Sealing film compositions for sealing microcells of electro-optic devices

Abstract

To provide sealing film compositions for sealing microcells of electro-optic devices.SOLUTION: The present invention is directed to an aqueous sealing composition that comprises a combination of polymers, a poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer and a polyurethane, a conductive filler, and a water-soluble ether in an aqueous carrier. The aqueous sealing composition may be used to form a sealing film in electro-optic devices having an electro-optic material layer disposed between two electrode layers and comprising (a) a plurality of microcells filled with charged particles and a non-polar fluid and (b) a sealing film. The device exhibits good electro-optic performance.SELECTED DRAWING: None

Description

[Technical Field]

[0001] Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 281,345, filed November 19, 2021. Any patents, published applications or other published documents referenced herein are incorporated by reference in their entirety.

[0002] FIELD OF THE INVENTION The present invention relates to a sealing film that can be used in electro-optical devices, such as electrophoretic displays. The sealing film comprises a poly(vinyl alcohol) homopolymer or a poly(vinyl alcohol-co-ethylene) copolymer, polyurethane, a conductive filler, and a water-soluble ether. The sealing film can be formed by curing or drying an aqueous sealing composition. [Background technology]

[0003] Background of the Invention The term "electro-optic," as applied to a material or display, is used herein in its conventional sense in the imaging arts to refer to a material having first and second display states that differ in at least one optical property, and that changes from its first display state to its second display state upon application of an electric field to the material. The optical property is typically color as perceived by the human eye, but may also be another optical property, such as light transmission, reflectance, luminescence, or, in the case of displays intended to be machine-readable, pseudocolor in the sense of a change in reflectance at electromagnetic wavelengths outside the visible range.

[0004] The terms "bistable" and "bistable" are used herein in their conventional sense in the art to refer to displays containing display elements having first and second display states that differ in at least one optical property, such that any given element is driven to assume either its first or second display state with an addressing pulse of finite duration, and that state persists after the addressing pulse has ended for at least several times, e.g., at least four times, the minimum duration of the addressing pulse required to change the state of the display element. U.S. Pat. No. 7,170,670 indicates that some particle-based electrophoretic displays capable of gray scale are stable not only in their extreme black and white states but also in intermediate gray states, and the same is true for some other types of electro-optical devices. Displays of this type are properly referred to as "multistable" rather than bistable, although for convenience the term "bistable" may be used herein to encompass both bistable and multistable displays.

[0005] One type of electro-optical device that has been the subject of intense research and development for many years is the particle-based electrophoretic display, in which a plurality of charged particles move through a fluid under the influence of an electric field. Electrophoretic displays can have attributes of good brightness and contrast, wide viewing angles, state bistability, and low power consumption when compared to liquid crystal displays.

[0006] Numerous patents and applications assigned to or in the name of Massachusetts Institute of Technology (MIT), E Ink Corporation, E Ink California, LLC, and affiliates describe various technologies used in encapsulated and microcell electrophoretic media, as well as other electro-optical media. Encapsulated electrophoretic media contain a large number of small capsules, each of which contains an internal phase containing electrophoretically movable particles in a fluid medium and a capsule wall surrounding the internal phase. Typically, the capsules are themselves held within a polymer binder to form a coherent layer positioned between two electrodes. In microcell electrophoretic displays, the charged particles and fluid are not encapsulated within microcapsules, but instead are held within a plurality of cavities formed within a carrier medium, typically a polymer film.

[0007] The technologies described in these patents and applications include:

[0008] (a) Electrophoretic particles, fluids and fluid additives, see, for example, US Pat. Nos. 7,002,728 and 7,679,814.

[0009] (b) Capsules, binders and encapsulation processes, see, e.g., U.S. Patent Nos. 6,922,276 and 7,411,719.

[0010] (c) Microcell structures, wall materials, and methods of forming microcells, see, for example, US Pat. Nos. 7,072,095 and 9,279,906.

[0011] (d) Methods for filling and sealing microcells, see, for example, U.S. Patent Nos. 7,144,942, 7,005,468, and 7,715,088, and U.S. Patent Application Publication Nos. 2004-0120024 and 2004-0219306.

[0012] (e) Films and subassemblies containing electro-optical materials, see, for example, US Pat. Nos. 6,982,178 and 7,839,564.

[0013] (f) Backplanes, adhesive layers and other auxiliary layers and methods used in displays, see, for example, US Pat. Nos. 7,116,318 and 7,535,624.

[0014] (g) Color formation and color adjustment, see, for example, U.S. Patent Nos. 7,075,502 and 7,839,564.

[0015] (h) Methods for driving displays, see, for example, US Pat. Nos. 7,012,600 and 7,453,445.

[0016] (i) Display applications, see, for example, US Pat. Nos. 7,312,784 and 8,009,348.

[0017] (j) Non-electrophoretic displays and non-display applications of encapsulation and microcell technology as described in U.S. Pat. No. 6,241,921 and U.S. Patent Application Publication No. 2015 / 0277160, see, e.g., U.S. Pat. No. 7,615,325, and U.S. Patent Application Publication Nos. 2015 / 0005720 and 2016 / 0012710.

[0018] The contents of all of the foregoing references are incorporated herein by reference in their entirety. Structures with multiple sealed microcells containing a dispersion of charged pigment particles in a nonpolar fluid are commercially used in electro-optical devices. Microcells are also known in the literature as microcavities or microcups. A typical method for fabricating sealed microcell structures for electro-optical devices involves (a) fabricating a polymer sheet with multiple microcavities, each with an opening, by microembossing; (b) filling the microcavities with an electrophoretic medium, which is a dispersion of charged pigment particles in a nonpolar fluid; and (c) sealing the microcavities with an aqueous sealing composition to form a sealing film. The sealed microcavities containing the electrophoretic medium form the electro-optical material layer of the device. The electro-optical material layer is disposed between a front electrode and a back electrode. Application of an electric field across the electrophoretic medium by these electrodes causes the pigment particles to migrate through the electrophoretic medium, producing an image. The sealing film plays an important role in the device's function and performance. First, because the sealing film contacts the electrophoretic medium and seals it inside the microcavities, the sealing layer must (1) be practically insoluble in the nonpolar fluid of the electrophoretic medium and (2) be a good barrier to the nonpolar fluid so that it does not diffuse out of the microcells during the device's lifetime. Second, the sealing film must not absorb significant amounts of moisture from the environment; that is, it must prevent environmental moisture from entering the device's electrophoretic medium. Such moisture can negatively affect the device's electro-optical performance. The sealing film should be mechanically resilient over the device's useful lifetime and have an optimal volume resistivity that remains constant over time. Poor barrier properties of the sealing film to nonpolar fluids can result in loss of fluid from the electrophoretic medium and sagging of the sealing film. Finally, the conductive properties of the sealing film are important because electrical potentials are applied throughout the device and are transmitted through the sealing film, among other components.The technical challenge of providing an aqueous sealing composition that forms a sealing film having these characteristics is challenging because different formulation strategies may be required for different purposes. For example, barrier properties against non-polar fluids typically require more hydrophilic components, while such components absorb more moisture from the environment. If the sealing film has low electrical conductivity, increased power consumption will be required for device operation, while too high conductivity can cause poor image quality due to blooming. Therefore, there is a need for an aqueous sealing composition that forms a sealing film optimized for improved barrier properties against non-polar fluids, reduced moisture absorption, and improved electro-optical performance. The present inventors have discovered that a sealing film composition containing a combination of poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer, polyurethane, conductive carbon black, and a water-soluble ether provides a sealing film with good electro-optical performance and excellent color. [Prior art documents] [Patent documents]

[0019] [Patent Document 1] U.S. Patent No. 7,170,670 [Patent Document 2] U.S. Patent No. 7,002,728 [Patent Document 3] U.S. Patent No. 7,679,814 [Patent Document 4] U.S. Patent No. 6,922,276 [Patent Document 5] U.S. Patent No. 7,411,719 [Patent Document 6] U.S. Patent No. 7,072,095 [Patent Document 7] U.S. Patent No. 9,279,906 [Patent Document 8] U.S. Patent No. 7,144,942 [Patent Document 9] U.S. Patent No. 7,005,468 [Patent Document 10] U.S. Patent No. 7,715,088 [Patent Document 11] US Patent Application Publication No. 2004 / 0120024 [Patent Document 12] US Patent Application Publication No. 2004 / 0219306 [Patent Document 13] U.S. Patent No. 6,982,178 [Patent Document 14] U.S. Patent No. 7,839,564 [Patent Document 15] U.S. Patent No. 7,116,318 [Patent Document 16] U.S. Patent No. 7,535,624 [Patent Document 17] U.S. Patent No. 7,075,502 [Patent Document 18] U.S. Patent No. 7,012,600 [Patent Document 19] U.S. Patent No. 7,453,445 [Patent Document 20] U.S. Patent No. 7,312,784 [Patent Document 21] U.S. Patent No. 8,009,348 [Patent Document 22] U.S. Patent No. 6,241,921 [Patent Document 23] US Patent Application Publication No. 2015 / 0277160 [Patent Document 24] U.S. Patent No. 7,615,325 [Patent Document 25] US Patent Application Publication No. 2015 / 0005720 [Patent Document 26] US Patent Application Publication No. 2016 / 0012710 Summary of the Invention [Means for solving the problem]

[0020] Summary of the Invention In one aspect, the present invention is directed to a seal film comprising: a water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer in a content of 15% to 60% by weight, based on the weight of the seal film, wherein the poly(vinyl alcohol) homopolymer has a degree of hydrolysis of 90% to 99.5%, and the poly(vinyl alcohol-co-ethylene) copolymer has a degree of hydrolysis of 90% to 99.5% and an ethylene content of less than 10%; polyurethane in a content of 7% to 29% by weight, based on the weight of the seal film; carbon black in a content of 5% to 70% by weight, based on the weight of the seal film; and a water-soluble ether in a content of 0.5% to 25% by weight, based on the weight of the seal film.

[0021] The poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer can have a number-average molecular weight of 1,000 to 1,000,000 daltons. The poly(vinyl alcohol) polymer or poly(vinyl alcohol-co-ethylene) copolymer can have a degree of hydrolysis of 92% to 99%. The polyurethane polymer can have a number-average molecular weight of 1,000 to 2,000,000 daltons. The polyurethane can be an ester polyurethane, a polycarbonate polyurethane, or a combination thereof. The total surface energy of the sealing film can be less than 60 mN / m. The interfacial tension between the water-soluble poly(vinyl alcohol) polymer or poly(vinyl alcohol-co-ethylene) copolymer and the polyurethane can be less than 2 mN / m. The sealing film can further include an organic silicone wetting agent.

[0022] The water-soluble ether has a molecular weight of 75 to 5,000 daltons and optionally contains a hydroxy group. The water-soluble ether is represented by Formula I, Formula II, or Formula III. [ka] Represented by [wherein n is 1 to 145, R1 is hydrogen, a methyl or ethyl group, R2, R3, R4, R5, R6, and R7 are independently selected from the group consisting of hydrogen, a linear or branched alkyl group containing 1 to 6 carbon atoms, phenyl, and a benzyl group, and Formula I contains at least one ether functional group, Formula II contains at least one ether functional group, and Formula III contains at least one ether functional group]. For Formula I, n can be 1 to 10. The seal film is 10 8 ~10 10 It may have a volume resistivity of ohm.cm.

[0023] In another aspect, the present invention is directed to an electrophoretic device comprising: a conductive layer; a microcell layer including a plurality of microcells, each microcell including an opening, each microcell including an electrophoretic medium, the electrophoretic medium including charged particles in a non-polar carrier; a sealing film spanning the opening of each microcell; an adhesive layer; and an electrode layer. The seal film comprises a water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer in a content of 15% to 60% by weight based on the weight of the seal film, the poly(vinyl alcohol) homopolymer having a degree of hydrolysis of 90% to 99.5%, and the poly(vinyl alcohol-co-ethylene) copolymer having a degree of hydrolysis of 90% to 99.5% and an ethylene content of less than 10%; a polyurethane in a content of 7 to 29% by weight based on the weight of the seal film; carbon black in a content of 5 to 70% by weight based on the weight of the seal film; and a water-soluble ether in a content of 0.5 to 25% by weight based on the weight of the seal film, the water-soluble ether having a molecular weight of 70 to 5,000 daltons, and optionally containing a hydroxyl group. The electrophoretic medium may include at least three types of charged pigment particles, one type of charged particle having a color selected from the group consisting of blue, green, red, cyan, magenta, and yellow.

[0024] In yet another aspect, the present invention is directed to an aqueous sealing composition comprising: a water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer in a content of 14% to 55% by weight, based on the weight of the sealing composition excluding water, wherein the poly(vinyl alcohol) homopolymer has a degree of hydrolysis of 90% to 99.5% and the poly(vinyl alcohol-co-ethylene) copolymer has a degree of hydrolysis of 90% to 99.5% and an ethylene content of less than 10%; polyurethane in a content of 6% to 27% by weight, based on the weight of the aqueous sealing composition excluding water; carbon black in a content of 5% to 64% by weight, based on the weight of the aqueous sealing composition excluding water; a water-soluble ether in a content of 1.0% to 40% by weight, based on the weight of the aqueous sealing composition excluding water, the water-soluble ether having a molecular weight of 75 to 5,000 daltons and optionally containing a hydroxy group; and water in a content of 20% to 95% by weight, based on the weight of the aqueous sealing composition excluding water. The aqueous sealing composition may further comprise a crosslinking agent in an amount of 0.1 to 8% by weight, based on the weight of the aqueous sealing composition excluding water, and the crosslinking agent may be polyisocyanate, polycarbodiimide, polyfunctional aziridine, silane coupling agent, boron / titanium / zirconium-based crosslinking agent, or melamine formaldehyde. The aqueous sealing composition may further comprise a rheology modifier in an amount of 0.05 to 5% by weight, based on the weight of the aqueous sealing composition excluding water. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 shows a side view of a multi-microcell structure before it is filled and sealed.

[0026] [Figure 2] FIG. 2 shows a side view of an example electro-optical device including a microcell structure.

[0027] [Figure 3]FIG. 3 shows a side view of an example front plane laminate assembly that can be used to form an electro-optical device that includes a microcell structure.

[0028] [Figure 4] FIG. 4 shows a side view of an example of a dual release sheet that can be used to form an electro-optical device containing a microcell structure.

[0029] [Figure 5] FIG. 5 illustrates a method for fabricating a microcell using a roll-to-roll process.

[0030] [Figure 6-1] 6A and 6B detail the creation of microcells using photolithographic exposure through a photomask of a conductor film coated with a thermoset precursor.

[0031] [Figure 6-2] 6C and 6D detail an alternative embodiment of the fabrication of a microcell array using photolithography, in which a combination of top and bottom exposures is used, allowing one horizontal partition wall to be cured by a top photomask exposure and another horizontal partition wall to be cured by a bottom exposure through an opaque base conductor film.

[0032] [Figure 7A] 7A-7D show the steps of filling and sealing the array of microcells. [Figure 7B] 7A-7D show the steps of filling and sealing the array of microcells. [Figure 7C] 7A-7D show the steps of filling and sealing the array of microcells. [Figure 7D] 7A-7D show the steps of filling and sealing the array of microcells.

[0033] [Figure 8-1] 8A-8D show various components constructed for evaluation of the volume resistivity of the sealing film.

[0034] [Figure 8-2] Figures 8A-8D show various components constructed for evaluation of the volume resistivity of the sealing film, and Figure 8E shows the waveform used for evaluation of the volume resistivity of the sealing film.

[0035] [Figure 9] FIG. 9 shows the electrical impedance spectroscopy results of the control and inventive seal films.

[0036] [Figure 10] FIG. 10 shows the structure of the electro-optical device used to evaluate the electro-optical performance of the water-based sealing composition.

[0037] [Figure 11] FIG. 11 shows the waveforms used to determine the color gamut of the inventive and control electro-optical devices.

[0038] [Figure 12] FIG. 12 shows a side view of the electro-optical device structure used to evaluate the barrier properties of the aqueous sealing composition.

[0039] [Figure 13A] 13A-13D show microscopic images of the microcells evaluated for barrier properties. [Figure 13B] 13A-13D show microscopic images of the microcells evaluated for barrier properties. [Figure 13C] 13A-13D show microscopic images of the microcells evaluated for barrier properties. [Figure 13D] 13A to 13D show microscopic images of the microcells evaluated for barrier properties.

[0040] [Figure 14] FIG. 14 shows microscopic images of polymeric sealing films containing combinations of poly(vinyl alcohol-co-ethylene) copolymer and polyurethane with various interfacial tensions. DETAILED DESCRIPTION OF THE INVENTION

[0041] Detailed Description of the Invention As used herein, "molecular weight" refers to the weight average molecular weight of a compound, unless otherwise stated. Molecular weight is measured using gel permeation chromatography, an industry standard method.

[0042] The degree of hydrolysis of a poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer is the ratio of the moles of vinyl alcohol groups to the sum of the moles of vinyl alcohol groups and the moles of vinyl acetate groups in the polymer. Thus, for the simplified polyvinyl alcohol formula example provided below as (Formula IV), the degree of hydrolysis is calculated according to Equation 1: Degree of hydrolysis=100×p / (p+q) Equation 1 Typically, manufacturers of polyvinyl alcohol report the degree of hydrolysis of their products. This parameter affects important physical properties of the polymer, such as the polymer's water solubility and the water resistance of the corresponding dry film. To determine the degree of hydrolysis of polyvinyl alcohol (homopolymer and copolymer), a titration method is used. Details of the method are described in JIS K 6726 (Japanese Standards Association, 94th edition, October 20, 2017). [ka]

[0043] The terms "sealing film" and "sealing layer" are synonymous and are used interchangeably with respect to electro-optical devices.

[0044] The terms "adhesive film" and "adhesive layer" are synonymous and are used interchangeably with respect to electro-optical devices.

[0045] Unless otherwise stated, the disclosed content of a component of a sealing film is calculated as the weight % of the component relative to the weight of the sealing film excluding water. Unless otherwise stated, the disclosed content of a component of an aqueous sealing composition is calculated as the weight % of the component relative to the weight of the aqueous sealing composition excluding water.

[0046] A. Microcell Structure

[0047] 1 shows a side view of a structure of multiple microcells 100 before being filled and sealed. Each microcell includes a base 101, a partition wall 102, and an opening 103.

[0048] B. Structure of an electro-optical device including a microcell structure

[0049] FIG. 2 shows a side view of an example electro-optical device 200 including microcells. The example electro-optical device 200 includes a first light-transmitting electrode layer 210, a microcell layer 220, a sealing film 230, an adhesive layer 240, and a second electrode layer 250. The microcell layer includes a plurality of microcells defined by a base 221 and a partition wall 222. Each of the plurality of microcells contains an electrophoretic medium 225, which includes charged particles in a non-polar fluid. The microcells are sealed with a sealing film 230, which spans the openings of the plurality of microcells. The second electrode layer 250 is connected to the sealing film 230 using an adhesive layer 240. The plurality of microcells sealed by the sealing layer 230 and containing the electrophoretic medium 225 constitute the electro-optical material layer of the electro-optical device 200. A source of electric field may connect the first light-transmissive electrode layer 210 with the second electrode layer 250. Application of an electric field across the electrophoretic material layer causes charged particles to move in the electrophoretic medium to create an image that can be viewed by an observer looking from the viewing side 215 of the electro-optic device 200. An optional primer layer (not shown in FIG. 2) may be disposed between the first light-transmissive electrode layer 210 and the plurality of microcells 222.

[0050] The example electro-optical device shown in FIG. 2 can be constructed using a front plane laminate 300 shown in FIG. 3. The front plane laminate 300 includes a first light-transmitting electrode layer 310, a microcell layer 320 containing a plurality of microcells 325, a sealing film 330, an adhesive layer 340, and a release sheet 360. Each microcell of the plurality of microcells contains an electrophoretic medium 325, which includes charged particles in a non-polar fluid. The microcells 325 are sealed with a sealing film 330, which spans the openings of the plurality of microcells. The release sheet 360 is connected to the sealing film 330 using an adhesive layer 340. Removal of the release sheet 360 exposes the surface of the adhesive layer 340, which can be connected onto a second electrode layer to form an electro-optical device. An optional primer layer (not shown in FIG. 3) can be disposed between the first light-transmitting electrode layer 310 and the plurality of microcells 330.

[0051] The example electro-optical device shown in FIG. 2 can also be constructed using a dual release sheet 400 shown in FIG. 4. The dual release sheet 400 includes a first release sheet 480, a first adhesive layer 470, a microcell layer 420 containing a plurality of microcells 425, a sealing film 430, a second adhesive layer 440, and a second release sheet 460. Each of the microcells contains an electrophoretic medium 425, which includes charged particles in a non-polar fluid. The microcells are sealed with a sealing film 430, which spans the openings of the microcells. The first release sheet 480 is connected to the microcell layer 420 using the first adhesive layer 470. The second release sheet 460 is connected to the sealing film 430 using the second adhesive layer 440. Removal of the first release sheet 480 exposes the surface of the first adhesive layer 470, which can be connected to a first light-transmitting electrode layer. Removal of the second release sheet 460 exposes the surface of the second adhesive layer 440, which may be connected onto a second electrode layer to form an electro-optical device. An optional primer layer (not shown in FIG. 4) may be disposed between the first adhesive layer 470 and the microcell layer 430.

[0052] C. Formation of Microcell Structure

[0053] Techniques for Constructing Microcells. Microcells can be formed either in a batch process or a continuous roll-to-roll process as disclosed in U.S. Pat. No. 6,933,098. The latter provides a continuous, low-cost, high-throughput manufacturing technique for generating compartments for use in a variety of applications, including benefit agent delivery and electrophoretic displays. Microcell arrays suitable for use with the present invention can be created using microembossing, as shown in FIG. 5. A male mold (500) can be placed either above the web 504 or below the web 504 (not shown). However, alternative arrangements are possible. See, for example, U.S. Pat. No. 7,715,088, which is incorporated herein by reference in its entirety. Conductive substrates can be constructed by forming a conductor film 501 on a polymer substrate that will become the backing layer for the device. A composition 502 containing a thermoplastic, thermoset, or precursor thereof is then coated onto the conductor film. The thermoplastic or thermoset precursor layer is embossed by a male mold in the form of a roller, plate or belt at a temperature above the glass transition temperature of the thermoplastic or thermoset precursor layer.

[0054] The thermoplastic or thermosetting precursors for the preparation of microcells can be multifunctional acrylates or methacrylates, vinyl ethers, epoxides, and their oligomers or polymers. The combination of multifunctional epoxides and multifunctional acrylates is also very useful for achieving desirable physical and mechanical properties. Crosslinkable oligomers that impart flexibility, such as urethane acrylates or polyester acrylates, can be added to improve the bending resistance of the embossed microcells. The composition can contain polymers, oligomers, monomers, and additives, or it can contain only oligomers, monomers, and additives. The glass transition temperature (T g ) is typically in the range of about -70°C to about 150°C, or about -20°C to about 50°C. The microembossing process is typicallyg A heated male mold, or a heated housing substrate against which the mold exerts pressure, can be used to control the temperature and pressure of the microembossing.

[0055] As shown in FIG. 5, the mold is released during or after the precursor layer is cured to reveal an array of microcells 503. Curing of the precursor layer can be achieved by cooling, solvent evaporation, cross-linking by radiation, heat, or moisture. If curing of the thermosetting precursor is achieved by UV radiation, the UV can be emitted onto the transparent conductor film from the bottom or top of the web, as shown in the two figures. Alternatively, a UV lamp can be placed inside the mold. In this case, the mold must be transparent to allow UV light to be emitted through the pre-patterned male mold onto the thermosetting precursor layer. The male mold can be prepared by any suitable method, such as a diamond turning process or a photoresist process, followed by either etching or electroplating. A master template for the male mold can be manufactured by any suitable method, such as electroplating. In electroplating, a thin layer of seed metal, such as chrome Inconel, is sputtered onto a glass base. (typically 3000 Å). The mold is then coated with a layer of photoresist and exposed to UV light. A mask is placed between the UV and the photoresist layer. The exposed areas of the photoresist are hardened. The unexposed areas are then removed by washing with an appropriate solvent. The remaining hardened photoresist is dried, and a thin layer of seed metal is sputtered again. This prepares the master for electroforming. A typical material used for electroforming is nickel-cobalt. Alternatively, the master can be made from nickel by electroforming or electroless nickel deposition. The floor of the mold is typically between about 50 and 400 microns. The master can be fabricated as described in "Replication techniques for micro-optics", SPIE Proc. Vol. 3099, pp. 76-82 (1997) Other microengineering techniques can also be used, including e-beam writing, dry etching, chemical etching, laser writing, or laser interference. Alternatively, molds can be made using plastics, ceramics, or metals by photomachining.

[0056] Before applying the UV-curable resin composition, the mold may be treated with a release agent to aid in the demolding process. The UV-curable resin may be degassed before dispensing and may contain a solvent, if present. The solvent, if present, evaporates easily. The UV-curable resin is dispensed over the male mold by any suitable method, such as coating, dipping, or pouring. The dispensing device may be moving or stationary. A conductor film is then superimposed on the UV-curable resin. If necessary, pressure may be applied to ensure proper bonding between the resin and the plastic and to control the thickness of the microcell floor. Pressure may be applied using laminating rollers, vacuum forming, compression devices, or any other similar means. If the male mold is metallic and opaque, the plastic substrate is typically transparent to the actinic radiation used to cure the resin. Conversely, the male mold may be transparent, and the plastic substrate may not be transparent to actinic radiation. To ensure good transfer of the molded features onto the transfer sheet, the conductor film must have good adhesion to the UV-curable resin, and the resin should have good release properties relative to the mold surface.

