JP2008256987A - Electrophoretic display, controller, display alteration method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophoretic display which can prevent the image contrast from degrading. <P>SOLUTION: When carrying out an erasing step, a pulse voltage of a rise time period T1 and of a voltage V1 in the positive direction is applied N1 times with a certain interval (every T3 time period). And when a T3 time period has passed after applying this first voltage, a pulse voltage of a rise time period T1 and of a voltage V2 in the positive direction is applied N2 times with a certain interval (every T3 time period). When carrying out a writing step, a pulse voltage of a rise time period T1 and of a voltage -V1 in the negative direction is applied N1 times with a certain interval (every T3 time period). And when a T3 time period has passed after applying this voltage, a pulse voltage of a rise time period T1 and of a voltage -V2 in the negative direction is applied N2 times with a certain interval (every T3 time period). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  As an electrophoretic display device that displays characters, graphics, etc., for example, from a pair of transparent electrodes at least one of which is disposed to face each other via a spacer, and a display liquid containing charged particles and enclosed between the electrodes What was comprised is known (for example, refer patent document 1).

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

Here, in the electrophoretic display device, when a voltage is applied to the electrodes, the charged particles move, and the display is changed. By the way, in the electrophoretic display device, the contrast tends to be lowered according to the number of executions of display change or the passage of time. When the contrast is lowered, the clearness of the display is lost, and the display quality is lowered.
The present invention has been made to solve the above technical problems, and an object of the present invention is to provide an electrophoretic display device and the like that can suppress a decrease in contrast.

  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 opposite to the first electrode, and the charged particles and the charged particles are dispersed. An electrophoretic display panel including an electrophoretic ink including at least a dispersion medium to be disposed between the first electrode and the second electrode, and the first electrode and the second electrode of the electrophoretic display panel. Applying means for applying a voltage to the electrophoretic display panel, the applying means applying a predetermined voltage a plurality of times and then applying a voltage smaller than the predetermined voltage a plurality of times. And

  Here, the application means may be characterized in that the number of times of application of the predetermined voltage is made larger than the number of times of application of the small voltage. Further, the applying means may apply a predetermined voltage and a small voltage at regular intervals. Further, the applying means may be characterized in that each application time at a predetermined voltage and a small voltage is substantially constant.

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 charged particles, A control device for controlling an electrophoretic display panel in which an electrophoretic ink including at least a dispersion medium for dispersing charged particles is disposed between a first electrode and a second electrode. In changing the display, a predetermined voltage is applied to the first electrode and the second electrode a plurality of times, and then a voltage smaller than the predetermined voltage is applied a plurality of times.
Here, the control device may be characterized in that an added value of each application time of a predetermined voltage is made larger than an added value of each application time of a small voltage.

  Further, when the present invention is regarded as a display change method, the display change method 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 is charged. An electrophoretic display panel in which an electrophoretic ink including at least a particle and a dispersion medium for dispersing charged particles is disposed between a first electrode and a second electrode. A voltage smaller than the predetermined voltage is applied a plurality of times after a predetermined voltage is applied to the first electrode and the second electrode a plurality of times.

  Further, when the present invention is regarded as a program, the program 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 charged particles and charged particles. When changing the display of the electrophoretic display panel to a computer device for controlling the electrophoretic display panel in which the electrophoretic ink containing at least a dispersion medium for dispersing the electrophoretic ink is disposed between the first electrode and the second electrode, A function of applying a voltage smaller than the predetermined voltage a plurality of times after applying a predetermined voltage a plurality of times to the first electrode and the second electrode is realized.

  According to the present invention, it is possible to provide an electrophoretic display device and the like that can suppress a decrease in contrast as compared with the case where this configuration is not employed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram illustrating an electrophoretic display device 1 according to the present 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 an electronic shelf label used in, for example, a clock, a calendar, electronic paper, a supermarket, a convenience store, and the like.

Although details will be described later, the electrophoretic display panel 10 includes a common electrode 13, a pixel electrode 14, an electrophoretic ink 15 in which charged particles are dispersed, and the like, and displays characters, numbers, figures, and the like.
The control device 20 includes a driver 30 and a control unit 40 as main parts.
The driver 30 is in a state in which a voltage is applied from a power supply unit (not shown), and the driver 30 is in a state in which a plurality of switching units are provided. Details of the driver 30 will be described later.

