JP2009276673A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that luminance deterioration cannot be exactly compensated because luminance is increased when deterioration of a light emitting element is detected as rise of inter-terminal voltage and a drive current is corrected according to a result of the detection. <P>SOLUTION: A display device has: the light emitting element; a drive part to supply the drive current to the light emitting element; a voltage detection part to detect the rise of inter-terminal voltage of the light emitting element; a correction part to decide a deterioration amount of the light emitting element from the detected rise of voltage and to hold it as correction data of the drive current; and a control part to control the drive part to supply the drive current corrected according to the correction data to the light emitting element. The correction part decides the deterioration amount of the light emitting element according to the detected rise of voltage, offset voltage recovered owing to stop of the drive current, and the rise of voltage corresponding to the deterioration amount when starting the drive of the light emitting element. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a display device, and more particularly to a display device including a light emitting element such as an organic EL element that emits light when energized.

  In recent years, self-luminous devices compatible with flat panels have attracted attention. Examples of the self-luminous device include a plasma light-emitting display element, a field emission element, and an electroluminescence (EL) element.

  In particular, organic EL elements are being researched and developed vigorously, and an array of area color types that add a single color such as green, blue, red, etc. has been commercialized and is now full color. Development is becoming more active.

  By the way, in an organic EL element, it is known that the luminance is lowered and the voltage is increased by continuously emitting light at a constant current.

As a technique for compensating for such a change in the organic EL element, Patent Document 1 detects a driving voltage of the organic EL element, corrects corresponding pixel data according to the voltage, and uses this to correct the luminance of each light emitting element. Disclosed is a display device that compensates for the decrease in pixel units.
JP 2006-091709 A

  When the driving voltage is detected by the conventional method and the pixel data is corrected according to the change in the voltage, it is determined that the luminance has decreased even if there is no luminance decrease in order to compensate for the luminance decrease, so that more light is emitted. In order to operate, there is a case where more light is emitted from only that portion, and there is a problem that it is not possible to accurately compensate for a decrease in luminance simply by detecting the voltage of the light emitting element.

The present invention has been made in view of the above circumstances,
A light emitting element;
A driving unit for supplying a driving current to the light emitting element;
A voltage detector for detecting a voltage rise between the terminals of the light emitting element;
A correction unit that determines a deterioration amount of the light emitting element from the detected voltage increase, and holds the deterioration amount as correction data of the drive current;
A control unit that controls the driving unit so that the driving unit supplies a driving current corrected according to the correction data to the light emitting element;
In a display device having
The correction unit is configured to degrade the light emitting element by the detected voltage rise, an offset voltage recovered by stopping the driving current, and a voltage rise corresponding to a degradation amount at the time when the light emitting element is started to be driven. It is characterized by determining the quantity.

  According to the present invention, it is possible to obtain a display device in which a change in luminance is suppressed.

  Hereinafter, the present invention will be described in detail with reference to FIGS.

  FIG. 1 is a conceptual diagram for explaining a configuration of a display device according to an embodiment of the present invention.

  1 includes an organic EL element 1 that is a light emitting element, a drive unit 2 that supplies power to the organic EL element, a control unit 3 that controls the drive unit according to an input signal, and the organic EL. Deterioration detecting means 4 for detecting the deterioration amount of the element, and a correction unit 5 for correcting the output to the organic EL element 1 in accordance with the deterioration of the organic EL element 1 are provided. As will be described later, the correction unit 5 uses the correction coefficient determined from the deterioration amount of the organic EL element and the luminance to be displayed on the organic EL element, through the control unit and the driving unit, The output to the organic EL element is corrected.

  FIG. 2 shows the relationship between the luminance due to the deterioration of the organic EL element and the correction coefficient.

  FIGS. 2A and 2B show changes in luminance of the organic EL element and voltage between terminals when the organic EL element is continuously driven at a constant current to emit light. The luminance was normalized with an initial value of 1. The voltage is a change from the initial inter-terminal voltage (time 0). Thus, the decrease in brightness corresponds to the increase in voltage on a one-to-one basis.

  FIG. 2C shows the relationship between the luminance drop (horizontal axis) and the voltage rise (vertical axis) derived from FIGS. 2A and 2B, that is, deterioration characteristics.

  If the relationship of FIG. 2C is known, it is possible to estimate the amount of decrease in luminance from the increase value of the voltage between terminals and correct the drive current, thereby maintaining the luminance constant, that is, to perform deterioration compensation. it can. When a voltage increase of 0.05 V is detected, it is considered that the luminance has deteriorated by 95% of the initial value, and the drive current may be corrected to increase the luminance by 5%. As described above, since the luminance reduction and the voltage increase amount are in a fixed relationship with respect to continuous light emission, the luminance reduction can be accurately compensated.

  However, in an actual electronic device such as a television or a mobile phone, light emission is not continuously performed, and power is frequently turned on and off.

  FIGS. 3A and 3B show temporal changes in luminance decrease and voltage increase when the organic EL element is repeatedly driven and paused. The horizontal axis represents the cumulative driving time. A branch extending from time 0 is a voltage change in the first drive. The second branch shows the voltage increase when the driving is stopped once after 33 hours of continuous driving and then restarted. The third branch thereafter is the voltage rise when resting after 65 hours and then restarting.

  As shown in FIG. 3A, the luminance does not change before and after the driving pause, and when the driving is resumed, light is emitted again with the luminance immediately before the pause. The amount of decrease in luminance is determined by the cumulative driving time.

  On the other hand, as shown in FIG. 3B, the voltage that has been raised during driving falls slightly due to the suspension of driving, and a part of the rising voltage during driving is recovered. After restarting, the voltage rises rapidly. When the voltage approaches the voltage before the pause, the rise becomes moderate and returns to the voltage rise rate before the pause.

  FIG. 3C is a diagram illustrating the relationship between the decrease in luminance and the increase in voltage corresponding to FIGS. 3A and 3B. Each branch corresponds to the branch in FIG. A broken line A is a curve obtained by connecting points plotted with voltage and luminance immediately after resumption of driving. A broken line B is an envelope created from the relationship between voltage and luminance after driving for a sufficiently long time after restarting driving. Both are nearly straight, but this is not essential to the invention.

  The voltage ΔVos between the broken lines A and B is the voltage recovery due to the pause. This voltage change is reversible and is recovered to zero during the driving pause. In addition, immediately after the restart of driving, the value rapidly returns to the value before suspension.

  In general, the decrease in luminance of the organic EL element is considered to be an irreversible change, that is, deterioration inside the light emitting element. However, according to the cases shown in FIGS. 3B and 3C, there is a rapid voltage increase with almost no decrease in luminance for a certain period immediately after the start of driving, and this voltage change is based on the fact that light emission stops. It turned out to be a reversible change.

  It can be considered that the reversible voltage change is a phenomenon of charging and discharging the parasitic capacitance between both terminals of the light emitting element. This parasitic capacitance is charged during the drive period and discharged during the rest period. When the driving or resting time is sufficiently long, the parasitic capacitance voltage is saturated, but when the driving period is short or the resting period is short, charging / discharging is not saturated and an intermediate voltage appears.

  The irreversible voltage increase and luminance decrease indicated by the broken line A are considered to be indicators representing the deterioration of the element in view of the irreversible nature. Hereinafter, the relationship of the broken line A is referred to as deterioration characteristic A. Both the luminance and voltage indicated by the deterioration characteristic A are indicators of deterioration, and these are hereinafter referred to as deterioration amounts.

  On the other hand, the luminance-voltage relationship indicated by the broken line B is a characteristic including a reversible voltage change. Hereinafter, the relationship of the broken line B is referred to as deterioration characteristic B. The time change of the voltage between the terminals of the organic EL element detected as the deterioration characteristic B is a combination of the irreversible change and the reversible change ΔVos.

  4A to 4C show a case where the pause time of T1 and T2 is shorter than that shown in FIGS. 3A to 3C, and the voltage recovers only partially during the pause period. Yes. The voltage immediately after resuming after resting is recovered to the voltage of the degradation characteristic A when the resting time is sufficiently long, but it is recovered only to an intermediate value in the brief resting, and the voltage immediately after restarting is in the resting period. Depends on length.

  The voltage after a sufficiently long time after the restart of driving converges on one line (broken line B). If the deterioration characteristic B is measured in advance, a change in luminance can be known from the detected voltage after a sufficiently long time after restarting driving.

  Alternatively, the deterioration characteristic A and the voltage ΔVos corresponding to the difference between the broken line A and the broken line B are measured in advance, and are subtracted from the detected voltage value, and the amount of decrease in luminance is known from the voltage-luminance relationship of the deterioration characteristic A. be able to. Hereinafter, the voltage ΔVos corresponding to the difference between the broken line A and the broken line B is referred to as an offset voltage.

  Since the voltage value depends on the length of the pause time immediately after the voltage is restarted and until the voltage converges on the broken line B, it is not possible to uniquely determine the luminance drop only by the voltage value. However, since the change during this time occurs in a relatively short time, it may be considered that only a reversible change has occurred. In other words, the deterioration does not proceed until the voltage after the restart of driving reaches the deterioration characteristic B, and during this period, it is assumed that the luminance does not decrease. Make corrections.

  The amount of deterioration immediately before the stop is equal to the amount of deterioration at the time of restarting driving. As described above, since the detection voltage immediately after the resumption of driving depends on the length of the pause, the amount of deterioration cannot be known by that. It is not necessary to measure the length of the pause by storing the deterioration amount at the time when the drive is stopped before the pause.

It can be determined from the detected voltage whether the voltage change after the resumption of driving is within the range of reversible change or includes an irreversible change, that is, whether the voltage has reached the deterioration characteristic B or not. That is, the detection voltage after the restart of driving is compared with the voltage obtained by subtracting the reversible change from the detection voltage immediately before the suspension (that is, the voltage V _A of the deterioration characteristic _A ), and the absolute value of the difference between the two is smaller than the offset voltage ΔVos. The time is considered to be a reversible change in progress, and an irreversible change occurs when the offset voltage ΔVos is exceeded (the voltage change reaches the deterioration characteristic B).

  The deterioration characteristic A is a relationship between a voltage increase and a luminance decrease that do not change due to suspension or resumption of driving. As an indicator of deterioration, either a voltage increase or a luminance decrease corresponding to the deterioration characteristic A may be taken. The deterioration amount or the deterioration index referred to in the present invention is a voltage increase or a luminance decrease in a relationship expressed by the deterioration characteristic A.

  A specific procedure for determining the deterioration amount will be described below.

  1) The deterioration characteristic B (broken line B) is measured in advance by continuously driving the sample display device. Further, the specimen display device is intermittently driven, and a plurality of relations between the voltage and the luminance immediately after the restart of driving are measured, and the plots are connected to obtain the deterioration characteristic A (broken line A). The drive pause period during intermittent drive is made sufficiently long so that the voltage rise is restored to the voltage of the degradation characteristic A.

  2) The luminance-voltage relationship and the difference voltage (offset voltage ΔVos) of the above deterioration characteristic A or deterioration characteristic B are stored in the display device to be corrected.

  3) The voltage between the terminals of the organic EL element is detected for a while after the display device is turned on and the drive is started, but the value is not used for the correction, and is corrected by the deterioration characteristic A (broken line A). To do. In other words, the luminance decrease during that period is considered to be the same as the previous decrease in luminance (the decrease in luminance at the start of driving, which is assumed to be stored). Make corrections accordingly.

  The detected inter-terminal voltage is compared with the voltage of the deterioration characteristic A corresponding to the luminance reduction at that time, and this correction is continued until the absolute value of the difference exceeds the stored offset voltage ΔVos.

  4) When the absolute value of the voltage difference exceeds ΔVos, the detected voltage is regarded as a voltage on the deterioration characteristic B, and a voltage obtained by subtracting ΔVos from this is obtained, and the luminance on the corresponding deterioration characteristic A From this, the luminance reduction is determined. Correction is performed based on this.

  5) The deterioration amount determined at each voltage detection time, that is, the luminance or voltage on the deterioration characteristic A is stored each time. In the case of 3), since the luminance does not change, the position of the point on the deterioration characteristic A does not change, and the deterioration amount is not updated. In the case of 4), since new degradation has occurred, the point on the degradation characteristic A moves, and the luminance or voltage at that point is replaced with the previous value and stored as the degradation amount. Even when the power is turned off and the drive is stopped, the deterioration amount immediately before that is stored.

  Thereafter, when the driving is resumed, the operations 3) and 5) or the operations 4) and 5) are repeated.

Thus, after the voltage detecting its voltage is compared with the voltage value on the deterioration characteristic A, the difference is if [Delta] V _OS less are considered reversible change, driven by degradation amount up to that by the method of the 3) Current correction is performed. When the difference is larger than ΔV _OS , it is considered that an irreversible change has occurred, and a new deterioration amount (luminance or voltage) is determined by the method 4) above, and the drive current is corrected accordingly. .

  The correction performed after 3) or 4) is correction of the drive current. If the calculated luminance reduction is x%, the current is corrected to increase by x%. Thereby, the luminance is kept constant.

  The brightness drop determined at each time point is stored and saved. When the brightness decrease is newly determined by the voltage detected at the next voltage detection time, it is updated to that value. Instead of reducing the luminance, a voltage increase value determined by the deterioration characteristic A may be stored. In that case, the luminance reduction is calculated again from the voltage and the current is corrected.

  As described above, when the off period is sufficiently long, the voltage returns to the point on the deterioration characteristic A, but when the off period is short, the return amount varies depending on the length of the off period. According to the correction of the present invention, after restarting driving, the detected inter-terminal voltage is compared with the stored voltage, and when the difference is less than a certain value, the inter-terminal voltage is not the detected voltage but immediately before the power is turned off. Since it is regarded as being equal to the stored voltage determined from the luminance and the luminance is corrected from the value, the correction can be performed regardless of the length of the pause period.

  In addition, during the period in which the voltage change is in the reversible change range, it is assumed that there is no decrease in luminance, so the stored luminance value is not updated, and the value stored at the previous power-off remains as it is. If the power is turned off, the value is stored again. As a result, even if the power ON / OFF interval is short and the power is turned off during the reversible change period, the luminance at that time or the voltage of the broken line A corresponding thereto is correctly stored, and correct correction can be performed after restarting. it can.

  In the present invention, the amount of increase in the voltage between the terminals of the organic EL element is not detected and used as it is for correction, but is compared with the voltage of the deterioration characteristic A corresponding to the decrease in luminance at the start of driving, and the detected voltage Is less than that value, the voltage change is considered to be reversible, and if the detected voltage is greater than that value, it is assumed that an irreversible voltage change or deterioration has occurred, and the amount of deterioration at each time point is determined. To do. Since the amount of irreversible change in voltage is used as the amount of deterioration (amount used as an indicator of deterioration), there is a one-to-one correspondence with the decrease in luminance, and the decrease in luminance is known from voltage detection without performing direct luminance measurement. be able to. Further, by storing the amount of deterioration at each voltage detection time, it is possible to determine whether the subsequent voltage change is reversible or irreversible. As a result, the correction independent of the length of the driving pause time can be performed.

  Even when the offset voltage ΔVos is not constant and varies depending on the cumulative driving time, the relationship between the brightness and the offset voltage is measured in advance and stored in the display device, so that the offset voltage is obtained from the brightness value each time and the amount of deterioration. Can be determined.

  Since the luminance of the light emitting element in an actual display device is kept constant by correction, it does not serve as an indicator of deterioration. In the present invention, an indicator of deterioration is a decrease in luminance when driving at a constant current is continued. In an actual light emitting element, the current constantly changes due to the correction, and therefore, it is different from the deterioration when a constant current is continuously supplied. However, since the detection current when detecting the voltage between the terminals of the light emitting element is kept constant, the luminance decrease or the irreversible voltage increase obtained from the detection voltage by the procedure described above can be an indicator of luminance.

