KR20200071433A - Display device - Google Patents

Abstract

The present invention is an invention relating to a display device. A display device according to one embodiment of the present invention includes: a display panel including a plurality of pixels disposed in an active area wherein an image is displayed, and one or more dummy pixels disposed in an inactive area which is adjacent to the active area; and a compensating part configured to apply a compensation voltage due to deterioration of the pixels disposed in the display panel, wherein the plurality of pixels include a light emitting part including a light emitting element, and a pixel driving part configured to control driving of the light emitting part and at least one of which includes a thin film transistor having a double gate structure, and the compensation voltage applied by the compensation part is applied to the thin film transistor having the double gate structure. Accordingly, the display device according to one embodiment of the present invention may be more advantageous in securing the area of the display device while minimizing degradation of the image quality of the display device.

Description

Display device {DISPLAY DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device, and more particularly, to a display device for improving a problem caused by a change in threshold voltage characteristics of a thin film transistor made of an oxide semiconductor material.

With the recent advent of the information age, the display field for visually expressing electrical information signals has rapidly developed, and in response to this, various display devices having excellent performance of thinning, lightening, and low power consumption have been developed. Is being developed.

Specific examples of the display device include a liquid crystal display device (LCD), a plasma display panel device (PDP), a field emission display device (FED), and an organic light emitting display device ( Organic Light Emitting Display device (OLED).

The display device includes a display panel in which a plurality of pixels are arranged, and a driving unit for driving the display panel, and a light emitting element, a switching thin film transistor, and a driving thin film transistor are formed in each of the plurality of pixels.

Recently, as the display device is implemented in a large area and a high resolution, a thin film transistor is required that secures stable operation and durability along with a faster signal processing speed.

Accordingly, studies have been actively conducted to form an active layer of a thin film transistor with an oxide semiconductor material having excellent mobility characteristics in order to improve the mobility of the thin film transistors constituting each of the plurality of pixels.

However, a thin film transistor made of an oxide semiconductor material has excellent mobility characteristics and has a problem in that its reliability is deteriorated due to a large change in bias stress and a large change in threshold voltage (Vth) and a change in transmission characteristics. .

Accordingly, the inventors of the present invention proposed a method of detecting a threshold voltage shift of a thin film transistor made of an oxide semiconductor material and applying a compensation voltage to compensate for a change in the threshold voltage.

The problem to be solved by the present invention is to provide a display device capable of minimizing image quality degradation of a display device due to a threshold voltage variation of a thin film transistor made of an oxide semiconductor material.

The problems of the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

A display device according to an exemplary embodiment of the present invention is disposed on a display panel and a display panel in which a plurality of pixels arranged in an active area in which an image is displayed and one or more dummy pixels arranged in adjacent inactive areas of the active area are arranged. A compensation unit configured to apply a compensation voltage according to the deterioration of the pixel, wherein the plurality of pixels control a light emitting unit including a light emitting element and driving of the light emitting unit, and at least one pixel including a thin film transistor having a double gate structure. A driving unit, and a compensation voltage applied from the compensation unit may be configured to be applied to the thin film transistor having the double gate structure. Accordingly, the display device according to an exemplary embodiment of the present invention may be more advantageous in securing an area of the display device while compensating for a change in a threshold voltage of the pixel.

A display device according to another exemplary embodiment of the present invention includes an active area in which a plurality of pixels for displaying an image are disposed, and an inactive area in which a driving circuit is disposed around the active area to drive each of the plurality of pixels, Each of the plurality of pixels includes a light emitting unit including a light emitting element that emits light, a driving thin film transistor that controls light emission current flowing through the light emitting element, and a scan signal supplied through a corresponding gate line, and data supplied through the data line It may include a pixel driving unit including one or more switching thin film transistors to charge a voltage to a capacitor, and a compensation unit applying a compensation voltage to any one of the switching thin film transistors. Accordingly, in the display device according to another exemplary embodiment of the present invention, compensation is performed in each pixel by arranging a compensation unit for compensating for a change in a threshold voltage characteristic of a switching thin film transistor made of an oxide semiconductor material in a pixel. Can be.

Details of other embodiments are included in the detailed description and drawings.

According to the present invention, a threshold voltage change of a thin film transistor made of an oxide semiconductor material is detected, and a threshold voltage is compensated according to the detected result, thereby reducing luminance and image quality degradation of the display device.

According to the present invention, the threshold voltage change in the active region can be more precisely and accurately estimated by detecting a threshold voltage change in the pixel in the active region using a dummy pixel, a detector for detecting a threshold voltage change in the thin film transistor made of an oxide semiconductor material. .

According to the present invention, by compensating a threshold voltage change of a thin film transistor made of an oxide semiconductor material in each pixel, compensation according to a threshold voltage change can be performed for each pixel.

In the present invention, a gate electrode of a thin film transistor made of an oxide semiconductor material is formed in a double gate structure, and different signals are applied to each of the double gate electrodes, thereby compensating for a change in the threshold voltage of each pixel and displaying a display device. It may be more advantageous to secure the area.

In the present invention, the pixel electrode compensation may be directly performed by forming a gate electrode of a thin film transistor made of an oxide semiconductor material in a double gate structure, but applying a compensation voltage according to a threshold voltage change to the lower gate electrode.

The present invention can further improve device characteristics by forming a thin film transistor made of two different types of semiconductor materials on the same substrate, and having a feature that another thin film transistor complements the disadvantages of one thin film transistor.

The effect according to the present invention is not limited by the contents exemplified above, and more various effects are included in the present invention.

1 is a block diagram schematically illustrating a display device according to an exemplary embodiment of the present invention.
2 is a circuit diagram for describing a pixel circuit of a general display device.
3 is a waveform diagram showing a signal input to a pixel circuit of the general display device shown in FIG. 2.
4 is a circuit diagram schematically illustrating a pixel circuit of an active region and a pixel circuit of a dummy pixel region of a display device according to an exemplary embodiment of the present invention.
5 is a cross-sectional view schematically showing a structure of a portion of a pixel circuit in an active area of a display device according to an exemplary embodiment of the present invention.
6 is a circuit diagram schematically illustrating a pixel structure of an active area of a display device according to another exemplary embodiment of the present invention.
7 is a circuit diagram schematically illustrating a structure of a part of a pixel circuit in an inactive area of a display device according to another exemplary embodiment of the present invention.
8 is a waveform diagram illustrating a signal input to a pixel circuit according to an embodiment of the present invention.

Advantages and features of the present invention, and methods for achieving them will be clarified with reference to embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only the embodiments allow the disclosure of the present invention to be complete, and the ordinary knowledge in the technical field to which the present invention pertains. It is provided to fully inform the holder of the scope of the invention, and the invention is only defined by the scope of the claims.

The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for describing the embodiments of the present invention are exemplary and the present invention is not limited to the illustrated matters. The same reference numerals refer to the same components throughout the specification. In addition, in the description of the present invention, when it is determined that detailed descriptions of related known technologies may unnecessarily obscure the subject matter of the present invention, detailed descriptions thereof will be omitted. When'include','have','consist of', etc. mentioned in this specification are used, other parts may be added unless'~man' is used. When a component is expressed as a singular number, the plural number is included unless otherwise specified.

In interpreting the components, it is interpreted as including the error range even if there is no explicit description.

In the case of the description of the positional relationship, for example, when the positional relationship of two parts is described as'~top','~upper','~bottom','~side', etc.,'right' Alternatively, one or more other parts may be located between the two parts unless'direct' is used.

An element or layer being referred to as being "on" another element or layer includes all instances of another layer or other element immediately above or in between.

Although the first, second, etc. are used to describe various components, these components are not limited by these terms. These terms are only used to distinguish one component from another component. Therefore, the first component mentioned below may be the second component within the technical spirit of the present invention.

The same reference numerals refer to the same components throughout the specification.

The size and thickness of each component shown in the drawings are illustrated for convenience of description, and the present invention is not necessarily limited to the size and thickness of the illustrated component.

Each of the features of the various embodiments of the present invention may be partially or totally combined or combined with each other, and technically various interlocking and driving may be possible as those skilled in the art can fully understand, and each of the embodiments may be implemented independently of each other. It can also be implemented together in an associative relationship.

