JPH07175424A - Electrophoresis matrix display device - Google Patents

Abstract

PURPOSE:To provide an electrophotoreis matrix display device which is shortened in rewriting time and with which high-speed rewriting is possible. CONSTITUTION:This electrophoresis matrix display device has a display device in which one electrode of one set of electrodes is constituted as a full-surface electrode and the other electrode as divided electrodes to permit discrete impression of voltages and a switching circuit SC which has a pair of transistors(TRs) Q constituted by cacade connecting emitters and collectors, connecting one terminal to a positive power source and the other terminal to a negative power source, connecting an output terminal T to the middle of both TRs Q, Q, connecting power sources of the same polarity as the polarity of the emitters of the respective TRs Q via capacitive elements C respectively to the respective bases and connecting the circuit elements of the previous stage thereto and impresses the positive voltage or negative voltage to one of the divided electrodes. The display device is so constituted as to hold the operation of the TRs Q for the time determined by discharge of the capacitive elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for performing a display operation by utilizing an electrophoretic effect, and more particularly to the structure of a circuit for applying a voltage to electrodes for the display operation.

[0002]

2. Description of the Related Art In an electrophoretic display device, for example, a display dispersion system in which white pigment fine particles are dispersed in a black liquid dispersion medium is arranged between a pair of electrodes arranged facing each other, and rewriting should be performed between the electrodes. By applying an electric field according to the content to cause an electrophoretic action and moving the fine particles, the desired content is displayed. In this case, the moving state of the fine particles is determined by the applied electric field, and the display is performed so that the moving state is observed through the transparent electrode.

In the display, contrast is produced depending on the strength and direction of the applied electric field, and a selection signal is supplied from one of the two electrode groups facing each other.
By supplying a positive electric field or a negative electric field as an information signal from the electrode group of the other set, the display is rewritten one element or one column.

It suffices that the electric field is applied while the selected display element and the non-selected display element are distinguished from each other, but an unnecessary voltage is applied to the non-selected display element.
That is, a so-called crosstalk voltage may be applied, and the display becomes unclear.

In order to prevent this, one of the facing electrodes is used as a full-scale electrode and the other is used as a split electrode, and a switch element is provided for each split electrode. Then, for rewriting the display, power is supplied only to the row to be rewritten, a control signal is applied to each column, and an output from the drive transistor is given only for the response time of the display element to perform display one row at a time.

[0006]

Since a signal is applied for each row in a matrix composed of display elements for the response time of the display elements, it takes a long time to rewrite the entire surface of the matrix, which causes an unnatural display. . In addition, when the display device has a multi-dot structure, the rewriting time increases in proportion to the number of lines and becomes too long to be practical.

The present invention has been made in view of the above points, and an object of the present invention is to provide an electrophoretic matrix display device capable of shortening the rewriting time and enabling high-speed rewriting.

[0008]

In order to achieve the above object, the present invention provides a dispersion for electrophoretic display containing a liquid phase dispersion medium and particles between a pair of electrodes facing each other according to claim 1. In an electrophoretic matrix display device configured by arranging a system and performing display by applying an electric field between the electrodes to cause migration of the dispersion medium, one of the pair of electrodes is a full surface electrode. , A display device in which the other electrode is configured as a split electrode to which a voltage can be applied individually, and an emitter-
The collectors are connected in tandem, one end is connected to the positive power supply, the other end is connected to the negative power supply, the output terminal is connected between the two transistors, and each base is connected to each base via a capacitive element. A capacitive element having a switching circuit for applying a positive voltage or a negative voltage to one of the divided electrodes, which has a pair of transistors to which a power source having the same polarity as that of the emitter is connected and a circuit element in the preceding stage is connected. 3. An electrophoretic matrix display device, characterized in that the transistor is kept in operation for a time determined by the discharge of an element, and one row or one column of the matrix in the device according to claim 1 according to claim 2. An electrophoretic matrix display device, wherein the capacitive element is charged as a unit, in the device according to claim 3 or 4. The electrophoretic matrix display device in which the discharge time of the capacitive element is longer than the display response time of the display element, and rewriting is performed while temporally overlapping each row or column of the matrix. ,I will provide a.

