JP2010211048A - Method of driving electrohoretic display device, electrohoretic display device, and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of driving an electrohoretic display device, adjusting the line width in a display device simplex to improve representation ability. <P>SOLUTION: According to this method of driving an electrohoretic display device, first or second potential is input to a pixel electrode, a pulse wave in which periodically repeats the first potential and the second potential is input to a common electrode, and when the potential of the common electrode is the potential displaying a specific gray scale, the input of the pulse wave is stopped, thereby displaying an image in which the contour of an image element formed in a specific gray scale is expanded on a display unit. <P>COPYRIGHT: (C)2010,JPO&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 Documents 1 and 2 below. 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. The driving method described in Patent Document 1 employs a driving method (common swing driving) in which a pulse wave that periodically repeats a low level and a high level is input to the common electrode.

JP-A 52-70791 JP 2003-140199 A

  By the way, not only in an electrophoretic display device but in a display device in general, the display resolution is defined by the pixel size and the pixel pitch, and the displayed line width is fixed to the width of one pixel unit. In recent years, it has been possible to artificially adjust the line width by performing image processing such as anti-aliasing, but it has not been studied to enable line width adjustment by a single display device.

  The present invention has been made in view of the above circumstances, and provides an electrophoretic display device driving method and an electrophoretic display device capable of adjusting the line width of a display device alone and improving expressive power. One of the purposes is to provide.

  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 first electrodes A method of driving an electrophoretic display device having electrodes, wherein the first potential and the second potential are periodically input to the common electrode while the first potential or the second potential is input to the pixel electrode. When the pulse wave to be repeated is input, and the potential of the common electrode is a potential for displaying a specific gradation, the input of the pulse wave is stopped, so that an image element having the specific gradation is displayed on the display unit. An image with an extended outline is displayed.

  This driving method employs so-called common swing driving in which the electrophoretic element is driven by inputting a pulse wave that periodically repeats the first potential and the second potential to the common electrode. The timing of stopping the potential input to the common electrode in the common swing drive is set to the potential for displaying the specific gradation, thereby making it possible to extend the contour of the image element having the specific gradation. .

  In the common swing drive, the electrophoretic element between the pixel electrode held at the second potential is driven in a period in which the common electrode is at the first potential, and in the period in which the common electrode is at the second potential, The electrophoretic element between the pixel electrode held at the first potential is driven. Therefore, during the period when the common electrode is at the first potential, the pixel to which the pixel electrode held at the second potential belongs does not substantially operate, and during the period when the common electrode is at the second potential, A pixel to which a pixel electrode held at a potential of 1 belongs substantially does not operate.

  In addition, since the common electrode has a larger planar area than the pixel electrode and faces the plurality of pixel electrodes, an electric field formed between the pixel electrode and the common electrode during operation is narrow on the pixel electrode side, The electric field spreads as it approaches the common electrode.

  From the above, when the electrophoretic display device is driven in a common manner, the pixel electrode held at the first potential (hereinafter referred to as the first pixel electrode) and the pixel electrode held at the second potential (hereinafter referred to as the first electrode). In a region adjacent to the second pixel electrode), a period in which an electric field extending from the first pixel electrode to the second pixel electrode is formed in accordance with the potential change of the common electrode, and from the second pixel electrode to the first The period in which the electric field extending to the pixel electrode is formed is alternately repeated.

  Since the electrophoretic particles contained in the electrophoretic element move along the above-described electric field, the display corresponding to the potential of the first pixel electrode is displayed in the first pixel during the period in which the pixel to which the first pixel electrode belongs is operating. It covers a wider area than the electrode. Conversely, during the period in which the pixel to which the second pixel electrode belongs operates, the display corresponding to the potential of the second pixel electrode covers a wider area than the second pixel electrode.

  The driving method of the present invention can display the image element having a specific gradation by freely expanding the outline by appropriately controlling the timing of stopping the potential input to the common electrode by using the above-described action. It is a thing. According to this driving method, the line width can be adjusted by a single display device, and a display with excellent expressive power is possible.

It is preferable that the pulse width of the latter half of the last pulse of the pulse wave is larger than the pulse width of other pulses constituting the pulse wave.
According to this driving method, since the last voltage application period that defines the line width is lengthened, it is possible to obtain a display with a more expanded contour.

It is preferable that the period of the last pulse of the pulse wave is longer than the period of other pulses constituting the pulse wave.
According to this driving method, by extending the last voltage application period that defines the line width, it is possible to obtain a display with a more expanded contour. Furthermore, potentials having different polarities with respect to the pixel electrode and the common electrode and the electrophoretic element can make the input period uniform. Thereby, deterioration of an electrode or an electrophoretic element can be suppressed.

It is preferable that the extension width of the contour is adjusted according to the pulse width or the length of the period.
According to this driving method, it is possible to adjust the extended width of the contour by a simple operation of adjusting the pulse width or the cycle, and it is possible to obtain a display with excellent expressive power.

The specific gradation is preferably a first gradation having a maximum gradation value or a second gradation having a minimum gradation value.
According to this driving method, for example, display in which the outline of an image element displayed in black is expanded or display in which the outline of an image element displayed in white is expanded is possible.

It is also preferable that the specific gradation is an intermediate gradation.
According to this driving method, for example, display in which the outline of an image element displayed in gray is expanded is also possible.

  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 side of the electrophoretic element of the first substrate corresponding to the pixel, a common electrode formed on the side of the electrophoretic element of the second substrate and facing the plurality of first electrodes, A control unit that controls a potential input to the pixel electrode and the common electrode, wherein the control unit inputs the first or second potential to the pixel electrode, A pulse wave that periodically repeats the first potential and the second potential is input to the common electrode, and the input of the pulse wave is stopped when the potential of the common electrode is a potential that displays a specific gradation. As a result, the display unit has the specific gradation. The contour of the image element and displaying the expanded image.

  According to this configuration, by appropriately controlling the timing of stopping the potential input to the common electrode, it is possible to freely expand and display the contour of the image element having a specific gradation. Therefore, the line width can be adjusted by a single display device, and an electrophoretic display device capable of displaying with excellent expressive power can be realized.

It is preferable that a pulse width of the latter half of the last pulse of the pulse wave is larger than a pulse width of other pulses constituting the pulse wave.
According to this configuration, since the last voltage application period that defines the line width becomes longer, it is possible to obtain a display with a more expanded contour.

It is preferable that the period of the last pulse of the pulse wave is longer than the period of other pulses constituting the pulse wave.
According to this configuration, since the last voltage application period that defines the line width becomes longer, it is possible to obtain a display with a more expanded contour. Furthermore, potentials having different polarities with respect to the pixel electrode and the common electrode and the electrophoretic element can make the input period uniform. Thereby, deterioration of an electrode or an electrophoretic element can be suppressed.

The control unit may be configured to adjust an extension width of the contour according to the pulse width or the length of the cycle.
According to this configuration, an electrophoretic display device that can adjust the extended width of the contour with a simple operation of adjusting the pulse width or cycle and obtain a display with excellent expressive power can be obtained.

The specific gradation is preferably a first gradation having a maximum gradation value or a second gradation having a minimum gradation value.
According to this configuration, for example, display in which the outline of an image element displayed in black is expanded or display in which the outline of an image element displayed in white is expanded is possible.

It is also preferable that the specific gradation is an intermediate gradation.
According to this configuration, for example, display in which the outline of an image element displayed in gray is expanded is also possible.

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 device including a display unit having excellent expressive power.

1 is a schematic configuration diagram of an electrophoretic display device according to a first embodiment. The figure which shows the cross-section of an electrophoretic display device, and a microcapsule. Operation | movement explanatory drawing of an electrophoretic element. Explanatory drawing which shows the state transition of the pixel by the 1st drive method of 1st Embodiment. The timing chart in the 1st drive method of a 1st embodiment. Explanatory drawing which shows the state transition of the pixel by the 2nd drive method of 1st Embodiment. The timing chart in the 2nd drive method 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 of an electrophoretic display device according to a second embodiment. Explanatory drawing which shows the image display operation | movement by the 1st drive method of 2nd Embodiment. The timing chart in the 1st drive method of 2nd Embodiment. Explanatory drawing which shows the image display operation | movement by the 2nd drive method of 2nd Embodiment. The timing chart in the 2nd drive method of 2nd Embodiment. Explanatory drawing which shows the image display operation | movement by the 3rd drive method of 2nd Embodiment. Explanatory drawing which shows the drive method of a reference example. 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) 35 are formed on the electrophoretic element 32 side of the first substrate 30, and a common electrode 37 is formed on the electrophoretic element 32 side of the second substrate 31. 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 affixing the said electrophoretic sheet which peeled 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.

[First driving method (displaying thick black lines)]
Next, a driving method of the electrophoretic display device having the above configuration will be described.
FIG. 4 is an explanatory diagram showing state transition of the pixel 40 by the first driving method of the electrophoretic display device according to the invention. FIG. 4A and FIG. 4B are a plan view and a cross-sectional view showing an initial state of the five pixels 40. FIG. 4C and FIG. 4D are a plan view and a cross-sectional view showing the state of the pixel 40 after the writing operation. FIG. 5 is a timing chart in the first driving method.

  In the first driving method according to the present embodiment, only the central pixel 40 to which the pixel electrode SEG0 (pixel electrode 35) belongs among the five pixels 40 displayed in white shown in FIG. In this driving method, as shown in c), the display is shifted to black display (specific gradation) and an area wider than the width of one pixel is displayed in black. Hereinafter, this driving method will be described in detail.

  In the white display pixel 40 shown in FIGS. 4A and 4B, 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. As a driving method for shifting to such a display state, for example, a low level (for example, 0 V) potential is input to the two pixel electrodes SEG0 and SEG1, and a low level potential and a high level (to the common electrode 37) are input. For example, a pulse wave that periodically repeats a potential of 15 V) is input. Thereby, all of the five pixels 40 can be in a white display state. A similar display state can be obtained even when the common electrode COM is held at a high level potential.

  Note that the initial state shown in FIG. 4A merely shows a state in which all the pixels 40 are displayed in white for the sake of simplicity of explanation. That is, in the driving method of the present embodiment, the initial state before the display is updated can be an arbitrary display state. For example, the state where all the five pixels 40 are displayed in black may be set as the initial state, and the state where the white display pixels 40 and the black display pixels 40 are mixed may be set as the initial state.

  Next, in order to change from the white display state shown in FIG. 4A to the state where the white display and the black display shown in FIG. 4C are mixed, the pixel electrode SEG0 is applied to the pixel electrode SEG0 as shown in FIG. While a high level (15V) potential is input, a low level (for example, 0V) potential is input to the pixel electrode SEG1. Then, a rectangular wave pulse wave that periodically repeats a low level (for example, 0 V) and a high level (for example, 15 V) is input to the common electrode COM.

Thereby, in the pixel 40 to which the pixel electrode SEG0 belongs, the electrophoretic element 32 is driven by the potential difference between the pixel electrode SEG0 (high level) and the common electrode COM during a period in which the common electrode COM is at the low level, and the pixel 40 is black. Display operation.
On the other hand, in the pixel 40 to which the pixel electrode SEG1 belongs, a potential difference is generated between the pixel electrode SEG1 and the common electrode COM during a period in which the common electrode COM is at a high level, and a white display operation is performed. However, the display of these pixels 40 does not change because the initial state is white display.

  Here, in the driving method of the present embodiment, as shown in FIG. 5A, the final pulse Pn among the pulse waves input to the common electrode COM is a pulse having a pulse width different from that of the other pulses. Yes. More specifically, pulses other than the final pulse Pn are pulses having a duty ratio of 1: 1 and a pulse width Pw1, whereas the final pulse Pn has a duty ratio (eg, 1: 3) having a large pulse width in the latter half. The latter pulse width Pw2 is set larger than the first pulse width Pw1.

  As shown in FIG. 4D, when the pixel 40 to which the pixel electrode SEG0 belongs performs a black display operation, since the common electrode COM is wider than the pixel electrode SEG0, the electric field directed from the pixel electrode SEG0 to the common electrode COM. E is formed so as to spread outward from the end of the pixel electrode SEG0. On the other hand, when the pixel 40 performs a white display operation, an electric field extending from the pixel electrode SEG1 to a part on the pixel electrode SEG0 is formed.

  That is, the black display region by the pixel 40 to which the pixel electrode SEG0 belongs changes in conjunction with the potential of the common electrode COM being switched between the high level and the low level. The width (line width) of the black display region is determined depending on the state of the electric field when the potential input to the common electrode COM is stopped. That is, it is determined by the potential of the common electrode COM at the timing when the potential input to the common electrode COM is stopped.

  In this embodiment, in order to expand the line width displayed by the pixel 40 to which the pixel electrode SEG0 belongs, the timing of stopping the potential input to the common electrode COM is as shown in FIG. It is set to a period during which COM is at a low level. As a result, as shown in FIG. 4D, when the electric field E capable of expanding the black display region is formed, the voltage application to the electrophoretic element 32 is stopped, and the display with the expanded contour is displayed. It is to be retained.

Furthermore, in the driving method of the present embodiment, since the pulse width of the second half portion of the final pulse Pn input to the common electrode COM is longer, the pulse width Pw1 than when another pulse is input is shown in FIG. The time during which the oblique electric field shown in (d) acts on the electrophoretic particles becomes longer.
Therefore, the black particles 26 are attracted to the common electrode COM side in a wider range than the pixel electrode SEG0, and as shown in FIG. 4C, a display in which the black display region is expanded from the end of the pixel electrode SEG0 to the outside. Obtainable.

  Furthermore, according to the driving method of the present embodiment, it is possible to adjust the expansion width Wb of the black display region by adjusting the pulse width Pw2 of the latter half of the final pulse Pn. Specifically, the expansion width Wb can be expanded and contracted by expanding and contracting the length of the pulse width Pw2. As shown in FIG. 4D, the electric field extending in the oblique direction from the end of the pixel electrode SEG0 is weaker than the electric field formed in the electrode normal direction from the pixel electrode SEG0. This is because the moving distance of the electrophoretic particles moved by is increased.

  Therefore, when the pulse width Pw2 is shortened, the black particles 26 cannot reach the vicinity of the common electrode COM at a position distant from the pixel electrode SEG0 side, and the extension width Wb is narrowed. Conversely, when the pulse width Pw2 is increased, the black particles 26 that are moved by the oblique electric field can reach the vicinity of the common electrode COM, and the expansion width Wb can be increased.

  Since the region where the electric field E shown in FIG. 4D spreads is limited, the extension width Wb does not change when the pulse width Pw2 is made longer than a certain time. The range in which the expansion width Wb can be adjusted is approximately 0.5 pixels, although it depends on the structure of the electrophoretic display device 100 and the characteristics of the electrophoretic element 32. Therefore, according to the driving method of the present embodiment, the line width can be freely adjusted between one pixel and approximately two pixels.

  In this embodiment, the case where the pulse width Pw2 is larger than the pulse width Pw1 has been described. However, as described above, if the timing of stopping the potential input to the common electrode COM is appropriately defined, the line width is reduced. An expansion effect can be obtained. Therefore, the pulse width Pw2 and the pulse width Pw1 may be the same length. Therefore, the lower limit value of the pulse width Pw2 is Pw1, and the upper limit value is a length at which the extension width Wb does not change.

  In the driving method of the present invention, it is more preferable to employ the timing chart shown in FIG. In the timing chart shown in FIG. 5B, the last pulse Pn input to the common electrode COM is a pulse having a pulse width Pw2 in both the first half and the second half. That is, the pulse width of the first half of the pulse is also longer than the pulse width of the other pulses, and the duty ratio is changed to 1: 1.

By adopting the timing chart shown in FIG. 5B, deterioration of the electrophoretic element 32, the pixel electrode 35, and the common electrode 37 can be suppressed.
More specifically, in the final pulse Pn shown in FIG. 5A, the period during which the pixel 40 to which the pixel electrode SEG0 belongs is displayed in black is longer than the period during which the same pixel 40 is displayed in white. In addition, the period during which the pixel 40 to which the pixel electrode SEG1 belongs is operated for white display is longer than the period during which the same pixel 40 is operated for black display. If the electric field acting on the electrophoretic element 32 is thus biased, the pixel electrode 35 and the common electrode 37 may be deteriorated by an electrochemical reaction, and the life of the electrophoretic element 32 may be shortened.
On the other hand, in the timing chart shown in FIG. 5B, since the duty ratio of the final pulse Pn is 1: 1, the bias of the electric field applied to the electrophoretic element 32 does not occur, and the above-mentioned It is possible to avoid such deterioration of the electrophoretic element 32 and the electrode, and to obtain a good display over a long period of time.

[Second Driving Method (Thick White Line Display Method)]
Next, the second driving method of this embodiment will be described.
FIG. 6 is an explanatory diagram showing the state transition of the pixel 40 by the second driving method of the electrophoretic display device according to the invention. FIG. 6A and FIG. 6B are a plan view and a cross-sectional view showing an initial state of the five pixels 40. FIG. 6C and FIG. 6D are a plan view and a cross-sectional view showing the state of the pixel 40 after the writing operation. FIG. 7 is a timing chart in the driving method of the present invention.

  In the first driving method according to the present embodiment, only the central pixel 40 to which the pixel electrode SEG1 (pixel electrode 35) belongs is selected from the five pixels 40 displayed in black in FIG. As shown in c), the driving method shifts to white display (specific gradation) and displays white in an area wider than the width of one pixel. Hereinafter, this driving method will be described in detail.

  Note that the initial state shown in FIG. 6A is merely a state in which all the pixels 40 are displayed in black for the sake of simplicity, as in the first driving method, and is arbitrary. The display state can be set to the initial state.

  In order to change from the black display state shown in FIG. 6A to the state where the white display and the black display shown in FIG. 6C are mixed, as shown in FIG. 7A, the pixel electrode SEG0 has a high level ( 15V) potential is input, while a low level (for example, 0V) potential is input to the pixel electrode SEG1. Then, a rectangular wave pulse wave that periodically repeats a low level (for example, 0 V) and a high level (for example, 15 V) is input to the common electrode COM.

Thereby, in the pixel 40 to which the pixel electrode SEG1 belongs, the electrophoretic element 32 is driven by the potential difference between the pixel electrode SEG1 and the common electrode COM during a period in which the common electrode COM is at a high level, and the pixel 40 performs a white display operation.
On the other hand, in the pixel 40 to which the pixel electrode SEG0 belongs, the electrophoretic element 32 is driven by the potential difference between the pixel electrode SEG0 and the common electrode COM during a period in which the common electrode COM is at a low level, and the pixel 40 performs a black display operation. However, since the initial state of the pixel 40 to which the pixel electrode SEG0 belongs is black, the display does not change.

  Also in the second driving method, as shown in FIG. 7A, the final pulse Pn among the pulse waves input to the common electrode COM is a pulse having a pulse width different from that of the other pulses. That is, the duty ratio of the final pulse Pn is set to a duty ratio (for example, 1: 3) in which the latter pulse width Pw2 is larger than the former pulse width Pw1.

As shown in FIG. 6D, when the pixel 40 to which the pixel electrode SEG1 belongs performs a white display operation, since the common electrode COM is wider than the pixel electrode SEG1, the electric field from the common electrode COM toward the pixel electrode SEG1. E is formed so as to spread over a plane area wider than the pixel electrode SEG1 on the common electrode COM side.
In the present driving method, since the potential input to the common electrode COM is stopped in a state where the electric field E shown in FIG. 6D is formed, the display state in which the white display line is expanded can be maintained. it can.

  Furthermore, in the present embodiment, since the pulse width of the second half of the final pulse Pn input to the common electrode COM is longer, the oblique angle shown in FIG. 6D is more than that when a pulse having the pulse width Pw1 is input. The time during which the electric field in the direction acts on the electrophoretic particles becomes longer. Thereby, since the white particles 27 are attracted toward the common electrode COM in a wider range, it is possible to obtain a display in which the line width of white display is expanded with a larger expansion width Ww.

  Furthermore, also in the driving method of the present embodiment, it is possible to adjust the expanded width Ww of the white display region by adjusting the pulse width Pw2 of the latter half of the final pulse Pn. That is, the expansion width Ww can be expanded and contracted by expanding and contracting the length of the pulse width Pw2. When the pulse width Pw2 is shortened, the white particles 27 cannot reach the vicinity of the common electrode COM at a position distant from the pixel electrode SEG1 side, and the extended width Ww becomes narrow. Conversely, when the pulse width Pw2 is increased, the white particles 27 that are moved by the oblique electric field can reach the vicinity of the common electrode COM, and the extended width Ww can be increased.

  Since there is a limit to the region where the electric field E shown in FIG. 6 (d) spreads, when the length of the pulse width Pw2 reaches a certain time, the effect of extending the extension width Ww beyond that cannot be obtained. The range in which the expansion width Wb can be adjusted is approximately 0.5 pixels, although it depends on the structure of the electrophoretic display device 100 and the characteristics of the electrophoretic element 32. Therefore, according to the driving method of the present embodiment, the line width can be freely adjusted between one pixel and approximately two pixels.

  Also in the second driving method, similarly to the first driving method, the pulse width Pw2 may be equal to the pulse width Pw1. Also in this case, since the electric field E shown in FIG. 6D acts on the electrophoretic element 32 at the end of image writing, some of the white particles 27 are outside the common electrode COM outside the pixel 40 to which the pixel electrode SEG1 belongs. The application of voltage to the electrophoretic element 32 is stopped in the state of being pulled toward the side, and a state in which white display is performed in a wider range than the pixel electrode SEG1 is obtained. Therefore, the lower limit value of the pulse width Pw2 is Pw1, and the upper limit value is a length at which the extension width Ww does not change.

  Also in the second driving method, it is more preferable to employ the timing chart shown in FIG. In the timing chart shown in FIG. 7B, the last pulse Pn input to the common electrode COM is a pulse having a pulse width Pw2 in both the first half and the second half. That is, the pulse width of the first half of the pulse is also longer than the pulse width of the other pulses, and the duty ratio is changed to 1: 1. By adopting the timing chart shown in FIG. 7B, the deterioration of the electrophoretic element 32, the pixel electrode 35, and the common electrode 37 can be suppressed as in the first driving method described above.

(Second Embodiment)
According to the driving method of the present invention, not only the line width in black display or white display but also the line width in halftone display (gray display) can be expanded. In the present embodiment, a driving method for performing halftone display (specific gradation display) with an expanded line width will be described with reference to the drawings.

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 case where the driving method according to the present invention is applied to an active matrix electrophoretic display device will be described.
However, the driving method for performing halftone line width extended display described below can be applied to the segment-type electrophoretic display device 100 according to the first embodiment without any problem. The driving method according to the first embodiment can also be applied to the active matrix type electrophoretic display device according to the second embodiment.

FIG. 8 is a diagram illustrating a schematic configuration of the electrophoretic display device 200 according to the second embodiment. FIG. 9 is a diagram illustrating a pixel circuit of the electrophoretic display device 200 according to the second embodiment.
In FIG. 8 and FIG. 9, 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. 8, 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 163, the common power supply modulation circuit 164 generates various signals to be supplied to each of the wirings, and electrically connects and disconnects (high impedance) the 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. 9) 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 illustrated in FIG. 9, 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.

[First driving method (displaying thick light gray line)]
FIG. 10 is an explanatory diagram showing an image display operation by the first driving method of the present embodiment. FIG. 11 is a timing chart showing potential states of the common electrode 37 (Vcom), the first control line 91 (S1), and the second control line 92 (S2) corresponding to FIG.

As shown in FIG. 11, the driving method of the present embodiment includes a white display step S101 and a gray display step S102. FIGS. 10A and 10B show the display state corresponding to the execution result of the white display step S101, and FIGS. 10C and 10D correspond to the execution result of the gray display step S102. The display state to be displayed is shown.
In FIG. 11, the white display step S <b> 101 and the gray display step S <b> 102 are displayed with an interval in order to make the drawing easy to see.

The white display step S101 is a step of performing white display on a partial region of the display unit 5 including a portion displayed in gray or the entire display unit 5 prior to gray display. The white display step S101 is provided as necessary, and may not be executed when the area to be displayed in gray is previously displayed in white. In the white display step S101, it is only necessary that the gray display area can be displayed in white. Therefore, an image erasing step in which the entire display unit 5 is displayed in white may be executed. A monochrome image display step for displaying (image) may be executed.
The gray display step S102 is a step in which the pixel 140 in the area displayed in white on the display unit 5 is shifted from white display to gray display by performing black display operation.

  Hereinafter, the driving method of this embodiment will be described in detail with reference to FIGS. 10 and 11.

<White display step S101>
First, in the white display step S101, image data corresponding to the display state shown in FIG. 10A is input to the controller 163 shown in FIG. In the present embodiment, since all of the pixels 140A to 140E are displayed in white, image data including pixel data “1” (high level (H) image signal) is present at positions corresponding to these pixels 140A to 140E. Entered.

  Then, image data is transmitted to the display unit 5 based on a control signal supplied from the controller 163 to the scanning line driving circuit 161 and the data line driving circuit 162. The scanning line driving circuit 161 inputs a selection signal to the scanning line 66 based on the control signal. On the other hand, the data line driving circuit 162 supplies the image signal supplied from the controller 163 to the pixels 140 (pixels 140A to 140E) in synchronization with the selection operation by the scanning line driving circuit 161.

  As a result, the image data corresponding to FIG. 10A is input to the latch circuits 70 of the pixels 140 </ b> A to 140 </ b> E of the display unit 5. In the pixels 140 </ b> A to 140 </ b> E to which pixel data corresponding to white display is input, a high level (H) image signal is held in the latch circuit 70, and the second transmission gate TG <b> 2 is turned on by the output from the latch circuit 70. Become. Therefore, the second control line 92 and the pixel electrodes 35A to 35E are connected via the second transmission gate TG2.

  Next, the controller 163 pulse-drives the common electrode 37 to the common power supply modulation circuit 164, and outputs control signals for setting the first and second control lines 91 and 92 to predetermined potentials, respectively. Based on the input control signal, the common power supply modulation circuit 164 sets the first control line 91 (potential S1) to the high level (H; for example, 15 V) and the second control line 92 (see FIG. 11). The potential S2) is held at a low level (L; for example, 0 V), and a rectangular wave pulse wave that periodically repeats a high level and a low level is input to the common electrode 37 (potential Vcom).

Then, since the second control line 92 and the pixel electrode 35 are connected in the pixels 140A to 140E of the display unit 5, the low-level potential from the second control line 92 to the pixel electrodes 35A to 35E. Is entered. As a result, the electrophoretic element 32 is driven by a potential difference generated between the pixel electrodes 35A to 35E (low level) 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 FIGS. 10 (a) and 10 (b), the pixels 140A to 140E. Is displayed in white.

<Gray display step S102>
Next, when the process proceeds to the gray display step S102, image data corresponding to the pixels 140 displayed in gray and the pixels 140 whose display is not changed is input to the controller 163. In the case of the present embodiment, the center pixel 140C shown in the figure is operated for black display, and the other pixels 140A, 140B, 140D, 140E are operated for white display. Accordingly, the controller 163 receives image data “0” at the position of the pixel 140C and image data having the pixel data “1” at the positions of the other pixels 140A, 140B, 140D, and 140E.

The controller 163 drives the scanning line driving circuit 161 and the data line driving circuit 162 to transfer the image data to the pixels 140A to 140E.
In the pixel 140 </ b> C, the low-level image signal is held in the latch circuit 70. As a result, the first transmission gate TG1 is turned on based on the output of the latch circuit 70, and the pixel electrode 35C and the first control line 91 are connected.
On the other hand, in the other pixels 140A, 140B, 140D, and 140E, a high-level image signal is held in the latch circuit 70. As a result, the second transmission gate TG2 is turned on based on the output of the latch circuit 70, and the pixel electrodes 35A, 35B, 35D, 35E and the second control line 92 are connected.

  Next, the controller 163 inputs predetermined potentials to 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 modulation circuit 164. Based on the input control signal, the common power supply modulation circuit 164 inputs a high level potential to the first control line 91 and applies a low level potential to the second control line 92, as shown in FIG. input. A pulse wave that periodically repeats a high level and a low level is input to the common electrode 37.

In the pixel 140C to which an image signal corresponding to black display (pixel data “0”) is input, a high-level potential is input to the pixel electrode 35C via the first control line 91. Then, the electrophoretic element 32 is driven by a potential difference generated between the pixel electrode 35 </ b> C and the common electrode 37 during a period in which the common electrode 37 is at a low level.
At this time, the electrophoretic element 32 performs a black display operation. However, as shown in FIG. 11, the voltage application period in the gray display step S102 is shorter than that in the white display step S101. Instead of black display, the display is light gray.

  On the other hand, in the other pixels 140A, 140B, 140D, and 140E, a low-level potential is input to the pixel electrodes 35A, 35B, 35D, and 35E, and white display operation is performed during a period in which the common electrode 37 is at a high level. However, since these pixels 140A, 140B, 140D, and 140E are originally white display, the display does not change.

  Here, in the driving method of the present embodiment, as shown in FIG. 11, the timing of stopping the potential input to the common electrode 37 in the gray display step S102 is that the final pulse Pn input to the common electrode 37 is at a low level. The period is set. That is, the voltage application to the electrophoretic element 32 is stopped in a period in which the pixel 140C is operated to perform black display while the other pixels 140A, 140B, 140D, and 140E are not operated.

  In this period, as shown in FIG. 10D, an electric field E is formed from the pixel electrode 35C of the pixel 140C toward the common electrode 37, and the electric field E is a plane of the pixel electrode 35C toward the common electrode 37. It is wider than the area. Then, due to the presence of the oblique direction component of the electric field E, the black particles 26 are attracted toward the common electrode 37 also in the region outside the pixel electrode 35C, and a part of the pixels 140B and 140D are also displayed in gray as shown in the figure. By stopping the potential input in this state, it is possible to obtain a gray display state in a wider range than the pixel 140C.

  Through the gray display step S102 described above, a part of the region (pixel 140C) that was white-displayed in the white display step S101 is changed to a light gray halftone display, and a multi-gradation display including a halftone is realized.

  In the above driving method, a low-level potential is supplied to the second control line 92 in the gray display step S102 so that the display of the pixels 140A, 140B, 140D, and 140E is not changed. However, in the gray display step S102, The second control line 92 may be in a high impedance state that is electrically disconnected. In this case, in the gray display step S102, the pixel electrodes 35A, 35B, 35D, and 35E are all in a high impedance state, and no voltage is applied to the electrophoretic element 32 regardless of the potential of the common electrode 37. Thus, a gray display in a wider range than the pixel 140C can be obtained.

  In the present embodiment, the pulse width and period of the final pulse Pn are set to the same length as other pulses. This is because, in the gray display step S102, the voltage application is stopped during a period in which the reflectance change of the electrophoretic element 32 is large immediately after the voltage application is started. In other words, during such a period, the electrophoretic particles respond sensitively to the electric field and thus are easily affected by the oblique electric field. Therefore, even if the pulse width and period of the final pulse Pn are not changed, it is possible to obtain a gray display in which the line width is sufficiently expanded only by controlling the timing of stopping the potential input to the common electrode 37.

  However, in the driving method of the present embodiment, it is not prevented that the pulse width of the latter half of the last pulse Pn in the gray display step S102 or the period of the last pulse Pn is made longer than the pulse width or period of other pulses. Absent. Although the effect varies depending on the response characteristics of the electrophoretic element 32, the extension width Wg in FIG. 10D can be expanded and contracted by adjusting the pulse width and the period.

[Second driving method (displaying thick dark gray line)]
FIG. 12 is an explanatory diagram illustrating an image display operation according to the second driving method of the present embodiment. FIG. 13 is a timing chart showing potential states of the common electrode 37 (Vcom), the first control line 91 (S1), and the second control line 92 (S2) corresponding to FIG.

As shown in FIG. 13, the driving method of the present embodiment includes a black display step S201 and a gray display step S202. 12A and 12B show display states corresponding to the execution result of the black display step S201, and FIGS. 12C and 12D correspond to the execution result of the gray display step S202. The display state to be displayed is shown.
In FIG. 13, the black display step S <b> 201 and the gray display step S <b> 202 are displayed with an interval in order to make the drawing easy to see.

The black display step S201 is a step of displaying a partial region of the display unit 5 including the gray display portion or the entire display unit 5 in black prior to the gray display. The black display step S201 is provided as necessary, and may not be executed when the area to be displayed in gray is previously displayed in black. Further, since it is sufficient that the gray display area can be displayed in black, it can also be an image erasing step for displaying the entire display unit 5 in black, and a monochrome image display step for displaying a binary image. You can also.
The gray display step S202 is a step of shifting from black display to gray display by performing the white display operation on the pixels 140 in the black display region.

  Hereinafter, the driving method of this embodiment will be described in detail with reference to FIGS. 12 and 13.

<Black display step S201>
First, in black display step S201, image data corresponding to FIG. 12A is input to the controller 163 shown in FIG. In the present embodiment, since all of the pixels 140A to 140E are displayed in black, image data including pixel data “0” (low level (L) image signal) is present at positions corresponding to these pixels 140A to 140E. Entered.

  Then, image data is transferred to the display unit 5 based on control signals supplied from the controller 163 to the scanning line driving circuit 161 and the data line driving circuit 162. As a result, the image data shown in FIG. 12A is input to the latch circuits 70 of the pixels 140A to 140E of the display unit 5 and is turned on by the output from the latch circuit 70. The first control line 91 and the pixel electrodes 35A to 35E are connected via the.

  The controller 163 pulse-drives the common electrode 37 to the common power supply modulation circuit 164, and outputs a control signal for setting the first and second control lines 91 and 92 to predetermined potentials, respectively. Based on the input control signal, the common power supply modulation circuit 164 sets the first control line 91 (potential S1) to a high level (H; for example, 15 V) and the second control line 92 (see FIG. 13). The potential S2) is held at a low level (L; for example, 0 V), and a rectangular wave pulse wave that periodically repeats a high level and a low level is input to the common electrode 37 (potential Vcom).

Then, in the pixels 140A to 140E of the display unit 5, a high level potential is input from the first control line 91 to the pixel electrodes 35A to 35E via the first transmission gate TG1, and the common electrode 37 is at the low level. The electrophoretic element 32 is driven during the period.
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), and as shown in FIGS. 12 (a) and 12 (b), the pixels 140A to 140E. Is displayed in black.

<Gray display step S202>
Next, when the process proceeds to the gray display step S202, image data corresponding to the pixels 140 displayed in gray and the pixels 140 whose display is not changed is input to the controller 163. The input image data has pixel data “1” corresponding to white display at a position corresponding to the pixel 140C, and pixel data corresponding to black display at positions corresponding to the other pixels 140A, 140B, 140D, and 140E. This is image data having “0”.

The controller 163 drives the scanning line driving circuit 161 and the data line driving circuit 162 to transfer the image data to the pixels 140A to 140E.
The high-level image signal is held in the latch circuit 70 of the pixel 140C, and the pixel electrode 35C and the second control line 92 are connected via the second transmission gate TG2 turned on by the output of the latch circuit 70. The
On the other hand, low-level image signals are held in the other pixels 140A, 140B, 140D, and 140E, and the pixel electrodes 35A, 35B, and 35D are passed through the first transmission gate TG1 that is turned on by the output of the latch circuit 70. , 35E and the first control line 91 are connected.

  Next, the controller 163 inputs predetermined potentials to 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 modulation circuit 164. Based on the input control signal, the common power supply modulation circuit 164 inputs a high level potential to the first control line 91 and applies a low level potential to the second control line 92, as shown in FIG. input. A pulse wave that periodically repeats a high level and a low level is input to the common electrode 37.

  In the pixel 140C to which an image signal corresponding to white display (pixel data “1”) is input, a low-level potential is input to the pixel electrode 35C via the second control line 92. Then, the electrophoretic element 32 is driven by a potential difference generated between the pixel electrode 35 </ b> C and the common electrode 37 during a period when the common electrode 37 is at a high level. At this time, although the electrophoretic element 32 performs a white display operation, as shown in FIG. 13, the voltage application period of the gray display step S202 is shorter than that of the black display step S201. Instead of white display, the display is dark gray.

  On the other hand, in the other pixels 140A, 140B, 140D, and 140E, a high-level potential is input to the pixel electrodes 35A, 35B, 35D, and 35E, so that black display operation is performed during a period in which the common electrode 37 is at a low level. Therefore, the display of these pixels 140A, 140B, 140D, and 140E that originally displayed black does not change.

  Here, in the second driving method, as shown in FIG. 13, the timing of stopping the potential input to the common electrode 37 in the gray display step S202 is the period in which the final pulse Pn input to the common electrode 37 is at a high level. Is set to That is, while applying the white display operation to the pixel 140C, the voltage application to the electrophoretic element 32 is stopped in a period in which the other pixels 140A, 140B, 140D, and 140E are not operated.

  During this period, as shown in FIG. 12D, an electric field E is formed from the common electrode 37 toward the pixel electrode 35C, and the electric field E is larger than the pixel electrode 35C on the common electrode 37 side. For this reason, the white particles 27 are also attracted to the area on the common electrode 37 side located outside the pixel electrode 35C, and in this state, the potential input is stopped, and the state is displayed in gray over a wider range than the pixel 140C. Can be obtained.

  Through the gray display step S202 described above, a part of the region (pixel 140C) that was displayed in white in the black display step S201 is changed to a dark gray halftone display, and a multi-tone display including an intermediate gray level is realized.

  Note that, also in the second driving method, the first control line 91 can be brought into a high impedance state in which the first control line 91 is electrically disconnected in the gray display step S202. In this case, since all of the pixel electrodes 35A, 35B, 35D, and 35E are in a high impedance state in the gray display step S202 and no voltage is applied to the electrophoretic element 32 regardless of the potential of the common electrode 37, the same result as above is obtained. Obtainable.

  In the second driving method, the pulse width and period of the final pulse Pn are set to the same length as other pulses for the same reason as in the first driving method, but the final pulse Pn in the gray display step S202 is the same. It is not impeded that the pulse width of the latter half or the period of the final pulse Pn is longer than the pulse width or period of other pulses.

[Third driving method (displaying two types of gray lines)]
FIG. 14 is an explanatory diagram illustrating an image display operation according to the third driving method of the present embodiment. FIG. 14A is a diagram conceptually showing image data transferred to the display unit 5 in each step of the present driving method. FIG. 14B is a diagram illustrating a display state of the display unit 5 in each step. FIG. 14C is a timing chart showing the potential states of the common electrode 37 (Vcom), the first control line 91 (S1), and the second control line 92 (S2) in each step.

  As shown in FIG. 14C, the driving method of the present embodiment includes a monochrome image display step S301, a first gray display step S302, and a second gray display step S303. In FIG. 14C, steps S301 to S303 are displayed with an interval in order to make the drawing easier to see.

The monochrome image display step S301 is a step of displaying a monochrome image (monochrome image) composed of a black display area and a white display area on the display unit 5 prior to gray display.
In the first gray display step S302, the pixel 140 in the region displayed in black in the monochrome image display step S301 is white-displayed to shift the pixel 140 in a partial region of the display unit 5 from black display to gray display. It is a step.
In the second gray display step S303, the pixel 140 in the region displayed in white in the monochrome image display step S301 is black-displayed to shift the pixel 140 in a partial region of the display unit 5 from white display to gray display. It is a step.

  Hereinafter, the driving method of the present embodiment will be described in detail with reference to FIG.

<Monochrome Image Display Step S301>
First, in the monochrome image display step S301, the image data D1 corresponding to FIG. 14A is input to the controller 163 shown in FIG. In the image data D1, the left half area of the figure is composed of pixel data “0” (low level image signal), and the right half area of the figure is composed of pixel data “1” (high level image signal).

The image data D1 is transferred to the display unit 5 by the scanning line driving circuit 161 and the data line driving circuit 162 under the control of the controller 163.
In the pixel 140 to which the pixel data “0” (low level image signal) is input, the pixel electrode 35 and the first control line 91 are connected via the first transmission gate TG1. On the other hand, in the pixel 140 to which the pixel data “1” (high-level image signal) is input, the pixel electrode 35 and the second control line 92 are connected via the second transmission gate TG2.

  Under the control of the controller 163, the common power supply modulation circuit 164 sets the first control line 91 (potential S1) to the high level (H; for example, 15V) and the second control line as shown in FIG. 92 (potential S2) is held at a low level (L; for example, 0 V), and a rectangular wave pulse wave that periodically repeats a high level and a low level is input to the common electrode 37 (potential Vcom).

  In the pixel 140 belonging to the left half area A1 of the display unit 5 shown in FIG. 14B, a high-level potential is input from the first control line 91 to the pixel electrode 35 via the first transmission gate TG1. The electrophoretic element 32 is driven during a period when the common electrode 37 is at a low level. As a result, the pixels 140 belonging to the region are in a black display state.

  On the other hand, in the pixel 140 belonging to the right half area A2 of the display unit 5, a low-level potential is input from the second control line 92 to the pixel electrode 35 via the second transmission gate TG2, and the common electrode 37 is connected. The electrophoretic element 32 is driven during a high level period. Thereby, the pixels 140 belonging to the area are in a white display state.

  As a result of the above operation, as shown in FIG. 14B, a monochrome image composed of the area A1 displayed in black and the area A2 displayed in white is displayed on the display unit 5.

<First Gray Display Step S302>
Next, when the process proceeds to the first gray display step S302, the image data D2 shown in FIG. In the image data D2, the area corresponding to the gray line written in a part of the black display area A1 (the vertical line area Dg1 in the figure) is composed of the pixel data “0”, and the other areas are composed of the pixel data “1”. Image data.

The image data D 2 is transferred to the display unit 5 by the scanning line driving circuit 161 and the data line driving circuit 162 under the control of the controller 163.
In the pixel 140 belonging to the region G1 shown in FIG. 14B, a low-level image signal (pixel data “0” corresponding to the region Dg1) is input to the latch circuit 70, and is turned on by the output of the latch circuit 70. The pixel electrode 35 and the first control line 91 are connected via the first transmission gate TG1.
On the other hand, in the pixels 140 belonging to the regions A1 and A2 other than the region G1, a high-level image signal is input to the latch circuit 70, and the second transmission gate TG2 turned on by the output of the latch circuit 70 is passed through. The pixel electrode 35 and the second control line 92 are connected.

  The common power supply modulation circuit 164 inputs a low-level potential to the first control line 91 as shown in FIG. 14C under the control of the controller 163. On the other hand, a pulse wave that periodically repeats a high level and a low level is input to the second control line 92 and the common electrode 37. The pulse waves input to the second control line 92 and the common electrode 37 are the same synchronized pulse waves.

In the pixel 140 belonging to the region G <b> 1, a low-level potential is input to the pixel electrode 35 through the first control line 91. Then, the electrophoretic element 32 is driven by a potential difference generated between the pixel electrode 35 and the common electrode 37 during a period in which the common electrode 37 is at a high level.
At this time, the electrophoretic element 32 performs a white display operation. However, as shown in FIG. 14C, the voltage application period of the first gray display step S302 is shorter than that of the monochrome image display step S301. The pixel 140 that has been displayed is not displayed in white, but is displayed in dark gray.

  Also in the third driving method, as shown in FIG. 14C, the timing of stopping the potential input to the common electrode 37 in the first gray display step S302 is that the final pulse Pn1 input to the common electrode 37 is high. It is set to a period that is a level. That is, the voltage application to the electrophoretic element 32 is stopped in a period in which the pixels 140 belonging to the region G1 are displayed in white while the pixels 140 in other regions are not substantially operated. Thereby, it is possible to obtain a state in which gray display is performed in a wider range than the region G1.

On the other hand, in the pixels 140 belonging to the regions A1 and A2 other than the region G1, the pixel electrode 35 connected to the second control line 92 has the same potential as the common electrode 37, so the display of these pixels 140 does not change. Therefore, the black display in the area A1 excluding the area G1 and the white display in the area A2 are maintained.
Through the first gray display step S302 described above, a dark gray line can be selectively displayed in the region G1 while maintaining the display state of the monochrome images (regions A1 and A2).

<Second Gray Display Step S303>
Next, when the process goes to the second gray display step S303, the image data D3 shown in FIG. In the image data D3, the area corresponding to the gray line written in a part of the white display area A2 (the vertical line area Dg2 in the drawing) is composed of the pixel data “0”, and the other areas are composed of the pixel data “1”. Image data.

The image data D3 is transferred to the display unit 5 by the scanning line driving circuit 161 and the data line driving circuit 162 under the control of the controller 163.
In the pixel 140 belonging to the region G2 shown in FIG. 14B, a low-level image signal (pixel data “0” corresponding to the region Dg2) is input to the latch circuit 70, and is turned on by the output of the latch circuit 70. The pixel electrode 35 and the first control line 91 are connected via the first transmission gate TG1.
On the other hand, in the pixels 140 belonging to the regions A1 and A2 other than the region G2, a high-level image signal is input to the latch circuit 70, and the second transmission gate TG2 turned on by the output of the latch circuit 70 is passed through. The pixel electrode 35 and the second control line 92 are connected.

  Next, under the control of the controller 163, the common power supply modulation circuit 164 inputs a high-level potential to the first control line 91 as shown in FIG. On the other hand, a pulse wave that periodically repeats a high level and a low level is input to the second control line 92 and the common electrode 37. The pulse waves input to the second control line 92 and the common electrode 37 are the same synchronized pulse waves.

In the pixel 140 belonging to the region G <b> 2, a high level potential is input to the pixel electrode 35 via the first control line 91. Then, the electrophoretic element 32 is driven by a potential difference generated between the pixel electrode 35 and the common electrode 37 during a period in which the common electrode 37 is at a low level.
At this time, the electrophoretic element 32 performs a black display operation. However, as shown in FIG. 14C, the voltage application period in the second gray display step S303 is shorter than that in the monochrome image display step S301. The pixel 140 in the region G2 that has been displayed does not display white but displays light gray.

  In the second gray display step S303, the potential input stop timing to the common electrode 37 is set to a period in which the final pulse Pn2 input to the common electrode 37 is at a low level, as shown in FIG. ing. That is, the voltage application to the electrophoretic element 32 is stopped in a period in which the pixels 140 belonging to the region G2 are displayed in black while the pixels 140 in other regions are not substantially operated. Thereby, it is possible to obtain a state in which gray display is performed in a wider range than the region G2.

On the other hand, in the pixels 140 belonging to the regions A1 and A2 other than the region G2, the pixel electrode 35 connected to the second control line 92 has the same potential as the common electrode 37, so the display of these pixels 140 does not change. . Accordingly, the black display in the area A1 excluding the area G2, the white display in the area A2, and the gray display in the area G1 are maintained.
By the second gray display step S303 described above, it is possible to selectively display a light gray line in the region G2 while maintaining the display state of the regions A1, A2, and G1.

  Through the above steps S301 to S303, gray lines with expanded line widths can be displayed in the areas G1 and G2 on the monochrome image.

  In the third driving method, the gray display step is divided into the first gray display step S302 and the second gray display step S303, so that both the gray lines of the regions G1 and G2 having different background colors are used. A display with an expanded line width can be obtained.

  In the electrophoretic display device 200 according to the second embodiment, a partial rewriting operation in which only a partial region of the display unit 5 is rewritten is possible. Therefore, gray lines are written in the regions G1 and G2 without dividing the gray display step. Is possible. However, if the gray lines in the regions G1 and G2 are written together, only one of the gray line in the region G1 and the gray line in the region G2 becomes a line with an expanded line width.

  FIG. 15 is an explanatory diagram showing a driving method when the gray display step as a reference example is not divided. FIG. 15A is a diagram conceptually showing image data transferred to the display unit 5 in each step of the driving method according to the reference example. FIG. 15B is a diagram illustrating a display state of the display unit 5 in each step. FIG. 15C is a timing chart showing potential states of the common electrode 37 (Vcom), the first control line 91 (S1), and the second control line 92 (S2) in each step.

As shown in FIG. 15C, the driving method according to the reference example includes a monochrome image display step S501 and a gray display step S502.
The monochrome image display step S501 is the same as the monochrome image display step S301 in the third driving method, and a description thereof will be omitted.
The gray display step S502 is a step of displaying gray lines in both the areas G1 and G2 of the display unit 5 by one writing operation.

  In the gray display step S502 according to the reference example, image data D4 shown in FIG. 15A is used. In the image data D4, the pixel data “0” is arranged in the area corresponding to the area A1 and the area corresponding to the area G2 of the display unit 5, and the pixel data “1” is set in the area corresponding to the area A2 and the area corresponding to the area G1. "Is the image data arranged.

The image data D4 is transferred to the pixel 140 of the display unit 5 under the control of the controller 163.
In the pixels 140 belonging to the regions A1 and G2, a low-level image signal is input to the latch circuit 70, and the pixel electrode 35 is connected to the first electrode via the first transmission gate TG1 turned on by the output of the latch circuit 70. A control line 91 is connected.
In the pixels 140 belonging to the regions A2 and G1, a high-level image signal is input to the latch circuit 70, and the pixel electrode 35 and the second signal are transmitted via the second transmission gate TG2 turned on by the output of the latch circuit 70. A control line 92 is connected.

  Under the control of the controller 163, the common power supply modulation circuit 164 supplies a high level potential to the first control line 91, while supplying a low level to the second control line 92, as shown in FIG. And a pulse wave that periodically repeats a high level and a low level is input to the common electrode 37.

In the pixel 140 belonging to the region A <b> 1 and the region G <b> 2, a high level potential is input to the pixel electrode 35 through the first control line 91. Then, the electrophoretic element 32 is driven by a potential difference generated between the pixel electrode 35 and the common electrode 37 during a period in which the common electrode 37 is at a low level.
At this time, since the electrophoretic element 32 performs a black display operation, the display of the pixel 140 in the area A1 where the original display was black does not change. On the other hand, the pixel 140 in the region G2 that originally displayed white becomes a light gray display by applying a voltage for a short period.

In the pixel 140 belonging to the region A <b> 2 and the region G <b> 1, a low level potential is input to the pixel electrode 35 via the second control line 92. Then, the electrophoretic element 32 is driven by a potential difference generated between the pixel electrode 35 and the common electrode 37 during a period in which the common electrode 37 is at a high level.
At this time, since the electrophoretic element 32 performs a white display operation, the display of the pixel 140 in the region A2 that originally displayed the white display does not change. On the other hand, the pixel 140 in the region G1 that originally displayed black is dark gray by applying a voltage for a short period.

With the above operation, as shown in FIG. 15B, gray lines can be written in the regions G1 and G2.
However, as shown in FIG. 15C, in the gray display step S502, the timing of stopping the potential input to the common electrode 37 is set to a period in which the final pulse Pn input to the common electrode 37 is at a low level. Yes.
In such a period, the pixel 140 belonging to the region G2 performs a black display operation, and the pixel 140 belonging to the region A2 surrounding the region G2 does not substantially operate. Therefore, the pixel electrode 35 belonging to the pixel 140 in the region G2 is changed to the common electrode 37. An electric field spreading outward is formed. Therefore, in the region G2, a line in which a region wider than the pixel electrode 35 is displayed in gray can be displayed.
However, during the above period, the pixels 140 belonging to the region G1 do not substantially operate, and the pixels 140 belonging to the region A1 surrounding the region G1 perform a black display operation. Therefore, the gray line displayed in the region G1 is not a display with an expanded line width.

  Thus, when displaying gray lines with different backgrounds, if a plurality of gray lines are written together, the line width differs depending on the background color. Therefore, it is necessary to sequentially execute the first gray display step S302 and the second gray display step S303 as in the third driving method.

  In the third driving method, the pulse width and cycle of the final pulse Pn are set to the same length as other pulses for the same reason as in the first driving method, but the first and second grays are the same. It is not impeded that the pulse width of the latter half of the last pulses Pn1 and Pn2 in the display steps S302 and S303 or the period of the last pulses Pn1 and Pn2 is longer than the pulse width or period of other pulses.

  In the third driving method, the pulse wave synchronized with the potential Vcom of the common electrode 37 is input to the second control line 92 in steps S302 and S303. In these steps, the second control is performed. The line 92 may be in a high impedance state (Hi-Z). Also in this case, since a potential difference does not occur between the pixel electrode 35 connected to the second control line 92 and the common electrode 37, these pixels 140 do not substantially operate and the display does not change. Therefore, it is possible to obtain the same effect as described above.

(Electronics)
Next, the case where the electrophoretic display device of the above embodiment is applied to an electronic device will be described.
FIG. 16 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. 17 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. 18 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, since the electrophoretic display device 100 (200) according to the present invention is employed in the display unit, the electronic apparatus including the display unit with excellent expressive power. It has become.
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, 20 microcapsule, 32 electrophoretic element, 35 pixel electrode, 37 common electrode, 40,140 pixel, 60 pixel electrode drive circuit, 61 pixel electrode wiring, 62 common electrode wiring, 63,163 controller (Control unit), 64 common electrode drive circuit, 70 latch circuit, 80 switch circuit, 91 first control line, 92 second control line, 161 scanning line drive circuit, 162 data line drive circuit, 164 common power supply modulation circuit

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; and a common electrode formed on the electrophoretic element side of the second substrate and facing the plurality of first electrodes. There,
While inputting the first or second potential to the pixel electrode, a pulse wave that periodically repeats the first potential and the second potential is input to the common electrode, and the potential of the common electrode is specified. Electricity characterized by displaying an image in which an outline of an image element composed of the specific gradation is expanded on the display unit by stopping the input of the pulse wave when the potential is to display gradation. Driving method of electrophoretic display device.   2. The driving method of the electrophoretic display device according to claim 1, wherein a pulse width of the latter half of the last pulse of the pulse wave is made larger than a pulse width of another pulse constituting the pulse wave.   The driving method of the electrophoretic display device according to claim 1, wherein a period of the last pulse of the pulse wave is longer than a period of other pulses constituting the pulse wave.   The driving method of the electrophoretic display device according to claim 2, wherein an extended width of the contour is adjusted according to the pulse width or the length of the period.   5. The specific gradation according to claim 1, wherein the specific gradation is a first gradation having a maximum gradation value or a second gradation having a minimum gradation value. 6. A driving method of the electrophoretic display device described.   The driving method of the electrophoretic display device according to claim 1, wherein the specific gradation is an intermediate gradation. 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 pixel electrode formed on the electrophoretic element side, a common electrode formed on the electrophoretic element side of the second substrate and opposed to the plurality of first electrodes, and input to the pixel electrode and the common electrode An electrophoretic display device having a control unit for controlling a potential to be generated,
The controller is
While inputting the first or second potential to the pixel electrode, a pulse wave that periodically repeats the first potential and the second potential is input to the common electrode, and the potential of the common electrode is specified. Electricity characterized by displaying an image in which an outline of an image element composed of the specific gradation is expanded on the display unit by stopping the input of the pulse wave when the potential is to display gradation. Electrophoretic display device.   The electrophoretic display device according to claim 7, wherein a pulse width of the latter half of the last pulse of the pulse wave is larger than a pulse width of other pulses constituting the pulse wave.   The electrophoretic display device according to claim 7, wherein a period of a final pulse of the pulse wave is longer than a period of other pulses constituting the pulse wave.   The electrophoretic display device according to claim 8, wherein the control unit adjusts an extended width of the contour according to the pulse width or the length of the cycle.   11. The specific gradation according to claim 7, wherein the specific gradation is a first gradation having a maximum gradation value or a second gradation having a minimum gradation value. The electrophoretic display device described.   The electrophoretic display device according to claim 7, wherein the specific gradation is an intermediate gradation.   An electronic apparatus comprising the electrophoretic display device according to claim 7.

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