KR100722117B1 - Pixel and organic light emitting display device - Google Patents

Abstract

SUMMARY OF THE INVENTION An object of the present invention is to provide an organic light emitting display device in which a plurality of driving transistors are formed in one pixel so that current density of the anode electrode is uniform to prevent color irregularity.

According to an embodiment of the present invention, a first driving transistor allows a first driving current to flow in response to a predetermined voltage applied to a gate, and a second driving current corresponding to a predetermined voltage applied to the gate by a second driving transistor and a scan signal. A switching transistor for selectively applying the predetermined voltage to gates of the first and second driving transistors, and a capacitor for storing the predetermined voltage and transferring the predetermined voltage to the gates of the first and second driving transistors. And one organic light emitting diode which emits light by receiving the first and second driving currents from the first and second driving transistors, wherein the drains of the first driving transistor and the second driving transistor are formed of the organic light emitting diode. The present invention provides a pixel and an organic light emitting diode display connected to different points of an anode electrode.

Description

Pixel and organic light emitting display device {PIXEL CIRCUIT AND ORGANIC LIGHT EMITTING DISPLAY}

1 is a circuit diagram of a pixel of an organic light emitting diode display according to the related art.

2 is a structural diagram illustrating a structure of an organic light emitting display device according to an exemplary embodiment of the present invention.

FIG. 3 is a circuit diagram illustrating a pixel employed in the OLED display illustrated in FIG. 2.

4 is a structural diagram illustrating a second embodiment of an organic light emitting diode display according to the present invention.

FIG. 5 is a circuit diagram illustrating a pixel employed in the OLED display illustrated in FIG. 4.

*** Explanation of symbols on main parts of drawings ***

100: pixel portion 101; Pixel

200: data driver 300: scan driver

MS: switching transistors MD1, MD2: first and second drive transistors

Cst: Capacitor OLED: Organic Light Emitting Diode

The present invention relates to a pixel and an organic light emitting display device, and more particularly, to a pixel and an organic light emitting display device for reducing color unevenness by reducing an unevenness of current density of an anode electrode.

Recently, various flat panel displays have been developed to reduce weight and volume, which are disadvantages of cathode ray tubes. As a flat panel display, an organic light emitting diode (LCD) using a liquid crystal display, a field emission display, a plasma display panel, and an organic light emitting device (hereinafter referred to as OLED) is used. And a light emitting display device.

Among the flat panel display, the organic light emitting device is a self-light emitting device that emits a fluorescent material by recombination of electrons and holes, and has a fast response speed as a cathode ray tube compared to a light emitting device which requires a separate light source such as a liquid crystal display. Have

The anode electrode of the organic light emitting element is connected to the pixel circuit and the cathode electrode is connected to the second voltage power supply VSS. The organic light emitting diode includes an emission layer (EML), an electron transport layer (ETL), and a hole transport layer (HTL) formed between the anode electrode and the cathode electrode. In addition, the OLED may further include an electron injection layer (EIL) and a hole injection layer (HIL).

In the organic light emitting diode, when a voltage is applied between the anode electrode and the cathode electrode, electrons generated from the cathode electrode move toward the light emitting layer through the electron injection layer and the electron transport layer, and holes generated from the anode electrode are transferred to the hole injection layer and the hole. It moves toward the light emitting layer through the transport layer.

Accordingly, in the light emitting layer, light is generated by collision between electrons and holes supplied from the electron transporting layer and the hole transporting layer and recombination.

1 is a circuit diagram of a pixel of an organic light emitting diode display according to the related art. Referring to FIG. 1, a pixel includes an organic light emitting diode OLED, a driving transistor TD, a capacitor Cst, and a switching transistor TS. The scan line Sn, the data line Dm, and the power supply line ELVDD are connected to the pixel. The scanning line Sn is formed in the row direction, and the data line Dm and the power supply line ELVDD are formed in the column direction.

The driving transistor TD supplies a current for emitting light to the organic light emitting diode. The current amount of the driving transistor TD is controlled by the data voltage applied through the switching transistor TS.

