JP3346354B2 - LCD panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an IPS(in-plane switching) mode liquid crystal display device in which black unevenness scarcely occurs even in the cases laser repair is applied to a short circuit in gate signal wiring or a defect such as a pinhole exists in a gate insulation layer. SOLUTION: In a liquid crystal display panel provided with source signal wiring and gate signal wiring arranged in a matrix, switching elements arranged corresponding to respective intersections of the source signal wiring and the gate signal wiring, pixel electrodes connected to the switching elements, a common electrode formed opposite to the pixel electrodes, common wiring connecting the common electrode and an alignment layer formed on the surface of the liquid crystal layer on the counter surface of the one substrate, apart from the respective wiring and electrodes a neutralizing electrode is formed at least a part of which is in contact with the liquid crystal layer or the alignment layer.

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 an IPS mode liquid crystal display panel in which liquid crystals are driven by applying a substantially parallel electric field to a substrate surface.

[0002]

2. Description of the Related Art Active matrix type liquid crystal displays using thin film transistors (TFTs) are thin, light, and can be driven at a low voltage because of their advantages, such as displays for camcorders, personal computers, and personal computers. It is used in various fields such as processor displays and forms a large market.

In recent years, in particular, in personal computer applications, there has been an increasing demand for a liquid crystal display panel having a wider viewing angle in order to cope with a larger screen. As a method for widening the angle, a horizontal electric field method in which a pixel electrode and a counter electrode are formed on the same substrate and a liquid crystal molecule is operated by applying a horizontal electric field has been proposed in Japanese Patent Application Laid-Open No. Hei 6-160878. . This method is also called an IPS (In-Plane-Switching) mode or a comb-shaped electrode method. In this display method, the major axis of the liquid crystal molecules is almost always parallel to the substrate and does not rise. The change in brightness when changed is small and a wide viewing angle can be obtained.

However, this IPS mode TFT
When the liquid crystal display is used continuously, display irregularities appearing as black dots may occur. This black spot-like unevenness is very problematic because it degrades the display quality. The countermeasure and the solution for the black dot display unevenness are described in JP-A-10-206857. According to the document, black spot-like unevenness occurs at a crack portion of a protective layer of a pixel electrode and a source signal line, and the voltage holding ratio of a liquid crystal layer is reduced due to generation of an ionic substance. By making the thickness of the protective layer larger than the thickness of the electrode or by forming a protective layer of an organic polymer, it is possible to eliminate black spot unevenness.

Hereinafter, a conventional liquid crystal display panel will be described with reference to the drawings.

FIG. 10 is a schematic diagram showing a plane of one pixel of an array substrate constituting a conventional liquid crystal display panel, and FIGS.
FIG. 11 is a sectional view taken along line BB ′ and AA ′ in FIG. In FIG. 10, reference numeral 101 denotes a gate signal line, and 103 denotes a common electrode formed in the same layer. An insulating layer 104 is formed thereon, and a thin film transistor (TFT) 107 including a semiconductor layer 106, a source signal wiring 108, and a pixel electrode 109 are pattern-formed, and a protective layer 111 is formed thereon.
Are deposited to form an array substrate. An alignment film 113 is formed on the array substrate and on the side of the color filter substrate facing the array substrate, and a liquid crystal layer 114 is formed between the two substrates to form a liquid crystal display panel.

In the manufacturing process of the liquid crystal display panel as described above, a very fine processing process is required.
If foreign matter is present in the process, a short circuit will occur at the intersection of the gate signal wiring and the source signal wiring, or in the vicinity of the gate signal wiring and the common electrode, and this will be a major factor in lowering the production yield. ing. Figure 10
As shown in FIG. 12, when the gate signal wiring 101 and the common electrode 103 are formed on the same surface, an electrode material is usually deposited by a sputtering method or the like, and a pattern is formed by a photolithographic method. In addition, as shown in FIG. 12, when foreign matter 115 contained in a resist material or the like is present at a position where the electrode material is to be removed, the foreign matter cannot be exposed, and is originally removed as shown in FIG. In some cases, a portion to be formed as an electrode remains, resulting in a continuous wiring as shown in FIG.

