KR100599800B1 - Display panel and inspection apparatus thereof - Google Patents

Abstract

The present invention relates to a display panel and an inspection apparatus thereof. An inspection apparatus for a display panel according to the present invention is an inspection apparatus for a display panel including a plurality of pixels, the pixel including a transistor for outputting a current corresponding to a data signal, and an organic EL element connected between the transistor and the first power supply. The test apparatus includes a controller configured to generate a control signal for inspecting the display panel and apply the control signal to the display panel, and a voltage adjuster for adjusting a voltage of the first power supply.

Display panel, inspection device, power supply voltage, organic EL, driving transistor

Description

Display panel and its inspection apparatus {DISPLAY PANEL AND INSPECTION APPARATUS THEREOF}

1 shows a conventional organic EL display panel and an inspection apparatus for inspecting the same.

2 illustrates an organic EL display panel and an inspection apparatus for inspecting the same according to an embodiment of the present invention.

3 is a circuit diagram illustrating a pixel according to an exemplary embodiment of the present invention.

4 is a graph illustrating a current according to a voltage applied to a drain electrode of a driving transistor.

The present invention relates to a display device, and more particularly, to an organic electroluminescent (EL) display panel and an inspection device for inspecting the same.

In general, an organic EL display device is a display device for electrically exciting a fluorescent organic compound to emit light, and is capable of representing an image by driving voltage or current driving NxM organic light emitting cells. The organic light emitting cell has a structure of an anode (ITO), an organic thin film, and a cathode layer (metal). The organic thin film has a multilayer structure including an emitting layer (EML), an electron transport layer (ETL), and a hole transport layer (HTL) to improve the emission efficiency by improving the balance between electrons and holes. It also includes a separate electron injecting layer (EIL) and a hole injecting layer (HIL).

The organic light emitting cell may be driven using a simple matrix method and an active matrix method using a thin film transistor (TFT) or a MOSFET. In the simple matrix method, the anode and the cathode are orthogonal and the line is selected and driven, whereas the active driving method connects the thin film transistor and the capacitor to each indium tin oxide (ITO) pixel electrode to maintain the voltage by the capacitor capacitance. It is a driving method. In this case, the active driving method is divided into a voltage programming method and a current programming method according to the type of signal applied to maintain the voltage on the capacitor.

When the display device using the organic light emitting cell is implemented, a defect may occur during the manufacturing process, and thus the pixel may not emit light properly. Therefore, after the pixel is formed on the display panel, a process for inspecting the defect of the pixel is necessary.

1 illustrates a conventional organic EL display panel 10 and a controller 20 for inspecting the same.

As illustrated in FIG. 1, in the display panel 10, a plurality of data lines D1 -Dm and a plurality of scan lines S1 -Sn are formed to be orthogonal to each other, and a plurality of pixels are adjacent to two neighboring data lines. It is formed in the pixel area defined by one or two scanning lines. Then, a power supply line 12 for applying a power supply VSS to the plurality of pixels is formed.

In addition, the data lines D1 -Dm are commonly connected to a test line for transferring a test voltage, and the switch SW1 causes the test voltage Vtest to be applied to the test line in response to a control signal (not shown). .

The scan driver 12 sequentially applies a selection signal to the plurality of scan lines S1 -Sn in response to a control signal from the controller 20.

The controller 20 is configured to inspect a light emission state of the pixels formed on the display panel 10. The control unit 20 applies a control voltage to the scan driver 12 so that the scan driver 12 supplies a test selection signal to the plurality of scan lines S1 -Sn. ) To be applied sequentially.

As described above, the conventional display device connects the data lines D1 -Dm to one test electrode to apply a test voltage Vtest, and the control unit 20 provides a control signal to the scan driver 12 so that the scan driver ( 12) sequentially applies the test selection signals to the scan lines S1 -Sn. As a result, it is possible to check whether the pixels connected to each data line and the scan line emit light normally.

However, this method has a problem in that the driving transistor included in the pixel 11 cannot operate optimally by applying a constant power supply voltage VSS to the pixel 11 formed in the display panel 10.

An object of the present invention is to control the current characteristics in the saturation region of the driving transistor so that the driving transistor operates in an optimal saturation state during the on / off inspection of the display panel.

In order to achieve the above object, an inspection apparatus for a display panel according to an aspect of the present invention is an inspection apparatus for a display panel including a plurality of pixels, the pixels including a transistor for outputting a current corresponding to a data signal; And an organic EL element connected between a first power source, wherein the inspection device generates a control signal for inspecting the display panel and applies it to the display panel; and a voltage adjusting unit for adjusting a voltage of the first power source. It includes.

In the inspection apparatus of the display panel according to an aspect of the present invention, the display panel further comprises a plurality of data lines for transmitting the data signal to the pixel, and a voltage supply line for transferring the voltage of the first power supply. Include.