[0057] Microcell arrays for the present invention typically include a preformed conductor film, such as indium tin oxide (ITO) conductor lines, although other conductive materials, such as silver or aluminum, may also be used. The conductive layer may be backed by or integrated into a substrate, such as polyethylene terephthalate, polyethylene naphthalate, polyaramid, polyimide, polycycloolefin, polysulfone, epoxy, and composites thereof. The conductor film may be coated with a radiation-curable polymer precursor layer. The film and precursor layer are then imagewise exposed to radiation to form the microcell wall structure. After exposure, the precursor material is removed from the unexposed areas, leaving hardened microcell partition walls bonded to the conductor film / support web. Imagewise exposure may be achieved by passing UV or other forms of radiation through a photomask to generate an exposure image or predetermined exposure pattern of the radiation-curable material coated on the conductor film. Although not generally necessary, the mask can be positioned and aligned relative to the conductor film, i.e., the ITO lines, so that the transparent mask portions align with the spaces between the ITO lines and the opaque mask portions align with the ITO material (intended for the cell bottom regions of the microcells).

[0058] Photolithography. Microcells can also be generated using photolithography. A photolithography process for fabricating a microcell array is shown in FIGS. 6A and 6B. As shown in FIGS. 6A and 6B, a microcell array 600 can be prepared by exposing a radiation-curable material 601a, coated on a conductor electrode film 602 by known methods, to UV light (or alternatively other forms of radiation, e-beam, etc.) through a mask 606 to form partition walls 601b corresponding to the image imaged through the mask 606. The base conductor film 602 is preferably mounted on a supporting substrate base web 603, which may comprise a plastic material.

[0059] In the photomask 606 of Figure 6A, the dark squares 604 represent opaque areas, and the spaces between the dark squares represent transparent areas 605 of the mask 606. UV is emitted through the transparent areas 605 onto the radiation curable material 601a. ​​The exposure is preferably performed directly on the radiation curable material 601a, i.e., the UV does not pass through to the substrate 603 or to the base conductors 602 (top exposure). For this reason, neither the substrate 603 nor the conductors 602 need to be transparent to the UV or other wavelengths of radiation used.

[0060] As shown in Figure 6B, the exposed areas 601b are cured. The unexposed areas (protected by the opaque areas 604 of the mask 606) are then removed with a suitable solvent or developer to form the microcells 607. The solvent or developer is selected from those commonly used to dissolve or reduce the viscosity of radiation-curable materials, such as methyl ethyl ketone (MEK), toluene, acetone, isopropanol, etc. Preparation of the microcells can also be achieved by placing a photomask underneath the conductor film / substrate support web; in this case, UV light is emitted from the bottom through the photomask, and the substrate must be transparent to the radiation.

[0061] Imagewise Exposure. Yet another alternative method for preparing the microcell array of the present invention by imagewise exposure is shown in Figures 6C and 6D. If opaque conductor lines are used, they can be used as a photomask for bottom exposure. Durable microcell partition walls are formed by further exposure from the top through a second photomask having opaque lines perpendicular to the conductor lines. Figure 6C illustrates the use of both top and bottom exposure principles to produce the microcell array 610 of the present invention. The base conductor film 612 is opaque and patterned with lines. The radiation-curable material 611a coated on the base conductor 612 and substrate 613 is exposed from the bottom through the conductor line pattern 612, which acts as the first photomask. A second exposure is performed from the "top" side through a second photomask 616 having a line pattern perpendicular to the conductor lines 612. The spaces 615 between the lines 614 allow substantial transmission of UV light. In this process, the wall material 611b cures laterally from the bottom up and vertically from the top down, together forming the complete microcell 617. The unexposed areas are then removed with a solvent or developer as previously described to reveal the microcell 617, as shown in Figure 6D.

[0062] The microcells can be constructed from thermoplastic elastomers that have good compatibility with the microcell and do not interact with the medium. Examples of useful thermoplastic elastomers include diblock, triblock, and multiblock copolymers of the ABA and (AB)n type, where A is styrene, α-methylstyrene, ethylene, propylene, or norbornene, and B is butadiene, isoprene, ethylene, propylene, butylene, dimethylsiloxane, or propylene sulfide, and A and B cannot be the same in the formula. The number n is ≧1, preferably 1 to 10. Particularly useful are diblock or triblock copolymers of styrene or ox-methylstyrene, such as SB (poly(styrene-b-butadiene)), SBS (poly(styrene-b-butadiene-b-styrene)), SIS (poly(styrene-b-isoprene-b-styrene)), and SEBS (poly(styrene-b-ethylene / butylene-b-styrene)). Examples of suitable styrene block copolymers include 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), and poly(α-methylstyrene-b-dimethylsiloxane-b-α-methylstyrene). Commercially available styrene block copolymers, such as the Kraton D and G series (Kraton Polymer, Houston, Tex.), are particularly useful. Crystalline rubbers, such as poly(ethylene-co-propylene-co-5-methylene-2-norbornene) or EPDM (ethylene-propylene-diene terpolymer) rubbers, such as Vistalon 6505 (Exxon Mobil, Houston, Tex.) and their grafted copolymers have also been found to be very useful.

[0063] The thermoplastic elastomer can be dissolved in a solvent or solvent mixture that is immiscible with the carrier in the microcells and exhibits a specific gravity lower than that of the carrier. Low surface tension solvents are preferred for the overcoating composition because they have better wetting properties than the microcell partition walls and their fluids. Solvents or solvent mixtures having a surface tension lower than 35 dynes / cm are preferred. A surface tension lower than 30 dynes / cm is more preferred. Suitable solvents include alkanes (preferably C 6~12 Alkanes, such as heptane, octane or Isopar solvents from Exxon Chemical Company, nonane, decane and their isomers), cycloalkanes (preferably C 6~12 Cycloalkanes, such as cyclohexane and decalin, alkylbenzenes (preferably mono- or di-C 1~6 Alkylbenzenes, such as toluene and xylene, alkyl esters (preferably C 2~5 Alkyl esters, such as ethyl acetate, isobutyl acetate, etc.) and C 3~5 Included are alkyl alcohols (e.g., isopropanol, etc. and their isomers). Mixtures of alkyl benzenes and alkanes are particularly useful.

[0064] In addition to the polymer additive, the polymer mixture may contain a wetting agent (surfactant). Wetting agents (e.g., FC surfactants from 3M Company, Zonyl fluorosurfactants from DuPont, fluoroacrylates, fluoromethacrylates, fluoro-substituted long-chain alcohols, perfluoro-substituted long-chain carboxylic acids and their derivatives, and Silwet silicone surfactants from OSi, Greenwich, Conn.) may also be included in the composition to improve adhesion of the sealant to the microcells and provide a more flexible coating process. Other ingredients are also very useful to enhance the physical and mechanical properties of the seal film by crosslinking or polymerization reactions during or after the overcoating process, including crosslinking agents (e.g., bisazides, such as 4,4'-diazidodiphenylmethane and 2,6-di-(4'-azidobenzal)-4-methylcyclohexanone), vulcanizing agents (e.g., 2-benzothiazolyl disulfide and tetramethylthiuram disulfide), multifunctional monomers or oligomers (e.g., hexanediol, diacrylates, trimethylolpropane, triacrylates, divinylbenzene, diallylphthalene), thermal initiators (e.g., dilauroyl peroxide, benzoyl peroxide), and photoinitiators (e.g., isopropylthioxanthone (ITX), Irgacure 651 and Irgacure 369 from Ciba-Geigy).

[0065] A microcell array, such as the array 700 shown in FIG. 7A, can be prepared by any of the methods described above. As shown in the cross-sectional views of FIGS. 7A-7D, microcell divider walls 702 extend upward from microcell bottoms 701 and conductive layer 710 to form open microcells. In one embodiment, conductive layer 710 is formed on or at microcell bottoms 701. While FIGS. 7A-7D show conductive layer 710 extending continuously above microcell bottoms 701, conductive layer 710 can also extend continuously below or within bottoms 701, or be interrupted by microcell divider walls 702.

[0066] The microcells are then filled with an electrophoretic medium 725 containing charged particles in a non-polar fluid to form a plurality of filled microcells 770. The microcells may be filled using a variety of techniques. In some embodiments, blade coating may be used to fill the microcells to the depth of the microcell partition walls 702.

[0067] 7C, after filling, the microcells are sealed by applying an aqueous sealing composition to form sealed microcells 780 containing sealing film 730. In some embodiments, the sealing process may include exposure to heat, dry hot air, or UV radiation. The sealing film should have good barrier properties to the non-polar fluid of the electrophoretic medium 725.

[0068] In an alternative embodiment, various individual microcells can be filled with a desired mixture by using iterative photolithography. This process typically involves coating an array of empty microcells with a layer of positive-acting photoresist, selectively opening a certain number of microcells by imagewise exposing the positive photoresist, subsequently developing the photoresist, filling the open microcells with the desired mixture, and sealing the filled microcells by a sealing process. These steps can be repeated to create sealed microcells filled with other mixtures. This procedure allows for the formation of large sheets of microcells having the desired ratios or concentrations of mixtures.

[0069] Sealing of filled microcells can be achieved in several ways. One approach involves mixing an aqueous sealing composition with an electrophoretic medium composition. The aqueous sealing composition can be immiscible with the electrophoretic medium composition, preferably having a specific gravity lower than that of the electrophoretic medium composition. The two compositions, the sealing composition and the electrophoretic medium composition, are thoroughly mixed and immediately coated onto multiple microcells using a precise coating mechanism, such as a Mayer bar, gravure, doctor blade, slot coating, or slit coating. Excess fluid is scraped off with a wiper blade or similar device. A small amount of a weak solvent or solvent mixture, such as isopropanol, methanol, or an aqueous solution thereof, can be used to clean any fluid remaining on the upper surface of the microcell partition walls. The aqueous sealing composition is then separated from the electrophoretic medium composition and floats on top of the electrophoretic medium liquid composition. Alternatively, after the mixture of the electrophoretic medium composition and the aqueous sealing composition is filled into the microcells, a substrate can be laminated on top to control the metering of the composition mixture and promote phase separation of the aqueous sealing composition from the electrophoretic medium composition to form a uniform sealing film. The substrate used may be a functional substrate in the final structure, or it may be a sacrifice substrate, such as a release substrate, that can be removed later. The sealing film is then formed by curing the aqueous sealing composition in situ (i.e., while in contact with the electrophoretic medium composition). Curing of the aqueous sealing composition can be achieved by UV or other forms of radiation, such as visible light, IR, or electron beam. Alternatively, if a heat- or moisture-curable aqueous sealing composition is used, heat or moisture can also be used to cure the aqueous sealing composition.

[0070] In the second approach, the electrophoretic medium composition can be first filled into the microcells, and then the filled microcells are overcoated with an aqueous sealing composition. Overcoating can be achieved by conventional coating and printing processes, such as blanket coating, inkjet printing, or other printing processes. In this approach, the sealing film is formed in situ by curing the aqueous sealing composition through solvent evaporation, radiation, heat, moisture, or interfacial reaction. Interfacial polymerization followed by UV curing is beneficial to the sealing process. Intermixing between the electrophoretic medium composition and the sealing overcoat is significantly suppressed by the formation of a thin barrier layer at the interface by interfacial polymerization. A post-curing step, such as UV radiation, then completes the sealing. The degree of intermixing can be further reduced by using an aqueous sealing composition with a specific gravity lower than that of the electrophoretic medium composition. Volatile organic solvents can be used to adjust the viscosity and thickness of the sealing overcoat. The rheology of the aqueous sealing composition determines optimal sealability and coating properties. The volatile solvent can be adjusted for coatability. When used, the volatile solvent is preferably immiscible with the solvent in the electrophoretic medium composition.

[0071] After the microcells are filled and sealed, a second electrode layer 750 including multiple electrodes can be laminated to the sealed microcell array, as shown in FIG. 7D . The second electrode layer 750 is bonded onto the sealing film 730 to form an electro-optical device 790, as shown in FIG. 7D . An adhesive can be used to bond the second electrode layer 750 onto the sealing film 730. The adhesive layer is not shown in FIG. 7D . The adhesive material of the adhesive layer can be conductive. The adhesive of the adhesive layer can be a pressure-sensitive adhesive, a hot-melt adhesive, or a heat-, moisture-, or radiation-curable adhesive. The laminating adhesive can be post-cured by radiation, e.g., UV, through the top conductive layer if the top conductive layer is radiation-transparent. In other embodiments, multiple electrodes can be bonded directly to the sealed array of microcells.

