JP2002533754A - Electrophoretic display protection electrode - Google Patents

Abstract

  (57) [Summary] The present invention is an electrophoretic display having a protective electrode that reduces display degradation caused by mechanical or electrochemical effects. The electrode may include a protective layer that reduces mechanical or electrochemical damage to the transparent conductive electrode. The protective electrode can be a vapor permeable electrode that is a reticulated conductive structure, such as a metal screen or wire mesh, or a reticulated structure coated or impregnated with a conductive material. The protective electrode may include a layer that protects the display medium from physical abrasion or removal by mechanical action and allows for the application of an electric field that causes the display to be addressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an electronic display, and more particularly, to an electrode for preventing display degradation, a display use mode, and a display manufacturing method.

[0002] This application is related to US patent application Ser. No. 60 / 113,078, filed Dec. 21, 1998, and US patent application Ser. Claims priority over patent application serial number 60 / 113,418 and U.S. patent application serial number 60 / 115,052, filed January 8, 1999. All of these contents are incorporated herein by reference.

BACKGROUND OF THE INVENTION In recent years, research and development on electrophoretic displays have been actively conducted.
Electrophoretic displays have good brightness and contrast properties, wide viewing angles, state bistability, and low power consumption compared to liquid crystal displays. Nevertheless, the long-term image quality problems of these displays have hampered their widespread use. For example, the particles that make up such displays are prone to clustering and sedimentation, resulting in an inadequate service life for these displays.

[0004] Encapsulation of electrophoretic displays typically eliminates the risk of bunching and settling failure modes as in conventional electrophoretic devices, and allows the use of various types of flexible and rigid substrates. Further advantages are possible, such as the ability to print or coat the display on the display.

Conventionally, a method for manufacturing an electronic display such as a liquid crystal display has been to sandwich an optoelectronically active material between two sheets of glass. In many cases, each glass plate has an etched transparent electrode structure formed using indium tin oxide ("ITO"). The first electrode structure controls all of the segments of the display, and these segments are addressable (i.e., their respective viewing states change). The second electrode (also called the counter electrode) addresses the entire display segment as one large electrode and is typically designed so that none of the unwanted back electrode wiring connections overlap in the final image. . Alternatively, the second electrode is patterned to control a particular segment of the display. In these displays, the unaddressed areas of the display have a certain appearance.

[0006] In the case of electrophoretic displays, it has been common for the display to fail after a certain amount of time. One of the causes of such display failure
One is that the material making up the display is damaged by repeated processing of the electrical address signals. Another reason for failure of such a display is that elements or electrodes of the display are subject to mechanical or electrochemical damage.

SUMMARY OF THE INVENTION In one aspect, the present invention provides novel devices and methods that provide protective electrodes for use in electrically addressable displays, including electrophoretic displays. The invention further discloses the use of these methods and materials for displays. The display is flexible, has a wide range of applications, is low cost, and can be a durable application that operates in a variety of environments.

In one aspect, the invention relates to a display, the display including a display element capable of changing its appearance in response to an electric field, and a first electrode adjacent the display element. , Whereby the first electrode provides a protective layer adapted to protect the display element from mechanical or electrochemical damage.

[0009] In one embodiment, the display includes one electrophoretic display element. The electrophoretic display element comprises a capsule and a first inside the capsule.
A dispersion fluid having the following optical properties; and at least one dispersion fluid provided in the capsule.
And two electrophoretically movable particles as constituent elements. The at least one electrophoretically movable particle has a second optical property different from the first optical property, and the at least one electrophoretically movable particle is under the influence of an applied electric field. so,
It can change its position within the capsule. The appearance of the display element may change depending on whether the at least one electrophoretically movable particle is located within the capsule.

[0010] In another embodiment, the protective layer is flexible, and the protective layer prevents the electrophoretic element from being mechanically removed from the display. In yet another embodiment, the protective layer includes a plurality of conductors penetrating the same. In yet another embodiment, the first electrode is transparent, the protective layer is disposed on the transparent electrode, and the protective layer degrades when the transparent electrode is applied with a potential. The situation can be prevented. In a further embodiment, the first electrode is transparent and comprises one or more oxides selected from the group consisting of indium oxide, tin oxide and indium tin oxide.

In another embodiment, the protective layer is formed of nickel, palladium, platinum, ruthenium.
Metals such as aluminum, rhodium, silver, aluminum, gold, titanium, chromium and zinc
, Silver oxide (AgO), aluminum oxide (Al_TwoO_Three), Gold (III) oxide (Au _Two O_Three), Titanium oxide (II) (TiO), titanium oxide (IV) (TiO_Two),acid
Chromium (III) chloride (Cr_TwoO_Three), Chromium oxide (VI) (CrO_Three), Zinc oxide
(ZnO), nickel (II) oxide (NiO), palladium (II) oxide (Pd
O), platinum oxide (IV) (PtO_Two), Ruthenium (IV) oxide (RuO_Two) And
Rhodium (III) oxide (Rh_TwoO_Three) And oxides
At least one chemical composition. In a preferred embodiment, the protective layer is
Contains palladium. In yet another embodiment, the protective layer is less than about 10 nm.
Has full thickness.

In another aspect, the invention relates to a display that includes a display element and a vapor-permeable electrode adjacent the display element. In one embodiment, the display includes one electrophoretic display element, wherein the electrophoretic display element includes a capsule, a dispersion fluid having a first optical property within the capsule, and disposed within the capsule. And at least one electrophoretically movable particle to be formed. The at least one electrophoretically movable particle has a second optical property different from the first optical property, and
Two electrophoretically mobile particles can change their position within the capsule under the influence of an applied electric field. The appearance of the display element can change depending on the position of the at least one electrophoretically movable particle within the capsule.

[0013] In another embodiment, the vapor permeable electrode comprises an electrode permeable to water vapor. In another embodiment, the vapor permeable electrode includes a reticulated conductive structure.
The reticulated conductive structure may be a wire mesh. The wire mesh may be composed of copper or bronze or other metals. The net-like conductive structure,
A reticulated layer at least partially coated with a conductive material, or
It may be a mesh layer at least partially impregnated with a conductive material.

[0014] In another aspect, the invention relates to an electrostatically addressable display. The electrostatically addressable display includes a display element having a first surface and a second surface, and a protective layer disposed adjacent to the first surface of the display element and capable of transmitting charges. The second of the display elements
And an electrode disposed adjacent to the surface of the substrate.

[0015] In one embodiment, the protective layer is flexible. In one particular embodiment, the protective layer comprises an anisotropic material. For example, the protective layer may include a plastic sheet and a plurality of conductive elements vertically embedded in the sheet. The conductive element may include a plurality of rods. The conductive element may be substantially invisible. Alternatively, the protective layer may include a semiconductor. For example,
The protective layer may include a polymer semiconductor including a plurality of photoconductors. The protective layer,
It may include a polymer material layer such as mylar.

[0016] In another embodiment, the display includes one electrophoretic display element. The electrophoretic display element includes a capsule, a dispersion fluid having a first optical property within the capsule, and at least one dispersion fluid disposed within the capsule.
And two electrophoretically movable particles as constituent elements. The at least one electrophoretically movable particle has a second optical property different from the first optical property, and the at least one electrophoretically movable particle is under the influence of an applied electric field. so,
It can change its position within the capsule. The movement of the at least one electrophoretically movable particle within the capsule changes the appearance of the display element.

[0017] In another embodiment, applying an electrostatic voltage of less than 1000 volts to the display generates an electrostatic voltage of at least 5 volts across the electrophoretic element. In still another embodiment, the protective layer disposed adjacent to the first surface of the capsule has a layer having a resistivity of less than 10 ¹² Ω · cm, and the electrophoretic element has a resistivity of less than 10 ¹² Ω · cm. Contains materials greater than 10 ¹² Ω · cm. In still another embodiment, the protective layer includes a material having a resistivity higher than that of the electrophoretic element and having a thickness of 20% or less of a layer thickness of the electrophoretic element, whereby the protective layer is formed. The resistance of the layer is about 20% of the resistance of the electrophoretic element. In a further embodiment, the protective layer disposed adjacent to the first surface of the display element includes a layer of a polymeric material. In yet another embodiment, the protective layer disposed adjacent to the first surface of the display element includes a layer that conducts charges substantially perpendicular to the layer. In a further embodiment, the protective layer disposed adjacent to the first surface of the display element includes a layer of insulating material having a plurality of conductive structures therein. In a further embodiment, the protective layer disposed adjacent to the first surface of the display element comprises a first region having a first resistivity and a second region having a second resistivity. And

In still another embodiment, the first region having the first resistivity and the second region having the second resistivity are different from each other in the first region and the second region. Including materials that are otherwise doped. In one detailed embodiment, the first region includes a first material, and the second region includes another second material.
In another embodiment, the first region and the second region having a lower conductivity continuously surround an insulated segment array of the first region and the second region having a higher conductivity. In a further embodiment, the lower conductivity first and second regions include vias that provide access to the isolated segment array. In another embodiment, the lower conductive first and second materials comprise an area that continuously surrounds an island array of the higher conductive first and second materials. Including. The first and second materials having lower conductivity include pinholes that provide access to the island array. The plurality of pinholes may include a pinhole large enough to receive a printhead. The island array can form a visible pixel array when driven by an electrostatic printhead. In another embodiment, the protective layer has a first surface and a second surface, wherein the second surface of the protective layer is electrically connected to the first surface of the electrophoretic material layer. Includes the island array in communication. The island array may be in physical contact with the electrophoretic material. The protective layer may include one or more vias that provide access to the island array. The protective layer may include one or more pinholes that provide access to the island array. The pinholes form an array corresponding to the island array.

In another embodiment, the protective layer disposed adjacent to the first surface of the display element has a first region having a first resistivity and a second region having a second resistivity. And a plurality of regions. In yet another embodiment, the plurality of regions having the second resistivity include an array of three islands.

In yet another embodiment, the protective layer comprises a substrate, the substrate having a substantially transparent coating of a radiation-responsive charge-emitting material on its surface.
The coating can be light- or heat-responsive. The surface having the coating may be disposed adjacent to the electrophoretic material.

[0021] In still another embodiment, the protective layer includes an anisotropic conductor. In one particular embodiment, the anisotropic conductor comprises an array of substantially linear, colloidal metal spheres. The substantially linear array may be substantially perpendicular to a plane of the protective layer. In one embodiment, the colloidal metal spheres are packed substantially intimately, thereby forming a vertical conductive path. In another embodiment, the colloidal metal spheres are partially packed closely together, thereby forming a vertical conductive path when pressed. The colloidal metal spheres can be pressed with a stylus or printhead.

In yet another embodiment, providing the protective layer may include coating the substrate with a substantially transparent radiation-responsive charge emitting material. In one embodiment, providing the protective layer may include coating the substrate with a substantially transparent photoresponsive charge emitting material. In another embodiment, providing the protective layer may include coating the substrate with a substantially transparent thermoresponsive charge emitting material. In yet another embodiment, providing the protective layer includes disposing a conductive material layer on a substrate and partially etching the layer to form an island array.

In another aspect, the invention relates to a method of addressing an electrostatically addressable display element, the method comprising steps (a)-(e). Step (a)
Then, an electrophoretic element is provided. The electrophoretic element includes a capsule, a dispersion fluid having a first optical property in the capsule, and at least one electrophoretically movable particle disposed in the capsule. The at least one electrophoretically movable particle has a second optical property different from the first optical property;
The at least one electrophoretically movable particle may change its position within the capsule under the influence of an applied electric field. The visual appearance of the display element changes as the at least one electrophoretically movable particle in the capsule moves. Steps (b)-(e) provide (b) a protective layer disposed adjacent to the capsule, wherein the protective layer is adapted to transfer charge. c) providing a first electrode disposed adjacent to the capsule; (d) arranging an address electrode adjacent to the protective layer; and (e) connecting the address electrode to the first electrode. Activating the electrophoretic element with the electrodes to cause the electrophoretic element to be addressed between the first electrode and the address electrode to address the electrophoretic element; Exposing to a selected one of the following. The method of addressing the display may include addressing with an electrostatic printhead having a first electrode.

In one embodiment, step (b) comprises providing an insulating material layer having a plurality of conductive structures disposed therethrough, and step (e) comprises providing the address electrode Activating the first electrode and the conductive structure to address the electrophoretic element, wherein the first step is performed between the first electrode and the conductive structure. This is done by contacting at least one of the conductive structures so as to apply a selected one of an applied electric field and the second applied electric field.

In another embodiment, step (b) comprises providing a material layer having a higher resistance region and a lower resistance region, wherein the lower resistance region is an island adjacent to the electrophoretic element And the higher resistance region has at least one pinhole therethrough, the at least one pinhole providing access to the island of the at least one higher conductive material. And step (e) includes activating the address electrode together with the first electrode,
The activating step is selected from the first applied electric field and the second applied electric field generated between the first electrode and the at least one island to address the electrophoretic element. This is done by discharging the charge passing through the at least one pinhole so as to apply one more.

In another embodiment, the present invention provides a display, the display comprising an electrophoretic display element capable of changing its appearance in response to an electric field, and a protection secured to the display element. A protective layer adapted to avoid mechanical damage to itself and capable of transferring charge to said display element. Preferably, the display element is substantially laminar, has opposing first and second surfaces, and a protective layer is fixed to both the first and second surfaces. .

DETAILED DESCRIPTION OF THE INVENTION It is an object of the present invention to have a long lasting, good flexibility, easy to manufacture and low power consumption (or power consumption in the case of a bistable display). It is therefore an object of the present invention to provide a reflective display which can be incorporated into various applications. The present invention features an apparatus and method for providing an electrophoretic display that includes an encapsulated electrophoretic display medium and a protective electrode, thereby reducing display degradation caused by mechanical and electrochemical effects, The life of the electrophoretic display can be extended.

When the word “print” is used, it is intended to include all forms of prints and coatings, including, but not limited to, a premetered coating (eg, a patch die coating). Slot or extrusion coating, slide or cascade coating, and curtain coating), roll coating (eg, knife over roll coating, forward and reverse roll coating), gravure coating, dip coating, spray coating, meniscus coating, spin coating, Brush coating, air knife coating, silk screen printing, electrostatic printing, thermal type There are printing processes, and other similar techniques. Thus, the resulting display can be flexible. Further, since the display medium is printable (using various methods), the display itself can be manufactured at low cost.

In general terms, the present invention provides a flexible reflective display that is easy to fabricate and consumes low power (or consumes no power for certain states of bistable displays). Such encapsulated electrophoretic displays and materials and methods useful in constructing such displays. Therefore, such a display can be used for various applications. The display is formed from and may include particles that move in response to a charge. This mode of operation is typical in the field of electrophoresis. On the display,
The particles can be ordered by charge, take a particular configuration, and the display can take a variety of forms. After the electric field is removed, the particles can be generally stable (eg, bistable)
. Further, when a charge is applied thereafter, the particle configuration up to that time may change. Some encapsulated electrophoretic displays may include two or more different types of particles. Such displays can include, for example, displays that include a plurality of anisotropic particles and a plurality of second particles in a suspending fluid. When the first electric field is applied,
These anisotropic particles can have a particular orientation and exhibit optical properties. Next, when a second electric field is applied, the plurality of second particles move, whereby the anisotropic particles lose their orientation and the optical properties are dispersed. Alternatively, this orientation of the anisotropic particles may allow the plurality of second particles to move more easily. These particles may have a refractive index that substantially matches the refractive index of the suspending fluid.

An encapsulated electrophoretic display can be constructed such that the optical state of the display is stable for a particular time. The display is in this stable form 2
If it has two states, the display is bistable. Display 2
If one or more states are stable, the display is polystable. For the purposes of the present invention, the term bistability refers to a display in which any optical state remains constant after the address voltage has been removed. However, the definition of the bistable state depends on the application of the display. If the optical state does not substantially change over the required viewing time, the slow-decaying optical state is completely bistable. For example, for a display that is updated every few minutes, a display image that is stable for hours or days is completely bistable for a particular application. Thus, for the purposes of the present invention, the term bistable also refers to a display that has a sufficiently long-lived optical state to be completely bistable for a particular application.
Alternatively, it is possible to construct an encapsulated electrophoretic display (ie, a display that is not bistable or multi-stable), where the image rapidly decays after the address voltage to the display is removed. Whether an encapsulated electrophoretic display is bistable and the degree of bistability depends on the size of the electrophoretic particles, the suspension fluid,
It can be controlled by subjecting the capsule and binder materials to appropriate chemical changes.

An encapsulated electrophoretic display can take a variety of forms. The display may include a capsule dispersed in a binder. Capsules can be of any size or shape. Capsules can be, for example, spherical and have a diameter in the millimeter or micron range, but are preferably from about 10 to about several hundred microns.
Capsules can be formed using encapsulation techniques. The particles can be encapsulated. The particles may be one or more different types of particles. The particles can be, for example, colored, luminescent, light absorbing or transparent. The particles may comprise, for example, neat pigments, dyed (lake) pigments or pigment / polymer composites. The display may further include a suspending fluid for dispersing the particles.

In general, an encapsulated electrophoretic display comprises a capsule having one or more types of particles, which are either light absorbing or light scattering,
Suspended in a fluid. One example is a system having a capsule containing one or more types of electrophoretically mobile particles dispersed in a stained suspension fluid. As another example, a capsule suspends two distinct types of particles in a clear suspending fluid, one particle is absorbing (black) and the other is light scattering (white). There are systems with certain capsules. There are also other modifications (eg, use or no use of more than one type of particle, dye). These particles are generally solid pigments, dyed particles, or pigment / polymer composites.

In an electrophoretic display, particles can be oriented or moved by applying an electric field to the capsule. The electric field may include an alternating or direct electric field. The electric field may be provided by at least one pair of electrodes located adjacent to the display containing the capsule.

Successful fabrication of an encapsulated electrophoretic display requires all appropriate interactions of these materials and processes. Macromolecular binders (eg, for binding the capsule to the substrate), electrophoretic particles, fluids (eg, surrounding the electrophoretic particles and providing a medium for migration), and (eg, electrophoretic particles and fluids) All of the materials, such as the encapsulation (to encapsulate the encapsulant) must be chemically compatible. The capsule skin may effect useful surface interactions with the electrophoretic particles or may act as an inert physical interface between the fluid and the binder. The polymeric binder can act as an adhesive between the capsule skin and the electrode surface.

The materials used to make the electrophoretic display relate to, but are not limited to, the type of material used in manufacturing the display, including particles, dyes, suspending fluids, and binders. In one embodiment, the types of particles that can be used to make a suspended particle display include scattering pigments, absorbing pigments, and luminescent particles. Such particles can also be transparent. Exemplary particles include, for example, titania, which can be coated with one or more layers of a metal oxide, such as aluminum oxide or silicon oxide. Such particles can be configured as corner cubes. The luminescent particles can include, for example, zinc sulfide particles. Zinc sulfide particles
It can also be encapsulated with an insulating coating to reduce conductivity. The light-shielding particles or light-absorbing particles may include, for example, a dye or a pigment. The types of dyes used in electrophoretic displays are generally known in the art. Useful dyes are usually soluble in the suspending fluid and may be part of a polymer chain. Dyes can be polymerized by heat treatment, photochemical treatment, and chemical diffusion treatment. A single dye or a mixture of dyes may also be used.

[0036] The suspending (ie, electrophoretic) fluid can be a high resistance fluid. The suspending fluid may be a single fluid or a mixture of two or more fluids. The suspending fluid, whether a single fluid or a mixture of fluids, can have its density substantially matched to the density of the particles within the capsule. The suspending fluid can be, for example, a halogenated hydrocarbon such as tetrachloroethylene. Halogenated hydrocarbons can also be low molecular weight polymers. One such low molecular weight polymer is poly (chlorotrifluoroethylene). The degree of polymerization of the polymer may be from about 2 to about 10.

Further, the capsule may be formed in a binder, or may be later dispersed in the binder. Materials used as binders include water-soluble polymers, water-dispersible polymers, oil-soluble polymers, thermosetting polymers, thermoplastic polymers, and ultraviolet or radiation curable polymers. The materials used as the substrate to support the electrophoretic display and the electrodes for addressing must also be compatible with the materials and processes described above.

Although an example using an encapsulated electrophoretic display has been described here, other well-functioning encapsulated suspended particles and a rotating ball display (rotat
There are particle-based display media, including ing ball displays. Other display media such as liquid crystals and magnetic particles may also be useful.

In some cases, a separate encapsulation step of the process is not required. The electrophoretic fluid may be directly dispersed or emulsified in a binder (or a precursor of the binder material) to form a so-called “polymer dispersed electrophoretic display”. In such a display, the individual electrophoretic phases may be referred to as capsules or microcapsules, even if no capsule coating is present. Such a polymer dispersed electrophoretic display is considered as a kind of encapsulated electrophoretic display.

In an encapsulated electrophoretic display, a binder material surrounds the capsule and
Separate the two bounding electrodes. The binder material must be compatible with the capsule and the bounding electrode and have properties that allow for smooth printing or coating. It may also have barrier properties to water, oxygen, ultraviolet light, electrophoretic fluid, or other materials. In addition, it can include surfactants and crosslinkers, which can aid in coating or durability. Polymer dispersed electrophoretic displays may be emulsified or phase separated.

The electronic ink contains at least two phases. That is, an electrophoretic contrast media phase
hase), and an optoelectronically active material, including a coating / binding phase. The electrophoretic phase, in certain embodiments, is a single species of electrophoretic particles dispersed in a transparent or colored medium, or electrophoresis having unique physical and electrical characteristics dispersed in a transparent or colored medium. Contains multiple species of particles. In some embodiments, the electrophoretic phase is encapsulated. That is, there is a capsule wall phase between the two phases. The coating / binding phase, in one embodiment, comprises a polymeric matrix surrounding the electrophoretic phase. In this embodiment, the polymer in the polymer binder may be dry, cross-linkable, or cured like conventional inks. Therefore, a printing process can be used to deposit electronic ink on the substrate. Electronic inks can be printed by several different processes, depending on the mechanical properties of the particular ink used. For example, different processes may be selected depending on the brittleness or viscosity of a particular ink. Very viscous inks are not suitable for deposition by an inkjet printing process, while brittle inks may not be used in a knife over roll coating process.

The optical quality of electronic ink is quite different from other electronic display materials. The most notable difference is that electronic inks are pigment-based (similar to normal printing inks), so both reflectivity and contrast are high. Light scattered from the electronic ink enters from a very thin layer of pigment near the top of the viewing surface. In this respect, it is similar to a normal print image. Also, electronic ink, like printed pages, is easily seen from a wide viewing angle. Such an ink approximates the Lambertian contrast curve closer than any other electronic display material.
Because electronic inks can be printed, they can be included on the same surface with any other printing material, including conventional inks. Electronic inks can be optically stable in all display configurations. That is, the ink can be in an optical state continuously. Manufacturing displays by printing electronic ink is particularly useful for low power applications because of this stability.

Electronic ink displays are novel in that they are addressed by a DC voltage and draw a small amount of current. Thus, the conductive leads and electrodes used to apply voltage to electronic ink displays have relatively high resistivity.
The ability to use resistive conductors substantially expands the number and types of materials that can be used as conductors in electronic ink displays. In particular, the use of expensive vacuum sputtered ITO conductors, a standard material in liquid crystal devices, is not required. Apart from cost savings, replacing ITO with other materials offers advantages in appearance, throughput (printed conductors), flexibility, and durability. Also, the printed electrodes are in contact only with a solid binder, not with a fluid layer (such as liquid crystal). This involves dissolving some conductive materials in contact with the liquid crystal,
Or it decomposes, but it means that it can be used for applications using electronic ink. These include opaque metallic inks (eg, silver and graphite inks) used for the back electrode, as well as conductive transparent inks used for either substrate. These conductive coatings include, for example, semiconductor colloids such as ITO and antimony-doped tin oxide. Organic conductors (polymeric and molecular organic conductors) can also be used. The polymer includes polyaniline and its derivatives, polythiophene and its derivatives, poly 3,4-ethylenedioxythiophene (PEDOT) and its derivatives, polypyrrole and its derivatives, and polyphenylenevinylene (PPV) and its derivatives. , But is not limited to this. Organic molecular conductors include, but are not limited to, derivatives of naphthalene, phthalocyanine, and pentacene. The polymer layers are thinner and more transparent than those used in conventional displays because the required electrical conductivity is less stringent.

One example is a class of materials called electrically conductive powders that are also useful as transparent conductors that can be coated in electronic ink displays. One example is DuPont Chemical Co. of Wilmington, Delaware. Z
elect ECP electrically conductive powder.

Referring now to FIGS. 1A, 1B, and 1 C, an addressing mechanism for controlling a particle-based display in which electrodes are located on opposite sides of the display, enabling addressing of the display, according to the present invention. Show. The top electrode can be manufactured from a transparent conductive material such as ITO, which allows the state of the display element to be observed via the top electrode.

FIG. 1A shows a single capsule 20 of an encapsulated display element.
Briefly, the embodiment shown in FIG. 1A includes a capsule 20 containing at least one particle 50 dispersed in a suspending fluid 25. Capsule 20 is addressed by first electrode 30 and second electrode 40. Either or both of the electrodes 30, 40 can be transparent conductive electrodes. In one embodiment, the first electrode 30 is located above the display element capsule 20 while the second electrode 40 is located below the display element capsule 20. The first electrode 30 and the second electrode 40 can be set to a potential that affects the position of the particles 50 within the capsule 20.

The particles 50 correspond to between 0.1% and 20% of the volume enclosed by the capsule 20. In some embodiments, particles 50 represent between 0.1% and 10% of the volume enclosed by capsule 20. In a preferred embodiment, particles 50 represent 0.5% to 10% of the volume enclosed by capsule 20. In a further preferred embodiment, the particles 50 represent between 1% and 5% of the volume defined by the capsule 20. In general, the percentage of the volume of the capsule 20 that the particles 50 represent should be selected to provide a noticeable visual effect when the particles 50 are located on top of the capsule 20. As described in more detail below, particles 50 may have any one of a number of optical properties, such as color, reflectivity, retroreflectivity, and emission. Particles 50 can be either positively charged or negatively charged.

The particles 50 are dispersed in the dispersion fluid 25. This dispersion fluid 25 must have a low dielectric constant. Fluid 25 may be transparent or substantially transparent, so that fluid 25 does not prevent viewing particles 50 and lower electrode 40 from location 10.
In another embodiment, the fluid 25 is colored. In some embodiments, the dispersion fluid 25 has a specific gravity that matches the density of the particles 50. The particles 50 are
These embodiments may provide a bi-stable display medium because the electric field applied through zero tends to not move in certain compositions that are not present.

The proper size and position of the electrodes 30, 40 allow addressing of the entire capsule 20. Exactly one pair of electrodes 30, 40 for one capsule 20, or several pairs of electrodes 3 for one capsule 20
Although there may be 0,40, a pair of electrodes 30,40 may span multiple capsules 20. In the embodiment shown in FIGS. 1A-1C, the capsule 20 has a flat, rectangular shape. In these embodiments, the electrodes 30, 40 are the electrodes 3
Address most or all of its flat surface portion adjacent to 0,40.

The electrodes 30 can be made of any material capable of conducting current,
, 40 may apply an electric field to the capsule 20. 1A-1C, the electrodes 40 can be manufactured from opaque materials such as solder paste, copper, copper-coated polyimide, graphite ink, silver ink, and other metal-containing conductive inks. is there. The electrode 30 can be manufactured using a transparent material such as ITO and a conductive polymer such as polyaniline or polythiophene. The electrode 40 can also be manufactured using a transparent material. Electrode 40 may be provided with contrasting optical properties. In some embodiments, electrode 40 has optical properties that are complementary to the optical properties of particles 50.

In one embodiment, the capsule 20 comprises black particles 50 with a positive charge,
And a colored suspension fluid 25. The upper electrode 30 is transparent, and the lower electrode 40 is opaque. When the upper electrode 30 is applied at a negative potential with respect to the lower electrode 40, the positively charged particles 50 move to the upper electrode 30. The effect on the observer of the capsule 20 at the position 10 is a capsule having a surface covered with black particles 50, which produces the effect that most are black. Referring to FIG. 1B, when the upper electrode 30 is applied at a positive potential with respect to the lower electrode 40, the particles 50 move to the lower electrode 40, and to the observer, via the transparent upper electrode 30. The view of the colored suspension fluid 25 that is observed is visible, producing the effect that the majority of the appearance is of the colored suspension fluid 25. Similarly, capsule 20 may be addressed to indicate either the visible state characteristic of colored fluid 25 or the black visible state.

Other two-color configurations are easily provided by changing the color of the suspension fluid 25 and the particles 50. For example, changing the color of the suspension fluid 25 allows for the manufacture of a two-color display where one color is black. Alternatively, changing the color of the particles 50 allows for the production of a two-color system, one of which is the color of the colored suspension fluid 25. In certain embodiments, particles 50 exhibit bistability. That is,
In the absence of an electric field, it is substantially stationary.

Another alternative embodiment is that when a first potential is applied across electrodes 30 and 40, one of the species, eg, particles 50, moves toward upper electrode 30. , When a second potential is applied across electrodes 30 and 40, two different colors, and two, so that another species of particles, 50 ′, moves toward upper electrode 30.
It can be configured with two species of particles 50, 50 'having two different electrophoretic mobilities. For example, a first species of particles 50 may be black and have a positive charge, while a second species of particles 50 'may be white and have a negative charge. In such an embodiment, when the upper electrode 30 is held at a more positive potential than the electrode 40, the white negative particles 50 'move toward the upper electrode 30, and the black positive particles 50 In order to move toward the lower electrode 40, the particles 5
It has a white visual appearance characteristic of 0 '. When the upper electrode 30 is held at a more negative potential than the electrode 40, the white negative particles 50 'move toward the lower electrode 40, and the black positive particles 50 move toward the upper electrode 30. The capsule has the black visual appearance characteristics of the particles 50 for movement. In other two-color embodiments, the selection of appropriate colors for the positive and negative particles allows for the realization of an electrophoretic element that can display the desired two colors.

Referring now to FIGS. 2A and 2B, an addressing mechanism for control of a particle-based display is shown, in which electrodes are located on only one side of the display, thereby allowing for rear addressing of the display. Utilizing only one side of the display for the electrodes simplifies the manufacture of the display. For example, if the electrodes are located only behind the display, both electrodes can be manufactured using an opaque material because the electrodes need not be transparent.

FIG. 2A shows a single capsule 20 of an encapsulated display medium. Briefly, the embodiment shown in FIG. 2A has at least one dispersed in a suspending fluid 25.
And a capsule 20 containing two particles 50. The capsule 20 includes a first electrode 30
And the second electrode 40. The first electrode 30 is connected to the second electrode 4
Less than 0. The first electrode 30 and the second electrode 40 can be set to a potential that affects the position of the particles 50 within the capsule 20.

The particles 50 correspond to 0.1% to 20% of the volume enclosed by the capsule 20. In some embodiments, particles 50 represent between 0.1% and 10% of the volume enclosed by capsule 20. In a preferred embodiment, particles 50 represent 0.5% to 10% of the volume enclosed by capsule 20. In a more preferred embodiment, the particles 50 represent between 1% and 5% of the volume defined by the capsule 20. Generally, the percentage of the volume of capsule 20 indicated by particles 50 is
It is selected to expose most of the second large electrode 40 when 0 is located above the first small electrode 30. As described in more detail below, the particles 50 may be colored in any one of a number of colors. Particles 50 can be either positively charged or negatively charged.

The particles 50 are dispersed in the dispersion fluid 25. This dispersion fluid 25 has a low dielectric constant. Because the fluid 25 is transparent or substantially transparent, the fluid 25 does not prevent viewing of the particles 50 and the electrodes 30, 40 from the location 10. In another embodiment, the fluid 25 is colored. In some embodiments, the dispersion fluid 25 comprises
It has a specific gravity adapted to the density of the particles 50. These embodiments can provide a bistable display medium because the particles 50 tend not to move in certain compositions, in the absence of an electric field applied through the electrodes 30,40.

The proper size and location of the electrodes 30, 40 together allow addressing of the entire capsule 20. Exactly one pair of electrodes 30, 40 for one capsule 20, or several pairs of electrodes 30, 4 for one capsule 20
0 may be present, but a pair of electrodes 30, 40 may span multiple capsules 20. In the embodiment shown in FIGS. 2A and 2B, the capsule 20 has a flat, rectangular shape. In these embodiments, the electrodes 30, 40 are
, 40 address most or all of its flat surface portion. The small electrode 30 is at most half the size of the large electrode 40. In a preferred embodiment, the small electrode is one-fourth the size of the large electrode 40, and in a more preferred embodiment, the small electrode 30 is one-eighth the size of the large electrode 40. In an even more preferred embodiment, the small electrode 30 is one sixteenth the size of the large electrode 40. The expression “small” with respect to the electrode 30 means that the electrode 30 addresses a smaller area of the surface portion of the capsule 20 and does not necessarily mean that the electrode 30 is physically smaller than the large electrode 40. Note that it is not. For example, even if both electrodes 30, 40 were the same size, multiple capsules 20 could be arranged such that a smaller area of each capsule 20 would be addressed by “small” electrodes 30. As shown in FIG. 2C, the electrode 30 requires that the large electrode 40 surround two sides of the small electrode 30 in order to properly address the capsule 20;
Note also that only a small corner of the rectangular capsule 20 (shown in phantom in FIG. 2C) can be addressed. Thus, the selection of the volume percentage of particles 50 and electrodes 30, 40 allows the encapsulated display media to be addressed as follows.

Since the electrodes can be made from any material capable of conducting an electric current, the electrodes 30,
40 may apply an electric field to the capsule 20. As described above, according to the rear address embodiment shown in FIGS. 2A and 2B, the electrodes 30, 40 are solder paste, copper,
It can be manufactured from opaque materials such as copper-coated polyimide, graphite ink, silver ink, and other metal-containing conductive inks. Alternatively, the electrodes can be manufactured using a transparent material such as ITO and a conductive polymer such as polyaniline or polythiophene. The electrodes 30, 40 can be provided with contrasting optical properties. In some embodiments, one of the electrodes has an optical property that is complementary to the optical property of particle 50.

In one embodiment, the capsule 20 comprises black particles 50 with a positive charge,
And a substantially transparent suspending fluid 25. The first small electrode 30 is colored black and colored white, or smaller than the second electrode 40 having a high reflectance. When the small black electrode 30 is applied at a negative potential with respect to the large white electrode 40, the positively charged particles 50 move to the small black electrode 30. The effect of the capsule 20 at the position 10 on the observer is large white electrode 40.
And the small black electrode 30, which produces an effect that the majority is white.
Referring to FIG. 2B, when the small black electrode 30 is applied at a positive potential with respect to the large white electrode 40, the particles 50 move to the large white electrode 40 and give the observer a large white electrode. The mixture of the black particles 50 covering the electrode 40 and the small white electrode 30 can be seen, producing an effect that most of the particles are black. In this way, capsule 20 may be addressed to display either a white visible state or a black visible state.

Other two-color configurations are easily provided by changing the color of the small electrode 30 and the particles 50, or changing the color of the large electrode 40. For example, changing the color of the large electrode 40 allows the manufacture of a rear address two-color display where one color is black. Alternatively, changing the colors of the small electrodes 30 and the particles 50 allows for the manufacture of a rear-addressed two-color system where one color is white. Further, it is contemplated that the particles 50 and the small electrodes 30 may be of different colors. In these embodiments, the two-color display may be manufactured to have a second color different from the colors of the small electrodes 30 and the particles 50. For example, a rear-addressed orange-white display may be fabricated by providing blue particles 50, red small electrodes 30, and white (or highly reflective) large electrodes 40. Generally, the electrodes 30, 40,
And the optical properties of the particles 50 can be independently selected to provide the desired display characteristics. In certain embodiments, the optical properties of the dispersion fluid 25 can be altered, for example, such that the fluid 25 can be colored.

In another embodiment, large electrode 40 may be reflective instead of white. In these embodiments, when the particles 50 move to the small electrode 30, the light
Reflecting from the reflective surface 60 associated with the large electrode 40, the capsule 20 appears as colored, for example, white light (see FIG. 3A). When the particles 50 move to the large electrode 40, the light is absorbed by the particles 50 before reaching the reflecting surface 60, so that the reflecting surface 6
0 appears cloudy and capsule 20 appears dark (see FIG. 3B). The reflection surface 60 for the large electrode 40 has a retro-reflection characteristic, a specular reflection characteristic, a diffuse reflection characteristic, or a gain reflection characteristic (g
ain reflective properties). In some embodiments, reflective surface 60 reflects light in a Lambertian distribution. The surface 60 includes a plurality of glass spheres disposed on the electrode 40, a diffraction reflection layer such as a holographically formed reflection plate, a surface patterned to totally reflect incident light, and a brightness enhancement film (
It can be a bright-enhancing film, a diffuse reflective layer, an embossed plastic or metal film, or any other known reflective surface. The reflective surface 60 may be provided as a separation layer laminated on the large electrode 40, or the reflective surface 60 may be provided integrally with the large electrode 40. In the embodiment shown in FIGS. 3C and 3D, the reflective surface is
It may be located below the electrodes 30,40. In these embodiments, electrode 30 is transparent so that light can be reflected by surface 60. In other embodiments,
Proper switching of the particles can be achieved by a combination of alternating current (AC) and direct current (DC) electric fields, as described below with respect to FIGS.

In yet another embodiment, the above-described rear address display may be configured for a transition between a mostly transparent mode of operation and a largely opaque mode of operation (hereinafter “shutter”). mode"). Referring to FIGS. 2A and 2B, in these embodiments, the capsule 20 includes at least one positively charged particle 50 dispersed in a substantially transparent dispersion fluid 25. Large electrode 40
Is transparent, and the small electrode 30 is opaque. When the small opaque electrode 30 is applied to a negative potential with respect to the large transparent electrode 40, the particles 50 move to the small opaque electrode 30. The effect of the capsule 20 at the position 10 on the observer is a mixture of the large transparent electrode 40 and the small opaque electrode 30, which produces an effect that is largely transparent. Referring to FIG. 2B, when the small opaque electrode 30 is applied at a positive potential with respect to the large transparent electrode 40, the particles 50 move to the second electrode 40 and provide the observer with a large transparent electrode. The mixture of the opaque particles 50 covering the electrode 40 and the small opaque electrode 30 is visible, producing the effect that the majority is opaque. Thus, a display formed using the capsule shown in FIGS. 2A and 2B can switch between a transparent mode and an opaque mode. Such a display can be used to create windows that can be opaque. 2A-3D show a pair of electrodes associated with each capsule 20, it should be understood that each pair of electrodes may be associated with more than one capsule 20.

A similar technique may be used in connection with the embodiments of FIGS. 4A, 4B, 4C, and 4D. Referring to FIG. 4A, capsule 20 contains at least one dark or black particle 50 dispersed in a substantially transparent dispersion fluid 25. The small opaque electrode 30 and the large transparent electrode 40 provide a direct current (DC) electric field and an alternating current (AC).
) Both electric fields are applied to the capsule 20. When a DC electric field is applied to the capsule 20, the particles 50 can move to the small electrodes 30. For example, when the particles 50 have a positive charge, a voltage is applied so that the small electrode is more negative than the large electrode 40. Although FIGS. 4A-4D show only one capsule for a pair of electrodes, multiple capsules can be addressed using the same pair of electrodes.

The small electrode 30 is large and half the size of the large electrode 40. In a preferred embodiment, the small electrode 30 is one-fourth the size of the large electrode 40, and in a more preferred embodiment, the small electrode 30 is one-eighth the size of the large electrode 40. In an even more preferred embodiment, the small electrode 30 is one sixteenth the size of the large electrode 40.

As shown in FIG. 4A, moving the particles 50 to the small electrode 30 allows incident light to pass through the large transparent electrode 40 and be reflected by the reflection surface 60. In the shutter mode, the reflective surface 60 is replaced by a translucent layer, or a transparent layer, or no layer is provided, allowing incident light to pass through the capsule 20 (ie, the capsule 20 is transmitted). Sex).

Next, referring to FIG. 4B, the particles 50 are transferred to the capsule 20 via the electrodes 30 and 40.
Are applied to the capsule 20 by applying an AC electric field. The particles 50 dispersed in the capsule 20 by the AC electric field prevent the incident light from passing through the capsule 20 and make the capsule 20 appear dark at the observation point 10. The embodiment shown in FIGS. 4A-4B does not provide a reflective surface 60, but instead can be used in a shutter mode by providing a translucent or transparent layer or providing no layer at all. . In the shutter mode, the capsule 20 appears opaque due to the application of an AC electric field. The transparency of the shutter mode display formed by the devices shown in FIGS. 4A-4D can be controlled by the number of capsules addressed using DC and AC electric fields. For example, a display where every other capsule 20 is addressed using an AC electric field would have a transmission of 50%.

FIGS. 4C and 4D show one embodiment of the above-described electrode structure in which the electrodes 30, 40 are “above” the capsule 20, ie, the electrodes 30, 40 are between the observation point 10 and the capsule 20. Is shown. In these embodiments, both electrodes 30, 40 are transparent. The transparent polymer can be manufactured using a conductive polymer such as polyaniline, polythiophene, or ITO. Since these materials can be soluble, the electrodes can be manufactured using coating techniques such as spin coating, spray coating, meniscus coating, printing techniques, forward and reverse roll coating, and the like. In these embodiments, the light is applied to the electrodes 30,
40, is absorbed by the particles 50, is reflected by the retroreflective layer 60 (if provided), or is transmitted throughout the capsule 20 (the retroreflective layer 6).
0 is not provided).

The address structures shown in FIGS. 4A-4D can be used with electrophoretic display media and encapsulated electrophoretic display media. 4A to 4D show electrodes 3
0, 40 show an embodiment where the display media is statically attached. In certain embodiments, particles 50 exhibit bistability. That is, in the absence of an electric field, the particles 50 are substantially stationary. In these embodiments, the electrode 3
0, 40 may be provided as part of a "stylus" or other device that is scanned over the material to address each capsule or chunk of capsules. This mode of addressing the particle-based display is described in further detail below with respect to FIGS.

Referring now to FIGS. 5A and 5B, an electrically addressable medium capsule 20 is shown in which the above-exemplified technique is used with a plurality of rear address electrodes. Capsule 20 includes at least one particle 50 dispersed within a clear suspending fluid 25. The capsule 20 is addressed by a plurality of small electrodes 30 and a plurality of large electrodes 40. In these embodiments, the small electrodes 30 should be selected to be collectively large and half the size of the large electrode 40. In a further embodiment, the small electrodes 30 are collectively one quarter the size of the large electrodes 40. In a further embodiment, the small electrodes 30 are collectively one-eighth the size of the large electrodes 40. In a preferred embodiment, the small electrodes 30 are collectively one sixteenth the size of the large electrodes. Each electrode 30 may be provided as a separate electrode that is controlled in parallel to control the display. For example, each individual electrode can be set substantially simultaneously to the same voltage as all other electrodes of that size. Alternatively, electrode 3
0, 40 may intertwine with each other to provide the embodiment shown in FIGS. 5A and 5B.

The operation of the rear address electrode structure shown in FIGS. 5A and 5B is similar to the operation described above. For example, the capsule 20 may be dispersed in a substantially transparent suspending fluid 25,
It may include positively charged black particles 50. The small electrode 30 is colored black and the large electrode 40 is colored white or highly reflective. Referring to FIG. 5A, small electrode 3
0 is applied to the negative potential with respect to the large electrode 40, causing the particles 50 to move in the capsule toward the small electrode 30. The capsule 20 has a large white electrode 4 at the observation point 10.
It appears as a mixture of 0 and a small black electrode 30, producing an effect that most are white. Referring to FIG. 5B, when the small electrode 30 is applied at a positive potential with respect to the large electrode 40, the particles 50 move to the large electrode 40, and the capsule 20 is closed by the black particles 50. By expressing the mixture of the white electrode 40 and the small black electrode 30, an effect is obtained in which the majority is black. The techniques for making a two-color display described above with respect to the embodiments shown in FIGS. 2A and 2B work equally well with these embodiments.

FIG. 6A is a schematic exploded perspective view of an electrophoretic display without a protective electrode immersed in a fluid to test the display for degradation. In this test, FIG.
A display having the general features represented by １1C is located with one end immersed in a fluid 95, such as water, that may contain dissolved ionic material contained in a glass container 90. The temperature is room temperature and the pressure is normal atmospheric pressure. The display is shown in exploded form for clarity, with electrode 40 closest to the viewer, capsule 20 adjacent electrode 40, and electrode 30 adjacent capsule 20. It should be understood that the contents of the capsule 20, ie, at least one particle 50 dispersed in the suspending fluid 25, are not shown, but are present. For testing purposes, electrode 40 is a transparent conductive electrode, for example, an ITO layer that can be supported on a substrate not shown. The electrode 40 has at least one
Exposed on the surface to the fluid 95, the electrodes 30 are also in electrical contact with the fluid. If a potential is applied from a power source (not shown) between the electrodes 30 and 40, the electrochemical process can degrade if the electrode 40 is biased as a cathode at a potential of 25 volts for 90 seconds. The degradation is shown as region 92. The degradation may be due to the reduction of the mixed metal oxide to a metallic state. The deterioration of the electrode 40 is visually observed as darkening, reduced transparency, or reduced transmittance of the electrode 40. Such degradation can cause a change in the appearance of the electrophoretic device,
If the degradation is severe, the device may be useless. The test is intended to simulate exposure of the electrode 40 to conditions that can cause electrophoretic degradation, such as exposure to high humidity or exposure to sea air, and observe the results.

After observing the detrimental effects of the test illustrated in FIG. 6A, an attempt is made to prevent the problem. FIG. 6B is a schematic exploded perspective view of an embodiment of an electrophoretic display having a protective electrode immersed in a fluid to test for improved display degradation, according to the present invention. The electrode 40 is again supported by an IT that can be supported on a substrate not shown.
It is a transparent conductive electrode such as an O layer. In this embodiment, an overcoating having a protective layer 45 is applied, the protective layer 45 comprising a metal such as nickel, palladium, platinum, ruthenium, rhodium, silver, aluminum, gold, titanium, chromium, and zinc, and an oxide. Silver (AgO), aluminum oxide (Al ₂ O ₃ ),
Gold (III) oxide (Au ₂ O ₃ ), titanium oxide (II) (TiO), titanium oxide (I
V) (TiO ₂ ), chromium (III) oxide (Cr ₂ O ₃ ), chromium oxide (VI) (
CrO ₃ ), zinc oxide (ZnO), nickel oxide (II) (NiO), palladium oxide (II) (PdO), platinum oxide (IV) (PtO ₂ ), ruthenium oxide (I
V) (RuO ₂ ) and at least one chemical composition selected from the group consisting of oxides such as rhodium (III) oxide (Rh ₂ O ₃ ). In particular, the protective layer 45 containing palladium is preferable. The protective layer 45 is, for example, 10 nanometers (n
It may be very thin, such as less than m). Such a layer can be applied by various processes such as evaporation, sputtering, metal deposition followed by oxidation, plating, electroplating, electroless metal deposition, or deposition of oxide from solution.

As shown in FIG. 6B, the electrode 40 overcoated with the protective layer 45 is
When immersed in the fluid (water) 95 contained in the container 90 and applying the same potential of 25 volts as the cathode for 90 seconds, the region 94 will correspond to the unprotected electrode 40 of FIG. 6A.
It is observed that the deterioration is much lower than the deterioration of the region 92 of FIG. Area 94 does not suffer from appreciable darkening or loss of transparency. Testing using immersion in a fluid 95 such as water is intended for accelerated testing under harsh conditions,
Represents accelerated test. For example, electrode 40 is not immersed in water, but also has a potential of 25.
The portion where volts are applied as cathode for 90 seconds has not been noticeably degraded. Under milder conditions (e.g., not immersed in water), the electrodes 40 protected by the overcoated protective layer 45 described above extend at a much better level than the corresponding unprotected electrodes 40. Expected to do that time.

Since a single protective layer 45 may be useful, a multi-layer protective structure may also be useful. FIG. 6C is a schematic side view of an embodiment of a protective electrode 100 having multiple layers according to the present invention. In FIG. 6C, electrode 40 is overcoated with two layers 42 and 44. Layers 42 and 44 may each include one or more materials selected from the group consisting of the metals and metal oxides listed above.
It is well known in the optical arts that a single layer functions as an anti-reflective coating on a lens. It is also known that enhanced anti-reflective coatings are often produced from multiple layers, each having the appropriate thickness and optical properties. In some cases, such coatings are applied to provide mechanical protection of the lens and enhance the optical properties of the lens. Here, the transparent conductive electrode 4
The 0 can be protected against both electrochemical and mechanical damage, such as scratches, by a suitable combination of multiple overcoating layers, such as layers 42 and 44. Also, the optical properties of the transparent conductive electrode 40 depend on the layers 42 and 44.
Can be adjusted or changed by a suitable combination of multiple overcoating layers.

Another problem observed relates to the effect of water vapor on electrophoretic device performance. During manufacturing and testing of many devices, high temperature and high humidity (60 ° C.)
And 95% relative humidity), the remaining time at 60 ° C. and low humidity (eg, 6-12 hours) may need to be significant before the device is normally switched on. It was noticed. Furthermore, it has been noted that device degradation occurs when exposed to harsh and humid conditions.

FIG. 7 is a schematic side view of an embodiment of an electrophoretic display having vapor permeable electrodes according to the present invention. FIG. 7 shows a front electrode 30, which may be an ITO layer deposited on a substrate such as polyester (PET). Adjacent to the electrode 30 is a layer of an electrophoretic display element comprising the capsule 20 and at least one particle 5
Each capsule 20 containing 0 (not shown) is dispersed in a suspending fluid 25 (not shown). The vapor permeable electrode 40 is provided adjacent to the electrophoretic display element capsule 20. The vapor-permeable electrode 40 has a net-like conductive structure. In one embodiment, the vapor permeable electrode 40 is a wire mesh. In other embodiments, the vapor permeable electrode 40 may be a mesh-like structure coated with a conductive material, such as a metal-coated plastic mesh, or the vapor permeable electrode 40 may be made of a metal. A network-like structure impregnated with a conductive material, such as a structure of impregnated paper, may be used. The vapor permeable electrode 40 allows the passage of vapor, such as water vapor, between the capsule 20 and the atmosphere, so that the concentration of water at and within the capsule 20 does not increase or decrease. To be observed.

Many unlaminated samples of the dispersion, stored under the same conditions (60 ° C. and 95% relative humidity), showed no degradation and were not exposed to a dry environment at 60 ° C. If it is kept in a humid room temperature for less than an hour, it will recover enough to turn it on. It is decided to produce a stacked device that achieves the phenomenon of high permeability to water vapor. The test uses an electrode structure made from copper and bronze screens and uses conductive paper (eg, coated with a thin metal layer, IP
This is done using a dispersion of conductive metals and metal oxides in a polymerized film such as CD-100 or a siliconized paper such as phase-separation paper. A standard resin binder is used to disperse the microcapsules 20 and a "topcoat" of the same resin is used to shield the electrodes from intimate contact with the microcapsules 20.

Compared to a standard device made from a microcapsule dispersion laminated between two 4 ml thick polyester (PET) substrates, the device with one highly permeable electrode has a lower exposure to humidity. The recovery is much faster and the quality is substantially less degraded in the same time.

The back electrode can also be made from cellulose hydrophilic paper treated with a crosslinked resin or cellophane. Both of these materials are coated with a conductive material, such as CD100, polypyrrole or similar functional materials. A typical configuration is shown in FIG.

The electronic display device of the present invention includes an electronic display medium, a first electrode adjacent to the medium, and a second electrode adjacent to the medium. The second electrode is made of a material having high permeability to water vapor. In one embodiment of the invention, the second electrode is a siliconized paper. In another embodiment of the present invention, the second electrode is a metal screen, preferably a copper screen or a bronze screen. In other embodiments, the second electrode comprises a thin layer of a conductive metal or metal oxide dispersed in a polymeric binder, such as, for example, CD100 located on paper. In another embodiment, the second electrode also includes a thin layer of polypyrrole.

The method of manufacturing an electronic display device according to the present invention comprises: (a) providing a first electrode; (b) arranging a display medium adjacent to the first electrode; and (c) And b) placing a second electrode adjacent to the display medium. The second electrode is manufactured from a material having high permeability to water vapor.
In an embodiment of the present invention, step (a) comprises providing a first electrode having high permeability to water vapor. In one embodiment, the second electrode is a metal screen, preferably a copper screen or a bronze screen. In another embodiment, the second electrode is a siliconized paper. The paper is preferably treated with a conductive metal or metal oxide dispersed in a polymeric binder, such as, for example, CD100.

It is known in the art that electrophoretic display media can be moved by an electrophoretic printhead, including a rechargeable or connected stylus, or other pointing device. Although the use of a moveable printhead offers some advantages, there are also problems associated with the mechanical interaction of the addressable printhead and the display.

A problem with this approach is that the electrophoretic media of the display is scraped or damaged when exposed to possible contact with a moveable printhead. Intervening coatings or plastic layers can be introduced, but intervening layers can be problematic. If the layer has high resistivity, it acts as a dielectric and reduces the amount of electric field experienced by the electrophoretic medium. If the layer is conductive, the charge generated on the surface by the printhead can spread in the X and Y dimensions to neighboring areas, interfering with the sharp image created.

In one approach, conductive islands, such as square pixels, are arranged on the surface of the intervening layer. As the printhead touches each conductive island, a charge that lasts for some time is transferred. This allows the electrophoretic display media to experience weaker field effects for longer periods of time.

The present invention nonetheless uses an intervening layer that allows charge to be transferred to the electrophoretic medium in a manner that allows for increased image sharpness compared to current approaches. Consisting of

FIGS. 8A-8G, described separately below, illustrate various implementations of a protective layer adapted to be used with an addressing device that may be movably positioned adjacent to an electrophoretic display according to the present invention. It is the schematic of a form. FIG. 8A is a schematic perspective view of an embodiment of an electrophoretic display that includes a protective layer 110 with an addressing device 120, such as a printhead, that can be movably positioned adjacent to the electrophoretic display according to the present invention. The addressing device 120 comprises one or more electrodes 1 that may be arranged to address at least one electrophoretic display element.
22. Address device 120 may operate electrostatically, may operate electrodynamically, may operate using ionography, or may operate optically, as described below. May work. The display comprises a protective layer 110 adjacent to at least one capsule 20. FIG. 8A illustrates a layer of such a capsule 20. Each capsule 20 includes at least one particle 50 (not shown) dispersed in a suspending fluid 25 (not shown). Adjacent to the layer of capsule 20 is an electrode 40, and adjacent to electrode 40 is a substrate 46. 1
If one or more electrodes 122 are correctly located, the electric field resulting from the signal applied between electrodes 40 and 122 may be applied to one or more capsules 20 and capsule 2
Addressing 0 causes the visual state of the capsule 20 to change. With this schematic description of the method of operation of this type of addressable display in mind, various embodiments of the protective layer 110 that may be used in the present invention may be considered.

FIG. 8B is a schematic perspective view of an embodiment of a protective layer having two regions 112 and 114 of different resistivity and conductivity according to the present invention. In one aspect, the protective layer is composed of a material exhibiting anisotropic properties. Such a material may be a sheet of plastic with conductive elements embedded vertically during construction.
The elements may be relatively large, such as in a Z-strip configuration, or quite small, such as small rods of conductive material. Such an element may be opaque when presented visually in an edge direction that is barely visible to the user, no matter how suitable it is for such material to be invisible.

FIG. 8C is a schematic side view of a protective layer 110 having a first electrical conductivity and having a conductive object 116 having a greater electrical conductivity extending through the protective layer 110 according to the present invention. The electrostatic addressing head 120 may contact one or more conductive objects 116, which may be conductive pins or wires,
An electric field is applied across one or more capsules 20 located between and capsule 40.

FIG. 8D shows 117 having the first conductivity and extending through the protective layer according to the present invention.
Protective layer 110 having a region 118 with greater conductivity interconnected with
FIG. 3 is a schematic side view of the embodiment of FIG. In another aspect, the protective layer 110 is a single relatively conductive layer of a polymeric material such as Mylar,
18 contacts (or is in electrical communication with) the electrophoretic capsule 20
It is printed and arranged on one surface.

FIG. 8E is a schematic side view of an embodiment of a protective layer having a first conductivity and having vias 119 or holes extending through the protective layer 110 according to the present invention.
In the system described above, one or more through holes 119 or vias may be introduced so that charge from the printhead 120 can easily migrate through the intervening layer 110 and communicate with the conductive island 118. An example of such a configuration includes making a number of pinholes 119 in the intervening protective layer 110 and then printing a conductive island 118 using a transparent conductor. In one approach, the transparent conductor enters the pinhole 119 by gravity or pressure and the local via 11
9 is formed and set. In another approach, vias 119 are filled with different conductive materials by other processes, and again, conductive vias 119 are formed in all or most of the holes that can communicate with conductive islands 118. .

In yet another approach, the pinhole is wide enough so that the passing printhead 120 can actually enter the hole 119 and contact the conductive island 118. In one embodiment, the pinholes are arranged in a grid-like pattern and the electrostatic printhead 120 has protrusions that fit into the pattern and enter the pinhole 119 to transfer charge to the conductive islands 118. Have. In another example, the printhead 120 may include a plurality of conductive needles 12 on a spring that contact and enter the conductive island 118 as the needle 122 passes through the hole 119.
Consists of two. In another example, the print head 120 is itself very resilient, and when pressing on the intervening layer 110, temporarily extends and enters the hole 119,
The charge is transmitted to the conductive island 118. Similarly, if the electrophoretic display media and conductive island material are sufficiently resilient, they may be pushed into contact with printhead 120.

In another approach, ions can be delivered by the printhead 120 using ionography and strike the intervening protective layer 110 without visual effects. If the beam of ions is in line with the pinhole 119, the charge is successfully transferred to the conductive island 118. The ions may be generated as is known in the art, for example, by a printhead 120 using suitable ionography.

When the term pinhole 119 is used above, it is clear that any dimensional hole that serves the purpose can be employed.

In another approach, the substantially transparent intervening protective layer 110 is coated with a sufficiently bright light source or a substantially transparent material that releases charge when given a particular wavelength. This side is placed in contact with the electrophoretic display medium. A light emitting device (instead of printhead 120) is used to project the media. Similarly, the intervening protective layer 110 can be coated with a material that releases charge when exposed to a heat source, and a suitable heat source is used to project the medium. In such cases, islands of excitable material may also be used as appropriate.

FIG. 8F illustrates an associated interconnect 132 and three islands 130 having a higher conductivity that have a first conductivity and extend through the protective layer 110 according to the present invention.
FIG. 4 is a schematic side view of an embodiment of a protective layer 110 having a region with More conductive material may be placed on the island, surrounded by less conductive material. Thus, the electrostatic printhead 120 primarily activates the ink under the separate island 130. In this manner, the protective layer 110, when activated by the electrostatic printhead 120, can be organized into an array of regions that form a visible array of pixels. Alternatively, the same intervening material can be used throughout the medium, but this material is doped with a conductivity enhancer to create conductive islands.

FIG. 8G shows a protective layer according to the present invention having a region having an associated interconnect 132 and three islands 130 having a higher conductivity, having a first conductivity and extending through the protective layer. It is a schematic plan view of 110. The method of operation is the same as the method described above with respect to FIG. 8F.

FIG. 9 illustrates a “printer” similar to a sheet of paper, such as a conventional electrophotographic printer.
FIG. 8B is a view, similar to FIG. 8A, of an improved display of the present invention in the form of an electrically rewritable sheet that can be written and rewritten by the method. In the display of FIG. 9, the substrate 46 present in the display of FIG. 8A is similar to the protective layer 110, with a protective layer 110 ′ that can take any of the forms described with reference to FIGS. 8B-8G. Be replaced. The protective layer 110 'allows for the transfer of charge from the permanent electrodes mounted on the printer to the electrodes 40, which are otherwise obtained from a display that comes into contact with the permanent electrodes mounted on the printer. Protected from damage.

FIG. 10 shows a further improved display of the present invention, intended for use as a rewritable sheet that can be written and rewritten by a suitable printer, in a form similar to FIGS. 8A and 9. The figure is shown. The display of FIG. 10 includes a layer of capsule 20 disposed between protective layers 110 and 110 ', respectively, that allows transfer of charge from printheads 120 and 120' to the layer of capsule 20.

It is clear that conductive islands can also be formed in the above case by coating the entire sheet of protective layer 110 with a material and then etching or removing them to form islands. It is. Furthermore, Ward Island
land) should be taken to include stripes, rectangles, triangles, and various regions of any or random shapes and patterns.

In each of the island approaches described above, the islands can be arranged in a suitable pattern, such as a triad, for electrophoretic display media patterned into regions of different types of ink, such as different colors. Positioned. In this manner, for example,
The electrostatic printhead can operate cyan, magenta, and yellow electrophoretic displays to obtain color images.

Although the examples described herein have been described using an encapsulated electrophoretic display, other displays of particle systems that function similarly, including encapsulated suspended particles and a rotating ball display. There is a medium.

While the invention has been particularly shown and described with reference to certain preferred embodiments, those skilled in the art will depart from the spirit and scope of the invention as defined by the appended claims. Rather, it should be understood that various changes in form and detail may be made.

The invention is pointed out with particularity in the appended claims. The above and further advantages of the present invention may be better understood when the following description is read in conjunction with the accompanying drawings. In the drawings, like reference numbers generally indicate identical components from different perspectives. Also, these drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the present invention.

FIGS. 8A-8G, described separately below, illustrate various implementations of a protective layer adapted to use an addressing device that can be movably positioned adjacent to an electrophoretic display according to the present invention. It is the schematic of a form.

[Brief description of the drawings]

FIG. 1A is a schematic side view of an embodiment of an address electrode structure of a particle-based display element, wherein no electric field is applied to the display element, and particles are dispersed throughout the display element. I have.

FIG. 1B is a schematic side view of an embodiment of an address electrode structure of a particle-based display element, wherein a lower electrode is energized with respect to an upper electrode so that particles are applied to the lower electrode. I'm moving.

FIG. 1C is a schematic side view of an embodiment of an address electrode structure of a particle-based display element, wherein the lower electrode is energized with respect to the upper electrode, so that particles are applied to the upper electrode. I'm moving.

FIG. 2A is a schematic side view of an embodiment of an electrode structure of a particle-based display after addressing, wherein the small electrodes are energized relative to the large electrodes so that the particles are small. Have moved to.

FIG. 2B is a schematic side view of an embodiment of an electrode structure of a particle-based display after addressing, in which the large electrode has a voltage applied to the small electrode so that the particles are large. Have moved to.

FIG. 2C is a schematic top view of one embodiment of the electrode structure after addressing.

FIG. 3A is a schematic side view of an embodiment of an electrode structure after addressing, the electrode structure having a retroreflective layer integral with a large electrode, wherein a small electrode is attached to a large electrode. A voltage is applied to the electrodes, so that the particles move to the small electrodes.

FIG. 3B is a schematic side view of an embodiment of an electrode structure after addressing, the electrode structure having a retroreflective layer integral with a large electrode, wherein the large electrode is In contrast, a voltage is applied, and as a result, the particles are moving to the large electrode.

FIG. 3C is a schematic side view of an embodiment of an electrode structure after addressing, the electrode structure having a retroreflective layer integral with a large electrode, wherein a small electrode is attached to a large electrode. A voltage is applied to the electrodes, so that the particles move to the small electrodes.

FIG. 3D is a schematic side view of an embodiment of an electrode structure after addressing, the electrode structure having a retroreflective layer disposed below a large electrode, wherein the large electrode comprises a small electrode; Are applied to the electrodes, and as a result, the particles are moving to the large electrode.

FIG. 4A is a schematic side view of an embodiment of the addressing structure, wherein a DC electric field is applied to the capsule, resulting in particles moving to the small electrodes.

FIG. 4B is a schematic side view of an embodiment of the addressing structure, wherein an alternating electric field is applied to the capsule so that the particles are dispersed within the capsule.

FIG. 4C is a schematic side view of an embodiment of an addressing structure having a transparent electrode;
A DC electric field is applied to the capsule, causing the particles to move to the small electrodes.

FIG. 4D is a schematic side view of an embodiment of an addressing structure having a transparent electrode;
An alternating electric field is applied to the capsule so that the particles are dispersed within the capsule.

FIG. 5A is a schematic side view of an embodiment of an electrode structure of a particle-based display after addressing, wherein a plurality of small electrodes are energized to a plurality of large electrodes; Particles are moving to the small electrode.

FIG. 5B is a schematic side view of an embodiment of an electrode structure of a particle-based display after addressing, wherein a plurality of large electrodes have a voltage applied to a plurality of small electrodes; Particles are moving to the large electrode.

FIG. 6A is a schematic exploded perspective view of an electrophoretic display without a protective electrode, the electrophoretic display being immersed in a fluid for the purpose of testing the display for degradation.

FIG. 6B is a schematic exploded perspective view of an embodiment of an electrophoretic display with a protective electrode, wherein the electrophoretic display is for the purpose of testing the display degradation with the improvement according to the present invention. Immersed in a fluid.

FIG. 6C is a schematic side view of an embodiment of a protection electrode according to the present invention.

FIG. 7 is a schematic side view of an embodiment of an electrophoretic display having a vapor permeable electrode according to the present invention.

FIG. 8A is a schematic perspective view of an embodiment of an electrophoretic display that includes a protective layer with an addressing device that can be movably positioned adjacent to the electrophoretic display according to the present invention.

FIG. 8B is a schematic perspective view of an embodiment of a protective layer having two regions of different resistivity and conductivity according to the present invention.

FIG. 8C is a schematic side view of an embodiment of a protection layer having a first conductivity and having an object having a greater conductivity extending through the protection layer according to the present invention.

FIG. 8D is a schematic side view of an embodiment of a protective layer according to the present invention, the protective layer having a first electrical conductivity and a greater electrical conductivity, and extending through the protective layer. And interconnected regions.

FIG. 8E is a schematic side view of an embodiment of a protection layer, according to the present invention, having a first conductivity and vias and holes through the protection layer.

FIG. 8F is a schematic side view of an embodiment of a protective layer according to the present invention, the protective layer having a first conductivity and associated interconnects extending through the protective layer. And an area with three islands having higher conductivity.

FIG. 8G is a schematic plan view of an embodiment of a protective layer according to the present invention, the protective layer having a first conductivity and associated interconnects extending through the protective layer. And an area with three islands having higher conductivity.

FIG. 9 shows a view of an embodiment of the present invention, similar to FIG. 8A, having a protective layer on both sides and intended for use with a printer.

FIG. 10 shows a diagram of another embodiment of the present invention, similar to FIGS. 8A and 9, intended for use with a printer.

──────────────────────────────────────────────────続 き Continued on the front page (31) Priority claim number 60 / 115,052 (32) Priority date January 8, 1999 (1999.1.8) (33) Priority claim country United States (US) ( 81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, TZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, R, CU, CZ, DE, DK, DM, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI SK, SL, TJ, TM, TR, TT, TZ, UA, UG, UZ, VN, YU, ZA, ZW (72) Inventor Dozaic, Paul United States Massachusetts 02420, Lexington, Lexington Ridge Drive 6234 (72) Inventors Kazulas, Peter Tea. United States Massachusetts 02446, Brookline, Washington Street 447 (72) Inventors Wilcox, Russell Jay. United States Massachusetts 01760, Natick, Winniemae Treat 17 (72) Inventor Finney, Robert United States Massachusetts 02066, Situation, Foxwell Lane 20

Claims (22)

[Claims] 1. A display comprising an electrophoretic display element (20) and an electrode (40, 110) adjacent to the display element (20), wherein the electrode (40, 110) has vapor permeability. Features a display. 2. Display according to claim 1, characterized in that the electrodes (40, 110) are permeable to water vapor. 3. The display according to claim 1, wherein the electrodes (40, 110) comprise a reticulated conductive structure. 4. The reticulated conductive structure comprises: (a) a wire mesh; (b) a reticulated layer at least partially coated with a conductive material; and (c) at least partially a conductive material. The display of claim 3, comprising: an impregnated mesh layer. 5. A display comprising: (a) an electrophoretic display element capable of changing its appearance in response to an electric field; and (b) a first electrode (40) adjacent to the display element. Wherein the first electrode (40) comprises a protective layer (42, 44, 45) adapted to prevent mechanical or electrochemical damage of the display element. 6. The display according to claim 5, wherein the protective layer (42, 44, 45) is adapted to prevent mechanical removal of the electrophoretic element from the display. 7. The protection layer (42), wherein the first electrode (40) is transparent.
44. The display according to claim 5, wherein each of the displays has an ability to protect the transparent electrode from deterioration by application of an electric potential. 8. The display according to claim 5, wherein the protective layer has a plurality of conductors extending through the protective layer. 9. An electrostatically addressable display, comprising: an electrophoretic display element (20) having a first surface and a second surface; and an adjoining second surface of the display element (20). Electrode (40) arranged
And wherein a protective layer (110) is disposed adjacent to a first surface of the display element (20), the protective layer (110) having the ability to transfer charge. , display. 10. The display according to claim 1, wherein the protective layer (42, 44, 45, 110) is flexible. 11. The electrophoretic display element (20) comprises: a capsule; a dispersion fluid having a first optical property dispersed in the capsule; and a second fluid having a different first optical property. By being adapted to change its position within the capsule under the influence of an applied electric field,
At least one electrophoretic movable particle disposed in said capsule, which changes an optical property of said display element (20). Display as described. 12. The protective layer (110) includes a layer having a resistivity of less than 10 ¹² Ω · cm, and the electrophoretic element (20) is made of a material having a resistivity of greater than 10 ¹² Ω · cm. The display according to claims 9 and 11, characterized in that it comprises: 13. The electrophoretic element (20), wherein the protective layer (110) includes a material having a resistivity higher than that of the electrophoretic element (20).
The protective layer (110) has a thickness of 0% or less and the resistance of the electrophoretic element (20)
13. A display according to claim 12, comprising a material that makes it about 20% of the resistance of the display. 14. The protective layer (110) comprises: (a) a layer of a polymeric material; (b) a layer that transmits charges in a direction substantially perpendicular to the layer; A layer of insulating material having a plurality of conductive structures (116) through it; and (d) a first region (112) having a first resistivity and a second region (114) having a second resistivity. The display according to claims 9 and 10, characterized in that it comprises: 15. The paragraph (d) comprising: (a) the first and second regions include materials that are doped differently in the two regions; and (b) the two regions. The less conductive of the two regions continuously surrounding the array of the more conductive but isolated segments of the two regions;
The display according to claim 14, characterized in that: 16. A protection comprising an electrophoretic display element (20) capable of changing appearance in response to an electric field, wherein said display is adapted to prevent mechanical damage and has the ability to transfer charge. Display, characterized in that the layers (110, 110 ') are fixed to the display element (20). 17. The display element (20) is essentially laminar facing the first and second surfaces, and the protective layer (110, 110 ′) has both the first and second surfaces. 17. The display according to claim 16, wherein the display is fixed to. 18. The protective layer is transparent, indium oxide, tin oxide,
And at least one of indium tin oxide.
A display according to any one of the preceding claims. 19. The protective layer is made of nickel, palladium, platinum, ruthenium, rhodium, silver, aluminum, gold, titanium, chromium, zinc, silver oxide (AgO), aluminum oxide (Al ₂ O ₃ ), gold oxide (III). ) (Au ₂ O ₃ ), titanium oxide (II
) (TiO), titanium oxide (IV) (TiO ₂ ), chromium oxide (III) (Cr ₂ O ₃ ), chromium oxide (VI) (CrO ₃ ), zinc oxide (ZnO), nickel oxide (I
I) (NiO), palladium oxide (II) (PdO), platinum oxide (IV) (Pt
O ₂ ), ruthenium (IV) oxide (RuO ₂ ), and rhodium (III) oxide (
Rh ₂ O _3), characterized in that it comprises any one or more display as claimed in any one of claims 5-17. 20. The display according to claim 19, wherein said protective layer comprises palladium. 21. The protective layer according to claim 5, wherein the protective layer has a thickness of 10 nm or less.
0. The display according to any one of 0. 22. A method for addressing an electrostatically addressable display element, comprising a capsule, wherein a dispersion fluid having a first optical property is disposed within the capsule, and wherein at least one electrophoretic movable particle is provided. Having a second optical property, different from the first optical property, disposed within the capsule and adapted to change a position within the capsule under the influence of an applied electric field; Thereby altering the optical properties of the display element, the display element further comprising a first electrode adjacent to the capsule and an address electrode adjacent to the capsule, and the address electrode together with the first electrode. Activating the electrodes, exposing the electrophoretic element to an applied electric field, and addressing the electrophoretic element, comprising: In the step of providing a protective layer characterized, the protective layer is adapted to transmit a charge method.