JP2013122482A - Display device, drive method therefor, and electronic device - Google Patents

Abstract

A display device capable of reducing a decrease in light emission luminance caused by a depletion shift, a driving method thereof, and an electronic device including the display device are provided.
A display device includes a display unit having a light emitting element and a pixel circuit for each pixel, and a drive unit that drives the pixel circuit based on a video signal. The pixel circuit includes a driving transistor that drives the light emitting element, and a writing transistor that controls application of a signal voltage corresponding to the video signal at the gate of the driving transistor. The driving unit can apply at least two kinds of voltages to the gate of the writing transistor as voltages for turning off the writing transistor.
[Selection] Figure 3

Description

  The present technology relates to a display device including a light emitting element such as an organic EL (Electro Luminescence) element for each pixel and a driving method thereof. The present technology also relates to an electronic device including the display device.

  In recent years, in the field of display devices that perform image display, display devices that use current-driven light-emitting elements, such as organic EL elements, whose light emission luminance changes according to the value of a flowing current have been developed as light-emitting elements for pixels. Is being promoted. 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), so that it can be made thinner and brighter than a liquid crystal display device that requires a light source. . In particular, when the active matrix method is used as the driving method, each pixel can be lighted on hold and power consumption can be reduced. Therefore, organic EL display devices are expected to become the mainstream of next-generation flat panel displays.

  By the way, in general, the current-voltage (IV) characteristics of the organic EL element deteriorate (deteriorate with time) as time elapses. In a pixel circuit that current-drives an organic EL element, when the IV characteristic of the organic EL element changes with time, the voltage division ratio between the organic EL element and the drive transistor connected in series to the organic EL element changes. The gate-source voltage of the transistor also changes. As a result, since the current value flowing through the drive transistor changes, the current value flowing through the organic EL element also changes, and the light emission luminance also changes according to the current value.

  In addition, the threshold voltage and mobility of the driving transistor may change over time, and the threshold voltage and mobility may vary from pixel circuit to pixel circuit due to variations in the manufacturing process. When the threshold voltage and mobility of the driving transistor differ from pixel circuit to pixel circuit, the current value flowing through the driving transistor varies from pixel circuit to pixel circuit. Therefore, even if the same voltage is applied to the gate of the driving transistor, the organic EL element emits light. The brightness varies, and the uniformity of the screen is lost.

  Therefore, even if the IV characteristic of the organic EL element changes with time or the threshold voltage or mobility of the driving transistor changes with time, the light emission luminance of the organic EL element is kept constant without being affected by them. In order to maintain the display device, a display device has been developed that incorporates a compensation function for variation in the IV characteristics of the organic EL element and a correction function for variation in the threshold voltage and mobility of the driving transistor (for example, Patent Document 1). reference).

JP 2008-083272 A

  By the way, the mobility correction period is determined by the width of the write pulse applied to the gate of the write transistor connected to the gate of the drive transistor (that is, the ON period of the write transistor). However, the write pulse is not a perfect rectangular wave but has a dullness as shown in FIG. Therefore, in practice, the mobility correction period can vary depending on the threshold voltage of the writing transistor, as shown in FIG. When the mobility correction period varies, as shown in FIG. 11, the magnitude of the current Ids that flows through the organic EL element when the organic EL element emits light changes, and the emission luminance also changes accordingly. Therefore, it is preferable that the mobility correction period does not vary as much as possible.

  The threshold voltage of the write transistor changes (decreases), for example, when a negative bias is continuously applied to the gate-source voltage of the write transistor. That is, the threshold voltage characteristic of the write transistor shifts from enhancement to depletion. Here, the negative bias refers to a bias state in which the gate potential is negative with respect to the source potential. Enhancement refers to a state where a channel is formed when a write pulse is applied to the gate and a current flows between the source and drain. Depletion refers to a state in which a current flows between the source and drain without applying a write pulse to the gate.

  Usually, a negative bias is applied to the write transistor during the light emission period and extinction period of the organic EL element. When a negative bias is continuously applied to the gate-source voltage of the write transistor, a depletion shift occurs in the threshold voltage characteristic of the write transistor. For example, as shown in FIG. 10B, the threshold voltage is changed from Vth1 to Vth2. Fluctuates (decreases). As a result, the mobility correction period becomes longer by Δt1 + Δt2 than the initial period. As a result, as shown in FIG. 11, when the organic EL element emits light, the current Ids flowing through the organic EL element is reduced by ΔIds, and the emission luminance is also reduced accordingly. That is, the light emission luminance decreases with the passage of the use period of the organic EL display device.

