TWI815316B - Method of making a laminate for an electrophoretic display - Google Patents

Abstract

A polymeric film includes a plurality of tapered microcells containing a dispersion of a first group and a second group of charged particles. The first group and second group of charged particles having opposite charge polarities. The tapered microcells include a wall and at least a portion of the wall is configured to repel the first group of charged particles. Also provided is a method of making a laminate for an electrophoretic display comprising embossing a plurality of tapered microcells through a layer of polymeric film and into a release sheet to form an embossed film; laminating the embossed film to a layer of conductive material on a protective sheet to form a laminated film; removing the release sheet from the polymeric film to form an opening to an interior of each microcell of the laminated film; filling the microcells with a dispersion fluid; and sealing the microcells.

Description

Method for manufacturing laminate for electrophoretic display

The present invention relates to electrophoretic displays. In particular, in one aspect, the present invention relates to improved microcells containing electrophoretic fluids for use in electrophoretic displays. In another aspect, the invention relates to methods of making improved microcells for use in electrophoretic displays.

The term "electro-optic" applies to materials or displays and is used here in its conventional sense in imaging technology to refer to a material that has at least one first and second display state that differ in optical properties by applying an electric field to the material. causing it to change from the first display state to the second display state. Although the optical property visible to the human eye is generally color, it can also be other optical properties such as optical transmittance, reflectivity, illumination, or, for machine-readable displays, electromagnetic wavelengths outside the visible range. Color (pseudo-color) reflectance changes.

The term "grayscale state" is used here in its conventional sense in imaging technology and refers to a state between two extreme optical states of a pixel, and does not necessarily mean a black-and-white transition between the two extreme states. For example, the extreme states of electrophoretic displays described in several electronic ink patents and published applications referenced below are white and dark blue, so the "grayscale state" in the middle actually refers to light blue. As mentioned above, optical state changes may indeed be other than color changes. The terms "black" and "white" may be used hereafter to refer to the two extreme optical states of a display, and should be understood to generally include extreme optical states other than just black and white, such as the aforementioned white and cyan states. The term "monochromatic" may henceforth refer to a driving mechanism that only drives pixels to two extreme optical states without intermediate grayscale states.

The terms "bistable" and "bistable" are used here in their conventional meanings in the art and mean that a display includes a display unit having at least one first and second display state with different optical properties, and Such that after driving any given cell with a finite duration addressing pulse, assuming it is in the first or second display state, after terminating the addressing pulse, this state will persist for at least several times (e.g., at least 4 times) to change the display cell state. Minimum duration of addressing pulse required. US Patent No. 7,170,670 shows that some particle-based electrophoretic displays with grayscale are stable not only in extreme black and white states, but also in their intermediate grayscale states, and the same is true for some other types of electro-optical displays. Such displays are appropriately termed "multistable" rather than bistable, although for convenience the term "bistable" is used here to cover both bistable and multistable displays.

One type of electro-optical display that has been the subject of intensive research and development for many years is particle-based electrophoretic displays, in which a plurality of charged particles travel through a fluid under an electric field. Compared with liquid crystal displays, electrophoretic displays can have the following properties: good brightness and contrast, wide viewing angles, bistable state, and low power consumption. However, problems with long-term image quality of these displays prevent widespread adoption. For example, the particles that make up electrophoretic displays tend to settle, causing these displays to have a poor service life.

As mentioned above, the electrophoresis medium requires the presence of fluid. In most prior art electrophoretic media, this fluid is a liquid, but electrophoretic media can be made using gaseous fluids; see, for example, Kitamura, T. et al., IDW Japan, 2001, Paper HCS1-1 ("Electronic paper-like displays" "Electrical toner movement for electronic paper-like display"), and Yamaguchi, Y. et al. IDW Japan, 2001, Paper AMD4-4 ("Toner display using triboelectrically charged insulating particles") insulative particles charged triboelectrically)"). See also U.S. Patent Nos. 7,321,459 and 7,236,291. Such gas-based electrophoretic media appear just like particle-based electrophoretic media and are susceptible to similar problems due to particle sedimentation when the media is used in an orientation that allows for such precipitation, such as in a sign where the media is in a vertical plane. Particle precipitation in gas-based electrophoretic media does appear to be more severe than in liquid-based ones because the low viscosity of gaseous suspension fluids allows electrophoretic particles to settle more quickly compared to liquids.

