JPS583558B2 - Display element driving method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a driving method for a matrix panel.

As introduced in Japanese Patent Application No. 47-7465 (Japanese Unexamined Patent Publication No. 48-77727) filed by the present applicant, the thin film EL matrix panel exhibits a negative voltage after a time t after applying a positive pulse voltage. Even if a pulse is applied, a large amount of light emission can be obtained. Conventionally, this has been used to utilize the X (horizontal) electrode and the Y (vertical) electrode at each period T1 and T2, as shown in Figure 1. A large amount of light emission was obtained by applying a voltage vx-vy in the opposite direction to .

That is, in period T1, a voltage of +E is applied to the selected element portion of the thin film EL matrix panel, and in period T2, a voltage of -E is applied to the panel by applying the opposite voltage. In this case, all the control transistors included in the drive circuit must have a withstand voltage of E or higher, and the input voltage must be reversed every cycle, making the circuit complicated. It has some drawbacks.

The present invention utilizes the property that this EL matrix panel does not emit light with a single polarity, and the property that when a bipolar pulse is applied, a large amount of light is obtained regardless of the application time, so that it can be incorporated into a drive circuit. This makes it possible to reduce the breakdown voltage of control transistors to half that of conventional devices.

Hereinafter, one specific example will be described in detail with reference to the accompanying drawings.

The present invention actively utilizes the phenomenon that no light is emitted when a pulse in a single direction is applied, and the beginning of the period is positive. A method is adopted in which a reverse voltage is applied to all elements at the same time at the end of a cycle after operating with a voltage of one negative polarity. No light is emitted because only the voltage is applied.

However, the selected element portion continues to emit light because the voltages applied during selection and when the above-mentioned reverse voltage is applied have opposite polarities.

The details will be explained below.

In FIGS. 2 and 3, at a time t2 when a voltage is applied to cause the element portion Z22 of the thin film EL matrix panel 1 to emit light, a voltage is applied to the element portion Z22 in the horizontal electrode group at time t2. By simultaneously applying a voltage of +E to all the vertical electrodes Y1 to Yn at y2-YX2, an inverted voltage of +E is applied to the element portion Z22 at time tr.

In this case, each time tl. t3. t4. t5
In each vertical electrode Y1. No light is emitted because there is no current flowing through it.

Then, drop the entire vertical electrode again in time tr.
The above-mentioned light emission is maintained by repeatedly applying a voltage of +E to Yn.

An example of a circuit used for such a voltage application method is shown in FIG.

In the figure, A is a drive circuit for the horizontal electrode X, and the other side is a drive circuit for the vertical electrode Y.

Inserted PNP transistor (drive transistor)
This transistor Tx2 is grounded via Tx1 and an NPN transistor (switch transistor) Tx2.
An input terminal P is provided at the base of the transistor Tx1 to which the drive signal χ is input, and an output terminal O is provided at the collector of the transistor Tx1 to which all of the horizontal electrodes X are connected, to which the drive signal χ is input. At this time, from the above output terminal O, as is clear from this explanation, since a unidirectional voltage (approximately 120 to 150 V) is sufficient for driving the X electrode, the withstand voltage of the driving transistor is approximately 120 to 150 V. In the case of a conventional drive device or a diagram related to a drive of a Y electrode, a control signal can be input to the base of the drive transistor TY1 via the input terminal Q, and the collector of the transistor TY1 can be inputted to the base of the drive transistor TY1. is 2 contact switch S
It can be selectively connected to the power supply of the ground terminal S and 10E through W1, and furthermore, the emitter and base are connected in a switchable manner.
In such a circuit, the switch SW2 is turned on at the time of selection, and the switch SW1 is also turned on by passing it to the terminal S. When it should be turned off and turned on, the output or the above two-contact switch SW
1 is connected to the +E power supply, a drive signal with a voltage value of +E is output from the output terminal T, and a voltage of +E is applied to all vertical electrode groups.

That is, the driving transistors as described above are connected in parallel according to the number of vertical electrodes, and each transistor TY1. TY2・
. . . are the above-mentioned input terminals Q1. Q2...
...and output terminal TI. T2..., and these transistors TY1. are commonly related to.

The drive circuit based on the drive method of the present invention is constructed as described above, and its operation is illustrated in FIGS. 2 and 3 above.
This will be explained according to the diagram.

As mentioned above, in order to make the element part Z22 emit light, it is necessary to select the vertical electrode Y2, but in this case, turn on the switch SW2 in advance and connect the switch SW1 to the ground terminal S. In this state, when a control signal is applied to the base of transistor TYI via input terminal Q1 at time t2, it is then applied to output pole Y2.