  The present technology has been made in view of such problems, and an object of the present technology is to provide a display device capable of reducing a decrease in light emission luminance due to a depletion shift, a driving method thereof, and an electronic device including the display device. To provide equipment.

  The display device of the present technology includes a display unit having a light emitting element and a pixel circuit for each pixel, and a drive unit that drives the pixel circuit based on a video signal. The pixel circuit includes a driving transistor that drives the light emitting element, and a writing transistor that controls application of a signal voltage corresponding to the video signal at the gate of the driving transistor. The driving unit can apply at least two kinds of voltages to the gate of the writing transistor as voltages for turning off the writing transistor. An electronic apparatus of the present technology includes the display device described above.

  The display device driving method of the present technology is a driving method of a display device including a light emitting element and a pixel circuit for each pixel. The pixel circuit includes a driving transistor that drives the light emitting element, and a writing transistor that controls application of a signal voltage corresponding to the video signal at the gate of the driving transistor. The display device driving method of the present technology includes a step of applying at least two kinds of voltages to the gate of the writing transistor as voltages for turning off the writing transistor in the display device having such a configuration.

  In the display device, the driving method thereof, and the electronic device of the present technology, at least two kinds of voltages are applied to the gate of the writing transistor as voltages for turning off the writing transistor. Thus, for example, a voltage at which the negative bias of the writing transistor becomes relatively small, zero volts, or a positive bias that does not turn on the writing transistor can be applied. As a result, the depletion shift of the threshold voltage characteristic of the write transistor can be reduced.

  According to the display device, the driving method thereof, and the electronic device of the present technology, the depletion shift of the threshold voltage characteristic of the writing transistor can be reduced, so that the reduction in the light emission luminance due to the depletion shift can be reduced. Can do.

1 is a schematic configuration diagram of a display device according to an embodiment of the present technology. It is a figure showing an example of the circuit structure of the pixel of FIG. It is a wave form diagram for demonstrating an example of operation | movement of the display apparatus of FIG. 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 light-emitting device of each 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 figure explaining an example of the pulse waveform applied to the gate of a writing transistor. It is a figure explaining an example of the relationship between the length of a mobility correction | amendment period, and the electric current value which flows into an organic EL element.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the invention will be described in detail with reference to the drawings. The description will be given in the following order.

1. Embodiment 2. FIG. Modules and application examples

<1. Embodiment>
[Constitution]
FIG. 1 illustrates a schematic configuration of a display device 1 according to an embodiment of the present technology. The display device 1 includes a display panel 10 and a drive circuit 20 that drives the display panel 10 based on a video signal 20A input from the outside. The drive circuit 20 includes, for example, a timing generation circuit 21, a video signal processing circuit 22, a signal line drive circuit 23, a scanning line drive circuit 24, and a power supply line drive circuit 25.

(Display panel 10)
The display panel 10 has a plurality of pixels 11 two-dimensionally arranged over the entire display area 10 </ b> A of the display panel 10. The display panel 10 displays an image based on the video signal 20 </ b> A input from the outside when each pixel 11 is driven in an active matrix by the drive circuit 20. FIG. 2 illustrates an example of a circuit configuration of the pixel 11. The pixel 11 includes, for example, a pixel circuit 12 and an organic EL element 13. The organic EL element 13 has, for example, a configuration in which an anode electrode, an organic layer, and a cathode electrode are sequentially stacked.

  For example, the pixel circuit 12 includes a drive transistor Tr1, a write transistor Tr2, and a storage capacitor Cs, and has a circuit configuration of 2Tr1C. The write transistor Tr2 controls application of a signal voltage corresponding to the video signal to the gate of the drive transistor Tr1. Specifically, the write transistor Tr2 samples a voltage of a signal line DTL described later and writes it to the gate of the drive transistor Tr1. The drive transistor Tr1 drives the organic EL element 13. Specifically, the drive transistor Tr1 controls the current flowing through the organic EL element 13 in accordance with the magnitude of the voltage written by the write transistor Tr2. The holding capacitor Cs holds a predetermined voltage between the gate and source of the driving transistor Tr1. Note that the pixel circuit 12 may have a circuit configuration different from the above-described 2Tr1C circuit configuration.