Various patents and applications assigned to or owned by the Massachusetts Institute of Technology (MIT), E Ink Corporation, E Ink California, LLC, and related companies describe methods used in encapsulated and microcell electrophoresis and other electro-optical media. Various technologies. Encapsulated electrophoretic media include a plurality of small capsules, each of which itself includes an internal phase containing electrophoretically mobile particles in a fluid medium and a capsule wall surrounding the internal phase. In microcellular electrophoretic displays, charged particles and fluids are not encapsulated within microcapsules but are retained within multiple cavities formed within a carrier medium (usually a polymer film). See, for example, International Application Publication No. WO 02/01281 and Published United States Application No. 2002/0075556. The technology described above can be found, for example, in the following patents and applications: (a) Electrophoretic particles, fluids and fluid additives; for details, see U.S. Patent Nos. 7,002,728 and 7,679,814; (b) Capsules, adhesives and encapsulation processes; for details, see U.S. Patent Nos. 6,922,276 and 7,411,719; (c) Microcell structure, wall material and method of forming microcells; for details, see U.S. Patent Nos. 6,672,921; 6,751,007; 6,753,067; 6,781,745; 6,788,452; 6,795,229; 6,806,995; 6,829,078; 6,833,177; 6,850,355 ;6,865,012;6,870,662;6,885,495;6,906,779 ; 6,930,818; 6,933,098; 6,947,202; 6,987,605; 7,046,228; 7,072,095; 7,079,303; 7,141,279; 7,156,945; 7,205,355; 7,233,429; 7,261,920; 7,271,947;7,304,780;7,307,778;7,327,346;7,347,957;7,470,386;7,504,050; 7,580,180; 54,790 ; 8,169,690; 8,441,432; 8,582,197; 8,891,156; 9,279,906; 9,291,872; and 9,388,307 and U.S. Patent Application Publication Nos. 2003/0175480; 2003/0175481; 2003/0179437; 3/0203101; 2013/0321744; 2014/0050814; 2015/0085345 ;2016/0059442; 2016/0004136; and 2016/0059617; (d) Methods for filling and sealing microcells; see U.S. Patent Nos. 7,144,942 and 7,715,088 for details; (e) Films and sub-assemblies containing electro-optical materials; see U.S. Patent Nos. 6,982,178 and 7,839,564 for details; (f) Backsheets, adhesive layers and other auxiliary layers and methods for displays; see U.S. Patent Nos. 7,116,318 and 7,535,624 for details; (g) Color formation and color adjustment; for details, see U.S. Patent Nos. 7,075,502 and 7,839,564; (h) Methods for driving displays; see U.S. Patent Nos. 7,012,600 and 7,453,445 for details; (i) Applications of displays; for details, see U.S. Patent Nos. 7,312,784 and 8,009,348; (j) Non-electrophoretic displays; see U.S. Patent Application No. 6,241,921 and U.S. Patent Application Publication No. 2015/0277160; and applications of encapsulation and microcell technology other than displays; see U.S. Patent Application Publication No. 2015/ No. 0005720 and 2016/0012710.

Microcell electrophoretic displays are generally immune to the clustering and stereotyping error modes of traditional electrophoretic devices and offer further advantages such as the ability to print or coat the display on a variety of flexible and rigid substrates.

Electrophoretic displays generally include a layer of electrophoretic material and at least two other layers disposed on opposite sides of the electrophoretic material, one of which is an electrode layer. In most such displays, both layers are electrode layers, and one or both electrode layers are patterned to define display pixels. For example, one electrode layer may be patterned into elongated column electrodes and another patterned into elongated row electrodes extending at right angles to the column electrodes, with the intersection of the column and row electrodes defining the pixels. Or more commonly, one electrode layer has a single continuous electrode shape and the other electrode layer is patterned into a matrix of pixel electrodes, each of which defines a pixel of the display. In another type of electrophoretic display used as a stylus, print head or similar movable electrode separate from the display, only one of the layers adjacent to the electrophoretic layer includes the electrode, the layer on the opposite side of the electrophoretic layer It is generally a protective layer to prevent the movable electrode from damaging the electrophoretic layer.

