KR20150077897A - Organic light emitting diode display device and method for driving the same - Google Patents

Abstract

The present invention relates to an organic light emitting diode display apparatus, which enables to display an image as each sub pixel of an organic light emitting diode display panel compensates a data voltage with a compensation reference voltage as well as improving image quality efficiency by minimizing a noise influence when compensating the data voltage, and an operating method thereof. The organic light emitting diode display apparatus comprises: the display panel formed to display the image as a plurality of sub pixels compensate the data voltage with the compensation reference voltage; a gate operating portion for operating a gate line of the display panel and light emitting control lines; and a power supply portion for respectively supplying a high potential voltage and a low potential voltage to first and second power lines of the display panel, and supplying the compensation reference voltage to a compensation power line, wherein each sub pixel receives the low potential voltage or a direct current voltage from the outside as at least one capacitor reference point voltage, and compensates the data voltage by charging and discharging the compensation reference voltage through at least one capacitor.

Description

Technical Field [0001] The present invention relates to an organic light emitting diode (OLED) display device,

The present invention relates to an organic light emitting diode (OLED) display panel in which each sub pixel compensates a data voltage by a compensated reference voltage to display an image and minimizes the influence of noise during data voltage compensation, A display device and a driving method thereof.

BACKGROUND ART [0002] Recently, flat panel displays that are emerging include liquid crystal displays (LCDs), field emission displays, plasma display panels, and organic light emitting diodes Emitting Display). Among them, organic light emitting diode display devices are self-luminous devices that emit organic light emitting layers by recombination of electrons and holes, and are expected to be a next generation display device because they have a high brightness, a low driving voltage and an ultra thin film.

Each of the plurality of sub-pixels constituting the organic light emitting diode display device includes an organic light emitting diode composed of an organic light emitting layer between an anode and a cathode, and a pixel circuit for independently driving each organic light emitting diode.

The pixel circuit includes a plurality of switching transistors, at least one capacitor, and a driving transistor. The plurality of switching transistors are responsive to the control signals generated in units of horizontal periods to charge the data signals to the capacitors. The driving transistor adjusts the gradation of each pixel by adjusting the magnitude of the current supplied to the organic light emitting diode so as to correspond to the magnitude of the image voltage charged in the capacitor in response to the separate light emission signal.

In recent years, pixel structures for displaying high-resolution images have been variously presented. However, there are limitations in simplifying the pixel structure and the pixel driving period, and there is a limitation in designing and implementing a high-resolution panel.

In recent years, a method has been proposed and applied in which driving signals for driving sub-pixels adjacent to each other and a light emission control signal are overlapped with each other to increase the data voltage charge and compensation period of each sub-pixel Respectively.

However, since conventional sub-pixels which can increase the data voltage charging period or compensate the data voltage level to a specific voltage level directly receive the influence of noise of the voltage source or driving signals supplied from the outside, And so on. For example, among the elements constituting the pixel circuits of each sub-pixel, a capacitor configured to charge / discharge a data voltage, a capacitor configured to compensate for a data voltage level, and the like are directly connected to a voltage source or drive signal supply lines supplied from the outside Respectively. Accordingly, each of the conventional pixel circuits is directly affected by noise of a voltage source or driving signals supplied from the outside, and thus is vulnerable to noise, resulting in various problems such as image quality deterioration.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide an organic light emitting diode display panel in which each sub pixel compensates a data voltage with a compensated reference voltage to display an image, And an organic light emitting diode (OLED) display device and method for driving the same.

According to an aspect of the present invention, there is provided an organic light emitting diode (OLED) display device including: a display panel configured to display an image by compensating a data voltage of a plurality of sub-pixels with a compensation reference voltage; A gate driver for driving gate lines and emission control lines of the display panel; And a power supply unit for supplying a high potential and a low potential voltage to the first and second power supply lines of the display panel respectively and supplying a compensated reference voltage as a compensating power supply line, And a DC voltage from an external source is supplied to at least one capacitor reference point voltage to charge and discharge the compensation reference voltage through the at least one capacitor to compensate the data voltage.