  The drive transistor Tr1 and the write transistor Tr2 are formed of, for example, an n-channel MOS thin film transistor (TFT (Thin Film Transistor)). Note that the type of TFT is not particularly limited, and may be, for example, an inverted staggered structure (so-called bottom gate type) or a staggered structure (top gate type). The drive transistor Tr1 or the write transistor Tr2 may be a p-channel MOS type TFT.

  The display panel 10 includes a plurality of scanning lines WSL extending in the row direction, a plurality of signal lines DTL extending in the column direction, and a plurality of power supply lines DSL extending in the row direction. Pixels 11 are provided in the vicinity of intersections between the signal lines DTL and the scanning lines WSL. Each signal line DTL is connected to an output terminal (not shown) of a signal line drive circuit 23 described later and the source or drain of the write transistor Tr2. Each scanning line WSL is connected to an output terminal (not shown) of a scanning line driving circuit 24 described later and a gate of the writing transistor Tr2. Each power supply line DSL is connected to an output terminal (not shown) of a power supply that outputs a fixed voltage and the source or drain of the drive transistor Tr1.

  The gate of the writing transistor Tr2 is connected to the scanning line WSL. The source or drain of the write transistor Tr2 is connected to the signal line DTL, and the terminal not connected to the signal line DTL among the source and drain of the write transistor Tr2 is connected to the gate of the drive transistor Tr1. The source or drain of the drive transistor Tr1 is connected to the power supply line DSL, and the terminal not connected to the power supply line DSL among the source and drain of the drive transistor Tr1 is connected to the anode of the organic EL element 13. One end of the storage capacitor Cs is connected to the gate of the drive transistor Tr1, and the other end of the storage capacitor Cs is connected to the source of the drive transistor Tr1 (terminal on the organic EL element 13 side in FIG. 2). That is, the storage capacitor Cs is inserted between the gate and source of the drive transistor Tr1. The organic EL element 13 has an element capacitance Coled.

  The display panel 10 further includes a cathode line CTL connected to the cathode of the organic EL element 13 as shown in FIG. The cathode line CTL is electrically connected to an external circuit (not shown) having a reference potential (for example, ground potential). The cathode line CTL is, for example, a sheet-like electrode formed over the entire display area 10A. The cathode line CTL may be a strip-like electrode formed in a strip shape corresponding to a pixel row or a pixel column. The display panel 10 further includes, for example, a frame region 10B that does not display an image at the periphery of the display region 10A. The frame region 10B is covered with, for example, a light shielding member.

(Drive circuit 20)
Next, the drive circuit 20 will be described. As described above, the drive circuit 20 includes, for example, the timing generation circuit 21, the video signal processing circuit 22, the signal line drive circuit 23, the scanning line drive circuit 24, and the power supply line drive circuit 25. The timing generation circuit 21 controls each circuit in the drive circuit 20 to operate in conjunction with each other. The timing generation circuit 21 outputs a control signal 21A to each circuit described above, for example, in response to (in synchronization with) the synchronization signal 20B input from the outside.

  For example, the video signal processing circuit 22 performs predetermined correction on a digital video signal 20A input from the outside, and outputs the video signal 22A obtained thereby to the signal line drive circuit 23. Examples of the predetermined correction include gamma correction and overdrive correction.

  For example, the signal line drive circuit 23 applies an analog signal voltage corresponding to the video signal 22A input from the video signal processing circuit 22 to each signal line DTL in response to (in synchronization with) the input of the control signal 21A. To do. The signal line drive circuit 23 can output, for example, two types of voltages (Vofs, Vsig). Specifically, the signal line driving circuit 23 supplies two types of voltages (Vofs, Vsig) to the pixel 11 selected by the scanning line driving circuit 24 via the signal line DTL. Here, Vsig is a voltage value corresponding to the video signal 20A. Vofs is a constant voltage unrelated to the video signal 20A. The minimum voltage of Vsig is a voltage value lower than Vofs, and the maximum voltage of Vsig is a voltage value higher than Vofs.

  For example, the scanning line driving circuit 24 sequentially selects a plurality of scanning lines WSL for each predetermined unit in response to (in synchronization with) the input of the control signal 21A. The scanning line driving circuit 24 can output, for example, three types of voltages (Von, Voff1, Voff2). Specifically, the scanning line driving circuit 24 supplies three types of voltages (Von, Voff1, Voff2) to the pixel 11 to be driven via the scanning line WSL, and performs on / off control of the writing transistor Tr2. It has become.

