KR100903496B1 - Organic Light Emitting Display - Google Patents

Organic Light Emitting Display Download PDF

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KR100903496B1
KR100903496B1 KR1020070004862A KR20070004862A KR100903496B1 KR 100903496 B1 KR100903496 B1 KR 100903496B1 KR 1020070004862 A KR1020070004862 A KR 1020070004862A KR 20070004862 A KR20070004862 A KR 20070004862A KR 100903496 B1 KR100903496 B1 KR 100903496B1
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electrode
electrically connected
power supply
rgb
supply voltage
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KR1020070004862A
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KR20080067489A (en
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김양완
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삼성모바일디스플레이주식회사
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Abstract

The present invention relates to an organic light emitting display device, and the technical problem to be solved is as follows.
In an organic electroluminescent display device which displays color by controlling the number of emission or emission intensity of an organic electroluminescent element expressing three primary colors of red, green, and blue, a time period of white balance compensation in the middle of the emission period is obtained. This is to improve the problem that the white balance is changed over time and the desired color cannot be reproduced.
To this end, the present invention provides a plurality of RGB switching elements and RGB data electrically connected to RGB data lines and applying a data voltage through the RGB data lines. A plurality of demultiplexers having a plurality of initialization switching elements electrically connected to the wires, respectively, for applying an initialization power supply voltage through the RGB data lines, and a plurality of electrically connected to the Algibi (RGB) switching elements of the demultiplexer. Pixel circuits of the demultiplexer, and an initial power supply voltage and an RGB data voltage of the demultiplexer are applied to the Al pixel pixels. An organic light emitting display device is disclosed.
Figure R1020070004862
White balance, organic electroluminescent display, AMOLED, demultiplexer, organic electroluminescent element

Description

Organic Light Emitting Display

1 is a schematic diagram showing the basic structure of a conventional organic electroluminescent device.

2 is a schematic diagram illustrating a basic pixel circuit of a voltage driving method.

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

4 is a block diagram illustrating a basic structure of an organic light emitting display device when the demultiplexer is not used.

5 is a circuit diagram illustrating a pixel circuit according to an exemplary embodiment of the organic light emitting display device of the present invention.

FIG. 6 is a driving timing diagram of the pixel circuit shown in FIG. 5.

FIG. 7 illustrates a current flow during the data writing period T1 in the pixel circuit shown in FIG. 5.

FIG. 8 illustrates a current flow during the threshold voltage storage period T2 of the driving transistor in the pixel circuit shown in FIG. 5.

FIG. 9 illustrates a current flow during the light emitting period T3 in the pixel circuit shown in FIG. 5.

10 is a circuit diagram illustrating a pixel circuit according to another exemplary embodiment of the organic light emitting display device of the present invention.

FIG. 11 illustrates an electrical connection relationship according to an embodiment of the RGB pixel circuits and the demultiplexer of the present invention.

FIG. 12 is a driving timing diagram according to an exemplary embodiment of the Aljibi (RGB) pixel circuits of the present invention shown in FIG.

FIG. 13 is a driving timing diagram according to another exemplary embodiment of the RGB pixel circuits of the present invention shown in FIG. 11.

FIG. 14 illustrates an electrical connection relationship according to another embodiment of the RGB pixel circuits and the demultiplexer of the present invention.

FIG. 15 is a driving timing diagram of an AlGeB (RGB) pixel circuit of the present invention shown in FIG.

<Description of the symbols for the main parts of the drawings>

100; Organic electroluminescent display device according to the present invention

110; A scan signal driver 120; Data signal driver

130; A light emission control signal driver 140; Organic electroluminescent display panel

142; The pixel circuit P 150; First power supply voltage

D [M]; Data line 160; Second power supply

S [N]; Scan line EM [N]; Emission control line

VDD; A first power supply voltage line VSS; Second power supply voltage line

SW_TR1; First switching element SW_TR2; Second switching element

C1; A first capacitive element C2; Second capacitive element

DR_TR; Drive transistor EM_TR; Light emission control transistor

Organic light emitting diode (OLED); Organic electroluminescent element

1000: demultiplexer SW_TR3: Algi ratio (RGB) switching element

SW_TR4: Initializing Switching Device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent display, and more particularly, when an RGB data signal is applied using a demultiplexer (hereinafter referred to as Demux), a white balance in the middle of a light emission period. The present invention relates to a demux driving method for improving a problem in which a white balance is changed over time and a desired color cannot be reproduced by progressing a compensation period.

In addition, the present invention provides a method of driving the pixel circuit in the case of applying an RGB data signal using a demultip lexer (hereinafter referred to as Demux). A demux for applying the RGB data signal during the On period of the light emission control signal regardless of the Off so that the RGB data can be correctly stored in each capacitive element of the pixel circuits. Contains information about the driving method.

In addition, the present invention discloses an invention related to a pixel circuit of an organic light emitting display device. More specifically, by using a smaller number of transistors than conventional pixel circuits, it is possible to achieve high integration and further high resolution of the pixel circuits, and to properly adjust the ratio of the first capacitive element and the second capacitive element in the pixel circuit. An organic light emitting display device capable of compensating a threshold voltage and improving a voltage drop (IR-DROP) phenomenon caused by a first power supply voltage line is disclosed.

Recently, an organic light emitting display device has been spotlighted as a next-generation flat panel display due to advantages such as thin thickness, wide viewing angle, and fast response speed.

Such an organic light emitting display device controls the amount of current flowing through the organic light emitting diode OLED of each pixel, thereby controlling the brightness of each pixel and displaying an image.

In other words, a current corresponding to the data voltage is supplied to the organic EL device, and the organic EL device emits light corresponding to the supplied current. At this time, the applied data voltage has a multi-level value in a predetermined range in order to express the gray scale.

In the case of using a thin film transistor (TFT) using amorphous silicon (a-si) as a driving transistor, current driving capability is relatively low, but the display device has excellent uniformity and an advantage in a large area process.

In the case of a full color organic light emitting display device, a full color is realized by providing an organic light emitting device that emits three colors of red (R), green (G), and blue (B) as an organic light emitting device. However, materials used as the organic electroluminescent layer may be degraded by the heat generated during self-emission. Due to such deterioration, the organic light emitting diode OLED may have a luminance deterioration phenomenon, which may result in a decrease in the lifespan of the organic light emitting diode OLED.

The degree of degradation of the organic electroluminescent layer forming red (R, R), green (G) and blue (Blue, B) in the organic light emitting diode (OLED) is different, respectively, The luminance difference between the (R) organic electroluminescent layer, the green (G) organic electroluminescent layer, and the blue (B) organic electroluminescent layer may increase with time. Therefore, the white balance is changed over time compared to the initial setting value, so that a color coordinate transition occurs, thereby causing a problem in that a desired color cannot be reproduced.

That is, the light emitting layer corresponding to each of red (R), green (G), and blue (B) has different life characteristics, and thus, it is difficult to maintain white balance when driving for a long time.

In addition, in the case where the RGB data signals are applied to the pixel circuits using Demux, the emission control signals applied through the emission control line EM [N] electrically connected to the pixel circuits may be applied. In the off state, the RGB data signals may not be properly stored in the capacitive element in the pixel circuit.

That is, while the Algibi (RGB) data signals (voltage) already stored in the capacitive elements are not initialized, the Demux is continuously driven to continuously apply the Algibi (RGB) data signal (voltage). In this case, there is a problem that correct RGB data signals (voltages) cannot be stored in the capacitive elements.

In addition, the driving transistors of the pixel circuits of the organic light emitting display device may have different threshold voltages Vth, resulting in a problem of lowering uniformity of luminance of the display panel. In addition, as the first power supply voltage line VDD passes each pixel circuit, a voltage drop IR-DROP is generated, and thus the luminance of the pixel decreases toward the lower end of the panel.

In addition, when the pixel circuit of the organic light emitting display device includes a plurality of transistors, it is impossible to achieve high integration, which impedes a high resolution of a display panel equipped with the pixel circuit.

In the above-described conventional circuits for compensating the threshold voltage of the driving transistor in the pixel circuit, a path is formed from the control electrode and the control electrode of the driving transistor toward a negative power source, whereby a leakage current flows through the path. This makes it possible to cause inadequate light emission of the organic electroluminescent device.

The present invention is to overcome the above-mentioned conventional problems,

An object of the present invention is to provide white color compensation in the middle of a light emission period in an organic electroluminescent display device which displays a color by controlling the number of emission or emission intensity of an organic light emitting device representing three primary colors of red, green, and blue. As time goes by, the white balance changes over time, and thus the problem that the desired color cannot be reproduced is improved.

In order to realize the main object of the present invention in detail,

An RGB data signal may be applied to the Demux while the scan signal and the light emission control signal are on.

In addition, a white balance compensation period may be performed while applying the RGB data signal.

During the white balance compensation period, a current flows through the organic electroluminescent device, and a current flows through the organic electroluminescent device for white balance compensation from a long time from green (G), red (R), and blue ( This can be done in the order of B). In addition, the current may be greater than the current flowing through the organic EL device during the light emission period.

As such, the green organic electroluminescent device, which can be said to have the longest lifetime, is supplied with a current for white balance compensation for a longer period of time than the blue organic electroluminescent device having a relatively short lifespan. It can be compensated as a current of.

