JP2002221937A - Light emission device and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce crosstalk in a light emission device. SOLUTION: A TFT (TFT for discharge) for controlling the magnitude of a current which is made to flow through a power source supplying line when an EL element does not emit light is provided in each pixel in order to suppress a potential difference which is to be generated by the part of the power source supplying line from being fluctuated by a picture to be displayed. When a TFT (TFT for driving the EL element) controlling the light emission of the EL element is turned ON and the element emits light, the TFT for discharge is turned OFF and, conversely, when the TFT for driving the element is turned OFF and the element does not emits light, the TFT for discharge is turned ON. As a result, the potential difference which is to be generated by the part of the power supplying line is suppressed from being fluctuated by the picture to be displayed and the difference of the magnitude of the current flowing through the element emitting light which is generated in adjacent element each other is suppressed and the crosstalk is suppressed from being generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an EL panel in which an EL element formed on a substrate is sealed between the substrate and a cover material. In addition, E in which an IC is mounted on the EL panel
Regarding the L module. In this specification, the EL panel and the EL module are collectively referred to as a light emitting device. The invention further relates to an electronic device using the light emitting device.

[0002]

2. Description of the Related Art An EL element emits light by itself and thus has high visibility, does not require a backlight necessary for a liquid crystal display (LCD), is optimal for thinning, and has no restriction on a viewing angle. Therefore, in recent years, light emitting devices using EL
It is attracting attention as a display device replacing T and LCD.

An EL element has a layer containing an organic compound capable of obtaining luminescence (Electro Luminescence) generated by applying an electric field (hereinafter, referred to as an EL layer), an anode layer, and a cathode layer. The luminescence of the organic compound includes light emission (fluorescence) when returning from the singlet excited state to the ground state and light emission (phosphorescence) when returning from the triplet excited state to the ground state. In the light emitting device of the present invention, Either light emission may be used.

[0004] In this specification, all layers formed between an anode and a cathode are defined as EL layers. Specifically, the EL layer includes a light emitting layer, a hole injection layer, an electron injection layer, a hole transport layer,
An electron transport layer and the like are included. Basically, the EL element has an anode /
It has a structure in which a light emitting layer / cathode is laminated in order. In addition to this structure, an anode / hole injection layer / light emitting layer / cathode or anode / hole injection layer / light emitting layer / electron transport layer / cathode Etc. in some cases.

[0005] In this specification, a light emitting element formed by an anode, an EL layer and a cathode is called an EL element. In this specification, emission of an EL element is referred to as driving of the EL element.

By the way, the driving method of a light emitting device having an EL element mainly includes analog driving and digital driving. Digital driving is promising because digital video signals (digital video signals) having image information can be used as they are without converting them into analog signals in response to the digitization of broadcast radio waves. ing.

The configuration of a pixel portion of a general light emitting device driven by the time division driving method will be described below with reference to FIG.

FIG. 17 is a circuit diagram of a pixel portion of a general light emitting device. The pixel portion 9001 includes source signal lines S1 to S
x, power supply lines V1 to Vx, and gate signal lines G1 to G
y. The pixel portion 9001 includes a plurality of pixels 90
02 are formed in a matrix.

The pixel 9002 includes source signal lines S1 to Sx
, One of the power supply lines V1 to Vx, and one of the gate signal lines G1 to Gy. Pixel 9002
Is a switching TFT 9003 and an EL driving TFT 9
004 and an EL element 9006.

The gate electrode of the switching TFT 9003 is connected to any one of the gate signal lines G1 to Gy. One of a source region and a drain region of the switching TFT 9003 is connected to one of the source signal lines S1 to Sx, the other is connected to a gate electrode of the EL driving TFT 9004, and a capacitor 9005 included in each pixel.

The capacitor 9005 is a switching TF
When T9003 is in a non-selection state (off state), it is provided to hold a gate voltage (a potential difference between a gate electrode and a source region) of the EL driving TFT 9004.

The source region of the EL driving TFT 9004 is connected to one of the power supply lines V1 to Vx, and the drain region is connected to the EL element 9006. The power supply lines V1 to Vx are connected to the capacitors 9005 of each pixel.

The EL element 9006 includes an anode and a cathode, and an EL layer provided between the anode and the cathode. When the anode is connected to the drain region of the EL driving TFT 9004, the anode serves as a pixel electrode and the cathode serves as a counter electrode. Conversely, when the cathode is connected to the drain region of the EL driving TFT 9004, the cathode is a pixel electrode and the anode is a counter electrode.

A potential (counter potential) is applied to a counter electrode of the EL element 9006 by a power supply provided outside the EL panel. The power supply lines V1 to Vx are also supplied with a potential (power supply potential V) by a power supply provided outside the EL panel.
p) is given.

Next, the operation of the pixel portion 9001 shown in FIG. 17 will be described.

The gate signal line G1 is selected by the selection signal input to the gate signal line G1, and the gate signal line G1 is selected.
Switching TFT 900 with gate electrode connected to
3 are all turned on. Note that in this specification, selecting a signal line means that all TFTs whose gate electrodes are connected to the signal line are turned on.

A digital signal (hereinafter, referred to as a digital video signal) having image information input to the source signal lines S1 to Sx is turned on by a switching TFT 90.
The signal is input to the gate electrode of the EL driving TFT 9004 via the input terminal 03.

The switching of the EL driving TFT 9004 is controlled by 1 or 0 information included in the digital video signal input to the gate electrode of the EL driving TFT 9004.

When the EL driving TFT 9004 is turned off, the potentials of the power supply lines V1 to Vx change to the EL element 9006.
Is not given to the pixel electrode of the EL element 900
6 does not emit light. When the EL driving TFT 9004 is turned on, the potentials of the power supply lines V1 to Vx are supplied to the pixel electrodes of the EL element 9006,
6 emits light.

Next, the selection of the gate signal line G1 is completed.
The gate signal line G2 is selected, and the above-described operation is similarly repeated. An image is displayed by selecting all the gate signal lines G1 to Gy and performing the above operation in each pixel.

[0021]

In the above driving method, the power supply potential Vp applied to each power supply line by a power supply provided outside the EL panel is equal to the E potential of each pixel.
This is supplied to the source region of the L driving TFT 9004. Then, all the EL driving Ts connected to the same power supply line
The source region of the FT9004 is ideally supplied with the same potential Vp.

However, actually, since the power supply line itself has a resistance (wiring resistance), a potential difference occurs depending on a portion of the power supply line. The potential of the power supply line is closer to the ground potential as the position is farther from the power supply, and has a larger potential difference from the power supply potential Vp due to wiring resistance. Therefore, even if they are connected to the same power supply line, the EL driving TFT 900 depends on the connected part.
In this case, the potentials applied to the source regions 4 are different.

Further, the larger the current flowing through the power supply line, the larger the potential difference caused by the portion of the power supply line. In other words, even at the same distance from the power supply, as the current flowing through the power supply line increases, the potential difference caused by the wiring resistance increases and approaches the ground potential from the power supply potential Vp.

The magnitude of the current flowing through the power supply line changes depending on the image to be displayed. This is because the ratio of the pixels that emit light to the pixels that do not emit light varies among the plurality of pixels having the same power supply line depending on the image.

When the number of pixels that emit light according to the displayed image increases, the current flowing through the power supply line increases, and the potential difference generated by the portion of the power supply line increases. Conversely, when the number of pixels that do not emit light due to an image to be displayed increases, the current flowing through the power supply line decreases, and the potential difference caused by the portion of the power supply line decreases.

If there is a difference in the potential applied to the source region, the EL element 900
A difference also occurs in the potentials applied to the six pixel electrodes. Therefore, even if the pixel electrode is connected to the same power supply line via the EL driving TFT 9004, E is changed depending on the position of the pixel.
The magnitude of the current flowing through the L element differs, and the luminance of the light emitted from the EL element differs. Note that, in this specification, luminance refers to EL at the moment when the EL element emits light.
It means the brightness per unit area of the element.

The larger the potential difference between the power supply lines, the greater the difference in luminance between the pixels.

FIG. 18 is a diagram schematically showing the gradation of a pixel included in the pixel portion. Note that FIG. 18 illustrates a case where nine pixels are provided in the pixel portion for simplicity.

The pixel (1,1), the pixel (1,2) and the pixel (1,3) have the same power supply line V1. In other words, the pixel electrodes of the EL elements included in the pixel (1, 1), the pixel (1, 2), and the pixel (1, 3) are connected to the same power supply line V1 via the EL driving TFT.
Pixel (2, 1), pixel (2, 2) and pixel (2, 2)
3) has the same power supply line V2. Pixel (3,
1), the pixel (3, 2) and the pixel (3, 3) have the same power supply line V3.

Then, the pixel (1, 1) and the pixel (2, 1)
In addition, it is assumed that the source region of the EL driving TFT included in the pixel (3, 1) is connected to the power supply lines V1, V2, and V3 closest to the power supply.

When it is intended to display the same intermediate gradation in all the pixels, the power supply lines V1, V2, V3
Are the same. Then, as the distance from the power supply increases, the potential of the power supply line approaches the potential of the ground due to the wiring resistance. Therefore, the pixel (1, 1), the pixel (2, 1), and the pixel (3, 1) become the brightest, and the pixel (1, 3), the pixel (2, 3), and the pixel (3, 3) become the darkest. Become.

However, in this case, the difference in luminance between adjacent pixels is not so large as to be visually recognized by human eyes. Further, the difference in luminance between the pixel closest to the power supply of the power supply line and the pixel farthest from the power supply line is the largest, but the difference in luminance between pixels far from the human eyes is not noticeable.

Next, let us consider a case where the pixel (2, 2) does not emit light, and all the remaining pixels display the same intermediate gradation. Power supply line V2
Is smaller than the current flowing through each of the power supply lines V1 and V3. Therefore, the potential difference caused by the portions of the power supply lines V2 is smaller than the potential difference caused by the portions of the power supply lines V1 and V3.

As the potential difference caused by the portion of the power supply line decreases, the potential of the power supply line approaches the power supply potential Vp from the ground potential. Accordingly, the potential difference between the pixel electrode and the counter electrode of the EL element is increased, so that the current flowing through the EL element is increased and the luminance of the pixel having the power supply line is increased.

Therefore, as shown in FIG. 18A, the luminance of the pixel (2, 1) is changed to the pixel (1, 1) and the pixel (3, 1).
Brightness. Further, the luminance of the pixel (2, 3) becomes higher than the luminance of the pixel (1, 3) and the pixel (3, 3).

When viewed from a human, the difference in luminance between distant pixels is less noticeable. Therefore, the luminance of the pixel (1,1) and the pixel (3,1) and the luminance of the pixel (1,3) and the pixel (3,1)
The difference in luminance of 3) is hardly noticeable to human eyes. However, if the difference in luminance between adjacent pixels is large, the pixels are easily noticeable to human eyes and easily recognized. Therefore, the difference in luminance between the pixel (2, 1), the pixel (1, 1), and the pixel (3, 1) is easily noticeable to human eyes. Also, the difference in luminance between the pixel (2, 3) and the pixel (1, 3) and the pixel (3, 3) tends to be noticeable to human eyes.

Also, consider a case in which the pixel (2, 2) displays a gray level having the highest luminance and all the remaining pixels display an intermediate gray level. In this case, the current flowing through the power supply line V2 is larger than the current flowing through each of the power supply lines V1 and V3. Therefore, the potential difference caused by the portion of the power supply line V2 is
1. The potential difference is larger than the potential difference caused by V3.

As the potential difference caused by the portion of the power supply line increases, the potential of the power supply line approaches the ground potential from the power supply potential Vp. Therefore, the potential difference between the pixel electrode and the counter electrode of the EL element is reduced, so that the current flowing through the EL element is reduced and the luminance of the pixel including the power supply line is reduced.

Therefore, as shown in FIG. 18B, the luminance of the pixel (2, 1) is changed to the pixel (1, 1) and the pixel (3, 1).
Is lower than the brightness of. Further, the luminance of the pixel (2, 3) is lower than the luminance of the pixel (1, 3) and the pixel (3, 3).

As in the case of FIG.
Also in the case of (B), the difference in luminance between pixels that are distant from human eyes is not noticeable. Therefore, the difference between the luminance of the pixel (1, 1) and the luminance of the pixel (3, 1) and the luminance of the pixel (1, 3) and the luminance of the pixel (3, 3) are hardly noticeable to human eyes. However, if the difference in luminance between adjacent pixels is large, the pixels are easily visible to human eyes and easily recognized. Therefore, the difference in luminance between the pixel (2, 1), the pixel (1, 1), and the pixel (3, 1) is easily noticeable to human eyes. Pixel (2, 3) and pixel (1, 3)
Also, the difference in luminance between the pixels (3, 3) is easily noticeable to human eyes.

The phenomenon shown in FIGS. 18A and 18B is called crosstalk. Crosstalk becomes more prominent as the area of the pixel portion increases and the wiring resistance of the power supply line increases.

[0042] It is an object of the present invention to devise a light emitting device capable of suppressing occurrence of crosstalk.

[0043]

The present inventor has considered that in order to suppress the occurrence of crosstalk, it is important to suppress a variation in a potential difference caused by a portion of a power supply line depending on an image to be displayed. . Therefore, a TFT (discharge TFT) for controlling the amount of current flowing to the power supply line when the EL element does not emit light is provided in each pixel.

One of a source region and a drain region of the discharge TFT is connected to a power supply line, and the other is supplied with a predetermined potential (reference potential). When the potential of the counter electrode (counter potential) is higher than the potential of the power supply line (power supply potential), the reference potential is set higher than the power supply potential. Conversely, when the potential of the counter electrode (counter potential) is lower than the potential of the power supply line (power potential), the reference potential is set lower than the power supply potential.

In this specification, the term “connection” means an electrical connection.

In the present invention, the light emission of the EL element is controlled by the EL driving TFT. The switching of the EL driving TFT is controlled by the digital video signal. When the EL driving TFT is turned on, the EL element emits light, and the discharging TFT is turned off.

Conversely, the switching of the EL driving TFT is controlled by the digital video signal, and the EL driving TF
When T is turned off, the EL element does not emit light and enters a non-emission state. At this time, the discharge TFT is turned on, and the discharge TFT is turned on.
A current flows through the channel formation region of.

The current flowing in the channel forming region of the discharge TFT flows from the drain region to the source region when the discharge TFT is an n-channel type TFT. Conversely, in the case of a p-channel TFT, the current flows from the source region to the drain region.

The current flowing at this time is preferably the same as the current flowing to the EL element when the EL element emits light, but the present invention is not limited to this configuration. The current flowing in the channel forming region of the discharge TFT is:
It is sufficient that the size is small enough to suppress the occurrence of crosstalk.

According to the above configuration, it is possible to suppress a potential difference caused by a portion of the power supply line from fluctuating depending on an image to be displayed. Therefore, depending on the image to be displayed, the light emitting E which is generated between adjacent pixels.
The difference in the magnitude of the current flowing through the L element can be suppressed,
The occurrence of crosstalk can be suppressed.

Further, according to the present invention, the potential difference caused by the portion of the power supply line does not depend on the image to be displayed. Therefore, the height of the potential of the pixel electrode of the EL element can be predicted only by the position of the pixel. Therefore, based on the height of the potential of the pixel electrode calculated based on the position of the pixel, the digital video signal is corrected to adjust the period during which the EL element emits light. The same gradation can be displayed.

The configuration of the present invention will be described below.

According to the present invention, one power supply line is provided with a plurality of EL driving TFT source regions and a plurality of discharging TFTs.
The drain region of the FT is connected to the plurality of ELs.
Pixel electrodes of a plurality of EL elements are respectively connected to a drain region of the driving TFT, and the plurality of discharging TFTs are connected to each other.
Is supplied with a predetermined potential, and when the plurality of EL elements do not emit light, a current flows in the channel forming region of the plurality of discharge TFTs, and the plurality of EL elements A light emitting device is provided, wherein the plurality of discharge TFTs are off when emitting light.

