JP2009205003A - Method for driving electrophoretic display device, electrophoretic display device, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for driving an electrophoretic display device driven with low voltage and providing high contrast display, to provide an electrophoretic display device driven by the driving method, and to provide electronic equipment having high reliability, equipped with the electrophoretic display device. <P>SOLUTION: The method of driving an electrophoretic display device 20 comprises: a pair of base parts 1, 2 disposed opposite to each other, a pair of electrodes 3, 4 disposed inside the base parts, microcapsules 40 disposed between the electrodes 3, 4 and having inner spaces filled with an electrophoretic dispersion liquid 10, and a sealing part 7 tightly sealing the gap between the base parts 1, 2. Charges are prevented from being accumulated in a capacitive component induced in a portion other than the electrophoretic particles 5 by applying periodical pulse voltages between the electrodes 3, 4, thereby preventing adverse influences of charges accumulated in the capacitive component on migration of the electrophoretic particles 5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

Generally, it is known that when an electric field is applied to a dispersion system in which fine particles are dispersed in a liquid, the fine particles move (migrate) in the liquid by Coulomb force. This phenomenon is called electrophoresis. In recent years, an electrophoretic display device that displays desired information (image) using this electrophoresis has attracted attention as a new display device.
This electrophoretic display device has characteristics such as a display memory property and a wide viewing angle property in a state where voltage application is stopped, and a high-contrast display with low power consumption.

In addition, since the electrophoretic display device is a non-light emitting (reflective) display device, the electrophoretic display device also has a feature that is easier on the eyes than a light emitting display device such as a cathode ray tube.
As such an electrophoretic display device, one in which a dispersion system in which electrophoretic particles (fine particles) are dispersed is disposed between a pair of substrates provided with electrodes.
In this electrophoretic display device, a voltage is applied between a pair of electrodes for each pixel to cause an electric field to act on the electrophoretic particles (for example, see Patent Document 1). As a result, the electrophoretic particles migrate and the reflectance in the dispersion system changes. As a result, the reflected light can be controlled and desired information can be displayed.

However, in such an electrophoretic display device, it is generally necessary to apply a high voltage between a pair of electrodes. When the voltage is low, the electrophoresis of the electrophoretic particles becomes unstable, and there is a problem that the contrast of display is lowered.
Further, in order to stably migrate the electrophoretic particles, when the voltage applied between the pair of electrodes is increased, an increase in power consumption in the electrophoretic display device is inevitable.
Furthermore, there is a problem that it takes a lot of cost to boost the voltage of the power supply.

JP 2000-66247 A

  An object of the present invention is to provide an electrophoretic display device driving method capable of low-voltage driving and high-contrast display, an electrophoretic display device driven by such a driving method, and such an electrophoretic display device. An object of the present invention is to provide a highly reliable electronic device provided.

Such an object is achieved by the present invention described below.
An electrophoretic display device driving method according to the present invention includes a pair of electrodes arranged opposite to each other, and an electrophoretic layer provided between the pair of electrodes and including at least one type of electrophoretic particle. In
When switching the display, it is utilized that there is a difference in the charge accumulation rate accompanying the application of an electric field between the capacitive component caused by the electrophoretic particles and the capacitive component caused by a site other than the electrophoretic particles. Then, a voltage is applied between the pair of electrodes in such a pattern that charges are not accumulated in a capacitive component caused by a part other than the electrophoretic particles.
Accordingly, the electrophoretic display device can be driven so as to enable low voltage driving and display with high contrast.

In the method for driving an electrophoretic display device according to the aspect of the invention, it is preferable that the voltage applied between the pair of electrodes is a periodic pulse voltage in which a pulsed voltage is repeatedly applied.
Thereby, it is possible to prevent electric charges from being accumulated in a capacitive component caused by a part other than the electrophoretic particles.
In the driving method of the electrophoretic display device of the present invention, it is preferable that the waveform of the pulse voltage is a rectangular wave.
Thereby, since a voltage is rapidly applied between a pair of electrodes, display of the electrophoretic display device can be switched at high speed.

In the driving method of the electrophoretic display device of the present invention, it is preferable that the voltage application time in the periodic pulse voltage is 1 to 50 msec.
Thereby, it is possible to reliably prevent the charge from being accumulated in the capacitive component caused by the part other than the electrophoretic particles.
In the driving method of the electrophoretic display device of the present invention, it is preferable that the voltage pause time in the periodic pulse voltage is 50 to 1000 msec.
As a result, even if charges are accumulated in the capacitive component caused by the site other than the electrophoretic particles, sufficient time is secured for the charges to be discharged. As a result, it is possible to prevent a significant increase in the amount of electricity stored in this capacitive component.

In the driving method of the electrophoretic display device of the present invention, it is preferable that the number of cycles of the periodic pulse voltage is 3 to 200 cycles.
Thereby, the display of an electrophoretic display device can be switched reliably.
In the driving method of the electrophoretic display device according to the aspect of the invention, it is preferable that the pair of electrodes be short-circuited during the voltage pause time in the periodic pulse voltage.
As a result, the impedance between the pair of electrodes becomes low, and even if charges are accumulated in a capacitive component caused by a portion other than the electrophoretic particles, the accumulated charges can be discharged quickly.

In the driving method of the electrophoretic display device according to the aspect of the invention, it is preferable that the pair of electrodes is grounded in the short circuit state.
Thereby, it is possible to discharge the charges accumulated in the parts other than the electrophoretic particles particularly efficiently.
In the driving method of the electrophoretic display device of the present invention, it is preferable that the voltage applied between the pair of electrodes is 1 to 15V.
Thereby, it is possible to perform display with excellent contrast while preventing a significant increase in power consumption of the electrophoretic display device.

In the electrophoretic display device driving method of the present invention, the electrophoretic display device has bistability that can maintain a display when a voltage between the pair of electrodes is applied even when no voltage is applied. Preferably there is.
As a result, since the electrophoretic particles migrate stably, the voltage can be applied in various patterns, such as applying a voltage between the pair of electrodes in small increments, thereby controlling the electrophoretic particle migration more complicatedly. It becomes possible. For this reason, the display quality of the electrophoretic display device can be improved.