An apparatus for inspecting a display panel according to an aspect of the present invention, the display panel further includes a plurality of scan lines for transmitting a selection signal to the plurality of pixels, wherein the pixels comprise the first electrode of the transistor and And a switching element configured to transfer the data signal to the capacitor in response to the selection signal from the scan line.

A display panel according to an aspect of the present invention is a display panel including a plurality of data lines for transmitting a data signal, a plurality of scanning lines for transmitting a selection signal, and a plurality of pixel circuits connected to the data lines and the scanning lines, The pixel circuit includes a transistor including first to third electrodes and outputs a current corresponding to a voltage applied between the first and second electrodes to the third electrode, the third electrode of the transistor, and a first power source. A display element for displaying an image corresponding to a current electrically connected to and applied between the display device, a capacitor connected between the first electrode and the second electrode of the transistor, and the data signal in response to the selection signal. A first switching element that transfers to a first electrode and is electrically connected to the display element The voltage is variable.

A display panel according to an aspect of the present invention, the display panel further includes a test line for applying a test voltage when the display panel is inspected, and a plurality of second switching elements connecting the test line and the data line during the test. do.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In the following description, when a part is connected to another part, it includes not only the case where it is directly connected but also the case where it is electrically connected with another element between them. In the drawings, parts irrelevant to the present invention are omitted for clarity, and like reference numerals designate like parts throughout the specification.

2 illustrates an organic EL display panel and an inspection apparatus for inspecting the same according to an embodiment of the present invention.

As shown in Fig. 2, the organic EL display panel 100 according to the embodiment of the present invention includes a display area 110 in which an actual image is displayed and a peripheral area in which no image is displayed. In the display area 110, a plurality of data lines D1 -Dm extending in a column direction, a plurality of scanning lines S1 -Sn extending in a row direction, a power supply line 112, and a plurality of pixel circuits 110 are provided. Is formed. In the peripheral region, the scan driver 130, the test lines Tr, Tg, and Tb, and the switching element 113 connected between the test lines Tr, Tg and Tb and the data lines D1 to Dm are formed. It is. According to an embodiment of the present invention, the data lines D1 -Dm transmit data signals corresponding to red, green, and blue, respectively. That is, in FIG. 2, the data line D1 is connected to the test line Tr through the switching element, and the data line D2 is connected to the test line Tg through the switching element. The data line D3 is connected to the test line Tb through a switching element.

Although not shown in FIG. 2, the voltage VSS of the first power supply is transmitted to the cathode of the organic EL element. In addition, a power supply line for transmitting the voltage VDD of the second power supply to the pixel is further formed. The second power source is connected to the driving transistor included in the pixel, and the connection relationship between the pixel and the first and second power sources will be described in detail later.

The data lines D1 -Dm transmit a data voltage representing an image signal to the pixel circuit 110, and the scan lines S1 -Sn transmit a selection signal for selecting the pixel circuit 110 to the pixel circuit 110. do. The pixel circuit 110 is formed in a pixel area defined by two neighboring data lines D1 -Dm and two neighboring scan lines S1 -Sn. The power supply line 112 transfers the voltage VSS of the first power input from the voltage adjustor 300 to the pixel circuit 110.

The scan driver 130 sequentially applies a selection signal to the plurality of scan lines S1 -Sn, and the test lines Tr, Tg, and Tb are test voltages V _R and V corresponding to red, green, and blue, respectively. _G and V _B are transferred to the data lines D1 -Dm.

The switching element 113 is turned on in response to the control signal Vctr when the controller 200 starts inspecting the display panel 100, and the test voltage V _R applied to the test lines Tr, Tg, and Tb. , V _G , V _B ) is transferred to the data lines D1 -Dm.

The controller 200 generates a control signal such as a start signal VSP, a clock signal CLK, a frame period signal Vsync, and outputs the control signal to the scan driver 130. Then, the scan driver 130 generates a test selection signal according to the control signal applied and sequentially applies the test selection signal to the plurality of scan lines S1 -Sn.

At this time, the scan driver 130 sequentially shifts the start signal VSP in synchronization with the clock signal CLK by the frame period signal Vsync and outputs the same. Specific configurations and operations of the controller 200 and the scan driver 130 will be apparent to those skilled in the art to which the present invention pertains, and thus detailed descriptions thereof will be omitted.

The voltage adjusting unit 300 adjusts the voltage VSS of the first power supply and transmits the voltage VSS to the power supply line 112. According to an embodiment of the present invention, a regulator using a variable resistor or a switching mode power supply (SMPS) may be used as the voltage adjusting unit 300 for adjusting the voltage VSS of the first power supply. In FIG. 2, the voltage adjusting unit 300 is formed separately from the control unit 200, but may be formed in the control unit 200 according to an embodiment.

3 is a circuit diagram illustrating a pixel according to an exemplary embodiment of the present invention. In FIG. 3, pixels connected to the data line Dm and the scan line Sn among the plurality of pixels are representatively shown.

The pixel circuit according to an embodiment of the present invention includes transistors M1 and M2, an organic EL element OLED, and a capacitor Cst as shown in FIG.

