JPH077247B2 - Driving method of matrix display panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] A method for driving a matrix display panel, which is at least larger than light emission at a voltage in which a half-select voltage by a data signal voltage or a scanning signal voltage is superimposed immediately before a reference voltage is applied. In addition, the display cell is configured to apply a compensation voltage at a level that does not emit light by itself, and the electric field inside the light emitting layer at the time of applying all selection voltages can be made constant to eliminate the brightness variation on the entire surface of the pulse.

[Industrial application field]

The present invention relates to a method for driving a matrix display panel, and more particularly to a method for driving a matrix display panel in which the electric field inside a light emitting layer is kept constant so as to eliminate the brightness variation over the entire pulse surface.

Matrix display panels, especially thin-film electroluminescence panels (hereinafter referred to as EL panels), are about to be applied to the display parts of office terminals and general-purpose small computers, and in addition to cost reduction and high reliability of EL panels, Improvement of display quality is desired.

[Conventional technology]

FIG. 6 shows a conventional EL panel drive circuit configuration diagram, and FIG. 7 shows a conventional drive waveform diagram.

In FIG. 6, the EL panel 1 has a plurality of data electrodes D1 to Dm and scan electrodes S1 to Sn arranged in a grid pattern with a light emitting layer (not shown) interposed therebetween, and a display cell is formed at the intersection thereof.

The driving circuit for driving these display cells is the data electrode D1.
~ Data signal generation circuit 2 for supplying data pulse to Dm
And a scan electrode drive circuit 3 which supplies a scan pulse to the scan electrodes S1 to Sn.

The data signal generation circuit 2 includes push-pull I of N-channel and P-channel field effect transistors (FETs).
C driver (hereinafter referred to as push-pull driver) 4-1
.About.4-m and the DC power source 5 of the push-pull drivers 4-1 to 4-m.

Further, the scan electrode drive circuit 3 connects push-pull drivers 7-1 to 7-n to the respective scan electrodes S1 to Sn,
Source side wiring of push-pull drivers 7-1 to 7-n 15
Further, the first reference voltage generating circuit 8 and the first scanning pulse generating circuit 10 are provided, and the drain side wiring 16 is provided with the second reference voltage generating circuit 9 and the second scanning pulse generating circuit 11.

The first and second reference voltage generating circuits 8 and 9 are of negative polarity,
And negative power supplies 8-1 and 9-1 of the same voltage (-165V),
Positive power sources 8-2 and 9-2 having the positive polarity and the same voltage (+ 165V), the negative power sources 8-1 and 9-1 and the positive power source 8-
2 and 9-2, and switches 8-3 and 9-3, respectively.

The first and second scan pulse generation circuits 10 and 11 are power supplies for obtaining a predetermined scan pulse voltage, for example, the first scan pulse generation circuit 10 has -190V power supply 10-1 and + 190V power supply 10-.
2 and a switch 10-3 for switching between both power supplies, and the second scanning pulse generating circuit 11 is provided with a -165V power supply 11-1 and a + 215V power supply 11-2, and a switch 11-3 for switching between both power supplies. I am trying.

Further, the Zener diode 12 is provided between the source side wiring 15 and the drain side wiring 16 of the push-pull drivers 7-1 to 7-n.
Is connected to protect the driver.

Now, the light emitting operation of the display cell will be described with reference to the drive waveform diagram of FIG.

In the first frame of FIG. 7, the switches 8-3 and 9-3 of the first and second reference voltage generating circuits 8 and 9 of FIG. 6 are turned on to the -165V power supplies 8-1 and 9-1, respectively. , -165V output from the power supplies 8-1 and 9-1 is connected to the source side wiring 15 of the push-pull drivers 7-1 to 7-n.
And the drain side wiring 16 to form a reference voltage VP of -165V as shown in FIGS. 7 (b) to 7 (d) to form a fully selected state, and to form each selected scanning electrode S1, S2 ... Sn. Apply.

In this all-selected state, the first and second scan pulse generation circuits 10 and 1 are generated by a scan switching signal input from the outside.
The switches 10-3 and 11-3 of 1 are turned on to the −190V power source 10-1 and the −165V power source 11-1, and the power source 10-1 and the power source 11 are turned on.
Push-pull driver 7-190V and -165V from -1
It is output to the source side wiring 15 and the drain side wiring 16 of 1 to 7-n.