Wherein at least one of the plurality of sub-pixels includes first and second switching elements, a light emission control switching element, a driving switching element, and first and second capacitors, And a data voltage from the data line is supplied to a gate terminal of the first switching element and a gate terminal of the first switching element and to a first node to which the first capacitor is connected in common And the second switching element is turned on or off according to a scan signal of a current stage or a scan signal of a previous stage. The second reference voltage is applied to the source of the drive switching element Terminal to a second node to which the second capacitor and the light emitting diode are commonly connected, And turns on or off according to a control signal to connect a high potential voltage to the drain electrode of the driving switching element when the transistor is turned on and the driving switching element applies a high potential voltage The second capacitor adjusts the amount of light emitted from the light emitting diode by controlling the amount of current supplied to the light emitting diode according to the voltage level of the first node, and the second capacitor is supplied with the low potential voltage And the second node is connected between the second power supply line and the low potential voltage as a reference point voltage to charge and discharge the voltage of the second node to maintain the voltage of the second node and the voltage applied to the light emitting diode .

Wherein the second capacitor receives the low potential voltage as the reference point voltage and charges the compensation reference voltage input through the second node during the initialization period, discharges during the light emission period, And the voltage applied to the diode is maintained.

The second power supply line may be formed on a substrate on which the pixel circuits of the sub-pixels are formed in units of horizontal lines along the direction of each gate line to supply the low potential voltage to the second capacitors of the sub-pixels .

The second capacitor is connected between the second node and a DC voltage source applied from the outside, and receives the external DC voltage as a reference point voltage to charge and discharge the voltage of the second node, The voltage applied to the gate electrode is maintained.

According to another aspect of the present invention, there is provided a method of driving an organic light emitting diode (OLED) display device, including a display panel configured to display an image by compensating a data voltage of a plurality of sub- A driving method of an organic light emitting diode display device, comprising: driving a gate line and emission control lines of the display panel; And supplying a high reference voltage and a low reference voltage to the first and second power supply lines of the display panel, respectively, and supplying a compensated reference voltage as a reference power supply line, A DC voltage from the outside is supplied to at least one capacitor reference point voltage, and the compensating reference voltage is charged and discharged through the at least one capacitor to compensate the data voltage.

Wherein at least one of the plurality of sub-pixels includes first and second switching elements, a light emission control switching element, a driving switching element, and first and second capacitors, And a data voltage from the data line is supplied to a gate terminal of the first switching element and a gate terminal of the first switching element and to a first node to which the first capacitor is connected in common And the second switching element is turned on or off according to a scan signal of a current stage or a scan signal of a previous stage. The second reference voltage is applied to the source of the drive switching element Terminal to a second node to which the second capacitor and the light emitting diode are commonly connected, And turns on or off according to a control signal to connect a high potential voltage to the drain electrode of the driving switching element when the transistor is turned on and the driving switching element applies a high potential voltage The second capacitor adjusts the amount of light emitted from the light emitting diode by controlling the amount of current supplied to the light emitting diode according to the voltage level of the first node, and the second capacitor is supplied with the low potential voltage And the second node is connected between the second power supply line and the low potential voltage as a reference point voltage to charge and discharge the voltage of the second node to maintain the voltage of the second node and the voltage applied to the light emitting diode .

Wherein the second capacitor receives the low potential voltage as the reference point voltage and charges the compensation reference voltage input through the second node during the initialization period, discharges during the light emission period, And the voltage applied to the diode is maintained.

The organic light emitting diode display device and the driving method thereof according to the present invention are characterized in that each sub pixel of the organic light emitting diode display panel compensates a data voltage to a compensated reference voltage to display an image, The influence can be minimized, the image quality improvement efficiency can be improved, and the reliability can be further increased.

1 is a block diagram illustrating an organic light emitting diode display device according to an embodiment of the present invention.
2 is an equivalent circuit diagram showing a sub-pixel of the display panel shown in Fig.
BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic light emitting diode (OLED) display device.
4 is a timing chart showing voltage variations of the first and second nodes at the time of driving the pixel circuits of the respective sub-pixels.

Hereinafter, an organic light emitting diode display device and a driving method thereof according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram illustrating an organic light emitting diode display according to an embodiment of the present invention. 2 is an equivalent circuit diagram showing a sub-pixel of the display panel shown in Fig.

