JP2011197513A - Method of driving electrophoretic display device, and electrophoretic display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of driving electrophoretic display device which performs display with stable response regardless of whether ambient temperature is high or low during use, and the electrophoretic display device.SOLUTION: The method of driving the electrophoretic display device 30 that performs display of a plurality of gradations by applying driving pulses with a predetermined voltage between electrodes to make electrophoresis particles of two different colors disposed between the electrodes and differing in charging polarity be shifted according to the number of the driving pulses, includes: a pulse-length setting process of setting as a one-pulse length of the driving pulses the shortest transition time among inter-gradation transition times of the plurality of gradations at assumed maximum in-use temperature; a pulse-number determining process of determining the number of respective inter-gradation driving pulses corresponding to the inter-gradation transition times on the basis of the set one-pulse length; and a display process of making display of the plurality of gradations by applying the driving pulses between the electrodes according to the respective determined number of inter-gradation driving pulses.

Description

  In the present invention, a driving pulse having a predetermined voltage is applied between the electrodes, and electrophoretic particles of two colors having different charging polarities arranged between the electrodes are transitioned according to the number of pulses of the driving pulse, thereby displaying multiple gradations. The present invention relates to an electrophoretic display device driving method and an electrophoretic display device.

Conventionally, as this type of electrophoretic display device, one that uses white and black electrophoretic particles and displays eight gradations including a plurality of intermediate colors is known (for example, Patent Document 1).
The electrophoretic display device has a large number of microcapsules in which a positively charged white electrophoretic particle and a negatively charged black electrophoretic particle are enclosed in a dispersion, and the large number of microcapsules are formed by a transparent electrode. The front-side common electrode and the back-side pixel electrode are sandwiched. When a high level voltage is applied to the common electrode and a low level voltage is applied to the pixel electrode to generate an electric field, black electrophoretic particles are applied to the common electrode side and white electrophoretic particles are applied to the pixel electrode side by Coulomb force. Runs and displays black. Conversely, when a low level voltage is applied to the common electrode and a high level voltage is applied to the pixel electrode to generate an electric field opposite to the above, white electrophoretic particles migrate to the common electrode side and black electrophoreses to the pixel electrode side. Each particle migrates (transitions), and white color is displayed.
In this case, a driving pulse of a predetermined voltage is applied to the common electrode, and the white color transits from the intermediate color to black according to the increase in the number of driving pulses, and the black color transits from the intermediate color to white. For this reason, the relationship between the number of drive pulses and the transition time is defined in advance, and the display of eight gradations is made possible by applying to the electrodes the number of pulses necessary for transition to an arbitrary gradation.

JP 2008-8832 A

By the way, in this type of electrophoretic display device using microcapsules, it is known that the dispersion liquid serving as a migration medium of white migration particles and black migration particles changes in viscosity depending on temperature and affects responsiveness.
On the other hand, in the conventional electrophoretic display device, the number of drive pulses corresponding to the necessary transition time (amount of electricity) is applied to the electrodes so as to appropriately perform gradation display while suppressing so-called kickback. However, there is no specific countermeasure for temperature, and there is a problem that the responsiveness deteriorates particularly when the operating temperature is low.

  It is an object of the present invention to provide an electrophoretic display device driving method and an electrophoretic display device capable of performing display with stable responsiveness regardless of the ambient temperature during use.

  According to the driving method of the electrophoretic display device of the present invention, a driving pulse having a predetermined voltage is applied between the electrodes, and electrophoretic particles of two colors having different charging polarities arranged between the electrodes are caused to transition according to the number of driving pulses. A method for driving an electrophoretic display device that performs display of a plurality of gradations, wherein the shortest shortest transition time among a plurality of gradation transition times at a maximum assumed operating temperature is set as one pulse length of a drive pulse A pulse length setting step for determining the number of drive pulses between gradations corresponding to the transition time between gradations at the actual use temperature based on the set one pulse length, and the determined drive pulses between the gradations And a display step of displaying a plurality of gradations by applying a drive pulse between the electrodes based on the number.

