JPH08254712A - Liquid crystal display element - Google Patents

Abstract

PURPOSE: To provide an active matrix type liquid crystal display element of a transverse electric field system featuring high productivity and high image quality. CONSTITUTION: This liquid crystal display element has thin-film transistor elements which are disposed at each of pixels and are connected to pixel electrodes 11, signal electrodes 9 and scanning electrodes 4 and wiring means for impressing voltage signal waveforms between common electrodes 2 and the pixel electrodes 11. The pixel electrodes 11 and the common electrodes 2 are arranged within the same substrate plane. Scanning wirings 5 connected to the scanning electrodes and common wirings 3 connected to the common electrodes 2 are arranged in parallel with the row direction of the plural pixels arranged in a matrix form. The common wirings 3 are commonly used by the two pixels connected in the column direction when the signal wirings 10 connected to the signal electrodes 9 are arranged in parallel with the column direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high image quality active matrix type liquid crystal display device having a pixel structure without display unevenness.

[0002]

2. Description of the Related Art In recent years, as a display device for personal computers, word processors, and other information devices, a thin, lightweight and low power consumption display device using a liquid crystal display element has been widely used.

A liquid crystal display element basically has a matrix formed of a large number of electrodes arranged horizontally and vertically and a liquid crystal layer between the horizontal and vertical electrodes, and has a crossing portion of two electrodes. The pixels are configured to display a two-dimensional image.

For this type of liquid crystal display device, a so-called simple matrix system in which predetermined pixels are selected at the timing of pulses applied to horizontal and vertical electrodes, and a non-linear device such as a transistor arranged in each image are provided. There is a so-called active matrix method for selecting the non-linear element.

The active matrix type liquid crystal display device is provided with a non-linear element (switching element) corresponding to each of a plurality of pixel electrodes arranged in a matrix. Since the liquid crystal in each pixel is theoretically always driven (duty ratio 1.0), the active system has better contrast than the so-called simple matrix system which employs the time-division driving system. It is becoming an indispensable technology for display devices. A typical example of the switching element is a thin film transistor (TFT).

In the conventional thin film transistor type liquid crystal display element, transparent electrodes formed facing each other on the interface between two substrates are used as electrodes for driving the liquid crystal layer.

With such an electrode structure, a display system represented by a so-called twisted nematic display system in which the direction of the electric field applied to the liquid crystal is substantially perpendicular to the interface of the substrate is adopted.

On the other hand, as a display system in which the direction of the electric field applied to the liquid crystal is substantially parallel to the interface of the substrate, a system using a comb-teeth electrode pair in which the electrodes for driving the liquid crystal layer are parallel to the substrate surface (so-called lateral The electric field method) is, for example, Japanese Patent Publication No. Sho 63-2190.
It is proposed by Japanese Patent Publication No. However, this method has not been put to practical use as a display device.

[0009]

[Problems to be Solved by the Invention] Japanese Patent Publication No. 63-21
No. 907, the structure of electrodes arranged in a matrix as a liquid crystal display element and the structure of thin film transistors are not disclosed.

In the structure in which the pixel electrode and the common electrode are arranged in the same substrate plane in order to apply the electric field in a direction substantially parallel to the interface of the substrate, the common wiring is arranged and the liquid crystal of the conventional vertical electric field method is used. As compared with the structure of the display element, the opening area contributing to display is reduced.

Further, since the number of intersections of wirings arranged in a matrix increases, short-circuiting between wirings and parasitic capacitance between signal lines increase, which causes a problem that smooth signal transmission is hindered.

Further, while the pixel electrode of the conventional vertical electric field type liquid crystal display element has a planar shape, the pixel electrode of the horizontal electric field type has a narrow line shape, so that a pixel defect defect due to disconnection occurs. There is a problem that it easily occurs.

It is an object of the present invention to solve the above-mentioned problems of the prior art and to provide a high productivity, high image quality, horizontal electric field type active matrix type liquid crystal display element.