The organic light emitting diode display device shown in FIG. 1 includes a display panel 1 configured to display an image by compensating a data voltage by a plurality of sub-pixels P with a compensation reference voltage V_init; A gate driver 2 for driving the gate lines GL1 to GLn and the emission control lines EL1 to ELn of the display panel 1; A data driver 3 for driving the data lines DL1 to DLm of the display panel 1; The high and low potential voltages VDD and VSS are supplied to the first and second power supply lines PL1 to PLn and VL of the display panel 1 and the compensation power supply line CPL is supplied with the compensated reference voltage V_init, or initialization voltage) to the power supply unit 4; And a timing control unit 5 for supplying image data from outside to the data driving unit 3 in a state of being aligned in accordance with driving of the display panel 1. Here, each of the sub-pixels P supplies a low-potential voltage VSS or a direct-current voltage from the outside to at least one capacitor reference-point voltage, and charges and discharges the compensating reference voltage V_init through at least one capacitor Thereby compensating the data voltage.

The display panel 1 displays a plurality of subpixels P arranged in a matrix form in each pixel region so that each subpixel P has a light emitting diode OLED and the light emitting diode OLED independently And a pixel circuit for driving the pixel circuit. More specifically, each sub-pixel P as shown in FIG. 2 includes a gate line GL, a data line DL, a compensation power line CPL, a light emission control line EL, And a light emitting diode (OLED) connected between the pixel circuits and the low potential voltage (VSS) connected to the two power supply lines (PL1 to PLn, VL) and equivalently represented by a diode. Here, the high-potential voltage VDD has a voltage level higher than the low-potential voltage VSS. And the low potential voltage VSS may be ground or ground voltage.

The pixel circuit of each sub-pixel P includes first and second switching elements T1 and T2, a light emission control switching element ET, a driving switching element DT and first and second capacitors Cst and Cdt. Respectively.

The first and second switching elements T1 and T2, the emission control switching element ET and the driving switching element DT may be formed of an NMOS transistor or a PMOS transistor. Hereinafter, the first and second switching elements T1, and T2, the emission control switching element ET, and the driving switching element DT are NMOS transistors will be described.

The first switching element T1 is turned on or off according to the scan signal Scan supplied through the gate line GLn and is turned on when the data voltage from the data line DL at the turn- N1. The first node N1 is a node to which the output terminal of the first switching device T1 and the gate terminal of the driving switching device DT and the first capacitor Cst are commonly connected. The first switching device T1 is turned on during the initialization period and the sampling period in each horizontal period (initialization period, sampling period, data injection period, light emission period), and is turned on between the data line DL and the first node N1 Thereby forming a current path.

The second switching element T2 is turned on or off according to the scan signal of the present stage or the scan signal of the previous stage and is supplied with the compensation reference voltage V_init applied to the turn- ). The second node N2 is a node to which the source terminal of the drive switching element DT, the second capacitor Cdt and the light emitting diode OLED are connected in common. The second switching device T2 supplies the compensated reference voltage Vini to the second node N2 so that the data voltage can be compensated for during the sampling period and the light emitting period during each horizontal period.

The emission control switching element ET is turned on or off according to the emission signal EM and connects the high potential source VDD to the drain electrode of the driving switching element DT at turn-on.

The driving switching element DT is supplied with the high potential voltage VDD through the emission control switching element ET and supplies the amount of current supplied to the light emitting diode OLED according to the voltage level of the first node N1 Thereby controlling the amount of light emitted from the light emitting diode OLED.

The first capacitor Cst is constituted between the first and second nodes N1 and N2 and receives the voltage VS of the second node N2 as a reference point voltage to charge and discharge the voltage of the first node N1, Thereby maintaining the output terminal voltage of the first node N1 and the drive switching element DT. In other words, the first capacitor Cst charges the voltage supplied to the first node N1 during the sampling period and the data injection period, discharges during the light emitting period, and the first node N1 and the drive switching element DT Output voltage is maintained. The first capacitor Cst receives the second node voltage Vs floating in the sampling period and the data injection period as the reference voltage, charges the voltage of the first node N1, and discharges in the light emitting period . Since the first capacitor Cst formed between the first and second nodes N1 and N2 does not receive an external signal or a voltage source directly, the noise due to an external signal or a voltage source is insignificant.

