JP2010014746A - Display device, method of driving the same, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive method, a drive device, and a display device which prevent a potential difference V<SB>gs</SB>from being smaller than V<SB>th</SB>in correcting V<SB>th</SB>. <P>SOLUTION: In Vth correction preparation periods (T1-T3), the voltage of a gate line WSL is raised to a voltage (V<SB>on1</SB>) higher than a voltage (V<SB>on2</SB>) applied on a drain line DSL afterwards. Thereby, when the voltage of a gate line WSL is lowered from V<SB>on1</SB>to V<SB>off</SB>with a writing scanning circuit 23, a gate voltage V<SB>g</SB>is temporarily lowered by ΔV1, and a source voltage V<SB>s</SB>is temporarily lowered by ΔV2. As the result, values of the gate voltage V<SB>g</SB>and the source voltage V<SB>s</SB>just before starting second Vth correction are suppressed lower. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a display device using an organic light emitting element as a light emitting element of a pixel and a driving method thereof. Moreover, this invention relates to the electronic device provided with the said display apparatus.

  In recent years, in the field of display devices that perform image display, display devices that use current-driven optical elements, such as organic EL (electroluminescence) elements, whose light emission luminance changes according to the value of a flowing current are used as light emitting elements of pixels. Developed and commercialized.

  Unlike a liquid crystal element or the like, the organic EL element is a self-luminous element. Therefore, a display device (organic EL display device) using an organic EL element does not require a light source (backlight), and thus has higher image visibility and lower power consumption than a liquid crystal display device that requires a light source. And the response speed of the element is fast.

  An organic EL element used in a display device has a laminated structure in which an anode, an organic layer (organic compound layer), and a cathode are laminated in this order. Therefore, in the process of forming the organic EL element, defects such as pinholes may be formed in the thin organic layer due to minute particles or the like. For example, in the case of a top emission type organic EL display device, since the thickness of the organic layer is as thin as several nm to several tens of nm, even if particles of about 1 μm are mixed into the organic EL element, Holes and the like can occur.

  When defects such as pinholes exist in the organic layer, an electrical short circuit is formed between the anode and the cathode, and all or part of the current that should flow through the organic layer may flow into the short circuit. is there. In such a case, a phenomenon occurs in which the organic layer does not emit light or the emission luminance of the organic layer is lowered. A pixel in which this phenomenon has occurred is called a dark spot pixel.

  The generation of the dark dot pixels causes a decrease in yield. For this reason, various countermeasures have been taken for the dark spot pixels. For example, Patent Document 1 proposes a method of applying a reverse bias voltage to a dark spot pixel to cause a current to flow, and using a heat generation phenomenon caused by the current to increase the resistance or insulate the defective portion. Yes.

JP 2003-51384 A

FIG. 13 shows an example of the internal configuration of each pixel arranged in a matrix in the organic EL display device. A pixel 100 shown in FIG. 13 has a structure generally adopted when an active matrix method is used as a driving method, and is configured by an organic EL element 110 and a pixel circuit 120 connected thereto. Yes. The pixel circuit 120 includes a sampling transistor T _WS , a storage capacitor C _s , and a driving transistor T _Dr , and has a circuit configuration of 2Tr1C.

In the pixel circuit 120, a gate line WSL is connected to the gate of the transistor _{T WS,} drain line DSL is connected to the drain of the transistor _{T Dr,} the signal line DTL is connected to the drain of the transistor _{T WS.} The source of the transistor _{T WS} is the gate of the transistor _{T Dr,} is connected to one end of the storage capacitor _{C s,} and the other end of the source and the storage capacitor _{C s} of the transistor _{T Dr} is connected to the anode of the organic EL element 110 Yes. The cathode of the organic EL element 110 is connected to the ground line GND.

  In the display device including the pixel 100 having such a configuration, the pixel circuit 120 is controlled to be turned on / off in each pixel 100, and a driving current is injected into the organic EL element 110 of each pixel 100, thereby generating holes and electrons. Recombination causes light emission. This light is multiple-reflected between the anode and the cathode, passes through the cathode and the like, and is extracted to the outside. As a result, an image is displayed.

By the way, when a dark spot occurs in the pixel 100 described above, for example, repair of the pixel 100 where the dark spot has occurred can be considered as follows. That is, the voltage of the drain line DSL is set to V _ini (<0) in a state where both the transistors T _WS and T _Dr are turned on in the pixel 100 where the dark spot has occurred. At this time, since the pixel 100 is represented by the equivalent circuit shown in FIG. 14, a reverse bias voltage V _EL1 represented by the following expression is applied to the organic EL element 110.
V _EL1 = (V _ini −V _ca ) × (R _EL / (R _EL + R _Dr ))

Here, R _Dr represents the ON resistance of the transistor T _Dr , R _EL represents the short resistance of the organic EL element 110, and V _ca represents the cathode voltage of the organic EL element 110.

By the way, R _Dr is very large as compared with R _EL, and the partial pressure ratio of the organic EL element 110 is extremely small. Therefore, a voltage (V _ini ) that is normally applied to the drain line DSL when driving each pixel 100 is applied to the organic EL element 110 by applying the voltage (V _ini ) to the drain line DSL of the pixel 100 where the dark spot has occurred. Even when a reverse bias voltage is applied, there is a problem that a defective portion of the organic EL element 110 may not be increased in resistance or insulation.

  The present invention has been made in view of such a problem, and an object of the present invention is to have a size suitable for increasing the resistance or insulation of a defective portion of an organic light emitting element with respect to a pixel having a dark spot. The present invention relates to a display device capable of applying a reverse bias voltage, a driving method thereof, and an electronic device.

