JPH07234420A - Active matrix liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent defects in lines and decrease in the numerical aperture by forming a gate bus line and a common data bus line on each individual substrate. CONSTITUTION:On a TFT substrate 100, amorphous silicon (a-Si or amorphous silicon hydroxide exporessed also by a-Si:H) thin film transistor elements TFT1 which are MOS transistors and gate bus lines 2 are formed, while common data bus lines 3 which are used as both of data bus lines and common bus lines are formed on the counter substrate 200. The common data bus line 3 also acts as a display electrode, and is formed as a transparent electrode comprising a conductive material having high transmittance for visible rays, preferably, such as ITO (indium tin lead) and tin oxide. The drain 6 and the source 7 of the TFT1 are disposed in opposite to the respective common data bus lines 3 with liquid crystal electrodes 8 interposed so that the element has two display electrodes. Thus, one TFT is provided with a pair of display electrodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device, and more particularly to an active matrix type liquid crystal display device having a structure in which a gate bus line and a data bus line are provided on opposing substrates.

[0002]

2. Description of the Related Art FIG. 9 shows an equivalent circuit of a conventional active matrix type liquid crystal display device, in which a gate bus line (also called "scan line" or "scan bus line") 2 and a data bus line 10 are orthogonal to each other. They are formed on the same substrate so as to intersect with each other, and a thin film transistor (referred to as “TFT”) 1 is provided at the intersection. And T
The gate 5 of the FT1 is connected to the gate bus line 2 and the drain 6 thereof.
Is connected to the data bus line 10 and the source 7 is connected to the display electrode of the liquid crystal 12.

The TFT 1 plays the role of a switching element. For example, in the case of 1280 × 1024 pixels, the gate bus line 2
A pulse signal having a frequency of 60 Hz and an on time of 20 μs is applied to turn on / off the TFT1. A signal to be written in the liquid crystal is added to the data bus line 10, and the signal is sequentially written in each liquid crystal element 12 along the data bus line 10.

When the TFT1 is on, the data bus line 10
The voltage applied to the liquid crystal element 12 is written to the TFT 1
When is turned off, the liquid crystal element 12 holds the voltage, and the liquid crystal voltage is kept constant even while the data signal is writing to other liquid crystal elements. There is.

However, in the conventional device shown in FIG. 9, since the gate bus line 2 and the data bus line 10 intersect on the same substrate via an insulating film, for example, if there is a pinhole in the insulating film, the gate bus line 2 Line 2 and data bus line 10 are short-circuited, resulting in a line defect in the display device.

When the gate 5 and the drain 6 are short-circuited in the TFT 1, not only a pixel abnormality corresponding to the element but also a line defect occurs.

In order to avoid these drawbacks, for example, in Japanese Patent Laid-Open No. 2-1822, as shown in FIG. 10, a gate bus line 2 is provided on one substrate and a data bus line 10 is provided on the other substrate. There is disclosed a technique which is provided above the gate bus line 2 and the data bus line 10 so as not to cross each other to prevent a short circuit therebetween.

Further, in Japanese Patent Laid-Open No. 62-133478, there is shown in FIG.
1, a TFT 1, a gate bus line 2 and a common ground bus line 13 connected to the drain electrode 6 of the TFT 1 are provided on one substrate, and a transparent electrode and a data bus line 10 are formed on an opposite substrate. Has proposed a configuration of a liquid crystal panel that avoids the intersection of the gate bus line 2 and the data bus line 10 on the same substrate.

FIG. 12 shows a waveform diagram for explaining the driving method of the conventional example shown in FIG. In FIG. 12, the gate signal represents the signal of the gate bus line 2 applied to the gate 5 of the TFT 1 shown in FIG. 11, the data signal V _D represents the signal of the data bus line 2, and is an alternating voltage of ± 4V. . Further, the source potential represents the potential of the source 7 of the TFT 1, the liquid crystal writing voltage V _LC is a voltage obtained by subtracting the voltage of the display electrode from the data signal voltage, and V _LC = V _D −
It becomes V _S.

When the gate signal becomes high potential and the TFT 1 is turned on, the drain 6 is connected to the ground (ground) 9, so that the source potential V _S becomes 0V.

After that, the gate signal becomes low potential and the TFT1
When is turned off, the source 7 of the TFT 1 is separated from the ground 9 and becomes floating. Since the source 7 is capacitively coupled to the data bus line 10 via the capacitance of the liquid crystal 12, if the data signal V _{D is set} to 4 V when the TFT 1 is in the ON state, the data bus line 10 will change from 4 V to −.
When you change to 4V, the source potential V _S is from 0V -8V
Changes to.