Usually, the short-circuited portion is often several places in the liquid crystal display panel. As a countermeasure, it is very effective to repair the portion by cutting it with a means such as a laser to improve the yield. It is a means.

[0009]

However, even if laser protection is performed to increase the thickness of the protective layer so as not to cause cracks in the protective layer as described above, the gate signal wiring is formed as shown in FIG. Has a problem that the cut surface is exposed to the liquid crystal layer, causing the above-described electrochemical reaction to cause black spot unevenness. As measures against this, pixel electrodes, source signal wiring, common wiring,
It is conceivable to supply a positive potential to the gate signal wiring directly from the common electrode to the liquid crystal layer to neutralize the generated ionic substance, but these wirings and electrodes are all necessary to drive the liquid crystal layer. It is not only a problem in terms of display image quality that the potential required for driving the wirings / electrodes changes due to an electrode reaction with the liquid crystal, but also from the viewpoint of long-term reliability. Absent.

The present invention has been made in view of the above-mentioned inconveniences of the conventional liquid crystal display panel. Even when laser repair is performed or a defect such as a pinhole is present in an insulating layer on a gate signal wiring, a black spot is formed. It is an object to provide a liquid crystal display panel free from unevenness.

[0011]

In order to achieve the above object, the liquid crystal display panel of the present invention has at least the following constitution.

In the means 1, the neutralizing electrode is configured to be in contact with the liquid crystal layer or the alignment layer in addition to the source signal wiring, the gate signal wiring, the pixel electrode, the common electrode, and the common wiring.

[0013] In the means 2, in addition to the source signal wiring, the gate signal wiring, the pixel electrode, the common electrode, and the common wiring, a neutralizing electrode is formed so as to be in contact with the liquid crystal layer or the alignment layer.
The neutralizing electrode is provided with means for supplying a positive potential to the gate signal wiring.

In the means 3, in addition to the source signal wiring, the gate signal wiring, the pixel electrode, the common electrode, and the common wiring, a neutralizing electrode is formed along the gate signal wiring so as to be in contact with the liquid crystal layer or the alignment layer. The neutralizing electrode is provided with means for supplying a positive potential to the gate signal wiring.

In the means 4, a neutralizing electrode is formed on the substrate facing the substrate on which the gate signal wiring is formed so as to be in contact with the liquid crystal layer or the alignment layer along the gate signal wiring. A means for supplying a positive potential to the signal wiring is provided.

In the means 5, a neutralizing electrode is formed on the substrate facing the substrate on which the gate signal wiring is formed so as to be in contact with the liquid crystal layer or the alignment layer. A means for supplying a potential is provided, and the neutralizing electrode is configured to be a black matrix.

In the means 1, by providing the neutralizing electrode so as to be in contact with the liquid crystal layer or the alignment layer, the occurrence of black spot unevenness is suppressed. The reason is considered as follows.

That is, the cause of black spot unevenness is that electrons are injected into the liquid crystal layer from the gate signal wiring, which has a negative potential for most of the period, through a defect in the upper insulating layer caused by laser repair, pinholes, or the like. This is because generated ions (anions) are generated. Since the generated ions are not neutralized, the ion concentration in the liquid crystal near the defect increases, the voltage holding ratio decreases, and the liquid crystal looks black. This is schematically shown in FIG.

However, when there is a neutralizing electrode directly exposed to the liquid crystal layer or electrically connected to the liquid crystal layer via the alignment film, electrons can be supplied to the electrode again by the neutralizing electrode. Therefore, the ion concentration in the vicinity of the insulating layer defective portion does not increase so much, the decrease in the voltage holding ratio can be minimized, and the occurrence of black spot unevenness can be suppressed. This is schematically shown in FIG.

In the means 2, by providing a means for supplying a positive potential to the gate signal wiring to the neutralizing electrode, it is possible to more effectively neutralize the generated anions and suppress the occurrence of black spot unevenness. I can do it.

In the means 3, since the neutralizing electrode is formed along the gate signal wiring, the generated anions can be neutralized more efficiently before diffusing from the anion generating source to the pixel.

