Sealing film and sealing composition for sealing microcells of electro-optic devices

Abstract

To provide a sealing film and a sealing composition for sealing a microcell of an electrooptical device.SOLUTION: The present invention relates to the use of a polymer, poly (vinyl alcohol) The present invention is directed to an aqueous sealing composition comprising a combination of a homopolymer or poly (vinyl alcohol-co-ethylene) copolymer, a polyurethane, and a rheology modifier. The aqueous sealing composition can be used to form a low-defect sealing film in an electro-optic device having (a) a plurality of microcells filled with charged particles and a non-polar fluid and (b) an electro-optic material layer comprising the sealing film, wherein the electro-optic material layer is disposed between two electrode layers. The corresponding electro-optical device shows good electro-optical performance.SELECTED DRAWING: None

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 357,745, filed July 1, 2022. 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, comprising a poly(vinyl alcohol) homopolymer or a poly(vinyl alcohol-co-ethylene) copolymer, a polyurethane, and a rheology modifier selected from the group consisting of hydrophobically modified ethoxylated urethane and alkali-swellable emulsion polymers. [Background technology]

[0003] Background of the Invention The term "electro-optic," as applied to a material, device, 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: (a) electrophoretic particles, fluids and fluid additives, see, e.g., U.S. Patent Nos. 7,002,728 and 7,679,814; (b) capsules, binders and encapsulation processes, see, e.g., U.S. Patent Nos. 6,922,276 and 7,411,719; (c) Microcell structures, wall materials, and methods of forming microcells, see, e.g., U.S. Patent Nos. 7,072,095 and 9,279,906; (d) methods for filling and sealing microcells, see, e.g., 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; (e) films and subassemblies containing electro-optical materials, see, e.g., U.S. Patent Nos. 6,982,178 and 7,839,564; (f) backplanes, adhesive layers and other auxiliary layers and methods used in displays, see, e.g., U.S. Pat. Nos. 7,116,318 and 7,535,624; (g) color formation and color adjustment, see, e.g., U.S. Patent Nos. 7,075,502 and 7,839,564; (h) methods for driving displays, see, e.g., U.S. Patent Nos. 7,012,600 and 7,453,445; (i) display applications, see, e.g., U.S. Pat. Nos. 7,312,784 and 8,009,348; and (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.

[0008] The contents of all of the foregoing references are incorporated herein by reference in their entirety.

[0009] 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, generating 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 microcavity, 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 microcell during the device's lifetime. Poor barrier properties of the sealing film to the nonpolar fluid will result in fluid loss in the electrophoretic medium and sagging of the sealing film. Second, the sealing film must not absorb significant amounts of moisture from the environment. That is, the sealing film must prevent environmental moisture from entering the device's electrophoretic medium. Such moisture could negatively affect the device's electro-optical performance. Third, because significant coating defects negatively affect the corresponding device's electro-optical performance, the sealing composition must be coated onto the microcell layer to form a sealing film without such defects. Fourth, the sealing film must be mechanically resilient during the device's useful lifetime.Finally, the sealing film should have an optimum volume resistivity that remains practically constant over time. The conductive properties of the sealing film are important because an electrical potential is applied across the device and conducted 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. Furthermore, if the sealing film has low electrical conductivity, increased power consumption is required for device operation, while too high conductivity can cause deterioration of image quality due to blooming. Therefore, there is a need for an aqueous sealing composition that forms an optimized sealing film with fewer defects for improved barrier against non-polar fluids, reduced moisture absorption, and improved electro-optical performance. The inventors have discovered that a sealing film composition comprising a combination of a poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer, a polyurethane, and a rheology modifier, where the rheology modifier is a hydrophobically modified ethoxylated urethane or an alkali-swellable emulsion polymer, provides a sealing film with fewer defects and good electro-optical performance. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] U.S. Patent No. 7,002,728 [Patent Document 2] U.S. Patent No. 7,679,814 [Patent Document 3] U.S. Patent No. 6,922,276 [Patent Document 4] U.S. Patent No. 7,411,719 [Patent Document 5] U.S. Patent No. 7,072,095 [Patent Document 6] U.S. Patent No. 9,279,906 [Patent Document 7] U.S. Patent No. 7,144,942 [Patent Document 8] U.S. Patent No. 7,005,468 [Patent Document 9] U.S. Patent No. 7,715,088 [Patent Document 10] US Patent Application Publication No. 2004 / 0120024 [Patent Document 11] US Patent Application Publication No. 2004 / 0219306 [Patent Document 12] U.S. Patent No. 6,982,178 [Patent Document 13] U.S. Patent No. 7,839,564 [Patent Document 14] U.S. Patent No. 7,116,318 [Patent Document 15] U.S. Patent No. 7,535,624 [Patent Document 16] U.S. Patent No. 7,075,502 [Patent Document 17] U.S. Patent No. 7,839,564 [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]

[0011] Summary of the Invention In one embodiment, the present invention is directed to a seal film comprising 15 to 60 wt. % of a water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer based on the weight of the seal film, 7 to 29 wt. % of a polyurethane based on the weight of the seal film, and 0.05 to 10 wt. % of a rheology modifier based on the weight of the seal film. The poly(vinyl alcohol) homopolymer has a degree of hydrolysis of 90 to 99.5%. 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 rheology modifier is selected from the group consisting of hydrophobically modified ethoxylated urethane and alkali-swellable emulsion polymer. The seal film may further comprise 0.001 to 5 wt. % of a surfactant based on the weight of the seal film. The seal film may comprise 0.01 to 5 wt. % of a surfactant based on the weight of the seal film, or 0.01 to 2 wt. % of a surfactant based on the weight of the seal film. The surfactant of the sealing film may be a fluorosurfactant. The sealing film may further comprise 5 to 70 wt. % carbon black, based on the weight of the sealing film. The carbon black may have an oil absorption of less than 100 mL per 100 mg of carbon black, as measured using the OAN method according to ASTM 2414. The carbon black may have an oil absorption of less than 70 mL per 100 mg of carbon black, as measured using the nitrogen adsorption method according to ASTM D6556. 2 / g.

[0012] The sealing film may further contain 4.5 to 25% by weight of a water-soluble ether based on the weight of the sealing film, the water-soluble ether having a molecular weight of 75 to 5,000 daltons and optionally containing a hydroxyl group.

[0013] The total surface energy of the sealing film may be lower 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 may be less than 2 mN / m. The sealing film may be 10 7 ~10 11 It can have a volume resistivity of ohm·cm.

[0014] The polyurethane of the seal film can be an ester polyurethane, a polycarbonate polyurethane, or a combination thereof. The polyurethane of the seal film can have a number average molecular weight of 1,000 to 2,000,000 Daltons.

[0015] The poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer of the sealing film 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 of the sealing film can have a degree of hydrolysis of 92% to 99%. The poly(vinyl alcohol-co-ethylene) copolymer of the sealing film can have an ethylene content of less than 9%.

[0016] In another aspect, the present invention is directed to an electro-optical device including a conductive layer, a microcell layer, a sealing film, an adhesive layer, and an electrode layer. The microcell layer includes a plurality of microcells, each having an opening, and each containing an electrophoretic medium. The electrophoretic medium includes charged particles in a non-polar carrier. The sealing film of the electro-optical device includes 15 to 60 wt. % of a water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer based on the weight of the sealing film, 7 to 29 wt. % of a polyurethane based on the weight of the sealing film, and 0.05 to 10 wt. % of a rheology modifier based on the weight of the sealing film. The poly(vinyl alcohol) homopolymer has a degree of hydrolysis of 90% to 99.5%. 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 rheology modifier is selected from the group consisting of hydrophobically modified ethoxylated urethane and alkali-swellable emulsion polymer. The electrophoretic medium of the electro-optical device can include at least three types of charged pigment particles, with at least one type of charged particle having a color selected from the group consisting of blue, green, red, cyan, magenta, and yellow.

[0017] In yet another aspect, the present invention is directed to an aqueous sealing composition comprising 15 to 60 wt. % of a water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer, based on the weight of the aqueous sealing composition excluding water; 7 to 29 wt. % of a polyurethane, based on the weight of the aqueous sealing composition excluding water; 0.05 to 5 wt. % of a rheology modifier, based on the weight of the aqueous sealing composition excluding water; 0.01 to 5 wt. % of a surfactant, based on the weight of the aqueous sealing composition excluding water; and 20 to 95 wt. % of water, based on the weight of the aqueous sealing composition. The poly(vinyl alcohol) homopolymer has a degree of hydrolysis of 90% to 99.5%. 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 rheology modifier is selected from the group consisting of hydrophobically modified ethoxylated urethanes and alkali-swellable emulsion polymers. The surfactant in the aqueous sealing composition may be a fluorosurfactant.