As described above, the voltage between the data signal V _D and the source potential V _S of the TFT1 is kept at 4 V, and the liquid crystal write voltage V _LC is constant regardless of the potential change of the data bus line 10 after the TFT1 is turned off. Therefore, the voltage written in the liquid crystal 12 is held even while the TFT 1 is off.

[0013]

However, as shown in FIG.
Also in the conventional device shown in FIG. 1, since the gate bus line 2 and the common ground bus line 13 are present in the same substrate, the pixel area is reduced and the aperture ratio is reduced. In addition, the number of processes increases compared to the case where no common bus line is provided,
This may cause a decrease in yield.

As described above, in the conventional active matrix type liquid crystal display device, the gate bus lines 2 are formed on the same substrate.
Since the common bus line 11 or the common ground bus line 13 is formed, there is a problem that a line defect occurs due to a short circuit between the two or the aperture ratio decreases. In addition, the gate bus line 2 and the common bus line 11 or the common ground bus line 13
Therefore, there is a problem in that the number of process steps is large and the yield is low as compared with the case where only the gate bus lines are formed on the substrate.

Therefore, the present invention solves the above-mentioned problems, eliminates line defects due to a short circuit between the gate bus line and the data bus line, prevents the aperture ratio from decreasing, and reduces the number of process steps to improve the yield. Further, it is an object of the present invention to provide an active matrix type liquid crystal display device which reduces the manufacturing cost.

[0016]

In order to achieve the above object, the present invention provides a matrix of MOS transistors and a source of the MOS transistors on one of the transparent substrates facing each other. A pair of display electrodes respectively connected to the terminal and the drain terminal, and a scanning bus line connected to the gate terminal of the MOS transistor,
An active matrix having a data bus line pair arranged on the other substrate in a direction orthogonal to the scanning bus line so as to face the display electrode pair, and the display electrode pair is one pixel. Type liquid crystal display device is provided.

In the active matrix type liquid crystal display device according to the present invention, the MOS transistor is preferably an amorphous silicon thin film transistor.

In the active matrix type liquid crystal display device according to the present invention, the display electrodes and the data bus lines are made of a transparent conductive material, and the transparent conductive material is preferably made of ITO (indium tin lead). It is a thing.

Further, the active matrix type liquid crystal display device according to the present invention is characterized in that a part of the data bus line is lined with Cr.

The active matrix type liquid crystal display device according to the present invention is characterized in that data signals of opposite phases are supplied to the data bus line pair.

Further, in the present invention, the data bus line has an insulating protective film formed on the opposing substrate, and IT
It is characterized in that it is formed by patterning O.

As another preferred embodiment of the present invention, MOS transistors arranged in a matrix on one substrate of transparent substrates arranged to face each other, and connected to a source terminal and a drain terminal of the MOS transistor, respectively. A pair of display electrodes and a scanning bus line connected to the gate terminal of the MOS transistor, and the data is provided on the other substrate so as to face the display electrode pair in a direction orthogonal to the scanning bus line. The display electrode pair includes a bus line and a common bus line, the display electrode pair includes a relatively large display electrode and a relatively small display electrode, and the display electrode pair is arranged to face the data bus line and the common bus line and serves as a display pixel. The liquid crystal pixels connected to the relatively small display electrodes are used, and the liquid crystal pixels connected to the relatively large display electrodes are covered with a light shielding film. Providing Restorative matrix type liquid crystal display device.

According to the principle of the present invention, the above-described aspect of the present invention is such that the MOS transistor is made of an amorphous silicon thin film transistor, the display electrodes, the data bus lines, and the common bus line are made of a transparent conductive material, and Part of the bus wire and / or common bus wire is Cr
Includes a configuration lined with.

[0024]

According to the present invention having the above-mentioned structure, the line defect caused by the short circuit between the gate bus line and the data bus line, which is a problem in the conventional technique, and the opening caused by the structure for suppressing the line defect are formed. In addition to avoiding the problem of lowering the rate, only the gate bus lines need be formed on the TFT substrate, so that the number of manufacturing steps can be reduced, yield can be improved, and manufacturing cost can be reduced.

In the present invention, the MOS transistor comprises an amorphous silicon thin film transistor,
(EN) Provided is an active matrix type liquid crystal display device of high image quality, which can be easily formed on a large area and inexpensive glass substrate at a relatively low temperature.

In the present invention, ITO (indium tin lead) having a small specific resistance is preferably used as the transparent conductive material.