[0014]

In order to achieve the above object, the present invention has a structure in which a common wiring and a signal electrode are shared by two pixels continuous in the column direction.

That is, the first aspect of the present invention provides a pair of substrates, at least one of which is transparent, and a dielectric anisotropy and a refractive index anisotropy sandwiched between the substrates and oriented. A liquid crystal composition having, a polarizing means, a plurality of pixels arranged in a matrix, a thin film transistor element provided for each pixel and connected to a pixel electrode, a signal electrode and a scanning electrode, a common electrode, and Wiring means for applying a voltage signal waveform between the pixel electrode and the common electrode, the pixel electrode and the common electrode are arranged in the same substrate surface, and the pixel electrode and the common electrode are provided between the pixel electrode and the common electrode. In a liquid crystal display element that drives the pixels by an electric field formed substantially parallel to the surface of the substrate, a plurality of scanning wirings connected to the scanning electrodes and common wirings connected to the common electrode are arranged in a matrix. Picture When the signal wirings connected to the signal electrodes are arranged parallel to the row direction and parallel to the column direction, two common pixels in the column direction share the common wiring. Characterize.

According to a second aspect of the present invention, in the first aspect of the invention, the scanning electrodes, the scanning wirings, and the thin film transistor elements of two pixels continuous in the column direction are arranged to face each other, The two pixels share the signal electrode, and wirings from the signal electrode to the signal wiring are arranged between the scanning wirings facing each other.

Further, the third invention according to claim 3 is
In the second aspect of the invention, the number of the thin film transistors corresponding to the pixel electrodes is formed in one pixel along the scanning wiring.

[0018]

The common wiring and the signal electrode are shared by two pixels which are continuous in the column direction to reduce the parasitic capacitance between the wirings.
It is possible to improve the yield of productivity, secure the opening in the pixel, and reduce the common wiring resistance.

That is, in the structure of the first aspect of the invention, the scanning wirings connected to the scanning electrodes and the common wirings connected to the common electrode are arranged parallel to the row direction of a plurality of pixels arranged in a matrix. However, by arranging the signal wirings connected to the signal electrodes in parallel in the column direction while sharing the common wiring between the two pixels continuous in the column direction, the parasitic capacitance between the wirings is reduced and the productivity is improved. It is possible to improve yield, secure an opening in a pixel, and reduce common wiring resistance.

Further, in the structure of the second invention, the scanning electrodes, the scanning wirings, and the thin film transistor elements of two pixels continuous in the column direction in the first invention are arranged to face each other, and the two pixels are arranged. Since the signal electrode is shared and the wiring from the signal electrode to the signal wiring is arranged between the scanning wirings facing each other, the parasitic capacitance between the wirings is reduced, the yield of productivity is improved, and It is possible to further secure the opening and reduce the common wiring resistance.

Further, in the configuration of the third invention, the number of the thin film transistors corresponding to the pixel electrodes is formed along the scanning wiring in one pixel of the second invention, so that the parasitic capacitance between the wirings is reduced. It is possible to further reduce the production yield, secure the opening in the pixel, and reduce the common wiring resistance.

[0022]

Embodiments of the present invention will now be described in detail with reference to the drawings.

First, the operation of the liquid crystal display device to which the present invention is applied will be described before describing the embodiments of the present invention.

FIG. 1 is a schematic diagram for one pixel for explaining the operation of a liquid crystal display device to which the present invention is applied. FIG. 1 (a) is a sectional view when no voltage is applied, and FIG. FIG. 6C is a cross-sectional view when voltage is applied, FIG. 7C is a plan view when no voltage is applied, and FIG. In the figure, 1 and 1'are transparent glass substrates (hereinafter, also simply referred to as substrates), 2 is a common electrode, 6 is an insulating film, 10 is signal wiring, 11 is a pixel electrode,
Reference numerals 13 and 13 ′ are polarizing plates, 14 is a polarizing axis of the polarizing plates, 15 is an alignment direction of liquid crystal molecules, 16 is an electric field direction, 17 is a black matrix (BM), 18 is a color filter, 19 is a flattening film, 20, Reference numeral 20 'is an alignment film, and 21 is a liquid crystal (rod-shaped liquid crystal molecule).

