JPH06202149A - Liquid crystal display device and its driving method - Google Patents

Abstract

PURPOSE:To drive a battery for a long time by reducing crosstalk by a current meandering from a drain wiring and an address wiring to another data wiring, improving display quality, reducing the power consumption of a driver, and reducing a heat generating value. CONSTITUTION:A thin film transistor 24 and a display electrode 25 connected to either the source electrode or drain electrode of the transistor form a display area in a matrix shape at each crossing part of plural address wirings 22 and plural data wirings 23, and the address wiring 22 is connected to a gate electrode, and the data wiring 23 to either the source electrode or drain electrode to which no wiring is performed, respectively, and a short-circuit wiring 26 crossing with the address wiring 22 and the data wiring 23 is formed in the periphery of a thin film transistor array, the short-circuit wiring 26 and the address wiring 22 and the data wiring 23 are connected to a protective element 27 with bidirectional voltage-current characteristic, respectively. A draw-out terminal 30 from the short-circuit wiring 26, and a short-ring driver 35 which impresses a compensation voltage to the terminal are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor drive type liquid crystal display device provided with a device for preventing generation of defects due to static electricity and a method for driving the same.

[0002]

2. Description of the Related Art Conventionally, a thin film transistor (hereinafter referred to as a TFT
(Hereinafter referred to as)) and a display electrode are arranged in a matrix, and an active matrix type liquid crystal display element (hereinafter referred to as TFT-LCD) is used. As such a conventional TFT-LCD,
For example, JP-A-63-85586 and JP-A-3-1-1.
The liquid crystal display element disclosed in Japanese Patent No. 34628 is known, and an equivalent circuit of its TFT array is shown in FIG.

As shown in FIG. 4, the TFT array is
A plurality of address wirings 2 and data wirings 3 are arranged in a row direction and a column direction on an insulating transparent substrate 1 such as a glass substrate so as to intersect each other at a right angle, and these address wirings 2 and data wirings 3 are arranged. A plurality of TFTs 4, 18 and 19 each having a gate electrode connected to the address wiring 2 and a drain electrode connected to the data wiring 3 are arranged at the intersections.
A plurality of display electrodes 5 connected to the source electrodes 18 and 19 are formed in a matrix. On the outer peripheral portion of the transparent substrate 1, a short circuit metal wiring 6 is formed so as to surround the outer periphery of the transparent substrate 1. The short circuit metal wiring 6 intersects the address wiring 2 and the data wiring 3 with an insulating film interposed therebetween. A protection element 7 (7a1 to 7am and 7b1 to 7b3) having a bidirectional IV characteristic is provided in the vicinity of the intersection, and the protection element 7 allows the short-circuit metal wiring 6 to be connected to the address wiring 2 and the data wiring. 3 are connected to each other. Each pixel has a storage capacitor 8.

As a result, during the manufacturing process of the TFT array shown in FIG. 4, all the address wirings and the data wirings are connected to the short-circuiting metal wirings (short ring) on the outer periphery of the transparent substrate, so that they are kept at the same potential. The generation of defects due to static electricity during the process is controlled. here,
The above-mentioned protective elements 7 (7a1-7am and 7b1-7b)
3) is installed in order to protect the TFT 4 from static electricity generated during the TFT manufacturing process and the liquid crystal cell manufacturing process, and during the assembly process after cutting the glass substrate (for example, the liquid crystal injection process and the polarization film attachment process). Process, drive circuit connection process), due to static electricity, dielectric breakdown, disconnection, TFT
It is possible to prevent the occurrence of characteristic fluctuations, and solve the problem that the manufacturing yield is reduced due to the display defect of the liquid crystal display device.

[0005]

However, in the TFT LCD shown in FIG. 4 in which the short-circuit metal wiring 6 and the protection element 7 are added, n address wirings and n data wirings are provided.
As shown in FIG. 5 which is a schematic equivalent circuit diagram of the n × m matrix liquid crystal panel for this line as seen from the address wiring of the TFT in the first row and first column, the data signal 11 at the on level is
A so-called crosstalk occurs, which passes through the protection element 7al-short-circuit metal wiring 6-protection element 7a2 and flows into another data wiring 16. That is, in FIG. 5, the solid line arrow indicates the original signal, and the dotted line arrow indicates the crosstalk supply path. In this way, since the crosstalk current is mixed with the data signal supplied to the other TFTs 18 and 19 arranged in the row direction and applied to the display electrode connected to the other TFT, this display is performed. The pixel corresponding to the electrode operates at a voltage different from that of the supplied data signal, which causes a problem that display quality deteriorates.

That is, in FIG. 5, each data wiring 1
The potential states of 5, 16 and 17 depend on the voltage modulation level of the data signal supplied to the data wiring and the number of data wirings to which the ON data is supplied. When the number of data lines to which a voltage is applied is small, the resistance value seen from the short-circuiting metal line side is small, so that crosstalk current easily flows into the data line, and this crosstalk current is a data signal (display pattern signal). Change depending on.

This problem becomes noticeable in the case of gradation display in which the voltage of the data signal is changed over several stages and an intermediate color is displayed. In addition, the current of the signal supplied from each data wire is about doubled when viewed from the side of each driver connected to each data wire, because the bidirectional protection element is installed in the TFT array. . That is, the data signal 1
1 passes through the protection element 7al and the short-circuit metal wiring 6 and flows into the protection elements 7b2 to 7bn installed on the address wiring side. The resistance value of the short-circuited metal wiring is very small because it is a metal, and since n protection elements on the address wiring side are connected in parallel, the resistance value is as small as 1 / n, and the resistance value of the address wiring is ignored. .

Therefore, approximately, the resistance value of this wiring is determined by the protection element 7al on the data signal wiring side. For example, when the value of the protection element is designed to be approximately the same as the ON resistance of the TFT and the driver potential on the address wiring side is set to the ground level during non-scanning, the current flowing in becomes maximum. About twice as much current is supplied from the driver as compared with the case where the protection element 7 is not provided.

As a result, the current supply to the driver is increased, resulting in an increase in power consumption of the liquid crystal display device and an increase in the amount of heat generated by the driver. This is an obstacle to driving the battery to reduce the size and weight, and shortens the battery life. The present invention eliminates the above problems, reduces crosstalk due to current flowing from the drain and gate drivers to the data wiring, improves display quality, reduces driver power consumption, and reduces heat generation. An object of the present invention is to provide a liquid crystal display device and a method for driving the same, which can be driven by a battery for a long time.

[0010]

In order to achieve the above object, the present invention provides a thin film transistor and a source of the thin film transistor at each intersection of a plurality of address wirings and a plurality of data wirings arranged to intersect each other. A plurality of display electrodes connected to one of the electrodes and the drain electrode are arranged in a matrix to form a display region, and the address wiring is formed on the gate electrode of the thin film transistor, and the data is formed on the other of the source electrode and the drain electrode. In a liquid crystal display device comprising a thin film transistor array to which wirings are respectively connected, a counter substrate on which a counter electrode facing the plurality of display electrodes is formed, and a liquid crystal sealed between the counter substrate and the thin film transistor array, A plurality of address lines and data lines are crossed around the display area of the thin film transistor array. Formed Te, each of address lines,
A short-circuit line connected to each data line by a protection element having a bidirectional voltage-current characteristic, a lead terminal extended from the short-circuit line, and a compensating voltage is applied to the lead terminal. And means.

Further, a thin film transistor and a display electrode connected to one of a source electrode and a drain electrode of the thin film transistor are provided at each intersection of a plurality of address lines and a plurality of data lines arranged to intersect each other. Are arranged in a matrix to form a display region, and the address wiring is formed on the gate electrode of the thin film transistor.
A thin film transistor array in which data lines are respectively connected to the other of the source electrode and the drain electrode, a counter substrate on which a counter electrode facing the plurality of display electrodes is formed, and a thin film transistor array enclosed between the counter substrate and the thin film transistor array. In a method of driving a liquid crystal display device including a liquid crystal, the plurality of address wirings and the data wirings are formed around the display area of the thin film transistor array so as to intersect each of the address wirings and the data wirings. It is characterized in that short-circuit wirings are respectively connected by protection elements having current characteristics having bidirectional characteristics, and a compensation voltage is applied to the short-circuit wirings.

[0012]

According to the present invention, as described above, short-circuit wirings intersecting the address wiring group and the data wiring group are formed around the display area of the thin film transistor array, and the short-circuit wirings, the respective address wirings and the respective data are formed. In the liquid crystal display device including the thin film transistor array in which the wiring and the IV characteristic are connected by the protection element having the bidirectional characteristic, since the compensating voltage is applied to the short-circuited wiring, The potential difference between the data wiring and address wiring and the short-circuit wiring can be reduced.

Therefore, crosstalk due to current flowing from the driver of the data wiring (drain) and the address wiring (gate) to the data wiring is reduced. Further, since the output current of the driver on the data wiring (drain) side can be reduced, the heat generation amount of the driver can be reduced. In this case, the compensation voltage of the short-circuit wiring is the lowest voltage of the AC inversion of the data signal supplied to the data wiring,
Similarly, in synchronization with the highest voltage of the alternating voltage inversion of the data signal, the potential of the signal supplied to the counter electrode of the liquid crystal display device, the data signal supplied to the data wiring,
Either one of the data signal and the voltage that changes at the same potential is selected. When any of the above voltages is supplied to the short-circuit wiring, the average potential difference between the short-circuit wiring and the address wiring and the data wiring becomes small, and crosstalk is reduced.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 is a schematic diagram showing an electrical circuit connection of a liquid crystal display device showing an embodiment of the present invention, FIG. 2 is an equivalent circuit diagram of a TFT array of the liquid crystal display device seen from one data wiring, and FIG. It is a wave form diagram of the signal supplied to each wiring of the TFT array.

In FIG. 1, a plurality of address wirings 22 and a plurality of data wirings 23 are provided on an insulating transparent substrate 21 such as a glass substrate so as to be orthogonal to each other. These address wirings 22 and data wirings 23 are provided. A TFT 24 is arranged at each intersection of the display electrodes 25 and a plurality of display electrodes 25 connected to the TFT 24 are arranged in a matrix, and a display region is formed by the plurality of display electrodes.
Then, a short circuit wiring 26 is formed adjacent to the outer peripheral portion of the display area so as to intersect the plurality of address wirings 22 and the plurality of data wirings 23. A protection element 27 having a bidirectional −V characteristic is arranged so as to connect these wirings to each other.

The protective element 27 is provided to protect the TFT 24 from static electricity generated in the TFT process and the liquid crystal cell process, and has the same function as the above-mentioned conventional example. A connection terminal 28 is formed on the address wiring 22, and an address line driver 31 that generates an address signal is connected to the connection terminal 28. Further, a connection terminal 29 is formed on the data wiring 23, and a data line driver 32 that generates a data signal at the connection terminal 29.
Are connected. A counter electrode 36 formed on a counter substrate (not shown) is arranged so as to face the display electrode, and a common driver 37 that generates a common signal is supplied to the counter electrode 36.
Are connected. Liquid crystal is sealed between the TFT array and the counter substrate.

The clock / timing signal generating circuit 33 generates various synchronizing signals, and the obtained signals are sent to the address line driver 31, the data line driver 32 and the common driver 37. Further, the voltage generating circuit 34 generates a voltage corresponding to each potential for forming an address signal and a data signal, and outputs the voltage to the address line driver 31, the data line driver 32 and the common driver 37.

In the present invention, the lead-out terminal 30 for applying a short-circuit wiring voltage (hereinafter referred to as short-circuit wiring compensation voltage) is formed when the short-circuit wiring 26 is formed, and the lead-out terminal 30 is formed.
A short ring driver 35 to which the synchronizing signal from the clock timing signal generating circuit and the power supply voltage from the power supply circuit are supplied is connected to the. The short ring driver 35 generates a predetermined short circuit wiring compensation voltage, and the short circuit wiring 2 is generated via the lead terminal 30.
6 is applied. Although only one lead terminal 30 is formed in the upper right corner 26a of the short circuit wire 26,
You may make it form multiple pieces. That is, in addition to the upper right corner 26a of the short circuit wire 26, the upper left corner 2 of the short circuit wire 26
6d, the lower left corner 26c, and the lower right corner 26b may also be formed and connected to the short ring driver 35, respectively.

Here, the lead-out terminal 30 is connected to the short-circuit wiring 2
In the same manner as 6, aluminum, aluminum alloys,
Gate electrode and address wiring 22 made of a material such as tantalum, a tantalum alloy, or chromium, and aluminum,
It is formed simultaneously with the drain electrode and the data wiring 23 made of a material such as an aluminum alloy, tantalum, a tantalum alloy, or chromium.

The short-circuit wiring 26 is connected via the lead-out terminal 30.
Is applied with one of the short-circuit wiring compensation voltages shown below. FIG. 3 shows various modes of the short-circuit wiring compensation potentials S1 to S4 (illustrated by thick solid lines) together with the address signal G (broken line) and the data signal D (dotted line). Here, the data signal has a voltage waveform that is inverted in the positive and negative directions with respect to the common signal potential applied to the counter electrode of the counter substrate, with one frame as a synchronization. In FIG. 3, (1) As shown in FIG. 3A, the short circuit wiring compensation voltage is set to the lowest potential Vd Low of the data signal (for example, 3.5.
Voltage S1 held at V).

(2) As shown in FIG. 3B, the short-circuit wiring compensation voltage is synchronized with the inversion cycle of the data signal to have the same potential (for example, Low is 3.5V and High is 13.5V).
Voltage to be changed to. That is, the voltage S2 that is inverted in synchronization with the inversion period of Vd. (3) As shown in FIG. 3C, the short-circuit wiring compensation voltage is applied to the potential Vcom (for example, 8.
Voltage S3 held at 5V).

(4) As shown in FIG. 3D, a voltage S4 for inverting the short-circuit wiring compensation voltage to the same potential by shifting the data signal inversion cycle by a half cycle. An example of the power consumed by each driver when any one of the above short-circuit wiring compensation voltages S1 to S4 is applied to the short-circuit wiring of the liquid crystal display device of the present invention is shown below. Conventionally, for example, (a) the average voltage of the data signal D is 8.5V.
Assuming that the average voltage of the address signal G is 25V, the total power consumption is 535nW.

On the other hand, in the method of applying the short circuit wiring compensation voltage of the present invention, (1) If the short circuit wiring compensation voltage is set to the voltage S1 that holds the lowest potential of the data signal, it is consumed by each driver. The total power consumption is 130 nW. (2) In the case of the voltage S2 in which the short circuit wiring compensation voltage is changed so as to have the same potential in synchronization with the inversion cycle of the data signal D, the total power consumption consumed by each driver is 35.
It is 0 nW.

(3) When the short circuit wiring compensation voltage is the voltage S3 held at the potential of the opposing electrode of the opposing substrate, the total power consumption of each driver is 365 nW. (4) When the short circuit wiring compensation voltage is the voltage S4 that shifts the inversion cycle of the data signal and the half cycle phase to invert to the same potential, the total power consumption of each driver is 440.
nW.

As described above, as shown in FIG. 2, the data signal 11 at the on level is connected to the short-circuit wiring 26 through the lead-out terminal 3
By applying the short-circuit wiring compensation voltage from the short-ring driver 35 via 0, the average value of the potential difference between the potential of the short-circuit wiring 26 and each average potential of the data signal and the address signal becomes small. Therefore, the protection element 27a
The so-called crosstalk current, which passes through l-short-circuit metal wiring 26-protection element 27a2 and flows into another data wiring 16, is reduced, and display quality can be improved.

Further, the current flowing from the data line driver 32 to the short circuit metal wiring 26 can be reduced,
Power consumption can be reduced. Therefore, the amount of heat generation is reduced and the battery can be driven for a long time. The present invention is not limited to the above-mentioned embodiment, and various modifications can be made based on the spirit of the present invention.
They are not excluded from the scope of the invention.

[0027]

As described above in detail, according to the present invention, the lead-out terminal led out from the short-circuit wiring is formed,
Since the compensating voltage is applied to the short-circuited wiring through the lead terminal, the following effects can be obtained. (1) Crosstalk due to current flowing from the driver of the data wiring (drain) and the address wiring (gate) to the data wiring is reduced, and the display quality of the liquid crystal display device can be improved.

(2) Since the output current of the driver on the data wiring (drain) side can be reduced, the amount of heat generated by the driver can be reduced. (3) Since the power consumption can be reduced, the battery can be driven for a long time, and the size and weight can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a liquid crystal display device showing an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram seen from one address wiring in a TFT array of a liquid crystal display device showing an embodiment of the present invention.

FIG. 3 is a voltage waveform diagram showing a short-circuit wiring compensation voltage applied to a short-circuit current of a TFT array of a liquid crystal display device showing an embodiment of the present invention together with an address signal and a data signal.

FIG. 4 is a schematic configuration diagram of a TFT array of a conventional liquid crystal display device.

FIG. 5: 1 in a TFT array of a conventional liquid crystal display device
It is the equivalent circuit diagram seen from one address wiring.

[Explanation of symbols]

 21 Insulating Transparent Substrate 22 Plural Address Wirings 23 Data Wiring 24 TFT 25 Display Electrode 26 Short Circuit Wiring 27 Protective Device 28, 29 Connection Terminal 30 Lead-out Terminal 31 Address Line Driver 32 Data Line Driver 33 Clock / Timing Signal Generation Circuit 34 Voltage Generation Circuit 35 short ring driver

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Okimoto 2951-5 Ishikawa-cho, Hachioji-shi, Tokyo Casio Computer Co., Ltd. Hachioji Research Institute (72) Inventor Makoto Sasaki 2951-5 Ishikawa-cho, Hachioji-shi, Tokyo Casio total Inside the Hachioji Research Center

Claims (6)

[Claims] 1. A thin film transistor and a display electrode connected to one of a source electrode and a drain electrode of the thin film transistor at each intersection of a plurality of address lines and a plurality of data lines arranged to intersect each other. Are arranged in a matrix to form a display region, the address wiring is connected to the gate electrode of the thin film transistor, and the data wiring is connected to the other of the source electrode and the drain electrode, respectively, and the plurality of display electrodes. A liquid crystal display device comprising a counter substrate on which a counter electrode is formed and a liquid crystal enclosed between the counter substrate and a thin film transistor array, wherein: (a) the plurality of addresses are provided around a display region of the thin film transistor array; The address wiring and the data wiring are formed by intersecting the wiring and the data wiring. And, short-circuit wiring connected respectively with a protection element having voltage-current characteristics bidirectional characteristics,
A liquid crystal display device comprising: (b) a lead-out terminal extending from the short-circuit wiring; and (c) means for applying a compensation voltage to the lead-out terminal. 2. A thin film transistor, and a display electrode connected to one of a source electrode and a drain electrode of the thin film transistor, at each intersection of a plurality of address lines and a plurality of data lines arranged to intersect each other. Are arranged in a matrix to form a display region, the address wiring is connected to the gate electrode of the thin film transistor, and the data wiring is connected to the other of the source electrode and the drain electrode, respectively, and the plurality of display electrodes. In a method of driving a liquid crystal display device, which comprises a counter substrate on which a counter electrode is formed and a liquid crystal enclosed between the counter substrate and a thin film transistor array, the plurality of addresses are provided around a display area of the thin film transistor array. The address lines and the data lines are formed by intersecting the data lines and the data lines. In the wiring, a voltage - current characteristic with a shorting bar which are respectively connected with a protective element having a bidirectional characteristic, the driving method of a liquid crystal display device and applying a compensation voltage to the short-circuit wiring. 3. The compensation voltage of the short-circuited line is inverted between positive and negative with a potential of a common signal applied to the counter electrode of the counter substrate as a center, and is the lowest voltage on the data signal side supplied to the data line. The method for driving a liquid crystal display device according to claim 2, wherein the method is provided. 4. The compensation voltage of the short-circuit wiring is the highest voltage of the data signal supplied to the data wiring, which is inverted between positive and negative with the potential of the common signal applied to the counter electrode of the counter substrate as the center. The method for driving a liquid crystal display device according to claim 2, wherein 5. The method of driving a liquid crystal display device according to claim 2, wherein the compensation voltage of the short-circuit wiring is a voltage substantially equal to the common signal applied to the counter electrode of the counter substrate. 6. The compensation voltage of the short-circuited wiring is inverted between positive and negative with a potential of a common signal applied to a counter electrode of the counter substrate as a center and is synchronized with a data signal supplied to the data wiring, 3. The method of driving a liquid crystal display device according to claim 2, wherein the voltage is a voltage that is the highest voltage and the lowest voltage of the data signal.