KR20110067365A - Organic electroluminescent display device and method of driving the same - Google Patents

Abstract

PURPOSE: An organic electroluminescent display device and a method of driving the same are provided to improve an afterimage by lowering the temperature of a white color. CONSTITUTION: In an organic electroluminescent display device and a method of driving the same, an organic electroluminescence panel(200) comprises an R pixel, and B pixel and G pixel. A gamma voltage generator(400) selectively outputs first gamma voltages and second gamma voltages. The first gamma voltages implement a white having a first color temperature. A second gamma voltage implement a white having a second color temperature. A data driver(330) generates the data voltage. A data line(DL) transfers the data voltage to a pixel.

Description

Organic electroluminescent display device and method of driving the same

The present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device and a driving method thereof.

As the information society develops, the demand for display devices for displaying images is increasing in various forms. Recently, liquid crystal displays (LCDs), plasma display panels (PDPs), organic fields Various flat display devices such as organic electroluminescent display devices (OELD) are being utilized.

Among these flat panel display devices, the organic light emitting display device is capable of low voltage driving, is thin, has excellent viewing angles, and has a fast response speed.

As an organic light emitting display device, an active matrix type organic light emitting display device in which pixels are arranged in a matrix and displaying an image is widely used.

When a data voltage is applied to a pixel of the organic light emitting display device, a current corresponding to the data voltage value is generated and applied to the organic light emitting diode of the pixel. Accordingly, the organic light emitting diode emits light having luminance corresponding to the amount of current applied.

Such an organic light emitting display device includes R (red) pixels, G (green) pixels, and B (blue) pixels in order to display color images. Such R pixels, G pixels, and B pixels include R organic light emitting diodes, G organic light emitting diodes, and B organic light emitting diodes that emit red, green, and blue light. Through the combination of the light emitted from the organic light emitting diode, it is possible to implement a color image.

On the other hand, in the case of displaying white in the organic light emitting display device, the color temperature of white is determined by a combination of luminance ratios between red, green, and blue. In general, as the color temperature of white increases, the luminance ratio of blue increases.

However, the life of the B organic light emitting diode is shorter than that of the R organic light emitting diode and the G organic light emitting diode. Accordingly, when the color temperature of the displayed white is increased, the luminance ratio of blue is increased, which results in accelerating the shortening of the life of the B organic light emitting diode.

Therefore, when white having a high color temperature is displayed for a long time, deterioration occurs to the B organic light emitting diode located in the region displaying white, resulting in afterimages. Regarding such afterimage generation, reference may be made to FIG. 1.

1 is a photograph showing a state in which an afterimage occurs on a screen of a mobile phone using a conventional organic light emitting display device.

Referring to FIG. 1, when the screen display is changed after displaying white having a high color temperature for a long time in a portion of the screen, it may be confirmed that an afterimage occurs in a region where white is displayed for a long time. In this regard, as mentioned above, as white with high color temperature is displayed for a long time, the B organic light emitting diode in the area where white is displayed is deteriorated. For this reason, the luminescence brightness deviation of the B organic light emitting diode is generated above a level that can be recognized by a person. Accordingly, even when the displayed image is switched, luminance deviation exists in an area where white is displayed, and afterimages are generated.

The present invention has an object to provide an organic light emitting display device capable of improving afterimages, a driving method thereof, and a manufacturing method thereof.

In order to achieve the above-described problem, the present invention is an organic electroluminescent panel comprising an R organic light emitting diode, a G organic light emitting diode, and a B organic light emitting diode each comprising an R pixel, a G pixel, and a B pixel. and; A gamma voltage generator capable of selectively outputting first gamma voltages implementing white with a first color temperature and second gamma voltages implementing white with a second color temperature lower than the first color temperature; A data driver for generating and outputting a data voltage corresponding to the image data using the selected gamma voltages; And a data line that receives the data voltage output from the data driver and transfers the data voltage to the corresponding pixel. When white is displayed in the same area of the screen for more than a threshold time, the gamma voltage generator generates the second gamma voltages. Provided is an organic light emitting display device for selecting and outputting.