According to another aspect of the present invention, when applying an RGB data signal using a demultiplexer, the ALG ratio is turned on during the on period of the emission control signal regardless of whether the scan signal is on or off. By applying the (RGB) data signal, the RGB data can be correctly stored in each capacitive element of the pixel circuits.

Another object of the present invention is to achieve high integration and to enable high resolution by using three transistors having a smaller number than the conventional pixel circuit. More specifically, by adjusting the ratio (C1: C2) of the first capacitive element and the second capacitive element appropriately, the uniformity of luminance can be improved by compensating the threshold voltage Vth of the driving transistor. The purpose of the present invention is to improve the voltage drop (IR-DROP) phenomenon caused by the first power voltage line VDD according to the ratio of the second capacitive element.

In addition, an improper light emission of the organic EL device due to the leakage current flowing through the path is avoided by providing a path through which the leakage current can flow from the control electrode of the driving transistor in the pixel circuit toward the negative power source. The purpose is to prevent.

In general, the organic light emitting display panel displays an image by voltage driving or current driving the NxM organic light emitting cells arranged in a matrix form.

Organic electroluminescent device with diode characteristics (generally called OLED)

As shown in FIG. 1, the anode is composed of an anode (ITO), an organic thin film (organic layer), and a cathode (Cathode; Metal). The organic thin film has a light emitting layer (EMitting Layer, EML), an electron transport layer (ETL) for transporting electrons, and a hole transport layer (Hole Transport Layer, HTL) for transporting holes in order to improve hole balance and improve luminous efficiency. It can be made of a multi-layer structure including. In addition, an electron injection layer (EIL) for injecting electrons to one side of the electron transport layer and a hole injection layer for injecting holes to one side of the hole transport layer may be further formed. have.

In addition, in the case of a phosphorescent organic EL device, a hole blocking layer (HBL) may be selectively formed between the emission layer (EML) and the electron transport layer (ETL), and an electron blocking layer EBL may be selectively formed between the emission layer EML and the hole transport layer HTL.

In addition, the organic thin film (organic layer) may be formed in a slim organic light emitting device (Slim OLED) structure to reduce the thickness by mixing the two types of layers. For example, a hole injection transport layer (HITL) structure for simultaneously forming the hole injection layer (HIL) and the hole transport layer (HTL), and the electron injection layer (EIL) and the electron transport layer (ETL) An electron injection transport layer (EITL) structure that is formed at the same time may be selectively formed. The slim organic electroluminescent device as described above has an object of use for increasing luminous efficiency.

In addition, a buffer layer may be selectively formed between the anode and the light emitting layer EML. The buffer layer may be divided into an electron buffer layer that buffers electrons and a hole buffer layer that buffers holes. The electron buffer layer may be selectively formed between the cathode and the electron injection layer EIL, and may be formed in place of the function of the electron injection layer EIL. In this case, the stacked structure of the organic thin film may be an emission layer (EML) / electron transport layer (ETL) / electron buffer layer / cathode. In addition, the hole buffer layer may be selectively formed between the anode and the hole injection layer EIL, and may be formed in place of the function of the hole injection layer HIL. At this time, the laminated structure of the organic thin film may be an anode / hole buffer layer (Hole buffer layer) / hole transport layer (HTL) / light emitting layer (EML).

The possible laminated structure with respect to the above structure is described as follows.

a) Normal Stack Structure

1) anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode

2) anode / hole buffer layer / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode

3) anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / electron buffer layer / cathode

4) anode / hole buffer layer / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / electron buffer layer / cathode

5) Anode / hole injection layer / hole buffer layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode

6) anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron buffer layer / electron injection layer / cathode

b) Normal Slim Structure

1) anode / hole injection transport layer / light emitting layer / electron transport layer / electron injection layer / cathode

2) anode / hole buffer layer / hole injection transport layer / light emitting layer / electron transport layer / electron injection layer / cathode

3) Anode / hole injection layer / hole transport layer / light emitting layer / electron injection transport layer / electron buffer layer / cathode

4) Anode / hole buffer layer / hole transport layer / light emitting layer / electron injection transport layer / electron buffer layer / cathode

5) Anode / hole injection transport layer / hole buffer layer / light emitting layer / electron transport layer / electron injection layer / cathode

6) Anode / hole injection layer / hole transport layer / light emitting layer / electron buffer layer / electron injection transport layer / cathode

c) Inverted Stack Structure

1) cathode / electron injection layer / electron transport layer / light emitting layer / hole transport layer / hole injection layer / anode

2) cathode / electron injection layer / electron transport layer / light emitting layer / hole transport layer / hole injection layer / hole buffer layer / anode

3) cathode / electron buffer layer / electron injection layer / electron transport layer / light emitting layer / hole transport layer / hole injection layer / anode

4) cathode / electron buffer layer / electron injection layer / electron transport layer / light emitting layer / hole transport layer / hole buffer layer / anode

5) cathode / electron injection layer / electron transport layer / light emitting layer / hole transport layer / hole buffer layer / hole injection layer / anode

6) cathode / electron injection layer / electron buffer layer / electron transport layer / light emitting layer / hole transport layer / hole injection layer / anode

d) Inverted Slim Structure

1) cathode / electron injection layer / electron transport layer / light emitting layer / hole injection layer / anode

2) cathode / electron injection layer / electron transport layer / light emitting layer / hole injection transport layer / hole buffer layer / anode

3) cathode / electron buffer layer / electron injection transport layer / light emitting layer / hole transport layer / hole injection layer / anode

4) cathode / electron buffer layer / electron injection transport layer / light emitting layer / hole transport layer / hole injection layer / anode

5) cathode / electron injection layer / electron transport layer / light emitting layer / hole buffer layer / hole injection transport layer / anode

6) Cathode / electron injection transport layer / electron buffer layer / light emitting layer / hole transport layer / hole injection layer / anode

Here, cathode means cathode and anode means anode.

In addition, such an organic light emitting display device may be classified into a voltage programming organic light emitting display device and a current programming organic electroluminescent display device according to a data type written in a data line.

As a driving method of such an organic EL device, a passive matrix method and an active matrix method are known. In the passive matrix method, the anode and the cathode are formed to be orthogonal and the lines are selected and driven, thereby simplifying the manufacturing process and reducing the investment cost. The active matrix method has the advantage of being able to expand to medium-large size by forming active elements such as thin film transistors and capacitive elements in each pixel, with low current consumption and excellent image quality and lifetime.

As described above, in the active matrix method, a pixel circuit configuration based on an organic light emitting device and a thin film transistor is essential. In this case, an amorphous silicon thin film transistor or a polycrystalline silicon thin film transistor is used as the thin film transistor. Referring to FIG. 2, a pixel circuit of an organic light emitting display device is illustrated, and referring to FIG. 3, a driving timing diagram of the pixel circuit illustrated in FIG. 2 is illustrated. This pixel circuit representatively shows one of the N x M pixels.

As shown in FIG. 2, the pixel circuit of the organic light emitting display device includes a scan line S [N] for supplying a scan signal, a data line D [M] for supplying a data signal, and a first power supply voltage. The first power supply voltage line VDD, the second power supply voltage line VSS supplying the second power supply voltage, the driving transistor DR_TR, the switching element SW_TR, the capacitive element C, and the organic electroluminescent element OLED Include. Here, the first power supply voltage may be a voltage of a relatively higher level than the second power supply voltage.

An operation during one frame of the above-described pixel circuit will be described with reference to FIG.

As shown in Fig. 3, the scanning signal is supplied, and then the data signal is supplied with a slight time difference. The reason for the slight time difference is to secure a margin from the turn-on time of the switching element by the supply of the scan signal to the supply time of the data signal.

Referring back to the pixel circuit of FIG. 2 according to the timing diagram of FIG. 3, when the scan signal is supplied from the scan line S [N], the switching element SW_TR is turned on. Therefore, the data signal (voltage) from the data line D [M] is supplied to the control electrode of the driving transistor DR_TR and the first electrode A of the capacitive element C. Therefore, the first power voltage from the first power voltage line VDD is supplied to the organic light emitting diode OLED through the driving transistor DR_TR, so that the organic light emitting diode OLED is constant for one frame. It emits light with brightness. Of course, since the data voltage supplied from the data line D [M] is stored in the capacitive element C, even if the supply of the scan signal from the scan signal line S [N] is interrupted for one frame, The driving transistor DR_TR remains turned on.

However, materials used as the organic electroluminescent layer (for example, DCM2, kinaclean, DPVBi, etc.) may be degraded by the heat generated during self-emission. Due to such deterioration, the organic light emitting diode OLED may have a luminance deterioration phenomenon, which may result in a decrease in the lifespan of the organic light emitting diode OLED.

In addition, the degree of degradation of organic electroluminescent layers forming red (R, R), green (G) and blue (Blue, B) in the organic light emitting diode OLED is different. Therefore, the luminance difference between the red (R) organic electroluminescent layer, the green (G) organic electroluminescent layer, and the blue (B) organic electroluminescent layer may increase with time. As the time changes, the white balance is changed compared to the initial setting value, and thus a color coordinate transition occurs, and thus there is a problem that a desired color cannot be reproduced.