Further, according to the present invention, the IT is formed on the counter substrate.
A part of the common data bus line formed of O etc. is made of metal C
By backing with r, the wiring resistance is lowered, the transmission characteristic of the drive signal waveform is improved, and protection against line disconnection and the like is given.

Further, according to the present invention, by inputting the data signals of opposite phases to the data bus line pair, the liquid crystal writing voltage does not change even after the TFT element changes from the ON state to the OFF state, The voltage is maintained at the same voltage as when it is turned on, and the liquid crystal panel can be driven by using this constant liquid crystal writing voltage.

Further, in the present invention, the data bus line has an insulating protective film formed on the opposing substrate, and IT
It is formed by patterning O to ensure electrical insulation between the light-shielding metal Cr of the color filter and the data bus line.

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

[0031]

[Embodiment 1] FIG. 1 shows an equivalent circuit of a first embodiment of the present invention, and FIG. 2 is a perspective view thereof. As shown,
In the active matrix liquid crystal display device of the present invention, TF
Amorphous silicon (a-Si; hydrogenated amorphous silicon, also referred to as a-Si: H) thin film transistor element TF, which is a MOS transistor, is provided on the T substrate 100 side.
A T1 and a gate bus line 2 are provided, and a common data bus line 3 which also serves as a data bus line and a common bus line is provided on the counter substrate 200 side.

The common data bus line 3 also serves as a display electrode and is preferably ITO (Indium-Tin-Lead; Indium-Tin).
-Oxide), tin oxide, and other transparent electrodes made of a conductive material having a high visible light transmittance.

The drain 6 and the source 7 of the TFT 1 have two display electrodes which are arranged to face the common data bus line 3 via the liquid crystal electrode 8, respectively.

In this embodiment, the gate bus line 2 and the common data bus line 3 are formed on different substrates in this manner, so that the gate bus line 2 and the common data bus line, which have been problems of the prior art, are generated. It is possible to avoid the occurrence of line defects and the reduction of the aperture ratio due to the short circuit with 3.

Further, in this embodiment, the source 7 of the TFT 1 is
Display electrodes are provided on both the drain 6 and the drain 6. As described above, the aperture ratio of the liquid crystal panel can be improved by providing a pair of display electrodes on one TFT.

In this embodiment, since only the gate bus line 2 needs to be formed on the TFT substrate 100, the manufacturing process can be simplified and the yield can be prevented from decreasing.
As a result, the manufacturing cost is reduced.

Next, an example of the driving method of the active matrix liquid crystal display device according to this embodiment will be described with reference to FIGS. The time axes of FIGS. 3 and 4 correspond to each other.

As shown in FIG. 3, the common data bus lines 3 and 4 in FIG. 1 have mutually inverted (opposite phase) data signals 1 and 2 having a period of 120 μs centered at 0 V and an amplitude of ± 2 V.
(1002, 1003) is supplied.

The signal 1001 of FIG. 3 is connected to the gate bus line 2.
As shown in FIG. 5, a TFT 1 is turned on / off by applying a gate signal having an on-voltage of 15 V, an off-voltage of -15 V, an on-time (pulse width) of 20 μs and a period of 16.7 ms. As shown in FIG. 3, the gate signal 1 is applied for a period of about 320 μs to 20 μs on the time axis.
001 is an on-voltage, and at this time, the influences of the data signals 1 and 2 (1002, 1003) having opposite phases are offset, and the drain potential 1004 and the source potential 1005 of the TFT1 become 0V as shown in FIG. .

When the TFT 1 is turned off, the drain 6 and the source 7 become floating, so that the data signals 1, 2 (1
002, 1003), for example, if the voltage of the data signal drops by -4V, the drain potential 1004
And the source potential 1005 is the variation of the data signal −4
The potential changes by V.

The liquid crystal write voltage V _LC is determined by the difference between the potential of the data signal and the source potential when the TFT 1 is on (that is, V _LC
LC = V _D −V _S ), the liquid crystal writing voltage V _LC is kept constant even if the TFT 1 is turned off, and this is utilized to drive the liquid crystal panel.

In this embodiment, one TFT element 1
Is provided with a pair of display electrodes, and two liquid crystals 12 connected to the pair of display electrodes are written with the same writing voltage.
Twelve will form one pixel.

[0043]

Second Embodiment A second embodiment of the present invention will be described below with reference to FIG. As shown in the figure, the drain 6 side of the TFT 1 is arranged to face the data bus line 10 via a large liquid crystal electrode (also referred to as “display electrode”), and the source 7 side is common via a relatively small liquid crystal electrode. It is located opposite the bus line 11.

