JP2008216380A - Electrophoresis display device, control device, method of driving electrophoresis display panel, and display system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophoresis display device or the like capable of substantially suppressing a decrease in display quality due to sticking of charge particles on an electrode. <P>SOLUTION: After display changing operation is performed, an alternating voltage is applied three time at a predetermined period T1, and then display changing operation is performed. The alternating voltage is applied to a common electrode and a pixel electrode. More specifically, a pulsed voltage of 50V which rises and a pulsed voltage of (-)50V which falls are applied to the common electrode and pixel electrode alternately at a predetermined frequency. Consequently, an alternating electric field is produced between both the electrodes. Further, predetermined display is impaired depending upon the frequency, voltage value, etc., of the alternating voltage and the display quality possibly decreases much. For the purpose, the alternating voltage is applied preferably at a frequency with a voltage value such that the display state can be maintained substantially without being impaird. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrophoretic display device using an electrophoretic phenomenon or the like.

  As a display device for displaying characters, graphics, etc., for example, it is composed of a pair of electrodes that are arranged opposite to each other via a spacer and the like, and a display liquid that contains charged particles and is sealed between the electrodes. Are known (for example, see Patent Document 1).

U.S. Pat. No. 3,612,758

Here, in the display device, generally, a first display that performs a predetermined display by applying a predetermined voltage to a pair of electrodes for a predetermined time and moving one charged particle to the electrode on the display surface side. The action is executed. Further, a voltage having a polarity different from that of the predetermined voltage is applied to the pair of electrodes for a predetermined time, and another charged particle different from the one charged particle is moved to the electrode on the display surface side to thereby display another display. A second display operation is performed.
By the way, in the display device, for example, when the first display operation is performed and a predetermined display is performed, the adhesion strength between the one charged particle and the electrode increases as time passes, and the one charged particle becomes the electrode. There is a possibility that a phenomenon of so-called image sticking that sticks firmly to the surface may occur. When this burn-in occurs, the contrast is lowered and the display quality is lowered.

  Therefore, a method has been proposed in which the second display operation is performed while the predetermined display is being performed, and the first display operation is performed again after the second display operation is performed. In this method, as a result of the one charged particle being temporarily separated from the electrode, the adhesion strength between the one charged particle and the electrode is weakened, and it is possible to suppress the occurrence of image sticking as described above. However, in the case of this method, the predetermined display cannot be performed while the second display operation and the first display operation are being performed, and the display quality is deteriorated.

  The present invention has been made in order to solve the technical problems as described above, and an object of the present invention is to substantially suppress a reduction in display quality due to sticking of charged particles to an electrode. An object is to provide an electrophoretic display device or the like.

  For this purpose, an electrophoretic display device to which the present invention is applied includes a first electrode and a second electrode disposed at a position facing the first electrode, and includes at least a dispersion medium and an electric field. An electrophoretic ink including charged particles that move due to an action is provided between the first electrode and the second electrode, and the first electrode and the second electrode of the electrophoretic display panel. Application means for applying a voltage to the electrode, and the application means vibrates the charged particles during display on the electrophoretic display panel, but the display is substantially before and after the application. It is characterized by applying a vibration pulse that is not impaired.

  Here, the apparatus further comprises setting means for setting the vibration pulse size, frequency, number of times of application, application period, or application time based on the number of display changes in the electrophoretic display panel or the usage time of the electrophoretic display panel. Can be a feature. In addition, when the vibration pulse is applied, the Y value of the XYZ color system of the electrophoretic display panel before application and the Y value of the XYZ color system of the electrophoretic display panel after application have the following relationship: Can be a feature. (Y value of XYZ color system before application) / (Y value of XYZ color system after application) = 0.80 to 1.20.

  Further, when the present invention is regarded as a control device, the control device to which the present invention is applied includes a first electrode and a second electrode disposed at a position opposite to the first electrode, and at least distributed An electrophoretic ink including a medium and charged particles that move by the action of an electric field is a control device that controls an electrophoretic display panel disposed between a first electrode and a second electrode. While the display is being performed on the display panel, there is provided application means for applying a vibration pulse that applies vibrations to the charged particles but can maintain the display before and after the application.

  Here, the apparatus further comprises setting means for setting the vibration pulse size, frequency, number of times of application, application period, or application time based on the number of display changes in the electrophoretic display panel or the usage time of the electrophoretic display panel. Can be a feature. In addition, when the vibration pulse is applied, the Y value of the XYZ color system of the electrophoretic display panel before application and the Y value of the XYZ color system of the electrophoretic display panel after application have the following relationship: Can be a feature. (Y value of XYZ color system before application) / (Y value of XYZ color system after application) = 0.80 to 1.20. Further, the display device further includes a changing unit that changes a display state of the electrophoretic display panel, and the applying unit applies the vibration pulse at a constant interval after a predetermined time has elapsed since the display state was changed by the changing unit. be able to.

