JPH06175103A - Active matrix display - Google Patents

Abstract

PURPOSE:To realize an active matrix display device without affecting a driving element by the adverse effect of an instantaneous voltage drop given by a scanning signal with the timing when a video signal falls from H to L regardless of the packaging system of the driving element and capable of considerably improving the quality of display and reliability. CONSTITUTION:A thin film cut-off transistor 9 is provided between a gate line driving element 5 and a gate line 7. Synchronizing with the fall from H to L of a video signal 11 given to a source line 8, the thin film cut-off transistor 9 is turned off and the line between the gate line driving element 5 and the gate line 7 is transiently and electrically released, consequently, so that the driving element 5 is not affected by the adverse effect of the instantaneous voltage drop generated in the scanning signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix display device in which, for example, liquid crystal is used as a display medium, and scanning line driving elements and signal line driving elements are connected to or built in the periphery of a substrate display portion. A COG (Chip) in which a driving element is directly mounted on a display substrate pattern
The present invention relates to an active matrix display device suitable for a display device of On Glass type.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional example of an active matrix display substrate which constitutes an active matrix display device. A plurality of gate lines 7, 7 which are scanning lines and a plurality of source lines 8, 8 which are signal lines are formed on a rectangular transparent insulating substrate 2 which is made of a glass substrate and is long in the left-right direction.
Are wired so as to be orthogonal to each other. That is, the gate lines 7, 7 ... Are wired in the horizontal direction, and the source lines 8, 8 ... Are wired in the vertical direction.

In each area surrounded by the gate line 7 and the source line 8, picture elements 3 are provided in a matrix.
In addition, at the intersection of the gate line 7 and the source line 8,
A thin film transistor (T
FT) 4 are provided respectively.

In addition, a gate line driving element (IC driver) 5 is arranged in the width direction (vertical direction) at one end of the transparent insulating substrate 2 in the longitudinal direction (horizontal direction). One end of each gate line 7, 7 ... Is connected to the device 5. Further, the source line driving element 6 is arranged in the longitudinal direction at one end portion in the width direction of the transparent insulating substrate 2, and the source line driving element 6 has one end portion of each source line 8, 8 ... Each is connected. A plurality of input terminal lines 10 are connected to the gate line driving element 5.

The driving elements 5 and 6 allow the active matrix display device to perform a display operation by a method of sequentially scanning the gate line 7 in the vertical direction and applying a video signal to the source line 8 to write each row. .

The portion of the transparent insulating substrate 2 excluding the portion where the gate line driving element 5 and the source line driving element 6 are arranged is the display section 1.

[0007]

However, since the above-mentioned conventional active matrix display device has a structure in which a plurality of gate lines 7 and a plurality of source lines 8 are arranged on the transparent insulating substrate 2 at right angles, The scan signal 12 given to the line 7 (see FIG. 6B) and the source line 8
The video signals 11 (see FIG. 6 (a)) given to each other interfere with each other or affect each other as the coupling noise, so that in some cases, the driving elements 5 and 6 are driven.
It had the drawback of adversely affecting

[0008] Here, in the case of a liquid crystal display device, imaging signal 11 applied to the source line 8, the liquid crystal deterioration prevention, for high contrast and flicker reduction, frequency of several 10KH _z, maximum amplitude 6~10V AC drive is generally performed with a square wave of _pp . Regarding the scanning signal 12 applied to the gate line 7, it is necessary to sufficiently turn on and off the thin film transistor 4 of each pixel 3 within a short time. Therefore, the difference between the ON voltage and the OFF voltage is generally Is set to about 15 to 30V.

In such a liquid crystal display device, the most serious problem among the mutual influences of the scanning signal 12 and the video signal 11 is that the video signal 11 is "H" (= high level) → "L".
Scan signal 12 at the timing of falling to (= low level)
Is an instantaneous voltage drop 15 (see FIG. 6 (b))
The value is about 1 to 3V.

Since this instantaneous voltage drop 15 is transmitted to the gate line driving element 5 through the gate line 7, not only the output signal of the gate line driving element 5 but also the output signal of the gate line driving element 5 as shown in FIG. An instantaneous voltage drop 15 is brought to various signals 14 in the gate line driving element 5. If such an instantaneous voltage fluctuation occurs, it may cause malfunction of the gate line driving element 5 or may cause element breakdown due to over breakdown of voltage.

In particular, in order to realize fine pitch connection, low cost and high reliability connection, the gate line driving element 5 is used.
In the COG display device in which the source line driving element 6 is directly mounted on the transparent insulating substrate 2, that is, the display substrate, the input line 10 of the gate line driving element 5 also has a connection resistance and a display substrate pattern wiring. Since a resistance obtained by adding the resistance and the like is added, the instantaneous voltage drop 15 further increases to about 2 to 6 V, which is a serious problem.

For the above reasons, the conventional active matrix display device has a limit in improving the display quality and reliability, and it has been a serious problem especially in the COG connection type active matrix display device.

The present invention solves the problems of the prior art as described above, and the scanning signal is received at the timing when the video signal falls from "H" to "L" regardless of the mounting method of the driving element. It is an object of the present invention to provide an active matrix display device in which a driving element is not adversely affected by an instantaneous voltage drop and display quality and reliability can be significantly improved.

[0014]

In the active matrix display device of the present invention, a plurality of scanning lines and a plurality of signal lines are formed on a substrate so as to intersect with each other, and a first switching element is formed at each intersection. At the same time, in an active matrix display device in which a scanning line driving element for driving the scanning line and a signal line driving element for driving the signal line are formed, the plurality of scanning lines and the scanning line driving element A second switching element is provided between them, and the second switching element is temporarily set to the switch open state in synchronization with the fall of the video signal applied to the signal line. Is achieved.

Preferably, the first switching device has a third switching device for switching a scanning signal and an external power supply input terminal connected to an external power supply, and when the second switching device is in a switch open state. A power source switching control signal is applied to the input terminal of the third switching element so that the element is sufficiently turned off, while an OFF voltage is applied to the first switching element via the external power source input terminal.

[0016]

As described above, the second switching element is provided between each of the plurality of scanning lines and the scanning line driving element,
When the second switching element is temporarily set to the switch open state in synchronization with the fall of the video signal applied to the signal line, the scanning line and the scanning line driving element are temporarily electrically disconnected. Since the video signal is "H" → "
The instantaneous voltage drop due to the fall to L ″ is not transmitted to the scanning line driving element.

As a result, various signals in the scanning line driving element can maintain a stable state. Therefore, it is possible to prevent malfunction of the scanning line driving element and destruction of the element due to the breakdown voltage being exceeded.

Further, since the instantaneous voltage fluctuation caused by the instantaneous voltage drop is eliminated, the ON / OFF voltage difference of the first switching element can be made large within the withstand voltage range of the scanning line driving element, and the display quality can be improved.

While the scanning line and the scanning line driving element are separated from each other, the potential of the scanning line may become unstable and the first switching element may not be sufficiently turned off.
According to the configuration in which the power supply switching control signal is applied to the input terminal of the third switching element and the OFF voltage is applied to the first switching element via the external power supply input terminal as described above, the first switching element is sufficiently supplied. Since it can be turned off, this problem can be easily solved.

[0020]

EXAMPLES Examples of the present invention will be shown below.

(Embodiment 1) FIGS. 1 and 2 show Embodiment 1 of the active matrix display device of the present invention. Rectangular transparent insulating substrate 2 made of glass substrate and long in the left-right direction
A plurality of gate lines 7, 7 ... Which are scanning lines and a plurality of source lines 8, 8 ... which are signal lines are laid out orthogonally to each other. That is, the gate line 7,
7 are wired in the horizontal direction, and the source lines 8, 8 ... Are wired in the vertical direction.

The picture elements 3 are provided in a matrix in each area surrounded by the gate lines 7 and the source lines 8.
In addition, at the intersection of the gate line 7 and the source line 8,
Each thin film transistor 4 that functions as a switching element is provided.

In addition, a gate line driving element 5 is arranged in the width direction at one end of the transparent insulating substrate 2 in the longitudinal direction, and the gate line driving element 5 has gate lines 7, 7 ... Are connected at one end thereof. Further, the source line driving element 6 is arranged in the longitudinal direction at one end portion in the width direction of the transparent insulating substrate 2, and the source line driving element 6 has one end portion of each source line 8, 8 ... Each is connected. The gate line driving element 5
The source line driving element 6 is specifically COG.
It is provided on the transparent insulating substrate pattern by connection. A plurality of input terminal lines 10 are connected to the gate line driving element 5.

The driving elements 5 and 6 allow the active matrix display device to perform a display operation by a method of sequentially scanning the gate line 7 in the vertical direction and applying a video signal to the source line 8 to write the data line by line. .

The portion of the transparent insulating substrate 2 excluding the portion where the gate line driving element 5 and the source line driving element 6 are arranged is the display section 1.