In the present invention, the thin film transistor TFT may be configured as a P type or an N type, and in the following embodiments, the thin film transistor is configured as an N type for convenience of description. In addition, in describing a pulse type signal, a gate high voltage (VGH) state is defined as a "high state", and a gate low voltage (VGL) state is defined as a "low state."

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

1 is a block diagram schematically illustrating a display device according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the display device 100 according to an exemplary embodiment of the present invention includes a display panel 110, a gate driver 120, a data driver 130, and a timing controller 140.

The display panel 110 includes n gate lines GL1, …, and GLn arranged in a first direction, m data lines DL1, …, DLm arranged in a direction different from the first direction, and n gate lines. It includes (GL1, ..., GLn) and a plurality of pixels (P) electrically connected to the m data lines (DL1, ..., DLm). Accordingly, the plurality of pixels P displays an image by a driving signal or a driving voltage applied through the gate lines GL1, …, GLn and the data lines DL1, …, DLm.

The display panel 110 includes an active area (A/A) and a non-active area (N/A) adjacent to the active area (A/A).

A plurality of pixels P capable of displaying an image is disposed in the active area A/A. Each of the plurality of pixels P is provided with a light emitting unit through which light is emitted by the light emitting element and a pixel driving unit in which a plurality of driving elements for driving the light emitting element are disposed.

The light emitting device of the pixel P disposed in the active area A/A may be an organic light emitting device. In an exemplary embodiment of the present invention, it is assumed that the light emitting element of the pixel P of the display device 100 is an organic light emitting element, but is not limited thereto. That is, the present invention can be applied not only to an organic light emitting display device, but also to a quantum dot light emitting display device (QLED) or various other display devices (for example, a liquid crystal display device). More specifically, an embodiment of the present invention is an invention for compensating for a shift in the negative polarity of a threshold voltage (Vth) characteristic of a thin film transistor made of an oxide semiconductor, and thus, as an oxide semiconductor in a pixel circuit constituting the pixel P It can be applied to all of the display device including the transistor made.

The driver of the pixel P disposed in the active area A/A includes one or more switching thin film transistors, driving thin film transistors, and capacitors. At this time, one or more switching thin film transistors and driving thin film transistors may be formed of different semiconductor materials. For example, the switching thin film transistor may be formed of a semiconductor material made of oxide, and the driving thin film transistor may be made of a semiconductor material made of low temperature polysilicon material. At this time, at least one of the one or more switching thin film transistors may have a double gate structure. In more detail, the switching thin film transistor having a double gate structure may be a thin film transistor in which threshold voltage characteristics are shifted to a negative polarity while driving the display device 100. The pixel circuit of the pixel P disposed in the active area A/A according to an embodiment of the present invention will be described in more detail with reference to FIG. 4 below.

The inactive area N/A is an area adjacent to the active area A/A. More specifically, the inactive area N/A is an area surrounding the active area A/A adjacent to the active area A/A. The inactive area (N/A) is an area in which an image is not displayed, driving dummy pixels, signal lines for transmitting signals to pixels disposed in the active area (A/A), and pixels in the active area (A/A). A circuit portion or the like may be disposed. For example, an anti-static element, a signal pad, and a signal link line may be disposed in the non-active area N/A.

The dummy pixel DP may be further disposed in the inactive area N/A in which a plurality of rows in which the pixels P arranged in the active area A/A extend in the first direction. More specifically, a dummy pixel DP may be disposed in an area of the inactive area N/A closest to the active area A/A. That is, the dummy pixel DP is disposed in the same row as the pixel P disposed in the active area A/A, but is disposed in an area adjacent to the active area A/A. Accordingly, if n rows of pixels P of the active area A/A are arranged in the first direction, n dummy pixels DP may also be disposed. Meanwhile, FIG. 1 illustrates that the dummy pixel DP is disposed on only one side of the active area A/A among the inactive areas N/A, but is not limited thereto, and the active area A/A is not limited thereto. ) May be disposed on both sides of the active area A/A in the inactive area N/A adjacent to the active area A/A, and may be disposed above and below the inactive area N/A adjacent to the active area A/A. It may be.

The dummy pixel DP may have a structure similar to the pixel P disposed in the active area A/A. However, since it is disposed in the inactive region N/A, the light emitting element does not emit light. Accordingly, in general, the dummy pixel DP is used in various forms such as using it as a test pattern to test the abnormality of the pixel P during the process. The dummy pixel DP according to an embodiment of the present invention may be configured to determine whether the pixel P disposed in the active area A/A is deteriorated. That is, the dummy pixel DP may further include a sensing driving element capable of sensing the degree of deterioration of the pixel P of the active area A/A, for example, a sensing thin film transistor. The structure of the dummy pixel DP will be described in more detail with reference to FIG. 4 below.

The timing controller 140 processes image data (RGB) input from the outside to be suitable for the size and resolution of the display panel 110 and supplies it to the data driver 130. The timing controller 140 receives synchronization signals SYNC input from the outside, for example, a dot clock signal DCLK, a data enable signal DE, a horizontal synchronization signal Hsync, and a vertical synchronization signal Vsync. Use to generate a number of gate control signal (GCS) and data control signal (DCS). The timing controller 140 supplies the generated gate control signal GCS and data control signal DCS to the gate driver 120 and the data driver 130, respectively, thereby providing the gate driver 120 and the data driver 130. Control.

The timing controller 140 compares the sensing value input from the sensing driving element included in the dummy pixel DP with a preset reference value, and then controls to apply a compensation voltage to the pixel P according to the comparison result. It may contain wealth. On the other hand, in an embodiment of the present invention, the compensation unit comparing the value sensed by the dummy pixel DP and the preset reference value is described as being included in the timing controller 140, but is not limited thereto, and the degree of degradation is determined. The compensation unit for doing so may be included in the gate driver 120.

Meanwhile, when the compensation unit is disposed in the pixel P, the timing controller 140 may control the compensation voltage to be applied to the compensation unit disposed in the pixel when the second scan signal SCAN2 is applied in the sampling and programming period. have. A more detailed description of this will be provided with reference to FIGS. 6 and 7 below.

The gate driver 120 supplies gate signals to the n gate lines GL1,..., GLn according to the gate control signal GCS supplied from the timing controller 140. Here, the gate signal includes at least one scan signal SCAN and a light emission control signal EM.

The gate driver 120 applies a compensation voltage according to the degradation of the pixel P to the lower gate of the thin film transistor having a double gate structure according to the detection signal detecting the degree of degradation of the pixel P supplied from the timing controller 140. Can apply.

The data driver 130 converts the image data RGB into a data voltage according to the data control signal DCS supplied from the timing controller 140, and converts the converted data voltage into m data lines DL1, …, DLm. Is supplied to the pixel P through.

Each pixel P of the display device 100 according to an exemplary embodiment of the present invention includes an organic light emitting element and a pixel circuit that controls driving of the organic light emitting element. The organic light emitting device is composed of an anode, a cathode, and a light emitting layer between the anode and the cathode. The pixel circuit includes a switching transistor, a driving transistor and a capacitor. More specifically, the driving transistor controls the amount of current supplied to the organic light emitting device according to the data voltage charged in the capacitor to control the amount of light emitted from the organic light emitting device, and the switching transistor scan signal SCAN supplied through the gate line GL ) To charge the data voltage (Vdata) to the capacitor.

As described above, the display device 100 according to an exemplary embodiment of the present invention has a threshold voltage of a thin film transistor made of an oxide semiconductor material among pixel circuits constituting the pixel P disposed in the active area A/A. It is an invention for compensating the threshold voltage characteristic shifted by the negative characteristic because the image quality of the display device is deteriorated by the characteristic being shifted by the negative polarity. Accordingly, before looking at the present invention in more detail, a pixel circuit disposed in a general active region is as follows.

2 is a circuit diagram for describing a pixel circuit of a general display device.

Referring to FIG. 2, a pixel circuit of a typical display device includes a driving thin film transistor DT, one or more switching thin film transistors T1, T2, T3, T4, and T5, and a capacitor Cst. At this time, the one or more switching thin film transistors T1, T2, T3, T4, and T5 and the driving thin film transistor DT may be made of different semiconductor materials. For example, at least one of the switching thin film transistors T1, T2, T3, T4, and T5 of the one or more switching thin film transistors T1, T2, T3, T4, and T5 may be made of an oxide semiconductor material. 2 may be a switching thin film transistor T2.

