TWI757867B - Polymeric film - 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

polymer film

The present invention relates to electrophoretic displays. Specifically, in one aspect, the present invention relates to improved micelles comprising electrophoretic fluids for electrophoretic displays. In another aspect, the present invention relates to methods of making improved micelles for use in electrophoretic displays.

The term "electro-optic" applies to a material or display, as used herein in its conventional sense in imaging technology, to refer to a material having at least one first and second display state of differing optical properties by applying an electric field to the material It changes from the first display state to the second display state. Although the optical property generally visible to the human eye is color, it can also be other optical properties, such as optical transmittance, reflectivity, illuminance, or, in the case of machine-readable displays, the false value of electromagnetic wavelengths outside the visible range. Pseudo-color reflectance changes.

The term "gray-scale state" is used herein 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 e-ink patents and published applications referred to below are white and dark blue, so the "gray-scale state" in the middle actually refers to light blue. As previously mentioned, optical state changes may indeed be non-color changes. The terms "black" and "white" may be used hereinafter to refer to the two extreme optical states of a display, and should be understood to generally include the extreme optical states of not only black and white, such as the aforementioned white and cyan states. The term "monochromatic" may hereinafter refer to a drive mechanism that only drives the pixel to the two extreme optical states without intermediate grayscale states.

The terms "bistable" and "bistable" are used herein in their conventional meanings in the art, and refer to a display that includes a display unit having at least one first and second display state that differ in optical properties, and such that after driving any given cell with a finite-duration addressing pulse, it is assumed to be in a first or second display state which, after terminating the addressing pulse, will persist at least several times (eg, at least 4 times) for changing display cell states The minimum duration of the desired addressing pulse. In US Pat. No. 7,170,670 there are shown particle-based electrophoretic displays with some grayscales that are stable not only in extreme black and white states, but also in intermediate grayscale states, as well as for some other types of electro-optical displays. Such displays are appropriately referred to as "multi-stable" rather than bistable, although for convenience the term "bistable" may be used herein to encompass both bistable and multi-stable displays.

One type of electro-optic 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 in an electric field. Compared with liquid crystal displays, electrophoretic displays can have the following properties: good brightness and contrast ratio, wide viewing angle, bistable, and low power consumption. However, the long-term image quality problems of these displays prevent widespread adoption. For example, the particles that make up electrophoretic displays tend to precipitate, resulting in poor service life for these displays.

As mentioned above, the electrophoretic medium requires the presence of a fluid. In most prior art electrophoretic media, this fluid is a liquid, but electrophoretic media can be made from gaseous fluids; see eg Kitamura, T. et al. IDW Japan, 2001, Paper HCS1-1 ("Electrophores for 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 US Patent Nos. 7,321,459 and 7,236,291. Such gas-based electrophoretic media look like particle-based electrophoretic media, subject to similar problems with particle precipitation when the media is used to allow orientation of such precipitation, such as in signs 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 because the lower viscosity of gaseous suspending fluids allows for faster precipitation of electrophoretic particles compared to liquids.

Assigned or assigned to various patents and applications in the names of the Massachusetts Institute of Technology (MIT), E Ink Corporation, E Ink California, LLC and related companies describing encapsulated and microcellular electrophoresis and other electro-optical media used in various technologies. An encapsulated electrophoretic medium includes a plurality of small capsules, each of which itself includes an inner phase and a capsule wall surrounding the inner phase, the inner phase containing electrophoretically mobile particles in a fluid medium. In a microcellular electrophoretic display, charged particles and fluids are not encapsulated within microcapsules, but are retained within a plurality of cavities formed within a carrier medium, typically a polymer film. See, eg, International Application Publication No. WO 02/01281 and Published US Application No. 2002/0075556. Such techniques can be found, for example, in the following patents and applications: (a) Electrophoretic Particles, Fluids and Fluid Additives; see eg US Pat. Nos. 7,002,728 and 7,679,814; (b) Capsules, binders and encapsulation treatments; see eg US Pat. Nos. 6,922,276 and 7,411,719; (C) the micelle structure, the wall material and the method of forming micelles; see U.S. Pat. Ser. No. 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; 7,715,087; 7,767,126; 7,880,958; 8,002,948; 8,154,790 ; 8,169,690; 8,441,432; 8,582,197; 8,891,156; 9,279,906; 9,291,872; and No. 9,388,307 and U.S. Patent application Publication No. 2003/0175480; 2003/0175481; 2003/0179437; 2003/0203101; 2013/0321744; 2014/0050814; 2015/0085345 ; 2016/0059442; 2016/0004136; and 2016/0059617; (d) Methods for filling and sealing micelles; see for example US Pat. Nos. 7,144,942 and 7,715,088; (e) Films and subassemblies containing electro-optical materials; see for example US Pat. Nos. 6,982,178 and 7,839,564; (f) Backsheets, adhesive layers and other auxiliary layers and methods for displays; see for example US Pat. Nos. 7,116,318 and 7,535,624; (g) Color formation and color adjustment; see for example US Pat. Nos. 7,075,502 and 7,839,564; (h) A method for driving a display; see for example US Pat. Nos. 7,012,600 and 7,453,445; (i) Application of displays; see for example US Pat. Nos. 7,312,784 and 8,009,348; (j) Non-electrophoretic displays; see US Patent No. 6,241,921 and US Patent Application Publication No. 2015/0277160; and applications of encapsulation and microcellular technology other than displays; 0005720 and 2016/0012710.

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

Electrophoretic displays generally include one 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 yet most such displays, both layers are electrode layers, and one or both of the electrode layers are patterned to define display pixels. For example, one electrode layer can be patterned as elongated column electrodes and another as elongated row electrodes extending at right angles to the column electrodes, where the columns and row electrodes intersect to define pixels. Or more commonly, one electrode layer has the shape of a single continuous electrode 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 electrodes, the layer on the opposite side of the electrophoretic layer It is generally a protective layer to prevent the electrophoretic layer from being damaged by the movable electrode.

Electro-optical displays, including electrophoretic displays, are expensive, and the price of color LCDs such as those found in portable computers generally accounts for the majority of the overall computer sales price. With the expansion of such displays into devices such as cell phones and personal digital assistants (PDAs), the pressure on reducing the cost of such displays is even higher because their prices are much lower than those of portable computers. The ability to form electrophoretic dielectric layers by printing techniques on flexible substrates, as previously described, opens the possibility of reducing the cost of display electrophoretic components using mass production techniques such as roll-to-roll Commercially available equipment for 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 cells 10 imprinted in a polymer film are filled with an electrophoretic fluid, which includes a black pigment 12 and a white pigment 14 . The micelles 10 can be incorporated as a layer in a black and white electrophoretic display. When one or more pixels of the display are displaying a white optical state (viewed from above in FIG. 1 ), a substantial amount of light can penetrate the white pigment layer 14 rather than being reflected back to the viewer. Light entering the micelles 10 may be lost and possibly absorbed by the black pigment layer 12 . Loss of light can result in a dull color state.

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

In one aspect of the invention there is provided a polymer film comprising a plurality of cone-shaped micelles comprising a dispersion of charged particles of a first population and a second population. The charged particles of the first population are light absorbing and have a charge polarity opposite to the charge polarity of the charged particles of the second population. The cone-shaped micelles comprise a wall and at least a portion of the wall is configured to repel the charged particles of the first population.

In another aspect of the invention there is provided a method of fabricating a laminate for an electrophoretic display comprising imprinting a plurality of cone-shaped cells through a polymer film and into a release sheet to form an imprint film; laminate the imprinted film to a layer of conductive material on a protective sheet to form a laminate film; remove the release sheet from the polymer film to form an opening to the interior of each cell of the laminate film ; filling the micelles with the dispersion fluid; and sealing the micelles.

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

In the following detailed description, various specific details are presented by way of example to facilitate a thorough understanding of the relevant teachings. However, those skilled in the art should know that the present teachings may be practiced without these details.

The present invention seeks to provide a cell design that improves light reflectivity and minimizes light loss. Cell designs according to various 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 the micelles are exhibiting extreme optical states, such as a white state. When films comprising micelles according to the present invention are combined with a color filter array (CFA), increasing the white state can improve display visibility in low light conditions and can improve the color gamut of electrophoretic displays.

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

The geometry of the cells according to 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 walls 11 of the cells 10 and back through the white pigment layer 14 to the viewer. As is known to those skilled in the art, light 16 represents only a single possible path for some of the light to enter the micelle 10 and is not intended to refer to the path traveled by all light passing through the white pigment 14 into the micelle 10. Using a polymeric material with highly reflective properties to form the walls 11 of the cells 10, the light scattered by the cells 10 will have several points where it can be reflected back to the viewer. The beveled walls 11 of the cells 10 are preferably mirror-like/mirror such that the walls of the cells form retroreflectors. In another embodiment, the walls 11 of the cells 10 may be configured as diffuse reflectors rather than mirror/mirror-like surfaces. This can be achieved by imprinting the cells 10 in a polymer film filled with a reflective filler such as titanium dioxide.

The geometry of the micelles can have various shapes. For example, referring to the plan views of the various embodiments illustrated in Figures 3a, 3b and 3c, the cell geometry may be a quadrangular, triangular or hexagonal pyramid. The geometry is not limited to pyramid structures. For example, the geometry can be in the shape of a cone or a triangular prism, but an equilateral polygonal pyramid system is preferred because its geometry allows tight encapsulation of cells with bevel-like walls in the display area. In addition, the tips of the conical geometry of the micelles can be chosen to be truncated or hemispherical. However, the hemispherical geometry is slightly worse, since the coating of black or other color pigments by this geometry cannot be as small as the area away from the viewer.

Providing a steeper (ie more acute angle at the tip) wall angle of the cell geometry prevents the black pigment from sticking to the wall and minimizes the exposed area of the pigment coating the tip. Additionally, steeper walls may result in a more uniform coating of the viewing surface with the pigment. For example, when switching from the black optical state to the white optical state, the white pigment is initially encapsulated in the tips of the micelles and must then migrate from the tips to the viewing surface of the micelles. If the cells are too narrow, the vertical distance that the white pigment travels is shorter than the lateral dimension of the viewing area. For relatively steep walls, the ratio of lateral to vertical distance of pigment travel is low. High ratios may result in a thicker coating of pigment in the center of the viewing area, and a thinner, more light-transmitting coating at the periphery of the viewing area, as soon as the optical state is switched. The ratio of lateral to vertical movement of the pigment should be selected to promote substantially uniform coverage of the pigment over the entire viewing area of each cell. Other factors may also be considered when selecting the cell geometry. For example, narrow geometries will promote reflectivity by providing a shorter light reflection path. The size of the cell geometry can also be selected based on the desired display resolution, contrast, and switching speed of the electrophoretic display. In a preferred embodiment, the micelle depth is 20 to 50 microns.

Providing cells with a tapered geometry can also result in an increase in the optically active surface area of the electrophoretic display. Referring again to Figure 1, increasing the active surface of an electrophoretic display requires reducing the vertical wall thickness of the cubic cells 10 or incorporating microlenses into the cells. However, making vertical walls for micelles becomes increasingly difficult as the wall thickness decreases due to the risk of some of the micelles falling off the film and remaining on the imprinting tool during the imprinting process. In addition, the use of microlenses may result in reduced viewing angles. Thus, the use of cone-shaped geometry cells provides a simpler fabrication method, increasing the potential optically active surface area without sacrificing the viewing angle range of an electrophoretic display.

Referring to FIG. 4 , for example, a polymer film embossed with cells 10 having a tapered geometry may be incorporated into an electrophoretic display 30 . As can be appreciated by those skilled in the art, FIG. 4 is not drawn to scale but is a schematic cross-sectional view of a multilayer electrophoretic display. The polymer film 18 embossed with the plurality of sealed cells 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) thin layer. 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 laminate display 30 further includes a protective light transmissive layer 24 such as PET and an optical CFA 26 that includes red (R), green (G) and blue (B) regions that are also light transmissive. Each of the cells 10 is filled with a dispersion fluid containing charged white pigment 14 and charged black pigment 12 . Therefore, in addition to the optical CFA 26, a black and white display will be provided. An adhesive layer may be incorporated between one or more pairs of the aforementioned adjacent layers such 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 micelles. In this embodiment, the single continuous electrode layer does not need to transmit light, but the pixel electrode needs to transmit light. In this arrangement, 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 micelles is provided. As known to those skilled in the art of formation of micelles, an embossing technique is generally employed in which a tool such as an imprinted cylinder having a pattern of exocellular patterns on the surface is rolled onto a polymer film. After embossing, the micelles are filled with a dispersion containing charged pigments. To seal the micelles, a crosslinkable oligomer or monomer fluid can be applied to the filled micelles. An alternative sealing step may involve laminating a layer of sealant on the cup.

Referring to FIG. 5, the best method for making and sealing micelles according to the present invention includes imprinting the micelles in a polymer film with a plurality of micelles having a tapered geometry; laminating the imprinted polymer films to a continuous front electrode layer; forming openings in the micelles; filling the interior of the micelles with dispersion fluid through the small openings; and sealing the micelles.