  The display device of the present invention includes a display unit having an organic light emitting element and a pixel circuit for each pixel, and a drive unit for driving the pixel circuit. The pixel circuit is provided with a first transistor, a second transistor, a third transistor, and a storage capacitor. The driving unit includes a first driving unit, a second driving unit, a control unit, a first wiring, a second wiring, a third wiring, a fourth wiring, a fifth wiring, and a reference voltage. The sixth wiring is provided. The gate of the first transistor is connected to the first wiring. The drain or source of the first transistor is connected to the third wiring. Of the drain and source of the first transistor, the one not connected to the third wiring is connected to the gate of the second transistor and one end of the storage capacitor. The drain or source of the second transistor is connected to the second wiring. Of the drain and source of the second transistor, the one not connected to the second wiring is connected to the drain or source of the third transistor, the other end of the storage capacitor, and the anode of the organic light emitting element. Of the drain and source of the third transistor, the one not connected to the anode of the organic light emitting device is connected to the first drive unit via the fourth wiring. The gate of the third transistor is connected to the second drive unit via the fifth wiring. The cathode of the organic light emitting element is connected to the sixth wiring. The first drive unit can output at least a first voltage lower than the threshold voltage of the organic light emitting element to the fourth wiring. The second driver can output at least a second voltage equal to or higher than the ON voltage of the third transistor to the fifth wiring. The control unit outputs a control signal instructing the first driving unit and the second driving unit to set the voltage of the fourth wiring to the first voltage and the voltage of the fifth wiring to the second voltage. It has become.

  An electronic apparatus according to the present invention includes the display device.

  According to the display device driving method of the present invention, the first driving unit and the second driving unit of the display device having the following configuration set the voltage of the fourth wiring to the first voltage and the voltage of the fifth wiring to the second voltage. The step of making a voltage is executed.

  A display device using the driving method includes a display unit having an organic light emitting element and a pixel circuit for each pixel, and a driving unit for driving the pixel circuit. The pixel circuit is provided with a first transistor, a second transistor, a third transistor, and a storage capacitor. The driving unit includes a first driving unit, a second driving unit, a first wiring, a second wiring, a third wiring, a fourth wiring, a fifth wiring, and a sixth voltage set to a reference voltage. Wiring is provided. The gate of the first transistor is connected to the first wiring. The drain or source of the first transistor is connected to the third wiring. Of the drain and source of the first transistor, the one not connected to the third wiring is connected to the gate of the second transistor and one end of the storage capacitor. The drain or source of the second transistor is connected to the second wiring. Of the drain and source of the second transistor, the one not connected to the second wiring is connected to the drain or source of the third transistor, the other end of the storage capacitor, and the anode of the organic light emitting element. Of the drain and source of the third transistor, the one not connected to the anode of the organic light emitting device is connected to the first drive unit via the fourth wiring. The gate of the third transistor is connected to the second drive unit via the fifth wiring. The cathode of the organic light emitting element is connected to the sixth wiring. The first drive unit can output at least a first voltage lower than the threshold voltage of the organic light emitting element to the fourth wiring. The second driver can output at least a second voltage equal to or higher than the ON voltage of the third transistor to the fifth wiring.

In the display device, the driving method thereof, and the electronic device of the present invention, the voltage of the fourth wiring is set to the first voltage and the voltage of the fifth wiring is set to the second voltage in the pixel where the dark spot has occurred. Accordingly, when the on-resistance of the third transistor is R _RS , the short-circuit resistance of the organic light emitting device is R _EL , the first voltage is V _ss , and the cathode voltage of the organic light emitting device is V _ca , A reverse bias voltage of V _ss −V _ca ) × (R _EL / (R _EL + R _RS )) can be applied. Here, since the first voltage is a voltage applied to a fourth wiring different from the third wiring, the first voltage can be made lower than a voltage applied to the third wiring. Accordingly, a larger reverse bias voltage can be applied to the organic light emitting element than when a reverse bias voltage is applied to the organic light emitting element from the third wiring.

  According to the display device, the driving method thereof, and the electronic device of the present invention, the voltage of the fourth wiring is set to the first voltage different from the voltage applied to the third wiring and the fifth wiring in the pixel where the dark spot has occurred. Since the second voltage can be set to the second voltage, a large reverse bias voltage can be applied to the organic light emitting device. Thereby, a reverse bias voltage having a magnitude suitable for increasing the resistance or insulation of the defective portion of the organic light emitting element can be applied.

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

  FIG. 1 shows an example of the entire configuration of a display device 1 according to an embodiment of the present invention. The display device 1 includes, for example, a display unit 10 and a peripheral circuit unit 20 (driving unit) formed around the display unit 10 on a substrate (not shown) made of glass, silicon (Si) wafer, resin, or the like. ).

  The display unit 10 has a plurality of pixels 11 arranged in a matrix over the entire surface of the display unit 10, and displays an image based on the video signal 20a input from the outside by active matrix driving. Each pixel 11 includes a red pixel 11R, a green pixel 11G, and a blue pixel 11B.

  FIG. 2 illustrates an example of the internal configuration of the pixels 11R, 11G, and 11B. In the pixels 11R, 11G, and 11B, as shown in FIG. 2, organic EL elements 12R, 12G, and 12B (light emitting elements) and a pixel circuit 13 are provided.

  The organic EL elements 12R, 12G, and 12B (hereinafter referred to as the organic EL element 12R and the like) have, for example, a configuration in which an anode (anode), an organic layer, and a cathode (cathode) are sequentially stacked, although not shown. Yes. The organic layer is, for example, sequentially from the anode side, a hole injection layer that increases hole injection efficiency, a hole transport layer that increases hole transport efficiency to the light emitting layer, and light emission by recombination of electrons and holes. Has a stacked structure in which a light-emitting layer that generates light and an electron-transporting layer that increases the efficiency of electron transport to the light-emitting layer are stacked. The material of each layer (hole injection layer, hole transport layer, light emitting layer, electron transport layer, etc.) included in the organic layer is a material corresponding to the light emission color of the organic EL element 12R and the like.

The pixel circuit 13 includes a sampling transistor T _WS (first transistor), a driving transistor T _Dr (second transistor), a reverse bias voltage applying transistor T _RS (third transistor), and a storage capacitor C _s . 3Tr1C circuit configuration. The transistors T _WS , T _Dr , and T _RS are formed by, for example, n-channel MOS thin film transistors (TFTs).

