KR20120063398A - Flat panel display - Google Patents

Abstract

PURPOSE: A flat panel display device is provided to reduce leakage current by reducing gate bias stress. CONSTITUTION: A display panel(150) defines intersection pixels. A plurality of inspection switching devices is respectively one-to-one corresponded to a plurality of gate lines(GL1-GLn) and a plurality of data lines(DL1-DLm). A switch control signal is provided as a pulse shape. A gate lighting inspection unit(200) comprises a plurality of gate inspection switching devices(TG1-TGn). A data lighting inspection unit(300) includes a plurality of data inspection switching devices(TD1-TDm).

Description

Flat Panel Display {FLAT PANEL DISPLAY}

The present invention relates to a flat panel display that can reduce the variation of characteristics of the inspection switching elements due to the gate bias stress.

Recently, various flat panel displays have been developed to reduce weight and volume, which are disadvantages of cathode ray tubes. The flat panel display includes a liquid crystal display, an organic light emitting diode display, and most of them are commercially available.

When the display panel is completed during manufacturing, the flat panel display performs a module process of performing a drive IC (Flex) bonding and a flexible printed circuit (FPC) bonding, and a lighting test is performed before the module process. Conventionally, a plurality of inspection switching elements are provided to which a lighting inspection data signal and a lighting inspection gate signal are applied to a non-display area of a flat panel display for lighting inspection.

In the plurality of inspection switching elements, a disable voltage is continuously supplied to the gate electrode in order to prevent interference with signals supplied to the plurality of gate lines and the plurality of data lines during display driving. However, as a plurality of test switching devices are supplied with the disable voltage for a long time, characteristics change due to gate bias stress occurs. Accordingly, the plurality of inspection switching elements interfere with signals supplied to the plurality of gate lines and the data lines due to the characteristic change, and as a result, the quality of the image quality defects such as cross talk is caused.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a flat panel display device capable of reducing a characteristic change of inspection switching elements due to a gate bias stress.

In order to achieve the above object, a flat panel display device according to an exemplary embodiment of the present invention may include a display panel that defines an intersection pixel of a plurality of gate lines and a plurality of data lines; And a plurality of inspection switching elements corresponding one-to-one with the plurality of gate lines and the plurality of data lines; The switch control signal for switching the plurality of inspection switching elements in a period of displaying an image may be supplied in a pulse form.

The switch control signal is output in a high state in a blank period, and is output in a low state in a period other than the blank period.

In the blank period, the plurality of test switching elements are kept switched on.

The plurality of test switching elements maintain a switched off state in a period other than the blank period.

The plurality of test switching elements are n type thin film transistors.

The blank period may be a non-display period between a frame on which an image is displayed and a frame.

According to the present invention, the gate bias stress can be reduced as the plurality of gate check switching devices TG1 to TGn and the plurality of data check switching devices TD1 to TDm are temporarily switched on in the blank period. . As a result, the plurality of gate check switching devices TG1 to TGn and the plurality of data check switching devices TD1 to TDm maintain a definite off-switching state, and the leakage current is reduced to reduce image quality defects such as cross talk. You can prevent it.

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention.
FIG. 2 is a waveform diagram of the switching control signal SW_EN shown in FIG. 1.
FIG. 3 is a simulation comparing characteristics change of the test switching element when the pulsed switching control signal SW_EN is applied and when the DC type switching control signal SW_EN is applied.

Hereinafter, a flat panel display according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Meanwhile, the flat panel display according to the exemplary embodiment of the present invention may be applied to a liquid crystal display, an organic light emitting diode display, or the like. Hereinafter, the liquid crystal display will be described by way of example for convenience of description.

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention.

The liquid crystal display shown in FIG. 1 includes a liquid crystal display panel 150. The liquid crystal display panel 150 includes a plurality of data lines DL1 to DLm to which image data is applied and a plurality of gate lines GL1 to GLn to which a gate driving signal Vg is applied on a substrate using glass or the like. Are formed to cross each other.

A pixel P is defined in an area where the plurality of data lines DL1 to DLm and the plurality of gate lines GL1 to GLn intersect. The pixel pixel P includes a driving switching element TFT-SW, which is controlled to be controlled by a gate driving signal Vg, and includes a liquid crystal capacitor Clc and a storage capacitor Cst.

