JPH0667200A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display device in which work in the case of switching two or more systems of redundant scanning line driving circuits and signal line driving circuits is simplified, whose production cost is kept low and which has sufficient reliability. CONSTITUTION:Connection control switches 21 and 23 consisting of TFT having the active layer of polycrystal silicon formed of the same material and in the same layer structure as a TFT 3 for switching a picture element part are inserted between the scanning line driving circuits 13 and 15 and a scanning line 5, and between the signal line driving circuits 17 and 19 and a signal line 7 in every scanning line 3 and every signal line 7, so that electric disconnection and connection between them are executed.

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, and more particularly to a drive circuit integrated active matrix liquid crystal display device.

[0002]

2. Description of the Related Art In order to realize high definition and high quality image display in a liquid crystal display device, a thin film transistor (hereinafter referred to as T
An active matrix type liquid crystal display device has been developed in which FT (abbreviated as FT) is arranged at each intersection of a scanning line and a signal line as a switching element for a liquid crystal applied voltage.

In this active matrix type liquid crystal display device, further, the scanning line driving circuit and the signal line driving circuit are formed on the same TFT array substrate by using the same material as the switching element of the liquid crystal display element. In recent years, a so-called integrated drive circuit type has been developed in order to reduce the size and simplify the manufacturing process. TF of the active matrix type liquid crystal display device integrated with the drive circuit
It is considered to use a polycrystalline silicon thin film transistor as T.

However, in such a conventional liquid crystal display device integrated with a drive circuit, the TFTs of the scanning line drive circuit and the signal line drive circuit must be formed defect-free over a large area and a number corresponding to a large number of pixels. Therefore, there is a problem that the yield is low and the manufacturing cost is high. Therefore, as a technique for improving the yield of the TFTs of the scanning line driving circuit and the signal line driving circuit, a technique of giving redundancy to the scanning line driving circuit and the signal line driving circuit is disclosed in, for example, Japanese Patent Laid-Open No. No. 57-132191.

In this technique, as shown in FIG. 6, a scanning line (gate line) driving circuit 501 is provided on the left and right of a display portion 505 of a TFT substrate 503, and a signal line driving circuit 507 is provided on a TFT.
The scanning lines 5 are provided above and below the display portion 505 of the substrate 503, respectively.
09, and two or more lines are redundantly provided for each signal line 511. In the display portion 505, TF
T513 is arranged as a switching element at each intersection of the scanning line 509 and the signal line 511.

When there is a defective portion in the scanning line driving circuit 501 or the signal line driving circuit 507, the liquid crystal display element does not operate in the case where the driving circuit is integrated even if there is no defective portion in the display portion 505. Therefore, for one scanning line 509 or signal line 511, there are two or more scanning line driving circuits 50.
1 or the signal line driver circuit 507 is connected in advance, and then 2
When a defect is generated in any of the above systems, the system having the defect is identified and then separated from the scan line 509 or the signal line 511 by a laser repair device or the like, and a scan line of a system that operates normally without any defect. By using the driver circuit 501 or the signal line driver circuit 507, the TFT substrate 50
The purpose of the present invention is to improve the yield of the liquid crystal display device by avoiding that the whole 3 is not used as a defect.

However, when the redundant structure as described above is adopted, for example, when the scanning line driving circuits 501 are connected to both sides of the scanning line 509, one of the scanning line driving circuits 501 is defective and malfunction occurs. Then, the scan line 509 connected to the scan line drive circuit 501 also adversely affects the other normal scan line drive circuit 501, so that normal display cannot be performed. As described above, even if drive circuits are formed at both ends, a redundant structure is not actually formed. Therefore, it is necessary to disconnect all the connection between the scanning line drive circuit 501 and the scanning line 509 on the defect side. There is a problem that the cutting work is very complicated and difficult in an active matrix type liquid crystal display device in which the number of pixels and the definition are remarkably increased.

