KR100699999B1 - Organic electroluminiscent display device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent display, and more particularly, to an organic electroluminescent display using a new layout for preventing crosstalk due to a voltage drop of an initial voltage line between each pixel.

An organic electroluminescent display device according to the present invention comprises a plurality of pixel circuits arranged in columns and rows on a display panel; A plurality of data lines formed in a first direction for transmitting data signals to the plurality of pixel circuits; A plurality of scan lines which transmit a selection signal to the plurality of pixel circuits and are formed in a second direction crossing the first direction; A plurality of power supply voltage lines formed in the first direction to transfer power supply voltages to the plurality of pixel circuits; A plurality of initial voltage lines formed in the first direction to transfer initial voltages to the plurality of pixel circuits; And a plurality of light emission control lines formed in the second direction for transmitting light emission control signals to the plurality of pixel circuits.

Organic light emitting display device, voltage drop, layout

Description

Organic electroluminescent display device

1 is a circuit diagram of a unit pixel of a conventional organic electroluminescent display.

2 is another circuit diagram of a unit pixel of a conventional organic light emitting display device.

FIG. 3 is a timing diagram for driving the pixel circuit shown in FIG. 2.

4 is a layout diagram of unit pixels of an organic light emitting display device according to a first embodiment of the present invention.

5 is a circuit diagram of a unit pixel of FIG. 4.

6 is a circuit diagram of a unit pixel of an organic light emitting display device according to a second embodiment of the present invention.

FIG. 7 is a timing diagram for driving the pixel circuit shown in FIG. 6.

FIG. 8 is a layout diagram of the pixel circuit of FIG. 6.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent display, and more particularly, to an organic electroluminescent display using a new layout for preventing crosstalk due to a voltage drop of an initial voltage line between each pixel.

In general, an organic light emitting display device is a display device using an organic light emitting diode (OLED) made of a fluorescent or phosphorescent organic compound that is electrically excited. The organic light emitting device displays a predetermined image according to a voltage or a current to be supplied and has a laminated structure consisting of an anode, an organic light emitting layer, and a cathode. The organic light emitting layer has a multilayer structure including a hole injecting layer and an electron injecting layer on both sides of the emitting layer in order to improve injection characteristics of electrons and holes. In addition, the organic thin film layer may optionally include an electron transporting layer, a hole transporting layer, a hole blocking layer, etc. in order to improve light emission characteristics of the organic light emitting device.

The above-described method of driving the organic light emitting display device includes a passive matrix driving method and an active matrix driving method. The passive matrix driving scheme is, for example, a driving scheme in which a pixel connected to a scan line of a specific row receives a current only for a selected time and has a corresponding luminance. The active matrix driving scheme refers to a driving scheme for storing a voltage for displaying a predetermined gray scale in a capacitor and applying the stored voltage to the pixel for the entire frame time, for example. The active matrix driving method is divided into a voltage programming method and a current programming method according to the type of a signal applied to store a voltage in a capacitor.

1 is a circuit diagram of a pixel circuit of a conventional organic light emitting display device. The pixel circuit shown in FIG. 1 represents a pixel circuit connected to the m-th data line Dm and the n-th scan line Sn of the NxM pixel circuits.

Referring to FIG. 1, a pixel circuit includes a driving transistor M2, a switching transistor M1, and a capacitor Cst to drive an organic light emitting diode OLED. The driving transistor M2 is connected between the power supply voltage Vdd and the organic light emitting diode OLED. The switching transistor M1 is controlled on / off in response to a selection signal applied to the scan line Sn and is connected between the data line Dm and the gate of the driving transistor M1. The capacitor Cst is connected between the power supply voltage Vdd and the gate of the driving transistor M1.

The operation of the pixel circuit described above is as follows. First, when the selection signal is applied to the scan line Sn, the switching transistor M1 is turned on. In this state, the data voltage applied to the data line Dm is applied to one end of the capacitor Cst through the switching transistor M1, and the capacitor Cst corresponds to the voltage difference between the power supply voltage Vdd and the data voltage. Voltage is stored. The driving transistor M2 operates as a constant current source by a predetermined voltage stored in the capacitor Cst, and supplies a current to the organic light emitting element OLED.