The imprinting step of a preferred method may include imprinting an array of cells 10 having a tapered geometry into a polymer film 32, such as polyester, laminated to a release liner 34. The film should be made highly reflective, eg, by metallization or incorporation of reflective additives in the polymer film. If the polymer film is metallized before imprinting, the metal layer is likely to be discontinuous at all edges of the cells, thereby avoiding shorting the front and rear electrodes of the display. Non-conductive reflective coatings designed for constructive interference can also be applied to thin films, such as commercially available thin films, to improve, for example, emissive display backlighting efficiency known to those skilled in the art. The non-conductive reflective coating is preferably applied after embossing, since the coating generally consists of oxides that are not resistant to embossing.

In a preferred embodiment of the present invention, the reflective coating on the imprinted polymer film may 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 a dielectric mirror depend on the type of dielectric material and the thickness of the coating. 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 the dielectric mirror 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 cell walls, embodiments of the present invention may include features to prevent black pigment from sticking to the cell walls. To limit the presence of black pigment spread over the front viewing surface or encapsulated in the tips of the cells, 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 cell walls. Alternatively, after metallizing the micelle surface, the micelle walls can be treated with the same chargeable groups used to form the electrophoretic black pigment. If the cell wall has a charge polarity similar to that of the black pigment, the cell wall will repel the black pigment.

In one embodiment, the metallized surface of the imprinted polymer film includes reactive sites that can interact with silane moieties having silane moieties bonded to one or more polar groups and/or one or more polymeric/polymerizable groups reagent reaction. The reactive sites can be hydroxyl groups, amine groups, carboxylic acid groups or derivatives thereof (eg, amides or esters), alcohol or phenol groups, or halogens, depending on the chemical function of the material used to provide a reflective surface for the cell walls. 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 US Patent No. 13/149,599 filed on May 31, 2011, the entire content of which is described in Incorporated herein by reference.

The polar groups of the reagents can contribute charges to the surface of the microcell wall. For example, polar groups such as --NH-- can provide a positive charge, while polar groups such as --OH or --COOH can provide a negative charge. Polymeric/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 (Z-6032 from Dow Corning).

Coupling reactions of reagents with silanes on the surface of micelles can be initiated by first hydrolyzing the silane moiety to form reactive silanol groups (Si-OH), which can then react with silanols on the surface of the imprinted film by condensation reactions. hydroxyl bonding.

In order to avoid strong adhesion of white pigments with opposite charge polarities to the cell walls, a steric stabilization layer can be added to the walls as is done for black pigments. For example, after the silane coupling reaction, if desired, the polymer/polymerizable groups can be polymerized with one or more types of monomers, oligomers, or polymers, and combinations thereof, to form polymeric stabilizers. The polymeric stabilizer desirably produces a steric barrier layer on the surface of the micelle cell wall of about 1 nm to about 50 nm, preferably about 5 nm to about 30 nm, 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-octyl acrylate and n-octadecyl methacrylate. The choice of material for the polymeric stabilizer will depend on the compatibility of the material with the solvent used in the electrophoretic fluid.

The combined thickness of the polymer film 32 and release liner 34 should be greater than the final dimension of the desired cell geometry. The polymer film 32 depth should be less than the corresponding pattern height on the imprinting tool to ensure that the imprinting tool penetrates the polymer film 32 and into the release liner 34 during imprinting. The release sheet 34 should have approximately the same modulus of elasticity as the polymer film 32 and sufficient thickness so that the imprinted cylinder will not be damaged by the opposing cylinder tool surface. In a preferred embodiment, the release liner may comprise 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 ends of the micelles, such as in Figure 5 Pyramidal micelles 10 at the base. An electrical passivation layer can also be incorporated between the micelles and the PET-ITO layer and the adhesive layer. The PET-ITO layer is preferably laminated to the polymer film prior to filling and sealing the micelles, so that the micelle pattern contains tightly packed cells, maximizing the active area ratio of the display.

The formation of openings in each of the cells may include isolating the release sheet 34 and the polymer film 32 to remove the bottom of the imprinted cells 10 , thereby forming a bottom of each of the cells 10 . small holes. The pore width should be large enough to allow easy passage of the dispersion fluid into and out of the interior of the micelles, but the size should be minimized to facilitate sealing after filling.

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

In one method, the micelles can be filled by first evacuating their interiors, for example by placing the laminated polymer film 32 and PET-ITO layer in a vacuum chamber with the release liner 34 removed. Immediately after a vacuum is applied to evacuate the micelles of the gas, the dispersion fluid can be applied to the surface of the polymer film 32 containing the pores, and then the vacuum is released to draw the dispersion fluid into the micelles. In order to minimize the possibility of solvent evaporation in the dispersion fluid, it is preferable to place the combined polymer film 32 and PET-ITO layer in a volume having as small a volume as possible, i.e., a smaller combined polymer film 32 and PET-ITO layer. The ITO layer is placed in a somewhat larger volume vacuum chamber, and the vacuum is released once sufficient dispersion fluid to fill the micelles has been applied to the polymer film 32.

Another method of filling the micropores may include immersing the laminated polyester film 32 with the PET-ITO layer except the release sheet 34 in an ultrasonic bath filled with dispersion fluid. Ultrasonic agitation will dislodge the gas from the micelles, allowing them to be replaced by the dispersion fluid. If necessary, the bath can be kept under a slight vacuum to speed up the procedure. Ultrasonic agitation is the preferred filling method because of the potential for visual continuous program adjustment.

Still another filling method may include filling the cells with a solvent vapor having a boiling point below ambient temperature but above the flow point or freezing temperature of the dispersion fluid, for example. 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 below the boiling point of the solvent vapor in the micelles. This will cause the solvent vapor to condense and draw the dispersion fluid into the micelles. The solvent vapor is preferably miscible with the dispersion fluid.

When filling the micelles with a dispersion fluid, the micelles are preferably sealed with a sealant that is miscible in the dispersion. Laminate adhesives that meet the electrical, optical and mechanical requirements of electrophoretic displays and have low solvent permeability can be used to seal cells and form front plate laminates (FPLs), including the cell design of the present invention. Alternatively, the cells can be sealed with a separate sealant prior to application of the laminate adhesive layer and optional release sheet to form the FPL. Since the encapsulant is applied to the non-viewing surface behind the electrophoretic display of the preferred method, the encapsulant 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 is to be understood that these embodiments are provided by way of example only. Numerous changes, modifications, and substitutions will occur to those skilled in the art without departing from the spirit of the invention. Accordingly, it is intended to cover by the appended claims all such changes that come within the spirit and scope of the present invention.

10: Microcells 11: Wall 12: Black Pigment 14: White Pigment 16: Light 18: Polymer film 20: Front electrode 22: Pixel electrode 24: Protective light-transmitting layer 26: Optical Color Display Array 28: Backplane 30: Laminate Displays 32: Polymer Film 34: Release film R: red G: green B: blue

The drawings depicted in accordance with one or more implementations of the present concepts are by way of example only, and are not intended to be limiting. Like numbers in the drawings refer to the same or similar elements. Figure 1 is a side cross-sectional view of a series of micelles 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 micelle of Figure 2a in a black optical state. Figure 3a is a plan view of four micelles according to another embodiment of the present invention. Figure 3b is a plan view of 6 micelles according to yet another embodiment of the present invention. Figure 3c is a plan view of three micelles according to yet another embodiment of the present invention. Figure 4 is a schematic side cross-sectional view of an electrophoretic display incorporating the micelle of Figure 2a. 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: Microcells

12: Black Pigment

14: White Pigment

18: Polymer film

20: Front electrode

22: Pixel electrode

24: Protective light-transmitting layer

26: Optical Color Display Array

28: Backplane

30: Laminate Displays

R: red

G: green

B: blue

Claims (12)

A polymer film comprising a plurality of cone-shaped cells, the plurality of cone-shaped cells comprising a dispersion of charged particles of a first population and a second population, the charged particles of the first population being light absorbing and having a charge polarity opposite to the charge polarity of the second population of charged particles, the second population of charged particles being light-scattering, wherein the cone-shaped cells comprise a wall and at least a portion of the wall is configured to repel the A first population of charged particles, wherein the portion of the wall includes a mirror surface. The polymer film of claim 1, wherein the charged particles of the first group are black. The polymer film of claim 1, wherein the charged particles of the second group are white. The polymer film of claim 1, wherein the pyramidal micelles are conical. The polymer film of claim 1, wherein the pyramidal micelles are pyramid-shaped. The polymer film of claim 1, wherein the pyramidal micelles have a chamfered pyramid shape. The polymer film of claim 1, wherein the pyramidal micelles have an inverted cone shape. The polymer film of claim 1, wherein the pyramidal micelles have an inverted triangular prism shape. The polymer film of claim 1, wherein the portion of the wall includes a diffusely reflective surface. The polymer film of claim 1, wherein the portion of the wall has a charge polarity similar to the charge polarity of the first population of charged particles. The polymer film of claim 1, wherein the portion of the wall comprises a low energy surface material. The polymer film of claim 11, wherein the low energy surface material comprises a fluorinated polymer.

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