JPH10232399A - Liquid crystal display device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate defective display caused by alignment defect occurring on liquid crystal molecules between pixels electrodes. SOLUTION: When this device is configured so that pixel electrodes 6 formed on a thin film transistor(TFT) substrate 12 have a structure formed further on a planarization layer 9 formed on the TFT and the signal wiring, separation recessed groove 11 is formed on the flattened layer 9 between the pixel electrodes 6. Further, defective display is eliminated by aligning the molecules of the liquid crystal 3 in the area always orthogonal to the substrates 1, 2 by means of forming a vertical film 7 in the bottom of the separation recessed groove 11 and a substrate area opposed to the area.

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 having a switching element such as a thin film transistor (hereinafter referred to as a TFT) and a method for manufacturing the same, and more particularly, to a structure having a structure for improving display quality and manufacturing yield. The present invention relates to a liquid crystal display device and a method for manufacturing the same.

[0002]

2. Description of the Related Art The structure of a liquid crystal display device includes signal lines, TFs, and the like.
T, a TFT substrate on which a pixel electrode and the like are formed, and a counter substrate on which a color filter, a counter electrode, and the like are formed are attached with a predetermined gap therebetween, and a liquid crystal is sealed in the gap. .

The cross-sectional structure of a conventional general liquid crystal display device is shown in FIG.
2 and a TFT (not shown), a flattening layer 103 for flattening irregularities is formed thereon, and a pixel electrode 104 is further formed thereon to form a TFT substrate 1.
10 and a counter substrate 111 formed by forming a counter electrode 106 on a substrate 105 are arranged facing each other with a predetermined gap so that the electrodes face each other, and a liquid crystal 107 is sealed in the gap. ing. The connection between the pixel electrode 104 and the TFT is made via a contact hole (not shown) provided in the planarization layer 103. Further, the TFT substrate 110 and the counter substrate 111
An alignment film (not shown) is formed on the uppermost layer, and is provided with alignment characteristics by a rubbing process or the like.

In the above configuration, the planarizing layer 103 rises above the signal line 102, so that the pixel electrode 104 is formed in a recess surrounded by the periphery. Therefore, when the rubbing process is performed on the substrate 101 on which the alignment film is formed on the uppermost layer, desired rubbing is performed only on the pixel electrode 104, and the liquid crystal molecules 10 in the region are not rubbed.
7a is oriented correctly (hereinafter referred to as forward tilt state)
However, the desired rubbing is not performed in the vicinity of the region of the slope which becomes a shadow with respect to the rubbing direction.
07b is oriented along the slope in a direction opposite to the forward tilt state (hereinafter referred to as a reverse tilt state). For this reason, there has been a problem that disclination (poor alignment) occurs at the boundary between the two states, and the display quality deteriorates.

In order to eliminate such an alignment defect, FIG.
As shown in (2), the thickness of the flattening layer 103 is made sufficiently larger than the thickness of the signal line 102 to completely flatten the surface of the flattening layer 103, thereby eliminating a region where the liquid crystal 107 is in a reverse tilt state. Can be considered.

In Japanese Patent Application Laid-Open No. Hei 7-20497,
As shown in FIG. 9, separation grooves 108 are formed along the periphery of each pixel electrode 104, and the pixel electrodes 1 adjacent to each other are formed.
04 by functional separation, the separation groove 10
A liquid crystal display device in which the alignment state of eight parts of liquid crystal molecules is forcibly controlled is disclosed.

[0007]

However, if the pitch between the pixel electrodes 104 is reduced in accordance with the high definition of the liquid crystal display device, the pitch between the pixel electrodes 104 may be smaller than the thickness of the liquid crystal layer. Come up. In such a case, in the liquid crystal display device shown in FIG. 8, compared to the normal vertical electric field acting between the pixel electrode 104 and a counter electrode (not shown), There is a problem that the next horizontal electric field becomes larger and normal image display is impaired.