The peripheral circuit unit 20 includes a timing control circuit 21 (control unit), a horizontal drive circuit 22 (fifth drive unit), a write scan circuit 23 (third drive unit), and a power supply scan circuit 24 (fourth drive unit). And a reverse bias horizontal drive circuit 25 (first drive unit) and a reverse bias scanning circuit 26 (second drive unit). The timing control circuit 21 includes a signal generation circuit 21A and a signal holding control circuit 21B. The peripheral circuit unit 20 includes a gate line WSL (first wiring), a drain line DSL (second wiring), a signal line DTL (third wiring), and a reverse bias signal line RBL (fourth wiring). A gate line RSL (fifth wiring) and a ground line GND (sixth wiring) are provided. Further, as the reverse bias signal line RBL, and the reverse bias signal line RBL _R for an organic EL element 12R, and the reverse bias signal line RBL _G of organic EL element 12G, and the reverse bias signal line RBL _B for organic EL device 12B Are provided separately. Further, as the gate lines RSL, and the gate line RSL _R for an organic EL element 12R, a gate line RSL _G of organic EL element 12G, and the gate line RSL _B for organic EL element 12B are provided separately. The ground line GND is connected to the ground and is set to the ground voltage (reference voltage).

  The signal generation circuit 21A generates a display signal 21a to be displayed on the display unit 10 for each screen (for each display of one field), for example, based on the video signal 20a input from the outside. In addition, the signal generation circuit 21A applies a predetermined reverse bias voltage to the pixels 11R, 11G, and 11B where the dark spots are to be repaired, for example, based on the repair signal 20b input from the outside. The bias signal 21e is generated.

  The signal holding control circuit 21B stores the display signal 21a output from the signal generation circuit 21A for each screen (for each field display), for example, in a field memory composed of SRAM (Static Random Access Memory) or the like. It comes to hold. Further, the signal holding control circuit 21B stores and holds the bias signal 21e output from the signal generating circuit 21A in a field memory composed of, for example, an SRAM.

  In the signal holding control circuit 21B, a horizontal driving circuit 22, a writing scanning circuit 23, a power scanning circuit 24, a reverse bias horizontal driving circuit 25, and a reverse bias scanning circuit 26 that drive each pixel 11 operate in conjunction with each other. It also plays a role to control. Specifically, the signal holding control circuit 21B receives the control signal 21b for the write scanning circuit 23, the control signal 21c for the power supply scanning circuit 24, and the control signal 21d for the horizontal drive circuit 22. The control signal 21f is output to the reverse bias horizontal drive circuit 25, and the control signal 21g is output to the reverse bias scanning circuit 26.

The horizontal drive circuit 22 can output two types of voltages (V _ofs1 (seventh voltage), V _sig (eighth voltage)) in accordance with the control signal 21d output from the signal holding control circuit 21B. . Specifically, the horizontal drive circuit 22 _applies two types of voltages (V _ofs1 , V _sig) to the pixel 11 selected by the write scanning circuit 23 via the signal line DTL connected to each pixel 11 of the display unit 10. ).

Here, V _ofs1 has a voltage value lower than the threshold voltage V _el of the organic EL element 12R or the like. Also, V _sig is a voltage value corresponding to the video signal 20a and is higher than V _ofs1 .

The write scanning circuit 23, in response to the control signal 21b outputted from the signal holding control circuit 21B, 2 kinds of voltages _{(V on1} (fourth _{voltage), V off1} (third voltage)) is able to output a . Specifically, the writing scanning circuit 23 through the gate line WSL connected to each pixel 11 of the display unit 10, to the drive target pixel 11 supplies two kinds of voltages _{(V on1,} V _off1), The sampling transistor _TWS is controlled.

_{Here, V on1} is in an ON voltage higher than a value of the transistor _{T WS.} V _on1 is a voltage value output from the write scanning circuit 23 in a “Vth correction preparation period” and a “first Vth correction period” described later. _{Also, V off1} has a value lower than the ON voltage of transistor _{T WS, and} has a value lower than _{V on1.} V _off1 is a voltage value output from the writing scanning circuit 23 in “Vth correction pause period” and “light emission period” described later.

The power supply scanning circuit 24 can output two types of voltages (V _ini (fifth voltage), V _cc (sixth voltage)) in accordance with the control signal 21c output from the signal holding control circuit 21B. . Specifically, the power supply scanning circuit 24 supplies two types of voltages (V _ini , V _cc ) to the drive target pixel 11 via the drain line DSL connected to each pixel 11 of the display unit 10, Light emission and quenching of the organic EL element 12R and the like are controlled.

Here, V _ini is a voltage value lower than a voltage (V _el + V _ca ) obtained by adding the threshold voltage V _el of the organic EL element 12R and the like and the cathode voltage V _ca of the organic EL element 12R and the like. V _cc is a voltage value equal to or higher than the voltage (V _el + V _ca ).

The reverse bias horizontal drive circuit 25 can output two types of voltages (V _ofs2 , V _ss (first voltage)) in accordance with the control signal 21f output from the signal holding control circuit 21B. Specifically, the reverse bias horizontal drive circuit 25 is connected to each pixel 11 of the display unit 10 via a reverse bias signal line RBL (RBL _R , RBL _G , RBL _B ). Two types of voltages (V _ofs2 , V _ss ) are supplied to the pixel 11 selected by.

Here, V _ofs2 is lower than the threshold voltage V _el of the organic EL element 12R and the like, and has a voltage value equivalent to that of V _ofs1 . Further, V _ss has a lower voltage value than V _{ofs1 and} V _ofs2 . V _ss is a voltage value output from the reverse bias horizontal drive circuit 25 during a _dark spot correction period to be described later, and V _ofs2 is output from the reverse bias horizontal drive circuit 25 during a period for displaying an image. It is a voltage value.

