JP2000322006A - Electrophoretic display - Google Patents

Abstract

[PROBLEMS] To provide an electrophoretic display device having good image quality, low cost and low power consumption by reducing a voltage applied to an electrode. An electrophoretic display device 1 includes a recording medium transport unit 5 that relatively transports a sheet-shaped recording medium PP in which microcapsules enclosing charged particles and a liquid dispersion medium are formed in a layer, and a voltage is applied. An electrode voltage application circuit 6 for controlling the voltage, and a control unit 4 for controlling the voltage. The urging unit 25 is formed in a rotatable roller shape and urges the surface of the recording medium PP to contact the recording medium PP. Upper electrode part 2 for applying a voltage
And a lower electrode portion 3 disposed to face the recording medium PP so as to sandwich the recording medium PP. It is configured with. The upper electrode portion 2 is configured to make the distance between the electrodes close to the thickness of the recording medium PP so as to apply an electric field by abutting on the recording medium PP by rolling contact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an electrode of an electrophoretic display device.

[0002]

[Prior art]

Conventionally, a recording medium is used in which a layer of transparent resin microcapsules formed by dispersing and enclosing a large number of charged particles of two colors, each charged to a positive and a negative potential, in a liquid dispersion medium is used for this recording. An electrode provided so as to sandwich the medium, a voltage of a predetermined polarity is applied to this electrode, and a control electric field is applied to the recording medium to move the charged particles encapsulated in the microcapsules in an arbitrary direction. There has been proposed an electrophoretic display device in which one of two colors of charged particles is gathered on one surface of a recording medium as a display surface to display an image for an observer. In such an electrophoretic display device, a control electric field is generated by applying a voltage to electrodes provided to face each other across a recording medium, and the charged particles of the recording medium migrate according to the direction of the electric field. The charged particles of the color desired to be displayed are gathered on the display surface, and the charged particles of the color not desired to be displayed are migrated in the opposite direction to the display surface and hidden, and only the color desired to be displayed is displayed to the observer. After the control electric field is eliminated, the image displayed by the so-called memory effect is maintained, in which the state in which the charged particles adhere to the wall of the microcapsule is maintained by a mirror image effect generated between the charged particles and the wall of the microcapsule. Will be maintained. Therefore, the electrodes are configured to be relatively movable with respect to the recording medium so that a control electric field can be applied to predetermined pixels on the recording medium. In the recording medium of the above-described electrophoretic display device, a large number of spherical microcapsules are formed in layers and the surface has irregularities. Sometimes interfered with the recording medium. For this reason, conventionally, the electrodes are arranged far away from the recording medium surface so as not to be affected by the irregularities on the recording medium surface. Although it is conceivable to apply a large pressure to flatten the surface of the recording medium and flatten it, it is difficult to completely flatten it because applying too much pressure may damage the internal microcapsules. is there. Further, there is a method of flattening the surface of the recording medium such that the irregularities of the microcapsules are flatly covered with a transparent resin or the like, but in this case, a thick resin layer had to be formed.

[0004]

However, when the electrodes are arranged at a position distant from the surface of the recording medium, the distance between the electrodes increases, and a large voltage is applied to the electrodes to apply a predetermined control electric field to the microcapsules. If the voltage applying means is capable of applying a large voltage, there is a problem that the size of the device is increased, the cost is increased, and the power consumption is increased. On the other hand, if the surface is flattened with a resin layer or the like, the electrodes can be arranged close to the recording medium surface, but the same is true in that a large voltage must be applied since the distance between the electrodes is eventually increased by the resin layer. However, since the recording medium is rather thick, it is difficult to have flexibility and the portability of the recording medium is impaired. Further, when the electrodes are separated, the control range of the control electric field applied by the pair of electrodes is blurred, and there is a problem that the quality of an image formed is deteriorated.

The present invention has been made to solve the above-mentioned problems, and the image quality is good, the cost is low, and the cost is reduced by reducing the distance between the electrodes and reducing the voltage applied to the electrodes for applying the control electric field. An object of the present invention is to provide a power electrophoretic display device.

[0006]

In order to achieve this object, in the electrophoretic display device according to the first aspect of the present invention, charged particles and a liquid dispersion medium for dispersing the charged particles so as to be able to migrate are enclosed. Conveying means for relatively conveying a sheet-shaped recording medium in which microcapsules are formed in a multi-layered form,
An electrode unit for applying a control electric field to the recording medium; a voltage application unit for applying a voltage to the electrode unit; and a control unit for controlling a voltage applied by the voltage application unit, wherein the electrode unit is rotatable. A biasing means which is formed in the shape of a simple roller and biases the surface of the recording medium so as to abut against the surface of the recording medium with a predetermined pressure. And the first electrode so as to sandwich the recording medium conveyed by the conveying means.
And a second electrode that is arranged to face the first electrode and forms a control electric field by applying a voltage for each pixel unit of the recording medium in cooperation with the first electrode. It is characterized by.

[0007] In the electrophoretic display device according to this configuration, the first electrode of the electrodes constituting the electrode portion is formed in a rotatable roller shape urged by the urging means, and is provided on the surface of the recording medium in a predetermined manner. Since the electric field is applied by contacting with the pressure, the electrode is in rolling contact with the surface of the recording medium and does not slide, and the recording medium is not damaged even if the roller-shaped electrode contacts the recording medium. . Therefore, the distance between the first electrode and the recording medium can be brought close to the position where the first electrode contacts the surface of the recording medium, and thus the first electrode and the second electrode of the electrode section can be moved. The distance between them can be reduced. Therefore, the voltage applied to the electrodes of the electrode unit for applying the control electric field having a predetermined strength can be reduced, and the size, cost, and power consumption of the electrophoretic display device can be reduced. Further, by bringing the electrodes close to each other, the control range of the control electric field can be clarified, and a high-quality image can be formed.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the second electrode may apply a voltage to each pixel of the recording medium. And a plurality of small electrodes divided into an array.

In the electrophoretic display device according to this configuration, one of the electrodes is formed of an array of electrodes having a large number of divided small electrodes capable of applying a voltage to each pixel of the recording medium, thereby forming a roller. Using the formed electrode as a common electrode,
The configuration can be simplified.

According to a third aspect of the present invention, in addition to the configuration of the electrophoretic display device according to the first aspect,
The second electrode includes a roller-shaped electrode having a large number of divided small electrodes to which a voltage can be applied to each pixel of the recording medium.

In the electrophoretic display device according to this configuration, since the electrodes are all roller-shaped electrodes, the distance between the electrodes can be minimized without damaging the recording medium. Therefore, the voltage applied to the electrode for applying a predetermined control electric field can be reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electrophoretic display device according to the present invention will be described with reference to the accompanying drawings, using an electrophoretic display device 1 as a preferred embodiment.

FIG. 1 is a schematic view showing the outline of the configuration of the electrophoretic display device 1. As shown in FIG. As shown in FIG. 1, the electrophoretic display device 1 includes two pairs of conveyance rollers 51 and 52 that cooperate and convey the recording medium PP from both sides thereof, and the upper electrode unit 2.
A recording medium transport unit 5 that relatively moves the lower electrode unit 3 and the recording medium PP is provided. Further, the electrode voltage application circuit 6 is disposed between the two pairs of conveyance rollers 51 and 52 and is urged by the urging unit 25 to come into contact with the recording medium PP while rotating toward the display surface side (upper side in FIG. 1) of the recording medium PP. The upper electrode portion 2 to which a voltage is applied from the upper side and the side opposite to the display surface side of the recording medium PP (FIG.
And a lower electrode section 3 for applying a voltage in contact with or in proximity to the lower side). The upper electrode section 2 is a common electrode, and the lower electrode section 3 is configured as a segment electrode corresponding to each pixel (see FIG. 3), and each electrode is connected to the control section 4 by a wiring 8. . The controller 4 applies a voltage to the electrodes based on the image data, and applies a control electric field to the recording medium PP to form an image.

The recording medium transport section 5 has a drive motor 9. The drive motor 9 is connected to a computer 10 of the control unit 4.
Sends a control signal to the motor drive circuit 7, and upon receiving the control signal, a drive signal from the motor drive circuit 7 is sent to the drive motor 9 to be controlled and rotated. This rotation is transmitted to the pair of transport rollers 51, and the transport rollers 51 cooperate to move the recording medium PP in the X direction (left direction in FIG. 1), which is the transport direction, while holding the recording medium PP. Rotate. Similarly, the other pair of transport rollers 52
And is rotated through a power transmission means (not shown) to rotate in synchronization with the transport roller 51. The transport rollers 51 and 52 are urged in the direction of the recording medium PP to be pressed against the recording medium PP, and transport the recording medium PP by frictional force.

FIG. 3 shows an upper electrode section 2 of the electrophoretic display device 1.
FIG. 3 is a perspective view showing a part of the configuration of a lower electrode unit 3. Roller electrode 21 arranged above recording medium PP to be conveyed
Is a cylindrical roller made of a highly conductive metal such as stainless steel or a copper alloy, the surface of which is formed as the electrode 22, and a highly conductive material protruding from both ends thereof;
For example, a roller shaft 23 made of stainless steel is provided, and is rotatably supported by the shaft support portion 24. Shaft support 24
Has a fixed portion 24b of a shaft support portion 24, one end of which is fixed to a main body frame (not shown), and the roller shaft 23 is rotatably movable so as to be vertically movable (Z direction and anti-Z direction in FIG. 3). A support hole 24a, which is a slit-shaped opening for supporting, is formed. There is provided an urging portion 25 as urging means for urging the support shaft 23 pivotally supported in this manner from above to below (Z direction in FIG. 3). The urging portion 25 includes a support shaft 23
A leaf spring 25a for urging the plate from the top to the bottom (Z direction in FIG. 3) is provided, and its base is fixed to the fixing portion 25b. This leaf spring 25a has a function as a contact,
The wiring 8 is connected to the electrode voltage application circuit 6 (see FIG. 1), and is configured to be able to apply a voltage to the electrode 22 by being urged and pressed against a roller shaft 23 made of highly conductive stainless steel.

The lower electrode portion 3 is composed of a large number of minute pieces of metal such as stainless steel or a thin metal film.
a, 32b, 32c, 32d, 32e, 32f ... 3
2n (not shown) is arranged to be able to contact a position corresponding to a pixel on the lower surface side of the recording medium PP to be conveyed. Since the lower electrode portion 3 is in contact with the surface opposite to the display surface side of the recording medium PP, even if the recording medium PP slides and is slightly damaged, the image is not affected. Therefore, it is disposed at a position very close to the lower side of the recording medium PP (the Z direction in the drawing). The segment electrodes are linearly arranged in the width direction of the recording medium PP, which is perpendicular to the transport direction X of the recording medium PP, and are configured as array electrodes 31. Then, each of the electrodes 32a, 32b, 32
From c, 32d, 32e, 32f to 32n (not shown) are connected to the electrode voltage application circuit 6 by the wiring 8, so that a voltage can be individually applied to each electrode 32. Therefore, in the present embodiment, scanning is performed by moving the recording medium PP in the X direction while forming an image by applying an electric field to each pixel in the width direction of the recording medium PP by the roller electrodes 21 and the array electrodes 31 at a time. The configuration is the same as that of a so-called page printer that forms an image of the entire page.

The control unit 4 shown in FIG. 1 includes a well-known computer 10 having a CPU, a RAM, and a ROM (not shown) for control. This computer 10 may be configured by an external computer. Control unit 4
The computer 10 receives image information via an interface (not shown), and the computer 10 generates a control signal based on the image information. In response to a weak control signal from the computer 10, the recording medium P
An electrode voltage application circuit 6 so that a sufficient electric field can be applied to P
Is provided. Although not shown, the electrode voltage application circuit 6 is provided with a power supply unit for voltage application and a voltage control unit for opening / closing the circuit and selecting the polarity based on image information sent from the computer 10. A drive signal is output from the electrode voltage application circuit 6 via the wiring 8 and the respective electrodes 22 and 32 are output.
To form an image by applying an electric field from each electrode to the recording medium PP to be conveyed so that the electric field has a direction corresponding to each pixel. Further, as described above, a motor drive circuit 7 for outputting a drive signal to drive the drive motor 9 provided in the recording medium transport unit 5 based on a control signal from the computer 10 is provided.

Here, the recording medium PP used in the electrophoretic display device 1 according to the first embodiment will be described. FIG.
(A) is a schematic sectional view showing an example of a configuration of a recording medium PP.

As shown in FIG. 5A, the recording medium PP
Base layer P1 made of a flexible resin thin film made of polyethylene terephthalate (PET) having a thickness of 50 (μm)
A large number of microcapsules P10 are arranged in a plane on the surface of the substrate, and the gaps between the microcapsules P10 are filled with a transparent flexible medium P12 made of, for example, PET having a thickness of about 150 (μm). It is formed by forming a layered charged display layer P3 of up to 200 (μm). In this case, it is difficult to form the surface of the recording medium PP flat with the flexible medium P12 due to the shape of the microcapsule P10.
Many fine irregularities can be formed. In FIG. 5A, the unevenness is emphasized for the sake of explanation. As shown in FIG. 5 (A), this charged display layer P3
In addition to the one in which the layer 10 is formed in a single layer, a layer in which a plurality of layers are stacked may be used.

The provision of the thin and high-strength tape-shaped base layer 1 facilitates the molding process of the recording medium PP and improves the flatness. Further, the strength of the recording medium PP can be increased, and elongation and cracks can be effectively prevented. The base layer P
1 may be formed integrally with the charged display layer P3 by PET or the like. Here, the base layer P1 is colored white, and the white charged particles P2 are formed on the display surface P11 of the microcapsule P10.
a are gathered to display white, the microcapsule P
Even if the base layer P1 can be seen from the gaps of 10, the white layer is formed as a white colored layer so that white color is not turbid.

FIG. 5B is a schematic sectional view showing another example of the recording medium PP having no base layer 1. The base layer 1 is not always essential, and as shown in FIG.
Without the base layer P1, the microcapsule P10 and the flexible medium P12 can be used. in this case,
Although there is an advantage that the entire thickness can be reduced by not having the base layer 1, it is disadvantageous in terms of flatness and strength as a recording medium. In the case where the base layer 1 is not provided, the microcapsule layer is moved to the display surface side as shown in FIG. Is formed to secure the strength of the recording medium PP.

The recording medium PP thus configured is sandwiched between an upper electrode portion 2 and a lower electrode portion 3 provided in an electrophoretic display device 1 as shown in FIG. By applying an electric field in pixel units based on the information,
A large number of charged particles P2a and P2b (see FIG. 6) having different charging characteristics and different colors enclosed in the microcapsule P10 move to display a desired image on the upper display surface P11 in FIG. is there. Hereinafter, this recording medium PP
Will be described in detail.

FIGS. 6A, 6B, and 6C are diagrams showing how the microcapsules P10 change. here,
FIG. 6A is a schematic diagram illustrating a structure of the microcapsule P10 before a control electric field is applied to the recording medium PP of the present embodiment. The microcapsule P10 has a structure in which a dispersion system in which charged particles P2a and P2b are dispersed in a liquid dispersion medium P4 is included in a spherical transparent outer shell P5.

First, the outline of the method for producing the microcapsule P10 will be described. As a method of microencapsulation, it can be prepared by a method already known in the art. For example, a phase separation method from an aqueous solution as described in US Pat. Nos. 2,800,457 and 2,800,458, and the like,
19574, JP-B-42-446, JP-B-42-7
No. 71, etc., an interfacial polymerization method,
-9168, JP-A-51-9079, etc., by in-situ polymerization by monomer polymerization.
u) Method, British Patent Nos. 952807 and 965074
And the like, but are not limited thereto. The method for producing the microcapsules P10 of the present embodiment is performed by an interfacial polymerization method.
Will be described.

As a material for forming the outer shell P5 of the microcapsule P10, the outer shell P5 is formed by the above-described capsule manufacturing method.
As long as 5 can be manufactured, an inorganic substance or an organic substance may be used, but a material that sufficiently transmits light is preferable. Specific examples include gelatin, gum arabic, starch, sodium alginate, polyvinyl alcohol, polyethylene,
Examples include polyamide, polyester, polyurethane, polyurethane, polystyrene, nitrocellulose, ethylcellulose, methylcellulose, melamine-formaldehyde resin, urea-formaldehyde resin, and copolymers thereof.

The microcapsule P10 shown in FIG.
Is theoretically preferably smaller for realizing a high-resolution display device. However, since it has a structure including the charged particles P2a and P2b, it is actually about 5 (μm ) Or more and about 200 (μm) or less. In the recording medium PP of the present embodiment, the two types of charged particles P2a and P2b are about 30 to 1 together with the dispersant.
It is encapsulated in a microcapsule P10 of 00 (μm).

The charged particles P2a and P2b include an organic compound in which a dye or a pigment is dispersed, and an inorganic compound such as a pigment. Examples of the dye include the following. Any dye conventionally used in oil-based ink compositions can be used, but azo dyes, metal complex dyes,
Oil-soluble dyes such as naphthyl dyes, anthraquinone dyes, indigo dyes, carbonium dyes, quinoimine dyes, cyanine dyes, quinoline dyes, nitro dyes, nitroso dyes, benzoquinone dyes, naphthoquinone dyes, naphthalimide dyes, penoline dyes, phthalocyanine dyes, and the like are preferable. These dyes can be used in combination.

As the pigment, the following can be used. As a common name for organic pigments that are accepted in Japan,
In yellow, Hansa Yellow, Benzine
Yellow or the like can be used. In red, Parma
Nent Red, benzine orange, p
yrazolone orange, vulcanor
angel, orange lake, para re
d, rake red, toluidine red,
brill fast scarlet, brill
carmine, brill scarlet, bor
do, watchung red, lithol re
d, bon maroon, lakebordo, rh
odamine, madder lake and the like can be used. For purple, rhodamine blake, d
ioxazine violet, crystal v
iolet lake or the like can be used. In blue, vi
ctria pure blue lake, vic
toria bluelake, phthalocya
nine blue, fast sky blue, t
hrene blue rs and the like can be used. In green, diamond green lake, phth
alocyanine green, pigment
Green b, green gold and the like can be used. For black, diamond black can be used.

The following can be used as the inorganic pigment. For black, carbon black or the like can be used, and for white, titanium oxide, aluminum oxide, zinc oxide, lead oxide, tin oxide, or the like can be used.

As the organic compound, synthetic compounds such as the following synthetic resins and synthetic waxes, and natural waxes can be used.

As a synthetic resin or synthetic wax, methyl acrylate, ethyl acrylate,
n-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate,
Methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate,
2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, iso-butyl vinyl ether, n-butyl vinyl ether, styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl chloride, vinyl chloride , Vinylidene chloride, vinyl fluoride, vinylidene fluoride, ethylene, propylene, isoprene, chloroprene, butadiene and the like can be used.

Further, a monomer having a functional group such as a carboxyl group, a hydroxyl group, a methylol group, an amino group, an acid amide group and a glycidyl group may be mixed with the monomer. Those having a carboxyl group are acrylic acid, methacrylic acid, itaconic acid, etc., those having a hydroxyl group are β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, allyl alcohol, etc. Those having a methylol group include N-methylol acrylamide and N-methylol methacrylamide; those having an amino group include dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate; those having an acid amide group include acrylamide and methacrylamide such as a glycidyl group Are exemplified by glycidyl acrylate, glycidyl methacrylate, glycidyl allyl ether and the like. These monomers can be used alone or as a mixture of a plurality of monomers.

As the natural wax, the following plant, animal, mineral and petroleum waxes can be used.

As the plant wax, candelilla wax, carnauba wax, rice wax, wood wax,
Jojoba oil or the like can be used. As animal wax,
Beeswax, lanolin, whale wax, etc., mineral waxes such as montan wax, ozokerite and ceresin, and petroleum waxes such as paraffin wax,
Microcrystalline wax, petrolatum, etc. can be used respectively.

Next, the liquid dispersion medium P4 is required to have at least high insulation properties and colorless transparency, and include water, alcohols, various esters, aliphatic hydrocarbons, aromatic hydrocarbons,
In addition to tetracyclic hydrocarbons, halogenated hydrocarbons and the like, various natural or synthetic oils and the like can be used.

In order to form a dispersion system, first, a liquid dispersion medium P
In FIG. 4, black charged particles P2a having a positive charging polarity and white charged particles P2b having a negative charging polarity are uniformly dispersed. Further, this dispersion and distilled water to which a surfactant has been added are stirred and mixed to prepare an emulsion of the dispersion. The size of the dispersion emulsion is adjusted to a desired size by the stirring speed or the types and amounts of the emulsifier and the surfactant. If necessary, one or more kinds of emulsifiers, surfactants, electrolytes, lubricants, stabilizers and the like can be appropriately added.

At this time, the degree of dispersion of the particle size distribution of the charged particles P2a and P2b represented by volume average particle diameter / number average particle diameter is preferably about 2 or less.

Further, the charged particles P2a and P2a shown in FIG.
The average particle diameter d of P2b is preferably about 1/1000 or more and about 1/5 or less with respect to the particle diameter D of the microcapsule P10. Charged particles P2a and P2b whose particle diameter d is about 1/5 or more of particle diameter D of microcapsule P10
When the image is formed by applying an electric field, the charged particles P2a and P2a having different polarities
2b hinders each other's migration, and the response speed is extremely reduced. Further, the charged particles P2a, P2 having a particle diameter d of about 1/1000 or less of the particle diameter D of the microcapsule P10.
2b aggregates in the microcapsule P10,
In some cases, the responsiveness to an electric field is reduced, and display unevenness is caused. In the recording medium PP of the present embodiment, the fine particles have an average particle size of about 1 to 10 (μm),
Two types of black positive charged particles P2a and white negative charged particles P2b are used.

The amount of the charged particles P2a and P2b is such that the volume of the charged particles P2a and P2b in the microcapsule P10 is about 1.5% or more and about 25% or less with respect to the volume of the microcapsule P10, respectively. And all the charged particles P2 contained in the microcapsules P10
It is preferable to adjust the sum of the volumes of a and P2b to be about 1.5% or more and about 50% or less with respect to the volume of the microcapsule P10, respectively.

The volume of the charged particles P2a and P2b contained in the microcapsule P10 is
When each of the charged particles P2a and P2b is less than about 1.5% with respect to the volume of
Even if it moves to the wall end of the outer shell part P5 of 0, it cannot occupy half of the capsule hemispherical surface, leading to low contrast, or other colored particles behind or electrodes such as electrodes on the back side. The colors are noticeable to the observer.

The charged particles P2a,
The volume of P2b is about 25% or more with respect to the volume of microcapsule P10, and the sum of the volumes of charged particles P2a and P2b contained in microcapsule P10 is about 50% with respect to the volume of microcapsule P10. In such a case, the charged particles P2a,
When P2b responds, each other's charged particles P
2a and P2b hinder electrophoresis. For this reason,
The response speed from application of the control electric field to completion of image formation is significantly reduced.

The recording medium PP according to the present embodiment has the above-described configuration, and thus has the following operation. Here, the microcapsule P10 shown in FIG. 6A is in a state where no electric field is applied yet, and the charged particles P2a and P2b
Are dispersed in the microcapsules in a uniform state. Here, the upper part of the figure (the direction opposite to the Z direction) is the display direction which is the display surface P11 of the microcapsule P10.

FIG. 7 is a schematic diagram showing a state in which an electric field is applied to the recording medium PP by the electrodes 22a and 22b of the upper electrode unit 2 and the electrodes 32a and 32b of the lower electrode unit 3. As shown in FIG. 7, when a voltage is applied to the corresponding electrodes 22a and 32a and 22b and 32b of the corresponding upper electrode portion 2 and lower electrode portion 3, an electric field having a direction corresponding to the polarity of the applied voltage is generated. Occurs. Here, the lines of electric force are indicated by EL. The electrode 22a of the upper electrode unit 2 shown on the left side of FIG.
2a is an anode. Therefore, an upward electric field is generated,
The microcapsule P10a placed in this electric field will be described as an example. FIG. 6B shows the charged particles P2 in the microcapsule P10a in a state where a uniform upward electric field is applied.
It is a schematic diagram which shows the state of a and P2b. In FIG. 6B, when a voltage is applied such that the upper electrode portion 2 is a cathode and the lower electrode portion 3 is an anode, an upward electric field is generated, and the positively charged black charged particles P2a are the cathodes. Electrode 22
In the direction of a, the negatively charged white charged particles P2b
Are attracted in the direction of the lower electrode 32a, which is the anode, and the charged particles P2a and P2b are
It adheres to the inner wall surface of the outer shell part P5 of 10a.

FIG. 6C shows that the charged particles P2a and P2b are
The drawing shows a state where the microcapsule P10a is attracted to the electrodes 22 and 32 and adheres to the inner wall surface of the outer shell P5 of the microcapsule P10a. Therefore, in the case of the left side of FIG.
When viewed in the Z direction from the side, that is, the display surface P11 on the front side, only the charged particles P2a are observed, and only the colored black of the charged particles P2a is displayed on the display surface.

In this state, even if the application of the voltage is stopped, the viscosity and the image force of the liquid dispersion medium P4 cause the liquid dispersion medium P4 to have the configuration shown in FIG.
Is maintained, that is, there is a so-called memory effect.
In this state, even if an electric field up to a certain intensity is received, this state is maintained due to hysteresis.
That is, the image formed here is stably recorded on the recording medium PP.

On the other hand, the upper electrode part 2 and the lower electrode part 3 are
When a voltage is applied again with a polarity different from that of (B), if an electric field exceeding the hysteresis limit is applied, the charged particles P2a and P2b move again and their positions are reversed as shown on the right side of FIG. P10 charged particles P2a,
The image formed by P2b is rewritten.

The electrophoretic display device 1 and the recording medium PP
The configuration is as described above. Next, the operation of the thus configured electrophoretic display device 1 when recording on the recording medium PP will be described in comparison with a conventional electrophoretic display device.

FIG. 8 is a schematic view showing the outline of the configuration of a conventional electrophoretic display device 101. As shown in FIG. FIG.
FIG. 1 is a perspective view schematically showing an arrangement of an upper electrode portion 2 and a lower electrode portion 3 of a conventional electrophoretic display device 101. The conventional electrophoretic display device 101 has an upper electrode unit 10 as shown in FIG.
Reference numeral 2 denotes electrodes 122a, 122b, 122 made of a large number of minute pieces of metal such as stainless steel or a metal thin film.
The distance L1 from the position corresponding to the pixel on the front side of the recording medium PP to be conveyed is approximately 500.
(Μm) so as to be spaced apart from each other in the direction opposite to the Z direction so as not to cause interference with the surface of the recording medium PP.
Therefore, the distance L2 between the electrodes is approximately 650 to 700 (μ
m) away. Perpendicular to the transport direction X of the recording medium PP,
That is, the segment electrodes 122 are arranged in the width direction of the recording medium PP.
are arranged linearly and the electrode array 12
1 is configured. Further, the lower electrode portion 103 has the same configuration as the upper electrode portion 102, and the respective electrodes 122a, 122b, 122c,.
Electrodes 132a, 132b, 132 corresponding to 122n
The electrode array 131 provided with c,... 132n is arranged so as to be in contact with or close to the lower surface (Z direction side) of the recording medium PP. Therefore, only the configuration of the upper electrode unit 2 is different from the electrophoretic display device 1. That is, the conventional upper electrode portion 102
In the electrophoretic display device 1 of the present embodiment, the upper electrode unit 2 includes the roller electrode 21, whereas the fixed array electrode 121 similar to the lower electrode unit 103 is separated from the recording medium PP by a certain distance. It differs by being arranged and configured.

Due to such a difference in configuration, the electrophoretic display device 1 according to the present embodiment is different from the conventional electrophoretic display device 1 in the present embodiment.
There are the following actions and effects, unlike the action of No. 01.
In the conventional electrophoretic display device 101, in order to apply a control electric field of about 400 (V / mm) to the microcapsule P10, two electrodes are applied to the electrodes separated by about 700 (μm).
It was necessary to apply a voltage of 80 (V) for about 0.5 seconds. In contrast, in the electrophoretic display device 1 according to the present embodiment, since the upper electrode unit 2 is in contact with the surface of the recording medium PP, the distance between the upper electrode unit 2 and the lower electrode unit 3 is smaller than the recording medium PP.
Can be set to 150 (μm) to 200 (μm), so that the voltage applied to the electrodes in order to apply the same control electric field to the recording medium PP as in the related art can be set to 70 (V). .

Therefore, since the voltage applied to the electrodes may be lower than in the prior art, the output of the electrode voltage application circuit 6 (voltage application means) can be reduced in the electrophoretic display device 1 of the present embodiment. There is. Therefore, the electrode voltage application circuit 6 can also have a lower voltage circuit configuration than before. Further, since the applied voltage can be reduced, power consumption can be reduced, and power saving can be achieved. Further, by reducing the distance between the upper electrode unit 2, the lower electrode unit 3, and the electrode, there is an effect that the control of the pixels of the recording medium PP can be performed more accurately, and the quality of the image formed thereby is improved. There is an effect that can be made.

The present invention has been described based on the first embodiment. However, the present invention can be implemented with modifications such as the following modifications.

FIG. 2 is a schematic diagram showing an outline of the configuration of a first modification of the electrophoretic display device 1. For example, in the first modification shown in FIG. 2, not only the upper electrode section 202 but also the lower electrode section 203
Also, the present invention is implemented with a configuration in which a roller electrode is also used. The configuration other than the electrodes is the same as that of the electrophoretic display device 1.

FIG. 4 is a perspective view showing a part of the configuration of the upper electrode portion 202 and the lower electrode portion 203 in the first modification of the electrophoretic display device 1. FIG. As shown in FIG.
2 is a cylindrical roller whose surface is covered with an insulator;
Electrode portions 222a, 222b, 222c, 222d, 22 made of a metal having excellent conductivity, such as stainless steel or a copper alloy, which is formed in a ring shape and is wrapped around a cylindrical roller.
2e to 222n (not shown) are provided at positions corresponding to the pixels of the recording medium PP. A roller shaft 223 protruding from both ends is provided, and is rotatably supported by the shaft support portion 224. The shaft support portion 224 includes an upper portion 224.
a and a lower portion 224b, and a protruding portion of the upper portion 224a is formed so as to be insertable into a hole provided in the lower portion 224b, and the entire shaft support portion 224 is configured to be expandable and contractible. Upper part 224
a is fixed to a main body frame (not shown).
The roller shaft 223 is rotatably supported by a bearing (not shown) disposed at the lower end of the roller shaft 4b. An urging portion 225 is provided as urging means for urging the support shaft 223 thus pivotally supported from above (Z direction in FIG. 3). Energizing part 2
25 is a spring 225 which is a compression coil spring.
a. The urging portion 225 has a spring 225a fixed at its upper portion to a spring receiving portion 225c provided on an upper portion 224a of the shaft support portion 224 so as to urge the support shaft 223 from above (the Z direction in FIG. 3). Lower part 22
4b, it is fixed to a spring receiving portion 225b and urges the shaft support portion 224 to extend. Although not shown, the roller shaft 233 of the lower electrode unit 203 is also connected to the upper electrode unit 20.
3 to be supported.

At one end of the roller electrode 221, for example, 8
A plurality of annular electrodes 228 are provided, and the contacts 226 come into contact with the electrodes, respectively, and transmit a control signal and a drive current. The contact 226 is connected to the electrode voltage application circuit 6 by the wiring 8.
Is connected to and receives a control signal. A flip-flop circuit (not shown) is provided in the roller electrode 221, and a required voltage is applied to a predetermined electrode corresponding to a pixel.

In the electrophoretic display device according to the first modification having the above-described configuration, the upper electrode portion 202 and the lower electrode portion 203 are both formed as roller-shaped electrodes, so that the recording medium PP can be contacted only by rolling contact. Because there is no sliding
The distance between the electrodes of the upper electrode portion 202 and the lower electrode portion 203 can be reduced to the thickness of the recording medium PP without damaging the recording medium PP. Therefore, the voltage applied to the electrodes for applying the predetermined control electric field can be minimized.

While the present invention has been described with reference to one embodiment and a modification, the present invention can be implemented as follows.

It is sufficient that at least one of the electrode portions can apply an electric field to each pixel, and the arrangement of the electrodes can be variously modified.

The biasing means may be a spring using a leaf spring 25a shown in the electrophoretic display device 1, a coil spring 225a used in the first modification, etc., as well as various springs or a torsion bar or rubber. Elastic body etc. may be used,
It just needs to be energized in some way.

The recording medium PP is not limited to the configuration as shown above, and various recording media can be used as long as an image can be displayed by electrophoresis between electrodes.

The present invention has been described with reference to the electrophoretic display device 1 according to the first embodiment of the invention and the first modification thereof. However, the present invention relates to the electrophoretic display device 1 according to the embodiment of the present invention and its modifications. It is needless to say that the present invention is not limited to Example 1 and can be implemented with various modifications without departing from the invention described in the claims.

[0061]

As is apparent from the above description, claim 1
According to the electrophoretic display device of the invention, among the electrodes constituting the electrode portion, the first electrode is formed in a rotatable roller shape urged by the urging means, and a predetermined pressure is applied to the surface of the recording medium. In order to apply an electric field by abutting, the electrode does not slide because of rolling contact with the recording medium surface,
There is an effect that the recording medium is not damaged even if the roller-shaped electrode contacts the recording medium. Therefore, the distance between the first electrode and the recording medium can be brought close to the position where the first electrode contacts the surface of the recording medium, and thus the first electrode and the second electrode of the electrode section can be moved. This has the effect of reducing the distance between them. Therefore, it is possible to reduce the voltage applied to the electrodes of the electrode unit in order to apply a control electric field having a predetermined strength, and to reduce the size, cost, and power consumption of the electrophoretic display device. It also has an effect. Further, there is an effect that the control range of the control electric field is clarified by bringing the electrodes close to each other, so that a high-quality image can be formed.

According to the electrophoretic display device of the second aspect of the present invention, in addition to the effects of the electrophoretic display device of the first aspect of the present invention, it is possible to apply a voltage to one electrode for each pixel of the recording medium. The configuration using an array of electrodes having a large number of small electrodes that can be divided has an effect that the configuration can be simplified by using a roller-shaped electrode as a common electrode.

According to the electrophoretic display device of the third aspect of the present invention, in addition to the effects of the electrophoretic display device of the first aspect of the present invention, all the electrodes are formed as roller-shaped electrodes.
There is an effect that the distance between the electrodes can be minimized without damaging the recording medium. Therefore, there is an effect that the voltage applied to the electrode for applying the predetermined control electric field can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a schematic configuration of an electrophoretic display device 1. FIG.

FIG. 2 is a schematic diagram illustrating a schematic configuration of a first modification of the electrophoretic display device 1.

FIG. 3 is a perspective view showing a part of the configuration of an upper electrode unit 2 and a lower electrode unit 3 of the electrophoretic display device 1.

FIG. 4 is a perspective view showing a part of a configuration of an upper electrode unit 202 and a lower electrode unit 203 in a first modification of the electrophoretic display device 1.

FIG. 5A is a schematic sectional view illustrating an example of a configuration of a recording medium PP. FIG. 3B is a schematic sectional view showing another example of the recording medium PP having no base layer 1.

FIG. 6 is a diagram illustrating a state of change of a microcapsule P10. (A) is a schematic diagram showing a structure of the microcapsule P10 before a control electric field is applied to the recording medium PP of the present embodiment. (B) is a schematic diagram showing a state of charged particles P2a and P2b in a microcapsule P10a in a state where a uniform upward electric field is applied. (C) The electric particles P2a and P2b are respectively
The state where the microcapsule P10a is attracted to the inner wall surface of the outer shell part P5 of the microcapsule P10a is shown.

FIG. 7 shows electrodes 22a and 22 of an upper electrode unit 2 on a recording medium PP.
FIG. 4B is a schematic diagram illustrating a state in which an electric field is applied by electrodes b and electrodes 32a and 32b of a lower electrode unit 3;

FIG. 8 is a schematic diagram illustrating a schematic configuration of a conventional electrophoretic display device 101.

FIG. 9 is a perspective view schematically showing the arrangement of an upper electrode section 2 and a lower electrode section 3 of a conventional electrophoretic display device 101.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 electrophoretic display device 2 upper electrode section 2 (electrode section / first electrode) 3 lower electrode section 3 (electrode section / second electrode) 4 control section 4 (control means) 5 recording medium transport section 6 electrode voltage application Circuit 6 (voltage application means) 7 Motor drive circuit 8 Wiring 9 Drive motor 10 Computer 21 Roller electrode 22 Electrode 23 Roller shaft 24 Shaft support 25 Energizing part 31 Array electrode 32 Electrode PP Recording medium P1 Base layer P2a, P2b Charged particles P3 Charged Display layer P4 Liquid dispersion medium P5 Shell part P10 Microcapsule P11 Display surface P12 Flexible medium

Claims (3)

[Claims] 1. A transport means for relatively transporting a sheet-like recording medium in which a plurality of microcapsules enclosing charged particles and a liquid dispersion medium for dispersing the charged particles so as to be able to migrate are formed, An electrode unit for applying a control electric field to the recording medium; a voltage application unit for applying a voltage to the electrode unit; and a control unit for controlling a voltage applied by the voltage application unit. The electrode unit is rotatable. It has a biasing means which is formed in a roller shape and biases the surface of the recording medium so as to contact with a predetermined pressure,
A first electrode that contacts the recording medium and applies a voltage while rotating according to the conveyance of the recording medium; and a first electrode facing the first electrode so as to sandwich the recording medium conveyed by the conveyance unit. And a second electrode for forming a control electric field by applying a voltage for each pixel of the recording medium in cooperation with the first electrode. . 2. The apparatus according to claim 1, wherein the second electrode comprises an array of electrodes having a large number of divided small electrodes to which a voltage can be applied to each pixel of the recording medium. An electrophoretic display device according to item 1. 3. The apparatus according to claim 1, wherein the second electrode comprises a roller-shaped electrode having a large number of divided small electrodes capable of applying a voltage to each pixel of the recording medium. An electrophoretic display device according to item 1.