JP2005189643A - Display device and method for driving display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a current driven self-luminous display device of an organic EL display device or the like effectively avoiding influence from a neighboring pixel by reducing power consumption. <P>SOLUTION: In configuration driving a light emitting element 12 by a transistor TR2 by source follower circuit configuration from gate source voltage Vgs by voltage between terminals of a capacitor C2 for holding a signal level, the gate voltage of the transistor TR2 is set at cut-off voltage to control light emission and non-light emission of the light emitting element 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a display device and a display device driving method, and can be applied to a self-luminous display device driven by current, such as an organic EL (Electro Luminescence) display device. According to the present invention, in a configuration in which a light emitting element is driven by a transistor having a source follower circuit configuration by a gate source voltage based on a voltage between terminals of a signal level holding capacitor, the gate voltage of the transistor TR2 is set to a cut-off voltage, thereby the light emitting element By controlling light emission and non-light emission, power consumption can be reduced, and further, the influence from adjacent pixels can be effectively avoided.

  Conventionally, in organic EL display devices, various applications to display devices have been proposed, for example, in US Pat. No. 5,684,365 and JP-A-8-234683.

  That is, as shown in FIG. 7, in this type of display device 1, the pixel unit 2 is provided with scanning lines SCN in the horizontal direction in units of lines with respect to the pixels (PX) 3 arranged in a matrix. A signal line SIG is provided in the vertical direction for each column so as to be orthogonal to the scanning line SCN. For the pixel portion 2 formed in this way, the display device 1 drives the scanning line SCN by the vertical drive circuit 4 to sequentially select the pixels 3 of the pixel portion 2 in units of lines, and this pixel 3 The gray level of each pixel 3 is set by driving the signal line SIG by the horizontal drive circuit 5 so as to correspond to the selection.

  For this reason, the vertical drive circuit 4 generates a write signal ws for sequentially instructing writing to each pixel 3 in line units by the write scan circuit (WSCN) 4A, and outputs the write signal ws to the scan line SCN. The setting of gradation in the pixel 3 is controlled. The horizontal drive circuit 5 generates a drive signal in accordance with the gradation data D1 indicating the gradation of each pixel 3, distributes this drive signal to each signal line SIG by the horizontal selector (HSEL) 5A, and outputs it. Thus, the display device 1 is configured to set the gradation of each pixel 3 in line units.

  In the display device of the organic EL element, each pixel 3 driven in this way is an organic EL element based on an organic EL that is a self-luminous element driven by current, and driving of each pixel that drives the organic EL element. The circuit is formed by a circuit (hereinafter referred to as a pixel circuit).

  In the display device thus formed, the organic EL element and the pixel circuit are integrally formed on the glass substrate by forming each pixel circuit by an n-channel MOS type TFT (Thin Film Transistor). Accordingly, as shown in FIG. 8, the organic EL element 12 is driven by the source follower circuit configuration.

  That is, the display device 11 shown in FIG. 8 is formed in each pixel 3 so that the organic EL element 12 is current-driven by the transistor TR2 having a source follower circuit configuration in which the source is connected to the anode of the organic EL element 12. A signal level holding capacitor C1 is provided at the gate of the transistor TR2. In the display device 11, the signal level holding capacitor C1 is connected to the signal line SIG by the transistor TR1 which is turned on by the write signal ws output from the write scan 4A, whereby the signal line is moved in response to the write signal ws. The gate voltage Vg of the transistor TR2 is set according to the signal level of the drive signal output to SIG. As a result, the display device 1 drives the organic EL element 12 with a current corresponding to the gate voltage Vg thus set, and emits the organic EL element 12 of each pixel 3 with a gradation corresponding to the gradation data D1. Thus, a desired image can be displayed.