According to the present invention, one power supply line has a plurality of source regions of EL driving TFTs and a plurality of discharge TFTs.
The drain region of the FT is connected to the plurality of ELs.
Pixel electrodes of a plurality of EL elements are respectively connected to a drain region of the driving TFT, and the plurality of discharging TFTs are connected to each other.
Is supplied with a predetermined potential, and when the plurality of EL elements emit light, a current flows through a channel forming region of the plurality of EL driving TFTs. Is not emitting light, a current is flowing through the channel forming regions of the plurality of discharge TFTs,
When the plurality of EL elements emit light, the plurality of discharge TFTs are turned off.

According to the present invention, a single power supply line is provided with a plurality of source regions of EL driving TFTs and a plurality of discharging TFTs.
The drain region of the FT is connected to the plurality of ELs.
Pixel electrodes of a plurality of EL elements are respectively connected to a drain region of the driving TFT, and the plurality of discharging TFTs are connected to each other.
A predetermined potential is applied to the source region of the plurality of EL elements, and when the plurality of EL elements emit light, a current flows through the channel formation region of the plurality of EL driving TFTs and the plurality of discharges When the plurality of EL elements do not emit light, a current flows through the channel forming regions of the plurality of discharging TFTs, and the channel forming regions of the plurality of EL driving TFTs are turned off. Current flowing from the source region to the drain region,
The current flowing in the channel forming regions of the plurality of discharge TFTs flows from the drain region to the source region, and the current flowing in the channel forming regions of the plurality of EL driving TFTs flows from the drain region to the source region. If
A light emitting device is provided, wherein a current flowing in a channel forming region of the plurality of discharge TFTs flows from a source region to a drain region.

According to the present invention, one power supply line is provided with a plurality of source regions of EL driving TFTs and a plurality of discharge TFTs.
The drain region of the FT is connected to the plurality of ELs.
Pixel electrodes of a plurality of EL elements are respectively connected to a drain region of the driving TFT, and the plurality of discharging TFTs are connected to each other.
A predetermined potential is applied to the source region of the plurality of EL elements, and when the plurality of EL elements emit light, a current flows through the channel formation region of the plurality of EL driving TFTs and the plurality of discharges When the plurality of EL elements do not emit light, a current flows through the channel forming regions of the plurality of discharging TFTs, and the channel forming regions of the plurality of EL driving TFTs are turned off. Current flowing from the source region to the drain region,
The current flowing in the channel forming regions of the plurality of discharge TFTs flows from the drain region to the source region, and the current flowing in the channel forming regions of the plurality of EL driving TFTs flows from the drain region to the source region. If
The current flowing in the channel forming regions of the plurality of discharge TFTs flows from the source region to the drain region, and the current flowing in the channel forming regions of the plurality of EL driving TFTs and the channel forming region of the plurality of discharge TFTs. A light-emitting device is provided, wherein the light-emitting device has the same magnitude as the current flowing in the region.

According to the present invention, one power supply line is provided with a plurality of source regions of EL driving TFTs and a plurality of discharging TFTs.
The drain region of the FT is connected to the plurality of ELs.
Pixel electrodes of a plurality of EL elements are respectively connected to a drain region of the driving TFT, and the plurality of discharging TFTs are connected to each other.
A predetermined potential is applied to the source region of the plurality of EL driving TFTs, and the gate electrodes of the plurality of EL driving TFTs and the gate electrodes of the plurality of discharging TFTs are connected to each other. When no light is emitted, a current flows in the channel forming region of the plurality of discharge TFTs, and when the plurality of EL elements emit light, the plurality of discharge TFTs are off. A light emitting device characterized by the above is provided.

According to the present invention, one power supply line has a plurality of source regions of EL driving TFTs and a plurality of discharge TFTs.
The drain region of the FT is connected to the plurality of ELs.
Pixel electrodes of a plurality of EL elements are respectively connected to a drain region of the driving TFT, and the plurality of discharging TFTs are connected to each other.
A predetermined potential is applied to the source regions of the plurality of EL driving TFTs, and the gate electrodes of the plurality of EL driving TFTs and the gate electrodes of the plurality of discharging TFTs are connected to each other. And the plurality of discharge TFTs have different polarities. When the plurality of EL elements do not emit light, a current flows through the channel forming region of the plurality of discharge TFTs, and A light emitting device is provided, wherein the plurality of discharge TFTs are off when the element emits light.

According to the present invention, a single power supply line has a plurality of source regions of EL driving TFTs and a plurality of discharge TFTs.
The drain region of the FT is connected to the plurality of ELs.
Pixel electrodes of a plurality of EL elements are respectively connected to a drain region of the driving TFT, and the plurality of discharging TFTs are connected to each other.
A predetermined potential is applied to the source region of the plurality of EL driving TFTs, and the gate electrodes of the plurality of EL driving TFTs and the gate electrodes of the plurality of discharging TFTs are connected to each other. Is emitting light, a current is flowing in the channel forming region of the plurality of EL driving TFTs, and the plurality of discharging TFTs are off, and the plurality of EL elements are not emitting light. In some cases, a light emitting device is provided in which a current flows through a channel forming region of the plurality of discharge TFTs.

According to the present invention, one power supply line is provided with a plurality of source regions of EL driving TFTs and a plurality of discharging TFTs.
The drain region of the FT is connected to the plurality of ELs.
Pixel electrodes of a plurality of EL elements are respectively connected to a drain region of the driving TFT, and the plurality of discharging TFTs are connected to each other.
A predetermined potential is applied to the source region of the plurality of EL driving TFTs, and the gate electrodes of the plurality of EL driving TFTs and the gate electrodes of the plurality of discharging TFTs are connected to each other. Is emitting light, a current is flowing in the channel forming region of the plurality of EL driving TFTs, and the plurality of discharging TFTs are off, and the plurality of EL elements are not emitting light. When current flows in the channel forming regions of the plurality of discharge TFTs and current flows in the channel forming regions of the plurality of EL driving TFTs from the source region to the drain region, The current flowing in the channel forming region of the discharge TFT flows from the drain region to the source region, and the current flowing in the channel forming region of the plurality of EL driving TFTs is If the drain region flows to the source region, the current flowing through the channel formation region of the plurality of the discharge TFT, the light emitting apparatus characterized by flowing from the source region to the drain region is provided.

According to the present invention, one power supply line has a plurality of source regions of a plurality of EL driving TFTs and a plurality of discharge TFTs.
The drain region of the FT is connected to the plurality of ELs.
Pixel electrodes of a plurality of EL elements are respectively connected to a drain region of the driving TFT, and the plurality of discharging TFTs are connected to each other.
A predetermined potential is applied to the source region of the plurality of EL driving TFTs, and the gate electrodes of the plurality of EL driving TFTs and the gate electrodes of the plurality of discharging TFTs are connected to each other. Is emitting light, a current is flowing in the channel forming region of the plurality of EL driving TFTs, and the plurality of discharging TFTs are off, and the plurality of EL elements are not emitting light. When current flows in the channel forming regions of the plurality of discharge TFTs and current flows in the channel forming regions of the plurality of EL driving TFTs from the source region to the drain region, The current flowing in the channel forming region of the discharge TFT flows from the drain region to the source region, and the current flowing in the channel forming region of the plurality of EL driving TFTs is When the current flows from the drain region to the source region, the current flowing to the channel forming region of the plurality of discharge TFTs flows from the source region to the drain region, and the current flows to the channel forming region of the plurality of EL driving TFTs. And a current flowing through the channel forming region of the plurality of discharge TFTs is the same in magnitude.

According to the present invention, a single power supply line is provided with a plurality of source regions of EL driving TFTs and a plurality of discharging TFTs.
The drain region of the FT is connected to the plurality of ELs.
Pixel electrodes of a plurality of EL elements are respectively connected to a drain region of the driving TFT, and the plurality of discharging TFTs are connected to each other.
A predetermined potential is applied to the source regions of the plurality of EL driving TFTs, and the gate electrodes of the plurality of EL driving TFTs and the gate electrodes of the plurality of discharging TFTs are connected to each other. And the plurality of discharge TFTs have different polarities. When the plurality of EL elements emit light, a current flows in a channel formation region of the plurality of EL drive TFTs, and The discharge TFT is turned off, and when the plurality of EL elements do not emit light, a current flows through a channel forming region of the plurality of discharge TFTs.

According to the present invention, a single power supply line is provided with a plurality of EL drive TFT source regions and a plurality of discharge TFTs.
The drain region of the FT is connected to the plurality of ELs.
Pixel electrodes of a plurality of EL elements are respectively connected to a drain region of the driving TFT, and the plurality of discharging TFTs are connected to each other.
A predetermined potential is applied to the source regions of the plurality of EL driving TFTs, and the gate electrodes of the plurality of EL driving TFTs and the gate electrodes of the plurality of discharging TFTs are connected to each other. And the plurality of discharge TFTs have different polarities. When the plurality of EL elements emit light, a current flows in a channel formation region of the plurality of EL drive TFTs, and Is turned off, and when the plurality of EL elements do not emit light, a current flows in the channel forming region of the plurality of discharge TFTs and the channel of the plurality of EL drive TFTs When the current flowing in the formation region flows from the source region to the drain region, the current flowing in the channel formation region of the plurality of discharge TFTs changes from the drain region to the source region. When the current flowing to the channel forming regions of the plurality of EL driving TFTs flows from the drain region to the source region, the current flowing to the channel forming regions of the plurality of discharging TFTs is changed from the source region to the drain region. There is provided a light emitting device characterized by flowing in an area.

According to the present invention, a plurality of EL driving TFT source regions and a plurality of discharging T
The drain region of the FT is connected to the plurality of ELs.
Pixel electrodes of a plurality of EL elements are respectively connected to a drain region of the driving TFT, and the plurality of discharging TFTs are connected to each other.
A predetermined potential is applied to the source regions of the plurality of EL driving TFTs, and the gate electrodes of the plurality of EL driving TFTs and the gate electrodes of the plurality of discharging TFTs are connected to each other. And the plurality of discharge TFTs have different polarities. When the plurality of EL elements emit light, a current flows in a channel formation region of the plurality of EL drive TFTs, and Is turned off, and when the plurality of EL elements do not emit light, a current flows in the channel forming region of the plurality of discharge TFTs and the channel of the plurality of EL drive TFTs When the current flowing in the formation region flows from the source region to the drain region, the current flowing in the channel formation region of the plurality of discharge TFTs changes from the drain region to the source region. When the current flowing to the channel forming regions of the plurality of EL driving TFTs flows from the drain region to the source region, the current flowing to the channel forming regions of the plurality of discharging TFTs is changed from the source region to the drain region. A light-emitting device, wherein a current flowing in a region and flowing in a channel forming region of the plurality of EL driving TFTs and a current flowing in a channel forming region of the plurality of discharging TFTs are the same. Is provided.

According to the present invention, the digital video signals are input to the gate electrodes of the plurality of EL driving TFTs and the gate electrodes of the plurality of discharge TFTs, whereby the plurality of EL driving TFTs are input.
The switching of the L driving TFT and the plurality of discharging TFTs may be controlled.

According to the present invention, the digital video signal is inputted to the gate electrodes of the plurality of EL driving TFTs and the plurality of discharge TFTs via the plurality of switching TFTs. It may be a feature.

According to the present invention, it is preferable that one of the source region or the drain region of the plurality of discharge TFTs, which is not connected to the power supply line, is connected to the plurality of switching TFTs.
May be characterized by being connected one-to-one with the gate electrode.

According to the present invention, it is preferable that one of the source region or the drain region of the plurality of discharge TFTs, which is not connected to the power supply line, is connected to the plurality of switching TFTs.
And the digital video signal is input to the gate electrodes of the corresponding plurality of discharge TFTs via the plurality of switching TFTs, respectively. Is also good.

According to the present invention, the one of the source and drain regions of the plurality of discharge TFTs, which is not connected to the power supply line, is connected to the opposing electrodes of the plurality of EL elements. May be featured.

According to the present invention, the one of the plurality of discharge TFTs, which is not connected to the power supply line among the source region or the drain region, and the plurality of switching TFTs are
May be connected to each other through the first current control element.

According to the present invention, the plurality of switching TFs
T and the plurality of discharge TFTs may have the same polarity.

According to the present invention, the one of the plurality of discharge TFTs, which is not connected to the power supply line among the source region or the drain region, and the opposing electrode of the EL element are provided with a first electrode.
The current control elements may be connected to each other.

According to the present invention, a first current control element is connected to a source region of the plurality of discharge TFTs, and a source region of the plurality of discharge TFTs is connected to the source region of the plurality of discharge TFTs via the first current control element. It may be characterized in that a predetermined potential is given.

The present invention may be characterized in that the first current control element is a resistor, a diode or a TFT.

The present invention may be characterized in that the drain regions of the plurality of discharge TFTs are connected to the power supply line via a second current control element.

In the present invention, the second current control element may be a resistor, a diode or a TFT.

According to the present invention, the power supply lines of the source regions or the drain regions of the plurality of EL driving TFTs are changed depending on the positions of the power supply lines connected to the source regions or the drain regions of the plurality of EL driving TFTs. And the plurality of Es respectively connected to the unconnected one
The light emission period of the L element may be adjusted.

The present invention may be an electronic device having the light emitting device.

[0079]

(Embodiment 1) FIG. 1 shows a configuration of a pixel of a light emitting device of the present invention. A plurality of pixels 101 are provided in a pixel portion included in the light emitting device of the present invention. The pixel 101 includes a source signal line Si (one of S1 to Sx),
A power supply line Vi (one of V1 to Vx), a gate signal line Gj (one of G1 to Gy), and a reference power line Cj (C1 to Cx)
Cy). The pixel 101 includes a switching TFT 102, an EL driving TFT 103, a discharging TFT 104, an EL element 105, and a capacitor 1
06.

EL driving TFT 103 and discharging TFT 1
04 have mutually inverted polarities. Therefore, the EL drive T
When the FT103 is an n-channel TFT, a discharging TFT
104 is a p-channel TFT. Conversely, T for EL drive
When the FT103 is a p-channel TFT, a discharging TFT
Reference numeral 104 denotes an n-channel TFT.

The gate electrode of the switching TFT 102 is connected to the gate signal line Gj. One of the source region and the drain region of the switching TFT 102 is connected to the source signal line Si, and the other is connected to the EL driving TFT 10.
3 and the gate electrode of the discharge TFT 104.

A capacitor 106 is provided between the gate electrodes of the EL driving TFT 103 and the discharging TFT 104 and the power supply line Vi. Capacitor 106
When the switching TFT 102 is in a non-selected state (off state), the EL driving TFT 103 and the discharging TF
It is provided to hold the potential of the gate electrode of T104.

The source region of the EL driving TFT 103 is connected to the power supply line Vi, and the drain region is connected to the pixel electrode of the EL element 105.

One of the source region and the drain region of the discharge TFT 104 is connected to the power supply line Vi, and the other is connected to the reference power line Cj.

The EL element 105 includes an anode and a cathode, and an EL layer provided between the anode and the cathode. When the anode is connected to the drain region of the EL driving TFT 103, the anode serves as a pixel electrode and the cathode serves as a counter electrode. Conversely, the cathode is EL
When connected to the drain region of the driving TFT 103, the cathode is a pixel electrode and the anode is a counter electrode.

A potential (counter potential) is applied to a counter electrode of the EL element 105 by a power supply provided outside the EL panel. The power supply line Vi is also provided with a potential (power supply potential) by a power supply provided outside the EL panel. The reference power supply line Cj is also supplied with a potential (reference potential) by a power supply provided outside the EL panel.

Next, the operation of the pixel 101 shown in FIG. 1 will be described. In driving the light emitting device of the present invention, a plurality of subframe periods are provided in one frame period.
The operation of each pixel in one sub-frame period can be described separately for a writing period and a display period.

First, in the writing period, the power supply line V
The power supply potential of i and the counter potential of the counter electrode are kept at the same height. More strictly, the power supply potential of the power supply line Vi and the counter potential of the counter electrode have such a potential difference that the EL element 105 does not emit light when the power supply potential is applied to the pixel electrode. In the writing period, the power supply potential of the power supply line Vi and the reference potential of the reference power supply line Cj are kept at the same height.

Then, all the gate signal lines G1 to Gy included in the pixel portion are sequentially selected by the selection signal. Further, during a period in which each gate signal line is selected, a digital video signal corresponding to each pixel is input to the source signal lines S1 to Sx. A more detailed operation of each pixel during a writing period will be described using a pixel having a source signal line Si and a gate signal line Gj as an example.

When the gate signal line Gj is selected by the selection signal input to the gate signal line Gj, the switching TFT 1 having the gate electrode connected to the gate signal line Gj.
02 are all turned on.

Then, 1 input to the source signal line Si
A digital video signal corresponding to bits is input to the gate electrodes of the EL driving TFT 103 and the discharging TFT 104 via the ON switching TFT 102.

The digital video signal for one bit has information of 1 or 0. The information of 1 or 0 included in the 1-bit digital video signal is used to generate EL.
Switching between the driving TFT 103 and the discharging TFT 104 is controlled. EL drive TFT 103 and discharge TF
Since the polarity of T104 is inverted, the discharge TFT 104 is turned off when the EL drive TFT 103 is on, and the discharge TF is turned off when the EL drive TFT 103 is off.
T104 is turned on.

When a 1-bit digital video signal is input to all the pixels, the writing period ends. Note that input of a digital video signal to a pixel in this specification means that a digital video signal is input to a gate electrode of an EL driving TFT and a discharge TFT included in the pixel.

When the writing period ends, the display period starts. In the display period, the power supply potential of the power supply line Vi and the counter potential of the counter electrode have a potential difference such that the EL element 105 emits light when the power supply potential is applied to the pixel electrode. In the display period, the power supply potential of the power supply line Vi and the reference potential of the reference power supply line Cj also have a potential difference.

The one-bit digital video signal input to the pixel during the writing period causes the EL driving TFT 1
When 03 is on and the discharge TFT 104 is off, the power supply potential of the power supply line Vi is applied to the pixel electrode of the EL element 105 via the ON EL drive TFT. As a result, the EL element 105 emits light.

On the contrary, the 1 input to the pixel during the writing period
A bit of digital video signal allows the EL drive T
When the FT 103 is off and the discharging TFT 104 is on, the power supply potential of the power supply line Vi is changed to the EL element 105.
Are not provided to the pixel electrodes of As a result, the EL element 105
Does not emit light. Then, the power supply potential of the power supply line Vi,
The potential difference between the reference power supply line Cj and the reference potential causes a discharge TFT 104 between the power supply line Vi and the reference power supply line Cj.
The current flows through. This current flows in the same direction as the current flowing in the power supply line Vi when the EL element emits light.

More preferably, the current flowing in the channel forming region of the discharge TFT 104 when the discharging TFT 104 is on is the same as the current flowing in the channel forming region of the EL driving TFT 103 when the EL element 105 emits light. It is good to be. To do so, the power supply line V
It is necessary to adjust the potential difference between the power supply potential of i and the reference potential of the reference power supply line Cj.

When the display period ends, the writing period of the next subframe period starts, and the above-described operation is performed again. However, in the writing period of the next subframe period, a digital video signal of the next bit is input to each pixel.

When all the sub-frame periods end, 1
The frame period ends.

FIG. 2 shows the timing at which n subframe periods appear in one frame period. The horizontal axis indicates time, and the vertical axis indicates the position of the gate signal line of the pixel.

Each of the n sub-frame periods has a writing period and a display period. Therefore, in one frame period, at least n write periods (Ta
1 to Tan) and n display periods (Td1 to Tdn) appear.

N writing periods (Ta1 to Tan)
And n display periods (Td1 to Tdn) correspond to each bit of the n-bit digital video signal. When displaying an image using an n-bit digital video signal,
At least n writing periods and n display periods are provided in one frame period.

A writing period Ta and a display period Td appear repeatedly during one frame period. When one frame period ends, one image is displayed.

The length of the display periods Td1 to Tdn is Td
1: Td2: ...: Tdn = 2 0: 2 1: ...: meet the 2 ^n-1. The gradation of each pixel is obtained from the sum of the lengths of all the display periods that emit light during one frame period. Therefore,
By controlling the sum of the lengths of the light-emitting display periods in one frame period, a desired gradation can be displayed.

Note that the order in which the sub-frame periods appear is not limited to the configuration shown in FIG. The order in which the subframe periods SF1 to SFn appear is not limited, and they may appear in any order.

In this embodiment mode, a structure in which all the EL elements do not emit light during the writing period has been described. However, the present invention is not limited to this structure. In the writing period, display may be performed by emitting light from the EL element.

In this case, during the writing period, the power supply potential of the power supply line Vi and the counter potential of the counter electrode have such a potential difference that the EL element 105 emits light when the power supply potential is applied to the pixel electrode. . Then, the display period Td1
The length of Tdn is Td1: Td2: ...: Tdn =
2 ⁰ : 2 ¹ : ...: 2 ^n-1 does not have to be satisfied, and instead, the length of the sub-frame periods SF1 to SFn is SF1: S
^{F2: ...: SFn = 2 0} : 2 1: ...: meet 2 ^n-1.

In the present embodiment, the power supply potential of the power supply line Vi and the reference potential of the reference power supply line Cj are kept at the same height during the writing period, but the present invention is not limited to this configuration. In the writing period, similarly to the display period, the power supply potential of the power supply line Vi and the reference potential of the reference power supply line Cj may have a potential difference.

According to the present invention, even in a pixel in which the EL element does not emit light, a current flows between the power supply line and the reference power supply line via the discharge TFT. Fluctuation depending on the displayed image can be suppressed, and the difference in the magnitude of the current flowing through the light-emitting EL element, which occurs between adjacent pixels, can be suppressed. Therefore, the difference in luminance between adjacent pixels can be reduced, and the occurrence of crosstalk can be suppressed.

(Embodiment 2) In this embodiment, FIG.
In the pixel of the light emitting device indicated by the mark, a current control element is provided between the source or drain region of the discharge TFT and the power supply line Vi, and the source or drain region of the discharge TFT is connected to the reference power supply line Vi. A configuration in which a current control element is provided also between Cj and Cj will be described.

FIG. 3 shows a configuration of a pixel according to the present embodiment.
The pixel 201 has a source signal line Si (one of S1 to Sx)
, A power supply line Vi (one of V1 to Vx), a gate signal line Gj (one of G1 to Gy), and a reference power line Cj (C
1 to Cy). The pixel 201 includes a switching TFT 202 and an EL driving TFT 203.
, A discharge TFT 204, an EL element 205, a capacitor 206, and current control elements 207a and 207b.

As in the case of FIG. 1, the EL driving TFT 2
03 and the discharge TFT 204 have opposite polarities. Therefore, the EL driving TFT 203 is an n-channel type TF
In the case of T, the discharging TFT 204 is a p-channel TFT. Conversely, the EL driving TFT 203 is a p-channel type TF
In the case of T, the discharging TFT 204 is an n-channel TFT.

The gate electrode of the switching TFT 202 is connected to the gate signal line Gj. One of a source region and a drain region of the switching TFT 202 is connected to the source signal line Si, and the other is connected to the gate electrodes of the EL driving TFT 203 and the discharging TFT 204.

A capacitor 206 is provided between the gate electrodes of the EL driving TFT 203 and the discharging TFT 204 and the power supply line Vi. Capacitor 206
When the switching TFT 202 is in a non-selected state (off state), the EL driving TFT 203 and the discharging TF
It is provided to hold the potential of the gate electrode of T204.

The source region of the EL driving TFT 203 is connected to the power supply line Vi, and the drain region is connected to the pixel electrode of the EL element 205.

In this embodiment, the discharge TFT 2
One of a source region and a drain region of the transistor 04 is connected to a power supply line Vi via a current control element 207a.
The other is connected to the reference power supply line C via the current control element 207b.
j.

The EL element 205 comprises an anode and a cathode, and an EL layer provided between the anode and the cathode. When the anode is connected to the drain region of the EL driving TFT 203, the anode serves as a pixel electrode and the cathode serves as a counter electrode. Conversely, the cathode is EL
When connected to the drain region of the driving TFT 203, the cathode is a pixel electrode and the anode is a counter electrode.

A potential (counter potential) is applied to a counter electrode of the EL element 205 by a power supply provided outside the EL panel. The power supply line Vi is also provided with a potential (power supply potential) by a power supply provided outside the EL panel. The reference power supply line Cj is also supplied with a potential (reference potential) by a power supply provided outside the EL panel.

Since the detailed operation of the pixel 201 is the same as that of the first embodiment, the description is omitted here.

The current control elements 207a and 207b are elements that can control the magnitude of the current flowing through the channel forming region of the discharge TFT 204. By providing the current control elements 207a and 207b, the discharge T
Even when the power supply potential of the power supply line Vi and the reference potential of the reference power supply line Cj are fixed when the FT 204 is on, the EL element 205 emits light when the current flowing in the channel formation region of the discharging TFT 204 is emitted. T for EL drive
The current can be made equal to the current flowing in the channel formation region of the FT 203.

In the present embodiment, the current control elements are provided on both the source region side and the drain region side of the discharge TFT 204, but the present invention is not limited to this configuration. The current control element may be provided only on the source region side of the discharge TFT 204 or may be provided only on the drain region side.
Further, two or more current control elements may be provided on the source region side of the discharge TFT 204, or two or more current control elements may be provided on the drain region side.

However, it is preferable that the source region of the discharge TFT 204 be directly connected to a wiring without providing a current control element between them, because the magnitude of the current flowing in the channel formation region of the discharge TFT 204 can be easily controlled.

According to the present invention, even in a pixel where the EL element does not emit light, a current flows between the power supply line and the reference power supply line via the discharging TFT, so that a potential difference caused by a portion of the power supply line is reduced. Fluctuation depending on the displayed image can be suppressed, and the difference in the magnitude of the current flowing through the light-emitting EL element, which occurs between adjacent pixels, can be suppressed. Therefore, the difference in luminance between adjacent pixels can be reduced, and the occurrence of crosstalk can be suppressed.

(Embodiment 3) In this embodiment, FIG.
In the pixel of the light emitting device indicated by, the configuration of the pixel when the gate signal line Gj is used instead of the reference power supply line Cj will be described.

FIG. 4 shows a configuration of a pixel according to the present embodiment.
The pixel 301 has a source signal line Si (one of S1 to Sx)
And a power supply line Vi (one of V1 to Vx) and a gate signal line Gj (one of G1 to Gy). The pixel 301 includes a switching TFT 302, an EL driving TFT 303, a discharging TFT 304, and an EL element 30.
5 and a capacitor 306.

The gate electrode of the switching TFT 302 is connected to the gate signal line Gj. One of a source region and a drain region of the switching TFT 302 is connected to the source signal line Si, and the other is connected to the gate electrodes of the EL driving TFT 303 and the discharging TFT 304.

Further, a capacitor 306 is provided between the gate electrodes of the EL driving TFT 303 and the discharging TFT 304 and the power supply line Vi. Capacitor 306
When the switching TFT 302 is in a non-selected state (off state), the EL driving TFT 303 and the discharging TF
It is provided to hold the potential of the gate electrode of T304.

Further, the source region of the EL driving TFT 303 is connected to the power supply line Vi, and the drain region is connected to the pixel electrode of the EL element 305.

In this embodiment, the discharge TFT 3
One of the source region and the drain region 04 is connected to the power supply line Vi, and the other is connected to the gate signal line Gj.

When the source region or the drain region of the discharge TFT 304 is connected to the gate signal line,
When the EL driving TFT 303 is a p-channel TFT, the potential of the gate signal line when it is not selected must be lower than the power supply potential. Conversely, the EL driving T
If the FT 303 is an n-channel TFT, the potential of the gate signal line when it is not selected must be higher than the power supply potential. Therefore, in the present embodiment, the switching TFT 302 and the discharging TFT 304 have the same polarity. The switching TFT 302, the discharging TFT 304, and the EL driving TFT 303 have opposite polarities. Therefore, when the EL driving TFT is an n-channel TFT, the switching TFT 302 and the discharging TFT are p-channel TFTs. Conversely, when the EL driving TFT is a p-channel TFT, the switching T
The FT 302 and the discharge TFT are n-channel TFTs.

The EL element 305 includes an anode and a cathode, and an EL layer provided between the anode and the cathode. When the anode is connected to the drain region of the EL driving TFT 303, the anode serves as a pixel electrode and the cathode serves as a counter electrode. Conversely, the cathode is EL
When connected to the drain region of the driving TFT 303, the cathode is a pixel electrode and the anode is a counter electrode.

A potential (counter potential) is applied to a counter electrode of the EL element 305 by a power supply provided outside the EL panel. The power supply line Vi is also provided with a potential (power supply potential) by a power supply provided outside the EL panel.

Next, the operation of the pixel 301 shown in FIG. 4 will be described. Also in the present embodiment, as in the first embodiment, a plurality of subframe periods are provided in one frame period. The operation of each pixel in one sub-frame period can be described separately for a writing period and a display period.

First, in the writing period, the power supply line V
The power supply potential of i and the counter potential of the counter electrode are kept at the same height. More precisely, the power supply potential of the power supply line Vi and the counter potential of the counter electrode have such a potential difference that the EL element 305 does not emit light when the power supply potential is applied to the pixel electrode.

In this embodiment, the potential difference between the gate signal line Gj when not selected and the power supply potential of the power supply line Vi is equal to the gate signal line Gj when selected.
Is larger than the potential difference between the power supply potential and the power supply potential of the power supply line Vi.
In the present embodiment, the power supply potential of the power supply line Vi is always constant.

Then, all the gate signal lines G1 to Gy included in the pixel portion are sequentially selected by the selection signal. Further, during a period in which each gate signal line is selected, a digital video signal corresponding to each pixel is input to the source signal lines S1 to Sx. A more detailed operation of each pixel during a writing period will be described using a pixel having a source signal line Si and a gate signal line Gj as an example.

When the gate signal line Gj is selected by the selection signal input to the gate signal line Gj, the switching TFT 3 having the gate electrode connected to the gate signal line Gj.
02 are all turned on.

[0138] Then, the 1 input to the source signal line Si is
A digital video signal for bits is input to the gate electrodes of the EL driving TFT 303 and the discharging TFT 304 via the ON switching TFT 302.

A 1-bit digital video signal has 1 or 0 information. The information of 1 or 0 included in the 1-bit digital video signal is used to generate EL.
Switching between the driving TFT 303 and the discharging TFT 304 is controlled. EL driving TFT 303 and discharging TF
Since the polarity of T304 is inverted, the discharge TFT 304 is turned off when the EL drive TFT 303 is on, and the discharge TF is turned off when the EL drive TFT 303 is off.
T304 is turned on.

When a 1-bit digital video signal is input to all the pixels, the writing period ends.

When the writing period ends, the display period starts. In the display period, the height of the counter potential of the counter electrode changes, and the power potential of the power supply line Vi and the counter potential of the counter electrode are set such that the EL element 305 emits light when the power potential is applied to the pixel electrode. It has a potential difference.

In response to the 1-bit digital video signal input to the pixel during the writing period, the EL driving TFT 3
When the reference numeral 03 is ON and the discharge TFT 304 is OFF, the power supply potential of the power supply line Vi is supplied to the pixel electrode of the EL element 305 via the ON EL driving TFT 303. As a result, the EL element 305 emits light.

Conversely, the 1 input to the pixel during the writing period
A bit of digital video signal allows the EL drive T
When the FT 303 is off and the discharge TFT 304 is on, the power supply potential of the power supply line Vi is the EL element 305
Are not provided to the pixel electrodes of As a result, the EL element 305
Does not emit light. Then, the power supply potential of the power supply line Vi,
Due to a potential difference from the reference potential of the gate signal line Gj, a current flows between the power supply line Vi and the gate signal line Gj via the channel forming region of the discharging TFT 304. This current flows in the same direction as the current flowing in the power supply line Vi when the EL element emits light.

More preferably, the current flowing in the channel forming region of the discharge TFT 304 when the discharging TFT 304 is on is the same as the current flowing in the channel forming region of the EL driving TFT 303 when the EL element 305 emits light. It is good to be.

When the display period ends, the writing period of the next subframe period starts, and the above-described operation is performed again. However, in the writing period of the next subframe period, a digital video signal of the next bit is input to each pixel.

When all the sub-frame periods end, 1
The frame period ends.

The timing at which the n sub-frame periods appear in one frame period is the same as that of the first embodiment with respect to the detailed operation of the pixel 301, and therefore the description is omitted here.

In this embodiment mode, a structure in which all the EL elements do not emit light during the writing period has been described. However, the present invention is not limited to this structure. In the writing period, display may be performed by emitting light from the EL element.

In this case, during the writing period, the power supply potential of the power supply line Vi and the counter potential of the counter electrode have such a potential difference that the EL element 305 emits light when the power supply potential is applied to the pixel electrode. . Then, the display period Td1
The length of Tdn is Td1: Td2: ...: Tdn =
2 ⁰ : 2 ¹ : ...: 2 ^n-1 does not have to be satisfied, and instead, the length of the sub-frame periods SF1 to SFn is SF1: S
^{F2: ...: SFn = 2 0} : 2 1: ...: meet 2 ^n-1.

In this embodiment, a current control element may be provided as described in the second embodiment. When the current control element is provided in the present embodiment, the discharge T
A current control element is provided between a source region or a drain region of the FT 304 and the power supply line Vi, and a discharge TFT is provided.
A current control element is provided between the source or drain region 304 and the gate signal line Gj. Further, the current control element may be provided only on the source region side of the discharge TFT 304 or may be provided only on the drain region side. Further, two or more current control elements may be provided on the source region side of the discharge TFT 304, or two or more current control elements may be provided on the drain region side.

By providing the current control element, even when the power supply potential of the power supply line Vi and the potential of the gate signal line Gj are fixed when the discharge TFT 304 is on,
When the EL element 305 emits light, the current flowing through the channel forming region of the discharge TFT 304 is used as the EL driving TFT.
The current can be made more equal to the current flowing through the channel formation region 303.

The gate signal line connected to the source or drain region of the discharge TFT 304 may be a gate signal line of another pixel. In particular, in the case of the driving method in which the EL element emits light even in the writing period, when the gate signal line Gj is selected, the potential of the preceding gate signal line G (j-1) is already constant.
It is preferable to connect the source region or the drain region of the discharge TFT 304 to the gate signal line G (j-1) in the preceding stage.

According to the present invention, even in a pixel where the EL element does not emit light, a current flows between the power supply line and the gate signal line via the discharging TFT, so that the potential difference generated by the portion of the power supply line is reduced. Fluctuation depending on the displayed image can be suppressed, and the difference in the magnitude of the current flowing through the light-emitting EL element, which occurs between adjacent pixels, can be suppressed. Therefore, the difference in luminance between adjacent pixels can be reduced, and the occurrence of crosstalk can be suppressed.

In the present embodiment, unlike the pixel shown in the first embodiment, there is no need to provide a reference power supply line, so that the yield can be increased. When light is emitted from the EL element toward the substrate, the aperture ratio is higher than that of the pixel described in Embodiment 1. When the aperture ratio increases, the luminance of the pixel increases even if the current flowing through the EL element is the same.

(Embodiment 4) In this embodiment, FIG.
In the pixel of the light emitting device indicated by, the structure of the pixel in the case where the power supply that applies the potential to the opposite electrode of the EL element and the source region or the drain region of the discharge TFT are connected without using the reference power supply line Cj Will be described.

FIG. 5 shows a configuration of a pixel according to the present embodiment.
The pixel 401 has a source signal line Si (one of S1 to Sx)
And a power supply line Vi (one of V1 to Vx) and a gate signal line Gj (one of G1 to Gy). The pixel 401 includes a switching TFT 402, an EL driving TFT 403, a discharging TFT 404, and an EL element 40.
5 and a capacitor 406.

EL driving TFT 403 and discharging TFT 4
04 have mutually inverted polarities. Therefore, the EL drive T
When the FT403 is an n-channel TFT, a discharging TFT
Reference numeral 404 denotes a p-channel TFT. Conversely, T for EL drive
When the FT403 is a p-channel TFT, a discharging TFT
Reference numeral 404 denotes an n-channel TFT.

The gate electrode of the switching TFT 402 is connected to the gate signal line Gj. One of a source region and a drain region of the switching TFT 402 is connected to the source signal line Si, and the other is connected to the gate electrodes of the EL driving TFT 403 and the discharging TFT 404.

Further, a capacitor 406 is provided between the gate electrodes of the EL driving TFT 403 and the discharging TFT 404 and the power supply line Vi. Capacitor 406
When the switching TFT 402 is in a non-selected state (off state), the EL driving TFT 403 and the discharging TF
It is provided for holding the potential of the gate electrode of T404.

The source region of the EL driving TFT 403 is connected to the power supply line Vi, and the drain region is connected to the pixel electrode of the EL element 405.

In the present embodiment, the discharge TFT 4
One of the source region and the drain region 04 is connected to a power supply line Vi, and the other is connected to a power supply (opposite power supply) 407 connected to a counter electrode of the EL element 405.

The EL element 405 includes an anode and a cathode, and an EL layer provided between the anode and the cathode. When the anode is connected to the drain region of the EL driving TFT 403, the anode serves as a pixel electrode and the cathode serves as a counter electrode. Conversely, the cathode is EL
When connected to the drain region of the driving TFT 403, the cathode serves as a pixel electrode and the anode serves as a counter electrode.

A potential (counter potential) is applied to a counter electrode of the EL element 405 by a counter power supply 407 provided outside the EL panel. Further, one of the source region and the drain region of the discharge TFT 404 connected to the opposite power supply 407 is supplied with the opposite potential.
The power supply line Vi is also supplied with a potential (power supply potential) by a power supply provided outside the EL panel.

Next, the operation of the pixel 401 shown in FIG. 5 will be described. Also in the present embodiment, as in the first embodiment, a plurality of subframe periods are provided in one frame period. The operation of each pixel in one sub-frame period can be described separately for a writing period and a display period.

First, in the writing period, the power supply line V
The power supply potential of i and the counter potential of the counter electrode are kept at the same height. More strictly, the power supply potential of the power supply line Vi and the counter potential of the counter electrode have such a potential difference that the EL element 405 does not emit light when the power supply potential is applied to the pixel electrode.

Then, all the gate signal lines G1 to Gy of the pixel portion are sequentially selected by the selection signal. Further, during a period in which each gate signal line is selected, a digital video signal corresponding to each pixel is input to the source signal lines S1 to Sx. A more detailed operation of each pixel during a writing period will be described using a pixel having a source signal line Si and a gate signal line Gj as an example.

When the gate signal line Gj is selected by the selection signal input to the gate signal line Gj, the switching TFT 4 having the gate electrode connected to the gate signal line Gj.
02 are all turned on.

Then, 1 input to the source signal line Si
A digital video signal for bits is input to the gate electrodes of the EL driving TFT 403 and the discharging TFT 404 via the ON switching TFT 402.

A 1-bit digital video signal has information of 1 or 0. The information of 1 or 0 included in the 1-bit digital video signal is used to generate EL.
Switching between the driving TFT 403 and the discharging TFT 404 is controlled. EL driving TFT 403 and discharge TF
Since the polarity of T404 is inverted, the discharge TFT 404 is turned off when the EL driving TFT 403 is on, and the discharge TF is turned off when the EL driving TFT 403 is off.
T404 is turned on.

When a 1-bit digital video signal is input to all the pixels, the writing period ends.

When the writing period ends, the display period starts. In the display period, the height of the common potential of the common electrode changes, and the power supply potential of the power supply line Vi and the common potential of the common electrode are set such that the EL element 405 emits light when the power supply potential is applied to the pixel electrode. It has a potential difference.

The 1-bit digital video signal input to the pixel during the writing period causes the EL driving TFT 4
When 03 is on and the discharge TFT 404 is off, the power supply potential of the power supply line Vi is supplied to the pixel electrode of the EL element 405 via the ON EL driving TFT. As a result, the EL element 405 emits light.

Conversely, the 1 input to the pixel during the writing period
A bit of digital video signal allows the EL drive T
When the FT 403 is off and the discharging TFT 404 is on, the power supply potential of the power supply line Vi is changed to the EL element 405.
Are not provided to the pixel electrodes of As a result, the EL element 405
Does not emit light. Then, the power supply potential of the power supply line Vi,
A current flows between the power supply line Vi and the opposite power supply via the discharge TFT 404 due to a potential difference from the opposite potential.
This current flows in the same direction as the current flowing through the power supply line Vi when the EL element 405 emits light.

More preferably, the current flowing in the channel forming region of the discharge TFT 404 when the discharging TFT 404 is on is the same as the current flowing in the channel forming region of the EL driving TFT 403 when the EL element 405 emits light. It is good to be.

When the display period ends, the writing period of the next subframe period starts, and the above-described operation is performed again. However, in the writing period of the next subframe period, a digital video signal of the next bit is input to each pixel.

When all the sub-frame periods end, 1
The frame period ends.

The timing at which the n sub-frame periods appear in one frame period is the same as that of the first embodiment with respect to the detailed operation of the pixel 401, and the description is omitted here.

[0178] In this embodiment, the structure in which all the EL elements are not caused to emit light during the writing period has been described. However, the present invention is not limited to this structure. In the writing period, display may be performed by emitting light from the EL element.

In this case, in the writing period, the power supply potential of the power supply line Vi and the counter potential of the counter electrode have such a potential difference that the EL element 405 emits light when the power supply potential is applied to the pixel electrode. . Then, the display period Td1
The length of Tdn is Td1: Td2: ...: Tdn =
2 ⁰ : 2 ¹ : ...: 2 ^n-1 does not have to be satisfied, and instead, the length of the sub-frame periods SF1 to SFn is SF1: S
^{F2: ...: SFn = 2 0} : 2 1: ...: meet 2 ^n-1.

In this embodiment, a current control element may be provided as described in the second embodiment. When the current control element is provided in the present embodiment, the discharge T
A current control element is provided between the source or drain region of the FT 404 and the power supply line Vi, and a discharge TFT is provided.
A current control element is provided between the source or drain region 404 and the counter electrode. Further, the current control element may be provided only on the source region side of the discharge TFT 404, or may be provided only on the drain region side. Further, two or more current control elements may be provided on the source region side of the discharge TFT 404, or two or more current control elements may be provided on the drain region side.

By providing the current control element, even if the power supply potential of the power supply line Vi and the opposite potential are fixed when the discharge TFT 404 is on, the discharge TFT 4
The current flowing through the channel forming region of the EL element 40
5 can be made more equal to the current flowing in the channel formation region of the EL driving TFT 403 when light is emitted.

According to the present invention, even in a pixel where the EL element does not emit light, a current flows between the power supply line and the opposite power supply via the discharging TFT, so that the potential difference caused by the portion of the power supply line is displayed. Can be suppressed by the image to be performed, and it occurred between adjacent pixels,
The difference in the magnitude of the current flowing through the light emitting EL element can be suppressed. Therefore, the difference in luminance between adjacent pixels can be reduced, and the occurrence of crosstalk can be suppressed.

In the present embodiment, unlike the pixel shown in the first embodiment, there is no need to provide a reference power supply line, so that the yield can be increased. When light is emitted from the EL element toward the substrate, the aperture ratio is higher than that of the pixel described in Embodiment 1. When the aperture ratio increases, the luminance of the pixel increases even if the current flowing through the EL element is the same.

In all the embodiments, when the anode is used as the pixel electrode and the cathode is used as the counter electrode, the p-channel TFT is more preferable as the EL driving TFT. Conversely, when the cathode is used as the pixel electrode and the anode is used as the counter electrode, the EL driving TFT is preferably an n-channel TFT.

[0185]

Embodiments of the present invention will be described below.

(Embodiment 1) In this embodiment, a case where a resistor is used as a current control element of the pixel shown in FIG. 3 will be described.

FIG. 6 shows the structure of a pixel according to this embodiment. FIG.
Are already given the same reference numerals. In this embodiment, the current control elements 207a and 207 shown in FIG.
As b, a resistor (current control resistor) is used.

The current control resistors 207a and 207b are
Switching TFT 202, EL driving TFT 203
Since the current control resistors 207a and 207b can be formed simultaneously with the discharge TFT 204, the number of steps does not increase.

The current control resistors 207a and 207
“b” can control the magnitude of the current flowing through the channel forming region of the discharge TFT 204. Therefore, by providing the current control resistors 207a and 207b,
Even when the power supply potential of the power supply line Vi and the reference potential of the reference power supply line Cj are fixed when the discharge TFT 204 is on, the EL element 205 emits light by flowing a current flowing in the channel formation region of the discharge TFT 204. Then, the current can be made more equal to the current flowing in the channel forming region of the EL driving TFT 203.

In this embodiment, the current control resistors are provided on both the source region side and the drain region side of the discharge TFT 204, but the present invention is not limited to this configuration. The current control element may be provided only on the source region side of the discharge TFT 204 or may be provided only on the drain region side. Further, two or more current control resistors may be provided on the source region side of the discharge TFT 204, and two or more current control resistors may be provided on the drain region side.

The current control resistors used in this embodiment are:
The pixel shown in FIGS. 4 and 5 can be provided as a current control element.

The current control element of the present invention is not limited to the structure shown in this embodiment. Any element that can control the magnitude of the current can be used as the current control element of the present invention. Embodiment 2 In this embodiment, a case will be described in which a diode is used as a current control element included in the pixel shown in FIG.

FIG. 7 shows the structure of a pixel according to this embodiment. FIG.
Are already given the same reference numerals. In this embodiment, the current control elements 207a and 207 shown in FIG.
As b, a diode (current control diode) is used.

Current Control Diodes 207a and 207
b is a semiconductor diode having a function of rectification that allows current to flow only in one direction. Current control diode 2
As 07a and 207b, for example, a pn junction diode using a pn junction, a pin junction diode using a pin junction, a Schottky diode using contact between a metal and a semiconductor, a MOS diode (MOS (MOS))
Element) can be used.

Current Control Diodes 207a and 207
b is connected so that the direction of the current flowing through the channel forming region of the discharge TFT 204 is set to the forward direction.

Current control diodes 207a and 207
b is a switching TFT 202, an EL driving TFT
Since it can be formed simultaneously with the TFT 203 and the discharge TFT 204, the current control diodes 207 a and 207 a
Providing 07b does not lead to an increase in the number of steps.

The current control diodes 207a and 207b can control the magnitude of the current flowing through the channel forming region of the discharge TFT 204. Therefore,
By providing the current control diodes 207a and 207b, even if the power supply potential of the power supply line Vi and the reference potential of the reference power supply line Cj are fixed when the discharge TFT 204 is on, the channel of the discharge TFT 204 is fixed. The current flowing in the formation region can be made more equal to the current flowing in the channel formation region of the EL driving TFT 203 when the EL element 205 emits light.

In this embodiment, the current controlling diodes are provided on both the source region side and the drain region side of the discharging TFT 204, but the present invention is not limited to this configuration. The current control element may be provided only on the source region side of the discharge TFT 204 or may be provided only on the drain region side. Further, two or more current control diodes may be provided on the source region side of the discharge TFT 204, and two or more current control diodes may be provided on the drain region side.

The current control diode used in this embodiment can be provided as a current control element in the pixels shown in FIGS.

In particular, when a gate signal line is used instead of the reference power supply line as shown in FIG. 4, the potential of the selected gate signal line becomes lower than the power supply potential even if the opposite potential is higher than the power supply potential. There is. Conversely, even when the opposite potential is lower than the power supply potential, the potential of the selected gate signal line may be higher than the power supply potential. In this case, the current flowing in the channel forming region of the discharge TFT flows from the source region to the drain region when the discharge TFT is an n-channel type,
When the discharge TFT is of a p-channel type, it flows from the drain region to the source region. It is effective to provide a current control diode to prevent this.

The current control element of the present invention is not limited to the configuration shown in this embodiment. Any element that can control the magnitude of the current can be used as the current control element of the present invention.

This embodiment can be implemented in combination with the structure of the first embodiment. Embodiment 3 In this embodiment, a case where a TFT is used as a current control element included in the pixel shown in FIG. 3 will be described.

FIG. 8 shows a configuration of a pixel according to this embodiment. FIG.
Are already given the same reference numerals. However, in this embodiment, the EL driving TFT 203 is a p-channel TFT and the discharging TFT 20
The case where 4 is an n-channel TFT will be described.

In this embodiment, the current control elements 207a and 207b shown in FIG.
FT). In FIG. 8, the current control TFT is p
It is a channel type TFT.

One of the source region and the drain region of the current control TFT 207a is connected to the power supply line Vi, and the other is connected to the drain region of the discharge TFT. One of a source region and a drain region of the current control TFT 207b is connected to the reference power supply line Cj,
The other is connected to the source region of the discharge TFT.

The gate electrodes of the current control elements 207a and 207b are kept at the same potential as the drain regions of the current control elements 207a and 207b. Therefore, when the discharge TFT is on, the current flowing in the channel forming region of the discharge TFT flows from the drain region to the source region when the discharge TFT is n-channel type, and flows when the discharge TFT is p-channel type. It flows from the source region to the drain region.

The current controlling TFTs 207a and 207b
Are the switching TFT 202 and the EL driving TFT 2
03 and the discharge TFT 204 can be formed at the same time, so that the current control TFTs 207a and 207b
Does not lead to an increase in the number of steps.

The current control TFTs 207a and 207a
7b can control the magnitude of the current flowing through the channel forming region of the discharge TFT 204. Therefore, by providing the current control TFTs 207a and 207b, the power supply line Vi is supplied when the discharge TFT 204 is turned on.
Current and the reference potential of the reference power supply line Cj are fixed, the current flowing through the channel forming region of the discharging TFT 204 is reduced by the E when the EL element 205 emits light.
The current can be made more equal to the current flowing in the channel forming region of the L driving TFT 203.

In this embodiment, the current control TFTs are provided on both the source region side and the drain region side of the discharge TFT 204, but the present invention is not limited to this configuration. The current control element may be provided only on the source region side of the discharge TFT 204 or may be provided only on the drain region side.
Further, two or more current control TFTs may be provided on the source region side of the discharge TFT 204, and two or more current control TFTs may be provided on the drain region side.

The current controlling TFT of this embodiment is not limited to the p-channel type TFT. FIG. 9 shows a current controlling TFT.
Shows the configuration of a pixel when is an n-channel TFT.
In FIG. 9, similarly to FIG.
The gate electrodes a and 207b are connected to the current control TFT 20.
It is kept at the same potential as the drain regions 7a and 207b.

In this embodiment, the EL driving TFT 2
Although the case where 03 is a p-channel TFT and the discharging TFT 204 is an n-channel TFT has been described, the present embodiment is not limited to this configuration. Even when the EL driving TFT 203 is an n-channel TFT and the discharging TFT 204 is a p-channel TFT, a current control TFT can be used as a current control element.

The current controlling TFT used in this embodiment
Can be provided as a current control element in the pixel shown in FIGS.

In particular, when a gate signal line is used instead of the reference power supply line as shown in FIG. 4, the potential of the selected gate signal line becomes lower than the power supply potential even if the opposite potential is higher than the power supply potential. There is. Conversely, even when the opposite potential is lower than the power supply potential, the potential of the selected gate signal line may be higher than the power supply potential. In this case, the current flowing in the channel forming region of the discharge TFT flows from the source region to the drain region when the discharge TFT is an n-channel type,
When the discharge TFT is of a p-channel type, it flows from the drain region to the source region. It is effective to provide a current controlling TFT to prevent this.

The current control element of the present invention is not limited to the configuration shown in this embodiment. Any element that can control the magnitude of the current can be used as the current control element of the present invention.

Note that this embodiment can be implemented in combination with the configuration of the first or second embodiment.

(Embodiment 4) In this embodiment, the order in which the sub-frame periods SF1 to SFn appear in driving the light emitting device of the present invention corresponding to an n-bit digital video signal will be described.

In FIG. 10, in one frame period, n writing periods (Ta1 to Tan) and n display periods (T
d1 to Tdn). The horizontal axis indicates time, and the vertical axis indicates the position of the gate signal line of the pixel. For the detailed driving method of each pixel, the embodiment mode can be referred to; therefore, the description is omitted here.

In the driving method of this embodiment, the subframe period (SFn in this embodiment) having the longest display period in one frame period is not provided at the beginning and end of one frame period. In other words, another subframe period included in the same frame period appears before and after the subframe period having the longest display period in one frame period.

With the above structure, when performing display of an intermediate gradation, display unevenness caused by adjacent display periods emitting light between adjacent frame periods can be hardly recognized by human eyes. Can be.

In this embodiment, the structure in which all the EL elements do not emit light during the writing period has been described. However, the present invention is not limited to this structure. In the writing period, display may be performed by emitting light from the EL element.

In this case, during the writing period, the power supply
The power supply potential of the supply line and the counter potential of the counter electrode
The EL element emits light when applied to the
It has a difference. Then, the display periods Td1 to Tdn are
The length is Td1: Td2: ...: Tdn = 2⁰: 2¹:…:
2^n-1Does not need to be satisfied, instead
The length of the interval SF1 to SFn is SF1: SF2: ...: SF
n = 2⁰: 2¹:…: 2 ^n-1Meet.

The configuration of this embodiment is effective when n ≧ 3. This embodiment can be implemented by freely combining with Embodiments 1 to 3.

Embodiment 5 In this embodiment, an example will be described in which the light emitting device of the present invention is driven by using a 6-bit digital video signal.

FIG. 11 shows timings at which six writing periods (Ta1 to Ta6) and six display periods (Td1 to Td6) appear in one frame period. The horizontal axis indicates time, and the vertical axis indicates the position of the gate signal line of the pixel. For the detailed driving method of each pixel, the embodiment mode can be referred to; therefore, the description is omitted here.

In the case of driving using a 6-bit digital video signal, at least six sub-frame periods SF1 to SF6 are provided in one frame period.

The subframe periods SF1 to SF6 correspond to each bit of the 6-bit digital signal. The sub-frame periods SF1 to SF6 include six writing periods (Ta1 to Ta6) and six display periods (Td1 to Td6).
d6).

The sub-frame period including the writing period Tam and the display period Tdm corresponding to the m-th (m is an arbitrary number from 1 to 6) bit is SFm. Write period T
After am, a display period corresponding to the same bit number, in this case, Tdm appears.

A single image can be displayed by repeatedly appearing the writing period Ta and the display period Td during one frame period.

The length of the display periods Td1 to Td6 is Td
1: Td2: ...: Td6 = 2 0: 2 1: ...: meet the 2 ^5.

In the driving method of the present invention, gradation is displayed by controlling the sum of the lengths of the display periods during which light is emitted during one frame period.

In this embodiment, the structure in which all the EL elements do not emit light during the writing period has been described, but the present invention is not limited to this structure. In the writing period, display may be performed by emitting light from the EL element.

In this case, in the writing period, the power supply potential of the power supply line and the counter potential of the counter electrode have such a potential difference that the EL element emits light when the power supply potential is applied to the pixel electrode. The length of the display periods Td1 to Td6 is Td1: Td2:...: Td6 = 2 ⁰ : 2 ¹ :.
²⁵ may not be satisfied, and instead, the length of the sub-frame periods SF1 to SF6 is SF1: SF2: ...: SF6
= 2 ⁰ : 2 ¹ : ...: 2 ⁵ is satisfied.

The structure of this embodiment can be implemented by freely combining with Embodiments 1 to 4.

Embodiment 6 In this embodiment, an example of a driving method different from that in FIG. 2 using an n-bit digital video signal will be described.

FIG. 12 shows that n +
The timing at which one writing period (Ta1 to Ta (n + 1)) and n display periods (Td1 to Td (n + 1)) appear is shown. The horizontal axis indicates time, and the vertical axis indicates the position of the gate signal line of the pixel. For the detailed driving method of each pixel, the embodiment mode can be referred to; therefore, the description is omitted here.

In this embodiment, n + 1 sub-frame periods SF1 to SFn + 1 are provided within one frame period corresponding to an n-bit digital video signal. The sub-frame periods SF1 to SFn + 1 have n + 1 writing periods (Ta1 to Ta (n + 1)) and n display periods (Td1 to Td (n + 1)).

The sub-frame period including the writing period Tam (m is an arbitrary number from 1 to n + 1) and the display period Tdm is SFm. After the writing period Tam, a display period corresponding to the same bit number, in this case, Tdm appears.

Subframe periods SF1 to SF (n-1)
Corresponds to each bit of the digital signal of 1 to (n-1) bits. The sub-frame periods SFn and SF (n +
1) corresponds to the n-th bit digital video signal.

In this embodiment, the sub-frame periods SFn and SF corresponding to the digital video signal of the same bit are used.
(N + 1) does not appear continuously. In other words, another subframe period is provided between the subframe periods SFn and SF (n + 1) corresponding to the digital video signal of the same bit.

[0240] One image can be displayed by the repetition of the writing period Ta and the display period Td during one frame period.

The length of the display periods Td1 to Tdn + 1 is T
d1: Td2:...: (Tdn + Td (n + 1)) =
2 ⁰ : 2 ¹ : ...: 2 ^n-1 is satisfied.

In the driving method of the present invention, gradation is displayed by controlling the sum of the lengths of the light emitting display periods in one frame period.

In the present embodiment, the display unevenness caused by the adjacent display periods being adjacent to each other during the display of the intermediate gray scale due to the above-described configuration is shown in FIGS. 2 and 10. This makes it harder for human eyes to recognize as compared with the case.

In this embodiment, the case where there are two subframe periods corresponding to the same bit has been described.
The present invention is not limited to this. Three or more subframe periods corresponding to the same bit may be provided in one frame period.

In this embodiment, a plurality of subframe periods corresponding to the most significant bit digital video signal are provided, but the present invention is not limited to this. A plurality of subframe periods corresponding to digital video signals of bits other than the most significant bit may be provided. Further, the number of bits provided with a plurality of corresponding subframe periods is not limited to one, and a configuration may be employed in which a plurality of subframe periods correspond to each of several bits.

In this embodiment, the structure in which all the EL elements do not emit light during the writing period has been described, but the present invention is not limited to this structure. In the writing period, display may be performed by emitting light from the EL element.

In this case, in the writing period, the power supply potential of the power supply line and the counter potential of the counter electrode have such a potential difference that the EL element emits light when the power supply potential is applied to the pixel electrode. Then, the display periods Td1 to Td (n
+1) is Td1: Td2: ... :( Tdn + Td
(N + 1)) = 2 ⁰ : 2 ¹ :...: 2 ^n-1 need not be satisfied. Instead, the length of the subframe periods SF1 to SFn is SF1: SF2:...: (SFn + SF (n + 1)).
= 2 ⁰ : 2 ¹ : ...: 2 ^n-1 is satisfied.

The configuration of this embodiment is effective when n ≧ 2. This embodiment can be implemented in any combination with Embodiments 1 to 5.

(Embodiment 7) In this embodiment, the TFT (switching TFT 510) of the pixel portion of the light emitting device of the present invention is used.
0, discharge TFT 5101, EL drive TFT 510
The method of manufacturing 2) will be described. Note that a driver circuit (source signal line side driver circuit,
The TFTs included in the writing gate signal line side driver circuit and the display gate signal line side driver circuit) may be simultaneously formed over the same substrate as the TFTs in the pixel portion.

First, as shown in FIG. 13 (A), oxidation is performed on a substrate 5001 made of glass such as barium borosilicate glass represented by Corning # 7059 glass or # 1737 glass, or aluminoborosilicate glass. A base film 5002 made of an insulating film such as a silicon film, a silicon nitride film, or a silicon oxynitride film is formed.
For example, a plasma CVD method SiH _4, NH _3, N ₂ silicon oxynitride film 5002a made from O 10 to 2
00 [nm] (preferably 50-100 [nm]),
Similarly, a silicon oxynitride hydride film 5002b made of SiH ₄ and N ₂ O is formed in a thickness of 50 to 200 [nm] (preferably 100 to 150 [nm]). Although the base film 5002 has a two-layer structure in this embodiment, the base film 5002 may have a single-layer structure or a structure in which two or more insulating films are stacked.

[0251] The island-shaped semiconductor layers 5004 to 5006 are formed using a crystalline semiconductor film formed by using a semiconductor film having an amorphous structure by a laser crystallization method or a known thermal crystallization method.
The thickness of the island-shaped semiconductor layers 5004 to 5006 is 25 to 8
It is formed with a thickness of 0 [nm] (preferably 30 to 60 [nm]). The material of the crystalline semiconductor film is not limited, but is preferably formed of silicon or a silicon germanium (SiGe) alloy.

In order to form a crystalline semiconductor film by a laser crystallization method, a pulse oscillation type or continuous emission type excimer laser, a YAG laser, or a YVO ₄ laser is used.
In the case of using these lasers, it is preferable to use a method in which laser light emitted from a laser oscillator is linearly condensed by an optical system and irradiated on a semiconductor film. The crystallization conditions are appropriately selected by the practitioner. When an excimer laser is used, the pulse oscillation frequency is set to 300 [Hz], and the laser energy density is set to 100 to 400 [mJ / cm ² ] (typically, 200 to 300 [mJ / cm ² ]). Also, Y
When an AG laser is used, the pulse oscillation frequency is set to 30 to 300 [kHz] using the second harmonic, and the laser energy density is set to 300 to 600 [mJ / cm ² ] (typically 350 to 500 [mJ / cm]. ² ]) Then, a laser beam condensed linearly at a width of 100 to 1000 [μm], for example, 400 [μm] is irradiated over the entire surface of the substrate, and the superposition rate (overlap rate) of the linear laser light at this time is 50. Perform as ~ 90 [%].

As a laser, a continuous wave or pulsed gas laser or solid laser can be used. Excimer lasers, Ar lasers, Kr lasers, and the like are available as gas lasers.
Laser, YVO ₄ laser, YLF laser, YAlO ₃ laser, glass laser, ruby laser, alexandrite laser, Ti: sapphire laser, and the like. As solid-state lasers, Cr, Nd, Er, Ho, Ce,
YAG, YVO doped with Co, Ti or Tm
₄ , a laser using a crystal such as YLF, YAlO ₃ or the like can also be used. The fundamental wave of the laser depends on the material to be doped, and a laser beam having a fundamental wave of about 1 μm can be obtained. Harmonics with respect to the fundamental wave can be obtained by using a nonlinear optical element.

In order to obtain a crystal having a large grain size during crystallization of an amorphous semiconductor film, a solid-state laser capable of continuous oscillation is used, and the second to fourth harmonics of a fundamental wave are applied. Is preferred. Typically, an Nd: YVO ₄ laser (fundamental wave 1
064 nm) or the third harmonic (332.
(55 nm). Specifically, laser light emitted from a continuous-wave YVO ₄ laser having an output of 10 W is converted into a harmonic by a nonlinear optical element. Also,
Put YVO ₄ crystal and nonlinear optical element in the resonator,
There is also a method of emitting harmonics. Then, the laser light is preferably shaped into a rectangular or elliptical laser beam on the irradiation surface by an optical system, and the laser light is irradiated on the object to be processed. At this time, the energy density of approximately 0.01 to 100 MW / cm ² (preferably 0.1 to 10 MW / cm ²⁾ is required. And 1
Irradiation is performed by moving the semiconductor film relatively to laser light at a speed of about 0 to 2000 cm / s.

Next, island-like semiconductor layers 5003 to 5006
Is formed to cover the gate insulating film 5007. The gate insulating film 5007 is formed by a plasma CVD method or a sputtering method.
The insulating film containing silicon is formed with a thickness of 40 to 150 [nm]. In this embodiment, a silicon oxynitride film is formed with a thickness of 120 [nm]. Needless to say, the gate insulating film is not limited to such a silicon oxynitride film, and another insulating film containing silicon may be used as a single layer or a stacked structure. For example, when a silicon oxide film is used, TEOS (Tetraethyl Orthosi
licate) and O ₂ , a reaction pressure of 40 [Pa], a substrate temperature of 300 to 400 [° C.]
Hz]) and discharge at a power density of 0.5 to 0.8 [W / cm ² ]. The silicon oxide film thus manufactured can obtain favorable characteristics as a gate insulating film by subsequent thermal annealing at 400 to 500 [° C.].

[0256] Then, a first conductive film 5008 and a second conductive film 5009 for forming a gate electrode are formed over the gate insulating film 5007. In this embodiment, the first conductive film 5008 is formed to a thickness of 50 to 100 [nm] by Ta, and the second conductive film 5009 is formed to 100 to 300 [nm] by W.
Formed to a thickness of

The Ta film is formed by a sputtering method by sputtering a Ta target with Ar. in this case,
When an appropriate amount of Xe or Kr is added to Ar, the internal stress of the Ta film can be relaxed and the film can be prevented from peeling. Also, α
The phase Ta film has a resistivity of about 20 [μΩcm] and can be used for a gate electrode, but the β phase Ta film has a resistivity of about 180 [μΩcm] and is not suitable for a gate electrode. . In order to form an α-phase Ta film, α
Tantalum nitride having a crystal structure close to the phase is 10 to 50 [n
m] and a thickness of about α m
The film a can be easily obtained.

When a W film is formed, it is formed by a sputtering method using W as a target. Alternatively, it can be formed by a thermal CVD method using tungsten hexafluoride (WF ₆ ). In any case, it is necessary to lower the resistance in order to use it as a gate electrode.
It is desirable to set it to [μΩcm] or less. The resistivity of the W film can be reduced by enlarging the crystal grains.
When there are many impurity elements such as oxygen therein, crystallization is inhibited and the resistance is increased. From this, in the case of using the sputtering method, a W target having a purity of 99.9999 [%] is used, and a W film is formed by giving sufficient consideration so as not to mix impurities from the gas phase during film formation. Resistivity 9-20
[μΩcm] can be realized.

In this embodiment, the first conductive film 500
8 was Ta, and the second conductive film 5009 was W. However, there is no particular limitation, and any of Ta, W, Ti, Mo, Al, and Cu was used.
Alternatively, it may be formed of an element selected from the above, or an alloy material or a compound material containing the element as a main component. Also,
A semiconductor film typified by a polycrystalline silicon film doped with an impurity element such as phosphorus may be used. As a desirable example of another combination other than this embodiment, a combination in which the first conductive film 5008 is formed of tantalum nitride (TaN) and the second conductive film 5009 is W, Is formed of tantalum nitride (TaN), the second conductive film 5009 is made of Al, the first conductive film 5008 is made of tantalum nitride (TaN), and the second conductive film 5009 is made of Cu. No.
(FIG. 13A)

Next, a mask 5010 made of a resist is formed, and a first etching process for forming electrodes and wirings is performed. In this embodiment, ICP (Inductively Coupled)
d Plasma: Inductively coupled plasma) etching method,
CF ₄ and Cl ₂ are mixed as an etching gas, and 500 (W) RF (13.56) is applied to the coil-type electrode at a pressure of 1 [Pa].
[MHz]) Power is supplied to generate plasma. 100 [W] RF (13.5) is also provided on the substrate side (sample stage).
6 [MHz]) Power is applied and a substantially negative self-bias voltage is applied. When CF ₄ and Cl ₂ are mixed, both the W film and the Ta film are etched to the same extent.

[0261] Under the above etching conditions, the shape of the resist mask is made appropriate, and the edges of the first conductive layer and the second conductive layer are tapered due to the effect of the bias voltage applied to the substrate side. Become. The angle of the tapered portion is 15 to 45 °. In order to perform etching without leaving a residue on the gate insulating film, the etching time may be increased by about 10 to 20%. Since the selectivity ratio of the silicon oxynitride film to the W film is 2 to 4 (typically 3), the exposed surface of the silicon oxynitride film is etched by about 20 to 50 [nm] by the over-etching process. become. Thus, by the first etching process, the first shape conductive layers 5011 to 5015 (the first conductive layer 5) including the first conductive layer and the second conductive layer are formed.
011a to 5015a and second conductive layers 5011b to 5011b
15b) is formed. At this time, the gate insulating film 5007
In the above, the region not covered with the first shape conductive layers 5011 to 5015 is etched by about 20 to 50 [nm] to form a thinned region.

Then, a first doping process is performed to perform an n-type
Is added. The doping method is
This may be performed by an ion doping method or an ion implantation method. I
The condition of the on-doping method is that the dose amount is 1 × 10¹³~ 5 × 10
¹⁴[atoms / cm^Two] And the acceleration voltage is 60 to 100
Performed as [keV]. As an impurity element imparting n-type
Group 15 elements, typically phosphorus (P) or arsenic
(As) is used, but phosphorus (P) is used here. This
In this case, the conductive layers 5012 to 5015 do not provide n-type.
It acts as a mask for the pure element and is self-aligned with the first defect.
Pure regions 5017 to 5023 are formed. The first impurity
1 × 10 in object areas 5017 to 5023 ²⁰~ 1 × 10^{twenty one}
[atoms / cm^ThreeImpurities that give n-type in the concentration range of
Substance element is added. (FIG. 13 (B))

Next, as shown in FIG. 13C, a second etching process is performed without removing the resist mask. Using CF ₄ , Cl ₂ and O _{2 as an} etching gas,
The film is selectively etched. At this time, the second shape conductive layers 5025 to 5029 are formed by the second etching process.
(First conductive layers 5025a to 5029a and second conductive layers 5025b to 5029b) are formed. At this time, in the gate insulating film 5007, the second shape conductive layer 50 is formed.
The area not covered by 25 to 5029 is another 20 to 50
A thinned region is formed by etching about [nm].

The etching reaction of the W film or the Ta film by the mixed gas of CF ₄ and Cl ₂ can be inferred from the generated radical or ion species and the vapor pressure of the reaction product.
Comparing the vapor pressures of fluorides and chlorides of W and Ta, W
WF ₆ is extremely high and other WC
l ₅ , TaF ₅ and TaCl ₅ are comparable. Therefore, C
With the mixed gas of F ₄ and Cl ₂ , both the W film and the Ta film are etched. However, when an appropriate amount of O ₂ is added to this mixed gas, CF ₄ and O ₂ react to form CO and F, and a large amount of F radicals or F ions are generated. As a result, the etching rate of the W film having a high fluoride vapor pressure increases. On the other hand, in Ta, the increase in the etching rate is relatively small even if F increases. Further, since Ta is more easily oxidized than W, the surface of Ta is oxidized by adding O ₂ .
Since the oxide of Ta does not react with fluorine or chlorine,
The etching rate of the a film decreases. Therefore, the W film and Ta
It is possible to make a difference in the etching rate with the film, and it is possible to make the etching rate of the W film larger than that of the Ta film.

Then, a second doping process is performed as shown in FIG. In this case, the dose is lower than that of the first doping process, and n is set as a condition of a high acceleration voltage.
Doping with an impurity element for giving a mold. For example, the acceleration voltage is set to 70 to 120 [keV], and 1 × 10 ¹³ [at
oms / cm ² ], and a new impurity region is formed inside the first impurity region formed in the island-shaped semiconductor layer in FIG. The doping is performed using the second shape conductive layers 5026 to 5029 as a mask for the impurity element, so that the impurity element is also added to the region below the first conductive layers 5026a to 5029a. Thus, third impurity regions 5032 to 5035 are formed. The third impurity regions 5032 to 5035
The concentration of phosphorus (P) added to the first conductive layer 502
It has a gentle concentration gradient according to the thickness of the tapered portion of 6a to 5029a. Note that the first conductive layer 5026a
In the semiconductor layer overlapping the tapered portion of 5029a to 5029a,
Although the impurity concentration is slightly reduced from the end of the tapered portion of the first conductive layers 5026a to 5029a toward the inside, the impurity concentration is substantially the same.

A third etching process is performed as shown in FIG. This is performed using a reactive ion etching method (RIE method) using CHF ₆ as an etching gas. Third
The first conductive layers 5025a to 5025a-5
029a is partially etched to form the first
The region where the conductive layer overlaps with the semiconductor layer is reduced. By the third etching treatment, the third shape conductive layer 5036 is formed.
To 5040 (first conductive layers 5036a to 5040a and second conductive layers 5036b to 5040b). At this time, in the gate insulating film 5007, a region which is not covered with the third shape conductive layers 5036 to 5040 is two more.
A region that is etched and thinned by about 0 to 50 [nm] is formed.

By the third etching process, third impurity regions 5032 to 5035 overlap with first conductive layers 5037a to 5040a in third impurity regions 5032 to 5035a.
32a to 5035a, and second impurity regions 5032b to 5035 between the first impurity region and the third impurity region.
b is formed.

Then, as shown in FIG. 14C, the first island-like semiconductor layer 5006 forming the p-channel type TFT is formed.
4th impurity region 5049-of the conductivity type opposite to the conductivity type of
5054 is formed. Using the conductive layer 5040b having the third shape as a mask for an impurity element, an impurity region is formed in a self-aligned manner. At this time, the entire surface of the island-shaped semiconductor layers 5004 and 5005 and the wiring portion 5036 forming the n-channel TFT is covered with a resist mask 5200. Each of the impurity regions 5049 to 5054 is doped with phosphorus at a different concentration, but is formed by an ion doping method using diborane (B ₂ H ₆ ), and the impurity concentration in each of the regions is 2 × 10 ²⁰ to 50 ×. 2 × 10 ²¹ [atom
s / cm ³ ].

Through the above steps, impurity regions are formed in the respective island-like semiconductor layers. Third overlapping with the island-shaped semiconductor layer
Of conductive layers 5037 to 5040 function as gate electrodes. 5036 functions as an island-shaped source signal line.

After the resist mask 5200 is removed, a step of activating the impurity elements added to the respective island-shaped semiconductor layers is performed for the purpose of controlling the conductivity type. This step is performed by a thermal annealing method using a furnace annealing furnace.
In addition, a laser annealing method or a rapid thermal annealing method (RTA method) can be applied. In the thermal annealing method, the oxygen concentration is 400 to 700 in a nitrogen atmosphere of 1 [ppm] or less, preferably 0.1 [ppm] or less.
In this embodiment, the heat treatment is performed at 500 ° C. for 4 hours.
However, when the wiring material used for the third shape conductive layers 5036 to 5040 is weak to heat, activation is performed after forming an interlayer insulating film (mainly containing silicon) to protect the wiring and the like. It is preferred to do so.

When the laser annealing method is used, the laser used for crystallization can be used. In the case of activation, the moving speed is the same as the crystallization, and 0.01
About 100 MW / cm ² (preferably 0.01 to 10 MW / cm ²⁾
MW / cm ² ) of energy density is required.

Further, a heat treatment is performed at 300 to 450 ° C. for 1 to 12 hours in an atmosphere containing 3 to 100% of hydrogen to hydrogenate the island-like semiconductor layer. In this step, dangling bonds in the semiconductor layer are terminated by thermally excited hydrogen. As another means of hydrogenation, plasma hydrogenation (using hydrogen excited by plasma) may be performed.

Next, as shown in FIG.
Of the interlayer insulating film 5055 from the silicon oxynitride film to 100
It is formed with a thickness of about 200 [nm]. After forming a second interlayer insulating film 5056 made of an organic insulating material thereon,
First interlayer insulating film 5055, second interlayer insulating film 505
6, a contact hole is formed in the gate insulating film 5007, and the connection wirings 5058 to 5063 are formed by patterning. Then, the pixel electrode 5064 in contact with the connection wiring (drain wiring) 5063 is formed by patterning. Note that the connection wiring includes a source wiring and a drain wiring. The source wiring is a wiring connected to the source region of the active layer, and the drain wiring is a wiring connected to the drain region.

As the second interlayer insulating film 5056, a film made of an organic resin is used, and as the organic resin, polyimide, polyamide, acrylic, BCB (benzocyclobutene), or the like can be used. In particular, since the second interlayer insulating film 5056 has a strong meaning of flattening, acrylic having excellent flatness is preferable. In this embodiment, an acrylic film is formed with a thickness that can sufficiently flatten a step formed by a TFT. Preferably, it is 1-5 [μm] (more preferably, 2-4 [μm]).

The contact holes are formed by dry etching or wet etching to form n-type impurity regions 5017 to 5021 or p-type impurity regions 504.
9, contact hole reaching 5054, wiring 5036
, A contact hole (not shown) reaching the power supply line, and a contact hole (not shown) reaching the gate electrode.

As the connection wirings 5058 to 5063, a laminated film having a three-layer structure in which a Ti film is 100 [nm], an aluminum film containing Ti is 300 [nm], and a Ti film 150 [nm] is continuously formed by sputtering. Is used by patterning it into a desired shape. Of course, another conductive film may be used.

In this embodiment, an ITO film having a thickness of 110 [nm] was formed as the pixel electrode 5064, and patterning was performed. A contact is made by arranging the pixel electrode 5064 so as to be in contact with and overlap with the connection wiring 5063. Alternatively, a transparent conductive film in which 2 to 20% of zinc oxide (ZnO) is mixed with indium oxide may be used. This pixel electrode 5064 becomes the anode of the EL element. (FIG. 15
(A))

Next, as shown in FIG. 15B, an insulating film containing silicon (a silicon oxide film in this embodiment) is formed to a thickness of 500 nm.
And an opening is formed at a position corresponding to the pixel electrode 5064, and a third interlayer insulating film 5065 functioning as a bank is formed. When the opening is formed, a tapered side wall can be easily formed by using a wet etching method. Care must be taken because if the side wall of the opening is not sufficiently smooth, deterioration of the EL layer due to the step will become a significant problem.

Next, the EL layer 5066 and the cathode (MgA
g electrode) 5067 is continuously formed using a vacuum deposition method without opening to the atmosphere. Note that the thickness of the EL layer 5066 is 80
~ 200 [nm] (typically 100-120 [nm]),
The thickness of the cathode 5067 may be 180 to 300 [nm] (typically 200 to 250 [nm]).

In this step, an EL layer and a cathode are sequentially formed for a pixel corresponding to red, a pixel corresponding to green, and a pixel corresponding to blue. However, since the EL layer has poor resistance to a solution, it must be formed individually for each color without using a photolithography technique. Therefore, it is preferable that a metal mask is used to hide portions other than the desired pixels and an EL layer is selectively formed only at a necessary portion.

That is, first, a mask for hiding all pixels other than pixels corresponding to red is set, and an EL layer for emitting red light is selectively formed using the mask. Next, a mask for hiding all pixels other than pixels corresponding to green is set, and a green light-emitting EL layer is selectively formed using the mask. Next, a mask for covering all pixels other than the pixel corresponding to blue is similarly set, and an EL layer for emitting blue light is selectively formed using the mask. Note that all the masks are described herein as being different, but the same mask may be used again.

Here, a method of forming three types of EL elements corresponding to RGB is used. However, a method of combining a white light emitting EL element and a color filter, a blue or blue-green light emitting EL element and a phosphor (fluorescent And a method in which an EL element corresponding to RGB is stacked on a cathode (a counter electrode) using a transparent electrode.

A known material can be used for the EL layer 5066. As a known material, it is preferable to use an organic material in consideration of a driving voltage. For example, a four-layer structure including a hole injection layer, a hole transport layer, a light emitting layer, and an electron injection layer may be used as the EL layer.

Next, a cathode 5067 is formed. In this embodiment, MgAg is used as the cathode 5067, but the present invention is not limited to this. As the cathode 5067, another known material may be used.

Finally, a passivation film 5068 made of a silicon nitride film is formed to a thickness of 300 [nm]. By forming the passivation film 5068, the EL layer 5
066 can be protected from moisture and the like, and the reliability of the EL element can be further improved. Note that the passivation film 5068 is not necessarily provided.

Thus, a light emitting device having a structure as shown in FIG. 15B is completed. In the manufacturing process of the light emitting device in this embodiment, a source signal line is formed by Ta and W which are materials forming a gate electrode, and a source and a drain electrode are formed in view of a circuit configuration and a process. Although the gate signal line is formed of Al, which is the wiring material used, a different material may be used.

By the way, the light emitting device of this embodiment exhibits extremely high reliability and can improve the operating characteristics by arranging the TFT having the optimum structure not only for the pixel portion but also for the driving circuit. It is also possible to add a metal catalyst such as Ni in the crystallization step to enhance the crystallinity. Thereby, the driving frequency of the source signal line driving circuit is set to 10 [MHz].
It is possible to do the above.

When the structure shown in FIG. 15B is actually completed, a protective film (laminate film, ultraviolet curable resin film, etc.) with high airtightness and little degassing or a transparent film is provided so as not to be further exposed to the outside air. It is preferable to package (enclose) with an optical sealing material. At this time, the reliability of the EL element is improved by setting the inside of the sealing material to an inert atmosphere or disposing a hygroscopic material (for example, barium oxide) inside.

When the airtightness is enhanced by processing such as packaging, a connector (flexible printed circuit: FPC) for connecting terminals routed from elements or circuits formed on the substrate to external signal terminals. Attach.

According to the steps described in this embodiment, the number of photomasks required for manufacturing a light emitting device can be reduced. As a result, the process can be shortened, which can contribute to a reduction in manufacturing cost and an improvement in yield.

This embodiment can be implemented by freely combining with Embodiments 1 to 6.

(Embodiment 8) In the present invention, by using an EL material capable of utilizing phosphorescence from triplet excitons for emission, external light emission quantum efficiency can be remarkably improved. As a result, the power consumption and the life of the EL element can be reduced,
And weight reduction becomes possible.

Here, a report is shown in which the triplet exciton is used to improve the external emission quantum efficiency. (T.Tsutsui, C.Adac
hi, S. Saito, Photochemical Processes in Organized
Molecular Systems, ed.K. Honda, (Elsevier Sci. Pub.,
Tokyo, 1991) p.437.)

The molecular formula of the EL material (coumarin dye) reported in the above paper is shown below.

[0295]

Embedded image

(MABaldo, DFO'Brien, Y. You, A. Shou
stikov, S. Sibley, METhompson, SRForrest, Nature
395 (1998) p.151.)

The EL materials (P
The molecular formula of (t complex) is shown below.

[0298]

Embedded image

(MABaldo, S. Lamansky, PEBurrrows,
METhompson, SRForrest, Appl.Phys.Lett., 75 (199
9) p.4.) (T.Tsutsui, M.-J.Yang, M.Yahiro, K.Nakamu
ra, T.Watanabe, T.tsuji, Y.Fukuda, T.Wakimoto, S.Ma
yaguchi, Jpn.Appl.Phys., 38 (12B) (1999) L1502.)

The EL materials (I
The molecular formula of (r complex) is shown below.

[0301]

Embedded image

As described above, if the phosphorescence emission from the triplet exciton can be used, the external emission quantum efficiency three to four times higher than the case of using the fluorescence emission from the singlet exciton can be realized in principle. .

The structure of this embodiment can be implemented by freely combining with any structure of Embodiments 1 to 7.

(Embodiment 9) In this embodiment, an example will be described in which a digital video signal is corrected to adjust a period during which an EL element emits light, based on a potential of a pixel electrode calculated based on a pixel position. .

FIG. 19 is a block diagram of a light emitting device of this embodiment. The pixel portion 700 has source signal lines S1 to Sx, power supply lines V1 to Vx, gate signal lines G1 to Gy, and reference power lines C1 to Cy.

One of the source signal lines S1 to Sx, one of the power supply lines V1 to Vx, and one of the gate signal lines G1 to Gy
And a region having one of the reference power supply lines C1 to Cy corresponds to the pixel 701.

[0307] Further, the light emitting device of the present invention has a source signal line driving circuit 702 and a gate signal line driving circuit 703 as driving circuits. Note that FIG. 19 shows that the source signal line driving circuit 702 and the gate signal line driving circuit 703 are
Although the light-emitting devices each having one light-emitting device are shown, this embodiment is not limited to this structure. Source signal line driving circuit 702
May be provided, or two or more gate signal line driving circuits 703 may be provided. Further, the driver circuit may be formed over the same substrate as the pixel portion 700 or may be formed over a different substrate and connected through a connector such as an FPC.

Further, the light emitting device of the present invention has a correction circuit 704, a VRAM 705, and a digital video signal generation circuit 706.

A video signal input from outside the EL panel is input to the correction circuit 704. When the video signal is digital, it is directly input to the correction circuit 704.
If it is analog, it is converted to digital before or after input to the correction circuit 704.

The correction circuit 704 corrects the input video signal according to the following equation (1). Note that L _in means the number of tones that the signal input to the correction circuit 704 has as information, and L _out means the number of tones that the signal output from the correction circuit 704 has as information.

[0311]

[Equation 1] L _out = L _in × (β + α × number of gates)

Α and β are constants, and α is a constant (correction coefficient) determined by the wiring resistance and the magnitude of the current flowing through the EL element when the EL driving TFT is on.
Β is the number of gradations displayed by each pixel when it is assumed that there is no wiring resistance. The number of gates is the number of the gate signal line. The gate signal line of the pixel closest to the power supply of the power supply line is the first, and the number increases in order as the distance from the power supply increases.

FIG. 20 shows the actual gradation number (solid line) of the pixel having each gate signal line when the correction is not made by the correction circuit 704 and the number of the gate signal lines when the correction is made by the correction circuit 704. And the actual number of gradations (dotted line) of the pixel. In the solid line, the number of the gate signal line increases, and as the pixel moves away from the power supply line, the number of gray scales actually displayed decreases. However, the correction circuit 7
After the correction in step 04, the number of gradations becomes constant in all the pixels, as indicated by the dotted line.

A video signal (corrected video signal) having as information the number of gradations L _out calculated based on Equation 1 is VR
Once stored in the AM 705, it is input to the digital video signal generation circuit 706.

[0315] In the digital video signal generation circuit 706, the corrected video signal is converted into a digital video signal for performing time-division gray scale, and is input to the latch A 702b. The digital video signal generation circuit 706 is also a circuit that generates a timing pulse and the like necessary for performing time-division gray scale display.

This digital video signal generation circuit 706
May be provided outside the light emitting device of the present invention. In that case, the digital video signal formed there is input to the light emitting device of the present invention. In this case, an electronic device including the light emitting device of the present invention in the display portion includes the light emitting device of the present invention and a digital video signal generation circuit as separate components.

Also, the digital video signal generation circuit 706
May be formed on an IC chip and mounted on the light emitting device of the present invention. In that case, a digital video signal formed by the IC chip is input to the light emitting device of the present invention. In this case, an electronic device having the light emitting device of the present invention in the display portion includes, as a component, the light emitting device of the present invention on which an IC chip including a digital video signal generation circuit is mounted.

Finally, the digital video signal generating circuit 706 is connected to the pixel section 700 and the source signal line driving circuit 70.
2. TF on the same substrate as the gate signal line driving circuit 703
It can be formed using T. In this case, if a video signal containing image information is input to the light-emitting device, all can be processed on the substrate. In this case, the digital video signal generation circuit may be formed by a TFT using a polysilicon film as an active layer. In this case, in the electronic device having the light-emitting device of the present invention as a display, the digital video signal generation circuit is incorporated in the light-emitting device itself, so that the size of the electronic device can be reduced.

[0319] The digital video signal output from the digital video signal generation circuit 706 is input to a latch A 702b of the source signal line driver circuit 702.

The source signal line driver circuit 702 includes a shift register 702a, a latch A 702b, and a latch B 702c.
have.

[0321] In the source signal line driver circuit 702, a clock signal (CLK) and a start pulse (SP) are input to the shift register 702a. The shift register 702a sequentially generates a timing signal based on the clock signal (CLK) and the start pulse (SP), and sequentially inputs the timing signal to a subsequent circuit through a buffer or the like (not shown).

The timing signal from shift register 702a is buffer-amplified by a buffer or the like. The wiring to which the timing signal is input has a large load capacitance (parasitic capacitance) because many circuits or elements are connected. This buffer is provided to prevent "dulling" of the rise or fall of the timing signal caused by the large load capacitance. It is not always necessary to provide a buffer.

The timing signal buffer-amplified by the buffer is input to the latch A 702b. Latch A7
02b has a plurality of stages of latches for processing an n-bit digital video signal. Latch A 702b
Receives the timing signal, sequentially captures and holds the n-bit digital video signal input from the digital video signal generation circuit 706.

When a digital video signal is taken into the latch A 702b, the digital video signal may be sequentially input to a plurality of stages of latches of the latch A 702b. However, the present invention is not limited to this configuration. The so-called divided drive in which the latches of the plurality of stages included in the latch A 702b are divided into several groups and digital video signals are input simultaneously in parallel for each group may be performed. The number of groups at this time is called a division number. For example, when the latch is divided into groups for every four stages, it is referred to as divided drive in four divisions.

The time until the writing of the digital video signal to the latches of all the stages of the latch A 702b is completed is called a line period. Actually, the line period may include a period obtained by adding the horizontal retrace period to the line period.

When one line period ends, latch B70
A latch signal (Latch Signal) is input to 2c.
At this moment, the digital video signal written and held in the latch A 702b is simultaneously sent to the latch B 702c, and written and held in all the latches of the latch B 702c.

[0327] The latch A 702b which has finished sending the digital video signal to the latch B 702c has a shift register 7
Digital video signals are sequentially written based on the timing signal from 02a.

During the second one line period, the digital video signal written and held in the latch B 702c is input to the source signal line.

The gate signal line driving circuit 703 has a shift register (not shown) and a buffer (not shown). In some cases, a level shift may be provided.

[0330] In the gate signal line driver circuit 703, a timing signal from the shift register is input to the buffer and input to the corresponding gate signal line. The gate signal line is connected to the gate electrode of the switching TFT of one line of pixels. Since the switching TFTs of the pixels for one line must be turned ON all at once, a buffer capable of flowing a large current is used.

According to the present invention, by providing the correction circuit, the same gradation can be displayed even if a difference in luminance occurs in the EL element depending on the position of the pixel.

The structure of this embodiment can be implemented by freely combining with any structure of Embodiments 1 to 8. Embodiment 10 Since a light emitting device using an EL element is a self-luminous type, it has better visibility in a bright place and a wider viewing angle than a liquid crystal display device. Therefore, it can be used for display portions of various electronic devices.

As electronic equipment using the light emitting device of the present invention, a video camera, a digital camera, a goggle type display (head mounted display), a navigation system, a sound reproducing device (car audio, audio component, etc.), a notebook personal computer, Game devices, portable information terminals (mobile computers, mobile phones, portable game machines or electronic books, etc.), and image reproducing devices provided with recording media (specifically, reproducing a recording medium such as a digital video disc (DVD), Device having a display capable of displaying the image). In particular, it is desirable to use a light-emitting device for a portable information terminal that often has a chance to see a screen from an oblique direction because a wide viewing angle is important. FIG. 16 shows specific examples of these electronic devices.

[0334] FIG. 16A illustrates an EL display device which includes a housing 2001, a support base 2002, a display portion 2003, a speaker portion 2004, a video input terminal 2005, and the like. The light emitting device of the present invention can be used for the display portion 2003.
Since the light-emitting device is a self-luminous type, it does not require a backlight and can have a thinner display portion than a liquid crystal display device. Note that the EL display device includes all information display devices for personal computers, TV broadcast reception, advertisement display, and the like.

FIG. 16B shows a digital still camera, which includes a main body 2101, a display portion 2102, an image receiving portion 2103,
An operation key 2104, an external connection port 2105, a shutter 2106, and the like are included. The light emitting device of the present invention has a display unit 210.
2 can be used.

[0336] FIG. 16C illustrates a notebook personal computer, which includes a main body 2201, a housing 2202, and a display portion 2.
203, keyboard 2204, external connection port 220
5, including a pointing mouse 2206 and the like. The light emitting device of the present invention can be used for the display portion 2203.

FIG. 16D shows a mobile computer, which includes a main body 2301, a display portion 2302, and a switch 230.
3, an operation key 2304, an infrared port 2305, and the like. The light emitting device of the present invention can be used for the display portion 2302.

FIG. 16E shows a portable image reproducing device (specifically, a DVD reproducing device) provided with a recording medium, and includes a main body 2401, a housing 2402, a display portion A 2403, a display portion B 2404, a recording medium ( DVD, etc.) reading unit 240
5, operation keys 2406, a speaker unit 2407, and the like. The display portion A 2403 mainly displays image information, and the display portion B 2404 mainly displays character information. In the light emitting device of the present invention, the display portions A, B 2403 and 2404 are used.
Can be used. Note that the image reproducing device provided with the recording medium includes a home game machine and the like.

FIG. 16F shows a goggle-type display (head-mounted display).
1, including a display unit 2502 and an arm unit 2503. The light emitting device of the present invention can be used for the display portion 2502.

FIG. 16G shows a video camera, which includes a main body 2601, a display portion 2602, a housing 2603, an external connection port 2604, a remote control receiving portion 2605, and an image receiving portion 260.
6, a battery 2607, a voice input unit 2608, operation keys 2609, and the like. The light emitting device of the present invention has a display section 260.
2 can be used.

Here, FIG. 16H shows a mobile phone, which includes a main body 2701, a housing 2702, a display portion 2703, a voice input portion 2704, a voice output portion 2705, operation keys 2706,
An external connection port 2707, an antenna 2708, and the like are included.
The light emitting device of the present invention can be used for the display portion 2703. Note that the display portion 2703 displays white characters on a black background, so that power consumption of the mobile phone can be suppressed.

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

[0343] The electronic device may be the Internet or C.
Information distributed through an electronic communication line such as an ATV (cable television) is frequently displayed, and in particular, opportunities to display moving image information are increasing. Since the response speed of the EL material is extremely high, the light-emitting device is preferable for displaying moving images.

In the light emitting device, the light emitting portion consumes power. Therefore, it is desirable to display information so that the light emitting portion is reduced as much as possible. Therefore, when a light emitting device is used for a portable information terminal, particularly a display portion mainly for character information such as a mobile phone or a sound reproducing device, the light emitting portion is driven to form character information with a non-light emitting portion as a background. It is desirable to do.

As described above, the applicable range of the present invention is extremely wide, and the present invention can be used for electronic devices in various fields. Further, the electronic apparatus of this embodiment may use the light emitting device having any of the structures shown in Embodiments 1 to 9.

[0346]

According to the above configuration, it is possible to suppress a potential difference caused by a portion of the power supply line from fluctuating depending on an image to be displayed. Therefore, depending on the image to be displayed, the light emitting E which is generated between adjacent pixels.
The difference in the magnitude of the current flowing through the L element can be suppressed,
The occurrence of crosstalk can be suppressed.

Further, in the present invention, the potential difference caused by the portion of the power supply line does not depend on the image to be displayed. Therefore, the height of the potential of the pixel electrode of the EL element can be predicted only by the position of the pixel. Therefore, based on the height of the potential of the pixel electrode calculated based on the position of the pixel, the digital video signal is corrected to adjust the period during which the EL element emits light. The same gradation can be displayed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a pixel of a light emitting device of the present invention.

FIG. 2 illustrates a method for driving a light emitting device of the present invention.

FIG. 3 is a circuit diagram of a pixel of the light emitting device of the present invention.

FIG. 4 is a circuit diagram of a pixel of the light emitting device of the present invention.

FIG. 5 is a circuit diagram of a pixel of the light emitting device of the present invention.

FIG. 6 is a circuit diagram of a pixel of the light emitting device of the present invention.

FIG. 7 is a circuit diagram of a pixel of the light emitting device of the present invention.

FIG. 8 is a circuit diagram of a pixel of the light emitting device of the present invention.

FIG. 9 is a circuit diagram of a pixel of the light emitting device of the present invention.

FIG. 10 illustrates a method for driving a light-emitting device of the present invention.

FIG. 11 illustrates a method for driving a light emitting device of the present invention.

FIG. 12 illustrates a method for driving a light emitting device of the present invention.

FIG. 13 illustrates a method for manufacturing a light-emitting device.

FIG. 14 illustrates a method for manufacturing a light-emitting device.

FIG. 15 illustrates a method for manufacturing a light-emitting device.

FIG. 16 is a diagram of an electronic device using the light-emitting device of the present invention.

FIG. 17 is a circuit diagram of a pixel portion of a general light-emitting device.

FIG. 18 is a diagram of a pixel portion where crosstalk occurs.

FIG. 19 is a block diagram of a light-emitting device having a correction circuit.

FIG. 20 shows the number of gradations before correction and the number of gradations after correction depending on the position of a pixel.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09G 3/20 624 G09G 3/20 624B 641 641E H05B 33/14 H05B 33/14 A F term (Reference) 3K007 AB02 AB17 BA06 CA01 CB01 DA01 DB03 EB00 GA04 5C080 AA06 BB05 DD05 DD10 EE29 FF11 JJ02 JJ03 JJ05 JJ06 5C094 AA04 AA07 AA08 AA09 AA53 BA03 BA12 BA27 CA19 CA24 DA09 DA13 DB01 DB04 EA04 EB01 EB01 FB05

Claims (30)

[Claims] 1. A plurality of pixels sharing one power supply line, wherein the plurality of pixels includes an EL driving TFT and a discharging TFT.
And an EL element and a reference power supply line, wherein the EL driving TFT has a source region connected to the power supply line, a drain region connected to a pixel electrode of the EL element, The light emitting device according to claim 1, wherein the discharge TFT has a drain region connected to the power supply line and a source region connected to the reference power line. 2. A pixel having a plurality of pixels sharing one power supply line, wherein the plurality of pixels includes an EL driving TFT and a discharging TFT.
And an EL element and a reference power supply line, wherein the EL driving TFT has a source region connected to the power supply line, a drain region connected to a pixel electrode of the EL element, In the discharging TFT, a drain region is connected to the power supply line, a source region is connected to the reference power line, and the EL driving TFT and the discharging TFT have gate electrodes connected to each other. A light emitting device, wherein the EL driving TFT and the discharging TFT have reversed polarities. 3. A plurality of pixels sharing one power supply line, wherein the plurality of pixels includes an EL driving TFT and a discharging TFT.
And an EL element, and a reference power supply line, wherein the EL driving TFT is connected to the power supply line through the EL device.
The discharge TFT controls the amount of current supplied from the power supply line to the reference power supply line when the EL driving TFT is off. A light-emitting device, comprising: 4. A plurality of EL driving T-lines are connected to one power supply line.
A source region of the FT is connected to a drain region of the plurality of discharge TFTs, and a plurality of E are connected to the drain region of the plurality of EL driving TFTs.
The pixel electrodes of the L elements are connected to each other, a predetermined potential is applied to the source regions of the plurality of discharge TFTs, and when the plurality of EL elements do not emit light, the plurality of discharge TFTs are A light-emitting device, wherein a current flows in a channel formation region of a TFT, and the plurality of discharge TFTs are off when the plurality of EL elements emit light. 5. A plurality of EL driving T-lines are connected to one power supply line.
A source region of the FT is connected to a drain region of the plurality of discharge TFTs, and a plurality of E are connected to the drain region of the plurality of EL driving TFTs.
The pixel electrodes of the L elements are connected to each other, a predetermined potential is applied to the source regions of the plurality of discharge TFTs, and the plurality of EL drivings are performed when the plurality of EL elements emit light. When a current flows in the channel forming region of the discharge TFT and the plurality of EL elements do not emit light, a current flows in the channel forming region of the plurality of discharge TFTs and the plurality of EL elements emit light. Wherein the plurality of discharge TFTs are turned off during the operation. 6. A plurality of EL driving T-lines are connected to one power supply line.
A source region of the FT is connected to a drain region of the plurality of discharge TFTs, and a plurality of E are connected to the drain region of the plurality of EL driving TFTs.
The pixel electrodes of the L elements are connected to each other, a predetermined potential is applied to the source regions of the plurality of discharge TFTs, and the plurality of EL drivings are performed when the plurality of EL elements emit light. Current flows in the channel forming region of the discharge TFT, and the plurality of discharge TFTs are turned off, and when the plurality of EL elements do not emit light, the channel formation region of the plurality of discharge TFTs When the current flowing in the channel forming regions of the plurality of EL driving TFTs flows from the source region to the drain region, the current flowing in the channel forming regions of the plurality of discharging TFTs is From the region to the source region,
When the current flowing in the channel forming regions of the plurality of EL driving TFTs flows from the drain region to the source region, the current flowing in the channel forming regions of the plurality of discharging TFTs flows from the source region to the drain region. A light-emitting device, characterized in that: 7. A plurality of EL driving T-lines are connected to one power supply line.
A source region of the FT is connected to a drain region of the plurality of discharge TFTs, and a plurality of E are connected to the drain region of the plurality of EL driving TFTs.
The pixel electrodes of the L elements are connected to each other, a predetermined potential is applied to the source regions of the plurality of discharge TFTs, and the plurality of EL drivings are performed when the plurality of EL elements emit light. Current flows in the channel forming region of the discharge TFT, and the plurality of discharge TFTs are turned off, and when the plurality of EL elements do not emit light, the channel formation region of the plurality of discharge TFTs When the current flowing in the channel forming regions of the plurality of EL driving TFTs flows from the source region to the drain region, the current flowing in the channel forming regions of the plurality of discharging TFTs is From the region to the source region,
When the current flowing in the channel forming regions of the plurality of EL driving TFTs flows from the drain region to the source region, the current flowing in the channel forming regions of the plurality of discharging TFTs flows from the source region to the drain region. And a current flowing in the channel forming regions of the plurality of EL driving TFTs and a current flowing in the channel forming regions of the plurality of discharging TFTs are equal in magnitude. 8. A plurality of EL driving T-lines are connected to one power supply line.
A source region of the FT is connected to a drain region of the plurality of discharge TFTs, and a plurality of E are connected to the drain region of the plurality of EL driving TFTs.
The pixel electrodes of the L element are connected to each other, a predetermined potential is applied to the source regions of the plurality of discharge TFTs, the gate electrodes of the plurality of EL driving TFTs, and the plurality of discharge TFTs. Are connected to each other, and when the plurality of EL elements do not emit light, a current flows in the channel forming region of the plurality of discharge TFTs, and the plurality of EL elements emit light. Wherein the plurality of discharge TFTs are turned off during the operation. 9. A plurality of EL driving T-lines are connected to one power supply line.
A source region of the FT is connected to a drain region of the plurality of discharge TFTs, and a plurality of E are connected to the drain region of the plurality of EL driving TFTs.
The pixel electrodes of the L element are connected to each other, a predetermined potential is applied to the source regions of the plurality of discharge TFTs, the gate electrodes of the plurality of EL driving TFTs, and the plurality of discharge TFTs. The plurality of EL driving TFTs and the plurality of discharging TFTs are connected to each other.
Have different polarities, and when the plurality of EL elements do not emit light, a current flows in the channel forming region of the plurality of discharge TFTs, and when the plurality of EL elements emit light, 2. The light emitting device according to claim 1, wherein the plurality of discharge TFTs are off. 10. A plurality of EL driving TFT source regions and a plurality of discharging TFT drain regions are connected to one power supply line, and a plurality of EL driving TFT drain regions are connected to the plurality of EL driving TFT drain regions. E
The pixel electrodes of the L element are connected to each other, a predetermined potential is applied to the source regions of the plurality of discharge TFTs, the gate electrodes of the plurality of EL driving TFTs, and the plurality of discharge TFTs. Are connected to each other, and when the plurality of EL elements emit light, a current flows through a channel forming region of the plurality of EL driving TFTs, and the plurality of discharge electrodes A light emitting device, wherein the TFT is off, and a current flows to a channel forming region of the plurality of discharge TFTs when the plurality of EL elements do not emit light. 11. A power supply line connected to source regions of a plurality of EL driving TFTs and drain regions of a plurality of discharging TFTs, wherein a plurality of EL driving TFTs have drain regions connected thereto. E
The pixel electrodes of the L element are connected to each other, a predetermined potential is applied to the source regions of the plurality of discharge TFTs, the gate electrodes of the plurality of EL driving TFTs, and the plurality of discharge TFTs. Are connected to each other, and when the plurality of EL elements emit light, a current flows through a channel forming region of the plurality of EL driving TFTs, and the plurality of discharge electrodes The TFT is turned off, and when the plurality of EL elements do not emit light, current flows to the channel forming regions of the plurality of discharge TFTs. When the flowing current flows from the source region to the drain region, the current flowing to the channel forming regions of the plurality of discharge TFTs flows from the drain region to the source region. And,
When the current flowing in the channel forming regions of the plurality of EL driving TFTs flows from the drain region to the source region, the current flowing in the channel forming regions of the plurality of discharging TFTs flows from the source region to the drain region. A light-emitting device, characterized in that: 12. A power supply line connected to source regions of a plurality of EL driving TFTs and drain regions of a plurality of discharge TFTs, wherein a plurality of EL driving TFTs have drain regions connected thereto. E
The pixel electrodes of the L element are connected to each other, a predetermined potential is applied to the source regions of the plurality of discharge TFTs, the gate electrodes of the plurality of EL driving TFTs, and the plurality of discharge TFTs. Are connected to each other, and when the plurality of EL elements emit light, a current flows through a channel forming region of the plurality of EL driving TFTs, and the plurality of discharge electrodes The TFT is turned off, and when the plurality of EL elements do not emit light, current flows to the channel forming regions of the plurality of discharge TFTs. When the flowing current flows from the source region to the drain region, the current flowing to the channel forming regions of the plurality of discharge TFTs flows from the drain region to the source region. And,
When the current flowing in the channel forming regions of the plurality of EL driving TFTs flows from the drain region to the source region, the current flowing in the channel forming regions of the plurality of discharging TFTs flows from the source region to the drain region. And a current flowing in the channel forming regions of the plurality of EL driving TFTs and a current flowing in the channel forming regions of the plurality of discharging TFTs are equal in magnitude. 13. A plurality of EL driving TFT source regions and a plurality of discharging TFT drain regions are connected to one power supply line, and a plurality of EL driving TFT drain regions are connected to the plurality of EL driving TFT drain regions. E
The pixel electrodes of the L element are connected to each other, a predetermined potential is applied to the source regions of the plurality of discharge TFTs, the gate electrodes of the plurality of EL driving TFTs, and the plurality of discharge TFTs. The plurality of EL driving TFTs and the plurality of discharging TFTs are connected to each other.
Have different polarities. When the plurality of EL elements emit light, a current flows in the channel forming region of the plurality of EL driving TFTs, and the plurality of discharge TFTs are turned off. A light-emitting device wherein current flows through a channel formation region of the plurality of discharge TFTs when the plurality of EL elements do not emit light. 14. A plurality of EL driving TFT source regions and a plurality of discharging TFT drain regions are connected to one power supply line, and a plurality of EL driving TFT drain regions are connected to the plurality of EL driving TFT drain regions. E
The pixel electrodes of the L element are connected to each other, a predetermined potential is applied to the source regions of the plurality of discharge TFTs, the gate electrodes of the plurality of EL driving TFTs, and the plurality of discharge TFTs. The plurality of EL driving TFTs and the plurality of discharging TFTs are connected to each other.
Have different polarities. When the plurality of EL elements emit light, a current flows in the channel forming region of the plurality of EL driving TFTs, and the plurality of discharge TFTs are turned off. When the plurality of EL elements do not emit light, a current flows through the channel forming regions of the plurality of discharge TFTs, and a current flows through the channel forming regions of the plurality of EL driving TFTs. When the current flows from the drain region to the drain region, the current flowing to the channel forming region of the plurality of discharge TFTs flows from the drain region to the source region,
When the current flowing in the channel forming regions of the plurality of EL driving TFTs flows from the drain region to the source region, the current flowing in the channel forming regions of the plurality of discharging TFTs flows from the source region to the drain region. A light-emitting device, characterized in that: 15. A plurality of EL driving TFT source regions and a plurality of discharging TFT drain regions are connected to one power supply line, and a plurality of EL driving TFT drain regions are connected to the plurality of EL driving TFT drain regions. E
The pixel electrodes of the L element are connected to each other, a predetermined potential is applied to the source regions of the plurality of discharge TFTs, the gate electrodes of the plurality of EL driving TFTs, and the plurality of discharge TFTs. The plurality of EL driving TFTs and the plurality of discharging TFTs are connected to each other.
Have different polarities. When the plurality of EL elements emit light, a current flows in the channel forming region of the plurality of EL driving TFTs, and the plurality of discharge TFTs are turned off. When the plurality of EL elements do not emit light, a current flows through the channel forming regions of the plurality of discharge TFTs, and a current flows through the channel forming regions of the plurality of EL driving TFTs. When the current flows from the drain region to the drain region, the current flowing to the channel forming region of the plurality of discharge TFTs flows from the drain region to the source region,
When the current flowing in the channel forming regions of the plurality of EL driving TFTs flows from the drain region to the source region, the current flowing in the channel forming regions of the plurality of discharging TFTs flows from the source region to the drain region. And a current flowing in the channel forming regions of the plurality of EL driving TFTs and a current flowing in the channel forming regions of the plurality of discharging TFTs are equal in magnitude. 16. A digital video signal according to claim 8, wherein a digital video signal is inputted to a gate electrode of said plurality of EL driving TFTs and a gate electrode of said plurality of discharge TFTs. The plurality of EL driving TFs
A light emitting device, wherein switching of T and the plurality of discharge TFTs is controlled. 17. The digital video signal according to claim 16, wherein the digital video signal is input to a gate electrode of the plurality of EL driving TFTs and a gate electrode of the plurality of discharge TFTs via each of a plurality of switching TFTs. A light-emitting device, characterized in that: 18. The switching TFT according to claim 17, wherein one of a source region or a drain region of the plurality of discharge TFTs which is not connected to the power supply line and a gate electrode of the plurality of switching TFTs are one-to-one. A light emitting device characterized by being connected by: 19. The device according to claim 16, wherein one of a source region or a drain region of the plurality of discharge TFTs that is not connected to the power supply line and a gate electrode of the plurality of switching TFTs have a one-to-one correspondence. The digital video signal is connected to the plurality of discharge TFTs via the plurality of switching TFTs.
A light emitting device characterized in that the light is input to each of the gate electrodes. 20. The method according to claim 18, wherein
The plurality of switching TFTs and the plurality of discharge TFTs
A light emitting device having the same FT polarity. 21. The plurality of ELs according to claim 4, wherein one of the source region or the drain region of the plurality of discharge TFTs which is not connected to the power supply line and the plurality of ELs. A light-emitting device, wherein opposing electrodes of the element are connected to each other. 22. The switching TFT according to claim 17, wherein one of a source region or a drain region of the plurality of discharge TFTs that is not connected to the power supply line and a gate electrode of the plurality of switching TFTs are connected to each other. A light-emitting device, wherein the light-emitting devices are connected to each other via one current control element. 23. A light emitting device according to claim 22, wherein said plurality of switching TFTs and said plurality of discharge TFTs have the same polarity. 24. The device according to claim 4, wherein a source region or a drain region of the plurality of discharge TFTs that is not connected to the power supply line is connected to the plurality of discharge TFTs. A light-emitting device, wherein the light-emitting device is connected to the counter electrode via a first current control element. 25. The method according to claim 4, wherein a first region is provided in a source region of the plurality of discharge TFTs.
Are connected, and the plurality of discharge T
A light-emitting device, wherein a predetermined potential is applied to the source region of the FT via the first current control element. 26. One of claims 22 to 25.
3. The light emitting device according to claim 1, wherein the first current control element is a resistor, a diode, or a TFT. 27. The drain region of the plurality of discharge TFTs according to claim 4, wherein:
The light emitting device is connected to the power supply line via a second current control element. 28. A light emitting device according to claim 27, wherein said second current control element is a resistor, a diode or a TFT. 29. The plurality of EL driving TFTs according to claim 4, wherein a position of a power supply line connected to a source region or a drain region of the plurality of EL driving TFTs is determined. A light emitting device, wherein a light emitting period of the plurality of EL elements respectively connected to a source region or a drain region of a TFT which is not connected to the power supply line is adjusted. 30. An electronic apparatus according to claim 1, comprising the light emitting device.