JPH0961855A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To expand the effective display region of a liquid crystal display device while lessening the abnormality in light transmittance, such as light drop-out, by suppressing the occurrence of a reverse tilt, thereby enhancing an opening rate without the degradation in contrast and the deterioration in image quality, such as after-image. SOLUTION: This liquid crystal display device is constituted by forming pixel electrodes 3 and thin-film transistors 4 controlling the conduction between source lines 2 and the pixel electrodes by the potential of gate liens 2 at the respective intersected points of the gate lines 1 and source lines 2 formed to a matrix form on an array substrate and enclosing liquid crystals between a counter substrate formed with counter electrodes and the array substrate. The source lines 2 are so formed as to be paralleled with the orientation direction of the liquid crystal molecules in the position where the intensity of the transverse electric fields formed between the source lines 2 and the pixel electrodes 3 is maximized.

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 which realizes high image quality and high aperture ratio.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been widely used in workstations, personal computers, portable televisions, and the like, and their use range tends to expand. FIG. 3 shows a plan view of an array substrate of a conventional thin film transistor type liquid crystal display device. As shown in the drawing, the gate line 1 and the source line 2 are formed so as to be orthogonal to each other, and the pixel electrode 3, the thin film transistor 4, and the storage capacitor 5 are formed at the intersections thereof. The thin film transistor 4 controls conduction between the source line 2 and the pixel electrode 3 by the potential of the gate line 1. The storage capacitor 5 includes a part of the pixel electrode 3 and
It is formed by facing the adjacent gate line 1 through the insulating layer. In the figure, 6, 7, and 8 are the alignment directions of liquid crystal molecules in the array substrate, the intermediate layer, and the counter substrate in the state where no voltage is applied.

FIG. 4 shows a BB cross section of FIG. 3, that is, a cross section in a direction perpendicular to the source line. The gate line 1, the source line 2, the pixel electrode 3, the thin film transistor 4, and the storage capacitor 5 are formed on the array substrate 9, and the insulating film 10 is formed thereon.
And the alignment film 11 is formed. A counter electrode 12 is formed on the counter substrate 13, and an alignment film 11 is formed thereon. Liquid crystal 14 is sealed between the array substrate 9 and the counter substrate 13.

[0004]

The dimming effect of the thin film transistor liquid crystal display device is obtained by controlling the liquid crystal molecule alignment between the pixel electrode 3 and the counter electrode 12 by an electric field. Ideally, a vertical electric field is applied. However, in practice, different potentials are generally applied to the source line 2 and the pixel electrode 3, and a large lateral electric field 15 is generated because the distance between the two is narrow. Since the liquid crystal molecules tend to be aligned in the direction of the electric lines of force of the lateral electric field in the periphery of the electrodes, there is a portion that is aligned in the tilt direction (reverse tilt) different from the tilt direction (normal tilt) that can be pretilted. At the boundary between the normal tilt and the reverse tilt, there is a portion where the liquid crystal molecule orientation changes abruptly. This is one of the causes of the reduction in the aperture ratio due to the black matrix shielding this portion.

Therefore, an object of the present invention is to realize a high aperture ratio by suppressing the occurrence of reverse tilt without deterioration of image quality such as contrast reduction and afterimage phenomenon.

[0006]

In order to achieve the above object, a liquid crystal display device according to the present invention has a liquid crystal sealed between a first substrate and a second substrate and has a first substrate and a second substrate. A column-shaped or matrix-shaped electrode wiring is formed on either one or both of them, and the feature thereof is that the column-shaped electrode wiring or one of the matrix-shaped electrode wiring is The point is parallel to the alignment direction of the liquid crystal molecules at the position where the electric field strength in the substrate surface direction is maximum. As a method for making the alignment directions of the electrode wiring and the liquid crystal parallel, either a method of changing the formation direction of the electrode wiring or a method of changing the alignment direction of the liquid crystal may be used.

The specific structure of the liquid crystal display device is a simple matrix type or an active matrix (thin film transistor).
It depends on the type. In a simple matrix liquid crystal display device in which scanning lines are formed on a first substrate and signal lines in a direction intersecting with the scanning lines are formed on a second substrate,
The scanning line or the signal line is parallel to the alignment direction of liquid crystal molecules at the position where the electric field strength in the substrate surface direction is maximum.

Further, pixel electrodes are formed at the intersections of the gate lines and the source lines formed in a matrix on the array substrate, and thin film transistors for controlling conduction between the source lines and the pixel electrodes by the potential of the gate lines are formed. In the thin film transistor liquid crystal display device in which the counter electrode is formed on the counter substrate and the liquid crystal is sealed between the array substrate and the counter substrate, the gate line or the source line is connected in the substrate surface direction. It is parallel to the alignment direction of liquid crystal molecules at the position where the electric field strength is maximum.