  However, in the organic EL element, as shown in FIG. 9, the current-voltage characteristics change in a direction in which current hardly flows by use. In FIG. 9 and FIG. 10, the symbol L1 indicates the initial characteristics, and the symbol L2 indicates the characteristics due to changes over time. On the other hand, in the driving by the sofa follower circuit described above with reference to FIG. 8, the characteristic curve due to the load intersects the characteristic curve of the drain-source voltage Vds−drain source current Ids of the transistor TR2, as shown in FIG. The intersecting point becomes the operating point. Accordingly, in the organic EL element, when the voltage-current characteristic is changed, the current flowing through the organic EL element is reduced correspondingly, thereby causing a problem that the luminance of each pixel is gradually lowered.

As one method for solving this problem, a method of controlling the drive current of the organic EL element 12 by setting the gradation by the gate-source voltage Vgs instead of simply setting the gradation by the gate voltage Vg can be considered. That is, the drain current Ids of the TFT is expressed by (1/2) × μ × (W / L) Cox (Vgs−Vth) ² (1), whereby the gradation is set by the gate-source voltage Vgs. Thus, it is possible to prevent a change in drive current due to a change with time. Here, μ is the carrier mobility, W is the gate width, L is the gate length, Cox is the gate capacitance per unit area, and Vth is the threshold voltage.

  Thus, as shown in FIG. 11 in comparison with FIG. 8, in each pixel 22, in place of the signal level holding capacitor C1 with respect to the gate of the transistor TR2, a signal level holding signal is provided between the gate and source of the transistor TR2. The capacitor C2 is disposed, and the signal level of the signal line SIG is set in the signal level holding capacitor C2. Further, the transistor TR3 which is turned on by the drive scan signal ds is connected to the source of the transistor TR2, and during the period in which the signal level of the signal line SIG is set in the signal level holding capacitor C2, the transistor TR3 causes the source potential of the transistor TR2 to be set. Is set to a constant potential. In FIG. 11, this constant potential is a ground potential. Corresponding to the configuration of the pixel portion 23 by such pixels 22, in the vertical drive circuit 24, in addition to the write scan circuit 24A, the drive scan signal is synchronized with the output of the write signal ws by the write scan circuit 24A. A drive scan circuit (DSCN) 24B for outputting ds is provided.

  In practice, however, as shown in FIGS. 12 and 13, even if the transistor TR3 is switched to the ON state in this way, it takes time to fall at the source potential of the transistor TR2. As a result, prior to setting the signal level of the signal line SIG to the capacitor C2 by the write signal ws, the transistor TR3 is turned on by the drive scan signal ds, and the source voltage Vs of the transistor TR2 becomes a sufficiently constant potential. Thereafter, the transistor TR3 is turned on by the write signal ws, and the signal level Vin of the signal line SIG is set in the signal level holding capacitor C2. After that, the write signal ws is lowered to set the transistor TR2 to the OFF state, and then the drive scan signal ds is lowered, whereby the source voltage Vs rises and the signal level Vin set in the signal level holding capacitor C2 is set. The organic EL element 12 starts to emit light by current driving according to the above. 13A to 13D are connection diagrams illustrating settings of the transistors TR2 and TR3 corresponding to the periods T1 to T4 in FIG.

  In this way, if the drive current of the organic EL element 12 is controlled by setting the gradation based on the gate-source voltage Vgs, even if the characteristics of the organic EL element 12 change, the constant current determined by the gradation data is used. Accordingly, it is possible to effectively avoid degradation of image quality due to changes over time.

  However, in the configuration shown in FIG. 11, the through current continues to flow from the power supply Vcc to the transistors TR2 and TR3 during the periods T2, T3, and T4 during which the transistor TR3 is turned on by the drive scan signal ds. As a result, there is a problem that power consumption increases.

