JP3153369B2 - Liquid crystal display device and driving method thereof - Google Patents

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 driving type liquid crystal display device provided with a device for preventing occurrence of defects due to static electricity and a driving method thereof.

[0002]

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

[0003] As shown in FIG.
A plurality of address wirings 2 and data wirings 3 are arranged on an insulating transparent substrate 1 such as a glass substrate in a row direction and a column direction so as to intersect at right angles with each other. 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 arranged in a matrix. A short-circuit metal wiring 6 is formed on the outer peripheral portion of the transparent substrate 1 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 via an insulating film. A protection element 7 (7a1 to 7am and 7b1 to 7b3) having a bidirectional IV characteristic is provided near 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 respectively connected. Each pixel has an auxiliary capacitance 8.

Thus, 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-circuited metal wirings (short rings) on the outer periphery of the transparent substrate, so that they are kept at the same potential. The occurrence of defects due to static electricity during the process is configured to be controlled. here,
The protection element 7 (7a1 to 7am and 7b1 to 7b
3) is provided to protect the TFT 4 from static electricity generated during the TFT manufacturing process and the liquid crystal cell manufacturing process, and during the assembling process after cutting the glass substrate (for example, the liquid crystal injecting process, the polarizing film attaching process). Process, drive circuit connection process), dielectric breakdown, disconnection, TFT
This prevents the occurrence of fluctuations in characteristics of the liquid crystal display and solves the problem that the production yield is reduced due to display defects of the liquid crystal display device.

[0005]

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

That is, in FIG. 5, each data line 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 wirings to which voltage is applied is small, the resistance value seen from the short-circuit metal wiring side becomes small, so that a crosstalk current easily flows into the data wiring, and the crosstalk current is a data signal (display pattern signal). It depends on.

This problem is remarkable in the case of a gray scale display in which the voltage of the data signal is changed over several steps to display an intermediate color. In addition, the current of the signal supplied from each data line is approximately doubled from the viewpoint of each driver connected to each data line due to the provision of the bidirectional protection element in the TFT array. . That is, data signal 1
Numeral 1 passes through the protection element 7al and the short-circuit metal wiring 6, and flows into the protection elements 7b2 to 7bn provided on the address wiring side. The resistance value of the short-circuit metal wiring is very small because it is a metal, and since n protection elements on the address wiring side are connected in parallel, it becomes 1 / n, which is very small, 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 about 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 maximum current flows. About twice the 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, and as a result, problems such as an increase in power consumption of the liquid crystal display device and an increase in the amount of heat generated by the driver occur. This hinders battery driving for reduction in size and weight, and shortens battery life. The present invention eliminates the above problems, reduces crosstalk due to current flowing from a drain and gate driver to a data wiring, improves display quality, reduces power consumption of a driver, and reduces heat generation. It is an object of the present invention to provide a liquid crystal display device that can be driven for a long time by a battery and a driving method thereof.

[0010]

The present invention SUMMARY OF], in order to achieve the above object, at each intersection of the plurality of address lines and a plurality of data lines which is placed by intersecting each other, a thin film transistor, the thin-film transistor A plurality of display electrodes connected to one of the source electrode 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 display electrode 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 data 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. Crossing the plurality of address lines and data lines around a display area of the thin film transistor array. It is formed, the respective address lines, to the respective data lines, the voltage - a lead terminal which current characteristics and short wires connected respectively with a protective element having a bidirectional characteristic, is formed so as to extend from the short wire, this The potential of the data signal supplied to the data wiring is
And a means for applying a compensation voltage having at least the lowest potential .

Further, at each intersection of the plurality of address lines and a plurality of data lines which is placed by intersecting each other, a thin film transistor and, connected display electrodes to either the source electrode and the drain electrode of the thin film transistor And a plurality of display electrodes are arranged in a matrix to form a display area, wherein the address wiring is connected to a gate electrode of the thin film transistor, and a data wiring is connected to the other of a source electrode and a drain electrode, and the plurality of display electrodes A driving method for a liquid crystal display device comprising a counter substrate on which a counter electrode is formed, and liquid crystal sealed between the counter substrate and the thin film transistor array. It is formed so as to intersect the address wiring and the data wiring. A short-circuit wiring connected to each of the data wirings by a protection element having a voltage-current characteristic having a bidirectional characteristic, wherein the short-circuit wiring has at least the lowest potential among the potentials of data signals supplied to the data wiring. And applying a compensation voltage having the following.

