JP2017013315A - Light-emitting device - Google Patents

Light-emitting device Download PDF

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JP2017013315A
JP2017013315A JP2015131200A JP2015131200A JP2017013315A JP 2017013315 A JP2017013315 A JP 2017013315A JP 2015131200 A JP2015131200 A JP 2015131200A JP 2015131200 A JP2015131200 A JP 2015131200A JP 2017013315 A JP2017013315 A JP 2017013315A
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light emitting
emitting element
light
current
power supply
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JP6533107B2 (en
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照彦 市村
Teruhiko Ichimura
照彦 市村
勝美 青木
Katsumi Aoki
勝美 青木
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京セラディスプレイ株式会社
Kyocera Display Corp
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Abstract

PROBLEM TO BE SOLVED: To accurately measure the degree of change in luminance of a light emitting element, to control the luminance of the light emitting element with high accuracy based on this, and to extract even if the threshold current of the light emitting element changes. The light-emitting device can be used.
A light-emitting device includes light-emitting elements 3a and 3b, light-receiving elements 7a and 7b that receive light emitted from the light-emitting elements 3a and 3b, and a correction unit that corrects the luminance of the light-emitting elements 3a and 3b. The correction unit includes a first correction for extracting a threshold current in the power supply current of the light emitting elements 3a and 3b based on the detection current that is information obtained from the light receiving elements 7a and 7b, and the light emitting elements 3a and 3b. Second correction is performed to correct the power supply current of the light emitting elements 3a and 3b based on the impedance of the light emitting elements 3a and 3b obtained from the value of the flowing power supply current.
[Selection] Figure 1

Description

  The present invention is a light-emitting device including a light-emitting element that tends to decrease in luminance over time, such as an organic electroluminescence (EL) element or an organic LED (Organic Light Emitting diode: OLED) element. The present invention relates to a light emitting device having correction means for correcting a luminance change such as a typical luminance drop.

  An example of a conventional light emitting device is shown in FIG. FIG. 9A is a plan view of the entire light emitting device, and FIG. 9B is an enlarged circuit diagram showing the drive element 24 composed of part B and IC, LSI, etc. of FIG. This light-emitting device is applied to an organic LED printer (OLEDP) head, and a plurality of light-emitting elements 23 that drive light emission (lighting) of a plurality of light-emitting elements 23 on one surface of a long plate-like substrate 21 made of a glass substrate or the like. Drive circuit block 22, a plurality of light emitting elements 23 arranged in two columns (two rows or two stages) along the longitudinal direction of the substrate 1, and wiring and drive circuit block constituting the drive circuit block 22 The wiring connecting 22 and the light emitting element 23 is formed by a thin film forming method such as a CVD (Chemical Vapor Deposition) method. The plurality of drive circuit blocks 22 are arranged in a line along the row of the plurality of light emitting elements 23. For example, one drive circuit block 22 drives 400 light emitting elements 23. Twenty blocks 22 are arranged. Therefore, there are a total of 8000 light emitting elements 23. A driving element 24 that drives the driving circuit block 22 and the light emitting element 23 to control light emission of the light emitting element 23 is mounted on one end of one surface of the substrate 21 by a chip-on-glass (COG) mounting method or the like. It is installed by. In addition, a flexible printed circuit (FPC) 25 is installed on an edge portion in the vicinity of the drive element 24 installation portion on one surface of the substrate 21. The FPC 25 inputs and outputs drive signals, control signals and the like with the drive element 24.

  As shown in FIG. 9B, one set of drive circuits is formed for two light emitting elements 23a and 23b in two rows. The set of drive circuits includes a shift register 30 and a logical sum negation. (NOR) circuit 31, inverter 32, CMOS transfer gate elements 33a and 33b, and thin film transistors (TFTs) 34a and 34b. Light emitting elements 23a and 23b made of organic LED elements or the like are connected to the drain electrode portions of the TFTs 34a and 34b, respectively.

  One set of drive circuits operates sequentially as follows. The shift register 30 has an output terminal when a high (“1”) clock signal (CLK) is input to the clock terminal (CLK) and a high synchronization signal (Vsync) is input to the input terminal (in). A high signal is output from (Q) and a low (“0”) signal is output from the inverting output terminal (XQ). Next, the NOR circuit 31 receives a low signal from the inverting output terminal (XQ) and a low signal that is the inverting enable signal (XENB), and outputs a high signal. Next, the inverter 32 outputs a low signal. Next, in the CMOS transfer gate element 33a, a high signal from the NOR circuit 31 is input to the gate electrode portion of the n-type MOS transistor, and a low signal from the inverter 32 is input to the gate electrode portion of the p-type MOS transistor. And the data signal (DATA 11) is output. Next, the data signal (DATA11) is input to the gate electrode portion of the TFT 34a, the TFT 34a is turned on, and the power supply current by the power supply voltage (VDD) corresponding to the data signal (DATA11) is supplied to the light emitting element 23a. At the same time, in the CMOS transfer gate element 33b, a high signal from the NOR circuit 31 is input to the gate electrode portion of the n-type MOS transistor, and a low signal from the inverter 32 is input to the gate electrode portion of the p-type MOS transistor. Turns on and outputs a data signal (DATA 12). Next, the data signal (DATA 12) is input to the gate electrode portion of the TFT 34b, the TFT 34b is turned on, and the power source current by the power source voltage (VDD) corresponding to the data signal (DATA 12) is supplied to the light emitting element 23b. The series of operations described above are sequentially executed by the drive circuit at the next stage, and all the light emitting elements 3 emit light sequentially.

  Further, as another conventional example, a line head driving device including a light emitting element array in which a plurality of EL elements are arranged, which is measured by a measuring unit that measures voltage-current characteristics of each EL element, and measured by the measuring unit. And a control unit that controls the voltage applied to each EL element based on the voltage-current characteristics of each EL element, thereby varying the emission luminance between the EL elements and the emission intensity of the EL element over time. There has been proposed a line head driving device capable of correcting a change and obtaining a constant luminance from the line head (see, for example, Patent Document 1). As another conventional example, a circuit having a drive transistor for flowing a drive current corresponding to an input signal to a load is provided, and the circuit supplies a correction signal corresponding to the impedance of the load to the gate of the drive transistor. In addition, by having a correction circuit that corrects the drive current that the drive transistor flows to the load, even if it is a light-emitting element that has characteristics that degrade over time, it can detect a decrease in luminance due to deterioration of the light-emitting element for each pixel. In addition, there has been proposed a driving circuit that realizes stable image formation for a long time by correcting (see, for example, Patent Document 2). Furthermore, as another conventional example, a light detection element that detects light output from the light emitting element is provided, and the light detection element is configured by a transistor and is configured to operate in an off region, thereby efficiently. An optical head capable of performing high-precision optical detection has been proposed (see, for example, Patent Document 3).

JP 2006-56010 A JP 2005-258427 A JP 2007-290329 A

  Since the conventional light emitting device shown in FIG. 9 has a light emitting element 23 that tends to decrease in luminance over time, such as an organic LED element, the luminance of the light emitting element 23 decreases when used for a long time. There was a problem. Therefore, as in Patent Document 1, it is conceivable to control the voltage applied to each EL element based on the measured voltage-current characteristics of each EL element. In such a case, if the impedance of the EL element can be measured, the luminance of the EL element can be controlled with higher accuracy. For that purpose, it is difficult to measure the current flowing in the TFT itself when measuring the current flowing in the TFT as a switch connected to the EL element in the light emitting state and the anode (anode electrode) side. There was a case. Although the detailed cause is unknown about this, the cathode (cathode electrode) of an EL element often includes an aluminum (Al) layer, and when an attempt is made to measure using the aluminum layer, the aluminum layer is often used for light-emitting devices. This is considered to be caused by being susceptible to the effects of capacitive coupling or the like with the aluminum layer other than the cathode electrode.

  Moreover, even if the impedance of the EL element can be measured, it is only necessary to change the power supply current value flowing through the EL element in accordance with the change in impedance over time. However, it is difficult to control the luminance near the threshold current of the EL element. There was a problem. In other words, there is a problem in that the EL element may be turned off by mistake when attempting to control the light emission of the EL element in a luminance region where the luminance of the EL element is low.

  Further, in the case of a configuration having a correction circuit that automatically corrects the luminance of the light emitting element as in Patent Document 2, when the light emitting element is in a light emitting state, it is necessary to operate the correction circuit to perform correction. There has been a problem that the power consumption of the light emitting device becomes very large. For example, a light-emitting device having a correction circuit that operates when a light-emitting element is in a light-emitting state may consume several hundred times more power than a light-emitting device that does not have the correction circuit. Also, as in Patent Document 3, when a photodetection element composed of a transistor operating in the off region is provided, the off-leak current detected by the transistor is weak, so that it is difficult to use to correct the luminance of the light-emitting element. There was a problem.

  The present invention has been completed in view of the above-described conventional problems, and an object of the present invention is to accurately measure the degree of change in luminance of a light emitting element, and based on this, the luminance of the light emitting element can be accurately measured. And a light emitting device that can extract even if a threshold current that is a light emission start current of the light emitting element changes.

The light emitting device of the present invention includes a light emitting element, a light receiving element that receives light emitted from the light emitting element, and a correction unit that corrects the luminance of the light emitting element.
The correction unit is configured to extract a threshold current in the power supply current of the light emitting element based on information obtained from the light receiving element, and the value of the power supply current flowing through the light emitting element. And a second correction for correcting the power supply current of the light emitting element by impedance.

  In the light emitting device of the present invention, it is preferable that the correction unit determines the threshold current as the minimum luminance of the light emitting element by the first correction, and corrects the power supply current equal to or higher than the threshold current by the second correction. To do.

  In the light emitting device of the present invention, preferably, the second correction corrects the power supply current so as to correspond to a specific luminance.

In the light emitting device of the present invention, preferably, for the current path of the power supply current in the light emitting element, the first current path including the thin film transistor and the light emitting element connected thereto, and the thin film transistor and the light emitting element are connected. A second current path that does not include the light emitting element branched from the middle of the connecting line to be formed,
The correction unit includes an impedance calculation unit that calculates an impedance of the light emitting element from a first current value in the first current path and a second current value in the second current path.

  In the light-emitting device of the present invention, it is preferable that the second current path has one electrode connected in parallel to the connection line, the other electrode connected to a ground portion through a resistor, and an impedance of the thin film transistor It includes other thin film transistors that are smaller than the impedance.

  In the light emitting device of the present invention, preferably, the other thin film transistor has an impedance of 1/100 or less of the impedance of the thin film transistor.

The light emitting device of the present invention includes a light emitting element, a light receiving element that receives light emitted from the light emitting element, and a correction unit that corrects the luminance of the light emitting element.
The correction unit is configured to extract a threshold current in the power supply current of the light emitting element based on information obtained from the light receiving element, and the value of the power supply current flowing through the light emitting element. Since the second correction for correcting the power supply current of the light emitting element is performed by impedance, the luminance is controlled with high accuracy even in the vicinity of the threshold current that is the light emission start current value of the light emitting element. Becomes easier.

  In the light emitting device of the present invention, it is preferable that the correction unit determines the threshold current as the minimum luminance of the light emitting element by the first correction, and corrects the power supply current equal to or higher than the threshold current by the second correction. Therefore, the minimum brightness of the light emitting element can be accurately determined by the first correction, and the brightness above the minimum brightness can be accurately corrected by the second correction. As a result, for example, even if the luminance of the light emitting element decreases with time, the luminance equal to or higher than the minimum luminance of the light emitting element can be controlled with high accuracy.

  In the light emitting device of the present invention, it is preferable that the second correction corrects the power supply current so as to correspond to a specific luminance. For example, it is assumed that the power supply current for a specific luminance decreases due to a change over time or the like. However, it can be accurately corrected by the second correction so as to maintain a specific luminance.

  In the light emitting device of the present invention, preferably, with respect to the current path of the power source current in the light emitting element, the first current path including the thin film transistor and the light emitting element connected to the thin film transistor, and the connection line connecting the thin film transistor and the light emitting element. A second current path not including the branched light emitting element is formed, and the correction unit emits the light emitting element from the first current value in the first current path and the second current value in the second current path. Therefore, the impedance of the light emitting element can be acquired, and as a result, the luminance of the light emitting element can be controlled with higher accuracy.

  In the light emitting device of the present invention, preferably, the second current path has one electrode connected in parallel to the connection line, the other electrode connected to the ground through a resistor, and an impedance higher than that of the thin film transistor. Since the small other thin film transistor is included, the impedance of the light emitting element can be derived from the impedance of the thin film transistor.

  Further, in the light emitting device of the present invention, preferably, the impedance of the other thin film transistor is 1/100 or less of the impedance of the thin film transistor, so that the impedance of the light emitting element can be more accurately derived from the impedance of the thin film transistor.

1A to 1C are diagrams showing an example of an embodiment of a light-emitting device according to the present invention. FIG. 1A is a plan view of the entire light-emitting device, and FIG. The circuit diagram of a part and a drive element, (c) is a circuit diagram of the site | part of the 1st thin-film transistor of FIG. FIG. 2 is a diagram showing an example of an embodiment of a drive element in the light emitting device of FIG. 1, and is a block circuit diagram for explaining an internal function of the drive element. FIG. 3 is a diagram showing another example of the embodiment of the drive element in the light emitting device of FIG. 1, and is a block circuit diagram for explaining the internal function of the drive element. 4A to 4C are diagrams showing another example of the embodiment of the light-emitting device of the present invention, and FIG. 4A is a graph showing that the luminance of the light-emitting element in the light-emitting device deteriorates with time. b) is a graph showing that the impedance of the light emitting element changes with time, and (c) is a graph showing that the power supply current of the light emitting element changes with time when the power supply voltage is kept constant. 5A and 5B are diagrams showing another example of the embodiment of the light-emitting device of the present invention. FIG. 5A is a graph showing that the threshold voltage and the power supply voltage of the light-emitting element change over time. (B) is a graph which shows that the threshold current and power supply current of a light emitting element change with time. FIG. 6 is a diagram showing another example of the embodiment of the light emitting element in the light emitting device of the present invention, and is a plan view of a light emitting element composed of three organic EL elements of the light emitting device and its peripheral part. 7 is a cross-sectional view taken along line C1-C2 of FIG. 8A and 8B are diagrams showing another example of the embodiment of the light-emitting device of the present invention. FIG. 8A is a plan view of the entire light-emitting device, and FIG. 8B is A1 in FIG. It is a circuit diagram of a part and a drive element. 9A and 9B are diagrams showing a conventional light emitting device, where FIG. 9A is a plan view of the entire light emitting device, and FIG. 9B is a circuit diagram of a portion B and a driving element of FIG. is there.

  Hereinafter, embodiments of a light-emitting device of the present invention will be described with reference to the drawings. However, each drawing referred to below shows a main part for explaining the light emitting device of the present invention among the constituent members in the embodiment of the light emitting device of the present invention. Therefore, the light-emitting device of the present invention may include well-known components such as a circuit board, a wiring conductor, a control IC, and an LSI that are not shown in the drawing.

  1 to 5 show a light emitting device of the present invention, and FIGS. 1A to 1C are diagrams showing an example of an embodiment of the light emitting device of the present invention. FIG. FIG. 5B is a plan view of the entire light emitting device, FIG. 5B is a circuit diagram of the A part and the driving element in FIG. It is. As shown in FIGS. 1 to 5, the light emitting device of the present invention includes a light emitting element 3 (3a, 3b), light receiving elements 7a, 7b for receiving light emitted from the light emitting elements 3a, 3b, and a light emitting element 3a. , 3b for correcting the brightness of the light emitting elements 3a, 3b based on the detection current, which is information obtained from the light receiving elements 7a, 7b. The first correction and the second correction for correcting the power supply current of the light emitting elements 3a and 3b based on the impedance of the light emitting elements 3a and 3b obtained from the value of the power supply current flowing through the light emitting elements 3a and 3b. is there. With this configuration, it is easy to control the luminance with high accuracy even in the vicinity of the threshold current that is the light emission start current value of the light emitting elements 3a and 3b.

  First, the basic configuration of the light emitting device of the present invention will be described below. The light emitting device of the present invention is applied to an organic LED printer (OLEDP) head or the like, and emits light (lights) of a plurality of light emitting elements 3 on one surface of a long plate-like substrate 1 made of a glass substrate or the like. A plurality of driving circuit blocks 2 to be driven; a plurality of light emitting elements 3 arranged in two columns (two rows or two stages) along the longitudinal direction of the substrate 1; wirings constituting the driving circuit block 2; The wiring connecting the drive circuit block 2 and the light emitting element 3 is formed by a thin film forming method such as a CVD method. The plurality of drive circuit blocks 2 are arranged in a line along the row of the plurality of light emitting elements 3. For example, one drive circuit block 2 drives 400 light emitting elements 3. Twenty blocks 2 are arranged. Therefore, there are a total of 8000 light emitting elements 3. A driving element 4 that drives the driving circuit block 2 and the light emitting element 3 and controls the light emission of the light emitting element 3 is installed at one end of one surface of the substrate 1 by a mounting method such as a COG method. In addition, an FPC 5 is installed on an edge near the drive element 4 installation portion on one surface of the substrate 1. The FPC 5 inputs and outputs drive signals, control signals, and the like with the drive element 4.

  As shown in FIG. 1B, a set of drive circuits is formed for two light emitting elements 3a and 3b in two rows. The set of drive circuits includes a shift register 10 and a logical sum negation. A (NOR) circuit 11, an inverter 12, CMOS transfer gate elements 13a and 13b, first TFTs 14a and 14b, and second TFTs 15a and 15b are provided. Connection lines connected to the light emitting elements 3a and 3b made of organic LED elements are connected to the drain electrode portions of the first TFTs 14a and 14b, respectively. There are also light receiving elements 7a and 7b that receive light emitted from the light emitting elements 3a and 3b. The light receiving elements 7a and 7b are made of, for example, TFTs. The current value Isd1 between the source and the drain when the light emitting elements 3a and 3b emit light, and the current between the source and drain when the light emitting elements 3a and 3b do not emit light. The threshold current is specified by taking the difference from the value (off-leakage current value) Isd2. The light receiving elements 7a and 7b are connected in series with TFTs 6a and 6b (hereinafter also referred to as third TFTs 6a and 6b) as switches for controlling on and off of the light receiving elements 7a and 7b. The light receiving elements 7a and 7b are not limited to TFTs, and may be formed of photodiodes or the like.

  The set of drive circuits operates sequentially as follows. The shift register 10 has an output terminal when a high (“1”) clock signal (CLK) is input to the clock terminal (CLK) and a high synchronization signal (Vsync) is input to the input terminal (in). A high signal is output from (Q) and a low (“0”) signal is output from the inverting output terminal (XQ). Next, the NOR circuit 11 receives a low signal from the inverting output terminal (XQ) and a low signal that is the inverted enable signal (XENB), and outputs a high signal. Next, the inverter 12 outputs a low signal. Next, in the CMOS transfer gate element 13a, a high signal from the NOR circuit 11 is input to the gate electrode portion of the n-type MOS transistor, and a low signal from the inverter 12 is input to the gate electrode portion of the p-type MOS transistor. And the data signal (DATA 11) is output. Next, the data signal (DATA11) is input to the gate electrode portion of the first TFT 14a to turn on the first TFT 14a, and the power supply current by the power supply voltage (VDD) corresponding to the data signal (DATA11) is changed to the light emitting element 3a. To be supplied. At the same time, in the CMOS transfer gate element 13b, a high signal from the NOR circuit 11 is input to the gate electrode portion of the n-type MOS transistor and a low signal from the inverter 12 is input to the gate electrode portion of the p-type MOS transistor. Turns on and outputs a data signal (DATA 12). Next, the data signal (DATA 12) is input to the gate electrode portion of the first TFT 14b, the first TFT 14b is turned on, and the power source current by the power source voltage (VDD) corresponding to the data signal (DATA 12) is changed to the light emitting element 3b. To be supplied. The series of operations described above are sequentially executed by the drive circuit at the next stage, and all the light emitting elements 3 emit light sequentially.

  In the light emitting device of the present invention, preferably, the correction unit determines the threshold current corrected by the first correction as the minimum luminance of the light emitting element 3, and corrects the power supply current equal to or higher than the threshold current by the second correction. In this case, the minimum brightness of the light emitting element 3 can be accurately determined by the first correction, and the brightness above the minimum brightness can be accurately corrected by the second correction. As a result, for example, even if the luminance of the light emitting element 3 decreases with time, the luminance equal to or higher than the minimum luminance of the light emitting element 3 can be controlled with high accuracy.

  For example, as shown in FIG. 4A, the luminance of the light emitting element 3 decreases with time. As shown in (b), the impedance of the light emitting element 3 increases with time. As shown in (c), the power supply current flowing through the light emitting element 3 decreases with time if the power supply voltage is constant. From the above, for example, in order to correct the power supply current flowing through the light emitting element 3 to be constant and maintain the luminance constant even when time elapses, it is applied to the light emitting element 3 as shown in FIG. What is necessary is just to correct | amend so that a power supply voltage may be enlarged. In FIG. 5A, Vth1, Vth2, and Vth3 are threshold voltages corresponding to the light emission start voltages at timings t1, t2, and t3, respectively. Thus, as time elapses, the threshold voltages Vth1, Vth2, and Vth3 and the power supply voltage corresponding to a certain brightness increase, and the power supply voltage characteristic curve corresponding to the brightness, that is, the power supply voltage-luminance characteristics. The curve draws a quadratic increase curve. Therefore, for example, correction data of threshold voltage Vth1, Vth2, Vth3 and power supply voltage-luminance characteristic curve is stored in advance, and specific luminance (for example, minimum luminance + ΔL () of light-emitting element 3 is stored based on the correction data. ΔL can keep the luminance increment)) constant, or the luminance can be controlled with high accuracy regardless of changes over time. Further, since the threshold voltages Vth1, Vth2, and Vth3 can be specified, the luminance of the light emitting element 3 in a wide luminance range from the minimum luminance corresponding to the threshold voltage of the light emitting element 3 to the maximum luminance as described above. Can be controlled with high accuracy. The initial threshold voltage Vth1 is about 2V to 5V, the threshold voltage Vth2 when the time of about 100 hours elapses is about 3V to 6V, and the threshold voltage Vth3 when the time of about 1000 hours elapses is 4V to It is about 7V.

  Further, as shown in FIG. 5B, the power supply current applied to the light emitting element 3 can be corrected to be increased. In FIG. 5B, Ith1, Ith2, and Ith3 are threshold currents corresponding to the light emission start currents at timings t1, t2, and t3, respectively. Thus, as time elapses, the threshold currents Ith1, Ith2, Ith3 and the power supply current corresponding to a certain luminance increase, and the characteristic curve of the power supply current corresponding to the luminance, that is, the power supply current-luminance characteristic. The curve draws an increasing straight line like a linear function. Therefore, for example, correction data of threshold currents Ith1, Ith2, Ith3 and a characteristic line of power supply current-luminance are stored in advance, and specific luminance (for example, minimum luminance + ΔL (for example) of the light emitting element 3 is stored based on the correction data. ΔL can keep the luminance increment)) constant, or the luminance can be controlled with high accuracy regardless of changes over time. Further, since the threshold currents Ith1, Ith2, Ith3 can be specified, as described above, the luminance of the light emitting element 3 in a wide luminance range from the minimum luminance corresponding to the threshold current of the light emitting element 3 to the maximum luminance. Can be controlled with high accuracy. The initial threshold current Ith1 is about 0.5 μA to 1 μA, and the threshold current Ith2 when about 100 hours have elapsed is about 0.7 μA to 1.1 μA, when about 1000 hours have elapsed. The threshold current Ith3 is about 0.9 μA to 1.3 μA. As described above, in the light emitting device of the present invention, preferably, the second correction corrects the power supply current so as to correspond to a specific luminance. In this case, for example, even if the power supply current decreases due to a change over time, it can be accurately corrected by the second correction so as to correspond to a specific luminance.

  In the light emitting device of the present invention, preferably, one electrode (for example, a source electrode) is connected in parallel to the connection line between the first TFTs 14a, 14b and the light emitting elements 3a, 3b, and the other electrode (for example, for example) The drain electrode) is connected to the ground (VSS) through the resistor 18, and has second TFTs 15a and 15b which are other TFTs whose impedance is set smaller than the impedance of the first TFTs 14a and 14b. ing. In this case, as will be described later, the impedance of the light emitting elements 3a and 3b can be derived from the impedance of the first TFTs 14a and 14b.

  FIG. 2 is a diagram showing a preferred example of the embodiment of the drive element 4 in the light emitting device of FIG. 1, and is a block circuit diagram for explaining the internal functions of the drive element 4. As shown in FIG. 2, the driving element 4 includes a control unit 41 that controls driving of the light emitting element 3, a driving unit 42 that transmits data according to luminance for driving to the light emitting element 3, and a correction processing unit (current). (Path switching unit) A (41b), correction processing unit B (43), correction processing unit C (44), and control unit 41 includes correction control unit 41a and correction processing unit A (41b). Yes. That is, the correction unit includes a correction control unit 41a, a correction processing unit A (41b), a correction processing unit B (43), and a correction processing unit C (44).

  The light-emitting device of the present invention can be controlled by the correction control unit 41a so as to always or intermittently correct the luminance decrease due to the deterioration of the light-emitting element 3 with the lapse of time by the power supply current supplied to the light-emitting element 3. Hereinafter, a description will be given of a case where the luminance decrease due to deterioration with time of the light emitting element 3 is intermittently corrected by the power supply current. The correction control unit 41a can also perform control so that the intermittent period for intermittently correcting the power supply current is lengthened. In this case, the luminance of the light emitting element 3 can be controlled with high accuracy by correcting the power supply current by shortening the intermittent period in the initial stage where the light emitting element 3 is likely to deteriorate with time. Moreover, since the brightness | luminance fall by the deterioration with time of the light emitting element 3 is correct | amended intermittently with the power supply current supplied to the light emitting element 3, the increase in power consumption can be suppressed.

  The correction processing units A (41b), B (43), and C (44) perform correction processing based on an instruction from the correction control unit 41a. The correction processing units A (41b) and B (43) perform first correction for extracting the threshold current in the power supply current of the light emitting element 3 based on the detection currents of the light receiving elements 7a and 7b. The correction processing units A (41b) and C (44) measure the impedance of the light emitting element 3 from the value of the power supply current flowing through the light emitting element 3, and correct the power supply current of the light emitting element 3 based on the impedance of the light emitting element 3. 2 correction is performed.

  The control unit 41 includes a correction control unit 41a that performs correction, stop control, intermittent period control, and the like, and a correction processing unit A (41b) as a current path switching unit. The control unit 41 outputs a clock signal (CLK), a synchronization signal (Vsync), an inversion enable signal (XENB), and a power supply voltage (VDD). The correction control unit 41a selects one of a first state (MODE 1) in which the light emitting element 3 is in a normal light emitting state and a second state (MODE 2) in which the luminance of the light emitting element 3 is corrected.

  When MODE2 is selected, the operation is as follows. First, the correction processing unit A is activated and the gate signal Vn is turned on, the third TFT 6a is turned on, and the light receiving element 7a can be driven. However, the gate signal Vm is in an off state, the second TFT 15a is not turned on, and the switch 17 is connected to the ground portion (VSS). Then, the correction processing unit B is activated, and the power supply current value is changed from near the maximum value to a smaller value in order to specify the threshold current of the light emitting element 3a. The detection current measurement unit 43a measures the power supply current value when the detection current of the light receiving element 7a is no longer detected and the power supply current value when the detection current of the light reception element 7a starts to be detected. The difference is calculated by the difference calculation unit 43b. Next, the threshold current value and the threshold voltage value of the light emitting element 3a are extracted from the difference by the correction data storage unit B (43c). Next, the extracted threshold current value and threshold voltage value are transmitted to the drive unit 42, and the drive unit 42 changes the threshold current value and the threshold voltage value and holds them thereafter. Thereby, the first correction is completed.

  Next, a second correction is performed. First, the correction signal processing unit A is not activated and the gate signal Vm is turned off, and the first current value I1 is measured. The correction processing unit C is activated, and the current measurement unit 44a measures the power supply current value based on the power supply voltage (VDD). The power supply current value at this time is the first current value I1 in the first current path IK1 including the first TFT 14a and the light emitting element 3a connected thereto. Next, the correction processing unit A outputs a gate signal Vm for turning on the second TFT 15a, and switches the switch 17 so that the power supply voltage (VDD2) side is closed (conductive state). Is output, the light emitting element 3a is brought into a non-light emitting state, and the second current value I2 in the second current path IK2 including the first TFT 14a, the second TFT 15a, and the resistor 18 but not including the light emitting element 3a is measured. .

  Next, the impedance calculator 44b calculates the impedance of the light emitting element 3a from the first current value I1 and the second current value I2. The first current value I1 is determined by the impedance of the first TFT 14a, the impedance of the light emitting element 3a, and the power supply current value of the power supply voltage (VDD), and the second current value I2 is the impedance of the first TFT 14a and the second current value I2. This is determined by the impedance of the TFT 15a, the resistor 18, and the power supply current value of the power supply voltage (VDD). Since the resistor 18 is known and the first current value I1 and the second current value I2 are obtained by measurement, the impedance of the second TFT 15a is set to be very small so as to be negligible than the impedance of the first TFT 14a. Then, the impedance of the light emitting element 3a can be obtained.

  Next, the correction data storage unit C (44c) storing the correction data corresponding to the impedance of the light emitting element 3a inputs the correction data to the drive unit 42, and the drive unit 42 corrects the correction data (corrected DATA 11). To the data line. The drive unit 42 rewrites the data to correction data and holds the correction data. At this time, DATA 12 is not input to the data line, and the light emitting element 3b side is turned off. Thereby, the second correction is completed.

  Next, the above-described correction operation is performed on the light emitting element 3b with the light emitting element 3a turned off without inputting the DATA 11 to the data line. Thereby, the light emitting element 3b is also driven by the correction data. Next, the correction operation is similarly performed for the light emitting elements 3 in the subsequent stages, and the data of all the light emitting elements 3 are corrected.

As shown in FIG. 1C, the light-emitting device of the present invention has a first current path IK1 including a first TFT 14a and a light-emitting element 3a connected thereto, A second current path IK2 that does not include the light emitting element 3a branched from the middle of the connection line connecting the first TFT 14a and the light emitting element 3a is formed, and the correction processing unit C (44) It is preferable to have an impedance calculation unit 44b that calculates the impedance of the light emitting element 3a from the first current value I1 in the current path IK1 and the second current value I2 in the second current path IK2. In this case, the impedance of the light emitting element 3a can be acquired, and as a result, the luminance of the light emitting element 3a can be controlled with higher accuracy. As described above, the first current value I1 is determined by the impedance of the first TFT 14a, the impedance of the light emitting element 3a, and the power supply current value of the power supply voltage (VDD), and the second current value I2 is the first TFT 14a. , The impedance of the second TFT 15a, the resistor 18 (FIG. 1B), and the power supply current value of the power supply voltage (VDD). Since the resistor 18 is known and the first current value I1 and the second current value I2 are obtained by measurement, the impedance of the second TFT 15a is set to be very small so as to be negligible than the impedance of the first TFT 14a. Then, the impedance of the light emitting element 3a can be obtained. That is, I1 = VDD / (R 1 + R OLED ), I2 = VDD / (R 1 + R 2 + R) (R 1 is the impedance of the first TFT 14a, R OLED is the impedance of the light emitting element 3a, and R 2 is the second R OLED can be obtained from the impedance of the TFT 15a, R 2 ≈0, and R is the value of the resistor 18.

  In the light emitting device of the present invention, the second TFT 15a preferably has an impedance of 1/100 or less of the impedance of the first TFT 14a. In this case, the impedance of the light emitting element 3a can be more accurately derived from the impedance of the first TFT 14a. As described above, when deriving the impedance of the light emitting element 3a from the first current value I1 and the second current value I2, the impedance of the second TFT 15a is much more negligible than the impedance of the first TFT 14a. This is because the impedance of the light emitting element 3a can be obtained by setting it small. For example, when the impedance of the first TFT 14a is about 200 kΩ to 300 kΩ, the impedance of the second TFT 15a is about 2 kΩ to 3 kΩ. In this case, if the resistance 18 is set to 100 kΩ, the impedance of the light emitting element 3a is about 500 kΩ. Further, for example, VDD and VDD2 are 10V, Vm and Vn are 10V to 16V, and VSS is 0V.

  In the light emitting device of the present invention, when the light emitting element 3 is composed of an organic EL element, the first TFT 14a is connected to the anode (anode electrode) side of the light emitting element 3 in the light emitting state 3, A second TFT 15a is connected in parallel to the connection line between the first TFT 14a and the light emitting element 3a, and the cathode side of the light emitting element 3 is connected to VDD2 to measure the second current value I2, so that no light is emitted. It is preferable to be in a state. In this case, it becomes easy to measure the current flowing through the first TFT 14a itself. In other words, the cathode of the organic EL element often includes an Al layer, and when an attempt is made to measure the current flowing through the first TFT 14a itself using the Al layer, it is easily affected by the Al layer in parts other than the cathode. It is thought that it is possible to prevent this.

  The correction control unit 41a in the light emitting device of the present invention preferably controls so as to gradually increase the intermittent period for correcting the power supply current intermittently. This is because the deterioration with time of the light emitting element 3 is in the initial stage of use. It is based on the fact that it is relatively large and then gradually changes and becomes smaller as it gradually approaches a certain level.

The intermittent period can be determined as follows. When the change in the luminance k of the light emitting element 3 is expressed by, for example, a curve k = a · exp (−t 2 ) + b asymptotic to the asymptotic line k = b (a and b are constants and t is time), t Is represented by t = (ln (a / (k−b))) 1/2 . Accordingly, during the first intermittent period, Δt 10 = (ln (a / (k1-b))) 1/2 − (ln () when the change in luminance k Δk 10 = k1−k0 becomes a predetermined value. a / (k0−b))) 1/2 is obtained, and the intermittent period can be set to Δt 10 . Note that k0 is the luminance at the start of use of the light emitting device, and k1 is the luminance at the end of the first intermittent period. Similarly, after the second time, the intermittent periods Δt 21 , Δt 32 ... Δt nn-1 (n is an integer of 1 or more) can be determined.

  Further, in the light emitting device of the present invention, the deterioration with time of the light emitting element 3 can correspond to the accumulated light emitting time of the light emitting element 3, so that the correction control unit 41a has the accumulated light emitting time of the light emitting element 3 as shown in FIG. It is preferable to execute the correction process based on the result of the light emission time measuring unit 41aa that measures the above. In this case, correction data based on the correlation between the accumulated light emission time of the light emitting element 3 and the luminance decrease due to deterioration with time of the light emitting element 3 is obtained in advance, and is supplied to the light emitting element 3 with high accuracy based on the correction data. The luminance of the light emitting element 3 can be corrected intermittently by the power supply current. The accumulated light emission time of the light emitting element 3 can be counted as, for example, the supply time of the power supply current supplied to the light emitting element 3, or a light receiving element such as a photodiode that receives light emitted from the light emitting element 3 is provided. You may count as light reception time of a light receiving element. In addition, as the intermittent period, a value obtained by multiplying the accumulated light emission time of the light emitting element 3 by the current value passed through the light emitting element 3 may be used. In this case, the degree of deterioration of the light emitting element 3 can be predicted more accurately.

  Further, in the light emitting device of the present invention, when the cumulative light emission time of the light emitting element 3 is divided into the initial period, the middle period, and the final period, the intermediate period is 1.1 to 3 times the initial intermittent period, and the final intermittent period Is preferably 2 to 5 times the initial intermittent period. In this case, it corresponds to the initial stage of the cumulative light emission time in which the light emitting element 3 has a long time deterioration, the middle stage of the cumulative light emission time in which the light emitting element 3 has the next long time deterioration, and the latter period of the cumulative light emission time in which the light emitting element 3 has a small time deterioration. Thus, the length of the intermittent period can be adjusted. As a result, it is possible to suppress a reduction in luminance due to deterioration with time of the light emitting element 3 from being recognized or detected over a long period of time. The setting of the length of the initial intermittent period, the length of the intermediate intermittent period, and the length of the final intermittent period may be performed by an average value of the intermittent periods. That is, the average value of the intermediate intermittent period may be 1.1 to 3 times the average value of the initial intermittent period, and the average value of the final intermittent period is 2 times the average value of the initial intermittent period. You may make it become 2-5 times.

  In the light emitting device of the present invention, the initial period is a period from 0 to 100 hours, the middle period is a period from 100 hours to 1000 hours, and the final period is a period from 1000 hours. It is preferable. In this case, each of the initial period of the accumulated light emission time in which the light emitting element 3 has a large deterioration with time, the middle period of the accumulated light emission time in which the light emitting element 3 has the next largest deterioration in time, and the latter period of the accumulated light emission time in which the light emitting element 3 has a small deterioration with time, It can set more correctly with respect to the light emitting element 3 which has deterioration with time, such as an organic EL element. As a result, it is possible to suppress a reduction in luminance due to deterioration with time of the light emitting element 3 from being recognized or detected over a long period of time. Note that the various types of driving and control in the driving element 4 described above can be executed by, for example, program software stored in a ROM, RAM, or the like in the driving element 4.

  FIG. 6 and FIG. 7 show the detailed configuration of the light emitting element and its peripheral portion when the light emitting element of the light emitting device of the present invention is an organic EL element having an organic light emitting layer. FIG. 6 is a plan view of the three light emitting elements of the light emitting device and the periphery thereof. FIG. 7 is a cross-sectional view of the light-emitting element and its peripheral portion, and is a cross-sectional view taken along line C1-C2 of FIG. As shown in these drawings, the light emitting device includes a TFT (first TFT) 62 formed on a translucent substrate 51 such as a glass substrate, and a first made of acrylic resin or the like on the TFT 62. The organic light emitting unit 71 includes an organic light emitting unit 71 stacked with an insulating layer 57 interposed therebetween, and a light emitting unit including a contact hole 72 that conductively connects the organic light emitting unit 71 and the drain electrode 56b of the TFT 62. The body portion 71 includes a first electrode layer 58, an organic light emitting layer 60, and a second electrode layer 61 that are electrically connected to the contact hole 72 from the TFT 62 side. A second insulating layer 59 made of acrylic resin or the like is formed on the first electrode layer 58 so as to surround the organic light emitting layer 60. 6 and 7, the second TFT is not shown, but is connected in parallel to a connection line between the light emitting element 70 and the TFT 62.