However, when the voltage driving is used in the conventional structure as described above, there is a problem in that it is difficult to obtain a high gradation due to the irregularity of the threshold voltage (Vth) of the thin film transistor (TFT) used as the driving transistor. For example, when driving a pixel at 3V, in order to express an 8-bit 256 gray level, 3/256 = 12 mV has a unit of 10 mV, whereas the threshold voltage Vth of a thin film transistor has a unit of 100 mV. Therefore, there is a problem that it is difficult to express high gradation.

In addition, since the current driving the organic light emitting diode OLED is supplied from the first power supply line VDD, the larger the number of pixels, the greater the amount of current must be supplied from the VDD. Therefore, as the number of pixels increases in the ROW direction, a voltage drop IR-DROP occurs due to the line resistance in the VDD supply line. (Ie V = I x R)

This causes the Vgs value of the TFTs disposed in each pixel to be different, causing a current difference of the organic light emitting diode OLED. This current difference becomes more severe as the area becomes larger, resulting in uneven image quality. do.

Although the pixel circuit may be variously configured for the above-described threshold voltage Vth compensation and compensation of the voltage drop IR-DROP of the VDD line, the pixel circuit may be complicated, and the complexity of the pixel circuit makes it difficult to achieve high integration. do. High integration enables high resolution, and simplification of the pixel circuit is a necessary task for high resolution of an organic light emitting display device.

In addition, when applying Algivy (RGB) data signals to the pixel circuits using Demux, the emission control signals (signal from EM [N]) electrically connected to the pixel circuits are turned off. In this state, the RGB data signals may not be stored correctly in the capacitive element in the pixel circuit. That is, while the Algibi (RGB) data signals (voltage) already stored in the capacitive elements are not initialized, the Demux is continuously driven to continuously apply the Algibi (RGB) data signal (voltage). In this case, there is a problem in that correct RGB data signals (voltages) cannot be stored in the capacitive elements.

In order to solve the above problem, the organic light emitting display device according to the present invention is electrically connected to each of RGB data lines, and a plurality of OLEDs sequentially apply data voltages through the RGB data lines. A demultiplexer electrically connected to an RGB switching element and an RGB data line, the demultiplexer having a plurality of initialization switching elements sequentially applying an initialization power supply voltage through the RGB data lines; And a plurality of RGB pixel circuits electrically connected to the RGB switching elements of the demultiplexer, wherein the demultiplexer is configured to apply a turn-on light emission control signal to the RGB pixel circuits. An initializing power supply voltage and an RGB data voltage may be applied.

The RGB data voltage may be applied in the order of green (G) data voltage, red (R) data voltage, and blue (B) data voltage.

The initialization power supply voltage may be applied before the RGB data voltages.

While the turn-on scan signal is applied to the RGB pixel circuits, the RGB data voltages of the demultiplexer may be applied.

Each of the RGB pixel circuits may be electrically connected to a common scan line and a common emission control line.

Each of the RGB pixel circuits may be electrically connected to a common first power supply voltage line and a common second power supply voltage line.

The image display period of one frame is divided into a white balance compensation period and a light emission period, and the emission period may be longer than the white balance compensation period.

The white balance compensation may be performed while a turn-on scan signal is applied to the RGB pixel circuits.

During the emission period, a turn-off scan signal and a turn-on emission control signal may be applied to the RGB pixel circuits.

During the white balance compensation period, a current for white balance compensation may flow in the green organic EL device, the red organic EL device, and the blue organic EL device.

The current flowing through the organic EL device during the white balance compensation period may be greater than the current flowing through the organic EL device during the light emission period.

The time for allowing a current to flow in the organic electroluminescent device for white balance compensation may be made in the order of green (G), red (R), and blue (B) from the longer time.

The RGB pixel circuits,

A first switching device electrically connected to a scan line and a data line, a control electrode connected to the scan line, and electrically connected between a control electrode of the driving transistor and the data line, and a control electrode connected to the first switching device. A driving transistor connected to the first power supply line and electrically connected between the first power supply voltage line and the second power supply voltage line, a first capacitive element electrically connected between the first switching element, the first power supply voltage line, and the driving transistor; A second switching element, a first switching element, the first capacitive element, the second switching element, and the driving device, wherein a control electrode is electrically connected to a line, and is electrically connected between the first power supply voltage line and the driving transistor. A second capacitive element electrically connected between a transistor, the driving transistor, and the second power supply It may include an organic electroluminescent device electrically connected between the wire.

In the first switching device, a control electrode may be electrically connected to the scan line, a first electrode may be connected to the data line, and a second electrode may be connected to the control electrode of the driving transistor.

In the first switching device, a control electrode is electrically connected to the scan line to apply data from the first electrode to the second electrode.

In the driving transistor, a control electrode is electrically connected to a second electrode of the first switching device, a first electrode is connected to a second electrode of the second switching device, and a second electrode is an anode of the organic electroluminescent device. It can be electrically connected to the electrode.

In the driving transistor, a control electrode may be electrically connected to the second electrode of the first switching device to control the driving current from the first power voltage line.

In the first capacitive element, a first electrode may be electrically connected to the first power supply voltage line, and a second electrode may be electrically connected to a second electrode of the first switching element and a control electrode of the driving transistor.

In the first capacitive element, a first electrode may be electrically connected to the first power voltage line, and a second electrode may be electrically connected to a second electrode of the second capacitive element.

In the second switching device, a control electrode may be electrically connected to the emission control line, a first electrode may be electrically connected to the first power supply voltage line, and a second electrode may be electrically connected to the first electrode of the driving transistor. have.

In the second switching device, a control electrode is electrically connected to the emission control line, a first electrode is electrically connected to the first power supply voltage line, and a second electrode is electrically connected to the first electrode of the second capacitive element. Can be connected.

In the second capacitive element, a first electrode is electrically connected to a second electrode of the second switching element and a first electrode of the driving transistor, and the second electrode is a second electrode of the first capacitive element and the first electrode. The second electrode of the switching device and the first electrode of the driving transistor may be electrically connected.

The second capacitive element may be electrically connected between a control electrode of the driving transistor and a first electrode of the driving transistor.

In the organic EL device, an anode electrode may be electrically connected to a second electrode of the driving transistor, and a cathode electrode may be electrically connected to the second power voltage line.

The first switching element, the second switching element, and the driving transistor may be N-type channel transistors.

The first switching element, the second switching element, and the driving transistor may be a P-type channel transistor.

The second power supply voltage of the second power supply voltage line may be lower than the first power supply voltage of the first power supply voltage line.

The second power supply voltage of the second power supply voltage line may be a ground voltage.

An emission control switching device may be further included between the driving transistor and the organic light emitting device.

The control electrode of the emission control switching device is electrically connected to the emission control line, and the first electrode of the emission control switching device is electrically connected to the second electrode of the driving transistor. The second electrode may be electrically connected to the anode electrode of the organic electroluminescent device.

As described above, in the organic electroluminescent display device according to the present invention, when the RGB data signal is applied using a demultiplexer, the white balance is increased by passing the white balance compensation period in the middle of the emission period. It is characteristic to improve the problem that it becomes different and cannot reproduce a desired color.

Looking at the driving method in detail,

An RGB data signal may be applied to the Demux while the scan signal and the light emission control signal are on.

In addition, a white balance compensation period may be performed while applying the RGB data signal.

During the white balance compensation period, a current flows through the organic electroluminescent device, and a current flows through the organic electroluminescent device for white balance compensation from a long time from green (G), red (R), and blue ( This can be done in the order of B). In addition, the current may be greater than the current flowing through the organic EL device during the light emission period.

As such, the green organic electroluminescent device, which can be said to have the longest lifetime, is supplied with a current for white balance compensation for a longer time than the blue organic electroluminescent device having a relatively short lifespan. It can be compensated as a current.

Hereinafter, preferred 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.

In order to clearly describe the present invention, parts not related to the present invention are omitted in the accompanying drawings. The same reference numerals are used to designate parts having similar configurations and operations throughout the specification. When a part is electrically connected to another part, this includes not only an electrically connected part but also a case where another part is connected in between.

Referring to FIG. 4, the configuration of the organic light emitting display device when the demultiplexer is not used is shown as a block diagram.

As shown in FIG. 4, the organic light emitting display device 100 includes a scan signal driver 110, a data signal driver 120, a light emission control signal driver 130, and an organic light emitting display panel 140 (hereinafter, referred to as a panel). 140), a first power supply voltage supply unit 150, and a second power supply voltage supply unit 160.

The scan signal driver 110 may sequentially supply scan signals to the panel 140 through a plurality of scan lines S [1], S [N].

The data signal driver 120 may supply a data signal to the panel through a plurality of data lines D [1], ..... D [M].

The emission control signal driver 130 may sequentially supply emission control signals to the panel 140 through a plurality of emission control lines EM [1] .. EM [N].

In addition, the panel 140 has a plurality of scanning lines S [1], S [N] and emission control lines EM [1] .. EM [N] arranged in a column direction and a row direction. A plurality of data lines D [1], ... D [M] arranged together with the scanning lines S [1], S [N], and the emission control lines EM [1] .., EM Pixel circuits 142 and Pixel defined by [N]) and data lines D [1], ... D [M].

