JP5286738B2 - Electrophoretic display sheet, electrophoretic display device, and electronic apparatus - Google Patents

Description

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

For example, an electrophoretic display using particle electrophoresis is known as an image display unit of electronic paper (see, for example, Patent Document 1). The electrophoretic display has excellent portability and power saving, and is particularly suitable as an image display unit of electronic paper.
Patent Document 1 discloses an electrophoretic display device that constitutes a pixel of an electrophoretic display. The electrophoretic display device includes a cell, and in the cell, a transparent insulating liquid, positively charged white electrophoretic particles (hereinafter simply referred to as “white particles”), and negatively charged black Electrophoretic particles (hereinafter simply referred to as “black particles”) are enclosed. Further, a transparent electrode is installed on one side of the cell, and a colored plate is installed on the other side. Furthermore, the 1st electrode and the 2nd electrode are provided on the colored plate (refer FIG. 3 of patent document 1).

Such an electrophoretic display device has a white color by applying a voltage between the transparent electrode and the first and second electrodes, or applying a voltage between the first electrode and the second electrode. The desired color is displayed by causing the particles and the black particles to migrate in the transparent insulating liquid, thereby causing the white particles and the black particles to be unevenly distributed at desired portions.
Here, in the electrophoretic display device of Patent Document 1, when a voltage is applied to the first electrode and the second electrode, for example, black particles are unevenly distributed in the vicinity of the first electrode, and white particles are in the vicinity of the second electrode. Is unevenly distributed.

  At this time, when the inside of the cell is visually recognized through the transparent electrode, the color plate has a larger area than the total area of the aggregate of white particles and the aggregate of black particles. It becomes. However, since white particles and black particles are unevenly distributed between the transparent electrode and the colored plate, the white particles and the black particles are affected, and the color purity of the colored plate is lowered. It becomes difficult to display colors.

JP 2005-31345 A

  An object of the present invention is to provide an electrophoretic display sheet, an electrophoretic display device, and an electronic apparatus that can exhibit excellent color display properties.

Such an object is achieved by the present invention described below.
The electrophoretic display sheet of the present invention includes a packed portion filled with a liquid phase dispersion medium containing three kinds of particles having different colors from each other;
A substantially transparent transparent electrode provided on one side of the filling portion;
A counter electrode comprising a pair of electrode pieces provided on the other side of the filling portion,
Each of the three types of particles is an uncharged particle that is not substantially charged, a positively charged particle that is positively charged, and a negatively charged particle that is negatively charged.
By applying a positive voltage to the transparent electrode and a negative voltage to the counter electrode, the negatively charged particles are unevenly distributed on the transparent electrode and the positively charged particles are unevenly distributed on the counter electrode, A first state in which the color of the negatively charged particles is visually recognized;
By applying a negative voltage to the transparent electrode and a positive voltage to the counter electrode, the positively charged particles are unevenly distributed on the transparent electrode and the negatively charged particles are unevenly distributed on the counter electrode, A second state in which the color of the positively charged particles is visually recognized;
By applying a voltage between the pair of electrode pieces, the positively charged particles are unevenly distributed in one of the pair of electrode pieces and the negatively charged particles are unevenly distributed in the other, One state can be selected from the third state in which the color of the uncharged particles is visually recognized,
Furthermore, in the first state or the second state, a voltage having a polarity opposite to that of the particles unevenly distributed on the transparent electrode side is applied to one of the pair of electrode pieces, and the counter electrode is applied to the other. By applying a voltage having a polarity opposite to that of the particles that are unevenly distributed, the particles that are unevenly distributed on the transparent electrode are migrated toward the one electrode piece, and the particles that are unevenly distributed on the transparent electrode By adjusting the distance from the transparent electrode, it is possible to display an intermediate color between the color visually recognized in the first state or the second state and the color visually recognized in the third state. An electrophoretic display sheet characterized in that the potential difference between the one electrode piece and the transparent electrode is smaller than the potential difference between the other electrode piece and the transparent electrode .
Thereby, the colors of the three particles can be clearly displayed, and excellent display characteristics can be exhibited. Furthermore, by adjusting the average particle size and / or the amount of the uncharged particles, the reactivity when changing the color can be easily adjusted, so that versatility is enhanced.

In the electrophoretic display sheet of the present invention, it is preferable that the uncharged particles have excellent dispersibility in a liquid phase dispersion medium as compared with the positively charged particles and the negatively charged particles.
Thereby, sedimentation of uncharged particles in the liquid phase dispersion medium can be suppressed, and the uncharged particles can be more uniformly dispersed in the liquid phase dispersion medium.

In the electrophoretic display sheet of the present invention, it is preferable that at least one of the positively charged particles and the negatively charged particles is an achromatic particle.
As a result, monochrome display is possible, and visibility, particularly contrast, is improved.
In the electrophoretic display sheet of the present invention, the uncharged particles are preferably chromatic color particles.
Thereby, color display becomes possible and versatility increases.

In the electrophoretic display sheet of the present invention, the uncharged particles are preferably white particles.
Thereby, light can be effectively scattered by the non-charged particles in the liquid phase dispersion medium, and excellent white display characteristics can be exhibited. As a result, an extremely high contrast can be expressed.

In the electrophoretic display sheet of the present invention, it is preferable that one of the positively charged particles and the negatively charged particles is a chromatic color particle and the other is a black particle.
Thereby, monochrome display and color display are possible, and versatility is enhanced.
In the electrophoretic display sheet of the present invention, the chromatic color is preferably cyan, magenta, or yellow.
Thereby, the color display excellent in visibility is attained.
In the electrophoretic display sheet of the present invention, the chromatic color is preferably red (R), green (G), or blue (B).
Thereby, the color display excellent in visibility is attained.

The electrophoretic display device of the present invention includes an electrophoretic display sheet of the present invention,
And a substrate provided on the other side of the filling portion.
Thus, an electrophoretic display device that can exhibit excellent display characteristics can be provided.
An electronic apparatus according to the present invention includes the electrophoretic display device according to the present invention.
Thereby, an electronic device that can exhibit excellent display characteristics can be provided.

