JP2009169365A - Electrophoresis display device, its driving method, and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a leak current between electrodes in an electrophoresis display device. <P>SOLUTION: The electrophoresis display device includes: a pair of first and second substrates (28, 29); an electrophoresis element (80) interposed between the first and the second substrates and including electrophoresis particles (82, 83); a plurality of pixel electrodes (21) provided on the first substrate; a common electrode (22) provided on the second substrate so as to be opposed to the plurality of pixel electrodes; pixel electrode potential supplying means (25, 91, 92, 210) supplying either one of a first potential (VH) and a second potential (VL) lower than the first potential to the pixel electrodes by selecting either one potential according to an image signal in an image writing period; and a common potential supplying means (93, 220) supplying a common potential (Vcom) to the common electrode so that the common electrode has an intermediate potential (VI) between the first and the second potentials in at least a first period (ST2) of the image writing period. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophoretic display device, a driving method thereof, and a technical field related to an electronic apparatus.

  This type of electrophoretic display device displays an image by moving an electrophoretic particle by applying a potential difference between a pixel electrode and a common electrode facing each other across an electrophoretic element including the electrophoretic particle (for example, Patent Documents). 1). The common electrode is sometimes called a counter electrode. The electrophoretic element is composed of, for example, a plurality of microcapsules each including a plurality of electrophoretic particles, and is fixed between the pixel electrode and the common electrode by, for example, a binder made of resin or an adhesive. In order to reliably move the electrophoretic particles between the pixel electrode and the common electrode, a potential difference of, for example, 10 V or more is often applied continuously or intermittently between the pixel electrode and the common electrode.

JP 2003-84314 A

  However, when a potential difference of, for example, 10 V or more is applied between the pixel electrode and the common electrode continuously or intermittently, the pixel electrode and the common electrode are connected to each other via the surface of the microcapsule or the binder. There is a technical problem that leakage current may occur in the meantime. In particular, the degree of occurrence of leakage current between pixel electrodes was larger.

  For this reason, there exists a possibility that the power consumption in an electrophoretic display device may increase. In addition, there is a possibility that electrochemical corrosion due to ion migration or the like may occur in the pixel electrode due to the leak current.

  The present invention has been made in view of the above-described problems, for example, and an electrophoretic display device capable of reducing a leakage current that can be generated between electrodes, a driving method thereof, and an electronic device including the electrophoretic display device. It is an object to provide a device.

  In order to solve the above problems, an electrophoretic display device of the present invention includes a pair of first and second substrates, an electrophoretic element that is sandwiched between the first and second substrates and includes electrophoretic particles, A plurality of pixel electrodes provided on the first substrate; a common electrode provided on the second substrate so as to face the plurality of pixel electrodes; and a first potential and the first on the pixel electrode. A pixel electrode potential supply means that selectively supplies one of the second potentials lower than the potential in accordance with an image signal in the image writing period, and a common potential to the common electrode. Of these, at least in the first period, there is provided common potential supply means for supplying the intermediate potential between the first potential and the second potential.

  According to the electrophoretic display device of the present invention, during the operation, the electrophoretic display device is sandwiched between the pixel electrode provided for each pixel on the first substrate and the common electrode provided for the plurality of pixels on the second substrate. By applying a voltage (that is, a potential difference) corresponding to an image signal to the electrophoretic element, an image is displayed on a display unit including a plurality of pixels. More specifically, for example, the electrophoretic element, which is a microcapsule, includes, as the electrophoretic particles, for example, a plurality of negatively charged white particles and a plurality of positively charged black particles. Yes. According to the voltage applied between the pixel electrode and the common electrode, one of a plurality of negatively charged white particles and a plurality of positively charged black particles moves (that is, migrates) to the pixel electrode side, By moving the other side toward the common electrode, an image is displayed on the second substrate side where the common electrode is provided. The electrophoretic element is fixed between the first and second substrates with, for example, a resin binder or adhesive.

  In the present invention, in the image writing period for writing an image on the display portion (or rewriting an image already displayed on the display portion), the pixel electrode has a first potential and a second potential lower than the first potential. Either one of the potentials is selected (that is, selectively) supplied by the pixel electrode potential supply unit according to the image signal, and the common potential is supplied to the common electrode by the common potential supply unit. Therefore, a potential difference between the first potential and the common potential or a potential difference between the second potential and the common potential is applied to the electrophoretic element sandwiched between the pixel electrode and the common electrode in accordance with the image signal.

  The first and second potentials are set such that the potential difference between the first potential and the second potential is the maximum potential difference required to drive the electrophoretic display device. This maximum potential difference is determined, for example, as the potential difference required to start moving the electrophoretic particles.

  Here, in this type of electrophoretic display device, in general, during the image writing period, the above-mentioned maximum potential difference is applied continuously or intermittently between the pixel electrode and the common electrode to move the electrophoretic particles. Thus, an image is displayed. As described above, if the above-described maximum potential difference is applied between the pixel electrode and the common electrode continuously or intermittently, an electrophoretic element or a binder is interposed between the pixel electrode and the common electrode. There is a risk that leakage current will occur.

  However, in the present invention, the common potential supply means supplies the common potential to the common electrode so that it has an intermediate potential between the first potential and the second potential in at least the first period of the image writing period. Here, the “intermediate potential” means a potential lower than the first potential and higher than the second potential, and means a potential having a magnitude between the first and second potentials. That is, it is not intended to be limited to the intermediate value. The “first period” is a period during which the electrophoretic particles start to move by applying the above-described maximum potential difference between the pixel electrode and the common electrode in the image writing period (in other words, for example, an electric current that is a microcapsule). To move the electrophoretic particles (that is, migrate) following the maximum potential difference between the pixel electrode and the common electrode in order to peel off the electrophoretic particles fixed to the film of the electrophoretic element. Is set as the period.

  Therefore, in the first period, the electrophoretic particles can be moved by the potential difference between the first potential and the intermediate potential or the potential difference between the second potential and the intermediate potential, which is smaller than the maximum potential difference described above. . Here, after the electrophoretic particles start to move, the potential difference required to move the electrophoretic particles (in other words, the electrophoretic particles that are not fixed to the film of the electrophoretic element, eg, a microcapsule, are moved). (The potential difference necessary for this) is smaller than the potential difference necessary to start moving the electrophoretic particles, and therefore depends on the potential difference between the first potential and the intermediate potential or the potential difference between the second potential and the intermediate potential. Electrophoretic particles can be reliably moved. Note that the length of the first period depends on the potential difference between the first potential and the intermediate potential or the potential difference between the second potential and the intermediate potential. The length required for movement from the electrode side to the pixel electrode side may be set as appropriate.

  Thus, in the present invention, in particular, at least in the first period of the image writing period, between the pixel electrode and the common electrode, the potential difference between the first potential and the second potential (in other words, the above-described maximum potential difference). A small potential difference is applied. That is, in the first period, the first potential or the second potential is supplied to the pixel electrode, and the common potential having an intermediate potential between the first potential and the second potential is supplied to the common electrode. A potential difference between the first potential and the intermediate potential or a potential difference between the second potential and the intermediate potential is applied between the pixel electrode and the common electrode.

  Therefore, it is possible to suppress or prevent the occurrence of a leak current between the pixel electrode and the common electrode via the electrophoretic element or the binder. Thereby, an increase in power consumption in the electrophoretic display device can be suppressed or prevented. Further, the electrochemical corrosion due to ion migration or the like that can occur in the pixel electrode due to the leakage current can be almost or completely eliminated.

  As described above, according to the electrophoretic display device of the present invention, the common potential is selectively supplied to the pixel electrode according to the image signal in at least the first period of the image writing period. Since the supply is made so as to have an intermediate potential between the first and second potentials, the occurrence of a leak current between the pixel electrode and the common electrode can be suppressed or prevented.

  In one aspect of the electrophoretic display device of the present invention, the common potential supply means sets the common potential to the same potential as the first potential in a second period prior to the first period in the image writing period. Then, the same potential as the second potential is supplied so as to be repeated at a predetermined cycle.

  According to this aspect, in the second period of the image writing period, the potential difference between the first potential and the second potential is repeatedly applied at a predetermined cycle between the pixel electrode and the common electrode. In other words, in the second period, a period in which the potential difference between the first potential and the second potential is applied between the pixel electrode and the common electrode and a period in which the potential difference is not applied between the pixel electrode and the common electrode are repeated. Composed. Here, in the present specification, “common oscillation” means that the common potential is supplied to the common electrode so that the common potential is repeatedly supplied with the same potential as the first potential and the same potential as the second potential. This is appropriately referred to as “drive”. That is, according to this aspect, the common swing drive is performed in the second period preceding the first period in the image writing period. Therefore, in the second period, a potential difference between the first potential and the second potential can be applied between the pixel electrode and the common electrode, and the electrophoretic particles start to move reliably (in other words, for example, an electric current that is a microcapsule). Electrophoretic particles fixed to the film of the electrophoretic element can be peeled off). Accordingly, in the first period subsequent to the second period, the potential difference between the first potential and the intermediate potential or the potential difference between the second potential and the intermediate potential is applied, so that the electrophoretic particles are reliably moved. Can be made. Note that, by setting the second period as a period shorter than the first period, it is possible to reliably suppress or prevent the occurrence of a leak current between the pixel electrode and the common electrode.

  In another aspect of the electrophoretic display device of the present invention, the common potential supply means sets the common potential equal to the first potential in a third period following the first period in the image writing period. A potential and the same potential as the second potential are supplied so as to be repeated at a predetermined cycle.

  According to this aspect, common swing driving is performed in the third period following the first period in the image writing period. Therefore, in the third period, a potential difference between the first potential and the second potential can be applied between the pixel electrode and the common electrode, and the electrophoretic particles can be fixed to the film of the electrophoretic element, for example, a microcapsule. it can. Therefore, it is possible to lengthen the time for holding the image displayed on the display portion in a state where no voltage is applied between the pixel electrode and the common electrode.

  In another aspect of the electrophoretic display device according to the aspect of the invention, the pixel electrode potential supply unit may include the plurality of pixel electrodes in a period in which the common electrode is supplied with the same potential as the first potential as the common potential. Among the plurality of pixel electrodes, the first potential is supplied to the pixel electrode to which the second potential is supplied as the one potential, and the first potential is supplied to the pixel electrode as the one potential. In a high-impedance state where the first electrode is electrically disconnected, and the first potential is used as the first potential among the plurality of pixel electrodes in a period in which the common electrode is supplied with the same potential as the second potential. The first potential is supplied to the pixel electrode to which the potential is to be supplied, and the pixel electrode to which the second potential is to be supplied as the one potential among the plurality of pixel electrodes is electrically connected. The high impedance state of being cut.

  According to this aspect, when the first potential is supplied to the pixel electrode to which the first potential is to be supplied among the plurality of pixel electrodes, the pixel electrode to which the second potential is to be supplied among the plurality of pixel electrodes is high. When the second potential is supplied to the pixel electrode to be supplied with the second potential among the plurality of pixel electrodes, the impedance state (that is, the electrically disconnected state) is set. The pixel electrode to which one potential is to be supplied is in a high impedance state. That is, the pixel electrode potential supply means supplies the other potential when supplying one of the plurality of pixel electrodes to the pixel electrode to which one of the first and second potentials should be supplied. The pixel electrode to be set is set to a high impedance state.

  Here, if the first and second potentials are respectively supplied to the pixel electrodes adjacent to each other among the plurality of pixel electrodes, the pixel electrode to which the first potential is supplied and the pixel electrode to which the second potential is supplied. Are adjacent to each other, a leak current may be generated between the adjacent pixel electrodes via an electrophoretic element or a binder.

  However, in this aspect, as described above, the pixel electrode potential supply means supplies one of the plurality of pixel electrodes to the pixel electrode to which one of the first and second potentials should be supplied. At this time, since the pixel electrode to which the other potential is to be supplied is set to a high impedance state, the pixel electrode to which the first potential is supplied and the pixel electrode to which the second potential is supplied are adjacent to each other. It can be lost. Therefore, it is possible to suppress or prevent the occurrence of leakage current between adjacent pixel electrodes.

  The driving method of the electrophoretic display device according to the present invention includes a pair of first and second substrates, an electrophoretic element sandwiched between the first and second substrates and containing electrophoretic particles, and the first Driving an electrophoretic display device for driving an electrophoretic display device comprising a plurality of pixel electrodes provided on a substrate and a common electrode provided on the second substrate so as to face the plurality of pixel electrodes In the method, either one of a first potential and a second potential lower than the first potential is selectively supplied to the pixel electrode in accordance with an image signal in a predetermined image writing period. And supplying a common potential to the common electrode so as to have an intermediate potential between the first potential and the second potential in at least a predetermined first period of the image writing period. Including.

  According to the driving method of the electrophoretic display device according to the present invention, a leak current is generated between the pixel electrode and the common electrode via the electrophoretic element or the binder, as in the above-described electrophoretic display device of the present invention. This can be suppressed or prevented. Thereby, an increase in power consumption in the electrophoretic display device can be suppressed or prevented. Further, the electrochemical corrosion due to ion migration or the like that can occur in the pixel electrode due to the leakage current can be almost or completely eliminated.

  Note that the driving method of the electrophoretic display device according to the present invention can also adopt various aspects similar to the various aspects of the electrophoretic display apparatus of the present invention described above.

  In order to solve the above problems, an electronic apparatus of the present invention includes the above-described electrophoretic display device of the present invention (including various aspects thereof).

  According to the electronic apparatus of the present invention, since the electrophoretic display device of the present invention described above is provided, power consumption is small and high-quality image display can be performed. For example, wristwatches, electronic paper, electronic Various electronic devices such as notebooks, mobile phones, and portable audio devices can be realized.

  The operation and other advantages of the present invention will become apparent from the best mode for carrying out the invention described below.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<First Embodiment>
The electrophoretic display device according to the first embodiment will be described with reference to FIGS.

  First, the overall configuration of the electrophoretic display device according to the present embodiment will be described with reference to FIGS. 1 and 2.

  FIG. 1 is a block diagram showing the overall configuration of the electrophoretic display device according to this embodiment.

  1, the electrophoretic display device 1 according to the present embodiment includes a display unit 3, a controller 10, a scanning line driving circuit 60, a data line driving circuit 70, a power supply circuit 210, a common potential supply circuit 220, and the like. It has.

  In the display unit 3, m rows × n columns of pixels 20 are arranged in a matrix (in a two-dimensional plane). The display unit 3 includes m scanning lines 40 (that is, scanning lines Y1, Y2,..., Ym) and n data lines 50 (that is, data lines X1, X2,..., Xn). It is provided so as to cross each other. Specifically, the m scanning lines 40 extend in the row direction (that is, the X direction), and the n data lines 50 extend in the column direction (that is, the Y direction). The pixels 20 are arranged corresponding to the intersections of the m scanning lines 40 and the n data lines 50.

