JPS59228698A - Driving of matrix display panel - Google Patents

Abstract

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

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method of driving a matrix display element such as an EL display panel, and more particularly to a method of driving a matrix display element such as an EL display panel, and more particularly to a method of driving a matrix display element such as an EL display panel. .

Prior art and problems Here, we will discuss EL, which is known as one of matrix display elements.
The explanation will proceed using a display panel as an example.

EL display panels are made of zinc sulfide (Zn) with manganese added.
It has a basic structure in which a light-emitting layer (S:Mn) is sandwiched between insulating films on both sides, and scan electrodes and data electrodes arranged in a matrix are provided on both sides, and ACIJ flexible drive is generally used. An example of the configuration of a drive circuit for this purpose is shown in FIG.

In the figure, the data line trino<DD is the driving transistor Q1. Q2, each input terminal (al
, cap)+(a2+N2)... are given mutually contradictory data〇On the other hand, the scanning line driver SD is
Each trace is connected to a voltage of 4ir, BS+ to 5100[+ corresponding to a driving transistor Q3. Q4 is provided.

Then, each ml' IJ transistor Q3. Q4
input terminals (b++ bt), (b2+ b2)...
Scan data is given to the transistors, and the transistors are sequentially driven to supply ground to the scan electrodes S1HS2+... A pulse of voltage Vs is given from SS.

In this way, while the scanning electrodes SI, S21, . . . are sequentially selectively driven, each scanning electrode SI, S2, .
Each time ... is selected, the first 'a source line 11
A bias voltage pulse of voltage Vp is supplied from the Asumi source PS through the input terminals Cal1al), (a21a2), and display data corresponding to the scanning voltage lAs1ts2+ selected by the control device (not shown) is input to the input terminals Cal1al) and (a21a2). )
l”” is given.

In other words, if you want to emit light, the logical value (1, 0) is used, and if you do not want to emit light, (0, 1) is the logic value of each input terminal (a++a+L(a2
1: “Given to 2L...

As a result, the data voltages to be emitted = D, , D2. ...
・A data power supply DS is provided via the second power supply line 12.
The data pulse VD of the voltage VD becomes the bias pulse Vp.
0 superimposed on and supplied to the display panel DISP
In the above, only the display cell at the intersection of the selected scan electrode, that is, the grounded scan electrode and the data electrode on which the data pulse VD is superimposed, emits light.

Such an operation is performed by sequentially scanning electrodes S1. S2... is carried out, and when the last scan electrode 5100O is selectively driven, the refresh pulse V is generated from the refresh power supply RS next day.
R is given.

As a result, the charge accumulated in the light-emitting layer of the display cell that has emitted light flows in the opposite direction to that at the time of light emission, and only the display cell that has emitted light emit light.

Note that the light emitting characteristics of each display cell are shown in FIG. 2, and only by applying the bias pulse Vp,
A low luminance level LDL was not obtained, and there was almost no change in visual observation. On the other hand, when the data pulse VD is added, the brightness level becomes high LS and a bright and shining display effect is obtained.

Now, attempts have been made to apply such a display panel DISP to a dog-shaped display panel by taking advantage of its thin bottle structure, but data
tJMr'll D 1 to D1ooo use a transparent electrode made of a mixture of tin oxide and indium oxide.Due to the red resistance property of the material, the display cell is similar to that when viewed from the data line driver DD. There is a problem in that the rise of the voltage waveform applied to the cell differs in characteristics between the display cell and the distant display cell, resulting in a difference in luminance.

Such conventional problems will be explained in detail with reference to FIGS. 3 to 6.

Prisoner 3 shows a schematic diagram of the panel. Figure 4 is data electricity! It is an equivalent circuit diagram of one drive load seen from the data line driver that drives D+, and represents the case where the load seen from one data line driver is maximum. Figure 5 is an equivalent circuit diagram of the driving load seen from the bias voltage at this time.

In these figures, 1 is the substrate, sn is the display cell closest to the data power supply (hereinafter referred to as the nearest cell in the panel), and S
f is the display cell farthest from the data power supply (hereinafter referred to as the farthest cell in the panel). rd indicates the resistance value in the data power supply per cell and the CSU cell capacity.