In the case of the liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. Hei 7-20497, since the liquid crystal molecules are aligned along the slope of the separation groove 108, the separation groove 108 has a tapered structure. However, when the pixel electrode 106 is patterned on the separation groove 108 having the taper, the transparent conductive film is formed to have substantially the same thickness over the entire surface of the substrate. When taken into the separation groove 108, the resist film remains easily due to poor photosensitivity, so that there is a problem that leakage between the pixel electrodes 104 frequently occurs and the manufacturing yield is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a liquid crystal display device capable of preventing a decrease in display quality due to poor alignment of liquid crystal molecules and a decrease in manufacturing yield. An object of the present invention is to provide a manufacturing method thereof.

[0010]

According to a first aspect of the present invention, there is provided a liquid crystal display device comprising: a pair of substrates arranged to face each other with a predetermined gap therebetween; and a liquid crystal layer held in the gap. Has a cell structure, one substrate includes a region where a thin film transistor and a signal line are formed, an insulating film formed thereover, and a pixel electrode formed thereover, and the other substrate has a In a liquid crystal display device having a counter electrode, wherein a separation groove is formed in the insulating film along the periphery of the pixel electrode, a vertical alignment film is formed on a bottom portion of the separation groove and a counter electrode region facing the bottom. Is formed.

According to a second aspect of the present invention, there is provided a liquid crystal display device comprising:
2. The liquid crystal display device according to claim 1, wherein the separation groove is formed such that an end thereof is substantially perpendicular to a substrate surface.

According to a third aspect of the present invention, there is provided a liquid crystal display device comprising:
3. The liquid crystal display device according to claim 1, wherein a chamfer is formed at a corner of the pixel electrode.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a liquid crystal display device, comprising: forming a thin film transistor and a signal line on a substrate; and forming an insulating film on the entire surface of the substrate so as to cover the thin film transistor and the signal line. Forming an isolation groove by performing anisotropic etching on a predetermined region of the insulating film; forming a transparent conductive film covering the insulating film and the isolation groove; and forming the transparent conductive film. Patterning the pixel electrode by performing isotropic etching on a predetermined area of the pixel electrode.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a liquid crystal display device according to the fourth aspect of the present invention, the method comprising vertically covering the pixel electrode and the isolation groove formed on one substrate. Forming an alignment film, forming a horizontal alignment film in a region other than the separation groove, rubbing the horizontal alignment film, and forming a vertical alignment film on the entire surface of the other substrate on which the counter electrode is formed. And forming a horizontal alignment film in a region corresponding to the pixel electrode, and rubbing the horizontal alignment film.

The operation of the above configuration will be described below.

In the liquid crystal display device according to the present invention, the vertical alignment film is formed on the bottom of the separation groove and on the opposing electrode region facing the separation groove, so that the liquid crystal molecules around the pixel electrode are formed by the vertical alignment film. Since alignment can be always performed perpendicular to the substrate by the alignment control force, it is possible to suppress the occurrence of disclination in the region.

Further, by forming the separation groove so that its end is substantially perpendicular to the substrate surface, the transparent conductive film formed thereon is locally thinned at this end. As a result, it is possible to suppress the occurrence of a film residue when performing patterning later.

Further, by forming a chamfer at the corner of the pixel electrode, it is possible to prevent a local pressure from being applied to the corner of the rubbing cloth when the tip of the rubbing cloth passes through the corner of the pixel electrode. Can be prevented.

In the method of manufacturing a liquid crystal display device according to the present invention, the separation groove formed in the insulating film formed so as to cover the thin film transistor and the signal line is formed by anisotropic etching. Can be formed so as to be substantially perpendicular to the substrate surface, and a thin transparent conductive film to be formed later at the end can be formed.

Further, by forming a transparent conductive film formed so as to cover the insulating film and the isolation groove by isotropic etching, it is possible to prevent foreign matter from being mixed into the isolation groove and resist remaining. Even so, at the end of the separation groove in which the transparent conductive film is thinly formed, the etchant goes around the foreign matter or the remaining resist, so that it is possible to prevent leakage between pixel electrodes.