  The controller 10 controls operations of the scanning line driving circuit 60, the data line driving circuit 70, the power supply circuit 210, and the common potential supply circuit 220. For example, the controller 10 supplies timing signals such as a clock signal and a start pulse to each circuit.

  Based on the timing signal supplied from the controller 10, the scanning line driving circuit 60 sequentially supplies a scanning signal in a pulse manner to each of the scanning lines Y1, Y2,.

  The data line driving circuit 70 supplies image signals to the data lines X1, X2,..., Xn based on the timing signal supplied from the controller 10. The image signal takes a binary level of a high potential level (hereinafter referred to as “high level”, for example, 5 V) or a low potential level (hereinafter referred to as “low level”, for example, 0 V). In this embodiment, a low-level image signal is supplied to the pixel 20 that should display black, and a high-level image signal is supplied to the pixel 20 that should display white.

  The power supply circuit 210 supplies a constant high potential power supply potential Vdd at a high potential VH (for example, 15 V) to the high potential power supply line 91 and a constant low potential power supply at a low potential VL (for example, 0 V) to the low potential power supply line 92. A potential Vss is supplied. The power supply circuit 210, together with a first control line 91, a second control line 92, and a memory circuit 25, which will be described later, constitutes an example of a “pixel electrode potential supply unit” according to the present invention.

  The common potential supply circuit 220 supplies the common potential Vcom to the common potential line 93. The common potential supply means constitutes an example of the “common potential supply means” according to the present invention together with a common potential line 93 to be described later.

  Various signals are input to and output from the controller 10, the scanning line driving circuit 60, the data line driving circuit 70, the power supply circuit 210, and the common potential supply circuit 220. However, those not particularly related to the present embodiment. Description is omitted.

  FIG. 2 is an equivalent circuit diagram illustrating the electrical configuration of the pixel.

  In FIG. 2, the pixel 20 includes a pixel switching transistor 24, a memory circuit 25, a pixel electrode 21, a common electrode 22, and an electrophoretic element 23.

  The pixel switching transistor 24 is an N-type transistor. The pixel switching transistor 24 has its gate electrically connected to the scanning line 40, its source electrically connected to the data line 50, and its drain electrically connected to the input terminal N 1 of the memory circuit 25. It is connected to the. The pixel switching transistor 24 is configured to pulse the image signal supplied from the data line driving circuit 70 (see FIG. 1) via the data line 50 via the scanning line 40 from the scanning line driving circuit 60 (see FIG. 1). Is output to the input terminal N1 of the memory circuit 25 at a timing corresponding to the scanning signal supplied to the memory circuit 25.

  The memory circuit 25 includes inverter circuits 25a and 25b, and is configured as an SRAM (Static Random Access Memory).

  The inverter circuits 25a and 25b have a loop structure in which the other output terminal is electrically connected to the input terminals of each other. That is, the input terminal of the inverter circuit 25a and the output terminal of the inverter circuit 25b are electrically connected to each other, and the input terminal of the inverter circuit 25b and the output terminal of the inverter circuit 25a are electrically connected to each other. The input terminal of the inverter circuit 25a is configured as the input terminal N1 of the memory circuit 25, and the output terminal of the inverter circuit 25a is configured as the output terminal N2 of the memory circuit 25.

  The inverter circuit 25a has an N-type transistor 25a1 and a P-type transistor 25a2. The gates of the N-type transistor 25 a 1 and the P-type transistor 25 a 2 are electrically connected to the input terminal N 1 of the memory circuit 25. The source of the N-type transistor 25a1 is electrically connected to a low potential power supply line 92 to which a low potential power supply potential Vss is supplied. The source of the P-type transistor 25a2 is electrically connected to a high potential power supply line 91 to which a high potential power supply potential Vdd is supplied. The drains of the N-type transistor 25 a 1 and the P-type transistor 25 a 2 are electrically connected to the output terminal N 2 of the memory circuit 25.

  The inverter circuit 25b has an N-type transistor 25b1 and a P-type transistor 25b2. The gates of the N-type transistor 25 b 1 and the P-type transistor 25 b 2 are electrically connected to the output terminal N 2 of the memory circuit 25. The source of the N-type transistor 25b1 is electrically connected to a low potential power supply line 92 to which a low potential power supply potential Vss is supplied. The source of the P-type transistor 25b2 is electrically connected to a high potential power supply line 91 to which a high potential power supply potential Vdd is supplied. The drains of the N-type transistor 25 b 1 and the P-type transistor 25 b 2 are electrically connected to the input terminal N 1 of the memory circuit 25.

  When a high-level image signal is input to the input terminal N1, the memory circuit 25 outputs a low-potential power supply potential Vss from the output terminal N2, and when a low-level image signal is input to the input terminal N1. The high potential power supply potential Vdd is output from the output terminal N2.

  The pixel electrode 21 is electrically connected to the output terminal N2 of the memory circuit 25. A high potential power supply potential Vdd or a low potential power supply potential Vss is supplied from the memory circuit 25 to the pixel electrode 21 in accordance with an image signal input to the memory circuit 25. For example, when a high-level image signal is input to the memory circuit 25, the pixel electrode 21 is set to the low potential VL by supplying the constant low-potential power supply potential Vss with the low potential VL from the memory circuit 25. On the other hand, when a low-level image signal is input to the memory circuit 25, the pixel electrode 21 is supplied with a high potential VH from the memory circuit 25 at a high potential VH, so that the pixel electrode 21 has a high potential VH. Is done. The pixel electrode 21 is disposed so as to face the common electrode 22 through the electrophoretic element 23.

  The common electrode 22 is electrically connected to a common potential line 93 to which a common potential Vcom is supplied.

  The electrophoretic element 23 is composed of a plurality of microcapsules each containing electrophoretic particles.

  Next, a specific configuration of the display unit of the electrophoretic display device according to the present embodiment will be described with reference to FIGS.

  FIG. 3 is a partial cross-sectional view of the display unit of the electrophoretic display device according to this embodiment.

  In FIG. 3, the display unit 3 is configured such that an electrophoretic element 23 is sandwiched between an element substrate 28 and a counter substrate 29. In the present embodiment, description will be made on the assumption that an image is displayed on the counter substrate 29 side. The element substrate 28 is an example of a “first substrate” according to the present invention, and the counter substrate 29 is an example of a “second substrate” according to the present invention.

  The element substrate 28 is a substrate made of, for example, glass or plastic. Although not shown here on the element substrate 28, the pixel switching transistor 24, the memory circuit 25, the scanning line 40, the data line 50, the high potential power supply line 91, and the low potential power supply described above with reference to FIG. 2. A laminated structure in which the line 92, the common potential line 93, and the like are formed is formed. A plurality of pixel electrodes 21 are provided in a matrix on the upper layer side of the stacked structure.

  The counter substrate 29 is a transparent substrate made of, for example, glass or plastic. On the surface of the counter substrate 29 facing the element substrate 28, the common electrode 22 is formed in a solid shape so as to face the plurality of pixel electrodes 9a. The common electrode 22 is formed of a transparent conductive material such as magnesium silver (MgAg), indium / tin oxide (ITO), indium / zinc oxide (IZO), or the like.

