JPH0748138B2 - Driving method of electroluminescence display device - Google Patents

Abstract

PURPOSE: To realize light control function without degrading the quality of a display screen by applying a write pulse and then a light control pulse with polarity reversed from that of a write pulse and making the applied voltage of a luminous layer changeable by means of a row direction electrode and a column direction electrode. CONSTITUTION: A row direction electrode Y is controlled by being divided into an alternately selected one group and the remaining the other group, constituting one screen and the other screen which are alternately repeated by the one group and the other group of the row direction electrode Y, to which a write pulse is alternately applied with a positive and a negative polarity, and by a column direction electrode X. Then, in each screen, after the write pulse is applied, a light control pulse is applied which is provided a polarity reversed from that of the write pulse, making the applied voltage for a luminous layer changeable by means of the row direction electrode Y and the column direction electrode X. With such change of the applied voltage for the luminous layer, a light control level can be changed for each screen. As a result, light control variation can be realized for a wide area without degrading the quality of a displayed screen, with stability improved for a display device.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC driving type capacitive flat matrix display panel having a dimming function, that is, a driving method carried out in a thin film electroluminescence (EL) display device.

Prior Art FIG. 9 is a perspective view in which a part of a typical prior art thin film electroluminescent display device (hereinafter referred to as EL display device) 9 is cut away. The EL display device 9 has a strip-shaped transparent electrode 2 arranged in parallel on a glass substrate 1, on which an EL layer 4 sandwiched between dielectric material layers 3 and 3a is laminated, and further the transparent layer 2 is formed thereon. A strip-shaped back electrode 5 in a direction orthogonal to the electrode 2
Are arranged in parallel.

Since the EL layer 4 is interposed between the dielectric material layers 3 and 3a,
The equivalent circuit can be regarded as a capacitive element. The EL layer 4 is driven by applying a relatively high voltage of about 250 V, as shown in the applied voltage-luminance characteristic of FIG.

Conventionally, as a driving method of such an EL display device 9, either the transparent electrode 2 or the back electrode 5 is used as a scanning side electrode, and an N channel driving circuit and a P channel driving circuit are used in the driving circuit of the scanning side electrode. A so-called field inversion drive method has been used which includes a drive circuit and inverts the polarity of the write voltage applied to each pixel for each field.

Further, by changing the polarity of the writing voltage applied to the picture element for each scanning line, the variation in the light emission intensity of each picture element is averaged and the generation of flicker is suppressed (Japanese Patent Application No. 59-59). -105375) was proposed. In addition, the positive polarity pulse voltage waveform and the negative polarity pulse voltage waveform applied to each picture element are made completely symmetrical to eliminate a burning phenomenon due to polarization, thereby improving the quality of the EL layer 4 and reducing power consumption. A driving method that can reduce the number of the driving methods has also been proposed.

Problems to be Solved by the Invention Although various methods have been proposed as a method for driving the EL display device 9 as described above, a driving method for realizing a dimming function has not been so far proposed. One of the reasons for this is
The following is fried.

That is, the applied voltage-luminance characteristic of the EL layer 4 has a steep gradient up to a constant voltage as shown in FIG. 10, but the luminance is saturated at a voltage higher than that. Also,
This applied voltage-luminance characteristic has a time-dependent characteristic in which its characteristic curve changes from the line l1 to the line l2 shown in FIG. 10 with the lapse of time when the EL display device 9 is driven.

When the normal drive voltage VA is applied, the amount of change ΔA is relatively small even if the applied voltage-luminance characteristic changes with the elapse of the drive time.
When a voltage VB that is lower than VA is applied, the amount of change ΔB with the passage of time becomes very large, and the pixel that was operating in the light-emitting state and the pixel that was operating in the non-light-emitting state increased over the operating time. The brightness difference increased, and the desired dimming function could not be realized.

Further, as a method for realizing the dimming function, a method of changing the frequency of the driving voltage or a method of applying an asymmetrical pulse can be considered, but it has not been realized due to the problem of flicker or reliability of display quality.

An object of the present invention is to solve the above-mentioned problems and to provide a driving method of an electroluminescence display device capable of realizing a dimming function without deteriorating the quality of a display screen.

Means for Solving the Problems According to the present invention, a plurality of row-direction electrodes extending in one direction, a plurality of column-direction electrodes extending in a direction intersecting with the row direction, and a row-direction electrode and a column-direction electrode are interposed. Used for an electroluminescence display device including an electroluminescence layer, and the row electrodes are controlled by being divided into one group selected every other row and the other group remaining, and writing in positive polarity and negative polarity. One group and the other group of the row-direction electrodes to which pulses are alternately applied and the one-screen and the other screen that are alternately repeated by the column-direction electrodes are formed, and the emission threshold of the electroluminescence layer is exceeded in each screen. , And after applying a write pulse having a voltage corresponding to the gradation of brightness, a dimming pulse having a polarity opposite to that of the write pulse and having a light emission threshold value or less is applied, A driving method of an electroluminescence display device, characterized in that a voltage applied to an electroluminescence layer is changed by a row direction electrode and a column direction electrode.

Operation In the display device used in the present invention, one group of row direction electrodes to which the writing pulse of one polarity is applied and the other group of row direction electrodes to which the writing pulse of the other polarity is applied and the column direction electrode are used to display one screen. And the other group of the row-direction electrodes to which the write pulse of one polarity is applied and the one group of the row-direction electrodes to which the write pulse of the other polarity is applied and the column-direction electrode form the other screen. The configured one and the other screens are displayed alternately.

According to the present invention, the applied voltage of the electroluminescent layer applied by the row-direction electrodes and the column-direction electrodes is changed. Thereby, the dimming level on each screen can be changed. Further, since the writing pulse is applied to each screen and then the dimming pulse having the opposite polarity to the writing pulse is applied, the characteristic curve showing the applied voltage-luminance characteristic of the light emitting layer is changed as desired. Therefore, it is possible to change the dimming level without degrading the quality of each screen.

Embodiment FIG. 1 is a waveform diagram for explaining the drive system of this embodiment in principle. In the driving method of this embodiment, the polarity of the write pulse applied to each picture element is set to 1 field (1 /
Every 60 seconds), by applying a dimming pulse having a polarity opposite to the writing pulse in each field period, the applied voltage-luminance characteristics of each pixel are stabilized,
It is arranged to eliminate the variation in luminance due to the time-dependent change characteristic described in the section of the prior art.

FIG. 2 is a block diagram showing the electrical configuration of the thin film electroluminescent display device 11 used in one embodiment of the present invention. The thin film electroluminescence display section (hereinafter referred to as EL display section) 10 has a light emission threshold V _W set to, for example, 190 V, and has a plurality of data side electrodes X1, X2, ..., Xi.
(Hereinafter, when collectively referred to, it is referred to as the data-side electrode X)
, And a plurality of scanning-side electrodes Y1, Y2, ..., Yi (hereinafter collectively referred to as data-side electrodes Y) are arranged so as to intersect with each other.

The scanning-side electrode Y has, for example, an N-channel high breakdown voltage MOS (M
There are provided first switching circuits 12 and 13 realized by an etal oxide semiconductor type integrated circuit and second switching circuits 14 and 15 realized by, for example, a P-channel high breakdown voltage MOS integrated circuit.

Each data side electrode X is provided with a data side drive circuit 20, and the data side drive circuit 20 has a common source side voltage.
Transistors UT1 to UTi having a pull-up function connected to the power supply line l3 of V _m (= 0 to 60 V) and a transistor DT having a pull-down function in which the sources are commonly grounded.
1 to DTi, diodes UD1 to UDi for flowing a current in the direction opposite to that of each of the transistors, and DD1 to DDi, each of which is selectively driven by the selection circuit 21.

The power supply voltage of the power supply circuit 23 is supplied to the source side of each transistor in the second switching circuit 14. In this power supply circuit 23, two kinds of power supply voltage V _W (= 190 V), V
Three switching elements SW based on _m = (0 to 60V)
0V, 190V, depending on the combination of conduction / cutoff of 1 to SW3
One of three types of voltage from 190 to 250V is set.

For example, when the switching element SW3 becomes conductive,
The power source voltage V _W (= 190 V) is charged to the capacitor CM1 at a voltage of 190 V, and then the switching elements SW1 and SW2 are both turned on to make the output voltage of the power source circuit 23 190 to 250 V (= V _W + V _m ) is set. In addition, by connecting / disconnecting the switching element SW2, 190V
The potential of and the potential of 0V are switched. In addition, these three switching elements SW1 to SW3 are control signals PSW and PS described later.
Controlled by C.

The output voltage of the power supply circuit 24 is supplied to the source side of each transistor of the first switching circuits 12 and 13. This power supply circuit 24 is controlled by the conduction / interruption state of the switching element SW4 controlled by a control signal NSC described later.
Power supply voltage -190V (= - V _W) and are switched and 0V. The output voltage of the power supply circuit 26 is supplied to the power supply line 13 in which the transistors UT1 to UTi and the diodes UD1 to UDi in the data side drive circuit 20 are commonly connected.

This power supply circuit 26 controls the voltage applied to the power supply line l3 to a predetermined level by controlling conduction / cutoff of the four switching elements SW5 to SW8 based on the power supply voltage 1/2 V _m (= 0 to 30 V). Can be set to.

For example, when the switching element SW6 is turned on and the switching element SW5 is turned off, the capacitor CM is charged with a power supply voltage of 1/2 V _m (= 0 to 30 V), and then the switching element SW7 is turned on and the switching element SW6 is turned on. Is cut off, the potential applied to the power supply line 13 is raised to 0 to 30 V (= 1/2 V _m ). After that, when the switching element SW5 is turned on, a potential of 0 to 60 V (= V _M ) is applied to the power supply line 13.

Conduction / cutoff control of these four switching elements SW5 to SW8 is performed by three control signals T1, T2, T3 described later. It should be noted that 0 to 60 V (= V
_The reason why the applied voltage is increased stepwise when _m ) is applied is to reduce power consumption during modulation.

FIG. 3 is a timing chart for explaining the operation of this embodiment. Here, it is assumed that the scan electrode Y1 including the picture element A and the scan electrode Y2 including the picture element B are selected. The EL display device 11 is driven by reversing the polarity of the voltage applied to the picture element for each scanning electrode Y.

Here, for convenience of description, the first switching circuits 12 and 13 are provided.
Driving timing for applying a negative writing pulse to the picture element on the scanning-side selection electrode is hereinafter referred to as Nch driving timing, and an arbitrary transistor in the second switching circuits 14 and 15 is turned on. The drive timing for applying a positive write pulse to the picture element on the scanning-side selection electrode with the transistor made conductive is referred to as Pch drive timing.

A field (screen) in which Nch driving is performed on odd-numbered scan electrodes Y and Pch driving is performed on even-numbered scan electrodes Y is called an NP field, and a field opposite to this is called a PN field.

The waveform of the horizontal synchronizing signal H is shown in FIG.
The level period indicates the validity period of the data. FIG. 2B shows the waveform of the vertical synchronizing signal V, and driving of one frame is started from the rising edge of the vertical synchronizing signal V.
The data latch signal DLS waveform is shown in FIG.
The data latch signal DLS is output after the data transfer of one line is completed in each line corresponding to each scanning side electrode Y.

A clock signal for data side data transfer is shown in FIG.
The DCK waveform is shown. FIG. 5 (5) shows the waveform of the data inversion signal RVC, which is at the H level in the data transfer period of the line in which the Pch drive is performed, and all the data in this period is inverted. The display data DA is shown in FIG.
The waveform of T is shown. In Fig. 7 (7), the data side drive circuit 2
The waveforms of the data D1 to Di input to the 0 transistors are shown. The waveforms of the control signals T1, T2, and T3 supplied to the power supply circuit 26 are shown in FIGS. 8 to 10 respectively. As described above, each signal shown in (3) to (10) of the same figure is a signal related to the data-side electrode X.

The waveforms of the signals related to the first switching circuits 12 and 13 are shown in (11) to (16) of FIG.
7) to (23) show waveforms of signals related to the second switching circuits 14 and 15. The signals shown in FIGS. 11 to 23, that is, the signals related to the scanning-side electrode Y will be described below in Table 1.

Further, FIG. 24 (24) shows a voltage waveform applied to the data side electrode X2, and FIG. 25 (25) and FIG. 27 (27) show the voltage applied to the scanning side electrodes Y1 and Y2, respectively. Waveforms are shown. In Fig. 26 (26), the data side electrode X2 and the scanning side electrode
The voltage waveform applied to the picture element A based on the voltage applied to Y1 is shown. Further, FIG. 28 (28) shows a voltage waveform applied to the picture element B based on the voltages applied to the data side electrode X2 and the scanning side electrode Y2, respectively.