Further, after the vertical alignment film is formed on the entire surface of the substrate, the horizontal alignment film is formed in a predetermined region, and a rubbing process is performed only on the region where the horizontal alignment film is formed. Unnecessary rubbing can be prevented from being performed on the formed region.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view showing the structure of the liquid crystal display device of the present embodiment. As shown in FIG. 1, the liquid crystal display device according to the present embodiment includes a pair of substrates 1 and 2 that are arranged to face each other with a predetermined gap, and a liquid crystal 3 sealed between the pair of substrates 1 and 2. And a cell structure consisting of

A TFT (not shown) is provided on the one substrate 1.
And a signal line 8, on which a planarization layer 9 is formed. The flattening layer 9 completely flattens the unevenness of the surface of the substrate 1 due to the TFTs, the signal lines 8 and the like, and a separation groove 11 is provided at a peripheral edge of the pixel electrode 6 formed on the flattening layer 9. I have. Further, a vertical alignment film 7 is formed further above the separation groove 11 and the pixel electrode 6. Further, a horizontal alignment film 5 is formed on the pixel electrode 6 via the vertical alignment film 7 to form a TFT substrate 12.

On the other substrate 2, a counter electrode 10 is formed on the entire surface, and a vertical alignment film 7 is formed on the counter electrode 10. In this case, the horizontal alignment film 5 is formed in a region facing the pixel electrode 6, and the counter substrate 13 is configured.

The flattening layer 9 can be made of an organic resin material such as an acrylic resin, an imidized resin, and a fluorine resin.

The separation groove 11 formed in the flattening layer 9
Are formed so as to be narrower than the width of the signal line existing under the separation groove. This is to make it possible to slightly overlap the signal line 8 with the end of the pixel electrode 6 formed thereon. In addition, the separation groove 1
The depth 1 is formed so as to be smaller than the thickness of the flattening layer 9. This is because, when the edge of the pixel electrode 6 formed on the upper portion is in the separation groove 11 to such an extent that it does not leak with the adjacent pixel electrode, it is formed below the pixel electrode 6 and the separation groove 11. This is to prevent a leak with the signal line 8 that has occurred.

The vertical alignment film 7 can be made of a nonpolar polymer such as tetrafluoroethylene, a long-chain alkyl group-containing silane coupler, a long-chain alkyl group-containing polyimide, or a fluorine-containing polyimide.

The horizontal alignment film 5 may be made of a polar polymer such as polyimide, polyamide, polyvinyl alcohol or the like.

Hereinafter, a method for manufacturing the liquid crystal display device according to the present embodiment will be described.

First, a method of manufacturing the TFT substrate 12 will be described with reference to FIGS. As shown in FIG. 2A, a signal line 8 such as a gate wiring and a source wiring and a TFT (not shown) are sequentially formed on one substrate 1.

Next, as shown in FIG. 2B, the flattening layer 9 is applied by spin coating to flatten the irregularities on the surface of the TFT substrate 1 formed by the signal lines 8 and the TFTs. It is formed to a thickness of about 4 μm.

Subsequently, as shown in FIG. 2C, a region of the flattening layer 9 which is to be the separation groove 11 is etched to a predetermined depth by anisotropic etching such as dry etching. As described above, by forming the separation grooves 11 by anisotropic etching, the edge portions of the planarization layer 9 can be formed sharply. Also,
Before or after this step, a contact hole for obtaining conduction between the pixel electrode 6 to be formed later and the TFT is formed at a predetermined position of the flattening layer 9.