  Further, when the present invention is regarded as a driving method of an electrophoretic display panel, the driving method of the electrophoretic display panel to which the present invention is applied is a first electrode and a first electrode disposed at a position opposite to the first electrode. An electrophoretic display panel in which an electrophoretic ink including at least a dispersion medium and charged particles that move by the action of an electric field is disposed between the first electrode and the second electrode. A driving method is characterized in that vibration pulses are applied to a charged particle while a display is being performed on an electrophoretic display panel, but the display is not substantially impaired before and after the application. It can be.

  Further, when the present invention is regarded as a display system, the display system to which the present invention is applied includes a first electrode and a second electrode disposed at a position facing the first electrode, and at least a dispersion is provided. An electrophoretic display panel in which an electrophoretic ink including a medium and charged particles that move by the action of an electric field is disposed between the first electrode and the second electrode, and the first electrode of the electrophoretic display panel A plurality of display devices each including an application means for applying a voltage to the second electrode and the second electrode, and vibrates the charged particles while being displayed on the electrophoretic display panel. And a control terminal that controls each of the application means such that a vibration pulse is applied to the first electrode and the second electrode that does not substantially impair the display before and after its application.

  ADVANTAGE OF THE INVENTION According to this invention, the electrophoretic display apparatus etc. which can suppress substantially the fall of the display quality resulting from sticking to the electrode of a charged particle can be provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram showing an electrophoretic display device according to this embodiment.
The electrophoretic display device 1 shown in the figure is a display device that can reversibly change the visual state by the action of an electric field. The electrophoretic display device 1 is schematically composed of an electrophoretic display panel 10 and a control device 20 that controls the electrophoretic display panel 10. Such an electrophoretic display device 1 is used for, for example, a clock, a calendar, electronic paper, an electronic shelf label used in a supermarket, a convenience store, and the like.

Although details will be described later, the electrophoretic display panel 10 as a display body includes a common electrode, a pixel electrode, and electrophoretic ink in which charged particles are dispersed, and displays characters, numbers, figures, and the like.
The control device 20 includes a driver 30 and a control unit 40.
The driver 30 is in a state where two types of voltages are applied from a power supply unit (not shown), and the driver 30 is in a state where a plurality of switching units are provided. Details of the driver 30 will be described later.

  The control unit 40 that functions as one of the application unit and the change unit includes a CPU (Central Processing Unit) and a ROM (Read Only Memory) in which a program and the like are recorded. The panel 10 is controlled. Further, when a control terminal such as a host computer is separately provided outside the electrophoretic display device 1, the control unit 40 communicates with the control terminal via an interface unit (not shown).

Next, the electrophoretic display panel 10 and the driver 30 will be described in detail.
FIG. 2 is a diagram for explaining the electrophoretic display panel 10 and the driver 30. In addition, in this figure, illustration of the control part 40 shown in FIG. 1 is abbreviate | omitted.

The electrophoretic display panel 10 in this embodiment is a panel that can obtain a desired display by controlling the direction of an electric field. In addition, the electrophoretic display panel 10 has advantages such as low manufacturing cost and a wide viewing angle as a normal printed matter. Further, the electrophoretic display panel 10 has a display memory property that allows the display to be maintained without applying power, and as a result, has an advantage of low power consumption.
More specifically, the electrophoretic display panel 10 according to this embodiment includes a substrate 11, a counter substrate 12, a common electrode 13, a pixel electrode 14, and an electrophoretic ink 15 in which charged particles are dispersed. Yes. In addition, the electrophoretic display panel 10 has a gap material (not shown) for maintaining a gap between the substrates 11 and the counter substrate 12 at a specified value, and an end portion of the substrate 11 and the counter substrate 12. A sealing material (not shown) for preventing the electrophoretic ink 15 from leaking out is provided.

The substrate 11 is a member that becomes a base of the electrophoretic display panel 10 and has a function of supporting members such as the pixel electrode 14.
The counter substrate 12 is a member that serves as a base of the electrophoretic display panel 10, similarly to the substrate 11. The counter substrate 12 is disposed at a position facing the substrate 11 with the electrophoretic ink 15 in between. Further, the counter substrate 12 is attached to the substrate 11 through a predetermined gap. The counter substrate 12 has a function of supporting members such as the common electrode 13.

The common electrode 13 as the first electrode is formed over the entire inner surface of the counter substrate 12. In addition, a predetermined voltage is applied from the driver 30 to the common electrode 13.
A plurality of pixel electrodes 14 as second electrodes are provided on the inner surface of the substrate 11 and at positions facing the common electrode 13. Further, the pixel electrode 14 is configured to be applied with a predetermined voltage from the driver 30 in the same manner as the common electrode 13. The pixel electrode 14 may be a segmented electrode as well as a dot-shaped electrode capable of matrix display. Further, the electrode substrate composed of the pixel electrode 14 and the substrate 11 may be a TFT substrate widely used in liquid crystals.

  Here, in the electrophoretic display panel 10, at least one side becomes a display surface (observation surface). For this reason, the substrate and the electrodes on the display surface side need to be transparent. This transparency is a concept including translucent and colored transparency. Therefore, in the present embodiment, the counter substrate 12 and the common electrode 13 are configured using a transparent material. In the present embodiment, the counter substrate 12 and the common electrode 13 are made of a transparent material and the counter substrate 12 side is used as a display surface. However, if the substrate 11 and the pixel electrode 14 are made of a transparent material, the other side is used. The side can also be a display surface. When flexibility is required for the electrophoretic display panel 10, a film-like or sheet-like resin substrate is used for the substrate 11 and the counter substrate 12.

