JP5353165B2 - Electrophoretic display device driving method, electrophoretic display device, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for driving an electrophoretic display device which can prevent a boundary of pixels having different gradations from blotting and can obtain clear display. <P>SOLUTION: The method for driving the electrophoretic display device includes a first image display step ST21 for inputting first potential or second potential corresponding to image data to a plurality of pixel electrodes, inputting a signal in which the first potential and the second potential are periodically repeated to a common electrode and driving an electrophoretic element to display an image based on the image data and a second image display step ST22 for holding the plurality of pixel electrodes at the potential and inputting potential between the first potential and the second potential to the common electrode. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

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

As an electrophoretic display device, a type in which a plurality of microcapsules are sandwiched between a pair of substrates is known (see, for example, Patent Document 1). This type of electrophoretic display device includes a pixel electrode provided for each of a plurality of pixels, a common electrode provided to face the plurality of pixel electrodes, and an electrophoresis held between the plurality of pixel electrodes and the common electrode. An electrophoretic element including particles is provided, and display driving is performed by causing the electrophoretic particles to migrate by an electric field generated by a potential difference between the pixel electrode and the common electrode.
For example, Patent Document 1 discloses a “common swing drive” in which the potential of each pixel electrode is switched using two potentials having a height relationship, and the common electrode is also rewritten by switching the two potentials. There is a description about.
JP 2003-84314 A

FIG. 12 is an explanatory diagram of an image display step by common swing driving. FIG. 12 shows the change with time of the potential of each electrode in the common swing drive in steps ST0 to ST5 constituting the image display step, and the behavior of the particles in the microcapsule in each step.
In step ST0, the pixel electrodes PX1 and PX2 and the common electrode COM arranged adjacent to each other are in a high impedance state (electrically disconnected state). When common swing driving is started in step ST1, a high level potential is input to the pixel electrode PX1, a low level potential is input to the pixel electrode PX2, and a high level potential and a low level potential are input to the common electrode COM for each of steps ST1 to ST4. Are input in the form of rectangular waves.

  In step ST1, a high level potential is input to the common electrode COM. As a result, an electric field is formed between the pixel electrode PX2 having a low level potential and the common electrode COM, and the electrophoretic particles in the microcapsule located on the pixel electrode PX2 are driven. When the white particles are negatively charged and the black particles are positively charged, the white particles are attracted toward the common electrode COM by the electric field, and the black particles are attracted toward the pixel electrode PX2 (black display). In step ST1, since the pixel electrode PX1 and the common electrode COM are at the same potential, the electrophoretic particles are not driven, and the display of the pixel corresponding to the pixel electrode PX1 does not change.

  Next, in step ST2, a low level potential is input to the common electrode COM. As a result, an electric field is formed between the pixel electrode PX1 having a high level potential and the common electrode COM, and the electrophoretic particles in the microcapsule positioned on the pixel electrode PX1 are driven. That is, black particles are attracted to the common electrode COM side, and white particles are attracted to the pixel electrode PX1 side (white display). In step ST2, since the pixel electrode PX2 and the common electrode COM are at the same potential, the electrophoretic particles are not driven, and the display of the pixel corresponding to the pixel electrode PX2 does not change.

  Thereafter, similarly, in step ST3, only the pixel (white display pixel) corresponding to the pixel electrode PX2 is driven, and in step ST4, only the pixel (black display pixel) corresponding to the pixel electrode PX1 is driven. In this way, desired black display and white display are achieved in the pixels corresponding to the pixel electrodes PX1 and PX2.

  According to the driving method employing the above-described common swing driving, it is possible to reliably bring the white particles and the black particles to the desired electrode side in each pixel, and a high-contrast display can be obtained. However, in the common swing driving, the white display pixels and the black display pixels are alternately driven independently of each other, so that there is a problem that the boundary between the white display pixels and the black display pixels blurs.

  More specifically, as shown in FIG. 12, in steps ST1 to ST4, since an electric field is formed only between one of the pixel electrodes PX1 and PX2 and the common electrode COM, the formed electric field is on the common electrode COM side. In FIG. Then, due to the influence of the electric field, the non-operating pixel adjacent to the operation target pixel is affected. For example, in step ST3, only the region on the pixel electrode PX2 should be displayed in white, but the white display spreads to a partial region on the pixel electrode PX1. In step ST4, the black display spreads to a partial area on the pixel electrode PX2.

  In the common swing drive, as shown in the figure, the white display operation or the black display operation is always executed at the end of the image display step. Therefore, when the image display step is completed by driving with the white display pixel, the white display pixel is displayed. When a black display pixel is generated in a part of the black display pixel adjacent to the black display pixel and the image display step is completed by driving the black display pixel, the black display part is displayed in a part of the white display pixel adjacent to the black display pixel. Will occur.

  The present invention has been made in view of the above-described problems of the prior art, and prevents the blurring of pixels with different gradations from being blurred, and a driving method of an electrophoretic display device capable of obtaining a clear display and An object is to provide an electrophoretic display device.

  In order to solve the above problems, a driving method of an electrophoretic display device of the present invention sandwiches an electrophoretic element including electrophoretic particles between a pair of substrates, and a plurality of electrophoretic elements on one side of the substrate are arranged on the electrophoretic element side. A driving method of an electrophoretic display device in which a pixel electrode is formed and a common electrode facing the plurality of pixel electrodes is formed on the electrophoretic element side of the other substrate, the plurality of the pixel electrodes The first potential or the second potential corresponding to the image data is input to the common electrode, and a signal that periodically repeats the first and second potentials is input to the common electrode to drive the electrophoretic element. A first image display step for displaying an image based on the image data; and holding a plurality of the pixel electrodes at the potential, while a potential between the first potential and the second potential at the common electrode Enter the second And having an image display step.

  According to this driving method, since the second image display step is provided, display blur that inevitably occurs in the first image display step of displaying an image by common swing driving can be applied to pixels of different gradations simultaneously. It can be removed in the second image display step that is driven. Accordingly, it is possible to prevent blurring between pixels of different gradations and obtain a clear display.

In the second image display step, a potential difference between the first potential and the second potential is ΔV, and an intermediate potential between the first potential and the second potential is centered on the common electrode. It is preferable to input a potential within a range of ± 0.3 ΔV or less.
According to this driving method, in the second image display step, the intensity of the electric field formed on the pixel electrode held at the first potential and the pixel electrode held at the second potential are formed. Since the intensity of the electric field can be made substantially equal, display blur at the boundary between pixels of different gradations can be effectively removed.

In the second image display step, it is preferable to input an intermediate potential between the first potential and the second potential to the common electrode.
With such a driving method, in the second image display step, the electric field strength formed on the pixel electrode held at the first potential and the pixel electrode held at the second potential are formed. Since the strength of the applied electric field can be made substantially equal, the display blur at the boundary between pixels of different gradations can be more reliably removed.

In the second image display step, the contour width of the display image can be adjusted by the potential input to the common electrode.
In the driving method of the present invention, when the potential input to the common electrode is changed in the second image display step, the degree of display blur after the execution of the second image display step changes. Therefore, by using this action, it is also possible to adjust the contour width of the display image by the potential input to the common electrode.

After the second image display step, an image holding step for holding the pixel electrode and the common electrode in a high impedance state, and the same potential as the second image display step is input to the pixel electrode and the common electrode. The driving method may include a refresh step.
With such a driving method, when the display image is held using the memory property of the electrophoretic element, the display can be held while maintaining the contrast of the display image by the refresh step. Further, since the same potential as that in the second image display step is input to the common electrode in the refresh step, display blur does not occur as in the case where the refresh operation is performed by the common swing drive.

  Next, the electrophoretic display device of the present invention sandwiches an electrophoretic element including electrophoretic particles between a pair of substrates, and a plurality of pixel electrodes are formed on the electrophoretic element side of one of the substrates, An electrophoretic display device in which a common electrode facing a plurality of the pixel electrodes is formed on the electrophoretic element side of the other substrate, the electrophoretic display device being connected to the common electrode, And a second potential different from the first potential, and a potential between the first potential and the second potential can be supplied.

  According to this configuration, an electrophoretic display device capable of executing the driving method of the present invention described above can be realized.

  An electrophoretic element including electrophoretic particles is sandwiched between a pair of substrates, and a plurality of pixel electrodes are formed on the electrophoretic element side of one of the substrates, and on the electrophoretic element side of the other substrate An electrophoretic display device in which a common electrode facing a plurality of the pixel electrodes is formed, and a first potential or a second potential corresponding to image data is input to the plurality of pixel electrodes during an image display operation. A first image display step of inputting a signal that periodically repeats the first and second potentials to the common electrode and driving the electrophoretic element to display an image based on the image data; And a second image display step of inputting a potential between the first potential and the second potential to the common electrode while holding the pixel electrode at the potential. Have The features.

  According to this configuration, the first and second image display steps executed by the control unit prevent the occurrence of display blur in the black-and-white boundary region, thereby providing an electrophoretic display device that can obtain a clear display.

A display unit including a plurality of pixels is provided, and the pixel electrode, a pixel switching element, and a memory circuit connected between the pixel electrode and the pixel switching element are provided for each pixel. A configuration is preferable.
According to this configuration, since an image signal is held in the memory circuit, a periodic refresh operation is unnecessary, and an electrophoretic display device with excellent power saving can be realized.

A switch circuit provided for each of the pixels and connected between the pixel electrode and the memory circuit; first and second control lines connected to the switch circuit and supplying a potential to the pixel electrode; It is preferable to have a configuration having
According to this configuration, since the potential of the pixel electrode can be directly controlled by controlling the potential of the first and second control lines, the display image can be easily erased and inverted with less power consumption. A feasible electrophoretic display device can be realized.

Preferably, the pixel switching element is a transistor, and the potential input to the common electrode in the second image display step is the same potential as a potential input to the gate electrode of the transistor.
According to this configuration, since the potential input to the common electrode 37 in the second image display step can be generated by the circuit that generates the potential of the selection signal of the pixel switching element, it is not necessary to increase the number of generated potentials. Therefore, an increase in the scale of the power supply circuit can be avoided, and the configuration is advantageous in terms of manufacturability and cost.

An electronic apparatus according to the present invention includes the electrophoretic display device described above.
According to this configuration, it is possible to provide an electronic apparatus including a display unit that clearly displays a boundary region between pixels of different gradations and has excellent display quality.

Hereinafter, an electrophoretic display device according to the present invention will be described with reference to the drawings. In the present embodiment, an electrophoretic display device driven by an active matrix method will be described.
Note that this embodiment shows one aspect of the present invention, and does not limit the present invention, and can be arbitrarily changed within the scope of the technical idea of the present invention. Further, in the following drawings, in order to make the drawings easy to see, the actual configuration is appropriately displayed.

(First embodiment)
FIG. 1A is a schematic configuration diagram of an electrophoretic display device 100 according to the present embodiment.
The electrophoretic display device 100 includes a display unit 5 in which a plurality of pixels 40 are arranged in a matrix. Around the display unit 5, a scanning line driving circuit 61, a data line driving circuit 62, a controller (control unit) 63, and a common power supply modulation circuit 64 are arranged. The scanning line driving circuit 61, the data line driving circuit 62, and the common power supply modulation circuit 64 are each connected to the controller 63. The controller 63 comprehensively controls these based on image data and synchronization signals supplied from the host device.

  A plurality of scanning lines 66 extending from the scanning line driving circuit 61 and a plurality of data lines 68 extending from the data line driving circuit 62 are formed in the display unit 5, and the pixels 40 are provided corresponding to the intersection positions thereof. It has been.

  The scanning line driving circuit 61 is connected to each pixel 40 via m scanning lines 66 (Y1, Y2,..., Ym). Under the control of the controller 63, 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. 2) provided in the pixel 40 is supplied via the selected scanning line 66.

The data line driving circuit 62 is connected to each pixel 40 via n data lines 68 (X1, X2,..., Xn), and corresponds to each pixel 40 under the control of the controller 63. An image signal defining 1-bit pixel data is supplied to the pixel 40.
In the present embodiment, a low level (L) image signal is supplied to the pixel 40 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 40.

  The display unit 5 is also provided with a low potential power line 49, a high potential power line 50, and a common electrode wiring 55 extending from the common power modulation circuit 64, and each wiring is connected to the pixel 40. The common power supply modulation circuit 64 generates various signals to be supplied to each of the wires under the control of the controller 63, and electrically connects and disconnects these wires (high impedance (Hi-Z)). )I do.

Furthermore, in the case of the present embodiment, the configuration shown in FIG. 1B is adopted for the common power supply modulation circuit 64 in order to enable the driving method described later. FIG. 1B is a diagram showing the main parts of the controller 63 and the common power supply modulation circuit 64.
As shown in FIG. 1B, the common power supply modulation circuit 64 is provided with a potential selection circuit 67 that selects a potential supplied to the common electrode wiring 55. The potential selection circuit 67 is connected to a power supply circuit 65 provided in the controller 63. The potential selection circuit 67 switches the four types of potentials (0V, 7.5V, 15V, Hi-Z) supplied from the power supply circuit 65 by the control signal input from the controller 63, and selects the common electrode wiring 55. To the potential state.

FIG. 2 is a circuit configuration diagram of the pixel 40.
The pixel 40 includes a selection transistor (Thin Film 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. Is 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 connected to the pixel 40. . 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 a pixel switching element composed of 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 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).

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, and the gate terminal of the N-MOS transistor 82 is connected to the data output terminal N2 of the latch circuit 70.

  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. Further, the electrophoretic element 32 is sandwiched between the pixel electrode 35 and the common electrode 37.

In the pixel 40 having the above configuration, 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 S1 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.

  In the electrophoretic display device 100, the electrophoretic element 32 is based on the potential difference between the potentials S1 and S2 input to the pixel electrode 35 and the potential Vcom input to the common electrode 37 via the common electrode wiring 55 (FIG. 1). To display an image on the display unit 5.

  Next, FIG. 3A is a partial cross-sectional view of the electrophoretic display device 100 in the display unit 5. The electrophoretic display device 100 includes a configuration in which an electrophoretic element 32 formed by arranging a plurality of microcapsules 20 is sandwiched between an element substrate (first substrate) 30 and a counter substrate (second substrate) 31. Yes.

In the display unit 5, the circuit layer 34 on which the scanning line 66, the data line 68, the selection transistor 41, the latch circuit 70, and the like illustrated in FIG. 1 and FIG. A plurality of pixel electrodes 35 are arranged on the circuit layer 34.
The element 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 has a voltage applied to an electrophoretic element 32 formed by laminating nickel plating and gold plating on a Cu (copper) foil in this order, Al (aluminum), ITO (indium tin oxide), or the like. Is an electrode to which is applied.

On the other hand, a planar common electrode 37 facing the plurality of pixel electrodes 35 is formed on the electrophoretic element 32 side of the counter substrate 31, and the electrophoretic element 32 is provided on the common electrode 37.
The counter 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 an electrode for applying a voltage to the electrophoretic element 32 together with the pixel electrode 35, and is formed of MgAg (magnesium silver), ITO (indium tin oxide), IZO (indium zinc oxide) or the like. It is a transparent electrode.
The electrophoretic element 32 and the pixel electrode 35 are bonded via the adhesive layer 33, so that the element substrate 30 and the counter substrate 31 are bonded.

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

  FIG. 3B is a schematic cross-sectional view of the microcapsule 20. The microcapsule 20 has a particle size of, for example, about 50 μm and encloses therein a dispersion medium 21, a plurality of white particles (electrophoretic particles) 27, and a plurality of black particles (electrophoretic particles) 26. It is a spherical body. As shown in FIG. 3A, the microcapsule 20 is sandwiched between the common electrode 37 and the pixel electrode 35, and one or more microcapsules 20 are disposed in one pixel 40.

The outer shell (wall film) of the microcapsule 20 is formed using a transparent polymer resin such as acrylic resin such as polymethyl methacrylate and polyethyl methacrylate, urea resin, and 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. 4 is an operation explanatory diagram of the electrophoretic element. 4A shows a case where the pixel 40 displays white, and FIG. 4B shows a case where the pixel 40 displays black.
In the case of white display shown in FIG. 4A, 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. 4B, the common electrode 37 is held at a relatively low potential, and the pixel electrode 35 is held at a relatively high potential. As a result, the positively charged black particles 26 are attracted to the common electrode 37, while the negatively charged white particles 27 are attracted to the pixel electrode 35. As a result, when this pixel is viewed from the common electrode 37 side, black (B) is recognized.

[Driving method]
Next, a driving method of the electrophoretic display device of this embodiment will be described with reference to FIGS.
FIG. 5 is a flowchart showing a method for driving the electrophoretic display device 100. FIG. 6 is a timing chart corresponding to the flowchart of FIG. FIG. 7 is a diagram illustrating a potential state of two adjacent pixels, which is an object for explaining the driving method of the present embodiment. FIG. 8 is an operation explanatory diagram of the driving method of the present embodiment.

5 and 6 show a flow when the pixel 40A shown in FIG. 7 is displayed in black and the pixel 40B is displayed in white.
In FIG. 6, the potential G of the scanning line 66, the potential Vdd of the high potential power supply line 50, the potential Vss of the low potential power supply line 49, the potential Da of the data line 68a, the potential Db of the data line 68b, and the potential Va of the pixel electrode 35a. The potential Vb of the pixel electrode 35b, the potential Vcom of the common electrode 37, the potential S1 of the first control line 91, and the potential S2 of the second control line 92 are shown.
In FIG. 7, the subscripts “A”, “B”, “a”, and “b” in each symbol clearly distinguish the two pixels 40 (40A, 40B) that are the objects of the description and the components that belong to them. It is attached to do so and has no other intention.

  As shown in FIG. 5, the driving method according to the present embodiment includes a power-on step ST10, an image signal input step ST11, an image display step ST12, a power-off step ST13, an image holding step ST14, and a refresh step ST15. And including.

  First, in the display unit 5 before the power-on step ST10, each circuit is in a power-off state. Therefore, as shown in FIG. 6, the pixel electrode 35a (potential Va), the pixel electrode 35b (potential Vb), the common electrode 37 (potential Vcom), the first control line 91 (potential S1), and the second control line 92 All of (potential S2) are in a high impedance state.

  In the power-on step ST10, power is supplied to the scanning line drive circuit 61, the data line drive circuit 62, and the common power supply modulation circuit 64, and the wiring connected to each circuit is in a state where potential can be supplied. In addition, power is supplied to the latch circuit 70 of the pixel 40 via the high potential power supply line 50 and the low potential power supply line 49, and the image signal can be stored.

  In this embodiment, the low level (L) potential of the data line 68 and the low level potential VL of the low potential power supply line 49 are both assumed to be 0 (zero) V. Further, the potentials of 0V, 5V, 7V, 15V, etc. shown in each part of FIG. 6 are given as an example for explaining the invention, and the potential of each wiring is limited to these specific numerical values. is not.

  Next, in an image signal input step ST11, an image signal is input to the latch circuit 70 of each pixel 40. That is, a high-level (H; for example, 7 V) pulse that is a selection signal is input to the scanning line 66, the selection transistor 41 connected to the scanning line 66 is turned on, and the data line 68 and the latch circuit 70 are connected. Connected. As a result, an image signal is input to the latch circuit 70.

In the pixel 40A shown in FIG. 7, a low level (L) image signal is input from the data line 68a to the latch circuit 70a via the selection transistor 41a.
In the case of the present embodiment, in the image signal input step ST11, the potential Vdd (high level potential for image signal input) supplied via the high potential power line 50 is changed to the potential Vdd (image display) in the subsequent image display step ST12. For example, about 5V, which is lower than the high-level potential (for example, 15V). Therefore, the potential of the data output terminal N2a of the latch circuit 70a of the pixel 40A in which the image signal is written becomes a high level potential (for example, 5 V) for inputting the image signal. Note that the potential of the data input terminal N1a is at a low level (eg, 0 V).

  On the other hand, in the pixel 40B, a high level (H) image signal is input from the data line 68b to the latch circuit 70b via the selection transistor 41b, and the potential of the data input terminal N1b of the latch circuit 70b is high level for image signal input. The potential (for example, 5V) becomes low, and the potential of the data output terminal N2b becomes low level (L; for example, 0V).

  In the image signal input step ST11, the switch circuits 80a and 80b are operated by the potentials output from the latch circuits 70a and 70b, and the first and second control lines 91 and 92, the pixel electrode 35a and the pixel electrode 35b, Is connected. However, since the first and second control lines 91 and 92 are both in a high impedance state, the pixel electrodes 35a and 35b remain in a high impedance state, and the common electrode 37 is also in a high impedance state. Therefore, the display state of the electrophoretic element 32 does not change at the time of the image signal input step ST11.

  If an image signal is input to each of the pixels 40A and 40B, the process proceeds to the image display step ST12. The image display step ST12 of the present embodiment includes a first image display step ST21 and a second image display step ST22, as shown in FIGS.

  In the first image display step ST21, the potential Vdd of the high potential power supply line 50 is raised from a high level potential for image signal input (for example, 5V) to a high level potential VH for image display (for example, 15V). The potential Vss of the low potential power line 49 is set to a low level potential VL (for example, 0 V). Further, a high level potential VH for image display is supplied to the first control line 91, and a low level potential VL is supplied to the second control line 92. Further, a rectangular pulse that repeats the high level potential VH and the low level potential VL in a predetermined cycle is input to the common electrode 37.

Thereby, in the pixel 40A, the potential of the data output terminal N2a of the latch circuit 70a becomes the high level potential VH, and the potential of the data input terminal N1a becomes the low level potential VL. Then, the first transmission gate TG1a of the switch circuit 80a is turned on, and the pixel electrode 35a and the first control line 91 are connected. As a result, the pixel electrode 35a becomes the high level potential VH.
The electrophoretic element 32 is driven by the potential difference between the pixel electrode 35 a and the common electrode 37 during a period in which the common electrode 37 to which the rectangular wave pulse is input is at the low level potential VL. That is, as shown in FIG. 8B, the positively charged black particles 26 are attracted to the common electrode 37 side, the negatively charged white particles 27 are attracted to the pixel electrode 35a side, and the pixel 40A displays black. Is done.

On the other hand, in the pixel 40B, since the data output terminal N2b of the latch circuit 70b is at the low level potential VL and the data input terminal N1a is at the high level potential VH, the second transmission gate TG2b of the switch circuit 80b is turned on, and the pixel electrode 35b and the second control line 92 are connected. As a result, the pixel electrode 35b becomes the low level potential VL.
The electrophoretic element 32 is driven by the potential difference between the pixel electrode 35 b and the common electrode 37 during a period in which the common electrode 37 is at the high level potential VH. That is, as shown in FIG. 8C, the negatively charged white particles 27 are attracted to the common electrode 37 side, the positively charged black particles 26 are attracted to the pixel electrode 35a side, and the pixel 40B displays white. Is done.

  In the first image display step ST21, a rectangular pulse that repeats the high level potential VH and the low level potential VL in a predetermined cycle is input to the common electrode 37. That is, in the first image display step ST21, an image display operation is executed by common swing driving. Therefore, the black display operation in the pixel 40 </ b> A and the white display operation in the pixel 40 </ b> B are performed independently of each other according to the potential of the common electrode 37.

According to the driving method adopting the common swing driving, the black particles and the white particles can be moved to the desired electrode more reliably, so that the contrast can be increased. In addition, since the potential applied to the pixel electrode and the common electrode can be controlled by binary values of the high level potential VH and the low level potential VL, the voltage can be reduced and the circuit configuration can be simplified. Further, when a TFT is used as the switching element of the pixel electrode 35, there is an advantage that the reliability of the TFT can be secured by low voltage driving.
In addition, it is preferable that the frequency and the number of cycles of the common swing drive are appropriately determined according to the specifications and characteristics of the electrophoretic element 32.

When the first image display step ST21 is completed, the process proceeds to the second image display step ST22.
In the second image display step ST22, as shown in FIG. 6, the common electrode 37 is held at a constant potential. In the present embodiment, an intermediate potential VM (for example, 7.5 V) that is an intermediate potential between a high level potential VH (for example, 15 V) and a low level potential VL (for example, 0 V) is input to the common electrode 37. On the other hand, the potential states of the pixel electrodes 35a and 35b are the same as in the first image display step ST21. The pixel electrode 35a is at the high level potential VH and the pixel electrode 35b is at the low level potential VL.

Then, as shown in FIG. 8D, in the pixel 40A, an electric field from the pixel electrode 35a (high level potential VH; for example, 15V) to the common electrode 37 (intermediate potential VM; for example, 7.5V) is formed. The electrophoretic element 32 of the pixel 40A performs a black display operation. On the other hand, in the pixel 40B, an electric field is formed from the common electrode 37 (intermediate potential VM; for example, 7.5V) toward the pixel electrode 35b (low level potential VL; for example, 0V), so that the electrophoretic element 32 of the pixel 40B is white. Display operation.
Accordingly, in the second image display step ST22, the pixel 40A displayed in black and the pixel 40B displayed in white are simultaneously driven.

  In the first image display step ST21, the pixel 40A and the pixel 40B are driven by the common swing drive so as not to overlap with each other in time, so that during the period in which the pixel 40A is driven, as shown in FIG. As a result of the electric field spreading on the common electrode 37 side, a black display portion is formed in a part of the white display pixel 40B, and the black display region becomes larger. On the other hand, in the period in which the pixel 40B is driven, as shown in FIG. 8C, a white display portion is formed in a part of the black display pixel 40A, and the white display region becomes large.

  On the other hand, in the second image display step ST22, the pixels 40A and 40B are driven at the same time. Therefore, as shown in FIG. 8D, between the pixel electrode 35a and the common electrode 37, and the pixel electrode 35b. Electric fields opposite to each other are formed between the common electrode 37 and the common electrode 37. As a result, the electric field at the boundary between the pixels 40A and 40B is canceled and the electric field does not spread to adjacent pixels. As a result, display blur at the boundary between the pixels 40A and 40B shown in FIGS. 8B and 8C is removed, and a clear display can be obtained.

The voltage application time in the second image display step ST22 can be set to any length as long as the display blur formed in the first image display step ST21 can be removed.
The degree of display blur varies depending on the intensity of the electric field applied to the electrophoretic element 32 in the first image display step ST21, the interval between the pixels 40A and 40B, and the period of pulses input to the common electrode 37. On the other hand, these parameters greatly affect the display quality.
Therefore, the above-mentioned parameters are set so that a good display can be obtained in the first image display step ST21, and the voltage application time is set so that the resulting display blur can be removed in the second image display step ST22. It is good to set.

  When the second image display step ST22 is completed, the power supply to each circuit is stopped in the power-off step ST13. Thereby, the wiring connected to the pixels 40A and 40B is set to a high impedance state, and the pixel electrodes 35a and 35b and the common electrode 37 are also set to a high impedance state. Thereafter, in the image holding step ST14, by holding the high impedance state, it is possible to continue displaying images on the display unit 5 without consuming power.

  Since the electrophoretic element 32 has a memory property, the image can be continuously displayed even when the pixel 40 is turned off as described above, but the display is gradually lost as time passes. Therefore, it is preferable to execute the refresh step ST15 when a predetermined time has elapsed after the shift to the image holding step ST14. The length of the image holding step ST14 can be appropriately set according to the display holding characteristic (memory property) of the electrophoretic element 32 and the type of display image.

In the refresh step ST15, the same operation as in the second image display step ST22 is executed. That is, a high level potential VH and a low level potential VL are input to the pixel electrodes 35a and 35b, respectively, and an intermediate potential VM (for example, 7.5V) is input to the common electrode 37.
Although not shown, a step for executing the same operation as the power-on step ST10 is provided immediately before the refresh step ST15.

As a result, as shown in FIG. 8D, the pixels 40A and 40B can be made to perform a black display operation and a white display operation, respectively, and the black particles 26 that have moved away from the vicinity of the common electrode 37 with the passage of time. The (pixel 40A) and the white particles 27 (pixel 40B) can be attracted again to the common electrode 37 side.
Through the above operation, the display contrast can be increased and the display quality can be recovered.

In the present embodiment, since the latch circuits 70a and 70b are also turned off in the image holding step ST14, the stored contents of the latch circuits 70a and 70b are lost when the power is turned on at the start of the refresh step ST15. Therefore, in the refresh step ST15 according to the present embodiment, before the refresh operation for driving the electrophoretic element 32, the scanning line driving circuit 61 and the data line driving circuit 62 are driven, and an image signal corresponding to the display image is latched. Steps for inputting to 70a and 70b are provided.
On the other hand, if the latch circuits 70a and 70b are energized in the image holding step ST14, the stored contents of the latch circuits 70a and 70b can be held. In the refresh step ST15 in this case, the refresh operation can be performed only by inputting a potential to the first and second control lines 91 and 92 and the common electrode 37.

  When the refresh step ST15 is completed, the process proceeds to the image holding step by a power-off operation similar to the previous power-off step ST13. Thereafter, when the display is maintained, the image holding step and the refreshing step are repeated every predetermined period. Further, when changing the display image of the display unit 5, a new image is displayed on the display unit 5 by executing the power-on step ST10 to the power-off step ST13.

  As described above in detail, in the method for driving the electrophoretic display device 100 of this embodiment, the common electrode 37 is held at the intermediate potential VM after the first image display step ST21 in which an image is displayed by common swing driving. A second image display step ST22 is provided. As a result, display blur that inevitably occurs in the first image display step ST21 can be removed in the second image display step ST22, and a display with a clear black and white boundary region can be obtained.

In the present embodiment, since the intermediate potential VM is input to the common electrode 37 in the refresh step ST15 as in the second image display step ST22, a clear refresh display can be obtained.
In the refresh step ST15, the common swing drive similar to that in the first image display step ST21 can be adopted. However, when the common swing drive is performed, the display blurs as shown in FIGS. 8B and 8C. May occur. On the other hand, in the present invention, also in the refresh step ST15, the intermediate potential VM is input to the common electrode 37, and the black display pixel 40A and the white display pixel 40B are simultaneously driven to perform the refresh operation. As a result, the contrast of the display image can be recovered without causing display blur.

  In the present embodiment, the intermediate potential VM input to the common electrode 37 in the second image display step ST22 is an intermediate potential (for example, between the high level potential VH (for example, 15V) and the low level potential VL (for example, 0V)). 7.5V), but the intermediate potential VM is not limited to this. The intermediate potential VM can be an arbitrary potential between a high level potential VH (for example, 15V) and a low level potential VL (for example, 0V).

For example, the driving method may be such that the same potential (for example, 7 V) as the high level (H) of the selection signal input via the scanning line 66 is input as the intermediate potential VM.
With such a driving method, a potential close to an intermediate potential between the high-level potential VH and the low-level potential VL is input to the common electrode 37, so that the operation in the second image display step ST22 is hardly changed. Moreover, since the potential corresponding to the high level (H) of the selection signal is a potential prepared in advance in the power supply circuit of the electrophoretic display device 100, a potential to be used in the second image display step ST22 is newly set. Therefore, the power supply circuit can be used efficiently, which is advantageous in terms of manufacturability and cost.

Further, as the intermediate potential VM, a high level potential (for example, 5 V) for image signal input used in the image signal input step ST11 may be used. Even in this case, this is a significant driving method in terms of effective use of the power supply circuit.
However, in the second image display step ST22, the intensity of the electric field formed in the pixel 40A is larger than the intensity of the electric field formed in the pixel 40B. The action of removing the protrusion is reduced.
Therefore, as the intermediate potential VM, it is preferable to set a potential within a range of ± 30% with respect to an intermediate potential between the high level potential VH and the low level potential VL. That is, the intermediate potential VM is within a range of ± 0.3 ΔV centered on an intermediate potential between the high level potential VH and the low level potential VL when the potential difference between the high level potential VH and the low level potential VL is ΔV. It is preferable to set to. By setting such a range, the black and white border region can be clearly displayed.

  By the way, if the intermediate potential VM input to the common electrode 37 in the second image display step ST22 is a potential shifted from an intermediate potential (for example, 7.5 V) between the high level potential VH and the low level potential VL, the second potential is displayed. In the image display step ST22, the balance of the electric field strength formed in each of the pixels 40A and 40B changes. Then, the degree of blurring of the black and white border region in the display after the execution of the second image display step ST22 also changes in accordance with the balance of the electric field intensity. This means that the display quality can be adjusted by the intermediate potential VM in the driving method of the present embodiment.

Therefore, for example, in the second image display step ST22, the value of the intermediate potential VM is adjusted in accordance with the type of display image, and the driving method for controlling the degree of blurring (the contour width of the display image) in the black-and-white boundary region is also possible. Good. Specifically, when the display image is character information, the intermediate potential VM is set so that the black display area becomes relatively wide so that the jagged edges of the character outline become inconspicuous. In the case of a photograph or a photograph, a driving method in which the intermediate potential VM is set so that the black-and-white boundary region is clear may be employed.
With such a driving method, it is possible to obtain a display state in accordance with the display image, and the electrophoretic display device 100 capable of high-quality display is obtained.

In the above embodiment, the electrophoretic display device 100 in which the pixel 40 is provided with the latch circuit 70 and the switch circuit 80 and the driving method thereof have been described. However, the technical scope of the present invention is limited to such an embodiment. Is not to be done.
For example, an electrophoretic display device in which the pixel 40 is not provided with the switch circuit 80 and the pixel electrode 35 is connected to the data output terminal N2 of the latch circuit 70 (5-transistor type), the latch circuit 70, and the switch Instead of the circuit 80, the present invention is applied to an electrophoretic display device having a configuration in which capacitors are provided (one transistor and one capacitor type) or a configuration in which each pixel electrode 35 is directly driven by a drive circuit (segment method). May be.

(Electronics)
Next, a case where the electrophoretic display device 100 of each of the above embodiments is applied to an electronic device will be described.
FIG. 9 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.
On the front surface of the watch case 1002, a display unit 1005 including the electrophoretic display device 100 of the above embodiment, a second hand 1021, a minute hand 1022, and an hour hand 1023 are provided. 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. 10 is a perspective view illustrating a configuration of the electronic paper 1100. An electronic paper 1100 includes the electrophoretic display device 100 of the above embodiment 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. 11 is a perspective view showing the configuration of the electronic notebook 1200. An electronic notebook 1200 is obtained by bundling a plurality of the electronic papers 1100 and sandwiching them between covers 1201. The cover 1201 includes display data input means (not shown) for inputting display data sent from an external device, for example. Thereby, according to the display data, the display content can be changed or updated while the electronic paper is bundled.

