JP2003122311A - Electrical discharge method and device for image display panel, image display panel, and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To speedily eliminate a residual image at the time of switching OFF the power source of an image display device. SOLUTION: This invention relates to an electrical discharge device for an image display panel in the image display device having the image display panel comprising scanning signal lines, image signal lines, transistors connected with the scanning signal lines and image signal lines, pixel electrodes connected with the transistors, and common electrodes provided to face the pixel electrodes, and the electrical discharge device is provided with an analog switch 110 to drop the potential of the common electrodes lower than the lowest value of the gate potential of the transistors when the image display panel ceases to operate, and the transistors are brought into ON state by the operation of the analog switch 110, to discharge residual charges on the pixel electrodes to the image signal lines.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display panel such as an active matrix type liquid crystal display panel, and a method of discharging an image display panel for quickly erasing the display image when the power of the display device main body is turned off. The present invention relates to an image display panel discharge device, an image display panel, and an image display device.

[0002]

2. Description of the Related Art Recently, an active matrix type liquid crystal display device has been widely used as a display device in a word processor, a personal computer, a television device and the like. The feature of this active matrix type liquid crystal display device is that a TFT type transistor is arranged for each display pixel of liquid crystal.

FIG. 3 shows a block diagram of an active matrix type liquid crystal display device. In addition, 1 is an image signal line driving circuit, 2 is a scanning signal line driving circuit, 3 is an image signal line connected to the image signal line driving circuit, 4 is a scanning signal line connected to the scanning signal line driving circuit, 5 Is a liquid crystal panel. The liquid crystal panel 5 has a structure in which the source wirings 3 and the gate wirings 4 are arranged to intersect each other in a matrix, and the transistors provided near the intersections and liquid crystal display pixels are provided. And at the gate of this transistor,
By applying a scanning voltage from the gate wiring 4 and a signal voltage corresponding to a display signal from the source wiring 3 to the source or the drain, liquid crystal display pixels arranged in a matrix in the liquid crystal panel 5 are individually provided. Drive to obtain the desired display pattern.

Next, in FIG. 4, in the liquid crystal panel 5,
A structure of a thin film transistor and its vicinity is shown. In the figure, the same parts as those in FIG.
Detailed description is omitted. Further, 6 is a transistor, 7 is a pixel electrode, 8 is a storage capacitor, and 9 is an auxiliary capacitance wiring.

As shown in FIG. 4, in the conventional liquid crystal display device, while the scanning signal line 4 is set to the high level, the image signal line 3 is supplied with the image signal line voltage of the high level or the low level to display the liquid crystal display pixel. Charge the pixel voltage. In order to bring the entire apparatus into a non-operating state after the operation in this way, the power is turned off in the entire apparatus.

As a result, regarding each pixel, the transistor 6 is also turned off, and the charge accumulated in the storage capacitor 8 is also uniquely confined. Therefore, this electric charge is not discharged immediately but gradually due to leakage. In this way, after the power is turned off, the electric charge in the capacitor has no way to escape and is gradually discharged due to leakage.Therefore, there is an image like a hazy afterimage for a period. It will be clearly visible.

[0007]

In the liquid crystal display device according to the prior art, when the power of the device is turned off, the driver output such as the image signal line driving circuit 1 and the scanning signal line driving circuit 2 has a high impedance. Becomes In addition, the pixel retains the previous potential. Then, the pixel potential is determined by the peripheral wiring (image signal line 3, scanning signal line 4,
It is gradually discharged due to a leak current passing through the auxiliary capacitance line 9), the high resistance path of the TFT and the LCD, and finally becomes the same potential as the counter electrode COM (= auxiliary capacitance line CS).

However, if the pixel potential is the counter electrode COM.
Since it takes a considerable time (about several seconds) until the potential becomes almost the same as the above, the display screen immediately before disappears gradually. This time is for the human eye
Since it is a relatively long time, in other words, it is a sufficiently visible time, the display screen immediately before is held and gradually disappears when the power is turned off. Further, there is a problem that the residual voltage deteriorates the liquid crystal display panel.