  The electrophoretic element 23 is composed of a plurality of microcapsules 80 each including electrophoretic particles, and is fixed between the element substrate 28 and the counter substrate 29 by a binder 30 and an adhesive layer 31 made of, for example, resin. . In the electrophoretic display device 1 according to the present embodiment, in the manufacturing process, an electrophoretic sheet in which the electrophoretic element 23 is previously fixed to the counter substrate 29 side by the binder 30 is separately manufactured, such as the pixel electrode 21. Is adhered to the element substrate 28 side on which is formed by an adhesive layer 31.

  One or a plurality of microcapsules 80 are sandwiched between the pixel electrode 21 and the common electrode 22 and arranged in one pixel 20 (in other words, with respect to one pixel electrode 21).

  FIG. 4 is a schematic diagram showing the configuration of the microcapsule. In addition, in FIG. 4, the cross section of the microcapsule is shown typically.

  In FIG. 4, the microcapsule 80 is formed by enclosing a dispersion medium 81, a plurality of white particles 82, and a plurality of black particles 83 inside a coating 85. The microcapsule 80 is formed in a spherical shape having a particle size of about 50 μm, for example. The white particles 82 and the black particles 83 are examples of the “electrophoretic particles” according to the present invention.

  The coating 85 functions as an outer shell of the microcapsule 80 and is formed of a translucent polymer resin such as acrylic resin such as polymethyl methacrylate and polyethyl methacrylate, urea resin, and gum arabic.

  The dispersion medium 81 is a medium for dispersing the white particles 82 and the black particles 83 in the microcapsules 80 (in other words, in the coating 85). Examples of the dispersion medium 81 include water, alcohol solvents such as methanol, ethanol, isopropanol, butanol, octanol, and methyl cellosolve, various esters such as ethyl acetate and butyl acetate, and ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone. , Aliphatic hydrocarbons such as pentane, hexane and octane, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, benzene, toluene, xylene, hexylbenzene, hebutylbenzene, octylbenzene, nonylbenzene, decylbenzene, undecyl Aromatic hydrocarbons such as benzenes with long chain alkyl groups such as benzene, dodecylbenzene, tridecylbenzene, tetradecylbenzene, etc., halo such as methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane, etc. Emissions of hydrocarbons, carboxylate or other oils may be used singly or as a mixture. In addition, a surfactant may be added to the dispersion medium 81.

  The white particles 82 are particles (polymer or colloid) made of a white pigment such as titanium dioxide, zinc white (zinc oxide), and antimony trioxide, and are negatively charged, for example.

  The black particles 83 are particles (polymer or colloid) made of a black pigment such as aniline black or carbon black, and are positively charged, for example.

  For this reason, the white particles 82 and the black particles 83 can move in the dispersion medium 81 by the electric field generated by the potential difference between the pixel electrode 21 and the common electrode 22.

  These pigments include electrolytes, surfactants, metal soaps, resins, rubbers, oils, varnishes, charge control agents composed of particles such as compounds, 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.

  FIG. 5 is a schematic diagram for explaining the basic operation of the microcapsule 40.

  As shown in FIG. 5A, when a voltage is applied between the pixel electrode 21 and the common electrode 22 so that the potential of the common electrode 22 is relatively high, the positively charged black The particles 83 are attracted to the pixel electrode 21 side in the microcapsule 80 by the Coulomb force, and the negatively charged white particles 82 are attracted to the common electrode 22 side in the microcapsule 80 by the Coulomb force. As a result, the white particles 82 gather on the display surface side (that is, the common electrode 22 side) in the microcapsule 80, and the color of the white particles 82 (that is, white) is displayed on the display surface of the display unit 3. Will be displayed.

  On the contrary, as shown in FIG. 5B, when a voltage is applied between the pixel electrode 21 and the common electrode 22 so that the potential of the pixel electrode 21 becomes relatively high, it is negatively charged. The white particles 82 attracted to the pixel electrode 21 side by the Coulomb force, and the positively charged black particles 83 are attracted to the common electrode 22 side by the Coulomb force. As a result, the black particles 83 are collected on the display surface side of the microcapsule 80, and the color of the black particles 83 (that is, black) is displayed on the display surface of the display unit 3.

  In addition, red, green, blue, etc. can be displayed by replacing the pigment used for the white particle 82 and the black particle 83 with pigments, such as red, green, and blue, for example.

  Next, a driving method of the electrophoretic display device according to this embodiment will be described with reference to FIGS. Hereinafter, among the plurality of pixel electrodes 21 arranged in the display unit 3, the pixel electrode 21 of the pixel 20 that should display black is referred to as a pixel electrode 21 </ b> B, and the pixel electrode 21 of the pixel 20 that should display white. Is described as a pixel electrode 21W.

  FIG. 6 is a timing chart showing a driving method of the electrophoretic display device according to this embodiment. FIG. 6 shows changes over time in the common potential Vcom (that is, the potential of the common electrode 22), the potential of the pixel electrode 21B, and the potential of the pixel electrode 21W during the image writing period.

As shown in FIG. 6, first, in the period ST1 of the image writing period, the common potential supply circuit 220 (see FIG. 1) applies the common potential Vcom to the common electrode 22 via the common potential line 93 and the low potential VL. (For example, 0 V) and a high potential VH (for example, 15 V) are supplied so as to be repeated at a predetermined cycle. That is, common swing driving is performed in the period ST1 in the image writing period.
In the period ST1, the pixel electrode 21B of the pixel 20 that should display black (that is, the pixel 20 to which the low-level image signal is supplied) changes from the memory circuit 25 (see FIG. 2) to the low-level image signal. Accordingly, the pixel electrode 21W of the pixel 20 that is made constant at the high potential VH and supplied with white (that is, the pixel 20 to which a high-level image signal is supplied) is supplied by supplying the high-potential power supply potential Vdd. The low potential power supply potential Vss is supplied from the memory circuit 25 (see FIG. 2) in accordance with the high level image signal, so that the low potential VL is kept constant.

  FIG. 7 is a schematic diagram showing a movement state of the electrophoretic particles in the period ST1. 7A shows a movement state of the electrophoretic particles during the period ST1 in which the common potential Vcom is set to the high potential VH, and FIG. 7B shows a state in which the common potential Vcom is low in the period ST1. The movement state of the electrophoretic particles during the period of the potential VL is shown. In FIG. 7A and FIG. 7B, a pixel for displaying black and a pixel for displaying white are shown in comparison. FIG. 7A shows two pixels that are displayed in black until just before the period ST1, and FIG. 7B shows two pixels that are displayed in white until just before the period ST1. Show.

  As shown in FIG. 7A, in the period in which the common potential Vcom is set to the high potential VH in the period ST1, between the pixel electrode 21B and the common electrode 22 (whichever of the pixel electrode 21B and the common electrode 22 is present). Since no voltage is applied to the pixel electrode 21W and the common electrode 22, the pixel electrode 21W having the low potential VL and the common potential having the high potential VH are shared between the pixel electrode 21W and the common electrode 22. A potential difference (that is, voltage) from the electrode 22 is applied. For this reason, the black particles 83 and the white particles 82 in the microcapsule 80 sandwiched between the pixel electrode 21B and the common electrode 22 do not move. On the other hand, the black particles 83 in the microcapsule 80 sandwiched between the pixel electrode 21W and the common electrode 22 begin to move from the common electrode 22 side to the pixel electrode 21W side, and between the pixel electrode 21W and the common electrode 22 The white particles 82 in the microcapsule 80 held between the pixel electrode 21W start to move from the pixel electrode 21W side to the common electrode 22 side. More specifically, in order to display another image (as a black image in FIG. 7A) immediately before the period ST1 (that is, immediately before the image writing period), the common electrode in the coating 85 of the microcapsule 80 is displayed. The black particles 83 that have been fixed to the side 22 are peeled off by the Coulomb force caused by the potential difference between the pixel electrode 21W and the common electrode 22, and are moved to the pixel electrode 21W side in the coating 85 of the microcapsule 80. The white particles 82 that have been fixed are peeled off by the Coulomb force caused by the potential difference between the pixel electrode 21 </ b> W and the common electrode 22.