  6 and 7, reference numeral 70 denotes a light emitting element as a light emitting region that emits light when an electric field is directly applied to the organic light emitting layer 60 by the first electrode layer 58 and the second electrode layer 61. The first electrode layer 58 is an anode and is made of a transparent electrode such as indium tin oxide (ITO), and the second electrode layer 61 is a cathode and is made of Al, Al-Li alloy, Mg. -Work function (about 4.0V or less) such as an Ag alloy (including about 5 to 10% by weight of Ag), Mg-Cu alloy (including about 5 to 10% by weight of Cu), etc. is low in light shielding and light reflecting properties. In the case of being made of a metal or alloy, light emitted from the organic light emitting layer 60 is emitted from the substrate 51 side. That is, a bottom emission type light emitting device in which the light emitting direction (the direction indicated by the white arrow in FIG. 7) is downward (bottom direction) is obtained. On the other hand, when the first electrode layer 58 is a cathode and is made of the above-described light-shielding and light-reflecting metals or alloys thereof, and the second electrode layer 61 is an anode and is made of a transparent electrode, the light emitting direction Is a top emission type light emitting device in which is upward (top direction).

The TFT 62 includes, from the substrate 51 side, a semiconductor film including a gate electrode 52, a gate insulating film 53, a polysilicon film 54 as a channel portion, and a high-concentration impurity region 54a in which polysilicon contains impurities at a higher concentration than the channel portion. The insulating film 55 made of silicon nitride (SiN x ), silicon oxide (SiO 2 ), etc., the source electrode 56a, and the drain electrode 56b are sequentially stacked. In FIG. 6, 56aL is a source signal line (power supply line) for transmitting a source signal (power supply current) to the source electrode 56a, and 52L is a gate signal line for transmitting a gate signal to the gate electrode 52. By controlling the voltage of the gate signal input to each gate signal line 52L, the light emission intensity of each organic light emitting layer 60 can be controlled. Thus, the source signal line 56aL functions as a power supply line.

  The transparent electrode used for the first electrode layer 58 or the second electrode layer 61 includes indium tin oxide (ITO), indium zinc oxide (IZO), indium tin oxide added with silicon oxide (ITSO), oxidation It is made of a conductive material such as zinc (ZnO), phosphorus, or silicon (Si) containing boron and having a light transmitting property. The first insulating layer 57 and the second insulating layer 59 are made of acrylic resin, polyimide, polyamide, polyimide amide, benzocyclobutene, tetrafluoroethylene / perfluoroalkoxyethylene copolymer (PFA resin), polysiloxane, polysilazane. Etc. can be used. Polysiloxane has a skeletal structure formed by the bond of silicon (Si) and oxygen (O). The polysiloxane has an organic group containing at least hydrogen as an oxygen substituent, such as an alkyl group or an aromatic hydrocarbon group, and an organic group containing at least hydrogen and a fluoro group as an oxygen substituent. It may be. Polysilazane is a material formed using a polymer material having a bond of silicon (Si) and nitrogen (N) as a starting material. When an insulating layer made of the above organic material is used, the flatness of the surface can be improved and a flattening layer can be easily obtained.

The TFT 62 includes, from the substrate 51 side, a semiconductor film including a gate electrode 52, a gate insulating film 53, a polysilicon film 54 as a channel portion, and a high-concentration impurity region 54a in which polysilicon contains impurities at a higher concentration than the channel portion. The insulating film 55 made of silicon nitride (SiN x ), silicon oxide (SiO 2 ), etc., the source electrode 56a, and the drain electrode 56b are sequentially stacked. The semiconductor composing the TFT 62 may be made of an oxide semiconductor such as low-temperature polysilicon (LTPS), amorphous silicon, or indium gallium zinc oxide (IGZO). The TFT 62 shown in FIG. 7 is a bottom gate type TFT in which the gate electrode 52 is below the channel part, but may be a top gate type TFT in which the gate electrode 52 is above the channel part. It may be a double gate type TFT located both below and above the channel portion. A top gate type TFT and a double gate type TFT are generally preferable because a gate electrode 52 made of a light-shielding metal or the like is above the channel part, so that light can be further prevented from entering the channel part. .

  The organic light emitting layer 60 has a self-emitting organic electroluminescent property that does not require a backlight. For example, the organic light emitting layer 60 is a laminated structure having a thickness of about several hundred nm, and is formed by laminating an electron transport layer, a light emitting layer, a hole transport layer, a hole injection layer, and an anode from the cathode side. The thickness of each layer between the electrode layers is about several nm to several hundred nm. The thickness including the electrode layer is about 1 μm. As the light emitting material of the light emitting layer of the organic light emitting layer 60, a low molecular fluorescent dye material, a fluorescent polymer material, a metal complex material, or the like can be adopted.

In order to facilitate the injection of holes into the light emitting layer, the ionization energy of the light emitting layer is preferably 6.0 eV or less, and in order to facilitate the injection of electrons into the light emitting layer, the electron affinity of the light emitting layer is 2.5 eV. It is good that it is above. As the light emitting material of the light emitting layer, tris (8-quinolinolato) aluminum complex (Alq), bis (benzoquinolinolato) beryllium complex (BeBq), tri (dibenzoylmethyl) phenanthroline europium complex (Eu (DBM) 3 (Phen) )), Ditoluyl vinyl biphenyl (DTVBi) and the like. Examples of the polymer material include π-conjugated polymers such as fluorescent poly (p-phenylene vinylene) and polyalkylthiophene, and these polymer materials can control carrier transport properties by introducing substituents. As the material for the electron transport layer, an anthraquinodimethane derivative, a diphenylquinone derivative, an oxadiazole derivative, a perylenetetracarboxylic acid derivative, and the like can be employed. As a material for the hole transport layer, 1,1-bis (4-di-p-aminophenyl) cyclohexane, a triphenylamine derivative, a carbazole derivative, or the like can be employed. Copper phthalocyanine, metal-free phthalocyanine, aromatic diamine, etc. can be adopted as the material for the hole injection layer that injects holes into the hole transport layer.

  The first electrode layer 58, the organic light emitting layer 60, and the second electrode layer 61 can be formed by a thin film forming method such as an evaporation method or a sputtering method. For example, the first electrode layer 58 can be formed by a sputtering method or the like, the organic light emitting layer 60 can be formed by a vacuum deposition method, an ink jet method, a spin coating method, a printing method, or the like, and the second electrode layer 61 can be formed by an electron beam (Electron). Beam: EB) It can be formed by vapor deposition or sputtering.

  8A and 8B are diagrams showing another example of the embodiment of the light-emitting device of the present invention. FIG. 8A is a plan view of the entire light-emitting device, and FIG. 8B is A1 in FIG. It is a circuit diagram of a part and a drive element. As shown in FIG. 8, a set of drive circuits may be formed for four light emitting elements 3a, 3b, 3c, and 3d in four rows. In this case, a set of drive circuits includes a shift register 10, a logical sum negation (NOR) circuit 11, an inverter 12, CMOS transfer gate elements 13a, 13b, 13c, 13d, first TFTs 14a, 14b, 14c, 14d, 2 TFTs 15a, 15b, 15c, 15d, light receiving elements 7a, 7b, 7c, 7d, and third TFTs 6a, 6b, 6c, 7d. The light emitting elements 3 may be arranged to form 2m rows (m is an integer of 1 or more).

  In the example of the above embodiment, the light receiving elements 7a and 7b are used to extract the threshold currents of the light emitting elements 3a and 3b. However, the light receiving elements 7a and 7b can be used to control the luminance of the light emitting elements 3a and 3b. . For example, since the impedance of the light emitting elements 3a and 3b tends to change when the temperature of the light emitting elements 3a and 3b changes, the temperature of the light emitting elements 3a and 3b changes from a predetermined reference value (for example, 25 ° C. near room temperature) to some extent ( For example, in the case of a change, the power supply current of the light emitting elements 3a and 3b can be corrected based on the luminance information obtained from the light receiving elements 7a and 7b. Alternatively, the correction of the power supply current based on the impedance of the light emitting elements 3a and 3b and the correction of the power supply current based on the luminance information obtained from the light receiving elements 7a and 7b can be combined.

  Note that the light-emitting device of the present invention is not limited to the above-described embodiment, and appropriate design changes and improvements may be made.

  The light emitting device of the present invention is configured as an organic LED printer (OLEDP) head by forming a plurality of light emitting elements in a row in the longitudinal direction of a long plate-like substrate 1 as shown in FIG. Can do. In addition, the substrate 1 has a rectangular shape or the like, and a plurality of light emitting elements 3 are formed so as to be arranged two-dimensionally (planarly), so that an organic EL display device can be configured. Furthermore, the light emitting device and the organic EL display device using the light emitting device of the present invention can be applied to various electronic devices. The electronic devices include lighting devices, automobile route guidance systems (car navigation systems), ship route guidance systems, aircraft route guidance systems, indicators for vehicles such as automobiles, instrument panels, smartphone terminals, mobile phones, tablets. Terminals, personal digital assistants (PDAs), video cameras, digital still cameras, electronic notebooks, electronic books, electronic dictionaries, personal computers, copiers, game machine terminal devices, televisions, product display tags, price display tags, industrial use Programmable display device, car audio, digital audio player, facsimile machine, printer, automatic teller machine (ATM), vending machine, medical display device, digital display wristwatch, smart watch and the like.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Drive circuit block 3, 3a, 3b Light emitting element 4 Drive element 5 FPC
6a, 6b Third TFT
7a, 7b Light receiving elements 14a, 14b First TFT
15a, 15b Second TFT
18 Resistance 41a Correction control unit 41b Correction processing unit A (Current path switching unit)
42 Drive unit 43 Correction processing unit B
43a Detected current measuring unit 43b Difference calculating unit 43c Correction data storage unit B
44 Correction processing unit C
44a Current measurement unit 44b Impedance calculation unit 44c Correction data storage unit C

Claims (6)

  1. A light emitting element; a light receiving element that receives light emitted from the light emitting element; and a correction unit that corrects the luminance of the light emitting element.
    The correction unit is configured to extract a threshold current in the power supply current of the light emitting element based on information obtained from the light receiving element, and the value of the power supply current flowing through the light emitting element. And a second correction for correcting the power supply current of the light emitting element by impedance.
  2.   2. The light emitting device according to claim 1, wherein the correction unit determines the threshold current as the minimum luminance of the light emitting element by the first correction, and corrects the power supply current equal to or higher than the threshold current by the second correction.
  3.   The light emitting device according to claim 1, wherein the second correction corrects the power supply current so as to correspond to a specific luminance.
  4. About the current path of the power supply current in the light emitting element, the light emitting element branched from a first current path including a thin film transistor and the light emitting element connected thereto, and a connecting line connecting the thin film transistor and the light emitting element And a second current path not including
    The correction unit includes an impedance calculation unit that calculates an impedance of the light emitting element from a first current value in the first current path and a second current value in the second current path. The light emitting device according to claim 3.
  5.   The second current path includes another thin film transistor in which one electrode is connected in parallel to the connection line, the other electrode is connected to the ground through a resistor, and the impedance is smaller than the impedance of the thin film transistor. The light emitting device according to claim 4.
  6.   The light emitting device according to claim 5, wherein the other thin film transistor has an impedance of 1/100 or less of the impedance of the thin film transistor.
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JP2007290329A (en) * 2006-04-27 2007-11-08 Matsushita Electric Ind Co Ltd Light-receiving element, light-emitting device, light head and image forming apparatus
US20070290958A1 (en) * 2006-06-16 2007-12-20 Eastman Kodak Company Method and apparatus for averaged luminance and uniformity correction in an amoled display
WO2015011159A1 (en) * 2013-07-24 2015-01-29 Koninklijke Philips N.V. Electronic control of oleds with distributed electrodes

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998040871A1 (en) * 1997-03-12 1998-09-17 Seiko Epson Corporation Pixel circuit, display device and electronic equipment having current-driven light-emitting device
JP2005258427A (en) * 2004-02-12 2005-09-22 Canon Inc Drive circuit and image forming apparatus using the same
JP2006056010A (en) * 2004-08-17 2006-03-02 Seiko Epson Corp Driving device and method for line head, line head, and image forming apparatus
JP2006133307A (en) * 2004-11-02 2006-05-25 Matsushita Toshiba Picture Display Co Ltd Spontaneous light emission type display apparatus
JP2007290329A (en) * 2006-04-27 2007-11-08 Matsushita Electric Ind Co Ltd Light-receiving element, light-emitting device, light head and image forming apparatus
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