In the driving method of the electrophoretic display device according to the aspect of the invention, it is preferable that the electrophoretic particles include titanium oxide particles and titanium black particles.
Since these particles have high responsiveness to an electric field and a large difference in reflectance, display with high contrast in an electrophoretic display device is possible.
The electrophoretic display device of the present invention is configured to be driven by the driving method of the electrophoretic display device of the present invention.
Thus, an electrophoretic display device that can be driven at a low voltage and can display with high contrast is obtained.
An electronic apparatus according to the present invention includes the electrophoretic display device according to the present invention.
As a result, a highly reliable electronic device can be obtained.

Hereinafter, a driving method, an electrophoretic display device, and an electronic apparatus of an electrophoretic display device of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
<Electrophoretic display device>
First, the electrophoretic display device of the present invention will be described.
FIG. 1 is a diagram schematically showing a longitudinal section of an electrophoretic display device of the present invention. In the following description, for convenience of explanation, the upper side in FIG. 1 will be described as “upper” and the lower side as “lower”.
The electrophoretic display device 20 shown in FIG. 1 includes an electrophoretic display sheet (front plane) 21, a circuit board (back plane) 22, an adhesive layer 8 that joins the electrophoretic display sheet 21 and the circuit board 22, A sealing portion 7 that hermetically seals a gap between the electrophoretic display sheet 21 and the circuit board 22 is provided.

The electrophoretic display sheet 21 is provided on a substrate 12 having a flat base 2 and a second electrode 4 provided on the lower surface of the base 2, and on the lower surface (one surface) side of the substrate 12, and is provided with a microcapsule. 40 and a microcapsule-containing layer 400 composed of a binder 41.
On the other hand, the circuit board 22 includes a counter substrate 11 including a flat base 1 and a plurality of first electrodes 3 provided on the upper surface of the base 1, and the counter substrate 11 (base 1), for example, And a circuit (not shown) including a switching element such as a TFT.

Hereinafter, the structure of each part is demonstrated sequentially.
The base 1 and the base 2 are each composed of a sheet-like (flat plate) member, and have a function of supporting and protecting each member disposed therebetween.
Each of the base portions 1 and 2 may be either flexible or hard, but is preferably flexible. By using the flexible base portions 1 and 2, it is possible to obtain a flexible electrophoretic display device 20, that is, an electrophoretic display device 20 useful for constructing, for example, electronic paper.

  Moreover, when each base part (base material layer) 1 and 2 shall have flexibility, as the constituent material, for example, polyolefin, such as polyethylene, modified polyolefin, polyamide, thermoplastic polyimide, polyether, Examples include polyetheretherketone, polyurethane-based, chlorinated polyethylene-based thermoplastic elastomers, etc., and copolymers, blends, polymer alloys, etc. mainly composed of these, and one or more of these Can be mixed and used.

  The average thicknesses of the bases 1 and 2 are appropriately set depending on the constituent material, application, etc., and are not particularly limited. However, when having flexibility, it is preferably about 20 to 500 μm, More preferably, it is about 25-250 micrometers. As a result, the electrophoretic display device 20 can be reduced in size (particularly thinner) while achieving harmony between the flexibility and strength of the electrophoretic display device 20.

The first electrode 3 and the second electrode 4 that form a layer (film shape) are provided on the surfaces of the bases 1 and 2 on the side of the microcapsule 40, that is, on the upper surface of the base 1 and the lower surface of the base 2, respectively. ing.
When a voltage is applied between the first electrode 3 and the second electrode 4, an electric field is generated between them, and this electric field acts on the electrophoretic particles (display particles) 5.

In the present embodiment, the second electrode 4 is a common electrode, the first electrode 3 is an individual electrode (pixel electrode connected to a switching element) divided in a matrix (matrix), A portion where two electrodes 4 and one first electrode 3 overlap constitute one pixel.
Note that the second electrode 4 may also be divided into a plurality of parts in the same manner as the first electrode 3.
Alternatively, the first electrode 3 may be divided into stripes, and the second electrode may be similarly divided into stripes and arranged so as to intersect with each other.

The constituent materials of the electrodes 3 and 4 are not particularly limited as long as they are substantially conductive, for example, metal materials such as copper, aluminum or alloys containing these, and carbon-based materials such as carbon black. An ion in which an ionic substance such as NaCl, Cu (CF ₃ SO ₃ ) ₂ is dispersed in a material, an electronically conductive polymer material such as polyacetylene, polyfluorene or a derivative thereof, or a matrix resin such as polyvinyl alcohol or polycarbonate. Various conductive materials such as conductive polymer materials and conductive oxide materials such as indium oxide (IO) can be used, and one or more of these can be used in combination.

The average thicknesses of the electrodes 3 and 4 are appropriately set depending on the constituent materials and applications, and are not particularly limited, but are preferably about 0.05 to 10 μm, and about 0.05 to 5 μm. Is more preferable.
Of the bases 1, 2 and the electrodes 3, 4, the base and the electrodes (in the present embodiment, the base 2 and the second electrode 4) disposed on the display surface side each have light transmittance. In other words, substantially transparent (colorless transparent, colored transparent or translucent). Thereby, the state of the electrophoretic particles 5 in the electrophoretic dispersion liquid 10 described later, that is, the information (image) displayed on the electrophoretic display device 20 can be easily recognized visually.

In the electrophoretic display sheet 21, a microcapsule-containing layer 400 is provided in contact with the lower surface of the second electrode 4.
The microcapsule-containing layer 400 is configured by fixing (holding) a plurality of microcapsules 40 in which the electrophoretic dispersion liquid 10 is sealed in a capsule body (shell) 401 with a binder 41.

The microcapsules 40 are arranged between the counter substrate 11 and the substrate 12 in a single layer (one by one without overlapping in the thickness direction) so as to be parallel in the vertical and horizontal directions.
Examples of the constituent material of the capsule body (shell) 401 include gelatin, a composite material of gum arabic and gelatin, a urethane resin, a melamine resin, a urea resin, an epoxy resin, a phenol resin, an acrylic resin, and urethane. Various resin materials such as resin, olefin resin, polyamide, and polyether can be used, and one or more of these can be used in combination.

Moreover, the capsule main body 401 may be comprised by the laminated body of a some layer. In this case, the constituent material of the innermost layer is preferably an amino resin such as a melamine resin or a urea resin, or a composite resin thereof. On the other hand, an epoxy resin is preferably used as the constituent material of the outermost layer.
Moreover, in the constituent material of the capsule main body 401, you may make it form bridge | crosslinking (stereocrosslinking) with a crosslinking agent. Thereby, intensity | strength can be improved, maintaining the softness | flexibility of the capsule main body 401. FIG. As a result, it is possible to prevent the microcapsules 40 from easily collapsing.

Such microcapsules 40 are preferably substantially uniform in size. Thereby, in the electrophoretic display device 20, the occurrence of display unevenness is prevented or reduced, and more excellent display performance can be exhibited.
The microcapsules 40 are preferably present in a spherical shape. Thereby, the microcapsule 40 has excellent pressure resistance and bleed resistance. Therefore, when the electrophoretic display device 20 is operated in this way or while the electrophoretic display device 20 is stored, an impact is applied to the electrophoretic display device 20 or the display surface is pressed. Even in this case, destruction of the microcapsules 40 and dissipation of the electrophoretic dispersion liquid 10 can be prevented, and stable operation can be performed for a long time.

  In addition, it is preferable that the average particle diameter of the microcapsule 40 is about 5-50 micrometers, and it is more preferable that it is about 10-30 micrometers. By setting the average particle diameter of the microcapsules 40 within the above range, the electrophoresis of the electrophoretic particles 5 can be more reliably controlled in the electrophoretic display device 20. That is, even when a pulsed electric field is applied to the electrophoretic particles 5, the electrophoresis can be reliably performed up to the end of the microcapsule 40. As a result, display contrast can be increased.

In the electrophoretic dispersion liquid 10 enclosed in the capsule body 401, at least one type of electrophoretic particles 5 (in this embodiment, two types of colored particles 5b and white particles 5a) are dispersed in the liquid phase dispersion medium 6 ( Suspended).
For example, the electrophoretic particles 5 are dispersed in the liquid phase dispersion medium 6 by combining one or more of paint shaker method, ball mill method, media mill method, ultrasonic dispersion method, stirring dispersion method, and the like. be able to.

As the liquid phase dispersion medium 6, a medium having a low solubility in the capsule body 401 and a relatively high insulating property is preferably used.
Examples of the liquid phase dispersion medium 6 include various types of water (for example, distilled water and pure water), alcohols such as methanol, cellosolves such as methyl cellosolve, esters such as methyl acetate, ketones such as acetone, Aliphatic hydrocarbons such as pentane (liquid paraffin), alicyclic hydrocarbons such as cyclohexane, aromatic hydrocarbons such as benzene, halogenated hydrocarbons such as methylene chloride, and aromatic complex rings such as pyridine. , Nitriles such as acetonitrile, amides such as N, N-dimethylformamide, carboxylates or other various oils, and the like can be used alone or as a mixture.

  Among these, the liquid phase dispersion medium 6 is preferably one having aliphatic hydrocarbons (liquid paraffin) as the main component. The liquid phase dispersion medium 6 containing liquid paraffin as a main component is preferable because it has a high aggregation suppressing effect on the electrophoretic particles 5 and low affinity (low solubility) with the constituent material of the capsule body 401. Thereby, it can prevent or suppress more reliably that the display performance of the electrophoretic display device 20 deteriorates with time. In addition, liquid paraffin is preferable because it does not have an unsaturated bond and has excellent weather resistance and high safety.

  Further, in the liquid phase dispersion medium 6 (electrophoretic dispersion liquid 10), for example, a surfactant (anionic or cationic) such as an electrolyte or an alkenyl succinate, a metal soap, a resin material, if necessary. Various additives such as a charge control agent composed of particles such as rubber materials, oils, varnishes, and compounds, a dispersant such as a silane coupling agent, a lubricant, and a stabilizer may be added.

Further, when the liquid phase dispersion medium 6 is colored, various dyes such as anthraquinone dyes, azo dyes, and indigoid dyes may be dissolved in the liquid phase dispersion medium 6 as necessary.
The electrophoretic particles 5 are particles that have an electric charge and can be electrophoresed in the liquid phase dispersion medium 6 by the action of an electric field.

Any electrophoretic particle 5 may be used as long as it has a charge, and is not particularly limited. However, at least one of pigment particles, resin particles, or composite particles thereof is preferably used. used. These particles have the advantage that they can be easily manufactured and the amount of charge can be controlled relatively easily.
Examples of the pigment constituting the pigment particles include black pigments such as aniline black, carbon black, and titanium black, white pigments such as titanium oxide and antimony oxide, azo pigments such as monoazo, yellow such as isoindolinone and yellow lead. Pigments, red pigments such as quinacridone red and chrome vermilion, blue pigments such as phthalocyanine blue and indanthrene blue, green pigments such as phthalocyanine green, and the like, and one or a combination of two or more of these may be used it can.

  Among these, as pigment particles, titanium oxide particles are suitably used as white particles 5a, and titanium black particles are suitably used as black particles 5b. These particles have high responsiveness to an electric field and a large difference in reflectance, so that display with high contrast is possible. In particular, when a pulse voltage is applied to the electrodes 3 and 4, the electrophoretic particles 5 can be reliably migrated even if the voltage application time is short.

Examples of the resin material constituting the resin particles include acrylic resin, urethane resin, urea resin, epoxy resin, polystyrene, polyester, and the like, and one or more of these are combined. Can be used.
The composite particles include, for example, those in which the surface of the pigment particles is coated with a resin material or other pigment, those in which the surface of the resin particles is coated with a pigment, or a mixture in which the pigment and the resin material are mixed at an appropriate composition ratio. The particle | grains comprised by these, etc. are mentioned.

Examples of particles obtained by coating the surface of pigment particles with other pigments include those obtained by coating the surface of titanium oxide particles with silicon oxide or aluminum oxide.
Further, the shape of the electrophoretic particles 5 is not particularly limited, but is preferably spherical.
In consideration of dispersibility in the liquid phase dispersion medium 6, smaller particles are preferably used as the electrophoretic particles 5. Specifically, the average particle diameter is preferably about 10 to 500 nm. More preferably, it is about 20 to 300 nm. By setting the average particle diameter of the electrophoretic particles 5 within the above range, aggregation of the electrophoretic particles 5 and sedimentation in the liquid phase dispersion medium 6 can be reliably prevented and dispersed in the liquid phase dispersion medium 6. As a result, deterioration of display quality of the electrophoretic display device 20 can be suitably prevented.