As a work for switching the redundant scanning line driving circuit 501 and the signal line driving circuit 507 of two or more systems, specifically, for example, the above-mentioned laser repair method is used to interpose an interlayer insulating layer. Connections in different layers or connections between lines in the same layer are performed, but this has a problem that the man-hour cost becomes high and the contact resistance of the connection and the reliability of the contact are not sufficient.

In addition to the drive circuit integrated active matrix type liquid crystal display device composed of the above-mentioned polycrystalline silicon thin film transistor, a COG (chip on glass) mounted integrated circuit which is not easily repaired after mounting, and the like. The active matrix type liquid crystal display device used in the drive circuit also has the same problem as described above.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and its object is to switch redundant scanning line drive circuits and signal line drive circuits of two or more systems. An object of the present invention is to provide a liquid crystal display device which has a simple operation, a low manufacturing cost, and sufficient reliability.

[0011]

A liquid crystal display device according to a first invention is a switching element having a thin film transistor element, a scanning line and a signal line connected to the thin film transistor element, and a pixel electrode connected to the thin film transistor element. An array substrate, a counter substrate having a counter electrode arranged to face the switching element array substrate, a liquid crystal composition enclosed and sandwiched between the switching element array substrate and the counter substrate, and a scanning signal for the scanning line. In a liquid crystal display device having a scanning line drive circuit for applying a signal and a signal line drive circuit for applying a video signal to the signal line,
A plurality of scanning line driving circuits are connected to the same scanning line, and a connection control switch for controlling transmission of the scanning signal to the scanning line is provided.

The liquid crystal display device according to the second invention is
A switching element array substrate having a thin film transistor element, a scanning line and a signal line connected to the thin film transistor element, and a pixel electrode connected to the thin film transistor element, and a counter substrate having a counter electrode arranged to face the switching element array substrate. A liquid crystal composition enclosed and sandwiched between the switching element array substrate and the counter substrate, a scanning line driving circuit for applying a scanning signal to the scanning line, and a signal line for applying a video signal to the signal line. A liquid crystal display device having a drive circuit, wherein a plurality of signal line drive circuits are connected to the same signal line, and a connection control switch for controlling transmission of the video signal to the signal line is provided. There is.

The scanning line drive circuit, the signal line drive circuit, and the connection control switch may be formed of thin film transistor elements having polycrystalline silicon in an active layer and arranged on the switching element array substrate. Good.

Further, the connection control switch may be formed of a thin film transistor element having polycrystalline silicon in an active layer, and a plurality of gate lines to which the gates of the plurality of thin film transistor elements are connected may be provided.

Further, the connection control switch may be a clocked inverter.

A double-gate thin film transistor element may be used as the connection control switch.

Further, a COG (chip on glass) mounted integrated circuit may be used for the scanning line driving circuit and the signal line driving circuit, and a thin film transistor element may be used for the connection control switch.

[0018]

In the liquid crystal display device of the present invention, a plurality of scanning line driving circuits or signal line driving circuits are connected to the same scanning line or signal line, and a video signal is a signal line or a scanning signal is a scanning line. A connection control switch for controlling transmission can be provided, and the connection control switch can be controlled to electrically disconnect the defective scan line driver circuit or signal line driver circuit from the scan line or the signal line. To do so.

As a result, for example, of the two scanning line driving circuits connected to both sides of one scanning line, even if one scanning line driving circuit has a defect and malfunctions, the other normally operates. In the case of the scanning line driving circuit, the connection control switch is used to electrically disconnect the defective and malfunctioning scanning line driving circuit from the scanning line connected thereto. Therefore, it is possible to easily electrically disconnect only the scanning line drive circuit which is not operating properly while leaving only the scanning line drive circuit which normally operates connected to the scanning line, and the disconnection is sufficiently reliable. Can be expensive.

If the scanning line driving circuit, the signal line driving circuit and the connection control switch are formed from thin film transistor elements having polycrystalline silicon in the active layer and are arranged on the same switching element array substrate, the same material is used. Since the scanning line driving circuit, the signal line driving circuit, and the connection control switch can be formed by using the and the layer structure, the structure can be simplified, the yield can be improved, and the manufacturing cost can be suppressed low. .

Further, the connection control switch may be formed of a thin film transistor element, and each may have a plurality of gate lines to which the gates of the plurality of thin film transistor elements are connected. That is, the connection control switches composed of thin film transistor elements are divided into a plurality of groups, and the gate lines for connection are arranged by the number of the groups, and the connection control switches corresponding to each group are controlled to control the scanning line drive circuit. Since the electrical connection between the scanning lines or between the signal line driver circuit and the signal line can be controlled for each set, the redundancy of the scanning line driver circuit and the signal line driver circuit can be further effective. Can be one. In particular, when this connection control switch is provided in the signal line, the output of the analog switch that writes the video signal using the outputs from the plurality of shift registers in the signal line drive circuit is divided into blocks by the number of shift registers, etc. By using a redundant structure, it becomes possible to deal with defects in each shift register in the signal line drive circuits of two or more systems.

In particular, in the case of a liquid crystal display device integrated with a drive circuit, since an inverter circuit composed of transistor elements is usually provided as a buffer circuit in the final output stage of the drive circuit, both ends of this inverter circuit are arranged. If the transistor elements are connected to form a clocked inverter circuit, and the control input lines with different polarities are connected to the transistor elements at both ends of the circuit to configure the connection control switch, the structure of the device can be simplified. be able to.

Further, a thin film transistor element having a double gate structure is used as the connection control switch, one gate portion is used as a gate of an analog switch for outputting a liquid crystal drive voltage, and the other gate portion is used as the connection control switch. If the structure is used as the gate of the device, the structure of the device can be simplified.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the liquid crystal display device according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a diagram showing the structure of a TFT substrate in the liquid crystal display device according to the present invention.

On the TFT substrate 1 of this liquid crystal display device, a pixel portion switching TFT 3 composed of a thin film transistor element (hereinafter abbreviated as TFT) having an active layer of polycrystalline silicon, and the pixel portion switching TFT 3 are connected. A screen display portion 11 in which a scanning line 5 and a signal line 7 and a pixel electrode 9 connected to the pixel portion switching TFT 3 are arranged, and the scanning line 5 and the signal line 7 arranged around the screen display portion 11. Of the two scanning line driving circuits of the first scanning line driving circuit 13 and the second scanning line driving circuit 15 and the first signal line driving circuit 17 and the second signal line driving circuit 19 which are connected to both ends of Two lines of signal line drive circuits are formed respectively.

The entire liquid crystal display device according to the present invention is
Although not shown in the figure, the main components are a counter substrate having counter electrodes arranged to face the TFT substrate 1 and a liquid crystal composition enclosed and sandwiched between the TFT substrate 1 and the counter substrate. Parts are made up.

The first scanning line driving circuit 13 and the second scanning line driving circuit 15 of this liquid crystal display device are shift registers (which apply scanning signals (Vg) to the respective scanning lines 5 in a fixed order at the same timing. The main part is composed of (not shown).

Between the first scanning line driving circuit 13 and the second scanning line driving circuit 15 and each scanning line 5, the same material as that of the pixel switching TFT 3 is formed in the same structure. The connection control switches 21 and 23, which are TFTs having an active layer of polycrystalline silicon, are respectively inserted.

On / off control of the connection control switches 21 and 23 group is collectively performed to control application of the scanning signal (Vg) to each scanning line 5, so that the gate electrode of each scanning switch 21 is It is commonly connected to the first scanning signal control line 25 having the input terminal C11, and the gate electrode of each scanning switch 23 is also commonly connected to the second scanning signal control line 27 having the input terminal C12. It is connected to the.

The video signal input lines 321 to 32 of the first signal line driving circuit 17 and the second signal line driving circuit 19 are also provided.
Video signals (Vs1) to (Vs4) divided into four are inputted to 8 and four shift registers (SR1) to
The video signal input line 3 by the selection switch (SW) controlled by the outputs of (SR4), (SR5) to (SR8)
Video signals (Vs1) to (Vs4) input to 21 to 328
Are sequentially sampled and output.

In this way, the first signal line drive circuits 17, 1
9 are four shift registers (SR1) to (S)
R4) and (SR5) to (SR8) are driven separately, so that the shift registers (SR1) to (SR4) and (SR
5)-(SR8) operation speed can be reduced to about 4 times that of the case where the signal line drive circuit is composed of one shift register, and there is no distortion of video signals (Vs1)-(Vs4)
Can be applied to each signal line 7.

The pixel switching TFT 3 is provided between the signal line drive circuits 17 and 19 and the signal line 7.
A connection control switch 29 comprising a TFT having an active layer of polycrystalline silicon formed of the same material as and having a similar structure,
31 is provided for each signal line 7.

The gate electrodes of the connection control switches 29 and 31 connected to the signal line 7 to which the video signal (Vs1) selected by the first shift register (SR1) and the fifth shift register (SR5) are applied are , Input terminals (C
1), video signal control lines 331, 335 provided with (C5)
Are commonly connected to.

Regarding the gate electrodes of the connection control switches 29 and 31 connected to the signal line 7 to which the video signal (Vs2) selected by the second shift register (SR2) and the sixth shift register (SR6) is applied. Similarly, they are commonly connected to video signal control lines 332 and 336 having input terminals (C2) and (C6) at both ends.

The third shift register (SR3),
Similarly, for the gate electrodes of the connection control switches 29 and 31 connected to the signal line 7 to which the video signal (Vs3) selected by the seventh shift register (SR7) is applied, the input terminals (C3), It is commonly connected to video signal control lines 333 and 337 having (C7).

Similarly, the fourth shift register (SR4
) And the gate electrodes of the connection control switches 29 and 31 connected to the signal line 7 to which the video signal (Vs4) selected by the eighth shift register (SR8) is applied, similarly at both ends thereof. ) And (C8) are commonly connected to video signal control lines 334 and 338.

According to such a configuration, when a malfunction occurs in the shift register inside the first scanning line driving circuit 13, the first scanning signal connected to the first connection control switch 21 is generated. By applying the OFF signal to the input terminal (C11) of the control line 25 and the ON signal to the input terminal (C12) of the second scanning signal control line 27 connected to the second connection control switch 23, the normal operation is achieved. Only the operating second scan line driving circuit 15 can be electrically connected to the scan line 5.

Further, for example, when the first shift register (SR1) forming the first signal line drive circuit 17 becomes defective, normal operation can be obtained as follows. .

That is, the first signal line driving circuit 17
Connection control switch 2 connected to the switch element (SW) controlled by the output of the shift register (SR1)
9 to control the video signal control line 331 to both ends of the input signal (C1) off signal, the second shift register (S
R2) to input terminals (C2) to (C4) at both ends of video signal control lines 332 to 334 for controlling the connection control switch 29 connected to the switch element controlled by the output of the fourth shift register (SR4). The ON signal is applied respectively.

On the other hand, the fifth signal line driving circuit 19
Connection control switch 3 connected to the switch element (SW) controlled by the output of the shift register (SR5)
The ON signal is applied to the input terminals (C5) at both ends of the video signal control line 335 for controlling the first signal, and the sixth shift register (SR6
) To video signal control lines 336 to 338 for controlling the connection control switch 31 connected to the switch element (SW) controlled by the output of the eighth shift register (SR8)
An off signal is applied to the input terminals (C6) to (C8) at both ends of each.

In this way, the first shift register (SR) of the first signal line drive circuit 17 in which the malfunction has occurred
By electrically disconnecting 1) and connecting the fifth shift register (SR5) of the second signal line drive circuit 19 to drive by this, a normal operation of the liquid crystal display device can be obtained. Other than the above example, the same operation is appropriately performed in each shift register to obtain a normal operation of the liquid crystal display device.

As described above, particularly in this embodiment, the signal line drive circuits 17 and 19 are provided with a plurality of shift registers (SR1).
.. (SR8), each shift register (SR1) to (SR1) to (SR8) is controlled so that the transmission of the output to the signal line 7 can be controlled.
A plurality of video signal control lines 331 corresponding to (SR8)
.About.338. As a result, even if one of the shift registers on the first signal line drive circuit 17 side or the second signal line drive circuit 19 side malfunctions, the input of the video signal control lines 331 to 338 is switched and each connection control switch is switched. By properly controlling 29 and 31 in the above manner,
By electrically disconnecting the malfunctioning shift register from the signal line 7 and connecting the normal shift register to the signal line 7, it is possible to obtain a normal operation of the liquid crystal display device and improve the redundancy effect.

In the above-described embodiment, the configuration in which the input terminals are provided at both ends of each of the video signal control lines 331 to 338 to apply the control signal is applied to the video signal control lines 331 to 331.
This is because even if the wire 338 is broken, the left and right input terminals can control the connection control switches 29 and 31.

By the way, the connection control switches 21 and 2 inserted between the scanning line driving circuits 13 and 15 and the scanning line 5 are connected.
As 3, the polycrystalline silicon TFT may be added to each scanning line 5 as described above, but may be configured as follows.

That is, as shown in FIG. 2, the scanning line driving circuit is a buffer circuit of an inverter structure having a large channel W / L (width / length) ratio due to a decrease in impedance at the final stage of output to the scanning line 5. Has 201. Therefore, FIG.
As shown in FIG.
The two control input lines 303 and 3 with different polarities
It is preferable that the connection control switches 21 and 23 have a structure in which connection is controlled by 05 and that the connection control switches 21 and 23 are simple in terms of circuit configuration and the pattern design and manufacturing process can be simplified. Moreover, the clocked inverter circuit is configured by connecting transistor elements on both sides of the transistor element of the double gate structure of the inverter,
By using this as the connection control switches 21 and 23, the structure becomes simpler than the case where the connection control switches are separately provided, and the pattern design and the manufacturing process can be simplified, which is preferable.

Further, as shown in FIG. 4, the connection control switch 29 is formed in series with the selection switch (SW), and further the video input lines 321 to 324 and the video signal control lines 331 to 331 are formed.
34 and 34 may be arranged alternately. If the wirings are alternately arranged in this manner, the video input line 321
It is possible to add an effect of reducing crosstalk between adjacent wirings of .about.324.

The structure of the connection control switch 29 and the selection switch (SW) formed in series as described above is shown in FIG. 5 instead of individually patterning two TFT elements. As described above, if the structure is such that the output line 407 from the driving circuit and the video signal control line 409 are connected to the respective gate electrodes 401 and 402 of the double-gate structure TFT 400, the circuit configuration becomes simple. It is preferable because the pattern design and manufacturing process can be simplified.

As described above, in the liquid crystal display device integrated with the drive circuit according to the present invention, the transmission of the scanning signal or the video signal to the scanning line or the signal line can be electrically disconnected or connected by the connection control switch. it can. This allows the selection of redundant drive circuits from being physically disconnected or connected by laser light after confirming the defective portion in the past, but the selection of redundant drive circuits is connected to the connection control switch. The control input to the line can be switched by switching the input to the line, so that the switching work can be easily performed even in the final inspection stage of the liquid crystal display device, reducing the man-hours and saving labor. The manufacturing cost can be reduced. Further, in addition to omitting the step of physically cutting the wiring, it is possible to make the contact reliability of the connection portion particularly sufficient.