In the means 4, the neutralizing electrode is formed on the opposite substrate, whereby the distance between the neutralizing electrode and the gate signal line is widened, the parasitic capacitance formed between the neutralizing electrode and the gate signal wiring can be reduced, and the delay of the gate signal can be reduced. Can be eliminated.

In the means 5, since the neutralizing electrode is a black matrix, the number of steps for forming the electrode can be reduced.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a liquid crystal display panel of the present invention will be described more specifically with reference to the drawings.

(Embodiment 1) The diagonal of the screen is 15.2 inches, the aspect ratio is 16: 9, and the resolution is 768 × 13.
A 64 RGB IPS mode TFT liquid crystal display panel was manufactured as follows. FIG. 1 is a schematic plan view of an array shape in a pixel portion of this panel, and FIG.
FIG. 2 shows a schematic sectional view.

1 and 2, a gate signal wiring 1, a common wiring 2, and a common electrode 3 are formed of a metal film containing aluminum as a main component on an array substrate 20 based on a glass substrate. Patterns were formed on the same plane. The material used for the gate signal wiring is desirably a metal having a low wiring resistance. However, the material is not particularly limited to an aluminum-based metal, and may be a single-layer film or a multilayer film. Next, after depositing the anodic oxide layer of the aluminum film and silicon nitride (SiNx) as the insulating layer 4 and amorphous silicon as the semiconductor layer 6, the gate signal wiring 1
A thin film transistor (TFT) serving as a switching element by removing a part of the upper insulating layer and depositing two layers of aluminum / titanium (Al / Ti) by a sputtering method
7, the source signal wiring 8 and the pixel electrode 9 were patterned by photolithography, and a storage capacitor 10 was formed between the pixel electrode 9 and the common wiring 2. Further, after silicon nitride (SiNx) is deposited as a protective layer 11 by a CVD method, a metal film containing aluminum as a main component is formed as a neutralizing electrode 12 thereon, and a pattern is formed along a gate signal wiring by a photolithographic method. It was formed so that each neutralization electrode was connected outside the display area.

The array substrate 2 formed as described above
0, an alignment film 13 (AL5417: manufactured by JSR) is printed and formed on the opposite surface side of the color filter substrate 21 on which a black matrix and RGB are formed so as to face the array substrate, and after performing a rubbing process, a gap 3 is formed. The two substrates were bonded together at an interval of 0.5 μm, and the liquid crystal 14 was injected under vacuum to form an IPS panel. The injected liquid crystal is a p-type nematic liquid crystal mainly containing cyano-substituted phenylcyclohexane as a p-type component. The liquid crystal is aligned without twist between the upper and lower substrates when no electric field is applied, and its director direction forms an angle of 80 degrees with the gate signal wiring 1.
The polarizing plates were attached on the upper and lower sides of the substrate so that their polarizing axes were orthogonal to each other, and one of the polarizing axes was aligned with the director direction of the liquid crystal.

In the liquid crystal display panel prepared as described above, a laser beam was irradiated to the gate signal wiring portion in the same manner as when performing laser repair, so that the gate signal wiring portion was exposed to the liquid crystal layer.

A driving circuit was connected to the panel, and the panel was continuously driven at an ambient temperature of 60 ° C. for up to 300 hours.
Until 00 hours, no black spot unevenness was observed from a defective portion of the insulating layer on the gate signal wiring, and minute black spot unevenness was observed after 300 hours.

In this embodiment, since the insulating layer does not exist on the pixel electrode and the source signal wiring and the electrode is exposed, even if there is a defective portion of the insulating layer on the gate signal wiring, occurrence of black spot unevenness is minimized. Can be minimized.

In the present embodiment, the neutralizing electrode is formed of a metal containing aluminum as a main component.
And the like.

Although the neutralizing electrode 12 is also formed on the source signal wiring, it is formed only on the gate signal wiring 1 as shown in FIG. 3 so that the neutralizing electrodes are connected outside the display area. It may be formed. In this case, the parasitic capacitance formed between the source signal wiring 8 and the neutralizing electrode 12 can be eliminated, and the delay of the source signal can be suppressed. Further, as shown in FIG. 4, the neutralizing electrode 11 may be formed so as to be shifted from above the gate signal wiring 1, and in this case, the parasitic capacitance formed between the gate signal wiring and the neutralizing electrode can be reduced. And delay of the gate signal can be suppressed. Regarding the protective layer 10 formed between the gate signal wiring 1 and the neutralizing electrode 12, it is better to form the protective layer 10 to have a large thickness in order to suppress the parasitic capacitance and reduce the probability of occurrence of pinholes.
It is better to form with a thickness of 500 ° or more.