[0009]

In the device according to the first aspect, an electric field is applied between the whole surface electrode of the display device and each divided electrode. A voltage is applied to each divided electrode from the selected one of the pair of transistors of the switching circuit via the output terminal.
The selection of the transistor is performed by the circuit element in the preceding stage operating according to the control signal and turning on only one of the pair of transistors. At this time, the operating time of the transistor is held for the discharging time of the capacitive element provided on the bases of the pair of transistors. Display is performed by applying a voltage between the divided electrode and the entire surface electrode by the selected transistor and causing particles in the display dispersion medium to migrate. Then, no voltage is applied to the unselected transistors, and thus the divided electrodes corresponding to the unselected transistors do not display.

In the apparatus according to the second aspect, the display contents are rewritten by charging the capacitive element in units of one row or one column of the matrix.

According to a third aspect of the present invention, a display device in which the discharge time of the capacitive element is longer than the response time of the display element is rewritten while temporally superimposing one row or one column of the matrix. To do.

[0012]

Since the present invention is configured as described above, it has the following effects.

According to the first aspect of the invention, since the capacitive element is connected to the base of the transistor for selecting only the transistor connected to the desired divided electrode of the electrophoretic matrix device, the discharge time of the capacitive element is used. Thus, the transistor can be held in operation.

According to the second aspect of the present invention, the display content is performed in units of one row or one column of the matrix, so that the display content can be rewritten quickly.

Further, according to the third aspect of the present invention, since the discharge time of the capacitive element that determines the display time is longer than the response time of the display element, the display content is displayed even if the display content is quickly rewritten. Can be sustained only for the discharge time of
The display can be easily read.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the structure of an electrophoretic matrix display device to which the present invention is applied. In the figure,
E1 is an entire surface electrode, which is connected to GND and is in a grounded state. E2 is a divided electrode which is arranged so as to face the entire surface electrode E1, and each divided electrode has terminals T1, T2, T3 ...
It is connected to Tn. These terminals T1, T2, T3
Tn is connected to a positive or negative power source + V or -V depending on the display content to be displayed by the display device.

In the display element having the terminal T1 to which the split electrode is connected to the positive power source + V, the particles are closer to the split electrode side as shown in the figure, whereas the terminal T2 which is connected to the negative power source -V. In the display element having, the particles are closer to the entire surface electrode side. The display can be rewritten by moving the particles by an electrophoretic action. The rewritten display maintains the same display even when the voltage application is stopped.

FIG. 2 shows a circuit for applying a voltage to the four display elements for each divided electrode in FIG. One of the four display elements in the figure will be described with reference numerals.

This circuit has terminals T1, T2, and T2 of the display element.
A switching circuit SC having an output terminal T connected to T3 ... Is constructed as a circuit provided for each display element. The switching circuits SC are arranged in rows and columns so as to form a matrix as shown in the figure, and control input terminals S are provided for applying control signals to each row.
And a control signal input terminal C for providing a control signal for each column. The connection with the power supply is not shown.

FIG. 3 shows the internal structure of the switching circuit SC of FIG. 2 in detail. That is, one switching circuit SC has four transistors Q1, Q2, Q3, Q4 as switching elements. These transistors Q1 to Q4 are control transistors Q1 and Q2 which are output transistors and which are arranged in the preceding stage.
3 and Q4. Where P
The NP type output transistor Q1 has an NPN type control transistor Q3, and the NPN type output transistor Q2.
Is combined with a PNP type control transistor Q4. The control transistors Q3 and Q4 have their emitters connected to the control signal input terminals S1 and S2 for row selection, and their bases to the control signal input terminal C for column selection.
1 and C2.

A combination of a control transistor and an output transistor, for example, an NPN type control transistor Q3.
And a PNP type output transistor Q1, the collector of the control transistor Q3 is connected to the base of the output transistor Q1 via the resistor R1, and the capacitor C
1 is connected to the power supply + V, the emitter of the output transistor Q1 is connected to the power supply + V, the collector is commonly connected to the collector of another NPN type output transistor Q2, and is connected to the output terminal T. .