The capacitor Cst is connected between the source electrode and the gate electrode of the driving transistor TD, and maintains the voltage between the source electrode and the gate electrode applied by the data voltage for a predetermined period of time.

Due to this configuration, when the switching transistor TS is turned on by the scan signal applied to the gate electrode of the switching transistor TS, the data voltage is applied to the gate electrode of the driving transistor TD through the data line Dm. do.

In addition, in response to the data voltage applied to the gate electrode of the driving transistor TD, current flows through the driving transistor TD to emit light.

The driving transistor MD or the switching transistor TS included in the pixel is a P-type metal oxide semiconductor field effect transistor (MOSFET). The reason for using P-type transistors is that the manufacturing process is simpler than using N-type transistors, which is advantageous for mass-producing organic light emitting display devices.

However, in the pixel configured as described above, one driving transistor is connected to the anode electrode of the organic light emitting diode, and the anode electrode of the organic light emitting diode emits light by receiving a current through a contact point connected to the driving transistor. Therefore, the current density near the contact point where the anode electrode is connected to the driving transistor is high and the current density is far away from the contact point, and the current density of the anode electrode is different depending on the position. As described above, when a difference in current density occurs in the same anode electrode, there is a problem in that a difference in brightness occurs and color unevenness occurs in one pixel.

Accordingly, the present invention has been made to solve the problems of the prior art, and an object of the present invention is to form a plurality of driving transistors in one pixel so that the current density of the anode electrode can be uniform to prevent color unevenness. A pixel and an organic light emitting display device are provided.

In order to achieve the above object, a first aspect of the present invention provides a first driving transistor for flowing a first driving current corresponding to a predetermined voltage applied to a gate, and a second driving corresponding to a predetermined voltage applied to the gate. A switching transistor for applying a predetermined voltage to gates of the first and second driving transistors selectively by a second driving transistor, a scan signal, and storing the predetermined voltage, and storing the predetermined voltages of the first and second driving transistors. And a capacitor which transmits the predetermined voltage to the gate and one organic light emitting diode which emits light by receiving first and second driving currents from the first and second driving transistors, wherein the first driving transistor and the first driving transistor are configured to emit light. 2, the drain of the driving transistor may provide a pixel connected to different points of the anode electrode of the organic light emitting diode. .

A second aspect of the present invention includes a plurality of driving transistors for selectively flowing a current from a source to a drain in response to a voltage of a gate, an anode, and a cathode, and emits light when current flows from the anode to the cathode electrode. A light emitting device is provided, wherein the anode electrode is connected to a plurality of driving transistors through a plurality of contacts to provide a pixel to which a current is supplied.

According to a third aspect of the present invention, a first driving transistor allows a first driving current to flow in response to a predetermined voltage applied to a gate, and a second driving transistor corresponding to a predetermined voltage applied to the gate. A switching transistor for applying the predetermined voltage to the gates of the first and second driving transistors by a scan signal, storing the predetermined voltages, and applying the predetermined voltages to the gates of the first and second driving transistors. The capacitor includes a first organic light emitting device that receives the first sphere coin and emits light from the first driving transistor, and a second organic light emitting device that receives the second driving current from the second driving transistor and emits light. The first organic light emitting diode includes a first sub-anode electrode, a light emitting layer, and a cathode, and the second organic light emitting diode includes a second The anode, the light-emitting layer and comprising the cathode electrode, the anode electrode part 1 is connected with the first driving transistor and the part 2 the anode is to provide a pixel connected to the second drive transistor.

A fourth aspect of the present invention includes a pixel portion including a plurality of pixels, a data driver transferring a data signal to the pixel portion, and a scan driver transferring a scan signal to the pixel portion, wherein the plurality of pixels are formed of the first pixel. An organic light emitting display device which is a pixel according to at least one of the first to third aspects is provided.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

2 is a structural diagram illustrating a first embodiment of an organic light emitting diode display according to the present invention. Referring to FIG. 2, the organic light emitting diode display includes a pixel unit 100 including a plurality of pixels, a data driver 200 transferring a data signal of the pixel unit 100, and a specific row of the pixel unit 100. And a scan driver 300 to transmit a scan signal to transmit the data signal to the selected row.