  Further, in such periods T2, T3, and T4, it is necessary to make the signal level S of the signal level holding capacitor C2 wider than the period T3 in which the signal level of the signal line SIG is set by the write signal ws. These periods T2, T3, and T4 overlap in the line, thereby causing the influence of adjacent pixels. Specifically, as shown in FIG. 14, when a current of a pixel circuit in which these periods T2 to T4 are overlapped flows in a wiring pattern for setting the source potential of the transistor TR3, and in this wiring pattern, By having the resistance value, for example, when these wiring patterns are grounded above and below the pixel portion 23, the source potential of the transistor TR3 rises as the pixel is closer to the center of the screen in the vertical direction, and the signal level is maintained accordingly. As a result, the inter-terminal voltage of the capacitor C2 is lowered, and as shown in FIG. 15, shading occurs such that the brightness decreases at the center side.

  Further, as shown in FIG. 16, when the periphery is set to an intermediate gradation and a low gradation area is formed at the center, a high gradation area is formed below the low gradation area, so-called Vertical crosstalk occurs.

Even during the period in which the organic EL element 12 is caused to emit light, a current flows through the transistor TR2 in each pixel 23, and this current flows out from the earth line through the organic EL element 12. However, the earth line from which the current flows out from the organic EL element 12 is the earth line on the counter substrate side provided to face the substrate on which the pixel circuit is provided. As a result, when the periods T2, T3, and T4 in the non-light emitting period overlap with each other in a plurality of lines and current flows out of the transistor TR2 in these periods T2, T3, and T4, the adjacent pixels due to shading and the like The effect of.
USP 5,684,365 JP-A-8-234683

  The present invention has been made in consideration of the above points, and reduces power consumption in a configuration in which a light emitting element is driven by a transistor having a source follower circuit configuration by a gate source voltage based on a voltage between terminals of a signal level holding capacitor. In addition, the present invention intends to propose a display device and a display device driving method capable of effectively avoiding the influence from adjacent pixels.

  In order to solve this problem, in the invention of claim 1, a display device having a pixel portion in which pixels driven by current are arranged in a matrix and a drive circuit for driving the pixel portion to set the gradation of the pixel. The source follower circuit in which the pixel holds a signal level holding capacitor between the light emitting element and the gate source, and drives the light emitting element by the gate-source voltage by the voltage between the terminals of the signal level holding capacitor. And a drive circuit having a switch circuit for a signal line for connecting the gate of the transistor to the signal line, and a switch circuit for a cut-off for connecting the gate of the transistor to a cut-off voltage for cutting off the transistor Cuts off the transistor by setting the cutoff switch circuit to the ON state. Set the period to stop the light emission of the light emitting element, set the cut-off switch circuit to the on state, set the signal line switch circuit to the on state, and hold the signal level according to the signal level of the signal line Set the voltage across the capacitor terminals.

  According to a second aspect of the present invention, the pixel is applied to a display device having a pixel portion in which pixels driven by current are arranged in a matrix, and the pixel has a signal level holding capacitor between the light emitting element and the gate source. The transistor by the source follower circuit that drives the light emitting element by the gate-source voltage by the voltage between the terminals of the capacitor for holding the signal level and the gate of the transistor is temporarily connected to the cutoff voltage, and the transistor is cut off The cut-off switch circuit that stops the light emission of the light-emitting element, and the turn-off operation of the cut-off switch circuit, the transistor gate is connected to the signal line between the terminals of the signal level holding capacitor A signal line switch circuit for setting the voltage according to the signal level of the signal line. To.

  According to a third aspect of the present invention, the pixel is applied to a display device having a pixel portion in which pixels of an organic EL element are arranged in a matrix, and the pixel is for holding a signal level between the organic EL element and the gate source. A transistor with a source follower circuit that holds the capacitor and drives the organic EL element by the gate-source voltage by the voltage between the terminals of the capacitor for holding the signal level, and the transistor gate is temporarily connected to the cut-off voltage. After the cut-off switch circuit for stopping the light emission of the organic EL element by the cut-off operation and the cut-off switch circuit off operation, the transistor gate is connected to the signal line to hold the signal level. Switch for signal line that sets the voltage between terminals of the capacitor according to the signal level of the signal line To have a road.