[0018] The aqueous sealing composition may further comprise 5 to 70 wt. % carbon black, based on the weight of the aqueous sealing composition excluding water. The carbon black may have an oil absorption of less than 100 mL per 100 mg of carbon black, as measured using the OAN method according to ASTM 2414. The carbon black may have an oil absorption of less than 70 mL per 100 mg of carbon black, as measured using the nitrogen adsorption method according to ASTM D6556. 2 / g.

[0019] The aqueous sealing composition may further comprise 1.0 to 40% by weight of a water-soluble ether, 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 (grams per mole) and optionally containing a hydroxyl group.

[0020] The aqueous sealing composition may also contain 0.1 to 8 wt % of a polyurethane crosslinker, based on the weight of the aqueous sealing composition excluding water, which may be a polyisocyanate, a polyfunctional polycarbodiimide, a polyfunctional aziridine, a silane coupling agent, a boron / titanium / zirconium-based crosslinker, or melamine formaldehyde.

[0021] 10 -4 The viscosity of the aqueous sealing composition at a shear rate of 1 / sec was 10 2 The ratio divided by the viscosity of the aqueous sealing composition at a shear rate of 1 / sec may be 7 or less. -4 The viscosity of the aqueous sealing composition at a shear rate of 1 / sec was 10 2 The ratio divided by the viscosity of the aqueous sealing composition at a shear rate of 1 / sec can be 1 to 7. The aqueous sealing composition can have an HB rate index of 0.7 or higher. The aqueous sealing composition can have an HB rate index of 0.7 to 1, 0.7 to 0.9, or 0.7 to 2. The aqueous sealing composition can have a thixotropy index of 1.5 or higher. The aqueous sealing composition can have a thixotropy index of 1.5 to 3. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 shows the structure of multiple microcells before they are filled and sealed (side view).

[0023] [Figure 2] FIG. 2 shows an example of an electro-optical device including a microcell structure (side view).

[0024] [Figure 3] FIG. 3 shows an example of a front plane laminate assembly that can be used to form an electro-optical device that includes a microcell structure (side view).

[0025] [Figure 4]FIG. 4 shows an example of a dual release sheet that can be used to form an electro-optical device containing a microcell structure (side view).

[0026] [Figure 5] FIG. 5 illustrates a method for fabricating a microcell using a roll-to-roll process.

[0027] [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.

[0028] [Figure 6-2] Figures 6C and 6D detail an alternative embodiment in which the microcells are fabricated using photolithography, where a combination of top and bottom exposures is used, allowing one lateral wall to be hardened by a top photomask exposure and another lateral wall to be hardened by a bottom exposure through an opaque base conductor film.

[0029] [Figure 7-1] 7A-7D show the steps of filling and sealing the array of microcells. [Figure 7-2] 7A-7D show the steps of filling and sealing the array of microcells.

[0030] [Figure 8] FIG. 8 shows the structure of the electro-optic device used to evaluate example water-based sealing compositions for electro-optic performance.

[0031] [Figure 9] FIG. 9 shows the structure of an electro-optical device used to evaluate example aqueous sealing compositions for barrier properties.

[0032] [Figure 10-1]10A-10D show microscopic images of the microcells evaluated for barrier properties. [Figure 10-2] 10A-10D show microscopic images of the microcells evaluated for barrier properties.

[0033] [Figure 11] FIG. 11 shows an example of a sealing film corresponding to a dewetting rating system.

[0034] [Figure 12] FIG. 12 shows an example of a sealing film corresponding to the peel rating system.

[0035] [Figure 13] FIG. 13 shows an example of a sealing film corresponding to the chattering ranking system.

[0036] [Figure 14] FIG. 14 shows an example of a seal film corresponding to the haze speckle mura ranking system.

[0037] [Figure 15] FIG. 12 shows microscopic images of polymer films containing combinations of poly(vinyl alcohol-co-ethylene) copolymer and polyurethane with various interfacial tensions. DETAILED DESCRIPTION OF THE INVENTION

[0038] Detailed Description of the Invention As used herein, "molecular weight" or "MW" refers to weight average molecular weight, unless otherwise stated. Molecular weight is measured using gel permeation chromatography ("GPC").

[0039] 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 example formula of polyvinyl alcohol provided below (Formula I), the degree of hydrolysis is calculated according to Equation 1: Degree of hydrolysis=100×p / (p+q) Equation 1 Because 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, manufacturers of polyvinyl alcohol typically report the degree of hydrolysis of their products. 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 K6726 (Japanese Standards Association, 94th edition, October 20, 2017). [ka]

[0040] The terms "sealing film" and "sealing layer" are synonymous and are used interchangeably with respect to electro-optical devices.

[0041] The terms "adhesive film" and "adhesive layer" are synonymous and are used interchangeably with respect to electro-optical devices.

[0042] The terms "surfactant," "surface-active agent," and "wetting agent" are synonymous herein. A "surfactant," "surface-active agent," or "wetting agent" is a substance that can reduce the surface tension of a liquid, the interfacial tension between two liquids, the interfacial tension between a gas and a liquid, and the interfacial tension between a liquid and a solid. Surfactants are typically amphiphilic organic compounds, meaning they contain both one or more hydrophobic functional groups (tails) and one or more hydrophilic groups (heads). A "fluorosurfactant" is a surfactant that has at least one fluorine atom in its molecular structure, more specifically, a fluorine atom in the alkyl chain of the surfactant's tail. A fluorosurfactant can have more than one fluorine atom in the alkyl chain of the surfactant's tail.

[0043] 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. Unless otherwise stated, the disclosed content of a component of an aqueous sealing composition is calculated as the weight % of the aqueous sealing composition excluding water (of course, excluding the disclosed content of water in the aqueous composition).

[0044] A. Microcell Structure

[0045] 1 shows the structure of a plurality of microcells 100 shown in side view. This view represents the plurality of microcells 100 before they are filled and sealed. Each microcell has a base 101, a wall 102, and an opening 103.

[0046] B. Construction of an electro-optical device containing a microcell structure

[0047] FIG. 2 illustrates an example electro-optical device 200 shown in side view. The example electro-optical device 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 microcell bottom 101 and a microcell wall 102. Each microcell of the plurality of microcells has an opening 103. Each microcell 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 102 of the plurality of microcells. A second electrode layer 250 is connected to the sealing film 230 using an adhesive layer 240. Each microcell of the plurality of microcells sealed with the sealing film forms an 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 microcell layer 220.

[0048] The example electro-optical device shown in FIG. 2 can be constructed with a front plane laminate 300, a side view of which is shown in FIG. 3. The front plane laminate 300 includes a first light-transmitting electrode layer 210, a microcell layer 220, a sealing film 230, an adhesive layer 240, and a release sheet 360. Each of the 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 microcells. The release sheet 360 is connected to the sealing film 230 using an adhesive layer 240. Removal of the release sheet 360 exposes the surface of the adhesive layer 240, 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 210 and the microcell layer 220.

[0049] The example electro-optical device shown in FIG. 2 can also be constructed with a dual release sheet 400, a side view of which is shown in FIG. 4. The dual release sheet 400 includes a first release sheet 480, a first adhesive layer 470, a microcell layer 220, a sealing film 230, a second adhesive layer 340, and a second release sheet 360. 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 first release sheet 480 is connected to the microcell layer 220 using a first adhesive layer 470. The second release sheet 360 is connected to the sealing film 230 using a second adhesive layer 240. Removal of first release sheet 460 exposes the surface of first adhesive layer 470, which can be connected onto a first light-transmitting electrode layer. Removal of second release sheet 360 exposes the surface of second adhesive layer 240, which can be connected onto a second electrode layer to form an electro-optical device. An optional primer layer (not shown in FIG. 4) can be disposed between first adhesive layer 470 and microcell layer 220.

[0050] C. Formation of Microcell Structure

[0051] Techniques for Constructing Microcells. Microcells can be formed either by a batch process or by the continuous roll-to-roll process 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 serve as the backing layer for the device. A composition containing a thermoplastic, a thermoset, or a precursor thereof is then coated onto the conductor film 501. The thermoplastic or thermoset precursor layer 502 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 502 material.