Hereinafter, an electrophoretic display sheet, an electrophoretic display device, and an electronic apparatus according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
<Electrophoretic display device>
<< First Embodiment >>
First, a first embodiment of an electrophoretic display device (electrophoretic display device of the present invention) to which the electrophoretic display sheet of the present invention is applied will be described.

  FIG. 1 is a schematic longitudinal sectional view showing a first embodiment of the electrophoretic display device of the present invention. FIGS. 2, 6, and 7 are examples of driving waveforms of the electrophoretic display device shown in FIG. FIGS. 3 to 5, 8, and 9 are schematic longitudinal sectional views showing the operation of the electrophoretic display device. In the following, for convenience of explanation, the upper side in FIGS. 1, 3 to 5, 8, and 9 is “upper”, the lower side is “lower”, the right side is “right”, and the left side is “left”. say.

An electrophoretic display device 1 shown in FIG. 1 includes a circuit board (back plane) 9 and an electrophoretic display sheet 2 bonded to the upper surface of the circuit board 9. Hereinafter, the structure of each part is demonstrated sequentially.
The circuit board 9 has a flat base 91 and a circuit (not shown) including a switching element such as a TFT provided on the base 91.

On the other hand, the electrophoretic display sheet 2 includes a base 3 in which a plurality of recesses 31 are regularly formed on the upper surface, and a lid 4 provided on the upper surface of the base 3 so as to close the upper opening of the recess 31. have. Such a base | substrate 3 and the cover part 4 are joined fluid-tightly.
The liquid-tight space formed by the inner wall of the recess 31 and the lid 4 is filled with a liquid-phase dispersion medium 5 containing three types of particles A to C (hereinafter simply referred to as “dispersion medium 5”). Has been. Hereinafter, this liquid-tight space is referred to as “filling portion 6”.

A plurality of transparent electrodes 7 are provided on the upper surface of the lid 4 so as to correspond to the respective recesses 31. In addition, a plurality of counter electrodes 8 are provided on the lower surface of the base 3 so as to correspond to the respective recesses 31. Each counter electrode 8 includes a pair of electrode pieces 81 and 82 that are spaced apart from each other.
In the electrophoretic display device 1 according to the present embodiment, each filling unit 6 constitutes one pixel. Since the plurality of pixels have the same configuration, one pixel (hereinafter referred to as “pixel P”) will be representatively described below, and description of other pixels will be omitted.

  The substrate 3 has insulating properties and impermeability of the dispersion medium 5. The constituent material of the substrate 3 is not particularly limited. For example, various resin materials such as an epoxy resin, an acrylic resin, a urethane resin, a melamine resin, and a phenol resin, silica, alumina, titania, and the like. These ceramic materials can be used, and one or more of them can be used in combination.

The lid part 4 is substantially colorless and transparent, and has a function as a visual recognition part for visually recognizing the inside of the filling part 6 from the outside of the filling part 6 (hereinafter, the lid part 4 is referred to as “visual recognition part 4”). Also called). In addition, as the cover part 4, if the inside of the filling part 6 can be visually recognized from the exterior of the filling part 6, it may not be colorless and transparent, and may be colored.
Such a lid 4 has insulating properties and impermeability of the dispersion medium 5. The constituent material of the lid 4 is not particularly limited. For example, polyolefin such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer, modified polyolefin, polyamide (eg, nylon 6, nylon 66), styrene Various thermoplastic elastomers such as polyvinyl chloride, polyurethane, polyester, fluororubber, chlorinated polyethylene, etc., or copolymers, blends, polymer alloys, etc. mainly composed of these. One or two or more of them can be used in combination.
The separation distance between the upper surface of the lid 4 and the lower surface of the substrate 3, that is, the separation distance between the transparent electrode 7 and the counter electrode 8 is not particularly limited, but is preferably about 10 to 500 μm, and about 20 to 100 μm. More preferably.

Next, the transparent electrode 7 and the counter electrode 8 will be described.
The transparent electrode 7 is provided so as to cover the entire upper opening of the recess 31 when the electrophoretic display device 1 is viewed from the upper side in FIG. With such a configuration, as will be described later, since the entire area of the visual recognition unit 4 can be covered with the electrophoretic particles, the color display characteristics are improved.
The transparent electrode 7 is substantially colorless and transparent. Thereby, the inside of the filling unit 6 can be viewed from the outside of the electrophoretic display device 1 through the transparent electrode 7 and the viewing unit 4. The transparent electrode 7 may not be colorless and transparent as long as the inside of the filling unit 6 can be visually recognized from the outside of the electrophoretic display device 1 and may be colored.

The constituent material of the transparent electrode 7 is not particularly limited as long as it is substantially conductive. For example, a metal material such as copper, aluminum or an alloy containing them, or a carbon-based material such as carbon black. Ionic substances such as NaCl, LiClO ₄ , KCl, LiBr, LiNO ₃ , and LiSCN in a matrix resin such as polyvinyl alcohol, polycarbonate, polyethylene oxide, and the like, and electroconductive polymer materials such as polyacetylene, polypyrrole, and derivatives thereof Conductive oxide materials such as ion-conductive polymer materials, indium tin oxide (ITO), fluorine-doped tin oxide (FTO), tin oxide (SnO ₂ ), indium oxide (IO), etc. Various kinds of conductive materials such as It can be used in conjunction.

The counter electrode 8 is composed of a pair of electrode pieces 81 and 82 as described above. Each of the electrode pieces 81 and 82 is provided so as to correspond to the bottom of the recess 31.
In the present embodiment, the pair of electrode pieces 81 and 82 are arranged apart from each other in the left-right direction in FIG. 1, the electrode piece 81 is on the left side in FIG. 1, and the electrode piece 82 is in FIG. Located on the right side.
The constituent material of the electrode pieces 81 and 82 is not particularly limited as long as it is substantially conductive. For example, the same material as the constituent material of the transparent electrode 7 described above can be used.

The shapes of the electrode pieces 81 and 82 are not particularly limited, and may be the same shape or different from each other. When the shapes are different, for example, the electrode piece 81 may be circular, and the electrode piece 82 may be annular to cover the periphery of the electrode piece 81.
Such electrode pieces 81 and 82 are each electrically connected to the circuit formed on the circuit board 9. The electrophoretic display device 1 is configured to control ON / OFF of voltage application to the electrode pieces 81 and 82 by a TFT (switching element) included in the circuit.

The electrophoretic display device 1 is configured so that a voltage can be applied independently to the transparent electrode 7, the electrode piece 81, and the electrode piece 82. In addition, the electrophoretic display device 1 can appropriately change the strength of the voltage applied to each electrode.
Specifically, when the voltage applied to the transparent electrode 7 is V1, the voltage applied to the electrode piece 81 is V2, and the voltage applied to the electrode piece 82 is V3, for example, the strength of V1, V2, and V3 is V1. >V2> V3, V1>V3> V2, V2>V1> V3, V2>V3> V1, V3>V1> V2, V3>V2> V1, V1> V2 = V3, V1 <V2 = V3, etc. can do.

Next, the dispersion medium 5 filled in the filling unit 6 will be described.
The dispersion medium 5 is preferably substantially colorless and transparent. As such a dispersion medium 5, a medium having a relatively high insulating property is preferably used. Examples of the dispersion medium 5 include various types of water (distilled water, pure water, ion-exchanged water, etc.), alcohols such as methanol, ethanol, and butanol, cellosolves such as methyl cellosolve, and esters such as methyl acetate and ethyl acetate. , Aromatic hydrocarbons such as ketones such as acetone and methyl ethyl ketone, aliphatic hydrocarbons such as pentane, alicyclic hydrocarbons such as cyclohexane, and benzenes having a long-chain alkyl group such as benzene and toluene Hydrogen, halogenated hydrocarbons such as methylene chloride and chloroform, aromatic heterocycles such as pyridine and pyrazine, nitriles such as acetonitrile and propionitrile, amides such as N, N-dimethylformamide, carboxylate Mineral oils such as liquid paraffin, vegetable oils such as linoleic acid, linolenic acid and oleic acid, Corn oil, methylphenyl silicone oil, silicone oils such as methyl hydrogen silicone oil, fluorine-based liquid, or other various oils such as hydrofluoroether and the like, these can be used alone or as a mixture.

Further, in the dispersion medium 5, if necessary, for example, a charge control agent composed of particles of electrolyte, surfactant, metal soap, resin material, rubber material, oils, varnish, compound, etc., titanium-based coupling You may make it add various additives, such as dispersing agents, lubricants, stabilizers, such as an agent, an aluminum coupling agent, and a silane coupling agent.
Such a dispersion medium 5 contains three types of particles A to C, respectively, as described above. The three types of particles A to C may be contained in the dispersion medium 5, respectively, but are preferably dispersed in the dispersion medium 5.

The three types of particles A to C are an uncharged particle A that is not substantially charged, a positively charged particle B that is positively charged, and a negatively charged particle C that is negatively charged. In other words, the three types of particles A to C are a pair of electrophoretic particles having different polarities and non-electrophoretic particles having no polarity, respectively.
The uncharged particle A is a particle having no charge. Therefore, the uncharged particles A are dispersed in the dispersion medium 5 regardless of whether or not a potential difference is generated between the three electrodes (that is, the transparent electrode 7, the electrode piece 81 and the electrode piece 82, and so on). Particles.

The positively charged particle B is a particle having a positive charge. For this reason, among the three electrodes, the particles migrate toward the electrode so as to be adsorbed (attached) to the electrode to which a negative voltage is applied.
The negatively charged particle C is a particle having a negative charge. For this reason, among the three electrodes, the particles migrate toward the electrode so as to be adsorbed to the electrode to which a positive voltage is applied.
Such uncharged particles A, positively charged particles B, and negatively charged particles C have different colors. The colors of the non-charged particles A, the positively charged particles B, and the negatively charged particles C are not particularly limited, and may be achromatic colors such as white, black, or an intermediate color (gray) thereof, or red, blue, green, or the like. Three colors can be arbitrarily selected from the chromatic colors.

  Moreover, the combination of the kind of particle (uncharged particle A, positively charged particle B, negatively charged particle C) and the color of the particle (white, black, blue, red, yellow, etc.) is not particularly limited. For example, the uncharged particles A are white particles, the positively charged particles B are black particles, the negatively charged particles C are yellow particles, the uncharged particles A are blue particles, the positively charged particles B are white particles, Examples include a combination of particles in which the negatively charged particles C are black.

  The positively charged particles B and the negatively charged particles C (hereinafter, the positively charged particles B and the negatively charged particles C are collectively referred to as “electrophoretic particles”) may be anything as long as they have a positive charge and a negative charge, respectively. Although not particularly limited, at least one of pigment particles, resin particles, ceramic particles, metal particles, metal oxide particles, or composite particles thereof is preferably used. These particles have the advantage that they are easy to manufacture and the charge can be controlled relatively easily.

  Examples of pigments constituting the pigment particles include black pigments such as aniline black, carbon black, and titanium black, white pigments such as titanium dioxide, antimony trioxide, zinc sulfide, and zinc white, and azo series such as monoazo, disazo, and polyazo. Pigments, yellow pigments such as isoindolinone, yellow lead, yellow iron oxide, cadmium yellow and titanium yellow, azo pigments such as monoazo, disazo and polyazo, red pigments such as quinacridone red and chrome vermilion, phthalocyanine blue and indanthrene Blue pigments such as blue, bitumen, ultramarine, and cobalt blue, green pigments such as phthalocyanine green, and the like can be used, and one or more of these can be used in combination.

Examples of the resin material constituting the resin particles include acrylic resin, urethane resin, urea resin, epoxy resin, rosin resin, polystyrene, polyester, AS resin copolymerized with styrene and acrylonitrile, and the like. These can be used alone or in combination of two or more.
The composite particles are, for example, composed of pigment particles whose surfaces are coated with a resin material, resin particles whose surfaces are coated with a pigment, or a mixture of a pigment and a resin material mixed in an appropriate composition ratio. Particles and the like.

  In addition, for the purpose of improving the dispersibility of the electrophoretic particles in the dispersion medium 5, a polymer highly compatible with the dispersion medium 5 is physically adsorbed on the surfaces of the particles A to C. Or chemically bonded. Among these, those in which the polymer is chemically bonded are particularly preferable because of the problem of detachment from the surface of the electrophoretic particles. With such a configuration, the affinity of the electrophoretic particles in the dispersion medium 5, that is, the dispersibility can be improved by acting in a direction in which the apparent specific gravity of the electrophoretic particles is reduced.

In this case, the number of bonds of the polymer is preferably about 300 to 2500 (pieces / μm ² ) in one positively charged particle B, more preferably about 500 to 1600 (pieces / μm ² ). preferable. By setting the number of polymer bonds within the above range, the affinity of the electrophoretic particles for the dispersion medium 5 can be increased and the dispersibility can be improved. In addition, it is possible to prevent a decrease in Coulomb force due to the charge on the surface of the electrophoretic particles being covered with the polymer.

  Examples of such a polymer include a polymer having a group reactive with the electrophoretic particle and a chargeable functional group, a group reactive with the electrophoretic particle, a long chain alkyl chain, a long chain ethylene oxide chain, and a long chain. Polymers having a chain fluorinated alkyl chain, a long dimethylsilicone chain, etc., groups having reactivity with electrophoretic particles, a chargeable functional group, a long alkyl chain, a long ethylene oxide chain, a long fluorinated alkyl chain And a polymer having a long-chain dimethyl silicone chain.

  In the polymer as described above, examples of groups having reactivity with the electrophoretic particles (hereinafter referred to as reactive groups) include, for example, epoxy groups, thioepoxy groups, alkoxysilane groups, silanol groups, alkylamide groups, aziridines. Group, oxazone group, isocyanate group and the like, and one or more of these can be selected and used, but depending on the type of electrophoretic particles to be used, etc. Good.

  The average particle size of the electrophoretic particles is not particularly limited, but is preferably about 0.1 to 10 μm, and more preferably about 0.1 to 7.5 μm. If the average particle size of the electrophoretic particles is too small, a sufficient concealment rate cannot be obtained mainly in the visible light range, and as a result, the display contrast of the electrophoretic display device 1 may be reduced. If the average particle size of the electrophoretic particles is too large, depending on the type or the like, the particles may easily settle in the dispersion medium 5, which may cause problems such as deterioration in display quality of the electrophoretic display device 1.

The constituent material of the non-charged particle A is the same as that of the positively charged particle B and the negatively charged particle C described above except that a material having no electric charge is appropriately selected.
The average particle size of the uncharged particles A is not particularly limited, but is preferably about 0.1 to 10 μm, and more preferably about 0.1 to 7.5 μm. If the average particle size of the non-charged particles A is too small, a sufficient concealment rate cannot be obtained mainly in the visible light range, and as a result, the display contrast of the electrophoretic display device 1 may be reduced. If the average particle size of the non-charged particles A is too large, depending on the type or the like, the particles may easily settle in the dispersion medium 5, which may cause problems such as deterioration in display quality of the electrophoretic display device 1.

  Further, it is preferable that the non-charged particles A have superior dispersibility in the dispersion medium 5 as compared with the positively charged particles B and the negatively charged particles C. Thereby, it is possible to reliably prevent the uncharged particles A from being settled in the dispersion medium 5 due to aggregation of the uncharged particles A. As a result, it is possible to prevent color unevenness in a chromatic color display state to be described later and improve the color display characteristics.

  In addition, in order to make the dispersibility of the uncharged particles A in the dispersion medium 5 superior to the positively charged particles B and the negatively charged particles C, the surface of the uncharged particles A is compatible with the dispersion medium 5. High molecular weight polymers can be physically adsorbed or chemically bonded. Among these, from the problem of detachment from the surface of the uncharged particle A, those in which the polymer is chemically bonded are particularly preferable. Thus, the apparent specific gravity of the non-charged particles A acts in a direction that decreases, and the affinity of the non-charged particles A to the dispersion medium 5, that is, the dispersibility is improved. Examples of the polymer include the same polymers as those exemplified in the description of the positively charged particles B described above.

The non-charged particles A, the positively charged particles B, and the negatively charged particles C have been described above. The dispersion of the three particles A to C in the dispersion medium 5 can be performed by, for example, a paint shaker method, a ball mill method, a media mill Method, ultrasonic dispersion method, stirring dispersion method and the like can be used alone or in combination of two or more.
The electrophoretic display device 1 configured as described above selects a voltage application pattern to the transparent electrode 7, the electrode piece 81, and the electrode piece 82, and converts the positively charged particles B and the negatively charged particles C into three electrodes, respectively. It can be unevenly distributed in the part corresponding to any one of these electrodes. Thereby, the color in the filling part 6 visually recognized through the transparent electrode 7 and the visual recognition part 4 (hereinafter also simply referred to as “display color”) is changed.

Hereinafter, the operation of the electrophoretic display device 1 will be described with reference to FIGS. Needless to say, FIG. 1, FIG. 3 to FIG. 5, FIG. 8, and FIG. 9 are schematically shown for convenience of explanation, and the number and size of each particle A to C are greatly different from actual ones. Is.
In this embodiment, as an example of the combination of the colors of the three particles A to C, the non-charged particle A is chromatic (yellow), the positively charged particle B is white, and the negatively charged particle C is black. Thus, by having at least white particles and black particles, monochrome display is possible, and visibility, particularly contrast, is improved.