[0072] In general, microcells can be any shape, and their size and shape can vary. Microcells can be of substantially uniform size and shape in some systems. However, it is possible to have microcells of a mixture of shapes and sizes. The openings of the microcells can be circular, square, rectangular, hexagonal, or any other shape. The size of the partition areas between the openings can also vary. The dimensions of each individual microcell are approximately 1 x 10 1 ~Approx. 1×10 6 μm 2 , or approximately 1 × 10 2 ~Approx. 1×10 6 μm 2 , or approximately 1 × 10 3 ~Approx. 1×10 5 μm 2 The range may be:

[0073] The depth of the microcells can be in the range of about 5 μm to about 200 μm, or about 10 μm to about 100 μm. The ratio of the opening area to the total area is in the range of 0.05 to 0.95, preferably 0.4 to 0.9.

[0074] Electrophoretic displays typically include a layer of electrophoretic material and at least two other layers disposed on either side of the electrophoretic material, one of which is an electrode layer. In most such displays, both layers are electrode layers, and one or both of these electrode layers are patterned to define the pixels of the display. For example, one electrode layer may be patterned into elongated row electrodes and the other into elongated column electrodes extending perpendicular to the row electrodes, with the pixels defined by the intersections of the row and column electrodes. Alternatively, and more commonly, one electrode layer has the form of a single continuous electrode, and the other electrode layer is patterned into a matrix of pixel electrodes, each of which defines one pixel of the display. In another type of electrophoretic display, intended for use with a stylus, printhead or similar movable electrode that is separate from the display, only one of the layers adjacent to the electro-optic material layer contains electrodes, and the layer opposite the electro-optic material layer is typically a protective layer intended to prevent the movable electrode from damaging the electro-optic material layer.

[0075] The manufacture of a three-layer electrophoretic display typically involves at least one lamination operation. For example, some of the aforementioned MIT and E Ink patents and applications describe methods for producing encapsulated electrophoretic displays in which an encapsulated electrophoretic medium containing capsules in a binder is coated onto a flexible substrate containing indium tin oxide (ITO) or a similar conductive coating coated onto a plastic film. Separately, a backplane is prepared containing an array of pixel electrodes and conductors in an arrangement suitable for connecting the pixel electrodes and driving circuitry. To form the final display, the substrate bearing the electro-optic material layer is laminated to the backplane using a laminating adhesive.

[0076] The aforementioned U.S. Patent No. 6,982,178 describes a method for assembling a solid-state electro-optic display that is well suited to mass production. Essentially, this patent describes a so-called "front plane laminate" ("FPL"), which includes, in order, a light-transmitting electrode layer, an electro-optic material layer in electrical contact with the light-transmitting electrode layer, an adhesive layer, and a release sheet, as shown in FIG. 3. Typically, the light-transmitting electrode layer is carried on a light-transmitting substrate, which is preferably flexible in the sense that it can be manually wrapped around a 10-inch (254 mm) diameter drum (for example) without permanent deformation. The term "light-transmitting" is used in this patent and herein to mean that a designated layer transmits sufficient light to enable an observer looking through the designated layer to observe a change in the display state of the electrophoretic medium, which change is usually seen through the light-transmitting electrode layer and the adjacent substrate (if present). If the electrophoretic medium exhibits a change in reflectivity at non-visible wavelengths, the term "light-transmitting" should, of course, be interpreted as referring to the transmission of the relevant non-visible wavelengths. The substrate is typically a polymer film, usually having a thickness ranging from about 1 to about 25 mils (25 to 634 μm), preferably from about 2 to about 10 mils (51 to 254 μm). The light-transmitting electrode layer can conveniently be a thin metal or metal oxide layer, e.g., aluminum or ITO, or a conductive polymer. Aluminum- or ITO-coated poly(ethylene terephthalate) (PET) films are commercially available, e.g., as "aluminized Mylar" ("Mylar" is a registered trademark) from EI du Pont de Nemours & Company, Wilmington, DE, and such commercially available materials can be used with good results in the front plane laminate.Assembly of an electrophoretic display using such a front plane laminate can be carried out by removing the release sheet from the front plane laminate and contacting the adhesive layer with the backplane under conditions effective to adhere the adhesive layer to the backplane, thereby securing the adhesive layer, electro-optic material layer, and light-transmitting electrode layer to the backplane. This process is well suited to mass production, as front plane laminates can be mass-produced, typically using roll-to-roll coating techniques, and then cut into pieces of any size required for use with a particular backplane.

[0077] U.S. Patent No. 7,561,324 describes a so-called "dual release sheet," which is essentially a simplified version of the front plane laminate of the aforementioned U.S. Patent No. 6,982,178. One form of dual release sheet includes a layer of electro-optic material sandwiched between two adhesive layers, one or both of which are covered by a release sheet, as shown in FIG. 4. Another form of dual release sheet includes a layer of solid electro-optic material sandwiched between two release sheets. Both forms of dual release film are intended for use in a process generally similar to the process for assembling electrophoretic displays from the previously described front plane laminates, but involving two separate laminates. Typically, in the first laminate, the dual release sheet is laminated to the front electrode to form the front subassembly, and then in the second laminate, the front subassembly is laminated to the backplane to form the final display, although these two lamination orders can be reversed if desired.

[0078] U.S. Patent No. 7,839,564 describes a so-called "inverted front plane laminate," which is a variation of the front plane laminate described in the aforementioned U.S. Patent No. 6,982,178. This inverted front plane laminate may include, in order, at least one of a light-transmitting protective layer and a light-transmitting electrode layer, an adhesive layer, an electro-optic material layer, and a release sheet. This inverted front plane laminate is used to form an electro-optic device having a layer of laminating adhesive between the electro-optic material layer and the light-transmitting electrode layer, with or without a typically thin second adhesive layer between the electro-optic material layer and the backplane. Such electro-optic displays can combine good resolution with good low-temperature performance.

[0079] Electrophoretic medium.

[0080] In the context of this invention, the term "electrophoretic medium" refers to a composition in a microcell. The microcell may be filled with at least one type of charged pigment particles in a nonpolar fluid for display applications. The electrophoretic medium may contain one type of charged particle, or one or more types of particles with different colors, charges, and charge polarities. The charged particles migrate in the electrophoretic medium under the influence of an electric field applied across the electro-optical material layer. The charged particles may be inorganic or organic pigments with a polymer surface treatment to improve their stability. The electrophoretic medium may contain pigments of white, black, cyan, magenta, yellow, blue, green, red, and other colors. The electrophoretic medium may also contain charge control agents, charge adjuvants, rheology modifiers, and other additives. Examples of non-polar fluids include hydrocarbons such as Isopar, decahydronaphthalene (decalin), 5-ethylidene-2-norbornene, fatty oils, paraffin oil, silicon fluids, aromatic hydrocarbons such as toluene, xylene, Phenylxylylethane, dodecylbenzene or alkylnaphthalenes, halogenated solvents such as perfluorodecalin, perfluorotoluene, perfluoroxylene, dichlorobenzotrifluoride, 3,4,5-trichlorobenzotrifluoride, chloropentafluorobenzene, dichlorononane or pentachlorobenzene, and perfluorinated solvents such as FC-43, FC-70 or FC-5060 from 3M Company, St. Paul, MN, low molecular weight halogen-containing polymers such as poly(perfluoropropylene oxide) from TCI America, Portland, Oregon, poly(chlorotrifluoroethylene) such as halocarbon oils from Halocarbon Product Corp., River Edge, NJ, perfluoropolyalkyl ethers such as Galden from Ausimont, or Krytox oils and Greases K-Fluid series from DuPont, Delaware, polydimethylsiloxane-based silicone oil (DC-200) from Dow-corning.

[0081] The electrophoretic medium may contain two types of charged particles having different colors, the first type of charged particles having a first charge polarity and the second type of charged particles having a second charge polarity opposite to the first charge polarity. The first type of charged particles may be black and the second type of charged particles may be white.

[0082] The electrophoretic medium may contain three types of charged particles, all having different colors, where the first type of charged particles has a first charge polarity, the second type of charged particles has a second charge polarity opposite to the first charge polarity, and the third type of charged particles has a third charge polarity the same as either the first or second charge polarity. The first type of charged particles may be black, the second type of charged particles may be white, and the third type of charged particles may be selected from the group consisting of red, yellow, blue, cyan, magenta, green, and orange.

[0083] The electrophoretic medium may contain four types of charged particles, all having different colors, where the first type of charged particles has a first charge polarity, the second type of charged particles has a first charge polarity, the third type of charged particles has a second charge polarity opposite to the first charge polarity, and the fourth type of charged particles has a second charge polarity. The magnitude of the charge of the first type of particles may be higher than the magnitude of the charge of the second type of particles, and the magnitude of the charge of the third type of particles may be higher than the charge of the fourth type of particles. In one example, the first type of charged particles is cyan, the second type of charged particles is magenta, the third type of particles is yellow, and the fourth type of charged particles is white.

[0084] The electrophoretic medium may contain four types of charged particles, all of different colors, with a first type of charged particles having a first charge polarity, a second type of charged particles having a first charge polarity, a third type of charged particles having a first charge polarity, and a fourth type of charged particles having a second charge polarity opposite to the first charge polarity. The magnitudes of the charges of the first, second, and third particles may be different from one another. The magnitude of the charge of the third type of particles may be higher than the magnitude of the charge of the first type of particles, and the magnitude of the charge of the first type of particles may be higher than the magnitude of the charge of the second type of particles. In one example, the first type of particles is cyan, the second type of particles is magenta, the third type of particles is yellow, and the fourth type of particles is white.

[0085] The electrophoretic medium may contain five types of charged particles, all of different colors, with the first type of charged particles having a first charge polarity, the second type of charged particles having a first charge polarity, the third type of particles having a first charge polarity, the fourth type of particles having a second charge polarity opposite to the first charge polarity, and the fifth type of particles having a second charge polarity. The magnitudes of the first, second, and third charges may be different from one another. The magnitude of the charge of the third type of particles may be higher than the magnitude of the charge of the first type of particles, which may be higher than the magnitude of the charge of the second type of particles. The fourth type of particles may have a higher charge than the fifth type of charged particles. In one example, the first type of particles are cyan, the second type of particles are magenta, the third type of particles are black, the fourth type of particles are yellow, and the fifth type of particles are white.

[0086] Sealing film from aqueous sealing composition

[0087] The sealing film that seals the microcell openings of an electro-optic display must provide a barrier to the electrophoretic medium so that non-polar fluids are not removed from the microcells. Furthermore, the sealing film must not negatively affect the electro-optic performance of the device.

[0088] One of the important properties of a sealing film is its electrical volume resistivity. If the volume resistivity of the sealing film is too high, a significant voltage drop occurs within the sealing film, necessitating a voltage increase across the electrodes to operate the device. Increasing the voltage across the electrodes in this manner is undesirable, as it increases the power consumption of the display and may require the use of more complex and expensive control circuitry to handle the increased voltage. On the other hand, if the volume resistivity of the sealing film is too low, undesirable crosstalk between adjacent pixel electrodes may be observed, resulting in poor image quality (blooming). In addition, since volume resistivity typically increases rapidly with decreasing temperature, too high a volume resistivity of the sealing film will negatively affect the electro-optical performance of the display at low temperatures. The sealing film should be 10 8 The seal film can have a volume resistivity of 3.5 x 10 ohm.cm or higher. 7 ~10 12 ohm.cm or 10 8 ~10 10 The sealing film can have a volume resistivity of 10 ohm.cm. 10 It may have a volume resistivity of ohm.cm or less.

[0089] Another important property of a sealing film besides its barrier properties and volume resistivity is its moisture absorption: if the sealing film absorbs significant amounts of moisture from the environment over time, the electro-optical performance of the device may be poor.

[0090] The sealing film can be prepared from an aqueous sealing composition comprising a water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer in an amount of 14% to 55% by weight, based on the weight of the aqueous sealing composition excluding water; a polyurethane in an amount of 6% to 27% by weight, based on the weight of the aqueous sealing composition excluding water; carbon black in an amount of 5% to 64% by weight, based on the weight of the aqueous sealing composition excluding water; a water-soluble ether in an amount of 1.0% to 40% by weight, based on the weight of the aqueous sealing composition excluding water; and water in an amount of 20% to 95% by weight, based on the weight of the aqueous sealing composition.

[0091] Poly(vinyl alcohol) homopolymers have a degree of hydrolysis of 90% to 99.5%. Poly(vinyl alcohol-co-ethylene) copolymers have a degree of hydrolysis of 90% to 99.5% and an ethylene content of less than 10%. The degree of hydrolysis of poly(vinyl alcohol) homopolymers and poly(vinyl alcohol-co-ethylene) copolymers can be 92% to 99%, or 92% to 95%. The ethylene content of poly(vinyl alcohol-co-ethylene) copolymers can be less than 9%, less than 8.5%, or less than 8%. The degree of hydrolysis of polyvinyl alcohol homopolymers and copolymers is conventionally reported by manufacturers of such polymers and indicates the ratio of moles of vinyl alcohol units in the polymer to total vinyl units. The other units are typically vinyl acetate (esters). The ethylene content of poly(vinyl alcohol-co-ethylene) copolymers is also reported by manufacturers and indicates the ratio of moles of ethylene units in the polymer to the other units. In this case, the other units are vinyl alcohol and vinyl acetate. The poly(vinyl alcohol) homopolymers and poly(vinyl alcohol-co-ethylene) copolymers of the aqueous sealing composition can have a weight average molecular weight of 1,000 to 1,000,000 daltons, or 10,000 to 500,000 daltons, or 20,000 to 400,000 daltons.

[0092] The content of the water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer in the aqueous sealing composition can be 14% to 53% by weight, or 25% to 50% by weight, or 30% to 48% by weight, or 33% to 46% by weight, based on the weight of the aqueous sealing composition excluding water.

[0093] Polyurethanes are typically prepared by a polyaddition process involving diisocyanates. Non-limiting examples of polyurethanes include polyether polyurethanes, polyester polyurethanes, polycarbonate polyurethanes, polyether polyureas, polyureas, polyester polyureas, polyester polyureas, polyisocyanates (e.g., polyurethanes containing isocyanate linkages), and polycarbodiimides (e.g., polyurethanes containing carbodiimide linkages). Generally, polyurethanes contain urethane groups. The polyurethanes utilized in the aqueous sealing compositions and sealing films described herein can be prepared using methods known in the art. The polyurethanes of the aqueous sealing compositions of the present invention include polyester polyurethanes, polycarbonate polyurethanes, and mixtures thereof. The polyurethanes of the aqueous sealing compositions can have a weight average molecular weight of 1,000 to 2,000,000 daltons, or 10,000 to 300,000 daltons, or 15,000 to 200,000 daltons. The polyurethane may be added to the aqueous sealing composition as an aqueous solution, dispersion, or emulsion, or as a latex.

[0094] The content of polyurethane in the aqueous sealing composition may be 7% by weight to 27% by weight, or 9% by weight to 24% by weight, or 11% by weight to 22% by weight, or 12% by weight to 20% by weight, based on the weight of the aqueous sealing composition excluding water.

[0095] The aqueous sealing composition may contain a crosslinking agent (also referred to as a crosslinking agent) in an amount of 0.1% to 8% by weight of the crosslinking agent, based on the weight of the aqueous sealing composition excluding water. The crosslinking agent forms chemical bonds between the polyurethane of the aqueous sealing composition and, potentially, the polymer molecules of the microcells during curing of the aqueous sealing composition to prepare a sealing film, thereby increasing adhesion between the sealing film and the microcells. The crosslinking agent is preferably soluble or dispersible in the aqueous carrier of the aqueous sealing composition. The crosslinking agent may be a monomer, oligomer, or polymer. Examples of crosslinking agents include polyisocyanates, multifunctional polycarbodiimides, multifunctional aziridines, silane coupling agents, boron / titanium / zirconium-based crosslinkers, or melamine formaldehyde. Polycarbodiimide crosslinkers are reactive under acidic pH conditions. Preferably, the crosslinking agent does not contain a sulfosuccinate surfactant. The content of the crosslinking agent in the aqueous sealing composition can be 0.1 wt % to 5 wt %, or 0.2 wt % to 4 wt %, or 0.3 wt % to 3.5 wt %, or 0.5 wt % to 3 wt %, or 0.8 wt % to 2.6 wt %, based on the weight of the aqueous sealing composition excluding water.

[0096] The present inventors have found that an aqueous sealing composition comprising a combination of a water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer and a polyurethane, wherein the interfacial tension between the water-soluble poly(vinyl alcohol) polymer or poly(vinyl alcohol-co-ethylene) copolymer and the polyurethane is less than 2 mN / m, can form a sealing film with excellent performance.

[0097] Extensive experimental studies have also revealed that superior performance has been observed from water-based sealing compositions containing a combination of water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer and polyurethane, where the polar component of the polyurethane surface energy is between 10 and 20 mN / m.

[0098] The aqueous sealing composition may also contain a conductive filler in a content of 5% to 64% by weight, based on the weight of the aqueous sealing composition excluding water. The filler in the aqueous sealing composition may be selected from the group consisting of carbon black, graphene, graphite, and carbon nanotubes. The filler reduces the volume resistivity of the sealing film but may also affect other properties of the layer, such as its surface energy. To be useful as a filler, carbon black must have good dispersibility in the aqueous sealing composition. The content of conductive carbon black in the aqueous sealing composition may be 10% to 55% by weight, or 20% to 50% by weight, or 25% to 45% by weight, or 30% to 40% by weight of the aqueous sealing composition.

[0099] The oil absorption of the carbon black used in the aqueous sealing composition is 100 cm per 100 mg of carbon black. 3 The oil absorption may be 0.05 or less. The oil absorption is typically reported by carbon black manufacturers as an OAN measured using a method according to ASTM 2414. It represents the structure and degree of agglomeration of the carbon black particles. That is, the higher the OAN, the more structured (connected to each other and having a branched structure) and / or the more agglomerated the particles are. Carbon black with higher structure / agglomeration generally can provide higher conductivity to the sealing film, but conductivity can also vary depending on the dispersibility of the filler, with a higher OAN indicating that the carbon black may be more difficult to disperse. The carbon black filler of the aqueous sealing composition preferably has an average primary particle diameter greater than 30 nm. The average diameter is another physical property of the carbon black grade that may be reported by the carbon black manufacturer. The primary particle size can be determined by electron microscopy. Typically, carbon black with very small average diameter primary particles is difficult to disperse. Carbon black is typically 80 nm or less. 2 / g or less than 75m 2 / g or less than 70m 2 / g. Total surface area is another common physical property routinely reported by carbon black manufacturers. Total surface area is measured using a nitrogen adsorption method according to ASTM D 6556. The carbon black can have a volume resistivity of greater than 0.1 ohm.cm, measured in powder form at a pressure of 40 MPa using ASTM D 2663 method.

[0100] The total surface energy of the conductive carbon black in the aqueous sealing composition may be greater than 40 mN / m or greater than 55 mN / m, as determined using the Washburn method with hexane as the test liquid. The total surface energy of the conductive carbon black in the aqueous sealing composition may be 40 mN / m to 80 mN / m, or 40 mN / m to 70 mN / m, or 40 mN / m to 65 mN / m. The dispersive component of the surface energy of the conductive carbon black may be greater than 15 mN / m, as determined using the Washburn method with hexane as the test liquid. The dispersive component of the conductive filler may be 15 mN / m to 40 mN / m, or 15 mN / m to 30 mN / m.

[0101] The aqueous sealing composition contains 1.0 wt% to 40 wt% of the water-soluble ether, based on the weight of the aqueous sealing composition excluding water. The aqueous sealing composition may contain 1.5 wt% to 35 wt%, or 2.0 wt% to 30 wt%, or 2.5 wt% to 25 wt%, or 4.0 wt% to 22 wt%, or 5.0 wt% to 20 wt%, based on the weight of the aqueous sealing composition excluding water. The content of the water-soluble ether in the aqueous sealing composition may be greater than 1.7 wt%, greater than 2 wt%, greater than 3 wt%, greater than 4 wt%, greater than 5 wt%, greater than 6 wt%, greater than 7 wt%, greater than 8 wt%, greater than 10 wt%, greater than 12 wt%, or greater than 15 wt%, based on the weight of the aqueous sealing composition excluding water. The content of the water-soluble ether in the aqueous sealing composition may be less than 40% by weight, or less than 30% by weight, or less than 25% by weight, based on the weight of the aqueous sealing composition excluding water.

[0102] The water-soluble ether has a weight average molecular weight of 75 to 5,000 daltons. The water-soluble ether can have a weight average molecular weight of 85 to 3,000 daltons, or 90 to 1,000 daltons, or 90 to 500 daltons, or 90 to 300 daltons. The water-soluble ether can have a weight average molecular weight greater than 75, or greater than 90, or greater than 100, or greater than 200. The water-soluble ether can have a weight average molecular weight less than 5,000, or less than 3,000, or less than 1,000, or less than 500, or less than 300, or less than 200, or less than 150.

[0103] Water-soluble ethers are polar compounds that are soluble in water and polar organic solvents. Water-soluble ethers can be represented by Formula I, Formula II, or Formula III. [ka] [ka] The value of n is 1 to 145. The value of n can be 1 to 100, or 1 to 50, or 1 to 20, or 1 to 10, or 1 to 5, or 1 to 4, or 1 to 3, or 1 to 2. R1 is hydrogen, a methyl or ethyl group, and R2, R3, R4, R5, R6, and R7 are independently selected from the group consisting of hydrogen, a straight-chain or branched alkyl group containing 1 to 6 carbon atoms, phenyl, and a benzyl group. Formula I contains at least one ether functional group. Formula II contains at least one ether functional group. Formula III contains at least one ether functional group.

[0104] Water-soluble ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol monoisopropyl ether, ethylene glycol n-monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol mono-t-butyl ether, ethylene glycol monobenzyl ether, ethylene glycol monophenyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol di-n-propyl ether, ethylene glycol diisopropyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol monoisopropyl ether, diethylene glycol n-monobutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol mono-t-butyl ether, diethylene glycol monobenzyl ether, diethylene glycol monophenyl ether, diethylene glycol dimethyl ether, and diethylene glycol Licor diethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol di-n-propyl ether, diethylene glycol diisopropyl ether, diethylene glycol di-n-butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol mono-n-propyl ether, triethylene glycol monoisopropyl ether, triethylene glycol n-monobutyl ether, triethylene glycol monoisobutyl ether, triethylene glycol mono-t-butyl ether, triethylene glycol monobenzyl ether, triethylene glycol monophenyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol di-n-propyl ether, triethylene glycol diisopropyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, triethylene glycol monophenyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol monomethyl etherPolyethylene glycol monoethyl ether, polyethylene glycol monophenyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol monoisopropyl ether, propylene glycol mono-n-butyl ether, propylene glycol monoisobutyl ether, propylene glycol monophenyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono The propylene glycol monoisopropyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol monoisobutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol di-n-propyl ether, dipropylene glycol diisopropyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol mono-n-propyl ether, tripropylene glycol monoisopropyl ether, tripropylene glycol mono-n-butyl ether, tripropylene glycol monoisobutyl ether, or mixtures thereof.

[0105] The aqueous sealing composition may also contain a rheology modifier in an amount of 0.05% to 10% by weight, or 0.05% to 5% by weight, or 0.1% to 3% by weight, based on the weight of the aqueous sealing composition excluding water. The rheology modifier increases the stability of the aqueous sealing composition during storage. The rheology modifier also promotes film formation, improves seal stability, and provides other functions. Examples include associative thickeners, alkali-swellable acrylic emulsions, and other polymer thickeners. The aqueous sealing composition may be shear-thinning, i.e., its viscosity decreases with higher shear. For example, the rheological profile of the aqueous sealing composition may be 10 -4 Viscosity at a shear rate of 1 / sec and 10 2The seal film may exhibit a viscosity reduction of 5 to 10,000 times between the viscosity at a shear rate of 1 / sec. The seal film may also contain a rheology modifier in an amount of 0.05% to 10% by weight, or 0.05% to 5% by weight, or 0.1% to 3% by weight, based on the weight of the seal film.

[0106] The aqueous sealing composition may also contain a wetting agent, also known as a surfactant. Non-limiting examples of wetting agents include FC surfactants from 3M Company, Zonyl fluorosurfactants, fluoroacrylates, fluoromethacrylates, fluoro-substituted long-chain alcohols, perfluoro-substituted long-chain carboxylic acids, and their derivatives from DuPont, and Silwet silicone surfactants from OSi, Greenwich, Conn. Wetting agents can increase the affinity between the sealing film and the microcells, enhance the interfacial area therebetween, improve adhesion of the sealing film to the microcells, and provide a more flexible coating process. The content of the wetting agent in the aqueous sealing composition may be 0.01% to 3.0% by weight, or 0.04% to 2.0% by weight, or 0.06% to 1.0% by weight, or 0.07% to 0.8% by weight, based on the weight of the aqueous sealing composition excluding water. The sealing film may contain a wetting agent. The content of the wetting agent in the sealing film may be 0.01 wt % to 3.0 wt %, or 0.04 wt % to 2.0 wt %, or 0.06 wt % to 1.0 wt %, or 0.07 wt % to 0.8 wt %, based on the weight of the sealing film.

[0107] The aqueous sealing composition may comprise 20% to 95% by weight, or 50% to 94% by weight, or 70% to 92% by weight, or 75% to 90% by weight, or 80% to 88% by weight of water, based on the weight of the aqueous sealing composition.

[0108] The aqueous sealing composition may also contain a pH adjuster. The pH adjuster is added to the aqueous sealing composition to adjust its pH to a value between 6.5 and 8.5. One example of a pH adjuster is ammonium hydroxide, but various acids and bases can be used. The pH adjuster increases the pH of the aqueous sealing composition, thereby reducing the crosslinking rate of the aqueous sealing composition before use. It also provides optimal pH conditions for the rheology modifier to interact with the particles of the aqueous sealing composition, improving its effectiveness. The pH adjuster may be used in an amount of 0.2% to 1% by weight based on the weight of the aqueous sealing composition excluding water.

[0109] The aqueous sealing composition can be used to form a sealing film by applying the aqueous sealing composition and drying or curing it. The sealing film can contain most of the components of the aqueous sealing composition. If the aqueous composition contains a crosslinker, the crosslinker is incorporated into the polyurethane polymer of the sealing film during curing. In addition, the water in the sealing composition evaporates during drying or curing of the aqueous sealing composition to form the sealing film. Experimental data shows that approximately 37% by weight of the initially added water-soluble ether also evaporates during drying or curing, leaving only approximately 63% by weight of the initially added water-soluble ether content of the aqueous sealing composition present in the sealing film. If any residual or absorbed water or moisture is present in the sealing film, the content of the components of the disclosed sealing film is calculated as the weight % of the component relative to the weight of the aqueous sealing composition, excluding any residual or absorbed water, unless otherwise stated.

[0110] The seal film contains a water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer in a content of 15% to 60% by weight based on the weight of the seal film, where the poly(vinyl alcohol) homopolymer has a degree of hydrolysis of 90% to 99.5% and the poly(vinyl alcohol-co-ethylene) copolymer has a degree of hydrolysis of 90% to 99.5% and an ethylene content of less than 10%. The seal film also contains a polyurethane in a content of 7% to 29% by weight based on the weight of the seal film, a carbon black in a content of 5% to 70% by weight based on the weight of the seal film, and a water-soluble ether in a content of 0.5% to 25% by weight based on the weight of the seal film. The water-soluble ether can have a molecular weight of 90 to 5,000 daltons. The water-soluble ether can optionally contain a hydroxy group.

[0111] The physical and chemical properties of various classes of seal film components have been detailed above.

[0112] The content of the water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer in the sealing film can be 16% to 55% by weight, or 28% to 52% by weight, or 33% to 50% by weight, or 35% to 48% by weight, based on the weight of the sealing film.

[0113] The content of polyurethane in the seal film may be 8% to 29% by weight, or 10% to 26% by weight, or 12% to 24% by weight, or 14% to 22% by weight, based on the weight of the seal film.

[0114] The sealing film may contain conductive carbon black in an amount of 11% to 60% by weight, or 24% to 55% by weight, or 29% to 50% by weight, or 30% to 45% by weight, based on the weight of the sealing film.

[0115] The seal film contains the water-soluble ether in an amount of 0.5 wt% to 25 wt% based on the weight of the seal film. The seal film may contain the water-soluble ether in an amount of 0.8 wt% to 20 wt%, or 1.0 wt% to 18 wt%, or 1.2 wt% to 20 wt%, or 1.5 wt% to 18 wt%, or 2.0 wt% to 16 wt% based on the weight of the seal film. The content of the water-soluble ether in the seal film may be greater than 0.5 wt%, greater than 0.6 wt%, greater than 0.7 wt%, greater than 0.8 wt%, greater than 0.9 wt%, greater than 1 wt%, greater than 1.5 wt%, greater than 2.0 wt%, greater than 3.0 wt%, or greater than 4 wt% based on the weight of the seal film. The content of the water-soluble ether in the seal film may be less than 25% by weight, or less than 20% by weight, or less than 18% by weight, or less than 15% by weight, or less than 12% by weight, or less than 10% by weight, based on the weight of the seal film.

[0116] The sealing film prepared from the aqueous sealing composition can be used to seal microcells of an electro-optical device, which includes a conductive layer, a microcell layer containing a plurality of microcells (each microcell containing an opening, each microcell containing an electrophoretic medium, the electrophoretic medium containing charged particles in a non-polar carrier), a sealing film (spanning the opening of each microcell), an adhesive layer, and an electrode layer.

[0117] Generally, the sealing film of an electro-optical device plays an important role in display performance. Poor barrier properties of the sealing film can lead to the leakage of non-polar fluids of the electrophoretic medium from the electro-optical material layer over time, thereby seriously degrading the electro-optical performance of the display. It has been observed that increasing the content of poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer in the sealing film improves its barrier properties. However, a sealing film with a high content of poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer increases the moisture absorption of the layer, which is also undesirable.

[0118] The present inventors have surprisingly found that optimal electro-optical performance in terms of color gamut can be achieved when the sealing film contains a combination of poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer and polyurethane, conductive carbon black, and a water-soluble ether having a molecular weight of 75 to 5,000 daltons. The addition of a water-soluble ether to the aqueous sealing composition and sealing film is believed to reduce the electrical resistance at one or both interfaces between the sealing film and adjacent layers, such as the seal film adhesive interface and the seal film electrophoretic medium interface. This reduction in interfacial electrical resistance was experimentally demonstrated using volume resistivity measurements and electrical impedance spectroscopy experiments, as shown in the Examples section. Importantly, this interfacial electrical resistance did not affect the electrical conductivity of the sealing film itself. In fact, the data demonstrate that the sealing films of the present invention have higher volume resistivities than control films lacking the water-soluble ether. As previously discussed, the higher volume resistivity of the sealing film contributes to reduced blooming, a phenomenon well known in the electro-optical field.

[0119] Improved performance is also observed when a combination of a poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer and a polyurethane is used, and the interfacial tension between the poly(vinyl alcohol) polymer or poly(vinyl alcohol-co-ethylene) copolymer and the polyurethane is less than 2 mN / m. Furthermore, the inventors have surprisingly found that optimal performance is also observed when a combination of a poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer and a polyurethane is used, and the polar component of the polyurethane's surface energy is between 10 and 20 mN / m.

[0120] These and other aspects of the present invention will be further understood in light of the following examples, which are intended to illustrate certain embodiments of the invention but are not intended to limit its scope, as defined by the claims. [Example]

[0121] Seal film evaluation method

[0122] A. Example of Preparation of Aqueous Seal Composition

[0123] A1. Example of Preparation of Carbon Black Dispersion. An aqueous solution of poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer was prepared containing 20% ​​by weight of polymer based on the volume of the solution. In one example, the polymer was poly(vinyl alcohol-co-ethylene) copolymer (Exceval® RS-1717 supplied by Kuraray). That is, the solution contained 200 g of polymer per liter of solution. Carbon black powder was mixed with the aqueous solution of poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer. In one example, an aqueous solution containing 106 g of poly(vinyl alcohol-co-ethylene) copolymer was mixed with 162 g of carbon black (Nerox® 3500 supplied by Orion Engineered Carbon). The dispersion was mixed in an overhead mixer (Hei-Torque Value 200) at 300 rpm for 30 minutes. The dispersion is then recirculated through a Generation 1 Q1375 Flocell sonicator and the sonicator jacket is cooled using cold water at 10° C. at 100% amplitude for 3 hours and 23 minutes. The dispersion was continuously stirred until used to prepare the seal composition.

[0124] A2. Example of Preparation of Aqueous Seal Composition. An aqueous polyurethane dispersion was combined with a wetting agent and an aqueous solution of poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer in a container. In one example, 194 g of a 35 wt. % polyurethane aqueous dispersion (L3838 aqueous dispersion supplied by Hauthaway) was mixed with 372 g of an aqueous solution of poly(vinyl alcohol-co-ethylene) copolymer (containing 20 wt. % copolymer based on the volume of the solution). In this example, the poly(vinyl alcohol-co-ethylene) copolymer was Exceval™ RS-1717 supplied by Kuraray. The mixture was mixed for 10 minutes at 90 rpm using a Hei-torque Value 200 overhead mixer. Next, the appropriate amount of dipropylene glycol dimethyl ether (45 g in one example) was added over 5 minutes while continuing to mix at 90 rpm. The resulting mixture was mixed for an additional 10 minutes at 90 rpm, and the appropriate amount of crosslinker was added. The mixture was mixed at 90 rpm for an additional 60 minutes. The appropriate amount of carbon black dispersion prepared in A1 was added (1.39 L in one example), and the resulting dispersion was mixed at 500 rpm for 60 minutes. The pH was then adjusted to 6.5-8.5 using ammonium hydroxide, and the dispersion was mixed for an additional 30 minutes. The appropriate amount of rheology modifier was added dropwise to the dispersion, and mixing was continued for an additional 60 minutes. The dispersion was then degassed under reduced pressure (25 mmHg) for 5 days. The resulting aqueous sealing composition was used for the preparation of a sealing film for the corresponding device within 7 days of preparing the sealing composition.

[0125] B1. Example of preparation of sealing film using the drawdown method.

[0126] The sealing composition prepared in A2 above was coated onto the indium tin oxide (ITO) side of the ITO-PET film using a Gardco drawdown coater. A square applicator with a 15 mil gap and eight passes was used. The drawdown speed was set at 2 m / min, targeting a dry film thickness of 30 + / - 2 μm. The coating was dried in an oven at 100°C for 15 minutes. The dried film was conditioned at 25°C and 55% RH for 24 hours.

[0127] B2. Example of preparation of sealing film using roll-to-roll coating line.

[0128] The sealing composition prepared in A2 above was coated onto the indium tin oxide (ITO) side of a 30 μm-thick ITO-PET thin film using a slot die on a roll-to-roll coating line at a speed of 9 ft / min. The film was then passed through a convection oven consisting of four heating zones, each 5 ft long. The first zone was set at a temperature of 80°C, and the remaining heating zones were set at a temperature of 100°C. Once dried, the sealing film on the ITO-PET was passed through a drying oven, and the film was cut into three sections, each approximately 24-30 inches long, and placed in a clean room with a controlled environment of 25°C and 55% relative humidity (RH).

[0129] C. Determination of volume resistivity - TCBC method.

[0130] Seal films prepared according to the previously described "Seal Film Preparation Method" B2 (Seal Film Preparation Method) were evaluated for volume resistivity. The "TCBC Method" was used to describe the transient background current method of measuring volumetric resistivity. For volume resistivity determination, Labview 2014 software and the TCBC waveform program, an NI USB 6211 multifunction device, and a Model 603 power amplifier were used. The device allows the user to measure the volumetric resistivity of electrode-laminated samples by applying a waveform at a preset voltage, measuring the output current, and calculating the resistance. The method included (a) preparation of the seal film according to the previously disclosed "Seal Film Preparation Method" B2, (b) lamination of the seal film with a conductive adhesive and a graphite backplane, and (c) a test method using the waveform program and setup. Film thickness was measured using a Mitutoyo Model S112EXB thickness gauge. After the lamination process, the samples were conditioned at 25°C / 55% RH for 10 days before testing. The reported resistance and measured thickness were then used to calculate the volume resistivity using the following equation: r=R / t, where r is the resistivity, R is the resistivity, and t is the thickness.

[0131] One panel of each seal coated on ITO-PET was collected from the roll-to-roll coating line described in Method B2 above. The seal was cut into 12-inch long strips. The 12-inch long strips were cut into 4.5-inch wide strips, as shown in the image in Figure 8A. The excess ITO on the edges was not trimmed off.

[0132] Graphite backplane preparation: One sheet (5 pixels) of graphite backplane per seal film was collected for testing. One of the pixels was cut off from the end so that only 4 pixels remained. As shown in the image in Figure 8B, the top and side edges (where the pixel line runs) were cut off. The other side edge was not cut off.

[0133] Preparation of KA2 film: A long roll of qualified 6 μm thick KA2 conductive adhesive film was collected for use in testing. The KA2 film was cut into 3-inch wide strips. The 3-inch wide strips were cut into 10-inch lengths, as shown in the image in Figure 8C. Only one side was cut so that the release liner overhang remained on the other side.

[0134] Lamination of TCBC samples: A 6 μm thick conductive adhesive KA2 was laminated onto the dried seal film using a hot roll laminator. For this lamination, the bottom plate and top roller of the laminator were set to 80°C, and the lamination speed was set to 17 mm / s. The cut KA2 film was taped to the cut seal, with the protective sheet on the KA2 touching the seal. The bottom and right edges of the KA2 film were aligned with the bottom and right edges of the seal. The top of the KA2 film was taped to the seal. The top of the seal was taped to the laminator plate so that the top edge of the seal was directly under the center of the roller. While holding the top sheet together with the KA2, the KA2 protective sheet was gently removed. While still holding the KA2, lamination began, slowly pressing the KA2 onto the seal with the roller. After lamination, the tape was removed, and the layer was released from the KA2. A graphite backplane was carefully placed on the KA2. The electrode was placed in the center of the KA2. The sample was laminated, and the final preparation is shown in Figure 8D. The final TCBC sample 800 included an ITO / PET conductive film 801, a sealing film 802, a KA2 adhesive 803, and a graphite backplane 804. An area of ​​the conductive film 801 and a first test point on the graphite backplane 804 were electrically connected via a voltage source. The sample was then conditioned at 25°C / 55% RH for 10 days to ensure complete humidification.

[0135] Testing of TCBC Samples: After conditioning for 10 days at 25°C / 55% RH, the samples were ready for testing. Testing of the samples was also performed in a controlled environment chamber set at 25°C / 55% RH to minimize variability due to temperature or relative humidity. To perform the TCBC test, we began by opening the corresponding software. A ½ inch segment of the sticker was peeled off the side of the sample to expose the ITO-PET surface. On a computer with Windows® 10, we opened the TCBC resistivity program using Labview 2014 and the TCBC waveform program. The contact area of ​​the single pixel area used to measure the resistivity of the sample was determined to be 25 cm. 2 The voltage was set to 0.05 V. The range was set to 200 μA (also compatible with the Model 6487 Electrometer). One alligator clip was connected to the ITO-PET seal resistivity sample. The other alligator clamp was connected to the first test pixel on the graphite backplane. Once the connections were set, the test was initiated. During the test, the following waveform was executed to pulse to a magnitude of 15 volts for a total of 26,699 milliseconds, as shown in Figure 8E. During this time, the software program and electrometer measured the current as a function of time. The software then calculated the resistance of the sample from the measured current and input voltage based on Ohm's law: R = (V / I), where V is the input voltage, I is the measured current, and R is the resistance. To calculate the final volume resistivity of the sample, the following equation was used: r = R / t, where R is the resistance from the test and t is the thickness of the seal film measured using a thickness gauge to complete the test.

[0136] D. Electrical Impedance Spectroscopy (EIS): Electrical impedance spectroscopy (EIS) was used to understand how the presence of a water-soluble ether (dipropylene glycol dimethyl ether) in the sealing film affects the electro-optical performance without increasing the film's volume resistivity. EIS determined the interfacial resistivity between the sealing film and the electrophoretic medium (containing a non-polar solvent and charged yellow pigment particles).

[0137] The EIS results were used to calculate the distribution of relaxation times (DRT). Figure 9 shows a graph of gamma versus relaxation time (tau) from EIS data for the seal film of the present invention (containing a water-soluble ether) versus the control seal film (containing no water-soluble ether) for two different electrophoretic media, A and B. The different peaks in gamma (tau) at different relaxation times correlate with different parallel resistor and capacitor (RC) elements in the electro-optical device containing the seal film in contact with the electrophoretic medium. Each peak is the average relaxation time for all RC elements with similar relaxation times in the electro-optical device. The gamma value for each relaxation time is a measure of the resistance of the corresponding RC element. A relaxation time (tau) of 4 1 / sec most likely corresponds to the RC element at the seal film-electrophoretic medium interface. As can be seen for both electrophoretic media A and B, the resistance at the interface between the seal film and the electrophoretic medium is lower for the seal film containing the water-soluble ether (dipropylene glycol dimethyl ether). Lower interfacial resistance corresponds to improved electro-optical performance, as per the data in the Examples table.

[0138] E. Determination of the surface energy of the film.

[0139] The surface energy of the prepared seal film (as described in B1 above) was measured using a drop shape analyzer supplied by Kruss GmbH. A 2.6 μL droplet of deionized water was placed on the top surface of the seal film using a syringe equipped with a needle, and the contact angle between the liquid (water) and the seal film was measured. The measurement was repeated by replacing the water droplet with a diiodomethane droplet. The surface energy of the film was calculated by performing contact measurements using these two liquids with known surface energies. The contact angle measurement was repeated three times for each liquid (water and diiodomethane). The contact angle between the liquid and the top surface of the seal film was measured using a high-resolution camera 5, 30, and 55 seconds after the droplet was placed on the sample film. The total surface energy, as well as its polar and dispersive components, was then calculated for each data point using the method of Owens, Wendt, Rabel, and Kaelble (OWRK). The reported surface energy was the average of nine data points (three drops x three scales).

[0140] F. Preparation of electro-optical devices.

[0141] An electro-optical device was prepared by filling multiple microcells with a mixture of electrically charged pigment particles (white, cyan, magenta, and yellow) in Isopar E. The white and yellow particles were negatively charged, and the cyan and magenta particles were positively charged. An aqueous sealing composition was then coated onto the microcell openings as described in Section B above. The device shown in Figure 10 was constructed. The electro-optical device 1000 included, in order, a protective film 1001, an optically transparent first adhesive layer 1002, a substrate 1003, a light-transmitting conductive layer 1004, a primer layer 1005, a microcell layer 1006, a sealing film 1007, a second adhesive layer 1008, an ITO electrode layer 1009, and a glass layer 1010. An electric field source 1011 electrically connected the light-transmitting conductive layer 1004 to the ITO electrode layer 1009. This source applied a waveform to drive the desired optical state. The first light-transmitting layer 1002 had a thickness of approximately 25 μm. The substrate 903 had a thickness of approximately 100 μm. The primer layer The microcell layer 1005 had a thickness of approximately 0.4 μm. The adhesive film 807 contained a plurality of microcells. Each microcell had a bottom thickness of approximately 0.4 μm and a height of approximately 10 μm. The sealing film 807 had a thickness of approximately 10 μm, and the second adhesive layer had a thickness of approximately 4.5 μm.

[0142] G. Color gamut measurement.

[0143] The electro-optical device prepared by Method F was electrically driven to produce eight optical states. The electrophoretic device was addressed using a series of electrical pulses (such a series is called a "waveform"). In the following description, the voltages used in the waveforms are the voltages supplied to the rear electrode of the display, assuming that the electrode on the front (viewing) surface of the display is common to all pixels and grounded. The test waveform includes a series of "dipoles," as shown in FIG. 11. Each dipole is composed of two monopoles, each a pulse of length t and magnitude V. The two monopoles in each dipole are of opposite polarity.

[0144] The voltages used in the test waveforms were + / -24V, + / -18V, + / -15V, and + / -10V. Time was discretized into 11.74 millisecond increments, called "frames." Each frame is expected to correspond to one scan of a thin-film transistor array backplane refreshed at a frequency of 85 Hz, although in the described tests the backplane was segmented and directly driven.

[0145] Two types of test waveforms were used to assess the electro-optical performance of the device. The waveform used in the first test was 18 frames in length, while the waveform used in the second test was 42 frames in length. In each case, the waveform was injected with as many identical dipoles as would fit within the allowed number of frames. This is shown in Tables 1 and 2, corresponding to the 18 and 42 frame waveform types, respectively.

[0146] [Table 1]

[0147] [Table 2]

[0148] The length of the second monopole was the length of the dipole minus the length of the first monopole. It should be noted that "first" and "second" do not necessarily imply a particular time order of the monopoles that make up the dipole. Not all dipoles conforming to these rules were used. To test for more reasonable lengths, only waveforms with (V2*t2) / (V1*t1)<2 were used.

[0149] Each waveform was preceded by a DC balance pulse (having an equal and opposite impulse to the particular test waveform) and a reset of the display to a white state. Each waveform was terminated by a 3 second ground.

[0150] The color states of the display (measured in CIELab L*, a*, and b* units) were recorded after a 3-second grounding period. The color gamut of the display was measured by computing the volume of a convex hull containing all color states generated by a set of test waveforms. The eight color states produced were red, green, blue, yellow, cyan, magenta, white, and black (R, G, B, Y, C, M, W, and K). The color gamut was calculated using the DE 3 The wider the color gamut, i.e., the larger the space, the better the electro-optical performance of the electro-optical device.

[0151] H. Determination of interfacial tension of polymers.

[0152] For a particular combination of polymers, the interfacial tension between polymer 1 and polymer 2 was calculated from the surface tension values ​​(determined by the method described in H above). Calculation of the interfacial tension between two components was performed by using the surface energy values ​​of each component and the following geometric equation:

number

[0153] Similarly, the interfacial tension between the seal film and the adhesive layer can be measured.Polyurethane-containing adhesive layer standards were formed with an aqueous dispersion of water-dispersible polyurethane.

[0154] I. Evaluation of the barrier properties of sealing films against non-polar fluids.

[0155] An aqueous dispersion was prepared by mixing 10 grams of poly(vinyl alcohol) homopolymer or 10 grams of poly(vinyl alcohol-co-ethylene) copolymer and 10 grams of polyurethane in 100 mL of water. The dispersion was used as the aqueous polymer composition to form the sealing film of device 1200 shown in FIG. 12. The sealing film was formed by the method described in B1 above. Device 1200 included, in order, substrate 1203, light-transmitting conductive layer 1204, primer layer 1205, microcell layer 1206, and sealing film 1207. The microcell was formed using Isopar The electro-optical device 1200 contained an electrophoretic medium containing white, black, and red pigment particles in E. The device 1200 was stored at 70°C for at least 24 hours. After this period, the electro-optical device was inspected using an optical microscope for sagging of the sealing film caused by loss of the non-polar fluid of the electrophoretic medium. If the distance between the bottom of the inspected microcavity and the lowest point on the bottom surface of the sealing film was less than 85% of the distance between the bottom of the microcavity and the highest point on the bottom surface of the sealing film in the same microcell, the aqueous polymer composition was classified as "fail" for its barrier properties. Otherwise, if the distance between the bottom of the inspected microcell and the lowest point on the sealing film was 85% or greater of the distance between the bottom of the microcell and the highest point on the bottom surface of the sealing film in the inspected microcell, the sealing aqueous polymer composition was classified as "pass" for its barrier properties. For example, the aqueous polymer composition used to prepare the electro-optical device shown in FIG. 13C was classified as "pass" because the h2:h1 ratio was 1 (no sag), while the aqueous polymer composition used to prepare the electro-optical device shown in FIG. 13D was classified as "fail" because the h2:h1 ratio was 35% (a sag level of over 85%). Evaluation of barrier properties can also be performed qualitatively by observing the prepared electro-optical device from the observation side of the device with an optical microscope. A device containing a severely sagged sealing film has a significantly different appearance (uniform vs. non-uniform surface) than a device containing a sealing film with good barrier properties against non-polar fluids. For example, a microcell having an aqueous polymer composition corresponding to the sealing film of FIG. 13C ("pass") appears uniform, as shown in FIG. 13A, in contrast to a microcell having an aqueous polymer composition corresponding to the sealing film of FIG. 13D ("fail"), which appears non-uniform, as shown in FIG. 13B. The evaluation of various combinations of (1) poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer and (2) polyurethane is shown in Table 10.Polymer 1 is a poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer, and Polymer 2 is a polyurethane. Details regarding the commercial materials for Polymer 1 and Polymer 2 can be found in Table 11.

[0156] J. Determination of the content of water-soluble ethers in sealing films.

[0157] The content of water-soluble ether in the sealing film was determined by a combination of thermogravimetric analysis (TGA) and Karl Fischer (KF) moisture analysis. The total amount of water-soluble ether and moisture in the sealing film was determined by the following thermogravimetric analysis method: The moisture content in the sealing film was measured using the Karl Fischer method at 150°C. The content of water-soluble ether in the sealing film was then calculated by subtracting the moisture content (KF) from the total amount of water-soluble ether and moisture (TGA). The thermogravimetric analysis included (a) taring the sample holder, (b) placing the sample in the sample holder and weighing it, (c) equilibrating the sample at 30 °C, (d) heating the sample to 105 °C at a heating rate of 50 °C / min, (e) holding the sample at 105 °C for 10 minutes to evaporate moisture and other volatile materials from the sample, (f) heating the sample to 215 °C at a rate of 50 °C / min, (g) holding the sample at 215 °C for 10 minutes to evaporate the water-soluble ether, and (h) heating the sample to 650 °C at a rate of 20 °C / min to completely decompose the sample. The sample was maintained under nitrogen gas during the thermogravimetric analysis. The total amount of moisture and water-soluble ether was obtained by measuring the weight loss of the sample from 40 °C to 220 °C using Trios software.

[0158] Evaluation results

[0159] Unless otherwise stated, the amount of ingredients in the disclosed compositions in the following tables is provided as a weight percentage of the ingredient relative to the weight of the composition excluding water. To express the content of water carrier, the term QS (quantity sufficient) is used in some compositions. This term means that the content of water in the composition is the amount necessary to achieve and not exceed 100% of the total composition.

[0160] If any residual or absorbed water or moisture is present in the seal film, the disclosed content of the ingredients of the seal film is calculated as the weight % of the ingredient relative to the weight excluding residual or absorbed water, unless otherwise stated.

