JP3933485B2 - Matrix driven display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a matrix drive type display including a display panel configured by arranging a plurality of pixels in a matrix like an organic electroluminescence display.
[0002]
[Prior art]
In recent years, organic electroluminescence displays (hereinafter referred to as organic EL displays) have been developed, and for example, adopting organic EL displays in mobile phones has been studied.
As shown in FIG. 8, in the organic EL display (1), an organic hole transport layer (15) and an organic electron transport layer (16) are arranged on both sides of an organic light emitting layer (14) on a glass substrate (11). The organic layer (13) is formed, and the anode (12) and the cathode (17) are arranged on both sides of the organic layer (13) to form an organic EL panel. The anode (12) and the cathode By applying a predetermined voltage during (17), the organic light emitting layer (14) is caused to emit light.
[0003]
The anode (12) is made of transparent indium tin oxide (ITO), and the cathode (17) is made of, for example, an Al—Li alloy, and is formed in stripes and arranged in a matrix in a direction crossing each other.
For example, the anode (12) is used as a data electrode, and the cathode (17) is used as a scan electrode. With one scan electrode extending in the horizontal direction selected, each data electrode extending in the vertical direction is adapted to the input data. By applying the applied voltage, the organic layer (13) is caused to emit light at the intersection of the scanning electrode and each data electrode, thereby displaying one line. Then, scanning is performed in the vertical direction by sequentially switching the scanning electrodes in the vertical direction, and display for one field is performed.
[0004]
As a driving method for such an organic EL display, in addition to the passive matrix driving type in which the scanning electrode and the data electrode are used for time-sharing driving as described above, the active light emission for each pixel is maintained for one vertical scanning period. A matrix drive type is known.
[0005]
In the active matrix driving type organic EL display, as shown in FIG. 9, each pixel (52) is energized to the organic EL element (50) constituted by a part of the organic layer and the organic EL element (50). The driving transistor TR2 to be controlled, the writing transistor TR1 that becomes conductive in response to the application of the scanning voltage SCAN by the scanning electrode, and the data voltage DATA from the data electrode is applied when the writing transistor TR1 becomes conductive. Thus, the capacitive element C that accumulates electric charges is provided, and the output voltage of the capacitive element C is applied to the gate of the driving transistor TR2.
[0006]
First, a voltage is sequentially applied to each scan electrode to turn on the plurality of first transistors TR1 connected to the same scan electrode, and a data voltage (input signal) is applied to each data electrode in synchronization with this scan. At this time, since the first transistor TR1 is in a conductive state, the data voltage is stored in the capacitive element C.
Next, the operating state of the second transistor TR2 is determined by the amount of charge of the data voltage stored in the capacitive element C. For example, when the second transistor TR2 is turned on, a current having a magnitude corresponding to the data voltage is supplied to the organic EL element (50) through the second transistor TR2. As a result, the organic EL element (50) is lit with brightness according to the data voltage. This lighting state is maintained for one vertical scanning period (one field period).
[0007]
[Problems to be solved by the invention]
By the way, in the organic EL display, the light emission characteristic of the organic EL element deteriorates as the light emission time elapses, and the luminance obtained by the same input current is lowered. Accordingly, when the light emission frequency of a specific pixel is high, for example, when an icon is always displayed at a certain position on the screen, the light emission characteristics of these pixels are significantly deteriorated compared to other pixels, so-called “burn-in”. There is a problem that occurs.
[0008]
Therefore, an object of the present invention is to solve the problem of “burn-in” in a matrix drive type display such as an organic EL display.
[0009]
[Means for solving the problems]
A matrix drive type display according to the present invention comprises a display panel configured by arranging pixels having display elements such as organic EL elements in a matrix, and a drive circuit for driving the display panel in accordance with input data. It is.