Electro-optical displays, including electrophoretic displays, are expensive. For example, the price of color LCDs found in portable computers generally accounts for the majority of the overall computer price. As such displays are used more widely in devices such as mobile phones and personal digital assistants (PDAs), which are much cheaper than portable computers, there is greater pressure to reduce the cost of such displays. The ability to form electrophoretic dielectric layers through printing techniques on flexible substrates, as mentioned above, opens up the possibility of reducing the cost of display electrophoretic components using mass production techniques such as roll-to-roll coating, which utilizes materials used to produce coated papers, polymers Commercially available equipment for thin films and similar media.

Current electrophoretic displays may also be limited by insufficient reflectivity in the white optical state. For example, referring to FIG. 1 , a plurality of cubic microcells 10 imprinted in a polymer film are filled with electrophoretic fluid, which includes black pigment 12 and white pigment 14 . Microcell 10 can be incorporated as a layer in a black and white electrophoretic display. When one or more pixels of the display are displaying the white optical state (viewed from above in Figure 1), a large amount of light can penetrate the white pigment layer 14 rather than being reflected back to the viewer. Light entering the microcell 10 may be lost and may be absorbed by the black pigment layer 12 . Light loss can result in a flat color state.

Therefore, there is a need for microcell designs for electrophoretic displays with improved reflectivity during specific optical states, such as the white optical state.

In one aspect of the present invention, a polymer film is provided, which includes a plurality of cone-shaped microcells, which include a dispersion of a first group and a second group of charged particles. The first population of charged particles is light absorbing and has a charge polarity opposite to the charge polarity of the second population of charged particles. The pyramidal microcells include a wall and at least a portion of the wall is configured to repel the first population of charged particles.

In another aspect of the invention, a method of manufacturing a laminate for an electrophoretic display is provided, which includes imprinting a plurality of cone-shaped microcells through a layer of polymer film and into a release sheet to form an imprint. Film; laminating the imprinted film to a layer of conductive material on a protective sheet to form a laminated film; removing the release sheet from the polymer film to form an opening to the interior of each microcell of the laminated film ; filling the microcells with dispersion fluid; and sealing the microcells.

These and other aspects of the invention will be apparent from the following description.

In the following detailed description, various specific details are presented through examples to facilitate a comprehensive understanding of the relevant teachings. However, those skilled in the art should be aware that this teaching may be practiced without such details.

The present invention seeks to provide a microcell design that improves light reflectivity and minimizes light loss. Microcell designs according to embodiments of the present invention may include tapered geometries to provide angled reflective walls that repel black or dark pigments. Embodiments of the present invention can substantially improve reflectivity when microcells are exhibiting extreme optical states, such as a white state. When a film including microcells according to the invention is combined with a color filter array (CFA), increasing the white state can improve display visibility under low light conditions and can improve the color gamut of electrophoretic displays.

According to an embodiment of the present invention illustrated in Figures 2a and 2b, the microcells 10 may include white pigments 14 and black pigments 12 in a light-transmitting fluid, wherein the microcells 10 are cone-shaped, such as a chamfered pyramid, and the base of the pyramid is Facing the viewer and the peak of the pyramid facing away from the viewer. By providing a cone-like geometry, when the pixel including the microcell 10 has switched to the white state, the black pigment 12 will be at the tip of the microcell 10 (Fig. 2b). Therefore, unlike the cubic geometry of the microcell design of Figure 1, the area of the black pigment 12 on the viewing side in the cone-shaped microcell of Figure 2b is smaller than the viewing area of the white pigment 14, thereby reducing the absorption of the black pigment 12 possibility of light loss.

The geometry of the microcells according to various embodiments of the present invention may also promote reflection. For example, in Figure 2b, at least part of the light 16 passing through the white pigment 14 may be reflected back by the wall 11 of the microcell 10 and back through the white pigment layer 14 to the viewer. As those skilled in the art will appreciate, light 16 only represents a single possible path for some light to enter microcell 10, and is not intended to refer to the path taken by all light entering microcell 10 through white pigment 14. Using a polymer material with highly reflective properties to form the walls 11 of the microcell 10, light scattered by the microcell 10 will have several points at which it can be reflected back to the viewer. The angled walls 11 of the microcell 10 are preferably mirror-like/reflective, so that the walls of the microcell form a retroreflector. In another embodiment, the wall 11 of the microcell 10 may be configured as a diffuse reflector rather than as a mirror/reflective surface. This can be achieved by imprinting microcells 10 into a polymer film filled with a reflective filler such as titanium dioxide.

The geometric shapes of microcells can have various shapes. For example, referring to the plan views of the embodiments illustrated in Figures 3a, 3b and 3c, the microcell geometry may be a four-sided, three-sided or six-sided pyramid. The geometry is not limited to pyramid structures. For example, the geometric shape may be in the shape of a cone or a triangular prism, but an equilateral polygonal pyramid system is preferred because its geometry allows for a tight wrapping of microcells with similar beveled walls in the display area. In addition, the tip of the microcell's pyramidal geometry can be chosen to be truncated or hemispherical. However, the hemispherical geometry is slightly inferior because the coverage of black or other color pigments by this geometric shape cannot be as small as an area far away from the viewer.

Wall angles that provide a steeper cell geometry (i.e., a sharper angle at the tip) prevent the black pigment from sticking to the wall and minimize the exposed area of pigment coating the tip. Additionally, steeper walls may result in a more even coating of pigment on the viewing surface. For example, when switching from a black optical state to a white optical state, the white pigment is initially coated in the microcell tip and must then migrate from the tip to the viewing surface of the microcell. If the cells are too narrow, the vertical distance the white pigment travels is shorter than the lateral size of the viewing area. For fairly steep walls, the lateral to vertical distance ratio of paint runs is low. A high ratio may result in a thicker pigment coating in the center of the viewing area and a thinner, more translucent coating at the periphery of the viewing area upon switching optical states. The ratio of lateral to vertical movement of the pigment should be selected to promote substantially uniform coverage of the pigment throughout the viewing area of each microcell. Other factors may also be considered when selecting microcell geometry. For example, narrow geometries will promote reflectivity by providing shorter light reflection paths. The size of the microcell geometry may also be selected based on the desired display resolution, contrast, and switching speed of the electrophoretic display. In a preferred embodiment, the microcell depth is 20 to 50 microns.

Providing microcells with a tapered geometry also results in an increase in the optically active surface area of the electrophoretic display. Referring again to Figure 1, increasing the active surface of the electrophoretic display requires reducing the vertical wall thickness of the cubic microcell 10 or incorporating microlenses into the microcell. However, fabricating vertical walls for microcells becomes increasingly difficult as the wall thickness decreases due to the risk that some microcells will detach from the film during the imprinting process and remain on the imprinting tool. In addition, the use of microlenses may result in reduced viewing angles. Therefore, using microcells with a pyramidal geometry provides a simpler fabrication method that increases the potential optically active surface area without sacrificing the viewing angle range of the electrophoretic display.

Referring to FIG. 4 , for example, a polymer film imprinted with microcells 10 having a pyramidal geometry may be incorporated into an electrophoretic display 30 . As those familiar with this art will know, Figure 4 is not drawn to scale but is a schematic cross-sectional view of the laminated electrophoretic display. A polymer film 18 imprinted with a plurality of sealed microcells 10 can be layered between a series of pixel electrodes 22 and a continuous front electrode 20 made of a light-transmitting conductive material such as indium tin oxide (ITO). TLC. The pixel electrode 22 may be disposed on the backplane 28 in the form of a thin film transistor (TFT). The top layer of the laminated display 30 further includes a protective light-transmissive layer 24 such as PET and an optical CFA 26, which includes red (R), green (G) and blue (B) regions that are also light-transmissive. Microcells 10 are each filled with a dispersion fluid containing charged white pigment 14 and charged black pigment 12 . Therefore, a black and white display will be available in addition to the optical CFA 26. An adhesive layer may be incorporated between one or more pairs of adjacent layers described above so that the layers may be laminated together.

In an alternative embodiment of an electrophoretic display, the positions of the single continuous electrode layer and the pixel electrodes may be reversed, such that the single continuous electrode layer is on the backplane and the pixel electrodes are on the viewing side of the microcell. In this embodiment, the single continuous electrode layer does not need to be light-transmitting, but the pixel electrode must be light-transmitting. In this setup, colored pixel electrodes can be provided so that the pixel electrodes can simultaneously function as CFAs.

In another embodiment of the present invention, a method of manufacturing cone-shaped microcells is provided. As is known to those familiar with the art of microcell formation, an imprinting technique is generally used, in which a tool such as an imprinting cylinder having a microcell-like pattern on its surface is rolled onto a polymer film. After imprinting, the microcells are filled with a dispersion containing charged pigments. To seal the microcells, a cross-linkable oligomer or monomer fluid can be applied to the filled microcells. An alternative sealing step may include laminating a layer of sealant onto the cup.

Referring to Figure 5, the best method of manufacturing and sealing microcells according to the present invention includes imprinting the microcells in a polymer film, which has a plurality of microcells with a conical geometric shape; laminating the imprinted polymer films to the continuous front electrode layer; forming an opening in the microcell; filling the dispersion fluid inside the microcell through the small opening; and sealing the microcell.

The imprinting step of the preferred method may include imprinting an array of microcells 10 with a tapered geometry into a polymer film 32, such as polyester, laminated to a release sheet 34. The film should be made highly reflective, for example by metallization or the incorporation of reflective additives into the polymer film. If the polymer film is metallized before imprinting, the metal layer is likely to be discontinuous at all edges of the microcells, thus preventing short circuits between the front and rear electrodes of the display. Non-conductive reflective coatings designed for constructive interference can also be applied to films, such as commercially available films, to improve the efficiency of emissive display backlights, such as are known to those skilled in the art. The non-conductive reflective coating is preferably applied after imprinting because the coating is generally composed of oxides that are not resistant to imprinting.

In a preferred embodiment of the present invention, the reflective coating on the embossed polymer film can be a dielectric mirror. As known to those skilled in the art, a dielectric mirror includes a plurality of thin layers of dielectric material deposited on a substrate. The reflective properties of dielectric mirrors depend on the type of dielectric material and coating thickness. Dielectric mirrors can be fabricated using various thin film deposition methods, such as physical vapor deposition (eg, vapor deposition and ion beam assisted deposition), chemical vapor deposition, ion beam deposition, molecular beam epitaxy, and sputter deposition. Dielectric materials used to form dielectric mirrors include, but are not limited to, aluminum, magnesium fluoride, silicon dioxide, tantalum pentoxide, zinc sulfide (n=2.32), and titanium dioxide (n=2.4).

To further enhance the reflectivity of the microcell walls, embodiments of the present invention may include features to prevent black pigment from adhering to the microcell walls. To limit the presence of black pigment spread across the front viewing surface or coated in the cell tips, the walls can be surface treated to repel black pigment. For example, fluorinated polymers or other low surface energy materials can be coated on the microcell walls. Alternatively, after metalizing the microcell surface, the microcell walls can be treated with the same chargeable groups used to form the electrophoretic black pigment. If the charge polarity of the microcell wall is similar to that of the black pigment, the microcell wall will repel the black pigment.

In one embodiment, the metallized surface of the embossed polymer film contains reactive sites that may have silane moieties bonded to one or more polar groups and/or one or more polymeric/polymerizable groups. reagent reaction. The reactive site may be a hydroxyl group, an amine group, a carboxylic acid group or a derivative thereof (such as an amide or ester), an alcoholic or phenolic group, or a halogen, depending on the chemical functionality of the material used to provide the microcell wall with a reflective surface. The reaction site can also be implanted on the surface of the microcell wall by conventional means or by special treatment, such as the hydration treatment described in U.S. Patent No. 13/149,599 filed on May 31, 2011, the entire content of which is Incorporated herein by reference.

The polar groups of the reagent can contribute charge to the surface of the microcell wall. For example, a polar group such as --NH-- can provide a positive charge, while a polar group such as --OH or --COOH can provide a negative charge. Polymer/polymerizable groups include, but are not limited to, vinyl groups, acrylate groups, methacrylate groups, and the like.

Reactants may include, but are not limited to, N-(3-acryloyloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane (Gelest), 3-(N-allylamino)propyl Trimethoxysilane (Gelest), 3-(N-styrylmethyl-2-aminoethylamino)-propyltrimethoxysilane (Gelest) or vinylbenzylaminoethylaminopropyl-trimethoxy Silane (Dow Corning's Z-6032).

The coupling reaction of the reagent with the silane on the microcell surface can be initiated by first hydrolyzing the silane moiety to form reactive silanol groups (Si-OH), which can then react via condensation with the silanol groups on the surface of the imprinted film. Hydroxyl bonding.

To avoid strong adhesion of white pigments with opposite charge polarity to the microcell walls, a stereostabilizing layer can be added to the walls in the same manner as for black pigments. For example, after the silane coupling reaction, if desired, the polymer/polymerizable group can be polymerized with one or more types of monomers, oligomers, or polymers, and combinations thereof, to form a polymer stabilizer. The polymer stabilizer is expected to produce a three-dimensional barrier layer on the surface of the microcell wall with a thickness of about 1 nm to about 50 nm, preferably about 5 nm to about 30 nm, and more preferably about 10 nm to about 20 nm.

In the context of the present invention, suitable polymers may include, but are not limited to, polyethylene, polypropylene, polyacrylates, polyurethanes, polyesters or polysiloxanes. Suitable monomers include, but are not limited to, lauryl acrylate, lauryl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, hexyl acrylate, hexyl methacrylate, n-octyl acrylate , n-octyl methacrylate, n-octadecyl acrylate and n-octadecyl methacrylate. The choice of material for the polymer stabilizer will depend on the compatibility of the material with the solvent used in the electrophoresis fluid.

The combined thickness of the polymer film 32 and the release sheet 34 should be greater than the final size of the desired microcell geometry. The depth of the polymer film 32 should be smaller than the corresponding pattern height on the imprinting tool to ensure that the imprinting tool penetrates the polymer film 32 and enters the release sheet 34 during imprinting. The release sheet 34 should have nearly the same elastic modulus as the polymer film 32 and be thick enough so that the embossed cylinder will not be damaged by the opposite cylinder tool surface. In a preferred embodiment, the release sheet may include silicone-coated polyethylene terephthalate.

The lamination step of the preferred method may include laminating a protective PET layer, optical CFA and front plate electrode film (ITO), such as 24, 26 and 20 in Figure 4, on the open end of the microcell, such as in Figure 5 on the base of pyramidal microcells 10. The electrical passivation layer can also be incorporated between the microcells and the PET-ITO layer and adhesive layer. It is preferable to laminate the PET-ITO layer to the polymer film before filling and sealing the microcells, so that the microcell pattern includes tightly wrapped cells to maximize the active area ratio of the display.

The formation of the opening in each of the microcells may include isolating the release sheet 34 and the polymer film 32 to remove the bottom of the imprinted microcells 10, thereby forming an opening at the bottom of each of the microcells 10. Small holes. The pore width should be large enough to allow the dispersion fluid to easily enter and exit the microcell interior, but the size should be minimized to facilitate sealing after filling.

The filling step of the preferred method can be accomplished by a variety of techniques.

In one method, the microcells may be filled by first emptying the interior of the microcells, such as by placing the laminated polymer film 32 and PET-ITO layer in a vacuum chamber with the release sheet 34 removed. Immediately after applying a vacuum to evacuate the microcells of air, the dispersion fluid can be applied to the surface of the polymer film 32 containing the pores, and the vacuum is subsequently released to draw the dispersion fluid into the microcells. To minimize the possibility of solvent evaporation in the dispersion fluid, it is preferred to place the combined polymer film 32 and PET-ITO layer in a volume that is as small as possible, i.e., a smaller volume than the combined polymer film 32 and PET-ITO layer. The ITO layer is placed in a slightly larger vacuum chamber and the vacuum is released once a sufficient amount of the dispersion fluid for filling the microcells has been applied to the polymer film 32 .

Another method of filling micropores may include immersing the laminated polyester film 32 and the PET-ITO layer except the release sheet 34 in an ultrasonic bath filled with a dispersion fluid. Ultrasonic stirring will expel the gas in the microcells and replace them with the dispersion fluid. If necessary, the bath can be kept under a slight vacuum to speed up the process. Ultrasonic stirring is the preferred filling method because of its potential for visual continuous program adjustment.

Still another filling method may include filling the microcells with, for example, a solvent vapor having a boiling point below ambient temperature but above the flow point or solidification temperature of the dispersion fluid. The laminated polymer film 32 and the PET-ITO layer with the release sheet 34 removed can then be immersed in the dispersion fluid, and then cooled to a temperature lower than the boiling point of the solvent vapor in the microcells. This will cause the solvent vapor to condense and draw the dispersion fluid into the microcells. The solvent vapor is preferably miscible with the dispersion fluid.

When the microcells are filled with a dispersion fluid, the microcells are preferably sealed with a sealant that is miscible in the dispersion. Laminate adhesives that simultaneously meet the electrical, optical, and mechanical requirements of electrophoretic displays and have low solvent permeability can be used to seal microcells and form front plate laminates (FPL), including the microcell designs of the present invention. Alternatively, a separate sealant can be used to seal the microcells before applying the laminate adhesive layer and optional release sheet to form the FPL. Because the sealant is applied to the electrophoretic display of the preferred method behind the viewing surface, the sealant is less likely to interfere with the optical properties of the display.

While preferred embodiments of the invention have been shown and described herein, it will be understood that these embodiments are provided by way of example only. Those skilled in the art will be able to make various changes, changes and substitutions without departing from the spirit of the invention. The appended claims are therefore intended to cover all such changes within the spirit and scope of the invention.

10: Microcell 11: wall 12: black pigment 14: white pigment 16:Light 18:Polymer film 20: Front electrode 22: Pixel electrode 24: Protective translucent layer 26: Optical color display array 28:Back panel 30: Multilayer display 32:Polymer film 34: Release sheet R:Red G: green B: blue

The drawings depict one or more implementations of the present concept and are examples only and are not intended to be limiting. Similar reference numbers in the drawings refer to the same or similar components. Figure 1 is a side cross-sectional view of a series of cells containing black and white pigments in a dispersion fluid. Figure 2a is a side cross-sectional view of a microcell in a white optical state according to the first embodiment of the present invention. Figure 2b is a side cross-sectional view of the microcell of Figure 2a in a black optical state. Figure 3a is a plan view of four microcells according to another embodiment of the present invention. Figure 3b is a plan view of six microcells according to yet another embodiment of the present invention. Figure 3c is a plan view of three microcells according to yet another embodiment of the present invention. Figure 4 is a schematic side cross-sectional view of an electrophoretic display incorporating the microcells of Figure 2a. Figure 5 is a side cross-sectional view of an embossed polymer film and a release sheet used in a method according to another embodiment of the present invention.

10: Microcell

12: black pigment

14: white pigment

18:Polymer film

20: Front electrode

22: Pixel electrode

24: Protective translucent layer

26: Optical color display array

28:Back panel

30: Multilayer display

R:Red

G: green

B: blue

Claims (12)

A method of manufacturing a laminate for an electrophoretic display, the method comprising: imprinting a plurality of cone-shaped microcells through a layer of polymer film and into but not through a release sheet to form an imprinted film; on the contrary The embossed film is laminated to a layer of conductive material on a protective sheet on the side of the release sheet to form a laminated film; the release sheet is removed from the laminated film to form one of each microcell of the laminated film an opening inside; filling the microcells with a dispersion fluid; and sealing the microcells. The method of claim 1, wherein the polymer film includes a metallized surface. The method of claim 1, further comprising applying a non-conductive reflective coating to a surface of the polymer film before the lamination step. The method of claim 1, wherein the polymer film includes a reflective additive. The method of claim 1, wherein a color filter array is located between the protective sheet and the layer of conductive material. The method of claim 1, wherein the filling step includes: placing the laminated film having the opening to the interior of each microcell in a vacuum chamber; Evacuating the interior of each microcell to create a vacuum within the vacuum chamber; applying the dispersion fluid to the opening of each microcell; and releasing the vacuum within the vacuum chamber. The method of claim 1, wherein the filling step includes immersing the laminated film having the opening to the interior of each microcell in an ultrasonic bath filled with the dispersion fluid. The method of claim 1, wherein the filling step includes: filling the interior of each microcell with a solvent with a boiling point higher than the flow point or freezing point of the dispersion fluid; and providing the opening to the interior of each microcell. The laminated film is immersed in the dispersion fluid; and the temperature of the solvent is lowered below the boiling point of the solvent to introduce the dispersion fluid into the interior of each microcell. The method of claim 1, wherein the sealing step includes covering the opening of each microcell with a sealant. The method of claim 1, wherein the cone-shaped microcells have a chamfered pyramid shape. The method of claim 1, wherein the cone-shaped microcells have an inverted cone shape. The method of claim 1, wherein the cone-shaped microcells have an inverted triangular prism shape.