JPH0369990A - Driving method for thin film el display device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for driving an AC-driven capacitive flat matrix display panel (hereinafter referred to as a thin 11!JEL display).

Prior Art FIG. 10 shows a typical prior art double-insulated (or triple-insulated)
7111) is a partially cutaway perspective view of a thin film EL element 6. This thin film EL element 6 has a strip-shaped transparent electrode 2 made of In2O3 provided in parallel on a glass substrate 1, and a strip-shaped transparent electrode 2 made of In2O3, for example, Y2O, Si3N4, etc. T i 0
2. A dielectric material layer 3 such as Al T i○2゜A
A material layer 3a such as 1203 is sequentially laminated to a thickness of 500 to 10,000 layers using a thin film technique such as vapor deposition or sputtering to form a three-layer structure, and a layer 3a of a material such as 1203 is layered on top of the layer 3a in a direction perpendicular to the transparent electrode 2. A strip-shaped back electrode 5 is provided in parallel to A1.

The thin IIIEL element 6 has a dielectric material layer 3 between its electrodes.
, 3a, and therefore can be seen as a capacitive element in terms of an equivalent circuit.

Further, as is clear from the voltage-luminance characteristics shown in FIG. 11, this thin film EL element 6 is driven by applying a relatively high voltage of about 250V.

Conventionally, a display panel using such a thin film EL element 6 as a display panel has been used.
An N-channel MOS driver and a P-channel MOS driver are used as a drive circuit for the scanning side electrode of an i-film EL display device, and the polarity is reversed for each field (line sequential drive for one screen), which is so-called field inversion drive. method has been used.

Furthermore, Japanese Patent Application No. 59-105375 describes a drive that can reduce flicker by changing the polarity of the write voltage waveform applied to the picture elements for each scanning line, thereby averaging out variations in light emission intensity due to the polarity of the voltage applied to the display panel. A method is proposed. Furthermore, Japanese Patent Application No. 60-125384 uses a push-pull configuration driver IC as a data side drive circuit, and makes the positive and negative polarity pulse voltage waveforms applied to the picture elements of the display panel completely symmetrical. A driving method has been proposed that eliminates the 1-inch phenomenon, improves long-term reliability, and reduces power consumption.

Figure 12 shows the waveform of the voltage applied to the picture element of the display panel (Figure 12 (1)) and the light emission waveform of the picture element at that time (Figure 12 (2) and This is a timing chart showing the timing chart at a distance corresponding to f.Here, a case is shown in which a voltage above (■, +VTI) corresponding to light emission is applied.

As shown in FIG. 12, in the symmetric AC driving method, the voltage applied to the picture element has a different polarity for each field, and the operation is repeated with two fields as one cycle. In the case of an AC-driven thin film EL element, as long as the absolute value of the voltage applied to the picture element exceeds the emission threshold voltage, it emits light regardless of the polarity, and when a voltage of one polarity is applied, the picture element The light emitting current that flows when the pixel emits light forms internal polarization in the picture element.

Therefore, when a voltage of opposite polarity is applied to the picture element in the next field, the previous internal polarization voltage is superimposed on the external electric field, which acts to intensify the light emission, resulting in efficient light emission.

In addition, as an improvement on the above-mentioned symmetrical AC driving method, the polarization generated inside the picture element due to the light emission caused by the application of the write voltage is
After that, in the same field, the original state is restored by applying a polarization correction voltage of opposite polarity to the write voltage,
A driving method has also been proposed in which the polarization is not influenced by the light emitting state of the picture element due to the application of a write voltage in the next field, and high display quality can be obtained even in high-speed scroll display.

Figure 13 shows the waveform of the voltage applied to the picture element in the above driving method using the polarization correction voltage (Figure 13 (1)) and the light emission waveform of the picture element at that time (Figure 13 (2)). This is a timing chart showing the relationship between the write voltage and the voltage corresponding to light emission (V w + V s
) is applied as the polarization correction voltage. is applied.

FIG. 14 is a circuit diagram showing an electrical equivalent circuit per picture element of a thin film EL element constituting a display panel. That is, in FIG. 14, capacitors C+ and C2 are the first
It corresponds to the dielectric material 13.3a in Fig.
A series circuit consisting of two Zener diodes D8 and a resistor R corresponds to the EL layer 4 in FIG.

Now, as shown in FIG. 13 (1), in one field, a voltage of positive polarity (data (with reference to the Il electrode) exceeding the emission threshold voltage Vw is applied to a pixel in a non-polarized state as a writing voltage. (V.

+V, ) is applied (V, I is the modulation voltage, for example, OV is applied to the data side electrode, while scanning (II
Assume that (V11+VN) is applied to the electrode>, in the equivalent circuit of the picture element shown in FIG.
For, V, = V,, + V,
-(1) voltage is applied. However, Vzw is the breakdown voltage of the Zener diode D, and is the voltage applied to the light emitting layer C2 when the light emission threshold voltage Vw is applied as the write voltage. Also, VAN is the write voltage (vw+V, I
) is the voltage applied to the light emitting layer C2 due to the modulation voltage VC.

As shown in the first equation, the voltage v2 applied to the light emitting NIC is the breakdown voltage of the Zener diode D2. At this time, a current of Ih=Vtn/R...(2>) flows inside the picture element, and as a result, the voltage Vz of the light emitting layer C2 becomes VZ
II, and polarization is formed within the picture element by the voltage -Vo of the change. The amount of light emitted by the picture element at this time is the current 1.
is proportional to.

Next, the above write voltage (v) within the same field.

When a polarization correction voltage -Vo having a polarity opposite to lV, ) is applied to a picture element (for example, -Vc is applied to the scanning side electrode), -(■ straw.

+ V t, lV z-) / R current flows (Vz
c is the polarization correction voltage -■. voltage applied to the light-emitting layer C2>, light emission proportional to this current is obtained, and the voltage (Vxc
-V, , ) polarization remains within the picture element. In this case, the polarization correction voltage Vc is set to be equal to the emission threshold voltage v1, and therefore, v2° - VZ, =
0, (3). As a result, no polarization remains inside the picture element.

That is, in this field, the write voltage (V11+V
Current of the second equation when applying 1. flows, while when applying the polarization correction voltage -V c (-V -), (Vzc
+Vzw−Vzv) /R,= −Vt1. l/R-(
4) will flow, and the total amount of light emission will be a value proportional to 2Ia.

In the next field, the write voltage is -(Vw+■8
>, and V, (=V,) is applied as a polarization correction voltage. In other words, these polarities are only opposite to those in the previous field, and their absolute values remain unchanged.Also, since no polarization remains in the previous field, this field also displays the same full luminescence as the previous field. will be held.

In addition, following the above field of light emission display (the write voltage is positive polarity), in the next field, the write voltage of -V for non-light emission is set.
When w is applied, since no polarization remains in the previous field, no voltage v z −L is applied to the light emitting layer C8 and no current flows, so no polarization is formed. Similarly, when the polarization correction voltage VC (=V,) is applied within the same field, no current flows and no polarization is formed, so the picture element does not emit light.

By applying the polarization correction voltage in this manner, a state in which no polarization remains is always obtained at the end of each field.

Problems to be Solved by the Invention However, in the symmetrical AC driving method shown in FIG. 12, the internal polarization and light emission of the picture element are strongly influenced by the structure of the thin film EL element, The light emission is not necessarily the same when a voltage of negative polarity is applied and when a voltage of negative polarity - (V, lV, ) is applied. Different cases occur, and this causes a problem in which flickering of the light emission intensity appears on the screen.

The driving method shown in the aforementioned Japanese Patent Application No. 59-105375 in which the polarity of the write voltage waveform applied to the picture element is changed for each scanning line is one method for averaging the flickering of the light emission intensity mentioned above. However, in this driving method,
For example, if the displayed content is a straight line every other horizontal line, this has no effect at all.

Separately, by changing the waveform of the voltage applied to the picture elements for each field, the kpJ
It is conceivable to eliminate the imbalance in light emission when a voltage of negative polarity is applied. However, this method does not solve the above problem because of the internal polarization that occurs with light emission.
In other words, using this method, for example, if you increase the applied voltage (for example, increase the voltage) in a field where the luminescence intensity of a pixel is low to increase the luminescence intensity, the luminescence current increases accordingly and the internal polarization increases. , the voltage of that internal polarization is superimposed on the external electric field in the next field, and the emission intensity in that field increases accordingly, making it impossible to adjust the emission intensity independently for each field. .

Also, in the case of the driving force characteristic shown in Fig. 13, in which a polarization correction voltage is applied, although the polarity of the write voltage and polarization correction voltage is changed for each field, these waveforms (peak value and pulse width) themselves are different for each field. Therefore, as described above, the unbalance of light emission due to the polarity of the applied voltage is not resolved, and flickering of the light emission intensity appears on the screen.

Therefore, an object of the present invention is to provide a method for driving a thin film EL display device that can provide a flicker-free screen with good display quality and no variation in emission intensity between fields.

Means for Solving the Problems The present invention provides a plurality of scanning side electrodes arranged in directions crossing each other and a multi-tough data side electrode with an EL layer interposed between the poles, and data (11 is taken as a reference to the pole). The display of one frame is completed by the first field in which a write pulse of one polarity is applied to the scanning side @pole, and the second field in which a write voltage of the other polarity is applied to the scanning side electrode with the data side electrode as a reference. In a method for driving a thin film EL display device,
For each field, after applying a write voltage to the scan side electrode, a polarization correction voltage with the opposite polarity to the write voltage and for erasing the polarization caused by the write voltage is applied to the same scan@electrode, and at the same time, the write voltage Alternatively, a thin film characterized in that the absolute amount of the polarization correction voltage is made different between the first field and the second field so that the emission intensity in the first field is equal to the emission intensity in the second field. This is a method of driving an EL display device.

Effect According to the present invention, when the luminescence intensity of the picture element in the first field is larger than that in the second field, for example, by slightly reducing the absolute amount of the write voltage in the first field, Without leaving any polarization inside the picture element, the emission intensity can be suppressed to be as low as the emission intensity of the second field, and a flicker-free screen can be obtained.

Embodiment First, the schematic structure of a thin film EL display device to which the driving method which is the basis of the embodiment of the present invention is applied will be explained with reference to FIG. 1. In FIG. , its emission threshold voltage 1 is 190V, and the display panel 10 has a plurality of data rs voltages 1fiX1.
．． X2. −． Xi lt (generally referred to as data-side electrodes X), and a plurality of scanning-side electrodes Yl, Y2 .・・・
, Yi (hereinafter collectively referred to as data side electrodes Y) are arranged so as to intersect with each other.

For example, the scanning side electrode Y is an N-channel high voltage MOS.
(Metal Oxide Sem1conduct
or) type integrated circuit, and a second switching circuit 40, which is realized by, for example, a P-channel high voltage MO3 type integrated circuit.
．． 50 are provided.

Each data side electrode UTI to UTi, transistors DTI to DTi having a pull-down function whose source sides are commonly grounded, and diodes UDI to UD for flowing current in the opposite direction to each of the above transistors.
i and DD1 to DDi, each of which is selectively driven by a selection circuit 201.

The source side of each transistor in the second switching circuit 40 is supplied with the power supply voltage of the power supply circuit 300 .

In this power supply circuit 300, two types of power supply voltages V1
Based on 1+V, (=250V), and Vi (=190V), one of three voltages, OV, 250V, and 190V, is set depending on the combination of on/off states of the two switching elements SWI and SW2. .

For example, by turning off the switching element SW1 and turning on the switching element SW2, 190V (=V,) is set as the output voltage of the power supply circuit 300, and by turning on the switching element SWI and turning off the switching element SW2. Then, the output voltage of the power supply circuit 300 is set to 250V (=Vw+V,), and two switching elements swl are set.

When SW2 is turned off, OV is set as the output voltage of the power supply circuit 300. Note that these two switching elements SW1 and SW2 are controlled by control signals psc and psc, which will be described later.
Controlled by sw.

The output voltage of the power supply circuit 400 is supplied to the source side of each transistor of the first switching circuit 20.

In this power supply circuit 400, the power supply voltage -■ (=-1
90V) and one of two voltages, OV and -190V, is set by turning on/off the switching element SW3.

For example, by turning on the switching element SW3, the output voltage of the power supply circuit 400 is set to -190V.
(=-V,) is set, and when switching element SW3 is turned off, OV is set as the output voltage of power supply circuit 400. Note that this switching element SW3 is controlled by a control signal NSC, which will be described later.

In addition, each transistor UT in the data side drive circuit 200
I~UT I t3 and each diode UDI~LID
A power supply circuit 6 is connected to the power supply line 11 to which I is commonly connected.
An output voltage of 00 is provided.

This power supply circuit 600 has a power supply voltage of 1/2V, (=30V
), four switching elements SW4 to SW7
By controlling on/off the power supply line 1
1 can be set to a predetermined level.

For example, when the switching element SW5 is turned on and the switching element SW4 is turned off, the capacitor CM is charged with the power supply voltage 1/2V (=30V), and then the switching element SW6 is turned on and the switching element SW5 is charged.
When turned off, the potential applied to the power supply line /fl becomes 3
It is pulled up to 0V (=1/2V,). After this, when the switching element SW4 is turned on, 60V (=V, ) is applied to the power supply line 11.

Turn on/off these four switching elements SW4 to SW7
The off control is performed using three M control signals Tl, T2 . T
3. Note that when applying 60V (=V) to the power supply line 11, the applied voltage is raised in stages in order to reduce power consumption during modulation.

FIG. 2 is a timing chart for explaining the operation of the thin film EL display device. Here, picture element Af! −
Curtain scanning (11 electrodes Y1 and scanning side electrode Y2 including picture element B)
is selected. Note that this thin film EL
In the display device, each scanning side electrode YtG is driven by inverting the polarity of the voltage applied to the picture element.

