JP2012078379A - Display device - Google Patents

Abstract

In an organic EL display device according to the prior art, it is impossible to detect characteristics of a driving transistor with high accuracy and high speed.
A display device includes a plurality of pixels each having a light emitting element and a driving transistor that supplies a current corresponding to a gradation value to the light emitting element, and detection for detecting characteristics of each driving transistor. Means for supplying a first voltage signal between the gate and the source of each driving transistor after the light emission of each light emitting element; and after the first voltage signal is supplied, the gate of each driving transistor Means for supplying a second voltage signal different from the first voltage signal between the sources, and the detection means is configured to supply each of the drive transistors during a period of supplying the second voltage signal. A characteristic is detected, and the first voltage signal is a voltage signal having a voltage capable of supplying more current between the source and drain of the driving transistor than the second voltage signal.
[Selection] Figure 3

Description

  The present invention relates to a display element, and more particularly to a display device having a self-luminous element.

  In recent years, a display device using a self-luminous body called an organic EL (Organic Electro-luminescent) element typified by an organic light emitting diode (hereinafter referred to as “organic EL display device”) has been put into practical use. It is in. Since this organic EL display device uses a self-luminous body as compared with a conventional liquid crystal display device, it is not only superior in terms of visibility and response speed, but also has an auxiliary illumination device such as a backlight. Since it is not necessary, further thinning is possible.

  Such an organic EL display device has a display panel in which a large number of pixels are arranged in a matrix. Each pixel includes an organic EL element and a drive transistor that drives the organic EL element. Since the driving transistor is generally composed of a thin film transistor (Thin Film-Transistor), the threshold voltage of each driving transistor varies due to manufacturing problems. Therefore, there is a problem in that the light emission characteristics of each pixel vary, and as a result, display on the display panel becomes non-uniform.

  Accordingly, the following organic EL display device in the prior art is known. In the organic EL display device, a current flowing through each pixel is detected, and a correction offset is calculated based on the detected current value. Then, by adding the correction offset to the image data, non-uniform display of the screen is prevented (see Patent Documents 1 and 2 below). Alternatively, a method of detecting a variation in threshold voltage by connecting a constant current source to the source of a driving transistor and measuring the voltage has been proposed (see Patent Document 3 below).

JP 2004-264793 A JP 2005-284172 A JP 2010-170079

  However, in the organic EL display device according to the above-described prior art, there is a problem that if the detection accuracy of the characteristics of the drive transistor is increased, the detection time becomes longer.

  Specifically, considering the influence of hysteresis in the drive transistor, a standby time of several milliseconds is required as a standby time until the characteristics of the drive transistor become stable. Here, when a sufficient standby time is not secured, there is a problem that the detection accuracy is greatly lowered because of being affected by the hysteresis. On the other hand, when the voltage range is taken into consideration, only a current of the order of μA per pixel can flow at the maximum, the detection speed is limited, and as a result, a sufficient standby time cannot be secured.

  Accordingly, an object of the present invention is to provide a display device that can detect the characteristics of the drive transistor included in each pixel with high accuracy and high speed.

  The display device of the present invention includes a plurality of pixels each having a light emitting element and a driving transistor that supplies a current corresponding to a gradation value to the light emitting element, and a detection unit that detects characteristics of each driving transistor, Means for supplying a first voltage signal between the gate and source of each driving transistor after light emission of each of the light emitting elements; and between the gate and source of each driving transistor after the first voltage signal is supplied. And a means for supplying a second voltage signal different from the first voltage signal, and the detecting means detects the characteristics of the drive transistors during the period of supplying the second voltage signal. The first voltage signal is a voltage signal having a voltage that can supply more current between the source and drain of the driving transistor than the second voltage signal.

  In the display device of the present invention, the period for supplying the second voltage signal may be longer than the period for supplying the first voltage signal.

  In the display device of the present invention, the display device may further include a correction unit that corrects a data signal supplied to each of the plurality of pixels based on a detection result of the detection unit.

  In the display device according to the aspect of the invention, the detection unit may include a current source that supplies a constant current to the source of each driving transistor, and the detection unit may detect a source potential of each driving transistor. Good.

  In the display device according to the aspect of the invention, the detection unit includes a voltage source that supplies a constant voltage to the source of each driving transistor, and the detection unit detects a potential at one end of each light emitting element. Also good.

  In the display device of the present invention, the light emitting element may be an organic light emitting diode.

  In the display device of the present invention, the driving transistor may be a TFT.

  In the display device of the present invention, the TFT may be a polycrystalline Si semiconductor device.

  In the display device of the present invention, the TFT may be a microcrystalline Si semiconductor device.

  In the display device of the present invention, the TFT may be an amorphous semiconductor device.

  In the display device of the present invention, the TFT may be an oxide semiconductor device.

  It is possible to provide a display device that can detect the characteristics of the drive transistor included in each pixel with high accuracy and high speed.

It is a figure which shows the display apparatus in embodiment of this invention. It is a figure for demonstrating the structure of the display apparatus shown in FIG. It is a figure for demonstrating the structure of the display apparatus shown in FIG. FIG. 2 is a diagram for explaining a configuration of a data line driving unit illustrated in FIG. 1. It is a figure for demonstrating the outline | summary of the detection operation | movement of the characteristic of a drive transistor. It is a figure for demonstrating the hysteresis characteristic of the drive transistor contained in a pixel. It is a figure for demonstrating the hysteresis characteristic of the drive transistor contained in a pixel. It is a figure for demonstrating the hysteresis characteristic of the drive transistor contained in a pixel. It is a figure for demonstrating the timing chart of the signal controlled in the case of the detection operation as the whole display apparatus. It is a figure for demonstrating the example about mounting of the display apparatus in this Embodiment. It is a figure for demonstrating the example about mounting of the display apparatus in this Embodiment. It is a figure for demonstrating each pixel and the detection part in the modification of this invention. It is a figure for demonstrating the outline | summary of the detection operation | movement of the characteristic of the drive transistor in a modification.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, about drawing, the same code | symbol is attached | subjected to the same or equivalent element, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a diagram showing a display device according to an embodiment of the present invention. As shown in FIG. 1, a display device 100 is a circuit including an upper frame 110 and a lower frame 120 that are fixed so as to sandwich a TFT (Thin Film Transistor) substrate 200 having a display panel, and circuit elements that generate information to be displayed. The substrate 140 and a flexible substrate 130 that transmits RGB information generated on the circuit substrate 140 to the TFT substrate 200 are configured.

  2 and 3 are diagrams for explaining the configuration of the display device shown in FIG. As shown in FIG. 2, the display device 100 includes a display scanning unit 201, a display area 203, a detection scanning unit 208, a data line driving unit 211, and the like. In FIG. 2, for simplification of description, the switches represented by DT (v), Dt (v + 1), Data (h), and Data (h + 1) are respectively connected to the detection scanning unit 208 and the data line. Although shown outside the driving unit 211, it is actually formed inside the detection scanning unit 208 and the data line driving unit 211.

  The display scanning unit 201, the detection scanning unit 208, and the data line driving unit 211 may be formed of separate LSIs or the like, or may be formed of a single LSI or the like. The display scanning unit 201, the detection scanning unit 208, the data line driving unit 211, and the like are formed on the TFT substrate 200, for example.

  The display scanning unit 201 outputs a display scanning signal to the display region 203 via the scanning line 202, whereby the pixels 204, 205, 206, and 207 that write data signals during the display operation and the pixels 204 and 205 that emit light. , 206, 207 are selected.

  As shown in FIG. 2, the scanning lines 202 are arranged in the row direction of the pixels 204, 205, 206, and 207 arranged in a matrix, and the detection lines 210 and the data lines 209 are arranged in a matrix. The pixels 204, 205, 206, and 207 are arranged in the column direction.

  The detection scanning unit 208 selects the pixels 204, 205, 206, and 207 to which the trap voltage and the detrapping voltage are added during the detection operation by outputting an inspection scanning signal to the display region 203 through the scanning line 202. .

  Here, the trap voltage is a voltage applied to the gate of the drive transistor 301 in order to sufficiently suppress fluctuations in the hysteresis of the drive transistor 301 in the detrap period, which is a period during which the characteristics of the drive transistor 301 are actually detected. Equivalent to. The detrapping voltage corresponds to a voltage applied to the gate of the driving transistor 301 in the detrapping period. The trap voltage, detrap voltage, etc. will be described in detail later.

  The display operation refers to an operation related to display of each of the pixels 204, 205, 206, and 207. Specifically, a data signal writing operation to each of the pixels 204, 205, 206, and 207, and each pixel 204 , 205, 206, and 207. The detection operation refers to an operation related to the detection of the characteristics of the drive transistors 301 included in the pixels 204, 205, 206, and 207, and will be specifically described later. The detection operation may be performed, for example, between the light emission period of the display operation and the writing operation, or when the display device 100 is, for example, a mobile phone, the mobile phone is folded. It may be performed at a time when it is not necessary to display the screen.

  The display area 203 includes a plurality of pixels 204, 205, 206, and 207 arranged in a matrix. Each pixel 204, 205, 206, and 207 includes a drive transistor 301, an organic EL element 302, a capacitor 303, and a select switch 304. In FIG. 2, only four pixels 204, 205, 206, and 207 are shown for simplification of the drawing, but it goes without saying that other numbers are used as necessary.

  As shown in FIG. 3A, the drive transistor 301 has a source connected to one end of a capacitor 303, a drain connected to the anode of the organic EL element 302, and a gate connected to the drain of the select switch 304.

  The organic EL element 302 has the anode connected as described above and the cathode grounded.

  The select switch 304 has a gate connected to the scanning line 202, a source connected to the data line 209, and a drain connected to the other end of the capacitor 303.

  The capacitor 303 has one end connected to the source of the drive transistor 301 and the other end connected to the gate of the drive transistor 301 and the drain of the select switch 304.

  The current source 213 is connected to the source of the drive transistor 301 via the switch 214, and outputs a constant current I to each detection line 210 during the detection period. The voltage source 215 is connected to the source of the driving transistor 301 via the switch 216, and supplies a power supply Voled that drives the driving transistor 301 during display operation. Further, the switch 214 is turned on during the detection operation for detecting the characteristics of the drive transistor 301, and the switch 216 is turned on during the display operation of the display device 100.

  In the display operation, the select switch 304 is turned on in response to a signal from the display scanning unit 201, and a signal corresponding to a data signal from the data line driving unit 211 described later is written in the capacitor 303. Then, the drive transistor 301 causes the organic EL element 302 to emit light according to the written signal, so that the display region 203 displays an image. Since the display operation of the display device 100 is well known, detailed description thereof is omitted.

  As shown in FIG. 4, the data line driving unit 211 includes a data signal driving unit 401, a detection signal driving unit 402, and a correction unit 403. During the display operation of the display device 100, the data signal driving unit 401 transmits a data signal corresponding to the gradation values of the pixels 204, 205, 206, and 207 to be displayed via the data line 209 to each of the pixels 204, 205, 206, It outputs to 207.

  The detection signal driver 402 outputs a trap voltage and a detrap voltage to the gate of the drive transistor 301 of each pixel 204, 205, 206, 207 via the data line 209 during the detection operation of the display device 100.

  The correction unit 403 uses the source voltage of each driving transistor 301 from the detection unit 212 and the detrapping voltage applied to the gate of each corresponding driving transistor 301 from the detection signal driving unit 402 in the detection period. A threshold voltage Vth is obtained.

  Specifically, when the select switch 304 is turned on during a detrap period to be described later, a gate voltage (Vg) is applied from the data line 209 to the gate terminal of the drive transistor 301. In this state, the detection unit 212 detects the voltage at the source terminal of the drive transistor 301.

  Here, driving is performed under the condition that the source-drain voltage Vds of the driving transistor 301 is sufficiently larger than the overdrive voltage that is a value obtained by subtracting the absolute value of the threshold voltage Vth of the driving transistor 301 from the voltage Vg applied to the data line 209. The transistor 301 maintains a saturation region. Therefore, the gate-source voltage Vgs of the drive transistor 301 when the constant current I is supplied from the current source 213 to the drive transistor 301 is detected from the detection voltage (source voltage) and the voltage (gate voltage Vg) applied to the data line 209. can do. This gate-source voltage Vgs corresponds to the variation of the threshold voltage Vth of the drive transistor 301. Therefore, the threshold voltage Vth of the driving transistor 301 can be obtained from the gate-source voltage Vgs.

  For example, as illustrated in FIG. 3B, the transistor characteristics of the drive transistor 301 included in each of the pixels 204, 205, 206, and 207 are any of TFT characteristics 1 to 3. The threshold voltage Vth of each driving transistor 301 can be obtained by detecting the gate-source voltages Vgs1 to Vgs3 corresponding to the TFT characteristics 1 to 3, respectively. In the example of FIG. 3, the gate voltage Vg corresponds to a detrapping voltage, which will be described in detail later.

  As described above, the correction unit 403 is based on the source voltage of each driving transistor 301 from the detection unit 212 and the gate voltage Vg applied from the detection signal driving unit 402 to the corresponding gate of each driving transistor 301. The threshold voltage of the driving transistor 301 is obtained. Then, based on the variation in the threshold voltage Vth of each driving transistor 301, a correction signal for correcting the data signal so as to reduce the variation in luminance of each pixel 204, 205, 206, 207 is calculated, and the data signal driving unit 401 Output to.

  Needless to say, the data signal driver 401 outputs a data signal to each of the pixels 204, 205, 206, and 207 based on the correction signal. For specific calculation of the correction signal and the like, for example, the methods described in Patent Documents 1 and 2 may be used.

  The detection unit 212 is connected to the source of each drive transistor 301 via the detection line 210, and detects the source voltage of the drive transistor 301 when a constant current from the current source 213 is supplied to the drive transistor 301 during the detection period. To do.

  Specifically, the detection unit 212 includes, for example, a buffer circuit 305, a low-pass filter 306, and an A / D converter 307 as illustrated in FIG.

  The buffer circuit 305 is disposed between the current source 213 and the low pass filter 306. Specifically, for example, the buffer circuit 305 is formed from an OP amplifier. The non-inverting input terminal of the OP amplifier is connected to the source of the driving transistor 301, and the inverting input terminal of the OP amplifier is connected to the output terminal of the OP amplifier.

  The low-pass filter 306 has an input side connected to the output terminal of the buffer circuit 305 and an output side connected to the A / D converter 307.

  The A / D converter 307 converts the source voltage of the driving transistor 301 into digital data and outputs the data to the correction unit 403.

  Next, an outline of an operation for detecting the threshold voltage Vth of each of the pixels 204, 205, 206, and 207 will be described with reference to FIG.

  First, in the standby period, the drive transistor 301 is off. During the detection period of one pixel, all other pixels are turned off as described later.

  In the next trap period, a trap voltage is input to the gate of the drive transistor 301. In FIG. 5, the trap voltage corresponds to ΔVp, and the trap period corresponds to ΔTp.

  In the next detrapping period, a detrapping voltage is input to the gate of the driving transistor 301. At this time, the detection unit 212 detects the source voltage of the driving transistor 301. In FIG. 5, the detrapping voltage corresponds to ΔVd.

  As described above, a trap voltage is applied during the trap period, and fluctuation due to hysteresis of each drive transistor 301 during the de-trap period is suppressed. This point will be described in detail below.

  6, 7, and 8 are diagrams for explaining the hysteresis characteristics of the drive transistors 301 in the pixels 204, 205, 206, and 207.

  The relationship between the gate voltage and the drain current of the driving transistor 301 may have hysteresis characteristics as shown in FIG. In FIG. 6, the vertical axis represents the drain current of the driving transistor 301, and the horizontal axis represents the gate-source voltage of the driving transistor 301.

  This hysteresis characteristic is caused by the number of carriers (mainly positive charges) trapped in the gate oxide film of the drive transistor 301 as shown in FIG.

  Specifically, the gate oxide film of the driving transistor 301 has a state where carriers are trapped in the gate as shown in FIG. 7A, while carriers are trapped in the gate as shown in FIG. There is a state to detrap. The threshold voltage of the driving transistor 301 is enhanced when carriers are trapped at the gate, and is depleted when the trapped carriers are detrapped. In addition, the time for detrapping is sufficiently longer than the time for trapping carriers at the gate.

  As shown in FIG. 8A, when a predetermined potential difference is applied between the gate and source of the driving transistor 301 for a predetermined period, the larger the potential difference ΔVg and the longer the period ton, ), The characteristics of the drive transistor 301 after application of the potential difference hardly change over time.

  Specifically, for example, as shown in FIG. 8 (a), when a large potential difference is given for a long time compared to the case shown in FIG. 8 (c), as shown in FIG. The relationship between the gate voltage and the drain current of the driving transistor 301 after the potential difference is applied is less changed over time than in the case shown in FIG. In other words, in the case shown in FIG. 8 (a), the characteristic C1 close to the state shown in B of FIG. 8 (b) is maintained even when time elapses, whereas that shown in FIG. 8 (d). In this case, the characteristic C2 shown in FIG. 8D approaches the characteristic indicated by A in FIG. 8D faster than the case shown in FIG. 8B.

  In the case shown in FIG. 6, the characteristics of the drain current and elapsed time of the driving transistor 301 from A shown in FIG. 6 according to the magnitude and time of the potential difference applied to the gate of the driving transistor 301. It was explained that it varied to the state of B. Also, the characteristics A and B shown in FIGS. 6 and 8 correspond to each other, and the characteristic C corresponds to C1 or C2.

  Therefore, by appropriately adjusting ΔVg and the period during which ΔVg is applied as described above, the time constant for recovering from the characteristic B of the driving transistor 301 shown in FIGS. 6 and 8 to the characteristic A is increased and actually detected. Detection can be performed after the characteristics of the drive transistors 301 are made to be close to the characteristics B in the detrap period during which the operation is performed.

  That is, the trap voltage and the trap period correspond to a period ton that gives ΔVg and ΔVg, respectively, that can sufficiently suppress the characteristic variation of the drive transistor 301 in the detrap period after the application of ΔVg as described above. The detrapping period corresponds to a period during which a detection operation is actually performed after the trap period in which the trap voltage is applied. In other words, the trap voltage is a voltage applied between the gate and the source of the drive transistor 301 in order to sufficiently suppress the characteristic variation of the drive transistor 301 in the detrap period, and is applied to the gate of the drive transistor 301. Corresponds to voltage. In other words, if described with reference to the example of FIG. 8, the voltage is applied to the gate of the driving transistor 301 in the trap period so as to have a characteristic (for example, C1 in FIG. 8B) close to the characteristic B in FIG. Corresponds to the voltage to be applied.

  Specifically, ΔVp is preferably a value of 0.5 V or more and 10 V or less. In particular, in order to obtain the maximum effect while minimizing the burden on the voltage generation circuit mounted on the display device 100, 1V More preferably, the voltage is 5 V or less, and the optimum value is around 3 V. The trap period ΔTp is preferably 0.1 μs or more. In particular, in order to obtain the maximum effect without hindrance to high-speed driving associated with the increase in the number of pixels, the trap period ΔTp is more preferably 1 μs to 1 ms. Desirably, the optimum value is around 10 microseconds. Thus, the detection operation can be performed more stably by setting the detrap period longer than the trap period ton.

  Next, a timing chart of signals controlled in the detection operation of the display device 100 as a whole in this embodiment will be described with reference to FIG. 2 and 3, in this embodiment, since the select switch 304 is an nMOS, it is turned on when the gate voltage is high, and the drive transistor 301 is a pMOS. Needless to say, it is turned on when the gate voltage is low.

  At time T0, DT (v) and Dt (v + 1) are turned on, and Data (h) and Data (h + 1) are set to a high voltage. As a result, the select switch 304 included in each of the pixels 204 to 207 is turned on, and the gate voltage of the drive transistor 301 is set to a high voltage. As a result, the drive transistors 301 of all the pixels 204 to 207 are turned off.

  At time T1, DT (v) is kept on and Dt (v + 1) is turned off. Data (h) is the trap voltage. Thereby, a trap voltage is applied to the gate terminal of the driving transistor 301 of the pixel 204. In FIG. 9, a period from the time T1 to the next time T2 corresponds to a trap period. ΔVp corresponds to the trap voltage.

  At time T2, Data (h) is set as the detrapping voltage. Therefore, a detrapping voltage is applied to the gate terminal of the driving transistor 301 of the pixel 204. At this time, as described above, the source voltage of the driving transistor 301 of the pixel 204 is detected. In FIG. 9, the period from the time T2 to the next time T3 is a detrapping period. ΔVd corresponds to the detrapping voltage.

  For the other pixels 205 to 207, a trapping period and a detrapping period are provided in the same manner as described above. Specifically, at time T3, DT (v) is kept on and Dt (v + 1) is turned on. Further, Data (h) is set to a high voltage, and Data (h + 1) is maintained at a high voltage state. As a result, similarly to the time T1, the driving transistors 301 of all the pixels 204 to 207 are turned off.

  At time T4, DT (v) is turned off, and switches other than DT (V) such as Dt (v + 1) are kept on. Data (h) is a trap voltage. Data lines other than Data (h) remain at a high voltage. Thereby, a trap voltage is applied to the gate terminal of the driving transistor 301 of the pixel 205. Note that the period from the time T4 to the next time T5 corresponds to the trap period.

  At time T5, Data (h) is set as a detrapping voltage. At this time, the voltage of the source of the driving transistor 301 of the pixel B is detected. A period from the time T5 to the next time T6 is a detrap period.

  At time T6, DT (v) is turned on and Dt (v + 1) is kept on. Further, Data (h) is set to a high voltage, and Data (h + 1) is maintained at a high voltage state. Thereby, like the time T1, the driving transistors 301 of all the pixels are turned off.

  At time T7, switches other than DT (V + 1) such as DT (v) are kept on, and Dt (v + 1) is turned off. Data (h + 1) is the trap voltage. Data lines other than Data (h + 1) remain at a high voltage. Thereby, a trap voltage is applied to the gate terminal of the driving transistor 301 of the pixel 206. Note that a period from the time T7 to the next time T8 corresponds to a trap period.

  At time T8, Data (h + 1) is set as the detrapping voltage. At this time, the voltage of the source of the driving transistor 301 of the pixel 206 is detected. A period from the time T8 to the next time T9 is a detrap period.

  At time T9, DT (v) is kept on and Dt (v + 1) is turned on. Further, Data (h) is kept at a high voltage, and Data (h + 1) is made a high voltage. Thereby, like the time T1, the driving transistors 301 of all the pixels are turned off.

  At time T10, DT (v) is turned off and Dt (v + 1) is kept on. Data (h + 1) is the trap voltage. Thereby, a trap voltage is applied to the gate terminal of the drive transistor 301 of the pixel 207. Note that a period from the time T10 to the next time T11 corresponds to a trap period.

  At time T11, Data (h + 1) is set as the detrapping voltage. At this time, the voltage of the source of the driving transistor 301 of the pixel 207 is detected. A period from the time T11 to the next time T12 is a detrap period.

  At time T12, DT (v) is turned on and Dt (v + 1) is kept on. Further, Data (h) is kept at a high voltage state, and Data (h + 1) is set to a high voltage. As a result, the driving transistors 301 of all the pixels 204 to 207 are turned off.

  As described above, the source voltage of the drive transistor 301 included in each of the pixels 204, 205, 206, and 207 is sequentially detected in the order of the pixels 204, 205, 206, and 207 illustrated in FIG. 2 and 9, for the sake of simplification of the drawings, the case where the display area 203 has only four pixels has been described. Similarly, when the display region 203 has other numbers of pixels, the pixels are sequentially included in each pixel. Needless to say, the source voltage of the driving transistor is detected.

  Note that the display device 100 according to the present embodiment is mounted on, for example, a mobile terminal such as a mobile phone 150 or a PDA 160, a television 170, a video camera 180, or the like as shown in FIG. In addition, the display device 100 according to the present embodiment can be employed as a display device for displaying various information such as a personal computer display and a notification display. Further, it can be used as a display unit of various electronic devices such as a digital still camera, a car navigation system, a car audio, a game device, and a portable information terminal.

  In the above description, the organic EL element 302 is used as the light emitting element. However, the present invention is not limited to this, and the display device 100 according to the present embodiment includes, for example, an inorganic EL element, an FED (Field-Emission Device), and the like. The display device 100 using various light emitting elements may be used. The drive transistor 301 is formed of, for example, a polycrystalline Si semiconductor device, a microcrystalline Si semiconductor device, an amorphous semiconductor device, or an oxide semiconductor device.

  With the configuration described above, according to display device 100 according to the present embodiment, it is possible to detect the characteristics of each driving transistor while suppressing the influence of hysteresis of the driving transistor included in each pixel. Therefore, it is possible to detect the characteristics of each driving transistor with higher accuracy and higher speed than in the prior art. In addition, by correcting the data signal according to the detection result, it is possible to improve the image quality as compared with the prior art.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, a configuration that is substantially the same as the configuration described in the above embodiment, a configuration that exhibits the same effects, or a configuration that can achieve the same object may be used.