For the substrate 11 and the counter substrate 12, for example, a resin material can be used. In addition, when high transparency is requested | required like the opposing board | substrate 12 located in the display surface side, a polyethylene terephthalate (PET), polyether sulfone (PES), a polycarbonate (PC) etc. are used.
For the common electrode 13 and the pixel electrode 14, for example, a general conductive material such as aluminum or copper can be used. In addition, when transparency is requested | required like the common electrode 13 located in the display surface side, conductive oxides, such as ITO (indium tin oxide), etc. are used, for example. Of course, this conductive oxide can also be used for the pixel electrode 14.
The electrophoretic ink 15 is sealed between the substrate 11 and the counter substrate 12. In the present embodiment, the electrophoretic ink 15 is composed of positively charged white particles 15a, negatively charged black particles 15b, and a dispersion medium 15c that disperses these particles.

As the white particles 15a as the charged particles, for example, a white pigment such as titanium oxide, white resin particles, or resin particles colored white can be used.
As the black particles 15b as the charged particles, for example, black pigments such as titanium black and carbon black, resin particles colored in black, and the like can be used.
In addition, these particles can be arbitrarily used in various colors as long as the contrast can be displayed, and can be a combination of white and red, white and blue, yellow and black, and the like.
For the dispersion medium 15c, various low-dielectric constant organic solvents conventionally used for electrophoretic display can be used. For the dispersion medium 15c, additives such as a dispersant and a charge control agent are used. Can also be used.

  The driver 30 functioning as one of the applying means and changing means applies a voltage to the common electrode 13 and each pixel electrode 14 in response to a command from the control unit 40. More specifically, the driver 30 includes a plurality of switching units (not shown) that can select one voltage from two types of voltages (Vp, Vs) applied from a power source unit (not shown), and each switching unit. A plurality of output terminals (not shown) provided corresponding to the units are provided. One voltage selected by each switching unit is applied to the common electrode 13 and the pixel electrode 14 via the output terminal. In the present embodiment, the driver 30 is applied with 50V as the voltage Vp and 0V (ground voltage) as the voltage Vs.

Next, the operation of the electrophoretic display panel 10 in the present embodiment will be described.
FIG. 3 is a diagram for explaining the operation of the electrophoretic display panel 10.
As described above, a voltage is applied from the driver 30 to the common electrode 13 and the pixel electrode 14 in the present embodiment. Several methods have been proposed for applying a voltage. In the present embodiment, one voltage is selectively applied from two types of voltages not only to the pixel electrode 14 but also to the common electrode 13. So-called common swing is adopted.

First, when displaying on the electrophoretic display panel 10 according to the present embodiment, first, a reset operation for displaying the whole as white is performed, and then a display operation is performed. Then, after the display operation is performed, the display change operation for changing the display is repeated.
When performing the reset operation, as shown in FIG. 3A, the voltage Vs (= 0 V) is applied to the common electrode 13 and the voltage Vp (= 50 V) is applied to all the pixel electrodes 14. . As a result, an electric field is generated from the pixel electrode 14 toward the common electrode 13, the positively charged white particles 15 a move toward the common electrode 13, and the negatively charged black particles 15 b move toward the pixel electrode 14. . For this reason, the white particles 15a are located on the common electrode 13 side located on the display surface side, and the entire display is white. When the reset operation is performed, the voltage Vs and the voltage Vp are applied for about 0.5 seconds. In this embodiment, positively charged white particles 15a and negatively charged black particles 15b are used. However, such a charged state is an example, and the white particles 15a can be negatively charged. In addition, the black particles 15b can be positively charged.

  Next, a display operation is performed. In the present embodiment, an operation when part of the display is black will be described. When a part of white display is black display, as shown in FIG. 3B, the voltage Vp (= 50 V) with respect to the common electrode 13 and the pixel electrode 14 corresponding to the region where black display is to be performed (FIG. The voltage Vs (= 0 V) with respect to the middle center pixel electrode 14), and the voltage Vp (at the pixel electrode 14 at both ends in the figure) corresponding to the area where the display is not changed (area where the display is maintained). = 50V) is applied. When the display operation is performed, the voltage Vs and the voltage Vp are applied for 0.5 seconds.

  As a result, an electric field from the common electrode 13 toward the pixel electrode 14 is generated between the pixel electrode 14 to which the voltage Vs (= 0 V) is applied and the common electrode 13, and black display is performed in the portion where the electric field is generated. . Further, the pixel electrode 14 to which the voltage Vp (= 50 V) is applied and the common electrode 13 are substantially equipotential. That is, the electric field strength is substantially zero. For this reason, the movement of the white particles 15a and the black particles 15b is suppressed, and the black display is not performed in this portion, and the white display is maintained. Then, after such a display is made, the display changing operation for changing the display is repeated.