More specifically, in the case of a simple matrix liquid crystal display device, the scanning line is the twist direction of the liquid crystal defined by the second substrate with respect to the alignment direction of the liquid crystal molecules in the portion in contact with the first substrate. Further, it is preferable to form an angle within the range of 5 degrees to 40 degrees. Or the second
The signal line may form an angle within the range of 5 to 40 degrees with respect to the orientation direction of the liquid crystal molecules in the portion in contact with the substrate in the twist direction of the liquid crystal defined by the first substrate. .

Further, in the case of the thin film transistor liquid crystal display device, the gate line or the source line is oriented from 5 degrees in the twist direction of the liquid crystal defined by the counter substrate with respect to the alignment direction of the liquid crystal molecules in the portion contacting the array substrate. It is preferable to form an angle within the range of 40 degrees.

In order to obtain symmetrical viewing angle characteristics in a liquid crystal display device, a twist structure in which an alignment direction of liquid crystal molecules in a portion in contact with the first substrate is orthogonal to an alignment direction of liquid crystal molecules in a portion in contact with the second substrate. In the above, a configuration in which the alignment direction of the liquid crystal of the intermediate layer of both substrates is oriented in the front-back direction is often adopted, but the above specific configuration is extremely effective in such a case.

Further, in the simple matrix liquid crystal display device, it is preferable that the scanning lines and the signal lines intersect at an angle within the range of 50 to 85 degrees. Similarly, in the thin film transistor liquid crystal display device, the gate line and the source line are 5
It is preferable that they intersect at an angle within the range of 0 to 85 degrees.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In this embodiment, in the twisted thin film transistor liquid crystal display device in which the alignment direction of the liquid crystal molecules in the portion in contact with the array substrate and the alignment direction of the liquid crystal molecules in the portion in contact with the counter substrate are orthogonal to each other, the gate line and the source line are slanted. By intersecting with the alignment direction of the liquid crystal molecules in the portion in contact with the array substrate, the source line forms an angle with the twist direction of the liquid crystal defined by the counter substrate. The orientation of the liquid crystal at the position where the electric field strength in the plane direction is maximum and the direction of the source line are parallel to each other.

FIG. 1 is a plan view of the liquid crystal display device according to this embodiment. In the figure, 1 is a gate line, 2 is a source line, and both intersect at an angle of 75 degrees. A pixel electrode 3, a thin film transistor 4, and a storage capacitor 5 are formed at each intersection of the gate line 1 and the source line 2. The thin film transistor 4 controls conduction between the source line 2 and the pixel electrode 3 by the potential of the gate line 1. The storage capacitor 5 is formed by overlapping a part of the pixel electrode 3 and the adjacent gate line 1 with an insulating layer interposed therebetween. In the figure, reference numerals 6, 7, and 8 respectively indicate the alignment directions of the liquid crystal molecules in the array substrate, the intermediate layer, and the counter substrate in the state where no voltage is applied. The alignment direction 6 of the liquid crystal molecules in the part in contact with the array substrate and the alignment direction 8 of the liquid crystal molecules in the part in contact with the counter substrate are orthogonal to each other, and the alignment direction 7 of the liquid crystal molecules in the middle part of the layer is the middle of those alignment directions. Located at (facing rear).

FIG. 2 shows a cross section taken along the line AA 'of FIG. 1, that is, a cross section in a direction perpendicular to the source line. Since the gate line and the source line are not orthogonal to each other, the cross section and the gate line are not parallel to each other. The gate line 1, the source line 2, the pixel electrode 3, the thin film transistor 4, and the storage capacitor 5 are formed on the array substrate 9, an insulating film 10 is formed thereon, and an alignment film 11 is formed thereon. Counter electrode 12
Is formed on the counter substrate 13, and like the array substrate 9,
An alignment film 11 is formed on it. Liquid crystal 14 is sealed between the array substrate 9 and the counter substrate 13.

As can be seen from FIG. 2, the position at which the intensity of the transverse electric field (electric field in the substrate surface direction) 15 indicated by the line of electric force formed between the source line 2 and the pixel electrode 3 becomes maximum is. , The array substrate 9 is provided between the source line 2 and the pixel electrode 3.
It is located at a portion slightly away from the surface of the (alignment film 11). The alignment direction (long axis direction) of the liquid crystal molecules 14 at this position is perpendicular to the paper surface, that is, parallel to the source line 2. Therefore, the liquid crystal molecules 14 are orthogonal to the horizontal electric field 15.

A liquid crystal material having a positive dielectric anisotropy used in a liquid crystal display device has a spheroidal dielectric constant distribution whose major axis is the molecular orientation direction, and therefore, when the electric field and the orientation direction are orthogonal to each other. , The torque on the liquid crystal molecules by the electric field is zero. At this time, the force acting on the molecular orientation is dominated by the elastic force of adjacent molecules. Most of the liquid crystal molecules on the pixel electrode rise in the normal tilt direction which can be pretilted, and accordingly, the liquid crystal molecules in the lateral electric field also rise in the normal tilt direction. Therefore, the entire pixel rises in the normal tilt direction without the occurrence of reverse tilt, and uniform transmitted light characteristics can be obtained.