Here, an area in which the image data is written in the pixel P in the liquid crystal display panel 150 to display the image is defined as an active area (A / A). Although not shown, a source driver providing image data through a plurality of data lines DL1 through DLm and a gate driver providing a gate driving signal Vg through a plurality of gate lines GL1 through GLn. The driver may be configured in a chip-on-glass (COG) manner on the periphery of the active area A / A on the liquid crystal display panel 150.

The liquid crystal display panel 150 further includes a gate lighting inspection unit 200 and a data lighting inspection unit 300 each having a plurality of lighting inspection transistors for lighting inspection.

The gate lighting inspection unit 200 is electrically connected to each of the plurality of gate lines GL1 to GLn in a one-to-one correspondence. The gate lighting inspection unit 200 includes a plurality of gate inspection switching elements TG1 to TGn that are controlled to be switched by the switching control signal SW_EN to provide the gate inspection signal g_sig to the gate lines GL1 to GLn. do.

The data lighting inspecting unit 300 is connected to each of the plurality of data lines DL1 to DLm in a one-to-one correspondence. The data lighting inspection unit 300 is controlled by the switching control signal SW_EN to provide the data inspection signals R_sig, G_sig, and B_sig to the data lines DL1 to DLm, respectively. TDm). Here, the data test signals R_sig, G_sig, and B_sig may all be the same test signal or different test signals for each RGB color.

According to an exemplary embodiment of the present invention, a switching control signal SW_EN for switching and controlling a plurality of gate check switching devices TG1 to TGn and a plurality of data check switching devices TD1 to TDm is provided in pulse form during display driving. It is done. Accordingly, the embodiment of the present invention can reduce the variation of the characteristics of the plurality of gate check switching devices TG1 to TGn and the data check switching devices TD1 to TDm due to the gate bias stress. Such an embodiment of the present invention will first be described for each configuration, and will be described later in detail.

On the other hand, it is advantageous in the manufacturing process that the plurality of gate check switching devices TG1 to TGn and the plurality of data check switching devices TD1 to TDm are thin film transistors (TFTs) of the same type. Illustrated as a thin film transistor. In addition, the gate lighting inspection unit 200 and the data lighting inspection unit 300 may be mounted on the liquid crystal display panel 150 in a chip-on-glass (COG) manner.

The lighting test of the liquid crystal display panel 150 as described above is as follows.

First, an enable voltage, for example, a switching control signal SW_EN of a high state, is supplied to the gate electrodes of the plurality of gate check switching devices TG1 to TGn and the plurality of data check switching devices TD1 to TDm.

Next, when the gate check switching devices TG1 to TGn and the data check switching devices TD1 to TDm are both turned on by the switching control signal SW_EN, the gate check signal g_sig is turned on. And data check signals R_sig, G_sig, and B_sig through a plurality of gate check switching devices TG1 to TGn and a plurality of data check switching devices TD1 to TDm and a plurality of gate lines GL1 to GLn and a plurality of data. The lighting test of the pixel P is performed by applying the lines DL1 to DLm, respectively.

In this case, the gate check signal g_sig is a voltage signal for on-switching the driving switching element TFT-SW configured in the pixel P, and its voltage level according to the type of the driving switching element TFT-SW. This is determined.

Finally, when the lighting test is completed, the voltage level of the switching control signal SW_EN is changed to turn off the plurality of gate check switching devices TG1 to TGn and the plurality of data check transistors TD1 to TDm. The reason for this is as follows.

The plurality of gate check switching devices TG1 to TGn and the plurality of data check switching devices TD1 to TDm are unnecessary to operate the liquid crystal display panel 150 when the lighting test is completed. However, when the plurality of gate check switching elements TG1 to TGn and the plurality of data check transistors TD1 to TDm are left after the lighting test, the plurality of gate check switching elements TG1 to TGn and the plurality of data check switching The gate electrode of each of the elements TD1 to TDm is in a floating state.

