JPS5922947B2 - Electrophoretic display panel driving method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a driving method for an electrophoretic display panel comprising a plurality of elements in which one electrode is common and the other electrode is divided into a plurality of segment electrodes.

Figure 1 shows the basic structure of an electrophoretic display panel, which includes transparent electrodes 2 provided on glass 1 and spacers 3.
An electrophoretic display dispersion system 6 is sandwiched between divided electrodes 4 provided on a substrate 5 separated by.

An example of this electrophoretic display dispersion system 6 is one in which white pigment particles 8 are dispersed in a black liquid dispersion medium T. It is assumed that it is positively charged inside. As shown in FIG. 1, when a voltage is applied between the divided electrode 4 and the transparent electrode 2 so that the direction of the electric field applied to the dispersed system is reversed,
The positively charged pigment particles 8 are electrophoresed toward the cathode by Coulomba, resulting in a particle distribution as shown in the figure. At this time, when looking at the dispersion system 6 through the transparent electrode 2, the left side appears white due to the white particle layer 8 adhering to the transparent electrode 2, while the right side looks white because the white particle layer 8 is hidden behind the black liquid T. It will appear black. If the polarity of the applied voltage is reversed, the left and right colors will be reversed, but when the applied voltage is removed, the adhered particles will remain adhered mainly due to the Van der Waals attraction between them and the electrodes, resulting in almost no contrast. No change occurs.

FIG. 2 shows an example of such an electrophoretic display panel and a seven-segment type numeric display panel, and parts corresponding to the display panel shown in FIG. 1 are given the same symbols.

The structure of the numeric display panel 20 shown in FIG. 2 is almost the same as the basic structure shown in FIG. 2｜Seven elements a3b3c3・
...g, each segment electrode 4a, 4b
, 4c, 4d, 4e, 4f, and 4g. Use the numeric display panel 20 to display the time from the completely erased (black display) state.

In order to display the number 2 at , and then update the display to the number 3 at time tl, it is sufficient to apply voltages as shown in the time chart in FIG. 3 to each electrode of the number display panel 20. I understand. However, in order to supply the voltage shown in Figure 3, two voltage sources, +V and -V, and a switch element that can select three levels, 0 and -V, are required, and the circuit configuration is as follows: It becomes complicated and expensive. The present invention aims to improve the above-mentioned drawbacks with a simple and inexpensive circuit configuration by controlling the voltage applied to the common electrode.

FIG. 4 shows the configuration of a device to which the display method according to the present invention is applied, in which the common electrode 2 of the numeric display panel 20 and each segment electrode 4a, 4b, 4c, 4d, 4e, 4f,
4g each is Switch S.

, Sl, S2, S3, . . . S7, and the voltage applied to each electrode is controlled by a control signal supplied from a control signal source 30. Figure 5 A,
The opening, the hall, and the bottom are the voltage waveforms applied to each electrode in order to realize the same display as in FIG. 3 using the electrophoretic numeric display panel 20 shown in FIG. It shows the voltage waveform applied to the element. The voltage supplied to the common electrode 2 is determined by the amplitude, repetition period Tc, and duty factor (D
It consists of three cycles of a rectangular wave pulse voltage of 50% (utyfactOr), and is given when updating the display. On the other hand, the voltage supplied to each of the segment electrodes 4a, 4b, . When the element updates the display, it is a constant voltage of V or O during the period T corresponding to the voltage applied to the common electrode, and when the element does not update the display, it is the same voltage as the voltage applied to the common electrode. If we rewrite the voltage applied to element a with the common electrode 2 as a reference from FIG. Similarly, the voltage waveforms applied to elements C and e from A and II, respectively, are shown in the figure. As mentioned above, in an electrophoretic display panel, even if the applied voltage is removed, the distribution state of the particles is maintained. Therefore, when applying multiple short pulses in succession, responds by an accumulation of pulses.

Figure 6 shows the relationship between the pulse width Tc and response speed of each pulse when pulses with a duty factor of 50% are applied continuously.The part indicated by A is the response due to a single pulse. corresponds to As is clear from this figure, the response time is reduced by approximately 2 by the accumulation of narrow pulses.
Although it is about twice as long, there is no problem in updating the display. Therefore, it is understood that each element of the numeric display panel 20 to which a voltage is applied as shown in FIG. 5 changes its display state depending on the polarity of the applied voltage. Also, as is clear from Fig. 5, the voltage applied to each electrode is either O or O, and the switch S
.

, Sl, . . . S7 can be selected from two levels of voltage. Therefore, when configuring these switches using transistors, they can be realized with an extremely simple configuration, the transistor's breakdown voltage can be half of that of the conventional example explained in Figure 3, and only one type of voltage source can be used. There are advantages such as being able to FIG. 7 shows another numerical element panel using electrophoretic display elements.

In the same figure, A shows the arrangement of segment electrodes, the opening shows the structure of the digit electrode, and C shows a cross-sectional view of the panel along the A-N plane. The configuration of the numeric display panel 21 shown in FIG. 7 is approximately the same as the numeric display panel 20 shown in FIG. The other part is the background electrode 4B.
The three common electrodes are divided into a segment common electrode 2S that mainly includes a segment part and a leader line part common electrode 2L that mainly includes a leader line part. It's different. The numerical display on the numerical display panel 21 is performed in the following procedure.

For example, if you want to display white text on a black background,
Prior to display, +V is applied to the two common electrodes ZS and 2L.
, all segment electrodes 4a, 4b, 4c,...4g
Then, an O voltage is applied to the background electrode 4B to erase all elements. During the subsequent numerical display period, +V is always applied to the leader line portion common electrode ZL, and the same voltage as the segment common electrode 2S is always applied to the background electrode 4B. The segment common electrode Zs and the respective segment electrodes 4a to 4g are driven by the method explained in FIG. 5 using the display device of the present invention shown in FIG. As a result, in the background electrode part and the leader line part, excluding the segment part, the erasing state is memorized or a voltage is applied in the direction of clearing again, and in the segment electrode part, the display is displayed according to the control signal. It can be seen that the is updated. Reversing the colors of the background and displayed characters can be achieved by reversing the direction of the electric field during erasing and reversing the voltage applied to the segment electrodes during display updating. In the above description, only one type of dispersion system for electrophoretic display has been described regarding the display of a numeric display panel, but the present invention is not limited to this. As is clear from the above embodiments, the present invention provides control signals for controlling each element of an electrophoretic display panel composed of a plurality of elements in which one electrode is common and the other electrode is divided into a plurality of segment electrodes. By controlling the voltage applied to the common electrode and each segment electrode according to the voltage applied to the common electrode and each segment electrode, it can be driven using a two-circuit changeover switch element, and has the advantage of being inexpensive with a simple circuit configuration. .

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of an electrophoretic display element, Fig. 2 is a numeric display panel using an electrodynamic dispersion system, Fig. 3 is a diagram for explaining the operation of the numeric display panel, and Fig. 4 is a diagram of the present invention. FIG. 5 is a diagram for explaining its operation. FIG. 6 is a diagram showing the response speed of the electrophoretic display panel. FIG. 7 is a diagram showing the response speed of the electrophoretic display panel. 1 is a diagram showing the structure of another type of numeric display panel using an electrophoretic dispersion system. 20...Display panel, 4a, 4b to 4g...
...Segment electrode, SO, Sl~S7...
Switch.

Claims (1)

[Claims] 1. In an electrophoretic display panel composed of multiple elements in which one electrode is common and the other electrode is divided into multiple segment electrodes, the segment electrode of the element whose display state is to be changed is divided into two segments for a certain period T. is held at a different potential V_1 or V_2,
A pulse voltage that changes between the two different potentials V_1 and V_2 for at least one cycle or more is applied to the common electrode during the certain period T, and the segment electrodes of the elements that do not change the display state are applied to the common electrode. A driving method for an electrophoretic display panel characterized in that a pulse voltage same as a pulse voltage applied to the electrophoretic display panel is applied.