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

Where I _OLED is the current flowing through the OLED, Vgs is the voltage between the gate and the source of the driving transistor M2, Vth is the threshold voltage of the driving transistor M2, Vdata is the data voltage, and β is a constant. Indicates a value.

On the other hand, the conventional active matrix drive type organic light emitting display device mainly uses a thin film transistor that is easy to manufacture and has excellent characteristics as a switching element for controlling each pixel. However, in the conventional organic electroluminescent display, the amount of current supplied to the organic light emitting element OLED varies according to the variation in the threshold voltage Vth of the driving transistor caused by the nonuniformity of the manufacturing process, whereby the luminance nonuniformity. There is a problem that occurs.

In order to solve this problem, there has been a method of compensating threshold voltage according to manufacturing process variables by adding a threshold voltage compensation transistor. US Patent No. 6,229,506 discloses an organic electroluminescent display for compensating for variation in threshold voltage. The US patent discloses a pixel structure in which a current source adjusts a source-gate voltage with respect to an overdrive voltage of a driving transistor and compensates for a threshold voltage deviation of the driving transistor. The organic electroluminescent display of the U.S. patent has a two-step operation of a data loading (data writing) step and a continuous light emitting step, in which a current source is a voltage between the source and gate of a driving transistor with respect to an overdrive voltage. Was adjusted to compensate for the deviation of the threshold voltage of the driving transistor.

However, the organic electroluminescent display device as described above is a current driving method for driving an organic light emitting device according to a data signal of a current level applied from a current source, and has difficulty in charging a data line. That is, since the parasitic capacitance of the data line is relatively large, and the current level of the data signal provided from the current source is relatively small, it takes a long time to charge the data line and there is a problem that the data becomes unstable.

In order to solve the problem of the current line data line charge as described above, an organic light emitting display having a mirror-type pixel structure has been proposed. 2 illustrates a voltage driving pixel circuit having a mirror type in a conventional voltage driving organic light emitting display device.

Referring to FIG. 2, a first transistor M11 having a gate connected to a current scan line Sn applied to a corresponding scan line among a plurality of scan lines and a data signal applied to a corresponding data line among a plurality of data lines applied to a source ), A second transistor M12 to which a previous selection signal applied to the scan line Sn-1 immediately before the current scan line is applied to the gate, and an initialization voltage Vinit is applied to the drain, and a mirror-shaped second transistor. Third and fourth transistors M13 and M14, a fifth transistor M15 connected to a gate of the emission control line Em and a drain connected to a drain of the fourth transistor M14, and the fifth transistor ( An organic light emitting diode OLED is connected between the M15 and the reference voltage Vss, and a capacitor Cst is connected between the gate and the source of the fourth transistor M14.

The operation of the pixel of the organic light emitting display device having the above structure will be described with reference to the timing diagram of FIG. 3.

First, during the initialization operation, a low level selection signal is applied to the previous scan line Sn-1, a high level selection signal is applied to the current scan line Sn, and the light emission control line Em When a light emission control signal of a high level is applied, the second transistor M12 is turned on, and the first transistor M11 and the fifth transistor M15 are turned off to form the third and fourth mirror type. Transistors M13 and M14 are also turned off. Therefore, the data stored in the capacitor Cst is initialized to the initialization voltage Vinit through the second transistor M12.

On the other hand, during data programming, a high level selection signal is applied to the previous scan line Sn-1, a low level selection signal is applied to the current scan line Sn, and the emission control line Em When the light emission control signal of a high level is applied, the second and fifth transistors M12 and M15 are turned off and the first transistor M11 is turned on so that the mirror type third and fourth transistors ( M13 and M14 are turned on.

Therefore, the data signal Vdata of the voltage level applied to the data line is transmitted to the gate of the fourth transistor M14 through the third transistor M13.

Next, during the light emission, a high level selection signal is applied to the previous scan line Sn-1, a high level selection signal is applied to the current scan line Sn, and the emission control line Em is applied. When the light emission control signal having a low level is applied to the fifth transistor, the fifth transistor M15 is turned on by the light emission control signal, and thus corresponds to the data signal Vdata of the voltage level applied to the gate of the fourth transistor M14. The driving current flows to the OLED and emits light.