  By the way, in the electrophoretic display panel 10 according to the present embodiment, the charged particles 15a and 15b may gradually aggregate over time, and a dot-like defect may be generated in the display. Further, as the time passes, the adhesion strength between the charged particles 15a and 15b and the common electrode 13 (pixel electrode 14) increases, and so-called seizure occurs in which the charged particles 15a and 15b firmly adhere to the common electrode 13 (pixel electrode 14). There is a case. As a result, a decrease in contrast occurs and the display quality deteriorates. Therefore, in the present embodiment, an alternating voltage as an example of a vibration pulse is applied to the common electrode 13 and the pixel electrode 14 a plurality of times while the display is performed on the electrophoretic display panel 10. The vibration pulse in the present embodiment refers to a voltage that gives vibration to the charged particles 15a and 15b but does not substantially impair the display on the electrophoretic display panel 10 before and after the application. The alternating voltage is an example of a vibration pulse, and it is of course possible to apply other forms of voltage.

  FIG. 4 shows the voltage (V) applied to the common electrode 13 and the pixel electrode 14. In this figure, the applied voltage (V) is positive when the electric field is formed from the pixel electrode 14 toward the common electrode 13, and the electric field is formed from the common electrode 13 toward the pixel electrode 14. The case is shown as negative.

FIG. 4A shows an applied voltage (V) applied to the common electrode 13 and the pixel electrode 14 when an alternating voltage is applied three times during display on the electrophoretic display panel 10. It is a thing.
More specifically, in FIG. 4A, after the display change operation is executed, an alternating voltage is applied three times at a predetermined cycle T1, and then the display change operation is executed. In this figure, the display change operation for the third and subsequent times is omitted, but the display change operation is executed at a predetermined cycle after the third time, and the alternating voltage is also applied at the predetermined cycle T1. In this embodiment, the case where the alternating voltage is applied three times will be described as an example. However, depending on the cycle in which the display change operation is executed, the alternating voltage may be applied only once.

First, the display change operation will be described.
The display change operation in the present embodiment is executed at a predetermined cycle as described above. This display change operation is executed by the control unit 40 and the driver 30.
The display changing operation includes two steps: a step of changing a black display that needs to be erased to a white display and a step of changing a predetermined white display to a black display. Note that these two steps are performed first by changing the black display to the white display.

In the step of changing the black display requiring erasure to the white display, a pulse voltage rising in the positive direction is applied to the common electrode 13 and the pixel electrode 14 (hereinafter, this pulse voltage is referred to as “erase pulse”). Called). Specifically, the voltage Vs (= 0 V) is applied to the common electrode 13 (see FIG. 2), and the voltage Vp (= 50 V) is applied to the pixel electrode 14 (see FIG. 2) corresponding to the region to be changed to white display. Is done. For example, when the black display at the center in the state of FIG. 3B is changed to white display, the voltage Vs (= 0 V) is applied to the common electrode 13 and the white display is changed as described above. A voltage Vp (= 50 V) is applied to the pixel electrode 14 corresponding to (the pixel electrode 14 in the center in the figure). As a result, the black display at the center in the figure becomes white display.
On the other hand, the same voltage Vs (= 0 V) as the voltage applied to the common electrode 13 is applied to the pixel electrode 14 corresponding to an area other than the area where the display is changed to white display (area where the display state is maintained). . In other words, the pixel electrode 14 corresponding to a region other than the common electrode 13 and the region to be changed to white display has a potential difference of 0V.

  In the step of changing the predetermined white display to the black display, a pulse voltage rising in the negative direction is applied to the common electrode 13 and the pixel electrode 14 (hereinafter, this pulse voltage is referred to as “display pulse”). "). Specifically, the voltage Vp (= 50V) is applied to the common electrode 13, and the voltage Vs (= 0V) is applied to the pixel electrode 14 corresponding to the region to be changed to black display.

For example, when the white display at the right end in the state of FIG. 3B is changed to black display, the voltage Vp (= 50 V) is applied to the common electrode 13 and the voltage Vs ( = 0V) is applied. As a result, the white display at the right end in the figure is black.
On the other hand, the same voltage Vp (= 50 V) as the voltage applied to the common electrode 13 is applied to the pixel electrode 14 corresponding to the area other than the area where the display is changed to black display (area where the display state is maintained). . In other words, the pixel electrode 14 corresponding to a region other than the common electrode 13 and the region for changing to black display has a potential difference of 0V.

  Each display change operation can also be performed by executing a reset operation to display the entire area as white, and after displaying the entire area as a white display, the predetermined area is displayed as black. However, in the case of this operation, a display that does not change is once erased. For this reason, for example, in the clock display, the whole is erased every minute, resulting in a problem that visibility is deteriorated. For this reason, the display changing operation is preferably configured by two steps: a step of changing the black display that needs to be erased to a white display and a step of changing a predetermined white display to a black display.

Next, the alternating voltage applied at the cycle T1 will be described.
In the present embodiment, as described above, the alternating voltage is applied three times at the period T1. In other words, in the present embodiment, the alternating voltage is applied twice at a constant interval T1 after a predetermined time T1 has elapsed since the display change operation was performed. Each alternating voltage is applied at a predetermined frequency for a predetermined time (indicated as “T2” in the figure). The period T1, the application time T2, and the like are managed by a timer unit (not shown) provided in the control unit 40.

