JP5072218B2 - Display device - Google Patents

Description

  The present invention relates to an active matrix display device and a driving method thereof. The present invention particularly relates to a display device having a switching element such as a thin film transistor (hereinafter referred to as TFT) and a light emitting element for each pixel, and a driving method thereof. The present invention also relates to an electronic device using the display device and a driving method thereof.

  In recent years, the technology for forming TFTs has greatly advanced, and application development to active matrix display devices has been promoted. In particular, a TFT using a polysilicon film as an active layer has higher field effect mobility (also referred to as mobility) than a TFT using a conventional amorphous silicon film, and thus can operate at high speed. Therefore, the pixel can be controlled by a driver circuit formed using a TFT over the same substrate on which the pixel is formed. In a display device having various circuits formed of TFTs on the same substrate as a substrate on which pixels are formed, various advantages such as a reduction in manufacturing cost, a reduction in size, an increase in yield, and a reduction in throughput can be obtained.

  As a display element included in each pixel of the display device, research on an active matrix EL display device having an electroluminescence element (hereinafter referred to as an EL element) which is a light emitting element has been activated. The EL display device is also called an organic EL display (OELD) or an organic light emitting diode (OLED).

In general, since the current value flowing through the EL element and the light emission luminance of the EL element are in a proportional relationship, in an EL display device using the EL element as a display element, the luminance is controlled by the current value. For this reason, an EL display device has been proposed that has a pixel configuration different from that of a liquid crystal display device that controls luminance with a voltage value (see Patent Document 1).
International Publication No. 01/06484 Pamphlet

Further, a driving circuit for inputting a video signal to each pixel of an EL display device described in Patent Document 1 has been proposed (see Patent Document 2).
International Publication No. 02/39420 Pamphlet

  In the invention described in Patent Document 1, a driving method is used in which a current having a current value proportional to the gradation is input to each pixel as a video signal, and a current value flowing through the EL element of each pixel is determined. However, in this driving method, as shown in Patent Document 2, a driving circuit that inputs a video signal to a pixel needs to have a configuration having a large number of current sources in order to output a current having an analog current value. There is. This complicates the configuration of the drive circuit. In addition, the input of the video signal to the pixel tends to be incomplete in the input of the video signal having an intermediate gray level close to black, and the display quality of the intermediate gray level is deteriorated. Further, since the TFT connected in series with the EL element is operated in the saturation region in order to control the current value of the EL element, the power consumption of the EL display device is increased and the heat generation is large.

  The present invention solves the above-described drawbacks, and provides a display device and a driving method thereof in which the configuration of a driving circuit for inputting a video signal to a pixel is simple, the display quality of intermediate gradation is high, and the power consumption is low. Objective.

  The present invention includes a plurality of pixels, a light emitting element sandwiched between a pair of electrodes in each of the plurality of pixels, and a capacitor element that holds a voltage between the pair of electrodes, and the pair of electrodes of the light emitting element One of them is connected to the other electrode of the capacitor, and a voltage equal to or higher than the threshold voltage Vth of the light emitting element is applied to one electrode of the light emitting element. Then, the potential of the node where one electrode of the light emitting element and the other electrode of the capacitor element are connected is equal to the threshold voltage Vth, and the voltage corresponding to the threshold voltage Vth of the light emitting element is applied to the capacitor element. Is retained. Further, by changing the potential of one electrode of the capacitor, the potential of one electrode of the light emitting element becomes the sum of the threshold voltage Vth and the change amount Vg of the potential of the capacitor, and the light emitting element emits light. It is characterized by that. For example, by increasing the potential of one electrode of the capacitor, the potential of the other electrode of the capacitor and the potential of one electrode of the light-emitting element are increased by the increase in the potential of one electrode of the capacitor. . Thus, the light emitting element emits light.

  In other words, the structure of the present invention includes a plurality of pixels, and each of the plurality of pixels includes a light-emitting element sandwiched between a pair of electrodes and a capacitor element that holds a voltage between the pair of electrodes. One electrode of the light emitting element is connected to the other electrode of the capacitor element, and a voltage equal to or higher than the threshold voltage Vth of the light emitting element is applied to one electrode of the light emitting element to change the potential of one electrode of the capacitor element. The light emitting element emits light by changing the potential of one electrode of the light emitting element.

  The above-described configuration can be applied when the voltage divided by the capacitive element and the light emitting element is not considered. Note that in the case of considering the capacitance-divided voltage, in the above structure, at the potential of the node where one electrode of the light-emitting element and the other electrode of the capacitor are connected (that is, one electrode of the light-emitting element), The potential change amount Vg at one electrode is increased by the voltage divided by the capacitive element and the light emitting element. That is, the potential of one electrode of the light-emitting element is (capacitance element capacitance C / (capacitance element capacitance C + light-emitting element capacitance Cel)) × (potential change Vg at one electrode of the capacitance element) + threshold value. The voltage becomes Vth.

  The threshold voltage Vth of the light emitting element is a voltage applied to the light emitting element when current starts to flow through the light emitting element. That is, the light emitting element emits light when a voltage equal to or higher than the threshold voltage Vth is applied.

  The luminance of the light-emitting element may be controlled by controlling the potential of one electrode of the capacitor (the potential change amount Vg) to express the gray level of the display portion. Further, like the digital time gradation, the luminance of the light emitting element may be controlled by controlling the time during which the light emitting element of each pixel emits light, thereby expressing the gradation of the display portion.

  A structure of a display device that performs display by the above driving method will be described below.

(First configuration)
The present invention includes a first wiring, a second wiring, a third wiring, and a plurality of pixels. Each of the plurality of pixels includes a switching element, a capacitor having a pair of electrodes, and a pair. And one electrode of the capacitor element is connected to the first wiring, and the other electrode of the capacitor element is connected to one electrode of the light emitting element and the switching element in the ON state. The display device is connected to the second wiring, and an ON state or an OFF state of the switching element is controlled by a signal input to the third wiring.

  Note that in the above structure, a predetermined potential is applied to the other electrode of the light-emitting element.

(Second configuration)
The present invention includes a first wiring, a second wiring, a third wiring, a fourth wiring, a fifth wiring, and a plurality of pixels. A switching element, a second switching element, a third switching element, a first capacitor element having a pair of electrodes, a second capacitor element having a pair of electrodes, and a light emitting element having a pair of electrodes, One electrode of the first capacitor element is connected to the first wiring, and the other electrode of the first capacitor element is one electrode of the light emitting element and the first switching element in the ON state and the ON state. The second switching element is connected to the third wiring through the second switching element in order, and the electrode for controlling the ON state or the OFF state of the second switching element is one electrode of the second capacitor element and the ON state. The fourth switching element via the third switching element The ON state or OFF state of the first switching element is controlled by a signal input to the second wiring, and the ON state or OFF state of the third switching element is input to the fifth wiring. The display device is controlled by a signal to be transmitted.