The reverse bias scanning circuit 26 can output two types of voltages (V _on2 (second voltage), V _off2 ) in accordance with the control signal 21g output from the signal holding control circuit 21B. Specifically, the reverse bias scanning circuit 26 supplies two types of signals to the pixel 11 to be driven via the gate line RSL (RSL _R , RSL _G , RSL _B ) connected to each pixel 11 of the display unit 10. Voltages (V _on2 , V _off2 ) are supplied, and the reverse bias voltage application transistor _TRS is controlled.

_{Here, V on2} is in an ON voltage higher than a value of the transistor _{T RS. Also, V off2} has a value lower than the ON voltage of the transistor _{T RS, and} has a value lower than _{V on2.} V _on2 is a voltage value that is output to the dark spot correction period described later from the reverse bias scanning circuit 26, V _off2, the voltage value output from the reverse bias scanning circuit 26 in such a period when an image is displayed It is.

Next, with reference to FIG. 1 and FIG. 2, the connection relationship of each component is demonstrated. The gate line WSL led out from the write scanning circuit 23 is formed to extend in the row direction and is connected to the gate of the transistor _TWS . A drain line DSL drawn from the power supply scanning circuit 24 is also formed extending in the row direction, and is connected to the drain of the transistor _TDr . The signal line DTL drawn from the horizontal drive circuit 22 is formed extending in the column direction, and is connected to the drain of the transistor _TWS . The reverse bias signal line RBL led out from the reverse bias horizontal drive circuit 25 is formed to extend in the column direction, and is connected to the source or drain of the transistor _TRS . The reverse bias signal line RBL _R is connected to the source or drain of the transistor T _RS for the organic EL element 12R, and the reverse bias signal line RBL _G is connected to the source or drain of the transistor T _RS for the organic EL element 12G, and the reverse bias signal line RBL _B are connected to the source or drain of the transistor T _RS for the organic EL element 12B is. The gate line RSL drawn from the reverse bias scanning circuit 26 is formed to extend in the column direction, and is connected to the source or drain of the transistor _TRS . The gate line RSL _R is the gate of the transistor T _RS for the organic EL element 12R, the gate line RSL _G is the gate of the transistor T _RS for the organic EL element 12G, and the gate line RSL _B is the transistor T _RS for the organic EL element 12B. Are connected to each gate. The source of the transistor T _WS is connected to the gate of the transistor T _Dr for driving, to one end of the storage capacitor C _s. The source of the transistor T _Dr is connected to the other end of the storage capacitor C _s , the anode of the organic EL element 12R and the like, and the source or drain of the transistor T _RS which is not connected to the reverse bias signal line RBL. A cathode of the organic EL element 12R and the like is connected to the ground line GND.

Next, an example of the operation (operation from extinction to light emission) of the display device 1 of the present embodiment will be described. In the present embodiment, or the I-V characteristic changes over time, such as an organic EL element 12R, also the threshold voltage V _th and the mobility μ of the transistor T _Dr is or change over time, without receiving their effects In order to keep the light emission luminance of the organic EL element 12R and the like constant, the compensation operation for the variation of the IV characteristics of the organic EL element 12R and the like, and the variation of the threshold voltage _Vth and mobility μ of the transistor T _Dr A correction operation is incorporated.

FIG. 3 shows an example of various waveforms in the display device 1. 3 shows two kinds of voltage to the gate line WSL _{(V on1,} V _off1) is the drain line DSL to the two kinds of voltages _{(V cc,} V _ini) is, the signal line DTL to the two kinds of voltages _{(V sig} , V _ofs1 ) is applied. Further, FIG. 3 shows how the gate voltage V _g and the source voltage V _{s of} the transistor T _Dr change from moment to moment in response to voltage application to the gate line WSL, the drain line DSL, and the signal line DTL. ing.

(Vth correction preparation period)
First, preparation for Vth correction is performed. Specifically, when the voltage of the gate line WSL is V _off1 , the voltage of the signal line DTL is V _sig, and the voltage of the drain line DSL is V _cc (that is, the organic EL element 12R). The power supply scanning circuit 24 lowers the voltage of the drain line DSL from _Vcc to _Vini according to the control signal 21c (T ₁ ). Then, the source voltage Vs becomes V _ini and the organic EL element 12R and the like are quenched. Next, after the horizontal drive circuit 22 switches the voltage of the signal line DTL from V _sig to V _ofs1 in accordance with the control signal 21d, the write scanning circuit 23 _operates while the voltage of the drain line DSL is V _ini. in response to the control signal 21b increasing the voltage of the gate line WSL from _{V off1} to _{V on1 (T} 2). Then, the gate voltage _{V g} drops to _{V ofs1.} At this time, the power supply scanning circuit 24 and the horizontal drive circuit 22 are set so that the potential difference V _gs (= V _{ofs 1} −V _ini ) between the gate voltage V _g and the source voltage V _s becomes larger than the threshold voltage V _th of the transistor T _Dr. In this case, applied voltages (V _ini , V _ofs1 ) to the drain line DSL and the signal line DTL are set.

(First Vth correction period)
Next, _Vth is corrected. Specifically, while the voltage of the signal line DTL is V _ofs1 , the power supply scanning circuit 24 increases the voltage of the drain line DSL from V _ini to V _cc according to the control signal 21c (T ₃ ). Then, a current I _ds flows between the drain and source of the transistor T _Dr , and the source voltage V _s increases. Thereafter, V the voltage of the signal line DTL in response to the horizontal drive circuit 22 the control signal 21d before switching from _{V ofs1} to _{V sig,} the voltage of the gate line WSL from _{V on1} write scanning circuit 23 in response to the control signal 21b _Lower to _off1 (T ₄ ). Then, the gate of the transistor _TDr becomes floating, and the correction of _Vth is temporarily stopped.