The pixel circuit 142 (Pixel) may be formed in the pixel area defined by the scan line and the data line. Of course, as described above, a scan signal may be supplied from the scan signal driver 110 to the scan lines S [1] and S [N], and the data lines D [1], ... D A data signal may be supplied from the data driver 120 to [M], and a light emission control signal from the light emission control signal driver 130 may be supplied to the light emission control signal lines EM [1] .. EM [N]. Can be supplied.

In addition, the first power supply voltage supply unit 150 and the second power supply voltage supply unit 160 serve to supply the first power supply voltage and the second power supply voltage to each pixel circuit 142 of the panel 140. .

Meanwhile, as shown in FIG. 4, the scan signal driver 110, the data signal driver 120, the emission control signal driver 130, the panel 140, the first power voltage supply unit 150, and the second power voltage. The supply unit 160 may be all formed on one substrate 102.

In particular, the driving units and the power supply units 110, 120, 130, 150, and 160 are scan lines S [1], S [N], data lines D [1], D [M], and light emission control lines EM. [1] .., EM [N]) and the transistor (not shown) of the pixel circuit 142 may be formed on the same layer. Of course, the driving units and the power supply units 110, 120, 130, 150, and 160 may be formed on another substrate (not shown) separately from the substrate 102, and may be electrically connected to the substrate 102. In addition, the driving units and the power supply units 110, 120, 130, 150, and 160 are a tape carrier package (TCP), a flexible printed circuit (FPC), a tape automatic bonding (TAB), and a chip on glass (COG) electrically connected to the substrate 102. And the equivalents may be formed in any one selected form, and the present invention is not limited to the shape and the formation position of the driving unit and the power supply (110, 120, 130, 150, 160).

Referring to FIG. 5, a pixel circuit of an organic light emitting display device according to the present invention is illustrated. The pixel circuits described below all refer to one pixel circuit Pixel of the organic light emitting display device 100 illustrated in FIG. 4.

As shown in FIG. 5, the pixel circuit of the organic light emitting display device according to the present invention includes a scan line S [N], a data line D [M], a light emission control line EM [N], and a first pixel. The power supply voltage line VDD, the second power supply voltage line VSS, the first switching element SW_TR1, the second switching element SW_TR2, the driving transistor DR_TR, the first capacitive element C1, and the second capacitive element C2. ) And an organic electroluminescent element (OLED).

The scan line S [N] supplies a scan signal for selecting the organic light emitting diode OLED to be turned on to the control electrode of the first switching device SW_TR1. The scan line S [N] may be electrically connected to the scan signal driver 110 (see FIG. 4) that generates the scan signal.

The data line D [M] may transmit a data signal (voltage) proportional to light emission luminance, a second electrode of the first capacitive element C1, a second electrode of the second capacitive element C2, and the driving transistor. It serves to supply to the control electrode of DR_TR. Of course, the data line D [M] may be electrically connected to the data signal driver 120 (see FIG. 4) that generates the data signal.

The emission control line EM [N] is electrically connected to a control electrode of the second switching element SW_TR2 to supply an emission control signal. When the second switching device SW_TR2 is turned on by the light emission control signal, a first power supply voltage is applied from the first power supply voltage line VDD to the first electrode of the first capacitive device C1 and the second capacitive device ( The first electrode of C2 and the first electrode of the driving transistor DR_TR may be applied. Of course, the emission control line EM [N] may be electrically connected to the emission control signal driver 130 (see FIG. 4) that generates the emission control signal.

The first power supply voltage line VDD allows a first power supply voltage to be supplied to the organic light emitting diode OLED. Of course, the first power supply voltage line VDD may be electrically connected to the first power supply voltage supply unit 150 (see FIG. 4) that supplies the first power supply voltage.

The second power supply voltage line VSS allows the second power supply voltage to be supplied to the organic light emitting diode OLED. Of course, the second power supply voltage line VSS may be electrically connected to the second power supply voltage supply unit 160 (see FIG. 4) that supplies the second power supply voltage. In this case, the first power supply voltage may be generally higher than the second power supply voltage.

In addition, the second power supply voltage may use a ground voltage.

The first switching device SW_TR1 has a first electrode (source or drain electrode) electrically connected to the data line D [M], and a second electrode (source or drain electrode) is connected to the driving transistor DR_TR. Control electrode (gate electrode), the second electrode of the first capacitive element C1 and the second electrode of the second capacitive element C2 are electrically connected, and a control electrode (gate electrode) is connected to the scan line S [N]) may be electrically connected. The first switching element SW_TR1 may be a P-type channel transistor, and when the low level scan signal is applied to the control electrode through the scan line S [N], the data line D [M] The data voltage is applied to the second electrode of the first capacitive element C1, the second electrode of the second capacitive element C2, and the control electrode of the driving transistor DR_TR.

In the driving transistor DR_TR, a first electrode is electrically connected to the first electrode of the second capacitive element C2 and the second electrode of the second switching element SW_TR2, and the second electrode is the organic electroluminescence. The second electrode of the first switching element SW_TR1, the second electrode of the first capacitive element C1, and the second capacitive element are electrically connected to the anode of the device OLED. It may be electrically connected to the second electrode of (C2). The driving transistor DR_TR may be a P-type channel transistor. In operation, when a low level signal is applied through the control electrode and turned on, a predetermined amount of current is supplied from the first power voltage line VDD to the organic light emitting diode OLED. Of course, since the data signal is supplied to the capacitive element to charge it, even if the first switching element SW_TR1 is turned off and the electrical connection with the data line D [M] is broken for a certain period of time. The low level signal may be continuously applied to the control electrode of the driving transistor DR_TR by the voltage charged in the capacitive element.

The driving transistor DR_TR may be any one selected from an amorphous silicon thin film transistor, a polysilicon thin film transistor, an organic thin film transistor, a nano thin film transistor, and an equivalent thereof, but is not limited thereto.

In addition, when the driving transistor DR_TR is a polysilicon thin film transistor, as a crystallization method, a laser crystallization method (ELA) using an excimer laser and a metal catalyst crystallization method (MIC: Metal) using a metal catalyst (Promoting Material) Induced crystallization (SPC), solid phase crystallization (SPC), high pressure annealing (HPA) method for crystallization in high temperature and high humidity, and the use of additional masks (SLS: Sequential Lateral Solidfication methods are available.

There is also a micro silicon having a grain size between amorphous silicon (a-Si) and polycrystalline silicon (Poly Silicon).

The microsilicon generally refers to a grain size of 1 nm to 100 nm. The electron mobility of the microsilicon is 1 to 50 or less and the hole mobility is 0.01 to 0.2 or less. The microsilicon is characterized in that the size of the crystal grains are smaller than the polycrystalline silicon, and the protrusion region between the grains is smaller than that of the polysilicon, so that the electrons do not interfere when the electrons move between the grains, thereby showing uniform characteristics. The microsilicon grains can be classified into a thermal crystallization method and a laser crystallization method. The thermal crystallization method includes a method of obtaining an amorphous silicon and simultaneously obtaining a crystallization structure and a reheating method.

The thin film transistor (TFT) of the present invention may be formed by any one selected from the above crystallization methods and equivalent methods, but the present invention is not limited to the method of manufacturing the polysilicon thin film transistor.

The laser crystallization method is the most widely used method of crystallizing a thin film transistor with polysilicon (Poly Silicon). Not only can the crystallization method of the existing polycrystal liquid crystal display device be used as it is, but the process method is simple and the technology development of the process method is completed.

The metal catalyst crystallization method is one of methods that can be crystallized at low temperature without using the laser crystallization method. Initially, the metal catalyst metal, Ni, Co, Pd, Ti, etc., is deposited or spin-coated on the surface of the amorphous silicon (a-Si) so that the metal catalyst metal penetrates directly into the surface of the amorphous silicon to change the phase of the amorphous silicon. Crystallization method has the advantage that can be crystallized at low temperature.

Another method of the metal catalyst crystallization method has an advantage of suppressing the contamination of nickel silicide in a specific region of the thin film transistor using a mask when interposing a metal layer on the surface of the amorphous silicon. The crystallization method is referred to as metal catalyst induced side crystallization (MILC). A shadow mask may be used as a mask used in the metal catalyst-induced side crystallization method, and the shadow mask may be a linear mask or a pointed mask.

Another method of the metal catalyst crystallization method is a metal catalyst induction capping layer that controls the amount of metal catalyst introduced into the amorphous silicon through a capping layer first when depositing or spin coating a metal catalyst layer on the surface of the amorphous silicon. There is a crystallization method (MICC: Metal Induced Crystalization with Capping Layer). A silicon nitride layer may be used as the capping layer. The amount of the metal catalyst flowing into the amorphous silicon from the metal catalyst layer varies according to the thickness of the silicon nitride film. In this case, the metal catalyst flowing into the silicon nitride film may be formed on the entire silicon nitride film, or may be selectively formed using a shadow mask or the like. The capping layer may be selectively removed after the metal catalyst layer has crystallized the amorphous silicon into polycrystalline silicon. The capping layer may be removed by using a wet etching method or a dry etching method. In addition, after the polycrystalline silicon is formed, a gate insulating film is formed and a gate electrode is formed on the gate insulating film. An interlayer layer may be formed on the gate electrode. After forming a via hole on the interlayer insulating layer, impurities may be introduced into the crystallized polysilicon through the via hole to further remove metal catalyst impurities formed therein. A method of additionally removing the metal catalyst impurities is called a gettering process. The gettering process includes a heating process of heating the thin film transistor at a low temperature in addition to the process of injecting the impurities. Through the gettering process, a high quality thin film transistor can be realized.