In addition, between the gate line driving element 5 and each of the gate lines 7, 7, ..., There are provided cut-off thin film transistors 9, 9 ... Which function as switching elements for opening and connecting the two. There is. A cutoff signal input terminal 16 formed at a position slightly separated from the input terminal line 10 on the transparent insulating substrate 2 to one end side is connected to the gate electrode of the cutoff thin film transistor 9. A control signal 13 for shutting off is input from an external control circuit via 16.

2A, 2B, and 2C show a video signal 11 supplied to the source line 8, a scanning signal 12 supplied to the gate line 7, and a cutoff signal input terminal 16 of the cutoff thin film transistor 9. 2A and 2B respectively show signal waveforms of the cut-off control signal 13 inputted.
(D) shows signal waveforms of various signals in the gate line driving element 5.

Here, the blocking thin film transistor 9 is used.
Is "H" of the video signal 11 supplied to the source line 8.
→ It is provided to prevent the adverse effect of the instantaneous voltage drop 15 due to the fall to “L” from reaching the gate line driving element 5. The details will be described below with reference to FIG.

As shown in FIGS. 2 (a) and 2 (c), in the first embodiment, the video signal 11 is temporarily shut off in synchronization with the fall of the video signal 11 from "H" to "L". The cut-off signal input terminal 16 of the thin film transistor 9 is supplied with the control signal 13 having the illustrated waveform. This control signal 13
Is supplied, the shut-off thin film transistor 9 is turned off during that time, and the gate line 7 and the gate line driving element 5 are
The gate line 7 and the gate line driving element 5 are temporarily electrically disconnected from each other.

Here, in the timing in which the video signal 11 falls from "H" to "L", the scanning signal 12 is coupled to the scanning signal 12 and the video signal 11 as shown in FIG. 2B. An instantaneous voltage drop 15 has occurred due to noise.

In the first embodiment, however, the video signal 11
Since the gate line 7 and the gate line driving element 5 are temporarily electrically disconnected in synchronization with the fall of "H" to "L", the adverse effect of the instantaneous voltage drop 15 is It does not extend to the line driving element 5. As a result, as shown in FIG. 2D, the various signals 14 in the gate line driving element 5 are in a stable state without being adversely affected by the instantaneous voltage drop 15, that is, in a state where no fluctuation occurs.

At times other than the fall timing of the video signal 11, the shut-off thin film transistor 9 is turned on.
However, the gate line driving element 5 and the gate line 7 are in a connected state.

Therefore, according to the first embodiment, the gate line driving element 5 does not malfunction and the element breakdown due to the breakdown voltage overshoot does not occur. Furthermore, since there is no instantaneous voltage fluctuation and the ON / OFF voltage difference of the thin film transistor 4 can be made large within the breakdown voltage range of the gate line driving element 5, there is a margin in display quality, and the display quality can be easily improved by that amount. Can be achieved.

In addition, in the active matrix display device of the COG connection in which the resistance obtained by adding the connection resistance and the display substrate pattern wiring resistance and the like is added to the input terminal line 10 of the gate line driving element 5, the instantaneous voltage fluctuation is expanded. Can afford the operation of the gate line driving element 5 and the resistance specifications with respect to the display quality. Therefore, the original advantage of the COG connection type active matrix display device is a fine pitch, low cost and high reliability connection. Can enjoy.

(Embodiment 2) FIGS. 3 and 4 show Embodiment 2 of the active matrix display device of the present invention. In the second embodiment, when the gate line driving element 5 and the gate line 7 are opened by the shut-off thin film transistor 9, the potential of the gate line 7 becomes unstable and the thin film transistor 4 is sufficiently discharged. Take a configuration to prevent the situation that it does not turn off. The configuration will be described below. However, since most of the configuration is the same as that of the first embodiment, the corresponding parts are designated by the same reference numerals and the description thereof will be omitted. Only different parts will be described below.

On the transparent insulating substrate 2, gate line signal switching thin film transistors 17, 17 ... Are provided adjacent to the respective blocking thin film transistors 9, 9. The gate electrode of each switching thin film transistor 17 is connected to a control signal input terminal 19 provided in a portion of the transparent insulating substrate 2 adjacent to the cutoff signal input terminal 16, and the control signal input terminal 19 is connected from an external circuit. Via the control signal 20 for switching the power source (see FIG.
(See (e)) is input.

The source side of each switching thin film transistor 17 is connected to the thin film transistor 4, and the drain side is connected to the external power supply input terminal 18. The external power supply input terminal 18 is formed at a position slightly apart from the other end of the input terminal line 10, and the power supply switching control signal 2 is supplied from the external power supply via the external power supply input terminal 18.
0 is input.

