Indication device

Abstract

To suppress variation in a current value caused by variation in a threshold voltage of a transistor, and to provide a display device that has less deviation from luminance designated by a video signal and has a high duty ratio.SOLUTION: A display device includes pixels including a load, a transistor for controlling a current value supplied to the load, a holding capacitor, and first to fourth switches, inputs potential corresponding to a video signal to the pixels after allowing the holding capacitor to hold a threshold voltage of the transistor, and allows voltage obtained by adding the potential to the threshold voltage to be retained, thus suppressing variation in a current value caused by variation in a threshold voltage of the transistor. Therefore, a desired current can be supplied to the load as well as light-emitting elements. By varying potential of a power line, the display device having a high duty ratio can be provided.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a semiconductor device having a function of controlling a current supplied to a load by a transistor. Pixels formed by current-driven display elements whose luminance changes depending on a signal, and The present invention also relates to a display device including a signal line driver circuit and a scanning line driver circuit for driving the same. The present invention also relates to an electronic device having the display device in a display section. [Background technology]

[0002] In recent years, the pixels have been converted to electroluminescence (EL) Self-luminous display devices using light-emitting elements such as luminescence (LED) have been attracting attention. The light emitting element used in such a self-luminous display device is an organic light emitting diode. OLED (Organic Light Emitting Diode), EL These elements have attracted attention and are being used in EL displays and other applications. These light-emitting elements emit light by themselves, so the pixels are more visible than on LCDs, and In addition, it has the advantage of a fast response speed. are often controlled by the value of the current flowing through them.

[0003] In addition, an active matrix in which a transistor that controls the light emission of a light-emitting element is provided for each pixel is used. Active matrix display devices are a type of display that uses a passive This not only enables high-definition, large-screen display that is difficult to achieve with a conventional matrix display device, but also It is expected to be put to practical use because it operates with lower power consumption than sub-matrix display devices. .

[0004] FIG. 50 shows a pixel configuration of a conventional active matrix display device (Patent Document 1). The pixel shown in FIG. A TFT 11, a TFT 12, a capacitance element 13, and a light-emitting element 14 are provided. Either the source electrode or the drain electrode of the TFT 12 is connected to the line 16. A power supply potential Vdd is supplied to one of the electrodes of the light emitting element 14 and one of the electrodes of the capacitance element 13. The counter electrode is supplied with a ground potential.

[0005] At this time, the semiconductor of the TFT 12 that controls the current value supplied to the light emitting element, that is, the driving TFT When amorphous silicon is used for the semiconductor layer, the threshold voltage (Vth) fluctuates due to degradation, etc. In this case, even though the same potential is applied to different pixels from the signal line 15, The current flowing through the light emitting element 14 varies from pixel to pixel, causing the displayed brightness to be non-uniform from pixel to pixel. Even if polysilicon is used for the semiconductor layer of the driving TFT, The characteristics of the star may deteriorate or vary.

[0006] In order to solve this problem, Patent Document 2 proposes an operation method using the pixel shown in FIG. The pixel shown in FIG. 51 controls the current value supplied to the transistor 21 and the light emitting element 24. A driving transistor 22 for controlling the pixel, a capacitance element 23, and a light emitting element 24 are provided. , and is connected to the scanning line 26. The driving transistor 22 is an NMOS transistor. and either the source electrode or the drain electrode of the driving transistor 22 is A ground potential is supplied, and Vca is supplied to the counter electrode of the light emitting element 24 .

[0007] A timing chart for the operation of this pixel is shown in FIG. The write period consists of an initialization period 31, a threshold voltage (Vth) write period 32, and a data write period 33. A frame period is a period during which one screen's worth of images is displayed. This corresponds to the display period, and includes the initialization period, threshold voltage (Vth) write period, and data write period. The write period and the write period are collectively called the address period.

[0008] First, in the threshold voltage writing period 32, the threshold voltage of the driving transistor 22 is Then, in the data writing period 33, the luminance of the pixel is The data voltage (Vdata) shown in FIG. 1 is written to the capacitance element, and Vdata+Vth is the capacitance element. During the light emission period, the driving transistor 22 is turned on, and Vca By changing the data voltage, the light emitting element 24 emits light at a luminance specified by the data voltage. This operation reduces the luminance variation caused by the fluctuation of the threshold voltage of the driving transistor. It is decreasing.

[0009] In Patent Document 3, the gate potential is determined by adding the threshold voltage of the driving TFT to the data potential. Even if the TFT threshold voltage fluctuates, the current that flows is It is disclosed that there is no change. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 8-234683 [Patent Document 2] JP 2004-295131 A [Patent Document 3] JP 2004-280059 A Summary of the Invention [Problem to be solved by the invention]

[0011] As described above, in a display device, the variation in the current value caused by the variation in the threshold voltage of the driving TFT There was a need to suppress the variation.

[0012] In both of the operation methods described in Patent Documents 2 and 3, the potential of Vca is By changing the voltage several times per frame period, the above-mentioned initialization and writing of the threshold voltage can be performed. In these pixels, only one of the light-emitting elements to which Vca is supplied emits light. Since the electrode, i.e., the counter electrode, is formed over the entire pixel area, the initialization and threshold voltage If there is even one pixel in which data is being written other than by writing, the light-emitting element Therefore, as shown in FIG. The ratio of the light period (i.e., the duty ratio) becomes smaller.

[0013] If the duty ratio is low, it is necessary to increase the current flowing through the light-emitting element and the driving transistor. Therefore, the voltage applied to the light-emitting element increases, and the power consumption increases. This can cause image burn-in or the display may not be as bright as before the deterioration. To obtain a brightness equivalent to that, a larger power would be required.

[0014] In addition, since the opposing electrodes are connected to all pixels, the light-emitting elements function as high-capacity elements. Therefore, a large amount of power is required to change the potential of the counter electrode.

[0015] In view of the above problems, an object of the present invention is to provide a display device that consumes low power and is bright. In addition, the pixel configuration and semiconductor device have a small deviation from the brightness specified by the data potential. The present invention aims to obtain a display device having a light-emitting element. However, the present invention is not limited to the current value caused by the variation in the threshold voltage of the transistor. The objective is to suppress the variation in the [Means for solving the problem]

[0016] The display device according to the present invention is a display device that controls a current by supplying a current to a load (a display medium such as a light-emitting element). Between the gate and source of the transistor that controls the A potential obtained by adding a potential corresponding to a video signal input to the transistor and the potential is held. The pixel configuration has a capacitance section that allows the transistor to be connected to the capacitance section. The potential corresponding to the threshold voltage of the transistor and the potential corresponding to the video signal are added together to hold the potential. This reduces the current fluctuation caused by the characteristic variation of the current control transistor, i.e., the deterioration of image quality. The current supply is performed by adjusting the drain voltage of the transistor. This is done by varying the position.

[0017] When a potential corresponding to a video signal is input (write period), the transistor By making the transistor non-conductive or cutting off the current path, the current supplied from the transistor It is possible to suppress the fluctuation in the voltage of the capacitance element due to the change in the capacitance.

[0018] The display device according to the present invention includes a transistor for controlling a current and a The load is supplied with a current that is set to a predetermined value, and the load is an electroluminescence element (organic EL elements, inorganic EL elements, or EL elements containing organic and inorganic materials Not limited to this, it applies to display media that change brightness, color tone, polarization, etc. when an electric current flows through them. It is possible.

[0019] One aspect of the present invention is a transistor, a first switch, a second switch, and a third switch. a pixel including a transistor, one of a source electrode and a drain electrode of the transistor being a pixel electrode; and one of the source electrode and the drain electrode of the transistor is electrically connected to the second The transistor is electrically connected to a first wiring via a switch, and the source electrode and The other of the drain electrodes is electrically connected to a second wiring via the third switch, A gate electrode of the transistor is electrically connected to the second wiring via the first switch. and a signal according to a gradation is input to the gate electrode. be.

[0020] One aspect of the present invention is a semiconductor memory device including a transistor, a storage capacitor, a first switch, a second switch, and a third switch and a fourth switch, and the source electrode and the drain electrode of the transistor are connected to each other; One of the gate electrodes is electrically connected to the pixel electrode, and the source electrode and the drain electrode of the transistor are One of the electrodes of the transistor is electrically connected to the second wiring via the third switch. The other of the source electrode and the drain electrode of the transistor is electrically connected to a first wiring. The gate electrode of the transistor is connected to the first switch through the fourth switch and the second switch. The gate electrode of the transistor is electrically connected to the fourth switch and the A gate electrode of the transistor is electrically connected to a third wiring through a first switch. The source electrode and the drain electrode of the transistor are connected via the fourth switch and the storage capacitor. The semiconductor device is characterized in that the first insulating film is electrically connected to one of the first and second insulating electrodes.

[0021] One aspect of the present invention is a semiconductor memory device including a transistor, a storage capacitor, a first switch, a second switch, and a third switch and a fourth switch, and the source electrode and the drain electrode of the transistor are connected to each other; One of the gate electrodes is electrically connected to the pixel electrode, and the source electrode and the drain electrode of the transistor are One of the electrodes of the transistor is electrically connected to the second wiring via the third switch. The other of the source electrode and the drain electrode of the transistor is electrically connected to a first wiring. The gate electrode of the transistor is electrically connected to the first wiring through the second switch. The gate electrode of the transistor is connected to the fourth switch and the first switch. The gate electrode of the transistor is electrically connected to the fourth switch and and electrically connected to one of the source electrode and the drain electrode of the transistor via the storage capacitor. The semiconductor device is characterized in that

[0022] One aspect of the present invention is a semiconductor memory device including a transistor, a storage capacitor, a first switch, a second switch, and a third switch and a fourth switch, and the source electrode and the drain electrode of the transistor are connected to each other; One of the gate electrodes is electrically connected to the pixel electrode, and the source electrode and the drain electrode of the transistor are One of the electrodes of the transistor is electrically connected to the second wiring via the third switch. The other of the source electrode and the drain electrode of the transistor is connected to the first wiring via the fourth switch. The gate electrode of the transistor is electrically connected to the second switch. The gate electrode of the transistor is electrically connected to the first wiring via the first switch. The gate electrode of the transistor is electrically connected to a third wiring through the storage capacitor. and electrically connected to one of the source electrode and the drain electrode of the transistor. The semiconductor device is characterized by the above.

[0023] One aspect of the present invention is a semiconductor memory device including a transistor, a storage capacitor, a first switch, a second switch, and a third switch and a fourth switch, and the source electrode and the drain electrode of the transistor are connected to each other; One of the transistor electrodes is electrically connected to the pixel electrode via the fourth switch. One of the source electrode and the drain electrode of the transistor is connected to the fourth switch and the third switch. The source electrode and the drain electrode of the transistor are electrically connected to the second wiring via the The other pole is electrically connected to the first wiring, and the gate electrode of the transistor is connected to the second wiring. The gate electrode of the transistor is electrically connected to the first wiring through a switch. The gate of the transistor is electrically connected to a third wiring through the first switch. The gate electrode of the transistor is connected to the source electrode of the transistor through the storage capacitor and the fourth switch. and one of the drain electrodes is electrically connected to the first electrode.

[0024] The second wiring may be the same as the wiring that controls the third switch.

[0025] The second wiring is any one of the scanning lines that controls the first to fourth switches in the previous or next row. It can be either one.

[0026] The transistor may be an N-channel transistor. The semiconductor layer of the transistor may be made of an amorphous semiconductor film. The semiconductor layer of the transistor may be characterized by being made of amorphous silicon.

[0027] The semiconductor layer of the transistor may be made of a crystalline semiconductor film. stomach.

[0028] In the above invention, the potential input to the first wiring has two values, V1 and V2. , the first switch to the third switch are in a non-conducting state, and the fourth switch Only when the switch is in a conductive state does it take on the value of V2, and V1 is input to the second wiring. a potential higher than the potential of the transistor, the difference being greater than the threshold voltage of the transistor; V2 may be characterized as being higher than V1.

[0029] The transistor may be a P-channel transistor. In the above invention, the potential input to the first wiring has two values, V1 and V2. The first switch to the third switch are in a non-conducting state, and the fourth switch The value of V2 is only when the switch is in a conductive state, and V1 is lower than the potential input to the second wiring. the difference is greater than the absolute value of the threshold voltage of the transistor, V2 may be characterized as being lower than V1.

[0030] In one aspect of the present invention, one of the source electrode and the drain electrode is electrically connected to a first wiring, a transistor in which the other of the source electrode and the drain electrode is electrically connected to a second wiring; A storage capacitor that stores a gate-source voltage of the transistor and a voltage input to the first wiring A first potential is applied to one electrode of the storage capacitor, and a second potential is input to the second wiring. A second potential is applied to the other electrode of the storage capacitor, thereby causing the storage capacitor to store a first potential. means for discharging the voltage of the storage capacitor to a second voltage; A potential obtained by adding a third voltage to the first potential is applied to one electrode of the storage capacitor; a means for holding a fifth voltage obtained by adding the second voltage and the fourth voltage in the holding capacitor; A third potential different from the first potential is input to the first wiring, thereby and a means for supplying a current set in the input to a load. .

[0031] In one aspect of the present invention, one of the source electrode and the drain electrode is electrically connected to a first wiring, a transistor in which the other of the source electrode and the drain electrode is electrically connected to a second wiring; A storage capacitor that stores a gate-source voltage of the transistor and a voltage input to the first wiring A first potential is applied to one electrode of the storage capacitor, and a second potential is input to the second wiring. A second potential is applied to the other electrode of the storage capacitor, thereby causing the storage capacitor to store a first potential. a means for holding the voltage of the storage capacitor up to a threshold voltage of the transistor; a discharge means for discharging the first potential plus a second voltage at one of the storage capacitors; A fourth voltage obtained by adding the threshold voltage of the transistor and the third voltage is applied to the electrode. a means for holding the potential in the holding capacitor, and a third potential different from the first potential being applied to the first wiring and a means for supplying a current set in the transistor to a load by inputting a voltage. The semiconductor device is characterized in that

[0032] The transistor may be an N-channel transistor. The semiconductor layer of the transistor may be made of an amorphous semiconductor film. The semiconductor layer of the transistor may be characterized by being made of amorphous silicon.

[0033] The semiconductor layer of the transistor may be made of a crystalline semiconductor film. stomach.

[0034] In the above invention, the first potential is higher than the second potential, and the difference is greater than the threshold voltage of the transistor, and the first potential is greater than the third potential. It may be characterized in that the potential is lower than the potential.

[0035] The transistor may be a P-channel transistor. The first potential is lower than the second potential, and the difference between the first potential and the second potential is a threshold voltage of the transistor. the absolute value of the threshold voltage, and the first potential is higher than the third potential. The present invention may be characterized in that:

[0036] Another aspect of the present invention is a display device having the semiconductor device described above. The electronic device has a display device as a display unit.

[0037] The switches shown in the specification can be of various types. For example, There are electrical switches and mechanical switches. In other words, they are devices that can control the flow of electric current. For example, a transistor or a diode (PN diode) may be used. Diodes, PIN diodes, Schottky diodes, diode-connected transistors A transistor can be used as a switch, or a logic circuit that combines them. When a transistor is used, the transistor acts as a simple switch, so the transistor The polarity (conductivity type) of the transistor is not particularly limited. However, the transistor with the polarity that has the smaller off-current is It is preferable to use a transistor with a low off-current by providing an LDD region. Some have a multi-gate structure, while others operate as switches. The potential of the source electrode of the transistor to be connected to the low-potential power supply (Vss, GND, 0V, etc.) If the source electrode potential is close to the high potential power supply ( When operating at a voltage close to Vdd, it is preferable to use a P-channel type. Why? Therefore, the absolute value of the gate-source voltage can be increased, and the device operates as a switch. It is easy to use both N-channel and P-channel types. A CMOS switch can be used to adjust the output voltage for various input voltages. It is easy to control, so you can perform the appropriate operation.

[0038] In the present invention, being connected is synonymous with being electrically connected. Therefore, in the configuration disclosed in the present invention, in addition to the predetermined connection relationship, electrical Other elements that allow for suitable connections (e.g. switches, transistors, capacitors, inductors, etc.) Of course, other elements may be interposed between the two. The term "electrically connected" refers to a direct connection. This includes:

[0039] As mentioned above, the load is not limited to a light-emitting element such as an electroluminescent element. The display medium changes its brightness, color tone, polarization, etc. when an electric current flows through it. Examples of such display media include electron emission elements, liquid crystal elements, electronic ink, Grating light valve (GLV), plasma display (PDP), digital ma Display media in which contrast changes due to magnetic effects, such as micromirror devices (DMDs) It is also possible to use carbon nanotubes as electron emitters. It is possible. Display devices using EL elements include EL displays and electron emission devices. Display devices using this method include field emission displays (FED) and SED methods. Flat panel display (SED: Surface-conduction Electro In addition, display devices using liquid crystal elements are also available. The devices include LCDs, transmissive LCDs, semi-transmissive LCDs and reflectors. A projection type liquid crystal display and an example of a display device using electronic ink include electronic paper.

[0040] A transistor is defined as a semiconductor device including at least a gate electrode, a drain region, and a source region. Both are elements having three terminals, and a channel forming region is formed between the drain region and the source region. Here, the source region and the drain region are determined depending on the structure and operating conditions of the transistor. Since the temperature varies depending on the source and drain regions, it is difficult to precisely define the extent of the source or drain regions. Therefore, when explaining the connection relationship of a transistor, For two terminals, one of the electrodes connected to these regions is called the first electrode, and the other is called the second electrode. and will be used in the explanation.

[0041] In the present invention, the transistor may be of various types. There is no particular limitation on the type. Therefore, non-crystalline silicon, such as amorphous silicon and polycrystalline silicon, is used. Thin film transistors (TFTs) using single crystal semiconductor films, semiconductor substrates and SOI substrates Transistors formed: MOS transistors, junction transistors, bipolar transistors transistors using compound semiconductors such as ZnO and a-InGaZnO, organic Applying transistors using semiconductors, carbon nanotubes, and other transistors In addition, there are various types of substrates on which transistors are arranged. For example, a single crystal substrate, SOI Substrate, glass substrate, plastic substrate, paper substrate, cellophane substrate, quartz substrate, stone substrate, Can be placed on stainless steel substrates, substrates with stainless steel foil, etc. It is also possible to form a transistor on one substrate and then transfer the transistor to another substrate. Alternatively, the transistors may be disposed on a separate substrate.

[0042] As described above, the transistor in the present invention may be any type of transistor. The circuit may be a gate or may be formed on any substrate. It may be formed on a glass substrate, a plastic substrate, or a single crystal substrate. It may be formed on a silicon-on-insulator (SOI) substrate, or on any other substrate. Since the entire circuit is formed, the number of parts can be reduced, and the cost can be reduced. By reducing the number of connections to circuit components, reliability can be improved. Alternatively, a portion of the circuit may be formed on one substrate and another portion of the circuit may be formed on another substrate. That is, not all of the circuits need to be formed on the same substrate. For example, part of the circuits may be A transistor is formed on a glass substrate, and another part of the circuit is formed on a single crystal substrate, etc. The IC chip is then connected to the glass substrate by COG (Chip On Glass). Alternatively, the IC chip may be placed on a TAB (Tape Automated Bonding or a printed circuit board may be used to connect the glass substrate. Part of the circuit is formed on the same board, reducing the number of parts and lowering costs. In addition, the number of connection points with circuit components can be reduced, thereby improving reliability. In addition, parts with high drive voltages or high drive frequencies consume a lot of power. If such parts are not formed on the same substrate, an increase in power consumption can be prevented.

[0043] The structure of the transistor can take various forms and is not limited to a specific structure. For example, a multi-gate structure having two or more gates may be used. By using such a structure, the off-current can be reduced and the withstand voltage of the transistor can be improved. To improve reliability and reduce drain current caused by changes in drain-source voltage when operating in the saturation region. This reduces the change in current flowing between the in-source and the source. A structure in which a gate electrode is arranged above and below the channel may be used. By using this structure, the channel area increases, so the current value can be increased and the depletion layer can be reduced. This makes it easier to form a gate electrode on the channel, which reduces the S value. The structure may be such that the electrode is disposed under the channel, or the gate electrode is disposed under the channel. Alternatively, the channel region may have a staggered structure, a reverse staggered structure, or a multi-channel structure. The electrodes may be divided into several regions, connected in parallel, or connected in series. In addition, the source electrode and the drain electrode may overlap the channel (or a part of it). The source electrode and / or drain electrode may overlap the channel (or a part of it). This structure prevents charge from accumulating in part of the channel, causing the operation to become unstable. In addition, there is a LDD (Lightly Doped Drain) region. By providing the LDD region, the off-current can be reduced and the breakdown voltage of the transistor can be increased. When operating in the saturation region, the drain-source voltage is Even if the capacitance changes, the drain-source current does not change significantly.

[0044] In the present invention, one pixel refers to one element whose brightness can be controlled. Therefore, as an example, one pixel refers to one color element, and one color element It expresses brightness. Therefore, a color display device consists of the color elements R (red), G (green), and B (blue). In this case, the smallest unit of an image is composed of three pixels: an R pixel, a G pixel, and a B pixel. The number of color elements is not limited to three, but may be more than three. For example, RGB There are also W (W is white) and RGB with yellow, cyan, and magenta added. As another example, when controlling the brightness of one color element using multiple regions, One area is considered to be one pixel. For example, when performing area gradation, There are multiple areas that control the brightness, and the gradation is expressed as a whole. One controlled area is considered to be one pixel. In this case, one color element is composed of multiple pixels. In this case, the size of the area that contributes to the display differs depending on the pixel. In addition, in the case of multiple pixels that make up one color element, The signals may be slightly different to allow for a wider viewing angle.

[0045] In this specification, a semiconductor device refers to a semiconductor element (such as a transistor or a diode). It also refers to any device that can function by utilizing the characteristics of semiconductors. A display device may be a device that includes a plurality of pixels including a load on a substrate and a drive circuit for driving the pixels. The display panel itself is equipped with peripheral driving circuits that allow the display to be displayed on a flexible printhead. This includes those with flexible printed circuit (FPC) and printed wiring board (PWB) attached.

[0046] In the present invention, the term "formed on something" refers to a material that is formed on something. For example, the phrase "on" or "on top of" refers to something directly on top of something. It is not limited to being in contact with the object. It can be that the object is not in direct contact with the object, i.e., there is no other object between the object and the object. For example, if layer B is on layer A (or on layer A), When we say "formed," we mean when layer B is formed directly on layer A, or when layer A is formed directly on layer B. Another layer (such as layer C or layer D) is formed on top of that, and layer B is formed on top of that. The same applies to the description "above ~" and Not limited to being directly on top of an object, but also includes cases where another object is sandwiched between the object and the object Therefore, for example, if layer B is formed above layer A, Layer B may be formed directly on layer A, or another layer (such as layer C or layer D) may be formed on top of layer A. This also includes the case where a layer B is formed on the layer B. Similarly, in the case of being directly adjacent to or below ~, there is no direct contact. The above shall include the following. Effect of the Invention

[0047] The present invention reduces the variation in current value caused by the variation in threshold voltage of a transistor. Therefore, it is possible to supply a desired current to a load such as a light emitting element. In particular, when a light-emitting element is used as a load, the luminance variation is small and the It is possible to provide a display device in which the ratio of the light emitting period to the room period is high. [Brief description of the drawings]

[0048] [Figure 1] 1 illustrates a pixel configuration described in Embodiment 1. [Diagram 2] 2 is a timing chart illustrating the operation of the pixel shown in FIG. 1. [Diagram 3] 2 is a diagram for explaining the operation of the pixel shown in FIG. 1; [Figure 4] Model diagram of voltage-current characteristics due to channel length modulation. [Diagram 5] 1 illustrates a pixel configuration described in Embodiment 1. [Figure 6] 1 illustrates a pixel configuration described in Embodiment 1. [Figure 7] 1 illustrates a pixel configuration described in Embodiment 1. [Figure 8] 1 illustrates a pixel configuration described in Embodiment 1. [Figure 9] 1A to 1C illustrate a display device described in Embodiment 1. [Figure 10]1A to 1C illustrate a writing operation of the display device shown in Embodiment 1. [Figure 11] 1 illustrates a pixel configuration described in Embodiment 2. [Figure 12] 10A to 10C illustrate a pixel configuration described in Embodiment 3. [Figure 13] 10A to 10C illustrate a pixel configuration described in Embodiment 3. [Figure 14] 10A to 10C illustrate a pixel configuration described in Embodiment 3. [Figure 15] 10A to 10C illustrate a pixel configuration described in Embodiment 3. [Figure 16] 1 illustrates a pixel configuration described in Embodiment 1. [Figure 17] FIG. 13 is a partial cross-sectional view of a pixel shown in embodiment 7. [Figure 18] 13A to 13C illustrate a light-emitting element described in Embodiment 7. [Figure 19] 13A to 13C are diagrams illustrating the light extraction direction shown in Embodiment 7. [Figure 20] FIG. 13 is a partial cross-sectional view of a pixel shown in embodiment 7. [Figure 21] FIG. 13 is a partial cross-sectional view of a pixel shown in embodiment 7. [Figure 22] FIG. 13 is a partial cross-sectional view of a pixel shown in embodiment 7. [Figure 23] FIG. 13 is a partial cross-sectional view of a pixel shown in Embodiment 7. [Figure 24] FIG. 13 is a partial cross-sectional view of a pixel shown in embodiment 7. [Diagram 25] 13A to 13C illustrate a display device described in Embodiment 9. [Figure 26] 13A to 13C illustrate a display device described in Embodiment 9. [Figure 27] 13A to 13C illustrate a display device described in Embodiment 9. [Figure 28] FIG. 13 is a partial cross-sectional view of a pixel shown in Embodiment 9. [Figure 29] 13A to 13C illustrate a pixel configuration described in Embodiment 4. [Diagram 30] 13A to 13C illustrate a pixel configuration described in Embodiment 4. [Diagram 31] 13A to 13C illustrate a pixel configuration described in Embodiment 5. [Diagram 32] 32 is a timing chart illustrating the operation of the pixel shown in FIG. 31. [Diagram 33] 1A to 1C are diagrams illustrating electronic devices to which the present invention can be applied. [Diagram 34] FIG. 1 is a diagram showing an example of the configuration of a mobile phone. [Diagram 35] FIG. 1 shows an example of an EL module. [Diagram 36] FIG. 1 is a block diagram showing the main configuration of an EL television receiver. [Figure 37] 13A to 13C illustrate a pixel configuration described in Embodiment 5. [Figure 38] FIG. 6 is a top view of the pixel shown in FIG. [Figure 39] 13 illustrates a pixel configuration described in Embodiment 6. [Diagram 40] 40 is a timing chart illustrating the operation of the pixel shown in FIG. 39. [Diagram 41] 40A to 40C are diagrams for explaining the operation of the pixel shown in FIG. 39. [Diagram 42] 13A to 13C illustrate a pixel configuration described in Embodiment 5. [Diagram 43] 1 is a diagram for explaining a driving method in which a digital gray scale method and a time gray scale method are combined. [Diagram 44] 3A to 3C illustrate the operation of the pixel described in Embodiment 1. [Diagram 45] 1 illustrates a pixel configuration described in Embodiment 1. [Diagram 46] 13A to 13C illustrate a light-emitting element described in Embodiment 8. [Figure 47] 13A to 13C illustrate a light-emitting element described in Embodiment 8. [Figure 48] 1 illustrates a pixel configuration described in Embodiment 1. [Figure 49] 13 illustrates a pixel configuration described in Embodiment 6. [Figure 50] FIG. 1 is a diagram for explaining a pixel configuration of a conventional technique. [Figure 51] FIG. 1 is a diagram for explaining a pixel configuration of a conventional technique. [Figure 52] 1 is a timing chart for operating a pixel according to the prior art; [Diagram 53]FIG. 13 is a diagram for explaining the ratio of a light emitting period in one frame period when a conventional technique is used. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] The present invention will be described in detail below with reference to one embodiment thereof. However, the present invention can be embodied in many different embodiments. and changes in form and detail are possible without departing from the spirit and scope of the present invention. It will be readily understood by those skilled in the art that various modifications may be made. In the configuration of the present invention described below, The reference numerals denoting the above are commonly used among different drawings.

[0050] (Embodiment 1) The basic structure of the pixel of the present invention will be described with reference to FIG. A register 110, a first switch 111, a second switch 112, a third switch 113, The pixel includes a fourth switch 114, a capacitor 115, and a light-emitting element 116. line 117, first scan line 118, second scan line 119, third scan line 120, fourth scan line The power supply line 121, the power supply line 122, and the potential supply line 123 are connected to the power supply line 121, the power supply line 122, and the potential supply line 123. The transistor 110 is an N-channel transistor, and the gate-source voltage ( When the voltage Vgs exceeds the threshold voltage Vth, the transistor is in a conductive state. In the light emitting element 116, a current flows from the pixel electrode 4811 to the counter electrode 124 as shown in FIG. In this case, the pixel electrode 4811 of the light emitting element 116 is The gate-source electrode 124 functions as an anode and the counter electrode 124 functions as a cathode. The voltage is Vgs, the drain-source voltage is Vds, the threshold voltage is Vth, and the capacitance element is The multiplied voltage is denoted as Vcs, and the power supply line 122, the potential supply line 123, and the signal line 117 are The first scanning line 118 and the second scanning line 119 are also called the first wiring, the second wiring, and the third wiring, respectively. The first scanning line 119, the third scanning line 120, and the fourth scanning line 121 are respectively referred to as fourth wirings, These may also be called the fifth wire, sixth wire, and seventh wire.

[0051] A first electrode (one of a source electrode and a drain electrode) of the transistor 110 is The second electrode (the other of the source electrode and the drain electrode) is connected to the pixel electrode of 116. line 122, and the gate electrode is connected to the fourth switch 114 and the second switch 112. The fourth switch 114 is connected to the power supply line 122. 0 and the second switch 112. Also, the fourth switch 1 If the connection point between the first switch 14 and the second switch 112 is a node 130, the node 130 is the first The transistor 110 is connected to a signal line 117 via the switch 111. The first electrode is also connected to a potential supply line 123 via a third switch 113 .

[0052] Furthermore, a capacitor 115 is connected between the node 130 and the first electrode of the transistor 110. That is, the first electrode of the capacitance element 115 is connected to the fourth switch 114. The second electrode of the transistor 110 is connected to the gate electrode of the transistor 110. The capacitor element 115 is formed by sandwiching an insulating film between wiring, a semiconductor layer, and an electrode. In some cases, it may be omitted by using the gate capacitance of the transistor 110. The means for holding these voltages is called a holding capacitor. The connection point between the wiring to which the switch 111 and the first electrode of the capacitor element 115 are connected is The first electrode of the transistor 110, the second electrode of the capacitor 115, and the light emitting diode 131 are connected to each other. A connection point between the pixel electrode of the element 116 and the wiring that is connected thereto is taken as a node 132 .

[0053] The first scanning line 118, the second scanning line 119, the third scanning line 120, and the fourth scanning line By inputting a signal to 121, the first switch 111 and the second switch 122 are turned on and off, respectively. 12, the third switch 113, and the fourth switch 114 are controlled to be turned on and off.

[0054] A signal line 117 is connected to a signal corresponding to the gradation of a pixel, which corresponds to a video signal, that is, brightness data. A potential corresponding to the voltage is input.

[0055] Next, the operation of the pixel shown in FIG. 1 will be explained with reference to the timing chart of FIG. 2 and FIG. In FIG. 2, one frame period, which corresponds to the period for displaying one screen's worth of images, is , which is divided into an initialization period, a threshold voltage writing period, a data writing period, and a light emission period. The initialization period, threshold voltage write period, and data write period are addressed together. There is no particular limit to the length of one frame period, but if the person viewing the image notices flickering, It is preferable to set the shutter speed to 1 / 60 seconds or less so that the shutter speed is not noticeable.

[0056] The counter electrode 124 of the light emitting element 116 is supplied with a potential of V1, and the potential supply line 123 is supplied with a potential of V1. A potential of −Vth-α (α: any positive number) is input to the power supply line 122. During the light-emission period, the potential V1 is input, and during the light-emission period, the potential V2 is input. However, V2>V1. That is, the potential difference between the power supply line 122 and the potential supply line 123 during the initialization period is It is sufficient that the voltage is such that the transistor 110 turns on.

[0057] In order to explain the operation, the potential of the counter electrode 124 of the light emitting element 116 is set to the address However, since the light emitting element 116 emits light, The minimum required potential difference is V EL Then, the potential of the counter electrode 124 is V1-Vth -α―V EL In other words, during the address period, the light emitting It is sufficient that the potential across both ends of the element 116 is such that no current flows through the light emitting element 116. In addition, the potential V2 of the power supply line 122 during the light emission period is set to the potential of the counter electrode 124. The minimum potential difference (V EL ) is added. However, for the sake of explanation, the potential of the counter electrode 124 is set to V1, so V2 is V 1+V EL The larger the value, the better.

[0058] First, as shown in FIG. 2(A) and FIG. 3(A), in the initialization period, the first switch 111 is turned off, and the second switch 112, the third switch 113, and the fourth switch 114 are turned on. At this time, the first electrode of the transistor 110 becomes the source electrode, and the potential is equal to the potential supply line 123, so it is V1-Vth-α. On the other hand, the potential of the gate electrode Therefore, the gate-source voltage Vgs of the transistor 110 is Vth+α As a result, the transistor 110 is turned on. A capacitance element 115 provided between the first electrode and the second electrode holds Vth+α. The case where the switch 114 of the fourth embodiment is turned on has been described. It is sufficient to hold a voltage that makes the fourth switch 110 conductive. However, the fourth switch 11 may be turned off in the next threshold voltage writing period. 4 must be on.

[0059] In the threshold voltage writing period shown in FIG. 2B and FIG. 3B, the third switch 11 Therefore, the potential of the first electrode, i.e., the source electrode, of the transistor 110 is The first voltage rises to V1-Vth, that is, the gate-source voltage of the transistor 110 When the voltage Vgs reaches the threshold voltage (Vth), the transistor 110 is turned off. Therefore, the voltage held in the capacitance element 115 becomes approximately Vth.

[0060] In the subsequent data write period shown in FIG. 2(C) and FIG. 3(C), the second switch After turning off the first switch 112 and the fourth switch 114, the first switch 111 is turned on. During this period, a potential (V1+Vdata) corresponding to the luminance data is input from the signal line 117. By turning off the fourth switch 114, the transistor 110 is kept in a non-conducting state. Therefore, the current supplied from the power supply line 122 during data writing can be This can suppress a change in the potential of the second electrode of the capacitor 115. At this time, the voltage Vcs held in the capacitance element 115 is If the electrostatic capacitances are C1 and C2 respectively, they can be expressed as shown in equation (1).

number

[0061] However, the light-emitting element 116 has a smaller film thickness and a larger electrode area than the capacitor element 115. Therefore, C2>>C1. Therefore, C2 / (C1+C2)≈1, and the capacitance element 115 holds The voltage Vcs is expressed by the formula (2). If this is desired, a potential of Vdata≦0 should be input.

number

[0062] Next, in the light emission period shown in FIG. 2(D) and FIG. 3(D), the first switch 111 is turned off. Then, after the potential of the power supply line 122 is set to V2, the fourth switch 114 is turned on. The gate-source voltage of the transistor 110 is Vgs=Vth+Vdata. Therefore, a current corresponding to the brightness data flows through the transistor 1 10 and the light emitting element 116, causing the light emitting element 116 to emit light.

[0063] The current I flowing through the light emitting element 116 is the current I that flows when the transistor 110 is operated in the saturation region. In this case, it is expressed by equation (3).

number

[0064] When the transistor 110 is operated in the linear region, the current I flowing through the light emitting element is expressed by the formula: Expressed as (4).

number

[0065] where W is the channel width of the transistor 110, L is the channel length, μ is the mobility, and Cox refers to storage capacity.

[0066] From the formulas (3) and (4), it is possible to determine whether the operation region of the transistor 110 is a saturation region or a linear region. In any case, the current flowing through the light emitting element 116 is equal to or greater than the threshold voltage of the transistor 110. Therefore, the threshold voltage of the transistor 110 does not depend on the voltage (Vth). The variation in the current value caused by the difference is suppressed, and a current corresponding to the luminance data is supplied to the light emitting element 116. It is possible.

[0067] From the above, the variation in luminance caused by the variation in the threshold voltage of the transistor 110 is In addition, the potential of the opposing electrode is kept constant during operation, so power consumption is reduced. The force can be reduced.

[0068] Furthermore, when the transistor 110 is operated in the saturation region, the light emitting element 116 When the light emitting element 116 deteriorates, the light emitting element 11 V of 6 EL increases, and the potential at the first electrode, or source electrode, of transistor 110 rises. At this time, the source electrode of the transistor 110 is connected to the second electrode of the capacitor 115. The gate electrode of the transistor 110 is connected to the first electrode of the capacitance element 115, and The gate electrode side is in a floating state. Therefore, as the source potential rises, the gate Therefore, the gate potential of the transistor 110 also rises. Therefore, the Vgs of the transistor 110 is Therefore, even if the light emitting element deteriorates, the transistor 110 and the light emitting element 116 In addition, in equation (3), the current I flowing through the light-emitting element is the source voltage. It can be seen that the change does not depend on the potential or drain potential.

[0069] Therefore, when the transistor 110 is operated in the saturation region, The threshold voltage of the transistor 110 is varied due to the variation in the threshold voltage of the transistor 110 and the deterioration of the light emitting element 116. Therefore, the variation in the current flowing through the

[0070] When the transistor 110 is operated in the saturation region, the shorter the channel length L, the Due to the breakdown phenomenon, if the drain voltage is significantly increased, a large amount of current tends to flow.

[0071] In addition, when the drain voltage is increased beyond the pinch-off voltage, the pinch-off point moves toward the source. However, the effective channel length that functions as a real channel is reduced. This phenomenon is called channel length modulation. The pinch-off point is the point where the channel disappears. The pinch-off voltage is the boundary point where the channel thickness becomes zero under the gate. This refers to the voltage when the pinch-off point becomes the drain end. This phenomenon also becomes more pronounced as the channel length L becomes shorter. For example, a model diagram of the voltage-current characteristics due to channel length modulation is shown in Figure 4. In FIG. 4, the channel length L of the transistor is in the order of (a)>(b)>(c).

[0072] From the above, when the transistor 110 is operated in the saturation region, the drain-source It is preferable that the current I with respect to the inter-gate voltage Vds is as constant as possible. It is preferable that the channel length L of a transistor is long. For example, It is preferable that the channel length L is greater than the channel width W. The channel length L is 10 μm or more and 50 μm or less. More preferably, the channel length L is 15 μm or more and 40 μm or less. The width W is not limited to this.

[0073] In addition, since a reverse bias voltage is applied to the light emitting element 116 during the initialization period, This makes it possible to insulate short-circuited portions of the light-emitting element and to suppress deterioration of the light-emitting element. Therefore, the life of the light emitting element can be extended.

[0074] In addition, the variation in current value caused by the variation in the threshold voltage of the transistor is suppressed. Therefore, the supply destination of the current controlled by the transistor is not particularly limited. Therefore, the light-emitting element 116 shown in FIG. or EL elements containing organic and inorganic materials), electron emission elements, liquid crystal elements, electronic inks, etc. It can be used.

[0075] The transistor 110 has a function of controlling the current value supplied to the light emitting element 116. The type of transistor is not particularly limited, and various types can be used. Therefore, thin film transistors (TFTs) using crystalline semiconductor films, amorphous silicon and multi-crystal Thin film transistors using non-single crystal semiconductor films, such as crystalline silicon, semiconductor substrates, and SO Transistors formed using an I-substrate, MOS transistors, junction transistors, Bipolar transistors, transistors using compound semiconductors such as ZnO and a-InGaZnO transistors, organic semiconductors, carbon nanotube transistors, and other transistors A stamp can be applied.

[0076] The first switch 111 is a timing switch that inputs a signal according to the gradation of the pixel to the pixel through a signal line 117. The timing is selected to control the signal supplied to the gate electrode of the transistor 110. The second switch 112 is a type that applies a predetermined potential to the gate electrode of the transistor 110. Selecting the timing and controlling whether or not a predetermined potential is supplied to the gate electrode of the transistor 110. The third switch 113 initializes the potential written in the capacitor element 115. The timing for applying a predetermined potential to the first electrode of the transistor 110 is selected. The fourth switch 114 is used to lower the potential of the The first switch is used to suppress the change in the potential of the second electrode of the capacitor 115. The first switch 111, the second switch 112, the third switch 113, and the fourth switch 114 are There is no particular limitation as long as it has the above function. For example, a transistor or a diode may be used. Alternatively, a logic circuit that combines them may be used. There is no particular need for this as long as a signal or potential can be applied to the pixel at this timing.

[0077] Next, in FIG. 5, a first switch 111, a second switch 112, a third switch 113, The case where an N-channel transistor is used as the fourth switch 114 will be described. 1. The same reference numerals are used for the components common to those in FIG. 1, and the description thereof will be omitted.

[0078] The first switching transistor 511 corresponds to the first switch 111 in FIG. The second switching transistor 512 corresponds to the second switch 112, and the third switch The switching transistor 513 corresponds to the third switch 113, and the fourth switching transistor The transistor 514 corresponds to the fourth switch 114. The length of the first switching transistor 511 and the second switching transistor 51 2. The third switching transistor 513 and the fourth switching transistor 514 It is preferable that the channel length of the first transistor is longer than the channel length of any of the second transistors.

[0079] The first switching transistor 511 has a gate electrode connected to the first scanning line 118. , a first electrode is connected to the signal line 117 and a second electrode is connected to a node 131 .

[0080] The gate electrode of the second switching transistor 512 is connected to the second scanning line 119. 1, the first electrode of which is connected to the power supply line 122 and the second electrode of which is connected to the node 130. There are.

[0081] The third switching transistor 513 has a gate electrode connected to the third scanning line 120. 1, a first electrode is connected to a node 132, and a second electrode is connected to a potential supply line 123. do.

[0082] The gate electrode of the fourth switching transistor 514 is connected to the fourth scanning line 121. A first electrode is connected to the gate electrode of the transistor 110 and a second electrode is connected to the node It is connected to 130.

[0083] Each switching transistor is turned on when the signal input to the corresponding scanning line is at H level. When the input signal is at L level, it is turned on and when the input signal is at L level, it is turned off.

[0084] A top view of the pixel shown in FIG. 5 is shown in FIG. 38. The conductive layer 3810 is a first scan line. 118 and a portion that functions as a gate electrode of the first switching transistor 511. The conductive layer 3811 is connected to the signal line 117 and the first electrode of the first switching transistor 511. The conductive layer 3812 includes a portion that functions as a first switching transistor. The portion functioning as the second electrode of 511, the first electrode of the capacitor 115, and the second switch A portion serving as the second electrode of the fourth switching transistor 512 and a portion serving as the second electrode of the fourth switching transistor 513 are connected to the first electrode of the fourth switching transistor 514. The conductive layer 3813 includes a portion that functions as the second electrode of the transistor 514. The gate electrode of the switching transistor 512 is included, and the wiring 3821 is The conductive layer 3814 is connected to the second scanning line 119 via the second switching transistor 3815. A portion serving as a first electrode of the transistor 512 and a second electrode of the transistor 110 The conductive portion includes a portion that functions as a conductive portion, and is connected to the power supply line 122 via the wiring 3822. The layer 3815 serves as a first electrode of the fourth switching transistor 514. and a portion that functions as a gate electrode of the transistor 110 through a wiring 3823. The conductive layer 3817 is connected to the conductive layer 3816 which includes the fourth switching transistor. The fourth scanning line 3824 includes a portion that functions as a gate electrode of the transistor 514. The conductive layer 3818 is connected to the scan line 121. The conductive layer 3819 includes a portion that functions as a light-emitting element and is connected to a pixel electrode 3844 of the light-emitting element. serves as the gate electrode of the third scanning line 120 and the third switching transistor 513. The conductive layer 3820 includes a first electrode of the third switching transistor 513. The third switch 3842 includes a portion that functions as a third switch 3843 and is connected to the pixel electrode 3844. The conductive layer 3825 including a portion that functions as a second electrode of the switching transistor 513 is a wiring It is connected to the potential supply line 123 via 3826.

[0085] The gate electrode, the first electrode and the second electrode of the first switching transistor 511 are The portions functioning as electrodes are formed by overlapping a conductive layer including each of the electrodes and a semiconductor layer 3831. The gate electrode of the second switching transistor 512, the first electrode The portion functioning as the second electrode is formed by overlapping a conductive layer including each of the first and second electrodes and a semiconductor layer 3832. The gate of the third switching transistor 513 is also The portions functioning as the first electrode, the second electrode, and the conductive layer including each of them and the semiconductor layer are The fourth switching transistor 5 is formed by overlapping the semiconductor layer 3833. The portions functioning as the gate electrode, the first electrode, and the second electrode of 14 are conductive materials including the respective electrodes. The transistor 3834 is formed by overlapping the electric layer and the semiconductor layer 3834. In the case of 110, the portions that function as the gate electrode, the first electrode, and the second electrode are The conductive layer including these and the semiconductor layer 3830 are overlapped with each other. The element 115 is formed in a portion where the conductive layer 3812 and the pixel electrode 3844 overlap. .

[0086] In the pixel configuration of FIG. 5, the threshold voltage of the transistor 110 is controlled by the same operation method as in FIG. Therefore, the variation in the current value caused by the variation in the value voltage can be suppressed. A current corresponding to the data can be supplied to the light emitting element 116, and the variation in brightness can be suppressed. In addition, when the transistor 110 is operated in the saturation region, It is also possible to suppress the variation in luminance caused by the deterioration of the light emitting element 116. In a transistor, one of the source and drain electrodes is arranged so as to enclose the other electrode. By using such a structure, the channel width can be increased. The semiconductor layer of the transistor is formed by using an amorphous semiconductor layer having a lower mobility than a crystalline semiconductor layer. It is particularly effective when used

[0087] In addition, pixels can be constructed using only N-channel transistors, which simplifies the manufacturing process. In addition, the semiconductor layer of the transistor that constitutes the pixel can be made of amorphous silicon. Amorphous semiconductors such as amorphous semiconductors and semi-amorphous semiconductors (also called microcrystalline semiconductors) For example, amorphous silicon ( The use of these amorphous semiconductors allows for further manufacturing steps. Therefore, it is possible to reduce manufacturing costs and improve yields. Cut.

[0088] The first switching transistor 511 and the second switching transistor 51 2. The third switching transistor 513 and the fourth switching transistor 514 Since the transistor operates simply as a switch, the polarity (conductivity type) of the transistor is not particularly limited. However, it is preferable to use a transistor with low off-state current. The transistors that do not have this feature are those with an LDD region or a multi-gate structure. In addition, CMOS type switches are also available using both N-channel and P-channel types. It can also be switched to a switch.

[0089] In addition, as long as the operation is the same as that shown in Figure 1, the switch connections can take various configurations. As can be seen from FIG. 3, which explains the operation of the pixel configuration of FIG. 1, As described above, in the present invention, there are an initialization period, a threshold voltage writing period, a data writing period, and a light emission period. It is sufficient that conduction is maintained during the periods as shown by the solid lines in FIGS. Therefore, any configuration that can arrange and operate switches etc. to satisfy this requirement is sufficient. For example, The fourth switch 114 shown in FIG. 1 may be connected between the node 130 and the node 131. Such a configuration is shown in FIG. 6. The fourth switch 114 in FIG. 1 corresponds to the switch 614, and the same reference numerals are used to designate the same components as those in FIG. is omitted.

[0090] In the pixel configuration of FIG. 6, the threshold voltage of the transistor 110 is controlled by the same operation method as in FIG. Therefore, the variation in the current value caused by the variation in the value voltage can be suppressed. A current corresponding to the data can be supplied to the light emitting element 116, and the variation in brightness can be suppressed. In addition, when the transistor 110 is operated in the saturation region, It is also possible to suppress variations in luminance caused by deterioration of the light emitting elements 116.

[0091] 1. The fourth switch 114 shown in FIG. It may be provided on the path to the connection point between the second electrode and the power line 122 .

[0092] One such configuration is shown in Fig. 7. Note that the second electrode of the transistor 110 and the power supply line The connection point with 122 is node 134. In the configuration of FIG. The fourth switch 714 corresponds to the transistor 1. 10 and a node 134. Note that the same configuration as in FIG. Wherever possible, common reference symbols will be used and their explanations will be omitted.

[0093] The fourth switch 714 turns on the transistor 110 when writing data. Even if the fourth switch 714 is turned off, the transistor Therefore, the current to the capacitor 110 during the data writing period can be cut off. Fluctuations in the potential of the second electrode 115 can be suppressed.