According to the wristwatch 1000, the electronic paper 1100, and the electronic notebook 1200 described above, the electrophoretic display device 100 according to the present invention is employed, so that the electronic apparatus includes a display unit with excellent display quality.
In addition, said electronic device illustrates the electronic device which concerns on this invention, Comprising: The technical scope of this invention is not limited. 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.

1 is a schematic configuration diagram of an electrophoretic display device according to an embodiment. FIG. 6 illustrates a pixel circuit. The fragmentary sectional view of an electrophoretic display device, and the sectional view of a microcapsule. FIG. 6 is an operation explanatory diagram of the electrophoretic display device. The flowchart which shows the drive method which concerns on embodiment. 6 is a timing chart corresponding to FIG. The figure which shows the electric potential state of 2 pixels used as description object of the drive method. Action | operation explanatory drawing of the drive method which concerns on embodiment. The front view of the wristwatch which is an example of an electronic device. The perspective view of the electronic paper which is an example of an electronic device. The perspective view of the electronic notebook which is an example of an electronic device. Explanatory drawing of common swing drive.

Explanation of symbols

  100 electrophoretic display device, 5 display unit, 20 microcapsule, 32 electrophoretic element, 35, 35a, 35b pixel electrode, 37 common electrode, 40, 40A, 40B pixel, 61 scanning line driving circuit, 62 data line driving circuit, 63 controller (control unit), 64 common power supply modulation circuit (common electrode drive circuit), ST10 power on step, ST11 image signal input step, ST12 image display step, ST13 power off step, ST14 image holding step, ST15 refresh step, ST21 First image display step, ST22 Second image display step

Claims (10)

An electrophoretic element including electrophoretic particles is sandwiched between a pair of substrates, and a plurality of pixel electrodes are formed on the electrophoretic element side of one of the substrates, and on the electrophoretic element side of the other substrate A method of driving an electrophoretic display device in which a common electrode facing a plurality of the pixel electrodes is formed,
A first potential or a second potential corresponding to image data is input to the plurality of pixel electrodes, and a signal that periodically repeats the first and second potentials is input to the common electrode, and the electrophoresis is performed. A first image display step of driving an element to display an image based on the image data;
A second image display step of holding a plurality of the pixel electrodes at the potential while inputting a potential between the first potential and the second potential to the common electrode;
A method for driving an electrophoretic display device, comprising: In the second image display step,
A potential difference between the first potential and the second potential is ΔV, and the common electrode is within a range of ± 0.3 ΔV or less centered on an intermediate potential between the first potential and the second potential. The driving method of the electrophoretic display device according to claim 1, wherein a certain potential is input. In the second image display step,
The driving method of the electrophoretic display device according to claim 2, wherein an intermediate potential between the first potential and the second potential is input to the common electrode.   3. The driving method of the electrophoretic display device according to claim 1, wherein, in the second image display step, a contour width of a display image is adjusted by a potential input to the common electrode. After the second image display step,
An image holding step for holding the pixel electrode and the common electrode in a high impedance state;
A refresh step of inputting the same potential as in the second image display step to the pixel electrode and the common electrode;
5. The method for driving an electrophoretic display device according to claim 1, wherein: An electrophoretic element including electrophoretic particles is sandwiched between a pair of substrates, and a plurality of pixel electrodes are formed on the electrophoretic element side of one of the substrates, and on the electrophoretic element side of the other substrate An electrophoretic display device in which a common electrode facing a plurality of the pixel electrodes is formed,
In the image display operation, a first potential or a second potential corresponding to image data is input to the plurality of pixel electrodes, and a signal that periodically repeats the first and second potentials is input to the common electrode. A first image display step of driving the electrophoretic element to display an image based on the image data; and holding the plurality of pixel electrodes at the potential while the first potential is applied to the common electrode. An electrophoretic display device comprising: a control unit that executes a second image display step of inputting a potential between the second potential and the second potential. Having a display part composed of a plurality of pixels;
For each of the pixels, and the pixel electrode, and the pixel switching element, according to claim 6, characterized in that a memory circuit connected between the pixel electrode and the pixel switching element, is provided Electrophoretic display device. A switch circuit provided for each pixel and connected between the pixel electrode and the memory circuit;
First and second control lines connected to the switch circuit and supplying a potential to the pixel electrode;
The electrophoretic display device according to claim 7 , comprising: The pixel switching element is a transistor;
The potential input to the common electrode in the second image display step, an electrophoretic display according to claim 7 or 8, characterized in that it is the same as the potential inputted to the gate electrode of the transistor apparatus. An electronic apparatus comprising the electrophoretic display device according to any one of claims 6 9.

Images