[0012]

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

Therefore, crosstalk due to a 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 data wiring (drain) side driver can be reduced, the amount of heat generated by the driver can be reduced. In this case, the compensation voltage of the short-circuit wiring is the lowest voltage of the voltage at which the data signal supplied to the data wiring is AC-inverted,
Similarly, in synchronism with the highest voltage of the AC signal inverting data signal, the potential of the signal supplied to the counter electrode of the liquid crystal display device, and the data signal supplied to the data wiring,
Any one of the data signal and a 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, the address wiring and the data wiring is reduced, and crosstalk is reduced.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 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 viewed from one data line, and FIG. FIG. 3 is a waveform diagram of signals supplied to each wiring of a 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. TFTs 24 are arranged at the intersections of the two, and a plurality of display electrodes 25 connected to the TFTs 24 are arranged in a matrix, and a display area is formed by the plurality of display electrodes.
A short wiring 26 is formed adjacent to the outer peripheral portion of the display area so as to intersect with the plurality of address wirings 22 and the plurality of data wirings 23. A protection element 27 having a bidirectional -V characteristic is arranged to connect these wirings to each other.

The protection element 27 is provided to protect the TFT 24 from static electricity generated during the TFT process and the liquid crystal cell process, and has the same function as the above-described conventional example. A connection terminal 28 is formed on the address wiring 22, and an address line driver 31 for generating 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 for generating a data signal at the connection terminal 29.
Is connected. A counter electrode 36 formed on a counter substrate (not shown) is disposed so as to face the display electrode, and a common driver 37 for generating a common signal is provided on the counter electrode 36.
Is connected. Liquid crystal is sealed between the TFT array and the opposing substrate.

The clock / timing signal generation circuit 33 generates various synchronization signals, and the obtained signals are sent to the address line driver 31, data line driver 32 and common driver 37. Further, the voltage generating circuit 34 generates voltages corresponding to respective potentials for forming an address signal and a data signal, and sends them to the address line driver 31, the data line driver 32 and the common driver 37.

In the present invention, when forming the short-circuit wiring 26, a lead terminal 30 for applying a short-circuit wiring voltage (hereinafter, referred to as a short-circuit wiring compensation voltage) is formed.
Is connected to a short ring (short wiring) driver 35 to which a synchronization signal from the clock timing signal generation circuit and a power supply voltage from a power supply circuit are supplied. This short ring driver 35 generates a predetermined short-circuit wiring compensation voltage, and outputs the short-circuit wiring 2 via the lead-out terminal 30.
6 is applied. Here, although only one lead terminal 30 is formed at the upper right corner 26a of the short-circuit wiring 26,
A plurality may be formed. That is, in addition to the upper right corner 26a of the short-circuit wiring 26, the upper left corner 2
6d, the lower left corner 26c, and the lower right corner 26b may be formed and connected to the short ring driver 35, respectively.

Here, the lead terminal 30 is connected to the short-circuit wiring 2
6, aluminum, aluminum-based alloy,
A gate electrode and an address wiring 22 made of a material such as tantalum, a tantalum alloy, and chromium;
It is formed simultaneously with the drain electrode and the data wiring 23 made of a material such as an aluminum-based alloy, tantalum, a tantalum alloy, and chromium.

The short-circuit wiring 26 is connected to the
, One of the following short-circuit wiring compensation voltages is applied. FIG. 3 shows various aspects of the short-circuit wiring compensation potentials S1 to S4 (shown by thick solid lines) together with an address signal G (broken line) and a data signal D (dashed 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 being synchronized. In FIG. 3, (1) As shown in FIG. 3A, the short-circuit wiring compensation voltage is set to the lowest potential Vd Low (for example, 3.5) of the data signal.
V1).

(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, 3.5 V for Low and 13.5 V for High).
The voltage that changes so that That is, the voltage S2 to be inverted in synchronization with the inversion cycle of Vd. (3) As shown in FIG. 3 (C), the short-circuit wiring compensation voltage is applied to the potential Vcom (for example, 8.
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 inversion cycle of the data signal by a half cycle. An example of the power consumed by each driver when any one of the short-circuit wiring compensation voltages S1 to S4 is applied to the short-circuit wiring of the liquid crystal display element of the present invention will be described below. Conventionally, for example, (a) the average voltage of the data signal D is 8.5 V
Assuming that the average voltage of the address signal G is 25 V, the total power consumption is 535 nW.