The voltage applied to the gate of the fourth transistor M14 is Vdata-Vth _M13 , and a current flowing through the organic light emitting diode OLED is represented by Equation 2 below.

는 상수값을 각각 나타낸다.Here, I _OLED is a current flowing through the OLED, Vgs _M14 is a voltage between the source and the gate of the fourth transistor M14, Vth _M13 is the threshold voltage of the third transistor M13, and Vth _M14 is the fourth voltage. Threshold voltage of transistor M14, Vdata is the data voltage,

Denotes constant values, respectively.

At this time, if the threshold voltages of the third and fourth transistors M13 and M14 for the current mirror are the same, that is, if Vth _M13 = Vth _M14 is the same, the threshold voltage of the transistor can be compensated for, thereby driving the organic light emitting diode OLED. Can be kept uniform.

However, in the current mirror type voltage driving method as described above, even if the third and fourth transistors M13 and M14 constituting the current mirror are arranged adjacent to each other on the substrate, the same threshold voltage is obtained by the manufacturing process variables of the TFT. Is very difficult. Therefore, it is difficult to obtain a uniform driving current due to the variation of the threshold voltage of the TFT, thereby causing a problem of deterioration in image quality due to luminance unevenness.

In the voltage driving method of the current mirror type as described above, a technique for solving the problem of deterioration in image quality caused by the threshold voltage deviation between the current mirror TFTs has been disclosed in US Pat. No. 6,362,798. In the US patent, a diode-compensated thin film transistor is connected to a gate of a driving transistor to compensate for a threshold voltage of the driving transistor. However, the U.S. patent also has a problem in that the deviation of the threshold voltage of the driving transistor is not compensated if the threshold voltages of the compensation thin film transistor and the organic light emitting diode driving thin film transistor are not the same.

Meanwhile, when the initial voltage line for transmitting the initial voltage Vinit applied to the pixel circuit in the initialization step is formed as a horizontal line as shown in FIG. 2, when one scan line, for example, the nth scan line Sn is selected, the initial voltage line As a result, an initial voltage Vinit is applied to all the pixel circuits connected to the scan line Sn. At this time, cross talk occurs due to an IR drop due to the internal resistance of the initial voltage line. That is, in FIG. 4, the initial voltage Vinit applied to the right pixel of the initial voltage line is lower than the initial voltage Vinit applied to the left pixel, so that the gate voltage applied to the driving transistor is applied even if the same data voltage is applied to each pixel. As a result, the current flowing through the organic light emitting diode OLED is also changed, resulting in uneven brightness. This is more serious problem in the large panel.

The present invention was derived to solve the above-mentioned problems of the prior art, and an object of the present invention is to prevent cross talk due to a voltage drop occurring in an initial voltage line between each pixel, thereby preventing organic light emitting diodes from being uniform. An organic electroluminescent display device capable of displaying luminance is provided.

Another object of the present invention is to provide an organic light emitting display device capable of displaying uniform luminance by compensating for variations in threshold voltages of driving transistors included in a pixel circuit.

In order to achieve the above object, the organic light emitting display device of the present invention comprises a plurality of pixel circuits arranged in columns and rows on the display panel; A plurality of data lines formed in a first direction for transmitting data signals to the plurality of pixel circuits; A plurality of scan lines which transmit a selection signal to the plurality of pixel circuits and are formed in a second direction crossing the first direction; A plurality of power supply voltage lines formed in the first direction to transfer power supply voltages to the plurality of pixel circuits; A plurality of initial voltage lines formed in the first direction to transfer initial voltages to the plurality of pixel circuits; And a plurality of light emission control lines formed in the second direction for transmitting light emission control signals to the plurality of pixel circuits.

Each of the plurality of pixel circuits may include a first transistor configured to transfer a data signal in response to a current selection signal; A capacitor for storing the data signal; A second transistor generating a driving current according to the data signal stored in the capacitor; A third transistor for compensating the threshold voltage of the second transistor; A fourth transistor delivering an initial voltage to the capacitor in response to a previous selection signal; And an organic light emitting device emitting light in response to a driving current generated through the second transistor.