This NPN type output transistor Q2 is
It is combined with a PNP type control transistor Q4 and similarly connected with a resistor R2 and a capacitor C2. The other end of the capacitor C2 and the output transistor Q2 are also connected.
The power source to which the emitter of is connected is -V.

Turning on / off of each output transistor in this circuit is performed by controlling on / off of a control transistor. In the NPN type, this is done by making the base higher than the emitter.
This is done by setting the emitter to a higher level than the base.

Now, in this circuit, a control signal of-is provided from the control signal input terminal S1 for row selection, and control signals are input to the other control signal input terminals including the column selection control signal input terminal C1. If it is not given and has 0 potential,
Control transistor Q3 turns on and output transistor Q
1 turns on and charges capacitor C1. It is easy to set the charging time to several 100 ns.

The charged electric charge of the capacitor C1 is the same as the base of the resistor R1 and the output transistor Q1 at the same time that the emitter of the control transistor Q3 has the same zero potential as the base after the application of the-control signal to the control signal input terminal S1 is finished.
It begins to be discharged through the emitter by the time constant C1 · R1. During this discharge time, the output transistor Q
Since 1 is kept in the ON state, an output signal is generated at the output terminal T and the display by the display device is continued.

Each of the control signal input terminals S1, S2, C1 and C2 is 0 when there is no signal and + or − when there is a signal.
Voltage is applied. The signal levels in the presence of a signal and in the absence of a signal are shown in parentheses () shown beside each control signal input terminal in FIG.

FIG. 4 shows how the operation holding time of the output transistor Q2 changes when the capacitance of the other capacitor C2 in the circuit of FIG. 3 changes. This figure shows that when the resistance R2 is set to 1 MΩ and the capacitance of the capacitor C2 is changed from 47 nF to 130 nF, the operation holding time of the output transistor Q2 is changed from approximately 200 ms to 650 ms.

This means that the charging of the capacitor is several hundreds.
It can be done in n seconds, and the holding operation after charging lasts for several 100 ms, which means that the display content can be rewritten in an extremely short time and the display operation based on it can be continued 1000 times as long. . Therefore, even if the response of the display element is slow, regardless of that, if the capacitor for rewriting the display content is charged, the display element responds by the end of discharge and the output for display is displayed until the end of the discharge time. Keep holding. Although the bipolar type is used as the transistor in the above embodiment, other conductive type transistors such as a field effect type may be used.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an electrophoretic display device to which the present invention is applied.

FIG. 2 is a diagram showing a circuit for driving the display device shown in FIG.

FIG. 3 is a diagram showing a detailed configuration of a circuit in one embodiment of the present invention.

4 is a characteristic diagram showing the relationship between the capacitance of a capacitive element C2 and the operation holding time in the circuit of FIG.

[Explanation of symbols]

 E1 Full surface electrode E2 Split electrode Q transistor SC Switching circuit SW switch S Row selection control signal input terminal C Column selection control signal input terminal T Output terminal

Claims (3)

[Claims] 1. A display element, in which a dispersion system for electrophoretic display containing a liquid phase dispersion medium and particles is arranged between a pair of electrodes facing each other, is arranged in a matrix of rows and columns. In the electrophoretic matrix display device that performs display by applying an electric field between the electrodes of each display element to cause migration of the dispersion medium, one electrode of the pair of electrodes is a full surface electrode. In the matrix display device, the other electrode is configured as a divided electrode to which a voltage can be applied to each display element, and the emitter-collector is vertically connected so that one end is connected to the positive power supply and the other end is connected to the negative power supply. An output terminal is connected in the middle of both transistors, and a power source having the same polarity as the emitter of each transistor is connected to each base through a capacitive element and a preceding circuit element is connected thereto. A switching circuit that has a pair of transistors and applies a positive voltage or a negative voltage to one divided electrode corresponding to one of the display elements, and keeps the transistors operating for a time determined by the discharge of the capacitive element. An electrophoretic matrix display device characterized in that 2. The electrophoretic matrix display device according to claim 1, wherein the capacitive element is charged in units of one row or one column of the matrix. 3. The device according to claim 1, wherein a discharge time of the capacitive element is set longer than a display response time of the display element, and the matrix is temporally overlapped with each row or column as a unit. The electrophoretic matrix display device is adapted to be rewritten.