JP2006235614A - Driving method of display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device with high productivity and high display quality by suppressing production of a luminescent spot, and a driving method thereof. <P>SOLUTION: A first switching element and a second switching element each of which has a different polarity are disposed in series between a power source line for supplying power to a light-emitting element and a power source line having a potential which is equal to or lower than a threshold voltage of the light-emitting element, one electrode of the light-emitting element is connected to a connecting node of the two switching elements and in the case where a potential which is equal to or higher than the threshold voltage of the light-emitting element is applied to the light-emitting element regardless of an on/off state of the first switching element, a potential applied to the light-emitting element is set to be lower than the threshold voltage by turning the second switching element on and thus, the production of a luminescent spot is prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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 in which various circuits are formed using TFTs over the same substrate on which a pixel is formed, various advantages such as a reduction in manufacturing cost, a reduction in size, an increase in yield, and an improvement 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, the light emission luminance of an EL element is proportional to the current value flowing through the EL element. Therefore, in an EL display device using the EL element as a display element, the light emission luminance is controlled by the current value. In addition, there is a driving method in which the value of current flowing through the EL element is constant and the light emission luminance is controlled by the time when the current flows through the EL element.

Since the light emission luminance of the EL element is proportional to the current value flowing through the EL element, in an EL display device using the EL element as a display element, switching is performed when the EL element is connected to the EL element from the power line via the switching element. The off-state current of the element is a problem. The invention disclosed in Patent Document 1 has attempted to solve this problem.
JP 2002-323873 A

  In a display device, when a certain pixel always shines irrespective of a video signal, that is, when even one bright spot is generated, it is often a defective product. On the other hand, if a certain pixel does not always shine regardless of the video signal, that is, even if a dark spot occurs, if it is about several pixels, it will not be defective.

  In addition, a short circuit occurs between the source and drain of the TFT connected in series with the EL element, and the potential of one terminal of the source electrode and drain electrode of the TFT is different from the other terminal of the source electrode and drain electrode of the TFT. One of the causes of bright spots is that the EL element continues to emit light regardless of the potential of the gate electrode of the TFT.

  In the present invention, the above-described problems are solved, and even if a short circuit occurs between the source and drain of a TFT connected in series with an EL element, it does not become a bright spot but increases the yield rate by making it a dark spot. For the purpose.

  The present invention includes a plurality of pixels, a light emitting element, a first TFT for determining light emission luminance, a channel type second TFT opposite to the first TFT, and a power supply line in each of the plurality of pixels. The power supply line is connected to one electrode of the light emitting element via the first TFT, and the connection point between the one electrode of the light emitting element and the first TFT is one electrode of the light emitting element via the second TFT. Is connected to a wiring having a potential at which the potential difference between the first electrode and the other electrode is lower than the threshold voltage of the light-emitting element, the source and drain of the first TFT are short-circuited, and the potential of the anode of the light-emitting element Is a potential of a power supply line, and when a bright spot is generated, the second TFT is turned on to make the bright spot a dark spot. For example, when the second TFT is turned on, the potential difference between the one electrode and the other electrode of the light emitting element becomes lower than the threshold voltage of the light emitting element, so that the light emitting element does not emit light. Thus, a pixel where a bright spot is generated can be a dark spot.

  The low potential to which the second TFT is connected may be any potential as long as the potential difference between the one electrode and the other electrode of the light emitting element is lower than the threshold voltage of the light emitting element.

  The threshold voltage of the light emitting element is a potential applied to the light emitting element when the light emitting element starts to flow current. When a potential equal to or higher than a threshold voltage is applied to the light emitting element, current flows and light is emitted.

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 and a plurality of pixels, and each of the plurality of pixels includes a first switching element, a second switching element, a capacitor having a pair of electrodes, and a light-emitting element having a pair of electrodes. And the first wiring is connected to one electrode of the light emitting element through the first switching element and to the other electrode of the light emitting element through the first switching element and the second switching element. ON or OFF of the switching element and the second switching element is controlled by a potential held in the capacitor element by some method, and when the first switching element is ON, the second switching element is OFF, The display device is characterized in that the second switching element is turned on when the first switching element is turned off.

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

(Second configuration)
The present invention includes a first wiring, a second wiring, and a plurality of pixels, and each of the plurality of pixels includes a first switching element, a second switching element, a capacitor having a pair of electrodes, and a pair of electrodes. The first wiring is connected to one electrode of the light emitting element through the first switching element and to the second wiring through the first switching element and the second switching element. The ON or OFF of the first switching element and the second switching element is controlled by a potential held in the capacitor element by some method, and when the first switching element is ON, the second switching element The display device is characterized in that the second switching element is turned on when is turned off and the first switching element is turned off.

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

(Third 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 including a first switching element, a second switching element, a third switching element, A capacitor having a pair of electrodes, a light emitting element having a pair of electrodes, and the first wiring is connected to one electrode of the light emitting element through the first switching element, and the first switching element and the second switching element. The electrode that is connected to the other electrode of the light emitting element through the switching element and controls ON or OFF of the first switching element and the second switching element is one electrode of the capacitor element and the first electrode that is in the ON state. 3 is connected to the second wiring through the switching element, the other electrode of the capacitor is connected to the first wiring, and the electrode for controlling ON or OFF of the third switching element is connected to the third wiring. The display is characterized in that when the first switching element is ON, the second switching element is OFF, and when the first switching element is OFF, the second switching element is ON. Device.

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

(Fourth configuration)
The present invention includes a first wiring, a second wiring, a third wiring, a fourth wiring, and a plurality of pixels, each of the plurality of pixels including a first switching element, a second switching element, A third switching element, a capacitor having a pair of electrodes, a light emitting element having a pair of electrodes, and the first wiring is connected to one electrode of the light emitting element through the first switching element, and the first The electrode that is connected to the fourth wiring via the switching element and the second switching element and controls ON or OFF of the first switching element and the second switching element is one electrode of the capacitor element and the ON state. The third switching element is connected to the second wiring, the other electrode of the capacitive element is connected to the first wiring, and the electrode for controlling ON or OFF of the third switching element is 3 arrangements And when the first switching element is ON, the second switching element is OFF, and when the first switching element is OFF, the second switching element is ON. It is a display device.

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

(Fifth 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 and a plurality of pixels, and each of the plurality of pixels includes a first transistor, a second transistor, a light-emitting element having a pair of electrodes, and a capacitor having a pair of electrodes. The first wiring is connected to one terminal of the source electrode and the drain electrode of the first transistor, the other of the source electrode and the drain electrode of the first transistor is the one electrode of the light-emitting element, and the second electrode One of the source electrode and the drain electrode of the transistor is connected to one terminal, and the other of the source electrode and the drain electrode of the second transistor is connected to the other electrode of the light-emitting element, and the gate electrode of the first transistor And the gate electrode of the second transistor is connected to one electrode of the capacitor, the other electrode of the capacitor is connected to the first wiring, and the first transistor is turned on. Rutoki the second transistor is turned OFF, when the first transistor is turned OFF is a display device characterized by the second transistor is turned ON.

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

(Sixth 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, and a plurality of pixels, and each of the plurality of pixels includes a first transistor, a second transistor, a light emitting element having a pair of electrodes, and a pair of electrodes. A first wiring is connected to one terminal of the source electrode and the drain electrode of the first transistor, and the other of the source electrode and the drain electrode of the first transistor is one of the light-emitting elements. An electrode, and one terminal of the source electrode and the drain electrode of the second transistor, and the other terminal of the source electrode and the drain electrode of the second transistor is connected to the second wiring, and the first transistor And the gate electrode of the second transistor are connected to one electrode of the capacitor, the other electrode of the capacitor is connected to the first wiring, and the first transistor is turned on. When in the second transistor is turned OFF, when the first transistor is turned OFF is a display device characterized by the second transistor is turned ON.

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

(Seventh configuration)
A transistor can be used as the switching element having the third 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, and a third wiring, and each of the plurality of pixels includes a first transistor, a second transistor, a third transistor, and a pair of electrodes. The first wiring is connected to one terminal of the source electrode and the drain electrode of the first transistor, and the source electrode and the drain electrode of the first transistor are connected to each other. The other is connected to one electrode of the light emitting element and one terminal of the source electrode and the drain electrode of the second transistor, and the other terminal of the source electrode and the drain electrode of the second transistor is the other of the light emitting element. The gate electrode of the first transistor and the gate electrode of the second transistor are connected to one electrode of the capacitor and the source electrode and drain of the third transistor. One of the electrodes is connected, the other electrode of the capacitor is connected to the first wiring, the other of the source and drain electrodes of the third transistor is connected to the second wiring, The gate electrode of the third transistor is connected to the third wiring. When the first transistor is ON, the second transistor is OFF. When the first transistor is OFF, the second transistor is The display device is characterized by being turned on.

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

(Eighth configuration)
A transistor can be used as the switching element having the fourth 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, a fourth wiring, and a plurality of pixels, each of which includes a first transistor, a second transistor, 3 transistor, a capacitor having a pair of electrodes, and a light emitting element having a pair of electrodes, and the first wiring is connected to one terminal of the source electrode and the drain electrode of the first transistor, The other of the source electrode and the drain electrode of the transistor is connected to one electrode of the light emitting element and one of the source electrode and the drain electrode of the second transistor, and the source electrode and the drain electrode of the second transistor are connected to each other. The other terminal is connected to the fourth wiring. The gate electrode of the first transistor and the gate electrode of the second transistor are one electrode of the capacitor and the third transistor. The electrode is connected to one terminal of the drain electrode, the other electrode of the capacitor is connected to the first wiring, and the other terminal of the source electrode and the drain electrode of the third transistor is connected to the second wiring. The gate electrode of the third transistor is connected to the third wiring. When the first transistor is turned on, the second transistor is turned off. When the first transistor is turned off, the second transistor is turned off. The display device is characterized in that the transistor is turned on.

  Further, the terminal connected to the first wiring of the capacitor element may be connected anywhere as long as it is kept at a constant potential during operation. 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 lower than the threshold 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.

  Note that various types of switches can be used as a switch shown in the present invention, and examples thereof include an electrical switch and a mechanical switch. In other words, any device can be used as long as it can control the flow of current, and it is not limited to a specific device, and various devices can be used. For example, a transistor, a diode (a PN diode, a PIN diode, a Schottky diode, a diode-connected transistor, or the like), or a logic circuit that is a combination thereof may be used. Therefore, when a transistor is used as a switch, the transistor operates as a mere switch, and thus the polarity (conductivity type) of the transistor is not particularly limited. However, when it is desirable that the off-state current is small, it is desirable to use a transistor having a polarity with a small off-state current. As a transistor with low off-state current, there are a transistor provided with an LDD region and a transistor having a multi-gate structure. Further, when the transistor operated as a switch operates at a source terminal potential close to a low potential power source (Vss, GND, 0 V, etc.), the N-channel type is used. On the contrary, the source terminal potential is a high potential. When operating in a state close to the side power supply (Vdd or the like), it is desirable to use a P-channel type. This is because the absolute value of the voltage between the gate and the source can be increased, so that it can easily operate as a switch. Note that both N-channel and P-channel switches may be used as CMOS switches. When a CMOS type switch is used, even if the voltage (ie, input voltage) output through the switch is higher or lower than the output voltage and the situation changes, it can operate properly. I can do it.

  Note that in the present invention, the term “connected” includes the case of being electrically connected and the case of being directly connected. Therefore, in the configuration disclosed by the present invention, in addition to a predetermined connection relationship, other elements (for example, a switch, a transistor, a capacitor, an inductor, a resistor, a diode, etc.) that can be electrically connected are arranged. May be. Or you may arrange | position, without inserting another element in between. In addition, it is a case where it is connected without interposing other elements that enable electrical connection, and includes only the case where it is directly connected, and does not include the case where it is electrically connected Is described as being directly connected or directly connected. Note that the description of being electrically connected includes the case of being electrically connected and the case of being directly connected.

  Note that various forms of display elements can be used. For example, EL elements (organic EL elements, inorganic EL elements or EL elements including organic and inorganic substances), electron-emitting elements, liquid crystal elements, electronic ink, grating light valves (GLV), plasma displays (PDP), digital micromirror devices ( DMD), piezoelectric ceramic displays, carbon nanotubes, and the like, which can be applied to display media whose contrast is changed by an electromagnetic action. Note that a display device using an EL element is an EL display, and a display device using an electron-emitting device is a liquid crystal display such as a field emission display (FED) or a SED type flat display (SED: Surface-conduction Electron-Emitter Display). There is a liquid crystal display as a display device using an element, and an electronic paper as a display device using electronic ink.

  Note that in the present invention, various types of transistors can be used as a transistor. Thus, there is no limitation on the type of applicable transistor. Therefore, a thin film transistor (TFT) using a non-single crystal semiconductor film typified by amorphous silicon or polycrystalline silicon, a MOS transistor formed using a semiconductor substrate or SOI substrate, a junction transistor, a bipolar transistor, ZnO A transistor using a compound semiconductor such as a-InGaZnO, a transistor using an organic semiconductor or a carbon nanotube, or another transistor can be used. In addition, various types of substrates on which the transistor is arranged can be used, and the substrate is not limited to a specific type. Therefore, for example, it can be disposed on a single crystal substrate, an SOI substrate, a glass substrate, a plastic substrate, a paper substrate, a cellophane substrate, a stone substrate, or the like. Alternatively, a transistor may be formed using a certain substrate, and then the transistor may be moved to another substrate and placed on another substrate.

  Note that as described above, various types of transistors in the present invention can be used and can be formed over various substrates. Therefore, the entire circuit may be formed on a glass substrate, may be formed on a plastic substrate, may be formed on a single crystal substrate, or may be formed on an SOI substrate. Alternatively, it may be formed on any substrate. Since all the circuits are formed, the number of parts can be reduced to reduce the cost, and the number of connection points with circuit parts can be reduced to improve the reliability. Alternatively, a part of the circuit may be formed on a certain substrate, and another part of the circuit may be formed on another substrate. That is, all of the circuits may not be formed on the same substrate. For example, part of a circuit is formed using a transistor over a glass substrate, another part of the circuit is formed over a single crystal substrate, and the IC chip is connected with COG (Chip On Glass) to form a glass. You may arrange | position on a board | substrate. Alternatively, the IC chip may be connected to the glass substrate using TAB (Tape Auto Bonding) or a printed board. As described above, since a part of the circuit is formed on the same substrate, the number of parts can be reduced to reduce the cost, and the number of connection points with the circuit parts can be reduced to improve the reliability. In addition, since the power consumption increases in a portion where the drive voltage is high or a portion where the drive frequency is high, an improvement in power consumption can be prevented if such a portion is not formed on the same substrate.

  Note that the structure of the transistor can take a variety of forms. It is not limited to a specific configuration. For example, a multi-gate structure having two or more gates may be used. The multi-gate structure reduces the off current, improves the breakdown voltage of the transistor to improve reliability, and even when the drain-source voltage changes when operating in the saturation region. The inter-current does not change so much, and a flat characteristic can be obtained. Alternatively, a structure in which gate electrodes are arranged above and below the channel may be employed. By adopting a structure in which gate electrodes are arranged above and below the channel, the channel region increases, so that the current value can be increased, and a depletion layer can be easily formed to improve the S value. Further, a structure in which a gate electrode is disposed above a channel, a structure in which a gate electrode is disposed below a channel, a normal staggered structure, or an inverted staggered structure may be employed. The channel region may be divided into a plurality of regions, may be connected in parallel, or may be connected in series. In addition, a source electrode or a drain electrode may overlap with the channel (or a part thereof). By using a structure in which a source electrode or a drain electrode overlaps with a channel (or part of it), it is possible to prevent electric charges from being accumulated in part of the channel and unstable operation. There may also be an LDD region. By providing an LDD region, the off-current can be reduced, the breakdown voltage of the transistor can be improved to improve reliability, or the drain-source voltage can be changed even when the drain-source voltage changes when operating in the saturation region. The current does not change so much, and a flat characteristic can be obtained.

  In the present invention, one pixel represents one element whose brightness can be controlled. Therefore, as an example, one pixel represents one color element, and brightness is expressed by one color element. Therefore, at that time, in the case of a color display device composed of R (red), G (green), and B (blue) color elements, the minimum unit of an image is an R pixel, a G pixel, and a B pixel. It is assumed to be composed of three pixels. The color elements are not limited to three colors and may be more than that, for example, RGBW (W is white). As another example, in the case where brightness is controlled using a plurality of areas for one color element, one area corresponds to one pixel. Therefore, as an example, when performing area gradation, there are a plurality of areas for controlling the brightness for each color element, and the gradation is expressed as a whole. One portion is defined as one pixel. Therefore, in that case, one color element is composed of a plurality of pixels. In that case, the size of the region contributing to the display may be different depending on the pixel. Further, in a plurality of brightness control areas for one color element, that is, in a plurality of pixels constituting one color element, a signal supplied to each is slightly different to widen the viewing angle. You may do it. Note that the description of one pixel (for three colors) is a case where three pixels of R, G, and B are considered as one pixel. In the case of describing one pixel (for one color), it is assumed that when there are a plurality of pixels for one color element, they are collectively considered as one pixel.

  In the present invention, the pixels are arranged in a matrix, not only when the pixels are arranged in a so-called lattice pattern in which vertical stripes and horizontal stripes are combined, but also in full color display with three color elements (for example, RGB). When performing the above, the case where the dots of the three color elements are arranged in a so-called delta arrangement is also included. The color elements are not limited to three colors and may be more than that, for example, RGBW (W is white). In addition, the size of the light emitting area may be different for each dot of the color element.

  A transistor is an element having at least three terminals including a gate, a drain, and a source, and has a channel region between the drain region and the source region. Here, since the source and the drain vary depending on the structure and operating conditions of the transistor, it is difficult to limit which is the source or the drain.

  Note that a gate refers to the whole or part of a gate electrode and a gate wiring (also referred to as a gate line or a gate signal line). A gate electrode refers to a conductive film which overlaps with a semiconductor that forms a channel region, an LDD (Lightly Doped Drain) region, and the like with a gate insulating film interposed therebetween. The gate wiring refers to wiring for connecting between the gate electrodes of each pixel or connecting the gate electrode to another wiring. However, there is a portion that functions as a gate electrode and also functions as a gate wiring. Such a region may be called a gate electrode or a gate wiring. That is, there is a region where the gate electrode and the gate wiring cannot be clearly distinguished. For example, when there is a channel region that overlaps with an extended gate wiring, the region functions as a gate wiring, but also functions as a gate electrode. Therefore, such a region may be called a gate electrode or a gate wiring. A region formed of the same material as the gate electrode and connected to the gate electrode may also be called a gate electrode. Similarly, a region formed of the same material as the gate wiring and connected to the gate wiring may be called a gate wiring. In a strict sense, such a region may not overlap with the channel region or may not have a function of being connected to another gate electrode. However, there is a region that is formed of the same material as the gate electrode and the gate wiring and connected to the gate electrode and the gate wiring because of a manufacturing margin. Therefore, such a region may also be called a gate electrode or a gate wiring. For example, in a multi-gate transistor, the gate electrode of one transistor and the gate electrode of another transistor are often connected by a conductive film formed using the same material as the gate electrode. Such a region is a region for connecting the gate electrode and the gate electrode, and may be referred to as a gate wiring. However, a multi-gate transistor can be regarded as a single transistor, and thus the gate electrode You can call it. That is, what is formed of the same material as the gate electrode and the gate wiring and is connected to the gate electrode and the gate wiring may be called a gate electrode and a gate wiring. For example, a portion of the conductive film where the gate electrode and the gate wiring are connected may be called a gate electrode or a gate wiring. Note that a gate terminal refers to a part of a region of a gate electrode or a region electrically connected to the gate electrode.

  Note that a source refers to the whole or part of a source region, a source electrode, and a source wiring (also referred to as a source line, a source signal line, or the like). The source region refers to a semiconductor region containing a large amount of P-type impurities (such as boron and gallium) and N-type impurities (such as phosphorus and arsenic). Therefore, a region containing a little P-type impurity or N-type impurity, that is, a so-called LDD (Lightly Doped Drain) region is not included in the source region. A source electrode refers to a portion of a conductive layer which is formed using a material different from that of a source region and is electrically connected to the source region. However, the source electrode may be referred to as a source electrode including the source region. The source wiring is a wiring for connecting between the source electrodes of each pixel or connecting the source electrode and another wiring. However, there is a portion that functions as a source electrode and also functions as a source wiring. Such a region may be called a source electrode or a source wiring. That is, there is a region where the source electrode and the source wiring cannot be clearly distinguished. For example, when there is a source region that overlaps with an extended source wiring, the region functions as a source wiring, but also functions as a source electrode. Therefore, such a region may be called a source electrode or a source wiring. A region formed of the same material as the source electrode and connected to the source electrode, or a portion connecting the source electrode and the source electrode may also be referred to as a source electrode. A portion overlapping with the source region may also be called a source electrode. Similarly, a region formed of the same material as the source wiring and connected to the source wiring may be called a source wiring. In a strict sense, such a region may not have a function of connecting to another source electrode. However, there is a region formed of the same material as the source electrode and the source wiring and connected to the source electrode and the source wiring because of a manufacturing margin. Therefore, such a region may also be called a source electrode or a source wiring. Further, for example, a conductive film in a portion where the source electrode and the source wiring are connected to each other may be referred to as a source electrode or a source wiring. Note that a source terminal refers to a part of a source region, a source electrode, or a region electrically connected to the source electrode.

  The drain is the same as the source.

  Note that in the present invention, a semiconductor device refers to a device having a circuit including a semiconductor element (such as a transistor or a diode). In addition, any device that can function by utilizing semiconductor characteristics may be used. A display device refers to a device having a display element (such as a liquid crystal element or a light-emitting element). Note that a display panel body in which a plurality of pixels including a display element such as a liquid crystal element or an EL element and a peripheral driver circuit for driving these pixels are formed over a substrate may be used. Furthermore, the display device may include one provided with a flexible printed circuit (FPC) or a printed wiring board (PWB). A light-emitting device refers to a display device including a self-luminous display element such as an EL element or an element used in an FED. A liquid crystal display device refers to a display device having a liquid crystal element.

  In addition, in the present invention, it is formed on a certain object, or is formed on the top. It is not limited to being in direct contact with. This includes cases where they are not in direct contact, that is, cases where another object is sandwiched between them. Therefore, for example, when the layer B is formed on the layer A (or on the layer A), the case where the layer B is formed in direct contact with the layer A and the case where the layer B is formed In which another layer (for example, layer C or layer D) is formed in direct contact with layer B and layer B is formed in direct contact therewith. The same applies to the description of “above”, and it is not limited to being in direct contact with a certain object, and includes a case where another object is sandwiched therebetween. Therefore, for example, when the layer B is formed above the layer A, the case where the layer B is formed in direct contact with the layer A and the case where another layer is formed in direct contact with the layer A. (For example, the layer C or the layer D) is formed, and the layer B is formed in direct contact therewith. It should be noted that the same applies to the case of below or below, and includes the case of direct contact and the case of no contact.

  According to the present invention, in each pixel, one electrode of the light-emitting element is connected to the power supply line via the first switching element, and one electrode of the light-emitting element is connected to the power supply line via the second switching element. The other electrode or the other electrode of the light emitting element is connected to a wiring whose potential difference is less than the threshold voltage of the light emitting element. As a result, regardless of whether the first switching element is on or off, the second switching element is turned on when a potential difference equal to or greater than the threshold value of the light emitting element is applied between the electrodes of the light emitting element and the light emitting element emits light. Thus, the difference between the potential applied to one electrode of the light-emitting element and the potential applied to the other electrode of the light-emitting element is made less than the threshold voltage of the light-emitting element and non-light emission is performed, so that Regardless of the dark spot. Accordingly, since the defect rate can be reduced, an improvement in yield and productivity can be achieved, and a display device capable of high quality display can be provided.

  In the present invention, since the above operation is performed by a video signal, it is not necessary to complicate the configuration of the drive circuit.

  In addition, since a voltage signal 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.

  Further, in the fifth configuration, the sixth configuration, the seventh configuration, and the eighth configuration of the present invention, the transistor arranged for each pixel functions as a mere switching element, so that power consumption of the display device is reduced. can do.

  An embodiment of the present invention will be described. 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 the embodiment.

(First embodiment)
With respect to the display device having the fifth structure described above, the structure of the pixel will be described with reference to FIG.

  In FIG. 1, 101 and 102 are TFTs, 103 is a capacitor element, 104 is a light emitting element, 105 is a counter electrode which is the other of a pair of electrodes of the light emitting element 104, and 106 is a power line.

  Each pixel includes a capacitor 103, a light emitting element 104, a TFT 101, and a TFT 102.

  The power supply line 106 is connected to one terminal of the source electrode and the drain electrode of the TFT 101, the other one of the source electrode and the drain electrode of the TFT 101 is one electrode of the light emitting element 104, and one of the source electrode and the drain electrode of the TFT 102. The other terminal of the source electrode and the drain electrode of the TFT 102 is connected to the other electrode of the light emitting element 104, and the gate electrode of the TFT 101 and the gate electrode of the TFT 102 are connected to one electrode of the capacitor 103. The other electrode of the capacitor 103 is connected to the power supply line 106.

  A connection point between the TFT 101, the TFT 102, and one electrode of the light emitting element 104 is a node Vm107.

  The potential difference between the power supply line 106 and the other electrode of the light-emitting element 104 is higher than the threshold voltage of the light-emitting element 104.

  1 will be described with reference to a timing chart in FIG.

  First, a defective operation when the present invention is effective will be described.

  A state in which the potential of the power supply line 106 is applied to the node Vm107 regardless of whether the TFT 101 is on or off, or a potential at which the potential difference between the node Vm107 and the other electrode of the light emitting element is equal to or higher than the threshold voltage of the light emitting element. Such as when the source and drain of the TFT 101 are short-circuited.

  FIG. 5 shows the operation in the state where the source and drain of the TFT 101 are short-circuited. Note that the potential of the power supply line 106 in the drawing is higher than the potential of the counter electrode 105.

  The period T1 is a case where a signal for turning on the TFT 101 and turning off the TFT 102 is applied to the TFT 101 and the gate of the TFT 102 by some method. At this time, the potential of the power supply line 106 is supplied to the node Vm107. Thus, the potential difference between the node Vm 107 and the other electrode of the light-emitting element 104 is equal to or higher than the threshold voltage of the light-emitting element 104, so that the light-emitting element 104 emits light.

  The period T2 is when the TFT 101 is turned off and the signal to turn on the TFT 102 is applied to the TFT 101 and the gate of the TFT 102 by some method. At this time, the node Vm 107 and the other electrode of the light-emitting element 104 are electrically connected. Thus, the potential difference between the node Vm107 and the other electrode of the light-emitting element 104 is less than the threshold voltage of the light-emitting element 104, so that the light-emitting element 104 does not emit light.

  When a short circuit occurs between the source and the drain of the TFT 101 and the potential of the power supply line 106 is supplied to the node Vm 107, the bright spot may be a dark spot by applying a gate voltage that turns off the TFT 101 and turns on the TFT 102. it can.

  As the TFT of FIG. 1, the TFT 101 is a P-type TFT and the TFT 102 is an N-type TFT. However, the TFTs 101 and 102 only need to have opposite polarities, and the polarity of each TFT is not limited to this.

In FIG. 1, the other electrode of the capacitor 103 and the power supply line 106 are connected. However, if the other electrode of the capacitor 103 is kept at a constant potential when the TFT 101 and the TFT 102 are operated. , You can connect anywhere.
Note that there are a digital gray scale method and an analog gray scale method as drive methods for expressing the gray scale of the display device, and either of them can be applied. In the digital gradation method, gradation is expressed by turning on and off the light emitting element by digital control. On the other hand, the analog method includes a method of analog control of the light emission luminance of the light emitting element. As a method for driving the display device of the present invention, it is more effective to apply this analog method. The reason will be described below.
In the case of an analog method in which the light emission luminance of the light emitting element is controlled in an analog manner, an analog potential is input to the gate of the TFT 101, the TFT 101 is operated in a saturation region, and the light emission luminance of the light emitting element is analog controlled. Here, if the TFT 101 is short-circuited, the emission luminance cannot be controlled even if the gate potential of the TFT 101 is controlled. That is, even when it is desired to emit light with low luminance, the pixel becomes a bright spot because the luminance is higher than the desired luminance. However, by using the structure of the present invention, even when the TFT 101 is short-circuited, by inputting a signal for turning on the TFT 102, the pixel can always be a dark spot.

(Second Embodiment)
In the display device having the above-described sixth structure, the structure of the pixel will be described with reference to FIG.

  In FIG. 2, 201 and 202 are TFTs, 203 is a capacitor element, 204 is a light emitting element, 205 is a counter electrode which is the other of a pair of electrodes of the light emitting element 204, and 206 and 207 are power lines.

  Each pixel includes a capacitor 203, a light emitting element 204, a TFT 201, and a TFT 202.

  The power supply line 206 is connected to one terminal of the source electrode and the drain electrode of the TFT 201, the other one of the source electrode and the drain electrode of the TFT 201 is one electrode of the light emitting element 204, and one of the source electrode and the drain electrode of the TFT 202. The other terminal of the source electrode and the drain electrode of the TFT 202 is connected to the power supply line 207, the gate electrode of the TFT 201 and the gate electrode of the TFT 202 are connected to one electrode of the capacitor 203, and the capacitor element The other electrode 203 is connected to the power line 206.

  A connection point between the TFT 201, the TFT 202, and one electrode of the light emitting element 204 is defined as a node Vm208.

  The potential difference between the power supply line 206 and the other electrode of the light emitting element 204 is higher than the threshold voltage of the light emitting element 204, and the potential difference between the power supply line 207 and the other electrode of the light emitting element 204 is the threshold value of the light emitting element 204. The potential is lower than the voltage.

  2 will be described with reference to a timing chart in FIG.

  First, a defective operation when the present invention is effective will be described.

  A state where the potential of the power supply line 206 is applied to the node Vm 208 regardless of whether the TFT 201 is ON or OFF, or a potential where the potential difference between the node Vm 208 and the other electrode of the light emitting element is equal to or higher than the threshold voltage of the light emitting element. Such as when the source and drain of the TFT 201 are short-circuited.

  FIG. 6 shows the operation in the state where the source and drain of the TFT 201 are short-circuited. Note that the potential of the power supply line 206 in the drawing is higher than the potential of the power supply line 207.

  The period T1 is a case where a signal for turning on the TFT 201 and turning off the TFT 202 is applied to the TFT 201 and the gate of the TFT 202 by some method. At this time, the potential of the power supply line 206 is supplied to the node Vm 208. Thus, the potential difference between the node Vm 208 and the other electrode of the light-emitting element 204 is equal to or higher than the threshold voltage of the light-emitting element 204, so that the light-emitting element 204 emits light.

  The period T2 is a case where a signal for turning off the TFT 201 and turning on the TFT 202 is applied to the TFT 201 and the gate of the TFT 202 by some method. At this time, the node Vm 208 and the power supply line 207 are electrically connected. Thus, the potential difference between the node Vm 208 and the other electrode of the light-emitting element 204 is less than the threshold voltage of the light-emitting element 204, so that the light-emitting element 204 does not emit light.

  When a short circuit occurs between the source and drain of the TFT 201 and the potential of the power supply line 206 is supplied to the node Vm 208, a bright spot can be made a dark spot by applying a gate voltage that turns off the TFT 201 and turns on the TFT 202. it can.

  As the TFT in FIG. 2, the TFT 201 is a P-type TFT and the TFT 202 is an N-type TFT. However, the TFTs 201 and 202 only need to have opposite polarities, and the polarity of each TFT is not limited to this.

  In FIG. 2, the other electrode of the capacitor 203 is connected to the power supply line 206, but the other electrode of the capacitor 203 may be maintained at a constant potential when the TFT 201 and the TFT 202 are operated. , You can connect anywhere.

(Third embodiment)
In the display device having the seventh structure described above, the structure of the pixel will be described with reference to FIGS.

  In FIG. 3, reference numerals 301, 302, and 303 denote TFTs, 304 denotes a capacitor element, 305 denotes a light emitting element, 306 denotes a counter electrode which is the other of a pair of electrodes of the light emitting element 305, 307 denotes a power supply line, and 308 denotes a source signal line. , 309 are gate selection lines.

  Each pixel includes a capacitor 304, a light emitting element 305, a TFT 301, a TFT 302, and a TFT 303.

  The power supply line 307 is connected to one terminal of the source electrode and the drain electrode of the TFT 301, the other one of the source electrode and the drain electrode of the TFT 301 is one electrode of the light emitting element 305, and one of the source electrode and the drain electrode of the TFT 302. The other terminal of the source electrode and the drain electrode of the TFT 302 is connected to the other electrode of the light-emitting element 305, the gate electrode of the TFT 301, and the gate electrode of the TFT 302 are one electrode of the capacitor 304, and One of the source electrode and the drain electrode of the TFT 303 is connected to the other terminal, the other electrode of the capacitor 304 is connected to the power supply line 307, and the other of the source electrode and the drain electrode of the TFT 303 is connected to the source signal line 308. The gate electrode of the TFT 303 is connected to the gate selection line 309. To have.

  A connection point between the TFT 301, the TFT 302, and one electrode of the light emitting element 305 is a node Vm310.

  The potential difference between the power supply line 307 and the other electrode of the light-emitting element 305 is higher than the threshold voltage of the light-emitting element 305.

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

  First, a defective operation when the present invention is effective will be described.

  A state where the potential of the power supply line 307 is applied to the node Vm310 regardless of whether the TFT 301 is ON or OFF, or a potential where the potential difference between the node Vm310 and the other electrode of the light emitting element is equal to or higher than the threshold voltage of the light emitting element. Such as when the source and drain of the TFT 301 are short-circuited.

  FIG. 7 shows the operation in the state where the source and drain of the TFT 301 are short-circuited. Note that the potential of the power supply line 307 in the drawing is higher than the potential of the counter electrode 306.

  The period T1 is a case where a signal for turning on the TFT 301 and a signal for turning off the TFT 302 are applied to the TFT 301 and the gate of the TFT 302 through the TFT 303 which is turned on from the source signal line 308, respectively. At this time, the potential of the power supply line 307 is supplied to the node Vm310. Thus, the potential difference between the node Vm310 and the other electrode of the light-emitting element 305 is equal to or higher than the threshold voltage of the light-emitting element 305, so that the light-emitting element 305 emits light.

  A period T2 is a case where the TFT 301 is turned off and a signal for turning on the TFT 302 is applied to the TFT 301 and the gate of the TFT 302 through the TFT 303 which is turned on from the source signal line 308. At this time, the node Vm310 and the other electrode of the light emitting element 305 are electrically connected. Thus, the potential difference between the node Vm310 and the other electrode of the light-emitting element 305 is less than the threshold voltage of the light-emitting element 305, so that the light-emitting element 305 does not emit light.

  When a short circuit occurs between the source and the drain of the TFT 301 and the potential of the power supply line 307 is supplied to the node Vm 310, a bright voltage is made a dark spot by applying a gate voltage that turns off the TFT 301 and turns on the TFT 302. be able to.

  As the TFT of FIG. 3, TFT 301 is a P-type TFT, TFT 302 is an N-type TFT, and TFT 303 is an N-type TFT. However, the TFTs 301 and 302 need only have opposite polarities. It is not limited.

  Note that in FIG. 3, the other electrode of the capacitor 304 and the power supply line 307 are connected. However, the other electrode of the capacitor 304 is maintained at a constant potential when the TFT 301 and the TFT 302 are operated. , You can connect anywhere.

(Fourth embodiment)
Regarding the display device having the above-described eighth structure, the structure of the pixel will be described with reference to FIGS.

  4, 401, 402, and 403 are TFTs, 404 is a capacitor element, 405 is a light emitting element, 406 is a counter electrode which is the other of a pair of electrodes of the light emitting element 405, 407 and 410 are power supply lines, and 408 is a source. A signal line 409 is a gate selection line.

  Each pixel includes a capacitor 404, a light emitting element 405, a TFT 401, a TFT 402, and a TFT 403.

  The power supply line 407 is connected to one terminal of the source electrode and the drain electrode of the TFT 401, the other one of the source electrode and the drain electrode of the TFT 401 is one electrode of the light emitting element 405, and one of the source electrode and the drain electrode of the TFT 402. The other terminal of the source electrode and the drain electrode of the TFT 402 is connected to the power supply line 410, the gate electrode of the TFT 401, and the gate electrode of the TFT 402 are one electrode of the capacitor 404 and the source of the TFT 403 One of the electrode and the drain electrode is connected, the other electrode of the capacitor 404 is connected to the power supply line 407, and the other terminal of the source electrode and the drain electrode of the TFT 403 is connected to the source signal line 408. These gate electrodes are connected to a gate selection line 409.

  A connection point between the TFT 401, the TFT 402, and one electrode of the light emitting element 405 is a node Vm411.

  The potential difference between the power supply line 407 and the other electrode of the light emitting element 405 is higher than the threshold voltage of the light emitting element 405, and the potential difference between the power supply line 410 and the other electrode of the light emitting element 405 is the threshold value of the light emitting element 405. The potential is lower than the voltage.

  A driving method of the pixel in FIG. 4 will be described with reference to a timing chart in FIG.

  First, a defective operation when the present invention is effective will be described.

  A state in which the potential of the power supply line 407 is applied to the node Vm411 regardless of whether the TFT 401 is on or off, or a potential at which the potential difference between the node Vm411 and the other electrode of the light emitting element 405 is equal to or higher than the threshold voltage of the light emitting element. This is a state where the voltage is applied to Vm 411, that is, when the source and drain of the TFT 401 are short-circuited.

  FIG. 8 shows the operation in the state where the source and drain of the TFT 401 are short-circuited. Note that the potential of the power supply line 407 in the drawing is higher than the potential of the power supply line 410.

  The period T1 is a case where a signal for turning on the TFT 401 and turning off the TFT 402 are applied to the gates of the TFT 401 and the TFT 402 through the TFT 403 which is turned on from the source signal line 408, respectively. At this time, the potential of the power supply line 407 is supplied to the node Vm411. Thus, the potential difference between the node Vm411 and the other electrode of the light-emitting element 405 is equal to or higher than the threshold voltage of the light-emitting element 405, so that the light-emitting element 405 emits light.

  The period T2 is a case where the TFT 401 is turned off and the signal to turn on the TFT 402 is applied to the TFT 401 and the gate of the TFT 402 via the TFT 403 which is turned on from the source signal line 408. At this time, the node Vm411 and the power supply line 410 are electrically connected. Thus, the potential difference between the node Vm411 and the other electrode of the light-emitting element 405 is less than the threshold voltage of the light-emitting element 405, so that the light-emitting element 405 does not emit light.

  When a short circuit occurs between the source and the drain of the TFT 401 and the potential of the power supply line 407 is supplied to the node Vm411, a bright voltage is set as a dark spot by applying a gate voltage that turns off the TFT 401 and turns on the TFT 402. be able to.

  As the TFT of FIG. 4, the TFT 401 is a P-type TFT, the TFT 402 is an N-type TFT, and the TFT 403 is an N-type TFT, but the polarity of the TFT 402 is different from the polarity of the TFT 401 (that is, the TFT 401 is a P-type). Sometimes the TFT 402 is N-type, and when the TFT 401 is N-type, the TFT 402 is P-type), and the polarity of each TFT is not limited to this.

  In FIG. 4, the other electrode of the capacitor 404 and the power supply line 407 are connected. However, the other electrode of the capacitor 404 may be maintained at a constant potential when the TFT 401 and the TFT 402 are operated. , You can connect anywhere.

  In the first embodiment, the second embodiment, the third embodiment, and the fourth embodiment, the arrangement of TFTs has been described with reference to FIGS. 1, 2, 3, and 4. However, in the present invention, the arrangement of the TFTs is not limited to the arrangement shown in FIG. 1, FIG. 2, FIG. 3, and FIG. If the pixel can be operated according to the timing charts shown in FIGS. 5, 6, 7, and 8, it is possible to dispose TFTs at arbitrary positions. For example, an erasing TFT may be arranged in order to perform an erasing operation like a digital time gray scale method by adding a TFT.

  In addition, as a method of detecting a pixel in which a bright spot is generated, it may be detected by a current value when the light emitting element is turned on for each pixel and every several pixels. You may detect with the apparatus to detect. The method for detecting the bright spot is not limited.

  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 the pixel structure shown in FIGS. 3 and 4 will be described. FIG. 9 shows a configuration example of the display device. A plurality of pixels 900 includes a display portion 905 arranged in a matrix of m rows and n columns (m and n are natural numbers). Around the display portion 905, a source signal line driver circuit 903 and a write gate selection line are provided. A driving circuit 904 and an erasing gate selection line driving circuit 907 are provided. The source signal lines 901 represented by S1 to Sn are arranged corresponding to the respective columns of the pixels 900, and the gate selection lines 902 represented by G1 to Gm are arranged corresponding to the respective rows of the pixels 900. .

  A source signal line 308 in FIG. 3 corresponds to the source signal line 901 in FIG. The gate selection line 309 in FIG. 3 corresponds to the gate selection line 902 in FIG. The source signal line 408 in FIG. 4 corresponds to the source signal line 901 in FIG. The gate selection line 409 in FIG. 4 corresponds to the gate selection line 902 in FIG. Other wirings shown in FIGS. 3 and 4 are not shown in FIG.

  The display device illustrated in FIG. 9 uses a driving method in which writing and erasing can be performed with one gate selection line 902 by dividing one gate selection period into a writing period and an erasing period.

  Note that a known structure may be used for the source signal line driver circuit 903, the write gate selection line driver circuit 904, and the erase gate selection line driver circuit 907.

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

  FIG. 10A and FIG. 10B show the first embodiment, the second embodiment, the third embodiment, and the fourth embodiment described in the best mode for carrying out the invention. It is sectional drawing of the pixel of a display apparatus. An example in which TFTs are used as transistors arranged in the pixels of the first embodiment, the second embodiment, the third embodiment, and the fourth embodiment will be described.

  10A and 10B, 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 FIG. 10, the TFT 1100, the capacitor 1101, and the light emitting element 1011 are shown as representatives as elements constituting the pixel.

  A structure of FIG. 10A 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 containing stainless steel or a semiconductor substrate with an insulating film formed on the surface thereof may be used. A substrate made of a synthetic resin having flexibility such as plastic may be used. The surface of the substrate 1000 may be planarized by polishing such as a CMP (Chemical Mechanical Polishing) 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. Although the base film 1001 has a single-layer structure in FIG. 10, it may be formed of two or more layers. Note that the base film 1001 is not necessarily provided when diffusion of impurities such as a quartz substrate does not cause any problem.

  As the semiconductor layer 1002 and the semiconductor layer 1102, a selectively etched 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 RTA (Rapid Thermal Annealing) or a furnace annealing furnace, 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 an impurity element is added at a low concentration may be provided between the channel formation region and 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. 10, only the TFT 1100 connected to the first electrode 1007 of the light-emitting element 1011 is illustrated as a TFT included in the pixel; however, a structure including a plurality of TFTs may be used. 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. 10, as a capacitor element included in a pixel, one of a pair of electrodes is a semiconductor layer 1102 formed simultaneously with the semiconductor layer 1002 of the TFT 1100, and the other electrode is an electrode 1104 formed simultaneously with the gate electrode 1004 of the TFT 1100. However, the present invention is not limited to this configuration.

  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.

  Alternatively, the second insulating film 1005 may be formed using a material containing siloxane. Siloxane is a material in which a skeleton structure is formed by a bond of silicon (Si) and oxygen (O). As a substituent, an organic group containing at least hydrogen (for example, an alkyl group or an aromatic hydrocarbon) is 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.

  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, indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), zinc oxide to which gallium is added (GZO), or other light-transmitting oxide conductive materials can be used. . Indium tin oxide containing silicon oxide, indium tin oxide containing titanium oxide, indium tin oxide containing molybdenum oxide, ITO added with titanium, molybdenum or gallium, or indium oxide containing silicon oxide You may use what was formed using the target which mixed -20 wt% zinc oxide (ZnO).

The other of the first electrode 1007 and the second electrode 1010 may be formed using 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 CaN), 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 properties. 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. For each layer, an organic material or an inorganic material can be used. As the organic material, any of a high molecular weight material, a medium molecular weight material, and a low molecular weight 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 in FIG. 10B will be described. Note that the same portions as those in FIG. 10A are denoted by the same reference numerals, and description thereof is omitted.

  FIG. 10B 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. 11A is a top view of a display panel formed by sealing a display device. FIGS. 11B and 11C are respectively taken along line AA ′ of FIG. It is sectional drawing. FIG. 11B and FIG. 11C are examples in which sealing is performed by different methods.

  11A to 11C, a display portion 1302 including a plurality of pixels is provided over a substrate 1301, a sealing material 1306 is provided so as to surround the display portion 1302, and a sealing material 1307 is attached. It has been. 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. 11B, the sealing material 1307 in FIG. 11A 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. 11C, the sealing material 1307 in FIG. 11A 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 adsorbs moisture, oxygen, and the like in the sealed space 1308 to maintain a clean atmosphere, and suppresses deterioration of the light emitting element. Fulfill. 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 implemented by freely combining 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 a display panel is mounted.

  FIG. 12 shows a display module in which a display panel 1200 and a circuit board 1204 are combined.

  FIG. 12 shows an example in which the control circuit 1205, the signal dividing circuit 1206, and the like are formed on the circuit board 1204. The circuit formed on the circuit board 1204 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 1204 are input to the display panel 1200 through the connection wiring 1207.

  The display panel 1200 includes a display portion 1201, a source signal line driver circuit 1202, and a gate selection line driver circuit 1203. The configuration of the display panel 1200 can be the same as the configuration shown in the second embodiment. FIG. 12 illustrates an example in which the source signal line driver circuit 1202 and the gate selection line driver circuit 1203 are formed over the same substrate as the substrate over which the display portion 1201 is formed. However, the display module of the present invention is not limited to this. Only the gate selection line driving circuit may be formed on the same substrate as the substrate on which the display portion is formed, and the source signal line driving circuit may be formed on the circuit substrate. Both the source signal line driver circuit and the gate selection 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 electronic devices using the display module of the present invention, cameras such as video cameras and digital cameras, goggle type displays (head mounted displays), navigation systems, sound playback devices (car audio, audio components, etc.), personal computers, game machines , A portable information terminal (mobile computer, cellular phone, portable game machine, electronic book, etc.), an image reproducing device (specifically, a digital versatile disc (DVD)) provided with a recording medium, and the image And the like). 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.

  A specific example of the electronic device is illustrated in FIG. Note that the electronic device shown here is just an example, and the present invention is not limited to these applications.

  FIG. 13A illustrates a display, 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 display devices for displaying information such as for personal computers, for receiving TV broadcasts, and for displaying advertisements.

  FIG. 13B illustrates a digital 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. 13C illustrates a personal computer, which includes 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. 13D 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. 13E shows 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, a recording medium (DVD, etc.). 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. 13F 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. 13G 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 the like. . The display module of the present invention can be used for the display portion 2602.

  Here, FIG. 13H shows 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.

  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 luminescent material is very high, the display module of the present invention is preferable for displaying moving images.

  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. 3 is a circuit diagram illustrating a configuration of a pixel of the present invention. FIG. 3 is a circuit diagram illustrating a configuration 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. FIG. 6 is a diagram illustrating a timing chart of a pixel of the present invention. FIG. 6 is a diagram illustrating a timing chart 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. 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. FIG. 14 illustrates an example of an electronic device of the invention.

Explanation of symbols

101 TFT
102 TFT
103 capacitive element 104 light emitting element 105 counter electrode 106 power supply line 107 node Vm
201 TFT
202 TFT
203 Capacitor 204 Light-Emitting Element 205 Counter Electrode 206 Power Line 207 Power Line 208 Node Vm

Claims (7)

Wiring and
A first transistor;
A second transistor;
A light emitting device having a pair of electrodes;
A capacitive element having a pair of electrodes;
The wiring is electrically connected to one of a source electrode or a drain electrode of the first transistor;
The other of the source electrode and the drain electrode of the first transistor is electrically connected to one electrode of the light emitting element, and is electrically connected to one of the source electrode and the drain electrode of the second transistor,
The other of the source electrode and the drain electrode of the second transistor is electrically connected to the other electrode of the light emitting element;
A gate electrode of the first transistor and a gate electrode of the second transistor are electrically connected to one electrode of the capacitor;
The other electrode of the capacitive element is electrically connected to the wiring;
When the source electrode and the drain electrode of the first transistor are electrically short-circuited, and the potential of the wiring is applied to one electrode of the light-emitting element, the second transistor is turned on. Thus, the display device driving method is characterized in that the potential difference between the one electrode and the other electrode of the light emitting element is less than the threshold voltage of the light emitting element so as not to emit light. A first wiring;
A second wiring;
A first transistor;
A second transistor;
A light emitting device having a pair of electrodes;
A capacitive element having a pair of electrodes;
The first wiring is electrically connected to one of a source electrode and a drain electrode of the first transistor;
The other of the source electrode and the drain electrode of the first transistor is electrically connected to one electrode of the light emitting element, and is electrically connected to one of the source electrode and the drain electrode of the second transistor,
The other of the source electrode and the drain electrode of the second transistor is electrically connected to the second wiring;
A gate electrode of the first transistor and a gate electrode of the second transistor are electrically connected to one electrode of the capacitor;
The other electrode of the capacitive element is electrically connected to the first wiring;
When the source electrode and the drain electrode of the first transistor are electrically short-circuited and the potential of the first wiring is applied to one electrode of the light emitting element, the second transistor is turned on. By setting the state, the second wiring and one electrode of the light emitting element are short-circuited,
A driving method of a display device, wherein a potential difference between one electrode and the other electrode of the light-emitting element is less than a threshold voltage of the light-emitting element so as not to emit light. A first wiring;
A second wiring;
A third wiring;
A first transistor;
A second transistor;
A third transistor;
A capacitive element having a pair of electrodes;
A light-emitting element having a pair of electrodes,
The first wiring is electrically connected to one of a source electrode and a drain electrode of the first transistor;
The other of the source electrode and the drain electrode of the first transistor is electrically connected to one electrode of the light emitting element, and is electrically connected to one terminal of the source electrode or the drain electrode of the second transistor. And
The other of the source electrode and the drain electrode of the second transistor is electrically connected to the other electrode of the light-emitting element;
The gate electrode of the first transistor and the gate electrode of the second transistor are electrically connected to one electrode of the capacitor, and one of the source electrode or the drain electrode of the third transistor Electrically connected,
The other electrode of the capacitor is electrically connected to the first wiring, and the other of the source electrode or the drain electrode of the third transistor is electrically connected to the second wiring,
A gate electrode of the third transistor is electrically connected to the third wiring;
When the source electrode and the drain electrode of the first transistor are electrically short-circuited and the potential of the first wiring is applied to one electrode of the light-emitting element, the potential of the third wiring To the third transistor to turn on the third transistor;
By turning on the third transistor, the potential of the second wiring is applied to the second transistor, the second transistor is turned on,
A driving method of a display device, wherein a potential difference between one electrode and the other electrode of the light emitting element is less than a threshold voltage of the light emitting element so as not to emit light. A first wiring;
A second wiring;
A third wiring;
A fourth wiring;
A first transistor;
A second transistor;
A third transistor;
A capacitive element having a pair of electrodes;
A light-emitting element having a pair of electrodes,
The first wiring is electrically connected to one of a source electrode and a drain electrode of the first transistor;
The other of the source electrode and the drain electrode of the first transistor is electrically connected to one electrode of the light-emitting element, and is electrically connected to one of the source electrode and the drain electrode of the second transistor. ,
The other of the source electrode and the drain electrode of the second transistor is electrically connected to the fourth wiring;
The gate electrode of the first transistor and the gate electrode of the second transistor are electrically connected to one electrode of the capacitor, and electrically connected to one of the source electrode or the drain electrode of the third transistor. Connected,
The other electrode of the capacitive element is electrically connected to the first wiring;
The other of the source electrode and the drain electrode of the third transistor is connected to the second wiring;
A gate electrode of the third transistor is electrically connected to the third wiring;
When the source electrode and the drain electrode of the first transistor are electrically short-circuited and the potential of the first wiring is applied to one electrode of the light-emitting element, the potential of the third wiring To the third transistor to turn on the third transistor;
By turning on the third transistor, the potential of the second wiring is applied to the second transistor, and the second transistor is turned on.
By turning on the second transistor, the fourth wiring and one electrode of the light emitting element are short-circuited,
A driving method of a display device, wherein a potential difference between one electrode and the other electrode of the light-emitting element is less than a threshold voltage of the light-emitting element so as not to emit light. In any one of Claims 1 thru | or 4,
The display device driving method, wherein the first transistor and the second transistor have different conductivity types. In any one of Claims 1 thru | or 5,
The display device driving method, wherein the first transistor operates in a saturation region. In any one of Claims 1 thru | or 6,
A driving method of a display device, wherein the light emission intensity of the light emitting element is controlled using an analog method for controlling the light emission intensity in an analog manner.

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