Next, a pixel electrode 6 is formed as shown in FIG. 2D by forming a transparent conductive film such as ITO on the flattening film 9 and patterning it by photolithography. . The transparent conductive film is patterned using isotropic etching such as wet etching. At this time, since the separation groove 11 was formed by anisotropic etching and the end of the separation groove 11 was formed so as to be substantially perpendicular to the substrate 1, as shown in FIG. The transparent conductive film formed at the end of the separation groove 11 is thinner than the transparent conductive film formed at other portions,
In addition, they can be formed to have different film qualities. Therefore, even if a residual film of the resist or the like occurs in the separation groove 11, the transparent conductive film is patterned by isotropic etching such as wet etching.
The etching rate of the thinly formed portion of the transparent conductive film is locally increased, so that leakage between adjacent pixel electrodes due to the remaining film of the transparent conductive film can be prevented, and the manufacturing yield can be improved.

Subsequently, as shown in FIG. 2E, a vertical alignment film 7 is formed on the entire surface of the planarization layer 9 including the separation groove 11 and the pixel electrode 6. This can be formed by immersing the TFT substrate 1 in a container to which the film liquid for the vertical alignment film 7 has been supplied, and then applying heat and curing.

Subsequently, as shown in FIG. 2F, a horizontal alignment film 5 is formed on the pixel electrode 6 via the vertical alignment film 7 by a printing method, and is formed by heat curing. Rubbing is performed. At this time, since the vertical alignment film 7 is formed only on the base of the separation groove 11, unnecessary rubbing is not performed. Thus, the TFT substrate 12 is formed.

A method for manufacturing one counter substrate 13 will be described.
This will be described with reference to FIG. First, as shown in FIG. 4A, the counter electrode 10 is formed on the entire surface of the substrate 2. At this time, a color filter may be formed as needed.

Next, as shown in FIG. 4B, a vertical alignment film 7 is formed on the surface of the counter electrode 10 in the same manner as described above, and further, as shown in FIG. Horizontal alignment film 5
Is applied to a predetermined area by a printing method, and is cured by heating.

Subsequently, in the region where the horizontal alignment film 5 is formed,
An alignment process by rubbing is performed in a direction perpendicular to the alignment direction performed on the TFT substrate 1. In order to prevent unnecessary rubbing from being performed on the vertical alignment film 7, rubbing may be performed using, for example, a lattice-like mask that covers a region where the vertical alignment film 7 is formed. Thus, the opposing substrate 13 is formed.

Further, the TFT substrate 12 and the opposing substrate 13 thus formed are bonded together with a predetermined gap therebetween through a sealing agent and a spacer (not shown), and a liquid crystal having a chiral agent added to the gap is provided. 3, and a liquid crystal display device is completed by combining a drive circuit and a lighting device (not shown).

The liquid crystal molecules 3 in the liquid crystal display device thus manufactured behave as follows depending on whether or not a voltage is applied.

First, in the region sandwiched between the horizontal alignment films 5,
When no voltage is applied, the liquid crystal molecules are oriented almost horizontally with a pretilt angle on the alignment film surface, and when a voltage is applied, they are aligned in the vector direction of the electric field, that is, aligned substantially perpendicular to the alignment film surface. On the other hand, in the region sandwiched between the vertical alignment films 7, the liquid crystal molecules 3 are aligned almost perpendicular to the alignment film surface regardless of whether or not a voltage is applied.

Therefore, in the region sandwiched between the vertical alignment films 7, the liquid crystal molecules are always oriented almost perpendicularly to the alignment film surface by the alignment control force different from the other regions. The orientation of the region is not disturbed by the force, the occurrence of disclination can be suppressed, and the display quality can be improved.

(Embodiment 2) A second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a view showing a cross-sectional structure of the liquid crystal display device according to the present embodiment. In the liquid crystal display device according to the first embodiment, a separation groove 11 is formed so as to penetrate the flattening layer 9 in the first embodiment shown in FIG. The difference is that an insulating film 15 is formed above the line 8. For this reason, the separation groove 11 can be formed simultaneously with the formation of a contact hole (not shown) for connecting the pixel electrode 3 to a TFT (not shown).

Hereinafter, a method for manufacturing the liquid crystal display device according to the present embodiment will be described. First, a signal line 8 such as a gate wiring and a source wiring, an insulating film 15, and a TFT (not shown) are sequentially formed on the substrate 1. Usually, a metal oxide film formed by anodic oxidation or a gate insulating film made of SiN _x , SiO _2, etc. is formed on the upper part of the gate wiring in order to prevent a leak with a source wiring formed to be perpendicular to the gate wiring. Therefore, the insulating film 15 can also serve as the gate insulating film. Also, a metal oxide film by anodic oxidation and an insulating film made of SiN _x , SiO _2, etc. are formed on the source wiring.

Next, the flattening layer 9 is formed to a thickness of about 3 to 4 μm by spin coating in order to flatten the irregularities on the surface of the TFT substrate 1 formed by the signal lines 8 and the TFTs.

Subsequently, a region of the planarizing layer 9 to be the separation groove 11 and a region to be a contact hole (not shown) are etched by anisotropic etching such as dry etching. As described above, in the present embodiment, the separation groove 11 and the contact hole can be formed in the same step. At this time, of the resist formed on the flattening layer 9, the resist formed in the vicinity of the region serving as the contact hole is formed thinner than the resist formed in the other region, so that the contact is formed. A gentle taper can be provided at the end of the hole, and the end of the separation groove 11 can be formed so as to be substantially perpendicular to the substrate surface.

The subsequent steps are the same as in the first embodiment, and a description thereof will be omitted.

In the liquid crystal display device manufactured in this manner, as in the first embodiment, since the liquid crystal molecules 3 do not disturb the alignment in the region where the vertical alignment film 7 is formed, disclination is prevented. Occurrence can be suppressed.

Further, since the separation groove 11 and the contact hole can be formed in the same step, the productivity can be improved and the cost can be reduced.

(Embodiment 3) A third embodiment of the present invention will be described with reference to FIG. FIG. 6 is a plan view of the TFT substrate of the liquid crystal display device according to the present embodiment as viewed from above. As can be seen from this figure, in the present embodiment, when forming the separation groove 11, the chamfered portion is formed at the corner of the pixel electrode 6 according to the first embodiment.
Different from 2.

The chamfered portion is provided to prevent a local pressure from being applied to the corner of the pixel electrode 6 when the tip of the rubbing cloth passes through the corner when the rubbing process is performed on the TFT substrate. Things. When the liquid crystal display device of the present invention is formed, since the periphery of the pixel electrode 6 is surrounded by the separation groove 11, unevenness at the end of the pixel electrode 6 becomes large, and rubbing unevenness particularly occurs at a corner portion. However, by forming a chamfer at the corner of the pixel electrode 6 as in the present embodiment, this can be prevented. Therefore, the chamfered portion may be formed at least at the corner where the rubbing roller enters, among the four corners of the pixel electrode 6.

The liquid crystal display device according to the present embodiment can be manufactured by simply changing the mask pattern used when forming the separation groove 11 in the manufacturing method described in the first or second embodiment. it can. In addition, the liquid crystal display device can suppress the occurrence of disclination and can perform more uniform alignment processing in the plane of the pixel electrode 6.

[0053]

As described above, in the liquid crystal display device of the present invention, the vertical alignment film is formed on the bottom of the separation groove and on the opposing electrode region facing the bottom, so that the periphery of the pixel electrode can be reduced. Since the liquid crystal molecules can always be vertically aligned with respect to the substrate by the alignment regulating force of the vertical alignment film, the occurrence of disclination in the region can be suppressed, and the display quality can be improved. To play.

Further, by forming the separation groove so that the end is substantially perpendicular to the substrate surface, the transparent conductive film formed thereon is locally thinned at this end. As a result, it is possible to suppress the occurrence of a film residue when patterning is performed later, and it is possible to improve the manufacturing yield.

Further, by forming a chamfered portion at a corner of the pixel electrode, a local pressure is applied to the corner of the rubbing cloth when the tip of the rubbing cloth passes through the corner of the pixel electrode. This has the effect that it can be prevented.

In the method for manufacturing a liquid crystal display device according to the present invention, the separation groove formed in the insulating film formed so as to cover the thin film transistor and the signal line is formed by anisotropic etching. Can be formed so as to be substantially perpendicular to the surface of the substrate, and the transparent conductive film formed later at the end can be formed to be thin.

Further, by forming a transparent conductive film formed so as to cover the insulating film and the isolation groove by isotropic etching, foreign matter may be mixed into the isolation groove and a resist residue may be present. Even so, at the end of the separation groove in which the transparent conductive film is formed thin, the etchant goes around the foreign matter or the remaining resist, so that the effect of preventing leakage between pixel electrodes can be obtained.

Further, after the vertical alignment film is formed on the entire surface of the substrate, the horizontal alignment film is formed in a predetermined region, and rubbing is performed only on the region where the horizontal alignment film is formed, whereby the vertical alignment film is formed. There is an effect that unnecessary rubbing processing can be prevented from being performed on the formed region.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a cross-sectional structure of a liquid crystal display device in Embodiment 1.

FIG. 2 is a diagram showing a manufacturing process of the TFT substrate of the liquid crystal display device shown in FIG.

FIG. 3 is a diagram illustrating a state of an end of a separation groove when patterning a pixel electrode.

FIG. 4 is a diagram showing a manufacturing process of the counter substrate of the liquid crystal display device shown in FIG.

FIG. 5 is a diagram illustrating a cross-sectional structure of a liquid crystal display device in Embodiment 2.

FIG. 6 is a diagram illustrating a cross-sectional structure of a liquid crystal display device in Embodiment 3.

FIG. 7 is a diagram showing a cross-sectional structure of a conventional liquid crystal display device.

FIG. 8 is a diagram showing a cross-sectional structure of a conventional liquid crystal display device.

FIG. 9 is a diagram showing a cross-sectional structure of a conventional liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Substrate 3 Liquid crystal 5 Horizontal alignment film 6 Pixel electrode 7 Vertical alignment film 8 Signal line 9 Flattening layer 10 Counter electrode 11 Separation groove 12 TFT substrate 13 Counter substrate 15 Insulating film

Claims (5)

[Claims] 1. A cell structure comprising a pair of substrates disposed opposite to each other with a predetermined gap therebetween and a liquid crystal layer held in the gap, and one of the substrates has a thin film transistor and a signal line formed thereon. Region, an insulating film formed thereon, and a pixel electrode further formed thereon,
The other substrate is provided with a counter electrode, and in a liquid crystal display device in which a separation groove is formed in the insulating film along the periphery of the pixel electrode, on a bottom of the separation groove and a counter electrode region facing the bottom. A liquid crystal display device comprising a vertical alignment film formed thereon. 2. The liquid crystal display device according to claim 1, wherein the separation groove is formed so that an end thereof is substantially perpendicular to a substrate surface. 3. The liquid crystal display device according to claim 1, wherein a chamfered portion is formed at a corner of the pixel electrode. 4. A step of forming a thin film transistor and a signal line on a substrate; a step of forming an insulating film over the entire surface so as to cover the thin film transistor and the signal line; and an anisotropic etching on a predetermined region of the insulating film. Forming a transparent conductive film covering the insulating film and the separating groove; and performing a isotropic etching on a predetermined region of the transparent conductive film to form a pixel electrode. And a step of patterning the liquid crystal display device. 5. A step of forming a vertical alignment film covering the pixel electrode and the separation groove formed on one substrate, and forming a horizontal alignment film in a region other than the separation groove, Rubbing; forming a vertical alignment film on the entire surface of the other substrate on which the counter electrode is formed; forming a horizontal alignment film in a region corresponding to the pixel electrode; and rubbing the horizontal alignment film. 5. The method for manufacturing a liquid crystal display device according to claim 4, comprising: