JP2008242322A - Light-emitting display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve correction accuracy of luminance unevenness in a light-emitting display device. <P>SOLUTION: The light-emitting display device has light-emitting elements and element drives Tr2 which control current flowing in the light-emitting elements in the respective pixels and is provided with a light-receiving sensor circuit which detects emitted light of the light-emitting elements inside a display region. A drive circuit 200 for driving a display part 110 has a creation part 330 which makes the element drive Tr2 operate in a linear region to emit the light emission elements; detects the characteristic variations of the light-receiving sensor circuit, based on a detection signal obtained from the corresponding light-receiving sensor circuit and creates a sensor adjustment signal Va for adjusting the characteristic variations and data signal correcting parts (350, 250), which makes the element drive Tr2 operate in a saturated region, to emit the light-emitting element; detects the luminance variations of a pixel circuit, based on the detection signal obtained by a light-receiving sensor circuit 140; and corrects the luminance variations, after adjusting the sensor characteristic variations. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display device having a light-emitting element such as an electroluminescence element in each pixel, and particularly to correction of display variations.

  An EL display device that employs an electroluminescence element (hereinafter referred to as an EL element), which is a self-luminous element, as a display element of each pixel is expected as a next-generation flat display device, and is researched and developed.

  In such an EL display device, after an EL panel in which an EL element and a thin film transistor (TFT) for driving the EL element for each pixel are formed on a substrate such as glass or plastic, several inspections are performed. After being shipped as a product.

  In a current active matrix EL display device including a TFT in each pixel, display unevenness caused by the TFT, particularly, unevenness in luminance of the EL element due to variation in the threshold voltage Vth of the TFT occurs, and this is a major factor in yield reduction. It has become. Improvement of the yield of such products is very important, and it is required to reduce display defects and display unevenness (display variation) by improving the element design, material, manufacturing method, etc. When display unevenness occurs in such cases, an attempt is made to make a non-defective panel by correcting this.

  However, the method of measuring the luminance variation by causing the EL panel to emit light and measuring this with a camera as in Patent Document 1 cannot be performed after shipment, and correction corresponding to the temporal change of the panel is performed. It cannot be executed. In addition, when the number of pixels increases as the EL panel becomes higher in definition, there are many measurement and correction targets for measuring the luminance variation for each pixel, and the resolution of the camera is increased and the capacity of the correction information storage unit is increased. Necessary.

  As a simpler method, a light receiving sensor is incorporated in each pixel, the light emission luminance of the EL element of the corresponding pixel is detected by the light receiving sensor, and the luminance of the EL element is corrected according to the detected luminance. Has been proposed in

JP-A-2005-316408 JP 2006-251091 A

  The light receiving sensor employed in Patent Document 2 employs a TFT built in on the same panel substrate as the display unit. In such a TFT, a polycrystalline silicon (LTPS) film that has been polycrystallized at a low temperature by laser annealing is used as an active layer of the TFT. Since such a light receiving sensor can be formed on the panel at the same time as a pixel TFT or the like, it is not necessary to add a special process by adopting it, and it can be created for each pixel. However, TFTs that use a low-temperature polycrystallized silicon film as an active layer have variations in photoelectric characteristics, and this variation affects the light reception detection result, which can increase the variation in luminance of EL elements. There is also sex.

  The present invention has been made in view of the above problems, and an object of the present invention is to realize a function of correcting variation in light emission luminance of a light emitting element with high accuracy.

  The present invention is a light emitting display device including a display unit including a plurality of pixels and a drive control unit for controlling the display unit, wherein each of the plurality of pixels includes a light emitting element and the light emitting element. A pixel circuit having an element driving transistor for controlling a flowing current; and a light receiving sensor circuit for detecting light emitted from the light emitting element in the region of the display unit, wherein the drive control unit includes the element driving unit. A sensor variation detector for detecting a characteristic variation in the light receiving sensor circuit based on a detection signal obtained from the corresponding light receiving circuit when the light emitting element emits light by operating a transistor in a linear region; and a detection An adjustment signal generation unit for generating a sensor adjustment signal to be supplied to the light receiving sensor circuit in order to adjust the characteristic variation, and after adjusting the sensor characteristic variation, When the element driving transistor is operated in a saturation region to cause the light emitting element to emit light, a characteristic variation in the corresponding pixel circuit is detected based on a detection signal obtained from the corresponding light receiving sensor circuit, and the characteristic A data signal correction unit that corrects a data signal supplied to the pixel circuit in order to correct variation;

  In another aspect of the present invention, in the light emitting display device, the light receiving sensor circuit includes a light receiving sensor and a sensitivity setting element for the light receiving circuit, and outputs a detection signal according to a light receiving result of the light receiving sensor. The sensitivity setting element sets the sensitivity of the light receiving circuit in accordance with the adjustment signal.

  In another aspect of the present invention, in the light emitting display device, a sensor adjustment signal memory unit that stores the sensor adjustment signal, and a correction necessary for correcting the data signal according to a characteristic variation detection result in the pixel circuit. A correction signal memory unit for storing a signal for use.

  In another aspect of the present invention, in the light emitting display device, the sensor adjustment signal memory unit stores the sensor adjustment signal created in advance before shipment at the time of shipment of the light emitting display device.

  In another aspect of the present invention, in the light-emitting display device, the correction signal memory unit stores the correction signal created in advance before shipment at the time of shipment of the light-emitting display device.

  In another aspect of the present invention, in the light emitting display device, the correction signal is obtained from the corresponding light receiving sensor circuit when the light emitting element emits light by operating the element driving transistor in a saturation region. Luminance data corresponding to the detected signal.

  In another aspect of the present invention, in the light emitting display device, the correction signal memory unit may be configured such that, after the light emitting display device is shipped, the element driving transistor is operated in a saturation region to cause the light emitting element to emit light. In addition, luminance data corresponding to the detection signal obtained from the corresponding light receiving sensor circuit is stored.

  In another aspect of the present invention, in the light emitting display device, the sensor adjustment signal memory unit may be configured such that after the light emitting display device is shipped, the element driving transistor is operated in a linear region to cause the light emitting element to emit light. A new sensor adjustment signal obtained according to the detection signal obtained from the corresponding light receiving sensor circuit is stored, and the characteristic variation of the light receiving sensor circuit is adjusted using the new sensor adjustment signal. .

  According to the present invention, by operating the element driving transistor for driving the light emitting element in the linear region to emit light, the characteristic variation of the pixel circuit such as the element driving transistor does not affect the light emission luminance. The characteristics of the light receiving sensor circuit can be detected. Therefore, it is possible to accurately detect and adjust the characteristic variation of the light receiving sensor circuit. In addition, by operating the element driving transistor in the saturation region to cause the light emitting element to emit light, variation in light emission luminance due to characteristic variation of the element driving transistor or the like can be captured from the detection result from the light receiving sensor circuit, It is possible to accurately correct the luminance variation of the light emitting element during normal display.

  Furthermore, since the light receiving sensor circuit is provided in the display area, it is possible to detect the light emission luminance of the light emitting element at a predetermined timing even after the display device is shipped, and to increase the luminance variation due to the time-dependent change in the characteristics of the pixel circuit, etc. Can be prevented.

  The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described below with reference to the drawings.

[Embodiment 1]
In this embodiment, an electroluminescence (EL) element, for example, an organic EL element using an organic light emitting material for the light emitting element layer can be adopted as the light emitting element of the light emitting display device. In the following, a so-called active matrix organic EL display device using an EL element as a light emitting element and further including a switch element for individually driving the EL element in each pixel will be described as an example.

(Pixel outline)
FIG. 1 is a diagram showing an example of an equivalent circuit of the active matrix EL display device according to this embodiment, and FIG. 2 is a diagram showing an operation waveform of each pixel.

  The active matrix organic EL display device includes an EL panel 100 on which a display unit 110 including a plurality of pixels 120 is formed, and a drive control circuit 200 for driving the display unit 110. The display unit 110 includes a plurality of pixels 120 arranged in a matrix, and a selection line (gate line GL) 10 that sequentially outputs a selection signal is formed in the horizontal (H) scanning direction (row direction) of the matrix. In the vertical (V) scanning direction (column direction), a data line 12 (DL) from which a data signal (Vsig) is output and an organic EL element which is a driven element (hereinafter simply referred to as “EL element”). ) 18, a power supply line 16 (VL) for supplying the drive power supply PVDD is formed.

  Each pixel 120 is generally provided in a region partitioned by these lines, and each pixel includes a pixel circuit 130 and a light receiving sensor circuit 140 corresponding to the pixel circuit 130 in the present embodiment.

  The pixel circuit 130 includes the EL element 18, a selection transistor Tr1 (hereinafter referred to as “selection Tr1”) configured by an n-channel TFT, a storage capacitor Cs, and an element drive transistor Tr2 (hereinafter referred to as “selection transistor Tr2”) configured by a p-channel TFT. "Element drive Tr2").

  In the selection Tr1, the drain is connected to the data line 12 for supplying the data voltage (Vsig) to the pixels arranged in the vertical scanning direction, and the gate is connected to the gate line 10 for selecting the pixels arranged on the horizontal scanning line. The source is connected to the gate of the element drive Tr2.

  The source of the element drive Tr2 is connected to the power supply line 16, and the drain is connected to the anode of the EL element 18. The cathode of the EL element is formed in common for each pixel and is connected to a cathode power source CV.

  The EL element 18 has a diode structure and includes a light emitting element layer between a lower electrode and an upper electrode. The light-emitting element layer includes, for example, a light-emitting layer containing at least an organic light-emitting material, and can adopt a single-layer structure or a multilayer structure of two layers, three layers, or four layers or more depending on the material characteristics used for the light-emitting element layer. . In the present embodiment, the lower electrode is patterned into individual shapes for each pixel, functions as the anode, and is connected to the element drive Tr2. Further, the upper electrode functions in common with a plurality of pixels as a cathode.

  In an active matrix EL display device having a circuit configuration as described above for each pixel, if the operation threshold value Vth of the element drive Tr2 varies, the EL element is driven even if the same data signal is supplied to each pixel. The same current is not supplied from the power supply PVDD, which causes luminance variations (display variations).

  The light receiving sensor circuit 140 is preferably provided in a region close to the EL element 18 that emits light to be detected, and is provided in the region of the display unit 110. In the present embodiment, the light receiving sensor circuit 140 configures one pixel 120 in a one-to-one correspondence with each pixel circuit 130 and detects the light emission luminance of the corresponding EL element 18. The light receiving sensor circuit 140 includes a light receiving element that receives light emitted from the EL element 18 and generates a photocurrent. In the present embodiment, a phototransistor TrP that employs a thin film transistor similar to the transistors Tr1 and Tr2 of the pixel circuit 130 is employed as the light receiving element. When this phototransistor TrP is constituted by a top gate type transistor, a channel region formed in the active layer exists under the gate electrode through a gate insulating film, but is formed in an upper layer than the transistor. In order to prevent light from the light emitting layer of the EL element to be completely blocked by the gate electrode, the light emitted from the EL element 18 is obliquely incident on the channel region from the side of the gate electrode. Set the position. In the case of a bottom-gate transistor, the channel layer is located above the gate electrode, so that it is suitable for receiving light from the EL element located above, and a special device for layout is required so much. Not.

  In addition to the phototransistor TrP, the light receiving sensor circuit 140 includes a light receiving detection capacitor C1, a charge control transistor TrA, an output transistor TrB, an output adjustment transistor TrC, an adjustment signal setting transistor TrD, and a sensor adjustment capacitor C2.