In addition, when the driving transistor DR_TR is manufactured by the metal catalyst crystallization method, the driving transistor DR_TR includes nickel (Ni), cadmium (Cd), cobalt (Co), titanium (Ti), and palladium (Pd). , Tungsten (W), aluminum (Al), and any one of the equivalents may be further included.

In the organic light emitting diode OLED, an anode electrode may be electrically connected to a second electrode of the driving transistor DR_TR, and a cathode electrode may be electrically connected to a second power voltage line VSS. . The organic light emitting diode OLED emits light at a predetermined brightness by a current controlled by the driving transistor DR_TR while the second switching device SW_TR2 is turned on.

The organic light emitting diode OLED may include a light emitting layer (not shown), and the light emitting layer may be any one selected from a fluorescent material, a phosphorescent material, a mixture thereof, and an equivalent thereof. However, the material or type of the light emitting layer is not limited thereto.

In addition, the light emitting layer may be any one selected from a red light emitting material, a green light emitting material, a blue light emitting material, a mixture thereof, and an equivalent thereof, but is not limited thereto.

In the second switching device SW_TR2, a first electrode is electrically connected to the first power voltage line VDD and the first electrode of the first capacitive device C1, and the second electrode is connected to the second capacitive device ( The first electrode of C2 and the first electrode of the driving transistor DR_TR may be electrically connected, and a control electrode may be electrically connected to the emission control line EM [N]. The second switching device SW_TR2 may be a P-type channel transistor. When the low level signal is applied to the control electrode through the emission control line EM [N], the second switching device SW_TR2 is turned on from the first power voltage line VDD. Current flows to the organic electroluminescent device (OLED).

In the first capacitive element C1, a first electrode is electrically connected to a first electrode of the first power supply voltage line VDD and the second switching element SW_TR2, and a second electrode is connected to the second capacitive element ( The second electrode of C2, the second electrode of the first switching device SW_TR1, and the control electrode of the driving transistor DR_TR may be electrically connected to each other.

In the second capacitive element C2, a first electrode is electrically connected to a second electrode of the second switching element SW_TR2 and a first electrode of the driving transistor DR_TR, and the second electrode is connected to the first capacitor. The second electrode of the component C1, the second electrode of the first switching device SW_TR1, and the control electrode of the driving transistor may be electrically connected to each other.

The capacitive element maintains the data signal voltage and the threshold voltage of the driving transistor for a period of time, and a low level signal is applied to the control electrode of the second switching element SW_TR2 by the emission control line EM [N]. When turned on, a current proportional to the magnitude of the data signal flows from the first power supply voltage line to the organic light emitting device, thereby causing the organic light emitting device to emit light. In addition, by adjusting the ratio (C1: C2) of the first capacitive element and the second capacitive element in various manners, effects such as IR-DROP compensation or threshold voltage compensation of a driving transistor, which are described below, can be achieved.

The first switching device SW_TR1, the driving transistor DR_TR, and the second switching device SW_TR2 may be any one selected from a P-type channel transistor and its equivalent, but the type of the transistor is not limited thereto. .

Referring to FIG. 6, a driving timing diagram of the pixel circuit shown in FIG. 5 is illustrated. As illustrated in FIG. 6, one frame may be divided into a first period, a second period, and a third period in the pixel circuit of the organic light emitting display according to the present invention. More specifically, one frame may include a data writing period T1, a threshold voltage storing period T2 of the driving transistor, and a light emitting period T3. The ratio between the data writing period T1 and the threshold voltage storing period T2 of the driving transistor and the light emitting period T3 may be variously formed. Preferably, the data writing period T3 is compared to the light emitting period T3. T1) and the threshold voltage storage period T2 of the driving transistor are preferably short.

Referring to FIG. 7, the current flow during the data write period T1 in the pixel circuit shown in FIG. 5 is illustrated. Here, the operation of the pixel circuit will be described with reference to the timing diagram of FIG. 6.

First, a low level scan signal is applied from the scan line S [N] to the control electrode of the first switching device SW_TR1, thereby turning on the first switching device SW_TR1 and controlling the second switching device SW_TR2. The second switching device SW_TR2 is turned on by applying a low level signal of the emission control line EM [N] to an electrode.

As the first switching device SW_TR1 is turned on, the data voltage Vdata of the data line D [M] is applied from the first electrode of the first switching device SW_TR1 toward the second electrode. The data voltage is applied to the second electrode of the first switching element SW_TR1, the second electrode of the first capacitive element C1, the second electrode of the second capacitive element C2, and the control electrode of the driving transistor DR_TR. Vdata) can be applied.

At this time, as the second switching device SW_TR2 is turned on, a first power supply voltage is applied from the first electrode of the second switching device SW_TR2 toward the second electrode from the first power supply voltage line VDD. The first power supply voltage may be applied to a second electrode of the second switching element SW_TR2, a first electrode of the second capacitive element C2, and a first electrode of the driving transistor DR_TR.

In addition, a first power supply voltage from the first power supply voltage line VDD may be applied to the first electrode of the first capacitive element C1.

During this period, since the driving transistor DR_TR is turned off and no current flows to the organic light emitting diode OLED, the organic light emitting diode OLED does not emit light.

In other words, the control electrode (gate electrode) of the driving transistor DR_TR, the second electrode of the second capacitive element C2, and the second electrode of the first capacitive element C1 during the data writing period T1. A voltage of Vdata is applied (Vg = Vdata), a first electrode (source electrode) of the driving transistor DR_TR, a first electrode of the second capacitive element C2 and a first of the first capacitive element C1 A voltage of VDD is applied to one electrode (Vs = VDD). Therefore, the voltages VDD-Vdata are stored for a predetermined period by the capacitive elements as much as the value obtained by subtracting the data voltage Vdata from the first power supply voltage VDD.

Referring to FIG. 8, the current flow during the threshold voltage storage period T2 of the driving transistor in the pixel circuit shown in FIG. 5 is illustrated. Here, the operation of the pixel circuit will be described with reference to the timing diagram of FIG. 6.

First, a low level scan signal is applied from the scan line S [N] to the control electrode of the first switching device SW_TR1, thereby turning on the first switching device SW_TR1 and controlling the second switching device SW_TR2. The second switching device SW_TR2 is turned off by applying a high level signal of the emission control line EM [N] to the electrode.

As the first switching device SW_TR1 is turned on, the data voltage Vdata of the data line D [M] is applied from the first electrode of the first switching device SW_TR1 toward the second electrode. The data voltage is applied to the second electrode of the first switching element SW_TR1, the second electrode of the first capacitive element C1, the second electrode of the second capacitive element C2, and the control electrode of the driving transistor DR_TR. (Vdata) can be applied.

In this case, as the second switching device SW_TR2 is turned off, the first power supply voltage from the first power supply voltage line VDD may be applied only to the first electrode of the first capacitive element C1.

During this period, since the driving transistor DR_TR is turned off and no current flows to the organic light emitting diode OLED, the organic light emitting diode OLED does not emit light.

In other words, the control electrode (gate electrode) of the driving transistor DR_TR, the second electrode of the second capacitive element C2, and the first capacitive element C1 during the threshold voltage storage period T2 of the driving transistor. The voltage of Vdata is applied to the second electrode of (Vg = Vdata), and the voltage of VDD is applied to the first electrode of the first capacitive element C1. Therefore, the value VDD-Vdata obtained by subtracting the data voltage from the first power supply voltage VDD is stored in the first capacitive element C1 for a predetermined period.

At this time, the voltage Vs of the first electrode (source electrode) of the driving transistor DR_TR is a value obtained by adding the threshold voltage Vth of the driving transistor DR_TR to the data voltage Vdata (Vs = Vdata +). Vth) and the second capacitive element C2 includes a control electrode voltage of the driving transistor DR_TR at the first electrode voltage (source electrode voltage, Vs = Vdata + Vth) of the driving transistor DR_TR (gate electrode voltage, The value Vth minus Vg = Vdata is stored for a certain period of time.

Referring to the driving timing diagram of FIG. 6, a high level signal is applied from the scan line S [N] to the control electrode of the first switching element SW_TR1 between the second period T2 and the third period T3. As a result, the first switching device SW_TR1 is turned off, and a high level signal is applied from the emission control line EM [N] to the control electrode of the second switching device SW_TR2, thereby providing the second switching device SW_TR2. Is turned off.

Therefore, during this period, the voltage value stored in the capacitive element during the second period T2 is maintained.

Referring to FIG. 9, a current flow during the light emitting period T3 in the pixel circuit shown in FIG. 5 is illustrated. Here, the operation of the pixel circuit will be described with reference to the driving timing diagram of FIG. 6.

First, a high level signal is applied to the control electrode of the first switching element SW_TR1 from the scan line S [N] to turn off the first switching element SW_TR1 and to control the second switching element SW_TR2. The second switching device SW_TR2 is turned on by applying a low level signal of the emission control line EM [N] to an electrode.

As the first switching device SW_TR1 is turned off, the data voltage Vdata of the data line D [M] can no longer be applied to the pixel circuit.

At this time, as the second switching device SW_TR2 is turned on, the first power supply voltage is applied from the first electrode of the second switching device SW_TR2 toward the second electrode from the first power supply voltage line VDD. The first power supply voltage may be applied to the first electrode (source electrode) of the transistor DR_TR. The current generated by the first power supply voltage VDD may flow through the organic light emitting diode OLED in the direction of the second power supply voltage line VSS during the light emission period T3, and thus, the organic light emitting diode OLED. To emit light.

During the light emission period T3, the voltage Vs of the first electrode (source electrode) of the driving transistor DR_TR becomes VDD, and the voltage Vg of the control electrode (gate electrode) of the driving transistor DR_TR. And the source-gate voltage Vsg of the driving transistor DR_TR may be expressed by Equation 1 below.

Figure 112007004511439-pat00001

Figure 112007004511439-pat00002

Figure 112007004511439-pat00003

Figure 112007004511439-pat00004

In this case, the current flowing through the organic light emitting diode OLED may be expressed by Equation 2 below.

Figure 112007004511439-pat00005

That is, the present invention stores the threshold voltage Vth of the driving transistor DR_TR in the second capacitive element C2 during the second period T2, and then stores the data voltage Vdata and the data voltage during the light emission period T3. It is characterized by a method of representing data by the ratio of C1 and C2.

At this time, the optimal ratio of C1 and C2 varies depending on the distribution of the threshold voltage Vth of the driving transistor included in each pixel circuit. For example, if the distribution of the threshold voltage Vth in the panel of the organic light emitting display device is 0.1V, there may be no problem in image quality. If the distribution of the threshold voltage Vth of the process is 0.5V, Image quality problems may occur. In the above case, if the ratio of C1 and C2 is 1 to 5 (C1: C2 = 1: 5), even if the distribution of the threshold voltage (Vth) of the process is 0.5V, the distribution of the threshold voltage (Vth) felt by the panel is 0.1V. It can be made smaller so that there is no problem of image quality.

If the value of C2 is greater than the value of C1 (C2 >> C1), C2 / (C1 + C2) may be approximately 1. In this case, the value of Vsg of Equation 1 remains only Vth. When the value is substituted by the I OLED of Equation 2, the threshold voltage Vth of the driving transistor may be compensated for by the current flowing through the organic light emitting diode OLED.

However, if the value of C2 is much greater than the value of C1 and C2 / (C1 + C2) becomes 1, Vsg becomes Vth. In this case, Vsg of the driving transistor DR_TR is Vth no matter how the data voltage Vdata changes. As can be seen from Equation 2, the data voltage Vdata does not appear in the current formula of the organic light emitting diode, and thus there is a problem in that a desired current cannot be generated according to the data voltage Vdata. In other words, this means that the data range grows indefinitely. However, if the value of C1 is adjusted to be much larger than the value of C2, C2 / (C1 + C2) becomes approximately 0, and Vsg of Equation 1 becomes VDD-Vdata, in which case the data voltage Vdata Although a desired current may be generated, compensation of the threshold voltage Vth of the driving transistor DR_TR or compensation of the voltage drop IR-DROP of the first power voltage line VDD may not be performed properly.

In other words, the organic light emitting diode display according to the present invention adjusts the ratio of C1 and C2 appropriately so that the voltage drop IR-DROP due to the threshold voltage Vth of the driving transistor DR_TR and the first power voltage line VDD. Can compensate.

For example, if C2 / (C1 + C2) is 0.5, Vsg = VDD-Vdata-0.5 VDD + 0.5Vdata + 0.5Vth, and the data range is doubled, and the threshold of the driving transistor DR_TR is increased. The influence of the voltage Vth and the voltage drop IR-DROP of the first power voltage line VDD can be reduced by half. That is, it is preferable to minimize the influence of the threshold voltage Vth of the driving transistor DR_TR and the voltage drop IR-DROP of the first power voltage line VDD by adjusting the value of C2 larger than the value of C1. .

In addition, the circuits for compensating the threshold voltage of the driving transistor and the voltage drop of the first power supply voltage line require a larger number of elements than the pixel circuit according to the present invention, which may cause difficulty in high integration. However, the pixel circuit according to the present invention can achieve high integration by using only three transistors and two capacitive elements, and accordingly, a high resolution organic electroluminescent display device can be realized.

In addition, in a circuit for compensating the threshold voltage of the driving transistor, a path may be formed from the control electrode (gate electrode) of the driving transistor toward a negative power supply, such that leakage current may flow. Will be. If the leakage current (off current of the driving transistor) is large, although a black image should be expressed, leakage current may flow into the organic light emitting diode (OLED) to cause inappropriate light emission. . Since the leakage characteristics of the driving transistors in the panel are all different, some pixels having a large leakage characteristic may emit light even when a black image is to be represented. Such a phenomenon may reduce the leakage current of the driving transistor by applying reverse aging to the driving transistor, thereby reducing the above-mentioned improper light emission. However, the pixel circuit according to the present invention is composed of three transistors and two capacitive elements, and a path through which leakage current flows from the control electrode of the driving transistor toward the negative power source exists. In this case, it is not necessary to apply reverse aging of the driving transistor described above.

The data write period T1 and the threshold voltage storage period T2 of the driving transistor may be shorter than the emission period T3 so that the organic light emitting diode OLED emits light.

Referring to FIG. 10, a pixel circuit according to another embodiment of the pixel circuit shown in FIG. 5 is illustrated. The pixel circuit shown in FIG. 10 is similar to the pixel circuit shown in FIG. However, in the pixel circuit illustrated in FIG. 10, the light emission control switching element EM_TR is further included in the pixel circuit illustrated in FIG. 5.

In the emission control switching device EM_TR, a control electrode is electrically connected to the emission control line EM [N], a first electrode is electrically connected to a second electrode of the driving transistor, and the second electrode is organic. It is electrically connected to the anode electrode of the electroluminescent element (OLED). The light emission control transistor may control a current flowing through the organic light emitting diode OLED in a direction from the first power voltage line VDD to the second power voltage line VSS. That is, when a low level signal is applied from the emission control line EM [N] to the control electrode of the emission control switching element EM_TR during the emission period T3, the emission control switching element EM_TR is turned on. Accordingly, the organic light emitting diode OLED may emit light through a current flowing from the first power voltage line VDD to the second power voltage line VSS through the organic light emitting diode OLED. .

The emission control switching device EM_TR may use a P-type channel transistor as shown in FIG. 10.

Referring to FIG. 11, an electrical connection relationship according to an embodiment of the Aljibi (RGB) pixel circuits and the demultiplexer of the present invention is shown.

The demultiplexer 1000 according to the present invention is a demultiplexer having a layout structure for each of the RGB data signals in the data signal driver of the organic light emitting display device.

Recently, as the high resolution is required, the data line of the organic light emitting display device is increased, and more integrated circuits are included in the data signal driver driving the organic light emitting display device. In order to solve this problem, a demultiplexer in which the number of output lines of the data signal driver is reduced is used. The demultiplexer includes a plurality of data signal supply switching elements commonly connected to an output line of the data signal driver, and these data signal supply switching elements are electrically connected to predetermined data lines, respectively. Accordingly, the demultiplexer sequentially supplies the data signal to each data line through the operation of the data signal supply switching element.

Herein, RGB means red, red, green, and blue. In FIG. 11, three pixel circuits are electrically connected to the demultiplexer 1000, but the present invention is not limited thereto. In addition, the data signal may be applied to the pixel circuits using a plurality of demultiplexers, and the present invention is not limited to the number of demultiplexers used.

Referring to the demultiplexer 1000, a red data line, a green data line, and a blue data line are electrically connected to the data lines D [M] of the pixel circuits, respectively. In addition, each of the RGB ratio RGB data lines is electrically connected to the RGB ratio switching element SW_TR3. The switching device may again include a red data line switching device SW_TR3R, a green data line switching device SW_TR3G, and a blue data line switching device SW_TR3B. Al control ratio control signals may be applied to the control electrodes of the Al switching ratio (RGB) switching elements, respectively, through the control lines CR, CG, and CB.

When the RGB switching device is turned on by the RGB control signals CR, CG, and CB, data suitable for each RGB pixel circuit from the data signal driver through a demultiplexer is transmitted. A signal (voltage) can be applied.

The RGB switching elements may be a P-type channel transistor, but the present invention is not limited to the type of the transistor.

12 and 13, a driving timing diagram according to one embodiment and another embodiment of the RGB pixel circuits of the present invention illustrated in FIG. 11 is illustrated.

First, the operation of the RGB pixel circuits according to the present invention shown in FIG. 11 will be described with reference to the driving timing diagram of FIG. 12.

When a low level scan signal is applied through the scan line S [N], each of the first switching elements SW_TR1 of the RGB pixel circuits is turned on and is turned low through the emission control line EM [N]. When the emission control signal is applied, each of the second switching elements SW_TR2 of the RGB pixel circuits may be turned on.