The driving thin film transistor DT controls the light emission current applied to the light emitting device OD by the gate-source voltage Vgs. The driving thin film transistor DT includes a gate connected to the second node N2, a source connected to the third node N3, and a drain connected to the first node N1. Specifically, the gate of the driving thin film transistor DT stores the high potential voltage VDD when the second switching thin film transistor T2 and the third switching thin film transistor T3 are turned on. When the data voltage is supplied while the second switching thin film transistor T2 is turned on, the data voltage is written to the gate of the driving thin film transistor DT by a diode-connetion method. The driving thin film transistor DT supplies driving current to the light emitting device OD by the light emission control signal EM to control light emission of the light emitting device OD according to the amount of current.

The first switching thin film transistor T1 is turned on in response to the second scan signal SCAN2 applied to the second gate line, and the data voltage provided through the data line Data is applied to the driving thin film transistor DT. It is configured to be. The first switching thin film transistor T1 includes a gate connected to the second gate line, a drain connected to the data line, and a source connected to the third node N3. Specifically, when the second scan signal SCAN2 is supplied as a high state to the gate of the first switching thin film transistor T1, the data voltage is driven from the drain of the first switching thin film transistor T1 to the driving thin film transistor DT ) Is supplied to the third node N3 which is a source node.

The second switching thin film transistor T2 is connected between the gate and the drain of the driving thin film transistor DT, that is, between the first node N1 and the second node N2. The second switching thin film transistor T2 includes a gate connected to the first gate line, a source connected to the second node N2, and a drain connected to the first node N1. Specifically, when the first scan signal SCAN1 applied through the first gate line of the second switching thin film transistor T2 is in a high state, the second switching thin film transistor T2 is turned on. As described above, when the second switching thin film transistor T2 is turned on, the second switching thin film transistor T2 removes the high potential voltage VDD of the first node N1 or the sampled voltage of the driving thin film transistor DT. It is supplied to the two nodes N2 to initialize the data voltage written to the light emitting element OD, or to write the data voltage and sample the threshold voltage of the driving thin film transistor DT. The second switching thin film transistor T2 may be made of an oxide semiconductor material.

The third switching thin film transistor T3 controls the current path between the high potential voltage VDD and the driving transistor DT in response to the second emission control signal EM2 applied through the second emission control line. The third switching thin film transistor T3 includes a gate connected to the second emission control line, a drain of the driving transistor DT, that is, a source connected to the first node N1 and a drain connected to the high potential voltage VDD. Specifically, in the third switching thin film transistor T3, when the second emission control signal EM2 is in a high state, the third switching thin film transistor T3 is turned on, and the thin film driving the high potential voltage VDD from the source It is supplied to the first node N1 which is the drain node of the transistor DT.

The fourth switching thin film transistor T4 controls the current path between the light emitting device OD and the driving transistor DT in response to the first light emission control signal EM1 applied through the first light emission control line. The fourth switching thin film transistor T4 includes a gate connected to the first emission control line, a source connected to the light emitting device OD, and a drain connected to the third node N3. Specifically, in the fourth switching thin film transistor T4, when the first emission control signal EM1 is in a high state, the fourth switching thin film transistor T4 is turned on, and the third that is the source of the driving thin film transistor DT The node N3 and the fourth node N4, which is a source node of the fourth switching TFT T4, are electrically connected. Accordingly, when the fourth switching thin film transistor T4 is turned on by the first emission control signal EM1, the voltage of the third node N3 is supplied to the fourth node N4. When the fourth switching thin film transistor T4, the driving thin film transistor DT, and the third switching thin film transistor T3 are turned on, a high potential voltage VDD is supplied to the driving thin film transistor DT, and the light emitting device OD ), the driving current is supplied, and the light emitting element OD emits light.

The fifth switching thin film transistor T5 is turned on in response to the first scan signal SCAN1 applied through the first gate line, so that the initialization voltage VINI is the fourth node N4 and the fifth node ( N5). The fifth switching thin film transistor T5 includes a gate connected to the first gate line, a drain connected to the initialization voltage line, and a source connected to the fourth node N4 and the fifth node N5 which is an anode of the light emitting device OD. do. Specifically, when the first scan signal SCAN1 is in a high state, the fifth switching thin film transistor T5 is turned on to turn on the initialization voltage VINI to the fourth node N4 and It supplies to the fifth node N5. Accordingly, when the fifth switching thin film transistor T5 is turned on by the first scan signal SCAN1, the initialization voltage VINI is supplied to the fourth node N4 and the fifth node N5 to supply the light emitting device OD. ) Can initialize the data voltage.

The capacitor Cst may be a storage capacitor Cst that stores the gate voltage and the threshold voltage Vth of the driving thin film transistor DT until the next refresh frame. Here, the capacitor Cst is disposed between the second node N2 which is the gate of the driving thin film transistor DT and the fourth node N4 that is electrically connected to the anode of the light emitting element OD. That is, the capacitor Cst is electrically connected to the second node N2 and the fourth node N4 to determine the difference between the voltage of the gate of the driving thin film transistor DT and the voltage supplied to the anode of the light emitting device OD. To save.

The light emitting element OD emits light by the light emission current supplied from the driving transistor DT. The anode of the light emitting element OD is connected to the fifth node N5, and the cathode is connected to the low potential voltage VSS.

The operation of the pixel circuit of the general display device configured as described above is as follows.

3 is a waveform diagram showing a signal input to a pixel circuit of the general display device shown in FIG. 2.

Referring to FIG. 3, data voltages are written to each pixel disposed on one horizontal line through the initialization section P1, the sampling and programming section P2, the holding section P3, and the emission section P4, and each pixel It emits light.

In the initialization period P1, the first scan signal SCAN1 rises to a high state, and the second scan signal SCAN2 maintains a low state. At the same time, the first emission control signal EM1 falls to a low state, and the second emission control signal EM2 maintains a high state. Accordingly, in the initialization period P1, the second switching thin film transistor T2, the third switching thin film transistor T3, and the fifth switching thin film transistor T5 are turned on in the pixel circuit illustrated in FIG. 2, and the first switching The thin film transistor T1 and the fourth switching thin film transistor T4 are turned off. Accordingly. In the initialization period P1, the initialization voltage VINI is supplied to the fourth node N4 through the fifth switching thin film transistor T5, and is applied to the first node N1 through the third switching thin film transistor T3. The high potential voltage VDD is supplied to the second node N2 through the second switching thin film transistor T2. That is, as the initialization voltage VINI is supplied to the fifth node N5 that is the anode of the light emitting device OD, the data voltage written to the light emitting device OD is initialized, and the gate of the driving thin film transistor DT is damaged. The above voltage (VDD) is supplied.

In the sampling and programming period P2, the first scan signal SCAN1 rises from a low state to a high state, and the second scan signal SCAN2 also rises from a high state. In the sampling and programming period P2, the second emission control signal EM2 is polled to go low, and the first emission control signal EM1 is also kept low. Accordingly, in the sampling and programming period P2, the first switching thin film transistor T1, the second switching thin film transistor T2, and the fifth switching thin film transistor T5 are turned on, and the third switching thin film transistor T3 and The fourth switching thin film transistor T4 is turned off. Accordingly, the data voltage is supplied to the third node N3 through the first switching thin film transistor T1. Further, as the second switching thin film transistor T2 is turned on, the first node N1 which is a drain node of the driving thin film transistor DT and the second node N2 that is a gate node of the driving thin film transistor DT are By being connected, the gate-source voltage Vgs of the driving thin film transistor DT is sampled as a threshold voltage Vth of the driving thin film transistor DT by a diode-connection method. In addition, as the fifth switching thin film transistor T5 is turned on, the initialization voltage VINI is supplied to the fourth node N4, and the data voltage Vdata+threshold voltage Vth-initialization is applied to the capacitor Cst. The voltage (VINI) value is stored. Accordingly, during the sampling and programming period P2, the first node N1 and the second node N2 have a data voltage Vdata+threshold voltage Vth, and the third node N3 has a data voltage Vdata. ) Value, and the fourth node N4 may have an initialization voltage VINI value.

