JP2011170192A - Method for driving electrophoretic device, drive circuit, electrophoretic device, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving method or the like that performs at least one of holding and transition of a display state in an electrophoretic device more properly. <P>SOLUTION: The method for driving the electrophoretic device is configured such that electrophoretic particles 160 are interposed between a first electrode 110 and a second electrode 120. One of the first electrode 110 and the second electrode 120 enters a high impedance state, after a mode for using the color of the electrophoretic particles 160 is entered. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrophoretic device driving method whose display is changed by applying a predetermined voltage to an electrode pair, an electrophoretic device driving circuit, an electrophoretic device, and an electronic apparatus including the electrophoretic device.

  The electrophoretic device is known as a non-light emitting / reflective device utilizing an electrophoretic phenomenon, and is mainly used as a display device. The electrophoretic phenomenon is a phenomenon in which electrophoretic particles migrate by Coulomb force when an electric field is applied to a dispersion system in which fine particles (electrophoretic particles) are dispersed in a liquid (dispersion medium). The electrophoretic device has a pair of electrodes facing each other at a predetermined interval, and an electrophoretic element composed of a dispersion medium, black (low reflectance) electrophoretic particles, and white (high reflectance) electrophoretic particles is disposed therebetween. In general, the electrophoretic elements are arranged in an array.

  Here, as a method for driving the electrophoretic device, there is a method in which a constant voltage is applied between the electrodes of the electrophoretic device and then the electrode pair is made equipotential. Japanese Patent Laid-Open No. 2002-116733 (Patent Document 1) It is disclosed.

JP 2002-116733 A

  However, when the electrophoretic device is driven by the above-described conventional driving method, the display state of the electrophoretic device may not be maintained, or the transition of the display state may be insufficient.

  The present invention has been made in view of the above problems, and one of its objects is to solve at least one of the above problems and more appropriately perform at least one of holding and transition of a display state in an electrophoresis apparatus. It is an object of the present invention to provide a driving method or the like that makes it possible.

  In order to solve such a problem, an electrophoretic device driving method according to an embodiment of the present invention is an electrophoretic device driving method in which electrophoretic particles are interposed, and the state transitions to a display state based on the color of the electrophoretic particles. Then, either one of the first electrode and the second electrode is brought into a high impedance state.

  According to another aspect of the present invention, there is provided a driving circuit for an electrophoretic device that drives an electrophoretic device in which electrophoretic particles are interposed between a first electrode and a second electrode. One of the first electrode and the second electrode is set to a high impedance state after transition to a display state based on the color of the electrophoretic particles.

  In the above-described electrophoretic device, when the first electrode and the second electrode are set to the same potential after transition to the display state based on the color of the electrophoretic particles (for example, black), the display state in black is a slightly whitish display. The phenomenon of transitioning to a state occurs. In this case, there arises a problem that the electrophoretic device is not maintained in a desired black display state.

  According to the driving method or the driving circuit in one embodiment of the present invention, after the transition to the display state by the color of the electrophoretic particles (for example, black), either one of the first electrode and the second electrode is changed. At least one of the first electrode and the second electrode is driven so as to be in a high impedance state. Accordingly, the display of the electrophoretic device can be prevented from transitioning to a whitish display state, and the black display state can be maintained.

  The color of the electrophoretic particles may be other than black, for example, red, blue, or green. The color of the electrophoretic particles may be any color having a lower reflectance than the electrophoretic particles of other colors when the electrophoretic particles of other colors are present. Moreover, the color of this electrophoretic particle should just be a color which has a reflectance lower than a dispersion medium, when the electrophoretic particle of another color does not exist. This is the same for the electrophoretic particles described below, with black as an example.

  An electrophoretic device driving method according to another aspect of the present invention is an electrophoretic device driving method in which electrophoretic particles are interposed between a first electrode and a second electrode. After the transition to the display state by the color of the electrophoretic particles, either one of the first electrode and the second electrode is set to a high impedance state, or the first electrode and the second electrode are It is characterized by having the same potential.

  An electrophoretic device drive circuit according to another aspect of the present invention is a drive circuit for driving an electrophoretic device in which electrophoretic particles are interposed between a first electrode and a second electrode. After the transition to the display state by the color of the electrophoretic particles, either one of the first electrode and the second electrode is in a high impedance state, or the first electrode and the second electrode And are set to the same potential.

  In the above-described electrophoretic device, in order to transition the electrophoretic device to the white display state between the first electrode and the second electrode after transitioning to the display state based on the color (for example, white) of the electrophoretic particles. The write voltage (for example, −10 V which is the Lo potential) is applied again. Then, the reflectance of the electrophoretic device is lowered, and a phenomenon occurs in which the white display state transitions to a slightly blackish display state. In this case, there arises a problem that the electrophoretic device is not held in a desired white display state.

  According to the driving method or the driving circuit in one embodiment of the present invention, after the transition to the display state by the color of the electrophoretic particles (for example, white), either one of the first electrode and the second electrode is changed. At least one of the first electrode and the second electrode is driven so as to be in a high impedance state or at the same potential between the first electrode and the second electrode. Accordingly, it is possible to prevent the reflectance from being lowered in the display of the electrophoretic device and to maintain the white display state.

  The color of the electrophoretic particles is other than white, and when electrophoretic particles of other colors are present, the electrophoretic particles have a higher reflectance than the electrophoretic particles of other colors, for example, yellow or light blue. May be. Further, the color of the electrophoretic particles may be a color having a higher reflectance than the dispersion medium when no electrophoretic particles of other colors are present. This is the same for the electrophoretic particles described below, in which white is used as an example.

  An electrophoretic device driving method according to another aspect of the present invention is an electrophoretic device driving method in which electrophoretic particles are interposed between a first electrode and a second electrode. When the electrophoretic device is transitioned to the display state based on the color of the electrophoretic particles, a first voltage is applied between the first electrode and the second electrode, and the first electrode and the One of the first electrode and the second electrode is set to a high impedance state after a first time has elapsed since the first voltage was applied to the second electrode. And

  An electrophoretic device drive circuit according to another aspect of the present invention is a drive circuit for driving an electrophoretic device in which electrophoretic particles are interposed between a first electrode and a second electrode. When the electrophoretic device is changed to a display state by the color of the electrophoretic particles, a first voltage is applied between the first electrode and the second electrode, and the first electrode One of the first electrode and the second electrode is brought into a high impedance state after a first time has elapsed since the first voltage was applied between the first electrode and the second electrode. It is structured.

  In the above-described electrophoretic device, when transitioning from a display state of another color to a display state of an electrophoretic particle color (for example, black), first, the first electrode is placed between the first electrode and the second electrode. As a voltage, a writing voltage (for example, +10 V which is a potential of Hi) for applying the electrophoretic device to a black display state is applied. After that, if the first electrode and the second electrode are set to the same potential in order to maintain the display state of the electrophoretic device in the black display state, the black display state transitions to a slightly whitish display state. The phenomenon of end up occurs. As a result, there arises a problem that the electrophoretic device is not shifted to a desired black display state.

  According to the driving method or the driving circuit in one embodiment of the present invention, the first voltage is applied between the first electrode and the second electrode, and after the first time has elapsed, the first electrode One of the first electrode and the second electrode is set to a high impedance state. Accordingly, it is possible to prevent the display of the electrophoretic device once changed to the black display state from returning to the whitish display state, and to change the electrophoretic device to a desired black display state.

  An electrophoretic device driving method according to another aspect of the present invention is an electrophoretic device driving method in which electrophoretic particles are interposed between a first electrode and a second electrode. When the electrophoretic device is changed to a display state based on the color of the electrophoretic particles, a second voltage is applied between the first electrode and the second electrode, and the first electrode and the After the second time has elapsed since the second voltage was applied between the second electrode and the second electrode, the first electrode and the second electrode are set to the same potential, and the first electrode and the second electrode One of the first electrode and the second electrode is set to a high impedance state after a third time has elapsed since the two electrodes have the same potential.

  An electrophoretic device drive circuit according to another aspect of the present invention is a drive circuit for driving an electrophoretic device in which electrophoretic particles are interposed between a first electrode and a second electrode. When the electrophoretic device is changed to a display state based on the color of the electrophoretic particles, a second voltage is applied between the first electrode and the second electrode, and the first electrode And after the second time has elapsed since the second voltage was applied between the first electrode and the second electrode, the first electrode and the second electrode are set to the same potential, One of the first electrode and the second electrode is set to a high impedance state after a third time has elapsed since the second electrode is set to the same potential. .

  In the above-described electrophoretic device, when a transition is made from a display state of another color to a display state of an electrophoretic particle color (for example, white), first, the second electrode is placed between the first electrode and the second electrode. As a voltage, a writing voltage (for example, −10 V indicating Lo) for applying a transition to a white display state is applied. Here, even if the white write voltage is continuously applied as it is, the reflectivity does not rise to a certain extent. Therefore, the application of the write voltage is stopped and the first electrode and the second electrode are set to the same potential. By doing so, the reflectance is further increased, and the electrophoretic device can be changed to a desired white display state.

That is, according to the driving method or the driving circuit in one embodiment of the present invention described above,
(A) applying a second voltage between the first electrode and the second electrode;
(B) After the second time has elapsed since the second voltage was applied between the first electrode and the second electrode, the first electrode and the second electrode are set to the same potential,
(C) After the third time has elapsed since the first electrode and the second electrode are set to the same potential, either the first electrode or the second electrode is brought into a high impedance state. .

  By driving the electrophoretic device as described above, it is possible to obtain a high reflectivity that cannot be obtained only by applying the second voltage, and to maintain this reflectivity.

  An electrophoretic device drive circuit according to another aspect of the present invention is a method for driving an electrophoretic device in which electrophoretic particles are interposed between a first electrode and a second electrode, When the electrophoretic device is transitioned to the display state based on the color of the electrophoretic particles, a first voltage is applied between the first electrode and the second electrode, and the first electrode and the One of the first electrode and the second electrode is set to a high impedance state after a first time has elapsed since the first voltage was applied to the second electrode. And

  According to this, the electrophoretic device can be displayed in gray.

  Further, according to one aspect of the present invention, the first electrode, the second electrode, and the electrophoretic particles disposed between the first electrode and the second electrode, An electrophoretic device comprising the drive circuit according to any one of the above.

  According to such a configuration, for example, in an electrophoresis device that wants to maintain a black display state, it is possible to prevent the transition to a whitish display state, and to constitute an electrophoresis device having any of the above features. Can do.

  Moreover, the present invention includes an electronic apparatus including the above-described electrophoresis apparatus as one form thereof.

The figure which shows the structure of the pixel area | region of an electrophoresis apparatus. FIG. 6 is a first signal diagram illustrating a first operation example of a pixel region of the electrophoresis apparatus. The 2nd signal figure which shows the 1st operation example of the pixel area | region of an electrophoresis apparatus. FIG. 10 is a third signal diagram illustrating a first operation example of the pixel region of the electrophoresis apparatus. FIG. 10 is a fourth signal diagram illustrating a first operation example of the pixel region of the electrophoresis apparatus. The 1st signal figure which shows the 2nd operation example of the pixel area | region of an electrophoresis apparatus. FIG. 10 is a second signal diagram illustrating a second operation example of the pixel region of the electrophoresis apparatus. The figure which shows the structural example of the whole electrophoresis apparatus. FIG. 10 is a first diagram illustrating an example of a specific operation of the electrophoresis apparatus. FIG. 8 is a second diagram illustrating an example of a specific operation of the electrophoresis apparatus. FIG. 3 is a diagram illustrating a first specific example of an electronic apparatus including the electrophoresis apparatus according to the embodiment. FIG. 6 is a diagram illustrating a second specific example of an electronic apparatus including the electrophoresis apparatus according to the embodiment.

An embodiment according to the present invention will be specifically described according to the following configuration with reference to the drawings. However, the following embodiments are merely examples of the present invention, and do not limit the technical scope of the present invention. In the drawings, the same components are denoted by the same reference numerals.
1. 1. Configuration example of pixel region of electrophoresis apparatus First operation example of pixel region of electrophoretic device (1) Transition of display state from white to black (2) Transition of display state from black to white (3) Maintenance of black display state (4) White 2. Maintain display state 2. Second operation example of pixel region of electrophoretic device (1) Transition of display state from black to white (2) Retention of white display state 4. Configuration example of entire electrophoresis apparatus Example of specific operation of electrophoresis apparatus 6. Examples of using electrophoresis devices

<1. Configuration example of pixel region of electrophoresis apparatus>
The present invention relates to a method for driving an electrophoretic device, and the electrophoretic device can be widely used for, for example, a flexible electro-optical device.

  FIG. 1 is a diagram illustrating a configuration of a pixel region of an electrophoresis apparatus as one embodiment of the present invention. As shown in FIG. 1, the pixel region of the electrophoresis apparatus according to the present embodiment includes a substrate 100, a pixel electrode 110, a counter electrode 120, and a transmissive substrate 130. Further, an electrophoretic element 140 is included between the pixel electrode 110 and the counter electrode 120. The electrophoretic element 140 includes a dispersion medium 150 and a plurality of electrophoretic particles 160 and 170. Here, in the present embodiment, an example in which the first electrophoretic particle 160 is black and the second electrophoretic particle 170 is white having a higher reflectance than the first electrophoretic particle 160 will be described. Hereinafter, the first electrophoretic particles 160 and the second electrophoretic particles 170 are also referred to as “black electrophoretic particles 160” and “white electrophoretic particles 170”, respectively.

<Substrate 100>
The substrate 100 is configured to form a plurality of pixel electrodes 110 on the substrate. Although not shown, a plurality of semiconductor elements for driving the plurality of pixel electrodes 110 are formed on the substrate 100, and the potential of the pixel electrode 110 is reduced by operating these semiconductor elements. Can be changed.

<Pixel electrode 110>
A plurality of pixel electrodes 110 are formed in an array on the substrate as described above, and are configured such that the potential can be changed by a drive circuit described later. Specifically, the pixel electrode 110 has Hi (for example, +10 V), Lo (for example, −10 V), 0 V (also referred to as “ground potential” or “GND”) that is the same potential as the fixed potential of the counter electrode 120, and any It is possible to change to four states of a high impedance state that is not connected to any potential.

<Counter electrode 120>
The counter electrode 120 is formed to face the plurality of pixel electrodes 110 with a material having transparency. One pixel electrode 110 is formed for each pixel, whereas one counter electrode 120 is formed for a plurality of pixel electrodes 110. In general, one counter electrode 120 is formed in common in the entire pixel region of the electrophoretic device, but is not limited thereto. That is, the entire pixel region of the electrophoresis apparatus may be divided into a plurality of blocks, and one counter electrode may be formed in each block. The counter electrode 120 is formed to be fixed at a predetermined potential. In the present embodiment, the counter electrode 120 is described as having a fixed potential of 0 V (also referred to as “ground potential” or “GND”).

<Transparent substrate 130>
The transparent substrate 130 is formed in the viewing surface direction of the counter electrode 120. That is, a person viewing a drawn image of the electrophoretic device views the electrophoretic element 140 through the transmissive substrate 130 and the counter electrode 120 from a direction perpendicular to the substrate surface of the transmissive substrate 130 (upward in the drawing). As a material of the transmissive substrate 130, for example, glass, plastic or the like is used, but is not limited thereto.

<Electrophoretic element 140>
The electrophoretic element 140 has, for example, a round capsule shape, includes a dispersion medium 150 in the capsule, and includes black electrophoretic particles 160 and white electrophoretic particles 170 so as to float on the dispersion medium 150. . In the present embodiment, the electrophoretic element 140 has a round capsule shape. However, the electrophoretic element 140 does not necessarily have to be round, and may have a shape such as a cube. Further, the black electrophoretic particles 160 and the white electrophoretic particles 170 have characteristics that flow in different directions when an electric field is generated in the dispersion medium 150 that is the surrounding medium.

<Operating principle>
The pixel region of the electrophoretic device in the present embodiment has the above-described configuration, and the operation principle will be described here.

  As shown in FIG. 1, the electrophoretic element 140 is disposed between the pixel electrode 110 and the counter electrode 120. Here, as described above, the counter electrode 120 has a fixed potential of 0 V, and the potential of the pixel electrode 110 can be changed by a driving circuit. In other words, a potential difference is generated between the pixel electrode 110 and the counter electrode 120 by changing the potential of the pixel electrode 110 by the driving circuit, and an electric field is generated by this potential difference. When the electric field is generated in this manner, the black electrophoretic particles 160 and the white electrophoretic particles 170 included in the electrophoretic element 140 disposed between the pixel electrode 110 and the counter electrode 120 flow in different directions depending on the Coulomb force. To do. In the present embodiment, when the pixel electrode 110 becomes Hi potential (+10 V), the black electrophoretic particles 160 flow toward the counter electrode 120, and conversely, when the pixel electrode 110 becomes Lo potential (−10 V), white electrophoresis occurs. Particles 170 flow toward the counter electrode 120. When the black electrophoretic particles 160 flow toward the counter electrode 120, the black electrophoretic particles 160 are present near the viewing surface, and the region between the counter electrode 120 and the pixel electrode 110 is in a darker display state. On the contrary, when the white electrophoretic particles 170 flow toward the counter electrode 120, the white electrophoretic particles 170 exist near the viewing surface, and the region between the counter electrode 120 and the pixel electrode 110 has a more whitish display state. Become.

  In the electrophoretic device, each pixel (pixel) constituting a display image corresponds to one pixel electrode. A pixel that has transitioned to a white or black display state at a certain display update timing becomes a display state of the same color or a different color at the next display update timing. That is, there are four display state change patterns: transition from white to black, transition from black to white, black retention, and white retention. Each of these will be discussed below.

<Supplement>
The electrophoretic particles 160 and 170 can be a combination of various two types of colors other than black and white. However, even in this case, it is preferable that one color has a very high reflectance and the other color has a very low reflectance. By using the electrophoretic particles 160 and 170 having colors with greatly different reflectances as described above, it is possible to configure an electrophoretic device with clear contrast and excellent visibility.

  Further, the potentials of Hi, 0V, and Lo in the present embodiment are not limited to + 10V, 0V, and −10V, respectively. That is, these potentials may be a positive potential, the same potential, or a negative potential with respect to the counter electrode 120 as a reference. That is, when the potential of the counter electrode 120 is a predetermined reference potential, the reference potential is used instead of 0V. Further, Hi and Lo can be arbitrarily selected as long as the relationship of Hi> reference potential> Lo is established.

  In this embodiment, the configuration in which the electrophoretic element 140 is disposed between the pixel electrode 110 and the counter electrode 120 has been described. However, the present invention is not limited to this configuration. For example, an electrophoretic layer formed in a layer shape may be provided between the pixel electrode 110 and the counter electrode 120, and the electrophoretic layer may include a dispersion medium 150 and electrophoretic particles 160 and 170. . That is, the electrophoretic device only needs to have a configuration in which the electrophoretic particles 160 and 170 are interposed between the pixel electrode 110 and the counter electrode 120.

<2. First Operation Example of Pixel Region of Electrophoresis Device>
2 to 5 are signal diagrams illustrating a first operation example of the pixel region of the electrophoresis apparatus in the present embodiment.

  2A to 5A, FIG. 2A shows a time change of a voltage applied between the pixel electrode 110 and the counter electrode 120 (hereinafter, also referred to as “between electrodes”) in a certain pixel, and FIG. The time change of the reflectance of the electrophoretic element 140 in the pixel is shown. As already described, since the counter electrode 120 has a predetermined fixed potential in this embodiment, the time change of the voltage applied between the electrodes shown in (a) is the potential applied to the pixel electrode 110. It can also be said that this is a time change.

<(1) Transition of display state from white to black>
Conventionally, when an electrophoretic device is transitioned from a display state of another color to a black display state, first, a Hi voltage (+10 V) is applied between the electrodes in order to transition the electrophoretic device to a black display state. Was. Thereafter, the pixel electrode 110 and the counter electrode 120 were set to the same potential in order to maintain the display state of the electrophoretic device in a black display state. However, in this case, a phenomenon has been observed in which the black display state transitions to a slightly whitish display state. As a result, there has been a problem that the electrophoretic device is not shifted to a desired black display state. The operation example described below solves such a problem.

  FIG. 2 is a diagram illustrating temporal changes in the applied voltage between the electrodes and the reflectance of the electrophoretic device when the electrophoretic device according to the present embodiment transitions from a white color to a black display state.

  In FIG. 2, the reflectivity of the electrophoretic device is high before time t0, and the electrophoretic device is in a white display state. That is, in this display state, the white electrophoretic particles 170 are in the vicinity of the counter electrode 120 and the black electrophoretic particles 160 are in the vicinity of the pixel electrode 110.

  At time t0, the driving circuit applies a Hi potential (+10 V) to the pixel electrode 110, and a Hi voltage is applied between the electrodes. As a result, the reflectance of the electrophoretic device gradually decreases, and reaches the lowest reflectance at time t1. In other words, the electrophoretic device gradually transitions from white to black display state from time t0 to t1, and becomes black display state at time t1. At this time, the white electrophoretic particles 170 gradually flow toward the pixel electrode 110 and the black electrophoretic particles 160 gradually flow toward the counter electrode 120.

  Then, at the time t1 when the reflectivity of the electrophoretic device is reduced, the application of the potential from the driving circuit to the pixel electrode 110 is stopped, and thereby the pixel electrode 110 is brought into a high impedance state (HIZ). That is, in this display state, the white electrophoretic particles 170 are in the vicinity of the pixel electrode 110 and the black electrophoretic particles 160 are in the vicinity of the counter electrode 120.

  Thus, by changing the voltage between the electrodes, the electrophoretic device can be changed from the white display state to the black display state.

  According to the driving method in the present embodiment or the driving circuit configured to be driven as described above, the pixel electrode 110 is applied at a time t1 when a voltage of Hi is applied between the electrodes and then a predetermined time has elapsed. To the high impedance state. Accordingly, it is possible to prevent the display of the electrophoretic device that has once transited to the black display state from returning to the whitish display state, and to cause the electrophoretic device to transition to the desired black display state.

  In the case where the entire region where a certain counter electrode 120 exists is changed to the black display state, the counter electrode 120 is set to the high impedance state instead of the pixel electrode 110 of the counter electrode 120 to the high impedance state. May be. In this case, the drive circuit is configured to be able to change the potential of the counter electrode 120.

  Further, the display state before the time t0 does not necessarily have to be a white display state with high reflectance. For example, it is conceivable that the display is an intermediate color between white and black, and this embodiment includes such a state.

  The time t1 is a time sufficient for the display of the electrophoretic device to be in a desired black display state after applying a Hi voltage between the electrodes. For example, the time t1 is measured in advance in the manufacturing process of the electrophoretic device. It is something to keep. Here, the desired black display state differs depending on the product specifications, but may be arbitrarily determined, for example, set to 99% or 90% of the lowest reflectance expected for the electrophoresis apparatus. . Further, when the next display update (refresh) timing is time t1, and the same black display state should be maintained at the timing, the pixel electrode 110 may be set to the high impedance state.

<(2) Transition of display state from black to white>
FIG. 3 is a diagram illustrating a first example of a temporal change in the applied voltage between the electrodes and the reflectance of the electrophoretic device when the electrophoretic device according to the present embodiment transitions from a black color to a white display state.

  In FIG. 3, the reflectivity of the electrophoretic device is low before time t0, and the electrophoretic device is in a white display state. That is, in this display state, the black electrophoretic particles 160 are in the vicinity of the counter electrode 120, and the white electrophoretic particles 170 are in the vicinity of the pixel electrode 110.

  At time t0, the driving circuit applies a Lo potential (−10 V) to the pixel electrode 110, and a Lo voltage is applied between the electrodes. As a result, the reflectivity of the electrophoresis apparatus gradually increases. However, when the reflectance reaches a certain level, the increase in the reflectance stops, and thereafter the reflectance does not increase even if the Lo voltage is continuously applied between the electrodes. Therefore, at the time t2 when such a state is reached, the pixel electrode 110 and the counter electrode 120 are set to the same potential so that there is no potential difference between the electrodes. As a result, a phenomenon occurs in which the reflectance of the electrophoretic device, which has once stopped increasing, is further increased, whereby the white display state can be made clearer. In other words, the electrophoretic device undergoes a first-stage transition from black to white display state from time t0 to t2, and then performs a second-stage transition to white display state after time t2.

  This phenomenon is thought to stop the increase in reflectivity when the white electrophoretic particles 170 are densely packed in the dispersion medium 150 while the voltage between the electrodes is set to Lo. At this time, if both electrodes are set to the same potential, the electric field around the electrophoretic particles 160 and 170 is removed. Then, it is considered that the reflectance is further increased as a result of the white electrophoretic particles 170 in the dispersion medium 150 being moderately dispersed.

  As described above, the electrophoretic device can be changed from the black display state to the white display state by changing the voltage applied between the electrodes by the drive circuit.

  Note that the display state before the time t0 does not necessarily have to be a black display state with low reflectance. For example, the display may be an intermediate color between white and black. In other words, in the present embodiment, the electrophoretic device includes a state in which the display is in a neutral color at a time before time t0.

  The time t2 is the time from when the Lo voltage is applied between the electrodes until the increase in the reflectance of the electrophoretic device stops. For example, the time t2 is measured in advance in the manufacturing process of the electrophoretic device. is there. Here, the time until the increase in the reflectance of the electrophoresis apparatus stops does not mean only the time until the increase in the reflectance completely stops, but also the state in which the increase in the reflectance is reduced. Including.

  Further, if the application of the voltage from the drive circuit to the pixel electrode 110 is stopped at time t2 and the pixel electrode 110 is thereby brought into a high impedance state, electrophoresis is performed with a slightly lower reflectance instead of the above high reflectance. It is possible to maintain the display state of the device. That is, the electrophoretic device can be displayed in gray, which is an intermediate color between white and black.

<(3) Maintenance of black display state>
Conventionally, in an electrophoretic device, when a black display state is maintained after a transition to a black display state, the pixel electrode 110 and the counter electrode 120 have the same potential. However, in this case, a phenomenon has been observed in which the black display state transitions to a slightly whitish display state. In this case, there has been a problem that the electrophoretic device is not maintained in a desired black display state. The operation example described below solves such a problem.

  FIG. 4 is a diagram illustrating a change over time in the applied voltage between the electrodes when the electrophoresis apparatus according to the present embodiment is held in a black display state.

  In FIG. 4, the electrophoretic device is in a black display state before the time t0. That is, in this display state, the black electrophoretic particles 160 are in the vicinity of the counter electrode 120, and the white electrophoretic particles 170 are in the vicinity of the pixel electrode 110.

  At time t0, the driving circuit stops applying a potential to the pixel electrode 110. As a result, the pixel electrode 110 enters a high impedance state. Actually, the electrophoretic device is in a black display state before the time t0, and the pixel electrode 110 is not supplied with a potential from the driving circuit and is in a high impedance state. .

  According to the driving method in the present embodiment or the driving circuit configured to be drivable as described above, the pixel electrode 110 is held in a high impedance state. Accordingly, the display of the electrophoretic device can be prevented from transitioning to a whitish display state, and the black display state can be maintained.

<(4) Maintenance of white display state>
FIG. 5 is a diagram illustrating a change over time in the applied voltage between the electrodes when the electrophoresis apparatus according to the present embodiment is held in a white display state.

  In FIG. 5, the electrophoretic device is in a white display state before the time t0. That is, in this display state, the white electrophoretic particles 170 are in the vicinity of the counter electrode 120 and the black electrophoretic particles 160 are in the vicinity of the pixel electrode 110.

  At time t0, the driving circuit applies a voltage of 0 V to the pixel electrode 110. As a result, the pixel electrode 110 and the counter electrode 120 have the same potential. Actually, the electrophoretic device is in a white display state before the time t0, and the pixel electrode 110 is already in the state of 0 V, which is the same potential as the counter electrode 120. Hold.

  According to the driving method in the present embodiment or the driving circuit configured to be drivable as described above, the pixel electrode 110 and the counter electrode 120 are connected to each other after the electrophoretic device is shifted to the white display state. The voltage of the pixel electrode 110 is driven so as to be a potential. As a result, a white display state can be maintained.

<3. Second Operation Example of Pixel Region of Electrophoresis Device>
<(1) Transition of display state from black to white>
FIG. 6 is a diagram illustrating a second example of a temporal change in the applied voltage between the electrodes and the reflectance of the electrophoretic device when the electrophoretic device is transitioned from a black color to a white display state. This example includes the same part as the transition of the display state from black to white in the first operation example of the pixel region of the electrophoresis apparatus described with reference to FIG. Specifically, in the second operation example, in addition to changing the potential applied from the drive circuit to the pixel electrode 110 at time t2, the potential applied from the drive circuit to the pixel electrode 110 is also changed at time t3. Hereinafter, the operation after time t3, which is a difference from the first operation example, will be mainly described.

  In FIG. 6, when the pixel electrode 110 is set to 0 V at the time t2 to be the same potential as the counter electrode 120, the reflectivity of the electrophoretic device gradually increases. Then, after the reflectance of the electrophoretic device increases to some extent, the increase stops at time t3. That is, as already described, by setting the pixel electrode 110 and the counter electrode 120 to the same potential, the white electrophoretic particles 170 in the dispersion medium 150 are appropriately dispersed. However, after the elapse of a predetermined time (here, the time from time t2 to time t3), the dispersion of the white electrophoretic particles 170 becomes stable, and further dispersion is achieved even if both electrodes are set to the same potential. Does not occur and the reflectivity does not increase.

  Therefore, at time t3, the voltage application from the drive circuit to the pixel electrode 110 is stopped, and thereby the pixel electrode 110 is brought into a high impedance state. Even if it does in this way, the fall of a reflectance will not occur like the case where the electric potential of the pixel electrode 110 and the counter electrode 120 is made into the same electric potential.

  By driving the electrophoretic device as described above, the reflectance of the electrophoretic device that has once transitioned to the white display state is reduced, and it is prevented from returning to the black display state. The display state can be changed to a white display state.

  The time t3 is the time from when the pixel electrode 110 and the counter electrode 120 are set to the same potential until the increase in the reflectance of the electrophoretic device stops. For example, the time t3 is measured in advance in the manufacturing process of the electrophoretic device. It is something to keep. However, the time t3 may be determined at the time when the reflectance becomes equal to or higher than the desired reflectance without waiting for the increase in the reflectance of the electrophoresis apparatus to completely stop. That is, the time t3 may be arbitrarily determined, for example, by setting the time when the reflectance of the electrophoresis apparatus reaches 99% or 90% of the highest expected reflectance. Further, when the next display update (refresh) timing is time t3 and the same white display state should be maintained at the timing, the pixel electrode 110 may be set in a high impedance state.

  In addition, in order to achieve a desired reflectance, the voltage application from the driving circuit to the pixel electrode 110 is stopped at time t2, and thereby the pixel electrode 110 can be brought into a high impedance state. In this case, the display state of the electrophoretic device can be held with a slightly lower reflectance instead of the above high reflectance.

<(2) Maintenance of white display state>
FIG. 7 is a diagram illustrating a second example of the change over time in the applied voltage between the electrodes when the electrophoresis apparatus is held in a white display state. This example achieves the same purpose as the maintenance of the white display state in the first operation example of the pixel region of the electrophoresis apparatus described with reference to FIG. 5, but there is a difference in the operation. . That is, in the second operation example, as shown in FIG. 7, instead of setting the pixel electrode 110 and the counter electrode 120 to the same potential at time t <b> 0, the pixel electrode 110 is placed in a high impedance state, thereby performing electrophoresis. Hold the device in the white display state.

  According to the driving method in the present embodiment or the driving circuit configured to be drivable as described above, a potential is applied from the driving circuit to the pixel electrode 110 after the electrophoretic device is shifted to the white display state. And the pixel electrode 110 is put into a high impedance state. Accordingly, it is possible to prevent the reflectance from being lowered in the display of the electrophoretic device and to maintain the white display state.

<4. Configuration example of the entire electrophoresis apparatus>
FIG. 8 is a diagram illustrating a configuration example of the entire electrophoresis apparatus. As shown in FIG. 8, the electrophoretic device 200 includes a pixel region 210, a scanning line driving circuit 220, a data line driving circuit 230, a counter electrode control circuit 240, and a driving circuit 250.

  The pixel region 210 according to the present embodiment includes a plurality of pixels, and these pixels include a substrate 100, a pixel electrode 110, a counter electrode 120, a transmissive substrate 130, and an electrophoretic element 140. On the other hand, in the peripheral region of the pixel region 210, a scanning line driving circuit 220, a data line driving circuit 230, and a counter electrode control circuit 240 are formed. In the pixel region 210, a plurality of scanning lines 201 are formed in parallel along the X direction shown in the figure. In addition, a plurality of data lines 202 are formed in parallel along the Y direction orthogonal thereto. Each pixel is arranged in a matrix corresponding to the intersection of the scanning line 201 and the data line 202.

  A drive circuit 250 is provided in the peripheral circuit of the electrophoresis apparatus 200. The drive circuit 250 includes a display signal generator and a timing generator. Here, the display signal generation unit generates an image signal and a counter electrode control signal, and inputs them to the data line driving circuit 230 and the counter electrode control circuit 240, respectively. The counter electrode control circuit 240 supplies 0 V as a reference voltage to the counter electrode. Further, the timing generator generates various timing signals for controlling the scanning line driving circuit 220 and the data line driving circuit 230 when a reset setting or an image signal is output from the display signal generation unit.

<5. Example of specific operation of electrophoresis apparatus>
FIG. 9 is a first diagram illustrating an example of a specific operation of the electrophoresis apparatus. As shown in FIG. 9, the display of “Check me” is displayed on the electrophoresis apparatus 200, and an operation of underlining the display will be described as an example.

  The electrophoretic device 200 includes a touch sensor capable of sensing the pressure when a pressure is applied to the surface of the device with a predetermined strength. When the character “Check me” displayed on the electrophoretic device 200 is operated to be underlined using the writing device 400, the touch sensor displays the location where pressure is applied by the writing device 400. Sense and send information about the location to the drive circuit 250. Based on this information, the drive circuit 250 identifies a portion to be changed from the white display state to the black display state, and outputs a signal for making a desired display to the scanning line drive circuit 220 and the data line drive circuit. 230.

  FIG. 10 is a second diagram illustrating an example of a specific operation of the electrophoresis apparatus. In FIG. 10, the scanning line driving circuit 220 designates one of the scanning lines 201 to change the display state in the pixel region 210. The data line driving circuit 230 applies a desired voltage to each pixel electrode 110 in one of the scanning lines 201 whose display state should be changed. In the example of this embodiment, the underlined portion of the display “Check me” to which pressure is applied by the writing device 400 is changed from white to black, and the other portions remain in white. Need to hold.

  Therefore, the data line driving circuit 230 first applies a Hi voltage (+10 V) to the pixel electrode 110 of the electrophoretic device 200 where it is desired to transition from the white to the black display state. Then, the data line driving circuit 230 stops applying the voltage to the pixel electrode 110 after the time t1 has elapsed, whereby the pixel electrode 110 enters a high impedance state. On the other hand, the data line driving circuit 230 stops applying a voltage to the portion of the electrophoretic device 200 that is desired to be kept in the white display state and puts it in a high impedance state. When it is necessary to change the display state of the pixel region 210 over a plurality of scanning lines 201, the above processing is repeated for the necessary scanning lines 201.

  By doing so, as shown on the right side of FIG. 10, only the underlined portion of the “Check me” display is shifted from the white to the black display state, and the other portions remain in the white display state. Can be held.

  Note that, instead of applying 0 V, which is the same potential as the counter electrode 120, to the pixel electrode 110 where the white display state is to be maintained, 0 V, which is the same potential as the counter electrode 120, may be applied to the pixel electrode 110. . Even in this case, a white display state can be maintained.

<6. Examples of use of electrophoresis apparatus>
11 and 12 are diagrams illustrating specific examples of electronic apparatuses including the electrophoresis apparatus according to the present embodiment. FIG. 11 shows an example in which the electrophoretic device 200 of the present embodiment is applied to a touch panel type display device 500. FIG. 12 shows an example in which the electrophoresis apparatus 200 of this embodiment is applied to an electronic book 600. The electronic book 600 includes an electrophoresis device 200, a lid 601, operation buttons 602, and an outer frame 603. The electronic book 600 can write a memo in the electrophoresis apparatus 200.

  Thus, by providing the electrophoresis apparatus 200 of the present embodiment, for example, when a part of the display is to be changed to the black display state, the display once changed to the black display state is then displayed as a whitish display. It is possible to prevent returning to the state. Accordingly, it is possible to make electronic devices such as the display device 500 and the electronic book 600 transition to a desired display state or hold in a desired display state.

<Supplement>
In the present embodiment, the portion described as an example of setting the pixel electrode 110 to high impedance can be substituted by setting the counter electrode 120 to a high impedance state. That is, the same effect can be obtained by setting the counter electrode 120 in a high impedance state instead of the pixel electrode 110.

  In the present embodiment, an example in which the drive circuit is configured to be able to change the potential of at least one of the pixel electrode 110 and the counter electrode 120 has been described. The voltage change by the drive circuit is not necessarily made directly, but may be made indirectly through another circuit or the like.

  Further, the time for changing the potential applied to the pixel electrode 110 in the present embodiment may be changed according to conditions such as the temperature of the dispersion medium 150 in the electrophoresis apparatus. This is because the ease of flow of the electrophoretic particles 160 and 170 in the dispersion medium 150 changes as the temperature of the dispersion medium 150 changes. The temperature of the dispersion medium 150 may be a method in which the temperature of the dispersion medium 150 is directly measured, or the ambient temperature is measured and estimated from the ambient temperature.

DESCRIPTION OF SYMBOLS 100 ... Substrate, 110 ... Pixel electrode, 120 ... Counter electrode, 130 ... Transparent substrate, 140 ... Electrophoretic element, 150 ... Dispersion medium, 160 ... First electrophoretic particle (black electrophoretic particle), 170 ... Second Electrophoretic particles (white electrophoretic particles), 200 ... electrophoresis device, 201 ... scanning line, 202 ... data line, 210 ... pixel region, 220 ... scanning line driving circuit, 230 ... data line driving circuit, 240 ... counter electrode Control circuit 250 ... Drive circuit 400 ... Writing device 500 ... Display device 600 ... Electronic book 601 ... Cover part 602 ... Operation button 603 ... Outer frame part

Claims (11)

An electrophoretic device driving method in which electrophoretic particles are interposed between a first electrode and a second electrode,
A method for driving an electrophoretic device, wherein after making a transition to a display state based on the color of the electrophoretic particles, one of the first electrode and the second electrode is brought into a high impedance state. An electrophoretic device driving method in which electrophoretic particles are interposed between a first electrode and a second electrode,
After the transition to the display state based on the color of the electrophoretic particles, either one of the first electrode and the second electrode is in a high impedance state, or the first electrode and the second electrode A method for driving an electrophoresis apparatus. An electrophoretic device driving method in which electrophoretic particles are interposed between a first electrode and a second electrode,
When transitioning the electrophoretic device to a display state by the color of the electrophoretic particles,
Applying a first voltage between the first electrode and the second electrode;
After the first time has elapsed since the first voltage was applied between the first electrode and the second electrode, either one of the first electrode and the second electrode is set to high. A method for driving an electrophoretic device in an impedance state. An electrophoretic device driving method in which electrophoretic particles are interposed between a first electrode and a second electrode,
When transitioning the electrophoretic device to a display state by the color of the electrophoretic particles,
Applying a second voltage between the first electrode and the second electrode;
After the second time has elapsed since applying the second voltage between the first electrode and the second electrode, the first electrode and the second electrode are set to the same potential,
An electrophoretic device that places either the first electrode or the second electrode in a high-impedance state after a third time has elapsed since the first electrode and the second electrode are set to the same potential Driving method. An electrophoretic device driving method in which electrophoretic particles are interposed between a first electrode and a second electrode,
When transitioning the electrophoretic device to a display state by the color of the electrophoretic particles,
Applying a first voltage between the first electrode and the second electrode;
After the first time has elapsed since the first voltage was applied between the first electrode and the second electrode, either one of the first electrode and the second electrode is set to high. To impedance state,
The method for driving an electrophoresis apparatus according to claim 4. A drive circuit for driving an electrophoretic device in which electrophoretic particles are interposed between a first electrode and a second electrode;
A drive circuit for an electrophoretic device configured to bring one of the first electrode and the second electrode into a high impedance state after transitioning to a display state based on the color of the electrophoretic particles. A drive circuit for driving an electrophoretic device in which electrophoretic particles are interposed between a first electrode and a second electrode;
After the transition to the display state based on the color of the electrophoretic particles, either one of the first electrode and the second electrode is in a high impedance state, or the first electrode and the second electrode An electrophoretic device drive circuit configured to have the same potential. A drive circuit for driving an electrophoretic device in which electrophoretic particles are interposed between a first electrode and a second electrode;
When transitioning the electrophoretic device to a display state by the color of the electrophoretic particles,
Applying a first voltage between the first electrode and the second electrode;
After the first time has elapsed since the first voltage was applied between the first electrode and the second electrode, either one of the first electrode and the second electrode is set to high. An electrophoretic device drive circuit configured to be in an impedance state. A drive circuit for driving an electrophoretic device in which electrophoretic particles are interposed between a first electrode and a second electrode;
When transitioning the electrophoretic device to a display state by the color of the electrophoretic particles,
Applying a second voltage between the first electrode and the second electrode;
After the second time has elapsed since applying the second voltage between the first electrode and the second electrode, the first electrode and the second electrode are set to the same potential,
The first electrode and the second electrode are configured to be in a high impedance state after the third time has elapsed after the first electrode and the second electrode are set to the same potential. The drive circuit of the electrophoresis apparatus. A first electrode;
A second electrode;
Electrophoretic particles disposed between the first electrode and the second electrode;
An electrophoretic device comprising: the drive circuit according to claim 6.   An electronic apparatus comprising the electrophoresis apparatus according to claim 10.