(First Vth correction pause period)
During the period in which the Vth correction is paused (that is, while the voltage of the gate line WSL is V _off1 and the voltage of the drain line DSL is V _cc ), the row in which the previous Vth correction is performed. In another row (pixel) different from (pixel), the voltage of the signal line DTL is sampled. Specifically, the horizontal drive circuit 22, during the period in which the Vth correction is at rest, after switching the voltage of the signal line DTL from _{V ofs1} to _{V sig,} performs the operation of switching from _{V sig} to _{V ofs1,} writing While the voltage of the signal line DTL is V _sig , the scanning circuit 23 applies the voltage of the gate line WSL connected to another row (pixel) different from the row (pixel) subjected to the previous Vth correction. After raised to _{V on1} from V _off1, it switched from _{V on1} to _{V off1.} Accordingly, the horizontal drive circuit 22 sets the voltage of the signal line DTL to V _{ofs1 in} the first half of one cycle (period indicated by 1H in the figure) to execute Vth correction in a certain row (pixel), In order to perform sampling in (pixel), an operation is performed in which the voltage of the signal line DTL is set to V _{sig in} the second half of one cycle.

Note that when the Vth correction is insufficient, i.e., the gate of the transistor _{T Dr} - when the potential difference _{V gs} between the source is larger than the threshold voltage _{V th} of the transistor _{T Dr} is also in Vth correction stop period, previously In the row (pixel) subjected to the Vth correction, the current I _ds flows between the drain and source of the transistor T _Dr , the source voltage V _s rises, and the gate voltage V _g also rises due to the coupling through the storage capacitor Cs. To do.

(Second Vth correction period)
After the Vth correction pause period ends, _Vth is corrected again. Specifically, when the voltage of the drain line DSL is V _cc and the voltage of the signal line DTL is V _ofs1 and Vth correction is possible, the write scanning circuit 23 controls the control signal 21b. the voltage of the gate line WSL increased from _{V off1} to _{V on1 (T} 5), connects the gate of the transistor _{T Dr} to the signal line DTL in response to. At this time, when the source voltage V _s is lower than V _ofs1 −V _th (when Vth correction is not yet completed), until the transistor T _Dr is cut off (until the potential difference V _gs becomes V _th ). A current I _ds flows between the drain and source of the transistor T _Dr. Thus, increases the gate voltage _{V g} is next _{V ofs1,} the source voltage _{V s} is the result, the holding capacitor _{C s} is charged to _{V th,} the potential difference _{V gs} becomes _{V th.} Then, lowering the voltage of the signal line DTL horizontal drive circuit 22 before switching from the _{V ofs1} to _{V sig,} the voltage of the write scan circuit 23 is a gate line WSL from _{V on1} the _{V off1 (T} 6). Then, since the gate of the transistor T _Dr is in a floating state, the potential difference V _gs can be maintained as V _th regardless of the magnitude of the voltage of the signal line DTL. In this way, by setting the potential difference V _gs to V _{th, even} when the threshold voltage V _th of the transistor T _Dr varies from pixel circuit 13 to pixel circuit 13, the emission luminance of the organic EL element 12R and the like varies. Can be eliminated.

(Second Vth correction suspension period)
After that, during the rest period of Vth correction (that is, while the voltage of the gate line WSL is V _off1 and the voltage of the drain line DSL is V _cc ), the horizontal drive circuit 22 changes to the control signal 21d. Accordingly, the voltage of the signal line DTL is switched from V _ofs1 to V _sig .

(Writing / μ correction period)
After the second Vth correction pause period, writing and μ correction are performed. Specifically, while the voltage of the signal line DTL is _{V sig,} the voltage of the gate line WSL increased from _{V off1} to _{V on1} in response to a write scanning circuit 23 the control signal 21b _(T 7), the transistor The gate of T _Dr is connected to the signal line DTL. Then, the voltage of the gate of the transistor T _Dr becomes the voltage V _{sig of the} signal line DTL. At this time, the anode voltage of an organic EL element 12R is smaller than the threshold voltage _{V el} still such as organic EL devices 12R at this stage, the organic EL device 12R and the like is cut off. Therefore, the current I _ds flows to the element capacitance (not shown) such as the organic EL element 12R, and the element capacitance is charged. Therefore, the source voltage V _s increases by ΔV3, and the potential difference V _gs eventually becomes V _sig + V _th − ΔV3. In this way, μ correction is performed simultaneously with writing. Here, since ΔV3 increases as the mobility μ of the transistor T _Dr increases, variation in the mobility μ for each pixel can be eliminated by reducing the potential difference _Vgs by ΔV3 before light emission.

(Light emission)
Finally, reducing the voltage of the gate line WSL from _{V on1} the _{V off1} in response to a write scanning circuit 23 the control signal 21b _(T 8). Then, the gate of the transistor _{T Dr} is a floating, the drain of the transistor _{T Dr} - current _{I ds} flows between the source, the source voltage _{V s} rises. As a result, a voltage equal to or higher than the threshold voltage _Vel is applied to the organic EL element 12R and the like, and the organic EL element 12R and the like emit light with a desired luminance.

  In the display device 1 of the present embodiment, as described above, the pixel circuit 13 is controlled to be turned on / off in each pixel 11, and a driving current is injected into the organic EL element 12 </ b> R of each pixel 11. Light emission occurs due to recombination with electrons. This light is multiple-reflected between the anode and the cathode, passes through the cathode, etc., and is extracted outside. As a result, an image is displayed on the display unit 10.

  By the way, in the organic EL element 12R and the like described above, the thickness of the organic layer is very thin, from several nm to several tens of nm. Therefore, in the process of manufacturing the organic EL element 12R or the like, if particles of about 1 μm are mixed into the organic EL element 12R or the like, pinholes or the like may occur in the organic layer. When defects such as pinholes exist in the organic layer, an electrical short circuit is formed between the anode and the cathode, and all or part of the current that should flow through the organic layer may flow into the short circuit. is there. In such a case, the organic layer does not emit light, or the light emission luminance of the organic layer is lowered, and a dark spot pixel is generated.

  The generation of the dark dot pixels causes a decrease in yield. For this reason, it is necessary to suppress a decrease in yield by repairing the dark spot pixels. One method for repairing the dark spot pixel is to apply a reverse bias voltage to the organic EL element 12R or the like to increase the resistance or insulation of the defective portion of the organic EL element 12R or the like.