Each of the plurality of pixel circuits may include: a first transistor configured to transfer a data signal in response to a current selection signal; A second transistor configured to generate a driving current according to the data signal transmitted through the first transistor; A third transistor for self-compensating the threshold voltage deviation of the second transistor; A capacitor for storing a data signal transferred to the second transistor; A fourth transistor delivering an initial voltage to the capacitor in response to a previous selection signal; A fifth transistor transferring the power supply voltage to the second transistor in response to the emission control signal; And an organic light emitting device emitting light in response to a driving current generated through the second transistor.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention. Like parts are designated by like reference numerals throughout the specification. When a part is connected to another part, this includes not only a directly connected part but also an electrically connected part with another element in between.

Now, an organic light emitting display device according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

4 is a layout diagram of an organic light emitting display device according to a first embodiment of the present invention. In the organic electroluminescent display shown in FIG. 4, each pixel circuit is formed of a circuit including five transistors and one capacitor. The OLED display device illustrated in FIG. 4 is formed around the pixel circuit connected to the data line Dm, the n-1 th scan line Sn-1, and the n th scan line Sn among the NxM pixel circuits. .

Referring to FIG. 4, each pixel circuit of the organic light emitting display device includes mirror-shaped third and fourth transistors M13 and M14, a capacitor Cst, a first transistor M11, a second transistor M12, The fifth transistor M15 and the organic light emitting diode OLED are formed. Here, the first, second and fifth transistors M11, M12, and M15 serve as switching elements. With this arrangement, each pixel circuit supplies a predetermined current to the organic light emitting element so that the organic light emitting element OLED can emit light.

Each pixel circuit is connected to a data line Dm, a first scan line Sn-1, a second scan line Sn, a light emission control line Em, a power supply voltage line Vdd, and an initial voltage line Vinit.

The data line Dm extends in the first direction and is connected to one electrode of the first transistor M11.

The first scan line Sn-1 extends in the second direction to pass over the channel of the second transistor M12 and functions as a gate electrode of the second transistor M12. Here, the second direction intersects with the first direction.

The second scan line Sn extends in the second direction to pass over the channel of the first transistor M11 and functions as a gate electrode of the first transistor M11. Here, the second scan line Sn is parallel to the first scan line Sn-1 and intersects the data line Dm.

The light emission control line Em functions as a gate electrode of the fifth transistor M15 and extends in the second direction. Here, the emission control line Em is parallel to the first scan line Sn-1 and the second scan line Sn and intersects the data line Dm.

The power supply voltage line Vdd extends in the same direction as the first direction in which the data line is disposed in the pixel portion including the plurality of NxM pixels, and transmits a power supply voltage to each pixel circuit. In FIG. 4, the power supply voltage line Vdd becomes the first electrode of the capacitor Cst and is connected to the source electrode of the fourth transistor M14. Here, reference numeral Vdd is described as representing a power supply voltage line, but Vdd may refer to a power supply voltage transmitted through the power supply voltage line.

The initial voltage line Vinit extends in the same first direction as the first direction in which the data line Dm and the power supply voltage line Vdd are disposed, and transfers the initial voltage to the capacitor Cst. The initial voltage line Vinit is connected to the drain electrode of the second transistor M12. Here, although Vinit is described as indicating an initial voltage line, Vinit may indicate an initial voltage transferred through the initial voltage line. Since the initial voltage line Vinit is disposed in the horizontal direction to the vertical direction, when one scan line Sn is selected, an initial voltage is applied to only one pixel circuit, for example, through the initial voltage line Vinit. Since the initial voltage is not applied to the neighboring pixels, no voltage drop IR drop occurs due to the wiring of the initial voltage line Vinit.

As described above, in the first embodiment according to the present invention, the initial voltage line Vinit is disposed in the vertical direction as described above, so that the initial voltage is applied only to one pixel circuit connected to one scan line Sn and the initial voltage to the other pixel circuits. Since this is not applied, the problem of voltage drop (IR drop) due to the distance from the lead portion or the internal resistance does not occur. This allows a desired voltage to be stored in a capacitor that maintains the gate voltage of the driving transistor. Therefore, according to the present invention, since the desired current can be supplied to the organic light emitting device through the driving transistor, the luminance uniformity can be greatly improved.

Meanwhile, in the first embodiment according to the present invention, the data line, the power voltage line and the initial voltage line, and the scan line and the light emission control line extending in the first or second direction not only extend in a straight line but also in a predetermined curve. It includes extending with wealth or winding up.

FIG. 5 is a pixel circuit diagram of the organic light emitting display device of FIG. 4.

Referring to FIG. 5, the pixel circuit according to the first exemplary embodiment of the present invention extends in the second direction, such as the data line Dm, the power voltage line Vdd, and the second line extending in the first direction, as in the pixel circuit of FIG. 2. And a previous scan line Sn-1, a current scan line Sn and a light emission control line Em, first to fifth transistors M11 to M15, a capacitor Cst, and an organic light emitting diode OLED. In FIG. 2, the initial voltage line Vinit extends in the second direction. However, in FIG. 5, the initial voltage line Vinit extends in the first direction.

As described above, since the initial voltage line Vinit extends vertically, the voltage drop IR drop due to the wiring of the initial voltage line Vinit does not occur, thereby improving luminance uniformity. Since the operation principle of the pixel circuit of FIG. 5 is the same as that of the pixel circuit of FIG. 2, a detailed description thereof will be omitted.

4 and 5 as described above, by vertically extending the initial voltage line Vinit, the voltage drop IR drop due to the wiring of the initial voltage line Vinit does not occur, thereby improving the luminance uniformity. In the current mirror type voltage driving method according to the first embodiment of the present invention, even if the third and fourth transistors M13 and M14 constituting the current mirror are arranged adjacent to each other on the substrate, the same threshold voltage is determined by the manufacturing process variables of the TFT. It is very difficult to get. Another embodiment of the present invention for solving the above threshold voltage deviation is presented.

6 illustrates a structure of a pixel circuit in an organic light emitting display device according to a second embodiment of the present invention. The organic light emitting display device of the present invention includes a plurality of scan lines, a plurality of data lines, and a plurality of A power supply voltage line, a plurality of initial voltage lines, and a plurality of pixel circuits are respectively arranged on one of the plurality of scan lines, data lines, power supply voltage lines, and initial voltage lines, corresponding scan lines, data lines, power supply voltage lines, and initial voltage lines.

Referring to FIG. 6, each pixel of the organic light emitting display device of the present invention includes six transistors M21-M26, one capacitor Cst, and an organic light emitting diode OLED. That is, each pixel is an organic light emitting diode OLED that emits light corresponding to an applied driving current, and data applied to a corresponding data line Dm in response to a current selection signal applied to a corresponding scan line Sn. A second transistor M22 for transmitting a voltage, a first transistor M21 for supplying a driving current of the organic light emitting diode OLED in response to the data voltage input through the second transistor M22; And a third transistor M23 for diode-connecting the first transistor M21 and a capacitor Cst for storing a data voltage applied to the first transistor M21.

In this case, the second transistor M22 is applied with a current selection signal applied to the scan line Sn corresponding to a gate, a data line Dm is connected to a source, and a data signal is applied. It consists of a p-type thin film transistor connected to the source of M21).

The first transistor M21 includes a p-type thin film transistor having a gate connected to one terminal of the capacitor Cst and a drain connected to one terminal of the organic light emitting diode OLED. The third transistor M23 includes a p-type thin film transistor having a drain and a source respectively connected to the gate and the drain of the first transistor M21 and a current selection signal applied to the gate. The other side of the capacitor Cst is provided with a power supply voltage from a corresponding power supply voltage line Vdd.

Each pixel further includes a fifth transistor M25 for providing the power supply voltage Vdd to the first transistor M21 in response to a light emission control signal applied to the light emission control line Em, and a light emission control signal. In response, a sixth transistor M26 is provided to provide a driving current generated through the first transistor M21 to the organic light emitting diode OLED.

In this case, the fifth transistor M25 has a light emission control signal applied to a gate, a source voltage applied to a source from the power supply voltage line Vdd, and a drain connected to a drain of the second transistor M22. It consists of a thin film transistor. In the sixth transistor M26, a light emission control signal is applied to a gate, a source is connected to a drain of the first transistor M21, and a drain is connected to one end of the organic light emitting diode OLED. It consists of. The other end of the organic light emitting diode OLED is connected to a reference voltage Vss.

