JP2003195813A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To overcome the problem wherein a light emitting element has variance in luminance owing to characteristic variations of a driving transistor. <P>SOLUTION: A characteristic of the driving transistor provided to a pixel is specified and according to the results, a video signal inputted to the pixel is corrected. Consequently, a light emitting device which prevents effect of characteristic variations of a transistor and can make sharp multi-gradation display and its driving method can be provided. Further, a light emitting device which suppresses change in the amount of a current flowing between both electrodes of the light emitting element due to temporal variation and can make sharp multi-gradation display and its driving method can be provided. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device in which a light emitting element and a transistor for controlling the light emitting element are provided on a semiconductor substrate or an insulating surface, and a driving method thereof. More specifically, the present invention relates to a light emitting device and a method for driving the same that prevent the influence of characteristic variations of transistors that control light emitting elements. The present invention also belongs to the technical field of a light emitting device using a semiconductor element such as a transistor.

[0002]

2. Description of the Related Art In recent years, a light emitting device (image display device) using a light emitting element has been developed. Light emitting devices are roughly classified into passive type and active type.
The active type light emitting device has a light emitting element on an insulating surface,
A transistor for controlling the light emitting element is provided.

A transistor using a polysilicon film is
The field-effect mobility (also referred to as mobility) is higher than that of a transistor including a conventional amorphous silicon film, which enables high-speed operation. Therefore, it is possible to control a pixel, which is conventionally performed by a drive circuit outside the substrate, by a drive circuit formed on the same insulating surface as the pixel. Such an active type light emitting device has various advantages such as reduction in manufacturing cost, downsizing, increase in yield and reduction in throughput by forming various circuits and elements on the same insulating surface.

As a main driving method of the active type light emitting device, there are an analog method and a digital method. The former analog method is a method in which the luminance is controlled by controlling the current flowing through the light emitting element to obtain gradation. On the other hand, in the latter digital method, the light emitting element is driven only by two states, that is, an on state (a state in which the luminance is approximately 100%) and an off state (a state in which the luminance is approximately 0%). However, in the case of the digital method, since only two gradations can be displayed as it is, a technique for realizing multi-gradation by combining with a time gradation method, an area gradation method, or the like has been proposed (for example, see Patent Document 1). ).

[0005]

[Patent Document 1] Japanese Patent Laid-Open No. 2001-159878 (pages 6 and 7)

Here, a method of driving the light emitting device will be described in detail with reference to FIGS. 14 and 15. First, the structure of the light emitting device will be described with reference to FIG. FIG. 14 illustrates an example of a circuit diagram of the pixel portion 1800 included in the light-emitting device. The gate signal line (any one of G1 to Gy) for transmitting the gate signal supplied from the gate signal line driving circuit to the pixel is the switching transistor 1 included in each pixel.
It is connected to the gate electrode of 801. One of a source region and a drain region of a switching transistor 1801 included in each pixel is a source signal line (any one of S1 to Sx) for inputting a video signal, and the other is a driving transistor 1804 included in each pixel. And a capacitor 1808 included in each pixel.

A driving transistor 180 included in each pixel
The source region of No. 4 is connected to the power supply line (any one of V1 to Vx), and the drain region of the light emitting device 180.
Connected to 6. Note that the potential of the power supply line (any one of V1 to Vx) is called the power supply potential. The power supply line (one of V1 to Vx) is connected to the capacitor 1808 included in each pixel.

The light emitting element 1806 has an anode and a cathode, and an organic compound layer provided between the anode and the cathode. When the anode of the light emitting element 1806 is connected to the drain region of the driving transistor 1804, the anode of the light emitting element 1806 serves as a pixel electrode and the cathode serves as a counter electrode. On the contrary, the cathode of the light emitting element 1806 is the driving transistor 180.
Light emitting element 180 when connected to the drain region of
The anode of 6 serves as a counter electrode and the cathode serves as a pixel electrode.

The potential of the counter electrode is called the counter potential, and the power source for applying the counter potential to the counter electrode is called the counter power source. The potential difference between the potential of the pixel electrode and the potential of the counter electrode is the drive voltage, and this drive voltage is applied to the organic compound layer.

FIG. 15 shows a timing chart when the light emitting device shown in FIG. 14 is driven by an analog method. In FIG. 15, a period from the selection of one gate signal line to the selection of the next gate signal line is called one line period (L). Further, a period from the display of one image to the display of the next image is called one frame period (F). In the case of the light emitting device of FIG. 14, since there are y gate signal lines, y line periods (L1 to Ly) are provided in one frame period.

The power supply lines (V1 to Vx) are kept at a constant power supply potential. The counter potential, which is the potential of the counter electrode, is also kept at a constant potential. The opposing potential has a potential difference with the power supply potential to the extent that the light emitting element emits light.

In the first line period (L1), the gate signal supplied from the gate signal line drive circuit causes
The gate signal line (G1) is selected. Note that selection of a gate signal line means that a transistor whose gate electrode is connected to the gate signal line is turned on.

Then, analog video signals are sequentially input to the source signal lines (S1 to Sx). Since all the switching transistors 1801 connected to the gate signal line (G1) are in the ON state, the video signals input to the source signal lines (S1 to Sx) are for driving via the switching transistor 1801. It is input to the gate electrode of the transistor 1804.

The amount of current flowing through the channel forming region of the driving transistor 1804 is determined by the driving transistor 180.
The height of the potential of the signal input to the gate electrode of 4 (voltage)
Controlled by. Therefore, the potential applied to the pixel electrode of the light emitting element 1806 is determined by the height of the potential of the video signal input to the gate electrode of the driving transistor 1804. That is, the light-emitting element 1806 has a current flowing through the light-emitting element 1806 according to the height of the potential of the video signal and emits light according to the amount of the current.

When the input of the video signal to the source signal lines (S1 to Sx) is completed by repeating the above-mentioned operation, the first
Of the line period (L1) ends. Then, in the second line period (L2), the gate signal line (G2) is selected by the gate signal. And the first line period (L
Similar to 1), video signals are sequentially input to the source signal lines (S1 to Sx).

When the gate signals are input to all the gate signal lines (G1 to Gy) by repeating the above-mentioned operation, one frame period ends. All pixels display during one frame period and one image is formed.

As described above, a method in which the amount of current flowing through the light emitting element is controlled by the video signal and gradation display is performed in accordance with the amount of current is a driving method called an analog method. That is, in the analog method, gradation display is performed according to the potential of the video signal input to the pixel.

On the other hand, the digital method realizes multi-gradation by combining with the time gradation method as described above. Although a detailed timing chart is omitted, in the digital method combined with the time gray scale method, gray scale display is performed according to the length of time during which the current flows between both electrodes of the light emitting element.

Next, the voltage-current characteristics of the driving transistor 1804 and the light emitting element 1806 will be described with reference to FIGS.
3 will be used for the explanation. FIG. 11A shows only the components of the driving transistor 1804 and the light emitting element 1806 in the pixel shown in FIG. FIG. 11B shows
11 shows voltage-current characteristics of the driving transistor 1804 and the light emitting element 1806 shown in FIG. Note that FIG.
The graph of the voltage-current characteristics of the driving transistor 1804 shown in (B) shows the magnitude of the current flowing in the drain region of the driving transistor 1804 with respect to V _DS which is the voltage between the source region and the drain region. FIG. 12 shows a plurality of graphs in which the value of V _GS which is the voltage between the source region and the gate electrode of the driving transistor 1804 is different.

As shown in FIG. 11A, the light emitting element 1
The voltage applied between the pixel electrode of 806 and the counter electrode is V _EL ,
Terminal 3601 connected to power supply line and light emitting element 180
The voltage between the 6 counter electrode of the V _T. The value of V _T is fixed by the potential of the power supply lines (V1 to Vx). Further, the voltage between the source region and the drain region of the driving transistor 1804 is V _DS , the driving transistor 1
The voltage between the wiring 3602 connected to the gate electrode of 804 and the source region, that is, the driving transistor 1804.
Let V _GS be the voltage between the gate electrode and the source region.

Driving transistor 1804 and light emitting element 1
806 is connected in series. Therefore, both elements
Flow through the driving transistor 1804 and the light emitting element 1806)
The amount of current supplied is the same. Therefore, as shown in FIG.
The driving transistor 1804 and the light emitting element 1806 are
At the intersection (operating point) of the graph showing the voltage-current characteristics of both elements
Drive it. In FIG. 11B, V_ELIs the opposite
The voltage between the potential of the electrode 1809 and the potential at the operating point
Hit V_DSIs the terminal 3 of the driving transistor 1804.
Which corresponds to the voltage between the potential at 601 and the potential at the operating point.
It That is, V _TIs V_ELAnd V_DSIs equal to the sum of.

Now, consider the case where V _GS is changed. As can be seen from FIG. 11B, as | V _GS −V _TH | of the driving transistor 1804 increases,
In other words, the amount of current flowing through the driving transistor 1804 increases as | V _GS | increases. Note that V _TH is a threshold voltage of the driving transistor 1804. Therefore, as can be seen from FIG. 11 (B), | V _GS
When | becomes large, the amount of current flowing through the light emitting element 1806 at the operating point naturally becomes large. The brightness of the light emitting element 1806 increases in proportion to the amount of current flowing through the light emitting element 1806.

When the amount of current flowing through the light emitting element 1806 increases due to the increase of | V _GS |, the value of V _EL also increases according to the amount of current. Since the magnitude of V _T is determined by the potential of the power supply lines (V1 to Vx), the larger V _EL is, the smaller V _DS is.

Further, as shown in FIG. 11B, for driving
The voltage-current characteristic of the transistor 1804 is V_GSAnd V_DSof
It is divided into two areas according to the value. | V_GS-V_TH｜ ＜
| V _DSIs the saturation region, and is | V_GS-V_TH｜ ＞ ｜ V
_DSThe region that is | is the linear region.

In the saturation region, the following expression (1) is established. Note that I _DS is the amount of current flowing through the channel formation region of the driving transistor 1804. Also, β = μC ₀ W /
L, μ is the mobility of the driving transistor 1804,
C ₀ is the gate capacitance per unit area, and W / L is the ratio of the channel width W and the channel length L of the channel formation region.

[0026]

[Equation 1] I _DS = β (V _GS −V _TH ) ² ··· (1)

In the linear region, the following expression (2) is established.

[0028]

## EQU00002 ## I _DS = β {(V _GS −V _TH ) V _DS −V _DS ² } (2)

As can be seen from the equation (1), the current amount hardly changes with V _DS in the saturation region, and the current amount is determined only with V _GS .

As can be seen from the equation (2), the current amount is determined by V _DS and V _GS in the linear region. ｜
As V _GS | is increased, the driving transistor 180
4 will operate in the linear region. And V _EL also gradually increases. Therefore, V _DS becomes smaller as V _EL becomes larger. In the linear domain,
As V _DS decreases, the amount of current also decreases. Therefore, |
Even if V _GS | is increased, the amount of current becomes difficult to increase. When | V _GS | = ∞, the current amount = I _MAX . That is, no matter how large | V _GS |, I _MAX
The above current does not flow. Here, I _MAX is the amount of current flowing through the light emitting element 1806 when V _EL = V _T.

By controlling the magnitude of | V _GS | in this manner, the operating point can be set in the saturation region or the linear region.

By the way, all the driving transistors 18
Ideally, the characteristics of 04 are all the same, but in actuality, the threshold value V _TH and the mobility μ are often different in each driving transistor 1804. When the threshold V _TH and the mobility μ of each driving transistor 1804 are different from each other, as can be seen from the equations (1) and (2), even if the value of V _GS is the same, the channel of the driving transistor 1804 is the same. The amount of current flowing through the formation region is different.

FIG. 12 shows current-voltage characteristics of the driving transistor 1804 in which the threshold value V _TH and the mobility μ are different. A solid line 3701 is a graph of ideal current-voltage characteristics,
02 and 3703 are current-voltage characteristics of the driving transistor 1804 when the threshold V _TH and the mobility μ are different from ideal values.

Graphs of current-voltage characteristics 3702, 3703
Is the same amount of current ΔI in the saturation region₁Just the ideal feature
Deviates from the graph 3701 of the current-voltage characteristic with
The operating point 3705 of the current-voltage characteristic graph 3702 is
Operation of graph 3703 of current-voltage characteristics in the saturation region
It is assumed that the point 3706 is in the linear region. In that case, ideal
Operating point of graph 3701 of current-voltage characteristics having characteristics
Current amount at 3704, operating point 3705 and operating point
The deviation of the current amount in 3706 is ΔI ₂, ΔI₃
Then, at the operating point 3705 in the saturation region,
Re ΔI₂At operating point 3706 in the linear region rather than
Deviation ΔI₃Is smaller.

As a summary of the above operation analysis, a graph of the amount of current with respect to the gate voltage | V _GS | of the driving transistor 1804 is shown in FIG. When | V _GS | is increased and becomes larger than the absolute value | V _TH | of the threshold voltage of the driving transistor 1804, the driving transistor 1
804 becomes conductive and current starts flowing. And
When | V _GS | is further increased, | V _GS | becomes | V _GS
-V _TH | = | V _DS | A value that satisfies (here A
And), and the saturation region changes to the linear region. When | V _GS | is further increased, the current amount increases, and finally the current amount becomes saturated. At that time, | V _GS | = ∞.

As can be seen from FIG. 13, | V _GS | ≦ | V _TH
In the region of |, almost no current flows. ｜ V _TH ｜ ≦ ｜
The region of V _GS | ≦ A is a region called a saturation region, and |
The amount of current changes depending on V _GS |. This means that in the saturation region, if the voltage applied to the light emitting element 1806 changes even a little, the current flowing through the light emitting element 1806 changes exponentially. Then, the luminance of the light emitting element 1806 increases substantially in direct proportion to the current flowing through the light emitting element 1806. That is, | V
_The analog method, which is a method of controlling the luminance to obtain gradation by controlling the current flowing through the light emitting element according to the value of _GS |, is mainly operated in the saturation region.

On the other hand, in FIG. 13, the region of A ≦ | V _GS | is a linear region, and the amount of current flowing through the light emitting element is | V _GS.
| And | V _DS | change the current amount. In the linear region, the amount of current flowing through the light emitting element 1806 does not change significantly even if the magnitude of the voltage applied to the light emitting element 1806 is changed. In the digital method, the light emitting element is driven only by two states, that is, the on state (the luminance is almost 100%) or the off state (the luminance is almost 0%), but the light emitting element is turned on. To enter the state,
When operated with A ≦ | V _GS |, the current value is always I _MAX
Since the brightness is close to, the brightness is almost 100%. To turn off the light emitting element, | V _TH | ≧ |
When operated at V _GS |, the current value becomes almost zero and the luminance of the light emitting element becomes almost 0%. That is, the light-emitting device driven by the digital method is mainly | V _TH | ≧ | V _GS |, A ≦
_{Operated in} the region of | V _GS |.

[0038]

In the light emitting device driven by the analog method, when the switching transistor is turned on, the analog video signal input to the pixel becomes the gate voltage of the driving transistor. At this time, the potential of the drain region is determined according to the voltage of the analog video signal input to the gate electrode of the driving transistor, a predetermined drain current flows to the light emitting element, and the light emission amount ( The light emitting element emits light at the brightness. As described above, the light emission amount of the light emitting element is controlled by the video signal, and the gradation display is performed by controlling the light emission amount.

However, the above-mentioned analog method has a drawback that it is very weak in the characteristic variation of the driving transistor.
Even if an equal gate voltage is applied to the driving transistor of each pixel, the same drain current cannot be supplied if the driving transistor has characteristic variations. That is, even if a video signal of the same voltage is input, the light emission amount of the light emitting element greatly differs due to a slight variation in the characteristics of the driving transistor.

As described above, the analog system is sensitive to the characteristic variation of the driving transistor, which is an obstacle in the gradation display of the conventional active type light emitting device.

When the light emitting device is driven by a digital method in order to deal with the characteristic variation of the driving transistor, when the organic compound layer of the light emitting element deteriorates, the amount of current flowing through the organic compound layer changes. .

This is because the light emitting element has a property of being deteriorated with time. FIG. 18A shows a graph of voltage-current characteristics before and after deterioration of the light emitting element. As described above, the digital system operates in the linear region. Therefore, as shown in FIG. 18A, when the light emitting element deteriorates, the graph of the voltage-current characteristic changes, and the operating point shifts. Then, the amount of current flowing between both electrodes of the light emitting element changes.

The present invention has been made in view of the above problems, and in a light emitting device driven by an analog method,
It is an object of the present invention to provide a light-emitting device capable of preventing a characteristic variation of a transistor and capable of displaying a clear multi-gradation and a driving method thereof. It is another object of the present invention to provide an electronic device including the light emitting device as a display device.

Further, it is an object of the present invention to provide a light emitting device which can suppress a change in the amount of current flowing between both electrodes of a light emitting element due to a change with time and can perform a clear multi-gradation display, and a driving method thereof. . It is another object of the present invention to provide an electronic device including the light emitting device as a display device.

[0045]

In view of the above situation, the present invention identifies the characteristics of a driving transistor provided in a pixel and corrects a video signal input to the pixel based on the result. (EN) Provided are a light emitting device and a method for driving the light emitting device, which are prevented from being affected by characteristic variations of a driving transistor.

The present invention is also directed to the light emission amount (luminance) of the light emitting element.
, But is controlled by the amount of current flowing through the light emitting element. That is, if a desired amount of current flows through the light emitting element, a desired amount of light emission can be obtained by the light emitting element.
Therefore, a video signal according to the characteristics of the driving transistor of each pixel is input to each pixel so that a desired amount of current flows through the light emitting element. Then, desired light emission can be obtained by the light emitting element without being affected by the characteristic variation of the driving transistor.

A method of specifying the characteristics of the driving transistor, which is the basis of the present invention, will be described below. First, an ammeter is connected to the wiring supplying current to the light emitting element, and the value of the current flowing through the light emitting element is measured. For example, an ammeter is connected to a wiring that supplies a current to a light emitting element such as a power supply line or a counter power source line, and the value of the current flowing through the light emitting element is measured. At this time, the video signal is input only from a certain pixel (preferably one pixel or a plurality of pixels) from the source signal line driver circuit, and current does not flow to the light emitting elements of the other pixels. To do so. Then, the ammeter can measure the current value flowing only in a specific pixel. Also size (voltage value)
Inputting different video signals, it is possible to measure a plurality of current values corresponding to video signals having different magnitudes (voltage values) for each pixel.

According to the present invention, the video signal is represented by P (P1, P2,
..., Pn and n are natural numbers of at least 2 or more. The current value Q (Q1, Q2, ..., Qn) corresponding to the video signal P (P1, P2, ..., Pn) is displayed as the current value I0 when all the pixels of the display panel are not lit. Current value I1 when only one pixel on the panel is lit,
It is obtained by calculating the difference between I2, ..., In. After measuring P and Q for each pixel, the characteristics of the pixel are obtained by using the interpolation method. The interpolation method is a calculation method that uses the function values at two or more points of the function to obtain an approximate value of a point between the function values, or a function value is given (interpolated) to give a function value at the points between them. It is a way to expand. The equation that gives the approximate value is called an interpolation equation and is shown in equation (3).

[0049]

## EQU00003 ## Q = F (P) ... (3)

The video signal P (P
1, P2, ..., Pn) and the value of the current value Q (Q1, Q2, ..., Qn) corresponding to the video signal are given by equation (3).
Substituting into Then, the obtained interpolation function F is stored in a storage medium such as a semiconductor memory or a magnetic memory provided in the light emitting device.

When an image is displayed on the light emitting device, a video signal (P) corresponding to the characteristics of the driving transistor of each pixel is used by using the interpolation function F stored in the storage medium.
Calculate and obtain. And the required video signal (P)
By inputting to each pixel, a desired amount of current can be passed through the light emitting element, so that a desired brightness can be obtained.

The light emitting device in the present invention means a display panel (light emitting panel) in which a pixel portion having a light emitting element and a driving circuit are enclosed between a substrate and a cover material, and a light emitting module in which an IC or the like is mounted on the display panel. In the category, a light-emitting display used as a display device is included. That is, the light emitting device corresponds to a generic name of a light emitting panel, a light emitting module, a light emitting display, and the like. Note that a light-emitting element is not included as an essential component of the present invention, but a case where the light-emitting element is not included is also referred to as a light-emitting device here.

The present invention is a light emitting device having a display panel provided with a pixel including a light emitting element, the current measuring means for measuring the current value of the pixel, and the pixel output using the output of the current measuring means. It is characterized in that it has a calculation means for calculating a corresponding interpolation function, a storage means for storing the interpolation function, and a signal correction means for correcting the video signal using the interpolation function stored in the storage means.

The current measuring means has means for measuring the value of the current flowing between both electrodes of the light emitting element. For example, the current measuring means is composed of an ammeter, a resistance element and a capacitance element, and is measured by using resistance division. It corresponds to a circuit to be performed. The calculation means and the signal correction means have means for performing calculation, and correspond to, for example, a microcomputer or a CPU. The storage means corresponds to a known storage medium such as a semiconductor memory or a magnetic memory. The non-lighting state of a pixel corresponds to a non-light-emitting state of a light-emitting element included in the pixel, or a state of a pixel to which a “black” image signal is input. The state in which a pixel is lit corresponds to the state in which a light-emitting element included in the pixel emits light and the state in which a “white” image signal is input to the pixel.

The present invention is a method of driving a light emitting device having a display panel, wherein a current value I0 in a state where all the pixels of the display panel are not lit is measured, and a video signal P1 is supplied to each pixel of the display panel. , P2, ..., Pn (n is a natural number), current values I1, I2 ,.
In is measured, and the difference Q between the current value I0 and the current value In
1, Q2, ..., Qn and the video signals P1, P
2, ..., Pn and an interpolation formula Q = F (P) are used to calculate an interpolation function F, and the interpolation function F is used to correct a video signal input to each pixel of the display panel. And

As a typical configuration of the pixel in the present invention, a first semiconductor element for controlling a current flowing between both electrodes of the light emitting element, a second semiconductor element for controlling input of a video signal to the pixel, and A structure including a capacitor which holds the video signal can be given. In addition,
The semiconductor element corresponds to an element having a switching function such as a transistor. The capacitor has a function of holding electric charge, and a material of which the capacitor is formed is not particularly limited.

The present invention having the above-described structure provides a light emitting device driven by an analog method, which is capable of preventing the influence of variations in the characteristics of transistors and displaying a clear multi-gradation, and a driving method thereof. be able to.
Further, the present invention can provide a light emitting device and a driving method thereof that can suppress a change in the amount of current flowing between both electrodes of a light emitting element due to a change with time and can perform clear multi-gradation display.

[0058]

BEST MODE FOR CARRYING OUT THE INVENTION (Embodiment) An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows an example of a circuit diagram of the light emitting device. In FIG. 1, the light emitting device includes a pixel portion 103 and a pixel portion 103.
It has a source signal line drive circuit 101 and a gate signal line drive circuit 102 arranged in the periphery of. Note that the light-emitting device includes one source signal line driver circuit 101 and one gate signal line driver circuit 102 in FIG. 1, but the present invention is not limited to this. The numbers of the source signal line driver circuits 101 and the gate signal line driver circuits 102 can be arbitrarily determined depending on the structure of the pixel 100.

Further, the source signal line drive circuit 101 has a shift register 101a, a buffer 101b, and a sampling circuit 101c. However, the present invention is not limited to this, and may include a holding circuit or the like.

A clock signal (CLK) and a start pulse (SP) are input to the shift register 101a. The shift register 101a sequentially generates timing signals based on the clock signal (CLK) and the start pulse (SP), and the sampling circuit 10 via the buffer 101b.
1c are sequentially input.

The timing signal supplied from the shift register 101a is buffered and amplified by the buffer 101b. Since many circuits or elements are connected to the wiring to which the timing signal is input, the load capacitance becomes large. Therefore, the buffer 101b is provided to prevent the rising or falling of the timing signal caused by the large load capacitance.

The sampling circuit 101c includes the buffer 1
Video signals are sequentially output to the pixels 100 based on the timing signal input from 01b. The sampling circuit 101c has a video signal line 125 and sampling lines (SA1 to SAx). Note that the present invention is not limited to this structure and may have a semiconductor element such as an analog switch.

The pixel section 103 includes source signal lines (S1 to S).
x), gate signal lines (G1 to Gy), power supply lines (V1 to Vx), and counter power supply lines (E1 to Ey). Further, the pixel portion 103 is provided with a plurality of pixels 100 in a matrix.

The power supply lines (V1 to Vx) are connected to the ammeter 13
It is connected to the power supply 131 via 0. Ammeter 1
30 and the power source 131 may be formed on a substrate different from the substrate on which the pixel portion 103 is formed, and may be connected to the pixel portion 103 via a connector or the like. It may be formed on the same substrate. The numbers of the ammeters 130 and the power sources 131 are not particularly limited and can be set arbitrarily. In addition, the ammeter 130 may be provided on a wiring that supplies a current to the light emitting element 111, and the ammeter 130 may be connected to the opposing power supply lines (E1 to Ey), for example. That is, the place where the ammeter 130 is provided is not particularly limited. The ammeter 130 corresponds to a measuring means.

The current value measured by the ammeter 130 is sent to the correction circuit 210 as data. The correction circuit 210 includes a storage medium (storage means) 211, a calculation circuit (calculation means) 202, and a signal correction circuit (signal correction means).
It has 204. Note that the structure of the correction circuit 210 is not limited to the structure shown in FIG. 1 and an amplifier circuit, a conversion circuit, or the like may be provided. Further, if necessary, only the storage medium 211 may be provided, and the configuration of the correction circuit 210 can be arbitrarily determined.

The storage medium 211 has a first memory 200, a second memory 201 and a third memory 203. However, the present invention is not limited to this, and the number of memories can be freely designed by the designer. As the storage medium 211, a known storage medium such as a ROM, a RAM, a flash memory, or a magnetic tape can be used. However, when the storage medium 211 is integrally provided on a substrate or the like on which the pixel portion is provided, it is preferable to use a semiconductor memory, and particularly preferable to use a ROM. When the light emitting device of the present invention is used as a display device of a computer, the storage medium 211 may be provided in the computer.

The calculation circuit 202 has means for performing calculation. More specifically, the video signals P1 and P
Current values I1 and I when 2, ..., Pn are input
2, ..., In, the current value I0 in the state where the pixel portion 103 does not emit light is subtracted to obtain current values Q1, Q2, ...
., Has means for calculating Qn. Further, it has means for calculating the interpolation function of the above-mentioned formula (3). Note that as the calculation circuit 202, a known calculation circuit, a microcomputer, or the like can be used. When the light emitting device of the present invention is used as a display device of a computer, the calculation circuit 202 may be provided in the computer.

The signal correction circuit 204 has means for correcting the video signal. More specifically, it has a means for correcting the video signal input to the pixel 100 from the interpolation function F of the pixel 100 stored in the storage medium 211 and the above equation (3). As the signal correction circuit 204,
A known signal correction circuit, microcomputer, or the like can be used. When the light emitting device of the present invention is used as a display device of a computer, the signal correction circuit 204 may be provided in the computer.

The source signal lines (S1 to Sx) are connected to the video signal line 125 via the sampling transistor 126.
It is connected to the. Sampling transistor 126
One of the source region and the drain region of the source signal line S
(Any one of S1 to Sx) and the other is connected to the video signal line 125. The gate electrode of the sampling transistor 126 is connected to the sampling line SA (any one of SA1 to SAx).

Next, pixel 1 provided in the i-th column and the j-th row
An enlarged view of 00 is shown in FIG. At pixel (i, j),
111 is a light emitting element, 112 is a switching transistor, 113 is a driving transistor, and 114 is a capacitor.

The gate electrode of the switching transistor 112 is connected to the gate signal line (Gi). One of the source region and the drain region of the switching transistor 112 is connected to the source signal line (Si), and the other is connected to the gate electrode of the driving transistor 113. The switching transistor 112 is connected to the pixel 100.
A transistor that functions as a switching element when a signal is input to. The source signal line (Si) connected to the switching transistor 112 is as shown in FIG.
2 is connected to the video signal line 125 via the sampling transistor 126, but is not shown in FIG.

The capacitor 114 is provided to hold the gate voltage of the driving transistor 113 when the switching transistor 112 is in the non-selected state (OFF state). Although the capacitor 114 is provided in the present embodiment, the present invention is not limited to this, and the capacitor 114 may not be provided.

The source region of the driving transistor 113 is connected to the power supply line (Vi), and the drain region is connected to the light emitting element 111. The power supply line (Vi) is connected to the power supply 131 via the ammeter 130 and is always supplied with a constant power supply potential. In addition, the power supply line Vi
Is connected to the capacitor 114. The driving transistor 113 is a transistor which functions as an element (current control element) for controlling the current supplied to the light emitting element 111.

The light emitting device 111 comprises an anode and a cathode, and an organic compound layer provided between the anode and the cathode. When the anode is connected to the drain region of the driving transistor 113, the anode serves as the pixel electrode and the cathode serves as the counter electrode. Conversely, when the cathode is connected to the drain region of the driving transistor 113, the cathode serves as the pixel electrode and the anode serves as the counter electrode.

Note that the light emitting element has a structure in which an organic compound layer is sandwiched between a pair of electrodes (anode and cathode). The organic compound layer can be formed using a known light emitting material. The organic compound layer has two structures, a single-layer structure and a laminated structure, but either structure may be used. Luminescence in an organic compound layer includes light emission when returning from a singlet excited state to a ground state (fluorescence) and light emission when returning from a triplet excited state to a ground state (phosphorescence). You may use.

The counter electrode of the light emitting element is connected to the counter power supply 121. The potential of the counter power supply 121 is called a counter potential. The difference between the potential of the pixel electrode and the potential of the counter electrode is the drive voltage, and the drive voltage is applied to the organic compound layer.

Next, in the light emitting device of the present invention shown in FIGS. 1 and 2, the characteristics of the driving transistor 113 provided in the pixel 100 are specified, and the pixel 1 is determined based on the result.
A method for correcting a video signal input to 00 will be described with reference to FIG. Note that each step is referred to as Step 1 to Step 5 in order to make the description easy to understand. Further, since the correction circuit 210 is shown in FIG. 3B, refer to FIGS. 3A and 3B, respectively.

FIG. 4 shows a driving circuit (source signal line driving circuit 101, gate signal line driving circuit 10) provided in the light emitting device.
The timing chart of the signal output from 2) is shown. Since the pixel portion 103 is provided with y number of gate signal lines, y number of line periods (L
1 to Ly) are provided.

In FIG. 4A, in one line period (L), one gate signal line G (one of G1 to Gy) is selected and y gate signal lines (G1 to Gy) are selected. Shows that one frame period elapses when is selected. FIG. 4B shows x sampling lines SA (SA1
1 to SAx are sequentially selected and all the sampling lines (SA1 to SAx) are selected, one line period elapses. FIG. 4C shows how the video signal P0 is input to the source signal lines (S1 to Sx) in step 1. FIG. 4 (D) shows
It is shown that the video signals P1, P2, P3 and P0 are input to the source signal lines (S1 to Sx) in step 2.

First, in step 1, the pixel portion 103 is brought into a state of all black. All black state means all light emitting elements 1
11 is a non-light emitting state, and all pixels are in a non-lighting state. FIG. 4C shows how the video signal P0 is input to the source signal lines (S1 to Sx) in step 1. Note that FIG. 4C illustrates only a state where the video signal P0 is input to the source signal lines (S1 to Sx) in one line period.
Actually, it is performed in all the line periods (L1 to Ly) provided in one frame period (F). The same video signal P is supplied to all the pixels 100 in one frame period.
When 0 is input, all the light emitting elements 111 provided in the pixel portion 103 are in a non-light emitting state (all black state).

In such a state, the ammeter 130
Current value I0 flowing through the power supply lines (V1 to Vx) using
To measure. The current value I0 measured at this time is such that a part between the anode and the cathode of the light emitting element 111 is short-circuited, a part of the pixel 100 is short-circuited, or the FPC connected to the pixel portion 103 is accurate. It corresponds to the value of the current that has flowed when it is not connected. Then, the measured current value I0 is stored in the first memory 200 provided in the correction circuit 210, and step 1 ends.

Next, in step 2, the pixel portion 103
Different video signals P for the pixels 100 provided in the
Input 1, P2, P3 and P0.

In this embodiment, as shown in FIG. 4D, four video signals P1, P2, which are changed stepwise,
P3 and P0 are input to the source signal lines (S1 to Sx). That is, in one line period (L), four video signals P1, P2, P3, and P0 are input to one pixel 100, and
Four video signals P1, P2, P3, and P0 are supplied to all the pixels 100 provided in the pixel portion 103 in the frame period (F).
Enter.

The three video signals P1, P2, P
The current flowing through the driving transistor 113, that is, the current value flowing through the power supply lines (V1 to Vx) corresponding to No. 3 is measured by the ammeter 130.

Note that here, four video signals P1, P2, P3, and P0 which are stepwise changed are input to one pixel in one line period (L), but the present invention is not limited to this. For example, by inputting only the video signal P1 during one line period (L), inputting the video signal P2 during the next one line period (L), and inputting the video signal P3 during the next one line period (L). Good. Further, in the present embodiment,
Four video signals P1, P2, P changed stepwise
Although 3 and P0 are input, the present invention may input video signals having different magnitudes (voltage values) and measure the current values corresponding to the video signals having different magnitudes (voltage values). For example, a video signal changed into a ramp shape (saw-tooth shape) may be input, and the ammeter 130 may be used to measure a plurality of current values at regular intervals.

Here, as an example, the case where the gate signal line (Gj) on the j-th row is selected by the gate signal supplied from the gate signal line drive circuit 102 will be described. In one line period (Lj), 4 per pixel 100
Since the two video signals P1, P2, P3, and P0 are input, all are in the off state except for the pixel 100 to which the video signal is input (here, the pixel 100 provided in (1, j)). Therefore, the current value measured by the ammeter 130 is determined by a specific pixel (pixel of interest) 10
It is a value obtained by adding the current value flowing through the driving transistor 113 of 0 and the current value I0 measured in step 1. Then, in the pixel 100 provided in (1, j), P
Current value I corresponding to each video signal of 1, P2, P3
1, I2, I3 are measured and the current values IA, IB, IC
Are stored in the second memory 201.

Then, the video signal P0 is applied to the pixel (1, j).
Is input, the light emitting element 111 of the pixel 100 is set to a non-light emitting state, and the pixel (1, j) is set to a non-lighting state. This is to prevent a current from flowing when measuring the next pixel (2, j).

Then, four video signals P1, P2, P3 and P0 are input to the pixel 100 provided at (2, j). The current values I1, I2, I3 corresponding to the video signals P1, P2, P3 are acquired and stored in the second memory 201.

In this way, the above operation is repeated,
Pixels 100 from the 1st column to the xth column provided in the j-th row
Input of the video signal ends. That is, when the input of the video signal to all the source signal lines (S1 to Sx) ends, one line period Lj ends.

Then, in the next line period L _{j + 1} , the gate signal line G _{j + 1} is selected by the gate signal supplied from the gate signal line drive circuit 102. Then, four video signals P are provided to all the source signal lines (S1 to Sx).
1, P2, P3 and P0 are input.

In this way, the above operation is repeated,
When the gate signals are input to all the gate signal lines (G1 to Gy), all the line periods (L1 to Ly) are completed. When all the line periods (L1 to Ly) are finished, one frame period is finished.

The pixel 1 provided in the pixel portion 103 in this way
It is possible to measure the current values I1, I2, I3 corresponding to the three video signals P1, P2, P3 input to 00. Then, the obtained data is stored in the second memory 201.

Then, in the calculation circuit 202, the current values I1 and I1 are calculated for each pixel 100 provided in the pixel section 103.
2 and I3, the difference from the current value I0 stored in the first memory 200 in step 1 is calculated to obtain the current value Q1 (=
I1-I0), Q2 (= I2-I0), Q3 (= I3-I)
0) is calculated. Then, the current values Q1, Q2, Q3 are stored in the second memory 201, and step 2 ends.

If there is no short-circuited pixel in the pixel section 103 and the FPC or the like connected to the pixel section 103 is correctly connected, the current value I0 is zero or almost zero. May be measured. In such a case, the operation of subtracting the current value I0 or the operation of measuring the current value I0 from the current values I1, I2, and I3 for each pixel 100 provided in the pixel unit 103 may be deleted. It can be set arbitrarily.

In [0096] Next Step 3, using equation (1) described above, the calculation circuit 202, and acquires the current-voltage characteristics of the driving transistor of each pixel (I _DS -V _GS characteristic). In the formula (1), I _DS → I, V _GS →
When P, V _TH → B and Q = I−I0, the following equation (4) is obtained.

[0097]

[Equation 4] Q = A * (P−B) ² (4)

In the equation (4), A and B are constants.
The constant A and the constant B can be obtained if there are at least two sets of (Pn, Qn) data. That is, step 2
By substituting at least two video signals (Pn) having different magnitudes (voltage values) and the at least two current values (Qn) corresponding to the video signals (Pn) into Equation (3), the constant A And the constant B can be obtained. Then, the constant A and the constant B are stored in the third memory 203.

By using the constant A and the constant B stored in the third memory 203, the value of the video signal (Pn) required to flow a certain current value (Qn) can be obtained.
In that case, the following equation (5) is used.

[0100]

P = (Q / A) ^1/2 + B = {(I-I0) / A} ^1/2 + B (5)

Here, as an example, the values of the constant A and the constant B of the pixel D, the pixel E, and the pixel F are obtained by using the equations (4) and (5), and the results are shown in a graph in FIG. Shown in. Figure 5
As shown in, when the same video signal (here, the video signal P2 is used as an example) is input to the pixel D, the pixel E, and the pixel F, a current indicated by Iq flows in the pixel D and a current indicated by Ir in the pixel E. And a current indicated by Ip flows in the pixel F. That is, even if the same video signal (P2) is input, the current values are different because the characteristics of the transistors provided in the pixels D, E, and F are different. Therefore, according to the present invention, in order to suppress the influence of such characteristic variations, the video signal according to the characteristic of the pixel 100 is input to the pixel 100 by using the above-described formula (4).

In FIG. 5, the characteristics of the pixel D, the pixel E, and the pixel F are shown by quadratic curves using the equations (4) and (5), but the present invention is not limited to this. FIG. 16 shows the relationship between the video signal (P) input to the pixel D, the pixel E, and the pixel F using the following equation (6) and the current value (Q) corresponding to the video signal (P). A straight line graph is shown.

[0103]

(6) Q = a * P + b (6)

By substituting the voltage value (P) and the current value (Q) for each pixel obtained in step 2 into the equation (6), the constant a
And a constant b is obtained. Then, the obtained constant a and constant b
Is stored in the third memory 203 for each pixel 100, and step 3 ends.

Similar to the graph shown in FIG. 5, the graph shown in FIG. 16 shows that when the same video signal (here, as an example, the video signal P2) is input to the pixel D, the pixel E, and the pixel F, the pixel D The current indicated by Iq flows, the current indicated by Ir flows in the pixel E, and the current indicated by Ip flows in the pixel F. That is, even if the same video signal (P2) is input, the current value is different because the characteristics of the transistor provided in the pixel 100 are different. Therefore, the present invention, in order to suppress the influence of such characteristic variations,
A video signal according to the characteristics of the pixel 100 is input to the pixel 100 by using the above equation (6).

As a method of specifying the relationship between the voltage value (P) and the current value (Q) of the video signal, the relationship may be specified by using a quadratic curve as shown in FIG. 1
You may specify by showing it with a straight line as shown in FIG.
Further, it may be specified by a spline curve (spline function) or a Bezier curve (Bezier function). If the current value does not satisfactorily fit on the curve, the curve (linear function) is calculated using the least squares method. It may be optimized, and the method is not particularly limited.

Then, in step 4, in the signal correction circuit 204, the above equation (5) (or equation (6)) is given.
The value of the video signal according to the characteristic of each pixel 100 is calculated using, for example. Then, step 4 ends, and if the calculated video signal is input to the pixel 100 in step 5, it becomes possible to suppress the influence of the characteristic variation of the driving transistor and to flow a desired current to the light emitting element. As a result, a desired amount of light emission (luminance) can be obtained. The constant A and the constant B obtained for each pixel 100
Once the values of (or the constant a and the constant b) are stored in the third memory 203, step 4 and step 5 may be repeated thereafter.

Referring again to FIG. If you want to make pixel D, pixel E, and pixel F emit light with the same brightness,
It is necessary to flow the same current value Ir. For that purpose, it is necessary to input a video signal according to the characteristics of the driving transistor. As shown in FIG. 5, the video signal P1 is input to the pixel D and the video signal P2 is input to the pixel E.
, And it is necessary to input the video signal P3 to the pixel F. For that purpose, in step 4, it is essential to obtain a video signal according to the characteristic of each pixel and input the obtained signal to each pixel.

The operation of measuring a plurality of current values corresponding to a plurality of different video signals using the ammeter 130 (operations of steps 1 to 3) is performed immediately before or immediately after the actual image is displayed. It may be carried out, or may be carried out at a certain fixed period. Alternatively, it may be performed before the predetermined information is stored in the storage means. Further, it may be performed only before shipment, but in that case, the interpolation function F calculated by the calculation circuit 202 may be temporarily stored in the storage medium 211 and the storage medium 211 may be integrally formed with the pixel portion 103. . Then, the interpolation function F stored in the storage medium 211 will be used.
Since it is possible to calculate the video signal according to the characteristics of the pixel with reference to, it is not necessary to provide the ammeter 130 in the light emitting device.

In this embodiment, the interpolation function F
Is stored in the storage medium 211, pixel 1
The video signal input to 00 is calculated at any time in the calculation circuit 202 and the calculated video signal is input to the pixel 100, but the present invention is not limited to this.

For example, based on the interpolation function F stored in the storage medium 211, a video signal corresponding to the number of gradations of the image to be displayed is calculated in advance in the calculation circuit 202 for each pixel 100, and the calculation is performed. The video signal may be stored in the storage medium 211. For example, if an image is displayed with 16 gradations, 16 video signals for 16 gradations are calculated in advance for each pixel 100.
Then, the calculated video signal is stored in the storage medium 211. Then, the information of the video signal input when displaying a certain gradation for each pixel 100 is stored in the storage medium 21.
Since it is stored in No. 1, the image can be displayed based on the information. That is, an image can be displayed based on the information stored in the storage medium 211 without providing the calculation circuit 202 in the light emitting device.

A video signal corresponding to the number of gradations of a displayed image is calculated in advance for each pixel 100 by the calculation circuit 20.
2 is calculated, a video signal gamma-corrected with a gamma value is added to the storage medium 211.
It may be stored in. The gamma value to be used may be common in the pixel section or may be different in each pixel. Then, a clearer image can be displayed.

[0113]

EXAMPLE 1 The present invention can be applied to a light emitting device of a pixel having a structure different from that of FIG. In this embodiment, an example thereof will be described with reference to FIGS. 6 and 18B and 18C.

The pixel (i, j) shown in FIG.
11, a switching transistor 312, a driving transistor 313, an erasing transistor 315, and a storage capacitor 314. The pixel 100 has a source signal line (Si), a power supply line (Vi), and a gate signal line (G).
j), it is arranged in a region surrounded by the erase gate signal line (Rj).

The gate electrode of the switching transistor 312 is connected to the gate signal line (Gj). One of the source region and the drain region of the switching transistor 312 is connected to the source signal line (Si) and the other is connected to the gate electrode of the driving transistor 313. The switching transistor 312 is connected to the pixel 100.
A transistor that functions as a switching element when a signal is input to.

The capacitor 314 is provided to hold the gate voltage of the driving transistor 313 when the switching transistor 312 is in the non-selected state (OFF state). Although the capacitor 314 is provided in this embodiment, the present invention is not limited to this, and the capacitor 314 may not be provided.

The source region of the driving transistor 313 is connected to the power supply line (Vi), and the drain region is connected to the light emitting element 311. The power supply line (Vi) is connected to the power supply 131 via the ammeter 130 and is always supplied with a constant power supply potential. Also, power supply line (Vi)
Is connected to the capacitor 314. The driving transistor 313 is a transistor that functions as an element (current control element) for controlling the current supplied to the light emitting element 311.

The light emitting element 311 comprises an anode and a cathode, and an organic compound layer provided between the anode and the cathode. When the anode is connected to the drain region of the driving transistor 313, 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 driving transistor 313, the cathode serves as the pixel electrode and the anode serves as the counter electrode.

The gate electrode of the erasing transistor 315 is connected to the erasing gate signal line (Rj). One of the source region and the drain region of the erasing transistor 315 is connected to the power supply line (Vi) and the other is connected to the gate electrode of the driving transistor 313. The erasing transistor 315 is a transistor that functions as an element for erasing (resetting) the signal written in the pixel 100.

When the erasing transistor 315 is turned on, the capacitance held in the capacitor 314 is discharged. Then, the signal written in the pixel 100 is erased (reset), and the light emitting element does not emit light. That is, by turning on the erasing transistor 315, the pixel 100 is forced to emit no light. By providing the erasing transistor 315 in this manner, it is possible to forcibly make the pixel 100 not emit light, which has various effects. For example,
In the case of the digital method, since the lighting time of the light emitting element can be set arbitrarily, a high gradation image can be displayed. In the case of the analog method, the pixels can be brought into a non-light emitting state each time the frame period is switched, so that a moving image can be displayed neatly without leaving an afterimage.

The power supply line (Vi) is an ammeter 130.
It is connected to the power source 131 via. In addition, ammeter 1
30 and the power source 131 may be formed on a substrate different from the substrate on which the pixel portion 103 is formed, and may be connected to the pixel portion 103 via a connector or the like. It may be formed on the same substrate. The numbers of the ammeters 130 and the power supplies 131 are not particularly limited and can be set arbitrarily.

The current value measured by the ammeter 130 is sent to the correction circuit 210 as data. The correction circuit 210 has a storage medium 211, a calculation circuit 202, and a signal correction circuit 204. Note that the structure of the correction circuit 210 is not limited to the structure shown in FIG. 6 and an amplifier circuit or the like may be provided. A designer can freely design the configuration of the correction circuit 210.

The pixels (i, j) shown in FIG. 6 are arranged in a matrix in the pixel portion (not shown). Further, in the pixel portion, source signal lines (S1 to Sx), gate signal lines (G1 to Gy), and power supply lines (V1 to Vx).
And erasing gate signal lines (R1 to Ry) are provided.

FIG. 18B shows a pixel having a configuration in which a reset line Rj is added to the pixel shown in FIG. 2 and the capacitor 114 is connected to the reset line Rj instead of the power supply line Vi. ing. In this case, the capacitor 114 serves to reset the pixel (i, j).
Further, FIG. 18C shows a pixel in which a reset line Rj and a diode 150 are added to the pixel shown in FIG. 2, and the diode plays a role of resetting the pixel (i, j).

Note that the pixel structure of a light emitting device to which the present invention is applied is a structure having a light emitting element and a transistor. The connection relationship between the light emitting element and the transistor in the pixel is not particularly limited, and any connection relationship may be used.
The pixel configuration shown in this embodiment is one example.

Here, taking the pixel shown in FIG. 6 as an example,
The operation will be briefly described. Although either a digital method or an analog method can be applied to the pixel, an operation when a digital method combined with a time gray scale method is applied will be described here. The time gray scale method is a method of performing gray scale expression by controlling the lighting period of the light emitting element, as reported in detail in Japanese Patent Laid-Open No. 2001-343933. Specifically, one frame period is divided into a plurality of subframe periods having different lengths, and light emission or non-light emission of the light-emitting element in each period is selected, whereby the lighting period within one frame period can be reduced. Express the gradation with the difference. That is, gradation is expressed by controlling the length of the lighting period by the video signal.

In the digital system, the operation is mainly performed in the linear region as described above, but the operation may be performed in the saturation region. When operating in the linear region, the amount of current changes when the organic compound layer deteriorates. on the other hand,
When operating in the saturation region, the characteristics of the driving transistor are easily affected.

In the present invention, the influence of the characteristic variation of each pixel is suppressed by correcting the video signal input to each pixel. That is, in the light emitting device to which the analog method is applied, the correction of the video signal corresponds to the correction of the amplitude value of the video signal. Further, in a light emitting device to which a digital method combined with a time gray scale method is applied, correction of a video signal corresponds to correction of a length of a lighting period of a pixel to which the video signal is input.

In the light emitting device to which the digital method combined with the time gray scale method is applied, it is preferable to use the equation (6) shown by a straight line. However, in the digital method, since it is not necessary to measure the non-emission state, the formula (6)
The value of the constant b in is preferably zero. The characteristic of each pixel may be measured only once to obtain the value of the constant a.

The present invention having the above-described structure provides a light emitting device driven by an analog method, which is capable of preventing the influence of variations in the characteristics of transistors and capable of displaying clear multi-gradation, and a driving method thereof. be able to.
Further, the present invention can provide a light emitting device and a driving method thereof that can suppress a change in the amount of current flowing between both electrodes of a light emitting element due to a change with time and can perform clear multi-gradation display.

Note that this embodiment can be freely combined with the embodiment modes.

(Embodiment 2) In this embodiment, an example of a sectional structure of a pixel will be described with reference to FIG.

In FIG. 7, as the switching transistor 4502 provided on the substrate 4501, an n-channel type transistor formed by a known method is used. In addition,
Although a double gate structure is used in this embodiment, a single gate structure may be used, a triple gate structure or a multi-gate structure having more gates may be used. Alternatively, a p-channel transistor formed by a known method may be used.

As the driving transistor 4503, an n-channel type transistor formed by a known method is used. Drain wiring 45 of switching transistor 4502
Reference numeral 04 denotes a driving transistor 4 by wiring (not shown)
503 is electrically connected to the gate electrode 4506.

The driving transistor 4503 is the light emitting element 4
Since it is an element for controlling the amount of current flowing through 510, a large amount of current flows, and there is a high risk of deterioration due to heat or deterioration due to hot carriers. Therefore, a structure in which an LDD region is provided in the drain region of the driver transistor 4503 or both of the source region and the drain region so as to overlap with the gate electrode with the gate insulating film interposed therebetween is extremely effective. FIG. 7 shows an example in which LDD regions are formed in both the source region and the drain region of the driving transistor 4503 as an example.

In this embodiment, the driving transistor 4 is used.
Although 503 is illustrated as a single-gate structure, a multi-gate structure in which a plurality of transistors are connected in series may be used. Further, a structure may be adopted in which a plurality of transistors are connected in parallel and the channel formation region is substantially divided into a plurality of portions so that heat radiation can be performed with high efficiency. Such a structure is effective as a measure against deterioration due to heat.

A wiring (not shown) including the gate electrode 4506 of the driving transistor 4503 partially overlaps with the drain wiring 4512 of the driving transistor 4503 via the insulating film, and a storage capacitor is formed in that region. It This storage capacitor has a function of holding a voltage applied to the gate electrode 4506 of the driving transistor 4503.

A first interlayer insulating film 4514 is provided on the switching transistor 4502 and the driving transistor 4503, and a second resin insulating film is formed on the first interlayer insulating film 4514.
Interlayer insulating film 4515 is formed.

Reference numeral 4517 denotes a pixel electrode (anode of a light emitting element) made of a conductive film having a high light-transmitting property, which is a driving transistor 4
The drain region 503 is formed so as to partially cover the drain region and is electrically connected. As the pixel electrode 4517, it is preferable to use a compound of indium oxide and tin oxide (referred to as ITO) or a compound of indium oxide and zinc oxide. Of course, another translucent conductive film may be used.

Next, the organic resin film 4516 is formed on the pixel electrode 451.
7 and patterning the portion facing the pixel electrode 4517, an organic compound layer 4519 is formed. Although not shown here, R (red), G (green), B
The organic compound layer 4519 corresponding to each color of (blue) may be separately formed. A π-conjugated polymer material is used as a light emitting material for the organic compound layer 4519. A typical polymer material is polyparaphenylene vinylene (PP
V) type, polyvinylcarbazole (PVK) type, polyfluorene type and the like. In addition, the organic compound layer 45
19 has two structures, a single layer structure and a laminated structure, but either structure may be produced in the present invention. The organic compound layer 4519 (a layer for emitting light and moving carriers therefor) may be formed by freely combining known materials and structures.

For example, in this embodiment, an example in which a polymer material is used as the organic compound layer 4519 is shown, but a low molecular weight organic light emitting material may be used. Further, it is also possible to use an inorganic material such as silicon carbide for the charge transport layer and the charge injection layer. Known materials can be used as these organic light emitting materials and inorganic materials.

When the cathode 4523 is formed, the light emitting element 4510 is completed. Note that the light-emitting element 451 referred to here
0 means the pixel electrode 4517 and the organic compound layer 4519.
And a stacked body formed of the hole injection layer 4522 and the cathode 4523.

By the way, in this embodiment, a passivation film 4524 is provided on the cathode 4523. As the passivation film 4524, a silicon nitride film or a silicon nitride oxide film is preferable. The purpose of this is
10 is cut off, and has both the meaning of preventing deterioration of the light emitting material due to oxidation and the meaning of suppressing degassing from the organic light emitting material. This improves the reliability of the light emitting device.

As described above, the light-emitting device described in this embodiment has the pixel portion including the pixel having the structure shown in FIG. 7, the selection transistor having a sufficiently low off-current value, and the strong drive for hot carrier injection. And a transistor for use. Therefore, a light emitting device having high reliability and capable of displaying an excellent image can be obtained.

In the case of the light emitting device having the structure described in this embodiment, the light generated in the organic compound layer 4519 is
Substrate 4 on which transistors are formed as indicated by arrows
The light is emitted in the direction of 501. The light emitting element 4
The emission of light emitted from 510 toward the substrate 4501 is called bottom emission.

Next, a sectional structure of a light emitting device in which light emitted from the light emitting element is emitted in a direction opposite to the substrate 4510 (top emission) will be described with reference to FIG.

In FIG. 17A, a driving transistor 1601 is formed over a substrate 1600. The driving transistor 1601 includes a source region 1604a, a drain region 1604c, and a channel formation region 1604.
b and. In addition, the gate electrode 1 provided over the channel formation region 1604b through the gate insulating film 1605.
603a. Note that the driving transistor 1601
In addition to the structure shown in FIG. 17A, a transistor having a known structure can be freely used.

An interlayer film 1606 is formed on the driving transistor 1601. Then, a transparent conductive film such as ITO is formed and patterned into a desired shape to form a pixel electrode 1608. Here, the pixel electrode 1608 is
It functions as an anode of the light emitting element 1614.

The interlayer film 1606 forms contact holes reaching the source region 1604a and the drain region 1604c of the driving transistor 1601, and Ti,
A laminated film made of Al containing Ti and Ti is formed and patterned into a desired shape. Then, the wiring 160
7 and the wiring 1609 are formed.

Subsequently, an insulating film made of an organic resin material such as acrylic is formed, and the pixel electrode 160 of the light emitting element 1614 is formed.
An opening is formed at a position corresponding to 8 to form an insulating film 1610. Here, in order to avoid problems such as deterioration of the organic compound layer and step breakage due to steps on the side wall of the opening, the opening is formed to have a side wall with a sufficiently gentle taper shape.

Then, after forming the organic compound layer 1611, the counter electrode (cathode) 1612 of the light emitting element 1614 is
It is formed by a laminated film in which a cesium (Cs) film having a thickness of 2 nm or less and a silver (Ag) film having a thickness of 10 nm or less are sequentially formed. By making the counter electrode 1612 of the light emitting element 1614 extremely thin, the light emitted from the organic compound layer 1611 passes through the counter electrode 1612 and the substrate 1600.
Is emitted in the opposite direction. Then, the light emitting element 1614
A protective film 1613 is formed for the purpose of protecting

FIG. 17B is a sectional view of a structure different from that of FIG. 17A. Note that in FIG.
The same parts as (A) will be described using the same reference numerals. In FIG. 17B, the structure is the same as that shown in FIG. 17A until the driving transistor 1601 and the interlayer film 1606 are formed, and thus the description is omitted.

The driving transistor 1 is formed on the interlayer film 1606.
Source region 1604a and drain region 160 of 601
A contact hole reaching 4c is formed. Then T
A laminated film made of Al and Ti including i and Ti is formed, and then a transparent conductive film typified by ITO is formed. A laminated film of Ti, Al containing Ti and Ti, and
A transparent conductive film typified by ITO or the like is patterned into a desired shape to form a wiring 1607, a wiring 1608, a wiring 1.
609 and the pixel electrode 1620 are formed. The pixel electrode 1
620 functions as an anode of the light emitting element 1624.

Subsequently, an insulating film made of an organic resin material such as acrylic is formed, and the pixel electrode 162 of the light emitting element 1624 is formed.
An opening is formed at a position corresponding to 0 and an insulating film 1610 is formed. Here, in order to avoid problems such as deterioration of the organic compound layer and step breakage due to a step difference in the side wall of the opening, the opening is formed to have a sufficiently gentle tapered side wall.

Next, after forming the organic compound layer 1611, the counter electrode (cathode) 1612 of the light emitting element 1624 is formed.
It is formed by a laminated film in which a cesium (Cs) film having a thickness of 2 nm or less and a silver (Ag) film having a thickness of 10 nm or less are sequentially formed. By making the counter electrode 1612 of the light-emitting element 1624 extremely thin, light emitted from the organic compound layer 1611 passes through the counter electrode 1612 and the substrate 1600.
The light is emitted in the opposite direction. Then, the light emitting element 162
A protective film 1613 is formed for the purpose of protecting No. 4.

As described above, in the light emitting device which emits light in the direction opposite to the substrate 1600, the light emitted from the light emitting element 1614 is visually recognized through the elements such as the driving transistor 1601 formed on the substrate 1600. Since there is no need, the aperture ratio can be increased.

The pixel having the structure shown in FIG. 17B is the same as that shown in FIG.
Compared with the pixel having the structure shown in FIG. 7A, the wiring 1619 connected to the source region or the drain region of the driving transistor and the pixel electrode 1620 can be formed by patterning using a common photomask. Therefore, the number of photomasks required in the manufacturing process can be reduced and the process can be simplified.

Note that this embodiment can be freely combined with Embodiment Mode and Embodiment 1.

Example 3 In this example, the appearance of the light emitting device of the present invention will be described with reference to FIG.

FIG. 8A is a top view of the light emitting device.
8B is a cross-sectional view taken along line AA ′ of FIG.
FIG. 8C is a cross-sectional view taken along the line BB ′ of FIG.

Pixel portion 400 provided on substrate 4001
2, source signal line driver circuit 4003, first and second
A sealing material 4009 is provided so as to surround the gate signal line driver circuits 4004a and 4004b. In addition, the pixel portion 4002, the source signal line driver circuit 4003, the first
A sealing material 4008 is provided over the second gate signal line driver circuits 4004a and 4004b. Pixel part 4
002, the source signal line driver circuit 4003, and the first and second gate signal line driver circuits 4004a and 4004b include a substrate 4001, a sealant 4009, and a sealant 4008.
And are sealed together with the filler 4210.

Although one set (two) of gate signal line drive circuits is provided in this embodiment, the present invention is not limited to this, and the number of gate signal line drive circuits and source signal line drive circuits is not limited to this. Can be arbitrarily set by the designer.

The pixel portion 4 provided on the substrate 4001
002, the source signal line driver circuit 4003, and the first and second gate signal line driver circuits 4004a and 4004b include a plurality of transistors. In FIG. 8B, the source signal line driver circuit 400 formed over the base film 4010.
3 includes a drive circuit transistor included in No. 3 (however, an n-channel transistor and a p-channel transistor are shown here) 4201 and a drive transistor (transistor controlling current to the light-emitting element) 4202 included in the pixel portion 4002. Illustrated.

In this embodiment, the drive circuit transistor 4 is used.
A p-channel transistor or an n-channel transistor manufactured by a known method is used for 201, and a p-channel transistor manufactured by a known method is used for the driving transistor 4202. Further, the pixel portion 4002 is provided with a storage capacitor (not shown) connected to the gate electrode of the driving transistor 4202.

An interlayer insulating film (planarizing film) is formed on the driver circuit transistor 4201 and the driver transistor 4202.
4301 is formed, and the driving transistor 42 is formed thereon.
Pixel electrode (anode) 4 electrically connected to the drain of 02
203 is formed. A transparent conductive film having a high work function is used as the pixel electrode 4203. As the transparent conductive film, a compound of indium oxide and tin oxide, a compound of indium oxide and zinc oxide, zinc oxide, tin oxide or indium oxide can be used. Moreover, you may use what added gallium to the said transparent conductive film.

An insulating film 4302 is formed on the pixel electrode 4203, and the insulating film 4302 forms the pixel electrode 420.
3, an opening is formed on the upper part. In this opening, an organic compound layer 4204 is formed on the pixel electrode 4203. A known organic light emitting material or inorganic light emitting material can be used for the organic compound layer 4204. The organic light emitting material includes a low molecular weight (monomer) material and a high molecular weight (polymer) material, and either of them may be used.

As a method for forming the organic compound layer 4204, a known vapor deposition technique or coating technique may be used. The structure of the organic compound layer is a hole injection layer, a hole transport layer, a light emitting layer,
The electron transport layer or the electron injection layer may be freely combined to form a laminated structure or a single layer structure.

A cathode 4205 formed of a conductive film having a light-shielding property (typically, a conductive film containing aluminum, copper, or silver as a main component or a laminated film of these and another conductive film) is formed over the organic compound layer 4204. Is formed. Also, the cathode 4
It is desirable to remove water and oxygen existing at the interface between 205 and the organic compound layer 4204 as much as possible. Therefore, the organic compound layer 4204 is formed in a nitrogen or rare gas atmosphere,
It is necessary to devise a method of forming the cathode 4205 without exposing it to oxygen and moisture. In the present embodiment, the above-described film formation is possible by using a multi-chamber type (cluster tool type) film forming apparatus. And the cathode 42
05 is given a predetermined voltage.

As described above, the pixel electrode (anode) 42
03, the organic compound layer 4204, and the cathode 4205, a light emitting element 4303 is formed. And the light emitting element 430
A protective film 4209 is formed on the insulating film 4302 so as to cover the insulating film 4302. The protective film 4209 is formed on the light emitting element 4303.
It is effective in preventing oxygen and water from entering the body.

Reference numeral 4005a is a lead wiring connected to the power supply line and electrically connected to the source region of the driving transistor 4202. The lead wiring 4005a passes between the sealing material 4009 and the substrate 4001 and is electrically connected to the FPC wiring 4301 included in the FPC 4006 through the anisotropic conductive film 4300.

As the sealing material 4008, a glass material, a metal material (typically a stainless material), a ceramic material, a plastic material (including a plastic film) can be used. As a plastic material, FRP
(Fiberglass-Reinforced Pl
astics) plate, PVF (polyvinyl fluoride)
A film, mylar film, polyester film or acrylic resin film can be used. Alternatively, a sheet having a structure in which an aluminum foil is sandwiched between PVF films or mylar films can be used.

However, the cover material must be transparent when the direction of light emitted from the light emitting element is toward the cover material side. In that case, a transparent material such as a glass plate, a plastic plate, a polyester film or an acrylic film is used.

As the filler 4103, an ultraviolet curable resin or a thermosetting resin can be used in addition to an inert gas such as nitrogen or argon. PVC (polyvinyl chloride), acrylic, polyimide, epoxy resin, silicone can be used. Resin, PVB (polyvinyl butyral) or E
VA (ethylene vinyl acetate) can be used. In this example, nitrogen was used as the filler.

Further, in order to expose the filler 4103 to a hygroscopic substance (preferably barium oxide) or a substance capable of adsorbing oxygen, the substrate 400 of the sealing material 4008 is used.
A concave portion 4007 is provided on the surface on the first side, and a hygroscopic substance or a substance 4207 capable of adsorbing oxygen is arranged. The hygroscopic substance or the substance 4207 capable of adsorbing oxygen is held by the recessed cover material 4208 in the recess 4007 so that the hygroscopic substance or the substance 4207 capable of adsorbing oxygen does not scatter. Note that the recess cover material 4208 has a fine mesh shape and has a structure in which air and moisture can pass through and a hygroscopic substance or a substance that can adsorb oxygen 4207 cannot pass through. By providing the hygroscopic substance or the substance 4207 capable of adsorbing oxygen, deterioration of the light-emitting element 4303 can be suppressed.

As shown in FIG. 8C, the pixel electrode 420
Simultaneously with the formation of No. 3, a conductive film 4203a is formed so as to be in contact with the lead wiring 4005a.

The anisotropic conductive film 4300 has a conductive filler 4300a. Substrate 4001 and F
By thermocompression bonding with PC 4006, the conductive film 4203a on the substrate 4001 and the FPC wiring 4301 on the FPC 4006 are electrically connected by the conductive filler 4300a.

The ammeter and the correction circuit included in the light emitting device of the present invention are formed on a substrate (not shown) different from the substrate 4001, and the power supply line and the cathode 4205 formed on the substrate 4001 via the FPC 4006. Electrically connected to.

Note that this embodiment can be implemented by being freely combined with the embodiment mode and Embodiments 1 and 2.

(Embodiment 4) In this embodiment, an appearance of a light emitting device of the present invention different from that of Embodiment 3 will be described with reference to FIG. More specifically, the ammeter and the correction circuit are formed on a substrate different from the substrate on which the pixel portion is formed, and the wire bonding method, COG (chip on glass) method is used.
The appearance of the light emitting device when connected to the wiring on the substrate on which the pixel portion is formed by a method such as a method will be described with reference to FIG.

FIG. 9 is an external view of the light emitting device of this example. The pixel portion 5002 provided over the substrate 5001, the source signal line driver circuit 5003, and the first and second gate signal line driver circuits 5004a and 5004 are surrounded so that
A seal material 5009 is provided. In addition, the pixel portion 500
2, source signal line driver circuit 5003, first and second
A sealing material 5008 is provided on the gate signal line driver circuits 5004a and 5004b. Therefore, the pixel unit 50
02, the source signal line driver circuit 5003, and the first and second gate signal line line driver circuits 5004a and 5004b together with a filler (not shown) by the substrate 5001, the sealing material 5009, and the sealing material 5008. It is sealed.

Although two gate signal line driving circuits are provided in this embodiment, the number of gate signal line driving circuits and source signal line driving circuits is not limited to this, and the designer can arbitrarily determine the number. Can be done.

A concave portion 5007 is provided on the surface of the sealing material 5008 on the substrate 5001 side to dispose a hygroscopic substance or a substance capable of adsorbing oxygen.

The wiring routed over the substrate 5001 (routed wiring) is the sealing material 5009 and the substrate 5001.
And an external circuit or element of the light emitting device through the FPC 5006.

The ammeter and the correction circuit are formed on a substrate (hereinafter referred to as a chip) 5020 different from the substrate 5001 and attached on the substrate 5001 by means such as COG (chip on glass) method. It is electrically connected to a power supply line and a cathode (not shown) formed above.

In this embodiment, the chip 5020 is mounted on the substrate 5001 by the wire bonding method, the COG method, or the like, so that the light emitting device can be constituted by one substrate, the device itself becomes compact, and Strength also increases.

As a method of connecting the chip on the substrate, a known method can be used. In addition, the circuit and elements other than the ammeter and the correction circuit are connected to the substrate 5
It may be mounted on 001.

The present embodiment is an embodiment and Examples 1 to 3.
It is possible to implement by freely combining with.

(Embodiment 5) Since the light emitting device is a self-luminous type, it has better visibility in a bright place and a wider viewing angle than a liquid crystal display. Therefore, it can be used for a display unit 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 mount display), a navigation system, a sound reproducing device (car audio system, audio component system, etc.), a notebook type personal computer, A game device, a mobile information terminal (a mobile computer, a mobile phone, a portable game machine, an electronic book, or the like), an image reproducing device provided with a recording medium (specifically, a recording medium such as a digital video disk (DVD) or the like is reproduced, A device including a display capable of displaying the image) and the like. In particular, for a portable information terminal that often sees the screen from an oblique direction, since a wide viewing angle is important, it is preferable to use a light emitting device. Specific examples of these electronic devices are shown in FIGS.

FIG. 10A shows a light emitting device, which is a housing 30.
01, a support 3002, a display portion 3003, a speaker portion 3004, a video input terminal 3005 and the like. The light emitting device of the present invention can be used for the display portion 3003. 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.
The light emitting device includes all display devices for displaying information, such as those for personal computers, those for receiving TV broadcasts, and those for displaying advertisements.

FIG. 10B shows a digital still camera including a main body 3101, a display section 3102, an image receiving section 3103, and
An operation key 3104, an external connection port 3105, a shutter 3106 and the like are included. The light emitting device of the present invention includes a display unit 310.
2 can be used.

FIG. 10C shows a laptop personal computer, which includes a main body 3201, a housing 3202, and a display portion 3.
203, keyboard 3204, external connection port 320
5, including a pointing mouse 3206 and the like. The light emitting device of the present invention can be used for the display portion 3203.

FIG. 10D shows a mobile computer, which has a main body 3301, a display portion 3302, and a switch 330.
3, operation keys 3304, infrared port 3305 and the like. The light emitting device of the present invention can be used for the display portion 3302.

FIG. 10E shows a portable image reproducing device (specifically, a DVD reproducing device) provided with a recording medium, which includes a main body 3401, a housing 3402, a display portion A3403, a display portion B3404, a recording medium ( DVD, etc.) reading unit 340
5, an operation key 3406, a speaker portion 3407 and the like. The display portion A3403 mainly displays image information and the display portion B3404 mainly displays text information. However, the light-emitting device of the present invention has these display portions A, B3403, and 3404.
Can be used for. Note that the image reproducing device provided with the recording medium includes a home game machine and the like.

FIG. 10F shows a goggle type display (head mounted display), which is a main body 350.
1, a display portion 3502 and an arm portion 3503 are included. The light emitting device of the present invention can be used for the display portion 3502.

FIG. 10G shows a video camera, which includes a main body 3601, a display portion 3602, a housing 3603, an external connection port 3604, a remote control receiving portion 3605, and an image receiving portion 360.
6, a battery 3607, a voice input unit 3608, operation keys 3609, and the like. The light emitting device of the present invention includes a display unit 360.
2 can be used.

Here, FIG. 10H shows a mobile phone, which includes a main body 3701, a housing 3702, a display portion 3703, a voice input portion 3704, a voice output portion 3705, operation keys 3706,
An external connection port 3707, an antenna 3708, and the like are included.
The light emitting device of the present invention can be used for the display portion 3703. Note that the display portion 3703 can reduce power consumption of the mobile phone by displaying white characters on a black background.

If the emission brightness of the organic light emitting material becomes higher in the future, it is possible to magnify and project the output light containing the image information with a lens or the like and use it for a front type or rear type projector.

Further, the above electronic devices are the Internet or C
Information distributed through electronic communication lines such as ATV (cable television) is often displayed, and in particular, opportunities for displaying moving image information are increasing. Since the response speed of the organic light emitting material is very high, the light emitting device is suitable for displaying moving images.

Since the light emitting device consumes power in the light emitting portion, it is desirable to display information so that the light emitting portion is as small as possible. Therefore, when a light emitting device is used in a display unit mainly for character information such as a mobile information terminal, a mobile phone or a sound reproducing device, it is driven so that the character information is formed in the light emitting portion with the non-light emitting portion as the 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 applied to electronic devices in all fields.

[0202]

According to the present invention, the video signal according to the characteristics of the driving transistor of each pixel is calculated and obtained without changing the configuration of the pixel. By inputting the obtained video signal to each pixel, a desired amount of current can be passed through the light emitting element, and thus desired light emission can be obtained. As a result, it is possible to provide a light emitting device and a method for driving the light emitting device that prevent the influence of the characteristic variation of the transistor that controls the light emitting element.

Further, according to the present invention having the above-described structure, in a light emitting device driven by an analog method, a light emitting device capable of preventing an influence due to characteristic variation of a transistor and performing a clear multi-gradation display, and a driving method thereof. Can be provided. Further, the present invention can provide a light emitting device and a driving method thereof that can suppress a change in the amount of current flowing between both electrodes of a light emitting element due to a change with time and can perform clear multi-gradation display.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram of a light emitting device of the present invention.

FIG. 3 illustrates a method for driving a light emitting device of the present invention.

FIG. 4 is a diagram showing a timing chart of signals input to a light emitting device of the present invention.

FIG. 5 is a diagram showing a relationship between a video signal and a current value.

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

FIG. 7 is a diagram showing a cross-sectional structure (bottom emission) of a light emitting device of the present invention.

FIG. 8 is a diagram showing an appearance of a light emitting device of the present invention.

FIG. 9 is a diagram showing an appearance of a light emitting device of the present invention.

FIG. 10 is a diagram showing an example of an electronic device including the light emitting device of the present invention.

11A and 11B are diagrams showing a structure of connection between a light emitting element and a driving transistor and diagrams showing voltage-current characteristics of the light emitting element and a driving transistor.

FIG. 12 is a diagram showing voltage-current characteristics of a light emitting element and a driving transistor.

FIG. 13 is a diagram showing a relationship between a gate voltage and a drain current of a driving transistor.

FIG. 14 is a diagram showing a circuit diagram of a pixel portion of a light emitting device.

FIG. 15 illustrates a timing chart of signals input to a light-emitting device.

FIG. 16 is a diagram showing a relationship between a video signal and a current value.

FIG. 17 is a cross-sectional structure of a light emitting device of the present invention (top emission).
FIG.

18A and 18B are diagrams showing voltage-current characteristics of a light emitting element and a driving transistor and a circuit diagram of a pixel.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/20 641 G09G 3/20 641D 641P 642 642P 670 670J H05B 33/14 H05B 33/14 A

Claims (20)

[Claims] 1. A light emitting device having a display panel provided with a pixel including a light emitting element, comprising: storage means for storing an interpolation function corresponding to the pixel; and the interpolation function and the interpolation formula Q = F (P). A light-emitting device having a signal correction means for correcting a video signal by using. 2. A light emitting device having a display panel provided with a pixel including a light emitting element, comprising: current measuring means for measuring a current value of the pixel; calculating means for calculating an interpolation function corresponding to the pixel; A light emitting device comprising: a storage unit that stores an interpolation function; and a signal correction unit that corrects a video signal using the interpolation function and the interpolation formula Q = F (P). 3. A light emitting device for forming a display panel provided with a pixel including a light emitting element, the storage device storing an interpolation function corresponding to the pixel, and the interpolation function and the interpolation formula Q = F. A light emitting device having a signal correcting means for correcting a video signal by using (P). 4. A light emitting device for forming a display panel provided with a pixel including a light emitting element, comprising: current measuring means for measuring a current value of the pixel; calculation for calculating an interpolation function corresponding to the pixel. Means for storing the interpolation function; and signal correction means for correcting the video signal using the interpolation function and the interpolation formula Q = F (P). 5. A light emitting device for constituting a memory means and a signal correcting means, comprising a display panel provided with a pixel including a light emitting element, wherein the memory means corresponds to each pixel of the display panel. A light emitting device, wherein an interpolation function is stored, and the signal correction unit corrects a video signal using the interpolation function and the interpolation formula Q = F (P) stored in the storage unit. 6. A light emitting device for constituting a current measuring means, a calculating means, a storing means and a signal correcting means, comprising a display panel provided with a pixel including a light emitting element, wherein the current measuring means is The current value of the pixel is measured, the calculation means calculates an interpolation function corresponding to the pixel using the output of the current measurement means, the storage means stores the interpolation function, and the signal correction means stores the memory. A light emitting device, wherein a video signal is corrected by using the interpolation function and the interpolation formula Q = F (P) stored in the means. 7. The light-emitting device according to claim 1, wherein the signal correction unit is a CPU or a microcomputer. 8. The light-emitting device according to claim 1, wherein the storage unit is a semiconductor memory or a magnetic memory. 9. The transistor according to claim 1, wherein a transistor connected to the light emitting element and operating in a saturation region is arranged in the pixel, and characteristic variation of the transistor is corrected. A light emitting device characterized by. 10. The transistor according to claim 1, wherein a transistor connected to the light emitting element and operating in a linear region is arranged in the pixel, and deterioration of the light emitting element is corrected. A light emitting device characterized by. 11. The semiconductor device according to claim 1, wherein the pixel controls a first semiconductor element that controls a current flowing between both electrodes of the light emitting element and a video signal input to the pixel. A second light emitting device having a second semiconductor element, and a capacitor element for holding the video signal. 12. The first semiconductor element according to claim 1, wherein the pixel controls a current flowing between both electrodes of the light emitting element, and a video signal input to the pixel is controlled. A light-emitting device comprising: a second semiconductor element, a capacitive element that holds the video signal, and a third semiconductor element that discharges an electric charge held in the capacitive element. 13. The current measuring means according to claim 2, 4 or 6, wherein video signals P1 and P are applied to the pixels.
, Pn (n is a natural number of 2 or more) is input, current values Q1, Q2, ..., Qn are measured. 14. The current measuring means according to claim 2, 4 or 6, wherein the current value I0 when all the pixels of the display panel are in a non-illuminated state and the current value of 1 of the display panel.
Current values I1, I2, when only one pixel is lit,
The light emitting device is characterized by measuring In (n is a natural number of 2 or more). 15. The current measuring means according to claim 2, 4 or 6, wherein the current value I0 when all the pixels of the display panel are in a non-illuminated state, and the current value of 1 of the display panel.
Current values I1, I2, when only one pixel is lit,
..., In (n is a natural number of 2 or more), and the calculation means calculates a difference between the current value In and the current value I0. 16. The current measuring means according to claim 2, 4 or 6, selected from a current value I0 in a state where all pixels of the display panel are not lit and a plurality of pixels of the display panel. When only one pixel is lit, video signals P1, P2, ...
,, Pn (n is a natural number of 2 or more) is input, the current values I1, I2, ..., In are measured, and the calculation means calculates the current values I1, I2 ,.
, Qn of the current value I0 and the video signal P1, P2, ..., Pn and the interpolation formula Q = F (P) to calculate the interpolation function F. Characterized light emitting device. 17. The video signal P according to claim 2, 4 or 6, wherein said calculation means is input to said pixel.
1, P2, ..., Pn (n is a natural number of 2 or more) and current values Q1, Q2, ...
., Qn, and interpolation function Q = F (P)
A light-emitting device that calculates F. 18. The predetermined measuring operation by the current measuring means according to claim 2, 4 or 6, immediately before or after displaying an image using the display panel, or an interpolation function is stored in the storage means. The light-emitting device is characterized by being performed before the operation. 19. The light emitting device according to claim 2, 4 or 6, wherein the calculating means is a CPU or a microcomputer. 20. The interpolation formula Q = F (P) according to any one of claims 1 to 6, 16 and 17, wherein Q = A * (P-B) ² and Q = a *.
A light emitting device characterized by being represented by P + b, a spline function, a Bezier function, or a linear function.