  The control unit 40 includes a CPU (Central Processing Unit), a ROM (Read Only Memory) in which programs and the like are recorded, and controls the electrophoretic display panel 10 via the driver 30. The control unit 40 functions as one of application means. 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 an example of 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 an example of the second electrode are provided on the inner surface of the substrate 11 and at a position 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.

  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. When transparency is required like the counter substrate 12 located on the display surface side, polyethylene terephthalate (PET), polyethersulfone (PES), polycarbonate (PC), or the like is 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. The electrophoretic ink 15 includes 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 an example of the charged particles, for example, a white pigment such as titanium oxide, white resin particles, or resin particles colored in white can be used.
As the black particles 15b as an example of the charged particles, 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. In the present embodiment, two types of charged particles of white particles 15a and black particles 15b are used. However, only one type of charged particles may be used.
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 receives a command from the control unit 40 and applies a voltage to the common electrode 13 and each pixel electrode 14. The driver 30 functions as one application unit. The driver 30 includes a plurality of switching units (not shown) that can select one voltage from three types of voltages (V1, V2, Vs) applied from a power source unit (not shown), and each switching unit. Are provided with a plurality of output terminals (not shown). One voltage selected by each switching unit is applied to the common electrode 13 and the pixel electrode 14 via the output terminal. In this embodiment, for example, the driver 30 is applied with 50 [V] as the voltage V1, 35 [V] as the voltage V2, and 0 [V] (ground voltage) as the voltage Vs. It has become.

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 this embodiment, a so-called common oscillation is adopted in which a voltage is selectively applied not only to the pixel electrode 14 but also to the common electrode 13. Yes.

First, when displaying on the electrophoretic display panel 10 according to the present embodiment, for example, a reset operation for displaying the entire image in white is executed, and then a display operation is executed. 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 V1 (= 50 [V] is applied to all the pixel electrodes 14. ]) Is applied. 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 V1 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. Here, the operation when part of the display is black will be described. When a part of white display is black display, a voltage V1 (= 50 [V]) is applied to the common electrode 13, as shown in FIG. In addition, the voltage Vs (= 0 [V]) with respect to the pixel electrode 14 (center pixel electrode 14 in the figure) corresponding to the region where black display is to be performed, the region where the display is not changed (the region where the display is maintained) The voltage V1 (= 50 [V]) is applied to the pixel electrode 14 corresponding to ().

  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 a portion where the electric field is generated. Is made. Further, the pixel electrode 14 to which the voltage V1 (= 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 operation is performed, a display change operation for changing the display is repeated.

  Next, the display change operation will be described. The display change operation in the present embodiment includes a step of changing a black display that needs to be erased to white display (hereinafter referred to as “erase step”) and a step of changing the white display to black display (hereinafter referred to as “write step”). 2 steps). In these two steps, the erasing step is performed before the writing step.

FIG. 4 is a diagram for explaining the display change operation.
FIG. 4A shows the state of the electrophoretic display panel 10 in the erasing step.
In this erasing step, the voltage Vs (= 0 [V]) is applied to the common electrode 13, and the voltage V1 (= 50 [= 50 [V]) is applied to the pixel electrode 14 corresponding to the area to be changed to white display (area to erase display). V]) is applied. In addition, the voltage Vs (= 0 [V]) is applied to the pixel electrode 14 corresponding to a region other than the region where the display is changed to white display (the region where the display state is maintained). As a result, the predetermined area is changed to white display, and the display state is maintained in areas other than the predetermined area.

  For example, when the black display at the center in the figure is changed to the white display and the display is erased, the voltage Vs (= 0 [V]) is applied to the common electrode 13 and the voltage V1 ( = 50 [V]) is applied. As a result, the black display at the center in the figure is changed to white display. In addition, the same voltage Vs (= 0 [V]) as the voltage applied to the common electrode 13 is applied to the pixel electrodes 14 at both ends in the figure, and in regions corresponding to the pixel electrodes 14 located at both ends, The display state is maintained.

Next, the writing step will be described.
FIG. 4B shows the state of the electrophoretic display panel 10 in the writing step.
In the writing step, the voltage V1 (= 50 [V]) is applied to the common electrode 13, and the voltage Vs (= 0 [V]) is applied to the pixel electrode 14 corresponding to the region to be changed to black display. In addition, the voltage V1 (= 50 [V]) is applied to the pixel electrode 14 corresponding to a region other than the region where the display is changed to black display (region where the display state is maintained). As a result, the predetermined area is changed to black display, and the display state is maintained in areas other than the predetermined area.

  For example, when writing is performed by changing the white display at the right end to black display in the drawing, the voltage V1 (= 50 [V]) is applied to the common electrode 13, and the voltage Vs (= 0) is applied to the pixel electrode 14 at the right end in the drawing. [V]) is applied. As a result, the white display at the right end in the figure is changed to black display. Further, the same voltage V1 (= 50 [V]) as the voltage applied to the common electrode 13 is applied to the pixel electrode 14 at the center and the left end in the figure, and corresponds to the pixel electrode 14 located at the center and the left end in the figure. The display state is maintained in the area.

  By the way, in the electrophoretic display device as in the present embodiment, the contrast generally tends to decrease according to the number of executions of the display change operation, the usage time of the electrophoretic display panel, and the like. For this reason, even if clear display is possible at the beginning, the clearness is gradually lost and the display quality is deteriorated. Therefore, the present inventor conducted an experiment in which various forms of voltage were applied to the common electrode 13 and the pixel electrode 14 and the contrast was observed. And this inventor discovered the application form of the voltage which can suppress the fall of contrast by this experiment. Hereinafter, this application mode will be described.

  FIG. 5 shows voltages applied to the common electrode 13 and the pixel electrode 14 in the erase step and the write step. 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.

  As shown in the figure, in the present embodiment, when the erasing step is performed, the voltage is not applied without a break as in the prior art, but the voltage is divided and applied, and a predetermined voltage (hereinafter referred to as a predetermined voltage) is first applied. This voltage is referred to as “first voltage”) a plurality of times, and then a voltage smaller than the predetermined voltage (hereinafter, this voltage is referred to as “second voltage”) is applied a plurality of times. It is configured. The same applies to the writing step. Instead of applying the voltage without break, the voltage is divided and applied, and the first voltage is first applied a plurality of times, and then the second voltage is applied a plurality of times. It is configured to do.

More specifically, when the erasing step is performed, first, a pulse voltage (first voltage) having an application time T1 rising in the positive direction and a voltage value V1 (50 [V] in the present embodiment) is set at a constant interval. Applied N1 times every time (every time T3). A pulse voltage (second voltage) of application time T1 and voltage value V2 (35 [V] in the present embodiment) rising in the positive direction after time T3 elapses after application of the first voltage is completed. ) Is applied N2 times at regular intervals (every time T3).
Further, when the writing step is performed, first, a pulse voltage (first voltage) having an application time T1 rising in the negative direction and a voltage value −V1 (−50 [V] in the present embodiment) is set at regular intervals. (Every time T3), it is applied N1 times. A pulse voltage (second voltage) of application time T1, voltage value −V2 (−35 [V] in the present embodiment) rising in the negative direction after time T3 elapses after application of this voltage is completed. Are applied N2 times at regular intervals (every time T3). Although details will be described later, the voltage application mode in the present embodiment makes it possible to suppress a decrease in contrast as compared with a conventional application mode in which a voltage is applied without break.

  Hereinafter, the voltages applied in the present embodiment will be described in more detail using examples and comparative examples. First, the inventor applied the voltage in the mode shown in FIG. 5 and acquired the contrast value and the like (Examples 1 to 4). On the other hand, the present inventor applied a voltage in a conventional manner or the like applied without a break, and obtained a contrast value or the like (comparative example). Here, the experimental conditions in Examples 1 to 4 and the comparative example will be described in detail with reference to FIGS.

  FIG. 6 schematically shows experimental conditions in Examples 1 to 4 and a comparative example. FIG. 7 shows a voltage applied when the erasing step is performed.

First, experimental conditions in Examples 1 to 4 will be described.
(A1) First, as shown on the left side of FIG. 6A, a predetermined display was performed on the electrophoretic display panel 10.
(A2) After performing a predetermined display at A1, the common electrode 13 and the pixel electrode 14 corresponding to the predetermined display area A in the electrophoretic display panel 10 (hereinafter, these electrodes are referred to as “corresponding electrodes”). A voltage was applied to and a first erase step was performed. As a result, the display area A that has been displayed in black is displayed in white.

(A3) Next, the first writing step was performed by applying a voltage to the corresponding electrode. As a result, the display area A that has been displayed in white is displayed in black.
(A4) Thereafter, the voltage applied in the above A2 and A3 was taken as one voltage application unit, and this voltage application unit was repeated a plurality of times. Then, after the erasing step at the 1000th time is finished, arbitrary three points are selected in the display area A, and the Y value of the XYZ color system (hereinafter referred to as “the Y value of the XYZ color system”) is simply set at these three points. (Referred to as “Y value”). And the average value of three measured Y values was acquired. Note that when the 1000th erasing step is completed, the display area A is displayed in white, and therefore, in this step, the Y value in white display is acquired.

(A5) Next, after the writing step at the 1000th time was completed, Y values were acquired at almost the same locations as the arbitrary three points selected in A4. And the average value of three measured Y values was acquired. When the 1000th writing step is completed, the display area A is displayed in black, and in this step, the Y value in black display is acquired.
(A6) Thereafter, the above one unit is further repeated, and after the 2000th erasing step is completed, the above A4 processing is performed, and after the 2000th writing step is completed, the above A5 processing is executed, and Y in white display is performed. Value, Y value in black display. Further, the Y value in white display and the Y value in black display were also obtained at the 3000th and 4000th times.

(A7) Then, division and [average value of Y values (white) acquired at A4] / [average value of Y values (black) acquired at A5] are performed, and the 1000th erase step and write step ( The contrast value when the 1000th voltage application) was completed was obtained. Similarly, division was performed to obtain a contrast value when the 2000th erasing step and writing step were completed. Furthermore, the contrast value was acquired similarly about the 3000th time and the 4000th time.

(A8) Further, the present inventor investigated the degree of decrease in the contrast value using a calculation formula of [(contrast value at the 4000th time) / (contrast value at the 1000th time)] × 100 [%].
(A9) In the erasing step in the first embodiment, as shown in FIG. 7 (a1), first, a pulse voltage of the application time T1 = 50 [msec], V1 = voltage value 50 [V] (first voltage Voltage) was applied 6 times every 10 [msec]. Then, after 10 [msec] has elapsed from the end of the six voltage applications, every 10 [msec], a pulse-like voltage (the first voltage of application time T1 = 50 [msec], V2 = voltage value 35 [V]) 2) was applied 4 times. In the writing step in the first embodiment, a voltage obtained by reversing the voltage applied in the erasing step is applied.

  In the erasing step in the second embodiment (see FIG. 7A2), a pulse voltage (first voltage) having an application time T1 = 50 [msec] and a voltage value V1 = 50 [V] is set to 10 [msec]. ] Every 8 times. Then, after 10 [msec] has elapsed since the end of the eight voltage applications, every 10 [msec], a pulse voltage (first voltage) of application time T1 = 50 [msec] and voltage value V2 = 35 [V]. 2) was applied twice. That is, in Example 2, the number of times of application of the first voltage was increased twice compared to Example 1, and the number of times of application of the second voltage was decreased twice compared to Example 1. In the writing step in Example 2, a voltage obtained by reversing the voltage shown in FIG.

  In the erasing step in the third embodiment (see FIG. 7A3), a pulse voltage (first voltage) having an application time T1 = 50 [msec] and a voltage value V1 = 50 [V] is set to 10 [msec]. ] Every 4 times. Then, after 10 [msec] has elapsed from the end of the four times of voltage application, every 10 [msec], a pulse-like voltage (the first voltage of application time T1 = 50 [msec] and voltage value V2 = 35 [V]) 2) was applied 6 times. That is, in the third embodiment, the number of times of application of the first voltage is two times less than that of the first embodiment, and the number of times of application of the second voltage is two times that of the first embodiment. In the writing step in the third embodiment, a voltage obtained by reversing the voltage shown in FIG.

  Further, in the erasing step in the fourth embodiment (see FIG. 7A4), a pulse voltage (first voltage) having an application time T1 = 50 [msec] and a voltage value V1 = 50 [V] is set to 10 [ msec] was applied twice. Then, after 10 [msec] has elapsed from the end of the two voltage applications, every 10 [msec], a pulse-like voltage (application time T1 = 50 [msec], voltage value V2 = 35 [V]) 2) was applied 8 times. That is, in the fourth embodiment, the number of times of application of the first voltage is four times less than that of the first embodiment, and the number of times of application of the second voltage is four times that of the first embodiment. In the writing step in Example 4, a voltage obtained by reversing the voltage shown in FIG.

Next, experimental conditions in the comparative example will be described.
(B1) In the comparative example, the same processing as A1 to A8 described above was performed.
(B2) However, in the comparative example, as shown in FIG. 7B1, a voltage of 50 [V] is applied continuously for 500 [msec]. That is, the voltage is applied without a break (without interrupting the voltage application). In the writing step in this comparative example, a voltage obtained by reversing the voltage applied in the erasing step was applied.

In addition, the conditions common to the said Examples 1-4 and a comparative example 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
-Measurement method of Y value-It measured by the method based on JISZ8722 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, contrast values and the like in Examples 1 to 4 and the comparative example will be described with reference to FIGS.
FIG. 8 shows contrast values and the like in Examples 1 to 4 and the comparative example. 8A shows the Y value in white display and black display, FIG. 8B shows the contrast value, and FIG. 8C shows the degree of contrast reduction. FIG. 9 is a graph showing the contrast value in FIG. In FIG. 8A, the Y value in white display is displayed as “Y value (white)”, and the Y value in black display is displayed as “Y value (black)”.

First, referring to FIG. 8C, in the comparative example, the contrast value after the end of the 4000th voltage application is 52.8% of the contrast value after the end of the 1000th voltage application, and the contrast is greatly reduced. It has been found.
On the other hand, in Examples 1-4, it has confirmed that all exceeded the value in a comparative example significantly. For this reason, the voltage application mode in the present embodiment can suppress a decrease in contrast as compared with the conventional application mode. As a result, the voltage application mode in this embodiment can suppress the deterioration in display quality as compared with the conventional case.

Next, contrast values in Examples 1 to 4 and the comparative example will be described (see FIGS. 8B and 9).
First, the contrast value in Example 1 becomes the same value as that in the comparative example after the voltage application at the 1000th time is finished, and is higher than the contrast value in the comparative example after the voltage application at the 2000th time, 3000th time, and 4000th time. It became bigger. In addition, the contrast value in Example 2 is the same value as that in the comparative example after the 1000th voltage application is completed, and is higher than the contrast value in the comparative example after the 2000th, 3000th, and 4000th voltage applications. It became bigger.

  On the other hand, the contrast value in Example 3 becomes the same value as that in the comparative example after the 2000th voltage application is finished, and is larger than the contrast value in the comparative example after the 3000th and 4000th voltage application. became. However, after the 1000th voltage application, the contrast value was smaller than that in the comparative example. The same applies to Example 4, and after the 2000th voltage application, the value was the same as that of the comparative example, and after the 3000th and 4000th voltage application, the contrast value was larger than that of the comparative example. . However, after the 1000th voltage application, the contrast value was smaller than that in the comparative example.

That is, in Examples 1 and 2, a result that substantially exceeded the contrast value in the comparative example was obtained, but in Examples 3 and 4, after the 1000th voltage application, the result was lower than the contrast value in the comparative example. Obtained.
In the first and second embodiments and the third and fourth embodiments, the application ratio of the first voltage and the application ratio of the second voltage are different in terms of the number of application times. In Examples 1 and 2, the application rate of the first voltage is larger than the application rate of the second voltage. In Examples 3 and 4, the application rate of the first voltage is higher than the application rate of the second voltage. It is getting smaller.

In other words, in the first and second embodiments, the first voltage is applied more frequently than the second voltage is applied. In the third and fourth embodiments, the first voltage is applied more frequently. 2 is less than the number of times of voltage application. In other words, in the first and second embodiments, the added value obtained by adding the application times at the first voltage is larger than the added value obtained by adding the application times at the second voltage. In 3 and 4, the added value obtained by adding the application times at the first voltage is smaller than the added value obtained by adding the application times at the second voltage.
That is, according to the results of Examples 1 to 4 and the comparative example, it can be seen that the contrast value is affected by the application ratio of the first voltage and the application ratio of the second voltage. Therefore, from the viewpoint of improving the contrast, it is preferable that the application ratio of the first voltage is larger than the application ratio of the second voltage in terms of the number of voltage applications. In other words, it is preferable that the number of times of applying the first voltage is larger than the number of times of applying the second voltage.

  In the first to fourth embodiments, the first voltage is applied at regular intervals, and the second voltage is applied at regular intervals. By adopting such a configuration, it is possible to further simplify the control when applying a voltage. In the first to fourth embodiments, the first voltage and the second voltage are applied a plurality of times. However, each application time in the plurality of times of application is T1, as described above, and is constant. . As a result, also in this case, the control when applying the voltage can be simplified. In the present embodiment, the first voltage is initially applied a plurality of times, but the present invention excludes a configuration in which another voltage is applied before the plurality of times of application. is not.

In the above-described embodiment, the control unit 40 is provided with a timer unit (not shown) that manages the application time T1 and the like. By the way, 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. 10 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 inside the control unit 40, and the application time T1 and the like are managed using this 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 the present embodiment, the control terminal 70 is provided with a timer unit (not shown), and the control terminal 70 manages the application time T1 and the like in each electrophoretic display device 1.

  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. It is a figure for demonstrating display change operation | movement. The voltages applied to the common electrode and the pixel electrode in the erasing step and the writing step are shown. The experimental conditions in Examples 1-4 and a comparative example are shown typically. It shows the voltage applied when the erase step is performed. The contrast value etc. in Examples 1-4 and a comparative example are shown. The contrast value in FIG.8 (b) is shown as a graph. 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, 13 ... Common electrode, 14 ... Pixel electrode, 15 ... Electrophoretic ink, 15a ... White particle, 15b ... Black particle, 15c ... Dispersion medium, 20 ... Control apparatus, 30 ... Driver, 40 ... Control Part

Claims (8)

An electrophoretic ink comprising a first electrode and a second electrode disposed at a position opposite to the first electrode, wherein the electrophoretic ink includes at least charged particles and a dispersion medium for dispersing the charged particles. An electrophoretic display panel disposed between the first 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, when changing the display of the electrophoretic display panel, applies a predetermined voltage a plurality of times and then applies a voltage smaller than the predetermined voltage a plurality of times.   The electrophoretic display device according to claim 1, wherein the applying unit increases the number of times of applying the predetermined voltage more than the number of times of applying the small voltage.   The electrophoretic display device according to claim 1, wherein the applying unit applies the predetermined voltage and the small voltage at regular intervals.   The electrophoretic display device according to claim 1, wherein the applying unit makes each application time at the predetermined voltage and the small voltage substantially constant. An electrophoretic ink comprising a first electrode and a second electrode disposed at a position opposite to the first electrode, wherein the electrophoretic ink includes at least charged particles and a dispersion medium for dispersing the charged particles. And a control device for controlling an electrophoretic display panel disposed between the second electrode and the second electrode,
In changing the display of the electrophoretic display panel, a predetermined voltage is applied a plurality of times to the first electrode and the second electrode, and then a voltage smaller than the predetermined voltage is applied a plurality of times. Control device.   6. The control device according to claim 5, wherein the control device makes an added value of each application time of the predetermined voltage larger than an added value of each application time of the small voltage. An electrophoretic ink comprising a first electrode and a second electrode disposed at a position opposite to the first electrode, wherein the electrophoretic ink includes at least charged particles and a dispersion medium for dispersing the charged particles. And a display changing method in an electrophoretic display panel disposed between the second electrode and the second electrode,
A display changing method, comprising: applying a predetermined voltage to the first electrode and the second electrode of the electrophoretic display panel a plurality of times and then applying a voltage smaller than the predetermined voltage a plurality of times. An electrophoretic ink comprising a first electrode and a second electrode disposed at a position opposite to the first electrode, wherein the electrophoretic ink includes at least charged particles and a dispersion medium for dispersing the charged particles. And a computer device for controlling the electrophoretic display panel disposed between the second electrode and the second electrode,
In order to change the display of the electrophoretic display panel, to realize a function of applying a predetermined voltage to the first electrode and the second electrode a plurality of times and then applying a voltage smaller than the predetermined voltage a plurality of times. Program.

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