  Note that when a white image was displayed until immediately before the period ST1, it was fixed to the common electrode 22 side of the coating 85 of the microcapsule 80 in the period in which the common potential Vcom is set to the high potential VH in the period ST1. The white particles 82 that have been in a state are more firmly fixed to the coating film 85 by being pressed against the coating film 85 of the microcapsule 80 by the Coulomb force directed from the pixel electrode 21W side to the common electrode 22 side.

  On the other hand, as shown in FIG. 7B, a pixel electrode having a high potential VH is provided between the pixel electrode 21B and the common electrode 22 during the period in which the common potential Vcom is set to the low potential VL in the period ST1. A potential difference between the pixel electrode 21W and the common electrode 22 is set between the pixel electrode 21W and the common electrode 22 (both the pixel electrode 21W and the common electrode 22 are set to the low potential VL). Voltage) is not applied. Therefore, the black particles 83 in the microcapsule 80 sandwiched between the pixel electrode 21B and the common electrode 22 start to move from the pixel electrode 21B side to the common electrode 22 side, and the pixel electrode 21W and the common electrode 22 The white particles 82 in the microcapsule 80 sandwiched therebetween start to move from the common electrode 22 side to the pixel electrode 21W side. More specifically, in order to display another image (as a white image in FIG. 7B) immediately before the period ST1 (that is, immediately before the image writing period), the common electrode in the coating 85 of the microcapsule 80 is used. The white particles 82 fixed to the side 22 are peeled off by the Coulomb force caused by the potential difference between the pixel electrode 21B and the common electrode 22, and are moved to the pixel electrode 21B side in the coating 85 of the microcapsule 80. The black particles 83 that have been fixed are peeled off by the Coulomb force due to the potential difference between the pixel electrode 21 </ b> B and the common electrode 22. On the other hand, the black particles 83 and the white particles 82 in the microcapsule 80 sandwiched between the pixel electrode 21W and the common electrode 22 do not move.

  Note that when a black image is displayed until immediately before the period ST1, it is fixed to the common electrode 22 side in the coating 85 of the microcapsule 80 in the period ST1 in which the common potential Vcom is the low potential VL. The black particles 83 that have been in the state are more strongly fixed to the coating 85 by being pressed against the coating 85 of the microcapsule 80 by the Coulomb force from the pixel electrode 21 </ b> B to the common electrode 22.

  Note that the predetermined cycle in which the common potential Vcom repeats the low potential VL and the high potential VH in the period ST1 is set as a period of several ms to several tens of ms, for example, and the period ST1 is about 10 times the predetermined cycle. It is set as a length period.

  As shown in FIG. 6, in the period ST2 following the period ST1 in the image writing period, the common potential supply circuit 220 (see FIG. 1) applies the common potential Vcom to the common electrode 22 through the common potential line 93. An intermediate potential VI (for example, 7.5 V) between the low potential VL (for example, 0 V) and the high potential VH (for example, 15 V) is supplied. In the period ST2, the pixel electrode 21B is constant at the high potential VH as in the above-described period ST1, and the pixel electrode 21W is constant at the low potential VL as in the above-described period ST1.

  FIG. 8 is a schematic diagram showing a movement state of the electrophoretic particles in the period ST2. In FIG. 8, a pixel for displaying black and a pixel for displaying white are shown in comparison. More specifically, in FIG. 8, pixels that should display black are shown corresponding to the pixels including the pixel electrode 21B in FIG. 7B, and pixels that should display white are shown in FIG. The pixel electrode 21W is shown corresponding to the pixel in a).

  As shown in FIG. 8, in the period ST2, a potential difference between the pixel electrode 21B having the high potential VH and the common electrode 22 having the intermediate potential VI is applied between the pixel electrode 21B and the common electrode 22. A potential difference between the pixel electrode 21W having a low potential VL and the common electrode 22 having an intermediate potential VI is applied between the pixel electrode 21W and the common electrode 22. Therefore, the white particles 82 in the microcapsule 80 sandwiched between the pixel electrode 21B and the common electrode 22 move from the common electrode 22 side to the pixel electrode 21B side, and between the pixel electrode 21B and the common electrode 22. The black particles 83 in the microcapsule 80 sandwiched between the electrodes move from the pixel electrode 21B side to the common electrode 22 side. On the other hand, the black particles 83 in the microcapsule 80 sandwiched between the pixel electrode 21W and the common electrode 22 move from the common electrode 22 side to the pixel electrode 21W side, and between the pixel electrode 21W and the common electrode 22. The white particles 82 in the sandwiched microcapsule 80 move from the pixel electrode 21W side to the common electrode 22 side.

  The period ST2 is set as a period from several tens of ms to several s, for example. The length of the period ST2 depends on the potential difference between the high potential VH and the intermediate potential VI or the potential difference between the low potential VL and the intermediate potential VI from the pixel electrode 21 side to the common electrode 22 side (or The length required to move from the common electrode 22 side to the pixel electrode 21 side may be set as appropriate.

  Thus, in the present embodiment, in particular, in the period ST2 of the image writing period, the potential difference (15 V) between the high potential VH (for example, 15 V) and the low potential VL (for example, 0 V) is between the pixel electrode 21 and the common electrode 22. ) Smaller than the high potential VH (for example, 15V) and the intermediate potential VI (for example, 7.5V) (7.5V) or the low potential VL (for example, 0V) and the intermediate potential VI (for example, 7.5V). A potential difference (7.5 V) is applied.

  Therefore, in the period ST2, the microcapsule 80 can be driven between the pixel electrodes 21 and between the pixel electrode 21 and the common electrode 22 because it can be driven with a lower potential difference (that is, a lower electric field) than in the period ST1. It is possible to suppress the occurrence of a leak current through 85, the binder 30, the adhesive layer 31, and the like. Thereby, an increase in power consumption in the electrophoretic display device 1 according to the present embodiment can be suppressed. Furthermore, the electrochemical corrosion due to ion migration or the like that can occur in the pixel electrode 21 due to the leak current can be almost eliminated.

  In addition, as described above, the electrophoretic display device 1 according to the present embodiment sets the common potential Vcom to the low potential VL (for example, 0 V) and the high potential VH (for example, 15 V) in the period ST1 prior to the period ST2. Since the common swing driving is performed so as to be repeated at a predetermined cycle, the white particles 82 and the black particles 83 start to move reliably (in other words, the white particles 82 and the black particles 83 fixed to the coating 85 of the microcapsule 80 are pulled). Can be removed). Therefore, in the period ST2 following the period ST1, the white particles 82 are caused by the potential difference between the high potential VH and the intermediate potential VI or the potential difference between the low potential VL and the intermediate potential VI, which is smaller than the potential difference between the high potential VH and the low potential VL. And the black particle 83 can be moved reliably.

  As shown in FIG. 6, in the period ST3 following the period ST2 in the image writing period, the common potential supply circuit 220 (see FIG. 1) is connected to the common electrode via the common potential line 93 in the same manner as the period ST1 described above. 22, the common potential Vcom is supplied so as to repeat a low potential VL (for example, 0 V) and a high potential VH (for example, 15 V) at a predetermined cycle. That is, in the period ST3 in the image writing period, the common swing driving is performed as in the period ST1 described above. In the period ST3, the pixel electrode 21B is constant at the high potential VH as in the above-described periods ST1 and ST2, and the pixel electrode 21W is constant at the low potential VL as in the above-described periods ST1 and ST2. Is done.

  FIG. 9 is a schematic diagram showing the movement state of the electrophoretic particles in the period ST3. 9A shows the movement state of the electrophoretic particles during the period ST3 in which the common potential Vcom is the high potential VH, and FIG. 9B shows the common potential Vcom being low in the period ST3. The movement state of the electrophoretic particles during the period of the potential VL is shown. In FIG. 9A and FIG. 9B, a pixel for displaying black and a pixel for displaying white are shown in comparison.

  As shown in FIG. 9A, in the period ST3 in which the common potential Vcom is the high potential VH, between the pixel electrode 21B and the common electrode 22 (whichever of the pixel electrode 21B and the common electrode 22 is present). Since no voltage is applied to the pixel electrode 21W and the common electrode 22, the pixel electrode 21W having the low potential VL and the common potential having the high potential VH are shared between the pixel electrode 21W and the common electrode 22. A potential difference (that is, voltage) from the electrode 22 is applied. For this reason, the Coulomb force does not act on the black particles 83 and the white particles 82 in the microcapsule 80 sandwiched between the pixel electrode 21 </ b> B and the common electrode 22. On the other hand, the black particles 83 in the microcapsule 80 sandwiched between the pixel electrode 21W and the common electrode 22 are subjected to a Coulomb force from the common electrode 22 side toward the pixel electrode 21W side. The white particles 82 in the microcapsule 80 sandwiched between them are subjected to Coulomb force from the pixel electrode 21W side to the common electrode 22 side. More specifically, the black particles 83 that have been moved to the vicinity of the pixel electrode 21 side in the coating 85 of the microcapsule 80 in the period ST2 prior to the period ST3 are transferred to the pixel electrode 21W side from the common electrode 22 side in the period ST3. By being pressed against the coating 85 of the microcapsule 80 by force, the microcapsule 80 is fixed to the coating 85. Further, in the period ST2 prior to the period ST3, the white particles 82 moved to the vicinity of the common electrode 22 side in the coating 85 of the microcapsule 80 are microcapsules in the period ST3 due to the Coulomb force directed from the pixel electrode 21W side to the common electrode 22 side. By being pressed against the film 85 of 80, the film 85 is fixed.

  On the other hand, as shown in FIG. 9B, in the period ST3 in which the common potential Vcom is set to the low potential VL, the pixel electrode having the high potential VH is interposed between the pixel electrode 21B and the common electrode 22. A potential difference (that is, a voltage) between the common electrode 22 that is 21B and the low potential VL is applied, and between the pixel electrode 21W and the common electrode 22 (both the pixel electrode 21W and the common electrode 22 are low). Since the potential is VL, no voltage is applied. Therefore, the white particles 82 in the microcapsule 80 sandwiched between the pixel electrode 21B and the common electrode 22 are subjected to Coulomb force from the common electrode 22 side to the pixel electrode 21B side, and the pixel electrode 21B and the common electrode The black particles 83 in the microcapsule 80 sandwiched between them 22 are subjected to Coulomb force from the pixel electrode 21B side toward the common electrode 22 side. More specifically, the white particles 82 that have been moved to the vicinity of the pixel electrode 21B side in the coating 85 of the microcapsule 80 in the period ST2 prior to the period ST3 are transferred to the pixel electrode 21B side from the common electrode 22 side in the period ST3. By being pressed against the coating 85 of the microcapsule 80 by force, the microcapsule 80 is fixed to the coating 85. Further, in the period ST2 prior to the period ST3, the black particles 83 moved to the vicinity of the common electrode 22 side in the coating 85 of the microcapsule 80 are microcapsules in the period ST3 due to the Coulomb force directed from the pixel electrode 21B side to the common electrode 22 side. By being pressed against the film 85 of 80, the film 85 is fixed. On the other hand, the Coulomb force does not act on the black particles 83 and the white particles 82 in the microcapsule 80 sandwiched between the pixel electrode 21 </ b> W and the common electrode 22.

  Note that the predetermined cycle in which the common potential Vcom repeats the low potential VL and the high potential VH in the period ST3 is set as, for example, a period of several ms to several tens of ms, like the predetermined cycle in the period ST1, and the period ST3 Is set as a period of about 10 times the predetermined period.

  As described above, in the electrophoretic display device 1 according to this embodiment, in the period ST3 following the period ST2, the common potential Vcom is set to a low potential VL (for example, 0 V) and a high potential VH (for example, 15 V) at a predetermined period. Since the common swing driving is repeated so that the potential difference between the low potential VL and the high potential VH can be applied between the pixel electrode 21 and the common electrode 22, the white particles 82 and the black particles 83 are converted into the microcapsules 80. The film 85 can be firmly fixed. Therefore, after the image writing period, it is possible to extend the time for holding the image displayed on the display unit 3 in a state where no voltage is applied between the pixel electrode 21 and the common electrode 22.

  As described above, according to the electrophoretic display device 1 according to the present embodiment, the common potential Vcom is applied to the common electrode 22 between the high potential VH and the low potential VL in the period ST2 in the image writing period. Since the potential VI is supplied, leakage current between the pixel electrode 21 and the common electrode 22 can be suppressed. Further, in the period ST1 preceding the period ST2, common swing driving is performed to supply the common potential Vcom so that the low potential VL and the high potential VH are repeated in a predetermined cycle, so that the white particles 82 and the black particles 83 are reliably moved. In the period ST2, the white particles 82 and the black particles 83 can be reliably moved by a relatively small potential difference. In addition, in the period ST3 following the period ST2, the common swing driving is performed so that the common potential Vcom is supplied so as to repeat the low potential VL and the high potential VH at a predetermined cycle. The capsule 80 can be firmly fixed to the coating 85. As a result, it is possible to display a high-quality image while reducing power consumption.

In other words, according to the driving method of the electrophoretic display device according to the present embodiment, as the image writing period, the white particles 82 and the black particles 83 start to move reliably with a relatively large potential difference (that is, the coating of the microcapsule 80). The white particles 82 and the black particles 83 fixed to 85 are peeled off), the white particles 82 and the black particles 83 are reliably moved (that is, migrated) by a relatively small potential difference, and the relatively large potential difference. Since three periods including the period ST3 in which the white particles 82 and the black particles 83 are securely fixed to the coating 85 of the microcapsule 80 are included, the leakage current between the pixel electrode 21 and the common electrode 22 is suppressed, thereby reducing the power consumption. It is possible to display a high-quality image while reducing the size.
Second Embodiment
An electrophoretic display device according to a second embodiment will be described with reference to FIGS. 10 and 11.

  FIG. 10 is an equivalent circuit diagram illustrating an electrical configuration of a pixel of the electrophoretic display device according to the second embodiment. 10, the same reference numerals are given to the same components as those according to the first embodiment shown in FIGS. 1 and 2, and the description thereof will be omitted as appropriate.

  As shown in FIG. 10, the electrophoretic display device according to the second embodiment is described above in that the pixel 20 further includes a switch circuit 110 and the first control line 94 and the second control line 95. Unlike the electrophoretic display device 1 according to the first embodiment, the other configuration is substantially the same as the electrophoretic display device 1 according to the first embodiment described above.

  In FIG. 10, the switch circuit 110 includes a first transmission gate 111 and a second transmission gate 112.

  The first transmission gate 111 includes a P-type transistor 111p and an N-type transistor 111n. The sources of the P-type transistor 111p and the N-type transistor 111n are electrically connected to the first control line 94. The drains of the P-type transistor 111p and the N-type transistor 111n are electrically connected to the pixel electrode 21. The gate of the P-type transistor 111p is electrically connected to the input terminal N1 of the memory circuit 25, and the gate of the N-type transistor 111n is electrically connected to the output terminal N2 of the memory circuit 25.

  The second transmission gate 112 includes a P-type transistor 112p and an N-type transistor 112n. The sources of the P-type transistor 112p and the N-type transistor 112n are electrically connected to the second control line 95. The drains of the P-type transistor 112p and the N-type transistor 112n are electrically connected to the pixel electrode 21. The gate of the P-type transistor 112p is electrically connected to the output terminal N2 of the memory circuit 25, and the gate of the N-type transistor 112n is electrically connected to the input terminal N1 of the memory circuit 25.

  The switch circuit 110 selectively selects one of the first control line 94 and the second control line 95 according to the image signal input to the memory circuit 25, and selects one of the control lines. The control line is electrically connected to the pixel electrode 21.

  Specifically, when a high-level image signal is input to the input terminal N1 of the memory circuit 25, the low-potential power supply potential Vss is output from the memory circuit 25 to the gates of the N-type transistor 111n and the P-type transistor 112p. Since the high-potential power supply potential Vdd is output to the gates of the P-type transistor 111p and the N-type transistor 112n, only the P-type transistor 112p and the N-type transistor 112n constituting the second transmission gate 112 are turned on. The P-type transistor 111p and the N-type transistor 111n constituting the transmission gate 111 are turned off. On the other hand, when a low-level image signal is input to the input terminal N1 of the memory circuit 25, the high potential power supply potential Vdd is output from the memory circuit 25 to the gates of the N-type transistor 111n and the P-type transistor 112p, and the P-type transistor. Since the low-potential power supply potential Vss is output to the gates of the 111p and the N-type transistor 112n, only the P-type transistor 111p and the N-type transistor 111n constituting the first transmission gate 111 are turned on, and the second transmission gate The P-type transistor 112p and the N-type transistor 112n constituting the 112 are turned off. That is, when a high-level image signal is input to the input terminal N1 of the memory circuit 25, only the second transmission gate 112 is turned on, while the low-level image signal is input to the input terminal N1 of the memory circuit 25. Is input, only the first transmission gate 111 is turned on.

  The first control line 94 and the second control line 95 are configured to be able to supply the first potential S1 and the second potential S2 from the power supply circuit 90, respectively. The first control line 94 is electrically connected to the power supply circuit 90 via the switch 94s, and the second control line 95 is electrically connected to the power supply circuit 90 via the switch 95s. The switch 94s and the switch 95s are configured to be switched between an on state and an off state by the controller 10. When the switch 94s is turned on, the first control line 94 and the power supply circuit 90 are electrically connected, and when the switch 94s is turned off, the first control line 94 is electrically connected. The disconnected high impedance state is obtained. When the switch 95s is turned on, the second control line 95 and the power supply circuit 90 are electrically connected, and when the switch 95s is turned off, the second control line 95 is electrically connected. The disconnected high impedance state is obtained.

  Each pixel electrode 21 of the plurality of pixels 20 is electrically connected to a control line 94 or 95 that is alternatively selected according to an image signal by the switch circuit 110. At this time, the pixel electrode 21 of each of the plurality of pixels 20 is supplied with the first potential S1 or the second potential S2 from the power supply circuit 90 according to the on / off state of the switch 94s or 95s, or is in a high impedance state. It is said.

  More specifically, for the pixel 20 to which the low-level image signal is supplied (in other words, the pixel 20 that should display black), only the first transmission gate 111 is turned on, and the pixel electrode 21B is The first potential S1 is electrically connected to the first control line 94, and the first potential S1 is supplied from the power supply circuit 90 in accordance with the on / off state of the switch 94s, or is set to the high impedance state. On the other hand, for the pixel 20 to which the high-level image signal is supplied (in other words, the pixel 20 that is to display white), only the second transmission gate 112 is turned on, and the pixel electrode 21W is in the second state. Electrically connected to the control line 95, the second potential S2 is supplied from the power supply circuit 90 in accordance with the on / off state of the switch 95s, or the high impedance state is set.

  In the present embodiment, the first potential S1 is set as a constant potential at the high potential VL, and the second potential S2 is set as a constant potential at the low potential VL.

  FIG. 11 is a timing chart showing a driving method of the electrophoretic display device according to this embodiment. FIG. 11 shows changes over time of the common potential Vcom (that is, the potential of the common electrode 22), the potential of the pixel electrode 21B, and the potential of the pixel electrode 21W during the image writing period.

  In FIG. 11, the driving method of the electrophoretic display device according to the second embodiment differs from the driving method of the electrophoretic display device according to the first embodiment described above in the driving methods in the periods ST1 and ST3 in the image writing period. The driving method in the image writing period ST2 is substantially the same as the driving method of the electrophoretic display device according to the first embodiment described above. Here, the description of the same points as the driving method of the electrophoretic display device according to the first embodiment described above is omitted as appropriate, and the differences from the driving method of the electrophoretic display device according to the first embodiment described above are mainly described. Explained.

  As shown in FIG. 11, first, in the period ST1 of the image writing period, the common potential supply circuit 220 (see FIG. 1) applies the common potential Vcom to the common electrode 22 via the common potential line 93 and the low potential VL. (For example, 0 V) and a high potential VH (for example, 15 V) are supplied so as to be repeated at a predetermined cycle.

  Further, in the period ST1, the pixel electrode 21B of the pixel 20 that should display black (that is, the pixel 20 to which the low-level image signal is supplied) passes through the first transmission gate 111 that is turned on. When the switch 94s is electrically connected to the first control line 94 and the on / off state of the switch 94s is switched at a predetermined cycle, the high potential VH state and the high impedance state (Hi-Z) are repeated. On the other hand, the pixel electrode 21W of the pixel 20 that should display white (that is, the pixel 20 to which the high-level image signal is supplied) is connected to the second control line via the second transmission gate 112 that is turned on. When the switch 95s is electrically connected to the switch 95 and the switch 95s is switched on and off at a predetermined cycle, the low potential VL state and the high impedance state are repeated.

  More specifically, in the period in which the common potential Vcom is set to the high potential VH in the period ST1, the pixel electrode 21B is in a high impedance state by turning off the switch 94s, and the pixel electrode 21W is When the switch 95s is turned on, the second potential S2 is supplied from the power supply circuit 90 via the second control line 95, so that the low potential VL is obtained. During a period in which the common potential Vcom is set to the low potential VL in the period ST1, the pixel electrode 21B has the first potential from the power supply circuit 90 via the first control line 94 when the switch 94s is turned on. By supplying S1, the high potential VH is set, and on the other hand, the pixel electrode 21W is set to a high impedance state when the switch 95s is turned off. Therefore, it is possible to avoid a state in which the pixel electrode 21B having the high potential VH and the pixel electrode 21W having the low potential VL are adjacent to each other.

  Here, for example, as shown in FIG. 7 described above, when the pixel electrode 21B having the high potential VH and the pixel electrode 21W having the low potential VL are adjacent to each other, they are adjacent to each other. There is a possibility that a leakage current may be generated between the pixel electrode 21B and the pixel electrode 21W via the coating 85 of the microcapsule 80, the binder 30, the adhesive layer 31, and the like.

  However, according to the present embodiment, as described above, it is possible to avoid the state in which the pixel electrode 21B having the high potential VH and the pixel electrode 21W having the low potential VL are adjacent to each other. Generation of a leak current between the electrodes 21 can be suppressed. Thereby, an increase in power consumption in the electrophoretic display device can be further reliably suppressed. Furthermore, electrochemical corrosion due to ion migration or the like that can occur in the pixel electrode due to a leak current can be further reliably reduced.

  As shown in FIG. 11, in the period ST3 following the period ST2 in the image writing period, the common potential supply circuit 220 (see FIG. 1) is connected to the common electrode 22 via the common potential line 93, as in the period ST1. The common potential Vcom is supplied so that a low potential VL (for example, 0 V) and a high potential VH (for example, 15 V) are repeated at a predetermined cycle.

In the period ST3, the pixel electrode 21B of the pixel 20 in which black is to be displayed repeats the high potential state VH and the high impedance state (Hi-Z) as in the period ST1. On the other hand, in the pixel electrode 21W of the pixel 20 that should display white, the low potential VL state and the high impedance state are repeated similarly to the period ST1. Therefore, in the period ST3, similarly to the period ST1, it is possible to avoid a state in which the pixel electrode 21B having the high potential VH and the pixel electrode 21W having the low potential VL are adjacent to each other. Therefore, it is possible to suppress the occurrence of a leak current between the pixel electrodes 21 adjacent to each other.
<Electronic equipment>
Next, electronic devices to which the above-described electrophoretic display device is applied will be described with reference to FIGS. Below, the case where the electrophoretic display device described above is applied to electronic paper and an electronic notebook is taken as an example.

  FIG. 12 is a perspective view illustrating a configuration of the electronic paper 1400.

  As illustrated in FIG. 12, the electronic paper 1400 includes the electrophoretic display device according to the above-described embodiment as a display unit 1401. The electronic paper 1400 has flexibility, and includes a main body 1402 formed of a rewritable sheet having the same texture and flexibility as conventional paper.

  FIG. 13 is a perspective view showing the configuration of the electronic notebook 1500.

  As shown in FIG. 13, an electronic notebook 1500 is obtained by bundling a plurality of electronic papers 1400 shown in FIG. The cover 1501 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.

  Since the above-described electronic paper 1400 and electronic notebook 1500 include the electrophoretic display device according to the above-described embodiment, power consumption is small and high-quality image display can be performed.

  In addition to these, the electrophoretic display device according to the present embodiment described above can be applied to the display unit of an electronic device such as a wristwatch, a mobile phone, or a portable audio device.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification, and an electrophoretic display with such a change. The apparatus, the driving method of the electrophoretic display device, and the electronic apparatus provided with the electrophoretic display device are also included in the technical scope of the present invention.

1 is a block diagram illustrating an overall configuration of an electrophoretic display device according to a first embodiment. FIG. 3 is an equivalent circuit diagram illustrating an electrical configuration of a pixel of the electrophoretic display device according to the first embodiment. It is a fragmentary sectional view of the display part of the electrophoretic display device concerning a 1st embodiment. It is a schematic diagram which shows the structure of a microcapsule. It is a schematic diagram for demonstrating the basic operation | movement of a microcapsule. 3 is a timing chart illustrating a driving method of the electrophoretic display device according to the first embodiment. It is a schematic diagram which shows the movement state of the electrophoretic particle in period ST1. It is a schematic diagram which shows the movement state of the electrophoretic particle in period ST2. It is a schematic diagram which shows the movement state of the electrophoretic particle in period ST3. It is an equivalent circuit diagram which shows the electrical structure of the pixel of the electrophoretic display device which concerns on 2nd Embodiment. 6 is a timing chart illustrating a method for driving an electrophoretic display device according to a second embodiment. It is a perspective view which shows the structure of the electronic paper which is an example of the electronic device to which the electrophoretic display apparatus is applied. It is a perspective view which shows the structure of the electronic notebook which is an example of the electronic device to which an electrophoretic display apparatus is applied.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 21 ... Pixel electrode, 22 ... Common electrode, 25 ... Memory circuit, 28 ... Element substrate, 29 ... Opposite substrate, 80 ... Microcapsule, 82 ... White particle, 83 ... Black particle, 91 ... High potential power supply line, 92 ... Low Potential power supply line, 93 ... common potential line, 210 ... power supply circuit, 220 ... common potential line

Claims (6)

A pair of first and second substrates;
An electrophoretic element sandwiched between the first and second substrates and containing electrophoretic particles;
A plurality of pixel electrodes provided on the first substrate;
A common electrode provided on the second substrate so as to face the plurality of pixel electrodes;
Pixel electrode potential supply means for selectively supplying one of a first potential and a second potential lower than the first potential to the pixel electrode according to an image signal in an image writing period;
A common potential supply means for supplying a common potential to the common electrode so as to have an intermediate potential between the first potential and the second potential in at least a first period of the image writing period. An electrophoretic display device.   The common potential supply means sets the common potential to the same potential as the first potential and the same potential as the second potential in a second period prior to the first period in the image writing period. The electrophoretic display device according to claim 1, wherein the electrophoretic display device is supplied so as to be repeated at a cycle of   The common potential supply means supplies the common potential to the same potential as the first potential and the same potential as the second potential in a third period following the first period in the image writing period. The electrophoretic display device according to claim 1, wherein the electrophoretic display device is supplied so as to be repeated at a predetermined cycle. The pixel electrode potential supply means includes:
In a period in which the same potential as the first potential is supplied as the common potential to the common electrode, the first potential is supplied to the pixel electrode to which the second potential is supplied as the one potential among the plurality of pixel electrodes. 2 potentials are supplied, and the pixel electrode to which the first potential is supplied as the one potential among the plurality of pixel electrodes is set to a high impedance state in which the pixel electrode is electrically disconnected,
In a period in which the same potential as the second potential is supplied as the common potential to the common electrode, the first potential is supplied to the pixel electrode to which the first potential is supplied as the one potential among the plurality of pixel electrodes. The pixel electrode to which the second potential is supplied as the one potential among the plurality of pixel electrodes is set in a high-impedance state where the pixel electrode is electrically disconnected. 4. The electrophoretic display device according to 3. A pair of first and second substrates, an electrophoretic element sandwiched between the first and second substrates, and containing electrophoretic particles; a plurality of pixel electrodes provided on the first substrate; An electrophoretic display device driving method for driving an electrophoretic display device comprising a common electrode provided on a second substrate so as to face the plurality of pixel electrodes,
A step of selectively supplying one of a first potential and a second potential lower than the first potential to the pixel electrode according to an image signal in an image writing period;
Supplying a common potential to the common electrode so as to have an intermediate potential between the first potential and the second potential in at least a predetermined first period of the image writing period. A method for driving an electrophoretic display device.   An electronic apparatus comprising the electrophoretic display device according to claim 1.

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