JP5304324B2 - Electrophoretic display device driving method, electrophoretic display device, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for driving an electrophoretic display, which doesn't bring about persistence in a half-tone image, and an electrophoretic display. <P>SOLUTION: In the method for driving an electrophoretic display which includes: a display part wherein an electrophoretic element containing electrophoretic particles is held between a first substrate and a second substrate and a plurality of pixels are arranged; pixel electrodes formed on the electrophoretic element side of the first substrate correspondingly to respective pixels; and a common electrode formed on the electrophoretic element side of the second substrate and facing the plurality of first electrodes, an image display step of displaying an image on the display part includes a half-tone display step S103 of inputting a first pulse periodically alternating between a first potential and a second potential to the common electrode while inputting a second pulse having a wider pulse width than the first pulse and alternating between the first potential and the second potential to the pixel electrodes. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

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

  When an electric field is applied to a dispersion liquid in which electrophoretic particles are dispersed in a solution, a phenomenon (electrophoresis phenomenon) in which the electrophoretic particles migrate due to Coulomb force is known. Electrophoretic display using this phenomenon Equipment has been developed. Such an electrophoretic display device is disclosed, for example, in Patent Document 1 below.

JP 2008-249793 A

The electrophoretic display device can change the display color to a desired color by generating a potential difference between the common electrode and the pixel electrode divided into a plurality of parts.
In the driving method described in Patent Document 1, a halftone image is displayed by inputting a high level potential to the pixel electrode of a pixel displayed in white and inputting a low level potential to the common electrode.
However, the above driving method has a problem that the immediately preceding image remains as an afterimage in a pixel displaying a halftone image.

  SUMMARY An advantage of some aspects of the invention is that it provides an electrophoretic display device driving method and an electrophoretic display device that do not generate an afterimage in a halftone image. .

The driving method of the electrophoretic display device of the present invention includes a display unit in which an electrophoretic element including electrophoretic particles is sandwiched between a first substrate and a second substrate, and a plurality of pixels are arranged. A pixel electrode formed on the electrophoretic element side of the first substrate corresponding to each pixel, and a common electrode formed on the electrophoretic element side of the second substrate and facing the plurality of pixel electrodes The image display step of displaying an image on the display unit periodically repeats a first potential and a second potential on the common electrode. Is input to the pixel electrode, and a second pulse that periodically repeats the first potential and the second potential with a pulse width wider than one cycle of the first pulse is input to the pixel electrode. In the last period of two pulses. Characterized in that it comprises a halftone display method comprising a display state including a halftone.

In this driving method, a pulse that repeats a first potential and a second potential is input to the pixel electrode and the common electrode, respectively, in a period during which a halftone image is displayed. The pulse input to the pixel electrode is a pulse having a wider pulse width than the pulse input to the common electrode.
According to this driving method, since the first potential and the second potential are input to the common electrode during the period in which the pixel electrode is at the first potential, the pixel electrode is at the first potential and the common electrode is at the first potential. A display operation (for example, a black display operation) corresponding to the potential of 2 is executed. On the other hand, since the first potential and the second potential are input to the common electrode even during the period in which the pixel electrode is at the second potential, the pixel electrode has the second potential and the common electrode has the first potential. The corresponding display operation (for example, white display operation) is executed.
That is, in the present invention, the black display operation and the white display operation are repeatedly executed within the period during which the halftone image is displayed. Then, when a pixel for displaying a halftone image is shifted from black display to gray display (halftone display), the pixel repeats black display and gray display (becomes gray display by a white display operation). After that, it is grayed out.
Thereby, the electrophoretic element performs a display operation while stirring the electrophoretic particles inside. As a result, it is possible to display an image while effectively erasing the previous display state.
Therefore, according to the present invention, it is possible to obtain a halftone display with no afterimage.

Prior to the halftone display step, it is preferable to include a monochrome image display step for displaying an image not including a halftone on the display unit.
That is, after the monochrome image is displayed by the monochrome image display step, the monochrome image can be multi-graded by the halftone display step. According to this driving method, it is possible to display more various images and to obtain an advantage that the previous image can be more reliably erased by the monochrome image display step.

First and second control lines connected to each of the pixels are formed in the display unit, and for each pixel, a pixel switching element, a latch circuit connected to the pixel switching element, and the latch circuit And a switch circuit connected to the first and second control lines, and in the second writing step, the first or second connected to the pixel electrode. It is preferable to input the second pulse to the control line.
With such a driving method, it is possible to suppress the occurrence of an afterimage when displaying a halftone even in an active matrix electrophoretic display.

Prior to the monochrome image display step, it is preferable to have an inverted image display step of displaying an inverted image of the image displayed in the monochrome image display step on the display unit.
According to this driving method, the image of the previous frame is sufficiently erased in the reverse image display step and the monochrome image display step, and the halftone image is displayed while the electrophoretic particles are agitated. An electrophoretic display device driving method that does not generate an afterimage can be obtained.

In the halftone display step, the first potential and the second potential are applied to the first pixel electrode belonging to the pixel displaying the first halftone with a pulse width wider than that of the first pulse. And the second pulse input to the first pixel electrode is inverted to the second pixel electrode belonging to the pixel that displays the second intermediate gradation. It is preferable to input the second pulse.
According to this driving method, since multi-gradation display is realized with a binary pixel electrode potential, it is possible to provide a driving method for an electrophoretic display device with excellent display quality.

Prior to the halftone display step, a monochrome image display step for causing the display unit to display a first gradation at which the gradation value of the pixel is maximum and a second gradation at which the gradation value is minimum. And in the halftone display step, the second gray scale value of the first gray scale pixel is closer to the second gray scale value than the first gray scale gray scale value. It is preferable to shift to the intermediate gray level and shift the pixel of the second gray level to the first intermediate gray level.
According to this driving method, since the electrophoretic particles are further agitated in the halftone display step, it is possible to provide a driving method for the electrophoretic display device in which afterimage generation is further suppressed.

An electrophoretic display device of the present invention includes a display unit in which an electrophoretic element including electrophoretic particles is sandwiched between a first substrate and a second substrate, and a plurality of pixels are arranged. A pixel electrode formed on the electrophoretic element side of the first substrate corresponding to a pixel, a common electrode formed on the electrophoretic element side of the second substrate and opposed to the plurality of pixel electrodes, An electrophoretic display device comprising: a control unit that controls a potential input to the pixel electrode and the common electrode; wherein the control unit displays a first potential on the common electrode when displaying an image on the display unit. And the second potential are periodically input, and the first potential and the second potential are input to the pixel electrode with a pulse width wider than one cycle of the first pulse. Enter a second pulse that repeats And executes a halftone display operation of the display unit and the display state including a desired halftone in the last period of the second pulse.

According to this configuration, a pulse that repeats the first potential and the second potential is input to the pixel electrode and the common electrode, respectively, during a period in which a halftone image is displayed. The pulse input to the pixel electrode is a pulse having a wider pulse width than the pulse input to the common electrode.
According to this configuration, since the first potential and the second potential are input to the common electrode during a period in which the pixel electrode is at the first potential, the pixel electrode is the first potential and the common electrode is the second potential. A corresponding display operation (for example, a black display operation) is executed when the potential is set to. On the other hand, since the first potential and the second potential are input to the common electrode even during the period in which the pixel electrode is at the second potential, the pixel electrode has the second potential and the common electrode has the first potential. The corresponding display operation (for example, white display operation) is executed.
That is, in the present invention, the black display operation and the white display operation are repeatedly executed within the period during which the halftone image is displayed. Then, when a pixel for displaying a halftone image is shifted from black display to gray display (halftone display), the pixel repeats black display and gray display (becomes gray display by a white display operation). After that, it is grayed out.
Thereby, the electrophoretic element performs a display operation while stirring the electrophoretic particles inside. As a result, it is possible to display an image while effectively erasing the previous display state.
Therefore, according to the present invention, it is possible to obtain a halftone display with no afterimage.