  The charge control transistor TrA and the phototransistor TrP are both configured as n-channel TFTs in this example, and are connected in series between the high-voltage side power supply (PVDD) and the low-voltage side power supply (holding capacitor line power supply). Yes. The gate of the charge control transistor TrA is connected to the gate line 10, and the gate of the phototransistor TrP is connected to the gate line 10 of the next row as a predetermined bias signal Vbias. The first electrode of the light receiving detection capacitor C1 is connected to the high-voltage power supply (PVDD), and the second electrode is connected to the source of the charge control transistor TrA and the drain of the phototransistor TrP.

  Here, the output transistor TrB is configured by a p-channel TFT, the gate thereof is connected to the second electrode of the light receiving detection capacitor C1, the source is connected to the power supply line 16 (PVDD) as a high voltage side power supply, The drain is connected to the light detection line 22. Further, the drain of the output adjustment transistor TrC formed of an n-channel TFT is connected to the light detection line 22 and the drain of the output transistor TrB, and the source thereof is connected to the capacitor line 14 as a low voltage side power source. Yes.

  The sensor adjustment signal Va is applied to the gate of the output adjustment transistor TrC from the sensor adjustment line 24 via the adjustment signal setting transistor TrD which is formed of an n-channel TFT here. The first electrode of the sensor adjustment capacitor C2 for holding the sensor adjustment signal Va supplied from the sensor adjustment line 24 is connected to the gate of the output adjustment transistor TrC and the source of the adjustment signal setting transistor TrD. Has been. Note that the second electrode of the sensor adjustment capacitor C2 is connected to the gate line 10 of the next row as a bias power source, like the phototransistor TrP.

(Pixel operation)
Next, operations of the pixel circuit 130 and the light receiving sensor circuit 140 will be described with reference to FIG. When a selection signal is output to the gate line 10 (FIG. 2A), the selection Tr1 of the pixel circuit 130 connected to the gate line 10 operates. At this time, a voltage corresponding to the data signal Vsig output to the data line 12 is supplied to the gate of the element drive Tr2, and the potential is held for a certain period by the holding capacitor Cs. The element drive Tr2 supplies a current corresponding to the voltage Vsig supplied to its gate from the drive power supply PVDD to the EL element 18, and the EL element 18 emits light with a luminance corresponding to the current.

  When the charge control transistor TrA connected to the same gate line 10 as the selection Tr1 receives a pulse signal (selection signal) Vpulse as shown in FIG. 2A and is turned on during the H level period, the power supply PVDD supplies the transistor TrA. A current flows through the drain-source, and the light receiving detection capacitor C1 is charged. As shown in FIG. 2B, the potential N1 on the second electrode side is substantially equal to the power supply PVDD. Here, the Vbias voltage is supplied to the gate of the phototransistor TrP, and the phototransistor TrP is controlled to be in an off state. When the light emitted from the EL element 18 is irradiated to the channel, a photocurrent is generated, and the phototransistor TrP corresponds to the photocurrent. The electric charge is discharged through the phototransistor TrP, and the potential N1 on the second electrode side of the light receiving detection capacitor C1 decreases (FIG. 2B).

  When the potential N1 on the second electrode side becomes lower than the operation threshold value Vth of the output transistor TrB, the output transistor TrB is turned on. Here, the gate voltage of the output adjustment transistor TrC is set to the sensor adjustment signal Va supplied from the sensor adjustment line 24 via the adjustment signal setting transistor TrD, and the output adjustment transistor TrC corresponds to this Va. It functions as a resistance. As shown in FIG. 2C, when the output transistor TrB is in an OFF state, the output adjustment transistor TrC as a resistor causes the source voltage (output node voltage N2) of the output adjustment transistor TrC to be a low-voltage side power supply ( Here, it is kept equal to the capacitance line voltage).

  When the output transistor TrB is turned on as described above, the resistance value of the output transistor TrB (resistance value between the source and drain) is sufficiently smaller than the resistance value between the source and drain of the output adjustment transistor TrC, and the output node voltage N2 becomes a voltage substantially equal to the power supply voltage PVDD, and the level rises to an H level equal to the power supply voltage PVDD from the timing when the output transistor TrB is turned on as shown in FIG. Next, during a period until the charge control transistor TrA is turned on and the light receiving detection capacitor C1 is charged and the output transistor TrB is turned off, the output node N2 becomes H level, and the detection signal corresponds to the light receiving luminance of the phototransistor TrP. It is output to the detection output line 22 as a pulse signal of length.

  Here, the characteristics a and b in FIG. 2B indicate the change in the second electrode side potential N1 of the light reception detection amount capacitor C1 when the light reception luminance of the phototransistor TrP is different when the sensor adjustment signal Va is constant. Is shown. Since the light reception luminance of the characteristic a is larger than the light reception luminance in the characteristic b, the photocurrent of the phototransistor TrP is large, and the rate of decrease in the potential N1 is fast. As a result, as shown in FIG. 2C, the H level period of the detection signal has a length corresponding to the decreasing rate of the potential N1, that is, the received light luminance, and the luminance a is higher than the luminance b. The period is getting longer. As will be described in detail later by generating the pulse signal corresponding to the light reception luminance in this way, the luminance determination unit of the drive circuit 200 accurately determines the light reception luminance according to the H level period of the detection signal. be able to.