The second capacitor Cdt is connected between the second node N2 and the second power supply line VL to which the low potential VSS is supplied and receives the low potential voltage VSS as the reference point voltage, ) To charge and discharge the voltage of the second node N2 and the voltage applied to the light emitting diode OLED. In other words, the second capacitor Cdt charges the compensated reference voltage V_init supplied to the second node N2 in the setup period, and is discharged in the light emission period. The second capacitor Cdt receives the low potential voltage VSS having the smallest voltage level variation among the voltage sources input from the outside as a reference point voltage, charges the compensation reference voltage V_init in the initialization period, And maintains the voltage of the second node N2 and the voltage applied to the light emitting diode OLED. Although the second capacitor Cdt receives a low potential voltage VSS from the outside as a reference point voltage, the low potential voltage VSS has the smallest voltage variation among the voltage sources or signals input from the outside, Can be minimized.

In the case of the high-potential voltage (VDD), the level of the high-potential voltage (VDD) fluctuates in units of horizontal lines as the sub-pixels sequentially drive and emit light in every horizontal line unit though it is a direct current voltage. If the high-potential voltage VDD is input as the reference-point voltage of the second capacitor Cdt, the charging / discharging voltage level of the second capacitor Cdt may be influenced by each horizontal line and shaken. Therefore, it is preferable that the second capacitor Cdt receives the low potential voltage VSS having the smallest voltage variation as the reference point voltage to minimize the influence of the noise.

To this end, the second power supply line VL is formed on a substrate (for example, a lower substrate) on which the pixel circuits of the sub-pixels are formed in units of horizontal lines along the direction of each of the gate lines GL1 to GLn And supplies the low potential voltage VSS to the second capacitor Cdt of each sub-pixel. In general, when the low voltage VSS is supplied only to the anode electrode or the cathode electrode of the light emitting diode OLED, only the second power supply line VL is connected to only the substrate (for example, the upper substrate) . However, in the present invention, the second power supply line (VL) is also formed on the substrate in which the pixel circuit is configured to supply the low potential voltage (VSS) to the pixel circuits of the sub-pixels.

On the other hand, the second capacitor Cdt may receive a direct-current voltage applied from the outside, rather than a low-potential voltage VSS, as a reference-point voltage. That is, the second capacitor Cdt is constituted between the second node N2 and the DC voltage source applied from the outside and the second node N2, receives the external DC voltage as the reference point voltage, The voltage of the second node N2 and the voltage applied to the light emitting diode OLED may be maintained by charging and discharging the second node N2. In this case, a direct-current voltage supply line for supplying a direct-current voltage to each pixel circuit in the same configuration as the second power supply line VL is formed, so that the direct-current voltage can be supplied to the pixel circuits of the sub-pixels. Since the DC voltage supplied separately is not affected by the noise, the second capacitor Cdt can be prevented from being affected by the noise.

The light emitting diode OLED of each sub-pixel includes an organic layer formed between the anode electrode and the cathode electrode connected to the pixel circuit. The operation sequence and the light emission process of the pixel circuit and the light emitting diode (OLED) will be described in detail with reference to the driving waveform diagram attached hereto.

The gate driving unit 2 performs a scanning operation in response to a gate control signal GVS from the timing control unit 5, for example, a gate start pulse (GSP) and a plurality of gate shift clocks (GSC) Sequentially generates a signal (for example, a gate voltage of a low logic), and controls the pulse width of the scan signal in accordance with a gate output enable (GOE) signal. Then, the scan signals are sequentially supplied to the gate lines GL1 to GLn. Here, a gate-off voltage (for example, a gate voltage of high logic) is supplied during a period in which no scan signal is supplied to the gate lines GL1 to GLn.

Further, the gate driver 2 sequentially generates high-level or low-level emission control signals EM1 to EMn and supplies them to the respective emission control lines EL1 to ELn. The emission control signals EM1 to EMn sequentially output are supplied to the driving switching device DT during a period in which a current flows through the light emitting diode OLED, that is, during a period during which an image is displayed, Thereby adjusting the period of supplying the drain electrode.