In this embodiment, as can be seen from FIG. 1, the source line is 30 (75-75) in the twist direction of the liquid crystal defined by the counter substrate with respect to the alignment direction of the liquid crystal molecules in the portion in contact with the array substrate. Although an angle of 45) is formed, when an experiment was conducted by changing the alignment direction of the liquid crystal molecules in the portion in contact with the array substrate and the counter substrate, this angle was effective within the range of 5 to 40 degrees. In particular, a remarkable effect was obtained within the range of 15 to 30 degrees. Further, although the source line of the thin film transistor liquid crystal display device has been described in the present embodiment, the same effect can be obtained by making the gate line parallel to the alignment direction of the liquid crystal molecules at the position where the lateral electric field strength is maximum. Further, the present invention can be applied to not only the thin film transistor (active matrix) liquid crystal display device but also the scanning lines and signal lines of the simple matrix liquid crystal display device.

[0019]

As described above, according to the present invention,
By suppressing the occurrence of the reverse tilt, abnormal light transmittance such as light leakage at the portion where the liquid crystal molecule alignment at the boundary between the normal tilt and the reverse tilt changes rapidly is reduced, and the transmittance is reliably controlled. The effective display area can be enlarged in the state. As a result, the aperture ratio can be increased without deterioration of image quality such as reduction of contrast and afterimage phenomenon.

[Brief description of drawings]

FIG. 1 is a plan view of an array substrate of a thin film transistor liquid crystal display device according to an exemplary embodiment of the present invention.

2 is a view of A- of the thin film transistor liquid crystal display device of FIG.
A 'sectional view

FIG. 3 is a plan view of an array substrate of a thin film transistor liquid crystal display device according to a conventional example.

FIG. 4 is a B- of the thin film transistor liquid crystal display device of FIG.
B 'sectional view

[Explanation of symbols]

 1 gate line 2 source line 3 pixel electrode 4 thin film transistor 5 storage capacitor 6 liquid crystal molecule alignment direction of a portion in contact with the array substrate 7 liquid crystal molecule alignment direction of a middle portion of the layer 8 liquid crystal molecule alignment direction of a portion in contact with a counter substrate 9 array substrate 10 insulation Film 11 Alignment film 12 Counter electrode 13 Counter substrate 14 Liquid crystal 15 Horizontal electric field

Claims (9)

[Claims] 1. A liquid crystal is sealed between a first substrate and a second substrate, and column-shaped or matrix-shaped electrode wiring is formed on either or both of the first and second substrates. In the liquid crystal display device, one of the column-shaped electrode wirings or one of the matrix-shaped electrode wirings is parallel to the alignment direction of liquid crystal molecules at a position where the electric field strength in the substrate surface direction is maximized. Liquid crystal display device characterized by. 2. The scan line is formed on the first substrate, and the scan line is formed on the second substrate.
A simple matrix liquid crystal display device in which a signal line in a direction intersecting with the scanning line is formed on a substrate of the liquid crystal molecule at a position where the scanning line or the signal line has a maximum electric field strength in the substrate surface direction. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is parallel to the alignment direction of. 3. A pixel electrode is formed at each intersection of a gate line and a source line formed in a matrix on an array substrate, and a thin film transistor for controlling conduction between the source line and the pixel electrode by a potential of the gate line is formed. In the liquid crystal display device, a counter electrode is formed on a counter substrate, and liquid crystal is sealed between the array substrate and the counter substrate, wherein the gate line or the source line has a field strength in a substrate surface direction. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is parallel to the alignment direction of the liquid crystal molecules at the position where the maximum is. 4. An angle within a range of 5 to 40 degrees with respect to an alignment direction of liquid crystal molecules in a portion in contact with the first substrate, the scanning line being in a twist direction of liquid crystal defined by the second substrate. The liquid crystal display device according to claim 2, wherein 5. The signal line forms an angle within the range of 5 to 40 degrees with respect to the alignment direction of the liquid crystal molecules in the portion in contact with the second substrate, in the twist direction of the liquid crystal defined by the first substrate. The liquid crystal display device according to claim 2, wherein 6. A gate line or a source line forms an angle within a range of 5 to 40 degrees with respect to an alignment direction of liquid crystal molecules in a portion in contact with the array substrate, in a twist direction of liquid crystal defined by a counter substrate. The liquid crystal display device according to claim 3, wherein the liquid crystal display device is formed. 7. A structure having a twist arrangement in which an alignment direction of liquid crystal molecules in a portion in contact with the first substrate is orthogonal to an alignment direction of liquid crystal molecules in a portion in contact with the second substrate. The described liquid crystal display device. 8. The liquid crystal display device according to claim 2, wherein the scan line and the signal line intersect at an angle within a range of 50 degrees to 85 degrees. 9. The gate line and the source line are 50 degrees to 8 degrees.
4. The liquid crystal display device according to claim 3, wherein the liquid crystal display devices intersect at an angle of 5 degrees.