In this case, when the image display driving of the liquid crystal display panel 150 is performed, a plurality of gate inspection switching elements TG1 to TGn may be disposed on some of the plurality of data lines DL1 to DLm and the plurality of gate lines GL1 to GLn. Or a plurality of data inspection switching elements TD1 to TDm, which cause signal interference to another gate line or another data line.

For example, in the third data test switching device TD3 of FIG. 1, the gate electrode G is in a floating state after the lighting test of the third data test switching device TD3. When the image data voltage is applied to the third data line DL3, the voltage level of the third data line DL3 gradually increases, and thus the voltage level of the drain electrode D of the third data inspection switching element TD3. This gradually rises.

At this time, the voltage level of the gate electrode G of the third data inspection switching element TD3 in the floating state is raised as the voltage of the drain electrode D rises. Then, a leakage current in which the image data voltage applied to the third data line DL3 flows back through the source electrode S from the drain electrode D of the third data inspection switching element TD3 is generated. At this time, the reverse leakage current is transferred to the other data check switching device, which in turn flows into another data line and distorts the image data voltage. Therefore, there is a problem that an abnormal image is displayed on some lines or some areas.

Accordingly, according to an exemplary embodiment of the present invention, it is necessary to keep the plurality of gate check switching devices TG1 to TGn and the data check switching devices TD1 to TDm in an off switching state when driving an image display. However, when the switching control signal SW_EN is continuously output in the low state in order to keep the gate check switching elements TG1 to TGn and the plurality of data check switching elements TD1 to TDm in the off switching state, the gate check is performed. The switching elements TG1 to TGn and the plurality of data inspection switching elements TD1 to TDm have a problem in that a characteristic change occurs due to a gate bias stress, thereby increasing leakage current.

Therefore, the exemplary embodiment of the present invention outputs the switching control signal SW_EN in the form of a pulse when driving the image display as shown in FIG. 2. Specifically, the switching control signal SW_EN is output in the high state only in the blank period and is output in the low state in the remaining period. Here, the switching control signal SW_EN may be output in a low state only during a specific period according to the type of the test switching elements, and may be output in a high state during the remaining period.

That is, the blank period is a period in which the switching control signal SW_EN temporarily turns the plurality of gate check switching devices TG1 to TGn and the plurality of data check switching devices TD1 to TDm into the on switching state. Here, the blank period is preferably set to a non-display period between the frame on which the image is displayed and the frame.

As described above, according to the exemplary embodiment of the present invention, as the plurality of gate check switching devices TG1 to TGn and the plurality of data check switching devices TD1 to TDm are temporarily switched on in a blank period, the gate bias stress is reduced. Can be reduced. As a result, the plurality of gate check switching devices TG1 to TGn and the plurality of data check switching devices TD1 to TDm maintain a definite off-switching state, and the leakage current is reduced to reduce image quality defects such as cross talk. You can prevent it.

 3 is a simulation comparing the characteristic change of the test switching element when the pulsed switching control signal SW_EN and the DC type switching control signal SW_EN are applied.

Referring to FIG. 3, when the DC-type switching control signal SW_EN is applied, the threshold voltage of the test switching element is greatly shifted to a negative voltage, while when the pulse-type switching control signal SW_EN is applied, the test switching element. It can be seen that the threshold voltage of is shifted relatively less.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and it is common in the art that various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of.

SW_EN: Switch control signal 200: Gate lighting inspection unit
300: data lighting inspection unit

Claims (6)

A display panel defining pixels at intersections of the plurality of gate lines and the plurality of data lines; And
A plurality of inspection switching elements corresponding one-to-one with the plurality of gate lines and the plurality of data lines; And
And a switch control signal for switching the plurality of inspection switching elements in a period in which an image is displayed. The method of claim 1,
The switch control signal is
And a low state during a blank period, and a low state during a period other than the blank period. The method of claim 2,
And the plurality of test switching elements maintain a switching on state in the blank period. The method of claim 2,
And the plurality of test switching elements maintain a switching off state in a period other than the blank period. The method according to claim 3 or 4,
And the plurality of test switching elements are n type thin film transistors. The method of claim 2,
The blank period is
And a non-display period between the frame on which the image is displayed and the frame.

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