In the above structure, the gate electrode of the switching thin film transistor 17 has the timing shown in FIG. 4, that is, the video signal 11 falls from "H" to "L", and the blocking thin film transistor 9 controls the blocking. It is given when the signal 14 is input. At this time, the external power supply input terminal 18 and the switching thin film transistor 1
An OFF voltage is applied to the thin film transistor 4 via 7.

Therefore, according to the second embodiment, a sufficient OFF voltage is supplied to the thin film transistor 4 when the gate line driving element 5 and the gate line 7 are opened by the blocking thin film transistor 9. Therefore, it is possible to reliably prevent the situation where the potential of the gate line 7 becomes unstable and the thin film transistor 4 is not sufficiently turned off.

In each of the above embodiments, the case where the present invention is applied to the active matrix display device of the COG connection system has been described, but TAB (Tape Automat) is used.
edBonding (CO) (Chip O)
n Film) The present invention can also be applied to mounting or forming a driving element on a glass substrate.

As the thin film transistor used in the present invention, an insulated gate field effect transistor using amorphous silicon, polysilicon, Te or the like as a semiconductor material is generally used.

Further, it goes without saying that the active matrix display device of the present invention can be applied not only to a monochrome liquid crystal display device but also to a color liquid crystal display device using a color filter.

[0043]

According to the active matrix display device of the first aspect, the interval between the scanning line and the scanning line driving element is synchronized with the trailing edge of the video signal from "H" to "L". Since the configuration is such that the driving element is temporarily opened, the scanning line driving element is not adversely affected by the instantaneous voltage drop of the scanning signal due to the amplitude of the video signal, regardless of the type of mounting of the driving element.

As a result, various signals in the scanning line driving element can be maintained in a stable state, so that the malfunction of the scanning line driving element and the destruction of the element due to the over-voltage can be surely prevented.
Further, since the instantaneous voltage fluctuation caused by the instantaneous voltage drop is eliminated, the ON / OFF voltage difference of the first switching element can be made large within the withstand voltage range of the scanning line driving element.

Therefore, there is an effect that an active matrix display device of high quality and high reliability can be realized.

According to another aspect of the active matrix display device, the potential of the scanning line becomes unstable and the first switching is performed when the scanning line and the scanning line driving element are open. Since it is possible to surely prevent the element from not being sufficiently turned off, there is an effect that the reliability can be further improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of an active matrix display device of the present invention.

FIG. 2 is a timing chart showing ON / OFF timing of various signals in the active matrix display device according to the first embodiment.

FIG. 3 is a circuit diagram showing a second embodiment of the active matrix display device of the present invention.

FIG. 4 is a timing chart showing ON / OFF timing of various signals in the active matrix display device according to the second embodiment.

FIG. 5 is a circuit diagram showing a conventional active matrix display device.

FIG. 6 is a timing chart showing ON / OFF timings of various signals in a conventional active matrix display device.

[Explanation of symbols]

 1 Display Part 2 Transparent Insulating Substrate 3 Picture Element 4 Thin Film Transistor 5 Gate Line Driving Element 6 Source Line Driving Element 7 Gate Line 8 Source Line 9 Blocking Thin Film Transistor 10 Input Terminal Line of Gate Line Driving Element 11 Video Signal 12 Scan Signal 13 Control signal for interruption 14 Various signals in gate line driving element 15 Instantaneous voltage drop 16 Interruption signal input terminal 17 Switching thin film transistor 18 External power input terminal 19 Switching signal input terminal 20 Switching control signal

Claims (2)

[Claims] 1. A scanning line driving element for driving a scanning line, wherein a plurality of scanning lines and a plurality of signal lines are formed on a substrate so as to intersect with each other, and a first switching element is formed at each intersection. And an active matrix display device in which a signal line driving element for driving the signal line is formed, and a second line is provided between each of the plurality of scanning lines and the scanning line driving element.
An active matrix display device in which each switching element is provided and the second switching element is temporarily set to a switch open state in synchronization with a fall of a video signal applied to the signal line. 2. A third switching element for switching a scanning signal and an external power source input terminal connected to an external power source,
When the second switching element is in the switch open state, a power source switching control signal is applied to the input terminal of the third switching element so that the first switching element is sufficiently turned off, while the external power source is used. The active matrix display device according to claim 1, wherein an OFF voltage is applied to the first switching element via an input terminal.