Here, for convenience of explanation, switching circuit 20.
The driving timing for turning on any transistor in the second switching circuit 40 and applying a negative write voltage to the scanning side selection electrode is hereinafter referred to as the Nchil operation timing, and turning on any transistor in the second switching circuit 40 or 50. The drive timing for applying a positive write pulse to this scanning side selection electrode is referred to as Pch drive timing.

Also, perform Nch driving for the odd a-th scan $ pole side Y, and perform Pch drive for the even-numbered scan tll for the pole Y. The field (screen) is the NP field, and the opposite field is the PN field. It is called a field.

Figure 2 (1) shows the waveform of the horizontal synchronization signal H, and the high level period indicates the valid period of data.
, the waveform of the vertical synchronizing signal V is shown, and driving of one frame is started at the rising edge of this vertical synchronizing signal (2). The waveform of the data latch signal DLS is shown in (3) of the same figure, and this data latch signal DLS is output after one line of data transfer is completed in each line corresponding to each scanning m electrode element. .

FIG. 4(4) shows the waveform of the clock signal DCK for data transfer on the data side. FIG. 5(5) shows the waveform of the data inversion signal RVC, which becomes high level during the data transfer period of the line in which Pch driving is performed, and inverts all data during this period. The waveform of the display data DATA is shown in (6) of the same figure, and the waveform of the data DI to Di input to each transistor of the data side drive circuit 200 is shown in the same figure (7). Figure (8) to I2
1 (10), control signals Tl, T2 . The signals above 0 where the waveform of T3 is shown and the signals shown in <3> to (10) in the same figure are signals related to the data side electrode X.

The waveforms of signals related to the first switching circuits 20 and 30 are shown in FIG. 11 to FIG. 16, respectively.
The waveforms of signals related to the second switching circuit 40, 50 are shown in (17) to (23) of the same figure. below,
The signals shown in FIG. 11 (11) to (23), that is, the signals related to the scanning side electrode Y, are explained in Table 1 below.

(Margin below) In addition, the voltage waveform applied to the data side electrode X2 is shown in (24) of the same figure, and (25> and (27) of the same figure
, a scanning side electrode Yl, respectively.

The voltage waveform applied to Y2 is shown. FIG. 26 (26) shows a voltage waveform applied to the picture element A based on the voltages applied to the data-side electrode X2 and the scanning-side electrode Yl, respectively. Furthermore, in the same figure (28), the data side electrode
The voltage waveform applied to picture element B is shown based on the voltages applied to Y2 and scanning side electrode Y2, respectively.

Driving of the data side electrode
and V (=60V).

As mentioned above, the operation of this thin film EL display device is roughly divided into two types of timing: the NP field and the PN field, and by completing the execution of these two fields, all pixels of the thin film EL display device are This closes the alternating current pulse necessary for light emission. moreover,
Each field consists of two types of timing: Nch drive of the write voltage and Pch drive of the polarization correction voltage, and Pch drive of the write voltage and Nch drive of the polarization correction voltage. Executing Nch driving for the odd numbered selection lines on the scanning side and Pch driving for the even numbered selection lines,
The opposite driving is performed in the PN field.

During the polarization correction voltage application period, in the NP field, after performing Pch driving on the odd numbered selection lines on the scanning side, Nch driving is performed on the even numbered selection lines,
The opposite driving is performed in the PN field.

FIG. 3 is an equivalent circuit of the thin film EL display device shown in FIG. Referring to this equivalent circuit, the above thin III
The operation of the L display device during each driving period will be explained. Incidentally, an explanation of each symbol in FIG. 3 is shown in Table 2.

(Leaving space below) 2nd table Nch High voltage MOS) transistor source potential -
To make it 190V (--V, ), the signal 'NSC''
is turned on, and the signal "PSC" is turned off in order to set the source potential of the Pch high voltage MOS transistor to OV.

Then, according to the data of the shift register 21, the odd number side N
One line is selected from among the ch high voltage MOS transistors NTodd, and the transistor NT is turned on. All other Nch and Pch high voltage MO3) transistors are turned off. Data side transistors UT,,U
T.

DT,, DT, continues driving during the modulation period, and the line vc
c2 first turns on the switch T3, changes the potential from OV to 1/2V, then turns off the switch T2, turns on the switch T1, and raises the potential to V. This results in
The electrode containing the selected picture element on the data side has a potential of Vs = 60V, the non-selected electrode has a potential of OV, and the selected electrode on the scanning side has a potential of -V, =-
Since it is 190V, the picture element Cm1l between the selection electrode on the scanning side and the selection electrode on the data side has a voltage of 60V-(-190V).
=250V is applied and light is emitted. For the picture element Con between the non-selected electrodes on the data side, OV-(-190V) = 190V
is applied, but it does not emit light because it is below the threshold for emitting light.Also, for picture elements C,,C, on the non-selected line on the scanning side, the electrodes on the scanning side are floating, so they cannot be connected to the selected line on the data side. Ov varies from 60V to 60V depending on the ratio of non-selected lines.

In order to set the source potential of the Pch high voltage MOS)-transistor to 190V (=V, ), turn off the signal "psw" and turn on the signal PSC'',
S) In order to set the source potential of the transistor to o■, the signal "
Then, according to the data of the shift register 41, one line is selected from among the odd-numbered side Pc1] high voltage MOS transistors PTadd, and PT is turned on.The other Nch and Pch high voltage MOS transistors are turned on.
Transistors PT even, NT even,
Turn off all N T oclds.

On the data side, switch T3 is turned off to set it to OV.

As a result, all the electrodes on the data side have a potential of OV, and the picture elements of the scan ff1 selection odd line have a potential of 190V-O.
A polarization correction voltage of V=190V is applied with a polarity opposite to that of the write voltage.

3 Set the source potential of the transistor to NP full Pch (Miyan-Pch high voltage MOS) to V.
, +V, = 250V, turn on the signal “psw” and signal “PSC”, and turn on the signal “NSC” to make the source potential of the Nch high voltage MO8) transistor ov.
Turn off. Then, according to the data of the shift register 51, the even number side Pch high voltage MOS transistor PTev
Select one line from en and turn on transistor PT.

All other Nch and Pch high voltage withstand voltage MO3) transistors PT, NT, , NT are turned off. Data side transistors UT-, UT o, DT a,
DTr.

continues driving during the modulation period, and the line Vccz first turns on switch T3 and switches from oV to 1/2■a,
Next, switch T2 is turned off, switch T1 is turned on, and the potential becomes ■. raise it to As a result, the electrode containing the selected pixel on the data side has a potential of OV, the non-selected electrode has a potential of VM = 60 V, and the selected electrode on the scanning side has a potential of V11 + VW = 250 V.
However, 250V-OV=250V is applied to the picture element between the selection electrode on the scanning side and the selection electrode on the data side.
It will be applied with the opposite polarity to the drive write voltage,
Emits light. However, although 250V-60V=190V is applied to the picture element between the non-selected electrodes on the data side, it does not emit light because it is below the threshold for emitting light.

The source potential of the Nch high voltage Mos transistor is -Vw
= 190V, turn on the signal "NSC", and turn off the signal "Psc" to set the source potential of the Pch high voltage MOS) transistor to OV. Then, according to the data of shift register 3■, even number side Nch
One line is selected from among the high voltage Mos transistors NTeven, and the transistor NT is turned on. Other Nch and Pch high voltage MO3) transistors PTe
ven, PT odd, and N T odd are all turned off. On the data side, switch T3 is turned off to set it to oV. As a result, all the electrodes on the data side have a potential of oV, and the pixels on the even-numbered lines selected on the scanning side have a potential of 0V-19.
A polarization correction voltage of 0V=190V is applied with a polarity opposite to that of the write voltage.

5 Question for PN field Pch - NP except that the selection line on the scanning side is selected from the odd number side.
Drive similar to field Pch drive is performed.

Except for the odd and even sides being swapped, the N of the NP field
Performs the same drive as ch drive.

7 PN field Nc I]
Driving is performed in the same manner as in the NP field except that the selection line on the scanning side is selected from the even number side and the Nch high voltage MO3I transistor of that line is turned on.

P in the NP field except that the even and odd sides are swapped.
Driving similar to ch driving is performed.

Next, the thin II of the present invention! A first example of a method for driving an IEL display device will be described.

Figure 4 shows the voltage waveform applied to the picture element in this driving method (Figure 4 (1)) and the light emission waveform of the picture element at that time (Figure 4 (1)).
FIG. 2 is a timing chart showing a distance corresponding to that of FIG. 2 (2>). However, here the data is 1M! The polarity of the voltage applied to the picture element is shown based on I-electron aiX.

In this driving method, when the basic driving described above is performed on the thin film EL display device shown in FIG. 1 field), followed by a field in which N c tt driving corresponding to light emission is performed (
In this case, when there is a difference in the luminescence intensity of the picture elements as shown by the solid line in Figure 4 (2), this is corrected to make the luminescence intensity uniform in all fields. In order to apply this driving method, in place of the power supply circuit 300 in the thin film EL display device shown in FIG. 1, a power supply circuit 300A shown in FIG. 6 is employed in this embodiment.