The display device may further include a gamma control unit selectively outputting first and second color temperature data, wherein the gamma voltage generator may output the first and second data voltages in response to each of the first and second color temperature data. .

The gamma controller may include an image analyzer configured to analyze the input image data; A selection unit for selectively outputting first and second selection signals in response to an analysis result of the image analyzer; A register unit configured to store the first and second color temperature data and to output the first and second color temperature data in response to each of the first and second selection signals, wherein the white region is the same area of the screen in the image analyzer. If it is determined that the display is repeatedly displayed for more than a threshold time, the selector may output the second selection signal.

The image analyzer includes: a storage unit which stores image data of a previous frame; If the image data of the current frame and the image data of the previous frame is the same, it may include a count unit for increasing the number of counts.

In another aspect, the present invention relates to an organic electroluminescent light emitting diode comprising an organic electroluminescent panel comprising an R organic light emitting diode, a G organic light emitting diode, and a B organic light emitting diode, each of which comprises an R pixel, a G pixel, and a B pixel. In the driving method of the display device, the gamma voltage generation unit, the first gamma voltages for implementing a white color having a first color temperature, and the second gamma voltages for implementing a white having a second color temperature lower than the first color temperature Selectively outputting; Generating and outputting a data voltage corresponding to image data by using the selected gamma voltages in a data driver; And transmitting the data voltage output from the data driver to the corresponding pixel, and when the white is repeatedly displayed for more than a threshold time in the same area of the screen, the gamma voltage generator selects the second gamma voltages. The present invention provides a method of driving an organic light emitting display device.

The gamma control unit may further include selectively outputting first and second color temperature data, wherein the gamma voltage generator is further configured to output the first and second data voltages in response to each of the first and second color temperature data. can do.

Performing an analysis on the input image data in the image analysis unit of the gamma control unit; Selectively outputting first and second selection signals in response to an analysis result of the image analyzer; And in response to each of the first and second selection signals, outputting the first and second color temperature data stored in a register of the gamma control unit, wherein the white is repeated for a threshold time or more in the same area of the screen. If it is determined that the display, the second selection signal may be output.

In the present invention, when the same image is displayed for a long time, it is driven to lower the color temperature of the displayed white. As such, by lowering the color temperature of white, the luminance ratio of blue is relatively decreased, thereby increasing the lifetime of the B organic light emitting diode. Therefore, deterioration of the B organic light emitting diode is relatively reduced, and as a result, an effect of improving afterimages can be exerted.

Hereinafter, with reference to the drawings will be described embodiments of the present invention.

2 is a schematic view of an organic light emitting display device according to an embodiment of the present invention, and FIG. 3 is an equivalent circuit diagram of a pixel of the organic light emitting display device according to an embodiment of the present invention.

As illustrated, the organic light emitting display device 100 according to the embodiment of the present invention includes an organic light emitting panel 200 and a driver.

In the organic light emitting panel 200, a plurality of gate lines GL extend in a first direction, for example, in a row direction. A plurality of data lines DL extend in a second direction, for example, a column direction, which intersects the first direction. As such, the gate lines GL and the data lines DL that cross each other define a plurality of pixels P arranged in a matrix form.

Referring to FIG. 3, each pixel P of the organic light emitting panel 200 includes a switching transistor TS, a driving transistor TD, an organic light emitting diode OD, and a capacitor C. Can be formed.

The switching transistor TS is connected to the corresponding gate line and data line GL and DL. The driving transistor TD is connected to the switching transistor TS. For example, the gate electrode of the driving transistor TD is connected to the drain electrode of the switching transistor TS.

The organic light emitting diode OD is connected to the driving transistor TD. For example, a second electrode, for example, a cathode, of the organic light emitting diode OD is connected to the drain electrode of the driving transistor TD. Meanwhile, the first electrode, for example, the anode of the organic light emitting diode OD receives the first driving voltage VDD.

The capacitor C is connected between the gate electrode and the source electrode of the driving transistor TD. Meanwhile, the source electrode of the driving transistor TD receives the second driving voltage VSS. For example, the source electrode of the driving transistor TD may be grounded.

As described above, the pixel P configured in the organic light emitting panel 200 may include an R pixel emitting red, a G pixel emitting green, and a B pixel emitting blue. That is, the organic light emitting diode located in the R pixel emits red, the organic light emitting diode located in the G pixel emits green, and the organic light emitting diode located in the B pixel emits blue. Here, for convenience of description, the organic light emitting diodes positioned in each of the R pixels, the G pixels, and the B pixels may be referred to as R organic light emitting diodes, G organic light emitting diodes, and B organic light emitting diodes.

In the organic light emitting panel 200, neighboring R pixels, G pixels, and B pixels constitute one image display unit. Such an image display unit can realize color through a combination of red, green, and blue.

The driver may include a timing controller 310, a gate driver 320, a data driver 330, a gamma voltage generator 400, and a gamma controller 500.

The timing controller 310 generates a gate control signal GCS for controlling the gate driver 320 and a data control signal DCS for controlling the data driver 330. The gate control signal GCS and the data control signal DCS generated as described above are input to the gate driver 320 and the data driver 330, respectively.

Furthermore, the timing controller 310 supplies the video data Data supplied from the external system to the data driver 330 in synchronization with the data control signal DCS. Here, as the image data Data, R image data corresponding to the R pixel, G image data corresponding to the G pixel, and B image data corresponding to the B pixel are input.

The data driver 330 generates a data voltage corresponding to the input image data Data and outputs the data voltage to the corresponding data wiring DL. The data voltage is generated using the gamma voltages VG1 and VG2 generated by the gamma voltage generator 400. For example, the gamma voltages VG1 and VG2 input to the data driver 330 are divided. Among the voltages divided in this way, a voltage corresponding to the value of the input image data Data may be selected and output as a data voltage.

As described above, the data driver 330 converts the image data Data in the digital format into the data voltage in the analog format and outputs the data voltage.

The gate driver 320 may sequentially select the gate wiring GL in response to the gate control signal GCS supplied from the timing controller 310. For the selected gate wiring GL, a scan pulse having a turn on voltage is output. Accordingly, the switching transistor TS of the pixel P connected to the selected gate line GL is turned on. In synchronization with this, a data voltage is output to the data wiring DL and is input to the pixel P.

The data voltage input to the pixel P is applied to the gate electrode of the driving transistor TD through the switching transistor TS. Accordingly, a light emitting current corresponding to the applied data voltage value flows through the driving transistor TD, which is applied to the organic light emitting diode OD. As a result, the organic light emitting diode OD emits light having luminance corresponding to the applied light emission current value.

The gamma voltage generator 400 outputs gamma voltages VG1 and VG2 as described above. The gamma voltage generator 400 may generate a plurality of different gamma voltages VG1 and VG2, for example, first gamma voltages VG1 to n-th gamma voltages. N is a natural number of 2 or more. Each of the first to n gamma voltages corresponds to gamma voltages that may implement white having the first to n color temperatures.

In this case, for example, to implement the k-th color temperature, the gamma voltage generator 400 generates and outputs k-th gamma voltages. Here, k is 1 or more and n or less.

As such, the gamma voltage generator 400 may select one of the first to n gamma voltages and output the selected one.

Meanwhile, in the embodiment of the present invention, for convenience of description, the first and second gamma voltages VG1 and VG2 are generated as an example. Here, the first gamma voltages VG1 correspond to gamma voltages capable of implementing white having a relatively high color temperature, for example, a first color temperature. The second gamma voltages VG_2 correspond to gamma voltages capable of implementing white having a relatively low color temperature, for example, a second color temperature.

As such, the selective output of the gamma voltages VG and VG is controlled by the gamma voltage control unit 500. For example, the gamma voltage generator 400 generates the corresponding gamma voltages VG1 and VG2 in response to the color temperature data CCT1 and CCT2 output from the gamma controller 500.

To this end, the gamma controller 500 may selectively output the first to n color temperature data, for example, the first and second color temperature data CCT1 and CCT2.

Accordingly, when the first color temperature data CCT1 is selected and output, the gamma voltage generator 400 generates the first gamma voltages VG1. When the second color temperature data CCT2 is selected and output, the gamma voltage generator 400 generates the second gamma voltages VG2.

As described above, when the white color of the first color temperature is to be implemented, the gamma control unit 500 outputs the first color temperature data CCT1, and thus the gamma voltage generation unit 400 generates the first gamma voltage VG1. Will print. When the white color of the second color temperature is to be realized, the gamma control unit 500 outputs the second color temperature data CCT2, and thus the gamma voltage generation unit 400 outputs the second gamma voltage VG2. Done. Accordingly, the color temperature of white can be adjusted.

As described above, in the embodiment of the present invention, it is possible to perform the white color temperature adjustment, it is possible to effectively improve the afterimage problem that occurs in the prior art.

In this regard, in displaying the same image for a long time, when white having a high color temperature is continuously displayed in the same region, the blue luminance ratio in the region displaying white is relatively high. In general, the B organic light-emitting diode displaying blue has a characteristic that the shortening of its life is accelerated as the light emission luminance increases. For this reason, in the case of displaying white having a high color temperature, deterioration of the B organic light emitting diode is accelerated. However, in the related art, white having a relatively high color temperature, for example, a color temperature of about 9200K is set to be fixedly implemented. Accordingly, the deterioration of the conventional B organic light emitting diode is accelerated, resulting in a problem that an afterimage occurs.

In order to improve this, in the embodiment of the present invention, when displaying the same image for a long time, it is driven to lower the color temperature of the displayed white. For example, in a normal case of displaying a moving image or the like, white having a relatively high color temperature, for example, a color temperature of about 9200K may be implemented. On the other hand, when the same image is displayed for a long time, a white having a relatively low color temperature, for example, a color temperature of about 7000K is implemented.

As such, by lowering the color temperature of white, the luminance ratio of blue is relatively decreased, thereby increasing the lifetime of the B organic light emitting diode. Therefore, the deterioration of the B organic light emitting diode is relatively reduced, so that the effect of improving afterimages can be exerted.

As described above, the configuration and operation of the gamma control unit 500 to perform color temperature adjustment of the white according to the displayed image will be described in detail with reference to FIG. 4.

4 is a diagram illustrating an example of a configuration and an operation of a gamma control unit according to an exemplary embodiment of the present invention.

Referring to FIG. 4, the gamma controller 500 includes an image analyzer 510, a selector 520, and a register 530.

The image analyzer 510 may analyze the input image data (Data) on a frame basis and output the analysis result to the selector 520.

In this regard, for example, the image analyzer 510 may include a memory unit 511 and a count unit 512. Here, the frame memory may be used as the memory unit 511. In this case, the image data Data of the previous frame may be stored in the memory unit 511.

The image analyzer 510 may compare the image data of the previous frame and the image data of the current frame stored in the memory unit 511. As a result of the comparison, if it is determined that the same image, the counting unit 512 may increase the number of counts by one. Through the counting operation in the counting unit 512, the number of frames in which the same image is repeatedly input, that is, the time when the same image is displayed can be determined.

In this case, when the count reaches a set value, for example, the threshold number, the image analyzer 510 may analyze whether white is included in the corresponding image. Here, the threshold number may be set in consideration of the threshold time at which degradation of the B organic light emitting diode can be visually recognized in the case of continuously displaying white having the first color temperature. Therefore, when the count number is greater than or equal to the threshold number, afterimages may occur as the B organic light emitting diode deteriorates in the region where white is continuously displayed. Accordingly, when the count reaches a threshold number, an analysis may be performed as to whether white is included in the displayed image.

Here, when white is included in the image, the image analyzer 510 may also analyze whether the ratio of white is occupied. For example, in the entire image, an analysis may be performed to determine whether the ratio of white occupies or exceeds a predetermined threshold ratio. Here, the critical ratio may be less than 100%. It is apparent that such critical ratio can be adjusted as needed.

The analysis result of the image analyzer 510 as described above is input to the selector 520.

The selector 520 outputs the selection signals SEL1 and SEL2 corresponding to the analysis result in response to the analysis result. For example, as the selection signal, the first and second selection signals SEL1 and SEL2 may be selectively output.

The register unit 530 outputs corresponding color temperature data CCT1 and CCT2 in response to the input selection signals SEL1 and SEL2. For example, each of the first and second selection signals SEL1 and SEL2 corresponds to the first and second color temperature data CCT1 and CCT2. In this case, when the first selection signal SEL1 is input, the first color temperature data CCT1 is output. When the second selection signal SEL2 is input, the second color temperature data CCT2 is input.

As mentioned above, the first color temperature data CCT1 corresponds to data set to implement white having a first color temperature which is a relatively high color temperature. The second color temperature data CCT2 corresponds to data set to realize white having a second color temperature which is a relatively low color temperature.

Accordingly, when the first color temperature data CCT1 is output, the gamma voltage generator 400 is set to output the first gamma voltage VG1 corresponding to the first color temperature data CCT1. When the second color temperature data CCT2 is output, the gamma voltage generation unit 400 is set to output the second gamma voltage VG2 corresponding to the second color temperature data CCT2.

Therefore, when it is determined that the image including white is displayed for a long time as a result of the analysis of the image analyzer 510, the selector 520 outputs the second selection signal SEL1, and accordingly, the second color temperature data. (CCT2) is selected. As a result, the gamma voltage generator 400 may receive the second color temperature data CCT2 and output the second gamma voltages VG2 corresponding to the gamma voltage. As a result, the blue luminance ratio in the region displaying white can be relatively reduced. This makes it possible to relatively reduce the occurrence of degradation of the B organic light emitting diode. Accordingly, even if the image is changed, the afterimage generation can be improved due to the deterioration of the B organic light emitting diode in the region where white was displayed.

On the other hand, in a normal case of displaying a video or the like, as a result of the analysis of the image analyzer 510, it is not determined that the image containing white for a long time. Accordingly, the selector 520 may output the first selection signal SEL1, thereby selecting the first color temperature data CCT1. Accordingly, the gamma voltage generator 400 may receive the first color temperature data CCT1 and output the first gamma voltages VG1 corresponding to the gamma voltage. In this case, white with a high blue luminance ratio, that is, white with a relatively high color temperature can be realized.

The configuration and operation of the gamma control unit in the above-described embodiment of the present invention is an example, and various other configurations and operations are possible. For example, by performing image analysis, a gamma voltage capable of realizing a white color having a relatively high color temperature is output in a normal image display, and relatively relatively when white is repeatedly displayed for a predetermined time or more in a predetermined area of the screen. It may be configured to output a gamma voltage capable of realizing a low color temperature white. Here, the output of the gamma voltage capable of implementing a white of a relatively high color temperature may be set as a default output.

5 is an example according to an embodiment of the present invention, a picture showing a screen before and after the color temperature change of white.

Here, the left picture in FIG. 5 is for an image including white having a high color temperature, for example, a color temperature of approximately 9200K, and the right picture in FIG. 5 includes white having a low color temperature, for example, a color temperature of approximately 7000K. For the video.

Looking at the left and right images as described above, it can be seen that the color difference is not recognized for the displayed white. Therefore, even if the color temperature of the white is changed during the driving for a long time, the user will not feel the color difference with respect to the white. Accordingly, when the color temperature of the white is changed to improve the afterimage according to the embodiment of the present invention, the image quality deterioration will not occur.

Embodiment of the present invention described above is an example of the present invention, it is possible to change freely within the scope included in the spirit of the present invention. Accordingly, the invention includes modifications of the invention within the scope of the appended claims and their equivalents.

1 is a photograph showing a state in which an afterimage occurs on a screen of a mobile phone using a conventional organic light emitting display device.

2 is a schematic view of an organic light emitting display device according to an embodiment of the present invention;

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

4 is a view showing an example of the configuration and operation of the gamma control unit according to an embodiment of the present invention.

5 is a photograph showing a screen before and after a color temperature change of white as an example according to an embodiment of the present invention.

Description of the Related Art

100: organic light emitting display device 200: organic light emitting panel

310: timing controller 320: gate driver

330: data driver 400: gamma voltage generator

500: gamma control unit

CCT1, CCT2: first and second color temperature data

VG1, VG2: first and second gamma voltages

Claims (7)

An organic electroluminescent panel comprising an R organic light emitting diode, a G organic light emitting diode, and a B organic light emitting diode each comprising an R pixel, a G pixel, and a B pixel; A gamma voltage generator capable of selectively outputting first gamma voltages implementing white with a first color temperature and second gamma voltages implementing white with a second color temperature lower than the first color temperature; A data driver for generating and outputting a data voltage corresponding to the image data using the selected gamma voltages; And a data wiring that receives the data voltage output from the data driver and transfers the data voltage to the corresponding pixel. When white is displayed for more than a threshold time in the same area of the screen, the gamma voltage generator selects and outputs the second gamma voltages. Organic light emitting display device. The method of claim 1, Further comprising a gamma control unit for selectively outputting the first and second color temperature data, The gamma voltage generation unit outputs the first and second data voltages in response to the first and second color temperature data, respectively. Organic light emitting display device. The method of claim 2, The gamma control unit, An image analyzer which analyzes the input image data; A selection unit for selectively outputting first and second selection signals in response to an analysis result of the image analyzer; A register unit for storing the first and second color temperature data and outputting the first and second color temperature data in response to each of the first and second selection signals, If the image analyzer determines that the white is repeatedly displayed for more than a threshold time in the same area of the screen, the selector outputs the second selection signal. Organic light emitting display device. The method of claim 3, The image analyzer, A storage unit which stores image data of a previous frame; And a count unit for increasing the number of counts when the image data of the current frame and the image data of the previous frame are the same. Organic light emitting display device. A driving method of an organic light emitting display device comprising an organic light emitting panel including an R pixel comprising a R organic light emitting diode, a G organic light emitting diode, and a B organic light emitting diode, and a G pixel and a B pixel. Selectively outputting, by the gamma voltage generator, first gamma voltages implementing white with a first color temperature and second gamma voltages implementing white with a second color temperature lower than the first color temperature; Generating and outputting a data voltage corresponding to image data by using the selected gamma voltages in a data driver; Transferring the data voltage output from the data driver to the corresponding pixel; When white is repeatedly displayed for more than a threshold time in the same area of the screen, the gamma voltage generator selects and outputs the second gamma voltages. A method of driving an organic light emitting display device. The method of claim 5, In the gamma control unit, further comprising the step of selectively outputting the first and second color temperature data, The gamma voltage generator outputs the first and second data voltages in response to the first and second color temperature data, respectively. A method of driving an organic light emitting display device. The method of claim 6, Performing an analysis on the input image data in the image analysis unit of the gamma control unit; Selectively outputting first and second selection signals in response to an analysis result of the image analyzer; In response to each of the first and second selection signals, outputting the first and second color temperature data stored in a register of the gamma control unit, If it is determined that the white is repeatedly displayed for more than a threshold time in the same area of the screen, the second selection signal is output. A method of driving an organic light emitting display device.

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