JPH01303495A - Driving method for matrix display panel - Google Patents

Abstract

PURPOSE:To make a half-tone display by sending select data to a field an odd number of times and then nonselect data an even number of times and repeating this operation in the field inversion driving of a matrix display panel wherein the polarity of a voltage applied to a display cell is switched at intervals of one field. CONSTITUTION:When a data electrode is held at Ov in plus pulse driving and at Vm (data electrode voltage waveform A) at the time of minus pulse driving, the waveform of a voltage applied to an EL cell is as shown by (a). When the data electrode is at Vm in the plus pulse driving and at Ov (data electrode waveform B) at the time of the minus pulse driving, the waveform of the voltage applied to the EL cell is as shown by (b). Further, when Vm and Ov are switched at intervals of three fields like a data electrode voltage waveform C or D, the waveform of the EL applied voltage is as shown by (c) or (d) and a cycle wherein select data is sent an odd number of times and the nonselect data is sent an even number of times is repeated. Consequently, a stable gradational display is made.

Description

DETAILED DESCRIPTION OF THE INVENTION Door No. 1 This invention relates to a method for driving an IJ display panel such as a thin film EL display panel, and more particularly to a gradation display method.

[Follow-up] Month 1 Here, we will particularly explain the gradation display method of the matrix display panel.

An EL panel in which a large number of scan electrodes and data electrodes are arranged in rows and columns, and a display cell is placed at each intersection, has a driving method that uses, for example, a negative electrode in a certain field from one scan electrode north to the bottom in a time-division manner. There is a so-called field inversion method in which a polarity reading voltage is sequentially applied, and a positive polarity write voltage is sequentially applied in the next field.

An example of this field inversion drive will be explained in detail with reference to FIG.

FIG. 2 shows a large number of scan electrodes 81 to Sn and a data electrode D1.
~ Matrix E with display cells P arranged at the intersection with Dm
L panel 10, data electrodes D1-Dm are connected to switches 12.
．． 122. . . . 12□ to switch and drive the data driver head 11 and the scan electrodes 81 to Sn by the switch 13.
．． ．． 132. -...13n to switch and drive the scan driver 14 and the common of the scan driver 14
Circuits 15 and 1 for switching L1 and L2 voltages
It consists of 6. Here, each Commo
Among n, the circuit 15 that switches the positive voltage CommonLl is called a positive voltage switching circuit, and the circuit 15 that switches the positive voltage CommonLl.
The circuit 1B that switches nL2 is called a negative voltage switching circuit.

With this configuration, a negative polarity write pulse and a positive polarity write pulse are alternately applied for each field to perform field inversion driving.

The methods of negative polarity pulse driving and positive polarity pulse driving will be described below with reference to the timing chart of FIG. 3.

Negative polarity pulse drive> First, depending on whether the EL cell connected to the first scanning electrode S1 is emitted or not emitted by the data driver 11,
Select the data electrode at Vm or OVm level. After that, the driver connected to the selected scan electrode is selected to the negative voltage side, and then the rht voltage switching circuit 16 is set to -V
w (this is called negative voltage g drive). As a result, the selected scan electrode becomes -Vw, and as a result, the EL cell P of the data electrode or Vm becomes (V W + V m
) will be applied, so it will emit light, and the EL cell P of the data electrode Ov will not emit light because only the voltage -Vw will be applied.

These modulation drive and negative voltage write drive are sequentially repeated from the upper part S1 to the lower part Sn of the scanning electrode, and the field of negative polarity pulse drive is completed.

<Positive pulse drive> After the field of negative pulse drive is completed, the data electrode is set to Ov or Vm depending on whether the EL connected to the first scan electrode S1 emits or does not emit light. Select the level (opposite of the modulation voltage for light emission and non-light emission during negative polarity pulse drive). Thereafter, the driver connected to the selected scan electrode is selected to the positive voltage side, and subsequently, the positive voltage switching circuit 15 is set to Vw+Vm (this is referred to as positive voltage metering drive). As a result, the selected scan electrode is set to V
w + Vm, and as a result, a voltage of VW + Vm is applied to the EL cell P whose data electrode is Ov, so it emits light, and only a voltage of VW is applied to the EL cell P whose data electrode is Vm. Therefore, it does not emit light.

These modulation drive and positive voltage write drive are sequentially repeated from the upper part S1 to the lower part Sn of the scanning electrode, and 1 +ffl
The field of sexual pulse drive ends.

Thereafter, a predetermined display can be realized by alternately repeating two fields of driving.

In this driving method, in order to realize gradation display for each EL cell P, a driver is used which can arbitrarily set the voltage of the data electrode between Ov and Vm. For example, the above
If the voltage supplied to the data electrode during modulation drive of negative polarity pulse drive is 1/2 Vm, this EL cell has -
A voltage of (Vw+I/:"Vm) is applied, and the luminance is lower than when -(Vw+Vm) is applied, but higher than when -Vw is applied.

This also applies to positive pulse driving. Also, in the same field inversion drive, there is a method of precharging before writing drive (Japanese Patent Application Laid-Open No.
08798), the gradation display method is a method in which the modulation voltage of each EL cell P is changed by controlling the precharge time.

The above two methods are examples in which gradation display is achieved by providing an analog output function to the driver that drives the data electrodes.

In addition, a method of displaying gradations using a conventional driver with only two outputs, Ov and Vm, in which the data driver has an analog output function, is to select and deselect each field. There is also a method that makes it possible to display halftones by sending data (
Patent application 1986-70065). This will be explained with reference to FIG.