  The electrophoretic display device of the present invention applies a driving pulse of a predetermined voltage between the electrodes, makes two-color electrophoretic particles having different charging polarities arranged between the electrodes transition according to the number of driving pulses, and has a plurality of levels. An electrophoretic display device for displaying a tone, wherein the shortest shortest transition time among a plurality of grayscale transition times at an assumed maximum use temperature is stored as one pulse length of a drive pulse; , Based on the stored one pulse length, pulse number determining means for determining the number of drive pulses between the gray levels corresponding to the transition time between the gray levels at the actual use temperature, and on the basis of the determined number of drive pulses between the gray levels And display means for applying a drive pulse between them to display a plurality of gradations.

  According to these configurations, the shortest transition time among the transition times between gradations at the assumed maximum use temperature is set as one pulse of the drive pulse, and the number of drive pulses between gradations at the actual use temperature is determined based on this. Since display is performed, an arbitrary gradation can be expressed only by changing the number of drive pulses of a constant voltage applied between the electrodes. In addition, an appropriate display corresponding to the ambient temperature during use can be performed. That is, it is possible to display a plurality of gradations with stable responsiveness regardless of the ambient temperature at the time of use. Furthermore, the control system for driving can be simplified.

  According to another electrophoretic display device driving method of the present invention, a driving pulse having a predetermined voltage is applied between electrodes, and electrophoretic particles of two colors having different charging polarities arranged between the electrodes are selected according to the number of driving pulses. A method of driving an electrophoretic display device that performs transition and displays a plurality of gradations, wherein the shortest shortest transition time among a plurality of gradation transition times at an assumed maximum use temperature is set to one pulse length of a drive pulse. As described above, the number of drive pulses between gradations at the actual use temperature is determined based on a control table that defines the number of drive pulses between gradations corresponding to the transition time between gradations for each temperature in the temperature range of the assumed use temperature. And a display step of displaying a plurality of gradations by applying a drive pulse between the electrodes based on the determined number of drive pulses between gradations.

  In another electrophoretic display device of the present invention, a driving pulse having a predetermined voltage is applied between electrodes, and electrophoretic particles of two colors having different charging polarities arranged between the electrodes are transitioned according to the number of driving pulses, An electrophoretic display device that performs display of a plurality of gradations, wherein the shortest transition time among gradation transition times of a plurality of gradations at an assumed maximum use temperature is set to one pulse length of a drive pulse. Based on the control table storage means for storing the control table of the number of drive pulses between gradations corresponding to the transition time between gradations for each temperature in the temperature range of the assumed use temperature, and based on the stored control table. Pulse number determining means for determining the number of drive pulses between gradations at the operating temperature; and display means for displaying a plurality of gradations by applying drive pulses between the electrodes based on the determined number of drive pulses between gradations. Characterized by comprising a.

  Specifically, the number of drive pulses between gradations is 11 or 12 in the shortest transition time when the plurality of gradations are 8 gradations, the assumed maximum use temperature is 50 ° C., and the assumed use temperature is 25 ° C. It is preferable that the number of drive pulses between gradations in the shortest transition time when the assumed use temperature is 0 ° C. is 123 to 148 or 134 to 164.

  According to these configurations, the shortest shortest transition time among the transition times between gradations at the assumed maximum use temperature is defined as one pulse of the drive pulse, and each floor at each temperature in the temperature range of the assumed use temperature based on this. Since the display is performed according to the control table of the number of intermediary drive pulses, an appropriate display corresponding to the ambient temperature during use can be performed. That is, it is possible to display a plurality of gradations with stable responsiveness regardless of the ambient temperature at the time of use. Further, the control system for driving can be simplified.

  In this case, the two-color electrophoretic particles are preferably black electrophoretic particles and white electrophoretic particles, and the plurality of gradations are preferably four gradations of black, dark gray, gray and white.

  According to this configuration, since the number of drive pulses applied to the electrodes necessary for transition between gradations can be expressed at a clear ratio for each gradation, an appropriate number of pulses can be applied to express an arbitrary gradation. It can be applied to the electrodes, and the difference between the monochrome gradations can be clearly expressed.