The holding period P3 may include a first holding period P3-1 and a second holding period P3-2.

In the first holding period P3-1, the first scan signal SCAN1 and the second scan signal SCAN2 are polled to become low, and the first emission control signal EM1 and the second emission control signal EM2 are generated. Remains low. Accordingly, in the first holding period P3-1, all the switching thin film transistors T1, T2, T3, T4, and T5 are turned off. Accordingly, each of the first node N1, the second node N2, the third node N3, and the fourth node N4, which is sampled or data voltage is written during the sampling and programming period P2, is floating, The voltage at each node is maintained.

In the second holding period P3-2, the first scan signal SCAN1 and the second scan signal SCAN2 are polled to go low, and the first emission control signal EM1 rises from a low state to a high state. The second emission control signal EM2 maintains a low state. Accordingly, only the fourth switching thin film transistor T4 is turned on in the second holding period P3-2, the first switching thin film transistor T1, the second switching thin film transistor T2, and the third switching thin film transistor T3. ) And the fifth switching thin film transistor T5 are both turned off. Accordingly, the fourth switching thin film transistor T4 is turned on to connect the third node N3 and the fifth node N5, and the data voltage Vdata held at the third node N3 is the fifth node. (N5).

In the emission period P4, the first scan signal SCAN1 and the second scan signal SCAN2 are maintained in a low state, and the second emission control signal EM2 is raised to maintain a high state. In addition, the first emission control signal EM1 also maintains a high state. Accordingly, in the emission period P4, the first switching thin film transistor T1, the second switching thin film transistor T2, and the fifth switching thin film transistor T5 are turned off, and the third switching thin film transistor T3 and the fourth The switching thin film transistor T4 is turned on. In addition, the driving transistor DT is also turned on by the data voltage Vdata+threshold voltage Vth stored in the second node N2 until the second holding period P3-2 to turn on the high potential voltage VDD. A path through which the driving current flows from the line to the light emitting element OD is formed. That is, a light emission current (Ioled) flows to the light emitting device OD through the turned-on driving thin film transistor DT, the third switching thin film transistor T3 and the fourth switching thin film transistor T4 in the emission period P4.

The active layer of the second switching thin film transistor T2 of the pixel circuit of the general display device driven as described above may be made of an oxide semiconductor material, and a threshold due to a change in bias stress according to characteristics of the oxide semiconductor material is severe. The voltage Vth is shifted to the negative polarity. At this time, the second node N2, which is the source of the second switching thin film transistor T2, as described in FIG. 3, data voltage (Vdata) + threshold voltage from the sampling and programming period P2 to the holding period P3 (Vth) is a node that stores and is a node that affects the light emission of the light emitting element OD in the light emission section P4. However, when the characteristic of the threshold voltage Vth is shifted to the negative polarity according to the characteristic of the second switching thin film transistor T2, this causes a decrease in luminance of the display device and thus deteriorates the image quality of the display device. . In particular, as illustrated in FIG. 3, it can be seen that the voltage supplied to the second node N2 in the sampling and programming period P2 is shifted to the negative polarity as the second scan signal SCAN2 is turned on. .

Accordingly, in the present invention, a configuration capable of sensing whether the threshold voltage of the second switching thin film transistor T2 of the active area A/A is changed is a dummy pixel of the inactive area N/A or the active area A By adding to the pixel circuit configuration of /A), a method of detecting a change in the threshold voltage and compensating it according to the detection result is proposed to minimize the image quality degradation of the display device. Accordingly, first, a pixel deterioration sensing method using a dummy pixel and a compensation method thereof will be described in detail with reference to FIG. 4.

4 is a circuit diagram schematically illustrating a pixel circuit of an active region and a pixel circuit of a dummy pixel region of a display device according to an exemplary embodiment of the present invention. 5 is a cross-sectional view schematically showing a structure of a portion of a pixel circuit in an active area of a display device according to an exemplary embodiment of the present invention.

Referring to FIG. 4, the display device 100 according to an exemplary embodiment of the present invention includes a pixel 410 disposed in the active area A/A and an inactive area N/ adjacent to the active area A/A. The dummy pixel 420 and the compensation unit 430 disposed in A) may be included.

The pixel 410 disposed in the active area A/A includes a pixel driver 411 and a light emitting unit 412. The pixel driver 411 disposed in the active area A/A includes one or more switching thin film transistors T1, T2, T3, T4, and T5 for driving the light emitting device OD, a driving thin film transistor DT, and a capacitor (Cst). At this time, the second switching thin film transistor T2 of the driving thin film transistor DT and one or more switching thin film transistors T1, T2, T3, T4, and T5 constituting the pixel 410 disposed in the active area A/A ) The active layers constituting each may be made of different semiconductor materials. In this way, in one pixel circuit, at least one of the driving thin film transistor DT and the one or more switching thin film transistors T1-T5 may be referred to as a multi-type transistor configuration.

The structures of the driving thin film transistor DT and the second switching thin film transistor T2 will be described in more detail with reference to FIG. 5 below.

Referring to FIG. 5, the pixel 410 disposed in the active area A/A may include a substrate SUB, a buffer layer 111, a driving thin film transistor DT, and a second thin film transistor T2. .

The substrate SUB supports various components of the display panel 100. The substrate SUB may be made of glass or a plastic material having flexibility. When the substrate SUB is made of a plastic material, it may be made of, for example, polyimide (PI).

The buffer layer 111 may be formed on the entire surface of the substrate SUB. The buffer layer 111 may be formed of a single layer of silicon nitride (SiNx) or silicon oxide (SiOx) or multiple layers thereof. The buffer layer 111 may improve adhesion between the layers formed on the buffer layer 111 and the substrate SUB, and may serve to block alkali components, etc., from the substrate SUB. The buffer layer 111 is not an essential component, and may be omitted depending on the type and material of the substrate SUB and the structure and type of the thin film transistor.

The driving thin film transistor DT may be disposed on the buffer layer 111. The driving thin film transistor DT may include a first active layer 121, a first gate electrode 124, a first source electrode 122 and a first drain electrode 123.

The first active layer 121 of the driving thin film transistor DT may be disposed on the buffer layer 111. The first active layer 121 may include low temperature poly-silicon (LTPS). Since the polysilicon material has high mobility, low energy consumption, and high reliability, it can be applied to a gate driver and/or multiplexer (MUX) for driving thin film transistors for display elements. The first active layer 121 includes a first channel region 121a in which a channel is formed when driving the driving thin film transistor DT, a first source region 121b on both sides of the first channel region 121a, and a first drain. The region 121c may be included.

A gate insulating layer 112 may be disposed on the first active layer 121 of the driving thin film transistor DT. The first gate insulating layer 112 may be formed of a single layer of silicon nitride (SiNx) or silicon oxide (SiOx) or multiple layers thereof. In the first gate insulating layer 112, each of the first source electrode 122 and the first drain electrode 123 of the driving thin film transistor DT is the first of the first active layer 121 of the driving thin film transistor DT. A contact hole for connecting to the source region 121b and the first drain region 121c may be included.

The first gate electrode 124 of the driving thin film transistor DT may be disposed on the first gate insulating layer 112. The first gate electrode 124 is any one of molybdenum (Mo), copper (Cu), titanium (Ti), aluminum (Al), chromium (Cr), gold (Au), nickel (Ni), and neodymium (Nd) Or it may be formed of a single layer or multiple layers of these alloys. The first gate electrode 124 may be formed on the first gate insulating layer 112 to overlap the first channel region 121a of the first active layer 121 of the driving thin film transistor DT.

An interlayer insulating layer 113 may be disposed on the first gate insulating layer 112 and the first gate electrode 124. The interlayer insulating layer 113 may be composed of a single layer of silicon nitride (SiNx) or silicon oxide (SiOx) or multiple layers thereof. A contact hole for exposing the first source region 121b and the first drain region 121c of the first active layer 121 of the driving thin film transistor DT may be formed in the interlayer insulating layer 113.