[0161] The example compositions having numbers ending with the letter F correspond to seal film compositions, while the remaining example compositions correspond to aqueous seal compositions. The seal film composition examples correspond to the same example number (with the suffix F) as the aqueous seal composition used to prepare the seal film composition. Thus, Example 1F (seal film composition) was prepared from Example 1 (aqueous seal composition).

[0162] The content of water-soluble ether in the seal film of Example 19F was determined to be 8.6 wt. % based on the weight of the seal film using the method described above in J. The content of water-soluble ether in the other seal film examples was calculated as 63% of the total water-soluble ether in the aqueous seal composition.

[0163] [Table 3A]

[0164] [Table 3B]

[0165] Tables 3A and 3B show that aqueous sealing compositions containing a water-soluble ether, e.g., dipropylene glycol dimethyl ether or tetraethylene glycol dimethyl ether, form sealing films with higher volume resistivities, as opposed to a control aqueous sealing composition that does not contain a water-soluble ether. 9 The results show that the films form seal films with volume resistivities (TCBC) lower than ohm.cm. This is demonstrated by comparing Examples 1F-5F with Comparative Example 6F and Examples 7F-8F with Comparative Example 9F.

[0166] [Table 4A]

[0167] [Table 4B]

[0168] [Table 5A]

[0169] [Table 5B]

[0170] [Table 6A]

[0171] [Table 6B]

[0172] [Table 7A-1]

[0173] [Table 7A-2]

[0174] Tables 4A, 4B, 5A, 5B, 4A, 6B, 7A, and 7B show that aqueous sealing compositions containing a water-soluble ether, e.g., dipropylene glycol dimethyl ether or tetraethylene glycol dimethyl ether, form sealing films with a larger color gamut than control aqueous sealing compositions that do not contain a water-soluble ether. This is demonstrated by comparing examples of the present invention with the corresponding comparative examples. Improved electro-optical performance is consistently observed in the color gamut measured at different temperatures (0°C and 25°C).

[0175] [Table 8A]

[0176] [Table 8B]

[0177] [Table 9A]

[0178] [Table 9B]

[0179] Tables 8A, 8B, 9A, and 9B show that the aqueous sealing compositions containing a water-soluble ether, e.g., dipropylene glycol dimethyl ether (Examples 18-19 and Example 21), form sealing films with an interfacial tension with the adhesive layer of less than 20 mN / m, in contrast to the aqueous sealing compositions not containing a water-soluble ether (Comparative Example 20 and Comparative Example 22).

[0180] Poly(vinyl alcohol-co-ethylene) copolymer; Exceval™ RS-1717 supplied by Kuraray;

[0181] [2] Polyurethane aqueous dispersion; L3838 aqueous dispersion supplied by Hauthaway as a 35% dispersion in water;

[0182] [3] Carbon black; Nerox® 3500 supplied by Orion Engineered Carbon;

[0183] [4] Polycarbodiimide (multifunctional polycarbodiimide-aqueous solution); CARBODILITE® V-02-L2 supplied by Nisshinbo Chemical as a 40% solution in water;

[0184] [5] Hydrophobically modified alkali-swellable acrylic emulsion; Solthix™ A-100 supplied by Lubrizol;

[0185] [6] Siloxane polyalkylene oxide copolymer; Silwet® L-7607 copolymer supplied by Momentive;

[0186] [7] Dipropylene glycol dimethyl ether; Proglyde® DMM supplied by Dow Chemical;

[0187] [8] Tetraethylene glycol dimethyl ether; supplied by Sigma Aldrich (CAS143-24-8).

[0188] Table 10 includes surface energy data for various Polymer 1 species, which are water-soluble poly(vinyl alcohol) homopolymers or poly(vinyl alcohol-co-ethylene) copolymers, and Polymer 2 species, which are polyurethanes. Table 10 also includes calculated interfacial evaluations of the barrier properties of the various layers and various polymer combinations. The methods for preparing the corresponding polymer layers used to evaluate the barrier properties are described in Section I above. Surface energy determinations (following the method described in Section E above) were performed by first preparing and conditioning a seal film from the corresponding aqueous composition containing only one of the polymers. The interfacial tension for each polymer combination was calculated from the surface energy data and the calculation method described in Section H above.

[0189] [Table 10-1] [Table 10-2] [Table 10-3]

[0190] [Table 11-1] [Table 11-2]

[0191] The interfacial tension data for Polymer 1 and Polymer 2 in Table 10 demonstrate that a sealing film comprising (a) a poly(vinyl alcohol) polymer or poly(vinyl alcohol-co-ethylene) copolymer having a degree of hydrolysis of 90% to 99.5% and an ethylene content of less than 10%, and (b) a polyurethane in an aqueous carrier, wherein the interfacial tension between the two polymers (a) and (b) is less than 2 mN / m, forms a sealing film having good barrier properties against non-polar fluids.

[0192] The data in Table 10 also show that sealing films made from aqueous sealing compositions comprising (a) a poly(vinyl alcohol) polymer or poly(vinyl alcohol-co-ethylene) copolymer having a degree of hydrolysis of 90% to 99.5% and an ethylene content of less than 10%, and (b) a polyurethane in an aqueous carrier, wherein the polar component of the polyurethane's surface energy is between 10 and 25 mN / m, form sealing films with good barrier properties to non-polar fluids.

[0193] Microscopic evaluation of the sealing films prepared using the four aqueous sealing compositions prepared by the method described in B1 above showed a correlation between the uniformity of the film and the interfacial tension between the two polymers. The microscopic images in Table 12 and Figure 14 show that lower interfacial tension provides a more uniform sealing film. The improved compatibility achieved by the combination of polymers with lower interfacial tension may explain the improved barrier properties of the corresponding layers.

[0194] [Table 12]

[0195] During further investigation, it was observed that aqueous sealing compositions containing more than 70 wt. % of poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer, based on the weight of the aqueous sealing composition excluding water, formed sealing films that absorbed significant amounts of moisture from the environment, which negatively impacted the electro-optical performance of the display. The present invention provides, for example, the following items. (Item 1) a water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer in a content of 15% to 60% by weight based on the weight of the seal film, the poly(vinyl alcohol) homopolymer having a degree of hydrolysis of 90% to 99.5%, and the poly(vinyl alcohol-co-ethylene) copolymer having a degree of hydrolysis of 90% to 99.5% and an ethylene content of less than 10%; Polyurethane content of 7% to 29% by weight based on the weight of the seal film; Carbon black in an amount of 5% to 70% by weight based on the weight of the sealing film; A water-soluble ether having a content of 0.5% to 25% by weight based on the weight of the sealing film, a molecular weight of 75 to 5,000 daltons, and optionally containing a hydroxyl group. Contains a sealing film. (Item 2) Item 10. The seal film according to item 1, wherein the total surface energy of the seal film is lower than 60 mN / m. (Item 3) Item 2. The seal film according to item 1, wherein the interfacial tension between the water-soluble poly(vinyl alcohol) polymer or poly(vinyl alcohol-co-ethylene) copolymer and the polyurethane is less than 2 mN / m. (Item 4) Item 2. The seal film according to item 1, wherein the carbon black has an oil absorption of less than 100 mL per 100 mg of carbon black as measured using the OAN method according to ASTM 2414. (Item 5) The carbon black has a viscosity of 70 mPa s, as measured using nitrogen adsorption according to ASTM D 6556. 2 10. The sealing film according to item 1, having a total surface area of ​​less than 1000 nm / g. (Item 6) The water-soluble ether is represented by Formula I, Formula II, or Formula III [ka] [In the formula, n is 1 to 145; R1 is hydrogen, a methyl or ethyl group; R2, R3, R4, R5, R6, and R7 are independently selected from the group consisting of hydrogen, a linear or branched alkyl group containing 1 carbon atom to 6 carbon atoms, phenyl, and a benzyl group; Formula I contains at least one ether functional group, Formula II contains at least one ether functional group; Formula III contains at least one ether functional group. The sealing film according to item 1, represented by: (Item 7) 7. The seal film according to item 6, wherein n is 1 to 10. (Item 8) The water-soluble ether may be ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol monoisopropyl ether, ethylene glycol n-monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol mono-t-butyl ether, ethylene glycol monobenzyl ether, ethylene glycol monophenyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol di-n-propyl ether, ethylene glycol diisopropyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol monoisopropyl ether, diethylene glycol n-monobutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol mono-t-butyl ether, diethylene glycol monobenzyl ether, diethylene glycol monophenyl ether, diethylene glycol dimethyl ether, diethylene glycol glycol diethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol di-n-propyl ether, diethylene glycol diisopropyl ether, diethylene glycol di-n-butyl, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol mono-n-propyl ether, triethylene glycol monoisopropyl ether, triethylene glycol n-monobutyl ether, triethylene glycol monoisobutyl ether, triethylene glycol mono-t-butyl ether, triethylene glycol monobenzyl ether, triethylene glycol monophenyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol di-n-propyl ether, triethylene glycol diisopropyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, triethylene glycol monophenyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol monomethyl ether,Polyethylene glycol monoethyl ether, polyethylene glycol monophenyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol monoisopropyl ether, propylene glycol mono-n-butyl ether, propylene glycol monoisobutyl ether, propylene glycol monophenyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol monoiso propyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol monoisobutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol di-n-propyl ether, dipropylene glycol diisopropyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol mono-n-propyl ether, tripropylene glycol monoisopropyl ether, tripropylene glycol mono-n-butyl ether, and tripropylene glycol monoisobutyl ether. (Item 9) Item 10. The seal film of item 1, further comprising an organic silicone wetting agent. (Item 10) 10 8 ~10 10 Item 1. The sealing film according to item 1, having a volume resistivity of ohm.cm. (Item 11) Item 2. The seal film according to item 1, wherein the polyurethane is an ester polyurethane, a polycarbonate polyurethane, or a combination thereof. (Item 12) Item 2. The seal film according to item 1, wherein the polyurethane polymer has a number average molecular weight of 1,000 to 2,000,000 Daltons. (Item 13) Item 2. The seal film according to item 1, wherein the poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer has a number average molecular weight of 1,000 to 1,000,000 Daltons. (Item 14) Item 2. The seal film according to item 1, wherein the poly(vinyl alcohol) polymer or poly(vinyl alcohol-co-ethylene) copolymer has a degree of hydrolysis of 92% to 99%. (Item 15) Item 10. The seal film of item 1, wherein the poly(vinyl alcohol-co-ethylene) copolymer has an ethylene content of less than 9%. (Item 16) a conductive layer, a microcell layer including a plurality of microcells, each microcell including an opening, each microcell including an electrophoretic medium, the electrophoretic medium including charged particles in a non-polar carrier; Item 1, the seal film spanning the opening of each microcell. an adhesive layer, and electrode layer 1. An electro-optical device comprising: (Item 17) Item 17. The electro-optical device of item 16, wherein the electrophoretic medium comprises at least three types of charged pigment particles, one type of charged particle having a color selected from the group consisting of blue, green, red, cyan, magenta, and yellow. (Item 18) a water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer in a content of 14% to 55% by weight based on the weight of the aqueous sealant composition excluding water, wherein the poly(vinyl alcohol) homopolymer has a degree of hydrolysis of 90% to 99.5%, and the poly(vinyl alcohol-co-ethylene) copolymer has a degree of hydrolysis of 90% to 99.5% and an ethylene content of less than 10%; a polyurethane content of 6% to 27% by weight, based on the weight of the aqueous sealing composition excluding water; carbon black in an amount of 5% by weight to 64% by weight based on the weight of the aqueous sealing composition excluding water; a water-soluble ether in an amount of 1.0% by weight to 40% by weight based on the weight of the aqueous sealant composition excluding water, the water-soluble ether having a molecular weight of 75 to 5,000 daltons and optionally containing a hydroxyl group; Water content of 20% to 95% by weight based on the weight of the aqueous sealing composition 1. An aqueous sealing composition comprising: (Item 19) Item 19. The aqueous sealing composition according to item 18, further comprising a crosslinking agent in an amount of 0.1 wt % to 8 wt % based on the weight of the aqueous sealing composition excluding water, wherein the crosslinking agent is polyisocyanate, polyfunctional polycarbodiimide, polyfunctional aziridine, silane coupling agent, boron / titanium / zirconium-based crosslinking agent, or melamine formaldehyde. (Item 20) The aqueous sealing composition further comprises a rheology modifier in an amount of 0.05 wt% to 5 wt% based on the weight of the sealing film rheology, and -4 Viscosity at a shear rate of 1 / sec and 10 2 Item 19. The aqueous sealing composition according to item 18, having a rheological profile showing a viscosity reduction of 5 to 10,000 times between the viscosity at a shear rate of 1 / sec and the viscosity at a shear rate of 1 / sec.

Claims

[Claim 1] The invention described in the present specification.

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