  According to a fourth aspect of the present invention, the pixel is applied to a driving method of a display device having a pixel portion in which pixels driven by current drive are arranged in a matrix, and the pixel is for holding a signal level between a light emitting element and a gate source. A transistor with a source follower circuit that drives a light emitting element by a gate-source voltage by a voltage between terminals of a capacitor for holding a signal level, and a switch circuit for a signal line that connects the gate of the transistor to a signal line, A switch circuit for cut-off that connects the gate of the transistor to a cut-off voltage that cuts off the transistor, and the driving method of the display device sets the switch circuit for cut-off to an on state, Set the period to stop the light emission of the light emitting element by cutting off the transistor, After setting the switching circuit for cutoff off state, by setting the switching circuit for the signal lines to the ON state, so as to set the terminal voltage of the capacitor for the signal level held by the signal line for the signal level.

  According to the configuration of claim 1, the pixel is applied to a display device having a pixel portion in which pixels driven by current drive are arranged in a matrix and a driving circuit for driving the pixel portion to set the gradation of the pixel. A transistor having a source follower circuit that holds a signal level holding capacitor between the light emitting element and the gate source and drives the light emitting element by a gate-source voltage by a voltage between terminals of the signal level holding capacitor; and a gate of the transistor A signal line switch circuit for connecting the signal line to the signal line, a cut-off switch circuit for connecting the gate of the transistor to a cut-off voltage for cutting off the transistor, and the drive circuit is a switch for cut-off By setting the circuit to the on state, the transistor is cut off and the light emitting element stops emitting light. By setting the period, when the light emitting element emits no light can be prevented from consuming power transistors, thereby reducing the power consumption. Also, after setting the cut-off switch circuit to the ON state, setting the signal line switch circuit to the OFF state, and setting the voltage across the terminals of the signal level holding capacitor according to the signal level of the signal line, The period for setting the terminal voltage of the capacitor for holding the signal level can be set for each line sequentially so that the periods do not overlap with each other by a plurality of lines. Is set to a reference voltage such as a ground potential to set the voltage between terminals of the signal level holding capacitor, it is possible to effectively avoid the influence from adjacent pixels. As a result, in a configuration in which a light-emitting element is driven by a transistor having a source follower circuit configuration by a gate-source voltage based on a voltage between terminals of a signal level holding capacitor, power consumption is reduced and the influence from adjacent pixels is effectively avoided. can do.

  Thus, according to the configurations of claims 2 and 3, the power consumption is reduced in the configuration in which the light emitting element is driven by the transistor having the source follower circuit configuration by the gate source voltage by the voltage between the terminals of the signal level holding capacitor. In addition, it is possible to provide a display device capable of effectively avoiding the influence from adjacent pixels. According to the configuration of claim 4, the gate-source voltage by the voltage across the terminals of the signal level holding capacitor can be provided. In a configuration in which a light-emitting element is driven by a transistor having a source follower circuit configuration, it is possible to provide a method for driving a display device that can reduce power consumption and effectively avoid the influence from adjacent pixels.

  According to the present invention, in the configuration in which the light emitting element is driven by the transistor having the source follower circuit configuration by the gate source voltage by the voltage between the terminals of the capacitor for holding the signal level, the power consumption is reduced, and the influence from the adjacent pixel is further reduced. Can be effectively avoided.

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

(1) Configuration of Embodiment FIG. 2 is a block diagram showing a display device according to an embodiment of the present invention in comparison with FIG. In the display device 31, the pixel unit 32 includes current-driven pixels (PX) 33 arranged in a matrix, and three scanning lines SCN, SCN 1, SCN 2 are provided in the horizontal direction for each pixel 33. It is done. Further, a signal line SIG is provided in the vertical direction for each column so as to be orthogonal to these scanning lines SCN, SCN1, and SCN2. With respect to the pixel portion 32 formed in this way, the display device 31 drives the scanning lines SCN, SCN1, and SCN2 by the vertical drive circuit 34, and the operation of the pixel circuit provided in the pixel 33 sequentially in line units. And the gray level of each pixel 33 is set by driving the signal line SIG by the horizontal drive circuit 35 so as to correspond to the control of the pixel circuit.

  Therefore, the vertical drive circuit 34 generates a write signal ws for sequentially instructing writing to each pixel 33 in units of lines by the write scan circuit (WSCN) 34A, and outputs the write signal ws to the scan line SCN. The setting of gradation in the pixel 33 is controlled. In addition, a drive scan circuit (DSCN) 34B and a drive scan circuit (DSCN2) 34C for outputting drive scan signals ds1 and ds2 in synchronization with the output of the write signal ws by the write scan circuit 34A are provided.

  In the horizontal drive circuit 35, a drive signal is generated according to the gradation data D1 indicating the gradation of each pixel 33, and this drive signal is distributed to each signal line SIG by a horizontal selector (HSEL) 35A and output. It is made like that.

  FIG. 1 is a connection diagram showing each pixel 33 of the display device 31 in comparison with FIG. The transistors TR1 to TR4 constituting the pixel 33 are n-channel MOS type TFTs, and are integrally formed on the glass substrate together with the horizontal drive circuit 35 and the vertical drive circuit 34 by an amorphous process.

  In the pixel 33 related to the display device 31, the organic EL element 12 is driven by the transistor TR2 by a source follower circuit, and a terminal of a signal level holding capacitor C2 provided between the gate and source of the transistor TR2. By setting the inter-voltage, the gate source voltage Vgs of the transistor TR2 is set, and the drive current of the organic EL element 12 is set.

  In addition, a switch circuit including a transistor TR3 for setting the source side end of the signal level holding capacitor C2 to a reference voltage and a transistor TR1 for connecting the gate side end of the signal level holding capacitor C2 to the signal line SIG are provided. These transistors TR1 and TR2 set the voltage across the terminals of the signal level holding capacitor.

  The pixel 33 is further provided with a switch circuit for power supply by a transistor TR4 that connects the gate of the transistor TR2 to a cut-off voltage for cutting off the transistor TR2. In this embodiment, the reference voltage for the transistor TR3 and the cut-off voltage for the transistor TR4 are set to the ground voltage.

  Accordingly, in this embodiment, the transistor TR4 is set to cut off the transistor TR2 to control the organic EL element 12 so as not to emit light, so that no current flows through the transistor TR2 during the non-light emitting period. Thus, power consumption is reduced and various influences by pixels adjacent in the vertical direction are prevented.

  That is, as shown in FIGS. 3 and 4, in the vertical drive circuit 34, the write scan circuit 34A sequentially writes the write signal ws of the scanning line SCN in the horizontal scanning period (1H) of one frame (1f) based on the gradation data D1. (FIG. 3A), the transistor TR1 is turned on in the pixel circuit of the corresponding line, and one end of the signal level holding capacitor C2 is set to the voltage Vin of the signal line SIG. 4A to 4D show connections of the pixels 33 corresponding to the periods TA to TD in FIG. 3, respectively.

  When the signal level Vin of the signal line SIG is set in the signal level holding capacitor C2 in this way, the vertical drive circuit 34 raises the drive scan signal ds1 from the drive scan circuit 34B (FIG. 3B). Thus, the other end of the signal level holding capacitor C2 is set to the ground voltage which is a reference voltage. Thereby, in the display device 31, the signal level of the signal line SIG is reliably set in the capacitor C2 by a so-called bootstrap circuit.

  In this way, the vertical drive circuit 34 sets the voltage between the terminals of the signal level holding capacitor C2 by the signal level Vin of the signal line SIG by the rise of the write signal ws, and rises the write signal ws. The drive scan signal ds2 is raised from the drive scan circuit 34B for a predetermined period prior to (FIG. 3C), whereby the transistor TR2 is cut off and the driving of the organic EL element 12 is stopped (FIG. 3). (D) and (E)). In addition, by raising the drive scan signal ds1 in synchronization with the rise of the drive scan signal ds2, the light emission of the organic EL element 12 is immediately stopped by stopping the driving of the organic EL element 12 (FIG. 4 (B)).

  As a result, in this pixel 33, the transistor TR4 controls the light emission and non-light emission of the organic EL element 12, and the transistor TR2 uses the organic EL element by the gate-source voltage Vgs based on the voltage across the terminals of the signal level holding capacitor C2. 12 is driven (FIGS. 4A and 4D).

(2) Operation of the embodiment In the above configuration, the display device 31 (FIG. 2) is driven horizontally to the pixels 33 of the pixel unit 32 sequentially in units of lines by driving the scanning lines SCN, SCN1, and SCN2 by the vertical drive circuit 34. The signal level of the signal line SIG driven by the circuit 35 is set. In the display device 31, each pixel emits light according to the set signal level, and a desired image is displayed.

  In the display device 31 (FIGS. 1, 3, and 4), in each pixel 33, a signal level holding capacitor C <b> 2 is provided at the gate source of the transistor TR <b> 2 of the source follower circuit configuration that drives the organic EL element 12. In the state where the source side end of the signal level holding capacitor C2 is set to the ground potential as the reference voltage by the switch circuit by TR3, the gate side end of the signal level holding capacitor C2 is connected to the signal line by the switch circuit by the transistor TR1. By connecting to the SIG, the setting of each pixel 33 related to the signal level of the signal line SIG is executed.

  Thus, in the display device 31, even when the characteristics of the organic EL element 12 change with time, the organic EL element 12 can be driven by current driving according to the gradation data D1. Further, such a driving can be realized by configuring the pixel circuit by an n-channel MOS type TFT and driving the organic EL element 12 having a source follower circuit configuration by current driving.

  However, if no measures are taken, current continues to flow through the transistors TR2 and TR3 in the non-light emitting period, and power is consumed unnecessarily and power consumption increases. Further, the change in the reference voltage due to the current causes an influence by pixels adjacent in the vertical direction, and vertical shading and crosstalk occur.

  For this reason, in this embodiment, the transistor TR4 is provided at the gate of the transistor TR2, the organic EL element 12 is not driven by the transistor TR2, and the signal level holding capacitor C2 is connected to the signal line SIG. During a period other than the period set by the level Vin, the gate voltage of the transistor TR2 is set to a voltage that cuts off the transistor TR2. As a result, in the pixel 33, current can be prevented from flowing from the power source Vcc via the transistors TR2 and TR3, and an increase in power consumption due to the continued flow of such current is prevented.

  In this way, by setting the signal level Vin of the signal line SIG to each pixel sequentially in units of lines so that no current flows during the non-light emitting period, the reference voltage set by the transistor TR3 is almost equal. A constant voltage can be maintained, whereby the influence of pixels adjacent in the vertical direction can be prevented, vertical shading and crosstalk can be prevented, and high uniformity image quality can be obtained.

(3) Effects of the embodiment According to the above configuration, in the configuration in which the light emitting element is driven by the transistor having the source follower circuit configuration by the gate source voltage by the voltage between the terminals of the signal level holding capacitor, the gate voltage of the transistor TR2 Is set to the cut-off voltage to control light emission and non-light emission of the light emitting element, thereby reducing power consumption and effectively avoiding the influence from adjacent pixels.

  FIG. 5 is a connection diagram illustrating a display apparatus according to an embodiment of the present invention in comparison with FIG. In the display device 41, in each pixel 43, the transistor TR3 that sets the source side end of the signal level holding capacitor C2 to the reference voltage is controlled by the write signal ws. The display device 41 is configured in the same manner as the display device 31 of the first embodiment except that the configuration related to control by the write signal ws is different.

  As a result, in this display device 41, the vertical drive circuit 44 generates and outputs the write signal ws and the drive scan signal da2 by the write scan circuit (WSCN) 44A and the drive scan circuit (DSCN2) 44C, respectively, and the horizontal drive circuit. In 45, a drive signal corresponding to the gradation data D1 is output to each signal line SIG by a horizontal selector (HSEL) 45A.

  As shown in FIG. 6, the display device 41 is configured to control the transistor TR3 that sets the source side end of the signal level holding capacitor C2 to the reference voltage in accordance with the write signal ws. The write signal ws and the drive scan signal ds2 are output in the same manner as the display device 31 according to FIG. 6 (A) and (B). Thereby, in the display device 41, the rising of the drive scan signal ds2 cuts off the transistor TR2 and stops the supply of current to the organic EL element 12, thereby controlling the light emission and non-light emission of the organic EL element 12. It is made like that. Thus, when the supply of current to the organic EL 12 is stopped in this way, the terminal voltage of the organic EL element 12 is reduced to the threshold voltage VthEL of the organic EL element 12, whereby the organic EL element 12 stops emitting light. Will do.

  Further, the light emission of the organic EL element 12 is stopped in this way, and in the display device 41, the drive scan signal ds2 is lowered immediately before the corresponding horizontal scanning period, and then the signal is generated by the rise of the write signal ws. With the source side end of the level holding capacitor C2 set to the ground voltage, the other end of the signal level holding capacitor C2 is set by the signal level Vin of the signal line SIG, whereby the signal level holding capacitor The voltage between the terminals of C2 is set by the signal level Vin of the signal line SIG.

  Thus, also in this embodiment, the transistors TR2 and TR3 are only in a short period during the period in which the voltage between the terminals of the signal level holding capacitor C2 is set by the signal level Vin of the signal line SIG in the corresponding horizontal scanning period. As a result, the power consumption is reduced as a whole, and the influence from adjacent pixels can be effectively avoided.

  As in this embodiment, the transistor TR3 for setting the source side end of the signal level holding capacitor C2 to the reference voltage is controlled by the write signal ws, thereby reducing the number of scanning lines accordingly. The same effect can be obtained.

  In the above-described embodiment, the case where an organic EL element and a pixel circuit are formed on a glass substrate by applying an amorphous silicon process has been described. However, the present invention is not limited to this, and a transistor made of polysilicon is formed. In this case, the present invention can be widely applied to a case where a driver circuit is formed separately from the pixel portion using a silicon substrate and then connected to the pixel portion to be integrated.

  In the above-described embodiments, the case where the light emitting element by the organic EL element is current-driven has been described. However, the present invention is not limited to this, and can be widely applied to display devices using various light-emitting elements related to current driving. .

  The present invention relates to a display device and a display device driving method, and can be applied to a self-luminous display device driven by current, such as an organic EL display device.

It is a connection diagram which shows the pixel of the display apparatus which concerns on Example 1 of this invention with a periphery structure. It is a block diagram which shows the display apparatus which concerns on Example 1 of this invention. 2 is a time chart for explaining the operation of the pixel in FIG. 1. FIG. 4 is a connection diagram for explaining the time chart of FIG. 3. It is a connection diagram which shows the pixel of the display apparatus which concerns on Example 2 of this invention with a periphery structure. 6 is a time chart for explaining the operation of the pixel in FIG. 5. It is a block diagram which shows the structure of a display apparatus. It is a connection diagram which shows the structure of the display apparatus by an organic EL element. It is a characteristic curve figure which shows the characteristic of an organic EL element. It is a characteristic curve figure with which it uses for description of the change of the operating point of an organic EL element. FIG. 3 is a connection diagram illustrating a pixel circuit having a source follower circuit configuration along with a peripheral configuration. 12 is a time chart for explaining the operation of the pixel circuit in FIG. 11. FIG. 13 is a connection diagram for explaining the time chart of FIG. 12. It is a basic diagram with which it uses for description of the fluctuation | variation of a reference voltage. It is a basic diagram which shows vertical shading. It is a basic diagram which shows crosstalk.