The driving of the data side electrode X is basically performed by the display data (H
Level; light emission, L level; non-light emission), the voltage applied to each data line in a cycle of one horizontal synchronization period is set to 0V.
It is performed by switching the V _m (= 0~60V).

FIG. 4 shows a selection circuit provided in the data side drive circuit 20.
FIG. 23 is a block diagram showing a configuration of 21. This selection circuit 21
The shift register 27 has a storage capacity for one line, and a latch circuit 28 that latches the output of the shift register 27 and outputs the data D1 to Di to each transistor.

Hereinafter, the switching timing of the voltage applied to the data side electrode Y will be described with reference to FIG.

First, in a period in which driving of an arbitrary line is being executed, display data DAT (H level; light emission, L of the next line)
Level; non-light emission) and the data inversion signal RVC are input to the shift register 27 via the exclusive OR circuit 25 which is a data inversion control circuit. Display data DAT + data inversion signal R input to this shift register 27
VC is taken into the latch circuit 28 by the data latch signal DLS input after the end of the data transfer of one line, and thereafter, is stored in the latch circuit 28 until the end of the drive timing.

Based on the output of this latch circuit 28, each transistor UT
1 to UTi and DT1 to DTi are controlled respectively. Therefore,
The voltage applied to the data side electrode X is switched in a cycle of one horizontal synchronization period each time the data latch signal DLS is input.

The data inversion signal RVC is a signal that is at the H level during the data transfer period of the line in which the Pch drive is realized, and inverts the data during this period. Below, Pch
The reason for inverting the drive display data will be described.

As will be described later, in Pch driving, the corresponding transistors in the second switching circuits 14 and 15 are made conductive to be applied to the scanning side selection electrodes (hereinafter, referred to as scanning side selection electrodes Ys). Change the voltage to V _W + V _m (= 190 to 250
V), the voltage applied to the data-side selection electrode (hereinafter referred to as the data-side selection electrode Xs) is set to 0 V, and the voltage of V _W + V _m (= 190 to 250 V) is applied to the corresponding picture element. It emits light when applied.

At this time, the non-selection electrode on the data side (hereinafter, non-selection electrode Xd
0) to 60 V (= V _m ), and 190 V (= (V _W + V _m ) −V _m = V _W ) is applied to the corresponding picture element.
However, since this value is less than the light emission threshold value (= 190V), this pixel does not emit light.

In order to realize Pch drive like a roller, the transistor UTs corresponding to the selection electrode Xs on the data side is turned off, the transistor DTs is turned on, the transistor UTd corresponding to the non-selected electrode Xd is turned on, and the transistor DTd is turned on. It must be set to the blocking state.

That is, the input data D1 input by the selection circuit 21
~ Di, input data Ds corresponding to the selected electrode Xs is L
The input data Dd corresponding to the level and non-selection electrode Xd must be set to the H level. This is the opposite of the input display data (H level; light emission, L level; non-light emission),
A data inversion signal RVC for inverting the data is required.

5 and 6 are blocks showing the electrical configurations of the selection circuits 16 and 18 provided in the first switching circuits 12 and 13 and the selection circuits 17 and 19 provided in the second switching circuits 14 and 15, respectively. It is a figure and each truth table is shown in the following 2nd table and 3rd table. These two types of selection circuits
16, 18; 17 and 19 have complementary circuit configurations, and the logics thereof are all reversed but the configurations are the same, so only the selection circuits 16 and 18 will be described below.

The shift register 34 in the selection circuits 16 and 18 is a circuit for storing the scanning-side selection electrode Xs, and takes in the transfer data ▲ ▼ during the H level period of the scanning-side data transfer clock signal CK. , L level periods are used for transfer. In this EL display device 11, as the clock signal CK,
The selection circuit 16 has the strobe signal shown in FIG. 3 (13).
NSTo and the strobe signal NSTe shown in (15) of FIG.

As shown in (16) in the figure, the transfer data NDA becomes L level once in each field only while the strobe signals NSTo and NSTe input after the rise of the vertical synchronizing signal V are H level. Is set as follows. Strobe signal NSTo, NST at a rate of once for two horizontal synchronization periods
The reason for inputting e is that Nch drive and Pch drive are repeatedly performed for each line.

In order to apply a dimming pulse having a polarity opposite to that of the writing pulse during the driving period of one line,
Pch drive is performed after Nch drive.

For example, in the NP field, the strobe signal NSTo, N
By inputting STo to the selection circuits 16 and 17, respectively,
It is possible to perform Pch drive (application of dimming pulse) after performing Nch drive (application of write pulse) to odd-numbered selected lines. On the other hand, in the PN field, by inputting the strobe signals NSTe and PSTe to the selection circuits 18 and 19, respectively, even-numbered selection lines can be Nch-driven and then Pch-driven.

The logic circuit 35 has a strobe signal NST and a clear signal ▲
The two types of ▼ are used to make the transistor conductive,
It is a circuit for switching between three states of a cutoff state and a state according to the data from the shift register 34, and its logic follows the truth value in Table 2 above.

Next, the driving method during the period in which the dimming pulse is applied will be described.

First, the dimming pulse applied in the NP field will be described. Pch drive is performed for odd-numbered selection lines, the output voltage of the power supply circuit 23 is set to 190 V (= V _W ), and each transistor in the second switching circuit 14 is made conductive based on the data from the selection circuit 17. / Cut off control. On the other hand, Nch drive is performed on even-numbered selection lines, the output voltage of the power supply circuit 24 is set to −190 V (= −V _W ), and each transistor in the first switching circuit 13 is converted to data from the selection circuit 18. Therefore, conduction / interruption control is performed. In addition, since the output voltage of the power supply circuit 26 is set to 0V in this period, the electrodes X on the data side are all set to 0V.
become.

In the PN field, a desired AC pulse can be obtained by the operation opposite to the driving method in the NP field.

As described above, the operation according to the driving method of the present embodiment is composed of two kinds of timings, that is, the NP field and the PN field. By completing each driving operation in these two fields, an AC pulse necessary for light emission can be applied to all the picture elements of the EL display section 10.

Further, each of the two fields is composed of the following two types of timing. That is, in the NP field, Nch drive of the write pulse and Pch of the dimming pulse
It consists of two types of drive timing. In the PN field, Pch drive for write pulse and Nch for dimming pulse.
It is composed of two types of timings of driving.

In other words, each write pulse application period is Nch drive for the odd-numbered select line on the scanning side in the NP field,
Pch drive is executed for even-numbered select lines, and PN
In the field, the opposite drive is executed. On the other hand, during the dimming pulse application period, Pch drive is performed for the odd-numbered select lines on the scanning side in the NP field, and Nch drive is performed for the even-numbered select lines, and vice versa in the PN field. To execute.

FIG. 7 is an equivalent circuit diagram of the EL display device 11 shown in FIG. The operation in each drive period described above will be described below with reference to FIGS. 2 and 7. An explanation of each signal in FIG. 7 is given in Table 4 below.

Pulse application write period in NP field Nch drive.

In order to set the source potential of each transistor of the first switching circuits 12 and 13 to −V _W = −190V, the switch NSC is turned on, and the source potential of each transistor of the second switching circuits 14 and 15 is set to 0V. Then, the switch PSC is turned off. After this, according to the data of the selection circuit 16, the transistors NTs selected in the first switching circuit 12
Is made conductive, and the line corresponding to this is selected. All the other transistors of the first and second switching circuits 12, 13; 14 and 15 are turned off.

On the data side, each transistor UT _B , UT _D , DT _B , DT _D
Continues to drive during the modulation period, and controls the switches T1 to T3 to conduct or cut off, thereby raising the output voltage of the power supply circuit 26 to V _M. As a result, the selection electrode Xs on the data side is V _M =
0～60V, unselected electrodes Xd goes to the potential of 0V, since the selective electrode Ys of the scanning is -V _W = -190V, the scanning-side selection electrode
The pixel C _B s between Ys and the selection electrode Xs on the data side has (0 to 60
V)-(-190V) = 190 to 250V The voltage corresponding to the gradation exceeding the light emission threshold is applied and light is emitted.

The pixel C _D s between the non-selected electrodes on the data side has 0 V − (−190
V) = 190V is applied. It does not emit light because it is below the emission threshold. In addition, the pixel on the non-selection electrode Yd on the scanning side
Regarding C _B and C _D , since the scanning side electrode is floating, it changes from 0 V to 60 V depending on the ratio of the selection electrode Xs and the non-selection electrode Xd on the data side.

Light control pulse application period in NP field Nch drive.

In order to set the source potential of each transistor of the second switching circuits 14 and 15 to V _W = 190V, the switch PSW is turned off, the switch PSC is turned on, and the source potential of each transistor of the first switching circuits 12 and 13 is turned on. The switch NSC is turned off so that the voltage is set to 0V. After that, according to the data of the selection circuit 17, the selected transistor PTs in the second switching circuit 14 is made conductive, and the selection electrode Ys
To set. First and second switching circuits 12, 13; 1
All other transistors in 4, 15 are turned off.

On the data side, switch T3 is turned off and the power supply circuit 26
Set the output voltage of to 0V. As a result, all the electrodes X on the data side become 0V, and the dimming pulse of 190V-0V = 190V, which is equal to or less than the light emission threshold value, has a polarity opposite to that of the writing pulse in the picture element on the scanning side selection electrode Xs. Will be applied.

Write pulse application period in NP field Pch drive.

In order to set the source potential of each transistor in the second switching circuit 15 to V _W + V _M = 190 to 250 V, two switches P
In order to make SW and PSC conductive and set the source potential of the transistor in the first switching circuit 12 to 0V, switch NS
C is cut off. After that, the transistor DTs selected from the other transistors in the second switching circuit 15 according to the data of the selection circuit 19 is made conductive, and the selection electrode Ys is set. First and second switching circuits
All other transistors in 12,13; 14,15 are turned off.

On the data side, each transistor UT _B , UT _D , DT _B , DT _D
Continues to drive during the modulation period and controls the output voltage of the power supply circuit 26 to V _m (= 0 by controlling conduction / cutoff of the three switches T1 to T3).
~ 60V). As a result, the selection electrode Xs on the data side has a potential of 0 V, the pull selection electrode Xd has a potential of V _m = 0 to 60 V, and the selection electrode Xs on the scanning side has V _W + V _m = 190 to 250 V. In the picture element between the selection electrode Ys and the selection electrode Ys on the data side, a write pulse of 190 to 250V-0V = 190 to 250V is applied with the opposite polarity of the write pulse in the Nch drive, and light is emitted. On the other hand, in the picture element between the non-selected electrodes on the data side,
(190 to 250V)-(0 to 60V) = 190V is applied, but it does not emit light because it is below the emission threshold.

Light control pulse application period in NP field Nch drive.

The source potentials of the first switching circuits 12 and 13 are set to −V _W = −190
To bring it to V, the switch NSC is turned on and the source potential of each transistor of the second switching circuits 14 and 15 is set to 0V.
In order to turn on, the switch PSC is turned off. After that, according to the data of the selection circuit 18, the selected transistor NTs in the first switching circuit 13 is made conductive, and the selection electrode Xs is set. All other transistors in the first and second switching circuits 12, 13; 14 and 15 are turned off.

On the data side, the output voltage of the power supply circuit 26 is set to 0V by turning off the switch T3. As a result, all the electrodes X on the data side have a potential of 0 V, and the dimming pulse of 0 V-(-190 V) = 190 V is applied to the picture element on the scanning-side selection electrode Ys in the opposite polarity to the writing pulse. It will be.

Write pulse application period in NP field Pch drive.

NP except that the select electrode Xs on the scan side is selected from the odd side
Drive similar to field Nch drive.

PN field Nch drive dimming pulse application period.

The same drive as the Nch drive in the NP field is performed except that the odd number side and the even number side are switched.

PN field Application period of write pulse in Nch drive.

The same driving as in the NP field is performed except that the selection electrode Xs on the scanning side is selected from the even number side.

Light control pulse application period in PN field Pch drive.

The same drive as the Nch drive in the NP field is performed except that the even number side and the odd number side are switched.

As described above, according to the driving method of the present embodiment, when each picture element in the EL display unit 10 is caused to emit light, the applied voltage is 19
Dimming from 0 to 100% is possible by changing the voltage from 0 to 250V. Further, by applying a dimming pulse having a polarity opposite to that of the writing pulse for causing each picture element to emit light, the applied voltage-luminance characteristic in the EL display section 10 can be stabilized.

That is, the applied voltage-luminance characteristic when no dimming pulse is applied is shown by the line l4 in FIG. 8, and when this dimming pulse is applied, a stable gradient can be obtained as shown by the line l5. It is possible to obtain a similar characteristic curve (see line l6) even when the EL display unit 10 changes with time.

That is, even if the applied voltage of the write pulse is changed, the amount of change in the luminance due to the change with time of the applied voltage-luminance characteristic is kept small in any region. Therefore, even if the applied voltage of the write pulse is changed to realize the dimming function, the luminance difference between the picture element operating in the light emitting state and the picture element operating in the non-light emitting state due to the above-described change with time. Can be made sufficiently small, and a desired dimming function can be realized. By applying the dimming pulse in this way, it is possible to contribute to the improvement of the quality of the screen obtained by the EL display unit 10.

Referring again to FIG. 10 described in relation to the above-mentioned prior art, in the electroluminescence display device, the characteristics thereof change with time as the driving time elapses, and from line l1 to line l2 in FIG. Change. Therefore, the luminance changes with the lapse of time of use, and the luminance changes particularly in the low luminance region. In the conventional symmetrical drive, the reason why the luminance change is large in this low luminance region is that in the light emitting state, the polarization voltage always remains when the write pulse is applied, and the polarization voltage is superimposed on the applied voltage to emit light. Therefore, the slope of the low voltage portion of the voltage-luminance characteristic curve becomes steep, and the polarization voltage always remains until the next write pulse is applied. This is because stability is adversely affected. In the present invention, the voltage-luminance characteristic curve is obtained by removing the polarization voltage by applying a dimming pulse having a reverse polarity after applying a writing pulse, having a configuration as described in the claims above. By making the slope of the curved portion of the item (1) gentle, it is possible to suppress the change in the luminance due to the change with time of the electroluminescence display device to be small.

As described above, according to the present invention, it is possible to realize a wide range of dimming change without deteriorating the quality of the displayed screen, and the stability of the display device is significantly improved. .

[Brief description of drawings]

FIG. 1 is a waveform diagram for explaining in principle the driving method of one embodiment of the present invention, and FIG. 2 is a block diagram showing the electrical configuration of an EL display device 11 used in one embodiment of the present invention. FIG. 3 is a timing chart for explaining the drive system of this embodiment, FIG. 4 is a block diagram showing the configuration of the selection circuit 21 provided in the data side drive circuit 20, and FIG. 5 is the first switching circuit 12 FIG. 6 is a block diagram showing the electrical configuration of the selection circuits 16 and 18 provided in the first and second switching circuits 1 and 13.
FIG. 7 is a block diagram showing the electrical configuration of the selection circuits 17, 19 provided in 4, 15, FIG. 7 is an equivalent circuit diagram of the EL display device 11 shown in FIG. 2, and FIG. 8 shows the effect of this embodiment. FIG. 9 is a perspective view in which a typical prior art EL display device 9 is partially cut away, and FIG. 10 is a graph for explaining the prior art. 10 ... EL display unit, 11 ... EL display device, 12,13 ... first switching circuit, 14,15 ... second switching circuit, 16,
17,18,19,21 …… Selection circuit, 20 …… Data side drive circuit, 2
3,24,26 …… Power supply circuit, X …… Data side electrode, Y …… Scan side electrode, NT, PT …… Transistor

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hiroshi Kishishita 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka Within Sharp Corporation (56) Reference JP-A-60-88998 (JP, A) JP-A-61-282895 (JP, A)

Claims (1)

[Claims] 1. A plurality of row-direction electrodes extending in one direction, a plurality of column-direction electrodes extending in a direction intersecting with the row direction, and an electroluminescent layer interposed between the row-direction electrodes and the column-direction electrodes. Used in the electroluminescence display device including, the row electrodes were controlled by being divided into one group selected every other row and the other group remaining, and positive and negative write pulses were alternately applied. One group and the other group of the row-direction electrodes and the one-screen and the other screen which are alternately repeated by the column-direction electrodes are constituted, and in each screen, the emission threshold of the electroluminescence layer is exceeded and the brightness gradation is set. After applying a write pulse having a corresponding voltage, a dimming pulse having a polarity opposite to that of the write pulse and having a light emission threshold value or less is applied to the row-direction electrodes and the column-direction electrodes. A driving method for an electroluminescence display device, characterized in that the applied voltage of the electroluminescence layer is changed by the method.