Therefore, the present invention solves the problems of the prior art as described above, can quickly erase the afterimage of the display screen when the power is off, and prevent the deterioration of the display panel due to the residual voltage. It is an object of the present invention to provide an image display panel discharge method, an image display panel discharge device, an image display panel, and an image display device capable of performing the above.

[0010]

In order to achieve the above object, a first aspect of the present invention (corresponding to claim 1) is a scanning signal line, an image signal line, the scanning signal line and the image signal. Discharge of the image display panel in an image display device having an image display panel including a switching element connected to a line, a pixel electrode connected to the switching element, and a common electrode provided to face the pixel electrode When the image display device stops operating, the potential of the common electrode is lowered below the minimum value of the gate potential of the switching element, the switching element is turned on, and the residual charge of the pixel electrode is reduced. Is a method of discharging an image display panel, in which is discharged to the image signal line.

A second aspect of the present invention (corresponding to claim 2)
Is a scanning signal line, an image signal line, a switching element connected to the scanning signal line and the image signal line, a pixel electrode connected to the switching element, and a common provided opposite to the pixel electrode. An image display device having an image display panel including electrodes, which is a discharging device of the image display panel, wherein when the image display panel stops operating, the potential of the common electrode is set to the minimum value of the gate potential of the switching element. Is a discharging device of an image display panel, which includes a potential lowering means for lowering the voltage and further turns on the switching element by the operation of the voltage lowering means to discharge the residual charge of the pixel electrode to the image signal line.

A third aspect of the present invention (corresponding to claim 3)
Is a power source of the image display device.
It operates by detecting N / OFF, and when the image display device is powered on, the image signal line and scanning signal line sides of the image display panel are connected to the counter electrode side, and the power switch is turned off. When this is detected, the image display panel according to the second aspect of the present invention has switch means for opening the switching signal element and the scanning signal line side and the counter electrode side to turn on the switching element. Is a discharge device.

A fourth invention (corresponding to claim 4)
The power supply of the switch means is shared with the power supply of the image display device, and after the power supply is turned off, the power supply voltage remaining in the switch means is used to generate the image signal line and the scanning signal. It is a discharge device for an image display panel according to the third aspect of the present invention, which opens a space between a line side and the counter electrode side.

The fifth invention (corresponding to claim 5)
The switch means has a power supply terminal connected to an input terminal of a power supply voltage of the image signal line driving means, and a series circuit having a diode and a capacitor is connected between the input terminal and the power supply terminal. In the series circuit, the anode of the diode is connected to the input terminal, the cathode is connected to one end of the capacitor, the other end of the capacitor is grounded, and the power supply terminal of the switch means is the cathode. Is a discharge device for an image display panel according to the fourth aspect of the present invention, which is connected to a connection point between the capacitor and one end of the capacitor.

A sixth aspect of the present invention (corresponding to claim 6)
Is a discharge device for an image display panel according to the third aspect of the present invention, wherein the voltage drop means delays the fall of the potential of the common electrode later than the fall of the potential of the gate voltage.

A seventh aspect of the present invention (corresponding to claim 7)
Is a series circuit having a resistor and a diode provided between the common electrode and the output terminal of the power supply voltage of the scanning signal line drive circuit, A connection point to the diode is connected to the negative power supply terminal of the switch means, and a sixth capacitor is provided which has one end connected between the connection point and the negative power supply terminal and the other end grounded. It is a discharge device of an image display panel of the present invention.

The eighth invention (corresponding to claim 8)
Is an image display panel connected to the discharge device of the image display panel of the second aspect of the present invention.