[0052] The thermoplastic or thermosetting precursor layer 502 for the preparation of the microcells can be multifunctional acrylates or methacrylates, vinyl ethers, epoxides, and their oligomers or polymers, etc. 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 of the thermoplastic or thermosetting precursor layer 502 can contain polymers, oligomers, monomers, and additives, or it may contain only oligomers, monomers, and additives. The glass transition temperature (i.e., 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 typically g 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.

[0053] As shown in FIG. 5 , the mold is released during or after the thermoplastic or thermoset precursor layer 502 is cured, revealing an array of microcells 503. Curing of the thermoplastic or thermoset precursor layer 502 can be achieved by cooling, solvent evaporation, radiation, heat, or moisture-induced crosslinking. For a thermoset precursor layer, curing can be achieved by UV radiation. In such cases, 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 radiate through the pre-patterned male mold onto the thermoset 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. The 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 light source 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 mold floor is typically between about 50 and about 400 micrometers. The master can also be fabricated using other micro-engineering techniques, including e-beam writing, dry etching, chemical etching, laser writing, or laser interference, as described in "Replication techniques for micro-optics", SPIE Proc. Vol. 3099, pp. 76-82 (1997).Alternatively, the mold can be made using plastic, ceramic or metal by photomachining.

[0054] 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 necessary. The solvent, if present, evaporates easily. The UV-curable resin is dispensed onto 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 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 bottom (floor) of the microcell. 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, which should have good release properties relative to the mold surface.

[0055] Microcell arrays for the present invention typically include a conductive layer formed by 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 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 floor areas of the microcells).

[0056] 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 by known methods onto a conductor electrode film 602, to UV light (or alternatively other forms of radiation, e-beam, etc.) through a mask 606 to form wall portions 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.

[0057] 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 onto the radiation curable material 601a, i.e., the UV does not pass through to the supporting substrate base web 603 or the base conductor film 602 (top exposure). For this reason, neither the supporting substrate base web 603 nor the conductor 602 need to be transparent to the UV or other wavelengths of radiation used.

[0058] As shown in Figure 6B, the exposed areas harden, and then the unexposed areas (protected by opaque areas 604 of mask 606) are removed with a suitable solvent or developer to form 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 under the conductor film / support substrate base; in this case, UV light is emitted from the bottom through the photomask, and the support substrate base web 603 must be transparent to the radiation.

[0059] 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 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 film 612 and substrate 613 is exposed from the bottom through the base conductor film 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 base conductor film 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.

[0060] The microcells can be constructed from thermoplastic elastomers that have good compatibility with the microcells and do not interact with the medium. Examples of useful thermoplastic elastomers include ABA and (AB)n type diblock, triblock, and multiblock copolymers, 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)), SEBS (poly(styrene-b-ethylene / butylene-b-styrene)), poly(styrene-b-dimethylsiloxane-b-styrene), poly((α-methylstyrene-b-isoprene), poly(α-methylstyrene-b-isoprene-b-α-methylstyrene), poly(α-methylstyrene-b-propylene sulfide-b-α-methylstyrene), poly(α-methylstyrene-b-dimethylsiloxane-b-α-methylstyrene). Commercially available styrene block copolymers, such as the Kraton D and G series (Kraton Particularly useful are 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 grafted copolymers thereof.

[0061] 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 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.

[0062] 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).

[0063] The microcell array 700 can be prepared by any of the methods described above. As shown in the cross-sectional views of Figures 7A-7D, the microcell walls 102 extend upward from the backing layer 101 and the conductive layer 210 (first light-transmitting electrode layer 210) to form open microcells. In one embodiment, the first light-transmitting electrode layer 210 is formed on or in the backing layer 101. While Figures 7A-7D show the first light-transmitting electrode layer 210 extending continuously onto the backing layer 101, the first light-transmitting electrode layer 210 can also extend continuously below or within the backing layer 101 or be interrupted by the microcell walls 102. The microcell array 700 can be cleaned and sterilized before filling to ensure the beneficial agent is not damaged before use.

[0064] The microcells are then filled with an electrophoretic medium 225 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 walls 102. In other embodiments, inkjet-type micro-injection may be used to fill the microcells. In yet other embodiments, a microneedle array may be used to fill an array of microcells with the electrophoretic medium 225.

[0065] 7C, after filling, the microcells are sealed by applying an aqueous sealing composition to form sealed microcells 780 containing sealing film 230. 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 225.

[0066] 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.

[0067] 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 aqueous 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 electrophoretic medium composition and sealing composition is filled into the microcell, a substrate can be laminated on top to control the metering of the mixture of compositions and promote phase separation of the aqueous sealing composition from the electrophoretic medium composition to form a uniform sealing film. The substrate used can be a functional substrate in the final structure, or it can be a sacrifice substrate, such as a release substrate, that can be removed later. The aqueous sealing composition is then poured into the microcell. The sealing film is formed by curing in situ (i.e., when 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, when a heat- or moisture-curable aqueous sealing composition is used, heat or moisture can also be used to cure the aqueous sealing composition.

[0068] 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 can be tailored for optimal sealability and coatability. If a volatile solvent is used in the overcoat, it is preferred that the volatile solvent be immiscible with the solvent in the electrophoretic medium composition.

[0069] After the microcells are filled and sealed, a second electrode layer 250 containing multiple electrodes can be laminated to the sealed array. The second electrode layer 250 is bonded onto the sealing film 230 to form an electro-optical device 790, as shown in FIG. 7D. An adhesive can be used to bond the second electrode layer 250 onto the sealing film 230 (the adhesive layer is not shown in FIG. 7D). The adhesive can be conductive. The adhesive for 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.

[0070] In general, microcells can be any shape, and their size and shape can vary. Microcells can be uniform in 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 round, 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:

[0071] The depth of the microcells can be about 5 to about 200 μm, or about 10 to about 100 μm. The ratio of the area of ​​the microcell openings to the total area of ​​the microcell layer is about 0.05 to about 0.95, preferably about 0.4 to about 0.9. The total area of ​​the microcell layer is the total area of ​​the side of the microcell layer on the same side as the microcell openings.

[0072] 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.

[0073] 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.

[0074] The aforementioned U.S. Patent No. 6,982,178 describes a method for assembling a solid-state electro-optic device that is well suited for 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. An example of this structure is provided in FIG. 3, where the electrophoretic material layer includes a microcell layer and a seal film. Typically, the light-transmitting electrode layer is supported 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 allow 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). When 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, for example 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 front plane laminates.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.

[0075] 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. FIG. 4 shows an example of this form of dual release sheet. In FIG. 4, the electrophoretic material layer includes a microcell layer and a seal film. 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 processes generally similar to those for assembling electrophoretic displays from the front plane laminates already described, but involving two separate laminates. Typically, in a first lamination, a double release sheet is laminated to a front electrode layer (first light-transmitting electrode layer) to form a front subassembly, and then in a second lamination, the front subassembly is laminated to a backplane to form the final display, although these two lamination orders can be reversed if desired. The backplane includes a second electrode layer.

[0076] 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 an electro-optic device can combine good resolution with good low-temperature performance.

[0077] Electrophoretic medium.

[0078] 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), poly(chlorotrifluoroethylene), e.g., Halocarbon, from TCI America, Portland, Oregon. Halocarbon oils manufactured by Ausimont Products Corp., River Edge, NJ; perfluoropolyalkyl ethers such as Galden manufactured by Ausimont; or Krytox oils and greases K-Fluid series manufactured by DuPont, Delaware; and polydimethylsiloxane-based silicone oil (DC-200) manufactured by Dow-corning.

[0079] The electrophoretic medium may contain two types of charged particles having different colors: a first type of charged particles having a first charge polarity and a 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.

[0080] The electrophoretic medium may contain three types of charged particles, all of different colors: a first type of charged particles having a first charge polarity, a second type of charged particles having a second charge polarity opposite to the first charge polarity, and a third type of charged particles having 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.

[0081] The electrophoretic medium may contain four types of charged particles, all of different colors: a first type of charged particles having a first charge polarity, a second type of charged particles having the first charge polarity, a third type of charged particles having a second charge polarity opposite to the first charge polarity, and a fourth type of charged particles having the second charge polarity. The magnitude of the charge of the first type of particles may be greater 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 greater than the charge of the fourth type of particles. In one example, the first type of charged particles are cyan, the second type of charged particles are magenta, the third type of particles are yellow, and the fourth type of charged particles are white.