The first source electrode 122 and the first drain electrode 123 may be formed on the interlayer insulating layer 113. The first source electrode 122 and the first drain electrode 123 may be connected to the first active layer 121 through contact holes formed in the interlayer insulating layer 113 and the first gate insulating layer 112. The first source electrode 122 and the first drain electrode 123 may be formed of a three-layer structure of titanium (Ti)/aluminum (Al)/titanium (Ti) made of a conductive metal material, but are not limited thereto. For example, the first source electrode 122 and the first drain electrode 123 are molybdenum (Mo), copper (Cu), titanium (Ti), aluminum (Al), chromium (Cr), gold (Au), Nickel (Ni), neodymium (Nd) may be formed of a single layer or multiple layers of any one or alloys thereof.

The second switching thin film transistor T2 may be disposed on the interlayer insulating layer 113. The second switching thin film transistor T2 may have a double gate structure. More specifically, the second switching thin film transistor T2 includes a lower second gate electrode 134B, a second active layer 131, a second source electrode 132, a second drain electrode 133, and an upper second gate. An electrode 134T may be included. Meanwhile, in FIG. 5, the second switching thin film transistor T2 is described as being disposed on the interlayer insulating layer 113, but is not limited thereto. For example, the second switching thin film transistor T2 may be disposed on the isolation insulating layer 114.

The lower second gate electrode 134B of the second switching thin film transistor T2 is disposed on the interlayer insulating layer 113. The lower second gate electrode 134B of the second switching thin film transistor T2 is electrically connected to an external compensator 430 to compensate for a change in the threshold voltage characteristic of the second switching thin film transistor T2. This can be applied. The lower second gate electrode 134B of the second switching thin film transistor T2 may be formed of a three-layer structure of titanium (Ti)/aluminum (Al)/titanium (Ti) made of a conductive metal material, but is not limited thereto. Does not. For example, the lower second gate electrode 134B includes molybdenum (Mo), copper (Cu), titanium (Ti), aluminum (Al), chromium (Cr), gold (Au), nickel (Ni), and neodymium ( Nd), or a single layer or a multi-layer made of an alloy thereof. The lower second gate electrode 134B of the second switching thin film transistor T2 may be formed in the same process as the first source electrode 122 and the first drain electrode 123 of the driving thin film transistor DT.

The separation insulating layer 114 is disposed on the lower second gate electrode 134B of the interlayer insulating layer 113, the first source electrode 122, the first drain electrode 123, and the second switching thin film transistor T2. Can be. The isolation insulating layer 114 may be disposed between the driving thin film transistor DT and the second switching thin film transistor T2 to separate the driving thin film transistor DT and the second switching thin film transistor T2. The separation insulating layer 114 may be composed of a single layer of silicon nitride (SiNx) or silicon oxide (SiOx) or multiple layers thereof.

The second active layer 131 of the second switching thin film transistor T2 may be disposed on the isolation insulating layer 114. The second active layer 131 may be made of an oxide semiconductor material. The oxide semiconductor material is a material having a larger band gap compared to the polysilicon material. Accordingly, the second active layer 131 made of the oxide semiconductor material has a low off current because the electron does not cross the band gap in the off state of the oxide semiconductor material. Accordingly, the second switching thin film transistor T2 including the active layer made of an oxide semiconductor material may be suitable for a switching transistor having a short on time and a long off time, but is not limited thereto. . That is, a transistor made of an oxide semiconductor material may be applied as a driving transistor according to the characteristics of the display device. Meanwhile, the second active layer 131 may be formed of a metal oxide, for example, Indium-Gallium-Zinc-Oxide (IGZO), Indium-Zinc-Oxide (IZO), or Indium-Gallium-Oxide (IGO).

The second gate insulating layer 116 may be disposed on the second active layer 131. The second gate insulating layer 116 may be formed of a single layer of silicon nitride (SiNx) or silicon oxide (SiOx) or multiple layers thereof.

The upper second gate electrode 134T may be disposed on the second gate insulating layer 116. The upper second gate electrode 134T includes any of molybdenum (Mo), copper (Cu), titanium (Ti), aluminum (Al), chromium (Cr), gold (Au), nickel (Ni), and neodymium (Nd) It may be formed of a single layer or multiple layers of one or alloys thereof. The upper second gate electrode 134T may be patterned to overlap the second active layer 131 and the second gate insulating layer 114. A first scan signal SCAN1 that controls whether to switch the second switching thin film transistor T2 may be applied to the second upper second gate electrode 134T.

A protective layer 115 may be disposed on the isolation insulating layer 114, the second active layer 131, and the upper second gate electrode 134T. The protective layer 115 may be composed of a single layer of silicon nitride (SiNx) or silicon oxide (SiOx) or multiple layers thereof.

The second source electrode 132 and the second drain electrode 133 may be disposed on the protective layer 115. The second source electrode 132 and the second drain electrode 133 may be connected to the second active layer 131 through a contact hole formed in the protective layer 115.

The planarization layer 117 may be disposed on the second source electrode 132, the second drain electrode 133, and the protective layer 115. The planarization layer 117 may be made of an organic material for planarizing the upper portions of the driving thin film transistor DT and the second switching thin film transistor T2. Although not illustrated, a contact hole for exposing the second drain electrode 133 may be formed in the planarization layer 117 for electrical connection with the anode electrode of the light emitting device disposed on the planarization layer 117.

As described above, the second switching thin film transistor T2 disposed in the active area A/A of the display device 100 according to an exemplary embodiment of the present invention has a double gate structure and the lower second gate electrode 134B. By configuring the compensation voltage according to the threshold voltage change of the second switching thin film transistor T2 to be applied, the degradation of the image quality of the display device 100 according to an exemplary embodiment of the present invention can be minimized.

Meanwhile, referring to FIG. 4, the dummy pixel 420 may include a dummy pixel driver 421 and a detector 422. The dummy pixel 420 may have a structure similar to the pixel 410 disposed in the active area A/A, but the light emitting device is not formed. That is, the dummy pixel 420 does not include a light emitting unit. Accordingly, the dummy pixel 420 has a structure similar to the pixel 410 of the active area A/A, but does not emit light.

The dummy pixel driver 421 includes one or more switching thin film transistors T1-T5, a driving thin film transistor DT, and a capacitor Cst. That is, the dummy pixel driver 421 may have a structure similar to the pixel driver 411 disposed in the active area A/A. However, the second switching thin film transistor T2 of the dummy pixel driver 421 may have a single gate structure unlike the second switching thin film transistor disposed in the active area A/A. Since the dummy pixel driver 421 has a structure similar to that of the pixel driver 411 of the active area A/A, it can be formed in the same process. In addition, since the dummy pixel driver 421 has a structure similar to that of the pixel driver 411 of the active area A/A, a change in the threshold voltage of the second switching thin film transistor T2 can be more accurately detected.

The detector 422 may detect whether the threshold voltage of the second switching thin film transistor T2 is changed. The detector 422 may be configured as a sensing thin film transistor ST1. In this case, the active layer of the sensing thin film transistor ST1 may be made of a low temperature polysilicon material. The sensing thin film transistor ST1 is a gate connected between the fifth node N5 of the dummy pixel driver 421 and the low potential voltage VSS, an arbitrary voltage, for example, a reference voltage to receive a reference voltage Vref. A source connected to the line and a drain connected to the compensation unit 430 may be included. The sensing thin film transistor ST1 may be driven in response to every frame driven by the pixel 410 disposed in the active area A/A, and is active by applying a voltage applied through a source, that is, a deterioration stress voltage. Whether or not the pixel 410 disposed in the area A/A is deteriorated can be detected. That is, in the display device 100 according to an exemplary embodiment of the present invention, the sensing thin film transistor ST1 is further added to the dummy pixel 420 to be disposed, and an arbitrary stress voltage is applied to the sensing thin film transistor ST1. Deterioration of the pixel 410 formed in the active area A/A may be detected by artificially generating deterioration at a level substantially equal to the pixel 410 formed in the active area A/A.