  Note that in the above structure, a predetermined potential can be applied to the other electrode of the light-emitting element.

  Further, the other electrode of the second capacitor element may be connected anywhere as long as it is kept at a constant potential during the operation of the second switching element. For example, it may be connected to the other electrode of the light emitting element, or may be connected to other wiring.

(Third configuration)
A transistor can be used as the switching element having the first structure. A configuration in which a transistor is used as the switching element will be described.

  The present invention includes a first wiring, a second wiring, a third wiring, and a plurality of pixels. Each of the plurality of pixels includes a transistor, a capacitor having a pair of electrodes, and a pair of pixels. And one electrode of the capacitor is connected to the first wiring, and the other electrode of the capacitor is connected to one electrode of the light-emitting element and one of a source and a drain of the transistor The other of the source and the drain of the transistor is connected to the second wiring, and the gate of the transistor is connected to the third wiring.

  Note that in the above structure, a predetermined potential can be applied to the other electrode of the light-emitting element.

(Fourth configuration)
A transistor can be used as the switching element of the second configuration. A configuration in which a transistor is used as the switching element will be described.

  The present invention includes a first wiring, a second wiring, a third wiring, a fourth wiring, a fifth wiring, and a plurality of pixels. A first capacitor having a pair of electrodes, a second capacitor having a pair of electrodes, and a light-emitting element having a pair of electrodes, One electrode of the capacitor element is connected to the first wiring, the other electrode of the first capacitor element is connected to one of the source and drain of the first transistor, and one electrode of the light emitting element, The other of the source and drain of the first transistor is connected to one of the source and drain of the second transistor, the gate of the first transistor is connected to the second wiring, and the source and drain of the second transistor. The other is the third The gate of the second transistor is connected to one of the source and drain of the third transistor and one electrode of the second capacitor, and the other of the source and drain of the third transistor is The display device is connected to the fourth wiring and the gate of the third transistor is connected to the fifth wiring.

  Note that in the above structure, a predetermined potential can be applied to the other electrode of the light-emitting element.

  Further, the other electrode of the second capacitor element may be connected anywhere as long as it is kept at a constant potential during the operation of the second transistor. For example, it may be connected to the other electrode of the light emitting element, or may be connected to other wiring.

  Note that a state in which a voltage exceeding a threshold is applied between the gate and the source of the transistor and a current flows between the source and the drain is referred to as turning on the transistor. In addition, when a voltage equal to or lower than the threshold voltage is applied between the gate and the source of the transistor and no current flows between the source and the drain, the transistor is turned off.

  In the present invention, being connected is synonymous with being electrically connected. Therefore, in the configuration of the present invention, in addition to a predetermined connection relationship, other elements (for example, elements such as a switch, a transistor, a diode, and a capacitor) that can be electrically connected may be disposed therebetween. .

  In the third configuration and the fourth configuration, an example in which a transistor is used as an example of the switching element is shown, but the present invention is not limited to this. The switching element may be an electrical switch or a mechanical switch as long as it can control the flow of current. As the switching element, a diode may be used, or a logic circuit combining a diode and a transistor may be used.

  In the present invention, there is no limitation on the type of transistor that can be used as a switching element, and a TFT, a semiconductor substrate, or an SOI substrate using a non-single-crystal semiconductor film typified by amorphous silicon or polycrystalline silicon is used. A MOS transistor, a junction transistor, a bipolar transistor, a transistor using an organic semiconductor or a carbon nanotube, and other transistors can be applied. There is no limitation on the type of the substrate over which the transistor is formed, and a single crystal substrate, an SOI substrate, a quartz substrate, a glass substrate, a resin substrate, or the like can be used freely.

  Since the transistor operates as a simple switching element, the polarity (conductivity type) is not particularly limited, and may be either an N-type transistor or a P-type transistor. However, in the case where it is desirable that the off-state current is small, it is desirable to use a transistor having characteristics with a small off-state current. As a transistor with low off-state current, there is a transistor in which a region to which an impurity element imparting a conductivity type is added at a low concentration (referred to as an LDD region) is provided between a channel formation region and a source or drain region.

  In the case where the source potential of the transistor operates with a value closer to the power supply on the lower potential side than the drain potential, the transistor is preferably N-type. On the other hand, when the transistor operates in a state where the source potential is close to the high-potential side power supply, the transistor is preferably P-type. With such a structure, the absolute value of the voltage between the gate and the source of the transistor can be increased, so that the transistor can be easily operated as a switch. Note that a CMOS transistor may be used as a switching element by using both an N-type transistor and a P-type transistor.

  The present invention can be applied to a display device using an element in which a luminance value and a luminance flowing between a pair of electrodes are in a proportional relationship as a light emitting element. For example, the present invention can be applied to a display device using an EL element or a light emitting diode as a light emitting element.

  In addition, electronic devices, portable information terminals, and display modules using the configuration of the present invention are also included in the scope of the present invention.

  In the present invention, in each pixel, a voltage corresponding to the threshold voltage of the light emitting element is held in the capacitor element, and a voltage obtained by adding a threshold voltage to a predetermined voltage is applied to the light emitting element. Therefore, the light emitting element can emit light regardless of the threshold voltage of the light emitting element. In this way, a display device capable of displaying a correct gradation and displaying high quality without being affected by variations in threshold voltage of the light emitting element between pixels or deterioration of the light emitting element is provided. can do.

  In addition, since a voltage is used as a video signal in the present invention, the configuration of a drive circuit that inputs a video signal to a pixel can be simplified.

  Furthermore, in the third structure and the fourth structure of the present invention, the transistor arranged for each pixel functions as a mere switching element, so that power consumption of the display device can be reduced.

  Embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in many different modes, and those skilled in the art can easily understand that the modes and details can be variously changed without departing from the spirit and scope of the present invention. Is done. Therefore, the present invention is not construed as being limited to the description of this embodiment mode.

(Embodiment 1)
The structure of the pixel in the display device having the third structure described in [Means for Solving the Problems] is described with reference to FIG.

  In FIG. 1, each pixel has a capacitor 101, a light emitting element 102, and a TFT 103, 104 is a source signal line, 105 is a gate signal line, 106 is a light emission control line, 107 is a node Vm, and 108 is a light emitting element. The other of the pair of electrodes 102 is shown.

  One electrode of the capacitor 101 is connected to the light emission control line 106, the other electrode of the capacitor 101 is connected to one of the electrodes of the light emitting device 102 and the source and drain of the TFT 103, and the source and drain of the TFT 103. The other of them is connected to the source signal line 104, and the gate of the TFT 103 is connected to the gate signal line 105.