  Here, Von has a value equal to or higher than the ON voltage of the write transistor Tr2. Von is a peak value of a write pulse output from the scanning line driving circuit 24 in a “Vth correction period” or a “write / μ correction period” described later. Voff1 and Voff2 are values lower than the on-voltage of the write transistor Tr2, and are lower than Von. Voff2 is a voltage having a higher peak value than Voff1, and is, for example, a voltage in which the negative bias of the write transistor Tr2 becomes relatively smaller than when Voff1 is applied to the gate of the write transistor Tr2. Note that Voff2 may be zero volts or a voltage at which a positive bias that does not turn on the write transistor Tr2 is applied to the write transistor Tr2.

  The scanning line driving circuit 24 can apply two types of voltages (Voff1, Voff2) to the gate of the writing transistor Tr2 as voltages for turning off the writing transistor Tr2. At this time, the scanning line driving circuit 24 applies the two kinds of voltages (Voff1, Voff2) to the gate of the write transistor Tr2 as voltages for turning off the write transistor Tr2, and thereby the threshold voltage characteristics of the write transistor Tr2 are changed. The depletion shift is reduced.

  Voff1 is a peak value of a write pulse output from the scanning line driving circuit 24 in a “Vth correction pause period” or “light emission period” described later. Voff2 is a peak value of a write pulse output from the scanning line driving circuit 24 in a “Vth correction preparation period” to be described later. Accordingly, the scanning line driving circuit 24 applies two kinds of voltages (Voff1, Voff2) as voltages for turning off the writing transistor Tr2 to the gate of the writing transistor Tr2 during the extinction period of the organic EL element 13. It has become.

  For example, the power supply line drive circuit 25 sequentially selects a plurality of power supply lines DSL for each predetermined unit in response to (in synchronization with) the input of the control signal 21A. The power line drive circuit 25 can output, for example, two types of voltages (Vcc, Vss). Specifically, the power supply line drive circuit 25 supplies two types of voltages (Vcc, Vss) to the pixels 11 selected by the scanning line drive circuit 24 via the power supply line DSL. Here, Vss is a voltage value lower than a voltage (Vel + Vcath) obtained by adding the threshold voltage Vel of the organic EL element 13 and the cathode voltage Vcath of the organic EL element 13. Vcc is a voltage value equal to or higher than the voltage (Vel + Vcath).

[Operation]
Next, the operation (operation from quenching to light emission) of the display device 1 of the present embodiment will be described. In the present embodiment, even if the IV characteristic of the organic EL element 13 changes with time or the threshold voltage or mobility of the driving transistor Tr1 changes with time, the organic EL element is not affected by the change. In order to keep the light emission luminance of 13 constant, a compensation operation for variation of the IV characteristic of the organic EL element 13 and a correction operation for variation of the threshold voltage and mobility of the drive transistor Tr1 are incorporated.

  FIG. 3 shows an example of various waveforms in the display device 1. FIG. 3 shows a state in which a binary voltage change occurs in the power supply line DSL and the signal line DTL, and a state in which a ternary voltage change occurs in the scanning line WSL. ing. Further, FIG. 3 shows that the gate voltage Vg and the source voltage Vs of the drive transistor Tr1 change from moment to moment in accordance with the voltage change of the scanning line WSL, the power supply line DSL, and the signal line DTL. .

(Vth correction preparation period)
First, preparation for Vth correction is performed. Specifically, when the voltage of the scanning line WSL is Voff1, the voltage of the signal line DTL is Vofs, and the voltage of the power supply line DSL is Vcc (that is, the organic EL element 13 emits light). The power line drive circuit 25 lowers the voltage of the power line DSL from Vcc to Vss in response to the control signal 21A (T1). In synchronization with the voltage of the power supply line DSL decreasing from Vcc to Vss, the scanning line driving circuit 24 increases the voltage of the scanning line WSL from Voff1 to Voff2 (T1). Then, the source voltage Vs decreases to Vss, and the organic EL element 13 is quenched. At this time, the gate voltage Vg also decreases due to coupling via the storage capacitor Cs.

  By the way, the scanning line drive circuit 24 increases the voltage of the scanning line WSL from Voff1 to Voff2 in accordance with the control signal 21A in all or a part of the Vth correction preparation period. Is increased from Voff1 to Voff2. That is, the scanning line driving circuit 24 reduces the depletion shift of the threshold voltage characteristic of the write transistor Tr2 by applying a voltage (Voff2) higher than Voff1 to the gate of the write transistor Tr2.