Explanation of symbols

1, 11, 21, 31, 41 ... display device, 2, 22, 32, 42 ... pixel unit, 3, 23, 33, 43 ... pixel, 4, 24, 34, 44 ... vertical drive circuit, 4A, 24A, 34A, 44A: Light scan circuit, 5, 25, 35, 45 ... Horizontal drive circuit, 12 ... EL element, 24B, 34B, 34C, 44C ... Drive scan circuit, 25A, 35A, 45A ... Horizontal selector, C1, C2 ... Capacitors, TR1 to TR4 ... Transistors

Claims (4)

In a display device having a pixel portion in which pixels driven by current drive are arranged in a matrix, and a drive circuit that drives the pixel portion to set the gradation of the pixel.
The pixel is
A light emitting element;
A transistor having a source follower circuit that holds a signal level holding capacitor between a gate and a source and drives the light emitting element by a gate-source voltage based on a voltage between terminals of the signal level holding capacitor;
A switch circuit for a signal line connecting the gate of the transistor to the signal line;
A cut-off switch circuit for connecting the gate of the transistor to a cut-off voltage for cutting off the transistor;
The drive circuit is
By setting the cut-off switch circuit to an on state, the transistor is cut off to set a period for stopping light emission of the light-emitting element,
After setting the cut-off switch circuit to the OFF state, the signal line switch circuit is set to the ON state, and the voltage between the terminals of the signal level holding capacitor is set according to the signal level of the signal line. A display device characterized by: In a display device having a pixel portion formed by arranging pixels driven by current in a matrix,
The pixel is
A light emitting element;
A transistor having a source follower circuit that holds a signal level holding capacitor between a gate and a source and drives the light emitting element by a gate-source voltage based on a voltage between terminals of the signal level holding capacitor;
A switch circuit for cut-off that stops light emission of the light-emitting element by temporarily connecting the gate of the transistor to a cut-off voltage and cutting off the transistor;
Following the off operation of the cut-off switch circuit, the gate of the transistor is connected to a signal line, and the voltage between the terminals of the signal level holding capacitor is set according to the signal level of the signal line. A display device comprising: a switch circuit. In a display device having a pixel portion in which pixels by organic EL elements are arranged in a matrix,
The pixel is
The organic EL element;
A transistor by a source follower circuit that holds a signal level holding capacitor between a gate source and drives the organic EL element by a gate-source voltage by a voltage between terminals of the signal level holding capacitor;
A switch circuit for cut-off for stopping light emission of the organic EL element by temporarily connecting the gate of the transistor to a cut-off voltage and cutting off the transistor;
Subsequent to the off operation of the cut-off switch circuit, the gate of the transistor is connected to a signal line, and the voltage between the terminals of the signal level holding capacitor is set according to the signal level of the signal line. A display device comprising: a switch circuit. In a driving method of a display device having a pixel portion in which pixels by current driving are arranged in a matrix,
The pixel is
A light emitting element;
A transistor having a source follower circuit that holds a signal level holding capacitor between a gate and a source and drives the light emitting element by a gate-source voltage based on a voltage between terminals of the signal level holding capacitor;
A switch circuit for a signal line connecting the gate of the transistor to the signal line;
A cut-off switch circuit for connecting the gate of the transistor to a cut-off voltage for cutting off the transistor;
The driving method of the display device is:
By setting the cut-off switch circuit to an on state, the transistor is cut off to set a period for stopping light emission of the light-emitting element,
After setting the cut-off switch circuit to the OFF state, the signal line switch circuit is set to the ON state, and the voltage between the terminals of the signal level holding capacitor is set according to the signal level of the signal line. A method for driving a display device.

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