of parts common to the first embodiment is omitted, and different parts will be described.

(Embodiment 2) shows that after the pattern formation of the second insulator layer 6, n + amorphous silicon (n + -α-
Two layers of Si) and titanium (Ti) were successively deposited, and a collective pattern was formed by dry etching to form a pixel electrode 8, a storage capacitor portion 9, and a signal wiring portion as shown in the figure.

Further, aluminum (Al) was deposited, and the signal wiring 7 was formed by wet etching so as to overlap the signal wiring portion formed of titanium (Ti). This signal wiring 7 is made of titanium / aluminum (T
(Embodiment 1)
As compared with, the tolerance for the disconnection failure of the signal wiring 7 can be further increased, and the wiring resistance can be further reduced. When a lighting image inspection of this liquid crystal display device was performed, it was confirmed that there was no non-alignment light leakage near the pixel electrode 8 and an image with high contrast was obtained.

[0031]

As described above, the active matrix type liquid crystal display device of the present invention is a simple IPS type liquid crystal display device capable of realizing good multi-gradation display with a wide viewing angle by reducing the thickness of the signal wiring. With such a configuration, it is possible to prevent non-alignment light leakage near the pixel electrode and to suppress reflection of light outside the panel without reducing the margin for disconnection failure or increasing the wiring resistance.
An image with high contrast can be obtained.

[Brief description of the drawings]

FIGS. 1A and 1B are a plan view and a sectional view schematically showing a planar configuration of a pixel portion of an array substrate in an active matrix liquid crystal display device according to Embodiment 1 of the present invention. FIGS.

FIGS. 2A and 2B are a plan view and a sectional view schematically showing a planar configuration of a pixel portion of an array substrate in an active matrix liquid crystal display device according to a second embodiment of the present invention. FIGS.

FIG. 3 is a plan view and a cross-sectional view schematically showing a planar configuration of a pixel portion of an array substrate in a conventional active matrix liquid crystal display device.

[Explanation of symbols]

 Reference Signs List 1 glass substrate 2 scanning wiring 3 common electrode 4 first insulating layer 5 semiconductor layer 6 second insulating layer 7 signal wiring 8 pixel electrode 9 storage capacitor section 10 third insulating layer 11 TFT 12 array substrate 13 facing substrate 14 liquid crystal Layer 15 Light shielding film

Claims (3)

[Claims] 1. A plurality of signal wirings and scanning wirings arranged in a matrix, at least one or more switching elements corresponding to respective intersections thereof, a comb-shaped pixel electrode connected to the switching elements, and the pixel electrode An array substrate having a comb-shaped common electrode formed by engaging with the array substrate, a counter substrate disposed to face the array substrate, and a liquid crystal layer sandwiched between the array substrate and the counter substrate. An active matrix type liquid crystal display device, wherein the pixel electrode is formed in the same layer as the signal wiring, and is thinner than the film thickness of the signal wiring. 2. The active matrix liquid crystal display device according to claim 1, wherein the pixel electrode and the signal wiring are formed of different conductive materials. 3. The pixel electrode according to claim 1, wherein the outermost surface of the pixel electrode is formed of a conductive material having a lower reflectance than aluminum, or the pixel electrode is formed of a transparent conductive material. Active matrix type liquid crystal display device.