Here, the drive circuit accumulates input data for each pixel constituting the display panel for each pixel in a fixed period in a use state in which the display panel is driven, and for all pixels in a subsequent non-use state. The correction data obtained by subtracting the integrated value of each pixel from the maximum value among the integrated values is created, and the light emission characteristics of the display elements of each pixel are made uniform by causing each pixel to emit light based on the correction data. It is characterized by.
[0010]
In a specific configuration, the drive circuit includes an integration unit that integrates input data for each pixel constituting the display panel for each pixel at a constant period, and a maximum value detection unit that detects a maximum value among the integration values for all the pixels. Subtracting means for calculating correction data by subtracting the integrated value of each pixel from the maximum value, and data supply means for supplying constant luminance data to each pixel for a time proportional to the magnitude of the correction data. It has.
Alternatively, the drive circuit includes an integration unit that integrates input data for each pixel constituting the display panel for each pixel at a constant period, a minimum value detection unit that detects a minimum value among the integration values for all pixels, and A first subtracting means for calculating integrated difference data by subtracting the minimum value from an integrated value of pixels; a maximum value detecting means for detecting a maximum value in integrated difference data for all pixels; and Second subtracting means for calculating correction data by subtracting accumulated difference data of pixels and data supply means for supplying constant luminance data to each pixel for a time proportional to the magnitude of the correction data are provided.
[0011]
In the matrix-driven display of the present invention, for pixels with a high light emission frequency and a large amount of light emission, the integrated value of the input data is larger than the integrated value of the other pixels. It becomes smaller than the correction data. On the other hand, for pixels with low emission frequency and low light emission, the integrated value of the input data is smaller than the integrated value of the other pixels, and thus the correction data is larger than the correction data of the other pixels.
Therefore, in a non-use state, each pixel is caused to emit light based on the size of the correction data. For example, constant luminance data is supplied to each pixel for a time proportional to the size of the correction data. As a result, the total light emission amount of each pixel over the use state and the non-use state is equalized, and the light emission characteristics of the display elements of each pixel are aligned.
[0015]
【The invention's effect】
The matrix drive type display according to the present invention can solve the “burn-in” problem.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the embodiment in which the present invention is implemented in an organic EL display to be installed in a mobile phone will be specifically described with reference to the drawings.
[0017]
First embodiment An organic EL display according to this embodiment includes a drive circuit shown in FIG. The drive circuit includes a video signal processing circuit (3) that performs predetermined video signal processing on input data and supplies the input data to the organic EL panel. A changeover switch (2) is provided at the input end of the video signal processing circuit (3). ) Is connected.
In a use state where the organic EL panel is driven, the changeover switch (2) is switched to the a terminal side, and input data for image display is supplied to the video signal processing circuit (3). On the other hand, when the organic EL panel is not driven, the changeover switch (2) is switched to the b terminal side, and correction data to be described later is supplied to the video signal processing circuit (3).
[0018]
In the use state, the input data for each pixel is written into the memory (6) through the adder (4), and the data read from the memory (6) is supplied to the adder (4). Accumulated repeatedly at regular intervals. As a result, the integrated value of the input data for each pixel is stored in the memory (6) as shown in FIG.
The memory (6) is monitored by the overflow detection / minimum value detection circuit (7) shown in FIG. 1. When the memory (6) overflows, the minimum value of the integrated value is detected, and the detected minimum value is the selector. It is supplied to the subtracter (5) via (9). As a result, the minimum value is subtracted from the integrated value of each pixel, and the memory (6) is updated with the subtraction result (hereinafter referred to as integrated difference data).
As a result, the accumulated difference data for each pixel is stored in the memory (6) as shown in FIG. In this way, by storing the accumulated difference data while updating the memory (6), the required capacity of the memory (6) can be reduced.
[0019]
In the subsequent non-use state, the changeover switch (2) shown in FIG. 1 is switched to the b side. The maximum value detection circuit (8) detects the maximum value in the accumulated difference data stored in the memory (6), and the detected maximum value is passed through the selector (9) to the subtracter (5). Supplied. As a result, as shown in FIG. 3C, the accumulated difference data of each pixel is subtracted from the maximum value to create correction data for each pixel. The correction data represents a corrected light emission amount that should be supplemented to make the total light emission amount of each pixel uniform.