[0094] Therefore, in the pixel configuration of FIG. 7, transistor 1 is driven in the same manner as in FIG. It is possible to suppress the variation in the current value caused by the variation in the threshold voltage of 10. Thus, a current corresponding to the luminance data can be supplied to the light emitting element 116, and the luminance variation can be reduced. Furthermore, when the transistor 110 is operated in the saturation region, In this case, the variation in luminance caused by the deterioration of the light emitting element 116 can also be suppressed. In addition, when the fourth switch 114 is turned off during the initialization period, the power consumption is reduced. However, the connection point between the node 134 and the second switch 112 can be reduced. 35, the fourth switch 714 connects the nodes 134 and 135 as shown in FIG. When the fourth switch 714 is connected between the first switch 711 and the second switch 712, the fourth switch 714 is turned off during the initialization period. It is not possible to do so.

[0095] As described above, the first switch 111 outputs a signal according to the gradation of the pixel to the signal line 117. The timing of inputting the signal to the pixel is selected based on the The second switch 112 controls the gate electrode of the transistor 110. A timing for applying a certain potential is selected, and a certain potential is applied to the gate electrode of the transistor 110. The third switch 113 controls whether or not the power is supplied to the capacitance element 115. The timing for applying a specific potential to initialize the potential stored in the transistor can be selected. There is no particular limitation as long as it lowers the potential of the first electrode of the capacitor 110. The third switch can provide a signal or potential to the pixel at the above timing. For example, if a signal according to the pixel's gray level can be input to the pixel, In the pixel shown in FIG. 16, the first switch 111 may not be provided. , a transistor 110, a second switch 112, a third switch 113, a fourth switch 714, and the pixel electrode 1640. The first electrode (source electrode and The second electrode (one of the source and drain electrodes) is connected to the pixel electrode 1640. The other of the input electrodes is connected to the power supply line 122 via the fourth switch 714, and the gate electrode The transistor 1 is connected to the power supply line 122 via the second switch 112. The first electrode of 10 is also connected to a potential supply line 120 via a third switch 113. In addition, since the gate capacitance 1615 of the transistor 110 is used as a storage capacitance, There is no need to provide the capacitor element 115 in FIG. Each switch is operated according to the timing chart shown in FIG. By supplying the current to the transistor 110, the variation in the current value caused by the variation in the threshold voltage of the transistor 110 is reduced. In other words, the desired current can be supplied to the pixel electrode 1640. can be done.

[0096] Another configuration is shown in FIG. 8. In the configuration of FIG. 8, the fourth switch in FIG. The fourth switch 814 corresponds to the transistor 110. The first electrode of the transistor is connected to node 132. Note that the configuration in FIG. For the remainder, common reference symbols will be used and their explanations will be omitted.

[0097] The fourth switch 814 turns on the transistor 110 when writing data. Even in this state, the fourth switch 814 can be turned off to keep the node 132 in the ON state. Therefore, the current flowing through the capacitor element 1 during the data writing period can be cut off. Fluctuations in the potential of the second electrode 15 can be suppressed.

[0098] Therefore, in the pixel configuration of FIG. 8, transistor 1 is driven in the same manner as in FIG. It is possible to suppress the variation in the current value caused by the variation in the threshold voltage of 10. Thus, a current corresponding to the luminance data can be supplied to the light emitting element 116, and the luminance variation can be reduced. In addition, when the transistor 110 is operated in the saturation region, In this case, the variation in luminance caused by the deterioration of the light emitting element 116 can also be suppressed. In addition, in the initialization period, when the fourth switch 114 is turned off, the power consumption is reduced. is possible.

[0099] In addition, in the fourth switch 614, the fourth switch 714, and the fourth switch 814, However, like the first to third switches, the first to third switches may be transistors or diodes. It may also be a combinational logic circuit.

[0100] 7 and 8, a fourth switch is connected from node 132 to transistor 11. When the second electrode 120 is connected to the power supply line 122, It is also possible to forcibly create a non-light emitting state by turning off the fourth switch. By setting a non-light emitting period as part of the light emitting period by this operation, the light emitting time can be set freely. In addition, by inserting black display, afterimages are less visible and moving image characteristics are improved. It is also possible.

[0101] Next, a display device having the above-mentioned pixel of the present invention will be described with reference to FIG.

[0102] The display device includes a signal line driver circuit 911, a scanning line driver circuit 912, and a pixel portion 913. The pixel portion 913 includes a signal line driver circuit 911 and a plurality of signal lines extending in the column direction. S1 to Sm: a plurality of first scanning lines extending in the row direction from the scanning line driving circuit 912; G1_1 to Gn_1, the first scanning lines G1_2 to Gn_2, the third scanning lines G1_3 to Gn_ 3, the fourth scanning lines G1_4 to Gn_4, the power supply lines P1_1 to Pn_1 and the potential supply line P1_ 2 to Pn_2, and a plurality of pixels arranged in a matrix corresponding to the signal lines S1 to Sm. Each pixel 914 is connected to a signal line Sj (any of the signal lines S1 to Sm). the first scanning line Gi_1 (one of the scanning lines G1_1 to Gn_1), the second The scanning line Gi_2, the third scanning line Gi_3, the fourth scanning line Gi_4, the power supply line Pi_1 and the power It is connected to the position supply line Pi_2.

[0103] In addition, the signal line Sj, the first scanning line Gi_1, the second scanning line Gi_2, and the third scanning line Gi 1, the fourth scanning line Gi_3, the power supply line Pi_1, and the potential supply line Pi_2 are respectively A signal line 117, a first scanning line 118, a second scanning line 119, a third scanning line 120, a fourth scanning line 121, a They correspond to a scanning line 121 , a power supply line 122 , and a potential supply line 123 .

[0104] A row of pixels to be operated is selected by a signal output from the scanning line driving circuit 912. The operation shown in FIG. 2 is performed simultaneously for each pixel in the same row. In the data writing period, the signal line driver circuit 911 outputs the signal to the pixels of the selected row. A video signal is written. At this time, a potential corresponding to the brightness data of each pixel is applied to each signal line. Input to S1~Sm.

[0105] As shown in FIG. 10, when the data writing period for the i-th row is completed, the data belonging to the i+1-th row is written. In addition, in FIG. 10, the data writing period for each row is shown. In order to express this, the operation of the first switch 111 in FIG. 2 that can faithfully express this will be excerpted and described below. Then, the pixels in the i-th row that have completed the data writing period move on to the light emission period. The pixel emits light according to the signal written to it.

[0106] Therefore, as long as the data writing periods for each row do not overlap, each row can start initialization freely. In addition, each pixel can emit light except during its own address period. Therefore, the ratio of the light emission period in one frame period (i.e., the duty ratio) can be changed It is possible to always make it large, and even make it almost 100%. Therefore, the brightness variation is Therefore, a display device with a high duty ratio can be obtained.

[0107] In addition, it is possible to set the threshold voltage writing period to be long, so that the transistor Therefore, the threshold voltage of the display device can be written to the capacitor more accurately. The reliability of the system can be improved.

[0108] It should be noted that the configuration of the display device shown in FIG. 9 is merely an example, and the present invention is not limited to this. For example, the potential supply lines P1_2 to Pn_2 are arranged in parallel with the first scanning lines G1_1 to Gn_1. It is not necessary for the signal lines S1 to Sm to be arranged in parallel with each other, and they may be arranged in parallel with the signal lines S1 to Sm.

[0109] By the way, there are two driving methods for expressing the gradation of a display device: analog gradation method and digital gradation method. The analog gradation method is a method that controls the light emission intensity of the light emitting element in an analog manner, and a method that controls the light emission intensity in an analog manner. There is a method to control the light emission time of the element in an analogue manner. A method of controlling the light emission intensity by analog is often used. On the other hand, the digital gradation method uses The light-emitting element is turned on and off by digital control to express gradation. It has the advantage of being resistant to noise because it can process digital signals, but it has two states: emitting and not emitting light. Since there is only one way to express the image, only two gradations can be expressed as it is. Therefore, One method for achieving multiple gradations is to use a light emitting surface of a pixel. The area gradation method weights the product and selects the weight to display the gradation. The other method weights the light emission time. and a time gray scale method in which gray scale display is performed by selecting the time.

[0110] When this digital gray scale method is combined with the time gray scale method, as shown in Figure 43, The frame period is divided into a number of subframe periods (SFn). Each subframe period is An address period ( The subframe period is determined according to the number of display bits n. The number of subframe periods in one frame period is set to the same number. The ratio of the length of the light emission period between (n-1) :2 (n-2) : : 2:1, each During the light emission period, the light emitting element is selected to emit light or not emit light. The gradation is expressed by using the difference in the total time during one frame period. The longer the total time, the higher the brightness. The shorter the total time, the lower the brightness. This shows an example of 4-bit gradation, where one frame period is divided into four subframe periods, Depending on the combination of light emission periods, 4 = 16 gradations can be expressed. The ratio does not have to be a power of 2 to achieve gradation expression. The program period may be further divided.

[0111] In addition, when multiple gradations are achieved using the time gradation method as described above, the light emission period of the lower bits Since the duration of the light emission period is short, the data write operation for the next subframe period starts immediately after the end of the light emission period. If you try to start writing data during the previous subframe, it will overlap with the data writing operation during the previous subframe. Therefore, as shown in Figures 7 and 8, the fourth switch is turned on. Between the node 132 and the connection point between the second electrode of the transistor 110 and the power supply line 122 and forcibly creating a non-light emitting state by turning off the fourth switch during a part of the light emitting period. It is also possible to express light emission that is shorter than the data writing period required for all rows. It is of course particularly effective in log gradation, but it is also effective in digital gradation and time gradation. It is also effective to combine this method with the non-light-emitting method. Since no current should flow through the power supply line, the fourth switch is turned off as described above. The non-light emitting state can be obtained by lowering the potential of 122 or by turning on the third switch 113. In addition, the gate-source voltage of the transistor 110 can be set to a value equal to or lower than the threshold voltage. For example, a new switch is provided in parallel with the capacitance element 115. The transistor 110 is turned on in a non-light emitting state by turning on the gate-source of the transistor 110 using the switch. It is also possible to obtain a certain state.

[0112] The variation in threshold voltage includes the variation in the threshold voltage of each transistor between pixels. In addition to the differences, the change in threshold voltage over time for a single transistor is also In addition, the difference in threshold voltage of each transistor is caused by the manufacturing process of the transistor. This includes differences in transistor characteristics at the time of The transistor refers to a transistor having a function of supplying a current to a load such as a light emitting element.

[0113] (Embodiment 2) In this embodiment, a pixel having a different configuration from that in the first embodiment is shown in FIG. The same parts as those in the embodiment 1 are indicated by the same reference numerals and have the same parts or similar functions. A detailed description of the parts will be omitted.

[0114] The pixel shown in FIG. 11A includes a transistor 110, a first switch 111, a second switch switch 112, a fourth switch 114, a rectifying element 113, a capacitance element 115, a light emitting element 11 6. The pixel has a signal line 117, a first scanning line 118, a second scanning line 119, It is connected to the third scanning line 1120, the fourth scanning line 121 and the power supply line 122. The pixel shown in (A) uses a rectifying element 1113 for the third switch 113 in FIG. The second electrode of the capacitor 115, the first electrode of the transistor 110, and The pixel electrode of the light emitting element 116 is connected to the third scanning line 1120 via the rectifying element 1113. That is, the rectifying element 1113 is connected to the first electrode of the transistor 110 via the third scanning line. The wire 1120 is connected so that a current flows through it. Regarding the first switch 111, the second switch 112 and the fourth switch 114, A transistor or the like may be used as the rectifying element 1113. In addition to diodes such as the 1151 keyed barrier type, 1152 PIN type, and 1153 PN type, , diode-connected transistors 1154, 1155, etc. can be used. However, the transistors 1154 and 1155 are turned on and off depending on the direction of the current. The polarity of the transistor must be selected appropriately.

[0115] When a high-level signal is input to the third scanning line 1120, the rectifying element 1113 When an L level signal is input, no current flows through the rectifier element 1113. Therefore, when the pixel shown in FIG. 11 is operated in the same manner as the pixel shown in FIG. A signal of L level is input to the third scanning line 1120, and a signal of H level is input during the other periods. However, a low-level signal simply causes a current to flow through the rectifier element 1113. Instead, the potential of the second electrode of the capacitance element 115 is set to V1-Vth-α (α: any positive number). Therefore, the potential must be V1-Vth-α-β (α: any positive number). Here, β indicates the threshold voltage of the rectifying element 1113 in the forward direction. The signal of the bell is lowered below the potential of the counter electrode 124 of the light-emitting element, and the light-emitting element 116 is turned on during the initialization period. A reverse bias voltage may be applied. On the other hand, the H level signal is rectified as described above. Since no current should flow through the element 1113, the threshold voltage of the rectifier element 1113 is V1-Vth. It is sufficient that the value is greater than the value obtained by subtracting the smallest voltage, that is, V1-Vth-β.

[0116] Considering the above, the pixel configuration in FIG. 11 can be operated in the same manner as in FIG. To suppress the variation in current value caused by the variation in threshold voltage of the transistor 110 Therefore, a current corresponding to the luminance data can be supplied to the light emitting element 116. It is possible to suppress the variation in luminance. In the case where the light emitting element 116 is operated, the variation in luminance caused by the deterioration of the light emitting element 116 can be suppressed. Furthermore, by using the rectifying element 1113, the number of wirings can be reduced. This makes it possible to improve the aperture ratio.

[0117] The pixel shown in this embodiment can be applied to the display device shown in FIG. As with 1, as long as the data writing periods for each row do not overlap, each row can start initialization freely. In addition, each pixel can emit light except during its own address period. Therefore, the ratio of the light emission period in one frame period (i.e., the duty ratio) can be changed It can be always large, and can be made almost 100%. Therefore, the brightness variation is small. Therefore, a display device with a high duty ratio can be obtained.

[0118] In addition, it is possible to set the threshold voltage writing period to be long, so that the current It is possible to write the threshold voltage of the transistor that controls the current value to the capacitor more accurately. This improves the reliability of the display device.

[0119] This embodiment can be freely combined with the pixel configurations shown in the above-described FIG. 1 and other embodiments. For example, the fourth switch 114 may be connected to the nodes 130 and 133. 1 or between the first electrode of transistor 110 and node 132. The second electrode of the transistor 110 is connected to the power supply line 122 via the fourth switch 114. The rectifying element 1113 may be connected to a power supply 1114. This can also be applied to the pixel shown.

[0120] (Embodiment 3) In this embodiment, a pixel having a different configuration from those in the first and second embodiments is shown in FIGS. In the first and second embodiments, the description focuses on one pixel. It is possible to reduce the number of wirings by sharing the lines between pixels. If the pixel is always in operation, various wiring can be shared between pixels. It is possible to share wiring with other elements, and an example of this method will be described in this embodiment. In addition, the same reference numerals are used for the same parts as those in the first embodiment, and the same or similar parts are A detailed description of the functional parts will be omitted.

[0121] A pixel 1200 shown in FIG. 12 includes a transistor 110, a first switch 111, a second switch switch 112, a third switch 113, a fourth switch 114, a capacitance element 115, a light-emitting element 116. The pixel has a signal line 117, a first scanning line 1218, a second scanning line 1 19, the third scanning line 120, the fourth scanning line 121, the power supply line 122 and the first scanning line of the next row Connected to 1218.

[0122] In the pixel shown in FIG. 1 of the first embodiment, the second electrode of the capacitor 115 corresponds to the third switch 1. 13, whereas in FIG. 12, the first scanning This is not limited to the potential supply line 123, but can be connected to the line 1218 during the initialization period. This is because it is sufficient to supply a predetermined potential to the second electrode of the capacitor 115. Therefore, if a predetermined potential can be supplied to the second electrode of the capacitor 115 during the initialization period, The wiring that supplies the potential does not need to be constantly at a constant potential. In this way, the wiring can be shared with the next row. It is possible to reduce the number of lines and improve the aperture ratio.

[0123] In addition, the pixel configuration shown in FIG. 12 can be operated in the same manner as in the first embodiment. This suppresses the variation in current value caused by the variation in threshold voltage of the transistor 110. Therefore, a current corresponding to the luminance data can be supplied to the light emitting element 116. This makes it possible to suppress the variation in brightness. Since the transistor 110 is operated by the The operating region is not particularly limited, but the effect is more pronounced in the case of a saturated region. When the transistor 110 is operated in the saturation region, the deterioration of the light emitting element 116 The variation in the current flowing through the transistor 110 can be suppressed.

[0124] However, the signal that turns off the first switch 111 in the first scanning line 1218 is V1 -Vth-α (α: any positive number). Therefore, V1-Vth-α (α: any positive number) It is necessary to use a first switch 111 that is turned off at a potential of any positive number. The initialization period of the row to which element 1200 belongs must not overlap with the data write period of the row that shares the wiring. It is necessary to make it work like this.

[0125] When an N-channel transistor is used for the third switch 113, The potential that turns off the third switch 113 in 120 is the potential of the first scan line 1218. Therefore, the potential may be lowered below V1-Vth-α, which is a signal that turns off the first switch 111. In this case, the gate-source voltage when the transistor is turned off can be set to a negative value. Therefore, it is possible to reduce current leakage when the third switch 113 is turned off. can.

[0126] In the above, the potential V1-Vth-α is used as a signal for turning off the first switch 111. However, it may be used as a signal to turn on the first switch 111. Approx. varies.

[0127] 13, the potential supply line 123 in FIG. 1 is turned on in the second scanning direction of the next row. The pixel 1300 may also share the same operation as that of the first embodiment. However, the second switch 112 is turned off in the second scanning line 1319. It is preferable that the signal to be output has a potential of V1-Vth-α (α: any positive number). In this case, the second switch 112 is turned off at a potential of V1-Vth-α (α: any positive number). In addition, the initialization period of the row to which the pixel 1300 belongs must be performed using the row It is necessary to operate the threshold voltage writing period so as not to overlap with the threshold voltage writing period.

[0128] When an N-channel transistor is used for the third switch 113, The signal that turns off the third switch 113 in 120 is Therefore, the potential may be lowered below V1-Vth-α, which is a signal that turns off the second switch 112. In this case, it is possible to reduce current leakage when the third switch 113 is turned off.

[0129] In the above, the potential V1-Vth-α is used as a signal to turn off the second switch 112. However, it may be used as a signal to turn on the second switch 112. Approx. varies.

[0130] 14, the potential supply line 123 in FIG. 1 is turned on in the third scanning direction of the previous row. The pixel 1400 may be shared with the line 1420. The pixel 1400 may also operate in the same manner as in the first embodiment. However, in the third scanning line 1420, the third switch 113 is turned off. The signal that causes the output to change is the potential of V1-Vth-α (α: any positive number). It is necessary to use the third switch 113 that turns off at a potential of th-α (α: any positive number). In this case, the initialization period of the row to which the pixel 1400 belongs is longer than the initialization period of the row sharing the wiring. However, the initialization period must be shorter than the data writing period. If it is set, there is no problem.

[0131] In the above, the potential V1-Vth-α is used as a signal to turn off the third switch 113. However, it may be used as a signal to turn on the third switch 113. Approx. varies.

[0132] 15, the potential supply line 123 in FIG. 1 is turned on in the fourth scanning direction of the next row. The pixel 1500 may also share the same operation as that of the first embodiment. However, in the fourth scanning line 1521, V1-Vth-α (α: arbitrary It is preferable to use a fourth switch 114 that is turned on when a potential of (a positive number) is input. In this case, the initialization period of the row to which the pixel 1500 belongs is the same as the data writing period of the row that shares the wiring. In addition, the fourth When the switch 114 is turned off, the period is set so as not to overlap with the initialization period of the row that shares the wiring. It is necessary to make it work like this.

[0133] In the above, the potential V1-Vth-α is used as a signal for turning on the fourth switch 114. However, it may be used as a signal to turn off the fourth switch 114. Approx. varies.

[0134] In addition to the above, the potential supply line 123 in FIG. 1 may be shared with the power supply line 122 in the next row. In this case, the power supply line 122 is provided with V1-Vth-α (α: any positive number) in addition to V1 and V2. A pixel configuration may be provided that supplies a total of three types of potential and allows the same operation as in the first embodiment. .

[0135] In this embodiment, the potential supply line 123 in FIG. 1 is shared with the scanning line of the next row or the previous row. The case where a potential of V1-Vth-α (α: any positive number) is applied during the initialization period is shown. Any other wiring may be used as long as it is possible to supply power.

[0136] Furthermore, the pixel shown in this embodiment can be applied to the display device shown in FIG. In the display device, the constraints on the operation of each pixel and the data in each row shown in FIG. The initialization start time for each row can be set freely within the range where the data writing period does not overlap. In addition, each pixel can emit light except during its own address period, so The ratio of the light emission period to the light emission period (i.e., the duty ratio) can be made very large, so that Therefore, the brightness variation is small and the duty ratio is A high-quality display device can be obtained.

[0137] In addition, it is possible to set the threshold voltage writing period to be long, so that the current It is possible to write the threshold voltage of the transistor that controls the current value to the capacitor more accurately. This improves the reliability of the display device.

[0138] The fourth switch 114 is connected between the node 130 and the gate electrode of the transistor 110. Not limited to those connected between the nodes 130 and 131, but also between the transistors 110 and 112, and node 132. The second electrode may be connected to the power supply line 122 via the fourth switch 114 .

[0139] This embodiment is not limited to the above, and can be freely combined with the pixel configurations shown in other embodiments. It is possible.

[0140] (Embodiment 4) In this embodiment, a pixel having a different configuration from that in the first embodiment is shown in FIG. The same reference numerals are used for the same parts as those in the first embodiment, and the same parts or similar functions are shown. A detailed description of the included parts will be omitted.

[0141] The pixel shown in FIG. 29 includes a transistor 2910, a first switch 111, a second switch A switch 112, a third switch 113, a fourth switch 114, a capacitance element 115, a light-emitting element 1 16. The pixel has a signal line 117, a first scanning line 118, a second scanning line 119, and , connected to a third scanning line 120, a fourth scanning line 121, a power supply line 122 and a potential supply line 123. It has been done.

[0142] The transistor 2910 in this embodiment is a multi-transistor having two transistors connected in series. The transistor is a gate type transistor and is provided in the same position as the transistor 110 in the first embodiment. However, the number of transistors connected in series is not particularly limited.

[0143] 29 is operated in the same manner as the pixel of FIG. It is possible to suppress the variation in the current value caused by the variation in the threshold voltage of 0. Therefore, a current corresponding to the luminance data can be supplied to the light emitting element 116, and the luminance variation can be reduced. In addition, the potential of the opposing electrode is kept constant during operation, so the power consumption is It is possible to reduce the power. Note that the operating region of the transistor 2910 is particularly limited. However, the effect is more pronounced in the saturated region.

[0144] Furthermore, when the transistor 2910 is operated in the saturation region, the light emitting element 116 is deteriorated. This can suppress variation in the current flowing through the transistor 2910 due to the change in capacitance.

[0145] In this embodiment, the channel length L of the transistor 2910 is equal to that of two transistors connected in series. If the channel widths of the transistors are equal, it acts as the sum of the channel lengths of each transistor. Therefore, in the saturation region, the current is more constant regardless of the drain-source voltage Vds. In particular, the transistor 2910 has a long channel length L. This is effective when it is difficult to fabricate a transistor. The connection between the two transistors is made of a resistor. It acts as an antagonist.

[0146] The transistor 2910 has a function of controlling the current value supplied to the light-emitting element 116. The type of transistor is not particularly limited as long as it is a crystalline semiconductor film. thin-film transistors (TFTs), non-single-crystal transistors such as amorphous silicon and polycrystalline silicon Thin film transistors using crystalline semiconductor films, transistors formed using semiconductor substrates or SOI substrates transistor, MOS transistor, junction transistor, bipolar transistor, Zn Transistors using compound semiconductors such as O and a-InGaZnO, organic semiconductors and carbon A transistor using a silicon nanotube or other transistors can be applied.

[0147] 29 includes a first switch 111, a second switch 112, and a The first switch 112, the third switch 113, and the fourth switch 114 are implemented by transistors or the like. There can be.

[0148] The fourth switch 114 is connected between the node 130 and the gate electrode of the transistor 2910. Not limited to those connected between nodes 130 and 131, but also between transistors 29 10 and node 132. The second electrode of 910 may be connected to the power line 122 via the fourth switch 114. stomach.

[0149] Furthermore, the pixel shown in this embodiment can be applied to the display device of FIG. As with mode 1, as long as the data writing periods for each row do not overlap, each row can be initialized freely. The start time can be set. Also, each pixel emits light except during its own address period. Therefore, the ratio of the light emission period in one frame period (i.e., the duty ratio) can be It can be made very large, and can even be made almost 100%. Therefore, a display device with a high duty ratio can be obtained.

[0150] In addition, it is possible to set the threshold voltage writing period to be long, so that the current It is possible to write the threshold voltage of the transistor that controls the current value to the capacitor more accurately. This improves the reliability of the display device.

[0151] The transistor 2910 is not limited to a series-connected transistor, but may be any of the transistors shown in FIG. As shown in FIG. 3010, the transistors may be connected in parallel. The transistor 3010 allows a larger current to be supplied to the light emitting element 116. In addition, the characteristics of the two transistors connected in parallel are averaged. Therefore, the inherent characteristic variation of the transistors constituting the transistor 3010 is reduced. Therefore, if the variation is small, the variation in the threshold voltage of the transistor is small. This makes it easier to suppress the variation in current value caused by the above.

[0152] Also, each of the parallel connected transistors shown in transistor 3010 may be further illustrated. The transistors may be connected in series like the transistor 2910 shown in FIG.

[0153] This embodiment is not limited to the above, and can be freely combined with the pixel configurations shown in other embodiments. That is, the transistor 2910 or the transistor 3010 can be This can also be applied to the pixel configuration shown in the embodiment mode.

[0154] (Embodiment 5) In this embodiment, in the pixel of the present invention, a transistor is used to control the current value supplied to the light emitting element. A pixel that averages out the degradation of transistors over time by switching the transistors every period. The configuration will be described with reference to FIG.

[0155] The pixel shown in FIG. 31 includes a first transistor 3101, a second transistor 3102, and a third transistor 3103. A first switch 3111, a second switch 3112, a third switch 3113, a fourth switch a fifth switch 3103, a sixth switch 3104, a capacitance element 3115, The pixel has a light emitting element 3116. The pixel has a signal line 3117, a first scanning line 3118, a third The second scanning line 3119, the third scanning line 3120, the fourth scanning line 3121, the power line 3122, and and a potential supply line 3123. Furthermore, although not shown in FIG. The fifth and sixth scanning switches 3103 and 3104 are respectively controlled to be on and off. In this embodiment, the first transistor 3101 and The transistor 3102 in FIG. 2 is an N-channel transistor. When the gate-source voltage (Vgs) exceeds the threshold voltage, the transistor becomes conductive. The pixel electrode of the light emitting element 3116 is an anode, and the counter electrode 3124 is a cathode. The gate-source voltage of the transistor is Vgs, and the voltage stored in the capacitance element is Vcs. The threshold voltage of the first transistor 3101 is Vth1, and the threshold voltage of the second transistor The threshold voltage of the power supply line 3122, the potential supply line 3123, and The signal line 3117 is also referred to as a first wiring, a second wiring, and a third wiring, respectively.

[0156] A first electrode (one of a source electrode and a drain electrode) of the first transistor 3101 is The fifth switch 3103 is connected to the pixel electrode of the light-emitting element 3116, and the second electrode ( The other of the source electrode and the drain electrode is connected to a power supply line 3122, and the gate electrode is connected to a fourth It is connected to the power line 3122 via the switch 3114 and the second switch 3112. The fourth switch 3114 is connected between the gate electrode of the first transistor 3101 and the second A fourth switch 3114 is connected between the second switch 3112 and the third switch 3113. If the connection point with the switch 3112 is the node 3130, the node 3130 is the first switch 3 The first transistor 3101 is connected to a signal line 3117 via a resistor 111. The first electrode is connected to the potential supply line 3 through the fifth switch 3103 and the third switch 3113. It is also connected to 123.

[0157] A first electrode (one of a source electrode and a drain electrode) of the second transistor 3102 is The sixth switch 3104 is connected to the pixel electrode of the light-emitting element 3116, and the second electrode ( The other of the source electrode and the drain electrode is connected to a power supply line 3122, and the gate electrode is connected to a fourth A second transistor is connected to the node 3130 via the switch 3114. The first electrode of 3102 is electrically connected via a sixth switch 3104 and a third switch 3113. The gate electrode of the first transistor 3101 is also connected to a voltage supply line 3123. and the gate electrode of the second transistor 3102 are connected. The first electrode of the second transistor 3101 and the first electrode of the second transistor 3102 form a fifth switch. The fifth switch 3103 and the sixth switch 3104 are connected to each other. The connection point between switch 3103 and the sixth switch 3104 is node 3133.

[0158] Furthermore, a capacitive element 3115 is connected between the node 3133 and the node 3130. That is, the first electrode of the capacitor 3115 is connected to the fourth switch 3114 via the fourth switch 3114. The gate electrodes of the first transistor 3101 and the second transistor 3102 are connected to the capacitor element 31 The second electrode of the fifth switch 3103 is connected to the first electrode of the first transistor 3101. and a first electrode of the second transistor 3102 via a sixth switch 3104. The capacitor element 3115 is formed by sandwiching an insulating film between wiring, a semiconductor layer, and an electrode. Alternatively, the first transistor 3101 and the second transistor 3102 may be connected to each other. It can be omitted by using the gate capacitance of the transistor 3102. The first electrode of the fifth embodiment is connected to the wiring that connects the first switch 3111 and the node 3130. The node 3133 is connected to the second electrode of the capacitor 3115. A connection point between the wiring and the pixel electrode of the light emitting element 3116 is defined as a node 3132 .

[0159] In addition, the first scanning line 3118, the second scanning line 3119, the third scanning line 3120, the fourth scanning line By inputting a signal to the scanning line 3121, the first switch 3111 and the second switch The on / off of the switch 3112, the third switch 3113, and the fourth switch 3114 is controlled. In FIG. 31, the fifth switch 3103 and the sixth switch 3104 are turned on. The scan lines that control the OFF state are omitted.

[0160] A signal corresponding to the gradation of the pixel, which corresponds to a video signal, i.e., luminance data, is input to the signal line 3117. A potential according to the input is input.

[0161] Next, the operation of the pixel shown in FIG. 31 will be described with reference to the timing chart of FIG. In FIG. 32, one frame period, which corresponds to the period for displaying one screen's worth of image, is It is divided into an initialization period, a threshold voltage writing period, a data writing period, and a light emission period. .

[0162] The counter electrode 3124 of the light emitting element 3116 is supplied with a potential of V1. The potential V1-Vth-α (α: any positive number) is input. Vth is Vth1. The power supply line 3122 is set to V1 during the address period, and Vth2 during the address period. During the light emission period, the potential of V2 is input, where V2>V1.

[0163] In order to explain the operation, the potential of the counter electrode 3124 of the light emitting element 3116 is The potential of the power supply line 3122 is the same as that of the power supply line 3122 during the non-light emitting period. The minimum potential difference required to EL Then, the potential of the counter electrode 3124 is V 1-Vth-α―V EL The potential of the power supply line during the light emission period is preferably higher than the potential of the power supply line. The potential V2 of the counter electrode 3122 is small because the light emitting element 3116 emits light. At least the required potential difference (V EL ) is a value that is greater than the sum of the two. Here, the potential of the counter electrode 3124 is V1, so V2 is V1 + V EL With a larger value It would be good to have it.

[0164] First, as shown in FIG. 32(A), in the initialization period, the first switch 3111 and the sixth switch The switch 3104 is turned off, and the second switch 3112, the third switch 3113, and the fourth switch 3114 are turned on. The first switch 3114 and the fifth switch 3103 are turned on. The first electrode of the transistor 3101 is the source electrode, and its potential is equal to that of the potential supply line 3123. Therefore, the potential of the gate electrode becomes V1. The gate-source voltage Vgs of the first transistor 3101 is Vth+α. The gate electrode of the first transistor 3101 is turned on. A voltage Vth+α is held in a capacitor 3115 provided between the first electrode and the second electrode. Although the case where the switch 3114 of No. 4 is turned on has been described, it may be turned off. In the next threshold voltage writing period, the fourth switch 3114 must be turned on. stomach.

[0165] In the threshold voltage writing period shown in FIG. 32(B), the third switch 3113 is turned off. Therefore, the potential of the first electrode, i.e., the source electrode, of the first transistor 3101 gradually When the voltage Vth1 of the first transistor 3101 reaches V1-Vth1, When the source-to-source voltage Vgs reaches the threshold voltage (Vth1), the first transistor Therefore, the voltage held in the capacitance element 3115 is Vth1. become.

[0166] After that, in the data writing period shown in FIG. After turning off the fourth switch 3114, the first switch 3111 is turned on, and a signal A potential (V1+Vdata) corresponding to the luminance data is input from the line 3117. By turning off the switch 3114, the first transistor 3101 is turned off. Therefore, the current supplied from the power supply line 3122 during data writing can be This can suppress a change in the potential of the second electrode of the capacitor 3115. At this time, the voltage Vcs held in the capacitance element 3115 becomes Vth1+Vdata. If it is desired that the light emitting element 3116 does not emit light in the next light emitting period, a voltage of Vdata≦0 is applied. Enter the place.

[0167] Next, in the light emission period shown in FIG. 32(D), the first switch 3111 is turned off, and the power line After the potential of 3122 is set to V2, the fourth switch 3114 is turned on. The gate-source voltage of the transistor 3101 is Vgs=Vth1+Vdata. Therefore, a current according to the luminance data flows through the first transistor 3101. A current flows through the first transistor 3101 and the light emitting element 3116, causing the light emitting element 3116 to emit light.

[0168] By such an operation, the current flowing through the light emitting element 3116 is Whether the operation region of the first transistor 31 is the saturation region or the linear region, It does not depend on the threshold voltage (Vth1) of 01.

[0169] Furthermore, in the initialization period of the next frame period shown in FIG. 32(E), The second switch 3112, the third switch 3113, and the fourth switch 3114 are turned on. The sixth switch 3114 and the sixth switch 3104 are turned on. The first electrode of the capacitor 3102 becomes a source electrode, and its potential is equal to that of the potential supply line 3123. Therefore, the potential of the gate electrode is V1. The gate-source voltage Vgs of the transistor 3102 is Vth+α. The second transistor 3102 is turned on. A voltage Vth+α is held in the capacitor 3115 provided between the first electrode and the fourth electrode. Although the case where the switch 3114 is turned on has been described, it may be turned off. In the next threshold voltage writing period, the fourth switch 3114 must be turned on. .

[0170] Next, in the threshold voltage writing period shown in FIG. 32(F), the third switch 3113 is Therefore, the potential of the first electrode, i.e., the source electrode, of the second transistor 3102 is gradually increases and reaches V1-Vth2, that is, the gate of the second transistor 3102 When the gate-source voltage Vgs reaches the threshold voltage (Vth2), the second transistor The resistor 3102 is in a non-conducting state. Therefore, the voltage held in the capacitance element 3115 is Vt It becomes h2.

[0171] In the data writing period shown in FIG. 32(G), the second switch 3112 After turning off the fourth switch 3114, the first switch 3111 is turned on, and a signal A potential (V1+Vdata) corresponding to the luminance data is input from the line 3117. By turning off the switch 3114, the second transistor 3102 is made non-conductive. Therefore, the current supplied from the power supply line 3122 during data writing can be This can suppress a change in the potential of the second electrode of the capacitor 3115. At this time, the voltage Vcs held in the capacitance element 3115 becomes Vth2+Vdata.

[0172] Next, in the light emission period shown in FIG. 32(H), the first switch 3111 is turned off, and the power line After the potential of 3122 is set to V2, the fourth switch 3114 is turned on. The gate-source voltage of the transistor 3102 is Vgs=Vth2+Vdata. Therefore, a current according to the luminance data flows through the first transistor 3102. The current flows to the second transistor 3102 and the light emitting element 3116, causing the light emitting element 3116 to emit light.

[0173] In addition, when the operation region of the second transistor 3102 is either the saturation region or the linear region, In this case, the current flowing through the light emitting element 3116 does not depend on the threshold voltage (Vth2).

[0174] Therefore, both the first transistor 3101 and the second transistor 3102 Even if the current supplied to the light-emitting element is controlled using a resistor, the threshold voltage of the transistor will vary. The variation in the current value caused by the fluctuation is suppressed, and a current value corresponding to the luminance data is supplied to the light emitting element 31. 16. Note that the first transistor 3101 and the second transistor By switching between 3102, the load on one transistor can be reduced. This makes it possible to reduce the change in threshold voltage of the transistor over time.

[0175] From the above, the threshold voltages of the first transistor 3101 and the second transistor 3102 are The brightness variation caused by the voltage drop can be suppressed. Therefore, it is possible to reduce power consumption.

[0176] Furthermore, the first transistor 3101 and the second transistor 3102 are operated in the saturation region. In this case, the current flowing through each transistor due to the deterioration of the light emitting element 3116 It is also possible to suppress variation in

[0177] Note that the first transistor 3101 and the second transistor 3102 are operated in a saturation region. In this case, it is preferable that the channel length L of these transistors is long.

[0178] In addition, since a reverse bias voltage is applied to the light emitting element 3116 during the initialization period, Therefore, it is possible to insulate short-circuited portions in the light-emitting element and to suppress deterioration of the light-emitting element. Therefore, the life of the light emitting element can be extended.

[0179] In addition, the variation in current value caused by the variation in the threshold voltage of the transistor is suppressed. Therefore, the supply destination of the current controlled by the transistor is not particularly limited. Therefore, the light-emitting element 3116 shown in FIG. 31 is an EL element (organic EL element, inorganic EL element). elements or EL elements including organic and inorganic materials), electron emission elements, liquid crystal elements, electronic ink, etc. can be applied.

[0180] The first transistor 3101 and the second transistor 3102 form a light emitting element 3116 The type of transistor is not particularly limited as long as it has a function of controlling the current value supplied to the Therefore, thin film transistors (TFTs) using crystalline semiconductor films and amorphous silicon Thin film transistors using non-single crystal semiconductor films, such as polycrystalline silicon, Transistors formed using a silicon or silicon-on-insulator (SOI) substrate, MOS transistors, junction transistors, Using compound semiconductors such as ZnO and a-InGaZnO transistors using organic semiconductors and carbon nanotubes, and others A transistor can be applied.

[0181] The first switch 3111 inputs a signal according to the gradation of the pixel to the pixel through a signal line 3117. The second switch 3112 selects the timing at which the first transistor 31 01 or the timing of applying a predetermined potential to the gate electrode of the second transistor 3102 The third switch 3113 selects the potential written in the capacitor 3115. The fourth switch selects the timing for applying a predetermined potential to initialize the The switch 3114 suppresses the change in potential of the second electrode of the capacitor element 3115 when writing data. Therefore, the first switch 3111, the second switch 3112, the third switch The first switch 3113 and the fourth switch 3114 are not particularly limited as long as they have the above functions. For example, transistors and diodes can be used, or a logic circuit that combines them can be used. In addition, there is no particular limitation on the fifth switch 3103 and the sixth switch 3104. The input is not limited to a specific one, and may be, for example, a transistor or a diode, or a logic circuit that combines these. It could also be a road.

[0182] A first switch 3111, a second switch 3112, a third switch 3113, a fourth switch 3114, The switch 3114, the fifth switch 3103, and the sixth switch 3104 are connected to an N-channel When using transistors, pixels can be constructed using only N-channel transistors. This allows the manufacturing process to be simplified. The semiconductor layer is made of amorphous semiconductor or semi-amorphous semiconductor (also called microcrystalline semiconductor). For example, amorphous semiconductors such as amo These amorphous semiconductors are This allows the manufacturing process to be simplified, which reduces manufacturing costs and improves yields. Improvements can be achieved.

[0183] In addition, the first switch 3111, the second switch 3112, the third switch 3113, The fourth switch 3114, the fifth switch 3103, and the sixth switch 3104 are connected to a transistor. When a transistor is used, the polarity (conductivity type) of the transistor is not particularly limited. It is desirable to use transistors with low current.

[0184] In addition, the first transistor 3101, the fifth switch 3103, and the second transistor 3102 and the sixth switch 3104 are switched as shown in FIG. That is, the first transistor 3101 and the second transistor 3102 may be The electrode is connected to the first transistor 310 via a capacitor 3115 and a fourth switch 3114. The first and second transistors 3102 are connected to the gate electrodes of the first and second transistors 3103 and 3104. The second electrode of the transistor 3101 is connected to a power line 3122 via a fifth switch 3103. The second electrode of the second transistor 3102 is connected to the power supply line via the sixth switch 3104. It is connected to 3122.

[0185] In addition, in FIG. 31 and FIG. 37, a transistor and a switch are set, that is, the first transistor A transistor 3101 and a fifth switch 3103, a second transistor 3102 and a sixth switch The number of parallel switches is 2 for a set of 3104. is not particularly limited.

[0186] The fourth switch 3114 is connected between the node 3130 and the gate of the first transistor 3101. The present invention is not limited to a connection between the node 3130 and the node 3131, but may be applied to a connection between the node 3130 and the node 3131, or between the node 3132 and the 3133 and node 3132.

[0187] Also, as shown in FIG. 42, the fourth switch 3114 does not have to be provided. In the pixel shown in the embodiment, both the fifth switch 3103 and the sixth switch 3104 are set to the data By turning it off during the data writing period, the power line can be turned on without the fourth switch 3114. The current supplied from 3122 to node 3133 can be cut off. Since the fluctuation of the potential of the second electrode of the fourth switch 3115 can be suppressed, Without the need for 3114, the capacitance element 3115 is set to Vth1+Vdata or Vth Therefore, the fourth switch 31 can hold a voltage of 2+Vdata. 14, the light emitting element 311 can be supplied with a more accurate current according to the luminance data during the light emitting period. 6. Of course, the pixel shown in FIG. 31, i.e., the fifth switch 310 The third and sixth switches 3104 are connected to the first transistor 3101, the second transistor The same applies when the first electrode of the first transistor 3102 is connected to the node 3133. It can be said that...

[0188] In addition, during the light emission period, both the fifth switch 3103 and the sixth switch 3104 are turned on. By turning it off, it is possible to forcibly create a non-emitting state. Therefore, the light emission period can be freely set. Also, by inserting a black display, the afterimage can be prevented. It is also possible to make the image less visible and improve video characteristics.

[0189] In addition, by applying the pixel shown in this embodiment to the display device of FIG. 9, the same effect as that of the first embodiment can be obtained. As long as the data writing periods for each row do not overlap, each row can freely set the initialization start time. Also, each pixel can emit light except during its own address period. Therefore, the ratio of the light emission period in one frame period (i.e., the duty ratio) is set very large. It can be set to almost 100%. Therefore, the brightness variation is small and the duplex is Therefore, a display device with a high efficiency ratio can be obtained.

[0190] In addition, it is possible to set the threshold voltage writing period to be long, so that the current It is possible to write the threshold voltage of the transistor that controls the current value to the capacitor more accurately. This improves the reliability of the display device.

[0191] In this embodiment, as in the fourth embodiment, the potential supply line 3123 is connected to the other rows. In addition, the first transistor 3101 and the second transistor Each of the 3102 has a multi-gate transistor with transistors connected in series, Alternatively, transistors arranged in parallel may be used. The present invention can be applied to the pixel configurations shown in the first to fourth embodiments.

[0192] (Embodiment 6) In this embodiment, a P-channel transistor is used for controlling the current value supplied to the light emitting element. The case where a transistor is used will be described with reference to FIG.

[0193] The pixel shown in FIG. 39 includes a transistor 3910, a first switch 3911, a second switch A switch 3912, a third switch 3913, a fourth switch 3914, a capacitance element 3915, The pixel has a signal line 3917, a first scanning line 3918, a second the first scanning line 3919, the third scanning line 3920, the fourth scanning line 3921, the power supply line 3922, and The transistor 3910 is connected to a potential supply line 3923. A P-channel transistor is used. The absolute value of the gate-source voltage (|Vgs|) is When the threshold voltage (|Vth|) is exceeded (when Vgs falls below Vth), the transistor is in a conductive state. In addition, the light emitting element 3916 has a counter electrode 3924 as shown in FIG. An example of using an EL element in which a current flows from the pixel electrode 4911 to the pixel electrode 4912 will be described. The electrode 4911 functions as a cathode, and the counter electrode 3924 functions as an anode. The absolute value of the gate-source voltage is denoted as |Vgs|, and the absolute value of the threshold voltage is denoted as |Vth|, The power supply line 3922, the potential supply line 3923, and the signal line 3917 are connected to the first wiring and the second wiring, respectively. The first scanning line 3918, the second scanning line 3919, and the third scanning line are also called the first wiring and the third wiring. The third scanning line 3920 and the fourth scanning line 3921 are respectively referred to as the fourth wiring, the fifth wiring, and the third wiring. You can also call it the 6th wire or the 7th wire.

[0194] A first electrode (one of a source electrode and a drain electrode) of the transistor 3910 is The second electrode (the other of the source electrode and the drain electrode) is The gate electrode is connected to the fourth switch 3914 and the second switch 3922. The fourth switch 3914 is connected to a power supply line 3922 via a power supply line 3922. It is connected between the gate electrode of the transistor 3910 and the second switch 3912. A connection point between the fourth switch 3914 and the second switch 3912 is a node 3930. Then, the node 3930 is connected to the signal line 3917 via the first switch 3911. In addition, the first electrode of the transistor 3910 is supplied with a potential through a third switch 3913. It is also connected to the feeder line 3923.

[0195] Furthermore, a capacitor 391 is connected between the node 3930 and the first electrode of the transistor 3910. 5 is connected. That is, the first electrode of the capacitor 3915 is connected to the fourth switch 3914. The second electrode is connected to the gate electrode of the transistor 3910 via the first The capacitor element 3915 is connected to an insulating film formed by wiring, a semiconductor layer, and an electrode. It may be formed by sandwiching it, or in some cases, it may be formed by using the gate capacitance of the transistor 3910. The means for holding these voltages is called a storage capacitor. 3930, a first switch 3911, and a first electrode of a capacitor 3915 are connected. A connection point of the wiring is a node 3931, and a first electrode of the transistor 3910 and a A connection between the wiring to which the second electrode of the element 3915 and the pixel electrode of the light-emitting element 3916 are connected The connecting point is node 3932 .

[0196] In addition, the first scanning line 3918, the second scanning line 3919, the third scanning line 3920, the fourth scanning line By inputting a signal to the scanning line 3921, the first switch 3911 and the second switch The on / off of the switch 3912, the third switch 3913, and the fourth switch 3914 is controlled. will be done.

[0197] A signal corresponding to the gradation of the pixel, i.e., luminance data, is input to the signal line 3917. A potential according to the input is input.

[0198] Next, the operation of the pixel shown in FIG. 39 will be described with reference to the timing chart in FIG. 40 and FIG. In FIG. 40, one frame corresponds to a period for displaying one screen's worth of image. The system period is divided into an initialization period, a threshold voltage writing period, a data writing period, and a light emission period. The initialization period, threshold voltage write period, and data write period are also divided into The period is called the address period. There is no particular limit to the length of one frame, but it is important to consider whether the person viewing the image will notice flicker. It is preferable to set the delay time to 1 / 60 seconds or less so that flicker is not noticeable.

[0199] The counter electrode 3924 of the light emitting element 3916 is supplied with a potential of V1. A potential of V1+|Vth|+α (α: any positive number) is input to the power supply line 392. 2 is input with a potential of V1 during the address period and V2 during the light emission period. <V Let's say it's 1.

[0200] In order to explain the operation, the potential of the counter electrode 3924 of the light emitting element 3916 is The potential of the power supply line 3922 is the same as that of the power supply line 3922 during the non-light emitting period. The minimum potential difference required to EL Then, the potential of the counter electrode 3924 is The potential of the potential supply line 3923 is V EL It is good if the value is lower than the value obtained by adding During this period, the potential at both ends of the light emitting element 3916 is set so that no current flows through the light emitting element 3916. In addition, the potential V2 of the power supply line 3922 during the light emission period is The potential of the counter electrode 3924 is at least the potential required for the light emitting element 3116 to emit light. Difference (V EL ) should be smaller than the value obtained by subtracting Since the potential of is V1, V2 is V1-V EL The smaller the value, the better. do.

[0201] First, as shown in FIG. 40(A) and FIG. 41(A), in the initialization period, the first switch 3 911 is turned off, and the second switch 3912, the third switch 3913 and the fourth switch At this time, the first electrode of the transistor 3910 is connected to the source electrode. The potential becomes equal to that of the potential supply line 3923, so that it becomes V1+|Vth|+α. On the other hand, the potential of the gate electrode is V1. The absolute value of the voltage |Vgs| becomes |Vth|+α, and the transistor 3910 becomes conductive. A capacitance element provided between the gate electrode and the first electrode of the transistor 3910 is |Vth|+α is held in the transistor 3915. Note that when the fourth switch 3914 is turned on, However, it may be turned off in the next threshold voltage writing period. Then the fourth switch 3914 must be turned on.

[0202] In the threshold voltage writing period shown in FIG. 40(B) and FIG. 41(B), the third switch 3913 is turned off. Therefore, the first electrode, i.e., the source electrode, of the transistor 3910 is turned off. The potential gradually drops to V1+|Vth|, at which point the transistor 3910 becomes non-conductive. Therefore, the voltage held in the capacitance element 3915 is approximately |Vth|.

[0203] In the subsequent data write period shown in FIG. 40(C) and FIG. 41(C), After the switch 3912 and the fourth switch 3914 are turned off, the first switch 3911 is turned on, and a potential (V1-Vdata) corresponding to the luminance data is input from the signal line 3917. During this period, the fourth switch 3914 is turned off, and the transistor 3910 Therefore, the power supply line 3922 can be kept in a non-conducting state. Suppressing the fluctuation of the potential at the second electrode of the capacitor element 3915 due to the supplied current. Therefore, the voltage Vcs held in the capacitance element 3915 at this time is If the capacitances of the light emitting element 3915 and the light emitting element 3916 are C1 and C2, respectively, then the following formula (5) can be used: It is possible.

number

[0204] However, the light emitting element 3916 has a thinner film thickness and a larger electrode area than the capacitor element 3915. Therefore, C2>>C1. Therefore, C2 / (C1+C2)≒1, so the capacitance element is 3915. The voltage Vcs to be held is expressed by the formula (6). If it is desired to make the pixel non-emitting, a potential of Vdata≦0 should be input.

number

[0205] Next, in the light emission period shown in FIG. 40(D) ​​and FIG. 41(D), the first switch 3911 is After turning off the power supply line 3922 and setting the potential of the power supply line 3922 to V2, the fourth switch 3914 is turned on. At this time, the gate-source voltage of the transistor 3910 is Vgs=-Vdata-| Vth|, and the transistor 3910 becomes conductive. A current flows through the transistor 3910 and the light emitting element 3916, causing the light emitting element 3916 to emit light. .

[0206] The current I flowing through the light emitting element 3916 is set to a value that causes the transistor 3910 to operate in a saturation region. When this is done, it is expressed by equation (7).

number

[0207] Since the transistor 3910 is a P-channel transistor, Vth<0. Therefore, equation (7) can be transformed into equation (8).

number

[0208] When the transistor 3910 is operated in the linear region, the current I flowing through the light-emitting element is It is expressed by equation (9).

number

[0209] Since Vth<0, equation (9) can be transformed into equation (10).

number

[0210] where W is the channel width of the transistor 3910, L is the channel length, μ is the mobility, and Co x refers to the storage capacity.

[0211] From the formulas (8) and (10), the operation region of the transistor 3910 is the saturation region, the linear region, In either case, the current flowing through the light emitting element 3916 is It does not depend on the threshold voltage (Vth). Therefore, the threshold voltage of the transistor 3910 The variation in the current value caused by the variation is suppressed, and a current corresponding to the brightness data is supplied to the light-emitting element 3. It can be supplied to 916.

[0212] From the above, the variation in luminance caused by the variation in the threshold voltage of the transistor 3910 In addition, the potential of the opposing electrode is kept constant during operation, so power consumption is reduced. This allows the power consumption to be reduced.

[0213] Furthermore, when the transistor 3910 is operated in the saturation region, the light emitting element 39 It is also possible to suppress the variation in brightness caused by the deterioration of the light emitting element 3916. Child 3916 V EL increases, and the voltage at the first, or source, electrode of transistor 3910 increases. At this time, the source electrode of the transistor 3910 is connected to the second A gate electrode of the transistor 3910 is connected to a first electrode of a capacitor 3915. The gate electrode side is in a floating state. Accordingly, the gate potential of the transistor 3910 also decreases by the same amount. Since the Vgs of the transistor 3910 does not change, even if the light-emitting element deteriorates, 10 and the current flowing through the light-emitting element 3916. It can be seen that the current I flowing through the element does not depend on the source potential or the drain potential.

[0214] Therefore, when the transistor 3910 is operated in the saturation region, The transistor caused by the variation in threshold voltage of 3910 and the deterioration of the light-emitting element 3916 The variation in the current flowing through 3910 can be suppressed.

[0215] When the transistor 3910 is operated in the saturation region, breakdown and channel length modulation may occur. In order to suppress the increase in the amount of current due to the More preferred.

[0216] In addition, since a reverse bias voltage is applied to the light emitting element 3916 during the initialization period, Therefore, it is possible to insulate short-circuited portions in the light-emitting element and to suppress deterioration of the light-emitting element. Therefore, the life of the light emitting element can be extended.

[0217] The light-emitting element 3916 shown in FIG. 39 is not particularly limited and may be an EL element (organic EL element, Inorganic EL elements or EL elements containing organic and inorganic materials), electron emission elements, liquid crystal elements, electron Ink, etc. can be applied.

[0218] The transistor 3910 has a function of controlling a current value supplied to the light emitting element 3916. The type of transistor is not particularly limited as long as the transistor has a crystalline semiconductor film. The thin-film transistors (TFTs) used are non-monocrystalline silicon and polycrystalline silicon. Thin film transistors using crystalline semiconductor films, transistors formed using semiconductor substrates or SOI substrates Transistor, MOS transistor, junction transistor, bipolar transistor, Z Transistors using compound semiconductors such as nO and a-InGaZnO, organic semiconductors, Transistors using carbon nanotubes and other transistors can be used. .

[0219] The first switch 3911 inputs a signal according to the gradation of the pixel to the pixel through a signal line 3917. A second switch 3912 selects the timing of the transistor 3910. The timing for applying a predetermined potential to the gate electrode is selected, and the gate voltage of the transistor 3910 is The third switch 3913 controls whether a predetermined potential is supplied to the capacitor. The timing for applying a predetermined potential for initializing the potential written in the element 3915 is selected. The potential of the first electrode of the transistor 3910 is increased. The switch 3914 is a switch for changing the potential of the second electrode of the capacitor element 3915 when writing data. To suppress the fluctuation, the first switch 3911 and the second switch 391 2. The third switch 3913 and the fourth switch 3914 are particularly suitable as long as they have the above functions. For example, a transistor or a diode may be used, or a combination of these may be used. It may also be a logic circuit.

[0220] In the case where a transistor is used, the polarity (conductivity type) of the transistor is not particularly limited. However, it is preferable to use a transistor with low off-state current. The transistors include those with LDD regions and those with multi-gate structures. In addition, a CMOS switch can be made by using both N-channel and P-channel types. You may do so.

[0221] For example, a first switch 3911, a second switch 3912, a third switch 391 When a P-channel transistor is applied to the third and fourth switches 3914, The scanning line that controls the on / off state of the switch is connected to a L level signal when you want to turn it on, and to a When you want to turn it on, a H level signal is input.

[0222] In this case, pixels can be constructed using only P-channel transistors, making manufacturing The process can be simplified.

[0223] Furthermore, the pixel shown in this embodiment can be applied to the display device of FIG. Similarly, as long as the data writing periods for each row do not overlap, each row can freely start its initialization. In addition, each pixel can emit light except during its own address period. This allows the ratio of the light emission period in one frame period (i.e., the duty ratio) to be very It can be made as large as possible, or even approximately 100%. This means that there is little variation in brightness. A display device with a high duty ratio can be obtained.

[0224] In addition, it is possible to set the threshold write period to be long, so that the current flowing to the light emitting element can be The threshold voltage of the transistor that controls the current value can be written more accurately to the capacitance element. This improves the reliability of the display device.

[0225] This embodiment can be freely combined with the pixel configurations shown in other embodiments. For example, if the fourth switch 3914 is between the node 3930 and the node 3931, or between the first electrode of the transistor 3910 and the node 3932, A second electrode of the transistor 3910 is connected to a power supply line 3922 through a fourth switch 3914. However, the power line 3922 and the second switch 3912 may be connected. The connection point of the wiring that connects the second electrode of the transistor 3910 is a node 3935. Then, the fourth switch 3914 is connected between the node 3935 and the power line 3922. In this case, the fourth switch 3914 cannot be turned off during the initialization period.

[0226] The transistor 3910 described in this embodiment may be any of the transistors shown in other embodiments. It can also be applied to pixels.

[0227] (Embodiment 7) In this embodiment, one embodiment of a partial cross-sectional view of a pixel of the present invention will be described with reference to FIG. In addition, the transistor shown in the partial cross-sectional view of this embodiment is provided for a light emitting device. The transistor has the function of controlling the current value.

[0228] First, a base film 1712 is formed on a substrate 1711 having an insulating surface. The substrate 1711 may be a glass substrate, a quartz substrate, a plastic substrate (polyimide, acrylic, etc.) , polyethylene terephthalate, polycarbonate, polyarylate, polyether In addition to insulating substrates such as ceramic substrates, metal substrates (tantalum, tungsten It is also possible to use a substrate having an insulating film formed on the surface of a semiconductor substrate, etc. However, it is necessary to use a substrate that can at least withstand the heat generated during the process.

[0229] The undercoat film 1712 is a silicon oxide film, a silicon nitride film, or a silicon oxynitride film (SiO x N y The insulating film is formed as a single layer or as two or more layers. The film 1712 may be formed by using a sputtering method, a CVD method, or the like. Although 1712 is a single layer, it can of course be multiple layers of two or more.

[0230] Next, a transistor 1713 is formed over the base film 1712. At least a semiconductor layer 1714 and a gate insulating film 171 formed on the semiconductor layer 1714 5, and a gate electrode 171 formed on the semiconductor layer 1714 via a gate insulating film 1715. 6, where the semiconductor layer 1714 has a source region and a drain region.

[0231] The semiconductor layer 1714 may be made of amorphous silicon (a-Si:H), silicon, or silicon. Amorphous semiconductors that are mainly composed of silicon germanium (SiGe), and have an amorphous and crystalline state. Semi-amorphous semiconductors that contain a mixture of 0.5nm to 20nm crystals and amorphous semiconductors. A film having any amorphous state selected from microcrystalline semiconductors in which grains can be observed. (i.e., amorphous semiconductor film) or crystalline semiconductor film such as polysilicon (p-Si:H) In addition, microcrystalline grains of 0.5 nm to 20 nm can be observed. The state of the semiconductor layer 1714 is called a microcrystal. When a conductive film is used, it may be formed by a sputtering method, a CVD method, or the like. When a solid film is used, for example, an amorphous semiconductor film may be formed and then further crystallized. In addition, in order to control the threshold voltage of the transistor, a small amount of the above-mentioned main components may be added if necessary. A small amount of impurity elements (phosphorus, arsenic, boron, etc.) may be included.

[0232] Next, a gate insulating film 1715 is formed to cover the semiconductor layer 1714. The insulating layer 15 is made of a single layer or a plurality of films, for example, made of silicon oxide, silicon nitride, silicon oxynitride, or the like. The film is formed by stacking the layers. The film may be formed by a CVD method, a sputtering method, or the like. Cut.

[0233] Next, a gate electrode is formed above the semiconductor layer 1714 via a gate insulating film 1715. The gate electrode 1716 may be formed as a single layer, or may be formed by stacking multiple metal films. The gate electrode may be formed of tantalum (Ta), tungsten (W), Titanium (Ti), Molybdenum (Mo), Aluminum (Al), Copper (Cu), Chromium (C In addition to the metal elements selected from the above, alloy materials or compounds mainly composed of the above elements For example, the first conductive layer can be made of tantalum nitride (TaN). The second conductive layer is made of tungsten (W). The gate electrode may be formed as follows.

[0234] Next, the gate electrode 1716 or a resist is formed into a desired shape and used as a mask. The semiconductor layer 1714 is selectively doped with impurities that impart n-type or p-type conductivity. In this manner, a channel forming region and an impurity region (source The doped region includes the drain region, the GOLD region, and the LDD region. Depending on the conductivity type of the impurity element, it is called an N-channel transistor or a P-channel transistor. It is possible to create a separate system for the data.

[0235] In FIG. 17, the gate electrode 17 is formed in order to form the LDD region 1720 in a self-aligned manner. A silicon compound, for example, a silicon oxide film, a silicon nitride film, or an oxide film is formed so as to cover 16. After the silicon nitride film is formed, it is etched back to form side walls 1717 . Thereafter, impurities that impart conductivity to the semiconductor layer 1714 are added to form a source region 1718, drain region 1719, and LDD region 1720 can be formed. Therefore, the LDD region 1720 is located below the sidewall 1717. The hole 1717 is provided to form the LDD region 1720 in a self-aligned manner. The impurities that impart conductivity include phosphorus, arsenic, boron, and the like. etc. are used.

[0236] Next, the first insulating film 1730 is formed on the gate electrode 1716. A first insulating film 1721 and a second insulating film 1722 are laminated to form the insulating film. 1722 is a silicon oxide film, a silicon nitride film, or a silicon oxynitride film (SiOx N y ) etc. Uses an inorganic insulating film or a low-dielectric-constant organic resin film (photosensitive or non-photosensitive organic resin film). A film containing siloxane may also be used. The skeleton of this material is made up of silicon (Si) and oxygen (O) bonds, and the substituents are: Organic groups (e.g., alkyl groups, aromatic hydrocarbons) are used. Also, fluoro groups are used as substituents. It may also include.

[0237] The first insulating film 1721 and the second insulating film 1722 may be made of the same material. In this embodiment, the first interlayer insulating film 1730 has a two-layer laminated structure, but it may also be a single layer. Alternatively, a laminated structure of three or more layers may be used.

[0238] The first insulating film 1721 and the second insulating film 1722 are formed by a method such as a sputtering method, a CVD method, or a spin The insulating layer 11 may be formed by a coating method or the like, and an organic resin film or a film containing siloxane may be used. In this case, the film may be formed by a coating method.

[0239] Thereafter, a source electrode and a drain electrode 1723 are formed on the first interlayer insulating film 1730. The source electrode and the drain electrode 1723 are connected to the semiconductor substrate 1721 through contact holes. It is connected to the source region 1718 and the drain region 1719 .

[0240] The source and drain electrodes 1723 are made of silver (Ag), gold (Au), or copper (Cu). , Nickel (Ni), Platinum (Pt), Palladium (Pd), Iridium (Ir), Logic Rh, tungsten (W), aluminum (Al), tantalum (Ta), molybdenum (Mo) Mo, Cadmium (Cd), Zinc (Zn), Iron (Fe), Titanium (Ti), Silicon ( Metals such as Si), germanium (Ge), zirconium (Zr), barium (Ba), etc. An alloy thereof, a metal nitride thereof, or a laminated film thereof can be used.

[0241] Next, a second interlayer insulating film 1731 is formed to cover the source electrode and the drain electrode 1723. The second interlayer insulating film 1731 is an inorganic insulating film, a resin film, or a laminate of these. The inorganic insulating film may be a silicon nitride film, a silicon oxide film, a silicon oxynitride film, or As the resin film, polyimide, polyamide, etc. can be used. , acrylic, polyimide amide, epoxy, etc. can be used.

[0242] The pixel electrode 1724 is formed on the second interlayer insulating film 1731. An insulator 1725 is formed to cover the end of the emitter 4. The insulator 1725 is In order to facilitate the deposition of the layer 1726 containing the optical material, the upper end or It is preferable that the lower end portion is formed to have a curved surface having a curvature. For example, the insulator 172 When positive photosensitive acrylic is used as the material for 5, the insulator 1725 is bent only at the top end. It is preferable that the insulating material 1 has a curved surface having a radius of curvature (0.2 μm to 3 μm). 725, a negative type that becomes insoluble in the etchant when exposed to light, or Therefore, any positive type that is soluble in the etchant can be used. The material for the insulator 1725 is not limited to organic materials, but may also be inorganic materials such as silicon oxide and silicon oxynitride. It can be done as follows.

[0243] Next, a layer 1726 containing a light-emitting material and a counter electrode 1727 are formed on the pixel electrode 1724 and the insulator 1725. Forming pole 1727.

[0244] A layer 1726 containing a light-emitting material is sandwiched between the pixel electrode 1724 and the counter electrode 1727. In the removed area, a light emitting element 1728 is formed.

[0245] Next, the details of the light emitting element 1728 will be described with reference to FIG. The pixel electrode 1724 and the counter electrode 1727 are the same as the pixel electrode 1801 and the counter electrode 1802 in FIG. In FIG. 18(a), the pixel electrode corresponds to the anode and the counter electrode corresponds to the This is the cathode.

[0246] As shown in FIG. 18(a), a light-emitting layer is provided between a pixel electrode 1801 and a counter electrode 1802. In addition to 1813, a hole injection layer 1811, a hole transport layer 1812, an electron transport layer 1814, an electron injection These layers are arranged such that the potential of the pixel electrode 1801 is equal to the potential of the counter electrode 1802. When a voltage is applied so that the potential of the pixel electrode 1802 is higher than that of the pixel electrode 1802, holes The layers are laminated so that ions are injected from the counter electrode 1802 side and electrons are injected from the counter electrode 1802 side.

[0247] In such a light-emitting device, holes injected from the pixel electrode 1801 and the counter electrode 18 The electrons injected from 02 are recombined in the light-emitting layer 1813, and the light-emitting material is excited. When the excited luminescent material returns to the ground state, it emits light. The may be any material that can provide luminescence (electroluminescence).

[0248] There is no particular limitation on the material for forming the light-emitting layer 1813, and the light-emitting layer 1813 may be formed only from a light-emitting material. However, if concentration quenching occurs, the energy gap of the luminescent material must be smaller than that of the luminescent material. The light-emitting material is dispersed in a layer made of a substance (host) that has a larger energy gap than the It is preferable that the layers are mixed so as to prevent concentration quenching of the luminescent material. The energy gap is the lowest unoccupied molecular orbital (LUMO). Unoccupied Molecular Orbital (UNO) levels and the highest occupied molecular orbital Road(HOMO:Highest Occupied Molecular Orbita l) The energy difference between the levels.

[0249] The light-emitting material is not particularly limited, and any material capable of emitting light of a desired emission wavelength may be used. For example, to obtain red light emission, 4-dicyanomethylene-2-isopropanol is used. propyl-6-[2-(1,1,7,7-tetramethyljulolidin-9-yl)ethenyl ]-4H-pyran (abbreviation: DCJTI), 4-dicyanomethylene-2-methyl-6-[2 -(1,1,7,7-tetramethyljulolidin-9-yl)ethenyl]-4H-pyran (abbreviation: DCJT), 4-dicyanomethylene-2-tert-butyl-6-[2-(1, 1,7,7-Tetramethyljulolidin-9-yl)ethenyl]-4H-pyran (abbreviation: DCJTB), periflanthene, 2,5-dicyano-1,4-bis[2-(10-methoxyphenyl) 6 A substance that emits light with a peak in the emission spectrum from 00 nm to 680 nm is used. In addition, if you want to obtain green light, you can use N,N'-dimethylquinacridone (abbreviation Name: DMQd), Coumarin 6, Coumarin 545T, Tris(8-quinolinolato)aluminum Alq, N,N'-diphenylquinacridone (DPQd), etc., 50 Use a substance that emits light with a peak in the emission spectrum from 0 nm to 550 nm. If you want to obtain blue light, you can use 9,10-bis(2-naphthyl)-te rt-Butylanthracene (abbreviation: t-BuDNA), 9,9'-bianthryl, 9,1 0-Diphenylanthracene (abbreviation: DPA) and 9,10-bis(2-naphthyl)anthracene Helical (abbreviation: DNA), bis(2-methyl-8-quinolinolato)-4-phenylphenanthroline Bis(2-methyl-8-quinolinolato)-4-phenylfluorene Enolato-aluminum (BAlq), etc., with an emission spectrum from 420 nm to 500 nm Any material that exhibits a peaked emission can be used.

[0250] There is no particular limitation on the material used to disperse the luminescent material. 10-Di(2-naphthyl)-2-tert-butylanthracene (abbreviation: t-BuDNA ) or 4,4'-bis(N-carbazolyl)biphenyl (abbreviation In addition to carbazole derivatives such as carbazole (CBP), bis[2-(2-hydroxyphenyl)pyridine] zinc(abbreviation:Znpp2), bis[2-(2-hydroxyphenyl)benzox Metal complexes such as zinc(sazolato) (abbreviation: ZnBOX) can be used.

[0251] The anode material for forming the pixel electrode 1801 is not particularly limited, but it is preferable to use a material having a large work function ( (function 4.0 eV or more) Metals, alloys, electrically conductive compounds, and mixtures of these, etc. Specific examples of such anode materials include oxides of metal materials such as indium arsenide, Indium tin oxide (ITO), ITO containing silicon oxide (ITSO), A target of indium oxide mixed with 2-20 wt% zinc oxide (ZnO) was used. In addition to the indium zinc oxide (IZO) that is formed, gold (Au), platinum (Pt), Nickel (Ni), Tungsten (W), Chromium (Cr), Molybdenum (Mo), Iron (Fe ), cobalt (Co), copper (Cu), palladium (Pd), or nitrides of metallic materials (e.g. For example, TiN can be mentioned.

[0252] On the other hand, the material forming the counter electrode 1802 has a small work function (work function 3.8 (eV or less) metals, alloys, electrically conductive compounds, and mixtures thereof can be used. Specific examples of such cathode materials include elements belonging to Groups 1 and 2 of the periodic table, i.e. Alkali metals such as lithium (Li) and cesium (Cs) or magnesium (Mg) Alkaline earth metals such as calcium (Ca), strontium (Sr), and In addition, the counter electrode 1802 and the light-emitting layer 1803 may be made of an alloy containing the same (Mg:Ag, Al:Li). A layer having excellent electron injection properties is laminated between the counter electrode and the electrode 13. Regardless of the magnitude of the function, pixel electrodes such as Al, Ag, ITO, and ITO containing silicon oxide are Various conductive materials, including those listed as materials for 801, can be used as the counter electrode 1802. In addition, the electron injection layer 1815 described later can be formed from a material having excellent electron injection properties. A similar effect can be obtained by using a material having a different structure.

[0253] In order to extract the emitted light to the outside, the pixel electrode 1801 and the counter electrode 1802 are Either one or both should be transparent electrodes such as ITO, or several to several tens of electrodes that can transmit visible light. Preferably, the electrode is formed to a thickness of m.

[0254] Between the pixel electrode 1801 and the light-emitting layer 1813, a hole transport layer is provided as shown in FIG. The hole transport layer is a layer that transports holes injected from the pixel electrode 1801 to the light emitting layer 18. In this way, the hole transport layer 1812 is provided to By separating the electrode 1801 and the light-emitting layer 1813, the light emission is quenched due to the metal. This can be prevented.

[0255] Note that the hole transport layer 1812 is preferably formed using a substance with a high hole transport property. Especially 1×10 -6 cm 2 Formed using a material with hole mobility of / Vs or higher. Note that a substance with a high hole transporting property is a substance having a higher mobility of holes than that of electrons. Specific examples of materials that can be used to form the hole-transporting layer 1812 include 4, 4'-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB) , 4,4'-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl (abbreviation Name: TPD), 4,4',4''-tris(N,N-diphenylamino)triphenyla MIN (abbreviation: TDATA), 4,4',4''-tris[N-(3-methylphenyl)- N-phenylamino]triphenylamine (abbreviation: MTDATA), 4,4'-bis{N -[4-(N,N-di-m-tolylamino)phenyl]-N-phenylamino}biphenyl DNTPD, 1,3,5-tris[N,N-di(m-tolyl)amino]benzene Zene (abbreviation: m-MTDAB), 4,4',4''-tris(N-carbazolyl)triflate phenylamine (abbreviation: TCTA), phthalocyanine (abbreviation: H2Pc), copper phthalocyanine Examples include CuPc, vanadyl phthalocyanine (VOPc), etc. The hole transport layer 1812 is formed by combining two or more layers made of the above-mentioned materials. It may be a layer of a multi-layer structure.

[0256] In addition, between the counter electrode 1802 and the light-emitting layer 1813, an electron The electron transport layer 1814 may be provided. Here, the electron transport layer is a layer that transports electrons from the counter electrode 1802. The layer has a function of transporting the injected electrons to the light-emitting layer 1813. By providing a layer 1814 to separate the counter electrode 1802 from the light-emitting layer 1813, light is emitted through the electrode This can prevent quenching caused by the metal of the material.

[0257] The electron transport layer 1814 is not particularly limited, and may be formed of tris(8-quinolinolato)aluminum. Aluminum (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum (abbreviation: A lmq3), bis(10-hydroxybenzo[h]-quinolinato)beryllium (abbreviation: B eBq2), bis(2-methyl-8-quinolinolato)-4-phenylphenolato-aluminum Metal complexes with a quinoline or benzoquinoline skeleton, such as nium (abbreviation: BAlq) In addition, those formed by bis[2-(2-hydroxyphenyl)- Bis[2-(2-phenyl)-benzoxazolato]zinc (abbreviation: Zn(BOX)2), (1-hydroxyphenyl)-benzothiazolato]zinc (abbreviation: Zn(BTZ)2) It is formed by a metal complex having a xazole or thiazole ligand, etc. Also, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1 ,3,4-Oxadiazole (abbreviation: PBD) and 1,3-bis[5-(p-tert- butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD -7), 3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenyl 3-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), (4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazo p-EtTAZ, Bathophenanthroline (BPhen), Bathocu The electron transport layer 181 may be formed using proline (abbreviation: BCP) or the like. 4 is formed using a material having a higher electron mobility than the hole mobility as described above. In addition, the electron transport layer 1814 is preferably 10 -6 cm 2 Electron transfer above / Vs It is more preferable that the electron transport layer 1814 be formed using a material having a high conductivity. It may also be a multi-layer structure formed by combining two or more layers made of the above-mentioned materials.

[0258] Furthermore, between the pixel electrode 1801 and the hole transport layer 1812, as shown in FIG. In addition, the positive hole injection layer 1811 may be provided. Here, the positive hole injection layer functions as an anode. This layer has a function of promoting the injection of holes from the electrode connected to the hole transport layer 1812 .

[0259] The hole injection layer 1811 is not particularly limited, and may be made of molybdenum oxide (MoOx) or vanadium oxide (VAD). Ruthenium oxide (VOx), ruthenium oxide (RuOx), tungsten oxide (WOx) In addition, a material formed of a metal oxide such as manganese oxide (MnOx) can be used. In addition, phthalocyanine (abbreviation: H2Pc) and copper phthalocyanine (CuPc) are also available. Phthalocyanine compounds, 4,4-bis(N-(4-(N,N-di-m-tolylamino Aromatic amines such as phenyl-N-phenylamino-biphenyl (abbreviation: DNTPD) Compounds of the series, or poly(ethylenedioxythiophene) / poly(styrenesulfonic acid) The hole injection layer 1811 can also be formed from a polymer such as an aqueous solution (PEDOT / PSS). This can be done.

[0260] In addition, a mixture of the metal oxide and a material having a high hole transporting property is formed on the pixel electrode 180. 1 and the hole transport layer 1812. Such a layer can be formed thick and has a low driving voltage. Since there is no increase in the temperature, the microcavity effect and the optical interference effect can be achieved by adjusting the layer thickness. Therefore, it is possible to carry out optical design that utilizes the results of the above. It is possible to manufacture a high-quality light-emitting element with little color change. The unevenness that occurs on the surface of the pixel electrode 1801 due to the influence of minute residues remaining on the electrode surface and the unevenness that occurs on the surface of the electrode during film formation. It is possible to select a film thickness that prevents shorting between the counter electrode 1802 and the insulating film 1804 .

[0261] In addition, as shown in FIG. 18(a), between the counter electrode 1802 and the electron transport layer 1814, The electron injection layer 1815 may be an electron injection layer that functions as a cathode. The layer has a function of promoting the injection of electrons from the electrode to the electron transport layer 1814. When no transport layer is provided, an electron injection layer is provided between the electrode functioning as a cathode and the light emitting layer. , may assist in the injection of electrons into the light-emitting layer.

[0262] The electron injection layer 1815 is not particularly limited, and may be formed of lithium fluoride (LiF), cesium fluoride, or the like. Alkaline metals or alkaline earth metals such as cesium fluoride (CsF), calcium fluoride (CaF2), etc. In addition, those formed using compounds of metals such as Alq or 4 ,4-bis(5-methylbenzoxazol-2-yl)stilbene (BzOs), etc. In the case of a material having high electron transport properties, an alkali metal or alkali metal such as magnesium or lithium is used. Mixtures of alkaline earth metals can also be used for the electron-injecting layer 1815 .

[0263] The hole injection layer 1811, the hole transport layer 1812, the light emitting layer 1813, and the electron transport layer 181 4. The electron injection layer 1815 can be formed by a deposition method, an inkjet method, a coating method, or the like. The pixel electrode 1801 or the counter electrode 1802 may be formed by any method. The insulating film 11 may be formed by any method such as sputtering or vapor deposition.

[0264] The layer structure of the light-emitting device is not limited to that shown in FIG. 18(a) and may be any of the following: As shown in FIG. 1, the electrodes functioning as cathodes may be fabricated in order. That is, the pixel electrodes 180 1 is a cathode, and an electron injection layer 1815, an electron transport layer 1814, and a light-emitting layer 1813, a hole transport layer 1812, a hole injection layer 1811, and a counter electrode 1802 are laminated in this order. The counter electrode 1802 functions as an anode.

[0265] Although the light-emitting element has been described as having a single light-emitting layer, it may have a plurality of light-emitting layers. It is also possible to provide a plurality of light-emitting layers and mix the light emitted from each of the light-emitting layers. For example, in the case of a light-emitting element having two light-emitting layers, the first light-emitting layer Between the light emitting layer and the second light emitting layer, a spacing layer, a layer generating holes, and a layer generating electrons are provided. With such a configuration, each emitted light is visually different from the other emitted light. The light is mixed with the other light and is perceived as white light. Thus, white light can be obtained.

[0266] In addition, light is emitted from either the pixel electrode 1724 or the counter electrode 1727 in FIG. Therefore, the light is taken out through the pixel electrode 1724 or the counter electrode 1725. Either or both of 727 are made of a material having optical transparency.

[0267] When only the counter electrode 1727 is made of a material having light-transmitting properties, as shown in FIG. The emitted light passes through the counter electrode 1727 and is taken out from the opposite side of the substrate. When only the pixel electrode 17 is made of a material having light transmitting properties, light is emitted from the pixel electrode 17 as shown in FIG. The pixel electrode 1724 and the counter electrode 1727 are both connected to the substrate. If the material is made of a light-transmitting material, light is emitted from the pixel as shown in FIG. The electrode 1724 and the counter electrode 1727 are passed through the counter electrode 1727 from both the substrate side and the opposite side. It is served.

[0268] The wiring and electrodes are not limited to the above-mentioned materials, but may be made of aluminum (Al), tantalum (Ta), titanium (Ti), etc. Tungsten (Ti), Molybdenum (Mo), Tungsten (W), Neodymium (Nd), Chromium ( Cr), Nickel (Ni), Platinum (Pt), Gold (Au), Silver (Ag), Copper (Cu), Magnesium Magnesium (Mg), Scandium (Sc), Cobalt (Co), Nickel (Ni), Zinc (Zn), Niobium (Nb), Silicon (Si), Phosphorus (P), Boron (B), Arsenic (As ), gallium (Ga), indium (In), tin (Sn) or a compound or alloy material containing one or more elements selected from the above group (e.g., indium tin oxide (ITO), indium zinc oxide (IZO), silicon oxide ITO (ITSO), zinc oxide (ZnO), aluminum neodymium (Al-Nd), Magnesium silver (Mg-Ag), or combinations of these compounds. It can also be formed by using compounds of these with silicon (silicides) (e.g. For example, aluminum silicon, molybdenum silicon, nickel silicide, etc.) and nitrogen compounds ( For example, titanium nitride, tantalum nitride, molybdenum nitride, etc. may be used. Silicon (Si) contains a lot of n-type impurities (such as phosphorus) and p-type impurities (such as boron). The inclusion of these impurities improves the electrical conductivity, making it similar to that of a normal conductor. This makes it easier to use as wiring or electrodes. Either polycrystalline (polysilicon) or amorphous (amorphous silicon) may be used. When single crystal silicon or polycrystalline silicon is used, the resistance can be reduced, whereas when amorphous silicon is used, In Ricon, it can be made through a simple manufacturing process.

[0269] In addition, when aluminum or silver is used, the signal delay can be reduced due to its high conductivity. In addition, since etching is easy, patterning is easy and fine processing can be performed. In addition, copper also has high electrical conductivity, so signal delay can be reduced. Molybdenum does not cause material defects when it comes into contact with oxide semiconductors such as ITO and IZO or silicon. In addition, the manufacturing process can be performed without problems such as patterning and etching. Titanium is also preferred because it is easy to apply and has high heat resistance. It can be manufactured without causing problems such as material defects even when it comes into contact with the body or silicon, and Tungsten and neodymium are also desirable because they have excellent heat resistance. In addition, when neodymium is alloyed with aluminum, the heat resistance is improved. This can suppress the aluminum hillocks. It can be formed simultaneously with the semiconductor layer having the same structure, and has high heat resistance. Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), ITO with silicon oxide (ITSO), zinc oxide (ZnO), and silicon (Si) are transparent, so they transmit light. This is particularly desirable when used in areas where the pixel electrodes and common electrodes are to be connected. It can be used as such.

[0270] The wiring and electrodes are formed using the above-mentioned materials in a single-layer structure or a multi-layer structure. For example, when it is formed in a single layer structure, the manufacturing process can be simplified and the cost can be reduced. In addition, the multi-layer structure makes use of the advantages of each material, It is possible to reduce the disadvantages, and therefore form wiring and electrodes with excellent performance. For example, it is possible to include a low-resistance material (such as aluminum) in the multilayer structure. By forming the wiring, it is possible to reduce the resistance of the wiring. (For example, a material with low heat resistance but other advantages is replaced with a material with high heat resistance.) By using a laminated structure (sandwiching the two layers together), it is possible to improve heat resistance and also to utilize the properties that could not be achieved with a single layer. For example, it is possible to use the aluminum-containing layer by using molybdenum or titanium. It is preferable to use wiring or electrodes sandwiched between layers containing the same. If there are any parts that come into direct contact with wiring or electrodes, etc., they may have a detrimental effect on each other. For example, one material may mix with another, changing the properties of each material. It may become impossible to achieve the intended purpose, or problems may arise during production that may prevent normal production. In such cases, the problem can be solved by sandwiching or covering one layer with another. For example, indium tin oxide (ITO) can be brought into contact with aluminum. If you want to use a high-performance ferrite core, it is recommended to use titanium or molybdenum between the two. Similarly, when it is desired to bring aluminum into contact with the metal, it is preferable to sandwich titanium or molybdenum between them.

[0271] Next, a transistor 1713 is formed using a staggered structure in which an amorphous semiconductor film is used as a semiconductor layer. The transistor will be described. A partial cross-sectional view of a pixel is shown in FIG. The transistor with a staggered structure is described below, and the capacitance element of the pixel is also described. Reveal.

[0272] As shown in FIG. 20, a base film 2012 is formed on a substrate 2011. A pixel electrode 2013 is formed on the film 2012. A first electrode 2014 made of the same material is formed.

[0273] Furthermore, a wiring 2015 and a wiring 2016 are formed on the base film 2012, and the pixel electrode 20 The end of 13 is covered with wiring 2015. An N-type An N-type semiconductor layer 2017 and an N-type semiconductor layer 2018 having the same conductivity type are formed. In addition, a semiconductor layer 2019 is formed on the base film 2012 between the wiring 2015 and the wiring 2016. A part of the semiconductor layer 2019 is formed on the N-type semiconductor layer 2017 and the N-type semiconductor layer 2019. The semiconductor layer 2018 is made of amorphous silicon (a -Si:H) and other amorphous semiconductors, semi-amorphous semiconductors, microcrystalline semiconductors, and other non-crystalline semiconductors The gate insulating film 2020 is formed on the semiconductor layer 2019. In addition, an insulating film 2021 made of the same material as the gate insulating film 2020 is formed on the first insulating film 2021. The electrode 2014 is also formed on the other electrode 2014.

[0274] Further, a gate electrode 2022 is formed on the gate insulating film 2020, forming a transistor 2 A second electrode 2025 is formed in the same layer and made of the same material as the gate electrode 2022. 2023 is formed on the first electrode 2014 via an insulating film 2021, and the insulating film 2021 is A capacitor element 2024 is formed by being sandwiched between a first electrode 2014 and a second electrode 2023. In addition, the edge of the pixel electrode 2013, the transistor 2025, and the capacitor element 2024 An interlayer insulating film 2026 is formed covering the above.

[0275] A layer containing a light-emitting material is formed on the interlayer insulating film 2026 and the pixel electrode 2013 located at the opening of the interlayer insulating film 2026. The layer 2027 containing a light emitting material is formed on the pixel electrode 201. A light emitting element 2029 is formed in the region sandwiched between the light emitting element 3 and the counter electrode 2028 .

[0276] 20(a) is connected to the wiring 201 as shown in FIG. 20(b). 2016 and the insulating film 2021 is formed of the same material as the first electrode 2030 and the second electrode 2016. The capacitor 2031 may be sandwiched between the first electrode 2023 and the second electrode 2024. In this case, an N-channel transistor was used for the transistor 2025, but a P-channel transistor was used. Jista is fine too.

[0277] A substrate 2011, a base film 2012, a pixel electrode 2013, a gate insulating film 2020, a gate electrode The electrode 2022, the interlayer insulating film 2026, the layer 2027 containing a light-emitting material, and the counter electrode 2028 are The materials that can be used are the substrate 1711, the undercoat film 1712, the pixel electrode 1713, and the like, which are described in FIG. 24, gate insulating film 1715, gate electrode 1716, interlayer insulating films 1730 and 1731, The same materials as those of the layer 1726 containing a light-emitting material and the counter electrode 1727 can be used. The wiring 2015 and the wiring 2016 correspond to the source electrode and the drain electrode in FIG. The same material as pole 1723 may be used.

[0278] Next, as another structure of a transistor using an amorphous semiconductor film as a semiconductor layer, A structure in which a gate electrode is sandwiched between semiconductor layers, i.e., the gate electrode is located below the semiconductor layer. FIG. 21 shows a partial cross-sectional view of a pixel having a bottom-gate transistor.

[0279] An undercoat film 2112 is formed on a substrate 2111. A gate An electrode 2113 is formed. In addition, a second insulating film made of the same material as the gate electrode 2113 is formed in the same layer. The gate electrode 2113 is made of the same material as the gate electrode in FIG. In addition to the materials used for the 1716 electrode, phosphorus-doped polycrystalline silicon and metal-silica Silicide, which is a compound of silicide, may also be used.

[0280] A gate insulating film 2115 is formed so as to cover the gate electrode 2113 and the first electrode 2114. is formed.

[0281] A semiconductor layer 2116 is formed on the gate insulating film 2115. A semiconductor layer 2117 made of the same material as the semiconductor layer 16 is formed on the first electrode 2114. This semiconductor layer is made of amorphous semiconductor such as amorphous silicon (a-Si:H), The insulating film is formed of a non-crystalline semiconductor film such as a micamorphous semiconductor or a microcrystalline semiconductor.

[0282] An N-type semiconductor layer 2118 having an N-type conductivity and an N-type semiconductor layer 2119 having an N-type conductivity are provided on the semiconductor layer 2116. 2119 is formed on the semiconductor layer 2117, and an N-type semiconductor layer 2120 is formed on the semiconductor layer 2117.

[0283] A wiring 2121 and a wiring 2122 are provided on the N-type semiconductor layer 2118 and the N-type semiconductor layer 2119, respectively. 122 is formed, and a transistor 2129 is formed. A conductive layer 2123 made of the same material as the wiring 2121 and the wiring 2122 is formed on the The conductive layer 2123, the N-type semiconductor layer 2120, and the semiconductor layer 2117 form a second electrode. The second electrode and the first electrode 2114 form a gate insulating film 2115. A sandwiched capacitance element 2130 is formed.

[0284] One end of the wiring 2121 is extended, and the wiring 2121 is in contact with the upper part of the extended wiring 2121. A base electrode 2124 is formed.

[0285] In addition, the edge of the pixel electrode 2124, the transistor 2129, and the capacitor element 2130 are covered with a An insulator 2125 is formed as shown.

[0286] A layer 2126 containing a light-emitting material and a counter electrode 2127 are formed on the pixel electrode 2124 and the insulator 2125. 127 is formed, and a layer 2126 containing a light-emitting material is formed between the pixel electrode 2124 and the counter electrode 2127. A light emitting element 2128 is formed in the sandwiched region.

[0287] The semiconductor layer 2117 and the N-type semiconductor layer 212 which are to be a part of the second electrode of the capacitor element 2130 In other words, the second electrode is the conductive layer 2123, and the first electrode 21 A capacitor element having a structure in which the gate insulating film 2115 is sandwiched between the gate insulating film 2114 and the conductive layer 2123 may be used. .

[0288] In addition, an N-channel transistor is used for the transistor 2129, but a P-channel transistor is used. A transistor is also fine.

[0289] In FIG. 21(a), the pixel electrode 2124 is formed before the wiring 2121 is formed. As a result, a second electrode made of the same material as the pixel electrode 2124 is formed in the same layer as the pixel electrode 2124 as shown in FIG. A capacitance element having a structure in which a gate insulating film 2115 is sandwiched between an electrode 2131 and a first electrode 2114. 2132 can be formed.

[0290] We have shown a transistor with an inverted staggered channel etch structure, but of course the channel A transistor with a protection structure may also be used. Next, regarding a transistor with a channel protection structure, The following description will be given with reference to FIG. 22. In FIG. 22, the same elements as in FIG. 21 are used in common. The symbols are used to indicate the same.

[0291] The transistor 2201 having a channel-protected structure shown in FIG. The transistor 2129 having the channel etch structure has a channel in the semiconductor layer 2116. 2202 is provided on the region where the etching is to be performed. become.

[0292] Similarly, a transistor 2201 having a channel protection structure shown in FIG. The transistor 2129 with the channel etch structure shown in b) has a semiconductor layer 2116 An insulator 2202 is provided on the region where the channel is to be formed, which serves as an etching mask. The difference is that

[0293] By using an amorphous semiconductor film for the semiconductor layer of the transistor constituting the pixel of the present invention, In addition, the materials used are the same as those described in FIG. It can be used.

[0294] In addition, the structure of the transistor and the configuration of the capacitor are not limited to those described above, and various configurations may be used. A transistor or a capacitor having a structure or configuration can be used.

[0295] In addition, the semiconductor layer of the transistor is made of amorphous silicon (a-Si:H) In addition to non-crystalline semiconductor films such as semiconductors, semi-amorphous semiconductors, and microcrystalline semiconductors, A crystalline semiconductor film such as p-Si:H may also be used.

[0296] FIG. 23 is a partial cross-sectional view of a pixel having a transistor using a crystalline semiconductor film as a semiconductor layer. The transistor 2318 shown in FIG. 23 is the same as the transistor 2318 shown in FIG. This is a multi-gate transistor.

[0297] As shown in FIG. 23, a base film 2302 is formed on a substrate 2301, and a semiconductor layer The semiconductor layer 2303 is formed by forming a crystalline semiconductor film into a desired shape. Patterning and forming.

[0298] An example of a method for manufacturing a crystalline semiconductor film is described below. First, a crystalline semiconductor film is formed on a substrate 2301 by sputtering. An amorphous silicon film is formed by CVD or other methods. The present invention is not limited to a silicon film, and may be applied to amorphous semiconductors, semi-amorphous semiconductors, microcrystalline semiconductors, etc. Any amorphous semiconductor film is acceptable. Also, amorphous structures such as amorphous silicon germanium films are acceptable. A compound semiconductor film containing the above may be used.

[0299] The formed amorphous silicon film is then crystallized by thermal crystallization, laser crystallization, or The semiconductor film is crystallized by a thermal crystallization method using a catalytic element such as nickel, to obtain a crystalline semiconductor film. These crystallization methods may be used in combination.

[0300] When a crystalline semiconductor film is formed by a thermal crystallization method, a heating furnace, laser irradiation, or RTA (Rapid Thermal Annealing), or a combination of these It can be used.

[0301] In addition, when a crystalline semiconductor film is formed by a laser crystallization method, a continuous wave laser is used. CW laser beam and pulsed laser beam The laser beam that can be used here is an Ar laser, a Kr laser, Gas lasers such as excimer lasers, single crystal YAG, YVO4, forsterite ( Mg2SiO4), YAlO3, GdVO4, or polycrystalline (ceramic) YAG, Y2O3, YVO4, YAlO3, GdVO4 with Nd, Yb, Cr, The medium is doped with one or more of Ti, Ho, Er, Tm, and Ta. Laser, glass laser, ruby ​​laser, alexandrite laser, Ti:sapphire laser The laser is generated by one or more of the following lasers: copper vapor laser, gold vapor laser, or The fundamental waves of such laser beams and the second harmonics of these fundamental waves can be By irradiating the crystal with a fourth harmonic laser beam from 1000 Hz to 1000 Hz, it is possible to obtain crystals with large grain size. For example, the second harmonic (532 nm) and third harmonic (1064 nm) of the Nd:YVO4 laser A harmonic (355 nm) can be used. In this case, the laser energy density is 0.0 1~100MW / cm 2 (preferably 0.1 to 10 MW / cm 2 ) is necessary. The scanning speed is set to about 10 to 2000 cm / sec for irradiation.

[0302] In addition, single crystal YAG, YVO4, forsterite (Mg2SiO4), YAlO3 , GdVO4, or polycrystalline (ceramic) YAG, Y2O3, YVO4, YAlO 3. GdVO4 with Nd, Yb, Cr, Ti, Ho, Er, Tm, and Ta as dopants Lasers that use one or more of the above as a medium, Ar ion lasers, or The Ti:sapphire laser can be operated in continuous oscillation mode and can be Q-switched or By performing mode locking, etc., it is possible to generate pulse oscillation at an oscillation frequency of 10 MHz or more. When a laser beam is oscillated at a frequency of 10 MHz or more, the semiconductor film The next pulse is irradiated onto the semiconductor film between the time when the laser melts and when the laser solidifies. Therefore, unlike the case of using a pulsed laser with a low oscillation frequency, the solid-state laser is not generated in the semiconductor film. Since the liquid interface can be moved continuously, crystals grow continuously in the scanning direction. Crystal grains can be obtained.

[0303] In addition, when a crystalline semiconductor film is formed by a thermal crystallization method using a catalytic element such as nickel, In this case, it is preferable to perform a gettering process to remove catalytic elements such as nickel after crystallization. I wish.

[0304] The above-mentioned crystallization forms a partially crystallized region in the amorphous semiconductor film. This partially crystallized crystalline semiconductor film is patterned into a desired shape to form island-shaped semiconductor This semiconductor film is used as a semiconductor layer 2303 of a transistor.

[0305] The crystalline semiconductor layer is a channel formation region 2304 of the transistor 2318 and a source In addition to being used for the impurity region 2305 which becomes a source region or a drain region, It is also used in the semiconductor layer 2306 that becomes the lower electrode and the impurity region 2308. The region 2308 is not particularly required. The layer 306 may be channel doped.

[0306] Next, a gate insulating film 2309 is formed on the semiconductor layer 2303 and the lower electrode of the capacitor element 2319. Furthermore, a gate insulating film 2309 is formed on the semiconductor layer 2303. A gate electrode 2310 is provided on the semiconductor layer 2306 of the capacitance element 2319 . An upper electrode 2311 made of the same material as the gate electrode 2310 is formed in the same layer via the gate electrode 2310. In this manner, the transistor 2318 and the capacitor element 2319 are formed.

[0307] Next, an interlayer insulating film 2312 is formed to cover the transistor 2318 and the capacitor element 2319. On the interlayer insulating film 2312, a contact hole is formed, which contacts the impurity region 2305. A wiring 2313 is formed. A pixel electrode 2314 is formed, and the end of the pixel electrode 2314 and the wiring 2313 are covered and insulated. Further, a layer 2316 containing a light emitting material is formed on the pixel electrode 2314. A light-emitting material is emitted between the pixel electrode 2314 and the counter electrode 2317. A light emitting element 2320 is formed in the region where the containing layer 2316 is sandwiched.

[0308] In addition, a bottom gate semiconductor layer is formed using a crystalline semiconductor film such as polysilicon (p-Si:H). A partial cross section of a pixel having a gate type transistor is shown in FIG.

[0309] An undercoat film 2402 is formed on a substrate 2401, and a gate electrode 2403 is formed thereon. In addition, the first gate electrode 2403 is formed in the same layer and made of the same material as the gate electrode 2403. An electrode 2404 is formed.

[0310] A gate insulating film 2405 is formed so as to cover the gate electrode 2403 and the first electrode 2404. is formed.

[0311] In addition, a semiconductor layer is formed over the gate insulating film 2405. Amorphous semiconductor films, such as amorphous semiconductors, semi-amorphous semiconductors, and microcrystalline semiconductors, are thermally crystallized. , laser crystallization, or thermal crystallization using a catalytic element such as nickel. The resulting film is then patterned into a desired shape to form a semiconductor layer.

[0312] The channel formation region 2406 of the transistor 2422 and the LDD region 2404 are formed using a semiconductor layer. A region 2407 and an impurity region 2408 which becomes a source region or a drain region, and a capacitance element A region 2409 which becomes a second electrode of 2423, an impurity region 2410 and an impurity region 2411 The impurity region 2410 and the impurity region 2411 are not necessarily provided. In addition, the channel forming region 2406 and the region 2409 may be doped with impurities. .

[0313] In addition, in the capacitor 2423, the gate insulating film 2405 is formed between the first electrode 2404 and the semiconductor layer. The second electrode is formed of a region 2409 and the like.

[0314] Next, a first interlayer insulating film 2412 is formed to cover the semiconductor layer, and the first interlayer insulating film 24 A wiring 2413 is formed on the substrate 12, which is in contact with the impurity region 2408 through a contact hole. is.

[0315] In addition, an opening 2415 is formed in the first interlayer insulating film 2412. Transistor A second interlayer insulating film 2416 is formed to cover the insulating film 2422, the capacitor element 2423, and the opening 2415. is formed, and the wiring 2413 and the second interlayer insulating film 2416 are formed through contact holes. A pixel electrode 2417 is formed. An insulator 2418 is formed. A layer 24 containing a light-emitting material is then formed on the pixel electrode 2417. The pixel electrode 2417 and the counter electrode 2420 form a light-emitting element. A light emitting element 2421 is formed in the region where the layer 2419 containing the glass is sandwiched. The opening 2415 is located under the element 2421. When light is to be emitted from the substrate side, the first interlayer insulating film 2412 has an opening 2415. Therefore, the transmittance can be increased.

[0316] By using a crystalline semiconductor film for the semiconductor layer of the transistor constituting the pixel of the present invention, For example, the scanning line driver circuit 912 and the signal line driver circuit 911 in FIG. It becomes easier to shape the body.

[0317] The structure of a transistor using a crystalline semiconductor film as a semiconductor layer is the same as that described above. The same is true for the capacitance element. In addition, in this embodiment, unless otherwise specified, the materials in FIG. 17 are used appropriately. This can be done.

[0318] The transistor described in this embodiment mode can emit light in the pixel described in any of the embodiments 1 to 6. It can be used as a transistor to control the current value supplied to the element. By operating the pixel as described in the first to sixth embodiments, the threshold voltage of the transistor Therefore, the variation in the current value caused by the variation in the voltage can be suppressed. This allows a current corresponding to the amount of light emitted from the light emitting element to be supplied, making it possible to suppress variations in brightness. In addition, power consumption can be reduced because the potential of the opposing electrode is kept constant during operation. It is Noh.

[0319] Moreover, by applying such pixels to the display device of FIG. 9, each pixel has its own address. Since it is possible to emit light except during the period of the light emission, the ratio of the light emission period in one frame period ( That is, the duty ratio can be made very large, even reaching nearly 100%. As a result, a display device with less variation in luminance and a high duty ratio can be obtained.

[0320] In addition, it is possible to set the threshold voltage writing period to be long, so that the current It is possible to write the threshold voltage of the transistor that controls the current value to the capacitor more accurately. This improves the reliability of the display device.

[0321] (Embodiment 8) In this embodiment, an element having a different structure from the light-emitting element shown in the embodiment 7 will be described. explain.

[0322] Light-emitting elements that utilize electroluminescence are made of organic or inorganic light-emitting materials. Generally, the former are organic EL elements and the latter are inorganic EL elements. It is called.

[0323] Inorganic EL elements are classified into dispersion type inorganic EL elements and thin film type inorganic EL elements depending on the element structure. The former has a light-emitting layer in which particles of a light-emitting material are dispersed in a binder, while the latter has The difference is that it has a light-emitting layer made of a thin film of light-emitting material, but it emits electrons accelerated by a high electric field. The mechanism of light emission is similar to that of the donor level. and acceptor levels, and the inner shell of metal ions. In general, in dispersed inorganic EL devices, the donor-atom is In the case of thin-film inorganic EL elements, emission is often of the localized type.

[0324] The luminescent material used in this embodiment is composed of at least a host material and an impurity element that serves as a luminescence center. By changing the impurity elements contained, various The light-emitting materials can be produced by the solid-phase method or the liquid-phase method (coprecipitation method). ) and other methods can be used. In addition, spray pyrolysis, metathesis, and precursor - thermal decomposition reaction method, reverse micelle method, or a combination of these methods with high-temperature baking, A liquid phase method such as freeze-drying can also be used.

[0325] In the solid phase method, the base material and the impurity element or a compound containing the impurity element are weighed and mixed in a mortar. In this method, the base material is heated and sintered in an electric furnace to cause a reaction and incorporate impurity elements into it. The firing temperature is preferably 700 to 1500° C. If the temperature is too low, the solid-phase reaction does not proceed. If the temperature is too high, the base material will decompose. However, it is preferable to sinter the material in a pellet state. However, since it is a simple method, it is highly productive and suitable for mass production.

[0326] The liquid phase method (coprecipitation method) is a method in which a base material or a compound containing a base material and an impurity element or an impurity source are mixed together. This method involves reacting a compound containing an element in a solution, drying it, and then baking it. The particles are uniformly distributed and have a small particle size, so the reaction can proceed even at a low firing temperature.

[0327] The host material used for the light emitting material may be a sulfide, an oxide, or a nitride. Examples of sulfides include zinc sulfide (ZnS), cadmium sulfide (CdS), and calcium sulfide. CaS, yttrium sulfide (Y2S3), gallium sulfide (Ga2S3), sulphide Strontium (SrS), barium sulfide (BaS), etc. can be used. For example, zinc oxide (ZnO), yttrium oxide (Y2O3), etc. can be used. As the nitride, for example, aluminum nitride (AlN), gallium nitride, etc. GaN (GaN), indium nitride (InN), etc. can be used. Lead (ZnSe), zinc telluride (ZnTe), etc. can also be used, and calcium sulphide-gallium CaGa2S4, Strontium-gallium sulfide (SrGa2S4), Barium sulfide It may also be a ternary mixed crystal such as sodium-gallium (BaGa2S4).

[0328] The luminescent centers of localized luminescence are manganese (Mn), copper (Cu), samarium (Sm), Terbium (Tb), Erbium (Er), Thulium (Tm), Europium (Eu), Cerium (Ce), praseodymium (Pr), etc. can be used. As the halogen atom, a halogen element such as fluorine (F) or chlorine (Cl) may be added.

[0329] On the other hand, the first electrons that form the donor level act as the luminescence center of donor-acceptor recombination luminescence. A light-emitting material containing the first impurity element and a second impurity element that forms an acceptor level is used. The first impurity element can be, for example, fluorine (F), chlorine (Cl), aluminum (Al), or the like. The second impurity element can be, for example, copper (Cu). , silver (Ag), etc. can be used.

[0330] When synthesizing a donor-acceptor recombination type luminescent material using the solid-phase method, A material, a first impurity element or a compound containing the first impurity element, and a second impurity element or Compounds containing the two impurity elements were weighed out and mixed in a mortar, then heated and sintered in an electric furnace. The base material may be any of the above-mentioned base materials, and the first impurity element or The compounds containing the first impurity element include, for example, fluorine (F), chlorine (Cl), sulfide (S), and the like. Aluminum (Al2S3) or the like can be used, and the second impurity element or the second impurity Examples of compounds containing elements include copper (Cu), silver (Ag), copper sulfide (Cu2S), and sulfur. Silver oxide (AgS) can be used. The firing temperature is preferably 700 to 1500°C. If the temperature is too low, the solid-state reaction will not proceed, and if the temperature is too high, the base material will decompose. Although the firing may be performed in a powder state, it is preferable to perform firing in a pellet state. is preferred.

[0331] In addition, as impurity elements when using a solid-state reaction, a first impurity element and a second impurity element are In this case, the impurity element is diffused. This makes it easier to form a solid-state reaction, and therefore makes it possible to obtain a uniform light-emitting material. Since no extra impurity elements are added, a highly pure luminescent material can be obtained. Examples of compounds consisting of an impurity element and a second impurity element include copper chloride (CuCl), Silver chloride (AgCl) and the like can be used.

[0332] The concentration of these impurity elements is 0.01 to 10 atom% relative to the base material. The content is preferably in the range of 0.05 to 5 atom %.

[0333] In the case of a thin-film inorganic EL element, the light-emitting layer is a layer containing the above-mentioned light-emitting material, and is formed by a resistance heating deposition method. , vacuum deposition methods such as electron beam deposition (EB deposition), and physical vapor deposition methods such as sputtering. Chemical vapor deposition (CCVD) such as PVD, metal organic CVD, and hydride transport low pressure CVD. The thin film can be formed by using a method such as vapor deposition (VD), atomic epitaxy (ALE), or the like.

[0334] FIG. 46(A) to (C) show examples of thin-film inorganic EL elements that can be used as light-emitting elements. 46A to 46C, a light-emitting element includes a first electrode 4601, a light-emitting layer 4602 includes a second electrode 4603 .

[0335] The light emitting element shown in FIG. 46(B) and FIG. 46(C) is a light emitting element having an electrode and a light emitting element of the light emitting element shown in FIG. 46(A). The light-emitting element shown in FIG. 46(B) has a structure in which an insulating layer is provided between the first electrode 4 The light-emitting element shown in FIG. 46(C) has an insulating layer 4604 between the light-emitting layer 4601 and the light-emitting layer 4602. An insulating layer 4604a is provided between the first electrode 4601 and the light-emitting layer 4602, and a second electrode 460 The insulating layer 4604b is disposed between the light emitting layer 4603 and the insulating layer 4604b. The light-emitting layer may be disposed between only one of the pair of electrodes sandwiching the light-emitting layer, or between both electrodes. The insulating layer may be a single layer or a laminate of multiple layers.

[0336] In FIG. 46B, an insulating layer 4604 is provided so as to be in contact with a first electrode 4601. However, the order of the insulating layer and the light-emitting layer is reversed, and the insulating layer 460 is placed in contact with the second electrode 4603. 4 may be provided.

[0337] In the case of dispersion-type inorganic EL elements, particulate light-emitting material is dispersed in a binder to form a film-like light-emitting layer. If the method for preparing the luminescent material does not produce particles of the desired size, The binder is a material that disperses the granular light-emitting material. The luminescent material is a binder that fixes the luminescent layer in a fixed state and maintains its shape as a luminescent layer. The particles are uniformly dispersed and fixed in the light-emitting layer by the datum.

[0338] In the case of a dispersion type inorganic EL element, the method of forming the light-emitting layer is a droplet ejection method that can selectively form the light-emitting layer. Coating methods such as printing, printing (screen printing, offset printing, etc.), and spin coating Alternatively, a dipping method, a dispenser method, or the like may be used. The film thickness is not particularly limited. However, the thickness is preferably in the range of 10 to 1000 nm. In the light-emitting layer containing the above, the ratio of the light-emitting material is preferably 50 wt % or more and 80 wt % or less.

[0339] FIG. 47(A) to (C) show one example of a dispersion-type inorganic EL element that can be used as a light-emitting element. The light-emitting element in FIG. 47A includes a first electrode 4601, a light-emitting layer 4702, a third electrode 4703, and a fourth electrode 4704. The light-emitting layer 4702 has a laminated structure of two electrodes 4603 and a light-emitting layer 4702 held by a binder. The optical material 4710 is included.

[0340] The binder that can be used in this embodiment is an organic material having insulating properties or an inorganic material. Alternatively, a mixed material of an organic material and an inorganic material may be used. As for organic materials, polymers with relatively high dielectric constants, such as cyanoethyl cellulose resins, are used. -, polyethylene, polypropylene, polystyrene resin, silicone resin, epoxy Resins such as vinylidene fluoride can be used. Aromatic polyamides, polyamides, etc. Heat-resistant polymers such as polybenzimidazole, Alternatively, a siloxane resin may be used. Note that the siloxane resin is a resin containing a Si-O-Si bond. Siloxane is a resin that contains silicon (Si) and oxygen (O) bonds. and an organic group (e.g., an alkyl group, an aryl group) containing at least hydrogen as a substituent. In addition, a fluoro group may be used as a substituent. Alternatively, an organic group containing at least hydrogen and a fluoro group may be used. , polyvinyl alcohol, polyvinyl butyral and other vinyl resins, phenolic resins, Volac resin, acrylic resin, melamine resin, urethane resin, oxazole resin (polybe Resin materials such as barium titanate ( Fine particles with high dielectric constant such as BaTiO3 and strontium titanate (SrTiO3) are used. The dielectric constant can be adjusted by mixing the materials at different temperatures.

[0341] The inorganic material contained in the binder is silicon oxide (SiO x ), silicon nitride (Si N x ), silicon containing oxygen and nitrogen, aluminum nitride (AlN), aluminium containing oxygen and nitrogen Aluminum or aluminum oxide (Al2O3), titanium oxide (TiO2), BaTi O3, SrTiO3, lead titanate (PbTiO3), potassium niobate (KNbO3), Lead niobate (PbNbO3), tantalum oxide (Ta2O5), barium tantalate (Ba Ta2O6), lithium tantalate (LiTaO3), yttrium oxide (Y2O3), Select from materials including zirconium oxide (ZrO2), zinc sulfide (ZnS) and other inorganic materials. It can be made of materials that are widely used. By adding inorganic materials with high dielectric constants to organic materials (additives), By increasing the dielectric constant of the light-emitting layer made of the light-emitting material and the binder, It can be made easier.

[0342] In the manufacturing process, the light-emitting material is dispersed in a solution containing a binder. The solvent of the binder-containing solution that can be used is a solvent that dissolves the binder material and forms the light-emitting layer. It is possible to prepare a solution with a viscosity suitable for the formation method (various wet processes) and the desired film thickness. Such a solvent may be appropriately selected. An organic solvent or the like may be used. For example, When using siloxane resin, propylene glycol monomethyl ether, propylene Glycol monomethyl ether acetate (PGMEA), 3-methoxy-3 Methyl-1-butanol (also called MMB) and the like can be used.

[0343] The light emitting element shown in FIG. 47(B) and FIG. 47(C) is a light emitting element having an electrode and a light emitting element of the light emitting element shown in FIG. 47(A). The light-emitting element shown in FIG. 47B has a structure in which an insulating layer is provided between the first electrode 460 and the second electrode 461. The light-emitting element shown in FIG. 47(C) has an insulating layer 4604 between the first and light-emitting layers 4702. An insulating layer 4604a is provided between the first electrode 4601 and the light-emitting layer 4702, and an insulating layer 4604b is provided between the second electrode 4603 and the light-emitting layer 4702. The insulating layer 4604b is disposed between the light emitting layer 4702 and the insulating layer 4604b. The light-emitting layer may be disposed between only one of the pair of electrodes and the light-emitting layer, or between both electrodes. The insulating layer may be a single layer or a laminate of multiple layers.

[0344] In FIG. 47B, an insulating layer 4604 is provided so as to be in contact with a first electrode 4601. However, the order of the insulating layer and the light-emitting layer is reversed, and the insulating layer 460 is placed in contact with the second electrode 4603. 4 may be provided.

[0345] The insulating layers 4604, 4604a, 4604b in FIG. 46 and FIG. 47 are not particularly limited. However, it is preferable that the insulating film has high insulation resistance and is dense. Furthermore, the dielectric constant For example, silicon oxide (SiO2), yttrium oxide (YO 3), titanium oxide (TiO2), aluminum oxide (Al2O3), hafnium oxide (H fO2), Tantalum oxide (Ta2O5), Barium titanate (BaTiO3), Titanium oxide Strontium (SrTiO3), lead titanate (PbTiO3), silicon nitride (Si3 N4), zirconium oxide (ZrO2), etc., or a mixture of these or a laminated film of two or more types of these These insulating films can be formed by sputtering, vapor deposition, CVD, etc. The insulating layer may be formed by dispersing particles of these insulating materials in a binder. The binder material may be formed using the same material and method as the binder contained in the light-emitting layer. The thickness of the film is not particularly limited, but is preferably in the range of 10 to 1000 nm. .

[0346] Note that the first electrode 4601 and the second electrode 4603 may be formed of a metal, an alloy, a conductive compound, or For example, the pixel electrode described in the seventh embodiment may be used. The materials used for the electrode 1801 and the counter electrode 1802 can be appropriately selected and used.

[0347] Note that the light-emitting element shown in this embodiment mode has a light-emitting layer sandwiched between a pair of electrodes, i.e., a first Light emission is obtained by applying a voltage between the first electrode 4601 and the second electrode 4603 .

[0348] The inorganic EL element obtained in the above manner is used as a light-emitting element in the seventh embodiment. It can also be freely combined with other embodiments.

[0349] (Embodiment 9) In this embodiment mode, one mode of a display device of the present invention will be described with reference to FIG.

[0350] FIG. 25(a) is a top view showing the display device, and FIG. 25(b) is a cross-sectional view taken along line A-A' in FIG. 25(a). The display device is a plan view (a cross-sectional view taken along the line A-A'). A signal line driver circuit 2501, a pixel portion 2502, and a first scanning line driver circuit 250 3, and a second scanning line driver circuit 2506. Further, a sealing substrate 2504, a sealant 25 05, and the inside of the display device surrounded by these forms a space 2507.

[0351] The wiring 2508 is connected to the first scanning line driver circuit 2503 and the second scanning line driver circuit 2506. and a wiring for transmitting a signal input to the signal line driver circuit 2501, Video signals, clocks from the child FPC (flexible printed circuit) 2509 It receives the signal, start signal, etc. The IC chip is located on the connection between the FPC2509 and the display device. (semiconductor chips on which memory circuits, buffer circuits, etc. are formed) 2518 and 2519 The board is mounted using COG (Chip On Glass) and other methods. Although not shown in the figure, this FPC has a printed wiring board (PWB) attached. The display device of the present invention is not only the display device itself, but also the FPC or PWB attached thereto. This also includes devices with IC chips etc. do.

[0352] The cross-sectional structure will be described with reference to FIG. and its peripheral driving circuits (first scanning line driving circuit 2503, second scanning line driving circuit 2506, In this example, the signal line driver circuit 2501 and 2, a pixel portion 2502 is shown.

[0353] The signal line driver circuit 2501 includes N-channel transistors 2520 and 2521. Of course, P-channel transistors and CMOS circuits can be constructed using not only transistors of the same conductivity type but also P-channel transistors. In this embodiment, a display panel in which a peripheral driving circuit is integrally formed on a substrate may be used. However, this is not necessary, and all or part of the peripheral driving circuitry may be implemented as an IC chip. It may be formed on a chip or the like and mounted on COG or the like.

[0354] The pixel portion 2502 uses the pixel described in any of the embodiments 1 to 6. 5(b) shows a transistor 2511 functioning as a switch and a current supplying element A transistor 2512 for controlling the value and a light-emitting element 2528 are shown. A first electrode of the transistor 2512 is connected to a pixel electrode 2513 of the light-emitting element 2528 . In addition, an insulator 2514 is formed to cover the end of the pixel electrode 2513. The border 2514 is formed by using a positive type photosensitive acrylic resin film.

[0355] In order to improve the coverage, the upper and lower ends of the insulator 2514 are bent. For example, the material of the insulator 2514 is a positive type. When photosensitive acrylic is used, the radius of curvature (0.2 μm to 3 mm) is applied only to the upper end of the insulator 2514. It is preferable that the insulating material 2514 has a curved surface having a thickness of 1 μm. Negative type that becomes insoluble in etchant when exposed to light, or soluble in etchant when exposed to light Any positive type photoresist having a good photoresistivity can be used.

[0356] In addition, a layer 2516 containing a light-emitting material and a counter electrode 2517 are formed on the pixel electrode 2513. If at least a light-emitting layer is provided in the layer 2516 containing a light-emitting material, The other layers are not particularly limited and can be appropriately selected.

[0357] Furthermore, the sealing substrate 2504 and the substrate 2510 are bonded together using a sealing material 2505. As a result, a space 2 surrounded by the substrate 2510, the sealing substrate 2504, and the sealant 2505 is formed. The space 2507 is provided with a light emitting element 2528. In addition to being filled with active gas (nitrogen, argon, etc.), it is also possible to fill it with sealing material 2505. This also includes the composition of the

[0358] It is preferable to use an epoxy resin for the sealing material 2505. It is desirable to use a material that is as impermeable to moisture and oxygen as possible. The materials used for this include glass and quartz substrates, as well as FRP (Fiberglass-R reinforced plastics), PVF (polyvinyl fluoride), polyester A plastic substrate made of, for example, polyester or acrylic can be used.

[0359] The pixel portion 2502 is operated using the pixel described in any of the embodiments 1 to 6. Alternatively, the variation in luminance over time in the pixel can be suppressed, and the duty In the present invention, the potential of the counter electrode is set to Since it operates at a constant voltage, it is possible to reduce power consumption.

[0360] As shown in FIG. 25, a signal line driver circuit 2501, a pixel portion 2502, a first scanning line driver circuit By forming the second scanning line driver circuit 2503 and the second scanning line driver circuit 2506 in one body, the cost of the display device can be reduced. In this case, the signal line driver circuit 2501, the pixel portion 2502, the first Transistors used in the first scanning line driver circuit 2503 and the second scanning line driver circuit 2506 By making the transistors of the same conductivity type, the manufacturing process can be simplified, leading to further cost reduction. can be done.

[0361] In the manner described above, the display device of the present invention can be obtained. Note that the above-described configuration is only an example. However, the configuration of the display device of the present invention is not limited to this.

[0362] As shown in FIG. 26, the display device is configured as follows: a signal line driver circuit 2601 is an IC chip. It is also possible to form the semiconductor device on a chip and mount it on the display device using COG or the like. 2600, a pixel portion 2602, a first scanning line driver circuit 2603, a second scanning Line driver circuit 2604, FPC 2605, IC chip 2606, IC chip 2607, sealing The substrate 2608 and the sealant 2609 correspond to the substrate 2510 and the pixel portion in FIG. 2502, a first scanning line driver circuit 2503, a second scanning line driver circuit 2506, and an FPC 25 09, IC chip 2518, IC chip 2519, sealing substrate 2504, sealing material 2505 is equivalent to.

[0363] In other words, only the signal line driver circuit, which requires high-speed operation, is made of CMOS or the like. The IC chip is formed on a semiconductor such as a silicon wafer to reduce power consumption. By using a single chip, it is possible to achieve higher speed operation and lower power consumption.

[0364] The first scanning line driver circuit 2603 and the second scanning line driver circuit 2604 are connected to the pixel portion 260. By forming the first scanning line driving circuit 26 integrally with the first scanning line driving circuit 26, the cost can be reduced. 03, the second scanning line driver circuit 2604 and the pixel portion 2602 are made of transistors of the same conductivity type. By configuring the first scanning line driver circuit 2603, further cost reduction can be achieved. By using a boot trap circuit in the second scanning line driver circuit 2604, the output potential In addition, the first scanning line driver circuit 2603 and The semiconductor layer of the transistors constituting the second scanning line driver circuit 2604 is made of amorphous silicon. When a capacitor is used, the threshold voltage fluctuates due to degradation, so this function is used to correct this. It is preferable that

[0365] Note that the pixel portion 2602 is operated using any of the pixels described in any of the embodiments 1 to 6. It is possible to suppress the variation in luminance between pixels or in pixels over time, and further In the present invention, a high quality display device with a high efficiency can be obtained. It is possible to reduce power consumption by operating at a constant potential. An IC in which a functional circuit (memory or buffer) is formed at the connection between 05 and the substrate 2600 By mounting the chip, the board area can be utilized effectively.

[0366] In addition, the signal line driver circuit 2501, the first scanning line driver circuit 2503, and A signal line driver circuit 2611 corresponding to the second scanning line driver circuit 2506, a first scanning line driver circuit 2613 and the second scanning line driver circuit 2614 are mounted on an IC chip as shown in FIG. It is also possible to form the display panel on a substrate and mount it on the display panel using COG or the like. A substrate 2610, a pixel section 2612, an FPC 2615, an IC chip 2616, and an IC chip The substrate 2617, the sealing substrate 2618, and the sealant 2619 are the same as those in FIG. 2510, pixel unit 2502, FPC 2509, IC chip 2518, IC chip 2519 , a sealing substrate 2504 , and a sealant 2505 .

[0367] In addition, a non-crystalline semiconductor film, for example, an amorphous semiconductor film, is used as the semiconductor layer of the transistor in the pixel portion 2612. The use of fast silicon (a-Si:H) can reduce costs. Furthermore, it will be possible to manufacture large-sized display panels.

[0368] In addition, a first scanning line driving circuit, a second scanning line driving circuit and a signal line driving circuit are arranged in the row and column directions of the pixels. For example, as shown in FIG. 27(a), a signal line driver circuit is not required. The peripheral driver circuit 2701 thus constructed corresponds to the first scanning line driver circuit 2613 and the second scanning line driver circuit 2614 shown in FIG. The second scanning line driver circuit 2614 and the second signal line driver circuit 2611 may be provided. In addition, the substrate 2700, the pixel section 2702, the FPC 2704, and the IC The chip 2705, the IC chip 2706, the sealing substrate 2707, and the sealant 2708 are The substrate 2510 in FIG. 25(a), the pixel section 2502, the FPC 2509, the IC chip 2518, This corresponds to the IC chip 2519 , the sealing substrate 2504 , and the sealant 2505 .

[0369] FIG. 27(b) is a schematic diagram for explaining the wiring connections of the display device of FIG. 27(a). In addition, in FIG. 27(b), a substrate 2710, a peripheral driving circuit 2711, a pixel section 2712, an FP C2713 and FPC2714 are shown.

[0370] FPC2713 and FPC2714 are connected to the peripheral driver circuit 2711 for external signals and power supply. The output from the peripheral driver circuit 2711 is input to the pixel portion 2712. The signals are input to wiring in the row and column directions connected to the pixels.

[0371] In addition, when a white light emitting element is used as the light emitting element, a color filter is provided on the sealing substrate. By doing so, a full color display can be realized. The present invention can be applied to such a display device. Fig. 28 shows an example of a partial cross-sectional view of a pixel portion.

[0372] As shown in FIG. 28, a base film 2802 is formed on a substrate 2800, and a light-emitting element is formed thereon. A transistor 2801 is formed to control the current value supplied to the A pixel electrode 2803 is formed in contact with the first electrode, and a layer 2804 containing a light-emitting material is formed thereon. A counter electrode 2805 is formed.

[0373] A layer 2804 containing a light-emitting material is sandwiched between the pixel electrode 2803 and the counter electrode 2805. The part that is connected to the light emitting element is the light emitting element. In FIG. 28, it is assumed that the light emitting element emits white light. The upper part of the light-emitting element is fitted with a red color filter 2806R and a green color filter 2806G and blue color filter 2806B are provided to perform full color display. In addition, a black matrix is ​​used to separate these color filters. (also called BM) 2807 is provided.

[0374] The display device of this embodiment can be any of the display devices described in the seventh and eighth embodiments as well as the display devices described in the first to sixth embodiments. The display device may be appropriately combined with the above-mentioned configuration. The present invention can also be applied to display devices having other configurations.

[0375] (Embodiment 10) The display device of the present invention can be applied to various electronic devices. The display unit can be applied to electronic devices such as video cameras and digital cameras. Cameras, goggle-type displays, navigation systems, audio playback devices (car Audio, audio components, computers, game devices, mobile information terminals (mobile Computers, mobile phones, portable game consoles, electronic books, etc.), image reproduction with recording media Devices (specifically, recording media such as Digital Versatile Discs (DVDs) Examples of such devices include a device that can regenerate the body and display an image of it.

[0376] FIG. 33A shows a display, which includes a housing 3301, a support 3302, and a display unit 3303. , a speaker section 3304, a video input terminal 3305, etc.

[0377] Note that the pixel described in any of the embodiments 1 to 6 is used for the display portion 3303. By this, it is possible to suppress the variation in luminance between pixels or over time in a pixel, Furthermore, a display having a high quality display portion with a high duty ratio can be obtained. In addition, the present invention can reduce power consumption by maintaining the potential of the opposing electrode constant during operation. It is possible. The display is for personal computers and television broadcast reception. This includes all display devices for displaying information, such as for displaying advertisements.

[0378] In recent years, there has been a growing need for larger displays. As the mold becomes more complex, the price rise becomes a problem. Therefore, we are trying to reduce manufacturing costs and The challenge is to keep the price as low as possible while still providing high-quality products.

[0379] The pixels of the present invention can be manufactured using transistors of the same conductivity type, thereby reducing the number of manufacturing steps. This allows for reduced manufacturing costs. By using a non-crystalline semiconductor film, such as amorphous silicon (a-Si:H), This simplifies the process and further reduces costs. is formed on an IC chip and mounted on the display panel using COG (Chip On Glass) etc. In addition, a signal line driver circuit with a high operating speed is formed on an IC chip, and a signal line driver circuit with a relatively high operating speed is formed on the IC chip. The low-speed scanning line driver circuit is a circuit that is composed of transistors of the same conductivity type as the pixel section. It may be integrally formed.

[0380] FIG. 33B shows a camera, which includes a main body 3311, a display unit 3312, an image receiving unit 3313, and an operation unit. Includes a key 3314, an external connection port 3315, a shutter 3316, etc.

[0381] Note that the pixel described in any of the embodiments 1 to 6 is used for the display portion 3312. By this, it is possible to suppress the variation in luminance between pixels or over time in a pixel, Furthermore, a camera having a high-quality display with a high duty ratio can be obtained. In the present invention, the electric potential of the counter electrode is kept constant during operation, so that power consumption can be reduced. be.

[0382] In recent years, competition in production has intensified due to the increasing performance of digital cameras and other devices. It is important to keep high performance at a low price.

[0383] The pixels of the present invention can be manufactured using transistors of the same conductivity type, thereby reducing the number of manufacturing steps. This allows for reduced manufacturing costs. By using a non-crystalline semiconductor film, such as amorphous silicon (a-Si:H), This simplifies the process and further reduces costs. It is recommended to form the display on an IC chip and mount it on the display panel using COG or similar. The signal line driver circuit, which has a relatively low operating speed, is formed on the IC chip, and the scanning line driver circuit, which has a relatively low operating speed, is formed on the pixel The second portion may be integrally formed with a circuit having transistors of the same conductivity type.

[0384] FIG. 33C shows a computer, which includes a main body 3321, a housing 3322, a display unit 3323, Including a keyboard 3324, an external connection port 3325, a pointing device 3326, etc. Note that the pixels described in any of the embodiments 1 to 6 are used for the display portion 3323. The invention makes it possible to suppress luminance variations between pixels or over time within a pixel. Furthermore, a computer having a high-quality display with a high duty ratio can be obtained. In addition, the present invention operates with the potential of the opposing electrode kept constant, thereby reducing power consumption. In addition, the transistors constituting the pixel portion may be transistors or transistors of the same conductivity type. By using an amorphous semiconductor film for the semiconductor layer of the transistor, costs can be reduced. .

[0385] FIG. 33(D) shows a mobile computer, which includes a main body 3331, a display unit 3332, a switch The display unit 3332 includes a touch panel 3333, an operation key 3334, an infrared port 3335, etc. The pixel described in the first to sixth embodiments is used for the pixel. can suppress the luminance variation over time in the pixel, and the duty ratio is It is possible to obtain a mobile computer having a high quality display. In this case, the electric potential of the counter electrode is kept constant during operation, so power consumption can be reduced. In addition, the transistors constituting the pixel section are made of transistors of the same conductivity type or transistor semiconductors. By using an amorphous semiconductor film for the layer, costs can be reduced.

[0386] FIG. 33(E) shows a portable image reproducing device (specifically, a DVD reproducing device) equipped with a recording medium. A main body 3341, a housing 3342, a display unit A 3343, a display unit B 3344, a recording medium Includes a (DVD, etc.) reading section 3345, operation keys 3346, speaker section 3347, etc. The display unit A3343 mainly displays image information, and the display unit B3344 mainly displays text information. In addition, the display unit A3343 and the display unit B3344 can display the same as in the first embodiment. The pixels described in the above to 6 are used. This allows the suppression of uneven brightness over time, and also provides a high-quality display with a high duty ratio. In addition, in the present invention, the potential of the counter electrode is kept constant, and In addition, the transistors that make up the pixel section can be used to reduce power consumption. The transistors are of the same conductivity type as the transistors, and the semiconductor layer of the transistors is made of an amorphous semiconductor film. This will help reduce costs.

[0387] FIG. 33(F) shows a goggle-type display, which includes a main body 3351, a display unit 3352, and an articulated Note that the display portion 3352 includes the pixel portion 3353 described in any of the embodiments 1 to 6. The present invention suppresses the variation in luminance between pixels or in pixels over time. The goggle-type display has a high-quality display with a high duty ratio. In the present invention, the potential of the counter electrode is kept constant. This allows for low power consumption. By using a conductive transistor or an amorphous semiconductor film for the semiconductor layer of the transistor, Cost reduction is possible.

[0388] FIG. 33G shows a video camera, which includes a main body 3361, a display unit 3362, a housing 3363, External connection port 3364, remote control receiver 3365, image receiver 3366, battery 336 7, a voice input unit 3368, operation keys 3369, an eyepiece unit 3360, etc. The pixel 362 is the pixel described in the first to sixth embodiments. Alternatively, the variation in luminance over time in the pixel can be suppressed, and the duty In addition, the present invention provides a video camera having a high-quality display with a high image quality ratio. In addition, the electric potential of the counter electrode is kept constant during operation, so that power consumption can be reduced. The transistors constituting the pixel portion are of the same conductivity type, and the semiconductor layer of the transistor is By using an amorphous semiconductor film for the semiconductor device, costs can be reduced.

[0389] FIG. 33(H) shows a mobile phone, which includes a main body 3371, a housing 3372, a display unit 3373, and a sound unit. A voice input unit 3374, a voice output unit 3375, an operation key 3376, an external connection port 3377, The display unit 3373 includes an antenna 3378 and the like. The present invention reduces the luminance variation between pixels or over time in a pixel. A mobile phone having a high-quality display with a high duty ratio that can suppress noise and In addition, in the present invention, the potential of the counter electrode is kept constant during operation, so that the consumption It is possible to reduce power consumption. In addition, the transistors constituting the pixel section are of the same conductivity type. By using an amorphous semiconductor film for the semiconductor layer of a transistor, It is possible to achieve this.

[0390] In this way, the present invention can be applied to all kinds of electronic devices.

[0391] (Embodiment 11) In this embodiment, a configuration example of a mobile phone having a display device of the present invention in a display portion is shown. This will be explained using 34.

[0392] The display panel 3410 is removably mounted in the housing 3400. 00 can be changed in shape and dimensions as needed to match the size of the display panel 3410. The housing 3400 to which the display panel 3410 is fixed is fitted into the printed circuit board 3401. Assembled as modules.

[0393] The display panel 3410 is connected to the printed circuit board 3401 via an FPC 3411. The print board 3401 is provided with a speaker 3402, a microphone 3403, a transmitting / receiving circuit 3404, and a 404, a signal processing circuit 3405 including a CPU and a controller is formed. Such a module is combined with an input means 3406 and a battery 3407, and the housing 340 The display panel 3410 is housed in a housing 3412. The sensor is positioned so that it can be seen through the opening window.

[0394] The display panel 3410 includes a pixel section and a part of a peripheral driving circuit (a driving circuit having an operating frequency of 100 MHz). The low-numbered driving circuits are integrated on the substrate using transistors, and other peripheral driving circuits are A circuit (a driver circuit with a high operating frequency among multiple driver circuits) is formed on an IC chip, and its I The C chip may be mounted on the display panel 3410 by COG (Chip On Glass). Alternatively, the IC chip can be attached to a TAB (Tape Automated Bonding g) or a printed circuit board may be used to connect to the glass substrate. Also, all peripheral driving circuits may be It may be formed on an IC chip, and the IC chip may be mounted on the display panel using COG or the like.

[0395] Note that the pixel portion is formed using the pixel described in any one of the embodiments 1 to 6. This can suppress the variation in brightness between pixels or over time, and further reduces the duty cycle. It is possible to obtain a display panel 3410 having a high-quality display section with a high color ratio. In the present invention, the electric potential of the counter electrode is kept constant during operation, so that power consumption can be reduced. In addition, the transistors constituting the pixel portion may be transistors of the same conductivity type or transistors of different conductivity types. By using an amorphous semiconductor film for the semiconductor layer, costs can be reduced.

[0396] The configuration shown in this embodiment is an example of a mobile phone. The present invention can be applied to mobile phones of various configurations, without being limited to the above.

[0397] (Embodiment 12) In this embodiment, an EL module in which a display panel and a circuit board are combined is shown in FIG. 5 and FIG. 36.

[0398] As shown in FIG. 35, a display panel 3501 includes a pixel portion 3503, a scanning line driver circuit 3504, and a and a signal line driver circuit 3505. The circuit board 3502 includes, for example, a controller A filter circuit 3506 and a signal splitter circuit 3507 are formed on the display panel 350. 1 and the circuit board 3502 are connected by a connection wiring 3508. FPC, etc. can be used.

[0399] The display panel 3501 includes a pixel section and a part of a peripheral driving circuit (a driving circuit having an operating frequency of 100 MHz). The low-numbered driving circuits are integrated on the substrate using transistors, and other peripheral driving circuits are A circuit (a driver circuit with a high operating frequency among multiple driver circuits) is formed on an IC chip, and its I The C chip may be mounted on the display panel 3501 by COG (Chip On Glass). Alternatively, the IC chip can be attached to a TAB (Tape Automated Bonding g) or a printed circuit board may be used to connect to the glass substrate. Also, all peripheral driving circuits may be It may be formed on an IC chip, and the IC chip may be mounted on the display panel using COG or the like.

[0400] Note that the pixel portion is formed using the pixel described in any one of the embodiments 1 to 6. This can suppress the variation in brightness between pixels or over time, and further reduces the duty cycle. In the present invention, a high-quality display panel 3501 with a high contrast ratio can be obtained. It is possible to reduce power consumption by operating the device with the electrode potential kept constant. The transistors constituting the part are of the same conductivity type, and the semiconductor layer of the transistor is not bonded to By using a crystalline semiconductor film, costs can be reduced.

[0401] An EL television receiver can be completed using such an EL module. FIG. 36 is a block diagram showing the main components of an EL television receiver. The video signal is received by a video signal amplifier circuit 3602 and the audio signal is output from the video signal amplifier circuit 3602. A video signal processing circuit 3603 converts the signal into a color signal corresponding to each color of red, green, and blue, The video signal is processed by a control circuit 3506 to convert it into the input specifications of the driver circuit. The control circuit 3506 outputs signals to the scanning line side and the signal line side. In the case of digital driving, a signal dividing circuit 3507 is provided on the signal line side, and the input digital signal may be divided into m pieces and supplied.

[0402] Among the signals received by the tuner 3601, the audio signal is sent to an audio signal amplifier circuit 3604. The output is supplied to a speaker 3606 via an audio signal processing circuit 3605. The circuit 3607 receives control information for the receiving station (receiving frequency) and volume from the input unit 3608, The signal is sent to the speaker 3601 and the audio signal processing circuit 3605.

[0403] The EL module shown in FIG. 35 is mounted in the housing 3301 shown in FIG. 33(A) described in the tenth embodiment. By assembling them together, a television set can be completed.

[0404] Of course, the present invention is not limited to television receivers, and may be used with monitors of personal computers. In addition, it is also used for large-area displays such as information display boards at train stations and airports, and advertising display boards on the street. The present invention can be applied to various purposes as a display medium for products. [Explanation of symbols]

[0405] 110 Transistor 111 First Switch 112 Second Switch 113 The Third Switch 114 The Fourth Switch 115 Capacitive element 116 Light emitting element 117 Signal Line 118 1st scan line 119 Second Scan Line 120 3rd scan line 121 4th scan line 122 Power line 123 Potential supply line 124 Counter Electrode 511 First switching transistor 512 Second switching transistor 513 Third switching transistor 514 Fourth switching transistor 611 Signal Line Driver Circuit 612 Scanning line driver circuit 613 Pixel section 614 The Fourth Switch 714 The Fourth Switch 814 The Fourth Switch 911 Signal line driver circuit 912 Scanning line driver circuit 913 Pixel section 914 pixels 1113 Rectifier 1120 3rd scan line 1151 Schottky Barrier Diode 1152 PIN type diode 1153 PN type diode 1154 Transistor 1155 Transistor 1200 pixels 1218 1st scan line 1300 pixels 1319 Second Scan Line 1400 pixels 1420 3rd scan line 1500 pixels 1521 4th scan line 1615 Gate Capacitance 1640 pixel electrode 2910 Transistor 3010 Transistor 3101 Transistor 3102 Transistor 3103 The 5th Switch 3104 6th Switch 3111 First Switch 3112 Second Switch 3113 Third Switch 3114 The Fourth Switch 3115 Capacitive element 3116 Light emitting element 3117 Signal Line 3118 1st scan line 3119 Second Scan Line 3120 3rd scan line 3121 4th scan line 3122 Power line 3123 Potential supply line 3124 Counter electrode 3910 Transistor 3911 First Switch 3912 Second Switch 3913 Third Switch 3914 4th Switch 3915 Capacitive element 3916 Light emitting element 3917 Signal Line 3918 1st scan line 3919 Second Scan Line 3920 3rd scan line 3921 4th scan line 3922 Power line 3923 Potential supply line 3924 Counter electrode

Claims

1. A plurality of pixels arranged in a matrix form, At least one of the pixels is a display device including at least a first transistor to a fifth transistor and a light-emitting element, a gate of the first transistor electrically connected to a first scan line; a gate of the second transistor electrically connected to a second scan line; a gate of the third transistor electrically connected to a third scan line; a gate of the fourth transistor electrically connected to a fourth scan line; one of a source and a drain of the first transistor is electrically connected to a signal line; the other of the source and the drain of the first transistor is electrically connected to a gate of the fifth transistor through at least a channel formation region of the fourth transistor; one of a source and a drain of the fourth transistor is electrically connected to a gate of the fifth transistor; the other of the source and the drain of the fourth transistor is electrically connected to one of the source and the drain of the second transistor; one of a source and a drain of the third transistor is electrically connected to the light emitting element; the other of the source and the drain of the third transistor is electrically connected to a first wiring; the light-emitting element has a period during which it is electrically connected to a power supply line via at least the fifth transistor, a first conductive layer having a function as the power supply line; a second conductive layer having a function as the second scanning line; a third conductive layer having a region in contact with the first conductive layer and a region intersecting the second conductive layer; a fourth conductive layer having a function as the signal line; the first conductive layer is electrically connected to a semiconductor layer having a channel formation region of the fifth transistor via at least the third conductive layer; the first conductive layer has a region extending in a first direction; The fourth conductive layer has a region extending in a second direction intersecting the first direction.

2. A plurality of pixels arranged in a matrix form, At least one of the pixels is a display device including at least a first transistor to a fifth transistor and a light-emitting element, a gate of the first transistor electrically connected to a first scan line; a gate of the second transistor electrically connected to a second scan line; a gate of the third transistor electrically connected to a third scan line; a gate of the fourth transistor electrically connected to a fourth scan line; one of a source and a drain of the first transistor is electrically connected to a signal line; the other of the source and the drain of the first transistor is electrically connected to a gate of the fifth transistor through at least a channel formation region of the fourth transistor; one of a source and a drain of the fourth transistor is electrically connected to a gate of the fifth transistor; the other of the source and the drain of the fourth transistor is electrically connected to one of the source and the drain of the second transistor; one of a source and a drain of the third transistor is electrically connected to the light emitting element; the other of the source and the drain of the third transistor is electrically connected to a first wiring; the light-emitting element has a period during which it is electrically connected to a power supply line via at least the fifth transistor, a first conductive layer having a function as the power supply line; a second conductive layer having a function as the second scanning line; a third conductive layer having a region in contact with the first conductive layer and a region intersecting the second conductive layer; a fourth conductive layer having a function as the signal line; the first conductive layer is electrically connected to a semiconductor layer having a channel formation region of the fifth transistor via at least the third conductive layer; the first conductive layer has a region extending in a first direction; the fourth conductive layer has a region extending in a second direction intersecting the first direction, A display device, wherein a channel length of the fifth transistor is greater than a channel length of any of the first transistor, the second transistor, the third transistor, and the fourth transistor.

3. A plurality of pixels arranged in a matrix form, At least one of the pixels is a display device including at least a first transistor to a fifth transistor and a light-emitting element, a gate of the first transistor electrically connected to a first scan line; a gate of the second transistor electrically connected to a second scan line; a gate of the third transistor electrically connected to a third scan line; a gate of the fourth transistor electrically connected to a fourth scan line; one of a source and a drain of the first transistor is electrically connected to a signal line; the other of the source and the drain of the first transistor is electrically connected to a gate of the fifth transistor through at least a channel formation region of the fourth transistor; one of a source and a drain of the fourth transistor is electrically connected to a gate of the fifth transistor; the other of the source and the drain of the fourth transistor is electrically connected to one of the source and the drain of the second transistor; one of a source and a drain of the third transistor is electrically connected to the light emitting element; the other of the source and the drain of the third transistor is electrically connected to a first wiring; the light-emitting element has a period during which it is electrically connected to a power supply line via at least the fifth transistor, a first conductive layer having a function as the power supply line; a second conductive layer having a function as the second scanning line; a third conductive layer having a region in contact with the first conductive layer and a region intersecting the second conductive layer; a fourth conductive layer having a function as the signal line; the first conductive layer is electrically connected to a semiconductor layer having a channel formation region of the fifth transistor via at least the third conductive layer; the first conductive layer has a region extending in a first direction; the fourth conductive layer has a region extending in a second direction intersecting the first direction, The first scan line has an area extending in the first direction, the third scanning line has an area extending in the first direction, the fourth scanning line has an area extending in the first direction, The display device, wherein the first wiring has a region extending in the first direction.

4. A plurality of pixels arranged in a matrix form, At least one of the pixels is a display device including at least a first transistor to a fifth transistor and a light-emitting element, a gate of the first transistor electrically connected to a first scan line; a gate of the second transistor electrically connected to a second scan line; a gate of the third transistor electrically connected to a third scan line; a gate of the fourth transistor electrically connected to a fourth scan line; one of a source and a drain of the first transistor is electrically connected to a signal line; the other of the source and the drain of the first transistor is electrically connected to a gate of the fifth transistor through at least a channel formation region of the fourth transistor; one of a source and a drain of the fourth transistor is electrically connected to a gate of the fifth transistor; the other of the source and the drain of the fourth transistor is electrically connected to one of the source and the drain of the second transistor; one of a source and a drain of the third transistor is electrically connected to the light emitting element; the other of the source and the drain of the third transistor is electrically connected to a first wiring; the light-emitting element has a period during which it is electrically connected to a power supply line via at least the fifth transistor, a first conductive layer having a function as the power supply line; a second conductive layer having a function as the second scanning line; a third conductive layer having a region in contact with the first conductive layer and a region intersecting the second conductive layer; a fourth conductive layer having a function as the signal line; the first conductive layer is electrically connected to a semiconductor layer having a channel formation region of the fifth transistor via at least the third conductive layer; the first conductive layer has a region extending in a first direction; the fourth conductive layer has a region extending in a second direction intersecting the first direction, The first scan line has an area extending in the first direction, the third scanning line has an area extending in the first direction, the fourth scanning line has an area extending in the first direction, the first wiring has a region extending in the first direction, A display device, wherein a channel length of the fifth transistor is greater than a channel length of any of the first transistor, the second transistor, the third transistor, and the fourth transistor.

5. In any one of claims 1 to 4, the third transistor has a function of initializing a potential of a node to which one of a source and a drain of the third transistor and the light-emitting element are electrically connected in response to a potential of the first wiring.

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