In the case of using two different types of particles as in the present embodiment, the average particle size of the two types of particles is made different. In particular, the average particle size of the white particles 5a is larger than the average particle size of the black particles 5b. It is preferable to set. Thereby, the display contrast of the electrophoretic display device 20 can be further improved, and the holding characteristics can be improved.
Specifically, the average particle size of the black particles 5b is preferably about 20 to 100 nm, and the average particle size of the white particles 5a is preferably about 150 to 300 nm.

The specific gravity of the electrophoretic particles 5 is preferably set to be approximately equal to the specific gravity of the liquid phase dispersion medium 6. Thereby, even after the application of voltage between the electrodes 3 and 4 is stopped, the electrophoretic particles 5 can stay in a certain position in the liquid phase dispersion medium 6 for a long time.
That is, the electrophoretic display device 20 has a property (bistability) that can maintain a display state when a voltage is applied between the electrodes 3 and 4 even after the application of the voltage is stopped. .

  In the electrophoretic display device 20 having such a property (bistability), it is only necessary to apply a voltage between the electrodes 3 and 4 only at the time of switching the display, so that power consumption can be greatly reduced. In addition, since the electrophoretic particles 5 migrate stably, it is possible to apply voltages in various patterns, such as applying a voltage in small increments, and to control the electrophoretic particles 5 in a more complex manner. Become. For this reason, display quality can be improved.

The binder 41 is, for example, the purpose of bonding the counter substrate 11 and the substrate 12, the purpose of fixing the microcapsule 40 between the counter substrate 11 and the substrate 12, and the insulation between the first electrode 3 and the second electrode 4. Supplied for the purpose of securing the property. Thereby, durability and reliability of the electrophoretic display device 20 can be further improved.
The binder 41 is a resin material that is excellent in affinity (adhesion) with each of the electrodes 3 and 4 and the capsule body 401 (microcapsule 40) and has excellent insulating properties (resin material in which only insulating or minute current flows). ) Is preferably used.

Examples of the binder 41 include various types of thermoplastic resins such as polyethylene, polypropylene, ABS resin, methacrylate ester resin, methyl methacrylate resin, vinyl chloride resin, and cellulose resin, silicone resin, and urethane resin. Examples of the resin material include one or two or more of them.
In the present embodiment, the electrophoretic display sheet 21 and the circuit board 22 are bonded via the adhesive layer 8. Thereby, the electrophoretic display sheet 21 and the circuit board 22 can be more reliably fixed.
The adhesive layer 8 has a function of bonding (fixing) the electrophoretic display sheet 21 and the circuit board 22, I: an insulating material, and II: ions from the electrophoretic display sheet 21 side to the circuit board 22. III: It is preferable to have a function of mitigating stress when the electrophoretic display sheet 21 and the circuit board 22 are joined.

By having the function I, a short circuit between the first electrode 3 and the second electrode 4 can be reliably prevented, and an electric field can be reliably applied to the electrophoretic particles 5.
By having the function of II, it is possible to prevent or suppress the deterioration of the characteristics of the circuit (particularly the switching element) provided on the circuit board 22.
Further, by having the function III, it is possible to prevent the microcapsules 40 and the switching elements provided on the circuit board 22 from being destroyed during the manufacture (production) of the electrophoretic display device 20. In particular, in the present invention, since the microcapsule 40 and the adhesive layer 8 are in point contact, an excessive pressure is applied to the microcapsule 40 by providing the adhesive layer 8 with the function III. It is possible to prevent or suppress the microcapsule 40 from becoming non-spherical.

Such an adhesive layer 8 is preferably made of polyurethane as a main material. Polyurethane is preferable because it can reliably impart the various functions described above to the adhesive layer 8.
The constituent material of the adhesive layer 8 may be various resin materials such as polyethylene, chlorinated polyethylene, ABS resin, vinyl-acrylic acid ester copolymer, fluorine resin, and silicone resin instead of polyurethane. 1 type or 2 types or more of these can be used in combination.

  Further, a sealing portion 7 is provided between the base portion 1 and the base portion 2 and along the edge portions thereof. The electrodes 7 and 4, the microcapsule-containing layer 400, and the adhesive layer 8 are hermetically sealed by the sealing portion 7. Accordingly, it is possible to prevent moisture from entering the electrophoretic display device 20 and more reliably prevent display performance of the electrophoretic display device 20 from deteriorating.

Examples of the constituent material of the sealing portion 7 include thermoplastic resins such as acrylic resins, urethane resins, and olefin resins, epoxy resins, melamine resins, thermosetting resins such as phenol resins, and the like. Various resin materials etc. are mentioned, Among these, it can use combining 1 type (s) or 2 or more types.
In addition, the sealing part 7 should just be provided as needed, and can also be abbreviate | omitted.
Such an electrophoretic display device 20 operates as follows.

Hereinafter, an operation method of the electrophoretic display device 20 (a method for driving the electrophoretic display device of the present invention) will be described.
2 is a schematic diagram for explaining the operation method of the electrophoretic display device shown in FIG. 1, FIG. 3 is a diagram showing an example of a waveform of a voltage applied between the electrodes 3 and 4, and the application of this voltage. It is a graph which shows the reflectance change of the display of the accompanying electrophoretic display device 20. FIG. The display reflectance of the electrophoretic display device 20 is a ratio of the reflection amount of the display of the electrophoretic display device 20 when the reference white (standard sample) reflection amount is 100. In the following description, the upper side in FIG. 2 is referred to as “upper” and the lower side is referred to as “lower”.

First, in the state shown in FIG. 2A, the white particles 5 a are gathered near the second electrode 4. When this state is viewed from the display surface (base 2) side, white particles 5a can be seen. Therefore, this state is a white display state.
Here, when a voltage is applied between the electrodes 3 and 4, an electric field is generated between the electrodes 3 and 4. In accordance with this electric field, the electrophoretic particles 5 (black particles 5b, white particles 5a) are electrophoresed toward one of the electrodes. Along with this, the reflected light visible from the display surface changes and the display is switched (display switching state).

For example, positively charged particles are used as the white particles 5a, and negatively charged particles are used as the black particles (colored particles) 5b. As shown in FIG. 2B, the first electrode 3 has a negative potential. Thus, when a voltage is applied between the electrodes 3 and 4, the white particles 5a move to the first electrode 3 side. On the other hand, the black particles 5b move to the second electrode 4 side.
By the way, conventionally, when a voltage is applied between the electrodes of the electrophoretic display device, a DC voltage for a predetermined period is applied according to the migration speed of the electrophoretic particles. At this time, the electrophoresis of the electrophoretic particles takes a certain amount of time, and accordingly, it is necessary to apply a voltage accordingly.

However, such a voltage application method has a problem that the display contrast of the electrophoretic display device is not sufficient.
In addition, when the voltage applied between the electrodes is increased in order to increase the contrast, an increase in power consumption of the electrophoretic display device cannot be avoided.
Further, as the DC voltage application time becomes longer, there is a problem that the liquid phase dispersion medium and the binder are affected by the electric field and the characteristics deteriorate.

  Here, the inventor of the present invention has various components of the electrophoretic display device 20 such as the electrophoretic particles 5, the capsule body 401, the binder 41, and the liquid phase dispersion medium 6. It was found that there are a plurality of types depending on the constituent materials, and that the time until charge accumulation is saturated is different between these parts. Then, it has been clarified that the charges accumulated in these portions affect the migration of the electrophoretic particles 5 and as a result, the display quality of the electrophoretic display device 20 is lowered.

  In addition, the present inventor makes use of the fact that the charge accumulation speed varies depending on each part, so that the charge is not accumulated in the capacitive component caused by the part other than the electrophoretic particle 5. It has been found that by appropriately setting the application conditions of the voltage to be applied, the migration of the electrophoretic particles 5 can be prevented from being hindered by the charges accumulated in the portions other than the electrophoretic particles 5. In this way, since the electrophoretic particles 5 can migrate quickly according to the electric field, the electrophoretic particles 5 can be electrophoresed in a short time even at a low voltage. In addition, the power consumption of the electrophoretic display device 20 can be reduced.

  As described above, in order to apply a voltage between the electrodes 3 and 4 so as not to accumulate charges in the capacitive component caused by a part other than the electrophoretic particles 5, for example, the rate at which charges are accumulated in the capacitive component. It is ascertained whether or not (charge rate) is faster than the charge rate of the capacitive component caused by the electrophoretic particles 5, and the voltage applied between the electrodes 3 and 4 is applied based on the difference in charge rate. What is necessary is just to set conditions.

This charge speed is a factor related to the rotational speed of polar molecules in the constituent material of each part, the migration speed of ions, and the like, and can be estimated from the constituent material of each part.
The voltage application conditions to be set include parameters such as voltage magnitude, voltage application time, and voltage waveform.
As a specific example, consider a case where the charge rate of the capacitive component due to the portion other than the electrophoretic particle 5 is slower than the charge rate of the capacitive component due to the electrophoretic particle 5. In the following, the capacitive component due to the part other than the electrophoretic particle 5 is referred to as “slow capacitive component”, and the capacitive component due to the electrophoretic particle 5 is referred to as “fast capacitive component”.

In this case, it is possible to prevent the accumulation of a large amount of charges in the slow capacitance component by stopping the application of voltage before the accumulation of a large amount of charges in the slow capacitance component.
Specifically, it is preferable to use a periodic pulse voltage in which a pulsed voltage is repeatedly applied as the voltage applied between the electrodes 3 and 4. According to such a periodic pulse voltage, it is possible to reliably prevent charges from being accumulated in a capacitive component (slow capacitive component) caused by a portion other than the electrophoretic particles 5. Thereby, the electrophoretic particles 5 can be reliably migrated, and the display quality of the electrophoretic display device 20 can be improved.

In addition, although the power consumption by one pulse voltage is very small, the electrophoretic particles 5 can be reliably migrated. Therefore, even if the pulse voltage is repeatedly applied several times, the electricity required for the electrophoresis of the electrophoretic particles 5 is obtained. The amount can be greatly reduced compared to the conventional one. That is, the power consumption of the electrophoretic display device 20 can be greatly reduced.
Furthermore, according to the periodic pulse voltage, the influence of the electric field on the liquid phase dispersion medium 6 and the binder 41 can be minimized. As a result, the liquid phase dispersion medium 6 and the binder 41 can be prevented from being altered or deteriorated, and the life of the electrophoretic display device 20 can be extended.

In FIG. 3, no voltage is applied between the electrodes 3 and 4 in the period of time 0 → t ₁ , but the electrophoretic display device 20 is stable in the white display state shown in FIG.
In the period of time t ₁ → t ₂ , a periodic pulse voltage is applied between the electrodes 3 and 4. Thereby, as shown in FIG. 2B, the white particles 5a and the black particles 5b migrate along with the electric field. As a result, as shown in FIG. 3, the display reflectance of the electrophoretic display device 20 gradually decreases from the reflectance R ₁ in the white display time.

As shown in FIG. 3, the periodic pulse voltage has a voltage application time indicated by t _on and a voltage pause time indicated by t _off , and these periods are repeated.
Of these, the waveform of the voltage applied during the voltage application time is preferably a rectangular wave as shown in FIG. According to the rectangular voltage waveform, the voltage is applied abruptly, so that the display of the electrophoretic display device 20 can be switched at high speed.

Here, the present inventor considered that the voltage application time and the voltage pause time in the periodic pulse voltage of the rectangular wave are for a voltage application condition in which charge is not accumulated in a capacitive component caused by a part other than the electrophoretic particle 5. It was found that this is a particularly influential factor.
Specifically, the voltage application time is preferably about 1 to 50 msec, and more preferably about 5 to 40 msec. If the voltage application time is within the above range, it is possible to reliably prevent the charge from being accumulated in the capacitive component caused by the part other than the electrophoretic particles 5. The lower limit of the voltage application time is not necessarily limited, but is preferably set as described above in consideration of the efficiency of applying an electric field to the electrophoretic particles 5.

  On the other hand, the voltage pause time is preferably about 50 to 1000 msec, and more preferably about 50 to 500 msec. If the voltage quiescent time is within the above range, even if charges are accumulated in the capacitive component caused by the site other than the electrophoretic particles 5, sufficient time is secured for the charges to be discharged. Become. As a result, it is possible to prevent a significant increase in the amount of electricity stored in this capacitive component. Note that the upper limit value of the voltage pause time is not necessarily limited. However, if the voltage pause time becomes too long, the voltage application becomes extremely intermittent and the time required for switching the display becomes significantly longer. Since there is a fear, it is preferable to set as described above.

Moreover, it is preferable that the electrodes 3 and 4 are in a short circuit state during the voltage pause time. When the electrodes 3 and 4 are short-circuited, the impedance between the electrodes 3 and 4 becomes low, and even if charges are accumulated in a capacitive component caused by a portion other than the electrophoretic particles 5, the accumulated charges It can be discharged quickly.
Further, when the electrodes 3 and 4 are short-circuited, it is preferable that the electrodes 3 and 4 are grounded. By grounding the electrodes 3 and 4, it is possible to discharge the charges accumulated in the parts other than the electrophoretic particles 5 particularly efficiently.

Note that the electrodes 3 and 4 may be in a short-circuited state or a grounded state in the entire period of the voltage rest time, but may be in a short-circuited state or a grounded state in a part of the period.
Further, the voltage V ₁ applied between the electrodes 3 and 4 is preferably as low as possible from the viewpoint of power consumption, but is preferably about _{1 to 15} V, and more preferably about 3 to 8 V. By setting the voltage V ₁ in such a range, it is possible to perform display with excellent contrast while preventing a significant increase in power consumption of the electrophoretic display device 20.

Incidentally, when the voltages V ₁ exceeds the upper limit, although the contrast of the display is improved, may lead consumption significantly or increasing, the liquid phase dispersion medium 6, the capsule body 401, significant alteration and deterioration of the binder 41 There is. On the other hand, when the voltages V ₁ falls below the lower limit, but likely to reduce power consumption, there is a possibility that the contrast of the display is significantly reduced.
Further, the number of repetitions (number of cycles) of the pulse voltage in the display switching period from time t ₁ → t ₂ is appropriately set according to the migration speed of the electrophoretic particles 5, but preferably about 3 to 200 cycles. Is about 5 to 100 cycles. With such a number of cycles, the display of the electrophoretic display device 20 can be switched reliably, depending on the voltage application time and the voltage pause time.

After the display switching period as described above, the black particles 5b gather near the second electrode 4 as shown in FIG. When this state is viewed from the display surface (base 2) side, the black particles 5b can be seen. Therefore, the time t ₂ and later, which leads to black display state.
When the electrophoretic display device 20 has bistability, the black display state is maintained even when the application of the voltage between the electrodes 3 and 4 is finished. That is, the reflectance in the black display time, and thus to maintain a substantially reflectivity R ₂ shown in FIG.
Further, in such a configuration, by appropriately setting the charge amount of the electrophoretic particles 5 (white particles 5a, black particles 5b), the polarity of the electrodes 3 or 4, the potential difference between the electrodes 3 and 4, etc., electrophoresis is performed. On the display surface side of the display device 20, desired information (image) is displayed according to the combination of the colors of the white particles 5 a and the colored particles 5 b, the number of particles gathered on the electrodes 3 and 4, and the like.

Such an electrophoretic display device 20 can be manufactured as follows.
Hereinafter, a method for manufacturing the electrophoretic display device 20 will be described.
The manufacturing method of the electrophoretic display device 20 includes a microcapsule production step [1] for producing the microcapsules 40, a microcapsule dispersion preparation step [2] for preparing a microcapsule dispersion containing the microcapsules 40, and the substrate 12. A microcapsule-containing layer forming step [3] for forming the microcapsule-containing layer 400 including the microcapsules 40 on one surface side thereof, and forming the adhesive layer 8 on the surface side opposite to the substrate 12 of the microcapsule-containing layer 400 An adhesive layer forming step [4] to be performed, and a bonding step in which the counter substrate 11 is brought into contact with the surface of the adhesive layer 8 opposite to the microcapsule-containing layer 400 to bond the adhesive layer 8 and the counter substrate 11 to each other. 5] and a sealing step [6] for forming the sealing portion 7 along the edges of the base 1 and the base 2.

Hereinafter, each step will be described.
[1] Microcapsule production process The production method of the microcapsule 40 (method of encapsulating the electrophoretic dispersion 10 in the capsule body 401) is not particularly limited, and examples thereof include an interfacial polymerization method, an in-situ polymerization method, and a phase separation. Various microencapsulation methods such as a method (or a coacervation method), an interfacial sedimentation method, and a spray drying method can be used. The above microencapsulation method may be appropriately selected according to the constituent material of the microcapsule 40 and the like.
In addition, the microcapsules 40 having a uniform size can be obtained by using, for example, a screening method using a sieve, a filtration method, a specific gravity differential class method, or the like.

[2] Microcapsule Dispersion Preparation Step Next, a binder 41 is prepared, and the binder 41 and the microcapsules 40 prepared in the step [1] are mixed to prepare a microcapsule dispersion.
The content of the microcapsules 40 in the microcapsule dispersion is preferably about 30 to 60% by mass, and more preferably about 40 to 60% by mass.
When the content of the microcapsules 40 is set in the above range, the microcapsules 40 are arranged so as not to overlap in the thickness direction (single layer) and moved (rearranged) in the microcapsule-containing layer 400. Very advantageous.

[3] Microcapsule-containing layer forming step Next, the substrate 12 is prepared. Then, the microcapsule dispersion prepared in the step [2] is supplied onto the substrate 12.
Next, if necessary, in each part of the substrate 12, the microcapsule dispersion liquid is made uniform in thickness (amount), preferably one by one so that the microcapsules 40 do not overlap in the thickness direction (single Level) to be placed in the layer.
[4] Adhesive Layer Formation Step Next, the adhesive layer 8 is formed on the microcapsule-containing layer 400.

[5] Bonding Step Next, a circuit board 22 prepared separately is overlaid on the adhesive layer 8 so that the first electrode 3 is in contact with the adhesive layer 8.
As a result, the electrophoretic display sheet 21 and the circuit board 22 are bonded via the adhesive layer 8.
At this time, the microcapsule is pressed by pressurizing the adhesive layer 8 and the circuit board 22 by their own weights or bringing the circuit board 22 and the electrophoretic display sheet 21 close to each other (reducing the thickness of the microcapsule-containing layer 400). In the containing layer 400, the arrangement density of the microcapsules 40 can be made uniform.

[6] Sealing Step Next, the sealing portion 7 is formed along the edges of the electrophoretic display sheet 21 and the circuit board 22.
This is between the electrophoretic display sheet 21 (base part 2) and the circuit board 22 (base part 1), and a material for forming the sealing part 7 along these edges, for example, a dispenser or the like. And can be formed by solidifying or curing.
Through the above steps, the electrophoretic display device 20 is obtained.

<Electronic equipment>
The electrophoretic display device 20 as described above can be incorporated into various electronic devices. Hereinafter, the electronic apparatus of the present invention including the electrophoretic display device 20 will be described.
<< Electronic Paper >>
First, an embodiment when the electronic apparatus of the present invention is applied to electronic paper will be described.
FIG. 4 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. 4 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 20 as described above.

<< Display >>
Next, an embodiment when the electronic apparatus of the present invention is applied to a display will be described.
FIG. 5 is a diagram showing an embodiment when the electronic apparatus of the present invention is applied to a display. Among these, (a) in FIG. 5 is a sectional view and (b) is a plan view.
A display (display device) 800 illustrated in FIG. 5 includes a main body 801 and an electronic paper 600 that is detachably provided 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 its side (right side in FIG. 5A), and two pairs of conveying rollers 802a and 802b are provided inside. Yes. 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. 5B), 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.

Further, a terminal portion 806 is provided at the leading end portion (left side in FIG. 5) of the electronic paper 600 in the insertion direction, and the terminal with the electronic paper 600 installed on the main body portion 801 is provided inside 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.
In such a display 800, the electronic paper 600 is configured by the electrophoretic display device 20 as described above.

Note that the electronic apparatus of the present invention is not limited to the application to the above, and for example, 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 Examples include newspapers, word processors, personal computers, workstations, videophones, POS terminals, and devices equipped with touch panels. The electrophoretic display device 20 of the present invention is applied to the display units of these various electronic devices. Is possible.
As described above, the driving method of the electrophoretic display device, the electrophoretic display device, and the electronic apparatus according to the present invention have been described based on the illustrated embodiment, but the present invention is not limited to this, and the configuration of each unit is as follows. Any structure having a similar function can be substituted. In addition, any other component may be added to the present invention.

Next, specific examples of the present invention will be described.
1. <1> First, titanium oxide particles were prepared as white particles, and titanium black particles were prepared as black particles. Then, these particles were dispersed in dimethyl silicone oil (liquid phase dispersion medium) to prepare an electrophoretic dispersion. The titanium oxide particles and titanium black particles were each subjected to graft modification so as to be charged with opposite polarities.

Subsequently, melamine, urea, formaldehyde aqueous solution, and aqueous ammonia were mixed to prepare a capsule forming material of a composite resin of melamine resin and urea resin. Then, an electrophoretic dispersion was dropped onto the capsule forming material. Thus, a microcapsule precursor obtained by encapsulating an electrophoretic dispersion in a capsule made of the composite resin was obtained.
Next, the microcapsule precursor and deionized water were mixed to obtain a capsule dispersion.

Next, polycarboxylic acid, an epoxy compound, and water were mixed to prepare an epoxy resin capsule-forming material.
Next, an epoxy resin capsule-forming material was added to the previously prepared capsule dispersion, and a crosslinking agent was further added. As a result, an outer layer made of an epoxy resin was formed on the surface of the microcapsule precursor (inner layer).
Through the above steps, a microcapsule having an electrophoretic dispersion encapsulated in a capsule body having a two-layer structure was obtained. Thereafter, classification was performed to obtain microcapsules having an average particle size of 42 μm.

<2> Next, the acrylic binder was dissolved in ethanol to obtain an ethanol solution. Microcapsules were added to this ethanol solution to prepare a microcapsule dispersion. The mixing ratio of microcapsules and binder was 1: 1 by weight.
<3> Next, a PET-ITO substrate on which an electrode composed of ITO was formed was prepared.
Next, a microcapsule-containing layer having an average thickness of 45 μm was formed from the microcapsule dispersion on ITO of a PET-ITO substrate by a doctor blade method.
<4> Next, a circuit board on which an electrode made of ITO was formed was placed on the microcapsule-containing layer, and then joined using a roll laminator to obtain a joined body.
<5> Next, the edge (outer periphery) of the joined body was sealed with an epoxy adhesive. As a result, the electrophoretic display device shown in FIG. 1 was obtained.

2. Driving an electrophoretic display device (Example 1)
First, a voltage was applied between both electrodes of the electrophoretic display device to obtain a white display state.
Next, in order to switch to black display, a periodic pulse voltage of 8 V was applied for 60 cycles between both electrodes of the electrophoretic display device. Thereby, the display of the electrophoretic display device was switched from white display to black display.
In addition, the voltage application time of the periodic pulse voltage was 20 msec, and the voltage pause time was 390 msec. In addition, the two electrodes are not short-circuited during the voltage pause time.

(Example 2)
The display of the electrophoretic display device was switched in the same manner as in Example 1 except that the voltage application time was increased to 790 msec and the number of application cycles of the periodic pulse voltage was set to 15.
(Example 3)
The display of the electrophoretic display device was switched in the same manner as in Example 1 except that the voltage pause time was shortened to 70 msec and the number of application cycles of the periodic pulse voltage was 50.
Example 4
The display of the electrophoretic display device was switched in the same manner as in Example 3 except that both electrodes were short-circuited and grounded during the voltage pause time.

(Comparative Example 1)
The display of the electrophoretic display device was switched in the same manner as in Example 1 except that a DC voltage of 8 V was applied between both electrodes of the electrophoretic display device for 1 second.
(Comparative Example 2)
The display of the electrophoretic display device was switched in the same manner as in Comparative Example 1 except that the magnitude of the DC voltage was changed to 10V.

(Comparative Example 3)
The display of the electrophoretic display device was switched in the same manner as in Comparative Example 1 except that the magnitude of the DC voltage was changed to 12V.
(Comparative Example 4)
The display of the electrophoretic display device was switched in the same manner as in Comparative Example 1 except that the magnitude of the DC voltage was changed to 20V.
(Comparative Example 5)
The display of the electrophoretic display device is the same as the comparative example 1 except that a sine wave AC voltage having a voltage of 20 V and a frequency of 50 Hz is superimposed on a DC voltage of 10 V and this superimposed voltage is applied between both electrodes. Switched.

3. Evaluation of electrophoretic display device With respect to the display switching drive of the electrophoretic display device in each example and each comparative example, the reflectance in a black display state was measured. The reflectance was measured using a color luminance meter (manufactured by Topcon Corporation, BM-5A).
Moreover, after the application of the voltage between both electrodes was complete | finished, it confirmed whether the reflectance changed with time, and evaluated according to the following references | standards.

<Evaluation criteria for changes in reflectance>
○: Reflectance decreases with time or hardly changes. X: Reflectivity increases with time. Table 1 shows the evaluation results. 6 and 7 show the driving conditions of the electrophoretic display devices in Example 1, Example 4 and Comparative Examples 1 to 4 (changes in applied voltage waveform and reflectance).

  As shown in Table 1, the voltage applied between the electrodes when switching the display of the electrophoretic display device of each example is the same as the voltage applied between the electrodes of the electrophoretic display device of each comparative example. Although it was equivalent or less, the display could be switched sufficiently. As a result, it has been clarified that the driving conditions of the electrophoretic display device in each embodiment can reduce the voltage of the power source mounted in the device and reduce the power consumption associated therewith.

On the other hand, the black display state of the electrophoretic display device of each example has a reflectance equal to or less than that of each comparative example, and has sufficient “blackness (low reflectance)” for black display. Was. Therefore, it has been clarified that the driving conditions of the electrophoretic display device in each embodiment enable display with high contrast.
In each example, as shown in FIG. 6, the reflectance starts to decrease at the same time as a voltage is applied between both electrodes, and the reflectance immediately after the end of the application is maintained even after the end of the voltage application.

On the other hand, in each comparative example, as shown in FIG. 7, the reflectance starts to decrease at the same time as the voltage is applied between the two electrodes. It has increased. This is because the degree of “blackness” of the black display gradually decreases after the voltage application is finished, and as a result, it is presumed that the display contrast is decreased.
Further, in the driving method according to the fourth embodiment, considering that the reflectance of the black display is sufficiently low in spite of the short voltage application time and the voltage pause time, this driving method has a high display switching speed. In addition, it is particularly excellent as a device that enables high-contrast display with low power consumption.

It is a figure which shows typically the longitudinal cross-section of the electrophoretic display device of this invention. FIG. 2 is a schematic diagram for explaining an operation method of the electrophoretic display device shown in FIG. 1. It is a figure which shows an example of the waveform of the voltage applied between a pair of electrodes. 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. It is a figure which shows the drive conditions (change of the waveform of an applied voltage, and a reflectance) of the electrophoretic display apparatus in Example 1 and Example 4. FIG. It is a figure which shows the drive conditions (change of the waveform of an applied voltage, and a reflectance) of the electrophoretic display apparatus in Comparative Examples 1-4.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Base part 2 ... Base part 3 ... 1st electrode 4 ... 2nd electrode 5, 5a, 5b ... Electrophoretic particle 6 ... Liquid phase dispersion medium 7 ... Sealing part 8 ... Adhesive Layer 10 ... Electrophoretic dispersion 11 ... Substrate 12 ... Counter substrate 20 ... Electrophoretic display device 21 ... Electrophoretic display sheet 22 ... Circuit board 40 ... Microcapsule 400 ... Microcapsule-containing layer 401 ... ... capsule body 41 ... binder 600 ... electronic paper 601 ... main body 602 ... display unit 800 ... display 801 ... main body 802a, 802b ... conveying roller pair 803 ... hole 804 ... transparent glass plate 805 ... Insertion slot 806 ... Terminal part 807 ... Socket 808 ... Controller 809 ... Operation part

Claims (13)

In an electrophoretic display device having a pair of electrodes opposed to each other and an electrophoretic layer provided between the pair of electrodes and including at least one kind of electrophoretic particles,
When switching the display, it is utilized that there is a difference in the charge accumulation rate accompanying the application of an electric field between the capacitive component caused by the electrophoretic particles and the capacitive component caused by a site other than the electrophoretic particles. A method for driving an electrophoretic display device, wherein a voltage is applied between the pair of electrodes in a pattern in which charge is not accumulated in a capacitive component caused by a portion other than the electrophoretic particles.   The method for driving an electrophoretic display device according to claim 1, wherein the voltage applied between the pair of electrodes is a periodic pulse voltage in which a pulsed voltage is repeatedly applied.   The method of driving an electrophoretic display device according to claim 2, wherein the waveform of the pulse voltage is a rectangular wave.   The method for driving an electrophoretic display device according to claim 2, wherein a voltage application time in the periodic pulse voltage is 1 to 50 msec.   5. The driving method of the electrophoretic display device according to claim 2, wherein a voltage pause time in the periodic pulse voltage is 50 to 1000 msec.   6. The method for driving an electrophoretic display device according to claim 2, wherein the number of cycles of the periodic pulse voltage is 3 to 200 cycles.   The method for driving an electrophoretic display device according to claim 2, wherein the pair of electrodes are short-circuited during a voltage pause time in the periodic pulse voltage.   The method for driving an electrophoretic display device according to claim 7, wherein the pair of electrodes are grounded in the short-circuit state.   The method for driving an electrophoretic display device according to claim 1, wherein a voltage applied between the pair of electrodes is 1 to 15V.   The electrophoretic display device has bistability that can maintain display when a voltage between the pair of electrodes is applied even when no voltage is applied. Driving method of electrophoretic display device.   The method for driving an electrophoretic display device according to claim 1, wherein the electrophoretic particles include titanium oxide particles and titanium black particles.   An electrophoretic display device configured to be driven by the method for driving an electrophoretic display device according to claim 1.   An electronic apparatus comprising the electrophoretic display device according to claim 12.

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