In this liquid crystal display device, one of the two transparent glass substrates 1 and 1'is provided with a polarizing plate 13 'and a light-shielding B.
An M17, a color filter 18, a protective film 19, and an alignment film 20 'are formed. Further, a polarizing plate 13, an alignment film 20, a signal electrode 10, a pixel electrode 11, a common electrode 2, each wiring and a thin film transistor are formed on the other substrate via the liquid crystal 21. It should be noted that the wirings and thin film transistors are not shown in the figure.

As shown in (a) and (c) of FIG.
Alignment No. 1 is preliminarily aligned by an alignment film 20, 20 'in an electric field direction 16 (see (b) and (d) in the figure) and an alignment direction 15 substantially parallel to the interface between the substrates 1, 1'.
The pixel is in a non-display state because the molecular orientation direction of is crossed with the polarization axes of the polarizing plates 13 and 13 '.

Next, as shown in FIGS.
When a voltage is applied between the common electrode 2 and the pixel electrode 11 formed on the glass substrate 1 to form an electric field (electric field direction 16) in a direction substantially parallel to the interface between the substrates 1 and 1 ′, the molecules of the liquid crystal 21 become , 1 ′ is deflected and rotated in a plane parallel to the interface of the polarizing plates 13, 1 ′, and becomes in a state of being aligned with the polarization axes of the polarizing plates 13, 13 ′. This brings the pixel into a display state. A large number of these pixels are arranged to form a display panel.

[Embodiment 1] FIG. 2 is an explanatory view of the structure of a pixel substrate which constitutes a first embodiment of a liquid crystal display device according to the present invention, in which a plan view is shown in the center and a line AA ′ is A sectional view taken along the left side of the figure, a sectional view taken along the line BB 'is shown on the right side of the figure, and a sectional view taken along the line CC' is shown on the lower side of the figure.

In the figure, the same reference numerals as those in FIG. 1 correspond to the same portions, 3 is a common wiring, 4 is a scanning electrode, 5 is a scanning wiring, 7 is a semiconductor layer, 8 is a thin film transistor portion, 9 is a signal electrode, Reference numeral 12 is a protective film.

The scanning electrode 4, the scanning wiring 5, the common electrode 2 and the common wiring 3 are formed in the same layer and the same material. The semiconductor layer 7 is formed through each of these layers and the insulating film 6, and the signal electrode 9 and the signal wiring 1 are formed in the same layer and the same material as the electrodes and wiring.
0 and the pixel electrode 11 are formed.

Further, a part of the pixel electrode 11 is arranged so as to overlap with the common wiring 3 in the direction perpendicular to the substrate surface via the insulating film 6, and the pixel electrode 11 is provided with an electric capacitance.
The signal holding ability of holding the signal voltage applied between the common electrode 2 and the common electrode 2 is improved. In the liquid crystal display element having such a structure, when the common electrode formed on the glass substrate facing the pixel electrode in the conventional liquid crystal display element is formed on the same surface of the glass substrate 1 as the pixel electrode 11, Two pixels that are continuous in the column direction (vertical direction in the drawing) share a common wiring.

FIG. 3 is a plan view showing a structure of two pixels in which the liquid crystal display device according to the present invention is compared with a conventional liquid crystal display device. FIG. 3A shows a common wiring shared by two pixels continuous in the column direction. A lateral electric field type liquid crystal display device according to the present invention,
(B) is a horizontal electric field type liquid crystal display element having a structure in which common wiring is not shared, and (c) is a conventional vertical electric field type liquid crystal display element. Incidentally, reference numeral 23 in FIG. 3C is a holding electrode.

In FIG. 3C, since the transparent pixel electrode 22 and the common electrode are formed over almost the entire area of the pixel, the light transmittance of the opening of the pixel is lowered and the improvement of brightness is limited. On the other hand, in the lateral electric field method shown in FIGS. 3A and 3B, the pixel electrode 11 and the common electrode 2 are formed side by side on the substrate surface, and therefore, there is an advantage that bright display can be performed.