At this timing, when a control signal is applied to the base of the transistor Tx2 on the horizontal electrode side via the input terminal P, the drive transistor Tx1 turns ON and the output terminal becomes 0.
(applied simultaneously to other horizontal electrodes X1, X3, X4 and X5).

Therefore, in the element part Z22 corresponding to the intersection of this horizontal electrode X2 and the above-mentioned vertical electrode Y2, the voltage value becomes -E due to the relationship <VZ22=VY2-VX2 as shown in A in the time chart of FIG. 3, and strong light emission occurs. is obtained.

Then, at a timing Tr after time t2 when this light emission occurs, when switch SW1 in the drive circuit on the vertical electrode side is connected to the power supply side of 10E, all the horizontal electrodes Y
A drive signal with a voltage value of +E is applied at once to 1..., and since this has the opposite polarity to the voltage value -E given to the element part Z22, a strong signal is again applied to this element part Z22. Luminescence is obtained as shown in the mouth of FIG.

Thereafter, by repeatedly applying such a drive signal at times t2 and tr, the strong light emission in the element portion Z22 is maintained.

Figure 5 is a circuit diagram when the present invention drive circuit (vertical and horizontal electrode side drive circuit) is actually assembled.
Part (5) is the drive circuit part on the horizontal electrode side, and (8
) section is the drive circuit section on the vertical electrode side, and section (C) is the above-mentioned input terminals Q1, Q2, and Q2 of this drive circuit section (5).
. . . mainly includes a plurality of decoders DI. D2...
, and each output terminal y1 of such a decoder. y2,・
...yn are the input terminals Q1. Q2,...
...Connected to Qn.

In this circuit, the vertical electrode side drive circuit portion is slightly different from that shown in FIG. 4 described above.

That is, it corresponds to each drive transistor TY at the port in FIG.
1. In place of the switch SW2 provided in connection with the transistors TY2, . . . in FIG. 5, the transistors TY1. T
The switching transistor Ts1.Y2... is connected to the switching transistor Ts1. Ts2 is provided.

Further, the symbol PC in the figure indicates a photocoupler.

As described above, the present invention selectively applies a first drive signal to each electrode of a horizontal electrode group (or vertical electrode group), and at a certain timing, the vertical electrode group (or horizontal electrode group) group)
applying a second drive signal of opposite polarity to the first drive signal, and increasing the applied voltage value at the selection element portion where the first and second drive signals overlap to cause strong light emission; After this light emission, at an appropriate timing, all of the horizontal electrode groups (or vertical electrode groups) simultaneously generate a total drive signal which has a polarity opposite to that of the first drive signal, and whose voltage value is higher than that of the first drive signal. By applying voltage to the selected element portion, a voltage with a polarity opposite to that used when emitting light is applied to the selected element portion to cause it to emit strong light again, and this operation is sequentially repeated so that the selected element portion continues to emit light. This is an excellent invention because its drive circuit can be constructed much more simply than conventional ones.

[Brief explanation of the drawing]

FIG. 1 is a time chart showing voltage waveforms of the horizontal X and vertical Y electrodes and element parts obtained based on the conventional driving method, and FIG. 2 is a schematic diagram of the configuration of a matrix panel used in the driving method of the present invention. , FIG. 3 is a time chart showing the voltage waveform of each part obtained based on the driving method of the present invention,
Figures 4A and 4A show a drive circuit when the drive method of the present invention is implemented, the former being a circuit diagram of a horizontal electrode, the latter being a circuit diagram of a vertical electrode, and Figure 5 is a drive circuit shown in Figure 4. FIG. X1...: Horizontal electrode, ¥1... Two vertical electrodes, Z11...: Element part.

Claims (1)

[Claims] 1. A method for driving a display element disposed at an intersection of electrode groups arranged in a 7-trix pattern, the method comprising: a first driving signal selectively applied to each electrode of the horizontal (or vertical) electrode group; At a timing when the vertical (or horizontal) electrode group is applied with a second drive signal applied with a polarity different from the drive signal, the voltage applied to the selection element portion is increased to cause the selection element to emit light;
After such light emission, the above-mentioned horizontal (or vertical)
Simultaneously applying to the electrodes a total drive signal with a potential having a polarity opposite to that of the first drive signal, and applying a voltage of opposite polarity to the selection element portion to cause it to emit light again, and perform such an operation. A method of driving display elements arranged in a matrix in which the selected element portions continue to emit light by sequentially repeating the following steps.