On the other hand, in the method of applying the short-circuit wiring compensation voltage of the present invention, (1) When the short-circuit wiring compensation voltage is set to the voltage S1 for holding the lowest potential of the data signal, the short-circuit wiring compensation voltage 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 to the same potential in synchronization with the inversion cycle of the data signal D, the total power consumption consumed by each driver is 35
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 consumed by each driver is 365 nW. (4) In the case where the short-circuit wiring compensation voltage is the voltage S4 for shifting the data signal inversion cycle and half cycle and inverting to the same potential, the total power consumption consumed by each driver is 440.
nW.

As described above, as shown in FIG.
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 the average potentials of the data signal and the address signal decreases. Therefore, the protection element 27a
The so-called crosstalk current flowing through the 1-short metal wiring 26-protective element 27a2 and flowing into the other data wiring 16 is reduced, and the 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 calorific value is reduced and the battery can be driven for a long time. It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible based on the gist of the present invention.
They are not excluded from the scope of the invention.

[0027]

As described above, according to the present invention, a lead terminal derived from a short-circuit wiring is formed,
Since the compensation voltage is applied to the short-circuit wiring via 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 data wiring (drain) side driver 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 the 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 viewed from one address line in a TFT array of a liquid crystal display device according to 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 according to 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 shows 1 in a TFT array of a conventional liquid crystal display device.
FIG. 3 is an equivalent circuit diagram viewed from one address line.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Insulating transparent substrate 22 Plural address wiring 23 Data wiring 24 TFT 25 Display electrode 26 Short wiring 27 Protection element 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

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Okimoto 2951-5 Ishikawacho, Hachioji-shi, Tokyo Casio Computer Co., Ltd. Inside Hachioji Research Laboratory (72) Inventor Makoto Sasaki 2951-5 Ishikawacho, Hachioji-shi, Tokyo Casio Computer Co., Ltd. Hachioji Research Institute (56) References JP-A-3-296725 (JP, A) JP-A-3-216618 (JP, A) JP-A-61-290423 (JP, A) JP-A-61-230119 (JP, A A) JP-A-4-186219 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/133 G02F 1/1345 G02F 1/136 G09F 9/00-9/46 G09G 3/36 H01L 29/78

Claims (4)

(57) [Claims] At each intersection of claim 1 a plurality of address lines and a plurality of data lines which is placed by intersecting each other, a thin film transistor and, connected display electrodes to either the source electrode and the drain electrode of the thin film transistor And a plurality of display electrodes are arranged in a matrix to form a display area, the address wiring is connected to a gate electrode of the thin film transistor, and a data wiring is connected to the other of a source electrode and a drain electrode. A liquid crystal display device comprising a counter substrate having a counter electrode formed thereon and liquid crystal sealed between the counter substrate and the thin film transistor array, wherein: (a) the plurality of thin film transistors are arranged around a display region of the thin film transistor array; It is formed so as to intersect with the address wiring and the data wiring. The voltage - circuiting wires connected respectively with a protective device current characteristic has a bidirectional characteristic, and lead-out terminal which is formed so as to extend from (b) the short lines, the (c) the drawer terminals, the data Data supplied to the wiring
Data signal at least the lowest potential
The liquid crystal display device characterized by comprising a means for applying a that compensation voltage. At each intersection of 2. A plurality of address lines and a plurality of data lines which is placed by intersecting each other, a thin film transistor and, connected display electrodes to either the source electrode and the drain electrode of the thin film transistor And a plurality of display electrodes are arranged in a matrix to form a display area, wherein the address wiring is connected to a gate electrode of the thin film transistor, and a data wiring is connected to the other of a source electrode and a drain electrode, and the plurality of display electrodes A driving method for a liquid crystal display device, comprising: a counter substrate on which a counter electrode is formed, and liquid crystal sealed between the counter substrate and the thin film transistor array. Each of the address wirings and each data wiring are formed so as to intersect with the address wirings and the data wirings. In the line, the voltage - current characteristic with a shorting bar which are respectively connected with a protective element having a bidirectional characteristic, the short-circuit wiring, the data line
Of the potentials of the data signals supplied to the
A method for driving a liquid crystal display device, comprising applying a compensation voltage having a low potential . 3. A compensation voltage to be applied to the short-circuit wiring method for driving a liquid crystal display device according to claim 2, characterized in that the pre-Symbol lowest voltage of the data signal supplied to the data line. 4. A compensation voltage to be applied to the shorting bar in synchronization with the data signal supplied to the pre-Symbol data lines, to be a voltage that varies with the lowest voltage and the highest voltage of the data signal 3. The method for driving a liquid crystal display device according to claim 2, wherein: