JP2008292619A - Display device, drive method for display device, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve display of an image at light emission luminance corresponding to the voltage of a video signal, by preventing a change in the luminance of an electro-optical element due to the temperature change of the electro-optical element. <P>SOLUTION: The voltage change ΔV of both-end voltages Voled of an organic EL element 21 due to the temperature change of the organic EL element 21 of a pixel 20 is detected. For example, the high potential Vccp of a power supply line 32 is offset so that the value of a voltage Vds between the drain and the source of a drive transistor 22 does not change. Thereby a change in the light emission luminance of the organic EL element 21 due to the temperature change of the organic EL element 21 is corrected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display device, a display device driving method, and an electronic apparatus, and more particularly to a flat (flat panel) display device in which pixels including electro-optical elements are arranged in a matrix (matrix shape), and the display device And an electronic apparatus having the display device.

  In recent years, in the field of display devices that perform image display, flat display devices in which pixels (pixel circuits) including light emitting elements are arranged in a matrix are rapidly spreading. As a flat display device, as a light emitting element of a pixel, a so-called current-driven electro-optical element whose light emission luminance changes according to a current value flowing through the device, for example, a phenomenon that emits light when an electric field is applied to an organic thin film is used. An organic EL display device using an organic EL (Electro Luminescence) element has been developed and commercialized.

  The organic EL display device has the following features. That is, since the organic EL element can be driven with an applied voltage of 10 V or less, it has low power consumption and is a self-luminous element. Therefore, for each pixel including the liquid crystal cell, the liquid crystal cell emits light from the light source (backlight). Compared to a liquid crystal display device that displays an image by controlling the light intensity, the image is highly visible, and the liquid crystal display device does not require an illumination member such as a backlight. Is easy. Furthermore, since the response speed of the organic EL element is as high as about several μsec, an afterimage at the time of displaying a moving image does not occur.

  In the organic EL display device, as in the liquid crystal display device, a simple (passive) matrix method and an active matrix method can be adopted as the driving method. However, although the simple matrix display device has a simple structure, the light-emission period of the electro-optic element decreases with an increase in the number of scanning lines (that is, the number of pixels), thereby realizing a large-sized and high-definition display device. There are problems such as difficult.

  Therefore, in recent years, the current flowing through the electro-optical element is controlled by an active element provided in the same pixel circuit as the electro-optical element, for example, an insulated gate field effect transistor (generally, a TFT (Thin Film Transistor)). Active matrix display devices have been actively developed. An active matrix display device can easily realize a large-sized and high-definition display device because the electro-optic element continues to emit light over a period of one field (one frame).

  By the way, it is generally known that the IV characteristic (current-voltage characteristic) of the organic EL element is deteriorated with time (so-called deterioration with time). In a pixel circuit using an N-channel TFT as a transistor for driving an organic EL element with current (hereinafter referred to as “driving transistor”), the organic EL element is connected to the source side of the driving transistor. When the IV characteristic of the organic EL element deteriorates with time, the gate-source voltage Vgs of the driving transistor changes, and as a result, the emission luminance of the organic EL element also changes.

  This will be described more specifically. The source potential of the drive transistor is determined by the operating point of the drive transistor and the organic EL element. When the IV characteristic of the organic EL element deteriorates, the operating point of the driving transistor and the organic EL element fluctuates. Therefore, even if the same voltage is applied to the gate of the driving transistor, the source potential of the driving transistor changes. To do. As a result, since the source-gate voltage Vgs of the drive transistor changes, the value of the current flowing through the drive transistor changes. As a result, since the value of the current flowing through the organic EL element also changes, the light emission luminance of the organic EL element changes.

  In addition, in a pixel circuit using a polysilicon TFT, in addition to the deterioration over time of the IV characteristics of the organic EL element, the threshold voltage Vth of the driving transistor and the mobility of the semiconductor thin film that constitutes the channel of the driving transistor (hereinafter referred to as the following) Μ described as “driving transistor mobility” changes with time, and the threshold voltage Vth and mobility μ vary from pixel to pixel due to variations in the manufacturing process (individual transistor characteristics vary).

  If the threshold voltage Vth and mobility μ of the driving transistor differ from pixel to pixel, the current value flowing through the driving transistor varies from pixel to pixel. Therefore, even if the same voltage is applied to the gate of the driving transistor between the pixels, The light emission luminance of the EL element varies among the pixels, and as a result, the uniformity of the screen is lost.

  Therefore, even if the IV characteristic of the organic EL element deteriorates with time, or the threshold voltage Vth or mobility μ of the driving transistor changes with time, the light emission luminance of the organic EL element is not affected by those effects. In order to keep constant, the compensation function for the characteristic variation of the organic EL element, the correction for the variation of the threshold voltage Vth of the driving transistor (hereinafter referred to as “threshold correction”), the mobility μ of the driving transistor Each pixel circuit is provided with a correction function for correction of fluctuations (hereinafter referred to as “mobility correction”) (see, for example, Patent Document 1).

  As described above, each of the pixel circuits has the compensation function for the characteristic variation of the organic EL element and the correction function for the threshold voltage Vth and the mobility μ of the driving transistor, so that the IV characteristic of the organic EL element is improved. Even if the deterioration with time or the threshold voltage Vth or mobility μ of the driving transistor changes with time, the light emission luminance of the organic EL element can be kept constant without being affected by them.

JP 2006-133542 A

  In the organic EL display device according to the above-described prior art, a case where the organic EL element has a temperature change will be considered. FIG. 19 shows the temperature dependence of the V / I (voltage / current) characteristics of the organic EL element. FIG. 20 shows the Vd / Id (drain voltage / drain current) characteristics of the drive transistor.

  In the light emission period, the anode potential of the organic EL element rises according to the drive current. The increase in the anode potential of the organic EL element is also an increase in the source potential of the drive transistor. When the source potential of the driving transistor rises, the gate potential of the driving transistor also rises due to the bootstrap operation of the storage capacitor connected between the gate and source of the driving transistor. The amount of increase in gate potential at this time is equal to the amount of increase in source potential.

  Here, a case where a temperature change occurs in the organic EL element is considered. For example, if the temperature changes from 25 ° C. to 60 ° C., the IV characteristic of the organic EL element changes as shown by a broken line in FIG. When the current I flowing through the organic EL element is considered to be the same value, the voltage Voled across the organic EL element is smaller at 60 ° C. than at 25 ° C.

  When the voltage Voled across the organic EL element decreases due to the temperature change of the organic EL element, the drain-source voltage Vds of the drive transistor increases by the decrease. At this time, the driving transistor is assumed to be used in the saturation region.

  Here, when the drain-source voltage Vds of the driving transistor increases, the drain-source current Ids increases due to the Early effect in the saturation region of the driving transistor. When the current increases, the light emission luminance of the organic EL element increases. That is, the light emission luminance changes due to the temperature change of the organic EL element. As a result, it becomes impossible to realize image display with light emission luminance according to the signal voltage of the video signal.

  Therefore, the present invention eliminates a change in luminance of the electro-optical element due to a temperature change of the electro-optical element, and can realize an image display with light emission luminance according to the signal voltage of the video signal, a driving method of the display device, and An object is to provide an electronic device using the display device.

  In order to achieve the above object, the present invention provides an electro-optic element, a writing transistor for writing a video signal, a holding capacitor for holding the video signal written by the writing transistor, and the holding capacitor. In a display device in which pixels including drive transistors that drive the electro-optic element based on a video signal are arranged in a matrix, the light emission luminance of the electro-optic element changes as the temperature of the electro-optic element changes. When the luminance change is corrected, more specifically, the temperature change of the electro-optical element is detected, and the power supply potential applied to the drive transistor or the electro-optical element is controlled according to the detection result, Alternatively, a voltage drop element connected in series with the driving transistor can reduce the current flowing through the electro-optic element. It adopts a configuration of correcting the luminance change in the electro-optical element by generating Flip voltage drop.

  In the display device having the above-described configuration and the electronic apparatus having the display device, even if the temperature of the electro-optical element changes and the light emission luminance of the electro-optical element changes with the temperature change, the luminance change is corrected. Thus, the luminance change of the electro-optic element due to the temperature change of the electro-optic element can be suppressed.

  According to the present invention, it is possible to suppress the luminance change of the electro-optical element due to the temperature change of the electro-optical element, and thus it is possible to realize the image display with the light emission luminance according to the signal voltage of the video signal.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a system configuration diagram showing an outline of the configuration of an active matrix display device according to an embodiment of the present invention. Here, as an example, an active matrix organic EL display device using, as an example, a current-driven electro-optic element whose emission luminance changes according to the value of current flowing through the device, for example, an organic EL element as a light-emitting element of a pixel (pixel circuit) This case will be described as an example.

  As shown in FIG. 1, the organic EL display device 10 according to this embodiment includes a pixel array unit 30 in which pixels (PXLC) 20 are two-dimensionally arranged in a matrix (matrix shape), and the pixel array unit 30. It has a configuration that includes a drive unit that is disposed in the periphery and drives each pixel 20. For example, a writing scanning circuit 40, a power supply scanning circuit 50, and a horizontal driving circuit 60 are provided as driving units for driving the pixels 20.

  The pixel array unit 30 is provided with scanning lines 31-1 to 31-m and power supply lines 32-1 to 32-m for each pixel row with respect to a pixel array of m rows and n columns. The signal lines 33-1 to 33-n are wired.

  The pixel array unit 30 is usually formed on a transparent insulating substrate such as a glass substrate, and has a flat (flat) panel structure. Each pixel 20 of the pixel array unit 30 can be formed using an amorphous silicon TFT (Thin Film Transistor) or a low-temperature polysilicon TFT. When the low-temperature polysilicon TFT is used, the scanning circuit 40, the power supply scanning circuit 50, and the horizontal driving circuit 60 can also be mounted on the display panel (substrate) 70 that forms the pixel array section 30.

  The writing scanning circuit 40 is configured by a shift register or the like that sequentially shifts (transfers) the start pulse sp in synchronization with the clock pulse ck, and the scanning line 31-is used when writing the video signal to each pixel 20 of the pixel array unit 30. The scanning signals WS1 to WSm are sequentially supplied to 1 to 31-m, and the pixels 20 are sequentially scanned (line sequential scanning) in units of rows.

  The power supply scanning circuit 50 includes a shift register that sequentially shifts the start pulse sp in synchronization with the clock pulse ck, and the first potential Vccp and the first potential in synchronization with the line sequential scanning by the writing scanning circuit 40. By supplying the power supply line potentials DS1 to DSm that are switched at the second potential Vini lower than Vccp to the power supply lines 32-1 to 32-m, the drive transistor 22 (see FIG. 2), which will be described later, is turned on / off. Non-conduction (off) control is performed.

  The horizontal drive circuit 60 appropriately selects one of the signal voltage Vsig and the offset voltage Vofs of the video signal according to the luminance information supplied from a signal supply source (not shown), and the signal lines 33-1 to 33-33. For example, data is written all at once to each pixel 20 of the pixel array unit 30 via n. That is, the horizontal driving circuit 60 adopts a line-sequential writing driving mode in which the signal voltage Vsig of the video signal is written all at once in a row (line) unit.

  Here, the offset voltage Vofs is a reference voltage (for example, equivalent to a black level) of a signal voltage of a video signal (hereinafter sometimes referred to as “input signal voltage” or simply “signal voltage”) Vsig. is there. The second potential Vini is set to Vofs−Vth> Vini when the potential is sufficiently lower than the offset voltage Vofs, for example, when the threshold voltage of the drive transistor 22 is Vth.

(Pixel circuit)
FIG. 2 is a circuit diagram illustrating a specific configuration example of the pixel (pixel circuit) 20. As shown in FIG. 2, the pixel 20 includes a current-driven electro-optical element, for example, an organic EL element 21, whose light emission luminance changes according to a current value flowing through the device, and the organic EL element 21 includes In addition, it has a 2Tr / 1C pixel configuration including a drive transistor 22, a write transistor 23, and a storage capacitor 24, that is, two transistors (Tr) and one capacitor element (C).

  Here, N-channel TFTs are used as the drive transistor 22 and the write transistor 23. However, the combination of the conductivity types of the driving transistor 22 and the writing transistor 23 here is only an example, and is not limited to these combinations.

  The organic EL element 21 has a cathode electrode connected to a common power supply line 34 that is wired in common to all the pixels 20. The drive transistor 22 has a source electrode connected to the anode electrode of the organic EL element 21 and a drain electrode connected to the power supply line 32 (32-1 to 32-m).

  The writing transistor 23 has a gate electrode connected to the scanning line 31 (31-1 to 31-m), and one electrode (source electrode / drain electrode) connected to the signal line 33 (33-1 to 33-n). The other electrode (drain electrode / source electrode) is connected to the gate electrode of the drive transistor 22.

  The storage capacitor 24 has one end connected to the gate electrode of the drive transistor 22 and the other end connected to the source electrode of the drive transistor 22 (the anode electrode of the organic EL element 21). It is also possible to adopt a configuration in which an auxiliary capacitor is connected in parallel to the holding capacitor 24 to compensate for the shortage of the holding capacitor 24.

  In the pixel 20 having such a configuration, the writing transistor 23 becomes conductive in response to the scanning signal WS applied to the gate electrode from the writing scanning circuit 40 through the scanning line 31, and thereby from the horizontal driving circuit 60 through the signal line 33. The signal voltage Vsig or the offset voltage Vofs of the video signal corresponding to the supplied luminance information is sampled and written into the pixel 20. The written signal voltage Vsig or offset voltage Vofs is held in the holding capacitor 24.

  When the potential DS of the power supply line 32 (32-1 to 32-m) is at the first potential Vccp, the driving transistor 22 is supplied with current from the power supply line 32 and is held in the storage capacitor 24. By supplying the organic EL element 21 with a drive current having a current value corresponding to the voltage value of the signal voltage Vsig, the organic EL element 21 is driven by current.

(Pixel structure)
FIG. 3 is a cross-sectional view illustrating an example of the cross-sectional structure of the pixel 20. As shown in FIG. 3, in the pixel 20, an insulating film 202, an insulating planarizing film 203, and a window insulating film 204 are sequentially formed on a glass substrate 201 on which pixel circuits such as a driving transistor 22 and a writing transistor 23 are formed. The organic EL element 21 is provided in the recess 204A of the window insulating film 204.

  The organic EL element 21 includes an anode electrode 205 made of metal or the like formed on the bottom of the recess 204A of the window insulating film 204, and an organic layer (electron transport layer, light emitting layer, hole transport) formed on the anode electrode 205. Layer / hole injection layer) 206 and a cathode electrode 207 made of a transparent conductive film or the like formed on the organic layer 206 in common for all pixels.

  In the organic EL element 21, the organic layer 206 is formed by sequentially depositing a hole transport layer / hole injection layer 2061, a light emitting layer 2062, an electron transport layer 2063 and an electron injection layer (not shown) on the anode electrode 205. It is formed. Then, current flows from the driving transistor 22 to the organic layer 206 through the anode electrode 205 under current driving by the driving transistor 22 in FIG. 2, so that electrons and holes are recombined in the light emitting layer 2062 in the organic layer 206. It is designed to emit light.

  As shown in FIG. 3, after the organic EL element 21 is formed on a glass substrate 201 on which a pixel circuit is formed via the insulating film 202, the insulating flattening film 203, and the window insulating film 204, in units of pixels, The sealing substrate 209 is bonded by the adhesive 210 via the passivation film 208, and the organic EL element 21 is sealed by the sealing substrate 209, whereby the display panel 70 is formed.

(Threshold correction function)
Here, the power supply scanning circuit 50 supplies power while the horizontal drive circuit 60 supplies the offset voltage Vofs to the signal lines 33 (33-1 to 33-n) after the writing transistor 23 is turned on. The potential DS of the line 33 is switched from the second potential Vini to the first potential Vccp. By switching the potential DS of the power supply line 32, a voltage corresponding to the threshold voltage Vth of the drive transistor 22 is held in the holding capacitor 24.

  The voltage corresponding to the threshold voltage Vth of the driving transistor 22 is held in the holding capacitor 24 for the following reason.

  Due to variations in the manufacturing process of the driving transistor 22 and changes over time, transistor characteristics such as the threshold voltage Vth and mobility μ of the driving transistor 22 vary for each pixel. Due to this variation in transistor characteristics, even if the same gate potential is applied to the drive transistor 22 between the pixels, the drain-source current (drive current) Ids varies from pixel to pixel, resulting in variations in the light emission luminance of the organic EL element 21. It appears. In order to cancel (correct) the influence of the variation in threshold voltage Vth for each pixel, a voltage corresponding to the threshold voltage Vth is held in the holding capacitor 24.

  The threshold voltage Vth of the driving transistor 22 is corrected as follows. That is, by holding the threshold voltage Vth in the storage capacitor 24 in advance, the threshold voltage Vth of the drive transistor 22 is held in the storage capacitor 24 when the drive transistor 22 is driven by the signal voltage Vsig of the video signal. The voltage corresponding to the threshold voltage Vth is canceled out, in other words, the threshold voltage Vth is corrected.

  This is the threshold correction function. With this threshold correction function, even if the threshold voltage Vth varies or changes with time for each pixel, the light emission luminance of the organic EL element 21 can be kept constant without being influenced by the threshold voltage Vth. The principle of threshold correction will be described in detail later.

(Mobility correction function)
The pixel 20 shown in FIG. 2 has a mobility correction function in addition to the threshold correction function described above. Specifically, the scanning signal WS output from the writing scanning circuit 40 during the period in which the horizontal driving circuit 60 supplies the signal voltage Vsig of the video signal to the signal lines 33 (33-1 to 33-n). The mobility of the drain-source current Ids of the drive transistor 22 when the signal voltage Vsig is held in the storage capacitor 24 in the period in which the write transistor 23 is turned on in response to (WS1 to WSm), that is, the mobility correction period. A mobility correction that cancels the dependence on μ is performed. The specific principle and operation of this mobility correction will be described later.

(Bootstrap function)
The pixel 20 shown in FIG. 2 further has a bootstrap function. Specifically, the writing scanning circuit 40 supplies the scanning signals WS (WS1 to WSm) to the scanning lines 31 (31-1 to 31-m) when the signal voltage Vsig of the video signal is held in the storage capacitor 24. Is released, the writing transistor 23 is turned off, and the gate electrode of the driving transistor 22 is electrically disconnected from the signal line 33 (33-1 to 33-n) to be in a floating state.

  When the gate electrode of the driving transistor 22 is in a floating state, the storage capacitor 24 is connected between the gate and the source of the driving transistor 22, so that when the source potential Vs of the driving transistor 22 varies, the source potential Vs varies. Since the gate potential Vg of the drive transistor 22 also fluctuates in conjunction (following), the gate-source voltage Vgs of the drive transistor 22 is kept constant.

  As described above, the operation of keeping the gate-source voltage Vgs constant by causing the gate potential Vg of the driving transistor 22 to follow the source potential Vs by the action of the storage capacitor 24 is a bootstrap operation. By this bootstrap operation, even if the IV characteristic of the organic EL element 21 changes with time, the light emission luminance of the organic EL element 21 can be kept constant.

  That is, even if the IV characteristic of the organic EL element 21 changes with time and the source potential Vs of the driving transistor 22 changes accordingly, the gate-source potential Vgs of the driving transistor 22 is kept constant by the bootstrap operation. In order to be maintained, the current flowing through the organic EL element 21 does not change, and therefore the emission luminance of the organic EL element 21 is also kept constant. As a result, even if the IV characteristic of the organic EL element 21 changes with time, it is possible to realize an image display that does not have a luminance deterioration associated therewith.

(Basic circuit operation of organic EL display device)
Next, a basic circuit operation of the organic EL display device 10 according to the present embodiment will be described with reference to the operation waveform diagrams of FIGS. 5 and 6 based on the timing waveform diagram of FIG. In the operation explanatory diagrams of FIGS. 5 and 6, the write transistor 23 is illustrated by a switch symbol for simplification of the drawing. Further, since the organic EL element 21 has a parasitic capacitance Cel, the parasitic capacitance Cel is also illustrated.