Since the liquid crystal display element according to the present invention shown in FIG. 4A applies an electric field in a direction substantially parallel to the interface of the substrate 1, the pixel electrode 11 and the common electrode 2 are connected to each other. When arranged on the same substrate surface, without reducing the area of the opening of the pixel through which light can pass, compared with the pixel not sharing the common wiring 3 shown in FIG. The line width of the common wiring 3 can be expanded.

As a result, the resistance of the common wiring 3 becomes low, the propagation of the common signal becomes smooth, and the image quality can be improved and the power consumption of the common signal generation circuit can be reduced.

Further, by sharing the common wiring 3, the intersection of the signal wiring 10 and the common wiring 3 is shown in FIG.
This is about 25% less than that of the above structure, and short-circuit defects between the signal wiring 10 and the common wiring 3 are reduced.

FIG. 4 is a plan view of a plurality of pixels of a liquid crystal display panel formed by arranging a horizontal electric field type liquid crystal display element according to the present invention.

In the same drawing, the common wiring 3 is formed in common by two pixels continuous in the column direction indicated by arrow P.

FIG. 5 is an electrically equivalent circuit of a liquid crystal display panel using a lateral electric field type liquid crystal display device according to the present invention, in which 2 is a common electrode, 3 is a common wiring, 8 is a thin film transistor portion, and 9 is a signal electrode. 10 is a signal wiring, 24 is a wiring from the signal wiring 10 to the signal electrode 9, 25 is a liquid crystal capacitor, 26
Is a storage capacitor, 27 is a control circuit, 28 is a scan electrode drive circuit, 29 is a signal electrode drive circuit, and 30 is a common electrode drive circuit.

As shown in the figure, the liquid crystal display panel has a scan electrode drive circuit 28 under the control of the control circuit 27.
A predetermined pixel is selected by the signal electrode drive circuit 29. At this time, the common electrodes 2 for two pixels continuous in the column direction
A required common voltage is applied from the common electrode drive circuit 30 through the common wiring 3.

FIG. 6 shows an electrically equivalent circuit of two pixels which are continuous in the column direction and which constitutes the liquid crystal display device of the horizontal electric field type according to the present invention, and corresponds to the two pixels of FIG. 3 (a).

In the figure, 3 is a common wire, 5 is a scanning wire, 8 is a thin film transistor portion, 9 is a signal electrode, 10 is a signal wire, 24 is a wire from the signal wire 10 to the signal electrode 9, 31 is a common wire 3. Between the line and the signal wiring 10, 3
Reference numeral 2 is a line capacitance between the scanning wiring 5 and the signal wiring 10, and 33 is a line capacitance between the scanning electrode 5 and the pixel electrode 11.

As shown in the figure, with the structure shown in FIG. 3A, the parasitic capacitance 31 between the signal line 10 and the common line 3 is reduced, and the signal electrode 9 and the common electrode 2 are reduced.
It is possible to smoothly propagate the liquid crystal drive signal to the active filter wiring.

As described above, according to this embodiment, it is possible to improve the image quality and reduce the power consumption of the signal generating circuit.

Next, a second embodiment of the present invention will be described.

As shown in FIG. 2, the scanning electrode 4, the scanning wiring 5 and the thin film transistor 8 are made to correspond to two pixels which are continuous in the column direction, the signal electrode 9 is shared, and the signal from this shared signal electrode 9 is used. The wirings 24 up to the wiring 10 are arranged between the scanning wirings 5 facing each other.

With the structure of this embodiment, the signal electrode is formed on the scanning electrode as in the conventional vertical electric field type pixel shown in FIG. 3C or each independent pixel shown in FIG. 3B. The cross-sectional area between the signal electrode 9 and the scanning wiring 5 is smaller than that in the case where the signal electrodes 9 and the scanning wiring 5 are arranged, and short-circuit defects between the signal electrode 9 and the scanning wiring 5 can be reduced.