Further, since either one of the positively charged particles B and the negatively charged particles C that can migrate in the dispersion medium 5 is white and the other is black, the positively charged particles B and the negatively charged particles C are temporarily in the dispersion medium 5. Even if the liquid settles down, if a potential difference is applied between the three electrodes, the positively charged particles B and the negatively charged particles C can be unevenly distributed in desired portions, and black and white display can be reliably performed. .
Moreover, by setting the non-charged particles A to chromatic colors, excellent chromatic display characteristics can be exhibited as will be described later.

<1> Black Display First, a method for displaying black will be described.
For example, as shown in FIG. 2A, a positive voltage is applied to the transparent electrode 7 and a negative voltage is applied to the electrode pieces 81 and 82 (counter electrode 8). As a result, the positively charged particles B migrate toward the counter electrode 8 so as to be electrically adsorbed by the counter electrode 8 to which a negative voltage is applied. The negatively charged particles C migrate toward the transparent electrode 7 so as to be electrically adsorbed by the transparent electrode 7 to which a positive voltage is applied.

As a result, as shown in FIG. 3, the negatively charged particles C are unevenly distributed at the portion corresponding to the transparent electrode 7, and the positively charged particles B are unevenly distributed at the portion corresponding to the counter electrode 8. In this state, since the visual recognition part 4 is covered with the negatively charged particles C, black is visually recognized as a display color (hereinafter, this state is referred to as “black display state”).
In such an electrophoretic display device 1, even if the voltage application to the three electrodes is stopped, the positively charged particles B and the negatively charged particles C maintain the state immediately before the voltage application is stopped. It has characteristics. That is, after the black display state is reached, the black display state can be maintained even if the voltage application is stopped. The same applies to a white display state, a yellow display state, and the like described later.

<2> White Display Next, a method for displaying white will be described.
For example, as shown in FIG. 2B, a negative voltage is applied to the transparent electrode 7, and a positive voltage is applied to the electrode pieces 81 and 82 (counter electrode 8). As a result, the positively charged particles B migrate toward the transparent electrode 7 so as to be electrically adsorbed by the transparent electrode 7 to which a negative voltage is applied. The negatively charged particles C migrate toward the counter electrode 8 so as to be electrically adsorbed by the counter electrode 8 to which a positive voltage is applied.
As a result, as shown in FIG. 4, the positively charged particles B are unevenly distributed at the portion corresponding to the transparent electrode 7, and the negatively charged particles C are unevenly distributed at the portion corresponding to the counter electrode 8. In this state, since the visual recognition part 4 is covered with the positively charged particles B, white is visually recognized as a display color (hereinafter, this state is referred to as “white display state”).

<3> Yellow (Chromatic Color) Display Next, a method for displaying yellow will be described.
For example, as shown in FIG. 2 (c), a negative voltage is applied to the electrode piece 81 and a positive voltage is applied to the electrode piece 82. Thereby, the positively charged particles B migrate toward the electrode piece 81 so as to be electrically adsorbed by the electrode piece 81 to which a negative voltage is applied. Further, the negatively charged particles C migrate toward the electrode piece 82 so as to be electrically adsorbed by the electrode piece 82 to which a positive voltage is applied.
As a result, as shown in FIG. 5, the positively charged particles B are unevenly distributed at the portion corresponding to the electrode piece 81, and the negatively charged particles C are unevenly distributed at the portion corresponding to the electrode piece 82. That is, both the positively charged particles B and the negatively charged particles C are unevenly distributed on the lower surface of the filling portion 6.

On the other hand, as described above, the uncharged particles A are dispersed in the dispersion medium 5 regardless of whether or not a potential difference is generated between the three electrodes. The non-charged particles A absorb and reflect light, and yellow is visually recognized as a display color (hereinafter, this state is referred to as “yellow display state”).
Since the non-charged particles A are dispersed in the dispersion medium 5, the non-charged particles A can effectively absorb and reflect (scatter) light. As a result, a clearer yellow can be displayed.
As described above, the black display state, the white display state, and the yellow display state have been described in detail, but the electrophoretic display device 1 can further adjust the brightness of yellow. That is, yellow gradation expression is possible.

Hereinafter, a method of adjusting the brightness of yellow, that is, a case where the brightness of yellow is increased and a case where it is decreased will be described.
<4> Yellow display with higher brightness than the yellow display state << 4-1 >>
First, the yellow display state (state shown in FIG. 5) is set by the operation described in <3>.

Next, in this state, for example, as shown in FIG. 6A, a negative voltage is applied to the transparent electrode 7 and a positive voltage is applied to the electrode piece 81. Thus, the positively charged particles B migrate from the electrode piece 81 toward the transparent electrode 7 so as to be electrically adsorbed by the transparent electrode 7 to which a negative voltage is applied.
As the positively charged particles B migrate, the display color gradually changes from yellow to white. In other words, the lightness of yellow increases as the positively charged particles B approach the transparent electrode 7.

Here, as described above, even when the voltage application is stopped, the electrophoretic display device 1 can maintain the positively charged particles B in a state immediately before the voltage application is stopped. By utilizing such a property, it is possible to increase the brightness of yellow by controlling the strength and application time of the voltage applied between the transparent electrode 7 and the electrode piece 81.
For example, if the voltage application time is controlled so that the positively charged particles B arrive near the intermediate point between the electrode piece 81 and the transparent electrode 7, the voltage application to the transparent electrode 7 and the electrode piece 81 is stopped. 8 can be maintained, and an intermediate color between yellow and white, that is, yellow having a higher lightness than the yellow display state can be displayed.

≪4-2≫
First, the white display state (state shown in FIG. 4) is set by the operation described in <2>.
Next, in this state, for example, as shown in FIG. 6B, a negative voltage is applied to the electrode piece 81 and a positive voltage is applied to the electrode piece 82. Thereby, the positively charged particles B migrate from the transparent electrode 7 toward the electrode piece 81 so as to be electrically adsorbed to the electrode piece 81 to which a negative voltage is applied. Further, the negatively charged particles C migrate toward the electrode piece 82 so as to be electrically adsorbed to the electrode piece 82 to which a positive voltage is applied.

Therefore, similarly to the above-described <4-1>, the strength and / or time of the voltage applied to the electrode piece 81 is controlled so that the separation distance of the positively charged particles B from the transparent electrode 7 becomes a desired distance. Thus, the brightness of yellow can be adjusted.
In this case, the strength of the negative voltage applied to the electrode piece 81 is preferably weaker than the strength of the positive voltage applied to the electrode piece 82. Thereby, the electrophoresis speed of the positively charged particles B can be made relatively slow, and the brightness of yellow can be adjusted more accurately.

<5> Display of yellow having a lower brightness than the yellow display state << 5-1 >>
First, the yellow display state (state shown in FIG. 5) is set by the operation described in <3>.
Next, in this state, for example, as shown in FIG. 7A, a positive voltage is applied to the transparent electrode 7 and a negative voltage is applied to the electrode piece 82. Thus, the negatively charged particles C migrate from the electrode piece 82 toward the transparent electrode 7 so as to be electrically adsorbed by the transparent electrode 7 to which a positive voltage is applied.

As the negatively charged particles C migrate, the display color gradually changes from yellow to black. In other words, the lightness of yellow decreases as the negatively charged particles C approach the transparent electrode 7.
Therefore, by controlling the strength of the voltage applied between the transparent electrode 7 and the electrode piece 82 and the application time, the lightness of yellow can be made desired.
For example, if the voltage application time is controlled so that the negatively charged particles C arrive near the intermediate point between the electrode piece 82 and the transparent electrode 7, the voltage application to the transparent electrode 7 and the electrode piece 82 is stopped. 9 can be maintained, and an intermediate color between yellow and black, that is, yellow having a lower brightness than the yellow display state can be displayed.

≪5-2≫
First, the black display state (state shown in FIG. 3) is obtained by the operation described in the above <1>.
Next, in this state, for example, as shown in FIG. 7B, a positive voltage is applied to the electrode piece 81 and a negative voltage is applied to the electrode piece 82. Accordingly, the negatively charged particles C migrate from the transparent electrode 7 toward the electrode piece 81 so as to be electrically adsorbed to the electrode piece 81 to which a positive voltage is applied. The positively charged particles B migrate toward the electrode piece 82 so as to be electrically adsorbed to the electrode piece 82 to which a positive voltage is applied.

Therefore, similarly to the above << 5-1 >>, by controlling the strength and time of the voltage applied to the electrode piece 81 so that the separation distance of the positively charged particles B with respect to the transparent electrode 7 becomes a desired distance, yellow The brightness of can be adjusted.
In this case, the strength of the positive voltage applied to the electrode piece 81 is preferably weaker than the strength of the negative voltage applied to the electrode piece 82. Thereby, the electrophoretic speed of the negatively charged particles C can be made relatively slow, and the brightness of yellow can be adjusted more accurately.

As described above, the electrophoretic display device 1 can select a white display state, a black display state, and a yellow display state by selecting a voltage application pattern to the three electrodes. The brightness can be adjusted.
In addition, by adjusting the average particle size of the non-charged particles A and / or the amount of the non-charged particles A, the reactivity when switching the display state (white display state, black display state, yellow display state) can be easily adjusted. can do.

For example, when adjusting the average particle size of the uncharged particles A, the larger the average particle size of the uncharged particles A, the more the positively charged particles B migrate in the liquid phase dispersion medium 5. The number of times (frequency) of collision with the charged particles A can be increased, thereby increasing the migration distance of the positively charged particles B and slowing down the switching reaction. Is possible.
On the contrary, the smaller the average particle size of the non-charged particles A, the less the number (frequency) of collision of the positively charged particles B with the non-charged particles A when migrating in the liquid phase dispersion medium 5. Thus, the migration distance of the positively charged particles B can be shortened and the switching reaction can be accelerated.

Further, when adjusting the amount of the non-charged particles A, the more the number of the non-charged particles A is increased, the more the positively charged particles B collide with the non-charged particles A when migrating in the dispersion medium 5. The number of times (frequency) can be increased, whereby the migration distance of the positively charged particles B can be increased, the switching reaction can be delayed, and a multi-tone color expression can be achieved.
On the contrary, the smaller the number of uncharged particles A, the smaller the number (frequency) of collision of the positively charged particles B with the uncharged particles A when migrating in the liquid phase dispersion medium 5. Thereby, the migration distance of the positively charged particles B can be shortened, and the switching reaction can be accelerated.
The same applies to the negatively charged particles C.
According to the electrophoretic display device 1 having the above-described configuration, monochrome display and clear color display are possible, and high contrast can be achieved. Moreover, since the reactivity at the time of changing a color can be adjusted easily, versatility improves.

<< Second Embodiment >>
Next, a second embodiment of the electrophoretic display device of the present invention will be described.
FIG. 10 is a schematic longitudinal sectional view showing a second embodiment of the electrophoretic display device of the present invention.
Hereinafter, the electrophoretic display device according to the second embodiment will be described with a focus on differences from the above-described embodiments, and description of similar matters will be omitted.

The electrophoretic display device according to the second embodiment of the present invention is different except that the combination of the type of particle (uncharged particle, positively charged particle, negatively charged particle) and the color of the particle (white, black, chromatic color) is different. This is the same as the electrophoretic display device of the first embodiment. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment mentioned above.
In this embodiment, the uncharged particles A are white particles, the positively charged particles B are yellow particles, and the negatively charged particles C are black particles. Thus, since the non-charged particle A is a white particle, for example, a positive voltage is applied to the electrode piece 81 and a negative voltage is applied to the electrode piece 82, and the positively charged particle B and the negatively charged particle C are applied to the lower surface of the recess 31. By making it unevenly distributed, it becomes possible to display white.

In this state, light is scattered by the non-charged particles A, so that white is displayed. In this way, by performing light white display by scattering light with the non-charged particles A dispersed in the dispersion medium 5, light can be effectively scattered in the dispersion medium 5 and excellent white display is achieved. The characteristic can be exhibited. Therefore, the electrophoretic display device 1 of the present embodiment can express extremely high contrast.
According to the second embodiment as described above, the same effect as that of the first embodiment can be exhibited.

«Third embodiment»
Next, a third embodiment of the electrophoretic display device of the present invention will be described.
FIG. 11 is a schematic longitudinal sectional view showing a third embodiment of the electrophoretic display device of the invention.
Hereinafter, the electrophoretic display device according to the third embodiment will be described with a focus on differences from the above-described embodiments, and description of similar matters will be omitted.

The electrophoretic display device according to the third embodiment of the present invention is the same as the electrophoretic display device of the first embodiment except that the configuration of the pixels is different. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment mentioned above.
As shown in FIG. 11, the pixel P has three filling portions 61, 62, and 63 arranged in parallel in the left-right direction.

The positively charged particles B and the negatively charged particles C in the dispersion medium 5 filled in the filling portions 61, 62, and 63 are the same as those in the first embodiment described above. That is, the positively charged particles B in each dispersion medium 5 are white particles, and the negatively charged particles C are black particles.
Further, the color of the non-charged particles A in the dispersion medium 5 filled in the filling unit 61 is cyan, and the color of the non-charged particles A in the dispersion medium 5 filled in the filling unit 62 is magenta. The color of the non-charged particles A in the dispersion medium 5 filled in the filling unit 63 is yellow.

That is, the pixel P includes a filling unit 61 capable of displaying cyan as a display color, a filling unit 62 capable of displaying magenta, and a filling unit 63 capable of displaying yellow. According to such a pixel P, full color display is possible by arbitrarily combining the display colors of the three filling portions 61, 62, and 63.
For example, when displaying black, all three filling parts 61, 62, 63 may be in a black display state (a state where the negatively charged particles C cover the visual recognition part 4), and when magenta is desired to be displayed. The charging unit 62 is in a magenta display state (a state in which the positively charged particles B and the negatively charged particles C are unevenly distributed in a portion corresponding to the counter electrode 8), and the filling units 61 and 63 are in a white display state (a positively charged particle). B may cover the visual recognition part 4), and when it is desired to display an intermediate color between cyan and magenta, the filling part 61 is set to the cyan display state, the filling part 62 is set to the magenta display state, and the filling part 63 is displayed. May be in a white display state.

In addition, the arrangement | positioning, shape, etc. of the filling parts 61, 62, and 63 in such a pixel P are not specifically limited.
Further, the color of the non-charged particles A in the dispersion medium 5 filled in the filling unit 61 is cyan, the color of the non-charged particles A in the dispersion medium 5 filled in the filling unit 62 is magenta, and the filling unit 63 Although the non-charged particles A in the filled dispersion medium 5 have been described as yellow in color, the present invention is not limited to this. For example, the color of the uncharged particles A in the dispersion medium 5 filled in the filling portion 61 Is red (R), the color of the non-charged particles A in the dispersion medium 5 filled in the filling part 62 is green (G), and the color of the non-charged particles A in the dispersion medium 5 filled in the filling part 63 May be blue (B). This also enables full color display as in the present embodiment.

According to the third embodiment as described above, the same effect as that of the first embodiment can be exhibited.
The electrophoretic display device 1 as described above can be incorporated into various electronic devices. As an electronic apparatus of the present invention provided with an electrophoretic display device, for example, an electronic paper, an electronic book, a television, a viewfinder type, a monitor direct view type video tape recorder, a car navigation device, a pager, an electronic notebook, a calculator, an electronic newspaper, Examples include a word processor, a personal computer, a workstation, a videophone, a POS terminal, and a device equipped with a touch panel.

Of these electronic devices, an electronic paper will be described as an example for specific description.
FIG. 12 is a perspective view showing an embodiment when the electronic apparatus of the present invention is applied to electronic paper.
An electronic paper 600 shown in FIG. 12 includes a main body 601 composed of a rewritable sheet having the same texture and flexibility as paper, and a display unit 602.
In such an electronic paper 600, the display unit 602 includes the electrophoretic display device 1 as described above.

Next, an embodiment when the electronic apparatus of the present invention is applied to a display will be described.
FIG. 13 is a diagram showing an embodiment when the electronic apparatus of the present invention is applied to a display. Among these, (a) in FIG. 13 is a sectional view and (b) is a plan view.
A display (display device) 800 illustrated in FIG. 13 includes a main body 801 and an electronic paper 600 that is detachably attached to the main body 801. The electronic paper 600 has the same configuration as described above, that is, the configuration shown in FIG.

  The main body 801 has an insertion port 805 into which the electronic paper 600 can be inserted on the side (right side in FIG. 13), and two pairs of conveying rollers 802a and 802b are provided inside. When the electronic paper 600 is inserted into the main body 801 through the insertion port 805, the electronic paper 600 is installed in the main body 801 in a state of being sandwiched between the pair of conveyance rollers 802a and 802b.

  A rectangular hole 803 is formed on the display surface side of the main body 801 (the front side in FIG. 13B), and a transparent glass plate 804 is fitted in the hole 803. . Thereby, the electronic paper 600 installed in the main body 801 can be viewed from the outside of the main body 801. That is, in the display 800, the display surface is configured by visually recognizing the electronic paper 600 installed in the main body 801 on the transparent glass plate 804.

In addition, a terminal portion 806 is provided at a leading end portion (left side in FIG. 13) of the electronic paper 600 in the insertion direction, and the terminal is provided inside the main body portion 801 with the electronic paper 600 installed on the main body portion 801. A socket 807 to which the unit 806 is connected is provided. A controller 808 and an operation unit 809 are electrically connected to the socket 807.
In such a display 800, the electronic paper 600 is detachably installed on the main body 801, and can be carried and used while being detached from the main body 801.

  The electrophoretic display sheet, electrophoretic display device, and electronic apparatus of the present invention have been described above based on the illustrated embodiments, but the present invention is not limited to these. For example, in the electrophoretic display sheet, the electrophoretic display device, and the electronic apparatus of the present invention, the configuration of each part can be replaced with an arbitrary configuration that exhibits the same function, and an arbitrary configuration is added. You can also.

Further, in the above-described embodiment, the filling portion has been described as being formed by the lid portion and the concave portion formed in the base body. However, the present invention is not limited to this. For example, a so-called microcapsule may be used as the filling portion. .
In the above-described embodiment, the electrophoretic display device has been described as having a plurality of pixels. However, the number of pixels is not particularly limited, and may be one, for example.

1 is a schematic longitudinal sectional view showing a first embodiment of an electrophoretic display device of the present invention. It is a figure which shows an example of the drive waveform of the electrophoretic display apparatus shown in FIG. It is a typical longitudinal cross-sectional view which shows the action | operation of the electrophoretic display apparatus shown in FIG. It is a typical longitudinal cross-sectional view which shows the action | operation of the electrophoretic display apparatus shown in FIG. It is a typical longitudinal cross-sectional view which shows the action | operation of the electrophoretic display apparatus shown in FIG. It is a figure which shows an example of the drive waveform of the electrophoretic display apparatus shown in FIG. It is a figure which shows an example of the drive waveform of the electrophoretic display apparatus shown in FIG. It is a typical longitudinal cross-sectional view which shows the action | operation of the electrophoretic display apparatus shown in FIG. It is a typical longitudinal cross-sectional view which shows the action | operation of the electrophoretic display apparatus shown in FIG. It is a typical longitudinal section showing a 2nd embodiment of an electrophoretic display device of the present invention. It is a typical longitudinal section showing a 3rd embodiment of an electrophoretic display device of the present invention. It is a perspective view which shows embodiment at the time of applying the electronic device of this invention to electronic paper. It is a figure which shows embodiment at the time of applying the electronic device of this invention to a display.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electrophoretic display device 2 ... Electrophoretic display sheet 3 ... Base | substrate 31 ... Recessed part 4 ... Cover part (viewing part) 5 ... Liquid phase dispersion medium 6, 61-63 ... Filling part 7 ... Transparent electrode 8 ... Counter electrode 81, 82 ... Electrode piece 9 ... Circuit board 91 ... Base 600 ... Electronic paper 601 ... Main body 602 ... Display unit 800 ... Display 801 ... Main body 802a, 802b ... Transport roller pair 803 ... Hole 804 ... Transparent glass plate 805 ... Insert port 806 ... Terminal part 807 ... Socket 808 ... Controller

Claims (10)

A packed portion filled with a liquid phase dispersion medium containing three kinds of particles having different colors from each other;
A substantially transparent transparent electrode provided on one side of the filling portion;
A counter electrode comprising a pair of electrode pieces provided on the other side of the filling portion,
Each of the three types of particles is an uncharged particle that is not substantially charged, a positively charged particle that is positively charged, and a negatively charged particle that is negatively charged.
By applying a positive voltage to the transparent electrode and a negative voltage to the counter electrode, the negatively charged particles are unevenly distributed on the transparent electrode and the positively charged particles are unevenly distributed on the counter electrode, A first state in which the color of the negatively charged particles is visually recognized;
By applying a negative voltage to the transparent electrode and a positive voltage to the counter electrode, the positively charged particles are unevenly distributed on the transparent electrode and the negatively charged particles are unevenly distributed on the counter electrode, A second state in which the color of the positively charged particles is visually recognized;
By applying a voltage between the pair of electrode pieces, the positively charged particles are unevenly distributed in one of the pair of electrode pieces and the negatively charged particles are unevenly distributed in the other, One state can be selected from the third state in which the color of the uncharged particles is visually recognized,
Furthermore, in the first state or the second state, a voltage having a polarity opposite to that of the particles unevenly distributed on the transparent electrode side is applied to one of the pair of electrode pieces, and the counter electrode is applied to the other. By applying a voltage having a polarity opposite to that of the particles that are unevenly distributed, the particles that are unevenly distributed on the transparent electrode are migrated toward the one electrode piece, and the particles that are unevenly distributed on the transparent electrode By adjusting the distance from the transparent electrode, it is possible to display an intermediate color between the color visually recognized in the first state or the second state and the color visually recognized in the third state. An electrophoretic display sheet characterized in that the potential difference between the one electrode piece and the transparent electrode is smaller than the potential difference between the other electrode piece and the transparent electrode . The uncharged particles, said compared to the positively charged particles and the negatively charged particles, the electrophoretic display sheet according to claim 1 which is excellent in dispersibility in the liquid dispersion medium. Wherein at least one of the positively charged particles and the negatively charged particles, the electrophoretic display sheet according to claim 1 or 2 which is achromatic particles. The electrophoretic display sheet according to claim 1, wherein the uncharged particles are chromatic particles. The electrophoretic display sheet according to claim 1, wherein the uncharged particles are white particles. The electrophoretic display sheet according to claim 5 , wherein one of the positively charged particles and the negatively charged particles is a chromatic color particle, and the other is a black particle. The electrophoretic display sheet according to claim 4 , wherein the chromatic color is cyan, magenta, or yellow. The electrophoretic display sheet according to claim 4 , wherein the chromatic color is red (R), green (G), or blue (B). An electrophoretic display sheet according to any one of claims 1 to 8 ,
An electrophoretic display device comprising: a substrate provided on the other side of the filling portion. An electronic apparatus comprising the electrophoretic display device according to claim 9 .

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