  FIG. 3 shows an example in which the voltage fluctuation of the scanning line WSL (voltage fluctuation from Voff1 to Voff2) and the voltage fluctuation of the signal line DSL (voltage fluctuation from Vcc to Vss) are simultaneously performed. However, these may not be performed simultaneously. For example, the scanning line driving circuit 24 may increase the voltage of the scanning line WSL from Voff1 to Voff2 after the voltage of the power supply line DSL has dropped from Vcc to Vss.

  Next, while the voltage of the power supply line DSL is Vss and the voltage of the signal line DTL is Vofs, the scanning line driving circuit 24 changes the voltage of the scanning line WSL to Voff2 according to the control signal 21A. To Von (T2). Then, the gate voltage Vg decreases to Vofs. At this time, the potential difference Vgs between the gate voltage Vg and the source voltage Vs may be smaller than, equal to, or larger than the threshold voltage of the driving transistor Tr2.

(Vth correction period)
Next, Vth is corrected. Specifically, while the voltage of the signal line DTL is Vofs and the voltage of the scanning line WSL is Von, the power supply line driving circuit 25 sets the power supply line DSL according to the control signal 21A. The voltage is raised from Vss to Vcc (T3). Then, a current Ids flows between the drain and source of the drive transistor Tr1, and the source voltage Vs increases. At this time, when the source voltage Vs is lower than Vofs−Vth (when the Vth correction is not yet completed), until the drive transistor Tr1 is cut off (until the potential difference Vgs becomes Vth), A current Ids flows between the drain and the source. As a result, the gate voltage Vg becomes Vofs, the source voltage Vs rises, and as a result, the storage capacitor Cs is charged to Vth, and the potential difference Vgs becomes Vth.

  Thereafter, the signal line driving circuit 23 changes the voltage of the scanning line WSL from Von to Voff1 according to the control signal 21A before the scanning line driving circuit 24 switches the voltage of the signal line DTL from Vofs to Vsig according to the control signal 21A. (T4). Then, since the gate of the drive transistor Tr1 is in a floating state, the potential difference Vgs can be maintained as Vth regardless of the magnitude of the voltage of the signal line DTL. As described above, by setting the potential difference Vgs to Vth, even when the threshold voltage Vth of the drive transistor Tr1 varies for each pixel circuit 12, it is possible to eliminate the variation in the light emission luminance of the organic EL element 13. it can.

(Vth correction suspension period)
Thereafter, during the suspension period of Vth correction, the signal line drive circuit 23 switches the voltage of the signal line DTL from Vofs to Vsig.

(Signal writing / μ correction period)
After the Vth correction pause period ends, signal writing and μ correction are performed. Specifically, while the voltage of the signal line DTL is Vsig and the voltage of the power supply line DSL is Vcc, the scanning line driving circuit 24 determines the voltage of the scanning line WSL according to the control signal 21A. Is increased from Voff1 to Von (T5), and the gate of the driving transistor Tr1 is connected to the signal line DTL. Then, the gate voltage Vg of the drive transistor Tr1 becomes the voltage Vsig of the signal line DTL. At this time, the anode voltage of the organic EL element 13 is still lower than the threshold voltage Vel of the organic EL element 13 at this stage, and the organic EL element 13 is cut off. Therefore, the current Ids flows to the element capacitance Coled of the organic EL element 13 and the element capacitance Coled is charged. Therefore, the source voltage Vs increases by ΔVs, and the potential difference Vgs eventually becomes Vsig + Vth−ΔVs. In this way, μ correction is performed simultaneously with writing. Here, since ΔVs increases as the mobility μ of the drive transistor Tr1 increases, the variation in mobility μ for each pixel 11 can be eliminated by reducing the potential difference Vgs by ΔV before light emission.

(Light emission)
Finally, the scanning line driving circuit 24 lowers the voltage of the scanning line WSL from Von to Voff1 according to the control signal 21A (T6). Then, the gate of the drive transistor Tr1 becomes floating, the current Ids flows between the drain and source of the drive transistor Tr1, and the source voltage Vs rises. As a result, a voltage equal to or higher than the threshold voltage Vel is applied to the organic EL element 13, and the organic EL element 13 emits light with a desired luminance.

