KR101547215B1 - Organic electroluminescent display device and method of driving the same - Google Patents

Abstract

The present invention provides an organic light emitting display comprising: an organic light emitting panel including an R organic light emitting diode, a G organic light emitting diode, and an R pixel, a G pixel, and a B pixel, each of which comprises B organic light emitting diodes; A gamma voltage generator for selectively outputting first gamma voltages for realizing white having a first color temperature and second gamma voltages for realizing white having 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 for receiving the data voltage output from the data driver and transmitting 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 generates the second gamma voltages And an organic electroluminescent display device for selectively outputting the organic electroluminescent display device.

Description

[0001] The present invention relates to an organic electroluminescence display device and a driving method thereof,

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

2. Description of the Related Art [0002] With the development of an information society, demands for a display device for displaying images have been increasing in various forms. Recently, a liquid crystal display (LCD), a plasma display panel (PDP) Various flat display devices such as an organic electroluminescent display device (OELD) have been utilized.

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

As an organic electroluminescent display device, an active matrix type organic electroluminescent display device in which pixels are arranged in a matrix form to display an image is widely used.

When a data voltage is applied to a pixel of the organic light emitting display, 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 a luminance corresponding to the applied current amount.

Such an organic light emitting display device includes red (R), green (G), and blue (B) pixels for displaying a color image. The R pixel, the G pixel, and the B pixel constitute an R organic light emitting diode, a G organic light emitting diode, and a B organic light emitting diode that emit red, green, and blue light. Through the combination of light emitted from the organic light emitting diode, a color image can be realized.

On the other hand, when data voltages corresponding to the highest gradation are applied to the R pixel, the G pixel, and the B pixel of the organic electroluminescence display device so that white is displayed, the color temperature of white is set to a value between red, Luminance ratio combination. In general, the higher the color temperature of white is, the higher the luminance ratio of blue is.

However, the lifetime 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, if the color temperature of white to be displayed is high, the luminance ratio of blue becomes high, which results in accelerating the shortening of the lifetime of the B organic light emitting diode.

Therefore, when white having a high color temperature is displayed for a long time, deterioration of the B organic light emitting diode located in a region for displaying white occurs, resulting in a residual image. The occurrence of such residual image can be referred to Fig.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a photograph showing a state where a residual image is generated on a screen of a mobile phone using a conventional organic light emitting display device.

Referring to FIG. 1, it can be seen that a residual image is generated in a region where white is displayed for a long time when white display having a high color temperature is displayed in a part of the screen for a long time and the screen display is changed. In this regard, as described above, as white having a high color temperature is displayed for a long time, the B organic light emitting diode in the region where white is displayed is deteriorated. As a result, the emission luminance deviation of the B organic light emitting diode occurs at a level that can be recognized by a person. As a result, even if the displayed image is switched, a luminance deviation exists in the area where white is displayed, and a residual image is generated.

An object of the present invention is to provide an organic electroluminescence display device capable of improving a residual image, a driving method thereof, and a manufacturing method thereof.

According to an aspect of the present invention, there is provided an organic light emitting display comprising: an R organic light emitting diode; a G organic light emitting diode; an R pixel including each of the B organic light emitting diodes; a G pixel; and; A gamma voltage generator for selectively outputting first gamma voltages for realizing white having a first color temperature and second gamma voltages for realizing white having 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 for receiving the data voltage output from the data driver and transmitting 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 generates the second gamma voltages And an organic electroluminescent display device for selectively outputting the organic electroluminescent display device.

The apparatus may further include a gamma control unit for selectively outputting the first and second color temperature data, wherein the gamma voltage generating unit may output the first and second data voltages in response to the first and second color temperature data, respectively .

The gamma control unit includes an image analyzing unit for analyzing input image data; A selection unit for selectively outputting the first and second selection signals in response to the analysis result of the image analysis unit; And a register unit for storing the first and second color temperature data and outputting the first and second color temperature data in response to the first and second selection signals, The selection unit may output the second selection signal if it is determined that the second selection signal is repeatedly displayed for a predetermined time or more.

The image analysis unit may include: a storage unit for storing image data of a previous frame; And a counting unit for increasing the count number when the video data of the current frame and the video data of the previous frame are the same.

According to another aspect of the present invention, there is provided an organic electroluminescent display including an R organic light emitting diode, a G organic light emitting diode, an R pixel constituted by each of the B organic light emitting diodes, an G pixel, A method of driving a display device, the method comprising: a gamma voltage generating unit for generating first gamma voltages for realizing white having a first color temperature and second gamma voltages for realizing white having a second color temperature lower than the first color temperature Selectively outputting; Generating and outputting a data voltage corresponding to the image data using the selected gamma voltages in the data driver; And transmitting the data voltage output from the data driver to the corresponding pixel. When white is repeatedly displayed in the same region of the screen over a threshold time, the gamma voltage generator selects the second gamma voltages And a driving method of the organic light emitting display device.

Here, the gamma control unit may further include a step of selectively outputting the first and second color temperature data, wherein the gamma voltage generating unit outputs the first and second data voltages in response to each of the first and second color temperature data can do.

Performing an analysis on input image data in an image analysis unit of the gamma control unit; Selectively outputting first and second selection signals in response to an analysis result of the image analysis unit; Further comprising outputting the first and second color temperature data stored in the register unit of the gamma control unit in response to each of the first and second selection signals, wherein the white is repeated over a threshold time in the same area of the screen The second selection signal may be output.

In the present invention, when the same image is displayed for a long time, the color temperature of the displayed white is lowered. As described above, by decreasing the color temperature of white, the luminance ratio of blue is relatively decreased, and the lifetime of the organic light emitting diode B is relatively increased. Therefore, the deterioration of the B organic light emitting diode is relatively reduced, and as a result, the afterimage is improved.

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

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

As shown in the figure, the organic light emitting display 100 according to the embodiment of the present invention includes an organic electroluminescence panel 200 and a driver.

In the organic electroluminescence panel 200, a plurality of gate lines GL extend in the first direction, e.g., in the row direction. A plurality of data lines DL extend in a second direction that crosses the first direction, for example, in the column direction. The gate lines GL and the data lines DL intersecting with each other define a plurality of pixels P arranged in a matrix form.

3, a switching transistor TS, a driving transistor TD, an organic light emitting diode OD, and a capacitor C are connected to each pixel P of the organic electroluminescence panel 200, .

The switching transistor TS is connected to the corresponding gate wiring and data lines 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 of the organic light emitting diode (OD), for example, a cathode, is connected to the drain electrode of the driving transistor TD. On the other hand, the first electrode of the organic light emitting diode (OD), for example, the anode receives the first driving voltage VDD.

The capacitor C is connected between the gate electrode and the source electrode of the driving transistor TD. On the other hand, 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.

In the above description, the pixel P constituted in the organic electroluminescence panel 200 may include an R pixel for emitting red, a G pixel for emitting green, and a B pixel for emitting blue. That is, the organic light emitting diode located at the R pixel emits red light, the organic light emitting diode located at the G pixel emits green light, and the organic light emitting diode located at the B pixel emits blue light. For convenience of explanation, the organic light emitting diodes located in each of the R pixel, the G pixel, and the B pixel may be referred to as an R organic light emitting diode, a G organic light emitting diode, and a B organic light emitting diode.

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

The driving unit may include a timing control unit 310, a gate driving unit 320, a data driving unit 330, a gamma voltage generating unit 400, and a gamma control unit 500.

The timing control unit 310 generates a gate control signal GCS for controlling the gate driving unit 320 and a data control signal DCS for controlling the data driving unit 330. The gate control signal GCS and the data control signal DCS thus generated are input to the gate driver 320 and the data driver 330, respectively.

The timing control unit 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, R image data corresponding to R pixel, G image data corresponding to G pixel, and B image data corresponding to B pixel are inputted as image data (Data).

The data driver 330 generates a data voltage corresponding to the input image data Data and outputs the generated data voltage to the corresponding data line 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. The voltage corresponding to the value of the input image data (Data) among the voltages thus divided can be selected and output as the data voltage.

As described above, the data driver 330 converts the video data of the digital format into a data voltage of an analog format and outputs the converted data.

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

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

The gamma voltage generator 400 outputs the gamma voltages VG1 and VG2 as described above. Here, the gamma voltage generator 400 may generate a plurality of different gamma voltages VG1 and VG2, for example, first gamma voltages VG1 through n-th gamma voltages. Here, n is a natural number of 2 or more. Each of the first to n-th gamma voltages corresponds to the gamma voltages including the gamma voltage capable of implementing white having the first to n-th color temperatures. At this time, white is implemented when a gamma voltage corresponding to the highest gradation among the first to n-th gamma voltages is applied to each pixel P, respectively.

In such a case, for example, when it is desired to implement the kth color temperature, the gamma voltage generator 400 generates and outputs the kth gamma voltages. Here, k is 1 or more and n or less.

As described above, the gamma voltage generator 400 can select one of the first to n-th gamma voltages and output it.

In the embodiment of the present invention, for convenience of explanation, the first and second gamma voltages VG1 and VG2 are generated. Here, the first gamma voltages VG1 correspond to gamma voltages including a gamma voltage capable of realizing white having a relatively high color temperature, for example, a first color temperature. The second gamma voltages VG_2 correspond to gamma voltages including a gamma voltage capable of realizing white having a relatively low color temperature, for example, a second color temperature.

The selective output of the gamma voltages VG and VG is controlled by the gamma voltage controller 500 as described above. 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. [

For this purpose, the gamma control unit 500 can 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.

The gamma control unit 500 outputs the first color temperature data CCT1 so that the gamma voltage generator 400 generates the first gamma voltages VG1 and the second gamma voltages VG1, . The gamma controller 500 outputs the second color temperature data CCT2 and the gamma voltage generator 400 generates the second gamma voltages VG2 according to the second color temperature data CCT2. . Accordingly, the color temperature of white can be adjusted.

As described above, in the embodiment of the present invention, it becomes possible to perform the white color temperature control, thereby effectively improving the afterimage problem that occurs in the conventional 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 area, the blue luminance ratio in an area displaying white is relatively high. In general, a B organic light emitting diode that displays blue has a characteristic in which the shorter the lifetime is, the higher the luminescence brightness is. As a result, in the case of displaying white having a high color temperature, the deterioration of the B organic light emitting diode is accelerated. In the past, however, white having a relatively high color temperature, for example, a color temperature of about 9200K, has been set to be fixedly realized. As a result, the deterioration of the conventional B organic light emitting diode is accelerated, resulting in a problem of a residual image.

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

As described above, by decreasing the color temperature of white, the luminance ratio of blue is relatively decreased, and the lifetime of the organic light emitting diode B is relatively increased. Therefore, the deterioration of the B organic light emitting diode is relatively reduced, and the effect of improving the afterimage can be exhibited.

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

4 is a diagram showing an example of the configuration and operation of the gamma controller according to the embodiment of the present invention.

Referring to FIG. 4, the gamma control unit 500 includes an image analysis unit 510, a selection unit 520, and a register unit 530.

The image analyzing unit 510 may analyze the input image data (Data) in units of frames and output the analysis result to the selecting unit 520.

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

The image analysis unit 510 may compare the image data of the previous frame stored in the memory unit 511 with the image data of the current frame. As a result of the comparison, if it is determined that the same image is obtained, the counting unit 512 can increase the number of counts by one. Through the counting operation in the counting unit 512 as described above, it is possible to grasp the number of frames in which the same image is repeatedly input, that is, the time at which the same image is displayed.

In such a case, if the number of counts reaches a predetermined value, for example, a threshold number, the image analyzer 510 may analyze whether or not white is included in the image. Here, the critical number can be set in consideration of the threshold time at which the deterioration of the B organic light emitting diode can be visually recognized, when the white having the first color temperature is continuously displayed. Therefore, when the count number is greater than or equal to the critical number, a residual image will be generated in accordance with deterioration of the B organic light emitting diode in the region where white is continuously displayed. Accordingly, when the number of counts reaches the threshold, an analysis can be performed as to whether white is included in the displayed image.

Here, the image analyzing unit 510 can analyze whether the ratio of white occupies the image when white is included in the image. For example, an analysis can also be performed as to whether the ratio of white occupies less than or equal to a set threshold ratio in the entire image. Here, the critical ratio may be less than 100%. It is obvious that such threshold ratios can be adjusted as needed.

The analysis result of the image analysis unit 510 as described above is input to the selection unit 520. [

In response to the analysis result, the selection unit 520 outputs the selection signals SEL1 and SEL2 corresponding 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 the 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 implement 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 voltages VG1 corresponding to the first color temperature data CCT1. When the second color temperature data CCT2 is output, the gamma voltage generator 400 is set to output the second gamma voltages VG2 corresponding to the second color temperature data CCT2.

Accordingly, when the image analysis unit 510 determines that the image including white is displayed for a long time, the selection unit 520 outputs the second selection signal SEL1, and accordingly, the second color temperature data (CCT2) is selected. Accordingly, the gamma voltage generator 400 receives the second color temperature data CCT2 and can output the second gamma voltages VG2 corresponding to the gamma voltages. As a result, the blue luminance ratio in an area for displaying white can be relatively reduced. This makes it possible to relatively reduce the occurrence of deterioration of the B organic light emitting diode. Thus, even when the image is changed, the occurrence of the afterimage can be improved due to the decrease in the deterioration of the B organic light emitting diode in the area where white is displayed.

On the other hand, in a normal case of displaying a moving image or the like, the image analysis unit 510 can not determine that an image including white is displayed for a long time. Accordingly, the selecting unit 520 can output the first selection signal SEL1, and accordingly, the first color temperature data CCT1 is selected. Accordingly, the gamma voltage generator 400 receives the first color temperature data CCT1 and can output the first gamma voltages VG1 corresponding to the gamma voltages. In such a case, a white having a high blue luminance ratio, that is, a white having a relatively high color temperature can be realized.

The configuration and operation of the gamma control unit in the embodiment of the present invention described above are examples, and various other configurations and operations are possible. For example, image analysis is performed so that a gamma voltage capable of realizing white with a relatively high color temperature is output in a normal image display, and when relatively white is displayed repeatedly over a predetermined time in a certain region of the screen, And a gamma voltage capable of realizing low-color-temperature white can be output. Here, the output of the gamma voltage capable of realizing a relatively high white color temperature may be set as a default output.

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

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

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

The embodiment of the present invention described above is an example of the present invention, and variations are possible within the spirit of the present invention. Accordingly, the invention includes modifications of the invention within the scope of the appended claims and equivalents thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a photograph showing a state in which a residual image occurs on a screen of a mobile phone using a conventional organic light emitting display device. FIG.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic light emitting display.

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

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

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

Description of the Related Art

100: organic electroluminescent display device 200: organic electroluminescent panel

310: timing control unit 320: gate driving unit

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 including an R organic light emitting diode, a G organic light emitting diode, and an R pixel, a G pixel, and a B pixel, each of which is configured with B organic light emitting diodes; The first gamma voltages including a gamma voltage that implements white having a first color temperature and the second gamma voltages including a gamma voltage that implements white having a second color temperature lower than the first color temperature are selectively output A gamma voltage generator for generating a gamma voltage; A data driver for generating and outputting a data voltage corresponding to the image data using the selected gamma voltages; And a data line for receiving the data voltage output from the data driver and transferring the data voltage to the corresponding pixel, When white is displayed for more than the threshold time in the same area of the screen, the gamma voltage generator selects and outputs the second gamma voltages Organic electroluminescence display device. The method according to claim 1, Further comprising a gamma control unit for selectively outputting 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 Organic electroluminescence display device. 3. The method of claim 2, The gamma control unit includes: An image analyzer for analyzing input image data; A selection unit for selectively outputting the first and second selection signals in response to the analysis result of the image analysis unit; And a register unit for storing the first and second color temperature data and outputting the first and second color temperature data in response to the first and second selection signals, When the image analyzing unit determines that the white is repeatedly displayed in the same area of the screen over a threshold time period, the selecting unit outputs the second selection signal Organic electroluminescence display device. The method of claim 3, Wherein the image analyzing unit comprises: A storage unit for storing image data of a previous frame; And a counting unit for increasing the count number when the video data of the current frame and the video data of the previous frame are the same Organic electroluminescence display device. A method of driving an organic light emitting display device including an R organic light emitting diode, a G organic light emitting diode, an R pixel including each of the B organic light emitting diodes, an G pixel, and an organic electroluminescent panel including B pixels, A second gamma voltage generating unit configured to generate a gamma voltage in the gamma voltage generating unit based on a first gamma voltage including a gamma voltage that implements white having a first color temperature and a second gamma voltage including a gamma voltage that implements white having a second color temperature lower than the first color temperature Selectively outputting voltages; Generating and outputting a data voltage corresponding to the image data using the selected gamma voltages in the data driver; And transferring the data voltage output from the data driver to the corresponding pixel, When white is repeatedly displayed in the same area of the screen over a threshold time, the gamma voltage generator selects and outputs the second gamma voltages A method of driving an organic electroluminescent display device. 6. The method of claim 5, Further comprising the step of selectively outputting the first and second color temperature data in the gamma control unit, Wherein the gamma voltage generator outputs the first and second data voltages in response to each of the first and second color temperature data A method of driving an organic electroluminescent display device. The method according to claim 6, Performing an analysis on input image data in an image analysis unit of the gamma control unit; Selectively outputting first and second selection signals in response to an analysis result of the image analysis unit; Further comprising outputting the first and second color temperature data stored in the register unit of the gamma control unit in response to each of the first and second selection signals, If it is determined that the white is repeatedly displayed in the same area of the screen over a threshold time period, A method of driving an organic electroluminescent display device.

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