  FIG. 2D shows the waveform of the detection signal when the sensor adjustment signal Va is changed under the same conditions as the case where the received light luminance is the above characteristic b. 2D, the same sensor adjustment signal Va as in FIG. 2C is set to the output adjustment transistor TrC, and the pulse width of the detection signal is the characteristic b of FIG. 2C. Is the same. For the characteristic b1, the voltage value of the sensor adjustment signal Va is set lower than that for the characteristic b, and conversely, the characteristic b2 is set higher than the characteristic b. When the voltage value of Va is low, the resistance value (resistance value between the source and drain) of the n-channel output adjustment transistor TrC is high. Therefore, even when the timing at which the output transistor TrB is turned on is the same as in the case of the characteristic b, the rate of increase in the voltage value of the detection signal determined by the product of the current supplied from the output transistor TrB and the resistance value of the output adjustment transistor TrC is As a result, the start timing of the H level period of the output detection signal is advanced as shown in the characteristic b1 in FIG. Conversely, when the voltage value of Va is high, the resistance value of the output adjustment transistor TrC is low, and the rising speed of the voltage value of the detection signal is lower than that of the characteristic b as compared with the characteristic b. The start timing of the period can be sent. Thus, the detection signal timing, that is, the sensitivity of the light receiving sensor circuit 140 can be adjusted by the sensor adjustment signal Va.

  The light receiving sensor circuit 140 is formed in the pixel 120 as shown in FIG. 1 and is formed on a one-to-one basis with the pixel circuit 130. However, the light receiving sensor circuit 140 is common to the plurality of pixel circuits 130. The luminance may be measured using

(Description of drive circuit)
Next, adjustment of characteristic variation of the light receiving sensor circuit and correction of luminance variation in the pixel circuit will be described. FIG. 3 shows the overall configuration of the light emitting display device according to the present embodiment, which adjusts the characteristic variation of the light receiving sensor circuit and corrects the luminance variation of the pixel circuit. As described above, the light-emitting display device includes the EL panel 100. The panel 100 includes the display unit 110 in which a plurality of pixels as illustrated in FIG. 1 are formed on a substrate such as glass, and the display unit 110. A drive circuit 200 for driving is provided.

  As illustrated in FIG. 3, the driving circuit 200 includes, as an example, a driving unit 210 that performs processing necessary to drive the display unit 110, and variation correction that performs sensor adjustment and luminance variation correction based on a luminance test. The unit 300 is provided. The drive circuit 200 can be configured as an integrated circuit in which all or a part of these components are integrated, and can be mounted on a substrate by a technique such as COG (chip on glass). it can.

  The driving unit 210 includes a driver circuit 220, a signal processing unit 230, a timing control (T / C) unit 240, and the like.

  The signal processing unit 230 is a processing unit for creating a data signal to be supplied to each pixel based on a video signal supplied from the outside. A serial-parallel (S / P) conversion unit, a luminance / contrast adjustment unit that adjusts brightness and contrast according to the characteristics and environment of the display panel, and a gamma that performs gamma correction, as needed, from an external video signal A correction unit, a data adjustment unit that adjusts the data signal according to the determination result of the external light luminance, a digital-analog conversion unit that converts the data subjected to correction processing and the like into an analog signal before being supplied to the display unit, and the like.

  The timing control unit 240 generates timing signals (H clock, V clock, H start signal, V start signal, etc.) necessary for display from externally supplied synchronization signals (Vsync, Hsync), clock signals (dotclock), etc. To do.

  The driver 220 is a circuit that outputs a drive signal and a display data signal to the display 110 of the panel 100 at a predetermined timing. In the example of FIG. 1, a pixel as a panel built-in driver circuit is provided around the display unit of the EL panel 100. It is formed on the panel simultaneously with the 110 TFTs. In the example of FIG. 1, the panel built-in driver circuit corresponds to the V driver 220V that sequentially outputs a selection signal to each gate line 10 and the display contents of the pixels selected by the gate line 10 for the data line 12. And an H driver 220H for supplying the data signal Vsig. The V driver 220V and the H driver 220H can be built in the integrated drive circuit 200 as the driver 220, or can be mounted on the panel 100 as an integrated circuit independent of the integrated circuit. good.

  The variation correction unit 300 executes luminance determination, sensor adjustment, luminance variation measurement, and luminance variation correction in accordance with control by the luminance inspection control unit 310. The luminance determination unit 320 receives the detection signal from the detection output line 24 shown in FIG. 1 and determines the luminance of the light detected by the corresponding light receiving sensor circuit 140.

  In this embodiment, the sensor adjustment signal creation unit 330 detects a characteristic variation of the light receiving sensor circuit from the brightness determination result obtained at the time of the brightness inspection, and creates a sensor adjustment signal Va for adjusting the variation. To do. The sensor adjustment signal Va is stored in the sensor adjustment signal memory 340 for each pixel, and is output to the sensor adjustment line 24 of FIG. 1 as necessary, and the adjustment signal setting transistor TrD of the corresponding light receiving sensor circuit 140. Is held in the sensor adjustment capacitor C2.

  The luminance data obtained by the luminance determination unit 320 at the time of luminance variation inspection (or at the time of inspection during normal display) is stored in the correction memory 400.

  The correction data creation unit 350 reads the luminance data from the correction memory 400 and creates correction data necessary for two-dimensional variation correction to be performed on a data signal supplied to each pixel circuit 130 as will be described later. In the present embodiment, the correction data generation unit 350 and a two-dimensional variation correction unit 520 described later constitute a data signal correction unit.

  The correction memory 400 includes an initial luminance data memory that stores luminance data of initial luminance (during pre-shipment inspection), and an actual operation luminance data memory that stores luminance data during actual operation after shipment. Further, a correction data memory for storing the correction data created by the correction data creation unit 350 may be provided. Corresponding data is stored in the corresponding memory, and data is read from the corresponding memory as necessary.