Further, as the neutralizing electrode 12, a light-shielding material mainly composed of a conductive polymer such as chromium metal or polypyrrole is used, and as shown in FIG. It may be formed so as to shield the gap between the signal wiring and the common electrode from light. In this case, there is no need to form a black matrix on the color filter substrate 21, and the number of steps and costs can be reduced.

(Comparative Example 1) 15.2 inch diagonal of screen
Aspect ratio 16: 9, resolution is 768 vertical x 1364 horizontal
An RGB IPS mode TFT liquid crystal display panel was manufactured as follows. FIG. 10 is a schematic plan view of an array shape in a pixel portion of this panel, and FIG. 11 is a schematic cross-sectional view thereof.

10 and 11, the gate signal wiring 10
1. The common electrode 103 was formed by forming a metal film containing aluminum as a main component and patterning it on the same plane by photolithography. The material used for the gate signal wiring is desirably a metal having a low wiring resistance. However, the material is not particularly limited to an aluminum-based metal, and may be a single-layer film or a multilayer film. Next, after an anodic oxide layer of the aluminum film and silicon nitride (SiNx) are deposited as an insulating layer and amorphous silicon is deposited as a semiconductor layer, a part of the anodic oxide layer and the silicon nitride layer on the gate signal line 1 is removed, and sputtering is performed. Aluminum / titanium (Al / T
i) depositing two layers, thin film transistor (TFT),
The source signal wiring 108 and the pixel electrode 109 were patterned by photolithography. A storage capacitor 110 was formed between the pixel electrode 109 and the gate signal line. Further, silicon nitride (SiNx) was deposited as a protective layer 111 on the entire surface of the pixel portion.

The array substrate and the color filter substrate were bonded at a gap of 3.5 μm, and liquid crystal was injected under vacuum to form an IPS panel. The injected liquid crystal is a p-type nematic liquid crystal mainly containing cyano-substituted phenylcyclohexane as a p-type component. The liquid crystal is aligned without twist between the upper and lower substrates when no electric field is applied, and its director direction forms an angle of 80 degrees with the gate signal wiring 1. The polarizing plates were attached on the upper and lower sides of the substrate so that their polarizing axes were orthogonal to each other, and one of the polarizing axes was aligned with the director direction of the liquid crystal.

In order to modelly form a defective portion of the insulating layer on the gate signal wiring, the gate signal wiring was irradiated with a laser beam to remove a part of the insulating layer in the gate signal wiring.

When a drive circuit was connected to the panel and the panel was continuously driven at an ambient temperature of 60 ° C., black spot unevenness was observed from a defective portion of the insulating layer on the gate signal wiring in 20 hours.

In this comparative example, all the other electrodes are covered with the insulating layer in the vicinity of the defective portion of the insulating layer on the gate signal wiring, so that black spots are generated in a relatively short time.

(Embodiment 2) A drive circuit is connected to the liquid crystal display panel prepared in Embodiment 1, and one end of the neutralizing electrode is connected to a power supply circuit of this drive circuit so that a potential of +6 V is applied. did. The panel was continuously driven in an atmosphere temperature of 60 ° C. for up to 500 hours, but no black spot unevenness was observed from a defective portion of the insulating layer on the gate signal wiring.

(Embodiment 3) An array substrate was formed in the same manner as in Embodiment 1 except that a neutralizing electrode was formed. As shown in FIGS. 6 and 7, a neutralizing electrode was pattern-formed on the black matrix of the color filter substrate 21 on which the black matrix and RGB were formed, facing the array substrate. An alignment film (AL5417: manufactured by JSR) is printed and formed on the opposing surfaces of the two substrates, and a rubbing process is performed.
The two substrates were bonded at an interval, and a p-type nematic liquid crystal mainly containing cyano-substituted phenylcyclohexane as a p-type component was vacuum-injected to form an IPS panel. The polarizing plates were attached on the upper and lower sides of the substrate so that their polarizing axes were orthogonal to each other, and one of the polarizing axes was aligned with the director direction of the liquid crystal.

In the liquid crystal display panel prepared as described above, a laser beam was irradiated to the gate signal wiring portion in the same manner as when performing laser repair, so that the gate signal wiring portion was exposed to the liquid crystal layer.

A drive circuit is connected to this panel, and one end of the neutralizing electrode is connected to a power supply of the drive circuit, and a voltage of +6 V
Was applied. This liquid crystal display panel
The device was continuously driven for up to 500 hours in an atmosphere temperature of 0 ° C., but no black spot unevenness was observed from a defective portion of the insulating layer on the gate signal wiring.

In this embodiment, since the neutralizing electrode is formed, black spot unevenness can be prevented even if there is a defect in the insulating layer on the gate signal wiring. Further, in the present embodiment, the neutralizing electrode is formed on the color filter substrate side instead of the array substrate side, so that the parasitic capacitance of the gate signal wiring and the video signal wiring hardly increases and the liquid crystal display panel without signal delay Is obtained.

In the present embodiment, the neutralizing electrode is formed on the source signal wiring, but may be formed only on the gate signal wiring as shown in FIG. Also, the neutralizing electrode was separately formed on the black matrix, but as shown in FIG. 9, the black matrix was formed mainly of a conductive material, for example, a conductive polymer such as metal chromium or polypyrrole,
The black matrix itself may be used as the neutralizing electrode. In this case, since it is not necessary to separately form a neutralizing electrode, the number of steps and cost can be reduced.

[0046]

As described above, according to the present invention, even when laser repair is performed by providing a neutralizing electrode or when a defect such as a pinhole is present in an insulating layer on a gate signal wiring, black spot unevenness is generated. It is possible to obtain a liquid crystal display panel that does not cause any problem, and easily manufacture a panel with high display quality.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing a shape of a pixel portion of an array substrate in a liquid crystal display panel of Embodiment 1.

FIG. 2 is a schematic cross-sectional view showing a shape of an AA ′ part of FIG. 1 in the liquid crystal display panel of Embodiment 1.

FIG. 3 is a schematic plan view showing a shape of a pixel portion of an array substrate in the liquid crystal display panel of Embodiment 1.

FIG. 4 is a schematic plan view illustrating a shape of a pixel portion of an array substrate in the liquid crystal display panel of Embodiment 1.

FIG. 5 is a schematic cross-sectional view illustrating a shape of a pixel portion in the liquid crystal display panel of Embodiment 1.

FIG. 6 is a schematic plan view illustrating a shape of a pixel portion of a color filter substrate in a liquid crystal display panel of Embodiment 3.

FIG. 7 is a schematic cross-sectional view showing a shape of an AA ′ part of FIG. 6 in the liquid crystal display panel of Embodiment 3.

FIG. 8 is a schematic plan view showing the shape of a pixel portion of a color filter substrate in a liquid crystal display panel of Embodiment 3.

FIG. 9 is a schematic plan view illustrating a shape of a pixel portion of a color filter substrate in a liquid crystal display panel of Embodiment 3.

FIG. 10 is a schematic plan view showing the shape of a pixel portion of an array substrate in liquid crystal display panels of a conventional example and a comparative example.

11 is a schematic cross-sectional view showing the shape of a BB ′ part in FIG. 10 in the conventional and comparative liquid crystal display panels.

FIG. 12 is a schematic cross-sectional view showing the shape of the AA ′ portion in FIG. 10 when foreign matter adheres to the liquid crystal display panels of the conventional and comparative examples.

FIG. 13 is a schematic view showing the mechanism of occurrence of black spot unevenness.