As the display pixel, the liquid crystal pixel 12 connected to the source 7 side is used, and the liquid crystal pixel connected to the drain 6 side is covered with a light shielding film. This is because the potential applied to the larger liquid crystal electrode is irrespective of whether the gate signal is on or off.
Since the liquid crystal write voltage changes when the data bus line 10 changes, it is not used as a display device, and is therefore covered with a light shielding film.

Next, with reference to FIG. 6, a method of driving the device according to this embodiment will be described. A pulse signal as shown in the figure is input as the gate signal 1001, a data signal V _D (1002) is supplied to the common data bus line 10, and a constant potential V _C such as a common potential 1006 is supplied to the common bus line 11. .

When the gate signal is at a high potential and the TFT 1 is in the ON state, the liquid crystal capacitance connected to the drain 6 side of the TFT ₁ is C ₁ and the liquid crystal capacitance connected to the source 7 side is C ₂ Since the electric potential is V _P = C ₁ / (C ₁ + C ₂ ) × (V _D −V _C ) + V _C , when C ₁ >> C ₂ (C ₁ is larger than C ₂ ),
Since V _P = V _D , the data signal V _D (1002) is written in the source 7.

When the gate signal is low and the TFT 1 is off, the source potential 1005 is constant and the liquid crystal potential is maintained constant.

[0048]

Third Embodiment A third embodiment of the present invention will be described below with reference to FIG. As shown, in this embodiment, a part of the common data bus line 3 is lined with a metal Cr14.
As described in the first embodiment, when the common data bus line 3 is formed only by the transparent electrodes such as ITO, the wiring resistance becomes large, and therefore, the transmission characteristics of the drive signal such as the distortion of the data signal are generated. Although there is a possibility of deterioration or disconnection, in this embodiment, by lining a part of the common data bus line 3 with metal Cr14,
These problems are solved.

As a mode of lining with metallic Cr14,
For example, as shown in FIG. 7 (A), a liner of Cr is formed in the central portion of the common data bus line 3 along the longitudinal direction, or as shown in FIG. The end of the common data bus line is metal Cr14
There are things such as lining and interconnecting.

In FIG. 7B, the common data bus line 3 is divided into upper and lower parts in the figure, but this is shown in FIG.
In the configuration (A), since the Cr lining line is provided in the central portion of the common data bus line 3, it is possible to prevent the aperture ratio from decreasing.

[0051]

Fourth Embodiment FIG. 8 shows a sectional view of a liquid crystal panel according to a fourth embodiment of the present invention. FIG. 8A is a cross-sectional view of the counter substrate 200 facing the TFT substrate 100, and FIG.
Cross-sectional views of the T-substrate 100 are each shown.

Since the metal Cr 14 is used to shield the ordinary color filter 15 from light, if the common data bus line 3 is formed immediately above it, these will be short-circuited.
For this reason, as shown in FIG.
Then, the ITO is patterned. As the insulating protective film 16, a thermosetting acrylic resin (for example, Optomer SS manufactured by Nippon Synthetic Rubber Co., Ltd.) or the like is used.

Although the present invention has been described with reference to the above various embodiments, it goes without saying that the present invention includes various combinations of these embodiments, and further various embodiments according to the principle of the present invention. Is included.

[0054]

As described above, according to the present invention, by forming the gate bus line and the common data bus line on different substrates, the gate bus line and the data bus line, which have been problems of the prior art, are present. It is possible to prevent the occurrence of line defects due to the short-circuiting and the decrease in the aperture ratio caused by the structure for suppressing the line defects. Furthermore, according to the present invention, a TFT
Since only the gate bus line needs to be formed on the substrate, the number of manufacturing steps can be reduced by one as compared with the conventional technique, and the yield can be improved and the manufacturing cost can be reduced.

In the present invention, the MOS transistor comprises an amorphous silicon thin film transistor,
(EN) Provided is an active matrix type liquid crystal display device of high image quality, which can be easily formed on a large area and inexpensive glass substrate at a relatively low temperature.

Further, according to the present invention, the display electrodes and the data bus lines are made of a transparent conductive material to enhance the transmittance of visible light in the liquid crystal panel. In the present invention, ITO (indium tin lead) having a small specific resistance is preferably used as the transparent conductive material.

Further, according to the present invention, IT is formed on the counter substrate.
A part of the common data bus line formed of O etc. is made of metal C
By backing with r, the wiring resistance is reduced to improve the transmission characteristics of the drive signal waveform, and protection against line disconnection and the like is provided.