For example, in a display device including the pixel 100 having a 2Tr1C circuit configuration as shown in FIG. 13, in order to apply a reverse bias voltage to the organic EL element 110, the transistor T The voltage of the drain line DSL may be set to V _ini (<0) with both _WS and T _Dr turned on. At this time, since the pixel 100 is represented by the equivalent circuit shown in FIG. 14, a reverse bias voltage V _EL1 represented by the following equation can be applied to the organic EL element 110.
V _EL1 = (V _ini −V _ca ) × (R _EL / (R _EL + R _Dr ))

Here, R _Dr represents the ON resistance of the transistor T _Dr , R _EL represents the short resistance of the organic EL element 110, and V _ca represents the cathode voltage of the organic EL element 110.

By the way, R _Dr is very large compared with R _EL and the partial pressure ratio of the organic EL element 110 is small. Therefore, a voltage (V _ini ) that is normally applied to the drain line DSL when driving each pixel 100 is applied to the organic EL element 110 by applying the voltage (V _ini ) to the drain line DSL of the pixel 100 where the dark spot has occurred. Even if a reverse bias voltage is applied, the defective portion of the organic EL element 110 may not be increased in resistance or insulation.

On the other hand, in the display device 1 of this embodiment, as shown in FIG. 2, the circuit arrangement of 2Tr1C 13, further are added transistor T _RS for applying a reverse bias voltage, the display of the image- Applying a reverse bias voltage to the organic EL element 12R or the like from the reverse bias signal line RBL (RBL _R , RBL _G , RBL _B ) connected to the transistor T _RS instead of from the drain line DSL used for non-display. Can be done.

As a result, in the pixels 11R, 11G, and 11B where the _dark spots occur, for example, as illustrated in FIG. 4, the voltage of the gate line WSL is V _off1 and the voltage of the drain line DSL is V _ini. cage, and when the voltage of the signal line DTL is _{V ofs1} (i.e., when the transistors _{T WS, T Dr} are both turned off), the reverse bias the horizontal driving circuit 25 in response to the control signal 21f opposite The voltage of the bias signal line RBL (RBL _R , RBL _G , RBL _B ) is set to V _ss , and the reverse bias scanning circuit 26 determines the gate line RSL (RSL _R , RSL _G , RSL _B ) according to the control signal 21 g. _Is set to V _on2 (T ₁₀ ). After that, when a predetermined period has passed, the reverse bias horizontal drive circuit 25 sets the voltage of the reverse bias signal line RBL (RBL _R , RBL _G , RBL _B ) to V _ofs2 according to the control signal 21f (T _11). ).

In FIG. 4, before the reverse bias scanning circuit 26 sets the voltage of the gate line RSL (RSL _R , RSL _G , RSL _B ) to V _on2 , the reverse bias horizontal drive circuit 25 previously outputs the reverse bias signal. The case where the voltage of the line RBL (RBL _R , RBL _G , RBL _B ) is set to V _ss is illustrated, but the reverse bias scanning circuit 26 is configured as the gate line RSL (RSL _R , RSL _G , RSL _B ). The reverse bias horizontal drive circuit 25 sets the voltage of the reverse bias signal line RBL (RBL _R , RBL _G , RBL _B ) to V _ss at the same time (or after the voltage is set to V _on2 ). Also good. FIG. 4 illustrates the case where the reverse bias voltage is intermittently applied to the organic EL element 12R and the like, but the reverse bias voltage may be continuously applied.

When the voltage of the gate line RSL is set to V _on2 as described above, the pixels 11R, 11G, and 11B are represented by the equivalent circuit shown in FIG. Accordingly, the reverse bias voltage V _EL2 represented by the following expression is applied to the organic EL element 12R and the like. In the following equation, R _RS is the on-resistance of the transistor T _RS .
V _EL2 = (V _ss −V _ca ) × (R _EL / (R _EL + R _RS ))

Here, V _ss is lower than V _ofs output from the horizontal drive circuit 22. Therefore, as compared with the case where a reverse bias voltage is applied to the organic EL element 12R or the like by turning on the transistors _{T Dr} with the voltage of the signal line DTL to _{V ofs1,} a large reverse bias voltage to the organic EL device 12R and the like Can be applied. As a result, a reverse bias voltage having a magnitude suitable for increasing the resistance or insulation of a defective portion such as the organic EL element 12R can be applied, so that the dark spot pixel can be repaired more reliably.

[Modification]
In the above embodiment, when the dark spot pixel is repaired, the single voltage V _ss is applied to the reverse bias signal lines RBL _R , RBL _G , RBL _B , but the reverse bias signal lines RBL _R , RBL _G , RBL are applied. Different voltages may be applied for each _B. In such a case, different reverse bias voltages can be applied to the organic EL elements 12R, 12G, and 12B.

In general, in the organic EL elements 12R, 12G, and 12B, the organic layer has a thickness corresponding to the wavelength of the emission color, and the optimum reverse bias voltage for repairing the dark spot pixel depends on the thickness of the organic layer. Are different. For example, as shown in FIG. 6, the optimum voltage _{V R} of the organic EL element 12R that emits red light, the optimum voltage of the organic EL element 12B that emits optimum voltage _{V G} and blue light of the organic EL element 12G that emits green light greater than V _B, optimum voltage _{V G} of the organic EL element 12G is larger than the optimum voltage _{V B} of the organic EL element 12B that emits blue light. Therefore, when a single voltage V _ss is applied to the reverse bias signal lines RBL _R , RBL _G , RBL _B uniformly regardless of the thickness of the organic layer as in the above embodiment, a certain organic layer For this reason, there is a possibility that the reverse bias voltage does not have the optimum magnitude for repairing the dark spot pixel.

On the other hand, when different voltages are applied to the reverse bias signal lines RBL _R , RBL _G , and RBL _B as in this modification, it is optimal for repairing the dark spot pixels according to the thickness of the organic layer. A reverse bias voltage (V _R , V _G , V _B ) having a large magnitude can be applied to the organic EL elements 12R, 12G, 12B. Thereby, it is possible to eliminate the dark spot pixels by repair.