As is clear from Figure 4, the load seen from the data line driver is an RC ladder circuit consisting of panel electric/water resistance and panel cell capacitance, so there are parts near and far from the data line driver. A large difference occurs in the IR time constant seen from the driver. Furthermore, regarding the CR time constant at a portion far from the driver, when comparing the case where the data line driver is involved and the case where it is applied from the bias power supply shown in FIG. 5, it can be seen that the time constant in the former is extremely large.

That is, in the former case, it is 10002·rd-Cs/2, and in the latter case, it is 1000·rd-cs.

This results in a pulse waveform shown in FIG.

That is, the data pulse VD of (a) supplied to the data electrode D1 by the data line tri-baccara and the bias pulse Vp of (d) supplied from the bias power supply are in contact with each other (b) and (e) at the electrode portion closer to the driver. ), the data pulse VD is applied as a pulse with almost the same rising edge, but in the farthest part of the electrode, as shown in (e) and (f), only the data pulse VD has a very rounded rising edge (7'C). It will be applied as a pulse.

Here, pulse potentials are applied to the data electrodes and the scan electrodes in order to discharge the polarized charges accumulated in the display cells in the period between the pulses. Therefore (g
) and the voltage waveform PSn of the nearest cell Sn in the panel in (j) added by combining the running voltage pulses Vs H, Vs+ooo of the scanning electrodes s1 and 5looo shown in (i).
There is a significant difference in the rise of the light emitting potential between the voltage waveform PSf of the farthest cell Sf in the panel and the voltage waveform PSf of the farthest cell Sf in the panel, and especially in the case of the farthest cell Sf, it has recently become difficult to obtain sufficient voltage to cause light emission. The luminance of the cell Sn also decreased, resulting in a disadvantage that the luminance of the luminance varied across all the display cells.

In the figure, T1 indicates a write cycle, and T2 indicates a refresh cycle.

Such a problem occurs in the same way when the length and size of the electrodes are different even if the electrode material is the same (for example, a long electrode will have a high resistance of 1).

Purpose of the Invention In view of the above-mentioned circumstances, it is an object of the present invention to provide a driving method that reduces variations in luminance of light emitted from matrix display elements.

Structure of the Invention In order to achieve the above object, the present invention includes a display medium layer, a constant strain electrode and a data electrode in an IJ array that are capacitively coupled to the display medium layer, and a display at the intersection of each electrode. In a matrix display device that obtains an electro-optical display effect by applying a predetermined display voltage to the cell from both electrodes, the scanning electrode is provided with a scanning driver for selectively connecting each electrode to a reference potential in sequence. The data electrode is provided with a first means for applying a common bias voltage to a plurality of data electrodes, and a second means for applying a voltage depending on whether or not to cause the display cell to emit light. Depending on which of these means has a higher resistance, the rise time of the voltage applied to the data electrode is made earlier than that of the other means by the first means or the second means, and furthermore,
When making adjacent display cells on the same data electrode emit light,
The present invention provides a method for driving a matrix display panel, characterized in that the full voltage is continuously applied using the first or second means in which the voltage application rise timing is advanced.

Embodiment of the Invention Hereinafter, one embodiment of the present invention will be described in detail with reference to the circuit example shown in FIG. 7 and the drive voltage waveform shown in FIG.

Here, in FIG. 7, the same symbols as in FIG. 1 indicate the same functions, and what is different from FIG.
1 is on, the voltage is applied to the data electrode all the time, and in the scanning line driver SD, the selected scanning electrode is at the reference potential, that is, the ground, but the unselected scanning electrode is disconnected from the power supply. This is the point at which the two parts are separated and become 70-tings.

Therefore, this situation will be explained according to the voltage waveform shown in FIG.

Note that the same reference numerals as in FIG. 6 indicate the same functions.