  A connection point between the other electrode of the capacitor 101 and one electrode of the light-emitting element 102 is a node Vm107.

  A driving method of the pixel in FIG. 1 will be described with reference to a timing chart in FIG.

  A method for holding the threshold voltage of the light-emitting element 102 in the capacitor 101 will be described. The threshold voltage of the light emitting element 102 is indicated by Vth in FIG. In the Data writing period indicated by T1 in FIG. 2, the TFT 103 is turned on, and the potential applied to the source signal line 104 is input to the node Vm107. Here, the potential applied to the source signal line 104 may be determined so that the potential difference with the potential of the other electrode 108 of the light-emitting element 102 is equal to or higher than the threshold voltage of the light-emitting element 102. The potential applied to the source signal line 104 is indicated by Vdata in FIG. The potential of the other electrode 108 of the light emitting element 102 is indicated by Vo in FIG. Further, the capacitance value of the capacitor 101 is indicated by C101 in FIG. 2, and the capacitance value of the light emitting element 102 is indicated by Cel in FIG. Thus, the capacitor 101 holds a voltage corresponding to the potential difference between the potential of the source signal line 104 and the potential of the light emission control line 106. Next, when the TFT 103 is turned off in the light emitting element threshold voltage acquisition period indicated by T2 in FIG. 2, the potential of the node Vm107 decreases. The decrease in the potential of the node Vm107 continues until the potential difference between the potential of the node Vm107 and the potential of the other electrode 108 of the light emitting element 102 becomes equal to the threshold voltage of the light emitting element 102. Thus, the potential of the node Vm107 becomes a value corresponding to the threshold voltage Vth of the light emitting element 102.

  Next, in the display period indicated by T3 in FIG. 2, the potential of the light emission control line 106 connected to the capacitor 101 is increased by Vg. In this manner, the potential of the other electrode of the capacitor 101, that is, the potential of the node Vm107 is increased by the voltage divided by the capacitor 101 and the light emitting element 102 at the increased voltage Vg of the light emission control line 106. That is, it is increased by (C101 / (C101 + Cel)) × Vg. Here, in the light emitting element threshold voltage acquisition period indicated by T 2 in FIG. 2, the potential difference between the potential of the node Vm 107 and the potential of the other electrode 108 of the light emitting element 102 is the threshold voltage of the light emitting element 102. . Therefore, when the potential of the light emission control line 106 is increased by Vg in the display period T3, the potential difference between the potential of the node Vm107 and the potential of the other electrode 108 of the light emitting element 102 is a capacitance at the increased voltage Vg of the light emission control line 106. The sum of the voltage divided by the element 101 and the light emitting element 102 and the threshold voltage of the light emitting element 102 ((C101 / (C101 + Cel)) × Vg + Vth). Accordingly, a voltage obtained by correcting the threshold voltage of the light emitting element 102 can be applied to the light emitting element 102, and the light emitting element 102 can be brought into a light emitting state.

  Here, a gradation expression method will be described. The display device of the present invention can express gradation by an analog voltage gradation method or a digital time gradation method. In the analog voltage gradation method, gradation is expressed by changing the value of Vg in FIG. 2 in an analog manner. In the digital time gray scale method, one frame is divided into a plurality of subframes having different light emission times (the light emission times may be the same), and the light emitting state or the non-light emitting state of the light emitting element 102 is selected for each subframe. The gradation is expressed by controlling the time during which the light emission state is selected per frame.

  Although the analog voltage gray scale method and the digital time gray scale method have been described above, the gray scale can be expressed by another method. One frame is divided into a plurality of subframes having different Vg's in FIG. 2 (Vg may be the same), and the light emitting state or the non-light emitting state of the light emitting element 102 is selected for each subframe. Then, gradation is expressed by controlling the sum of the charges supplied to the light emitting element 102 per frame.

  In the digital time gray scale method, the potential of the light emission control line 106 is increased by a constant voltage Vg in the display period T3 regardless of the gray scale to be displayed. Therefore, when selecting the non-light emitting state, it is necessary to set the potential of the node Vm107 low so that the light emitting element 102 does not enter the light emitting state even if the potential of the light emission control line 106 is increased by the voltage Vg in the display period T3. There is. Hereinafter, an operation of setting the potential of the node Vm107 low is referred to as an erasing operation. The erase operation will be described below with reference to FIGS.

  In the Data writing period indicated by T1 in FIG. 2, the TFT 103 is turned on, and the potential applied to the source signal line 104 is input to the node Vm107. In the erasing operation, the potential applied to the source signal line 104 is the voltage (C101 / (C101 + Cel)) × the threshold voltage of the light-emitting element 102 with respect to the potential of the other electrode 108 of the light-emitting element 102 × The voltage is equal to or lower than the voltage obtained by subtracting the absolute value of Vg. Next, in the light emitting element threshold voltage acquisition period indicated by T2 in FIG. 2, even if the TFT 103 is turned off, the potential of the node Vm107 does not change. Even if the potential of the light emission control line 106 is increased by the voltage (C101 / (C101 + Cel)) × Vg in the display period indicated by T3 in FIG. 2, the potential difference of the potential of the node Vm107 with respect to the potential of the other electrode 108 of the light emitting element 102 is Since the voltage is lower than the threshold voltage of the light-emitting element 102, the light-emitting element 102 can be in a non-light-emitting state.

  As a method of selecting the non-light emitting state in the digital time gray scale method, there is a method different from the method of performing the erasing operation. The non-light emitting state may be selected without changing the potential of the light emission control line 106 also in the display period T3.

  In the present invention, a known driving circuit can be used in the present invention.

  Note that in the analog voltage gradation method, the light emission control line 106 is connected to a drive circuit, and the voltage Vg shown in FIG. 2 is controlled by the drive circuit. In the digital time gray scale method, the light emission control line 106 is connected to an external circuit via an FPC, and a clock signal supplied from the external circuit is supplied to the light emission control line 106.

  The display device of the present invention and the driving method thereof shown in FIGS. 1 and 2 are not affected even if the threshold voltage of the light emitting element 102 varies between pixels or the light emitting element 102 deteriorates. Therefore, it is possible to provide a display device capable of displaying correct gradation and capable of high quality display.

(Embodiment 2)
A pixel structure of the display device having the fourth structure described in [Means for Solving the Problems] will be described with reference to FIGS.

  In FIG. 3, each pixel includes a capacitor 300, a capacitor 301, a light emitting element 302, a TFT 303, a TFT 304, and a TFT 305.

  Reference numeral 306 denotes a source signal line, 307 denotes a gate signal line, 308 denotes a precharge selection line, 309 denotes a clock signal line, 310 denotes the other electrode of the light emitting element 302, 311 denotes a node Vm, and 312 denotes a power supply line Vpc.

  One electrode of the capacitor 301 is connected to the clock signal line 309, the other electrode of the capacitor 301 is connected to one of the electrodes of the light emitting element 302 and the source and drain of the TFT 305, and the source and drain of the TFT 305 The other of them is connected to one of the source and drain of the TFT 304, the gate of the TFT 305 is connected to the precharge selection line 308, the gate of the TFT 304 is one electrode of the capacitor 300, and one of the source and drain of the TFT 303. The other of the source and drain of the TFT 304 is connected to the power supply line Vpc 312 and the other electrode of the capacitor 300, the other of the source and drain of the TFT 303 is connected to the source signal line 306, and the gate of the TFT 303 is The gate signal line 307 is connected.

  A connection point between the other electrode of the capacitor 301 and one electrode of the light-emitting element 302 is a node Vm311.

  Next, a driving method of the pixel in FIG. 3 will be described with reference to a timing chart in FIG.

  In the pixel driving method, a series of operations until the source signal line selects the light emitting state of the light emitting element will be described. First, a method for holding the threshold voltage of the light emitting element 302 in the capacitor 301 is described.

  First, the TFT 303 is turned on, and the potential applied to the source signal line 306 is input to the gate of the TFT 304. The potential applied to the source signal line 306 at this time is set so that the TFT 304 is turned on when the light emission state is selected. Thereafter, the TFT 303 is turned off. The voltage between the gate and the source that turns on the TFT 303 is held in the capacitor 300. Therefore, the TFT 304 is kept on until the TFT 303 is selected by the gate signal line 307 next time.

  In the writing period T1 in FIG. 4, the TFT 305 is turned on. Since the TFT 304 is in the ON state, the potential of the power supply line Vpc 312 is supplied to the node Vm 311 when the TFT 305 is in the ON state. The potential of the power supply line Vpc 312 is indicated by Vpc in FIG.

  The ON or OFF state of the TFT 305 is selected by a signal input to the precharge selection line 308 shown in FIG. In the configuration shown in FIG. 3, since the TFT 305 is an N-type transistor, the TFT 305 is turned on when the signal of the precharge selection line 308 becomes Hi. When the TFT 305 is a P-type transistor, the polarity of the signal of the precharge selection line 308 may be reversed in the timing chart of FIG.

  In the period T1, when the TFT 305 is turned on, the potential of the power supply line Vpc 312 is supplied to the node Vm311. Here, the potential Vpc supplied to the power supply line Vpc 312 may be determined so that the potential difference with the potential (Vo) of the other electrode 310 of the light-emitting element 302 is equal to or higher than the threshold voltage of the light-emitting element 302. The potential of the other electrode 310 of the light emitting element 302 is indicated by Vo in FIG. The capacitance value of the capacitor 301 is indicated by C301 in FIG. 4, and the capacitance value of the light emitting element 302 is indicated by Cel in FIG. Thus, the capacitor 301 holds a voltage corresponding to the potential difference between the potential of the power supply line Vpc 312 and the potential of the clock signal line 309. Next, when the TFT 305 is turned off in the light emitting element threshold voltage acquisition period indicated by T2 in FIG. 4, the potential of the node Vm311 decreases. The decrease in the potential of the node Vm311 continues until the potential difference between the potential of the node Vm311 and the potential of the other electrode 310 of the light emitting element 302 becomes equal to the threshold voltage Vth of the light emitting element 302. Thus, the potential of the node Vm311 becomes a value corresponding to the threshold voltage Vth of the light-emitting element 302.

  Next, in the display period indicated by T3 in FIG. 4, the potential of the clock signal line 309 connected to the capacitor 301 is increased by Vg. In this manner, the potential of the other electrode of the capacitor 301, that is, the potential of the node Vm311 is increased by the voltage obtained by dividing the voltage Vg of the clock signal line 309 by the capacitor 301 and the light emitting element 302. That is, it is increased by (C301 / (C301 + Cel)) × Vg. Here, in the light emitting element threshold voltage acquisition period indicated by T 2 in FIG. 4, the potential difference between the potential of the node Vm 311 and the potential of the other electrode 310 of the light emitting element 302 is the threshold voltage of the light emitting element 302. . Therefore, when the potential of the clock signal line 309 is increased by Vg in the display period T3, the potential difference between the potential of the node Vm311 and the potential of the other electrode 310 of the light-emitting element 302 causes the increased voltage Vg of the clock signal line 309 to be capacitance. The voltage divided by the element 301 and the light emitting element 302, that is, (C301 / (C301 + Cel)) × Vg is increased, and the sum of the threshold voltage of the light emitting element 302 ((C301 / (C301 + Cel)) × Vg + Vth) It becomes. Accordingly, a voltage obtained by correcting the threshold voltage of the light emitting element 302 can be applied to the light emitting element 302.

  Next, the operation when the non-light emitting state is selected will be described.

  The TFT 303 is turned on, and the potential applied to the source signal line 306 is input to the gate of the TFT 304. The potential applied to the source signal line 306 at this time is set so that the TFT 304 is turned off when the non-light emitting state is selected. Thereafter, the TFT 303 is turned off. The voltage between the gate and the source that turns off the TFT 303 is held in the capacitor 300. Therefore, the TFT 304 continues to be kept off until the TFT 303 is selected by the gate signal line 307 next time.

  In the writing period T1 in FIG. 4, the TFT 305 is turned on. Since the TFT 304 is in an OFF state, even when the TFT 305 is in an ON state, the potential of the node Vm311 does not change.

  Next, the TFT 305 is turned off in the light emitting element threshold voltage acquisition period indicated by T2 in FIG.

  Next, in the display period indicated by T3 in FIG. 4, the potential of the clock signal line 309 connected to the capacitor 301 is increased by Vg. Even when the potential of the clock signal line 309 is increased by Vg, the potential difference of the potential of the node Vm 311 with respect to the potential of the other electrode 310 of the light emitting element 302 is equal to or lower than the threshold voltage of the light emitting element 302.

  When the non-light-emitting state is selected, the potential difference of the potential of the node Vm 311 with respect to the potential of the other electrode 310 of the light-emitting element 302 is equal to or lower than the threshold voltage of the light-emitting element 302 in the display period indicated by T3 in FIG. The reason will be described below.

  When the non-light-emitting state is selected after the light-emitting state is selected, the potential difference of the potential of the node Vm 311 with respect to the potential of the other electrode 310 of the light-emitting element 302 becomes the threshold voltage of the light-emitting element 302 before the writing period T1. ing. In the writing period T1, when the potential of the clock signal line 309 becomes Low and the potential of the node Vm311 decreases by the voltage (C301 / (C301 + Cel)) × Vg, the potential of the node Vm311 with respect to the potential of the other electrode 310 of the light-emitting element 302 is reduced. The potential difference is a voltage (Vth− | (C301 / (C301 + Cel)) × Vg |) obtained by subtracting the absolute value of (C301 / (C301 + Cel)) × Vg from the threshold voltage of the light emitting element 302. Accordingly, even if the potential of the clock signal line 309 becomes Hi next, the potential difference of the potential of the node Vm 311 with respect to the potential of the other electrode 310 of the light emitting element 302 becomes equal to or higher than the threshold voltage of the light emitting element 302. There is no.

  Thus, the light-emitting element 302 can be brought into a non-light-emitting state.

  3 and 4, the display device of the present invention and the driving method thereof are not affected even if the threshold voltage of the light emitting element 302 varies between pixels or the light emitting element 302 deteriorates. Therefore, it is possible to provide a display device capable of displaying correct gradation and capable of high quality display. In addition, gradation can be expressed in the same manner as in the first embodiment.

  In FIG. 3, the other electrode of the capacitor 300 and the power supply line Vpc 312 are connected. However, the other electrode of the capacitor 300 is connected to any position as long as it is kept at a constant potential when the TFT 304 is operated. May be.

  Note that the power supply line Vpc 312 only needs to be kept at a predetermined potential when the TFT 305 is in the ON state, and can be connected to the gate signal line 307 or the precharge selection line 308. It may be connected to the clock signal line 309.

  Further, the precharge selection line 308 and the clock signal line 309 are each connected to an external circuit via the FPC. These signal lines may be connected to an external circuit via a level shift circuit, an inverter circuit, etc., respectively.

  Note that a clock signal having a fixed duty ratio is supplied to the precharge selection line 308 and the clock signal line 309, respectively. Therefore, the signals supplied to the precharge selection line 308 and the clock signal line 309 may be input directly from an external circuit via the FPC without passing through a drive circuit that controls timing.

  In Embodiments 1 and 2, the arrangement of TFTs has been described with reference to FIGS. However, in the present invention, the arrangement of TFTs is not limited to the arrangement shown in FIGS. If the pixel can be operated according to the timing chart shown in FIG. 2 or FIG. 4, it is possible to dispose the TFT at an arbitrary place. In addition, although an N-type TFT is shown as the TFT in FIGS. 1 and 3, the polarity of each TFT is not limited to this.

  In the present invention, a known driver circuit for inputting a signal to a pixel can be used.

  In this embodiment, in the best mode for carrying out the invention, a display device having a pixel having the structure shown in FIGS. 1 and 3 will be described. FIG. 5 shows a configuration example of the display device. A plurality of pixels 500 includes a display portion 505 arranged in a matrix of m rows (m is a natural number) and n columns (n is a natural number). A source signal line driver circuit 503 and a writing signal are provided around the display portion 505. A gate signal line driver circuit 504 and an erasing gate signal line driver circuit 507 are provided. The source signal lines 501 represented by S1 to Sn are arranged corresponding to the respective columns of the pixels 500, and the gate signal lines 502 represented by G1 to Gm are arranged corresponding to the respective rows of the pixels 500. .

  The source signal line 104 in FIG. 1 corresponds to the source signal line 501 in FIG. The gate signal line 105 in FIG. 1 corresponds to the gate signal line 502 in FIG. A source signal line 306 in FIG. 3 corresponds to the source signal line 501 in FIG. The gate signal line 307 in FIG. 3 corresponds to the gate signal line 502 in FIG. The other wirings shown in FIGS. 1 and 3 are not shown in FIG.

  In the display device illustrated in FIG. 5, driving in which writing and erasing can be performed with one gate signal line 502 is performed by dividing one gate selection period into a writing period and an erasing period.

  The source signal line driver circuit 503, the write gate signal line driver circuit 504, and the erase gate signal line driver circuit 507 may be configured in a known manner.

  An example in which the display device of the present invention is actually manufactured will be described.

  7A and 7B are cross-sectional views of a pixel of the display device having the third structure or the fourth structure described in the best mode for carrying out the invention. An example in which a TFT is used as a transistor arranged in a pixel having the third structure or the fourth structure will be described.

  7A and 7B, 1000 is a substrate, 1001 is a base film, 1002 is a semiconductor layer, 1102 is a semiconductor layer, 1003 is a first insulating film, 1004 is a gate electrode, 1104 is an electrode, 1005 Is a second insulating film, 1006 is an electrode, 1007 is a first electrode, 1008 is a third insulating film, 1009 is a light emitting layer, and 1010 is a second electrode. Reference numeral 1100 denotes a TFT, 1011 denotes a light emitting element, and 1101 denotes a capacitor element.

  In FIGS. 7A and 7B, the TFT 1100 and the capacitor 1101 are representatively shown as elements constituting the pixel.

  The structure in FIG. 7A will be described.

  As the substrate 1000, for example, a glass substrate such as barium borosilicate glass or alumino borosilicate glass, a quartz substrate, a ceramic substrate, or the like can be used. Alternatively, a metal substrate including stainless steel or a semiconductor substrate with an insulating film formed on the surface thereof may be used, or a substrate made of a synthetic resin having flexibility such as plastic may be used. Note that the surface of the substrate 1000 may be planarized by polishing such as a CMP method.

  As the base film 1001, an insulating film such as silicon oxide, silicon nitride, or silicon nitride oxide can be used. The base film 1001 can prevent alkali metal such as Na or alkaline earth metal contained in the substrate 1000 from diffusing into the semiconductor layer 1002 and adversely affecting the characteristics of the TFT 1100. In FIG. 7A, the base film 1001 has a single-layer structure; however, the base film 1001 may be formed of two or more layers. Note that the base film 1001 is not necessarily provided when a substrate that does not cause a problem of impurity diffusion, such as a quartz substrate, is used.

  As the semiconductor layer 1002 and the semiconductor layer 1102, a patterned crystalline semiconductor film or amorphous semiconductor film can be used. The crystalline semiconductor film can be obtained by crystallizing an amorphous semiconductor film. As a crystallization method, a laser crystallization method, a thermal crystallization method using an RTA method or a furnace annealing method, a thermal crystallization method using a metal element that promotes crystallization, or the like can be used. The semiconductor layer 1002 includes a channel formation region and a pair of impurity regions to which an impurity element imparting a conductivity type is added. Note that an impurity region to which the impurity element is added at a low concentration may be provided between the channel formation region and at least one of the pair of impurity regions. The semiconductor layer 1102 can have a structure in which an impurity element imparting conductivity is added to the whole.

  As the first insulating film 1003, silicon oxide, silicon nitride, silicon nitride oxide, or the like can be used, and a single layer or a plurality of films can be stacked.

  As the gate electrode 1004 and the electrode 1104, a single layer or a stacked structure including one kind of element selected from Ta, W, Ti, Mo, Al, Cu, Cr, and Nd, or an alloy or compound containing a plurality of such elements is used. Can do.

  The TFT 1100 includes a semiconductor layer 1002, a gate electrode 1004, and a first insulating film 1003 between the semiconductor layer 1002 and the gate electrode 1004. In FIG. 7A, only the TFT 1100 electrically connected to the first electrode 1007 of the light-emitting element 1011 is illustrated as a TFT included in the pixel; however, the pixel portion may include a plurality of TFTs. In this embodiment, the TFT 1100 is shown as a top gate type transistor. However, it may be a bottom gate type transistor having a gate electrode below the semiconductor layer, or a dual gate having gate electrodes above and below the semiconductor layer. It may be a gate type transistor.

  The capacitor 1101 includes a first insulating film 1003 as a dielectric, and a semiconductor layer 1102 and an electrode 1104 that face each other with the first insulating film 1003 interposed therebetween as a pair of electrodes. Note that in FIG. 7A, as the capacitor 1101 included in the pixel, one electrode of a pair of electrodes is a semiconductor layer 1102 formed at the same time as the semiconductor layer 1002 of the TFT 1100, and the other electrode is a gate electrode 1004 of the TFT 1100. Although an example in which the electrode 1104 is formed at the same time is shown, the present invention is not limited to this structure.

  As the second insulating film 1005, a single layer or a stacked layer of an inorganic insulating film or an organic insulating film can be used. As the inorganic insulating film, a silicon oxide film formed by a CVD method, a silicon oxide film applied by an SOG (Spin On Glass) method, or the like can be used. As an organic insulating film, polyimide, polyamide, BCB (benzoic acid) is used. A film such as cyclobutene), acrylic or positive photosensitive organic resin, or negative photosensitive organic resin can be used.

  As the second insulating film 1005, a skeleton structure is formed by a bond of silicon (Si) and oxygen (O), and an organic group containing at least hydrogen (for example, an alkyl group or an aromatic hydrocarbon) is used as a substituent. Can be used. A fluoro group may be used as a substituent. Alternatively, an organic group containing at least hydrogen and a fluoro group may be used as a substituent. Typical examples of these materials include polymers having siloxane.

  As the electrode 1006, a single layer or a multilayer structure made of one kind of element selected from Al, Ni, C, W, Mo, Ti, Pt, Cu, Ta, Au, and Mn or an alloy containing a plurality of such elements is used. Can do.

  One or both of the first electrode 1007 and the second electrode 1010 can be a transparent electrode. As the transparent electrode, other translucent oxides such as indium tin oxide (hereinafter referred to as ITO, Indium Tin Oxide), zinc oxide (ZnO), indium zinc oxide (IZO), zinc oxide added with gallium (GZO), etc. A conductive material can be used. Indium tin oxide containing ITO and silicon oxide (hereinafter referred to as ITSO), Indium tin oxide containing ITO and titanium oxide (hereinafter referred to as ITTO), Indium tin oxide containing ITO and molybdenum oxide (hereinafter referred to as ITMO) Or a material obtained by adding titanium, molybdenum or gallium to ITO, or a material obtained by further adding 2 to 20 atomic% of zinc oxide (ZnO) to indium oxide containing silicon oxide.

One of the first electrode 1007 and the second electrode 1010 may be formed of a material that does not transmit light. For example, alkali metals such as Li and Cs, and alkaline earth metals such as Mg, Ca, and Sr, alloys containing these (Mg: Ag, Al: Li, Mg: In, etc.), and compounds thereof (CaF ₂ , In addition to calcium nitride), rare earth metals such as Yb and Er can be used.

  The third insulating film 1008 can be formed using a material similar to that of the second insulating film 1005. The third insulating film 1008 is formed around the first electrode 1007 so as to cover the end portion of the first electrode 1007, and has a function of separating the light emitting layer 1009 in adjacent pixels.

  The light emitting layer 1009 is composed of one or more layers. When composed of a plurality of layers, these layers can be classified into a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and the like from the viewpoint of carrier transport characteristics. Note that the boundaries between the layers are not necessarily clear, and there are cases where the materials constituting the layers are partially mixed and the interface is unclear. An organic material or an inorganic material can be used for each layer. As the organic material, any of a high molecular material, a medium molecular material, and a low molecular material can be used.

  The light-emitting element 1011 includes a light-emitting layer 1009 and a first electrode 1007 and a second electrode 1010 that overlap with each other with the light-emitting layer 1009 interposed therebetween. One of the first electrode 1007 and the second electrode 1010 corresponds to an anode, and the other corresponds to a cathode. When a voltage larger than the threshold voltage is applied between the anode and the cathode with a forward bias, the light-emitting element 1011 emits light by current flowing from the anode to the cathode.

  The structure of FIG. 7B will be described. Note that the same portions as those in FIG. 7A are denoted by the same reference numerals, and description thereof is omitted.

  FIG. 7B illustrates a structure in which the insulating film 1108 is provided between the second insulating film 1005 and the third insulating film 1008 in FIG.

  The electrode 1006 and the first electrode 1007 are connected to each other through the electrode 1106 in a contact hole provided in the insulating film 1108.

  The insulating film 1108 can have a structure similar to that of the second insulating film 1005. The electrode 1106 can have a structure similar to that of the electrode 1006.

  This embodiment can be carried out in any combination with the best mode for carrying out the invention and Embodiment 1.

  In this embodiment, a structure in which a display device is sealed will be described with reference to FIGS. FIG. 8A is a top view of a display panel formed by sealing a display device. FIGS. 8B and 8C are respectively taken along line AA ′ of FIG. 8A. It is sectional drawing. 8B and 8C are examples in which sealing is performed by different methods.

  8A to 8C, a display portion 1302 having a plurality of pixels is provided over a substrate 1301, a sealing material 1306 is provided so as to surround them, and a sealing material 1307 is attached. . As for the structure of the pixel, the best mode for carrying out the invention described above and the configurations shown in Embodiments 1 and 2 can be used.

  In the display panel in FIG. 8B, the sealing material 1307 in FIG. 8A corresponds to the counter substrate 1321. A transparent counter substrate 1321 is attached using the sealant 1306 as an adhesive layer, and a sealed space 1322 is formed by the substrate 1301, the counter substrate 1321, and the sealant 1306. The counter substrate 1321 is provided with a color filter 1320 and a protective film 1323 for protecting the color filter. Light emitted from the light emitting elements arranged in the display portion 1302 is emitted to the outside through the color filter 1320. The sealed space 1322 is filled with an inert resin or liquid. Note that a light-transmitting resin in which a hygroscopic material is dispersed may be used as the resin filled in the sealed space 1322. Alternatively, the sealing material 1306 and the material filled in the sealed space 1322 may be the same material, and the counter substrate 1321 may be bonded and the display portion 1302 may be sealed at the same time.

  In the display panel illustrated in FIG. 8C, the sealing material 1307 in FIG. 8A corresponds to the sealing material 1324. A sealing material 1324 is attached using the sealing material 1306 as an adhesive layer, and a sealed space 1308 is formed by the substrate 1301, the sealing material 1306, and the sealing material 1324. The sealing material 1324 is provided with a hygroscopic agent 1309 in the concave portion in advance, and plays a role in adsorbing moisture, oxygen, and the like in the sealed space 1308 to keep a clean atmosphere and suppressing deterioration of the light emitting element. This concave portion is covered with a fine mesh-shaped cover material 1310. The cover member 1310 allows air and moisture to pass through, but does not allow the moisture absorbent 1309 to pass. Note that the sealed space 1308 may be filled with a rare gas such as nitrogen or argon, and may be filled with a resin or a liquid if inactive.

  An input terminal portion 1311 for transmitting a signal to the display portion 1302 or the like is provided on the substrate 1301, and a signal such as a video signal is transmitted to the input terminal portion 1311 via an FPC (flexible printed circuit) 1312. The In the input terminal portion 1311, the wiring formed over the substrate 1301 and the wiring provided in the FPC 1312 are electrically connected using a resin in which a conductor is dispersed (anisotropic conductive resin: ACF). .

  A driver circuit that inputs a signal to the display portion 1302 may be formed over the substrate 1301 over which the display portion 1302 is formed. A driver circuit for inputting a signal to the display portion 1302 may be formed using an IC chip and connected to the substrate 1301 using COG (Chip On Glass), or the IC chip may be connected using a TAB (Tape Auto Bonding) or a printed circuit board. You may arrange | position on the board | substrate 1301. FIG.

  This embodiment can be carried out in any combination with the best mode for carrying out the invention, Embodiment 1 and Embodiment 2.

  The present invention can be applied to a display module in which a circuit for inputting a signal to the display panel is mounted on the display panel.

  FIG. 9 shows a display module in which a display panel 900 and a circuit board 904 are combined.

  FIG. 9 shows an example in which the control circuit 905, the signal dividing circuit 906, and the like are formed on the circuit board 904. The circuit formed on the circuit board 904 is not limited to this. Any circuit may be formed as long as the circuit generates a signal for controlling the display panel.

  Signals output from these circuits formed on the circuit board 904 are input to the display panel 900 through the connection wiring 907.

  The display panel 900 includes a display portion 901, a source signal line driver circuit 902, and a gate signal line driver circuit 903. The configuration of the display panel 900 can be the same as the configuration shown in the second embodiment. FIG. 9 illustrates an example in which the source signal line driver circuit 902 and the gate signal line driver circuit 903 are formed over the same substrate as the substrate over which the display portion 901 is formed. However, the display module of the present invention is not limited to this. Only the gate signal line driver circuit 903 may be formed over the same substrate as the substrate over which the display portion 901 is formed, and the source signal line driver circuit may be formed over the circuit substrate. Both the source signal line driver circuit and the gate signal line driver circuit may be formed on the circuit board.

  By incorporating such a display module, display portions of various electronic devices can be formed.

  This embodiment can be carried out in any combination with the best mode for carrying out the invention and Embodiments 1 to 3.

  As an electronic device using the display module of the present invention, a camera such as a video camera or a digital camera, a goggle type display (head mounted display), a navigation system, a sound reproduction device (car audio, audio component, etc.), a notebook type personal computer, Reproducing a recording medium such as a game machine, a portable information terminal (mobile computer, cellular phone, portable game machine, electronic book, etc.), an image reproducing apparatus (specifically, Digital Versatile Disc (DVD)) equipped with a recording medium, And a device provided with a display capable of displaying the image). In particular, a portable information terminal that often has an opportunity to see the screen from an oblique direction emphasizes the wide viewing angle, and thus it is desirable to use a self-luminous display device. The present invention is particularly effective for portable information devices in which reduction of power consumption is an important issue.

  Specific examples of the electronic devices are illustrated in FIGS. 6A to 6H. Note that the electronic device shown here is just an example, and the present invention is not limited to these applications.

  FIG. 6A illustrates a display (display device) which includes a housing 2001, a support base 2002, a display portion 2003, a speaker portion 2004, a video input terminal 2005, and the like. The display module of the present invention can be used for the display portion 2003. The display includes all information display devices for personal computers, TV broadcast reception, advertisement display, and the like.

  FIG. 6B shows a digital camera (digital still camera), which includes a main body 2101, a display portion 2102, an image receiving portion 2103, operation keys 2104, an external connection port 2105, a shutter 2106, and the like. The display module of the present invention can be used for the display portion 2102.

  FIG. 6C illustrates a laptop personal computer including a main body 2201, a housing 2202, a display portion 2203, a keyboard 2204, an external connection port 2205, a pointing pad 2206, and the like. The display module of the present invention can be used for the display portion 2203.

  FIG. 6D illustrates a mobile computer, which includes a main body 2301, a display portion 2302, a switch 2303, operation keys 2304, an infrared port 2305, and the like. The display module of the present invention can be used for the display portion 2302.

  FIG. 6E illustrates a portable image reproducing device (specifically, a DVD reproducing device) provided with a recording medium, which includes a main body 2401, a housing 2402, a display portion A2403, a display portion B2404, and a recording medium (DVD or the like). A reading unit 2405, operation keys 2406, a speaker unit 2407, and the like are included. Although the display portion A 2403 mainly displays image information and the display portion B 2404 mainly displays character information, the display module of the present invention can be used for the display portion A 2403 and the display portion B 2404. Note that an image reproducing device provided with a recording medium includes a home game machine and the like.

  FIG. 6F illustrates a goggle type display (head mounted display), which includes a main body 2501, a display portion 2502, and an arm portion 2503. The display module of the present invention can be used for the display portion 2502.

  FIG. 6G illustrates a video camera, which includes a main body 2601, a display portion 2602, a housing 2603, an external connection port 2604, a remote control receiving portion 2605, an image receiving portion 2606, a battery 2607, an audio input portion 2608, operation keys 2609, and an eyepiece. Part 2610 and the like. The display module of the present invention can be used for the display portion 2602.

  FIG. 6H illustrates a mobile phone, which includes a main body 2701, a housing 2702, a display portion 2703, an audio input portion 2704, an audio output portion 2705, operation keys 2706, an external connection port 2707, an antenna 2708, and the like. The display module of the present invention can be used for the display portion 2703. Note that the display portion 2703 can further reduce power consumption of the mobile phone by displaying white characters on a black background.

  If the light emission luminance of the light emitting element is increased in the future, the light including the output image information can be enlarged and projected by a lens or the like and used for a front type or rear type projector.

  In addition, the electronic devices often display information distributed through electronic communication lines such as the Internet and CATV (cable television), and in particular, opportunities to display moving image information are increasing. Since the response speed of the light-emitting material (the speed from when an electric current is applied to the light-emitting element including the light-emitting material until light is emitted) is very high, the display module of the present invention is suitable for displaying moving image information.

  In the display device of the present invention, since the light emitting portion consumes power, it is desirable to display information so that the light emitting portion is minimized. Therefore, when a display module is used for a display unit mainly including character information such as a portable information terminal, particularly a mobile phone or a sound reproduction device, it is driven so that character information is formed by the light emitting part with the non-light emitting part as the background. It is desirable to do.

  As described above, the applicable range of the present invention is so wide that it can be used for electronic devices in various fields.

  This embodiment can be carried out in any combination with the best mode for carrying out the invention and Embodiments 1 to 4.

FIG. 3 is a circuit diagram illustrating a configuration of a pixel of the present invention. FIG. 6 is a diagram illustrating a timing chart of a pixel of the present invention. FIG. 3 is a circuit diagram illustrating a configuration of a pixel of the present invention. FIG. 6 is a diagram illustrating a timing chart of a pixel of the present invention. The figure which shows Example 1 of this invention. FIG. 14 illustrates an example of an electronic device of the invention. The figure which shows Example 2 of this invention. The figure which shows Example 3 of this invention. The figure which shows Example 4 of this invention.

Claims (5)

A first wiring, a second wiring, a third wiring, a first switching element, a second switching element, a third switching element, a capacitor having a pair of electrodes, and a pair of A light emitting device having an electrode,
One electrode of the capacitive element is electrically connected to the first wiring,
The other electrode of the capacitive element is electrically connected to one electrode of the light emitting element,
The other electrode of the capacitive element is electrically connected to the second wiring through the first switching element and the second switching element in order,
An electrode that controls an on state or an off state of the second switching element is electrically connected to the third wiring through the third switching element,
The first wiring has a function of supplying a first potential or a second potential for changing a potential of one electrode of the light emitting element ,
The second wiring has a function of supplying a potential such that a voltage between a pair of electrodes of the light emitting element is equal to or higher than a threshold voltage of the light emitting element.
The third wiring has a function of supplying a signal for controlling an on state or an off state of the second switching element,
The first switching element is turned on, the second switching element is turned on or off, the third switching element is turned off, and the first potential is supplied by the first wiring. The first switching element is turned off, the second switching element is turned on or off, the third switching element is turned off, and the first potential is changed. Is supplied by the first wiring, the first switching element is turned off, the second switching element is turned on or off, and the third switching element is turned off. a state, have a, a third period supplied by said second potential is the first wiring,
Prior to the first period, the third switching element is turned on, and a signal for controlling the on or off state of the second switching element from the third wiring is the second signal. A display device comprising: an electrode for controlling an on state or an off state of the switching element . A first wiring, a second wiring, a third wiring, a transistor, a capacitor having a pair of electrodes, and a light-emitting element having a pair of electrodes,
One electrode of the capacitive element is electrically connected to the first wiring,
The other electrode of the capacitive element is electrically connected to one electrode of the light emitting element,
The other electrode of the capacitor is electrically connected to one of a source and a drain of the transistor;
The other of the source and the drain of the transistor is electrically connected to the second wiring,
A gate of the transistor is electrically connected to the third wiring;
The first wiring has a function of supplying a first potential or a second potential for changing a potential of one electrode of the light emitting element ,
The second wiring has a function of supplying a potential such that a voltage between a pair of electrodes of the light emitting element is equal to or higher than a threshold voltage of the light emitting element
The third wiring has a function of supplying a signal for controlling an on state or an off state of the transistor;
A first period in which the transistor is turned on and the first potential is supplied by the first wiring; and the transistor is turned off and the first potential is supplied by the first wiring. a second time period that is, the transistor is turned off, the display device characterized by having a third period supplied to said second potential by the first wiring. A first wiring, a second wiring, a third wiring, a fourth wiring, a fifth wiring, a first transistor, a second transistor, a third transistor, and a pair A capacitor having electrodes and a light emitting element having a pair of electrodes,
One electrode of the capacitive element is electrically connected to the first wiring,
The other electrode of the capacitor is electrically connected to one of a source and a drain of the first transistor;
The other electrode of the capacitive element is electrically connected to one electrode of the light emitting element,
The other of the source and drain of the first transistor is electrically connected to one of the source and drain of the second transistor;
A gate of the first transistor is electrically connected to the second wiring;
The other of the source and the drain of the second transistor is electrically connected to the third wiring,
A gate of the second transistor is electrically connected to one of a source and a drain of the third transistor;
The other of the source and the drain of the third transistor is electrically connected to the fourth wiring,
A gate of the third transistor is electrically connected to the fifth wiring;
The first wiring has a function of supplying a first potential or a second potential for changing a potential of one electrode of the light emitting element ,
The second wiring has a function of supplying a signal for controlling an on state or an off state of the first transistor;
The third wiring has a function of supplying a potential such that a voltage between a pair of electrodes of the light emitting element is equal to or higher than a threshold voltage of the light emitting element
The fourth wiring has a function of supplying a signal for controlling an on state or an off state of the second transistor;
The fifth wiring has a function of supplying a signal for controlling an on state or an off state of the third transistor;
The first transistor is turned on, the second transistor is turned on or off, the third transistor is turned off, and the first potential is supplied from the first wiring. In the first period, the first transistor is turned off, the second transistor is turned on or off, the third transistor is turned off, and the first potential is changed to the first wiring. The second transistor is turned off, the second transistor is turned on or off, the third transistor is turned off, and the second potential is have a, a third period provided by the first wiring,
Prior to the first period, the third transistor is turned on, and a signal for controlling an on state or an off state of the second transistor from the fourth wiring is the second transistor. A display device, characterized by being supplied to the gate . In any one of Claim 1 thru | or 3 ,
A display module using the display device. In any one of Claim 1 thru | or 3 ,
A portable information terminal using the display device.

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