Further, in the equivalent circuit shown in FIG. 6 corresponding to FIG. 3A, the parasitic capacitance (line capacitance) 32 between the signal electrode 9 and the scanning wiring 5 is reduced, and the scanning electrode 4 is reduced.
Signal can be smoothly propagated to improve the image quality and reduce the power consumption of the signal generation circuit.

The structure described in the first and second embodiments in which two pixels in the column direction share common wiring and share signal electrodes can be applied to a conventional vertical electric field type liquid crystal display panel.

FIG. 7 is a plan view showing two pixels of a liquid crystal display panel for explaining a third embodiment of the present invention in which the present invention is applied to a conventional vertical electric field type liquid crystal display panel, and 22 is a transparent pixel electrode. , 23 are holding electrodes, 24 is a wiring from the signal electrode 9 to the signal wiring 10, and the same reference numerals as those in the above embodiment correspond to the same portions.

FIG. 5A is a structural diagram of a conventional vertical electric field type liquid crystal display panel, and FIG. 6B is a structural diagram in which the present invention is applied to FIG.

In FIG. 10B, a wiring for forming a capacitance (capacitance wiring 34) corresponding to the common wiring is newly formed in the same layer and with the same material as the scanning wiring 5, and two pixels continuous in the column direction are formed. Sharing. The wiring capacitance is equal to that of the holding electrode 23 via the insulating layer.
And electric capacity is formed to improve the signal retention rate of the pixel.

At this time, an electric capacitance is formed by the scanning wiring 5 connected to the scanning electrode of the pixel in the previous stage in the column direction and the capacitance electrode in the next stage, which is the conventional structure shown in FIG. On the other hand, since the capacitive load of the scanning wiring 5 is reduced, the power consumption of the scanning signal generating circuit can be reduced or the width of the scanning wiring 5 can be narrowed.

Further, by sharing the signal electrode 9, the short-circuit defect between the signal electrode 9 and the scanning wiring 5 is reduced, and the parasitic capacitance between the signal electrode 9 and the scanning wiring 5 is reduced. It is possible to improve the image quality and reduce the power consumption of the signal generation circuit.

A fourth embodiment of the present invention will be described below.

In the pixel structure of the second embodiment, the signal electrode is shared and the wiring 2 from the shared signal electrode to the signal wiring
4 is arranged between the scanning wirings facing each other.

Thus, the position of the thin film transistor can be moved on the scanning wiring without increasing the cross area of the signal electrode and the scanning electrode.

By the way, since the pixel electrode of the liquid crystal display device according to the present invention has a narrow line shape, a pixel defect defect due to disconnection is likely to occur.

FIG. 8 is an explanatory view of the structure of the pixel substrate which constitutes the fifth embodiment of the liquid crystal display device according to the present invention, and is a plan view and a sectional view similar to FIG.

As shown in the drawing, the thin film transistors 8 are provided by the number of the pixel electrodes 11 by utilizing the characteristics of each of the above-described embodiments, the signal electrodes 9 are shared, and the wiring from the signal electrodes to the signal wirings 10 is formed. By forming between the scanning wirings facing each other, even when one of the pixel electrodes 11 is broken midway, the display of the pixel can be obtained in a state close to normal.

If any one of the thin film transistors is defective, the pixel electrode 11 connected to the defective thin film transistor is cut by a laser correction means or the like to cause another normal thin film transistor to perform pixel display. You can

As described above, according to the above-mentioned embodiments,
It is possible to obtain a high image quality active matrix type liquid crystal display device with high productivity.

[0063]

As described above, according to the present invention, by disposing the common electrode on the same substrate as the pixel electrode, an electric field is generated in a direction parallel to the substrate and the electric field drives the liquid crystal molecules. Type liquid crystal display element, or a conventional vertical electric field type liquid crystal display element having capacitive wiring,
By sharing the common wiring or the capacitive wiring by two adjacent pixels and sharing the signal electrode by two adjacent pixels, the wiring width can be increased without impairing the opening area of the pixel contributing to display. It is possible to improve the image quality and reduce the power consumption of the drive circuit by reducing the resistance of the drive circuit.