  In the timing waveform diagram of FIG. 4, the time axis is shared, the change in potential (scanning signal) WS of the scanning line 31 (31-1 to 31-m) in 1H (H is the horizontal scanning period), and the power supply line 32. A change in the potential DS of (32-1 to 32-m) and a change in the gate potential Vg and the source potential Vs of the drive transistor 22 are shown.

<Light emission period>
In the timing chart of FIG. 4, before the time t1, the organic EL element 21 is in a light emission state (light emission period). In this light emission period, the potential DS of the power supply line 32 is at the high potential Vccp (first potential), and the writing transistor 23 is in a non-conduction state. At this time, since the driving transistor 22 is set to operate in the saturation region, the gate-source voltage of the driving transistor 22 is supplied from the power supply line 32 through the driving transistor 22 as shown in FIG. A drive current (drain-source current) Ids corresponding to Vgs is supplied to the organic EL element 21. Therefore, the organic EL element 21 emits light with a luminance corresponding to the current value of the drive current Ids.

<Threshold correction preparation period>
At time t1, a new field of line sequential scanning is entered, and as shown in FIG. 5B, the potential DS of the power supply line 32 is sufficiently lower than the offset voltage Vofs of the signal line 33 from the high potential Vccp. It switches to the potential Vini (second potential). Here, when the threshold voltage of the organic EL element 21 is Vel and the potential of the common power supply line 34 is Vcath, if the low potential Vini is Vini <Vel + Vcath, the source potential Vs of the drive transistor 22 is substantially equal to the low potential Vini. Therefore, the organic EL element 21 is extinguished in a reverse bias state.

  Next, when the potential WS of the scanning line 31 transits from the low potential side to the high potential side at time t2, as shown in FIG. 5C, the writing transistor 23 becomes conductive. At this time, since the offset voltage Vofs is supplied from the horizontal drive circuit 60 to the signal line 33, the gate potential Vg of the drive transistor 22 becomes the offset voltage Vofs. Further, the source potential Vs of the drive transistor 22 is at a potential Vini that is sufficiently lower than the offset voltage Vofs.

  At this time, the gate-source voltage Vgs of the drive transistor 22 is Vofs-Vini. Here, if Vofs−Vini is not larger than the threshold voltage Vth of the drive transistor 22, the above-described threshold correction operation cannot be performed, so it is necessary to set Vofs−Vini> Vth. In this way, the operation of fixing and fixing the gate potential Vg of the drive transistor 22 to the offset voltage Vofs and the source potential Vs to the low potential Vini is an operation for preparing for threshold correction.

<Threshold correction period>
Next, at time t3, as shown in FIG. 5D, when the potential DS of the power supply line 32 is switched from the low potential Vini to the high potential Vccp, the source potential Vs of the drive transistor 22 starts to rise. Eventually, the gate-source voltage Vgs of the drive transistor 22 becomes the threshold voltage Vth of the drive transistor 22, and a voltage corresponding to the threshold voltage Vth is written into the storage capacitor 24.

  Here, for convenience, a period during which a voltage corresponding to the threshold voltage Vth is written to the storage capacitor 24 is referred to as a threshold correction period. In the threshold correction period, the common power supply line 34 is set so that the organic EL element 21 is cut off in order to prevent the current from flowing exclusively to the storage capacitor 24 side and to the organic EL element 21 side. The potential Vcath is set in advance.

  Next, at time t4, the potential WS of the scanning line 31 shifts to the low potential side, so that the writing transistor 23 is turned off as illustrated in FIG. At this time, the gate electrode of the driving transistor 22 is in a floating state, but the driving transistor 22 is in a cut-off state because the gate-source voltage Vgs is equal to the threshold voltage Vth of the driving transistor 22. Therefore, the drain-source current Ids does not flow through the driving transistor 22.

<Writing period / mobility correction period>
Next, at time t5, as shown in FIG. 6B, the potential of the signal line 33 is switched from the offset voltage Vofs to the signal voltage Vsig of the video signal. Subsequently, at time t6, the potential WS of the scanning line 31 transitions to the high potential side, so that the writing transistor 23 becomes conductive as shown in FIG. 6C, and the signal voltage Vsig of the video signal is sampled. To write in the pixel 20.

  By writing the signal voltage Vsig by the writing transistor 23, the gate potential Vg of the driving transistor 22 becomes the signal voltage Vsig. When the driving transistor 22 is driven by the signal voltage Vsig of the video signal, the threshold voltage correction is performed by canceling the threshold voltage Vth of the driving transistor 22 with a voltage corresponding to the threshold voltage Vth held in the holding capacitor 24. Done. The principle of threshold correction will be described later.

  At this time, since the organic EL element 21 is initially in a cut-off state (high impedance state), a current (drain-source current Ids) that flows from the power supply line 32 to the drive transistor 22 according to the signal voltage Vsig of the video signal. Flows into the parasitic capacitance Cel of the organic EL element 21, and charging of the parasitic capacitance Cel is started.

  Due to the charging of the parasitic capacitance Cel, the source potential Vs of the drive transistor 22 rises with time. At this time, the variation in the threshold voltage Vth of the drive transistor 22 has already been corrected, and the drain-source current Ids of the drive transistor 22 depends on the mobility μ of the drive transistor 22.

  Eventually, when the source potential Vs of the drive transistor 22 rises to the potential of Vofs−Vth + ΔV, the gate-source voltage Vgs of the drive transistor 22 becomes Vsig−Vofs + Vth−ΔV. That is, the increase ΔV of the source potential Vs is subtracted from the voltage (Vsig−Vofs + Vth) held in the holding capacitor 24, in other words, acts to discharge the charged charge of the holding capacitor 24, and negative feedback Has been applied. Therefore, the increase ΔV of the source potential Vs becomes a feedback amount of negative feedback.

  As described above, the drain-source current Ids flowing through the drive transistor 22 is negatively fed back to the gate input of the drive transistor 22, that is, the gate-source voltage Vgs, so that the drain-source current Ids of the drive transistor 22 is reduced. Mobility correction is performed to cancel the dependence on the mobility μ, that is, to correct the variation of the mobility μ for each pixel.

  More specifically, since the drain-source current Ids increases as the signal voltage Vsig of the video signal increases, the absolute value of the feedback amount (correction amount) ΔV of negative feedback also increases. Therefore, the mobility correction according to the light emission luminance level is performed. Further, when the signal voltage Vsig of the video signal is constant, the absolute value of the feedback amount ΔV of the negative feedback increases as the mobility μ of the driving transistor 22 increases, so that variation in the mobility μ for each pixel is removed. Can do. The principle of mobility correction will be described later.

<Light emission period>
Next, when the potential WS of the scanning line 31 transitions to the low potential side at time t7, the writing transistor 23 is turned off as illustrated in FIG. 6D. As a result, the gate electrode of the drive transistor 22 is disconnected from the signal line 33. At the same time, the drain-source current Ids starts to flow through the organic EL element 21, whereby the anode potential of the organic EL element 21 rises according to the drain-source current Ids.

