JP2011164393A - Display device and driving method thereof, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device capable of preventing the occurrence of a stripe pattern in unit scanning, a driving method thereof, and an electronic apparatus. <P>SOLUTION: A plurality of pixel rows are taken as one unit U, and one power supply line PSL is provided for each unit U. In each unit, a voltage of the power supply line PSL is V<SB>cc2</SB>in the first half period Ta from the first repetition to the k-th (X<k<N) repetition of threshold correction and threshold correction pausing, and the voltage of the power supply line PSL is V<SB>cc1</SB>(<V<SB>cc2</SB>) in the latter half period Tb from the (k+1)th repetition to the N-th repetition. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a display device that displays an image with a light emitting element arranged for each pixel and a driving method thereof. Moreover, this invention relates to the electronic device provided with the said display apparatus.

  2. Description of the Related Art 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 (Electro Luminescence) 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.

  In the organic EL display device, similarly to the liquid crystal display device, there are a simple (passive) matrix method and an active matrix method as its driving method. Although the former has a simple structure, there is a problem that it is difficult to realize a large-sized and high-definition display device. For this reason, active matrix systems are currently being actively developed. In this method, a current flowing through a light emitting element arranged for each pixel is controlled by a driving transistor.

In general, the threshold voltage V _th and the mobility μ of the driving transistor may change with time, or the threshold voltage V _th and the mobility μ may vary from pixel to pixel due to manufacturing process variations. When the threshold voltage V _th and the mobility μ are different for each pixel, the current value flowing through the driving transistor varies from pixel to pixel. Variation and uniformity of the screen are lost. In view of this, a display device incorporating a correction function for variations in threshold voltage V _th and mobility μ has been developed (see, for example, Patent Document 1).

  By the way, in an active matrix display device, a horizontal drive circuit that drives signal lines, a write scanning circuit that sequentially selects each pixel, and a power supply scanning circuit that supplies power to each pixel are all basically shift registers ( The signal output unit (not shown) is provided for each stage corresponding to each column or each row of pixels. For this reason, as the number of pixel columns and rows increases, the number of signal lines and gate lines increases accordingly, and the number of output stages of the shift register also increases accordingly, leading to an increase in the size of peripheral circuits of the display device.

  Thus, measures have been conventionally taken to reduce the size of peripheral circuits by sharing the output stage of the shift register. For example, Patent Document 2 proposes a method in which a signal line is shared by a plurality of pixels. In this way, the output stage of the shift register in the horizontal drive circuit can be shared by a plurality of pixel columns, and accordingly, the circuit scale can be reduced, the circuit area can be reduced, and the circuit cost can be reduced.

JP 2008-083272 A JP 2006-251322 A

  Patent Document 2 describes that the output stage of the shift register in the horizontal drive circuit is shared by a plurality of pixel columns. However, the output stage of the shift register is also shared in the write scanning circuit and the power supply scanning circuit. It is important to increase the cost performance of the display device. In particular, for the power supply scanning circuit, it is necessary to increase the size of the signal output unit in order to stabilize the current supply capability. Therefore, the output stage of the shift register in the power supply scanning circuit is shared by a plurality of pixel rows, By reducing the number of output units, the cost and size of the display device can be effectively reduced.

  FIG. 12 illustrates a schematic configuration of a display device in which a signal output unit in the power supply scanning circuit is shared by a plurality of pixel rows. In the display device 100 shown in FIG. 12, one power supply line PSL (PSL1, PSL2,...) Is connected to each signal output unit in the power supply line driving circuit 140, and each power supply line PSL (PSL1) is connected. , PSL2,..., Pixels 111 belonging to a plurality of pixel rows (three rows in FIG. 12) are connected. On the other hand, one signal line DTL (DTL1, DTL2,...) Is connected to each signal output unit in the signal line driving circuit 120, and each row is connected to each signal line (DTL1, DTL2,...). Pixels 111 are connected one by one. In addition, one write line WSL (WSL1, WSL2,...) Is connected to each signal output unit in the write line driving circuit 130, and each write line WSL (WSL1, WSL2,. ) Is connected to one pixel 111 in each column.

FIG. 13 shows an example of various waveforms in the display device 100 shown in FIG. In FIG. 13, two kinds of voltages (V _cc , V _ss (<V _cc )) are applied to the power supply line PSL, and two kinds of voltages (V _on , V _off (<V _on )) are applied to the write lines WSL1 to WSL6. A state in which is applied is shown. As can be seen from FIG. 13, in the display device 100, a plurality of pixel rows (three rows in FIG. 13) are used as one unit, and are common to each pixel 111 from the power supply line PSL (DSL1, DSL2,. A unit scan for applying V _cc and V _ss at timing is performed.