In the present invention, the polycrystalline silicon TFT as described above is used as the scanning line driving circuit and the signal line driving circuit.
It is also effective for a circuit using a COG (chip on glass) mounting type integrated circuit in addition to the circuit consisting of the
Alternatively, an amorphous silicon TFT may be used.

Needless to say, the structure of the scanning signal control line or the video signal control line connected to the connection control switch and the gate line thereof is not limited to the above. Besides this, for example, a transfer gate structure or the like can be used.

[0052]

As is apparent from the above detailed description, according to the present invention, the work for switching between the redundant scanning line drive circuits and signal line drive circuits of two or more systems is simple and the manufacturing cost is reduced. It is possible to provide a liquid crystal display device that is kept low and has sufficient reliability.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a TFT substrate of a liquid crystal display device according to the present invention.

FIG. 2 is a diagram showing a buffer circuit portion in a drive circuit of a liquid crystal display device according to the present invention.

FIG. 3 is a diagram showing a connection control switch including an inverter circuit of the liquid crystal display device according to the present invention.

FIG. 4 is a diagram showing a signal line drive circuit of a liquid crystal display device according to the present invention.

FIG. 5 is a diagram showing a connection control switch including an inverter circuit of the liquid crystal display device according to the present invention.

FIG. 6 is a TFT of a liquid crystal display device having a conventional redundant structure.
The figure which shows the structure of a board | substrate.

[Explanation of symbols]

1 ... TFT substrate, 3 ... Pixel part switching TFT, 5
... scanning line, 7 ... signal line, 9 ... pixel electrode, 11 ... screen display portion, 13 ... first scanning line drive circuit, 15 ... second scanning line drive circuit, 17 ... first signal line drive circuit, 19 ... Second
Signal line drive circuit, 21, 23 ... Connection control switch on scanning side, 25 ... First scan signal control line, 27 ... Second scan signal control line, 29, 31 ... Connection control switch on signal side,
321 to 328 ... Video signal input lines, 331 to 338 ... Video signal control lines

Claims (6)

[Claims] 1. A switching element array substrate having a thin film transistor element, a scanning line and a signal line connected to the thin film transistor element, and a pixel electrode connected to the thin film transistor element, and a counter arranged to face the switching element array substrate. A counter substrate having electrodes,
A liquid crystal composition enclosed and sandwiched between the switching element array substrate and the counter substrate, a scanning line driving circuit for applying a scanning signal to the scanning line, and a signal line driving circuit for applying a video signal to the signal line. A liquid crystal display device having a plurality of scanning line driving circuits connected to the same scanning line, and further comprising a connection control switch for controlling transmission of the scanning signal to the scanning lines. Display device. 2. A switching element array substrate having a thin film transistor element, a scanning line and a signal line connected to the thin film transistor element, and a pixel electrode connected to the thin film transistor element, and a counter arranged to face the switching element array substrate. A counter substrate having electrodes,
A liquid crystal composition enclosed and sandwiched between the switching element array substrate and the counter substrate, a scanning line driving circuit for applying a scanning signal to the scanning line, and a signal line driving circuit for applying a video signal to the signal line. A liquid crystal display device having: a plurality of signal line drive circuits connected to the same signal line, the liquid crystal display device comprising a connection control switch for controlling transmission of the video signal to the signal line. Display device. 3. The scanning line drive circuit, the signal line drive circuit, and the connection control switch are formed of thin film transistor elements having polycrystalline silicon in an active layer, and are integrally arranged on the switching element array substrate. The liquid crystal display device according to claim 1 or 2. 4. The connection control switch is formed of a thin film transistor element having polycrystalline silicon in an active layer, and each of the connection control switches includes a plurality of gate lines to which gates of a plurality of the thin film transistor elements are connected. The liquid crystal display device according to claim 1 or 2. 5. The liquid crystal display device according to claim 1, wherein the connection control switch comprises a clocked inverter. 6. The liquid crystal display device according to claim 1, wherein a thin film transistor element having a double gate structure is used as the connection control switch.