The pixel portion 100 is a means for displaying an image, and includes a plurality of scan lines S1, S2, ..., Sn-1, Sn and a plurality of data lines D1, D2 ... Dm-1, Dm, and A plurality of pixel power lines ELVdd are arranged, a plurality of scan lines S1, S2, ..., Sn-1, Sn, a plurality of data lines D1, D2 ... Dm-1, Dm and a plurality of The pixel 101 is formed in an area defined by the pixel power supply line, and the scan lines S1, S2, ..., Sn-1, Sn and the data lines D1, D2 ... Dm-1, Dm. The plurality of pixels 101 are configured to emit light by being supplied with power through the pixel power line ELVdd corresponding to the scanning signal and the data signal. Each pixel 101 includes an organic light emitting element and a driving circuit for driving the organic light emitting element, and the organic light emitting element emits light by receiving a current through the driving circuit. The pixel 101 includes a plurality of driving transistors to receive current through a plurality of driving transistors in one organic light emitting diode.

The data driver 200 is connected to the data lines D1, D2 ... Dm-1, Dm of the pixel unit 100 and applies a data signal to the pixels. The scan lines S1, S2, ..., Data signals are applied in parallel to the plurality of pixels 101 selected by Sn-1, Sn.

The scan driver 300 is a means for generating a selection signal for selecting a specific row of the pixel unit 100 and transmitting the selected signal to the scan lines S1, S2, ..., Sn-1, Sn of the pixel unit 100. The data signal is transmitted to the pixel 101 that receives the scan signal through the scan line.

FIG. 3 is a circuit diagram illustrating a pixel employed in the OLED display illustrated in FIG. 2. Referring to FIG. 3, the pixel includes a switching transistor MS, a first driving transistor MD1, a second driving transistor MD2, a capacitor Cst, and an organic light emitting diode OLED.

The switching transistor MS has a source connected to the data line Dm, a drain connected to the first node A, a gate connected to the scan line Sn, and the scan line Sn by the switching operation of the switching transistor MS. When the scan signal is transmitted through the data signal transmitted through the data line Dm is transmitted to the first node (A).

The capacitor Cst has a first electrode connected to the first node A, a second electrode connected to the pixel power line ELVdd, and the first node A receives a data signal by the operation of the switching transistor MS. Even though the second electrode receives the pixel voltage and stores the voltage corresponding to the difference between the pixel voltage and the data signal, the switching node MS is turned off in the first node A connected to the second electrode. Maintain the voltage of the data signal.

The first driving transistor MD1 has a source connected to the pixel power line ELVdd, a drain connected to a first point C1 of the anode electrode of the organic light emitting diode OLED, and a gate connected to the first node A. As a result, the voltage corresponding to the data signal is received by the voltage stored in the capacitor Cst so that current flows through the first point C1 of the anode electrode of the organic light emitting diode OLED.

The second driving transistor MD2 has a source connected to the pixel power line ELVdd, a drain connected to a second point C2 of the anode electrode of the organic light emitting diode OLED, and a gate connected to the first node A. As a result, the voltage corresponding to the data signal is received by the voltage stored in the capacitor Cst so that current flows through the second point C2 of the anode electrode of the organic light emitting diode OLED.

The organic light emitting diode OLED is connected to the first and second driving transistors MD1 and MD2 and the anode electrode and is connected to the first and second driving transistors through the first point C1 and the second point C2 of the anode electrode. The drain electrodes of MD1 and MD2 are connected. Accordingly, the anode electrode receives the driving current from two different points C1 and C2 and has a more uniform value than the current density of the anode electrode from one driving transistor. Accordingly, the driving current is received from the first and second driving transistors MD1 and MD2 to reduce the variation of the current density of the anode electrode, thereby preventing the color irregularity caused by the current density difference.