The ninth invention (corresponding to claim 9)
An image display device comprising the image display panel of the eighth aspect of the present invention, image signal output means for outputting an image signal to the image display panel, and scanning signal output means for outputting a scanning signal to the image display panel. Is.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment) FIG. 1 is a block diagram of an OFF afterimage circuit according to an embodiment of the present invention. In the figure,
Reference numeral 100 is an OFF afterimage circuit of the present embodiment provided in the same liquid crystal display device as shown in FIG. 3, and 110 is an analog switch. Further, 101 is a diode (D1) which receives an input of the operating power supply voltage AVDD of the image signal line drive circuit 1, and 102 is a capacitor (C which has one end connected to the cathode of the diode (D1) 101 and the other end grounded.
1). A connection point α between the diode (D1) 101 and the capacitor (C1) 102 is connected to the terminal S8 of the analog switch. 103 is a resistor (R1)
Reference numeral 104 denotes a diode (D2) whose anode is connected to the other end of the resistor (R1) 103 and whose cathode is on the operating power supply voltage side of the scanning signal line drive circuit 2. One end of the resistor (R1) 103 has a terminal S6 of the analog switch.
Are connected at a connection point β, and the connection point β supplies the voltage Vcom of the common electrode. Also, the resistance (R1) 1
A connection point γ between 03 and the diode (D2) 104 is connected to the terminal S3 of the analog switch. Further, in the wiring between the terminal S3 of the analog switch and the connection point γ, a capacitor (C2) 105 having one end connected at the connection point δ and the other end grounded is provided. Further, in the analog switch 110, the terminal S1 and the terminal S6 are opened and closed by the voltage supplied from the terminal S8, and the terminal S5 is opened.
The continuity is always ensured between the terminal S3 and the terminal S3.

The operation of the OFF afterimage circuit having the above-described structure according to the embodiment of the present invention will be described below, and the embodiment of the method for discharging the image display panel of the present invention will be described. To do.

First, when the power switch of the liquid crystal display device is ON, the operating power supply voltage AVDD of the image signal line drive circuit 1 outputs the ON potential to the terminal S8 of the analog switch 110, and the analog switch 110 The electrical continuity between the terminals S1 and S6 is secured.

On the other hand, when the power switch of the liquid crystal display device is turned off, the terminal S8 of the analog switch 110 is
The OFF potential is output from AVDD. At this time, the potential when AVDD is ON remains in the analog switch, and this potential cuts off the conduction between the terminals S1 and S6 of the analog switch 110. Further, the OFF potential from AVDD is also supplied from the terminal S5 to the terminal S3.

At this time, the negative side power source voltage of the analog switch IC 110, which is the OFF potential from AVDD, is applied to the connection point β by the charged capacitor (C2) 105 from the negative side gate voltage VGL through the diode (D2) 104. Supplied.

As a result, as shown in FIG. 2, the common voltage VCOM (counter voltage) supplied to the common electrode of the liquid crystal display panel 5 drops, and its value becomes lower than the minimum value of the gate voltage VGL. At this time, the fall of VCOM is
It starts later than the fall of VGL, but this is due to the contribution of the series circuit of the resistor (R1) 103 and the diode (D1) 104. If it is not necessary to delay the fall, the resistor (R1) 103 and the diode (D1) 104 may be omitted.

When the transistor is an N-channel type TFT, the potential of the drain voltage connected to the common electrode is
When the gate voltage becomes lower than the minimum voltage, the transistor is turned on even when an off potential is applied to the gate voltage.

As a result, the storage capacitor 8 stored in the pixel electrode is discharged to the image signal line 3 and the afterimage of the display screen when the power is turned off can be quickly erased. In addition, deterioration of the liquid crystal display panel due to the residual voltage can be prevented.

In the above embodiment, OFF
The afterimage circuit corresponds to the discharging device of the present invention, the analog switch 110 and the capacitor (C2) 105 correspond to the potential lowering means of the present invention, and the analog switch 110 corresponds to the switching means of the present invention. The transistor 6 is an example of the switching element of the present invention.

Further, in the above embodiment, the transistor 6 is an N-channel type TFT, but the same effect can be obtained even when it is of another type.

Further, in the above embodiment, the discharge device is described as being mounted on the liquid crystal display device, but it may be used alone.

Further, in the above embodiment, the discharge device has been described as being used in a liquid crystal display panel, but it may be used in another image display panel such as a plasma display.

Further, the present invention may be realized as an image display panel equipped with a discharge device.

Further, the present invention may be realized as an image display device provided with an image display panel having the discharge device of the present invention.

[0034]

As is apparent from the above description, the present invention reduces the afterimage of the display panel and prevents the image display panel from being deteriorated even when the image display device is powered off. There is an effect that excellent image display of can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an OFF afterimage circuit according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of the VCOM and VGL of the present invention and the conventional invention when the power supply is OFF.

FIG. 3 is a configuration diagram of a liquid crystal display device according to an embodiment of the present invention and a conventional technique.

FIG. 4 is a configuration diagram of a liquid crystal display device according to an embodiment of the present invention and a conventional technique.

[Explanation of symbols]

1 Image signal line drive circuit 2 Scan signal line drive circuit 3 image signal lines 4 scanning signal lines 5 Liquid crystal display panel 6 transistors 7 LCD display pixels 8 storage capacity 9 auxiliary capacitance wiring 100 OFF afterimage circuit 101 diode (D1) 102 capacitor (C1) 103 resistance (R1) 104 diode (D2) 105 Capacitor (C2) 110 analog switch

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H093 NC10 NC13 NC18 NC22 NC34                       ND02 ND12 ND34 ND41 ND42                       ND48 ND50 ND58                 5C006 AC25 AF67 BB16 BF36 BF37                       FA34                 5C080 AA10 BB05 DD18 DD29 FF11                       JJ02 JJ03 JJ04

Claims (9)

[Claims] 1. A scanning signal line, an image signal line, a switching element connected to the scanning signal line and the image signal line, and a pixel electrode connected to the switching element.
A method of discharging the image display panel in an image display device having an image display panel including a common electrode provided to face the pixel electrode, wherein when the image display device stops operating, A discharging method of an image display panel, wherein a potential is made lower than a minimum value of a gate potential of the switching element, the switching element is turned on, and residual charge of the pixel electrode is discharged to the image signal line. 2. A scanning signal line, an image signal line, a switching element connected to the scanning signal line and the image signal line, and a pixel electrode connected to the switching element.
In an image display device having an image display panel including a common electrode provided facing the pixel electrode, a discharge device of the image display panel, wherein when the image display panel stops operating, the common electrode A potential lowering unit that lowers the potential lower than the minimum value of the gate potential of the switching element is provided, the switching element is turned on by the operation of the voltage lowering unit, and the residual charge of the pixel electrode is discharged to the image signal line. Discharge device for image display panel. 3. The potential lowering means operates by detecting ON / OFF of a power source of the image display device, and when the power source of the image display device is turned on, the image signal line and the scanning signal of the image display panel. The switching element is formed by connecting the line side and the counter electrode side, and opening the image signal line / scanning signal line side and the counter electrode side when it is detected that the power switch is turned off. The discharge device for an image display panel according to claim 2, further comprising switch means for turning on the switch. 4. The power source of the switch means is shared with the power source of the image display device, and the power source voltage remaining in the switch means after the power source is turned off is used for the image signal line. The discharge device for an image display panel according to claim 3, wherein a space between the scanning signal line side and the counter electrode side is opened. 5. The switch means has a power supply terminal connected to an input terminal of a power supply voltage of the image signal line driving means, and a serial circuit having a diode and a capacitor between the input terminal and the power supply terminal. Circuit is connected, in the series circuit, the anode of the diode is connected to the input terminal, the cathode is connected to one end of the capacitor, the other end of the capacitor is grounded, the power supply terminal of the switch means is The discharge device for an image display panel according to claim 4, wherein the discharge terminal is connected to a connection point between the cathode and one end of the capacitor. 6. The discharge device for an image display panel according to claim 3, wherein the voltage drop unit delays the fall of the potential of the common electrode with respect to the fall of the potential of the gate voltage. 7. The voltage drop means includes the common electrode,
And a series circuit having a resistor and a diode provided between the scanning signal line drive circuit and an output terminal of a power supply voltage, wherein a connection point between the resistor and the diode is a negative power source of the switch means. 7. A capacitor, which is connected to a terminal, has one end connected between the connection point and the negative power supply terminal, and has the other end grounded.
The electric discharge device for an image display panel according to. 8. An image display panel connected to the discharge device of the image display panel according to claim 2. 9. The image display panel according to claim 8, an image signal output unit for outputting an image signal to the image display panel, and a scanning signal output unit for outputting a scanning signal to the image display panel. Image display device.