JP2004536344A5 - - Google Patents

Description

In-plane switching electrophoretic display

  Electrophoretic displays (EPDs) are non-emissive devices based on electrophoretic phenomena that act on charged dye particles suspended in a colored (or colored) dielectric solvent. This general type of display was first proposed in 1969. EPDs typically comprise a pair of opposed, spaced-apart plate-like electrodes, with a spacer pre-determining a predetermined distance between the electrodes. At least one electrode (typically the viewing side) is transparent. For a passive type EPD, driving the display requires row and column electrodes on the top (display side) and bottom plates, respectively. Active EPDs, on the other hand, require an array of thin film transistors (TFTs) on the bottom plate and an unpatterned common transparent conductor plate on the top display substrate. An electrophoretic fluid composed of a colored dielectric solvent and charged dye particles dispersed therein is confined between the two electrodes.

  When a voltage difference is applied between the two electrodes, the pigment particles move by being attracted to a plate of the opposite polarity. Thus, by selectively charging the plate, the color seen on the transparent plate can be determined to be either the color of the solvent or the color of the pigment particles. Reversing the plate polarity allows the particles to move back to the opposite plate, thereby inverting the color. By controlling the charging of the plate in the voltage range, an intermediate color density (or gray density) with an intermediate dye density can be realized on the transparent plate. No backlight is required for this type of reflective EPD display.

  Transmissive EPDs are disclosed in U.S. Patent No. 6,184,856, which uses a substrate having a backlight, a color filter, and two transparent electrodes. The electrophoresis cell functions as a light valve. In the assembled state, the particles are arranged to minimize coverage of the lateral area of the cell, thereby allowing the backlight to pass through the cell. In a distributed (or scattered) state, the particles are placed over the lateral area of the pixel and scatter or absorb the backlight. However, the backlight and color filters used in this device consume large amounts of power, which is undesirable for portable devices such as PDAs (Personal Digital Assistants) and electronic books.

  In addition to the normal top / bottom (or top / bottom) electrode switching modes of EPDs, reflective "in-plane" switching EPDs have been described in EP. Kishi et al., "5.1: Development of In-Plane EPD", Canon Research Center, SID 00 Digest, pp. 24-27 (2000); Swanson et al., "5.2: High Performance Electrophoretic Displays", IBM Almaden Research Center, SID 00 Digest, pp. 29-31 (2000). However, these documents only disclose a monochrome in-plane switching EPD. To produce a multi-color display, either color filters or isolated color pixels or cell structures are needed for color separation and color rendering. Color filters are typically expensive and not power efficient. On the other hand, producing isolated pixels or cells for color separation and color rendering in in-plane switching mode has not been taught so far.

  EPDs having different pixel or cell structures are known in the art, such as partitioned EPDs (MA Hopper and V. Novotny, IEEE Trans. Electr. Dev.). ED 26, No. 8, pp. 1148-1152 (1979)) and microencapsulated EPDs (U.S. Pat. Nos. 5,961,804 and 5,930,026), which are incorporated herein by reference. Each has its own problems as described below.

  In partitioned EPDs, a partition (or partition) is provided between the two electrodes to divide the space into smaller cells to prevent unwanted movement of the particles, such as settling. However, the process of forming partitions, filling the display with fluid, confining the fluid in the display, and keeping different color suspensions separate from each other is difficult.

  Microencapsulated EPDs have a substantially two-dimensional arrangement of microcapsules, each having an electrophoretic composition of a dielectric fluid and a dispersion of charged dye particles, wherein the particles are made of a dielectric material. Visually contrast with solvent. Microcapsules are typically prepared in an aqueous solution to obtain a useful contrast ratio, and their average particle size is relatively large (50-150 microns). Since the microcapsule size is large, the scratch resistance is poor, and a large gap is required between two electrodes for a large capsule, so that the response time to a predetermined voltage is slow. Also, the hydrophilic shell of microcapsules prepared in aqueous solutions is typically sensitive to high humidity and temperature conditions. Embedding the microcapsules in a large amount of polymer matrix to avoid these drawbacks results in slower response times and / or lower contrast ratios due to the use of the matrix. This type of EPD often requires a charge control agent to improve switching speed. However, the microencapsulation process in aqueous solutions limits the types of charge control agents that can be used. Other disadvantages of the microcapsule system include low resolution and poor addressability when applying color.

  In recent years, improved EPD technology has been disclosed in co-pending US application Ser. No. 09 / 518,488 filed Mar. 3, 2000 (corresponding to WO 01/67170), Jan. 11, 2001. US application Ser. No. 09 / 759,212, filed on Jun. 28, 2000 and US Ser. No. 09 / 606,654 filed on Jun. 28, 2000 (corresponding to WO 02/01281) and February 2001. No. 09 / 784,972, filed on the 15th. All of which are incorporated herein by reference. The improved EPDs are formed from microcups having well-defined shapes, dimensions and aspect ratios, and are filled with charged dye particles dispersed in a dielectric solvent, closed, isolated. Cells included. The electrophoretic fluid is isolated and sealed within each microcup.

  In fact, the microcup structure allows for a format-flexible and efficient roll-to-roll continuous manufacturing process to manufacture EPDs. This display is prepared by coating a radiation curable composition on a continuous web made of a conductive film such as ITO / PET, for example, by (1) coating the ITO / PET film on (2) micro-embossing or photolithography. Forming a microcup structure, (3) filling the electrophoretic fluid, sealing the microcup, (4) laminating another conductive film to the sealed microcup, and (5) assembling (or assembling) By slicing and cutting the display to the desired size or format.

  The advantage of this EPD design is that the microcup wall is effectively a built-in (or built-in) spacer that keeps the top and bottom substrates a predetermined distance apart. The mechanical properties and structural integrity of microcup displays are significantly better than any conventional display, including those made by using spacer particles. In addition, displays including microcups have desirable mechanical properties, including reliable display performance when the display is bent, rolled, and under compressive pressure, such as when applied to a touch screen. Also, the use of microcup technology eliminates the need for edge seal adhesives that limit and predetermine the dimensions of the display panel and confine the display fluid within predetermined areas. The display fluid in conventional displays manufactured by the edge seal bonding method leaks completely when the display is cut or pierced by any means. Damaged displays no longer function. In contrast, the display fluid in a display manufactured by microcup technology is encapsulated and isolated within each cell. The microcup display can be cut to almost any size without the danger of compromising display performance by losing display fluid in the active area. In other words, the microcup structure allows for a format versatile display manufacturing method that allows for continuous production of displays in large area sheet format that can be sliced and diced into any desired format. An isolated microcup or cell structure is particularly important when filling cells with fluids that differ in certain properties, such as color and switching speed. Without the microcup structure, it is difficult to prevent fluids in adjacent regions from intermixing or creating crosstalk during operation.

  Thus, multi-color displays may be manufactured with spatially adjacent arrays having small pixels formed from microcups filled with dyes of different colors (eg, red, green or blue). However, this type of system having a traditional top / bottom electrode switching mode has significant disadvantages. The white light reflected from the colored pixels in the "turn off" state greatly reduces the color saturation of the "turn on" state. More details regarding this will be described in the section “Detailed description of the invention” below.

  This drawback can be remedied by an overlay shutter device, such as a polymer dispersed liquid crystal, that switches (or switches) each pixel to black, but the disadvantage of this method is that the overlay device is expensive and the drive circuit design is complicated. That is what.

  Thus, there remains a need for EPDs having improved properties and which can also be manufactured in an efficient manner.

Summary of the invention

  The present invention relates to an improved EPD with an in-plane switching (or plane switching or IPS) mode for forming an image. More particularly, the EPD of the present invention includes isolated cells formed from microcups having well-defined dimensions, shapes and aspect ratios, controlling the movement of particles within the cells in an in-plane switching mode. I do. The EPDs of the present invention can be manufactured in a continuous roll-to-roll manufacturing process, whereby the resulting display has improved saturation and contrast ratio.

DETAILED DESCRIPTION OF THE INVENTION

  Unless defined otherwise herein, all technical terms are used based on conventional definitions, as they are commonly used and understood by those skilled in the art. . The terms “cell,” “microcup,” “well-defined,” “aspect ratio,” and “imagewise exposure” are the same as indicated above. As defined in the pending application specification.

  The term "isolated" refers to an individually sealed electrophoretic cell, wherein the fluid within the cell cannot transfer from one cell to another.

I. Disadvantages of Electrophoretic Display Using Conventional Top / Bottom Switching The EPD of FIG. 1 has a conventional top / bottom (or top / bottom) electrode switching mode. The cell is filled with a suspension of white charged particles dispersed in a colored (red, green and blue) dielectric solvent. All three cells in FIG. 1 are shown charged by the voltage difference between the top and bottom electrodes (or top and bottom electrodes, not shown). In the green and blue cells, the white particles migrate to the transparent top display electrode, so that the color of the particles (ie, white) is reflected to the viewer through the transparent conductor films in the two cells. In the red cell, the white particles migrate to the bottom of the cell and the solvent color (ie, red) is seen through the top transparent conductor film. In FIG. 1, the white light reflected from the green and blue cells reduces the saturation and contrast ratio of red.

  In addition to the above-mentioned problems, poor solubility and poor fastness of dyes in very polar dielectric solvents, such as perfluoro and hydrocarbon solvents, make top / bottom type EPDs difficult. To achieve a high contrast ratio.

II. Electrophoretic Display of the Present Invention FIG. 2 illustrates a typical electrophoretic cell of the present invention. The cell (20) includes a top (or top) layer (21) and a bottom (or bottom) layer (22). The bottom layer has in-plane switching electrodes (23) and (24) and a background (or background) layer (25). A common electrode (29) is arranged between the two in-plane electrodes and separated by a gap (30). Alternatively, the bottom layer may have only one in-plane switching electrode and one common electrode with a gap between them. In another alternative, the background layer (25) is on top of the electrodes on the bottom layer (not shown). The in-plane electrode layer may also function as a background layer, in which case the in-plane electrode may be white or colored.

  Typically, the cell of FIG. 2 is filled with a dispersion of colored (or colored) particles (31) in a transparent dielectric solvent (32). The particles may be white, black or colored (ie, red, green or blue). The background layer (25) may be colorless, white, black or colored. The filled cells are then sealed (or sealed) with a sealing layer (26). Thereafter, an upper layer (21) having a transparent insulator layer (27) and preferably an adhesive layer (28) is laminated (or overlaid) over the sealed cells.

  Preferably, the microcup array is made in an upside-down (or inverted) manner. No. 09 / 518,488 filed on Mar. 3, 2000 (corresponding to WO 01/67170), filed Jan. 11, 2001, which is a co-pending patent application. No. 09 / 759,212, filed on Jun. 28, 2000, and filed on Feb. 15, 2001, US Ser. No. 09 / 606,654 (corresponding to WO 02/01281). The micro-cup array is top transparent insulating either by micro-embossing or photolithography as disclosed in US application Ser. No. 09 / 784,972, incorporated herein by reference. Form on body substrate. The microcup is filled with the electrophoretic fluid and then sealed with a sealing layer. Thereafter, a bottom layer having a patterned electrode and preferably an adhesive layer is laminated onto the sealed microcup. A colored background can be added by painting, printing, coating or laminating a color layer on the bottom electrode substrate.

  One of the advantages of the in-plane switching mode is that a microcup can be formed on a transparent plastic insulator substrate. This eliminates the risk of breaking fragile conductor electrodes such as, for example, ITO / PET during micro-embossing and other web handling steps. The patterned in-plane conductor film is used only in the final step of laminating on the filled and sealed microcup to complete the fabrication of the display panel.

(1) Reflective monochrome display In a cell as shown in FIG. 3A, white particles are dispersed in a colorless and transparent dielectric solvent. The background of all cells is the same color (black, blue, cyan, red, magenta, etc.). When there is a voltage difference between the common (not shown) and the two in-plane switching electrodes (not shown), the white particles move to the side of the cell, thereby increasing the background color (or top or top or bottom). Top view) seen through the transparent opening. When there is no voltage difference between the common and the two in-plane electrodes, the white particles are distributed in the dielectric solvent, so that the color of the particles (ie, white) is seen through the upper transparent insulator layer.

  Alternatively, as shown in FIG. 3B, the particles of the same color are dispersed in a colorless and transparent dielectric solvent in all cells, and the background of the cells is white. When there is a voltage difference between the common (not shown) and the two in-plane switching electrodes (not shown), the colored particles move to the sides of the cell, thereby increasing the background color (ie, white) Seen through the transparent opening. When there is no voltage difference between the common and the two in-plane electrodes, the colored particles are distributed in the dielectric solvent, so that the color of the particles is seen through the top transparent layer.

(2) Reflective multi-color display FIGS. 4A to 4D illustrate a multi-color display of the present invention.

  In FIG. 4A, the cell is filled with a colorless dielectric solvent in which white charged particles are dispersed, and the cell has a different background color (ie, red, green or blue). When there is a voltage difference between the common and the two in-plane electrodes (not shown), the white particles move to each side of the cell and the background color (ie, red, green or blue) changes from the top transparent opening. Can be seen. When there is no voltage difference between the common and the two in-plane electrodes, the particles are distributed in the dielectric solvent, so that white (i.e., the color of the particles) is seen from the top transparent opening.

  In FIG. 4B, the cell is filled with a colorless dielectric solvent in which black particles are dispersed, and the cell has a different background color (ie, red, green or blue). When there is a voltage difference between the common and in-plane electrodes (not shown), the particles move to each side of the cell and the background color (ie, red, green or blue) is visible from the top transparent opening. When there is no voltage difference between the common and in-plane electrodes, the particles are distributed in the dielectric solvent, so that black (ie, the color of the particles) is seen from the top transparent opening.

  FIG. 4C shows a cell filled with a colorless dielectric solvent in which particles of different colors (ie, red, green or blue) are dispersed. The cell background is black. When there is a voltage difference between the common and in-plane electrodes (not shown), the colored charged particles move to each side of the cell and the background color (ie, black) is seen through the top transparent opening. When there is no voltage difference between the common and in-plane electrodes, the colored particles are distributed in the dielectric solvent, so that the color of the particles (ie, red, green or blue) is visible through the top transparent opening. In this design, the black state has a high quality.

  In FIG. 4D, the cell is filled with a colorless dielectric solvent in which particles of different colors (ie, red, green or blue) are dispersed. The background of the cell is white. When there is a voltage difference between the common and in-plane electrodes (not shown), the particles move to each side of the cell, and the background color (ie, white) is seen through the top transparent opening, which allows High white state is obtained. When there is no voltage difference between the common and in-plane electrodes, the particles are distributed in the dielectric solvent, so that the color of the particles (ie, red, green or blue) is visible through the top transparent opening.

  As shown in FIGS. 4A-4D, the in-plane switching mode allows the particles to move in a planar (right / left) direction and different color combinations of particles, background and fluid (each individually white, black, red, green). Or blue) can be used to form various multi-color EPDs.

  In addition, the particles in the dielectric solvent may be mixed color, and the cells have the same background color.

  In an alternative reflective display of the present invention, the upper transparent display layer of the display may be colored or provided with a color filter. In this case, the cell is filled with an electrophoretic composition containing white charged particles in a transparent, colorless or colored dielectric solvent, and the background of the cell may be black. In a monochrome display, the transparent display layer at each pixel has the same color (eg, black, red, green, blue, yellow, cyan, magenta, etc.). In a multi-color display, the transparent display layers may have different colors.

III. Production of Microcup Arrays of the Present Invention Microcups are generally described in U.S. patent application Ser. No. 09 / 518,488, filed Mar. 3, 2000 (corresponding to WO 01/67170); It can be manufactured by microembossing or photolithography as disclosed in US patent application Ser. No. 09 / 784,972 filed on Nov. 15, 2009.

III (a) Production of microcup array by microembossing
Manufacture of the male mold The male mold can be manufactured by any suitable method, for example, a diamond turn process or a photoresist process followed by etching or electroplating. The master template for the male mold can be manufactured by any suitable method, for example, by electroplating. Electroplating is used to sputter a thin layer (typically 3000 angstroms) of a seed metal such as chrome inconel on a glass base. Next, it is coated with a layer of photoresist and exposed to radiation, for example, ultraviolet (UV). A mask is placed between the UV and the layer of photoresist. The exposed area of the photoresist is in a cured state. Next, the non-exposed area is removed by washing with a suitable solvent. The remaining hardened photoresist is dried and a thin layer of seed metal is sputtered again. Thus, a master for electroforming is completed. A typical material used for electroforming is nickel cobalt. Alternatively, the master may write "Continuous manufacturing of thin cover sheet optical media", SPIE Proc. 1663, 324 ( 1992) may be formed from nickel by electroless nickel deposition or electroforming. The mold floor (bottom portion) is typically about 50-400 microns thick. The master may be an e-master, as described, for example, in "Replication techniques for micro-optics", SPIE Proc. 3099, pp. 76-82 (1997). It can also be formed using other micro-engineering techniques including (electron) -beam writing, dry etching, chemical etching, laser writing or laser interference. Alternatively, the mold can be formed by photomachining using plastic, ceramic or metal.

  Male molds produced in this manner typically have protrusions of about 1-500 microns, preferably about 2-100 microns, and most preferably about 4-50 microns. The male mold may be in the form of a belt, roller or sheet. For continuous production, a belt type mold is preferred. Before applying (or applying) the UV curable resin composition, the male mold may be treated with a release agent to assist in the demolding process.

  The microcups can be formed either in a batch process or in a continuous roll-to-roll process as disclosed in US application Ser. No. 09 / 784,972, filed Feb. 15, 2001.

  In the first step of the micro-embossing process, the UV curable resin is first applied to the substrate (by any suitable means, such as roller coating, die coating, slot coating, slit coating and doctor blade coating). (Preferably a transparent insulator). Suitable transparent insulator substrates include polyethylene terephthalate, polyethylene naphthalate, polyaramid, polyimide, polycycloolefin, polysulfone, epoxy and composites thereof. The radiation-curable materials used are thermoplastic or thermoset precursors, such as polyfunctional acrylates or methacrylates, vinyl ethers, epoxides and their oligomers and polymers. Multifunctional acrylates and their oligomers are most preferred. Also, combinations of multifunctional epoxides and multifunctional acrylates are very useful for obtaining the desired physical-mechanical properties. The UV curable resin may be degassed before dispensing and may optionally include a solvent. The solvent, if present, evaporates easily.

  The radiation-curable material coated on the substrate is embossed with a male mold under pressure. Where the male mold is metallic and opaque, the plastic insulator is typically transparent to actinic radiation used to cure the resin. Conversely, the male mold may be transparent to actinic radiation and the plastic insulator may be opaque. Since the plastic insulator is typically on the display side, it is preferably transparent. In this case, the electrodes may be opaque. Alternatively, micro-embossing may be performed on the substrate having the electrodes.

  After exposure to radiation, the radiation-curable material cures. Thereafter, the male mold is removed to reveal the formed microcup.

III (b) Fabrication of microcup array by photolithography A photolithography process for fabricating a microcup array is illustrated in FIGS. 5A and 5B.

  As shown in FIGS. 5A and 5B, the microcup array (50) comprises a radiation curable material (51a) coated on an insulator substrate base (53) by any known method by UV light (or alternatively It can be manufactured by exposing through a mask (56) with other forms of radiation and an electron beam to form a wall (51b) corresponding to the image (or image) projected through the mask (56).

  In the photomask (56) in FIG. 5A, the dark squares (54) indicate areas that are opaque to the radiation used, and the spaces between the dark squares (55) indicate areas that are transparent to the radiation. The radiation curable material (51a) is irradiated with UV through the opening area (55).

  As shown in FIG. 5B, the exposed areas (51b) are cured, and then the unexposed (or unexposed) areas (protected by the opaque areas (54) of the mask (56)) are replaced with a suitable solvent or developer. To form a microcup (57). The solvent or developer is selected from those commonly used for dissolving or dispersing radiation-curable materials, such as, for example, methyl ethyl ketone, toluene, acetone or isopropanol.

  Alternatively, exposure can be performed by placing a photomask under the insulator substrate. In this case, the substrate must be transparent to the radiation wavelength used for exposure.

  The openings of the microcups produced by the method described above may be circular (or round), square, rectangular, hexagonal or any other shape. The partition area between the openings is preferably kept small to achieve high chroma and contrast while maintaining desirable mechanical properties. Therefore, honeycomb-shaped openings are preferred over, for example, circular openings.

For reflective electrophoretic displays, the dimension of each individual microcups, about 10 ² to about 1 × 10 ⁶ [mu] m ^2, preferably be in the range of about 10 ³ to about 1 × 10 ⁵ μm ^2. The microcup depth is in the range of about 5 to about 200 microns, preferably about 20 to 100 microns. The opening to total area ratio (or the ratio of the opening to the total area, where the total area is defined as the area of one cup containing the wall measured from the center of the wall) is from about 0.2 to about 0.95, preferably Is in the range of about 0.5 to about 0.9. The opening distance is usually in the range of about 15 to about 450 microns, preferably about 25 to about 300 microns, from edge to edge of the opening.

III (c) Sealing microcups After filling the electrophoresis fluid into the microcups, they are sealed (or sealed). The important step of sealing the microcups can be performed in many ways. A preferred method is to disperse the UV curable composition in an electrophoretic fluid containing charged dye particles dispersed in a colored dielectric solvent. Suitable UV curable materials include acrylates, methacrylates, styrene, alpha-methylstyrene, butadiene, isoprene, allyl acrylate, polyvalent acrylates or methacrylates, cyanoacrylates, vinylbenzenes, polyvinyls including vinylsilanes, vinylethers, polyvalents Epoxides, polyvalent isocyanates, polyvalent allyls, and oligomers or polymers containing crosslinkable (or crosslinkable) functional groups are included. The UV curable composition is immiscible with the dielectric solvent and has a lower specific gravity than the electrophoretic fluid (ie, the combination of the dielectric solvent and the dye particles). The two components (UV curable composition and electrophoretic fluid) are thoroughly blended in an in-line mixer to provide a precise coating mechanism, such as Myrad bar, gravure printing, doctor blade, slot coating or slit. Immediately coat the microcups with the coating. Remove excess fluid with a wiper blade or similar device. A small amount of a weak solvent or solvent mixture, such as isopropanol or methanol, may be used to remove any residual electrophoretic fluid on the upper surface of the microcup partition. Volatile organic solvents may be used to control the viscosity and coverage of the electrophoretic fluid. Thereafter, the microcups thus filled are dried, and the UV-curable composition floats on top of the electrophoretic fluid. The microcup can be sealed by curing the UV curable layer of the supernatant while or after it floats over. UV or other forms of radiation, such as visible light, IR and electron beam, may be used to cure the sealing layer to seal the microcup. Alternatively, if a heat or moisture curable composition is used, heat or moisture may be used to cure the sealing layer to seal the microcup.

  A preferred group of dielectric solvents that exhibit desirable density and solubility differences for acrylate monomers and oligomers are halogenated hydrocarbons and derivatives thereof. Surfactants can be used to improve wetting and adhesion at the interface between the electrophoretic fluid and the sealing material. Surfactants include FC surfactant (manufactured by 3M), Zonyl fluorosurfactant (manufactured by DuPont), fluoroacrylate, fluoromethacrylate, fluorine-substituted long-chain alcohol, perfluoro-substituted long-chain carboxylic acid, and the like. And derivatives thereof.

  Alternatively, if the sealing precursor is at least partially compatible with the dielectric solvent, the electrophoretic fluid and sealing precursor may be sequentially coated in the microcup to avoid mixing. Thus, sealing of the microcups can be performed by overcoating the filled microcups with a thin layer of sealing material that can be cured by radiation, heat, moisture or interfacial reactions. Volatile organic solvents can be used to adjust the viscosity and thickness of the coating. When a volatile solvent is used in the overcoat, the volatile solvent is preferably immiscible with the dielectric solvent to reduce the degree of mixing between the sealing layer and the electrophoretic fluid. It is highly desirable that the specific gravity of the overcoating be significantly less than the specific gravity of the electrophoretic fluid to further reduce the degree of mixing. In co-pending US patent application Ser. No. 09 / 874,391, filed Jun. 4, 2001, a thermoplastic elastomer is disclosed as a preferred sealing material.

  Examples of useful thermoplastic elastomers include ABA and (AB) n types, where A is styrene, α-methylstyrene, ethylene, propylene or norbornene; B is butadiene, isoprene, ethylene, propylene, butylene, Dimethylsiloxane or propylene sulfide; and A and B are not the same in the formulas). The number n is ≧ 1, preferably 1-10. Particularly useful are diblock or triblock copolymers of styrene or α-methylstyrene, such as SB (poly (styrene-b-butadiene)), SBS (poly (styrene-b-butadiene-b-styrene)), SIS (poly ( Styrene-b-isoprene-b-styrene)), SEBS (poly (styrene-b-ethylene / butylene-b-styrene)), poly (styrene-b-dimethylsiloxane-b-styrene), poly (α-methylstyrene) -B-isoprene), poly (α-methylstyrene-b-isoprene-b-α-methylstyrene), poly (α-methylstyrene-b-propylene sulfide-b-α-methylstyrene), poly (α-methyl) Styrene-b-dimethylsiloxane-b-α-methylstyrene).

  Alternatively, interfacial polymerization and subsequent UV curing have been found to be very advantageous for the sealing process. Mixing between the electrophoretic layer and the overcoat is significantly suppressed by forming a thin barrier layer at the interface by interfacial polymerization. Thereafter, the sealing is completed by a post-curing step (preferably by UV irradiation). The two-step overcoat process is particularly useful when the dyes used are at least partially soluble in the thermoset precursor.

III (d) Lamination of the microcups The laminated microcups are then laminated (or superimposed) to the top layer including the patterned in-plane conductor film and preferably an adhesive layer. Suitable adhesive materials include pressure-sensitive adhesives of the acrylic and rubber type, for example UV-curable adhesives, including polyfunctional acrylates, epoxides or vinyl ethers, and moisture or heat-curable adhesives, such as epoxies, polyurethanes and cyanoacrylates. Is included.

  The cells manufactured by the methods of Sections III (a) to III (d) can be used in an upside-down manner with the transparent display layer on top and the layer with in-plane electrodes on the bottom.

The III (e) alternatively by methods, in the micro embossing process, any suitable means of UV curable resins, for dispensing for example coating, onto the dip and poured male like. The dispenser may be movable or fixed. A patterned in-plane conductive film on a plastic substrate such as polyethylene terephthalate, polyethylene naphthalate, polyaramid, polyimide, polycycloolefin, polysulfone, epoxy and composites thereof is overlaid on the UV curable resin. Pressure may be applied to ensure proper bonding between the resin and plastic substrate and to control the thickness of the microcup floor. Where the male mold is metallic and opaque, the plastic substrate is typically transparent to actinic radiation used to cure the resin. Conversely, the male mold may be transparent to actinic radiation and the plastic substrate may be opaque.

  After exposure to UV radiation, the UV curable resin is cured, after which the male mold can be removed. The formed microcup array is filled and sealed as described above. Thereafter, a transparent insulator layer is laminated on the sealed microcup, preferably using an adhesive.

  Although less preferred, photolithographic exposure may be performed on a substrate having in-plane electrodes. A radiation curable material is coated on the patterned conductor film. The microcup is formed by exposing the radiation curable material to radiation through a photomask, as shown in FIG. 5 and as described in Section III (b) above.

  Thereafter, the microcup thus produced is filled and sealed as described above, and a transparent insulator layer is laminated thereon, preferably with an adhesive.

  In any of the microcup manufacturing methods disclosed in this section, a substrate comprising an array of thin film transistors (TFTs) can be used as the bottom in-plane electrode layer, in which case the TFT layer also provides an active drive mechanism.

IV. Preparation of the Suspension The suspension filled in the microcup contains a dielectric solvent with the charged dye particles dispersed therein, which particles are moved by the action of an electric field. The suspension may optionally contain another colorant that does not move in the electric field. This dispersion can be prepared by methods well known in the art, for example, US Pat. Nos. 6,017,584, 5,914,806, 5,573,711, 5,403,518, 5,380. No. 3,362, No. 4,680,103, No. 4,285,801, No. 4,093,534, No. 4,071,430 and No. 3,668,106, etc. -IEEE Trans. Electron Devices, ED-24, p. 827 (1977) and Journal of Applied Physics (J. Appl. Phys.), 49 (9), It can be prepared based on the method as described on page 4820 (1978).

  The suspending fluid medium is a dielectric solvent that preferably has a low viscosity due to the high mobility of the particles and a dielectric constant in the range of about 2 to about 30, preferably about 2 to about 15. Examples of suitable dielectric solvents include: hydrocarbons such as decahydronaphthalene (DECALIN), 5-ethylidene-2-norbornene, fatty oils, paraffin oils, aromatic hydrocarbons such as Toluene, xylene, phenylxylylethane, dodecylbenzene and alkylnaphthalene, halogenated solvents such as dichlorobenzotrifluoride, 3,4,5-trichlorobenzotrifluoride, chloropentafluoro-benzene, dichlorononane, pentachlorobenzene and perfluoro Solvents such as perfluorodecalin, perfluorotoluene, perfluoroxylene, FC-43, FC-70 and FC-5060 (from 3M, St. Paul, Minn.), Low molecular weight fluorine-containing polymers such as poly (perflu Oropropylene oxide) (TCI America, Portland, Oregon), poly (chlorotrifluoroethylene) such as Halocarbon Oils (Halocarbon Product Corp., (Riveredge, NJ), perfluoropolyalkyl ethers, such as Galden, HT-200 and Fluorolink (from Ausimont) or Krytox Oils and Glysees K -Greases K-Fluid Series (DuPont, Delaware). In one preferred embodiment, poly (chlorotrifluoroethylene) is used as the dielectric solvent. In another preferred embodiment, poly (perfluoropropylene oxide) is used as the dielectric solvent.

  The immobile fluid colorant may be formed by a dye or pigment (pigment). Nonionic azo and anthraquinone dyes are particularly useful. Examples of useful dyes include, but are not limited to: Oil Red EGN, Sudan Red, Sudan Blue, oil -Blue (Oil Blue), Macrolex Blue, Solvent Blue 35, Pyram Spirit Black and Fast Spirit Black (Pyram Products) (Pylam Products, Arizona), Thermoplastic Black X-70 (BASF), anthraquinone blue, anthraquinone yellow 114, anthraquinone yellow 114 Anthraquinone red 111 and 135, anthraquinone green 28) and Sudan Black B (manufactured by Aldrich). When using a perfluorosolvent, fluorinated dyes are particularly useful. In the case of dyes, dye particles that produce a fluid colorant that does not migrate may be dispersed in a dielectric medium, and these colored particles are preferably uncharged. If the pigment particles that produce the immobile fluid colorant are charged, they preferably have a charge opposite that of the charged migrating pigment particles. If both types of dye particles carry the same charge, they need to have different charge densities or different electrophoretic mobilities. Dyes or pigments that produce immobile fluid colorants must be chemically stable and compatible (or compatible) with the other components in the suspension.

Preferably charged pigment particles to be moved are white, organic pigment or inorganic pigment may be, for example, TiO _2.

  When using colored moving particles, these include phthalocyanine blue, phthalocyanine green, diarylide yellow, diarylide AAOT Yellow, and quinacridone ( quinacridone), azo, rhodamine, perylene dye series (manufactured by Sun Chemical), Hansa yellow G particles (manufactured by Kanto Chemical) and carbon -It may be formed by Lamp Lamp (Carbon Lampblack) (manufactured by Fisher). Submicron particle sizes are preferred. These particles must have acceptable optical properties, must not swell or soften by the dielectric solvent, and must be chemically stable. The suspension obtained must also be stable against sedimentation, creaming or flocculation under normal conditions of use.

  The migrating dye particles may initially exhibit a charge, or may be charged so as to be evident using a charge control agent, or may acquire a charge when suspended in a dielectric solvent. Suitable charge control agents are well known in the art, may be polymeric in nature, non-polymeric, and may be ionic or non-ionic. It often contains the following ionic surfactants: Aerosol OT, sodium dodecylbenzenesulfonate, metal soap, polybutene succinimide, maleic anhydride copolymer, vinylpyridine copolymer, vinylpyrrolidone copolymer (eg, Ganex, International -Specialty Products (manufactured by International Specialty Products), (meth) acrylic acid copolymers, and N, N-dimethylaminoethyl (meth) acrylate copolymers. Fluorosurfactants are particularly useful as charge control agents in perfluorocarbon solvents. It includes FC fluorosurfactants such as FC-170C, FC-171, FC-176, FC430, FC431 and FC-740 (from 3M) and Zonyl fluorosurfactants such as Zonyl FSA, FSE, FSN, FSN-100, FSO, FSO-100, FSD and UR (manufactured by DuPont).

  Suitable charged dye dispersions may be manufactured by any of the well-known methods, including grinding, milling, attriting, microfluidizing, and microfluidizing. Techniques that use ultrasound are included. For example, pigment particles in the form of a fine powder are added to a suspending solvent, and the resulting mixture is milled or attrited in a ball mill for several hours to break up highly agglomerated dry pigment powder into primary particles. To a lesser extent, a dye or pigment providing a fluid colorant that does not migrate may be added to the suspension during ball milling.

  Sedimentation or creaming of the pigment particles can be eliminated by microencapsulating the particles with a suitable polymer to match the specific gravity of the dielectric solvent. Microencapsulation of the pigment particles can be performed chemically or physically. Typical microencapsulation methods include interfacial polymerization, in situ polymerization, phase separation, coacervation, electrostatic coating, spray drying, fluidized bed coating and solvent evaporation.

In the case of dye suspensions, there are many possibilities. For color system subtractive, charged TiO ₂ particles cyan, may be suspended in yellow or magenta color of the dielectric fluid. Cyan, yellow or magenta colors can be developed by using dyes or pigments. In the case of an additive color system, the charged TiO ₂ particles may be suspended in a red, green or blue dielectric fluid developed by using a dye or pigment. Red, green and blue colors are preferred for most applications.

  Although the invention has been described with reference to particular embodiments of the invention, it will be understood that various changes can be made and equivalents can be substituted without departing from the true concept and scope of the invention. It should be understood by those skilled in the art. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process step or steps, to the objective, concept and scope of the present invention. All such modifications are intended to fall within the scope of the appended claims.

  Accordingly, it is desired that the present invention, in light of the present specification, be defined by the appended claims as broadly as the prior art allows.

  Note that all figures are shown schematically and not to scale.

FIG. 1 illustrates the general disadvantages of a conventional EPD having only a top / bottom switching mode. FIG. 2 illustrates the general arrangement of a representative electrophoresis cell and in-plane switching electrodes of the present invention. FIG. 3A illustrates the monochrome display of the present invention. FIG. 3B illustrates the monochrome display of the present invention. FIG. 4A illustrates a multi-color scenario (or plan) of the present invention. FIG. 4B illustrates the multi-color scenario of the present invention. FIG. 4C illustrates the multi-color scenario of the present invention. FIG. 4D illustrates the multicolor scenario of the present invention. FIG. 5A illustrates fabrication of a microcup including photolithographic image exposure through a photomask. FIG. 5B illustrates fabrication of a microcup including photolithographic image exposure through a photomask.

Claims (58)

(1) An isolated electrophoresis cell formed from microcups having appropriately defined dimensions, shapes and aspect ratios, wherein the microcups are filled with an electrophoretic composition, and the filled microcups are An electrophoretic cell sealed with a sealing layer formed from a sealing composition having a lower specific gravity than the electrophoretic composition; and (2) an electrophoretic display including an in-plane switching mode.   2. The electrophoretic display of claim 1, wherein each of the isolated electrophoresis cells has two in-plane electrodes, or each of the isolated electrophoresis cells has one in-plane electrode.   An electrophoretic display comprising isolated cells formed from microcups having well-defined dimensions, shapes and aspect ratios, the microcups comprising charged particles dispersed in a dielectric solvent or solvent mixture. The electrophoretic composition is filled, and the filled microcups are sealed with a sealing layer formed from a sealing composition having a lower specific gravity than the electrophoretic composition, each of the isolated cells being on one side. An electrophoretic display including a transparent display layer and a layer including one common electrode and an in-plane electrode on the opposite side.   4. The electrophoretic display of claim 3, wherein each of said isolated cells further comprises a separate background layer.   The electrophoretic display according to claim 3, wherein the transparent display layer is colorless.   5. The method of claim 4, wherein the separate background layer is on top of a layer including one common electrode and an in-plane electrode, or the separate background layer is below a layer including one common electrode and an in-plane electrode. Electrophoretic display.   The electrophoretic display according to claim 3, wherein the layer including one common electrode and an in-plane electrode functions as a background layer, and the in-plane electrode is white or colored.   The electrophoretic display according to claim 3, wherein the display is a monochrome display.   The electrophoretic display according to claim 8, wherein the dielectric solvent is colorless and transparent.   The electrophoretic display according to claim 9, wherein the charged particles are white and the cells have a solid color background.   The electrophoretic display according to claim 10, wherein the background color is black, red, green, blue, yellow, cyan or magenta.   The electrophoretic display according to claim 9, wherein the charged particles are of one color and the cells have a white background.   13. The electrophoretic display according to claim 12, wherein the charged particles are black, red, green, blue, yellow, cyan or magenta.   The electrophoretic display according to claim 9, wherein the charged particles are mixed colors in all of the cells having a single color background.   15. The electrophoretic display according to claim 14, wherein the mixed color is two or more colors selected from the group consisting of black, white, red, green, blue, yellow, cyan and magenta.   The electrophoretic display of claim 15, wherein the background is a color selected from the group consisting of black, white, red, green, blue, yellow, cyan, and magenta.   The electrophoretic display according to claim 3, wherein the display is a multi-color display.   18. The electrophoretic display of claim 17, wherein the charged particles are white and the cells have a different color background, or the charged particles are black and the cells have a different color background.   The cell is filled with an electrophoretic composition comprising charged particles of different colors dispersed in a dielectric solvent or solvent mixture, and all of the cells have a white background, or the cell is a dielectric solvent or solvent. 19. The electrophoretic display of claim 17, wherein the electrophoretic display is filled with an electrophoretic composition comprising charged particles of different colors dispersed in a mixture, and all of the cells have a black background.   The electrophoretic display according to claim 3, wherein the transparent display layer is colored or includes a color filter.   Each of the isolated cells further includes a separate background layer on top of the layer that includes one common electrode and an in-plane electrode, or each of the isolated cells includes one common electrode and an in-plane electrode 21. The electrophoretic display of claim 20, further comprising a separate background layer below the layer.   21. The electrophoretic display according to claim 20, wherein the layer including one common electrode and an in-plane electrode functions as a background layer, and the in-plane electrode is white or colored.   21. The electrophoretic display of claim 20, wherein said charged particles are white and said cells have a black background.   24. The electrophoretic display of claim 23, wherein all of the cells have a same color transparent display layer, or wherein the cells have different color transparent display layers. A method of making an electrophoretic display having isolated cells formed from microcups having well-defined dimensions, shapes and aspect ratios, comprising:
a) forming a layer by coating a radiation-curable material on a transparent insulator substrate;
b) forming microcups on the radiation curable material by microembossing or image exposure with radiation;
c) filling the microcup with the electrophoretic composition;
d) sealing the microcup with a sealing composition having a lower specific gravity than the electrophoretic composition; and e) sealing the substrate comprising one common electrode and an in-plane electrode in the sealed microcup. A method comprising laminating on each of the microcups.   The method for manufacturing an electrophoretic display according to claim 25, wherein the base material including one common electrode and the in-plane electrode is coated with an adhesive. A method of making an electrophoretic display having isolated cells formed from microcups having well-defined dimensions, shapes and aspect ratios, comprising:
a) forming a layer by coating a radiation-curable material on a substrate including a common electrode and an in-plane electrode;
b) forming microcups on the radiation curable material by microembossing or image exposure with radiation, thereby positioning each of the microcups on a substrate including one common electrode and an in-plane electrode. ;
c) filling the microcup with the electrophoretic composition;
d) sealing the microcup with a sealing composition having a lower specific gravity than the electrophoretic composition; and e) laminating a transparent insulator substrate to the sealed microcup.   The method for manufacturing an electrophoretic display according to claim 27, wherein the transparent insulator substrate is coated with an adhesive.   26. The method of claim 25, wherein the transparent insulator substrate is colorless.   30. The method of claim 29, wherein the cell has a background of the same color and is filled with an electrophoretic composition comprising charged particles of the same color dispersed in a colorless transparent dielectric solvent.   30. The method of claim 29, wherein the cells have different colored backgrounds and are filled with an electrophoretic composition comprising charged particles of the same color dispersed in a colorless transparent dielectric solvent.   30. The method of claim 29, wherein the cells have the same color background and are filled with an electrophoretic composition comprising charged particles of different colors dispersed in a colorless transparent dielectric solvent.   28. The method of claim 27, wherein the transparent insulator substrate is colorless.   34. The method of claim 33, wherein the cell has a background of the same color and is filled with an electrophoretic composition comprising charged particles of the same color dispersed in a colorless transparent dielectric solvent.   34. The method of claim 33, wherein the cells have different colored backgrounds and are filled with an electrophoretic composition comprising charged particles of the same color dispersed in a colorless transparent dielectric solvent.   34. The method of claim 33, wherein the cell has the same color background and is filled with an electrophoretic composition comprising charged particles of different colors dispersed in a colorless transparent dielectric solvent.   26. The method of claim 25, wherein the transparent insulator substrate is colored.   38. The method of claim 37, wherein the cell has a black background and is filled with an electrophoretic composition comprising white charged particles dispersed in a transparent and colorless dielectric solvent.   39. The method of claim 38, wherein the cells have a same color of transparent insulator substrate, or the cells have a different color of transparent insulator substrate.   28. The method of claim 27, wherein the transparent insulator substrate is colored.   41. The method of claim 40, wherein the cell has a black background and is filled with an electrophoretic composition comprising white charged particles dispersed in a colorless transparent dielectric solvent.   42. The method of claim 41, wherein the cells have the same color transparent insulator substrate, or the cells have different color transparent insulator substrates.   The electrophoretic display according to claim 3, wherein a substrate including an array of thin film transistors is used as a layer including one common electrode and an in-plane electrode.   The electrophoretic display according to claim 1, wherein the sealing composition is a radiation, heat or moisture curable composition.   The sealing composition is acrylate, methacrylate, styrene, α-methylstyrene, butadiene, isoprene, allyl acrylate, polyvalent acrylate, polyvalent methacrylate, cyanoacrylate, polyvinyl, polyepoxide, polyisocyanate, polyallyl, The electrophoretic display according to claim 1, comprising a material selected from the group consisting of and oligomers or polymers containing crosslinkable functional groups.   The electrophoretic display according to claim 1, wherein the sealing composition comprises a thermoplastic elastomer.   47. The electrophoretic display according to claim 46, wherein the thermoplastic elastomer is a diblock or triblock copolymer of styrene or [alpha] -methylstyrene.   The thermoplastic elastomer is SB (poly (styrene-b-butadiene)), SBS (poly (styrene-b-butadiene-b-styrene)), SIS (poly (styrene-b-isoprene-b-styrene)), SEBS (Poly (styrene-b-ethylene / butylene-b-styrene)), poly (styrene-b-dimethylsiloxane-b-styrene), poly (α-methylstyrene-b-isoprene), poly (α-methylstyrene) b-isoprene-b-α-methylstyrene), poly (α-methylstyrene-b-propylene sulfide-b-α-methylstyrene) or poly (α-methylstyrene-b-dimethylsiloxane-b-α-methylstyrene) 47. The electrophoretic display of claim 46, wherein   4. The electrophoretic display according to claim 3, wherein the sealing composition is a radiation, heat or moisture curable composition.   The sealing composition is acrylate, methacrylate, styrene, α-methylstyrene, butadiene, isoprene, allyl acrylate, polyvalent acrylate, polyvalent methacrylate, cyanoacrylate, polyvinyl, polyepoxide, polyisocyanate, polyallyl, 4. The electrophoretic display according to claim 3, comprising a material selected from the group consisting of and oligomers or polymers containing crosslinkable functional groups.   The electrophoretic display according to claim 3, wherein the sealing composition comprises a thermoplastic elastomer.   52. The electrophoretic display according to claim 51, wherein the thermoplastic elastomer is a diblock or triblock copolymer of styrene or [alpha] -methylstyrene.   The thermoplastic elastomer is SB (poly (styrene-b-butadiene)), SBS (poly (styrene-b-butadiene-b-styrene)), SIS (poly (styrene-b-isoprene-b-styrene)), SEBS (Poly (styrene-b-ethylene / butylene-b-styrene)), poly (styrene-b-dimethylsiloxane-b-styrene), poly (α-methylstyrene-b-isoprene), poly (α-methylstyrene) b-isoprene-b-α-methylstyrene), poly (α-methylstyrene-b-propylene sulfide-b-α-methylstyrene) or poly (α-methylstyrene-b-dimethylsiloxane-b-α-methylstyrene) 52. The electrophoretic display according to claim 51, wherein   Steps (c) and (d) comprise (1) filling a mixture of the sealing composition and the electrophoretic composition, and (2) the sealing composition undergoing phase separation and supernatant on the electrophoretic composition. 26. The method of claim 25, wherein the method is performed by sealing the filled microcups during or after forming the layer by curing the sealing composition.   26. The method of claim 25, wherein step (d) is performed by (1) overcoating the sealing composition over the electrophoretic composition, and (2) curing the sealing composition.   Steps (c) and (d) comprise (1) filling a mixture of the sealing composition and the electrophoretic composition, and (2) the sealing composition undergoing phase separation and supernatant on the electrophoretic composition. 28. The method of claim 27, wherein the method is performed by sealing the filled microcups during or after forming the layer by curing the sealing composition.   28. The method of claim 27, wherein step (d) is performed by (1) overcoating the sealing composition over the electrophoretic composition, and (2) curing the sealing composition.   The layer including one common electrode and the in-plane electrode includes one common electrode and two in-plane electrodes, or the layer including one common electrode and the in-plane electrode includes one common electrode and one in-plane electrode The electrophoretic display according to claim 3, comprising: