JP2009134245A - Drive method for electrophoretic display device and electrophoretic display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive method for an electrophoretic display device which suppresses flicker and achieves sufficient reflectance (contrast) with a single write operation. <P>SOLUTION: The electrophoretic display device 3 includes: a display panel 30 having electrophoretic particles; a drive circuit 43 to drive the electrophoretic display element by applying voltage between the common electrode and the pixel electrodes; and a controller 42 to control the drive circuit 43. The controller 42 has a displayed image redrawing step of changing the displayed image by applying a common electrode drive pulse that repeats two different potentials to the common electrode, and applying either of the two different potentials to the pixel electrodes according to the updated display content, the displayed image redrawing step further includes applying a first pulse train to the common electrode, and applying a second pulse train, to the common electrode, each pulse of the second pulse train having a longer width than that of each pulse of the first pulse train. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophoretic display device driving method and an electrophoretic display device.

  When an electric field is applied to a dispersion liquid in which electrophoretic particles are dispersed in a solution, a phenomenon (electrophoresis phenomenon) in which electrophoretic particles migrate due to Coulomb force is known. Electrophoretic display using this phenomenon Equipment has been developed. However, the conventional electrophoretic display device still has much room for improvement in image quality.

For example, as a typical driving method for a liquid crystal display or other displays, a method of making the potential of the pixel electrode variable and also making the potential of the common electrode variable (usually called common swing) is known. A driving method of this common swing has also been proposed for electrophoretic display devices (see Patent Document 1).
According to this driving method, the potentials of the pixel electrode and the common electrode can be controlled by binary values of a high potential and a low potential. Therefore, the driving potential can be lowered, the circuit configuration is simplified, and the manufacturing can be performed at low cost. Further, when a TFT (Thin Film Transistor) is used as the drive circuit, the reliability of the TFT can be ensured by reducing the drive potential.

JP-A 52-70791

However, this common driving method has the following problems.
For example, when a pulse signal having a pulse width of 200 milliseconds is applied to the common electrode and the common swing is performed, flicker occurs and the user feels stress. That is, when driving by common swing is performed, flicker is likely to occur because the color change is rapid especially in the initial stage of driving.
As a countermeasure, flicker can be prevented by inputting a short pulse, for example, a pulse signal having a pulse width of 20 milliseconds, and flickering can be prevented. However, since the pulse width of the voltage applied is short, Cannot be moved, and there is a problem that only a slightly low reflectance can be obtained.
Furthermore, when a pulse signal with a short pulse width is used, sufficient reflectivity cannot be obtained with a single write. For this reason, for example, in an electrophoretic display device using white and black electrophoretic particles, the reflectance of a pixel rewritten from white display to white display is different from that of a pixel rewritten from black display to white display. The problem of unevenness and afterimages also occurred.

  Accordingly, an object of the present invention is to provide an electrophoretic display device driving method and an electrophoretic display device capable of suppressing the occurrence of flicker and obtaining a sufficient reflectance (contrast) by one writing. is there.

  An electrophoretic display device driving method according to the present invention includes an electrophoretic element in which a dispersion containing electrophoretic particles is interposed between a common electrode and a plurality of pixel electrodes, the common electrode, and the plurality of pixel electrodes. Driving means for driving the electrophoretic display element by applying a voltage between them and a control means for controlling the driving means, wherein the common electrode includes two driving means. A common electrode driving pulse for repeating two different potentials, and an image rewriting step for changing an image by applying one of the two different potentials to each pixel electrode in accordance with display update contents, The rewriting step is performed after the first pulse applying step of applying a first pulse to the common electrode as the common electrode driving pulse, and after the first pulse applying step, and is used as the common electrode driving pulse. Characterized in that it comprises a second pulse application step of applying a second pulse width being longer than the first pulse to the common electrode.

Here, specific examples of the pulse widths of the first pulse and the second pulse are set according to the characteristics of the electrophoretic display device to be driven.
Specifically, the pulse width of the first pulse is as long as possible within a range in which flicker does not occur when the first pulse is applied to the electrophoretic display device to be driven in the first half of the image rewriting process. Just make it wide. That is, if a pulse having a relatively long pulse width is applied in the first half of the image rewriting process, flicker may occur because the color change is rapid at the initial stage of driving by common swing. On the other hand, if a pulse with a short pulse width is applied, flicker can be prevented, but rewriting of an image takes time. Therefore, it is preferable that the first pulse applied in the first half of the image rewriting process has a pulse width as long as possible within a range in which flicker does not occur.
On the other hand, the pulse width of the second pulse is such that when the second pulse is applied to the electrophoretic display device to be driven in the latter half of the image rewriting process, the contrast of the display image can be increased and the retention property can be maintained. What is necessary is just to set to the range which can prevent deterioration. That is, in the second half of the image rewriting process, even if a pulse longer than the first pulse width is applied, the color change becomes dull due to saturation, and flicker is unlikely to occur. Since the contrast increases as the second pulse width is increased, the lower limit of the pulse width of the second pulse may be set so that the contrast ratio is equal to or greater than a predetermined value set in advance. Further, since it has been confirmed by the inventors' experiments that if the second pulse width is too long, the retention of the rewritten image decreases, the upper limit of the pulse width of the second pulse is a value that does not decrease the image retention. Should be set.

As described above, the pulse widths of the first pulse and the second pulse may be set according to the characteristics of the electrophoretic display device to be driven. For example, the pulse width of the first pulse may be set to less than 25 milliseconds, and the pulse width of the second pulse may be set to 25 milliseconds or more. For example, the pulse width of the first pulse may be set to 20 milliseconds and the pulse width of the second pulse may be set to 100 to 200 milliseconds.
The pulse width means a pulse length of a signal portion of V1 = H level in a pulse signal that alternately applies two different potentials, for example, two different potentials of V1 = H level and V2 = L level. To do. Since the pulse width of V1 = H level and the pulse width of V2 = L level are usually the same, the pulse width may be the pulse length of the signal portion of V2 = L level.

According to the present invention, in the image rewriting process for rewriting an image, the first pulse applying process is performed first, and then the second pulse applying process is performed, thereby changing the pulse width of the pulse signal applied to the common electrode. be able to.
Here, since the first pulse has a shorter pulse width than the second pulse, the amount of movement of the electrophoretic particles is reduced, but the occurrence of flicker as perceived by the user can be prevented.
On the other hand, since the second pulse has a longer pulse width than the first pulse, there is a risk of flickering as perceived by the user. However, the amount of movement of the electrophoretic particles can be increased and, for example, black Electrophoretic particles can be moved until sufficient reflectivity is obtained for display or white display.
Therefore, in the present invention, for example, a section where flicker becomes conspicuous when the second pulse is applied, for example, a section from the start of change from black display to the time when the display approaches white display to some extent when changing from black display to white display. In the first half of the image rewriting process, when the first pulse is applied and flicker is not noticeable even when the second pulse is applied, for example, when changing from black display to white display, The second pulse can be applied in the section (second half of the image rewriting process).
For this reason, generation | occurrence | production of a flicker can be suppressed and sufficient reflectance (contrast) can be obtained by one-time writing.

In the present invention, the image rewriting step performs the first pulse applying step until the reflectance of the changed image reaches a threshold value set to at least 80% of a target limit reaching reflectance, After reaching the threshold, it is preferable to execute the second pulse applying step.
Here, the target limit reaching reflectance means a reflectance set as a target in designing an electrophoretic display device in consideration of current consumption, display response, and the like.
For example, the limit reaching reflectance for black display can be set to 4%, or can be set to another reflectance such as 6%. In the case of black display, the smaller the reflectance, the higher the contrast with the white display and the display quality can be improved. However, since the amount of movement of the black particles also increases, the power consumption increases and the display response decreases. Therefore, the limit reaching reflectance for black display may be set in consideration of the balance between display quality, power consumption, display response, and the like.
Similarly, the limit reaching reflectance for white display can be set to 47%, or can be set to another reflectance such as 45%. In the case of white display, the greater the reflectance, the higher the contrast with the black display and the display quality can be improved, but the amount of movement of white particles also increases, resulting in an increase in power consumption and a decrease in display response. Therefore, the limit reaching reflectance for white display may be set in consideration of the balance between display quality, power consumption, display response, and the like.
For example, when the limit reaching reflectance targeted for white display is set to 47%, and the image is updated from black display to white display, the threshold is set to 90% of the limit reaching reflectance. The first pulse application step is executed until the reflectance reaches a threshold value of 47% × 0.9 = 42.3%, and the second pulse application step is executed when the threshold value reaches 42.3%.
On the other hand, assuming that the target ultimate reflectance for black display is set to 4% and the image is updated from white display to black display, and the threshold is set to 90% of the critical ultimate reflectance, the reflectance The first pulse application step is executed until the threshold value reaches 13.6%, and the second pulse application step is executed when the threshold value reaches 13.6%. The black display threshold value may be obtained by replacing 0% reflectance with -100%. That is, reflectivity 4% = 4-100 = −96%, −96% × 0.9 = −86.4%, and threshold = 100−86.4 = 13.6%.

According to the present invention, since the first pulse is applied and driven until the reflectance reaches the threshold value that is a predetermined ratio of the target limit reaching reflectance, the occurrence of flicker can be prevented. That is, flicker is likely to occur because the color change is rapid in the first half of driving for rewriting to a different color, but in the present invention, the first half of driving until the reflectance reaches the threshold is the first pulse having a short pulse width. Since one pulse is applied, occurrence of flicker can be prevented.
On the other hand, when the reflectance exceeds the threshold value, the second pulse is applied to drive the reflectance, so that the reflectance can be sufficiently increased and display quality can be improved. That is, in the second half of the driving for rewriting to a different color, the movement of each particle is also saturated, and the color change is slowed down, so that flicker hardly occurs. In the present invention, since the second pulse having a long pulse width is applied in the second half of driving after the reflectance reaches the threshold value, display quality can be improved while preventing the occurrence of flicker.
In addition, what is necessary is just to set the said threshold value in 80 to 90% of range normally. If the threshold value is less than 80%, the reflectance change rate becomes a large region, and flicker may be noticeable when switching to the second pulse. On the other hand, when the threshold value is 90% or more, the period for driving with the first pulse becomes long, and the time until the target limit achievement rate is reached becomes long. Therefore, although depending on the characteristics of the electrophoretic display device, the threshold value is usually set to about 80 to 90%.
However, depending on the electrophoretic display device, necessary characteristics may be ensured even if the threshold is set to less than 80% or 90% or more of the limit reaching reflectance. In such a case, the threshold value may be set to less than 80% or 90% or more of the limit reaching reflectance. That is, the threshold value may be set according to the characteristics of the electrophoretic display device to which the present invention is applied.

In the present invention, the pulse width of the second pulse is preferably in the range of 2 to 30 times the pulse width of the first pulse.
If the pulse width of the second pulse is less than twice the pulse width of the first pulse, the difference in pulse width of each pulse is small, so there is not much difference in characteristics when switching pulses, and effective drive control Can not do.
On the other hand, when the pulse width of the second pulse is larger than 30 times the pulse width of the first pulse, the difference in characteristics when the pulses are switched is too large, and effective drive control cannot be performed. Furthermore, if the pulse width of the second pulse is too large, the display retention may be deteriorated after the driving is completed.
On the other hand, if the pulse width of the second pulse is set in the range of 2 to 30 times the pulse width of the first pulse as in the present invention, the balance of the characteristic change when each pulse is switched is good. Thus, effective drive control can be performed, and deterioration of display retention can be prevented.
However, depending on the electrophoretic display device, necessary characteristics may be ensured even if the pulse width of the second pulse is slightly changed from the range of 2 to 30 times the pulse width of the first pulse. In such a case, the pulse width of the second pulse may be set in a range exceeding 2 to 30 times the pulse width of the first pulse.

In the present invention, the electrophoretic element includes a first color electrophoretic particle for performing a first color display and a second color electrophoretic particle for performing a second color display. The electrophoretic particles and the second color electrophoretic particles have different particle sizes. The common electrode drive pulse repeats a first color writing voltage for changing an image to a first color display and a second color writing voltage for changing an image to a second color display. The last pulse of the common electrode driving pulse in the image rewriting step is a voltage for writing the first color when the electrophoretic particles of the first color are larger than the electrophoretic particles of the second color, When the electrophoretic particles of two colors are larger than the electrophoretic particles of the first color, the voltage for writing the second color is preferable.
In the electrophoretic display device, second color particles (for example, black particles) and first color particles (for example, white particles) are arranged in a dispersion within a microcapsule. For this reason, when the size of each particle is different, the larger particle has a larger resistance during movement and is difficult to move. Furthermore, if the last pulse in the image rewriting process is a pulse for driving large particles, the large particles can be moved further toward the capsule wall, and the contrast can be improved.
For example, when the first color particle is larger than the second color particle, the reflectivity may drop at the final time when the second color write voltage is applied last after the first color write voltage is applied. is there.
On the other hand, if the voltage for writing the first color is applied last as in the present invention, it is possible to prevent the reflectivity from dropping at the final time point.

At this time, when the electrophoretic particles of the first color are larger than the electrophoretic particles of the second color, the first pulse of the common electrode driving pulse in the image rewriting process is a voltage for writing the first color. If the electrophoretic particles of the second color are larger than the electrophoretic particles of the first color, the first pulse of the common electrode driving pulse in the image rewriting process is a voltage for writing the second color. It is preferable.
In the present invention, the common electrode driving pulse starts with application of a voltage for writing large particles, and then continues to alternately apply a voltage for writing each particle, and finally applies a voltage for writing large particles. Will do. For example, when the first color particle is larger than the second color particle, the first color writing voltage starts and then the second color writing voltage and the first color writing voltage are applied alternately. Then, finally, the voltage for writing the first color is applied.
That is, according to the present invention, the number of times of applying the voltage for writing large particles can be made larger than the number of times of applying the voltage for writing small particles.
In the electrophoretic display device, particles having a large particle size move at a slower speed than particles having a small size. Therefore, by increasing the number of times of voltage application for writing large particles, large particles having a low moving speed can be sufficiently moved, and display quality can be improved.

  The electrophoretic display device of the present invention includes an electrophoretic element in which a dispersion containing electrophoretic particles is interposed between a common electrode and a plurality of pixel electrodes, and the common electrode and the plurality of pixel electrodes. An electrophoretic display device comprising: a driving means for applying a voltage to the electrophoretic display element to drive the electrophoretic display element; and a control means for controlling the driving means, wherein the control means repeats two different potentials in common. Image rewriting means for applying an electrode driving pulse to the common electrode and changing the image by applying one of the two different potentials to each pixel electrode according to the display update content, the image rewriting means, A first pulse applying unit that applies a first pulse to the common electrode as the common electrode driving pulse; and the first pulse applying unit that is operated after the first pulse is applied to the common electrode by the first pulse applying unit; Pulse width than the first pulse as the drive pulse; and a second pulse applying unit applying a long second pulse to the common electrode.

According to the present invention, since the image rewriting means for rewriting an image includes the first pulse applying unit and the second pulse applying unit, the pulse width of the pulse signal applied to the common electrode can be changed.
Here, since the first pulse has a shorter pulse width than the second pulse, the amount of movement of the electrophoretic particles is reduced, but the occurrence of flicker as perceived by the user can be prevented.
On the other hand, since the second pulse has a longer pulse width than the first pulse, there is a risk of flickering as perceived by the user. However, the amount of movement of the electrophoretic particles can be increased and, for example, black Electrophoretic particles can be moved until sufficient reflectivity is obtained for display or white display.
Therefore, in the present invention, for example, when the second pulse is applied, the flicker becomes conspicuous, for example, when changing from black display to white display, from the start of change from black display to the time when the white display approaches to some extent. When one pulse is applied and the flicker is not noticeable even when the second pulse is applied, for example, when changing from black display to white display, the second pulse can be applied after approaching white display to some extent. .
For this reason, generation | occurrence | production of a flicker can be suppressed and sufficient reflectance (contrast) can be obtained by one-time writing.

  According to the method for driving an electrophoretic display device and the electrophoretic display device of the present invention, generation of flicker can be suppressed, and sufficient reflectance (contrast) can be obtained by one writing.

Embodiments of the present invention will be described below with reference to the drawings.
In addition, regarding the description after the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS.
[1. overall structure]
FIG. 1 is a front view of an electronic timepiece 1 using the electrophoretic display device of the present embodiment. The electronic timepiece 1 includes a rectangular annular case 2 and an electrophoretic display device 3. The case 2 is provided with a crown 5 and buttons 6 and 7.

[2. Configuration of electrophoretic display device]
As shown in FIG. 2, the electrophoretic display device 3 includes a display panel 30 and drive control means 40 that drives the display panel 30 and includes a timer unit.

[3. Configuration of drive control means]
The drive control means 40 includes a power source 41, a controller 42 that controls the entire timepiece 1, a drive circuit 43, a detection circuit 44, and a timer 45.
The drive circuit 43 includes a driver IC and executes display control of the display panel 30. The detection circuit 44 detects the operation of the crown 5 and the buttons 6 and 7. The clock unit 45 includes a crystal oscillation circuit and clocks time.
The controller 42 constitutes the control means of the present invention, and the drive circuit 43 constitutes the drive means.

The controller 42 controls the driving circuit 43 and includes a data transfer unit 421 and an image rewriting unit 422. The image rewriting unit 422 includes a first pulse applying unit 423 and a second pulse applying unit 424.
The data transfer unit 421 includes an image signal processing circuit and a timing generator. The data transfer unit 421 generates display data indicating images and characters to be displayed on the display panel 30, refresh data for maintaining display, and the like, and outputs them to the drive circuit 43.
In addition, the image rewriting unit 422 is pulsed to the common electrode (not shown in FIG. 2) by the first pulse applying unit 423 and the second pulse applying unit 424 in conjunction with the output of display data and refresh data from the data transfer unit 421. A signal (common electrode drive pulse) is output.

The drive circuit 43 controls the display panel 30 based on a signal output from the controller 42. In this embodiment, as will be described later, the display panel 30 is an active matrix drive and includes a circuit such as a low-temperature polysilicon TFT for driving each pixel.
Therefore, the driving circuit 43 includes a scanning line driving circuit 431 that outputs a predetermined scanning line signal to the scanning line of the TFT circuit, and a data line driving circuit 432 that outputs a predetermined data line signal to the data line of the TFT circuit. I have.

[4. Display panel configuration]
As shown in FIG. 3, the display panel 30 is configured by laminating a front glass 31, a common electrode 32, an electrophoretic layer 33, a pixel electrode 34, a TFT circuit layer 35, and a back glass 36 from the front side. The front glass 31 and the back glass 36 are not limited to transparent glass, and may be made of a transparent resin.
The TFT circuit layer 35 includes a scanning line driving circuit 431 and a TFT circuit driven by the scanning line driving circuit 431. As schematically shown in FIG. 2, the TFT circuit layer 35 includes a plurality of scanning lines 351 and a plurality of data lines 352 arranged orthogonal to each other. A switching transistor or a memory cell (not shown) is provided at the intersection of the scanning line 351 and the data line 352. Each transistor is connected to a pixel electrode 34 provided for each pixel and controls voltage supply to the pixel electrode 34.

  On the other hand, the common electrode 32 is made of a transparent electrode material such as ITO (Indium Tin Oxide). The common electrode 32 is provided over substantially the entire display panel 30. That is, the pixel electrode 34 is provided for each pixel of the display panel 30, but the common electrode 32 is common to each pixel.

  The electrophoretic layer 33 includes a plurality of microcapsules 330 bonded to the common electrode 32. As shown in FIG. 4, the microcapsule 330 encloses an electrophoretic particle dispersion in which a large number of charged particles are dispersed. In the electrophoretic particle dispersion liquid, black electrophoretic particles (hereinafter referred to as black particles) 331 and white electrophoretic particles (hereinafter referred to as white particles) 332 are dispersed, and two-color powder fluid type electricity is used. An electrophoretic layer is configured. The black particles 331 and the white particles 332 are charged with different polarities, and in this embodiment, the black particles 331 are charged negative (negative) and the white particles 332 are charged positive (positive).

In the present embodiment, the diameter of the microcapsule 330 is about 30 μm (0.03 mm), the diameter of the black particles 331 is 10 to 30 nm, and the diameter of the white particles 332 is 100 to 300 nm.
As shown in FIG. 3, the width dimension L1 of the pixel electrode 34 is about 0.09 mm, and the width dimension L2 of the gap between the pixel electrodes 34 is about 0.01 mm.
In this embodiment, the first color is white, and the white particles 332 form the first color particles. The second color is black, and the black particles 331 constitute second color particles.

  The side surface of the display panel 30 is sealed with a sealing agent or the like provided across the front glass 31 and the back glass 36. The electrophoretic layer 33 and the like are hermetically sealed by the front glass 31, the back glass 36, and the sealant.

[5. Display by electrophoresis]
The black particles 331 and the white particles 332 of each microcapsule 330 are electrophoresed by generating a potential difference between the common electrode 32 and the pixel electrode 34, and the display of each microcapsule 330 when viewed from the surface glass 31 side. The color changes.
That is, when the pixel electrode 34 is at a low level potential (L potential, “−” in FIG. 3) and the common electrode 32 is at a high level potential (H potential), the common electrode 32 changes to the pixel electrode 34 due to the potential difference. An electric field is generated. For this reason, the positively charged white particles 332 move to the pixel electrode 34 side, and the negatively charged black particles 331 move to the common electrode 32 side. Therefore, a portion where the potential of the pixel electrode 34 is lower than the potential of the common electrode 32 is displayed in black when viewed from the surface glass 31 side.

Contrary to the black display, when the pixel electrode 34 is set to a high level potential (H potential, “+” in FIG. 3) and the common electrode 32 is switched to a low level potential (L potential), The direction is reversed, and the display on the display panel 30 is white.
Further, by adjusting the movement amount of the black particles 331 and the white particles 332 according to the voltage application time, it is possible to display an intermediate color with a color gradation between black and white.
When the application of the electric field is stopped, the movement of the black particles 331 and the white particles 332 is stopped, and the display color is maintained as it is.

[6. Display panel drive process]
Next, a driving process of the display panel 30 will be described.
First, drive characteristics of the display panel 30 will be described. As described above, when performing drive control by common swing, a rectangular pulse signal to which H potential and L potential are alternately applied is input to the common electrode 32. In FIG. 5, as the pulse signal, a first pulse having a pulse width of 20 milliseconds and a second pulse having a pulse width of 100 milliseconds and longer than the first pulse are added. The change of the reflectance in a case is shown.
The reflectance is a measured value obtained by measuring the display on the display panel 30 with a reflectance meter. When the display panel 30 of the present embodiment is black, the reflectance shown in FIG. In this case, the reflectance is about 45 to 47%.

FIG. 5 shows an example in which a black display with a reflectivity of about 4% is initially displayed, and the drive signal is input and changed to a white display when 2 seconds elapse on the horizontal axis of the graph.
A dotted line 51 in FIG. 5 is an example in which the second pulse is applied to the common electrode 32. Since the second pulse has a long pulse width of 100 milliseconds, the reflectivity changes rapidly, but when the second pulse changes from L to H, the reflectivity drops, and this reflectivity drop changes. Since it is relatively large, it is recognized as a flicker phenomenon.
However, the final reflectance reaches about 47%, and the quality of white display is superior to that of the solid line 52.

On the other hand, the solid line 52 in FIG. 5 is an example in which the first pulse is applied to the common electrode 32. Since the first pulse has a short pulse width of 20 milliseconds, the change in reflectance is gentler than that of the dotted line 51, but the drop in reflectance when the first pulse changes from L to H is small, and the flicker phenomenon. Not recognized as.
However, the final reflectance is only about 45%, and the quality of white display is inferior to that of the dotted line 51.

When the pulse applied to the common electrode 32 changes from the L level to the H level, an H level signal is applied to the pixel electrode 34 for white display, and a voltage having the same potential is applied to the common electrode 32 and the pixel electrode 34. Therefore, theoretically, a potential difference does not occur between the electrodes 32 and 34, the particles 331 and 332 do not move, and the reflectance should not drop.
However, in actuality, for example, when the black display pixel electrode 34 to which the L level signal is applied is disposed adjacent to the pixel electrode 34, the TFT circuit layer 35 or the like generates a leak current. As a result, the reflectance drops due to various factors such as a voltage drop.

The present invention grasps the characteristics depending on the pulse width of the pulse signal applied to the common electrode 32, and performs drive control that can prevent the flicker phenomenon from being recognized and can improve the display quality.
That is, in the process of rewriting the display, the display quality is improved by applying the first pulse having a short pulse width and then applying the second pulse having a long pulse width.

Here, the reason why the flicker phenomenon can be prevented and the display quality can be improved by performing such control will be described with reference to FIG.
FIG. 6 is a diagram schematically showing the microcapsule 330, the black particles 331, and the white particles 332. For this reason, in FIG. 6, each particle | grain 331,332 is expressed by the same magnitude | size.
As described above, the particles 331 and 332 are charged. For this reason, energy (attraction) is acting between the particles 331 and 332 and the capsule wall 330A or between the particles 331 and 332.
Here, the particles of different colors, that is, the black particles 331 and the white particles 332 are charged with different signs (plus and minus), and therefore are in contact with each other with strong energy.
Further, between the same color particles, that is, between the black particles 331 and between the white particles 332 are charged with the same sign, but because there is a difference in charge between the particles 331 and 332, they are contacted with weak energy. It's meeting.
In FIG. 6, energy acting between the particles 331 and 332 or between the particles 331 and 332 and the capsule wall 330 </ b> A is schematically represented by arrows. Note that the thickness and length of the arrow indicate the strength of energy, and the thicker and longer the arrow, the stronger the energy is working.

When rewriting an image, it is necessary to move the particles 331 and 332 by overcoming the energy (attraction) acting between the particles 331 and 332. That is, each particle 331, 332 needs to be peeled off from the other particles 331, 332 and the capsule wall 330A, and further moved toward the opposite capsule wall 330A to be sufficiently pressed against the capsule wall 330A. Therefore, the pulse width (first pulse and second pulse) applied for image rewriting needs to have a pulse width of a predetermined width or more so that a certain amount of energy can be applied.
On the other hand, if the pulse width is too long, a flicker phenomenon occurs. That is, if the pulse width is long, the energy acting on each particle 331, 332 is also large, and the amount of movement of each particle 331, 332 also increases. In addition, when the voltage of the applied pulse is switched, theoretically, a potential difference also occurs between the electrodes 32 and 34 that should have the same potential. Therefore, when the pulse width is long, the particles 331 and 332 return in the opposite direction. The amount of movement also increases. For example, in the state where the black particles 331 in FIG. 6 are gathered on the surface side of the microcapsule 330, if a pulse having a long pulse width that moves the black particles 331 to the opposite side (back side) of the microcapsule 330 is input, Since energy is applied, the amount of movement of the black particles 331 also increases and moves greatly in the dispersion. For this reason, the black particle 331 moves to a position where it cannot be visually recognized from the surface side, for example. When the potential of the pulse applied to the common electrode 32 changes between L and H, theoretically, no potential difference occurs between the electrodes 32 and 34, and the particles 331 and 332 should not move. Actually, the potential change occurs due to various factors as described above, for example, an electric field generated in adjacent pixel electrodes having different voltages, a voltage drop due to a lateral leakage current, and the black particles 331 also move in the opposite direction. For example, it returns to a position where it can be visually recognized to some extent from the surface side. As a result, as shown in FIG. 5, the reflectance changes greatly in a short time, and thus a flicker phenomenon occurs.

On the other hand, if the pulse width is short, the movement amount of each particle 331, 332 is also small, and the return amount is also smaller. For this reason, as shown in FIG. 5, since the rate of change in the reflectance is small, the occurrence of the flicker phenomenon can be prevented.
Then, after the particles 331 and 332 move to some extent in the microcapsule 330 and become invisible, the change in reflectance is small even when a pulse having a large pulse width (second pulse) is applied. Does not occur. For example, when the black particles 331 are moved from the front surface side to the back surface side of the microcapsule 330, the black particles 331 are moved by applying a pulse having a larger pulse width from the state where the black particles 331 cannot be visually recognized. To do. Next, when the electric potential of the common electrode 32 is switched, the black particles 331 slightly return in the reverse direction, but the return amount is smaller than the movement amount in the movement direction, so that the state where the black particles 331 cannot be visually recognized does not change. For this reason, as shown in FIG. 5, the change in reflectance is also reduced, and the flicker phenomenon does not occur.

Further, when the second pulse is applied in the latter half of the rewriting process, a large energy can be applied to each of the particles 331 and 332. For this reason, each particle 331,332 can be moved to the wall on the opposite side of the microcapsule 330, and it can fully be pressed against the wall, and contrast can be raised.
However, if the pulse width of the second pulse is too long according to the experiment of the present inventor, the particles 331 and 332 that become pigments do not remain even after the drive is finished, and as a result, fading occurs and the image is lost. It was found that retention was reduced.
Therefore, in the first half of the image rewriting process (from the initial period to the middle period), it is preferable to apply a pulse having a short pulse width (first pulse) in terms of preventing flicker phenomenon. In the latter half of the process (from the middle period to the latter period), Applying a pulse having a long pulse width (second pulse) is preferable in that the contrast can be increased.

In view of the above, the first pulse preferably has a pulse width as long as possible within a range in which the flicker phenomenon does not occur, because the movement amount of the particles 331 and 332 decreases when the pulse width is short.
On the other hand, when the pulse width of the second pulse is short, the force for pressing the particles 331 and 332 against the capsule wall 330A is weakened and the contrast is lowered. When the pulse width is too long, the particles 331 and 332 do not stay and the image retention is lowered. Therefore, the pulse width may be set within a range in which a predetermined contrast can be ensured and a decrease in retention can be prevented.

Next, a driving method of the electrophoretic display device 3 will be described with reference to the flowcharts of FIGS.
As shown in the flowchart of FIG. 7, when rewriting the display on the display panel 30, the controller 42 first executes a data transfer process in which the data transfer unit 421 controls the drive circuit 43 to transfer data to each pixel. (S1).

Next, the controller 42 executes an image rewriting process in which the image rewriting unit 422 rewrites an image displayed on the display panel 30 based on the transferred data (S2).
In the image rewriting step S2, as shown in FIG. 8, the controller 42 applies the first pulse to the common electrode 32 by the first pulse applying unit 423 (S21). In the present embodiment, as shown in FIG. 9, the first pulse applied to the common electrode (COM) 32 is a rectangular wave whose pulse width (the signal level is the H level portion and the L level portion) is 20 milliseconds. Signal. That is, the first pulse is a pulse signal having a period of 40 milliseconds.
The first pulse applying unit 423 outputs the first pulse a predetermined number of times. This number of times may be determined in advance by experimentally determining the number of times to reach a predetermined ratio (for example, about 80 to 90%) with respect to the target limit ultimate reflectance of the display panel 30, and set based on the experimental result. . In the present embodiment, the first pulse applying unit 423 outputs the first pulse having one period of 40 milliseconds for 100 periods, that is, 40 milliseconds × 100 = 4 seconds, when changing the black display pixel to white display. It is set to be.

In the image rewriting step S2, the controller 42 outputs an L level signal to the pixel that displays black and outputs an H level signal to the pixel that displays white. To do.
In the timing chart of FIG. 9, since the pixel A is displayed in white, an H level signal is output to the pixel electrode 34. Since the pixel B is displayed in black, an L level signal is output to the pixel electrode 34.

FIG. 10 schematically shows the movement state of the black particles 331 and the white particles 332 when signals of various levels are applied to the common electrode 32 and the pixel electrode 34.
That is, as shown in FIG. 10A, when the H level signal is applied to the common electrode 32, the pixel A to which the same H level signal is applied is between the common electrode 32 and the pixel electrode 34. Therefore, the particles 331 and 332 do not move.
On the other hand, when an H level signal is applied to the common electrode 32, a potential difference occurs between the common electrode 32 and the pixel electrode 34 in the pixel B to which the L level signal is applied. For this reason, the black particles 331 applied negatively move to the common electrode 32 side to which the H level signal is applied, and the white particles 332 applied to positive side move to the pixel electrode 34 side to which the L level signal is applied. Moving.

Further, as shown in FIG. 10B, when the L level signal is applied to the common electrode 32, the pixel B to which the same L level signal is applied is between the common electrode 32 and the pixel electrode 34. Therefore, the particles 331 and 332 do not move.
On the other hand, when an L level signal is applied to the common electrode 32, a potential difference occurs between the common electrode 32 and the pixel electrode 34 in the pixel A to which the H level signal is applied. Therefore, the white particles 332 applied to the plus move to the common electrode 32 side to which the L level signal is applied, and the black particles 331 applied to the minus side to the pixel electrode 34 side to which the H level signal is applied. Moving.

Therefore, in the present embodiment, when the common electrode 32 is at the H level, the L level signal is input to the pixel electrode 34 and the black display is written to the pixel for which the black display is selected. Further, when the common electrode 32 is at the L level, an H level signal is input to the pixel electrode 34 and the white display is written to the pixel for which the white display is selected.
In the present embodiment, since the first pulse starts from the L level, white display writing is performed, then black display writing and white display writing are alternately performed, and finally the black display writing ends. ing. Further, since the second pulse also starts from the L level, white display writing is performed, then black display writing and white display writing are performed, and finally the black display writing is completed.
Strictly speaking, the writing control for white display and the writing control for black display are performed with a delay of 20 milliseconds, but since the switching time is short, it seems that the display changes simultaneously from the user. Visible.

  As shown in FIG. 11, in the first pulse application step S21, since the pulse width of the first pulse applied to the common electrode 32 is as short as 20 milliseconds, the drop in reflectance at the time of switching the signal level of the first pulse. Becomes smaller. This drop in reflectance occurs when the first pulse changes from the L level to the H level when switching from black display to white display as shown in FIG. 11, but the pulse width of the first pulse is 20 milliseconds. By shortening such as, it can be reduced to such an extent that the user who is viewing the display panel 30 can not be recognized as flicker. This prevents the user from being stressed by flicker.

When the first pulse applying step S21 is completed, the controller 42 applies the second pulse to the common electrode 32 by the second pulse applying unit 424 (S22). In the present embodiment, as shown in FIG. 9, the second pulse is a rectangular wave signal having a pulse width (the signal level is the H level portion and the L level portion) of 100 milliseconds. That is, the second pulse is a pulse signal having a cycle of 200 milliseconds.
Then, the second pulse applying unit 424 outputs the second pulse a predetermined number of times. This number of times may be determined in advance by experimentally obtaining the number of times to reach the target limit reaching reflectance of the display panel 30 and set based on the experimental result. In the present embodiment, when changing the black display pixel to the white display, the controller 42 outputs the second pulse having one period of 200 milliseconds for two periods, that is, 200 milliseconds × 2 = 0.4 seconds. Is set to

  At the end of the second pulse applying step S22, as shown in FIG. 10C, in each of the pixels A and B, the black particles 331 and the white particles 332 are on the common electrode 32 side and the pixel electrode 34 side, respectively. When viewed from the common electrode 32 side, that is, the surface glass 31 side, white display (pixel A) and black display (pixel B) are obtained.

  In the second pulse applying step S22, the second pulse having a pulse width larger than that of the first pulse is used. Therefore, as shown in FIG. The drop in reflectance is suppressed to such an extent that it cannot be recognized as flicker. In addition, since the second pulse has a pulse width that is about five times larger than that of the first pulse, the voltage application time by one pulse also becomes longer, and the movement of each particle 331 and 332 increases correspondingly, and the reflectance changes. Can also be larger. For this reason, the final arrival reflectance at the end time of the second pulse applying step S22 can be made higher than when only the first pulse is used, and the display quality is also improved.

  When the second pulse applying step S22 is completed, the controller 42 stops inputting signals to the common electrode 32 and the pixel electrode 34 and controls the electrodes 32 and 34 to a high impedance state (S23). In this drive stop state (S23), no potential difference is generated between the common electrode 32 and the pixel electrode 34, and display on the display panel 30 is performed in the image rewriting step S2 (first pulse applying step S21, second pulse applying step S22). The image written by is maintained.

  The controller 42 performs display update control according to the flowcharts of FIGS. 7 and 8 every time the image displayed on the display panel 30 is updated. For example, when year, month, day, hour, and minute time data is displayed as shown in FIG. 1, the display of the minute portion is updated every minute, so the controller 42 has a pixel portion that displays the minute. In response to this, display update control is performed every minute. The controller 42 also performs display update control for the other data display portions in accordance with the respective update intervals.

According to the above embodiment, the following effects are obtained.
(1) Since the first pulse applying step S21 is first performed in the image rewriting step S2, the drop in reflectance can be reduced, and the occurrence of flicker can be prevented. In addition, since the second pulse applying step S22 is performed at the end of the image rewriting step S2, it is possible to reach a higher reflectance than when only the first pulse is applied to the common electrode 32, and the electrophoretic display. It is possible to perform control that brings out the contrast performance of the device, and to improve display quality.
Accordingly, in the display panel 30 using the electrophoretic display element, smooth high-quality display rewriting can be realized, and display characteristics can be improved without causing the user to feel stress.

(2) Further, the total driving time in the image rewriting step S2 is almost the same as the case of driving with one kind of pulse as shown in FIG. Therefore, there is no power consumption when maintaining the image display, and the characteristics of the electrophoretic display device that can realize power saving are not hindered.

(3) Furthermore, by providing the first pulse application step S21 and the second pulse application step S22, saturation driving can be performed in which the particles 331 and 332 are completely moved to the electrodes 32 and 34 side. For this reason, the afterimage phenomenon in which the previous image is raised can be reduced.

[Second Embodiment]
Next, a timepiece according to a second embodiment of the invention will be described.
As shown in FIG. 12, the timepiece of the second embodiment differs from the first embodiment in the number of drive pulses input by the controller 42, particularly the number of second pulses input in the second pulse applying step S22. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

That is, when the display update control is performed, the controller 42 performs control based on the flowcharts of FIGS. 7 and 8 of the first embodiment.
Here, in the first pulse applying step S21, as shown in FIG. 12, the controller 42 (first pulse applying unit 423) performs the same control as in the first embodiment. That is, a first pulse is applied to the common electrode 32, an H level signal is applied to the pixel A that performs white display, and an L level signal is applied to the pixel B that performs black display.

The controller 42 continues the first pulse applying step S21 for 4 seconds, and then performs the second pulse applying step S22 by the second pulse applying unit 424. In the second pulse applying step S <b> 22, the controller 42 applies one L-level second pulse having a pulse width of 100 milliseconds to the common electrode 32.
Thereafter, the controller 42 stops the supply of signals to the electrodes 32 and 34, and executes a drive stop step S23 for setting the high impedance state.
In such a second embodiment, the reflectance changes as shown in the graph of FIG.

In such a second embodiment, the same operational effects as the first embodiment can be obtained.
(4) Furthermore, as the second pulse in the second pulse applying step S22, only the L level signal is added and the white display is completed, so there is no change from the L level to the H level in the second pulse. As shown in FIG. 13, it is possible to prevent a drop in reflectance in the second pulse applying step S22.
On the other hand, in the first embodiment, since the second pulse is input for two periods (100 millisecond L level signals twice), the final reflectance can be further increased.

(5) Since the first pulse application step S21 starts with writing of L level, that is, white display, and the second pulse application step S22 ends with writing of L level, that is, white display, compared with writing of black display. White writing can be increased by one time.
For this reason, the reflectance of white display can be improved and display quality can be improved. That is, as described above, in the present embodiment, since the black particles 331 are smaller than the white particles 332, the response speed of black display is faster than that of white display, and even a short pulse can sufficiently move. For this reason, even if the number of black display writings is smaller than the number of white display writings, a sufficient reflectance (for example, 4%) for black display can be obtained.
Therefore, as in the present embodiment, the number of white display writings, which is slower in response speed than the black display, is increased, and further, a white display writing signal is applied as the second pulse having a long pulse width. As a result, both the black display and the white display reach the target limit reaching reflectance (for example, 4% for the black display and 48% for the white display), and the electrophoretic display element of the display panel 30 is surely saturated. It can be driven.

[Third Embodiment]
Next, a third embodiment of the present invention will be described.
As shown in FIG. 14, the third embodiment also differs from the first and second embodiments in the number of drive pulses input by the controller 42, particularly the number of second pulses input in the second pulse applying step S <b> 22. Since other configurations are the same as those of the first and second embodiments, the description is simplified or omitted.

That is, when the display update control is performed, the controller 42 performs control based on the flowcharts of FIGS. 7 and 8 of the first embodiment.
Here, in the first pulse applying step S21, as shown in FIG. 14, the controller 42 performs the same control as in the first embodiment. That is, a first pulse is applied to the common electrode 32, an H level signal is applied to the pixel A that performs white display, and an L level signal is applied to the pixel B that performs black display.
However, the third embodiment is different in that the input of the first pulse starts from writing of H level, that is, black display.

The controller 42 performs the second pulse application step S22 after continuing the first pulse application step S21 for 4 seconds. In the second pulse application step S22, the controller 42 applies the second pulse of the H level and the L level having a pulse width of 100 milliseconds to the common electrode 32 for one period. That is, the second pulse is terminated by inputting an L level signal having a pulse width of 100 milliseconds after an H level signal having a pulse width of 100 milliseconds.
Thereafter, the controller 42 stops the supply of signals to the electrodes 32 and 34, and executes a drive stop step S23 for setting the high impedance state.
In the third embodiment, the reflectance changes as shown in FIG.

Also in the third embodiment, the same operational effects as those of the first and second embodiments can be obtained.
(6) Furthermore, as the second pulse in the second pulse applying step S22, the L level signal is added after the H level signal is input, and the white display is completed. Therefore, as shown in FIG. At the end of the second pulse applying step S22, the reflectance can be improved to finish the control, and the drop in the reflectance can be suppressed accordingly. That is, when switching from the first pulse applying step S21 to the second pulse applying step S22, the pulse signal applied to the common electrode 32 changes from the L level signal to the H level signal, but the pulse width is short in the first pulse. For this reason, the drop in reflectance is reduced when switching to the H level signal in the second pulse applying step S22. And in 2nd pulse application process S22, since it does not switch from L level signal with a long pulse width to H level signal like 1st Embodiment, in 2nd pulse application process S22 like 1st Embodiment. The drop in reflectance at the end can be prevented. Accordingly, the reflectance of white display can be improved, and the display quality can be improved.

[Modification of the present invention]
Although the embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiments, and various improvements and modifications can be made without departing from the scope of the present invention.

In each of the embodiments described above, the image rewriting step S2 including the first pulse applying step S21 and the second pulse applying step S22 is always performed when the image display is updated. On the other hand, depending on the display content, it may be possible to select the drive control with anti-flicker by the image rewriting step S2 of the present invention and the drive control without anti-flicker using only a pulse with a long pulse width.
For example, the drive control with anti-flicker of the present invention is usually performed, and only when the display change is positively appealed, the drive control without anti-flicker is performed to use flicker as one of the image display effects. May be. When appealing the display change, for example, when the alarm time comes, when displaying a warning screen, or when effectively expressing the state of falling snow and dead leaves in the display expression, Conversely, when flicker is generated and an image can be displayed effectively, drive control without flicker countermeasures may be performed.

Further, the pulse width of the first pulse and the pulse width of the second pulse are not limited to the example of the embodiment. These pulse widths may be set according to the characteristics of the electrophoretic display element to be controlled.
Specifically, the first pulse may be set to such a short pulse width that the evaluator cannot recognize the occurrence of flicker even when the first pulse is applied at the initial stage of the image rewriting process. In order to increase the amount of movement of each of the particles 331 and 332, it is preferable to set the pulse width as long as possible within a range where the occurrence of flicker cannot be recognized.
Further, the pulse width of the second pulse may be set within a range where the contrast of the image can be improved and the image retainability can be secured when the second pulse is applied in the latter half of the image rewriting process.
For example, the pulse width of the first pulse is preferably less than 25 milliseconds, and the pulse width of the second pulse is preferably 25 milliseconds or more.
In particular, it is preferable to set the pulse width of the second pulse to about 2 to 30 times the pulse width of the first pulse.

Note that if the pulse width of the first pulse is too short, the particles 331 and 332 cannot be moved, so a predetermined width is required. That is, the lower limit value of the pulse width of the first pulse needs to be set as appropriate, and is set to 15 milliseconds or more, for example.
In addition, if the pulse width of the second pulse is too long, it is determined by the user that writing of black display and white display is performed alternately, and it takes time to rewrite the image and the image is retained. The nature is also reduced. For this reason, it is necessary to set the upper limit of the pulse width of the second pulse as appropriate, for example, 200 to 300 milliseconds or less.
Therefore, the pulse width of the second pulse is not limited to the range of 2 to 30 times the pulse width of the first pulse, but exceeds the range of 2 to 30 times as long as the above conditions are satisfied. It may be a thing.

  The threshold value for switching the application of various pulses having different pulse widths is not limited to the range of 80 to 90% of the target limit reaching reflectance, and may be less than 80% or greater than 90%. Good. A specific threshold value may be set according to the electrophoretic display device 3 to which the present invention is applied.

Furthermore, in the above embodiment, two types of pulses, the first pulse and the second pulse, are applied. However, three or more types of pulses having different pulse widths are applied by switching in order from the pulse having the short pulse width. Also good.
For example, a first pulse having a pulse width of 20 milliseconds is first applied, and when the reflectance reaches 70% of the target ultimate reflectance, a second pulse having a pulse width of 60 milliseconds is applied and reflected. When the rate reaches 85% of the target limit achievement rate, a third pulse having a pulse width of 100 milliseconds may be applied.
Further, the first to nth pulses having a pulse width of 20, 21, 22,... 97, 98, 99, and 100 milliseconds, which are longer by 1 millisecond per cycle, may be sequentially applied.
If the applied pulse width can be changed in multiple stages, flicker is less noticeable and the reflectance can be changed smoothly to the target limit-arrival reflectance, resulting in a smooth, high-quality display. There is an advantage that rewriting can be realized.

In each of the above embodiments, the present invention is applied to the dot matrix type display panel 30 using an active matrix driving circuit using a TFT circuit. However, the segment type having electrodes having shapes corresponding to display patterns such as numbers. The present invention may be applied to these display panels. In the case of a segment type display panel, it is not necessary to provide the data transfer means 421 or the data transfer step S1.
In the above-described embodiment, black and white two-particle electrophoresis using black particles 331 and white particles 332 is performed. However, the present invention is not limited to this, and one-particle electrophoresis such as blue and white may be performed. Other combinations may be used.

  In addition, it has been confirmed by experiments of the inventor that the electrophoretic display device 3 and the driving method thereof according to the present invention are effective even when the temperature of the environment in which the electrophoretic display device 3 is used changes. . Therefore, the present invention can be used in various electrophoretic display devices used in various temperature environments.

  The electrophoretic display device of the present invention can be widely applied to various electronic devices having a display panel using an electrophoretic display element. Examples of such devices include PDA (Personal Digital Assistants), cellular phones, and digital cameras. A video camera, a printer, a personal computer, etc.

The best configuration, method and the like for carrying out the present invention have been disclosed in the above description, but the present invention is not limited to this. That is, the invention has been illustrated and described primarily with respect to particular embodiments, but may be configured for the above-described embodiments without departing from the scope and spirit of the invention. Various modifications can be made by those skilled in the art in terms of materials, quantity, and other detailed configurations.
Therefore, the description limited to the shape, material, etc. disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such restrictions is included in this invention.

The front view which shows the timepiece in 1st Embodiment of this invention. The block diagram which shows the circuit structure of the timepiece of the said embodiment. Sectional drawing of the display panel of the said embodiment. The schematic diagram which shows the microcapsule of the said embodiment. The graph which shows the change of the reflectance by the drive method used as the comparative example of this invention. Explanatory drawing which shows the energy which acts between the particle | grains and capsule wall of the said embodiment. The flowchart which shows the display process process of the said embodiment. The flowchart which shows the image rewriting process of the said embodiment. The timing chart which shows the drive signal of the said embodiment. Explanatory drawing explaining the display rewriting state of the said embodiment. The graph which shows the change of the reflectance by the said embodiment. The timing chart which shows the drive signal of 2nd Embodiment of this invention. The graph which shows the change of the reflectance by 2nd Embodiment. The timing chart which shows the drive signal of 3rd Embodiment of this invention. The graph which shows the change of the reflectance by 3rd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electronic timepiece, 3 ... Electrophoretic display device, 30 ... Display panel, 32 ... Common electrode, 33 ... Electrophoretic layer, 34 ... Pixel electrode, 35 ... TFT circuit layer, 40 ... Drive control means, 42 ... Controller, 43 DESCRIPTION OF SYMBOLS ... Drive circuit, 44 ... Detection circuit, 45 ... Time measuring part, 421 ... Data transfer means, 422 ... Image rewriting means, 423 ... 1st pulse application part, 424 ... 2nd pulse application part.

Claims (6)

An electrophoretic element in which a dispersion containing electrophoretic particles is interposed between a common electrode and a plurality of pixel electrodes;
Drive means for driving the electrophoretic display element by applying a voltage between the common electrode and the plurality of pixel electrodes;
Control means for controlling the drive means;
A method for driving an electrophoretic display device comprising:
An image rewriting process in which a common electrode driving pulse that repeats two different potentials is applied to the common electrode, and an image is changed by applying one of the two different potentials to each pixel electrode in accordance with display update contents. Have
The image rewriting step includes
A first pulse applying step of applying a first pulse to the common electrode as the common electrode driving pulse;
And a second pulse applying step which is executed after the first pulse applying step and applies a second pulse having a longer pulse width than the first pulse as the common electrode driving pulse to the common electrode. A method for driving an electrophoretic display device. The method for driving an electrophoretic display device according to claim 1,
The image rewriting step performs the first pulse applying step until the reflectance of the changed image reaches a threshold value set to at least 80% of the target limit reaching reflectance,
After reaching the threshold value, the second pulse applying step is executed. The method for driving an electrophoretic display device. In the driving method of the electrophoretic display device according to claim 1 or 2,
The method of driving an electrophoretic display device, wherein the pulse width of the second pulse is in a range of 2 to 30 times the pulse width of the first pulse. In the driving method of the electrophoretic display device according to any one of claims 1 to 3,
The electrophoretic element includes electrophoretic particles of a first color for performing a first color display and electrophoretic particles of a second color for performing a second color display, and the electrophoretic particles of the first color And the second color electrophoretic particles have different particle sizes,
The common electrode drive pulse repeats a voltage for writing a first color for changing an image to a first color display and a voltage for writing a second color for changing an image to a second color display,
The last pulse of the common electrode driving pulse in the image rewriting step is
A voltage for writing the first color when the electrophoretic particles of the first color are larger than the electrophoretic particles of the second color;
The method for driving an electrophoretic display device, wherein the electrophoretic display device has a voltage for writing a second color when the electrophoretic particles of the second color are larger than the electrophoretic particles of the first color. The method for driving an electrophoretic display device according to claim 4,
When the electrophoretic particles of the first color are larger than the electrophoretic particles of the second color, the first pulse of the common electrode driving pulse in the image rewriting process is a voltage for first writing,
When the electrophoretic particles of the second color are larger than the electrophoretic particles of the first color, the first pulse of the common electrode driving pulse in the image rewriting process is a voltage for writing the second color. A method for driving an electrophoretic display device. An electrophoretic element in which a dispersion containing electrophoretic particles is interposed between a common electrode and a plurality of pixel electrodes;
Drive means for driving the electrophoretic display element by applying a voltage between the common electrode and the plurality of pixel electrodes;
Control means for controlling the drive means;
An electrophoretic display device comprising:
The control means includes
Image rewriting means for applying a common electrode driving pulse that repeats two different potentials to the common electrode, and applying one of the two different potentials to each pixel electrode in accordance with the display update contents to change the image. ,
The image rewriting means includes
A first pulse applying unit that applies a first pulse to the common electrode as the common electrode driving pulse;
The second pulse is applied after the first pulse is applied to the common electrode by the first pulse applying unit, and the second pulse having a longer pulse width than the first pulse is applied to the common electrode as the common electrode driving pulse. An electrophoretic display device comprising: a two-pulse application unit.

Images