JP2003195808A - Display device using organic el element and its driving method, and portable information terminal - Google Patents

Display device using organic el element and its driving method, and portable information terminal

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Publication number
JP2003195808A
JP2003195808A JP2001391436A JP2001391436A JP2003195808A JP 2003195808 A JP2003195808 A JP 2003195808A JP 2001391436 A JP2001391436 A JP 2001391436A JP 2001391436 A JP2001391436 A JP 2001391436A JP 2003195808 A JP2003195808 A JP 2003195808A
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Japan
Prior art keywords
transistor
signal line
voltage
reverse bias
element
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Pending
Application number
JP2001391436A
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Japanese (ja)
Inventor
Hitoshi Tsuge
仁志 柘植
Original Assignee
Matsushita Electric Ind Co Ltd
松下電器産業株式会社
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Filing date
Publication date
Application filed by Matsushita Electric Ind Co Ltd, 松下電器産業株式会社 filed Critical Matsushita Electric Ind Co Ltd
Priority to JP2001391436A priority Critical patent/JP2003195808A/en
Publication of JP2003195808A publication Critical patent/JP2003195808A/en
Application status is Pending legal-status Critical

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Abstract

(57) [Problem] In a display device using an EL element or the like, when driving is performed for a long time, luminance is reduced and a voltage between terminals of the EL element is increased. SOLUTION: In order to apply a reverse bias voltage to an EL element 266, a switching transistor 2 is provided between the EL element 266 and a driving transistor 267a for controlling a current value.
67d is provided, and is in a non-conductive state during a reverse bias application period. Further, another voltage value other than the reverse bias power supply 332 can be applied to the reverse bias signal line 269 for applying a reverse bias to the EL element 266. Selection of reverse bias application is performed using the switching element 331, Whether to apply a reverse bias is determined by the voltage of the line 269.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent device.
For example, the present invention relates to a display device that performs grayscale display by the amount of current. [0002] Organic light-emitting devices are self-luminous devices.
The backlight required for liquid crystal display devices is unnecessary.
And with the advantage of a wide viewing angle,
Is expected. [0003] As in the case of an organic light emitting device,
Is proportional to the emission intensity of the device and the electric field applied to the device.
The emission intensity of the device and the current density flowing through the device
Because of the example relationship, the variation in the element film thickness and the input signal
In contrast to variations in values, variations in emission intensity are used for current control.
Performing the gradation display can make the size smaller. When used in a portable information terminal or the like, the power supply
Due to the limited amount, low power driving is required. In general,
-During periods when there is no external input compared to periods during input operations, calls, etc.
Because the waiting period is longer, the waiting period
Devising a method for reducing power consumption in the
It can be said that it is effective for As a method for achieving this, in a liquid crystal display device,
It is called partial display mode that displays only a part of the screen
Mode, and as shown in FIG.
Some rows are always in a non-lighting state (non-display area 55b).
Display only the information necessary at the time of standby.
There is a method of setting the display state as shown in FIGS. [0006] In addition, even in the case of a foldable terminal, a closed state is required.
Small display so that you can understand the receipt of mail in the state
May be provided. Therefore, as shown in FIG.
A hole 61 is provided in place of a simple display unit, and the display of the display unit 60 is
There is also a method of viewing through the hole 61. In this case, the display unit 60
Only needs to perform partial display of only the region 60b. Like this
Partial display on portable information terminals enables limited power supply
It is a mandatory condition to use. In a display device using an organic light emitting element,
Similarly, low power consumption can be achieved by providing a non-display section.
Considering the characteristics of the organic light emitting element,
Is a system configuration that takes advantage of almost zero power consumption.
Devising that it will be [0008] In order to solve the above problems,
The active matrix type display device of the present invention
During display, both display and non-display areas are powered by power supply voltage or pixels.
Characterized in that the current to be applied is reduced. In a display device using an organic light emitting element,
Redox of organic molecules by injection of carriers into organic layer
Degradation and Driving due to Chemical Reaction and Space Charge Formation
Apply a reverse bias to the organic light emitting device to prevent the dynamic voltage from rising.
The configuration is such that the lifetime is increased and the drive voltage is prevented from rising. [0010] Further, in a transmissive liquid crystal display device, a portable information processing device is provided.
Perform key operations for a certain period of time when creating an information terminal
If there is no, there is a way to reduce the power by turning off the backlight
However, in a display device using an organic light emitting element, similarly,
After a certain period of time, lower the brightness and lower the power.
did. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described.
The description will be made with reference to the drawings. (Embodiment 1) FIG. 2 shows a first embodiment of the present invention.
It is a block diagram of a display in an embodiment. Display area
Area storage means 12, and the size of the display area of the display unit 16
And the position can be changed, and the partial switching unit
13 to select the full screen display mode or the partial display mode.
Can be selected. The display area storage means 12 includes a controller 11
Stores the size and start line of the display area specified by
You. The output of the partial switching unit 13 depends on the number of display rows.
Source driver 15 so as to change the horizontal scanning period.
And the input to the gate driver 17, the information of the display area is
Sent. In the gate driver 17, a non-display row and
Different output on display line. The display unit 16 is, for example, as shown in FIG.
The pixels are arranged in a matrix as shown in
Are shown in FIGS. 3, 7, 8, 10, and 13, for example.
One of the pixel configurations is formed. In a non-display row, the transistor of each pixel
Of these, the transistor connected to the EL element is always turned off.
By conducting, no current flows to the EL element and no light is emitted
State. The following is an example of five pixel configurations
The operation will be described. FIG. 3 shows a game in one horizontal scanning period of one frame.
A signal indicating the conduction state is applied to the signal line 1 (22),
Current flowing through the source signal line 21 to the active transistor 27a
Program so that the same current flows. In the rest period
The gate signal line 1 (22) is turned off and the gate signal
The line 2 (23) is turned on, and the drive transistor 27 is turned on.
The current flowing to a is passed to the EL element 26. In this way,
Gradation control by changing the current value flowing through the source signal line
I do. As shown in FIG. 4, only a part of the screen is displayed.
During the partial display, the black is displayed on the non-display part by the above scanning.
May be passed, but easily form a non-display part
In the non-display area during the entire period of one frame
Signal line 2 (23) is turned off, and the EL element 26 is turned off.
What is necessary is just to prevent the electric current from flowing through. Gate signal line 1
Similarly, (22) is turned off. This allows the game
Since the non-conducting signal always flows through the signal lines 1 and 2,
Power due to charging / discharging of the stray capacitance existing on the
It becomes. Also, when writing black in the non-display area,
The current flowing through the source signal line 21 in black writing
And the apparent resistance of the driving transistor 27a is large.
And the product of the parasitic capacitance of the source signal line 21 and
Due to the effect of waveform rounding due to
The problem of not being able to write can be avoided and black display
Display with low brightness at the time is possible. Transistors generated in a liquid crystal display device
The luminance change due to the off-leak current of the
Even if the current flowing through the transistor 27d is large in the element 26,
About several nA, which is smaller than the current value at which the EL element 26 emits light.
Does not change with off-leak current
There is an advantage. In order to perform such display, the game of the present invention is used.
Driver 17 at the time of partial display as shown in FIG.
The feature is that it is possible to output a great amount. This figure 5
In this example, the (i + 1) th row to the jth row are non-display rows.
During the period, both gate signal lines 1 and 2 pass a non-conduction signal,
The other display lines are scanned sequentially. In this example, the display line next to the i-th line is
All rows are not selected while selecting the (j + 1) th row
The horizontal scanning period is changed, and the i-th row
Next, the (j + 1) th row may be immediately selected. An example of generating such a gate signal line is as follows.
The circuit is shown in FIG. FIG. 6A shows a transfer gate.
FIG. 6B shows a latch unit 227 using
FIG. 2 shows a block diagram for outputting signal lines. The cycle of the clock depends on the length of one horizontal scanning period.
Clock A 221a and clock B 221b
Are inverted outputs from each other. The enable signal 222 is
High active, high level on non-display row, display row
Is input a low level. Selector 228 latches the gate signal line output
Select whether to output the output of the unit or the output based on the enable signal
The output of the latch section is displayed on the display row, and
Select the output based on the output signal. Note that the enable signal
The output based on the signal is gate signal line 1 and gate signal line 2
The non-conductive level is output. The configuration in FIG.
If there are as many gate signal lines as there are pixels, the waveform of FIG.
Shape can be realized. In the waveform of FIG.
Cable signal 222 is input only to the selection unit 228,
There is no need for an enable signal for the switch 227. On the other hand, the i-th line
When scanning the (j + 1) th row in the next horizontal scanning period,
Using the enable signal 222 of the latch unit 227,
Transfer data without latching the latch unit 227 of the display unit
What should I do? The circuit shown in FIG. 6 is merely an example.
The present invention is implemented as long as the circuit can output a waveform such as
Can be FIG. 7 shows an EL element from the driving transistor 47a.
Switching transistor for controlling the connection of current to element 46
A switching transistor 47e is connected in parallel with the star 47d.
And EL through a switching transistor 47e.
The voltage supplied from the reverse bias power supply line 48 to the element 46 is
4 shows a pixel configuration that can be applied. The switching transistor 47d is a p-type transistor.
In the case of a transistor, the switching transistor 47
The gate signal line 2 (4
When 3) is at a low level, the driving transistor 47a is
The flowing current flows to the EL element 46, and when the current is at a high level,
A reverse bias voltage can be applied. A waveform similar to that shown in FIG. 5 is applied to the gate signal line.
The switching transistor 47d in the non-display row.
Is non-conductive, and the switching transistor 47e is conductive.
Therefore, the power of the EL element 46 is connected to the reverse bias power supply line 48.
Reverse voltage by applying a voltage lower than the sword potential
Can be applied, and the life can be prolonged.
Note that applying a reverse voltage will extend the life.
Literature (Applied Physics Letter)
s, Vol. 69, no. 15, p. 2160-
2162, 1996). Therefore, the use of the configuration of FIG.
In addition to the power reduction in the case of the
In addition, there is an advantage that the life can be extended. FIG. 8 shows the flow through the source signal line 81 as in FIG.
The charge of the storage capacitor 84 is controlled by the current flowing through the
The current flowing through the transistors 87a and 87c can be controlled.
With this, the luminance of the EL element 86 is changed to perform gradation display.
Circuit. In the display row, each gate signal line 1 (8
2), 2 (83) and 3 (88) are as shown in FIG.
The gate signal lines 1 and 2 are conductive during one horizontal scanning period.
And a current is stored from the source signal line 81.
Flow to volume 84 (selection period). Next, as a non-conductive state,
The charge stored in the storage capacitor 84 is held and the gate signal line 3
A signal indicating the conduction state is output to (88), and the transistor 8
A current is supplied to the EL element 86 via 7e. On the other hand, in the non-display row, three games
As shown in FIG. 9B, a signal indicating a non-conductive state is
Signal, and almost eliminates the current flowing through the EL element 86.
Set to the non-display state. Also in this method, the non-display section is used as the display section.
Similarly, output to the gate signal line and black display current to the source signal line
Is flowing, the apparent resistance of the driving transistor 87a becomes
And the product of this resistance and the stray capacitance of the source signal line.
Waveform becomes larger than the white signal,
During the scanning period, the current does not change to a predetermined
It is said that the brightness increases due to the accumulation of
Problem. On the other hand, the gate signal line 3 according to the present invention
(88) and the transistor 87e are added,
Makes the transistor 87e non-conductive,
The problem is solved, and a display with blackened out is enabled. Ma
In addition, similarly to FIG.
By connecting to the negative electrode,
Reverse bias can be applied at all times to extend the life
The effect is also obtained. FIG. 10 shows the storage of the voltage of the source signal line 121.
It is stored in the capacitor 124, and the driving transformer is operated based on the stored electric charge.
The current flowing through the transistor 127a changes, and the EL element 126
Pixel structure when gradation display is performed by changing the
It shows the result. In the present invention, the switching transformer
The feature is that a resistor 127c is provided. To form a non-display line in the conventional configuration,
Display black at least every 10 frames
It was necessary to store the signal voltage in the storage capacitor 124.
This means that, for example, once a voltage indicating black is stored in the storage capacitor 124.
And the transistor 127b is turned off.
However, even when the transistor 127b is off,
Current (off-leak current) flows through the storage capacitor 124
This voltage (= the gate voltage of the driving transistor 127a)
Voltage) to be equal to the voltage of the source signal line 121.
It is because it becomes. Therefore, the source signal line 121
When a voltage indicating white is applied to the transistor 127,
drive transistor 127a gradually due to the leakage current of
Of the EL element 12 changes to a voltage value indicating white.
6, the current of the same gradation as that of white flows, and the brightness of the non-display area
The problem is that the degree changes according to the video signal of the display
appear. In the present invention, the gate signal line 2 (12
3) and drive transistor 127c
On the current path between transistor 127a and EL element 126
In the non-display row, the switching transistor 12
7c is turned off so that the transistor 127b
Current of drive transistor 127a due to off-leak current
This has the effect of enabling black display without being affected by changes in the value.
You. FIG. 11 shows gates in a display area row and a non-display area row.
3 shows a signal line waveform. It is assumed that the switching transistor 12
Even if an off-leak current is generated in 7c, its value is about several nA.
Because of the degree, black display is possible. Like this, switchon
Off-leakage current by adding a transistor 127c.
It is possible to prevent the display quality from deteriorating due to the flow. FIG. 12 also shows this pixel configuration.
As shown in FIG.
Sometimes, a reverse voltage can be applied to the EL element 126.
Switching transistor 237 and reverse bias power supply line 23
8 and apply a reverse voltage to the EL element 126.
This can extend the life. In this configuration,
Simply switch the switching transistors 237 and 127c
Although they are composed of n-type and p-type, respectively, they may be reversed.
Both are n-type or p-type,
The other inverted signal may be input to the gate input of the transistor.
No. FIG. 13 shows the conduction of the driving transistor 107a.
Even if the threshold voltage varies between pixels, the same drain
It can be corrected by providing a capacitor 108 so that
The configuration is as follows. The display line is shown in FIG.
Show. The EL element is changed according to the electric charge stored in the storage capacitor 104.
A current flows through the child 106. In the non-display row, as shown in FIG.
The transistor 107d is connected to the gate signal line 3 (109).
In a non-conducting state so that no current flows through the EL element 106.
Thus, black display can be performed in the non-display section. Also in this pixel configuration, the transistor
Transistor that operates exclusively with the
Non-display row by providing between 106 and reverse bias power supply
Reverse voltage can be applied to the EL element 106 of
The service life can be extended. (Embodiment 2) FIG.
FIG. 1 shows a circuit configuration for realizing low power consumption. Source Driver 146 and Gate Driver
147 to perform full screen display, or display area storage unit 1
Parsers to select whether to display the row stored in 43
Output of the output switching unit 144 to the EL power supply unit 145
The EL power supply voltage changes between full screen display and partial display.
It was made to be. This EL power supply unit 145 is provided for each pixel.
Connected to the connected EL power line and applied to the EL element
Voltage is supplied to the EL power supply unit 14 via a driving transistor.
Supplied from 5. Excludes voltage drop across drive transistor
More specifically, a voltage is applied to the EL element 152 as shown in FIG.
Is applied to change the output of the EL power supply unit 145.
Changes the power supply voltage Vdd151. FIG. 16 (a) shows the current of a typical EL element.
Luminance (153 (a)) and current-voltage (154) characteristics.
You. If the required luminance is up to Lw, then
Current flowing through the EL element 152 is a straight line of 153 (a).
Iw, and the voltage applied to the EL element 152 at that time
Becomes Vw. Therefore, the voltage required for the power supply voltage Vdd is
At least margin such as Vw and variation of EL element
If it sees, it is about Vdd1. Here, the power supply voltage Vdd was reduced to Vdd2.
Then, the voltage applied to the EL element becomes Vdd2 or more.
No luminance is generated, and as shown by the dashed line in 153 (b).
Above a certain luminance, it does not increase even if the current value is increased. That is,
The gradation near white has almost the same luminance. At the time of partial display, minimum necessary information
Display is often used, so the number of display gradations is 2 to 8 floors
Tone and less than the maximum displayable number of 64 tones
Therefore, luminance change per gradation is large, and Vdd2 is adjusted.
By doing so, the current-brightness as shown by the one-dot chain line in 153 (b)
Even if the characteristics are obtained, the display is not affected. Also, partial display
In some cases, adjusting the necessary gradation method affects the display.
It is possible to increase the range of Vdd2 that is not used.
In this way, low power driving is realized by lowering the power supply voltage.
Can be (Embodiment 3) When displaying a partial image,
When the number of display gradations is smaller than that of the screen display, the brightness between the gradations
The amount of change increases. This is the power source in FIG.
Even when the voltage Vdd is set to Vdd2, the brightness becomes constant.
The number of gradations that take a current value decreases. For example, the number of display gradations
Becomes 1/4, only 1/4 gradation has the same brightness.
Become. Therefore, the lower the number of colors, the lower
153 (b) little display degradation due to dashed-dotted line characteristics
Therefore, the power supply voltage can be reduced. Generally, each power supply of the display device is a certain reference.
The voltage is generated by increasing or decreasing the voltage several times.
The value of the EL power supply value must be an integer multiple of the reference voltage value.
Thus, the power of the entire display device can be used effectively. So
Here, the voltage value of the power supply voltage Vdd 151 is an integer of the reference power supply.
One of the times, and when displaying partial, compared to full screen
If a voltage with a small magnification is used, the power supply voltage can be generated.
The extra power required to achieve
The power consumed by the EL element 152 can be reduced.
Wear. (Embodiment 4) FIG. 17 shows a fourth embodiment of the present invention.
Block diagram showing one embodiment and one pixel circuit.
It is. The source signal line 201 responds to input data
Digital-to-analog converter (D / A converter) 20
9 and the voltage according to the data through the output buffer 203.
The value is applied. At this time, the maximum voltage applied to the source signal line
The large voltage value is based on Vref output from the voltage generation unit 204.
Can be decided. A voltage generator 204 is connected to the EL power supply line 208.
Is output. At the time of partial display, the minimum necessary information
Must be displayed with as little power as possible.
The luminance at the time of display may be lower than that at the time of full screen display. When lowering the luminance, the voltage of the EL power supply line 208
Are equal, the source signal line voltage needs to be higher.
You. On the other hand, the EL power supply line 208 and Vref have the same voltage value.
It is possible to obtain the same luminance even if only the brightness is reduced. Shine
If the degree decreases, the voltage applied to the EL element 206 also decreases.
And can be displayed. To reduce the voltage of all power supplies,
The reference voltage V1 input to the pressure generation unit may be reduced.
No. Partial switching as control signal input for reference voltage
The output of the data format detecting means 200b.
The power supply voltage depending on the size of the display area and the number of colors.
Can be changed and the number of colors in the partial display is small.
The reference voltage V1 can be made the lowest. This
Display device that can switch between image quality priority and power priority display.
Can be realized. Note that the data format detection means 200b
Control bits or packets detected for force data
Then, for example, assume that data is sent as shown in FIG.
And the contents of 183 containing information on the number of colors
It is possible to identify the number of colors. (Embodiment 5) FIG. 19 shows a fifth embodiment of the present invention.
FIG. 2 shows a block diagram in the embodiment. Duplicate
Oscillators 161 and one of the plurality of oscillators 161
Switching circuit 162 and frequency divider 163 for selecting an output
Is a feature of the present invention. The switching circuit 162 and the frequency dividing circuit 163
The output is controlled by the partial switching unit 167,
Change the oscillation frequency between screen display and partial display.
The frame frequency and horizontal scanning period
Can be made. Here, lowering the frame frequency means
Means that the charge and discharge power of each signal line can be reduced
Indicates that Also, assume that the frame frequency is the same,
The horizontal scanning period can be extended according to changes in the number of rows.
Wear. This is particularly true for the EL element according to the current value of the source signal line.
In the case of performing gray scale display of a child, for example, the pixel configuration of FIG.
Of the drive transistor 27a in a display device having
The apparent resistance is large and depends on the product of the capacitance of the source signal line 21 and the capacitance.
Time constant also increases, making it difficult to rise during the horizontal scanning period.
However, it is not possible to change the oscillation frequency according to the present invention.
Extending the horizontal scanning period with the
This is effective for facilitating the operation. Pixel configuration of FIG.
Also, the apparent resistance value of the driving transistor 87a
, The effect of the present invention can be similarly obtained. In general, when a partial display is performed as compared with a full screen display
Then, the number of display colors decreases. In this case, the gradation display method and
And use the frame rate control method (FRC)
Flicker between full screen display and partial display
The minimum frame frequency that can be displayed without
15Hz, 4096 colors full screen display at the time of display
80Hz (if the display color in full screen display increases,
Of course, the frame frequency also increases). Oscillation in the present invention
Unit 1 (161a) is used as an oscillator at the time of full screen display,
2 (161b) as the oscillator for partial display,
By setting the wave number, the frame frequency during partial display is reduced
Can be done. (Embodiment 6) The current value of the source signal line
When performing more gradation control, for example, a pixel configuration as shown in FIG.
Can be considered. One horizontal operation by operating the gate signal line 1
Drives the same current as the current flowing in the source signal line during the scanning period
The potential of the contact 28A is set so as to flow through the transistor 27a.
To change. At this time, the potential of the contact 28A is changed.
Is supplied through the driving transistor 27a.
You. If the current flowing through the source signal line is
From the current-voltage characteristics of the active transistor 27a.
The resistance value is very large, and the product with the stray capacitance is large.
Therefore, the time required for the change is 250 μsec or more. So
Therefore, at 220 lines and at a frame frequency of 60 Hz, the input data
Data cannot be displayed in gradation.
Was. As a method for solving this, a predetermined floor
X times the current (where X is a natural number of 2 or more)
Then, the apparent resistance value of the driving transistor 27a is reduced,
The change of the source signal line current is made faster. Predetermined brightness
To adjust the degree, adjust the pulse width applied to the gate signal line 2.
To control the period during which current flows through the EL element 26
I went in. At this time, the wave of the source signal line and the gate signal line
The shape is shown in FIG. The horizontal scanning period can be extended during partial display.
In the fifth embodiment, the current of the source signal line
The time required to change the value may be delayed. Frame circumference
When the wave number is constant, if the display row is half, horizontal scanning
The period will be approximately doubled. The number of partial display lines is about one third or less of the whole screen
If the frame frequency is 60 Hz,
However, since one horizontal scanning period is 230 μsec or more,
It is possible to lower the magnification of the writing current compared to when displaying the screen.
it can. If one horizontal scanning period is 250 μsec or more,
What is necessary is just to write according to an electric current. With this method, you can write
Required current value may decrease during a certain period of time
If the current value flowing through the EL element decreases,
Is applied to the EL power supply line 25 because the
Voltage value can also be reduced, reducing power consumption
be able to. For example, writing with 10 times current
Is written at a predetermined current, the EL power supply voltage is about 30%
Power consumption by 30%. (Embodiment 7) FIG. 21 shows a seventh embodiment of the present invention.
Input data processing unit and source signal for implementing the embodiment
3 shows a line output unit. As a feature of the present invention, the data RAM 174
To the source signal line for the data sent from
The setting of the flow value can be changed in the conversion table 176.
The operation of the conversion table 176 is performed by the timer 175 and
Data format detection unit 173, partial switching unit 17
2 can be changed by the output. For example, in the timer 175, FIG.
And button operation on the information terminal shown in FIG.
Detects signals and displays at a predetermined brightness after button operation
However, after a certain time, the value of the conversion table 176 is changed.
And display it so that it is reduced to 10% or more and 60% or less of the predetermined brightness
Change the way the current source 177 is selected for the data value
Can be This allows the user to perform an operation
Is displayed, gradation is displayed with display priority, and after a certain time
Lower the brightness and lower the current value to drive low power.
So that limited power can be used effectively
I do. Note that this method can be applied to devices other than portable information devices.
Use as a power saving mode for monitors, etc.
And lower power consumption, helping to protect the global environment.
stand. The data format detection means 173 inputs
Detected display data and determine the number of colors, video still images, etc.
Perform settings. This means that the data is transmitted as shown in FIG.
If so, the flag unit 181 indicating the start of each packet
Detection, the header section 182, the number of colors 183, and the control signal 1
The determination can be made by detecting the value of 84. The result determined in this way is stored in the data RAM.
174 and the conversion table 176. Data RA
In M174, based on the output of the data format detecting means 173,
Then, select the method of storing in RAM according to the number of colors, etc.
The limited capacity can be used effectively. On the other hand, the conversion table 176 has a data format
According to the number of display gradations detected by the detecting means 173, the gradation-
Brightness characteristics can be changed. This is the display floor
It is possible to obtain an optimum gradation characteristic for each key. Further, the timer 175 and the data format detecting means
By combining the step 173, when the number of display gradations is small,
When the user looks at the display screen, such as when operating keys
It is possible to change the display brightness after a certain time
is there. For example, as shown in FIG.
In the case of performing 4-gradation display in the device, in addition to gradations 0 and 15,
In many cases, two gradations are used. During or after key operation
In a certain period, the gradation is obtained in this way, and the timer 175
After a certain period of time, for example, 4-gradation display of gradation 0 to 3 is performed.
So that By performing this operation, the flow to the EL element
Low power because large current value can be reduced from I15 to I3
Driving becomes possible. Note that luminance and power are trade-offs.
Because of the relationship, depending on the power and required luminance,
The manner of connection may be changed. As another method for reducing power consumption, a current source 177 is used.
Can also be realized by reducing the respective current values. Current
Timer 175 is used as a means for determining whether to decrease the value.
Data type detecting means 173 is used. In this case, the display gradation
Since the maximum brightness can be reduced regardless of the number, power consumption can be reduced.
You. (Embodiment 8) In the configuration of FIG.
The output of the partial switching unit 172 is sorted as shown in FIG.
Data to the driver and gate driver.
By sending to AM 174 and conversion table 176,
The effective use of the data RAM 174 area during display
Can be For example, one picture is stored in the data RAM 174.
Assuming that surface data can be stored,
Depending on the display ratio to the screen, data for multiple screens
Can accumulate. As a result, the display data can be externally transferred to the data R.
There is no need to transfer data to AM 174, reducing power consumption
be able to. Also, in the conversion table 176,
The number of display gradations is the same during screen display and partial display, and the same gradation
Changing the selected current source 177 for data
Image quality priority during full screen display,
It is possible to set to display with priority on power at the time of partial display
It works. Although not shown in FIG.
Provided, time setting of timer 175, conversion table 176
May be adjusted from outside. (Embodiment 9) FIG. 24 shows a ninth embodiment of the present invention.
It is a figure showing an embodiment. FIG. 24 differs from FIG.
(A) As shown in FIG.
Reverse bias voltage applied between the switching transistor and EL element
Transistor 267e for the EL element 266
The point is that a directional voltage can be applied. The operation of the circuit shown in FIG. table
In the row of the display area, as shown in FIG.
Transit once by gate signal line 1 (261)
The stars 267b and 267c are turned on (first period).
while). At this time, the gate signal line 2 (262)
The transistor 267d is turned off, and the source signal line 260
Flows through the drive transistor 267a. Accumulation
The product capacitance 264 is the gate of the driving transistor 267a at this time.
Charge corresponding to the gate potential. EL element 2
The potential of the anode electrode 66 is equal to or higher than the cathode potential.
Therefore, the transistor 267e is turned on or off.
The conduction state depends on the potential of the reverse bias signal line 269.
Can be decided. The reverse bias power supply Va268 is the length of the EL element.
Since the purpose is to extend the life and prevent the terminal voltage from rising, EL
5 V or more and 15 V or less than the anode potential of the element 266
The voltage must be lower by the value. Emission of EL element 266
It is desirable that a reverse voltage higher than the driving voltage during light is applied.
In FIG. 24, the voltage value is approximately −15 V or more and −5 V or less.
Take. Therefore, the reverse bias is supplied by the reverse bias control line 259.
The reverse bias voltage Va is applied to the bias signal line 269
In this case, the transistor 267e is turned on, and the EL element
A reverse bias voltage is applied to the element 266. On the other hand, the voltage value of the gate-off power supply Vb258
The gate signal line 3 (263) of the transistor 267e
Apply the above voltage. The voltage value to be applied is transistor 2
A voltage between 0 V and 3 V depending on the threshold voltage of 67e
May be applied. Especially when applying 0V, the power supply must be
The circuit configuration can be simplified because there is no need to create
You. As a result, the gate-off voltage is applied to the reverse bias signal line 269.
When the voltage Vb is applied, the transistor 267e is turned off.
State. In the first period, the transistor 267d is non-conductive.
Current flows through the EL element 266
As shown in FIG.
Thus, the potential of the reverse bias signal line 269 is Va or Vb.
The deviation may be taken. Extends life and prevents terminal voltage rise
To the reverse bias signal line 269
It is desirable to apply a potential Va of 268. A predetermined charge is stored in the storage capacitor 264.
When the first period ends, the gate signal line 1 (261) and
24 and the gate signal line 2 (262) in the second period of FIG.
The potential of the transistor 267b
And 267c are turned off, and transistor 267d is turned on.
State. As a result, the driving transistor 267a
Current is supplied from the EL power supply line 265 according to the gate voltage.
The EL element 266 is turned on. At this time, the current flows through the drive transistor 267a.
Current is approximately equal to the current flowing through the EL element 266
Otherwise, the brightness may be reduced.
e must be non-conductive. EL element 266
The anode potential is higher than the gate potential of the transistor 267e.
Is high, the potential of the reverse bias signal line 269 is gated.
If it is equal to the off power supply Vb258, the transistor 26
7e can be made non-conductive. for that reason,
The potential of the reverse bias signal line 269 in the second period is Vb.
is there. As described above, the first period and the second period
As one frame, lighting and non-lighting of predetermined brightness
Reverse bias voltage applied to EL element 266 at the time
it can. On the other hand, in the row of the non-lighting area, black display is performed.
In order to perform the operation, the transistor is connected by the gate signal line 2 (262).
267d is always in a non-conductive state. This allows the storage volume
There is no need to store charge corresponding to black display in the quantity 264.
Therefore, there is no need to take in the black display current from the source signal line.
Gate signal line 1 (261) is also always in a non-conductive state.
You. Also, a reverse via is connected to the reverse bias signal line 269.
The transistor 267 is applied by applying the
e becomes conductive, and the reverse bias voltage Va becomes the EL element 2
66 is applied. Thereby, the EL element 2 in the display area
The predetermined current value flows only during the lighting period of 66, and during the non-lighting period,
Is applied with a reverse bias voltage. The advantages of the pixel configuration shown in FIG.
Therefore, the potential of the gate signal line 3 (263) is always constant.
Noise due to coupling to source signal lines, etc.
Sound, and the gate signal line 3 (263)
Is at the same potential as the cathode electrode of the EL element 266.
From the gate signal line 3 (263) and the EL element for each pixel.
266 cathode electrodes are connected using through holes
As shown in FIG. 25, there is no lead line to the outside of the pixel.
Reduces the number of output terminals of the gate driver 328
In addition, the frame can be reduced. Each transaction in the pixel
The voltage applied to the transistor 267 is 10V to 12V at the maximum.
It is possible to use transistors with low breakdown voltage
It is. Further, a reverse bias voltage is applied to a plurality of lines simultaneously.
When applying at the timing, the reverse bias control line 259
And the number of reverse bias signal lines 269 is equal to the number of simultaneously selected lines.
The gate driver 328 can be reduced by the increase.
Can be reduced in circuit scale. For example, reverse
Apply all bias within the blanking period in one frame.
When the voltage is applied simultaneously to the pixels, the reverse bias control line 259 and
Only one reverse bias signal line 269 is required. The conduction / non-conduction state of the transistor 267e
Is controlled by changing the voltage of the gate signal line 3 (263).
Instead of changing the potential of the source or drain electrode.
And control the gate signal line 1 (261) and
Different from the gate voltage of the gate signal line 2 (262)
The gate signal line 3 (263)
By setting a constant 1 value from the 2
The number of voltage values required for the bus 328 can be reduced.
Was. Further, the potential of the gate signal line 3 (263) is
By setting the voltage value equal to the potential, the number of voltage sources can be further increased.
Could be reduced. Note that the transistor forming the current copier is
The four transistors of the transistors 267a to 267d
That is, at least the current supplied from the EL power supply line 265 is
When the transistor 267a to be controlled is an n-type transistor,
In the case, the transistor 2 determines whether to apply a reverse bias.
67e is a p-type transistor 267j as shown in FIG.
And it is sufficient. This means that the driving transistor is changed from p-type to n-type.
By changing the direction, the direction of the current flowing in the pixel changes,
EL element to which a transistor that determines bias application is connected
To determine whether to supply current to the element 266 and the EL element 266.
At the contact 257 between the transistors, the emission of the EL element 266 occurs.
This is because the level of the light potential and the non-light emission potential are inverted. When using the p-type drive transistor 267a,
In this case, the potential of the contact 257 is (when light is emitted)> (when no light is emitted).
When the n-type drive transistor 267i is used,
The potential of 257 is (non-light emission)> (light emission). Reverse bar
Transistor that determines bias application is conductive when not emitting light
State and non-conducting state at the time of light emission. Gate signal
With the voltage value of line 3 (263) constant, the source or
If you try to achieve by changing the drain voltage,
The p-type drive transistor 267a emits light (source
Or drain voltage)> (gate voltage) non-conductive
State, non-emission (gate voltage)> (source or
It is necessary to be in the conductive state at the rain voltage).
Transistor 267e and an n-type drive transistor 267
At f, during light emission (gate voltage)> (source or drain)
(Rain voltage), non-conducting state, non-light emitting (source if
(Drain voltage)> (Gate voltage)
Therefore, a p-type transistor 267j is used. The gate of p-type transistor 267j
The potential of the signal line 3 (263) is the reverse bias power supply Vc268.
EL power line 265
From the voltage value lowered in the EL element 266 from
The gate signal line 3 (263) may be connected to the EL
A signal line that is drawn out of the pixel by connecting to the source line 265
Since the number can be reduced, the EL power supply line 265 and the
It is desirable to connect. At this time, the gate-off power supply Vd
258 is equal to or less than the same potential as the EL power supply line 265 and is 3
What is necessary is just to be equal to or higher than the potential lowered by about V. Also reverse via
The power supply Vc 268 is 5 V or more from the EL power supply line 265 and 15
What is necessary is just to output high voltage below V. Desiring
Or the voltage value applied to the EL element 266 during light emission
The value may be such that a large voltage value is applied in the direction. FIG. 26 shows drive waveforms in the rows of the display area.
FIG. 26B shows a driving waveform in a row of the non-display area in FIG.
It is shown in (c). Thus, the reverse bias is applied.
The gate potential of the switching element is fixed, and the reverse bias
By controlling the pressure, the on / off of the switching element is controlled.
And decide whether to apply a reverse bias to the EL element 266
The method of current copier type shown in FIGS.
In addition to the pixel configuration shown in FIG.
As shown in FIG.
The transistor 2 according to the voltage value of the source signal line 260
Pixel configuration for controlling current flowing through 67a and performing gradation display
But it is possible. In the pixel configuration shown in FIG.
As shown in FIG. 27 (b), one frame
Once the transistors 267d and 267b are turned on.
The current of the source signal line 260 to the transistor 267a
Pour The gate potential of the transistor 267a is the drain
It changes according to the current value, which causes the gate electrode to
The drain of the transistor 267c which is a line
The same current as the source signal line current flows. At this time, the gate signal line 3 (303) is high.
Either level or low level may be used.
To prevent the L terminal voltage from rising, set the transistor to high level.
The star 267g is turned off, and the cathode of the EL element 266 is turned off.
Reverse bias power supply Va268 that is lower than
When applied to the ground signal line 269, the transistor 26
7e has a source or drain potential higher than the gate potential
Transistor 267e is conductive because it is low enough
And a reverse bias voltage is applied to the EL element 266.
You. When the row selection period ends, the gate signal line 1
(301) and gate signal line 2 (302)
The transistors 267b and 267d are turned off.
According to the charge stored in the storage capacitor 264 during the row selection period
A current flows through the transistor 267c. Current value at this time
Was flowing through the source signal line 260 during the row selection period.
Equal to the current value. The transistor 267g is turned on.
Then, a predetermined luminance is displayed by applying a current to the EL element 266.
I do. At this time, the transistor 267e is turned off.
For this purpose, the gate signal line 4 is connected to the reverse bias signal line 269.
(304) The above potential is applied. For this reason
Operates the reverse bias control line 259 to supply the gate-off power
Select Vb258 and change the value of Vb from 0V to 3V
Set to. Thus, the current flows through the transistor 267c.
The current leaks through the transistor 267e,
Luminance decreases due to decrease in current flowing through EL element 266
Problems can be avoided. On the other hand, in the row of the non-display area, FIG.
As shown, the gate signal line 3 (303)
The star 267g is turned off and the EL element 266 is turned off.
Cut the direction current. To apply reverse bias at the same time
The reverse bias power supply Va268 to the reverse bias signal line 269.
To make the transistor 267e conductive, and reverse
An ass voltage is applied to the EL element 266. FIG. 28A shows the response to the voltage value of the source signal line.
Control the drain current of drive transistor 267a
In addition, the pixel configuration controls the luminance of the EL element 266. The rows in the display area are shown in FIG.
In this way, the voltage of the source signal line is
Take in. Transistor is connected to gate signal line 2 (312).
A signal for turning on the transistor 267g is applied to the EL element.
A predetermined luminance is output when a current flows through the 266. this
At this time, the gate-off power supply Vb2 is connected to the reverse bias signal line 269.
58 to turn off the transistor 267e.
Keep it. In the row of the non-display area, FIG.
As shown, the gate signal line 1 (311) and the gate signal line
2 (312) is a signal for turning off the transistor.
No forward current flows through EL element 266 by applying
To do. In addition, a reverse bias is applied to apply a reverse bias.
Apply bias power Va268 to reverse bias signal line 269
As a result, the transistor 267e is turned on,
A bias is applied to EL element 266. The voltage of the gate-off power supply Vb258 is
A potential higher than the gate voltage value of the transistor 267e (0 V or more)
3 V or less), and the value of the reverse bias power supply Va is EL element.
The absolute value is higher than the forward voltage applied to the
Is higher than the cathode potential of the EL element 266 by 5%.
Apply a low voltage in the range from V to 15V.
Just do it. This is because the EL element 2 is a p-type transistor.
When controlling the current value flowing through the pixel 66, the pixel configuration
It is common regardless. Also, in FIG. 27 and FIG.
Using the transistors 267a and 267c as n-type transistors
Is also feasible. At this time, reverse bias is applied as in FIG.
Transistor 267e that determines whether to apply voltage is p-type
It is a transistor, and the direction of current flow is reversed.
The connection direction of the EL element 266 and the power supply voltage.
It can be realized by making Current within the dotted line in FIG. 26
A circuit that performs gradation control according to the mirror type circuit and source voltage
You can change to the road. In the above invention, the switching transformer
267b, 267c, 267d, 267g, 26
7h, 267i are p-type transistors and n-type transistors
In both cases, it is practical to apply a reverse bias.
It is possible. Inverting the polarity of the gate signal line;
It only requires a change to adjust the voltage value
Therefore, the potential of the contact 257, the EL power line 265, and the reverse
Since the value of the bias power supply 268 does not change, the transistor
Because there is no change in the operation of 267e or 267j
It is. (Embodiment 10) FIG. 29A shows the present invention.
Shows a circuit configuration for realizing the tenth embodiment of FIG.
It is a thing. The difference from the ninth embodiment is that
Signal line 269 can be in a high impedance state.
And the potential of the gate signal line 3 (263) is applied with a reverse bias.
And when no voltage is applied. In the row of the display area, as shown in FIG.
And the current value corresponding to the display gradation once per frame is EL
The current flowing through the source signal line 260 to flow to the element 266
Capture the flow into the pixel. At this time, the transistor 267b
And 267c are turned on, and the transistor 267d is turned on.
The source signal is supplied to the drive transistor 267a as a non-conductive state.
The same current as the current flowing through the line 260 flows. At this time,
Since the L element 266 is in a non-light emitting state, a reverse bias voltage is applied.
Apply it. Reverse bias power supply Va268
The gate signal line 3 (26
3) as a potential higher than the reverse bias power supply Va
The transistor 267e is turned on and a reverse bias is applied.
You. The value of the reverse bias power supply Va is the same as in FIG.
Effective for longer life and prevention of terminal voltage rise
It should be a value. When the transistor 267d is turned on, E
While the L element 266 is outputting the predetermined luminance,
The star 267e needs to be turned off. for that reason
The gate signal line 3 (263) to the source / drain voltage
Make it all low. Here, the reverse bias control line 259 is operated.
Then, the reverse bias signal line 269 is connected to the reverse bias power supply 268.
Disconnection increases the source / drain voltage,
Increase the voltage value applied to the signal line 3 (263).
Can be. This is the reverse bias signal line 269
Compared to when the power supply 268 is applied (about -15 V)
Approximately 0V to 3V due to high impedance state
Can be Therefore, the breakdown voltage of the transistor
Can be designed low. In the row of the non-display area, as shown in FIG.
As described above, the reverse bias power supply 268 is connected to the reverse bias signal line 269.
And a reverse bias voltage is applied to the gate signal line 3 (263).
Voltage higher than the
A reverse bias is applied to the EL element 266 as a conduction state.
At this time, to cut off the current from the EL power supply line 265,
The transistor 267d needs to be turned off. Note that this configuration is different from the driving transistor 267
The same can be realized even if a is an n-channel. Power supply
Changing the voltage and the direction of the current change the EL element.
It is only necessary to reverse the connection direction of the child 266. Further, as described above, the gate signal line 3 (26
In the method of changing the potential in 3), is a reverse bias applied?
The selection transistor is the same as the drive transistor.
Use as a transistor with one carrier transport
Can simplify the film-forming process.
This is advantageous. The circuit configuration at this time is shown in FIG.
You. Gate signal line 1 (261) and gate signal
The waveform of line 2 (262) is similar to the pixel configuration of FIG.
You. Transistor connected to reverse bias signal line 269
Since 267f is a p-type transistor, the gate signal line
3 (263) is only inverted. Also,
The potential of the gate signal line 3 (263) is
7f is higher than the source or drain electrode when non-conductive
Potential (more than the drive voltage of EL element 266, drive voltage + 3V)
Below), and when the transistor 267f conducts, the source also
Or lower potential than the drain electrode (reverse bias power supply 2
68, a value about 5V to 15V lower than the voltage value Va).
Add. The signal polarity of the gate signal line 3 (263) and
It can be realized in the same manner as in FIG. 29 except that the voltage value is different.
You. The same applies to the rows in the non-display area in FIG. Also, only the pixel configuration of the current copier is used.
And gray scale table by current mirror and source signal line voltage
The method can be realized in the same manner as described above. Not only p-type drive transistors but also n-type
The same can be realized with a driving transistor. (Embodiment 11) FIGS. 1, 31 to 3
FIG. 3 shows an eleventh embodiment of the present invention. Current path flowing from power supply to EL element 266
Separately, a terminal connected to the power supply of the EL element 266
Connect a switching element to the terminal opposite to
A reverse bias signal line 269 is connected to the other end of the switching element.
You. Voltage value applied to reverse bias signal line 269
ON / OFF of switching element by changing
During the off period, the voltage controlled by the drive transistor
Current flows to the EL element 266, and the reverse bias signal
The voltage value applied to the signal line 269 is applied to the EL element,
A reverse voltage can be applied to the EL element 266. For example, in the pixel configuration shown in FIG.
As shown in FIG. 1 (b), the first
There is a second period, and in the first period, the gate signal line 1
The current flowing through the source signal line 260 is reduced by (261).
It flows to the active transistor 267a. The drive tiger at this time
The gate voltage of transistor 267a is stored in storage capacitor 264
I do. Transistor 2 for supplying current to EL element 266
The EL element 266 does not emit light because 67d is turned off.
It is. To apply a reverse voltage to the EL element 266
A reverse bias voltage is applied to the reverse bias signal line 269.
The change of the reverse bias voltage value is controlled by the reverse bias control line 259.
By changing the value of the control and reverse bias power supply 332,
Wear. At this time, the voltage across the switching element 331 becomes
The reverse bias signal line 269 is lower than the contact 334.
The switching element 331 is in a conductive state.
And switches from the voltage value of the reverse bias power supply 332.
The voltage value increased by the threshold voltage of the
And a reverse voltage is applied to the EL element 266.
You. Next, in the second period, the gate signal
Drive transistors by lines 1 (261) and 2 (262)
A current flowing through the EL element 266 flows through the EL element 266. Drive
The current value corresponding to the gray scale is output from the driving transistor 267a to E.
Since it is necessary to flow through the L element 266, the switching element
331 needs to be turned off. Therefore, the contact 33
4, the voltage value applied to the reverse bias signal line 269 is
Make it higher. Off power supply 33 by reverse bias control line 259
3 is applied to the reverse bias signal line 269 to turn off the
Switching element 331 is turned off by value Va of source 333
And Note that the value of the off power supply Va333 is different from that of the contact 334.
Higher, but preferably from the viewpoint of reducing the number of power supplies
To the EL power supply line 265, and connect the EL power supply.
You. Thereby, a reverse voltage is applied to the EL element 266.
As a result, the space charge accumulated inside the EL element 266 during light emission
Can release the charge and the chemical degradation of the molecule due to space charge
Decrease in luminance caused by the
The effect of extending the life is obtained. In FIG. 1, all the transistors in the pixel are provided.
In the above description, an example in which a p-type transistor is used is used.
Even if an n-type transistor is used as shown in FIG.
It is feasible. When an n-type transistor is used, the current flowing
Since the directions are opposite, the power supply, EL element, switch
It is necessary to reverse the direction of the chin element. Reverse bias
The power supply 342 applies a voltage higher than the EL power supply line 265
In the off power supply 343, when the EL element 266 is turned on, the contact
A voltage lower than 344 may be applied. Preferably this
In this circuit diagram, it is preferable to apply a ground potential.
This is because the number of power supplies required for the circuit is reduced. In this way, the EL element 266 emits light.
The off power supply 3 to the reverse bias signal line 269
By applying the output of 43, the switching element 341 is
When the EL element 266 is in a non-conductive state and does not emit light,
Output reverse bias power supply 342 to reverse bias signal line 269
The switching element 341 becomes conductive.
A reverse voltage can be applied to the EL element 266,
Emitting space charges accumulated inside the L element 266
Thus, the life can be extended. Further, the present invention is shown in FIGS.
It is also applicable to a display element having a pixel circuit. Reverse via
And the gate value of each transistor.
32 (b) and 33, respectively.
It is shown in (b). In each figure, the switching element is
It is desirable to use an element such as an ion. As shown in FIG. 34, the reverse bias signal line
Instead of pulling out the pixels, the power from the source signal line
Switch to the control line of the transistor to form the flow path.
One end of the switching element 392 is connected to the gate signal line 1 (3
A reverse bias is applied to the EL element 266 by the voltage value of (91).
You may set whether to add. This allows reverse vias
The aperture ratio can be increased because there are no signal lines
It is. Transistor is caused by gate signal line 2 (262).
Switching is performed during a period in which the star 267d is in a conductive state.
Element 392 needs to be off. At this time, the gate
The signal line 1 (391) receives the current from the source signal line 260.
Transistors 267c and 267b are turned off to shut off.
A voltage value for turning on is applied (second period).
The voltage at this time must be a p-type transistor
, The value becomes almost the same as that of the EL power supply line 265, and the contact 397
The potential of the gate signal line 1 (391) is higher than
The switching element 392 is turned off. On the other hand, the gate signal line 2 (262)
During the period when the transistor 267d is in the non-conductive state, the switch
The switching element 392 is turned on and the EL element 266 is inverted.
Applying the bias voltage (this reduces the life of the EL element 266).
Can prolong life). Gate signal line 1 (39
The potential of 1) should be sufficiently lower than the potential of the contact 397.
And the switching element 392 is turned on.
A reverse bias voltage is applied to element 266. At this time
Is the current of the source signal line 260 and the driving transistor 267
transistors 267c and 267b
Gate signal line 1 (391) has a low potential
And the switching element can be turned on.
You. (Embodiment 12) FIG. 35 shows a first embodiment of the present invention.
FIG. 9 is a diagram showing a second embodiment. Switch in FIG.
Transistor 371 in place of the switching element 331
What has been realized is a different point. In order to turn off the transistor 371,
The off power supply 333 is output to the IAS signal line 269. off
The voltage value of the power supply is the contact 257 when the EL element 266 emits light.
Can be realized by applying a higher voltage than the
You. It is preferable to match the power supply line with the EL power supply line 265.
Good. In order to turn on the transistor 371,
The voltage value of the bias signal line 269 is supplied to the reverse bias power supply 332.
Connected, and apply a voltage value sufficiently lower than that of the contact 257.
Just fine. To apply a reverse voltage to the EL element 266
Since the transistor 371 is turned on, a reverse bias is applied.
The value of the ground power supply 332 is a voltage sufficiently lower than that of the contact 257.
And the EL element in the configuration shown in FIG.
266 can be applied with a reverse voltage. FIG. 35B shows a gate signal line and a reverse bias.
7 shows a waveform of a ground signal line 269. EL element is not emitting light
In the first period, the voltage value of the reverse bias signal line 269 is
Is the reverse bias voltage value Vb and the reverse voltage is applied to the EL element.
During the second period in which the EL element is in a light emitting state.
The voltage value of the bias signal line 269 is set to the value of the off power supply Va.
By setting the transistor 371 to a non-conductive state,
The current supplied from the driving transistor 267a to the EL element
266 to perform gradation display. By this, hidden period
By applying a reverse bias voltage to the EL element between
The service life can be extended. Further, as a feature of the present invention, a transistor
Can be formed in p-type.
Gate voltage of the transistor that forms the
Because the pole is connected to the source or drain electrode,
Reverse the organic EL element without increasing the number of
This has the advantage that bias can be applied. The driving transistor is formed by the n-type transistor.
In the same way, realization with only n-type transistors
It is possible. This is shown in FIG. Also at that time
FIG. 36 (b) shows the driving waveform of FIG. Relationship between high and low potential
Only the direction of the current and the direction of the connection of the EL element have changed
In the same way, a reverse voltage can be applied to the EL element
It is. Further, similar to the eleventh embodiment, other pixel structures are used.
32 and FIG. 33.
When a pixel circuit is provided, the switching element 331 is
Replaced with a resistor and the figure for the case of two p-type power supplies
35, In the case of n-type, it is sufficient to set as shown in FIG.
No. (Embodiment 13) Reverse biasing shown in FIG.
By using the transistor 371, the pixel of the current copier
EL connection transistor that allows current to flow through the EL element 266 in the configuration
The inspection of the transistor 267d can be performed. EL
Before forming the element 266, the reverse bias control line 259 is operated.
And apply a reverse bias power source 332 to
The transistor 371 is turned on, and the current flows to the reverse bias power supply.
Measure the current value. White to black on the source signal line 260
The current flowing to the reverse bias power supply changes when the indicated current value flows
Observe whether current is flowing almost always
In this case, if the EL connection transistor 267d is conductive,
It can be seen that there is no defective state. As described above, before forming an EL element, a transistor is formed.
Inspection of the transistor 267d can be performed. Also, as shown in FIG.
Similarly, the current is controlled in the pixel configuration of the mirror.
Apply current to the driving transistor 267c and the EL element 266.
The supply transistor 267g can be tested
You. FIG. 37B shows a signal wave applied to each signal line.
Show the shape. Gate signal lines 1 to 3 are set to 1 as before.
Change on / off between frames. In the row selection period,
Operate the gate signal lines 1 and 2 to make the transistor conductive
And the transistor connected to the gate signal line 3 is turned off.
State so that a predetermined current flows through the transistor 267a.
The charge is stored in the storage capacitor 264. Next, during the non-selection period
Turns off the transistors connected to the gate signal lines 1 and 2.
The transistor connected to the gate signal line 3
By setting the conduction state, a predetermined current value is applied to the EL element 266.
Flows. According to the present invention, the switching element 331 is inserted.
Thus, even if the EL element 266 is not connected, the driving
The current flowing through the transistor 267c is applied to the switching element 3
31 and taken out by the current measuring means 431.
By measuring the current value, the EL element can be
Also determine whether transistors 267c and 267g operate.
Can be inspected. As described above, before forming the EL element, TF
The inspection of the array substrate on which T is formed can be performed.
This is a feature of the present invention. (Embodiment 14) FIG. 38 shows the first embodiment of the present invention.
FIG. 14 is a diagram showing a fourth embodiment. Depending on the value of the current flowing through source signal line 260,
In a display device that performs gradation display, the
Charge and discharge of stray capacitance that is parasitic on the source signal line
Because it becomes difficult, the current value changes to the specified current value.
It takes time for the transistor 2 within one horizontal scanning period.
A predetermined current is supplied to the driving transistor 267a via the switching transistor 67c.
There is a problem that values cannot be passed. Also, the drive transformer
The current flowing through the apparent resistance value of the transistor 267a is small.
When it is the product of capacitance and resistance
The constant becomes large and it takes time to change the waveform. Therefore, several times (X times) the predetermined current value
The current value is applied to the source signal line 260, and is shown in FIG.
In the first period, data is recorded in the driving transistor. Second period
The transistor 267d is turned on between
A current flows through the element 266. X times the current flows
Therefore, the required
The ON time is 1 / X times as long as the ON period of the transistor 267d.
The brightness can be adjusted by setting the lighting period. In the remaining period (third period) of one frame
Indicates that the transistor 267d is turned off and the EL element 2
Reference numeral 66 indicates a non-light emitting state. Therefore, in the present invention, the conventional first period is added.
The transistor 26 connected to the source signal line 260
7c and the transistor 26 connected to the EL element 266
Also during the third period when 7d is turned off, the EL element
A reverse bias voltage is applied to the
A longer service life was achieved. The reverse bias signal line 26 at that time
9 and the waveform of the gate signal line.
This is shown in FIG. Source signal line as above
And a current X times the predetermined current flows through the EL element 266.
By making the period of flowing the current 1 / X times, the reverse bias is applied to the EL element.
The period during which the ass voltage is applied can be lengthened. Therefore, as shown in FIG.
, The reverse bias signal line 269 of three rows is shared,
A selection unit for selecting a voltage by the reverse bias control line 259
I thought about reducing the number. The reverse bias control line is the same as the normal gate signal line.
Thus, signals shifted by one horizontal scanning period are sent to the selection unit of each row.
Reverse bias control with shift register etc.
A signal to be output to the control line 259 is generated. like this
First, a plurality of rows of reverse bias control lines are put together according to the present invention.
Thus, the number of shift registers can be reduced. When controlling all screens collectively,
There is an advantage that the shift register itself becomes unnecessary. Three
Gate signal lines and reverse vias for each row when rows are combined
FIG. 40 shows the waveform of the signal line. Reverse the EL element 266
Voltage of reverse bias signal line 269 for applying bias
Vb is applied when all three gate signal lines 2 are off
(Period A). If even one row is lit,
Bias cannot be applied, the reverse bias signal line 269
The voltage becomes Va. Simultaneous control using the same reverse bias signal line
It is desirable that the number of lines is large. In this example, the gate signal lines G21, G2
2 and G23 are shifted by one horizontal scanning period each.
Operates all three signal lines at the same timing as G23
You may let it. Each gate signal line G11 and G21, G12
And G22, G13 and G23 are on
If they do not overlap, each gate signal line G21, G22, G2
The timing of the ON of 3 may be any timing
No. As a result, the length of the period A is further two horizontal scanning periods
It is also possible to make the gate signal line 2
Has the effect of reducing the number of stages of the shift register. Also, in any of the embodiments of the present invention,
The source driver 71 and the gate driver 70 of FIG.
Formed on glass substrates of display devices using low-temperature polysilicon
May be. Alternatively, the source driver 71 and the gated
The driver 70 is created as a semiconductor circuit and assembled with a display panel.
May be combined. Also, install one driver at low temperature policy.
Formed on the glass substrate of the display device by recon
By forming it as a circuit and combining it with a display panel
Good. In addition, as shown in FIG.
It may be mounted in the direction. The mounting in this way also requires FIG.
22 in the portable information terminal shown in FIG.
The display section is symmetrical to the device compared to
There is an advantage that it can be arranged. In this example, a P-channel is used as a switching element.
The explanation has been given by taking the switching element of the channel as an example,
N-channel switching element or combination thereof
Depending on the situation, it can be realized in the same manner. For example, in FIG.
In the case of the pixel configuration shown, the gate signal line 1 (22) and the gate
N-channel voltage value to be applied to the gate signal line 2 (23)
When using switching elements, consider at the logic level.
The inverted signal of the signal of the P-channel switching element
The current flowing through the source signal line 21
Reverses the direction of current flow and is supplied from EL power line 25.
The applied voltage is the lowest potential on the pixel circuit. Figure this
FIG. 43A shows a gate signal line waveform in a non-display row.
43 (b). In addition, other FIG. 8, FIG. 10, and FIG.
Similarly, in the configuration of FIG.
It can also be realized by using. For use as a switching element in the present invention
The explanation of the transistor used was a thin film transistor as an example.
We did, but we were not limited to thin film transistors.
Lister, ring diode, thin film diode (TFD,
Similar effects can be obtained by using (MIM) or the like. The description will be made using an EL element as a display element.
However, organic electroluminescent elements and inorganic electroluminescent
For example, a sensing element or a light emitting diode may be used. As described above, the present invention is directed to the EL power supply line.
Between the drive transistor that adjusts the current of the
A current cut-off means is provided to protect against the current change of the drive transistor.
To prevent the brightness of the non-display area from increasing,
Black display is possible without black writing. this
As a result, crosstalk in the non-display portion could be prevented. [0156] In addition, between the driving transistor and the EL element,
Apply a reverse voltage to the EL element while interrupting the current path
Configuration can extend the life.
Was. When the number of display colors is small, how to take the gradation
Or reduce the power supply voltage to reduce power consumption.
The brightness is reduced after a certain period by the timer,
Equipped with multiple oscillators, depending on display color and display area
Low power by changing drive frequency using oscillator
Now you can. As described above, according to the present invention, the black brightness of the non-display area
Prevention of temperature rise, long life, and low power consumption were realized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a pixel configuration for applying a reverse bias to an EL element by using a switching element as a reverse bias signal line. FIG. 2 is a first embodiment of the present invention. FIG. 3 is a diagram showing a control signal block necessary for switching a full screen or a partial display according to FIG. 3 FIG. 3 is a diagram showing one embodiment of a pixel configuration applicable to the present invention FIG. FIG. 5 is a diagram showing a waveform of a gate signal line when partial display is performed using the pixel configuration shown in FIG. 3 and the embodiment of the present invention. FIG. 6 is a first embodiment of the present invention. FIG. 7 is a block diagram showing an example of a pixel configuration capable of applying a reverse bias to an EL element. FIG. 8 is a diagram showing an example of a pixel configuration capable of applying a reverse bias to an EL element. FIG. 9 shows the pixel configuration of FIG. FIG. 10 shows waveforms of gate signal lines in a display row and a non-display row in a current mirror pixel configuration. FIG. 10 shows a pixel configuration in which gradation control is performed by a source signal line voltage, between a driving transistor and an EL element. FIG. 11 is a diagram showing an example in which current cutting means is provided. FIG. 11 is a diagram showing a gate signal line waveform in the case of the pixel configuration of FIG. 10 using the first embodiment of the present invention. FIG. 13 is a diagram showing a pixel configuration in which a reverse voltage can be applied to an EL element when gradation display is performed in accordance with a voltage flowing through the pixel. FIG. 14 is a diagram showing an example of a pixel configuration including a function of correcting a variation in threshold voltage. FIG. 14 is a diagram showing a gate signal line waveform of a display row and a non-display row according to the first embodiment of the present invention in the circuit configuration of FIG. Figure showing [Figure 5 is a block diagram for changing the EL power supply voltage depending on the size of the display area. FIG. 16 is a diagram showing current-voltage-luminance characteristics of the EL element. FIG. 17 is a diagram showing a reference voltage and voltage generation. FIG. 18 is a diagram illustrating a relationship between a unit and a voltage output, a source signal line, and a pixel. FIG. 18 is a diagram illustrating an example of a display data input format. FIG. FIG. 20 is a diagram showing an application pattern of source and gate signal lines during full screen display and partial display according to the sixth embodiment of the present invention. FIG. 22 is a diagram showing that different current outputs can be selected for the same input data depending on the size of the area and time. FIG. 22 is a diagram showing an example of performing partial display in a foldable portable information terminal. FIG. And electricity FIG. 24 is a diagram illustrating a relationship between values. FIG. 24 is a diagram illustrating a pixel configuration and a driving waveform when a p-type driving transistor according to a ninth embodiment of the present invention is used. FIG. 25 is a ninth embodiment of the present invention. FIG. 26 is a diagram showing a configuration of a display device according to an embodiment of the present invention. FIG. 26 is a diagram showing a pixel configuration and a driving waveform when an n-type driving transistor is used according to a ninth embodiment of the present invention. FIG. 28 is a diagram showing a current mirror type pixel configuration and a drive waveform according to a ninth embodiment. FIG. 28 shows a pixel configuration in which a current is controlled according to a source signal line voltage value according to a ninth embodiment of the present invention. FIG. 29 is a diagram showing a circuit and a driving waveform at the time. FIG. 29 is a diagram showing a reverse bias applying circuit using an n-type transistor and a driving waveform according to the tenth embodiment of the present invention. In the embodiment of FIG. 31 is a diagram showing a reverse bias application circuit using a p-type transistor and a driving waveform. FIG. 31 is a diagram showing a pixel configuration for applying a reverse bias to an EL element when an n-type transistor is used as a driving transistor. 32 is a diagram showing a pixel configuration for applying a reverse bias to an EL element in a pixel configuration of a current mirror. FIG. 33 is a diagram showing a pixel configuration in a case where gradation display is performed according to a voltage value applied to a source signal line. FIG. 34 is a diagram showing a circuit configuration for applying a reverse bias to an EL element. FIG. 34 shows that a reverse bias signal line is connected to one of gate signal lines.
FIG. 35 shows a pixel configuration for applying a reverse bias voltage to an EL element when a transistor is used as a switching element. FIG. 36 shows an n-type drive transistor. FIG. 37 is a diagram showing a pixel configuration and a waveform for applying a reverse bias voltage to an EL element when a switching element is realized using a transistor in the case of FIG. 37. FIG. 37 shows a circuit for inspecting a transistor in a current mirror pixel configuration. FIG. 38 is a diagram showing a built-in pixel structure. FIG. 38 shows a case where a transistor is used as a switching element and a current several times larger than a predetermined current is applied to an EL element.
FIG. 39 is a diagram showing a pixel configuration for applying a reverse bias voltage to an L element and waveforms of respective gate signal lines. FIG. 39 shows a pixel configuration in a case where a plurality of rows of reverse bias signal lines are simultaneously controlled, in a case where three rows are simultaneously controlled FIG. 40 is a diagram showing an example of waveforms of gate signal lines and reverse bias signal line voltages in each row when a plurality of rows of reverse bias signal lines are simultaneously controlled. FIG. 41 is a display device of the present invention. FIG. 42 is a diagram showing an example in which a driving semiconductor circuit is arranged in a display device. FIG. 43 is a diagram showing a case in which an n-channel transistor is used. 13 Partial switching unit 14 Data RAM 15 Source driver 16 Display unit 17 Gate driver 21 Source signal line 22 Gate signal line 1 23 Gate signal line 2 24 Storage capacity 25 EL power line 26 EL element 27 Transistor 28 Contact 251 Display unit 252 Gate driver 253 Source driver 254 Substrate 257 Contact 258 Gate off power supply 259 Reverse bias control line 260 Source signal line 261 Gate signal line 1 262 Gate signal line 2 263 Gate signal line 3 264 Storage capacitor 265 EL power supply line 266 EL element 267 Transistor 268 Reverse bias power supply 269 Reverse bias signal line 301, 311, 391 Gate signal line 1 302, 312 Gate signal line 2 303, 313 Gate signal line 3 304 Gate signal line 4 331,341,392 Switching elements 332,342 Reverse bias power supply 333,343 Off power supply 334,344,354,397,424 Contact 371,421 Transistor 431 Current measuring means

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. 7 Identification symbol FI Theme coat ゛ (Reference) G09G 3/20 624 G09G 3/20 624B 641 641D 680 680T H05B 33/14 H05B 33/14 A F term (Reference) 3K007 AB11 AB17 DB03 GA04 5C080 AA06 BB06 CC03 DD03 DD05 DD10 DD23 DD24 DD25 DD26 DD29 EE17 EE29 EE30 FF03 FF11 HH09 HH13 JJ02 JJ03 JJ04 JJ05 JJ07 KK07

Claims (1)

1. A display device using an organic EL element, comprising: a switching element forming a voltage path for applying a voltage in a direction opposite to a direction in which light is emitted to the organic EL element; A reverse bias signal line connected to the organic EL element via the switching element; a plurality of voltage sources; and a voltage selector for selecting one of the plurality of voltage sources and outputting the selected voltage source to the reverse bias signal line. A display device using an organic EL element, wherein a voltage applied to the switching element is changed by operating the voltage selection unit, so that a voltage can be applied to the EL element in a direction opposite to light emission. . 2. A method for driving a display device using an organic EL element, wherein a voltage application path different from a path for performing a gray scale display is formed at one end of the organic EL element via a switching element. When a gradation display is performed, a voltage higher than a terminal voltage between the organic EL element and the switching element is applied to a terminal of the element different from the organic EL element. A method for driving a display device using an organic EL element, wherein a voltage equal to or lower than a voltage obtained by subtracting a threshold voltage of the switching element from a terminal voltage between the switching elements is applied. 3. The display device using an organic EL element according to claim 1, wherein said switching element is formed of a diode. 4. A method for driving a display device using an organic EL element, wherein a reverse bias transistor is formed at one end of the organic EL element to form a voltage application path different from a path for performing gray scale display. A gate electrode and a source or drain electrode of the reverse bias transistor are connected to a reverse bias signal line, and the reverse bias signal line voltage is made different between a first period and a second period; A method for driving a display device using an organic EL element, wherein the EL element emits light, and a voltage is applied to the organic EL element in the second period in a direction opposite to a direction in which light was emitted. 5. In a first period, a current is applied to a source signal line through the driving transistor and a voltage is applied to the driving transistor in a direction opposite to a direction in which light is emitted to a display element through a reverse bias transistor. In the second period, a current flows to the display element through the driving transistor, and in the third period,
A method of driving a display device that applies a voltage in a direction opposite to a direction in which light is emitted to a display element through the reverse bias transistor, wherein the reverse bias transistor has a gate electrode and a source or drain electrode connected to a reverse bias signal line, In the first and third periods, the reverse bias signal line has a voltage value applied in the reverse direction to the light emitting element. In the second period, the potential of the reverse bias signal line is lower than the potential at which the display element and the reverse bias transistor are connected. A method for driving a display device using an organic EL element, wherein a high voltage value is applied. 6. A display device using an organic EL element, comprising: a driving transistor for controlling a current supplied from a power supply; and a signal line connection transistor for forming a current path from a source signal line to the driving transistor. An EL connection transistor for forming a path for supplying the current of the driving transistor to the display element, and a reverse bias switching for forming a path for applying a voltage in a direction opposite to a voltage applied when the display element emits light. An organic EL device, comprising: a control signal of the signal line connection transistor connected to a terminal of the reverse bias switching element that is different from a terminal connected to the display element.
A display device using an element. 7. A driving transistor for controlling a current supplied from a power supply, a signal line connection transistor for forming a current path from a source signal line to the driving transistor, and a current for the driving transistor supplied to a display element. And a reverse bias transistor in which a source or drain electrode is connected to a signal line connecting the EL connection transistor and the display element, wherein the display includes a drain or source electrode of the reverse bias transistor. An electrode that is not connected to an element and a gate electrode are connected, a load is connected to a gate electrode of the reverse bias transistor, and a current value or a voltage value of the load is measured.
Inspection method of connection transistor. 8. A driving transistor for controlling a current supplied from a power supply, a signal line connection transistor for forming a current path from a source signal line to the driving transistor, and supplying a current of the driving transistor to a display element. And a reverse bias transistor having a source or drain electrode connected to a signal line connecting the EL connection transistor and the display element, wherein the reverse bias transistor has a drain or source electrode. An electrode that is not connected to a display element and a gate electrode are connected; a load is connected to the gate electrode of the reverse bias transistor; and a current value or a voltage value of the load is measured, wherein the inspection of the EL connection transistor is performed. apparatus. 9. A display device using an organic EL element, comprising: a driving transistor for controlling a current supplied from a power supply; and a signal line connection transistor for forming a current path from a source signal line to the driving transistor. An EL connection transistor forming a path for supplying the current of the driving transistor to the display element; one end connected to a signal line connecting the EL connection transistor and the display element; and the other end connected to a reverse bias signal line. A switching element, a plurality of voltage sources, and a selection unit for connecting one of the plurality of voltage sources to the reverse bias signal line, wherein one of the plurality of voltage sources includes the display element. Is set to a voltage value for applying a reverse voltage, and another is connected to a power supply for supplying a current to the EL element, and the EL connection transistor When conducting, a power supply for supplying a current to the EL element is applied to the reverse bias signal line, and when the EL connection transistor is non-conductive, a voltage value for applying the reverse voltage to the reverse bias signal line is applied. A display device using an organic EL element. 10. A current flows to a source signal line of the driving transistor through the driving transistor during the first period, and a current flows to the organic EL element through the driving transistor during the second period. A method for driving a display device in which a current does not flow through the organic EL element during the third period, wherein a reverse bias transistor having a gate electrode and a source or drain electrode connected to a reverse bias signal line comprises the reverse bias transistor. The terminal not connected to the signal line is the organic EL
Connected to an element, the reverse bias signal line is further connected to a plurality of the reverse bias transistors, and the voltage value of the reverse bias signal line is such that all of the driving transistors corresponding to the plurality of connected reverse bias transistors are connected. Applying a voltage value for applying a reverse voltage to the organic EL element during the first period or the third period;
When all the driving transistors corresponding to the plurality of connected reverse bias transistors are not in the first period or the third period, the plurality of reverse bias transistors connected to one reverse bias signal line are A method for driving an organic EL display device, comprising applying a voltage value in which all the elements are turned off. 11. A plurality of driving transistors for controlling a current supplied from a power supply, and a signal line connection transistor for forming a current path from a source signal line to at least one of the plurality of driving transistors. An EL connection transistor that forms a path for supplying a current of at least one of the plurality of driving transistors that is not connected to the signal line connection transistor to a display element; the EL connection transistor and the display element A reverse bias transistor having a source or drain electrode connected to a signal line connecting the reverse bias transistor, wherein an electrode of the drain or source electrode of the reverse bias transistor that is not connected to the display element is connected to a gate electrode; For the gate electrode of a transistor Connect a load, testing device of at least one driving transistor, wherein connected to the EL-connected transistor and the EL-connected transistor and measuring a current value or voltage value of the load. 12. A portable information terminal characterized in that an antenna, a demodulation device and a button are attached to the display device according to claim 1.
JP2001391436A 2001-12-25 2001-12-25 Display device using organic el element and its driving method, and portable information terminal Pending JP2003195808A (en)

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