As shown in FIG. 13, in the same unit, the time (waiting time) from when the voltage of the power supply line PSL rises from V _ss to V _cc (T ₁ ) to when threshold correction starts (T ₂ ) Varies by line. For example, when 30 lines are included in the same unit, the difference between the waiting time for the first line and the waiting time for the 30th line is 29H. Since current leakage occurs in the pixel circuit during this waiting time, the source voltage of the driving transistor increases as the waiting time increases. Therefore, in the same unit, the gate-source voltage of the pixel 111 of the last line is smaller than the gate-source voltage of the pixel 111 of the first line. As a result, if the number of lines included in the same unit is too large, the luminance of the last line becomes darker than the luminance of the first line between times T _{1 and} T ₂ , resulting in a streak between adjacent units. Will occur.

Further, as shown in FIG. 13, in the same unit, the time (waiting time) from the time when quenching is started (T ₃ ) to the time when the voltage of the power supply line PSL is lowered from V _cc to V _ss (T ₄ ). ) Also varies from line to line. For example, when 30 lines are included in the same unit, the difference between the waiting time for the first line and the waiting time for the 30th line is 29H. During this waiting time, but decreases the source voltage gradually, since decreases slowly due like the capacity of such organic EL devices 111R, between times T ₃ through T _4, (not shown) pixel circuits A weak current flows inside. As a result, if the number of lines included in the same unit is too large, the luminance of the first line becomes brighter than the luminance of the last line between times T _{3 and} T ₄ , resulting in a streak between adjacent units. Will occur.

  As described above, conventionally, there is a problem that a streak-like pattern occurs between adjacent units due to a difference in waiting time for each line.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a display device capable of preventing the occurrence of streak-like patterns in unit scanning, a driving method thereof, and an electronic apparatus. It is in.

  A display device according to the present invention includes a display unit including a plurality of scanning lines and a plurality of power supply lines arranged in rows, a plurality of signal lines arranged in columns, and a plurality of pixels arranged in a matrix. It is provided. The display device further includes a drive unit that drives each pixel based on the video signal. Each pixel has a light emitting element and a pixel circuit. The pixel circuit includes a first transistor that controls a current flowing through the light emitting element, and a second transistor that writes a voltage of a signal line to the first transistor. The plurality of power supply lines are provided for each unit, with a plurality of pixel rows as one unit. The driving unit applies a plurality of first pulse signals for turning on the second transistor to each first scanning line included in the same unit among the plurality of scanning lines when a predetermined signal is applied to each signal line. The following operations are performed when the threshold voltages of the first transistors included in the unit are corrected by applying the voltages to the first scanning lines in order and applying the voltages to the first scanning lines. That is, the driving unit continuously applies the first voltage to the power supply line corresponding to the unit including the first scanning line in the first half period of the correction, and is lower than the first voltage in the second half period following the first half period of the correction. The second voltage is continuously applied.

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

According to the display device driving method of the present invention, in a display device having the following configuration, when a predetermined signal is applied to each signal line, a plurality of first pulse signals for turning on the second transistor are provided. When applying to each first scanning line included in the same unit among the scanning lines and sequentially applying to the plurality of first scanning lines to correct the threshold voltage of each first transistor included in the unit, The following steps are executed.
(1) The first voltage is continuously applied to the power supply line corresponding to the unit including the first scanning line in the first half period of the correction, and the first voltage lower than the first voltage is applied in the second half period following the first half period of the correction. Step to continue applying two voltages

  A display device using the above driving method includes a plurality of scanning lines and a plurality of power supply lines arranged in rows, a plurality of signal lines arranged in columns, and a plurality of pixels arranged in a matrix. A display unit is provided. The display device further includes a drive unit that drives each pixel based on the video signal. Each pixel has a light emitting element and a pixel circuit. The pixel circuit includes a first transistor that controls a current flowing through the light emitting element, and a second transistor that writes a voltage of a signal line to the first transistor. The plurality of power supply lines are provided for each unit, with a plurality of pixel rows as one unit.

  In the display device, the driving method thereof, and the electronic apparatus of the present invention, a plurality of first pulse signals are applied to each first scanning line included in the same unit and sequentially applied to the plurality of first scanning lines. When correcting the threshold voltage of each first transistor included in the unit, the first voltage is applied in the first half period of the correction, and the second voltage lower than the first voltage is applied in the second half period. Thereby, in the first half period, the first current flows through the first transistor included in the unit, and in the second half period, the second current smaller than the first current flows through the first transistor included in the unit. This means that the threshold correction is more strongly applied in the first half period than in the second half period, and the number of times the threshold correction is strongly applied gradually decreases from the first stage to the last stage of the unit, Conversely, this means that the number of times that the threshold correction is weakly increased gradually from the first stage to the last stage of the unit. Therefore, as the unit moves from the first stage to the last stage, the gate-source voltage of the first transistor after the threshold correction increases, and the luminance decreases.

  According to the display device, the driving method thereof, and the electronic device of the present invention, the voltage between the gate and the source of the first transistor after the threshold correction is increased and the luminance is decreased as the unit moves from the first stage to the last stage. did. As a result, the brightness of the brightness distribution in the column direction caused by the threshold correction is opposite to the brightness of the brightness distribution in the column direction caused by the difference in waiting time for each line. Can be offset. As a result, it is possible to prevent streak-like patterns from occurring during unit scanning.

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 conceptual diagram for demonstrating the unit scan of the display apparatus of FIG. It is a wave form diagram for demonstrating an example of operation | movement of the display apparatus of FIG. It is a wave form chart for explaining an example of operation in one pixel. It is a top view showing schematic structure of the module containing the display apparatus of the 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 conventional display apparatus. FIG. 13 is a waveform diagram for explaining an example of the operation of the display device of FIG. 12. FIG. 13 is a circuit diagram for explaining current leakage in the display device of FIG. 12.

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 (FIGS. 1 to 5)
2. Module and application examples (FIGS. 6 to 11)
3. Conventional example (FIGS. 12 to 14)

<Embodiment>
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 panel 10 (display unit) and a drive circuit 20 (drive unit).

(Display panel 10)
The display panel 10 has a display area 10A in which three types of organic EL elements 11R, 11G, and 11B (light emitting elements) having different emission colors are two-dimensionally arranged. The display area 10A is an area for displaying an image using light emitted from the organic EL elements 11R, 11G, and 11B. The organic EL element 11R is an organic EL element that emits red light, the organic EL element 11G is an organic EL element that emits green light, and the organic EL element 11B is an organic EL element that emits blue light. Hereinafter, the organic EL element 11 is appropriately used as a general term for the organic EL elements 11R, 11G, and 11B.

(Display area 10A)
FIG. 2 shows an example of a circuit configuration in the display area 10A. In the display area 10 </ b> A, a plurality of pixel circuits 12 are two-dimensionally arranged in pairs with the individual organic EL elements 11. In the present embodiment, the pair of organic EL elements 11 and the pixel circuit 12 constitute one pixel 13. More specifically, as shown in FIG. 1, the pair of organic EL elements 11R and the pixel circuit 12 constitute one pixel 13R (red pixel), and the pair of organic EL elements 11G and the pixel circuit 12 are one. One pixel 13G (green pixel) is configured, and the pair of organic EL elements 11B and the pixel circuit 12 configure one pixel 13B (blue pixel). Further, the three pixels 13R, 13G, and 13B adjacent to each other constitute one display pixel 14.

Each pixel circuit 12 includes, for example, a drive transistor Tr ₁ (first transistor) that controls a current flowing through the organic EL element 11 and a write transistor Tr ₂ (second transistor) that writes the voltage of the signal line DTL into the drive transistor Tr _1. And a storage capacitor C _s, and has a 2Tr1C circuit configuration. The drive transistor Tr ₁ and the write transistor Tr ₂ are formed by, for example, n-channel MOS type thin film transistors (TFTs). The drive transistor Tr ₁ or the write transistor Tr ₂ may be, for example, a p-channel MOS type TFT.

In the display area 10A, a plurality of write lines WSL (scanning lines) are arranged in rows, and a plurality of signal lines DTL are arranged in columns. In the display region 10A, a plurality of power supply lines PSL (members to which power supply voltage is supplied) are further arranged in a row along the write lines WSL. One organic EL element 11 is provided near the intersection of each signal line DTL and each scanning line WSL. Each signal line DTL is the output end of the later of the signal line drive circuit 23 (not shown) is connected to either the drain electrode and source electrode of the writing transistor Tr ₂ (not shown). Each scanning line WSL is the output end of the write line drive circuit 24 will be described later (not shown) is connected to the gate electrode of the writing transistor Tr ₂ (not shown). Each power supply line PSL is connected to an output end (not shown) of a power supply line drive circuit 25 described later and either _one of a drain electrode and a source electrode (not shown) of the drive transistor Tr1. Of the drain electrode and the source electrode of the write transistor Tr ₂ , the one not connected to the signal line DTL (not shown) is connected to the gate electrode (not shown) of the drive transistor Tr ₁ and one end of the storage capacitor C _s. ing. Of the drain electrode and the source electrode of the driving transistor Tr ₁ , the one not connected to the power supply line PSL (not shown) and the other end of the storage capacitor C _s are connected to the anode electrode (not shown) of the organic EL element 11. Has been. A cathode electrode (not shown) of the organic EL element 11 is connected to the ground line GND, for example.

  As shown in FIGS. 1 and 3, one power supply line PSL is provided for each unit U with a plurality of pixel rows as one unit U. FIG. 3 illustrates the case where five units U are provided, but the number of units is not limited thereto. Further, in FIG. 3, suffixes that are increased by one are given to the five units U in the scanning direction of the power supply line driving circuit 25. Accordingly, the unit U1 corresponds to the initial unit in the scanning direction, and the unit U5 corresponds to the final unit in the scanning direction.

(Drive circuit 20)
Next, each circuit in the drive circuit 20 will be described with reference to FIG. The drive circuit 20 includes a timing generation circuit 21, a video signal processing circuit 22, a signal line drive circuit 23, a write line drive circuit 24, and a power supply line drive circuit 25.

  The timing generation circuit 21 controls the video signal processing circuit 22, the signal line drive circuit 23, the write line drive circuit 24, and the power supply line drive circuit 25 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.

  The video signal processing circuit 22 performs predetermined correction on the video signal 20 </ b> A input from the outside, and outputs the corrected video signal 22 </ b> A to the signal line driving circuit 23. Examples of the predetermined correction include gamma correction and overdrive correction.

The signal line driving circuit 23 applies the video signal 22A (signal voltage V _sig ) 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. This is to be written to the target pixel 13. Note that writing refers to applying a predetermined voltage to the gate of the driving transistor Tr ₁ .

The signal line driving circuit 23 is configured by, for example, a shift register (not shown), and includes a signal output unit (not shown) for each stage corresponding to each column of the pixels 13. The signal line drive circuit 23 can output three types of voltages (V _sig , V _ofs , V _ers ) to each signal line DTL in response to (in synchronization with) the input of the control signal 21A. Yes. Specifically, the signal line drive circuit 23 supplies three types of voltages (V _sig , V _ofs , V) to the pixel 13 selected by the write line drive circuit 24 via the signal line DTL connected to each pixel 13. V _ers ) are supplied in order.

Here, V _sig is a voltage value corresponding to the video signal 22A. The minimum voltage of V _sig is a voltage value lower than V _ofs, and the maximum voltage of V _sig is a voltage value higher than V _ofs . Also, V _ofs is irrelevant non-gradation signal to the video signal 22A, and has a voltage value lower than V _ers (fixed value). V _ers has a voltage value (fixed value) lower than the threshold voltage V _el of the organic EL element 11.

The write line driving circuit 24 is configured by, for example, a shift register (not shown), and includes a signal output unit (not shown) for each stage corresponding to each row of the pixels 13. The write line drive circuit 24, control signals 21A inputs corresponding to (in synchronization with) the of, with respect to Kakushokomisen WSL, 3 kinds of voltages _{(V on, V off1, V} off2) and can be output It has become. Specifically, the write line drive circuit 24, via the write line WSL connected to each pixel 13, the drive target pixel 13 3 kinds of voltages _{(V on, V off1, V} off2) supply The write transistor Tr ₂ is controlled.

Here, the voltage V _on is a value equal to or higher than the on-voltage of the write transistor Tr ₂ . V _on is a voltage value output from the write line driving circuit 24 at the time of extinction or threshold correction described later. V _off1, V _off2 has a value lower than the ON voltage of the writing transistor Tr _2. V _off2 has a voltage value lower than V _off1.

  The power supply line driving circuit 25 is configured by, for example, a shift register (not shown), and corresponds to each unit (U1 to U5) and has a number of stages equal to the number of rows included in each unit (U1 to U5). Each is provided with a signal output unit (not shown). That is, in this embodiment, the output stage of the shift register in the power supply line driving circuit 25 is shared for each unit (U1 to U5), and the unit scan method is adopted. Therefore, the number of signal output units in the power supply line driving circuit 25 is small as compared with the case where the signal output unit is provided for each stage corresponding to each pixel column.

The power supply line drive circuit 25, control signals 21A in response to an input (in synchronization with), and can output three kinds of voltages _{(V ss, V cc1, V} cc2). Specifically, the power supply line drive circuit 25 via a power line PSL connected to each pixel 13, the drive target pixel 13 3 kinds of voltages _{(V ss, V cc1, V} cc2) supplies, The light emission and quenching of the organic EL element 11 are controlled.

Here, V _ss 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 11 and the voltage V _ca of the cathode of the organic EL element 11. Also, V _cc1, V _cc2 is the voltage value of the above voltage (V _el + V _ca). V _cc2 has a value greater than V _cc1.

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, even if the threshold voltage V _th and the mobility μ of the driving transistor Tr ₁ change with time, the light emission luminance of the organic EL element 11 is kept constant without being affected by them. For this reason, a correction operation for variations in the threshold voltage V _th and the mobility μ is incorporated.

FIG. 4 shows an example of various waveforms in the display device 1. 4 shows, three types of voltages to the power supply line _{PSL (V ss, V cc1,} V cc2) is write lines WSL1~WSL6 three kinds of voltages _{(V on, V off1, V} off2) is applied The situation is shown. As can be seen from FIGS. 1 and 4, in the display device 1, V _ss , V _cc1 , V _ss , V _cc1 , and the like are shared from the power line PSL (PSL 1, PSL 2,...) To each pixel 13. V _cc2 is applied.