In addition, each pixel includes a fourth transistor M24 for initializing a data signal stored in the capacitor Cst in response to a previous selection signal applied to the scan line Sn-1 immediately before the corresponding scan line Sn-1. Include. The fourth transistor M24 is a p-type thin film transistor in which a previous selection signal is applied to a gate, a source is connected to one terminal of the capacitor Cst, and a drain is connected to the initial voltage line Vinit to apply an initial voltage. Is done.

The operation of the pixel circuit according to the second embodiment of the present invention having the above-described configuration will be described with reference to the timing diagram of FIG.

First, in the initialization operation, as shown in FIG. 7, in the initialization section in which the previous selection signal Sn-1 is low level and the current selection signal Sn and the emission control signal Em are high level, The fourth transistor M24 is turned on by the previous selection signal Sn-1, and the first to third transistors M21-M23 are connected to each other by the high level current selection signal Sn and the emission control signal Em. The fifth and sixth transistors M25 and M26 are turned off. Therefore, the data stored in the capacitor Cst, that is, the gate voltage of the first transistor M21 is initialized.

Next, in the data program operation, as shown in FIG. 7, in the program section in which the previous selection signal Sn-1 is high level, the current selection signal Sn is low level, and the emission control signal Em is high level, The fourth transistor M24 is turned off, the third transistor M23 is turned on by the low level current selection signal Sn, and the first transistor M21 is diode-connected.

At this time, the second transistor M22 is also turned on by the current selection signal Sn, and the fifth and sixth transistors M25 and M26 are turned off by the light emission control signal Em. That is, since the first transistor M21 is diode-connected, Vdata-Vth _M21 is applied to the gate voltage of the first transistor M21, and the gate voltage is stored in the capacitor Cst to complete the program operation.

Lastly, as shown in Fig. 7, the light emission in which the previous selection signal Sn-1 is at high level, the current selection signal Sn is at high level, and the light emission control signal Em is at low level during light emission. In the period, the fifth and sixth transistors M25 and M26 are turned on by the low level emission control signal Em, and the fourth transistor M24 is turned on by the previous selection signal Sn-1 of the high level. The third transistor M23 and the second transistor M22 are turned off by the high level current selection signal Sn. Therefore, a driving current generated in response to the data signal of the voltage level applied to the gate of the first transistor M21 flows to the organic light emitting diode OLED through the first transistor M21, and thus the organic light emitting diode OLED. Will emit light.

At this time, the current flowing to the organic light emitting diode OLED is shown in Equation 3 below.

는 상수값을 각각 나타낸다.Here, I _OLED is a current flowing through the OLED, Vgs _M21 is a voltage between the source and the gate of the first transistor _M21 , Vth _M21 is a threshold voltage of the first transistor M21, Vdata is a data voltage, Vdd is the supply voltage,

Denotes constant values, respectively.

As can be seen from Equation 3 above, the driving current flows through the organic light emitting diode OLED in response to the data signal of the voltage level applied to the data line, regardless of the threshold voltage of the first transistor M21. That is, in the present invention, since the deviation of the threshold voltage of the first transistor M21 is detected through the third transistor M23 and compensates for itself, the luminance unevenness according to the threshold voltage deviation can be improved.

Also, as shown in FIG. 6, one pixel circuit positioned in a row selected by a selection signal applied to one scan line Sn by arranging the initial voltage line Vinit in a vertical direction parallel to the data line and intersecting the scan line as shown in FIG. 6. Since only the initial voltage is applied and the initial voltage is not applied to the remaining pixel circuits, a problem of voltage drop (IR drop) due to the distance from the lead portion or the internal resistance does not occur. Therefore, since the desired current can be supplied to the organic light emitting device through the driving transistor, the luminance uniformity can be greatly improved.

In the second embodiment of the present invention, the pixel circuit is composed of six transistors and one capacitor, but it is possible to have a structure in which a threshold voltage is detected and self-compensated. In addition to the PMOS transistor, it is also possible to configure an NMOS transistor or a CMOS transistor.

FIG. 8 is a diagram illustrating a layout of the pixel circuit of FIG. 6.

Referring to FIG. 8, each pixel circuit of the organic light emitting display device includes first to sixth transistors M21 to M26, a capacitor Cst, and an organic light emitting diode OLED. Here, the first transistor M21 is a current driving transistor, and the second through sixth transistors M22-M26 serve as switching transistors. With this arrangement, each pixel circuit supplies a predetermined current to the organic light emitting element so that the organic light emitting element OLED can emit light.

Each pixel circuit is connected to a data line Dm, a first scan line Sn-1, a second scan line Sn, a light emission control line Em, a power supply voltage line Vdd, and an initial voltage line Vinit.

The data line Dm extends in the first direction and is connected to the source electrode of the second transistor M22.

The first scan line Sn-1 extends in the second direction to pass over the channel of the fourth transistor M24 and functions as a gate electrode of the fourth transistor M24. Here, the second direction intersects with the first direction.

The second scan line Sn extends in the second direction to pass over the channels of the second and third transistors M22 and M23 and functions as a gate electrode of the second and third transistors M22 and M23. Here, the second scan line Sn is parallel to the first scan line Sn-1 and intersects the data line Dm.

The light emission control line Em functions as a gate electrode of the fifth and sixth transistors M25 and M26 and extends in the second direction. Here, the emission control line Em is parallel to the first scan line Sn-1 and the second scan line Sn and intersects the data line Dm.

The power supply voltage line Vdd extends in the first direction parallel to the first direction in which the data line Dm is disposed in the pixel portion including the plurality of NxM pixels, and transmits a power supply voltage to each pixel circuit. In FIG. 8, the power supply voltage line Vdd becomes the first electrode of the capacitor Cst and is connected to the source electrode of the fifth transistor M25. Here, reference numeral Vdd is described as representing a power supply voltage line, but Vdd may refer to a power supply voltage transmitted through the power supply voltage line.

The initial voltage line Vinit extends in the first direction in parallel with the first direction in which the data line Dm and the power supply voltage line Vdd are disposed, and transfers the initial voltage to the capacitor Cst. The initial voltage line Vinit is connected to the drain electrode of the fourth transistor M24. Here, although Vinit is described as indicating an initial voltage line, Vinit may indicate an initial voltage transferred through the initial voltage line. Since the initial voltage line Vinit is disposed in the first direction, one pixel circuit positioned in a row selected when a selection signal is applied to one scan line Sn, for example, only the first pixel circuit is connected to the initial voltage line Vinit. Since the initial voltage is applied and the initial voltage is not applied to the neighboring pixels, no voltage drop IR drop occurs due to the wiring of the initial voltage line Vinit.

Meanwhile, in the second embodiment according to the present invention, the data line, the power voltage line and the initial voltage line, and the scan line and the emission control line extending in the first or second direction are not only extended in a straight line but also in a predetermined curve. It includes extending with wealth or winding up.

As described above, in the second embodiment according to the present invention, the initial voltage is applied to only one pixel circuit connected to one scan line Sn by disposing the initial voltage line Vinit in the first direction, and the initial voltage is applied to the other pixel circuits. Since no voltage is applied, a problem of voltage drop (IR drop) due to the distance from the lead portion or the internal resistance does not occur. In addition, since the deviation of the threshold voltage of the first transistor M21 is detected through the third transistor M23 and compensates for itself, the luminance non-uniformity according to the threshold voltage deviation can be improved. Therefore, according to the second embodiment of the present invention, since the desired current can be supplied to the organic light emitting device through the driving transistor, the luminance uniformity can be greatly improved.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

 According to the present invention, since the initial voltage line is disposed parallel to the data line and perpendicular to the scan line, no voltage drop occurs due to the internal resistance of the initial voltage line, thereby preventing cross talk due to the voltage drop, thereby improving luminance uniformity. have.

In addition, a uniform luminance may be displayed by self-compensating the deviation of the threshold voltage of the driving transistor.

Claims (26)

A plurality of pixel circuits arranged in columns and rows on the display panel; A plurality of data lines formed in a first direction for transmitting data signals to the plurality of pixel circuits; A plurality of scan lines which transmit a selection signal to the plurality of pixel circuits and are formed in a second direction crossing the first direction; A plurality of power supply voltage lines formed in the first direction to transfer power supply voltages to the plurality of pixel circuits; A plurality of initial voltage lines formed in the first direction to transfer initial voltages to the plurality of pixel circuits; And And a plurality of light emission control lines formed in the second direction to transmit light emission control signals to the plurality of pixel circuits. The method of claim 1, And the plurality of initial voltage lines are formed in parallel with the plurality of data lines with respect to the plurality of pixel circuits. The method of claim 1, And the plurality of initial voltage lines are formed between the plurality of pixel circuits and the plurality of data lines. The method of claim 1, And the plurality of initial voltage lines are formed between the plurality of pixel circuits and the plurality of power supply voltage lines. The method of claim 1, And the plurality of power supply voltage lines are formed between the plurality of pixel circuits and the plurality of initial voltage lines. The method of claim 1, And the plurality of power supply voltage lines are formed between the plurality of pixels and the plurality of data lines. The method of claim 1, And the plurality of data lines, the plurality of scan lines, the plurality of power supply voltage lines, the plurality of initial voltage lines, and the plurality of light emission control lines are formed in a straight line or have a predetermined curvature. The method of claim 1, Each of the plurality of pixel circuits A first transistor transferring a data signal in response to a current selection signal; A capacitor for storing the data signal; A second transistor generating a driving current according to the data signal stored in the capacitor; A third transistor for compensating the threshold voltage of the second transistor; A fourth transistor delivering an initial voltage to the capacitor in response to a previous selection signal; And And an organic light emitting element emitting light in response to a driving current generated through the second transistor. The method of claim 8, And wherein the first transistor has a source connected to the data line, a gate connected to the current scan line, and a drain connected to a source of the third transistor. The method of claim 8, The capacitor is an organic light emitting display device, characterized in that the first electrode is connected to the power supply voltage line, the second electrode is connected to the gate of the second transistor. The method of claim 8, The second transistor has a source connected to the power supply voltage line and a gate connected to the gate of the third transistor. The method of claim 8, The third transistor has a source connected to a drain of the first transistor and a gate and a drain connected to each other. The method of claim 8, The fourth transistor has a source connected to a drain of the third transistor, a gate connected to the previous scan line, and a drain connected to the initial voltage line. The method of claim 8, And each of the plurality of pixel circuits further comprises a fifth transistor configured to transfer a driving current generated by the second transistor to the organic light emitting element in response to the emission control signal. The method of claim 14, The fifth transistor has a source connected to a drain of the second transistor, a gate connected to the emission control line, and a drain connected to the first electrode of the organic light emitting diode. The method of claim 14, And the first to fifth transistors have the same channel type. The method of claim 1, Each of the plurality of pixel circuits A first transistor transferring a data signal in response to a current selection signal; A second transistor configured to generate a driving current according to the data signal transmitted through the first transistor; A third transistor for self-compensating the threshold voltage deviation of the second transistor; A capacitor for storing a data signal transferred to the second transistor; A fourth transistor delivering an initial voltage to the capacitor in response to a previous selection signal; A fifth transistor transferring the power supply voltage to the second transistor in response to the emission control signal; And And an organic light emitting element emitting light in response to a driving current generated through the second transistor. The method of claim 17, And the source is connected to the power supply line, the gate is connected to the current scan line, and the drain is connected to the source of the second transistor. The method of claim 17, The second transistor has a source connected to a drain of the first transistor, a gate connected to a second electrode of the capacitor, and a drain connected to the organic light emitting diode. The method of claim 17, And the third transistor has a gate connected to the current scan line, a source and a drain connected to a drain and a gate of the second transistor, respectively, to connect the second transistor in the form of a diode. The method of claim 17, And the capacitor has a first electrode connected to the power supply voltage line and a second electrode connected to a gate of the second transistor. The method of claim 17, The fourth transistor has a source connected to a second electrode of the capacitor, a gate connected to the previous scan line, and a drain connected to the initial voltage line. The method of claim 17, The fifth transistor has a source connected to the power supply voltage line, a gate connected to the emission control line, and a drain connected to the source of the second transistor. The method of claim 17, And each of the plurality of pixel circuits further includes a sixth transistor configured to transfer a driving current generated by the second transistor to the organic light emitting element in response to the emission control signal. The method of claim 24, And the source is connected to the drain of the second transistor, the gate is connected to the emission control line, and the drain is connected to the organic light emitting diode. The method of claim 24, And the first to sixth transistors have the same conductivity type.

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