The data driver 3 is connected to the timing controller 5 using a source start pulse SSP and a source shift clock SSC among data control signals DVS from the timing controller 5. [ That is, the analog data voltage. In response to a source output enable (SOE) signal, a data voltage is supplied to each data line DL1 to DLm. Specifically, the data driver 3 latches the digital image data Data input in accordance with the SSC, and then, in response to the SOE signal, outputs the gate-on signal to the gate lines GL1 to GLn every 1 horizontal period 1 And supplies the data voltages of the horizontal lines to the data lines DL1 to DLm.

The timing controller 5 aligns image data RGB input from the outside in accordance with the size and resolution of the display panel 1 and supplies the aligned digital image data Data to the data driver 3. The timing control unit 5 uses the sync signals input from the outside, for example, a dot clock DCLK, a data enable signal DE, a horizontal synchronizing signal Hsync, a vertical synchronizing signal Vsync, Gate and data control signals GVS and DVS and supplies them to the gate driver 2 and the data driver 3, respectively. Particularly, the timing controller 5 controls each of the emission control signals EM1 to EMn to turn-off level during a period when the gate driver 2 supplies the compensated reference voltage V_init during the driving period of each subpixel P And supplies the gate control signal GVS to the gate driver 2. [

3 is a waveform diagram for explaining a driving method of the organic light emitting diode display according to the present invention. 4 is a timing chart showing voltage variations of the first and second nodes at the time of driving the pixel circuits of the sub-pixels.

Referring to FIGS. 3 and 4, a frame period of each sub-pixel or a driving period of one horizontal line is divided into an initialization period (intial), a sampling period, a data injection period (writing) . At this time, initialization is possible even using the previous horizontal period.

First, the first and second switching elements T1 and T2 are turned on in the initialization period Intial. During this initialization period, the first and second nodes N1 and N2 are initialized to a predetermined reference voltage Vini. During the initialization period, the respective emission control signals EM1 to EMn are maintained and supplied at the turn-off level, so that the emission control switching element ET maintains the turn-off state. Therefore, the high voltage VDD is not supplied to the first node N1 including the drive switching element DT.

In the sampling period, the light emitting control switching element ET and the driving switching element DT are turned off and supplied to the first node N1 through the data voltage first switching element T1. The current flowing through the driving switching element DT flows into the second node N2 and senses the threshold voltage Vth of the driving switching element DT. At this time, the voltage level of the second node N2 converges to "VDD-Vth" from the compensated reference voltage Vini.

In the data writing period, the data voltage is injected into the first node N1. Since the second node N2 is in the floating state, the data voltage is increased by the changed voltage to maintain the sampling value of the previous period.

In the next light emission period, the light emission control switching element ET and the driving switching element DT are turned on. The driving transistor DT supplies the driving current to the light emitting diode OLED according to the voltage level of the first node N1 that was injected in the previous period.

As described above, in the present invention, each sub-pixel P of the organic light emitting diode display panel 1 compensates the data voltage by the compensated reference voltage V_init to display an image, It is possible to minimize the influence of noise, thereby improving the image quality improvement efficiency and further improving the reliability thereof.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Will be apparent to those of ordinary skill in the art.

Claims (10)