[Modification]
12 and 13 are diagrams for explaining a modification of the present invention. In this modification, the arrangement of the detection unit 212 is mainly different from that in the above embodiment. Other points are the same as those in the above embodiment, and the description of the same points is omitted.

  As shown in FIGS. 12 and 13, one end of a resistor 217 is connected to the cathode of the organic EL element 302, and the other end of the resistor 217 is grounded.

  The detection unit 212 is connected to a connection portion of the resistor 217 of the organic EL element 302. That is, in this modification, the detection unit 212 detects the product of the resistance value R of the resistor 217 and the current value Id flowing through the resistor 217 (for example, Id1 to Id3 in FIG. 3B). Then, the correction unit 403 obtains the threshold voltage of each driving transistor 301 based on the product. That is, in the present modification, the current source 213 and its switch 214 are unnecessary. Since other configurations and operations are the same as those in the above embodiment, the description thereof is omitted. In addition, here, an example in which the detection unit is provided on the cathode side of the organic EL element 302 has been described. However, depending on the electrode configuration of the organic EL element, the detection unit may be on the anode side.

  With the configuration described above, as in the above embodiment, the display device 100 according to the present modification detects the characteristics of each drive transistor while suppressing the influence of hysteresis of the drive transistor included in each pixel. can do. Therefore, it is possible to detect the characteristics of each driving transistor with higher accuracy and higher speed than in the prior art. In addition, by correcting the data signal according to the detection result, it is possible to improve the image quality as compared with the prior art.

  In addition, this invention is not limited to the said embodiment and modification, A various deformation | transformation is possible. For example, the configuration may be replaced with a configuration that is substantially the same as the configuration described in the above modification, a configuration that exhibits the same effects, or a configuration that can achieve the same purpose.

  100 display device, 110 upper frame, 120 lower frame, 130 flexible substrate, 140 circuit substrate, 200 TFT substrate, 201 display scanning unit, 202 scanning line, 203 display region, 204, 205, 206, 207 pixels, 208 for detection Scanning unit, 209 data line, 210 detection line, 211 data line drive unit, 212 detection unit, 213 current source, 214 switch, 215 voltage source, 301 drive transistor, 302 organic EL element, 303 capacitance, 304 select switch, 401 data Signal drive unit, 402 detection signal drive unit, 403 correction unit.

Claims (11)

A plurality of pixels each having a light emitting element and a driving transistor for supplying a current corresponding to a gradation value to the light emitting element; a detecting means for detecting a characteristic of each driving transistor; and after light emission of each light emitting element , Means for supplying a first voltage signal between the gate and source of each driving transistor, and the first voltage between the gate and source of each driving transistor after the first voltage signal is supplied. Means for supplying a second voltage signal different from the signal, and the detecting means detects the characteristics of the respective drive transistors during the period of supplying the second voltage signal,
The display device, wherein the first voltage signal is a voltage signal having a voltage capable of supplying more current between the source and the drain of the driving transistor than the second voltage signal.   The display device according to claim 1, wherein a period during which the second voltage signal is supplied is longer than a period during which the first voltage signal is supplied.   The display device according to claim 1, further comprising a correction unit that corrects a data signal supplied to each of the plurality of pixels based on a detection result of the detection unit.   The detection means includes a current source that supplies a constant current to the source of each of the drive transistors, and the detection means detects a source potential of each of the drive transistors. A display device according to any one of the above.   The detection means includes a voltage source that supplies a constant voltage to the source of each driving transistor, and the detection means detects a potential at one end of each light emitting element. The display apparatus in any one.   The display device according to claim 1, wherein the light emitting element is an organic light emitting diode.   6. The display device according to claim 1, wherein the driving transistor is a TFT.   The display device according to claim 7, wherein the TFT is a polycrystalline Si semiconductor device.   The display device according to claim 7, wherein the TFT is a microcrystalline Si semiconductor device.   The display device according to claim 7, wherein the TFT is an amorphous semiconductor device.   The display device according to claim 7, wherein the TFT is an oxide semiconductor device.

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