It is preferable that the control unit executes a monochrome image display operation for displaying an image including no intermediate gradation on the display unit prior to the halftone display operation.
That is, after the monochrome image is displayed by the monochrome image display operation, the monochrome image can be multi-graded by the halftone display operation. According to this configuration, it is possible to display more various images and to obtain an advantage that the previous image can be erased more reliably by the monochrome image display operation.

First and second control lines connected to each of the pixels are formed in the display unit, and for each pixel, a pixel switching element, a latch circuit connected to the pixel switching element, and the latch circuit And a switch circuit connected to the first and second control lines, and the control unit is connected to the pixel electrode in the halftone display operation. Alternatively, it is preferable to input the second pulse to the second control line.
According to this configuration, it is possible to suppress the occurrence of an afterimage when displaying a halftone even in an active matrix electrophoretic display.

Prior to the monochrome image display operation, the control unit preferably performs an inverted image display operation for displaying an inverted image of an image displayed by the monochrome image display operation on the display unit.
According to this configuration, the image of the previous frame is sufficiently erased in the reverse image display step and the monochrome image display step, and the halftone image is displayed while stirring the electrophoretic particles. It can be set as the electrophoretic display device which is not generated.

In the halftone display operation, the control unit applies the first potential to the first pixel electrode belonging to the pixel displaying the first halftone with a pulse width wider than that of the first pulse. The second pulse that repeats the second potential is input, while the second pixel electrode belonging to the pixel that displays the second intermediate gradation is input to the first pixel electrode. It is preferable to input a second pulse obtained by inverting the two pulses.
According to this configuration, since multi-gradation display can be realized with a binary pixel electrode potential, an electrophoretic display device with excellent display quality can be obtained.

Prior to the halftone display operation, the control unit displays a first gradation at which the gradation value of the pixel is maximized and a second gradation at which the gradation value is minimized on the display unit. A gradation value closer to the second gradation than the gradation value of the first intermediate gradation in the halftone display operation. It is preferable to shift to the second intermediate gray level, and to shift the pixel of the second gray level to the first intermediate gray level.
According to this configuration, since the electrophoretic particles can be further agitated in the halftone display step, an electrophoretic display device in which the occurrence of an afterimage is further suppressed can be obtained.

An electronic apparatus according to the present invention includes the electrophoretic display device described above.
According to this configuration, it is possible to provide an electronic apparatus including an excellent display unit that does not display an afterimage in a halftone image.

1 is a schematic configuration diagram of an electrophoretic display device according to a first embodiment. The figure which shows the cross-section of the principal part of an electrophoretic display apparatus. Operation | movement explanatory drawing of an electrophoretic element. Explanatory drawing which shows the drive method of the electrophoretic display device of 1st Embodiment. FIG. 6 is a schematic configuration diagram of an electrophoretic display device according to a second embodiment. FIG. 6 is a diagram illustrating a pixel circuit according to a second embodiment. The block diagram which shows the detail of a controller. 10 is a flowchart according to an image display operation in the second embodiment. Explanatory drawing which shows the drive method of an electrophoretic display apparatus. Explanatory drawing which shows the drive method of a 1st modification. Explanatory drawing which shows the drive method of a 2nd modification. FIG. 14 illustrates an example of an electronic device. FIG. 14 illustrates an example of an electronic device. FIG. 14 illustrates an example of an electronic device.

The electrophoretic display device of the present invention will be described below with reference to the drawings.
The scope of the present invention is not limited to the following embodiment, and can be arbitrarily changed within the scope of the technical idea of the present invention. Moreover, in the following drawings, in order to make each configuration easy to understand, the actual structure is different from the scale and number of each structure.

(First embodiment)
FIG. 1 is a schematic configuration diagram of an electrophoretic display device 100 according to a first embodiment of the present invention. FIG. 2A is a diagram showing an electrical configuration together with a cross-sectional structure of the electrophoretic display device 100.

  The electrophoretic display device 100 includes a display unit 5 in which a plurality of pixels (segments) 40 are arranged, a controller (control unit) 63, and a pixel electrode drive circuit 60 connected to the controller 63. The pixel electrode drive circuit 60 is connected to each pixel 40 via a pixel electrode wiring 61. Further, the display unit 5 is provided with a common electrode 37 (see FIG. 2) common to the respective pixels 40. In FIG. 1, the common electrode 37 is shown as a wiring for convenience.

  The electrophoretic display device 100 is a segment drive type electrophoretic display device that transfers image data from the controller 63 to the pixel electrode drive circuit 60 and directly inputs a potential based on the image data to each pixel 40.

  As shown in FIG. 2A, the display unit 5 of the electrophoretic display device 100 has a configuration in which an electrophoretic element 32 is sandwiched between a first substrate 30 and a second substrate 31. A plurality of pixel electrodes (segment electrodes; first electrodes) 35 are formed on the electrophoretic element 32 side of the first substrate 30, and a common electrode (second electrode) 37 is formed on the electrophoretic element 32 side of the second substrate 31. Has been. The electrophoretic element 32 has a configuration in which a plurality of microcapsules 20 enclosing electrophoretic particles are arranged in a plane. The electrophoretic display device 100 displays an image formed by the electrophoretic element 32 on the common electrode 37 side.

The first substrate 30 is a substrate made of glass, plastic, or the like and is not required to be transparent because it is disposed on the side opposite to the image display surface. The pixel electrode 35 is formed using a laminate of nickel plating and gold plating in this order on a Cu (copper) foil, Al (aluminum), ITO (indium tin oxide), or the like.
The second substrate 31 is a substrate made of glass, plastic, or the like, and is a transparent substrate because it is disposed on the image display side. The common electrode 37 is a transparent electrode formed using MgAg (magnesium silver), ITO, IZO (registered trademark; indium / zinc oxide), or the like.

A pixel electrode drive circuit 60 is connected to each pixel electrode 35 via a pixel electrode wiring 61. The pixel electrode driving circuit 60 is provided with switching elements 60s corresponding to the respective pixel electrode wirings 61. The operation of the switching element 60s performs input of electric potential to the pixel electrode 35 and electrical disconnection (high impedance). .
On the other hand, a common electrode drive circuit 64 is connected to the common electrode 37 via a common electrode wiring 62. The common electrode driving circuit 64 is provided with a switching element 64 s connected to the common electrode wiring 62, and a potential input to the common electrode 37 and electrical disconnection (high impedance) are performed by the operation of the switching element 64 s.

  In general, the electrophoretic element 32 is formed in advance on the second substrate 31 side and is handled as an electrophoretic sheet including the adhesive layer 33. In the manufacturing process, the electrophoretic sheet is handled in a state where a protective release sheet is attached to the surface of the adhesive layer 33. And the display part 5 is formed by sticking the said electrophoresis sheet which peeled off the peeling sheet with respect to the 1st board | substrate 30 (pixel electrode 35 grade | etc., Formed separately) manufactured separately. For this reason, the adhesive layer 33 exists only on the pixel electrode 35 side.

  FIG. 2B is a schematic cross-sectional view of the microcapsule 20. The microcapsule 20 has a particle size of, for example, about 30 to 50 μm, and contains therein a dispersion medium 21, a plurality of white particles (electrophoretic particles) 27, and a plurality of black particles (electrophoretic particles) 26. An encapsulated spherical body. As shown in FIG. 2, the microcapsule 20 is sandwiched between the common electrode 37 and the pixel electrode 35, and one or a plurality of microcapsules 20 are arranged in one pixel 40.

The outer shell portion (wall film) of the microcapsule 20 is formed using a translucent polymer resin such as an acrylic resin such as polymethyl methacrylate or polyethyl methacrylate, a urea resin, or gum arabic.
The dispersion medium 21 is a liquid that disperses the white particles 27 and the black particles 26 in the microcapsules 20. Examples of the dispersion medium 21 include water, alcohol solvents (methanol, ethanol, isopropanol, butanol, octanol, methyl cellosolve, etc.), esters (ethyl acetate, butyl acetate, etc.), ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.). ), Aliphatic hydrocarbons (pentane, hexane, octane, etc.), alicyclic hydrocarbons (cyclohexane, methylcyclohexane, etc.), aromatic hydrocarbons (benzene, toluene, benzenes having a long-chain alkyl group ( Xylene, hexylbenzene, hebutylbenzene, octylbenzene, nonylbenzene, decylbenzene, undecylbenzene, dodecylbenzene, tridecylbenzene, tetradecylbenzene)), halogenated hydrocarbons (methylene chloride, chloroform, tetrachloride) Element, and 1,2-dichloroethane), can be exemplified a carboxylate, it may be other oils. These substances can be used alone or as a mixture, and a surfactant or the like may be further blended.

The white particles 27 are particles (polymer or colloid) made of a white pigment such as titanium dioxide, zinc white, and antimony trioxide, and are used, for example, by being negatively charged. The black particles 26 are particles (polymer or colloid) made of a black pigment such as aniline black or carbon black, and are used by being charged positively, for example.
These pigments include electrolytes, surfactants, metal soaps, resins, rubbers, oils, varnishes, compound charge control agents, titanium-based coupling agents, aluminum-based coupling agents, silanes as necessary. A dispersant such as a system coupling agent, a lubricant, a stabilizer, and the like can be added.
Further, instead of the black particles 26 and the white particles 27, for example, pigments such as red, green, and blue may be used. According to such a configuration, red, green, blue, or the like can be displayed on the display unit 5.

FIG. 3 is an operation explanatory diagram of the electrophoretic element. 3A shows a case where the pixel 40 displays white, and FIG. 3B shows a case where the pixel 40 displays black.
In the case of white display shown in FIG. 3A, the common electrode 37 is held at a relatively high potential and the pixel electrode 35 is held at a relatively low potential. As a result, the negatively charged white particles 27 are attracted to the common electrode 37, while the positively charged black particles 26 are attracted to the pixel electrode 35. As a result, when this pixel is viewed from the common electrode 37 side which is the display surface side, white (W) is recognized.
In the case of black display shown in FIG. 3B, the common electrode 37 is held at a relatively low potential, and the pixel electrode 35 is held at a relatively high potential. As a result, the positively charged black particles 26 are attracted to the common electrode 37, while the negatively charged white particles 27 are attracted to the pixel electrode 35. As a result, when this pixel is viewed from the common electrode 37 side, black (B) is recognized.

[Driving method]
Next, a driving method of the electrophoretic display device having the above configuration will be described.
FIG. 4 is an explanatory diagram showing a method for driving an electrophoretic display device according to the present invention. FIGS. 4A and 4B are plan views showing state transitions of the pixels 40 in the driving method described below. FIG. 4C is a timing chart showing potentials input to the pixel electrode and the common electrode.

  In the present embodiment, a driving method in the case of shifting the two pixels 40 displayed in black and white as shown in FIG. 4A to the halftone display (gray display) as shown in FIG. 4 will be described.

  In the white display pixel 40 shown in FIG. 4A, the black particles 26 are attracted to the pixel electrodes SEG0 and SEG1, and the white particles 27 are attracted to the common electrode 37 side. As a driving method for shifting to such a display state, a conventionally known driving method can be employed. For example, high level (for example, 15 V) and low level (for example, 0 V) potentials are input to the two pixel electrodes SEG0 and SEG1, respectively, and a low level potential and a high level potential are periodically input to the common electrode COM (common electrode 37). By inputting repeated pulses, the two pixels 40 can be brought into a black display state and a white display state, respectively.

  Next, in order to change from the black display state and the white display state shown in FIG. 4A to the gray display state shown in FIG. 4B, as shown in FIG. 15V) and a pulse (first pulse) that periodically repeats a low level (for example, 0V). Further, a rectangular wave pulse (second pulse) that periodically repeats a low level (for example, 0 V) and a high level (for example, 15 V) is input to the pixel electrode SEG0, and the second pulse is inverted to the pixel electrode SEG1. Input the signal. At this time, the pulse width T2 of the second pulse input to the pixel electrodes SEG0 and SEG1 is set to be wider than the pulse width T1 of the first pulse input to the common electrode COM (T1> T2). ). As shown in FIG. 4C, the step of inputting the first pulse to the common electrode COM and inputting the second pulse (or the inverted signal of the second pulse) to the pixel electrodes SEG0 and SEG1 is a halftone display. Corresponds to a step.

  Specifically, the pulse width of the pulses input to the pixel electrodes SEG0 and SEG1 is 3.0 times the pulse width of the pulses input to the common electrode COM. Further, the rise and fall of the pulse input to the pixel electrode SEG0 are synchronized with the fall and rise of the pulse input to the common electrode COM, respectively. The rise and fall of the pulse input to the pixel electrode SEG1 is synchronized with the rise and fall of the pulse input to the common electrode COM.

  Thereby, in the pixel 40 to which the pixel electrode SEG0 belongs, the electrophoretic element is driven when the common electrode COM becomes high level during the period in which the pixel electrode SEG0 is low level. Then, as shown in FIG. 4B, the pixel 40 to which the pixel electrode SEG0 belongs is displayed in gray. Further, when the common electrode COM is at a low level during a period in which the pixel electrode SEG0 is at a high level, the electrophoretic element is driven. Then, as shown in FIG. 4A, the pixel 40 to which the pixel electrode SEG0 belongs is displayed in black. Thus, the pixel 40 to which the pixel electrode SEG0 belongs is displayed in gray after repeating gray display and black display.

  On the other hand, in the pixel 40 to which the pixel electrode SEG1 belongs, when the pixel electrode SEG1 is in the high level period and the common electrode COM is in the low level period, the electrophoretic element is driven. Then, as shown in FIG. 4B, the pixel 40 to which the pixel electrode SEG0 belongs is displayed in gray. Further, when the common electrode COM becomes low level during the period in which the pixel electrode SEG1 is high level, the electrophoretic element is driven. Then, as shown in FIG. 4A, the pixel 40 to which the pixel electrode SEG1 belongs is displayed in white. Thus, the pixel 40 to which the pixel electrode SEG1 belongs is displayed in gray after repeating gray display and white display.

In the driving method of the present embodiment described above, a pulse that periodically repeats a high level and a low level is input to the common electrode 37, and the pixel electrode 35 belonging to the pixel 40 that shifts to gray display is connected to the common electrode 37. A pulse that periodically repeats a high level and a low level with a wider pulse width than the input pulse is input.
As described above, in the driving method of the present embodiment, the electrophoretic particles (black particles 26 and white particles 27) of the electrophoretic elements 32 belonging to the pixels 40 that shift to gray display are agitated, and a gray frame image is displayed in the previous frame. Image does not remain as an afterimage.

In addition, a period for erasing the image displayed on the display unit 5 may be provided before inputting a pulse that periodically repeats the high level and the low level to the pixel electrode 35 belonging to the pixel 40 that shifts to gray display. Good.
With such a driving method, in the pixel 40 that shifts to gray display, after the image of the previous frame is erased, the electrophoretic particles are further stirred and displayed in gray. Therefore, the image of the previous frame is surely erased, no afterimage is generated in the gray-displayed image, and the display performance can be improved.

(Second Embodiment)
In the first embodiment, the case where the driving method according to the present invention is applied to the segment type electrophoretic display device has been described. In this embodiment, the driving method according to the present invention is applied to an active matrix electrophoretic display device, which will be described in more detail.

FIG. 5 is a diagram illustrating a schematic configuration of the electrophoretic display device 200 according to the second embodiment. FIG. 6 is a diagram illustrating a pixel circuit of the electrophoretic display device 200 according to the second embodiment.
5 and 6, the same reference numerals are given to the same components as those in the first embodiment, and detailed description thereof will be omitted.

  As shown in FIG. 5, the electrophoretic display device 200 includes a display unit 5 in which pixels 140 are arranged in a matrix, a scanning line driving circuit 161, a data line driving circuit 162, a controller 163 (control unit), A common power supply modulation circuit 164. The controller 163 comprehensively controls the electrophoretic display device 200 based on image data and synchronization signals supplied from the host device.

In the display unit 5, a plurality of scanning lines 66 extending from the scanning line driving circuit 161 and a plurality of data lines 68 extending from the data line driving circuit 162 are formed, and each is connected to the pixel 140.
Further, the display unit 5 is provided with a low potential power line 49, a high potential power line 50, a common electrode line 55, a first control line 91, and a second control line 92 extending from the common power modulation circuit 164. Each wiring is also connected to the pixel 140. Under the control of the controller 63, the common power supply modulation circuit 64 generates various signals to be supplied to each of the above wirings, and electrically connects and disconnects (high impedance) these wirings.

  The scanning line driving circuit 161 is connected to each pixel 140 via m scanning lines 66 (Y1, Y2,..., Ym). Under the control of the controller 163, the first to mth rows are connected. The scanning lines 66 are sequentially selected, and a selection signal defining the ON timing of the selection transistor 41 (see FIG. 6) provided in the pixel 140 is supplied via the selected scanning line 66.

  The data line driving circuit 162 is connected to each pixel 140 via n data lines 68 (X1, X2,..., Xn), and corresponds to each pixel 140 under the control of the controller 163. An image signal defining 1-bit pixel data is supplied to the pixel 140.

  In the present embodiment, a low level (L) image signal is supplied to the pixel 140 when the pixel data “0” is defined, and a high level (H) image is defined when the pixel data “1” is defined. It is assumed that a signal is supplied to the pixel 140.

  As shown in FIG. 6, the pixel 140 includes a selection transistor 41 (pixel switching element), a latch circuit (memory circuit) 70, a switch circuit 80, an electrophoretic element 32, a pixel electrode 35, and a common electrode 37. And are provided. A scanning line 66, a data line 68, a low potential power line 49, a high potential power line 50, a first control line 91, and a second control line 92 are arranged so as to surround these elements. The pixel 40 has an SRAM (Static Random Access Memory) type configuration in which the latch circuit 70 holds an image signal as a potential.

  The selection transistor 41 is an N-MOS (Negative Metal Oxide Semiconductor) transistor. The selection transistor 41 has a gate terminal connected to the scanning line 66, a source terminal connected to the data line 68, and a drain terminal connected to the data input terminal N 1 of the latch circuit 70.

  The data input terminal N1 and the data output terminal N2 of the latch circuit 70 are connected to the switch circuit 80. Further, the switch circuit 80 is connected to the pixel electrode 35 and to the first and second control lines 91 and 92. The electrophoretic element 32 is sandwiched between the pixel electrode 35 and the common electrode 37.

  The latch circuit 70 includes a transfer inverter 70t and a feedback inverter 70f. Both the transfer inverter 70t and the feedback inverter 70f are C-MOS inverters. The transfer inverter 70t and the feedback inverter 70f have a loop structure in which the other output terminal is connected to each other's input terminal, and each inverter has a high potential connected via a high potential power supply terminal PH. A power supply voltage is supplied from the power supply line 50 and the low potential power supply line 49 connected via the low potential power supply terminal PL.

  The transfer inverter 70t includes a P-MOS (Positive Metal Oxide Semiconductor) transistor 71 and an N-MOS transistor 72 each having a drain terminal connected to the data output terminal N2. The source terminal of the P-MOS transistor 71 is connected to the high potential power supply terminal PH, and the source terminal of the N-MOS transistor 72 is connected to the low potential power supply terminal PL. The gate terminals of the P-MOS transistor 71 and the N-MOS transistor 72 (input terminal of the transfer inverter 70t) are connected to the data input terminal N1 (output terminal of the feedback inverter 70f).

  The feedback inverter 70f has a P-MOS transistor 73 and an N-MOS transistor 74 whose drain terminals are connected to the data input terminal N1. The gate terminals of the P-MOS transistor 73 and the N-MOS transistor 74 (input terminal of the feedback inverter 70f) are connected to the data output terminal N2 (output terminal of the transfer inverter 70t).

  When the high-level (H) image signal (pixel data “1”) is stored in the latch circuit 70 configured as described above, a low-level (L) signal is output from the data output terminal N2 of the latch circuit 70. On the other hand, when a low level (L) image signal (pixel data “0”) is stored in the latch circuit 70, a high level (H) signal is output from the data output terminal N2.

The switch circuit 80 includes a first transmission gate TG1 and a second transmission gate TG2.
The first transmission gate TG1 includes a P-MOS transistor 81 and an N-MOS transistor 82. The source terminals of the P-MOS transistor 81 and the N-MOS transistor 82 are connected to the first control line 91, and the drain terminals of the P-MOS transistor 81 and the N-MOS transistor 82 are connected to the pixel electrode 35. The gate terminal of the P-MOS transistor 81 is connected to the data input terminal N1 of the latch circuit 70 (the drain terminal of the selection transistor 41), and the gate terminal of the N-MOS transistor 82 is connected to the data output terminal N2 of the latch circuit 70. It is connected to the.

  The second transmission gate TG 2 includes a P-MOS transistor 83 and an N-MOS transistor 84. The source terminals of the P-MOS transistor 83 and the N-MOS transistor 84 are connected to the second control line 92, and the drain terminals of the P-MOS transistor 83 and the N-MOS transistor 84 are connected to the pixel electrode 35. The gate terminal of the P-MOS transistor 83 is connected to the data output terminal N 2 of the latch circuit 70, and the gate terminal of the N-MOS transistor 84 is connected to the data input terminal N 1 of the latch circuit 70.

Here, when a low level (L) image signal (pixel data “0”) is stored in the latch circuit 70 and a high level (H) signal is output from the data output terminal N2, the first transmission gate TG1. Is turned on, and the potential S <b> 1 supplied via the first control line 91 is input to the pixel electrode 35.
On the other hand, when a high level (H) image signal (pixel data “1”) is stored in the latch circuit 70 and a low level (L) signal is output from the data output terminal N2, the second transmission gate TG2 The potential S <b> 2 supplied through the second control line 92 is input to the pixel electrode 35.

FIG. 7 is a block diagram showing details of the controller 163 provided in the electrophoretic display device 200.
The controller 163 includes a control circuit 261 as a CPU (Central Processing Unit), a storage unit 262, a voltage generation circuit 263, a data buffer 264, a frame memory 265, and a memory control circuit 266.

  The control circuit 261 generates control signals (timing pulses) such as a clock signal CLK, a horizontal synchronization signal Hsync, and a vertical synchronization signal Vsync, and supplies these control signals to each circuit arranged around the control circuit 261. The control circuit 261 receives a control signal Cmd from a host device (not shown), and the control device 261 controls each circuit based on the control signal Cmd and executes various image display operations.

The storage unit 262 is a nonvolatile memory including, for example, an EEPROM (Electrically-Erasable and Programmable Read-Only Memory), a flash memory, and the like, and setting values (mode setting values and volumes) necessary for controlling the operation of each circuit by the control circuit 261. Value) and the like. For example, the setting value of the drive sequence for each operation mode is stored as a LUT (Look Up Table).
The storage unit 262 may store preset image data used for the operation of the electrophoretic display device. For example, logo image data used when the electrophoretic display device 200 is activated, warning display image data, and the like may be stored.

The voltage generation circuit 263 is a circuit that supplies a driving voltage to the scanning line driving circuit 161, the data line driving circuit 162, and the common power supply modulation circuit 164.
The data buffer 264 is an interface unit with the host device in the controller 163, holds the image data D of the display image input from the host device, and transmits the image data D to the control circuit 261.

The frame memory 265 is a readable / writable memory having a readable / writable memory space corresponding to the arrangement of the pixels 140 of the display unit 5. The memory control circuit 266 develops the image data D supplied from the control circuit 261 in correspondence with the pixel array of the display unit 5 in accordance with the control signal, and writes it in the frame memory 265. The frame memory 265 sequentially transmits a group of stored image data D to the data line driving circuit 162 as an image signal.
The data line driving circuit 162 latches the image signal transmitted from the frame memory 265 one line at a time based on the control signal supplied from the control circuit 261. Then, the latched image signal is supplied to the data line 68 in synchronization with the sequential selection operation of the scanning line 66 by the scanning line driving circuit 161.

[Driving method]
FIG. 8 is a flowchart relating to an image display operation in the electrophoretic display device having the above-described configuration.
As shown in FIG. 8, the driving method of the present embodiment includes a reverse image display step S101, a monochrome image display step S102, and a halftone display step S103.

  FIG. 9 is an explanatory diagram showing an image display operation in the electrophoretic display device. FIG. 9A is a diagram conceptually showing image data transferred to the display unit 5, and FIG. 9B is a diagram showing a display state of the display unit 5 corresponding to FIG. 9A. . FIG. 9C is a timing chart showing the potential states of the common electrode 37, the first control line 91, and the second control line 92 corresponding to FIGS. 9A and 9B.

  Hereinafter, the driving method of this embodiment will be described in detail with reference to FIGS. 8 and 9.

[Reverse Image Display Step S101]
First, in the reverse image display step S101, the image data D1 shown in FIG. 8A is input to the control circuit 261 via the data buffer 264. In addition, a control signal Cmd for displaying an image of the display unit 5 in the pixel electrode constant potential driving mode is input to the control circuit 261.
In the pixel electrode constant potential driving mode, the pixel electrode 35 is fixed at a high level or a low level, and a pulse (first pulse) that repeats a high level and a low level is input to the common electrode 37, whereby the electrophoretic element 32 is controlled. This is an operation mode for driving.

  A portion (black data) displayed in black in the image data D1 corresponds to pixel data “0” (low level (L) image signal). On the other hand, the portion (white data) displayed in white in the image data D1 corresponds to the pixel data “1” (high level (H) image signal).

  The control circuit 261 transfers the input image data D1 to the memory control circuit 266. The memory control circuit 266 expands the input image data D1 into the memory space of the frame memory 265. As a result, the image signal corresponding to the image data D1 can be supplied from the frame memory 265 to the data line driving circuit 162.

  After that, the control circuit 261 transmits a control signal to the scanning line driving circuit 161 and the data line driving circuit 162. The scanning line driving circuit 161 inputs a pulse as a selection signal to the scanning line 66 based on the control signal. On the other hand, the data line driving circuit 162 supplies an image signal supplied from the frame memory 265 to the selected pixel 140 in synchronization with the selection operation by the scanning line driving circuit 161.

Thus, the image data D1 shown in FIG. 9A is input to the pixel 140 of the display unit 5.
In the pixel 140 corresponding to the black data of the image data D1, a low level (L) image signal is held in the latch circuit 70, and the first signal is transmitted via the transmission gate TG1 that is turned on by the output from the latch circuit 70. The control line 91 and the pixel electrode 35 are connected.
On the other hand, in the pixel 140 corresponding to the white data of the image data D1, a high level (H) image signal is held in the latch circuit 70, and the second control line 92 and the pixel electrode 35 are connected via the transmission gate TG2. Is done.

Next, the control circuit 261 pulse-drives the common electrode 37 to the common power supply driving circuit 164, and outputs a control signal for setting the first and second control lines 91 and 92 to a predetermined constant potential.
Based on the input control signal, the common power supply driving circuit 164 sets the first control line 91 (potential S1) to the low level (L; for example, 0V) and the second level as shown in FIG. 9C. The control line 92 (potential S2) is held at a high level (H; for example, 15 V), and a rectangular wave pulse that periodically repeats the high level and the low level is input to the common electrode 37 (potential Vcom).

  Then, since the first or second control lines 91 and 92 and the pixel electrode 35 are connected to all the pixels 140 of the display unit 5, the pixel electrode 35 connected to the first control line 91 is connected to the pixel electrode 35. A level potential and a high level potential are input to the pixel electrode 35 connected to the second control line 92.

As a result, the electrophoretic element 32 is driven by a potential difference generated between the first control line 91 and the pixel electrode 35 during a period in which the common electrode 37 is at a high level. As a result, the black particles 26 are attracted toward the common electrode 37 and the white particles 27 are attracted toward the pixel electrode 35 (see FIG. 3). As shown in FIG. 9B, white data (pixel data “1”) is obtained. The input pixel 140 is in a black display state.
On the other hand, the electrophoretic element 32 is driven by a potential difference generated between the second control line 92 and the pixel electrode 35 during a period in which the common electrode 37 is at a low level. As a result, the white particles 27 are attracted toward the common electrode 37 and the black particles 26 are attracted toward the pixel electrode (see FIG. 3), and black data (pixel data “0”) is input as shown in FIG. 9B. The displayed pixel 140 is in a white display state.

[Monochrome image display step S102]
Next, when the process proceeds to the monochrome image display step S102, the control signal Cmd for displaying the entire white surface of the display unit 5 in the pixel electrode constant potential driving mode is input to the control circuit 261. The image data D1 input to the control circuit 261 via the data buffer 264 is the same as in the reverse image display step S101. Thereafter, the image data D1 is transferred to the display unit 5 under the control of the control circuit 261.
If the display unit 5 continues to hold the image data D1 transferred in the reverse image display step S101, the transfer operation of the image data D1 is unnecessary, and the supply of the image data D1 to the controller 163 is also unnecessary. is there.

Next, the control circuit 261 pulse-drives the common electrode 37 with respect to the common power supply driving circuit 164, and outputs a control signal for setting the first and second control lines 91 and 92 to a predetermined constant potential.
Based on the input control signal, the common power supply driving circuit 164 holds the first control line 91 at a high level and the second control line 92 at a low level as shown in FIG. A rectangular wave pulse that repeats a high level and a low level is input to the common electrode 37.

  When the potential is input as described above, the potentials of the first and second control lines 91 and 92 are input to the pixel electrode 35 and the pixel electrodes connected to the first control line 91 in all the pixels 140. A high level potential is input to 35, and a low level potential is input to the pixel electrode 35 connected to the second control line 92.

The electrophoretic element 32 is driven by a potential difference generated between the pixel electrode 35 connected to the first control line 91 and the common electrode 37 during a period in which the common electrode 37 is at a low level. As a result, the black particles 26 are attracted to the common electrode 37 side, and the white particles 27 are attracted to the pixel electrode 35 side (see FIG. 3). As shown in FIG. 140 is in a black display state.
On the other hand, the electrophoretic element 32 is driven by a potential difference generated between the pixel electrode 35 connected to the second control line 92 and the common electrode 37 during a period in which the common electrode 37 is at a high level. As a result, the white particles 27 are attracted to the common electrode 37 side and the black particles 26 are attracted to the pixel electrode 35 side (see FIG. 3), and as shown in FIG. 140 is in a white display state.
That is, in the monochrome image display step S102, a reverse image of the image displayed in the reverse image display step S101 is displayed on the display unit 5.

[Halftone Display Step S103]
Next, when proceeding to the halftone display step S103, the image data D2 shown in FIG. 9A is input to the control circuit 261 via the data buffer 264. In addition, a control signal Cmd including a command for operating the display unit 5 in the pixel electrode pulse drive mode is input to the control circuit 261.
In the pixel electrode pulse drive mode, a pulse (first pulse) that repeats a high level and a low level is input to the common electrode 37, and a high level and a low level are input to the pixel electrode 35 with a wider pulse width than the first pulse. This is an operation mode in which the electrophoretic element is driven by inputting a pulse that repeats the level (second pulse).
Thereafter, the image data D <b> 2 is transferred to the display unit 5 under the control of the control circuit 261.

Next, the control circuit 261 inputs a predetermined potential to each of the first and second control lines 91 and 92 and outputs a control signal for driving the common electrode 37 to the common power supply driving circuit 164. Based on the input control signal, the common power supply driving circuit 164 applies a pulse (second pulse) that periodically repeats a high level and a low level to the first control line 91 as shown in FIG. 9C. ) And the inverted pulse of the pulse input to the first control line 91 is input to the second control line 92. A pulse (first pulse) that periodically repeats the high level and the low level is input to the common electrode 37.
At this time, the pulse input to the first and second control lines 91 and 92 is set to have a wider pulse width (T2> T1) than the pulse input to the common electrode 37.

In the pixels 140 belonging to the areas A2 and A4 in FIG. 9B to which black data (pixel data “0”) is input, a potential is input to the pixel electrode 35 via the first control line 91 (potential S1). The
During a period in which a high level potential is input to the pixel electrode 35 and a low level potential is input to the common electrode 37, the electrophoretic element 32 is driven by a potential difference generated between the pixel electrode 35 and the common electrode 37.

  At this time, the electrophoretic element 32 performs a black display operation. However, as shown in FIG. 9C, the pulse width T2 of the pulse input to the pixel electrode 35 is set short in the halftone display step S103. For this reason, the pixel 140 in the area A2 that originally displayed white is not displayed black, but is displayed light gray. On the other hand, the display of the pixel 140 in the area A4 that was originally black is not changed.

  Next, during a period in which a low-level potential is input to the pixel electrode 35 of the pixel 140 belonging to the regions A2 and A4 and a high-level potential is input to the common electrode 37, the pixel electrode 35 is interposed between the pixel electrode 35 and the common electrode 37. The electrophoretic element 32 is driven by the generated potential difference.

  At this time, the electrophoretic element 32 performs a white display operation. In the halftone display step S103, the pulse width T2 of the pulse input to the pixel electrode 35 is set to be short. The A4 pixel 140 does not display white but displays dark gray. On the other hand, the pixel 140 in the area A2 that was originally displayed in light gray is displayed in white.

  As described above, by inputting a plurality of pulses to the pixel electrode 35, the above black display operation and white display operation are repeatedly executed. Finally, when a high level potential is input to the pixel electrode 35 and gray display is performed, the display operation ends.

On the other hand, in the pixel 140 (regions A 1 and A 3) to which white data (pixel data “1”) is input, a potential is input to the pixel electrode 35 via the second control line 92.
During a period in which a low level potential is input to the pixel electrode 35 and a high level potential is input to the common electrode 37, the electrophoretic element 32 is driven by a potential difference generated between the pixel electrode 35 and the common electrode 37.

  At this time, the electrophoretic element 32 performs a white display operation. In the halftone display step S103, the pulse width T2 of the pulse input to the pixel electrode 35 is set to be short. The A3 pixel 140 does not display white but displays dark gray. On the other hand, the display of the pixel 140 in the area A1 that was originally white is not changed.

  Next, a potential difference generated between the pixel electrode 35 and the common electrode 37 during a period in which a high level potential is input to the pixel electrode 35 of the pixel 140 belonging to the regions A1 and A3 and a low level is input to the common electrode 37. Thus, the electrophoretic element 32 is driven.

  At this time, the electrophoretic element 32 performs a black display operation. In the halftone display step S103, the pulse width T2 of the pulse input to the pixel electrode 35 is set to be short. The A1 pixel 140 does not display black but displays light gray. On the other hand, the pixel 140 in the area A3 that was originally dark gray is displayed in black.

  A plurality of pulses are inputted to the pixel electrode 35, and the black display operation and the white display operation are repeatedly executed. Finally, when a low level potential is input to the pixel electrode 35 and gray display is performed, the display operation ends.

  Through the above halftone display step S103, part of the area (area A3) displayed in black in the monochrome image display step S103 is changed to dark gray halftone display, and part of the area displayed in white (area A2). ) Becomes a light gray halftone display. As a result, four gradation display including intermediate gradation is realized.

As described above, in the driving method according to the present embodiment, in the halftone display step S103 in which a halftone image is displayed on the display unit 5, the common electrode 37 is repeatedly pulsed between the high level and the low level with the pulse width T1. (First pulse) is input, and a pulse repeating a high level and a low level is input to the pixel electrode 35 with a pulse width T2 wider than the first pulse.
As a result, light gray is displayed after repeating light gray and white in the area A2, and dark gray is displayed after repeating dark gray and black in the area A3.

  Thus, the display operation is performed while the electrophoretic element 32 is driven. As a result, the image can be displayed while effectively erasing the image of the previous frame. Can be obtained.

  In the inverted pixel display step S101 and the monochrome image display step S102, all the pixels 140 constituting the display unit 5 are displayed in white and black, and after the previous frame image is erased, the halftone display step S103 is further performed. Since the halftone image is displayed while deleting the afterimage of the previous frame, the display quality can be further improved.

In addition, as described above, the electrophoretic display device 200 according to the present embodiment includes the switch circuit 80 connected to the first and second control lines 91 and 92 in the pixel 140. By controlling the potential of the control lines 91 and 92, the potential of the pixel electrode 35 can be directly controlled.
Therefore, if the display unit 5 holds the pixel data D, the potential of the pixel electrode 35 can be directly controlled by controlling the potentials of the first and second control lines 91 and 92, and the image display operation can be performed. It can be simplified.

  Further, the halftone display areas A2 and A3 are further divided, and the first and second control lines 91 and 92 are connected to the pixel electrodes 35 of the pixels 140 belonging to each of the divided areas, thereby displaying the halftone display. By executing step S103, a multi-tone image can be displayed.

(First modification)
In the above embodiment, after each pixel 140 is displayed in white and black in the reverse image display step S101 and the monochrome image display step S102, a halftone image is displayed in the halftone display step S103. A driving method that simplifies the previous step of the halftone display step S103 may be employed.

  FIG. 10 is an explanatory diagram showing an image display operation by the driving method of the first modified example according to the present embodiment. 10A is a diagram conceptually showing image data transferred to the display unit 5, and FIG. 10B is a diagram showing a display state of the display unit 5 corresponding to FIG. 10A. . FIG. 10C is a timing chart showing potential states of the common electrode 37, the first control line 91, and the second control line 92 corresponding to FIGS. 10A and 10B.

  As shown in FIG. 10, the driving method of the first modification of the present embodiment includes a monochrome image display step S102 and a halftone display step S103.

  When the previous frame image is deleted in the monochrome image display step S101, the process proceeds to a halftone display step S103.

  When the process proceeds to the halftone display step S103, the electrophoretic element 32 repeats black display and white display and erases the previous frame image, while the area A1 is displayed in white, the area A2 is displayed in light gray, and the area A3 is displayed in dark gray The area A4 shifts to black display.

  Also in the driving method according to the first modification described above, the halftone image is erased in the monochrome image display step S102, and the halftone image is erased in the halftone display step S103 while the halftone image is erased. 5 can be displayed. Therefore, it is possible to provide a high-quality electrophoretic display device capable of suppressing the occurrence of afterimages and displaying a halftone image.

(Second modification)
The second modification of the present embodiment is an embodiment in which the pulse width of a pulse (second pulse) input to the first and second control lines 91 and 92 is changed.

  FIG. 11 is an explanatory diagram showing an image display operation by the driving method of the first modified example according to the present embodiment. FIG. 11A is a diagram conceptually showing image data transferred to the display unit 5, and FIG. 11B is a diagram showing a display state of the display unit 5 corresponding to FIG. 11A. . FIG. 11C is a timing chart showing the potential states of the common electrode 37, the first control line 91, and the second control line 92 corresponding to FIGS. 11A and 11B.

  As shown in FIG. 11, the driving method of the second modified example of the present embodiment includes a reverse image display step S101, a monochrome image display step S102, and a halftone display step S103.

  When the image of the previous frame is deleted in the reverse image display step S101 and the monochrome image display step S102, the process proceeds to a halftone display step S103.

When the process proceeds to the halftone display step S103, a pulse (second pulse) that periodically repeats the high level and the low level is input to the first control line 91, and the first control line 92 receives the first control. An inversion pulse of the pulse input to the line 91 is input. A pulse (first pulse) that periodically repeats the high level and the low level is input to the common electrode 37.
At this time, the pulse width T3 of the pulses input to the first and second control lines 91 and 92 is set wider than the pulse width T2 shown in FIG. 9 (T3> T2).

  Specifically, the pulse width T2 input to the pixel electrode 35 in the above embodiment is four times the pulse width T1 input to the common electrode 37, but is input to the pixel electrode 35 in the present modification. The pulse width T3 is set to 6 times the pulse width T1 input to the common electrode 37.

In the pixels 140 belonging to the regions A2 and A4 in FIG. 11B to which black data (pixel data “0”) is input, a high level potential is input to the pixel electrode 35 and a low level potential is input to the common electrode 37. During the input period, the electrophoretic element 32 performs a black display operation due to a potential difference generated between the pixel electrode 35 and the common electrode 37.
At this time, as shown in FIG. 11C, the pulse width T3 of the pulse input to the pixel electrode 35 is set wider than the pulse width T2 shown in FIG. The pixel 140 in the region A2 that was the first gradation) is dark gray (second intermediate gradation). On the other hand, the display of the pixel 140 in the area A4 that was originally black is not changed.

Next, during a period in which a low-level potential is input to the pixel electrode 35 of the pixel 140 belonging to the regions A2 and A4 and a high-level potential is input to the common electrode 37, the pixel electrode 35 is interposed between the pixel electrode 35 and the common electrode 37. The electrophoretic element 32 performs a white display operation due to the generated potential difference.
At this time, as shown in FIG. 11C, the pulse width T3 of the pulse input to the pixel electrode 35 is set wider than the pulse width T2 shown in FIG. The pixel 140 in the region A4 that is the second gradation) is displayed in a light gray display (first intermediate gradation). On the other hand, the pixel 140 in the region A2 that was originally dark gray is displayed in white.

  A plurality of pulses are inputted to the pixel electrode 35, and the black display operation and the white display operation are repeatedly executed. Finally, when a high level potential is input to the pixel electrode 35 and gray display is performed, the display operation ends.

In the pixels 140 belonging to the areas A1 and A3 in FIG. 11B to which white data (pixel data “1”) is input, a low-level potential is input to the pixel electrode 35 and a high-level potential is input to the common electrode 37. During the input period, the electrophoretic element 32 performs a white display operation due to a potential difference generated between the pixel electrode 35 and the common electrode 37.
At this time, as shown in FIG. 11C, the pulse width T3 of the pulse input to the pixel electrode 35 is set wider than the pulse width T2 shown in FIG. The pixel 140 in the area A3 is light gray. On the other hand, the display of the pixel 140 in the area A1 that was originally white display does not change.

Electrophoresis is caused by a potential difference generated between the pixel electrode 35 and the common electrode 37 during a period in which a high level potential is input to the pixel electrode 35 of the pixel 140 belonging to the regions A1 and A3 and a low level is input to the common electrode 37. The element 32 performs a black display operation.
At this time, as shown in FIG. 11C, the pulse width T3 of the pulse input to the pixel electrode 35 is set wider than the pulse width T2 shown in FIG. The pixel 140 in the area A1 is dark gray. On the other hand, the pixel 140 in the region A3, which was originally light gray, is displayed in black.

  A plurality of pulses are inputted to the pixel electrode 35, and the black display operation and the white display operation are repeatedly executed. Finally, when a low-level potential is input to the pixel electrode 35 and a gray display is obtained, the display operation ends.

  As a result, in the area A2, after dark gray and white are repeated, dark gray is displayed, and in the area A3, after light gray and black are repeated, light gray is displayed.

  According to the driving method according to the second modification described above, since the time for driving the electrophoretic element 32 is extended and the halftone image is displayed, the electrophoretic particles are further agitated. In addition, the afterimage of the previous frame can be made less likely to occur.

  Also in the driving method of the second modified example, the driving method including the monochrome image display step S102 and the halftone display step S103 can be adopted by simplifying the steps preceding the halftone display step S103. .

(Electronics)
Next, the case where the electrophoretic display device of the above embodiment is applied to an electronic device will be described.
FIG. 12 is a front view of the wrist watch 1000. The wrist watch 1000 includes a watch case 1002 and a pair of bands 1003 connected to the watch case 1002.
A display unit 1005 including the electrophoretic display device 100 (200) of the above embodiment, a second hand 1021, a minute hand 1022, and an hour hand 1023 are provided on the front surface of the watch case 1002. On the side surface of the watch case 1002, a crown 1010 and an operation button 1011 are provided as operation elements. The crown 1010 is connected to a winding stem (not shown) provided inside the case, and is integrally provided with the winding stem so that it can be pushed and pulled in multiple stages (for example, two stages) and can be rotated. . The display unit 1005 can display a background image, a character string such as date and time, or a second hand, a minute hand, and an hour hand.

  FIG. 13 is a perspective view illustrating a configuration of the electronic paper 1100. An electronic paper 1100 includes the electrophoretic display device 100 (200) of each of the above embodiments in a display area 1101. The electronic paper 1100 is flexible and includes a main body 1102 made of a rewritable sheet having the same texture and flexibility as conventional paper.

  FIG. 14 is a perspective view showing the configuration of the electronic notebook 1200. An electronic notebook 1200 is obtained by bundling a plurality of the electronic papers 1100 and sandwiching them between covers 1201. The cover 1201 includes display data input means (not shown) for inputting display data sent from an external device, for example. Thereby, according to the display data, the display content can be changed or updated while the electronic paper is bundled.

According to the wristwatch 1000, the electronic paper 1100, and the electronic notebook 1200 described above, the electrophoretic display device 100 (200) according to the present invention is employed in the display unit, so that an afterimage can be suppressed and a halftone image can be displayed. It is an electronic device equipped with a display portion with excellent display performance.
In addition, the electronic device shown in each figure illustrates the electronic device which concerns on this invention, and does not limit the technical scope of this invention. For example, the electrophoretic display device according to the present invention can be suitably used for a display portion of an electronic device such as a mobile phone or a portable audio device.

  100,200 electrophoretic display device, 32 electrophoretic element, 35 pixel electrode, 37 common electrode, 40,140 pixel, 63,163 controller (control unit), 70 latch circuit, 80 switch circuit, 91 first control line, 92 second control line,

Claims (13)

An electrophoretic element including electrophoretic particles is sandwiched between a first substrate and a second substrate, and a display unit is formed by arranging a plurality of pixels. The first substrate corresponds to each of the pixels. A driving method of an electrophoretic display device, comprising: a pixel electrode formed on the electrophoretic element side of the second substrate; and a common electrode formed on the electrophoretic element side of the second substrate and facing the plurality of pixel electrodes. And
An image display step of displaying an image on the display unit;
A first pulse that periodically repeats a first potential and a second potential is input to the common electrode, while the first pulse is input to the pixel electrode with a pulse width wider than one cycle of the first pulse. A halftone display step of inputting a second pulse that periodically repeats a potential and the second potential, and setting the display unit to a display state including a desired halftone in the last period of the second pulse. A method for driving an electrophoretic display device, comprising: Prior to the halftone display step,
2. The electrophoretic display device according to claim 1, further comprising a monochrome image display step of causing the display unit to display an image that does not include an intermediate gradation based on image data common to the halftone display step. Driving method. A first control line and a second control line connected to each of the pixels are formed in the display unit, and for each pixel, a pixel switching element, a latch circuit connected to the pixel switching element, a switch circuit output terminal coupled to said first control line and the second control line of said latch circuit, is provided with,
In the second writing step,
The driving method of the electrophoretic display device according to claim 1 or 2, characterized in that inputting the second pulse to the first control line or the second control line connected to the pixel electrode. 3. The electrophoretic display device according to claim 2, further comprising a reverse image display step for displaying a reverse image of the image displayed in the monochrome image display step on the display unit prior to the monochrome image display step. Driving method. In the halftone display step,
A second pulse that repeats the first potential and the second potential with a wider pulse width than the first pulse on the first pixel electrode belonging to the pixel that displays the first intermediate gradation. While typing
An inverted signal of a second pulse obtained by inverting the second pulse input to the first pixel electrode is input to the second pixel electrode belonging to the pixel displaying the second intermediate gradation. The method for driving an electrophoretic display device according to claim 1, wherein: Prior to the halftone display step, a monochrome image display step for causing the display unit to display a first gradation at which the gradation value of the pixel is maximum and a second gradation at which the gradation value is minimum. Including
In the halftone display step,
The pixel of the first gradation is shifted to the second intermediate gradation having a gradation value closer to the second gradation than the gradation value of the first intermediate gradation, and the second gradation 6. The driving method of an electrophoretic display device according to claim 5, wherein the pixel having the gray level is shifted to the first intermediate gray level. An electrophoretic element including electrophoretic particles is sandwiched between a first substrate and a second substrate, and a display unit is formed by arranging a plurality of pixels. The first substrate corresponds to each of the pixels. the electrophoretic element pixels formed on the side electrode is formed on the electrophoretic element side of the second substrate, a common electrode facing the plurality of pixel electrodes, and inputs to the pixel electrode and the common electrode An electrophoretic display device having a control unit for controlling a potential,
The controller is
When displaying an image on the display unit,
A first pulse that periodically repeats a first potential and a second potential is input to the common electrode, while the first pulse is input to the pixel electrode with a pulse width wider than one cycle of the first pulse. A halftone display operation in which a second pulse that periodically repeats a potential and the second potential is input, and the display unit is in a display state including a desired halftone in the last period of the second pulse. An electrophoretic display device comprising: The controller is
Prior to the halftone display operation , a monochrome image display operation for displaying an image not including a halftone on the display unit is executed based on image data common to the halftone display operation. Item 8. The electrophoretic display device according to Item 7. A first control line and a second control line connected to each of the pixels are formed in the display unit, and for each pixel, a pixel switching element, a latch circuit connected to the pixel switching element, a switch circuit output terminal coupled to said first control line and the second control line of said latch circuit, is provided with,
The controller is
In the halftone display operation,
The electrophoretic display device according to claim 7 or 8, characterized in that inputting the second pulse to the first control line or the second control line connected to the pixel electrode. The controller is
9. The electrophoretic display according to claim 8, wherein an inverted image display operation is performed to display an inverted image of an image displayed by the monochrome image display operation on the display unit prior to the monochrome image display operation. apparatus. The controller is
In the halftone display operation,
A second pulse that repeats the first potential and the second potential with a wider pulse width than the first pulse on the first pixel electrode belonging to the pixel that displays the first intermediate gradation. While typing
An inverted signal of a second pulse obtained by inverting the second pulse input to the first pixel electrode is input to the second pixel electrode belonging to the pixel displaying the second intermediate gradation. The electrophoretic display device according to any one of claims 7 to 10, wherein The controller is
Prior to the halftone display operation, a monochrome image display operation for causing the display unit to display a first gradation with the maximum gradation value of the pixel and a second gradation with the minimum gradation value. Run
The pixel of the first gradation is shifted to the second intermediate gradation having a gradation value closer to the second gradation than the gradation value of the first intermediate gradation, and the second gradation The electrophoretic display device according to claim 11, wherein the pixel having the gray level is shifted to the first intermediate gray level.   An electronic apparatus comprising the electrophoretic display device according to claim 7.

Images