FIG. 3 shows a timing chart of field inversion driving of the matrix display panel, in which the data electrode is set to V m + Ov during positive pulse drive (data electrode voltage waveform). A
), the voltage waveform applied to the EL cell is as shown in a. In addition, completely opposite to this, the data electrode is Ov during negative polarity pulse driving.

When the data electrode is set to Vm during positive pulse driving (data electrode voltage waveform B), the voltage waveform applied to the EL cell becomes as shown in b. In addition to these, in both negative pulse drive and positive pulse drive, the data electrode is set to Vm or O
v (data electrode voltage waveform C or D), EL
The voltage waveform applied to the cell becomes C or d, allowing halftone display.

As mentioned above, the gradation display method that requires a driver that can change the output of the data driver in an analog manner is technically difficult to implement and costly. was also disadvantageous.

In addition, in a method that makes it possible to display halftones by sending selection and non-selection data for each field, one of the polarities of the voltages applied to the display cells is always +3. There were some problems, such as a negative effect on the display cell. In particular, when the display cell is an EL, this voltage asymmetry lowers the emission threshold voltage of the EL and further lowers the saturation brightness, causing a so-called afterimage problem and significantly deteriorating the display quality.

-nf! In order to solve the above-mentioned problems, the present invention provides a matrix display panel in which scan electrodes and data electrodes are arranged in rows and columns, and a display cell is placed at each intersection, and a A reading drive means for supplying a read-in voltage, and a modulation drive means for supplying a modulation voltage to each data electrode of the display panel according to selection or non-selection of the display cell, the voltage being applied to the display cell. In field reversal driving of a matrix display panel in which the voltage polarity is switched field by field, selection (or non-selection) data is sent to the field an odd number of times, and then non-selection (or non-selection) data is sent to the field even number of times. Halftone display is performed by repeating the cycle of sending data (selection).

By using the above method, no special data driver is required, and the positive and negative voltages applied to the display cells are always symmetrical throughout, making them stable without deteriorating the quality of the display cells. (This symmetry will be discussed later).

Husband Gohan FIG. 1 shows a timing chart of the present invention.

The data electrode is set to Ov during positive pulse drive, and the data electrode is set to Vm during negative pulse drive (data electrode voltage waveform A).
), the voltage waveform applied to the EL cell is as shown in a. In addition, on the contrary, the data electrode is set to Vm during positive pulse drive.

When the data electrode is set to OV during negative polarity pulse drive (data electrode voltage waveform B), EL-C! The voltage waveform applied to the circuit is as shown in b. The two patterns described above are data input methods without gradation display.

In addition to these, if Vm and Ov are switched once every three fields as shown in data electrode voltage waveform C or D,
The EL applied voltage waveform is like C or d, and it sends selection (in the case of d; non-selection in the case of C) data an odd number of times (here, once), and then an even number of times (here, twice). ), unselected (d).

In the case of C, the cycle of sending the selected data is repeated.

That is, each EL applied voltage waveform a, b, c.

Corresponding to d, the EL emission waveforms are a", b".

c'+d", and the emission brightness is a゛〉c'>
It is clear that d">b'. By carrying out the above method, it is possible to achieve a four-level gradation display (usually b' is set to non-emission and bell).

Of course, by repeating the cycle of sending selection (or non-selection) data three or more odd times, and then sending non-selection (or selection) data an even number of four or more times,
Needless to say, a more multi-gradation display can be realized.

According to the present invention, the positive and negative voltages applied to the EL cell are always symmetrical as a whole, which will be explained using the timing chart of FIG. 1. In the figure, for example, the EL application waveform C sends selected data an even number of times (in this case, twice), but the EL
The applied voltage waveform is rotationally symmetrical. To be more specific, when looking at the EL applied voltage waveform over the field (2 (1 + 2) = 6 fields in this case), which is doubled by adding the odd number of times (non-selected) and even number of times (selected), the upper and lower (positive,
The number of non-selections (here, once each) and the number of selections (here, twice each) at the negative electrode) are equal, so the positive and negative voltages applied to the EL cell are always symmetrical throughout. I understand. Note that, of course, this also holds true even for combinations such as the above-mentioned odd number times and even number times.

Gradation display using the above-mentioned method is advantageous in terms of cost since it is unnecessary for the data driver as well as the scan driver to have an analog output function. Furthermore, since the positive and negative voltages applied to the display cells are always symmetrical throughout, stable multi-gradation display can be achieved without adversely affecting the display quality of the display cells. Note that this method can also be applied to display panels driven by alternating current pulses, such as matrix LCD panels.

[Brief explanation of the drawing]

FIG. 1 is a timing chart of the EL gradation display method according to the present invention, FIG. 2 is a circuit diagram of the field inversion drive method of an EL panel, and FIG. 3 is a timing chart of the field inversion drive method of a conventional EL panel. It is a diagram. 10... Matrix display panel (matrix display panel), 11... Modulation drive means, 14.15.16... Write drive means, S1
~Sn...EL panel scanning electrode, D1~Dm・
...EL panel data electrode, -Vw, Vw+Vm
....a input voltage, Vm ....modulation voltage. Patent applicant: Kansai NEC Corporation Figure 2

Claims (1)

[Scope of Claims] A matrix display panel in which scan electrodes and data electrodes are arranged in a matrix and display cells are arranged at each intersection, write drive means for supplying a write voltage to each scan electrode of the display panel, and a display panel. and a modulation drive means for supplying a modulation voltage to each data electrode according to selection or non-selection of the display cell, the matrix display panel being configured to switch the polarity of the voltage applied to the display cell for each field. In the driving method, by repeating the cycle of sending selection (or non-selection) data to the field an odd number of times, and then sending non-selection (or selection) data to the field an even number of times,
A method for driving a matrix display panel characterized by displaying halftones.