FIG. 5 shows an example of a voltage waveform applied to one pixel 13 of the display device 1. Specifically, three kinds of voltages to the power supply line _{PSL (V ss, V cc1,} V cc2) is, the signal line DTL to 3 kinds of voltages _{(V sig, V ers, V} ofs)) is, the write line WSL 3 kinds of voltages _{(V on, V off1, V} off2) how the is applied is shown in. Further, FIG. 5 shows that the gate voltage V _g and the source voltage V _{s of} the drive transistor Tr ₁ change from time to time in response to voltage application to the power supply line PSL, signal line DTL, and write line WSL. It is shown. Note that V _el described above is a threshold voltage of the organic EL element 11.

(Extinction period)
First, the organic EL element 11 is quenched. Specifically, when the voltage of the power supply line PSL is V _cc1 and the voltage of the signal line DTL is V _ers , the write line drive circuit 24 changes the voltage of the write line WSL from V _off1. The voltage is raised to V _on (T ₁ ), and the gate of the drive transistor Tr ₁ is connected to the signal line DTL. Then, the driving gate voltage V _g of the transistor Tr ₁ started is lowered, due to coupling via the retention capacitor C _s begins to decrease also the source voltage V _s of the drive transistor Tr _1. Thereafter, the gate voltage V _g becomes V _ers , the source voltage V _s becomes V _el + V _ca (V _ca is the cathode voltage of the organic EL element 11), and the write line drive circuit 24 is activated when the organic EL element 11 is extinguished. The voltage of the write line WSL is lowered from V _on to V _off1, and the gate of the drive transistor Tr ₁ is floated (T ₂ ).

(Threshold correction preparation period)
Next, preparation for threshold correction is performed. More specifically, when the voltage of the write line WSL is in the V _off2, power line drive circuit 25 lowers the voltage of the power line PSL to V _ss from V _cc1 (T _3). Then, the current I _d flows between the drain and source of the drive transistor Tr _{1 with} the power supply line PSL side of the drive transistor Tr _{1 as} a source, and the current I _d stops when the gate voltage V _g becomes V _ss + V _th. . At this time, the source voltage V _s is V _el + V _ca − (V _ers − (V _ss + V _th ), and the potential difference V _gs is smaller than V _th .

Subsequently, the power supply line driving circuit 25 increases the voltage of the power supply line PSL from V _ss to V _cc2 (T ₄ ). Then, the current I _d flows between the drain and source of the driving transistor Tr ₁ , and the gate voltage V _g and the source voltage V _s are the capacitance between the parasitic capacitance between the gate and drain of the driving transistor Tr ₁ and the holding capacitance C _s. Ascends by bonding. At this time, the potential difference V _gs is still smaller than V _th .

(First threshold correction period)
Next, threshold correction is performed. Specifically, when the voltage of the power supply line PSL is V _cc2 and the voltage of the signal line DTL is V _ofs (threshold correction signal with a fixed peak value), the write line driving circuit 24 There are raised to V _on the voltage of the write line WSL from V _off2, applying a selection pulse (first pulse signal) to the write line WSL (T _5). Then, a current I _d (first current) flows between the drain and source of the drive transistor Tr ₁ , and the gate voltage V _g and the source voltage V _s are the parasitic capacitance between the gate and drain of the drive transistor Tr ₁ , and the holding capacitance. Increased by capacitive coupling with C _s . Here, since the holding capacity C _s is extremely smaller than the element capacity of the organic EL element 11 and the increase amount of the source voltage V _s is sufficiently smaller than the increase amount of the gate voltage V _g , the potential difference V _gs becomes large. Then, when the potential difference V _gs becomes larger than V _th , the write line driving circuit 24 lowers the voltage of the write line WSL from V _on to V _off1 (T ₆ ). Then, the gate of the drive transistor Tr ₁ becomes floating, and the threshold correction is temporarily stopped.

(First threshold correction suspension period)
During the period when the threshold correction is paused, for example, the voltage of the signal line DTL is sampled in another row (pixel) different from the row (pixel) on which the threshold correction has been performed. At this time, since the source voltage V _s is lower than V _ofs −V _th in the row (pixel) in which the previous threshold correction has been performed, the row in which the previous threshold correction has been performed even during the threshold correction pause period ( In the pixel), the current I _d flows between the drain and source of the driving transistor Tr ₁ , the source voltage V _s rises, and the gate voltage V _g also rises due to coupling via the storage capacitor C _s .

(Second threshold correction period)
After the threshold correction suspension period ends, threshold correction is performed again. Specifically, when the voltage of the signal line DTL is V _ofs and threshold correction is possible, the write line drive circuit 24 increases the voltage of the write line WSL from V _off1 to V _on ( T ₅ ), the gate of the driving transistor Tr ₁ is connected to the signal line DTL. At this time, when the source voltage V _s is lower than V _ofs −V _th (when threshold correction is not yet completed), until the drive transistor Tr ₁ is cut off (until the potential difference V _gs becomes V _th). ), the drain of the drive transistor Tr ₁ - current I _d flows between the source. Thereafter, before the signal line drive circuit 23 switches the voltage of the signal line DTL from V _ofs to V _sig , the write line drive circuit 24 lowers the voltage of the write line WSL from V _on to V _off1 (T ₆ ). Then, since the gate of the drive transistor Tr ₁ is in a floating state, the potential difference V _gs can be maintained constant regardless of the voltage level of the signal line DTL.

Incidentally, in the threshold correction period, the holding capacitor C _s is charged to V _th, when the potential difference V _gs becomes V _th is to end the threshold value correction, not reached the potential difference V _gs until the V _th In this case, the threshold correction and the threshold correction pause are repeatedly executed until the potential difference V _gs reaches V _th . In this embodiment, the threshold correction and the threshold correction pause are repeatedly executed N times. Note that N is a positive number that is at least X + (X−1) or more when the number of units is X (5 in the present embodiment).

Furthermore, in the present embodiment, for example, as illustrated in FIG. 4, the number of repetitions of threshold correction and threshold correction pause is in the first half period Ta from the first to the k-th (X <k <N). the voltage of the power supply line PSL has become a V _cc2, in the latter half of the period Tb from the k + 1-th to N-th, the voltage of the power supply line PSL is V _cc1. Specifically, when executing the first threshold correction, the power supply line driving circuit 25 raises the voltage of the power supply line PSL from V _ss to V _cc2 in advance, and the power supply is maintained until the kth threshold correction suspension is completed. Continue to apply V _cc2 to line PSL. Then, during threshold correction from the first time to the k-th time, a current I _d (first current) corresponding to the magnitude of the voltage V _cc2 of the power supply line PSL flows between the drain and source of the drive transistor Tr ₁ , and the threshold correction is performed. Strongly applied (the potential difference V _gs is greatly displaced). Subsequently, in performing the k + 1 th threshold correction until the power line drive circuit 25 is the way down in advance the voltage of the power supply line PSL to V _cc1 from V _cc2, the threshold correction suspension of N-th is completed, the further quenching During this time, V _cc1 is continuously applied to the power supply line PSL. Then, at the time of threshold correction from the (k + 1) th time to the Nth time, a current I _d (second current) corresponding to the magnitude of the voltage V _cc1 of the power supply line PSL flows between the drain and source of the drive transistor Tr ₁ , and the threshold correction is performed. It is weak (the potential difference V _gs is displaced relatively small).

(Writing / μ correction period)
After the threshold correction pause period ends, writing and μ correction are performed. Specifically, while the voltage of the signal line DTL is V _sig , the write line drive circuit 24 _raises the voltage of the write line WSL from V _off1 to V _on (T ₇ ), and the drive transistor Tr ₁ Are connected to the signal line DTL. Then, the gate voltage of the drive transistor Tr ₁ becomes V _sig . At this time, the anode voltage of the organic EL element 11 is still lower than the threshold voltage V _el of the organic EL element 11 at this stage, and the organic EL element 11 is cut off. Therefore, the current I _d flows into the element capacitance of the organic EL element 11 and the element capacitance is charged. Therefore, the source voltage V _s increases by ΔV, and the potential difference V _gs eventually becomes V _sig + V _th −ΔV. In this way, μ correction is performed simultaneously with writing.

(Light emission)
Finally, the write line drive circuit 24 lowers the voltage of the write line WSL from V _on to V _off1 (T ₈ ). Then, the gate of the drive transistor Tr ₁ becomes floating, the current I _d flows between the drain and source of the drive transistor Tr ₁ , and the source voltage V _s increases. As a result, the organic EL element 11 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 13, and a driving current is injected into the organic EL element 11 of each pixel 13, thereby generating holes and electrons. Recombine with each other to emit light, and the light is extracted outside. As a result, an image is displayed in the display area 10 </ b> A of the display panel 10.

Incidentally, for example, in the unit scan method in the conventional display device 100 as shown in FIG. 12, for example, as shown in FIG. 13, the voltage of the power supply line PSL rises from V _ss to V _cc in the same unit. The time (waiting time) from the time (T ₁ ) to the time (T ₂ ) when threshold correction starts is different for each line. For example, when 30 lines are included in the same unit, the difference between the waiting time for the first line and the waiting time for the 30th line is 29H. During this waiting time, for example, as shown in FIG. 14, the leakage current I _Dr of the driving transistor Tr _1, since the leakage current I _EL of the organic EL device 111 occurs, the source voltage of the drive transistor Tr ₁ V _s increases as the waiting time increases. Therefore, in the same unit, the gate-source voltage (potential difference V _gs ) of the pixel 111 in the last line is smaller than the gate-source voltage (potential difference V _gs ) of the pixel 111 in the first line. As a result, if the number of lines included in the same unit is too large, the luminance of the last line becomes darker than the luminance of the first line between times T _{1 and} T ₂ , resulting in a streak between adjacent units. Will occur.

Further, as shown in FIG. 13, in the same unit, the time (waiting time) from the time when quenching is started (T ₃ ) to the time when the voltage of the power supply line PSL is lowered from V _cc to V _ss (T ₄ ). ) Also varies from line to line. For example, when 30 lines are included in the same unit, the difference between the waiting time for the first line and the waiting time for the 30th line is 29H. During this waiting time, the source voltage V _s gradually decreases, but slowly decreases due to the capacitance of the organic EL element 111 and the like, so that the pixel circuit (not shown) is between time T _{3 and} T _4. A weak current flows in). As a result, if the number of lines included in the same unit is too large, the luminance of the first line becomes brighter than the luminance of the last line between times T _{3 and} T ₄ , resulting in a streak between adjacent units. Will occur.

  As described above, the conventional method has a problem that a streak-like pattern occurs between adjacent units due to a difference in waiting time for each line.

On the other hand, in the display device 1 according to the present embodiment, the voltage of the power supply line PSL is changed in the first half period Ta from the first time to the kth time (X <k <N). has become a V _cc2, in the latter half of the period Tb from the k + 1-th to N-th, the voltage of the power supply line PSL is V _cc1. As a result, during threshold correction from the first time to the k-th time, a current I _d (first current) corresponding to the magnitude of the voltage V _cc2 of the power supply line PSL flows between the drain and source of the drive transistor Tr ₁ , and threshold correction is performed. Is strongly applied (the potential difference V _gs is greatly displaced). On the other hand, at the time of threshold correction from the (k + 1) th time to the Nth time, a current I _ds (second current) corresponding to the magnitude of the voltage V _cc1 of the power supply line PSL flows between the drain and source of the drive transistor Tr ₁ , and threshold correction is performed. It is weak (the potential difference V _gs is displaced relatively small). This means that the threshold correction is more strongly applied in the first half period Ta than in the second half period Tb, and the number of times the threshold correction is strongly applied gradually decreases from the first stage to the last stage of the unit. On the contrary, as the unit moves from the first stage to the last stage, it means that the number of times that the threshold correction is weakly increased gradually. Therefore, as the unit moves from the first stage to the last stage, the gate-source voltage of the drive transistor Tr ₁ after threshold correction increases, and the luminance decreases. As a result, the brightness of the brightness distribution in the column direction caused by the threshold correction is opposite to the brightness of the brightness distribution in the column direction caused by the difference in waiting time for each line. Can be offset. As a result, it is possible to prevent streak-like patterns from occurring during unit scanning.

<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, a region 210 exposed from the sealing substrate 32 that seals the display region 10A is provided on one side of the substrate 31, and the wiring of the drive circuit 20 is extended to the exposed region 210 to provide an external connection terminal. (Not shown) is formed. The external connection terminal may be provided with a flexible printed circuit (FPC) 220 for signal input / output.

(Application example 1)
FIG. 7 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. 8 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. 9 shows an 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. 10 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. 11 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 12 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 12. In that case, a necessary drive circuit may be added in addition to the signal line drive circuit 23, the write line drive circuit 24, and the power supply line drive circuit 25 described above in accordance with the change of the pixel circuit 12.

  In the above embodiment and the like, the timing control circuit 21 controls the drive of the signal line drive circuit 23, the write line drive circuit 24, and the power supply line drive circuit 25, but other circuits control these drives. You may make it do. The control of the signal line drive circuit 23, the write line drive circuit 24, and the power supply line drive circuit 25 may be performed by hardware (circuit) or software (program).

  In the above-described embodiment and the like, the pixel circuit 12 has a 2Tr1C circuit configuration. However, as long as the pixel circuit 12 includes a circuit configuration in which a dual-gate transistor is connected to the organic EL element 11 in series. The circuit configuration may be other than the 2Tr1C circuit configuration.

In the above-described embodiment and the like, the case where the drive transistor Tr ₁ and the write transistor Tr ₂ are formed of n-channel MOS thin film transistors (TFTs) has been exemplified, but a p-channel transistor (for example, a p-channel MOS) is exemplified. Type TFT). However, in this case, the source and drain of the transistor Tr ₂ that are not connected to the power supply line PSL and the other end of the storage capacitor C _s are connected to the cathode of the organic EL element 11 and the anode of the organic EL element 11 is connected. Is preferably connected to GND or the like.

DESCRIPTION OF SYMBOLS 1,100 ... Display apparatus, 10, 110 ... Display panel, 10A ... Display area, 11, 11R, 11G, 11B, 111R, 111G, 111B ... Organic EL element, 12 ... Pixel circuit, 13, 13R, 13G, 13B, DESCRIPTION OF SYMBOLS 111 ... Pixel, 14 ... Display pixel, 20 ... Drive circuit, 20A, 22A ... Video signal, 20B ... Synchronization signal, 21 ... Timing generation circuit, 21A ... Control signal, 22 ... Video signal processing circuit, 23, 120 ... Signal line Drive circuit, 24, 130 ... Write line drive circuit, 25, 140 ... Power supply line drive circuit, 31 ... Substrate, 32 ... Substrate for sealing, 210 ... Area, 220 ... FPC, 300 ... Video display screen section, 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 ... Connecting portion, 740 ... Display, 750 ... Sub display , 760 ... picture light, 770 ... camera, C _s ... holding capacity, DTL (DTL1, DTL2, ...... ) ... signal line, I _d ... current, I _Dr, I _EL ... leakage current, GND ... ground line, k, N: number of repetitions, PSL (PSL1, PSL2,...) ... power supply line, Tr ₁ ... drive transistor, Tr ₂ ... write transistor, V _g ... gate voltage, V _gs ... potential difference, V _s ... source voltage, V _sig ... signal _{voltage, V cc1, V cc2, V} off, V ofs, V on, V ss, ΔV ... voltage, V _th, V _el ... threshold voltage, WSL (WSL1, WSL2, ...... ) Write lines, X ... the number of units, μ ... mobility.

Claims (5)

A display unit including a plurality of scanning lines and a plurality of power lines arranged in a row, a plurality of signal lines arranged in a column, and a plurality of pixels arranged in a matrix;
A drive unit for driving each pixel based on the video signal,
Each pixel has a light emitting element and a pixel circuit,
The pixel circuit includes a first transistor that controls a current flowing through the light emitting element, and a second transistor that writes a voltage of the signal line to the first transistor,
The plurality of power supply lines are provided for each unit, with a plurality of pixel rows as one unit,
The driving unit applies a plurality of first pulse signals for turning on the second transistor when a predetermined signal is applied to each signal line, to each first included in the same unit among the plurality of scanning lines. When correcting the threshold voltage of each first transistor included in the unit by applying to the scanning lines and sequentially applying to the plurality of first scanning lines, the first half of the correction is applied to the power supply line corresponding to the unit. A display device that continues to apply a first voltage during a period and continues to apply a second voltage that is lower than the first voltage in a second half period following the first half period of the correction. The drive unit applies a first voltage to the power supply line corresponding to the unit during the first half period of the correction, thereby causing the first current to flow through the first transistor included in the unit, and during the second half period of the correction. The display device according to claim 1, wherein a second current smaller than the first current is caused to flow through a first transistor included in the unit by continuing to apply the second voltage. The display device according to claim 1, wherein the predetermined signal is a threshold correction signal having a fixed peak value. A display unit including a plurality of scanning lines and a plurality of power lines arranged in a row, a plurality of signal lines arranged in a column, and a plurality of pixels arranged in a matrix;
A drive unit for driving each pixel based on the video signal,
Each pixel has a light emitting element and a pixel circuit,
The pixel circuit includes a first transistor that controls a current flowing through the light emitting element, and a second transistor that writes a voltage of the signal line to the first transistor,
In the display device in which the plurality of power supply lines are provided with one unit for each of the plurality of pixel rows, and when a predetermined signal is applied to each signal line, the second transistor is A plurality of first pulse signals that are turned on are applied to each first scanning line included in the same unit among the plurality of scanning lines and are sequentially applied to the plurality of first scanning lines and included in the unit. When correcting the threshold voltage of each first transistor, the first voltage is continuously applied to the power supply line corresponding to the unit in the first half period of the correction, and the first voltage is applied in the second half period following the first half period of the correction. A method for driving a display device, wherein a second voltage having a lower voltage is continuously applied. A display device,
The display device
A display unit including a plurality of scanning lines and a plurality of power lines arranged in a row, a plurality of signal lines arranged in a column, and a plurality of pixels arranged in a matrix;
A drive unit for driving each pixel based on the video signal,
Each pixel has a light emitting element and a pixel circuit,
The pixel circuit includes a first transistor that controls a current flowing through the light emitting element, and a second transistor that writes a voltage of the signal line to the first transistor,
The plurality of power supply lines are provided for each unit, with a plurality of pixel rows as one unit,
The driving unit applies a plurality of first pulse signals for turning on the second transistor when a predetermined signal is applied to each signal line, to each first included in the same unit among the plurality of scanning lines. When correcting the threshold voltage of each first transistor included in the unit by applying to the scanning lines and sequentially applying to the plurality of first scanning lines, the first half of the correction is applied to the power supply line corresponding to the unit. An electronic apparatus that continuously applies a first voltage during a period and continues to apply a second voltage that is lower than the first voltage in a second half period following the first half period of the correction.

Images