Further, it is possible to reduce the crossing point or the crossing area between the wirings, and it is possible to improve the picture quality and reduce the power consumption of the driving circuit by reducing the short circuit defect between the wirings and the parasitic capacitance between the wirings.

Furthermore, by utilizing the above-described effect of sharing the signal electrodes, the number of thin film transistors in one pixel can be increased without increasing the cross-sectional area between wirings. In the liquid crystal display element of the type in which the electric field is formed, the thin film transistors are provided at both ends of the pixel electrode, so that normal display can be performed even if the pixel electrode is broken in the middle.

Further, even if one of the thin film transistors is defective, a normal display can be performed by the repair work for separating the thin film transistor.

[Brief description of drawings]

FIG. 1 is a schematic diagram for one pixel for explaining the operation of a liquid crystal display element to which the present invention is applied.

FIG. 2 is an explanatory diagram of a structure of a pixel substrate which constitutes a first embodiment of a liquid crystal display element according to the present invention.

FIG. 3 is a plan view showing a structure of two pixels of a liquid crystal display device according to the present invention compared with a conventional liquid crystal display device.

FIG. 4 is a plan view of a plurality of pixels of a liquid crystal display panel formed by arranging a horizontal electric field type liquid crystal display element according to the present invention.

FIG. 5 is an electrical equivalent circuit of a liquid crystal display panel using a horizontal electric field type liquid crystal display element according to the present invention.

FIG. 6 is an electrical equivalent circuit of two pixels which are continuous in the column direction and which constitute the horizontal electric field type liquid crystal display element according to the present invention.

FIG. 7 is a plan view showing two pixels of a liquid crystal display panel for explaining a third embodiment of the present invention in which the present invention is applied to a conventional vertical electric field type liquid crystal display panel.

FIG. 8 is an explanatory diagram of a structure of a pixel substrate which constitutes a fifth embodiment of the liquid crystal display device according to the present invention.

[Explanation of reference numerals] 1,1 'Transparent glass substrate 2 Common electrode 3 Common wiring 4 Scan electrode 5 Scan wiring 6 Insulating film 7 Semiconductor layer 8 Thin film transistor part 9 Signal electrode 10 Signal wiring 11 Pixel electrode 12 Protective film 13, 13' Polarization Plate 14 Polarizing axis of polarizing plate 15 Alignment direction of liquid crystal molecules 16 Electric field direction 17 Black matrix (BM) 18 Color filter 19 Flattening film 20, 20 'Alignment film 21 Liquid crystal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masuyuki Ota 7-1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory

Claims (3)

[Claims] 1. A pair of substrates, at least one of which is transparent, a liquid crystal composition having dielectric anisotropy and refractive index anisotropy sandwiched between the substrates and oriented, a polarizing means, and a matrix form. A plurality of pixels arranged in each pixel, a thin film transistor element provided for each pixel and connected to a pixel electrode, a signal electrode and a scan electrode, a common electrode, and a voltage signal between the pixel electrode and the common electrode. An electric field formed between the pixel electrode and the common electrode substantially parallel to the surface of the substrate. In the liquid crystal display element for driving the pixels, the scanning wirings connected to the scanning electrodes and the common wirings connected to the common electrode are arranged in parallel in a row direction of a plurality of pixels arranged in a matrix, and Belief A liquid crystal display element, wherein when the signal wirings connected to the signal electrodes are arranged in parallel in the column direction, the two common pixels in the column direction share the common wiring. 2. The scan electrode, the scan wiring, and the thin film transistor element of two pixels continuous in the column direction are arranged to face each other, and the two pixels share the signal electrode and the signal is provided. A liquid crystal display device, wherein wirings from electrodes to the signal wirings are arranged between scanning wirings facing each other. 3. A liquid crystal display element according to claim 2, wherein a number of thin film transistors corresponding to the pixel electrodes are formed along one of the scanning lines in one pixel.