A display panel formed so that a plurality of sub-pixels compensate a data voltage with a compensated reference voltage to display an image;
A gate driver for driving gate lines and emission control lines of the display panel; And
And a power supply unit for supplying a high potential and a low potential voltage to the first and second power supply lines of the display panel and supplying a compensated reference voltage as a compensating power supply line,
Each of the sub-pixels supplies the low-potential voltage or a direct-current voltage from the outside as at least one capacitor reference-point voltage to charge and discharge the compensating reference voltage through the at least one capacitor to compensate the data voltage. The organic light emitting diode display device. The method according to claim 1,
At least one sub-pixel among the plurality of sub-
A first switching element, a second switching element, a light emission control switching element, a driving switching element, and first and second capacitors,
Wherein the first switching element is turned on according to a scan signal supplied through the gate line so that a data voltage from the data line is applied to the output terminal of the first switching element and the gate terminal of the driving switching element, To a first node connected in common,
The second switching element is turned on or off according to the scan signal of the current stage or the scan signal of the previous stage. The second reference voltage is applied to the source terminal of the drive switching element, A second capacitor, and a light emitting diode to a second node connected in common,
The light emission control switching element may be turned on or off according to a light emission control signal, and a high-potential voltage may be connected to the drain electrode of the driving switching element when the light-
Wherein the driving switching element controls an amount of light emitted from the light emitting diode by controlling an amount of current supplied to the light emitting diode according to a voltage level of the first node when a high potential voltage is supplied to the source electrode through the light emission control switching element,
Wherein the second capacitor is configured between the second node and the second power supply line to which the low potential voltage is supplied and receives the low potential voltage as the reference point voltage to charge and discharge the voltage of the second node, The voltage of the node and the voltage applied to the light emitting diode are maintained. 3. The method of claim 2,
The second capacitor
And a control unit configured to charge the compensation reference voltage input through the second node during the initialization period and to discharge the voltage of the second node and the voltage applied to the light emitting diode, And the organic light emitting diode display device. The method of claim 3,
The second power supply line
Wherein each of the plurality of sub-pixels is formed in a unit of a horizontal line along a direction of each gate line on a substrate constituting the pixel circuit of each of the sub-pixels, and supplies the low potential voltage to a second capacitor of each of the sub- Display device. 3. The method of claim 2,
The second capacitor
And a DC voltage source applied from the outside to the second node to receive the external DC voltage as a reference point voltage to charge and discharge the voltage of the second node so that a voltage applied to the second node and a voltage applied to the light emitting diode And the organic light emitting diode display device. A method of driving an organic light emitting diode display device having a display panel formed with a plurality of sub-pixels compensating for a data voltage with a compensated reference voltage to display an image,
Driving gate lines and emission control lines of the display panel;
Supplying a high-potential and a low-potential voltage to the first and second power supply lines of the display panel, respectively, and supplying a compensated reference voltage as a compensating power supply line,
Each of the sub-pixels supplies the low-potential voltage or a direct-current voltage from the outside as at least one capacitor reference-point voltage to charge and discharge the compensating reference voltage through the at least one capacitor to compensate the data voltage. And a driving method of the organic light emitting diode display device. The method according to claim 6,
At least one sub-pixel among the plurality of sub-
A first switching element, a second switching element, a light emission control switching element, a driving switching element, and first and second capacitors,
Wherein the first switching element is turned on according to a scan signal supplied through the gate line so that a data voltage from the data line is applied to the output terminal of the first switching element and the gate terminal of the driving switching element, To a first node connected in common,
The second switching element is turned on or off according to the scan signal of the current stage or the scan signal of the previous stage. The second reference voltage is applied to the source terminal of the drive switching element, A second capacitor, and a light emitting diode to a second node connected in common,
The light emission control switching element may be turned on or off according to a light emission control signal, and a high-potential voltage may be connected to the drain electrode of the driving switching element when the light-
Wherein the driving switching element controls the amount of light emitted from the light emitting diode by controlling the amount of current supplied to the light emitting diode according to a voltage level of the first node when a high potential voltage is supplied to the source electrode through the light emission control switching element,
Wherein the second capacitor is configured between the second node and the second power supply line to which the low potential voltage is supplied and receives the low potential voltage as the reference point voltage to charge and discharge the voltage of the second node, The voltage of the node and the voltage applied to the light emitting diode are maintained. 8. The method of claim 7,
The second capacitor
And a control unit configured to charge the compensation reference voltage input through the second node during the initialization period and to discharge the voltage of the second node and the voltage applied to the light emitting diode, Wherein the organic light emitting diode (OLED) display device includes a plurality of organic light emitting diodes (OLEDs). 9. The method of claim 8,
The second power supply line
Wherein each of the plurality of sub-pixels is formed in a unit of a horizontal line along a direction of each gate line on a substrate constituting the pixel circuit of each of the sub-pixels, and supplies the low potential voltage to a second capacitor of each of the sub- A method of driving a display device. 8. The method of claim 7,
The second capacitor
And a DC voltage source applied from the outside to the second node to receive the external DC voltage as a reference point voltage to charge and discharge the voltage of the second node so that the voltage of the second node and the voltage applied to the light emitting diode And driving the organic light emitting diode display device.

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