That is, this power supply circuit 300A has a switching element S
Voltage source V via Wa and SWb. is the second
The switching circuit 40.50 (scanning side) is connected to the power supply line 12, and the voltage source Vw is connected to the switching element S.
We and SWb are connected to the power supply line 12, and a voltage source Vwv having a slightly lower voltage than the voltage source V is connected to the power supply line 12 via the switching element SWb.

Further, the voltage source Vw is connected to the switching elements SWe, SW c
, capacitor Ca, and switching element S W a .

It is connected to the power supply line 12 via SWb, and the voltage source Vw
v is the switching element S W c and the capacitor C
a, connected to the power supply line 12 via switching elements SWa and SWb. Furthermore, the switching element S
The connection point between Wc and the capacitor Ca is connected via a three-isolating element SWd.

In this power supply circuit 300A, the switching element SW
When d is on, capacitor Ca is charged with voltage ■A, and then when switching element SWd is off and switching elements SWc and SWe are on, the charging potential of capacitor Ca becomes (V w + V N ), and this If the switching elements SWa and Swb are on in this state, a positive voltage (V w
+ V M ) is supplied.

In addition, a voltage V is applied to the capacitor Ca. After charging, switching element SWd turns off and switching element SW
When c is on and switching element SWc is off, the charging potential of capacitor Ca is (V w +
V x V ), and if the switching elements SWa and SWb are on in this state, a positive voltage (V w + V n V ) is supplied to the power supply line 12 .

On the other hand, when the switching element S W a is off and the switching elements SWe and SWb are on, the voltage ■ is supplied to the power supply line 12 . In addition, the switching element SW
a, when SWe is off and the switching element SWb is on, a voltage (V, -v) is supplied to the power supply line 12. That is, in the power supply circuit 300A, four types of voltages (VIl+V%> + (VW+VN
-v), Vw.

(Vwv) can be switched and supplied.

As shown by the solid line in FIG. 4 (2), when the emission intensity in the first field tends to be smaller than the emission intensity in the second field, in this driving method, in the first field which is Pch drive, , scanning side electrode Y during the writing period
The original voltage (v w + V N
) slightly lower voltage (v.

+V n v ) is supplied by turning on/off a switching element in the power supply circuit 300A.

In Pch driving, since the voltage corresponding to light emission applied to the data side electrode is OV, the voltage level shown by the broken line in FIG. 4 (1) is written to the picture element, which is slightly lower than the original writing voltage (vw + vx). A voltage (V w + V Hv) will be applied. As a result, the emission intensity at this time becomes slightly smaller than the original emission intensity (solid line), as shown by the broken line in FIG. 4(2). This write voltage (V
After the application of w + V s V ), the application of the polarization correction voltage, which takes place within the same first field, takes place as in the original case. That is, during the polarization correction voltage application period of this P c t+ drive, a negative polarization correction voltage -■ is applied from the power supply circuit 400 in FIG. 1 to the scanning side electrode Y. In this case, the write voltage (V1+
With the application of V s v ), the polarization remaining inside the picture element is smaller than the original case, so the polarization correction voltage −V,
The emission intensity when the voltage is applied also decreases by that amount, as shown by the broken line in FIG. 4(2). That is, the total amount of light emission in the first field is smaller than in the original case.

On the other hand, in the second field where the polarity of the write voltage and the polarization correction voltage is opposite to that of the first field, the voltage level of both the write voltage and the polarization correction voltage cannot be changed, that is, the write voltage is −(V w +
VH) and (1) are applied as a polarization correction voltage. Therefore, the light emission intensity in the second field is the same as the original light emission intensity. That is, only the emission intensity of the first field is independently corrected to be small, and thereby the emission intensities of the first field and the second field are made uniform.

FIG. 5 shows the applied voltage waveform to the picture element (FIG. 5 (1)) in the second embodiment of the driving method of the present invention and the light emission waveform of the picture element at that time (FIG. 5 (2)). This is a timing chart showing the relationship between data (1g@
The polarity of the voltage applied to the picture element is shown with reference to the pole X.

In this driving method, when the basic driving described above is performed on the thin film EL display device shown in FIG. When the light emission intensity in the second field, where Nch drive corresponding to light emission is subsequently performed, is greater than the light emission intensity, as shown by the solid line in Figure 5 (2), this is corrected to determine which field. However, in order to apply this driving method, in place of the power supply circuit 400 in the thin film EL display device shown in Elil 11, in this embodiment, the power supply circuit shown in FIG. 400A is adopted.

That is, this power supply circuit 400A has a switching element S
The voltage source -■o is connected to the power supply line 13 of the first switching circuit 20.30 (scanning 111) in FIG. - (V knee v) is connected via the switching element SWf, and the power supply line 13
is grounded via a diode Da.

In this power supply circuit 400A, switching elements SWf,
When both SWg are on, power supply line N3. In other words, the negative polarity voltage -Vw is supplied to the scanning side electrode Y. Also,
Switching element SWg is off, switching element S
When Wf is on, the voltage -(V, -v) is on the power supply line 13.
Further, when both switching elements SWf and SWg are off, the potential of the power supply line 13 becomes 0■.

As shown by the solid line in FIG. 5 (2>), when the emission intensity in the second field tends to be larger than the emission intensity in the first field, in this driving method, the second In the field, during the polarization correction voltage application period, the original voltage ■1 is applied to the scanning side electrode Y by turning on/off the switching element in the power supply circuit 400A.
A slightly lower voltage (V, -v) is applied as a polarization correction voltage. Prior to this, during the write period performed in the same second field, the same voltage -(V w + V s ) as the original write voltage is applied to the picture element (voltage -■1 on the scanning side tiY). is applied, while a voltage vlI corresponding to light emission is applied to the data side electrode.
The effect of canceling the polarization that occurs inside the picture element during the writing period is
It becomes weaker than the original polarization correction voltage vl, and as a result, the internal electrode of the picture element is completely canceled out.9 The luminescence intensity of the picture element is shown by the broken line in Figure 5 (2) by the amount that the polarization correction voltage is corrected to be lower. As such, the original thirst luminescence intensity (becomes smaller than the actual thirst).

On the other hand, in the first field, both the write voltage and the polarization correction voltage are applied to the same voltages as in the original drive, but the internal polarization of the picture element is completely removed prior to the write period (original When driving, the effect of the polarization correction voltage in the second field is slightly larger than the appropriate value, so polarization remains which acts to reduce the effect of the write voltage in the first field〉, and the write voltage in the first field (■
As shown by the broken line, the light emission intensity of the picture element due to the application of 1+Vs) becomes larger than the light emission intensity (solid line) in the case of original driving.

In this way, in the first field, the emission intensity is corrected to be slightly larger than in the case of original driving, and in the second field, it is corrected to be slightly smaller than in the case of original driving. This makes the emission intensities of the first field and the second field uniform.

In addition, in the first and second embodiments described above, the case where the emission intensity is made uniform by correcting the voltage levels of the write voltage and the polarization correction voltage is explained, but by correcting the pulse width of these voltages, each The light emission intensity in the field may be made uniform.

FIG. 8 shows a power supply circuit 300B employed in the third embodiment, which improves the imbalance in emission intensity between fields by correcting the pulse width. That is, in this embodiment, when the emission intensity differs between the first field and the second field as shown in FIG. 4(2), the above power supply is used instead of the power supply circuit 300 of the thin film EL display device shown in FIG. Circuit 300B is used.

The power supply circuit 300B includes switching elements SWh, S
A voltage source VN is connected to the power supply line 12 via Wi,
Further, a voltage source (2) is connected to the power line 12 via a switching element SWj, a capacitor Cb, and switching elements SWh, SWi, and a voltage source Vw is separately connected to the power line 12 via a switching element SWi. Furthermore, the connection point between the switching element SWj and the capacitor cb is grounded via the switching element SWk, and the power supply line 12 is grounded via the switching element SW1.

In this power supply circuit 300B, when the switching element SWk is on, a voltage ■ is applied to the capacitor CIJ.

is charged, and then when the switching element SWk is turned off and the switching element SWj is turned on, the charging potential of the capacitor Cb becomes (V, +VTI), and this state!
If the switching elements SWh and SWi are on and the switching element SWl is off, a positive voltage (V − + V x ) is supplied to the power supply line 12, that is, the scanning side type [Y].

On the other hand, when the switching elements SWh and SW1 are off and the switching element SWi is on, the voltage Vl is supplied to the power supply line 12. Voltage (vw+vn), Vw
The pulse width is variably set according to the timing at which the switching element SW1 is switched from off to on.

In this embodiment, the voltage level of the write voltage applied in the first field in the first embodiment is changed from the original voltage
The emission intensity was corrected to a smaller value by setting the voltage (V11+V11-v) slightly lower than V, ), whereas the pulse width of the write voltage (V w + V n ) was changed to the pulse width of the original drive. By making the light a little more chivalrous than the above, the emission intensity can be reduced.

That is, during the write period of the first field, a voltage (Vll+V,) is applied from the power supply circuit 300A to the scanning side type IY.
When the switching element SW1 is supplied with the switching element SW1, the timing at which the switching element SW1 is switched from off to on is set earlier than in the original drive.

The polarization correction voltage -Vw in the same first field, the write voltage -(vw+vx) in the second field, and the polarization correction voltage ■. is set to the same pulse width as in the original drive.

In this way, the emission intensity is corrected to be uniform between the first field and the second field.

FIG. 9 shows a power supply circuit 400B employed in the fourth embodiment, which corrects the imbalance in emission intensity between fields by correcting the pulse width. That is, in this embodiment, when the light emission intensity is different between the first field and the second field as shown in FIG. 5 (2>), the above power source is Circuit 400B is used.

In the above-mentioned source circuit 400B, the voltage source -1 is connected to the power supply line 13 via the switching element SWm, and the power supply line 13 is grounded via the switching element 5Wrl.

In this power supply circuit 400B, the switch>・G element SW
When m is on and the switching element S W r+ is off, a voltage -■ is supplied to the power supply line 13, that is, the scanning side electrode Y, and its pulse width is equal to the switching element S W n
It is set variably according to the switching timing from off to on.

In this embodiment, the emission intensity is reduced to a small value by setting the voltage level of the polarization correction voltage applied in the second field to a voltage (V W -v) slightly lower than the original voltage ■1, unlike the second embodiment described above. In contrast, by making the pulse width of the polarization correction voltage Vw a little narrower than the original driving pulse width, the emission intensity can be reduced.

That is, during the polarization correction voltage application period of the second field, the voltage -■ is applied from the power supply circuit 400B to the scanning side 1c pole Y.
o is supplied, the switching element S W n
The timing for switching from off to on is set earlier than in the case of original drive.

Write voltage in the same second field - (V w + V
M ) and the write voltage in the first field (V w
+Vs) and the polarization correction voltage -Vw are set to the same pulse width as the original drive width.

In this way, the emission intensity during the polarization correction voltage application period in the second field is reduced, and along with the correction in the second field, the reduction in the emission intensity during the writing period in the first field is reduced to the second field. It is carried out in the same way as in the example thirst. Therefore, the emission intensity between the first field and the second field is corrected to be uniform.

Effects of the Invention As described above, according to the method for driving a thin film EL display device of the present invention, when light emission asymmetry appears between fields, the absolute it of the write voltage or polarization correction voltage in the first field or the second field (By adjusting the voltage level and pulse width, the luminescence intensity is corrected to be uniform between fields without leaving any polarization inside the picture element in each field, so flicker-free display is possible.) A screen with good quality can be displayed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the general configuration of a thin film EL display device to which a driving method which is the basis of the driving method of the present invention is applied, FIG. 2 is a timing chart showing the operation of the thin film EL display device, and FIG. The figure is a circuit diagram showing an equivalent circuit of the thin FF1EL display device, FIG. 4 is a timing chart showing a first embodiment of the driving method of the present invention, and FIG. 5 is a second embodiment of the driving method of the present invention. Timing chart showing 6th
The figure is a circuit diagram showing a power supply circuit applied to the first embodiment. 712I is a circuit diagram showing a power supply circuit applied to the second embodiment, FIG. 8 is a circuit diagram showing a power supply circuit applied to the third embodiment of the driving method of the present invention, and FIG. A circuit diagram showing a power supply circuit applied to the fourth embodiment of the driving method of the invention, FIG. 10 is a partially cutaway perspective view of a typical thin film EL device, and FIG. 11 is a diagram of the thin film EL device. Graph showing applied voltage-luminance characteristics, Fig. 12 is a timing chart showing a conventional symmetrical driving method, Fig. 13 is a timing chart showing a conventional driving method using polarization correction voltage, Fig. 14
The figure shows a circuit 28I21 which shows an equivalent circuit corresponding to one picture element of a thin film EL element. 10... Display panel, 20.30... First switching circuit, 40.50... Second switching circuit, 2
00...Data side drive circuit, 300, 300A. 300B, 400A, 400B, 600...power supply circuit, X...data side Th pole, Y...scanning side electrode, NT
. PT, UT, DT...transistor

Claims (1)

[Claims] An EL layer is interposed between a plurality of scan-side electrodes and a plurality of data-side electrodes arranged in a direction crossing each other, and a write pulse of one polarity is applied to the scan-side electrodes with the data-side electrode as a reference. A first field is applied to the scan side electrode, and a second field is applied to the scan side electrode with a write voltage of the other polarity based on the data side electrode.
In a method of driving a thin-film EL display device that completes one frame of display in each field, after applying a writing voltage to the scanning side electrode for each field, a By applying a polarization correction voltage for erasing polarization to the same scanning side electrode and by making the absolute amount of the write voltage or polarization correction voltage different between the first field and the second field, A method for driving a thin film EL display device, characterized in that the light emission intensity and the light emission intensity in the second field are made equal.