The correction data for each pixel is supplied to the memory (6) through the adder (4) shown in FIG. 1 and written in the memory (6).
It should be noted that the correction for each pixel shown in FIG. 3C is made directly from the integrated value of the input data for each pixel shown in FIG. 3A without creating the integration difference data for each pixel shown in FIG. It is also possible to create data.
[0020]
The selector (9) shown in FIG. 1 is supplied with a predetermined constant a which will be described later, and the constant a is supplied to the subtracter (5) through the selector (9). The constant a is subtracted from the correction data, and the result is written in the memory (6). Then, the subtraction result read from the memory (6) is supplied to the binarization circuit (10) and binarized for each pixel according to the presence or absence of data.
In addition, luminance data with all bits “1” is created for pixels with binary data of 1, and luminance data with all bits “0” is created for pixels with binary data 0. Then, the luminance data for all the pixels is supplied to the b terminal of the changeover switch (2).
[0021]
The subtraction of the constant a described above, binarization, creation and supply of luminance data are repeated until all the binarized data becomes zero. Thus, the maximum luminance data is supplied to each pixel for a time proportional to the magnitude of the correction data, and each pixel emits a light emission amount corresponding to the light emission amount in the use state.
[0022]
FIG. 2 shows an operation when the above-described drive circuit is installed in a mobile phone. First, in step S1, it is determined whether the image is displayed on the display of the mobile phone or not, and if it is determined to be yes, the input data is accumulated for each pixel in step S2. In step S3, the integration result is written in the memory.
Subsequently, in step S4, it is determined whether or not the memory has overflowed. If it is determined as NO, the process returns to step S2 to repeat data integration and memory writing at a constant cycle.
[0023]
Thereafter, when the memory overflows and it is determined YES in step S4, the process proceeds to step S5, and the minimum value is detected from the integrated values of all the pixels. In step S6, the minimum value is subtracted from the integrated value of each pixel, the memory is updated with the subtraction result (integrated difference data), and then the process returns to step S2 and steps S2 to S6 are repeated.
[0024]
On the other hand, in a non-use state in which no image is displayed on the display of the mobile phone, for example, during charging, it is determined NO in step S1, and the process proceeds to step S7 to correct variations in the light emission amount of each pixel. Is executed. That is, in step S7, the maximum value in the accumulated difference data stored in the memory is detected, and in step S8, the accumulated difference data for each pixel is subtracted from the maximum value to create correction data for each pixel. To do. Next, in step S9, the constant a is subtracted from the correction data of each pixel, and the result is written in the memory.
[0025]
The above constant a is calculated by the following formula 1.
[Expression 1]
a = (100% white brightness at the time of correction / 100% white brightness at the time of use) × 100% white data Here, for example, 100% white brightness at the time of correction is 2 of 100% white brightness at the time of use. By doubling, the correction time can be shortened to one half of the usage time.
[0026]
Subsequently, after the subtraction result is written in the memory in step S10, in step S11, the subtraction result of each pixel is binarized according to the presence or absence of data (whether it is a non-zero value). Then, in step S12, it is determined whether or not the binarized data of all the pixels is 0. When it is determined as no, the process proceeds to step S13, and for the pixels whose binarized data is 1, Luminance data with all bits “1” is created, and for pixels with binarized data 0, luminance data with all bits “0” is created and output to the organic EL panel.
Thereafter, returning to step S9, the subtraction of the constant a, binarization, creation and supply of luminance data are repeated at a constant period T, whereby all the binarized data becomes 0, and yes in step S12. When it is determined that charging is completed, charging is started on the assumption that the correction of the light emission amount has been completed.