  The alternating voltage is applied to the common electrode 13 and the pixel electrode 14. Specifically, a 50V pulse voltage rising in the positive direction and a (−) 50V pulse voltage rising in the negative direction are alternately applied to the common electrode 13 and the pixel electrode 14 at a predetermined frequency (for example, 500 Hz). Is done. As a result, an alternating electric field is formed between both electrodes.

The period T1 can be set as appropriate. For example, it can be set to 1 hour, half a day (12 hours), or the like. The period T1 is preferably set according to the period (interval) of the display change operation. Further, if the period T1 is short, the number of times of applying the alternating voltage naturally increases, so that power consumption increases. For this reason, it is preferable to make the period T1 as long as possible from the viewpoint of power consumption.
The application time T2 can be set as appropriate similarly to the cycle T1. For example, it can be set to 4 seconds to be described later. If the application time T2 is too short, image sticking or the like cannot be effectively suppressed, and if the application time T2 is too long, the display may be disturbed.

Also, the voltage value to be applied can be set as appropriate, and for example, it can be set to the same voltage value as the voltage value applied when the display change operation is executed. If the voltage value is too small, burn-in or the like cannot be effectively suppressed, and if the voltage value is too large, the display may be disturbed.
Further, the frequency of the alternating voltage to be applied can be set as appropriate. If the frequency is too low, the charged particles 15a and 15b may move greatly and display disturbance may occur. On the other hand, if the frequency is too high, the charged particles 15a and 15b will not vibrate on the contrary, and seizure or the like tends to occur.

By the way, between the first display change operation and the second display change operation in the figure, a predetermined display is performed.
For this reason, depending on the frequency, voltage value, and the like of the alternating voltage, the predetermined display may be impaired, and the display quality may be significantly reduced. In some cases, the display state is disturbed to a level where information cannot be transmitted to the user or the like.

Further, in the configuration in which the application of the voltage is stopped after the application of the alternating voltage as in the present embodiment, the display disorder is maintained thereafter. If the display is disturbed immediately before the display change operation, the display change operation can be corrected by including the reset operation. However, the display is disturbed by the alternating voltage applied immediately after the display change operation. If this happens, the disordered state is maintained until the next display change operation.
Further, it is possible to perform a reset operation every time an alternating voltage is applied and perform a re-display, but there is a problem that the original display is not performed during the reset operation. Further, if the reset operation is performed, the power consumption increases, and the merit of the electrophoretic display device that uses the memory effect to reduce the power consumption cannot be utilized. For this reason, it is preferable to apply the alternating voltage at a frequency and voltage that can maintain the display state without substantially impairing the display state.

  In addition, the charged particles 15a and 15b are more likely to aggregate in a region where the number of executions of the display change operation (the number of display changes) is smaller. Further, in the region where the display change operation is executed less frequently, the charged particles 15a and 15b are more likely to adhere to the common electrode 13 or the pixel electrode 14 and cause burn-in. For this reason, for example, it is desirable to count the number of display changes for each region, and increase the number of alternating voltage applications or increase the voltage value of the alternating voltage in regions where the number of display changes is small. Further, by adopting such a configuration, voltage application variation between display regions is reduced, and the life of the electrophoretic display panel 10 can be extended.

Further, the withstand voltage characteristics of the charged particles 15a and 15b change depending on the usage time of the electrophoretic display panel 10 and the like. For this reason, it is preferable to (re) set the magnitude (voltage value), frequency, number of applications, application period, application time, and the like of the alternating voltage based on the usage time of the electrophoretic display panel 10.
It should be noted that the control unit 40 grasps the number of executions of the display change operation and the usage time of the electrophoretic display panel 10. The magnitude of the alternating voltage is set by the control unit 40 as setting means. In the present embodiment, the alternating voltage is applied. However, it is of course possible to apply a voltage other than the alternating voltage.

Next, FIG. 4B will be described.
FIG. 4B shows a case where an alternating voltage having a voltage value larger than the voltage value of the alternating voltage applied in FIG. 4A is applied.
More specifically, FIG. 4 (b) shows the same frequency as the alternating voltage in FIG. 4 (a), a voltage value larger than the voltage value of the alternating voltage in FIG. 4 (a) (for example, 70V), and FIG. This shows a state in which an alternating voltage having an application time T4 shorter than the application time T2 of the alternating voltage in a) is applied twice in a cycle T3.
The voltage value or the like of the alternating voltage can be various values, and as described above, the voltage value can be larger than the voltage value of the alternating voltage shown in FIG. However, when the voltage value is increased, the charged particles 15a and 15b are excessively moved and the display is easily disturbed. For this reason, in the alternating voltage in this figure, as above-mentioned, application time T4 shall be shorter than application time T2 in Fig.4 (a).

In addition, the application cycle can also be varied, and this figure shows a state in which the alternating voltage is applied at a cycle T3 longer than the cycle T1 in FIG. Note that the cycle of the display change operation is the same as that in FIG. Further, if the voltage value is too large, display disturbance may occur as described above. Therefore, the voltage value in the present embodiment is set to a magnitude that does not cause display disturbance. Note that the display changing operation in the present embodiment is the same as that shown in FIG.
Although not described in detail, the voltage value of the alternating voltage can be made smaller than the voltage value shown in FIG. However, in this case, the magnitude of the alternating electric field acting on the charged particles 15a and 15b is also small, and seizure or the like is likely to occur. For this reason, when making the voltage value of an alternating voltage small, it is preferable to lengthen application time.

Here, the present inventor conducted the following two experiments (Experiment 1 and Experiment 2), and verified the effect in the present embodiment. First, Experiment 1 will be described.
(Experiment 1)
The inventor applies several types of alternating voltages having different application times T2 and the like, and simply converts the Y value of the XYZ color system (hereinafter referred to as “Y value of the XYZ color system”) before the application of the alternating voltage to “Y value”. And the contrast value was obtained from the Y value after application of the alternating voltage (Examples 1 to 3). On the other hand, contrast values were obtained even under conditions where no alternating voltage was applied (Comparative Examples 1 to 3). Here, the experimental conditions in Examples 1 to 3 and Comparative Examples 1 to 3 will be described in detail with reference to FIG.

FIG. 5 schematically shows experimental conditions in Examples and Comparative Examples.
Experimental conditions in Examples 1 to 3 (A1) As shown in FIG. 5A, after a predetermined display (hereinafter referred to as “initial display”) is performed, in a region where white display is performed Three arbitrary points were selected, and the Y value was measured at each of these three points. And the average value of three measured Y values was acquired.
(A2) Thereafter, an alternating voltage was applied at a cycle T1 = 3 hours. At this time, in Example 1, an alternating voltage of voltage value = ± 50 V and application time T2 = 4 seconds is applied, and in Example 2, an alternating voltage of voltage value = ± 70 V and application time T2 = 2 seconds is applied. In Example 3, an alternating voltage having a voltage value of ± 40 V and an application time T2 of 6 seconds was applied. In any of the examples, the frequency was 50 Hz.

(A3) After applying the alternating voltage for the seventh time and after 24 hours from the initial display, the area where the black display was made was changed to the white display, and the white display was made. Changed the area to black. That is, a display change operation for inverting the display was executed.
(A4) Next, the Y value was measured again at any three points selected in (A1) above, and the average value was obtained from the three measured Y values. Note that the measurement of the Y value at this stage is performed in black display because the display is inverted in (A3) above.
(A5) Then, division and [average value of Y values acquired in (A1)] / [average value of Y values acquired in (A4)] were performed to obtain contrast values.

Experimental condition (B1) in the comparative example First, similarly to the above (A1), after performing a predetermined display, arbitrary three points are selected in the area where the white display is made, and Y is determined at each of the three points. The value was measured. And the average value of three measured Y values was acquired.
(B2) Thereafter, the display made in (B1) was maintained for 24 hours. At this time, the application of the alternating voltage as in Examples 1 to 3 was not performed.
(B3) Then, 24 hours after the predetermined display was made in (B1), a display change operation for inverting the display was performed in the same manner as in (A3) above.
(B4) Next, the average value of Y values was obtained in the same manner as in (A4) above.
(B5) Then, similarly to the above (A5), division is performed, [average value of Y values acquired in (B1)] / [average value of Y values acquired in (B4)], and the contrast value is calculated. I got it.

(Experiment 2)
Next, Experiment 2 will be described.
In Experiment 2, an alternating voltage was applied under the same conditions as in Examples 1 to 3 above, and the rate of change (%) was obtained according to the following procedure, and the display state was visually confirmed (Examples 4 to 4). 6).
(C1) First, as shown in FIG. 5A, the Y value was acquired before the seventh application of the alternating voltage (hereinafter, this Y value is referred to as “Y value (A)”). Note that this Y value (A) is an average value of three Y values measured at arbitrary three points in a region where white display is performed, as in the case of (A1).

(C2) Similarly, as shown in FIG. 5A, the Y value was acquired after the seventh application of the alternating voltage (hereinafter, this Y value is referred to as “Y value (B)”). The Y value (B) is an average value of three Y values measured again at three arbitrary points selected in (C1).
(C3) Next, the fluctuation rate (%) of the Y value was obtained using the calculation formula [(Y value (A)) / (Y value (B)] × 100.
(C4) Further, in this experiment, the display state before the seventh application of the alternating voltage and the display state after the seventh application of the alternating voltage were visually observed to confirm the disorder of the display state.

The conditions common to the above (Experiment 1) and (Experiment 2) are as follows.
・ White particles 15a: Titanium oxide (average diameter: 0.3 to 0.5 μm)
Black particles 15b: acrylic resin particles colored with carbon black (average diameter 5 μm)
・ Dispersion medium 15c: xylene ・ Gap between common electrode 13 and pixel electrode 14: 50 μm
・ Voltage value of voltage applied for initial display ... 50V
-Application time of voltage applied to perform initial display ... 0.5 seconds-Voltage value of voltage applied when display inversion is performed ... 50V
-Application time of voltage applied at the time of display reversal-0.5 seconds-Y value measurement method-Measured by the method based on JIS Z8722 under the following conditions.
・ Measuring equipment: Suga Test Instruments Co., Ltd. MSC-IS-2B
・ Light source: 12V50W halogen lamp ・ Colorimetric conditions: D65 light 10 ° field of view ・ Measurement area: 5φ
・ Standard white surface ... Included white standard plate

