JP2002072923A - Electro-optic element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such an electro-optic element that a selection period per each scanning line is no shortened and occurrence of a moving picture false outline is less. SOLUTION: Relating to an electro-optic element which controls electric charges made to flow through an optical element connected indirectly or directly with a drain terminal or a source terminal of a 1st active element by voltage applied to agate terminal of the 1st active element, the electro-optic element is provided with a capacitor of which one terminal is connected to the gate terminal of the 1st active element, and a 2nd active element connected with the capacitor in series or in parallel, and the voltage to be applied to the gate terminal of the 1st active element is controlled to control the change amount flowing through the optical element by holding the electric charges for supplying the capacitor with the voltage to be applied to the gate terminal of the 1st active element, and discharging the electric charges through the 2nd active element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thin film EL (Electro
Luminescence element and FED (Field Emission Devis)
e) and the like, and particularly to an active driving element structure and a driving method thereof.

[0002]

2. Description of the Related Art As a candidate for a flat panel display to compete with a liquid crystal display in the future, a thin-film EL element represented by an organic EL display and an FED are attracting attention.

FIG. 1 shows a Japanese Patent Publication No. 62-16426,
FIG. 1 is a configuration conceptual diagram of an active element circuit disclosed in Japanese Patent No. 2642197 and Japanese Patent Application Laid-Open No. 8-234683. That is, an area surrounded by a broken line 101 in FIG. 1 is a pixel, and each pixel includes two TFTs 102 and 103, a storage capacitor 104, and an electro-optical element 105 such as a liquid crystal element or an EL element. In the method of driving the active element, a voltage for turning on the TFT 102 is applied from the gate line Yj to control the display state of the pixel connected to the gate line Yj, and the potential of the terminal of the capacitor 104 on the TFT 102 side is changed. The voltage is supplied from the source line Xi + 1. Thereafter, a voltage for turning off the TFT 102 is applied from the gate line Yj. By driving in this manner, charges for setting the gate voltage of the TFT 103 are stored in the capacitor 104, and the ON resistance of the TFT 103 is controlled by the voltage. Electro-optical element 105 and TFT 10
3 is connected in series between the power supply and GND (that is, “ground”), so that by controlling the ON resistance of the TFT 103, the current value flowing through the electro-optical element 105 is controlled according to the luminance to be displayed. It becomes possible.

FIG. 2 shows Japanese Patent Application Laid-Open No. 8-2346.
It is a conceptual diagram of the actual device structure at the time of using organic EL as an electro-optic element shown by 83. That is, TFT
102 connects the gate bus (row electrodes) Y _i to the source bus (column electrode) X i _{+ 1} connected to the gate electrode to the source electrode,
In this configuration, the drain electrode is connected to the gate electrode of the TFT 103 and the capacitor 104. The TFT 103 has a configuration in which the source electrode is connected to the ground path GND, and the drain electrode is connected to the anode of the organic EL element. The other terminal of the capacitor 104 is connected to the ground path GND, and the cathode of the organic EL is connected to a power supply (not shown, a negative power supply in this conventional example).

FIG. 3 is a sectional view of the active element shown in FIG.
4 and FIG. That is, FIG. 3 is a sectional view taken along line AA ′ in FIG. 2, and FIG. 4 is a sectional view taken along line BB ′ in FIG. The method of fabricating this active element is to deposit a polysilicon layer 111 on a transparent insulating substrate 110 such as quartz or low temperature glass,
Are patterned into islands by photolithography. Next, an insulated gate material 112, such as silicon dioxide, is deposited on the polysilicon island 111 and over the surface of the insulated substrate 110 to a thickness of about 1000 angstroms.

Next, a polysilicon layer 113 formed of amorphous silicon is deposited on the gate insulating layer 112, and photolithography is performed on the polysilicon island so that after ion implantation, source and drain regions are formed in the polysilicon region. To be patterned. The ion implant is made conductive with an N-type dopant that is arsenic. The polysilicon gate electrode 113 is also used as a bottom electrode of the capacitor 104.
Gate bus 114 is formed from a metal silicide such as tungsten silicide (WSi2) and is patterned.

Next, an insulating layer 115 such as silicon dioxide is deposited on the entire surface of the device, and contact holes 116, 117 and the like are formed in a part thereof to form a contact of the thin film transistor. The electrode material 116 applied to the source region of the TFT 103 is also formed as the upper electrode 116 of the capacitor. The source bus and the ground bus are also connected to this insulating layer 115.
Formed on Transparent electrode 11 made of ITO or the like
Reference numeral 8 contacts the drain region of the TFT 103, which is provided as an anode of the organic EL.

Next, an insulating passivation layer 119, such as silicon dioxide, is deposited on the device surface in a thickness of about 0.5 to about 1 micron. The passivation layer 119 is tapered at the ITO-side end face 120. The organic EL layer 121 is deposited on the passivation layer 119 and the EL anode layer 118.

Finally, an organic EL cathode 122 formed of a metal material such as aluminum is deposited on the surface of the device. There are several types of configurations of the organic EL layer 121. For example, in Japanese Patent Application Laid-Open No. 8-234683, the organic EL layer 121 has an organic hole injection and transfer zone in contact with the anode,
It is composed of an organic hole injection / migration zone and an electron injection / migration band forming a junction. The structural formula of each of these organic layers is described in JP-A-8-234683.

FIG. 5 shows a device configuration of a blue light emitting organic EL disclosed in SID'97 DIGEST P1073-1076.
The configuration of (A) is used. That is, in the same paper,
An anode 131 is formed on 30, and a hole entrance layer 132, a hole transport layer 133, a light emitting layer 134, an electron transport layer 135, and a cathode 136 are stacked thereon. Also,
In this paper, a configuration is used in which monochromatic blue emission is converted into a full color by color conversion using a color conversion filter. As the light-emitting layer 134, one whose structural formula is shown in FIG. 5B is used.

In order to uniformly display the EL display device thus formed in a plane, it is necessary to emit the same amount of light from the organic EL layers constituting each pixel. However, since the characteristics of the TFTs 103 constituting each pixel vary, the amount of current supplied to the EL element cannot be made uniform in the circuit configuration of FIG. There is a disadvantage that it appears as unevenness.

That is, variations in the threshold characteristics of the TFTs 103 of the respective pixels due to variations in ion doping during the manufacture of the TFTs, and variations in the sizes of the TFTs 103 of the respective pixels due to mask pattern shifts and the like occur during the manufacture of the TFTs. Even if the same gate voltage is applied to the TFT 103,
The resistance value of the TFT 103 varies, and the current value flowing to the drain varies. Therefore, even if the same voltage is stored in the capacitor 104, the current value supplied to the gate voltage EL element varies for each pixel, and the EL value is proportional to the current value.
There is a disadvantage that the light emission luminance of the element also varies and appears as display unevenness.

Therefore, as an active element configuration and a driving method for solving this problem, for example, Japanese Unexamined Patent Application Publication No.
For example, an element configuration of No. 72235, a driving method of Japanese Patent Application Laid-Open No. H10-214060, and an element configuration of Japanese Patent Application Laid-Open No. H8-241057 are proposed.

That is, the driving method of Japanese Patent Application Laid-Open No. H10-214060 uses the TFT 103 in the active element configuration shown in FIG.
Is always saturated (completely ON or completely OFF)
This is a method of relatively reducing the variation in the characteristics of the TFT 103 for each pixel.

[0015] The one frame period T _F as the driving method shown in FIG. 6 is divided into eight subframes SF1 to SF8, divides each of these sub-frames SF1 to SF8 in the address period Tadd and discharge period Ton. The display discharge time Ton of each of the sub-fields SF1 to SF8 is set to be different from each other, and the address period Tadd of all the sub-frames SF1 to SF8 is the same time. For this reason, depending on whether the ON voltage or the OFF voltage is stored in the capacitor constituting the pixel in each of the eight sub-frames SF1 to SF8 or whether or not the OFF voltage is stored, the total of the light emission time for each pixel can be changed and the gradation can be expressed. Becomes

On the other hand, the circuit configuration of the active element disclosed in Japanese Patent Application Laid-Open No. H11-272235 is as shown in FIG. That is, the third TFT 182 is made conductive, the fourth TFT 186 is made non-conductive, electric charge is accumulated in the charge capacitor 181, and the charge is transferred to the third TFT 182 in a non-conductive state, and the fourth TFT 186 is made conductive. Discharging through 170 alleviates the variation in the resistance of the second TFT 150 in the conductive state.

FIG. 9 shows a circuit configuration of another active element disclosed in JP-A-11-272235. That is, a positive potential is applied to the drive power supply 250, and the first diode 27
By setting 0 to the forward potential, setting the second diode 280 to the reverse potential, storing charge in the charging capacitor 251, and applying the negative potential to the drive power supply 250, the first diode 270 to the reverse potential. By setting the second diode 280 to a forward potential and discharging through the organic EL element 240, the variation in the resistance value of the second TFT 220 in the conductive state is reduced.

FIG. 11A shows the element configuration of Japanese Patent Application Laid-Open No. H08-241057. That is, a charge corresponding to a signal to be displayed on the charging capacitor 302 is stored when the TFT 304 is conductive, and the charge capacity 3 is stored when the TFT 304 is non-conductive.
The effects of potential data line X ₂ by pooled in charge to 02 is discharged through the TFT 304, TFT 3
A resistor 303 having a resistance lower than the ΔFF resistance of the resistor 04 is inserted in parallel with the capacitor 302 to reduce the resistance, thereby obtaining a display with less crosstalk.

Further, the conventional apparatus will be described in detail. Hereinafter, the circuit configuration of FIG. 7 shown in JP-A-11-272235 will be described. That is, FIG. 7 is a diagram showing a pixel TFT circuit configuration, in which a first TFT 140, a second TFT 150, a storage capacitor 160, an organic EL element 170, a driving power supply 180, a third
And fourth TFTs 182 and 186 and a charging capacitor 181
And consists of Also, as shown in FIG.
The T140 and the storage capacitor 160 have the same circuit configuration and driving method as those in FIG.

The gate electrode 151 of the second TFT 150
Is connected to the source electrode 143 of the first TFT 140 and one electrode of the storage capacitor 160, and the drain electrode 1
53 is connected to the drive power supply 180 of the organic EL element 170. The source electrode 154 is connected to a third TFT.
182 is connected to the drain electrode 184. Gate electrodes 183, 1 of third and fourth TFTs 182, 186
87 has periodic signals VG3, VG4
Is supplied. The signals VG3 and VG4 are signals whose phases are inverted from each other. The source electrode 185 of the third TFT 182 and the drain electrode 18 of the fourth TFT 186
8 is connected. The third and fourth TFTs 18
2, 186, a charging capacity 181 is connected. The source electrode 189 of the fourth TFT 186 is connected to the anode 171 of the organic EL element 170, and the cathode 172 of the organic EL element 170 is connected to the display electrode 190.

The driving method of the active element shown in FIG.
This is as shown in FIG. That is, in FIG. 8, (a) shows the signal VG1 supplied to the gate electrode of the first TFT 140,
(B) is the signal VG2 supplied to the gate electrode of the second TFT 150, (c) is the signal V0 of the drive power supply, and (d) is the signal VG supplied to the gate electrode of the third TFT 182.
3, (e) is a signal VG4 supplied to the gate electrode of the fourth TFT 186, (f) is a signal VC2 stored in the charging capacitor 181, and (g) is a signal of the light emission signal VEL of the organic EL element 170. It is a waveform diagram. Then, the first TFT 1
As shown in FIG. 8A, the gate signal VG1 of the gate signal line G is supplied to the gate electrode 141 of the first TFT 40, and the first TFT
140 turns on. Then, a predetermined voltage VG2 from the drain signal line D is supplied to the gate electrode 151 and the storage capacitor 160 of the second TFT 150, and FIG.
As shown in (b), VG2 is applied to the second TFT 150, and the second TFT 150 is applied by the voltage VG2.
Is set, and this state is maintained for one field period.

Then, the driving power supply 180 (potential V0)
Accordingly, a voltage corresponding to the voltage VG2 of the gate electrode 151 is supplied to the drain electrode 184 of the third TFT 182.
At this time, the signal voltages VG3 and VG4 shown in FIGS. 8D and 8E are supplied to the gate electrodes 183 and 187 of the third and fourth TFTs 182 and 186. As shown in the drawing, the phases of the signals VG3 and VG4 are inverted with each other, whereby the third and fourth TFTs 182 and 186 are alternately turned on.

That is, the voltage VC2 of the charging capacitor 181 is
As shown in FIG. 8F, the signal VG3 is an ON signal and the signal VG
When the signal 4 becomes an off signal, the battery is charged, and when the signal VG3 becomes an off signal and the signal VG4 becomes an on signal, the battery is discharged. As described above, the charge / discharge (one light emission cycle) is repeated by the signals VG3 and VG4. Therefore, when the third TFT 182 is turned on, the fourth TFT 186 is turned off, so that the third TFT 1 is connected via the second TFT 150.
The drive power supply 180 supplied to the drain electrode 184 of FIG.
Is stored in the charging capacitor 181.

When the third TFT 182 is turned off, the fourth TFT 186 is turned on.
The charge stored in the charging capacitor 181 is discharged. Thus, when the third TFT 182 is turned on, the charge charged in the charging capacitor 181 is transferred to the drain electrode of the fourth TFT 186 when the third TFT 182 is turned off and the fourth TFT 186 is turned on. It is supplied to the anode 171 of the organic EL element 170 via the source electrode 188 and the source electrode 189. By doing so, as shown in VEL in FIG. 8 (g), the organic E
The L element 170 emits light.

The circuit configuration of FIG. 9 shown in Japanese Patent Application Laid-Open No. H11-272235 will be described below. As shown in FIG. 9, the first TFT 210 and the storage capacitor 230 are the same as the circuit configuration of FIG. The gate electrode 221 of the second TFT 220 is connected to the source electrode 21 of the first TFT 210.
3 and one electrode of the storage capacitor 230, and the drain electrode 223 is connected to the drive power supply 25 of the organic EL element 240.
Connected to 0. The source electrode 224 is
It is connected to the anode 271 of the first diode 270.

The cathode 272 of the first diode 270
And the anode 281 of the second diode 280 are connected in series. The first and second diodes 27
One electrode of the charging capacitor 251 is connected between 0 and 280. The other electrode of the charging capacitor 251 is grounded. The cathode 282 of the second diode 280
Is connected to the anode 241 of the organic EL element 240.

The cathode 242 of the organic EL element 240 is connected to a driving power supply 250. By arranging the display pixels 1 configured as described above in a matrix,
An organic EL display device is formed.

The driving method of the active element shown in FIG.
This is as shown in FIG. That is, FIG. 9 is a configuration diagram of a pixel TFT circuit, and FIG. 10 is a signal waveform diagram of each terminal. 10A shows a signal VG1 supplied to the gate electrode of the first TFT 210, FIG. 10B shows a signal VG2 supplied to the gate electrode of the second TFT 220, and FIG.
0 is a signal V0, (d) is a signal VD1 supplied to the first diode 270, (e) is a signal VD2 supplied to the second diode 280, and (f) is a signal stored in the charging capacitor 251. VC2, (g) is a signal waveform diagram of a light emission signal VEL of the organic EL element 240. And the first T
The gate signal VG1 of the gate signal line G is supplied to the gate electrode 211 of the FT 210 as shown in FIG. 10A, and the first TFT 210 is turned on. Then, the drain signal from the drain signal line D is applied to the second TFT 220
, And the VG is applied to the second TFT 220 as shown in FIG.
2 is applied and the ON state is held for one field period (at this time, one electrode potential VC1 of the storage capacitor 230 becomes V
G2).

The driving power supply 250 alternately switches a charging voltage V10 and a discharging voltage V20 for causing the organic EL element 240 to emit light at a predetermined period, for example, a frequency of 10 kHz, as shown in FIG. 10C. Supplying. At this time,
The charging voltage V10 is higher than the voltage charged in the charging capacitor 251 and the discharging voltage V20 is lower than the voltage charged in the charging capacitor 251.

That is, when the voltage of the driving power supply 250 is the charging voltage V10, a current flows in the direction of the first diode 270 (FIG. 10D), and the charging capacitor 251 is charged (FIG. 10D). (F)), when the voltage of the driving power supply 250 is the discharging voltage V20, a current flows in the direction of the second diode 280 ((e) of FIG. 10), and the charging capacitor 251 is used.
(FIG. 10 (f)) is discharged from the organic EL element 240
Is supplied with the current to emit light (FIG. 10 (g)).

Hereinafter, the circuit configuration of FIG. 11A shown in Japanese Patent Application Laid-Open No. H8-241057 will be described. That is, in FIG. 11A, reference numeral 307 denotes a shift register for the X-axis;
08 is a shift register for the Y-axis, A11, A12, A2
1, A22... Are pixels constituting a screen portion.

The pixel A22 is a thin-film EL element 3 for light emission.
05 and a TFT 3 for controlling light emission of the EL element 305.
01, a capacitor 302 connected to the gate electrode of the TFT 301, a resistor 303 connected in parallel to the capacitor 302, and a TFT 304 for writing a signal to the capacitor 302. Other pixel A1
., A12, A21,... Have the same configuration as the pixel A22.

The gate electrode of the TFT 304 is connected to the terminal Y 2 of the Y coordinate shift register 308, and the source electrode or the drain electrode is connected to the X coordinate shift register 307.

Therefore, when the selection signal is output from the terminal Y2, the TFTs 305... Of the pixels A21 and A22 are turned on. At this time, a voltage corresponding to the image data signal output from the X coordinate shift register 307 is applied to the TFT 304.
Is held in the capacitor 302 via the source electrode or the drain electrode. The on / off state of the TFT 301 is controlled by the potential of the capacitor 302, a current corresponding to the image data signal flows through the EL element 305, and light emission is controlled based on the image data signal.

Thereafter, when a non-selection signal is output from the terminal Y2, the TFTs 305... Of the pixels A21 and A22 are turned off, and the electric charge charged in the capacitor 302 becomes TF
Through the resistor 303 having a value smaller than the off-resistance value of T305, discharge is performed as shown in FIG.

[0036]

In the circuit configuration of the active element shown in FIG. 1, since the threshold characteristic and the ON resistance characteristic of the TFT 103 vary, even if the same gate voltage is applied to the TFT 103, the TFT 103 is supplied to the EL element. It has already been shown that the current value to be applied varies from pixel to pixel and causes display unevenness.

As a countermeasure, time division gray scale display as shown in FIG. 6 is effective.
In the time division gray scale display method shown in FIG.
The ratio of the address period to the frame period is small, and a plurality of scans must be performed in the small address period. Therefore, there is a disadvantage that the selection period for each scanning line is shortened.

For example, when the frame period is 16.6 [ms] and the number of scanning electrodes is 480, one frame electrode
In the circuit configuration of FIG. 1 in which scanning is performed only once, the selection period per scanning line is 16.6 [ms] / 480 [lines] ≒ 34.6 [μs]. In the driving method shown in FIG. 6, the ratio of the address period is 50%.
% ((16.6 [ms] × 0.5) / 8) / 480 [lines]
≒ 2.2 [μs], and the selection period for each scanning line becomes extremely short. In this case, it is necessary to reduce the wiring resistance and the stray capacitance of the gate line and the source line in FIG. 1 and to increase the driving capability of the gate driver for driving the gate line and the source driver for driving the source line, resulting in a new cost. It becomes an up factor.

In the time division gray scale display method shown in FIG.
There is also a disadvantage that a false contour of a moving image as seen in a PDP occurs. Therefore, a time-division gray scale display is obtained only by scanning once in one frame period, and the electric charge stored in the charging capacitor is discharged through the resistor using the circuit of FIG. Thus, a method of obtaining a time division gray scale is also conceivable. However, in such a method of discharging through a resistor, the discharge time varies due to the variation in the resistance value. That is, even if the same charge is stored in the same charge capacity, the discharge time also varies if the resistance value varies, and the display time of the TFT 301 in FIG. Issues.

The first and second inventions of the present invention have been made for such a problem, and the circuit configuration shown in FIG. 11A has less display unevenness than the time-division gray scale display, and can be performed in one frame period. It is an object of the present invention to obtain a time-division gray scale display that is scanned only once.

In the time-division gray scale display method as shown in FIG. 11A and the time-division gray scale display method as in the first and second inventions of the present invention, the potential of the charge capacity is directly applied to the organic EL. Since the voltage is applied to the gate electrode of the driving TFT, T
Even if the voltage applied to the FT follows exactly the same locus, the variation in the threshold voltage between the source and the gate of the TFT and the T
There is a second problem that display unevenness appears due to variation in the resistance value of the FT in the unsaturated conductive state.

The third invention of the present invention has been made to solve such a problem, and has a variation in a threshold voltage between a source and a gate of a TFT for driving an organic EL and a variation in a resistance value of a TFT in an unsaturated conductive state. And to obtain a more uniform display.

On the other hand, a method using a capacitor as shown in FIG. 7 is also effective. However, in the active element configuration shown in FIG. 7 shown in JP-A-11-272235, the TFT 150 is connected between the capacitor 181 and the driving power supply 180. TFT 183 is inserted in series. The capacitor 181 and the organic E
A TFT 186 is also inserted between L170. Generally, in order to drive an organic EL, p-si-TFT (polysilicon TF)
T) is required and a-si-TFT (amorphous silicon TF)
In T), the mobility of charges is low and it is considered impossible.
This is because the TFT for driving the organic EL needs to have a low resistance value in the conductive state. Therefore, the size of the TFT 103 for driving the organic EL is considerably larger than the size of the TFT 102 for driving the charge capacity as shown in FIG.

As described above, the active element configuration shown in FIG. 7 has a problem that three large-sized TFTs which are connected in series with the organic EL are required. This reduces the space for arranging the organic EL in the pixel, and it is necessary to increase the light emission luminance of the organic EL. Since the luminous efficiency of the organic EL generally becomes maximum at a certain luminance (applied voltage) as shown in FIG. 27, if the space for arranging the organic EL is limited as described above, the organic EL emits light with an appropriate luminous efficiency. There is a third problem that is not possible.

In FIG. 27, the horizontal axis represents the voltage applied to the organic EL, and the left vertical axis represents the luminance corresponding to the line a.
The vertical axis on the right side shows the luminous efficiency corresponding to the line b. As can be seen from the TFT configuration in FIG. 2, the source, gate, and drain of the active element are arranged in the lateral direction in the TFT process. It is difficult to form a diode by such a process, and in general, a TFT is used as a diode by short-circuiting between a source and a gate of a TFT.

Therefore, even in the active element configuration shown in FIG. 9, three large-sized TFTs which are connected in series with the organic EL are required (one is a TFT 230, and the other is a diode 27).
There is a problem that the source and the gate used as 0,280 are short-circuited. This also means that the space for arranging the organic EL in the pixel is reduced, and has the third problem.

The fourth and fifth inventions of the present invention have been made to solve such a problem. Unlike the active element configurations shown in FIGS. 7 and 9, the TFTs (including the diode) directly entering the organic EL are used. It is an object of the present invention to reduce the variation in the brightness of electro-optical elements such as organic EL even if there is a variation in the conduction resistance of the same active element.

[0048]

Means for Solving the Problems In order to solve the first problem of the present invention, the time division gray scale display means according to the first invention of the present invention comprises a first active element (1 in FIG. 12). The control voltage applied to the gate terminal controls the conduction state of the first active element and controls the electric charge flowing through the optical element whose one terminal is connected to the drain terminal (or the source terminal) ( 12) controlling the fourth active element (4 in FIG. 12) to a conductive state and holding a predetermined voltage to one terminal of the first capacitor (2 in FIG. 12); And discharging the electric charge from the first capacitor while the active element of No. 4 is in a non-conducting state. While the voltage held in the first capacitor is equal to or more than a certain value, the gate terminal of the first active element is Make it conductive And in one frame period to allow time division gradation display in one scan, a means for controlling the amount of charge flowing through the optical element.

In particular, the above means of the present invention connects the source terminal of the second active element (6 in FIG. 12) to one terminal of the first capacitor, and connects the second terminal to the drain terminal of the second active element. (2 in FIG. 12) is connected, a part of the electric charge held in the first capacitor is moved to the second capacitor through the second active element, and discharged.

In order to solve the first problem of the present invention, the time division gray scale display means according to the second invention of the present invention comprises:
The conduction state of the first active element (5 in FIG. 17) is controlled by the control voltage applied to the gate terminal of the active element (1 in FIG. 17), and the charge flowing through the optical element connected to the drain terminal is controlled. And controlling the fourth active element (4 in FIG. 17) to a conductive state to hold a predetermined voltage to one terminal of the first capacitor (2 in FIG. 17). The voltage applied to the other terminal of the first capacitor is changed while the active element is in a non-conductive state, and the gate of the first active element is changed while the voltage of the first capacitor is equal to or higher than a predetermined value. By turning the terminal into a conductive state, it is possible to perform time-division gray scale display by one scan in one frame period, and to control the total amount of charges flowing through the optical element.

A time-division gradation display means according to a third invention of the present invention for solving the second problem of the present invention is a time-division gradation changing means which changes the potential of the charging capacitor as in the above two examples. In the means for obtaining a gray scale display, a second active element (FIG. 19) is provided between the gate terminal of the first active element (1 in FIG. 19) and the first capacitor (2 in FIG. 19).
10), the drain terminal of the second active element is connected to the gate terminal of the first active element, and the first terminal is connected to the gate terminal of the second active element.
And the conduction resistance of the first active element saturates through the second active element to the gate terminal of the first active element while the voltage held in the first capacitor is equal to or greater than a predetermined value. This is a means for applying a voltage VON.

The means of the present invention for eliminating the influence of the characteristic variation of the first active element configuration, which is the fourth invention of the present invention for solving the third problem of the present invention, is the first invention.
The conductive state of the first active element is controlled by a control voltage applied to the gate terminal of the active element (1 in FIG. 20), and one of the terminals is indirectly or directly connected to the drain terminal (or source terminal). 20. A control means of an electro-optical element for controlling electric charge flowing through an optical element (5 in FIG. 20), wherein a second terminal is connected to a gate terminal of the first active element.
The drain terminal (or source terminal) of the active element (10 in FIG. 20) is connected, and the second capacitor 8 is connected to the drain terminal (or source terminal) of the first active element connected to the optical element. 12), a voltage applied to a source terminal (or a drain terminal) of the second active element, a voltage applied to a terminal of the second capacitor not connected to the first active element, A source terminal (or a drain terminal) of the first active element not connected to the optical element;
By controlling the voltage applied to the first capacitor and discharging the charge charged in the first capacitor, the total amount of charge flowing through the optical element is controlled, and the influence of the characteristic variation of the first active element configuration is eliminated. Means.

A specific first means for realizing the means according to the fourth invention of the present invention is a source terminal (or a drain terminal) of the second active element (10 in FIG. 20).
While applying the voltage VON that makes the first active element (1 in FIG. 20) conductive, the voltage applied to the other terminal of the optical element is controlled to make the optical element non-conductive, The first capacitor (12 in FIG. 20) is charged with electric charge, and a voltage VOFF for turning off the first active element is applied to a source terminal (or a drain terminal) of the second active element. While controlling the voltage applied to the other terminal of the optical element and discharging the electric charge charged in the first capacitor, the total amount of electric charge flowing through the optical element is controlled. This is a means for eliminating the influence of the characteristic variation of the configuration.

A specific second means for realizing the means according to the fourth invention of the present invention is to control a voltage applied to the other terminal of the optical element and to make the optical element non-conductive. In the meantime, the second active element (1 in FIG. 30)
0) to the source terminal (or drain terminal) of the first active element (1 in FIG. 30).
ON, the first capacitor (12 in FIG. 30)
While applying a voltage VOFF to turn off the first active element to the source terminal (or drain terminal) of the second active element.
The voltage applied to the other terminal of the optical element is controlled to charge the first capacitor through the optical element, and the total amount of charge flowing through the optical element is controlled. It is a means to eliminate the influence of.

A specific third means for realizing the means according to the fourth invention of the present invention is a drain terminal (or a source terminal) of the first active element (1 in FIG. 22) and the optical element. A third active element (13 in FIG. 22) is interposed between (5 in FIG. 22) and a source terminal (or a drain terminal) of the second active element (10 in FIG. 22).
22, the voltage applied to the gate electrode of the third active element, and the voltage applied to the first capacitor (FIG. 22).
And 12) controlling the voltage to be applied to the terminal not connected to the first active element and applying the voltage VOFF for turning off the first active element to the source terminal of the second active element. During the operation, the third active element is turned on, and the electric charge charged in the first capacitor is discharged to control the total amount of electric charge flowing through the first active element. This is a means for eliminating the influence of variation in characteristics of the active element configuration.

The means of the present invention for eliminating the influence of the characteristic variation of the first active element configuration, which is the fifth invention of the present invention for solving the third problem of the present invention, is the first invention.
24, one terminal of the first capacitor (14 in FIG. 24) is connected to the drain terminal (or source terminal) of the active element (1 in FIG. 24), and the optical element (FIG. 24) is connected to the other terminal of the first capacitor. 5) is connected at 24 to control the voltage applied to the source terminal (or the drain terminal) of the first active element and the voltage applied to the other terminal of the optical element, so that the voltage is applied to the first capacitor. A certain amount of electric charge is accumulated, and thereafter, a voltage applied to a source terminal (or a drain terminal) of the first active element and a voltage applied to the other terminal of the optical element are controlled to be accumulated in the first capacitor. By discharging this constant charge and repeating this operation, a constant charge is periodically supplied to the optical element, whereby the total amount of charge flowing through the first active element is controlled, and the first active element is controlled. A means to eliminate the influence of variation in characteristics of the I blanking element configuration.

[0057]

[Embodiment 1] In Embodiment 1, a first specific electro-optical element using an organic EL as an optical element in the time division gray scale display means according to the first invention of the present invention. A configuration and a driving method thereof will be described.

The method of manufacturing an active element using the organic EL and the material constituting each layer are described in detail in Japanese Patent Application Laid-Open No. 8-234683 described in the conventional example. Omitted.

Assuming that the number of pixels of the organic EL panel used in the first embodiment is m × n, an equivalent circuit of the first means of the time division gray scale display means of the first invention can be expressed as shown in FIG. . That is, in the organic EL panel of the first embodiment, the plurality of scanning electrodes G1, G2,... Gm and the plurality of signal electrodes S1,
.. Sn and pixels A11, A1 at their intersections
.. Are provided.

That is, as shown in the square of the broken line in FIG. 12, each pixel Aij (i = 1 to m, j = 1 to n)
Is composed of an active element (TFT) 1, a capacitor 2, an active element (TFT) 4, an organic EL element 5, an active element (TFT) 6, a diode 7, and a capacitor 8, and the source terminal (or drain) of the active element 1 Terminal) and a power supply VDD connected to the capacitor 2,
Source terminal (or drain terminal) of active element 4
A scanning electrode Gj connected to the gate terminal of the active element 4, an active element 6 connected to the drain terminal (or source terminal) of the active element 4 and a drain terminal (or source terminal) thereof, A control electrode PGj connected to a gate terminal or a cathode terminal of a diode 7 (formed by short-circuiting a source-gate electrode or a drain-gate electrode of a TFT);
Source terminal (or drain terminal) of active element 6
And a ground terminal GND connected to the organic EL element 5.

The voltage of each terminal for driving the pixel Aij is shown in FIG. That is, the active element 4
1) is a voltage VG1 applied to the scanning electrode G1, and 2) is a scanning electrode G
2 is a voltage VG2 applied to the scanning electrode G3.
Is the voltage VG3 applied to. 4) is the voltage VS1 applied to the signal electrode S1, and 5) is the voltage VS2 applied to the signal electrode S2. 6) is a voltage VPG1 applied to the control electrode PG1, which is a voltage VG1 of the scan electrode G1, a voltage VS1 of the signal electrode S1, and a voltage VPG1 of the control electrode PG1.
The gate terminal voltage VC1 of the active element 1 in FIG. 12 becomes as shown by 7) in FIG. 14 by the voltage VPG1 of FIG. 12, and the active element 6 by the voltage VPG1 of the control electrode PG1.
Therefore, the drain terminal voltage VP1 of the active element 6 in FIG. 12 is as shown by 8) in FIG.

That is, first, the gate voltage VG1 of the active element 4 becomes the voltage VON, the conduction between the source and the drain of the active element 4 becomes conductive, and the potential of the drain terminal side of the active element 4 of the capacitor 2 becomes the potential of the signal electrode S1. VS11. Next, the gate voltage VG1 of the active element 4 becomes the voltage VOFF, and the source-drain of the active element 4 is turned off.

Thereafter, the control electrode PG1 becomes the voltage VON (high voltage state), the diode 7 becomes the reverse polarity state, the gate voltage VPG1 of the active element 6 becomes the voltage VON, and the source-drain of the active element 6 becomes conductive. Become. Then, part of the electric charge stored on the drain terminal side of the active element 4 of the capacitor 2 moves to the drain side terminal of the active element 6 of the capacitor 8.

Next, the gate voltage VPG of the active element 6
1 becomes the voltage VOFF, and the source
The drain becomes non-conductive, the control electrode PG1 becomes the voltage VOFF (low voltage state), and the diode 7 becomes the forward polarity state. By doing so, part of the electric charge stored on the drain terminal side of the active element 6 of the capacitor 8 is discharged to the ground terminal GND through the diode 7. At this time, the capacitance C2 of the capacitor 2 and the capacitor 8
The gate potential VC11 of the active element 1 after this cycle T1 is VC11 = VS11 × C2 / (C2 + C8).

In this manner, the voltage of the control electrode PG1 is changed to HIGH / LOW in the period T1 while the source-drain of the active element 4 is in a non-conductive state, and the capacitor 2 is connected to the drain terminal of the active element 4 on the drain terminal side. Is discharged through the capacitor 8.

When the active element 1 is an n-type TFT, the gate voltage VC1 of the active element 1 is reduced to the potential Vth at which the active element 1 becomes conductive by the electric charge stored on the drain terminal side of the active element 4 of the capacitor 2. During a period longer than that, the active element 1 is in a conductive state, during which a current flows to the organic EL 5. When the active element 1 is a p-type TFT, this capacitor 2
After the gate voltage VC1 of the active element 1 becomes lower than the potential Vth at which the active element 1 is turned on by the electric charge accumulated on the drain terminal side of the active element 4, the active element 1 is turned on and the organic EL 5 Electric current flows. Therefore, the potential VS held in the capacitor 2 when the active element 4 is turned on.
By controlling 11, the emission time of the organic EL can be controlled, and time-division gray scale display becomes possible.

As described above, in the first embodiment, time-division gradation display is performed by selecting a pixel once in one frame period (turning on the active element 4 of each pixel once in one frame period). Japanese Patent Application Laid-Open No. H10-2
Unlike the time division gray scale display method of FIG.
There is no disadvantage that the selection period for each scanning line is shortened.

Also, since the organic EL constituting each pixel emits light continuously for a period depending on the voltage held in the capacitor 2 after the pixel is always selected, the organic EL device shown in FIG. Unlike the time-division gradation display method of No. 6, the generation of false contours of the moving image is small.

Since the electric charge stored in the capacitor 2 is discharged using the capacitor 8 formed in the same process, the capacitor and the resistor disclosed in Japanese Patent Application Laid-Open No. H08-241057 shown in the prior art are used. Unlike the circuit configuration of
Capacitance ratios of the capacitors 2 and 8 are easy to be uniform, and a display with little variation among pixels can be obtained.

The diode 7 in FIG. 12 may be configured by short-circuiting between the source and the gate or between the drain and the gate of the TFT element. A similar organic EL diode may be used.

Therefore, experimental results are shown in the case where the FET is used instead of the TFT and the LED is used instead of the organic EL in the active element configuration shown in FIG. The voltage of the control electrode PG1 in FIG. 12 is shown in FIG. 28A, and the gate terminal voltage of the active element 1 (holding voltage of the capacitor 2) is shown in FIG. FIG. 28C shows the voltage at the source terminal (or drain terminal) of the active element 1 when a resistor is inserted between the power supply VDD and the source terminal (or drain terminal) of the active element 1 in FIG. In FIG. 28C, a period in which the voltage is reduced to 3 V is a period in which the active element 1 is in a conductive state, a period in which the voltage is maintained at 5 V is a period in which the active element 1 is in a non-conductive state, A period during this period is a period during which the active element 1 is in an intermediate conductive state.

When the pixel TFT circuit configuration shown in FIG. 12 is used and the control is performed as shown in FIG. 14, time-division gradation display can be realized as shown in FIG.

In the pixel TFT circuit configuration of FIG. 12, the control terminal PGj and the gate line Gj are described in association with each scanning line, but as can be seen from FIG. High / Low for each scanning line selection period
Since only the row is repeated, a signal common to all the scanning lines can be used, and the pixels A21, A22... Can be inverted in the vertical direction to be integrated into one electrode as the control terminal PG.

Further, if the active element 6 is an n-type TFT in the pixel TFT circuit configuration of FIG.
In order to operate in the FT, the pixel TF of the present invention is generally used.
The T circuit configuration can be represented as shown in FIG.

In the first embodiment, the electric charge stored in the capacitor 8 in FIG. 12 is discharged through the diode 7, but may be discharged through the active element 9 as shown in FIG. The driving timing chart at this time is as shown in FIG. [Second Embodiment] In a second embodiment of the present invention, a specific electro-optical element configuration using an organic EL as an optical element in the time division gray scale display means according to the second invention of the present invention and a driving method thereof will be described.

The method of manufacturing the active element using the organic EL and the material constituting each layer are not described in the second embodiment as in the first embodiment. FIG. 17 shows an equivalent circuit of each pixel of the organic EL panel used in the present embodiment. That is, in the second embodiment, as in the first embodiment, a plurality of scanning electrodes G1,
Gm and a plurality of signal electrodes S1, S2,.
Pixels A11, A12,... Located at these intersections are provided. Each pixel Aij in FIG. 17 (i is an integer of 1 to m, j
The configuration of (= 1 to n) is a configuration in which the capacitor 2, the active element (TFT) 6, and the diode 7 of FIG. 12 are connected to the ground terminal, and the capacitor 2 of FIG. 17 is connected to the control terminal Rj. is there.

The voltage of each terminal for driving the pixel Aij is as shown in FIG. That is, 1) is the voltage VG1 applied to the scanning electrode G1, 2) is the voltage VG2 applied to the scanning electrode G2, and 3) is the voltage VG3 applied to the scanning electrode G3. 4) is a voltage VS1 applied to the signal electrode S1, 5) is a voltage VS2 applied to the signal electrode S2, and 6) is a voltage VR1 applied to the control electrode R1. The voltage VG1 of the scan electrode G1,
Due to the voltage VS1 of the signal electrode S1 and the voltage VR1 applied to the control electrode R1, the gate terminal voltage VC1 of the active element 1 in FIG. 17 becomes as indicated by 7) in FIG.

That is, in the first embodiment, the charge stored in the capacitor 2 is discharged while the source-drain of the active element 4 is in a non-conductive state, whereas in the second embodiment, the capacitor 2 is discharged. Without discharging the electric charge stored in the active element 4 of the capacitor 2 by gradually changing the voltage VR1 applied to the terminal of the active element 4 opposite to the drain terminal of the active element 4 of the capacitor 2.
Of the active element 1 is gradually changed, and the active element 1 is turned on only while the gate voltage VC1 of the active element 1 is higher than the potential Vth at which the active element is turned on. I have.

As described above, in the second embodiment, time-division gradation display is performed by selecting a pixel once in one frame period (turning on the active element 4 of each pixel once in one frame period). Japanese Patent Application Laid-Open No. H10-2
Unlike the time division gray scale display method of FIG.
There is no disadvantage that the selection period for each scanning line is shortened.

Further, since the organic EL constituting each pixel emits light continuously for a period depending on the voltage held in the capacitor 2 after the pixel is necessarily selected, the organic EL device disclosed in Japanese Patent Application Laid-Open No. Unlike the time-division gradation display method of No. 6, the generation of false contours of the moving image is small.

Further, instead of discharging using the capacitor and the resistor shown in FIG. 11 shown in Japanese Patent Application Laid-Open No. H8-241057, or discharging by the capacitance ratio between the capacitors 2 and 8 shown in FIG. Since the terminal voltage was controlled, a display was obtained without depending on the pixels without depending on the discharge characteristics. [Embodiment 3] The following problems exist in the above two time division gray scale display methods and the time division gray scale display method described in the circuit configuration disclosed in Japanese Patent Application Laid-Open No. H08-241057.

That is, the voltage applied to the gate terminal of the active element 1 shown in FIG. 12 and the like in the above-described first and second embodiments and in JP-A-8-241057 shown in the conventional example is shown in FIG. As a result, the voltage gradually decreases while the source and drain of the active element 4 are in a non-conductive state. As described above, the voltage applied to the gate terminal of the active element 1 decreases, so that the active element 1 is not in a certain period (a period in which FIG. 28C is transitioning between a potential of about 3 V and a potential of 5 V). Used at a voltage that saturates.
At this time, if there is a variation in the threshold voltage between the source and the gate of the active element 1, whether the active element 1 is in a conductive state, a non-conductive state, or an intermediate state even when the same gate voltage is applied. Different results are obtained. Therefore, even if the same voltage is applied to the charging capacity for the same halftone display, the same halftone state is not always displayed. This is the second problem described in the problem of the present invention.

Therefore, in order to solve the above-mentioned problem, the time division gradation display means according to the third invention of the present invention is used. That is, as shown in FIG. 19, another active element (TFT) 10 is inserted between the active element 1 and the capacitor 2 for driving the organic EL 5 having the active element configuration shown in FIG. Then, the drain terminal (or source terminal) of the active element 10 is connected to the gate terminal of the active element 1 that drives the organic EL, and the active element 10
Is connected to the capacitor 2 for controlling the time-division gray scale display period.

A voltage for bringing the active element 1 into saturation conduction is supplied to the drain terminal (or source terminal) of the active element 10 through the resistor 11 (or another active element), and the potential held in the capacitor 2 is applied to the active element 10. To the gate electrode. When the resistor 11 is used, its value is set to a value of a few to a hundredth of the ON resistance of the active element 10 in the non-saturated conductive state. Regardless of the voltage supplied from the source terminal of the active element 10, the voltage VOFF for turning off the active element 1 is applied to the gate terminal of the active element 1.
When the active element 10 is turned off, the saturation conduction voltage VON supplied from the source terminal of the active element 10 is supplied to the gate terminal of the active element 1.

Therefore, when the active element 1 is an n-type TFT, the potential held in the capacitor 2 changes, and even if the active element 10 is used in the non-saturated conducting state, the gate electrode of the active element 1 (the capacitor 2) Since the saturation conduction voltage VON or the saturation non-conduction voltage VOFF is applied (regardless of the held potential), the variation in the ON resistance of the active element 1 can be relatively suppressed.

In fact, by using the configuration of FIG.
Display unevenness was reduced as compared with the case of using the configuration (A). Therefore, experimental results are shown in the case where an FET is used instead of the TFT and an LED is used instead of the organic EL in the active element configuration of FIG. When a voltage similar to that of FIG. 28A is applied to the control electrode PG1 of FIG. 19, the gate terminal voltage (holding voltage of the capacitor 2) of the active element 10 of FIG. 19 is as shown in FIG.
The gate terminal voltage of the active element 1 is shown in FIG. FIG. 29C shows the voltage at the source terminal (or drain terminal) of the active element 1 when a resistor is inserted between the power supply VDD of FIG. 19 and the source terminal (or drain terminal) of the active element 1. In FIG. 29C,
The period in which the voltage is reduced to 3 V is a period in which the active element 1 is in a conductive state, the period in which the voltage is maintained at 5 V is a period in which the active element 1 is in a non-conductive state, and the period during which the active element 1 is in a non-conductive state. Is a period during which the conductive state is intermediate.

As can be seen by comparing FIGS. 28 (C) and 29 (C), in the pixel TFT circuit configuration of FIG. 19 using the third means of the present invention, the active element is compared with the circuit configuration of FIG. The period during which 1 is in an intermediate conduction state is significantly reduced. Since the configuration of the active element 10 in FIG. 19 is an inverting amplifier circuit, in FIG. 29C, the active element 1 becomes conductive when the holding voltage of the capacitor 2 is low, and the behavior in FIG. The opposite is true.

As described above, according to the present invention, by shortening the period during which the active element 1 is in the intermediate conductive state, the variation in the threshold voltage between the source and gate of the TFT driving the organic EL, It is possible to reduce the influence of the variation of the resistance value in the unsaturated conductive state and obtain a more uniform display.

In order to enable gradation display when the means of the third embodiment is used, it is necessary to use a time division method as described in the first and second embodiments and the conventional example of Japanese Patent Application Laid-Open No. 10-214060. It is effective to perform gradation display by gradation display or pixel division gradation display in which one pixel is composed of a plurality of sub-pixels. [Embodiment 4] In Embodiment 4, the active element configuration according to the fourth invention of the present invention is used. Hereinafter, the configuration of an electro-optical element for eliminating the influence of the variation in the conduction resistance of the active element and a driving method thereof will be described.

Also in the fourth embodiment, the ON resistance in the saturated conduction state between the source and the drain of the active element 1 shown in FIG. 19 varies with the size of the active element 1 of each pixel due to a mask pattern shift or the like during TFT manufacturing. There is a problem of variation due to factors such as.

Therefore, in order to solve the above-mentioned problem, the preferable first configuration of the electro-optical element for preventing variation according to the fourth invention of the present invention is used. That is, as shown in FIG.
One terminal of the organic EL 5 and the capacitor 12 are connected to the drain terminal (or source terminal) of the active element 1 for driving L5, and the other terminal of the organic EL 5 is connected to the control electrode NVj. Further, the drain terminal (or source terminal) of another active element 10 is connected to the gate terminal of the active element 1, the control electrode PVj is connected to the source terminal (or drain terminal) of this active element 10, and the gate electrode is time-divided. A capacitor 2 for controlling the gradation display period is connected.

The voltage for driving the pixel Aij is shown in FIG.
It looks like 1. That is, an n-type T
Since FT is assumed, 1) is a voltage VG1 applied to the scan electrode G1, 2) is a voltage VG2 applied to the scan electrode G2, and 3) is a voltage VG3 applied to the scan electrode G3. It is. 4) is the voltage VS1 applied to the signal electrode S1, and 5) is the voltage VS2 applied to the signal electrode S2. Due to the voltage VG1 of the scan electrode G1 and the voltage VS1 of the signal electrode S1, the gate terminal voltage VC1 of the active element 10 in FIG. 7) is a voltage VPV1 applied to the control electrode PV1, and 8) is a voltage VNV1 applied to the control electrode NV1.
It is. Since the active elements 1 and 10 are assumed to be n-type TFTs, the gate terminal voltage VC1 of the active element 10 and the voltage VPV1 applied to the control electrode PV1
And the voltage VNV1 applied to the control electrode NV1,
The drain terminal (or source terminal) voltage VC2 of the active element 1 in FIG. 20 is as indicated by 9) in FIG.

That is, first, the gate voltage VG1 of the active element 4 becomes the voltage VON, the conduction between the source and the drain of the active element 4 becomes conductive, and the potential of the drain terminal side of the active element 4 of the capacitor 2 becomes the potential of the signal electrode S1. VS11. Next, the gate voltage VG1 of the active element 4 becomes the voltage VOFF, and the source-drain of the active element 4 is turned off.

The electric charge stored in the capacitor 2 is discharged by the resistor 3, and while the potential VC1 of the capacitor 2 shown in 6) of FIG. 21 is higher than the gate threshold voltage Vth of the active element 10, A conduction state is established between the source and the drain.

That is, during this time, the voltage of the control terminal PV1 is applied to the gate terminal of the active element 1 through the active element 10. Therefore, the control electrode NV1 is set to HIGH.
(High voltage state), the organic EL 5 is turned off, and the voltage VON at which the source and the drain are turned on through the source and drain terminals of the active element 10 to the gate terminal of the active element 1 is applied to the voltage PV1 of 7) in FIG. The voltage is applied, and the electric charge passed between the source and the drain of the active element 1 is stored in the capacitor 12 as the voltage of the terminal VC2 of 9) in FIG.

Next, a voltage VOFF for turning off the source / drain of the gate terminal A of the active element 1 through the source / drain terminals of the active element 10 is applied as the voltage PV1 of 7) in FIG. Terminal NV
By decreasing 1, the electric charge stored in the capacitor 12 is discharged through the organic EL 5 like the voltage VC2 of 9) in FIG.

By repeating this operation, the organic EL 5 emits light while the potential VC1 is higher than the gate threshold voltage Vth of the active element 10. Thereafter, when the potential VC1 decreases, the gate voltage of the active element 1 becomes the GND potential and the active element 1 is turned off, so that the organic EL 5 does not emit light. As described above, the electric charge passing through the organic EL 5 is determined by the electric charge stored in the capacitor 12 irrespective of the ON resistance between the source and the drain of the active element 1. Of the active element 1 can be eliminated.

In FIG. 20, the conventional time-division gradation display means electro-optical element configuration is used as the time-division gradation display means, but as shown in FIG. A first specific electro-optical element configuration of the divided gradation display means or another time division gradation display means may be used. [Fifth Embodiment] The fifth embodiment also uses the active element configuration according to the fourth invention of the present invention. Hereinafter, a preferred second configuration of the electro-optical element for preventing the variation of the conduction resistance of the active element will be described. That is, as shown in FIG. 30, one terminal of the organic EL 5 and the capacitor 12 are connected to a drain terminal (or a source terminal) of the active element 1 for driving the organic EL 5, and the other terminal of the organic EL 5 is connected to a counter electrode. , And the other terminal of the capacitor 12 is connected to the organic EL driving power supply VOLED. Further, the drain terminal (or source terminal) of another active element 10 and the resistor 11 are connected to the gate terminal of the active element 1, and the source terminal (or drain terminal) of this active element 10 is connected to GND.
The gate terminal of the active element 10 is connected to a capacitor 2 for controlling the time-division gray scale display period, and the source terminals (or drain terminals) of the active elements 4 and 6 for controlling the charge of the capacitor 2. . The scanning electrode Gj is connected to the gate terminal of the active element 4, and the signal electrode Si is connected to the other drain terminal (or source terminal). The other drain terminal (or source terminal) of the active element 6 has (organic E)
A diode 7 in which the source-gate electrode or the drain-gate electrode of L or TFT is short-circuited)
The other terminal of the diode 7, the gate terminal of the active element 6, and the other terminal of the resistor 11 are connected to the control electrode PG. The other terminal of the capacitor 8 is connected to GND.

The voltage for driving the pixel Aij is shown in FIG.
It looks like 1. The active elements are all n-type TF
T is assumed. That is, 1) is the voltage VG1 applied to the scanning electrode G1, 2) is the voltage VG2 applied to the scanning electrode G2, and 3) is the voltage VG3 applied to the scanning electrode G3. 4) is the voltage VS1 applied to the signal electrode S1, and 5) is the voltage VS2 applied to the signal electrode S2. 6) is a voltage VPG applied to the control electrode PG.
The voltage VS1 of the signal electrode S1 and the voltage VP of the control electrode PG
Due to G, the terminal voltage VP1 on the active element 6 side of the capacitor 8 in FIG. 30 becomes like 8), and the gate terminal voltage VC1 of the active element 10 becomes like 7). While the gate terminal voltage VC1 is equal to or higher than the threshold value Vth, the active element 10 is in a conductive state, so that the gate terminal voltage VR1 of the active element 1 is as shown in 9). Therefore, when the potential of the counter electrode of the organic EL 5 (on the opposite side to the electrode connected to the active element 1) is changed to 10), the drain terminal (or source terminal) of the active element 1 connected to the organic EL is turned off. The voltage is as shown in 11).

That is, first, the gate voltage VG1 of the active element 4 becomes the voltage VON, the conduction between the source and the drain of the active element 4 becomes conductive, and the potential on the drain terminal side of the active element 4 of the capacitor 2 becomes the potential of the signal electrode S1. VS11. Next, the gate voltage VG1 of the active element 4 becomes the voltage VOFF, and the source-drain of the active element 4 is turned off.

The charge stored in the capacitor 2 is discharged by the active element 6, the capacitor 8 and the diode 7, and the potential VC1 of the capacitor 2 shown in 7) of FIG. 31 is higher than the gate threshold voltage Vth of the active element 10. While it is large, the conduction between the source and the drain of the active element 10 is conducted.

When the active element 10 is conducting, the gate terminal voltage of the active element 1 becomes GND, and when the active element 10 is non-conducting, the gate terminal voltage of the active element 1 becomes the same potential as the terminal PG.

If the opposing electrode of the organic EL 5 is set to LOW (low voltage state) when the active element 1 is in the non-conductive state, the organic EL driving voltage VOLED is first applied to the capacitor 12 side terminal of the organic EL 5. . Then, the positive charge is discharged from the capacitor 12 through the organic EL 5 (the capacitor 12 is charged). This capacitor 12
When the discharge from the battery is almost stopped, the potential of the counter electrode COM of the organic EL 5 and the potential of the control terminal PG are inverted, the active element 1 is turned on, and the organic EL 5 is turned off (stored in the capacitor 12). Discharge the charge.

By repeating this operation, the organic EL 5 emits light while the potential VC1 is lower than the gate threshold voltage Vth of the active element 10. Since the electric charge passing through the organic EL 5 is determined by the electric charge stored in the capacitor 12 irrespective of the source-drain ON resistance of the active element 1, the capacitance of the capacitor 12 is precisely adjusted to form the active element 1 constituting each pixel. The effect of the variation of the conduction resistance can be eliminated.

Thus, experimental results in the case of using the FET instead of the TFT and using the LED instead of the organic EL in the active element configuration of FIG. 30 are shown. The gate terminal voltage of the active element 10 (holding voltage of the capacitor 2) in FIG. 30 is shown in FIG. 32A, and the gate terminal voltage of the active element 1 is shown in FIG. Further, when a resistor is inserted between the power supply VOLED of FIG.
2 (C). In FIG. 32C, a period in which the voltage is momentarily reduced to 3 V is a period in which the active element 1 is in a conductive state, and in this period, the charge of the capacitor 12 is discharged. The voltage at the other drain terminal (or source terminal) of the active element 1 is shown in FIG. In FIG. 32D, when the active element 1 is in the conductive state, the potential is equal to that in FIG. 32C. When the active element 1 is in the non-conductive state, the potential is reduced.
The potential of the other terminal of the capacitor 12 is equal to the power supply voltage VO
Since it is an LED (here, 5 V), the potential difference is proportional to the charge stored in the capacitor 12.

It is understood that the current flowing through the optical element 5 can be controlled by the electric charge stored in the capacitor 12 by using the pixel TFT circuit configuration of FIG. 30 and controlling as shown in FIG. [Embodiment 6] Also in Embodiment 6, the active element configuration according to the fourth invention of the present invention is used. Hereinafter, a preferred third configuration of the electro-optical element for preventing variation in the conduction resistance of the active element will be described. That is, the organic E of FIG.
Instead of the element configuration in which L5 is connected to the control terminal NVj,
This is an element configuration in which the organic EL 5 and the active element 13 of FIG. 22 are connected in series to a ground terminal.

The voltage for driving the pixel Aij is shown in FIG.
It looks like 3. That is, an n-type T
Since FT is assumed, 1) is a voltage VG1 applied to the scan electrode G1, 2) is a voltage VG2 applied to the scan electrode G2, and 3) is a voltage VG3 applied to the scan electrode G3. It is. 4) is the voltage VS1 applied to the signal electrode S1, and 5) is the voltage VS2 applied to the signal electrode S2. The voltage VG1 of the scan electrode G1 and the voltage VS1 of the signal electrode S1 make the gate terminal voltage VC1 of the active element 10 in FIG. 22 as 6). In addition, since the active elements 1, 10, and 13 are assumed to be n-type TFTs, 7) is the voltage VPV1 applied to the control electrode PV1, and 8) is the voltage VVG1 applied to the control electrode VG1. The gate terminal voltage VC1 of the active element 10 and the voltage V applied to the control electrode PV1
Due to PV1 and the voltage VVG1 applied to the control electrode VG1, the drain terminal (or source terminal) voltage VC2 of the active element 1 in FIG. 22 becomes as indicated by 9) in FIG.

That is, as shown in the first embodiment, first, the gate voltage VG1 of the active element 4 becomes the voltage VON, the source-drain of the active element 4 becomes conductive, and the drain terminal of the active element 4 of the capacitor 2 is turned on. The potential on the (or source terminal) side becomes the potential VS11 of the signal electrode S1. Next, the gate voltage V of the active element 4
G1 becomes the voltage VOFF, and the source and drain of the active element 4 become non-conductive.

The electric charge stored in the capacitor 2 is discharged by the resistor 3, and while the potential VC1 of the capacitor 2 shown in 6) of FIG. 23 is higher than the gate threshold voltage Vth of the active element 10, A conduction state is established between the source and the drain.

Therefore, the voltage VO for turning off the source and drain of the active element 13 is applied to the control electrode VG1.
FF is applied to make the active element 13 non-conductive,
A voltage VON at which a source-drain conduction state is applied to the gate terminal of the active element 1 through the source-drain terminal of the active element 10 as the voltage PV1 of 7) in FIG. The electric charge passed through is stored in the capacitor 12.

Next, a voltage VOFF for turning off the source and the drain through the source and drain terminals of the active element 10 to the gate terminal of the active element 1 is shown in FIG.
3) 7) is applied as the voltage of PV1, and the control electrode VG1 is applied.
A voltage VON for turning on the source and drain of the active element 13 is applied to the active element 13 to turn on the active element 13 and discharge the charge stored in the capacitor 12 through the organic EL 5.

By repeating this operation, the organic EL 5 emits light while the potential VC1 is higher than the gate threshold voltage Vth of the active element 10. The charge passing through the organic EL 5 is independent of the source-drain ON resistance of the active element 1. Since it is determined by the electric charge stored in the capacitor 12, the influence of the characteristic variation of the active element 1 constituting each pixel can be eliminated by accurately adjusting the capacitance of the capacitor 12.

Although the active element 13 is inserted between the organic EL 5 and the drain terminal (or source terminal) of the active element 1 in the element configuration shown in FIG. 22, the active element 13 is inserted between the organic EL 5 and the ground terminal GND. May be. [Embodiment 7] In Embodiment 7, an active element configuration according to the fifth invention of the present invention is used. Hereinafter, the configuration of an electro-optical element for eliminating the influence of the variation in the conduction resistance of the active element and a driving method thereof will be described.

Also in the third embodiment, the ON resistance in the saturated conduction state between the source and the drain of the active element 1 shown in FIG. 19 varies with the size of the active element 1 of each pixel due to a mask pattern shift or the like during TFT manufacturing. There is a problem of variation due to factors such as.

Therefore, in order to solve the above-mentioned problem, the electromechanical element structure for preventing variation according to the fifth invention of the present invention is used. That is, as shown in FIG. 24, one terminal of the capacitor 14 is connected to the drain terminal (or source terminal) of the active element 1 for driving the organic EL 5, and one terminal of the organic EL 5 is connected to the other terminal of the capacitor 14. Connect the terminals. Then, the source terminal (or drain terminal) of the active element 1 is connected to the control electrode PPj, and the organic EL
5 is connected to the control electrode NPj. An organic EL 15 having a polarity opposite to that of the organic EL 5 or a diode auto 15 formed by short-circuiting between the source and gate of the TFT is connected in parallel with the organic EL 5.

The drain terminal (or source terminal) of another active element 10 is connected to the gate terminal of the active element 1, and the source terminal (or drain terminal) of this active element 10 is connected to the saturation conduction voltage VON. The capacitor 2 for controlling the time division gray scale display period is connected to the terminal.

The voltage for driving the pixel Aij is shown in FIG.
It looks like 6. That is, an n-type T
Since FT is assumed, 1) is a voltage VG1 applied to the scan electrode G1, 2) is a voltage VG2 applied to the scan electrode G2, and 3) is a voltage VG3 applied to the scan electrode G3. It is. 4) is the voltage VS1 applied to the signal electrode S1, and 5) is the voltage VS2 applied to the signal electrode S2. The gate terminal voltage VC1 of the active element 10 shown in FIG. 24 becomes 6) by the voltage VG1 of the scan electrode G1 and the voltage VS1 of the signal electrode S1. Also, since the active elements 1 and 10 are assumed to be n-type TFTs, 7) is the voltage VP applied to the control electrode PP1.
P1; 8) is a voltage V applied to the control electrode NP1.
NP1. The gate terminal voltage VC1 of the active element 10 and the voltage VPP1 applied to the control electrode PP1
And the voltage VNP1 applied to the control electrode NP1,
One terminal voltage VC2 of the organic EL 5 in FIG. 24 is as shown in 9) in FIG.

That is, as shown in the first embodiment, first, the gate voltage VG1 of the active element 4 becomes the voltage VON, the source-drain of the active element 4 becomes conductive, and the drain terminal of the active element 4 of the capacitor 2 is turned on. The potential on the (or source terminal) side becomes the potential VS11 of the signal electrode S1. Next, the gate voltage V of the active element 4
G1 becomes the voltage VOFF, and the source and drain of the active element 4 become non-conductive.

The electric charge stored in the capacitor 2 is discharged by the resistor 3, and while the potential VC1 of the capacitor 2 shown in 6) of FIG. 26 is higher than the gate threshold voltage Vth of the active element 10, A conduction state is established between the source and the drain.

Therefore, a voltage VON is applied to the gate terminal of the active element 1 so as to establish a saturated conduction state between the source and the drain of the active element 1. At this time, when a positive voltage is applied to the source terminal (or drain terminal) PPj of the active element 1 and a negative voltage is applied to the other terminal NPj of the organic EL 5, the capacitor 14 connected to the drain terminal (or source terminal) of the active element 1 Charge accumulates in one terminal of the organic EL, and a negative charge corresponding to the positive charge is
5 is discharged. This discharge continues until the potential of one terminal of the capacitor 14 becomes the same as the voltage applied to the source terminal (or drain terminal) PPj of the active element 1.

Next, when a negative voltage is applied to the source terminal (or drain terminal) PPj of the active element 1 and a positive voltage is applied to the other terminal NPj of the organic EL 5, the active element 1
The positive charges accumulated in one terminal of the capacitor 14 connected to the drain terminal of the organic EL are discharged, and instead, the negative charges accumulate.
15 (or the diode 15). This charging continues until the potential of one terminal of the capacitor 14 becomes the same as the voltage applied to the source terminal (or drain terminal) PPj of the active element 1.

By repeating this action, the organic EL 5 emits light while the potential VC1 is higher than the gate threshold voltage Vth of the active element 10. The charge passing through the organic EL 5 is independent of the source-drain ON resistance of the active element 1. Since it is determined by the electric charge stored in the capacitor 14, it is possible to eliminate the influence of the variation in the conduction resistance of the active element 1 constituting each pixel by accurately adjusting the capacitance of the capacitor 14.

Although the capacitor 14 is inserted between the active element 1 and the organic EL 5 in FIG. 24, the organic EL is connected to the drain terminal (or the source terminal) of the active element 1.
5 may be directly connected, and the capacitor 14 may be connected to a source terminal (or a drain terminal) of the active element 1 to which the organic EL 5 is not connected.

[0124]

According to the first aspect of the present invention, as described above,
According to the invention described above, by selecting a pixel once in one frame period regardless of the variation in resistance value, there is an effect that time division gray scale display can be performed without shortening the selection period for each scanning line. In addition, since the organic EL constituting each pixel emits light continuously for a period depending on the voltage held in the capacitor 2 after the pixel is always selected, there is also an effect that generation of false contours of a moving image is small.

Also, according to the second aspect of the present invention, the same effect as that of the time division gray scale display means can be obtained. According to the third aspect of the present invention, an organic EL device is provided.
Variations in the threshold voltage between the source and gate of the TFT driving T and variations in the resistance value of the non-saturated conductive state of the TFT can be reduced, and a more uniform display can be obtained.

Further, according to the fourth and fifth aspects of the present invention, it is possible to eliminate the influence of the variation in the characteristics of the active elements constituting each pixel, so that there is an effect that display unevenness is reduced.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an active element configuration shown in a conventional example of the present invention.

FIG. 2 is a conceptual diagram of an actual device structure when the organic EL shown in the conventional example of the present invention is used.

FIG. 3 is a cross-sectional view taken along line AA ′ of FIG. 2 shown in the conventional example of the present invention.

FIG. 4 is a cross-sectional view taken along line BB ′ of FIG. 2 shown in the conventional example of the present invention.

FIG. 5 is a conceptual diagram of a device configuration of a blue light emitting organic EL shown in a conventional example of the present invention.

FIG. 6 is a conceptual diagram of scanning timing of time division gray scale display shown in the conventional example of the present invention.

FIG. 7 is a conceptual diagram of another active element configuration shown in the conventional example of the present invention.

FIG. 8 is a conceptual diagram of drive timing of the active element of FIG. 7 shown in the conventional example of the present invention.

FIG. 9 is a conceptual diagram of an active element configuration shown in a conventional example of the present invention.

FIG. 10 is a conceptual diagram of an active element configuration shown in a conventional example of the present invention.

FIG. 11 is a conceptual diagram of an active element configuration shown in a conventional example of the present invention.

FIG. 12 is a conceptual diagram of an active element configuration shown in the first embodiment of the present invention.

FIG. 13 is a similar conceptual diagram of the active element configuration shown in the first embodiment of the present invention.

FIG. 14 is a conceptual diagram of drive timing of the active element of FIG. 12 shown in the first embodiment of the present invention.

FIG. 15 is a conceptual diagram of another active element configuration shown in the first embodiment of the present invention.

FIG. 16 is a conceptual diagram of the drive timing of the active element of FIG. 15 shown in the first embodiment of the present invention.

FIG. 17 is a conceptual diagram of an active element configuration shown in Embodiment 2 of the present invention.

FIG. 18 is a conceptual diagram of the drive timing of the active element of FIG. 17 shown in the second embodiment of the present invention.

FIG. 19 is a conceptual diagram of an active element configuration shown in Embodiment 3 of the present invention.

FIG. 20 is a conceptual diagram of the active element configuration shown in Embodiment 4 of the present invention.

FIG. 21 is a conceptual diagram of drive timing of the active element of FIG. 20 shown in the fourth embodiment of the present invention.

FIG. 22 is a conceptual diagram of an active element configuration shown in Embodiment 6 of the present invention.

FIG. 23 is a conceptual diagram of the drive timing of the active element of FIG. 22 shown in Embodiment 6 of the present invention.

FIG. 24 is a conceptual diagram of the active element configuration shown in Embodiment 7 of the present invention.

FIG. 25 is a conceptual diagram of another active element configuration shown in the fourth embodiment of the present invention.

FIG. 26 is a conceptual diagram of drive timing of the active element of FIG. 24 shown in the seventh embodiment of the present invention.

FIG. 27 is a diagram showing VI characteristics and V-efficiency characteristics of the organic EL shown in the subject of the present invention. It is an example.

FIG. 28 is an actual operation measurement result of the active element configuration of FIG. 12 shown in the first embodiment of the present invention.

FIG. 29 is an actual operation measurement result of the active element configuration of FIG. 19 shown in the third embodiment of the present invention.

FIG. 30 is a conceptual diagram of the active element configuration shown in Embodiment 5 of the present invention.

FIG. 31 is a conceptual diagram of the drive timing of the active element of FIG. 30 shown in the fifth embodiment of the present invention.

FIG. 32 is an actual operation measurement result of the active element configuration of FIG. 30 shown in the fifth embodiment of the present invention.

[Explanation of symbols]

1: active element, 2: capacitor, 3: resistor, 4:
Active element, 5: organic EL element, 6: active element, 7: diode element, 8: capacitor, 9: active element, 10: active element, 11: resistance, 12:
Capacitor, 13: Active element, 14: Capacitor, 15: Organic EL element 101: Pixel, 102: TFT, 103: TFT, 10
4: capacitor, 105: electro-optical element, 110: insulating substrate, 111: polysilicon layer, 112: insulating gate material, 113: polysilicon layer, 114: gate bus, 1
15: insulating layer, 116: contact hole and electrode material, 117:
Contact hole and electrode material, 118: transparent electrode, 119: insulating passivation layer, 120: ITO-side end face, 121:
Organic EL layer, 122: cathode, 130: substrate, 131: anode, 132: hole ingress layer, 133: hole transport layer, 134:
Light-emitting layer, 135: electron transport layer, 136: cathode, 140:
1st TFT, 141: gate electrode, 142: drain electrode, 143: source electrode, 150: second TFT, 1
51: gate electrode, 153: drain electrode, 154: source electrode, 160: storage capacitor, 170: organic EL element,
171: anode, 172: cathode, 180: drive power supply, 18
1: charging capacity, 182: third TFT, 183: gate electrode, 184: drain electrode, 185: source electrode,
186: fourth TFT, 187: gate electrode, 188:
Drain electrode, 189: source electrode, 190: display electrode,

Claims (8)

[Claims] 1. An electro-optical element for controlling a charge flowing through an optical element connected indirectly or directly to a drain terminal or a source terminal of the first active element by a voltage applied to a gate terminal of the first active element. And a capacitor for controlling a voltage of a gate terminal of the first active element, and a second active element connected in series or in parallel with the capacitor, wherein the first active element is provided in the capacitor. The first element holds the charge for controlling the voltage of the gate terminal of the active element and discharges the charge through the second active element.
An electro-optical element, wherein the voltage applied to the gate terminal of the active element is controlled to control the amount of charge flowing through the optical element. 2. An electro-optical element for controlling an electric charge flowing through an optical element connected indirectly or directly to a drain terminal or a source terminal of a first active element by a voltage applied to a gate terminal of the active element. A capacitor for controlling a voltage of a gate terminal of the active element, and a charge applied to the one terminal of the capacitor and a voltage applied to the other terminal of the capacitor applied to a gate terminal of the active element. An electro-optical element, wherein the voltage is controlled to control the amount of charge flowing through the optical element. 3. A first active element, an optical element indirectly or directly connected to a drain terminal or a source terminal of the first active element, and a drain terminal or a source connected to a gate terminal of the first active element. A second active element having a terminal connected thereto; and a capacitor for supplying a control voltage for controlling a conductive / non-conductive state of the second active element, wherein the first active element is connected to the first active element through the second active element. An electro-optical element, wherein a voltage for controlling a non-conductive state / saturated conductive state of the element is applied to control an amount of charge flowing through the optical element. 4. A first active element, an optical element indirectly or directly connected to a drain terminal or a source terminal of the first active element, and a connection point between the optical element and the first active element A first capacitor having one terminal connected to the first active element, a second active element having a drain terminal or a source terminal connected to a gate terminal of the first active element, and a conductive / non-conductive state of the second active element. And a second capacitor for providing a control voltage for controlling a conduction state. An electro-optical element for discharging electric charges held in the first capacitor through the optical element. 5. A conductive / non-conductive voltage is supplied to the first active element through the conductive second active element, and the optical element through a control electrode when the first active element is conductive. To supply a non-conduction voltage to the first
A charge based on the conduction voltage is held by the capacitor, and when the first active element is in a non-conductive state, a conduction voltage is supplied to the optical element through a control electrode, and the charge held by the first capacitor is 5. The electro-optical element according to claim 4, wherein is discharged to the optical element. 6. When the first active element is in a non-conductive state, charges the first capacitor through the optical element, and charges the first capacitor when the first active element is in a conductive state.
5. The electro-optical device according to claim 4, wherein the capacitor is discharged. 7. A third active device is connected between the first active device and the optical device, and the one terminal of the first capacitor is connected to the first active device and the third active device. The first active element is connected to a connection point of an active element,
A conducting / non-conducting voltage is supplied to the third active element through the control electrode when the first active element is in a conducting state, and the optical element is brought into a non-conducting state. The first capacitor holds a charge based on the conduction voltage, and when the first active element is in a non-conduction state, supplies a conduction voltage to the third active element through a control electrode; 5. The element is brought into a conductive state, and the electric charge held in the first capacitor is discharged to the optical element.
3. The electro-optical element according to claim 1. 8. An optical element, a first capacitor having one terminal connected to the optical element, and a drain terminal or a source terminal of the first active element having the other terminal connected thereto, and the first active element. A second capacitor for providing a control voltage for controlling a conduction / non-conduction state of an active element of the element; and a polarity inversion of the one terminal of the first capacitor via the first active element. Electro-optics in which the first control voltage is applied at a predetermined cycle and a control voltage having a polarity opposite to the first polarity is applied to the other terminal of the first capacitor through the optical element at the same cycle as the cycle. element.