  In the display device 1 according to the present embodiment, as described above, the pixel circuit 12 is controlled to be turned on / off in each pixel 11, and a driving current is injected into the organic EL element 13 of each pixel 11. And recombine to emit light. As a result, an image is displayed in the display area 10A.

[effect]
Next, the effect in the display apparatus 1 of this Embodiment is demonstrated.

  The mobility correction period is determined by the width of the write pulse applied to the gate of the write transistor Tr2 (that is, the ON period of the write transistor Tr2). However, the write pulse is not a perfect rectangular wave but has a dullness as shown in FIG. Therefore, in practice, the mobility correction period can vary depending on the threshold voltage of the writing transistor, as shown in FIG. When the mobility correction period varies, as shown in FIG. 11, the magnitude of the current Ids that flows through the organic EL element when the organic EL element emits light changes, and the emission luminance also changes accordingly. Therefore, it is preferable that the mobility correction period does not vary as much as possible.

  A negative bias is applied to the writing transistor Tr2 during the light emission period. Even during the threshold correction preparation period after the end of light emission, the write transistor Tr2 is negatively biased. As described above, when a negative bias is continuously applied to the gate-source voltage of the write transistor Tr2, a depletion shift occurs in the threshold voltage characteristic of the write transistor Tr2. For example, as shown in FIG. The threshold voltage varies (decreases) from Vth1 to Vth2. As a result, the mobility correction period becomes longer by Δt1 + Δt2 than the initial period. As a result, as shown in FIG. 11, when the organic EL element emits light, the current Ids flowing through the organic EL element is reduced by ΔIds, and the emission luminance is also reduced accordingly. That is, the light emission luminance decreases with the passage of the use period of the organic EL display device.

  On the other hand, in this embodiment, two kinds of voltages (Voff1, Voff2) are applied to the gate of the write transistor Tr2 as voltages for turning off the write transistor Tr2. As a result, as described above, Voff1 in the whole or part of the Vth correction preparation period (the period during which the organic EL element 13 is extinguished and before the gate-source voltage of the driving transistor Tr1 is corrected). Voff2 having a higher peak value can be applied to the gate of the write transistor Tr2. As a result, the depletion shift of the threshold voltage characteristic of the write transistor Tr2 can be reduced, so that a decrease in light emission luminance due to the depletion shift can be reduced.

<2. 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 illustrated in FIG. In this module, for example, an area 210 exposed from a member (not shown) for sealing the display unit 10 is provided on one side of the substrate 3, and the timing control circuit 21 and the video signal processing circuit 22 are provided in the exposed area 210. The signal line driving circuit 23, the scanning line driving circuit 24, and the power line driving circuit 25 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. 5 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. 6 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. 7 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. 8 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. 9 shows an 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 technology has been described with the embodiment and application examples, the present technology is not limited to the above-described embodiment and the like, and various modifications are possible.

  For example, in the above-described embodiment and the like, there are two types of voltages for turning off the write transistor Tr2, but it may be three or more types.

  In the above embodiment and the like, the scanning line driving circuit 24 outputs two types of voltages (Voff1, Voff2) as voltages for turning off the writing transistor Tr2, during the Vth correction preparation period. , After Vth correction, it may be output before the signal writing / μ correction period. When the Vth correction period is divided into a plurality of periods, the scanning line driving circuit 24 uses two types of voltages (Voff1, Voff2) as voltages for turning off the writing transistor Tr2, and the divided Vth correction period. It may be configured to output during the period between. Further, the scanning line driving circuit 24 may output two kinds of voltages (Voff1, Voff2) as voltages for turning off the writing transistor Tr2 in whole or in part during the light emission period.

  In the above embodiment and the like, the configuration of the pixel circuit 12 for active matrix driving is not limited to that described in each of the above embodiments, and a capacitor and a transistor may be added as necessary. In that case, necessary drive circuits may be added in addition to the signal line drive circuit 23, the scanning line drive circuit 24, the power supply line drive circuit 25, and the like described above in accordance with the change of the pixel circuit 12.

For example, this technique can take the following composition.
(1)
A display unit having a 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 driving transistor for driving the light emitting element;
A write transistor for controlling application of a signal voltage corresponding to a video signal at a gate of the drive transistor;
The drive unit can apply at least two kinds of voltages to the gate of the writing transistor as voltages for turning off the writing transistor.
(2)
The display according to (1), wherein the driving unit is configured to reduce a depletion shift of a threshold voltage characteristic of the write transistor by applying the at least two kinds of voltages to the gate of the write transistor. apparatus.
(3)
The driving unit applies a second voltage having a peak value higher than a first voltage for turning off the writing transistor during the light emitting period of the light emitting element to the gate of the writing transistor during the extinction period of the light emitting element. The display device according to (1) or (2).
(4)
The driving unit applies the second voltage to the gate of the writing transistor during the extinction period of the light emitting element and before the correction of the gate-source voltage of the driving transistor. The display device according to (3).
(5)
A display device,
The display device
A display unit having a 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 driving transistor for driving the light emitting element, and a writing transistor for controlling application of a signal voltage corresponding to a video signal to a gate of the driving transistor,
The electronic device in which the drive unit can apply at least two kinds of voltages to the gate of the write transistor as voltages for turning off the write transistor.
(6)
A light emitting element and a pixel circuit are provided for each pixel, and the pixel circuit includes a driving transistor that drives the light emitting element, and a writing transistor that controls application of a signal voltage corresponding to a video signal to the gate of the driving transistor. A method for driving a display device, comprising: applying at least two kinds of voltages to a gate of the write transistor as voltages for turning off the write transistor.

  DESCRIPTION OF SYMBOLS 1 ... Display apparatus, 3 ... Board | substrate, 10 ... Display panel, 10A ... Display area, 10B ... Frame area, 11 ... Pixel, 12 ... Pixel circuit, 13 ... Organic EL element, 20 ... Drive circuit, 20A ... Video signal, 20B DESCRIPTION OF SYMBOLS ... Sync signal, 21 ... Timing generation circuit, 21A ... Control signal, 22 ... Video signal processing circuit, 23 ... Signal line drive circuit, 24 ... Scan line drive circuit, 25 ... Power line drive circuit, 210 ... Area, 220 ... FPC , 300 ... Video display screen part, 310 ... Front panel, 320 ... Filter glass, 410 ... Light emitting part, 420, 530, 640 ... Display part, 430 ... Menu switch, 440 ... Shutter button, 510 ... Main body, 520 ... Keyboard, 610... Main body, 620. Lens, 630. Start / stop switch, 710. Upper housing, 720. Lower housing, 730. Connection part, 740 ... Display, 750 ... Sub display, 760 ... Picture light, 770 ... Camera, Coled ... Element capacity, Cs ... Holding capacity, CTL ... Cathode line, DTL ... Signal line, DSL ... Power line, Ids ... Current, Tr1 ... Drive transistor, Tr2 ... Write transistor, Vcc, Vofs1, Vofs2, Von, Vss ... Voltage, Vg ... Gate voltage, Vgs ... Gate-source voltage, Voled ... Organic EL element voltage, Vs ... Source voltage, Vsig Signal voltage, Vth, Vth1, Vth2 Threshold voltage, WSL Scan line, ΔT1 μ correction period ΔT2 Vth correction period

Claims (6)

A display unit having a 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 driving transistor for driving the light emitting element;
A write transistor for controlling application of a signal voltage corresponding to a video signal at a gate of the drive transistor;
The drive unit can apply at least two kinds of voltages to the gate of the writing transistor as voltages for turning off the writing transistor. The display according to claim 1, wherein the driving unit is configured to reduce a depletion shift of a threshold voltage characteristic of the write transistor by applying the at least two kinds of voltages to a gate of the write transistor. apparatus. The driving unit applies a second voltage having a peak value higher than a first voltage for turning off the writing transistor during the light emitting period of the light emitting element to the gate of the writing transistor during the extinction period of the light emitting element. The display device according to claim 2. The driving unit applies the second voltage to the gate of the writing transistor during the extinction period of the light emitting element and before the correction of the gate-source voltage of the driving transistor. The display device according to claim 3. A display device,
The display device
A display unit having a 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 driving transistor for driving the light emitting element, and a writing transistor for controlling application of a signal voltage corresponding to a video signal to a gate of the driving transistor,
The electronic device in which the drive unit can apply at least two kinds of voltages to the gate of the write transistor as voltages for turning off the write transistor. A light emitting element and a pixel circuit are provided for each pixel, and the pixel circuit includes a driving transistor that drives the light emitting element, and a writing transistor that controls application of a signal voltage corresponding to a video signal to the gate of the driving transistor. A method for driving a display device, comprising: applying at least two kinds of voltages to a gate of the write transistor as voltages for turning off the write transistor.

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