FIG. 14 is a schematic view showing a mechanism for suppressing black spot unevenness.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gate signal wiring 2 Common wiring 3 Common electrode 4 Insulating layer 7 Thin film transistor (TFT) 8 Source signal wiring 9 Pixel electrode 10 Storage capacitor part 11 Protective layer 12 Neutralizing electrode 13 Hardening film 14 Liquid crystal layer 20 Array substrate 21 Color filter substrate BM Black matrix R Color filter (red) G Color filter (green) B Color filter (blue)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2000-284319 (JP, A) JP-A-2000-206510 (JP, A) JP-A-11-295763 (JP, A) (58) Fields surveyed ( Int.Cl. ⁷ , DB name) G02F 1/1368 G02F 1/1343 G02F 1/13 101

Claims (6)

(57) [Claims] 1. A source signal line and a gate signal line arranged in a matrix on a surface of one of two substrates opposed to each other with a liquid crystal layer interposed therebetween, and the source signal line and the gate signal A switching element provided corresponding to each intersection of wiring, a pixel electrode connected to the switching element, a common electrode formed so as to face the pixel electrode, a common wiring connecting the common electrode, and the liquid crystal In a liquid crystal display panel having at least an alignment layer formed on a layer surface, a neutralizing electrode is formed so that at least a part thereof is in contact with the liquid crystal layer or the alignment layer, separately from the wirings or the electrodes. A liquid crystal display panel characterized by the following. 2. A source signal line and a gate signal line arranged in a matrix on a surface of one of two substrates opposed to each other with a liquid crystal layer sandwiched therebetween, and the source signal line and the gate signal A switching element provided corresponding to each intersection of wiring, a pixel electrode connected to the switching element, a common electrode formed so as to face the pixel electrode, a common wiring connecting the common electrode, and the liquid crystal In a liquid crystal display panel having at least an alignment layer formed on a layer surface, separately from the wirings or the electrodes, at least a part thereof is formed with a neutralizing electrode so as to be in contact with the liquid crystal layer or the alignment layer, A liquid crystal display panel characterized in that a means for supplying a positive potential to the gate signal wiring is provided to the neutralizing electrode. 3. A source signal line and a gate signal line arranged in a matrix on a surface of one of two substrates opposed to each other with a liquid crystal layer interposed therebetween, and the source signal line and the gate signal A switching element provided corresponding to each intersection of wiring, a pixel electrode connected to the switching element, a common electrode formed so as to face the pixel electrode, a common wiring connecting the common electrode, and the liquid crystal A liquid crystal display panel having at least an alignment layer formed on the surface of the layer, in addition to each of the wirings or the electrodes, at least a portion along the gate signal wiring so as to be in contact with the liquid crystal layer or the alignment layer. A liquid crystal display panel comprising: a neutralizing electrode; and means for supplying a positive potential to the neutralizing electrode with respect to a gate signal line. 4. A source signal line and a gate signal line arranged in a matrix on a surface of one of two substrates opposed to each other with a liquid crystal layer interposed therebetween, and the source signal line and the gate signal A switching element provided corresponding to each intersection of wiring, a pixel electrode connected to the switching element, a common electrode formed so as to face the pixel electrode, a common wiring connecting the common electrode, and the liquid crystal A liquid crystal display panel having at least an alignment layer formed on the surface of the layer, wherein at least a portion of the liquid crystal display panel is neutralized along the gate signal line on the opposite surface side of the other substrate so as to be in contact with the liquid crystal layer or the alignment layer. A liquid crystal display panel comprising: an electrode; and a means for supplying a positive potential to the neutralizing electrode with respect to a gate signal line. 5. A source signal line and a gate signal line which are arranged in a matrix on a surface of one of two substrates opposed to each other with a liquid crystal layer interposed therebetween. A switching element provided corresponding to each intersection of wiring, a pixel electrode connected to the switching element, a common electrode formed so as to face the pixel electrode, a common wiring connecting the common electrode, and the liquid crystal A liquid crystal display panel having at least an alignment layer formed on the surface of the layer, wherein at least a portion of the light-shielding neutralizing electrode is arranged along the gate signal wiring or the video signal wiring so as to be in contact with the liquid crystal layer or the alignment layer. And a means for supplying a positive potential to the gate signal wiring is provided to the neutralizing electrode, and the neutralizing electrode becomes a black matrix. A liquid crystal display panel characterized by the following. 6. The liquid crystal display panel according to claim 1, wherein the neutralizing electrode is formed on the color filter substrate side.