  In this case, it is preferable that the number of inter-tone drive pulses determined in the pulse number determination step is an integer.

  According to this configuration, it is possible to easily control the number of drive pulses for expressing an arbitrary gradation.

  In this case, it is preferable that temperature detecting means for detecting the actual use temperature is further provided, and the pulse number determining means determines the number of drive pulses between gradations based on the detection result of the temperature detecting means.

  According to this configuration, it is possible to determine the number of drive pulses between gradations according to the actual use temperature detected by the temperature detection means, so even if the use temperature environment changes, the optimum number of pulses can be driven in real time. Pulses can be supplied to the electrodes.

FIG. 3 is a schematic diagram showing a configuration of a display panel according to the first embodiment. It is a block diagram which shows the structure of the control board which concerns on 1st Embodiment. It is an example of the graph showing the voltage application time which concerns on 1st Embodiment, and the relationship of a color. It is a figure showing an example of the relationship between the number of drive pulses which concerns on 1st Embodiment, and a color. It is a figure which shows the test result of the Example of this embodiment.

  Hereinafter, an electrophoretic display device driving method and an electrophoretic display device according to an embodiment of the present invention will be described with reference to the accompanying drawings. In this electrophoretic display device, white electrophoretic particles and black electrophoretic particles encapsulated in microcapsules are moved (transitioned) in the front and back directions by electrostatic force (Coulomb force), respectively, and a monochrome image is displayed. This eliminates the effect of ambient temperature and enhances the display response.

FIG. 1 is a schematic diagram illustrating a configuration of a display panel of the electrophoretic display device 30.
The display panel 1 includes an electrophoretic layer 6 having microcapsules 7 constituting pixels, a common electrode 3 stacked on the front side of the electrophoretic layer 6, a pixel electrode 5 stacked on the back side of the electrophoretic layer 6, It has. The common electrode 3 is composed of a transparent electrode formed of ITO (Indium Tin Oxide) which is a transparent conductive material. The common electrode 3 and the pixel electrode 5 are electrically connected to the control substrate 20 (see FIG. 2), and a voltage (driving pulse) input from the control substrate 20 is applied to the common electrode 3 and the pixel electrode 5. Thus, display by the microcapsule 7 is performed. That is, although omitted in the drawing, the electrophoretic display device 30 (see FIG. 2) is configured by the display panel 1 and the control board 20 directly connected so as to be attached thereto.

  The electrophoretic layer 6 has a plurality of microcapsules 7, and each microcapsule 7 formed into a spherical shape with a film body includes black electrophoretic particles (hereinafter, black electrophoretic particles) 9 and white electrophoretic particles. Electrophoretic particles (hereinafter, white electrophoretic particles) 10 are enclosed together with the electrophoretic dispersion liquid 18. That is, the display panel 1 according to the embodiment includes an electrophoretic layer 6 of a two-color black and white powder fluid system. The black electrophoretic particles 9 and the white electrophoretic particles 10 are charged with different polarities.

  The control substrate 20 applies a high level voltage to one of the common electrode 3 and the pixel electrode 5 and a low level voltage to the other electrode to generate an electric field. Electrophoretic particles corresponding to are migrated and attracted respectively. For example, when a voltage is applied so that the common electrode 3 side is positive and the pixel electrode 5 side is negative while the black electrophoretic particles 9 are charged with positive charges and the white electrophoretic particles 10 are charged with negative charges, respectively. The negatively charged white electrophoretic particles 10 in the microcapsule 7 are concentrated on the common electrode 3 side, and the positively charged black electrophoretic particles 9 are concentrated on the pixel electrode 5 side.