  These three types of memories may be stored at different addresses on a single memory, or different memories may be used. Further, the initial luminance data memory and the actual operation luminance data memory may be integrated as a luminance data memory. In this case, as will be described later, two-dimensional variation correction is performed using the initial luminance data when the device is displayed for the first time after the device is shipped, and the actual operation luminance data is used as a detection signal of the light receiving sensor circuit 140 after the shipment. Once obtained, the actual operating luminance data may be overwritten on the initial luminance data, or may be stored at different addresses. In the case where the initial luminance data is left even during actual operation, a change with time in the luminance of the EL element 18 is determined from the difference between the initial luminance data and the actual operation luminance data, and the correction data is taken into consideration that change. And two-dimensional variation correction may be performed.

  The two-dimensional variation correction unit 250 uses the correction data of the corresponding pixels created by the correction data creation unit 350 for the data signals for the pixels sequentially supplied from the signal processing unit 230, and sequentially converts the two-dimensional variation. Perform correction.

  The data signal subjected to the two-dimensional variation correction in this manner is supplied to the driver 220, and is output from the driver 220 (H driver 220H) to the corresponding data line 12 of the display unit 110.

  Note that a power supply is required for the drive circuit 200 and the display unit 110 to operate, but a power supply circuit for generating the power supply is incorporated in the drive circuit 200 (not shown in FIG. 3). Alternatively, the power supply circuit may employ a dedicated power supply circuit IC separately from the drive circuit 200. As an example, the power supply circuit includes a circuit that boosts the power supply for operating the drive power supply PVDD, the H driver 220H, and the V driver 220V by using an externally supplied power supply, and supplies the generated power supply voltage to each unit. (You may supply to each part as it is from the outside.)

(Variation correction)
Next, with reference to FIG. 4 further, a luminance variation correction procedure according to this embodiment will be described. FIG. 4 shows a procedure for variation correction. In the present embodiment, the luminance variation is corrected by first correcting the variation in sensor characteristics of the light receiving sensor circuit 140 for detecting the emission luminance, and then measuring the luminance variation and correcting it.

  When inspecting the sensor characteristics of the light receiving sensor circuit 140, the element driving Tr2 of each pixel is operated in a linear region to cause the corresponding EL element 18 to emit light (S1).

  The corresponding light receiving sensor circuit 140 receives the light emitted from the EL element 18. Note that the data signal (inspection data signal) supplied to each pixel at the time of the inspection of the sensor characteristics is the same value for each pixel, and the sensor adjustment signal Va is also set to be the same for all pixels. deep.

  For example, when the operation threshold value of the element drive Tr2 of the pixel circuit 130 varies, the EL element 18 is caused to emit light by operating the element drive Tr2 in a so-called saturation region during normal display. Thus, a difference occurs in the amount of current supplied, which becomes a difference in light emission luminance.

  Specifically, this will be described below with reference to FIG. FIG. 5 shows the Vds-Ids characteristics of the element drive Tr2 and the EL element when the characteristic variation of the element drive Tr2 (current supply characteristic variation, for example, variation in the operation threshold value Vth) occurs. When the voltage applied to the element drive Tr2 satisfies Vgs−Vth <Vds, the element drive Tr2 operates in the saturation region. Note that Vds is a drain-source voltage of the transistor, Ids is a drain-source current, Vgs is a gate-source voltage, and Vth is an operation threshold.

  In the saturation region, in the pixel where the operation threshold Vth of the element drive Tr2 is higher than that of the normal pixel, the drain-source current Ids of the transistor is smaller than that of the normal transistor, and the amount of current supplied to the EL element, that is, the EL element Is smaller than that of a normal pixel (large ΔI). Therefore, the light emission luminance of this pixel is lower than the light emission luminance of the normal pixel. On the contrary, in the pixel where the operation threshold Vth of the element drive Tr2 is lower than that of the normal pixel, the drain-source current Ids of the transistor is larger than that of the normal transistor, and the current flowing through the EL element is larger than that of the normal pixel. Thus, the light emission luminance is increased. Therefore, when the element drive Tr2 is operated in the saturation region, the luminance variation becomes large.

  On the other hand, when the voltage applied to the element drive Tr2 satisfies Vgs−Vth> Vds, the element drive Tr2 operates in a linear region, and in this linear region, the element drive Tr2 having a high threshold Vth and the low element drive are operated. The difference in Vds-Ids characteristics with Tr2 is small. Therefore, the difference (ΔI) in the amount of current supplied to the EL element is also small, and the EL element shows substantially the same light emission luminance regardless of the presence or absence of characteristic variation of the element drive Tr2.

  Therefore, in the present embodiment, when inspecting the sensor characteristics of the light receiving sensor circuit 140, the luminance inspection control unit 310 operates the element driving Tr2 in a linear region and causes the EL elements of each pixel to emit light with uniform luminance. If the corresponding light receiving sensor circuit 140 receives the emitted light, the characteristic variation of each light receiving sensor circuit 140 can be determined based on the obtained detection data. As described above, the luminance determination unit 320 obtains luminance data from the detection signal and stores it in the correction memory 400. The sensor adjustment signal creation unit 330 reads the luminance data, creates an optimum sensor adjustment signal Va according to the luminance data, and stores this in the sensor adjustment signal memory 340 for each pixel (S2).

  Here, for the sensor adjustment signal Va, an optimum value may be strictly obtained from the luminance data by calculation, or may be determined by a simpler method. For example, the sensor adjustment signal creation unit 330 determines whether the luminance data is within the reference range, and if it is within the range (no variation), selects the sensor adjustment signal Va so that the sensor sensitivity becomes the reference value (for example, Va corresponding to characteristic b in FIG. If the luminance data is larger than the upper limit value (high luminance = high sensitivity determination), the sensor adjustment signal Va at a level capable of reducing the sensor sensitivity is selected (in the case of the circuit configuration in FIG. 1, higher than the standard). Voltage level Va: Va corresponding to characteristic b2 in FIG. Conversely, if the luminance data is smaller than the lower limit value (low luminance = low sensitivity determination), the sensor adjustment signal Va at a level that can increase the sensor sensitivity is selected (in the case of the circuit configuration in FIG. Low voltage level Va: Va corresponding to characteristic b1 in FIG. If more comparison values are set and corresponding Va is prepared accordingly, more accurate sensor sensitivity adjustment (correction of variations in sensor characteristics) can be performed.