The compensation unit 430 compares the detection result detected by the detection unit 422 of the dummy pixel 420 with a preset reference value Vr, and generates a compensation voltage according to the result to generate the compensation voltage of the active area A/A. The compensation voltage is applied to the lower second gate electrode 134B of the second switching thin film transistor T2. That is, one end of the compensation unit 430 is connected to the detection unit 422 of the dummy pixel 420, and the other end of the pixel 410 of the active area A/A, more specifically, the second switching thin film transistor T2. It can be electrically connected to. In this case, the compensation voltage corresponds to a timing at which the second scan signal SCAN2 is turned on in the sampling and programming period, and the lower second gate electrode 134B of the second switching thin film transistor T2 in the active area A/A. Can be applied to. The compensator 430 may be referred to as a comparator, and may be, for example, an op amp. On the other hand, in one embodiment of the present invention, the compensation unit 430 may be disposed on the timing controller 140, but is not limited thereto and may be arranged on the gate driver 120.

As described above, in the display device 100 according to an exemplary embodiment of the present invention, the sensing thin film transistor ST1 is further disposed on the dummy pixel 420 and the pixel according to the change in the threshold voltage disposed in the active area A/A. Arbitrary deterioration stress voltage is applied every frame using the sensing thin film transistor ST1 disposed in the dummy pixel 420 to be similar to the deterioration degree of 410, so that it is more accurately disposed in the active region A/A. The degree of deterioration of the pixel 410 can be detected.

Also, the display device 100 according to an embodiment of the present invention compensates the pixel 410 of the active area A/A in response to a result detected by the detector 422 disposed in the dummy pixel 420. By configuring the compensation voltage to be applied through the compensation unit 430, the image quality degradation of the display device 100 due to the change in the threshold voltage of the second switching thin film transistor T2 can be minimized.

The display device 100 according to an exemplary embodiment of the present invention uses the dummy pixel DP of the non-active area N/A having a structure similar to the pixel P of the active area A/A. After detecting a change in the threshold voltage of the second switching thin film transistor T2, a compensation voltage according to the detection result is generated and configured to be applied to the second switching thin film transistor T2, so that the second switching thin film of the active area A/A The threshold voltage compensation of the transistor T2 can be more accurately performed.

Accordingly, the display device 100 according to an exemplary embodiment of the present invention can minimize a decrease in luminance and a decrease in image quality of the display device 100 due to a change in the threshold voltage of the second switching thin film transistor T2.

Meanwhile, the display device 100 according to an exemplary embodiment of the present invention uses a dummy pixel DP disposed in each of the same pixel rows to threshold voltage of the second switching thin film transistor T2 in the active area A/A. Threshold voltage compensation may be performed for each pixel row by detecting a change.

The following embodiments will be described with reference to FIGS. 6 and 7 for other embodiments in which threshold voltage compensation is performed for each pixel to minimize image quality degradation.

6 is a circuit diagram schematically illustrating a pixel structure of an active area of a display device according to another exemplary embodiment of the present invention. Referring to FIG. 6, a pixel disposed in an active area A/A of a display device according to another exemplary embodiment of the present invention may include a pixel driver 610, a light emitting unit 620, and a compensation unit 630. have. The pixel driving unit 610 and the light emitting unit 620 provided in each pixel of the active area illustrated in FIG. 6 are the pixel driving unit 410 of the active area A/A described with reference to FIGS. 4 and 5 and Since it has the same structure as the light emitting unit 420, a detailed description of the pixel driving unit 610 and the light emitting unit 620 will be omitted, and the description will be focused on the compensation unit 630.

Referring to FIG. 6, the compensation unit 630 may include a sensing thin film transistor ST1. The gate of the sensing thin film transistor ST1 is connected to the drain of the second switching thin film transistor T2, the source is connected to the reference voltage line Vref, and the drain is the lower second gate of the second switching thin film transistor T2. It is connected to the electrode 134B. At this time, when the reference voltage is applied from the reference voltage line Vref, the compensation unit 630 senses the reduced reference voltage, that is, the compensation voltage, while the sensing thin film transistor ST1 acts as one variable resistor. T2) is applied to the lower second gate electrode 134B. More specifically, the sum of the threshold voltage Vth and the data voltage Vdata may be applied to the drain terminal of the second switching thin film transistor T2 in the sampling and programming period. However, as described above, since the active layer of the second switching thin film transistor T2 is made of an oxide semiconductor material, the threshold voltage (Vth) characteristic is shifted to a negative characteristic due to its unique characteristic, and thus shifted to a negative polarity. Since the characteristic of the threshold voltage Vth also affects the light emission section P4, it causes a decrease in image quality of the display device. Accordingly, in order to compensate for the threshold voltage (Vth) characteristic of the second switching thin film transistor T2, the compensation voltage of the positive characteristic is applied to the lower second gate electrode 134B of the second switching thin film transistor T2 having the double gate structure. To be applied. In this case, the size of the variable resistance of the sensing thin film transistor ST1 may be increased if the drain terminal of the second switching thin film transistor T2 or the threshold voltage Vth of the second node N2 has a negative characteristic. In this case, the reference voltage applied from the reference voltage line Vref may be a positive (+) bias voltage. More specifically, in the display device according to another embodiment of the present invention, the second scan signal SCAN2 is applied to turn on the second switching thin film transistor T2 and at the same time, the sensing thin film transistor ST1 is also turned on. The positive bias voltage applied through the voltage line may be applied to the lower second gate electrode 134B of the second switching thin film transistor T2. In this case, the sensing thin film transistor ST1 may be one variable resistor. That is, the sensing thin film transistor ST1 adjusts the voltage applied from the reference voltage line Vref according to a signal input to the gate of the sensing thin film transistor ST1 connected to the second node N2 so that a compensation voltage is applied. can do.

Accordingly, in the display device according to another exemplary embodiment of the present invention, a compensation unit 630 capable of generating and applying a compensation voltage according to a threshold voltage change of the second switching thin film transistor T2 for each pixel is disposed in the pixel circuit. By doing so, the threshold voltage change of the second switching thin film transistor T2 may be compensated for each pixel.

Meanwhile, the active layer of the sensing thin film transistor ST1 constituting the compensation unit 630 according to another embodiment of the present invention may be made of low-temperature polysilicon. This is because, as described above, the characteristics of the low-temperature polysilicon have more stable properties.

However, the compensation unit 630 of FIG. 6 consists of only one sensing thin film transistor ST1 and uses the sensing thin film transistor ST1 as a variable resistor to increase the magnitude of the compensation voltage applied to the second switching thin film transistor T2. However, the magnitude of the voltage applied to the second switching thin film transistor T2 is not stable, and may be shaken according to the step of driving the pixel. Accordingly, a more stable circuit configuration is proposed as another embodiment, and the configuration of the compensation unit according to another embodiment will be described with reference to FIG. 7 below.

7 is a circuit diagram schematically illustrating a structure of a portion of a pixel circuit in an active area of a display device according to another exemplary embodiment of the present invention.

Referring to FIG. 7, a pixel disposed in the active area A/A of a display device according to another exemplary embodiment of the present invention includes a pixel driver 610, a light emitting unit 620, and a compensation unit 730. Can be. The pixel driving unit 610 and the light emitting unit 620 of the pixel in the active area illustrated in FIG. 7 are the pixel driving unit 410 and the light emitting unit (in the active area A/A) described with reference to FIGS. 4 and 5 described above. Since it has the same structure as 420, a detailed description of the pixel driver 610 and the light emitting unit 620 will be omitted, and the description will be focused on the compensation unit 730.

Referring to FIG. 7, the compensation unit 730 may include a first sensing thin film transistor ST1 and a second sensing thin film transistor ST2. In this case, the active layers of the first sensing thin film transistor ST1 and the second sensing thin film transistor ST2 may be made of different semiconductor materials. The compensation unit 730 may be configured to apply a compensation voltage when the second scan signal SCAN2 is applied in the sampling and programming period.