  In such a state, the black electrophoretic particles 9 concentrated on the pixel electrode 5 are hidden behind the white electrophoretic particles 10 concentrated on the common electrode 3 side and are difficult to visually recognize. As a result, the white electrophoretic particles 9 concentrated on the common electrode 3 side are difficult to see. The color of the electrophoretic particles 10 is visually recognized on the surface of the display panel 1. That is, in this case, white display is strong on the surface of the display panel 1. Conversely, when a voltage is applied so that the common electrode 3 side is negative and the pixel electrode 5 side is positive, the negatively charged white electrophoretic particles 10 are common to the pixel electrode 5 side and the positively charged black electrophoretic particles 9 are common. Concentrating on the electrode 3 side, the black display becomes stronger on the surface of the display panel 1.

  In addition, by controlling the voltage applied to each electrode, when the electrophoretic particles of each color are not concentrated on the common electrode 3, the display color of the display panel 1 is expressed as an intermediate color between the black and white of the electrophoretic particles. Is also possible. That is, the display color of the display panel 1 is irreversibly changed by controlling the application time of the voltage applied between the electrodes (controlled by the number of pulses of the drive signal) with the control substrate 20. Thereby, monochrome display of 4 gradations or 8 gradations is possible. In the embodiment, one microcapsule 7 is used as one pixel, but a plurality of microcapsules 7 may be used as one pixel.

  FIG. 2 is a block diagram illustrating an example of the configuration of the control board 20. As shown in the figure, the control board 20 has an operation control circuit 21, a voltage control circuit 22, a temperature sensor 28, a temperature control circuit 29, a control circuit 23 and a display drive circuit 24. The operation control circuit 21 determines the operation content from the operation switch 25 installed outside the electrophoretic display device 30 and transmits the operation content to the control circuit. The voltage control circuit 22 controls the voltage supplied from the power supply 26 and supplies it to the control circuit 23. The temperature sensor 28 detects the current use temperature of the electrophoretic display device 30 (use environment temperature of the electrophoretic display device 30), and notifies the temperature control circuit 29 of it. The temperature control circuit 29 converts the temperature information detected by the temperature sensor 28 into an electrical signal and notifies the control circuit 23 of the electrical information.

  On the other hand, the control circuit 23 stores image information of the display panel 1, drive pulse number information (control table) necessary for transition between gradations corresponding to temperature, and the current display color (transition state) of the display panel 1. In accordance with an operation command from the operation control circuit 21, the current temperature information received from the temperature control circuit 29, the current electrophoretic particle transition state, and the drive information applied to the electrodes from the image information to be displayed next. Are read from the control table and notified to the display drive circuit 24. The display drive circuit 24 is connected to the outside of the control board 20 via an interface (I / F) 27, and the display drive circuit 24 itself is directly electrically connected to the display panel 1, and in accordance with a command from the control circuit 23. A drive pulse is generated and applied to the common electrode 3 and the pixel electrode 5 of the display panel 1.

  FIG. 3 is an example of a graph showing the relationship between voltage application time and gradation (color change) according to the embodiment of the present invention. The embodiment is an electrophoretic display device 30 capable of four-tone monochrome display. In FIGS. 3A, 3B, and 3C, the horizontal axis indicates the voltage application time to the electrodes. The vertical axis represents the color contrast from black to white. In this embodiment, the number of gradations is four gradations of black, dark gray, gray, and white, and the voltage application time to the electrodes necessary for transitioning between the gradations is represented by a saturation curve. In addition, the voltage applied here assumes 15V.

  3A shows an actual use temperature of 50 ° C., FIG. 3B shows an actual use temperature of 25 ° C., and FIG. 3C shows a voltage application time with respect to gradation transition at the actual use temperature of 0 ° C. Thus, the voltage application time required for this transition between gradations depends on the temperature environment, the voltage application time is short when the temperature is high, and the application time is long as the temperature is low. For example, FIG. 3A shows the voltage application time with respect to gradation transition at an actual use temperature of 50 ° C., and when applying a voltage to the electrode from the black display state, the black changes to dark gray. The voltage application time is 15 msec, the voltage application time from black to gray is 50 msec, and the voltage application time from black to white is 150 msec. On the other hand, FIG. 3B shows the voltage application time for the gradation transition at the actual use temperature of 25 ° C. The voltage application time from black to dark gray is 30 msec, and the voltage application time from black to gray is The voltage application time from black to white is 120 msec and 300 msec. As described above, the lower the actual use temperature, the longer the voltage application time required for transition between the gradations.

  The actual use temperature of 50 ° C. in FIG. 3A indicates the voltage application time necessary for transition between gradations at the assumed maximum use temperature. In this temperature environment, the shortest voltage application time required for transition between gradations is set as the minimum unit of voltage application time to the electrodes, so that the voltage application time required for transition between each gradation is driven pulse. It becomes easy to control with. That is, in this embodiment, the voltage application time of 15 msec from black to dark gray, which is the shortest voltage application time among the transition times between gradations at the assumed maximum use temperature, is defined as one pulse length of the drive pulse (hereinafter, this The display color of the display panel is controlled (the drive pulse having a pulse length is described as the shortest pulse). For example, under the assumed maximum operating temperature of this embodiment (FIG. 3 (a)), the number of drive pulses applied to the electrode to make the transition from black to dark gray is 1, and the electrode has to be applied to make the transition from black to gray. The number of drive pulses to be applied is 3, and the number of drive pulses applied to the electrodes in order to transition from black to white is 27. Note that. In this case, the number of drive pulses is all an integer in consideration of control.

  FIG. 4 is a table showing the number of drive pulses required for transition from black to white and transition from white to black at actual usage temperatures of 0 ° C., 25 ° C., and 50 ° C. in accordance with the above rules. It is. Since the voltage application time differs between the case of transition from black to white and the case of transition from white to black, the number of drive pulses for four gradations is defined for both. In practice, the number of drive pulses is specified in units of 1 ° C. or several ° C. between the actual use temperatures of 0 ° C. and 50 ° C. (not shown in the figure), and is specified according to this temperature correspondence. Control of the electrophoretic display device 30 is performed based on the number of drive pulses. That is, in the above control table, the number of drive pulses is defined in units of 1 ° C. or several ° C.

  In the electrophoretic display device 30 having the above configuration, the control circuit 23 of the control board 20 stores the number of drive pulses necessary for transition between gradations at the actual use temperature as shown in FIG. 4 as a control table. ing. As a result, the control circuit 23 can notify the display drive circuit 24 of a drive pulse supply command that is optimal for transition between gradations in accordance with the actual use temperature information acquired from the temperature sensor 28 and the temperature control circuit 29. In the display drive circuit 24, the shortest pulse is generated as a drive pulse and applied to the electrodes, so that a clear image is displayed on the display panel 1.

  As described above, according to the first embodiment, an arbitrary color can be expressed by setting the shortest shortest transition time among gradation transition times within the assumed maximum use temperature range as one pulse of the drive pulse. It is possible to control the optimal number of pulses by the control board 20 and apply it to the electrodes, thereby expressing a clearer color. Furthermore, since the number of pulses is determined based on a control table generated in consideration of the assumed operating temperature range, the optimal number of pulses is displayed to represent any color even when the operating temperature environment changes. As a result, a clear color can be expressed without depending on the operating temperature environment.

  In addition, although the electrophoretic display device in the present embodiment uses an electrophoretic display device having four gradations, the driving method of the present invention is applied to an electrophoretic display device having eight gradations. May be applied.

  In this embodiment, the black electrophoretic particles 9 charged to positive charge and the white electrophoretic particles 10 charged to negative charge are used for the microcapsules 7 of the electrophoretic layer 6. May be used in reverse. That is, black electrophoretic particles 9 charged to negative charge and white electrophoretic particles 10 charged to positive charge may be used.

  Further, the color of each gradation in the present embodiment is according to the definition of the present embodiment, and the voltage application time required for the fiber between the gradations also depends on the characteristics (pulse amplitude value) of the control board of the present embodiment. is there. Therefore, the definition of the color expressed by each gradation and the time for applying the voltage to the electrodes differ depending on the design requirements.

  The electrophoretic display device 30 using the driving method according to the present embodiment is applicable not only in the display panel 1 having a screen form but also in a wide range of fields such as a watch using a flexible electrophoretic display device.

  In the above-described embodiment, the number of drive pulses necessary for transition between gradations is stored in the control circuit 23 of the control board 20 as a control table, and after the number of pulses corresponding to the actual use temperature is allocated, the display drive circuit 24, the correlation between the temperature and the voltage application time required for transition between each gradation is derived, and the control circuit 23 calculates the number of drive pulses from the temperature information acquired from the temperature control circuit 29. You may decide. According to this method, it was possible to apply to the electrodes only with the number of pulses stored for each temperature in the control table, but by deriving the number of pulses by calculation, pulses between temperatures that cannot be expressed in the temperature table The number can be complemented.

  It should be noted that an operator or an input terminal may be installed on the electrophoretic display device 30 used in this embodiment so that the information in the control table can be changed. Thereby, the display color expressed by each gradation of the electrophoretic display device 30 can be adjusted.

Next, the verification result when the number of gradations is 8 gradations in the drive pulse determination result (control table) will be described (see FIG. 5).
Here, the assumed operating temperatures are 0 ° C., 25 ° C., 50 ° C., and the pulse length (unit pulse) of the drive pulse is from gray scale 1 to gray scale when the electrophoretic display device of 8 gray scale expression is 50 ° C. The voltage application time required for transition to 2 is set.
In the test, the number of drive pulses between gradations at each assumed use temperature is represented by an arbitrary multiple of the number of drive pulses between gradations at 50 ° C., and each gradation (monochrome color) at that time is measured and evaluated by reflectance. did. The evaluation method will be described in detail later. Note that this test was conducted at the assumed operating temperature and over 8 gradations, and was comprehensively evaluated. Here, gradation 1 to gradation 2 at 0 ° C., 25 ° C., and 50 ° C. is used. Only the result of the transition is shown.

As an evaluation method, the transmittance of light with a wavelength of 380 to 750 nm in the display panel is measured to obtain the reflectance from the average value, and the reflectance at 25 ° C. is set as a reference (1), and the other 0 ° C. And the difference with the reflectance in the case of 50 degreeC was calculated | required and evaluated by%.
The evaluation criteria are “A” when the difference from the reflectance at 25 ° C. is less than 0 to 3%, “B” when less than 3 to 10%, and “C” when 10% or more. Furthermore, the evaluation is performed for 8 gradations (total of 16 states) at 0 ° C. and 50 ° C., and as a comprehensive evaluation, the above evaluation criteria, when “C” is absent and “B” is within 3 pieces, When there is no “total A” and “C” and there are four or more “B”, it is defined as “total B” and when “C” is present, “total C”.

FIG. 5 shows test results of examples of the present embodiment. As a result, with respect to Examples 1 to 5 having an overall evaluation of “A” (best) or an overall evaluation of “B” (better), the shortest voltage for transition from gradation 1 to gradation 2 at 50 ° C. The application time (shortest transition time) is a unit pulse (1 pulse). The shortest transition time at 25 ° C. is 11 times as many pulses, the shortest transition time at 0 ° C. is 123 to 148 times as many pulses, or 25 ° C. Thus, it was confirmed that it is appropriate to set the number of pulses to 12 times, and at 0 ° C., the number of pulses is 134 to 164 times.
On the other hand, about Examples 6-11 which became comprehensive evaluation "C" (NG), it was confirmed that it deviates from said numerical range.

  1: Display panel, 3: Common electrode, 5: Pixel electrode, 6: Electrophoresis layer, 7: Microcapsule, 9: Black electrophoretic particle, 10: White electrophoretic particle, 18: Electrophoretic dispersion liquid, 20: Control Substrate 28: temperature sensor 29: temperature control circuit 30: electrophoretic display device

Claims (9)

Electrophoresis in which a driving pulse of a predetermined voltage is applied between the electrodes, and electrophoretic particles of two colors having different charging polarities disposed between the electrodes are transitioned according to the number of pulses of the driving pulse to display a plurality of gradations A driving method of a display device,
A pulse length setting step of setting a shortest shortest transition time among the transition times between the gradations of the plurality of gradations at an assumed maximum use temperature as one pulse length of the drive pulse;
A pulse number determination step for determining the number of drive pulses between gradations corresponding to the transition time between the gradations at the actual use temperature based on the set one pulse length;
And a display step of performing display of the plurality of gradations by applying the drive pulse between the electrodes based on the determined number of drive pulses between the gradations. . Electrophoresis in which a driving pulse of a predetermined voltage is applied between the electrodes, and electrophoretic particles of two colors having different charging polarities disposed between the electrodes are transitioned according to the number of pulses of the driving pulse to display a plurality of gradations A driving method of a display device,
The transition between the gradations for each temperature in the temperature range of the assumed use temperature, with the shortest shortest transition time among the transition times between the gradations at the assumed maximum use temperature as one pulse length of the drive pulse Based on a control table that defines the number of drive pulses between gradations corresponding to time, a pulse number determination step of determining the number of drive pulses between gradations at an actual use temperature;
And a display step of performing display of the plurality of gradations by applying the drive pulse between the electrodes based on the determined number of drive pulses between the gradations. . The plurality of gradations are 8 gradations, and the assumed maximum use temperature is 50 ° C.
The number of drive pulses between the gradations in the shortest transition time when the assumed use temperature is 25 ° C. is 11 or 12,
3. The driving of an electrophoretic display device according to claim 2, wherein the number of driving pulses between gradations in the shortest transition time when the assumed use temperature is 0 ° C. is 123 to 148 or 134 to 164. Method. The two-color electrophoretic particles are black electrophoretic particles and white electrophoretic particles,
4. The method for driving an electrophoretic display device according to claim 1, wherein the plurality of gradations are four gradations of black, dark gray, gray, and white.   5. The driving method of an electrophoretic display device according to claim 1, wherein, in the pulse number determining step, the determined number of driving pulses between gradations is an integer. Electrophoresis in which a driving pulse of a predetermined voltage is applied between the electrodes, and electrophoretic particles of two colors having different charging polarities disposed between the electrodes are transitioned according to the number of pulses of the driving pulse to display a plurality of gradations A display device,
Pulse length storage means for storing the shortest shortest transition time among the plurality of gradation transition times at the assumed maximum use temperature as one pulse length of the drive pulse;
Pulse number determining means for determining the number of drive pulses between gradations corresponding to the transition time between gradations at the actual use temperature based on the stored one pulse length;
An electrophoretic display device comprising: a display unit configured to apply the drive pulse between the electrodes based on the determined number of drive pulses between gradations and to display the plurality of gradations. Electrophoresis in which a driving pulse of a predetermined voltage is applied between the electrodes, and electrophoretic particles of two colors having different charging polarities disposed between the electrodes are transitioned according to the number of pulses of the driving pulse to display a plurality of gradations A display device,
The shortest shortest transition time among the plurality of gradation transition times at the assumed maximum use temperature is defined as one pulse length of the drive pulse, and each temperature in the temperature range of the assumed use temperature based on the one pulse length. Control table storage means for storing a control table of the number of drive pulses between the gray levels corresponding to the transition time between the gray levels,
Based on the stored control table, pulse number determination means for determining the number of drive pulses between the gradations at the actual use temperature;
An electrophoretic display device comprising: a display unit configured to apply the drive pulse between the electrodes based on the determined number of drive pulses between gradations and to display the plurality of gradations. The plurality of gradations are 8 gradations, and the assumed maximum use temperature is 50 ° C.
The number of drive pulses between the gradations in the shortest transition time when the assumed use temperature is 25 ° C. is 11 or 12,
The electrophoretic display device according to claim 7, wherein the number of driving pulses between gradations in the shortest transition time when the assumed use temperature is 0 ° C. is 123 to 148 or 134 to 164. A temperature detecting means for detecting the actual use temperature,
The electrophoretic display device according to claim 6, wherein the pulse number determining unit determines the number of driving pulses between the gray levels based on a detection result of the temperature detecting unit.

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