Here, the result of Experiment 1 will be described.
FIG. 6 is an explanatory diagram showing the results of Examples 1 to 3 and Comparative Examples 1 to 3.
As shown in the figure, in Example 1, the contrast value was 7.93, and in Comparative Example 1, the contrast value was 7.33. That is, the contrast value in Example 1 was larger than the contrast value in Comparative Example 1. In Example 2, the contrast value was 7.89, and in Comparative Example 2, the contrast value was 6.86. That is, the contrast value in Example 2 was larger than the contrast value in Comparative Example 2. Further, in Example 3, the contrast value was 7.38, and in Comparative Example 3, the contrast value was 6.57. That is, the contrast value in Example 3 was larger than the contrast value in Comparative Example 3.

As described above, when image sticking occurs, the contrast is lowered. In other words, the contrast (value) decreases as the degree of image sticking increases, and the contrast (value) increases as the degree of image sticking decreases.
In the experiment 1, as described above, it was confirmed that any of the contrast values in Examples 1 to 3 exceeded the contrast value in Comparative Examples 1 to 3. For this reason, it turns out that the structure of this embodiment which applies an alternating voltage in the middle of a display can suppress generation | occurrence | production of image sticking compared with the aspect which does not apply an alternating voltage.

Next, the result of Experiment 2 will be described.
FIG. 7 is an explanatory diagram showing the results of Examples 4-6.
As shown in the figure, the variation rate was 103% in Example 4, 105% in Example 5, and 101% in Example 6. This variation rate means that the larger the value is, the darker the display is and the more the display is impaired. However, in all of Examples 4 to 6, the fluctuation rate was small. For this reason, when an alternating voltage is applied on conditions like Examples 4-6, it turns out that a display is maintainable, without impairing a display. According to the knowledge of the present inventor, when the variation rate is 80% to 120%, an impression that the display is not impaired can be given to the person who visually recognizes the display. Further, in this experiment 2, the variation rate of white display was investigated, but the same applies to the case of black display. When the variation rate is 80% to 120%, the display is impaired for the person viewing the display. It is possible to give the impression that there is no.

  Further, as described above (C4), the display state before the seventh application of the alternating voltage and the display state after the seventh application of the alternating voltage were visually grasped, and the disorder of the display state was confirmed. As a result, when the alternating voltage was applied for the seventh time, when it was confirmed from a position of about 10 cm, a dot-like defect or the like was observed, but the customer placed a shelf label (price tag etc.) in a store such as a supermarket. ) Was observed at a general distance (3 m in this experiment), the above dot-like defects could not be recognized.

  In consideration of other experimental results by the present inventor, the energy amount of the alternating voltage (one alternating voltage) (the time integrated value obtained by integrating the alternating voltage with time) is the energy amount of the voltage applied in the display changing operation. (Time integration value obtained by integrating the applied voltage with time) is 300% or less, the magnitude of the alternating voltage is 50% to 300% of the magnitude of the applied voltage applied in the display change operation, and the alternating voltage application time T2 Is 8 seconds or less and the frequency of the alternating voltage is 100 Hz to 2 kHz, it has been found that the same result as above can be obtained.

By the way, in the said embodiment, although it was set as the structure which provides a timer part (not shown) in the control part 40, it can also be set as the structure which provides a timer part other than the control part 40. FIG. Hereinafter, this point will be described.
FIG. 8 is a schematic configuration diagram showing an outline of a display system configured by a plurality of electrophoretic display devices 1.
As shown in the figure, this display system includes a plurality of (three in this embodiment) electrophoretic display devices 1 connected to a network, and each of the electrophoretic display devices 1 that are also connected to a network. And a control terminal 70 to be controlled.

Each electrophoretic display device 1 includes an electrophoretic display panel 10 and a control device 20 in the same manner as the electrophoretic display device 1 shown in FIG. The control device 20 includes a driver 30 and a control unit 40. In addition, the control device 20 in the present embodiment includes an interface unit 50 that connects the control unit 40 and the control terminal 70 and enables communication between the control unit 40 and the control terminal 70. The configuration and function of each device (each unit) are the same as those of the electrophoretic display device 1 shown in FIG.
As described above, the control terminal 70 individually controls each of the electrophoretic display devices 1. The control terminal 70 includes a timer unit (not shown).

  In the electrophoretic display device 1 shown in FIG. 1, a timer unit (not shown) is provided in the control unit 40, and the application period T1 and the application time T2 are managed using the timer unit. However, in the case of a display system including a plurality of electrophoretic display devices 1, if a timer unit is provided in each electrophoretic display device 1, the cost of the entire system is increased. Therefore, in this embodiment, a timer unit (not shown) is provided in the control terminal 70, and the application terminal T1 and the application time T2 in each electrophoretic display device 1 are managed by the control terminal 70.