The first sensing thin film transistor ST1 may be configured to more stably configure the compensation unit 730. The first sensing thin film transistor ST1 may be configured to create a driving environment similar to the second switching thin film transistor T2. Accordingly, the active layer of the first sensing thin film transistor ST1 may be made of an oxide semiconductor material. The first sensing thin film transistor ST1 is turned on when the second scan signal SCAN2 is applied, and the second sensing thin film transistor ST2 is also turned on so that the compensation voltage is applied while the second scan signal SCAN2 is applied. It can be done. The gate of the first sensing thin film transistor ST1 is connected to the second gate line, the source is connected to the gate of the second sensing thin film transistor ST2, and the drain terminal is connected to the high potential voltage line VDD. The first sensing thin film transistor ST1 may serve to increase the gate potential of the second sensing thin film transistor ST2 to compensate for the negative characteristic of the threshold voltage of the second switching thin film transistor T2.

The second sensing thin film transistor ST2 may serve as a variable resistor in the compensation unit 730. The gate of the second sensing thin film transistor ST2 is connected to the drain of the first sensing thin film transistor ST1, the source is connected to the reference voltage line Vref, and the drain is the bottom second of the second switching thin film transistor T2. It is connected to the gate electrode 134B. In this case, the level of the reference voltage applied from the reference voltage line Vref may be a negative bias voltage. Because, as the gate of the second sensing thin film transistor ST2 is opened, that is, the second sensing thin film transistor ST2 is turned on, the potential applied to the lower second gate electrode of the second switching thin film transistor T2 is greatly increased. This is because the negative characteristic of the threshold voltage of the second switching thin film transistor T2 can be compensated.

The active layer of the second sensing thin film transistor ST2 may be made of a low temperature polysilicon semiconductor material. Here, the second sensing thin film transistor ST2 acts as a variable resistor having a larger resistance value as the threshold voltage characteristic of the drain of the second switching thin film transistor T2 is negatively shifted. In the second sensing thin film transistor ST2, as the potential of the gate terminal increases, a resistance value as a variable resistor may decrease. Accordingly, the compensation unit 730 according to another embodiment of the present invention may reduce the width at which the potential of the compensation voltage fluctuates and stably apply a positive voltage to the second switching thin film transistor T2 stably. Can be. That is, when the second scan signal SCAN2 is applied to the compensation unit 730, the first sensing thin film transistor ST1 and the second sensing thin film transistor ST2 are turned on and the source terminal of the second sensing thin film transistor ST2 is turned on. The compensation voltage is applied to the lower second gate electrode 134B of the second switching thin film transistor T2 through the second sensing thin film transistor ST2 whose reference voltage Vref is applied from the variable resistor.

As described above, the compensation unit 730 disposed in the active area A/A of the display device according to another embodiment of the present invention is the same as the second switching thin film transistor T2 compared to the embodiment of FIG. 6. When the second scan signal SCAN2 is applied, the compensation voltage is stably applied by adding the first sensing thin film transistor ST1 that is turned on when the second scan signal SCAN2 is applied, and the magnitude of the compensation voltage It is configured to include a second sensing thin film transistor ST2 capable of controlling the voltage, thereby more stably applying a compensation voltage as the threshold voltage characteristic of the second switching thin film transistor T2 is shifted to a negative characteristic.

In addition, the display device according to another exemplary embodiment of the present invention is configured to further include a compensation unit 730 for each pixel of the active area A/A so that compensation for a threshold voltage change is directly performed for each pixel. can do.

8 is a waveform diagram illustrating a signal input to a pixel circuit according to an embodiment of the present invention.

Referring to FIG. 8, a pixel circuit according to an exemplary embodiment of the present invention is a pixel disposed on one horizontal line through an initialization section P1, a sampling and programming section P2, a holding section P3, and a light emitting section P4. A data voltage is written in each, and each pixel emits light.

In the initialization period P1, the first scan signal SCAN1 rises to a high state, and the second scan signal SCAN2 maintains a low state. At the same time, the first emission control signal EM1 falls to a low state, and the second emission control signal EM2 maintains a high state. Accordingly, in the initialization period P1, the second switching thin film transistor T2, the third switching thin film transistor T3, and the fifth switching thin film transistor T5 are turned on in the pixel circuit illustrated in FIG. 2, and the first switching The thin film transistor T1 and the fourth switching thin film transistor T4 are turned off. Accordingly. In the initialization period P1, the initialization voltage VINI is supplied to the fourth node N4 through the fifth switching thin film transistor T5, and is applied to the first node N1 through the third switching thin film transistor T3. The high potential voltage VDD is supplied to the second node N2 through the second switching thin film transistor T2. That is, as the initialization voltage VINI is supplied to the fifth node N5 that is the anode of the light emitting device OD, the data voltage written to the light emitting device OD is initialized, and the gate of the driving thin film transistor DT is damaged. The above voltage (VDD) is supplied.

In the sampling and programming period P2, the first scan signal SCAN1 rises from a low state to a high state, and the second scan signal SCAN2 also rises from a high state. In the sampling and programming period P2, the second emission control signal EM2 is polled to go low, and the first emission control signal EM1 is also kept low. Accordingly, in the sampling and programming period P2, the first switching thin film transistor T1, the second switching thin film transistor T2, and the fifth switching thin film transistor T5 are turned on, and the third switching thin film transistor T3 and The fourth switching thin film transistor T4 is turned off. Accordingly, the data voltage is supplied to the third node N3 through the first switching thin film transistor T1. Further, as the second switching thin film transistor T2 is turned on, the first node N1 which is a drain node of the driving thin film transistor DT and the second node N2 that is a gate node of the driving thin film transistor DT are By being connected, the gate-source voltage Vgs of the driving thin film transistor DT is sampled as a threshold voltage Vth of the driving thin film transistor DT by a diode-connection method. In addition, as the fifth switching thin film transistor T5 is turned on, the initialization voltage VINI is supplied to the fourth node N4, and the data voltage+threshold voltage-initialization voltage value is stored in the capacitor Cst. Accordingly, during the sampling and programming period P2, the first node N1 and the second node N2 have a data voltage + threshold voltage value, the third node N3 has a data voltage value, and the fourth node ( N4) has an initialization voltage value.

In addition, when the second scan signal SCAN2 is applied, the first sensing thin film transistor ST1 and the second sensing thin film transistor ST2 of the compensation unit 730 illustrated in FIG. 7 are turned on to turn on the reference voltage line Vref. The voltage applied from) opens the gate of the second sensing thin film transistor ST2, and as the gate is opened, the potential applied to the lower second gate electrode of the second switching thin film transistor T2 is greatly increased. As can be seen, the voltage of the second node N2 is shifted to a positive characteristic.

In addition, the sensing thin film transistor ST1 of the compensation unit 730 illustrated in FIG. 6 is referenced through a reference voltage line when the second scan signal SCAN2 is raised from a low level to a high level in the sampling and programming period P2. It is possible to prevent or minimize a decrease in display quality by supplying a voltage so that a compensation voltage is applied to the second switching thin film transistor T2.

Since the operation of the holding section P3 and the light emitting section P4 is driven in the same manner as described in FIG. 3 above, detailed description will be omitted.

In addition, as illustrated in FIG. 8, the compensation voltage is applied to the second switching thin film transistor T2 while the second scan signal SCAN2 is turned on, so that the holding period P3 and the emission period P4 are also applied. The display device according to an exemplary embodiment of the present invention can be stably driven by minimizing a change in the characteristic of the threshold voltage due to the compensation voltage.

A display device according to various embodiments of the present invention may be described as follows.

A display device according to an exemplary embodiment of the present invention is disposed on a display panel and a display panel in which a plurality of pixels arranged in an active area in which an image is displayed and one or more dummy pixels arranged in adjacent inactive areas of the active area are arranged. A compensation unit configured to apply a compensation voltage according to the deterioration of the pixel, wherein the plurality of pixels control a light emitting unit including a light emitting element and driving of the light emitting unit, and at least one pixel including a thin film transistor having a double gate structure. A driving unit, and a compensation voltage applied from the compensation unit may be configured to be applied to the thin film transistor having the double gate structure.

According to another feature of the present invention, the pixel driver receives a data voltage by receiving a capacitor that stores a data voltage supplied to a pixel, a driving thin film transistor that controls a light emission current flowing through a light emitting element, and a scan signal supplied through a gate line of a pixel. And one or more switching thin film transistors to be charged in the capacitor, and among the one or more switching thin film transistors, a switching transistor adjacent to a node having a sum of a data voltage and a threshold voltage may have a double gate structure.