Note that it is not preferable to greatly exceed the reverse bias voltage optimum for repairing the dark spot pixels. For example, as shown in FIG. 6, when the significant voltage greater than V _B (for example, a voltage of about V _G) is applied to the organic EL element 12B is made often destroy the organic layer, This is because the dark spot pixels cannot be eliminated.

(Modules and application examples)
Hereinafter, application examples of the display device 1 described in the above embodiment will be described. The display device 1 according to the above embodiment is a television device, a digital camera, a notebook personal computer, a mobile terminal device such as a mobile phone, or a video camera, such as an externally input video signal or an internally generated video signal. The present invention can be applied to display devices for electronic devices in various fields that display images or videos.

(module)
The display device 1 according to the above-described embodiment is incorporated into various electronic devices such as application examples 1 to 5 described later, for example, as a module as illustrated in FIG. In this module, for example, an area 210 exposed from a member (not shown) that seals the display unit 10 is provided on one side of the substrate 2, and the timing control circuit 21, the horizontal drive circuit 22, The wiring lines of the write scanning circuit 23 and the power supply scanning circuit 24 are extended to form external connection terminals (not shown). The external connection terminal may be provided with a flexible printed circuit (FPC) 220 for signal input / output.

(Application example 1)
FIG. 8 illustrates an appearance of a television device to which the display device 1 of the above embodiment is applied. The television apparatus has, for example, a video display screen unit 300 including a front panel 310 and a filter glass 320, and the video display screen unit 300 is configured by the display device 1 according to the above embodiment. .

(Application example 2)
FIG. 9 shows the appearance of a digital camera to which the display device 1 of the above embodiment is applied. The digital camera includes, for example, a flash light emitting unit 410, a display unit 420, a menu switch 430, and a shutter button 440. The display unit 420 is configured by the display device 1 according to the above embodiment. Yes.

(Application example 3)
FIG. 10 shows the appearance of a notebook personal computer to which the display device 1 of the above embodiment is applied. The notebook personal computer has, for example, a main body 510, a keyboard 520 for inputting characters and the like, and a display unit 530 for displaying an image. The display unit 530 is a display device according to the above embodiment. 1.

(Application example 4)
FIG. 11 shows the appearance of a video camera to which the display device 1 of the above embodiment is applied. This video camera has, for example, a main body 610, a subject photographing lens 620 provided on the front side surface of the main body 610, a start / stop switch 630 at the time of photographing, and a display 640. Reference numeral 640 denotes the display device 1 according to the above embodiment.

(Application example 5)
FIG. 12 shows the appearance of a mobile phone to which the display device 1 of the above embodiment is applied. For example, the mobile phone is obtained by connecting an upper housing 710 and a lower housing 720 with a connecting portion (hinge portion) 730, and includes a display 740, a sub-display 750, a picture light 760, and a camera 770. Yes. The display 740 or the sub-display 750 is configured by the display device 1 according to the above embodiment.

  While the present invention has been described with the embodiment and application examples, the present invention is not limited to the above-described embodiment and the like, and various modifications can be made.

  For example, in the above-described embodiment, the case where the display device 1 is an active matrix type has been described. However, the configuration of the pixel circuit 13 for driving the active matrix is not limited to that described in the above-described embodiment, and is necessary. Depending on the case, a capacitor or a transistor may be added to the pixel circuit 13. In that case, a necessary drive circuit may be added in addition to the above-described horizontal drive circuit 22, write scan circuit 23, and power supply scan circuit 24 according to the change of the pixel circuit 13.

  In the above embodiment and the like, the signal holding control circuit 21B controls the driving of the horizontal driving circuit 22, the writing scanning circuit 23, and the power supply scanning circuit 24. However, other circuits control the driving of these circuits. May be. The control of the horizontal drive circuit 22, the write scanning circuit 23, and the power supply scanning circuit 24 may be performed by hardware (circuit) or software (program).

It is a block diagram showing an example of the display apparatus which concerns on one embodiment of this invention. It is a block diagram showing an example of the internal structure of the pixel of FIG. It is a wave form diagram for demonstrating an example of the light emission operation | movement of the display apparatus of FIG. It is a wave form diagram for demonstrating an example of the operation | movement of dark spot correction | amendment of the display apparatus of FIG. It is an equivalent circuit diagram for demonstrating the reverse bias at the time of dark spot correction | amendment. It is a characteristic view showing an example of the relationship between a reverse bias voltage and the number of dark spots for each luminescent color of an organic EL element. It is a top view showing schematic structure of the module containing the display apparatus of each said embodiment. It is a perspective view showing the external appearance of the application example 1 of the display apparatus of the said embodiment. (A) is a perspective view showing the external appearance seen from the front side of the application example 2, (B) is a perspective view showing the external appearance seen from the back side. 12 is a perspective view illustrating an appearance of application example 3. FIG. 14 is a perspective view illustrating an appearance of application example 4. FIG. (A) is a front view of the application example 5 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, and (E) is a right side view, (F) is a top view and (G) is a bottom view. It is a block diagram showing an example of the internal structure of the pixel of the conventional display apparatus. It is an equivalent circuit diagram for demonstrating the reverse bias at the time of dark spot correction | amendment in the structure of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Display apparatus, 10 ... Display part, 11, 11R, 11G, 11B ... Pixel, 12R, 12G, 12B ... Organic EL element, 13 ... Pixel circuit, 20 ... Peripheral circuit part, 21 ... Timing control circuit, 21A ... Display signal generating circuit, 21B ... display signal holding control circuit, 22 ... The horizontal drive circuit, 23 ... writing scanning circuit, 24 ... power supply scanning circuit, 25 ... reverse bias the horizontal driving circuit, 26 ... reverse bias scanning circuit, C _s ... storage capacitor, DSL ... drain line, DTL ... signal line, I _{ds ... current, T Dr, T WS ...} transistors, V g _... gate voltage, V _{gs ...} potential, V s _... source voltage, V _{th ...} threshold voltage, WSL ... gate lines.

