JP5148951B2 - Image display device and driving method of image display device - Google Patents

Description

  The present invention relates to an image display device and a driving method thereof.

  Conventionally, an image display device including an organic EL (Electroluminescence) element using electroluminescence has been known. In such an image display device, generally, an organic EL element and a thin film transistor (TFT) that controls light emission are electrically connected in series.

  By the way, for a thin film transistor that controls light emission of an organic EL element (hereinafter referred to as “control transistor”), there is a threshold voltage at which current starts to flow between a source and a drain. This threshold voltage is slightly different depending on the control transistor that constitutes each pixel, which may cause unevenness in image display.

  Therefore, there has been proposed an image display device in which a transistor for compensating the threshold voltage of the control transistor is electrically connected between the gate and drain of the control transistor (for example, Patent Documents 1 and 2).

JP 2004-280059 A JP 2004-341359 A

  However, the organic EL element also has a threshold voltage at which current starts to flow between both electrodes, and this threshold voltage fluctuates due to aging degradation or the like, which may cause unevenness in image display.

  Such a problem is common to image display apparatuses in which light emitting elements whose light emission luminance is adjusted by the amount of current are used.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique capable of suppressing deterioration in image quality in consideration of a change in characteristics of a light emitting element.

  In order to solve the above-mentioned problems, the invention of claim 1 is an image display device, comprising: a light-emitting element whose light emission luminance changes according to an amount of current; and first, second, and third electrodes, A first transistor that adjusts an amount of current between the first electrode and the second electrode by a potential applied to the third electrode; and fourth, fifth, and sixth electrodes A second transistor that adjusts an amount of current between the fourth electrode and the fifth electrode by a potential applied to the sixth electrode, and seventh and eighth electrodes, A capacitor configured to obtain an electric capacity between the seventh electrode and the eighth electrode, wherein the second electrode is electrically connected to the light emitting element; By adjusting the amount of current between the first electrode and the second electrode, The amount of current in the element is controlled, the third and fourth electrodes are electrically connected to the seventh electrode, and the fifth electrode is electrically connected to the first electrode. It is connected.

  The invention according to claim 2 is the image display device according to claim 1, wherein a first potential is applied to the sixth electrode in a state where electric charges are accumulated in the capacitor, and the first potential is applied. By setting the two transistors in a conductive state in which current can flow between the fourth electrode and the fifth electrode, the second transistor, the first transistor, and the light-emitting element are interposed. The amount of charge accumulated in the capacitor due to the transferred charge is set to a charge amount corresponding to a voltage including at least a voltage obtained by combining the threshold voltage of the first transistor and the threshold voltage of the light emitting element. One potential applying means is provided.

  The invention of claim 3 is the image display device according to claim 2, further comprising second potential applying means for applying a potential according to an image signal to the eighth electrode, wherein the first potential is provided. The applying unit applies the first potential to the sixth electrode in a state where the potential corresponding to the image signal is applied to the eighth electrode by the second potential applying unit. By setting the transistor in the conductive state, the amount of charge accumulated in the capacitor due to the movement of charge through the second transistor, the first transistor, and the light emitting element can be reduced. The threshold voltage of one transistor, the threshold voltage of the light emitting element, and the voltage corresponding to the image signal are used as a charge amount corresponding to a voltage.

  According to a fourth aspect of the present invention, there is provided the image display device according to the first aspect, comprising the ninth, tenth and eleventh electrodes, and between the ninth electrode and the tenth electrode. A third transistor that adjusts the amount of current in accordance with the potential applied to the eleventh electrode, twelfth, thirteenth, and fourteenth electrodes, and the twelfth electrode, the thirteenth electrode, And a fourth transistor that adjusts the amount of current between them according to the potential applied to the fourteenth electrode, wherein the ninth electrode is electrically connected to the twelfth electrode, The tenth electrode is electrically connected to the first electrode, and the thirteenth electrode is electrically connected to the seventh electrode.

  The invention according to claim 5 is the image display device according to claim 4, wherein the first potential applying means for applying a first potential to the twelfth electrode, and the first electrode to the twelfth electrode. In the state where the potential of 1 is applied, by applying a second potential to the 14th electrode, a current flows between the 12th electrode and the 13th electrode in the fourth transistor. A second potential applying unit configured to store a charge in the capacitor, and a third potential is applied to the sixth electrode so that the second transistor is connected to the fourth electrode; And the fifth electrode are set in a conductive state in which a current can flow, so that the amount of electric charge accumulated in the capacitor is changed to the second transistor, the first transistor, and the light emitting element. The first transistor by the movement of the charge through the first transistor; A third potential applying means for setting a charge amount corresponding to a voltage including at least a voltage obtained by combining a threshold voltage and a threshold voltage of the light emitting element; and a potential corresponding to the charge amount accumulated in the capacitor. And a third potential is applied to the eleventh electrode in a state where a predetermined potential is applied to the ninth electrode by the first potential applying means. Is set to a conductive state in which a current can flow between the ninth electrode and the tenth electrode, thereby providing fourth potential applying means for causing the light emitting element to emit light.

  The invention of claim 6 is a driving method of an image display device for driving the image display device according to claim 1, and (A) the sixth electrode in a state where electric charges are accumulated in the capacitor. And applying the first potential to the second transistor, setting the second transistor to a conductive state in which a current can flow between the fourth electrode and the fifth electrode. The amount of charge accumulated in the capacitor due to movement of charge through the first transistor and the light emitting element is a voltage obtained by combining the threshold voltage of the first transistor and the threshold voltage of the light emitting element. A charge amount corresponding to a voltage including at least, and (B) the potential corresponding to the charge amount stored in the capacitor in the step (A) is applied to the third electrode, For the first electrode By applying a constant electric potential, and having a step of emitting the light emitting element.

  A seventh aspect of the invention is a method for driving an image display device for driving the image display device according to the fourth aspect, wherein (a) the first potential is applied to the twelfth electrode. By applying a second potential to the fourteenth electrode, the fourth transistor is set in a conductive state in which a current can flow between the twelfth electrode and the thirteenth electrode, (B) applying a third potential to the sixth electrode, and connecting the second transistor between the fourth electrode and the fifth electrode. By setting the conductive state in which a current can flow, the amount of charge accumulated in the capacitor is changed by the movement of the charge through the second transistor, the first transistor, and the light emitting element. Threshold voltage of the transistor and the light emitting element A charge amount corresponding to a voltage including at least a voltage including a threshold voltage, and (c) a potential corresponding to the charge amount stored in the capacitor is applied to the third electrode, and the first electrode The third transistor is connected between the ninth electrode and the tenth electrode by applying a fourth potential to the eleventh electrode while a predetermined potential is applied to the nine electrodes. And a step of causing the light emitting element to emit light by setting to a conductive state in which a current can flow between them.

<Terminology>
In the present specification, the term “electrically connected” means that one member and the other member are always connected in a conductive manner via wiring or the like, and one member and the other member Is used in a sense that includes not only conductive wiring and the like, but also a mode of being indirectly connected by other members. In other words, the term “electrically connected” means that one member and the other member are connected to each other depending on the state of other members (for example, a conductive state in which a current can flow between the source and the drain of the transistor). Is used in a meaning including a mode in which the wiring is conductively connected by wiring and other members.

  The “gate voltage” in this specification refers to a potential difference between a source and a gate with respect to the potential of the source with respect to the transistor.

  In addition, the “threshold voltage” in this specification includes a threshold voltage of a transistor and a threshold voltage of a light emitting element. The threshold voltage of a transistor refers to a gate voltage that serves as a boundary when the transistor changes from an off state (a state where a drain current does not flow) to an on state (a state where a drain current flows). The threshold voltage of the light emitting element is a state in which the light emitting element emits light (a state in which no current flows between both electrodes of the light emitting element) (a state in which the light emitting element emits light between the two electrodes of the light emitting element). This is the voltage applied between the electrodes of the light emitting element which becomes the boundary when the current state changes. The “threshold voltage” is abbreviated as “threshold” as appropriate.

  According to the invention of any one of claims 1 to 7, the amount of charge accumulated in the capacitor can be reduced by setting the second transistor in a conductive state with the charge accumulated in the capacitor. The amount of charge depends on a voltage that includes at least the threshold voltage of the transistor and the threshold voltage of the light-emitting element, so that deterioration in image quality can be suppressed in consideration of changes in characteristics of the light-emitting element. .

  According to the third aspect of the present invention, since charge accumulation according to an image signal and compensation of threshold voltages of the first transistor and the light emitting element are performed simultaneously, light emission occupying a period of one frame. The preparation period for can be compressed.

  In addition, according to any of the fourth, fifth, and seventh aspects of the invention, excessive supply of current to the light emitting element during a period in which the light emitting element should not emit light is prevented, so that the image quality is further deteriorated. Can be suppressed.

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

<Schematic configuration of image display device>
FIG. 1 is a diagram illustrating a schematic configuration of an image display apparatus 100 according to an embodiment of the present invention.

  The image display device 100 is a mobile phone including a main body 110 and a display unit 120, that is, a portable electronic device, and displays various images such as moving images and still images on the display unit 120.

  The main body 110 includes a communication function, a power supply function such as a battery, and an operation unit.

  The display unit 120 includes, for example, an organic EL display (organic electroluminescence display) having a substantially rectangular outline, and driver means to which various signals supplied from the main body unit 110 are input. Note that the organic EL display is a self-luminous image display device having a self-luminous light emitting element that emits light by flowing current through the organic material.

  The organic EL display also has an image signal line (for example, a data line Ldata described later) for supplying each pixel with a potential corresponding to an image signal corresponding to the emission luminance (for example, a pixel data signal for each pixel). And a scanning signal line (for example, a sense / select line Lss described later) that is provided so as to be substantially orthogonal to the image signal line and supplies a scanning signal to each pixel. The scanning signal is a signal that controls the timing at which charges corresponding to the pixel data signal are accumulated in each pixel via the image signal line.

  On the other hand, the driver means is electrically connected to the image signal line and is electrically connected to the scanning signal line and an X driver (image signal line driving circuit) for controlling the timing of supplying the pixel data signal to the image signal line. And a Y driver (scanning signal line driving circuit) for controlling the timing of supplying the scanning signal to the scanning signal line. For example, in the image display apparatus 100, the X driver is disposed along the short side of the organic EL display, and the Y driver is disposed along the long side of the organic EL display.

<Functional configuration of image display device>
FIG. 2 is a block diagram illustrating a functional configuration of the image display apparatus 100.

  The image display apparatus 100 mainly includes a control unit 111, an operation unit 112, an X driver Xd, a dedicated driver Sd, and a display panel 121.

  The control unit 111 is a part that performs overall control of the operation of the image display apparatus 100. The control unit 111 includes a CPU, a RAM, a ROM, and the like. For example, various operations and controls are realized by the CPU reading and executing a program stored in the ROM or the like. Note that the control unit 111 also has a function of controlling transmission of signals from the X driver Xd and the dedicated driver Sd.

  The operation unit 112 includes various buttons such as a so-called numeric keypad, and sends various signals to the control unit 111 when the various buttons are pressed.

  The display panel 121 includes a large number of pixel circuits 1A arranged in a lattice pattern. Here, the circuit configuration of the pixel circuit 1A will be described.

  FIG. 3 is a diagram illustrating a circuit configuration of the pixel circuit 1A.

  The pixel circuit 1A includes an organic EL element OLED, four transistors Q1 to Q4, and a capacitor C1.

  The organic EL element OLED is a light-emitting element that is made of an organic material and the like, and whose emission luminance varies depending on the amount of current (current amount) flowing through the light-emitting layer. This organic EL element OLED has an anode electrode and a cathode electrode, and the anode electrode is electrically connected to a power supply line (here, VDD line) Ld that becomes a high potential side when the organic EL element OLED emits light. Connected to. On the other hand, the cathode electrode is grounded so as to be on the low potential side when the organic EL element OLED emits light.

  The transistors Q1 to Q4 are thin film transistors (TFTs) which are a kind of field effect transistors (FETs) adopting a type (n-type) MIS (Metal Insulator Semiconductor) structure in which carriers are electrons. That is, it is composed of n-MISFET TFTs.

  The transistor (also referred to as “driving transistor” as appropriate) Q1 has an organic EL element in which a source electrode and a drain electrode are electrically connected in series to the organic EL element OLED, and the amount of current in the organic EL element OLED is adjusted. The light emission luminance of the element OLED is controlled.

  The transistor Q1 has first to third electrodes E1 to E3. Specifically, the first electrode E1 is electrically connected to the VDD line Ld via the transistor Q3. The first electrode E1 functions as a drain electrode (hereinafter abbreviated as “drain”) when the organic EL element OLED emits light, that is, when a forward current flows through the organic EL element OLED. The second electrode E2 is electrically connected to the anode electrode of the organic EL element OLED, and functions as a source electrode (hereinafter abbreviated as “source”) when a forward current flows through the organic EL element OLED. To do. The third electrode E3 is electrically connected to the capacitor C1 and functions as a so-called gate electrode (hereinafter abbreviated as “gate”).

  In the transistor Q1, the potential applied to the third electrode E3, more specifically, the voltage value applied between the second electrode E2 and the third electrode E3 (that is, between the source and the gate) is adjusted. Thus, the amount of current flowing between the first electrode E1 and the second electrode E2 (hereinafter also referred to as “between the first and second electrodes”) is adjusted. And with the adjustment of the amount of current between the first and second electrodes, the amount of current in the organic EL element OLED is controlled. The potential applied to the third electrode (gate) E3 causes the transistor Q1 to be in a state where the current can flow between the first and second electrodes (that is, between the drain and the source) (conductive state) and the current flows. It is selectively set to an unobtainable state (non-conducting state).

  The transistor (referred to as “Vth compensation transistor” as appropriate) Q2 has a gate voltage (specifically, the second electrode E2 and the third electrode with reference to the potential of the second electrode E2) when the transistor Q1 becomes conductive. The lower limit value (threshold voltage of the transistor Q1) of the potential difference from E3 and the lower limit value of the potential difference between the two electrodes at which current can flow between the anode electrode and the cathode electrode in the organic EL element OLED (threshold voltage of the organic EL element OLED) ) And compensation. More specifically, in the transistor Q2, the gate voltage of the transistor Q1 depends on the threshold voltage of the transistor Q1 (hereinafter also referred to as “threshold Vthtr”) and the threshold voltage of the organic EL element OLED (hereinafter also referred to as “threshold Vthol”). Shift by that amount.

  The transistor Q2 has fourth to sixth electrodes E4 to E6. Specifically, the fourth electrode E4 is conductively connected to a wiring that electrically connects the third electrode E3 and the capacitor C1. That is, the fourth electrode E4 is electrically connected to the gate E3 of the transistor Q1. The fifth electrode E5 is conductively connected to a wiring that electrically connects the first electrode E1 and the transistor Q3. That is, the fifth electrode E5 is electrically connected to the first electrode E1 of the transistor Q1. The sixth electrode E6 is electrically connected to the sense / select line Lss and functions as a so-called gate electrode.

  Note that the sense / select line Lss applies a potential to the sixth electrode E6 for controlling the timing of performing Vth compensation processing and writing processing described later.

  In the transistor Q2, the potential applied to the sixth electrode E6, more specifically, the voltage value applied between the fifth electrode E5 and the sixth electrode E6 (that is, between the source and the gate) is adjusted. As a result, the amount of current flowing between the fourth electrode E4 and the fifth electrode E5 (hereinafter also referred to as “between the fourth and fifth electrodes”) is adjusted. The transistor Q2 is capable of flowing a current between the fourth and fifth electrodes (between the drain and the source) (conductive state) and a current by the potential applied to the sixth electrode (gate) E6. It is selectively set to a non-conducting state (non-conducting state).

  Here, since the light emission luminance of the organic EL element OLED is controlled by the current value, the light emission luminance fluctuates sensitively to fluctuations in the gate voltage of the transistor Q1 during light emission. In particular, when the transistor Q1 is configured using amorphous silicon, the threshold value Vthtr tends to be different for each transistor Q1. Further, the organic EL element OLED also tends to have a different threshold value Vthol for each organic EL element OLED due to deterioration over time. Therefore, if a function for compensating the threshold value Vthtr and the threshold value Vthol (Vth compensation function) different for each pixel is not provided, there is a slight difference between the desired light emission luminance and the actual light emission luminance, and as a result, between pixels. Uneven light emission brightness occurs.

  In view of this, in the image display device 100, processing for compensating for variations in the threshold value Vthtr and the threshold value Vthol in the transistor Q1 by setting the gate voltage of the transistor Q1 to a value corresponding to the threshold value Vthtr and the threshold value Vthol before each light emission (Vth). The transistor Q2 is provided to realize the compensation process.

  Capacitor C1 has seventh electrode E7 electrically connected to third electrode E3 and transistor Q2 of transistor Q1, and eighth electrode E8 electrically connected to data line Ldata. The electric capacity is obtained between the seventh electrode E7 and the eighth electrode E8. The holding capacity of the capacitor C1 is set to a predetermined value (for example, 1 pF).

  The data line Ldata applies a potential according to the pixel data signal to the eighth electrode E8.

  A transistor (referred to as “emission control transistor” as appropriate) Q3 controls the light emission timing of the organic EL element OLED.

  The transistor Q3 has ninth to eleventh electrodes E9 to E11. Specifically, the ninth electrode E9 is electrically connected to the VDD line Ld. The tenth electrode E10 is conductively connected to a wiring that electrically connects the first electrode E1 and the fifth electrode E5. That is, the tenth electrode E10 is electrically connected to the first electrode E1 of the transistor Q1 and the fifth electrode E5 of the transistor Q2. The eleventh electrode E11 is electrically connected to the merge line Lm and functions as a so-called gate electrode.

  The merge line Lm gives a potential for controlling the light emission timing of the organic EL element OLED to the eleventh electrode E11.

  In the transistor Q3, the potential applied to the eleventh electrode E11, more specifically, the voltage value applied between the tenth electrode E10 and the eleventh electrode E11 (that is, between the source and the gate) is adjusted. This adjusts the amount of current flowing between the ninth electrode E9 and the tenth electrode E10 (hereinafter also referred to as “between the ninth and tenth electrodes”). Further, the potential applied to the eleventh electrode (gate) E11 causes the transistor Q3 to have a state in which a current can flow between the ninth and tenth electrodes (that is, between the drain and the source) (conductive state) and a current flow. It is selectively set to an unobtainable state (non-conducting state).

  A transistor (referred to as a “precharge transistor” as appropriate) Q4 controls the timing at which charges are accumulated in the capacitor C1.

  The transistor Q4 has twelfth to fourteenth electrodes E12 to E14. Specifically, the twelfth electrode E12 is electrically connected to a wiring that electrically connects the VDD line Ld and the ninth electrode E9. That is, the twelfth electrode E12 is electrically connected to the VDD line Ld and the ninth electrode E9. The thirteenth electrode E13 is conductively connected to a wiring that electrically connects the fourth electrode E4, the third electrode E3, and the seventh electrode E7. That is, the thirteenth electrode E13 is electrically connected to the third electrode E3, the fourth electrode E4, and the seventh electrode E7. The fourteenth electrode E14 is electrically connected to the precharge line Lp and functions as a so-called gate electrode.

  The precharge line Lp applies a potential for controlling the timing at which a certain amount of charge is accumulated in the capacitor C1 to the fourteenth electrode E14.

  In the transistor Q4, the potential applied to the 14th electrode E14, more specifically, the voltage value applied between the 13th electrode E13 and the 14th electrode E14 (that is, between the source and the gate) is adjusted. Thus, the amount of current flowing between the twelfth electrode E12 and the thirteenth electrode E13 (hereinafter also referred to as “between the twelfth and thirteenth electrodes”) is adjusted. Further, the transistor Q4 has a state in which a current can flow between the twelfth and thirteenth electrodes (that is, between the drain and the source) and a current flows by the potential applied to the fourteenth electrode (gate) E14. It is selectively set to an unobtainable state (non-conducting state).

  In the display panel 121 having such a pixel circuit, as shown in FIG. 2, a common data line Ldata is electrically connected to the plurality of pixel circuits 1A arranged along the column direction, and along the row direction. A common sense / select line Lss is electrically connected to the plurality of arranged pixel circuits 1A.

  The X driver Xd supplies a potential corresponding to the pixel data signal to the data line Ldata in response to a signal from the control unit 111. For example, the control unit 111 synchronizes with the image data transmitted from the outside, and sends a signal for controlling the potential supply timing corresponding to the pixel data signal to each data line Ldata from the X driver Xd to the X driver Xd. Send to

  The dedicated driver Sd applies a potential to the VDD line Ld, the merge line Lm, the precharge line Lp, and the sense / select line Lss with a waveform corresponding to the control signal from the control unit 111.

  The dedicated driver Sd includes, for example, a Y driver and first to fourth shift registers. The Y driver has a function of applying a potential to the VDD line Ld, the merge line Lm, the precharge line Lp, and the sense / select line Lss based on the data stored in the first to fourth shift registers.

  For example, the first shift register holds data of a potential V1 (hereinafter also referred to as “power supply line potential”) to be applied to the VDD line Ld. Here, the power supply line potential V1 is a predetermined high potential value (for example, 10 V). The second shift register holds data of a potential Vm to be applied to the merge line Lm (hereinafter also referred to as “merge line potential”) Vm. Here, as the merge line potential Vm, two values of potentials Vh and Vl are appropriately adopted. The third shift register holds data of a potential Vp to be applied to the precharge line Lp (hereinafter also referred to as “precharge line potential”). Here, as the precharge line potential Vp, binary values of potentials Vh and Vl are appropriately employed. Further, the fourth shift register holds data of potential Vs (hereinafter also referred to as “sense / select line potential”) to be applied to the sense / select line Lss. Here, as the sense / select line potential Vs, two values of potentials Vh and Vl are appropriately adopted.

  The power supply line potential V1, the merge line potential Vm, the precharge line potential Vp, and the sense / select line potential Vs controlled by the Y driver and the first to fourth shift registers correspond to the control signal from the control unit 111. Each waveform is shown.

<Driving of image display device>
FIG. 4 is a timing chart showing a signal waveform (driving waveform) when the organic EL element OLED emits light, and FIG. 5 is a flowchart showing an operation flow of the pixel circuit 1A. FIGS. 4 and 5 focus on driving that causes one pixel circuit 1A included in the display panel 121 to emit light once, and a plurality of frames constituting a moving image or the like are temporally continuous in the image display device 100. FIG. In the case of display, the drive waveform shown in FIG. 4 and the operation flow shown in FIG. 5 are repeated in time sequence for the number of times corresponding to the number of frames. 4 and the operation flow shown in FIG. 5 are realized under the control of the control unit 111.

  In FIG. 4, the horizontal axis indicates time, and in order from the top, (a) a merge line potential (hereinafter simply referred to as “potential”) Vm applied to the merge line Lm, and (b) applied to the precharge line Lp. Precharge line potential (hereinafter simply referred to as “potential”) Vp, (c) sense / select line potential applied to sense / select line Lss (hereinafter simply referred to as “potential”) Vs, (d) data The waveform of the potential (potential Vd) of the signal applied to the line Ldata is shown. When the organic EL element OLED emits light, a predetermined positive high potential Vdd (for example, 10 V) is applied to the VDD line Ld regardless of the light emission preparation stage and the actual light emission stage. Is maintained. In addition, a period related to one light emission includes a preparation period Pp (time t1 to t10) for adjusting light emission luminance and a light emission period Pe (to time t1 and time t10) in which the organic EL element OLED actually emits light. And is configured.

  Hereinafter, the operation flow of the pixel circuit 1A shown in FIG. 5 will be described with reference to FIG.

  First, in step S1, the potential Vm applied to the merge line Lm is set to a predetermined low potential Vl (time t1). At this time, the potential Vp and the potential Vs are set to a predetermined low potential Vl. For this reason, the transistors Q2 to Q4 are in a non-conductive state. The potential Vd is set to 0 V (GND). If light emission is performed a plurality of times, in step S1, the previous light emission is terminated, and if light emission is the first time, the preparation period Pp is simply started.

  In step S2, the potential Vp applied to the precharge line Lp is set to a predetermined high potential Vh (time t2).

  In step S3, the potential Vp applied to the precharge line Lp is set to a predetermined low potential Vl (time t3). At this time, transistor Q4 is set to a non-conductive state.

  Here, at times t2 to t3, the potential Vp is maintained at a predetermined high potential Vh. At this time, a predetermined high potential Vh is applied to the fourteenth electrode E14, and the transistor Q4 becomes conductive. In addition, a predetermined high potential Vdd is applied to the VDD line Ld, and 0 V (GND) is applied to the data line Ldata. For this reason, a predetermined high potential Vdd is applied to the twelfth electrode E12, and charges corresponding to the predetermined high potential Vdd are accumulated in the capacitor C1. At this time, a positive potential is applied to the third electrode E3 by the electric charge accumulated in the capacitor C1, and the transistor Q1 is set in a conductive state.

  In step S4, the potential Vd applied to the data line Ldata is set to the potential −Vdata corresponding to the pixel data signal (time t4 to t5). At this time, by applying the potential −Vdata according to the pixel data signal, a process (writing process) in which charges according to the pixel data signal are accumulated in the capacitor C1 is started.

  In step S5, the potential Vs applied to the sense / select line Lss is set to a predetermined high potential Vh (time t6). At this time, a predetermined high potential Vh is applied to the sixth electrode E6, and the transistor Q2 is set in a conductive state.

  In step S6, the potential Vs applied to the sense / select line Lss is set to a predetermined low potential Vl (time t7). At this time, transistor Q2 is set to a non-conductive state.

  Here, from time t6 to t7, the potential Vs is maintained at a predetermined high potential Vh, and the conduction state of the transistor Q2 is maintained. In the initial stage of time t6 to t7, the transistor Q1 is also set in a conductive state by the electric charge accumulated in the capacitor C1, and the second electrode E2 is grounded via the organic EL element OLED. For this reason, the electric charge accumulated in the capacitor C1 sequentially moves through the fourth electrode E4 to the fifth electrode E5 of the transistor Q2, the first electrode E1 to the second electrode E2 of the transistor Q1, and the organic EL element OLED. . Due to the movement of the electric charge, the electric charge accumulated in the capacitor C1 is gradually reduced, and the potential applied to the third electrode E3 is also gradually reduced. Finally, when the potential difference between the seventh electrode E7 and the cathode electrode of the organic EL element OLED reaches a voltage obtained by combining the threshold value Vthtr of the transistor Q1 and the threshold value Vthol of the organic EL element OLED, charge transfer Stops.

  In step S7, the potential Vd applied to the data line is set to GND (time t8 to t9). At this time, the potential applied to the eighth electrode E8 of the capacitor C1 becomes Vdata higher than the state in which the movement of charges from the capacitor C1 is stopped in steps S5 to S6. That is, the gate voltage of the transistor Q1 increases by the voltage Vdata. At this time, the amount of charge accumulated in the capacitor C1 is the amount of charge corresponding to the voltage obtained by combining the threshold value Vthtr of the transistor Q1, the threshold value Vthol of the organic EL element OLED, and the voltage Vdata corresponding to the pixel data signal. It has become. That is, the transistor Q1 is set in a conductive state in which a current corresponding to the potential Vdata corresponding to the pixel data signal can flow between the first and second electrodes. That is, in this operation flow, the Vth compensation process and the writing process are performed in parallel in time.

  In step S8, the potential Vm applied to the merge line Lm is set to a predetermined high potential Vh (time t10). At this time, a predetermined high potential Vh is applied to the eleventh electrode E11, and the transistor Q3 is set in a conductive state. In addition, a predetermined high potential Vdd is applied to the VDD line Ld, that is, the ninth electrode E9, a predetermined potential corresponding to the potential Vdd is applied to the first electrode E1, and 0 V (GND) is applied to the data line Ldata. It is in the granted state. Furthermore, in consideration of the threshold value Vthtr and the threshold value Vthol, the potential Vdata corresponding to the pixel data signal is applied to the third electrode E3. For this reason, the current corresponding to the pixel data signal Vdata flows between the first and second electrodes of the transistor Q1. That is, a current corresponding to the pixel data signal Vdata flows through the organic EL element OLED, and the organic EL element OLED emits light with a light emission luminance corresponding to the pixel data signal Vdata.

  By the processing in steps S1 to S8, light emission for one frame is realized in the organic EL element OLED, and light emission for a plurality of frames is performed by sequentially repeating the processing in steps S1 to S8.

  In the above, the description has been given focusing on the driving of one pixel circuit 1A included in the display panel 121. However, the following driving is performed on the plurality of pixel circuits 1A included in the display panel 121. Here, it is assumed that the display panel 121 has a predetermined number (here, assumed to be 100) of columns of pixel circuits 1A of horizontal lines.

  First, as in the drive waveforms at times t2 to t3 in FIG. 4, the application of the high potential Vh to the precharge line Lp is performed simultaneously for all the pixel circuits 1A.

  Next, a writing process in the pixel circuit 1A arranged in the first line of the display panel 121, a writing process in the pixel circuit 1A arranged in the second line of the display panel 121, and an arrangement in the third line of the display panel 121 The driving waveform from time t4 to t9 is the number of horizontal lines, such as the writing process in the pixel circuit 1A to be written,..., The writing process in the pixel circuit 1A arranged on the 100th line of the display panel 121. Minutes and hours are performed sequentially.

  Then, when the writing process for all the pixel circuits 1A is completed, the predetermined high potential Vh is applied to the merge line Lm in all the pixel circuits 1A, so that the organic EL elements OLEDs of all the pixel circuits 1A simultaneously. Light is emitted.

  As described above, when the transistor Q2 is turned on while the electric charge is accumulated in the capacitor C1, the amount of the electric charge accumulated in the capacitor C1 is changed from the threshold voltage (threshold Vthtr) of the transistor Q1 to the organic EL. The charge amount corresponds to a voltage including a voltage obtained by combining the threshold voltage (threshold value Vthol) of the element OLED. For this reason, deterioration in image quality can be suppressed in consideration of a change in characteristics of the light emitting element (here, the organic EL element OLED).

  Further, charge accumulation corresponding to the image signal to the capacitor C1 and compensation of the threshold voltages (threshold Vthtr and threshold Vthol) of the transistor Q1 and the organic EL element OLED are simultaneously performed. For this reason, the preparation period for light emission which occupies the period for 1 frame can be compressed.

  Further, the provision of the transistor Q3 prevents excessive supply of current to the organic EL element OLED during a period in which the organic EL element OLED should not emit light. For this reason, it is possible to further suppress deterioration in image quality.

  Further, since the cathode electrode of the organic EL element OLED is grounded, the cathode electrode can be made common to all (or a plurality of) pixel circuits 1A arranged on the display panel 121. That is, the cathode electrode in the display panel 121 can be configured with a simple structure, and various merits such as an improvement in yield due to simplification of the manufacturing process, an improvement in production efficiency, a simplification of manufacturing equipment, and a reduction in cost are provided. Can be obtained.

  Since the Vth compensation process generally requires a time of about 0.1 to 1 millisecond, if the number of horizontal lines increases, the preparation period Pp will be lengthened. Therefore, the pixel circuit 1A according to the present embodiment is preferably applied to, for example, a small display panel having a relatively small number of pixels up to about 100 horizontal lines.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the thing of the content demonstrated above.

<Modification 1>
For example, in the above embodiment, the four transistors Q1 to Q4 constituting the pixel circuit 1A are all n-type TFTs. However, the present invention is not limited to this. For example, all transistors are of a type in which carriers are holes. A thin film transistor (TFT) which is a kind of field effect transistor (FET) adopting a (p-type) MIS (Metal Insulator Semiconductor) structure, that is, a p-MISFET TFT may be used.

  Here, a circuit configuration of the pixel circuit 1B according to the first modification configured using the p-type TFT will be described.

  FIG. 6 is a diagram illustrating a circuit configuration of the pixel circuit 1B according to the first modification.

  Compared with the pixel circuit 1A according to the above-described embodiment, the pixel circuit 1B according to the modification 1 has four transistors Q1 to Q4 changed to transistors Qb1 to Qb4 that are p-MISFET TFTs, and the cathode of the organic EL element OLED. The difference is that the electrode and the anode electrode are inverted. Since the transistors Qb1 to Qb4 have different structures from the transistors Q1 to Q4 according to the above embodiment, the symbols of the first to sixth electrodes E1 to E6 and the ninth to fourteenth electrodes E9 to E14 are denoted by Eb1 to Eb1. It is changed to Eb6, Eb9 to Eb14. The other configurations are exactly the same, so the same reference numerals are given and description thereof is omitted.

  Next, driving of the pixel circuit 1 </ b> B according to the modification 1 configured using p-type TFTs will be described.

  FIG. 7 is a timing chart showing a signal waveform (driving waveform) when the organic EL element OLED emits light in the pixel circuit 1B, and FIG. 8 is a flowchart showing an operation flow of the pixel circuit 1B. FIGS. 7 and 8 focus on driving for causing one pixel circuit 1B included in the display panel 121 to emit light once. In the case where a plurality of frames are continuously displayed in time, FIG. 8 and the operation flow shown in FIG. 8 are repeated in time sequence by the number of times corresponding to the number of frames. 7 and the operation flow shown in FIG. 8 are realized under the control of the control unit 111.

  In FIG. 7, as in FIG. 4, the horizontal axis indicates time, and waveforms of (a) potential Vm, (b) potential Vp, (c) potential Vs, and (d) potential Vd are shown in order from the top. Yes. When the organic EL element OLED emits light, a predetermined negative high potential Vdd (for example, −10 V) is applied to the VDD line Ld regardless of the light emission preparation stage and the actual light emission stage. State is maintained. In addition, the period related to one light emission includes a preparation period Pp (time t1 to t10) for adjusting the light emission luminance and a light emission period Pe (time t1, time t10) in which the organic EL element OLED emits light. It is prepared for.

  The drive waveform shown in FIG. 7 is obtained by vertically inverting the drive waveforms of the potentials Vm, Vp, Vs, and Vd as compared with the drive waveform shown in FIG. That is, in the drive waveform shown in FIG. 4, the portion having the predetermined high potential Vh becomes the predetermined low potential Vl in the drive waveform shown in FIG. 7, and in the drive waveform shown in FIG. In the drive waveform shown in FIG. 7, the portion that is at the potential Vl has a predetermined high potential Vh. Further, the sign of the potential Vd applied to the data line Ldata is reversed. That is, in the drive waveform shown in FIG. 4, the portion having the potential −Vdata is the potential + Vdata in the drive waveform shown in FIG.

  Therefore, the operation flow shown in FIG. 8 also has the predetermined high potential Vh, the predetermined low potential Vl, and the potential −Vdata corresponding to the pixel data signal in the processes of steps S1 to S8 according to the above embodiment. In steps ST1 to ST8 according to the first modification, the portions are changed to a predetermined low potential Vl, a predetermined high potential Vh, and a potential + Vdata corresponding to the pixel data signal, respectively.

<Modification 2>
In the above embodiment, the Vth compensation processing and the writing processing are performed in parallel in time, so that the amount of charge accumulated in the capacitor C1 is such that the threshold value Vthtr of the transistor Q1 and the organic EL element OLED The amount of charge corresponding to a voltage obtained by combining the threshold value Vthol and the voltage Vdata corresponding to the pixel data signal is not limited to this.

  For example, after the amount of charge accumulated in the capacitor C1 is set to a charge amount corresponding to a voltage obtained by adding the threshold value Vthtr and the threshold value Vthol, a potential corresponding to the pixel data signal is applied to the capacitor C1. The embedding process may be performed. Even if such a configuration is adopted, deterioration in image quality can be suppressed in consideration of changes in characteristics of the organic EL element. Therefore, in the Vth compensation processing, the amount of charge accumulated in the capacitor C1 is changed from the threshold value Vthtr of the transistor Q1 to the threshold value of the organic EL element OLED due to the movement of charges through the transistor Q2, the transistor Q1, and the organic EL element OLED. What is necessary is just to set it as the electric charge amount corresponding to the voltage at least including the voltage which combined Vthol.

  Here, a specific example of a pixel circuit according to Modification 2 in which Vth compensation processing and writing processing are performed in time sequence in each pixel circuit will be described.

  FIG. 9 is a diagram illustrating a circuit configuration of a pixel circuit 1C according to the second modification.

  The pixel circuit 1C has the same configuration as the organic EL element OLED, the four transistors Q1 to Q4, the capacitor C1, and the like as compared with the pixel circuit 1A according to the above-described embodiment. However, in the pixel circuit 1C, the sense / select line Lss according to the above embodiment is used as the sense line Lsn, and a separate select line Lsl is provided. Further, three transistors Q5 to Q7 for performing a writing process are provided. , And a capacitor C2.

  Hereinafter, in the circuit configuration of the pixel circuit 1 </ b> C according to the modified example 2, a part different from the pixel circuit 1 </ b> A according to the above embodiment will be described. In addition, about the same part, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The sixth electrode (gate) E6 of the transistor Q2 is electrically connected to the sense line Lsn. The sense line Lsn applies a potential for controlling the timing of performing the Vth compensation process to the sixth electrode E6.

  The transistors Q5 to Q7 are configured by so-called n-MISFET TFTs.

  The transistor Q5 has 15th to 17th electrodes E15 to E17. Specifically, the fifteenth electrode E15 is electrically connected to the eighth electrode E8 of the capacitor C1, and the sixteenth electrode E16 is electrically connected to a wiring that grounds the organic EL element OLED. The seventeenth electrode E17 is electrically connected to the sense line Lsn and functions as a so-called gate electrode.

  In the transistor Q5, the potential applied to the seventeenth electrode E17, more specifically, the voltage value applied between the sixteenth electrode E16 and the seventeenth electrode E17 (that is, between the source and the gate) is adjusted. Thus, the amount of current flowing between the fifteenth electrode E15 and the sixteenth electrode E16 (hereinafter also referred to as “between the fifteenth and sixteenth electrodes”) is adjusted. Further, the potential applied to the seventeenth electrode (gate) E17 causes the transistor Q5 to have a state in which a current can flow between the fifteenth and sixteenth electrodes (that is, between the drain and the source) (conductive state) and a current flow. It is selectively set to an unobtainable state (non-conducting state).

  The transistor Q7 has 21st to 23rd electrodes E21 to E23. Specifically, the twenty-first electrode E21 is electrically connected to the eighth electrode E8 of the capacitor C1, and the twenty-second electrode E22 is electrically connected to a wiring that grounds the organic EL element OLED. The twenty-third electrode E23 is electrically connected to the precharge line Lp and functions as a so-called gate electrode.

  In this transistor Q7, the potential applied to the 23rd electrode E23, more specifically, the voltage value applied between the 22nd electrode E22 and the 23rd electrode E23 (that is, between the source and the gate) is adjusted. This adjusts the amount of current flowing between the twenty-second electrode E22 and the twenty-third electrode E23 (hereinafter also referred to as “between the twenty-second and twenty-third electrodes”). Further, the potential applied to the 23rd electrode (gate) E23 causes the transistor Q7 to be in a state where the current can flow between the 21st and 22nd electrodes (that is, between the drain and the source) (conducting state) and the current flows. It is selectively set to an unobtainable state (non-conducting state).

  The capacitor C2 has 24th and 25th electrodes E24 and E25. Specifically, the twenty-fourth electrode E24 is electrically connected to the eighth electrode E8 of the capacitor C1, and the twenty-fifth electrode E25 is electrically connected to the wiring for grounding the organic EL element OLED. The electric capacity is obtained between the 24th electrode E24 and the 25th electrode E25.

  That is, the transistors Q5 and Q7 and the capacitor C2 are electrically connected in parallel between the capacitor C1 and the wiring for grounding the organic EL element OLED. In other words, the eighth electrode E8 of the capacitor C1 is grounded via the transistors Q5 and Q7 and the capacitor C2.

  The transistor Q6 has 18th to 20th electrodes E18 to E20. Specifically, the eighteenth electrode E18 is electrically connected to the data line Ldata. The nineteenth electrode E19 is electrically connected to the wiring that electrically connects the eighth electrode E8 of the capacitor C1, the fifteenth electrode E15, the twenty-first electrode E21, and the twenty-fourth electrode E24. That is, the nineteenth electrode E19 is electrically connected to the eighth electrode E8, the fifteenth electrode E15, the twenty-first electrode E21, and the twenty-fourth electrode E24. Furthermore, the twentieth electrode E20 is electrically connected to the select line Lsl and functions as a so-called gate electrode. Note that the select line Lsl applies a potential for controlling the timing of performing the writing process to the twentieth electrode E20.

  In the transistor Q6, the potential applied to the twentieth electrode E20, more specifically, the voltage value applied between the nineteenth electrode E19 and the twentieth electrode E20 (that is, between the source and the gate) is adjusted. Thus, the amount of current flowing between the 18th electrode E18 and the 19th electrode E19 (hereinafter also referred to as “between the 18th and 19th electrodes”) is adjusted. Further, the potential applied to the twentieth electrode (gate) E20 causes the transistor Q6 to have a state in which a current can flow between the eighteenth and nineteenth electrodes (that is, between the drain and the source) (conduction state) and a current flow. It is selectively set to an unobtainable state (non-conducting state).

  Next, driving of the pixel circuit 1C according to Modification 2 will be described.

  FIG. 10 is a timing chart showing a signal waveform (drive waveform) when the organic EL element OLED emits light in the pixel circuit 1C, and FIG. 11 is a flowchart showing an operation flow of the pixel circuit 1C. FIGS. 10 and 11 focus on driving for causing one pixel circuit 1C included in the display panel 121 to emit light once. In the case where a plurality of frames are continuously displayed in time, FIG. 11 and the operation flow shown in FIG. 11 are repeated in time sequence for the number of times corresponding to the number of frames. 10 and the operation flow shown in FIG. 11 are realized under the control of the control unit 111.

  In FIG. 10, the horizontal axis indicates time, and in order from the top, (a) the potential (potential Vm) applied to the merge line Lm, (b) the potential (potential Vp) applied to the precharge line Lp, (c The waveforms of the potential applied to the sense line Lsn (potential Vsn), (d) the potential of the signal applied to the data line Ldata (potential Vd), and (e) the potential applied to the select line Lsl (potential Vsl). It is shown. When the organic EL element OLED emits light, a predetermined positive high potential Vdd (for example, 10 V) is applied to the VDD line Ld regardless of the light emission preparation stage and the actual light emission stage. In addition, a period related to one light emission includes a preparation period Pp (time T1 to T12) for adjusting light emission luminance and a light emission period Pe (to time T1, time T12 to) in which the organic EL element OLED actually emits light. And is configured.

  Hereinafter, the operation flow of the pixel circuit 1C shown in FIG. 11 will be described with reference to FIG.

  First, in step SP1, the potential Vm is set to a predetermined low potential Vl (time T1). At this time, the potential Vp, the potential Vsn, and the potential Vsl are set to a predetermined low potential Vl, and the potential Vd is set to 0 V (GND). That is, the transistors Q2 to Q7 are nonconductive. If the light emission is performed a plurality of times, the previous light emission is terminated in step SP1, and if the light emission is the first time, the preparation period Pp is simply started.

  In step SP2, the potential Vp is set to a predetermined high potential Vh (time T2). Here, a predetermined high potential Vh is applied to the fourteenth electrode E14 and the twenty-third electrode E23, and the transistors Q4 and Q7 are turned on.

  In step SP3, the potential Vp is set to a predetermined low potential Vl (time T3). At this time, transistors Q4 and Q7 are set in a non-conductive state.

  Here, at times T2 to T3, the transistors Q4 and Q7 are maintained in the conductive state, and therefore, the predetermined high potential Vdd is applied to the seventh electrode E7 of the capacitor C1, and the eighth electrode E8 is grounded. It becomes. For this reason, a charge corresponding to the predetermined high potential Vdd is accumulated in the capacitor C1. At this time, the electric charge accumulated between the capacitor C2 and the capacitor C1 is swept out. Further, due to the accumulation of electric charge in the capacitor C1, a positive potential is applied to the third electrode E3, and the transistor Q1 is set in a conductive state.

  In step SP4, the potential Vsn is set to a predetermined high potential Vh (time T4). At this time, a predetermined high potential Vh is applied to the sixth and seventeenth electrodes E6 and E17, respectively, and the transistors Q2 and Q5 are set in a conductive state.

  In step SP5, the potential Vsn is set to a predetermined low potential Vl (time T5). At this time, transistors Q2 and Q5 are set to a non-conductive state.

  Here, at times T4 to T5, the potential Vsn is maintained at a predetermined high potential Vh. In the initial stage of times T4 to T5, the transistor Q1 is set in a conductive state by the electric charge accumulated in the capacitor C1. In addition, since the second electrode E2 of the transistor Q1 is in a grounded state, the charges accumulated in the capacitor C1 are transferred from the fourth electrode E4 to the fifth electrode E5 of the transistor Q2 and from the first electrode E1 to the second electrode of the transistor Q1. The electrode E2 and the organic EL element OLED are sequentially moved through. Due to the movement of the electric charge, the electric charge accumulated in the capacitor C1 is gradually reduced, and the potential applied to the third electrode E3 is also gradually reduced. Since the eighth electrode E8 of the capacitor C1 is grounded, the potential difference between the seventh electrode E7 and the cathode electrode of the organic EL element OLED finally becomes the threshold value Vthtr of the transistor Q1 and the organic EL element OLED. When the voltage combined with the threshold value Vthol is reached, the movement of charges stops. At this time, a potential corresponding to the sum of the threshold value Vthtr and the threshold value Vthol is applied to the third and seventh electrodes E3 and E7.

  In step SP6, the potential Vd is set to the potential + Vdata corresponding to the pixel data signal (time T6 to T7). At this time, by applying the potential + Vdata according to the pixel data signal, a process (writing process) in which charges according to the pixel data signal are accumulated in the capacitor C2 is started.

  In step SP7, the potential Vsl is set to a predetermined high potential Vh (time T8). At this time, a predetermined high potential Vh is applied to the twentieth electrode E20 of the transistor Q6, and the transistor Q6 is set in a conductive state. At this time, since the 25th electrode E25 of the capacitor C2 is grounded, a potential difference Vdata corresponding to the pixel data signal is generated between the 24th electrode E24 and the 25th electrode E25.

  In step SP8, the potential Vsl is set to a predetermined low potential Vl (time T9). At this time, transistor Q6 is set to a non-conductive state.

  From time T4 to time T5, electric charge corresponding to the potential + Vdata corresponding to the pixel data signal is accumulated in the capacitor C2. Therefore, the potential Vdata is applied to the 24th electrode E24 of the capacitor C2. Therefore, the potential Vdata is applied to the eighth electrode E8 of the capacitor C1. Accordingly, the potential applied to the third and seventh electrodes E3 and E7 is obtained by adding the potential Vdata to a value obtained by adding the threshold value Vthtr of the transistor Q1 and the threshold value Vthol of the organic EL element OLED. At this time, since the gate voltage of the transistor Q1 rises by Vdata, the transistor Q1 is set to a conductive state in which a current corresponding to the potential Vdata corresponding to the pixel data signal can flow between the first and second electrodes. That is, in this operation flow, the writing process is performed after the Vth compensation process.

  In step SP9, the potential Vd is set to 0 V (GND) (time T10 to T11).

  In step SP10, the potential Vm is set to a predetermined high potential Vh (time T12). At this time, the transistor Q3 is in a conductive state, and a predetermined high potential Vdd is applied to the ninth electrode E9. In addition, in consideration of the threshold value Vthtr and the threshold value Vthol, the potential Vdata corresponding to the pixel data signal is applied to the third electrode E3. For this reason, the current corresponding to the pixel data signal Vdata flows between the first and second electrodes of the transistor Q1. That is, a current corresponding to the pixel data signal Vdata flows through the organic EL element OLED, and the organic EL element OLED emits light with a light emission luminance corresponding to the pixel data signal Vdata.

  Through the processing in steps SP1 to SP10, one light emission is realized in the organic EL element OLED, and the processing in steps SP1 to SP10 is repeated in time sequence, so that light emission is performed a plurality of times.

  In the above description, the driving of one pixel circuit 1C included in the display panel 121 has been described. However, the driving of the plurality of pixel circuits 1C included in the display panel 121 will be described here.

  On the display panel 121, a large number (here, N lines) of horizontal lines each constituted by a large number of pixel circuits 1C are arranged. Then, horizontal lines (for example, the first horizontal line, the second horizontal line, the third horizontal line,..., The Nth horizontal line) arranged in order from the top of the display panel 121 are little by little in time. By driving the pixel circuit 1C while shifting, an image of one frame is displayed. Further, the display of one frame image is continuously performed in time, whereby a plurality of frame images are displayed.

  As described above, in the configuration of the second modification, the pixel circuits 1C are sequentially arranged in time order without performing driving that causes all the pixel circuits 1A arranged in the display panel 121 to emit light simultaneously as in the above embodiment. It is possible to emit light. For this reason, even if the pixel circuit 1C is applied to a large display panel having a large number of horizontal lines, it is difficult to cause a problem that a period necessary for displaying an image of one frame becomes long.

  In the configuration of the second modification, the charge adjustment in the Vth compensation process and the writing process is performed with reference to the electrode to which the organic EL element OLED is grounded. That is, the same GND is always set as the reference potential. For this reason, even if the GND slightly deviates from 0 V due to the increase in the potential Vdd accompanying the large display panel, the light emission luminance corresponding to the image signal is realized in the organic EL element OLED. That is, since unevenness is unlikely to occur in image display, the image quality can be further improved.

<Other variations>
In the above-described embodiment, a mobile phone has been described as an example of the image display device. However, the present invention is not limited to this, and other image display devices such as a notebook personal computer and a home-use thin-screen TV device are used. Even if the present invention is applied to an image display apparatus including the same, the same effects as those of the above embodiment can be obtained.

  In the above embodiment, the image display device using the organic EL display is described as an example. However, the application target of the present invention is not limited to this. The present invention can be generally applied to an image display apparatus in which light emitting elements of a type (current control type) whose light emission luminance is adjusted are arranged.

It is a figure which illustrates schematic structure of the image display apparatus which concerns on embodiment of this invention. It is a block diagram which shows the function structure of an image display apparatus. It is a figure which illustrates the circuit structure of a pixel circuit. It is a timing chart which shows the signal waveform at the time of making an organic EL element light-emit. It is a flowchart which shows the operation | movement flow of a pixel circuit. 10 is a diagram illustrating a circuit configuration of a pixel circuit according to Modification Example 1. FIG. 10 is a timing chart showing signal waveforms according to Modification 1. 10 is a flowchart showing an operation flow of a pixel circuit according to Modification Example 1. 10 is a diagram illustrating a circuit configuration of a pixel circuit according to Modification Example 2. FIG. 10 is a timing chart showing signal waveforms according to Modification 2. 14 is a flowchart showing an operation flow of a pixel circuit according to Modification 2.

Explanation of symbols

1A to 1C Pixel circuit 100 Image display device 111 Control unit 121 Display panel C1, C2 Capacitor E1-E25, Eb1-Eb6, Eb9-Eb14 Electrode Ld Power supply line Ldata Data line Lm Merge line Lp Precharge line Lsl Select line Lsn Sense line Lss sense / select line OLED organic EL element Q1-Q7, Qb1-Qb4 transistor

Claims (2)

An image display device,
A light-emitting element whose emission luminance varies depending on the amount of current;
A first transistor having first, second, and third electrodes, wherein the amount of current between the first electrode and the second electrode is adjusted by a potential applied to the third electrode; When,
A second transistor having fourth, fifth, and sixth electrodes, wherein a current amount between the fourth electrode and the fifth electrode is adjusted by a potential applied to the sixth electrode; When,
A first capacitor having seventh and eighth electrodes and configured to obtain a capacitance between the seventh electrode and the eighth electrode;
A third transistor having ninth, tenth and eleventh electrodes, wherein the amount of current between the ninth electrode and the tenth electrode is adjusted by a potential applied to the eleventh electrode; When,
A fourth transistor having twelfth, thirteenth and fourteenth electrodes, wherein the amount of current between the twelfth electrode and the thirteenth electrode is adjusted by a potential applied to the fourteenth electrode; When,
A fifth transistor having fifteenth, sixteenth and seventeenth electrodes, wherein the amount of current between the fifteenth electrode and the sixteenth electrode is adjusted by a potential applied to the seventeenth electrode; When,
A sixth transistor having eighteenth, nineteenth and twentieth electrodes, wherein the amount of current between the eighteenth electrode and the nineteenth electrode is adjusted by a potential applied to the twentieth electrode; When,
A seventh transistor having twenty-first, twenty-second and twenty-third electrodes, wherein the amount of current between the twenty-first electrode and the twenty-second electrode is adjusted by a potential applied to the twenty-third electrode; When,
A second capacitor having twenty-fourth and twenty-fifth electrodes and configured to obtain a capacitance between the twenty-fourth electrode and the twenty-fifth electrode;
With
The second electrode is electrically connected to one electrode of the light emitting element, and the amount of current between the first electrode and the second electrode is adjusted, The amount of current in the light emitting element is controlled,
The third and fourth electrodes are electrically connected to the seventh electrode;
The fifth electrode is electrically connected to the first electrode;
The ninth electrode is electrically connected to the twelfth electrode;
The tenth electrode is electrically connected to the first electrode;
The thirteenth electrode is electrically connected to the seventh electrode;
The fourteenth electrode is electrically connected to the twenty-third electrode;
The fifteenth, nineteenth, twenty-first and twenty-fourth electrodes are electrically connected to the eighth electrode;
The sixteenth, twenty-second, twenty-fifth electrodes and the other electrode of the light emitting element are grounded;
The seventeenth electrode is electrically connected to the sixth electrode;
further,
First potential applying means for applying a first potential to the twelfth electrode;
In the state where the first potential is applied to the twelfth electrode, by applying a second potential to the fourteenth and twenty-third electrodes, the fourth and seventh transistors are connected to the twelfth electrode. A second potential for storing electric charge in the first capacitor by setting a conductive state between the electrode and the thirteenth electrode and between the twenty-first electrode and the twenty-second electrode so that a current can flow. Granting means;
A third potential is applied to the sixth and seventeenth electrodes, and the second and fifth transistors are connected between the fourth electrode and the fifth electrode and between the fifteenth electrode and the fifteenth electrode. By setting the conductive state in which a current can flow between the sixteenth electrode, the amount of charge accumulated in the first capacitor is changed to the second transistor, the first transistor, and the light emitting element. A third potential applying means for making a charge amount corresponding to a voltage including at least a voltage obtained by combining a threshold voltage of the first transistor and a threshold voltage of the light-emitting element by movement of charge via
Fourth and fifth potential applying means for applying a fifth potential to the twentieth electrode in a state where a fourth potential is applied to the eighteenth electrode, and accumulating charges in the second capacitor;
A potential corresponding to the amount of charge accumulated in the first and second capacitors is applied to the third electrode, and a predetermined potential is applied to the ninth electrode by the first potential applying means. In this state, a sixth potential is applied to the eleventh electrode, and the third transistor is set in a conductive state in which a current can flow between the ninth electrode and the tenth electrode. A sixth potential applying means for causing the light emitting element to emit light,
An image display device comprising:
An image display device driving method for driving the image display device according to claim 1 , comprising:
(a) In the state where the first potential is applied to the twelfth electrode, by applying a second potential to the fourteenth and twenty-third electrodes, the fourth and seventh transistors are Charges are accumulated in the first capacitor while setting a conductive state in which a current can flow between the twelfth electrode and the thirteenth electrode and between the twenty-first electrode and the twenty-second electrode. Steps,
(b) A third potential is applied to the sixth and seventeenth electrodes, and the second and fifth transistors are connected between the fourth and fifth electrodes and the fifteenth electrode. By setting the conductive state in which a current can flow between an electrode and the sixteenth electrode, the amount of charge accumulated in the first capacitor is changed to the second transistor, the first transistor, and A charge amount corresponding to a voltage including at least a voltage obtained by combining a threshold voltage of the first transistor and a threshold voltage of the light-emitting element by movement of charge through the light-emitting element;
(c) applying a fifth potential to the twentieth electrode in a state where a fourth potential is applied to the eighteenth electrode, and accumulating charges in the second capacitor;
(d) In a state where a potential corresponding to the amount of charge accumulated in the first and second capacitors is applied to the third electrode and a predetermined potential is applied to the ninth electrode, By applying a sixth potential to the eleventh electrode, the third transistor is set to a conductive state in which a current can flow between the ninth electrode and the tenth electrode. Causing the light emitting element to emit light;
A method for driving an image display device, comprising:

Images