According to another feature of the present invention, the active layer of the driving thin film transistor may be made of a low temperature polysilicon material, and the active layer of the switching thin film transistor having a double gate structure may be made of an oxide semiconductor material.

According to another feature of the present invention, in a thin film transistor having a double gate structure, a signal for switching a thin film transistor is applied to an upper gate electrode, and a compensation voltage applied from the compensation unit may be applied to a lower gate electrode.

According to another feature of the invention, the dummy pixel may include a detection unit that detects a change in threshold voltage of the thin film transistor having the double gate structure.

According to another feature of the invention, the detection unit is composed of one thin film transistor, and the active layer of the thin film transistor may be made of a low temperature polysilicon material.

According to another feature of the present invention, the compensation unit may be connected to a detection unit at one end and a thin film transistor having a double gate structure at the other end.

According to another feature of the present invention, the compensation unit may generate a compensation voltage by comparing the detected value detected by the detection unit with a preset reference value.

A display device according to another exemplary embodiment of the present invention includes an active area in which a plurality of pixels for displaying an image are disposed, and an inactive area in which a driving circuit is disposed around the active area to drive each of the plurality of pixels, Each of the plurality of pixels includes a light emitting unit including a light emitting element that emits light, a driving thin film transistor that controls light emission current flowing through the light emitting element, and a scan signal supplied through a corresponding gate line, and data supplied through the data line It may include a pixel driving unit including one or more switching thin film transistors to charge a voltage to a capacitor, and a compensation unit applying a compensation voltage to any one of the switching thin film transistors.

According to another feature of the present invention, any one of the switching thin film transistors to which a compensation voltage is applied may have an active layer made of an oxide semiconductor material.

According to another feature of the present invention, any one of the switching thin film transistors has a double gate structure having an upper gate electrode and a lower gate electrode, and different signals may be applied to the upper gate electrode and the lower gate electrode.

According to another feature of the invention, the compensation voltage applied from the compensation unit may be applied to the lower gate electrode.

According to another feature of the invention, the compensation unit may be made of one sensing thin film transistor, and the active layer of the sensing thin film transistor may be made of a low temperature polysilicon material.

According to another feature of the present invention, the sensing thin film transistor has a gate terminal connected to a drain terminal of any one thin film transistor, a source terminal connected to a reference voltage line, and a drain terminal a lower gate electrode of one thin film transistor. Can be connected to.

According to another feature of the present invention, the reference voltage applied from the reference voltage line may have positive polarity.

According to another feature of the present invention, the compensation unit includes a first sensing thin film transistor and a first sensing thin film transistor turned on by a scan signal rising from a low level to a high level when a threshold voltage characteristic of any one thin film transistor is shifted to a negative polarity. A second sensing thin film transistor connected to a source terminal of the sensing thin film transistor and a lower gate electrode of any one of the thin film transistors may be included.

According to another feature of the present invention, the second sensing thin film transistor serves as a variable resistor in the compensation unit, and the variable resistance of the second sensing thin film transistor may be smaller as the gate of the second sensing thin film transistor is turned on. .

According to another feature of the invention, the active layer forming each of the first sensing thin film transistor and the second sensing thin film transistor may be made of different materials.

According to another feature of the invention, the active layer of the first sensing thin film transistor may be made of an oxide semiconductor material, and the active layer of the second sensing thin film transistor may be made of a low temperature polysilicon material.

According to another feature of the present invention, the voltage applied to the second sensing thin film transistor may be a negative bias voltage.

The embodiments of the present invention have been described in more detail with reference to the accompanying drawings, but the present invention is not necessarily limited to these embodiments, and may be variously modified without departing from the technical spirit of the present invention. . Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the scope of the technical spirit of the present invention is not limited by these embodiments. Therefore, it should be understood that the above-described embodiments are illustrative in all respects and not restrictive. The scope of protection of the present invention should be interpreted by the claims below, and all technical spirits within the equivalent range should be interpreted as being included in the scope of the present invention.

100: display device
110: display panel
120: gate driver
130: data driver
140: timing controller

Claims (20)

A display panel in which a plurality of pixels arranged in an active area in which an image is displayed and one or more dummy pixels arranged in adjacent inactive areas of the active area are arranged; And
It includes; a compensation unit configured to apply a compensation voltage according to the deterioration of the pixel disposed on the display panel;
The plurality of pixels control a light emitting unit including a light emitting element and the driving of the light emitting unit, and at least one includes a pixel driving unit including a thin film transistor having a double gate structure,
The compensation voltage applied from the compensation unit is applied to the thin film transistor having the double gate structure. According to claim 1, wherein the pixel driver,
A capacitor storing a data voltage supplied to the pixel;
A driving thin film transistor for controlling a light emission current flowing through the light emitting element;
And one or more switching thin film transistors receiving the scan signal supplied through the gate line of the pixel and charging the data voltage to the capacitor.
A display device of the one or more switching thin film transistors adjacent to a node where a sum of the data voltage and a threshold voltage is applied has a double gate structure. According to claim 2,
The active layer of the driving thin film transistor is made of a low temperature polysilicon material, and the active layer of the switching thin film transistor having the double gate structure is made of an oxide semiconductor material. According to claim 1,
In the thin film transistor having the double gate structure, a signal for switching a thin film transistor is applied to an upper gate electrode, and a compensation voltage applied from the compensation unit is applied to a lower gate electrode. According to claim 1,
The dummy pixel includes a detector configured to detect a threshold voltage change of the thin film transistor having the double gate structure. The method of claim 5,
The detection unit is composed of one thin film transistor,
The active layer of the thin film transistor is made of a low temperature polysilicon material. The method of claim 6,
The compensation unit has one end connected to the detection unit and the other end connected to the thin film transistor having the double gate structure. The method of claim 7,
The compensation unit generates a compensation voltage by comparing the detection value detected by the detection unit with a preset reference value. A display device comprising an active area in which a plurality of pixels for displaying an image are disposed and an inactive area in a vicinity of the active area and in which a driving circuit for driving each of the plurality of pixels is disposed.
Each of the plurality of pixels,
A light emitting unit including a light emitting element that emits light;
A pixel driver including a driving thin film transistor controlling a light emission current flowing through the light emitting device and one or more switching thin film transistors receiving a scan signal supplied through a corresponding gate line to charge a data voltage supplied through the data line to a capacitor. ; And
And a compensation unit applying a compensation voltage to any one of the one or more switching thin film transistors. The method of claim 9,
The display device of any one of the switching thin film transistors to which the compensation voltage is applied is made of an oxide semiconductor material. The method of claim 10,
Any one of the switching thin film transistors has a double gate structure having an upper gate electrode and a lower gate electrode,
A display device having different signals applied to the upper gate electrode and the lower gate electrode. The method of claim 11,
The compensation voltage applied from the compensation unit is applied to the lower gate electrode. The method of claim 9,
The compensation unit is made of one sensing thin film transistor, and the active layer of the sensing thin film transistor is made of a low temperature polysilicon material. The method of claim 13,
The gate of the sensing thin film transistor is connected to the drain of any one of the switching thin film transistors, a source is connected to a reference voltage line, and a drain is connected to the lower gate electrode of the one switching thin film transistor. The method of claim 14,
The voltage applied to the source of the sensing thin film transistor is a positive bias voltage. The method of claim 9,
The compensation unit may include: a first sensing thin film transistor turned on by a scan signal rising from a low level to a high level when the threshold voltage characteristic of any one of the thin film transistors is shifted to a negative polarity; And
And a second sensing thin film transistor connected to a source terminal of the first sensing thin film transistor and connected to a lower gate electrode of any one of the thin film transistors. The method of claim 16,
The second sensing thin film transistor serves as a variable resistor in the compensation unit, and the variable resistance of the second sensing thin film transistor decreases as the gate of the second sensing thin film transistor turns on. The method of claim 16,
The active layer forming each of the first sensing thin film transistor and the second sensing thin film transistor is formed of a different material. The method of claim 18,
The active layer of the first sensing thin film transistor is made of an oxide semiconductor material, and the active layer of the second sensing thin film transistor is made of a low temperature polysilicon material. The method of claim 17,
The voltage applied to the second sensing thin film transistor is a negative bias voltage.

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