  In addition, the electrophoretic display device 1 is used not only in a single form like a clock used at home, but also in a plurality of forms like an electronic shelf label such as a supermarket or a convenience store. There is. As described above, when a plurality of electrophoretic display devices 1 are used, if each electrophoretic display panel 10 is controlled by the control device 20 provided corresponding to each electrophoretic display device 1, It becomes complicated. Therefore, in the present embodiment, each electrophoretic display device 1 and the control terminal 70 are connected via a network, and each electrophoretic display panel 10 is managed by the control terminal 70.

  Note that the program for executing the processing as described in the above embodiment may be in the form of a storage medium or a program transmission device. That is, the program to be executed by the computer device can be stored in a storage medium such as a CD-ROM, DVD, memory, or hard disk so that the computer device can read the program. In addition, storage means such as a CD-ROM, DVD, memory, and hard disk that stores the program, and the apparatus that reads the program from the storage means and executes the program via a connector or a network such as the Internet or a LAN A program transmission apparatus including transmission means for transmitting a program can also be provided. In addition to this, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate without departing from the gist of the present invention.

1 is a schematic configuration diagram illustrating an electrophoretic display device according to an embodiment. It is a figure explaining an electrophoretic display panel and a driver. It is a figure for demonstrating operation | movement of an electrophoretic display panel. The voltage (V) applied to the common electrode and the pixel electrode is shown. The experimental condition in an Example and a comparative example is shown typically. It is explanatory drawing which showed the result of Examples 1-3 and Comparative Examples 1-3. It is explanatory drawing which showed the result of Examples 4-6. It is the schematic block diagram which showed the outline of the display system comprised by several electrophoretic display apparatuses.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Electrophoretic display panel, 11 ... Board | substrate, 12 ... Counter substrate, 13 ... Common electrode, 14 ... Pixel electrode, 15a ... White particle, 15b ... Black particle, 15c ... Dispersion medium, 20 ... Control apparatus, 30 ... Driver, 40 ... control unit, 70 ... control terminal

Claims (9)

An electrophoretic ink comprising a first electrode and a second electrode disposed at a position opposite to the first electrode, and including at least a dispersion medium and charged particles that move by the action of an electric field, An electrophoretic display panel disposed between the second electrode and the second electrode;
Applying means for applying a voltage to the first electrode and the second electrode of the electrophoretic display panel;
The application means applies a vibration pulse that gives vibration to the charged particles while displaying on the electrophoretic display panel, but does not substantially impair the display before and after the application. An electrophoretic display device.   The apparatus further comprises setting means for setting the magnitude, frequency, number of applications, application period, or application time of the vibration pulse based on the number of display changes in the electrophoretic display panel or the usage time of the electrophoretic display panel. The electrophoretic display device according to claim 1. When the vibration pulse is applied, the Y value of the XYZ color system of the electrophoretic display panel before the application and the Y value of the XYZ color system of the electrophoretic display panel after the application have the following relationship: The electrophoretic display device according to claim 1.
(Y value of XYZ color system before application) / (Y value of XYZ color system after application) = 0.80 to 1.20 An electrophoretic ink comprising a first electrode and a second electrode disposed at a position opposite to the first electrode, and including at least a dispersion medium and charged particles that move by the action of an electric field, A control device for controlling an electrophoretic display panel disposed between the second electrode and the second electrode,
While the display is performed on the electrophoretic display panel, the charged particle is vibrated, and an application means for applying a vibration pulse capable of maintaining the display before and after the application is provided. Control device.   The apparatus further comprises setting means for setting the magnitude, frequency, number of applications, application period, or application time of the vibration pulse based on the number of display changes in the electrophoretic display panel or the usage time of the electrophoretic display panel. The control device according to claim 4, characterized in that: When the vibration pulse is applied, the Y value of the XYZ color system of the electrophoretic display panel before the application and the Y value of the XYZ color system of the electrophoretic display panel after the application are as follows: The control device according to claim 4, wherein
(Y value of XYZ color system before application) / (Y value of XYZ color system after application) = 0.80 to 1.20 Further comprising changing means for changing a display state in the electrophoretic display panel;
The control device according to claim 4, wherein the applying unit applies the vibration pulse at regular intervals after a predetermined time has elapsed since the display state was changed by the changing unit. An electrophoretic ink comprising a first electrode and a second electrode disposed at a position opposite to the first electrode, and including at least a dispersion medium and charged particles that move by the action of an electric field, A method for driving an electrophoretic display panel disposed between the second electrode and the second electrode,
While the display is performed on the electrophoretic display panel, vibration pulses are applied to the charged particles so as to vibrate, but the display is not substantially impaired before and after the application. Driving method of electrophoretic display panel. An electrophoretic ink comprising a first electrode and a second electrode disposed at a position opposite to the first electrode, and including at least a dispersion medium and charged particles that move by the action of an electric field, An electrophoretic display panel disposed between the first electrode and the second electrode, and an applying means for applying a voltage to the first electrode and the second electrode of the electrophoretic display panel; A plurality of display devices each including
While the display is being performed on the electrophoretic display panel, vibration pulses are applied to the charged particles, but a vibration pulse that does not substantially impair the display before and after the application is applied to the first electrode and the first electrode. A control terminal for controlling each of the application means to be applied to two electrodes;
Including display system.

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