  According to an experiment, ΔVos also changes depending on the element driving method, and when performing so-called duty driving in which the light is extinguished for a certain period in one frame period, the value of ΔVos is smaller than the driving for lighting for all periods. In particular, when the duty ratio is small, ΔVos is small. Therefore, in a display device that can change the pulse width in the display state, the value of ΔVos may be changed according to the duty ratio.

  Hereinafter, a method for detecting the element voltage will be described.

  As an embodiment of the present invention, FIG. 6 shows an example of a configuration for reading a voltage applied to an element when a predetermined current value is passed.

  FIG. 6 illustrates one pixel of a matrix display device composed of a plurality of pixels. The pixel 100 includes first and second N-type transistors (NMOS) 101 and 102, first and second P-type transistors (PMOS) 103 and 104, a storage capacitor 105, a data line 106, a power supply line 107, a first , Second and third selection lines 108, 109, 110 and the organic EL element 1. The data line 106 is switched between the data signal output source 111, the current source 112, and the voltage detection unit 113 by a switch 115 outside the pixel.

  The data signal output source 111 constitutes the drive unit 2 of FIG. 1 together with a selection line drive circuit (not shown). The current source 112 and the voltage detection unit 113 constitute the voltage detection unit 4 in FIG.

  FIG. 7 is an operation timing chart of the circuit of FIG.

  At the time of writing to the pixel, the first selection line is set to High, and the second and third selection lines are set to Low. As a result, the first NMOS 101 is turned on, the second NMOS 102 is turned off, and the second PMOS 104 is turned on. At the same time, the data line 106 is connected to the data signal output source 111 side by the switch 115, and a data signal corresponding to the luminance is applied as shown by the data line potential in FIG. This data signal charges the storage capacitor 105, and the first PMOS 103 causes a current corresponding to the data signal to flow from the power supply line 107 to the organic EL element 1. As charging progresses, the organic EL element 1 starts to emit light. The state of light emission is shown by the light emission level in FIG.

  When the writing period to the pixel 100 is completed, all of the first, second, and third selection lines are set to Low, the first NMOS 101 and the second NMOS 102 are turned off, and the second PMOS 104 is turned on. A current corresponding to the voltage held in the holding capacitor 105 flows to the organic EL element 1, and light emission of the organic EL element continues.

  When the voltage between the terminals of the organic EL element 1 is detected, the first selection line is set to Low and the second and third selection lines are set to High during the voltage detection period of the pixel 100. The first NMOS 101 and the second PMOS 104 are turned off, and the second NMOS 102 is turned on. The data line is connected to the current source 112 side by the switch 115, and a detection current flows from the current source 112 to the organic EL element 1. At this time, since the data line potential is equal to the voltage applied to the organic EL element, this potential is detected by the voltage detector 113.

  At this time, for the pixels other than the pixel for which the deterioration amount has been detected, the first and second selection lines are set to Low and the third selection line is set to High. By doing so, the current from the current source can be made to flow only to the pixel for which the amount of deterioration is to be detected.

  The voltage detected by the voltage detection unit 113 is sent to the deterioration amount determination unit 114.

The degradation amount determination unit 114 stores the voltage-luminance relationship of the degradation characteristic A, the offset voltage ΔV _OS, and the luminance decrease for each pixel. The deterioration characteristics and the offset voltage ΔV _OS are stored as a reference table (look-up table) (not shown), and the luminance drop is stored for each pixel in a memory (not shown).

As described above, the luminance and voltage at the time of driving are measured in advance to determine the deterioration characteristic A and the offset voltage ΔV _OS . The deterioration characteristic a is obtained by repeating constant current driving for a sufficiently long period and sufficiently long standing, and plotting data immediately after restarting driving. The deterioration characteristic B is determined from the relationship between luminance and voltage after a sufficiently long time from the start of driving. An offset voltage is obtained from the difference between the deterioration characteristic A and the deterioration characteristic B.

  The deterioration amount determination unit 114 executes the procedure 3) or 4) described above, and determines a decrease in luminance of the pixel. When the procedure of 3) is executed, the luminance drop does not change and is stored as it is. When the procedure 4) is executed, it is stored in place of the newly determined luminance reduction.

  When the input signal of the next pixel 100 is input, another circuit of the correction unit 5 (FIG. 1) reads out the luminance reduction data of the pixel 100 stored in the memory, corrects the input signal based on the value, and performs control. Send to part 3. The control unit 3 sends the corrected signal to the data signal output source 111 of the drive unit 2, and the data signal output source 111 generates a drive signal for display.

  The correction operation is preferably performed for each display pixel, but can also be performed, for example, in an arbitrary area unit. In this way, the accuracy of deterioration correction is reduced, but the time required for detection can be shortened. The correction curve and the offset value can be determined by measuring the deterioration characteristics of the element in advance.

  When duty driving is performed, the duty ratio dependency of the offset voltage can be acquired and determined in advance by the method described above.

  As described above, the deterioration characteristics A or B and ΔVos are held in the display device, the element deterioration is estimated based on the voltage increase amount of the organic EL element, the current correction amount is obtained, and the input signal is determined accordingly. Can be corrected and output via the control unit. If it is determined that the luminance is degraded by 98% from the detected voltage, an operation of increasing the element drive current by 2% is performed. In the above description, the correction of the input signal is performed by the correction unit 4. However, even if the input signal is input to the driving unit 3, and the luminance reduction data is sent from the memory of the correction unit 4 and corrected by the driving unit 3. good.

  The deterioration characteristic A is shown as a difference from the substantial initial voltage at which the operation starts, but correction may be performed using the absolute value of the voltage instead of the difference.

  The deterioration characteristic A may be held in a lookup table, but a function approximating the deterioration characteristic A may be prepared.

  The present invention can be applied to a display device (for example, illumination) composed of one organic EL element, or can be applied to a display device composed of a plurality of organic EL elements. In a display device composed of one organic EL element, a change in luminance due to driving can be suppressed. When applied to a display device composed of a plurality of organic EL elements, a change in luminance can be compensated. Further, by determining the deterioration amount and correcting the luminance in each of the plurality of organic EL elements, it is possible to suppress the deterioration amount that is different for each element from being visually recognized as burn-in.

  Further, in a display device including a plurality of organic EL elements of different colors, correction data and offset voltage may be provided for each color. In general, since the organic EL element has different deterioration characteristics for each color, the correction amount determined by the deterioration amount and the luminance to be displayed needs to be different for each color.

  FIG. 5 shows an embodiment of the present invention in an RGB three-color organic EL display device.

  The deterioration amount of the organic EL element 11 of the first color (R) is detected by the first deterioration detection means 41, and the first correction means 51 determines a correction coefficient from the deterioration amount and the display luminance. Similarly, the deterioration amount and display luminance of the organic EL elements 12 and 13 of the second (G) and third (B) colors are the second and third detection means 42 and 43 and the second and third, respectively. It is determined by the correction means 52 and 53. Since it can correct | amend according to the deterioration characteristic of an organic EL element, the change of a brightness | luminance can be made smaller. In the example of FIG. 5, the deterioration detection unit is provided for each different color, but the voltage of the three colors of organic EL elements may be detected by one deterioration detection unit.

  The means for determining the deterioration amount does not necessarily need to be detected from the pixel itself to be corrected. The deterioration amount of the pixel may be estimated based on the deterioration amount of another pixel that has been driven in the same manner as the pixel.

  The frequency of detecting the voltage may be performed for each writing, or may be performed for each writing a certain number of times.

  The display device of the present invention can be used for illumination, a display, an exposure light source of an electrophotographic image forming apparatus, and the like. When used as illumination, one or several light emitting elements are used.

  When an organic EL element is used as an exposure light source for a display or an electrophotographic image forming apparatus, a display panel in which a large number of organic EL elements are arranged in a matrix is used. The display here includes a display unit of a television or a personal computer, a display unit mounted on an electronic device, or an image display device including them. Examples of the electronic apparatus provided with the display device of the present invention include a digital camera, a copying machine, and a laser beam printer.

Example 1
When a current was passed through the organic EL element at a current density of 30 mA / cm ² , the initial luminance was 1140 cd / m ² and the voltage was 4.03 V. When the on / off operation was repeated, the voltage rise-brightness characteristics shown in FIG. 8 were obtained. As a result, a curve C having a deterioration characteristic A and an offset voltage = 20 mV were obtained.

The voltage was measured while passing a current of 30 mA / cm ² in the same way to another element having the same configuration, and after deteriorating until it increased by 0.42 V, the power was turned off, and after a while, the power was turned on again. . Then, the current was corrected using curve C and an offset voltage of 20 mV, and light was emitted at a luminance of 1000 cd / m ^{2. Even} if the power was turned on and off repeatedly, the light was emitted at a constant luminance without decreasing over time. Continued.

(Comparative example)
Corrective driving was performed in the same manner as in the example except that the offset voltage was not taken into consideration (set to 0 V). When an attempt was made to display 1000 cd / m ² , when the power was turned off and then turned on again, the display was brighter than 1000 cd / m ² .

The conceptual diagram for demonstrating one Embodiment of this invention The figure showing an example of the time-dependent change of the brightness | luminance in an organic EL element The figure showing the change over time and the luminance and voltage of organic EL elements The figure showing the change of luminance and voltage with time under different conditions in organic EL elements and their relationship The conceptual diagram for demonstrating another embodiment of this invention The figure which shows the pixel and correction | amendment part of embodiment of this invention Timing chart showing the operation of the circuit of FIG. The figure showing the relationship between the brightness | luminance and voltage in the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Organic EL element 2 Drive part 3 Control part 4 Deterioration detection means 5 Means for correct | amending an output according to deterioration 11, 12, 13 Organic EL element of each RGB color 41, 42, 43 Terminal of organic EL element of each RGB color Inter-voltage detection means 51, 52, 53 Correction unit for organic EL elements of RGB colors 100 Pixel 101 First N-type transistor 102 Second N-type transistor 103 First P-type transistor 104 Second P-type transistor 105 Holding Capacitance 106 Data line 107 Power supply line 108 First selection line 109 Second selection line 110 Third selection line 111 Data signal output source 112 Current source 113 Voltage detection unit 114 Degradation amount determination unit 115 Switch

Claims (6)

A light emitting element;
A driving unit for supplying a driving current to the light emitting element;
A voltage detector for detecting a voltage rise between the terminals of the light emitting element;
A correction unit that determines a deterioration amount of the light emitting element from the detected voltage increase, and holds the deterioration amount as correction data of the drive current;
A control unit that controls the driving unit so that the driving unit supplies a driving current corrected according to the correction data to the light emitting element;
In a display device having
The correction unit determines the deterioration amount of the light emitting element based on the detected voltage rise, the offset voltage recovered by stopping the driving current, and the deterioration amount at the time when the driving of the light emitting element is started. A display device. The correction unit is
The amount of deterioration of the light emitting element is determined by a different method according to a result of comparing a voltage increase corresponding to the amount of deterioration at the start of driving of the light emitting element and the detected voltage increase. Item 4. The display device according to Item 1.   When the detected voltage increase is less than or equal to a voltage increase corresponding to a deterioration amount at the time when the light emitting element starts to be driven, the correction unit is configured to start driving the light emitting element. A deterioration amount is determined as the deterioration amount, and when the detected voltage increase is larger than a voltage increase corresponding to the deterioration amount at the time when driving of the light emitting element is started, the offset from the detected voltage increase The display device according to claim 1, wherein a voltage obtained by subtracting a voltage or a corresponding decrease in luminance is determined as the deterioration amount.   The deterioration amount at the start of driving of the light emitting element and the deterioration amount determined by the correction unit are either a voltage increase or a luminance decrease corresponding to each other through a predetermined relationship. The display device according to claim 1.   The display device according to claim 4, wherein the relationship between the voltage increase and the luminance decrease, which is the deterioration amount, is stored as a reference table or a function in the correction unit.   The display device according to claim 1, wherein the light emitting element is a plurality of light emitting elements including light emitting elements of three colors and includes a correction unit for each color.

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