Further, according to the present invention, by inputting the data signals of opposite phases to the data bus line pair, the liquid crystal write voltage is the same as when it is turned on even after the TFT element changes from the on state to the off state. The liquid crystal panel is held at the voltage of 1, and the liquid crystal writing voltage can be used to drive the liquid crystal panel.

Further, in the present invention, the data bus line has an insulating protective film formed on the opposing substrate and the IT
It is formed by patterning O to ensure electrical insulation between the light-shielding metal Cr of the color filter and the data bus line.

Further, as another preferred aspect of the present invention, a data bus line and a common bus line are provided on the counter substrate so as to face the display electrode pair in a direction orthogonal to the scanning bus line, and are connected to the source and drain of the thin film transistor. The display electrode pair is composed of a relatively large display electrode and a relatively small display electrode, and even if the data bus line and the common bus line are arranged to face each other, the gate bus line and the data bus line are short-circuited. It is possible to avoid problems such as generation of line defects and reduction of aperture ratio, reduce the number of manufacturing steps, improve yield, and reduce manufacturing cost.

[Brief description of drawings]

FIG. 1 is a diagram showing an equivalent circuit of a first exemplary embodiment of the present invention.

FIG. 2 is a perspective view of the first embodiment of the present invention.

FIG. 3 is a waveform diagram showing a driving method according to the first embodiment of the present invention.

FIG. 4 is a waveform diagram showing a driving method according to the first embodiment of the present invention.

FIG. 5 is a diagram showing an equivalent circuit of a second exemplary embodiment of the present invention.

FIG. 6 is a waveform diagram showing a driving method according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating a third embodiment of the present invention.

FIG. 8 is a sectional view illustrating a fourth embodiment of the present invention.

FIG. 9 is a diagram showing an equivalent circuit of a conventional liquid crystal panel.

FIG. 10 is a diagram showing an equivalent circuit of the liquid crystal panel disclosed in Japanese Patent Laid-Open No. 2-1822.

FIG. 11 is a diagram showing an equivalent circuit of the liquid crystal panel disclosed in JP-A-62-133478.

FIG. 12 is a waveform diagram showing a driving method of the panel disclosed in Japanese Patent Laid-Open No. 62-133489.

[Explanation of symbols]

 1 TFT element 2 gate bus line 3 common data bus line a 4 common data bus line b 5 gate 6 drain 7 source 8 liquid crystal electrode 9 ground 10 data bus line 11 common bus line 12 liquid crystal 13 common ground bus line 14 metal Cr 15 color Filter 16 Insulating protective film 100 TFT substrate 200 Counter substrate 1001 Gate signal 1002 Data signal 1 1003 Data signal 2 1004 Drain potential 1005 Source potential 1006 Common potential

Claims (8)

[Claims] 1. A MOS transistor arranged in a matrix, a display electrode pair connected to a source terminal and a drain terminal of the MOS transistor, respectively, on one substrate of transparent substrates opposed to each other, A scan bus line connected to the gate terminal of the MOS transistor,
On the other substrate, there is a data bus line pair arranged to face the display electrode pair in a direction orthogonal to the scanning bus line, and the display electrode pair forms one pixel. Matrix type liquid crystal display device. 2. The active matrix type liquid crystal display device according to claim 1, wherein the MOS transistor comprises an amorphous silicon thin film transistor. 3. The active matrix type liquid crystal display device according to claim 1, wherein the display electrodes and the data bus lines are made of a transparent conductive material. 4. The active matrix type liquid crystal display device according to claim 3, wherein the transparent conductive material is made of ITO (indium tin lead). 5. The active matrix type liquid crystal display device according to claim 1, wherein a part of the data bus line is lined with Cr. 6. The active matrix type liquid crystal display device according to claim 1, wherein data signals having mutually opposite phases are supplied to the data bus line pair. 7. The active matrix type liquid crystal display device according to claim 1, wherein the data bus line is formed by patterning ITO on an insulating protective film formed on the other substrate. . 8. A MOS transistor arranged in a matrix, a display electrode pair connected to a source terminal and a drain terminal of the MOS transistor, respectively, on one substrate of transparent substrates arranged facing each other. A scan bus line connected to the gate terminal of the MOS transistor,
A data bus line and a common bus line are provided on the other substrate in a direction orthogonal to the scanning bus line so as to face the display electrode pair, and the display electrode pair has a relatively large display electrode and a relatively small display. A liquid crystal pixel which is composed of an electrode and is arranged to face the data bus line and the common bus line and is connected to the relatively small display electrode is used as a display pixel, and is connected to a relatively large display electrode. An active matrix type liquid crystal display device characterized in that the liquid crystal pixels thus formed are covered with a light shielding film.