Claims (6)

A display unit having an organic light emitting element and a pixel circuit for each pixel;
A drive unit for driving the pixel circuit based on a video signal,
The pixel circuit includes a first transistor, a second transistor, a third transistor, and a storage capacitor.
The driving unit is set to a first driving unit, a second driving unit, a control unit, a first wiring, a second wiring, a third wiring, a fourth wiring, a fifth wiring, and a reference voltage. And a sixth wiring to be
A gate of the first transistor is connected to the first wiring;
A drain or a source of the first transistor is connected to the third wiring;
Of the drain and source of the first transistor, the one not connected to the third wiring is connected to the gate of the second transistor and one end of the storage capacitor,
A drain or a source of the second transistor is connected to the second wiring;
Of the drain and source of the second transistor, the one not connected to the second wiring is connected to the drain or source of the third transistor, the other end of the storage capacitor, and the anode of the organic light emitting element,
Of the drain and source of the third transistor, the one not connected to the anode of the organic light emitting device is connected to the first driving unit via the fourth wiring,
A gate of the third transistor is connected to the second driver through the fifth wiring;
A cathode of the organic light emitting device is connected to the sixth wiring;
The first driving unit can output at least a first voltage lower than a threshold voltage of the organic light emitting element to the fourth wiring,
The second driving unit can output at least a second voltage equal to or higher than an ON voltage of the third transistor to the fifth wiring,
The control unit instructs the first driving unit and the second driving unit to set the voltage of the fourth wiring to the first voltage and the voltage of the fifth wiring to the second voltage. A display device that outputs a control signal. The driving unit further includes a third driving unit, a fourth driving unit, and a fifth driving unit,
The third driving unit can output at least a third voltage lower than the on-voltage of the first transistor and a fourth voltage equal to or higher than the on-voltage of the first transistor to the first wiring.
The fourth driving unit includes at least a fifth voltage lower than the sum of the threshold voltage of the organic light emitting element and the reference voltage, and a sixth voltage equal to or higher than the sum of the threshold voltage of the organic light emitting element and the reference voltage. Can be output to the second wiring,
The fifth drive unit can output at least a seventh voltage lower than a threshold voltage of the organic light emitting element and an eighth voltage having a magnitude corresponding to the video signal to the third wiring. Item 4. The display device according to Item 1.   The display device according to claim 1, wherein the control unit outputs the control signal when the first transistor and the second transistor are off. The organic light emitting device has a laminated structure in which an anode, an organic light emitting layer formed of a material corresponding to the emission color of the organic light emitting device, and a cathode are laminated in this order,
The display device according to claim 1, wherein the first driving unit is capable of outputting a voltage having a magnitude corresponding to a thickness of the organic light emitting layer to the fourth wiring as the first voltage. A display unit having an organic light emitting element and a pixel circuit for each pixel;
A drive unit for driving the pixel circuit based on a video signal,
The pixel circuit includes a first transistor, a second transistor, a third transistor, and a storage capacitor.
The driving unit includes a first driving unit, a second driving unit, a first wiring, a second wiring, a third wiring, a fourth wiring, a fifth wiring, and a sixth voltage set to a reference voltage. Wiring and
A gate of the first transistor is connected to the first wiring;
A drain or a source of the first transistor is connected to the third wiring;
Of the drain and source of the first transistor, the one not connected to the third wiring is connected to the gate of the second transistor and one end of the storage capacitor,
A drain or a source of the second transistor is connected to the second wiring;
Of the drain and source of the second transistor, the one not connected to the second wiring is connected to the drain or source of the third transistor, the other end of the storage capacitor, and the anode of the organic light emitting element,
Of the drain and source of the third transistor, the one not connected to the anode of the organic light emitting device is connected to the first driving unit via the fourth wiring,
A gate of the third transistor is connected to the second driver through the fifth wiring;
A cathode of the organic light emitting device is connected to the sixth wiring;
The first driving unit can output at least a first voltage lower than a threshold voltage of the organic light emitting element to the fourth wiring,
The second driving unit includes at least the first driving unit and the second driving unit of the display device capable of outputting a second voltage equal to or higher than an ON voltage of the third transistor to the fifth wiring. A method for driving a display device, wherein a voltage of a fourth wiring is set to the first voltage and a voltage of the fifth wiring is set to the second voltage. A display device,
The display device
A display unit having an organic light emitting element and a pixel circuit for each pixel;
A drive unit for driving the pixel circuit based on a video signal,
The pixel circuit includes a first transistor, a second transistor, a third transistor, and a storage capacitor.
The driving unit is set to a first driving unit, a second driving unit, a control unit, a first wiring, a second wiring, a third wiring, a fourth wiring, a fifth wiring, and a reference voltage. And a sixth wiring to be
A gate of the first transistor is connected to the first wiring;
A drain or a source of the first transistor is connected to the third wiring;
Of the drain and source of the first transistor, the one not connected to the third wiring is connected to the gate of the second transistor and one end of the storage capacitor,
A drain or a source of the second transistor is connected to the second wiring;
Of the drain and source of the second transistor, the one not connected to the second wiring is connected to the drain or source of the third transistor, the other end of the storage capacitor, and the anode of the organic light emitting element,
Of the drain and source of the third transistor, the one not connected to the anode of the organic light emitting device is connected to the first driving unit via the fourth wiring,
A gate of the third transistor is connected to the second driver through the fifth wiring;
A cathode of the organic light emitting device is connected to the sixth wiring;
The first driving unit can output at least a first voltage lower than a threshold voltage of the organic light emitting element to the fourth wiring,
The second driving unit can output at least a second voltage equal to or higher than an ON voltage of the third transistor to the fifth wiring,
The control unit instructs the first driving unit and the second driving unit to set the voltage of the fourth wiring to the first voltage and the voltage of the fifth wiring to the second voltage. Electronic devices that output control signals.

Images