The push-pull drivers 7-1 to 7-n have both input voltages (-
190V, -165V) differential voltage (-25V) is taken out, a scan pulse VY of -25V is created by a scan position control signal input from the outside, and it is superposed on the reference voltage -165V.・ Sequentially apply to Sn.

On the other hand, the data signal generation circuit 2 generates a 25V data pulse VS shown in FIG. 7A in response to a data control signal externally input to the control terminals 3 of the push-pull drivers 4-1 to 4-m. , Is output to the selected electrode on the data electrode side in synchronization with the scanning pulse VY.

7 (e) to 7 (g) show cell drive waveforms applied as a composite voltage between the data electrode i and each scan electrode,
The selected display cell has a scan pulse VY on the reference voltage VP.
The write pulses e1, f1, g1 formed by superposing the data pulse VS and the data pulse VS are sequentially applied, whereby the selected display cell emits light.

After the above-mentioned writing drive of the first frame is completed, the next second
The frame is driven by the power supplies 8-2 and 9- provided in each circuit.
Use 2,10-2,11-2 and follow the same procedure as above
A write pulse having a polarity opposite to that of the frame is created to cause the selected display cell to emit light.

[Problems to be solved by the invention]

In the driving method using the alternating reference voltage whose polarity changes for each frame as described above, the reference voltage substantially fluctuates, and as shown in FIG.
The amount of remaining polarization charge (Q1-Q2) changes and the electric field inside the light emitting layer does not become constant, and the emission brightness of the EL element (display cell) in the fully selected state is There is a problem in that there is a large variation in luminance due to the drive waveform, which changes as shown by the characteristic A in FIG.

As can be seen from the characteristic A in FIG. 3, the light emission brightness is constant when the reference voltage fluctuates below a certain voltage (150 V or less), but in order to make the display cell emit light, it is superimposed on the reference voltage. The generated pulse voltage (data pulse or scan pulse) must be high, and a high breakdown voltage transistor is required to generate this pulse, which causes a problem of high circuit cost.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for driving a matrix display panel, which is low in cost and can keep the brightness of the entire panel constant.

[Means for solving problems]

FIG. 1 is a basic drive waveform diagram of the present invention, in which the reference voltage VP
Immediately before the application of the voltage, that is, every time the polarity of the reference voltage is inverted, the level is the same and is at least larger than the voltage (VB) on which the half-select voltage by the data pulse VS or the scan pulse VY is superimposed, but does not emit light by itself. The compensation voltage pulse D of (VD) is applied.

[Action]

By applying the compensating voltage pulse D at every polarity reversal of the alternating reference voltage, as shown in FIG. 2, the charge Q2 is changed from the polarization charge Q1 generated in one electrode A in the previous full selection state to the other. Of the remaining polarization charge (Q1-Q
Keep 2) constant. As a result, the electric field inside the light emitting layer when the full selection voltage is applied is made constant, and the luminance is kept constant without being affected by the fluctuation of the reference voltage as shown by the B characteristic in FIG.

〔Example〕

FIG. 4 is a diagram showing an example of the configuration of a drive circuit for realizing the drive method of the present invention, and FIG. 5 shows the drive waveform. The same parts as those in FIG. 6 are designated by the same reference numerals.

In this driving method, push-pull drivers 7-1 to 7-n are used.
A first compensation voltage generation circuit 13 and a second compensation voltage generation circuit 14 are attached to the source side wiring 15 and the drain side wiring 16.

The first compensating voltage generating circuit 13 is -195V power supply 13-1 and +19.
It is composed of a 5V power supply 13-2 and a switch 13-3, and the second compensation voltage generating circuit 14 has a -195V power supply 14-1 and a + 195V power supply 14-.
2 and switch 14-3.

The output voltage 195V of the compensation voltage generator is 165V, the reference voltage.
And scan pulse voltage 25V or data pulse voltage 25V 19
It is higher than 0V but lower than the voltage for emitting light from the display cell, and thus has no light emitting ability.

The operation of the drive circuit thus configured will be described with reference to the drive waveforms in FIG.

In the first frame of FIG. 5, assuming that the reference voltage is now inverted from the positive polarity to the negative polarity, referring to FIG. 4, the switch is first performed by the scan control signal input from the outside.
13-3 and switch 14-3 are -195V power supply 13-
It is turned on by 1 and 14-1, and is output from both power supplies −19
5V is input to the source side wiring 15 and the drain side wiring 16 of the push-pull drivers 7-1 to 7-n.

As a result, the push-pull drivers 7-1 to 7-n are
Compensation voltage pulses of -195V as shown by b1, c1, d1 in FIGS. 5B to 5D are created and applied to the scan electrodes S1 to Sm at the same time.

Next, after applying this compensation voltage pulse, the reference voltage VP (−16) is applied to the scan electrodes S1 to Sm by the operation described in the conventional example.
5V) and scan pulse VY (-25V), and data pulse (25V) is applied to data electrodes D1 to Dm, and write pulses e1, f1, g1 shown in (e) to (f) of FIG. (215V) is created to cause the selected display cell in the first frame to emit light.

In the next second frame, the + 195V power supplies 13-2 and 14-2 are used, and the + 195V compensation voltage pulse b1, c1, d1 of the opposite polarity to the first frame is applied to each scan electrode before applying the reference voltage. Apply to.

In this way, by applying the compensation voltage pulse (195V) of the same polarity as that before applying the reference voltage (165V),
As shown in FIG. 2, the polarization charge Q1 generated in one electrode A in the previous full selection state is moved from the charge Q2 to the other electrode B, and the remaining polarization charge (Q1-Q2) is kept constant. To take. As a result, the electric field inside the light emitting layer when the full selection voltage is applied is made constant, and the luminance is kept constant without being affected by the fluctuation of the reference voltage as shown by the B characteristic in FIG.

〔The invention's effect〕

As described above, according to the present invention, it is possible to eliminate the variation in luminance due to the variation in the reference voltage and improve the display quality of the matrix display panel.

[Brief description of drawings]

FIG. 1 is a basic driving waveform diagram of the present invention, FIG. 2 is a diagram for explaining the movement of polarization charge, FIG. 3 is a diagram showing a relationship between a reference voltage and brightness, and FIG. 4 is a diagram for carrying out the present invention. FIG. 5 is a drive waveform diagram of the embodiment, FIG. 6 is a conventional drive circuit configuration diagram, and FIG. 7 is a conventional drive waveform diagram. In the figure, 1 is an EL panel, 2 is a data signal generation circuit,
3 is a control terminal, 4-1 to 4-m are push-pull IC drivers, 7-1 to 7-n push-pull drivers, 8 and 9 are first
And the second reference voltage generation circuit, 8-1, 9-1 is -165V
Power supply, 8-2, 9-2 are + 165V power supply, 10 is the first scanning pulse generation circuit, 11 is the second scanning pulse generation circuit, 10-1 is -190V power supply, 10-2 is + 190V power supply, 11- 1 is -165V power supply, 11-2 is + 215V power supply, 12 is Zener diode, 15 is source side wiring, 16 is drain side wiring, 8-3,9-3,10-
3, 11-3, 13-3, 14-3 are switches, 13 is a first compensation voltage generation circuit, 14 is a second compensation voltage generation circuit, 13-1, 14-1
Indicates a -195V power supply, and 13-2 and 14-2 indicate a + 195V power supply.

Claims (1)

[Claims] 1. A plurality of scanning electrodes (S1 to S) arranged in a grid pattern.
m) and the data electrodes (D1 to Dm) at the intersections with electro-optical bodies to form a plurality of display cells.
A means (8, 9) for alternately applying a negative polarity and a positive polarity reference voltage (VP) is provided between the data electrodes, and the scanning pulse (VY) is superimposed on the reference voltage (VP) applied to the scan electrodes. ), And a data pulse (VS) is applied to the selected electrode of the data electrodes in synchronization with the scan pulse, so that the write pulse in the all-selected state for the selected display cell determined between those electrodes is applied. In the method for driving a matrix display panel, which is configured to emit light by adding (e1, f1, g1), each time the polarity of the reference voltage (VP) is reversed, the reference voltage has the same polarity immediately before the reference voltage and the reference voltage. In addition, a compensation voltage pulse (VD) of a level, which is higher than the superimposed voltage of the half-selection voltage of the data pulse or the scan pulse but cannot emit light to the display cell by itself, is applied. Matrix Method of driving a display panel.