[0027]
According to the organic EL display of the above embodiment, for a pixel having a large light emission amount in use, the integrated value of the input data is larger than the integrated value of the other pixels, whereby the correction data is corrected for the other pixels. Smaller than the data. On the other hand, for a pixel with a small amount of light emission, the integrated value of the input data is smaller than the integrated value of the other pixels, whereby the correction data is larger than the correction data of the other pixels.
Accordingly, in the non-use state, by repeating the steps S9 to S13, 0 or the maximum luminance data is supplied to each pixel for a time proportional to the size of the correction data, and each of the use state and the non-use state. The total light emission amount of the pixels is equalized. As a result, the light emission characteristics of the display elements of the respective pixels are aligned, and the organic EL panel is prevented from being burned.
[0028]
In the mobile phone having the organic EL display of the above embodiment, the light emission amount is corrected at the time of charging, so that the power consumption associated with the correction of the light emission amount is not a problem.
In the case of a foldable mobile phone, if the light emission amount is corrected in a state where the mobile phone is folded, a problem that a meaningless image is displayed on the organic EL display is not a problem. In this case, as other correction methods, there are a method of correcting by the power of the built-in battery when the cellular phone is folded, and a method of correcting the uncorrected amount at the time of charging when the total light emission amount cannot be equalized by the correction. It is also possible to adopt.
[0029]
Second embodiment The organic EL display of this embodiment includes a drive circuit shown in FIG. The drive circuit includes a video signal processing circuit (3) for performing predetermined video signal processing on input data and supplying the input data to an organic EL panel, and a first multiplier is provided at an input end of the video signal processing circuit (3). (21) is connected.
[0030]
Input data for each pixel is supplied to one input terminal of the first multiplier (21) and simultaneously supplied to one input terminal of the second multiplier (22). The total use time from the shipment of the organic EL display is counted by the total use time counting circuit (23), and the result is supplied to the correction coefficient circuit (24), so that the total use time is determined. A correction factor is derived.
Here, for example, as shown in FIG. 6, the correction coefficient gradually decreases from 1 as the total use time increases, and the degree of deterioration of the organic EL element with the lapse of the light emission time gradually decreases. Is taken into account.
[0031]
As shown in FIG. 4, the correction coefficient is supplied to the other input terminal of the second multiplier (22), multiplied by the input data, and the input data corrected thereby is passed through the adder (25) to the memory (26). Supplied to. Then, the input data read from the memory (26) is supplied to the adder (25), whereby the input data is integrated for each pixel at a constant period, and the result is written to the memory (26).
[0032]
After that, the integrated value for all pixels read from the memory (26) is supplied to the maximum value detection circuit (27), the maximum value of the integrated value is detected, and the result is supplied to the subtracter (28). Then, the integrated value of each pixel is subtracted from the maximum value, and correction data for each pixel is created. The correction data has a smaller value as the pixel has a larger total light emission amount.
[0033]
The correction data for each pixel is input to the correction coefficient table circuit (29), and a correction coefficient corresponding to the correction data is output from the correction coefficient table (lookup table).
Here, the correction coefficient table has an input-output relationship as shown in FIG. 7, for example, and outputs a correction coefficient whose value gradually decreases from 1 as the input (correction data) increases.
Accordingly, the correction coefficient has a value close to 1 as the pixel having a large total light emission amount, and a small value decreased from 1 as the pixel having a small total light emission amount.
[0034]
The correction coefficient for each pixel is supplied to the other input terminal of the first multiplier (21) and multiplied by the input data for each pixel. As a result, the pixel whose total light emission amount is small and whose light emission characteristics have not deteriorated is corrected so that the input data becomes small, and this corrected input data is supplied to the organic EL panel and an image is displayed. It will be.
[0035]
FIG. 5 shows an operation in the case where the above-described drive circuit is installed in a mobile phone.
In step S20, the total use time of the organic EL panel from the time of shipment is counted. In step S21, a correction coefficient corresponding to the total use time is derived, and the input coefficient data is multiplied by the correction coefficient. Correct the input data. Subsequently, the operation of accumulating the corrected input data for each pixel at a constant period and writing the result in the memory is repeated.
[0036]
In step S24, the maximum value is detected from the integrated values of all the pixels written in the memory at the predetermined period. In step S25, the integrated value of each pixel is subtracted from the detected maximum value. Create correction data for each.
In step S26, the correction coefficient corresponding to the correction data of each pixel is derived by referring to the correction coefficient table.
Thereafter, in step S27, the correction data of each pixel is multiplied by the input data of each pixel, the result is output to the organic EL panel, and the process returns to step S21.
The above correction process is performed for each pixel of RGB.
[0037]
According to the organic EL display of the above-described embodiment, a pixel having a large total light emission amount and a high degree of deterioration is corrected in a direction in which the original input data is slightly decreased, and a pixel having a small total light emission amount and a low degree of deterioration. Is corrected in a direction in which the original input data greatly decreases, and the organic EL panel is driven by the corrected input data.
As a result, in accordance with the degree of deterioration of the display element of each pixel, the luminance variation accompanying the deterioration is corrected, and the burn-in of the organic EL panel is prevented.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a first embodiment of a drive circuit in an organic EL display according to the present invention.
FIG. 2 is a flowchart showing a flow of correction processing in the first embodiment.
FIG. 3 is a diagram for explaining input data processing in the correction processing;
FIG. 4 is a block diagram showing the configuration of a second embodiment of the drive circuit in the organic EL display according to the present invention.
FIG. 5 is a flowchart showing a flow of correction processing in the second embodiment.
FIG. 6 is a graph for explaining correction based on the total use time in the correction processing.
FIG. 7 is a graph illustrating correction by a correction table in the correction process.
FIG. 8 is a diagram illustrating a panel structure of an organic EL display.
FIG. 9 is a diagram illustrating a circuit configuration of each pixel constituting the organic EL panel.
[Explanation of symbols]
(1) Organic EL display
(2) Changeover switch
(3) Video signal processing circuit
(4) Adder
(5) Subtractor
(6) Memory
(7) Overflow detection / minimum value detection circuit
(8) Maximum value detection circuit
(9) Selector
(10) Binary circuit

Claims (5)

In a matrix drive display comprising a display panel configured by arranging pixels having display elements in a matrix and a drive circuit for driving the display panel according to input data,
The driving circuit integrates input data for each pixel constituting the display panel for each pixel in a use cycle in which the display panel is driven, and an integrated value for all pixels in a subsequent non-use state. The correction data obtained by subtracting the integrated value of each pixel from the maximum value of the pixel is created, and each pixel is caused to emit light based on the correction data, thereby aligning the light emission characteristics of the display elements of each pixel Matrix drive type display.   The driving circuit includes an integrating unit that integrates input data for each pixel constituting the display panel for each pixel at a constant period, a maximum value detecting unit that detects a maximum value among integrated values for all pixels, and the maximum 2. The matrix drive display according to claim 1, further comprising subtracting means for subtracting the integrated value of each pixel from the value to calculate correction data. In a matrix drive display comprising a display panel configured by arranging pixels having display elements in a matrix and a drive circuit for driving the display panel according to input data,
The drive circuit includes an integration unit that integrates input data for each pixel constituting the display panel for each pixel at a fixed period, a minimum value detection unit that detects a minimum value among the integration values for all pixels, and each pixel A first subtracting means for subtracting the minimum value from the integrated value to calculate integrated difference data; a maximum value detecting means for detecting a maximum value in the integrated difference data for all pixels; and each pixel from the maximum value. second subtraction means and to which Ma Torikusu driven display comprising a for calculating the correction data by subtracting the integration difference data.   4. The matrix drive type display according to claim 1, further comprising data supply means for supplying constant luminance data to each pixel for a time proportional to the size of the correction data.   The matrix drive type display according to any one of claims 1 to 4, wherein the display element is an organic electroluminescence element.

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