  The sensor adjustment signal Va determined according to the sensor characteristics as described above and stored in the sensor adjustment signal memory 340 is stored in the memory when the luminance variation inspection of the EL element 18 of each pixel circuit 130 is executed. Read from 340. The sensor adjustment signal Va is supplied to the corresponding light receiving sensor circuit 140 via the sensor adjustment line 24, and is set to the sensor adjustment capacitor C2. Thereby, the dispersion | variation in the sensor characteristic of each light reception sensor circuit 140 is adjusted.

  Next, inspection and correction of luminance variations are performed. The luminance inspection control unit 310 operates the element drive Tr2 of each pixel in the saturation region, and causes the corresponding EL element 18 to emit light according to the inspection data signal (data signal indicating the same luminance level) (S3). In the saturation region, as can be understood from FIG. 5, since the amount of change in Ids with respect to the change in Vds of the element drive Tr2 is small, light emission with stable luminance is possible. Therefore, in the normal display mode, the element drive Tr2 often operates in the saturation region to cause the EL element 18 to emit light. On the other hand, as described above, when the element drive Tr2 is operated in the saturation region, the variation in the light emission luminance of the EL element 18 due to the characteristic variation of the pixel circuit 130 (particularly, the operation threshold Vth variation of the element drive Tr2). As a result, the luminance variation can be reliably detected. Therefore, in the present embodiment, the EL element 18 emits light under conditions where large luminance variations are likely to occur, and the light is received by the light receiving sensor circuit 140 whose sensor characteristics have already been adjusted. Then, the luminance determination unit 320 obtains initial luminance data from the detection signal, and this initial luminance data is stored in the correction memory 400 (S4).

  Based on the obtained initial luminance data, the correction data creating unit 350 creates correction data necessary for two-dimensional variation correction as will be described later, and this correction data is stored in the correction memory 400 and is stored before shipping. The process ends. Details of the creation of correction data and the correction of two-dimensional variation will be described later in detail.

  Before shipment, not only inspection of sensor and brightness variation, but also defect inspection, color adjustment, etc. are executed, and for products that can be adjusted and can be adjusted, the necessary adjustment value obtained from the inspection result is For example, it is set in the correction value storage unit 280 of FIG. The correction value storage unit 280 may be integrated with the correction memory 400.

  Prior to shipment, sensor adjustment and creation of correction data for correcting luminance variations in accordance with the initial luminance are executed as described above. Then, when the display is actually performed after shipment, two-dimensional variation correction is performed on the data signal supplied to each pixel. Specifically, after the shipment, the display device is activated, and the signal processing unit 230 generates a data signal Vsig suitable for the display device from the video signal and outputs the data signal Vsig to the two-dimensional variation correction unit 250. Using the correction data supplied from the data creation unit 350, a two-dimensional variation correction process is executed on the data signal Vsig (S7).

  The data signal Vsig subjected to the two-dimensional variation correction is output to the data line 12 of the display unit 110 through the driver 220 and supplied to the corresponding pixel circuit 130, and the EL element 18 has a luminance corresponding to the data signal Vsig. Display is performed by emitting light (S8).

  Hereinafter, a method for correcting the luminance variation will be described with reference to FIG. The data signal Vsig supplied to each pixel and the current Ioled flowing through the EL element have a correspondence relationship as shown by a solid line in FIG. In addition, the current Ioled flowing through the EL element is proportional to the light emission luminance.

  Therefore, when the operation threshold value Vth of the element drive Tr2 is deviated from the reference (normal) TFT, the correction data generation unit 350 operates based on the initial luminance data stored in the correction memory 400. Correction data that compensates for the deviation of the threshold value Vth is obtained. Conceptually, with this correction data, the voltage of the data signal supplied to each pixel is shifted according to the deviation of the operation threshold Vth as shown by the dotted line in FIG.

An example of a method of creating correction data for shifting the voltage of the data signal will be specifically described as follows. First, the deviation of the operation threshold value of each pixel from the reference can be obtained by the following equation (1).

  In equation (1), Vth (i), V (ΔBright), V (ΔBright-ref) Vsigon and γ are defined as follows.

Vth (i): Operation threshold deviation of inspection target pixel V (ΔBright: Brightness data (voltage data) of inspection target pixel
V (ΔBright-ref): Reference luminance data (voltage data)
Vsigon: gradation level of on-display signal for inspection γ: luminous efficiency characteristic of display panel (constant value)
When the gradation level [Vsignon] of the inspection ON display signal is set to 240 (0 to 255), for example, the gradation level 240, the luminance data [V (ΔBright)] of the pixel to be inspected, and the reference on / off cathode current Based on the value [V (ΔBright-ref)] and the constant luminous efficiency characteristic γ, the operation threshold deviation Vth (i) with respect to the reference of each pixel can be obtained from the above equation (1). For example, it is assumed that the threshold deviation amount Vth (i) from the reference is obtained for each of the pixels A to E as follows.

Vth (A) = 0
Vth (B) = 13.4
Vth (C) = 17.0
Vth (D) = 3.2
Vth (E) = 20.7
In the above example, the threshold value Vth shift of the pixel E is the maximum, and when the data signal of the same gradation level is supplied to each pixel, the pixel E emits light with the lowest luminance in the display portion. On the other hand, there is a limit to the maximum value of the data signal that can be supplied to each pixel. Therefore, the maximum value Vsig _max of the data signal is determined based on the pixel E of Vth (i) _max . That is, the maximum value Vth (i) _max is obtained from the obtained Vth (i) of each pixel, and the difference ΔVth (i) of Vth of other pixels with respect to this Vth (i) _max is obtained. Further, [Vsig _max −ΔVth (i)] is obtained by subtracting ΔVth (i) obtained from Vsig _max from the maximum value Vsig _max (i) of the data signal to be supplied to the pixel, which will be described later. The initial correction data RSFT (init) reflecting the correction value of Expression (2) is supplied to the variation correction unit 250.

The correction data for each pixel created by the correction data creation unit 350 is preferably stored in the correction memory 400 for the purpose of promptly supplying it to the two-dimensional variation correction unit 250. However, the initial luminance data is read from the correction amount memory 400 at any time necessary for the correction calculation in the two-dimensional variation correction unit 250 (according to the timing of the video signal), and correction data is obtained based on the initial luminance data. You may supply to the two-dimensional dispersion | variation correction | amendment part 250. FIG. In this case, Vsig _max (i) is stored in the correction memory 400 as described above, and the correction data generation unit 350 reads the initial luminance data for the necessary pixel address from the correction memory 400, and the data And Vsig _max (i) are used to create correction data, which is supplied to the two-dimensional variation correction unit 250.

式（２）において、ＲＳＦＴ（init）は、上記のように補正データ作成部３５０において求められた補正値を反映した初期補正データである。Ｒｉｎは、信号処理部２３０から供給される入力映像信号で、ここでは、９ビットデータであり、０〜５１１のいずれかの値を備える。ＡＤＪ＿ＳＦＴは、補正値調整（重み付け）パラメータであり、Ｒ＿ＳＦＴは、二次元表示ムラ補正後の表示データである。 The two-dimensional variation correction unit 250 uses the correction data from the correction data creation unit 350, and uses the following equation (2) as an example for the video signal supplied from the signal processing unit 230 to correct variation for each pixel. Execute (2D display unevenness correction).

In Expression (2), RSFT (init) is initial correction data reflecting the correction value obtained by the correction data creating unit 350 as described above. Rin is an input video signal supplied from the signal processing unit 230, and is 9-bit data here and has any value of 0 to 511. ADJ_SFT is a correction value adjustment (weighting) parameter, and R_SFT is display data after two-dimensional display unevenness correction.

  As shown in FIG. 6, when the operation threshold value Vth of the element drive Tr2 is deviated, the slope β of the characteristic curve of the TFT is different from the slope of the normal characteristic curve of the TFT. Therefore, accurate gradation expression cannot be achieved by simply shifting the data signal from the one-dot chain line to the dotted line in FIG. 6 by the deviation of Vth. Therefore, the two-dimensional variation correction unit 250 uses the above equation (2) or the like and considers the inclination β, that is, the weighting parameter of the above equation (2), and is optimal according to the value (luminance level) of the actual video signal. Thus, adjustment is made so that a cathode current suitable for normal TFT characteristics flows through the EL element. By such correction, it is possible to surely prevent white gradation on the low gradation side (shift to the high gradation side) or the like caused by a difference in the inclination of the TFT characteristics when only simple ΔVth shift correction is performed.

(Real-time variation correction)
Next, an example of a technique for correcting sensor characteristic variation and luminance variation at the time of display after shipment will be described with reference to FIG.

  In the example shown in FIG. 7, after shipment, first, two-dimensional variation correction for the data signal Vsig is executed according to the initial luminance data obtained before shipment and the correction data based thereon (S11), and display is performed (S11). S12).

  The brightness inspection control unit 310 determines whether or not a predetermined timing has been reached, for example, between normal display and immediately after the ideographic device is turned on. When the predetermined timing is reached (S13: Yes), the latest characteristics are displayed. Start inspection. First, the sensor adjustment signal Va of each pixel is set to an equal standard value, and the element driving Tr2 is operated in the linear region to cause the light emitting element to emit light (S14). The light receiving sensor circuit 140 receives the light, and the luminance determination unit 320 obtains luminance data from the obtained detection signal. The sensor adjustment signal creation unit 330 obtains a sensor adjustment signal Va for correcting variations in sensor characteristics based on the luminance data, stores the new sensor adjustment signal Va in the sensor adjustment signal memory 340, and each pixel. Are set in the light receiving sensor circuit 140 (S15).

  After the light receiving sensor circuit 140 is adjusted according to the latest characteristic by the latest sensor adjustment signal Va, the element driving Tr2 is caused to emit light in the saturation region (S17), and the luminance determination unit 320 determines the latest luminance from the obtained detection signal. Get the data. The latest luminance data is stored as actual operating luminance data in the correction memory 400 separately from the initial luminance data, or is overwritten on the initial luminance data (S18).

  The correction data creation unit 350 obtains correction data again by the above-described method based on the latest luminance data, and stores it in the correction memory 400. The next time the normal display is performed, the two-dimensional variation correction unit 250 performs the two-dimensional variation correction on the data signal Vsig using the new correction data, and the display is performed using the obtained data signal Vsig.

  As described above, even after shipment, for example, with a timer, etc., once a day, once a week, once a month, etc., the device power-on and other normal displays are not affected. During the period, the characteristics of the light receiving sensor circuit 140 are inspected. And the dispersion | variation in this light reception sensor circuit 140 is adjusted according to a new test result, and the light emission luminance of an EL element is measured on it.

  As described above, by performing inspection after shipment, for example, low-temperature polycrystalline silicon (LTPS) is used for the active layer, like the transistors Tr1 and Tr2 of the pixel circuit, and the pixel circuit is formed on the panel substrate at the same time. When the light receiving sensor circuit 140 is formed, even if the photoelectric conversion characteristic of the LTPS varies, the variation can be grasped and corrected. Of course, not only LTPS but also the method as in the present embodiment is adopted, the light emission luminance of the light emitting element is accurately detected over a long period of time without being affected by the characteristic variation of the light receiving sensor circuit 140, and the luminance. Variations can be corrected.