The transistor M1 is a driving transistor for driving the organic EL element OLED, and is connected between the second power supply VDD and the organic EL element OLED. As shown in FIG. 3, the transistor M1 and the transistor M2 according to the embodiment of the present invention are formed of a PMOS transistor. In the PMOS transistor, a gate electrode is formed as a first electrode, a source electrode is formed as a second electrode, and a drain electrode is formed as a third electrode. The source electrode of the transistor M1 is connected to the second power supply, the voltage VDD of the second power supply is transmitted, and the drain electrode is connected to the anode of the organic EL element OLED. The cathode of the organic EL element OLED is connected to the first power source, and the voltage VSS of the first power source is transmitted.

The transistor M2 has a gate electrode connected to the scan line Sn and transfers a data voltage from the data line Dm in response to a selection signal from the scan line Sn.

The capacitor Cst is connected between the gate electrode and the source electrode of the transistor M1 and maintains the data voltage transmitted from the transistor M2 for a predetermined period of time.

Hereinafter, the operation of the pixel circuit shown in FIG. 3 will be described.

When the transistor M2 is turned on, a data voltage is applied to the gate electrode of the transistor M1, and the capacitor C1 is charged with a voltage V _GS applied between the gate electrode and the source electrode. The current I _OLED flows through the transistor M1 in response to the voltage V _GS , and the organic EL element OLED emits light in response to the current I _OLED .

At this time, the current flowing through the organic EL element OLED is represented by Equation 1 below.

Here, I _OLED is a current flowing through the organic EL element OLED, V _GS is a voltage between the gate electrode and the source electrode of the transistor M1, V _TH is a threshold voltage of the transistor M1, V _DATA is a data voltage, β Denotes a constant value.

As shown in Equation 1, a current corresponding to the data voltage is supplied to the organic EL element OELD, and the organic EL element OELD emits light corresponding to the supplied current. At this time, if the applied data voltage is set to have a multi-level value in a predetermined range, a desired gray scale can be expressed.

FIG. 4 is a graph illustrating the current I _D according to the voltage V _D applied to the drain electrode of the driving transistor M1.

As shown in FIG. 4, the current I _D is increased by the voltage V _D applied to the drain electrode of the driving transistor M1, and when the constant voltage is reached, the current I _D is saturated. ) However, even when the voltage V _D applied to the drain electrode is increased even in the saturation state, the current I _D flowing to the drain electrode of the transistor M1 increases little by little. Therefore, by adjusting the first power supply voltage VSS applied to the cathode of the organic EL element OLED, it is possible to select a voltage capable of flowing an optimal saturation current.

Specifically, when the voltage VSS of the first power supply decreases, the voltage V _D applied to the drain electrode of the driving transistor M1 moves from V _D1 to V _D2 . Therefore, the voltage difference between the drain electrode and the source electrode increases, and the current flowing through the drain electrode increases, so that a desired current can flow in the organic EL element OLED.

Therefore, by adjusting the voltage VSS of the first power supply applied to the cathode of the organic EL element OLED, the current characteristics of the driving transistor can be controlled, and the driving transistor is optimally saturated during the on / off inspection of the display panel. Can be operated in a state.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

According to the present invention, by controlling the current characteristics in the saturation region of the driving transistor, the driving transistor can be operated in an optimal saturation state during the on / off inspection of the display panel.

Claims (5)

In the inspection apparatus of the display panel including a plurality of pixels, The pixel includes a transistor for outputting a current corresponding to a data signal, and an organic EL element connected between the transistor and a first power supply. The inspection device, A controller configured to generate a control signal for inspecting the display panel and apply the control signal to the display panel; And Voltage adjusting unit for adjusting the voltage of the first power supply Inspection device of the display panel comprising a. The method of claim 1, The display panel further includes a plurality of data lines for transmitting the data signal to the pixel, and a voltage supply line for transferring the voltage of the first power supply. The method of claim 2, The display panel further includes a plurality of scan lines for transmitting a selection signal to the plurality of pixels, And the pixel further includes a capacitor connected between the first electrode and the second electrode of the transistor, and a switching element configured to transfer the data signal to the capacitor in response to the selection signal from the scan line. A display panel comprising a plurality of data lines for transmitting a data signal, a plurality of scanning lines for transmitting a selection signal, and a plurality of pixel circuits connected to the data lines and the scanning lines. The pixel circuit, A transistor having first to third electrodes and outputting a current corresponding to a voltage applied between the first and second electrodes to the third electrode; A display element configured to display an image corresponding to a current electrically connected and applied between the third electrode and the first power source of the transistor; A capacitor connected between the first electrode and the second electrode of the transistor; And A first switching element transferring the data signal to the capacitor in response to the selection signal Including; And a voltage of the first power supply electrically connected to the display element. The method of claim 4, wherein And a test line for applying a test voltage when the display panel is inspected, and a plurality of second switching elements connecting the test line and the data line during the test.

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