The display cell group associated with the data electrode is selectively emitted as in the driving example of FIG. 6, but the voltage pulse waveform output from the data line driver is significantly different from that of FIG. In other words, the data pulse VD in this embodiment has a waveform having a pulse width that is longer than the address (writing) time for one display line (for example, 16 μ5 ec) in order to rise faster than the bias pulse Vp. shi, specifically the bias pulse V
It is set so that the rise of p is applied to the data electrodes 8 μsec before the rise of p.

Therefore, although the data pulse applied to the data electrode site on the farthest cell Sf in the panel has a blunted rise as shown in (C), the scan voltage pulse VSIO (IQ is applied to the corresponding scan electrode S 1000 ). In other words, when the bias pulse Vp is applied in a state where the ground is applied, the predetermined potential can be reached.Therefore, the voltage pulse PSf applied to the farthest cell Sf in the panel is as shown in (k). It has almost the same shape as the SnO applied voltage pulse PSn of the nearest cell in the panel shown in J), and the farthest cell Sf can be caused to emit light in the best form, that is, with high brightness.Thus, the light emission in the nearest cell in the panel and the farthest cell in the panel This means that there will be almost no difference in brightness.

In the above embodiment, the data pulse has a pulse width equivalent to one cell address time so that it rises significantly ahead of the bias pulse, but it is also possible to set the rise time a little later. Of course it is possible. However, in this case, if adjacent display cells on the same data electrode are made to emit light continuously, charging and discharging by the data pulse VD will be repeated for each display cell, which is not a desirable waveform in terms of power consumption. . Therefore, as shown in FIG. 7, it is preferable to connect the preceding and subsequent data pulses in order to reduce the power consumption of the drive. Especially in applications where actual characters and figures are displayed, a large amount of such display data is exposed, so it can be said that this is a very effective molding method in practice.

Note that this example has been explained on the assumption that the data electrodes have high resistance, but if the scanning electrodes have high resistance, the luminance can be similarly changed by reversing the waveform timing of the data pulse and bias pulse. Variations can be prevented.

(f) Effects of the Invention As is clear from the above explanation, according to the driving method of the present invention, the cell voltage waveforms applied to the nearest cell in the panel and the farthest cell in the panel are made almost the same, and both cells are Of course, the luminance of all cells can be made uniform, and the display quality of the panel can be greatly improved. It also has the effect of significantly reducing power consumption when displaying actual characters and graphics.

Therefore, it is extremely advantageous to apply this invention to EL panels for large displays.

[Brief explanation of the drawing]

Figure 1 is a conventional drive circuit diagram, Figure 2 is a light emission characteristic diagram of a display cell, Figure 3 is a schematic diagram of a conventional panel, and Figure 4 is an equivalent circuit diagram of a drive load seen from a data line driver. , FIG. 5 is an equivalent circuit diagram of the drive load seen from the bias power supply, FIG. 6 is a drive pulse waveform diagram in the conventional example, FIG. 7 is a drive circuit diagram according to an embodiment of the present invention, and FIG. 8 is the same. A drive pulse waveform diagram is shown. In the figure, DD is a data line driver, SD is a scanning line driver, DS is a data power supply, PS is a bias power supply,
R8 beam 7 receiver power supply, DISP is display panel, D1
~D100O are data electrodes, and 81-5looo are scan electrodes. -(2ri? Figure 4-641→ Figure 5

Claims (2)

[Claims] (1) It has a display medium layer and a matrix array of scanning electrodes and data electrodes capacitively coupled to the display medium layer, and a predetermined display voltage is applied from both electrodes to the display cell at the intersection of each electrode. In a matrix display device that obtains an electro-optical display effect, the scanning electrode is provided with a scanning driver that sequentially and selectively connects each electrode to a reference potential, and the data electrode is provided with a common bias for a plurality of data electrodes. A first means for applying a voltage and a second means for applying a voltage depending on whether or not to cause the display cell to emit light are provided. A method for driving a matrix display panel, characterized in that the voltage applied to the data electrodes is applied to the data electrodes at a higher rise timing than the other means. (2) When causing adjacent display cells on the same data electrode to emit light, the first or second
2. A method for driving a matrix display panel according to claim 1, characterized in that a voltage is continuously applied by the means described in claim 1.