  Further, as described above, when both the initial luminance data and the actual operating luminance data are stored in the memory 400, the luminance fluctuation amount, that is, the first characteristic variation over time of the pixel circuit is grasped from the comparison of the luminance data. In addition, by performing the two-dimensional variation correction in consideration of the variation, it is possible to reliably perform light emission display with uniform luminance even when the characteristic variation occurs.

  In the pixel circuit described above, a p-channel TFT is used as the element driving transistor, but an n-channel TFT may be used. Further, in the above pixel circuit, an example in which a configuration including two transistors, that is, a selection transistor and a drive transistor, is employed as a transistor for one pixel has been described. However, the transistors are not limited to the two types and the circuit configuration described above. . In addition, the light receiving sensor circuit 140 is not limited to the circuit configuration shown in FIG. 1, but it is necessary to include an adjustment unit that adjusts the sensor sensitivity using a sensor adjustment signal.

FIG. 3 is an equivalent circuit diagram illustrating a schematic circuit configuration of a pixel 110 of an EL display device according to an embodiment of the present invention. It is a figure which shows the operation | movement waveform of the light reception sensor circuit which concerns on embodiment of this invention. It is the schematic explaining the whole structure of the EL display apparatus which concerns on embodiment of this invention. It is a figure explaining the procedure for adjustment of sensor characteristic variation and brightness variation correction concerning an embodiment of the present invention. It is a figure explaining the inspection of the sensor characteristic and luminance variation which concern on embodiment of this invention. It is a figure explaining the concept of correction | amendment of the brightness variation which concerns on embodiment of this invention. It is a figure explaining the procedure for sensor characteristic dispersion | variation and luminance dispersion | variation correction after shipment which concerns on embodiment of this invention.

Explanation of symbols

  10 gate lines (GL), 12 data lines (DL), 14 capacitance lines, 16 power supply lines (VL), 18 EL elements, 22 detection output lines, 24 sensor adjustment lines, 100 panels, 110 display units, 120 pixels, 130 Pixel circuit, 140 Photo sensor circuit, 200 Drive control circuit (driver IC), 210 Drive unit, 220 driver, 220H H driver, 220V V driver, 230 Signal processing unit, 240 Timing control unit (T / C), 250 Two-dimensional Variation correction unit, 300 Variation correction unit, 310 Luminance inspection control unit, 320 Luminance determination unit, 330 Sensor adjustment signal creation unit, 340 Sensor adjustment signal memory, 350 Correction data creation unit, 400 Correction memory, TrP phototransistor, C1 light reception Detection capacity, TrA Charge control transistor, TrB output transistor, TrC output adjusting transistor, TrD adjustment signal setting transistors, C2 sensor adjustment capacity.

Claims (8)

A light emitting display device comprising: a display unit comprising a plurality of pixels; and a drive control unit for controlling the display unit,
Each of the plurality of pixels includes a pixel circuit having a light emitting element and an element driving transistor for controlling a current flowing through the light emitting element.
In the region of the display unit, a light receiving sensor circuit that detects light emitted from the light emitting element is provided,
The drive control unit
When the element driving transistor is operated in a linear region to cause the light emitting element to emit light, a sensor variation detecting unit that detects a characteristic variation in the light receiving sensor circuit based on a detection signal obtained from the corresponding light receiving circuit When,
An adjustment signal generator for generating a sensor adjustment signal to be supplied to the light receiving sensor circuit in order to adjust the detected characteristic variation;
After adjusting the sensor characteristic variation, when the element driving transistor is operated in a saturation region and the light emitting element emits light, the corresponding pixel circuit is based on a detection signal obtained from the corresponding light receiving sensor circuit. And a data signal correction unit that corrects a data signal supplied to the pixel circuit in order to detect the characteristic variation in and correct the characteristic variation. The light emitting display device according to claim 1.
The light receiving sensor circuit includes a light receiving sensor and a sensitivity setting element of the light receiving circuit, and includes an output unit that outputs a detection signal according to a light reception result of the light receiving sensor,
The light-emitting display device, wherein the sensitivity setting element sets sensitivity of the light receiving circuit in accordance with the adjustment signal. The light-emitting display device according to claim 1 or 2,
A sensor adjustment signal memory unit for storing the sensor adjustment signal;
A correction signal memory unit for storing a correction signal necessary for correcting the data signal according to a characteristic variation detection result in the pixel circuit;
A light-emitting display device comprising: The light-emitting display device according to claim 3.
2. The light emitting display device according to claim 1, wherein the sensor adjustment signal memory unit stores the sensor adjustment signal created in advance before shipment at the time of shipment of the light emitting display device. The light-emitting display device according to claim 3 or 4,
The light-emitting display device, wherein the correction signal memory unit stores the correction signal created in advance before shipment when the light-emitting display device is shipped. The light emitting display device according to claim 5.
The correction signal is luminance data corresponding to a detection signal obtained from a corresponding light receiving sensor circuit when the light emitting element emits light by operating the element driving transistor in a saturation region. A light-emitting display device. The light-emitting display device according to any one of claims 3 to 6,
In the correction signal memory unit, when the light emitting display device is shipped, the detection signal obtained from the corresponding light receiving sensor circuit when the light emitting element emits light by operating the element driving transistor in a saturation region. Luminance data corresponding to the brightness is stored. The light-emitting display device according to any one of claims 3 to 7,
In the sensor adjustment signal memory unit, when the light emitting display device is shipped, the detection signal obtained from the corresponding light receiving sensor circuit when the element driving transistor is operated in a linear region to emit light. A new sensor adjustment signal obtained according to the above is stored, and the characteristic variation of the light receiving sensor circuit is adjusted using the new sensor adjustment signal.

Images