KR20010085899A - Encapsulated electrophoretic displays having a monolayer of capsules - Google Patents

Abstract

An encapsulated electrophoretic display having a plurality of non-spherical capsules disposed substantially in a single layer on a substrate.

Description

ENCAPSULATED ELECTROPHORETIC DISPLAYS HAVING A MONOLAYER OF CAPSULES}

Cross-Reference to the Related Application

This application is U.S. Provisional Patent Application Serial No. 60 / 103,398 filed October 7, 1998 and U.S. Pat. Provisional patent application serial number 60 / 118,794 (filed February 4, 1999) is a priority and gains benefit. The entire contents of each of these provisional patent applications are incorporated herein by reference.

Government Rights

This invention was made possible by the government support of the agreement DAAN02-98-3-0004 awarded by SSCOM. The government has some rights in the invention.

Current electrophoretic display technologies produce displays that are not as bright or as much contrast as desired. Current displays cannot achieve uniform brightness or good contrast due to limitations in their construction. Thus, new materials and construction methods are needed to provide electrophoretic displays with satisfactory brightness and contrast.

Summary of the Invention

The present invention relates to a bright and high contrast encapsulated electrophoretic display. Such display can be accomplished with a variety of materials and methods that allow the display to be constructed such that a monolayer of capsule is formed on the substrate. Capsules contain one or more electrophorically mobile particles and suspension fluids. In addition to the formation of monolayers, the materials and methods of the present invention allow the capsules in a monolayer to be filled and / or modified together in certain useful forms. For example, the capsule may not be spherical.

In the specification, the invention is described as a display for ease of explanation. However, the compositions and methods described herein may equally apply to "elements." Display is an example of the concept of a broader range of elements. One or more elements may be arranged into a display or other article of manufacture. The element may include any of the features described for the display.

In general, particles migrate in capsules under the influence of voltage. Depending on the location of the particles and the composition of the suspension fluid, various visual states are possible. In a very generalized example, the reflective particles (toward the viewer) located in front of the capsule in the colored dye will reflect light and appear "white". When using the electricity, when the reflective particles move towards the back of the capsule (opposite to the viewer), the particles will be darkened by dyed repellent and appear to the viewer as "dark".

Successful construction of encapsulated electrophoretic displays requires the proper interaction of several different types of materials and methods. Materials such as polymeric binders, capsule membranes, and electrophoretic particles and fluids should all be chemically compatible. Capsule membranes may be involved in useful surface interactions with electrophoretic particles or may act as inert physical boundaries between the fluid and the binder. The polymeric binder can be set as an adhesive between the capsule membrane and the electrode surface.

In some cases, no separate encapsulation step of the method is required. The electrophoretic fluid may be dispersed or emulsified directly into the binder (or precursor of binder material) to form what may be referred to as an "electrophoretic display with dispersed polymer." In such displays, the individual electrophoretic phases may be referred to as capsules or microcapsules even if no capsule membrane is present. Electrophoretic displays in which such polymers are dispersed are considered a subset of encapsulated electrophoretic displays.

In an encapsulated electrophoretic display, the binder material surrounds the capsule and separates the two electrodes. Such binder material must be compatible with the capsule and the electrode and have the property of being easily printed or coated. It may also have barrier properties to water, oxygen, ultraviolet light, electrophoretic fluids, or other materials. It may also contain surfactants and crosslinkers, which may aid in coating or durability. The electrophoretic display in which the polymer is dispersed may be of emulsion or phase separation type.

In one aspect of the invention, the encapsulated electrophoretic element has a plurality of non-spherical capsules disposed in a substantially single layer on the substrate.

In another aspect of the invention, the encapsulated electrophoretic element has a plurality of capsules formed on the substrate in combination with the binder in a substantially single layer to form a film. The binder may include a binder solid and the ratio of the mass of the solid binder to the mass of the capsule of at least some elements may be about 1: 2 to about 1:20.

In another aspect of the invention, the encapsulated electrophoretic element has a plurality of capsules disposed substantially in a single layer on the substrate and combined with a binder to form a film. At least some of the elements have an optically active fraction of at least 70%.

Various aspects of the present invention may have any of the following features. In addition, these aspects of the elements or those described below may be used alone or in combination with any of the features described below to form a display. Multiple capsules can be placed on the substrate and combined with a binder to form a film. The film may have a binder comprising a binder solid and the ratio of the mass of the binder to the mass of the capsule of at least some elements may be about 1: 2 to about 1:20. At least some of the elements may have an optically active fraction of at least 70%. The capsule may be non-spherical and / or substantially planar in one or more sides adjacent to the substrate. The film may include closely filled capsules. One or more capsules may include a suspension fluid and one or more types of particles, or one or more capsules may include two or more types of particles such that the optical properties of the two or more particle types are different. The capsule may be a polymer matrix having a fluid-containing (eg oil) cavity. The capsule wall defines the capsule and its thickness may be about 0.2 to about 10 μm. The substrate may include a polymerizable material, a polyester film, and / or one or more electrodes (such as indium tin oxide). The thickness of the substrate may be about 25 to about 500 μm.

The element may have a layer of material that substantially fills the gap formed in the film or on the opposite side of the film, which may be substantially planar. The back substrate may be disposed adjacent to the layer of material. The layer of material may initially be combined with the film or the backing substrate. The capsule, binder, and layer of material may form a layer that is substantially uniform in thickness and / or a substantially voidless stratum. The thickness of this layer may be about 10 to about 500 μm, preferably about 50 to about 300 μm. The size of the capsule may be substantially uniform. The layer of material may be a binder. The layer of material may include an insulator, conductor or semiconductor. The layer of material may be tacky or liquid before substantially filling the gap in the film, during and / or after filling. The thickness of the layer of material may be about 50 μm or less. Layers of material include, for example, carbon particles, gold particles, aluminum particles, platinum particles, silver particles, plated polymer spheres, plated glass spheres, indium tin oxide particles, polyacetylene, polyaniline, polypyrrole, polyethylene dioxythiophene (" P-DOT ″) and / or polythiophene may be included.

The back substrate may include one or more electrodes, one or more transistors, and / or one or more diodes. The transistor may be one or more organic materials or silicon-based. The back substrate may include polymeric material, glass or metal.

In another aspect of the invention, the encapsulated electrophoretic element includes a plurality of non-spherical capsules disposed substantially in a single layer on a substrate to form a film. Typically, the elements of this embodiment are substantially free of binders. This aspect may have any of the features described above. In addition, this aspect may have any of the following features. The layer of capsule and material may form a layer that is substantially uniform in thickness and / or substantially free of voids. Additionally, one or more elements of this aspect of the invention may be combined with other elements of this aspect or other aspects of the invention to form a display.

In another aspect of the invention, a method of making an encapsulated electrophoretic element, which may have a plurality of capsules disposed on a substrate in substantially a single layer, comprises: (a) providing a capsule; (b) mixing one or more capsules with a binder to produce a capsule / binder mixture; (c) coating the capsule / binder mixture on at least partially conductive substrate to produce a film; And (d) curing the capsule / binder mixture.

This aspect of the invention may have any of the above listed features or any of the following features. The binder may be selected from the group consisting of acrylic products, urethanes and poly (vinyl alcohol). The binder may include a polymer latex. The binder may have a fraction that can evaporate. The conductive substrate may include a polyester film sputtered with indium tin oxide. One or more capsules may contain a plurality of particles (such as titanium dioxide particles) dispersed in a suspension fluid. Suspension fluids may include halogenated hydrocarbons and / or aliphatic hydrocarbons.

The coating step involves applying a pressurized gas to the capsule / binder mixture, causing the capsule / binder mixture to precipitate on the substrate, thereby placing the capsule on the substrate substantially in a single layer. The coating step may further include heating, cooling, and / or adding liquid to the pressurized gas prior to or during application of the pressurized gas to the capsule / binder mixture. The liquid may be in the form of droplets and / or may be an organic solvent. Organic solvents may include, for example, butyl acetate, methylene chloride and / or chlorobenzene. Organic solvents may include alcohols such as isopropyl alcohol, methanol and / or ethanol. The coating step may include applying a pressurized gas to the air knife at a distance of about 1 to about 15 cm from the surface of the capsule / binder mixture and / or at an angle of about 0 to about 90 degrees from the surface of the conductive substrate. Pressurized gas may include air.

The coating step may include coating at least a portion of the capsule onto the film through the coating head, for example with a pump that typically provides the pump pressure at low shear forces. At least some capsules may be arranged in a single layer to form a single layer. The coating head may be a slot die head coating. Typically, the slot width of the slot die coating head is about 1 to about 2.5 times the average diameter of the capsule.

Laminating the film to the backing substrate may be further included in the method. A layer of material may be disposed between the film and the back substrate. The layer of material may be combined with the backing substrate and / or with the film prior to lamination. Heating, pressurization and / or vacuuming of the gas may occur during the lamination step. The layer of material may be insulating, conductive or semiconducting. The layer of material may be tacky or liquid during at least some of the lamination steps. The layer of material may include a binder. In the lamination step a layer consisting of a layer of capsules, binders and materials can be produced. The layer may have one or more substantially planar faces proximate the back substrate, and / or the layer may be substantially void free, and / or the thickness of the layer is substantially uniform. The layer of material may substantially fill the gap in the film. The thickness of the layer of material may be about 50 μm or less. Layers of material include, for example, carbon particles, gold particles, aluminum particles, platinum particles, silver particles, plated polymer spheres, plated glass spheres, indium tin oxide particles, polyacetylene, polyaniline, polypyrrole, P-DOT and / or Adhesives containing polythiophene can be included. The binder may include a binder solid and the ratio of the mass of the binder solid to the mass of the at least some elements may be about 1: 2 to about 1:20.

Further removing the water from bonding with at least some capsules may be included in the method. Removing the water may include a method selected from the group consisting of centrifugation, absorption, evaporation, mesh filtration and osmotic separation.

In general, the present invention relates to materials and methods for forming monolayers of capsules for encapsulated electrophoretic displays.

According to a preferred and exemplary embodiment, together with further advantages of the invention, the invention is described more particularly in the following detailed description in conjunction with the accompanying drawings.

In the figures, like reference, generally, the letters indicate the same part in different observations. Moreover, the drawings need not be proportional, but instead emphasized generally illustrating the principles of the invention.

1A is a schematic representation of a cross section of a monolayer of a capsule.

1B is a schematic representation of a cross section of a monolayer of a deformable and non-spherical capsule.

2 schematically illustrates a coating process using a slot die coater according to one embodiment of the present invention.

3 schematically illustrates a slot die coater for depositing a monolayer of a capsule in accordance with one embodiment of the present invention.

4 schematically illustrates a coating process using an air knife coater according to one embodiment according to the invention.

5A is a schematic view of a film before contact with a layer of material to fill gaps in the film.

5B is a schematic of the film of FIG. 5A after a layer of material has been applied and laminated to the back substrate.

6A is a schematic top view of a display illustrating the calculation of an optically active fraction.

6B is a side view of the display illustrating the calculation of the optically active fraction.

7A is a schematic diagram of an apparatus for performing emulsion-based encapsulation.

7B is a schematic representation of an oil droplet of suspension fluid in which white and black particles are dispersed.

7C is a schematic representation of an oil droplet of a deeply dyed suspension fluid with white microparticles and a charge control agent dispersed.

8 schematically depicts the removal of water from engagement with a capsule.

9A is a schematic of a binder free film prior to contact with a layer of material to fill gaps in the film.

9B is a schematic view of the film of FIG. 9A after a layer of material has been applied and after lamination to the back substrate.

10 is a schematic representation of a capsule that is a cavity filled with fluid in the matrix.

The present invention provides materials and methods for improving the functionality of an encapsulated electrophoretic display device. In the construction of encapsulated electrophoretic display devices, capsules (typically containing electrophoretic particles) of a structure closely packed into a single layer are preferred. For example, capsules in tightly packed structures include high density and closely spaced forms. In addition, deformable capsules are preferred that allow the capsule walls to fit closely together with little or no binding material therebetween. For example, such capsules may be non-spherical in shape.

In general, encapsulated electrophoretic displays include one or more types of particles that absorb or scatter light. One example is a system in which a capsule contains one or more kinds of electrophorically mobile particles dispersed in a dyed suspension fluid. Another example is a system in which a capsule contains two separate types of particles suspended in a transparent suspension fluid, where one type of particles absorbs light (dark) while the other type scatters light (white ). In other instances (more than two kinds of particles, with or without dyes, etc.). The particles are generally solid pigments, dyed particles, or pigment / polymer composites.

In the closely packed state, typically, a single layer of capsules is desirable as the optically active portion of the device. Capsules typically contain an opaque pigment and transmit little or no light in any state of the device. Thus, light impinging on the first layer of closely filled capsules is scattered or absorbed. Light rarely passes through the capsule. When individual capsules (or second layer of capsules) are placed under the first layer of the capsule, little or no light reaches these capsules. As such, the second layer does not contribute significantly to the optical effect. In addition, the additional layers of the capsule thicken the film, thus increasing the voltage needed to operate the film without providing any optical benefit.

Therefore, it is desirable to construct an encapsulated electrophoretic display device having capsules in a closely packed monolayer. With respect to FIGS. 1A and 1B, Capsule 2 is typically substantially uniform in size. In addition, capsule 2 may be modified such that monolayer 4 may form a flat (or nearly flat) surface 6 as shown in FIG. 1B. In one example, the flat surface 6 allows the capsules 2 to be filled more closely, allowing the particles 8 in the capsule 2 to spread more evenly across the surface of the display (the distribution of particles 8 in FIG. 1A in FIG. 1B Compared to distribution). Additionally, the flat side of the other side of the capsule (not shown) allows the second substrate (or second conductive substrate) to be laminated which allows good contact with the capsule layer. This flat upper surface may be formed naturally or may be formed by coating or laminating another material on the capsule. Typically, the wall thickness of the capsule is about 0.2 to about 10 μm, more preferably about 1 to about 5 μm.

Indeed, one method of measuring the state of the display involves a variable called the "photoactively active fraction". This variable refers to the area of the display that may have a changed appearance compared to the total area of the display. The variable may be expressed as a ratio, ie (variable surface area of the display) / (total surface area of the display). When calculating the total area, it is easy to calculate the surface area of the display using conventional geometry. However, due to the nature of the capsule, the observer sees the optically active area of the capsule that is not in the plane of the display (ie, the visible portion of the capsule whose appearance changes), and the overall surface area is generally calculated on this plane. Therefore, the location of the optically active area must be extrapolated to the plane from which the total surface area is calculated to estimate the optically active fraction.

6A and 6B illustrate extrapolation of optically active areas for estimating optically active fractions. FIG. 6A is a top view and FIG. 6B is a side view of the same structure, and the two figures are aligned in line. Four capsules 100, 102, 104 and 106 are shown in schematic plane 110 of the display. This rectangular plane 110 represents the total surface area of the display. Due to the shape of the capsules 100, 102, 104, and 106, the optically active areas of the capsules 100, 102, 104, and 106 approximately coincident with the plane 110 (shown as broken lines in FIG. 6A) are the total optically active area (Fig. Slightly smaller than 6A). Thus, according to the extrapolation technique, the total optically active area represented by the band lines is superimposed on plane 110. 6B shows how capsules 100, 102, 104, and 106 are close to plane 110 of the display, but do not coincide with plane 110, and explain why the disconnection and strip lines of FIG. 6A do not coincide. In practice, useful optically active fractions are at least about 70%, more preferably at least about 90%.

Non-spherical microcapsules can be formed during the encapsulation step, for example using non-uniform shear or compression pressure. Such non-spherical capsules may be formed during processing of the display in which the binder is dried or cured. In such a system, as the binder shrinks, the capsules are pulled closely together and the capsules are pulled down towards the coated substrate. For example, aqueous evaporable binders such as water transport acrylic products, urethanes or poly (vinyl alcohol) tend to exhibit such shrinking properties. Typically, some of the binder, such as water, evaporates. Other evaporative binders, emulsions, or solutions are also suitable. The solvent need not be water, but may be an organic liquid or a combination of liquids.

In addition, non-spherical capsules may be formed, for example, by permanently deforming the capsule by applying force to the film when the film is dried or cured. Such force may be applied by a pair of rollers, vacuum lamination presses, mechanical presses or any other suitable means. Such non-spherical capsules may be formed by stretching the cured film to one or both planar axes of the film. After completion of the curing process, the capsule may come out over the surface of the cured film, resulting in a lens effect that enhances the optical properties of the capsule. Finally, it may be formed of a material that softens within the binder such that when the capsule and binder are placed and the binder cures, the capsule deforms to form a flat surface.

In another embodiment, a polymer dispersed electrophoretic display is constructed in a similar manner to a polymer dispersed liquid crystal display. Mix the fluid with the binder. Typically, the fluid may be oil. Once the binder has dried or cured, the fluid is pulled into the non-spherical capsule cavity. Such fluid-containing cavities can be elastomeric capsules. Such cavities typically lack capsule walls. For example, FIG. 10 shows a cavity 60 filled with oil 64. FIG. The cavity lies in matrix 62. Matrix 62 is adjacent substrate 66. Typically, matrix 62 is formed from a polymer that may be a binder. In a preferred embodiment, the aspect ratio (ie, the ratio of width (w) to height (h)) of these cavities is preferably greater than about 1.2. The aspect ratio is more preferably greater than about 1.5 and in particularly preferred embodiments the aspect ratio is greater than about 1.75. In a preferred embodiment, the binder volume fraction (ie, fraction of the total volume) of the display with non-spherical capsules is about 0 to about 0.9. More preferably, the volume fraction is about 0.05 to about 0.2.

Electrophoretic displays are constructed as encapsulated electrophoretic displays or polymer dispersed electrophoretic displays (similar to liquid crystal displays in which polymers are dispersed), and non-spherical capsules or liquid droplets can be flattened, contracted by a binder or mechanical force. Is formed. In each case, the capsule must be able to deform or rupture. In the case of electrophoretic displays in which the polymer is dispersed, the shape of the encapsulation phase changes when the polymer shrinks. In addition, the encapsulation phase can be asymmetrically modified by stretching of the substrate. Another technique that can be used is to first dry the binder in such a way that a rough top surface is formed. The remaining binder can then be dried slowly without worrying that the top surface is broken or too uneven.

One step away from the detailed description of the monolayer and the method of forming the monolayer according to the invention, in Section I some components of the electrophoretic display according to the invention are generally described. It is described in more detail in US patent application Ser. No. 09 / 141,105 (filed Aug. 27, 1998), which is incorporated by reference in its entirety. Section II describes the components of the display and how to build the display in a single layer.

I. Electrophoretic display components

A. Particle

There is a great deal of flexibility in the selection of particles for use in electrophoretic displays as described above. For the purposes of the present invention, a particle is any component that is charged or can acquire charge (i.e. have or obtain electrophoretic mobility), and in some cases such mobility is zero or close to zero. (Ie particles will not move). The particles can be pure pigments, dyed (laked) pigments or pigment / polymer composites, or any other component that can be charged or obtain a charge. Typical considerations for electrophoretic particles are their optical, electrical and surface chemistry. The particles can be organic or inorganic compounds and can absorb light or scatter light. Particles for use in the present invention may further comprise scattering pigments, absorbing pigments and luminescent particles. The particles may be retroreflective such as corner cubes, or may be electroluminescent, such as zinc sulfide particles that emit light when excited by an AC field, or may be photoluminescent. Finally, the particles can be surface treated to improve filler or interaction with the filler or to improve dispersibility.

One particle for use in the electrophoretic display of the present invention is titania. Titania particles may be coated with metal oxides, for example aluminum oxide or silicon oxide. Titania particles may have one or more metal oxide coating layers. For example, titania particles for use in the electrophoretic display of the present invention may have an aluminum oxide coating and a silicon oxide coating. The coating can be applied to the particles in any order.

Electrophoretic particles are generally pigments, polymers, laked pigments or some combination thereof. Pure pigments can be any pigment, and pigments such as rutile (titania), anatase (titania), barium sulfate, kaolin or zinc oxide are generally useful for pale particles. Some typical particles have high refractive index, high scattering coefficient and low absorption coefficient. Other particles are absorbent, such as carbon black or colored pigments used in paints and inks. In addition, the pigment should be insoluble in the suspension fluid. Yellow pigments such as diarylide yellow, Hansa yellow and benzidine yellow are also used in similar displays. Any other reflective material can be used for the pale particles, including non-pigment materials such as metallic particles.

Useful pure pigments include, but are not limited to, PbCrP ₄ , Cyan Blue GT 55-3295 (American Cyanamid Company, Wayne, NJ), Cibacron Black BG (Ciba Company, Inc., Newport, DE), Cibacron Turquoise Blue G ( Ciba), Cibalon Black BGL (Ciba), Orasol Black BRG (Ciba), Orasol Black RBL (Ciba), Acetamine Blac, CBS (EI du Pont de Nemours and Company, Inc., Wilmington, DE), Crocein Scarlet N Ex ( du Pont) (27290), Fiber Black VF (duPont) (30235), Luxol Fast Black L (duPont) (Solv. Black 17), Nirosine Base No. 424 (duPont) (50415B), Oil Black BG (duPont) (Solv. Black 16), Rotalin Black RM (duPont), Sevron Brilliant Red 3 B (duPont); Basic Black DSC (Dye Specialties, Inc.), Hectolene Black (Dye Specialties, Inc.), Azosol Brilliant Blue B (GAF, Dyestuff and Chemical Division, Wayne, NJ) (Solv. Blue 9), Azosol Brilliant Green BA (GAF (Solv. Green 2), Azosol Fast Brilliant Red B (GAF), Azosol Fast Orange RA Conc. (GAF) (Solv. Orange 20), Azosol Fast Yellow GRA Conc. (GAF) (13900 A), Basic Black KMPA (GAF), Benzofix Black CW-CF (GAF) (35435), Cellitazol BNFV Ex Soluble CF (GAF) (Disp.Black 9), Celliton Fast Blue AF Ex Conc (GAF ) (Disp.Blue 9), Cyper Black 1A (GAF) (Basic Blk. 3), Diamine Black CAP Ex Conc (GAF) (30235), Diamond Black EAN Hi Con. CF (GAF) (15710), Diamond Black PBBA Ex (GAF) (16505); Direct Deep Black EA Ex CF (GAF) (30235), Hansa Yellow G (GAF) (11680); Indanthrene Black BBK Powd. (GAF) (59850), Indocarbon CLGS Conc. CF (GAF) (53205), Katigen Deep Black NND Hi Conc. CF (GAF) (15711), Rapidogen Black 3 G (GAF) (Azoic Blk. 4); Sulphone Cyanine Black BA-CF (GAF) (26370), Zambezi Black VD Ex Conc. (GAF) 30015; Rubanox Red CP-1495 (The Sherwin-Williams Company, Cleveland, OH) (15630); Includes Raven 11 (Columbian Carbon Company, Atlanta, GA) (carbon black aggregates with a particle size of about 25 μm), Statex B-12 (Columbian Carbon Co.) (Fernas Black with 33 μm average particle size) and chrome green do.

The particles may also include pigments that are laked or dyed. Laked pigments are particles in which the dye is precipitated or colored. Lakes are metal salts of anionic dyes that can be readily dissolved. These are dyes of azo, triphenylmethane or anthraquinone structures containing one or more sulfonic acid or carboxylic acid groups. These are generally precipitated on the substrate by calcium, barium or aluminum salts. Typical examples are Peacock Blue Lake (CI Pigment Blue 24) and Persian Orange (Lake of CI Acid Orange 7), Black M Toner (GAF) (a mixture of carbon black and black dye precipitated on the lake).

Dark particles of the dyed type can be constructed from any light absorbing material, such as carbon bla, or inorganic assay material. Thicker substances can also be selectively absorbed. For example, dark green pigments can be used. The assay material can also be formed by coloring the latex with metal oxides, such latex copolymers can be any butadiene, styrene, isoprene, methacrylic acid, methyl methacrylate, acrylonitrile, vinyl chloride, acrylic acid, sodium styrene sulfo Acetates, vinyl acetate, chlorostyrene, dimethylaminopropylmethacrylamide, isocyanoethyl methacrylate and N- (isobutoxymethacrylamide), conjugated diene compounds such as diacrylates, triacrylates, Dimethyl acrylate and trimethyl acrylate are optionally included. The black particles may also be formed by dispersion polymerization techniques.

In systems containing pigments and polymers, the pigments and polymers may form multiple domains within the electrophoretic particles or may be aggregates of smaller pigment / polymer combined particles. Alternatively, the central pigment core may be surrounded by a polymer shell. Pigments, polymers, or both, may contain dyes. The optical purpose of the particles is to scatter light, absorb light, or scatter and absorb light. Useful sizes can range from 1 nm to about 100 μm as long as the particles are smaller than the binding capsule. The density of the electrophoretic particles can be substantially matched to the density of the suspended (ie electrophoretic) fluid. If the difference between the density of the suspension fluid and the density of the particles is between about 0 and about 2 g / ml, the density of the suspension fluid is defined herein as "substantially matched" with the density of the particles. This difference is preferably about 0 to about 0.5 g / ml.

Polymers useful for particles include, but are not limited to, polystyrene, polyethylene, polypropylene, phenolic resins, Du Pont Elvax resins (ethylene-vinyl acetate copolymers), polyesters, polyacrylates, polymethacrylates, ethylene acrylic acid Or methacrylic acid copolymers (Nucrel Resins-Dupont, Primacor Resins-Dow Chemical), acrylic acid copolymers and trimers (Elvacite Resins, DuPont) and PMMA. Materials useful for homopolymer / pigment phase separation with high shear melting include, but are not limited to, polyethylene, polypropylene, polymethylmethacrylate, polyisobutylmethacrylate, polystyrene, polybutadiene, polyisoprene, polyiso Butylene, polylauryl methacrylate, polystearyl methacrylate, polyisobornyl methacrylate, poly-t-butyl methacrylate, polyethyl methacrylate, polymethyl acrylate, polyethyl acrylate, Polyacrylonitrile, and copolymers of two or more such materials. Some useful pigment / polymer composites on the market include, but are not limited to, Process Magenta PM 1776 (Magruder Color Company, Inc., Elizabeth, NJ), Methyl Violet PMA VM6223 (Magruder Color Company, Inc., Elizabeth, NJ) and Naphthol FGR RF6257 (Magruder Color Company, Inc., Elizabeth, NJ).

Pigment-polymer composites can be formed by physical processes (eg, abrasion or ball milling), chemical processes (eg, microencapsulation or dispersion polymerization), or any other method known in the particle manufacturing art. For example, methods and materials for both the manufacture of liquid toner particles and the filling of such particles may be relevant.

While new and useful electrophoretic particles can still be found, many of the particles are already known to those skilled in the electrophoretic display art and liquid toners can also prove useful. In general, the polymer requirements for liquid toners and encapsulated electrophoretic inks are that pigments or dyes must be readily incorporated by physical, chemical or physicochemical processes, can aid in colloidal stability, contain or fill sites It is similar in that the substance containing the site can be incorporated. One common requirement from the liquid toner industry that encapsulated electrophoretic inks do not share is that the toners must be able to "freeze" the image, that is, to be heat fused together to produce a uniform film after placement of the toner particles. will be.

Typical particle manufacturing techniques can be obtained from liquid toners and other industries and include ball grinding, abrasion, jet grinding and the like. The process will be described for the case of pigmented polymerizable particles. In such cases the particles are generally mixed into the polymer in some sort of high shear mechanism such as a screw extruder. The composite material is then ground to a starting size of about 10 μm (wet or dry). This may then optionally be carried together with some charge control agent, for example a carrier liquid, for example ISOPAR (Exxon, Houston, TX) and disperse to final particle size and / or size distribution for several hours under high shear.

Another manufacturing technique for particles is the addition of polymers, pigments and suspension fluids to the media mill. The mill is operated and at the same time heated to a temperature at which the polymer swells substantially with the solvent. This temperature is typically around 100 ° C. In this state, the pigment is easily encapsulated into the swollen polymer. After a suitable time, typically a few minutes, the mill is gradually cooled to ambient temperature with stirring. Continue grinding for several minutes to achieve sufficiently small particle sizes, typically a few microns in diameter. Fillers may be added at this time. Optionally, more suspension fluid can be added.

Chemical methods such as dispersion polymerization, mini- or micro-emulsion polymerization, suspension polymerization precipitation, phase separation, solvent evaporation, in situ polymerization, seeding emulsion polymerization, or any method falling within the scope of general microencapsulation can be used. A typical method of this type is a phase separation process in which dissolved polymerizable material precipitates out of solution on a dispersed pigment surface through solvent dilution, evaporation or thermal change. Other methods include chemical means for coloring the polymerizable latex, for example with metal oxides or dyes.

B. Suspension Fluid

Suspension fluids containing particles may be selected based on properties such as density, refractive index and solubility. Preferred suspension fluids include low dielectric constant (about 2), high volume resistivity (about 10 ¹⁵ ohm-cm), low viscosity (less than 5 centistokes ("cst")), low toxicity and environmental impact, low water solubility (10 ppm) Less than), high specific gravity (greater than 1.5), high boiling point (greater than 90 ° C.) and low reflectivity (less than 1.2).

The choice of suspension fluid may be based on chemical inertness, density matched with electrophoretic particles, or chemical miscibility with both electrophoretic particles and binding capsules. The viscosity of the fluid should be low if the particles want to move. The refractive index of the suspension fluid can also be substantially matched to the refractive index of the particles. When the difference between the refractive index of the suspension fluid and the refractive index of the particles is about 0 to about 0.3, preferably about 0.05 to about 0.2, the refractive index of the suspension fluid is viewed as "substantially matched" with the refractive index of the particles. Used in the invention.

In addition, the fluid may be selected to be a poor solvent for some polymers, which is advantageous for use in the manufacture of microparticles because it increases the range of polymerizable materials useful for producing particles of polymers and pigments. Organic solvents such as halogenated organic solvents, saturated linear or branched hydrocarbons, silicone oils, and low molecular weight halogen-containing polymers are some useful suspension fluids. Suspension fluids may consist of a single fluid. However, a fluid will often be a mixture of one or more fluids to control its chemical and physical properties. The fluid may also contain surface modifiers for modifying the surface energy or charge of the electrophoretic particles or binding capsules. Reactants or solvents (eg, fat soluble monomers) of the microencapsulation process may also be contained in the suspension fluid. Charge control agents may also be added to the suspension fluid.

Useful organic solvents include, but are not limited to, epoxides such as decane epoxide and dodecane epoxide; Vinyl ethers such as cyclohexyl vinyl ether and Decave (International Flavors & Fragrances, Inc., New York, NY); And aromatic hydrocarbons such as toluene and naphthalene. Useful halogenated organic solvents include, but are not limited to, tetrafluorodibromoethylene, tetrachloroethylene, trifluorochloroethylene, 1,2,4-trichlorobenzene, carbon tetrachloride. The density of these materials is high. Useful hydrocarbons include, but are not limited to, dodecane, tetradecane, Isopar Aliphatic Hydrocarbons in the Series (Exxon, Houston, TX), Norpar (Serial paraffinic liquid), Shell-Sol (Shell, Houston, TX), and Sol-Trol Shell, naphtha, and other petroleum solvents. The density of these materials is generally low. Useful examples of silicone oils include, but are not limited to, octamethyl cyclosiloxanes and high molecular weight cyclic siloxanes, poly (methyl phenyl siloxanes), hexamethyldisiloxanes, and polydimethylsiloxanes. The density of these materials is generally low. Useful low molecular weight halogen-containing polymers include, but are not limited to, poly (chlorotrifluoroethylene) polymers (Halogenated hydrocarbon Inc., River Edge, NJ), Galden (Ausimont, Morristown, NJ, perfluorinated ether) or Krytox by Dupont (Wilmington, DE) This includes. In a preferred embodiment, the suspension fluid is a poly (chlorotrifluoroethylene) polymer. In a particularly preferred embodiment, the degree of polymerization of such polymers is from about 2 to about 10. Many of these materials are available in a wide range of viscosities, densities and boiling points.

The fluid must be able to form into small droplets before the capsule is formed. Processes for forming droplets include shear-based emulsification schemes, as well as flow-through jets, membranes, nozzles or holes. An electrical or ultrasonic field can assist in the formation of small droplets. Surfactants and polymers can be used to help stabilize and emulsify droplets for emulsion type encapsulation. One surfactant for use in the displays of the present invention is sodium dodecyl sulfate.

In some displays it may be advantageous that the suspension fluid contains an optically absorbing dye. Such dyes should be soluble in the fluid but will generally be insoluble in other components of the capsule. There is much flexibility in the choice of dye material. The dye may be a pure compound, or a mixture of dyes to reach a particular color, including blacks. The dye may be fluorescent, which will produce a display in which the fluorescence depends on the position of the particles. The dye may be photoactive, which may change color or become colorless upon irradiation with visible or ultraviolet light, providing another means for obtaining an optical response. The dye can also be polymerized to form a solid absorbent polymer in the binding shell.

There are many dyes to choose from for use in encapsulated electrophoretic displays. Important properties here include light resistance, solubility in suspension fluids, color and cost. They generally arise from the group of azo, anthraquinone, and triphenylmethane type dyes and can be chemically modified to increase solubility in oils and reduce absorption by particle surfaces.

It will be appreciated that many dyes already known to those skilled in the art of electrophoretic displays are useful. Useful azo dyes include, but are not limited to, Oil Red dyes and dyes of the Sudan Red and Sudan Black series. Useful anthraquinone dyes include, but are not limited to, Oil Blue dyes, and dyes of the Macrolex Blue series. Useful triphenylmethane dyes include, but are not limited to, Michler's hydrol, Malachite Green, Crystal Violet, and Auramine O.

C. Charge Controls and Particle Stabilizers

Charge control agents are used to provide good electrophoretic mobility to the electrophoretic particles. Stabilizers are used to prevent aggregation of the electrophoretic particles as well as to prevent the electrophoretic particles from being irreversibly deposited on the capsule wall. Each component can be constructed from materials that span a wide range of molecular weights (low molecular weight, oligomeric, or polymerizable), and can be pure or a mixture. Charge control agents used to modify and / or stabilize particle surface charges are applied as generally known in the art of liquid toners, electrophoretic displays, non-aqueous paint dispersions, and engine-oil additives. In all such industries, charged species can be added to non-aqueous media to increase electrophoretic mobility or increase electrostatic stabilization. The material can also improve steric stabilization. Different theories of charging are assumed, including selective ion adsorption, proton transfer and contact charging.

Optional charge control agents or charge waveguides can be used. Such components typically consist of a low molecular weight surfactant, polymerizable agent or a mixture of one or more components and help to stabilize or modify the signal and / or magnitude of the charge on the electrophoretic particles. The filling properties of the pigments themselves may be taken into account in consideration of the acidic or basic surface properties of the pigments, or the filling sites may take place on the carrier resin surface (if present) or a combination of the two. Additional pigment properties that may be involved are particle size distribution, chemical composition and light resistance. Charge control agents used to modify and / or stabilize particle surface charges can be applied as is generally known in the art of liquid toners, electrophoretic displays, non-aqueous paint dispersions, and engine-oil additives. In all such industries, charged species can be added to non-aqueous media to increase electrophoretic mobility or increase electrostatic stabilization. The material can also improve steric stabilization. Different theories of charging are assumed, including selective ion adsorption, proton transfer and contact charging.

Charge enhancers may also be added. These materials increase the effectiveness of charge control agents or charge waveguides. The charge enhancer may be a polyhydroxy compound or an aminoalcohol compound, which is preferably soluble in an amount of at least 2% by weight in the suspension fluid. Examples of polyhydroxy compounds containing two or more hydroxyl groups include, but are not limited to, ethylene glycol, 2,4,7,9-tetramethyl-decine-4,7-diol, poly (propylene glycol), penta Ethylene glycol, tripropylene glycol, triethylene glycol, glycerol, pentaerythritol, glycerol-tri-12 hydroxystearate, propylene glycerol monohydroxystearate, and ethylene glycol monohydroxystearate. Examples of aminoalcohol compounds containing at least one alcohol function and at least one amine function in the same molecule include, but are not limited to, triisopropanolamine, triethanolamine, ethanolamine, 3-amino-1 propanol, o-aminophenol, 5 -Amino-1-pentanol, and tetra (2-hydrocyethyl) ethylenediamine. The charge enhancer is preferably present in the suspension fluid in an amount of about 1 to about 100 mg (mg / g), more preferably about 50 to about 200 mg / g per gram of particle mass.

The surface of the particles can also be chemically modified, for example, to aid dispersion, improve surface charge, and improve the stability of the dispersion. Surface modifiers include organosiloxanes, organohalogen silanes and other functional silane coupling agents (Dow Corning). Z-6070, Z-6124 and 3 additives, Midland, MI); Organic Titanate and Zirconate (Tyzor TOT, TBT and TE series, Dupont, Wilmington, DE); Hydrophobing agents such as long chain (C12 to C50) alkyl and alkyl benzene sulfonic acids, fatty amines or diamines and salts or quaternary derivatives thereof; And amphoteric polymers that can be covalently bound to the particle surface.

In general, it is believed that the filling results in an acid-base reaction between some portions present in the continuous phase and the particle surface. Useful materials are therefore those which can participate in such a reaction or any other filling reaction known in the art.

Several non-limiting groups of useful charge control agents include organic sulfates or sulfonates, metal soaps, block or comb polymers, organic amides, organic zwitterions, and organic phosphates and phosphonates. Useful organic sulfates and sulfonates include, but are not limited to, bis (2-ethylhexyl) sodium sulfosuccinate, Carl dodecyl benzene sulfonate, calcium petroleum sulfonate, natural or basic barium dinonylnaphthalenesulfonate Natural or basic calcium dinonylnaphthalene sulfonate, dodecylbenzenesulfonate sodium salt, and ammonium lauryl sulfate. Useful metal soaps include, but are not limited to, basic or natural barium petroleum salts, calcium petronates, Co-, Ca-, Cu-, Mn-, Ni-, Zn- and Fe- salts of naphthenic acid, stearic acid. Ba-, Al-, Zn-, Cu-, Pb- and Fe- salts, divalent or trivalent metal carboxylates such as aluminum tristearate, aluminum octoate, lithium heptanoate, iron stearate, iron diss Tearate, barium stearate, chromium stearate, magnesium octoate, calcium stearate, iron naphthenate, and zinc naphthenate, Mn- and Zn-heptanoate, and Ba-, Al-, Co-, Mn And Zn-octoate. Useful block or comb copolymers include, but are not limited to, (A) polymers of 2- (N, N) dimethylaminoethyl methacrylate quaternized with methyl-p-toluenesulfonate and (B) poly-2- AB diblock copolymer of ethylhexyl methacrylate, and poly (12-hydroxystearic acid) fat-soluble tail, suspended on a fat-soluble anchor group of poly (methyl methacrylate-methacrylic acid) and comb teeth having a molecular weight of about 1800 Graft copolymers are included. Useful organic amides include, but are not limited to, polyisobutylene succinimides such as OLOA 1200, and N-vinyl pyrrolidone polymers. Useful organic zwitterions include, but are not limited to, lecithin. Useful organic phosphates and phosphonates include, but are not limited to, the sodium salts of phosphated mono- and diglycerides with saturated and unsaturated acid substituents.

Particle dispersion stabilizers can be used to prevent particle entanglement or adhesion to the capsule walls. For typical high resistivity liquids used as suspension fluids in electrophoretic displays, non-aqueous surfactants can be used. These include, but are not limited to, glycol ethers, acetylene glycols, alkanolamides, sorbitol derivatives, alkyl amines, quaternary amines, imidazolines, dialkyl oxides, and sulfosuccinates.

D. Encapsulation

Encapsulation on the inside can be accomplished in a number of different ways. Many suitable procedures for microencapsulation are described in Microencapsulation, Processes and Applications , (IE Vandegaer, ed.), Plenum Press, New York, NY (1974) and Gutcho, Microcapsules and Microencapsulation Techniques , Nuyes Data Corp., Park Ridge , NJ (1976). These procedures fall within several general categories, all of which can be applied to the present invention: interfacial polymerization, in situ polymerization, physical processes such as coextrusion and other phase separation processes, curing in liquids, and simple / composite coacervation.

Many materials and processes should prove useful for formulating the displays of the present invention. Materials useful for simple coacervation processes to form capsules include, but are not limited to, gelatin, polyvinyl alcohol, polyvinyl acetate, and cellulosic derivatives such as carboxymethylcellulose. Useful materials for complex coacervation processes include, but are not limited to, gelatin, acacia, carrageenan, carboxymethylcellulose, hydrolyzed styrene anhydride copolymers, agar, alginates, casein, albumin, methyl vinyl ether co-maleic acid Anhydrides, and cellulose phthalate. Materials useful for the phase separation process include, but are not limited to, polystyrene, PMMA, polyethyl methacrylate, polybutyl methacrylate, ethyl cellulose, polyvinyl pyridine, and poly acrylonitrile. Materials useful for in situ polymerization processes include, but are not limited to, aldehydes, melamines, or urea and formaldehyde, together with polyhydroxyamides; Water-soluble oligomers of melamine, or a condensate of urea and formaldehyde; And vinyl monomers such as styrene, MMA and acrylonitrile. Finally, materials useful for the interfacial polymerization process include, but are not limited to, diacyl chlorides such as sebacoyl, adipoyl, and di- or poly-amines or alcohols, and isocyanates. Useful emulsion polymeric materials include, but are not limited to, styrene, vinyl acetate, acrylic acid, butyl acrylate, t-butyl acrylate, methyl methacrylate, and butyl methacrylate.

The capsules produced can be dispersed into a curable carrier, resulting in an ink that can be printed or coated onto a large, arbitrary shaped or curved surface using conventional printing or coating techniques.

In the context of the present invention, one skilled in the art will select encapsulation procedures and wall materials based on the desired encapsulation properties. These properties include the distribution of capsule radius; Electrical, mechanical, diffusion, and optical properties of the capsule wall; And chemical miscibility with the internal phase of the capsule.

Capsule walls will generally have a high electrical resistivity. You can use a wall with a relatively low resistivity, but this can limit performance in demanding a relatively higher addressing voltage. The capsule wall must also be mechanically strong (although mechanical strength is not so important if the finished capsule powder is dispersed in the curable polymerizable binder for coating). Capsule walls should generally not be porous. However, to use the encapsulation procedure in which the porous capsule is made, it is possible to overcoat the porous capsules in a post-processing step (ie, secondary encapsulation). In addition, to disperse the capsule in the curable binder, the binder will contribute to close the pores. The capsule wall must be optically transparent. However, the wall material may be selected to match the index of refraction of the interior phase of the capsule (ie, the suspension fluid) or the binder into which the capsule will be dispersed. For some applications (eg insertion between two fixed electrodes), a monodisperse capsule radius is preferred.

Encapsulation techniques suitable for the present invention involve polymerization of urea and formaldehyde in the aqueous phase of an oil / water emulsion in the presence of a negatively charged carboxyl-substituted linear hydrocarbon polyelectrolyte material. The resulting capsule wall is an urea / formaldehyde copolymer, which directly surrounds the inner phase. Capsul is transparent, mechanically strong and has good resistivity properties.

A related technique of in situ polymerization uses oil / water emulsions, which are formed by dispersing an electrophoretic composition (ie, a dielectric liquid containing a suspension of pigment particles) in an aqueous environment. The monomer polymerizes to form a polymer with a higher affinity to the interior phase than the aqueous phase, thus condensing around the emulsified oily droplets. In an in situ polymerization process, urea and formaldehyde are condensed in the presence of poly (acrylic acid) (see, eg, U.S. Patent No. 4,001,140). U.S. In other processes described in patent 4,273,672, any of the various crosslinkers contained in the aqueous solution is deposited around the fine oil droplets. Such crosslinkers include aldehydes, in particular formaldehyde, glyoxal, or glutaraldehyde; Alum; Zirconium salts; And polyisocyanates.

The coacetation approach also uses oil / water emulsions. One or more colloids are coacervated from the aqueous phase (ie, aggregated) and deposited into the shell around the oily droplets through the control of temperature, pH and / or relative concentration, resulting in microcapsules. Suitable materials for coacervation include gelatin and gum arabic. For example, U.S. See patent 2,800,457.

The interfacial polymerization approach depends on the presence of fat-soluble monomers in the electrophoretic composition, which once again exist as an emulsion in the aqueous phase. The monomers in the micro hydrophobic droplets react with the monomers introduced into the aqueous phase to polymerize at the interface between the droplets and the surrounding aqueous medium and form a shell around the droplets. Although the resulting walls can be relatively thin and permeable, this method does not require elevated temperatures, which is characteristic of some other methods, and therefore provides greater flexibility in terms of selecting a dielectric liquid.

7A illustrates an example apparatus and environment for performing emulsion-based encapsulation. Oil / water emulsions are prepared in a vessel 76 equipped with a monitor 78 and a thermostat 80. pH monitor 82 may also be included. Impeller 84 can be used to maintain shaking during the encapsulation process and in combination with emulsifiers to control the size of emulsion droplets 86 in the finished capsule. Aqueous continuous phase 88 may contain, for example, prepolymers and various system modifiers.

FIG. 7B illustrates oil droplet 90 consisting of substantially transparent suspension fluid 92 in which white microparticles 94 and black particles 96 are dispersed. Preferably, particles 94 and 96 have a density that is substantially in harmony with the density of suspension fluid 92. The liquid phase may also contain some threshold / bi-stable modifiers, charge control agents and / or hydrophobic monomers to effect interfacial polymerization.

FIG. 7C illustrates a similar oil droplet 98 consisting of thickly stained suspension fluid 100 containing white particles 94 and a dispersion of a suitable charge control agent.

Coating aids can be used to improve the uniformity and quality of the coated or printed electrophoretic ink material. Wetting agents are typically used to control the interfacial tension and the liquid / air surface tension at the coating / substrate interface. Wetting agents include, but are not limited to, anionic and cationic surfactants, and nonionic species such as silicone or fluoropolymer based materials. Dispersants can be used to modify the interfacial tension between the capsule and the binder and provide control over entanglement and particle settling.

Surface tension modifiers can be added to adjust the air / ink interfacial tension. Polysiloxanes are commonly used in such applications to improve surface leveling while minimizing other drawbacks in the coating. Surface tension modifiers include, but are not limited to, fluorinated surfactants such as Zonyl from DuPont (Wilmington, DE). Fluorod of Series, 3M (St.Paul, MN) Series, and the fluoroalkyl series of Autochem (Glen Rock, NJ); Siloxanes such as Silwet of Union Carbide (Danbury, CT) ; And polyethoxy and polypropoxy alcohols. Anti-foaming agents such as silicone and silicone-free polymeric materials can be added to enhance the movement of air from the ink to the surface and promote the bursting of bubbles at the coating surface. Other useful antifoaming agents include, but are not limited to, glyceryl esters, polyhydric alcohols, mixed antifoaming agents such as oil solutions of alkyl benzenes, natural fats, fatty acids, and metallic soaps, and combinations of dimethyl siloxane polymers and silicas. Included are silicone antifoams. Stabilizers such as uv-absorbers and antioxidants may also be used to improve the life of the ink.

Other additives for controlling properties such as coating viscosity and foaming can also be used in coating fluids. Stabilizers (uv-absorbers, antioxidants) and other additives that may prove useful in real materials.

Example 1

The following procedures describe gelatin / acacia microencapsulation for use in the electrophoretic display of the present invention.

a. Preparation of oil (internal) phase

0.5 g Oil Blue N (Aldrich, Milwaukee, WI), 0.5 g Sudan Red 7B (Aldrich), 417.25 g halogenated hydrocarbon oil 0.8 (Halogenated hydrocarbon Products Corp., River Edge, NJ) and 73.67 g in a 1 L flask Isopar-G Add (Exxon, Houston, TX). The mixture is stirred at 60 ° C. for 6 hours and then cooled to room temperature. 50.13 g of the resulting solution is placed in a 50 ml polypropylene centrifuge tube, to which OLOA 1200 (Chevron, Somerset) in 1.8 g of titanium dioxide (TiO ₂ ) (DuPont, Wilmington, DE), 0.78 g of halogenated hydrocarbon oil 0.8 , NJ) 10% solution and 0.15 g Span 85 (Aldirch) are added. This mixture is then sonicated with Power 9 in an Aquasonic Model 75D sonicator (VWR, Westchester, Pa.) At 30 ° C. for 5 minutes.

b. Preparation of Aqueous Phase

10.0 g of Acacia (Aldrich) is dissolved in 100.0 g of water with stirring at room temperature for 30 minutes. The resulting mixture is poured into two 50 ml polypropylene centrifuge tubes and centrifuged at about 2000 rpm for 10 minutes to remove insoluble matter. 66 g of purified solution is then poured into 500 ml of unshielded jacketed reactor and then the solution is heated to 40 ° C. The 6 blade (vertical geometry) paddle shaker is then placed just below the surface of the liquid. While shaking the solution at 200 rpm, 6 g of gelatin (300 bloom, type A, Aldrich) are carefully added over about 20 seconds to avoid lumps. Agitation is then reduced at 50 rpm to reduce foaming. The resulting solution is then stirred for 30 minutes.

c. Encapsulation

While shaking at 200 rpm, the oil phase prepared as described above is likewise poured slowly over about 15 minutes into the aqueous phase prepared as described above. The resulting oil / water emulsion is emulsified for 20 minutes. To this emulsion is slowly added 200 g of water preheated to 40 ° C. over about 20 seconds. The pH is then reduced to 4.4 over 5 minutes with 10% acetic acid solution (Aldrich's acetic acid). The pH is monitored using a pH meter and pH 4.0 buffer previously calibrated to pH 7.0. Stir for 40 minutes. Then 150 g of water preheated to 40 ° C. are added and then the contents of the reactor are cooled to 10 ° C. When the solution temperature reaches 10 ° C., 3.0 ml of 37% formalin solution (Aldrich) is added and the solution is stirred for 60 more minutes. After addition of 20 g sodium carboxymethylcellulose (NaCMC), a 20 wt% solution of sodium hydroxide (NaOH) is added to raise the pH to 10.0. The thermostat is then set to 40 ° C. and stirred for 70 minutes. The slurry is cooled to room temperature overnight with stirring. The resulting capsules are then ready to be sieved.

d. Formation of display

Two procedures for making an electrophoretic display from the capsule slurry are described below.

i. Procedure using urethane binder

The resulting capsule slurry from above is mixed with an aqueous urethane binder NeoRez R-9320 (Zeneca Resins, Wilmington, Mass.) At a ratio of 1 part binder to 10 part capsules. The resulting mixture is then coated using scraping blades on a sheet of indium-tin oxide sputtered polyester film about 100 μm to about 125 μm thick. The blade gap of the blade is adjusted to 0.18 mm to form a monolayer of capsule. The coated film is then dried in hot air (60 ° C.) for 30 minutes. After drying, the dried film was heated at 60 ° C. at a high temperature of Cheminstruments (Fairfield, OH) at a pressure of 15 psi on the back of a sheet of polyester screen about 100 μm to about 125 μm thick printed with thick film silver and dielectric ink Hot lamination in roll laminate. Anisotropic tape is used to connect the backside to the film. The conductive region forms an addressable region of the generated display.

ii. Procedures Using Urethane / Polyvinyl Alcohol Binders

The resulting capsule slurry from above was prepared with an aqueous binder consisting of a mixture of 20% solution of NeoRez R-966 (Zeneca Resins) and Airvol 203 (polyvinyl alcohol, Airvol Industries, Allentown, PA) and 1 part Airvor 203 solution to 1 part Mix at the ratio of NeoRez R-966 to 5 parts capsules. The resulting mixture is then coated onto a sheet of polyester film sputtered with indium tin oxide of about 100 μm to about 125 μm using a scraping blade. The blade gap of the blade is adjusted to 0.18 mm so that a single layer of capsule is produced. The coated film is then dried at high temperature (60 ° C.) for 30 minutes. After drying, the thick film silver ink is printed directly behind the dried film and allowed to cure at 60 ° C. The conductive area forms an addressable area of the display.

2. Example 2

The following is an example of the preparation of microcapsules by in situ polymerization.

In a 500 ml unshielded jacketed reactor 50 ml of a 10 wt% solution of ethylene co-maleic anhydride (Aldrich), 100 ml of water, 0.5 g of resorcinol (Aldrich) and 5.0 g of urea (Aldrich) are mixed. The mixture is stirred at 200 rpm and the pH is adjusted to 3.5 with 25 wt% NaOH over 1 minute. The pH is monitored using a pH meter and pH 4.0 buffer previously calibrated to pH 7.0. To this, the oil phase prepared as described in Example 1 above is slowly added and the shaking is increased to 450 rpm to reduce the average particle size to less than 200 μm. Then 12.5 g of 37% aqueous formaldehyde solution are added and the temperature is increased to 55 ° C. The solution is heated at 55 ° C. for two hours.

3. Example 3

The following is an example of preparation of microcapsules by interfacial polymerization.

1.0 g of sebacoyl chloride (Aldrich) is added to 44 g of oil prepared as described in Example 1 above. The 3 ml mixture is then dispersed in 200 ml water with stirring at 300 rpm at room temperature. To this dispersion is then added 2.5 ml of a 10 wt% aqueous solution of 1,6-diaminohexane. After about 1 hour a capsule is formed.

E. Binder Material

The binder is typically used as an adhesive medium to support and protect the capsule as well as to bind the electrode material to the capsule dispersion. The binder may be nonconductive, semiconductive or conductive. Binders are available in many forms and chemical types. Among these are water-soluble polymers, water-containing polymers, fat-soluble polymers, thermosetting and thermoplastic polymers, and irradiation-curing polymers.

Among the water-soluble polymers, various polysaccharides, polyvinyl alcohol, N-methyl pyrrolidone, N-vinyl pyrrolidone, various Carbowax Species (Union Carbide, Danbury, CT), and poly-2-hydroxyethylacrylate.

Generally, a water-dispersed or water-containing system is Neorez And Neocryl Resin (Zeneca Resins, Wilmington, MA), Acrysol (Rohm and Haas, Philadelphia, PA), Bayhydrol (Bayer, Pittsburgh, Pa.), And Cytec Industries (West Paterson, NJ) HP lines are exemplified latex compositions. In general, these are often latexes of polyurethanes mixed with one or more acrylic products, polyesters, polycarbonates or silicones, which are respectively glass transition temperatures, tackiness, softness, transparency, flexibility, water permeability and solvent resistivity, elongation And a final set of properties of a specific set of properties defined by tensile strength, thermoplastic flow, and solids level. Some water-containing systems can be mixed and catalyzed with reactive monomers to form more complex resins. Some may be further crosslinked using, for example, crosslinking reagents such as azidine, which react with carboxyl groups.

Typical applications of water-containing resins and aqueous capsules are shown below. Excess water is separated by centrifuging a large amount of particles at low speed. After 10 minutes at a given centrifugation process, for example 60 × gravity (“G”), the capsule 180 is found at the bottom of the centrifuge tube 182 as shown in FIG. 8, while the water portion 184 is found at the top layer. . Carefully remove the water part (by pouring or pipetting). The mass of the remaining capsule is measured and the resin is added so that the mass of the resin is, for example, between 1/8 and 1/10 of the capsule weight. This mixture is mixed gently on a vibrating mixer for about 1.5 hours. After about an hour and a half, the mixture is ready to be coated on a suitable substrate.

Thermosetting systems are exemplified by the group of epoxides. These two pairs of systems can vary greatly in viscosity, and the pair's reactivity determines the “pot life” of the mixture. If the pot life is long enough to allow the coating process, the capsules may be coated in an ordered arrangement in the coating process prior to resin curing and solidification.

Thermoplastic polymers, which are often polyesters, melt at high temperatures. Typical applications of this type of product are hot-melt glues. Dispersions of heat resistant capsules may be coated on such media. The solidification process begins during cooling and the final hardness, transparency and flexibility are affected by the branching and molecular weight of the polymer.

Fat soluble or solvent soluble polymers are often similar in composition to water-containing systems except for the apparent differences in water itself. The range in the formation of solvent systems is limited only by solvent selection and polymer solubility and is broad. Consideration in the solvent-based system is the viability of the capsule itself-the integrity of the capsule wall cannot be compromised in any way by the solvent.

Spinning curable resins are generally found in solvent-based systems. Capsules can be dispersed and coated in such a medium and the resin can then be cured by exposure to a threshold value of long or short wave ultraviolet radiation for a specified time. As in the curing polymer resin in all cases. The final properties are determined by the branching and molecular weight of the monomers, oligomers and crosslinkers.

However, many "water-reducing" monomers and oligomers are commercially available. In the strictest judgment, they are not water soluble, but water is an acceptable diluent at low concentrations and can be dispersed in the mixture relatively easily. In this situation, water is used to reduce the viscosity (initially thousands to hundreds of thousands of centipoise). Water-based capsules, such as those made from protein or polysaccharide materials, can be dispersed and coated in such media, provided the viscosity can be sufficiently low. Curing in such systems is generally due to ultraviolet radiation.

II. Components of the fault and the display construction method to the fault

A. Coating of Capsules with Monolayers on Substrate

Once a capsule suitable for coating on a display to a monolayer is made, the present invention also provides a method of coating such a capsule to a monolayer. In general, encapsulated electrophoretic displays include dispersions of capsules in the polymerizable binder. Alternatively, dispersions can include dispersions of capsules in carriers (rather than binders) or capsules without binders or carriers. Capsules contain an electrophorically active suspension. Capsule dispersions (or “slurry”) are typically coated on a flexible polymerizable substrate that may soon be combined with the front electrode at some point, so that a monolayer of the capsule is achieved. Having a binder with certain properties and / or changing the physical properties of the binder, for example by changing pH or adding a surfactant, may be useful for depositing a monolayer of the capsule. This resulting film is then laminated to the back substrate. The back substrate can be patterned into a single or multilayer electrode structure that can be printed or formed by other methods on polymeric materials (which can be flexible), glass and / or metal substrates. Although the present invention is described in the context of microencapsulated electrophoretic displays, this may relate to the implementation of any electronic display in which the connection of an electrode (ie, a front that applies power to the display) to the back electrode substrate is desirable.

More particularly, after encapsulation, the capsule slurry is typically dehydrated to achieve the target solids content. Dehydration may be accomplished by centrifugation, absorption, evaporation, mesh filtration, or osmotic separation as described above. This slurry is then mixed with a binder such as a polymer latex (such as an aqueous polyurethane dispersion) and shaken to ensure a uniform distribution of the binder material. The binder can have various fractions. Some portions of the binder may be solids (“binder solids”), and some portions of the binder may be liquids, such as water, that can evaporate. Since the binder may have more than one type of solid, the term "binder solid" may include one or more types of solids in a particular binder (ie, the portion of solids in the binder relative to other fractions in the binder). In one example, the binder is typically an aqueous dispersion of latex particles. The solid may be integrated with the film.

In order for the film to be closely packed with the monolayer film, the ratio of binder solid mass to capsule mass should be kept as low as possible. Minimizing the amount of material that is not optically active (such as a binder) results in a good charge and as a result the contrast between the white and black states of the display is good. See, eg, FIGS. 1A and 1B. However, the binder is present in the film, providing structural integrity, causing a tension between reducing the amount of binder (for optical properties) and increasing amount of binder (for structural reasons). In films, useful binder solid mass to capsule mass ratios of about 1: 2 to about 1:20, preferably about 1: 4 to about 1:12, most preferably about 1: 6 to about 1:10 Range. This metering also applies to the polymer matrix content in the EPID in which the polymer is dispersed.

The slurry of the capsule in the aqueous binder prepared previously is coated onto the substrate in a single layer as described below. In one example, indium tin oxide ("ITO") coats the slurry on a polyester substrate disposed on the substrate, which will ultimately function as the front transparent electrode and substrate. The thickness of the substrate may be between about 25 μm and about 500 μm. Typically this film is dried at about 60 ° C. to evaporate the aqueous phase.

1. Slot die method

In one coating process, a slurry of capsules in a previously prepared aqueous binder is coated with a single layer. The coating process involves metering the capsule / binder slurry through the slot die coating head. 2 and 3, the head 20 attached to the pump 21 weighs a certain amount of slurry / binder 22 through the closely spaced gap 24. Gap 24 allows only a single layer of capsule 26 to pass through head 20. The flow rate of the slurry can be set such that a continuous monolayer 25 is formed when the head 20 moves past the receiving substrate 28 on the roller 29. The substrate 28 and the head 20 move relative to each other. For example, the substrate moves in a straight line (not shown) or on roll 29 (FIG. 2). The movement direction of the roll 29 and the base material 28 is shown by the arrow (gamma). Alternatively, head 20 can typically move in a straight line (FIG. 3). The direction of movement is indicated by the arrow ε. This may be a continuous or batch process. Capsule / binder slurry is typically deposited at a rate of about 0.1 to about 100 m / min, preferably about 0.2 to about 0.7 m / min. The fluid flow can be actively regulated, for example, to start or stop coating the area. The pump 21 used to provide the metering flow may be a low shear pump, for example a peristaltic pump. Low shear pumps can prevent breakage of the capsule during coating.

The slurry of the capsule can be deposited in a single layer by adjusting the width to average sphere diameter ratio of the gap. The gap / average sphere diameter ratio is the ratio of the width of the gap through which the slurry moves to the average of the diameter of the gap capsule moving through the gap. This ratio may be based on the deformation and surface properties of the spheres as well as the flow properties of the coating fluid, but in one embodiment is about 1 to about 2.5, preferably about 1.2 to about 1.6. Capsules are generally spherical in coating, but may change slightly due to deformation during processing so that their diameter may change slightly at any given time. In general, the equations for pump speed versus coating width, relative die speed and coating thickness are as follows.

Pump Speed = Coating Width × Die Speed × Coating Wet Thickness

The units for these variables are (length) ³ / (hour) for pump speed; For coating width (length); (Length) / (hour) for die speed; It is (length) for the coating wet thickness and the length and time can be measured in any suitable unit selected by the user. Since any deformation can change the thickness slightly, the coating wet thickness can deviate from certain values in the monolayer formed of particles that are large and easily deformable. Additionally, in some cases a film that is slightly thicker or slightly thinner than the diameter of one capsule may be desirable, based on the capsule / binder ratio, how precisely the capsule is transformed into the film, and / or the presence of any gap voids. have. For example, the softer / softer or elastic the capsule is, the thinner the film can be. The less soft / soft or elastic the capsule, the thicker the film can be. However, once the thickness of the film is determined (eg empirically), a change in die speed or coat width will be directly related to the equation.

2. Air knife way

In another embodiment of the invention, an air knife coater forms an encapsulated electrophoretic display having a monolayer of capsules. Air knife coaters can be used in a variety of coating applications, including carbon free paper and electroluminescent coatings, which contain encapsulating materials. However, the use of air knives in these applications is used for thickness control and not for forming a monolayer of stable and robust capsules.

In the method of the present invention, the capsule slurry is applied by applying pressure to a moving or stationary substrate such that the capsules in the slurry form a monolayer on the substrate. The substrate may be a conductive material such as polyester sputtered with ITO. The mixture is pressurized with a pressurized gas, typically air. An air knife can be used to apply pressure to distribute the slurry evenly. With respect to FIG. 4, the air knife 30 lies at a distance (distance a) of about 1 to about 15 cm from the surface of the slurry 35. The slurry is provided on the surface of the substrate 31 and moved in the δ direction by the coating roll 32. Air knife 30 is placed at an angle of about 0 to about 90 degrees from the surface of slurry 35 (eg, more positions are possible, but shown in three positions, air knife 30a, 30b, 30c in FIG. 4). The pressure source 34 supplies pressure to the air knife 30. Monolayers can be formed if conditions such as gas pressure, distance from the slurry, angle to the slurry, slurry viscosity, and relative speed between the air knife and the substrate on which the slurry is deposited are optimized. For example, an air knife can not only form a monolayer of capsules, but can also remove excess slurry. If an air knife is used with a controlled amount of capsule slurry, waste of the slurry may be limited. In addition, since the air knife is not in contact with the slurry, the possibility of scratching the substrate or breaking the capsule is reduced.

The gas blown into the coating material may be other than air at ambient temperature. The gas may be heated or cooled to change the coatability and viscosity properties of the capsule slurry. The gas may be wet (eg, liquid in droplets) or dried and blown to control evaporation of the solvent in the capsule slurry. The temperature or addition of the liquid can be controlled, for example, with a heater, refrigeration unit, liquid pump and / or other device known to those skilled in the art, as indicated by regulator 33 of FIG. 4. The gas may be mixed with a solvent to help cure the capsule slurry and / or to make the slurry more easily coated onto the substrate. The solvent is chosen to be miscible with the substrate layer. For example, if the substrate is water-based, the solvent is water or alcohol. Useful alcohols include isopropyl alcohol, methanol and ethanol. If the substrate is organic, miscible organic solvents may be mixed with the gas. For example, the butyl acetate substrate is coated with "acetate wetting" air. Other organic solvents useful for use in the process of the present invention include methylene chloride and chlorobenzene. In certain embodiments, the suspension fluid in the capsule is a halogenated hydrocarbon such as tetrachloroethylene or poly (chlorotrifluoroethylene). In addition, the evaporative binder in certain embodiments may be, for example, polymeric latex, acrylic, urethane, poly (vinyl alcohol), or water-based binder.

3. Coating substantially without binder

In some situations, it may be desirable to coat the capsule on the substrate substantially free of binder. For example, with respect to FIG. 9A, capsule 50 has capsule wall 52 constructed from a polymer. For example, the capsule can be formed from gelatin / cacacia as described above. Capsule wall 52 is heavily swollen with water and / or polar solvent. For example, about 1 to about 90%, preferably about 5 to about 20% of the capsule wall 52 can be formed from the polymer while about 10 to about 99%, preferably about 80 to about 95% is water And / or from polar solvents. This capsule 50 is coated onto the substrate 54 as described above for the slurry. Capsule 52 may be suspended in a carrier such as water or may not be suspended in any carrier. When the capsule 50 is dried, for example at 60 ° C., water and / or polar solvent evaporates from the capsule wall 52 of the capsule 50 in the coated monolayer. As the water and / or polar solvent evaporates, the capsule walls 52 mix and / or bond with and / or adhere to each other and / or the substrate 54. A film is formed. In some circumstances, without the binder in the film, the capsule may be modified more highly than there is a binder in the film.

B. Laminating Back Substrate

Once the capsule slurry is coated onto a flexible or rigid substrate (eg polymeric material or glass) to achieve a monolayer of microcapsules, this coated film is then laminated to the backing substrate (alternatively known as "back plate"). Let's do it. The back substrate may be, for example, a polymeric material (which may be flexible), glass or metal. The back substrate may be patterned into a single or multilayer electrode structure that can be printed or formed by other means on the secondary flexible polymeric substrate. Although the present invention is described in the context of an encapsulated display, this relates to the implementation of any electronic display for connecting the front active substrate to the back electrode substrate (with or without additional layers between the front surface and the back substrate). Can be.

Typically, lamination takes place under vacuum and involves the application of heat and / or pressure. For example, depending on the lamination procedure and / or lamination material used, a temperature of about 40 to about 150 ° C., more preferably about 50 to about 120 ° C. may be used. Typical back substrates are constructed from base substrates with or without electrodes stacked on the base substrate. One example of the backing substrate is a set of polyester or polyimide base films and patterned electrodes. In general, these electrodes are a single- or multilayer conductor / insulator stack that can be printed on a substrate. The substrate can be a polymeric material (which can be flexible), glass or metal. Typically, the conductors are conductive particles (eg, carbon, silver, palladium, tin oxide, plated tin oxide, copper), plated polyester, and screen printed and heat cured vinyl. The back substrate may also have transistors (organic and / or silicon-based), diodes, and / or electrodes disposed on the substrate.

The film can be combined with the back substrate in various ways. Typically, film 40 after coating with a monolayer has voids and irregularities in binder 44 between capsules 42, irregular surfaces on capsule 42, and / or irregular surfaces at the edges of binder 44, as shown in FIG. 5A. As described above, the binder level in the slurry is kept as low as possible to maximize the optically active area so that the binder flows little and absorbs the lamination stress. The capsule wall has most of these stresses, which can result in the capsule breaking. Additionally, without material filling the voids between the capsules as well as voids in the surface of the capsule or in other areas such as the edges of the binder, the laminated article can have trapped air or trapped vacuum packets, which is a mechanical experience of the film. It can change stresses and affect electrical characteristics (as a result, the switching can be non-uniform).

In one embodiment, a layer of additional material may be included between the film and the backing substrate to address this problem. The layer of such material can be an adhesive that can flow at the lamination temperature. The layer may also be tacky. For example, it may be the same or similar polymerizable material as the layer of binder material previously coated on the front substrate, or it may be a hot melt adhesive sheet, which may be thermoplastic or thermoset. Alternatively, it may be a material that is initially liquid at room temperature but forms a solid matrix after curing or crosslinking. This solution provides a flowable material that can fill any voids between the capsules during the lamination process without exerting excessive stress on the capsule wall itself and can soften the roughness of the back capsule surface. This final result can be seen in Figure 5B. An additional layer of material 46 fills the gap (including but not limited to the voids between the capsules 42, the irregular surface of the binder 44 and the irregular surface of the capsule 42) and is attached to the back substrate 48. An additional layer of material 46 may be initially coated on film 40 (ie, the back of the capsule) or back substrate 48 prior to the lamination procedure, or layer 46 may be introduced between the film and the back substrate during the lamination procedure. Thermoplastic or thermoset). The more uniform the size of the capsule and / or the simpler the dispersion of the capsule (ie, the more complete the monolayer), the thinner the layer of additional material will be, since a more uniform film is produced that contains fewer gaps and so on. Can lose. Uniform capsule size and distribution can be obtained as described above. The thickness of the layer of additional material may be about 50 μm or less. Typically, such layers and / or capsules and / or substrates form a uniform and thick layer. The thickness of this layer may be about 10 to about 500 μm, preferably about 50 to about 300 μm. Alternatively, some capsules may be used without a binder as described above. In this case, and with respect to FIG. 9B, a final structure can be formed in which the gap and irregular surface of the capsule 50 on the crawfish 54 are filled with a layer of material 56 adjacent to the back substrate 58.

If a layer of material is initially coated on the front film, this may provide a substantially planar and / or tacky surface of the capsule film towards the back substrate so that it can be laminated to the back substrate. Thus, the capsule film is planar before lamination and the adhesive front and back substrate need not be stored separately, since only the front substrate is tacky. In addition, the front film need not have a back substrate. For example, a film planarized with a layer of material can be operated with a stylus. This can occur with or without the backing substrate and the layer of material need not be sticky unless the backing substrate is used.

Semiconductive or anisotropically conductive adhesives can be used as additional layers. Such materials will conduct the electric field from the back plate to the capsule with little loss of electric field strength. Adhesives containing carbon particles, gold particles, aluminum particles, platinum particles, silver particles, plated polymer spheres, plated glass spheres or ITO particles can be used. In addition, conductive polymers such as polyacetylene, polyaniline, polypyrrole, P-DOT, or polythiophene can be used to dope additional layers of material to allow them to conduct well in the Z-axis rather than in the plane of the adhesive. Thus, the electric field is transmitted more effectively to the capsule. To produce such films, the adhesive sheet can be cast and stretched in one or both axes. The resistivity of the layer of material may be about 10 ⁵ to about 10 ¹⁵ ohm · cm, more preferably about 10 ⁸ to about 10 ¹³ ohm · cm. In addition, a layer of insulating material may be used.

Modifications, modifications, and other implementations of those described herein will occur to those skilled in the art without departing from the spirit and scope of the invention as claimed. In addition, the present invention is defined by the spirit and scope of the following claims rather than by the preceding exemplary technology.

Claims (205)

An encapsulated electrophoretic element containing a plurality of non-spherical capsules disposed substantially in a single layer on a substrate. The element of claim 1 wherein the capsule is of substantially uniform size. The element of claim 1, wherein the capsule is substantially planar in one or more sides adjacent to the substrate. The element of claim 1 wherein a plurality of capsules are disposed on a substrate and combined with a binder to form a film. The element of claim 4 wherein the film consists of closely filled capsules. The element of claim 4, wherein the binder consists of a binder solid and the ratio of the mass of the binder solid to the mass of the capsule of at least some elements is from about 1: 2 to about 1:20. The element of claim 4, wherein at least some elements have an optically active fraction of at least 70%. The element of claim 4 further comprising a layer of material substantially filling any gaps formed in the film. 9. The element of claim 8, wherein the layer of material is substantially planar on the opposite side of the film. 9. The element of claim 8, wherein the capsule, binder, and layer of material form a layer that is substantially uniform in thickness. The element of claim 10 wherein the layer has a thickness of about 10 to about 500 μm. The element of claim 8 wherein the layer of material consists of a binder. The element of claim 8 wherein the layer of material consists of an insulator. The element of claim 8, wherein the layer of material is tacky during, substantially during, or after filling the gap in the film. The element of claim 8, wherein the layer of material is in a liquid state either substantially before, during or after filling the gap in the film. 9. The element of claim 8, wherein the capsule, binder, and layer of material form a layer substantially free of voids. The element of claim 8, wherein the layer of material has a thickness of about 50 μm or less. The element of claim 8 wherein the layer of material consists of a conductor. The element of claim 8 wherein the layer of material consists of a semiconductor. 9. The material of claim 8 wherein the layer of material contains a material selected from the group consisting of carbon particles, gold particles, aluminum particles, platinum particles, silver particles, plated polymer spheres, plated glass spheres, and indium tin oxide particles. Element consisting of adhesives. 9. The element of claim 8, wherein the layer of material consists of an adhesive containing a material selected from the group consisting of polyacetylene, polyaniline, polypyrrole, polyethylene dioxythiophene, and polythiophene. 10. The element of claim 8, further comprising a backing substrate disposed near a layer of material. The element of claim 22 wherein the layer of material is initially associated with the film. The element of claim 22 wherein the layer of material is initially associated with the backing substrate. 23. The element of claim 22 wherein the back substrate consists of a material selected from the group consisting of polymeric materials, glass, and metals. The element of claim 22, wherein the backing substrate consists of one or more electrodes. The element of claim 22, wherein the backing substrate consists of one or more transistors. 28. The element of claim 27 wherein the transistor consists of a silicon-based material. 28. The element of claim 27 wherein the transistor consists of an organic material. The element of claim 22, wherein the backing substrate consists of one or more diodes. The element according to claim 1, wherein the substrate is made of a polymerizable material. The element of claim 1 wherein the substrate consists of one or more electrodes. 33. The element of claim 32 wherein the electrode consists of indium tin oxide. The element of Claim 1 in which a base material consists of a polyester film. The element of claim 1 wherein the substrate has a thickness of about 25 to about 500 μm. The element of claim 1, wherein each capsule is defined by a separate capsule wall having a thickness of about 0.2 to about 10 μm. The element of claim 1, wherein the capsule consists of a polymer matrix having fluid-containing cavities. The element of claim 1, wherein the one or more capsules comprise a suspension fluid and one or more kinds of particles. The element of claim 1, wherein the one or more capsules comprise two or more kinds of electrophoretic particles, wherein the optical properties of the first kind of particles are different from the second kind of particles. An encapsulated electrophoretic display consisting of one or more elements consisting of a plurality of non-spherical capsules disposed substantially in a single layer on a substrate. A method of making an encapsulated electrophoretic element, which may have a plurality of capsules disposed on a substrate substantially in a single layer, comprising the following steps: (a) providing a capsule; (b) mixing one or more capsules with a binder to produce a capsule / binder mixture; (c) coating the capsule / binder mixture on at least partially conductive substrate to produce a film; And (d) curing the capsule / binder mixture. 42. The method of claim 41, wherein the binder is selected from the group consisting of acrylic products, urethanes, and poly (vinyl alcohol). 42. The method of claim 41 wherein the binder consists of a polymer latex. 42. The method of claim 41 wherein the fraction of the binder can evaporate. 42. The method of claim 41 wherein the substrate is comprised of a polyester film sputtered with indium tin oxide. 42. The method of claim 41, wherein the one or more capsules contain a plurality of particles dispersed in the suspension fluid. 47. The method of claim 46, wherein the particulate consists of titanium dioxide. 47. The method of claim 46, wherein the suspension fluid consists of halogenated hydrocarbons. 47. The method of claim 46, wherein the suspension fluid consists of aliphatic hydrocarbons. 42. The method of claim 41 wherein the coating step consists of applying pressurized gas to the capsule / binder mixture to deposit the capsule / binder mixture on the substrate such that the capsule is disposed on the substrate in a substantially single layer. 51. The method of claim 50, further comprising heating the pressurized gas to a temperature above ambient temperature before applying the pressurized gas to the capsule / binder mixture. 51. The method of claim 50, further comprising cooling the pressurized gas to a temperature below ambient temperature before applying the pressurized gas to the capsule / binder mixture. 51. The method of claim 50, further comprising adding a liquid to the pressurized gas. 54. The method of claim 53, wherein the liquid consists of one or more drops. 54. The method of claim 53, wherein the liquid consists of an organic solvent. 56. The method of claim 55, wherein the organic solvent consists of an alcohol. 51. The method of claim 50, wherein the coating step consists in applying the pressurized gas to the air knife. 51. The method of claim 50, wherein the pressurized gas is applied from a distance of about 1 to about 15 cm from the surface of the capsule / binder mixture. 51. The method of claim 50, wherein the pressurized gas is applied at an angle of about 0 to about 90 degrees from the surface of the conductive substrate. 51. The method of claim 50, wherein the pressurized gas consists of air. 59. The method of claim 56, wherein the alcohol consists of a compound selected from the group consisting of isopropyl alcohol, methanol and ethanol. 56. The method of claim 55, wherein the organic solvent consists of a compound selected from the group consisting of butyl acetate, methylene chloride and chlorobenzene. 42. The method of claim 41, wherein the coating step comprises coating at least some capsules on the substrate via the coating head. 64. The method of claim 63, wherein at least some capsule is dispensed through the coating head with a pump. 65. The method of claim 64, wherein the pump provides pump pressure with low shear force. 64. The method of claim 63, wherein the coating head consists of a slot die coating head. 67. The method of claim 66, wherein the width of the slot of the slot die coating head is about 1 to about 2.5 times the average diameter of the capsule. 64. The method of claim 63, wherein at least some capsules are disposed in a single layer to form a single layer. 42. The method of claim 41, further comprising laminating the film with the back substrate. 70. The method of claim 69, wherein a layer of material is disposed between the film and the back substrate. The method of claim 70, wherein the layer of material is combined with the layer of material prior to lamination. The method of claim 70, wherein the layer of material is combined with the film prior to lamination. 70. The method of claim 69, wherein heating occurs during the lamination step. 70. The method of claim 69, wherein pressurization occurs during the lamination step. 70. The method of claim 69, wherein vaporization of the gas occurs during the lamination step. 71. The method of claim 70, wherein the layer of material consists of an insulator. 71. The method of claim 70, wherein the layer of material consists of a conductor. 71. The method of claim 70, wherein the layer of material consists of a semiconductor. 71. The method of claim 70, wherein the layer of material is in the liquid state during at least some of the lamination steps. 71. The method of claim 70, wherein the layer of material consists of a binder. 71. The method of claim 70, wherein the laminating step produces a layer consisting of layers of capsules, binders, and materials and having one or more substantially planar faces adjacent to the back substrate. 71. The method of claim 70, wherein the laminating step produces a layer consisting of a layer of capsules, binders, and materials and substantially free of voids. The method of claim 70, wherein the layer of material is about 50 μm or less. 71. The method of claim 70, wherein the laminating step is made of a layer of capsule, binder, and material, wherein the layer is substantially uniform in thickness. 71. The method of claim 70, wherein the layer of material is tacky during substantially before, during or after filling the gap in the film. 71. The method of claim 70, wherein the layer of material contains a material selected from the group consisting of carbon particles, gold particles, aluminum particles, platinum particles, silver particles, plated polymer spheres, plated glass spheres, and indium tin oxide particles. Method consisting of glue. 71. The method of claim 70, wherein the layer of material consists of an adhesive containing a material selected from the group consisting of polyacetylene, polyaniline, polypyrrole, polyethylene dioxythiophene, and polythiophene. The method of claim 70, wherein the layer of material substantially fills any gaps formed in the film. 42. The method of claim 41 wherein the binder consists of a binder solid and the ratio of the mass of the binder solid to the mass of the capsule of at least some elements is from about 1: 2 to about 1:20. 42. The method of claim 41, further comprising the step of removing water from engagement with at least some of the capsules. 93. The method of claim 90, wherein removing the water consists of a process selected from the group consisting of centrifugation, absorption, evaporation, mesh filtration, and osmotic separation. An encapsulated electrophoretic element consisting of a plurality of capsules forming a film by being bonded to a binder in a substantially single layer on a substrate, wherein the ratio of the binder solid mass to the mass of the binder solid to the capsule of at least some elements An element that is about 1: 2 to about 1:20. 93. The element of claim 92, wherein the capsule is non-spherical. 93. The element of claim 92, wherein the capsule is substantially planar in one or more sides adjacent the substrate. 93. The element of claim 92 wherein the film consists of closely filled capsules. 93. The element of claim 92, further comprising a layer of material substantially filling any gaps formed in the film. 97. The element of claim 96, further comprising a backing substrate disposed near the layer of material. 98. The element of claim 97, wherein the layer of material is initially associated with the film. 98. The element of claim 97, wherein the layer of material is initially associated with the backing substrate. 98. The method of claim 97, wherein the backing substrate consists of a material selected from the group consisting of polymeric materials, glass, and metals. 98. The element of claim 97, wherein the backing substrate consists of one or more electrodes. 98. The element of claim 97, wherein the backing substrate consists of one or more transistors. 103. The element of claim 102, wherein the transistor consists of a silicon-based material. 103. The element of claim 102, wherein the transistor consists of an organic material. 97. The element of claim 97, wherein the backing substrate consists of one or more diodes. 93. The element of claim 92 wherein the substrate consists of a polymeric material. 93. The element of claim 92 wherein the substrate consists of one or more electrodes. 107. The element of claim 107, wherein the electrode consists of indium tin oxide. 93. The element of claim 92 wherein the substrate is a polyester film. 93. The element of claim 92, wherein the substrate has a thickness of about 25 to about 500 microns. 97. The element of claim 96, wherein the layer of material is substantially planar on the opposite side of the film. 97. The element of claim 96, wherein the layer of capsule, binder, and material forms a layer that is substantially uniform in thickness. 112. The element of claim 112, wherein the layer has a thickness of about 10 to about 500 microns. 116. The element of claim 113, wherein the capsule is of substantially uniform size. 97. The element of claim 96, wherein the layer of material consists of an insulator. 97. The element of claim 96, wherein the layer of material is tacky for at least one of substantially before, during, and after filling the gaps in the film. 97. The element of claim 96, wherein the layer of material is in the liquid state either substantially before, during or after filling the gap in the film. 97. The element of claim 96, wherein the layer of capsule, binder, and material forms a substantially void free layer. 97. The element of claim 96, wherein the layer of material is about 50 micrometers or less. 97. The element of claim 96, wherein the layer of material consists of a conductor. 97. The element of claim 96, wherein the layer of material consists of a semiconductor. 98. The adhesive of claim 96, wherein the layer of material comprises a material selected from the group consisting of carbon particles, gold particles, aluminum particles, platinum particles, silver particles, plated polymer spheres, plated glass spheres, and indium tin oxide particles. Element consisting of. 97. The element of claim 96, wherein the layer of material consists of an adhesive containing a material selected from the group consisting of polyacetylene, polyaniline, polypyrrole, polyethylene dioxythiophene, and polythiophene. 97. The element of claim 96, having an optically active fraction of at least 70%. 97. The element of claim 96, wherein each capsule is defined by an individual capsule wall having a thickness of about 0.2 to about 10 microns. 93. The element of claim 92, wherein the capsule consists of a polymer matrix having fluid-containing cavities. 93. The element of claim 92, wherein the one or more capsules comprise a suspension fluid and one or more kinds of particles. 93. The element of claim 92, wherein the one or more capsules comprise two or more kinds of electrophoretic particles, wherein the optical properties of the first kind of particles are different from the second kind of particles. An encapsulated electrophoretic element consisting of a plurality of capsules disposed substantially in a single layer on a substrate and combined with a binder to form a film, wherein at least some elements have an optically active fraction of at least 70%. 131. The element of claim 129, wherein the plurality of capsules are non-spherical. 131. The element of claim 129, wherein the capsule is substantially planar in one or more sides adjacent the substrate. 131. The element of claim 129, wherein the film consists of closely filled capsules. 131. The element of claim 129, wherein the binder consists of a binder solid and the ratio of the mass of the binder solid to the mass of the capsule of at least some elements is from about 1: 2 to about 1:20. 129. The element of claim 129, further comprising a layer of material substantially filling any gaps formed in the film. 136. The element of claim 134, further comprising a backing substrate disposed near a layer of material. 137. The element of claim 135, wherein the layer of material is initially associated with the film. 136. The element of claim 135, wherein the layer of material is initially associated with the back substrate. 137. The method of claim 135, wherein the backing substrate consists of a material selected from the group consisting of polymeric materials, glass, and metals. 138. The element of claim 135, wherein the backing substrate comprises one or more electrodes. 137. The element of claim 135, wherein the backing substrate comprises one or more transistors. 141. The element of claim 140, wherein the transistor consists of a silicon-based material. 141. The element of claim 140, wherein the transistor consists of an organic material. 137. The element of claim 135, wherein the backing substrate consists of one or more diodes. 129. The element of claim 129, wherein the substrate consists of a polymeric material. 129. The element of claim 129, wherein the substrate consists of one or more electrodes. 145. The element of claim 145, wherein the electrode consists of indium tin oxide. 129. The element of claim 129, wherein the substrate is a polyester film. 131. The element of claim 129, wherein the substrate has a thickness of about 25 to about 500 microns. 138. The element of claim 134, wherein the layer of material is substantially planar on the opposite side of the film. 136. The element of claim 134, wherein the layer of capsule, binder, and material forms a layer that is substantially uniform in thickness. 162. The element of claim 150, wherein the layer has a thickness of about 10 to about 500 microns. 134. The element of claim 134, wherein the capsule is of substantially uniform size. 134. The element of claim 134, wherein the layer of material consists of a binder. 134. The element of claim 134, wherein the layer of material consists of an insulator. 136. The element of claim 134, wherein the layer of material is tacky for at least one of before, during, and after filling the gap in the film. 137. The element of claim 134, wherein the layer of material is in the liquid state either substantially before, during or after filling the gap in the film. 134. The element of claim 134, wherein the layer of capsule, binder, and material forms a substantially void free layer. 134. The element of claim 134, wherein the layer of material is about 50 μm or less in thickness. 134. The element of claim 134, wherein the layer of material consists of a conductor. 138. The element of claim 134, wherein the layer of material consists of a semiconductor. 143. The adhesive of claim 134, wherein the layer of material comprises a material selected from the group consisting of carbon particles, gold particles, aluminum particles, platinum particles, silver particles, plated polymer spheres, plated glass spheres, and indium tin oxide particles. Element consisting of. 137. The element of claim 134, wherein the layer of material consists of an adhesive containing a material selected from the group consisting of polyacetylene, polyaniline, polypyrrole, polyethylene dioxythiophene, and polythiophene. 129. The element of claim 129, wherein each capsule is defined by individual capsule walls having a thickness of about 0.2 to about 10 microns. 131. The element of claim 129, wherein the capsule consists of a polymer matrix with fluid-containing cavities. 131. The element of claim 129, wherein the one or more capsules contain a suspension fluid and one or more kinds of particles. 129. An element according to claim 129, wherein the one or more capsules contain two or more kinds of electrophoretic particles, and wherein the optical properties of the first kind of particles differ from the second kind of particles. An encapsulated electrophoretic display consisting of one or more elements consisting of a plurality of capsules disposed substantially in a single layer on a substrate and bonded with a binder to form a film, wherein the binder consists of a binder solid and the mass of the binder solid versus at least some elements And a ratio of the mass of the capsules of about 1: 2 to about 1:20. An encapsulated electrophoretic display consisting of one or more elements consisting of a plurality of capsules disposed substantially in a single layer on a substrate and combined with a binder to form a film, wherein the display has at least some of the elements having an optically active fraction of at least 70%. . An encapsulated electrophoretic element consisting of a plurality of non-spherical capsules disposed substantially in a single layer on a substrate to form a film. 171. The element of claim 169, wherein the capsule is of substantially uniform size. 171. The element of claim 169, wherein the capsule is substantially planar in one or more sides adjacent the substrate. 171. The element of claim 169, wherein the film consists of closely filled capsules. 171. The element of claim 169, wherein at least some of the elements have an optically active fraction of at least 70%. 171. The element of claim 169, further comprising a layer of material substantially filling any gaps formed in the film. 174. The element of claim 174, wherein the layer of material is substantially planar in side opposite the film. 174. The element of claim 174, wherein the layer of capsule and material forms a layer that is substantially uniform in thickness. 176. The element of claim 176, wherein the layer has a thickness of about 10 to about 500 microns. 174. The element of claim 174, wherein the layer of material consists of an insulator. 174. The element of claim 174, wherein the layer of material is tacky during at least one of before, during, and after filling the gap in the film. 174. The element of claim 174, wherein the layer of material is in the liquid state either substantially before, during or after filling the gap in the film. 174. The element of claim 174, wherein the layer of capsule and material forms a substantially void free layer. 174. The element of claim 174, wherein the layer of material has a thickness of about 50 μm or less. 174. The element of claim 174, wherein the layer of material consists of a conductor. 174. The element of claim 174, wherein the layer of material consists of a semiconductor. 174. The adhesive of claim 174, wherein the layer of material comprises a material selected from the group consisting of carbon particles, gold particles, aluminum particles, platinum particles, silver particles, plated polymer spheres, plated glass spheres, and indium tin oxide particles. Element consisting of. 174. The element of claim 174, wherein the layer of material consists of an adhesive containing a material selected from the group consisting of polyacetylene, polyaniline, polypyrrole, polyethylene dioxythiophene, and polythiophene. 174. The element of claim 174, further comprising a backing substrate disposed near the layer of material. 187. The element of claim 187, wherein the layer of material is initially associated with the film. 187. The element of claim 187, wherein the layer of material is initially associated with the backing substrate. 187. The element of claim 187, wherein the backing substrate consists of a material selected from the group consisting of polymeric materials, glass, and metals. 187. The element of claim 187, wherein the backing substrate consists of one or more electrodes. 187. The element of claim 187, wherein the backing substrate consists of one or more transistors. 192. The element of claim 192, wherein the transistor consists of a silicon-based material. 192. The element of claim 192, wherein the transistor consists of an organic material. 187. The element of claim 187, wherein the backing substrate consists of one or more diodes. 171. The element of claim 169, wherein the substrate consists of a polymeric material. 171. The element of claim 169, wherein the substrate consists of one or more electrodes. 197. The element of claim 197, wherein the electrode consists of indium tin oxide. 171. The element of claim 169, wherein the substrate is a polyester film. 171. The element of claim 169, wherein the substrate has a thickness of about 25 to about 500 microns. 171. The element of claim 169, wherein each capsule is defined by individual capsule walls having a thickness of about 0.2 to about 10 microns. 171. The element of claim 169, wherein the capsule consists of a polymer matrix with fluid-containing cavities. 171. The element of claim 169, wherein the one or more capsules comprise a suspension fluid and one or more kinds of particles. 171. The element of claim 169, wherein the one or more capsules comprise two or more kinds of electrophoretic particles, wherein the optical properties of the first kind of particles are different from the second kind of particles. An encapsulated electrophoretic display consisting of one or more elements consisting of a plurality of non-spherical capsules disposed substantially in a single layer on a substrate to form a film.