4 is a structural diagram illustrating a second embodiment of an organic light emitting diode display according to the present invention. Referring to FIG. 4, the organic light emitting diode display includes a pixel unit 1000 including a plurality of pixels, a data driver 2000 transferring a data signal of the pixel unit 1000, and a specific row of the pixel unit 1000. And a scan driver 3000 for transmitting a scan signal to transmit the data signal to the selected row.

The pixel unit 1000 is a means for displaying an image, and includes a plurality of scan lines S1, S2, ..., Sn-1, Sn and a plurality of data lines D1, D2 ... Dm-1, Dm, and A plurality of pixel power lines ELVdd are arranged, a plurality of scan lines S1, S2, ..., Sn-1, Sn, a plurality of data lines D1, D2 ... Dm-1, Dm and a plurality of The pixel 1001 is formed in an area defined by the pixel power line ELVdd, and the scan lines S1, S2, ..., Sn-1, Sn and the data lines D1, D2 ... Dm-1, A plurality of pixels 101 are supplied with power through the pixel power line ELVdd to emit light in response to a scan signal and a data signal applied to Dm). Each pixel 1001 includes an organic light emitting element and a driving circuit for driving the organic light emitting element, and the organic light emitting element emits light by receiving a current through the driving circuit. In addition, the pixel 1001 includes a plurality of driving transistors, and one organic light emitting diode receives current through a plurality of driving transistors (not shown).

In addition, in the organic light emitting diode included in each pixel 1001, an anode electrode is divided into a plurality of sub-anode electrodes 1001a and 1001b, and each sub-anode electrode 1001a and 1001b is connected to a plurality of driving transistors, respectively. The anode electrode receives the driving current from different driving transistors. Accordingly, the plurality of sub-anode electrodes 1001a and 1001b included in one pixel 1001 receive driving current from different driving transistors, and the anode electrode of one pixel 1001 receives the driving current through a plurality of contacts. It can be received to prevent the current density non-uniformity of the anode electrode.

The data driver 200 is connected to the data lines D1, D2 ... Dm-1, Dm of the pixel unit 100 and applies a data signal to the pixels. The scan lines S1, S2, ..., Data signals are applied in parallel to the plurality of pixels 101 selected by Sn-1, Sn.

The scan driver 300 is a means for generating a selection signal for selecting a specific row of the pixel unit 100 and transmitting the selected signal to the scan lines S1, S2, ..., Sn-1, Sn of the pixel unit 100. The data signal is transmitted to the pixel 101 that receives the scan signal through the scan line.

FIG. 5 is a circuit diagram illustrating a pixel employed in the OLED display illustrated in FIG. 4. Referring to FIG. 5, a pixel includes a switching transistor MSb, a first driving transistor MDb1, a second driving transistor MDb2, a capacitor Cstb, and a first organic light emitting diode OLED1 and a second organic layer. The light emitting device OLED2 is included.

 The switching transistor MSb has a source connected to the data line Dm, a drain connected to the first node A2, a gate connected to the scan line Sn, and the scan line Sn by the switching operation of the switching transistor MSb. When the scan signal is transmitted through the data signal, the data signal transmitted through the data line Dm is transmitted to the first node A2.

In the capacitor Cstb, the first electrode is connected to the first node A2, the second electrode is connected to the pixel power line ELVdd, and the first node A2 receives the data signal by the operation of the switching transistor MSb. The second electrode receives the pixel voltage and stores the voltage corresponding to the difference between the pixel voltage and the data signal so that the switching transistor MSb is turned off in the first node A2 connected to the second electrode. Maintain the voltage of the data signal. Accordingly, the capacitor Cstb maintains the voltage of the data signal, and the same voltage is applied to the gates of the first driving transistor MDb1 and the second driving transistor MDb2 so that the first driving transistor MDb1 and the second driving transistor are applied. MDb2 causes a current of the same magnitude to flow from the source to the drain.

The first driving transistor MDb1 has a source connected to the pixel power line ELVdd, a drain connected to an anode electrode of the first light emitting device OLED1, and a gate connected to the first node A2 to the capacitor Csta. The voltage corresponding to the data signal is received by the stored voltage to allow current to flow through the anode electrode of the first light emitting device OLED1.

The second driving transistor MDb2 has a source connected to the pixel power line ELVdd, a drain connected to an anode electrode of the second light emitting device OLED2, and a gate connected to the first node A2 to the capacitor Csta. The voltage corresponding to the data signal is received by the stored voltage so that a current flows through the anode electrode of the second light emitting device OLED2.

The first and second light emitting devices OLED1 and OLED2 are formed by the same anode electrode, the light emitting layer, and the cathode electrode, and the anode electrodes are divided into the negative anode electrodes, and the first and second light emitting devices OLED1 according to the secondary anode electrodes. , OLED2).

The first and second driving transistors MDa1 and MDb2 are connected to the respective sub-anode electrodes to receive driving currents through the drain electrodes of the first and second driving transistors MD1 and MD2, respectively. Accordingly, the anode electrodes can receive driving currents from the secondary anode electrodes to reduce the nonuniformity of the current density of the anode electrode, thereby preventing the color nonuniformity caused by the current density difference in one pixel.

According to the organic light emitting display device according to the present invention, at least two driving transistors are provided in one pixel so that the anode electrode can receive current from at least two places to prevent the nonuniformity of the current density of the anode electrode. Color unevenness can be prevented.

While the preferred embodiments of the present invention have been described using specific terms, such description is for illustrative purposes only and it is understood that various changes and changes may be made without departing from the spirit and scope of the following claims. Should be done.

Claims (8)

delete A first driving transistor configured to allow a first driving current to flow in response to a predetermined voltage applied to the gate; A second driving transistor corresponding to a predetermined voltage applied to the gate; A switching transistor selectively applying the predetermined voltage to gates of the first and second driving transistors by a scan signal; A capacitor that stores the predetermined voltage and transfers the predetermined voltage to the gates of the first and second driving transistors; And And one organic light emitting diode which receives the first and second driving currents from the first and second driving transistors and emits light, wherein the drains of the first driving transistor and the second driving transistor are anodes of the organic light emitting diode. Pixels connected to different points of the electrode. A plurality of driving transistors for selectively flowing a current from a source to a drain corresponding to the voltage of the gate; And An organic light-emitting device comprising an anode electrode and a cathode electrode and emits light when current flows from the anode to the cathode electrode. The anode electrode is connected to the drain of the plurality of driving transistor through a plurality of contacts to receive a current. The method of claim 3, wherein And a switching transistor for selectively transferring a predetermined voltage to the gate. The method of claim 3, wherein And a capacitor configured to maintain a predetermined voltage at the gate. The method of claim 3, wherein And the anode electrode is divided into a plurality of secondary anode electrodes, and each of the secondary anode electrodes is connected to the respective driving transistors. A first driving transistor configured to allow a first driving current to flow in response to a predetermined voltage applied to the gate; A second driving transistor corresponding to a predetermined voltage applied to the gate; A switching transistor configured to apply the predetermined voltage to gates of the first and second driving transistors by a scan signal; A capacitor that stores the predetermined voltage and transfers the predetermined voltage to the gates of the first and second driving transistors; A first organic light emitting diode emitting light by receiving the first driving current from the first driving transistor; And Including a second organic light emitting device for emitting light by receiving the second driving current from the second driving transistor, The first organic light emitting diode includes a first subanode electrode, a light emitting layer, and a cathode, and the second organic light emitting diode includes a second subanode electrode, the light emitting layer, and the cathode electrode, and the first subanode electrode Is connected to the first driving transistor and the second sub-anode electrode is connected to the second driving transistor. A pixel unit including a plurality of pixels; A data driver for transmitting a data signal to the pixel unit; And Including a scan driver for transmitting a scan signal to the pixel portion, The plurality of pixels are pixels according to at least one of the preceding claims.

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