[0082] The electrophoretic medium may contain four types of charged particles, all of different colors: a first type of charged particles having a first charge polarity, a second type of charged particles having the first charge polarity, a third type of charged particles having the 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 each other. The magnitude of the charge of the third type of particles may be greater than the magnitude of the charge of the first type of particles, which may be greater 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.

[0083] The electrophoretic medium may contain five types of charged particles, all of different colors: a first type of charged particles having a first charge polarity, a second type of charged particles having the first charge polarity, a third type of particles having the first charge polarity, a fourth type of particles having a second charge polarity opposite to the first charge polarity, and a fifth type of particles having a second charge polarity. The magnitudes of the first, second, and third charges may be different from each other. The magnitude of the charge of the third type of particles may be greater than the magnitude of the charge of the first type of particles, which may be greater than the magnitude of the charge of the second type of particles. The charge of the fourth type of particles may be higher than the charge of the fifth type of charged particles. In one example, the first type of particles is cyan, the second type of particles is magenta, the third type of particles is black, the fourth type of particles is yellow, and the fifth type of particles is white.

[0084] Sealing film derived from aqueous sealing composition

[0085] The sealing film plays an important role in the performance of a microcell electro-optical device. It can be formed by coating a sealing composition on the microcell layer of the electro-optical device. Because the sealing film contacts the electrophoretic medium and seals it inside the microcell, it must be practically insoluble in the non-polar fluid of the electrophoretic medium and provide a good barrier to the non-polar fluid so that the non-polar fluid does not scatter out of the microcell during the device's lifetime. Poor barrier properties of the sealing film against the non-polar fluid of the electrophoretic medium can result in a loss of the electrophoretic medium fluid and sagging of the sealing film. Furthermore, the sealing film must not absorb significant amounts of moisture from the environment. This prevents environmental moisture from entering the electrophoretic medium of the device. Such moisture could affect the conductivity of the sealing film and the electrophoretic medium, negatively impacting the electro-optical performance of the device. The sealing film that seals the microcell layer must be free of significant coating defects. Such defects could negatively impact the electro-optical performance of the device. The sealing film must be mechanically resilient during the useful life of the device and should have a volume resistivity that is practically optimal over time.

[0086] Another important property of the sealing film is its electrical volume resistivity. If the 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. In addition, because volume resistivity typically increases rapidly with decreasing temperature, a sealing film with too high a volume resistivity will negatively affect the electro-optical performance of the display at low temperatures. The sealing film should be 10 8The seal film can have a volume resistivity of 1.0 x 10 ohm-cm or higher. 7 ~1.0×10 12 ohm·cm, 1.0×10 7 ~1.0×10 11 ohm·cm, 1.0×10 8 ~1.0×10 11 , 3.5×10 7 ~×10 12 ohm·cm, or 1.0 x 10 8 ~1.0×10 10 The sealing film can have a volume resistivity of 10 ohm-cm. 11 ohm·cm or less, or 10 10 It can have a volume resistivity of ohm·cm or less.

[0087] The sealing film can be prepared from an aqueous sealing composition containing 15 to 60 wt. % of a water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer, based on the weight of the aqueous sealing composition excluding water; 7 to 29 wt. % of a polyurethane, based on the weight of the aqueous sealing composition excluding water; and 0.05 to 10 wt. % of a rheology modifier, based on the weight of the aqueous sealing composition excluding water. The rheology modifier can be a hydrophobically modified ethoxylated urethane or an alkali-swellable emulsion polymer, or a combination thereof.

[0088] The content of the rheology modifier in the aqueous sealing composition can be 0.05 to 10 wt %, 0.05 to 3 wt %, 0.05 to 2 wt %, 0.07 to 1 wt %, or 0.08 to 1 wt %, 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 reduces defects in the sealing film. Examples include associative thickeners, alkali-swellable acrylic emulsion polymers, and other polymer thickeners. The aqueous sealing composition can be shear-thinning, i.e., its viscosity decreases at higher shear rates. For example, the rheological profile of the aqueous sealing composition can be 10 -4 Viscosity at a shear rate of 1 / sec and 10 2 Viscosity reductions of 5 to 10,000 times can be observed between the viscosity at a shear rate of 1 / sec.

[0089] Hydrophobically modified ethoxylated urethanes (or HEURs) are rheology modifiers that may contain polyethylene glycol blocks covalently linked by urethane. They belong to the "associative thickener" family. Associative thickeners have both hydrophilic and hydrophobic regions. One example of a HEUR rheology modifier is a block of polyethylene oxide linked by urethane and modified with a nonylphenol hydrophobic group. The polyethylene oxide block of a HEUR rheology modifier has a relatively low molecular weight, e.g., less than 12,000 daltons (grams per mole), typically 50-700 daltons. HEUR rheology modifiers are typically nonionic polymers that are soluble in water at any pH. The water solubility of HEUR rheology modifiers is a result of the presence of ethylene oxide groups in their molecular structure. HEURs can be branched or unbranched polymers. HEURs can have terminal long-chain alkyl or alkylene groups with 8-30 carbon atoms. Typical alkyl groups are, for example, dodecyl or stearyl groups, typical alkenyl groups are, for example, oleyl groups, typical aryl groups are, for example, phenyl groups, and typical alkylated aryl groups are, for example, nonylphenyl groups. Some HEUR molecules also contain one or more internal hydrophobic blocks or groups.

[0090] Non-limiting examples of HEUR rheology modifiers include ACULYN™ 44, ACULYN™ 46, ACUSOL™ 880, ACUSOL™ 882, ACRYSOL™ RM-3000, ACRYSOL™ RM-895, ACRYSOL™ RM-8W, ACRYSOL™ RM-12W, ACRYSOL™ RM-995, ACRYSOL™ SCT-275, ACRYSOL™ RM-845, ACRYSOL™ RM-825, ACRYSOL™ RM-6000, ACRYSOL™ RM-5000, ACRYSOL™ RM 2020E, ACRYSOL™ RM-8W, ACRYSOL™ RM-725 supplied by Dow Chemical, and RHEOVIS® PU supplied by BASF. 1190, RHEOVIS® PU 1191, RHEOVIS® PU 1291, RHEOVIS® PU 1241 and RHEOVIS® PU 1331 supplied by Elementis Specialties, RHEOLATE® 212, RHEOLATE® 255, RHEOLATE® 655, RHEOLATE® 278, RHEOLATE® 678, RHEOLATE® 288, RHEOLATE® 299 and RHEOLATE® 475 supplied by BYK, OPTIFLO® T 1000, OPTIFLO® L 1400, OPTIFLO® M 2600 VF, OPTIFLO® H 7500 VF, OPTIFLO® 3300 supplied by TEGO. These include the ViscoPlus® range, as well as TAFIGEL® PUR 61, TAFIGEL® PUR 50, and TAFIGEL® PUR 85 supplied by Munzing. Alkali-swellable emulsion (ASE) rheology modifiers are polymers produced using emulsion polymerization. In contrast to HEUR rheology modifiers, ASE rheology modifiers are not associative thickeners. ASE rheology modifiers can be formed from hydrophilic monomers, such as (meth)acrylic acid monomers, and less hydrophilic monomers, such as (meth)acrylate ester monomers of lower alcohols (C1-C4 aliphatic alcohols, e.g., ethyl acrylate, propyl acrylate, butyl acrylate, and methyl methacrylate). ASE rheology modifiers can thicken aqueous compositions at high pH. At high pH values, (meth)acrylic acid groups are water-soluble, while (meth)acrylate esters are water-insoluble. At low pH values, the polymers are water-insoluble and do not thicken aqueous compositions. At high pH values, the acid is neutralized to its salt, causing the polymer to swell, resulting in a more viscous composition. Typically, ASE rheology modifiers have a relatively high weight average molecular weight, i.e., greater than 300,000 daltons (grams per mole), greater than 400,000 daltons, or greater than 500,000 daltons. Examples of hydrophilic groups include acrylic acid, methacrylic acid, and maleic acid. Examples of hydrophobic groups include acrylic and methacrylic acid esters of aliphatic alcohols. Non-limiting examples of ASE rheology modifiers include RHEOVIS® 1125, RHEOVIS® 1130, ACULYN™ 33, ACULYN™ 38, ACUSOL™ 810A, ACUSOL™ 830, ACUSOL™ 835, ACUSOL™ 842, and ACRYSOL™ RM-38 supplied by BASF (supplied by Dow Chemical), and Carbopol® Aqua 30 (supplied by Lubrizol Corporation).

[0091] Hydrophobically modified alkali-swellable emulsion polymer (HASE) rheology modifiers are not preferred rheology modifiers for the aqueous sealing compositions of the present invention. These rheology modifiers swell at high pH values ​​and thicken the aqueous composition. These rheology modifiers include monomers with highly hydrophobic properties. For example, ASE polymers can be formed from monomers such as (meth)acrylic acid monomers and (meth)acrylates of C1-C4 alcohols, while HASE polymers can be formed from monomers such as C8-C6 alcohols. 22 They can be formed by monomers such as (meth)acrylic acid monomers and (meth)acrylates of alcohols.

[0092] Non-limiting examples of HASE rheology modifiers include RHEOVIS® PU 1212, 1125, RHEOVIS® 1130 supplied by BASF, ACULYN™ Excel, ACRYSOL™ TT615, ACULYN™ 22, ACULYN™ 88, ACUSOL™ 801S, ACUSOL™ 805S, ACUSOL™ 820 and ACUSOL™ 823 supplied by Dow Chemical.

[0093] The aqueous sealing composition may further contain a conductive filler. The content of the conductive filler in the aqueous sealing composition may be 5 to 70 wt % 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 the conductive carbon black in the aqueous sealing composition may be 10 to 60 wt %, 15 to 50 wt %, 20 to 45 wt %, or 30 to 40 wt % of the aqueous sealing composition.

[0094] The oil absorption value of the carbon black used in the aqueous sealing composition is 100 cm per 100 mg of carbon black. 3 The oil absorption value is typically reported by carbon black manufacturers as an OAN (oil absorption number) measured using a method according to ASTM 2414. The oil absorption value represents the structure and degree of agglomeration of 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, and a higher OAN indicates 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. This is another physical characteristic of the carbon black grade that can be reported by carbon black manufacturers. The primary particle size can be determined by electron microscopy. Typically, carbon black with a very small average primary particle diameter is difficult to disperse. Carbon black is typically 80 nm or less. 2 / g or less, 75m 2 / g or less than 70m 2 / g, which is another common physical property routinely reported by carbon black manufacturers. Total surface area is measured using the nitrogen adsorption method according to ASTM D6556. Carbon black can have a volume resistivity higher than 0.1 ohm·cm, measured in powder form at a pressure of 40 MPa using method ASTM D2663.

[0095] The total surface energy of the conductive carbon black in the aqueous sealing composition, as determined using the Washburn method with hexane as the test liquid, may be greater than 40 mN / m or greater than 55 mN / m. The total surface energy of the conductive carbon black in the aqueous sealing composition may be 40 mN / m to 80 mN / m, 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, as determined using the Washburn method with hexane as the test liquid, may be greater than 15 mN / m. The dispersive component of the conductive filler may be 15 mN / m to 40 mN / m, or 15 mN / m to 30 mN / m.

[0096] The content of the water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer in the aqueous sealing composition can be 15 to 60 wt %, 18 to 55 wt %, 20 to 50 wt %, or 22 to 40 wt %, based on the weight of the aqueous sealing composition excluding water.

[0097] Poly(vinyl alcohol) homopolymers have a degree of hydrolysis of 90% to 99.5%, and 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 (MW) of 1,000 to 1,000,000 daltons (grams per mole), 10,000 to 500,000 daltons, or 20,000 to 400,000 daltons.

[0098] 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 are polyester polyurethanes, polycarbonate polyurethanes, and mixtures thereof. The polyurethanes of the aqueous sealing compositions can have a weight average molecular weight (MW) of 1,000 to 2,000,000 daltons (grams per mole), 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.

[0099] The content of polyurethane in the aqueous sealing composition may be 7 to 29 wt %, 8 to 25 wt %, 12 to 22 wt %, or 14 to 20 wt %, based on the weight of the aqueous sealing composition excluding water.

[0100] The aqueous sealing composition may contain a polyurethane crosslinker (or otherwise referred to as a polyurethane crosslinking agent). The content of the polyurethane crosslinker in the aqueous sealing composition may be 0.1 to 8 wt % of the polyurethane crosslinker, based on the weight of the aqueous sealing composition excluding water. During curing of the aqueous sealing composition to prepare a sealing film, the polyurethane crosslinker forms chemical bonds between the polyurethanes of the aqueous sealing composition and potentially with the polymer molecules of the microcells, increasing the adhesion between the sealing film and the microcells. The polyurethane crosslinker is preferably soluble or dispersible in the aqueous carrier of the aqueous sealing composition. The crosslinker may be a monomer, oligomer, or polymer. Examples of polyurethane crosslinkers 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 polyurethane crosslinker does not contain a sulfosuccinate surfactant. The content of the polyurethane crosslinker in the aqueous sealing composition can be 0.2 to 6 wt%, 0.4 to 4 wt%, 0.5 to 3 wt%, 0.6 to 2 wt%, or 0.7 to 1.8 wt%, based on the weight of the aqueous sealing composition excluding water.

[0101] 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.

[0102] Extensive experimental work has also revealed that superior performance has been observed from aqueous 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.

[0103] The aqueous sealing composition may further contain 1 to 40 wt % of a water-soluble ether, based on the weight of the aqueous sealing composition excluding water. The aqueous sealing composition may contain 1 to 30 wt %, 1 to 25 wt %, 1 to 22 wt %, 1 to 20 wt %, 1 to 15 wt %, 1 to 10 wt %, 1 to 5 wt %, or 1 to 3 wt % of the water-soluble ether, 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 0.2 wt %, greater than 0.5 wt %, greater than 1 wt %, greater than 2 wt %, greater than 5 wt %, greater than 6 wt %, greater than 7 wt %, greater than 8 wt %, or greater than 10 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 wt %, less than 30 wt %, less than 20 wt %, less than 15 wt %, less than 10 wt %, less than 5 wt %, or less than 2 wt %, based on the weight of the aqueous sealing composition excluding water.

[0104] The water-soluble ether has a weight average molecular weight of 75 to 5,000 daltons (grams per mole). The water-soluble ether can have a weight average molecular weight of 85 to 3,000 daltons, 90 to 1,000 daltons, 90 to 500 daltons, or 90 to 300 daltons. The water-soluble ether can have a weight average molecular weight greater than 75, greater than 90, greater than 100, or greater than 200. The water-soluble ether can have a weight average molecular weight less than 5,000, less than 3,000, less than 1,000, less than 500, less than 300, less than 200, or less than 150.

[0105] Water-soluble ethers are polar compounds that are soluble in water and polar organic solvents. Water-soluble ethers can be represented by Formula II, Formula III, or Formula IV. [ka] The value of n is 1 to 145. The value of n can be 1 to 100, 1 to 50, 1 to 20, 1 to 10, 1 to 5, 1 to 4, 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 or branched alkyl group containing 1 to 6 carbon atoms, phenyl, and a benzyl group. Formula II contains at least one ether functional group. Formula III contains at least one ether functional group. Formula IV contains at least one ether functional group.

[0106] 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.

[0107] 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 between them, improve adhesion of the sealing film to the microcells, and provide a more flexible coating process. The content of surfactant in the aqueous sealing composition may be 0.001 to 5 wt %, 0.01 to 5 wt %, or 0.01 to 2 wt %, based on the weight of the aqueous sealing composition excluding water.

[0108] The aqueous sealing composition may contain water in an amount of 20 to 95 wt %, 50 to 94 wt %, 70 to 92 wt %, 75 to 90 wt %, or 80 to 88 wt %, based on the weight of the aqueous sealing composition.

[0109] 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 and providing 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.

[0110] 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 comprise a majority of the components of the aqueous sealing composition. If the aqueous composition contains a polyurethane crosslinker, the polyurethane 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 prepare the sealing film. If the aqueous sealing composition contains a water-soluble ether, the formed sealing film also contains the water-soluble ether of the aqueous sealing composition, but some of the water-soluble ether evaporates during the formation of the sealing film. If any residual or absorbed water or moisture or water-soluble ether is present in the sealing film, the disclosed content of the sealing film's components is calculated as the weight percent of the component relative to the weight excluding residual water, residual water-soluble ether, and absorbed water, unless otherwise stated.

[0111] The seal film contains 15 to 60 wt % of a water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer, 7 to 29 wt % of a polyurethane, and 0.05 to 10 wt % of a rheology modifier. The poly(vinyl alcohol) homopolymer has a degree of hydrolysis of 90% to 99.5%. 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 rheology modifier is a hydrophobically modified ethoxylated urethane (HEUR) or an alkali-swellable emulsion polymer (ASE). The seal film may further contain a conductive filler. The conductive filler may be carbon black. The seal film may contain 11 to 60 wt %, 24 to 55 wt %, 29 to 50 wt %, or 30 to 45 wt % of conductive carbon black.

[0112] The sealing film may contain a surfactant (wetting agent). The content of the surfactant in the sealing film may be 0.001 to 5 wt %, 0.01 to 5 wt %, or 0.01 to 2 wt % based on the weight of the aqueous sealing composition. The surfactant may be an anionic, cationic, zwitterionic, or nonionic surfactant. The surfactant may be a fluorosurfactant. The surfactant may be a silicone surfactant containing a polydimethylsiloxane group in its molecular structure.

[0113] The seal film may contain 4.5 to 25 wt% of the water-soluble ether relative to the weight of the seal film. The seal film may contain 4.5 to 10 wt%, or 5 to 9 wt%, or 5 to 8 wt%, or 5 to 7 wt% of the water-soluble ether relative to the weight of the seal film. The content of the water-soluble ether in the seal film may be greater than 4.5 wt%, greater than 5 wt%, greater than 6 wt%, greater than 7 wt%, greater than 8 wt%, greater than 9 wt%, or greater than 10 wt% relative to the weight of the seal film. The content of the water-soluble ether in the seal film may be less than 25 wt%, less than 20 wt%, less than 15 wt%, less than 10 wt%, or less than 5 wt% relative to the weight of the seal film.

[0114] The addition of a water-soluble ether to the aqueous sealing composition and the sealing film is believed to reduce the electrical resistance at the interface between the sealing film and one or both adjacent layers, such as the interface between the sealing film and the adhesive layer and the interface between the sealing film and the electrophoretic medium. 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, as shown by the data, the sealing film of the present invention has a higher volume resistivity than the control film that does not contain a water-soluble ether. As mentioned above, a higher volume resistivity of the sealing film contributes to lower blooming, a phenomenon well known in the electro-optics field.

[0115] 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 including a plurality of microcells, each with an opening, each containing 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.

[0116] 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.

[0117] The present inventors have surprisingly found that aqueous compositions containing a rheology modifier selected from the group consisting of HEUR and ASE improve the coating quality of sealing films. That is, the present sealing films reduce coating defects, which, if present, result in poor electro-optical performance in the corresponding devices. Coating defects can be related to poor wetting, delamination, chattering, or cloudy spotting (CSM). These effects are described in detail below. Specifically, reduced defects (higher coating quality) in sealing films were observed when (a) the viscosity ratio was less than 7, and the viscosity ratio was 1 to 7, 2 to 7, or 0.5 to 7; (b) the HB rate index was 0.7 or higher, 0.7 to 1, 0.7 to 0.9, or 0.7 to 2; and (c) the thixotropy index was 1.5 or higher, or 1.5 to 3.

[0118] The viscosity ratio of an aqueous sealing composition is determined as the ratio of the viscosity at low shear rate divided by the viscosity at high shear rate, as described in the Examples section. The HB rate index of an aqueous sealing composition is determined by measuring the viscosity of the composition using a shear rate ramp, constructing a graph of stress versus shear rate, and analyzing the graph based on the Herschel-Bulkley model, as described in the Examples section. The thixotropy index is the ratio of the viscosities measured in a thixotropy loop experiment in which an aqueous composition is subjected to a shear rate from low to high, followed by a shear rate from high to low. The thixotropy index indicates the thixotropic behavior of the aqueous sealing composition. The inventors conducted a detailed study of the rheological characteristics of various aqueous sealing compositions, then used the aqueous compositions to form devices with corresponding films and determined the coating quality and performance of such sealing films. Surprisingly, they found that aqueous compositions containing HEUR and ASE rheology modifiers provided sealing films with better performance and significantly fewer defects. It was also observed that the use of fluorosurfactants in aqueous compositions showed less interaction between the surfactant and the rheology modifier. That is, the content of fluorosurfactants had less impact on the rheological characteristics of the aqueous compositions compared to other surfactants, allowing for greater flexibility in adjusting the surface energy of the resulting seal film, which was shown to have a significant effect on the performance of the seal film. Specifically, improved performance was observed when a combination of poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer and polyurethane was used as described above, and the interfacial tension between the poly(vinyl alcohol) polymer or poly(vinyl alcohol-co-ethylene) copolymer and the polyurethane was less than 2 mN / m. Furthermore, the inventors surprisingly found that optimal performance was also observed when a combination of poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer and polyurethane was used, and the polar component of the polyurethane's surface energy was 10 to 20 mN / m.

[0119] 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]

[0120] Method for evaluating aqueous sealing compositions and sealing films

[0121] A. Example of Preparation of Aqueous Seal Composition

[0122] 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.

[0123] 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, 227.17 g of a 35 wt. % polyurethane aqueous dispersion (L3838 aqueous dispersion supplied by Hauthaway) was mixed with 683.2 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 at 90 rpm for 10 minutes using a Hei-torque Value 200 overhead mixer. The appropriate amount of crosslinker was then added, and the dispersion was mixed at 90 rpm for an additional 60 minutes. The appropriate amount of carbon black dispersion prepared in A1 was added (0.530 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. An 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 to prepare sealing films for the corresponding devices within 7 days of preparing the sealing composition.

[0124] B1. Example of preparation of sealing film using the drawdown method.

[0125] 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.

[0126] B2. Example of preparation of sealing film using a roll-to-roll coating line.

[0127] The sealing composition prepared in A2 above was coated onto the indium tin oxide (ITO) side of the ITO-PET thin film to a dry thickness of 30 μm using a slot die on a roll-to-roll coating line at a speed of 9 ft / min. The film traveled at 9 ft / min through a conventional oven consisting of four heating zones. Each heating zone was 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. After the dried sealing film on the ITO-PET passed through the drying oven, the film was cut into three pieces, each approximately 24-30 inches long, and placed in a controlled cleanroom environment at 25°C and 55% relative humidity (RH).

[0128] C. Determining the surface energy of the film.

[0129] The surface energy of the prepared sealing 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 sealing film using a syringe equipped with a needle, and the contact angle between the liquid (water) and the sealing 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, whose surface energies are known. The contact angle measurements were repeated three times for each liquid (water and diiodomethane). The contact angle between the liquid and the top surface of the sealing 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, were then calculated for each data point using the method of Owens, Wendt, Rabel, and Kaelble (OWRK). The reported surface energies were the average of nine data points (three droplets x three time scales).

[0130] D. Preparation of electro-optical devices.

[0131] 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 8 was constructed. The electro-optical device 800 included, in order, a protective film 801, an optically transparent first adhesive layer 802, a substrate 803, a light-transmitting conductive layer 804, a primer layer 805, a microcell layer 806, a sealing film 807, a second adhesive layer 808, an ITO electrode layer 809, and a glass layer 810. An electric field source 811 electrically connected the light-transmitting conductive layer 804 to the ITO electrode layer 809. This source applied a waveform to drive the desired optical state. The first light-transmitting layer 802 had a thickness of approximately 25 μm. The substrate 803 had a thickness of approximately 100 μm. The primer layer 1005 had a thickness of approximately 0.4 μm. The microcell layer 806 included a plurality of microcells. Each microcell had a bottom thickness of approximately 0.4 μm and a height of approximately 10 μm. The seal film 807 had a thickness of approximately 10 μm, and the second adhesive layer had a thickness of approximately 4.5 μm.

[0132] E. Determination of interfacial tension of polymers.

[0133] 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 C 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

[0134] Similarly, the interfacial tension between the seal film and the adhesive layer can also be measured.The polyurethane-containing adhesive layer standards were formed from an aqueous dispersion of water-dispersible polyurethane.

[0135] F. Evaluation of the barrier properties of sealing films against non-polar fluids.

[0136] 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 900 shown in Figure 9. The sealing film was formed by the method described in B1 above. Device 900 included, in order, a substrate 903, a light-transmitting conductive layer 904, a primer layer 905, a microcell layer 906, and a sealing film 907. The microcell contained an electrophoretic medium comprising white, black, and red pigment particles in Isopar E. Device 900 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 nonpolar 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 is 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 is 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 is 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 is classified as "pass" for its barrier properties. For example, the aqueous polymer composition used to prepare the electro-optical device shown in FIG. 10C 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. 10D was classified as "fail" because the h2:h1 ratio was 35% (a sag level of more than 85%). Assessment of the barrier properties can also be carried out qualitatively by observing the prepared electro-optical device from the viewing side of the device with an optical microscope.A device containing a severely sagging sealing film has a significantly different appearance (uniform versus non-uniform surface) than a device containing a sealing film with good barrier properties against non-polar fluids. For example, a microcell containing an aqueous polymer composition corresponding to the sealing film of FIG. 10C ("pass") appears uniform as shown in FIG. 10A, in contrast to a microcell containing an aqueous polymer composition corresponding to the sealing film of FIG. 10D ("fail"), which appears non-uniform as shown in FIG. 10B. 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 3. Polymer 1 is a poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer, and Polymer 2 is a polyurethane. Details regarding the commercially available materials for Polymer 1 and Polymer 2 can be found in Table 4.

[0137] G. Method for determining the thixotropy index of an aqueous sealing composition.

[0138] The thixotropy index (TI) was used to describe one aspect of the rheological behavior of aqueous sealing compositions. The thixotropy index is the ratio of the viscosities measured by a rheometer during a thixotropy loop test. The thixotropy loop test was performed by ramping the shear rate to a low shear (10 -4 1 / sec) to high shear (10 3 The viscosity is measured at different shear rates up to 1 / sec (1 / sec), then measured from high shear to low shear in a second flow ramp (Flow Ramp 2), creating a shear loop. The thixotropy index is calculated as 10 0 The viscosity value at a shear rate of 1 / s was calculated using the following equation, where η(A) is the 10 0 η(B) is the viscosity at 1 / s, and η(B) is the viscosity at 1 / s. 0 is the viscosity at 1 / sec.

number

[0139] H. Method for determining the HB velocity index of a water-based sealing composition.

[0140] The HB velocity index (or Herschel-Bulkley velocity index) was also used to describe the rheological behavior of the water-based sealing composition. The shear stress of the water-based sealing composition was determined for shear rates from 0 to 600 1 / s. The Herschel-Bulkley parameters were fitted to the data using the TRIOS software, using the Herschel-Bulkley equation σ = σ y +Kγ n (σ is the shear stress, K is the consistency coefficient (viscosity), γ is the shear rate, n is the HB velocity index, and σ y where σ is the yield stress. The HB velocity index, n, quantifies the fluid behavior of the seal fluid. If n<1, the fluid has shear-thinning behavior. If n>1, the fluid has shear-thickening behavior. If n=1 and the yield stress (σ y) is equal to 0, the fluid is Newtonian. It was observed that the HASE rheology modifiers (Solthix™ A100 and Rheovis® HS1212) have a lower HB rate index than the ASE rheology modifier (Rheovis® AS1130) and HEUR rheology modifiers (Rheovis® PU 1191, ACRYSOL™ RM-8W, OPTIFLO® 3300), and that aqueous sealing compositions containing the ASE and HEUR rheology modifiers had improved coating quality (fewer defects).

[0141] I. Viscosity Ratio Method for Aqueous Sealing Compositions.

[0142] The viscosity ratio of the aqueous sealing compositions was determined by obtaining a rheological profile of each aqueous sealing composition using a TA Instruments HR30 Discovery series rheometer and a parallel plate sensor with a diameter of 40.0 mm and a geometry gap of 1000.0 μm, with the Peltier plate maintained at a temperature of 25° C. The viscosity of the aqueous sealing compositions was determined by a rheological profile of each aqueous sealing composition using a TA Instruments HR30 Discovery series rheometer and a parallel plate sensor with a diameter of 40.0 mm and a geometry gap of 1000.0 μm, with the Peltier plate maintained at a temperature of 25° C. -4 The viscosity was measured using a flow ramp at a shear rate range of 10 Hz to 1000 Hz, with two points taken every 10 Hz. The viscosity ratio was calculated based on the low shear viscosity (10 -3 1 / sec) to high shear viscosity (10 3 η(L) / η(H) is calculated as the ratio of the viscosity of the fluid to the viscosity of the fluid (at 1 / sec). That is, the equation viscosity ratio = η(L) / η(H) is used, where η(L) is the viscosity of the fluid (at 1 / sec). -3 is the viscosity at a shear rate of 1 / s, and η(H) is 10 3 Viscosity at a shear rate of 1 / sec.

[0143] J. Methods for determining the quality of coatings on sealing films.

[0144] A water-based sealing composition was coated onto a front plane laminate containing a microcell layer filled with an electrophoretic medium. The resulting panels were cut into panels approximately 32 inches long and inspected for coating quality. The panels were placed on a surface under fluorescent lighting (5000K fluorescent bulbs), and the sealing film was visually inspected. Coating quality was determined based on four different quality defects: poor wetting, delamination, chattering, and cloudy spotting (CSM). Each sealing film was graded based on a ranking system for each quality defect. Specifically, defects were graded on a scale of 0 to 3, with 0 representing no defects and 3 representing the highest level of defects. Thus, higher numbers indicate poorer quality. Figure 11 shows examples of sealing films corresponding to the poor wetting ranking system. Figure 12 shows examples of sealing films corresponding to the delamination ranking system. Figure 13 shows examples of sealing films corresponding to the chattering ranking system. Figure 14 shows examples of sealing films corresponding to the cloudy spotting ranking system.

[0145] Wetting failure occurs when the sealing fluid evaporates from the filled microcell layer before drying is complete, leaving one or more spots where the sealing fluid has been lost. Sealing films with more spots of wetting failure were given a higher wetting failure grade. Sealing films with one to two spots were given a grade of 1, three to five spots were given a grade of 2, and six or more spots were given a grade of 3.

[0146] Delamination occurs when the dried sealing film separates / peels from the filled microcells. Panels with 2-5 small specks (less than 0.25cm) were given a grade of 1, panels with 5-10 small or medium size specks (less than 1.25cm) were given a grade of 2, and sealing films with large specks (greater than 1.25cm) or specks across their entire surface were given a grade of 3.

[0147] Chattering describes vertical lines that occur across the entire panel. If a faint line is present but only visible at certain angles of light reflection, a grade of 1 is given. If the line is easily visible at all angles, a grade of 2 is given. If the line is dark and noticeable, a grade of 3 is given.

[0148] Cloudy Spot Mottling (CSM) is used to describe circular spots that are often present on the surface of a seal film. The size, shape, and thickness of CSM vary depending on many factors, including but not limited to the seal formulation, electrophoretic medium, and coating parameters. CSM that are bright and / or small in size (less than 0.25 cm) without a central nucleation spot (small dark central dot) were given a grade of 1. If the CSM had visible nucleation, a grade of 2 was given. If the CSM had nucleation and was very thick and / or large in size (greater than 1 cm), a grade of 3 was given.

[0149] Evaluation results

[0150] 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.

[0151] 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 any residual or absorbed water, unless otherwise stated.

[0152] The example compositions having numbers ending with the letter F correspond to seal film compositions, while the remainder of the 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) is prepared from Example 1 (aqueous seal composition).

[0153] [Table 1A]

[0154] [Table 1B] [1] Exceval™ RS-1717 supplied by Kuraray [2] L3838 aqueous dispersion supplied by Hauthaway as a 35% dispersion in water [3] Nerox® 3500 supplied by Orion Engineered Carbon [4] CARBODILITE® V-02-L2 supplied by Nisshinbo Chemical as a 40% solution in water [5] Solthix™ A-100 supplied by Lubrizol [6] Rheovis® HS 1212 supplied by BASF [7] Rheovis® AS 1130 supplied by BASF [8] Rheovis® PU 1191 supplied by BASF [9] Acrysol™ RM-8W supplied by Dow Chemical

[10] Optiflo® 3300 supplied by Byk

[11] Silwet® L-7607 copolymer supplied by Momentive

[0155] [Table 2A]

[0156] [Table 2B] [1] Exceval™ RS-1717 supplied by Kuraray [2] L3838 aqueous dispersion supplied by Hauthaway as a 35% dispersion in water [3] Nerox® 3500 supplied by Orion Engineered Carbon [4] CARBODILITE® V-02-L2 supplied by Nisshinbo Chemical as a 40% solution in water [5] Solthix™ A-100 supplied by Lubrizol [6] Rheovis® HS 1212 supplied by BASF [7] Rheovis® AS 1130 supplied by BASF [8] Rheovis® PU 1191 supplied by BASF [9] Acrysol™ RM-8W supplied by Dow Chemical

[10] Optiflo® 3300 supplied by Byk

[11] Silwet® L-7607 copolymer supplied by Momentive

[0157] Table 2B shows that aqueous sealing compositions containing a HEUR rheology modifier, such as Optiflo® 3300, improve the coating quality of the corresponding seal film compared to aqueous sealing compositions containing a HASE rheology modifier, such as Solthix™ A-1000. This can be demonstrated by the higher observed grades of cloudy spotting (CSM), poor wetting, and chatter (Comparison of Examples 4, 7, and 8 with Comparative Examples 5 and 9). The rheological characteristics of the aqueous sealing compositions containing a HEUR rheology modifier are clearly different from those of the aqueous sealing compositions containing a HASE rheology modifier. Specifically, the improved seal film is formed from an aqueous sealing composition having (a) an HB speed index of 0.7 or higher, or 0.7 to 1, or 0.7 to 0.9, or 0.7 to 2; (b) a viscosity ratio of 7 or less, or 1 to 7, or 2 to 7, or 0.5 to 7; and (c) a thixotropy index of 1.5 or higher, or between 1.5 and 3. Similarly, an aqueous sealing composition containing an ASE rheology modifier (Example 1) exhibits similar rheological characteristics and provides a seal film with good coating quality. Furthermore, when image resolution was measured at 50°C, the image resolution of a display device having a seal film formed with an aqueous sealing composition containing a HEUR rheology modifier was observed to be better than that of a display device having a seal film formed with an aqueous sealing composition containing a HASE rheology modifier.

[0158] [Table 2C-1] [Table 2C-2]

[0159] [Table 2D-1] [Table 2D-2] [1] Exceval™ RS-1717 supplied by Kuraray [2] L3838 aqueous dispersion supplied by Hauthaway as a 35% dispersion in water [3] Nerox® 3500 supplied by Orion Engineered Carbon [4] CARBODILITE® V-02-L2 supplied by Nisshinbo Chemical as a 40% solution in water [5] Solthix™ A-100 supplied by Lubrizol [6] Rheovis® HS 1212 supplied by BASF [7] Rheovis® AS 1130 supplied by BASF [8] Rheovis® PU 1191 supplied by BASF [9] Acrysol™ RM-8W supplied by Dow Chemical

[10] Optiflo® 3300 supplied by Byk

[11] Silwet® L-7607 copolymer supplied by Momentive

[12] Capstone™ FS-31 supplied by The Chemours Company

[13] Capstone™ FS-3100 supplied by The Chemours Company

[0160] Tables 2C and 2D disclose compositions containing a rheology modifier (Solthix™ A-100) and various different surfactants, such as siloxanes and fluorosurfactants. In the case of siloxane-based surfactants, it was observed that changing the surfactant content of the formulation resulted in a significant change in the viscosity of the aqueous sealing composition (see Examples 12 and 13). In contrast, the viscosity of aqueous compositions containing fluorosurfactants changed much less with changing surfactant content (see Examples 10 and 12). This phenomenon is not trivial, as the surfactant allows the aqueous sealing composition to adjust the surface energy of the aqueous sealing composition on the microcell layer, which affects the coating quality of the resulting sealing film. Therefore, aqueous sealing compositions can be tailored using different surfactant contents to achieve good coating quality, improve wetting, and minimize coating defects on various microcell layers. Different surfactants interact differently with the rheology modifiers in the aqueous composition. As observed when using siloxane surfactants, when there is a strong interaction between the surfactant and the rheology modifier, a small change in surfactant content significantly changes the coatability and rheology profile, increasing the sensitivity of the operable formulation window. That is, when the surfactant strongly interacts with the rheology modifier, it becomes impractical to select a high surfactant content and effectively control the surface energy and wettability of the aqueous sealing composition. The inventors surprisingly found that aqueous sealing compositions containing fluorosurfactants showed little change in their viscosity with changing surfactant content. Therefore, the use of fluorosurfactants allows for easier optimization of the rheology profile and optimal coating quality.

[0161] Table 3 contains 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. It also includes the barrier properties of the various layers and the calculated interfacial properties of the 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.

[0162] [Table 3-1] [Table 3-2]

[0163] [Table 4]

[0164] The interfacial tension data for Polymer 1 and Polymer 2 in Table 3 indicate 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, where the interfacial tension between the two polymers (a) and (b) is less than 2 mN / m, forms a sealing film with good barrier properties to non-polar fluids.

[0165] The data in Table 3 also show that sealing films made from aqueous polymer 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.

[0166] Microscopic evaluation of polymer 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. Table 5 and the microscopic images in Figure 15 show that lower interfacial tension provides a more uniform polymer film. The improved compatibility achieved by combining polymers with lower interfacial tension may explain the improved barrier properties of the corresponding layers.

[0167] [Table 5]

[0168] 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 sealing film, a water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer, in an amount 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%; 7 to 29% by weight of polyurethane relative to the weight of the seal film; a rheology modifier in an amount of 0.05 to 10% by weight based on the weight of the seal film, the rheology modifier being selected from the group consisting of hydrophobically modified ethoxylated urethane and alkali-swellable emulsion polymer; Contains a sealing film. (Item 2) Item 2. The seal film according to item 1, further comprising 0.01 to 5% by weight of a surfactant relative to the weight of the seal film. (Item 3) 3. The seal film according to item 2, wherein the surfactant is a fluorine-based surfactant. (Item 4) Item 2. The seal film according to item 1, further comprising 5 to 70% by weight of carbon black based on the weight of the seal film. (Item 5) 2. The seal film according to item 1, further comprising 4.5 to 25 wt% of a water-soluble ether based on the weight of the seal film, wherein the water-soluble ether has a molecular weight of 75 to 5,000 daltons and optionally contains a hydroxyl group. (Item 6) 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 7) 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 8) 1. An electro-optical device, comprising: a conductive layer; a microcell layer including a plurality of microcells, each microcell having an opening, each microcell containing 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; Electrode layer and an electro-optical device comprising: (Item 9) 1. An aqueous sealing composition comprising: a water-soluble poly(vinyl alcohol) homopolymer or poly(vinyl alcohol-co-ethylene) copolymer, in an amount of 15 to 60% 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%; 7 to 29% by weight of polyurethane based on the weight of the aqueous sealing composition excluding water; a rheology modifier in an amount of 0.05 to 10 wt. % based on the weight of the aqueous sealing composition excluding water, the rheology modifier being selected from the group consisting of hydrophobically modified ethoxylated urethanes and hydrophobically modified alkali swellable emulsion polymers; 0.01 to 5% by weight of a surfactant based on the weight of the aqueous sealant composition excluding water; 20 to 95% by weight of water based on the weight of the aqueous sealing composition 1. An aqueous sealing composition comprising: (Item 10) 10. The aqueous sealing composition according to item 9, wherein the surfactant is a fluorosurfactant. (Item 11) 10. The aqueous sealing composition according to item 9, further comprising 5 to 70% by weight of carbon black, based on the weight of the aqueous sealing composition excluding water. (Item 12) 10. The aqueous sealing composition according to item 9, further comprising 1.0 to 40% by weight of a water-soluble ether, based on the weight of the aqueous sealing composition excluding water, wherein the water-soluble ether has a molecular weight of 75 to 5,000 daltons and optionally contains a hydroxyl group. (Item 13) 10. The aqueous sealing composition according to item 9, further comprising 0.1 to 8% by weight of a polyurethane crosslinker, based on the weight of the aqueous sealing composition excluding water. (Item 14) Item 14. The aqueous sealing composition according to item 13, wherein the polyurethane crosslinker is a polyisocyanate, a polyfunctional polycarbodiimide, a polyfunctional aziridine, a silane coupling agent, a boron / titanium / zirconium-based crosslinker, or melamine formaldehyde. (Item 15) 10-4 of the aqueous sealing composition at a shear rate of 1 / sec. 2 10. The aqueous sealing composition according to item 9, wherein the viscosity ratio divided by the viscosity of the aqueous sealing composition at a shear rate of 1 / sec is 7 or less. (Item 16) 10 -4 of the aqueous sealing composition at a shear rate of 1 / sec. 2 Item 10. The aqueous sealing composition according to item 9, wherein the viscosity ratio obtained by dividing the viscosity of the aqueous sealing composition at a shear rate of 1 / sec is 1 to 7. (Item 17) 10. The aqueous sealing composition according to item 9, having an HB Speed ​​Index of 0.7 or higher. (Item 18) 10. The aqueous sealing composition according to item 9, having an HB speed index of 0.7 to 1. (Item 19) 10. The aqueous sealing composition according to item 9, having a thixotropy index of 1.5 or higher. (Item 20) 10. The aqueous sealing composition according to item 9, having a thixotropy index of 1.5 to 3.

Claims

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

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