  The increase in the anode potential of the organic EL element 21 is nothing but the increase in the source potential Vs of the drive transistor 22. When the source potential Vs of the drive transistor 22 rises, the gate potential Vg of the drive transistor 22 also rises in conjunction with the bootstrap operation of the storage capacitor 24. At this time, the increase amount of the gate potential Vg is equal to the increase amount of the source potential Vs. Therefore, the gate-source voltage Vgs of the drive transistor 22 is kept constant at Vsig−Vofs + Vth−ΔV during the light emission period. At time t8, the potential of the signal line 33 is switched from the signal voltage Vsig of the video signal to the offset voltage Vofs.

(Principle of threshold correction)
Here, the principle of threshold correction of the drive transistor 22 will be described. The drive transistor 22 operates as a constant current source because it is designed to operate in the saturation region. As a result, a constant drain-source current (drive current) Ids given by the following equation (1) is supplied from the drive transistor 22 to the organic EL element 21.
Ids = (1/2) · μ (W / L) Cox (Vgs−Vth) ² (1)
Here, W is the channel width of the drive transistor 22, L is the channel length, and Cox is the gate capacitance per unit area.

  FIG. 7 shows characteristics of the drain-source current Ids of the drive transistor 22 versus the gate-source voltage Vgs. As shown in this characteristic diagram, when correction for variation in the threshold voltage Vth of the drive transistor 22 is not performed, when the threshold voltage Vth is Vth1, the drain-source current Ids corresponding to the gate-source voltage Vgs becomes Ids1. On the other hand, when the threshold voltage Vth is Vth2 (Vth2> Vth1), the drain-source current Ids corresponding to the same gate-source voltage Vgs is Ids2 (Ids2 <Ids). That is, when the threshold voltage Vth of the driving transistor 22 varies, the drain-source current Ids varies even if the gate-source voltage Vgs is constant.

On the other hand, in the pixel (pixel circuit) 20 having the above-described configuration, as described above, the gate-source voltage Vgs of the driving transistor 22 at the time of light emission is Vsig−Vofs + Vth−ΔV. ), The drain-source current Ids is
Ids = (1/2) · μ (W / L) Cox (Vsig−Vofs−ΔV) ²
(2)
It is represented by

  That is, the term of the threshold voltage Vth of the drive transistor 22 is canceled, and the drain-source current Ids supplied from the drive transistor 22 to the organic EL element 21 does not depend on the threshold voltage Vth of the drive transistor 22. As a result, the drain-source current Ids does not vary even if the threshold voltage Vth of the drive transistor 22 varies for each pixel due to variations in the manufacturing process of the drive transistor 22 and changes over time. The emission brightness does not change.

(Principle of mobility correction)
Next, the principle of mobility correction of the drive transistor 22 will be described. FIG. 8 shows a characteristic curve in a state where a pixel A having a relatively high mobility μ of the driving transistor 22 and a pixel B having a relatively low mobility μ of the driving transistor 22 are compared. When the driving transistor 22 is composed of a polysilicon thin film transistor or the like, it is inevitable that the mobility μ varies between pixels like the pixel A and the pixel B.

  For example, when the input signal voltage Vsig of the same level is written to both the pixels A and B in a state where the mobility μ is varied between the pixel A and the pixel B, the mobility μ is not corrected. A large difference is generated between the drain-source current Ids1 ′ flowing in the pixel A having a large value and the drain-source current Ids2 ′ flowing in the pixel B having the small mobility μ. Thus, if a large difference occurs between the pixels in the drain-source current Ids due to the variation in the mobility μ, the uniformity of the screen is impaired.

  Here, as is clear from the transistor characteristic equation of Equation (1), the drain-source current Ids increases when the mobility μ is large. Therefore, the feedback amount ΔV in the negative feedback increases as the mobility μ increases. As shown in FIG. 8, the feedback amount ΔV1 of the pixel A having a high mobility μ is larger than the feedback amount ΔV2 of the pixel V having a low mobility. Therefore, by negatively feeding back the drain-source current Ids of the drive transistor 22 to the input signal voltage Vsig side by the mobility correction operation, the larger the mobility μ, the more negative feedback is applied. Can be suppressed.

  Specifically, when the feedback amount ΔV1 is corrected in the pixel A having a high mobility μ, the drain-source current Ids greatly decreases from Ids1 ′ to Ids1. On the other hand, since the feedback amount ΔV2 of the pixel B having a low mobility μ is small, the drain-source current Ids decreases from Ids2 ′ to Ids2, and does not decrease that much. As a result, since the drain-source current Ids1 of the pixel A and the drain-source current Ids2 of the pixel B are substantially equal, the variation in the mobility μ is corrected.

  In summary, when there are a pixel A and a pixel B having different mobility μ, the feedback amount ΔV1 of the pixel A having a high mobility μ is larger than the feedback amount ΔV2 of the pixel B having a low mobility μ. That is, the larger the mobility μ, the larger the feedback amount ΔV, and the larger the amount of decrease in the drain-source current Ids. Therefore, by negatively feeding back the drain-source current Ids of the driving transistor 22 to the input signal voltage Vsig side, the current value of the drain-source current Ids of the pixels having different mobility μ is made uniform. Variation in degree μ can be corrected.

  As described above, in the organic EL display device 10 in which the 2Tr / 1C pixels 20 including the drive transistor 22, the write transistor 23, and the storage capacitor 24 are arranged in a matrix in addition to the organic EL element 21, the drive transistor 22 The power supply potential (potential of the power supply line 32) DS to be supplied can be switched between a high potential (first potential) Vccp and a low potential (second potential) Vini, and the light emission period of the organic EL element 21 by switching the power supply potential / By adopting a configuration in which the drive transistor 22 has a function of controlling the non-light emission period, at least one transistor for controlling the light emission period / non-light emission period and one control for controlling the transistor per pixel. Since the wiring of the line can be omitted, the pixel size is reduced, and consequently the display device is highly accurate. It can contribute to the reduction.

  Further, in the organic EL display device 10 according to the present embodiment, the gate-source voltage Vgs of the drive transistor 22 is kept constant during the light emission period by the bootstrap operation by the storage capacitor 24, and thus the organic EL element 21. The current that flows through is not changed. Therefore, even if the IV characteristics of the organic EL element 21 deteriorate, a constant drain-source current Ids continues to flow through the organic EL element 21, so that the light emission luminance of the organic EL element 21 does not change ( Compensation function for characteristic variation of organic EL element 21).

  Furthermore, in the organic EL display device 10 according to the present embodiment, the drain-source current Ids, which is not affected by variations in the threshold voltage Vth of the drive transistor 22 or changes over time, is generated by the threshold correction function. And the mobility correction function cancels the dependence of the drain-source current Ids of the drive transistor 22 on the mobility μ, and the drain-source current Ids, which depends only on the signal voltage Vsig, is reduced to the organic EL element. Therefore, it is possible to obtain a display image with uniform image quality free from streaks and luminance unevenness due to variations in the threshold voltage Vth and mobility μ of the driving transistor 22 and changes with time.

(Brightness change due to temperature change)
By the way, as described in the section of the problem to be solved by the invention, the V / I characteristic of the organic EL element 21 shows temperature dependence (see FIG. 19), and when the temperature change occurs in the organic EL element 21, As a result, the light emission luminance of the organic EL element 21 changes. More specifically, when the temperature of the organic EL element 21 rises, the voltage Voled across the organic EL element 21 decreases, and the drain-source voltage Vds of the drive transistor 22 increases accordingly. In the saturation region, the drain-source current Ids increases due to the Early effect (see FIG. 20), and the light emission luminance of the organic EL element 21 increases.

[Characteristics of this embodiment]
Therefore, in the organic EL display device 10 according to the present embodiment, when the voltage Voled across the organic EL element 21 fluctuates according to the temperature change of the organic EL element 21, the light emission luminance of the organic EL element 21 changes accordingly. Further, the present invention is characterized in that the luminance change due to the temperature change of the organic EL element 21 is eliminated by correcting the luminance change.

  Hereinafter, when the light emission luminance of the organic EL element 21 changes with the temperature change of the organic EL element 21, the luminance correction means (hereinafter referred to as “brightness correction circuit”) that corrects the luminance change is described. ) Will be described.

Example 1
FIG. 10 is a system configuration diagram showing an outline of the configuration of the organic EL display device on which the brightness correction circuit according to the first embodiment is mounted. In FIG. 10, the same parts as those in FIG. .

  The luminance correction circuit 80A according to the first embodiment includes a dummy pixel 81, a temperature detection unit 82, and a control unit 83, and is the same as the pixel array unit 30, the writing scanning circuit 40, the power supply scanning circuit 50, and the horizontal driving circuit 60. It is mounted on the display panel 70.

  FIG. 11 shows an example of specific configurations of the dummy pixel 81 and the temperature detection unit 82. As shown in FIG. 11, the dummy pixel 81 includes an organic EL element 811 having the same configuration as the organic EL element 21 of the pixel 20, so that the light does not leak outside even if the organic EL element 811 emits light. In order not to affect the light emission luminance of the display panel 70, it is optically shielded by a light shielding means such as a black matrix. The dummy pixels 81 are arranged in the vicinity of the pixel array unit 30.

  The organic EL element 811 has the same configuration as the organic EL element 21 of the pixel 20, so that the V / I characteristic of the organic EL element 811 exhibits substantially the same temperature dependency as the V / I characteristic of the organic EL element 21. Further, since the dummy pixel 81 is disposed in the vicinity of the pixel array unit 30, the temperature of the dummy pixel 81 is substantially the same as that of the organic EL element 21 of the pixel 20. That is, when a temperature change occurs in the organic EL element 21 of the pixel 20, a temperature change occurs in the organic EL element 811 in substantially the same manner as the organic EL element 21.

  The temperature detection unit 82 includes a constant current source 821 that supplies a constant current to the organic EL element 811 of the dummy pixel 81 and a voltage detection unit 822 that detects a voltage across the organic EL element 811, and the organic EL element 21 in the pixel 20. This temperature change is detected as a change in the voltage across the organic EL element 811.

  In this temperature detection unit 82, when a constant current is supplied from the constant current source 821 to the organic EL element 811, a temperature change occurs in the organic EL element 21 of the pixel 20 as can be seen from the V / I characteristics of FIG. 19. Accordingly, when the voltage Voled across the organic EL element 21 varies by ΔV, the voltage across the organic EL element 811 also varies by ΔV. The voltage detector 822 detects this voltage variation ΔV as a temperature change of the organic EL element 21.

  In FIG. 10 again, the control unit 83 receives the detection result of the temperature detection unit 82, that is, the voltage variation ΔV of the organic EL element 811 detected by the voltage detection unit 822, and according to the voltage variation ΔV, for example, The voltage value of the high potential Vccp output from the power supply scanning circuit 50 is controlled.

  Specifically, when the voltage Voled across the organic EL element 21 decreases by ΔV due to the temperature rise of the organic EL element 21 of the pixel 20, the control unit 83 receives the detection result of the temperature detection unit 82, and the organic EL element A direction in which the voltage value of the high potential Vccp of the power supply line 32 decreases by a voltage variation ΔV so that the value of the drain-source voltage Vds of the driving transistor 22 does not change even if the voltage Voled across the element 21 decreases. To offset.

<Output circuit of power supply scanning circuit>
FIG. 12 is a circuit diagram showing an example of the configuration of the output circuit of the power supply scanning circuit 50. As shown in FIG. 12, the output circuit 51 of the power supply scanning circuit 50 is configured to have two stages of buffers 511 and 512 connected in cascade.

  The first-stage buffer 511 has a CMOS inverter configuration including a P-channel MOS transistor P11 and an N-channel MOS transistor N11 in which gate electrodes and drain electrodes are connected in common.

  Similarly, the second-stage buffer 512 has a CMOS inverter configuration including a P-channel MOS transistor P12 and an N-channel MOS transistor N12 in which gate electrodes and drain electrodes are connected in common.

  The source electrodes of the MOS transistors P11 and P12 are connected to the high potential (first potential) Vccp, and the source electrodes of the MOS transistors N11 and N12 are connected to the low potential (second potential) Vini. The high potential Vccp is supplied from the first power supply unit 52, and the low potential Vini is supplied from the second power supply unit 53.

  In the power supply scanning circuit 50 having the output circuit 51 configured as described above, the control unit 83 described above has a voltage value of the high potential Vccp output from the first power supply unit 52 to the power supply line 32 by a voltage variation ΔV. By offsetting in the decreasing direction, it is possible to perform correction to eliminate the luminance change due to the temperature change of the organic EL element 21.

  As described above, the voltage change ΔV of the voltage Voled across the organic EL element 21 due to the temperature change of the organic EL element 21 of the pixel 20 is detected. For example, the high potential Vccp of the power supply line 32 is applied to the drain − By offsetting so that the value of the source voltage Vds does not change, even if a temperature change occurs in the organic EL element 21, a change in the current flowing through the organic EL element 21 can be suppressed. The change in luminance of the organic EL element 21 due to the temperature change can be suppressed. As a result, it is possible to realize image display with light emission luminance corresponding to the signal voltage Vsig of the video signal.

  In the first embodiment, the voltage variation ΔV of the organic EL element 21 due to the temperature change of the organic EL element 21 is detected by the combination of the dummy pixel 81 arranged in the vicinity of the pixel array unit 30 and the temperature detection unit 82. However, a known temperature sensor may be arranged in the vicinity of the pixel array unit 30 so that the voltage variation ΔV of the organic EL element 21 due to a temperature change is detected by the temperature sensor.

  However, when the voltage variation ΔV using the dummy pixel 81 including the organic EL element 811 is detected, the V / I characteristic of the organic EL element 811 is different from the V / I characteristic of the organic EL element 21 in the pixel 20. Since the organic EL element 811 also has substantially the same temperature when the temperature of the organic EL element 21 changes, there is an advantage that the voltage variation ΔV due to the temperature change can be detected more reliably.

  In the first embodiment, the dummy pixels 81 are arranged at one location in the vicinity of the pixel array unit 30. However, the dummy pixels 81 are arranged at a plurality of locations, and the average value of these voltage fluctuations is determined as the final voltage. It is also possible to set the variation ΔV. Furthermore, a temperature sensor is formed on the opposite side of the light emitting surface for each pixel 20 to directly detect a temperature change of the organic EL element 21 of each pixel 20, and a high value is detected for each pixel row by an average value for each pixel row of the detection result. It is also possible to adopt a configuration in which the potential Vccp is offset.

  In the first embodiment, the high potential Vccp of the power supply line 32 is offset. However, the potential of the common power supply line 34 (see FIG. 2) that is commonly applied to the pixels 20, that is, the organic EL element 21. Even if the cathode potential Vcath is offset, it is possible to obtain the same effect as when the high potential Vccp is offset.

(Example 2)
FIG. 13 is a circuit diagram illustrating a circuit configuration of a pixel (pixel circuit) having a luminance correction circuit according to the second embodiment. In the figure, the same parts as those in FIG. 2 are denoted by the same reference numerals.

  The brightness correction circuit 80B according to the second embodiment is configured by a voltage drop element, for example, a resistance element 84, which is connected in series to the drive transistor 22 and generates a voltage drop according to the current flowing through the organic EL element 21. Yes. The resistance element 84 is connected to, for example, the drain side of the driving transistor 22, that is, between the power supply line 32 and the drain electrode of the driving transistor 22.

  In the resistance element 84, the temperature of the organic EL element 21 rises, and accordingly, the voltage Voled across the organic EL element 21 decreases, and the current flowing through the drive transistor 22 due to the Early effect (that is, the drain-source current Ids) is reduced. When increased, a voltage drop corresponding to the current is generated, thereby mitigating the Early effect.

  Since the Early effect is mitigated by the voltage drop due to the resistance element 84, an increase in the drain-source current Ids of the drive transistor 22 is suppressed, and thus the light emission of the organic EL element 21 accompanying the temperature rise of the organic EL element 21 An increase in luminance is suppressed.

  Here, the temperature change of the organic EL element 21 is a temperature change in the display driving state of the organic EL element 21, and thus generally refers to a temperature change when the temperature rises. Therefore, even if a voltage drop element is used as the luminance correction circuit 80B, a change in the light emission luminance of the organic EL element 21 due to a temperature change of the organic EL element 21 can be suppressed.

  When the resistance element 84 is used as the voltage drop element, the resistance value R of the resistance element 84 is set so as to satisfy the following condition.

When the current when the organic EL element 21 has the maximum luminance is Imax, the voltage drop at the resistance element 84 when the current Imax flows is R × Imax. Then, the resistance value R of the resistance element 84 is set under the condition that Vds− (R × Imax) is not linear. That is, since the saturation condition of the transistor is Vds−Vgs−Vth, the resistance value R of the resistance element 84 is set to satisfy the following expression (3).
Vds− (R × Imax) ≧ Vds−Vgs−Vth (3)

  As described above, the voltage drop element (in this example, the resistance element 84) is connected in series to the drive transistor 22, so that the Early effect is mitigated by the voltage drop caused by the voltage drop element, and the drain of the drive transistor 22 -Since the increase in the inter-source current Ids can be suppressed, the luminance change of the organic EL element 21 due to the temperature change of the organic EL element 21 can be suppressed. As a result, it is possible to realize image display with light emission luminance corresponding to the signal voltage Vsig of the video signal.

[Modification]
In the above embodiment, the drive transistor 22 that drives the organic EL element 21, the write transistor 23 that samples the signal voltage Vsig of the video signal and writes it in the pixel, and the gate electrode and the source electrode of the drive transistor 22 are connected. The case where the present invention is applied to the organic EL display device 10 having the pixel 20 having the 2Tr1C pixel configuration including the storage capacitor 24 that holds the signal voltage Vsig written by the write transistor 23 has been described as an example. It is not limited to application examples.

  That is, a pixel having a switching transistor that is connected between the drive transistor 22 and the power supply line and that selectively operates to supply drive current from the power supply line to the drive transistor 22, or a conductive state as appropriate Thus, the pixel further includes a switching transistor that detects the threshold voltage Vth of the drive transistor 22 prior to current driving of the organic EL element 21 and holds the detected threshold voltage Vth in the storage capacitor 24. The present invention can be applied to all organic EL display devices having the above.

  Furthermore, in the above embodiment, the case where the present invention is applied to an organic EL display device using an organic EL element as the electro-optical element of the pixel 20 has been described as an example. However, the present invention is not limited to this application example. The present invention can be applied to all display devices using current-driven electro-optic elements whose emission luminance varies depending on the value of current flowing through the device.

[Application example]
The display device according to the present invention described above is used in various electronic devices shown in FIGS. 14 to 18 as an example, for example, electronic devices such as digital cameras, notebook personal computers, mobile terminal devices such as mobile phones, and video cameras. The input video signal or the video signal generated in the electronic device can be applied to a display device of an electronic device in any field that displays an image or a video.

  As described above, by using the display device according to the present invention as a display device for electronic devices in all fields, the display device according to the present invention can be electro-optic with a smaller number of elements. Since it is possible to obtain a display image with uniform image quality without streaks and luminance unevenness due to element characteristic fluctuations and variations, it is possible to increase the definition of display devices in various electronic devices, and to improve the quality. Image display can be performed.

  Note that the display device according to the present invention includes a module-shaped one having a sealed configuration. For example, a display module formed by being affixed to an opposing portion such as transparent glass on the pixel array portion 30 is applicable. The transparent facing portion may be provided with a color filter, a protective film, and the like, and further, the above-described light shielding film. Note that the display module may be provided with a circuit unit for inputting / outputting a signal and the like from the outside to the pixel array unit, an FPC (flexible printed circuit), and the like.

  Specific examples of electronic devices to which the present invention is applied will be described below.

  FIG. 14 is a perspective view showing a television to which the present invention is applied. The television according to this application example includes a video display screen unit 101 including a front panel 102, a filter glass 103, and the like, and is created by using the display device according to the present invention as the video display screen unit 101.

  15A and 15B are perspective views showing a digital camera to which the present invention is applied. FIG. 15A is a perspective view seen from the front side, and FIG. 15B is a perspective view seen from the back side. The digital camera according to this application example includes a light emitting unit 111 for flash, a display unit 112, a menu switch 113, a shutter button 114, and the like, and is manufactured by using the display device according to the present invention as the display unit 112.

  FIG. 16 is a perspective view showing a notebook personal computer to which the present invention is applied. A notebook personal computer according to this application example includes a main body 121 including a keyboard 122 that is operated when characters and the like are input, a display unit 123 that displays an image, and the like, and the display device according to the present invention is used as the display unit 123. It is produced by this.

  FIG. 17 is a perspective view showing a video camera to which the present invention is applied. The video camera according to this application example includes a main body part 131, a lens 132 for photographing an object on the side facing forward, a start / stop switch 133 at the time of photographing, a display part 134, etc., and the display part 134 according to the present invention. It is manufactured by using a display device.

  FIG. 18 is a perspective view showing a mobile terminal device to which the present invention is applied, for example, a mobile phone, in which (A) is a front view in an opened state, (B) is a side view thereof, and (C) is closed. (D) is a left side view, (E) is a right side view, (F) is a top view, and (G) is a bottom view. The mobile phone according to this application example includes an upper housing 141, a lower housing 142, a connecting portion (here, a hinge portion) 143, a display 144, a sub display 145, a picture light 146, a camera 147, and the like. Alternatively, the sub-display 145 is manufactured by using the display device according to the present invention.

1 is a system configuration diagram illustrating an outline of a configuration of an organic EL display device according to an embodiment of the present invention. It is a circuit diagram which shows the specific structural example of a pixel (pixel circuit). It is sectional drawing which shows an example of the cross-sectional structure of a pixel. It is a timing waveform diagram with which it uses for description of the basic circuit operation | movement of the organic electroluminescence display which concerns on one Embodiment of this invention. It is explanatory drawing (the 1) of circuit operation | movement of the organic electroluminescence display which concerns on one Embodiment of this invention. It is explanatory drawing (the 2) of the circuit operation | movement of the organic electroluminescence display which concerns on one Embodiment of this invention. It is a characteristic view with which it uses for description of the subject resulting from the dispersion | variation in the threshold voltage Vth of a drive transistor. It is a characteristic view with which it uses for description of the subject resulting from the dispersion | variation in the mobility (mu) of a drive transistor. FIG. 10 is a characteristic diagram for explaining the relationship between the signal voltage Vsig of the video signal and the drain-source current Ids of the drive transistor depending on whether threshold correction and mobility correction are performed. 1 is a system configuration diagram illustrating an outline of a configuration of an organic EL display device equipped with a luminance correction circuit according to Embodiment 1. FIG. It is a circuit diagram which shows an example of a specific structure of a dummy pixel and a temperature detection part. It is a circuit diagram which shows an example of a structure of the output circuit of a power supply scanning circuit. It is a circuit diagram which shows the circuit structure of the pixel (pixel circuit) which has the brightness correction circuit which concerns on an Example. It is a perspective view which shows the television to which this invention is applied. It is the perspective view which shows the digital camera to which this invention is applied, (A) is the perspective view seen from the front side, (B) is the perspective view seen from the back side. 1 is a perspective view showing a notebook personal computer to which the present invention is applied. It is a perspective view which shows the video camera to which this invention is applied. It is a perspective view showing a cellular phone to which the present invention is applied, (A) is a front view in an open state, (B) is a side view thereof, (C) is a front view in a closed state, (D) Is a left side view, (E) is a right side view, (F) is a top view, and (G) is a bottom view. It is a characteristic view which shows the temperature dependence of the V / I characteristic of an organic EL element. It is a characteristic view which shows the Vd / Id characteristic of a drive transistor.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Organic EL display device, 20 ... Pixel (pixel circuit), 21 ... Organic EL element, 22 ... Drive transistor, 23 ... Write transistor, 24 ... Retention capacity, 30 ... Pixel array part, 31 (31-1 to 31-31) m) ... scanning line, 32 (32-1 to 32-m) ... power supply line, 33 (33-1 to 33-n) ... signal line, 34 ... common power supply line, 40 ... write scanning circuit, 50 ... Power supply scanning circuit 60 ... Horizontal drive circuit 70 ... Display panel 80A, 80B ... Luminance correction circuit 81 ... Dummy pixel 82 ... Temperature detection unit 83 ... Control unit 84 ... Resistance element

Claims (8)

An electro-optical element; a writing transistor for writing a video signal; a holding capacitor for holding the video signal written by the writing transistor; and driving the electro-optical element based on the video signal held in the holding capacitor. A pixel array unit in which pixels including drive transistors are arranged in a matrix;
A display device comprising: a luminance correction unit that corrects a change in luminance when the emission luminance of the electro-optical element changes with a change in temperature of the electro-optical element. The brightness correction unit includes a temperature detection unit that detects a temperature change of the electro-optical element, and a control unit that controls a power supply potential applied to the driving transistor or the electro-optical element according to a detection output of the temperature detection unit. The display device according to claim 1, further comprising: The temperature detecting unit includes a dummy pixel that is disposed in the vicinity of the pixel array unit and includes an electro-optic element having the same configuration as the electro-optic element of the pixel, and is based on a voltage across the electro-optic element of the dummy pixel. The display device according to claim 2, wherein a temperature change of the electro-optical element of the pixel is detected. The display device according to claim 1, wherein the brightness correction unit includes a voltage drop element that is connected in series to the drive transistor and generates a voltage drop according to a current flowing through the electro-optic element. An electro-optical element; a writing transistor for writing a video signal; a holding capacitor for holding the video signal written by the writing transistor; and driving the electro-optical element based on the video signal held in the holding capacitor. A driving method of a display device in which pixels including driving transistors are arranged in a matrix,
A method for driving a display device, comprising: correcting the luminance change when the emission luminance of the electro-optical element changes with a temperature change of the electro-optical element. A temperature change of the electro-optical element is detected, and a luminance change amount of the electro-optical element is corrected by controlling a power supply potential applied to the driving transistor or the electro-optical element according to the detection result. The method for driving a display device according to claim 5. A voltage drop element connected in series with the drive transistor corrects a luminance change of the electro-optic element by causing a voltage drop corresponding to a current flowing through the electro-optic element. The method for driving a display device according to claim 5. An electro-optical element; a writing transistor for writing a video signal; a holding capacitor for holding the video signal written by the writing transistor; and driving the electro-optical element based on the video signal held in the holding capacitor. A pixel array unit in which pixels including drive transistors are arranged in a matrix;
An electronic apparatus comprising: a display device comprising: a luminance correction unit that corrects a change in luminance when the emission luminance of the electro-optical element changes with a temperature change of the electro-optical element.

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