As described above, in the method of driving the organic light emitting display device according to the exemplary embodiment of the present invention illustrated in FIG. 12, an Al control ratio (RGB) control line (i. A low level signal is applied through the CR, CG, and CB to turn on the RGB switching elements SW_TR3. Thus, the RGB data signal can be applied during the period.

Of course, in the case of using the P-type channel transistor as shown in Figure 11, when the low-level signal is applied is turned on, as described above, when using the N-type channel transistors, the high-level signal The driving timing diagram may be different, such as turning on when it is applied, and the technical spirit of the present invention is not limited to the type of transistor and the driving timing diagram.

Next, the operation of the RGB pixel circuits according to the present invention shown in FIG. 11 will be described with reference to the driving timing diagram of FIG. 13.

When a high level scan signal is applied through the scan line S [N], each of the first switching elements SW_TR1 of the RGB pixel circuits is turned off and turned low through the emission control line EM [N]. When the light emission control signal of the level is applied, each of the second switching elements SW_TR2 of the RGB pixel circuits may be turned on.

As described above, in the method of driving the organic light emitting display device according to another exemplary embodiment of the present invention illustrated in FIG. 13, an algibi ( A low level signal is applied through the RGB control lines CR, CG, and CB to turn on the RGB switching elements SW_TR3. Thus, the RGB data signal can be applied during the period.

Of course, when the high level scan signal is applied to the control electrode of the first switching device SW_TR1 of the pixel circuit, the first switching device SW_TR1 is turned off. Therefore, the RGB data signal cannot be immediately applied to the capacitive element of the pixel circuit during the turn-off scan signal. However, after the data signal (voltage) is charged by the parasitic capacitor Cd formed on the data lines D [M], the turn-on scan signal controls the first switching device SW_TR1 of the pixel circuit. When the first switching device SW_TR1 is turned on and is applied to an electrode, data signals charged by parasitic capacitors Cd formed in the data lines D [M] through the first switching device SW_TR1 are stored. Can be applied. The parasitic capacitance Cd may be greater than the capacitance of the first capacitive element C1 and the second capacitive element C2 in the pixel circuit.

Of course, when the P-type channel transistor is used as shown in FIG. 11, when the low level signal is applied, the signal is turned on. However, as described above, when the N-type channel transistor is used, the high level signal is applied. The driving timing diagrams may be different, for example, when they are turned on. However, the technical spirit of the present invention is not limited to the type of transistor and the driving timing diagram.

As described above, regardless of whether a low level signal or a high level signal is applied from the scan line S [N], the low level signal is applied during the period during which the low level signal is applied from the emission control line EM [N]. The reason for turning on the algibi RGB switching elements SW_TR3 by applying a low level signal through the algibi RGB control lines CR, CR, and CB is from the emission control line EM [N]. This is because the capacitive elements, which previously stored the data voltage, may be electrically connected to the first power voltage line VDD until the second switching elements SW_TR2 of the pixel circuits are turned on to apply the low level signal. As such, it is a feature of the present invention that the correct data can be written to the capacitive elements by adding new RGB data signals after the capacitive elements are initialized.

Referring to FIG. 14, there is shown an electrical connection relationship according to another embodiment of the RDI pixel circuits and the demultiplexer of the present invention.

The demultiplexer 1000 according to the present invention is a demultiplexer having a layout structure for each of the RGB data signals in the data signal driver of the organic light emitting display device.

Recently, as high resolution is required, data lines of organic light emitting display devices are increased, and more integrated circuits are included in a data signal driver for driving the organic light emitting display device. In order to solve this problem, a demultiplexer in which the number of output lines of the data signal driver is reduced is used. The demultiplexer includes a plurality of data signal supply switching elements commonly connected to an output line of the data signal driver, and these data signal supply switching elements are electrically connected to predetermined data lines, respectively. Accordingly, the demultiplexer sequentially supplies the data signal to each data line through the operation of the data signal supply switching element.

Herein, RGB means red, red, green, and blue. In FIG. 11, three pixel circuits are electrically connected to the demultiplexer 1000, but the present invention is not limited thereto. In addition, the data signal may be applied to the pixel circuits using a plurality of demultiplexers, and the present invention is not limited to the number of demultiplexers used.

Referring to the demultiplexer 1000, a red data line, a green data line, and a blue data line are electrically connected to the data lines D [M] of the pixel circuits, respectively. In addition, each of the RGB ratio RGB data lines is electrically connected to the RGB ratio switching element SW_TR3. The switching device may again include a red data line switching device SW_TR3R, a green data line switching device SW_TR3G, and a blue data line switching device SW_TR3B. AlGBI (RGB) control signals may be applied to the control electrodes of the RGB switching devices through the RG control lines CR, CG, and CB, respectively.

When the RGB switching device is turned on by the RGB control signals CR, CG, and CB, data suitable for each RGB pixel circuit from the data signal driver through a demultiplexer is transmitted. A signal (voltage) can be applied.

The RGB switching elements may be a P-type channel transistor, but the present invention is not limited to the type of the transistor.

A thin film transistor (TFT) may be used as the AlGbi (RGB) switching device (SW_TR3) shown in FIG. 11 and the initialization switching device (SW_TR4) shown in FIG. 14, and the crystallization method of the thin film transistor The laser crystallization method (ELA) using an excimer laser, the metal catalyst crystallization method (MIC: Metal Induced Crystalization) and the solid phase crystallization (SPC) method using a metal catalyst (Promoting Material) . In addition, there are high pressure annealing (HPA) method for crystallization in a high temperature, high humidity atmosphere, and a sequential lateral solidfication (SLS) method using a mask in addition to an existing laser crystallization method.

The laser crystallization method is the most widely used method of crystallizing a thin film transistor with polysilicon (Poly Silicon). Not only can the crystallization method of the existing polycrystal liquid crystal display device be used as it is, but the process method is simple and the technology development of the process method is completed.

The metal catalyst crystallization method is one of methods that can be crystallized at low temperature without using the laser crystallization method. Initially, the metal catalyst metal, Ni, Co, Pd, Ti, etc., is deposited or spin-coated on the surface of the amorphous silicon (a-Si) so that the metal catalyst metal penetrates directly into the surface of the amorphous silicon to change the phase of the amorphous silicon. Crystallization method has the advantage that can be crystallized at low temperature.

Another method of the metal catalyst crystallization method has an advantage of suppressing the contamination of nickel silicide in a specific region of the thin film transistor using a mask when interposing a metal layer on the surface of the amorphous silicon. The crystallization method is referred to as metal catalyst induced side crystallization (MILC). A shadow mask may be used as a mask used in the metal catalyst-induced side crystallization method, and the shadow mask may be a linear mask or a pointed mask.

Another method of the metal catalyst crystallization method is a metal catalyst induction capping layer that controls the amount of metal catalyst introduced into the amorphous silicon through a capping layer first when depositing or spin coating a metal catalyst layer on the surface of the amorphous silicon. There is a crystallization method (MICC: Metal Induced Crystalization with Capping Layer). A silicon nitride layer may be used as the capping layer. The amount of the metal catalyst flowing into the amorphous silicon from the metal catalyst layer varies according to the thickness of the silicon nitride film. In this case, the metal catalyst flowing into the silicon nitride film may be formed on the entire silicon nitride film, or may be selectively formed using a shadow mask or the like. The capping layer may be selectively removed after the metal catalyst layer has crystallized the amorphous silicon into polycrystalline silicon. The capping layer may be removed by using a wet etching method or a dry etching method. In addition, after the polycrystalline silicon is formed, a gate insulating film is formed and a gate electrode is formed on the gate insulating film. An interlayer may be formed on the gate electrode. After forming a via hole on the interlayer insulating layer, impurities may be introduced into the crystallized polysilicon through the via hole to further remove metal catalyst impurities formed therein. A method of additionally removing the metal catalyst impurities is called a gettering process. The gettering process includes a heating process of heating the thin film transistor at a low temperature in addition to the process of injecting the impurities. Through the gettering process, a high quality thin film transistor can be realized.

Referring to FIG. 15, a driving timing diagram of the AlGeB (RGB) pixel circuits shown in FIG. 14 is shown.

Hereinafter, the operation of the RGB pixel circuits according to the present invention shown in FIG. 14 will be described with reference to the driving timing diagram of FIG. 15.

First, when the low level initialization signal is applied through the initialization signal line Rst, the initialization switching elements SW_TR4 in the demultiplexer are turned on. Accordingly, the data lines may be initialized by the initialization power supply voltage from the initialization power supply voltage line Vrst. .

On the other hand, when the low level light emission control signal is applied through the light emission control line EM [N] and the low level scan signal is applied from the scan line S [N], the algibi RGB control signal line during this period. The low level signal is applied through the switch, and the RGB switching switching elements SW_TR3R, SW_TR3G, and SW_TR3B in the demultiplexer may be turned on.

The RGB control signals are applied in the order of green (G), red (R), and blue (B) control signals, and thus the RGB data voltages are respectively green (G) and red (R). And sequentially applied to the pixel circuits of blue (B).

As shown in FIG. 15, the green organic electroluminescent element in the pixel circuit from the period in which the green (G) control signal is applied to the period in which a high level emission control signal is applied from the emission control line EM [N] ( OLED will emit light as current flows.

Current flows through the red organic electroluminescent element OLED Red in the pixel circuit from the period in which the red (R) control signal is applied to the period in which the high level emission control signal is applied from the emission control line EM [N]. To emit light.

In addition, a current is applied to the blue organic electroluminescent element OLED Blue in the pixel circuit from the period in which the blue (B) control signal is applied to the period in which the high level emission control signal is applied from the emission control line EM [N]. Will emit light.

That is, as shown in Fig. 15, the long-term current flows through the green (G) organic electroluminescent element during the white balance compensation period, followed by the red (R) organic electroluminescent element and the blue (B) organic. It becomes the order of the electroluminescent element.

Thus, the reason why the white balance compensation time is in the order of green (G), red (R) and blue (B) is that the green (G) signal is generally higher in luminous efficiency than the red (R) and blue (B) signals. Because it is high. In other words, in order to achieve the white balance, the green (G) organic electroluminescent device having the highest luminous efficiency is allowed to flow for the longest period of time during the non-luminous period (the white balance compensation period), and then the red (R), Next, the same luminance level may be realized by performing the white balancing period in the order of blue (B). The current flowing through the organic electroluminescent elements during the white balance period flows larger than the current flowing through the organic electroluminescent elements during the light emitting period.

During the image display period of one frame, the above white balance compensation period may be shorter than the light emitting period.

As described above, the organic electroluminescent display device according to the present invention allows the green (G) organic electroluminescent element having the highest luminous efficiency to flow for the longest period of time during the non-luminous period (white balance compensation period), and then The same luminance level can be realized by performing a white balancing period in the order of red (R) and then blue (B).

In other words, by performing the white balance compensation period in the middle of the light emission period, there is an effect of improving the problem that the white balance is changed over time so that a desired color cannot be reproduced.

In addition, the organic light emitting display device according to the invention,

First, high integration can be achieved by using three transistors having a smaller number than conventional pixel circuits, thereby enabling a high resolution.

Second, by adjusting the ratio (C1: C2) of the first capacitive element and the second capacitive element appropriately, the uniformity of luminance can be improved by compensating the threshold voltage (Vth) of the driving transistor. According to the ratio control of the capacitive element, there is an effect of improving the voltage drop (IR-DROP) phenomenon caused by the first power voltage line VDD.

Third, in the pixel circuit according to the present invention, since there is no electrical connection relationship in which leakage current can flow from the control electrode of the driving transistor toward the negative power source, the organic light emitting diode is not suitable for the organic light emitting device due to leakage current. There is an effect that can prevent the light emission.

In addition, in the driving method according to an embodiment of the present invention applying an RGB data signal using a demultiplexer, the emission control signal is turned on regardless of whether the scan signal is on or off. By applying the RGB data signal during the On period, the RGB data can be correctly stored in each capacitive element of the pixel circuits. In other words, before the RGB data is applied to each of the capacitive elements of the pixel circuits, each of the capacitive elements is initialized by the first power supply voltage of the first power supply voltage line VDD so that a new RGB ratio data signal is obtained. It has the effect of being stored correctly in the vocation.

The foregoing description is merely one embodiment for implementing the organic light emitting display device according to the present invention, and is not limited to the above-described embodiment of the present invention, as claimed in the following claims. Without departing from the gist of the present invention, those skilled in the art to which the present invention pertains to the technical spirit of the present invention to the extent that various modifications can be made.

Claims (30)

  1. Each of the plurality of RGB switching elements and RGB data lines electrically connected to RGB data lines to apply a data voltage through the RGB data lines, respectively. A demultiplexer connected with a plurality of initialization switching elements for applying an initialization power supply voltage through the RGB data lines; And
    And a plurality of RGB pixel circuits electrically connected to the scan line, the emission control line, and the ALGBI switching elements of the demultiplexer,
    An initialization power supply voltage and an RGB data voltage of the demultiplexer are applied during a period in which an emission control signal for turning on a switching element connected to the emission control lines of the RGB pixels circuits is applied. The image display period is divided into a white balance compensation period and a light emission period, wherein the emission period is longer than the white balance compensation period.
  2. The method of claim 1,
    The RGB data voltages are applied in the order of green (G) data voltages, red (R) data voltages, and blue (B) data voltages. .
  3. The method of claim 1,
    The initialization power supply voltage is applied before the RGB data voltages.
  4. The method of claim 1,
    And an RGB data voltage of the demultiplexer is applied while a scan signal of turn-on is applied to the RGB pixel circuits.
  5. The method of claim 1,
    And the scan line and the light emission control line are electrically connected to each other in common with each of the RGB pixel circuits.
  6. The method of claim 1,
    And each of the RGB pixel circuits is electrically connected to a common first power supply voltage line and a common second power supply voltage line.
  7. delete
  8. The method of claim 1,
    The white balance compensation period is performed during a period in which a turn-on scan signal is applied to the RGB pixel circuits.
  9. The method of claim 1,
    And a turn-off scan signal and a turn-on emission control signal are applied to the RGB pixel circuits during the emission period.
  10. The method of claim 1,
    And a current for white balance compensation flows through the green organic electroluminescent device, the red organic electroluminescent device, and the blue organic electroluminescent device during the white balance compensation period.
  11. The method of claim 1,
    And a current flowing through the organic EL device during the white balance compensation period is greater than a current flowing through the organic EL device during the light emission period.
  12. The method of claim 1,
    An organic electroluminescent display device according to claim 1, wherein the current flows through the organic electroluminescent element for white balance compensation in order of green (G), red (R), and blue (B).
  13. Each of the plurality of RGB switching elements and RGB data lines electrically connected to RGB data lines to apply a data voltage through the RGB data lines, respectively. A demultiplexer connected with a plurality of initialization switching elements for applying an initialization power supply voltage through the RGB data lines; And
    And a plurality of RGB pixel circuits electrically connected to the scan line, the emission control line, and the ALGBI switching elements of the demultiplexer,
    An organic electroluminescent display to which an initialization power supply voltage and an RGB data voltage of the demultiplexer are applied during a period in which an emission control signal for turning on a switching element connected to the emission control lines of the RGB pixels circuits is applied. In the apparatus,
    The RGB pixel circuits,
    Electrically connected to the scan line, the emission control line, and the data line;
    A first switching device in which a control electrode is electrically connected to the scan line, and a first electrode is electrically connected to the data line;
    A driving transistor electrically connected to a second electrode of the first switching device and electrically connected between a first power supply voltage line and a second power supply voltage line;
    A first capacitive element electrically connected between the first power voltage line and a control electrode of the driving transistor;
    A second switching element electrically connected to the emission control line and electrically connected between the first power voltage line and the first electrode of the driving transistor;
    A second capacitive element electrically connected between the first electrode and the control electrode of the driving transistor; And
    And an organic electroluminescent element electrically connected between the second electrode of the driving transistor and the second power supply voltage line.
  14. delete
  15. The method of claim 13,
    And the control electrode is electrically connected to the scan line to apply data in a direction from the first electrode to the second electrode.
  16. The method of claim 13,
    And a second electrode of the driving transistor is electrically connected to an anode of the organic light emitting element.
  17. The method of claim 13,
    And the control transistor is electrically connected to the second electrode of the first switching element to control the driving current from the first power supply voltage line.
  18. The method of claim 13,
    And a second electrode of the first capacitive element is electrically connected to a second electrode of the first switching element.
  19. The method of claim 13,
    And the first electrode is electrically connected to the first power voltage line, and the second electrode is electrically connected to a second electrode of the second capacitive element.
  20. The method of claim 13,
    In the second switching device, the control electrode is electrically connected to the emission control line, the first electrode is electrically connected to the first power supply voltage line, and the second electrode is electrically connected to the first electrode of the driving transistor. An organic light emitting display device.
  21. The method of claim 13,
    In the second switching device, the control electrode is electrically connected to the emission control line, the first electrode is electrically connected to the first power supply voltage line, and the second electrode is electrically connected to the first electrode of the second capacitive element. An organic light emitting display device, characterized in that connected.
  22. The method of claim 13,
    In the second capacitive element, a first electrode is electrically connected to a second electrode of the second switching element and a first electrode of the driving transistor, and the second electrode is a second electrode of the first capacitive element and the first electrode. The organic light emitting display device is electrically connected to a second electrode of a switching element and a control electrode of the driving transistor.
  23. delete
  24. The method of claim 13,
    And the anode electrode is electrically connected to the second electrode of the driving transistor, and the cathode electrode is electrically connected to the second power voltage line.
  25. The method of claim 13,
    And the first switching element, the second switching element, and the driving transistor are N-type channel transistors.
  26. The method of claim 13,
    And the first switching element, the second switching element, and the driving transistor are P-type channel transistors.
  27. The method of claim 13,
    The second power supply voltage of the second power supply voltage line is lower than the first power supply voltage of the first power supply voltage line.
  28. The method of claim 13,
    The second power supply voltage of the second power supply voltage line is a ground voltage.
  29. The method of claim 13,
    And an emission control switching device between the driving transistor and the organic light emitting device.
  30. The method of claim 29,
    The control electrode of the emission control switching device is electrically connected to the emission control line, and the first electrode of the emission control switching device is electrically connected to the second electrode of the driving transistor. And a second electrode is electrically connected to the anode of the organic light emitting diode.
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